[dpedu]

I think ZFS has the easiest way to do this sort of thing:

    # fallocate -l 256M disk.bin
    # zpool create filepool /root/disk.bin
    # zfs set mountpoint=/root/filepool filepool
    # df -h /root/filepool
    Filesystem      Size  Used Avail Use% Mounted on
    filepool        208M     0  208M   0% /root/filepool

[trm42]

Sure, ZFS has lots of awesome features, but the point of loopback device lets you to attach and mount basically any disk image that has kernel or fuse drivers.