mm: memcontrol: replace mem_cgroup_lruvec_online with mem_cgroup_online

mem_cgroup_lruvec_online() takes lruvec, but it only needs memcg.  Since
get_scan_count(), which is the only user of this function, now possesses
pointer to memcg, let's pass memcg directly to mem_cgroup_online() instead
of picking it out of lruvec and rename the function accordingly.

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -355,6 +355,13 @@ static inline bool mem_cgroup_disabled(void)
 	return !cgroup_subsys_enabled(memory_cgrp_subsys);
 }
 
+static inline bool mem_cgroup_online(struct mem_cgroup *memcg)
+{
+	if (mem_cgroup_disabled())
+		return true;
+	return !!(memcg->css.flags & CSS_ONLINE);
+}
+
 /*
  * For memory reclaim.
  */
@@ -363,20 +370,6 @@ int mem_cgroup_select_victim_node(struct mem_cgroup *memcg);
 void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru,
 		int nr_pages);
 
-static inline bool mem_cgroup_lruvec_online(struct lruvec *lruvec)
-{
-	struct mem_cgroup_per_zone *mz;
-	struct mem_cgroup *memcg;
-
-	if (mem_cgroup_disabled())
-		return true;
-
-	mz = container_of(lruvec, struct mem_cgroup_per_zone, lruvec);
-	memcg = mz->memcg;
-
-	return !!(memcg->css.flags & CSS_ONLINE);
-}
-
 static inline
 unsigned long mem_cgroup_get_lru_size(struct lruvec *lruvec, enum lru_list lru)
 {
@@ -589,13 +582,13 @@ static inline bool mem_cgroup_disabled(void)
 	return true;
 }
 
-static inline bool
-mem_cgroup_inactive_anon_is_low(struct lruvec *lruvec)
+static inline bool mem_cgroup_online(struct mem_cgroup *memcg)
 {
 	return true;
 }
 
-static inline bool mem_cgroup_lruvec_online(struct lruvec *lruvec)
+static inline bool
+mem_cgroup_inactive_anon_is_low(struct lruvec *lruvec)
 {
 	return true;
 }

mm/vmscan.c

@@ -1997,7 +1997,7 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
 	if (current_is_kswapd()) {
 		if (!zone_reclaimable(zone))
 			force_scan = true;
-		if (!mem_cgroup_lruvec_online(lruvec))
+		if (!mem_cgroup_online(memcg))
 			force_scan = true;
 	}
 	if (!global_reclaim(sc))