tun: switch to net core provided statistics counters

Switch tun to the standard statistics pattern:
- use netdev->stats for the less frequently accessed counters
- use netdev->tstats for the frequently accessed per-cpu counters

v3:
- add atomic_long_t member rx_frame_errors for making counter updates
  atomic
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/tun.c

@@ -107,17 +107,6 @@ struct tap_filter {
 
 #define TUN_FLOW_EXPIRE (3 * HZ)
 
-struct tun_pcpu_stats {
-	u64_stats_t rx_packets;
-	u64_stats_t rx_bytes;
-	u64_stats_t tx_packets;
-	u64_stats_t tx_bytes;
-	struct u64_stats_sync syncp;
-	u32 rx_dropped;
-	u32 tx_dropped;
-	u32 rx_frame_errors;
-};
-
 /* A tun_file connects an open character device to a tuntap netdevice. It
  * also contains all socket related structures (except sock_fprog and tap_filter)
  * to serve as one transmit queue for tuntap device. The sock_fprog and
@@ -207,7 +196,7 @@ struct tun_struct {
 	void *security;
 	u32 flow_count;
 	u32 rx_batched;
-	struct tun_pcpu_stats __percpu *pcpu_stats;
+	atomic_long_t rx_frame_errors;
 	struct bpf_prog __rcu *xdp_prog;
 	struct tun_prog __rcu *steering_prog;
 	struct tun_prog __rcu *filter_prog;
@@ -1066,7 +1055,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
 	return NETDEV_TX_OK;
 
 drop:
-	this_cpu_inc(tun->pcpu_stats->tx_dropped);
+	atomic_long_inc(&dev->tx_dropped);
 	skb_tx_error(skb);
 	kfree_skb(skb);
 	rcu_read_unlock();
@@ -1103,37 +1092,12 @@ static void tun_set_headroom(struct net_device *dev, int new_hr)
 static void
 tun_net_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
 {
-	u32 rx_dropped = 0, tx_dropped = 0, rx_frame_errors = 0;
 	struct tun_struct *tun = netdev_priv(dev);
-	struct tun_pcpu_stats *p;
-	int i;
-
-	for_each_possible_cpu(i) {
-		u64 rxpackets, rxbytes, txpackets, txbytes;
-		unsigned int start;
 
-		p = per_cpu_ptr(tun->pcpu_stats, i);
-		do {
-			start = u64_stats_fetch_begin(&p->syncp);
-			rxpackets	= u64_stats_read(&p->rx_packets);
-			rxbytes		= u64_stats_read(&p->rx_bytes);
-			txpackets	= u64_stats_read(&p->tx_packets);
-			txbytes		= u64_stats_read(&p->tx_bytes);
-		} while (u64_stats_fetch_retry(&p->syncp, start));
+	dev_get_tstats64(dev, stats);
 
-		stats->rx_packets	+= rxpackets;
-		stats->rx_bytes		+= rxbytes;
-		stats->tx_packets	+= txpackets;
-		stats->tx_bytes		+= txbytes;
-
-		/* u32 counters */
-		rx_dropped	+= p->rx_dropped;
-		rx_frame_errors	+= p->rx_frame_errors;
-		tx_dropped	+= p->tx_dropped;
-	}
-	stats->rx_dropped  = rx_dropped;
-	stats->rx_frame_errors = rx_frame_errors;
-	stats->tx_dropped = tx_dropped;
+	stats->rx_frame_errors +=
+		(unsigned long)atomic_long_read(&tun->rx_frame_errors);
 }
 
 static int tun_xdp_set(struct net_device *dev, struct bpf_prog *prog,
@@ -1247,7 +1211,7 @@ static int tun_xdp_xmit(struct net_device *dev, int n,
 		void *frame = tun_xdp_to_ptr(xdp);
 
 		if (__ptr_ring_produce(&tfile->tx_ring, frame)) {
-			this_cpu_inc(tun->pcpu_stats->tx_dropped);
+			atomic_long_inc(&dev->tx_dropped);
 			xdp_return_frame_rx_napi(xdp);
 			drops++;
 		}
@@ -1283,7 +1247,7 @@ static const struct net_device_ops tap_netdev_ops = {
 	.ndo_select_queue	= tun_select_queue,
 	.ndo_features_check	= passthru_features_check,
 	.ndo_set_rx_headroom	= tun_set_headroom,
-	.ndo_get_stats64	= tun_net_get_stats64,
+	.ndo_get_stats64	= dev_get_tstats64,
 	.ndo_bpf		= tun_xdp,
 	.ndo_xdp_xmit		= tun_xdp_xmit,
 	.ndo_change_carrier	= tun_net_change_carrier,
@@ -1577,7 +1541,7 @@ static int tun_xdp_act(struct tun_struct *tun, struct bpf_prog *xdp_prog,
 		trace_xdp_exception(tun->dev, xdp_prog, act);
 		fallthrough;
 	case XDP_DROP:
-		this_cpu_inc(tun->pcpu_stats->rx_dropped);
+		atomic_long_inc(&tun->dev->rx_dropped);
 		break;
 	}
 
