[PATCH 6.12.y 1/2] mm: replace READ_ONCE() with standard page table accessors

Sasha Levin
2026-04-01T17:06:46Z

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>
---
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(-)

diff --git a/mm/gup.c b/mm/gup.c
index d105817a0c9aa..937865ecfae00 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1013,7 +1013,7 @@ static struct page *follow_pud_mask(struct vm_area_struct *vma,
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)) {
@@ -1038,7 +1038,7 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma,
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))
@@ -3301,7 +3301,7 @@ static int gup_fast_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr,

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)))
@@ -3327,7 +3327,7 @@ static int gup_fast_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr,

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))
@@ -3349,7 +3349,7 @@ static void gup_fast_pgd_range(unsigned long addr, unsigned long end,

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))
diff --git a/mm/hmm.c b/mm/hmm.c
index a67776aeb0199..a27866a1d9bd5 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -423,7 +423,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
/* 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);
diff --git a/mm/memory.c b/mm/memory.c
index 090e9c6f99920..d27cd9a7443ce 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6451,12 +6451,12 @@ int follow_pfnmap_start(struct follow_pfnmap_args *args)
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)) {
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 6f450af3252eb..a7c2d7c68a6a5 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -447,7 +447,7 @@ static inline long change_pud_range(struct mmu_gather *tlb,
break;
}

- pud = READ_ONCE(*pudp);
+ pud = pudp_get(pudp);
if (pud_none(pud))
continue;

diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index c3353cd442a5d..3e88708886e37 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -337,7 +337,7 @@ int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end,
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);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0ceed77af0fbd..deeb4310fd54c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3631,7 +3631,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end,
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);

--
2.53.0