net: sch: api: add extack support in qdisc_alloc

This patch adds extack support for the function qdisc_alloc which is
a common used function in the tc subsystem. Callers which are interested
in the receiving error can assign extack to get a more detailed
information why qdisc_alloc failed.

Cc: David Ahern <dsahern@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Alexander Aring <aring@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sch_generic.h

@@ -471,7 +471,8 @@ void qdisc_destroy(struct Qdisc *qdisc);
 void qdisc_tree_reduce_backlog(struct Qdisc *qdisc, unsigned int n,
 			       unsigned int len);
 struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
-			  const struct Qdisc_ops *ops);
+			  const struct Qdisc_ops *ops,
+			  struct netlink_ext_ack *extack);
 struct Qdisc *qdisc_create_dflt(struct netdev_queue *dev_queue,
 				const struct Qdisc_ops *ops, u32 parentid);
 void __qdisc_calculate_pkt_len(struct sk_buff *skb,

net/sched/sch_api.c

@@ -1052,7 +1052,7 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 		goto err_out;
 	}
 
-	sch = qdisc_alloc(dev_queue, ops);
+	sch = qdisc_alloc(dev_queue, ops, extack);
 	if (IS_ERR(sch)) {
 		err = PTR_ERR(sch);
 		goto err_out2;

net/sched/sch_generic.c

@@ -755,7 +755,8 @@ static struct lock_class_key qdisc_tx_busylock;
 static struct lock_class_key qdisc_running_key;
 
 struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
-			  const struct Qdisc_ops *ops)
+			  const struct Qdisc_ops *ops,
+			  struct netlink_ext_ack *extack)
 {
 	void *p;
 	struct Qdisc *sch;
@@ -764,6 +765,7 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
 	struct net_device *dev;
 
 	if (!dev_queue) {
+		NL_SET_ERR_MSG(extack, "No device queue given");
 		err = -EINVAL;
 		goto errout;
 	}
@@ -835,7 +837,7 @@ struct Qdisc *qdisc_create_dflt(struct netdev_queue *dev_queue,
 	if (!try_module_get(ops->owner))
 		return NULL;
 
-	sch = qdisc_alloc(dev_queue, ops);
+	sch = qdisc_alloc(dev_queue, ops, NULL);
 	if (IS_ERR(sch)) {
 		module_put(ops->owner);
 		return NULL;