linux-kernel - Re: [PATCH 1/3] mm/io-mapping: precompute remap protection flags for clarity

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Message-ID: <aBBynJxyJXHPG-Fn@kernel.org>
Date: Tue, 29 Apr 2025 09:33:00 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Ye Liu <ye.liu@...ux.dev>
Cc: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, lorenzo.stoakes@...cle.com,
	Liam.Howlett@...cle.com, david@...hat.com, harry.yoo@...cle.com,
	riel@...riel.com, vbabka@...e.cz, liuye@...inos.cn
Subject: Re: [PATCH 1/3] mm/io-mapping: precompute remap protection flags for
 clarity

On Sun, Apr 27, 2025 at 06:04:40PM +0800, Ye Liu wrote:
> From: Ye Liu <liuye@...inos.cn>
> 
> In io_mapping_map_user(), precompute the page protection flags in a local
> variable before calling remap_pfn_range_notrack().
> 
> No functional change.
> 
> Signed-off-by: Ye Liu <liuye@...inos.cn>

Reviewed-by: Mike Rapoport (Microsoft) <rppt@...nel.org>

> ---
>  mm/io-mapping.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/io-mapping.c b/mm/io-mapping.c
> index 01b362799930..f44a6a134712 100644
> --- a/mm/io-mapping.c
> +++ b/mm/io-mapping.c
> @@ -21,9 +21,10 @@ int io_mapping_map_user(struct io_mapping *iomap, struct vm_area_struct *vma,
>  	if (WARN_ON_ONCE((vma->vm_flags & expected_flags) != expected_flags))
>  		return -EINVAL;
>  
> +	pgprot_t remap_prot = __pgprot((pgprot_val(iomap->prot) & _PAGE_CACHE_MASK) |
> +				       (pgprot_val(vma->vm_page_prot) & ~_PAGE_CACHE_MASK));
> +
>  	/* We rely on prevalidation of the io-mapping to skip track_pfn(). */
> -	return remap_pfn_range_notrack(vma, addr, pfn, size,
> -		__pgprot((pgprot_val(iomap->prot) & _PAGE_CACHE_MASK) |
> -			 (pgprot_val(vma->vm_page_prot) & ~_PAGE_CACHE_MASK)));
> +	return remap_pfn_range_notrack(vma, addr, pfn, size, remap_prot);
>  }
>  EXPORT_SYMBOL_GPL(io_mapping_map_user);
> -- 
> 2.25.1
> 

-- 
Sincerely yours,
Mike.