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Wed, 21 Oct 2026 16:12:47 +0000 X-Mizu-Trace-ID: d1bddb8955e5cc6b X-Migadu-Flow: FLOW_OUT Message-ID: <167a14f0-6a6f-4db1-a34b-905a33d5290d@linux.dev> Date: Thu, 22 Oct 2026 00:12:32 +0800 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/ksm: keep soft-dirty and uffd-wp when merging a page From: Lance Yang To: samarth.colleges@gmail.com Cc: akpm@linux-foundation.org, xu.xin@linux.dev, Kiryl Shutsemau , chengming.zhou@linux.dev, peterx@redhat.com, rppt@kernel.org, "David Hildenbrand (Arm)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20261020055518.36087-1-lance.yang@linux.dev> <3da45e6d-2b46-4fff-9ff3-241f70d68296@kernel.org> <68f17ee7-d272-4475-8a59-645442e2c210@kernel.org> <2329ee64-f9be-4826-a496-65344e9a9c18@linux.dev> Content-Language: en-US In-Reply-To: <2329ee64-f9be-4826-a496-65344e9a9c18@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: B5D0B40002 X-Stat-Signature: yhktbnhrhjwafyh7k74jjasd7cp37ifj X-Rspamd-Server: rspam04 X-Spam-Status: No, score=-7.3 required=3.0 tests=BAYES_00,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-Rspam-User: X-HE-Tag: 1792599168-106690 X-HE-Meta: U2FsdGVkX18eMg4zTpaZT1davoHmk9ygiwd7Nb71nMlcxP9AASgtsMyxxTgsMLEQSXGMBklZwjdvMQA9CV5cUEWX2590Qgl5c5CdZ78kz1Xj8fZUmcPwvyvZ5JstNPaDzGPxsRBeCuxgmcW3J8ExxDbaP3vLZMU2nrrsiwbQRq1FZRECCyg+1UBLE9UTvqs1cDGca5FKJ8awTtpqOwv8zbqTZEIlOrdjsWV3KzKIUNFO9jk+g3QHOmsclWIdJBfyFy1+kCgDgrT0gmGUwWZPUKjikjintDN+bq/Acds72IxsLmQXDoJWtPLvmJgGL0ltG0j2c3QSd+OG0VDuSiTBH/TjdzdMoNfzwyQ9kvkkt82FjzzrKLTqZmkksXqjLIC8GA+5QEWNxiAr2xfuiab2VFZu2nQjHIHAV+D97+wfYXiGX5ISA7i6u310dlsuT89MQuqAIEqLysZajycsmZGl+nKvgHLas9YCe4txsOWYDrfThl4OGnQGUUsODb4MoerJhmrscl84uM1FvFXob/U2EwhloZ1eJ0jKCtvZXIIxFIfvpYwtawHyj2YFSvXUUb7kr43yGDKJ+U92lW5SigP9eAcDUzEJyIYahwS7EvLhWJr/AL4SmtC3VTvpZqkaHc9IA1GhAoSoaHGhhrEy5DXzL1Nbkgrm778o5+G7h9XwkCC4V89w4HfjMd7t4WFBC8lN+DyNNWWmivIHcgmpKNMYAWnauP4zyv3MpwhcUylwb9Fu6UADYFdiROQIIzQE/pXsffvYewnJPUkFcrvqWHRljv7cSPxT6NS8lWT2dV8LLuEXwKuyvZkMdsn3IlqGKVb3rrU6oAQKZ3sntulYG+DyR1MLIb+xCcWZ3HpSC5VXk5zZBS0gHoaitiRbSkNxOP+yopZXfrOgww/POBPPUx4V0kWjrBdBU62EhEqcwceLFdQsWLgZrVuj2neRJCIplXmDO3Hg64ZPIFPzYPMP9Pr 5OMGjRlb lM45B1va3zZhvCe0hhCP2ASAEUjL5xrGTrdn7+9H4hQRmM2Ov/dtOJbTSE8kNluG+MqcD8J6SIZW+7vznQflmksPCLOYiCT1iCBSFzpas2OjZCSlbzDphepCCx/BAsqObmwb21jiHCgFph7q3emQYCXhhB0ih1Xm/g4aRZPDpg8AFcHHe6a+YloV2c6JIyEMfq0FBNbH5+//v/SI5H0ncpQo0AWBmPpYghp+f+s0IzExKPte0F4ggf7lJRRN7vw19Cum2OEGJvOWEyDpGdbQIHhl2PE4cGfWd8QpPGpVisUj6ol4uaI6t5Yz2qeY8btbhET5XHvg5rBXscNQ8HpYYcJIcCfUkvn3pXggl8XJqNxzI5HyRwKWQ6SQGX3yX7ESlWZSx 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 Hi Samarth, Could you send a v3 with just the soft-dirty fix, as David suggested? Leave the uffd-wp/RWP bits to me (I'll take a closer look). On 2026/10/21 17:49, Lance Yang wrote: > > > On 2026/10/21 16:55, Kiryl Shutsemau wrote: >> On Wed, Oct 21, 2026 at 10:21:53AM +0200, David Hildenbrand (Arm) wrote: >>>> +1. Did it ever actually work there :) Why not just skip them and >>>> call it a day :D >>> >>> I think QEMU just always sets MADV_MERGABLE and later activates uffd. >>> So that >>> needs some care to not disable them. So let's rather try to get it >>> fixed properly. >>> >>> Can you send out proper patches? Thanks! > > Thanks David! Will take it over next week and get proper patches out :) > >> >> +1. >> >> Lance's direction is right. Unsharing is not an access: do_wp_page() >> already skips the uffd-wp fault on FAULT_FLAG_UNSHARE, and RWP should do >> the same. > > Thanks Kiryl! Will take a close look at that :) > > Cheers, Lance >