net: core: introduce mini_Qdisc and eliminate usage of tp->q for clsact fastpath

In sch_handle_egress and sch_handle_ingress tp->q is used only in order
to update stats. So stats and filter list are the only things that are
needed in clsact qdisc fastpath processing. Introduce new mini_Qdisc
struct to hold those items. Also, introduce a helper to swap the
mini_Qdisc structures in case filter list head changes.

This removes need for tp->q usage without added overhead.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -1559,6 +1559,8 @@ enum netdev_priv_flags {
  *
  *	@rx_handler:		handler for received packets
  *	@rx_handler_data: 	XXX: need comments on this one
+ *	@miniq_ingress:		ingress/clsact qdisc specific data for
+ *				ingress processing
  *	@ingress_queue:		XXX: need comments on this one
  *	@broadcast:		hw bcast address
  *
@@ -1576,7 +1578,8 @@ enum netdev_priv_flags {
  *	@tx_global_lock: 	XXX: need comments on this one
  *
  *	@xps_maps:	XXX: need comments on this one
- *
+ *	@miniq_egress:		clsact qdisc specific data for
+ *				egress processing
  *	@watchdog_timeo:	Represents the timeout that is used by
  *				the watchdog (see dev_watchdog())
  *	@watchdog_timer:	List of timers
@@ -1795,7 +1798,7 @@ struct net_device {
 	void __rcu		*rx_handler_data;
 
 #ifdef CONFIG_NET_CLS_ACT
-	struct tcf_proto __rcu  *ingress_cl_list;
+	struct mini_Qdisc __rcu	*miniq_ingress;
 #endif
 	struct netdev_queue __rcu *ingress_queue;
 #ifdef CONFIG_NETFILTER_INGRESS
@@ -1826,7 +1829,7 @@ struct net_device {
 	struct xps_dev_maps __rcu *xps_maps;
 #endif
 #ifdef CONFIG_NET_CLS_ACT
-	struct tcf_proto __rcu  *egress_cl_list;
+	struct mini_Qdisc __rcu	*miniq_egress;
 #endif
 
 	/* These may be needed for future network-power-down code. */