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| author | Qu Wenruo <quwenruo@cn.fujitsu.com> | 2014-08-20 16:10:15 +0800 |
|---|---|---|
| committer | Chris Mason <clm@fb.com> | 2014-09-17 13:38:22 -0700 |
| commit | 12b894cb288d57292b01cf158177b6d5c89a6272 (patch) | |
| tree | 42716fe99beca6af385745eb575a1c506b5acf5f | |
| parent | a583c02664eea8796e80dd192a3bcc1d521939e5 (diff) | |
| download | op-kernel-dev-12b894cb288d57292b01cf158177b6d5c89a6272.zip op-kernel-dev-12b894cb288d57292b01cf158177b6d5c89a6272.tar.gz | |
btrfs: Fix a deadlock in btrfs_dev_replace_finishing()
btrfs-transacion:5657
[stack snip]
btrfs_bio_map()
btrfs_bio_counter_inc_blocked()
percpu_counter_inc(&fs_info->bio_counter) ###bio_counter > 0(A)
__btrfs_bio_map()
btrfs_dev_replace_lock()
mutex_lock(dev_replace->lock) ###wait mutex(B)
btrfs:32612
[stack snip]
btrfs_dev_replace_start()
btrfs_dev_replace_lock()
mutex_lock(dev_replace->lock) ###hold mutex(B)
btrfs_dev_replace_finishing()
btrfs_rm_dev_replace_blocked()
wait until percpu_counter_sum == 0 ###wait on bio_counter(A)
This bug can be triggered quite easily by the following test script:
http://pastebin.com/MQmb37Cy
This patch will fix the ABBA problem by calling
btrfs_dev_replace_unlock() before btrfs_rm_dev_replace_blocked().
The consistency of btrfs devices list and their superblocks is protected
by device_list_mutex, not btrfs_dev_replace_lock/unlock().
So it is safe the move btrfs_dev_replace_unlock() before
btrfs_rm_dev_replace_blocked().
Reported-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Cc: Stefan Behrens <sbehrens@giantdisaster.de>
Signed-off-by: Chris Mason <clm@fb.com>
| -rw-r--r-- | fs/btrfs/dev-replace.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index 64657b3..a85b5f5 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -569,6 +569,8 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, btrfs_kobj_rm_device(fs_info, src_device); btrfs_kobj_add_device(fs_info, tgt_device); + btrfs_dev_replace_unlock(dev_replace); + btrfs_rm_dev_replace_blocked(fs_info); btrfs_rm_dev_replace_srcdev(fs_info, src_device); @@ -582,7 +584,6 @@ static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info, * superblock is scratched out so that it is no longer marked to * belong to this filesystem. */ - btrfs_dev_replace_unlock(dev_replace); mutex_unlock(&root->fs_info->fs_devices->device_list_mutex); mutex_unlock(&root->fs_info->chunk_mutex); |
