UDL_CMD_WRITE_HEAD_SIZE
cb->off -= UDL_CMD_WRITE_HEAD_SIZE;
cb->compblock -= UDL_CMD_WRITE_HEAD_SIZE;
cb->compblock += UDL_CMD_WRITE_HEAD_SIZE;
cb->compblock += UDL_CMD_WRITE_HEAD_SIZE;
#define UDL_CMD_WRITE_MAX_SIZE (UDL_CMD_WRITE_HEAD_SIZE + \