+ memcg-dont-need-to-get-a-reference-to-the-parent.patch added to -mm tree

+ memcg-dont-need-to-get-a-reference-to-the-parent.patch added to -mm tree

[akpm]

Subject: + memcg-dont-need-to-get-a-reference-to-the-parent.patch added to -mm tree
To: lizefan@huawei.com,glommer@openvz.org,hannes@cmpxchg.org,hughd@google.com,kamezawa.hiroyu@jp.fujitsu.com,mhocko@suse.cz,tj@kernel.org
From: akpm@linux-foundation.org
Date: Fri, 28 Jun 2013 16:00:32 -0700


The patch titled
     Subject: memcg: don't need to get a reference to the parent
has been added to the -mm tree.  Its filename is
     memcg-dont-need-to-get-a-reference-to-the-parent.patch

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------------------------------------------------------
From: Li Zefan <lizefan@huawei.com>
Subject: 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>
---

 mm/memcontrol.c |   19 +++----------------
 1 file changed, 3 insertions(+), 16 deletions(-)

diff -puN mm/memcontrol.c~memcg-dont-need-to-get-a-reference-to-the-parent mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-dont-need-to-get-a-reference-to-the-parent
+++ a/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
@@ -6230,19 +6229,10 @@ static void free_rcu(struct rcu_head *rc
 	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)
@@ -6345,12 +6335,9 @@ mem_cgroup_css_online(struct cgroup *con
 		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);
_

Patches currently in -mm which might be from lizefan@huawei.com are

origin.patch
linux-next.patch
memcg-update-todo-list-in-documentation.patch
revert-memcg-avoid-dangling-reference-count-in-creation-failure.patch
memcg-kmem-fix-reference-count-handling-on-the-error-path.patch
memcg-use-css_get-in-sock_update_memcg.patch
memcg-dont-use-mem_cgroup_get-when-creating-a-kmemcg-cache.patch
memcg-use-css_get-put-when-charging-uncharging-kmem.patch
memcg-use-css_get-put-when-charging-uncharging-kmem-fix.patch
memcg-use-css_get-put-for-swap-memcg.patch
memcg-dont-need-to-get-a-reference-to-the-parent.patch
memcg-kill-memcg-refcnt.patch
memcg-dont-need-to-free-memcg-via-rcu-or-workqueue.patch