tilegx: fix some issues in the SW TSO support

This change correctly computes the header length and data length in
the fragments to avoid a bug where we would end up with extremely
slow performance.  Also adopt use of skb_frag_size() accessor.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Cc: stable@vger.kernel.org [v3.6]
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/tile/tilegx.c

@@ -1334,11 +1334,11 @@ static int tso_count_edescs(struct sk_buff *skb)
 {
 	struct skb_shared_info *sh = skb_shinfo(skb);
 	unsigned int sh_len = skb_transport_offset(skb) + tcp_hdrlen(skb);
-	unsigned int data_len = skb->data_len + skb->hdr_len - sh_len;
+	unsigned int data_len = skb->len - sh_len;
 	unsigned int p_len = sh->gso_size;
 	long f_id = -1;    /* id of the current fragment */
-	long f_size = skb->hdr_len;  /* size of the current fragment */
-	long f_used = sh_len;  /* bytes used from the current fragment */
+	long f_size = skb_headlen(skb) - sh_len;  /* current fragment size */
+	long f_used = 0;  /* bytes used from the current fragment */
 	long n;            /* size of the current piece of payload */
 	int num_edescs = 0;
 	int segment;
@@ -1353,7 +1353,7 @@ static int tso_count_edescs(struct sk_buff *skb)
 			/* Advance as needed. */
 			while (f_used >= f_size) {
 				f_id++;
-				f_size = sh->frags[f_id].size;
+				f_size = skb_frag_size(&sh->frags[f_id]);
 				f_used = 0;
 			}
 
@@ -1384,13 +1384,13 @@ static void tso_headers_prepare(struct sk_buff *skb, unsigned char *headers,
 	struct iphdr *ih;
 	struct tcphdr *th;
 	unsigned int sh_len = skb_transport_offset(skb) + tcp_hdrlen(skb);
-	unsigned int data_len = skb->data_len + skb->hdr_len - sh_len;
+	unsigned int data_len = skb->len - sh_len;
 	unsigned char *data = skb->data;
 	unsigned int ih_off, th_off, p_len;
 	unsigned int isum_seed, tsum_seed, id, seq;
 	long f_id = -1;    /* id of the current fragment */
-	long f_size = skb->hdr_len;  /* size of the current fragment */
-	long f_used = sh_len;  /* bytes used from the current fragment */
+	long f_size = skb_headlen(skb) - sh_len;  /* current fragment size */
+	long f_used = 0;  /* bytes used from the current fragment */
 	long n;            /* size of the current piece of payload */
 	int segment;
 
@@ -1405,7 +1405,7 @@ static void tso_headers_prepare(struct sk_buff *skb, unsigned char *headers,
 	isum_seed = ((0xFFFF - ih->check) +
 		     (0xFFFF - ih->tot_len) +
 		     (0xFFFF - ih->id));
-	tsum_seed = th->check + (0xFFFF ^ htons(sh_len + data_len));
+	tsum_seed = th->check + (0xFFFF ^ htons(skb->len));
 	id = ntohs(ih->id);
 	seq = ntohl(th->seq);
 
@@ -1444,7 +1444,7 @@ static void tso_headers_prepare(struct sk_buff *skb, unsigned char *headers,
 			/* Advance as needed. */
 			while (f_used >= f_size) {
 				f_id++;
-				f_size = sh->frags[f_id].size;
+				f_size = skb_frag_size(&sh->frags[f_id]);
 				f_used = 0;
 			}
 
@@ -1478,14 +1478,14 @@ static void tso_egress(struct net_device *dev, gxio_mpipe_equeue_t *equeue,
 	struct tile_net_priv *priv = netdev_priv(dev);
 	struct skb_shared_info *sh = skb_shinfo(skb);
 	unsigned int sh_len = skb_transport_offset(skb) + tcp_hdrlen(skb);
-	unsigned int data_len = skb->data_len + skb->hdr_len - sh_len;
+	unsigned int data_len = skb->len - sh_len;
 	unsigned int p_len = sh->gso_size;
 	gxio_mpipe_edesc_t edesc_head = { { 0 } };
 	gxio_mpipe_edesc_t edesc_body = { { 0 } };
 	long f_id = -1;    /* id of the current fragment */
-	long f_size = skb->hdr_len;  /* size of the current fragment */
-	long f_used = sh_len;  /* bytes used from the current fragment */
-	void *f_data = skb->data;
+	long f_size = skb_headlen(skb) - sh_len;  /* current fragment size */
+	long f_used = 0;  /* bytes used from the current fragment */
+	void *f_data = skb->data + sh_len;
 	long n;            /* size of the current piece of payload */
 	unsigned long tx_packets = 0, tx_bytes = 0;
 	unsigned int csum_start;
@@ -1516,15 +1516,18 @@ static void tso_egress(struct net_device *dev, gxio_mpipe_equeue_t *equeue,
 
 		/* Egress the payload. */
 		while (p_used < p_len) {
+			void *va;
 
 			/* Advance as needed. */
 			while (f_used >= f_size) {
 				f_id++;
-				f_size = sh->frags[f_id].size;
-				f_used = 0;
+				f_size = skb_frag_size(&sh->frags[f_id]);
 				f_data = tile_net_frag_buf(&sh->frags[f_id]);
+				f_used = 0;
 			}
 
+			va = f_data + f_used;
+
 			/* Use bytes from the current fragment. */
 			n = p_len - p_used;
 			if (n > f_size - f_used)
@@ -1533,7 +1536,7 @@ static void tso_egress(struct net_device *dev, gxio_mpipe_equeue_t *equeue,
 			p_used += n;
 
 			/* Egress a piece of the payload. */
-			edesc_body.va = va_to_tile_io_addr(f_data) + f_used;
+			edesc_body.va = va_to_tile_io_addr(va);
 			edesc_body.xfer_size = n;
 			edesc_body.bound = !(p_used < p_len);
 			gxio_mpipe_equeue_put_at(equeue, edesc_body, slot);