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 4EC37C00528 for ; Fri, 4 Aug 2023 01:45:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232480AbjHDBpj (ORCPT ); Thu, 3 Aug 2023 21:45:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56214 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231321AbjHDBpg (ORCPT ); Thu, 3 Aug 2023 21:45:36 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5940E10D for ; Thu, 3 Aug 2023 18:45:35 -0700 (PDT) Received: from dggpemm100001.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4RH7m267YxzVjqW; Fri, 4 Aug 2023 09:43:46 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemm100001.china.huawei.com (7.185.36.93) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Fri, 4 Aug 2023 09:45:33 +0800 Message-ID: Date: Fri, 4 Aug 2023 09:45:32 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.10.1 From: Kefeng Wang Subject: Re: [PATCH 1/4] mm: migrate: use a folio in add_page_for_migration() To: Matthew Wilcox CC: Andrew Morton , , , Huang Ying , David Hildenbrand References: <20230802095346.87449-1-wangkefeng.wang@huawei.com> <20230802095346.87449-2-wangkefeng.wang@huawei.com> <001ee9b0-ea25-a896-e3ae-9a9b05a46546@huawei.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm100001.china.huawei.com (7.185.36.93) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/8/3 20:30, Matthew Wilcox wrote: > On Thu, Aug 03, 2023 at 03:13:21PM +0800, Kefeng Wang wrote: >> >> >> On 2023/8/2 20:21, Matthew Wilcox wrote: >>> On Wed, Aug 02, 2023 at 05:53:43PM +0800, Kefeng Wang wrote: >>>> err = -EACCES; >>>> - if (page_mapcount(page) > 1 && !migrate_all) >>>> - goto out_putpage; >>>> + if (folio_estimated_sharers(folio) > 1 && !migrate_all) >>>> + goto out_putfolio; >>> >>> I do not think this is the correct change. Maybe leave this line >>> alone. >> >> Ok, I am aware of the discussion about this in other mail, will not >> change it(also the next two patch about this function), or wait the >> new work of David. >>> >>>> - if (PageHuge(page)) { >>>> - if (PageHead(page)) { >>>> - isolated = isolate_hugetlb(page_folio(page), pagelist); >>>> + if (folio_test_hugetlb(folio)) { >>>> + if (folio_test_large(folio)) { >>> >>> This makes no sense when you read it. All hugetlb folios are large, >>> by definition. Think about what this code used to do, and what it >>> should be changed to. >> >> hugetlb folio is self large folio, will drop redundant check > > No, that's not the difference. Keep thinking about it. This is not > a mechanical translation! if (PageHuge(page)) // page must be a hugetlb page if (PageHead(page)) // page must be a head page, not tail isolate_hugetlb() // isolate the hugetlb page if head After using folio, if (folio_test_hugetlb(folio)) // only check folio is hugetlb or not I don't check the page is head or not, since the follow_page could return a sub-page, so the check PageHead need be retained, right?