linux-kernel - Re: [LKP] efad4e475c [ 40.308255] Oops: 0000 [#1] PREEMPT SMP PTI

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Date:   Mon, 18 Feb 2019 09:57:26 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Mike Rapoport <rppt@...ux.ibm.com>,
        Rong Chen <rong.a.chen@...el.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        linux-kernel@...r.kernel.org,
        Linux Memory Management List <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>, LKP <lkp@...org>,
        Oscar Salvador <osalvador@...e.de>
Subject: Re: [LKP] efad4e475c [ 40.308255] Oops: 0000 [#1] PREEMPT SMP PTI

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; ...)