Re: [PATCH 3/6] btrfs: make btrfs_free_stale_device() to iterate all stales

[Nikolay Borisov]

On 16.12.2017 04:13, Anand Jain wrote:
> 
> 
> On 12/15/2017 11:06 PM, Nikolay Borisov wrote:
>>
>>
>> On 15.12.2017 05:47, Anand Jain wrote:
>>> Let the list iterator iterate further and find other stale
>>> devices and delete it. This is in preparation to add support
>>> for user land request-able stale devices cleanup.
>>>
>>> Signed-off-by: Anand Jain 
>>
>> What is the lock protection of this function - uuid_mutex, it's not
>> really obvious. Perhaps adding a lockdep_assert_held for the correct
>> lock ? I guess David's earlier patch to document the locking in
>> volumes.c might shed some light on this one.
> 
>  I remembered your earlier similar comments and I thought of adding
>  lockdep here, but as such I am also working on cleaning up uuid_mutext
>  and device_list_mutex I would like to include such lockdep assert in
>  those patches.

Makes sense so long as this change lands

> 
> Thanks, Anand
>>> ---
>>>   fs/btrfs/volumes.c | 20 +---
>>>   1 file changed, 9 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
>>> index 0e89409112d5..70db6a1d5658 100644
>>> --- a/fs/btrfs/volumes.c
>>> +++ b/fs/btrfs/volumes.c
>>> @@ -610,19 +610,20 @@ static void pending_bios_fn(struct btrfs_work
>>> *work)
>>>     static void btrfs_free_stale_device(struct btrfs_device *cur_dev)
>>>   {
>>> -    struct btrfs_fs_devices *fs_devs;
>>> -    struct btrfs_device *dev;
>>> +    struct btrfs_fs_devices *fs_devs, *tmp_fs_devs;
>>> +    struct btrfs_device *dev, *tmp_dev;
>>>     if (!cur_dev->name)
>>>   return;
>>>   -    list_for_each_entry(fs_devs, _uuids, list) {
>>> -    int del = 1;
>>> +    list_for_each_entry_safe(fs_devs, tmp_fs_devs, _uuids, list) {
>>>     if (fs_devs->opened)
>>>   continue;
>>>   -    list_for_each_entry(dev, _devs->devices, dev_list) {
>>> +    list_for_each_entry_safe(dev, tmp_dev,
>>> + _devs->devices, dev_list) {
>>> +    int not_found;
>>>     if (dev == cur_dev)
>>>   continue;
>>> @@ -636,14 +637,12 @@ static void btrfs_free_stale_device(struct
>>> btrfs_device *cur_dev)
>>>    * either use mapper or non mapper path throughout.
>>>    */
>>>   rcu_read_lock();
>>> -    del = strcmp(rcu_str_deref(dev->name),
>>> +    not_found = strcmp(rcu_str_deref(dev->name),
>>>   rcu_str_deref(cur_dev->name));
>>>   rcu_read_unlock();
>>> -    if (!del)
>>> -    break;
>>> -    }
>>> +    if (not_found)
>>> +    continue;
>>>   -    if (!del) {
>>>   /* delete the stale device */
>>>   if (fs_devs->num_devices == 1) {
>>>   btrfs_sysfs_remove_fsid(fs_devs);
>>> @@ -654,7 +653,6 @@ static void btrfs_free_stale_device(struct
>>> btrfs_device *cur_dev)
>>>   list_del(>dev_list);
>>>   free_device(dev);
>>>   }
>>> -    break;
>>>   }
>>>   }
>>>   }
>>>
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> 
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Re: [PATCH 4/6] btrfs: make btrfs_free_stale_device() argument optional

[Nikolay Borisov]

On 16.12.2017 04:14, Anand Jain wrote:
>     /*
>>> @@ -637,8 +632,11 @@ static void btrfs_free_stale_device(struct
>>> btrfs_device *cur_dev)
>>>    * either use mapper or non mapper path throughout.
>>>    */
>>>   rcu_read_lock();
>>> -    not_found = strcmp(rcu_str_deref(dev->name),
>>> -    rcu_str_deref(cur_dev->name));
>>> +    if (cur_dev)
>>> +    not_found = strcmp(rcu_str_deref(dev->name),
>>> +   rcu_str_deref(cur_dev->name));
>>> +    else
>>> +    not_found = 0;
>>
>> nit: Perhaps put a proper documentation header at the beginning of the
>> function detailing this behavior. I.e.
>>
>> /*
>>   * btrfs_free_stale_device
>>   * 
>>
> 
>  Right. Will add.

I posted this comment before reading your other patches, having done
that I'd say it's best to add the documentation once all the cleanups
have been done, since you also add another semantics with the "path"
argument.


> 
> Thanks, Anand
> 
> 
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Re: [PATCH] btrfs: fix refcount_t usage when deleting btrfs_delayed_nodes

[Nikolay Borisov]

On 15.12.2017 21:58, Chris Mason wrote:
> refcounts have a generic implementation and an asm optimized one.  The
> generic version has extra debugging to make sure that once a refcount
> goes to zero, refcount_inc won't increase it.
  

I guess you meant to say refcount_add
> 
> The btrfs delayed inode code wasn't expecting this, and we're tripping
> over the warnings when the generic refcounts are used.  We ended up with
> this race:
> 
> Process A Process B
>   btrfs_get_delayed_node()
> spin_lock(root->inode_lock)
> radix_tree_lookup()
> __btrfs_release_delayed_node()
> refcount_dec_and_test(_node->refs)
> our refcount is now zero
> refcount_add(2) <---
> warning here, refcount
>   unchanged
> 
> spin_lock(root->inode_lock)
> radix_tree_delete()
> 
> With the generic refcounts, we actually warn again when process B above
> tries to release his refcount because refcount_add() turned into a
> no-op.
> 
> We saw this in production on older kernels without the asm optimized
> refcounts.
> 
> The fix used here is to use refcount_inc_not_zero() to detect when the
> object is in the middle of being freed and return NULL.  This is almost
> always the right answer anyway, since we usually end up pitching the
> delayed_node if it didn't have fresh data in it.
> 
> This also changes __btrfs_release_delayed_node() to remove the extra
> check for zero refcounts before radix tree deletion.
> btrfs_get_delayed_node() was the only path that was allowing refcounts
> to go from zero to one.
> 
> Signed-off-by: Chris Mason 
> Fixes: 6de5f18e7b0da
> cc:  #4.12+
> ---
>  fs/btrfs/delayed-inode.c | 45 ++---
>  1 file changed, 34 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
> index 5d73f79..84c54af 100644
> --- a/fs/btrfs/delayed-inode.c
> +++ b/fs/btrfs/delayed-inode.c
> @@ -87,6 +87,7 @@ static struct btrfs_delayed_node *btrfs_get_delayed_node(
>  
>   spin_lock(>inode_lock);
>   node = radix_tree_lookup(>delayed_nodes_tree, ino);
> +
>   if (node) {
>   if (btrfs_inode->delayed_node) {
>   refcount_inc(>refs);  /* can be accessed */
> @@ -94,9 +95,30 @@ static struct btrfs_delayed_node *btrfs_get_delayed_node(
>   spin_unlock(>inode_lock);
>   return node;
>   }
> - btrfs_inode->delayed_node = node;
> - /* can be accessed and cached in the inode */
> - refcount_add(2, >refs);
> +
> + /* it's possible that we're racing into the middle of
> +  * removing this node from the radix tree.  In this case,
> +  * the refcount was zero and it should never go back
> +  * to one.  Just return NULL like it was never in the radix
> +  * at all; our release function is in the process of removing
> +  * it.
> +  *
> +  * Some implementations of refcount_inc refuse to
> +  * bump the refcount once it has hit zero.  If we don't do
> +  * this dance here, refcount_inc() may decide to
> +  * just WARN_ONCE() instead of actually bumping the refcount.
> +  *
> +  * If this node is properly in the radix, we want to
> +  * bump the refcount twice, once for the inode
> +  * and once for this get operation.
> +  */
> + if (refcount_inc_not_zero(>refs)) {
> + refcount_inc(>refs);
> + btrfs_inode->delayed_node = node;
> + } else {
> + node = NULL;
> + }
> +
>   spin_unlock(>inode_lock);
>   return node;
>   }
> @@ -254,17 +276,18 @@ static void __btrfs_release_delayed_node(
>   mutex_unlock(_node->mutex);
>  
>   if (refcount_dec_and_test(_node->refs)) {
> - bool free = false;
>   struct btrfs_root *root = delayed_node->root;
> +
>   spin_lock(>inode_lock);
> - if (refcount_read(_node->refs) == 0) {
> - radix_tree_delete(>delayed_nodes_tree,
> -   delayed_node->inode_id);
> - free = true;
> - }
> + /*
> +  * once our refcount goes to zero, nobody is allowed to
> +  * bump it back up.  We can delete it now
> +  */
> + ASSERT(refcount_read(_node->refs) == 0);
> + radix_tree_delete(>delayed_nodes_tree,
> +   

Re: 4.15.0-0.rc2.git2.1.fc28.x86_64: possible circular locking dependency detected

[Tomasz Kłoczko]

On 12 December 2017 at 06:50, Chris Murphy  wrote:
>
> On Mon, Dec 11, 2017 at 10:12 PM, Tomasz Kłoczko
>  wrote:
> > Hi,
> >
> > Jut done upgrade on my laptop to the latest Fedora rawhide packages.
> > After reboot and login in dmesg I found logged btrfs issue:
> >
> > [   94.192907] ==
> > [   94.192911] WARNING: possible circular locking dependency detected
> > [   94.192917] 4.15.0-0.rc2.git2.1.fc28.x86_64 #1 Not tainted
>
> I'm not seeing it so far with 4.15.0-0.rc3.git0.1.fc28.x86_64+debug.

[   90.516496] 4.15.0-0.rc3.git1.1.fc28.x86_64 #1 Not tainted
[   90.516502] --
[   90.516509] mysqld/1236 is trying to acquire lock:
[   90.516515]  (>mmap_sem){}, at: [<4969b9d5>]
get_user_pages_unlocked+0x5b/0x1b0
[   90.516543]
   but task is already holding lock:
[   90.516550]  (>dio_sem){}, at: [<0cdc761a>]
btrfs_direct_IO+0x395/0x410 [btrfs]
[   90.516644]
   which lock already depends on the new lock.

[   90.516650]
   the existing dependency chain (in reverse order) is:
[   90.516654]
   -> #5 (>dio_sem){}:
[   90.516672]down_write+0x4d/0xb0
[   90.516732]btrfs_log_changed_extents+0x7c/0x680 [btrfs]
[   90.516807]btrfs_log_inode+0x9c0/0x11a0 [btrfs]
[   90.516864]btrfs_log_inode_parent+0x2d7/0xaa0 [btrfs]
[   90.516915]btrfs_log_dentry_safe+0x58/0x80 [btrfs]
[   90.516973]btrfs_sync_file+0x332/0x4e0 [btrfs]
[   90.516987]do_fsync+0x38/0x60
[   90.516997]SyS_fsync+0xc/0x10
[   90.517008]do_syscall_64+0x66/0x210
[   90.517020]return_from_SYSCALL_64+0x0/0x75
[   90.517026]
   -> #4 (>log_mutex){+.+.}:
[   90.517049]__mutex_lock+0x7f/0xa40
[   90.517126]btrfs_log_inode+0x162/0x11a0 [btrfs]
[   90.517202]btrfs_log_inode_parent+0x2d7/0xaa0 [btrfs]
[   90.517277]btrfs_log_dentry_safe+0x58/0x80 [btrfs]
[   90.517356]btrfs_sync_file+0x332/0x4e0 [btrfs]
[   90.517367]do_fsync+0x38/0x60
[   90.517378]SyS_fsync+0xc/0x10
[   90.517387]do_syscall_64+0x66/0x210
[   90.517400]return_from_SYSCALL_64+0x0/0x75
[   90.517406]
   -> #3 (sb_internal){.+.+}:
[   90.517499]free_extent_buffer+0x2f/0x90 [btrfs]
[   90.517505]
   -> #2 ((completion)>wait){+.+.}:
[   90.517529]wait_for_completion+0x63/0x1e0
[   90.517596]btrfs_async_run_delayed_refs+0x14b/0x170 [btrfs]
[   90.517668]__btrfs_end_transaction+0x1ee/0x2e0 [btrfs]
[   90.517739]btrfs_dirty_inode+0x6a/0xd0 [btrfs]
[   90.517756]file_update_time+0xce/0x110
[   90.517809]btrfs_page_mkwrite+0xff/0x560 [btrfs]
[   90.517816]do_page_mkwrite+0x2a/0xc0
[   90.517822]do_wp_page+0x234/0x5d0
[   90.517828]__handle_mm_fault+0x658/0x1330
[   90.517834]handle_mm_fault+0x14c/0x310
[   90.517840]__do_page_fault+0x28c/0x530
[   90.517845]do_page_fault+0x32/0x270
[   90.517853]page_fault+0x22/0x30
[   90.517856]
   -> #1 (sb_pagefaults){.+.+}:
[   90.517872]__sb_start_write+0x138/0x1b0
[   90.517915]btrfs_page_mkwrite+0x6a/0x560 [btrfs]
[   90.517921]do_page_mkwrite+0x2a/0xc0
[   90.517927]do_wp_page+0x234/0x5d0
[   90.517932]__handle_mm_fault+0x658/0x1330
[   90.517938]handle_mm_fault+0x14c/0x310
[   90.517943]__do_page_fault+0x28c/0x530
[   90.517949]do_page_fault+0x32/0x270
[   90.517956]page_fault+0x22/0x30
[   90.517959]
   -> #0 (>mmap_sem){}:
[   90.517973]lock_acquire+0x9f/0x1f0
[   90.517979]down_read+0x44/0xa0
[   90.517984]get_user_pages_unlocked+0x5b/0x1b0
[   90.517989]get_user_pages_fast+0xcf/0x140
[   90.517998]iov_iter_get_pages+0xc5/0x2f0
[   90.518006]do_blockdev_direct_IO+0x193c/0x2950
[   90.518050]btrfs_direct_IO+0x166/0x410 [btrfs]
[   90.518059]generic_file_direct_write+0x9d/0x160
[   90.518104]btrfs_file_write_iter+0x300/0x650 [btrfs]
[   90.518111]aio_write+0x116/0x1a0
[   90.518118]do_io_submit+0x42d/0x940
[   90.518125]entry_SYSCALL_64_fastpath+0x1f/0x96
[   90.518128]
   other info that might help us debug this:

[   90.518133] Chain exists of:
 >mmap_sem --> >log_mutex --> >dio_sem

[   90.518148]  Possible unsafe locking scenario:

[   90.518152]CPU0CPU1
[   90.518155]
[   90.518158]   lock(>dio_sem);
[   90.518164]lock(>log_mutex);
[   90.518170]lock(>dio_sem);
[   90.518176]   lock(>mmap_sem);
[   90.518182]
*** DEADLOCK ***

[   90.518189] 2 locks held by mysqld/1236:
[  

Re: exclusive subvolume space missing

[Duncan]

Tomasz Pala posted on Fri, 15 Dec 2017 09:22:14 +0100 as excerpted:

> I wonder how this one db-library behaves:
> 
> $  find . -name \*.sqlite | xargs ls -gGhS | head -n1
> -rw-r--r-- 1  15M 2017-12-08 12:14
> ./.mozilla/firefox/vni9ojqi.default/extension-data/ublock0.sqlite
> 
> $  ~/fiemap ./.mozilla/firefox/*.default/extension-data/ublock0.sqlite |
> head -n1
> File ./.mozilla/firefox/vni9ojqi.default/extension-data/ublock0.sqlite
> has 128 extents:
> 
> 
> At least every $HOME/{.{,c}cache,tmp} should be +C...

Many admins will put tmp, and sometimes cache or selected parts of it, on 
tmpfs anyway... thereby both automatically clearing it on reboot, and 
allowing enforced size control as necessary.

>> And if possible, use nocow for this file.
> 
> Actually, this should be officially advised to use +C for entire /var
> tree and every other tree that might be exposed for hostile write
> patterns, like /home or /tmp (if held on btrfs).
> 
> I'd say, that from security point of view the nocow should be default,
> unless specified for mount or specific file... Currently, if I mount
> with nocow, there is no way to whitelist trusted users or secure
> location, and until btrfs-specific options could be handled per
> subvolume, there is really no alternative.

Nocow disables many reasons people run btrfs in the first place, 
including checksumming and damage-detection, with auto-repair from other 
copies where available (raid1/10 and dup modes primarily), as well as 
btrfs transparent compression, for users using that.  Additionally, 
snapshotting, another feature people use btrfs for, turns nocow into cow1 
(cow the first time a block is written after a snapshot), since 
snapshotting locks down the previous extent in ordered to maintain the 
snapshotted reference.

And given that any user can create a snapshot any time they want (even if 
you lock down the btrfs executable, if they're malevolent users and not 
locked to only running specifically whitelisted executables, they can 
always get a copy of the executable elsewhere), and /home or individual 
user subvols may well be auto-snapshotted already, setting nocow isn't 
likely to be of much security value at all.

So nocow is, as one regular wrote, most useful for "this really should go 
on something other than btrfs, but I'm too lazy to set it up that way and 
I'm already on btrfs, so the nocow band-aid is all I got.  And yes, I try 
using my screwdriver as a hammer too, because that's what I have there 
too!"

In that sort of case, just use some other filesystem more appropriate to 
the use-case, and you won't have to worry about btrfs issues, cow-
triggered or otherwise, in the first place.

-- 
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"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

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[PATCH v3 6/6] btrfs: cleanup to make btrfs_free_stale_device() readable

[Anand Jain]

Now as the there is path in arg, so instead of reading the path from
cur_device just get it from the caller, and so the purpose of cur_device
is to skip the device, so rename it to skip_dev. Also drop the comment
about different path being used for the same device, since now we will
have cli to clean any device that's not a concern any more.

Signed-off-by: Anand Jain 
---
v3: add btrfs_free_stale_device() fn description, as suggested by
Nikolay
Fix line with longer than 80 char
v2: btrfs_device::name is null when we have missing device and
unmounted. So we still need to check for dev->name.

 fs/btrfs/volumes.c | 30 --
 1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 0bf3233859b6..6d3353ce50d8 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -607,8 +607,17 @@ static void pending_bios_fn(struct btrfs_work *work)
run_scheduled_bios(device);
 }
 
-
-static void btrfs_free_stale_device(struct btrfs_device *cur_dev, char *path)
+/*
+ * btrfs_free_stale_device()
+ *  Search and remove all stale (devices which are not mounted) devices.
+ *  When both inputs are NULL, it will search and release all stale devices.
+ *  path:  Optional. When provided will it release all unmounted devices
+ * matching this path only.
+ *  skip_dev:  Optional. Will skip this device when searching for the stale
+ * devices.
+ */
+static void btrfs_free_stale_device(const char *path,
+   struct btrfs_device *skip_dev)
 {
struct btrfs_fs_devices *fs_devs, *tmp_fs_devs;
struct btrfs_device *dev, *tmp_dev;
@@ -622,20 +631,13 @@ static void btrfs_free_stale_device(struct btrfs_device 
*cur_dev, char *path)
 _devs->devices, dev_list) {
int not_found;
 
-   if (cur_dev && (cur_dev == dev || !dev->name))
+   if (skip_dev && skip_dev == dev)
+   continue;
+   if (path && !dev->name)
continue;
 
-   /*
-* Todo: This won't be enough. What if the same device
-* comes back (with new uuid and) with its mapper path?
-* But for now, this does help as mostly an admin will
-* either use mapper or non mapper path throughout.
-*/
rcu_read_lock();
-   if (cur_dev)
-   not_found = strcmp(rcu_str_deref(dev->name),
-  
rcu_str_deref(cur_dev->name));
-   else if (path)
+   if (path)
not_found = strcmp(rcu_str_deref(dev->name), 
path);
else
not_found = 0;
@@ -784,7 +786,7 @@ static noinline int device_list_add(const char *path,
 
ret = 1;
device->fs_devices = fs_devices;
-   btrfs_free_stale_device(device, NULL);
+   btrfs_free_stale_device(path, device);
} else if (!device->name || strcmp(device->name->str, path)) {
/*
 * When FS is already mounted.
-- 
2.7.0

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Re: [PATCH 1/6] btrfs: cleanup btrfs_free_stale_device() usage

[Anand Jain]

@@ -788,6 +788,7 @@ static noinline int device_list_add(const char *path,


nit: not directly related to the series in question, but I think you can
add one more patch which sinks the devid argument passed to
device_list_add. We already pass the disk_super and we can get the devid
in device_list_add this reduced the cognitive load when reading the code


 I notice that too, yes it should be in a new patch. More cleanups
 around this is coming up.

Thanks, Anand
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Re: [PATCH 3/6] btrfs: make btrfs_free_stale_device() to iterate all stales

[Anand Jain]

On 12/15/2017 11:06 PM, Nikolay Borisov wrote:



On 15.12.2017 05:47, Anand Jain wrote:

Let the list iterator iterate further and find other stale
devices and delete it. This is in preparation to add support
for user land request-able stale devices cleanup.

Signed-off-by: Anand Jain 


What is the lock protection of this function - uuid_mutex, it's not
really obvious. Perhaps adding a lockdep_assert_held for the correct
lock ? I guess David's earlier patch to document the locking in
volumes.c might shed some light on this one.


 I remembered your earlier similar comments and I thought of adding
 lockdep here, but as such I am also working on cleaning up uuid_mutext
 and device_list_mutex I would like to include such lockdep assert in
 those patches.

Thanks, Anand

---
  fs/btrfs/volumes.c | 20 +---
  1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 0e89409112d5..70db6a1d5658 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -610,19 +610,20 @@ static void pending_bios_fn(struct btrfs_work *work)
  
  static void btrfs_free_stale_device(struct btrfs_device *cur_dev)

  {
-   struct btrfs_fs_devices *fs_devs;
-   struct btrfs_device *dev;
+   struct btrfs_fs_devices *fs_devs, *tmp_fs_devs;
+   struct btrfs_device *dev, *tmp_dev;
  
  	if (!cur_dev->name)

return;
  
-	list_for_each_entry(fs_devs, _uuids, list) {

-   int del = 1;
+   list_for_each_entry_safe(fs_devs, tmp_fs_devs, _uuids, list) {
  
  		if (fs_devs->opened)

continue;
  
-		list_for_each_entry(dev, _devs->devices, dev_list) {

+   list_for_each_entry_safe(dev, tmp_dev,
+_devs->devices, dev_list) {
+   int not_found;
  
  			if (dev == cur_dev)

continue;
@@ -636,14 +637,12 @@ static void btrfs_free_stale_device(struct btrfs_device 
*cur_dev)
 * either use mapper or non mapper path throughout.
 */
rcu_read_lock();
-   del = strcmp(rcu_str_deref(dev->name),
+   not_found = strcmp(rcu_str_deref(dev->name),
rcu_str_deref(cur_dev->name));
rcu_read_unlock();
-   if (!del)
-   break;
-   }
+   if (not_found)
+   continue;
  
-		if (!del) {

/* delete the stale device */
if (fs_devs->num_devices == 1) {
btrfs_sysfs_remove_fsid(fs_devs);
@@ -654,7 +653,6 @@ static void btrfs_free_stale_device(struct btrfs_device 
*cur_dev)
list_del(>dev_list);
free_device(dev);
}
-   break;
}
}
  }


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Re: [4.14.3] btrfs out of space error

[Hans van Kranenburg]

On 12/15/2017 09:53 AM, Qu Wenruo wrote:
> 
> 
> On 2017年12月15日 16:36, Ian Kumlien wrote:
>> On Fri, Dec 15, 2017 at 6:34 AM, Roman Mamedov  wrote:
>>> On Fri, 15 Dec 2017 01:39:03 +0100
>>> Ian Kumlien  wrote:
>>>
 Hi,

 Running a 4.14.3 kernel, this just happened, but there should have
 been another 20 gigs or so available.

 The filesystem seems fine after a reboot though
>>>
>>> What are your mount options, and can you show the output of "btrfs fi
>>> df" and "btrfs fi us" for the filesystem? And what does
>>> "cat /sys/block/sdb/queue/rotational" return.
>>
>> It's a btrfs raid1 mirror of two ssd:s
>>
>> mount options was:
>> defaults,acl,noatime,space_cache,autodefrag,compress=lzo
>>
>> btrfs fi df /
>> Data, RAID1: total=459.25GiB, used=372.42GiB
>> Data, single: total=8.00MiB, used=0.00B
>> System, RAID1: total=8.00MiB, used=80.00KiB
>> System, single: total=4.00MiB, used=0.00B
>> Metadata, RAID1: total=6.00GiB, used=3.69GiB
> 
> Both meta and data has a lot of space let.

The real question is how fragmented that free space is.

Here's a good starting point to read up about the -o ssd behavior pre 4.14:

https://www.spinics.net/lists/linux-btrfs/msg70622.html

>> Metadata, single: total=8.00MiB, used=0.00B
>> GlobalReserve, single: total=512.00MiB, used=0.00B
>>
>> btrfs fi us /
>> Overall:
>> Device size: 930.54GiB
>> Device allocated: 930.53GiB
>> Device unallocated:   20.05MiB
>> Device missing:  0.00B
>> Used: 752.22GiB
>> Free (estimated):   86.84GiB (min: 86.84GiB)
>> Data ratio:   2.00
>> Metadata ratio:   2.00
>> Global reserve: 512.00MiB (used: 0.00B)
>>
>> Data,single: Size:8.00MiB, Used:0.00B
>>/dev/sdb28.00MiB
>>
>> Data,RAID1: Size:459.25GiB, Used:372.42GiB
>>/dev/sdb2 459.25GiB
>>/dev/sdc2 459.25GiB
>>
>> Metadata,single: Size:8.00MiB, Used:0.00B
>>/dev/sdb28.00MiB
>>
>> Metadata,RAID1: Size:6.00GiB, Used:3.69GiB
>>/dev/sdb26.00GiB
>>/dev/sdc26.00GiB
>>
>> System,single: Size:4.00MiB, Used:0.00B
>>/dev/sdb24.00MiB
>>
>> System,RAID1: Size:8.00MiB, Used:80.00KiB
>>/dev/sdb28.00MiB
>>/dev/sdc28.00MiB
>>
>> Unallocated:
>>/dev/sdb2   24.00KiB
>>/dev/sdc2   20.02MiB
> 
> Well, at least no new chunk can be allocated.

Exactly.

> In v4.15, Josef introduced a new inode reservation system, which I think
> it would enhance metadata related reservation.
> 
> If you're hitting the problem quite frequently, please consider to try
> v4.15-rc* to see if it solves the problem.
> 
> Despite of that, there should be no damage to your fs.
> (except some unwritten data in buffer)
> 
> Thanks,
> Qu
> 
>>
>> And as expected:
>> cat /sys/block/sdb/queue/rotational
>> 0
>>
>>> I wonder if it's the same old "ssd allocation scheme" problem, and no
>>> balancing done in a long time or at all.

Looks like it. So, yay, you're on 4.14 already. Now just do a full
balance of your entire filesystem, only once (data only, metadata not
needed) and then you can forget about this again.

>> I had something similar happen on a laptop a while ago - took a while
>> before i could get it back in order
>> (in that case i think it was actually a oops --- it kept saying "no
>> space left" and switched to read only even
>> if you removed a lot of data, invalidated the space cache and so on)

-- 
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[PATCH v5 69/78] vmalloc: Convert to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

The radix tree of vmap blocks is simpler to express as an XArray.
Saves a couple of hundred bytes of text and eliminates a user of the
radix tree preload API.

Signed-off-by: Matthew Wilcox 
---
 mm/vmalloc.c | 39 +--
 1 file changed, 13 insertions(+), 26 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 673942094328..b6c138633592 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -23,7 +23,7 @@
 #include 
 #include 
 #include 
-#include 
+#include 
 #include 
 #include 
 #include 
@@ -821,12 +821,11 @@ struct vmap_block {
 static DEFINE_PER_CPU(struct vmap_block_queue, vmap_block_queue);
 
 /*
- * Radix tree of vmap blocks, indexed by address, to quickly find a vmap block
+ * XArray of vmap blocks, indexed by address, to quickly find a vmap block
  * in the free path. Could get rid of this if we change the API to return a
  * "cookie" from alloc, to be passed to free. But no big deal yet.
  */
-static DEFINE_SPINLOCK(vmap_block_tree_lock);
-static RADIX_TREE(vmap_block_tree, GFP_ATOMIC);
+static DEFINE_XARRAY(vmap_block_tree);
 
 /*
  * We should probably have a fallback mechanism to allocate virtual memory
@@ -865,8 +864,8 @@ static void *new_vmap_block(unsigned int order, gfp_t 
gfp_mask)
struct vmap_block *vb;
struct vmap_area *va;
unsigned long vb_idx;
-   int node, err;
-   void *vaddr;
+   int node;
+   void *ret, *vaddr;
 
node = numa_node_id();
 
@@ -883,13 +882,6 @@ static void *new_vmap_block(unsigned int order, gfp_t 
gfp_mask)
return ERR_CAST(va);
}
 
-   err = radix_tree_preload(gfp_mask);
-   if (unlikely(err)) {
-   kfree(vb);
-   free_vmap_area(va);
-   return ERR_PTR(err);
-   }
-
vaddr = vmap_block_vaddr(va->va_start, 0);
spin_lock_init(>lock);
vb->va = va;
@@ -902,11 +894,12 @@ static void *new_vmap_block(unsigned int order, gfp_t 
gfp_mask)
INIT_LIST_HEAD(>free_list);
 
vb_idx = addr_to_vb_idx(va->va_start);
-   spin_lock(_block_tree_lock);
-   err = radix_tree_insert(_block_tree, vb_idx, vb);
-   spin_unlock(_block_tree_lock);
-   BUG_ON(err);
-   radix_tree_preload_end();
+   ret = xa_store(_block_tree, vb_idx, vb, gfp_mask);
+   if (xa_is_err(ret)) {
+   kfree(vb);
+   free_vmap_area(va);
+   return ERR_PTR(xa_err(ret));
+   }
 
vbq = _cpu_var(vmap_block_queue);
spin_lock(>lock);
@@ -923,9 +916,7 @@ static void free_vmap_block(struct vmap_block *vb)
unsigned long vb_idx;
 
vb_idx = addr_to_vb_idx(vb->va->va_start);
-   spin_lock(_block_tree_lock);
-   tmp = radix_tree_delete(_block_tree, vb_idx);
-   spin_unlock(_block_tree_lock);
+   tmp = xa_erase(_block_tree, vb_idx);
BUG_ON(tmp != vb);
 
free_vmap_area_noflush(vb->va);
@@ -1031,7 +1022,6 @@ static void *vb_alloc(unsigned long size, gfp_t gfp_mask)
 static void vb_free(const void *addr, unsigned long size)
 {
unsigned long offset;
-   unsigned long vb_idx;
unsigned int order;
struct vmap_block *vb;
 
@@ -1045,10 +1035,7 @@ static void vb_free(const void *addr, unsigned long size)
offset = (unsigned long)addr & (VMAP_BLOCK_SIZE - 1);
offset >>= PAGE_SHIFT;
 
-   vb_idx = addr_to_vb_idx((unsigned long)addr);
-   rcu_read_lock();
-   vb = radix_tree_lookup(_block_tree, vb_idx);
-   rcu_read_unlock();
+   vb = xa_load(_block_tree, addr_to_vb_idx((unsigned long)addr));
BUG_ON(!vb);
 
vunmap_page_range((unsigned long)addr, (unsigned long)addr + size);
-- 
2.15.1

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[PATCH v5 42/78] shmem: Convert replace to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

shmem_radix_tree_replace() is renamed to shmem_xa_replace() and
converted to use the XArray API.

Signed-off-by: Matthew Wilcox 
---
 mm/shmem.c | 22 --
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index c5731bb954a1..fad6c9e7402e 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -321,24 +321,20 @@ void shmem_uncharge(struct inode *inode, long pages)
 }
 
 /*
- * Replace item expected in radix tree by a new item, while holding tree lock.
+ * Replace item expected in xarray by a new item, while holding xa_lock.
  */
-static int shmem_radix_tree_replace(struct address_space *mapping,
+static int shmem_xa_replace(struct address_space *mapping,
pgoff_t index, void *expected, void *replacement)
 {
-   struct radix_tree_node *node;
-   void **pslot;
+   XA_STATE(xas, >pages, index);
void *item;
 
VM_BUG_ON(!expected);
VM_BUG_ON(!replacement);
-   item = __radix_tree_lookup(>pages, index, , );
-   if (!item)
-   return -ENOENT;
+   item = xas_load();
if (item != expected)
return -ENOENT;
-   __radix_tree_replace(>pages, node, pslot,
-replacement, NULL);
+   xas_store(, replacement);
return 0;
 }
 
@@ -605,8 +601,7 @@ static int shmem_add_to_page_cache(struct page *page,
} else if (!expected) {
error = radix_tree_insert(>pages, index, page);
} else {
-   error = shmem_radix_tree_replace(mapping, index, expected,
-page);
+   error = shmem_xa_replace(mapping, index, expected, page);
}
 
if (!error) {
@@ -635,7 +630,7 @@ static void shmem_delete_from_page_cache(struct page *page, 
void *radswap)
VM_BUG_ON_PAGE(PageCompound(page), page);
 
xa_lock_irq(>pages);
-   error = shmem_radix_tree_replace(mapping, page->index, page, radswap);
+   error = shmem_xa_replace(mapping, page->index, page, radswap);
page->mapping = NULL;
mapping->nrpages--;
__dec_node_page_state(page, NR_FILE_PAGES);
@@ -1550,8 +1545,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t 
gfp,
 * a nice clean interface for us to replace oldpage by newpage there.
 */
xa_lock_irq(_mapping->pages);
-   error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
-  newpage);
+   error = shmem_xa_replace(swap_mapping, swap_index, oldpage, newpage);
if (!error) {
__inc_node_page_state(newpage, NR_FILE_PAGES);
__dec_node_page_state(oldpage, NR_FILE_PAGES);
-- 
2.15.1

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[PATCH v5 48/78] shmem: Convert shmem_alloc_hugepage to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

xa_find() is a slightly easier API to use than
radix_tree_gang_lookup_slot() because it contains its own RCU locking.

Signed-off-by: Matthew Wilcox 
---
 mm/shmem.c | 13 +++--
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 0f49edae05e4..bd66bbd40499 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1413,23 +1413,16 @@ static struct page *shmem_alloc_hugepage(gfp_t gfp,
struct shmem_inode_info *info, pgoff_t index)
 {
struct vm_area_struct pvma;
-   struct inode *inode = >vfs_inode;
-   struct address_space *mapping = inode->i_mapping;
-   pgoff_t idx, hindex;
-   void __rcu **results;
+   struct address_space *mapping = info->vfs_inode.i_mapping;
+   pgoff_t hindex;
struct page *page;
 
if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
return NULL;
 
hindex = round_down(index, HPAGE_PMD_NR);
-   rcu_read_lock();
-   if (radix_tree_gang_lookup_slot(>pages, , ,
-   hindex, 1) && idx < hindex + HPAGE_PMD_NR) {
-   rcu_read_unlock();
+   if (xa_find(>pages, , hindex + HPAGE_PMD_NR - 1))
return NULL;
-   }
-   rcu_read_unlock();
 
shmem_pseudo_vma_init(, info, hindex);
page = alloc_pages_vma(gfp | __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN,
-- 
2.15.1

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[PATCH v5 57/78] lustre: Convert to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Signed-off-by: Matthew Wilcox 
---
 drivers/staging/lustre/lustre/llite/glimpse.c   | 12 +---
 drivers/staging/lustre/lustre/mdc/mdc_request.c | 16 
 2 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/staging/lustre/lustre/llite/glimpse.c 
b/drivers/staging/lustre/lustre/llite/glimpse.c
index 5f2843da911c..25232fdf5797 100644
--- a/drivers/staging/lustre/lustre/llite/glimpse.c
+++ b/drivers/staging/lustre/lustre/llite/glimpse.c
@@ -57,7 +57,7 @@ static const struct cl_lock_descr whole_file = {
 };
 
 /*
- * Check whether file has possible unwriten pages.
+ * Check whether file has possible unwritten pages.
  *
  * \retval 1file is mmap-ed or has dirty pages
  *  0otherwise
@@ -66,16 +66,14 @@ blkcnt_t dirty_cnt(struct inode *inode)
 {
blkcnt_t cnt = 0;
struct vvp_object *vob = cl_inode2vvp(inode);
-   void  *results[1];
 
-   if (inode->i_mapping)
-   cnt += radix_tree_gang_lookup_tag(>i_mapping->pages,
- results, 0, 1,
- PAGECACHE_TAG_DIRTY);
+   if (inode->i_mapping && xa_tagged(>i_mapping->pages,
+   PAGECACHE_TAG_DIRTY))
+   cnt = 1;
if (cnt == 0 && atomic_read(>vob_mmap_cnt) > 0)
cnt = 1;
 
-   return (cnt > 0) ? 1 : 0;
+   return cnt;
 }
 
 int cl_glimpse_lock(const struct lu_env *env, struct cl_io *io,
diff --git a/drivers/staging/lustre/lustre/mdc/mdc_request.c 
b/drivers/staging/lustre/lustre/mdc/mdc_request.c
index 2ec79a6b17da..ea23247e9e02 100644
--- a/drivers/staging/lustre/lustre/mdc/mdc_request.c
+++ b/drivers/staging/lustre/lustre/mdc/mdc_request.c
@@ -934,17 +934,18 @@ static struct page *mdc_page_locate(struct address_space 
*mapping, __u64 *hash,
 * hash _smaller_ than one we are looking for.
 */
unsigned long offset = hash_x_index(*hash, hash64);
+   XA_STATE(xas, >pages, offset);
struct page *page;
-   int found;
 
-   xa_lock_irq(>pages);
-   found = radix_tree_gang_lookup(>pages,
-  (void **), offset, 1);
-   if (found > 0 && !xa_is_value(page)) {
+   xas_lock_irq();
+   page = xas_find(, ULONG_MAX);
+   if (xa_is_value(page))
+   page = NULL;
+   if (page) {
struct lu_dirpage *dp;
 
get_page(page);
-   xa_unlock_irq(>pages);
+   xas_unlock_irq();
/*
 * In contrast to find_lock_page() we are sure that directory
 * page cannot be truncated (while DLM lock is held) and,
@@ -992,8 +993,7 @@ static struct page *mdc_page_locate(struct address_space 
*mapping, __u64 *hash,
page = ERR_PTR(-EIO);
}
} else {
-   xa_unlock_irq(>pages);
-   page = NULL;
+   xas_unlock_irq();
}
return page;
 }
-- 
2.15.1

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[PATCH v5 17/78] xarray: Add xa_destroy

[Matthew Wilcox]

From: Matthew Wilcox 

This function frees all the internal memory allocated to the xarray
and reinitialises it to be empty.

Signed-off-by: Matthew Wilcox 
---
 include/linux/xarray.h |  1 +
 lib/xarray.c   | 25 +
 2 files changed, 26 insertions(+)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 1367d694eebd..fea81383a301 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -77,6 +77,7 @@ void *xa_load(struct xarray *, unsigned long index);
 void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
 void *xa_cmpxchg(struct xarray *, unsigned long index,
void *old, void *entry, gfp_t);
+void xa_destroy(struct xarray *);
 
 /**
  * xa_erase() - Erase this entry from the XArray.
diff --git a/lib/xarray.c b/lib/xarray.c
index e73ae7b57fc9..a51fa1e1f74f 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1418,6 +1418,31 @@ int xa_get_tagged(struct xarray *xa, void **dst, 
unsigned long start,
 }
 EXPORT_SYMBOL(xa_get_tagged);
 
+/**
+ * xa_destroy() - Free all internal data structures.
+ * @xa: XArray.
+ *
+ * After calling this function, the XArray is empty and has freed all memory
+ * allocated for its internal data structures.  You are responsible for
+ * freeing the objects referenced by the XArray.
+ */
+void xa_destroy(struct xarray *xa)
+{
+   XA_STATE(xas, xa, 0);
+   void *entry;
+
+   xas.xa_node = NULL;
+   xa_lock(xa);
+   entry = xa_head_locked(xa);
+   RCU_INIT_POINTER(xa->xa_head, NULL);
+   xas_init_tags();
+   /* lockdep checks we're still holding the lock in xas_free_nodes() */
+   if (xa_is_node(entry))
+   xas_free_nodes(, xa_to_node(entry));
+   xa_unlock(xa);
+}
+EXPORT_SYMBOL(xa_destroy);
+
 #ifdef XA_DEBUG
 void xa_dump_node(const struct xa_node *node)
 {
-- 
2.15.1

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[PATCH v5 53/78] fs: Convert buffer to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Mostly comment fixes, but one use of __xa_set_tag.

Signed-off-by: Matthew Wilcox 
---
 fs/buffer.c | 14 +++---
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 1a6ae530156b..e1d18307d5c8 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -592,7 +592,7 @@ void mark_buffer_dirty_inode(struct buffer_head *bh, struct 
inode *inode)
 EXPORT_SYMBOL(mark_buffer_dirty_inode);
 
 /*
- * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
+ * Mark the page dirty, and set it dirty in the page cache, and mark the inode
  * dirty.
  *
  * If warn is true, then emit a warning if the page is not uptodate and has
@@ -609,8 +609,8 @@ void __set_page_dirty(struct page *page, struct 
address_space *mapping,
if (page->mapping) {/* Race with truncate? */
WARN_ON_ONCE(warn && !PageUptodate(page));
account_page_dirtied(page, mapping);
-   radix_tree_tag_set(>pages,
-   page_index(page), PAGECACHE_TAG_DIRTY);
+   __xa_set_tag(>pages, page_index(page),
+   PAGECACHE_TAG_DIRTY);
}
xa_unlock_irqrestore(>pages, flags);
 }
@@ -1072,7 +1072,7 @@ __getblk_slow(struct block_device *bdev, sector_t block,
  * The relationship between dirty buffers and dirty pages:
  *
  * Whenever a page has any dirty buffers, the page's dirty bit is set, and
- * the page is tagged dirty in its radix tree.
+ * the page is tagged dirty in the page cache.
  *
  * At all times, the dirtiness of the buffers represents the dirtiness of
  * subsections of the page.  If the page has buffers, the page dirty bit is
@@ -1095,9 +1095,9 @@ __getblk_slow(struct block_device *bdev, sector_t block,
  * mark_buffer_dirty - mark a buffer_head as needing writeout
  * @bh: the buffer_head to mark dirty
  *
- * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
- * backing page dirty, then tag the page as dirty in its address_space's radix
- * tree and then attach the address_space's inode to its superblock's dirty
+ * mark_buffer_dirty() will set the dirty bit against the buffer, then set
+ * its backing page dirty, then tag the page as dirty in the page cache
+ * and then attach the address_space's inode to its superblock's dirty
  * inode list.
  *
  * mark_buffer_dirty() is atomic.  It takes bh->b_page->mapping->private_lock,
-- 
2.15.1

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[PATCH v5 77/78] irqdomain: Convert to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

In a non-critical path, irqdomain wants to know how many entries are
stored in the xarray, so add xa_count().  This is a pretty straightforward
conversion; mostly just removing now-redundant locking.  The only thing
of note is just how much simpler irq_domain_fix_revmap() becomes.

Signed-off-by: Matthew Wilcox 
---
 include/linux/irqdomain.h | 10 --
 include/linux/xarray.h|  1 +
 kernel/irq/irqdomain.c| 39 ++-
 lib/xarray.c  | 25 +
 4 files changed, 40 insertions(+), 35 deletions(-)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index a34355d19546..0efccfb9e9f1 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -33,8 +33,7 @@
 #include 
 #include 
 #include 
-#include 
-#include 
+#include 
 
 struct device_node;
 struct irq_domain;
@@ -151,7 +150,7 @@ struct irq_domain_chip_generic;
  * @revmap_direct_max_irq: The largest hwirq that can be set for controllers 
that
  * support direct mapping
  * @revmap_size: Size of the linear map table @linear_revmap[]
- * @revmap_tree: Radix map tree for hwirqs that don't fit in the linear map
+ * @revmap_array: hwirqs that don't fit in the linear map
  * @linear_revmap: Linear table of hwirq->virq reverse mappings
  */
 struct irq_domain {
@@ -177,8 +176,7 @@ struct irq_domain {
irq_hw_number_t hwirq_max;
unsigned int revmap_direct_max_irq;
unsigned int revmap_size;
-   struct radix_tree_root revmap_tree;
-   struct mutex revmap_tree_mutex;
+   struct xarray revmap_array;
unsigned int linear_revmap[];
 };
 
@@ -378,7 +376,7 @@ extern void irq_dispose_mapping(unsigned int virq);
  * This is a fast path alternative to irq_find_mapping() that can be
  * called directly by irq controller code to save a handful of
  * instructions. It is always safe to call, but won't find irqs mapped
- * using the radix tree.
+ * using the xarray.
  */
 static inline unsigned int irq_linear_revmap(struct irq_domain *domain,
 irq_hw_number_t hwirq)
diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index eba544f26b70..6af8b30a9310 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -145,6 +145,7 @@ int xa_get_entries(struct xarray *, void **dst, unsigned 
long start,
unsigned long max, unsigned int n);
 int xa_get_tagged(struct xarray *, void **dst, unsigned long start,
unsigned long max, unsigned int n, xa_tag_t);
+unsigned long xa_count(struct xarray *);
 
 /**
  * xa_get_maybe_tag() - Copy entries from the XArray into a normal array.
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 4f4f60015e8a..8225fe042f8a 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -114,7 +114,7 @@ EXPORT_SYMBOL_GPL(irq_domain_free_fwnode);
 /**
  * __irq_domain_add() - Allocate a new irq_domain data structure
  * @fwnode: firmware node for the interrupt controller
- * @size: Size of linear map; 0 for radix mapping only
+ * @size: Size of linear map; 0 for xarray mapping only
  * @hwirq_max: Maximum number of interrupts supported by controller
  * @direct_max: Maximum value of direct maps; Use ~0 for no limit; 0 for no
  *  direct mapping
@@ -209,8 +209,7 @@ struct irq_domain *__irq_domain_add(struct fwnode_handle 
*fwnode, int size,
of_node_get(of_node);
 
/* Fill structure */
-   INIT_RADIX_TREE(>revmap_tree, GFP_KERNEL);
-   mutex_init(>revmap_tree_mutex);
+   xa_init(>revmap_array);
domain->ops = ops;
domain->host_data = host_data;
domain->hwirq_max = hwirq_max;
@@ -241,7 +240,7 @@ void irq_domain_remove(struct irq_domain *domain)
mutex_lock(_domain_mutex);
debugfs_remove_domain_dir(domain);
 
-   WARN_ON(!radix_tree_empty(>revmap_tree));
+   WARN_ON(!xa_empty(>revmap_array));
 
list_del(>link);
 
@@ -462,9 +461,7 @@ static void irq_domain_clear_mapping(struct irq_domain 
*domain,
if (hwirq < domain->revmap_size) {
domain->linear_revmap[hwirq] = 0;
} else {
-   mutex_lock(>revmap_tree_mutex);
-   radix_tree_delete(>revmap_tree, hwirq);
-   mutex_unlock(>revmap_tree_mutex);
+   xa_erase(>revmap_array, hwirq);
}
 }
 
@@ -475,9 +472,7 @@ static void irq_domain_set_mapping(struct irq_domain 
*domain,
if (hwirq < domain->revmap_size) {
domain->linear_revmap[hwirq] = irq_data->irq;
} else {
-   mutex_lock(>revmap_tree_mutex);
-   radix_tree_insert(>revmap_tree, hwirq, irq_data);
-   mutex_unlock(>revmap_tree_mutex);
+   xa_store(>revmap_array, hwirq, irq_data, GFP_KERNEL);
}
 }
 
@@ -585,7 +580,7 @@ 

[PATCH v5 40/78] mm: Convert khugepaged_scan_shmem to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Slightly shorter and easier to read code.

Signed-off-by: Matthew Wilcox 
---
 mm/khugepaged.c | 17 +
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 9f49d0cd61c2..15f1b2d81a69 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1534,8 +1534,7 @@ static void khugepaged_scan_shmem(struct mm_struct *mm,
pgoff_t start, struct page **hpage)
 {
struct page *page = NULL;
-   struct radix_tree_iter iter;
-   void **slot;
+   XA_STATE(xas, >pages, start);
int present, swap;
int node = NUMA_NO_NODE;
int result = SCAN_SUCCEED;
@@ -1544,17 +1543,11 @@ static void khugepaged_scan_shmem(struct mm_struct *mm,
swap = 0;
memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
rcu_read_lock();
-   radix_tree_for_each_slot(slot, >pages, , start) {
-   if (iter.index >= start + HPAGE_PMD_NR)
-   break;
-
-   page = radix_tree_deref_slot(slot);
-   if (radix_tree_deref_retry(page)) {
-   slot = radix_tree_iter_retry();
+   xas_for_each(, page, start + HPAGE_PMD_NR - 1) {
+   if (xas_retry(, page))
continue;
-   }
 
-   if (radix_tree_exception(page)) {
+   if (xa_is_value(page)) {
if (++swap > khugepaged_max_ptes_swap) {
result = SCAN_EXCEED_SWAP_PTE;
break;
@@ -1593,7 +1586,7 @@ static void khugepaged_scan_shmem(struct mm_struct *mm,
present++;
 
if (need_resched()) {
-   slot = radix_tree_iter_resume(slot, );
+   xas_pause();
cond_resched_rcu();
}
}
-- 
2.15.1

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[PATCH v5 33/78] mm: Convert truncate to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

This is essentially xa_cmpxchg() with the locking handled above us,
and it doesn't have to handle replacing a NULL entry.

Signed-off-by: Matthew Wilcox 
---
 mm/truncate.c | 15 ++-
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/mm/truncate.c b/mm/truncate.c
index 69bb743dd7e5..70323c347298 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -33,15 +33,12 @@
 static inline void __clear_shadow_entry(struct address_space *mapping,
pgoff_t index, void *entry)
 {
-   struct radix_tree_node *node;
-   void **slot;
+   XA_STATE(xas, >pages, index);
 
-   if (!__radix_tree_lookup(>pages, index, , ))
+   xas_set_update(, workingset_update_node);
+   if (xas_load() != entry)
return;
-   if (*slot != entry)
-   return;
-   __radix_tree_replace(>pages, node, slot, NULL,
-workingset_update_node);
+   xas_store(, NULL);
mapping->nrexceptional--;
 }
 
@@ -746,10 +743,10 @@ int invalidate_inode_pages2_range(struct address_space 
*mapping,
index++;
}
/*
-* For DAX we invalidate page tables after invalidating radix tree.  We
+* For DAX we invalidate page tables after invalidating page cache.  We
 * could invalidate page tables while invalidating each entry however
 * that would be expensive. And doing range unmapping before doesn't
-* work as we have no cheap way to find whether radix tree entry didn't
+* work as we have no cheap way to find whether page cache entry didn't
 * get remapped later.
 */
if (dax_mapping(mapping)) {
-- 
2.15.1

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[PATCH v5 39/78] mm: Convert collapse_shmem to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

I found another victim of the radix tree being hard to use.  Because
there was no call to radix_tree_preload(), khugepaged was allocating
radix_tree_nodes using GFP_ATOMIC.

I also converted a local_irq_save()/restore() pair to
disable()/enable().

Signed-off-by: Matthew Wilcox 
---
 include/linux/swap.h |   4 +-
 mm/khugepaged.c  | 158 +--
 2 files changed, 67 insertions(+), 95 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 569a8ac4fe3f..9774f43d3e4f 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -300,12 +300,12 @@ bool workingset_refault(void *shadow);
 void workingset_activation(struct page *page);
 
 /* Do not use directly, use workingset_lookup_update */
-void workingset_update_node(struct xa_node *node);
+void workingset_update_node(struct radix_tree_node *node);
 
 /* Returns workingset_update_node() if the mapping has shadow entries. */
 #define workingset_lookup_update(mapping)  \
 ({ \
-   xa_update_node_t __helper = workingset_update_node; \
+   radix_tree_update_node_t __helper = workingset_update_node; \
if (dax_mapping(mapping) || shmem_mapping(mapping)) \
__helper = NULL;\
__helper;   \
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 55ade70c33bb..9f49d0cd61c2 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1282,17 +1282,17 @@ static void retract_page_tables(struct address_space 
*mapping, pgoff_t pgoff)
  *
  * Basic scheme is simple, details are more complex:
  *  - allocate and freeze a new huge page;
- *  - scan over radix tree replacing old pages the new one
+ *  - scan page cache replacing old pages with the new one
  *+ swap in pages if necessary;
  *+ fill in gaps;
- *+ keep old pages around in case if rollback is required;
- *  - if replacing succeed:
+ *+ keep old pages around in case rollback is required;
+ *  - if replacing succeeds:
  *+ copy data over;
  *+ free old pages;
  *+ unfreeze huge page;
  *  - if replacing failed;
  *+ put all pages back and unfreeze them;
- *+ restore gaps in the radix-tree;
+ *+ restore gaps in the page cache;
  *+ free huge page;
  */
 static void collapse_shmem(struct mm_struct *mm,
@@ -1300,12 +1300,11 @@ static void collapse_shmem(struct mm_struct *mm,
struct page **hpage, int node)
 {
gfp_t gfp;
-   struct page *page, *new_page, *tmp;
+   struct page *new_page;
struct mem_cgroup *memcg;
pgoff_t index, end = start + HPAGE_PMD_NR;
LIST_HEAD(pagelist);
-   struct radix_tree_iter iter;
-   void **slot;
+   XA_STATE(xas, >pages, start);
int nr_none = 0, result = SCAN_SUCCEED;
 
VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
@@ -1330,48 +1329,48 @@ static void collapse_shmem(struct mm_struct *mm,
__SetPageLocked(new_page);
BUG_ON(!page_ref_freeze(new_page, 1));
 
-
/*
-* At this point the new_page is 'frozen' (page_count() is zero), locked
-* and not up-to-date. It's safe to insert it into radix tree, because
-* nobody would be able to map it or use it in other way until we
-* unfreeze it.
+* At this point the new_page is 'frozen' (page_count() is zero),
+* locked and not up-to-date. It's safe to insert it into the page
+* cache, because nobody would be able to map it or use it in other
+* way until we unfreeze it.
 */
 
-   index = start;
-   xa_lock_irq(>pages);
-   radix_tree_for_each_slot(slot, >pages, , start) {
-   int n = min(iter.index, end) - index;
-
-   /*
-* Handle holes in the radix tree: charge it from shmem and
-* insert relevant subpage of new_page into the radix-tree.
-*/
-   if (n && !shmem_charge(mapping->host, n)) {
-   result = SCAN_FAIL;
+   /* This will be less messy when we use multi-index entries */
+   do {
+   xas_lock_irq();
+   xas_create_range(, end - 1);
+   if (!xas_error())
break;
-   }
-   nr_none += n;
-   for (; index < min(iter.index, end); index++) {
-   radix_tree_insert(>pages, index,
-   new_page + (index % HPAGE_PMD_NR));
-   }
+   xas_unlock_irq();
+   if (!xas_nomem(, GFP_KERNEL))
+   goto out;
+   } while (1);
 
-   /* We are done. */
-   if (index >= end)
-   break;
+   for (index = 

[PATCH v5 63/78] dax: Convert dax_insert_pfn_mkwrite to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Signed-off-by: Matthew Wilcox 
---
 fs/dax.c | 8 
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index d6dd779e1b46..9cfd4fcc0b0d 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1498,21 +1498,21 @@ static int dax_insert_pfn_mkwrite(struct vm_fault *vmf,
void *entry;
int vmf_ret, error;
 
-   xa_lock_irq(>pages);
+   xas_lock_irq();
entry = get_unlocked_mapping_entry();
/* Did we race with someone splitting entry or so? */
if (!entry ||
(pe_size == PE_SIZE_PTE && !dax_is_pte_entry(entry)) ||
(pe_size == PE_SIZE_PMD && !dax_is_pmd_entry(entry))) {
put_unlocked_mapping_entry(, entry);
-   xa_unlock_irq(>pages);
+   xas_unlock_irq();
trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf,
  VM_FAULT_NOPAGE);
return VM_FAULT_NOPAGE;
}
-   radix_tree_tag_set(>pages, index, PAGECACHE_TAG_DIRTY);
+   xas_set_tag(, PAGECACHE_TAG_DIRTY);
entry = lock_slot();
-   xa_unlock_irq(>pages);
+   xas_unlock_irq();
switch (pe_size) {
case PE_SIZE_PTE:
error = vm_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
-- 
2.15.1

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[PATCH v5 60/78] dax: More XArray conversion

[Matthew Wilcox]

From: Matthew Wilcox 

This time, we want to convert get_unlocked_mapping_entry() to use the
XArray.  That has a ripple effect, causing us to change the waitqueues
to hash on the address of the xarray rather than the address of the
mapping (functionally equivalent), and create a lot of on-the-stack
xa_state which are only used as a container for passing the xarray and
the index down to deeper function calls.

Also rename dax_wake_mapping_entry_waiter() to dax_wake_entry().

Signed-off-by: Matthew Wilcox 
---
 fs/dax.c | 72 +---
 1 file changed, 33 insertions(+), 39 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 46a4d83b1b46..2629ffa70575 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -120,7 +120,7 @@ static int dax_is_empty_entry(void *entry)
  * DAX radix tree locking
  */
 struct exceptional_entry_key {
-   struct address_space *mapping;
+   struct xarray *xa;
pgoff_t entry_start;
 };
 
@@ -129,9 +129,10 @@ struct wait_exceptional_entry_queue {
struct exceptional_entry_key key;
 };
 
-static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
-   pgoff_t index, void *entry, struct exceptional_entry_key *key)
+static wait_queue_head_t *dax_entry_waitqueue(struct xa_state *xas,
+   void *entry, struct exceptional_entry_key *key)
 {
+   unsigned long index = xas->xa_index;
unsigned long hash;
 
/*
@@ -142,10 +143,10 @@ static wait_queue_head_t *dax_entry_waitqueue(struct 
address_space *mapping,
if (dax_is_pmd_entry(entry))
index &= ~PG_PMD_COLOUR;
 
-   key->mapping = mapping;
+   key->xa = xas->xa;
key->entry_start = index;
 
-   hash = hash_long((unsigned long)mapping ^ index, DAX_WAIT_TABLE_BITS);
+   hash = hash_long((unsigned long)xas->xa ^ index, DAX_WAIT_TABLE_BITS);
return wait_table + hash;
 }
 
@@ -156,7 +157,7 @@ static int wake_exceptional_entry_func(wait_queue_entry_t 
*wait, unsigned int mo
struct wait_exceptional_entry_queue *ewait =
container_of(wait, struct wait_exceptional_entry_queue, wait);
 
-   if (key->mapping != ewait->key.mapping ||
+   if (key->xa != ewait->key.xa ||
key->entry_start != ewait->key.entry_start)
return 0;
return autoremove_wake_function(wait, mode, sync, NULL);
@@ -167,13 +168,12 @@ static int wake_exceptional_entry_func(wait_queue_entry_t 
*wait, unsigned int mo
  * The important information it's conveying is whether the entry at
  * this index used to be a PMD entry.
  */
-static void dax_wake_mapping_entry_waiter(struct address_space *mapping,
-   pgoff_t index, void *entry, bool wake_all)
+static void dax_wake_entry(struct xa_state *xas, void *entry, bool wake_all)
 {
struct exceptional_entry_key key;
wait_queue_head_t *wq;
 
-   wq = dax_entry_waitqueue(mapping, index, entry, );
+   wq = dax_entry_waitqueue(xas, entry, );
 
/*
 * Checking for locked entry and prepare_to_wait_exclusive() happens
@@ -205,10 +205,9 @@ static inline void *lock_slot(struct xa_state *xas)
  *
  * Must be called with xa_lock held.
  */
-static void *get_unlocked_mapping_entry(struct address_space *mapping,
-   pgoff_t index, void ***slotp)
+static void *get_unlocked_mapping_entry(struct xa_state *xas)
 {
-   void *entry, **slot;
+   void *entry;
struct wait_exceptional_entry_queue ewait;
wait_queue_head_t *wq;
 
@@ -216,22 +215,19 @@ static void *get_unlocked_mapping_entry(struct 
address_space *mapping,
ewait.wait.func = wake_exceptional_entry_func;
 
for (;;) {
-   entry = __radix_tree_lookup(>pages, index, NULL,
- );
-   if (!entry ||
-   WARN_ON_ONCE(!xa_is_value(entry)) || !dax_locked(entry)) {
-   if (slotp)
-   *slotp = slot;
+   entry = xas_load(xas);
+   if (!entry || WARN_ON_ONCE(!xa_is_value(entry)) ||
+   !dax_locked(entry))
return entry;
-   }
 
-   wq = dax_entry_waitqueue(mapping, index, entry, );
+   wq = dax_entry_waitqueue(xas, entry, );
prepare_to_wait_exclusive(wq, ,
  TASK_UNINTERRUPTIBLE);
-   xa_unlock_irq(>pages);
+   xas_pause(xas);
+   xas_unlock_irq(xas);
schedule();
finish_wait(wq, );
-   xa_lock_irq(>pages);
+   xas_lock_irq(xas);
}
 }
 
@@ -251,7 +247,7 @@ static void dax_unlock_mapping_entry(struct address_space 
*mapping,
xas_store(, entry);
/* Safe to not call xas_pause here -- we don't touch the array after */

[PATCH v5 06/78] xarray: Change definition of sibling entries

[Matthew Wilcox]

From: Matthew Wilcox 

Instead of storing a pointer to the slot containing the canonical entry,
store the offset of the slot.  Produces slightly more efficient code
(~300 bytes) and simplifies the implementation.

Signed-off-by: Matthew Wilcox 
---
 include/linux/xarray.h | 82 ++
 lib/radix-tree.c   | 65 +++
 2 files changed, 100 insertions(+), 47 deletions(-)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 49fffc354431..f175350560fd 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -49,6 +49,17 @@ static inline bool xa_is_value(const void *entry)
return (unsigned long)entry & 1;
 }
 
+/**
+ * xa_is_internal() - Is the entry an internal entry?
+ * @entry: Entry retrieved from the XArray
+ *
+ * Return: %true if the entry is an internal entry.
+ */
+static inline bool xa_is_internal(const void *entry)
+{
+   return ((unsigned long)entry & 3) == 2;
+}
+
 #define xa_trylock(xa) spin_trylock(&(xa)->xa_lock)
 #define xa_lock(xa)spin_lock(&(xa)->xa_lock)
 #define xa_unlock(xa)  spin_unlock(&(xa)->xa_lock)
@@ -61,4 +72,75 @@ static inline bool xa_is_value(const void *entry)
 #define xa_unlock_irqrestore(xa, flags) \
spin_unlock_irqrestore(&(xa)->xa_lock, flags)
 
+/* Everything below here is the Advanced API.  Proceed with caution. */
+
+/*
+ * The xarray is constructed out of a set of 'chunks' of pointers.  Choosing
+ * the best chunk size requires some tradeoffs.  A power of two recommends
+ * itself so that we can walk the tree based purely on shifts and masks.
+ * Generally, the larger the better; as the number of slots per level of the
+ * tree increases, the less tall the tree needs to be.  But that needs to be
+ * balanced against the memory consumption of each node.  On a 64-bit system,
+ * xa_node is currently 576 bytes, and we get 7 of them per 4kB page.  If we
+ * doubled the number of slots per node, we'd get only 3 nodes per 4kB page.
+ */
+#ifndef XA_CHUNK_SHIFT
+#define XA_CHUNK_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
+#endif
+#define XA_CHUNK_SIZE  (1UL << XA_CHUNK_SHIFT)
+#define XA_CHUNK_MASK  (XA_CHUNK_SIZE - 1)
+
+/*
+ * Internal entries have the bottom two bits set to the value 10b.  Most
+ * internal entries are pointers to the next node in the tree.  Since the
+ * kernel unmaps page 0 to trap NULL pointer dereferences, we can use values
+ * 0-1023 for special purposes.  Values 0-62 are used for sibling
+ * entries.  Value 256 is used for the retry entry.
+ */
+
+/* Private */
+static inline void *xa_mk_internal(unsigned long v)
+{
+   return (void *)((v << 2) | 2);
+}
+
+/* Private */
+static inline unsigned long xa_to_internal(const void *entry)
+{
+   return (unsigned long)entry >> 2;
+}
+
+/* Private */
+static inline bool xa_is_node(const void *entry)
+{
+   return xa_is_internal(entry) && (unsigned long)entry > 4096;
+}
+
+/* Private */
+static inline void *xa_mk_sibling(unsigned int offset)
+{
+   return xa_mk_internal(offset);
+}
+
+/* Private */
+static inline unsigned long xa_to_sibling(const void *entry)
+{
+   return xa_to_internal(entry);
+}
+
+/**
+ * xa_is_sibling() - Is the entry a sibling entry?
+ * @entry: Entry retrieved from the XArray
+ *
+ * Return: %true if the entry is a sibling entry.
+ */
+static inline bool xa_is_sibling(const void *entry)
+{
+   return IS_ENABLED(CONFIG_RADIX_TREE_MULTIORDER) &&
+   xa_is_internal(entry) &&
+   (entry < xa_mk_sibling(XA_CHUNK_SIZE - 1));
+}
+
+#define XA_RETRY_ENTRY xa_mk_internal(256)
+
 #endif /* _LINUX_XARRAY_H */
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index cda7a730e591..0a7a21dd9398 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -37,6 +37,7 @@
 #include 
 #include 
 #include 
+#include 
 
 
 /* Number of nodes in fully populated tree of given height */
@@ -97,24 +98,7 @@ static inline void *node_to_entry(void *ptr)
return (void *)((unsigned long)ptr | RADIX_TREE_INTERNAL_NODE);
 }
 
-#define RADIX_TREE_RETRY   node_to_entry(NULL)
-
-#ifdef CONFIG_RADIX_TREE_MULTIORDER
-/* Sibling slots point directly to another slot in the same node */
-static inline
-bool is_sibling_entry(const struct radix_tree_node *parent, void *node)
-{
-   void __rcu **ptr = node;
-   return (parent->slots <= ptr) &&
-   (ptr < parent->slots + RADIX_TREE_MAP_SIZE);
-}
-#else
-static inline
-bool is_sibling_entry(const struct radix_tree_node *parent, void *node)
-{
-   return false;
-}
-#endif
+#define RADIX_TREE_RETRY   XA_RETRY_ENTRY
 
 static inline unsigned long
 get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot)
@@ -128,16 +112,10 @@ static unsigned int radix_tree_descend(const struct 
radix_tree_node *parent,
unsigned int offset = (index 

[PATCH v5 44/78] shmem: Convert find_swap_entry to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

This is a 1:1 conversion.

Signed-off-by: Matthew Wilcox 
---
 mm/shmem.c | 23 +++
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 654f367aca90..ce285ae635ea 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1076,28 +1076,27 @@ static void shmem_evict_inode(struct inode *inode)
clear_inode(inode);
 }
 
-static unsigned long find_swap_entry(struct radix_tree_root *root, void *item)
+static unsigned long find_swap_entry(struct xarray *xa, void *item)
 {
-   struct radix_tree_iter iter;
-   void **slot;
-   unsigned long found = -1;
+   XA_STATE(xas, xa, 0);
unsigned int checked = 0;
+   void *entry;
 
rcu_read_lock();
-   radix_tree_for_each_slot(slot, root, , 0) {
-   if (*slot == item) {
-   found = iter.index;
+   xas_for_each(, entry, ULONG_MAX) {
+   if (xas_retry(, entry))
+   continue;
+   if (entry == item)
break;
-   }
checked++;
-   if ((checked % 4096) != 0)
+   if ((checked % XA_CHECK_SCHED) != 0)
continue;
-   slot = radix_tree_iter_resume(slot, );
+   xas_pause();
cond_resched_rcu();
}
-
rcu_read_unlock();
-   return found;
+
+   return xas_invalid() ? -1 : xas.xa_index;
 }
 
 /*
-- 
2.15.1

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[PATCH v5 30/78] page cache: Remove stray radix comment

[Matthew Wilcox]

From: Matthew Wilcox 

Signed-off-by: Matthew Wilcox 
---
 mm/filemap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 92ddee25f19b..75d1b32080a4 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2603,7 +2603,7 @@ static struct page *do_read_cache_page(struct 
address_space *mapping,
put_page(page);
if (err == -EEXIST)
goto repeat;
-   /* Presumably ENOMEM for radix tree node */
+   /* Presumably ENOMEM for xarray node */
return ERR_PTR(err);
}
 
-- 
2.15.1

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[PATCH v5 25/78] page cache: Add page_cache_range_empty function

[Matthew Wilcox]

From: Matthew Wilcox 

btrfs has its own custom function for determining whether the page cache
has any pages in a particular range.  Move this functionality to the
page cache, and call it from btrfs.

Signed-off-by: Matthew Wilcox 
---
 fs/btrfs/btrfs_inode.h  |  7 -
 fs/btrfs/inode.c| 70 -
 include/linux/pagemap.h |  2 ++
 mm/filemap.c| 26 ++
 4 files changed, 34 insertions(+), 71 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 63f0ccc92a71..a48bd6e0a0bb 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -365,6 +365,11 @@ static inline void btrfs_print_data_csum_error(struct 
btrfs_inode *inode,
logical_start, csum, csum_expected, mirror_num);
 }
 
-bool btrfs_page_exists_in_range(struct inode *inode, loff_t start, loff_t end);
+static inline bool btrfs_page_exists_in_range(struct inode *inode,
+   loff_t start, loff_t end)
+{
+   return page_cache_range_empty(inode->i_mapping, start >> PAGE_SHIFT,
+   end >> PAGE_SHIFT);
+}
 
 #endif
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index dbdb5bf6bca1..d7d2c556d5a2 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7541,76 +7541,6 @@ noinline int can_nocow_extent(struct inode *inode, u64 
offset, u64 *len,
return ret;
 }
 
-bool btrfs_page_exists_in_range(struct inode *inode, loff_t start, loff_t end)
-{
-   struct radix_tree_root *root = >i_mapping->pages;
-   bool found = false;
-   void **pagep = NULL;
-   struct page *page = NULL;
-   unsigned long start_idx;
-   unsigned long end_idx;
-
-   start_idx = start >> PAGE_SHIFT;
-
-   /*
-* end is the last byte in the last page.  end == start is legal
-*/
-   end_idx = end >> PAGE_SHIFT;
-
-   rcu_read_lock();
-
-   /* Most of the code in this while loop is lifted from
-* find_get_page.  It's been modified to begin searching from a
-* page and return just the first page found in that range.  If the
-* found idx is less than or equal to the end idx then we know that
-* a page exists.  If no pages are found or if those pages are
-* outside of the range then we're fine (yay!) */
-   while (page == NULL &&
-  radix_tree_gang_lookup_slot(root, , NULL, start_idx, 1)) {
-   page = radix_tree_deref_slot(pagep);
-   if (unlikely(!page))
-   break;
-
-   if (radix_tree_exception(page)) {
-   if (radix_tree_deref_retry(page)) {
-   page = NULL;
-   continue;
-   }
-   /*
-* Otherwise, shmem/tmpfs must be storing a swap entry
-* here so return it without attempting to raise page
-* count.
-*/
-   page = NULL;
-   break; /* TODO: Is this relevant for this use case? */
-   }
-
-   if (!page_cache_get_speculative(page)) {
-   page = NULL;
-   continue;
-   }
-
-   /*
-* Has the page moved?
-* This is part of the lockless pagecache protocol. See
-* include/linux/pagemap.h for details.
-*/
-   if (unlikely(page != *pagep)) {
-   put_page(page);
-   page = NULL;
-   }
-   }
-
-   if (page) {
-   if (page->index <= end_idx)
-   found = true;
-   put_page(page);
-   }
-
-   rcu_read_unlock();
-   return found;
-}
-
 static int lock_extent_direct(struct inode *inode, u64 lockstart, u64 lockend,
  struct extent_state **cached_state, int writing)
 {
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 0db127c3ccac..34d4fa3ad1c5 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -245,6 +245,8 @@ pgoff_t page_cache_next_gap(struct address_space *mapping,
 pgoff_t index, unsigned long max_scan);
 pgoff_t page_cache_prev_gap(struct address_space *mapping,
 pgoff_t index, unsigned long max_scan);
+bool page_cache_range_empty(struct address_space *mapping,
+   pgoff_t index, pgoff_t max);
 
 #define FGP_ACCESSED   0x0001
 #define FGP_LOCK   0x0002
diff --git a/mm/filemap.c b/mm/filemap.c
index 146e8ec16ec0..f1b4480723dd 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1398,6 +1398,32 @@ pgoff_t page_cache_prev_gap(struct address_space 
*mapping,
 }
 

[PATCH v5 14/78] xarray: Add xa_for_each

[Matthew Wilcox]

From: Matthew Wilcox 

This iterator allows the user to efficiently walk a range of the array,
executing the loop body once for each non-NULL entry in that range.
This commit also includes xa_find() and xa_next() which are helper
functions for xa_for_each() but may also be useful in their own right.

In the xas family of functions, we also have xas_for_each(),
xas_find(), xas_next(), xas_pause() and xas_jump().  xas_pause() allows
a xas_for_each() iteration to be resumed later from the next element
and xas_jump() allows an iteration to be resumed from a specified index.

Signed-off-by: Matthew Wilcox 
---
 include/linux/xarray.h | 111 ++
 lib/radix-tree.c   |   4 +-
 lib/xarray.c   | 166 +
 tools/testing/radix-tree/xarray-test.c | 114 ++
 4 files changed, 393 insertions(+), 2 deletions(-)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 56db23edac82..c4eef03ad12d 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -138,6 +138,35 @@ bool xa_get_tag(struct xarray *, unsigned long index, 
xa_tag_t);
 void xa_set_tag(struct xarray *, unsigned long index, xa_tag_t);
 void xa_clear_tag(struct xarray *, unsigned long index, xa_tag_t);
 
+void *xa_find(struct xarray *xa, unsigned long *index, unsigned long max);
+void *xa_find_after(struct xarray *xa, unsigned long *index, unsigned long 
max);
+
+/**
+ * xa_for_each() - Iterate over a portion of an XArray.
+ * @xa: XArray.
+ * @entry: Entry retrieved from array.
+ * @index: Index of @entry.
+ * @max: Maximum index to retrieve from array.
+ *
+ * Initialise @index to the minimum index you want to retrieve from
+ * the array.  During the iteration, @entry will have the value of the
+ * entry stored in @xa at @index.  The iteration will skip all NULL
+ * entries in the array.  You may modify @index during the
+ * iteration if you want to skip indices.  It is safe to modify the
+ * array during the iteration.  At the end of the iteration, @entry will
+ * be set to NULL and @index will have a value less than or equal to max.
+ *
+ * xa_for_each() is O(n.log(n)) while xas_for_each() is O(n).  You have
+ * to handle your own locking with xas_for_each(), and if you have to unlock
+ * after each iteration, it will also end up being O(n.log(n)).  xa_for_each()
+ * will spin if it hits a retry entry; if you intend to see retry entries,
+ * you should use the xas_for_each() iterator instead.  The xas_for_each()
+ * iterator will expand into more inline code than xa_for_each().
+ */
+#define xa_for_each(xa, entry, index, max) \
+   for (entry = xa_find(xa, , max); entry; \
+entry = xa_find_after(xa, , max))
+
 #define BITS_PER_XA_VALUE  (BITS_PER_LONG - 1)
 
 /**
@@ -577,6 +606,12 @@ static inline bool xas_valid(const struct xa_state *xas)
return !xas_invalid(xas);
 }
 
+/* True if the pointer is something other than a node */
+static inline bool xas_not_node(struct xa_node *node)
+{
+   return ((unsigned long)node & 3) || !node;
+}
+
 /* True if the node represents head-of-tree, RESTART or BOUNDS */
 static inline bool xas_top(struct xa_node *node)
 {
@@ -605,6 +640,7 @@ static inline bool xas_retry(struct xa_state *xas, const 
void *entry)
 void *xas_load(struct xa_state *);
 void *xas_store(struct xa_state *, void *entry);
 void *xas_create(struct xa_state *);
+void *xas_find(struct xa_state *, unsigned long max);
 
 bool xas_get_tag(const struct xa_state *, xa_tag_t);
 void xas_set_tag(const struct xa_state *, xa_tag_t);
@@ -612,6 +648,7 @@ void xas_clear_tag(const struct xa_state *, xa_tag_t);
 void xas_init_tags(const struct xa_state *);
 
 bool xas_nomem(struct xa_state *, gfp_t);
+void xas_pause(struct xa_state *);
 
 /**
  * xas_reload() - Refetch an entry from the xarray.
@@ -684,6 +721,80 @@ static inline void xas_set_update(struct xa_state *xas, 
xa_update_node_t update)
xas->xa_update = update;
 }
 
+/* Skip over any of these entries when iterating */
+static inline bool xa_iter_skip(const void *entry)
+{
+   return unlikely(!entry ||
+   (xa_is_internal(entry) && entry < XA_RETRY_ENTRY));
+}
+
+/*
+ * node->shift is always 0 for the inline iterators unless we're processing
+ * a multi-index entry.
+ */
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+#define xa_node_shift(node)node->shift
+#else
+#define xa_node_shift(node)0
+#endif
+
+/**
+ * xas_next_entry() - Advance iterator to next present entry.
+ * @xas: XArray operation state.
+ * @max: Highest index to return.
+ *
+ * xas_next_entry() is an inline function to optimise xarray traversal for
+ * speed.  It is equivalent to calling xas_find(), and will call xas_find()
+ * for all the hard cases.
+ *
+ * Return: The next present entry after the one currently referred to by @xas.
+ */
+static inline void *xas_next_entry(struct xa_state 

[PATCH v5 18/78] xarray: Add xas_next and xas_prev

[Matthew Wilcox]

From: Matthew Wilcox 

These two functions move the xas index by one position, and adjust the
rest of the iterator state to match it.  This is more efficient than
calling xas_set() as it keeps the iterator at the leaves of the tree
instead of walking the iterator from the root each time.

Signed-off-by: Matthew Wilcox 
---
 include/linux/xarray.h |  71 ++-
 lib/xarray.c   |  74 
 tools/testing/radix-tree/xarray-test.c | 213 +
 3 files changed, 356 insertions(+), 2 deletions(-)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index fea81383a301..2d889208b68d 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -640,6 +640,12 @@ static inline bool xas_not_node(struct xa_node *node)
return ((unsigned long)node & 3) || !node;
 }
 
+/* True if the node represents RESTART or an error */
+static inline bool xas_frozen(struct xa_node *node)
+{
+   return (unsigned long)node & 2;
+}
+
 /* True if the node represents head-of-tree, RESTART or BOUNDS */
 static inline bool xas_top(struct xa_node *node)
 {
@@ -758,8 +764,8 @@ static inline bool xa_iter_skip(const void *entry)
 }
 
 /*
- * node->shift is always 0 for the inline iterators unless we're processing
- * a multi-index entry.
+ * node->shift is always 0 for next_entry and next_tag unless we're processing
+ * a multi-index entry.  It can be non-0 for next/prev, so it's not used there.
  */
 #ifdef CONFIG_RADIX_TREE_MULTIORDER
 #define xa_node_shift(node)node->shift
@@ -767,6 +773,67 @@ static inline bool xa_iter_skip(const void *entry)
 #define xa_node_shift(node)0
 #endif
 
+void *__xas_next(struct xa_state *);
+void *__xas_prev(struct xa_state *);
+
+/**
+ * xas_prev() - Move iterator to previous index.
+ * @xas: XArray operation state.
+ *
+ * If the @xas was in an error state, it will remain in an error state
+ * and this function will return %NULL.  If the @xas has never been walked,
+ * it will have the effect of calling xas_load().  Otherwise one will be
+ * subtracted from the index and the state will be walked to the correct
+ * location in the array for the next operation.
+ *
+ * If the iterator was referencing index 0, this function wraps
+ * around to %ULONG_MAX.
+ *
+ * Return: The entry at the new index.  This may be %NULL or an internal
+ * entry, although it should never be a node entry.
+ */
+static inline void *xas_prev(struct xa_state *xas)
+{
+   struct xa_node *node = xas->xa_node;
+
+   if (unlikely(xas_not_node(node) || node->shift ||
+   xas->xa_offset == 0))
+   return __xas_prev(xas);
+
+   xas->xa_index--;
+   xas->xa_offset--;
+   return xa_entry(xas->xa, node, xas->xa_offset);
+}
+
+/**
+ * xas_next() - Move state to next index.
+ * @xas: XArray operation state.
+ *
+ * If the @xas was in an error state, it will remain in an error state
+ * and this function will return %NULL.  If the @xas has never been walked,
+ * it will have the effect of calling xas_load().  Otherwise one will be
+ * added to the index and the state will be walked to the correct
+ * location in the array for the next operation.
+ *
+ * If the iterator was referencing index %ULONG_MAX, this function wraps
+ * around to 0.
+ *
+ * Return: The entry at the new index.  This may be %NULL or an internal
+ * entry, although it should never be a node entry.
+ */
+static inline void *xas_next(struct xa_state *xas)
+{
+   struct xa_node *node = xas->xa_node;
+
+   if (unlikely(xas_not_node(node) || node->shift ||
+   xas->xa_offset == XA_CHUNK_MASK))
+   return __xas_next(xas);
+
+   xas->xa_index++;
+   xas->xa_offset++;
+   return xa_entry(xas->xa, node, xas->xa_offset);
+}
+
 /**
  * xas_next_entry() - Advance iterator to next present entry.
  * @xas: XArray operation state.
diff --git a/lib/xarray.c b/lib/xarray.c
index a51fa1e1f74f..a4975aeedf6b 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -838,6 +838,80 @@ void xas_pause(struct xa_state *xas)
 }
 EXPORT_SYMBOL_GPL(xas_pause);
 
+/*
+ * __xas_prev() - Find the previous entry in the XArray.
+ * @xas: XArray operation state.
+ *
+ * Helper function for xas_prev() which handles all the complex cases
+ * out of line.
+ */
+void *__xas_prev(struct xa_state *xas)
+{
+   void *entry;
+
+   if (!xas_frozen(xas->xa_node))
+   xas->xa_index--;
+   if (xas_not_node(xas->xa_node))
+   return xas_load(xas);
+
+   if (xas->xa_offset != get_offset(xas->xa_index, xas->xa_node))
+   xas->xa_offset--;
+
+   while (xas->xa_offset == 255) {
+   xas->xa_offset = xas->xa_node->offset - 1;
+   xas->xa_node = xa_parent(xas->xa, xas->xa_node);
+   if (!xas->xa_node)
+   return set_bounds(xas);
+   }
+
+   for (;;) {

[PATCH v5 51/78] shmem: Comment fixups

[Matthew Wilcox]

From: Matthew Wilcox 

Remove the last mentions of radix tree from various comments.

Signed-off-by: Matthew Wilcox 
---
 mm/shmem.c | 14 +++---
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index ecf05645509b..3cfc247e4796 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -743,7 +743,7 @@ void shmem_unlock_mapping(struct address_space *mapping)
 }
 
 /*
- * Remove range of pages and swap entries from radix tree, and free them.
+ * Remove range of pages and swap entries from page cache, and free them.
  * If !unfalloc, truncate or punch hole; if unfalloc, undo failed fallocate.
  */
 static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
@@ -1118,10 +1118,10 @@ static int shmem_unuse_inode(struct shmem_inode_info 
*info,
 * We needed to drop mutex to make that restrictive page
 * allocation, but the inode might have been freed while we
 * dropped it: although a racing shmem_evict_inode() cannot
-* complete without emptying the radix_tree, our page lock
+* complete without emptying the page cache, our page lock
 * on this swapcache page is not enough to prevent that -
 * free_swap_and_cache() of our swap entry will only
-* trylock_page(), removing swap from radix_tree whatever.
+* trylock_page(), removing swap from page cache whatever.
 *
 * We must not proceed to shmem_add_to_page_cache() if the
 * inode has been freed, but of course we cannot rely on
@@ -1187,7 +1187,7 @@ int shmem_unuse(swp_entry_t swap, struct page *page)
false);
if (error)
goto out;
-   /* No radix_tree_preload: swap entry keeps a place for page in tree */
+   /* No memory allocation: swap entry occupies the slot for the page */
error = -EAGAIN;
 
mutex_lock(_swaplist_mutex);
@@ -1862,7 +1862,7 @@ alloc_nohuge: page = 
shmem_alloc_and_acct_page(gfp, inode,
spin_unlock_irq(>lock);
goto repeat;
}
-   if (error == -EEXIST)   /* from above or from radix_tree_insert */
+   if (error == -EEXIST)
goto repeat;
return error;
 }
@@ -2474,7 +2474,7 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, 
struct iov_iter *to)
 }
 
 /*
- * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
+ * llseek SEEK_DATA or SEEK_HOLE through the page cache.
  */
 static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
pgoff_t index, pgoff_t end, int whence)
@@ -2562,7 +2562,7 @@ static loff_t shmem_file_llseek(struct file *file, loff_t 
offset, int whence)
 }
 
 /*
- * We need a tag: a new tag would expand every radix_tree_node by 8 bytes,
+ * We need a tag: a new tag would expand every xa_node by 8 bytes,
  * so reuse a tag which we firmly believe is never set or cleared on shmem.
  */
 #define SHMEM_TAG_PINNEDPAGECACHE_TAG_TOWRITE
-- 
2.15.1

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[PATCH v5 74/78] xfs: Convert mru cache to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

This eliminates a call to radix_tree_preload().

Signed-off-by: Matthew Wilcox 
---
 fs/xfs/xfs_mru_cache.c | 72 +++---
 1 file changed, 33 insertions(+), 39 deletions(-)

diff --git a/fs/xfs/xfs_mru_cache.c b/fs/xfs/xfs_mru_cache.c
index f8a674d7f092..2179bede5396 100644
--- a/fs/xfs/xfs_mru_cache.c
+++ b/fs/xfs/xfs_mru_cache.c
@@ -101,10 +101,9 @@
  * an infinite loop in the code.
  */
 struct xfs_mru_cache {
-   struct radix_tree_root  store; /* Core storage data structure.  */
+   struct xarray   store; /* Core storage data structure.  */
struct list_head*lists;/* Array of lists, one per grp.  */
struct list_headreap_list; /* Elements overdue for reaping. */
-   spinlock_t  lock;  /* Lock to protect this struct.  */
unsigned intgrp_count; /* Number of discrete groups.*/
unsigned intgrp_time;  /* Time period spanned by grps.  */
unsigned intlru_grp;   /* Group containing time zero.   */
@@ -232,22 +231,21 @@ _xfs_mru_cache_list_insert(
  * data store, removing it from the reap list, calling the client's free
  * function and deleting the element from the element zone.
  *
- * We get called holding the mru->lock, which we drop and then reacquire.
- * Sparse need special help with this to tell it we know what we are doing.
+ * We get called holding the mru->store lock, which we drop and then reacquire.
+ * Sparse needs special help with this to tell it we know what we are doing.
  */
 STATIC void
 _xfs_mru_cache_clear_reap_list(
struct xfs_mru_cache*mru)
-   __releases(mru->lock) __acquires(mru->lock)
+   __releases(mru->store) __acquires(mru->store)
 {
struct xfs_mru_cache_elem *elem, *next;
struct list_headtmp;
 
INIT_LIST_HEAD();
list_for_each_entry_safe(elem, next, >reap_list, list_node) {
-
/* Remove the element from the data store. */
-   radix_tree_delete(>store, elem->key);
+   __xa_erase(>store, elem->key);
 
/*
 * remove to temp list so it can be freed without
@@ -255,14 +253,14 @@ _xfs_mru_cache_clear_reap_list(
 */
list_move(>list_node, );
}
-   spin_unlock(>lock);
+   xa_unlock(>store);
 
list_for_each_entry_safe(elem, next, , list_node) {
list_del_init(>list_node);
mru->free_func(elem);
}
 
-   spin_lock(>lock);
+   xa_lock(>store);
 }
 
 /*
@@ -284,7 +282,7 @@ _xfs_mru_cache_reap(
if (!mru || !mru->lists)
return;
 
-   spin_lock(>lock);
+   xa_lock(>store);
next = _xfs_mru_cache_migrate(mru, jiffies);
_xfs_mru_cache_clear_reap_list(mru);
 
@@ -298,7 +296,7 @@ _xfs_mru_cache_reap(
queue_delayed_work(xfs_mru_reap_wq, >work, next);
}
 
-   spin_unlock(>lock);
+   xa_unlock(>store);
 }
 
 int
@@ -358,13 +356,8 @@ xfs_mru_cache_create(
for (grp = 0; grp < mru->grp_count; grp++)
INIT_LIST_HEAD(mru->lists + grp);
 
-   /*
-* We use GFP_KERNEL radix tree preload and do inserts under a
-* spinlock so GFP_ATOMIC is appropriate for the radix tree itself.
-*/
-   INIT_RADIX_TREE(>store, GFP_ATOMIC);
+   xa_init(>store);
INIT_LIST_HEAD(>reap_list);
-   spin_lock_init(>lock);
INIT_DELAYED_WORK(>work, _xfs_mru_cache_reap);
 
mru->grp_time  = grp_time;
@@ -394,17 +387,17 @@ xfs_mru_cache_flush(
if (!mru || !mru->lists)
return;
 
-   spin_lock(>lock);
+   xa_lock(>store);
if (mru->queued) {
-   spin_unlock(>lock);
+   xa_unlock(>store);
cancel_delayed_work_sync(>work);
-   spin_lock(>lock);
+   xa_lock(>store);
}
 
_xfs_mru_cache_migrate(mru, jiffies + mru->grp_count * mru->grp_time);
_xfs_mru_cache_clear_reap_list(mru);
 
-   spin_unlock(>lock);
+   xa_unlock(>store);
 }
 
 void
@@ -431,24 +424,24 @@ xfs_mru_cache_insert(
unsigned long   key,
struct xfs_mru_cache_elem *elem)
 {
+   XA_STATE(xas, >store, key);
int error;
 
ASSERT(mru && mru->lists);
if (!mru || !mru->lists)
return -EINVAL;
 
-   if (radix_tree_preload(GFP_NOFS))
-   return -ENOMEM;
-
INIT_LIST_HEAD(>list_node);
elem->key = key;
 
-   spin_lock(>lock);
-   error = radix_tree_insert(>store, key, elem);
-   radix_tree_preload_end();
-   if (!error)
-   _xfs_mru_cache_list_insert(mru, elem);
-   spin_unlock(>lock);
+   do {
+   xas_lock();
+   xas_store(, elem);
+ 

[PATCH v5 67/78] page cache: Finish XArray conversion

[Matthew Wilcox]

From: Matthew Wilcox 

With no more radix tree API users left, we can drop the GFP flags
and use xa_init() instead of INIT_RADIX_TREE().

Signed-off-by: Matthew Wilcox 
---
 fs/inode.c | 2 +-
 include/linux/fs.h | 2 +-
 mm/swap_state.c| 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index c7b00573c10d..2046ff6dd1b3 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -348,7 +348,7 @@ EXPORT_SYMBOL(inc_nlink);
 void address_space_init_once(struct address_space *mapping)
 {
memset(mapping, 0, sizeof(*mapping));
-   INIT_RADIX_TREE(>pages, GFP_ATOMIC | __GFP_ACCOUNT);
+   xa_init(>pages);
init_rwsem(>i_mmap_rwsem);
INIT_LIST_HEAD(>private_list);
spin_lock_init(>private_lock);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index c58bc3c619bf..b459bf4ddb62 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -410,7 +410,7 @@ int pagecache_write_end(struct file *, struct address_space 
*mapping,
  */
 struct address_space {
struct inode*host;
-   struct radix_tree_root  pages;
+   struct xarray   pages;
gfp_t   gfp_mask;
atomic_ti_mmap_writable;
struct rb_root_cached   i_mmap;
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 219e3b4f09e6..6ee5b17d7e79 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -573,7 +573,7 @@ int init_swap_address_space(unsigned int type, unsigned 
long nr_pages)
return -ENOMEM;
for (i = 0; i < nr; i++) {
space = spaces + i;
-   INIT_RADIX_TREE(>pages, GFP_ATOMIC|__GFP_NOWARN);
+   xa_init(>pages);
atomic_set(>i_mmap_writable, 0);
space->a_ops = _aops;
/* swap cache doesn't use writeback related tags */
-- 
2.15.1

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[PATCH v5 59/78] dax: Convert lock_slot to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Signed-off-by: Matthew Wilcox 
---
 fs/dax.c | 22 --
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index dd4674ce48f5..46a4d83b1b46 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -188,12 +188,11 @@ static void dax_wake_mapping_entry_waiter(struct 
address_space *mapping,
 /*
  * Mark the given slot as locked.  Must be called with xa_lock held.
  */
-static inline void *lock_slot(struct address_space *mapping, void **slot)
+static inline void *lock_slot(struct xa_state *xas)
 {
-   unsigned long v = xa_to_value(
-   radix_tree_deref_slot_protected(slot, >pages.xa_lock));
+   unsigned long v = xa_to_value(xas_load(xas));
void *entry = xa_mk_value(v | DAX_ENTRY_LOCK);
-   radix_tree_replace_slot(>pages, slot, entry);
+   xas_store(xas, entry);
return entry;
 }
 
@@ -244,7 +243,7 @@ static void dax_unlock_mapping_entry(struct address_space 
*mapping,
 
xas_lock_irq();
entry = xas_load();
-   if (WARN_ON_ONCE(!entry || !xa_is_value(entry) || !dax_locked(entry))) {
+   if (WARN_ON_ONCE(!xa_is_value(entry) || !dax_locked(entry))) {
xas_unlock_irq();
return;
}
@@ -303,6 +302,7 @@ static void put_unlocked_mapping_entry(struct address_space 
*mapping,
 static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
unsigned long size_flag)
 {
+   XA_STATE(xas, >pages, index);
bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
void *entry, **slot;
 
@@ -341,7 +341,7 @@ static void *grab_mapping_entry(struct address_space 
*mapping, pgoff_t index,
 * Make sure 'entry' remains valid while we drop
 * xa_lock.
 */
-   entry = lock_slot(mapping, slot);
+   entry = lock_slot();
}
 
xa_unlock_irq(>pages);
@@ -408,7 +408,7 @@ static void *grab_mapping_entry(struct address_space 
*mapping, pgoff_t index,
xa_unlock_irq(>pages);
return entry;
}
-   entry = lock_slot(mapping, slot);
+   entry = lock_slot();
  out_unlock:
xa_unlock_irq(>pages);
return entry;
@@ -640,6 +640,7 @@ static int dax_writeback_one(struct block_device *bdev,
pgoff_t index, void *entry)
 {
struct radix_tree_root *pages = >pages;
+   XA_STATE(xas, pages, index);
void *entry2, **slot, *kaddr;
long ret = 0, id;
sector_t sector;
@@ -676,7 +677,7 @@ static int dax_writeback_one(struct block_device *bdev,
if (!radix_tree_tag_get(pages, index, PAGECACHE_TAG_TOWRITE))
goto put_unlocked;
/* Lock the entry to serialize with page faults */
-   entry = lock_slot(mapping, slot);
+   entry = lock_slot();
/*
 * We can clear the tag now but we have to be careful so that concurrent
 * dax_writeback_one() calls for the same index cannot finish before we
@@ -1501,8 +1502,9 @@ static int dax_insert_pfn_mkwrite(struct vm_fault *vmf,
  pfn_t pfn)
 {
struct address_space *mapping = vmf->vma->vm_file->f_mapping;
-   void *entry, **slot;
pgoff_t index = vmf->pgoff;
+   XA_STATE(xas, >pages, index);
+   void *entry, **slot;
int vmf_ret, error;
 
xa_lock_irq(>pages);
@@ -1518,7 +1520,7 @@ static int dax_insert_pfn_mkwrite(struct vm_fault *vmf,
return VM_FAULT_NOPAGE;
}
radix_tree_tag_set(>pages, index, PAGECACHE_TAG_DIRTY);
-   entry = lock_slot(mapping, slot);
+   entry = lock_slot();
xa_unlock_irq(>pages);
switch (pe_size) {
case PE_SIZE_PTE:
-- 
2.15.1

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[PATCH v5 27/78] page cache: Convert page deletion to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

The code is slightly shorter and simpler.

Signed-off-by: Matthew Wilcox 
---
 mm/filemap.c | 26 --
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 91df92f5c96d..c9bc0dee0154 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -115,27 +115,25 @@
 static void page_cache_tree_delete(struct address_space *mapping,
   struct page *page, void *shadow)
 {
-   int i, nr;
+   XA_STATE(xas, >pages, page->index);
+   unsigned int i, nr;
 
-   /* hugetlb pages are represented by one entry in the radix tree */
+   xas_set_update(, workingset_lookup_update(mapping));
+
+   /* hugetlb pages are represented by a single entry in the xarray */
nr = PageHuge(page) ? 1 : hpage_nr_pages(page);
 
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageTail(page), page);
VM_BUG_ON_PAGE(nr != 1 && shadow, page);
 
-   for (i = 0; i < nr; i++) {
-   struct radix_tree_node *node;
-   void **slot;
-
-   __radix_tree_lookup(>pages, page->index + i,
-   , );
-
-   VM_BUG_ON_PAGE(!node && nr != 1, page);
-
-   radix_tree_clear_tags(>pages, node, slot);
-   __radix_tree_replace(>pages, node, slot, shadow,
-   workingset_lookup_update(mapping));
+   i = nr;
+repeat:
+   xas_store(, shadow);
+   xas_init_tags();
+   if (--i) {
+   xas_next();
+   goto repeat;
}
 
page->mapping = NULL;
-- 
2.15.1

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[PATCH v5 49/78] shmem: Convert shmem_free_swap to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

This is a perfect use for xa_cmpxchg().  Note the use of 0 for GFP
flags; we won't be allocating memory.

Signed-off-by: Matthew Wilcox 
---
 mm/shmem.c | 7 ++-
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index bd66bbd40499..dd663341e01e 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -635,16 +635,13 @@ static void shmem_delete_from_page_cache(struct page 
*page, void *radswap)
 }
 
 /*
- * Remove swap entry from radix tree, free the swap and its page cache.
+ * Remove swap entry from page cache, free the swap and its page cache.
  */
 static int shmem_free_swap(struct address_space *mapping,
   pgoff_t index, void *radswap)
 {
-   void *old;
+   void *old = xa_cmpxchg(>pages, index, radswap, NULL, 0);
 
-   xa_lock_irq(>pages);
-   old = radix_tree_delete_item(>pages, index, radswap);
-   xa_unlock_irq(>pages);
if (old != radswap)
return -ENOENT;
free_swap_and_cache(radix_to_swp_entry(radswap));
-- 
2.15.1

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[PATCH v5 20/78] xarray: Add MAINTAINERS entry

[Matthew Wilcox]

From: Matthew Wilcox 

Add myself as XArray and IDR maintainer.

Signed-off-by: Matthew Wilcox 
---
 MAINTAINERS | 12 
 1 file changed, 12 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 82ad0eabce4f..bb5ffa12cf8c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14894,6 +14894,18 @@ T: git 
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/vdso
 S: Maintained
 F: arch/x86/entry/vdso/
 
+XARRAY
+M: Matthew Wilcox 
+M: Matthew Wilcox 
+L: linux-fsde...@vger.kernel.org
+S: Supported
+F: Documentation/core-api/xarray.rst
+F: lib/idr.c
+F: lib/xarray.c
+F: include/linux/idr.h
+F: include/linux/xarray.h
+F: tools/testing/radix-tree
+
 XC2028/3028 TUNER DRIVER
 M: Mauro Carvalho Chehab 
 M: Mauro Carvalho Chehab 
-- 
2.15.1

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[PATCH v5 41/78] pagevec: Use xa_tag_t

[Matthew Wilcox]

From: Matthew Wilcox 

Removes sparse warnings.

Signed-off-by: Matthew Wilcox 
---
 fs/btrfs/extent_io.c| 4 ++--
 fs/ext4/inode.c | 2 +-
 fs/f2fs/data.c  | 2 +-
 fs/gfs2/aops.c  | 2 +-
 include/linux/pagevec.h | 8 +---
 mm/swap.c   | 4 ++--
 6 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 22948f4febe7..4301cbf4e31f 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3795,7 +3795,7 @@ int btree_write_cache_pages(struct address_space *mapping,
pgoff_t index;
pgoff_t end;/* Inclusive */
int scanned = 0;
-   int tag;
+   xa_tag_t tag;
 
pagevec_init();
if (wbc->range_cyclic) {
@@ -3922,7 +3922,7 @@ static int extent_write_cache_pages(struct address_space 
*mapping,
pgoff_t done_index;
int range_whole = 0;
int scanned = 0;
-   int tag;
+   xa_tag_t tag;
 
/*
 * We have to hold onto the inode so that ordered extents can do their
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 7df2c5644e59..2534304daec3 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2605,7 +2605,7 @@ static int mpage_prepare_extent_to_map(struct 
mpage_da_data *mpd)
long left = mpd->wbc->nr_to_write;
pgoff_t index = mpd->first_page;
pgoff_t end = mpd->last_page;
-   int tag;
+   xa_tag_t tag;
int i, err = 0;
int blkbits = mpd->inode->i_blkbits;
ext4_lblk_t lblk;
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 8f51ac47b77f..c8f6d9806896 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1640,7 +1640,7 @@ static int f2fs_write_cache_pages(struct address_space 
*mapping,
pgoff_t last_idx = ULONG_MAX;
int cycled;
int range_whole = 0;
-   int tag;
+   xa_tag_t tag;
 
pagevec_init();
 
diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
index 1daf15a1f00c..c78ecd008191 100644
--- a/fs/gfs2/aops.c
+++ b/fs/gfs2/aops.c
@@ -369,7 +369,7 @@ static int gfs2_write_cache_jdata(struct address_space 
*mapping,
pgoff_t done_index;
int cycled;
int range_whole = 0;
-   int tag;
+   xa_tag_t tag;
 
pagevec_init();
if (wbc->range_cyclic) {
diff --git a/include/linux/pagevec.h b/include/linux/pagevec.h
index 5fb6580f7f23..5168901bf06d 100644
--- a/include/linux/pagevec.h
+++ b/include/linux/pagevec.h
@@ -9,6 +9,8 @@
 #ifndef _LINUX_PAGEVEC_H
 #define _LINUX_PAGEVEC_H
 
+#include 
+
 /* 14 pointers + two long's align the pagevec structure to a power of two */
 #define PAGEVEC_SIZE   14
 
@@ -40,12 +42,12 @@ static inline unsigned pagevec_lookup(struct pagevec *pvec,
 
 unsigned pagevec_lookup_range_tag(struct pagevec *pvec,
struct address_space *mapping, pgoff_t *index, pgoff_t end,
-   int tag);
+   xa_tag_t tag);
 unsigned pagevec_lookup_range_nr_tag(struct pagevec *pvec,
struct address_space *mapping, pgoff_t *index, pgoff_t end,
-   int tag, unsigned max_pages);
+   xa_tag_t tag, unsigned max_pages);
 static inline unsigned pagevec_lookup_tag(struct pagevec *pvec,
-   struct address_space *mapping, pgoff_t *index, int tag)
+   struct address_space *mapping, pgoff_t *index, xa_tag_t tag)
 {
return pagevec_lookup_range_tag(pvec, mapping, index, (pgoff_t)-1, tag);
 }
diff --git a/mm/swap.c b/mm/swap.c
index 8d7773cb2c3f..31d79479dacf 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -991,7 +991,7 @@ EXPORT_SYMBOL(pagevec_lookup_range);
 
 unsigned pagevec_lookup_range_tag(struct pagevec *pvec,
struct address_space *mapping, pgoff_t *index, pgoff_t end,
-   int tag)
+   xa_tag_t tag)
 {
pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
PAGEVEC_SIZE, pvec->pages);
@@ -1001,7 +1001,7 @@ EXPORT_SYMBOL(pagevec_lookup_range_tag);
 
 unsigned pagevec_lookup_range_nr_tag(struct pagevec *pvec,
struct address_space *mapping, pgoff_t *index, pgoff_t end,
-   int tag, unsigned max_pages)
+   xa_tag_t tag, unsigned max_pages)
 {
pvec->nr = find_get_pages_range_tag(mapping, index, end, tag,
min_t(unsigned int, max_pages, PAGEVEC_SIZE), pvec->pages);
-- 
2.15.1

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[PATCH v5 34/78] mm: Convert add_to_swap_cache to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Combine __add_to_swap_cache and add_to_swap_cache into one function
since there is no more need to preload.

Signed-off-by: Matthew Wilcox 
---
 mm/swap_state.c | 93 ++---
 1 file changed, 29 insertions(+), 64 deletions(-)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 3f95e8fc4cb2..a57b5ad4c503 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -107,14 +107,15 @@ void show_swap_cache_info(void)
 }
 
 /*
- * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
+ * add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
  * but sets SwapCache flag and private instead of mapping and index.
  */
-int __add_to_swap_cache(struct page *page, swp_entry_t entry)
+int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp)
 {
-   int error, i, nr = hpage_nr_pages(page);
-   struct address_space *address_space;
+   struct address_space *address_space = swap_address_space(entry);
pgoff_t idx = swp_offset(entry);
+   XA_STATE(xas, _space->pages, idx);
+   unsigned long i, nr = 1UL << compound_order(page);
 
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageSwapCache(page), page);
@@ -123,50 +124,30 @@ int __add_to_swap_cache(struct page *page, swp_entry_t 
entry)
page_ref_add(page, nr);
SetPageSwapCache(page);
 
-   address_space = swap_address_space(entry);
-   xa_lock_irq(_space->pages);
-   for (i = 0; i < nr; i++) {
-   set_page_private(page + i, entry.val + i);
-   error = radix_tree_insert(_space->pages,
- idx + i, page + i);
-   if (unlikely(error))
-   break;
-   }
-   if (likely(!error)) {
+   do {
+   xas_lock_irq();
+   xas_create_range(, idx + nr - 1);
+   if (xas_error())
+   goto unlock;
+   for (i = 0; i < nr; i++) {
+   VM_BUG_ON_PAGE(xas.xa_index != idx + i, page);
+   set_page_private(page + i, entry.val + i);
+   xas_store(, page + i);
+   xas_next();
+   }
address_space->nrpages += nr;
__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
ADD_CACHE_INFO(add_total, nr);
-   } else {
-   /*
-* Only the context which have set SWAP_HAS_CACHE flag
-* would call add_to_swap_cache().
-* So add_to_swap_cache() doesn't returns -EEXIST.
-*/
-   VM_BUG_ON(error == -EEXIST);
-   set_page_private(page + i, 0UL);
-   while (i--) {
-   radix_tree_delete(_space->pages, idx + i);
-   set_page_private(page + i, 0UL);
-   }
-   ClearPageSwapCache(page);
-   page_ref_sub(page, nr);
-   }
-   xa_unlock_irq(_space->pages);
+unlock:
+   xas_unlock_irq();
+   } while (xas_nomem(, gfp));
 
-   return error;
-}
-
-
-int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
-{
-   int error;
+   if (!xas_error())
+   return 0;
 
-   error = radix_tree_maybe_preload_order(gfp_mask, compound_order(page));
-   if (!error) {
-   error = __add_to_swap_cache(page, entry);
-   radix_tree_preload_end();
-   }
-   return error;
+   ClearPageSwapCache(page);
+   page_ref_sub(page, nr);
+   return xas_error();
 }
 
 /*
@@ -220,7 +201,7 @@ int add_to_swap(struct page *page)
goto fail;
 
/*
-* Radix-tree node allocations from PF_MEMALLOC contexts could
+* XArray node allocations from PF_MEMALLOC contexts could
 * completely exhaust the page allocator. __GFP_NOMEMALLOC
 * stops emergency reserves from being allocated.
 *
@@ -232,7 +213,6 @@ int add_to_swap(struct page *page)
 */
err = add_to_swap_cache(page, entry,
__GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN);
-   /* -ENOMEM radix-tree allocation failure */
if (err)
/*
 * add_to_swap_cache() doesn't return -EEXIST, so we can safely
@@ -400,19 +380,11 @@ struct page *__read_swap_cache_async(swp_entry_t entry, 
gfp_t gfp_mask,
break;  /* Out of memory */
}
 
-   /*
-* call radix_tree_preload() while we can wait.
-*/
-   err = radix_tree_maybe_preload(gfp_mask & GFP_KERNEL);
-   if (err)
-   break;
-
/*
 * Swap entry may have been freed since our caller observed it.
 */
   

[PATCH v5 45/78] shmem: Convert shmem_tag_pins to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Simplify the locking by taking the spinlock while we walk the tree on
the assumption that many acquires and releases of the lock will be
worse than holding the lock for a (potentially) long time.

We could replicate the same locking behaviour with the xarray, but would
have to be careful that the xa_node wasn't RCU-freed under us before we
took the lock.

Signed-off-by: Matthew Wilcox 
---
 mm/shmem.c | 39 ---
 1 file changed, 16 insertions(+), 23 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index ce285ae635ea..2f41c7ceea18 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2601,35 +2601,28 @@ static loff_t shmem_file_llseek(struct file *file, 
loff_t offset, int whence)
 
 static void shmem_tag_pins(struct address_space *mapping)
 {
-   struct radix_tree_iter iter;
-   void **slot;
-   pgoff_t start;
+   XA_STATE(xas, >pages, 0);
struct page *page;
+   unsigned int tagged = 0;
 
lru_add_drain();
-   start = 0;
-   rcu_read_lock();
 
-   radix_tree_for_each_slot(slot, >pages, , start) {
-   page = radix_tree_deref_slot(slot);
-   if (!page || radix_tree_exception(page)) {
-   if (radix_tree_deref_retry(page)) {
-   slot = radix_tree_iter_retry();
-   continue;
-   }
-   } else if (page_count(page) - page_mapcount(page) > 1) {
-   xa_lock_irq(>pages);
-   radix_tree_tag_set(>pages, iter.index,
-  SHMEM_TAG_PINNED);
-   xa_unlock_irq(>pages);
-   }
+   xas_lock_irq();
+   xas_for_each(, page, ULONG_MAX) {
+   if (xa_is_value(page))
+   continue;
+   if (page_count(page) - page_mapcount(page) > 1)
+   xas_set_tag(, SHMEM_TAG_PINNED);
 
-   if (need_resched()) {
-   slot = radix_tree_iter_resume(slot, );
-   cond_resched_rcu();
-   }
+   if (++tagged % XA_CHECK_SCHED)
+   continue;
+
+   xas_pause();
+   xas_unlock_irq();
+   cond_resched();
+   xas_lock_irq();
}
-   rcu_read_unlock();
+   xas_unlock_irq();
 }
 
 /*
-- 
2.15.1

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[PATCH v5 31/78] mm: Convert page-writeback to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Includes moving mapping_tagged() to fs.h as a static inline, and
changing it to return bool.

Signed-off-by: Matthew Wilcox 
---
 include/linux/fs.h  | 17 +--
 mm/page-writeback.c | 62 +++--
 2 files changed, 32 insertions(+), 47 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index e4345c13e237..c58bc3c619bf 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -470,15 +470,18 @@ struct block_device {
struct mutexbd_fsfreeze_mutex;
 } __randomize_layout;
 
+/* XArray tags, for tagging dirty and writeback pages in the pagecache. */
+#define PAGECACHE_TAG_DIRTYXA_TAG_0
+#define PAGECACHE_TAG_WRITEBACKXA_TAG_1
+#define PAGECACHE_TAG_TOWRITE  XA_TAG_2
+
 /*
- * Radix-tree tags, for tagging dirty and writeback pages within the pagecache
- * radix trees
+ * Returns true if any of the pages in the mapping are marked with the tag.
  */
-#define PAGECACHE_TAG_DIRTY0
-#define PAGECACHE_TAG_WRITEBACK1
-#define PAGECACHE_TAG_TOWRITE  2
-
-int mapping_tagged(struct address_space *mapping, int tag);
+static inline bool mapping_tagged(struct address_space *mapping, xa_tag_t tag)
+{
+   return xa_tagged(>pages, tag);
+}
 
 static inline void i_mmap_lock_write(struct address_space *mapping)
 {
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 588ce729d199..0407436a8305 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2098,33 +2098,25 @@ void __init page_writeback_init(void)
  * dirty pages in the file (thus it is important for this function to be quick
  * so that it can tag pages faster than a dirtying process can create them).
  */
-/*
- * We tag pages in batches of WRITEBACK_TAG_BATCH to reduce xa_lock latency.
- */
 void tag_pages_for_writeback(struct address_space *mapping,
 pgoff_t start, pgoff_t end)
 {
-#define WRITEBACK_TAG_BATCH 4096
-   unsigned long tagged = 0;
-   struct radix_tree_iter iter;
-   void **slot;
+   XA_STATE(xas, >pages, start);
+   unsigned int tagged = 0;
+   void *page;
 
-   xa_lock_irq(>pages);
-   radix_tree_for_each_tagged(slot, >pages, , start,
-   PAGECACHE_TAG_DIRTY) {
-   if (iter.index > end)
-   break;
-   radix_tree_iter_tag_set(>pages, ,
-   PAGECACHE_TAG_TOWRITE);
-   tagged++;
-   if ((tagged % WRITEBACK_TAG_BATCH) != 0)
+   xas_lock_irq();
+   xas_for_each_tag(, page, end, PAGECACHE_TAG_DIRTY) {
+   xas_set_tag(, PAGECACHE_TAG_TOWRITE);
+   if (++tagged % XA_CHECK_SCHED)
continue;
-   slot = radix_tree_iter_resume(slot, );
-   xa_unlock_irq(>pages);
+
+   xas_pause();
+   xas_unlock_irq();
cond_resched();
-   xa_lock_irq(>pages);
+   xas_lock_irq();
}
-   xa_unlock_irq(>pages);
+   xas_unlock_irq();
 }
 EXPORT_SYMBOL(tag_pages_for_writeback);
 
@@ -2164,7 +2156,7 @@ int write_cache_pages(struct address_space *mapping,
pgoff_t done_index;
int cycled;
int range_whole = 0;
-   int tag;
+   xa_tag_t tag;
 
pagevec_init();
if (wbc->range_cyclic) {
@@ -2445,7 +2437,7 @@ void account_page_cleaned(struct page *page, struct 
address_space *mapping,
 
 /*
  * For address_spaces which do not use buffers.  Just tag the page as dirty in
- * its radix tree.
+ * the xarray.
  *
  * This is also used when a single buffer is being dirtied: we want to set the
  * page dirty in that case, but not all the buffers.  This is a "bottom-up"
@@ -2471,7 +2463,7 @@ int __set_page_dirty_nobuffers(struct page *page)
BUG_ON(page_mapping(page) != mapping);
WARN_ON_ONCE(!PagePrivate(page) && !PageUptodate(page));
account_page_dirtied(page, mapping);
-   radix_tree_tag_set(>pages, page_index(page),
+   __xa_set_tag(>pages, page_index(page),
   PAGECACHE_TAG_DIRTY);
xa_unlock_irqrestore(>pages, flags);
unlock_page_memcg(page);
@@ -2634,13 +2626,13 @@ EXPORT_SYMBOL(__cancel_dirty_page);
  * Returns true if the page was previously dirty.
  *
  * This is for preparing to put the page under writeout.  We leave the page
- * tagged as dirty in the radix tree so that a concurrent write-for-sync
+ * tagged as dirty in the xarray so that a concurrent write-for-sync
  * can discover it via a PAGECACHE_TAG_DIRTY walk.  The ->writepage
  * implementation will run either set_page_writeback() or set_page_dirty(),
- * at which stage we bring the page's dirty flag and radix-tree dirty tag
+ * at which stage we bring the page's dirty 

[PATCH v5 75/78] usb: Convert xhci-mem to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

The XArray API is a slightly better fit for xhci_insert_segment_mapping()
than the radix tree API was.

Signed-off-by: Matthew Wilcox 
---
 drivers/usb/host/xhci-mem.c | 68 +++--
 drivers/usb/host/xhci.h |  6 ++--
 2 files changed, 32 insertions(+), 42 deletions(-)

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 15f7d422885f..9a2a02d244b0 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -149,70 +149,60 @@ static void xhci_link_rings(struct xhci_hcd *xhci, struct 
xhci_ring *ring,
 }
 
 /*
- * We need a radix tree for mapping physical addresses of TRBs to which stream
- * ID they belong to.  We need to do this because the host controller won't 
tell
+ * We need to map physical addresses of TRBs to the stream ID they belong to.
+ * We need to do this because the host controller won't tell
  * us which stream ring the TRB came from.  We could store the stream ID in an
  * event data TRB, but that doesn't help us for the cancellation case, since 
the
  * endpoint may stop before it reaches that event data TRB.
  *
- * The radix tree maps the upper portion of the TRB DMA address to a ring
+ * The xarray maps the upper portion of the TRB DMA address to a ring
  * segment that has the same upper portion of DMA addresses.  For example, say 
I
  * have segments of size 1KB, that are always 1KB aligned.  A segment may
  * start at 0x10c91000 and end at 0x10c913f0.  If I use the upper 10 bits, the
- * key to the stream ID is 0x43244.  I can use the DMA address of the TRB to
- * pass the radix tree a key to get the right stream ID:
+ * index of the stream ID is 0x43244.  I can use the DMA address of the TRB as
+ * the xarray index to get the right stream ID:
  *
  * 0x10c90fff >> 10 = 0x43243
  * 0x10c912c0 >> 10 = 0x43244
  * 0x10c91400 >> 10 = 0x43245
  *
  * Obviously, only those TRBs with DMA addresses that are within the segment
- * will make the radix tree return the stream ID for that ring.
+ * will make the xarray return the stream ID for that ring.
  *
- * Caveats for the radix tree:
+ * Caveats for the xarray:
  *
- * The radix tree uses an unsigned long as a key pair.  On 32-bit systems, an
+ * The xarray uses an unsigned long for the index.  On 32-bit systems, an
  * unsigned long will be 32-bits; on a 64-bit system an unsigned long will be
  * 64-bits.  Since we only request 32-bit DMA addresses, we can use that as the
- * key on 32-bit or 64-bit systems (it would also be fine if we asked for 
64-bit
- * PCI DMA addresses on a 64-bit system).  There might be a problem on 32-bit
- * extended systems (where the DMA address can be bigger than 32-bits),
+ * index on 32-bit or 64-bit systems (it would also be fine if we asked for
+ * 64-bit PCI DMA addresses on a 64-bit system).  There might be a problem on
+ * 32-bit extended systems (where the DMA address can be bigger than 32-bits),
  * if we allow the PCI dma mask to be bigger than 32-bits.  So don't do that.
  */
-static int xhci_insert_segment_mapping(struct radix_tree_root *trb_address_map,
+
+static unsigned long trb_index(dma_addr_t dma)
+{
+   return (unsigned long)(dma >> TRB_SEGMENT_SHIFT);
+}
+
+static int xhci_insert_segment_mapping(struct xarray *trb_address_map,
struct xhci_ring *ring,
struct xhci_segment *seg,
-   gfp_t mem_flags)
+   gfp_t gfp)
 {
-   unsigned long key;
-   int ret;
-
-   key = (unsigned long)(seg->dma >> TRB_SEGMENT_SHIFT);
/* Skip any segments that were already added. */
-   if (radix_tree_lookup(trb_address_map, key))
-   return 0;
-
-   ret = radix_tree_maybe_preload(mem_flags);
-   if (ret)
-   return ret;
-   ret = radix_tree_insert(trb_address_map,
-   key, ring);
-   radix_tree_preload_end();
-   return ret;
+   return xa_err(xa_cmpxchg(trb_address_map, trb_index(seg->dma), NULL,
+   ring, gfp));
 }
 
-static void xhci_remove_segment_mapping(struct radix_tree_root 
*trb_address_map,
+static void xhci_remove_segment_mapping(struct xarray *trb_address_map,
struct xhci_segment *seg)
 {
-   unsigned long key;
-
-   key = (unsigned long)(seg->dma >> TRB_SEGMENT_SHIFT);
-   if (radix_tree_lookup(trb_address_map, key))
-   radix_tree_delete(trb_address_map, key);
+   xa_erase(trb_address_map, trb_index(seg->dma));
 }
 
 static int xhci_update_stream_segment_mapping(
-   struct radix_tree_root *trb_address_map,
+   struct xarray *trb_address_map,
struct xhci_ring *ring,
struct xhci_segment *first_seg,
struct xhci_segment *last_seg,
@@ -574,8 +564,8 @@ struct xhci_ring *xhci_dma_to_transfer_ring(
u64 

[PATCH v5 02/78] fscache: Use appropriate radix tree accessors

[Matthew Wilcox]

From: Matthew Wilcox 

Don't open-code accesses to data structure internals.

Signed-off-by: Matthew Wilcox 
---
 fs/fscache/cookie.c | 2 +-
 fs/fscache/object.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index ff84258132bb..e9054e0c1a49 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -608,7 +608,7 @@ void __fscache_relinquish_cookie(struct fscache_cookie 
*cookie, bool retire)
/* Clear pointers back to the netfs */
cookie->netfs_data  = NULL;
cookie->def = NULL;
-   BUG_ON(cookie->stores.rnode);
+   BUG_ON(!radix_tree_empty(>stores));
 
if (cookie->parent) {
ASSERTCMP(atomic_read(>parent->usage), >, 0);
diff --git a/fs/fscache/object.c b/fs/fscache/object.c
index 7a182c87f378..aa0e71f02c33 100644
--- a/fs/fscache/object.c
+++ b/fs/fscache/object.c
@@ -956,7 +956,7 @@ static const struct fscache_state 
*_fscache_invalidate_object(struct fscache_obj
 * retire the object instead.
 */
if (!fscache_use_cookie(object)) {
-   ASSERT(object->cookie->stores.rnode == NULL);
+   ASSERT(radix_tree_empty(>cookie->stores));
set_bit(FSCACHE_OBJECT_RETIRED, >flags);
_leave(" [no cookie]");
return transit_to(KILL_OBJECT);
-- 
2.15.1

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[PATCH v5 29/78] page cache: Convert delete_batch to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Rename the function from page_cache_tree_delete_batch to just
page_cache_delete_batch.

Signed-off-by: Matthew Wilcox 
---
 mm/filemap.c | 23 +--
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 94496567d2c2..92ddee25f19b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -276,7 +276,7 @@ void delete_from_page_cache(struct page *page)
 EXPORT_SYMBOL(delete_from_page_cache);
 
 /*
- * page_cache_tree_delete_batch - delete several pages from page cache
+ * page_cache_delete_batch - delete several pages from page cache
  * @mapping: the mapping to which pages belong
  * @pvec: pagevec with pages to delete
  *
@@ -289,23 +289,18 @@ EXPORT_SYMBOL(delete_from_page_cache);
  *
  * The function expects xa_lock to be held.
  */
-static void
-page_cache_tree_delete_batch(struct address_space *mapping,
+static void page_cache_delete_batch(struct address_space *mapping,
 struct pagevec *pvec)
 {
-   struct radix_tree_iter iter;
-   void **slot;
+   XA_STATE(xas, >pages, pvec->pages[0]->index);
int total_pages = 0;
int i = 0, tail_pages = 0;
struct page *page;
-   pgoff_t start;
 
-   start = pvec->pages[0]->index;
-   radix_tree_for_each_slot(slot, >pages, , start) {
+   xas_set_update(, workingset_lookup_update(mapping));
+   xas_for_each(, page, ULONG_MAX) {
if (i >= pagevec_count(pvec) && !tail_pages)
break;
-   page = radix_tree_deref_slot_protected(slot,
-  >pages.xa_lock);
if (xa_is_value(page))
continue;
if (!tail_pages) {
@@ -326,11 +321,11 @@ page_cache_tree_delete_batch(struct address_space 
*mapping,
 */
i++;
} else {
+   VM_BUG_ON_PAGE(page->index + HPAGE_PMD_NR - tail_pages
+   != pvec->pages[i]->index, page);
tail_pages--;
}
-   radix_tree_clear_tags(>pages, iter.node, slot);
-   __radix_tree_replace(>pages, iter.node, slot, NULL,
-   workingset_lookup_update(mapping));
+   xas_store(, NULL);
total_pages++;
}
mapping->nrpages -= total_pages;
@@ -351,7 +346,7 @@ void delete_from_page_cache_batch(struct address_space 
*mapping,
 
unaccount_page_cache_page(mapping, pvec->pages[i]);
}
-   page_cache_tree_delete_batch(mapping, pvec);
+   page_cache_delete_batch(mapping, pvec);
xa_unlock_irqrestore(>pages, flags);
 
for (i = 0; i < pagevec_count(pvec); i++)
-- 
2.15.1

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[PATCH v5 47/78] shmem: Convert shmem_add_to_page_cache to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

This removes the last caller of radix_tree_maybe_preload_order().
Simpler code, unless we run out of memory for new xa_nodes partway through
inserting entries into the xarray.  Hopefully we can support multi-index
entries in the page cache soon and all the awful code goes away.

Signed-off-by: Matthew Wilcox 
---
 mm/shmem.c | 87 --
 1 file changed, 39 insertions(+), 48 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index e4a2eb1336be..0f49edae05e4 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -558,9 +558,10 @@ static unsigned long shmem_unused_huge_shrink(struct 
shmem_sb_info *sbinfo,
  */
 static int shmem_add_to_page_cache(struct page *page,
   struct address_space *mapping,
-  pgoff_t index, void *expected)
+  pgoff_t index, void *expected, gfp_t gfp)
 {
-   int error, nr = hpage_nr_pages(page);
+   XA_STATE(xas, >pages, index);
+   unsigned long i, nr = 1UL << compound_order(page);
 
VM_BUG_ON_PAGE(PageTail(page), page);
VM_BUG_ON_PAGE(index != round_down(index, nr), page);
@@ -569,49 +570,47 @@ static int shmem_add_to_page_cache(struct page *page,
VM_BUG_ON(expected && PageTransHuge(page));
 
page_ref_add(page, nr);
-   page->mapping = mapping;
page->index = index;
+   page->mapping = mapping;
 
-   xa_lock_irq(>pages);
-   if (PageTransHuge(page)) {
-   void __rcu **results;
-   pgoff_t idx;
-   int i;
-
-   error = 0;
-   if (radix_tree_gang_lookup_slot(>pages,
-   , , index, 1) &&
-   idx < index + HPAGE_PMD_NR) {
-   error = -EEXIST;
+   do {
+   xas_lock_irq();
+   xas_create_range(, index + nr - 1);
+   if (xas_error())
+   goto unlock;
+   for (i = 0; i < nr; i++) {
+   void *entry = xas_load();
+   if (entry != expected)
+   xas_set_err(, -ENOENT);
+   if (xas_error())
+   goto undo;
+   xas_store(, page + i);
+   xas_next();
}
-
-   if (!error) {
-   for (i = 0; i < HPAGE_PMD_NR; i++) {
-   error = radix_tree_insert(>pages,
-   index + i, page + i);
-   VM_BUG_ON(error);
-   }
+   if (PageTransHuge(page)) {
count_vm_event(THP_FILE_ALLOC);
+   __inc_node_page_state(page, NR_SHMEM_THPS);
}
-   } else if (!expected) {
-   error = radix_tree_insert(>pages, index, page);
-   } else {
-   error = shmem_xa_replace(mapping, index, expected, page);
-   }
-
-   if (!error) {
mapping->nrpages += nr;
-   if (PageTransHuge(page))
-   __inc_node_page_state(page, NR_SHMEM_THPS);
__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
__mod_node_page_state(page_pgdat(page), NR_SHMEM, nr);
-   xa_unlock_irq(>pages);
-   } else {
+   goto unlock;
+undo:
+   while (i-- > 0) {
+   xas_store(, NULL);
+   xas_prev();
+   }
+unlock:
+   xas_unlock_irq();
+   } while (xas_nomem(, gfp));
+
+   if (xas_error()) {
page->mapping = NULL;
-   xa_unlock_irq(>pages);
page_ref_sub(page, nr);
+   return xas_error();
}
-   return error;
+
+   return 0;
 }
 
 /*
@@ -1159,7 +1158,7 @@ static int shmem_unuse_inode(struct shmem_inode_info 
*info,
 */
if (!error)
error = shmem_add_to_page_cache(*pagep, mapping, index,
-   radswap);
+   radswap, gfp);
if (error != -ENOMEM) {
/*
 * Truncation and eviction use free_swap_and_cache(), which
@@ -1677,7 +1676,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t 
index,
false);
if (!error) {
error = shmem_add_to_page_cache(page, mapping, index,
-   swp_to_radix_entry(swap));
+   swp_to_radix_entry(swap), gfp);
/*
 * We already confirmed swap under page lock, and make
 * no memory allocation here, so 

[PATCH v5 72/78] xfs: Convert pag_ici_root to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Rename pag_ici_root to pag_ici_xa and use XArray APIs instead of radix
tree APIs.  Shorter code, typechecking on tag numbers, better error
checking in xfs_reclaim_inode(), and eliminates a call to
radix_tree_preload().

