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Howlett" , Oscar Salvador , Suren Baghdasaryan , Andrea Arcangeli References: <20251014231501.2301398-1-peterx@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: <20251014231501.2301398-1-peterx@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 5JKiiRAD0xzCC7ECfWgS3sx_sWNq7-KUjkZ3TwjP0gs_1760967290 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Stat-Signature: t4j5jbqrskayywn3syhgfd4uw71tzt3n X-Rspam-User: X-Rspamd-Queue-Id: BD6CD40012 X-HE-Tag: 1760967293-443408 X-HE-Meta: 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 Ww/DYfYW 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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: On 15.10.25 01:14, Peter Xu wrote: > [based on latest akpm/mm-new of Oct 14th, commit 36c6c5ce1b275] > > v4: > - Some cleanups within vma_can_userfault() [David] > - Rename uffd_get_folio() to minor_get_folio() [David] > - Remove uffd_features in vm_uffd_ops, deduce it from supported ioctls [David] > > v1: https://lore.kernel.org/r/20250620190342.1780170-1-peterx@redhat.com > v2: https://lore.kernel.org/r/20250627154655.2085903-1-peterx@redhat.com > v3: https://lore.kernel.org/r/20250926211650.525109-1-peterx@redhat.com > > This series is an alternative proposal of what Nikita proposed here on the > initial three patches: > > https://lore.kernel.org/r/20250404154352.23078-1-kalyazin@amazon.com > > This is not yet relevant to any guest-memfd support, but paving way for it. > Here, the major goal is to make kernel modules be able to opt-in with any > form of userfaultfd supports, like guest-memfd. This alternative option > should hopefully be cleaner, and avoid leaking userfault details into > vm_ops.fault(). > > It also means this series does not depend on anything. It's a pure > refactoring of userfaultfd internals to provide a generic API, so that > other types of files, especially RAM based, can support userfaultfd without > touching mm/ at all. > > To achieve it, this series introduced a file operation called vm_uffd_ops. > The ops needs to be provided when a file type supports any of userfaultfd. > > With that, I moved both hugetlbfs and shmem over, whenever possible. So > far due to concerns on exposing an uffd_copy() API, the MISSING faults are > still separately processed and can only be done within mm/. Hugetlbfs kept > its special paths untouched. > > An example of shmem uffd_ops: > > static const struct vm_uffd_ops shmem_uffd_ops = { > .supported_ioctls = BIT(_UFFDIO_COPY) | > BIT(_UFFDIO_ZEROPAGE) | > BIT(_UFFDIO_WRITEPROTECT) | > BIT(_UFFDIO_CONTINUE) | > BIT(_UFFDIO_POISON), > .minor_get_folio = shmem_uffd_get_folio, > }; This looks better than the previous version to me. Long term the goal should be to move all hugetlb/shmem specific stuff out of mm/hugetlb.c and of course, we won't be adding any new ones to mm/userfaultfd.c I agree with Liam that a better interface could be providing default handlers for the separate ioctls [1], but there is always the option to evolve this interface into something like that later. [1] https://lkml.kernel.org/r/frnos5jtmlqvzpcrredcoummuzvllweku5dgp5ii5in6epwnw5@anu4dqsz6shy -- Cheers David / dhildenb