Btrfs: fix lock leak when resuming snapshot deletion

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,

Cc: stable@vger.kernel.org
Reported-by: Alex Lyakas <alex.btrfs@zadarastorage.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index a429704dd95f..e814b1312511 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -7523,6 +7523,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
                 while (1) {
                         btrfs_tree_lock(path->nodes[level]);
                         btrfs_set_lock_blocking(path->nodes[level]);
+                        path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
 
                         ret = btrfs_lookup_extent_info(trans, root,
                                                 path->nodes[level]->start,
@@ -7538,6 +7539,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
                                 break;
 
                         btrfs_tree_unlock(path->nodes[level]);
+                        path->locks[level] = 0;
                         WARN_ON(wc->refs[level] != 1);
                         level--;
                 }