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=-9.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY autolearn=unavailable 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 3915CC433DF for ; Tue, 18 Aug 2020 08:41:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0FC772067C for ; Tue, 18 Aug 2020 08:41:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726422AbgHRIlp (ORCPT ); Tue, 18 Aug 2020 04:41:45 -0400 Received: from out30-45.freemail.mail.aliyun.com ([115.124.30.45]:53664 "EHLO out30-45.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726043AbgHRIlp (ORCPT ); Tue, 18 Aug 2020 04:41:45 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R171e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01422;MF=richard.weiyang@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0U67nSO1_1597740082; Received: from localhost(mailfrom:richard.weiyang@linux.alibaba.com fp:SMTPD_---0U67nSO1_1597740082) by smtp.aliyun-inc.com(127.0.0.1); Tue, 18 Aug 2020 16:41:22 +0800 Date: Tue, 18 Aug 2020 16:41:21 +0800 From: Wei Yang To: David Hildenbrand Cc: Wei Yang , Alexander Duyck , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/page_reporting: the "page" must not be the list head Message-ID: <20200818084121.GA33710@L-31X9LVDL-1304.local> Reply-To: Wei Yang References: <20200817084836.29216-1-richard.weiyang@linux.alibaba.com> <20200818030558.GC29756@L-31X9LVDL-1304.local> <9656b6cb-23c7-7875-85e7-6aeea7c9dc2c@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9656b6cb-23c7-7875-85e7-6aeea7c9dc2c@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 18, 2020 at 09:23:12AM +0200, David Hildenbrand wrote: >On 18.08.20 05:05, Wei Yang wrote: >> On Mon, Aug 17, 2020 at 07:07:04PM +0200, David Hildenbrand wrote: >>> On 17.08.20 18:05, Alexander Duyck wrote: >>>> >>>> >>>> On 8/17/2020 2:35 AM, David Hildenbrand wrote: >>>>> On 17.08.20 10:48, Wei Yang wrote: >>>>>> If "page" is the list head, list_for_each_entry_safe() would stop >>>>>> iteration. >>>>>> >>>>>> Signed-off-by: Wei Yang >>>>>> --- >>>>>> mm/page_reporting.c | 2 +- >>>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>>> >>>>>> diff --git a/mm/page_reporting.c b/mm/page_reporting.c >>>>>> index 3bbd471cfc81..aaaa3605123d 100644 >>>>>> --- a/mm/page_reporting.c >>>>>> +++ b/mm/page_reporting.c >>>>>> @@ -178,7 +178,7 @@ page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone, >>>>>> * the new head of the free list before we release the >>>>>> * zone lock. >>>>>> */ >>>>>> - if (&page->lru != list && !list_is_first(&page->lru, list)) >>>>>> + if (!list_is_first(&page->lru, list)) >>>>>> list_rotate_to_front(&page->lru, list); >>>>>> >>>>>> /* release lock before waiting on report processing */ >>>>>> >>>>> >>>>> Is this a fix or a cleanup? If it's a fix, can this be reproduced easily >>>>> and what ere the effects? >>>>> >>>> >>>> This should be a clean-up. Since the &page->lru != list will always be true. >>>> >>> >>> Makes sense, maybe we can make that a little bit clearer in the patch >>> description. >>> >> >> Ok, do you have some suggestion on the description? >> >> A clean-up for commit xxx? >> >> I would appreciate your suggestion :-) >> > >I'd go with something like > >" >mm/page_reporting: drop stale list head check in page_reporting_cycle > >list_for_each_entry_safe() guarantees that we will never stumble over >the list head; "&page->lru != list" will always evaluate to true. Let's >simplify. >" > Looks really better than mine. Thanks a lot. >to stress that this is a pure simplifcation. > >Reviewed-by: David Hildenbrand > >>>> If I recall at some point the that was a check for &next->lru != list >>>> but I think I pulled out an additional conditional check somewhere so >>>> that we just go through the start of the loop again and iterate over >>>> reported pages until we are guaranteed to have a non-reported page to >>>> rotate to the top of the list with the general idea being that we wanted >>>> the allocator to pull non-reported pages before reported pages. >>> >>> -- >>> Thanks, >>> >>> David / dhildenb >> > > >-- >Thanks, > >David / dhildenb -- Wei Yang Help you, Help me