net_sched: act_gact: make tcfg_pval non zero

First step for gact RCU operation :

Instead of testing if tcfg_pval is zero or not, just make it 1.

No change in behavior, but slightly faster code.

The smp_rmb()/smp_wmb() barriers, while not strictly needed at this
stage are added for upcoming spinlock removal.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: 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>

diff --git a/net/sched/act_gact.c b/net/sched/act_gact.c
index a4f8af2..22a3a61 100644 (file)
--- a/net/sched/act_gact.c
+++ b/net/sched/act_gact.c
@@ -28,14 +28,16 @@
 #ifdef CONFIG_GACT_PROB
 static int gact_net_rand(struct tcf_gact *gact)
 {
-       if (!gact->tcfg_pval || prandom_u32() % gact->tcfg_pval)
+       smp_rmb(); /* coupled with smp_wmb() in tcf_gact_init() */
+       if (prandom_u32() % gact->tcfg_pval)
                return gact->tcf_action;
        return gact->tcfg_paction;
 }
 
 static int gact_determ(struct tcf_gact *gact)
 {
-       if (!gact->tcfg_pval || gact->tcf_bstats.packets % gact->tcfg_pval)
+       smp_rmb(); /* coupled with smp_wmb() in tcf_gact_init() */
+       if (gact->tcf_bstats.packets % gact->tcfg_pval)
                return gact->tcf_action;
        return gact->tcfg_paction;
 }
@@ -105,7 +107,11 @@ static int tcf_gact_init(struct net *net, struct nlattr *nla,
 #ifdef CONFIG_GACT_PROB
        if (p_parm) {
                gact->tcfg_paction = p_parm->paction;
-               gact->tcfg_pval    = p_parm->pval;
+               gact->tcfg_pval    = max_t(u16, 1, p_parm->pval);
+               /* Make sure tcfg_pval is written before tcfg_ptype
+                * coupled with smp_rmb() in gact_net_rand() & gact_determ()
+                */
+               smp_wmb();
                gact->tcfg_ptype   = p_parm->ptype;
        }
 #endif