net_sched: act_gact: use a separate packet counters for gact_determ()

Second step for gact RCU operation :

We want to get rid of the spinlock protecting gact operations.
Stats (packets/bytes) will soon be per cpu.

gact_determ() would not work without a central packet counter,
so lets add it for this mode.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tc_act/tc_gact.h

@@ -6,9 +6,10 @@
 struct tcf_gact {
 	struct tcf_common	common;
 #ifdef CONFIG_GACT_PROB
-        u16			tcfg_ptype;
-        u16			tcfg_pval;
-        int			tcfg_paction;
+	u16			tcfg_ptype;
+	u16			tcfg_pval;
+	int			tcfg_paction;
+	atomic_t		packets;
 #endif
 };
 #define to_gact(a) \

net/sched/act_gact.c

@@ -36,8 +36,10 @@ static int gact_net_rand(struct tcf_gact *gact)
 
 static int gact_determ(struct tcf_gact *gact)
 {
+	u32 pack = atomic_inc_return(&gact->packets);
+
 	smp_rmb(); /* coupled with smp_wmb() in tcf_gact_init() */
-	if (gact->tcf_bstats.packets % gact->tcfg_pval)
+	if (pack % gact->tcfg_pval)
 		return gact->tcf_action;
 	return gact->tcfg_paction;
 }