mm: add link from struct lruvec to struct zone

This is the first stage of struct mem_cgroup_zone removal.  Further
patches replace struct mem_cgroup_zone with a pointer to struct lruvec.

If CONFIG_CGROUP_MEM_RES_CTLR=n lruvec_zone() is just container_of().

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a8abf91..39b2c14 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4738,7 +4738,6 @@
 {
 	struct mem_cgroup_per_node *pn;
 	struct mem_cgroup_per_zone *mz;
-	enum lru_list lru;
 	int zone, tmp = node;
 	/*
 	 * This routine is called against possible nodes.
@@ -4756,8 +4755,7 @@
 
 	for (zone = 0; zone < MAX_NR_ZONES; zone++) {
 		mz = &pn->zoneinfo[zone];
-		for_each_lru(lru)
-			INIT_LIST_HEAD(&mz->lruvec.lists[lru]);
+		lruvec_init(&mz->lruvec, &NODE_DATA(node)->node_zones[zone]);
 		mz->usage_in_excess = 0;
 		mz->on_tree = false;
 		mz->memcg = memcg;