[PATCH net-next 10/12] net: hns3: add 8 BD limit for tx flow

[Huazhong Tan]

From: Peng Li <lipeng...@huawei.com>

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 <lipeng...@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazh...@huawei.com>
---
 .../net/ethernet/hisilicon/hns3/hns3_enet.c   | 28 ++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c 
b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
index 93e3e38ba852..216f3dd25cd6 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/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;
 
-- 
2.20.1