linux-kernel - Re: [PATCH] mm,memory_hotplug: Fix scan_movable

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Date:   Tue, 29 Jan 2019 08:33:32 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm,memory_hotplug: Fix scan_movable_pages for gigantic
 hugepages

On Mon 28-01-19 14:56:17, Andrew Morton wrote:
[...]
> --- a/mm/memory_hotplug.c~mmmemory_hotplug-fix-scan_movable_pages-for-gigantic-hugepages-fix
> +++ a/mm/memory_hotplug.c
> @@ -1305,28 +1305,27 @@ int test_pages_in_a_zone(unsigned long s
>  static unsigned long scan_movable_pages(unsigned long start, unsigned long end)
>  {
>  	unsigned long pfn;
> -	struct page *page;
> +
>  	for (pfn = start; pfn < end; pfn++) {
> -		if (pfn_valid(pfn)) {
> -			page = pfn_to_page(pfn);
> -			if (PageLRU(page))
> -				return pfn;
> -			if (__PageMovable(page))
> -				return pfn;
> -			if (PageHuge(page)) {
> -				struct page *head = compound_head(page);
> +		struct page *page, *head;
> +		unsigned long skip;
>  
> -				if (hugepage_migration_supported(page_hstate(head)) &&
> -				    page_huge_active(head))
> -					return pfn;
> -				else {
> -					unsigned long skip;
> +		if (!pfn_valid(pfn))
> +			continue;
> +		page = pfn_to_page(pfn);
> +		if (PageLRU(page))
> +			return pfn;
> +		if (__PageMovable(page))
> +			return pfn;
>  
> -					skip = (1 << compound_order(head)) - (page - head);
> -					pfn += skip - 1;
> -				}
> -			}
> -		}
> +		if (!PageHuge(page))
> +			continue;
> +		head = compound_head(page);
> +		if (hugepage_migration_supported(page_hstate(head)) &&
> +		    page_huge_active(head))
> +			return pfn;
> +		skip = (1 << compound_order(head)) - (page - head);
> +		pfn += skip - 1;
>  	}
>  	return 0;
>  }
> _
> 

LGTM
-- 
Michal Hocko
SUSE Labs