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 X-Spam-Level: X-Spam-Status: No, score=-17.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 06A6DC433F5 for ; Mon, 6 Sep 2021 09:39:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D503160F13 for ; Mon, 6 Sep 2021 09:39:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241208AbhIFJkM (ORCPT ); Mon, 6 Sep 2021 05:40:12 -0400 Received: from szxga08-in.huawei.com ([45.249.212.255]:15241 "EHLO szxga08-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239548AbhIFJkF (ORCPT ); Mon, 6 Sep 2021 05:40:05 -0400 Received: from dggeme703-chm.china.huawei.com (unknown [172.30.72.56]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4H33H65l13z1DGjC; Mon, 6 Sep 2021 17:38:10 +0800 (CST) Received: from [10.174.178.100] (10.174.178.100) by dggeme703-chm.china.huawei.com (10.1.199.99) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.8; Mon, 6 Sep 2021 17:38:59 +0800 Subject: Re: [PATCH] mm/page_isolation: fix potential missing call to unset_migratetype_isolate() To: David Hildenbrand , CC: , , , References: <20210904092053.33037-1-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: Date: Mon, 6 Sep 2021 17:38:58 +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: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.100] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggeme703-chm.china.huawei.com (10.1.199.99) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/9/6 17:27, David Hildenbrand wrote: > On 04.09.21 11:20, Miaohe Lin wrote: >> In start_isolate_page_range() undo path, pfn_to_online_page() just checks >> the first pfn in a pageblock while __first_valid_page() will traverse the >> pageblock until the first online pfn is found. So we may miss the call to >> unset_migratetype_isolate() in undo path and pages will remain isolated >> unexpectedly. Fix this by calling undo_isolate_page_range() and this will >> also help to remove some duplicated codes. >> >> Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages") > > While that is true, we shouldn't ever trigger, neither via cma, virtio-mem nor memory offlining, because essentially all operate on MAX_ORDER -1 -aligned ranges without memory holes. I think this should never trigger too. It's a theoretical issue. So is the Fixes tag necessary ? > >> Signed-off-by: Miaohe Lin >> --- >>   mm/page_isolation.c | 9 +-------- >>   1 file changed, 1 insertion(+), 8 deletions(-) >> >> diff --git a/mm/page_isolation.c b/mm/page_isolation.c >> index 471e3a13b541..9bb562d5d194 100644 >> --- a/mm/page_isolation.c >> +++ b/mm/page_isolation.c >> @@ -202,14 +202,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, >>       } >>       return 0; >>   undo: >> -    for (pfn = start_pfn; >> -         pfn < undo_pfn; >> -         pfn += pageblock_nr_pages) { >> -        struct page *page = pfn_to_online_page(pfn); >> -        if (!page) >> -            continue; >> -        unset_migratetype_isolate(page, migratetype); >> -    } >> +    undo_isolate_page_range(start_pfn, undo_pfn, migratetype); >>   > > It'd be even cleaner to drop the label completely and call it from the single callsite. We can even avoid undo_pfn ... > > if (page && set_migratetype_isolate(page, migratetype, flags)) { >     undo_isolate_page_range(start_pfn, pfn, migratetype); >     return -EBUSY; > } > Looks much better. Will do it later. Many thanks. :) > If pfn == start_pfn, undo_isolate_page_range() will simply do nothing. > >>       return -EBUSY; >>   } >> >