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authorLi Zefan <lizefan@huawei.com>2013-07-08 16:00:36 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-07-09 10:33:24 -0700
commit8d76a9797882fc517d87e2b5db2a4f04edaeccec (patch)
treea815aca84438215643689cc3687db1ba003d4298
parent4050377b509b326c14b275fedb2f69b46f37a7a9 (diff)
downloadlinux-8d76a9797882fc517d87e2b5db2a4f04edaeccec.tar.bz2
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>
-rw-r--r--mm/memcontrol.c19
1 files changed, 3 insertions, 16 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 76c0c99b002f..c508258d61a1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -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);