pkt_sched: set root qdisc before change() in attach_default_qdiscs()

edumazet · davem330 · commit e57a784d8cae · 2013-12-14T01:20:06.000-05:00
After commit 95dc192 ("pkt_sched: give visibility to mq slave qdiscs") we call disc_list_add() while the device qdisc might be the noop_qdisc one. This shows up as duplicates in "tc qdisc show", as all inactive devices point to noop_qdisc. Fix this by setting dev->qdisc to the new qdisc before calling ops->change() in attach_default_qdiscs() Add a WARN_ON_ONCE() to catch any future similar problem. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
@@ -273,8 +273,11 @@ static struct Qdisc *qdisc_match_from_root(struct Qdisc *root, u32 handle)
 
 void qdisc_list_add(struct Qdisc *q)
 {
+	struct Qdisc *root = qdisc_dev(q)->qdisc;
+
+	WARN_ON_ONCE(root == &noop_qdisc);
 	if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS))
-		list_add_tail(&q->list, &qdisc_dev(q)->qdisc->list);
+		list_add_tail(&q->list, &root->list);
 }
 EXPORT_SYMBOL(qdisc_list_add);
 
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
@@ -718,8 +718,8 @@ static void attach_default_qdiscs(struct net_device *dev)
 	} else {
 		qdisc = qdisc_create_dflt(txq, &mq_qdisc_ops, TC_H_ROOT);
 		if (qdisc) {
-			qdisc->ops->attach(qdisc);
 			dev->qdisc = qdisc;
+			qdisc->ops->attach(qdisc);
 		}
 	}
 }

Original file line number	Diff line number	Diff line change
`@@ -273,8 +273,11 @@ static struct Qdisc qdisc_match_from_root(struct Qdisc root, u32 handle)`
`273`	`273`
`274`	`274`	`void qdisc_list_add(struct Qdisc *q)`
`275`	`275`	`{`
	`276`	`+ struct Qdisc *root = qdisc_dev(q)->qdisc;`
	`277`	`+`
	`278`	`+ WARN_ON_ONCE(root == &noop_qdisc);`
`276`	`279`	`if ((q->parent != TC_H_ROOT) && !(q->flags & TCQ_F_INGRESS))`
`277`		`- list_add_tail(&q->list, &qdisc_dev(q)->qdisc->list);`
	`280`	`+ list_add_tail(&q->list, &root->list);`
`278`	`281`	`}`
`279`	`282`	`EXPORT_SYMBOL(qdisc_list_add);`
`280`	`283`
Original file line number	Diff line number	Diff line change
`@@ -718,8 +718,8 @@ static void attach_default_qdiscs(struct net_device *dev)`
`718`	`718`	`} else {`
`719`	`719`	`qdisc = qdisc_create_dflt(txq, &mq_qdisc_ops, TC_H_ROOT);`
`720`	`720`	`if (qdisc) {`
`721`		`- qdisc->ops->attach(qdisc);`
`722`	`721`	`dev->qdisc = qdisc;`
	`722`	`+ qdisc->ops->attach(qdisc);`
`723`	`723`	`}`
`724`	`724`	`}`
`725`	`725`	`}`