fscrypt_get_policy
ret = fscrypt_get_policy(inode, &existing_policy);
err = fscrypt_get_policy(file_inode(filp), &policy);
err = fscrypt_get_policy(file_inode(filp), policy);
err1 = fscrypt_get_policy(parent, &parent_policy);
err2 = fscrypt_get_policy(child, &child_policy);