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(p200300d82f4555008267647f4209dedd.dip0.t-ipconnect.de. [2003:d8:2f45:5500:8267:647f:4209:dedd]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-442d67d5c09sm26141235e9.7.2025.05.09.03.59.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 May 2025 03:59:19 -0700 (PDT) Message-ID: Date: Fri, 9 May 2025 12:59:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/3] mm: introduce new .mmap_prepare() file callback To: Lorenzo Stoakes Cc: Andrew Morton , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Alexander Viro , Christian Brauner , Jan Kara , Matthew Wilcox References: <2204037e-f0bd-4059-b32a-d0970d96cea3@redhat.com> <9f479d46-cf06-4dfe-ac26-21fce0aafa06@lucifer.local> <5a489fa9-b2c0-4a7d-aa0e-5a97381e6b33@redhat.com> <9b9fd5ce-c303-46c4-acc7-40db1201f70a@lucifer.local> 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: <9b9fd5ce-c303-46c4-acc7-40db1201f70a@lucifer.local> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: dIYCpRd9TNcbuX0_Zyw5DF5Q_PEuhCfMEHQqsLAbaZk_1746788360 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: c3e3dmeyjwqbhwgrcgd7tsjh1j6om56t X-Rspamd-Queue-Id: 5CD1C40008 X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1746788364-628189 X-HE-Meta: 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 oj8k9Aei nT91/VYiGpBd1U+XJt+gV1IhdbClxmZKG/R0EYTKuKtsXeEW8bT3qhCsitwXGxGJU0+quHkJjyIUM6XeoQCrCYzllh6alMEU8FXPn2N6UUeZw3W3SV6pmQRGj1jjjwUMdEG9FFfIp986AOUzgid5yGNnrZGNG2qGjxMwTG1t6kWLomgnX3nw5bQ6TEulItPE3GELuW362ZirNEUWo7BDiqKTceBTbtx2vQPQOcoKIaUsbCv4q2ExEl2ckwJnGGmDaBK0JCMIqSGO2VVImZbYuFh+ITXrMGXcqZgK5A8b6QnDMWB8YtJfiziPM7QDbQcmaExEYpEQ1/dkQWaSToqVWh2wvGlmYXwNTauTegklrDlCCptyj2xQWHAXWyvERlNRxdEQCg30ov/Tf1BDoyoMH/fAGHJBLgH0Ogrwz9kLxCfI7lWkJLl9Ma0OiHNIWb1r+Okuq7HfIT2JgJMY= 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 09.05.25 12:57, Lorenzo Stoakes wrote: > On Fri, May 09, 2025 at 12:51:14PM +0200, David Hildenbrand wrote: >> >>>>> + >>>>> +static inline int __call_mmap_prepare(struct file *file, >>>>> + struct vm_area_desc *desc) >>>>> +{ >>>>> + return file->f_op->mmap_prepare(desc); >>>>> +} >>>> >>>> Hm, is there a way avoid a copy of the exact same code from fs.h, and >>>> essentially test the implementation in fs.h (-> more coverage by using less >>>> duplciated stubs?). >>> >>> Not really, this kind of copying is sadly part of it because we're >>> intentionally isolating vma.c from everything else, and if we try to bring >>> in other headers they import yet others and etc. etc. it becomes a >>> combinatorial explosion potentially. >> >> I guess what would work is inlining __call_mmap_prepare() -- again, rather >> simple wrapper ... and having file_has_valid_mmap_hooks() + call_mmap() >> reside in vma.c. Hm. >> >> As an alternative, we'd really need some separate header that does not allow >> for any other includes, and is essentially only included in the other header >> files. >> >> Duplicating functions in such a way that they can easily go out of sync and >> are not getting tested is really suboptimal. :( > > This is a problem that already exists, if minimised. Perfect is the enemy of > good - if we had make these tests existence depend on being able to isolate > _everything_ they'd never happen :) > > But I will definitely try to improve the situation, as I couldn't agree more > about de-syncing and it's a concern I share with you. > > I think we have a bit of a mess of header files anyway like this, random helpers > put in random places etc. > > It doesn't help that a random driver/shm reference call_mmap()... Yes ... > > Anyway, this is somehwat out of scope for this series, as we already have a > number of instances like this and this is just symptomatic of an existing > problem rather than introducing it. > > I think one thing to do might be to have a separate header which is explicitly > for functions like these to at least absolutely highlight this case. Yes, and then just include it in the relevant header files. > > The VMA tests need restructuring anyway, so it can be part of a bigger project > to do some work cleaning up there. Cool! -- Cheers, David / dhildenb