ionic: Cleanups in the Tx hotpath code

Buffer DMA mapping happens in ionic_tx_map_skb() and this function is
called from ionic_tx() and ionic_tx_tso(). If ionic_tx_map_skb()
succeeds, but a failure is encountered later in ionic_tx() or
ionic_tx_tso() we aren't unmapping the buffers. This can be fixed in
ionic_tx() by changing functions it calls to return void because they
always return 0. For ionic_tx_tso(), there's an actual possibility that
we leave the buffers mapped, so fix this by introducing the helper
function ionic_tx_desc_unmap_bufs(). This function is also re-used
in ionic_tx_clean().

Fixes: 0f3154e6 ("ionic: Add Tx and Rx handling")
Signed-off-by: Brett Creeley <brett@pensando.io>
Signed-off-by: Shannon Nelson <snelson@pensando.io>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/pensando/ionic/ionic_txrx.c

@@ -669,27 +669,37 @@ static int ionic_tx_map_skb(struct ionic_queue *q, struct sk_buff *skb,
 	return -EIO;
 }
 
-static void ionic_tx_clean(struct ionic_queue *q,
-			   struct ionic_desc_info *desc_info,
-			   struct ionic_cq_info *cq_info,
-			   void *cb_arg)
+static void ionic_tx_desc_unmap_bufs(struct ionic_queue *q,
+				     struct ionic_desc_info *desc_info)
 {
 	struct ionic_buf_info *buf_info = desc_info->bufs;
-	struct ionic_tx_stats *stats = q_to_tx_stats(q);
-	struct ionic_qcq *qcq = q_to_qcq(q);
-	struct sk_buff *skb = cb_arg;
 	struct device *dev = q->dev;
 	unsigned int i;
-	u16 qi;
 
-	if (desc_info->nbufs) {
+	if (!desc_info->nbufs)
+		return;
+
 	dma_unmap_single(dev, (dma_addr_t)buf_info->dma_addr,
 			 buf_info->len, DMA_TO_DEVICE);
 	buf_info++;
 	for (i = 1; i < desc_info->nbufs; i++, buf_info++)
 		dma_unmap_page(dev, (dma_addr_t)buf_info->dma_addr,
 			       buf_info->len, DMA_TO_DEVICE);
-	}
+
+	desc_info->nbufs = 0;
+}
+
+static void ionic_tx_clean(struct ionic_queue *q,
+			   struct ionic_desc_info *desc_info,
+			   struct ionic_cq_info *cq_info,
+			   void *cb_arg)
+{
+	struct ionic_tx_stats *stats = q_to_tx_stats(q);
+	struct ionic_qcq *qcq = q_to_qcq(q);
+	struct sk_buff *skb = cb_arg;
+	u16 qi;
+
+	ionic_tx_desc_unmap_bufs(q, desc_info);
 
 	if (!skb)
 		return;
@@ -931,8 +941,11 @@ static int ionic_tx_tso(struct ionic_queue *q, struct sk_buff *skb)
 		err = ionic_tx_tcp_inner_pseudo_csum(skb);
 	else
 		err = ionic_tx_tcp_pseudo_csum(skb);
-	if (err)
+	if (err) {
+		/* clean up mapping from ionic_tx_map_skb */
+		ionic_tx_desc_unmap_bufs(q, desc_info);
 		return err;
+	}
 
 	if (encap)
 		hdrlen = skb_inner_transport_header(skb) - skb->data +
@@ -1003,7 +1016,7 @@ static int ionic_tx_tso(struct ionic_queue *q, struct sk_buff *skb)
 	return 0;
 }
 
-static int ionic_tx_calc_csum(struct ionic_queue *q, struct sk_buff *skb,
+static void ionic_tx_calc_csum(struct ionic_queue *q, struct sk_buff *skb,
 			       struct ionic_desc_info *desc_info)
 {
 	struct ionic_txq_desc *desc = desc_info->txq_desc;
@@ -1038,11 +1051,9 @@ static int ionic_tx_calc_csum(struct ionic_queue *q, struct sk_buff *skb,
 		stats->crc32_csum++;
 	else
 		stats->csum++;
-
-	return 0;
 }
 
-static int ionic_tx_calc_no_csum(struct ionic_queue *q, struct sk_buff *skb,
+static void ionic_tx_calc_no_csum(struct ionic_queue *q, struct sk_buff *skb,
 				  struct ionic_desc_info *desc_info)
 {
 	struct ionic_txq_desc *desc = desc_info->txq_desc;
@@ -1074,11 +1085,9 @@ static int ionic_tx_calc_no_csum(struct ionic_queue *q, struct sk_buff *skb,
 	desc->csum_offset = 0;
 
 	stats->csum_none++;
-
-	return 0;
 }
 
-static int ionic_tx_skb_frags(struct ionic_queue *q, struct sk_buff *skb,
+static void ionic_tx_skb_frags(struct ionic_queue *q, struct sk_buff *skb,
 			       struct ionic_desc_info *desc_info)
 {
 	struct ionic_txq_sg_desc *sg_desc = desc_info->txq_sg_desc;
@@ -1093,31 +1102,24 @@ static int ionic_tx_skb_frags(struct ionic_queue *q, struct sk_buff *skb,
 	}
 
 	stats->frags += skb_shinfo(skb)->nr_frags;
-
-	return 0;
 }
 
 static int ionic_tx(struct ionic_queue *q, struct sk_buff *skb)
 {
 	struct ionic_desc_info *desc_info = &q->info[q->head_idx];
 	struct ionic_tx_stats *stats = q_to_tx_stats(q);
-	int err;
 
 	if (unlikely(ionic_tx_map_skb(q, skb, desc_info)))
 		return -EIO;
 
 	/* set up the initial descriptor */
 	if (skb->ip_summed == CHECKSUM_PARTIAL)
-		err = ionic_tx_calc_csum(q, skb, desc_info);
+		ionic_tx_calc_csum(q, skb, desc_info);
 	else
-		err = ionic_tx_calc_no_csum(q, skb, desc_info);
-	if (err)
-		return err;
+		ionic_tx_calc_no_csum(q, skb, desc_info);
 
 	/* add frags */
-	err = ionic_tx_skb_frags(q, skb, desc_info);
-	if (err)
-		return err;
+	ionic_tx_skb_frags(q, skb, desc_info);
 
 	skb_tx_timestamp(skb);
 	stats->pkts++;