Index: linux-3.10.0-957.el7.x86_64/drivers/md/raid5.c
===================================================================
--- linux-3.10.0-957.el7.x86_64.orig/drivers/md/raid5.c
+++ linux-3.10.0-957.el7.x86_64/drivers/md/raid5.c
@@ -3266,6 +3266,8 @@ static int add_stripe_bio(struct stripe_
 	*bip = bi;
 	bio_inc_remaining(bi);
 	md_write_inc(conf->mddev, bi);
+	if ((bi->bi_rw & REQ_SYNC) && !forwrite)
+		clear_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);	/* force to read from disk. */
 
 	if (forwrite) {
 		/* check if page is covered */
@@ -5753,6 +5755,10 @@ static bool raid5_make_request(struct md
 	if (rw == WRITE)
 		md_write_end(mddev);
 	bio_endio(bi, 0);
+
+	if (bi->bi_rw & REQ_SYNC)
+		md_wakeup_thread(mddev->thread);
+
 	return true;
 }