+ mm-replace-read_once-with-standard-page-table-accessors.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: replace READ_ONCE() with standard page table accessors
has been added to the -mm mm-new branch.  Its filename is
     mm-replace-read_once-with-standard-page-table-accessors.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-replace-read_once-with-standard-page-table-accessors.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.

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------------------------------------------------------
From: Anshuman Khandual <anshuman.khandual@arm.com>
Subject: mm: replace READ_ONCE() with standard page table accessors
Date: Tue, 7 Oct 2025 07:31:00 +0100

Replace all READ_ONCE() with a standard page table accessors i.e
pxdp_get() that defaults into READ_ONCE() in cases where platform does not
override.

Link: https://lkml.kernel.org/r/20251007063100.2396936-1-anshuman.khandual@arm.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Dev Jain <dev.jain@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/gup.c            |   10 +++++-----
 mm/hmm.c            |    2 +-
 mm/memory.c         |    4 ++--
 mm/mprotect.c       |    2 +-
 mm/sparse-vmemmap.c |    2 +-
 mm/vmscan.c         |    2 +-
 6 files changed, 11 insertions(+), 11 deletions(-)

--- a/mm/gup.c~mm-replace-read_once-with-standard-page-table-accessors
+++ a/mm/gup.c
@@ -950,7 +950,7 @@ static struct page *follow_pud_mask(stru
 	struct mm_struct *mm = vma->vm_mm;
 
 	pudp = pud_offset(p4dp, address);
-	pud = READ_ONCE(*pudp);
+	pud = pudp_get(pudp);
 	if (!pud_present(pud))
 		return no_page_table(vma, flags, address);
 	if (pud_leaf(pud)) {
@@ -975,7 +975,7 @@ static struct page *follow_p4d_mask(stru
 	p4d_t *p4dp, p4d;
 
 	p4dp = p4d_offset(pgdp, address);
-	p4d = READ_ONCE(*p4dp);
+	p4d = p4dp_get(p4dp);
 	BUILD_BUG_ON(p4d_leaf(p4d));
 
 	if (!p4d_present(p4d) || p4d_bad(p4d))
@@ -3060,7 +3060,7 @@ static int gup_fast_pud_range(p4d_t *p4d
 
 	pudp = pud_offset_lockless(p4dp, p4d, addr);
 	do {
-		pud_t pud = READ_ONCE(*pudp);
+		pud_t pud = pudp_get(pudp);
 
 		next = pud_addr_end(addr, end);
 		if (unlikely(!pud_present(pud)))
@@ -3086,7 +3086,7 @@ static int gup_fast_p4d_range(pgd_t *pgd
 
 	p4dp = p4d_offset_lockless(pgdp, pgd, addr);
 	do {
-		p4d_t p4d = READ_ONCE(*p4dp);
+		p4d_t p4d = p4dp_get(p4dp);
 
 		next = p4d_addr_end(addr, end);
 		if (!p4d_present(p4d))
@@ -3108,7 +3108,7 @@ static void gup_fast_pgd_range(unsigned
 
 	pgdp = pgd_offset(current->mm, addr);
 	do {
-		pgd_t pgd = READ_ONCE(*pgdp);
+		pgd_t pgd = pgdp_get(pgdp);
 
 		next = pgd_addr_end(addr, end);
 		if (pgd_none(pgd))
--- a/mm/hmm.c~mm-replace-read_once-with-standard-page-table-accessors
+++ a/mm/hmm.c
@@ -491,7 +491,7 @@ static int hmm_vma_walk_pud(pud_t *pudp,
 	/* Normally we don't want to split the huge page */
 	walk->action = ACTION_CONTINUE;
 
-	pud = READ_ONCE(*pudp);
+	pud = pudp_get(pudp);
 	if (!pud_present(pud)) {
 		spin_unlock(ptl);
 		return hmm_vma_walk_hole(start, end, -1, walk);
--- a/mm/memory.c~mm-replace-read_once-with-standard-page-table-accessors
+++ a/mm/memory.c
@@ -6716,12 +6716,12 @@ retry:
 		goto out;
 
 	p4dp = p4d_offset(pgdp, address);
-	p4d = READ_ONCE(*p4dp);
+	p4d = p4dp_get(p4dp);
 	if (p4d_none(p4d) || unlikely(p4d_bad(p4d)))
 		goto out;
 
 	pudp = pud_offset(p4dp, address);
-	pud = READ_ONCE(*pudp);
+	pud = pudp_get(pudp);
 	if (pud_none(pud))
 		goto out;
 	if (pud_leaf(pud)) {
--- a/mm/mprotect.c~mm-replace-read_once-with-standard-page-table-accessors
+++ a/mm/mprotect.c
@@ -599,7 +599,7 @@ again:
 			break;
 		}
 
-		pud = READ_ONCE(*pudp);
+		pud = pudp_get(pudp);
 		if (pud_none(pud))
 			continue;
 
--- a/mm/sparse-vmemmap.c~mm-replace-read_once-with-standard-page-table-accessors
+++ a/mm/sparse-vmemmap.c
@@ -439,7 +439,7 @@ int __meminit vmemmap_populate_hugepages
 			return -ENOMEM;
 
 		pmd = pmd_offset(pud, addr);
-		if (pmd_none(READ_ONCE(*pmd))) {
+		if (pmd_none(pmdp_get(pmd))) {
 			void *p;
 
 			p = vmemmap_alloc_block_buf(PMD_SIZE, node, altmap);
--- a/mm/vmscan.c~mm-replace-read_once-with-standard-page-table-accessors
+++ a/mm/vmscan.c
@@ -3751,7 +3751,7 @@ static int walk_pud_range(p4d_t *p4d, un
 	pud = pud_offset(p4d, start & P4D_MASK);
 restart:
 	for (i = pud_index(start), addr = start; addr != end; i++, addr = next) {
-		pud_t val = READ_ONCE(pud[i]);
+		pud_t val = pudp_get(pud + i);
 
 		next = pud_addr_end(addr, end);
 
_

Patches currently in -mm which might be from anshuman.khandual@arm.com are

mm-thp-drop-follow_devmap_pmd-default-stub.patch
mm-ptdump-replace-read_once-with-standard-page-table-accessors.patch
mm-replace-read_once-with-standard-page-table-accessors.patch