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b=B4kVC4DGdBI0nHvQd38JB3xiE9r0i4N3qGwuJUEdjHaOsRrrDZWTPYEJgHeU9YP9E x5UEkksaPWu3fLn9gKPRdq9+DlZLl0tmGoNyWUTZOpghl1JA3iJtkPbRWENoHMLND0 8xydXSGcQL+2c4pEPRs5A5JdLRoUtySK0dNJxK8+ahLXPcv+8QCPc5omQkBWFUtcxY vA7PKr/GgjLz8qst218EKOSDbH04nxpTs0Dx06ndguB6lpIkRNDlWswaSwXP9c+WET C/MpOG0Myr+GqyGXVQ3kAUP5tjXu3f0N0sDBYOpKbf1s3bAHMKbcHbpeeWxIZKOy/I oC0Y/U9Fj1mgA== Message-ID: Date: Sun, 25 Oct 2026 13:36:12 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/ksm: keep soft-dirty when merging a page To: Andrew Morton , Samarth Narang Cc: Xu Xin , Chengming Zhou , Peter Xu , Kiryl Shutsemau , Mike Rapoport , Lance Yang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20261021182157.1873726-1-samarth.colleges@gmail.com> <20261023223352.c6de9f2b58fe999814e5bb17@linux-foundation.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: <20261023223352.c6de9f2b58fe999814e5bb17@linux-foundation.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: E481640003 X-Stat-Signature: kbqmncgjsq37up7eqykw6w9xbrg6oa3x X-Rspam-User: X-Spam-Status: No, score=-6.5 required=3.0 tests=BAYES_00,DATE_IN_PAST_12_24, DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1793007669-53337 X-HE-Meta: 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 CjS350Om WHqdkSEbthCCiMITb5NxEkzx9cf8zm9ikpxC4QNjIm2aLf9u7GfSBJ80H9eJHr1+ZxhOJhwr4oBOhQ3zrdHm6z12BN9i94pHCrGyaY7euUFnDiJ6QFZ1Qc+ecw6Uw5w52Km3OM/4f3ZBbEdTmTrr1Ime05F6lG2wZhsvzNviAhcORJqDswSjVJ/1TVnQ5gpjevayv7xWrxYsOZe2M016CMJ6cr/lx2g0QqHATZXi6UBIz3mPKboQNHeBt2oWsM0xbBCLzuvWYfVpL7CnWBajbN44sL9Z/2Rk5a9I8MUkd7qV0iRMoKV3g2wmNqGQ0KFvapSY7r5iR/AcOLywZRQa0yCaXj1DDIWiklOzw2QWOoBmEjfw= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 10/24/26 07:33, Andrew Morton wrote: > On Wed, 21 Oct 2026 11:21:57 -0700 Samarth Narang wrote: > >> replace_page() maps the KSM page with a PTE built from scratch, so the >> soft-dirty bit of the PTE it replaces is lost. A page written since >> "clear_refs 4" then no longer shows as soft-dirty once it is merged, and >> a soft-dirty based dumper treats it as unchanged. >> >> Copy the soft-dirty bit from the original PTE to the new PTE. > > Thanks. My LLM review thing says: > > : There's a separate, pre-existing problem with the KSM zero-page > : path which is worth pointing out. Cool, more AI schlop. TL;dr Sashiko raised this before and I commented why we don't care IIRC. -- Cheers, David