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 DC309C433F5 for ; Mon, 7 Mar 2022 12:04:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237304AbiCGMFB (ORCPT ); Mon, 7 Mar 2022 07:05:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232575AbiCGME5 (ORCPT ); Mon, 7 Mar 2022 07:04:57 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E28116E280 for ; Mon, 7 Mar 2022 04:04:02 -0800 (PST) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KBxsr1shRzdb05; Mon, 7 Mar 2022 20:02:40 +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 15.1.2308.21; Mon, 7 Mar 2022 20:04:00 +0800 Subject: Re: [PATCH 12/16] mm/migration: fix potential page refcounts leak in migrate_pages To: Baolin Wang , "Huang, Ying" CC: , , , , , , , , , , , , , , , , , 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> <6c65c8b7-9a62-c027-e2b9-7d1531e43dfa@linux.alibaba.com> From: Miaohe Lin Message-ID: Date: Mon, 7 Mar 2022 20:03:59 +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: <6c65c8b7-9a62-c027-e2b9-7d1531e43dfa@linux.alibaba.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) 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 2022/3/7 14:00, Baolin Wang wrote: > > > 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 Oh, I missed this email. So we should return -ENOMEM in this case. Many thanks for both of you. > .