net: hns3: add handling for xmit skb with recursive fraglist

Currently hns3 driver only handle the xmit skb with one level of
fraglist skb, add handling for multi level by calling hns3_tx_bd_num()
recursively when calculating bd num and calling hns3_fill_skb_to_desc()
recursively when filling tx desc.

When the skb has a fraglist level of 24, the skb is simply dropped and
stats.max_recursion_level is added to record the error. Move the stat
handling from hns3_nic_net_xmit() to hns3_nic_maybe_stop_tx() in order
to handle different error stat and add the 'max_recursion_level' and
'hw_limitation' stat.

Note that the max recursive level as 24 is chose according to below:
commit 48a1df65334b ("skbuff: return -EMSGSIZE in skb_to_sgvec to
prevent overflow").

And that we are not able to find a testcase to verify the recursive
fraglist case, so Fixes tag is not provided.

Reported-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.h b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.h
index d069b04ee587..e44224e23315 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.h
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.h
@@ -376,6 +376,8 @@ struct ring_stats {
 			u64 tx_l4_proto_err;
 			u64 tx_l2l3l4_err;
 			u64 tx_tso_err;
+			u64 over_max_recursion;
+			u64 hw_limitation;
 		};
 		struct {
 			u64 rx_pkts;