net/sched: act_nat: transition to percpu stats and rcu

The tc action act_nat was using shared stats and taking the per action
lock in the datapath. Improve it by using percpu stats and rcu.

perf before:
- 10.48% tcf_nat_act
   - 81.83% _raw_spin_lock
        81.08% native_queued_spin_lock_slowpath

perf after:
- 0.48% tcf_nat_act

tdc results:
1..27
ok 1 7565 - Add nat action on ingress with default control action
ok 2 fd79 - Add nat action on ingress with pipe control action
ok 3 eab9 - Add nat action on ingress with continue control action
ok 4 c53a - Add nat action on ingress with reclassify control action
ok 5 76c9 - Add nat action on ingress with jump control action
ok 6 24c6 - Add nat action on ingress with drop control action
ok 7 2120 - Add nat action on ingress with maximum index value
ok 8 3e9d - Add nat action on ingress with invalid index value
ok 9 f6c9 - Add nat action on ingress with invalid IP address
ok 10 be25 - Add nat action on ingress with invalid argument
ok 11 a7bd - Add nat action on ingress with DEFAULT IP address
ok 12 ee1e - Add nat action on ingress with ANY IP address
ok 13 1de8 - Add nat action on ingress with ALL IP address
ok 14 8dba - Add nat action on egress with default control action
ok 15 19a7 - Add nat action on egress with pipe control action
ok 16 f1d9 - Add nat action on egress with continue control action
ok 17 6d4a - Add nat action on egress with reclassify control action
ok 18 b313 - Add nat action on egress with jump control action
ok 19 d9fc - Add nat action on egress with drop control action
ok 20 a895 - Add nat action on egress with DEFAULT IP address
ok 21 2572 - Add nat action on egress with ANY IP address
ok 22 37f3 - Add nat action on egress with ALL IP address
ok 23 6054 - Add nat action on egress with cookie
ok 24 79d6 - Add nat action on ingress with cookie
ok 25 4b12 - Replace nat action with invalid goto chain control
ok 26 b811 - Delete nat action with valid index
ok 27 a521 - Delete nat action with invalid index
Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Pedro Tammela <pctammela@mojatatu.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

include/net/tc_act/tc_nat.h

@@ -5,13 +5,17 @@
 #include <linux/types.h>
 #include <net/act_api.h>
 
-struct tcf_nat {
-	struct tc_action common;
-
+struct tcf_nat_parms {
 	__be32 old_addr;
 	__be32 new_addr;
 	__be32 mask;
 	u32 flags;
+	struct rcu_head rcu;
+};
+
+struct tcf_nat {
+	struct tc_action common;
+	struct tcf_nat_parms __rcu *parms;
 };
 
 #define to_tcf_nat(a) ((struct tcf_nat *)a)

net/sched/act_nat.c

@@ -38,6 +38,7 @@ static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
 {
 	struct tc_action_net *tn = net_generic(net, act_nat_ops.net_id);
 	bool bind = flags & TCA_ACT_FLAGS_BIND;
+	struct tcf_nat_parms *nparm, *oparm;
 	struct nlattr *tb[TCA_NAT_MAX + 1];
 	struct tcf_chain *goto_ch = NULL;
 	struct tc_nat *parm;
@@ -59,8 +60,8 @@ static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
 	index = parm->index;
 	err = tcf_idr_check_alloc(tn, &index, a, bind);
 	if (!err) {
-		ret = tcf_idr_create(tn, index, est, a,
-				     &act_nat_ops, bind, false, flags);
+		ret = tcf_idr_create_from_flags(tn, index, est, a, &act_nat_ops,
+						bind, flags);
 		if (ret) {
 			tcf_idr_cleanup(tn, index);
 			return ret;
@@ -79,19 +80,31 @@ static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
 	err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
 	if (err < 0)
 		goto release_idr;
+
+	nparm = kzalloc(sizeof(*nparm), GFP_KERNEL);
+	if (!nparm) {
+		err = -ENOMEM;
+		goto release_idr;
+	}
+
+	nparm->old_addr = parm->old_addr;
+	nparm->new_addr = parm->new_addr;
+	nparm->mask = parm->mask;
+	nparm->flags = parm->flags;
+
 	p = to_tcf_nat(*a);
 
 	spin_lock_bh(&p->tcf_lock);
-	p->old_addr = parm->old_addr;
-	p->new_addr = parm->new_addr;
-	p->mask = parm->mask;
-	p->flags = parm->flags;
-
 	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
+	oparm = rcu_replace_pointer(p->parms, nparm, lockdep_is_held(&p->tcf_lock));
 	spin_unlock_bh(&p->tcf_lock);
+
 	if (goto_ch)
 		tcf_chain_put_by_act(goto_ch);
 
