tun: use per cpu variables for stats accounting

Currently the tun device accounting uses dev->stats without applying any
kind of protection, regardless that accounting happens in preemptible
process context.
This patch move the tun stats to a per cpu data structure, and protect
the updates with  u64_stats_update_begin()/u64_stats_update_end() or
this_cpu_inc according to the stat type. The per cpu stats are
aggregated by the newly added ndo_get_stats64 ops.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index a746616..faf9297 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -131,6 +131,17 @@ struct tap_filter {
 
 #define TUN_FLOW_EXPIRE (3 * HZ)
 
+struct tun_pcpu_stats {
+       u64 rx_packets;
+       u64 rx_bytes;
+       u64 tx_packets;
+       u64 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
@@ -205,6 +216,7 @@ struct tun_struct {
        struct list_head disabled;
        void *security;
        u32 flow_count;
+       struct tun_pcpu_stats __percpu *pcpu_stats;
 };
 
 #ifdef CONFIG_TUN_VNET_CROSS_LE
@@ -886,7 +898,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev)
        return NETDEV_TX_OK;
 
 drop:
-       dev->stats.tx_dropped++;
+       this_cpu_inc(tun->pcpu_stats->tx_dropped);
        skb_tx_error(skb);
        kfree_skb(skb);
        rcu_read_unlock();
@@ -949,6 +961,43 @@ static void tun_set_headroom(struct net_device *dev, int new_hr)
        tun->align = new_hr;
 }
 
+static struct rtnl_link_stats64 *
+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       = p->rx_packets;
+                       rxbytes         = p->rx_bytes;
+                       txpackets       = p->tx_packets;
+                       txbytes         = p->tx_bytes;
+               } while (u64_stats_fetch_retry(&p->syncp, start));
+
+               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;
+       return stats;
+}
+
 static const struct net_device_ops tun_netdev_ops = {
        .ndo_uninit             = tun_net_uninit,
        .ndo_open               = tun_net_open,
@@ -961,6 +1010,7 @@ static const struct net_device_ops tun_netdev_ops = {
        .ndo_poll_controller    = tun_poll_controller,
 #endif
        .ndo_set_rx_headroom    = tun_set_headroom,
+       .ndo_get_stats64        = tun_net_get_stats64,
 };
 
 static const struct net_device_ops tap_netdev_ops = {
@@ -979,6 +1029,7 @@ static const struct net_device_ops tap_netdev_ops = {
 #endif
        .ndo_features_check     = passthru_features_check,
        .ndo_set_rx_headroom    = tun_set_headroom,
+       .ndo_get_stats64        = tun_net_get_stats64,
 };
 
 static void tun_flow_init(struct tun_struct *tun)
@@ -1103,6 +1154,7 @@ 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;
@@ -1177,7 +1229,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
        skb = tun_alloc_skb(tfile, align, copylen, linear, noblock);
        if (IS_ERR(skb)) {
                if (PTR_ERR(skb) != -EAGAIN)
-                       tun->dev->stats.rx_dropped++;
+                       this_cpu_inc(tun->pcpu_stats->rx_dropped);
                return PTR_ERR(skb);
        }
 
@@ -1192,7 +1244,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
        }
 
        if (err) {
-               tun->dev->stats.rx_dropped++;
+               this_cpu_inc(tun->pcpu_stats->rx_dropped);
                kfree_skb(skb);
                return -EFAULT;
        }
@@ -1200,7 +1252,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
        if (gso.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
                if (!skb_partial_csum_set(skb, tun16_to_cpu(tun, gso.csum_start),
                                          tun16_to_cpu(tun, gso.csum_offset))) {
-                       tun->dev->stats.rx_frame_errors++;
+                       this_cpu_inc(tun->pcpu_stats->rx_frame_errors);
                        kfree_skb(skb);
                        return -EINVAL;
                }
@@ -1217,7 +1269,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
                                pi.proto = htons(ETH_P_IPV6);
                                break;
                        default:
-                               tun->dev->stats.rx_dropped++;
+                               this_cpu_inc(tun->pcpu_stats->rx_dropped);
                                kfree_skb(skb);
                                return -EINVAL;
                        }
@@ -1245,7 +1297,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
                        skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
                        break;
                default:
-                       tun->dev->stats.rx_frame_errors++;
+                       this_cpu_inc(tun->pcpu_stats->rx_frame_errors);
                        kfree_skb(skb);
                        return -EINVAL;
                }
@@ -1255,7 +1307,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 
                skb_shinfo(skb)->gso_size = tun16_to_cpu(tun, gso.gso_size);
                if (skb_shinfo(skb)->gso_size == 0) {
-                       tun->dev->stats.rx_frame_errors++;
+                       this_cpu_inc(tun->pcpu_stats->rx_frame_errors);
                        kfree_skb(skb);
                        return -EINVAL;
                }
@@ -1278,8 +1330,12 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
        rxhash = skb_get_hash(skb);
        netif_rx_ni(skb);
 
-       tun->dev->stats.rx_packets++;
-       tun->dev->stats.rx_bytes += len;
+       stats = get_cpu_ptr(tun->pcpu_stats);
+       u64_stats_update_begin(&stats->syncp);
+       stats->rx_packets++;
+       stats->rx_bytes += len;
+       u64_stats_update_end(&stats->syncp);
+       put_cpu_ptr(stats);
 
        tun_flow_update(tun, rxhash, tfile);
        return total_len;
@@ -1308,6 +1364,7 @@ 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;
@@ -1408,8 +1465,13 @@ static ssize_t tun_put_user(struct tun_struct *tun,
        skb_copy_datagram_iter(skb, vlan_offset, iter, skb->len - vlan_offset);
 
 done:
-       tun->dev->stats.tx_packets++;
-       tun->dev->stats.tx_bytes += skb->len + vlan_hlen;
+       /* caller is in process context, */
+       stats = get_cpu_ptr(tun->pcpu_stats);
+       u64_stats_update_begin(&stats->syncp);
+       stats->tx_packets++;
+       stats->tx_bytes += skb->len + vlan_hlen;
+       u64_stats_update_end(&stats->syncp);
+       put_cpu_ptr(tun->pcpu_stats);
 
        return total;
 }
@@ -1467,6 +1529,7 @@ static void tun_free_netdev(struct net_device *dev)
        struct tun_struct *tun = netdev_priv(dev);
 
        BUG_ON(!(list_empty(&tun->disabled)));
+       free_percpu(tun->pcpu_stats);
        tun_flow_uninit(tun);
        security_tun_dev_free_security(tun->security);
        free_netdev(dev);
@@ -1715,11 +1778,17 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
                tun->filter_attached = false;
                tun->sndbuf = tfile->socket.sk->sk_sndbuf;
 
+               tun->pcpu_stats = netdev_alloc_pcpu_stats(struct tun_pcpu_stats);
+               if (!tun->pcpu_stats) {
+                       err = -ENOMEM;
+                       goto err_free_dev;
+               }
+
                spin_lock_init(&tun->lock);
 
                err = security_tun_dev_alloc_security(&tun->security);
                if (err < 0)
-                       goto err_free_dev;
+                       goto err_free_stat;
 
                tun_net_init(dev);
                tun_flow_init(tun);
@@ -1763,6 +1832,8 @@ err_detach:
 err_free_flow:
        tun_flow_uninit(tun);
        security_tun_dev_free_security(tun->security);
+err_free_stat:
+       free_percpu(tun->pcpu_stats);
 err_free_dev:
        free_netdev(dev);
        return err;