net: usb: qmi_wwan: Leverage core stats allocator

With commit 34d21de9 ("net: Move {l,t,d}stats allocation to core and
convert veth & vrf"), stats allocation could be done on net core
instead of in this driver.

With this new approach, the driver doesn't have to bother with error
handling (allocation failure checking, making sure free happens in the
right spot, etc). This is core responsibility now.

Remove the allocation in the qmi_wwan driver and leverage the network
core allocation instead.
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20240409133307.2058099-1-leitao@debian.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/usb/qmi_wwan.c

@@ -133,6 +133,7 @@ static void qmimux_setup(struct net_device *dev)
 	dev->flags           = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
 	dev->netdev_ops      = &qmimux_netdev_ops;
 	dev->mtu             = 1500;
+	dev->pcpu_stat_type  = NETDEV_PCPU_STAT_TSTATS;
 	dev->needs_free_netdev = true;
 }
 
@@ -257,12 +258,6 @@ static int qmimux_register_device(struct net_device *real_dev, u8 mux_id)
 	priv->mux_id = mux_id;
 	priv->real_dev = real_dev;
 
-	new_dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
-	if (!new_dev->tstats) {
-		err = -ENOBUFS;
-		goto out_free_newdev;
-	}
-
 	new_dev->sysfs_groups[0] = &qmi_wwan_sysfs_qmimux_attr_group;
 
 	err = register_netdevice(new_dev);
@@ -295,7 +290,6 @@ static void qmimux_unregister_device(struct net_device *dev,
 	struct qmimux_priv *priv = netdev_priv(dev);
 	struct net_device *real_dev = priv->real_dev;
 
-	free_percpu(dev->tstats);
 	netdev_upper_dev_unlink(real_dev, dev);
 	unregister_netdevice_queue(dev, head);
 

drivers/net/usb/usbnet.c

@@ -1733,6 +1733,7 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 	dev->hard_mtu = net->mtu + net->hard_header_len;
 	net->min_mtu = 0;
 	net->max_mtu = ETH_MAX_MTU;
+	net->pcpu_stat_type = NETDEV_PCPU_STAT_TSTATS;
 
 	net->netdev_ops = &usbnet_netdev_ops;
 	net->watchdog_timeo = TX_TIMEOUT_JIFFIES;