net/mlx4_en: fix tx_dropped bug

1) mlx4_en_xmit() can increment priv->stats.tx_dropped, but this variable
is overwritten in mlx4_en_DUMP_ETH_STATS().

2) This increment was not SMP safe, as a port might have many TX queues.

Add a per TX ring tx_dropped to fix these issues.

This is u32 as mlx4_en_DUMP_ETH_STATS() will add a 32bit field.

So lets avoid bugs with SNMP agents having to cope with partial
overwraps. (One of these agents being bond_fold_stats())

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Willem de Bruijn <willemb@google.com>
Cc: Eugenia Emantayev <eugenia@mellanox.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index f6e61570cb2c..76aa4d27183c 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -726,12 +726,12 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 	bool inline_ok;
 	u32 ring_cons;
 
-	if (!priv->port_up)
-		goto tx_drop;
-
 	tx_ind = skb_get_queue_mapping(skb);
 	ring = priv->tx_ring[tx_ind];
 
+	if (!priv->port_up)
+		goto tx_drop;
+
 	/* fetch ring->cons far ahead before needing it to avoid stall */
 	ring_cons = ACCESS_ONCE(ring->cons);
 
@@ -1030,7 +1030,7 @@ tx_drop_unmap:
 
 tx_drop:
 	dev_kfree_skb_any(skb);
-	priv->stats.tx_dropped++;
+	ring->tx_dropped++;
 	return NETDEV_TX_OK;
 }