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

[Kamal Mostafa]

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-3.8.y-queue branch of the 3.8.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-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.6.

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

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From d663606fe70bdf5e2bfb6d536e1e400bf65ce566 Mon Sep 17 00:00:00 2001
From: Josef Bacik <jbacik at fusionio.com>
Date: Mon, 15 Jul 2013 12:41:42 -0400
Subject: 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: Kamal Mostafa <kamal 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 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