[PATCH v2 6/6] memcg: init/free swap cgroup strucutres upon create/free child memcg

[Jeff Liu <jeff.liu@oracle.com>]

Initialize swap_cgroup strucutres when creating a non-root memcg,
swap_cgroup_init() will be called for multiple times but only does
buffer allocation per the first non-root memcg.

Free swap_cgroup structures correspondingly on the last non-root memcg
removal.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
CC: Glauber Costa <glommer@parallels.com>
CC: Michal Hocko <mhocko@suse.cz>
CC: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
CC: Johannes Weiner <hannes@cmpxchg.org>
CC: Mel Gorman <mgorman@suse.de>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Sha Zhengju <handai.szj@taobao.com>

---
 mm/memcontrol.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index afe5e86..031d242 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5998,6 +5998,7 @@ static void free_work(struct work_struct *work)
 
 	memcg = container_of(work, struct mem_cgroup, work_freeing);
 	__mem_cgroup_free(memcg);
+	swap_cgroup_free();
 }
 
 static void free_rcu(struct rcu_head *rcu_head)
@@ -6116,6 +6117,8 @@ mem_cgroup_css_alloc(struct cgroup *cont)
 			INIT_WORK(&stock->work, drain_local_stock);
 		}
 	} else {
+		if (swap_cgroup_init())
+			goto free_out;
 		parent = mem_cgroup_from_cont(cont->parent);
 		memcg->use_hierarchy = parent->use_hierarchy;
 		memcg->oom_kill_disable = parent->oom_kill_disable;
-- 
1.7.9.5

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