[merged mm-stable] mm-rmap-use-huge_ptep_get-in-try_to_unmap_one.patch removed from -mm tree

The quilt patch titled
     Subject: mm/rmap: use huge_ptep_get() in try_to_unmap_one()
has been removed from the -mm tree.  Its filename was
     mm-rmap-use-huge_ptep_get-in-try_to_unmap_one.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: Dev Jain <[email protected]>
Subject: mm/rmap: use huge_ptep_get() in try_to_unmap_one()
Date: Fri, 3 Jul 2026 11:41:55 +0000

Patch series "Fix incorrect access of hugetlb pte entries", v3.

There are various places which use ptep_get() to get the pte entry
corresponding to a hugetlb folio.  Some arches (like s390) have special
handling to compute the pteval, so they provide huge_ptep_get().  Use this
helper consistently.

Additionally, some code paths may provide huge_ptep_get with an unaligned
address.  This is a problem on arm64 (I checked other arches and it looks
fine for them), which is fixed in patch 1.  The fix is made to be
backport-friendly: the cleaner fix would be to perhaps pass the hstate to
huge_ptep_get() - that is wider churn and we can do that later.


This patch (of 5):

try_to_unmap_one() handles hugetlb folios when memory failure needs to
replace a poisoned hugetlb mapping with a hwpoison entry.  In that case
page_vma_mapped_walk() returns the pte pointer to the hugetlb folio in
pvmw.pte, but the code reads it with ptep_get().

On arches which provide their own huge_ptep_get() to dereference a huge
pte pointer, accessing via ptep_get() would cause pte_pfn(), pte_present()
etc to misbehave.

It is not clear whether this has a trivially visible effect to userspace.

Just use huge_ptep_get() for dereferencing a huge pte pointer.

Link: https://lore.kernel.org/[email protected]
Link: https://lore.kernel.org/[email protected]
Fixes: c7ab0d2fdc84 ("mm: convert try_to_unmap_one() to use page_vma_mapped_walk()")
Signed-off-by: Dev Jain <[email protected]>
Reported-by: David Hildenbrand <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Acked-by: David Hildenbrand (Arm) <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Byungchul Park <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Gregory Price <[email protected]>
Cc: Harry Yoo <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Joshua Hahn <[email protected]>
Cc: Jun'ichi "Nick" Nomura <[email protected]>
Cc: Kiryl Shutsemau <[email protected]>
Cc: Lance Yang <[email protected]>
Cc: Liam R. Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matthew Brost <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Pedro Falcato <[email protected]>
Cc: Rakie Kim <[email protected]>
Cc: Ralph Campbell <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Zi Yan <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---

 include/linux/hugetlb.h |    2 ++
 mm/rmap.c               |   16 ++++++++++------
 2 files changed, 12 insertions(+), 6 deletions(-)

--- a/include/linux/hugetlb.h~mm-rmap-use-huge_ptep_get-in-try_to_unmap_one
+++ a/include/linux/hugetlb.h
@@ -1270,6 +1270,8 @@ static inline void hugetlb_count_sub(lon
 {
 }
 
+pte_t huge_ptep_get(struct mm_struct *mm, unsigned long addr, pte_t *ptep);
+
 static inline pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
 					  unsigned long addr, pte_t *ptep)
 {
--- a/mm/rmap.c~mm-rmap-use-huge_ptep_get-in-try_to_unmap_one
+++ a/mm/rmap.c
@@ -2095,14 +2095,19 @@ static bool try_to_unmap_one(struct foli
 		/* Unexpected PMD-mapped THP? */
 		VM_BUG_ON_FOLIO(!pvmw.pte, folio);
 
-		/*
-		 * Handle PFN swap PTEs, such as device-exclusive ones, that
-		 * actually map pages.
-		 */
-		pteval = ptep_get(pvmw.pte);
+		address = pvmw.address;
+		if (folio_test_hugetlb(folio)) {
+			pteval = huge_ptep_get(mm, address, pvmw.pte);
+		} else {
+			pteval = ptep_get(pvmw.pte);
+		}
 		if (likely(pte_present(pteval))) {
 			pfn = pte_pfn(pteval);
 		} else {
+			/*
+			 * Handle PFN swap PTEs, such as device-exclusive ones,
+			 * that actually map pages.
+			 */
 			const softleaf_t entry = softleaf_from_pte(pteval);
 
 			pfn = softleaf_to_pfn(entry);
@@ -2110,7 +2115,6 @@ static bool try_to_unmap_one(struct foli
 		}
 
 		subpage = folio_page(folio, pfn - folio_pfn(folio));
-		address = pvmw.address;
 		anon_exclusive = folio_test_anon(folio) &&
 				 PageAnonExclusive(subpage);
 
_

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

mm-rmap-convert-page-folio-for-hwpoison-checks.patch
mm-rmap-add-try_to_unmap_poisoned_hugetlb_one.patch
mm-rmap-refactor-some-code-around-lazyfree-folio-unmapping.patch
mm-rmap-refactor-anon-folio-unmap-in-try_to_unmap_one.patch
mm-rmap-add-anon-folio-unmap-dispatcher.patch
mm-memory-move-pte_install_uffd_wp_if_needed-into-memoryc.patch
mm-memory-batch-set-uffd-wp-markers-during-zapping.patch
mm-rmap-batch-unmap-file-folios-belonging-to-uffd-wp-vmas.patch