linux-kernel - Re: [PATCH v2 1/2] mm/page_alloc: drop the unnecessary pfn

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Date:   Mon, 24 Apr 2023 11:50:44 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc:     akpm@...ux-foundation.org, rppt@...nel.org, ying.huang@...el.com,
        mgorman@...hsingularity.net, vbabka@...e.cz, david@...hat.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] mm/page_alloc: drop the unnecessary pfn_valid()
 for start pfn

On Sun 23-04-23 18:59:10, Baolin Wang wrote:
> We've already used pfn_to_online_page() for start pfn to make sure

Who is we? I do not see any note explicitly requiring that start_pfn has
to be valid for __pageblock_pfn_to_page.

> it is online and valid, so the pfn_valid() for the start pfn is
> unnecessary, drop it.
> 
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Reviewed-by: David Hildenbrand <david@...hat.com>
> Reviewed-by: "Huang, Ying" <ying.huang@...el.com>
> ---
> Changes from v1:
>  - Collect reviewed tags. Thanks David and Ying.
> ---
>  mm/page_alloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 9de2a18519a1..6457b64fe562 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1512,7 +1512,7 @@ struct page *__pageblock_pfn_to_page(unsigned long start_pfn,
>  	/* end_pfn is one past the range we are checking */
>  	end_pfn--;
>  
> -	if (!pfn_valid(start_pfn) || !pfn_valid(end_pfn))
> +	if (!pfn_valid(end_pfn))
>  		return NULL;
>  
>  	start_page = pfn_to_online_page(start_pfn);
> -- 
> 2.27.0

-- 
Michal Hocko
SUSE Labs