[RFC, PATCH 09/12] mm/pagemap: add PAGE_IS_UFFD_DEACTIVATED to PAGEMAP_SCAN

["Kiryl Shutsemau (Meta)" <kas@kernel.org>]

Report deactivated anonymous pages in PAGEMAP_SCAN results.
Only set on anonymous VMAs (shmem cold = !PAGE_IS_PRESENT).
Both PTE and PMD (THP) levels handled.

Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
---
 fs/proc/task_mmu.c      | 11 ++++++++++-
 include/uapi/linux/fs.h |  1 +
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index e091931d7ca1..fc42cfd5720a 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -2329,7 +2329,7 @@ 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_UFFD_DEACTIVATED)
 #define PM_SCAN_FLAGS		(PM_SCAN_WP_MATCHING | PM_SCAN_CHECK_WPASYNC)
 
 struct pagemap_scan_private {
@@ -2354,6 +2354,10 @@ static unsigned long pagemap_page_category(struct pagemap_scan_private *p,
 
 		categories = PAGE_IS_PRESENT;
 
+		if (pte_protnone(pte) && vma_is_accessible(vma) &&
+		    vma_is_anonymous(vma) && userfaultfd_minor(vma))
+			categories |= PAGE_IS_UFFD_DEACTIVATED;
+
 		if (!pte_uffd_wp(pte))
 			categories |= PAGE_IS_WRITTEN;
 
@@ -2422,6 +2426,11 @@ static unsigned long pagemap_thp_category(struct pagemap_scan_private *p,
 		struct page *page;
 
 		categories |= PAGE_IS_PRESENT;
+
+		if (pmd_protnone(pmd) && vma_is_accessible(vma) &&
+		    vma_is_anonymous(vma) && userfaultfd_minor(vma))
+			categories |= PAGE_IS_UFFD_DEACTIVATED;
+
 		if (!pmd_uffd_wp(pmd))
 			categories |= PAGE_IS_WRITTEN;
 
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 70b2b661f42c..af5b28901800 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_UFFD_DEACTIVATED (1 << 9)
 
 /*
  * struct page_region - Page region with flags
-- 
2.51.2