From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: [PATCH 04/12] memcg, kmem: fix reference count handling on the error path Date: Mon, 8 Apr 2013 14:33:58 +0800 Message-ID: <516264D6.3090100@huawei.com> References: <5162648B.9070802@huawei.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5162648B.9070802-hv44wF8Li93QT0dZR+AlfA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Andrew Morton Cc: Tejun Heo , Glauber Costa , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org From: Michal Hocko 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 Signed-off-by: Michal Hocko Cc: # 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx144.postini.com [74.125.245.144]) by kanga.kvack.org (Postfix) with SMTP id C43BC6B0078 for ; Mon, 8 Apr 2013 02:34:32 -0400 (EDT) Message-ID: <516264D6.3090100@huawei.com> Date: Mon, 8 Apr 2013 14:33:58 +0800 From: Li Zefan MIME-Version: 1.0 Subject: [PATCH 04/12] memcg, kmem: fix reference count handling on the error path References: <5162648B.9070802@huawei.com> In-Reply-To: <5162648B.9070802@huawei.com> Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Tejun Heo , Glauber Costa , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , linux-mm@kvack.org From: Michal Hocko 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 Signed-off-by: Michal Hocko Cc: # 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934837Ab3DHGeX (ORCPT ); Mon, 8 Apr 2013 02:34:23 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:19944 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761255Ab3DHGeT (ORCPT ); Mon, 8 Apr 2013 02:34:19 -0400 Message-ID: <516264D6.3090100@huawei.com> Date: Mon, 8 Apr 2013 14:33:58 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 MIME-Version: 1.0 To: Andrew Morton CC: Tejun Heo , Glauber Costa , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , Subject: [PATCH 04/12] memcg, kmem: fix reference count handling on the error path References: <5162648B.9070802@huawei.com> In-Reply-To: <5162648B.9070802@huawei.com> Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.68.215] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Michal Hocko 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 Signed-off-by: Michal Hocko Cc: # 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