mlx4: get rid of frag_prefix_size

Using per frag storage for frag_prefix_size is really silly.

mlx4_en_complete_rx_desc() has all needed info already.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Acked-by: NTariq Toukan <tariqt@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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

@@ -588,15 +588,14 @@ static int mlx4_en_complete_rx_desc(struct mlx4_en_priv *priv,
 				    int length)
 {
 	struct skb_frag_struct *skb_frags_rx = skb_shinfo(skb)->frags;
-	struct mlx4_en_frag_info *frag_info;
-	int nr;
+	struct mlx4_en_frag_info *frag_info = priv->frag_info;
+	int nr, frag_size;
 	dma_addr_t dma;
 
 	/* Collect used fragments while replacing them in the HW descriptors */
-	for (nr = 0; nr < priv->num_frags; nr++) {
-		frag_info = &priv->frag_info[nr];
-		if (length <= frag_info->frag_prefix_size)
-			break;
+	for (nr = 0;;) {
+		frag_size = min_t(int, length, frag_info->frag_size);
+
 		if (unlikely(!frags[nr].page))
 			goto fail;
 
@@ -606,15 +605,16 @@ static int mlx4_en_complete_rx_desc(struct mlx4_en_priv *priv,
 
 		__skb_fill_page_desc(skb, nr, frags[nr].page,
 				     frags[nr].page_offset,
-				     frag_info->frag_size);
+				     frag_size);
 
 		skb->truesize += frag_info->frag_stride;
 		frags[nr].page = NULL;
+		nr++;
+		length -= frag_size;
+		if (!length)
+			break;
+		frag_info++;
 	}
-	/* Adjust size of last fragment to match actual length */
-	if (nr > 0)
-		skb_frag_size_set(&skb_frags_rx[nr - 1],
-			length - priv->frag_info[nr - 1].frag_prefix_size);
 	return nr;
 
 fail:
@@ -1197,7 +1197,6 @@ void mlx4_en_calc_rx_buf(struct net_device *dev)
 	if (priv->tx_ring_num[TX_XDP]) {
 		priv->rx_page_order = 0;
 		priv->frag_info[0].frag_size = eff_mtu;
-		priv->frag_info[0].frag_prefix_size = 0;
 		/* This will gain efficient xdp frame recycling at the
 		 * expense of more costly truesize accounting
 		 */
@@ -1212,7 +1211,6 @@ void mlx4_en_calc_rx_buf(struct net_device *dev)
 			priv->frag_info[i].frag_size =
 				(eff_mtu > buf_size + frag_sizes[i]) ?
 					frag_sizes[i] : eff_mtu - buf_size;
-			priv->frag_info[i].frag_prefix_size = buf_size;
 			priv->frag_info[i].frag_stride =
 				ALIGN(priv->frag_info[i].frag_size,
 				      SMP_CACHE_BYTES);
@@ -1232,10 +1230,9 @@ void mlx4_en_calc_rx_buf(struct net_device *dev)
 	       eff_mtu, priv->num_frags);
 	for (i = 0; i < priv->num_frags; i++) {
 		en_err(priv,
-		       "  frag:%d - size:%d prefix:%d stride:%d\n",
+		       "  frag:%d - size:%d stride:%d\n",
 		       i,
 		       priv->frag_info[i].frag_size,
-		       priv->frag_info[i].frag_prefix_size,
 		       priv->frag_info[i].frag_stride);
 	}
 }

drivers/net/ethernet/mellanox/mlx4/mlx4_en.h

@@ -472,9 +472,8 @@ struct mlx4_en_mc_list {
 
 struct mlx4_en_frag_info {
 	u16 frag_size;
-	u16 frag_prefix_size;
-	u32 frag_stride;
 	u16 rx_headroom;
+	u32 frag_stride;
 };
 
 #ifdef CONFIG_MLX4_EN_DCB