Merge branch 'sch_act_lockless'

Eric Dumazet says:

====================
net_sched: act: lockless operation

As mentioned by Alexei last week in Budapest, it is a bit weird
to take a spinlock in order to drop a packet in a tc filter...

Lets add percpu infra for tc actions and use it for gact & mirred.

Before changes, my host with 8 RX queues was handling 5 Mpps with gact,
and more than 11 Mpps after.

Mirred change is not yet visible if ifb+qdisc is used, as ifb is
not yet multi queue enabled, but is a step forward.
====================

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/act_api.h

@@ -21,6 +21,8 @@ struct tcf_common {
 	struct gnet_stats_rate_est64	tcfc_rate_est;
 	spinlock_t			tcfc_lock;
 	struct rcu_head			tcfc_rcu;
+	struct gnet_stats_basic_cpu __percpu *cpu_bstats;
+	struct gnet_stats_queue __percpu *cpu_qstats;
 };
 #define tcf_head	common.tcfc_head
 #define tcf_index	common.tcfc_index
@@ -68,6 +70,17 @@ static inline void tcf_hashinfo_destroy(struct tcf_hashinfo *hf)
 	kfree(hf->htab);
 }
 
+/* Update lastuse only if needed, to avoid dirtying a cache line.
+ * We use a temp variable to avoid fetching jiffies twice.
+ */
+static inline void tcf_lastuse_update(struct tcf_t *tm)
+{
+	unsigned long now = jiffies;
+
+	if (tm->lastuse != now)
+		tm->lastuse = now;
+}
+
 #ifdef CONFIG_NET_CLS_ACT
 
 #define ACT_P_CREATED 1
@@ -103,7 +116,7 @@ int tcf_hash_release(struct tc_action *a, int bind);
 u32 tcf_hash_new_index(struct tcf_hashinfo *hinfo);
 int tcf_hash_check(u32 index, struct tc_action *a, int bind);
 int tcf_hash_create(u32 index, struct nlattr *est, struct tc_action *a,
-		    int size, int bind);
+		    int size, int bind, bool cpustats);
 void tcf_hash_cleanup(struct tc_action *a, struct nlattr *est);
 void tcf_hash_insert(struct tc_action *a);
 

include/net/sch_generic.h

@@ -513,17 +513,20 @@ static inline void bstats_update(struct gnet_stats_basic_packed *bstats,
 	bstats->packets += skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 1;
 }
 
-static inline void qdisc_bstats_update_cpu(struct Qdisc *sch,
-					   const struct sk_buff *skb)
+static inline void bstats_cpu_update(struct gnet_stats_basic_cpu *bstats,
+				     const struct sk_buff *skb)
 {
-	struct gnet_stats_basic_cpu *bstats =
-				this_cpu_ptr(sch->cpu_bstats);
-
 	u64_stats_update_begin(&bstats->syncp);
 	bstats_update(&bstats->bstats, skb);
 	u64_stats_update_end(&bstats->syncp);
 }
 
+static inline void qdisc_bstats_cpu_update(struct Qdisc *sch,
+					   const struct sk_buff *skb)
+{
+	bstats_cpu_update(this_cpu_ptr(sch->cpu_bstats), skb);
+}
+
 static inline void qdisc_bstats_update(struct Qdisc *sch,
 				       const struct sk_buff *skb)
 {
@@ -547,16 +550,24 @@ static inline void __qdisc_qstats_drop(struct Qdisc *sch, int count)
 	sch->qstats.drops += count;
 }
 
-static inline void qdisc_qstats_drop(struct Qdisc *sch)
+static inline void qstats_drop_inc(struct gnet_stats_queue *qstats)
 {
-	sch->qstats.drops++;
+	qstats->drops++;
 }
 
-static inline void qdisc_qstats_drop_cpu(struct Qdisc *sch)
+static inline void qstats_overlimit_inc(struct gnet_stats_queue *qstats)
 {
-	struct gnet_stats_queue *qstats = this_cpu_ptr(sch->cpu_qstats);
+	qstats->overlimits++;
+}
 
-	qstats->drops++;
+static inline void qdisc_qstats_drop(struct Qdisc *sch)
+{
+	qstats_drop_inc(&sch->qstats);
+}
+
+static inline void qdisc_qstats_cpu_drop(struct Qdisc *sch)
+{
+	qstats_drop_inc(this_cpu_ptr(sch->cpu_qstats));
 }
 
 static inline void qdisc_qstats_overlimit(struct Qdisc *sch)

