ceph_fname_to_usr
int ceph_fname_to_usr(const struct ceph_fname *fname, struct fscrypt_str *tname,
err = ceph_fname_to_usr(&fname, NULL, &oname, NULL);
err = ceph_fname_to_usr(&fname, NULL, &oname, &is_nokey);
err = ceph_fname_to_usr(&fname, &tname, &oname, &rde->is_nokey);