md: reduce CPU wastage on idle md array with a write-intent bitmap

Recent patch titled
  Reduce CPU wastage on idle md array with a write-intent bitmap.

would sometimes leave the array with dirty bitmap bits that stay dirty.  A
subsequent write would sort things out so it isn't a big problem, but should
be fixed nonetheless.

We need to make sure that when the bitmap becomes not "allclean", the
daemon_sleep really does get set to a sensible value.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/md/bitmap.c

@@ -1045,7 +1045,8 @@ void bitmap_daemon_work(struct bitmap *bitmap)
 	if (bitmap == NULL)
 		return;
 	if (time_before(jiffies, bitmap->daemon_lastrun + bitmap->daemon_sleep*HZ))
-		return;
+		goto done;
+
 	bitmap->daemon_lastrun = jiffies;
 	if (bitmap->allclean) {
 		bitmap->mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT;
@@ -1142,6 +1143,7 @@ void bitmap_daemon_work(struct bitmap *bitmap)
 		}
 	}
 
+ done:
 	if (bitmap->allclean == 0)
 		bitmap->mddev->thread->timeout = bitmap->daemon_sleep * HZ;
 }