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Tue, 6 Aug 2024 11:44:27 +0800 Message-ID: <4e693aa6-d742-4fe7-bd97-3d375f96fcfa@huawei.com> Date: Tue, 6 Aug 2024 11:44:27 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Kefeng Wang Subject: Re: [PATCH 2/4] mm: memory_hotplug: check hwpoisoned page firstly in do_migrate_range() 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> <0ff4a4ac-7b7b-4e07-a5da-a4c4e41438d6@redhat.com> <7eb9436d-b4e5-4be1-adce-aa07cc493679@huawei.com> Content-Language: en-US In-Reply-To: <7eb9436d-b4e5-4be1-adce-aa07cc493679@huawei.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemf100008.china.huawei.com (7.185.36.138) X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 3F2DB40004 X-Stat-Signature: iskxenoaeqwuizik5edhedndwos54smh X-Rspam-User: X-HE-Tag: 1722915872-164108 X-HE-Meta: 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 UDQVjr02 lO3YLiCpbpAGFegzcTPGlbuo+EbnPspSvKGZaJVZc+bsYfXwyjmsf+X7Uclq6Ig+RFpa8BZof5hc8o/FNCH2mENHRwx/tDmPlP9ZVp2F2daZL7XcdrDXP+CpObT42fe17QJnfi9eEAZYN9JsgnSpKgkPxSOW6D73IzBgBAtelGnTy88aHA5ODjVPe892YrWZUsBZ9VQW+HP6HB8ypiBamfSt8r9FxVdDbgRUbenVQ61PMFC9ovncQgcJmXyesWPm3oDAOYaVnt4pj7WHbyjZlPf20wg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000191, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi David, I have some question, On 2024/8/2 16:02, Kefeng Wang wrote: > ... >>>            */ >>> -        if (PageHWPoison(page)) { >>> +        if (unlikely(PageHWPoison(page))) { >>> +            folio = page_folio(page); >>> + >>>               if (WARN_ON(folio_test_lru(folio))) >>>                   folio_isolate_lru(folio); >>> + >>>               if (folio_mapped(folio)) >>> -                try_to_unmap(folio, TTU_IGNORE_MLOCK); >>> +                unmap_posioned_folio(folio, TTU_IGNORE_MLOCK); >>> + >>> +            if (folio_test_large(folio)) >>> +                pfn = folio_pfn(folio) + folio_nr_pages(folio) - 1; >>>               continue; >>>           } >>> +        if (PageHuge(page)) { >>> +            pfn = page_to_pfn(head) + compound_nr(head) - 1; >>> +            isolate_hugetlb(folio, &source); >>> +            continue; >>> +        } else if (PageTransHuge(page)) If the page is a tail page, we will BUG_ON(DEBUG_VM enabled) here, but it seems that we don't guarantee the page won't be a tail page. >>> +            pfn = page_to_pfn(head) + thp_nr_pages(page) - 1; thp_nr_pages() need a head page, I think it should use head here, so we can directly use folio_nr_pages(). >> >> If we can use a folio in the PageHWPoison() case, can we use one here >> as well? I know that it's all unreliable when not holding a folio >> reference, and we have to be a bit careful. > > Using a folio here is part of patch4, I want to unify hugetlb/thp(or > large folio) with "pfn = folio_pfn(folio) + folio_nr_pages(folio) - 1" > when large folio after get a ref. Think it again, even the folio don't hold a ref(splitting concurrently or something else), folio_nr_pages return incorrect, it won't cause issue since we will loop and find movable pages again in scan_movable_pages() and try to isolate pages, so directly use if (folio_test_large(folio)) { pfn = folio_pfn(folio) + folio_nr_pages(folio) - 1; if (folio_test_hugetlb(folio)) isolate_hugetlb(folio, &source); } Correct me if I am wrong, thanks. > >> >> It feels like using folios here would mostly be fine, because things >> like PageHuge() already use folios internally. >> >> And using it in the PageHWPoison() but not here looks a bit odd. > > We will convert to use folio in the following patch. > >> >> The important part is that we don't segfault if we'd overshoot our >> target. >> >