zlc_setup(): handle jiffies wraparound

jiffies subtraction may cause an overflow problem.  It should be using
time_after().

[akpm@linux-foundation.org: include jiffies.h]
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -19,6 +19,7 @@
 #include <linux/swap.h>
 #include <linux/interrupt.h>
 #include <linux/pagemap.h>
+#include <linux/jiffies.h>
 #include <linux/bootmem.h>
 #include <linux/compiler.h>
 #include <linux/kernel.h>
@@ -1276,7 +1277,7 @@ static nodemask_t *zlc_setup(struct zonelist *zonelist, int alloc_flags)
 	if (!zlc)
 		return NULL;
 
-	if (jiffies - zlc->last_full_zap > 1 * HZ) {
+       if (time_after(jiffies, zlc->last_full_zap + HZ)) {
 		bitmap_zero(zlc->fullzones, MAX_ZONES_PER_ZONELIST);
 		zlc->last_full_zap = jiffies;
 	}