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From: "Henrik Rydberg" <rydberg@euromail.se>
Date: Thu, 6 Dec 2012 22:39:09 +0100
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>, Jan Kara <jack@suse.cz>,
        linux-mm <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Oops in 3.7-rc8 isolate_free_pages_block()
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> There is also a
> 
>     low_pfn += pageblock_nr_pages;
>     low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
> 
> that looks suspicious for similar reasons. Maybe
> 
>     low_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages) - 1;
> 
> instead? Although that *can* result in the same low_pfn in the end, so
> maybe that one was correct after all? I just did some grepping, no
> actual semantic analysis...

Here is a totally obscure version:

	low_pfn |= pageblock_nr_pages - 1;

It simply moves to the very end of the block, which seems to be what
was intended.

Henrik