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) \

include/net/tc_act/tc_mirred.h

@@ -8,7 +8,7 @@ struct tcf_mirred {
 	int			tcfm_eaction;
 	int			tcfm_ifindex;
 	int			tcfm_ok_push;
-	struct net_device	*tcfm_dev;
+	struct net_device __rcu	*tcfm_dev;
 	struct list_head	tcfm_list;
 };
 #define to_mirred(a) \

net/core/dev.c

@@ -3646,7 +3646,7 @@ static inline struct sk_buff *handle_ing(struct sk_buff *skb,
 
 	qdisc_skb_cb(skb)->pkt_len = skb->len;
 	skb->tc_verd = SET_TC_AT(skb->tc_verd, AT_INGRESS);
-	qdisc_bstats_update_cpu(cl->q, skb);
+	qdisc_bstats_cpu_update(cl->q, skb);
 
 	switch (tc_classify(skb, cl, &cl_res)) {
 	case TC_ACT_OK:
@@ -3654,7 +3654,7 @@ static inline struct sk_buff *handle_ing(struct sk_buff *skb,
 		skb->tc_index = TC_H_MIN(cl_res.classid);
 		break;
 	case TC_ACT_SHOT:
-		qdisc_qstats_drop_cpu(cl->q);
+		qdisc_qstats_cpu_drop(cl->q);
 	case TC_ACT_STOLEN:
 	case TC_ACT_QUEUED:
 		kfree_skb(skb);

net/sched/act_api.c

@@ -27,6 +27,15 @@
 #include <net/act_api.h>
 #include <net/netlink.h>
 
+static void free_tcf(struct rcu_head *head)
+{
+	struct tcf_common *p = container_of(head, struct tcf_common, tcfc_rcu);
+
+	free_percpu(p->cpu_bstats);
+	free_percpu(p->cpu_qstats);
+	kfree(p);
+}
+
 void tcf_hash_destroy(struct tc_action *a)
 {
 	struct tcf_common *p = a->priv;
@@ -41,7 +50,7 @@ void tcf_hash_destroy(struct tc_action *a)
 	 * gen_estimator est_timer() might access p->tcfc_lock
 	 * or bstats, wait a RCU grace period before freeing p
 	 */
-	kfree_rcu(p, tcfc_rcu);
+	call_rcu(&p->tcfc_rcu, free_tcf);
 }
 EXPORT_SYMBOL(tcf_hash_destroy);
 
@@ -230,15 +239,16 @@ void tcf_hash_cleanup(struct tc_action *a, struct nlattr *est)
 	if (est)
 		gen_kill_estimator(&pc->tcfc_bstats,
 				   &pc->tcfc_rate_est);
-	kfree_rcu(pc, tcfc_rcu);
+	call_rcu(&pc->tcfc_rcu, free_tcf);
 }
 EXPORT_SYMBOL(tcf_hash_cleanup);
 
 int tcf_hash_create(u32 index, struct nlattr *est, struct tc_action *a,
-		    int size, int bind)
+		    int size, int bind, bool cpustats)
 {
 	struct tcf_hashinfo *hinfo = a->ops->hinfo;
 	struct tcf_common *p = kzalloc(size, GFP_KERNEL);
+	int err = -ENOMEM;
 
 	if (unlikely(!p))
 		return -ENOMEM;
@@ -246,18 +256,32 @@ int tcf_hash_create(u32 index, struct nlattr *est, struct tc_action *a,
 	if (bind)
 		p->tcfc_bindcnt = 1;
 
+	if (cpustats) {
+		p->cpu_bstats = netdev_alloc_pcpu_stats(struct gnet_stats_basic_cpu);
+		if (!p->cpu_bstats) {
+err1:
+			kfree(p);
+			return err;
+		}
+		p->cpu_qstats = alloc_percpu(struct gnet_stats_queue);
+		if (!p->cpu_qstats) {
+err2:
+			free_percpu(p->cpu_bstats);
+			goto err1;
+		}
+	}
 	spin_lock_init(&p->tcfc_lock);
 	INIT_HLIST_NODE(&p->tcfc_head);
 	p->tcfc_index = index ? index : tcf_hash_new_index(hinfo);
 	p->tcfc_tm.install = jiffies;
 	p->tcfc_tm.lastuse = jiffies;
 	if (est) {
-		int err = gen_new_estimator(&p->tcfc_bstats, NULL,
-					    &p->tcfc_rate_est,
-					    &p->tcfc_lock, est);
+		err = gen_new_estimator(&p->tcfc_bstats, p->cpu_bstats,
+					&p->tcfc_rate_est,
+					&p->tcfc_lock, est);
 		if (err) {
-			kfree(p);
-			return err;
+			free_percpu(p->cpu_qstats);
+			goto err2;
 		}
 	}
 
