memcg: add accessor to mem_cgroup.css

So that an outside user can free the reference count grabbed by
try_get_mem_cgroup_from_page().

CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Hugh Dickins <hugh.dickins@tiscali.co.uk>
CC: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
CC: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b5ac61ce7346..9eee80d6d490 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -282,6 +282,11 @@ mem_cgroup_zoneinfo(struct mem_cgroup *mem, int nid, int zid)
         return &mem->info.nodeinfo[nid]->zoneinfo[zid];
 }
 
+struct cgroup_subsys_state *mem_cgroup_css(struct mem_cgroup *mem)
+{
+        return &mem->css;
+}
+
 static struct mem_cgroup_per_zone *
 page_cgroup_zoneinfo(struct page_cgroup *pc)
 {