diff --git a/drivers/md/md.c b/drivers/md/md.c
index 021e522001c1125d2360662718628b0b3f779685..d0f688399a56a735dcc8c613d74bc9933d80b1aa 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -427,6 +427,7 @@ static void submit_flushes(struct work_struct *ws)
 	struct mddev *mddev = container_of(ws, struct mddev, flush_work);
 	struct md_rdev *rdev;
 
+	mddev->start_flush = ktime_get_boottime();
 	INIT_WORK(&mddev->flush_work, md_submit_flush_data);
 	atomic_set(&mddev->flush_pending, 1);
 	rcu_read_lock();
@@ -467,6 +468,7 @@ static void md_submit_flush_data(struct work_struct *ws)
 	 * could wait for this and below md_handle_request could wait for those
 	 * bios because of suspend check
 	 */
+	mddev->last_flush = mddev->start_flush;
 	mddev->flush_bio = NULL;
 	wake_up(&mddev->sb_wait);
 
@@ -481,15 +483,32 @@ static void md_submit_flush_data(struct work_struct *ws)
 
 void md_flush_request(struct mddev *mddev, struct bio *bio)
 {
+	ktime_t start = ktime_get_boottime();
 	spin_lock_irq(&mddev->lock);
 	wait_event_lock_irq(mddev->sb_wait,
-			    !mddev->flush_bio,
+			    !mddev->flush_bio ||
+			    ktime_after(mddev->last_flush, start),
 			    mddev->lock);
-	mddev->flush_bio = bio;
+	if (!ktime_after(mddev->last_flush, start)) {
+		WARN_ON(mddev->flush_bio);
+		mddev->flush_bio = bio;
+		bio = NULL;
+	}
 	spin_unlock_irq(&mddev->lock);
 
-	INIT_WORK(&mddev->flush_work, submit_flushes);
-	queue_work(md_wq, &mddev->flush_work);
+	if (!bio) {
+		INIT_WORK(&mddev->flush_work, submit_flushes);
+		queue_work(md_wq, &mddev->flush_work);
+	} else {
+		/* flush was performed for some other bio while we waited. */
+		if (bio->bi_iter.bi_size == 0)
+			/* an empty barrier - all done */
+			bio_endio(bio);
+		else {
+			bio->bi_opf &= ~REQ_PREFLUSH;
+			mddev->pers->make_request(mddev, bio);
+		}
+	}
 }
 EXPORT_SYMBOL(md_flush_request);
 
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 2deb84fa93f98af2b60f428d470939812075ec3e..257cb4c9e22bad7718a046cf4b614420a0730752 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -463,6 +463,9 @@ struct mddev {
 	 */
 	struct bio *flush_bio;
 	atomic_t flush_pending;
+	ktime_t start_flush, last_flush; /* last_flush is when the last completed
+					  * flush was started.
+					  */
 	struct work_struct flush_work;
 	struct work_struct event_work;	/* used by dm to report failure event */
 	void (*sync_super)(struct mddev *mddev, struct md_rdev *rdev);