net: hns3: fix for not calculating tx bd num correctly

mainline inclusion
from mainline-5.1-rc1
commit 5f543a54eec08228ab0cc0a49cf5d79dd32c9e5e
category: bugfix
bugzilla: NA
CVE: NA

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

When there is only one byte in a frag, the current calculation
using "(size + HNS3_MAX_BD_SIZE - 1) >> HNS3_MAX_BD_SIZE_OFFSET"
will return zero, because HNS3_MAX_BD_SIZE is 65535 and
HNS3_MAX_BD_SIZE_OFFSET is 16. So it will cause tx error when
a frag's size is one byte.

This patch fixes it by restoring the calculation back to
((S) + HNS3_MAX_BD_SIZE - 1) / HNS3_MAX_BD_SIZE.

Fixes: 3fe13ed95dd3 ("net: hns3: avoid mult + div op in critical data path")
Signed-off-by: NYunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
[hanjun: rebase to hulk-4.19 kernel]
Signed-off-by: NHanjun Guo <guohanjun@huawei.com>
Reviewed-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

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

@@ -23,6 +23,7 @@
 #include "hns3_enet.h"
 
 #define hns3_set_field(origin, shift, val)	((origin) |= ((val) << (shift)))
+#define hns3_tx_bd_count(S) (((S) + HNS3_MAX_BD_SIZE - 1) / HNS3_MAX_BD_SIZE)
 
 static void hns3_clear_all_ring(struct hnae3_handle *h);
 static void hns3_force_clear_all_rx_ring(struct hnae3_handle *h);
@@ -1095,7 +1096,7 @@ static int hns3_fill_desc(struct hns3_enet_ring *ring, void *priv,
 
 	desc_cb->length = size;
 
-	frag_buf_num = (size + HNS3_MAX_BD_SIZE - 1) >> HNS3_MAX_BD_SIZE_OFFSET;
+	frag_buf_num = hns3_tx_bd_count(size);
 	sizeoflast = size & HNS3_TX_LAST_SIZE_M;
 	sizeoflast = sizeoflast ? sizeoflast : HNS3_MAX_BD_SIZE;
 
@@ -1160,15 +1161,13 @@ static int hns3_nic_maybe_stop_tso(struct sk_buff **out_skb, int *bnum,
 	int i;
 
 	size = skb_headlen(skb);
-	buf_num = (size + HNS3_MAX_BD_SIZE - 1) >> HNS3_MAX_BD_SIZE_OFFSET;
+	buf_num = hns3_tx_bd_count(size);
 
 	frag_num = skb_shinfo(skb)->nr_frags;
 	for (i = 0; i < frag_num; i++) {
 		frag = &skb_shinfo(skb)->frags[i];
 		size = skb_frag_size(frag);
-		bdnum_for_frag =
-			(size + HNS3_MAX_BD_SIZE - 1) >>
-			HNS3_MAX_BD_SIZE_OFFSET;
+		bdnum_for_frag = hns3_tx_bd_count(size);
 		if (unlikely(bdnum_for_frag > HNS3_MAX_BD_PER_FRAG))
 			return -ENOMEM;
 
@@ -1179,8 +1178,7 @@ static int hns3_nic_maybe_stop_tso(struct sk_buff **out_skb, int *bnum,
 		if (!hns3_check_skb_need_linearize(skb))
 			goto out;
 
-		buf_num = (skb->len + HNS3_MAX_BD_SIZE - 1) >>
-			  HNS3_MAX_BD_SIZE_OFFSET;
+		buf_num = hns3_tx_bd_count(skb->len);
 		if (ring_space(ring) < buf_num)
 			return -EBUSY;
 		/* manual split the send packet */
@@ -1210,8 +1208,7 @@ static int hns3_nic_maybe_stop_tx(struct sk_buff **out_skb, int *bnum,
 	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_OFFSET;
+		buf_num = hns3_tx_bd_count(skb->len);
 		if (ring_space(ring) < buf_num)
 			return -EBUSY;
 		/* manual split the send packet */

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

@@ -193,7 +193,6 @@ enum hns3_nic_state {
 #define HNS3_VECTOR_INITED			1
 
 #define HNS3_MAX_BD_SIZE			65535
-#define HNS3_MAX_BD_SIZE_OFFSET		16
 #define HNS3_MAX_BD_PER_FRAG			8
 #define HNS3_MAX_BD_PER_PKT			MAX_SKB_FRAGS