static int sync_io(struct dm_io_client *client, unsigned int num_regions,
		   struct dm_io_region *where, blk_opf_t opf, struct dpages *dp,
		   unsigned long *error_bits)
static int sync_io(struct dm_io_client *client, unsigned int num_regions,
		   struct dm_io_region *where, blk_opf_t opf, struct dpages *dp,
		   unsigned long *error_bits, unsigned short ioprio)