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b=RfC32sDL3NtG3+/o+07Lq/rjstQv2xyLocAqV9oPXSA4nBVibyrg6/bcfKYfiaN4G lBRQX9cppyKT71GeqZcH8XZlgEHif37s//+6yMXWAKJG0PPyBLbRNvpWoMprC3dTu9 tVqR4WQObWLcRiGO86tKbXFN6igpw7VYOluC5Lde5wMP5htyRb2Rj26cpO34B/Tx96 2OkXskeL6dckpJ5x81YuGBXNM+TuQXGZbaF8PDfmR0mU/T36Eez3YBdxVKTFY9LYPi NA+smvuFGXBrxiD76lFQxLbMYpGiD0hFHK6eVeSx5tQrsagk2z8++qRYyQfXI7cHWs TOjBuXnORV31w== Message-ID: <220524ba-e39a-4d7f-b44f-d4e2e7132397@kernel.org> Date: Tue, 12 May 2026 12:35:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/memory: avoid unnecessary #PF on mTHP allocation race To: Wandun Chen , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com References: <20260512095031.1333997-1-chenwandun@lixiang.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: <20260512095031.1333997-1-chenwandun@lixiang.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 158EE2000A X-Rspamd-Server: rspam04 X-Stat-Signature: xpzsb9n8766u5a7bqgr4joy8aqa9c34f X-HE-Tag: 1778582110-788176 X-HE-Meta: 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 yYMYI030 vJy+xyHeT08X9cAfxV7flWubOsEBk9S9CyvJn9UPwPmIgoBxjYBhNn7xRXd/dCcxtXQxpEOjf5TYoiRxAvireA0SS/VkuysMf+ok28A43Uw1LwesNM3d3d+RmTAmwORarpKn43Vbnu4LvNObELDObZDtol9oOydaIhN71BloxUKsVYN4jiw6k+D2hYz3gF0OPDuzFkowOjhf1JLMBz6Eu3c/vjsxymcNkeJfcyLqetF7VGeMLzjjnWQIuxnDGBncfS0Gs Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 5/12/26 11:50, Wandun Chen wrote: > When an mTHP folio is allocated in do_anonymous_page() and the target > pte range is not fully empty, current code would release the folio > and return. > > This results an illusion that a page fault has already been processed > even if the fact is vmf->address itself is still pte_none(). Another > page fault will be triggered again. Yes. Why is that a problem? -- Cheers, David