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[47.88.44.37]) by mx.google.com with ESMTPS id x5si1784646pjp.75.2019.06.19.09.21.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 19 Jun 2019 09:21:26 -0700 (PDT) Received-SPF: pass (google.com: domain of yang.shi@linux.alibaba.com designates 47.88.44.37 as permitted sender) client-ip=47.88.44.37; Authentication-Results: mx.google.com; spf=pass (google.com: domain of yang.shi@linux.alibaba.com designates 47.88.44.37 as permitted sender) smtp.mailfrom=yang.shi@linux.alibaba.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=alibaba.com X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R221e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07487;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0TUcmGMH_1560961263; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0TUcmGMH_1560961263) by smtp.aliyun-inc.com(127.0.0.1); Thu, 20 Jun 2019 00:21:06 +0800 Subject: Re: [PATCH] mm: mempolicy: handle vma with unmovable pages mapped correctly in mbind To: Vlastimil Babka , Michal Hocko Cc: akpm@linux-foundation.org, mgorman@techsingularity.net, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Eric Dumazet , "David S. Miller" , netdev@vger.kernel.org References: <1560797290-42267-1-git-send-email-yang.shi@linux.alibaba.com> <20190618130253.GH3318@dhcp22.suse.cz> <20190618182848.GJ3318@dhcp22.suse.cz> <68c2592d-b747-e6eb-329f-7a428bff1f86@linux.alibaba.com> <20190619052133.GB2968@dhcp22.suse.cz> <21a0b20c-5b62-490e-ad8e-26b4b78ac095@suse.cz> From: Yang Shi Message-ID: <687f4e57-5c50-7900-645e-6ef3a5c1c0c7@linux.alibaba.com> Date: Wed, 19 Jun 2019 09:21:01 -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: <21a0b20c-5b62-490e-ad8e-26b4b78ac095@suse.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US 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 6/19/19 1:22 AM, Vlastimil Babka wrote: > On 6/19/19 7:21 AM, Michal Hocko wrote: >> On Tue 18-06-19 14:13:16, Yang Shi wrote: >> [...] >>> I used to have !__PageMovable(page), but it was removed since the >>> aforementioned reason. I could add it back. >>> >>> For the temporary off LRU page, I did a quick search, it looks the most >>> paths have to acquire mmap_sem, so it can't race with us here. Page >>> reclaim/compaction looks like the only race. But, since the mapping should >>> be preserved even though the page is off LRU temporarily unless the page is >>> reclaimed, so we should be able to exclude temporary off LRU pages by >>> calling page_mapping() and page_anon_vma(). >>> >>> So, the fix may look like: >>> >>> if (!PageLRU(head) && !__PageMovable(page)) { >>>     if (!(page_mapping(page) || page_anon_vma(page))) >>>         return -EIO; >> This is getting even more muddy TBH. Is there any reason that we have to >> handle this problem during the isolation phase rather the migration? > I think it was already said that if pages can't be isolated, then > migration phase won't process them, so they're just ignored. Yes，exactly. > However I think the patch is wrong to abort immediately when > encountering such page that cannot be isolated (AFAICS). IMHO it should > still try to migrate everything it can, and only then return -EIO. It is fine too. I don't see mbind semantics define how to handle such case other than returning -EIO.