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b=ajc0ZCrp48qFOd5YeMwU6awPpTlPgOEdgiCW6t9HWpyQfnzlwVgfg/AsqhiG7oyXm nLr+XUl4e20NWvAyngeSQ/T3A9cPeh/iLU2MRydo/sXPwUCq5tStnSMWlbWdk4nxe2 SJC4gavTW9vPFR/OyBPrPy5s+tZ95aIdgN9CMgH8/WkWaJKy/rl5orib3fJXfcnm3N jodgITL9XOiwf+y6glhCkD9qRLxtg1dsbYBzawQcSNn1jKjWe63AYk3tLP1Kn1QIh6 B0XR3httHFjAONX3ZES54kIkzsRSYch53zvV0eJKuxBxnzUiQd02TbR5wDRafb3c9L +LlLcE2o2QiwA== Message-ID: <875dc63b-0cd2-49e5-8b0d-3fb062789813@kernel.org> Date: Wed, 15 Apr 2026 16:36:46 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: shmem: don't set large-order range for internal shmem mount To: Baolin Wang , akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, ziy@nvidia.com, ljs@kernel.org, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <2d138a3f-0006-4a01-852a-4570d7ba781d@linux.alibaba.com> <1a3cb6b2-94e0-4268-8cd9-1f9a9deb6c6b@linux.alibaba.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+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: <1a3cb6b2-94e0-4268-8cd9-1f9a9deb6c6b@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 00AC114000E X-Rspam-User: X-Stat-Signature: 3f4zei6fncimigog11prtym7ysxradf3 X-Rspamd-Server: rspam10 X-HE-Tag: 1776263815-792275 X-HE-Meta: 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 G9q8Xm7J 36Plguxv4zjwqrNxPeRq7w0ATkECCm/sF4KNrnhOLaYAniR55sO04SweT1YlnoytLHgco3IS5HuKfrzFYpo/VDxKvy8ahe1ELr0fyeLAw77eJqY6Q03PMrlrluvFj8GyUfgEJP0vMNd+j11EAGeRxKPgWeNin6qISbaiI0gx4Lkj2BM1+C8hTQ3th092SGzY0OkUNGnUzP7ZFfI7YKY0Q8uD0LVaMx+1qH9qteXa1Qh/Qosrd3rTeFJftMqpKgWJdy9uoS+wTtKDt0tKK4svFt15XGA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/15/26 12:05, Baolin Wang wrote: > > > On 4/15/26 5:54 PM, David Hildenbrand (Arm) wrote: >>> >>> Yes, that makes sense. >>> >>> However, it’s also possible that the mapping does not support large >>> folios, yet anonymous shmem can still allocate large folios via the >>> sysfs interfaces. That doesn't make sense, right? >> >> That's what I am saying: if there could be large folios in there, then >> let's tell the world. >> >> Getting in a scenario where the mapping claims to not support large >> folios, but then we have large folios in there is inconsistent, not? >> >> [...] >> >>> >>> For the current anonymous shmem (tmpfs is already clear, no questions), >>> I don’t think there will be any "will never have/does never allow" >>> cases, because it can be changed dynamically via the sysfs interfaces. >> >> Right. It's about non-anon shmem with huge=off. >> >>> >>> If we still want that logic, then for anonymous shmem we can treat it as >>> always "might have large folios". > > OK. To resolve the confusion about 1, the logic should be changed as > follows. Does that make sense to you? > > if (sbinfo->huge || (sb->s_flags & SB_KERNMOUNT)) >     mapping_set_large_folios(inode->i_mapping); I think that's better. But has Willy says, maybe we can just unconditionally set it and have it even simpler. -- Cheers, David