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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=no 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 BF17AC7618F for ; Wed, 17 Jul 2019 18:39:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8B3F52184B for ; Wed, 17 Jul 2019 18:39:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388918AbfGQSjJ (ORCPT ); Wed, 17 Jul 2019 14:39:09 -0400 Received: from out4436.biz.mail.alibaba.com ([47.88.44.36]:10599 "EHLO out4436.biz.mail.alibaba.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727377AbfGQSjJ (ORCPT ); Wed, 17 Jul 2019 14:39:09 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04407;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0TX8zwcd_1563388743; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0TX8zwcd_1563388743) by smtp.aliyun-inc.com(127.0.0.1); Thu, 18 Jul 2019 02:39:06 +0800 Subject: Re: [v2 PATCH 2/2] mm: mempolicy: handle vma with unmovable pages mapped correctly in mbind From: Yang Shi To: Vlastimil Babka , mhocko@kernel.org, mgorman@techsingularity.net, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1561162809-59140-1-git-send-email-yang.shi@linux.alibaba.com> <1561162809-59140-3-git-send-email-yang.shi@linux.alibaba.com> <0cbc99f6-76a9-7357-efa7-a2d551b3cd12@suse.cz> <9defdc16-c825-05b7-b394-abdf39000220@linux.alibaba.com> <3197a7df-c7bc-2bac-3d40-dbfc97d4a909@linux.alibaba.com> Message-ID: Date: Wed, 17 Jul 2019 11:39:02 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <3197a7df-c7bc-2bac-3d40-dbfc97d4a909@linux.alibaba.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/17/19 11:23 AM, Yang Shi wrote: > > > On 7/16/19 10:28 AM, Yang Shi wrote: >> >> >> On 7/16/19 5:07 AM, Vlastimil Babka wrote: >>> On 6/22/19 2:20 AM, Yang Shi wrote: >>>> @@ -969,10 +975,21 @@ static long do_get_mempolicy(int *policy, >>>> nodemask_t *nmask, >>>>   /* >>>>    * page migration, thp tail pages can be passed. >>>>    */ >>>> -static void migrate_page_add(struct page *page, struct list_head >>>> *pagelist, >>>> +static int migrate_page_add(struct page *page, struct list_head >>>> *pagelist, >>>>                   unsigned long flags) >>>>   { >>>>       struct page *head = compound_head(page); >>>> + >>>> +    /* >>>> +     * Non-movable page may reach here.  And, there may be >>>> +     * temporaty off LRU pages or non-LRU movable pages. >>>> +     * Treat them as unmovable pages since they can't be >>>> +     * isolated, so they can't be moved at the moment.  It >>>> +     * should return -EIO for this case too. >>>> +     */ >>>> +    if (!PageLRU(head) && (flags & MPOL_MF_STRICT)) >>>> +        return -EIO; >>>> + >>> Hm but !PageLRU() is not the only way why queueing for migration can >>> fail, as can be seen from the rest of the function. Shouldn't all cases >>> be reported? >> >> Do you mean the shared pages and isolation failed pages? I'm not sure >> whether we should consider these cases break the semantics or not, so >> I leave them as they are. But, strictly speaking they should be >> reported too, at least for the isolation failed page. > > By reading mbind man page, it says: > > If MPOL_MF_MOVE is specified in flags, then the kernel will attempt to > move all the existing pages in the memory range so that they follow > the policy.  Pages that are shared with other processes will not be > moved.  If MPOL_MF_STRICT is also specified, then the call fails with > the error EIO if some pages could not be moved. > > It looks the code already handles shared page correctly, we just need > return -EIO for isolation failed page if MPOL_MF_STRICT is specified. Second look shows isolate_lru_page() returns error when and only when the page is *not* on LRU. So, we don't need change anything to this patch. > >> >> Thanks, >> Yang >> >>> >>>>       /* >>>>        * Avoid migrating a page that is shared with others. >>>>        */ >>>> @@ -984,6 +1001,8 @@ static void migrate_page_add(struct page >>>> *page, struct list_head *pagelist, >>>>                   hpage_nr_pages(head)); >>>>           } >>>>       } >>>> + >>>> +    return 0; >>>>   } >>>>     /* page allocation callback for NUMA node migration */ >>>> @@ -1186,9 +1205,10 @@ static struct page *new_page(struct page >>>> *page, unsigned long start) >>>>   } >>>>   #else >>>>   -static void migrate_page_add(struct page *page, struct list_head >>>> *pagelist, >>>> +static int migrate_page_add(struct page *page, struct list_head >>>> *pagelist, >>>>                   unsigned long flags) >>>>   { >>>> +    return -EIO; >>>>   } >>>>     int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from, >>>> >> >