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authorQu Wenruo <quwenruo@cn.fujitsu.com>2014-08-20 16:10:15 +0800
committerChris Mason <clm@fb.com>2014-09-17 13:38:22 -0700
commit12b894cb288d57292b01cf158177b6d5c89a6272 (patch)
tree42716fe99beca6af385745eb575a1c506b5acf5f /fs/btrfs/dev-replace.c
parenta583c02664eea8796e80dd192a3bcc1d521939e5 (diff)
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>
Diffstat (limited to 'fs/btrfs/dev-replace.c')
-rw-r--r--fs/btrfs/dev-replace.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 64657b3ae97a..a85b5f53856e 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);