net: hns3: add 8 BD limit for tx flow

A single transmit packet can span up to 8 descriptors according
to the HW limit. If a skb has more than 8 frags, driver uses
skb_copy to get a new skb which has less frags.

Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hns3/hns3_enet.c

@@ -1133,6 +1133,7 @@ static int hns3_nic_maybe_stop_tso(struct sk_buff **out_skb, int *bnum,
 				   struct hns3_enet_ring *ring)
 {
 	struct sk_buff *skb = *out_skb;
+	struct sk_buff *new_skb = NULL;
 	struct skb_frag_struct *frag;
 	int bdnum_for_frag;
 	int frag_num;
@@ -1155,7 +1156,19 @@ static int hns3_nic_maybe_stop_tso(struct sk_buff **out_skb, int *bnum,
 		buf_num += bdnum_for_frag;
 	}
 
-	if (buf_num > ring_space(ring))
+	if (unlikely(buf_num > HNS3_MAX_BD_PER_FRAG)) {
+		buf_num = (skb->len + HNS3_MAX_BD_SIZE - 1) / HNS3_MAX_BD_SIZE;
+		if (ring_space(ring) < buf_num)
+			return -EBUSY;
+		/* manual split the send packet */
+		new_skb = skb_copy(skb, GFP_ATOMIC);
+		if (!new_skb)
+			return -ENOMEM;
+		dev_kfree_skb_any(skb);
+		*out_skb = new_skb;
+	}
+
+	if (unlikely(ring_space(ring) < buf_num))
 		return -EBUSY;
 
 	*bnum = buf_num;
@@ -1166,11 +1179,24 @@ static int hns3_nic_maybe_stop_tx(struct sk_buff **out_skb, int *bnum,
 				  struct hns3_enet_ring *ring)
 {
 	struct sk_buff *skb = *out_skb;
+	struct sk_buff *new_skb = NULL;
 	int buf_num;
 
 	/* No. of segments (plus a header) */
 	buf_num = skb_shinfo(skb)->nr_frags + 1;
 
+	if (unlikely(buf_num > HNS3_MAX_BD_PER_FRAG)) {
+		buf_num = (skb->len + HNS3_MAX_BD_SIZE - 1) / HNS3_MAX_BD_SIZE;
+		if (ring_space(ring) < buf_num)
+			return -EBUSY;
+		/* manual split the send packet */
+		new_skb = skb_copy(skb, GFP_ATOMIC);
+		if (!new_skb)
+			return -ENOMEM;
+		dev_kfree_skb_any(skb);
+		*out_skb = new_skb;
+	}
+
 	if (unlikely(ring_space(ring) < buf_num))
 		return -EBUSY;