From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 50253C433E1 for ; Thu, 13 Aug 2020 06:20:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 357B020716 for ; Thu, 13 Aug 2020 06:20:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726082AbgHMGUw (ORCPT ); Thu, 13 Aug 2020 02:20:52 -0400 Received: from mx2.suse.de ([195.135.220.15]:48952 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725954AbgHMGUv (ORCPT ); Thu, 13 Aug 2020 02:20:51 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 32076ACA3; Thu, 13 Aug 2020 06:21:12 +0000 (UTC) Date: Thu, 13 Aug 2020 08:20:49 +0200 From: Michal Hocko To: Alex Shi Cc: akpm@linux-foundation.org, Johannes Weiner , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [Resend PATCH 2/6] mm/memcg: remove useless check on page->mem_cgroup Message-ID: <20200813062049.GA9477@dhcp22.suse.cz> References: <1597144232-11370-1-git-send-email-alex.shi@linux.alibaba.com> <1597144232-11370-2-git-send-email-alex.shi@linux.alibaba.com> <20200811113008.GK4793@dhcp22.suse.cz> <776b0e6f-4129-9fb9-0f66-47757cf320d5@linux.alibaba.com> <20200811135626.GL4793@dhcp22.suse.cz> <0b5e1ac3-c9c7-35e9-2661-b58430314d0a@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0b5e1ac3-c9c7-35e9-2661-b58430314d0a@linux.alibaba.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 12-08-20 11:25:53, Alex Shi wrote: > >From 999b0fe5fc65865c3b59ff28500d45572a4a9570 Mon Sep 17 00:00:00 2001 > From: Alex Shi > Date: Wed, 5 Aug 2020 21:02:30 +0800 > Subject: [PATCH 2/6] mm/memcg: bail out early from swap accounting when memcg > is disabled > > If we disabled memcg by cgroup_disable=memory, page->memcg will be NULL > and so the charge is skipped and that will trigger a warning like below. > Let's return from the funcs earlier. > > ---[ end trace f1f34bfc3b32ed2f ]--- > anon flags:0x5005b48008000d(locked|uptodate|dirty|swapbacked) > raw: 005005b48008000d dead000000000100 dead000000000122 ffff8897c7c76ad1 > raw: 0000000000000022 0000000000000000 0000000200000000 0000000000000000 > page dumped because: VM_WARN_ON_ONCE_PAGE(!memcg) Yes this is better. It would be even more informative if you added the backtrace. > Signed-off-by: Alex Shi > Reviewed-by: Roman Gushchin > Acked-by: Michal Hocko > Cc: Johannes Weiner > Cc: Michal Hocko > Cc: Vladimir Davydov > Cc: Andrew Morton > Cc: cgroups@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > --- > mm/memcontrol.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 299382fc55a9..419cf565f40b 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -7098,6 +7098,9 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry) > VM_BUG_ON_PAGE(PageLRU(page), page); > VM_BUG_ON_PAGE(page_count(page), page); > > + if (mem_cgroup_disabled()) > + return; > + > if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) > return; > > @@ -7163,6 +7166,9 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry) > struct mem_cgroup *memcg; > unsigned short oldid; > > + if (mem_cgroup_disabled()) > + return 0; > + > if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) > return 0; > > -- > 1.8.3.1 -- Michal Hocko SUSE Labs