igb: cleanup igb xmit frame path

This patch cleans up the xmit frame path for igb to better handle xmit
frame errors and avoid null pointer exceptions.  It also cleans up some
whitespace issues found in the xmit frame path.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/igb/igb_main.c

@@ -3245,9 +3245,9 @@ set_itr_now:
 #define IGB_TX_FLAGS_VLAN		0x00000002
 #define IGB_TX_FLAGS_TSO		0x00000004
 #define IGB_TX_FLAGS_IPV4		0x00000008
-#define IGB_TX_FLAGS_TSTAMP             0x00000010
-#define IGB_TX_FLAGS_VLAN_MASK	0xffff0000
-#define IGB_TX_FLAGS_VLAN_SHIFT	16
+#define IGB_TX_FLAGS_TSTAMP		0x00000010
+#define IGB_TX_FLAGS_VLAN_MASK		0xffff0000
+#define IGB_TX_FLAGS_VLAN_SHIFT		        16
 
 static inline int igb_tso_adv(struct igb_ring *tx_ring,
 			      struct sk_buff *skb, u32 tx_flags, u8 *hdr_len)
@@ -3346,6 +3346,7 @@ static inline bool igb_tx_csum_adv(struct igb_ring *tx_ring,
 
 		if (tx_flags & IGB_TX_FLAGS_VLAN)
 			info |= (tx_flags & IGB_TX_FLAGS_VLAN_MASK);
+
 		info |= (skb_network_offset(skb) << E1000_ADVTXD_MACLEN_SHIFT);
 		if (skb->ip_summed == CHECKSUM_PARTIAL)
 			info |= skb_network_header_len(skb);
@@ -3462,17 +3463,17 @@ static inline int igb_tx_map_adv(struct igb_ring *tx_ring, struct sk_buff *skb,
 	tx_ring->buffer_info[i].skb = skb;
 	tx_ring->buffer_info[first].next_to_watch = i;
 
-	return count + 1;
+	return ++count;
 }
 
 static inline void igb_tx_queue_adv(struct igb_ring *tx_ring,
 				    int tx_flags, int count, u32 paylen,
 				    u8 hdr_len)
 {
-	union e1000_adv_tx_desc *tx_desc = NULL;
+	union e1000_adv_tx_desc *tx_desc;
 	struct igb_buffer *buffer_info;
 	u32 olinfo_status = 0, cmd_type_len;
-	unsigned int i;
+	unsigned int i = tx_ring->next_to_use;
 
 	cmd_type_len = (E1000_ADVTXD_DTYP_DATA | E1000_ADVTXD_DCMD_IFCS |
 			E1000_ADVTXD_DCMD_DEXT);
@@ -3505,18 +3506,18 @@ static inline void igb_tx_queue_adv(struct igb_ring *tx_ring,
 
 	olinfo_status |= ((paylen - hdr_len) << E1000_ADVTXD_PAYLEN_SHIFT);
 
-	i = tx_ring->next_to_use;
-	while (count--) {
+	do {
 		buffer_info = &tx_ring->buffer_info[i];
 		tx_desc = E1000_TX_DESC_ADV(*tx_ring, i);
 		tx_desc->read.buffer_addr = cpu_to_le64(buffer_info->dma);
 		tx_desc->read.cmd_type_len =
 			cpu_to_le32(cmd_type_len | buffer_info->length);
 		tx_desc->read.olinfo_status = cpu_to_le32(olinfo_status);
+		count--;
 		i++;
 		if (i == tx_ring->count)
 			i = 0;
-	}
+	} while (count > 0);
 
 	tx_desc->read.cmd_type_len |= cpu_to_le32(IGB_ADVTXD_DCMD);
 	/* Force memory writes to complete before letting h/w
@@ -3568,8 +3569,7 @@ netdev_tx_t igb_xmit_frame_ring_adv(struct sk_buff *skb,
 	unsigned int first;
 	unsigned int tx_flags = 0;
 	u8 hdr_len = 0;
-	int count = 0;
-	int tso = 0;
+	int tso = 0, count;
 	union skb_shared_tx *shtx = skb_tx(skb);
 
 	/* need: 1 descriptor per page,
@@ -3587,7 +3587,7 @@ netdev_tx_t igb_xmit_frame_ring_adv(struct sk_buff *skb,
 		tx_flags |= IGB_TX_FLAGS_TSTAMP;
 	}
 
-	if (adapter->vlgrp && vlan_tx_tag_present(skb)) {
+	if (vlan_tx_tag_present(skb) && adapter->vlgrp) {
 		tx_flags |= IGB_TX_FLAGS_VLAN;
 		tx_flags |= (vlan_tx_tag_get(skb) << IGB_TX_FLAGS_VLAN_SHIFT);
 	}
@@ -3598,6 +3598,7 @@ netdev_tx_t igb_xmit_frame_ring_adv(struct sk_buff *skb,
 	first = tx_ring->next_to_use;
 	if (skb_is_gso(skb)) {
 		tso = igb_tso_adv(tx_ring, skb, tx_flags, &hdr_len);
+
 		if (tso < 0) {
 			dev_kfree_skb_any(skb);
 			return NETDEV_TX_OK;
@@ -3611,12 +3612,11 @@ netdev_tx_t igb_xmit_frame_ring_adv(struct sk_buff *skb,
 		tx_flags |= IGB_TX_FLAGS_CSUM;
 
 	/*
-	 * count reflects descriptors mapped, if 0 then mapping error
+	 * count reflects descriptors mapped, if 0 or less then mapping error
 	 * has occured and we need to rewind the descriptor queue
 	 */
 	count = igb_tx_map_adv(tx_ring, skb, first);
-
-	if (!count) {
+	if (count <= 0) {
 		dev_kfree_skb_any(skb);
 		tx_ring->buffer_info[first].time_stamp = 0;
 		tx_ring->next_to_use = first;