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 <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: KAMEZAWA Hiroyuki <[e-mail]>
Acked-by: Hugh Dickins <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/mmzone.h

···
 struct lruvec {
 	struct list_head lists[NR_LRU_LISTS];
 	struct zone_reclaim_stat reclaim_stat;
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+	struct zone *zone;
+#endif
 };
 
 /* Mask used at gathering information at once (see memcontrol.c) */
···
 extern int init_currently_empty_zone(struct zone *zone, unsigned long start_pfn,
 				     unsigned long size,
 				     enum memmap_context context);
+
+extern void lruvec_init(struct lruvec *lruvec, struct zone *zone);
+
+static inline struct zone *lruvec_zone(struct lruvec *lruvec)
+{
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+	return lruvec->zone;
+#else
+	return container_of(lruvec, struct zone, lruvec);
+#endif
+}
 
 #ifdef CONFIG_HAVE_MEMORY_PRESENT
 void memory_present(int nid, unsigned long start, unsigned long end);

mm/memcontrol.c

···
 {
 	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.
···
 
 	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;

mm/mmzone.c

···
 	return 1;
 }
 #endif /* CONFIG_ARCH_HAS_HOLES_MEMORYMODEL */
+
+void lruvec_init(struct lruvec *lruvec, struct zone *zone)
+{
+	enum lru_list lru;
+
+	memset(lruvec, 0, sizeof(struct lruvec));
+
+	for_each_lru(lru)
+		INIT_LIST_HEAD(&lruvec->lists[lru]);
+
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+	lruvec->zone = zone;
+#endif
+}

mm/page_alloc.c

···
 	for (j = 0; j < MAX_NR_ZONES; j++) {
 		struct zone *zone = pgdat->node_zones + j;
 		unsigned long size, realsize, memmap_pages;
-		enum lru_list lru;
 
 		size = zone_spanned_pages_in_node(nid, j, zones_size);
 		realsize = size - zone_absent_pages_in_node(nid, j,
···
 		zone->zone_pgdat = pgdat;
 
 		zone_pcp_init(zone);
-		for_each_lru(lru)
-			INIT_LIST_HEAD(&zone->lruvec.lists[lru]);
-		zone->lruvec.reclaim_stat.recent_rotated[0] = 0;
-		zone->lruvec.reclaim_stat.recent_rotated[1] = 0;
-		zone->lruvec.reclaim_stat.recent_scanned[0] = 0;
-		zone->lruvec.reclaim_stat.recent_scanned[1] = 0;
+		lruvec_init(&zone->lruvec, zone);
 		zap_zone_vm_stats(zone);
 		zone->flags = 0;
 		if (!size)