pkt_sched: give visibility to mq slave qdiscs

Commit 6da7c8fcbcbd ("qdisc: allow setting default queuing discipline")
added the ability to change default qdisc from pfifo_fast to say fq

But as most modern ethernet devices are multiqueue, we cant really
see all the statistics from "tc -s qdisc show", as the default root
qdisc is mq.

This patch adds the calls to qdisc_list_add() to mq and mqprio

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/pkt_sched.h

@@ -88,6 +88,7 @@ int unregister_qdisc(struct Qdisc_ops *qops);
 void qdisc_get_default(char *id, size_t len);
 int qdisc_set_default(const char *id);
 
+void qdisc_list_add(struct Qdisc *q);
 void qdisc_list_del(struct Qdisc *q);
 struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle);
 struct Qdisc *qdisc_lookup_class(struct net_device *dev, u32 handle);

net/sched/sch_api.c

@@ -271,11 +271,12 @@ static struct Qdisc *qdisc_match_from_root(struct Qdisc *root, u32 handle)
 	return NULL;
 }
 
-static void qdisc_list_add(struct Qdisc *q)
+void qdisc_list_add(struct Qdisc *q)
 {
 	if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS))
 		list_add_tail(&q->list, &qdisc_dev(q)->qdisc->list);
 }
+EXPORT_SYMBOL(qdisc_list_add);
 
 void qdisc_list_del(struct Qdisc *q)
 {

net/sched/sch_mq.c

@@ -78,14 +78,19 @@ static void mq_attach(struct Qdisc *sch)
 {
 	struct net_device *dev = qdisc_dev(sch);
 	struct mq_sched *priv = qdisc_priv(sch);
-	struct Qdisc *qdisc;
+	struct Qdisc *qdisc, *old;
 	unsigned int ntx;
 
 	for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
 		qdisc = priv->qdiscs[ntx];
-		qdisc = dev_graft_qdisc(qdisc->dev_queue, qdisc);
-		if (qdisc)
-			qdisc_destroy(qdisc);
+		old = dev_graft_qdisc(qdisc->dev_queue, qdisc);
+		if (old)
+			qdisc_destroy(old);
+#ifdef CONFIG_NET_SCHED
+		if (ntx < dev->real_num_tx_queues)
+			qdisc_list_add(qdisc);
+#endif
+
 	}
 	kfree(priv->qdiscs);
 	priv->qdiscs = NULL;

net/sched/sch_mqprio.c

@@ -167,15 +167,17 @@ static void mqprio_attach(struct Qdisc *sch)
 {
 	struct net_device *dev = qdisc_dev(sch);
 	struct mqprio_sched *priv = qdisc_priv(sch);
-	struct Qdisc *qdisc;
+	struct Qdisc *qdisc, *old;
 	unsigned int ntx;
 
 	/* Attach underlying qdisc */
 	for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
 		qdisc = priv->qdiscs[ntx];
-		qdisc = dev_graft_qdisc(qdisc->dev_queue, qdisc);
-		if (qdisc)
-			qdisc_destroy(qdisc);
+		old = dev_graft_qdisc(qdisc->dev_queue, qdisc);
+		if (old)
+			qdisc_destroy(old);
+		if (ntx < dev->real_num_tx_queues)
+			qdisc_list_add(qdisc);
 	}
 	kfree(priv->qdiscs);
 	priv->qdiscs = NULL;