Signed-off-by: Matthew Wilcox 
---
 fs/xfs/libxfs/xfs_sb.c |   2 +-
 fs/xfs/libxfs/xfs_sb.h |   2 +-
 fs/xfs/xfs_icache.c| 111 +++--
 fs/xfs/xfs_icache.h|   4 +-
 fs/xfs/xfs_inode.c |  24 ---
 fs/xfs/xfs_mount.c |   3 +-
 fs/xfs/xfs_mount.h |   3 +-
 7 files changed, 56 insertions(+), 93 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 3b0b65eb8224..8fb7c216c761 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -76,7 +76,7 @@ struct xfs_perag *
 xfs_perag_get_tag(
struct xfs_mount*mp,
xfs_agnumber_t  first,
-   int tag)
+   xa_tag_ttag)
 {
XA_STATE(xas, >m_perag_xa, first);
struct xfs_perag*pag;
diff --git a/fs/xfs/libxfs/xfs_sb.h b/fs/xfs/libxfs/xfs_sb.h
index 961e6475a309..d2de90b8f39c 100644
--- a/fs/xfs/libxfs/xfs_sb.h
+++ b/fs/xfs/libxfs/xfs_sb.h
@@ -23,7 +23,7 @@
  */
 extern struct xfs_perag *xfs_perag_get(struct xfs_mount *, xfs_agnumber_t);
 extern struct xfs_perag *xfs_perag_get_tag(struct xfs_mount *, xfs_agnumber_t,
-  int tag);
+  xa_tag_t tag);
 extern voidxfs_perag_put(struct xfs_perag *pag);
 extern int xfs_initialize_perag_data(struct xfs_mount *, xfs_agnumber_t);
 
diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index f56e500d89e2..39e2a6bd92da 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -186,7 +186,7 @@ xfs_perag_set_reclaim_tag(
 {
struct xfs_mount*mp = pag->pag_mount;
 
-   lockdep_assert_held(>pag_ici_lock);
+   lockdep_assert_held(>pag_ici_xa.xa_lock);
if (pag->pag_ici_reclaimable++)
return;
 
@@ -205,7 +205,7 @@ xfs_perag_clear_reclaim_tag(
 {
struct xfs_mount*mp = pag->pag_mount;
 
-   lockdep_assert_held(>pag_ici_lock);
+   lockdep_assert_held(>pag_ici_xa.xa_lock);
if (--pag->pag_ici_reclaimable)
return;
 
@@ -228,16 +228,16 @@ xfs_inode_set_reclaim_tag(
struct xfs_perag*pag;
 
pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));
-   spin_lock(>pag_ici_lock);
+   xa_lock(>pag_ici_xa);
spin_lock(>i_flags_lock);
 
-   radix_tree_tag_set(>pag_ici_root, XFS_INO_TO_AGINO(mp, ip->i_ino),
+   __xa_set_tag(>pag_ici_xa, XFS_INO_TO_AGINO(mp, ip->i_ino),
   XFS_ICI_RECLAIM_TAG);
xfs_perag_set_reclaim_tag(pag);
__xfs_iflags_set(ip, XFS_IRECLAIMABLE);
 
spin_unlock(>i_flags_lock);
-   spin_unlock(>pag_ici_lock);
+   xa_unlock(>pag_ici_xa);
xfs_perag_put(pag);
 }
 
@@ -246,7 +246,7 @@ xfs_inode_clear_reclaim_tag(
struct xfs_perag*pag,
xfs_ino_t   ino)
 {
-   radix_tree_tag_clear(>pag_ici_root,
+   __xa_clear_tag(>pag_ici_xa,
 XFS_INO_TO_AGINO(pag->pag_mount, ino),
 XFS_ICI_RECLAIM_TAG);
xfs_perag_clear_reclaim_tag(pag);
@@ -367,8 +367,8 @@ xfs_iget_cache_hit(
/*
 * We need to set XFS_IRECLAIM to prevent xfs_reclaim_inode
 * from stomping over us while we recycle the inode.  We can't
-* clear the radix tree reclaimable tag yet as it requires
-* pag_ici_lock to be held exclusive.
+* clear the xarray reclaimable tag yet as it requires
+* pag_ici_xa.xa_lock to be held exclusive.
 */
ip->i_flags |= XFS_IRECLAIM;
 
@@ -393,7 +393,7 @@ xfs_iget_cache_hit(
goto out_error;
}
 
-   spin_lock(>pag_ici_lock);
+   xa_lock(>pag_ici_xa);
spin_lock(>i_flags_lock);
 
/*
@@ -410,7 +410,7 @@ xfs_iget_cache_hit(
init_rwsem(>i_rwsem);
 
spin_unlock(>i_flags_lock);
-   spin_unlock(>pag_ici_lock);
+   xa_unlock(>pag_ici_xa);
} else {
/* If the VFS inode is being torn down, pause and try again. */
if (!igrab(inode)) {
@@ -471,17 +471,6 @@ xfs_iget_cache_miss(
goto out_destroy;
}
 
-   /*
-* Preload the radix tree so we can insert safely under the
-* write spinlock. Note that we cannot sleep inside the preload
-* region. Since we can be called from transaction context, don't
-* recurse into the file system.
-*/
-   if (radix_tree_preload(GFP_NOFS)) {
-   error = -EAGAIN;
-   

[PATCH v5 62/78] dax: Convert dax_writeback_one to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Likewise easy

Signed-off-by: Matthew Wilcox 
---
 fs/dax.c | 17 +++--
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index d3894c15609a..d6dd779e1b46 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -633,8 +633,7 @@ static int dax_writeback_one(struct block_device *bdev,
struct dax_device *dax_dev, struct address_space *mapping,
pgoff_t index, void *entry)
 {
-   struct radix_tree_root *pages = >pages;
-   XA_STATE(xas, pages, index);
+   XA_STATE(xas, >pages, index);
void *entry2, *kaddr;
long ret = 0, id;
sector_t sector;
@@ -649,7 +648,7 @@ static int dax_writeback_one(struct block_device *bdev,
if (WARN_ON(!xa_is_value(entry)))
return -EIO;
 
-   xa_lock_irq(>pages);
+   xas_lock_irq();
entry2 = get_unlocked_mapping_entry();
/* Entry got punched out / reallocated? */
if (!entry2 || WARN_ON_ONCE(!xa_is_value(entry2)))
@@ -668,7 +667,7 @@ static int dax_writeback_one(struct block_device *bdev,
}
 
/* Another fsync thread may have already written back this entry */
-   if (!radix_tree_tag_get(pages, index, PAGECACHE_TAG_TOWRITE))
+   if (!xas_get_tag(, PAGECACHE_TAG_TOWRITE))
goto put_unlocked;
/* Lock the entry to serialize with page faults */
entry = lock_slot();
@@ -679,8 +678,8 @@ static int dax_writeback_one(struct block_device *bdev,
 * at the entry only under xa_lock and once they do that they will
 * see the entry locked and wait for it to unlock.
 */
-   radix_tree_tag_clear(pages, index, PAGECACHE_TAG_TOWRITE);
-   xa_unlock_irq(>pages);
+   xas_clear_tag(, PAGECACHE_TAG_TOWRITE);
+   xas_unlock_irq();
 
/*
 * Even if dax_writeback_mapping_range() was given a wbc->range_start
@@ -718,9 +717,7 @@ static int dax_writeback_one(struct block_device *bdev,
 * the pfn mappings are writeprotected and fault waits for mapping
 * entry lock.
 */
-   xa_lock_irq(>pages);
-   radix_tree_tag_clear(pages, index, PAGECACHE_TAG_DIRTY);
-   xa_unlock_irq(>pages);
+   xa_clear_tag(>pages, index, PAGECACHE_TAG_DIRTY);
trace_dax_writeback_one(mapping->host, index, size >> PAGE_SHIFT);
  dax_unlock:
dax_read_unlock(id);
@@ -729,7 +726,7 @@ static int dax_writeback_one(struct block_device *bdev,
 
  put_unlocked:
put_unlocked_mapping_entry(, entry2);
-   xa_unlock_irq(>pages);
+   xas_unlock_irq();
return ret;
 }
 
-- 
2.15.1

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[PATCH v5 00/78] XArray v5

[Matthew Wilcox]

From: Matthew Wilcox 

Again, this patch set does not apply to any particular tree
because it depends on things which are purely noise, and I'm trying
to keep the patch count down [1].  If you want it in a git tree, try
http://git.infradead.org/users/willy/linux-dax.git/shortlog/refs/heads/xarray-2017-12-11
(note change of date from last posting)

I've been getting progressively fewer bug reports from 0day.  I might
almost consider booting this on one of my test machines soon.  The only
bug report I don't believe I've addressed yet is a compile failure
on ia64.  I've resurrected my old McKinley and I'm building gcc 6.4 on
it to see if I can reproduce it (Debian only has 4.8 for ia64).

I'd really like an ACK from Darrick on patch 1 (and then I'll stop
posting it).  I'd like ACKs from the other maintainers whose radix
trees I'm converting:

  mm-cgroup-writeback
  vmalloc
  brd
  xfs (again, Dave's feedback has been invaluable)
  xhci-mem 
  raid5-cache
  irqdomain
  fscache

I don't imagine anybody has the stomach to review the entire pagecache
conversion, but you don't have to do all 44 patches at once.  Please don't
make me beg for reviewers in Park City.

[1] 78 patches.  Haha.  I can squash a bunch of them together for
posting in future if you like, but the diffstat is still intense:
162 files changed, 6305 insertions(+), 4595 deletions(-).

In case the +/- worries you, each user of the xarray has, so far, lost
lines of code, and deleting the radix tree code once all the users are
converted will net us back 2270 lines.  And there's way more documentation
of the XArray than there was of the radix tree.

Bug fixes:
 - Fixed bisectability bug (thanks, 0day!)
 - Fixed builds with !CONFIG_RADIX_TREE_MULTIORDER
 - Fixed shmem_add_to_page_cache() and add_to_swap_cache().  Just a typo.
 - Changed xa_ functions which return an error to use xa_err instead of ERR_PTR.
 - Fixed a bug which could cause xas_for_each_tag() to terminate early.
 - Removed spurious VM_BUG_ON_PAGE in page_cache_delete_batch
 - Clear tags before erasing an entry

Cleanup:
 - Renamed node->root to ->array.
 - Renamed node->exceptional to ->nr_values.
 - Improved debug output.
 - Removed xa_lock_held.  The few users opencode lockdep_is_held().
 - Made xas_error use unlikely().  Errors are always unlikely.
 - Changed xas errors to be the same as xa errors.
 - Changed xa_set_tag(), xa_clear_tag(), __xa_set_tag() and __xa_get_tag() to
   return void.  The functionality is not being used.
 - Rewrote xa_to_node() to be more efficient.
 - Replaced license text with SPDX tags
 - Pulled some boilerplate out of __xa_erase, xa_store and xa_cmpxchg into
   the new xas_result()
 - Applied several of Randy's suggestions to the documentation.  Also lots
   of tweaking.

New features:
 - Added xa_count()
 - Added xa_store_empty() as a convenience function.
 - Changed xarray to not use irqsafe locks by default.  The IDR continues to
   use irqsafe locks for now.
 - Added __xa_store and __xa_cmpxchg variations so users can do their own
   locking.
 - Exposed & documented the xa_lock member of struct xarray.
 - Converted fscache to XArray
 - Converted irqdomain to XArray
 - Converted raid5-cache to XArray


Matthew Wilcox (78):
  xfs: Rename xa_ elements to ail_
  fscache: Use appropriate radix tree accessors
  xarray: Add the xa_lock to the radix_tree_root
  page cache: Use xa_lock
  xarray: Replace exceptional entries
  xarray: Change definition of sibling entries
  xarray: Add definition of struct xarray
  xarray: Define struct xa_node
  xarray: Add documentation
  xarray: Add xa_load
  xarray: Add xa_get_tag, xa_set_tag and xa_clear_tag
  xarray: Add xa_store
  xarray: Add xa_cmpxchg
  xarray: Add xa_for_each
  xarray: Add xas_for_each_tag
  xarray: Add xa_get_entries, xa_get_tagged and xa_get_maybe_tag
  xarray: Add xa_destroy
  xarray: Add xas_next and xas_prev
  xarray: Add xas_create_range
  xarray: Add MAINTAINERS entry
  xarray: Add ability to store errno values
  idr: Convert to XArray
  ida: Convert to XArray
  page cache: Convert hole search to XArray
  page cache: Add page_cache_range_empty function
  page cache: Add and replace pages using the XArray
  page cache: Convert page deletion to XArray
  page cache: Convert page cache lookups to XArray
  page cache: Convert delete_batch to XArray
  page cache: Remove stray radix comment
  mm: Convert page-writeback to XArray
  mm: Convert workingset to XArray
  mm: Convert truncate to XArray
  mm: Convert add_to_swap_cache to XArray
  mm: Convert delete_from_swap_cache to XArray
  mm: Convert __do_page_cache_readahead to XArray
  mm: Convert page migration to XArray
  mm: Convert huge_memory to XArray
  mm: Convert collapse_shmem to XArray
  mm: Convert khugepaged_scan_shmem to XArray
  pagevec: Use xa_tag_t
  shmem: Convert replace to XArray
  shmem: Convert shmem_confirm_swap to XArray
  shmem: Convert find_swap_entry to XArray
  shmem: Convert shmem_tag_pins to XArray
  

[PATCH v5 55/78] nilfs2: Convert to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

I'm not 100% convinced that the rewrite of nilfs_copy_back_pages is
correct, but it will at least have different bugs from the current
version.

Signed-off-by: Matthew Wilcox 
---
 fs/nilfs2/btnode.c | 37 +++-
 fs/nilfs2/page.c   | 72 +++---
 2 files changed, 56 insertions(+), 53 deletions(-)

diff --git a/fs/nilfs2/btnode.c b/fs/nilfs2/btnode.c
index 9e2a00207436..b5997e8c5441 100644
--- a/fs/nilfs2/btnode.c
+++ b/fs/nilfs2/btnode.c
@@ -177,42 +177,36 @@ int nilfs_btnode_prepare_change_key(struct address_space 
*btnc,
ctxt->newbh = NULL;
 
if (inode->i_blkbits == PAGE_SHIFT) {
-   lock_page(obh->b_page);
-   /*
-* We cannot call radix_tree_preload for the kernels older
-* than 2.6.23, because it is not exported for modules.
-*/
+   void *entry;
+   struct page *opage = obh->b_page;
+   lock_page(opage);
 retry:
-   err = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
-   if (err)
-   goto failed_unlock;
/* BUG_ON(oldkey != obh->b_page->index); */
-   if (unlikely(oldkey != obh->b_page->index))
-   NILFS_PAGE_BUG(obh->b_page,
+   if (unlikely(oldkey != opage->index))
+   NILFS_PAGE_BUG(opage,
   "invalid oldkey %lld (newkey=%lld)",
   (unsigned long long)oldkey,
   (unsigned long long)newkey);
 
-   xa_lock_irq(>pages);
-   err = radix_tree_insert(>pages, newkey, obh->b_page);
-   xa_unlock_irq(>pages);
+   entry = xa_cmpxchg(>pages, newkey, NULL, opage, GFP_NOFS);
/*
 * Note: page->index will not change to newkey until
 * nilfs_btnode_commit_change_key() will be called.
 * To protect the page in intermediate state, the page lock
 * is held.
 */
-   radix_tree_preload_end();
-   if (!err)
+   if (!entry)
return 0;
-   else if (err != -EEXIST)
+   if (xa_is_err(entry)) {
+   err = xa_err(entry);
goto failed_unlock;
+   }
 
err = invalidate_inode_pages2_range(btnc, newkey, newkey);
if (!err)
goto retry;
/* fallback to copy mode */
-   unlock_page(obh->b_page);
+   unlock_page(opage);
}
 
nbh = nilfs_btnode_create_block(btnc, newkey);
@@ -252,9 +246,8 @@ void nilfs_btnode_commit_change_key(struct address_space 
*btnc,
mark_buffer_dirty(obh);
 
xa_lock_irq(>pages);
-   radix_tree_delete(>pages, oldkey);
-   radix_tree_tag_set(>pages, newkey,
-  PAGECACHE_TAG_DIRTY);
+   __xa_erase(>pages, oldkey);
+   __xa_set_tag(>pages, newkey, PAGECACHE_TAG_DIRTY);
xa_unlock_irq(>pages);
 
opage->index = obh->b_blocknr = newkey;
@@ -283,9 +276,7 @@ void nilfs_btnode_abort_change_key(struct address_space 
*btnc,
return;
 
if (nbh == NULL) {  /* blocksize == pagesize */
-   xa_lock_irq(>pages);
-   radix_tree_delete(>pages, newkey);
-   xa_unlock_irq(>pages);
+   xa_erase(>pages, newkey);
unlock_page(ctxt->bh->b_page);
} else
brelse(nbh);
diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index 1c6703efde9e..31d20f624971 100644
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -304,10 +304,10 @@ int nilfs_copy_dirty_pages(struct address_space *dmap,
 void nilfs_copy_back_pages(struct address_space *dmap,
   struct address_space *smap)
 {
+   XA_STATE(xas, >pages, 0);
struct pagevec pvec;
unsigned int i, n;
pgoff_t index = 0;
-   int err;
 
pagevec_init();
 repeat:
@@ -317,43 +317,56 @@ void nilfs_copy_back_pages(struct address_space *dmap,
 
for (i = 0; i < pagevec_count(); i++) {
struct page *page = pvec.pages[i], *dpage;
-   pgoff_t offset = page->index;
+   xas_set(, page->index);
 
lock_page(page);
-   dpage = find_lock_page(dmap, offset);
+   do {
+   xas_lock_irq();
+   dpage = xas_create();
+   if (!xas_error())
+   break;
+   xas_unlock_irq();
+   if (!xas_nomem(, GFP_NOFS)) {
+   

[PATCH v5 58/78] dax: Convert dax_unlock_mapping_entry to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Replace slot_locked() with dax_locked() and inline unlock_slot() into
its only caller.

Signed-off-by: Matthew Wilcox 
---
 fs/dax.c | 48 
 1 file changed, 16 insertions(+), 32 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 92693859efb5..dd4674ce48f5 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -73,6 +73,11 @@ fs_initcall(init_dax_wait_table);
 #define DAX_ZERO_PAGE  (1UL << 2)
 #define DAX_EMPTY  (1UL << 3)
 
+static bool dax_locked(void *entry)
+{
+   return xa_to_value(entry) & DAX_ENTRY_LOCK;
+}
+
 static unsigned long dax_radix_sector(void *entry)
 {
return xa_to_value(entry) >> DAX_SHIFT;
@@ -180,16 +185,6 @@ static void dax_wake_mapping_entry_waiter(struct 
address_space *mapping,
__wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, );
 }
 
-/*
- * Check whether the given slot is locked.  Must be called with xa_lock held.
- */
-static inline int slot_locked(struct address_space *mapping, void **slot)
-{
-   unsigned long entry = xa_to_value(
-   radix_tree_deref_slot_protected(slot, >pages.xa_lock));
-   return entry & DAX_ENTRY_LOCK;
-}
-
 /*
  * Mark the given slot as locked.  Must be called with xa_lock held.
  */
@@ -202,18 +197,6 @@ static inline void *lock_slot(struct address_space 
*mapping, void **slot)
return entry;
 }
 
-/*
- * Mark the given slot as unlocked.  Must be called with xa_lock held.
- */
-static inline void *unlock_slot(struct address_space *mapping, void **slot)
-{
-   unsigned long v = xa_to_value(
-   radix_tree_deref_slot_protected(slot, >pages.xa_lock));
-   void *entry = xa_mk_value(v & ~DAX_ENTRY_LOCK);
-   radix_tree_replace_slot(>pages, slot, entry);
-   return entry;
-}
-
 /*
  * Lookup entry in radix tree, wait for it to become unlocked if it is
  * a DAX entry and return it. The caller must call
@@ -237,8 +220,7 @@ static void *get_unlocked_mapping_entry(struct 
address_space *mapping,
entry = __radix_tree_lookup(>pages, index, NULL,
  );
if (!entry ||
-   WARN_ON_ONCE(!xa_is_value(entry)) ||
-   !slot_locked(mapping, slot)) {
+   WARN_ON_ONCE(!xa_is_value(entry)) || !dax_locked(entry)) {
if (slotp)
*slotp = slot;
return entry;
@@ -257,17 +239,19 @@ static void *get_unlocked_mapping_entry(struct 
address_space *mapping,
 static void dax_unlock_mapping_entry(struct address_space *mapping,
 pgoff_t index)
 {
-   void *entry, **slot;
+   XA_STATE(xas, >pages, index);
+   void *entry;
 
-   xa_lock_irq(>pages);
-   entry = __radix_tree_lookup(>pages, index, NULL, );
-   if (WARN_ON_ONCE(!entry || !xa_is_value(entry) ||
-!slot_locked(mapping, slot))) {
-   xa_unlock_irq(>pages);
+   xas_lock_irq();
+   entry = xas_load();
+   if (WARN_ON_ONCE(!entry || !xa_is_value(entry) || !dax_locked(entry))) {
+   xas_unlock_irq();
return;
}
-   unlock_slot(mapping, slot);
-   xa_unlock_irq(>pages);
+   entry = xa_mk_value(xa_to_value(entry) & ~DAX_ENTRY_LOCK);
+   xas_store(, entry);
+   /* Safe to not call xas_pause here -- we don't touch the array after */
+   xas_unlock_irq();
dax_wake_mapping_entry_waiter(mapping, index, entry, false);
 }
 
-- 
2.15.1

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[PATCH v5 64/78] dax: Convert dax_insert_mapping_entry to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Signed-off-by: Matthew Wilcox 
---
 fs/dax.c | 18 ++
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 9cfd4fcc0b0d..a3e795ad2493 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -498,9 +498,9 @@ static void *dax_insert_mapping_entry(struct address_space 
*mapping,
  void *entry, sector_t sector,
  unsigned long flags, bool dirty)
 {
-   struct radix_tree_root *pages = >pages;
void *new_entry;
pgoff_t index = vmf->pgoff;
+   XA_STATE(xas, >pages, index);
 
if (dirty)
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
@@ -516,7 +516,7 @@ static void *dax_insert_mapping_entry(struct address_space 
*mapping,
PAGE_SIZE, 0);
}
 
-   xa_lock_irq(>pages);
+   xas_lock_irq();
new_entry = dax_radix_locked_entry(sector, flags);
 
if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
@@ -528,21 +528,15 @@ static void *dax_insert_mapping_entry(struct 
address_space *mapping,
 * existing entry is a PMD, we will just leave the PMD in the
 * tree and dirty it if necessary.
 */
-   struct radix_tree_node *node;
-   void **slot;
-   void *ret;
-
-   ret = __radix_tree_lookup(pages, index, , );
-   WARN_ON_ONCE(ret != entry);
-   __radix_tree_replace(pages, node, slot,
-new_entry, NULL);
+   void *prev = xas_store(, new_entry);
+   WARN_ON_ONCE(prev != entry);
entry = new_entry;
}
 
if (dirty)
-   radix_tree_tag_set(pages, index, PAGECACHE_TAG_DIRTY);
+   xas_set_tag(, PAGECACHE_TAG_DIRTY);
 
-   xa_unlock_irq(>pages);
+   xas_unlock_irq();
return entry;
 }
 
-- 
2.15.1

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[PATCH v5 08/78] xarray: Define struct xa_node

[Matthew Wilcox]

From: Matthew Wilcox 

This is a direct replacement for struct radix_tree_node.  A couple of
struct members have changed name, so convert those.  Use a #define so
that radix tree users continue to work without change.

Signed-off-by: Matthew Wilcox 
---
 include/linux/radix-tree.h| 29 +++--
 include/linux/xarray.h| 24 ++
 lib/radix-tree.c  | 48 +--
 mm/workingset.c   | 16 ++--
 tools/testing/radix-tree/multiorder.c | 30 +++---
 5 files changed, 74 insertions(+), 73 deletions(-)

diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 260fef3c9bc2..64b7eff74278 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -32,6 +32,7 @@
 
 /* Keep unconverted code working */
 #define radix_tree_rootxarray
+#define radix_tree_nodexa_node
 
 /*
  * The bottom two bits of the slot determine how the remaining bits in the
@@ -60,41 +61,17 @@ static inline bool radix_tree_is_internal_node(void *ptr)
 
 /*** radix-tree API starts here ***/
 
-#define RADIX_TREE_MAX_TAGS 3
-
 #define RADIX_TREE_MAP_SHIFT   XA_CHUNK_SHIFT
 #define RADIX_TREE_MAP_SIZE(1UL << RADIX_TREE_MAP_SHIFT)
 #define RADIX_TREE_MAP_MASK(RADIX_TREE_MAP_SIZE-1)
 
-#define RADIX_TREE_TAG_LONGS   \
-   ((RADIX_TREE_MAP_SIZE + BITS_PER_LONG - 1) / BITS_PER_LONG)
+#define RADIX_TREE_MAX_TAGSXA_MAX_TAGS
+#define RADIX_TREE_TAG_LONGS   XA_TAG_LONGS
 
 #define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
 #define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
  RADIX_TREE_MAP_SHIFT))
 
-/*
- * @count is the count of every non-NULL element in the ->slots array
- * whether that is a data entry, a retry entry, a user pointer,
- * a sibling entry or a pointer to the next level of the tree.
- * @exceptional is the count of every element in ->slots which is
- * either a data entry or a sibling entry for data.
- */
-struct radix_tree_node {
-   unsigned char   shift;  /* Bits remaining in each slot */
-   unsigned char   offset; /* Slot offset in parent */
-   unsigned char   count;  /* Total entry count */
-   unsigned char   exceptional;/* Exceptional entry count */
-   struct radix_tree_node *parent; /* Used when ascending tree */
-   struct radix_tree_root *root;   /* The tree we belong to */
-   union {
-   struct list_head private_list;  /* For tree user */
-   struct rcu_head rcu_head;   /* Used when freeing node */
-   };
-   void __rcu  *slots[RADIX_TREE_MAP_SIZE];
-   unsigned long   tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
-};
-
 /* The top bits of xa_flags are used to store the root tags and the IDR flag */
 #define ROOT_IS_IDR((__force gfp_t)(1 << __GFP_BITS_SHIFT))
 #define ROOT_TAG_SHIFT (__GFP_BITS_SHIFT + 1)
diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 920f5a809df6..a9e064067b29 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -146,6 +146,30 @@ static inline bool xa_is_internal(const void *entry)
 #endif
 #define XA_CHUNK_SIZE  (1UL << XA_CHUNK_SHIFT)
 #define XA_CHUNK_MASK  (XA_CHUNK_SIZE - 1)
+#define XA_MAX_TAGS3
+#define XA_TAG_LONGS   DIV_ROUND_UP(XA_CHUNK_SIZE, BITS_PER_LONG)
+
+/*
+ * @count is the count of every non-NULL element in the ->slots array
+ * whether that is a value entry, a retry entry, a user pointer,
+ * a sibling entry or a pointer to the next level of the tree.
+ * @nr_values is the count of every element in ->slots which is
+ * either a value entry or a sibling entry to a value entry.
+ */
+struct xa_node {
+   unsigned char   shift;  /* Bits remaining in each slot */
+   unsigned char   offset; /* Slot offset in parent */
+   unsigned char   count;  /* Total entry count */
+   unsigned char   nr_values;  /* Value entry count */
+   struct xa_node __rcu *parent;   /* NULL at top of tree */
+   struct xarray   *array; /* The array we belong to */
+   union {
+   struct list_head private_list;  /* For tree user */
+   struct rcu_head rcu_head;   /* Used when freeing node */
+   };
+   void __rcu  *slots[XA_CHUNK_SIZE];
+   unsigned long   tags[XA_MAX_TAGS][XA_TAG_LONGS];
+};
 
 /*
  * Internal entries have the bottom two bits set to the value 10b.  Most
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 930eb7d298d7..aa9fd729205e 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -259,11 +259,11 @@ static void dump_node(struct radix_tree_node *node, 
unsigned long index)
 {
unsigned long i;
 
-   pr_debug("radix node: %p offset %d indices 

[PATCH v5 54/78] fs: Convert writeback to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

A couple of short loops.

Signed-off-by: Matthew Wilcox 
---
 fs/fs-writeback.c | 25 +
 1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index e2c1ca667d9a..897a89489fe9 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -339,9 +339,9 @@ static void inode_switch_wbs_work_fn(struct work_struct 
*work)
struct address_space *mapping = inode->i_mapping;
struct bdi_writeback *old_wb = inode->i_wb;
struct bdi_writeback *new_wb = isw->new_wb;
-   struct radix_tree_iter iter;
+   XA_STATE(xas, >pages, 0);
+   struct page *page;
bool switched = false;
-   void **slot;
 
/*
 * By the time control reaches here, RCU grace period has passed
@@ -375,25 +375,18 @@ static void inode_switch_wbs_work_fn(struct work_struct 
*work)
 * to possibly dirty pages while PAGECACHE_TAG_WRITEBACK points to
 * pages actually under writeback.
 */
-   radix_tree_for_each_tagged(slot, >pages, , 0,
-  PAGECACHE_TAG_DIRTY) {
-   struct page *page = radix_tree_deref_slot_protected(slot,
-   >pages.xa_lock);
-   if (likely(page) && PageDirty(page)) {
+   xas_for_each_tag(, page, ULONG_MAX, PAGECACHE_TAG_DIRTY) {
+   if (PageDirty(page)) {
dec_wb_stat(old_wb, WB_RECLAIMABLE);
inc_wb_stat(new_wb, WB_RECLAIMABLE);
}
}
 
-   radix_tree_for_each_tagged(slot, >pages, , 0,
-  PAGECACHE_TAG_WRITEBACK) {
-   struct page *page = radix_tree_deref_slot_protected(slot,
-   >pages.xa_lock);
-   if (likely(page)) {
-   WARN_ON_ONCE(!PageWriteback(page));
-   dec_wb_stat(old_wb, WB_WRITEBACK);
-   inc_wb_stat(new_wb, WB_WRITEBACK);
-   }
+   xas_set(, 0);
+   xas_for_each_tag(, page, ULONG_MAX, PAGECACHE_TAG_WRITEBACK) {
+   WARN_ON_ONCE(!PageWriteback(page));
+   dec_wb_stat(old_wb, WB_WRITEBACK);
+   inc_wb_stat(new_wb, WB_WRITEBACK);
}
 
wb_get(new_wb);
-- 
2.15.1

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[PATCH v5 56/78] f2fs: Convert to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

This is a straightforward conversion.

Signed-off-by: Matthew Wilcox 
---
 fs/f2fs/data.c   |  3 +--
 fs/f2fs/dir.c|  5 +
 fs/f2fs/inline.c |  6 +-
 fs/f2fs/node.c   | 10 ++
 4 files changed, 5 insertions(+), 19 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index c8f6d9806896..1f3f192f152f 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2175,8 +2175,7 @@ void f2fs_set_page_dirty_nobuffers(struct page *page)
xa_lock_irqsave(>pages, flags);
WARN_ON_ONCE(!PageUptodate(page));
account_page_dirtied(page, mapping);
-   radix_tree_tag_set(>pages,
-   page_index(page), PAGECACHE_TAG_DIRTY);
+   __xa_set_tag(>pages, page_index(page), PAGECACHE_TAG_DIRTY);
xa_unlock_irqrestore(>pages, flags);
unlock_page_memcg(page);
 
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index b5515ea6bb2f..296070016ec9 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -708,7 +708,6 @@ void f2fs_delete_entry(struct f2fs_dir_entry *dentry, 
struct page *page,
unsigned int bit_pos;
int slots = GET_DENTRY_SLOTS(le16_to_cpu(dentry->name_len));
struct address_space *mapping = page_mapping(page);
-   unsigned long flags;
int i;
 
f2fs_update_time(F2FS_I_SB(dir), REQ_TIME);
@@ -739,10 +738,8 @@ void f2fs_delete_entry(struct f2fs_dir_entry *dentry, 
struct page *page,
 
if (bit_pos == NR_DENTRY_IN_BLOCK &&
!truncate_hole(dir, page->index, page->index + 1)) {
-   xa_lock_irqsave(>pages, flags);
-   radix_tree_tag_clear(>pages, page_index(page),
+   xa_clear_tag(>pages, page_index(page),
 PAGECACHE_TAG_DIRTY);
-   xa_unlock_irqrestore(>pages, flags);
 
clear_page_dirty_for_io(page);
ClearPagePrivate(page);
diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
index 7858b8e15f33..d3c3f84beca9 100644
--- a/fs/f2fs/inline.c
+++ b/fs/f2fs/inline.c
@@ -204,7 +204,6 @@ int f2fs_write_inline_data(struct inode *inode, struct page 
*page)
void *src_addr, *dst_addr;
struct dnode_of_data dn;
struct address_space *mapping = page_mapping(page);
-   unsigned long flags;
int err;
 
set_new_dnode(, inode, NULL, NULL, 0);
@@ -226,10 +225,7 @@ int f2fs_write_inline_data(struct inode *inode, struct 
page *page)
kunmap_atomic(src_addr);
set_page_dirty(dn.inode_page);
 
-   xa_lock_irqsave(>pages, flags);
-   radix_tree_tag_clear(>pages, page_index(page),
-PAGECACHE_TAG_DIRTY);
-   xa_unlock_irqrestore(>pages, flags);
+   xa_clear_tag(>pages, page_index(page), PAGECACHE_TAG_DIRTY);
 
set_inode_flag(inode, FI_APPEND_WRITE);
set_inode_flag(inode, FI_DATA_EXIST);
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 6b64a3009d55..0a6d5c2f996e 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -88,14 +88,10 @@ bool available_free_memory(struct f2fs_sb_info *sbi, int 
type)
 static void clear_node_page_dirty(struct page *page)
 {
struct address_space *mapping = page->mapping;
-   unsigned int long flags;
 
if (PageDirty(page)) {
-   xa_lock_irqsave(>pages, flags);
-   radix_tree_tag_clear(>pages,
-   page_index(page),
+   xa_clear_tag(>pages, page_index(page),
PAGECACHE_TAG_DIRTY);
-   xa_unlock_irqrestore(>pages, flags);
 
clear_page_dirty_for_io(page);
dec_page_count(F2FS_M_SB(mapping), F2FS_DIRTY_NODES);
@@ -1142,9 +1138,7 @@ void ra_node_page(struct f2fs_sb_info *sbi, nid_t nid)
return;
f2fs_bug_on(sbi, check_nid_range(sbi, nid));
 
-   rcu_read_lock();
-   apage = radix_tree_lookup(_MAPPING(sbi)->pages, nid);
-   rcu_read_unlock();
+   apage = xa_load(_MAPPING(sbi)->pages, nid);
if (apage)
return;
 
-- 
2.15.1

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[PATCH v5 32/78] mm: Convert workingset to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

We construct a fake XA_STATE and use it to delete the node with xa_store()
rather than adding a special function for this unique use case.

Signed-off-by: Matthew Wilcox 
---
 include/linux/swap.h |  4 ++--
 mm/workingset.c  | 49 +
 2 files changed, 23 insertions(+), 30 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index c2b8128799c1..e4a8afcb214c 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -300,12 +300,12 @@ bool workingset_refault(void *shadow);
 void workingset_activation(struct page *page);
 
 /* Do not use directly, use workingset_lookup_update */
-void workingset_update_node(struct radix_tree_node *node);
+void workingset_update_node(struct xa_node *node);
 
 /* Returns workingset_update_node() if the mapping has shadow entries. */
 #define workingset_lookup_update(mapping)  \
 ({ \
-   radix_tree_update_node_t __helper = workingset_update_node; \
+   xa_update_node_t __helper = workingset_update_node; \
if (dax_mapping(mapping) || shmem_mapping(mapping)) \
__helper = NULL;\
__helper;   \
diff --git a/mm/workingset.c b/mm/workingset.c
index 91b6e16ad4c1..405076233999 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -148,7 +148,7 @@
  * and activations is maintained (node->inactive_age).
  *
  * On eviction, a snapshot of this counter (along with some bits to
- * identify the node) is stored in the now empty page cache radix tree
+ * identify the node) is stored in the now empty page cache
  * slot of the evicted page.  This is called a shadow entry.
  *
  * On cache misses for which there are shadow entries, an eligible
@@ -162,7 +162,7 @@
 
 /*
  * Eviction timestamps need to be able to cover the full range of
- * actionable refaults. However, bits are tight in the radix tree
+ * actionable refaults. However, bits are tight in the xarray
  * entry, and after storing the identifier for the lruvec there might
  * not be enough left to represent every single actionable refault. In
  * that case, we have to sacrifice granularity for distance, and group
@@ -338,7 +338,7 @@ void workingset_activation(struct page *page)
 
 static struct list_lru shadow_nodes;
 
-void workingset_update_node(struct radix_tree_node *node)
+void workingset_update_node(struct xa_node *node)
 {
/*
 * Track non-empty nodes that contain only shadow entries;
@@ -370,7 +370,7 @@ static unsigned long count_shadow_nodes(struct shrinker 
*shrinker,
local_irq_enable();
 
/*
-* Approximate a reasonable limit for the radix tree nodes
+* Approximate a reasonable limit for the nodes
 * containing shadow entries. We don't need to keep more
 * shadow entries than possible pages on the active list,
 * since refault distances bigger than that are dismissed.
@@ -385,11 +385,11 @@ static unsigned long count_shadow_nodes(struct shrinker 
*shrinker,
 * worst-case density of 1/8th. Below that, not all eligible
 * refaults can be detected anymore.
 *
-* On 64-bit with 7 radix_tree_nodes per page and 64 slots
+* On 64-bit with 7 xa_nodes per page and 64 slots
 * each, this will reclaim shadow entries when they consume
 * ~1.8% of available memory:
 *
-* PAGE_SIZE / radix_tree_nodes / node_entries * 8 / PAGE_SIZE
+* PAGE_SIZE / xa_nodes / node_entries * 8 / PAGE_SIZE
 */
if (sc->memcg) {
cache = mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid,
@@ -408,11 +408,11 @@ static unsigned long count_shadow_nodes(struct shrinker 
*shrinker,
 static enum lru_status shadow_lru_isolate(struct list_head *item,
  struct list_lru_one *lru,
  spinlock_t *lru_lock,
- void *arg)
+ void *arg) __must_hold(lru_lock)
 {
+   XA_STATE(xas, NULL, 0);
struct address_space *mapping;
-   struct radix_tree_node *node;
-   unsigned int i;
+   struct xa_node *node;
int ret;
 
/*
@@ -420,7 +420,7 @@ static enum lru_status shadow_lru_isolate(struct list_head 
*item,
 * the shadow node LRU under the mapping->pages.xa_lock and the
 * lru_lock.  Because the page cache tree is emptied before
 * the inode can be destroyed, holding the lru_lock pins any
-* address_space that has radix tree nodes on the LRU.
+* address_space that has nodes on the LRU.
 *
 * We can then safely transition to the mapping->pages.xa_lock to
 * pin only 

[PATCH v5 35/78] mm: Convert delete_from_swap_cache to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Both callers of __delete_from_swap_cache have the swp_entry_t already,
so pass that in to make constructing the XA_STATE easier.

Signed-off-by: Matthew Wilcox 
---
 include/linux/swap.h |  5 +++--
 mm/swap_state.c  | 24 ++--
 mm/vmscan.c  |  2 +-
 3 files changed, 14 insertions(+), 17 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index e4a8afcb214c..569a8ac4fe3f 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -413,7 +413,7 @@ extern void show_swap_cache_info(void);
 extern int add_to_swap(struct page *page);
 extern int add_to_swap_cache(struct page *, swp_entry_t, gfp_t);
 extern int __add_to_swap_cache(struct page *page, swp_entry_t entry);
-extern void __delete_from_swap_cache(struct page *);
+extern void __delete_from_swap_cache(struct page *, swp_entry_t entry);
 extern void delete_from_swap_cache(struct page *);
 extern void free_page_and_swap_cache(struct page *);
 extern void free_pages_and_swap_cache(struct page **, int);
@@ -588,7 +588,8 @@ static inline int add_to_swap_cache(struct page *page, 
swp_entry_t entry,
return -1;
 }
 
-static inline void __delete_from_swap_cache(struct page *page)
+static inline void __delete_from_swap_cache(struct page *page,
+   swp_entry_t entry)
 {
 }
 
diff --git a/mm/swap_state.c b/mm/swap_state.c
index a57b5ad4c503..219e3b4f09e6 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -154,23 +154,22 @@ int add_to_swap_cache(struct page *page, swp_entry_t 
entry, gfp_t gfp)
  * This must be called only on pages that have
  * been verified to be in the swap cache.
  */
-void __delete_from_swap_cache(struct page *page)
+void __delete_from_swap_cache(struct page *page, swp_entry_t entry)
 {
-   struct address_space *address_space;
+   struct address_space *address_space = swap_address_space(entry);
int i, nr = hpage_nr_pages(page);
-   swp_entry_t entry;
-   pgoff_t idx;
+   pgoff_t idx = swp_offset(entry);
+   XA_STATE(xas, _space->pages, idx);
 
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(!PageSwapCache(page), page);
VM_BUG_ON_PAGE(PageWriteback(page), page);
 
-   entry.val = page_private(page);
-   address_space = swap_address_space(entry);
-   idx = swp_offset(entry);
for (i = 0; i < nr; i++) {
-   radix_tree_delete(_space->pages, idx + i);
+   void *entry = xas_store(, NULL);
+   VM_BUG_ON_PAGE(entry != page + i, entry);
set_page_private(page + i, 0);
+   xas_next();
}
ClearPageSwapCache(page);
address_space->nrpages -= nr;
@@ -246,14 +245,11 @@ int add_to_swap(struct page *page)
  */
 void delete_from_swap_cache(struct page *page)
 {
-   swp_entry_t entry;
-   struct address_space *address_space;
-
-   entry.val = page_private(page);
+   swp_entry_t entry = { .val = page_private(page) };
+   struct address_space *address_space = swap_address_space(entry);
 
-   address_space = swap_address_space(entry);
xa_lock_irq(_space->pages);
-   __delete_from_swap_cache(page);
+   __delete_from_swap_cache(page, entry);
xa_unlock_irq(_space->pages);
 
put_swap_page(page, entry);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 96316bd91f91..51df3f9ba0bc 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -715,7 +715,7 @@ static int __remove_mapping(struct address_space *mapping, 
struct page *page,
if (PageSwapCache(page)) {
swp_entry_t swap = { .val = page_private(page) };
mem_cgroup_swapout(page, swap);
-   __delete_from_swap_cache(page);
+   __delete_from_swap_cache(page, swap);
xa_unlock_irqrestore(>pages, flags);
put_swap_page(page, swap);
} else {
-- 
2.15.1

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[PATCH v5 21/78] xarray: Add ability to store errno values

[Matthew Wilcox]

From: Matthew Wilcox 

While the radix tree offers no ability to store IS_ERR pointers,
documenting that the XArray does not led to some concern.  Here is a
sanctioned way to store errnos in the XArray.  I'm concerned that it
will confuse people who can't tell the difference between xa_is_err()
and xa_is_errno(), so I've added copious kernel-doc to help them tell
the difference.

Signed-off-by: Matthew Wilcox 
---
 Documentation/core-api/xarray.rst  |  9 ---
 include/linux/xarray.h | 46 +-
 tools/testing/radix-tree/xarray-test.c |  8 +-
 3 files changed, 57 insertions(+), 6 deletions(-)

diff --git a/Documentation/core-api/xarray.rst 
b/Documentation/core-api/xarray.rst
index 706081bfe92f..57a494026d96 100644
--- a/Documentation/core-api/xarray.rst
+++ b/Documentation/core-api/xarray.rst
@@ -42,11 +42,12 @@ When you retrieve an entry from the XArray, you can check 
whether it is
 a value entry by calling :c:func:`xa_is_value`, and convert it back to
 an integer by calling :c:func:`xa_to_value`.
 
-The XArray does not support storing :c:func:`IS_ERR` pointers as some
+The XArray does not support storing :c:func:`IS_ERR` pointers because some
 conflict with value entries or internal entries.  If you need to store
-error numbers in the array, you can store ``(errno << 2)`` as these values
-will be aligned to a multiple of 4 and are not valid kernel pointers.
-The values 4, 8, ... 4092 are also not valid kernel pointers.
+error numbers in the array, you can encode them into error entries
+with :c:func:`xa_mk_errno`, check whether a returned entry is an error
+with :c:func:`xa_is_errno` and convert it back into an errno with
+:c:func:`xa_to_errno`.
 
