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 A49CEC433FE for ; Mon, 7 Mar 2022 05:59:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235437AbiCGGAU (ORCPT ); Mon, 7 Mar 2022 01:00:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234713AbiCGGAS (ORCPT ); Mon, 7 Mar 2022 01:00:18 -0500 Received: from out30-42.freemail.mail.aliyun.com (out30-42.freemail.mail.aliyun.com [115.124.30.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E84785D65B for ; Sun, 6 Mar 2022 21:59:24 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R631e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=20;SR=0;TI=SMTPD_---0V6Qe..f_1646632757; Received: from 30.97.48.83(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0V6Qe..f_1646632757) by smtp.aliyun-inc.com(127.0.0.1); Mon, 07 Mar 2022 13:59:19 +0800 Message-ID: <6c65c8b7-9a62-c027-e2b9-7d1531e43dfa@linux.alibaba.com> Date: Mon, 7 Mar 2022 14:00:20 +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 12/16] mm/migration: fix potential page refcounts leak in migrate_pages To: "Huang, Ying" Cc: Miaohe Lin , akpm@linux-foundation.org, mike.kravetz@oracle.com, shy828301@gmail.com, willy@infradead.org, ziy@nvidia.com, minchan@kernel.org, apopple@nvidia.com, dave.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> <20220304093409.25829-13-linmiaohe@huawei.com> <20f47ec9-3b5b-5326-b1c3-4b1a0c38ef46@linux.alibaba.com> <87mti25p98.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Baolin Wang In-Reply-To: <87mti25p98.fsf@yhuang6-desk2.ccr.corp.intel.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 On 3/7/2022 1:02 PM, Huang, Ying wrote: > Baolin Wang writes: > >> Hi Miaohe, >> >> On 3/4/2022 5:34 PM, Miaohe Lin wrote: >>> In -ENOMEM case, there might be some subpages of fail-to-migrate THPs >>> left in thp_split_pages list. We should move them back to migration >>> list so that they could be put back to the right list by the caller >>> otherwise the page refcnt will be leaked here. Also adjust nr_failed >>> and nr_thp_failed accordingly to make vm events account more accurate. >>> Fixes: b5bade978e9b ("mm: migrate: fix the return value of >>> migrate_pages()") >>> Signed-off-by: Miaohe Lin >>> --- >>> mm/migrate.c | 9 +++++++++ >>> 1 file changed, 9 insertions(+) >>> diff --git a/mm/migrate.c b/mm/migrate.c >>> index e0db06927f02..6c2dfed2ddb8 100644 >>> --- a/mm/migrate.c >>> +++ b/mm/migrate.c >>> @@ -1422,6 +1422,15 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, >>> } >>> nr_failed_pages += nr_subpages; >>> + /* >>> + * There might be some subpages of fail-to-migrate THPs >>> + * left in thp_split_pages list. Move them back to migration >>> + * list so that they could be put back to the right list by >>> + * the caller otherwise the page refcnt will be leaked. >>> + */ >>> + list_splice_init(&thp_split_pages, from); >>> + nr_failed += retry; >>> + nr_thp_failed += thp_retry; >> >> Yes, I think we missed this case before, and your patch looks >> right. But we should also update the 'rc' to return the correct number >> of pages that were not migrated, right? > > Per my understanding, -ENOMEM should be returned to indicate an fatal > error. > Ah, right. Sorry for noise. Reviewed-by: Baolin Wang