@@ -1683,7 +1647,6 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 	size_t total_len = iov_iter_count(from);
 	size_t len = total_len, align = tun->align, linear;
 	struct virtio_net_hdr gso = { 0 };
-	struct tun_pcpu_stats *stats;
 	int good_linear;
 	int copylen;
 	bool zerocopy = false;
@@ -1752,7 +1715,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 		 */
 		skb = tun_build_skb(tun, tfile, from, &gso, len, &skb_xdp);
 		if (IS_ERR(skb)) {
-			this_cpu_inc(tun->pcpu_stats->rx_dropped);
+			atomic_long_inc(&tun->dev->rx_dropped);
 			return PTR_ERR(skb);
 		}
 		if (!skb)
@@ -1781,7 +1744,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 
 		if (IS_ERR(skb)) {
 			if (PTR_ERR(skb) != -EAGAIN)
-				this_cpu_inc(tun->pcpu_stats->rx_dropped);
+				atomic_long_inc(&tun->dev->rx_dropped);
 			if (frags)
 				mutex_unlock(&tfile->napi_mutex);
 			return PTR_ERR(skb);
@@ -1795,7 +1758,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 		if (err) {
 			err = -EFAULT;
 drop:
-			this_cpu_inc(tun->pcpu_stats->rx_dropped);
+			atomic_long_inc(&tun->dev->rx_dropped);
 			kfree_skb(skb);
 			if (frags) {
 				tfile->napi.skb = NULL;
@@ -1807,7 +1770,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 	}
 
 	if (virtio_net_hdr_to_skb(skb, &gso, tun_is_little_endian(tun))) {
-		this_cpu_inc(tun->pcpu_stats->rx_frame_errors);
+		atomic_long_inc(&tun->rx_frame_errors);
 		kfree_skb(skb);
 		if (frags) {
 			tfile->napi.skb = NULL;
@@ -1830,7 +1793,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 				pi.proto = htons(ETH_P_IPV6);
 				break;
 			default:
-				this_cpu_inc(tun->pcpu_stats->rx_dropped);
+				atomic_long_inc(&tun->dev->rx_dropped);
 				kfree_skb(skb);
 				return -EINVAL;
 			}
@@ -1910,7 +1873,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 					  skb_headlen(skb));
 
 		if (unlikely(headlen > skb_headlen(skb))) {
-			this_cpu_inc(tun->pcpu_stats->rx_dropped);
+			atomic_long_inc(&tun->dev->rx_dropped);
 			napi_free_frags(&tfile->napi);
 			rcu_read_unlock();
 			mutex_unlock(&tfile->napi_mutex);
@@ -1942,12 +1905,9 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 	}
 	rcu_read_unlock();
 
-	stats = get_cpu_ptr(tun->pcpu_stats);
-	u64_stats_update_begin(&stats->syncp);
-	u64_stats_inc(&stats->rx_packets);
-	u64_stats_add(&stats->rx_bytes, len);
-	u64_stats_update_end(&stats->syncp);
-	put_cpu_ptr(stats);
+	preempt_disable();
+	dev_sw_netstats_rx_add(tun->dev, len);
+	preempt_enable();
 
 	if (rxhash)
 		tun_flow_update(tun, rxhash, tfile);
@@ -1979,7 +1939,6 @@ static ssize_t tun_put_user_xdp(struct tun_struct *tun,
 {
 	int vnet_hdr_sz = 0;
 	size_t size = xdp_frame->len;
-	struct tun_pcpu_stats *stats;
 	size_t ret;
 
 	if (tun->flags & IFF_VNET_HDR) {
@@ -1996,12 +1955,9 @@ static ssize_t tun_put_user_xdp(struct tun_struct *tun,
 
 	ret = copy_to_iter(xdp_frame->data, size, iter) + vnet_hdr_sz;
 
