umount.crypt - unmount a dm-crypt encrypted volume
umount.crypt [-n] directory
-f This option is ignored (originally is "force unmount for NFS"). -n Do not update /etc/mtab. -r Try mounting read-only if unmounting fails. This option is currently not implemented and is ignored.
umount.crypt will unmount directory and disassociates the underlying crypto device, and loop device if such was used.