linux-kernel - Re: [PATCH] mm/pgtable: convert pgtable

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Message-ID: <aV4h5vQUNXn5cpMY@kernel.org>
Date: Wed, 7 Jan 2026 11:05:42 +0200
From: Mike Rapoport <rppt@...nel.org>
To: alexs@...nel.org
Cc: Richard Henderson <richard.henderson@...aro.org>,
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Subject: Re: [PATCH] mm/pgtable: convert pgtable_t to ptdesc pointer

On Wed, Jan 07, 2026 at 02:46:35PM +0800, alexs@...nel.org wrote:
> From: Alex Shi <alexs@...nel.org>
> 
> After struct ptdesc introduced, pgtable_t should used it instead of old
> struct page pointer. The only thing in the way for this change is just
> pgtable->lru in pgtable_trans_huge_deposit/withdraw.
> 
> Let's convert them into ptdesc and use struct ptdesc* as pgtable_t.
> Thanks testing support from kernel test robot <lkp@...el.com>
> 
> Signed-off-by: Alex Shi <alexs@...nel.org>
> ---

...

> diff --git a/arch/arm/include/asm/pgalloc.h b/arch/arm/include/asm/pgalloc.h
> index a17f01235c29..1a3484c2df4c 100644
> --- a/arch/arm/include/asm/pgalloc.h
> +++ b/arch/arm/include/asm/pgalloc.h
> @@ -96,12 +96,12 @@ pte_alloc_one(struct mm_struct *mm)
>  {
>  	struct page *pte;
>  
> -	pte = __pte_alloc_one(mm, GFP_PGTABLE_USER | PGTABLE_HIGHMEM);
> +	pte = ptdesc_page(__pte_alloc_one(mm, GFP_PGTABLE_USER | PGTABLE_HIGHMEM));

When ptdesc will be separated from struct page, ptdesc_page() would fail if the
allocation failed. This line should be split into something like

	struct ptdesc *ptdesc = __pte_alloc_one(...);
	if (!ptesc)
		return NULL;
	pte = ptdesc_page(ptdesc);


>  	if (!pte)
>  		return NULL;
>  	if (!PageHighMem(pte))
>  		clean_pte_table(page_address(pte));
> -	return pte;
> +	return page_ptdesc(pte);
>  }
>  
>  static inline void __pmd_populate(pmd_t *pmdp, phys_addr_t pte,

-- 
Sincerely yours,
Mike.