[PATCH] Calculation fix for memory holes beyong the end of physical memory

absent_pages_in_range() made the assumption that users of the
arch-independent zone-sizing API would not care about holes beyound the end
of physical memory. This was not the case and was "fixed" in a patch
called "Account for holes that are outside the range of physical memory".
However, when given a range that started before a hole in "real" memory and
ended beyond the end of memory, it would get the result wrong. The bug is
in mainline but a patch is below.

It has been tested successfully on a number of machines and architectures.
Additional credit to Keith Mannthey for discovering the problem, helping
identify the correct fix and confirming it Worked For Him.

Signed-off-by: Mel Gorman <[e-mail]>
Cc: keith mannthey <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/page_alloc.c

···
 
 	/* Account for ranges past physical memory on this node */
 	if (range_end_pfn > prev_end_pfn)
-		hole_pages = range_end_pfn -
+		hole_pages += range_end_pfn -
 				max(range_start_pfn, prev_end_pfn);
 
 	return hole_pages;