NFSv4.1: Don't recheck delegations that have already been checked

Ensure we don't spam the server with test_stateid() calls for
delegations that have already been checked.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Tested-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

fs/nfs/nfs4proc.c

@@ -2459,6 +2459,11 @@ static void nfs41_check_delegation_stateid(struct nfs4_state *state)
 		return;
 	}
 
+	if (!test_and_clear_bit(NFS_DELEGATION_TEST_EXPIRED, &delegation->flags)) {
+		rcu_read_unlock();
+		return;
+	}
+
 	cred = get_rpccred(delegation->cred);
 	rcu_read_unlock();
 	status = nfs41_test_and_free_expired_stateid(server, &stateid, cred);