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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id CC23FC433EF for ; Mon, 7 Mar 2022 12:01:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3F8618D0002; Mon, 7 Mar 2022 07:01:26 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 3A8698D0001; Mon, 7 Mar 2022 07:01:26 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 270538D0002; Mon, 7 Mar 2022 07:01:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0110.hostedemail.com [216.40.44.110]) by kanga.kvack.org (Postfix) with ESMTP id 194418D0001 for ; Mon, 7 Mar 2022 07:01:26 -0500 (EST) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id B87928126981 for ; Mon, 7 Mar 2022 12:01:25 +0000 (UTC) X-FDA: 79217450130.27.7805801 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf05.hostedemail.com (Postfix) with ESMTP id 909F3100010 for ; Mon, 7 Mar 2022 12:01:24 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4KBxp80RDSzBrZP; Mon, 7 Mar 2022 19:59:28 +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 20:01:20 +0800 Subject: Re: [PATCH 12/16] mm/migration: fix potential page refcounts leak in migrate_pages To: Baolin Wang , CC: , , , , , , , , , , , , , , , , , References: <20220304093409.25829-1-linmiaohe@huawei.com> <20220304093409.25829-13-linmiaohe@huawei.com> <20f47ec9-3b5b-5326-b1c3-4b1a0c38ef46@linux.alibaba.com> From: Miaohe Lin Message-ID: Date: Mon, 7 Mar 2022 20:01:20 +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: <20f47ec9-3b5b-5326-b1c3-4b1a0c38ef46@linux.alibaba.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: 909F3100010 X-Stat-Signature: exsnccz7sxszpa5uygwupxxpohtbah5f Authentication-Results: imf05.hostedemail.com; dkim=none; spf=pass (imf05.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1646654484-102583 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/3/7 9:57, Baolin Wang wrote: > Hi Miaohe, >=20 > 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_pag= es()") >> Signed-off-by: Miaohe Lin >> --- >> =C2=A0 mm/migrate.c | 9 +++++++++ >> =C2=A0 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_p= age_t get_new_page, >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 } >> =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 nr_failed_pages +=3D nr_subpages; >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 /* >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0 * There might be some subpages of fail-to-mig= rate THPs >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0 * left in thp_split_pages list. Move them bac= k to migration >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0 * list so that they could be put back to the = right list by >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0 * the caller otherwise the page refcnt will b= e leaked. >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0 */ >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 list_splice_init(&thp_split_pages, from); >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 nr_failed +=3D retry; >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 nr_thp_failed +=3D thp_retry; >=20 > Yes, I think we missed this case before, and your patch looks right. Bu= t we should also update the 'rc' to return the correct number of pages th= at were not migrated, right? I'am not sure. -ENOMEM case always returns -ENOMEM since commit 95a402c38= 47c ("[PATCH] page migration: use allocator function for migrate_pages()"). So I did not change rc. But= I think you're right. We should return the correct number of pages that were not migrated in this case. Thanks. > .