From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx138.postini.com [74.125.245.138]) by kanga.kvack.org (Postfix) with SMTP id EFB406B00C7 for ; Mon, 11 Jun 2012 03:34:50 -0400 (EDT) Date: Mon, 11 Jun 2012 09:34:47 +0200 From: Michal Hocko Subject: Re: [PATCH] memcg: fix use_hierarchy css_is_ancestor oops regression Message-ID: <20120611073447.GA12402@tiehlicka.suse.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Hugh Dickins Cc: Andrew Morton , Johannes Weiner , Konstantin Khlebnikov , KAMEZAWA Hiroyuki , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Sun 10-06-12 11:54:47, Hugh Dickins wrote: > If use_hierarchy is set, reclaim testing soon oopses in css_is_ancestor() > called from __mem_cgroup_same_or_subtree() called from page_referenced(): > when processes are exiting, it's easy for mm_match_cgroup() to pass along > a NULL memcg coming from a NULL mm->owner. > > Check for that in __mem_cgroup_same_or_subtree(). Return true or false? > False because we cannot know if it was in the hierarchy, but also false > because it's better not to count a reference from an exiting process. > > Signed-off-by: Hugh Dickins Acked-by: Michal Hocko Thanks > --- > This a 3.5-rc issue: not needed for stable. > > mm/memcontrol.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- 3.5-rc2/mm/memcontrol.c 2012-05-30 08:17:19.400008280 -0700 > +++ linux/mm/memcontrol.c 2012-06-10 08:39:39.618182396 -0700 > @@ -1148,7 +1148,7 @@ bool __mem_cgroup_same_or_subtree(const > { > if (root_memcg == memcg) > return true; > - if (!root_memcg->use_hierarchy) > + if (!root_memcg->use_hierarchy || !memcg) > return false; > return css_is_ancestor(&memcg->css, &root_memcg->css); > } -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- 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