[ 3.5.y.z extended stable ] Patch "Btrfs: fix lock leak when resuming snapshot deletion" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    Btrfs: fix lock leak when resuming snapshot deletion

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 003fe9a435000b86c25f8a13bea664685e730768 Mon Sep 17 00:00:00 2001
From: Josef Bacik <jbacik at fusionio.com>
Date: Mon, 15 Jul 2013 12:41:42 -0400
Subject: [PATCH] Btrfs: fix lock leak when resuming snapshot deletion

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 at zadarastorage.com>
Signed-off-by: Josef Bacik <jbacik at fusionio.com>
Signed-off-by: Luis Henriques <luis.henriques at 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 9e99ea0..9b1dc7b 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -6905,6 +6905,7 @@ 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,
@@ -6921,6 +6922,7 @@ 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