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Kiryl Shutsemau (Meta)
3389648819
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. Link: https://lore.kernel.org/[email protected] Signed-off-by: Kiryl Shutsemau <[email protected]> Assisted-by: Claude:claude-opus-4-6 Acked-by: Mike Rapoport (Microsoft) <[email protected]> Cc: Andrea Arcangeli <[email protected]> Cc: David Hildenbrand <[email protected]> Cc: James Houghton <[email protected]> Cc: Jonathan Corbet <[email protected]> Cc: Liam Howlett <[email protected]> Cc: Lorenzo Stoakes <[email protected]> Cc: Paolo Bonzini <[email protected]> Cc: Peter Xu <[email protected]> Cc: Sean Christopherson <[email protected]> Cc: SeongJae Park <[email protected]> Cc: Suren Baghdasaryan <[email protected]> Cc: Vlastimil Babka <[email protected]> Cc: Zi Yan <[email protected]> Signed-off-by: Andrew Morton <[email protected]>