+ mm-mincore-remove-special-handling-for-vm_pfnmap.patch added to mm-new branch

The patch titled
     Subject: mm: mincore: remove special handling for VM_PFNMAP
has been added to the -mm mm-new branch.  Its filename is
     mm-mincore-remove-special-handling-for-vm_pfnmap.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mincore-remove-special-handling-for-vm_pfnmap.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Kefeng Wang <[email protected]>
Subject: mm: mincore: remove special handling for VM_PFNMAP
Date: Fri, 17 Jul 2026 17:13:43 +0800

As David pointed out, "it's hard to believe that someone depends on pages
in VM_PFNMAP to *not* be present", so remove the historical behavior that
always reports VM_PFNMAP pages as non-resident.

Adding mincore_pud_range() allows the page table walker to traverse the
full page table hierarchy without splitting a huge PUD, enabling much more
precise identification of resident pages in PFNMAP VMAs.

Link: https://lore.kernel.org/linux-mm/[email protected]/
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Kefeng Wang <[email protected]>
Suggested-by: David Hildenbrand (Arm) <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Pedro Falcato <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/mincore.c |   24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

--- a/mm/mincore.c~mm-mincore-remove-special-handling-for-vm_pfnmap
+++ a/mm/mincore.c
@@ -160,6 +160,21 @@ static int mincore_unmapped_range(unsign
 	return 0;
 }
 
+static int mincore_pud_range(pud_t *pudp, unsigned long addr, unsigned long end,
+		struct mm_walk *walk)
+{
+	if (pud_is_huge(pudp_get(pudp))) {
+		int nr = (end - addr) >> PAGE_SHIFT;
+		unsigned char *vec = walk->private;
+
+		memset(vec, 1, nr);
+		walk->action = ACTION_CONTINUE;
+		walk->private += nr;
+	}
+
+	return 0;
+}
+
 static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 			struct mm_walk *walk)
 {
@@ -232,6 +247,7 @@ static inline bool can_do_mincore(struct
 }
 
 static const struct mm_walk_ops mincore_walk_ops = {
+	.pud_entry		= mincore_pud_range,
 	.pmd_entry		= mincore_pte_range,
 	.pte_hole		= mincore_unmapped_range,
 	.hugetlb_entry		= mincore_hugetlb,
@@ -259,14 +275,6 @@ static long do_mincore(unsigned long add
 		return pages;
 	}
 
-	/*
-	 * mincore historically reports PFNMAP mappings as non-resident.
-	 */
-	if (vma->vm_flags & VM_PFNMAP) {
-		__mincore_unmapped_range(addr, end, vma, vec);
-		return (end - addr) >> PAGE_SHIFT;
-	}
-
 	err = walk_page_range_vma(vma, addr, end, &mincore_walk_ops, vec);
 	if (err < 0)
 		return err;
_

Patches currently in -mm which might be from [email protected] are

mm-migrate_device-fix-pte_pfn-pte_dirty-called-on-non-present-pte.patch
mm-remove-pagetranscompound.patch
mm-mincore-use-walk_page_range_vma-in-do_mincore.patch
mm-mprotect-use-walk_page_range_vma-in-mprotect_fixup.patch
mm-mlock-use-walk_page_range_vma-in-mlock_vma_pages_range.patch
mm-migrate_device-use-walk_page_range_vma-in-migrate_vma_collect.patch
mm-introduce-pud_is_huge-helper.patch
mm-mincore-remove-special-handling-for-vm_pfnmap.patch
mm-mincore-replace-__get_free_page-with-kmalloc.patch
mm-mincore-remove-xa_is_value-in-mincore_swap.patch
mm-mincore-improve-mincore_hugetlb.patch
mm-mincore-refactor-mincore_page.patch