@@ -615,10 +639,10 @@ int tcf_action_copy_stats(struct sk_buff *skb, struct tc_action *a,
 	if (err < 0)
 		goto errout;
 
-	if (gnet_stats_copy_basic(&d, NULL, &p->tcfc_bstats) < 0 ||
+	if (gnet_stats_copy_basic(&d, p->cpu_bstats, &p->tcfc_bstats) < 0 ||
 	    gnet_stats_copy_rate_est(&d, &p->tcfc_bstats,
 				     &p->tcfc_rate_est) < 0 ||
-	    gnet_stats_copy_queue(&d, NULL,
+	    gnet_stats_copy_queue(&d, p->cpu_qstats,
 				  &p->tcfc_qstats,
 				  p->tcfc_qstats.qlen) < 0)
 		goto errout;

net/sched/act_bpf.c

@@ -281,7 +281,7 @@ static int tcf_bpf_init(struct net *net, struct nlattr *nla,
 
 	if (!tcf_hash_check(parm->index, act, bind)) {
 		ret = tcf_hash_create(parm->index, est, act,
-				      sizeof(*prog), bind);
+				      sizeof(*prog), bind, false);
 		if (ret < 0)
 			goto destroy_fp;
 

net/sched/act_connmark.c

@@ -108,7 +108,8 @@ static int tcf_connmark_init(struct net *net, struct nlattr *nla,
 	parm = nla_data(tb[TCA_CONNMARK_PARMS]);
 
 	if (!tcf_hash_check(parm->index, a, bind)) {
-		ret = tcf_hash_create(parm->index, est, a, sizeof(*ci), bind);
+		ret = tcf_hash_create(parm->index, est, a, sizeof(*ci),
+				      bind, false);
 		if (ret)
 			return ret;
 

net/sched/act_csum.c

@@ -62,7 +62,8 @@ static int tcf_csum_init(struct net *n, struct nlattr *nla, struct nlattr *est,
 	parm = nla_data(tb[TCA_CSUM_PARMS]);
 
 	if (!tcf_hash_check(parm->index, a, bind)) {
-		ret = tcf_hash_create(parm->index, est, a, sizeof(*p), bind);
+		ret = tcf_hash_create(parm->index, est, a, sizeof(*p),
+				      bind, false);
 		if (ret)
 			return ret;
 		ret = ACT_P_CREATED;

net/sched/act_gact.c

@@ -28,14 +28,18 @@
 #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)
+	u32 pack = atomic_inc_return(&gact->packets);
+
+	smp_rmb(); /* coupled with smp_wmb() in tcf_gact_init() */
+	if (pack % gact->tcfg_pval)
 		return gact->tcf_action;
 	return gact->tcfg_paction;
 }
@@ -85,7 +89,8 @@ static int tcf_gact_init(struct net *net, struct nlattr *nla,
 #endif
 
 	if (!tcf_hash_check(parm->index, a, bind)) {
-		ret = tcf_hash_create(parm->index, est, a, sizeof(*gact), bind);
+		ret = tcf_hash_create(parm->index, est, a, sizeof(*gact),
+				      bind, true);
 		if (ret)
 			return ret;
 		ret = ACT_P_CREATED;
@@ -99,16 +104,19 @@ static int tcf_gact_init(struct net *net, struct nlattr *nla,
 
 	gact = to_gact(a);
 
-	spin_lock_bh(&gact->tcf_lock);
+	ASSERT_RTNL();
 	gact->tcf_action = parm->action;
 #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
-	spin_unlock_bh(&gact->tcf_lock);
 	if (ret == ACT_P_CREATED)
 		tcf_hash_insert(a);
 	return ret;
@@ -118,23 +126,21 @@ static int tcf_gact(struct sk_buff *skb, const struct tc_action *a,
 		    struct tcf_result *res)
 {
 	struct tcf_gact *gact = a->priv;
-	int action = TC_ACT_SHOT;
+	int action = READ_ONCE(gact->tcf_action);
 
