pdflush: use time_after() instead of open-coding it

Signed-off-by: NOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/pdflush.c

@@ -130,7 +130,7 @@ static int __pdflush(struct pdflush_work *my_work)
 		 * Thread creation: For how long have there been zero
 		 * available threads?
 		 */
-		if (jiffies - last_empty_jifs > 1 * HZ) {
+		if (time_after(jiffies, last_empty_jifs + 1 * HZ)) {
 			/* unlocked list_empty() test is OK here */
 			if (list_empty(&pdflush_list)) {
 				/* unlocked test is OK here */
@@ -151,7 +151,7 @@ static int __pdflush(struct pdflush_work *my_work)
 		if (nr_pdflush_threads <= MIN_PDFLUSH_THREADS)
 			continue;
 		pdf = list_entry(pdflush_list.prev, struct pdflush_work, list);
-		if (jiffies - pdf->when_i_went_to_sleep > 1 * HZ) {
+		if (time_after(jiffies, pdf->when_i_went_to_sleep + 1 * HZ)) {
 			/* Limit exit rate */
 			pdf->when_i_went_to_sleep = jiffies;
 			break;					/* exeunt */