+	if (oparm)
+		kfree_rcu(oparm, rcu);
+
 	return ret;
 release_idr:
 	tcf_idr_release(*a, bind);
@@ -103,6 +116,7 @@ TC_INDIRECT_SCOPE int tcf_nat_act(struct sk_buff *skb,
 				  struct tcf_result *res)
 {
 	struct tcf_nat *p = to_tcf_nat(a);
+	struct tcf_nat_parms *parms;
 	struct iphdr *iph;
 	__be32 old_addr;
 	__be32 new_addr;
@@ -113,18 +127,16 @@ TC_INDIRECT_SCOPE int tcf_nat_act(struct sk_buff *skb,
 	int ihl;
 	int noff;
 
-	spin_lock(&p->tcf_lock);
-
 	tcf_lastuse_update(&p->tcf_tm);
-	old_addr = p->old_addr;
-	new_addr = p->new_addr;
-	mask = p->mask;
-	egress = p->flags & TCA_NAT_FLAG_EGRESS;
-	action = p->tcf_action;
+	tcf_action_update_bstats(&p->common, skb);
 
-	bstats_update(&p->tcf_bstats, skb);
+	action = READ_ONCE(p->tcf_action);
 
-	spin_unlock(&p->tcf_lock);
+	parms = rcu_dereference_bh(p->parms);
+	old_addr = parms->old_addr;
+	new_addr = parms->new_addr;
+	mask = parms->mask;
+	egress = parms->flags & TCA_NAT_FLAG_EGRESS;
 
 	if (unlikely(action == TC_ACT_SHOT))
 		goto drop;
@@ -248,9 +260,7 @@ TC_INDIRECT_SCOPE int tcf_nat_act(struct sk_buff *skb,
 	return action;
 
 drop:
-	spin_lock(&p->tcf_lock);
-	p->tcf_qstats.drops++;
-	spin_unlock(&p->tcf_lock);
+	tcf_action_inc_drop_qstats(&p->common);
 	return TC_ACT_SHOT;
 }
 
@@ -264,15 +274,20 @@ static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
 		.refcnt   = refcount_read(&p->tcf_refcnt) - ref,
 		.bindcnt  = atomic_read(&p->tcf_bindcnt) - bind,
 	};
+	struct tcf_nat_parms *parms;
 	struct tcf_t t;
 
 	spin_lock_bh(&p->tcf_lock);
-	opt.old_addr = p->old_addr;
-	opt.new_addr = p->new_addr;
-	opt.mask = p->mask;
-	opt.flags = p->flags;
+
 	opt.action = p->tcf_action;
 
+	parms = rcu_dereference_protected(p->parms, lockdep_is_held(&p->tcf_lock));
+
+	opt.old_addr = parms->old_addr;
+	opt.new_addr = parms->new_addr;
+	opt.mask = parms->mask;
+	opt.flags = parms->flags;
+
 	if (nla_put(skb, TCA_NAT_PARMS, sizeof(opt), &opt))
 		goto nla_put_failure;
 
@@ -289,6 +304,16 @@ static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
 	return -1;
 }
 
+static void tcf_nat_cleanup(struct tc_action *a)
+{
+	struct tcf_nat *p = to_tcf_nat(a);
+	struct tcf_nat_parms *parms;
+
+	parms = rcu_dereference_protected(p->parms, 1);
+	if (parms)
+		kfree_rcu(parms, rcu);
+}
+
 static struct tc_action_ops act_nat_ops = {
 	.kind		=	"nat",
 	.id		=	TCA_ID_NAT,
@@ -296,6 +321,7 @@ static struct tc_action_ops act_nat_ops = {
 	.act		=	tcf_nat_act,
 	.dump		=	tcf_nat_dump,
 	.init		=	tcf_nat_init,
+	.cleanup	=	tcf_nat_cleanup,
 	.size		=	sizeof(struct tcf_nat),
 };