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Subject[PATCH 36/75] Btrfs: fix lock leak when resuming snapshot deletion
Date
3.8.13.6 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Josef Bacik <jbacik@fusionio.com>

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@zadarastorage.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
fs/btrfs/extent-tree.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index d170412..17cfffd 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -7023,6 +7023,7 @@ 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,
@@ -7039,6 +7040,7 @@ 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--;
}
--
1.8.1.2


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