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Fri, 2 Aug 2024 15:50:08 +0800 Message-ID: <05520370-6390-4b08-8fcb-01f255deecbc@huawei.com> Date: Fri, 2 Aug 2024 15:50:08 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/4] mm: memory_hotplug: check hwpoisoned page firstly in do_migrate_range() Content-Language: en-US To: David Hildenbrand , Andrew Morton CC: Oscar Salvador , Miaohe Lin , Naoya Horiguchi , References: <20240725011647.1306045-1-wangkefeng.wang@huawei.com> <20240725011647.1306045-3-wangkefeng.wang@huawei.com> <56b9a389-4c36-4892-962d-b45878f30f4d@huawei.com> <68067a56-4b9c-4636-9d07-41fee371d80c@redhat.com> From: Kefeng Wang In-Reply-To: <68067a56-4b9c-4636-9d07-41fee371d80c@redhat.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemf100008.china.huawei.com (7.185.36.138) X-Stat-Signature: j3mxowyt9hmsqxf318dg31bh5zrmx9mt X-Rspam-User: X-Rspamd-Queue-Id: 7AA431C000E X-Rspamd-Server: rspam02 X-HE-Tag: 1722585016-733499 X-HE-Meta: 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 Nt3UrI2B 8Af8KQRerMcf2E0rN/H3wGHX5JqEltb0srUDR9lbXrfSSv86uHWpuFZmxV4DQRdqO9/XLm5O1D/HrBY1XDZ6MYyIAYZCRn731WMafG/giJAjtvNY/lZ7GEXUdNWBShk2SBdcBbpS1vH8EeW7sXaUUXnb9HszlJK43oQKJKVauV69lUlUE3Vd24g4VQdLOFqUEDjNVuGbMfdWuAfrW8SnT16SADxs3XDWovo7g2nos8yqH4ycHHJaX62ZZP3RzrXunI44D9VuQqb9nziczIec0RIgaqmwPsh5LItmR 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: List-Subscribe: List-Unsubscribe: On 2024/8/2 4:10, David Hildenbrand wrote: > >>> >>> We're not checking the head page here, will this work reliably for >>> hugetlb? (I recall some difference in per-page hwpoison handling between >>> hugetlb and THP due to the vmemmap optimization) >> >> Before this changes, the hwposioned hugetlb page won't try to unmap in >> do_migrate_range(), we hope it already unmapped in memory_failure(), as >> mentioned from comments, there maybe fail to unmap, so a new safeguard >> to try to unmap it again here, but we don't need to guarantee it. > > Thanks for clarifying! > > But I do wonder if the PageHWPoison() is the right thing to do for hugetlb. > > IIUC, hugetlb requires folio_test_hwpoison() -- testing the head page > not the subpage. Reason is that due to the vmemmap optimization we might > not be able to modify subpages to set hwpoison. Yes, HVO is special(only head page with hwpoison), since we always want to check head page here (next pfn = head_pfn + nr), so it might be enough to only use PageHWpoison, but just in case, adding hwpoison check for the head page, if (unlikely(PageHWPoison(page) || folio_test_hwpoison(folio)))