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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 35DB0C54FCB for ; Thu, 23 Apr 2020 15:33:28 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id ECC1020767 for ; Thu, 23 Apr 2020 15:33:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chrisdown.name header.i=@chrisdown.name header.b="UUleoEnG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ECC1020767 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chrisdown.name Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 6B79B8E0005; Thu, 23 Apr 2020 11:33:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 667BB8E0003; Thu, 23 Apr 2020 11:33:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 57EF58E0005; Thu, 23 Apr 2020 11:33:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0071.hostedemail.com [216.40.44.71]) by kanga.kvack.org (Postfix) with ESMTP id 41D698E0003 for ; Thu, 23 Apr 2020 11:33:27 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 043E7181AC9BF for ; Thu, 23 Apr 2020 15:33:27 +0000 (UTC) X-FDA: 76739514054.28.vase46_f9950ab9c5c X-HE-Tag: vase46_f9950ab9c5c X-Filterd-Recvd-Size: 3373 Received: from mail-wm1-f66.google.com (mail-wm1-f66.google.com [209.85.128.66]) by imf10.hostedemail.com (Postfix) with ESMTP for ; Thu, 23 Apr 2020 15:33:26 +0000 (UTC) Received: by mail-wm1-f66.google.com with SMTP id g12so7010452wmh.3 for ; Thu, 23 Apr 2020 08:33:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chrisdown.name; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=W4yyff1bxIyXCcjIXtUoDnnedr3hHmKrkMXh2SX0RA0=; b=UUleoEnGMbi8J6q2gh2oXicaEKR+rQ+fEg5QOAG93t7lUoQ9Ped5KSKEAdtqwVkQ7m E6ctWfIAQnnwPAxdjEEWfrW/AEHu/rtIqQg4RApTHhadLH+PNAGezgUpA+rnhDezeup0 VL3YR/MJRiL2UBEA0PDt3b/7oy7tD8hxCeonA= 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=W4yyff1bxIyXCcjIXtUoDnnedr3hHmKrkMXh2SX0RA0=; b=p57vveYENyU71hOeRY1gMdUeG8iVJ9RvrVqJ8V5g0AXaq0nZx8DlHTQh38gplS55sk MNb5fMPG5JB3MGWm7dwYxi9VZCHEcF6puDNIlUJNeXuHCF3u8q9yt7zSu1pXf9cnnj4k DaBU4gKQJfFjebEJTfxzzDWQzUZppbLWdXsgr1K29uTFE9eoaDlH/raz1PHdP+Scc9Qq 4wDf2lQzf4WAQraF1Y80DsK1DVfBAIhPjIJv0DuSbo1KNYPj/0I6EfHktIehiZbz9+sW t7oQZLrE4fRv+ZnVMUz0cMex7UYvfQswFI65eHGvTGHbLlxc9URVnozGkMCBr97E0sNR rdtg== X-Gm-Message-State: AGi0PuYAIk0TBWZIZeRQTgujzIy1HPJHsM/7bGeUcexeD+XRStu3nDqO m5OkrZ6lMrY2SOahdA64DZdSdQ== X-Google-Smtp-Source: APiQypLuRIvaOlzsnUsi5FdIR0dI+2u8ZnoEpm45/HzqUm1iJqqMuYGUVleUiY5X8duXfQH1Of6bBg== X-Received: by 2002:a1c:bad4:: with SMTP id k203mr4712758wmf.15.1587656004853; Thu, 23 Apr 2020 08:33:24 -0700 (PDT) Received: from localhost ([2a01:4b00:8432:8a00:fa59:71ff:fe7e:8d21]) by smtp.gmail.com with ESMTPSA id l4sm4342292wrv.60.2020.04.23.08.33.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Apr 2020 08:33:24 -0700 (PDT) Date: Thu, 23 Apr 2020 16:33:23 +0100 From: Chris Down To: Yafang Shao Cc: akpm@linux-foundation.org, mhocko@kernel.org, vdavydov.dev@gmail.com, linux-mm@kvack.org, Roman Gushchin , stable@vger.kernel.org, hannes@cmpxchg.org Subject: Re: [PATCH] mm, memcg: fix wrong mem cgroup protection Message-ID: <20200423153323.GA1318256@chrisdown.name> References: <20200423061629.24185-1-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20200423061629.24185-1-laoar.shao@gmail.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000506, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Yafang, I'm afraid I'm just as confused as Michal was about the intent of this patch. Can you please be more concise and clear about the practical ramifications and demonstrate some pathological behaviour? I really can't visualise what's wrong here from your explanation, and if I can't understand it as the person who wrote this code, I am not surprised others are also confused :-) Or maybe Roman can try to explain, since he acked the previous patch? At least to me, the emin/elow behaviour seems fairly non-trivial to reason about right now. Thanks.