* - once filled in and attached to a key:
* - the payload struct is invariant may not be changed, only replaced
* - the payload must be read with RCU procedures or with the key semaphore
* - once filled in and attached to a key:
* - the payload struct is invariant may not be changed, only replaced
* - the payload must be read with RCU procedures or with the key semaphore
extern int user_instantiate(struct key *key, const void *data, size_t datalen);
extern int user_update(struct key *key, const void *data, size_t datalen);
extern int user_instantiate(struct key *key, const void *data, size_t datalen);
extern int user_update(struct key *key, const void *data, size_t datalen);