linux-kernel - Re: [PATCH v4 2/5] arm64: mm: factor out the address and ptep alignment into a new helper

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Message-ID: <6440050d-844b-4587-8531-038038d32f67@arm.com>
Date: Wed, 24 Dec 2025 13:51:22 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>, akpm@...ux-foundation.org,
 david@...nel.org, catalin.marinas@....com, will@...nel.org
Cc: lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, vbabka@...e.cz,
 rppt@...nel.org, surenb@...gle.com, mhocko@...e.com, riel@...riel.com,
 harry.yoo@...cle.com, jannh@...gle.com, willy@...radead.org,
 baohua@...nel.org, dev.jain@....com, linux-mm@...ck.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/5] arm64: mm: factor out the address and ptep
 alignment into a new helper

On 23/12/2025 05:48, Baolin Wang wrote:
> Factor out the contpte block's address and ptep alignment into a new helper,
> and will be reused in the following patch.
> 
> No functional changes.
> 
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>

LGTM:

Reviewed-by: Ryan Roberts <ryan.roberts@....com>

> ---
>  arch/arm64/mm/contpte.c | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
> index 589bcf878938..e4ddeb46f25d 100644
> --- a/arch/arm64/mm/contpte.c
> +++ b/arch/arm64/mm/contpte.c
> @@ -26,6 +26,26 @@ static inline pte_t *contpte_align_down(pte_t *ptep)
>  	return PTR_ALIGN_DOWN(ptep, sizeof(*ptep) * CONT_PTES);
>  }
>  
> +static inline pte_t *contpte_align_addr_ptep(unsigned long *start,
> +					     unsigned long *end, pte_t *ptep,
> +					     unsigned int nr)
> +{
> +	/*
> +	 * Note: caller must ensure these nr PTEs are consecutive (present)
> +	 * PTEs that map consecutive pages of the same large folio within a
> +	 * single VMA and a single page table.
> +	 */
> +	if (pte_cont(__ptep_get(ptep + nr - 1)))
> +		*end = ALIGN(*end, CONT_PTE_SIZE);
> +
> +	if (pte_cont(__ptep_get(ptep))) {
> +		*start = ALIGN_DOWN(*start, CONT_PTE_SIZE);
> +		ptep = contpte_align_down(ptep);
> +	}
> +
> +	return ptep;
> +}
> +
>  static void contpte_try_unfold_partial(struct mm_struct *mm, unsigned long addr,
>  					pte_t *ptep, unsigned int nr)
>  {
> @@ -569,14 +589,7 @@ void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
>  	unsigned long start = addr;
>  	unsigned long end = start + nr * PAGE_SIZE;
>  
> -	if (pte_cont(__ptep_get(ptep + nr - 1)))
> -		end = ALIGN(end, CONT_PTE_SIZE);
> -
> -	if (pte_cont(__ptep_get(ptep))) {
> -		start = ALIGN_DOWN(start, CONT_PTE_SIZE);
> -		ptep = contpte_align_down(ptep);
> -	}
> -
> +	ptep = contpte_align_addr_ptep(&start, &end, ptep, nr);
>  	__clear_young_dirty_ptes(vma, start, ptep, (end - start) / PAGE_SIZE, flags);
>  }
>  EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes);