linux-kernel - Re: [PATCH V2] mm: Remove unnecessary __GFP_HIGHMEM in __p*d_alloc_one

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Message-ID: <b64cd9ba-e80f-4ac5-810c-97af053e4700@arm.com>
Date: Mon, 10 Nov 2025 10:37:43 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Huacai Chen <chenhuacai@...ngson.cn>, Huacai Chen
 <chenhuacai@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>
Cc: Arnd Bergmann <arnd@...db.de>, Vishal Moola <vishal.moola@...il.com>,
 Kevin Brodsky <kevin.brodsky@....com>, Jan Kara <jack@...e.cz>,
 linux-mm@...ck.org, linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] mm: Remove unnecessary __GFP_HIGHMEM in
 __p*d_alloc_one_*()

On 09/11/25 7:48 AM, Huacai Chen wrote:
> __{pgd,p4d,pud,pmd,pte}_alloc_one_*() always allocate pages with GFP
> flag GFP_PGTABLE_KERNEL/GFP_PGTABLE_USER. These two macros are defined
> as follows:
> 
>  #define GFP_PGTABLE_KERNEL	(GFP_KERNEL | __GFP_ZERO)
>  #define GFP_PGTABLE_USER	(GFP_PGTABLE_KERNEL | __GFP_ACCOUNT)
> 
> There is no __GFP_HIGHMEM in them, so we needn't to clear __GFP_HIGHMEM
> explicitly.
> 
> Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
> ---
> V2: Change the subject line as Vishal suggested.
> 
>  include/asm-generic/pgalloc.h | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/include/asm-generic/pgalloc.h b/include/asm-generic/pgalloc.h
> index 3c8ec3bfea44..706e87b43b19 100644
> --- a/include/asm-generic/pgalloc.h
> +++ b/include/asm-generic/pgalloc.h
> @@ -18,8 +18,7 @@
>   */
>  static inline pte_t *__pte_alloc_one_kernel_noprof(struct mm_struct *mm)
>  {
> -	struct ptdesc *ptdesc = pagetable_alloc_noprof(GFP_PGTABLE_KERNEL &
> -			~__GFP_HIGHMEM, 0);
> +	struct ptdesc *ptdesc = pagetable_alloc_noprof(GFP_PGTABLE_KERNEL, 0);
>  
>  	if (!ptdesc)
>  		return NULL;
> @@ -172,7 +171,6 @@ static inline pud_t *__pud_alloc_one_noprof(struct mm_struct *mm, unsigned long
>  
>  	if (mm == &init_mm)
>  		gfp = GFP_PGTABLE_KERNEL;
> -	gfp &= ~__GFP_HIGHMEM;
>  
>  	ptdesc = pagetable_alloc_noprof(gfp, 0);
>  	if (!ptdesc)
> @@ -226,7 +224,6 @@ static inline p4d_t *__p4d_alloc_one_noprof(struct mm_struct *mm, unsigned long
>  
>  	if (mm == &init_mm)
>  		gfp = GFP_PGTABLE_KERNEL;
> -	gfp &= ~__GFP_HIGHMEM;
>  
>  	ptdesc = pagetable_alloc_noprof(gfp, 0);
>  	if (!ptdesc)
> @@ -270,7 +267,6 @@ static inline pgd_t *__pgd_alloc_noprof(struct mm_struct *mm, unsigned int order
>  
>  	if (mm == &init_mm)
>  		gfp = GFP_PGTABLE_KERNEL;
> -	gfp &= ~__GFP_HIGHMEM;
>  
>  	ptdesc = pagetable_alloc_noprof(gfp, order);
>  	if (!ptdesc)

Reviewed-by: Anshuman Khandual <anshuman.khandual@....com>