ceph_crypt
ret = ceph_crypt(&au->session_key, 0 /* dummy */,
ret = ceph_crypt(key, usage_slot, false, p, ciphertext_len,
ret = ceph_crypt(key, usage_slot, true, buf + sizeof(u32),
int ceph_crypt(const struct ceph_crypto_key *key, int usage_slot, bool encrypt,