On 07/07/2014 12:22, Miao Xie wrote:
On Mon, 7 Jul 2014 12:04:09 +0800, Anand Jain wrote:
when one of the device path is missing btrfs_device name is null. So this
patch will check for that.
stack:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
IP: [<ffffffff812e18c0>] strlen+0x0/0x30
[<ffffffffa01cd92a>] ? clone_fs_devices+0xaa/0x160 [btrfs]
[<ffffffffa01cdcf7>] btrfs_init_new_device+0x317/0xca0 [btrfs]
[<ffffffff81155bca>] ? __kmalloc_track_caller+0x15a/0x1a0
[<ffffffffa01d6473>] btrfs_ioctl+0xaa3/0x2860 [btrfs]
[<ffffffff81132a6c>] ? handle_mm_fault+0x48c/0x9c0
[<ffffffff81192a61>] ? __blkdev_put+0x171/0x180
[<ffffffff817a784c>] ? __do_page_fault+0x4ac/0x590
[<ffffffff81193426>] ? blkdev_put+0x106/0x110
[<ffffffff81179175>] ? mntput+0x35/0x40
[<ffffffff8116d4b0>] do_vfs_ioctl+0x460/0x4a0
[<ffffffff8115c72e>] ? ____fput+0xe/0x10
[<ffffffff81068033>] ? task_work_run+0xb3/0xd0
[<ffffffff8116d547>] SyS_ioctl+0x57/0x90
[<ffffffff817a793e>] ? do_page_fault+0xe/0x10
[<ffffffff817abe52>] system_call_fastpath+0x16/0x1b
reproducer:
mkfs.btrfs -draid1 -mraid1 /dev/sdg1 /dev/sdg2
btrfstune -S 1 /dev/sdg1
modprobe -r btrfs && modprobe btrfs
mount -o degraded /dev/sdg1 /btrfs
btrfs dev add /dev/sdg3 /btrfs
Signed-off-by: Anand Jain <anand.j...@oracle.com>
Signed-off-by: Miao Xie <mi...@cn.fujitsu.com>
---
Changelog v1->v2:
- Fix the problem that we forgot to set the missing flag for the cloned device
---
fs/btrfs/volumes.c | 25 ++++++++++++++++---------
1 file changed, 16 insertions(+), 9 deletions(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 1891541..4731bd6 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -598,16 +598,23 @@ static struct btrfs_fs_devices *clone_fs_devices(struct
btrfs_fs_devices *orig)
if (IS_ERR(device))
goto error;
- /*
- * This is ok to do without rcu read locked because we hold the
- * uuid mutex so nothing we touch in here is going to disappear.
- */
- name = rcu_string_strdup(orig_dev->name->str, GFP_NOFS);
- if (!name) {
- kfree(device);
- goto error;
+ if (orig_dev->missing) {
+ device->missing = 1;
+ fs_devices->missing_devices++;
as mentioned in some places we just check name (for missing device)
and don't set the missing flag so it better to ..
if (orig_dev->missing || !orig_dev->name) {
device->missing = 1;
fs_devices->missing_devices++;
I don't think we need check name pointer here because only missing device
doesn't have its own name. Or there is something wrong in the code, so
I add assert in else branch. Am I right?
At few critical code, the below and I guess in the chunk/strips
function as well, we don't make use of missing flag, but rather
->name.
-----
btrfsic_process_superblock
::
if (!device->bdev || !device->name)
continue;
-----
But here without !orig_dev->name check, is also good enough.
Thanks, Anand
+ } else {
+ ASSERT(orig_dev->name);
+ /*
+ * This is ok to do without rcu read locked because
+ * we hold the uuid mutex so nothing we touch in here
+ * is going to disappear.
+ */
+ name = rcu_string_strdup(orig_dev->name->str, GFP_NOFS);
+ if (!name) {
+ kfree(device);
+ goto error;
+ }
+ rcu_assign_pointer(device->name, name);
}
- rcu_assign_pointer(device->name, name);
list_add(&device->dev_list, &fs_devices->devices);
device->fs_devices = fs_devices;
Thanks, Anand
.
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