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Date: Mon, 8 Apr 2013 14:33:58 +0800 From: Li Zefan <lizefan@...wei.com> To: Andrew Morton <akpm@...ux-foundation.org> CC: Tejun Heo <tj@...nel.org>, Glauber Costa <glommer@...allels.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>, Johannes Weiner <hannes@...xchg.org>, LKML <linux-kernel@...r.kernel.org>, Cgroups <cgroups@...r.kernel.org>, <linux-mm@...ck.org> Subject: [PATCH 04/12] memcg, kmem: fix reference count handling on the error path From: Michal Hocko <mhocko@...e.cz> 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. Signed-off-by: Li Zefan <lizefan@...wei.com> Signed-off-by: Michal Hocko <mhocko@...e.cz> Cc: <stable@...r.kernel.org> # 3.8.x --- mm/memcontrol.c | 8 -------- 1 file changed, 8 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 44cec72..e65eaac 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -6243,14 +6243,6 @@ 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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