NFS/NFSD/SUNRPC: replace generic creds with 'struct cred'.

SUNRPC has two sorts of credentials, both of which appear as
"struct rpc_cred".
There are "generic credentials" which are supplied by clients
such as NFS and passed in 'struct rpc_message' to indicate
which user should be used to authorize the request, and there
are low-level credentials such as AUTH_NULL, AUTH_UNIX, AUTH_GSS
which describe the credential to be sent over the wires.

This patch replaces all the generic credentials by 'struct cred'
pointers - the credential structure used throughout Linux.

For machine credentials, there is a special 'struct cred *' pointer
which is statically allocated and recognized where needed as
having a special meaning.  A look-up of a low-level cred will
map this to a machine credential.

Signed-off-by: NeilBrown <neilb@suse.com>
Acked-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

include/linux/sunrpc/auth.h

@@ -67,7 +67,7 @@ struct rpc_cred {
 #define RPCAUTH_CRED_HASHED	2
 #define RPCAUTH_CRED_NEGATIVE	3
 
-struct rpc_cred *rpc_machine_cred(void);
+const struct cred *rpc_machine_cred(void);
 
 /*
  * Client authentication handle
@@ -196,21 +196,5 @@ struct rpc_cred *get_rpccred(struct rpc_cred *cred)
 	return NULL;
 }
 
-/**
- * get_rpccred_rcu - get a reference to a cred using rcu-protected pointer
- * @cred: cred of which to take a reference
- *
- * In some cases, we may have a pointer to a credential to which we
- * want to take a reference, but don't already have one. Because these
- * objects are freed using RCU, we can access the cr_count while its
- * on its way to destruction and only take a reference if it's not already
- * zero.
- */
-static inline struct rpc_cred *
-get_rpccred_rcu(struct rpc_cred *cred)
-{
-	return get_rpccred(cred);
-}
-
 #endif /* __KERNEL__ */
 #endif /* _LINUX_SUNRPC_AUTH_H */