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Tue, 21 Jan 2025 11:20:11 +0800 Subject: Re: [PATCH v2 1/3] mm: memory-failure: update ttu flag inside unmap_poisoned_folio To: David Hildenbrand CC: , , , , , , Wupeng Ma References: <20250116061657.227027-1-mawupeng1@huawei.com> <20250116061657.227027-2-mawupeng1@huawei.com> <21674fcc-bd5d-3e32-6e45-f0a16ab93202@huawei.com> <34ccd133-7623-4cd8-aad7-08526a97c472@redhat.com> <80984553-a2b9-46b4-acdc-f7abba3c755f@redhat.com> From: Miaohe Lin Message-ID: Date: Tue, 21 Jan 2025 11:20:10 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <80984553-a2b9-46b4-acdc-f7abba3c755f@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.173.127.72] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemd200019.china.huawei.com (7.221.188.193) X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 4A038100003 X-Stat-Signature: mfoso7nymp4gb16bxhnjby9crbcqnuj4 X-HE-Tag: 1737429615-427181 X-HE-Meta: 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 1t1RgImJ A3icg3XqWiw5ECIpuJhSnj4DbWYuoTULNtXxO9x+ShBlj/trOJgZas0q6IbeeQDsQTe97we0QEd5Q5XxcpFo7LRGkmZZaA4SnmMsuHM2SJImkMw/ObSIk6WSh0jRrIvAIKPwkRB71KLO0JzotIQuS8Qqp9OAo8GK+vfmlTuSZ7t84ZUKHgHi+KfFJzsr5IDzjQSAYUFArPEHNAMFfJT0+yBoF3q1GxB61ibsgPZ14cFKYblaGuQHCPFRExf3PKuTxZNB99sFmXk7+/vQ= 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 2025/1/20 16:46, David Hildenbrand wrote: > On 20.01.25 08:49, David Hildenbrand wrote: >> >>>>        if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) { >>>>            struct address_space *mapping; >>>>    @@ -1572,7 +1598,7 @@ void unmap_poisoned_folio(struct folio *folio, enum ttu_flags ttu) >>>>            if (!mapping) { >>>>                pr_info("%#lx: could not lock mapping for mapped hugetlb folio\n", >>>>                    folio_pfn(folio)); >>>> -            return; >>>> +            return -EBUSY; >>>>            } >>>>               try_to_unmap(folio, ttu|TTU_RMAP_LOCKED); >>>> @@ -1580,6 +1606,8 @@ void unmap_poisoned_folio(struct folio *folio, enum ttu_flags ttu) >>>>        } else { >>>>            try_to_unmap(folio, ttu); >>>>        } >>>> + >>>> +    return folio_mapped(folio) ? -EBUSY : 0; >>> >>> Do we really need this return value? It's unused in do_migrate_range(). >> >> I suggested it, because the folio_mapped() is nowadays extremely cheap. >> It cleans up hwpoison_user_mappings() quite nicely. > > I'm also wondering, if in do_migrate_range(), we want to pr_warn_ratelimit() in case still mapped after the call. IIUC, we don't really expect this to happen with SYNC set. Do you mean TTU_SYNC? It seems it's not set. There might be a race will hit the proposed pr_warn_ratelimit(): /* Assume folio is isolated for reclaim, so memory_failure failed to handle it at first time. Then it's put back to LRU. */ do_migrate_range folio_test_hwpoison folio_mapped unmap_poisoned_folio pr_warn_ratelimit(folio_mapped) But I might be miss something. And even this race is possible, it should be really hard to hit. Thanks. .