-	spin_lock(&gact->tcf_lock);
 #ifdef CONFIG_GACT_PROB
-	if (gact->tcfg_ptype)
-		action = gact_rand[gact->tcfg_ptype](gact);
-	else
-		action = gact->tcf_action;
-#else
-	action = gact->tcf_action;
+	{
+	u32 ptype = READ_ONCE(gact->tcfg_ptype);
+
+	if (ptype)
+		action = gact_rand[ptype](gact);
+	}
 #endif
-	gact->tcf_bstats.bytes += qdisc_pkt_len(skb);
-	gact->tcf_bstats.packets++;
+	bstats_cpu_update(this_cpu_ptr(gact->common.cpu_bstats), skb);
 	if (action == TC_ACT_SHOT)
-		gact->tcf_qstats.drops++;
-	gact->tcf_tm.lastuse = jiffies;
-	spin_unlock(&gact->tcf_lock);
+		qstats_drop_inc(this_cpu_ptr(gact->common.cpu_qstats));
+
+	tcf_lastuse_update(&gact->tcf_tm);
 
 	return action;
 }

net/sched/act_ipt.c

@@ -114,7 +114,7 @@ static int tcf_ipt_init(struct net *net, struct nlattr *nla, struct nlattr *est,
 		index = nla_get_u32(tb[TCA_IPT_INDEX]);
 
 	if (!tcf_hash_check(index, a, bind) ) {
-		ret = tcf_hash_create(index, est, a, sizeof(*ipt), bind);
+		ret = tcf_hash_create(index, est, a, sizeof(*ipt), bind, false);
 		if (ret)
 			return ret;
 		ret = ACT_P_CREATED;

net/sched/act_mirred.c

@@ -35,9 +35,11 @@ static LIST_HEAD(mirred_list);
 static void tcf_mirred_release(struct tc_action *a, int bind)
 {
 	struct tcf_mirred *m = to_mirred(a);
+	struct net_device *dev = rcu_dereference_protected(m->tcfm_dev, 1);
+
 	list_del(&m->tcfm_list);
-	if (m->tcfm_dev)
-		dev_put(m->tcfm_dev);
+	if (dev)
+		dev_put(dev);
 }
 
 static const struct nla_policy mirred_policy[TCA_MIRRED_MAX + 1] = {
@@ -93,7 +95,8 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
 	if (!tcf_hash_check(parm->index, a, bind)) {
 		if (dev == NULL)
 			return -EINVAL;
-		ret = tcf_hash_create(parm->index, est, a, sizeof(*m), bind);
+		ret = tcf_hash_create(parm->index, est, a, sizeof(*m),
+				      bind, true);
 		if (ret)
 			return ret;
 		ret = ACT_P_CREATED;
@@ -105,18 +108,18 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
 	}
 	m = to_mirred(a);
 
-	spin_lock_bh(&m->tcf_lock);
+	ASSERT_RTNL();
 	m->tcf_action = parm->action;
 	m->tcfm_eaction = parm->eaction;
 	if (dev != NULL) {
 		m->tcfm_ifindex = parm->ifindex;
 		if (ret != ACT_P_CREATED)
-			dev_put(m->tcfm_dev);
+			dev_put(rcu_dereference_protected(m->tcfm_dev, 1));
 		dev_hold(dev);
-		m->tcfm_dev = dev;
+		rcu_assign_pointer(m->tcfm_dev, dev);
 		m->tcfm_ok_push = ok_push;
 	}
-	spin_unlock_bh(&m->tcf_lock);
+
 	if (ret == ACT_P_CREATED) {
 		list_add(&m->tcfm_list, &mirred_list);
 		tcf_hash_insert(a);
@@ -131,20 +134,22 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
 	struct tcf_mirred *m = a->priv;
 	struct net_device *dev;
 	struct sk_buff *skb2;
+	int retval, err;
 	u32 at;
-	int retval, err = 1;
 
-	spin_lock(&m->tcf_lock);
-	m->tcf_tm.lastuse = jiffies;
-	bstats_update(&m->tcf_bstats, skb);
+	tcf_lastuse_update(&m->tcf_tm);
+
+	bstats_cpu_update(this_cpu_ptr(m->common.cpu_bstats), skb);
 
-	dev = m->tcfm_dev;
-	if (!dev) {
-		printk_once(KERN_NOTICE "tc mirred: target device is gone\n");
+	rcu_read_lock();
+	retval = READ_ONCE(m->tcf_action);
+	dev = rcu_dereference(m->tcfm_dev);
+	if (unlikely(!dev)) {
+		pr_notice_once("tc mirred: target device is gone\n");
 		goto out;
 	}
 
