From: Li Zefan Date: Mon, 8 Jul 2013 23:00:36 +0000 (-0700) Subject: memcg: don't need to get a reference to the parent X-Git-Tag: Ubuntu-5.0.0-8.9~13366^2~63 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=8d76a9797882fc517d87e2b5db2a4f04edaeccec;p=mirror_ubuntu-disco-kernel.git 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 Acked-by: Michal Hocko Acked-by: KAMEZAWA Hiroyuki Cc: Hugh Dickins Cc: Tejun Heo Cc: Glauber Costa Cc: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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);