diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index de6ea87d4d24..fa86d9fdb16f 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -598,13 +598,12 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 	const sector_t this_sector = r1_bio->sector;
 	int sectors;
 	int best_good_sectors;
-	int best_disk, best_dist_disk, best_pending_disk;
+	int best_disk, best_dist_disk, best_pending_disk, sequential_disk;
 	int disk;
 	sector_t best_dist;
 	unsigned int min_pending;
 	struct md_rdev *rdev;
 	int choose_first;
-	int choose_next_idle;
 
 	/*
 	 * Check if we can balance. We can balance on the whole
@@ -615,11 +614,11 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 	sectors = r1_bio->sectors;
 	best_disk = -1;
 	best_dist_disk = -1;
+	sequential_disk = -1;
 	best_dist = MaxSector;
 	best_pending_disk = -1;
 	min_pending = UINT_MAX;
 	best_good_sectors = 0;
-	choose_next_idle = 0;
 	clear_bit(R1BIO_FailFast, &r1_bio->state);
 
 	if ((conf->mddev->recovery_cp < this_sector + sectors) ||
@@ -712,7 +711,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 			int opt_iosize = bdev_io_opt(rdev->bdev) >> 9;
 			struct raid1_info *mirror = &conf->mirrors[disk];
 
-			best_disk = disk;
 			/*
 			 * If buffered sequential IO size exceeds optimal
 			 * iosize, check if there is idle disk. If yes, choose
@@ -731,15 +729,22 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 			    mirror->next_seq_sect > opt_iosize &&
 			    mirror->next_seq_sect - opt_iosize >=
 			    mirror->seq_start) {
-				choose_next_idle = 1;
-				continue;
+				/*
+				 * Add 'pending' to avoid choosing this disk if
+				 * there is other idle disk.
+				 */
+				pending++;
+				/*
+				 * If there is no other idle disk, this disk
+				 * will be chosen.
+				 */
+				sequential_disk = disk;
+			} else {
+				best_disk = disk;
+				break;
 			}
-			break;
 		}
 
-		if (choose_next_idle)
-			continue;
-
 		if (min_pending > pending) {
 			min_pending = pending;
 			best_pending_disk = disk;
@@ -751,6 +756,13 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 		}
 	}
 
+	/*
+	 * sequential IO size exceeds optimal iosize, however, there is no other
+	 * idle disk, so choose the sequential disk.
+	 */
+	if (best_disk == -1 && min_pending != 0)
+		best_disk = sequential_disk;
+
 	/*
 	 * If all disks are rotational, choose the closest disk. If any disk is
 	 * non-rotational, choose the disk with less pending request even the