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>
diff --git a/fs/nfs/nfs4session.c b/fs/nfs/nfs4session.c
index 769b856..a5489d7 100644
--- a/fs/nfs/nfs4session.c
+++ b/fs/nfs/nfs4session.c
@@ -573,12 +573,11 @@ static void nfs4_destroy_session_slot_tables(struct nfs4_session *session)
 void nfs4_destroy_session(struct nfs4_session *session)
 {
 	struct rpc_xprt *xprt;
-	struct rpc_cred *cred;
+	const struct cred *cred;
 
 	cred = nfs4_get_clid_cred(session->clp);
 	nfs4_proc_destroy_session(session, cred);
-	if (cred)
-		put_rpccred(cred);
+	put_cred(cred);
 
 	rcu_read_lock();
 	xprt = rcu_dereference(session->clp->cl_rpcclient->cl_xprt);