[Patch]Fix spanned_pages is not updated at a case of memory hot-add take 2..

[Yasunori Goto <y-goto@jp.fujitsu.com>]

I fixed redundant parentheses and tested this fix updating
spanned_pages patch.

Andrew-san.
Please apply.

------------------
If hot-added memory's address is smaller than old area,
spanned_pages will not be updated. It must be fixed.

example) Old zone_start_pfn = 0x60000, and spanned_pages = 0x10000
         Added new memory's start_pfn = 0x50000, and end_pfn = 0x60000

  new spanned_pages will be still 0x10000 by old code.
  (It should be updated to 0x20000.) Because old_zone_end_pfn will be
  0x70000, and end_pfn smaller than it. So, spanned_pages will not be
  updated.
  
In current code, spanned_pages is updated only when end_pfn is updated.
But, it should be updated by subtraction between bigger end_pfn and new
zone_start_pfn.

This is for 2.6.17-rc4-mm3.
I tested this patch on Tiger4 with my node emulation.

Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>

 mm/memory_hotplug.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

Index: pgdat15/mm/memory_hotplug.c
===================================================================
--- pgdat15.orig/mm/memory_hotplug.c	2006-05-25 12:22:54.000000000 +0900
+++ pgdat15/mm/memory_hotplug.c	2006-05-25 12:23:18.000000000 +0900
@@ -103,8 +103,8 @@ static void grow_zone_span(struct zone *
 	if (start_pfn < zone->zone_start_pfn)
 		zone->zone_start_pfn = start_pfn;
 
-	if (end_pfn > old_zone_end_pfn)
-		zone->spanned_pages = end_pfn - zone->zone_start_pfn;
+	zone->spanned_pages = max(old_zone_end_pfn, end_pfn) -
+				zone->zone_start_pfn;
 
 	zone_span_writeunlock(zone);
 }
@@ -118,8 +118,8 @@ static void grow_pgdat_span(struct pglis
 	if (start_pfn < pgdat->node_start_pfn)
 		pgdat->node_start_pfn = start_pfn;
 
-	if (end_pfn > old_pgdat_end_pfn)
-		pgdat->node_spanned_pages = end_pfn - pgdat->node_start_pfn;
+	pgdat->node_spanned_pages = max(old_pgdat_end_pfn, end_pfn) -
+					pgdat->node_start_pfn;
 }
 
 int online_pages(unsigned long pfn, unsigned long nr_pages)

-- 
Yasunori Goto