Re: [PATCH v3] mm/page_vma_mapped_walk: Use ptep_get_lockless() for lockless access

[Lorenzo Stoakes <ljs@kernel.org>]

On Thu, May 28, 2026 at 09:55:07AM +0200, Alexander Gordeev wrote:
> Switch from ptep_get() to ptep_get_lockless() accessor for
> PTE reads when no lock is taken.
>
> Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

Oh and the logic looks good so with the commit message updated, feel free to
add:

Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>

> ---
>  mm/page_vma_mapped.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
> index a4d52fdb3056..2ccbabfb2cc1 100644
> --- a/mm/page_vma_mapped.c
> +++ b/mm/page_vma_mapped.c
> @@ -41,7 +41,7 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, pmd_t *pmdvalp,
>  	if (!pvmw->pte)
>  		return false;
>
> -	ptent = ptep_get(pvmw->pte);
> +	ptent = ptep_get_lockless(pvmw->pte);
>
>  	if (pte_none(ptent)) {
>  		return false;
> @@ -183,6 +183,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>  	struct mm_struct *mm = vma->vm_mm;
>  	unsigned long end;
>  	spinlock_t *ptl;
> +	pte_t pteval;
>  	pgd_t *pgd;
>  	p4d_t *p4d;
>  	pud_t *pud;
> @@ -310,7 +311,11 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>  				goto restart;
>  			}
>  			pvmw->pte++;
> -		} while (pte_none(ptep_get(pvmw->pte)));
> +			if (!pvmw->ptl)
> +				pteval = ptep_get_lockless(pvmw->pte);
> +			else
> +				pteval = ptep_get(pvmw->pte);
> +		} while (pte_none(pteval));
>
>  		if (!pvmw->ptl) {
>  			spin_lock(ptl);
> --
> 2.51.0
>