[PATCH 6.18 274/277] mm: replace READ_ONCE() with standard page table accessors

Greg Kroah-Hartman
2026-04-08T18:39:07Z

From: Anshuman Khandual <anshuman.khandual@arm.com>

[ Upstream commit c0efdb373c3aaacb32db59cadb0710cac13e44ae ]

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>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stable-dep-of: ffef67b93aa3 ("mm/memory: fix PMD/PUD checks in follow_pfnmap_start()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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
+++ b/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
+++ b/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
+++ b/mm/memory.c
@@ -6691,12 +6691,12 @@ 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
+++ b/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
+++ b/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
+++ b/mm/vmscan.c
@@ -3783,7 +3783,7 @@ 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);