On Thu, 27 Jul 2023 at 11:37, Muhammad Usama Anjum usama.anjum@collabora.com wrote:
This IOCTL, PAGEMAP_SCAN on pagemap file can be used to get and/or clear the info about page table entries. The following operations are supported in this ioctl:
- Get the information if the pages have Async Write-Protection enabled (``PAGE_IS_WPALLOWED``), have been written to (``PAGE_IS_WRITTEN``), file mapped (``PAGE_IS_FILE``), present (``PAGE_IS_PRESENT``), swapped (``PAGE_IS_SWAPPED``) or page has pfn zero (``PAGE_IS_PFNZERO``).
- Find pages which have been written to and/or write protect (atomic ``PM_SCAN_WP_MATCHING + PM_SCAN_CHECK_WPASYNC``) the pages atomically. The (``PM_SCAN_WP_MATCHING``) is used to WP the matched pages. The (``PM_SCAN_CHECK_WPASYNC``) aborts the operation if non-Async-Write-Protected pages are found. Get is automatically performed if output buffer is specified.
This IOCTL can be extended to get information about more PTE bits. The entire address range passed by user [start, end) is scanned until either the user provided buffer is full or max_pages have been found.
Reviewed-by: Andrei Vagin avagin@gmail.com Reviewed-by: Michał Mirosław mirq-linux@rere.qmqm.pl Signed-off-by: Michał Mirosław mirq-linux@rere.qmqm.pl Signed-off-by: Muhammad Usama Anjum usama.anjum@collabora.com
Thanks for all the work!
Small request below.
--- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c
[...]
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE +static unsigned long pagemap_thp_category(pmd_t pmd) +{
unsigned long categories = 0;if (pmd_present(pmd)) {categories |= PAGE_IS_PRESENT;if (!pmd_uffd_wp(pmd))categories |= PAGE_IS_WRITTEN;if (is_zero_pfn(pmd_pfn(pmd)))categories |= PAGE_IS_PFNZERO;} else if (is_swap_pmd(pmd)) {categories |= PAGE_IS_SWAPPED;if (!pmd_swp_uffd_wp(pmd))categories |= PAGE_IS_WRITTEN;}return categories;+}
[...]
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+#ifdef CONFIG_HUGETLB_PAGE +static unsigned long pagemap_hugetlb_category(pte_t pte) +{
unsigned long categories = 0;if (pte_present(pte)) {categories |= PAGE_IS_PRESENT;if (!huge_pte_uffd_wp(pte))categories |= PAGE_IS_WRITTEN;if (!PageAnon(pte_page(pte)))categories |= PAGE_IS_FILE;if (is_zero_pfn(pte_pfn(pte)))categories |= PAGE_IS_PFNZERO;} else if (is_swap_pte(pte)) {categories |= PAGE_IS_SWAPPED;if (!pte_swp_uffd_wp_any(pte))categories |= PAGE_IS_WRITTEN;}return categories;+}
Could you add PAGE_IS_HUGE for THP and HugeTLB pages? This would help maintaining checkpointed process'es page sizes by CRIU when THP is used.
Best Regards Michał Mirosław