[ 17/39] Btrfs: fix lock leak when resuming snapshot deletion

From: Greg Kroah-Hartman
Date: Fri Aug 02 2013 - 06:18:26 EST

3.4-stable review patch. If anyone has any objections, please let me know.


From: Josef Bacik <jbacik@xxxxxxxxxxxx>

commit fec386ac1428f9c0e672df952cbca5cebd4e4e2f upstream.

We aren't setting path->locks[level] when we resume a snapshot deletion which
means we won't unlock the buffer when we free the path. This causes deadlocks
if we happen to re-allocate the block before we've evicted the extent buffer
from cache. Thanks,

Reported-by: Alex Lyakas <alex.btrfs@xxxxxxxxxxxxxxxxx>
Signed-off-by: Josef Bacik <jbacik@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

fs/btrfs/extent-tree.c | 2 ++
1 file changed, 2 insertions(+)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -6903,6 +6903,7 @@ int btrfs_drop_snapshot(struct btrfs_roo
while (1) {
+ path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;

ret = btrfs_lookup_extent_info(trans, root,
@@ -6919,6 +6920,7 @@ int btrfs_drop_snapshot(struct btrfs_roo

+ path->locks[level] = 0;
WARN_ON(wc->refs[level] != 1);

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