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=-10.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 B3B69C2B9F4 for ; Sat, 19 Jun 2021 12:23:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9A0DD6120A for ; Sat, 19 Jun 2021 12:23:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234100AbhFSMZy (ORCPT ); Sat, 19 Jun 2021 08:25:54 -0400 Received: from mail-m118208.qiye.163.com ([115.236.118.208]:46848 "EHLO mail-m118208.qiye.163.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234066AbhFSMZx (ORCPT ); Sat, 19 Jun 2021 08:25:53 -0400 Received: from 2CD-RMPB.local (unknown [113.118.120.96]) by mail-m118208.qiye.163.com (Hmail) with ESMTPA id DEC93E01C3; Sat, 19 Jun 2021 20:23:36 +0800 (CST) Subject: Re: [PATCH v1 6/6] mm/hwpoison: fix unpoison_memory() To: =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= Cc: Naoya Horiguchi , "linux-mm@kvack.org" , Andrew Morton , David Hildenbrand , Oscar Salvador , Michal Hocko , Tony Luck , "Aneesh Kumar K.V" , "linux-kernel@vger.kernel.org" References: <20210614021212.223326-1-nao.horiguchi@gmail.com> <20210614021212.223326-7-nao.horiguchi@gmail.com> <94984984-f123-85ae-20bc-b40e90d536f6@sangfor.com.cn> <20210618083625.GA2215283@hori.linux.bs1.fc.nec.co.jp> From: Ding Hui Message-ID: Date: Sat, 19 Jun 2021 20:22:32 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20210618083625.GA2215283@hori.linux.bs1.fc.nec.co.jp> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-HM-Spam-Status: e1kfGhgUHx5ZQUtXWQgYFAkeWUFZS1VLWVdZKFlBSE83V1ktWUFJV1kPCR oVCBIfWUFZGhpJS1ZCH0xMHU4fSUpDS09VEwETFhoSFyQUDg9ZV1kWGg8SFR0UWUFZT0tIVUpKS0 hKTFVLWQY+ X-HM-Sender-Digest: e1kMHhlZQR0aFwgeV1kSHx4VD1lBWUc6OBA6GBw5ST9DUTpKPyk6ODpW HigaCi9VSlVKTUlPSktOT0pMTkhCVTMWGhIXVR8SFRwTDhI7CBoVHB0UCVUYFBZVGBVFWVdZEgtZ QVlKSkhVSkpDVUpJS1VCTVlXWQgBWUFPQ01PNwY+ X-HM-Tid: 0a7a2439fa1f2c17kusndec93e01c3 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/6/18 4:36 下午, HORIGUCHI NAOYA(堀口 直也) wrote: > On Thu, Jun 17, 2021 at 06:00:21PM +0800, Ding Hui wrote: >> On 2021/6/14 10:12, Naoya Horiguchi wrote: >>> From: Naoya Horiguchi >>> >>> After recent soft-offline rework, error pages can be taken off from >>> buddy allocator, but the existing unpoison_memory() does not properly >>> undo the operation. Moreover, due to the recent change on >>> __get_hwpoison_page(), get_page_unless_zero() is hardly called for >>> hwpoisoned pages. So __get_hwpoison_page() mostly returns zero (meaning >>> to fail to grab page refcount) and unpoison just clears PG_hwpoison >>> without releasing a refcount. That does not lead to a critical issue >>> like kernel panic, but unpoisoned pages never get back to buddy (leaked >>> permanently), which is not good. >> >> As I mention in [1], I'm not sure about the exactly meaning of "broken" in >> unpoison_memory(). >> >> Maybe the misunderstanding is: >> >> I think __get_hwpoison_page() mostly returns one for hwpoisoned page. >> In 06be6ff3d2ec ("mm,hwpoison: rework soft offline for free pages"), >> page_handle_poison() is introduced, it will add refcount for all >> soft-offlineed hwpoison page. >> In memory_failure() for hard-offline，page_ref_inc() called on free page >> too, and for used page, we do not call put_page() after get_hwpoison_page() >> != 0. >> So all hwpoisoned page refcount must be great than zero when >> unpoison_memory() if regardless of racy. > > Hi, Ding, > > Thanks for the comment. I feel that I failed to define the exact issue in > unpoison. Maybe I saw and misinterpreted some random error as unpoison's > issue during developing other hwpoison patches, so please don't take serious > my previous wrong word "broken", sorry about that. > > Anyway I reconsider how to handle this 6/6, maybe it will be a clear > description of the problem, and will be simplified. > >> >> Recently I tested loop soft-offline random pages and unpoison them for days, >> it works fine to me. (with bac9c6fa1f92 patched) > > Thank you for testing, > Hi Naoya, I'm afraid of my description about testing is ambiguous for others, let me clarify that I ran stress soft-offline test case from mce-test project (https://git.kernel.org/pub/scm/utils/cpu/mce/mce-test.git) for days to verify my modify about NR_FREE_PAGES (bac9c6fa1f92), without your current patchset, the case is loop soft-offline random pages and unpoison them, and it works basic fine to me. -- Thanks, -dinghui