-	stats = get_cpu_ptr(tun->pcpu_stats);
-	u64_stats_update_begin(&stats->syncp);
-	u64_stats_inc(&stats->tx_packets);
-	u64_stats_add(&stats->tx_bytes, ret);
-	u64_stats_update_end(&stats->syncp);
-	put_cpu_ptr(tun->pcpu_stats);
+	preempt_disable();
+	dev_sw_netstats_tx_add(tun->dev, 1, ret);
+	preempt_enable();
 
 	return ret;
 }
@@ -2013,7 +1969,6 @@ static ssize_t tun_put_user(struct tun_struct *tun,
 			    struct iov_iter *iter)
 {
 	struct tun_pi pi = { 0, skb->protocol };
-	struct tun_pcpu_stats *stats;
 	ssize_t total;
 	int vlan_offset = 0;
 	int vlan_hlen = 0;
@@ -2091,12 +2046,9 @@ static ssize_t tun_put_user(struct tun_struct *tun,
 
 done:
 	/* caller is in process context, */
-	stats = get_cpu_ptr(tun->pcpu_stats);
-	u64_stats_update_begin(&stats->syncp);
-	u64_stats_inc(&stats->tx_packets);
-	u64_stats_add(&stats->tx_bytes, skb->len + vlan_hlen);
-	u64_stats_update_end(&stats->syncp);
-	put_cpu_ptr(tun->pcpu_stats);
+	preempt_disable();
+	dev_sw_netstats_tx_add(tun->dev, 1, skb->len + vlan_hlen);
+	preempt_enable();
 
 	return total;
 }
@@ -2235,11 +2187,11 @@ static void tun_free_netdev(struct net_device *dev)
 
 	BUG_ON(!(list_empty(&tun->disabled)));
 
-	free_percpu(tun->pcpu_stats);
-	/* We clear pcpu_stats so that tun_set_iff() can tell if
+	free_percpu(dev->tstats);
+	/* We clear tstats so that tun_set_iff() can tell if
 	 * tun_free_netdev() has been called from register_netdevice().
 	 */
-	tun->pcpu_stats = NULL;
+	dev->tstats = NULL;
 
 	tun_flow_uninit(tun);
 	security_tun_dev_free_security(tun->security);
@@ -2370,7 +2322,6 @@ static int tun_xdp_one(struct tun_struct *tun,
 	unsigned int datasize = xdp->data_end - xdp->data;
 	struct tun_xdp_hdr *hdr = xdp->data_hard_start;
 	struct virtio_net_hdr *gso = &hdr->gso;
-	struct tun_pcpu_stats *stats;
 	struct bpf_prog *xdp_prog;
 	struct sk_buff *skb = NULL;
 	u32 rxhash = 0, act;
@@ -2428,7 +2379,7 @@ static int tun_xdp_one(struct tun_struct *tun,
 	skb_put(skb, xdp->data_end - xdp->data);
 
 	if (virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
-		this_cpu_inc(tun->pcpu_stats->rx_frame_errors);
+		atomic_long_inc(&tun->rx_frame_errors);
 		kfree_skb(skb);
 		err = -EINVAL;
 		goto out;
@@ -2451,14 +2402,10 @@ static int tun_xdp_one(struct tun_struct *tun,
 
 	netif_receive_skb(skb);
 
-	/* No need for get_cpu_ptr() here since this function is
+	/* No need to disable preemption here since this function is
 	 * always called with bh disabled
 	 */
-	stats = this_cpu_ptr(tun->pcpu_stats);
-	u64_stats_update_begin(&stats->syncp);
-	u64_stats_inc(&stats->rx_packets);
-	u64_stats_add(&stats->rx_bytes, datasize);
-	u64_stats_update_end(&stats->syncp);
+	dev_sw_netstats_rx_add(tun->dev, datasize);
 
 	if (rxhash)
 		tun_flow_update(tun, rxhash, tfile);
@@ -2751,8 +2698,8 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 		tun->rx_batched = 0;
 		RCU_INIT_POINTER(tun->steering_prog, NULL);
 
-		tun->pcpu_stats = netdev_alloc_pcpu_stats(struct tun_pcpu_stats);
-		if (!tun->pcpu_stats) {
+		dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
+		if (!dev->tstats) {
 			err = -ENOMEM;
 			goto err_free_dev;
 		}
@@ -2807,16 +2754,16 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 	tun_detach_all(dev);
 	/* We are here because register_netdevice() has failed.
 	 * If register_netdevice() already called tun_free_netdev()
-	 * while dealing with the error, tun->pcpu_stats has been cleared.
+	 * while dealing with the error, dev->stats has been cleared.
 	 */
-	if (!tun->pcpu_stats)
+	if (!dev->tstats)
 		goto err_free_dev;
 
 err_free_flow:
 	tun_flow_uninit(tun);
 	security_tun_dev_free_security(tun->security);
 err_free_stat:
-	free_percpu(tun->pcpu_stats);
+	free_percpu(dev->tstats);
 err_free_dev:
 	free_netdev(dev);
 	return err;