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

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Message-ID: <CABzRoyYvdeX562ob6tf50O8gRoMKPp9-62FR5mcjTUNyGZSoTQ@mail.gmail.com>
Date: Tue, 30 Sep 2025 22:30:28 +0800
From: Lance Yang <lance.yang@...ux.dev>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>, 
	David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/ptdump: Replace READ_ONCE() with standard page table accessors

On Tue, Sep 30, 2025 at 10:56 AM Anshuman Khandual
<anshuman.khandual@....com> wrote:
>
> 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.
>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---

Nice cleanup! I assume it's a no-op change on all architectures for now ;)
Acked-by: Lance Yang <lance.yang@...ux.dev>

>  mm/ptdump.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/mm/ptdump.c b/mm/ptdump.c
> index b600c7f864b8..18861501b533 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)))
> --
> 2.30.2
>
>