md/bitmap: always wake up md_thread in timeout_store

md_wakeup_thread() can handle the case that pass in md_thread is NULL,
the only difference is that md_wakeup_thread() will be called when
current timeout is 'MAX_SCHEDULE_TIMEOUT', this should not matter
because timeout_store() is not hot path, and the daemon process is
woke up more than demand from other context already.

Prepare to factor out a helper to set timeout.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230523021017.3048783-4-yukuai1@huaweicloud.com

drivers/md/md-bitmap.c

@@ -2476,11 +2476,11 @@ timeout_store(struct mddev *mddev, const char *buf, size_t len)
 		 * the bitmap is all clean and we don't need to
 		 * adjust the timeout right now
 		 */
-		if (mddev->thread->timeout < MAX_SCHEDULE_TIMEOUT) {
+		if (mddev->thread->timeout < MAX_SCHEDULE_TIMEOUT)
 			mddev->thread->timeout = timeout;
-			md_wakeup_thread(mddev->thread);
-		}
 	}
+
+	md_wakeup_thread(mddev->thread);
 	return len;
 }