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(p200300d82f156200d4851bcdd708f5df.dip0.t-ipconnect.de. [2003:d8:2f15:6200:d485:1bcd:d708:f5df]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-442f3967f62sm20877615e9.25.2025.05.14.02.10.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 May 2025 02:10:17 -0700 (PDT) Message-ID: Date: Wed, 14 May 2025 11:10:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: remove WARN_ON_ONCE() in file_has_valid_mmap_hooks() 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: <20250514084024.29148-1-lorenzo.stoakes@oracle.com> <357de3b3-6f70-49c4-87d4-f6e38e7bec11@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 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: lo9DTGpCnGlzP7cNz98d6bm3BesG-7jAO0r32I2KYic_1747213818 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: kksc918c7scn6dbsb1o4pqasmotiyxbf X-Rspamd-Queue-Id: 29070C000F X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1747213820-406979 X-HE-Meta: U2FsdGVkX18qV/3wTuCo60H2UcxxIaYniSjKqprBrpJcCSumvHmRZhG1lfe+qalqoxop+5tUnf8Pz1Qx6Q5H9u6iXU0yzDzNz8s/YV1UGdR9tgNzo3EoVegqpNwRHPEzljrAXNwYfIEgeofH4U7qgL/ldp2rHiDXHnRMX4aJfJjvwrs8inIgGZ+B50liYSwK1GlM1BbbmR3UAwxlmLgPUl9XvMF3YprGyEwTZauldkKW2DUEoH7bgZZRv94btuF8W5R/FNaINpelmvfrVqWYB36pGktb2BVOUUEKQX0rqi27f7pp/J9jLsPE8eSrHnB4SDDL4IB3xJ+pki+S6rRCZaLhbnOcu/hAnerOTpapD9G7lvbBqH2sxIYCk0Ke2g7fQA8q7FR73Yo0EewqOScZ8IoZJ4rCZSAqiZC+iuxPEHs0g1l3SG25NokBl7H2Rn9xkOFd5TARNH8ccWlCnYXo+vARy+0AueZRy1/ZkpjEBM+D/TNexJ1AcZDPmW5ZjnRzQkNHwjxuty645uHbNIF6clBKrCGC+fbW1FnYJCqOMz/7KkRvQod7YyiA/EevCreCAvtHJvL/27bbGpCjOlYbVcbdN6jhI7HN13K5wkvOfTKozueOwgcUL5ncuEGIv5wpax6sOrqOX8YqKvIyIP+wwWzQQ/fa0vtBZT9GEc0PR6370rrOKEtIxwpHpGUXIr5Cx7djjddVTmbmUAAIU+hqhPBTAXcoM+gQAnIKpHKopWmv1/PW8C59fhj3ot273bQ5+xrsg/s66+ODddQcrjDe2adrYo1ux1KWXcAIhUaiW4WIb/PWb46bmSqfLiSz9eb0cNzm4/VSn6SabLPPty02F83J6ZACsr564pQDdNS/UQlEkJ5AkJftQsudCdJwX0hwaHdZMnYhrlq2X/zwW7VGTfxVPGLhwudsH5BFXx+G9rn1GUq00+4mLj6sHp8ZjtWnQl3stWQJtAI5Eazi2rB 6015MMOx zfLvz1nTCbcLtc04gAbh+Zqo6ERk+WagIJ4xNH0724TrgkHWjMfbf9UfkWXISD9osPUJKoBNEl6cDbYMdVvYI62bF97oD6uy68HoW3pMcC2OJFHXjx4oFXmGHpELZiVeJiSgY 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 14.05.25 10:56, Lorenzo Stoakes wrote: > On Wed, May 14, 2025 at 10:49:57AM +0200, David Hildenbrand wrote: >> On 14.05.25 10:40, Lorenzo Stoakes wrote: >>> Having encountered a trinity report in linux-next (Linked in the 'Closes' >>> tag) it appears that there are legitimate situations where a file-backed >>> mapping can be acquired but no file->f_op->mmap or file->f_op->mmap_prepare >>> is set, at which point do_mmap() should simply error out with -ENODEV. >>> >>> Since previously we did not warn in this scenario and it appears we rely >>> upon this, restore this situation, while retaining a WARN_ON_ONCE() for the >>> case where both are set, which is absolutely incorrect and must be >>> addressed and thus always requires a warning. >>> >>> If further work is required to chase down precisely what is causing this, >>> then we can later restore this, but it makes no sense to hold up this >>> series to do so, as this is existing and apparently expected behaviour. >>> >>> Reported-by: kernel test robot >>> Closes: https://lore.kernel.org/oe-lkp/202505141434.96ce5e5d-lkp@intel.com >>> Signed-off-by: Lorenzo Stoakes >>> --- >>> >>> Andrew - >>> >>> Since this series is in mm-stable we should take this fix there asap (and >>> certainly get it to -next to fix any further error reports). I didn't know >>> whether it was best for it to be a fix-patch or not, so have sent >>> separately so you can best determine what to do with it :) >> >> A couple more days in mm-unstable probably wouldn't have hurt here, >> especially given that I recall reviewing + seeing review yesterday? >> > > We're coming close to end of cycle, and the review commentary is essentially > style stuff or follow up stuff, and also the series has a ton of tags now, so I > - respectfully (you know I love you man :>) - disagree with this assessment :) > > This situation that arose here is just extremely weird, there's really no reason > anybody should rely on this scenario (yes we should probably try and chase this > down actually, perhaps though a driver somehow sets f_op->mmap to NULL somewhere > in some situation?) > > So I think this (easily fixed) situation doesn't argue _too_ much against that > :) Again, I am talking about a couple more days, not weeks or months ;) At least looking at the report it sounds like something the test bots would usually find given a bit more time on -next. I might be wrong. next-20250500 had the old version without WARN next-20250512 had the new version with WARN So the new version has been in -next (looks at calendar) .... for a short time. > > But I take your point obviously! > >> Fixes: c84bf6dd2b83 ("mm: introduce new .mmap_prepare() file callback") > > Is it worth having a fixes tag for something not upstream? This is why I > excluded that. I feel like it's maybe more misleading when the commit hashes are > ephemeral in a certain branch? mm-stable is supposed to have stable commit ids (unless Andrew rebases), so we usually use Fixes tags. -- Cheers, David / dhildenb