From: Mel Gorman <mel@skynet.ie>

absent_pages_in_range() made the assumption that users of the API would not
care about holes beyound the end of physical memory.  This was not the
case.  This patch will account for ranges outside of physical memory as
holes correctly.

Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: Andi Kleen <ak@muc.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "Keith Mannthey" <kmannth@gmail.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 arch/x86_64/mm/srat.c |    4 +++-
 mm/page_alloc.c       |   22 +++++++++++++++++++---
 2 files changed, 22 insertions(+), 4 deletions(-)

diff -puN arch/x86_64/mm/srat.c~account-for-holes-that-are-outside-the-range-of-physical-memory arch/x86_64/mm/srat.c
--- a/arch/x86_64/mm/srat.c~account-for-holes-that-are-outside-the-range-of-physical-memory
+++ a/arch/x86_64/mm/srat.c
@@ -240,7 +240,9 @@ static int reserve_hotadd(int node, unsi
 
 	/* This check might be a bit too strict, but I'm keeping it for now. */
 	if (absent_pages_in_range(s_pfn, e_pfn) != e_pfn - s_pfn) {
-		printk(KERN_ERR "SRAT: Hotplug area has existing memory\n");
+		printk(KERN_ERR
+			"SRAT: Hotplug area %lu -> %lu has existing memory\n",
+			s_pfn, e_pfn);
 		return -1;
 	}
 
diff -puN mm/page_alloc.c~account-for-holes-that-are-outside-the-range-of-physical-memory mm/page_alloc.c
--- a/mm/page_alloc.c~account-for-holes-that-are-outside-the-range-of-physical-memory
+++ a/mm/page_alloc.c
@@ -2157,6 +2157,10 @@ unsigned long __init __absent_pages_in_r
 	if (i == -1)
 		return 0;
 
+	/* Account for ranges before physical memory on this node */
+	if (early_node_map[i].start_pfn > range_start_pfn)
+		hole_pages = early_node_map[i].start_pfn - range_start_pfn;
+
 	prev_end_pfn = early_node_map[i].start_pfn;
 
 	/* Find all holes for the zone within the node */
@@ -2178,6 +2182,11 @@ unsigned long __init __absent_pages_in_r
 		prev_end_pfn = early_node_map[i].end_pfn;
 	}
 
+	/* Account for ranges past physical memory on this node */
+	if (range_end_pfn > prev_end_pfn)
+		hole_pages = range_end_pfn -
+				max(range_start_pfn, prev_end_pfn);
+
 	return hole_pages;
 }
 
@@ -2199,9 +2208,16 @@ unsigned long __init zone_absent_pages_i
 					unsigned long zone_type,
 					unsigned long *ignored)
 {
-	return __absent_pages_in_range(nid,
-				arch_zone_lowest_possible_pfn[zone_type],
-				arch_zone_highest_possible_pfn[zone_type]);
+	unsigned long node_start_pfn, node_end_pfn;
+	unsigned long zone_start_pfn, zone_end_pfn;
+
+	get_pfn_range_for_nid(nid, &node_start_pfn, &node_end_pfn);
+	zone_start_pfn = max(arch_zone_lowest_possible_pfn[zone_type],
+							node_start_pfn);
+	zone_end_pfn = min(arch_zone_highest_possible_pfn[zone_type],
+							node_end_pfn);
+
+	return __absent_pages_in_range(nid, zone_start_pfn, zone_end_pfn);
 }
 
 /* Return the zone index a PFN is in */
_