diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c
index 66f4c63..cea2b37 100644
--- a/drivers/md/dm-verity-fec.c
+++ b/drivers/md/dm-verity-fec.c
@@ -65,7 +65,7 @@ static u8 *fec_read_parity(struct dm_verity *v, u64 rsb, int index,
 	u8 *res;
 
 	position = (index + rsb) * v->fec->roots;
-	block = div64_u64_rem(position, v->fec->roots << SECTOR_SHIFT, &rem);
+	block = div64_u64_rem(position, v->fec->io_size, &rem);
 	*offset = (unsigned)rem;
 
 	res = dm_bufio_read(v->fec->bufio, block, buf);
@@ -154,7 +154,7 @@ static int fec_decode_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio,
 
 		/* read the next block when we run out of parity bytes */
 		offset += v->fec->roots;
-		if (offset >= v->fec->roots << SECTOR_SHIFT) {
+		if (offset >= v->fec->io_size) {
 			dm_bufio_release(buf);
 
 			par = fec_read_parity(v, rsb, block_offset, &offset, &buf);
@@ -742,8 +742,13 @@ int verity_fec_ctr(struct dm_verity *v)
 		return -E2BIG;
 	}
 
+	if ((f->roots << SECTOR_SHIFT) & ((1 << v->data_dev_block_bits) - 1))
+		f->io_size = 1 << v->data_dev_block_bits;
+	else
+		f->io_size = v->fec->roots << SECTOR_SHIFT;
+
 	f->bufio = dm_bufio_client_create(f->dev->bdev,
-					  f->roots << SECTOR_SHIFT,
+					  f->io_size,
 					  1, 0, NULL, NULL);
 	if (IS_ERR(f->bufio)) {
 		ti->error = "Cannot initialize FEC bufio client";
diff --git a/drivers/md/dm-verity-fec.h b/drivers/md/dm-verity-fec.h
index 42fbd3a..3c46c8d 100644
--- a/drivers/md/dm-verity-fec.h
+++ b/drivers/md/dm-verity-fec.h
@@ -36,6 +36,7 @@ struct dm_verity_fec {
 	struct dm_dev *dev;	/* parity data device */
 	struct dm_bufio_client *data_bufio;	/* for data dev access */
 	struct dm_bufio_client *bufio;		/* for parity data access */
+	size_t io_size;		/* IO size for roots */
 	sector_t start;		/* parity data start in blocks */
 	sector_t blocks;	/* number of blocks covered */
 	sector_t rounds;	/* number of interleaving rounds */