 An unusual feature of the XArray is the ability to create entries which
 occupy a range of indices.  Once stored to, looking up any index in
diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index bcc321fb280f..e0f8eb06b874 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -231,6 +231,50 @@ static inline bool xa_is_value(const void *entry)
return (unsigned long)entry & 1;
 }
 
+/**
+ * xa_mk_errno() - Create an XArray entry from an error number.
+ * @error: Error number to store in XArray.
+ *
+ * Return: An entry suitable for storing in the XArray.
+ */
+static inline void *xa_mk_errno(long error)
+{
+   return (void *)(error << 2);
+}
+
+/**
+ * xa_to_errno() - Get error number stored in an XArray entry.
+ * @entry: XArray entry.
+ *
+ * Calling this function on an entry which is not an xa_is_errno() will
+ * yield unpredictable results.  Do not confuse this function with xa_err();
+ * this function is for errnos which have been stored in the XArray, and
+ * that function is for errors returned from the XArray implementation.
+ *
+ * Return: The error number stored in the XArray entry.
+ */
+static inline long xa_to_errno(const void *entry)
+{
+   return (long)entry >> 2;
+}
+
+/**
+ * xa_is_errno() - Determine if an entry is an errno.
+ * @entry: XArray entry.
+ *
+ * Do not confuse this function with xa_is_err(); that function tells you
+ * whether the XArray implementation returned an error; this function
+ * tells you whether the entry you successfully stored in the XArray
+ * represented an errno.  If you have never stored an errno in the XArray,
+ * you do not have to check this.
+ *
+ * Return: True if the entry is an errno, false if it is a pointer.
+ */
+static inline bool xa_is_errno(const void *entry)
+{
+   return (((unsigned long)entry & 3) == 0) && (entry > (void *)-4096);
+}
+
 /**
  * xa_is_internal() - Is the entry an internal entry?
  * @entry: Entry retrieved from the XArray
@@ -277,7 +321,7 @@ static inline int xa_err(void *entry)
 
 /**
  * xa_store_empty() - Store this entry in the XArray unless another entry is
- * already present.
+ * already present.
  * @xa: XArray.
  * @index: Index into array.
  * @entry: New entry.
diff --git a/tools/testing/radix-tree/xarray-test.c 
b/tools/testing/radix-tree/xarray-test.c
index 43111786ebdd..b843cedf3988 100644
--- a/tools/testing/radix-tree/xarray-test.c
+++ b/tools/testing/radix-tree/xarray-test.c
@@ -29,7 +29,13 @@ void check_xa_err(struct xarray *xa)
assert(xa_err(xa_store(xa, 1, xa_mk_value(0), GFP_KERNEL)) == 0);
assert(xa_err(xa_store(xa, 1, NULL, 0)) == 0);
 // kills the test-suite :-(
-// assert(xa_err(xa_store(xa, 0, xa_mk_internal(0), 0)) == -EINVAL);
+// assert(xa_err(xa_store(xa, 0, xa_mk_internal(0), 0)) == -EINVAL);
+
+   assert(xa_err(xa_store(xa, 0, xa_mk_errno(-ENOMEM), GFP_KERNEL)) == 0);
+   assert(xa_err(xa_load(xa, 0)) == 0);
+   assert(xa_is_errno(xa_load(xa, 0)) == true);
+   assert(xa_to_errno(xa_load(xa, 0)) == -ENOMEM);
+   xa_erase(xa, 0);
 }
 
 void check_xa_tag(struct xarray *xa)
-- 
2.15.1

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[PATCH v5 26/78] page cache: Add and replace pages using the XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Use the XArray APIs to add and replace pages in the page cache.  This
removes two uses of the radix tree preload API and is significantly
shorter code.

Signed-off-by: Matthew Wilcox 
---
 mm/filemap.c | 143 +--
 1 file changed, 61 insertions(+), 82 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index f1b4480723dd..91df92f5c96d 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -112,35 +112,6 @@
  *   ->tasklist_lock(memory_failure, collect_procs_ao)
  */
 
-static int page_cache_tree_insert(struct address_space *mapping,
- struct page *page, void **shadowp)
-{
-   struct radix_tree_node *node;
-   void **slot;
-   int error;
-
-   error = __radix_tree_create(>pages, page->index, 0,
-   , );
-   if (error)
-   return error;
-   if (*slot) {
-   void *p;
-
-   p = radix_tree_deref_slot_protected(slot,
-   >pages.xa_lock);
-   if (!xa_is_value(p))
-   return -EEXIST;
-
-   mapping->nrexceptional--;
-   if (shadowp)
-   *shadowp = p;
-   }
-   __radix_tree_replace(>pages, node, slot, page,
-workingset_lookup_update(mapping));
-   mapping->nrpages++;
-   return 0;
-}
-
 static void page_cache_tree_delete(struct address_space *mapping,
   struct page *page, void *shadow)
 {
@@ -776,51 +747,44 @@ EXPORT_SYMBOL(file_write_and_wait_range);
  * locked.  This function does not add the new page to the LRU, the
  * caller must do that.
  *
- * The remove + add is atomic.  The only way this function can fail is
- * memory allocation failure.
+ * The remove + add is atomic.  This function cannot fail.
  */
 int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
 {
-   int error;
+   struct address_space *mapping = old->mapping;
+   void (*freepage)(struct page *) = mapping->a_ops->freepage;
+   pgoff_t offset = old->index;
+   XA_STATE(xas, >pages, offset);
+   unsigned long flags;
 
VM_BUG_ON_PAGE(!PageLocked(old), old);
VM_BUG_ON_PAGE(!PageLocked(new), new);
VM_BUG_ON_PAGE(new->mapping, new);
 
-   error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
-   if (!error) {
-   struct address_space *mapping = old->mapping;
-   void (*freepage)(struct page *);
-   unsigned long flags;
-
-   pgoff_t offset = old->index;
-   freepage = mapping->a_ops->freepage;
-
-   get_page(new);
-   new->mapping = mapping;
-   new->index = offset;
+   get_page(new);
+   new->mapping = mapping;
+   new->index = offset;
 
-   xa_lock_irqsave(>pages, flags);
-   __delete_from_page_cache(old, NULL);
-   error = page_cache_tree_insert(mapping, new, NULL);
-   BUG_ON(error);
+   xas_lock_irqsave(, flags);
+   xas_store(, new);
 
-   /*
-* hugetlb pages do not participate in page cache accounting.
-*/
-   if (!PageHuge(new))
-   __inc_node_page_state(new, NR_FILE_PAGES);
-   if (PageSwapBacked(new))
-   __inc_node_page_state(new, NR_SHMEM);
-   xa_unlock_irqrestore(>pages, flags);
-   mem_cgroup_migrate(old, new);
-   radix_tree_preload_end();
-   if (freepage)
-   freepage(old);
-   put_page(old);
-   }
+   old->mapping = NULL;
+   /* hugetlb pages do not participate in page cache accounting. */
+   if (!PageHuge(old))
+   __dec_node_page_state(new, NR_FILE_PAGES);
+   if (!PageHuge(new))
+   __inc_node_page_state(new, NR_FILE_PAGES);
+   if (PageSwapBacked(old))
+   __dec_node_page_state(new, NR_SHMEM);
+   if (PageSwapBacked(new))
+   __inc_node_page_state(new, NR_SHMEM);
+   xas_unlock_irqrestore(, flags);
+   mem_cgroup_migrate(old, new);
+   if (freepage)
+   freepage(old);
+   put_page(old);
 
-   return error;
+   return 0;
 }
 EXPORT_SYMBOL_GPL(replace_page_cache_page);
 
@@ -829,12 +793,15 @@ static int __add_to_page_cache_locked(struct page *page,
  pgoff_t offset, gfp_t gfp_mask,
  void **shadowp)
 {
+   XA_STATE(xas, >pages, offset);
int huge = PageHuge(page);
struct mem_cgroup *memcg;
int error;
+   void *old;
 
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageSwapBacked(page), page);
+   xas_set_update(, 

[PATCH v5 12/78] xarray: Add xa_store

[Matthew Wilcox]

From: Matthew Wilcox 

xa_store() differs from radix_tree_insert() in that it will overwrite an
existing element in the array rather than returning an error.  This is
the behaviour which most users want, and those that want more complex
behaviour generally want to use the xas family of routines anyway.

For memory allocation, xa_store() will first attempt to request memory
from the slab allocator; if memory is not immediately available, it will
drop the xa_lock and allocate memory, keeping a pointer in the xa_state.
It does not use the per-CPU cache, although those will continue to exist
until all radix tree users are converted to the xarray.

This patch also includes xa_erase() and __xa_erase() for a streamlined
way to store NULL.  Since there is no need to allocate memory in order
to store a NULL in the XArray, we do not need to trouble the user with
deciding what memory allocation flags to use.

Signed-off-by: Matthew Wilcox 
---
 include/linux/xarray.h| 124 +-
 lib/radix-tree.c  |   4 +-
 lib/xarray.c  | 643 ++
 tools/include/linux/spinlock.h|   6 +
 tools/testing/radix-tree/linux/kernel.h   |   4 +
 tools/testing/radix-tree/linux/rcupdate.h |   1 +
 tools/testing/radix-tree/xarray-test.c| 127 +-
 7 files changed, 904 insertions(+), 5 deletions(-)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 16d896861e33..05873095bc7f 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -74,6 +74,34 @@ static inline void xa_init(struct xarray *xa)
 }
 
 void *xa_load(struct xarray *, unsigned long index);
+void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
+
+/**
+ * xa_erase() - Erase this entry from the XArray.
+ * @xa: XArray.
+ * @index: Index of entry.
+ *
+ * This function is the equivalent of calling xa_store() with %NULL as
+ * the third argument.  The XArray does not need to allocate memory, so
+ * the user does not need to provide GFP flags.
+ *
+ * Return: The entry which used to be at this index.
+ */
+static inline void *xa_erase(struct xarray *xa, unsigned long index)
+{
+   return xa_store(xa, index, NULL, 0);
+}
+
+/**
+ * xa_empty() - Determine if an array has any present entries.
+ * @xa: XArray.
+ *
+ * Return: %true if the array contains only NULL pointers.
+ */
+static inline bool xa_empty(const struct xarray *xa)
+{
+   return xa->xa_head == NULL;
+}
 
 typedef unsigned __bitwise xa_tag_t;
 #define XA_TAG_0   ((__force xa_tag_t)0U)
@@ -83,9 +111,15 @@ typedef unsigned __bitwise xa_tag_t;
 
 #define XA_TAG_MAX XA_TAG_2
 #define XA_FREE_TAGXA_TAG_0
+#define XA_FLAGS_TRACK_FREE((__force gfp_t)(1U << __GFP_BITS_SHIFT))
 #define XA_FLAGS_TAG(tag)  ((__force gfp_t)((2U << __GFP_BITS_SHIFT) << \
(__force unsigned)(tag)))
 
+static inline bool xa_track_free(const struct xarray *xa)
+{
+   return xa->xa_flags & XA_FLAGS_TRACK_FREE;
+}
+
 /**
  * xa_tagged() - Inquire whether any entry in this array has a tag set
  * @xa: Array
@@ -194,7 +228,23 @@ static inline int xa_err(void *entry)
 #define xa_unlock_irqrestore(xa, flags) \
spin_unlock_irqrestore(&(xa)->xa_lock, flags)
 
-/* Versions of the normal API which require the caller to hold the xa_lock */
+enum xa_ctx {
+   XA_CTX_PRC,
+   XA_CTX_BH,
+   XA_CTX_IRQ,
+};
+
+/*
+ * Versions of the normal API which require the caller to hold the xa_lock.
+ * If the GFP flags allow it, will drop the lock in order to allocate
+ * memory, then reacquire it afterwards.
+ */
+void *__xa_erase(struct xarray *, unsigned long index);
+void *___xa_store(struct xarray *, unsigned long index,
+   void *entry, gfp_t, enum xa_ctx);
+#define __xa_store(x, i, e, g) ___xa_store(x, i, e, g, XA_CTX_PRC)
+#define __xa_store_bh(x, i, e, g)  ___xa_store(x, i, e, g, XA_CTX_BH)
+#define __xa_store_irq(x, i, e, g) ___xa_store(x, i, e, g, XA_CTX_IRQ)
 void __xa_set_tag(struct xarray *, unsigned long index, xa_tag_t);
 void __xa_clear_tag(struct xarray *, unsigned long index, xa_tag_t);
 
@@ -290,6 +340,10 @@ static inline void *xa_entry_locked(struct xarray *xa,
  * kernel unmaps page 0 to trap NULL pointer dereferences, we can use values
  * 0-1023 for special purposes.  Values 0-62 are used for sibling
  * entries.  Value 256 is used for the retry entry.
+ *
+ * Errors are also represented as internal entries, but use the negative
+ * space (-4094 to -2).  They're never stored in the slots array; only
+ * generated by the normal API.
  */
 
 /* Private */
@@ -304,6 +358,12 @@ static inline unsigned long xa_to_internal(const void 
*entry)
return (unsigned long)entry >> 2;
 }
 
+/* Private */
+static inline void *xa_mk_node(const struct xa_node *node)
+{
+   return (void *)((unsigned 

[PATCH v5 68/78] mm: Convert cgroup writeback to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

This is a fairly naive conversion, leaving in place the GFP_ATOMIC
allocation.  By switching the locking around, we could use GFP_KERNEL
and probably simplify the error handling.

Signed-off-by: Matthew Wilcox 
---
 include/linux/backing-dev-defs.h |  2 +-
 include/linux/backing-dev.h  |  2 +-
 mm/backing-dev.c | 23 +++
 3 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index bfe86b54f6c1..074a54aad33c 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -187,7 +187,7 @@ struct backing_dev_info {
struct bdi_writeback wb;  /* the root writeback info for this bdi */
struct list_head wb_list; /* list of all wbs */
 #ifdef CONFIG_CGROUP_WRITEBACK
-   struct radix_tree_root cgwb_tree; /* radix tree of active cgroup wbs */
+   struct xarray cgwb_xa;  /* radix tree of active cgroup wbs */
struct rb_root cgwb_congested_tree; /* their congested states */
 #else
struct bdi_writeback_congested *wb_congested;
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 2af5b8a62d1e..715e7582fa03 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -271,7 +271,7 @@ static inline struct bdi_writeback *wb_find_current(struct 
backing_dev_info *bdi
if (!memcg_css->parent)
return >wb;
 
-   wb = radix_tree_lookup(>cgwb_tree, memcg_css->id);
+   wb = xa_load(>cgwb_xa, memcg_css->id);
 
/*
 * %current's blkcg equals the effective blkcg of its memcg.  No
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 84b2dc76f140..04efdf2b401a 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -417,8 +417,8 @@ static void wb_exit(struct bdi_writeback *wb)
 #include 
 
 /*
- * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree,
- * blkcg->cgwb_list, and memcg->cgwb_list.  bdi->cgwb_tree is also RCU
+ * cgwb_lock protects bdi->cgwb_xa, bdi->cgwb_congested_tree,
+ * blkcg->cgwb_list, and memcg->cgwb_list.  bdi->cgwb_xa is also RCU
  * protected.
  */
 static DEFINE_SPINLOCK(cgwb_lock);
@@ -539,7 +539,7 @@ static void cgwb_kill(struct bdi_writeback *wb)
 {
lockdep_assert_held(_lock);
 
-   WARN_ON(!radix_tree_delete(>bdi->cgwb_tree, wb->memcg_css->id));
+   WARN_ON(xa_erase(>bdi->cgwb_xa, wb->memcg_css->id) != wb);
list_del(>memcg_node);
list_del(>blkcg_node);
percpu_ref_kill(>refcnt);
@@ -571,7 +571,7 @@ static int cgwb_create(struct backing_dev_info *bdi,
 
/* look up again under lock and discard on blkcg mismatch */
spin_lock_irqsave(_lock, flags);
-   wb = radix_tree_lookup(>cgwb_tree, memcg_css->id);
+   wb = xa_load(>cgwb_xa, memcg_css->id);
if (wb && wb->blkcg_css != blkcg_css) {
cgwb_kill(wb);
wb = NULL;
@@ -614,8 +614,8 @@ static int cgwb_create(struct backing_dev_info *bdi,
spin_lock_irqsave(_lock, flags);
if (test_bit(WB_registered, >wb.state) &&
blkcg_cgwb_list->next && memcg_cgwb_list->next) {
-   /* we might have raced another instance of this function */
-   ret = radix_tree_insert(>cgwb_tree, memcg_css->id, wb);
+   ret = xa_store_empty(>cgwb_xa, memcg_css->id, wb,
+   GFP_ATOMIC);
if (!ret) {
list_add_tail_rcu(>bdi_node, >wb_list);
list_add(>memcg_node, memcg_cgwb_list);
@@ -682,7 +682,7 @@ struct bdi_writeback *wb_get_create(struct backing_dev_info 
*bdi,
 
do {
rcu_read_lock();
-   wb = radix_tree_lookup(>cgwb_tree, memcg_css->id);
+   wb = xa_load(>cgwb_xa, memcg_css->id);
if (wb) {
struct cgroup_subsys_state *blkcg_css;
 
@@ -704,7 +704,7 @@ static int cgwb_bdi_init(struct backing_dev_info *bdi)
 {
int ret;
 
-   INIT_RADIX_TREE(>cgwb_tree, GFP_ATOMIC);
+   xa_init(>cgwb_xa);
bdi->cgwb_congested_tree = RB_ROOT;
 
ret = wb_init(>wb, bdi, 1, GFP_KERNEL);
@@ -717,15 +717,14 @@ static int cgwb_bdi_init(struct backing_dev_info *bdi)
 
 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
 {
-   struct radix_tree_iter iter;
-   void **slot;
+   XA_STATE(xas, >cgwb_xa, 0);
struct bdi_writeback *wb;
 
WARN_ON(test_bit(WB_registered, >wb.state));
 
spin_lock_irq(_lock);
-   radix_tree_for_each_slot(slot, >cgwb_tree, , 0)
-   cgwb_kill(*slot);
+   xas_for_each(, wb, ULONG_MAX)
+   cgwb_kill(wb);
 
while (!list_empty(>wb_list)) {
wb = list_first_entry(>wb_list, struct bdi_writeback,
-- 
2.15.1

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[PATCH v5 36/78] mm: Convert __do_page_cache_readahead to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

This one is trivial.

Signed-off-by: Matthew Wilcox 
---
 mm/readahead.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/mm/readahead.c b/mm/readahead.c
index f64b31b3a84a..66bcaffd47f0 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -174,9 +174,7 @@ int __do_page_cache_readahead(struct address_space 
*mapping, struct file *filp,
if (page_offset > end_index)
break;
 
-   rcu_read_lock();
-   page = radix_tree_lookup(>pages, page_offset);
-   rcu_read_unlock();
+   page = xa_load(>pages, page_offset);
if (page && !xa_is_value(page))
continue;
 
-- 
2.15.1

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[PATCH v5 09/78] xarray: Add documentation

[Matthew Wilcox]

From: Matthew Wilcox 

This is documentation on how to use the XArray, not details about its
internal implementation.

Signed-off-by: Matthew Wilcox 
---
 Documentation/core-api/index.rst  |   1 +
 Documentation/core-api/xarray.rst | 340 ++
 2 files changed, 341 insertions(+)
 create mode 100644 Documentation/core-api/xarray.rst

diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst
index d5bbe035316d..eb16ba30aeb6 100644
--- a/Documentation/core-api/index.rst
+++ b/Documentation/core-api/index.rst
@@ -18,6 +18,7 @@ Core utilities
local_ops
workqueue
genericirq
+   xarray
flexible-arrays
librs
genalloc
diff --git a/Documentation/core-api/xarray.rst 
b/Documentation/core-api/xarray.rst
new file mode 100644
index ..706081bfe92f
--- /dev/null
+++ b/Documentation/core-api/xarray.rst
@@ -0,0 +1,340 @@
+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+==
+XArray
+==
+
+:Author: Matthew Wilcox
+
+Overview
+
+
+The XArray is an abstract data type which behaves like a very large array
+of pointers.  It meets many of the same needs as a hash or a conventional
+resizable array.  Unlike a hash, it allows you to sensibly go to the
+next or previous entry in a cache-efficient manner.  In contrast to
+a resizable array, there is no need for copying data or changing MMU
+mappings in order to grow the array.  It is more memory-efficient,
+parallelisable and cache friendly than a doubly-linked list.  It takes
+advantage of RCU to perform lookups without locking.
+
+The XArray implementation is efficient when the indices used are densely
+clustered; hashing the object and using the hash as the index will not
+perform well.  The XArray is optimised for small indices, but still has
+good performance with large indices.  If your index can be larger than
+``ULONG_MAX`` then the XArray is not the data type for you.  The most
+important user of the XArray is the page cache.
+
+A freshly-initialised XArray contains a ``NULL`` pointer at every index.
+Each non-``NULL`` entry in the array has three bits associated with it
+called tags.  Each tag may be set or cleared independently of the others.
+You can iterate over entries which are tagged.
+
+Normal pointers may be stored in the XArray directly.  They must be 4-byte
+aligned, which is true for any pointer returned from :c:func:`kmalloc` and
+:c:func:`alloc_page`.  It isn't true for arbitrary user-space pointers,
+nor for function pointers.  You can store pointers to statically allocated
+objects, as long as those objects have an alignment of at least 4.
+
+You can also store integers between 0 and ``LONG_MAX`` in the XArray.
+You must first convert it into an entry using :c:func:`xa_mk_value`.
+When you retrieve an entry from the XArray, you can check whether it is
+a value entry by calling :c:func:`xa_is_value`, and convert it back to
+an integer by calling :c:func:`xa_to_value`.
+
+The XArray does not support storing :c:func:`IS_ERR` pointers as some
+conflict with value entries or internal entries.  If you need to store
+error numbers in the array, you can store ``(errno << 2)`` as these values
+will be aligned to a multiple of 4 and are not valid kernel pointers.
+The values 4, 8, ... 4092 are also not valid kernel pointers.
+
+An unusual feature of the XArray is the ability to create entries which
+occupy a range of indices.  Once stored to, looking up any index in
+the range will return the same entry as looking up any other index in
+the range.  Setting a tag on one index will set it on all of them.
+Storing to any index will store to all of them.  Multi-index entries can
+be explicitly split into smaller entries, or storing ``NULL`` into any
+entry will cause the XArray to forget about the range.
+
+Normal API
+==
+
+Start by initialising an XArray, either with :c:func:`DEFINE_XARRAY`
+for statically allocated XArrays or :c:func:`xa_init` for dynamically
+allocated ones.
+
+You can then set entries using :c:func:`xa_store` and get entries
+using :c:func:`xa_load`.  xa_store will overwrite any entry with the
+new entry and return the previous entry stored at that index.  You can
+use :c:func:`xa_erase` instead of calling :c:func:`xa_store` with a
+%NULL entry.  There is no difference between an entry that has never
+been stored to and one that has most recently had ``NULL`` stored to it.
+
+You can conditionally replace an entry at an index by using
+:c:func:`xa_cmpxchg`.  Like :c:func:`cmpxchg`, it will only succeed if
+the entry at that index has the 'old' value.  It also returns the entry
+which was at that index; if it returns the same entry which was passed as
+'old', then :c:func:`xa_cmpxchg` succeeded.
+
+If you want to only store a new entry to an index if the current entry
+at that index is ``NULL``, you can use :c:func:`xa_store_empty` which
+returns ``-EEXIST`` if the entry is not empty.
+
+You can 

[PATCH v5 70/78] brd: Convert to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Convert brd_pages from a radix tree to an XArray.  Simpler and smaller
code; in particular another user of radix_tree_preload is eliminated.

Signed-off-by: Matthew Wilcox 
---
 drivers/block/brd.c | 93 -
 1 file changed, 28 insertions(+), 65 deletions(-)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 8028a3a7e7fd..59a1af7aaa79 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -17,7 +17,7 @@
 #include 
 #include 
 #include 
-#include 
+#include 
 #include 
 #include 
 #include 
@@ -29,9 +29,9 @@
 #define PAGE_SECTORS   (1 << PAGE_SECTORS_SHIFT)
 
 /*
- * Each block ramdisk device has a radix_tree brd_pages of pages that stores
- * the pages containing the block device's contents. A brd page's ->index is
- * its offset in PAGE_SIZE units. This is similar to, but in no way connected
+ * Each block ramdisk device has an xarray brd_pages that stores the pages
+ * containing the block device's contents. A brd page's ->index is its
+ * offset in PAGE_SIZE units. This is similar to, but in no way connected
  * with, the kernel's pagecache or buffer cache (which sit above our block
  * device).
  */
@@ -41,13 +41,7 @@ struct brd_device {
struct request_queue*brd_queue;
struct gendisk  *brd_disk;
struct list_headbrd_list;
-
-   /*
-* Backing store of pages and lock to protect it. This is the contents
-* of the block device.
-*/
-   spinlock_t  brd_lock;
-   struct radix_tree_root  brd_pages;
+   struct xarray   brd_pages;
 };
 
 /*
@@ -62,17 +56,9 @@ static struct page *brd_lookup_page(struct brd_device *brd, 
sector_t sector)
 * The page lifetime is protected by the fact that we have opened the
 * device node -- brd pages will never be deleted under us, so we
 * don't need any further locking or refcounting.
-*
-* This is strictly true for the radix-tree nodes as well (ie. we
-* don't actually need the rcu_read_lock()), however that is not a
-* documented feature of the radix-tree API so it is better to be
-* safe here (we don't have total exclusion from radix tree updates
-* here, only deletes).
 */
-   rcu_read_lock();
idx = sector >> PAGE_SECTORS_SHIFT; /* sector to page index */
-   page = radix_tree_lookup(>brd_pages, idx);
-   rcu_read_unlock();
+   page = xa_load(>brd_pages, idx);
 
BUG_ON(page && page->index != idx);
 
@@ -87,7 +73,7 @@ static struct page *brd_lookup_page(struct brd_device *brd, 
sector_t sector)
 static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)
 {
pgoff_t idx;
-   struct page *page;
+   struct page *curr, *page;
gfp_t gfp_flags;
 
page = brd_lookup_page(brd, sector);
@@ -108,62 +94,40 @@ static struct page *brd_insert_page(struct brd_device 
*brd, sector_t sector)
if (!page)
return NULL;
 
-   if (radix_tree_preload(GFP_NOIO)) {
-   __free_page(page);
-   return NULL;
-   }
-
-   spin_lock(>brd_lock);
idx = sector >> PAGE_SECTORS_SHIFT;
page->index = idx;
-   if (radix_tree_insert(>brd_pages, idx, page)) {
+   curr = xa_cmpxchg(>brd_pages, idx, NULL, page, GFP_NOIO);
+   if (curr) {
__free_page(page);
-   page = radix_tree_lookup(>brd_pages, idx);
-   BUG_ON(!page);
-   BUG_ON(page->index != idx);
+   if (xa_err(curr)) {
+   page = NULL;
+   } else {
+   page = curr;
+   BUG_ON(!page);
+   BUG_ON(page->index != idx);
+   }
}
-   spin_unlock(>brd_lock);
-
-   radix_tree_preload_end();
 
return page;
 }
 
 /*
- * Free all backing store pages and radix tree. This must only be called when
+ * Free all backing store pages and xarray.  This must only be called when
  * there are no other users of the device.
  */
-#define FREE_BATCH 16
 static void brd_free_pages(struct brd_device *brd)
 {
-   unsigned long pos = 0;
-   struct page *pages[FREE_BATCH];
-   int nr_pages;
-
-   do {
-   int i;
-
-   nr_pages = radix_tree_gang_lookup(>brd_pages,
-   (void **)pages, pos, FREE_BATCH);
-
-   for (i = 0; i < nr_pages; i++) {
-   void *ret;
-
-   BUG_ON(pages[i]->index < pos);
-   pos = pages[i]->index;
-   ret = radix_tree_delete(>brd_pages, pos);
-   BUG_ON(!ret || ret != pages[i]);
-   __free_page(pages[i]);
-   }
-
-   pos++;
+   XA_STATE(xas, >brd_pages, 0);
+   struct 

[PATCH v5 13/78] xarray: Add xa_cmpxchg

[Matthew Wilcox]

From: Matthew Wilcox 

This works like doing cmpxchg() on an array entry.  Code which wants
the radix_tree_insert() semantic of not overwriting an existing entry
can cmpxchg() with NULL and get the action it wants.  Plus, instead of
having an error returned, they get the value currently stored in the
array, which often saves them a subsequent lookup.

Signed-off-by: Matthew Wilcox 
---
 include/linux/xarray.h | 33 +
 lib/xarray.c   | 65 ++
 2 files changed, 98 insertions(+)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 05873095bc7f..56db23edac82 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -75,6 +75,8 @@ static inline void xa_init(struct xarray *xa)
 
 void *xa_load(struct xarray *, unsigned long index);
 void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
+void *xa_cmpxchg(struct xarray *, unsigned long index,
+   void *old, void *entry, gfp_t);
 
 /**
  * xa_erase() - Erase this entry from the XArray.
@@ -216,6 +218,32 @@ static inline int xa_err(void *entry)
return 0;
 }
 
+/**
+ * xa_store_empty() - Store this entry in the XArray unless another entry is
+ * already present.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @entry: New entry.
+ * @gfp: Memory allocation flags.
+ *
+ * If you would rather see the existing entry in the array, use xa_cmpxchg().
+ * This function is for users who don't care what the entry is, only that
+ * one is present.
+ *
+ * Return: -EEXIST if another entry was present, 0 if the store succeeded,
+ * or another negative errno if a different error happened (eg -ENOMEM).
+ */
+static inline int xa_store_empty(struct xarray *xa, unsigned long index,
+   void *entry, gfp_t gfp)
+{
+   void *curr = xa_cmpxchg(xa, index, NULL, entry, gfp);
+   if (!curr)
+   return 0;
+   if (xa_is_err(curr))
+   return xa_err(curr);
+   return -EEXIST;
+}
+
 #define xa_trylock(xa) spin_trylock(&(xa)->xa_lock)
 #define xa_lock(xa)spin_lock(&(xa)->xa_lock)
 #define xa_unlock(xa)  spin_unlock(&(xa)->xa_lock)
@@ -242,9 +270,14 @@ enum xa_ctx {
 void *__xa_erase(struct xarray *, unsigned long index);
 void *___xa_store(struct xarray *, unsigned long index,
void *entry, gfp_t, enum xa_ctx);
+void *___xa_cmpxchg(struct xarray *, unsigned long index, void *old,
+   void *entry, gfp_t, enum xa_ctx);
 #define __xa_store(x, i, e, g) ___xa_store(x, i, e, g, XA_CTX_PRC)
 #define __xa_store_bh(x, i, e, g)  ___xa_store(x, i, e, g, XA_CTX_BH)
 #define __xa_store_irq(x, i, e, g) ___xa_store(x, i, e, g, XA_CTX_IRQ)
+#define __xa_cmpxchg(x, i, o, e, g)___xa_cmpxchg(x, i, o, e, g, XA_CTX_PRC)
+#define __xa_cmpxchg_bh(x, i, o, e, g) ___xa_cmpxchg(x, i, o, e, g, XA_CTX_BH)
+#define __xa_cmpxchg_irq(x, i, o, e, g) ___xa_cmpxchg(x, i, o, e, g, 
XA_CTX_IRQ)
 void __xa_set_tag(struct xarray *, unsigned long index, xa_tag_t);
 void __xa_clear_tag(struct xarray *, unsigned long index, xa_tag_t);
 
diff --git a/lib/xarray.c b/lib/xarray.c
index 64f88ce23392..ef3340471e5c 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -921,6 +921,71 @@ void *___xa_store(struct xarray *xa, unsigned long index, 
void *entry,
 }
 EXPORT_SYMBOL(___xa_store);
 
+/**
+ * xa_cmpxchg() - Conditionally replace an entry in the XArray.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @old: Old value to test against.
+ * @entry: New value to place in array.
+ * @gfp: Allocation flags.
+ *
+ * If the entry at @index is the same as @old, replace it with @entry.
+ * If the return value is equal to @old, then the exchange was successful.
+ *
+ * Return: The old value at this index or xa_err() if an error happened.
+ */
+void *xa_cmpxchg(struct xarray *xa, unsigned long index,
+   void *old, void *entry, gfp_t gfp)
+{
+   XA_STATE(xas, xa, index);
+   void *curr;
+
+   if (WARN_ON_ONCE(xa_is_internal(entry)))
+   return XA_ERROR(-EINVAL);
+
+   do {
+   xas_lock();
+   curr = xas_create();
+   if (curr == old)
+   xas_store(, entry);
+   xas_unlock();
+   } while (xas_nomem(, gfp));
+
+   return xas_result(, curr);
+}
+EXPORT_SYMBOL(xa_cmpxchg);
+
+/*
+ * ___xa_cmpxchg() - Store this entry in the XArray.
+ * @xa: XArray.
+ * @index: Index into array.
+ * @entry: New entry.
+ * @gfp: Allocation flags.
+ * @lock_type: Lock acquisition type.
+ *
+ * Internal implementation detail.
+ *
+ * Return: The old entry at this index or xa_err() if an error happened.
+ */
+void *___xa_cmpxchg(struct xarray *xa, unsigned long index,
+   void *old, void *entry, gfp_t gfp, enum xa_ctx ctx)
+{
+   XA_STATE(xas, xa, index);
+   void *curr;
+
+   if 

[PATCH v5 22/78] idr: Convert to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

The IDR distinguishes between unallocated entries (read as NULL) and
entries where the user has chosen to store NULL.  The radix tree was
modified to consider NULL entries which had tag 0 _clear_ as being
allocated, but it added a lot of complexity.

Instead, the XArray has a 'zero entry', which the normal API will treat
as NULL, but is distinct from NULL when using the advanced API.  The IDR
code converts between NULL and zero entries.

The idr_for_each_entry_ul() iterator becomes an alias for xa_for_each(),
so we drop the idr_get_next_ul() function as it has no users.

The exported IDR API was a weird mix of GPL-only and general symbols;
I converted them all to GPL as there was no way to use the IDR API
without being GPL.

Signed-off-by: Matthew Wilcox 
---
 Documentation/core-api/xarray.rst   |   6 +
 include/linux/idr.h | 154 ---
 include/linux/xarray.h  |  27 +++-
 lib/idr.c   | 298 ++--
 lib/radix-tree.c|  77 +-
 lib/xarray.c|  11 +-
 tools/testing/radix-tree/idr-test.c |  23 +++
 7 files changed, 382 insertions(+), 214 deletions(-)

diff --git a/Documentation/core-api/xarray.rst 
b/Documentation/core-api/xarray.rst
index 57a494026d96..8ba2a4dc021e 100644
--- a/Documentation/core-api/xarray.rst
+++ b/Documentation/core-api/xarray.rst
@@ -260,6 +260,12 @@ to :c:func:`xas_retry`, and retry the operation if it 
returns ``true``.
this RCU period.  You should restart the lookup from the head of the
array.
 
+   * - Zero
+ - :c:func:`xa_is_zero`
+ - Zero entries appear as ``NULL`` through the Normal API, but occupy an
+   entry in the XArray which can be tagged or otherwise used to reserve
+   the index.
+
 Other internal entries may be added in the future.  As far as possible, they
 will be handled by :c:func:`xas_retry`.
 
diff --git a/include/linux/idr.h b/include/linux/idr.h
index 45a77d32dcf6..08a3f5900d53 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -9,34 +9,34 @@
  * tables.
  */
 
-#ifndef __IDR_H__
-#define __IDR_H__
+#ifndef _LINUX_IDR_H
+#define _LINUX_IDR_H
 
 #include 
 #include 
 #include 
-#include 
+#include 
 
 struct idr {
-   struct radix_tree_root  idr_rt;
-   unsigned intidr_next;
+   struct xarray   idr_xa;
+   unsigned intidr_next;
 };
 
-/*
- * The IDR API does not expose the tagging functionality of the radix tree
- * to users.  Use tag 0 to track whether a node has free space below it.
- */
-#define IDR_FREE   0
-
-/* Set the IDR flag and the IDR_FREE tag */
-#define IDR_RT_MARKER  ((__force gfp_t)(3 << __GFP_BITS_SHIFT))
+#define IDR_INIT_FLAGS (XA_FLAGS_TRACK_FREE | XA_FLAGS_TAG(0))
 
 #define IDR_INIT(name) \
 {  \
-   .idr_rt = RADIX_TREE_INIT(name, IDR_RT_MARKER)  \
+   .idr_xa = __XARRAY_INIT(name.idr_xa, IDR_INIT_FLAGS),   \
+   .idr_next = 0,  \
 }
 #define DEFINE_IDR(name)   struct idr name = IDR_INIT(name)
 
+static inline void idr_init(struct idr *idr)
+{
+   __xa_init(>idr_xa, IDR_INIT_FLAGS);
+   idr->idr_next = 0;
+}
+
 /**
  * idr_get_cursor - Return the current position of the cyclic allocator
  * @idr: idr handle
@@ -65,62 +65,83 @@ static inline void idr_set_cursor(struct idr *idr, unsigned 
int val)
 
 /**
  * DOC: idr sync
- * idr synchronization (stolen from radix-tree.h)
+ * idr synchronization
  *
- * idr_find() is able to be called locklessly, using RCU. The caller must
- * ensure calls to this function are made within rcu_read_lock() regions.
- * Other readers (lock-free or otherwise) and modifications may be running
- * concurrently.
+ * The IDR manages its own locking, using irqsafe spinlocks for operations
+ * which modify the IDR and RCU for operations which do not.  The user of
+ * the IDR may choose to wrap accesses to it in a lock if it needs to
+ * guarantee the IDR does not change during a read access.  The easiest way
+ * to do this is to grab the same lock the IDR uses for write accesses
+ * using one of the idr_lock() wrappers.
  *
- * It is still required that the caller manage the synchronization and
- * lifetimes of the items. So if RCU lock-free lookups are used, typically
- * this would mean that the items have their own locks, or are amenable to
- * lock-free access; and that the items are freed by RCU (or only freed after
- * having been deleted from the idr tree *and* a synchronize_rcu() grace
- * period).
+ * The caller must still manage the synchronization and lifetimes of the
+ * items. So if RCU lock-free lookups are used, typically this would mean
+ * that the items have their own locks, or are amenable 

[PATCH v5 07/78] xarray: Add definition of struct xarray

[Matthew Wilcox]

From: Matthew Wilcox 

This is a direct replacement for struct radix_tree_root.  Some of the
struct members have changed name; convert those, and use a #define so
that radix_tree users continue to work without change.

Signed-off-by: Matthew Wilcox 
---
 include/linux/radix-tree.h   | 31 -
 include/linux/xarray.h   | 57 
 lib/Makefile |  2 +-
 lib/idr.c|  4 +-
 lib/radix-tree.c | 75 
 lib/xarray.c | 40 +
 tools/include/linux/spinlock.h   |  1 +
 tools/testing/radix-tree/.gitignore  |  1 +
 tools/testing/radix-tree/Makefile|  8 +++-
 tools/testing/radix-tree/linux/bug.h |  1 +
 tools/testing/radix-tree/linux/kconfig.h |  1 +
 tools/testing/radix-tree/linux/xarray.h  |  2 +
 tools/testing/radix-tree/multiorder.c|  6 +--
 tools/testing/radix-tree/test.c  |  6 +--
 14 files changed, 163 insertions(+), 72 deletions(-)
 create mode 100644 lib/xarray.c
 create mode 100644 tools/testing/radix-tree/linux/kconfig.h
 create mode 100644 tools/testing/radix-tree/linux/xarray.h

diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 3e4d700bd1bd..260fef3c9bc2 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -30,6 +30,9 @@
 #include 
 #include 
 
+/* Keep unconverted code working */
+#define radix_tree_rootxarray
+
 /*
  * The bottom two bits of the slot determine how the remaining bits in the
  * slot are interpreted:
@@ -59,10 +62,7 @@ static inline bool radix_tree_is_internal_node(void *ptr)
 
 #define RADIX_TREE_MAX_TAGS 3
 
-#ifndef RADIX_TREE_MAP_SHIFT
-#define RADIX_TREE_MAP_SHIFT   (CONFIG_BASE_SMALL ? 4 : 6)
-#endif
-
+#define RADIX_TREE_MAP_SHIFT   XA_CHUNK_SHIFT
 #define RADIX_TREE_MAP_SIZE(1UL << RADIX_TREE_MAP_SHIFT)
 #define RADIX_TREE_MAP_MASK(RADIX_TREE_MAP_SIZE-1)
 
@@ -95,35 +95,20 @@ struct radix_tree_node {
unsigned long   tags[RADIX_TREE_MAX_TAGS][RADIX_TREE_TAG_LONGS];
 };
 
-/* The top bits of gfp_mask are used to store the root tags and the IDR flag */
+/* The top bits of xa_flags are used to store the root tags and the IDR flag */
 #define ROOT_IS_IDR((__force gfp_t)(1 << __GFP_BITS_SHIFT))
 #define ROOT_TAG_SHIFT (__GFP_BITS_SHIFT + 1)
 
-struct radix_tree_root {
-   spinlock_t  xa_lock;
-   gfp_t   gfp_mask;
-   struct radix_tree_node  __rcu *rnode;
-};
-
-#define RADIX_TREE_INIT(name, mask){   \
-   .xa_lock = __SPIN_LOCK_UNLOCKED(name.xa_lock),  \
-   .gfp_mask = (mask), \
-   .rnode = NULL,  \
-}
+#define RADIX_TREE_INIT(name, mask)__XARRAY_INIT(name, mask)
 
 #define RADIX_TREE(name, mask) \
struct radix_tree_root name = RADIX_TREE_INIT(name, mask)
 
-#define INIT_RADIX_TREE(root, mask)\
-do {   \
-   spin_lock_init(&(root)->xa_lock);   \
-   (root)->gfp_mask = (mask);  \
-   (root)->rnode = NULL;   \
-} while (0)
+#define INIT_RADIX_TREE(root, mask) __xa_init(root, mask)
 
 static inline bool radix_tree_empty(const struct radix_tree_root *root)
 {
-   return root->rnode == NULL;
+   return root->xa_head == NULL;
 }
 
 /**
diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index f175350560fd..920f5a809df6 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -10,9 +10,66 @@
  */
 
 #include 
+#include 
+#include 
 #include 
 #include 
 
+/**
+ * struct xarray - The anchor of the XArray.
+ * @xa_lock: Lock that protects the contents of the XArray.
+ *
+ * To use the xarray, define it statically or embed it in your data structure.
+ * It is a very small data structure, so it does not usually make sense to
+ * allocate it separately and keep a pointer to it in your data structure.
+ *
+ * You may use the xa_lock to protect your own data structures as well.
+ */
+/*
+ * If all of the entries in the array are NULL, @xa_head is a NULL pointer.
+ * If the only non-NULL entry in the array is at index 0, @xa_head is that
+ * entry.  If any other entry in the array is non-NULL, @xa_head points
+ * to an @xa_node.
+ */
+struct xarray {
+   spinlock_t  xa_lock;
+/* private: The rest of the data structure is not to be used directly. */
+   gfp_t   xa_flags;
+   void __rcu *xa_head;
+};
+
+#define __XARRAY_INIT(name, flags) {   \
+   .xa_lock = __SPIN_LOCK_UNLOCKED(name.xa_lock),  \
+   .xa_flags = flags,  

[PATCH v5 01/78] xfs: Rename xa_ elements to ail_

[Matthew Wilcox]

From: Matthew Wilcox 

This is a simple rename, except that xa_ail becomes ail_head.