-	if (!(dev->flags & IFF_UP)) {
+	if (unlikely(!(dev->flags & IFF_UP))) {
 		net_notice_ratelimited("tc mirred to Houston: device %s is down\n",
 				       dev->name);
 		goto out;
@@ -152,7 +157,7 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
 
 	at = G_TC_AT(skb->tc_verd);
 	skb2 = skb_clone(skb, GFP_ATOMIC);
-	if (skb2 == NULL)
+	if (!skb2)
 		goto out;
 
 	if (!(at & AT_EGRESS)) {
@@ -168,16 +173,13 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
 	skb2->dev = dev;
 	err = dev_queue_xmit(skb2);
 
-out:
 	if (err) {
-		m->tcf_qstats.overlimits++;
+out:
+		qstats_overlimit_inc(this_cpu_ptr(m->common.cpu_qstats));
 		if (m->tcfm_eaction != TCA_EGRESS_MIRROR)
 			retval = TC_ACT_SHOT;
-		else
-			retval = m->tcf_action;
-	} else
-		retval = m->tcf_action;
-	spin_unlock(&m->tcf_lock);
+	}
+	rcu_read_unlock();
 
 	return retval;
 }
@@ -216,14 +218,16 @@ static int mirred_device_event(struct notifier_block *unused,
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 	struct tcf_mirred *m;
 
+	ASSERT_RTNL();
 	if (event == NETDEV_UNREGISTER)
 		list_for_each_entry(m, &mirred_list, tcfm_list) {
-			spin_lock_bh(&m->tcf_lock);
-			if (m->tcfm_dev == dev) {
+			if (rcu_access_pointer(m->tcfm_dev) == dev) {
 				dev_put(dev);
-				m->tcfm_dev = NULL;
+				/* Note : no rcu grace period necessary, as
+				 * net_device are already rcu protected.
+				 */
+				RCU_INIT_POINTER(m->tcfm_dev, NULL);
 			}
-			spin_unlock_bh(&m->tcf_lock);
 		}
 
 	return NOTIFY_DONE;

net/sched/act_nat.c

@@ -55,7 +55,8 @@ static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
 	parm = nla_data(tb[TCA_NAT_PARMS]);
 
 	if (!tcf_hash_check(parm->index, a, bind)) {
-		ret = tcf_hash_create(parm->index, est, a, sizeof(*p), bind);
+		ret = tcf_hash_create(parm->index, est, a, sizeof(*p),
+				      bind, false);
 		if (ret)
 			return ret;
 		ret = ACT_P_CREATED;

net/sched/act_pedit.c

@@ -57,7 +57,8 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 	if (!tcf_hash_check(parm->index, a, bind)) {
 		if (!parm->nkeys)
 			return -EINVAL;
-		ret = tcf_hash_create(parm->index, est, a, sizeof(*p), bind);
+		ret = tcf_hash_create(parm->index, est, a, sizeof(*p),
+				      bind, false);
 		if (ret)
 			return ret;
 		p = to_pedit(a);

net/sched/act_simple.c

@@ -103,7 +103,8 @@ static int tcf_simp_init(struct net *net, struct nlattr *nla,
 	defdata = nla_data(tb[TCA_DEF_DATA]);
 
 	if (!tcf_hash_check(parm->index, a, bind)) {
-		ret = tcf_hash_create(parm->index, est, a, sizeof(*d), bind);
+		ret = tcf_hash_create(parm->index, est, a, sizeof(*d),
+				      bind, false);
 		if (ret)
 			return ret;
 

net/sched/act_skbedit.c

@@ -99,7 +99,8 @@ static int tcf_skbedit_init(struct net *net, struct nlattr *nla,
 	parm = nla_data(tb[TCA_SKBEDIT_PARMS]);
 
 	if (!tcf_hash_check(parm->index, a, bind)) {
-		ret = tcf_hash_create(parm->index, est, a, sizeof(*d), bind);
+		ret = tcf_hash_create(parm->index, est, a, sizeof(*d),
+				      bind, false);
 		if (ret)
 			return ret;
 

net/sched/act_vlan.c

@@ -116,7 +116,8 @@ static int tcf_vlan_init(struct net *net, struct nlattr *nla,
 	action = parm->v_action;
 
 	if (!tcf_hash_check(parm->index, a, bind)) {
-		ret = tcf_hash_create(parm->index, est, a, sizeof(*v), bind);
+		ret = tcf_hash_create(parm->index, est, a, sizeof(*v),
+				      bind, false);
 		if (ret)
 			return ret;