On Mon, Feb 18, 2019 at 06:05:58PM +0100, Michal Hocko wrote:
> +	end_pfn = min(start_pfn + nr_pages,
> +			zone_end_pfn(page_zone(pfn_to_page(start_pfn))));
>  
>  	/* Check the starting page of each pageblock within the range */
> -	for (; page < end_page; page = next_active_pageblock(page)) {
> -		if (!is_pageblock_removable_nolock(page))
> +	for (; start_pfn < end_pfn; start_pfn = next_active_pageblock(start_pfn)) {
> +		if (!is_pageblock_removable_nolock(start_pfn))

If you have a zone which contains pfns that run from ULONG_MAX-n to ULONG_MAX,
end_pfn is going to wrap around to 0 and this loop won't execute.  I think
you should use:

	max_pfn = min(start_pfn + nr_pages,
			zone_end_pfn(page_zone(pfn_to_page(start_pfn)))) - 1;

	for (; start_pfn <= max_pfn; ...)