Re: [PATCH] mm/page_vma_mapped: revalidate and do proper check before return device-private pmd

[Lance Yang]

On 2026/6/22 21:46, Lorenzo Stoakes wrote:
> +cc Lance, linux-kernel

Thanks for the cc.

[...]

> ----8<----
>  From e6a3c1c782714ed831c4d46a14bb99226423bf59 Mon Sep 17 00:00:00 2001
> From: Wei Yang <richard.weiyang@xxxxxxxxx>
> Date: Mon, 22 Jun 2026 13:06:51 +0000
> Subject: [PATCH] refactored
>
> Signed-off-by: Lorenzo Stoakes <ljs@xxxxxxxxxx>
> ---
>   mm/page_vma_mapped.c | 20 +++++++++++++++-----
>   1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
> index 2ccbabfb2cc1..17dff8aab9f9 100644
> --- a/mm/page_vma_mapped.c
> +++ b/mm/page_vma_mapped.c
> @@ -269,14 +269,24 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>   			/* THP pmd was split under us: handle on pte level */
>   			spin_unlock(pvmw->ptl);
>   			pvmw->ptl = NULL;
> -		} else if (!pmd_present(pmde)) {
> -			const softleaf_t entry = softleaf_from_pmd(pmde);
> +		} else if (pmd_is_device_private_entry(pmde)) {
> +			softleaf_t entry;
> +
> +			pvmw->ptl = pmd_lock(mm, pvmw->pmd);
> +			pmde = *pvmw->pmd;
> +			entry = softleaf_from_pmd(pmde);
>
> -			if (softleaf_is_device_private(entry)) {
> -				pvmw->ptl = pmd_lock(mm, pvmw->pmd);
> +			if (likely(softleaf_is_device_private(entry))) {
> +				if (pvmw->flags & PVMW_MIGRATION)
> +					return not_found(pvmw);
> +				if (!check_pmd(softleaf_to_pfn(entry), pvmw))
> +					return not_found(pvmw);
>   				return true;
>   			}
> -
> +			/* device-private pmd was split under us: handle on pte level */
> +			spin_unlock(pvmw->ptl);
> +			pvmw->ptl = NULL;
> +		} else if (!pmd_present(pmde)) {
>   			if ((pvmw->flags & PVMW_SYNC) &&
>   			    thp_vma_suitable_order(vma, pvmw->address,
>   						   PMD_ORDER) &&
> --
> 2.54.0

Cool, looks way cleaner :) Nothing jumped out at me :)

Cheers, Lance