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b=QiSloQfro7y48xGi4gcFNCghKwpJoJ0tKGbEHTBRyyphetxebruHsVADA4ArSYXur 8hVsrDaMZUzgAXNsEMae6m8qD0JSY0GeC9mYZUYW3HBpFztHdb0544QYlbPpTVaWzz 7YBcsNT66LipxPoZ6bopJ4Pqe7irxDLQa6Eq96Wu1HSvlTlrWu1hy4ZackBV5OnSf6 KprOyE0ZVhA0yNVB5Sf8yMQwprTqDaGr5QY56YIcRQXyBpcIBhbRXjjW6aG03+v3Vl 4TcpefDK8jjvxK8uoAnrWkCx+40PxsMvF6jOFIiLFWiYcSz5nnu/hIm1g3ecCB/m8G 2thglL7zp4u8g== Message-ID: Date: Sun, 25 Oct 2026 13:36:27 +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: Samarth Narang , Andrew Morton 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> 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: <20261021182157.1873726-1-samarth.colleges@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 05650140005 X-Stat-Signature: yq48i5yy1oujnns96oba65x8sbnm1qea X-Spam-Status: No, score=-16.5 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,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793007672-25356 X-HE-Meta: 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 DCFpZaGR GeURUgFy1GyiT1+Nlp2RG4ve5gvrpPvIGxeOGWKWvuaibEVdATgvwQTatfY/8Nemr2MNW9F6M323+FuT15PHSj+tOjGN9rLzKXrYcRC+ScFNzOV1CeQ0nGHuheaLCDgWXInQqRyofvcCTDOa+0A002d5WSpkGEVRbEHZjC0huNhbzMG1yjkkYwD455aFOrSAdjsWPwH8BtmvF1NCu5C/p+Nt3uoJxzn4rPDPtzpSbKbKGYJCVsTDvxP064ETBXX2e8m9kH5bxpV6YI2/fmOtoMKgw0PZ6MqrK7rTwczloQe5YPjTUxOC56l1bOqgaODRl4rsNRNT+8k5NHN+2ZOulSEJXE0PQDc2bXC/WTsNd6OUwvLiZrD0P7ZKh4oDbrH++5trD 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 10/21/26 20:21, 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. > > Fixes: 0f8975ec4db2 ("mm: soft-dirty bits for user memory changes tracking") > Cc: stable@vger.kernel.org > Assisted-by: LLM > Signed-off-by: Samarth Narang > --- > > Notes: > v2: https://lore.kernel.org/all/20261019010934.697895-1-samarth.colleges@gmail.com/ > > Changes since v2: > - Keep only the soft-dirty fix, as David suggested; Lance will be handling > the uffd-wp/RWP part. > - Fixes tag reduced to the soft-dirty commit. > - Dropped the Tested-by tag, since the patch changed. > > mm/ksm.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/mm/ksm.c b/mm/ksm.c > index dbfb8f98b189..910a1307ac9f 100644 > --- a/mm/ksm.c > +++ b/mm/ksm.c > @@ -1463,6 +1463,10 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, > dec_mm_counter(mm, MM_ANONPAGES); > } > > + /* Preserve soft-dirty when replacing the page. */ > + if (pte_soft_dirty(orig_pte)) > + newpte = pte_mksoft_dirty(newpte); > + Acked-by: David Hildenbrand (Arm) -- Cheers, David