Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750849Ab2FJSzS (ORCPT ); Sun, 10 Jun 2012 14:55:18 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:57616 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751519Ab2FJSzQ (ORCPT ); Sun, 10 Jun 2012 14:55:16 -0400 Date: Sun, 10 Jun 2012 11:54:47 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Andrew Morton cc: Johannes Weiner , Konstantin Khlebnikov , KAMEZAWA Hiroyuki , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH] memcg: fix use_hierarchy css_is_ancestor oops regression Message-ID: User-Agent: Alpine 2.00 (LSU 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1287 Lines: 32 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 --- 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); } -- 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/