Question about this error: ‘bdget’ was not declared in this scope - linux

Question

trying to figure out why I’m getting this error about ’bdget’ (when on Linux Ubuntu, info below) and how to get rid of this error, maybe you could suggest some specific steps for me to try and/or ask me to provide you some additional info about the error, thank you for any help.
error: ‘bdget’ was not declared in this scope
b_dev = bdget(st.st_rdev);
The code (for a short sample/tester program put together quickly to demonstrate the problem here to you) that produces this error is below, here’s other info: When I comment out that ‘bdget’ line, the program (seen below) compiles, otherwise it doesn’t and produces the error. I understand from other stackoverflow.com questions that using bdget requires #include <linux/fs.h>, which I’ve done here as you can see in the code below.
I think this is my first question here at stackoverflow.com, haven’t yet learned what question-related actions I need to take here at stackoverflow.com about your answers such as accept, and the steps for taking those actions, so bear with me a bit.
Regards,
Yaman Aksu,PhD
The build used this g++ version (full path: /usr/bin/g++) :
g++ (Ubuntu 7.3.0-27ubuntu1-18.04) 7.3.0 <snip>
and was simple as follows:
g++ -Wall -03 tester.cpp -o tester
#include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/sysmacros.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <dirent.h>
#include <linux/fs.h>
#define FNABS_SIZE 1024
char prog[FNABS_SIZE];
using namespace std;
int main(int argc, char *argv[])
{
int rv=0;
struct dirent *de;
struct stat st;
struct block_device *b_dev;
char direc[FNABS_SIZE], fnabs[FNABS_SIZE], fnabs_bfile[FNABS_SIZE], hd_serial[NAME_MAX], hd_model[NAME_MAX];
int status;
unsigned int maj_rdev, min_rdev;
ios::sync_with_stdio();
strcpy(prog,argv[0]); argc--;
strcpy(direc,"/dev/disk/by-id");
for (DIR *p = opendir(direc); (de=readdir(p)); ) {
if (de->d_type==DT_LNK) {
sprintf(fnabs,"%s/%s",direc,de->d_name);
cout << "[glk] Now running 'stat' on this: " << fnabs << endl;
status = stat(fnabs, &st);
cout << "[glk] 'stat' results:" << endl;
cout << "[glk]\t return value:" << status << endl;
cout << "[glk]\t st.st_rdev:" << st.st_rdev << endl;
cout << "[glk]\t st.st_dev=" << st.st_dev << endl;
cout << "[glk]\t st.st_ino=" << st.st_ino << endl;
maj_rdev = major(st.st_rdev); min_rdev = minor(st.st_rdev);
printf("[glk]\t major:minor = %u:%u\n",maj_rdev, min_rdev);
if ((st.st_mode & S_IFMT) == S_IFBLK) {
printf("[glk]\t This is a 'block device' !!\n");
}
b_dev = bdget(st.st_rdev);
}
}
}