I get this error when I'm trying to do
sudo mount -t ecryptfs folder1 folder2 in my home folder (encrypted by ubuntu)
I tried the same command but folders at /tmp, it worked as expected.
The error message I got:
ecryptfs_unlink_sigs ecryptfs_key_bytes=16 ecryptfs_cipher=aes ecryptfs_sig=66cea2017ad38853 Error mounting eCryptfs: [-22] Invalid argument
kernel: [ 197.621331] Mount on filesystem of type eCryptfs explicitly disallowed due to known incompatibilities mount.ecryptfs: Failed to perform eCryptfs mount: [Invalid argument] kernel: [ 197.659287] Reading sb failed; rc = [-22]