# umount /mnt/crypto/
umount: /mnt/crypto: device is busy.
(In some cases useful info about processes that use
the device is found by lsof(8) or fuser(1))
# lsof /mnt/crypto/
#
# fuser -m /mnt/crypto/
#
??? Внутри ничего не намонтировано еще, просто файлы лежат.