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=-17.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 DD5A4C4338F for ; Mon, 23 Aug 2021 09:14:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C587C61357 for ; Mon, 23 Aug 2021 09:14:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235799AbhHWJPT (ORCPT ); Mon, 23 Aug 2021 05:15:19 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:14409 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235769AbhHWJPR (ORCPT ); Mon, 23 Aug 2021 05:15:17 -0400 Received: from dggeme703-chm.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4GtRKt1P9bzbdRw; Mon, 23 Aug 2021 17:10:42 +0800 (CST) Received: from [10.174.177.35] (10.174.177.35) by dggeme703-chm.china.huawei.com (10.1.199.99) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.8; Mon, 23 Aug 2021 17:14:30 +0800 Subject: Re: [PATCH 3/3] mm/memory_hotplug: make HWPoisoned dirty swapcache pages unmovable To: =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= CC: "akpm@linux-foundation.org" , "mhocko@suse.com" , "minchan@kernel.org" , "cgoldswo@codeaurora.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" References: <20210821094246.10149-1-linmiaohe@huawei.com> <20210821094246.10149-4-linmiaohe@huawei.com> <20210823082646.GB1452382@hori.linux.bs1.fc.nec.co.jp> From: Miaohe Lin Message-ID: Date: Mon, 23 Aug 2021 17:14:29 +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: <20210823082646.GB1452382@hori.linux.bs1.fc.nec.co.jp> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.35] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggeme703-chm.china.huawei.com (10.1.199.99) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/8/23 16:26, HORIGUCHI NAOYA(堀口 直也) wrote: > On Sat, Aug 21, 2021 at 05:42:46PM +0800, Miaohe Lin wrote: >> HWPoisoned dirty swapcache pages are kept for killing owner processes. >> We should not offline these pages or do_swap_page() would access the >> offline pages and lead to bad ending. >> > > Thank you for the report. I'm not yet sure of the whole picture of this > issue. do_swap_page() is expected to return with fault VM_FAULT_HWPOISON > when called via the access to the error page, so I wonder why this doesn't > work for your situation. And what is the "bad ending" in the description? > IMO we might hotremove the page while SwapCache still have ref to it. Thus the page struct would be accessed after offlined. The page struct should be invalid in this case and this would make do_swap_page fragile. Or am I miss something? > I feel that aborting memory hotremove due to a hwpoisoned dirty swapcache > might be too hard, so I'd like to find another solution if we have. If there is a better way, we can just drop this one. Many thanks for your review and reply! :) > # You may separate this patch from former two to make them merged to > # mainline soon. > > Thanks, > Naoya Horiguchi > >> Signed-off-by: Miaohe Lin >> --- >> mm/memory_hotplug.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >> index 9fd0be32a281..0488eed3327c 100644 >> --- a/mm/memory_hotplug.c >> +++ b/mm/memory_hotplug.c >> @@ -1664,6 +1664,12 @@ static int scan_movable_pages(unsigned long start, unsigned long end, >> */ >> if (PageOffline(page) && page_count(page)) >> return -EBUSY; >> + /* >> + * HWPoisoned dirty swapcache pages are definitely unmovable >> + * because they are kept for killing owner processes. >> + */ >> + if (PageHWPoison(page) && PageSwapCache(page)) >> + return -EBUSY;