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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,UNPARSEABLE_RELAY autolearn=ham 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 087FDC3279B for ; Mon, 2 Jul 2018 17:24:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AC1D9208C2 for ; Mon, 2 Jul 2018 17:24:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AC1D9208C2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752721AbeGBRYq (ORCPT ); Mon, 2 Jul 2018 13:24:46 -0400 Received: from out30-131.freemail.mail.aliyun.com ([115.124.30.131]:44634 "EHLO out30-131.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752254AbeGBRYp (ORCPT ); Mon, 2 Jul 2018 13:24:45 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07402;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=15;SR=0;TI=SMTPD_---0T3r6fys_1530552267; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0T3r6fys_1530552267) by smtp.aliyun-inc.com(127.0.0.1); Tue, 03 Jul 2018 01:24:35 +0800 Subject: Re: [RFC v3 PATCH 5/5] x86: check VM_DEAD flag in page fault To: Michal Hocko , Laurent Dufour Cc: willy@infradead.org, akpm@linux-foundation.org, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, tglx@linutronix.de, hpa@zytor.com, linux-mm@kvack.org, x86@kernel.org, linux-kernel@vger.kernel.org References: <1530311985-31251-1-git-send-email-yang.shi@linux.alibaba.com> <1530311985-31251-6-git-send-email-yang.shi@linux.alibaba.com> <84eba553-2e0b-1a90-d543-6b22c1b3c5f8@linux.vnet.ibm.com> <20180702121528.GM19043@dhcp22.suse.cz> <80406cbd-67f4-ca4c-cd54-aeb305579a72@linux.vnet.ibm.com> <20180702124558.GP19043@dhcp22.suse.cz> <20180702133733.GU19043@dhcp22.suse.cz> From: Yang Shi Message-ID: <6fd4eb3d-ef66-7a37-4adb-05c22ac51d95@linux.alibaba.com> Date: Mon, 2 Jul 2018 10:24:27 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180702133733.GU19043@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/2/18 6:37 AM, Michal Hocko wrote: > On Mon 02-07-18 15:33:11, Laurent Dufour wrote: >> >> On 02/07/2018 14:45, Michal Hocko wrote: >>> On Mon 02-07-18 14:26:09, Laurent Dufour wrote: >>>> On 02/07/2018 14:15, Michal Hocko wrote: > [...] >>>>> We already do have a model for that. Have a look at MMF_UNSTABLE. >>>> MMF_UNSTABLE is a mm's flag, here this is a VMA's flag which is checked. >>> Yeah, and we have the VMA ready for all places where we do check the >>> flag. check_stable_address_space can be made to get vma rather than mm. >> Yeah, this would have been more efficient to check that flag at the beginning >> of the page fault handler rather than the end, but this way it will be easier >> to handle the speculative page fault too ;) > The thing is that it doesn't really need to be called earlier. You are > not risking data corruption on file backed mappings. OK, I just think it could save a few cycles to check the flag earlier. If nobody think it is necessary, we definitely could re-use check_stable_address_space(), just return VM_FAULT_SIGSEGV for VM_DEAD vma, and check for both shared and non-shared. Thanks, Yang >