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b=WT4zpnkoSW0aOFSRV871WrRtxflVsRg9rfHguPcazzwrWmrC/RG7AybINjzCihbkh yCs1pC/0QDvYAO56mpWaBoVt/mQHviuWkrnoaVt9mstrNtdtXlgIZnJihiF0r0RDgA W/MdHETbaVIWDDHif6wwdkEX9FUCPRizYZSm4rqIEr9a50I2tqRY20v9OMnIrP1jeL 0giKpBOwxbEaQwo1jAHvwje6lQede9d1tDmLiy7jhu4HK9vkbN2QnVsgM/kwjCllem 9pbzGfC/J63+iwp/bdc/yd+AL/mLzQee4MOGBESGqmN9aOn8GhtRWsnDzuIPEZJbn1 B2MZkvXibqmdQ== Message-ID: Date: Wed, 15 Apr 2026 11:54:03 +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> 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: <2d138a3f-0006-4a01-852a-4570d7ba781d@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: octz6b713hif7z1bnk3e3wh16pcmc13z X-Rspamd-Queue-Id: DCF3080004 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1776246850-228840 X-HE-Meta: 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 Snw/kHBP IWlkTRbkGt+UWohKfBlNeVPSCzm2v4gqDjqMtTu0eb2Ujy2TqnBbGkL8sE15kdyDNb1N+J2A8QX00F6w+epVVL1YoZvyFh9eZwhNF1un2R1ITPZ1nKl7fyqecgVpac0s8DF9uZXXhZg+nAGvfazaiCNm+kgIWCItMGhX44LrLd29WvG15AOHMf4z7DrWTjZtbZ51DfOcj4CT1EwL+L6+4nYePcXTXpOUBA1Qd2MTmcgOEeehKNfgDVlkzTt8kJ8TRCcr1zTY+1bJYVZE0GE2/rhEO8w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >>> As I mentioned, the original logic has several issues for anonymous >>> shmem: >>> >>> 1. Whether anonymous shmem supports large folios can be dynamically >>> configured via sysfs interfaces, so mapping_set_large_folios() set >>> during initialization cannot accurately reflect whether anonymous shmem >>> actually supports large folios. >> >> Well, the mapping does support large folios, just the folio allocations >> are currently disable. >> >> It feels cleaner to say "there might be large folios in this mapping" >> than saying "there are no large folios in the mapping as the mapping >> does not support it", no? > > 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? [...] >> What if we say: >> >> shmem that *will never have*/*does never allow* large folios never sets >> mapping_set_large_folios(). >> >> shmem that *might* have large folios (in the past, now, or in the >> future) sets mapping_set_large_folios(). > > 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". Exactly. -- Cheers, David