fscrypt_add_key_arg
struct fscrypt_add_key_arg __user *uarg = _uarg;
struct fscrypt_add_key_arg arg;
#define FS_IOC_ADD_ENCRYPTION_KEY _IOWR('f', 23, struct fscrypt_add_key_arg)
#define FS_IOC_ADD_ENCRYPTION_KEY _IOWR('f', 23, struct fscrypt_add_key_arg)