[PKT_SCHED]: Report rate estimator configuration errors during qdisc allocation

Current behaviour is to not report an error if a rate
estimator is created together with a qdisc and the
configuration of the rate estimator is bogus. This leads
to unexpected behaviour because the user is not notified.

New behaviour is to report the error and let the whole
qdisc creation operation fail so the user is able to fix
his mistake.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_api.c

@@ -454,15 +454,27 @@ qdisc_create(struct net_device *dev, u32 handle, struct rtattr **tca, int *errp)
 	sch->handle = handle;
 
 	if (!ops->init || (err = ops->init(sch, tca[TCA_OPTIONS-1])) == 0) {
+#ifdef CONFIG_NET_ESTIMATOR
+		if (tca[TCA_RATE-1]) {
+			err = gen_new_estimator(&sch->bstats, &sch->rate_est,
+						sch->stats_lock,
+						tca[TCA_RATE-1]);
+			if (err) {
+				/*
+				 * Any broken qdiscs that would require
+				 * a ops->reset() here? The qdisc was never
+				 * in action so it shouldn't be necessary.
+				 */
+				if (ops->destroy)
+					ops->destroy(sch);
+				goto err_out3;
+			}
+		}
+#endif
 		qdisc_lock_tree(dev);
 		list_add_tail(&sch->list, &dev->qdisc_list);
 		qdisc_unlock_tree(dev);
 
-#ifdef CONFIG_NET_ESTIMATOR
-		if (tca[TCA_RATE-1])
-			gen_new_estimator(&sch->bstats, &sch->rate_est,
-				sch->stats_lock, tca[TCA_RATE-1]);
-#endif
 		return sch;
 	}
 err_out3: