linux-kernel - Re: [PATCH v5 5/5] mm,page_alloc: Drop unnecessary checks from pfn_range_valid

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Date:   Wed, 17 Mar 2021 12:15:48 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Oscar Salvador <osalvador@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>, Michal Hocko <mhocko@...nel.org>,
        Muchun Song <songmuchun@...edance.com>,
        Mike Kravetz <mike.kravetz@...cle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 5/5] mm,page_alloc: Drop unnecessary checks from
 pfn_range_valid_contig

On 17.03.21 12:12, Oscar Salvador wrote:
> pfn_range_valid_contig() bails out when it finds an in-use page or a
> hugetlb page, among other things.
> We can drop the in-use page check since __alloc_contig_pages can migrate
> away those pages, and the hugetlb page check can go too since
> isolate_migratepages_range is now capable of dealing with hugetlb pages.
> Either way, those checks are racy so let the end function handle it
> when the time comes.
> 
> Signed-off-by: Oscar Salvador <osalvador@...e.de>
> Suggested-by: David Hildenbrand <david@...hat.com>
> ---
>   mm/page_alloc.c | 6 ------
>   1 file changed, 6 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 4cb455355f6d..50d73e68b79e 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8685,12 +8685,6 @@ static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn,
>   
>   		if (PageReserved(page))
>   			return false;
> -
> -		if (page_count(page) > 0)
> -			return false;
> -
> -		if (PageHuge(page))
> -			return false;
>   	}
>   	return true;
>   }
> 

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb