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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 62D90C433EF for ; Tue, 8 Mar 2022 11:33:48 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EBA638D0002; Tue, 8 Mar 2022 06:33:47 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E685A8D0001; Tue, 8 Mar 2022 06:33:47 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D56CC8D0002; Tue, 8 Mar 2022 06:33:47 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.28]) by kanga.kvack.org (Postfix) with ESMTP id C5C408D0001 for ; Tue, 8 Mar 2022 06:33:47 -0500 (EST) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 9A455181C for ; Tue, 8 Mar 2022 11:33:47 +0000 (UTC) X-FDA: 79221009294.10.B7E3611 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf23.hostedemail.com (Postfix) with ESMTP id B574D14000D for ; Tue, 8 Mar 2022 11:33:46 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4KCY4S2c82z1GBw6; Tue, 8 Mar 2022 19:28:56 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Tue, 8 Mar 2022 19:33:43 +0800 Subject: Re: [PATCH 15/16] mm/migration: fix possible do_pages_stat_array racing with memory offline To: "Huang, Ying" , Muchun Song CC: Andrew Morton , Mike Kravetz , Yang Shi , Matthew Wilcox , Zi Yan , Minchan Kim , Alistair Popple , , , Mina Almasry , John Hubbard , Ralph Campbell , Peter Xu , =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= , Michal Hocko , , Linux Memory Management List , LKML References: <20220304093409.25829-1-linmiaohe@huawei.com> <20220304093409.25829-16-linmiaohe@huawei.com> <875yoq5od4.fsf@yhuang6-desk2.ccr.corp.intel.com> <87r17emcng.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Miaohe Lin Message-ID: <05c39882-0d61-92cb-9c63-479ea6dffb63@huawei.com> Date: Tue, 8 Mar 2022 19:33:42 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <87r17emcng.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: B574D14000D X-Stat-Signature: nczxqmg35xyqp349ctcedos4ksybu5kw Authentication-Results: imf23.hostedemail.com; dkim=none; spf=pass (imf23.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Rspam-User: X-HE-Tag: 1646739226-508507 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/3/7 15:42, Huang, Ying wrote: > Muchun Song writes: > >> On Mon, Mar 7, 2022 at 1:22 PM Huang, Ying wrote: >>> >>> Miaohe Lin writes: >>> >>>> When follow_page peeks a page, the page could be reclaimed under heavy >>>> memory pressure >>> >>> I don't think that memory pressure and reclaiming will be an issue. >> >> I think he means a page first to be reclaimed then to be offline >> could encounter this issue and reclaiming is a precondition. > > I don't think reclaiming is a precondition. It seems possible that the > virtual page is migrated, then the physical page is offlined. > What I indeed mean is a page could first be reclaimed, migrated and so on. And then be offlined. Sorry for confusing. Thanks both of you. > Best Regards, > Huang, Ying > >> Thanks. >> >>> >>>> and thus be offlined while it's still being used by the >>>> do_pages_stat_array(). >>> >>> "offline" seems a possible problem. > . >