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Commit 8d76a979 authored by Li Zefan's avatar Li Zefan Committed by Linus Torvalds
Browse files

memcg: don't need to get a reference to the parent 



The cgroup core guarantees it's always safe to access the parent.

Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4050377b

mm/memcontrol.c

+3 −16
Original line number Diff line number Diff line
@@ -503,7 +503,6 @@ enum res_type { 
 */

static DEFINE_MUTEX(memcg_create_mutex);



static void mem_cgroup_get(struct mem_cgroup *memcg);

static void mem_cgroup_put(struct mem_cgroup *memcg);



static inline
@@ -6239,19 +6238,10 @@ static void free_rcu(struct rcu_head *rcu_head) 
	schedule_work(&memcg->work_freeing);

}



static void mem_cgroup_get(struct mem_cgroup *memcg)

{

	atomic_inc(&memcg->refcnt);

}



static void __mem_cgroup_put(struct mem_cgroup *memcg, int count)

{

	if (atomic_sub_and_test(count, &memcg->refcnt)) {

		struct mem_cgroup *parent = parent_mem_cgroup(memcg);

	if (atomic_sub_and_test(count, &memcg->refcnt))

		call_rcu(&memcg->rcu_freeing, free_rcu);

		if (parent)

			mem_cgroup_put(parent);

	}

}



static void mem_cgroup_put(struct mem_cgroup *memcg)
@@ -6354,12 +6344,9 @@ mem_cgroup_css_online(struct cgroup *cont) 
		res_counter_init(&memcg->kmem, &parent->kmem);



		/*

		 * We increment refcnt of the parent to ensure that we can

		 * safely access it on res_counter_charge/uncharge.

		 * This refcnt will be decremented when freeing this

		 * mem_cgroup(see mem_cgroup_put).

		 * No need to take a reference to the parent because cgroup

		 * core guarantees its existence.

		 */

		mem_cgroup_get(parent);

	} else {

		res_counter_init(&memcg->res, NULL);

		res_counter_init(&memcg->memsw, NULL);