Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932400Ab2JZLiJ (ORCPT ); Fri, 26 Oct 2012 07:38:09 -0400 Received: from cantor2.suse.de ([195.135.220.15]:57416 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932348Ab2JZLiE (ORCPT ); Fri, 26 Oct 2012 07:38:04 -0400 From: Michal Hocko To: linux-mm@kvack.org Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Morton , Tejun Heo , Li Zefan , Johannes Weiner , KAMEZAWA Hiroyuki , Balbir Singh , Glauber Costa Subject: [PATCH v3 2/6] memcg: root_cgroup cannot reach mem_cgroup_move_parent Date: Fri, 26 Oct 2012 13:37:29 +0200 Message-Id: <1351251453-6140-3-git-send-email-mhocko@suse.cz> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1351251453-6140-1-git-send-email-mhocko@suse.cz> References: <1351251453-6140-1-git-send-email-mhocko@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1476 Lines: 45 The root cgroup cannot be destroyed so we never hit it down the mem_cgroup_pre_destroy path and mem_cgroup_force_empty_write shouldn't even try to do anything if called for the root. This means that mem_cgroup_move_parent doesn't have to bother with the root cgroup and it can assume it can always move charges upwards. Signed-off-by: Michal Hocko Reviewed-by: Tejun Heo --- mm/memcontrol.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 07d92b8..916132a 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2715,9 +2715,7 @@ static int mem_cgroup_move_parent(struct page *page, unsigned long uninitialized_var(flags); int ret; - /* Is ROOT ? */ - if (mem_cgroup_is_root(child)) - return -EINVAL; + VM_BUG_ON(mem_cgroup_is_root(child)); ret = -EBUSY; if (!get_page_unless_zero(page)) @@ -3823,6 +3821,8 @@ static int mem_cgroup_force_empty_write(struct cgroup *cont, unsigned int event) struct mem_cgroup *memcg = mem_cgroup_from_cont(cont); int ret; + if (mem_cgroup_is_root(memcg)) + return -EINVAL; css_get(&memcg->css); ret = mem_cgroup_force_empty(memcg); css_put(&memcg->css); -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/