linux-kernel - Re: [PATCH v8 7/7] mm,page_alloc: Drop unnecessary checks from pfn_range_valid

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Message-ID: <YHgmv68CC9hC8GEI@dhcp22.suse.cz>
Date:   Thu, 15 Apr 2021 13:42:55 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Muchun Song <songmuchun@...edance.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 7/7] mm,page_alloc: Drop unnecessary checks from
 pfn_range_valid_contig

On Thu 15-04-21 12:35:44, 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>
> Reviewed-by: David Hildenbrand <david@...hat.com>
> Acked-by: Mike Kravetz <mike.kravetz@...cle.com>

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  mm/page_alloc.c | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index b5a94de3cdde..c5338e912ace 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8901,12 +8901,6 @@ 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;
>  }
> -- 
> 2.16.3

-- 
Michal Hocko
SUSE Labs