linux-kernel - Re: [PATCH] mm/dirty: Replace READ_ONCE() with pudp

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Message-ID: <4b513d32-7795-4998-98df-d398c3d5462a@arm.com>
Date: Mon, 6 Oct 2025 11:37:48 +0530
From: Dev Jain <dev.jain@....com>
To: Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/dirty: Replace READ_ONCE() with pudp_get()


On 06/10/25 11:22 am, Anshuman Khandual wrote:
> Replace READ_ONCE() with a standard page table accessor i.e pudp_get() that
> anyways defaults 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>
> ---
>   mm/mapping_dirty_helpers.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/mapping_dirty_helpers.c b/mm/mapping_dirty_helpers.c
> index c193de6cb23a..737c407f4081 100644
> --- a/mm/mapping_dirty_helpers.c
> +++ b/mm/mapping_dirty_helpers.c
> @@ -149,7 +149,7 @@ static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end,
>   			      struct mm_walk *walk)
>   {
>   #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
> -	pud_t pudval = READ_ONCE(*pud);
> +	pud_t pudval = pudp_get(pud);
>   
>   	/* Do not split a huge pud */
>   	if (pud_trans_huge(pudval)) {

Talking about mm, why not also make changes for these READ_ONCE accesses
in gup, hmm, memory, mprotect, sparse-vmemmap?