[PATCH 4.20 219/352] net: hns3: fix the descriptor index when get rss type

[Greg Kroah-Hartman]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 31a16f99e02c2e0b40a5fb05d66f5e56721027e2 ]

Driver gets rss information from the last descriptor of the packet.
When driver handle the rss type, ring->next_to_clean indicates the
first descriptor of next packet.

This patch fix the descriptor index with "ring->next_to_clean - 1".

Fixes: 232fc64b6e62 ("net: hns3: Add HW RSS hash information to RX skb")
Signed-off-by: Peng Li <lipeng321@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/net/ethernet/hisilicon/hns3/hns3_enet.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
index beb5dbd5e98d..d424d5bc0507 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -2332,9 +2332,16 @@ static bool hns3_parse_vlan_tag(struct hns3_enet_ring *ring,
 static void hns3_set_rx_skb_rss_type(struct hns3_enet_ring *ring,
 				     struct sk_buff *skb)
 {
-	struct hns3_desc *desc = &ring->desc[ring->next_to_clean];
 	struct hnae3_handle *handle = ring->tqp->handle;
 	enum pkt_hash_types rss_type;
+	struct hns3_desc *desc;
+	int last_bd;
+
+	/* When driver handle the rss type, ring->next_to_clean indicates the
+	 * first descriptor of next packet, need -1 here.
+	 */
+	last_bd = (ring->next_to_clean - 1 + ring->desc_num) % ring->desc_num;
+	desc = &ring->desc[last_bd];
 
 	if (le32_to_cpu(desc->rx.rss_hash))
 		rss_type = handle->kinfo.rss_type;
-- 
2.19.1