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 <[email protected]> Assisted-by: Claude:claude-opus-4-6 --- Documentation/admin-guide/mm/pagemap.rst | 13 +++-- fs/proc/task_mmu.c | 63 +++++++++++++++++------- include/uapi/linux/fs.h | 1 + tools/include/uapi/linux/fs.h | 1 + 4 files changed, 57 insertions(+), 21 deletions(-) diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst index c57e61b5d8aa..ffa690a171c8 100644 --- a/Documentation/admin-guide/mm/pagemap.rst +++ b/Documentation/admin-guide/mm/pagemap.rst @@ -19,8 +19,11 @@ There are four components to pagemap: * Bit 55 pte is soft-dirty (see Documentation/admin-guide/mm/soft-dirty.rst) * Bit 56 page exclusively mapped (since 4.2) - * Bit 57 pte is uffd-wp write-protected (since 5.13) (see - Documentation/admin-guide/mm/userfaultfd.rst) + * Bit 57 pte is tracked by userfaultfd (since 5.13) — in a + ``VM_UFFD_WP`` VMA this indicates a write-protected PTE; in a + ``VM_UFFD_RWP`` VMA it indicates an RWP-protected PTE. WP and + RWP are mutually exclusive per VMA, so the meaning is + unambiguous. See Documentation/admin-guide/mm/userfaultfd.rst. * Bit 58 pte is a guard region (since 6.15) (see madvise (2) man page) * Bits 59-60 zero * Bit 61 page is file-page or shared-anon (since 3.5) @@ -244,7 +247,8 @@ in this IOCTL: Following flags about pages are currently supported: - ``PAGE_IS_WPALLOWED`` - Page has async-write-protection enabled -- ``PAGE_IS_WRITTEN`` - Page has been written to from the time it was write protected +- ``PAGE_IS_WRITTEN`` - Page in a ``UFFDIO_REGISTER_MODE_WP`` VMA has been + written to since it was write-protected. Only reported inside such VMAs. - ``PAGE_IS_FILE`` - Page is file backed - ``PAGE_IS_PRESENT`` - Page is present in the memory - ``PAGE_IS_SWAPPED`` - Page is in swapped @@ -252,6 +256,9 @@ Following flags about pages are currently supported: - ``PAGE_IS_HUGE`` - Page is PMD-mapped THP or Hugetlb backed - ``PAGE_IS_SOFT_DIRTY`` - Page is soft-dirty - ``PAGE_IS_GUARD`` - Page is a part of a guard region +- ``PAGE_IS_ACCESSED`` - Page in a ``UFFDIO_REGISTER_MODE_RWP`` VMA has been + accessed since RWP was applied. Only reported inside such VMAs. See + Documentation/admin-guide/mm/userfaultfd.rst for the RWP workflow. The ``struct pm_scan_arg`` is used as the argument of the IOCTL. diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index fbaede228201..42b99e482c98 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -2197,7 +2197,7 @@ static const struct mm_walk_ops pagemap_ops = { * Bits 5-54 swap offset if swapped * Bit 55 pte is soft-dirty (see Documentation/admin-guide/mm/soft-dirty.rst) * Bit 56 page exclusively mapped - * Bit 57 pte is uffd-wp write-protected + * Bit 57 pte is tracked by userfaultfd (uffd-wp or RWP) * Bit 58 pte is a guard region * Bits 59-60 zero * Bit 61 page is file-page or shared-anon @@ -2332,7 +2332,7 @@ static int pagemap_release(struct inode *inode, struct file *file) PAGE_IS_FILE | PAGE_IS_PRESENT | \ PAGE_IS_SWAPPED | PAGE_IS_PFNZERO | \ PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY | \ - PAGE_IS_GUARD) + PAGE_IS_GUARD | PAGE_IS_ACCESSED) #define PM_SCAN_FLAGS (PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC) struct pagemap_scan_private { @@ -2357,8 +2357,12 @@ static unsigned long pagemap_page_category(struct pagemap_scan_private *p, categories = PAGE_IS_PRESENT; - if (!pte_uffd(pte)) - categories |= PAGE_IS_WRITTEN; + if (!pte_uffd(pte)) { + if (userfaultfd_wp(vma)) + categories |= PAGE_IS_WRITTEN; + if (userfaultfd_rwp(vma)) + categories |= PAGE_IS_ACCESSED; + } if (p->masks_of_interest & PAGE_IS_FILE) { page = vm_normal_page(vma, addr, pte); @@ -2375,8 +2379,12 @@ static unsigned long pagemap_page_category(struct pagemap_scan_private *p, categories = PAGE_IS_SWAPPED; - if (!pte_swp_uffd_any(pte)) - categories |= PAGE_IS_WRITTEN; + if (!pte_swp_uffd_any(pte)) { + if (userfaultfd_wp(vma)) + categories |= PAGE_IS_WRITTEN; + if (userfaultfd_rwp(vma)) + categories |= PAGE_IS_ACCESSED; + } entry = softleaf_from_pte(pte); if (softleaf_is_guard_marker(entry)) @@ -2425,8 +2433,12 @@ static unsigned long pagemap_thp_category(struct pagemap_scan_private *p, struct page *page; categories |= PAGE_IS_PRESENT; - if (!pmd_uffd(pmd)) - categories |= PAGE_IS_WRITTEN; + if (!pmd_uffd(pmd)) { + if (userfaultfd_wp(vma)) + categories |= PAGE_IS_WRITTEN; + if (userfaultfd_rwp(vma)) + categories |= PAGE_IS_ACCESSED; + } if (p->masks_of_interest & PAGE_IS_FILE) { page = vm_normal_page_pmd(vma, addr, pmd); @@ -2440,8 +2452,12 @@ static unsigned long pagemap_thp_category(struct pagemap_scan_private *p, categories |= PAGE_IS_SOFT_DIRTY; } else { categories |= PAGE_IS_SWAPPED; - if (!pmd_swp_uffd(pmd)) - categories |= PAGE_IS_WRITTEN; + if (!pmd_swp_uffd(pmd)) { + if (userfaultfd_wp(vma)) + categories |= PAGE_IS_WRITTEN; + if (userfaultfd_rwp(vma)) + categories |= PAGE_IS_ACCESSED; + } if (pmd_swp_soft_dirty(pmd)) categories |= PAGE_IS_SOFT_DIRTY; @@ -2474,7 +2490,8 @@ static void make_uffd_wp_pmd(struct vm_area_struct *vma, #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #ifdef CONFIG_HUGETLB_PAGE -static unsigned long pagemap_hugetlb_category(pte_t pte) +static unsigned long pagemap_hugetlb_category(struct vm_area_struct *vma, + pte_t pte) { unsigned long categories = PAGE_IS_HUGE; @@ -2489,8 +2506,12 @@ static unsigned long pagemap_hugetlb_category(pte_t pte) if (pte_present(pte)) { categories |= PAGE_IS_PRESENT; - if (!huge_pte_uffd(pte)) - categories |= PAGE_IS_WRITTEN; + if (!huge_pte_uffd(pte)) { + if (userfaultfd_wp(vma)) + categories |= PAGE_IS_WRITTEN; + if (userfaultfd_rwp(vma)) + categories |= PAGE_IS_ACCESSED; + } if (!PageAnon(pte_page(pte))) categories |= PAGE_IS_FILE; if (is_zero_pfn(pte_pfn(pte))) @@ -2500,8 +2521,12 @@ static unsigned long pagemap_hugetlb_category(pte_t pte) } else { categories |= PAGE_IS_SWAPPED; - if (!pte_swp_uffd_any(pte)) - categories |= PAGE_IS_WRITTEN; + if (!pte_swp_uffd_any(pte)) { + if (userfaultfd_wp(vma)) + categories |= PAGE_IS_WRITTEN; + if (userfaultfd_rwp(vma)) + categories |= PAGE_IS_ACCESSED; + } if (pte_swp_soft_dirty(pte)) categories |= PAGE_IS_SOFT_DIRTY; } @@ -2773,7 +2798,8 @@ static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start, goto flush_and_return; } - if (!p->arg.category_anyof_mask && !p->arg.category_inverted && + if (userfaultfd_wp(vma) && !p->arg.category_anyof_mask && + !p->arg.category_inverted && p->arg.category_mask == PAGE_IS_WRITTEN && p->arg.return_mask == PAGE_IS_WRITTEN) { for (addr = start; addr < end; pte++, addr += PAGE_SIZE) { @@ -2848,7 +2874,8 @@ static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask, /* Go the short route when not write-protecting pages. */ pte = huge_ptep_get(walk->mm, start, ptep); - categories = p->cur_vma_category | pagemap_hugetlb_category(pte); + categories = p->cur_vma_category | + pagemap_hugetlb_category(vma, pte); if (!pagemap_scan_is_interesting_page(categories, p)) return 0; @@ -2860,7 +2887,7 @@ static int pagemap_scan_hugetlb_entry(pte_t *ptep, unsigned long hmask, ptl = huge_pte_lock(hstate_vma(vma), vma->vm_mm, ptep); pte = huge_ptep_get(walk->mm, start, ptep); - categories = p->cur_vma_category | pagemap_hugetlb_category(pte); + categories = p->cur_vma_category | pagemap_hugetlb_category(vma, pte); if (!pagemap_scan_is_interesting_page(categories, p)) goto out_unlock; diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 13f71202845e..c4aeaa0c31c7 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -455,6 +455,7 @@ typedef int __bitwise __kernel_rwf_t; #define PAGE_IS_HUGE (1 << 6) #define PAGE_IS_SOFT_DIRTY (1 << 7) #define PAGE_IS_GUARD (1 << 8) +#define PAGE_IS_ACCESSED (1 << 9) /* * struct page_region - Page region with flags diff --git a/tools/include/uapi/linux/fs.h b/tools/include/uapi/linux/fs.h index 24ddf7bc4f25..f0a26309b6d5 100644 --- a/tools/include/uapi/linux/fs.h +++ b/tools/include/uapi/linux/fs.h @@ -364,6 +364,7 @@ typedef int __bitwise __kernel_rwf_t; #define PAGE_IS_HUGE (1 << 6) #define PAGE_IS_SOFT_DIRTY (1 << 7) #define PAGE_IS_GUARD (1 << 8) +#define PAGE_IS_ACCESSED (1 << 9) /* * struct page_region - Page region with flags -- 2.51.2
