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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 309FCC433FE for ; Mon, 17 Oct 2022 13:29:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229914AbiJQN34 (ORCPT ); Mon, 17 Oct 2022 09:29:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36270 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229778AbiJQN3x (ORCPT ); Mon, 17 Oct 2022 09:29:53 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 91167316 for ; Mon, 17 Oct 2022 06:29:47 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Mrd5g2JjMzVhvS; Mon, 17 Oct 2022 21:25:11 +0800 (CST) Received: from [10.174.151.185] (10.174.151.185) 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 15.1.2375.31; Mon, 17 Oct 2022 21:29:45 +0800 Subject: Re: [PATCH v6 1/4] mm,hwpoison,hugetlb,memory_hotplug: hotremove memory section with hwpoisoned hugepage To: =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= CC: Naoya Horiguchi , "linux-mm@kvack.org" , Andrew Morton , David Hildenbrand , Mike Kravetz , Yang Shi , Oscar Salvador , Muchun Song , Jane Chu , "linux-kernel@vger.kernel.org" References: <20221007010706.2916472-1-naoya.horiguchi@linux.dev> <20221007010706.2916472-2-naoya.horiguchi@linux.dev> <20221017072423.GA3660733@hori.linux.bs1.fc.nec.co.jp> From: Miaohe Lin Message-ID: <8a89e602-f80c-f5b9-ca54-7082a429bd52@huawei.com> Date: Mon, 17 Oct 2022 21:29:44 +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: <20221017072423.GA3660733@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: [10.174.151.185] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/10/17 15:24, HORIGUCHI NAOYA(堀口 直也) wrote: > On Sat, Oct 15, 2022 at 09:58:09AM +0800, Miaohe Lin wrote: >> On 2022/10/7 9:07, Naoya Horiguchi wrote: > ... >>> @@ -1785,7 +1785,8 @@ void hugetlb_clear_page_hwpoison(struct page *hpage) >>> * -EBUSY - the hugepage is busy (try to retry) >>> * -EHWPOISON - the hugepage is already hwpoisoned >>> */ >>> -int __get_huge_page_for_hwpoison(unsigned long pfn, int flags) >>> +int __get_huge_page_for_hwpoison(unsigned long pfn, int flags, >>> + bool *migratable_cleared) >>> { >>> struct page *page = pfn_to_page(pfn); >>> struct page *head = compound_head(page); >>> @@ -1815,6 +1816,15 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags) >>> goto out; >>> } >>> >>> + /* >>> + * Clearing HPageMigratable for hwpoisoned hugepages to prevent them >>> + * from being migrated by memory hotremove. >>> + */ >>> + if (count_increased) { >>> + *migratable_cleared = true; >>> + ClearHPageMigratable(head); >> >> I think I might be nitpicking... But it seems ClearHPageMigratable is not enough here. >> 1. In MF_COUNT_INCREASED case, we don't know whether HPageMigratable is set. >> 2. Even if HPageMigratable is set, there might be a race window before we clear HPageMigratable? > > Maybe this race is what I mentioned in > https://lore.kernel.org/linux-mm/20220928012647.GA597297@u2004.lan/ > (the second scenario). My stance to this case is that the hugepage is not > hwpoisoned even if some hardware (not visible to kernel) issue is in it, > so hwpoison handler can/may not cope with the race. > I guess that this could be handled by applying memcpy_mcsafe() mechanism > to page migration, but I'm not sure of the feasibility. Thanks Naoya. memcpy_mcsafe() might be a good idea to handle hwpoison with the memory copy in page migration path. And [1] is doing the similar thing. If this mechanism is applicable, then we could handle more memory failure scene. ;) [1] https://lore.kernel.org/linux-mm/20221010160142.1087120-1-jiaqiyan@google.com/ > >> So "*migratable_cleared = TestClearHPageMigratable" might be better? But I might be wrong. > > Thanks, this seems work for 1 (I need testing to check it), so I'll do this > in the next post. Many thanks for your work. Thanks, Miaohe Lin > >> >> With above fixed (if it's really a problem), this patch looks good to me. >> >> Reviewed-by: Miaohe Lin > > Thank you very much. > > - Naoya Horiguchi >