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Tsirkin" Cc: linux-kernel@vger.kernel.org, Andrew Morton , Vlastimil Babka , Brendan Jackman , Michal Hocko , Suren Baghdasaryan , Jason Wang , Andrea Arcangeli , linux-mm@kvack.org, virtualization@lists.linux.dev, Johannes Weiner , Zi Yan , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , "Matthew Wilcox (Oracle)" , Muchun Song , Oscar Salvador , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Hugh Dickins , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , linux-fsdevel@vger.kernel.org References: <9dd9deabd42801f3c344326991d1431c3d8db39d.1776808210.git.mst@redhat.com> <20260422171315-mutt-send-email-mst@kernel.org> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: f38kiw3cye8p8yyfmygrehmkepqq8rbk X-Rspam-User: X-Rspamd-Queue-Id: E0507140012 X-Rspamd-Server: rspam05 X-HE-Tag: 1776937629-717741 X-HE-Meta: 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 T06w2Bi6 1KpkscY+xD5fkjCBxgEUuw7Pauh9Xsz84tgjMZ9xiEsrroMeuG09XH+sfoNvycLnrHFtqvShDwd2xnLl5ul8haHmgLD74W60mVKBuIAIlj1BAHSX/dFAp+u4ATeA49bPXkMESu9q/g920OyIfsuzp2QfVvumKpbk9kPDag7n7igwf9q/sCR7yZ9kdLaNNbhofpnW2+aEV0oiyKqp4naEqFh0KT1UdoPJWJdJ0VM/4JWEm1bmzY24pPc+icnYuRlo6flOV84psmXTqFHvbqBF//4WPlPCbW+BL7q628svlM6cBaT5jaLvUh+BUIWfVRemXJs/4MmcRkgxtvfJHLMhBvmuJY8az/EBAXwBSVA6rEzX7/L70PYjrTDshaHET+oenObOt+3Z8n1ZCkfw3krW1w8XgBg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/23/26 06:31, Gregory Price wrote: > On Wed, Apr 22, 2026 at 05:20:27PM -0400, Michael S. Tsirkin wrote: >> On Wed, Apr 22, 2026 at 03:47:07PM -0400, Gregory Price wrote: >>> >>> __alloc_user_pages(..., gfp_t gfp, user_addr) >> >> With a wrapper approach, looks like we'd need something like >> __GFP_SKIP_ZERO so post_alloc_hook doesn't zero sequentially, then the >> wrapper re-zeros with folio_zero_user(). But then the wrapper needs to >> know whether the page was pre-zeroed (PG_zeroed), which is cleared by >> post_alloc_hook before return. So the information doesn't survive to >> the wrapper. >> > > I was thinking more that internally you already have that information > you need to know to skip the zeroing - and so the wrapper can just pass > __GFP_ZERO and post_alloc_hook() would do the right thing regardless > > Then on the way out, the new wrapper would take care of cacheline piece. > > However, i explored this a bit - and while it saves some churn on the > interface, it adds two paths into the buddy - and that increase in > surface might not be worth it. > > So I see the tradeoff here. The churn is probably worth it. In v2 I commented [1] " For example, instead of changing all callers of post_alloc_hook() to pass USER_ADDR_NONE, can we make post_alloc_hook() a simple wrapper around a variant that consumes an address. So isn't there a way we can just keep the changes mostly to mm/page_alloc.c? " That should avoid most of the churn outside of page_alloc, no? [1] https://lore.kernel.org/r/4bdc66f2-1469-4b91-9935-74c3d3ca0ed9@kernel.org -- Cheers, David