From b8551182cba09339e98c3d72c51b76e1483ee48c Mon Sep 17 00:00:00 2001
From: Glauber Costa <glommer@parallels.com>
Date: Wed, 20 Feb 2013 13:14:47 +1100
Subject: [PATCH] memcg: avoid dangling reference count in creation failure.

When use_hierarchy is enabled, we acquire an extra reference count in our
parent during cgroup creation.  We don't release it, though, if any
failure exist in the creation process.

Signed-off-by: Glauber Costa <glommer@parallels.com>
Reported-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 mm/memcontrol.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f4f41c36e703..60d28e36f0e0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6196,6 +6196,8 @@ mem_cgroup_css_online(struct cgroup *cont)
 		 * call __mem_cgroup_free, so return directly
 		 */
 		mem_cgroup_put(memcg);
+		if (parent->use_hierarchy)
+			mem_cgroup_put(parent);
 	}
 	return error;
 }
-- 
2.39.5