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 9DC48C54FD0 for ; Thu, 23 Apr 2020 15:33:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7CE2D20767 for ; Thu, 23 Apr 2020 15:33:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chrisdown.name header.i=@chrisdown.name header.b="UUleoEnG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728990AbgDWPd2 (ORCPT ); Thu, 23 Apr 2020 11:33:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1728865AbgDWPd1 (ORCPT ); Thu, 23 Apr 2020 11:33:27 -0400 Received: from mail-wm1-x341.google.com (mail-wm1-x341.google.com [IPv6:2a00:1450:4864:20::341]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 462E4C09B040 for ; Thu, 23 Apr 2020 08:33:26 -0700 (PDT) Received: by mail-wm1-x341.google.com with SMTP id z6so7033125wml.2 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=bOMt7J2ZbgXaub793sSYZ3RoA8+fANBgzUGvmsDc3idFG7gDdd1Du6hLhVXH14VO/y okEE4iUWPLqfOqJ/1syOUHcegXuCRsxY0m8vI6NiBskLM9qAhzKngDHXv/TeZYEn5AIE YDzIhrMIOkRmJ5Z2R4QQSRzteyOIKAkpLbjKiMCu0Xw0zJynp8a6AoZpn4Muw/rAQFK4 v3pz6mcNvrAy65ydefqGBfssh9a7FkM8GucD+EvyP9FZYbVq4s/LA0SIJ18xwRfdibfG q2u6UaDQrcBdgH1XubGSebVhA/Tu/h2OUlcVlxgKa5pxPupNk091Ti7Q97aTjec2MUCo EDUg== X-Gm-Message-State: AGi0PuYKqAWyQws5m+p1Tt9FCkfUYmhVW33oNWfyb+GrniyEZWoe2JTB eBPe6FTmywMeEqR857l6iEG5zA== 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> Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 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.