linux-kernel - [PATCH 36/75] Btrfs: fix lock leak when resuming snapshot deletion

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Message-Id: <1375209919-1768-3-git-send-email-kamal@canonical.com>
Date:	Tue, 30 Jul 2013 11:44:40 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Josef Bacik <jbacik@...ionio.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 36/75] Btrfs: fix lock leak when resuming snapshot deletion

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

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

From: Josef Bacik <jbacik@...ionio.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@...arastorage.com>
Signed-off-by: Josef Bacik <jbacik@...ionio.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.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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