*** Description of problem:

In dosfstools-4.2 a new option appeared, called "--mbr". Under circumstances that matter much to libguestfs, namely when the disk being formatted is (a) non-removable and (b) unpartitioned (that is, a whole disk, not a partition), the "--mbr" option defaults to "yes". (For the sake of the reproducer below, we'll use an explicit "--mbr=yes".) When this option is in effect, "mkfs.fat" overlays the first sector of the medium (the FAT boot sector) with a bogus MBR partition table. The table has one entry, and it describes a partition that spans the entire disk, covering the partition table itself, resident in the first sector of the medium. This is supposed to placate Windows (otherwise Windows does not recognize the FAT filesystem on a non-removable device), and to work with Linux utilities as well (the kernel itself, and blkid, and so on).

In case the chosen FAT variant is FAT16 or FAT32, parted manages to parse the partition table, and prints the one entry in the table correctly. However, parted incorrectly reports the partition table type as "loop", rather than "msdos".

*** Version-Release number of selected component (if applicable):

- parted-3.4-6.el9.x86_64
  (it should reproduce with upstream parted too, as of commit b20227adf575)

- dosfstools-4.2-3.el9.x86_64

*** How reproducible:

Always.

*** Steps to Reproduce:

(1) rm -f image
    fallocate -l 255M image
    mkfs.fat -F 16 --mbr=yes image
    parted -m -s -- image unit b print 

(2) rm -f image
    fallocate -l 255M image
    mkfs.fat -F 32 --mbr=yes image
    parted -m -s -- image unit b print 

*** Actual results:

parted prints the following:

(1)

BYT;
/root/image:267386880B:file:512:512:loop::;
1:0B:267386879B:267386880B:fat16::;

(2)

BYT;
/root/image:267386880B:file:512:512:loop::;
1:0B:267386879B:267386880B:fat32::;

Note "loop" in both outputs.

*** Expected results:

Create a "normal" partition table:

  rm -f image
  fallocate -l 255M image
  fdisk image
    Command (m for help): n
    Select (default p): p
    Partition number (1-4, default 1): 1
    First sector ...: [accept default]
    Last sector ...: [accept default]

  Command (m for help): w

List it with "parted":

parted -m -s -- image unit b print

Output:

BYT;
/root/image:267386880B:file:512:512:msdos::;
1:1048576B:267386879B:266338304B:::;

Note that the device line contains "msdos", not "loop".