net: rcu-ify tcf_proto

rcu'ify tcf_proto this allows calling tc_classify() without holding
any locks. Updaters are protected by RTNL.

This patch prepares the core net_sched infrastracture for running
the classifier/action chains without holding the qdisc lock however
it does nothing to ensure cls_xxx and act_xxx types also work without
locking. Additional patches are required to address the fall out.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/sch_ingress.c b/net/sched/sch_ingress.c
index 62871c1..b351125 100644
--- a/net/sched/sch_ingress.c
+++ b/net/sched/sch_ingress.c
@@ -17,7 +17,7 @@
 
 
 struct ingress_qdisc_data {
-	struct tcf_proto	*filter_list;
+	struct tcf_proto __rcu	*filter_list;
 };
 
 /* ------------------------- Class/flow operations ------------------------- */
@@ -46,7 +46,8 @@
 {
 }
 
-static struct tcf_proto **ingress_find_tcf(struct Qdisc *sch, unsigned long cl)
+static struct tcf_proto __rcu **ingress_find_tcf(struct Qdisc *sch,
+						 unsigned long cl)
 {
 	struct ingress_qdisc_data *p = qdisc_priv(sch);
 
@@ -59,9 +60,10 @@
 {
 	struct ingress_qdisc_data *p = qdisc_priv(sch);
 	struct tcf_result res;
+	struct tcf_proto *fl = rcu_dereference_bh(p->filter_list);
 	int result;
 
-	result = tc_classify(skb, p->filter_list, &res);
+	result = tc_classify(skb, fl, &res);
 
 	qdisc_bstats_update(sch, skb);
 	switch (result) {