net: xfrm: use core API for updating/providing stats

Commit d3fd654 ("net: core: add dev_sw_netstats_tx_add") has added
function "dev_sw_netstats_tx_add()" to update net device per-cpu TX
stats.

Use this function instead of own code.

While on it, remove xfrmi_get_stats64() and replace it with
dev_get_tstats64().

Signed-off-by: Lev Stipakov <lev@openvpn.net>
Reviewed-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/20201113215939.147007-1-lev@openvpn.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: lstipakov

net/xfrm/xfrm_interface.c

@@ -319,12 +319,7 @@ xfrmi_xmit2(struct sk_buff *skb, struct net_device *dev, struct flowi *fl)
 
 	err = dst_output(xi->net, skb->sk, skb);
 	if (net_xmit_eval(err) == 0) {
-		struct pcpu_sw_netstats *tstats = this_cpu_ptr(dev->tstats);
-
-		u64_stats_update_begin(&tstats->syncp);
-		tstats->tx_bytes += length;
-		tstats->tx_packets++;
-		u64_stats_update_end(&tstats->syncp);
+		dev_sw_netstats_tx_add(dev, 1, length);
 	} else {
 		stats->tx_errors++;
 		stats->tx_aborted_errors++;
@@ -538,28 +533,18 @@ static int xfrmi_update(struct xfrm_if *xi, struct xfrm_if_parms *p)
 	return err;
 }
 
-static void xfrmi_get_stats64(struct net_device *dev,
-			       struct rtnl_link_stats64 *s)
-{
-	dev_fetch_sw_netstats(s, dev->tstats);
-
-	s->rx_dropped = dev->stats.rx_dropped;
-	s->tx_dropped = dev->stats.tx_dropped;
-}
-
 static int xfrmi_get_iflink(const struct net_device *dev)
 {
 	struct xfrm_if *xi = netdev_priv(dev);
 
 	return xi->p.link;
 }
 
-
 static const struct net_device_ops xfrmi_netdev_ops = {
 	.ndo_init	= xfrmi_dev_init,
 	.ndo_uninit	= xfrmi_dev_uninit,
 	.ndo_start_xmit = xfrmi_xmit,
-	.ndo_get_stats64 = xfrmi_get_stats64,
+	.ndo_get_stats64 = dev_get_tstats64,
 	.ndo_get_iflink = xfrmi_get_iflink,
 };