Signed-off-by: Matthew Wilcox 
---
 fs/xfs/xfs_buf_item.c|  10 ++--
 fs/xfs/xfs_dquot.c   |   4 +-
 fs/xfs/xfs_dquot_item.c  |  11 ++--
 fs/xfs/xfs_inode_item.c  |  22 +++
 fs/xfs/xfs_log.c |   6 +-
 fs/xfs/xfs_log_recover.c |  80 -
 fs/xfs/xfs_trans.c   |  18 +++---
 fs/xfs/xfs_trans_ail.c   | 152 +++
 fs/xfs/xfs_trans_buf.c   |   4 +-
 fs/xfs/xfs_trans_priv.h  |  42 ++---
 10 files changed, 175 insertions(+), 174 deletions(-)

diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index e0a0af0946f2..6c5035544a93 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -459,7 +459,7 @@ xfs_buf_item_unpin(
bp->b_fspriv = NULL;
bp->b_iodone = NULL;
} else {
-   spin_lock(>xa_lock);
+   spin_lock(>ail_lock);
xfs_trans_ail_delete(ailp, lip, SHUTDOWN_LOG_IO_ERROR);
xfs_buf_item_relse(bp);
ASSERT(bp->b_fspriv == NULL);
@@ -1056,13 +1056,13 @@ xfs_buf_do_callbacks_fail(
struct xfs_log_item *lip = bp->b_fspriv;
struct xfs_ail  *ailp = lip->li_ailp;
 
-   spin_lock(>xa_lock);
+   spin_lock(>ail_lock);
for (; lip; lip = next) {
next = lip->li_bio_list;
if (lip->li_ops->iop_error)
lip->li_ops->iop_error(lip, bp);
}
-   spin_unlock(>xa_lock);
+   spin_unlock(>ail_lock);
 }
 
 static bool
@@ -1215,7 +1215,7 @@ xfs_buf_iodone(
 *
 * Either way, AIL is useless if we're forcing a shutdown.
 */
-   spin_lock(>xa_lock);
+   spin_lock(>ail_lock);
xfs_trans_ail_delete(ailp, lip, SHUTDOWN_CORRUPT_INCORE);
xfs_buf_item_free(BUF_ITEM(lip));
 }
@@ -1236,7 +1236,7 @@ xfs_buf_resubmit_failed_buffers(
/*
 * Clear XFS_LI_FAILED flag from all items before resubmit
 *
-* XFS_LI_FAILED set/clear is protected by xa_lock, caller  this
+* XFS_LI_FAILED set/clear is protected by ail_lock, caller  this
 * function already have it acquired
 */
for (; lip; lip = next) {
diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c
index f248708c10ff..e2a466df5dd1 100644
--- a/fs/xfs/xfs_dquot.c
+++ b/fs/xfs/xfs_dquot.c
@@ -974,7 +974,7 @@ xfs_qm_dqflush_done(
 (lip->li_flags & XFS_LI_FAILED))) {
 
/* xfs_trans_ail_delete() drops the AIL lock. */
-   spin_lock(>xa_lock);
+   spin_lock(>ail_lock);
if (lip->li_lsn == qip->qli_flush_lsn) {
xfs_trans_ail_delete(ailp, lip, 
SHUTDOWN_CORRUPT_INCORE);
} else {
@@ -984,7 +984,7 @@ xfs_qm_dqflush_done(
 */
if (lip->li_flags & XFS_LI_FAILED)
xfs_clear_li_failed(lip);
-   spin_unlock(>xa_lock);
+   spin_unlock(>ail_lock);
}
}
 
diff --git a/fs/xfs/xfs_dquot_item.c b/fs/xfs/xfs_dquot_item.c
index 664dea105e76..62637a226601 100644
--- a/fs/xfs/xfs_dquot_item.c
+++ b/fs/xfs/xfs_dquot_item.c
@@ -160,8 +160,9 @@ xfs_dquot_item_error(
 STATIC uint
 xfs_qm_dquot_logitem_push(
struct xfs_log_item *lip,
-   struct list_head*buffer_list) __releases(>li_ailp->xa_lock)
- __acquires(>li_ailp->xa_lock)
+   struct list_head*buffer_list)
+   __releases(>li_ailp->ail_lock)
+   __acquires(>li_ailp->ail_lock)
 {
struct xfs_dquot*dqp = DQUOT_ITEM(lip)->qli_dquot;
struct xfs_buf  *bp = lip->li_buf;
@@ -208,7 +209,7 @@ xfs_qm_dquot_logitem_push(
goto out_unlock;
}
 
-   spin_unlock(>li_ailp->xa_lock);
+   spin_unlock(>li_ailp->ail_lock);
 
error = xfs_qm_dqflush(dqp, );
if (error) {
@@ -220,7 +221,7 @@ xfs_qm_dquot_logitem_push(
xfs_buf_relse(bp);
}
 
-   spin_lock(>li_ailp->xa_lock);
+   spin_lock(>li_ailp->ail_lock);
 out_unlock:
xfs_dqunlock(dqp);
return rval;
@@ -403,7 +404,7 @@ xfs_qm_qoffend_logitem_committed(
 * Delete the qoff-start logitem from the AIL.
 * xfs_trans_ail_delete() drops the AIL lock.
 */
-   spin_lock(>xa_lock);
+   spin_lock(>ail_lock);
xfs_trans_ail_delete(ailp, >qql_item, SHUTDOWN_LOG_IO_ERROR);
 
kmem_free(qfs->qql_item.li_lv_shadow);
diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
index 6ee5c3bf19ad..071acd4249a0 100644
--- a/fs/xfs/xfs_inode_item.c
+++ b/fs/xfs/xfs_inode_item.c
@@ -501,8 +501,8 @@ STATIC uint
 

[PATCH v5 76/78] md: Convert raid5-cache to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

This is the first user of the radix tree I've converted which was
storing numbers rather than pointers.  I'm fairly pleased with how
well it came out.  There's less boiler-plate involved than there was
with the radix tree, so that's a win.  It does use the advanced API,
and I think that's a signal that there needs to be a separate API for
using the XArray for only integers.

Signed-off-by: Matthew Wilcox 
---
 drivers/md/raid5-cache.c | 119 ---
 1 file changed, 40 insertions(+), 79 deletions(-)

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 39f31f07ffe9..2c8ad0ed9b48 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -158,9 +158,8 @@ struct r5l_log {
/* to disable write back during in degraded mode */
struct work_struct disable_writeback_work;
 
-   /* to for chunk_aligned_read in writeback mode, details below */
-   spinlock_t tree_lock;
-   struct radix_tree_root big_stripe_tree;
+   /* for chunk_aligned_read in writeback mode, details below */
+   struct xarray big_stripe;
 };
 
 /*
@@ -170,9 +169,8 @@ struct r5l_log {
  * chunk contains 64 4kB-page, so this chunk contain 64 stripes). For
  * chunk_aligned_read, these stripes are grouped into one "big_stripe".
  * For each big_stripe, we count how many stripes of this big_stripe
- * are in the write back cache. These data are tracked in a radix tree
- * (big_stripe_tree). We use radix_tree item pointer as the counter.
- * r5c_tree_index() is used to calculate keys for the radix tree.
+ * are in the write back cache. This counter is tracked in an xarray
+ * (big_stripe). r5c_index() is used to calculate the index.
  *
  * chunk_aligned_read() calls r5c_big_stripe_cached() to look up
  * big_stripe of each chunk in the tree. If this big_stripe is in the
@@ -180,9 +178,9 @@ struct r5l_log {
  * rcu_read_lock().
  *
  * It is necessary to remember whether a stripe is counted in
- * big_stripe_tree. Instead of adding new flag, we reuses existing flags:
+ * big_stripe. Instead of adding new flag, we reuses existing flags:
  * STRIPE_R5C_PARTIAL_STRIPE and STRIPE_R5C_FULL_STRIPE. If either of these
- * two flags are set, the stripe is counted in big_stripe_tree. This
+ * two flags are set, the stripe is counted in big_stripe. This
  * requires moving set_bit(STRIPE_R5C_PARTIAL_STRIPE) to
  * r5c_try_caching_write(); and moving clear_bit of
  * STRIPE_R5C_PARTIAL_STRIPE and STRIPE_R5C_FULL_STRIPE to
@@ -190,23 +188,13 @@ struct r5l_log {
  */
 
 /*
- * radix tree requests lowest 2 bits of data pointer to be 2b'00.
- * So it is necessary to left shift the counter by 2 bits before using it
- * as data pointer of the tree.
- */
-#define R5C_RADIX_COUNT_SHIFT 2
-
-/*
- * calculate key for big_stripe_tree
+ * calculate key for big_stripe
  *
  * sect: align_bi->bi_iter.bi_sector or sh->sector
  */
-static inline sector_t r5c_tree_index(struct r5conf *conf,
- sector_t sect)
+static inline sector_t r5c_index(struct r5conf *conf, sector_t sect)
 {
-   sector_t offset;
-
-   offset = sector_div(sect, conf->chunk_sectors);
+   sector_div(sect, conf->chunk_sectors);
return sect;
 }
 
@@ -2646,10 +2634,6 @@ int r5c_try_caching_write(struct r5conf *conf,
int i;
struct r5dev *dev;
int to_cache = 0;
-   void **pslot;
-   sector_t tree_index;
-   int ret;
-   uintptr_t refcount;
 
BUG_ON(!r5c_is_writeback(log));
 
@@ -2697,39 +2681,29 @@ int r5c_try_caching_write(struct r5conf *conf,
}
}
 
-   /* if the stripe is not counted in big_stripe_tree, add it now */
+   /* if the stripe is not counted in big_stripe, add it now */
if (!test_bit(STRIPE_R5C_PARTIAL_STRIPE, >state) &&
!test_bit(STRIPE_R5C_FULL_STRIPE, >state)) {
-   tree_index = r5c_tree_index(conf, sh->sector);
-   spin_lock(>tree_lock);
-   pslot = radix_tree_lookup_slot(>big_stripe_tree,
-  tree_index);
-   if (pslot) {
-   refcount = (uintptr_t)radix_tree_deref_slot_protected(
-   pslot, >tree_lock) >>
-   R5C_RADIX_COUNT_SHIFT;
-   radix_tree_replace_slot(
-   >big_stripe_tree, pslot,
-   (void *)((refcount + 1) << 
R5C_RADIX_COUNT_SHIFT));
-   } else {
-   /*
-* this radix_tree_insert can fail safely, so no
-* need to call radix_tree_preload()
-*/
-   ret = radix_tree_insert(
-   >big_stripe_tree, tree_index,
-   (void *)(1 << R5C_RADIX_COUNT_SHIFT));
- 

[PATCH v5 24/78] page cache: Convert hole search to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

The page cache offers the ability to search for a miss in the previous or
next N locations.  Rather than teach the XArray about the page cache's
definition of a miss, use xas_prev() and xas_next() to search the page
array.  This should be more efficient as it does not have to start the
lookup from the top for each index.

Signed-off-by: Matthew Wilcox 
---
 fs/nfs/blocklayout/blocklayout.c |   2 +-
 include/linux/pagemap.h  |   4 +-
 mm/filemap.c | 110 ++-
 mm/readahead.c   |   4 +-
 4 files changed, 55 insertions(+), 65 deletions(-)

diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
index 995d707537da..7bd643538cff 100644
--- a/fs/nfs/blocklayout/blocklayout.c
+++ b/fs/nfs/blocklayout/blocklayout.c
@@ -826,7 +826,7 @@ static u64 pnfs_num_cont_bytes(struct inode *inode, pgoff_t 
idx)
end = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
if (end != inode->i_mapping->nrpages) {
rcu_read_lock();
-   end = page_cache_next_hole(mapping, idx + 1, ULONG_MAX);
+   end = page_cache_next_gap(mapping, idx + 1, ULONG_MAX);
rcu_read_unlock();
}
 
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 80a6149152d4..0db127c3ccac 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -241,9 +241,9 @@ static inline gfp_t readahead_gfp_mask(struct address_space 
*x)
 
 typedef int filler_t(void *, struct page *);
 
-pgoff_t page_cache_next_hole(struct address_space *mapping,
+pgoff_t page_cache_next_gap(struct address_space *mapping,
 pgoff_t index, unsigned long max_scan);
-pgoff_t page_cache_prev_hole(struct address_space *mapping,
+pgoff_t page_cache_prev_gap(struct address_space *mapping,
 pgoff_t index, unsigned long max_scan);
 
 #define FGP_ACCESSED   0x0001
diff --git a/mm/filemap.c b/mm/filemap.c
index 309be963140c..146e8ec16ec0 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1327,86 +1327,76 @@ int __lock_page_or_retry(struct page *page, struct 
mm_struct *mm,
 }
 
 /**
- * page_cache_next_hole - find the next hole (not-present entry)
- * @mapping: mapping
- * @index: index
- * @max_scan: maximum range to search
- *
- * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
- * lowest indexed hole.
- *
- * Returns: the index of the hole if found, otherwise returns an index
- * outside of the set specified (in which case 'return - index >=
- * max_scan' will be true). In rare cases of index wrap-around, 0 will
- * be returned.
- *
- * page_cache_next_hole may be called under rcu_read_lock. However,
- * like radix_tree_gang_lookup, this will not atomically search a
- * snapshot of the tree at a single point in time. For example, if a
- * hole is created at index 5, then subsequently a hole is created at
- * index 10, page_cache_next_hole covering both indexes may return 10
- * if called under rcu_read_lock.
+ * page_cache_next_gap() - Find the next gap in the page cache.
+ * @mapping: Mapping.
+ * @index: Index.
+ * @max_scan: Maximum range to search.
+ *
+ * Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the
+ * gap with the lowest index.
+ *
+ * This function may be called under the rcu_read_lock.  However, this will
+ * not atomically search a snapshot of the cache at a single point in time.
+ * For example, if a gap is created at index 5, then subsequently a gap is
+ * created at index 10, page_cache_next_gap covering both indices may
+ * return 10 if called under the rcu_read_lock.
+ *
+ * Return: The index of the gap if found, otherwise an index outside the
+ * range specified (in which case 'return - index >= max_scan' will be true).
+ * In the rare case of index wrap-around, 0 will be returned.
  */
-pgoff_t page_cache_next_hole(struct address_space *mapping,
+pgoff_t page_cache_next_gap(struct address_space *mapping,
 pgoff_t index, unsigned long max_scan)
 {
-   unsigned long i;
+   XA_STATE(xas, >pages, index);
 
-   for (i = 0; i < max_scan; i++) {
-   struct page *page;
-
-   page = radix_tree_lookup(>pages, index);
-   if (!page || xa_is_value(page))
+   while (max_scan--) {
+   void *entry = xas_next();
+   if (!entry || xa_is_value(entry))
break;
-   index++;
-   if (index == 0)
+   if (xas.xa_index == 0)
break;
}
 
-   return index;
+   return xas.xa_index;
 }
-EXPORT_SYMBOL(page_cache_next_hole);
+EXPORT_SYMBOL(page_cache_next_gap);
 
 /**
- * page_cache_prev_hole - find the prev hole (not-present entry)
- * @mapping: mapping
- * @index: index
- * @max_scan: maximum range to search
- *
- * Search backwards in the 

[PATCH v5 11/78] xarray: Add xa_get_tag, xa_set_tag and xa_clear_tag

[Matthew Wilcox]

From: Matthew Wilcox 

XArray tags are slightly more strongly typed than the radix tree tags,
but occupy the same bits.  This commit also adds the xas_ family of tag
operations, for cases where the caller is already holding the lock, and
xa_tagged() to ask whether any array member has a particular tag set.

Signed-off-by: Matthew Wilcox 
---
 include/linux/xarray.h |  36 
 lib/radix-tree.c   |  52 +--
 lib/xarray.c   | 229 +
 3 files changed, 291 insertions(+), 26 deletions(-)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index df2ef4f19f3d..16d896861e33 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -11,6 +11,7 @@
 
 #include 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -74,6 +75,33 @@ static inline void xa_init(struct xarray *xa)
 
 void *xa_load(struct xarray *, unsigned long index);
 
+typedef unsigned __bitwise xa_tag_t;
+#define XA_TAG_0   ((__force xa_tag_t)0U)
+#define XA_TAG_1   ((__force xa_tag_t)1U)
+#define XA_TAG_2   ((__force xa_tag_t)2U)
+#define XA_NO_TAG  ((__force xa_tag_t)4U)
+
+#define XA_TAG_MAX XA_TAG_2
+#define XA_FREE_TAGXA_TAG_0
+#define XA_FLAGS_TAG(tag)  ((__force gfp_t)((2U << __GFP_BITS_SHIFT) << \
+   (__force unsigned)(tag)))
+
+/**
+ * xa_tagged() - Inquire whether any entry in this array has a tag set
+ * @xa: Array
+ * @tag: Tag value
+ *
+ * Return: %true if any entry has this tag set.
+ */
+static inline bool xa_tagged(const struct xarray *xa, xa_tag_t tag)
+{
+   return xa->xa_flags & XA_FLAGS_TAG(tag);
+}
+
+bool xa_get_tag(struct xarray *, unsigned long index, xa_tag_t);
+void xa_set_tag(struct xarray *, unsigned long index, xa_tag_t);
+void xa_clear_tag(struct xarray *, unsigned long index, xa_tag_t);
+
 #define BITS_PER_XA_VALUE  (BITS_PER_LONG - 1)
 
 /**
@@ -166,6 +194,10 @@ static inline int xa_err(void *entry)
 #define xa_unlock_irqrestore(xa, flags) \
spin_unlock_irqrestore(&(xa)->xa_lock, flags)
 
+/* Versions of the normal API which require the caller to hold the xa_lock */
+void __xa_set_tag(struct xarray *, unsigned long index, xa_tag_t);
+void __xa_clear_tag(struct xarray *, unsigned long index, xa_tag_t);
+
 /* Everything below here is the Advanced API.  Proceed with caution. */
 
 /*
@@ -473,6 +505,10 @@ static inline bool xas_retry(struct xa_state *xas, const 
void *entry)
 
 void *xas_load(struct xa_state *);
 
+bool xas_get_tag(const struct xa_state *, xa_tag_t);
+void xas_set_tag(const struct xa_state *, xa_tag_t);
+void xas_clear_tag(const struct xa_state *, xa_tag_t);
+
 /**
  * xas_reload() - Refetch an entry from the xarray.
  * @xas: XArray operation state.
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index cf5b84c9b890..d9e93b828ed0 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -126,19 +126,19 @@ static inline gfp_t root_gfp_mask(const struct 
radix_tree_root *root)
return root->xa_flags & __GFP_BITS_MASK;
 }
 
-static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
+static inline void rtag_set(struct radix_tree_node *node, unsigned int tag,
int offset)
 {
__set_bit(offset, node->tags[tag]);
 }
 
-static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
+static inline void rtag_clear(struct radix_tree_node *node, unsigned int tag,
int offset)
 {
__clear_bit(offset, node->tags[tag]);
 }
 
-static inline int tag_get(const struct radix_tree_node *node, unsigned int tag,
+static inline int rtag_get(const struct radix_tree_node *node, unsigned int 
tag,
int offset)
 {
return test_bit(offset, node->tags[tag]);
@@ -574,14 +574,14 @@ static int radix_tree_extend(struct radix_tree_root 
*root, gfp_t gfp,
if (is_idr(root)) {
all_tag_set(node, IDR_FREE);
if (!root_tag_get(root, IDR_FREE)) {
-   tag_clear(node, IDR_FREE, 0);
+   rtag_clear(node, IDR_FREE, 0);
root_tag_set(root, IDR_FREE);
}
} else {
/* Propagate the aggregated tag info to the new child */
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
if (root_tag_get(root, tag))
-   tag_set(node, tag, 0);
+   rtag_set(node, tag, 0);
}
}
 
@@ -646,7 +646,7 @@ static inline bool radix_tree_shrink(struct radix_tree_root 
*root,
 * one (root->xa_head) as far as dependent read barriers go.
 */
root->xa_head = (void __rcu *)child;
-

[PATCH v5 78/78] fscache: Convert to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Removes another user of radix_tree_preload().

Signed-off-by: Matthew Wilcox 
---
 fs/fscache/cookie.c |   6 +-
 fs/fscache/internal.h   |   2 +-
 fs/fscache/object.c |   2 +-
 fs/fscache/page.c   | 152 +---
 fs/fscache/stats.c  |   6 +-
 include/linux/fscache.h |   8 +--
 6 files changed, 76 insertions(+), 100 deletions(-)

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index e9054e0c1a49..6d45134d609e 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -109,9 +109,7 @@ struct fscache_cookie *__fscache_acquire_cookie(
cookie->netfs_data  = netfs_data;
cookie->flags   = (1 << FSCACHE_COOKIE_NO_DATA_YET);
 
-   /* radix tree insertion won't use the preallocation pool unless it's
-* told it may not wait */
-   INIT_RADIX_TREE(>stores, GFP_NOFS & ~__GFP_DIRECT_RECLAIM);
+   xa_init(>stores);
 
switch (cookie->def->type) {
case FSCACHE_COOKIE_TYPE_INDEX:
@@ -608,7 +606,7 @@ void __fscache_relinquish_cookie(struct fscache_cookie 
*cookie, bool retire)
/* Clear pointers back to the netfs */
cookie->netfs_data  = NULL;
cookie->def = NULL;
-   BUG_ON(!radix_tree_empty(>stores));
+   BUG_ON(!xa_empty(>stores));
 
if (cookie->parent) {
ASSERTCMP(atomic_read(>parent->usage), >, 0);
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index 0ff4b49a0037..468d9bd7f8c3 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -200,7 +200,7 @@ extern atomic_t fscache_n_stores_oom;
 extern atomic_t fscache_n_store_ops;
 extern atomic_t fscache_n_store_calls;
 extern atomic_t fscache_n_store_pages;
-extern atomic_t fscache_n_store_radix_deletes;
+extern atomic_t fscache_n_store_xarray_deletes;
 extern atomic_t fscache_n_store_pages_over_limit;
 
 extern atomic_t fscache_n_store_vmscan_not_storing;
diff --git a/fs/fscache/object.c b/fs/fscache/object.c
index aa0e71f02c33..ed165736a358 100644
--- a/fs/fscache/object.c
+++ b/fs/fscache/object.c
@@ -956,7 +956,7 @@ static const struct fscache_state 
*_fscache_invalidate_object(struct fscache_obj
 * retire the object instead.
 */
if (!fscache_use_cookie(object)) {
-   ASSERT(radix_tree_empty(>cookie->stores));
+   ASSERT(xa_empty(>cookie->stores));
set_bit(FSCACHE_OBJECT_RETIRED, >flags);
_leave(" [no cookie]");
return transit_to(KILL_OBJECT);
diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index 961029e04027..315e2745f822 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -22,13 +22,7 @@
  */
 bool __fscache_check_page_write(struct fscache_cookie *cookie, struct page 
*page)
 {
-   void *val;
-
-   rcu_read_lock();
-   val = radix_tree_lookup(>stores, page->index);
-   rcu_read_unlock();
-
-   return val != NULL;
+   return xa_load(>stores, page->index) != NULL;
 }
 EXPORT_SYMBOL(__fscache_check_page_write);
 
@@ -64,15 +58,15 @@ bool __fscache_maybe_release_page(struct fscache_cookie 
*cookie,
  struct page *page,
  gfp_t gfp)
 {
+   XA_STATE(xas, >stores, page->index);
struct page *xpage;
-   void *val;
 
_enter("%p,%p,%x", cookie, page, gfp);
 
 try_again:
rcu_read_lock();
-   val = radix_tree_lookup(>stores, page->index);
-   if (!val) {
+   xpage = xas_load();
+   if (!xpage) {
rcu_read_unlock();
fscache_stat(_n_store_vmscan_not_storing);
__fscache_uncache_page(cookie, page);
@@ -81,31 +75,32 @@ bool __fscache_maybe_release_page(struct fscache_cookie 
*cookie,
 
/* see if the page is actually undergoing storage - if so we can't get
 * rid of it till the cache has finished with it */
-   if (radix_tree_tag_get(>stores, page->index,
-  FSCACHE_COOKIE_STORING_TAG)) {
+   if (xas_get_tag(, FSCACHE_COOKIE_STORING_TAG)) {
rcu_read_unlock();
+   xas_retry(, XA_RETRY_ENTRY);
goto page_busy;
}
 
/* the page is pending storage, so we attempt to cancel the store and
 * discard the store request so that the page can be reclaimed */
-   spin_lock(>stores_lock);
+   xas_retry(, XA_RETRY_ENTRY);
+   xas_lock();
rcu_read_unlock();
 
-   if (radix_tree_tag_get(>stores, page->index,
-  FSCACHE_COOKIE_STORING_TAG)) {
+   xpage = xas_load();
+   if (xas_get_tag(, FSCACHE_COOKIE_STORING_TAG)) {
/* the page started to undergo storage whilst we were looking,
 * so now we can only wait or return */
spin_unlock(>stores_lock);
goto page_busy;
}
 
-   xpage = 

[PATCH v5 16/78] xarray: Add xa_get_entries, xa_get_tagged and xa_get_maybe_tag

[Matthew Wilcox]

From: Matthew Wilcox 

These functions allow a range of xarray entries to be extracted into a
compact normal array.

Signed-off-by: Matthew Wilcox 
---
 include/linux/xarray.h | 27 
 lib/xarray.c   | 88 ++
 2 files changed, 115 insertions(+)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 85a319463e46..1367d694eebd 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -140,6 +140,33 @@ void xa_clear_tag(struct xarray *, unsigned long index, 
xa_tag_t);
 
 void *xa_find(struct xarray *xa, unsigned long *index, unsigned long max);
 void *xa_find_after(struct xarray *xa, unsigned long *index, unsigned long 
max);
+int xa_get_entries(struct xarray *, void **dst, unsigned long start,
+   unsigned long max, unsigned int n);
+int xa_get_tagged(struct xarray *, void **dst, unsigned long start,
+   unsigned long max, unsigned int n, xa_tag_t);
+
+/**
+ * xa_get_maybe_tag() - Copy entries from the XArray into a normal array.
+ * @xa: The source XArray to copy from.
+ * @dst: The buffer to copy pointers into.
+ * @start: The first index in the XArray eligible to be copied from.
+ * @max: The last index in the XArray eligible to be copied from.
+ * @n: The maximum number of entries to copy.
+ * @tag: Tag number.
+ *
+ * If you specify %XA_NO_TAG as the tag number, this is the same as
+ * xa_get_entries().  Otherwise, it is the same as xa_get_tagged().
+ *
+ * Return: The number of entries copied.
+ */
+static inline int xa_get_maybe_tag(struct xarray *xa, void **dst,
+   unsigned long start, unsigned long max,
+   unsigned int n, xa_tag_t tag)
+{
+   if (tag == XA_NO_TAG)
+   return xa_get_entries(xa, dst, start, max, n);
+   return xa_get_tagged(xa, dst, start, max, n, tag);
+}
 
 /**
  * xa_for_each() - Iterate over a portion of an XArray.
diff --git a/lib/xarray.c b/lib/xarray.c
index 9ac1e9730c24..e73ae7b57fc9 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -1330,6 +1330,94 @@ void *xa_find_after(struct xarray *xa, unsigned long 
*indexp, unsigned long max)
 }
 EXPORT_SYMBOL(xa_find_after);
 
+/**
+ * xa_get_entries() - Copy entries from the XArray into a normal array.
+ * @xa: The source XArray to copy from.
+ * @dst: The buffer to copy pointers into.
+ * @start: The first index in the XArray eligible to be copied from.
+ * @max: The last index in the XArray eligible to be copied from.
+ * @n: The maximum number of entries to copy.
+ *
+ * Copies up to @n non-NULL entries from the XArray.  The copied entries will
+ * have indices between @start and @max, inclusive.
+ *
+ * This function uses the RCU lock to protect itself.  That means that the
+ * entries returned may not represent a snapshot of the XArray at a moment
+ * in time.  For example, if index 5 is stored to, then index 10 is stored to,
+ * calling xa_get_entries() may return the old contents of index 5 and the
+ * new contents of index 10.  Indices not modified while this function is
+ * running will not be skipped.
+ *
+ * If you need stronger guarantees, holding the xa_lock across calls to this
+ * function will prevent concurrent modification.
+ *
+ * Return: The number of entries copied.
+ */
+int xa_get_entries(struct xarray *xa, void **dst, unsigned long start,
+   unsigned long max, unsigned int n)
+{
+   XA_STATE(xas, xa, start);
+   void *entry;
+   unsigned int i = 0;
+
+   if (!n)
+   return 0;
+
+   rcu_read_lock();
+   xas_for_each(, entry, max) {
+   if (xas_retry(, entry))
+   continue;
+   dst[i++] = entry;
+   if (i == n)
+   break;
+   }
+   rcu_read_unlock();
+
+   return i;
+}
+EXPORT_SYMBOL(xa_get_entries);
+
+/**
+ * xa_get_tagged() - Copy tagged entries from the XArray into a normal array.
+ * @xa: The source XArray to copy from.
+ * @dst: The buffer to copy pointers into.
+ * @start: The first index in the XArray eligible to be copied from.
+ * @max: The last index in the XArray eligible to be copied from
+ * @n: The maximum number of entries to copy.
+ * @tag: Tag number.
+ *
+ * Copies up to @n non-NULL entries that have @tag set from the XArray.  The
+ * copied entries will have indices between @start and @max, inclusive.
+ *
+ * See the xa_get_entries() documentation for the consistency guarantees
+ * provided.
+ *
+ * Return: The number of entries copied.
+ */
+int xa_get_tagged(struct xarray *xa, void **dst, unsigned long start,
+   unsigned long max, unsigned int n, xa_tag_t tag)
+{
+   XA_STATE(xas, xa, start);
+   void *entry;
+   unsigned int i = 0;
+
+   if (!n)
+   return 0;
+
+   rcu_read_lock();
+   xas_for_each_tag(, entry, max, tag) {
+   if (xas_retry(, 

[PATCH v5 43/78] shmem: Convert shmem_confirm_swap to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

xa_load has its own RCU locking, so we can eliminate it here.

Signed-off-by: Matthew Wilcox 
---
 mm/shmem.c | 7 +--
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index fad6c9e7402e..654f367aca90 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -348,12 +348,7 @@ static int shmem_xa_replace(struct address_space *mapping,
 static bool shmem_confirm_swap(struct address_space *mapping,
   pgoff_t index, swp_entry_t swap)
 {
-   void *item;
-
-   rcu_read_lock();
-   item = radix_tree_lookup(>pages, index);
-   rcu_read_unlock();
-   return item == swp_to_radix_entry(swap);
+   return xa_load(>pages, index) == swp_to_radix_entry(swap);
 }
 
 /*
-- 
2.15.1

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[PATCH v5 10/78] xarray: Add xa_load

[Matthew Wilcox]

From: Matthew Wilcox 

This first function in the XArray API brings with it a lot of support
infrastructure.  The advanced API is based around the xa_state which is
a more capable version of the radix_tree_iter.

As the test-suite demonstrates, it is possible to use the xarray and
radix tree APIs on the same data structure.

Signed-off-by: Matthew Wilcox 
---
 include/linux/xarray.h  | 272 
 lib/radix-tree.c|  43 -
 lib/xarray.c| 184 +++
 tools/testing/radix-tree/.gitignore |   1 +
 tools/testing/radix-tree/Makefile   |   7 +-
 tools/testing/radix-tree/linux/radix-tree.h |   1 -
 tools/testing/radix-tree/linux/rcupdate.h   |   1 +
 tools/testing/radix-tree/linux/xarray.h |   1 +
 tools/testing/radix-tree/xarray-test.c  |  56 ++
 9 files changed, 520 insertions(+), 46 deletions(-)
 create mode 100644 tools/testing/radix-tree/xarray-test.c

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index a9e064067b29..df2ef4f19f3d 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -12,6 +12,8 @@
 #include 
 #include 
 #include 
+#include 
+#include 
 #include 
 #include 
 
@@ -70,6 +72,8 @@ static inline void xa_init(struct xarray *xa)
__xa_init(xa, 0);
 }
 
+void *xa_load(struct xarray *, unsigned long index);
+
 #define BITS_PER_XA_VALUE  (BITS_PER_LONG - 1)
 
 /**
@@ -117,6 +121,39 @@ static inline bool xa_is_internal(const void *entry)
return ((unsigned long)entry & 3) == 2;
 }
 
+/**
+ * xa_is_err() - Report whether an XArray operation returned an error
+ * @entry: Result from calling an XArray function
+ *
+ * If an XArray operation cannot complete an operation, it will return
+ * a special value indicating an error.  This function tells you
+ * whether an error occurred; xa_err() tells you which error occurred.
+ *
+ * Return: %true if the entry indicates an error.
+ */
+static inline bool xa_is_err(const void *entry)
+{
+   return unlikely(xa_is_internal(entry));
+}
+
+/**
+ * xa_err() - Turn an XArray result into an errno.
+ * @entry: Result from calling an XArray function.
+ *
+ * If an XArray operation cannot complete an operation, it will return
+ * a special pointer value which encodes an errno.  This function extracts
+ * the errno from the pointer value, or returns 0 if the pointer does not
+ * represent an errno.
+ *
+ * Return: A negative errno or 0.
+ */
+static inline int xa_err(void *entry)
+{
+   if (xa_is_err(entry))
+   return (long)entry >> 2;
+   return 0;
+}
+
 #define xa_trylock(xa) spin_trylock(&(xa)->xa_lock)
 #define xa_lock(xa)spin_lock(&(xa)->xa_lock)
 #define xa_unlock(xa)  spin_unlock(&(xa)->xa_lock)
@@ -171,6 +208,50 @@ struct xa_node {
unsigned long   tags[XA_MAX_TAGS][XA_TAG_LONGS];
 };
 
+#ifdef XA_DEBUG
+void xa_dump(const struct xarray *);
+void xa_dump_node(const struct xa_node *);
+#define XA_BUG_ON(node, x) do { \
+   if ((x) && (node)) \
+   xa_dump_node(node); \
+   BUG_ON(x); \
+   } while (0)
+#else
+#define XA_BUG_ON(node, x) do { } while (0)
+#endif
+
+/* Private */
+static inline void *xa_head(struct xarray *xa)
+{
+   return rcu_dereference_check(xa->xa_head,
+   lockdep_is_held(>xa_lock));
+}
+
+/* Private */
+static inline void *xa_head_locked(struct xarray *xa)
+{
+   return rcu_dereference_protected(xa->xa_head,
+   lockdep_is_held(>xa_lock));
+}
+
+/* Private */
+static inline void *xa_entry(struct xarray *xa,
+   const struct xa_node *node, unsigned int offset)
+{
+   XA_BUG_ON(node, offset >= XA_CHUNK_SIZE);
+   return rcu_dereference_check(node->slots[offset],
+   lockdep_is_held(>xa_lock));
+}
+
+/* Private */
+static inline void *xa_entry_locked(struct xarray *xa,
+   const struct xa_node *node, unsigned int offset)
+{
+   XA_BUG_ON(node, offset >= XA_CHUNK_SIZE);
+   return rcu_dereference_protected(node->slots[offset],
+   lockdep_is_held(>xa_lock));
+}
+
 /*
  * Internal entries have the bottom two bits set to the value 10b.  Most
  * internal entries are pointers to the next node in the tree.  Since the
@@ -191,6 +272,12 @@ static inline unsigned long xa_to_internal(const void 
*entry)
return (unsigned long)entry >> 2;
 }
 
+/* Private */
+static inline struct xa_node *xa_to_node(const void *entry)
+{
+   return (struct xa_node *)((unsigned long)entry - 2);
+}
+
 /* Private */
 static inline bool xa_is_node(const void *entry)
 {
@@ -224,4 +311,189 @@ static inline bool xa_is_sibling(const void *entry)
 
 #define XA_RETRY_ENTRY   

[PATCH v5 28/78] page cache: Convert page cache lookups to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Introduce page_cache_pin() to factor out the common logic between the
various lookup routines:

find_get_entry
find_get_entries
find_get_pages_range
find_get_pages_contig
find_get_pages_range_tag
find_get_entries_tag
filemap_map_pages

By using the xa_state to control the iteration, we can remove most of
the gotos and just use the normal break/continue loop control flow.

Also convert the regression1 read-side to XArray since that simulates
the functions being modified here.

Signed-off-by: Matthew Wilcox 
---
 include/linux/pagemap.h|   6 +-
 mm/filemap.c   | 380 +
 tools/testing/radix-tree/regression1.c |  68 +++---
 3 files changed, 129 insertions(+), 325 deletions(-)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 34d4fa3ad1c5..1a59f4a5424a 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -365,17 +365,17 @@ static inline unsigned find_get_pages(struct 
address_space *mapping,
 unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t start,
   unsigned int nr_pages, struct page **pages);
 unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t 
*index,
-   pgoff_t end, int tag, unsigned int nr_pages,
+   pgoff_t end, xa_tag_t tag, unsigned int nr_pages,
struct page **pages);
 static inline unsigned find_get_pages_tag(struct address_space *mapping,
-   pgoff_t *index, int tag, unsigned int nr_pages,
+   pgoff_t *index, xa_tag_t tag, unsigned int nr_pages,
struct page **pages)
 {
return find_get_pages_range_tag(mapping, index, (pgoff_t)-1, tag,
nr_pages, pages);
 }
 unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
-   int tag, unsigned int nr_entries,
+   xa_tag_t tag, unsigned int nr_entries,
struct page **entries, pgoff_t *indices);
 
 struct page *grab_cache_page_write_begin(struct address_space *mapping,
diff --git a/mm/filemap.c b/mm/filemap.c
index c9bc0dee0154..94496567d2c2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1401,6 +1401,32 @@ bool page_cache_range_empty(struct address_space 
*mapping, pgoff_t index,
 }
 EXPORT_SYMBOL_GPL(page_cache_range_empty);
 
+/*
+ * page_cache_pin() - Try to pin a page in the page cache.
+ * @xas: The XArray operation state.
+ * @pagep: The page which has been previously found at this location.
+ *
+ * On success, the page has an elevated refcount, but is not locked.
+ * This implements the lockless pagecache protocol as described in
+ * include/linux/pagemap.h; see page_cache_get_speculative().
+ *
+ * Return: True if the page is still in the cache.
+ */
+static bool page_cache_pin(struct xa_state *xas, struct page *page)
+{
+   struct page *head = compound_head(page);
+   bool got = page_cache_get_speculative(head);
+
+   if (likely(got && (xas_reload(xas) == page) &&
+   (compound_head(page) == head)))
+   return true;
+
+   if (got)
+   put_page(head);
+   xas_retry(xas, XA_RETRY_ENTRY);
+   return false;
+}
+
 /**
  * find_get_entry - find and get a page cache entry
  * @mapping: the address_space to search
@@ -1416,51 +1442,21 @@ EXPORT_SYMBOL_GPL(page_cache_range_empty);
  */
 struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
 {
-   void **pagep;
-   struct page *head, *page;
+   XA_STATE(xas, >pages, offset);
+   struct page *page;
 
rcu_read_lock();
-repeat:
-   page = NULL;
-   pagep = radix_tree_lookup_slot(>pages, offset);
-   if (pagep) {
-   page = radix_tree_deref_slot(pagep);
-   if (unlikely(!page))
-   goto out;
-   if (radix_tree_exception(page)) {
-   if (radix_tree_deref_retry(page))
-   goto repeat;
-   /*
-* A shadow entry of a recently evicted page,
-* or a swap entry from shmem/tmpfs.  Return
-* it without attempting to raise page count.
-*/
-   goto out;
-   }
-
-   head = compound_head(page);
-   if (!page_cache_get_speculative(head))
-   goto repeat;
-
-   /* The page was split under us? */
-   if (compound_head(page) != head) {
-   put_page(head);
-   goto repeat;
-   }
+   do {
+   page = xas_load();
+   if (xas_retry(, page))
+   continue;
+   if (!page 

[PATCH v5 05/78] xarray: Replace exceptional entries

[Matthew Wilcox]

From: Matthew Wilcox 

Introduce xarray value entries to replace the radix tree exceptional
entry code.  This is a slight change in encoding to allow the use of an
extra bit (we can now store BITS_PER_LONG - 1 bits in a value entry).
It is also a change in emphasis; exceptional entries are intimidating
and different.  As the comment explains, you can choose to store values
or pointers in the xarray and they are both first-class citizens.

Signed-off-by: Matthew Wilcox 
---
 arch/powerpc/include/asm/book3s/64/pgtable.h|   4 +-
 arch/powerpc/include/asm/nohash/64/pgtable.h|   4 +-
 drivers/gpu/drm/i915/i915_gem.c |  17 ++--
 drivers/staging/lustre/lustre/mdc/mdc_request.c |   2 +-
 fs/btrfs/compression.c  |   2 +-
 fs/btrfs/inode.c|   4 +-
 fs/dax.c| 115 
 fs/proc/task_mmu.c  |   2 +-
 include/linux/fs.h  |  48 ++
 include/linux/radix-tree.h  |  36 ++--
 include/linux/swapops.h |  19 ++--
 include/linux/xarray.h  |  40 +
 lib/idr.c   |  63 ++---
 lib/radix-tree.c|  21 ++---
 mm/filemap.c|  10 +--
 mm/khugepaged.c |   2 +-
 mm/madvise.c|   2 +-
 mm/memcontrol.c |   2 +-
 mm/mincore.c|   2 +-
 mm/readahead.c  |   2 +-
 mm/shmem.c  |  10 +--
 mm/swap.c   |   2 +-
 mm/truncate.c   |  12 +--
 mm/workingset.c |  12 ++-
 tools/testing/radix-tree/idr-test.c |   6 +-
 tools/testing/radix-tree/linux/radix-tree.h |   1 +
 tools/testing/radix-tree/multiorder.c   |  47 +-
 tools/testing/radix-tree/test.c |   2 +-
 28 files changed, 249 insertions(+), 240 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h 
b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 44697817ccc6..5025c26f1acd 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -649,9 +649,7 @@ static inline bool pte_user(pte_t pte)
BUILD_BUG_ON(_PAGE_HPTEFLAGS & (0x1f << _PAGE_BIT_SWAP_TYPE)); \
BUILD_BUG_ON(_PAGE_HPTEFLAGS & _PAGE_SWP_SOFT_DIRTY);   \
} while (0)
-/*
- * on pte we don't need handle RADIX_TREE_EXCEPTIONAL_SHIFT;
- */
+
 #define SWP_TYPE_BITS 5
 #define __swp_type(x)  (((x).val >> _PAGE_BIT_SWAP_TYPE) \
& ((1UL << SWP_TYPE_BITS) - 1))
diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h 
b/arch/powerpc/include/asm/nohash/64/pgtable.h
index abddf5830ad5..f711773568d7 100644
--- a/arch/powerpc/include/asm/nohash/64/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/64/pgtable.h
@@ -329,9 +329,7 @@ static inline void __ptep_set_access_flags(struct mm_struct 
*mm,
 */ \
BUILD_BUG_ON(_PAGE_HPTEFLAGS & (0x1f << _PAGE_BIT_SWAP_TYPE)); \
} while (0)
-/*
- * on pte we don't need handle RADIX_TREE_EXCEPTIONAL_SHIFT;
- */
+
 #define SWP_TYPE_BITS 5
 #define __swp_type(x)  (((x).val >> _PAGE_BIT_SWAP_TYPE) \
& ((1UL << SWP_TYPE_BITS) - 1))
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index ad4050f7ab3b..08a4e9b226cb 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5376,7 +5376,8 @@ i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
count = __sg_page_count(sg);
 
while (idx + count <= n) {
-   unsigned long exception, i;
+   void *entry;
+   unsigned long i;
int ret;
 
/* If we cannot allocate and insert this entry, or the
@@ -5391,12 +5392,9 @@ i915_gem_object_get_sg(struct drm_i915_gem_object *obj,
if (ret && ret != -EEXIST)
goto scan;
 
-   exception =
-   RADIX_TREE_EXCEPTIONAL_ENTRY |
-   idx << RADIX_TREE_EXCEPTIONAL_SHIFT;
+   entry = xa_mk_value(idx);
for (i = 1; i < count; i++) {
-   ret = radix_tree_insert(>radix, idx + i,
-   (void *)exception);
+   ret = radix_tree_insert(>radix, idx + i, entry);
if (ret && ret != -EEXIST)
goto scan;
}
@@ -5434,15 +5432,14 @@ 

[PATCH v5 50/78] shmem: Convert shmem_partial_swap_usage to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Simpler code because the xarray takes care of things like the limit and
dereferencing the slot.

