netdevsim: migrate to dstats stats collection

Replace custom statistics tracking with the kernel's dstats infrastructure
to simplify code and improve consistency with other network drivers.

This change:
- Sets dev->pcpu_stat_type = NETDEV_PCPU_STAT_DSTATS for automatic
  automatic allocation and deallocation.
- Removes manual stats fields and their update
- Replaces custom nsim_get_stats64() with dev_get_stats()
- Uses dev_dstats_tx_add() and dev_dstats_tx_dropped() helpers
- Eliminates the need for manual synchronization primitives

The dstats framework provides the same functionality with less code.

Suggested-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Joe Damato <joe@dama.to>
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20250618-netdevsim_stat-v4-1-19fe0d35e28e@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 6 insertions, 32 deletions

diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
index fa5fbd97ad69..5010d8eefc85 100644
--- a/drivers/net/netdevsim/netdev.c
+++ b/drivers/net/netdevsim/netdev.c
@@ -93,19 +93,14 @@ static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		hrtimer_start(&rq->napi_timer, us_to_ktime(5), HRTIMER_MODE_REL);
 
 	rcu_read_unlock();
-	u64_stats_update_begin(&ns->syncp);
-	ns->tx_packets++;
-	ns->tx_bytes += len;
-	u64_stats_update_end(&ns->syncp);
+	dev_dstats_tx_add(dev, skb->len);
 	return NETDEV_TX_OK;
 
 out_drop_free:
 	dev_kfree_skb(skb);
 out_drop_cnt:
 	rcu_read_unlock();
-	u64_stats_update_begin(&ns->syncp);
-	ns->tx_dropped++;
-	u64_stats_update_end(&ns->syncp);
+	dev_dstats_tx_dropped(dev);
 	return NETDEV_TX_OK;
 }
 
@@ -126,20 +121,6 @@ static int nsim_change_mtu(struct net_device *dev, int new_mtu)
 	return 0;
 }
 
-static void
-nsim_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
-{
-	struct netdevsim *ns = netdev_priv(dev);
-	unsigned int start;
-
-	do {
-		start = u64_stats_fetch_begin(&ns->syncp);
-		stats->tx_bytes = ns->tx_bytes;
-		stats->tx_packets = ns->tx_packets;
-		stats->tx_dropped = ns->tx_dropped;
-	} while (u64_stats_fetch_retry(&ns->syncp, start));
-}
-
 static int
 nsim_setup_tc_block_cb(enum tc_setup_type type, void *type_data, void *cb_priv)
 {
@@ -556,7 +537,6 @@ static const struct net_device_ops nsim_netdev_ops = {
 	.ndo_set_mac_address	= eth_mac_addr,
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_change_mtu		= nsim_change_mtu,
-	.ndo_get_stats64	= nsim_get_stats64,
 	.ndo_set_vf_mac		= nsim_set_vf_mac,
 	.ndo_set_vf_vlan	= nsim_set_vf_vlan,
 	.ndo_set_vf_rate	= nsim_set_vf_rate,
@@ -580,7 +560,6 @@ static const struct net_device_ops nsim_vf_netdev_ops = {
 	.ndo_set_mac_address	= eth_mac_addr,
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_change_mtu		= nsim_change_mtu,
-	.ndo_get_stats64	= nsim_get_stats64,
 	.ndo_setup_tc		= nsim_setup_tc,
 	.ndo_set_features	= nsim_set_features,
 };
@@ -594,7 +573,7 @@ static void nsim_get_queue_stats_rx(struct net_device *dev, int idx,
 	struct rtnl_link_stats64 rtstats = {};
 
 	if (!idx)
-		nsim_get_stats64(dev, &rtstats);
+		dev_get_stats(dev, &rtstats);
 
 	stats->packets = rtstats.rx_packets - !!rtstats.rx_packets;
 	stats->bytes = rtstats.rx_bytes;
@@ -606,7 +585,7 @@ static void nsim_get_queue_stats_tx(struct net_device *dev, int idx,
 	struct rtnl_link_stats64 rtstats = {};
 
 	if (!idx)
-		nsim_get_stats64(dev, &rtstats);
+		dev_get_stats(dev, &rtstats);
 
 	stats->packets = rtstats.tx_packets - !!rtstats.tx_packets;
 	stats->bytes = rtstats.tx_bytes;
@@ -618,7 +597,7 @@ static void nsim_get_base_stats(struct net_device *dev,
 {
 	struct rtnl_link_stats64 rtstats = {};
 
-	nsim_get_stats64(dev, &rtstats);
+	dev_get_stats(dev, &rtstats);
 
 	rx->packets = !!rtstats.rx_packets;
 	rx->bytes = 0;
@@ -890,6 +869,7 @@ static void nsim_setup(struct net_device *dev)
 			    NETIF_F_HW_CSUM |
 			    NETIF_F_LRO |
 			    NETIF_F_TSO;
+	dev->pcpu_stat_type = NETDEV_PCPU_STAT_DSTATS;
 	dev->max_mtu = ETH_MAX_MTU;
 	dev->xdp_features = NETDEV_XDP_ACT_HW_OFFLOAD;
 }
@@ -1022,7 +1002,6 @@ nsim_create(struct nsim_dev *nsim_dev, struct nsim_dev_port *nsim_dev_port)
 	dev_net_set(dev, nsim_dev_net(nsim_dev));
 	ns = netdev_priv(dev);
 	ns->netdev = dev;
-	u64_stats_init(&ns->syncp);
 	ns->nsim_dev = nsim_dev;
 	ns->nsim_dev_port = nsim_dev_port;
 	ns->nsim_bus_dev = nsim_dev->nsim_bus_dev;
diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h
index 511ed72a93ce..4a0c48c7a384 100644
--- a/drivers/net/netdevsim/netdevsim.h
+++ b/drivers/net/netdevsim/netdevsim.h
@@ -108,11 +108,6 @@ struct netdevsim {
 
 	int rq_reset_mode;
 
-	u64 tx_packets;
-	u64 tx_bytes;
-	u64 tx_dropped;
-	struct u64_stats_sync syncp;
-
 	struct nsim_bus_dev *nsim_bus_dev;
 
 	struct bpf_prog	*bpf_offloaded;