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[2003:d8:2f14:2400:afc:9797:137c:a25b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46e2a9bd9c3sm25328395e9.9.2025.09.24.03.00.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Sep 2025 03:00:41 -0700 (PDT) Message-ID: <5549ac3a-20cf-4959-ac53-0a89ed0eadd2@redhat.com> Date: Wed, 24 Sep 2025 12:00:40 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm: always call rmap_walk() on locked folios To: Lokesh Gidra Cc: akpm@linux-foundation.org, linux-mm@kvack.org, kaleshsingh@google.com, ngeoffray@google.com, jannh@google.com, Lorenzo Stoakes , Harry Yoo , Peter Xu , Suren Baghdasaryan , Barry Song , SeongJae Park , Dan Williams , Alistair Popple References: <20250918055135.2881413-1-lokeshgidra@google.com> <20250918055135.2881413-2-lokeshgidra@google.com> <2c9df5ee-6109-4fa5-b895-ad8e47d34bee@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: xRgFYy7RpPTaf2v1p_g-C3Us2HjYMzVLqAkP38MHR1E_1758708043 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: AC19240014 X-Stat-Signature: q3j83a9yzfrttignwbwo5ti8o6kukmag X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1758708048-834468 X-HE-Meta: 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 vB9H0yXA 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 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: >> >> Is mf_generic_kill_procs()->collect_procs() problematic? >> >> The dax_lock_folio/dax_unlock_folio part confuses me: I think it only >> locks an entry in the page cache but not the actual folio ("Lock the DAX >> entry corresponding to a folio")? > Yeah. The name dax_lock_folio() gives an impression as if the folio is > locked but it isn't :) Sorry for the late reply, I saw you posted v2 in the meantime. > > IIUC, a dax folio can't have an anon_vma (folio->mapping is actually > an address_space instead of anon_vma), right? We have these weird device-private dax folios that are anonymous and should have the anon_vma set up. > So, I thought it wasn't > required to actually lock the folio in this case. Please let me know > if you want me to still lock the folio around collect_procs(), or add > a comment? I think we can end up reaching memory_failure_dev_pagemap() with an anonymous dax folio. Not sure if anything would prevent us into calling mf_generic_kill_procs()->collect_procs()->collect_procs_anon()->folio_lock_anon_vma_read() CCing Dan and AAlistair -- Cheers David / dhildenb