extern struct user_namespace init_user_ns;
#ifdef CONFIG_USER_NS
#define current_user_ns() (current_cred_xxx(user_ns))
-#define task_user_ns(task) (task_cred_xxx((task), user_ns))
#else
#define current_user_ns() (&init_user_ns)
-#define task_user_ns(task) (&init_user_ns)
#endif