vfs: fsinfo sample: Mount listing program

Implement a program to demonstrate mount listing using the new fsinfo()
syscall, for example:

# ./test-mntinfo -M 21
MOUNT                                 MOUNT ID   CHANGE#    TYPE & DEVICE
------------------------------------- ---------- ---------- ---------------
21                                            21          8 sysfs 0:15
 \_ kernel/security                           24          0 securityfs 0:8
 \_ fs/cgroup                                 28         16 tmpfs 0:19
 |   \_ unified                               29          0 cgroup2 0:1a
 |   \_ systemd                               30          0 cgroup 0:1b
 |   \_ freezer                               34          0 cgroup 0:1f
 |   \_ cpu,cpuacct                           35          0 cgroup 0:20
 |   \_ devices                               36          0 cgroup 0:21
 |   \_ memory                                37          0 cgroup 0:22
 |   \_ cpuset                                38          0 cgroup 0:23
 |   \_ net_cls,net_prio                      39          0 cgroup 0:24
 |   \_ hugetlb                               40          0 cgroup 0:25
 |   \_ rdma                                  41          0 cgroup 0:26
 |   \_ blkio                                 42          0 cgroup 0:27
 |   \_ perf_event                            43          0 cgroup 0:28
 \_ fs/pstore                                 31          0 pstore 0:1c
 \_ firmware/efi/efivars                      32          0 efivarfs 0:1d
 \_ fs/bpf                                    33          0 bpf 0:1e
 \_ kernel/config                             92          0 configfs 0:10
 \_ fs/selinux                                44          0 selinuxfs 0:12
 \_ kernel/debug                              48          0 debugfs 0:7

Signed-off-by: David Howells <dhowells@redhat.com>
2 files changed