From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754172Ab1KXJET (ORCPT ); Thu, 24 Nov 2011 04:04:19 -0500 Received: from zene.cmpxchg.org ([85.214.230.12]:38677 "EHLO zene.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753915Ab1KXJEQ (ORCPT ); Thu, 24 Nov 2011 04:04:16 -0500 Date: Thu, 24 Nov 2011 10:04:09 +0100 From: Johannes Weiner To: KAMEZAWA Hiroyuki Cc: Andrew Morton , Michal Hocko , Balbir Singh , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [patch 5/8] mm: memcg: remove unneeded checks from newpage_charge() Message-ID: <20111124090409.GC6843@cmpxchg.org> References: <1322062951-1756-1-git-send-email-hannes@cmpxchg.org> <1322062951-1756-6-git-send-email-hannes@cmpxchg.org> <20111124090443.d3f720c5.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111124090443.d3f720c5.kamezawa.hiroyu@jp.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 24, 2011 at 09:04:43AM +0900, KAMEZAWA Hiroyuki wrote: > On Wed, 23 Nov 2011 16:42:28 +0100 > Johannes Weiner wrote: > > > From: Johannes Weiner > > > > All callsites pass in freshly allocated pages and a valid mm. As a > > result, all checks pertaining the page's mapcount, page->mapping or > > the fallback to init_mm are unneeded. > > > > Signed-off-by: Johannes Weiner > > Hmm, it's true now. But for making clear our assumption to all readers of code, > > could you add > VM_BUG_ON(!mm || page_mapped(page) || (page->mapping && !PageAnon(page)) ? Of course. Please find the delta patch below. I broke them up into three separate checks to make the problem easier to find if the BUG triggers. > Acked-by: KAMEZAWA Hiroyuki Thank you. --- From: Johannes Weiner Subject: mm: memcg: remove unneeded checks from newpage_charge() fix Document page state assumptions and catch if they are violated in newpage_charge(). Signed-off-by: Johannes Weiner --- mm/memcontrol.c | 3 +++ 1 files changed, 3 insertions(+), 0 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 0d10be4..f338018 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2679,6 +2679,9 @@ int mem_cgroup_newpage_charge(struct page *page, { if (mem_cgroup_disabled()) return 0; + VM_BUG_ON(page_mapped(page)); + VM_BUG_ON(page->mapping && !PageAnon(page)); + VM_BUG_ON(!mm); return mem_cgroup_charge_common(page, mm, gfp_mask, MEM_CGROUP_CHARGE_TYPE_MAPPED); } -- 1.7.6.4