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[79.241.253.87]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3f61703b206sm12603959f8f.6.2025.09.23.00.48.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Sep 2025 00:48:08 -0700 (PDT) Message-ID: <09284390-5a1a-47e0-9929-0a5ba98c836e@redhat.com> Date: Tue, 23 Sep 2025 09:48:07 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/page_alloc: fix alignment for alloc_contig_pages_noprof() To: Anshuman Khandual , Zi Yan , Wei Yang Cc: akpm@linux-foundation.org, vbabka@suse.cz, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, linux-mm@kvack.org, Oscar Salvador References: <20250923001943.2479-1-richard.weiyang@gmail.com> <3BF1389C-4B8E-4F50-AB0B-F0D96833D387@nvidia.com> <5491dfda-862a-4c31-b64f-5339007a5302@arm.com> 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: <5491dfda-862a-4c31-b64f-5339007a5302@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: IodPGLYtnqrHu68mWNP4hjTN1Ox5pAorvC8eQrwnEFk_1758613690 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: rspam02 X-Rspamd-Queue-Id: CA26E40003 X-Stat-Signature: oncrenmfdxehyoh6cszrrpgzmhsi9wba X-HE-Tag: 1758613693-259892 X-HE-Meta: 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 AmfpHLM+ 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 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 23.09.25 09:06, Anshuman Khandual wrote: > On 23/09/25 7:16 AM, Zi Yan wrote: >> On 22 Sep 2025, at 20:19, Wei Yang wrote: >> >>> Commit 5e27a2df03b8 ("mm/page_alloc: add alloc_contig_pages()") >>> introduced generic method for alloc_contig_pages(). But the alignment >>> calculation seems wrong. >>> >>> Since ALIGN() only accept power of two value, while nr_pages could be >>> any positive one, the result is not defined. >> >> The result would not be any value lower than zone->zone_start_pfn, >> so the worst case is getting an unaligned PFN range. I guess >> most of the time nr_pages would be power of 2. > > Agreed. > > Also as Dev had pointed out earlier, this function gives no > guarantee on alignment of non-power-of-2 requests. Hence I > don't have a strong opinion either way, but does it really > qualify for a "Fixes:" tag ? I'd say if there is nothing to fix, then this patch is not required. What likely does make sense would be that a non-power-of-2 would be aligned to the smallest contained power of 2. E.g., a 6 MiB request would be aligned to 2 MiB instead of multiples of 6 MiB. Not sure what the existing ALIGN would do with that ... -- Cheers David / dhildenb