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 4E6D9C433F5 for ; Mon, 7 Mar 2022 02:14:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234183AbiCGCPk (ORCPT ); Sun, 6 Mar 2022 21:15:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34334 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232085AbiCGCPd (ORCPT ); Sun, 6 Mar 2022 21:15:33 -0500 Received: from out30-54.freemail.mail.aliyun.com (out30-54.freemail.mail.aliyun.com [115.124.30.54]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EEE3712ACA for ; Sun, 6 Mar 2022 18:13:48 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R191e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01424;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=20;SR=0;TI=SMTPD_---0V6OapQN_1646619214; Received: from 30.97.48.83(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0V6OapQN_1646619214) by smtp.aliyun-inc.com(127.0.0.1); Mon, 07 Mar 2022 10:13:35 +0800 Message-ID: Date: Mon, 7 Mar 2022 10:14:37 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH 13/16] mm/migration: return errno when isolate_huge_page failed To: Miaohe Lin , akpm@linux-foundation.org Cc: mike.kravetz@oracle.com, shy828301@gmail.com, willy@infradead.org, ying.huang@intel.com, ziy@nvidia.com, minchan@kernel.org, apopple@nvidia.com, ave.hansen@linux.intel.com, o451686892@gmail.com, almasrymina@google.com, jhubbard@nvidia.com, rcampbell@nvidia.com, peterx@redhat.com, naoya.horiguchi@nec.com, mhocko@suse.com, riel@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220304093409.25829-1-linmiaohe@huawei.com> <20220304093409.25829-14-linmiaohe@huawei.com> From: Baolin Wang In-Reply-To: <20220304093409.25829-14-linmiaohe@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Miaohe, On 3/4/2022 5:34 PM, Miaohe Lin wrote: > We should return errno (-EBUSY here) when failed to isolate the huge page > rather than always return 1 which could confuse the user. > > 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 6c2dfed2ddb8..279940c0c064 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1618,10 +1618,8 @@ 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; Could you elaborate on which case the huge page isolation can be failed in this case? Or you met a real problem? Cause now we've got this head huge page refcnt, I can not see why we'll fail to isolate this huge page.