diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index cda6af0712b9..16f671ab12c0 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -62,7 +62,7 @@ static int check_and_add_serial(struct md_rdev *rdev, struct r1bio *r1_bio,
 	unsigned long flags;
 	int ret = 0;
 	sector_t lo = r1_bio->sector;
-	sector_t hi = lo + r1_bio->sectors;
+	sector_t hi = lo + r1_bio->sectors - 1;
 	struct serial_in_rdev *serial = &rdev->serial[idx];
 
 	spin_lock_irqsave(&serial->serial_lock, flags);
@@ -452,7 +452,7 @@ static void raid1_end_write_request(struct bio *bio)
 	int mirror = find_bio_disk(r1_bio, bio);
 	struct md_rdev *rdev = conf->mirrors[mirror].rdev;
 	sector_t lo = r1_bio->sector;
-	sector_t hi = r1_bio->sector + r1_bio->sectors;
+	sector_t hi = r1_bio->sector + r1_bio->sectors - 1;
 	bool ignore_error = !raid1_should_handle_error(bio) ||
 		(bio->bi_status && bio_op(bio) == REQ_OP_DISCARD);