linux-kernel - [ 39/99] Btrfs: fix lock leak when resuming snapshot deletion

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Date:	Fri,  2 Aug 2013 18:07:52 +0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Alex Lyakas <alex.btrfs@...arastorage.com>,
	Josef Bacik <jbacik@...ionio.com>
Subject: [ 39/99] Btrfs: fix lock leak when resuming snapshot deletion

3.10-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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/btrfs/extent-tree.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -7355,6 +7355,7 @@ int btrfs_drop_snapshot(struct btrfs_roo
 		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,
@@ -7370,6 +7371,7 @@ int btrfs_drop_snapshot(struct btrfs_roo
 				break;
 
 			btrfs_tree_unlock(path->nodes[level]);
+			path->locks[level] = 0;
 			WARN_ON(wc->refs[level] != 1);
 			level--;
 		}


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