linux-kernel - [54/84] Btrfs: fix lock leak when resuming snapshot deletion

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Message-ID: <lsq.1375276989.243471@decadent.org.uk>
Date:	Wed, 31 Jul 2013 15:23:09 +0200
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Josef Bacik" <jbacik@...ionio.com>,
	"Alex Lyakas" <alex.btrfs@...arastorage.com>
Subject: [54/84] Btrfs: fix lock leak when resuming snapshot deletion

3.2.50-rc1 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: Ben Hutchings <ben@...adent.org.uk>
---
 fs/btrfs/extent-tree.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -6614,6 +6614,7 @@ void btrfs_drop_snapshot(struct btrfs_ro
 		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,
@@ -6627,6 +6628,7 @@ void btrfs_drop_snapshot(struct btrfs_ro
 				break;
 
 			btrfs_tree_unlock(path->nodes[level]);
+			path->locks[level] = 0;
 			WARN_ON(wc->refs[level] != 1);
 			level--;
 		}

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