From: Li Zefan <lizefan@huawei.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Tejun Heo <tj@kernel.org>, Glauber Costa <glommer@parallels.com>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
LKML <linux-kernel@vger.kernel.org>,
Cgroups <cgroups@vger.kernel.org>,
linux-mm@kvack.org
Subject: [PATCH 2/9] memcg, kmem: fix reference count handling on the error path
Date: Fri, 17 May 2013 15:03:23 +0800 [thread overview]
Message-ID: <5195D63B.4010202@huawei.com> (raw)
In-Reply-To: <5195D5F8.7000609@huawei.com>
mem_cgroup_css_online calls mem_cgroup_put if memcg_init_kmem
fails. This is not correct because only memcg_propagate_kmem takes an
additional reference while mem_cgroup_sockets_init is allowed to fail as
well (although no current implementation fails) but it doesn't take any
reference. This all suggests that it should be memcg_propagate_kmem that
should clean up after itself so this patch moves mem_cgroup_put over
there.
Unfortunately this is not that easy (as pointed out by Li Zefan) because
memcg_kmem_mark_dead marks the group dead (KMEM_ACCOUNTED_DEAD) if it
is marked active (KMEM_ACCOUNTED_ACTIVE) which is the case even if
memcg_propagate_kmem fails so the additional reference is dropped in
that case in kmem_cgroup_destroy which means that the reference would be
dropped two times.
The easiest way then would be to simply remove mem_cgrroup_put from
mem_cgroup_css_online and rely on kmem_cgroup_destroy doing the right
thing.
Cc: <stable@vger.kernel.org> # 3.8+
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
mm/memcontrol.c | 8 --------
1 file changed, 8 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5918e90..4d0458d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6290,14 +6290,6 @@ mem_cgroup_css_online(struct cgroup *cont)
error = memcg_init_kmem(memcg, &mem_cgroup_subsys);
mutex_unlock(&memcg_create_mutex);
- if (error) {
- /*
- * We call put now because our (and parent's) refcnts
- * are already in place. mem_cgroup_put() will internally
- * call __mem_cgroup_free, so return directly
- */
- mem_cgroup_put(memcg);
- }
return error;
}
--
1.8.0.2
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next prev parent reply other threads:[~2013-05-17 7:04 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-17 7:02 [PATCH 0/12][V3] memcg: make memcg's life cycle the same as cgroup Li Zefan
2013-05-17 7:03 ` [PATCH 1/9] Revert "memcg: avoid dangling reference count in creation failure." Li Zefan
2013-05-17 7:03 ` Li Zefan [this message]
2013-05-17 7:03 ` [PATCH 3/9] memcg: use css_get() in sock_update_memcg() Li Zefan
2013-05-17 7:03 ` [PATCH 4/9] memcg: don't use mem_cgroup_get() when creating a kmemcg cache Li Zefan
2013-05-17 7:04 ` [PATCH 5/9] memcg: use css_get/put when charging/uncharging kmem Li Zefan
2013-05-17 18:08 ` Tejun Heo
2013-05-22 8:36 ` Li Zefan
2013-05-24 7:54 ` Michal Hocko
2013-05-30 5:48 ` Tejun Heo
2013-05-30 15:12 ` Michal Hocko
2013-05-17 7:04 ` [PATCH 6/9] memcg: use css_get/put for swap memcg Li Zefan
2013-05-17 7:04 ` [PATCH 7/9] memcg: don't need to get a reference to the parent Li Zefan
2013-05-17 7:05 ` [PATCH 8/9] memcg: kill memcg refcnt Li Zefan
2013-05-17 7:05 ` [PATCH 9/9] memcg: don't need to free memcg via RCU or workqueue Li Zefan
2013-05-17 7:06 ` [PATCH 0/12][V3] memcg: make memcg's life cycle the same as cgroup Li Zefan
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