sunrpc: add rpc_lookup_generic_cred

Add function rpc_lookup_generic_cred, which allows lookups of a generic
credential that's not current_cred().

[jlayton: add gfp_t parm]
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

include/linux/sunrpc/auth.h

@@ -167,6 +167,7 @@ void 			rpc_destroy_authunix(void);
 
 struct rpc_cred *	rpc_lookup_cred(void);
 struct rpc_cred *	rpc_lookup_cred_nonblock(void);
+struct rpc_cred *	rpc_lookup_generic_cred(struct auth_cred *, int, gfp_t);
 struct rpc_cred *	rpc_lookup_machine_cred(const char *service_name);
 int			rpcauth_register(const struct rpc_authops *);
 int			rpcauth_unregister(const struct rpc_authops *);

net/sunrpc/auth_generic.c

@@ -38,6 +38,13 @@ struct rpc_cred *rpc_lookup_cred(void)
 }
 EXPORT_SYMBOL_GPL(rpc_lookup_cred);
 
+struct rpc_cred *
+rpc_lookup_generic_cred(struct auth_cred *acred, int flags, gfp_t gfp)
+{
+	return rpcauth_lookup_credcache(&generic_auth, acred, flags, gfp);
+}
+EXPORT_SYMBOL_GPL(rpc_lookup_generic_cred);
+
 struct rpc_cred *rpc_lookup_cred_nonblock(void)
 {
 	return rpcauth_lookupcred(&generic_auth, RPCAUTH_LOOKUP_RCU);