Signed-off-by: Matthew Wilcox 
---
 mm/shmem.c | 18 +++---
 1 file changed, 3 insertions(+), 15 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index dd663341e01e..ecf05645509b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -658,29 +658,17 @@ static int shmem_free_swap(struct address_space *mapping,
 unsigned long shmem_partial_swap_usage(struct address_space *mapping,
pgoff_t start, pgoff_t end)
 {
-   struct radix_tree_iter iter;
-   void **slot;
+   XA_STATE(xas, >pages, start);
struct page *page;
unsigned long swapped = 0;
 
rcu_read_lock();
-
-   radix_tree_for_each_slot(slot, >pages, , start) {
-   if (iter.index >= end)
-   break;
-
-   page = radix_tree_deref_slot(slot);
-
-   if (radix_tree_deref_retry(page)) {
-   slot = radix_tree_iter_retry();
-   continue;
-   }
-
+   xas_for_each(, page, end - 1) {
if (xa_is_value(page))
swapped++;
 
if (need_resched()) {
-   slot = radix_tree_iter_resume(slot, );
+   xas_pause();
cond_resched_rcu();
}
}
-- 
2.15.1

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[PATCH v5 38/78] mm: Convert huge_memory to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Quite a straightforward conversion.

Signed-off-by: Matthew Wilcox 
---
 mm/huge_memory.c | 19 ---
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 28909c475ee5..5a41b00d86bd 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2379,7 +2379,7 @@ static void __split_huge_page_tail(struct page *head, int 
tail,
if (PageAnon(head) && !PageSwapCache(head)) {
page_ref_inc(page_tail);
} else {
-   /* Additional pin to radix tree */
+   /* Additional pin to page cache */
page_ref_add(page_tail, 2);
}
 
@@ -2450,13 +2450,13 @@ static void __split_huge_page(struct page *page, struct 
list_head *list,
ClearPageCompound(head);
/* See comment in __split_huge_page_tail() */
if (PageAnon(head)) {
-   /* Additional pin to radix tree of swap cache */
+   /* Additional pin to swap cache */
if (PageSwapCache(head))
page_ref_add(head, 2);
else
page_ref_inc(head);
} else {
-   /* Additional pin to radix tree */
+   /* Additional pin to page cache */
page_ref_add(head, 2);
xa_unlock(>mapping->pages);
}
@@ -2568,7 +2568,7 @@ bool can_split_huge_page(struct page *page, int 
*pextra_pins)
 {
int extra_pins;
 
-   /* Additional pins from radix tree */
+   /* Additional pins from page cache */
if (PageAnon(page))
extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
else
@@ -2664,17 +2664,14 @@ int split_huge_page_to_list(struct page *page, struct 
list_head *list)
spin_lock_irqsave(zone_lru_lock(page_zone(head)), flags);
 
if (mapping) {
-   void **pslot;
+   XA_STATE(xas, >pages, page_index(head));
 
-   xa_lock(>pages);
-   pslot = radix_tree_lookup_slot(>pages,
-   page_index(head));
/*
-* Check if the head page is present in radix tree.
+* Check if the head page is present in page cache.
 * We assume all tail are present too, if head is there.
 */
-   if (radix_tree_deref_slot_protected(pslot,
-   >pages.xa_lock) != head)
+   xa_lock(>pages);
+   if (xas_load() != head)
goto fail;
}
 
-- 
2.15.1

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[PATCH v5 15/78] xarray: Add xas_for_each_tag

[Matthew Wilcox]

From: Matthew Wilcox 

This iterator operates across each tagged entry in the specified range.
We do not yet have a user for an xa_for_each_tag iterator, but it would
be straight-forward to add one if needed.  This commit also includes
xas_find_tag() and xas_next_tag().

Signed-off-by: Matthew Wilcox 
---
 include/linux/xarray.h | 68 +++
 lib/xarray.c   | 78 ++
 2 files changed, 146 insertions(+)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index c4eef03ad12d..85a319463e46 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -645,6 +645,7 @@ void *xas_find(struct xa_state *, unsigned long max);
 bool xas_get_tag(const struct xa_state *, xa_tag_t);
 void xas_set_tag(const struct xa_state *, xa_tag_t);
 void xas_clear_tag(const struct xa_state *, xa_tag_t);
+void *xas_find_tag(struct xa_state *, unsigned long max, xa_tag_t);
 void xas_init_tags(const struct xa_state *);
 
 bool xas_nomem(struct xa_state *, gfp_t);
@@ -770,6 +771,55 @@ static inline void *xas_next_entry(struct xa_state *xas, 
unsigned long max)
return entry;
 }
 
+/* Private */
+static inline unsigned int xas_find_chunk(struct xa_state *xas, bool advance,
+   xa_tag_t tag)
+{
+   unsigned long *addr = xas->xa_node->tags[(__force unsigned)tag];
+   unsigned int offset = xas->xa_offset;
+
+   if (advance)
+   offset++;
+   if (XA_CHUNK_SIZE == BITS_PER_LONG) {
+   unsigned long data = *addr & (~0UL << offset);
+   if (data)
+   return __ffs(data);
+   return XA_CHUNK_SIZE;
+   }
+
+   return find_next_bit(addr, XA_CHUNK_SIZE, offset);
+}
+
+/**
+ * xas_next_tag() - Advance iterator to next tagged entry.
+ * @xas: XArray operation state.
+ * @max: Highest index to return.
+ * @tag: Tag to search for.
+ *
+ * xas_next_tag() is an inline function to optimise xarray traversal for
+ * speed.  It is equivalent to calling xas_find_tag(), and will call
+ * xas_find_tag() for all the hard cases.
+ *
+ * Return: The next tagged entry after the one currently referred to by @xas.
+ */
+static inline void *xas_next_tag(struct xa_state *xas, unsigned long max,
+   xa_tag_t tag)
+{
+   struct xa_node *node = xas->xa_node;
+   unsigned int offset;
+
+   if (unlikely(xas_not_node(node) || xa_node_shift(node)))
+   return xas_find_tag(xas, max, tag);
+   offset = xas_find_chunk(xas, true, tag);
+   xas->xa_offset = offset;
+   xas->xa_index = (xas->xa_index & ~XA_CHUNK_MASK) + offset;
+   if (xas->xa_index > max)
+   return NULL;
+   if (offset == XA_CHUNK_SIZE)
+   return xas_find_tag(xas, max, tag);
+   return xa_entry(xas->xa, node, offset);
+}
+
 /*
  * If iterating while holding a lock, drop the lock and reschedule
  * every %XA_CHECK_SCHED loops.
@@ -795,6 +845,24 @@ enum {
for (entry = xas_find(xas, max); entry; \
 entry = xas_next_entry(xas, max))
 
+/**
+ * xas_for_each_tag() - Iterate over a range of an XArray
+ * @xas: XArray operation state.
+ * @entry: Entry retrieved from array.
+ * @max: Maximum index to retrieve from array.
+ * @tag: Tag to search for.
+ *
+ * The loop body will be executed for each tagged entry in the xarray
+ * between the current xas position and @max.  @entry will be set to
+ * the entry retrieved from the xarray.  It is safe to delete entries
+ * from the array in the loop body.  You should hold either the RCU lock
+ * or the xa_lock while iterating.  If you need to drop the lock, call
+ * xas_pause() first.
+ */
+#define xas_for_each_tag(xas, entry, max, tag) \
+   for (entry = xas_find_tag(xas, max, tag); entry; \
+entry = xas_next_tag(xas, max, tag))
+
 /* Internal functions, mostly shared between radix-tree.c, xarray.c and idr.c 
*/
 void xas_destroy(struct xa_state *);
 
diff --git a/lib/xarray.c b/lib/xarray.c
index 4d8962d2341c..9ac1e9730c24 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -897,6 +897,84 @@ void *xas_find(struct xa_state *xas, unsigned long max)
 }
 EXPORT_SYMBOL_GPL(xas_find);
 
+/**
+ * xas_find_tag() - Find the next tagged entry in the XArray.
+ * @xas: XArray operation state.
+ * @max: Highest index to return.
+ * @tag: Tag number to search for.
+ *
+ * If the xas has not yet been walked to an entry, return the tagged entry
+ * which has an index >= xas.xa_index.  If it has been walked, the entry
+ * currently being pointed at has been processed, and so we move to the
+ * next tagged entry.
+ *
+ * If no tagged entry is found and the array is smaller than @max, @xas is
+ * set to the restart state and xas->xa_index is set to the smallest index
+ * not yet in the array.  This allows @xas to be immediately passed to
+ * xas_create().
+ *
+ * Return: 

[PATCH v5 03/78] xarray: Add the xa_lock to the radix_tree_root

[Matthew Wilcox]

From: Matthew Wilcox 

This results in no change in structure size on 64-bit x86 as it fits in
the padding between the gfp_t and the void *.

Signed-off-by: Matthew Wilcox 
---
 fs/f2fs/gc.c   |  2 +-
 include/linux/idr.h| 12 ++--
 include/linux/radix-tree.h |  7 +--
 include/linux/xarray.h | 33 +
 kernel/pid.c   |  2 +-
 tools/include/linux/spinlock.h |  1 +
 6 files changed, 47 insertions(+), 10 deletions(-)
 create mode 100644 include/linux/xarray.h

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index d844dcb80570..aac1e02f75df 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -991,7 +991,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync,
unsigned int init_segno = segno;
struct gc_inode_list gc_list = {
.ilist = LIST_HEAD_INIT(gc_list.ilist),
-   .iroot = RADIX_TREE_INIT(GFP_NOFS),
+   .iroot = RADIX_TREE_INIT(gc_list.iroot, GFP_NOFS),
};
 
trace_f2fs_gc_begin(sbi->sb, sync, background,
diff --git a/include/linux/idr.h b/include/linux/idr.h
index 8432bbfe02ce..45a77d32dcf6 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -31,11 +31,11 @@ struct idr {
 /* Set the IDR flag and the IDR_FREE tag */
 #define IDR_RT_MARKER  ((__force gfp_t)(3 << __GFP_BITS_SHIFT))
 
-#define IDR_INIT   \
+#define IDR_INIT(name) \
 {  \
-   .idr_rt = RADIX_TREE_INIT(IDR_RT_MARKER)\
+   .idr_rt = RADIX_TREE_INIT(name, IDR_RT_MARKER)  \
 }
-#define DEFINE_IDR(name)   struct idr name = IDR_INIT
+#define DEFINE_IDR(name)   struct idr name = IDR_INIT(name)
 
 /**
  * idr_get_cursor - Return the current position of the cyclic allocator
@@ -194,10 +194,10 @@ struct ida {
struct radix_tree_root  ida_rt;
 };
 
-#define IDA_INIT   {   \
-   .ida_rt = RADIX_TREE_INIT(IDR_RT_MARKER | GFP_NOWAIT),  \
+#define IDA_INIT(name) {   \
+   .ida_rt = RADIX_TREE_INIT(name, IDR_RT_MARKER | GFP_NOWAIT),\
 }
-#define DEFINE_IDA(name)   struct ida name = IDA_INIT
+#define DEFINE_IDA(name)   struct ida name = IDA_INIT(name)
 
 int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index fc55ff31eca7..d2253b540cd7 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -109,20 +109,23 @@ struct radix_tree_node {
 #define ROOT_TAG_SHIFT (__GFP_BITS_SHIFT + 1)
 
 struct radix_tree_root {
+   spinlock_t  xa_lock;
gfp_t   gfp_mask;
struct radix_tree_node  __rcu *rnode;
 };
 
-#define RADIX_TREE_INIT(mask)  {   \
+#define RADIX_TREE_INIT(name, mask){   \
+   .xa_lock = __SPIN_LOCK_UNLOCKED(name.xa_lock),  \
.gfp_mask = (mask), \
.rnode = NULL,  \
 }
 
 #define RADIX_TREE(name, mask) \
-   struct radix_tree_root name = RADIX_TREE_INIT(mask)
+   struct radix_tree_root name = RADIX_TREE_INIT(name, mask)
 
 #define INIT_RADIX_TREE(root, mask)\
 do {   \
+   spin_lock_init(&(root)->xa_lock);   \
(root)->gfp_mask = (mask);  \
(root)->rnode = NULL;   \
 } while (0)
diff --git a/include/linux/xarray.h b/include/linux/xarray.h
new file mode 100644
index ..931a0ff61315
--- /dev/null
+++ b/include/linux/xarray.h
@@ -0,0 +1,33 @@
+#ifndef _LINUX_XARRAY_H
+#define _LINUX_XARRAY_H
+/*
+ * eXtensible Arrays
+ * Copyright (c) 2017 Microsoft Corporation
+ * Author: Matthew Wilcox 
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include 
+
+#define xa_trylock(xa) spin_trylock(&(xa)->xa_lock)
+#define xa_lock(xa)spin_lock(&(xa)->xa_lock)
+#define xa_unlock(xa)  

[PATCH v5 46/78] shmem: Convert shmem_wait_for_pins to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

As with shmem_tag_pins(), hold the lock around the entire loop instead
of acquiring & dropping it for each entry we're going to untag.

Signed-off-by: Matthew Wilcox 
---
 mm/shmem.c | 59 ---
 1 file changed, 24 insertions(+), 35 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 2f41c7ceea18..e4a2eb1336be 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2636,9 +2636,7 @@ static void shmem_tag_pins(struct address_space *mapping)
  */
 static int shmem_wait_for_pins(struct address_space *mapping)
 {
-   struct radix_tree_iter iter;
-   void **slot;
-   pgoff_t start;
+   XA_STATE(xas, >pages, 0);
struct page *page;
int error, scan;
 
@@ -2646,7 +2644,9 @@ static int shmem_wait_for_pins(struct address_space 
*mapping)
 
error = 0;
for (scan = 0; scan <= LAST_SCAN; scan++) {
-   if (!radix_tree_tagged(>pages, SHMEM_TAG_PINNED))
+   unsigned int tagged = 0;
+
+   if (!xas_tagged(, SHMEM_TAG_PINNED))
break;
 
if (!scan)
@@ -2654,45 +2654,34 @@ static int shmem_wait_for_pins(struct address_space 
*mapping)
else if (schedule_timeout_killable((HZ << scan) / 200))
scan = LAST_SCAN;
 
-   start = 0;
-   rcu_read_lock();
-   radix_tree_for_each_tagged(slot, >pages, ,
-  start, SHMEM_TAG_PINNED) {
-
-   page = radix_tree_deref_slot(slot);
-   if (radix_tree_exception(page)) {
-   if (radix_tree_deref_retry(page)) {
-   slot = radix_tree_iter_retry();
-   continue;
-   }
-
-   page = NULL;
-   }
-
-   if (page &&
-   page_count(page) - page_mapcount(page) != 1) {
-   if (scan < LAST_SCAN)
-   goto continue_resched;
-
+   xas_set(, 0);
+   xas_lock_irq();
+   xas_for_each_tag(, page, ULONG_MAX, SHMEM_TAG_PINNED) {
+   bool clear = true;
+   if (xa_is_value(page))
+   continue;
+   if (page_count(page) - page_mapcount(page) != 1) {
/*
 * On the last scan, we clean up all those tags
 * we inserted; but make a note that we still
 * found pages pinned.
 */
-   error = -EBUSY;
+   if (scan == LAST_SCAN)
+   error = -EBUSY;
+   else
+   clear = false;
}
+   if (clear)
+   xas_clear_tag(, SHMEM_TAG_PINNED);
+   if (++tagged % XA_CHECK_SCHED)
+   continue;
 
-   xa_lock_irq(>pages);
-   radix_tree_tag_clear(>pages,
-iter.index, SHMEM_TAG_PINNED);
-   xa_unlock_irq(>pages);
-continue_resched:
-   if (need_resched()) {
-   slot = radix_tree_iter_resume(slot, );
-   cond_resched_rcu();
-   }
+   xas_pause();
+   xas_unlock_irq();
+   cond_resched();
+   xas_lock_irq();
}
-   rcu_read_unlock();
+   xas_unlock_irq();
}
 
return error;
-- 
2.15.1

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[PATCH v5 19/78] xarray: Add xas_create_range

[Matthew Wilcox]

From: Matthew Wilcox 

This hopefully temporary function is useful for users who have not yet
been converted to multi-index entries.

Signed-off-by: Matthew Wilcox 
---
 include/linux/xarray.h |  2 ++
 lib/xarray.c   | 22 ++
 2 files changed, 24 insertions(+)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 2d889208b68d..bcc321fb280f 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -685,6 +685,8 @@ void xas_init_tags(const struct xa_state *);
 bool xas_nomem(struct xa_state *, gfp_t);
 void xas_pause(struct xa_state *);
 
+void xas_create_range(struct xa_state *, unsigned long max);
+
 /**
  * xas_reload() - Refetch an entry from the xarray.
  * @xas: XArray operation state.
diff --git a/lib/xarray.c b/lib/xarray.c
index a4975aeedf6b..e3be7c0c2e35 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -605,6 +605,28 @@ void *xas_create(struct xa_state *xas)
 }
 EXPORT_SYMBOL_GPL(xas_create);
 
+/**
+ * xas_create_range() - Ensure that stores to this range will succeed
+ * @xas: XArray operation state.
+ * @max: The highest index to create a slot for.
+ *
+ * Creates all of the slots in the range between the current position of
+ * @xas and @max.  This is for the benefit of users who have not yet been
+ * converted to multi-index entries.
+ *
+ * The implementation is naive.
+ */
+void xas_create_range(struct xa_state *xas, unsigned long max)
+{
+   XA_STATE(tmp, xas->xa, xas->xa_index);
+
+   do {
+   xas_create();
+   xas_set(, tmp.xa_index + XA_CHUNK_SIZE);
+   } while (tmp.xa_index < max);
+}
+EXPORT_SYMBOL_GPL(xas_create_range);
+
 static void store_siblings(struct xa_state *xas,
void *entry, int *countp, int *valuesp)
 {
-- 
2.15.1

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[PATCH v5 23/78] ida: Convert to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Use the xarray infrstructure like we used the radix tree infrastructure.
This lets us get rid of idr_get_free() from the radix tree code.

Signed-off-by: Matthew Wilcox 
---
 include/linux/idr.h|   8 +-
 include/linux/radix-tree.h |   4 -
 lib/idr.c  | 320 ++---
 lib/radix-tree.c   | 126 --
 4 files changed, 187 insertions(+), 271 deletions(-)

diff --git a/include/linux/idr.h b/include/linux/idr.h
index 08a3f5900d53..17d7a673a93c 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -231,11 +231,11 @@ struct ida_bitmap {
 DECLARE_PER_CPU(struct ida_bitmap *, ida_bitmap);
 
 struct ida {
-   struct radix_tree_root  ida_rt;
+   struct xarray   ida_xa;
 };
 
 #define IDA_INIT(name) {   \
-   .ida_rt = RADIX_TREE_INIT(name, IDR_INIT_FLAGS | GFP_NOWAIT),   \
+   .ida_xa = __XARRAY_INIT(name.ida_xa, IDR_INIT_FLAGS)\
 }
 #define DEFINE_IDA(name)   struct ida name = IDA_INIT(name)
 
@@ -250,7 +250,7 @@ void ida_simple_remove(struct ida *ida, unsigned int id);
 
 static inline void ida_init(struct ida *ida)
 {
-   INIT_RADIX_TREE(>ida_rt, IDR_INIT_FLAGS | GFP_NOWAIT);
+   __xa_init(>ida_xa, IDR_INIT_FLAGS);
 }
 
 /**
@@ -267,6 +267,6 @@ static inline int ida_get_new(struct ida *ida, int *p_id)
 
 static inline bool ida_is_empty(const struct ida *ida)
 {
-   return radix_tree_empty(>ida_rt);
+   return xa_empty(>ida_xa);
 }
 #endif /* _LINUX_IDR_H */
diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 64b7eff74278..232f2603b0ed 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -301,10 +301,6 @@ int radix_tree_split(struct radix_tree_root *, unsigned 
long index,
 int radix_tree_join(struct radix_tree_root *, unsigned long index,
unsigned new_order, void *);
 
-void __rcu **idr_get_free(struct radix_tree_root *root,
- struct radix_tree_iter *iter, gfp_t gfp,
- unsigned long max);
-
 enum {
RADIX_TREE_ITER_TAG_MASK = 0x0f,/* tag index in lower nybble */
RADIX_TREE_ITER_TAGGED   = 0x10,/* lookup tagged slots */
diff --git a/lib/idr.c b/lib/idr.c
index a383a1c5767b..096a55b26eea 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -13,7 +13,6 @@
 #include 
 
 DEFINE_PER_CPU(struct ida_bitmap *, ida_bitmap);
-static DEFINE_SPINLOCK(simple_ida_lock);
 
 /* In radix-tree.c temporarily */
 extern bool idr_nomem(struct xa_state *, gfp_t);
@@ -337,26 +336,23 @@ EXPORT_SYMBOL_GPL(idr_replace);
 /*
  * Developer's notes:
  *
- * The IDA uses the functionality provided by the IDR & radix tree to store
- * bitmaps in each entry.  The XA_FREE_TAG tag means there is at least one bit
- * free, unlike the IDR where it means at least one entry is free.
- *
- * I considered telling the radix tree that each slot is an order-10 node
- * and storing the bit numbers in the radix tree, but the radix tree can't
- * allow a single multiorder entry at index 0, which would significantly
- * increase memory consumption for the IDA.  So instead we divide the index
- * by the number of bits in the leaf bitmap before doing a radix tree lookup.
- *
- * As an optimisation, if there are only a few low bits set in any given
- * leaf, instead of allocating a 128-byte bitmap, we store the bits
+ * The IDA uses the functionality provided by the IDR & XArray to store
+ * bitmaps in each entry.  The XA_FREE_TAG tag is used to mean that there
+ * is at least one bit free, unlike the IDR where it means at least one
+ * array entry is free.
+ *
+ * The XArray supports multi-index entries, so I considered teaching the
+ * XArray that each slot is an order-10 node and indexing the XArray by the
+ * ID.  The XArray has the significant optimisation of storing the first
+ * entry in the struct xarray and avoiding allocating an xa_node.
+ * Unfortunately, it can't do that for multi-order entries.
+ * So instead the XArray index is the ID divided by the number of bits in
+ * the bitmap
+ *
+ * As a further optimisation, if there are only a few low bits set in any
+ * given leaf, instead of allocating a 128-byte bitmap, we store the bits
  * directly in the entry.
  *
- * We allow the radix tree 'exceptional' count to get out of date.  Nothing
- * in the IDA nor the radix tree code checks it.  If it becomes important
- * to maintain an accurate exceptional count, switch the rcu_assign_pointer()
- * calls to radix_tree_iter_replace() which will correct the exceptional
- * count.
- *
  * The IDA always requires a lock to alloc/free.  If we add a 'test_bit'
  * equivalent, it will still need locking.  Going to RCU lookup would require
  * using RCU to free bitmaps, and that's not trivial without embedding an
@@ -366,104 +362,114 @@ EXPORT_SYMBOL_GPL(idr_replace);
 
 

[PATCH v5 66/78] dax: Fix sparse warning

[Matthew Wilcox]

From: Matthew Wilcox 

sparse doesn't know that follow_pte_pmd conditionally acquires the ptl,
so add an annotation to let it know what's going on.

Signed-off-by: Matthew Wilcox 
---
 fs/dax.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/dax.c b/fs/dax.c
index f591ab5be590..6ef727af30f0 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -531,6 +531,7 @@ static void dax_mapping_entry_mkclean(struct address_space 
*mapping,
 */
if (follow_pte_pmd(vma->vm_mm, address, , , , 
, ))
continue;
+   __acquire(ptl); /* Conditionally acquired above */
 
/*
 * No need to call mmu_notifier_invalidate_range() as we are
-- 
2.15.1

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[PATCH v5 04/78] page cache: Use xa_lock

[Matthew Wilcox]

From: Matthew Wilcox 

Remove the address_space ->tree_lock and use the xa_lock newly added to
the radix_tree_root.  Rename the address_space ->page_tree to ->pages,
since we don't really care that it's a tree.  Take the opportunity to
rearrange the elements of address_space to pack them better on 64-bit,
and make the comments more useful.

Signed-off-by: Matthew Wilcox 
---
 Documentation/cgroup-v1/memory.txt  |   2 +-
 Documentation/vm/page_migration |  14 +--
 arch/arm/include/asm/cacheflush.h   |   6 +-
 arch/nios2/include/asm/cacheflush.h |   6 +-
 arch/parisc/include/asm/cacheflush.h|   6 +-
 drivers/staging/lustre/lustre/llite/glimpse.c   |   2 +-
 drivers/staging/lustre/lustre/mdc/mdc_request.c |   8 +-
 fs/afs/write.c  |   9 +-
 fs/btrfs/compression.c  |   2 +-
 fs/btrfs/extent_io.c|  16 ++--
 fs/btrfs/inode.c|   2 +-
 fs/buffer.c |  13 ++-
 fs/cifs/file.c  |   9 +-
 fs/dax.c| 115 
 fs/f2fs/data.c  |   6 +-
 fs/f2fs/dir.c   |   6 +-
 fs/f2fs/inline.c|   6 +-
 fs/f2fs/node.c  |   8 +-
 fs/fs-writeback.c   |  20 ++---
 fs/inode.c  |  11 ++-
 fs/nilfs2/btnode.c  |  20 ++---
 fs/nilfs2/page.c|  22 ++---
 include/linux/backing-dev.h |  12 +--
 include/linux/fs.h  |  17 ++--
 include/linux/mm.h  |   2 +-
 include/linux/pagemap.h |   4 +-
 include/linux/xarray.h  |  11 +--
 mm/filemap.c|  84 +
 mm/huge_memory.c|  10 +--
 mm/khugepaged.c |  49 +-
 mm/memcontrol.c |   4 +-
 mm/migrate.c|  32 +++
 mm/page-writeback.c |  42 -
 mm/readahead.c  |   2 +-
 mm/rmap.c   |   4 +-
 mm/shmem.c  |  60 ++---
 mm/swap_state.c |  17 ++--
 mm/truncate.c   |  22 ++---
 mm/vmscan.c |  12 +--
 mm/workingset.c |  22 ++---
 40 files changed, 341 insertions(+), 374 deletions(-)

diff --git a/Documentation/cgroup-v1/memory.txt 
b/Documentation/cgroup-v1/memory.txt
index cefb63639070..f0ba3fc6f2d8 100644
--- a/Documentation/cgroup-v1/memory.txt
+++ b/Documentation/cgroup-v1/memory.txt
@@ -262,7 +262,7 @@ When oom event notifier is registered, event will be 
delivered.
 2.6 Locking
 
lock_page_cgroup()/unlock_page_cgroup() should not be called under
-   mapping->tree_lock.
+   the mapping's xa_lock.
 
Other lock order is following:
PG_locked.
diff --git a/Documentation/vm/page_migration b/Documentation/vm/page_migration
index 0478ae2ad44a..faf849596a85 100644
--- a/Documentation/vm/page_migration
+++ b/Documentation/vm/page_migration
@@ -90,7 +90,7 @@ Steps:
 
 1. Lock the page to be migrated
 
-2. Insure that writeback is complete.
+2. Ensure that writeback is complete.
 
 3. Lock the new page that we want to move to. It is locked so that accesses to
this (not yet uptodate) page immediately lock while the move is in progress.
@@ -100,8 +100,8 @@ Steps:
mapcount is not zero then we do not migrate the page. All user space
processes that attempt to access the page will now wait on the page lock.
 
-5. The radix tree lock is taken. This will cause all processes trying
-   to access the page via the mapping to block on the radix tree spinlock.
+5. The address space xa_lock is taken. This will cause all processes trying
+   to access the page via the mapping to block on the spinlock.
 
 6. The refcount of the page is examined and we back out if references remain
otherwise we know that we are the only one referencing this page.
@@ -114,12 +114,12 @@ Steps:
 
 9. The radix tree is changed to point to the new page.
 
-10. The reference count of the old page is dropped because the radix tree
+10. The reference count of the old page is dropped because the address space
 reference is gone. A reference to the new page is established because
-the new page is referenced to by the radix tree.
+the new page is referenced by the address space.
 
-11. The radix tree lock is dropped. With that lookups in the mapping
-

[PATCH v5 61/78] dax: Convert __dax_invalidate_mapping_entry to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Simple now that we already have an xa_state!

Signed-off-by: Matthew Wilcox 
---
 fs/dax.c | 10 +-
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 2629ffa70575..d3894c15609a 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -413,24 +413,24 @@ static int __dax_invalidate_mapping_entry(struct 
address_space *mapping,
XA_STATE(xas, >pages, index);
int ret = 0;
void *entry;
-   struct radix_tree_root *pages = >pages;
 
xa_lock_irq(>pages);
entry = get_unlocked_mapping_entry();
if (!entry || WARN_ON_ONCE(!xa_is_value(entry)))
goto out;
if (!trunc &&
-   (radix_tree_tag_get(pages, index, PAGECACHE_TAG_DIRTY) ||
-radix_tree_tag_get(pages, index, PAGECACHE_TAG_TOWRITE)))
+   (xas_get_tag(, PAGECACHE_TAG_DIRTY) ||
+xas_get_tag(, PAGECACHE_TAG_TOWRITE)))
goto out;
-   radix_tree_delete(pages, index);
+   xas_store(, NULL);
mapping->nrexceptional--;
ret = 1;
 out:
put_unlocked_mapping_entry(, entry);
-   xa_unlock_irq(>pages);
+   xas_unlock_irq();
return ret;
 }
+
 /*
  * Delete DAX entry at @index from @mapping.  Wait for it
  * to be unlocked before deleting it.
-- 
2.15.1

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[PATCH v5 71/78] xfs: Convert m_perag_tree to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Getting rid of the m_perag_lock lets us also get rid of the call to
radix_tree_preload().  This is a relatively naive conversion; we could
improve performance over the radix tree implementation by passing around
xa_state pointers instead of indices, possibly at the expense of extending
rcu_read_lock() periods.

Signed-off-by: Matthew Wilcox 
---
 fs/xfs/libxfs/xfs_sb.c |  9 -
 fs/xfs/xfs_icache.c| 35 +--
 fs/xfs/xfs_icache.h|  6 +++---
 fs/xfs/xfs_mount.c | 19 ---
 fs/xfs/xfs_mount.h |  3 +--
 5 files changed, 21 insertions(+), 51 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 9b5aae2bcc0b..3b0b65eb8224 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -59,7 +59,7 @@ xfs_perag_get(
int ref = 0;
 
rcu_read_lock();
-   pag = radix_tree_lookup(>m_perag_tree, agno);
+   pag = xa_load(>m_perag_xa, agno);
if (pag) {
ASSERT(atomic_read(>pag_ref) >= 0);
ref = atomic_inc_return(>pag_ref);
@@ -78,14 +78,13 @@ xfs_perag_get_tag(
xfs_agnumber_t  first,
int tag)
 {
+   XA_STATE(xas, >m_perag_xa, first);
struct xfs_perag*pag;
-   int found;
int ref;
 
rcu_read_lock();
-   found = radix_tree_gang_lookup_tag(>m_perag_tree,
-   (void **), first, 1, tag);
-   if (found <= 0) {
+   pag = xas_find_tag(, ULONG_MAX, tag);
+   if (!pag) {
rcu_read_unlock();
return NULL;
}
diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index 43005fbe8b1e..f56e500d89e2 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -156,13 +156,10 @@ static void
 xfs_reclaim_work_queue(
struct xfs_mount*mp)
 {
-
-   rcu_read_lock();
-   if (radix_tree_tagged(>m_perag_tree, XFS_ICI_RECLAIM_TAG)) {
+   if (xa_tagged(>m_perag_xa, XFS_ICI_RECLAIM_TAG)) {
queue_delayed_work(mp->m_reclaim_workqueue, >m_reclaim_work,
msecs_to_jiffies(xfs_syncd_centisecs / 6 * 10));
}
-   rcu_read_unlock();
 }
 
 /*
@@ -194,10 +191,7 @@ xfs_perag_set_reclaim_tag(
return;
 
/* propagate the reclaim tag up into the perag radix tree */
-   spin_lock(>m_perag_lock);
-   radix_tree_tag_set(>m_perag_tree, pag->pag_agno,
-  XFS_ICI_RECLAIM_TAG);
-   spin_unlock(>m_perag_lock);
+   xa_set_tag(>m_perag_xa, pag->pag_agno, XFS_ICI_RECLAIM_TAG);
 
/* schedule periodic background inode reclaim */
xfs_reclaim_work_queue(mp);
@@ -216,10 +210,7 @@ xfs_perag_clear_reclaim_tag(
return;
 
/* clear the reclaim tag from the perag radix tree */
-   spin_lock(>m_perag_lock);
-   radix_tree_tag_clear(>m_perag_tree, pag->pag_agno,
-XFS_ICI_RECLAIM_TAG);
-   spin_unlock(>m_perag_lock);
+   xa_clear_tag(>m_perag_xa, pag->pag_agno, XFS_ICI_RECLAIM_TAG);
trace_xfs_perag_clear_reclaim(mp, pag->pag_agno, -1, _RET_IP_);
 }
 
@@ -847,12 +838,10 @@ void
 xfs_queue_eofblocks(
struct xfs_mount *mp)
 {
-   rcu_read_lock();
-   if (radix_tree_tagged(>m_perag_tree, XFS_ICI_EOFBLOCKS_TAG))
+   if (xa_tagged(>m_perag_xa, XFS_ICI_EOFBLOCKS_TAG))
queue_delayed_work(mp->m_eofblocks_workqueue,
   >m_eofblocks_work,
   msecs_to_jiffies(xfs_eofb_secs * 1000));
-   rcu_read_unlock();
 }
 
 void
@@ -874,12 +863,10 @@ STATIC void
 xfs_queue_cowblocks(
struct xfs_mount *mp)
 {
-   rcu_read_lock();
-   if (radix_tree_tagged(>m_perag_tree, XFS_ICI_COWBLOCKS_TAG))
+   if (xa_tagged(>m_perag_xa, XFS_ICI_COWBLOCKS_TAG))
queue_delayed_work(mp->m_eofblocks_workqueue,
   >m_cowblocks_work,
   msecs_to_jiffies(xfs_cowb_secs * 1000));
-   rcu_read_unlock();
 }
 
 void
@@ -1542,7 +1529,7 @@ __xfs_inode_set_eofblocks_tag(
void(*execute)(struct xfs_mount *mp),
void(*set_tp)(struct xfs_mount *mp, xfs_agnumber_t agno,
  int error, unsigned long caller_ip),
-   int tag)
+   xa_tag_ttag)
 {
struct xfs_mount *mp = ip->i_mount;
struct xfs_perag *pag;
@@ -1566,11 +1553,9 @@ __xfs_inode_set_eofblocks_tag(
   XFS_INO_TO_AGINO(ip->i_mount, ip->i_ino), tag);
if (!tagged) {
/* propagate the eofblocks tag up into the perag radix tree */
-   spin_lock(>i_mount->m_perag_lock);
-   radix_tree_tag_set(>i_mount->m_perag_tree,
+  

[PATCH v5 73/78] xfs: Convert xfs dquot to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

This is a pretty straight-forward conversion.

Signed-off-by: Matthew Wilcox 
---
 fs/xfs/xfs_dquot.c | 38 +-
 fs/xfs/xfs_qm.c| 32 
 fs/xfs/xfs_qm.h| 18 +-
 3 files changed, 46 insertions(+), 42 deletions(-)

diff --git a/fs/xfs/xfs_dquot.c b/fs/xfs/xfs_dquot.c
index e2a466df5dd1..c6832db23ca8 100644
--- a/fs/xfs/xfs_dquot.c
+++ b/fs/xfs/xfs_dquot.c
@@ -44,7 +44,7 @@
  * Lock order:
  *
  * ip->i_lock
- *   qi->qi_tree_lock
+ *   qi->qi_xa_lock
  * dquot->q_qlock (xfs_dqlock() and friends)
  *   dquot->q_flush (xfs_dqflock() and friends)
  *   qi->qi_lru_lock
@@ -752,8 +752,8 @@ xfs_qm_dqget(
xfs_dquot_t **O_dqpp) /* OUT : locked incore dquot */
 {
struct xfs_quotainfo*qi = mp->m_quotainfo;
-   struct radix_tree_root *tree = xfs_dquot_tree(qi, type);
-   struct xfs_dquot*dqp;
+   struct xarray   *xa = xfs_dquot_xa(qi, type);
+   struct xfs_dquot*dqp, *duplicate;
int error;
 
ASSERT(XFS_IS_QUOTA_RUNNING(mp));
@@ -772,23 +772,24 @@ xfs_qm_dqget(
}
 
 restart:
-   mutex_lock(>qi_tree_lock);
-   dqp = radix_tree_lookup(tree, id);
+   mutex_lock(>qi_xa_lock);
+   dqp = xa_load(xa, id);
+found:
if (dqp) {
xfs_dqlock(dqp);
if (dqp->dq_flags & XFS_DQ_FREEING) {
xfs_dqunlock(dqp);
-   mutex_unlock(>qi_tree_lock);
+   mutex_unlock(>qi_xa_lock);
trace_xfs_dqget_freeing(dqp);
delay(1);
goto restart;
}
 
-   /* uninit / unused quota found in radix tree, keep looking  */
+   /* uninit / unused quota found, keep looking  */
if (flags & XFS_QMOPT_DQNEXT) {
if (XFS_IS_DQUOT_UNINITIALIZED(dqp)) {
xfs_dqunlock(dqp);
-   mutex_unlock(>qi_tree_lock);
+   mutex_unlock(>qi_xa_lock);
error = xfs_dq_get_next_id(mp, type, );
if (error)
return error;
@@ -797,14 +798,14 @@ xfs_qm_dqget(
}
 
dqp->q_nrefs++;
-   mutex_unlock(>qi_tree_lock);
+   mutex_unlock(>qi_xa_lock);
 
trace_xfs_dqget_hit(dqp);
XFS_STATS_INC(mp, xs_qm_dqcachehits);
*O_dqpp = dqp;
return 0;
}
-   mutex_unlock(>qi_tree_lock);
+   mutex_unlock(>qi_xa_lock);
XFS_STATS_INC(mp, xs_qm_dqcachemisses);
 
/*
@@ -854,20 +855,23 @@ xfs_qm_dqget(
}
}
 
-   mutex_lock(>qi_tree_lock);
-   error = radix_tree_insert(tree, id, dqp);
-   if (unlikely(error)) {
-   WARN_ON(error != -EEXIST);
+   mutex_lock(>qi_xa_lock);
+   duplicate = xa_cmpxchg(xa, id, NULL, dqp, GFP_NOFS);
+   if (unlikely(duplicate)) {
+   if (xa_is_err(duplicate)) {
+   mutex_unlock(>qi_xa_lock);
+   return xa_err(duplicate);
+   }
 
/*
 * Duplicate found. Just throw away the new dquot and start
 * over.
 */
-   mutex_unlock(>qi_tree_lock);
trace_xfs_dqget_dup(dqp);
xfs_qm_dqdestroy(dqp);
XFS_STATS_INC(mp, xs_qm_dquot_dups);
-   goto restart;
+   dqp = duplicate;
+   goto found;
}
 
/*
@@ -877,7 +881,7 @@ xfs_qm_dqget(
dqp->q_nrefs = 1;
 
qi->qi_dquots++;
-   mutex_unlock(>qi_tree_lock);
+   mutex_unlock(>qi_xa_lock);
 
/* If we are asked to find next active id, keep looking */
if (flags & XFS_QMOPT_DQNEXT) {
diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index ec952dfad359..c8bc3be157e0 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -67,7 +67,7 @@ xfs_qm_dquot_walk(
void*data)
 {
struct xfs_quotainfo*qi = mp->m_quotainfo;
-   struct radix_tree_root  *tree = xfs_dquot_tree(qi, type);
+   struct xarray   *xa = xfs_dquot_xa(qi, type);
uint32_tnext_index;
int last_error = 0;
int skipped;
@@ -83,11 +83,11 @@ xfs_qm_dquot_walk(
int error = 0;
int i;
 
-   mutex_lock(>qi_tree_lock);
-   nr_found = radix_tree_gang_lookup(tree, (void **)batch,
-   next_index, XFS_DQ_LOOKUP_BATCH);
+   mutex_lock(>qi_xa_lock);
+   nr_found = 

[PATCH v5 65/78] dax: Convert grab_mapping_entry to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Signed-off-by: Matthew Wilcox 
---
 fs/dax.c | 98 +---
 1 file changed, 26 insertions(+), 72 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index a3e795ad2493..f591ab5be590 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -44,6 +44,7 @@
 
 /* The 'colour' (ie low bits) within a PMD of a page offset.  */
 #define PG_PMD_COLOUR  ((PMD_SIZE >> PAGE_SHIFT) - 1)
+#define PMD_ORDER  (PMD_SHIFT - PAGE_SHIFT)
 
 static wait_queue_head_t wait_table[DAX_WAIT_TABLE_ENTRIES];
 
@@ -89,10 +90,10 @@ static void *dax_radix_locked_entry(sector_t sector, 
unsigned long flags)
DAX_ENTRY_LOCK);
 }
 
-static unsigned int dax_radix_order(void *entry)
+static unsigned int dax_entry_order(void *entry)
 {
if (xa_to_value(entry) & DAX_PMD)
-   return PMD_SHIFT - PAGE_SHIFT;
+   return PMD_ORDER;
return 0;
 }
 
@@ -299,10 +300,11 @@ static void *grab_mapping_entry(struct address_space 
*mapping, pgoff_t index,
 {
XA_STATE(xas, >pages, index);
bool pmd_downgrade = false; /* splitting 2MiB entry into 4k entries? */
-   void *entry, **slot;
+   void *entry;
 
+   xas_set_order(, index, size_flag ? PMD_ORDER : 0);
 restart:
-   xa_lock_irq(>pages);
+   xas_lock_irq();
entry = get_unlocked_mapping_entry();
 
if (WARN_ON_ONCE(entry && !xa_is_value(entry))) {
@@ -326,84 +328,36 @@ static void *grab_mapping_entry(struct address_space 
*mapping, pgoff_t index,
}
}
 
