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 6FCADC433EF for ; Tue, 12 Apr 2022 03:13:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344087AbiDLDPt (ORCPT ); Mon, 11 Apr 2022 23:15:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49758 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344254AbiDLDPh (ORCPT ); Mon, 11 Apr 2022 23:15:37 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E4A3431235 for ; Mon, 11 Apr 2022 20:13:19 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KcrNK3DZXzgYK6; Tue, 12 Apr 2022 11:11:29 +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 15.1.2375.24; Tue, 12 Apr 2022 11:13:16 +0800 Subject: Re: [PATCH 3/4] mm/migration: return errno when isolate_huge_page failed To: Christoph Hellwig CC: , , , , , , , , , , , , , , , , , , , References: <20220409073846.22286-1-linmiaohe@huawei.com> <20220409073846.22286-4-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: Date: Tue, 12 Apr 2022 11:13:16 +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: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] 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 2022/4/11 22:10, Christoph Hellwig wrote: > On Sat, Apr 09, 2022 at 03:38:45PM +0800, Miaohe Lin wrote: >> We might fail to isolate huge page due to e.g. the page is under migration >> which cleared HPageMigratable. So we should return -EBUSY in this case >> rather than always return 1 which could confuse the user. >> >> Fixes: e8db67eb0ded ("mm: migrate: move_pages() supports thp migration") >> Reviewed-by: Muchun Song >> Reviewed-by: Baolin Wang >> Signed-off-by: Miaohe Lin >> --- >> mm/migrate.c | 6 ++---- >> 1 file changed, 2 insertions(+), 4 deletions(-) >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index 381963231a62..044656a14ae2 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -1632,10 +1632,8 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, >> goto out_putpage; >> >> if (PageHuge(page)) { >> - if (PageHead(page)) { >> - isolate_huge_page(page, pagelist); >> - err = 1; >> - } >> + if (PageHead(page)) >> + err = isolate_huge_page(page, pagelist) ? 1 : -EBUSY; > > I think a: > > err = isolate_huge_page(page, pagelist); > if (!err) > err = 1; Many thanks for your comment. IIUC, isolate_huge_page does not return the wanted error code. So the above code won't do the right thing. Thanks. > > would be a lot more readable here. > > . >