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 9BBF0C433FE for ; Mon, 7 Mar 2022 12:11:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231319AbiCGMMs (ORCPT ); Mon, 7 Mar 2022 07:12:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55096 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235118AbiCGMMo (ORCPT ); Mon, 7 Mar 2022 07:12:44 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 042AE7B56B for ; Mon, 7 Mar 2022 04:11:49 -0800 (PST) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KBy2p53RtzdZlC; Mon, 7 Mar 2022 20:10:26 +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 20:11:46 +0800 Subject: Re: [PATCH 12/16] mm/migration: fix potential page refcounts leak in migrate_pages To: "Huang, Ying" CC: , , , , , , , , , , , , , , , , , References: <20220304093409.25829-1-linmiaohe@huawei.com> <20220304093409.25829-13-linmiaohe@huawei.com> <87r17e5pat.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Miaohe Lin Message-ID: <3a93cba2-c877-73c6-e355-0b73fcb02cc6@huawei.com> Date: Mon, 7 Mar 2022 20:11:46 +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: <87r17e5pat.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) 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 13:01, Huang, Ying wrote: > Miaohe Lin writes: > >> 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; > > It appears that we don't need to change nr_failed, because we don't use > it for this situation. Otherwise looks good to me. > You're right. nr_failed is not used for this case. > Reviewed-by: "Huang, Ying" Many thanks for your review. > > Best Regards, > Huang, Ying > >> + nr_thp_failed += thp_retry; >> goto out; >> case -EAGAIN: >> if (is_thp) > . >