mlx4: make validate_loopback() more generic

Testing a boolean in fast path is not worth duplicating
the code allocating packets, when GRO is on or off.

If this proves to be a problem, we might later use a jump label.

Next patch will remove this duplicated code and ease code review.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/en_rx.c

@@ -584,20 +584,17 @@ static struct sk_buff *mlx4_en_rx_skb(struct mlx4_en_priv *priv,
 	return skb;
 }
 
-static void validate_loopback(struct mlx4_en_priv *priv, struct sk_buff *skb)
+static void validate_loopback(struct mlx4_en_priv *priv, void *va)
 {
+	const unsigned char *data = va + ETH_HLEN;
 	int i;
-	int offset = ETH_HLEN;
 
-	for (i = 0; i < MLX4_LOOPBACK_TEST_PAYLOAD; i++, offset++) {
-		if (*(skb->data + offset) != (unsigned char) (i & 0xff))
-			goto out_loopback;
+	for (i = 0; i < MLX4_LOOPBACK_TEST_PAYLOAD; i++) {
+		if (data[i] != (unsigned char)i)
+			return;
 	}
 	/* Loopback found */
 	priv->loopback_ok = 1;
-
-out_loopback:
-	dev_kfree_skb_any(skb);
 }
 
 static bool mlx4_en_refill_rx_buffers(struct mlx4_en_priv *priv,
@@ -785,6 +782,11 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
 			}
 		}
 
+		if (unlikely(priv->validate_loopback)) {
+			validate_loopback(priv, va);
+			goto next;
+		}
+
 		/*
 		 * Packet is OK - process it.
 		 */
@@ -948,11 +950,6 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
 			goto next;
 		}
 
-		if (unlikely(priv->validate_loopback)) {
-			validate_loopback(priv, skb);
-			goto next;
-		}
-
 		if (ip_summed == CHECKSUM_COMPLETE) {
 			if (check_csum(cqe, skb, va, dev->features)) {
 				ip_summed = CHECKSUM_NONE;

drivers/net/ethernet/mellanox/mlx4/en_selftest.c

@@ -81,14 +81,11 @@ static int mlx4_en_test_loopback(struct mlx4_en_priv *priv)
 {
 	u32 loopback_ok = 0;
 	int i;
-	bool gro_enabled;
 
         priv->loopback_ok = 0;
 	priv->validate_loopback = 1;
-	gro_enabled = priv->dev->features & NETIF_F_GRO;
 
 	mlx4_en_update_loopback_state(priv->dev, priv->dev->features);
-	priv->dev->features &= ~NETIF_F_GRO;
 
 	/* xmit */
 	if (mlx4_en_test_loopback_xmit(priv)) {
@@ -111,9 +108,6 @@ static int mlx4_en_test_loopback(struct mlx4_en_priv *priv)
 
 	priv->validate_loopback = 0;
 
-	if (gro_enabled)
-		priv->dev->features |= NETIF_F_GRO;
-
 	mlx4_en_update_loopback_state(priv->dev, priv->dev->features);
 	return !loopback_ok;
 }