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=-6.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED 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 3F42CC46470 for ; Thu, 9 May 2019 12:25:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0839121773 for ; Thu, 9 May 2019 12:25:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="fXxBmE7z" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726690AbfEIMZb (ORCPT ); Thu, 9 May 2019 08:25:31 -0400 Received: from mail-lj1-f195.google.com ([209.85.208.195]:41512 "EHLO mail-lj1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726426AbfEIMZa (ORCPT ); Thu, 9 May 2019 08:25:30 -0400 Received: by mail-lj1-f195.google.com with SMTP id k8so1822364lja.8; Thu, 09 May 2019 05:25:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=bgwFcpr4h0CqLDwaKDRvVqsaxrlGDdYtmYdrXixSeUQ=; b=fXxBmE7ze/Z+gLUgPusLSOjeC8DPRni8xSXs72THlqUgvZ+YkB7C2X2joI2yabhZE3 8p3jL+zSxjqkE6WDx9RdpWMHV1BE+w1kk8V/mtEhJpgbCLjSPVymx2kjkrzPGSAIjr7D w45LanlpZrGomO0jnZvIOzl4VSSIY4E3z+gyzmExHr1o6buuZO0GHkOYXoWSCeqrQLSb FlCkYEZRTrKaSU02Al80SESzb5ftUvtSa4dEV1Il4KRbvvZUIkjl7K++UhJMBcIliYoC xFLukUi+LA2L9H8oQGAQXR71a6J/JTXgKcmL1WnzuE5ndqFELwKSjnp7ngbqhxZBf77S RirQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=bgwFcpr4h0CqLDwaKDRvVqsaxrlGDdYtmYdrXixSeUQ=; b=WG29ONTy+8hNEIqp57vq9kuI696SZwTlSrJv2O5qYfvzU5IRGYFKwSPhaBhjOSQBoa KaxKVRz7N2nup9BcW6gZagaIH9iA0xKSDAts0s44PlMFYuQyf/uySqfaKnGKaDV6+tUf lDzgt2HPDwf5/manucZ54R8EZRO8cZq3iTZkvmF5AD1c/oIffbTpzqP/Qz2maZWbChPo XzlRcGHAPGOCyPm7f00ai1x30GWC64zOTf9f8Bes25iIb5cOM9dXkcGU+TJW+/5a+On7 bucRI7xMOdt+lr00iW+vhMni2dOrRaL+qyZTQznJFE+xtXU9U1Y9lgcCaJsN4JfeXU2n TknA== X-Gm-Message-State: APjAAAUEZznMV7vnYefTRwKBufiZvKskb5cf/rYPU54xY0V4ViLF2Yol 9gmCtkp9gQ5Wx4CNOOJL/S/3YJ3+ X-Google-Smtp-Source: APXvYqwy62cie0c9VYiWdxvOgL2dz0bVljr6TDZHfH9f2UgG36OiRDna8QWxOvWyDUp4EYX5rZFmew== X-Received: by 2002:a2e:814e:: with SMTP id t14mr2163558ljg.25.1557404728231; Thu, 09 May 2019 05:25:28 -0700 (PDT) Received: from esperanza ([176.120.239.149]) by smtp.gmail.com with ESMTPSA id y7sm306917ljj.34.2019.05.09.05.25.27 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 09 May 2019 05:25:27 -0700 (PDT) Date: Thu, 9 May 2019 15:25:26 +0300 From: Vladimir Davydov To: Jiri Slaby Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Johannes Weiner , Michal Hocko , cgroups@vger.kernel.org, Raghavendra K T Subject: Re: [PATCH] memcg: make it work on sparse non-0-node systems Message-ID: <20190509122526.ck25wscwanooxa3t@esperanza> References: <359d98e6-044a-7686-8522-bdd2489e9456@suse.cz> <20190429105939.11962-1-jslaby@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190429105939.11962-1-jslaby@suse.cz> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 29, 2019 at 12:59:39PM +0200, Jiri Slaby wrote: > We have a single node system with node 0 disabled: > Scanning NUMA topology in Northbridge 24 > Number of physical nodes 2 > Skipping disabled node 0 > Node 1 MemBase 0000000000000000 Limit 00000000fbff0000 > NODE_DATA(1) allocated [mem 0xfbfda000-0xfbfeffff] > > This causes crashes in memcg when system boots: > BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 > #PF error: [normal kernel read fault] > ... > RIP: 0010:list_lru_add+0x94/0x170 > ... > Call Trace: > d_lru_add+0x44/0x50 > dput.part.34+0xfc/0x110 > __fput+0x108/0x230 > task_work_run+0x9f/0xc0 > exit_to_usermode_loop+0xf5/0x100 > > It is reproducible as far as 4.12. I did not try older kernels. You have > to have a new enough systemd, e.g. 241 (the reason is unknown -- was not > investigated). Cannot be reproduced with systemd 234. > > The system crashes because the size of lru array is never updated in > memcg_update_all_list_lrus and the reads are past the zero-sized array, > causing dereferences of random memory. > > The root cause are list_lru_memcg_aware checks in the list_lru code. > The test in list_lru_memcg_aware is broken: it assumes node 0 is always > present, but it is not true on some systems as can be seen above. > > So fix this by checking the first online node instead of node 0. > > Signed-off-by: Jiri Slaby > Cc: Johannes Weiner > Cc: Michal Hocko > Cc: Vladimir Davydov > Cc: > Cc: > Cc: Raghavendra K T > --- > mm/list_lru.c | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > diff --git a/mm/list_lru.c b/mm/list_lru.c > index 0730bf8ff39f..7689910f1a91 100644 > --- a/mm/list_lru.c > +++ b/mm/list_lru.c > @@ -37,11 +37,7 @@ static int lru_shrinker_id(struct list_lru *lru) > > static inline bool list_lru_memcg_aware(struct list_lru *lru) > { > - /* > - * This needs node 0 to be always present, even > - * in the systems supporting sparse numa ids. > - */ > - return !!lru->node[0].memcg_lrus; > + return !!lru->node[first_online_node].memcg_lrus; > } > > static inline struct list_lru_one * Yep, I didn't expect node 0 could ever be unavailable, my bad. The patch looks fine to me: Acked-by: Vladimir Davydov However, I tend to agree with Michal that (ab)using node[0].memcg_lrus to check if a list_lru is memcg aware looks confusing. I guess we could simply add a bool flag to list_lru instead. Something like this, may be: diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h index aa5efd9351eb..d5ceb2839a2d 100644 --- a/include/linux/list_lru.h +++ b/include/linux/list_lru.h @@ -54,6 +54,7 @@ struct list_lru { #ifdef CONFIG_MEMCG_KMEM struct list_head list; int shrinker_id; + bool memcg_aware; #endif }; diff --git a/mm/list_lru.c b/mm/list_lru.c index 0730bf8ff39f..8e605e40a4c6 100644 --- a/mm/list_lru.c +++ b/mm/list_lru.c @@ -37,11 +37,7 @@ static int lru_shrinker_id(struct list_lru *lru) static inline bool list_lru_memcg_aware(struct list_lru *lru) { - /* - * This needs node 0 to be always present, even - * in the systems supporting sparse numa ids. - */ - return !!lru->node[0].memcg_lrus; + return lru->memcg_aware; } static inline struct list_lru_one * @@ -451,6 +447,7 @@ static int memcg_init_list_lru(struct list_lru *lru, bool memcg_aware) { int i; + lru->memcg_aware = memcg_aware; if (!memcg_aware) return 0;