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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: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: KAMEZAWA 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Li Zefan 2013-07-08 16:00:36 -07:00 committed by Linus Torvalds
parent 4050377b50
commit 8d76a97978
1 changed files with 3 additions and 16 deletions
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19
mm/memcontrol.c
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@ -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);