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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 4D277CA9EC3 for ; Thu, 31 Oct 2019 04:16:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 14D6D2080F for ; Thu, 31 Oct 2019 04:16:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572495373; bh=TdavWRFLS/Lxw3pvDBh+4n0ncIlxfulsj9NTk8R2yXI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=ZxO6tCivvRhH+SQ2kKtakLBAK5lTWmpsoS9Onx451gAF5+EZn7v7IWSBqMlhDc1i8 oRtbBaVVNYIx1joy+gW943XQMVIc1ZMAm4JOare7LlZqxWxaaHtQBoVvWoNssOaoQt qB32dAMZwdHG0neXp3G7wfp46QNGFzF/pKTgyTG0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726555AbfJaEQK (ORCPT ); Thu, 31 Oct 2019 00:16:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:56206 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725816AbfJaEQK (ORCPT ); Thu, 31 Oct 2019 00:16:10 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 154D42080F; Thu, 31 Oct 2019 04:16:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572495369; bh=TdavWRFLS/Lxw3pvDBh+4n0ncIlxfulsj9NTk8R2yXI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=VoSZnYi/gWQldgzmpcUHJGLjbfRmcYdaPHP34Y5dGR5XV6mJu4e957W3ZqXGMNqKF fNrFI2YZhZ7jZNYC64cOHe9j5ZK+g41EDaLanHfzBmmUGWCP10M8wGBq4Md6Da8HR7 nYngzYFUl3qkZ465PWWNcA0nOYGrB9GkzEzaSjOA= Date: Wed, 30 Oct 2019 21:16:08 -0700 From: Andrew Morton To: Roman Gushchin Cc: , Michal Hocko , Johannes Weiner , , , Vladimir Davydov , Daniel Jordan , Naoya Horiguchi Subject: Re: [PATCH v2] mm: slab: make page_cgroup_ino() to recognize non-compound slab pages properly Message-Id: <20191030211608.29f8fc92e07fd2ac2ef4d1d3@linux-foundation.org> In-Reply-To: <20191031012151.2722280-1-guro@fb.com> References: <20191031012151.2722280-1-guro@fb.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 30 Oct 2019 18:21:51 -0700 Roman Gushchin wrote: > page_cgroup_ino() doesn't return a valid memcg pointer for non-compound > slab pages, because it depends on PgHead AND PgSlab flags to be set > to determine the memory cgroup from the kmem_cache. > It's correct for compound pages, but not for generic small pages. Those > don't have PgHead set, so it ends up returning zero. > > Fix this by replacing the condition to PageSlab() && !PageTail(). > > Before this patch: > [root@localhost ~]# ./page-types -c /sys/fs/cgroup/user.slice/user-0.slice/user@0.service/ | grep slab > 0x0000000000000080 38 0 _______S___________________________________ slab > > After this patch: > [root@localhost ~]# ./page-types -c /sys/fs/cgroup/user.slice/user-0.slice/user@0.service/ | grep slab > 0x0000000000000080 147 0 _______S___________________________________ slab > > Fixes: 4d96ba353075 ("mm: memcg/slab: stop setting page->mem_cgroup pointer for slab pages") > Signed-off-by: Roman Gushchin > Reviewed-by: Shakeel Butt > Cc: Vladimir Davydov > Cc: Daniel Jordan Affects /proc/kpagecgroup, but page_cgroup_ino() is also used in the memory-failure code - I wonder what effect this bug has there? IOW, should we backport this into -stable?