mlx4: handle non-napi callers to napi_poll

netcons calls napi_poll with a budget of 0 to transmit packets.
Handle this by:
 - skipping RX processing
 - do not try to recycle TX packets to the RX cache
Signed-off-by: Jonathan Lemon <jonathan.lemon@gmail.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -943,6 +943,9 @@ int mlx4_en_poll_rx_cq(struct napi_struct *napi, int budget)
 	bool clean_complete = true;
 	int done;
 
+	if (!budget)
+		return 0;
+
 	if (priv->tx_ring_num[TX_XDP]) {
 		xdp_tx_cq = priv->tx_cq[TX_XDP][cq->ring];
 		if (xdp_tx_cq->xdp_busy) {

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

@@ -350,7 +350,7 @@ u32 mlx4_en_recycle_tx_desc(struct mlx4_en_priv *priv,
 		.dma = tx_info->map0_dma,
 	};
 
-	if (!mlx4_en_rx_recycle(ring->recycle_ring, &frame)) {
+	if (!napi_mode || !mlx4_en_rx_recycle(ring->recycle_ring, &frame)) {
 		dma_unmap_page(priv->ddev, tx_info->map0_dma,
 			       PAGE_SIZE, priv->dma_dir);
 		put_page(tx_info->page);