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b=CXozVL06H6mQtJt/dPZugbcY1Wtz5JKZQhkY9wPHbHzhpadD9uVQw8ANnVwcPYBfc eV/gEI1zXwdtDRwPB66saJHit184PIr5iWqgXui1Cbo4jJEdt2Gt9jVob3PWe/jWK5 9Dp5IrsO15DBRbm9qJEygWyrs2mB3UGulU6C+jC/6nmKodXch7dDt6FUiOWWlZsmEF 4LkcaMIrJvFX4EIZYyqxXa3AaMGzwVAre8KVHG9UvmgBTqxrGto0hABG34/zUa68sW r2uEgZ3cFTzI8ZI2lzu9vZLKIqOXverboFWe8qcGSpfYsXUxmwrhHk6Putxj+4XAjc LNOo9o6oCu6Fw== Message-ID: Date: Mon, 2 Mar 2026 09:01:05 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: A potential refcount issue during __folio_split To: Wei Yang , Zi Yan Cc: Linux MM References: <20260222010425.gbsjzhrew3pg4qrw@master> <20260222010708.uohpmddmzaa4i4ic@master> <6346656B-7518-4A55-8DEF-C2E975714C8B@nvidia.com> <3e22afe6-ecf7-4180-9287-c48fea7b8be1@kernel.org> <20260223115948.sbylmtqhznmabcth@master> <097A507A-C60A-47AF-9590-1D6CF712B1FE@nvidia.com> <20260301235902.duqcfrymearzrpds@master> 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: <20260301235902.duqcfrymearzrpds@master> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: dj1f33hfns9oztwz1ek7xffh7cub47a6 X-Rspam-User: X-Rspamd-Queue-Id: 6CD091C0011 X-Rspamd-Server: rspam12 X-HE-Tag: 1772438470-661446 X-HE-Meta: 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 eZo/b/s5 ys6D0EhnwO7S7nr4OvmJ8zc+MB+joyI1+8VITLL4bQrUWSMCxfOr/a+G6QGfX1oK1BuvKPk0qL/+CV83JQdenE3PpFZNkZhW05sfkPogxiq9TidhhdgNyr6TKO0U/wW6FrWxCykjqWmMUnCAZmUBxEcGomy3A/h8TPYmEsXkGIY7Vn2/LMfEg23bFNvrk4Rvq/NPfQgawwCG49z9WcwosTj4jZ8Lis37xrxBSIKmOlloevcXmZLs5a2kBAZGEqmR3j9XqzMPczFDCUbQYa3BFjbEyrMzzf7VoM3EnIqkpZ1sRKjjb6LIZvbdsTcLokWaR7NdGVKamHuJpSIdhTs24fVGEewgf4BRg9xLEbPCdPYEoZRQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/2/26 00:59, Wei Yang wrote: > On Mon, Feb 23, 2026 at 11:00:01PM -0500, Zi Yan wrote: >> On 23 Feb 2026, at 6:59, Wei Yang wrote: >> >>> >>> Missed this. Agree. >>> >>> >>> I am afraid it would be complicated? >>> >>> Well, we don't have this usecase now, could decide it when we do need it. >> >> The patch below should work, but for now, since we do not have any user, >> it is better to update the comment and add a check to make sure @lock_at >> always points to the head page if @list is not NULL. >> > > Hi, Zi Yan > > Just want to confirm what we prefer to do now. We have three options: > > 1) update comment and a check on @lock_at > 2) fix it as you proposed below > 3) do nothing for now I'd go with 3). -- Cheers, David