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Subject: [PATCH net-next v2 01/12] net: add function dev_fetch_sw_netstats for
 fetching pcpu_sw_netstats
From:   Heiner Kallweit <hkallweit1@gmail.com>
To:     David Miller <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        =?UTF-8?Q?Bj=c3=b8rn_Mork?= <bjorn@mork.no>,
        Oliver Neukum <oneukum@suse.com>,
        Igor Mitsyanko <imitsyanko@quantenna.com>,
        Sergey Matyukevich <geomatsi@gmail.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        Roopa Prabhu <roopa@nvidia.com>,
        Nikolay Aleksandrov <nikolay@nvidia.com>,
        Andrew Lunn <andrew@lunn.ch>,
        Vivien Didelot <vivien.didelot@gmail.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Vladimir Oltean <olteanv@gmail.com>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Johannes Berg <johannes@sipsolutions.net>,
        Pravin B Shelar <pshelar@ovn.org>,
        Steffen Klassert <steffen.klassert@secunet.com>,
        Herbert Xu <herbert@gondor.apana.org.au>
Cc:     "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        linux-rdma@vger.kernel.org,
        Linux USB Mailing List <linux-usb@vger.kernel.org>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        bridge@lists.linux-foundation.org
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Date:   Mon, 12 Oct 2020 10:01:27 +0200
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In several places the same code is used to populate rtnl_link_stats64
fields with data from pcpu_sw_netstats. Therefore factor out this code
to a new function dev_fetch_sw_netstats().

v2:
- constify argument netstats
- don't ignore netstats being NULL or an ERRPTR
- switch to EXPORT_SYMBOL_GPL

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 include/linux/netdevice.h |  2 ++
 net/core/dev.c            | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a0df43b13..fa1d8d624 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -4495,6 +4495,8 @@ struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
 					struct rtnl_link_stats64 *storage);
 void netdev_stats_to_stats64(struct rtnl_link_stats64 *stats64,
 			     const struct net_device_stats *netdev_stats);
+void dev_fetch_sw_netstats(struct rtnl_link_stats64 *s,
+			   const struct pcpu_sw_netstats __percpu *netstats);
 
 extern int		netdev_max_backlog;
 extern int		netdev_tstamp_prequeue;
diff --git a/net/core/dev.c b/net/core/dev.c
index a146bac84..26bc10dec 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10319,6 +10319,40 @@ struct rtnl_link_stats64 *dev_get_stats(struct net_device *dev,
 }
 EXPORT_SYMBOL(dev_get_stats);
 
+/**
+ *	dev_fetch_sw_netstats - get per-cpu network device statistics
+ *	@s: place to store stats
+ *	@netstats: per-cpu network stats to read from
+ *
+ *	Read per-cpu network statistics and populate the related fields in @s.
+ */
+void dev_fetch_sw_netstats(struct rtnl_link_stats64 *s,
+			   const struct pcpu_sw_netstats __percpu *netstats)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		const struct pcpu_sw_netstats *stats;
+		struct pcpu_sw_netstats tmp;
+		unsigned int start;
+
+		stats = per_cpu_ptr(netstats, cpu);
+		do {
+			start = u64_stats_fetch_begin_irq(&stats->syncp);
+			tmp.rx_packets = stats->rx_packets;
+			tmp.rx_bytes   = stats->rx_bytes;
+			tmp.tx_packets = stats->tx_packets;
+			tmp.tx_bytes   = stats->tx_bytes;
+		} while (u64_stats_fetch_retry_irq(&stats->syncp, start));
+
+		s->rx_packets += tmp.rx_packets;
+		s->rx_bytes   += tmp.rx_bytes;
+		s->tx_packets += tmp.tx_packets;
+		s->tx_bytes   += tmp.tx_bytes;
+	}
+}
+EXPORT_SYMBOL_GPL(dev_fetch_sw_netstats);
+
 struct netdev_queue *dev_ingress_queue_create(struct net_device *dev)
 {
 	struct netdev_queue *queue = dev_ingress_queue(dev);
-- 
2.28.0