openwrt/target/linux/generic/backport-6.12/621-v6.17-ppp-convert-to-percpu-netstats.patch

From 1a3e9b7a6b09e8ab3d2af019e4a392622685855e Mon Sep 17 00:00:00 2001
From: Qingfang Deng <dqfext@gmail.com>
Date: Tue, 10 Jun 2025 16:32:10 +0800
Subject: [PATCH] ppp: convert to percpu netstats

Convert to percpu netstats to avoid lock contention when reading them.

Signed-off-by: Qingfang Deng <dqfext@gmail.com>
Link: https://patch.msgid.link/20250610083211.909015-1-dqfext@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 drivers/net/ppp/ppp_generic.c | 52 +++++++++++++----------------------
 1 file changed, 19 insertions(+), 33 deletions(-)

--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -108,18 +108,6 @@ struct ppp_file {
 #define PF_TO_CHANNEL(pf)	PF_TO_X(pf, struct channel)
 
 /*
- * Data structure to hold primary network stats for which
- * we want to use 64 bit storage.  Other network stats
- * are stored in dev->stats of the ppp strucute.
- */
-struct ppp_link_stats {
-	u64 rx_packets;
-	u64 tx_packets;
-	u64 rx_bytes;
-	u64 tx_bytes;
-};
-
-/*
  * Data structure describing one ppp unit.
  * A ppp unit corresponds to a ppp network interface device
  * and represents a multilink bundle.
@@ -162,7 +150,6 @@ struct ppp {
 	struct bpf_prog *active_filter; /* filter for pkts to reset idle */
 #endif /* CONFIG_PPP_FILTER */
 	struct net	*ppp_net;	/* the net we belong to */
-	struct ppp_link_stats stats64;	/* 64 bit network stats */
 };
 
 /*
@@ -1544,23 +1531,12 @@ ppp_net_siocdevprivate(struct net_device
 static void
 ppp_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats64)
 {
-	struct ppp *ppp = netdev_priv(dev);
-
-	ppp_recv_lock(ppp);
-	stats64->rx_packets = ppp->stats64.rx_packets;
-	stats64->rx_bytes   = ppp->stats64.rx_bytes;
-	ppp_recv_unlock(ppp);
-
-	ppp_xmit_lock(ppp);
-	stats64->tx_packets = ppp->stats64.tx_packets;
-	stats64->tx_bytes   = ppp->stats64.tx_bytes;
-	ppp_xmit_unlock(ppp);
-
 	stats64->rx_errors        = dev->stats.rx_errors;
 	stats64->tx_errors        = dev->stats.tx_errors;
 	stats64->rx_dropped       = dev->stats.rx_dropped;
 	stats64->tx_dropped       = dev->stats.tx_dropped;
 	stats64->rx_length_errors = dev->stats.rx_length_errors;
+	dev_fetch_sw_netstats(stats64, dev->tstats);
 }
 
 static int ppp_dev_init(struct net_device *dev)
@@ -1658,6 +1634,7 @@ static void ppp_setup(struct net_device
 	dev->type = ARPHRD_PPP;
 	dev->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
 	dev->priv_destructor = ppp_dev_priv_destructor;
+	dev->pcpu_stat_type = NETDEV_PCPU_STAT_TSTATS;
 	netif_keep_dst(dev);
 }
 
@@ -1803,8 +1780,7 @@ ppp_send_frame(struct ppp *ppp, struct s
 #endif /* CONFIG_PPP_FILTER */
 	}
 
-	++ppp->stats64.tx_packets;
-	ppp->stats64.tx_bytes += skb->len - PPP_PROTO_LEN;
+	dev_sw_netstats_tx_add(ppp->dev, 1, skb->len - PPP_PROTO_LEN);
 
 	switch (proto) {
 	case PPP_IP:
@@ -2482,8 +2458,7 @@ ppp_receive_nonmp_frame(struct ppp *ppp,
 		break;
 	}
 
-	++ppp->stats64.rx_packets;
-	ppp->stats64.rx_bytes += skb->len - 2;
+	dev_sw_netstats_rx_add(ppp->dev, skb->len - PPP_PROTO_LEN);
 
 	npi = proto_to_npindex(proto);
 	if (npi < 0) {
@@ -3311,14 +3286,25 @@ static void
 ppp_get_stats(struct ppp *ppp, struct ppp_stats *st)
 {
 	struct slcompress *vj = ppp->vj;
+	int cpu;
 
 	memset(st, 0, sizeof(*st));
-	st->p.ppp_ipackets = ppp->stats64.rx_packets;
+	for_each_possible_cpu(cpu) {
+		struct pcpu_sw_netstats *p = per_cpu_ptr(ppp->dev->tstats, cpu);
+		u64 rx_packets, rx_bytes, tx_packets, tx_bytes;
+
+		rx_packets = u64_stats_read(&p->rx_packets);
+		rx_bytes = u64_stats_read(&p->rx_bytes);
+		tx_packets = u64_stats_read(&p->tx_packets);
+		tx_bytes = u64_stats_read(&p->tx_bytes);
+
+		st->p.ppp_ipackets += rx_packets;
+		st->p.ppp_ibytes += rx_bytes;
+		st->p.ppp_opackets += tx_packets;
+		st->p.ppp_obytes += tx_bytes;
+	}
 	st->p.ppp_ierrors = ppp->dev->stats.rx_errors;
-	st->p.ppp_ibytes = ppp->stats64.rx_bytes;
-	st->p.ppp_opackets = ppp->stats64.tx_packets;
 	st->p.ppp_oerrors = ppp->dev->stats.tx_errors;
-	st->p.ppp_obytes = ppp->stats64.tx_bytes;
 	if (!vj)
 		return;
 	st->vj.vjs_packets = vj->sls_o_compressed + vj->sls_o_uncompressed;