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(p200300cbc723b8009a604b4649f987f3.dip0.t-ipconnect.de. [2003:cb:c723:b800:9a60:4b46:49f9:87f3]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4361b09fec0sm5160895e9.4.2024.12.10.08.59.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Dec 2024 08:59:09 -0800 (PST) Message-ID: <50e194c2-914d-43eb-bff8-47c4a1119dce@redhat.com> Date: Tue, 10 Dec 2024 17:59:08 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] MAINTAINERS: group all VMA-related files into the VMA section To: Lorenzo Stoakes Cc: Jann Horn , Vlastimil Babka , Andrew Morton , "Liam R . Howlett" , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20241206191600.45119-1-lorenzo.stoakes@oracle.com> <23d3d7f6-d6d1-430e-8ea0-ccae76b253fd@redhat.com> <41a14051-75ee-4de3-863c-d0532aa7e3aa@suse.cz> <1e4c3e31-ea9a-4af4-83f9-15a882732e69@redhat.com> <71beb3d1-21ac-4037-8363-6484c0c333b8@lucifer.local> <81fc4cd1-55f4-4569-aef7-0b0da9684fdf@lucifer.local> <67ae2a5f-0c86-446f-a122-f14decdb84d3@lucifer.local> From: David Hildenbrand Content-Language: en-US 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: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10.12.24 10:51, Lorenzo Stoakes wrote: > David, Hi Lorenzo, sorry for the late reply. > > To avoid an infinite back-and-forth... > > I think you're stuck on the idea that we are sat in a VMA 'vacuum', perhaps > because I put so much effort into separating out the VMA logic, for the > purpose of being able to userland test it, it's almost given the wrong > impression (I should perhaps have put less effort into this? :) Yes, that nicely summarizes it. In particular, because the patch description says "group all VMA-related files", and I am having a hard time to even identify *what* a "VMA-related" file is, really. For example, why not mempolicy.c->mbind()? Not that I would suggest that, because the file is filled with non-vma-related stuff. See below of what might make sense to me. > > But we have for quite some time now de facto been expected to maintain all > aspects of mapping, remapping, etc. INCLUDING page table considerations. > > We are more or less de facto maintaining all that (modulo madvise.c - I > grant you this is the odd one out). > > So you can imagine it's a bit frustrating, when that's the case, to be told > in effect - no this isn't for you - right? It isn't "VMA" group for me, independent of "who" is currently listed there. And maybe we now agree on that, maybe not. Talking about things that are frustrating: being called a "senior member of the kernel". :) > > For instance, as I said before, we have spent large parts of the 6.12 cycle > dealing with practical concerns specifically around page table > manipulation. > > Maintainership is more than setting up lei rules, obviously. One can set > lei rules for anything. It means that our say has more impact, and it also > means that we are (co-)responsible for the listed files, and that's acked > rather than disregarded. > > So, again, I politely disagree with your assessment re: page tables. > > I think their manipulation under circumstances where you > map/remap/mprotect/mlock is -inseparable- from memory mapping/VMA > logic. Otherwise, what's the point right? We'll likely have to agree to disagree. :) But again, my main point is that the VMA group is misleading. As a side note, I believe the code can be structures accordingly (call that separating it). mmap/munmap handling is the prime example right now for me. For example, I really enjoy how: munmap() (mmap.c) routes to __vm_munmap (vma.c) makes use of abstracted page table logic like free_pgtables() and unmap_vmas() (memory.c). This way it is clear what the rather high-level MM syscall implementation is (mmap.c), what the VMA handling is (vma.c) and what the abstracted page table handling logic is (memory.c). I don't think that page table handling code should be moved to either mmap.c or vma.c. I would enjoy if we would handle e.g., mprotect.c in a similar way, such that the helper like change_protection() -- again, used by completely mprotect()-unrelated code outside of mprotect.c -- would not reside in mprotect.c. But that code just evolved naturally after we kept reusing change_protection() outside of the file. Regarding mremap logic there once was a discussion about merging it with the uffdio_move logic, but not sure if that really makes sense. > > My suggestion is that: > > a. we put everything in MEMORY MAPPING > b. We drop mm/madvise.c from the list Sounds better, although I am still fuzzy on what is supposed to be in there and what not. See my mbind() example above .. I see how mmap/munmap/mprotect/mremap fall into the same category of MM syscalls that mainly affect the /proc/self/maps output (in contrast to a bunch of others). Which make sense to me to group in such a way. mseal.c and mlock.c likely as well. msync.c is a simple VMA walker ... not sure if it belongs in there, but who am I to tell. -- Cheers, David / dhildenb