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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: 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: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 3qlLbODZOyYYtB42WqUSanp7xBgxbUvZILTFH-GkuhU_1747126904 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: C4C6C12000A X-Stat-Signature: mdojnq9cen4r39ekxf46kb4zfai51oqm X-HE-Tag: 1747126906-498906 X-HE-Meta: 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 JYwGCeih dHRTutaLkYvoYBei7mYxmzExi5446tGu9Gp9gPHpUdzAxFe8r4szEduwKvMzS9YlMCoM08o9petqs0QvBFU4YRqL3aC/qwhP0HWfpRNMphJg5uCfubQ9RO38JZhD0ampAulj/K7x45CjLUdJ38GiT2y52WDQVGWcCpNND1NjTlNJNqU6oX6tYdcXCPP7qM9ElU1mp7QOX+wqqO+MWAS9rcsuZgUAYjQh3vkfPLEn/ANAIa0/NAsdaUxvMtazGyf5tz1HrWb4eD60MAvV5gLM8SJkCWjViqXQq0bfLxAZionyGEW9yVa6n+g7NFRanoy4Z3r29XOHkJBf7kNnIS6Xgb2G09rW6B2AuFGbWuB6xrGwzghfGZOoAWkN+7NaFsf93ImNxL1Z2t+DyF5t2S11hW/1twqGr5czm0DZtzk1KhixqntaGcFutfGhxKuJ6S56GidEi9wUCDm9xDQWh+Lgh2/sSHT056emq+Jy+ 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 14:13, Lorenzo Stoakes wrote: > Provide a means by which drivers can specify which fields of those > permitted to be changed should be altered to prior to mmap()'ing a > range (which may either result from a merge or from mapping an entirely new > VMA). > > Doing so is substantially safer than the existing .mmap() calback which > provides unrestricted access to the part-constructed VMA and permits > drivers and file systems to do 'creative' things which makes it hard to > reason about the state of the VMA after the function returns. > > The existing .mmap() callback's freedom has caused a great deal of issues, > especially in error handling, as unwinding the mmap() state has proven to > be non-trivial and caused significant issues in the past, for instance > those addressed in commit 5de195060b2e ("mm: resolve faulty mmap_region() > error path behaviour"). > > It also necessitates a second attempt at merge once the .mmap() callback > has completed, which has caused issues in the past, is awkward, adds > overhead and is difficult to reason about. > > The .mmap_prepare() callback eliminates this requirement, as we can update > fields prior to even attempting the first merge. It is safer, as we heavily > restrict what can actually be modified, and being invoked very early in the > mmap() process, error handling can be performed safely with very little > unwinding of state required. > > The .mmap_prepare() and deprecated .mmap() callbacks are mutually > exclusive, so we permit only one to be invoked at a time. > > Update vma userland test stubs to account for changes. > > Signed-off-by: Lorenzo Stoakes > --- > include/linux/fs.h | 25 ++++++++++++ > include/linux/mm_types.h | 24 +++++++++++ > mm/memory.c | 3 +- > mm/mmap.c | 2 +- > mm/vma.c | 68 +++++++++++++++++++++++++++++++- > tools/testing/vma/vma_internal.h | 66 ++++++++++++++++++++++++++++--- > 6 files changed, 180 insertions(+), 8 deletions(-) > > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 016b0fe1536e..e2721a1ff13d 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -2169,6 +2169,7 @@ struct file_operations { > int (*uring_cmd)(struct io_uring_cmd *ioucmd, unsigned int issue_flags); > int (*uring_cmd_iopoll)(struct io_uring_cmd *, struct io_comp_batch *, > unsigned int poll_flags); > + int (*mmap_prepare)(struct vm_area_desc *); > } __randomize_layout; > > /* Supports async buffered reads */ > @@ -2238,11 +2239,35 @@ struct inode_operations { > struct offset_ctx *(*get_offset_ctx)(struct inode *inode); > } ____cacheline_aligned; > > +/* Did the driver provide valid mmap hook configuration? */ > +static inline bool file_has_valid_mmap_hooks(struct file *file) > +{ > + bool has_mmap = file->f_op->mmap; > + bool has_mmap_prepare = file->f_op->mmap_prepare; > + > + /* Hooks are mutually exclusive. */ > + if (WARN_ON_ONCE(has_mmap && has_mmap_prepare)) > + return false; > + if (WARN_ON_ONCE(!has_mmap && !has_mmap_prepare)) > + return false; > + > + return true; > +} So, if neither is set, it's also an invalid setting, understood. So we want XOR. const bool has_mmap = file->f_op->mmap; const bool has_mmap_prepare = file->f_op->mmap_prepare; const bool mutual_exclusive = has_mmap ^ has_mmap_prepare; WARN_ON_ONCE(!mutual_exclusive) return mutual_exclusive; -- Cheers, David / dhildenb