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(p200300d82f4d9f003bce0123c78a0cc8.dip0.t-ipconnect.de. [2003:d8:2f4d:9f00:3bce:123:c78a:cc8]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a532131df6sm5079756f8f.0.2025.06.07.11.13.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 07 Jun 2025 11:13:08 -0700 (PDT) Message-ID: <366227be-e22d-4757-b3c7-3eedc07df1b2@redhat.com> Date: Sat, 7 Jun 2025 20:13:07 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/debug: Use BUILD_BUG_ON_INVALID() for VIRTUAL_BUG_ON() To: Tal Zussman Cc: Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250607-virtual_bug_on_invalid-v1-1-b792ac2b0920@columbia.edu> <2a768123-4423-4f52-a0ef-96fa69872949@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: 2B6-RmmjTfw9bTtus8sIM4MYJtp-_1ZpoQ1WS62Or4Y_1749319989 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: rspam01 X-Rspamd-Queue-Id: CFC2E140006 X-Stat-Signature: uf9z43nz1ab6nap8dp1xdqppfi6hiogu X-Rspam-User: X-HE-Tag: 1749319992-245521 X-HE-Meta: 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 Ao9Ebq8W 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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 07.06.25 18:21, Tal Zussman wrote: > On Sat, Jun 7, 2025 at 3:59 AM David Hildenbrand wrote: >> On 07.06.25 09:09, Tal Zussman wrote: >>> This allows the compiler to validate the condition even with >>> CONFIG_DEBUG_VIRTUAL disabled, and aligns VIRTUAL_BUG_ON() with the >>> other macros in mmdebug.h. >>> >> >> In the light of recent discussions, I think we should get rid of >> VIRTUAL_BUG_ON completely. >> >> There are only a hand full of callers, and I am preety sure for most of >> them VM_WARN_ON is a suitable replacement. > > Makes sense. However, all of the callers (except for vmalloc) are already > gated by CONFIG_DEBUG_VIRTUAL, which doesn't depend on CONFIG_DEBUG_VM, so > using VM_WARN_ON_ONCE() would break DEBUG_VIRTUAL on its own. It should either be folded or made dependent on DEBUG_VM > > Perhaps it makes sense to convert the non-vmalloc callers to WARN_ON_ONCE() > instead so DEBUG_VIRTUAL still works. > The vmalloc caller would then become> > if (IS_ENABLED(CONFIG_DEBUG_VIRTUAL)) > WARN_ON_ONCE(...); > > as opposed to VM_WARN_ON_ONCE(), in order to maintain the existing > DEBUG_VIRTUAL behavior. From a quick glimpse, I am not even sure Fedora/RHEL enable it in the debug config (and if so, probably it's not enabled by mistake) I think we can make it depend on DEBUG_VM. > > Alternatively, DEBUG_VIRTUAL could be folded into DEBUG_VM, but that seems > like a slightly more invasive change... I'd start with making it depend on DEBUG_VM. If there is good reason to not fold it, then all VIRTUAL_BUG_ON should be renamed to VIRTUAL_WARN_ON and get defined as VM_WARN_ON. If there is good reason to fold it, then all VIRTUAL_BUG_ON should be replaced by VM_WARN_ON. The only question is what the performance overhead is. I mean, performance with DEBUG_VM is already bad (debug kernels), so not sure if we really care that much. -- Cheers, David / dhildenb