ipv6: let trace_fib6_table_lookup() dereference the fib table

The perf traces for ipv6 routing code show a relevant cost around
trace_fib6_table_lookup(), even if no trace is enabled. This is
due to the fib6_table de-referencing currently performed by the
caller.

Let's the tracing code pay this overhead, passing to the trace
helper the table pointer. This gives small but measurable
performance improvement under UDP flood.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: David Ahern <dsa@cumulusnetworks.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/trace/events/fib6.h

@@ -12,9 +12,9 @@
 TRACE_EVENT(fib6_table_lookup,
 
 	TP_PROTO(const struct net *net, const struct rt6_info *rt,
-		 u32 tb_id, const struct flowi6 *flp),
+		 struct fib6_table *table, const struct flowi6 *flp),
 
-	TP_ARGS(net, rt, tb_id, flp),
+	TP_ARGS(net, rt, table, flp),
 
 	TP_STRUCT__entry(
 		__field(	u32,	tb_id		)
@@ -34,7 +34,7 @@ TRACE_EVENT(fib6_table_lookup,
 	TP_fast_assign(
 		struct in6_addr *in6;
 
-		__entry->tb_id = tb_id;
+		__entry->tb_id = table->tb6_id;
 		__entry->oif = flp->flowi6_oif;
 		__entry->iif = flp->flowi6_iif;
 		__entry->tos = ip6_tclass(flp->flowlabel);

net/ipv6/route.c

@@ -945,7 +945,7 @@ restart:
 
 	rcu_read_unlock();
 
-	trace_fib6_table_lookup(net, rt, table->tb6_id, fl6);
+	trace_fib6_table_lookup(net, rt, table, fl6);
 
 	return rt;
 
@@ -1682,7 +1682,7 @@ redo_rt6_select:
 	if (rt == net->ipv6.ip6_null_entry) {
 		rcu_read_unlock();
 		dst_hold(&rt->dst);
-		trace_fib6_table_lookup(net, rt, table->tb6_id, fl6);
+		trace_fib6_table_lookup(net, rt, table, fl6);
 		return rt;
 	} else if (rt->rt6i_flags & RTF_CACHE) {
 		if (ip6_hold_safe(net, &rt, true)) {
@@ -1690,7 +1690,7 @@ redo_rt6_select:
 			rt6_dst_from_metrics_check(rt);
 		}
 		rcu_read_unlock();
-		trace_fib6_table_lookup(net, rt, table->tb6_id, fl6);
+		trace_fib6_table_lookup(net, rt, table, fl6);
 		return rt;
 	} else if (unlikely((fl6->flowi6_flags & FLOWI_FLAG_KNOWN_NH) &&
 			    !(rt->rt6i_flags & RTF_GATEWAY))) {
@@ -1726,7 +1726,7 @@ redo_rt6_select:
 		}
 
 uncached_rt_out:
-		trace_fib6_table_lookup(net, uncached_rt, table->tb6_id, fl6);
+		trace_fib6_table_lookup(net, uncached_rt, table, fl6);
 		return uncached_rt;
 
 	} else {
@@ -1754,7 +1754,7 @@ uncached_rt_out:
 		}
 		local_bh_enable();
 		rcu_read_unlock();
-		trace_fib6_table_lookup(net, pcpu_rt, table->tb6_id, fl6);
+		trace_fib6_table_lookup(net, pcpu_rt, table, fl6);
 		return pcpu_rt;
 	}
 }
@@ -2195,7 +2195,7 @@ out:
 
 	rcu_read_unlock();
 
-	trace_fib6_table_lookup(net, rt, table->tb6_id, fl6);
+	trace_fib6_table_lookup(net, rt, table, fl6);
 	return rt;
 };