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b=d9oJ3s7+soX7DYUyP0ESJXspaTPr/B47iWffX9FN8OBabt/l9iSOyTpR9uJ9+XaNS IlnC7UL1NcTV73iIbeiayXFZP3AjjaJnWQWjduFuRpElSp6QJmlTtANDaATUIxQiB5 xWl1vUW+5u820yiGZaCnwMNgiuTXNYg7Y77csk35pMuVxlBq4F3NBCu5jUT5PQeCYq 0nxM2HF9q1cW5tjceh+u7lxbOzzlQ6JcSV8pTf6VJHKI7wFB9/5qmQ0Tw5uAvpDbE2 cOraQLUE0qHVrlC/IM9838zgCjXQj00KtdwWOTmeSaXrIrq6CBfbGyXWua3l0J8Xno fCg7HUOF45JKg== Date: Tue, 12 May 2026 20:41:45 +0300 From: Mike Rapoport To: "Kiryl Shutsemau (Meta)" Cc: akpm@linux-foundation.org, peterx@redhat.com, david@kernel.org, ljs@kernel.org, surenb@google.com, vbabka@kernel.org, Liam.Howlett@oracle.com, ziy@nvidia.com, corbet@lwn.net, skhan@linuxfoundation.org, seanjc@google.com, pbonzini@redhat.com, jthoughton@google.com, aarcange@redhat.com, sj@kernel.org, usama.arif@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, kvm@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH v2 10/14] mm/pagemap: add PAGE_IS_ACCESSED for RWP tracking Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 9B092C0002 X-Stat-Signature: 766wsedk91h3eyd9737fnzo8y45811kf X-Rspam-User: X-HE-Tag: 1778607717-307224 X-HE-Meta: U2FsdGVkX1/txG3YXdn+4Ph9lcfnEQzDVOmONCSKuoOkGGnOBEGsruBSfLXQ74rxEiN9QBKs2fshhYkgWa4QhEGNXXDFS+ssT7LttNlqel29i9v51p2W1rY8ptBEIovE6OhMhmRIBG4M8z44pkTFffNf1R9lIx/cvQZSo/9Kz2nTgH+eL3Zpbg7Op6qP8bniU7yeeUYB1wfAgvAYbQFWNQXuOviw1M4rGCmgK5JDlBLYtVYUtC8WFAXjngC4GM2PQD+2vnuETBAVx+Lfaqo8eLR7R++89lkiiUeb+XUIkskNxGSl6zgyMw3uN1Lws+KRdjukxTiyOoiDLbVI82L9R5PBuhkH9oWI6o4hVXXrBQhbYkukMjb4C78zbA0D1nNeV7j532lj1VBlPYAj+ops/utdoK3QOqyKAXjaILPtL883KR2NICWfu7VHmV/PLMhdzsis4RzimC6A4yLi7EbU5owJ/EoIlmqcqzkLNffUHp4zwjI3vmasJOEVTFZowxv9qwp7pfKKu1KFNWjjJG4ARVRH3rJTNrkcxr9IiPYvdWszvPVVPID2U+Jj/XXdFeO8L6hJ/p5tAg2cpwANUzXz0T8ZyOZ7Pz6Ggo/S0PhpEQn+UCp5KUwWFwEGMfX+o0Y5nteLrTW+W7eoQOlH5SDM0ZjmbJCBa/Y4v4yr/mSX1ZdD+SOcTBfl5oCT3IGQfTKxxaAMcQ9v7nmLIVylOXP3LJCek+BsFmOIqalxFPT+y4kv8FiOaeLTonZkZ2HjXvA3nmNUm6skfVFCklXX8IjghZD42ybVb35zbfltoIhuHDBzcCC48P6gQa6ObOtsFvRjtlbNszP1VCxt4nVhmcNSK7U220gYILcPRuxdHF2WfY4m4fW0ffz3t/M+jqwddb1CveFb3PA9KtCfbtPcvT1GBXsPkSlMs3I7tAvsUsMaaoYOJb41lI7zyCzio3uGPQQCbQjVhVnDM2zkY7jODkY XB+eADS2 pV4AlbtOnHwgPGL/XRq2m2G6bBLMfBMR+K6cUFRP1lOasLPOzZtLWIn7qMULEZeQfAjjYtfioY1VBHGb9CCFb7uekQ19mWL4csG4WjppAgZB3eGDTnf0LSlmr42jFV5XHxwBo9hvy8ZlMJOnse/vSM002eQ0HGxz4BKSvLuKjgWdMkaEMxEx65d9wd643OLNDRpVsAqlj0eZY4JYXaWA8tCjxUO9Ijyl0DkDwDbvMfTrthpOec38ZD0mbfQrJwC6yWjqlinB6eX+u0Rr39z3oYt9vLacho+Zvkkx4DdzLy/VMa6txEzFD2ZeC/sItS0jbBq3FlVSWdOIYyoXcxlvd8rH6oey0FCaHwd33 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, May 08, 2026 at 04:55:22PM +0100, Kiryl Shutsemau (Meta) wrote: > PAGEMAP_SCAN already reports PAGE_IS_WRITTEN from the inverted uffd > PTE bit, targeting the UFFDIO_WRITEPROTECT workflow. UFFDIO_RWPROTECT > reuses the same PTE bit as a marker for read-write protection, but > "has been written" and "has been accessed" are distinct semantic > signals — they happen to share one PTE bit today only because the two > implementations share infrastructure. > > Give RWP its own pagemap category so the UAPI does not conflate them: > > PAGE_IS_WRITTEN reported on VM_UFFD_WP VMAs, !pte_uffd(pte) > PAGE_IS_ACCESSED reported on VM_UFFD_RWP VMAs, !pte_uffd(pte) > > Both still read the same PTE bit today, but each is scoped to the VMA > whose registered mode makes the bit meaningful. If a future > implementation moves RWP to a separate PTE bit, only PAGE_IS_ACCESSED > switches over. > > This is a UAPI narrowing. Outside VM_UFFD_WP VMAs the uffd bit is > always clear, so PAGEMAP_SCAN used to flag PAGE_IS_WRITTEN on every > present PTE there — a meaningless duplicate of PAGE_IS_PRESENT. Now > PAGE_IS_WRITTEN fires only inside VM_UFFD_WP VMAs. > > pagemap_hugetlb_category() now takes the vma like its PTE/PMD peers. > > Signed-off-by: Kiryl Shutsemau > Assisted-by: Claude:claude-opus-4-6 Acked-by: Mike Rapoport (Microsoft) > --- > Documentation/admin-guide/mm/pagemap.rst | 13 ++++- > fs/proc/task_mmu.c | 73 ++++++++++++++++++------ > include/uapi/linux/fs.h | 1 + > tools/include/uapi/linux/fs.h | 1 + > 4 files changed, 67 insertions(+), 21 deletions(-) -- Sincerely yours, Mike.