I mounted a disk image using a few different FUSE modules and then subsequently renamed the parent directory.
The mounts have disappeared from the mtab and now the OS refuses to unmount them.
fusermount -u mnt
returns:
fusermount: entry for /home/catskul/foo/mnt not found in /etc/mtab
sudo fusermount -u mnt
returns:
fusermount: failed to unmount /home/catskul/foo/mnt: Device or resource busy
sudo fuser -a mnt
returns:
Cannot stat file /proc/986/fd/55: Permission denied
mnt:
Killing the process that had the "permission denied" fd and then subsequently issuing
fusermount -u mnt
did the trick.