-   /* No entry for given index? Make sure radix tree is big enough. */
-   if (!entry || pmd_downgrade) {
-   int err;
-
-   if (pmd_downgrade) {
-   /*
-* Make sure 'entry' remains valid while we drop
-* xa_lock.
-*/
-   entry = lock_slot();
-   }
-
-   xa_unlock_irq(>pages);
+   if (pmd_downgrade) {
+   entry = lock_slot();
/*
 * Besides huge zero pages the only other thing that gets
 * downgraded are empty entries which don't need to be
 * unmapped.
 */
-   if (pmd_downgrade && dax_is_zero_entry(entry))
+   if (dax_is_zero_entry(entry)) {
+   xas_pause();
+   xas_unlock_irq();
unmap_mapping_range(mapping,
(index << PAGE_SHIFT) & PMD_MASK, PMD_SIZE, 0);
-
-   err = radix_tree_preload(
-   mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM);
-   if (err) {
-   if (pmd_downgrade)
-   put_locked_mapping_entry(mapping, index);
-   return ERR_PTR(err);
+   xas_lock_irq();
}
-   xa_lock_irq(>pages);
-
-   if (!entry) {
-   /*
-* We needed to drop the pages lock while calling
-* radix_tree_preload() and we didn't have an entry to
-* lock.  See if another thread inserted an entry at
-* our index during this time.
-*/
-   entry = __radix_tree_lookup(>pages, index,
-   NULL, );
-   if (entry) {
-   radix_tree_preload_end();
-   xa_unlock_irq(>pages);
-   goto restart;
-   }
-   }
-
-   if (pmd_downgrade) {
-   radix_tree_delete(>pages, index);
-   mapping->nrexceptional--;
-   dax_wake_entry(, entry, true);
-   }
-
+   xas_store(, NULL);
+   mapping->nrexceptional--;
+   dax_wake_entry(, entry, true);
+   }
+   if (!entry || pmd_downgrade) {
entry = dax_radix_locked_entry(0, size_flag | DAX_EMPTY);
-
-   err = __radix_tree_insert(>pages, index,
-   dax_radix_order(entry), entry);
-   radix_tree_preload_end();
-   if (err) {
-   xa_unlock_irq(>pages);
-   /*
-* Our insertion of a DAX entry failed, most likely
-* because we were inserting a PMD entry and it
-* collided with a PTE sized entry at a different
-* index in the PMD range.  We haven't inserted
-* anything into the radix tree and have no waiters to
-* wake.
-*/
-   

[PATCH v5 37/78] mm: Convert page migration to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Signed-off-by: Matthew Wilcox 
---
 mm/migrate.c | 41 -
 1 file changed, 16 insertions(+), 25 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 75d19904dd9a..7122fec9b075 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -322,7 +322,7 @@ void __migration_entry_wait(struct mm_struct *mm, pte_t 
*ptep,
page = migration_entry_to_page(entry);
 
/*
-* Once radix-tree replacement of page migration started, page_count
+* Once page cache replacement of page migration started, page_count
 * *must* be zero. And, we don't want to call wait_on_page_locked()
 * against a page without get_page().
 * So, we use get_page_unless_zero(), here. Even failed, page fault
@@ -437,10 +437,10 @@ int migrate_page_move_mapping(struct address_space 
*mapping,
struct buffer_head *head, enum migrate_mode mode,
int extra_count)
 {
+   XA_STATE(xas, >pages, page_index(page));
struct zone *oldzone, *newzone;
int dirty;
int expected_count = 1 + extra_count;
-   void **pslot;
 
/*
 * Device public or private pages have an extra refcount as they are
@@ -466,21 +466,16 @@ int migrate_page_move_mapping(struct address_space 
*mapping,
oldzone = page_zone(page);
newzone = page_zone(newpage);
 
-   xa_lock_irq(>pages);
-
-   pslot = radix_tree_lookup_slot(>pages,
-   page_index(page));
+   xas_lock_irq();
 
expected_count += 1 + page_has_private(page);
-   if (page_count(page) != expected_count ||
-   radix_tree_deref_slot_protected(pslot,
-   >pages.xa_lock) != page) {
-   xa_unlock_irq(>pages);
+   if (page_count(page) != expected_count || xas_load() != page) {
+   xas_unlock_irq();
return -EAGAIN;
}
 
if (!page_ref_freeze(page, expected_count)) {
-   xa_unlock_irq(>pages);
+   xas_unlock_irq();
return -EAGAIN;
}
 
@@ -494,7 +489,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
if (mode == MIGRATE_ASYNC && head &&
!buffer_migrate_lock_buffers(head, mode)) {
page_ref_unfreeze(page, expected_count);
-   xa_unlock_irq(>pages);
+   xas_unlock_irq();
return -EAGAIN;
}
 
@@ -522,7 +517,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
SetPageDirty(newpage);
}
 
-   radix_tree_replace_slot(>pages, pslot, newpage);
+   xas_store(, newpage);
 
/*
 * Drop cache reference from old page by unfreezing
@@ -531,7 +526,7 @@ int migrate_page_move_mapping(struct address_space *mapping,
 */
page_ref_unfreeze(page, expected_count - 1);
 
-   xa_unlock(>pages);
+   xas_unlock();
/* Leave irq disabled to prevent preemption while updating stats */
 
/*
@@ -571,22 +566,18 @@ EXPORT_SYMBOL(migrate_page_move_mapping);
 int migrate_huge_page_move_mapping(struct address_space *mapping,
   struct page *newpage, struct page *page)
 {
+   XA_STATE(xas, >pages, page_index(page));
int expected_count;
-   void **pslot;
-
-   xa_lock_irq(>pages);
-
-   pslot = radix_tree_lookup_slot(>pages, page_index(page));
 
+   xas_lock_irq();
expected_count = 2 + page_has_private(page);
-   if (page_count(page) != expected_count ||
-   radix_tree_deref_slot_protected(pslot, >pages.xa_lock) 
!= page) {
-   xa_unlock_irq(>pages);
+   if (page_count(page) != expected_count || xas_load() != page) {
+   xas_unlock_irq();
return -EAGAIN;
}
 
if (!page_ref_freeze(page, expected_count)) {
-   xa_unlock_irq(>pages);
+   xas_unlock_irq();
return -EAGAIN;
}
 
@@ -595,11 +586,11 @@ int migrate_huge_page_move_mapping(struct address_space 
*mapping,
 
get_page(newpage);
 
-   radix_tree_replace_slot(>pages, pslot, newpage);
+   xas_store(, newpage);
 
page_ref_unfreeze(page, expected_count - 1);
 
-   xa_unlock_irq(>pages);
+   xas_unlock_irq();
 
return MIGRATEPAGE_SUCCESS;
 }
-- 
2.15.1

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[PATCH v5 52/78] btrfs: Convert page cache to XArray

[Matthew Wilcox]

From: Matthew Wilcox 

Signed-off-by: Matthew Wilcox 
---
 fs/btrfs/compression.c | 4 +---
 fs/btrfs/extent_io.c   | 6 ++
 2 files changed, 3 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index e687d06cd97c..4174b166e235 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -449,9 +449,7 @@ static noinline int add_ra_bio_pages(struct inode *inode,
if (pg_index > end_index)
break;
 
-   rcu_read_lock();
-   page = radix_tree_lookup(>pages, pg_index);
-   rcu_read_unlock();
+   page = xa_load(>pages, pg_index);
if (page && !xa_is_value(page)) {
misses++;
if (misses > 4)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 4301cbf4e31f..fd5e9d887328 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -5197,11 +5197,9 @@ void clear_extent_buffer_dirty(struct extent_buffer *eb)
 
clear_page_dirty_for_io(page);
xa_lock_irq(>mapping->pages);
-   if (!PageDirty(page)) {
-   radix_tree_tag_clear(>mapping->pages,
-   page_index(page),
+   if (!PageDirty(page))
+   __xa_clear_tag(>mapping->pages, page_index(page),
PAGECACHE_TAG_DIRTY);
-   }
xa_unlock_irq(>mapping->pages);
ClearPageError(page);
unlock_page(page);
-- 
2.15.1

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[PATCH] Btrfs: allow btrfs_defrag_file() uncompress files on defragmentation

[Timofey Titovets]

Currently defrag ioctl only support compress files with specified
compression type. Allow set compression type to none, while call defrag.

Signed-off-by: Timofey Titovets 
---
 fs/btrfs/btrfs_inode.h |  1 +
 fs/btrfs/inode.c   |  4 ++--
 fs/btrfs/ioctl.c   | 17 ++---
 3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 63f0ccc92a71..9eb0c92ee4b4 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -187,6 +187,7 @@ struct btrfs_inode {
 * different from prop_compress and takes precedence if set
 */
unsigned defrag_compress;
+   unsigned change_compress;
 
struct btrfs_delayed_node *delayed_node;
 
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 46df5e2a64e7..7af8f1784788 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -412,8 +412,8 @@ static inline int inode_need_compress(struct inode *inode, 
u64 start, u64 end)
if (btrfs_test_opt(fs_info, FORCE_COMPRESS))
return 1;
/* defrag ioctl */
-   if (BTRFS_I(inode)->defrag_compress)
-   return 1;
+   if (BTRFS_I(inode)->change_compress)
+   return BTRFS_I(inode)->defrag_compress;
/* bad compression ratios */
if (BTRFS_I(inode)->flags & BTRFS_INODE_NOCOMPRESS)
return 0;
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 12d4fa5d6dec..b777c8f53153 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1276,7 +1276,7 @@ int btrfs_defrag_file(struct inode *inode, struct file 
*file,
unsigned long cluster = max_cluster;
u64 new_align = ~((u64)SZ_128K - 1);
struct page **pages = NULL;
-   bool do_compress = range->flags & BTRFS_DEFRAG_RANGE_COMPRESS;
+   bool change_compress = range->flags & BTRFS_DEFRAG_RANGE_COMPRESS;
 
if (isize == 0)
return 0;
@@ -1284,11 +1284,10 @@ int btrfs_defrag_file(struct inode *inode, struct file 
*file,
if (range->start >= isize)
return -EINVAL;
 
-   if (do_compress) {
+   if (change_compress) {
if (range->compress_type > BTRFS_COMPRESS_TYPES)
return -EINVAL;
-   if (range->compress_type)
-   compress_type = range->compress_type;
+   compress_type = range->compress_type;
}
 
if (extent_thresh == 0)
@@ -1363,7 +1362,7 @@ int btrfs_defrag_file(struct inode *inode, struct file 
*file,
 
if (!should_defrag_range(inode, (u64)i << PAGE_SHIFT,
 extent_thresh, _len, ,
-_end, do_compress,
+_end, change_compress,
 compress_type)){
unsigned long next;
/*
@@ -1392,8 +1391,11 @@ int btrfs_defrag_file(struct inode *inode, struct file 
*file,
}
 
inode_lock(inode);
-   if (do_compress)
+   if (change_compress) {
+   BTRFS_I(inode)->change_compress = change_compress;
BTRFS_I(inode)->defrag_compress = compress_type;
+   }
+
ret = cluster_pages_for_defrag(inode, pages, i, cluster);
if (ret < 0) {
inode_unlock(inode);
@@ -1449,8 +1451,9 @@ int btrfs_defrag_file(struct inode *inode, struct file 
*file,
ret = defrag_count;
 
 out_ra:
-   if (do_compress) {
+   if (change_compress) {
inode_lock(inode);
+   BTRFS_I(inode)->change_compress = 0;
BTRFS_I(inode)->defrag_compress = BTRFS_COMPRESS_NONE;
inode_unlock(inode);
}
-- 
2.15.1

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Re: [PATCH v10 3/5] bpf: add a bpf_override_function helper

[Daniel Borkmann]

On 12/15/2017 09:34 PM, Alexei Starovoitov wrote:
[...]
> Also how big is the v9-v10 change ?
> May be do it as separate patch, since previous set already sitting
> in bpf-next and there are patches on top?

+1
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Re: [PATCH v10 3/5] bpf: add a bpf_override_function helper

[Alexei Starovoitov]

On 12/15/17 11:12 AM, Josef Bacik wrote:

+#ifdef CONFIG_BPF_KPROBE_OVERRIDE
+BPF_CALL_2(bpf_override_return, struct pt_regs *, regs, unsigned long, rc)
+{
+   __this_cpu_write(bpf_kprobe_override, 1);
+   regs_set_return_value(regs, rc);
+   arch_ftrace_kprobe_override_function(regs);
+   return 0;
+}


since you're doing a respin can you adopt the change I did to make
this helper fail at load time if that #config is not set
instead of runtime?

Also how big is the v9-v10 change ?
May be do it as separate patch, since previous set already sitting
in bpf-next and there are patches on top?

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[PATCH] btrfs: fix refcount_t usage when deleting btrfs_delayed_nodes

[Chris Mason]

refcounts have a generic implementation and an asm optimized one.  The
generic version has extra debugging to make sure that once a refcount
goes to zero, refcount_inc won't increase it.

The btrfs delayed inode code wasn't expecting this, and we're tripping
over the warnings when the generic refcounts are used.  We ended up with
this race:

Process A Process B
  btrfs_get_delayed_node()
  spin_lock(root->inode_lock)
  radix_tree_lookup()
__btrfs_release_delayed_node()
refcount_dec_and_test(_node->refs)
our refcount is now zero
  refcount_add(2) <---
  warning here, refcount
  unchanged

spin_lock(root->inode_lock)
radix_tree_delete()

With the generic refcounts, we actually warn again when process B above
tries to release his refcount because refcount_add() turned into a
no-op.

We saw this in production on older kernels without the asm optimized
refcounts.

The fix used here is to use refcount_inc_not_zero() to detect when the
object is in the middle of being freed and return NULL.  This is almost
always the right answer anyway, since we usually end up pitching the
delayed_node if it didn't have fresh data in it.

This also changes __btrfs_release_delayed_node() to remove the extra
check for zero refcounts before radix tree deletion.
btrfs_get_delayed_node() was the only path that was allowing refcounts
to go from zero to one.

Signed-off-by: Chris Mason 
Fixes: 6de5f18e7b0da
cc:  #4.12+
---
 fs/btrfs/delayed-inode.c | 45 ++---
 1 file changed, 34 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index 5d73f79..84c54af 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -87,6 +87,7 @@ static struct btrfs_delayed_node *btrfs_get_delayed_node(
 
spin_lock(>inode_lock);
node = radix_tree_lookup(>delayed_nodes_tree, ino);
+
if (node) {
if (btrfs_inode->delayed_node) {
refcount_inc(>refs);  /* can be accessed */
@@ -94,9 +95,30 @@ static struct btrfs_delayed_node *btrfs_get_delayed_node(
spin_unlock(>inode_lock);
return node;
}
-   btrfs_inode->delayed_node = node;
-   /* can be accessed and cached in the inode */
-   refcount_add(2, >refs);
+
+   /* it's possible that we're racing into the middle of
+* removing this node from the radix tree.  In this case,
+* the refcount was zero and it should never go back
+* to one.  Just return NULL like it was never in the radix
+* at all; our release function is in the process of removing
+* it.
+*
+* Some implementations of refcount_inc refuse to
+* bump the refcount once it has hit zero.  If we don't do
+* this dance here, refcount_inc() may decide to
+* just WARN_ONCE() instead of actually bumping the refcount.
+*
+* If this node is properly in the radix, we want to
+* bump the refcount twice, once for the inode
+* and once for this get operation.
+*/
+   if (refcount_inc_not_zero(>refs)) {
+   refcount_inc(>refs);
+   btrfs_inode->delayed_node = node;
+   } else {
+   node = NULL;
+   }
+
spin_unlock(>inode_lock);
return node;
}
@@ -254,17 +276,18 @@ static void __btrfs_release_delayed_node(
mutex_unlock(_node->mutex);
 
if (refcount_dec_and_test(_node->refs)) {
-   bool free = false;
struct btrfs_root *root = delayed_node->root;
+
spin_lock(>inode_lock);
-   if (refcount_read(_node->refs) == 0) {
-   radix_tree_delete(>delayed_nodes_tree,
- delayed_node->inode_id);
-   free = true;
-   }
+   /*
+* once our refcount goes to zero, nobody is allowed to
+* bump it back up.  We can delete it now
+*/
+   ASSERT(refcount_read(_node->refs) == 0);
+   radix_tree_delete(>delayed_nodes_tree,
+ delayed_node->inode_id);
spin_unlock(>inode_lock);
-   if (free)
-   kmem_cache_free(delayed_node_cache, delayed_node);
+   

Re: [PATCH] fs/*/Kconfig: drop links to 404-compliant http://acl.bestbits.at

[Steve French]

Acked-by: Steve French 

On Tue, Dec 12, 2017 at 11:38 PM, Adam Borowski  wrote:
> This link is replicated in most filesystems' config stanzas.  Referring
> to an archived version of that site is pointless as it mostly deals with
> patches; user documentation is available elsewhere.
>
> Signed-off-by: Adam Borowski 
> ---
> Sending this as one piece; if you guys would instead prefer this chopped
> into tiny per-filesystem bits, please say so.
>
>
>  Documentation/filesystems/ext2.txt |  2 --
>  Documentation/filesystems/ext4.txt |  7 +++
>  fs/9p/Kconfig  |  3 ---
>  fs/Kconfig |  6 +-
>  fs/btrfs/Kconfig   |  3 ---
>  fs/ceph/Kconfig|  3 ---
>  fs/cifs/Kconfig| 15 +++
>  fs/ext2/Kconfig|  6 +-
>  fs/ext4/Kconfig|  3 ---
>  fs/f2fs/Kconfig|  6 +-
>  fs/hfsplus/Kconfig |  3 ---
>  fs/jffs2/Kconfig   |  6 +-
>  fs/jfs/Kconfig |  3 ---
>  fs/reiserfs/Kconfig|  6 +-
>  fs/xfs/Kconfig |  3 ---
>  15 files changed, 15 insertions(+), 60 deletions(-)
>
> diff --git a/Documentation/filesystems/ext2.txt 
> b/Documentation/filesystems/ext2.txt
> index 55755395d3dc..81c0becab225 100644
> --- a/Documentation/filesystems/ext2.txt
> +++ b/Documentation/filesystems/ext2.txt
> @@ -49,12 +49,10 @@ sb=nUse alternate 
> superblock at this location.
>
>  user_xattr Enable "user." POSIX Extended Attributes
> (requires CONFIG_EXT2_FS_XATTR).
> -   See also http://acl.bestbits.at
>  nouser_xattr   Don't support "user." extended attributes.
>
>  aclEnable POSIX Access Control Lists support
> (requires CONFIG_EXT2_FS_POSIX_ACL).
> -   See also http://acl.bestbits.at
>  noacl  Don't support POSIX ACLs.
>
>  nobh   Do not attach buffer_heads to file pagecache.
> diff --git a/Documentation/filesystems/ext4.txt 
> b/Documentation/filesystems/ext4.txt
> index 75236c0c2ac2..8cd63e16f171 100644
> --- a/Documentation/filesystems/ext4.txt
> +++ b/Documentation/filesystems/ext4.txt
> @@ -202,15 +202,14 @@ inode_readahead_blks=nThis tuning parameter 
> controls the maximum
> the buffer cache.  The default value is 32 blocks.
>
>  nouser_xattr   Disables Extended User Attributes.  See the
> -   attr(5) manual page and http://acl.bestbits.at/
> -   for more information about extended attributes.
> +   attr(5) manual page for more information about
> +   extended attributes.
>
>  noacl  This option disables POSIX Access Control List
> support. If ACL support is enabled in the kernel
> configuration (CONFIG_EXT4_FS_POSIX_ACL), ACL is
> enabled by default on mount. See the acl(5) manual
> -   page and http://acl.bestbits.at/ for more information
> -   about acl.
> +   page for more information about acl.
>
>  bsddf  (*) Make 'df' act like BSD.
>  minixdfMake 'df' act like Minix.
> diff --git a/fs/9p/Kconfig b/fs/9p/Kconfig
> index 6489e1fc1afd..11045d8e356a 100644
> --- a/fs/9p/Kconfig
> +++ b/fs/9p/Kconfig
> @@ -25,9 +25,6 @@ config 9P_FS_POSIX_ACL
>   POSIX Access Control Lists (ACLs) support permissions for users and
>   groups beyond the owner/group/world scheme.
>
> - To learn more about Access Control Lists, visit the POSIX ACLs for
> - Linux website .
> -
>   If you don't know what Access Control Lists are, say N
>
>  endif
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 7aee6d699fd6..0ed56752f208 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -167,17 +167,13 @@ config TMPFS_POSIX_ACL
>   files for sound to work properly.  In short, if you're not sure,
>   say Y.
>
> - To learn more about Access Control Lists, visit the POSIX ACLs for
> - Linux website .
> -
>  config TMPFS_XATTR
> bool "Tmpfs extended attributes"
> depends on TMPFS
> default n
> help
>   Extended attributes are name:value pairs associated with inodes by
> - the kernel or by users (see the attr(5) manual page, or visit
> -  for details).
> + the kernel or by users (see the attr(5) manual page for details).
>
>   Currently this enables support for the trusted.* and

Re: [PATCH] Btrfs: make should_defrag_range() understood compressed extents

[Timofey Titovets]

Also,
in theory that break following case:
When fs mounted with compress=no, you can uncompress data by btrfs fi
def -vr , because of "bug" in logic/defaults.
And man page show that btrfs "Currently it’s not possible to select no
compression. See also section EXAMPLES."

I have a two simple patches that can provide a way (one to btrfs-progs
and one to btrfs.ko),
to uncompress data on fs mounted with compress=no, by run btrfs fi def
-vrcnone 
But behavior on fs mounted with compress, will be recompress data with
selected by "compress" algo,
because of inode_need_compression() logic.

In theory that also must be fixed.


2017-12-14 16:37 GMT+03:00 Timofey Titovets :
> Compile tested and "battle" tested
>
> 2017-12-14 16:35 GMT+03:00 Timofey Titovets :
>> Both, defrag ioctl and autodefrag - call btrfs_defrag_file()
>> for file defragmentation.
>>
>> Kernel target extent size default is 256KiB
>> Btrfs progs by default, use 32MiB.
>>
>> Both bigger then max (not fragmented) compressed extent size 128KiB.
>> That lead to rewrite all compressed data on disk.
>>
>> Fix that and also make should_defrag_range() understood
>> if requested target compression are same as current extent compression type.
>> To avoid useless recompression of compressed extents.
>>
>> Signed-off-by: Timofey Titovets 
>> ---
>>  fs/btrfs/ioctl.c | 28 +---
>>  1 file changed, 25 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>> index be5bd81b3669..12d4fa5d6dec 100644
>> --- a/fs/btrfs/ioctl.c
>> +++ b/fs/btrfs/ioctl.c
>> @@ -1008,7 +1008,7 @@ static bool defrag_check_next_extent(struct inode 
>> *inode, struct extent_map *em)
>>
>>  static int should_defrag_range(struct inode *inode, u64 start, u32 thresh,
>>u64 *last_len, u64 *skip, u64 *defrag_end,
>> -  int compress)
>> +  int compress, int compress_type)
>>  {
>> struct extent_map *em;
>> int ret = 1;
>> @@ -1043,8 +1043,29 @@ static int should_defrag_range(struct inode *inode, 
>> u64 start, u32 thresh,
>>  * real extent, don't bother defragging it
>>  */
>> if (!compress && (*last_len == 0 || *last_len >= thresh) &&
>> -   (em->len >= thresh || (!next_mergeable && !prev_mergeable)))
>> +   (em->len >= thresh || (!next_mergeable && !prev_mergeable))) {
>> ret = 0;
>> +   goto out;
>> +   }
>> +
>> +
>> +   /*
>> +* Try not recompress compressed extents
>> +* thresh >= BTRFS_MAX_UNCOMPRESSED will lead to
>> +* recompress all compressed extents
>> +*/
>> +   if (em->compress_type != 0 && thresh >= BTRFS_MAX_UNCOMPRESSED) {
>> +   if (!compress) {
>> +   if (em->len == BTRFS_MAX_UNCOMPRESSED)
>> +   ret = 0;
>> +   } else {
>> +   if (em->compress_type != compress_type)
>> +   goto out;
>> +   if (em->len == BTRFS_MAX_UNCOMPRESSED)
>> +   ret = 0;
>> +   }
>> +   }
>> +
>>  out:
>> /*
>>  * last_len ends up being a counter of how many bytes we've 
>> defragged.
>> @@ -1342,7 +1363,8 @@ int btrfs_defrag_file(struct inode *inode, struct file 
>> *file,
>>
>> if (!should_defrag_range(inode, (u64)i << PAGE_SHIFT,
>>  extent_thresh, _len, ,
>> -_end, do_compress)){
>> +_end, do_compress,
>> +compress_type)){
>> unsigned long next;
>> /*
>>  * the should_defrag function tells us how much to 
>> skip
>> --
>> 2.15.1
>>
>
>
>
> --
> Have a nice day,
> Timofey.



-- 
Have a nice day,
Timofey.
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[PATCH v10 1/5] add infrastructure for tagging functions as error injectable

[Josef Bacik]

From: Josef Bacik 

Using BPF we can override kprob'ed functions and return arbitrary
values.  Obviously this can be a bit unsafe, so make this feature opt-in
for functions.  Simply tag a function with KPROBE_ERROR_INJECT_SYMBOL in
order to give BPF access to that function for error injection purposes.

Signed-off-by: Josef Bacik 
Acked-by: Ingo Molnar 
---
 include/asm-generic/vmlinux.lds.h |  10 +++
 include/linux/bpf.h   |  11 +++
 include/linux/kprobes.h   |   1 +
 include/linux/module.h|   5 ++
 kernel/kprobes.c  | 163 ++
 kernel/module.c   |   6 +-
 6 files changed, 195 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/vmlinux.lds.h 
b/include/asm-generic/vmlinux.lds.h
index ee8b707d9fa9..a2e8582d094a 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -136,6 +136,15 @@
 #define KPROBE_BLACKLIST()
 #endif
 
+#ifdef CONFIG_BPF_KPROBE_OVERRIDE
+#define ERROR_INJECT_LIST(). = ALIGN(8);   
\
+   
VMLINUX_SYMBOL(__start_kprobe_error_inject_list) = .;   \
+   KEEP(*(_kprobe_error_inject_list))  
\
+   VMLINUX_SYMBOL(__stop_kprobe_error_inject_list) 
= .;
+#else
+#define ERROR_INJECT_LIST()
+#endif
+
 #ifdef CONFIG_EVENT_TRACING
 #define FTRACE_EVENTS(). = ALIGN(8);   
\
VMLINUX_SYMBOL(__start_ftrace_events) = .;  \
@@ -564,6 +573,7 @@
FTRACE_EVENTS() \
TRACE_SYSCALLS()\
KPROBE_BLACKLIST()  \
+   ERROR_INJECT_LIST() \
MEM_DISCARD(init.rodata)\
CLK_OF_TABLES() \
RESERVEDMEM_OF_TABLES() \
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index e55e4255a210..7f4d2a953173 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -576,4 +576,15 @@ extern const struct bpf_func_proto 
bpf_sock_map_update_proto;
 void bpf_user_rnd_init_once(void);
 u64 bpf_user_rnd_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
 
+#if defined(__KERNEL__) && !defined(__ASSEMBLY__)
+#ifdef CONFIG_BPF_KPROBE_OVERRIDE
+#define BPF_ALLOW_ERROR_INJECTION(fname)   \
+static unsigned long __used\
+   __attribute__((__section__("_kprobe_error_inject_list")))   \
+   _eil_addr_##fname = (unsigned long)fname;
+#else
+#define BPF_ALLOW_ERROR_INJECTION(fname)
+#endif
+#endif
+
 #endif /* _LINUX_BPF_H */
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 9440a2fc8893..963fd364f3d6 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -271,6 +271,7 @@ extern bool arch_kprobe_on_func_entry(unsigned long offset);
 extern bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, 
unsigned long offset);
 
 extern bool within_kprobe_blacklist(unsigned long addr);
+extern bool within_kprobe_error_injection_list(unsigned long addr);
 
 struct kprobe_insn_cache {
struct mutex mutex;
diff --git a/include/linux/module.h b/include/linux/module.h
index c69b49abe877..548fa09fa806 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -475,6 +475,11 @@ struct module {
ctor_fn_t *ctors;
unsigned int num_ctors;
 #endif
+
+#ifdef CONFIG_BPF_KPROBE_OVERRIDE
+   unsigned int num_kprobe_ei_funcs;
+   unsigned long *kprobe_ei_funcs;
+#endif
 } cacheline_aligned __randomize_layout;
 #ifndef MODULE_ARCH_INIT
 #define MODULE_ARCH_INIT {}
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index da2ccf142358..b4aab48ad258 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -83,6 +83,16 @@ static raw_spinlock_t *kretprobe_table_lock_ptr(unsigned 
long hash)
return &(kretprobe_table_locks[hash].lock);
 }
 
+/* List of symbols that can be overriden for error injection. */
+static LIST_HEAD(kprobe_error_injection_list);
+static DEFINE_MUTEX(kprobe_ei_mutex);
+struct kprobe_ei_entry {
+   struct list_head list;
+   unsigned long start_addr;
+   unsigned long end_addr;
+   void *priv;
+};
+
 /* Blacklist -- list of struct kprobe_blacklist_entry */
 static LIST_HEAD(kprobe_blacklist);
 
@@ -1394,6 +1404,17 @@ bool within_kprobe_blacklist(unsigned long addr)
return false;
 }
 
+bool within_kprobe_error_injection_list(unsigned long addr)
+{
+   struct kprobe_ei_entry *ent;
+
+   list_for_each_entry(ent, _error_injection_list, list) {
+   if (addr >= ent->start_addr && addr < 

[PATCH v10 0/5] Add the ability to do BPF directed error injection

[Josef Bacik]

Just one last go around I hope, fixed the preemption thing that Darrick
reported.

v9->v10:
- the kprobe dispather now requires us to re-enable preemption if we change the
  ip ourselves, so do that.

v8->v9:
- rebased onto the bpf tree.

v7->v8:
- removed the _ASM_KPROBE_ERROR_INJECT since it was not needed.

v6->v7:
- moved the opt-in macro to bpf.h out of kprobes.h.

v5->v6:
- add BPF_ALLOW_ERROR_INJECTION() tagging for functions that will support this
  feature.  This way only functions that opt-in will be allowed to be
  overridden.
- added a btrfs patch to allow error injection for open_ctree() so that the bpf
  sample actually works.

v4->v5:
- disallow kprobe_override programs from being put in the prog map array so we
  don't tail call into something we didn't check.  This allows us to make the
  normal path still fast without a bunch of percpu operations.

v3->v4:
- fix a build error found by kbuild test bot (I didn't wait long enough
  apparently.)
- Added a warning message as per Daniels suggestion.

v2->v3:
- added a ->kprobe_override flag to bpf_prog.
- added some sanity checks to disallow attaching bpf progs that have
  ->kprobe_override set that aren't for ftrace kprobes.
- added the trace_kprobe_ftrace helper to check if the trace_event_call is a
  ftrace kprobe.
- renamed bpf_kprobe_state to bpf_kprobe_override, fixed it so we only read this
  value in the kprobe path, and thus only write to it if we're overriding or
  clearing the override.

v1->v2:
- moved things around to make sure that bpf_override_return could really only be
  used for an ftrace kprobe.
- killed the special return values from trace_call_bpf.
- renamed pc_modified to bpf_kprobe_state so bpf_override_return could tell if
  it was being called from an ftrace kprobe context.
- reworked the logic in kprobe_perf_func to take advantage of bpf_kprobe_state.
- updated the test as per Alexei's review.

- Original message -

A lot of our error paths are not well tested because we have no good way of
injecting errors generically.  Some subystems (block, memory) have ways to
inject errors, but they are random so it's hard to get reproduceable results.

With BPF we can add determinism to our error injection.  We can use kprobes and
other things to verify we are injecting errors at the exact case we are trying
to test.  This patch gives us the tool to actual do the error injection part.
It is very simple, we just set the return value of the pt_regs we're given to
whatever we provide, and then override the PC with a dummy function that simply
returns.

Right now this only works on x86, but it would be simple enough to expand to
other architectures.  Thanks,

Josef
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[PATCH v10 5/5] btrfs: allow us to inject errors at io_ctl_init

[Josef Bacik]

From: Josef Bacik 

This was instrumental in reproducing a space cache bug.

Signed-off-by: Josef Bacik 
Acked-by: Ingo Molnar 
---
 fs/btrfs/free-space-cache.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 4426d1c73e50..fb1382893bfc 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -22,6 +22,7 @@
 #include 
 #include 
 #include 
+#include 
 #include "ctree.h"
 #include "free-space-cache.h"
 #include "transaction.h"
@@ -332,6 +333,7 @@ static int io_ctl_init(struct btrfs_io_ctl *io_ctl, struct 
inode *inode,
 
return 0;
 }
+BPF_ALLOW_ERROR_INJECTION(io_ctl_init);
 
 static void io_ctl_free(struct btrfs_io_ctl *io_ctl)
 {
-- 
2.7.5

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[PATCH v10 4/5] samples/bpf: add a test for bpf_override_return

[Josef Bacik]

From: Josef Bacik 

This adds a basic test for bpf_override_return to verify it works.  We
override the main function for mounting a btrfs fs so it'll return
-ENOMEM and then make sure that trying to mount a btrfs fs will fail.

Acked-by: Alexei Starovoitov 
Acked-by: Ingo Molnar 
Signed-off-by: Josef Bacik 
---
 samples/bpf/Makefile  |  4 
 samples/bpf/test_override_return.sh   | 15 +++
 samples/bpf/tracex7_kern.c| 16 
 samples/bpf/tracex7_user.c| 28 
 tools/include/uapi/linux/bpf.h|  7 ++-
 tools/testing/selftests/bpf/bpf_helpers.h |  3 ++-
 6 files changed, 71 insertions(+), 2 deletions(-)
 create mode 100755 samples/bpf/test_override_return.sh
 create mode 100644 samples/bpf/tracex7_kern.c
 create mode 100644 samples/bpf/tracex7_user.c

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index adeaa1302f34..4fb944a7ecf8 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -12,6 +12,7 @@ hostprogs-y += tracex3
 hostprogs-y += tracex4
 hostprogs-y += tracex5
 hostprogs-y += tracex6
+hostprogs-y += tracex7
 hostprogs-y += test_probe_write_user
 hostprogs-y += trace_output
 hostprogs-y += lathist
@@ -58,6 +59,7 @@ tracex3-objs := bpf_load.o $(LIBBPF) tracex3_user.o
 tracex4-objs := bpf_load.o $(LIBBPF) tracex4_user.o
 tracex5-objs := bpf_load.o $(LIBBPF) tracex5_user.o
 tracex6-objs := bpf_load.o $(LIBBPF) tracex6_user.o
+tracex7-objs := bpf_load.o $(LIBBPF) tracex7_user.o
 load_sock_ops-objs := bpf_load.o $(LIBBPF) load_sock_ops.o
 test_probe_write_user-objs := bpf_load.o $(LIBBPF) test_probe_write_user_user.o
 trace_output-objs := bpf_load.o $(LIBBPF) trace_output_user.o
@@ -101,6 +103,7 @@ always += tracex3_kern.o
 always += tracex4_kern.o
 always += tracex5_kern.o
 always += tracex6_kern.o
+always += tracex7_kern.o
 always += sock_flags_kern.o
 always += test_probe_write_user_kern.o
 always += trace_output_kern.o
@@ -155,6 +158,7 @@ HOSTLOADLIBES_tracex3 += -lelf
 HOSTLOADLIBES_tracex4 += -lelf -lrt
 HOSTLOADLIBES_tracex5 += -lelf
 HOSTLOADLIBES_tracex6 += -lelf
+HOSTLOADLIBES_tracex7 += -lelf
 HOSTLOADLIBES_test_cgrp2_sock2 += -lelf
 HOSTLOADLIBES_load_sock_ops += -lelf
 HOSTLOADLIBES_test_probe_write_user += -lelf
diff --git a/samples/bpf/test_override_return.sh 
b/samples/bpf/test_override_return.sh
new file mode 100755
index ..e68b9ee6814b
--- /dev/null
+++ b/samples/bpf/test_override_return.sh
@@ -0,0 +1,15 @@
+#!/bin/bash
+
+rm -f testfile.img
+dd if=/dev/zero of=testfile.img bs=1M seek=1000 count=1
+DEVICE=$(losetup --show -f testfile.img)
+mkfs.btrfs -f $DEVICE
+mkdir tmpmnt
+./tracex7 $DEVICE
+if [ $? -eq 0 ]
+then
+   echo "SUCCESS!"
+else
+   echo "FAILED!"
+fi
+losetup -d $DEVICE
diff --git a/samples/bpf/tracex7_kern.c b/samples/bpf/tracex7_kern.c
new file mode 100644
index ..1ab308a43e0f
--- /dev/null
+++ b/samples/bpf/tracex7_kern.c
@@ -0,0 +1,16 @@
+#include 
+#include 
+#include 
+#include "bpf_helpers.h"
+
+SEC("kprobe/open_ctree")
+int bpf_prog1(struct pt_regs *ctx)
+{
+   unsigned long rc = -12;
+
+   bpf_override_return(ctx, rc);
+   return 0;
+}
+
+char _license[] SEC("license") = "GPL";
+u32 _version SEC("version") = LINUX_VERSION_CODE;
diff --git a/samples/bpf/tracex7_user.c b/samples/bpf/tracex7_user.c
new file mode 100644
index ..8a52ac492e8b
--- /dev/null
+++ b/samples/bpf/tracex7_user.c
@@ -0,0 +1,28 @@
+#define _GNU_SOURCE
+
+#include 
+#include 
+#include 
+#include "libbpf.h"
+#include "bpf_load.h"
+
+int main(int argc, char **argv)
+{
+   FILE *f;
+   char filename[256];
+   char command[256];
+   int ret;
+
+   snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+
+   if (load_bpf_file(filename)) {
+   printf("%s", bpf_log_buf);
+   return 1;
+   }
+
+   snprintf(command, 256, "mount %s tmpmnt/", argv[1]);
+   f = popen(command, "r");
+   ret = pclose(f);
+
+   return ret ? 0 : 1;
+}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 4c223ab30293..cf446c25c0ec 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -677,6 +677,10 @@ union bpf_attr {
  * @buf: buf to fill
  * @buf_size: size of the buf
  * Return : 0 on success or negative error code
+ *
+ * int bpf_override_return(pt_regs, rc)
+ * @pt_regs: pointer to struct pt_regs
+ * @rc: the return value to set
  */
 #define __BPF_FUNC_MAPPER(FN)  \
FN(unspec), \
@@ -736,7 +740,8 @@ union bpf_attr {
FN(xdp_adjust_meta),\
FN(perf_event_read_value),  \
FN(perf_prog_read_value),   \
-   FN(getsockopt),
+   FN(getsockopt), \
+   FN(override_return),
 
 /* integer value in 'imm' field of BPF_CALL 

[PATCH v10 2/5] btrfs: make open_ctree error injectable

[Josef Bacik]

From: Josef Bacik 

This allows us to do error injection with BPF for open_ctree.

Signed-off-by: Josef Bacik 
Acked-by: Ingo Molnar 
---
 fs/btrfs/disk-io.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 10a2a579cc7f..02b5f5667754 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -30,6 +30,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 #include "ctree.h"
 #include "disk-io.h"
@@ -3123,6 +3124,7 @@ int open_ctree(struct super_block *sb,
goto fail_block_groups;
goto retry_root_backup;
 }
+BPF_ALLOW_ERROR_INJECTION(open_ctree);
 
 static void btrfs_end_buffer_write_sync(struct buffer_head *bh, int uptodate)
 {
-- 
2.7.5

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[PATCH v10 3/5] bpf: add a bpf_override_function helper

[Josef Bacik]

From: Josef Bacik 

Error injection is sloppy and very ad-hoc.  BPF could fill this niche
perfectly with it's kprobe functionality.  We could make sure errors are
only triggered in specific call chains that we care about with very
specific situations.  Accomplish this with the bpf_override_funciton
helper.  This will modify the probe'd callers return value to the
specified value and set the PC to an override function that simply
returns, bypassing the originally probed function.  This gives us a nice
clean way to implement systematic error injection for all of our code
paths.

Acked-by: Alexei Starovoitov 
Acked-by: Ingo Molnar 
Signed-off-by: Josef Bacik 
---
 arch/Kconfig |  3 ++
 arch/x86/Kconfig |  1 +
 arch/x86/include/asm/kprobes.h   |  4 +++
 arch/x86/include/asm/ptrace.h|  5 
 arch/x86/kernel/kprobes/ftrace.c | 14 +
 include/linux/filter.h   |  3 +-
 include/linux/trace_events.h |  1 +
 include/uapi/linux/bpf.h |  7 -
 kernel/bpf/core.c|  3 ++
 kernel/bpf/verifier.c|  2 ++
 kernel/events/core.c |  7 +
 kernel/trace/Kconfig | 11 +++
 kernel/trace/bpf_trace.c | 38 
 kernel/trace/trace_kprobe.c  | 64 +++-
 kernel/trace/trace_probe.h   | 12 
 15 files changed, 165 insertions(+), 10 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 400b9e1b2f27..d3f4aaf9cb7a 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -196,6 +196,9 @@ config HAVE_OPTPROBES
 config HAVE_KPROBES_ON_FTRACE
bool
 
+config HAVE_KPROBE_OVERRIDE
+   bool
+
 config HAVE_NMI
bool
 
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 8eed3f94bfc7..04d66e6fa447 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -154,6 +154,7 @@ config X86
select HAVE_KERNEL_XZ
select HAVE_KPROBES
select HAVE_KPROBES_ON_FTRACE
+   select HAVE_KPROBE_OVERRIDE
select HAVE_KRETPROBES
select HAVE_KVM
select HAVE_LIVEPATCH   if X86_64
diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h
index 9f2e3102e0bb..36abb23a7a35 100644
--- a/arch/x86/include/asm/kprobes.h
+++ b/arch/x86/include/asm/kprobes.h
@@ -67,6 +67,10 @@ extern const int kretprobe_blacklist_size;
 void arch_remove_kprobe(struct kprobe *p);
 asmlinkage void kretprobe_trampoline(void);
 
+#ifdef CONFIG_KPROBES_ON_FTRACE
+extern void arch_ftrace_kprobe_override_function(struct pt_regs *regs);
+#endif
+
 /* Architecture specific copy of original instruction*/
 struct arch_specific_insn {
/* copy of the original instruction */
diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index 14131dd06b29..6de1fd3d0097 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -109,6 +109,11 @@ static inline unsigned long regs_return_value(struct 
pt_regs *regs)
return regs->ax;
 }
 
+static inline void regs_set_return_value(struct pt_regs *regs, unsigned long 
rc)
+{
+   regs->ax = rc;
+}
+
 /*
  * user_mode(regs) determines whether a register set came from user
  * mode.  On x86_32, this is true if V8086 mode was enabled OR if the
diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c
index 8dc0161cec8f..1ea748d682fd 100644
--- a/arch/x86/kernel/kprobes/ftrace.c
+++ b/arch/x86/kernel/kprobes/ftrace.c
@@ -97,3 +97,17 @@ int arch_prepare_kprobe_ftrace(struct kprobe *p)
p->ainsn.boostable = false;
return 0;
 }
+
+asmlinkage void override_func(void);
+asm(
+   ".type override_func, @function\n"
+   "override_func:\n"
+   "   ret\n"
+   ".size override_func, .-override_func\n"
+);
+
+void arch_ftrace_kprobe_override_function(struct pt_regs *regs)
+{
+   regs->ip = (unsigned long)_func;
+}
+NOKPROBE_SYMBOL(arch_ftrace_kprobe_override_function);
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 0062302e1285..5feb441d3dd9 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -458,7 +458,8 @@ struct bpf_prog {
locked:1,   /* Program image locked? */
gpl_compatible:1, /* Is filter GPL compatible? 
*/
cb_access:1,/* Is control block accessed? */
-   dst_needed:1;   /* Do we need dst entry? */
+   dst_needed:1,   /* Do we need dst entry? */
+   kprobe_override:1; /* Do we override a kprobe? 
*/
enum bpf_prog_type  type;   /* Type of BPF program */
u32 len;/* Number of filter blocks */
u32 jited_len;  /* Size of jited insns in bytes 
*/
diff --git a/include/linux/trace_events.h