net: add dev_txq_stats_fold() helper

Some drivers ndo_get_stats() method need to perform txqueue stats folding.

Move folding from dev_get_stats() to a new dev_txq_stats_fold() function
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/netdevice.h

@@ -1941,6 +1941,7 @@ extern void		netdev_features_change(struct net_device *dev);
 extern void		dev_load(struct net *net, const char *name);
 extern void		dev_mcast_init(void);
 extern const struct net_device_stats *dev_get_stats(struct net_device *dev);
+extern void		dev_txq_stats_fold(const struct net_device *dev, struct net_device_stats *stats);
 
 extern int		netdev_max_backlog;
 extern int		weight_p;

net/core/dev.c

@@ -5169,22 +5169,14 @@ void netdev_run_todo(void)
 }
 
 /**
- *	dev_get_stats	- get network device statistics
+ *	dev_txq_stats_fold - fold tx_queues stats
  *	@dev: device to get statistics from
- *
- *	Get network statistics from device. The device driver may provide
- *	its own method by setting dev->netdev_ops->get_stats; otherwise
- *	the internal statistics structure is used.
+ *	@stats: struct net_device_stats to hold results
  */
-const struct net_device_stats *dev_get_stats(struct net_device *dev)
+void dev_txq_stats_fold(const struct net_device *dev,
+			struct net_device_stats *stats)
 {
-	const struct net_device_ops *ops = dev->netdev_ops;
-
-	if (ops->ndo_get_stats)
-		return ops->ndo_get_stats(dev);
-	else {
 	unsigned long tx_bytes = 0, tx_packets = 0, tx_dropped = 0;
-		struct net_device_stats *stats = &dev->stats;
 	unsigned int i;
 	struct netdev_queue *txq;
 
@@ -5199,8 +5191,26 @@ const struct net_device_stats *dev_get_stats(struct net_device *dev)
 		stats->tx_packets = tx_packets;
 		stats->tx_dropped = tx_dropped;
 	}
-		return stats;
-	}
+}
+EXPORT_SYMBOL(dev_txq_stats_fold);
+
+/**
+ *	dev_get_stats	- get network device statistics
+ *	@dev: device to get statistics from
+ *
+ *	Get network statistics from device. The device driver may provide
+ *	its own method by setting dev->netdev_ops->get_stats; otherwise
+ *	the internal statistics structure is used.
+ */
+const struct net_device_stats *dev_get_stats(struct net_device *dev)
+{
+	const struct net_device_ops *ops = dev->netdev_ops;
+
+	if (ops->ndo_get_stats)
+		return ops->ndo_get_stats(dev);
+
+	dev_txq_stats_fold(dev, &dev->stats);
+	return &dev->stats;
 }
 EXPORT_SYMBOL(dev_get_stats);