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Howlett" , Kalesh Singh , akpm@linux-foundation.org, minchan@kernel.org, kernel-team@android.com, android-mm@google.com, Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250903232437.1454293-1-kaleshsingh@google.com> <827c844f-7106-4f62-a108-1f83544aa56e@lucifer.local> <43ryds7hzhs5bpaxznco7fppmakdb4f46agwtsc5erudqfoz2x@7y4jgbtft7jj> <413ee338-1795-433c-b3d4-72c870488d95@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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <413ee338-1795-433c-b3d4-72c870488d95@lucifer.local> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: LIkfT_73wFsfOH2IvWx7Ui-IHmfiACI2pUYC1NcXvug_1757007719 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: rspam11 X-Rspamd-Queue-Id: 237C62000B X-Stat-Signature: 1ueoma1dgyqma5cxzhzbmqns8umj5pam X-HE-Tag: 1757007722-111144 X-HE-Meta: U2FsdGVkX1+aBBQk0e1V8BwBkfKFXETZprvd5Z3OmbVpbonVJniwj3b2NGqOddugQhB25xSFIJazS8VSw7tTlKU1C8fuy8qVMPqmrAxdWLW8K9sDOk3njRmFOP6SUrsRdDIvje+4seHCaaZHGuXZ8mm3v+9H1RAQd6ny6aghp2JQbF6l9gf4jHDg883+Z6Kciv9RpiSs6EIVcZ6VjOeyxt90EgNsSwTcv2ZxP5AQJSeJECnLJEWs+DLRgz7ZocikyHQ5l84Dldaf7/rIIuF8Q4pHBfsSv3/i/gDOlxf0fQSAthQTqiQcb+kdTS8kEvddBCSjaTHI04f3F5ZHon0lONB83s0/oj8dVqDCFP8raSlFY+2ZE+KU+3px10CwvRW+PCD3Yx9EGjDKFqZs+rCARjy4x0EqotdgiF4M0iIB+ISSGoNYfoGfQVTm67Ou1H19OmvU1ucpbfnHvdaFv5gkH+rO0IxmtMwj8OFIL+/Cnr7+EXIvWEoizXf6XDIsApi1n7IEvvJbpWeszIq6PhQxe8qUw2FtVmEgTBjo5P1VigY33Q+sl87IZ18WdgmObHosL7acSc/u1rD9UdVI/ljitq0K1rI7/cIiEIIG+lwjHTGH3l5M9Li0pulyrXDBtIpQuG7+wX4e+PM4DZr3bHrB8fVtY6ViSLKEreofma2/m8mpvEX0aKAWl/wk9TmJe1wKYI5qAMxWLSixzyFz3BGqb/6t9cPWk1jIlgSYOWLw67rHazszeD/FvvFhqt3NQPgGOgzPhpVoYbqnPVOh73gAJU9bmzgow+uK9TxKg2hpBTNqPaMpjOk/dEs3CMZWlfOWjH0Ln2yK4d4AqxUGNI/+1mtiMW1zER+L3UC5ZwMWqJk6G8OX8Ir/oeLADi6WC7TvpEyUc+pd8828S780a2uoeU/LaVip5VRazWxf/122ISKH7jexYp6uBn0DWfDOybPAqKwLDi23U/nHQWvfgOk UYCQiui3 sxATw2ar0v/dv5irJSHWaq0TV/b0V7zg+silk5mvQFfBjoxAdxh5HrIm4dQu+1Rysu/XFzFxffDQ+xn9bKdxh1VI0gVpLlweFn8qaNcVfyPDNBdN7HXM9X4FZqW7UjmcpPg2VDCO6jTZsEEtcx3VENHmJi2bVi0CyEvH+vsvylcCpxoN1jUY5qAoFFoOgtg+4ldtcR608uopNfbpwAzD/+pO0fOxba0GnLRmkRA6tJ2G490F4Mik0fLGUDV7auO07QXYYe6ISCGI9LcFE0ypo7qSE5VMcElow3xshMK62ZzBm7VeYYA0OjYc1VCKpHJIdJbcDochuP/BdyVWhN5kr/aDxDWY3iBFLLuVVJDqqvfLbmiHRpxIjihNC07Rlj1bubEGzuMlgZNXNekrKWUL19z+48r31PO7OOUY9j3Kvy4UQ3LUUTNsZU/hBug== 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 04.09.25 19:33, Lorenzo Stoakes wrote: > On Thu, Sep 04, 2025 at 01:22:51PM -0400, Liam R. Howlett wrote: >>>> diff --git a/mm/mremap.c b/mm/mremap.c >>>> index e618a706aff5..793fad58302c 100644 >>>> --- a/mm/mremap.c >>>> +++ b/mm/mremap.c >>>> @@ -1040,7 +1040,7 @@ static unsigned long prep_move_vma(struct vma_remap_struct *vrm) >>>> * We'd prefer to avoid failure later on in do_munmap: >>>> * which may split one vma into three before unmapping. >>>> */ >>>> - if (current->mm->map_count >= sysctl_max_map_count - 3) >>>> + if (exceeds_max_map_count(current->mm, 4)) >>>> return -ENOMEM; >>> >>> In my version this would be: >>> >>> if (map_count_capacity(current->mm) < 4) >>> return -ENOMEM; >>> >> >> Someone could write map_count_capacity(current->mm) <= 4 and reintroduce >> what this is trying to solve. And with the way it is written in this >> patch, someone could pass in the wrong number. > > Right, but I think 'capacity' is pretty clear here, if the caller does something > silly then that's on them... > >> >> I'm not sure this is worth doing. There are places we allow the count >> to go higher. > > ...But yeah, it's kinda borderline as to how useful this is. > > I _do_ however like the 'put map count in one place statically' rather than > having a global, so a minimal version of this could be to just have a helper > function that gets the sysctl_max_map_count, e.g.: > > if (current->mm->mmap_count >= max_map_count() - 3) I enjoy seeing sysctl_max_map_count hidden. But map_count_capacity() is even more readable, so I like it. I don't complete like the "capacity" term, but I cannot think of something better right now. Maybe something around "free" or "remaining", not sure. I also don't completely like "map_count" (I know, I know, we call it like that in structures), because it reminds me of the mapcount ... talking somehow about "vmas" would be quite clear. Anyhow, just as an inspiration my 2 cents ... -- Cheers David / dhildenb