[PATCH] Fix calculation of grow_pgdat_span() in mm/memory_hotplug.c

The calculation for node_spanned_pages at grow_pgdat_span() is clearly
wrong.  This is patch for it.

(Please see grow_zone_span() to compare. It is correct.)
Signed-off-by: Yasunori Goto <y-goto@jp.fujitsu.com>
Acked-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

mm/memory_hotplug.c

@@ -104,7 +104,7 @@ static void grow_pgdat_span(struct pglist_data *pgdat,
 		pgdat->node_start_pfn = start_pfn;
 
 	if (end_pfn > old_pgdat_end_pfn)
-		pgdat->node_spanned_pages = end_pfn - pgdat->node_spanned_pages;
+		pgdat->node_spanned_pages = end_pfn - pgdat->node_start_pfn;
 }
 
 int online_pages(unsigned long pfn, unsigned long nr_pages)