From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758381Ab2AMPlo (ORCPT ); Fri, 13 Jan 2012 10:41:44 -0500 Received: from zene.cmpxchg.org ([85.214.230.12]:33351 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752931Ab2AMPln (ORCPT ); Fri, 13 Jan 2012 10:41:43 -0500 From: Johannes Weiner To: Andrew Morton Cc: Hugh Dickins , KAMEZAWA Hiroyuki , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [patch] mm: memcg: update the correct soft limit tree during migration Date: Fri, 13 Jan 2012 16:41:31 +0100 Message-Id: <1326469291-5642-1-git-send-email-hannes@cmpxchg.org> X-Mailer: git-send-email 1.7.7.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org end_migration() passes the old page instead of the new page to commit the charge. This page descriptor is not used for committing itself, though, since we also pass the (correct) page_cgroup descriptor. But it's used to find the soft limit tree through the page's zone, so the soft limit tree of the old page's zone is updated instead of that of the new page's, which might get slightly out of date until the next charge reaches the ratelimit point. This glitch has been present since '5564e88 memcg: condense page_cgroup-to-page lookup points'. Reported-by: Hugh Dickins Signed-off-by: Johannes Weiner --- mm/memcontrol.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) This fixes a bug that I introduced in 2.6.38. It's benign enough (to my knowledge) that we probably don't want this for stable. diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 602207b..7a292a5 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3247,7 +3247,7 @@ int mem_cgroup_prepare_migration(struct page *page, ctype = MEM_CGROUP_CHARGE_TYPE_CACHE; else ctype = MEM_CGROUP_CHARGE_TYPE_SHMEM; - __mem_cgroup_commit_charge(memcg, page, 1, pc, ctype); + __mem_cgroup_commit_charge(memcg, newpage, 1, pc, ctype); return ret; } -- 1.7.7.5