linux-kernel - [PATCH V2] mm/ptdump: Replace READ_ONCE() with standard page table accessors

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Message-Id: <20251001042502.1400726-1-anshuman.khandual@arm.com>
Date: Wed,  1 Oct 2025 05:25:02 +0100
From: Anshuman Khandual <anshuman.khandual@....com>
To: linux-mm@...ck.org
Cc: Anshuman Khandual <anshuman.khandual@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>,
	linux-kernel@...r.kernel.org,
	Dev Jain <dev.jain@....com>,
	Lance Yang <lance.yang@...ux.dev>,
	SeongJae Park <sj@...nel.org>
Subject: [PATCH V2] mm/ptdump: Replace READ_ONCE() with standard page table accessors

Replace READ_ONCE() with standard page table accessors i.e pxdp_get() which
anyways default into READ_ONCE() in cases where platform does not override.
Also convert ptep_get_lockless() into ptep_get() as well.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: David Hildenbrand <david@...hat.com>
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org
Reviewed-by: Dev Jain <dev.jain@....com>
Acked-by: Lance Yang <lance.yang@...ux.dev>
Acked-by: SeongJae Park <sj@...nel.org>
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
Changes in V2:

- Replaced ptep_get_lockless() with ptep_get() per David

Changes in V1:

https://lore.kernel.org/all/20250930025246.1143340-1-anshuman.khandual@arm.com/

 mm/ptdump.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/mm/ptdump.c b/mm/ptdump.c
index b600c7f864b8..973020000096 100644
--- a/mm/ptdump.c
+++ b/mm/ptdump.c
@@ -31,7 +31,7 @@ static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr,
 			    unsigned long next, struct mm_walk *walk)
 {
 	struct ptdump_state *st = walk->private;
-	pgd_t val = READ_ONCE(*pgd);
+	pgd_t val = pgdp_get(pgd);
 
 #if CONFIG_PGTABLE_LEVELS > 4 && \
 		(defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS))
@@ -54,7 +54,7 @@ static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr,
 			    unsigned long next, struct mm_walk *walk)
 {
 	struct ptdump_state *st = walk->private;
-	p4d_t val = READ_ONCE(*p4d);
+	p4d_t val = p4dp_get(p4d);
 
 #if CONFIG_PGTABLE_LEVELS > 3 && \
 		(defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS))
@@ -77,7 +77,7 @@ static int ptdump_pud_entry(pud_t *pud, unsigned long addr,
 			    unsigned long next, struct mm_walk *walk)
 {
 	struct ptdump_state *st = walk->private;
-	pud_t val = READ_ONCE(*pud);
+	pud_t val = pudp_get(pud);
 
 #if CONFIG_PGTABLE_LEVELS > 2 && \
 		(defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS))
@@ -100,7 +100,7 @@ static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr,
 			    unsigned long next, struct mm_walk *walk)
 {
 	struct ptdump_state *st = walk->private;
-	pmd_t val = READ_ONCE(*pmd);
+	pmd_t val = pmdp_get(pmd);
 
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 	if (pmd_page(val) == virt_to_page(lm_alias(kasan_early_shadow_pte)))
@@ -121,7 +121,7 @@ static int ptdump_pte_entry(pte_t *pte, unsigned long addr,
 			    unsigned long next, struct mm_walk *walk)
 {
 	struct ptdump_state *st = walk->private;
-	pte_t val = ptep_get_lockless(pte);
+	pte_t val = ptep_get(pte);
 
 	if (st->effective_prot_pte)
 		st->effective_prot_pte(st, val);
-- 
2.30.2