mm: oom: add memcg to oom_control

It's a part of oom context just like allocation order and nodemask, so
let's move it to oom_control instead of passing it in the argument list.

Link: http://lkml.kernel.org/r/40e03fd7aaf1f55c75d787128d6d17c5a71226c2.1464358556.git.vdavydov@virtuozzo.com
Signed-off-by: Vladimir Davydov <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Cc: Tetsuo Handa <[email protected]>
Cc: David Rientjes <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8129922..f7bb1ae 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3105,6 +3105,7 @@
 	struct oom_control oc = {
 		.zonelist = ac->zonelist,
 		.nodemask = ac->nodemask,
+		.memcg = NULL,
 		.gfp_mask = gfp_mask,
 		.order = order,
 	};