[merged mm-stable] mm-mincore-remove-special-handling-for-vm_pfnmap.patch removed from -mm tree

[merged mm-stable] mm-mincore-remove-special-handling-for-vm_pfnmap.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm: mincore: remove special handling for VM_PFNMAP
has been removed from the -mm tree.  Its filename was
     mm-mincore-remove-special-handling-for-vm_pfnmap.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Kefeng Wang <wangkefeng.wang@huawei.com>
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.

[wangkefeng.wang@huawei.com: address David's comments]
  Link: https://lore.kernel.org/20260720124151.1483820-1-wangkefeng.wang@huawei.com
Link: https://lore.kernel.org/linux-mm/0e619d71-1c3d-4534-8376-2982c7348c31@kernel.org/
Link: https://lore.kernel.org/20260717091347.1144789-3-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mincore.c |   23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

--- a/mm/mincore.c~mm-mincore-remove-special-handling-for-vm_pfnmap
+++ a/mm/mincore.c
@@ -160,6 +160,20 @@ static int mincore_unmapped_range(unsign
 	return 0;
 }
 
+static int mincore_pud_entry(pud_t *pudp, unsigned long addr, unsigned long end,
+		struct mm_walk *walk)
+{
+	if (pud_is_huge(pudp_get(pudp))) {
+		const unsigned long nr = (end - addr) >> PAGE_SHIFT;
+
+		memset(walk->private, 1, nr);
+		walk->private += nr;
+		walk->action = ACTION_CONTINUE;
+	}
+
+	return 0;
+}
+
 static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 			struct mm_walk *walk)
 {
@@ -232,6 +246,7 @@ static inline bool can_do_mincore(struct
 }
 
 static const struct mm_walk_ops mincore_walk_ops = {
+	.pud_entry		= mincore_pud_entry,
 	.pmd_entry		= mincore_pte_range,
 	.pte_hole		= mincore_unmapped_range,
 	.hugetlb_entry		= mincore_hugetlb,
@@ -259,14 +274,6 @@ 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 wangkefeng.wang@huawei.com are