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[2003:cb:c714:d00:a1ab:bff4:268f:d7c5]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-37d1690f73csm352774f8f.24.2024.10.04.13.19.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 04 Oct 2024 13:19:35 -0700 (PDT) Message-ID: Date: Fri, 4 Oct 2024 22:19:33 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2] mm/gup: folio_split_user_page_pin To: Steven Sistare , Jason Gunthorpe Cc: linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Nico Pache References: <1727190332-385657-1-git-send-email-steven.sistare@oracle.com> <982f3e26-c998-4e72-b374-3f31bf0ca9f5@redhat.com> <20240927155848.GD4568@nvidia.com> <210cb725-fdc5-4878-9e6b-4357d34afb9f@redhat.com> <9dc54dbf-18b3-43f9-af4f-39ce44406ebe@oracle.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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <9dc54dbf-18b3-43f9-af4f-39ce44406ebe@oracle.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E2285180007 X-Stat-Signature: jj11ujsgrwrty1e7o35dd6zh84cwkfag X-Rspam-User: X-HE-Tag: 1728073179-588990 X-HE-Meta: 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 wt03cdYU FGh/HRPJIvClQ/RKhRSNN9ujj5geBIzbcrI5LJQxmtQ1P7CElPlSdISHTmb0KM+5BqN5DnS88xLDctnqeM/79YGJgDubXbV8gHaDJaI/gNYlh9h4wTVGyA+XApsA9bH3iwj3wm/mti4TcK0y2uYACLDeGdRT2ex+rh+2fxcfnMsVXX81Mm9KA17Tgzn3MY2WVevuTgQXJ11DAT4HQS2NGzFgvZ+JeyeajMgJhVkEyQLKlrYuviWuz6CQvCpjrOBW/en4i0ALxnDrtkyic2mCBy+qgYjEEBHZec0F79ejn9w/C894/h8eFnNwIboo/qzdKECjd33lpCKuFoFdeEPR89aanoA38HAANSGmmQOB8I1C0JxvyjVKFTXZnLb/fJU0u/aSHX8xZajSPBw67kj37E5Wwh8p6uXLLtOPXnvMAkehRrGJbhuZWMDZyvFPpQROaKdZQB2jcRPL6Eimu2M9l02HKmg== 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 04.10.24 19:20, Steven Sistare wrote: > On 10/4/2024 6:04 AM, David Hildenbrand wrote: >> On 01.10.24 19:17, Steven Sistare wrote: >>> On 9/27/2024 11:58 AM, Jason Gunthorpe wrote: >>>> On Fri, Sep 27, 2024 at 05:44:52PM +0200, David Hildenbrand wrote: >>>>> /** >>>>>    * folio_try_add_pins() - add pins to an already-pinned folio >>>>>    * @folio: the folio to add more pins to >>>>>    * >>>>>    * Try to add more pins to an already-pinned folio. The semantics >>>>>    * of the pin (e.g., FOLL_WRITE) follow any existing pin and cannot >>>>>    * be changed. >>>>>    * >>>>>    * This function is helpful when having obtained a pin on a large folio >>>>>    * using memfd_pin_folios(), but wanting to logically unpin parts >>>>>    * (e.g., individual pages) of the folio later, for example, using >>>>>    * unpin_user_page_range_dirty_lock(). >>>>>    * >>>>>    * This is not the right interface to initially pin a folio. >>>>>    */ >>>>> int folio_try_add_pins(struct folio *folio, unsigned int pins) >>>>> { >>>>>     VM_WARN_ON_ONCE(!folio_maybe_dma_pinned(folio)); >>>>> >>>>>     return try_grab_folio(folio, pins, FOLL_PIN); >>>>> } >>>> >>>> That looks pretty good to me too >>> >>> Looks good and passes my tests, I will add this version in V3 of the patch series. >>> >>> Are you sure you want "try" in the name folio_try_add_pins?  Usually try means >>> that any failure is transient and a future call may succeed >> >> And now I took another look at the codebase and we already do have folio_add_pin() that adds a single pin, but continues on overflows (not sure I like that, but at least it can be caught and debugged). >> >> So yes, we could simply turn folio_add_pin() into a wrapper around a folio_add_pins() that adds multiple pins. >> Looking at folio_add_pin() vs. try_grab_folio() I am not sure if the open-coding the logic in folio_add_pin() got the NR_FOLL_PIN_ACQUIRED accounting correct. > > To be clear, I am only suggesting that I use your folio_try_add_pins implementation, but > rename it to folio_add_pins. And not touch the existing folio_add_pin. This should be unified/cleaned up at some point. @Nico, interested in looking into this? Otherwise, I can add it to my todo list. -- Cheers, David / dhildenb