Messages in this thread Patch in this message | | | Date | Thu, 2 Nov 2023 10:33:57 -0700 | Subject | [PATCH] fs/proc/task_mmu: report SOFT_DIRTY bits through the PAGEMAP_SCAN ioctl | From | Andrei Vagin <> |
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The PAGEMAP_SCAN ioctl returns information regarding page table entries. It is more efficient compared to reading pagemap files. CRIU can start to utilize this ioctl, but it needs info about soft-dirty bits to track memory changes.
We are aware of a new method for tracking memory changes implemented in the PAGEMAP_SCAN ioctl. For CRIU, the primary advantage of this method is its usability by unprivileged users. However, it is not feasible to transparently replace the soft-dirty tracker with the new one. The main problem here is userfault descriptors that have to be preserved between pre-dump iterations. It means criu continues supporting the soft-dirty method to avoid breakage for current users. The new method will be implemented as a separate feature.
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com> Cc: Michał Mirosław <mirq-linux@rere.qmqm.pl> Signed-off-by: Andrei Vagin <avagin@google.com> --- fs/proc/task_mmu.c | 13 ++++++++++++- include/uapi/linux/fs.h | 1 + 2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index ef2eb12906da..cefa676bd33b 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1761,7 +1761,7 @@ static int pagemap_release(struct inode *inode, struct file *file) #define PM_SCAN_CATEGORIES (PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN | \ PAGE_IS_FILE | PAGE_IS_PRESENT | \ PAGE_IS_SWAPPED | PAGE_IS_PFNZERO | \ - PAGE_IS_HUGE) + PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY) #define PM_SCAN_FLAGS (PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC) struct pagemap_scan_private { @@ -1853,12 +1853,16 @@ static unsigned long pagemap_thp_category(struct pagemap_scan_private *p, if (is_zero_pfn(pmd_pfn(pmd))) categories |= PAGE_IS_PFNZERO; + if (pmd_soft_dirty(pmd)) + categories |= PAGE_IS_SOFT_DIRTY; } else if (is_swap_pmd(pmd)) { swp_entry_t swp; categories |= PAGE_IS_SWAPPED; if (!pmd_swp_uffd_wp(pmd)) categories |= PAGE_IS_WRITTEN; + if (pmd_swp_soft_dirty(pmd)) + categories |= PAGE_IS_SOFT_DIRTY; if (p->masks_of_interest & PAGE_IS_FILE) { swp = pmd_to_swp_entry(pmd); @@ -1905,10 +1909,14 @@ static unsigned long pagemap_hugetlb_category(pte_t pte) categories |= PAGE_IS_FILE; if (is_zero_pfn(pte_pfn(pte))) categories |= PAGE_IS_PFNZERO; + if (pte_soft_dirty(pte)) + categories |= PAGE_IS_SOFT_DIRTY; } else if (is_swap_pte(pte)) { categories |= PAGE_IS_SWAPPED; if (!pte_swp_uffd_wp_any(pte)) categories |= PAGE_IS_WRITTEN; + if (pte_swp_soft_dirty(pte)) + categories |= PAGE_IS_SOFT_DIRTY; } return categories; @@ -1991,6 +1999,9 @@ static int pagemap_scan_test_walk(unsigned long start, unsigned long end, if (vma->vm_flags & VM_PFNMAP) return 1; + if (vma->vm_flags & VM_SOFTDIRTY) + vma_category |= PAGE_IS_SOFT_DIRTY; + if (!pagemap_scan_is_interesting_vma(vma_category, p)) return 1; diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index da43810b7485..48ad69f7722e 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -316,6 +316,7 @@ typedef int __bitwise __kernel_rwf_t; #define PAGE_IS_SWAPPED (1 << 4) #define PAGE_IS_PFNZERO (1 << 5) #define PAGE_IS_HUGE (1 << 6) +#define PAGE_IS_SOFT_DIRTY (1 << 7) /* * struct page_region - Page region with flags -- 2.42.0.869.gea05f2083d-goog
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