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b=AIw83rrvDojvVU98Km7jgfMLQYlD4Up927bgO//SYFCBf2d4ITJVSDviqBB9vDYY9 svEuilKhHojgBQH+59FDI/vEUolOo/FvJJfsUtS7suKWEW69T0J7n74BdPO1IQLM5B rz47UNzz/tv19EHFMOYb/IW6GU2Mh1mbq4St/5aAA4qssffScHO065VyIWeF/JAAiP b4Wc22k4PjpnDFupQWOqOl73qUgeWaS+zDrhE7qndLRd6HgKegFvH5tWQUwTIJdGsz 76tAqhmucNKduRsTjx0wHQ2Jf58Nj6nAp8aRNqp15RQHu1ikJZ3tGU+kLO7vsjI4Qe HuDVBKGsF0V0g== Message-ID: <8e34b0a8-836f-44bb-a6b1-703f79c2ded3@kernel.org> Date: Wed, 8 Apr 2026 15:19:09 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: ksm: add mremap selftests for ksm_rmap_walk To: xu.xin16@zte.com.cn, hughd@google.com, akpm@linux-foundation.org, ljs@kernel.org Cc: michel@lespinasse.org, chengming.zhou@linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260408211552000LDjkQX010NY5GI_er7Qb1@zte.com.cn> 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: <20260408211552000LDjkQX010NY5GI_er7Qb1@zte.com.cn> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Stat-Signature: tc9ybrh4ny3o8bpkapi5ozgjjee65mup X-Rspamd-Queue-Id: 47DE480017 X-Rspam-User: X-HE-Tag: 1775654353-366310 X-HE-Meta: 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 qgk1eCKQ +Iz7Q+esdBc9H4I8Yxv42G6inFfO7wyLPWmsBIbQcWDu9l5dzPlStafZgvLwik2dV/0RIFBCqhoA7MmOe0L/g7UQI0m9n441eNU/BsxvUvLcilwXN28YW1wqgxtaxHXssA45JLiUTggH9q/qpAd8YT8s9caEqOs1lCDcW+GZoaMYVOEJHcRHku4wNOoG0D1NklL+bw+77AvTGmdfc7H0yDBf3NJKhffIM19J9Vlx5wAVTCroMT37fKLaKM8DSovEgQgKMfjhiSmJ2aROd0+Nri/0FAoDS5NbuzHeBiq9PmJtUxWmxqEe5WODxV23Pq/dTJ8kxMFNoZD/MTgJ+i3cv9TjfDrkmv7lKHXAs Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > > Oh, thanks to David and Hugh's reminder, I now understand the issue Hugh was pointing out, and I also > see why my current test program incorrectly passes: before migrating the memory page, the > mremap() operation has already turned a KSM page into an anonymous page, causing the code to > take rmap_walk_anon instead of rmap_walk_ksm. Therefore, to reproduce the issue Hugh described, > we only need to add a delay of wait_ksmd_scan_finish_two_truns before migration (after mremap) > > — simply wait for ksmd to merge the remapped page back into a KSM page. > > such testing code can reproduce what Hugh points out and FAIL to migrate: > Cool, please update the test to take that into account, and please also test with child processes involved (no mremap() in child, only mremap() before merging in the host). -- Cheers, David