The following patch:
btrfs: remove empty fs_devices to prevent memory runout
introduces @valid_dev_root aiming at recording @btrfs_device objects that
have corresponding block devices with btrfs.
But if a block device is broken or unplugged, no one tells the
@valid_dev_root to cleanup the "dead" objects.
To recycle the memory occuppied by those "dead"s, we could rely on
the shrinker. The shrinker's scan function will traverse the
@valid_dev_root and trys to open the devices one by one, if it fails
or encounters a non-btrfs it will remove the "dead" @btrfs_device.
A special case to deal with is that a block device is unplugged and
replugged, then it appears with a new @bdev->bd_dev as devnum.
In this case, we should remove the older since we should have a new
one for that block device already.
Signed-off-by: Gui Hecheng <guihc.f...@cn.fujitsu.com>
---
fs/btrfs/super.c | 10 ++++++++
fs/btrfs/volumes.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
fs/btrfs/volumes.h | 4 +++
3 files changed, 87 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 001cba5..022381e 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2017,6 +2017,12 @@ static struct miscdevice btrfs_misc = {
.fops = &btrfs_ctl_fops
};
+static struct shrinker btrfs_valid_dev_shrinker = {
+ .scan_objects = btrfs_valid_dev_scan,
+ .count_objects = btrfs_valid_dev_count,
+ .seeks = DEFAULT_SEEKS,
+};
+
MODULE_ALIAS_MISCDEV(BTRFS_MINOR);
MODULE_ALIAS("devname:btrfs-control");
@@ -2130,6 +2136,8 @@ static int __init init_btrfs_fs(void)
btrfs_init_lockdep();
+ register_shrinker(&btrfs_valid_dev_shrinker);
+
btrfs_print_info();
err = btrfs_run_sanity_tests();
@@ -2143,6 +2151,7 @@ static int __init init_btrfs_fs(void)
return 0;
unregister_ioctl:
+ unregister_shrinker(&btrfs_valid_dev_shrinker);
btrfs_interface_exit();
free_end_io_wq:
btrfs_end_io_wq_exit();
@@ -2183,6 +2192,7 @@ static void __exit exit_btrfs_fs(void)
btrfs_interface_exit();
btrfs_end_io_wq_exit();
unregister_filesystem(&btrfs_fs_type);
+ unregister_shrinker(&btrfs_valid_dev_shrinker);
btrfs_exit_sysfs();
btrfs_cleanup_valid_dev_root();
btrfs_cleanup_fs_uuids();
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 228a7e0..5462557 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -54,6 +54,7 @@ static void btrfs_dev_stat_print_on_load(struct btrfs_device
*device);
DEFINE_MUTEX(uuid_mutex);
static LIST_HEAD(fs_uuids);
static struct rb_root valid_dev_root = RB_ROOT;
+static atomic_long_t unopened_dev_count = ATOMIC_LONG_INIT(0);
static struct btrfs_device *insert_valid_device(struct btrfs_device *new_dev)
{
@@ -130,6 +131,8 @@ static void free_invalid_device(struct btrfs_device
*invalid_dev)
{
struct btrfs_fs_devices *old_fs;
+ atomic_long_dec(&unopened_dev_count);
+
old_fs = invalid_dev->fs_devices;
mutex_lock(&old_fs->device_list_mutex);
list_del(&invalid_dev->dev_list);
@@ -605,6 +608,7 @@ static noinline int device_list_add(const char *path,
list_add_rcu(&device->dev_list, &fs_devices->devices);
fs_devices->num_devices++;
mutex_unlock(&fs_devices->device_list_mutex);
+ atomic_long_inc(&unopened_dev_count);
ret = 1;
device->fs_devices = fs_devices;
@@ -778,6 +782,7 @@ again:
blkdev_put(device->bdev, device->mode);
device->bdev = NULL;
fs_devices->open_devices--;
+ atomic_long_inc(&unopened_dev_count);
}
if (device->writeable) {
list_del_init(&device->dev_alloc_list);
@@ -840,8 +845,10 @@ static int __btrfs_close_devices(struct btrfs_fs_devices
*fs_devices)
struct btrfs_device *new_device;
struct rcu_string *name;
- if (device->bdev)
+ if (device->bdev) {
fs_devices->open_devices--;
+ atomic_long_inc(&unopened_dev_count);
+ }
if (device->writeable &&
device->devid != BTRFS_DEV_REPLACE_DEVID) {
@@ -971,6 +978,7 @@ static int __btrfs_open_devices(struct btrfs_fs_devices
*fs_devices,
fs_devices->rotating = 1;
fs_devices->open_devices++;
+ atomic_long_dec(&unopened_dev_count);
if (device->writeable &&
device->devid != BTRFS_DEV_REPLACE_DEVID) {
fs_devices->rw_devices++;
@@ -6848,3 +6856,67 @@ void btrfs_update_commit_device_bytes_used(struct
btrfs_root *root,
}
unlock_chunks(root);
}
+
+static unsigned long shrink_valid_dev_root(void)
+{
+ struct rb_node *n;
+ struct btrfs_device *device;
+ struct block_device *bdev;
+ struct buffer_head *bh;
+ unsigned long freed = 0;
+ unsigned long possible_deads;
+ int ret = 0;
+ dev_t cur_devnum;
+
+ mutex_lock(&uuid_mutex);
+
+ possible_deads = atomic_long_read(&unopened_dev_count);
+ if (!possible_deads)
+ goto out;
+
+ for (n = rb_first(&valid_dev_root); n ; n = rb_next(n)) {
+ device = rb_entry(n, struct btrfs_device, rb_node);
+
+ if (device->bdev)
+ continue;
+ if (!device->name)
+ continue;
+
+ ret = btrfs_get_bdev_and_sb(device->name->str, FMODE_READ,
+ NULL, 0, &bdev, &bh);
+ /* can't open as btrfs, not valid, drop it */
+ if (ret)
+ goto shrink;
+
+ cur_devnum = bdev->bd_dev;
+
+ brelse(bh);
+ blkdev_put(bdev, FMODE_READ);
+
+ if (device->devnum == cur_devnum)
+ continue;
+ /* bdev->bd_dev changed, not valid, drop it */
+
+shrink:
+ rb_erase(n, &valid_dev_root);
+ free_invalid_device(device);
+
+ freed++;
+ }
+
+out:
+ mutex_unlock(&uuid_mutex);
+ return freed;
+}
+
+unsigned long btrfs_valid_dev_scan(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ return shrink_valid_dev_root();
+}
+
+unsigned long btrfs_valid_dev_count(struct shrinker *shrink,
+ struct shrink_control *sc)
+{
+ return atomic_long_read(&unopened_dev_count);
+}
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 7f5c7ea..49f4fff 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -432,6 +432,10 @@ struct btrfs_device *btrfs_alloc_device(struct
btrfs_fs_info *fs_info,
const u8 *uuid);
int btrfs_rm_device(struct btrfs_root *root, char *device_path);
void btrfs_cleanup_valid_dev_root(void);
+unsigned long btrfs_valid_dev_scan(struct shrinker *shrink,
+ struct shrink_control *sc);
+unsigned long btrfs_valid_dev_count(struct shrinker *shrink,
+ struct shrink_control *sc);
void btrfs_cleanup_fs_uuids(void);
int btrfs_num_copies(struct btrfs_fs_info *fs_info, u64 logical, u64 len);
int btrfs_grow_device(struct btrfs_trans_handle *trans,
--
1.8.1.4
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