diff options
| author | Qu Wenruo <quwenruo@cn.fujitsu.com> | 2014-08-20 16:10:15 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-10-30 09:43:04 -0700 |
| commit | c3caf69f3c53e4bd7da8247717d7b8957825e26b (patch) | |
| tree | 1a3047ee26b0f098a9c3411596025e73ac4cd9dc /fs | |
| parent | fe9133f10ca56e54c5f5075a802bc08e61ad8456 (diff) | |
btrfs: Fix a deadlock in btrfs_dev_replace_finishing()
commit 12b894cb288d57292b01cf158177b6d5c89a6272 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
| -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 eea26e1b2fda..d738ff8ab81c 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -567,6 +567,8 @@ 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); @@ -580,7 +582,6 @@ 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); |