[PATCH] memcg: use mem_cgroup_zone_lruvec inmem_cgroup_force_empty_list

[Hugh Dickins]

For no particularly good reason, mem_cgroup_force_empty_list() has
its own code for deciding lruvec. Change it to use the standard
mem_cgroup_zone_lruvec() and mem_cgroup_get_lru_size() too.
In fact it was already safe against oops after memory hotadd (see
"memcg: fix hotplugged memory zone oops" for more details) when lruvec
is not initialized yet (the lru lists in danger could only be empty),
but we're better proofed against future changes this way.

Reported-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
Cc: Wen Congyang <wency@xxxxxxxxxxxxxx>
---
 mm/memcontrol.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6c72d65..32f0ecf 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3710,15 +3710,15 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
 static void mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
 				int node, int zid, enum lru_list lru)
 {
-	struct mem_cgroup_per_zone *mz;
+	struct lruvec *lruvec;
 	unsigned long flags;
 	struct list_head *list;
 	struct page *busy;
 	struct zone *zone;
 
 	zone = &NODE_DATA(node)->node_zones[zid];
-	mz = mem_cgroup_zoneinfo(memcg, node, zid);
-	list = &mz->lruvec.lists[lru];
+	lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+	list = &lruvec->lists[lru];
 
 	busy = NULL;
 	do {
-- 
1.7.10.4

-- 
Michal Hocko
SUSE Labs
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