IB/ipoib: Scatter-Gather support in connected mode

By default, IPoIB-CM driver uses 64k MTU. Larger MTU gives better performance.
This MTU plus overhead puts the memory allocation for IP based packets at 32
4k pages (order 5), which have to be contiguous.
When the system memory under pressure, it was observed that allocating 128k
contiguous physical memory is difficult and causes serious errors (such as
system becomes unusable).
This enhancement resolve the issue by removing the physically contiguous memory
requirement using Scatter/Gather feature that exists in Linux stack.

With this fix Scatter-Gather will be supported also in connected mode
This change also revert the change made in commit e112373
("IPoIB/cm: Reduce connected mode TX object size)".

Orabug: 20422840

Reviewed-by: John Sobecki <[email protected]>
Signed-off-by: Yuval Shaia <[email protected]>

Author: Yuval Shaia

drivers/infiniband/ulp/ipoib/ipoib.h

@@ -176,11 +176,6 @@ struct ipoib_tx_buf {
 	u64		mapping[MAX_SKB_FRAGS + 1];
 };
 
-struct ipoib_cm_tx_buf {
-	struct sk_buff *skb;
-	u64		mapping;
-};
-
 /* in order to call dst->ops->update_pmtu out of spin-lock*/
 struct ipoib_pmtu_update {
 	struct work_struct work;
@@ -246,7 +241,7 @@ struct ipoib_cm_tx {
 	struct net_device   *dev;
 	struct ipoib_neigh  *neigh;
 	struct ipoib_path   *path;
-	struct ipoib_cm_tx_buf *tx_ring;
+	struct ipoib_tx_buf *tx_ring;
 	unsigned	     tx_head;
 	unsigned	     tx_tail;
 	unsigned long	     flags;
@@ -511,6 +506,8 @@ int ipoib_mcast_stop_thread(struct net_device *dev);
 void ipoib_mcast_dev_down(struct net_device *dev);
 void ipoib_mcast_dev_flush(struct net_device *dev);
 
+int ipoib_dma_map_tx(struct ib_device *ca, struct ipoib_tx_buf *tx_req);
+
 #ifdef CONFIG_INFINIBAND_IPOIB_DEBUG
 struct ipoib_mcast_iter *ipoib_mcast_iter_init(struct net_device *dev);
 int ipoib_mcast_iter_next(struct ipoib_mcast_iter *iter);

drivers/infiniband/ulp/ipoib/ipoib_cm.c

@@ -88,6 +88,31 @@ static void ipoib_cm_dma_unmap_rx(struct ipoib_dev_priv *priv, int frags,
 		ib_dma_unmap_page(priv->ca, mapping[i + 1], PAGE_SIZE, DMA_FROM_DEVICE);
 }
 
+static void ipoib_cm_dma_unmap_tx(struct ipoib_dev_priv *priv,
+				  struct ipoib_tx_buf *tx_req)
+{
+	struct sk_buff *skb;
+	int i, offs;
+
+	skb = tx_req->skb;
+	if (skb_shinfo(skb)->nr_frags) {
+		offs = 0;
+		if (skb_headlen(skb)) {
+			ib_dma_unmap_single(priv->ca, tx_req->mapping[0],
+					    skb_headlen(skb), DMA_TO_DEVICE);
+			offs = 1;
+		}
+		for (i = 0; i < skb_shinfo(skb)->nr_frags; ++i) {
+			const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+
+			ib_dma_unmap_page(priv->ca, tx_req->mapping[i + offs],
+					  skb_frag_size(frag), DMA_TO_DEVICE);
+		}
+	} else
+		ib_dma_unmap_single(priv->ca, tx_req->mapping[0], skb->len,
+				    DMA_TO_DEVICE);
+}
+
 static int ipoib_cm_post_receive_srq(struct net_device *dev, int id)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
@@ -707,11 +732,39 @@ static inline int post_send(struct ipoib_dev_priv *priv,
 	return ib_post_send(tx->qp, &priv->tx_wr, &bad_wr);
 }
 
+static inline int post_send_sg(struct ipoib_dev_priv *priv,
+			       struct ipoib_cm_tx *tx,
+			       unsigned int wr_id,
+			       struct sk_buff *skb,
+			       u64 mapping[MAX_SKB_FRAGS + 1])
+{
+	struct ib_send_wr *bad_wr;
+	int i, off;
+	skb_frag_t *frags = skb_shinfo(skb)->frags;
+	int nr_frags = skb_shinfo(skb)->nr_frags;
+
+	if (skb_headlen(skb)) {
+		priv->tx_sge[0].addr = mapping[0];
+		priv->tx_sge[0].length = skb_headlen(skb);
+		off = 1;
+	} else
+		off = 0;
+
+	for (i = 0; i < nr_frags; ++i) {
+		priv->tx_sge[i + off].addr = mapping[i + off];
+		priv->tx_sge[i + off].length = frags[i].size;
+	}
+	priv->tx_wr.num_sge = nr_frags + off;
+	priv->tx_wr.wr_id = wr_id | IPOIB_OP_CM;
+
+	return ib_post_send(tx->qp, &priv->tx_wr, &bad_wr);
+}
+
 void ipoib_cm_send(struct net_device *dev, struct sk_buff *skb, struct ipoib_cm_tx *tx)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
-	struct ipoib_cm_tx_buf *tx_req;
-	u64 addr;
+	struct ipoib_tx_buf *tx_req;
+	u64 addr = 0;
 	int rc;
 
 	if (unlikely(skb->len > tx->mtu)) {
@@ -735,24 +788,37 @@ void ipoib_cm_send(struct net_device *dev, struct sk_buff *skb, struct ipoib_cm_
 	 */
 	tx_req = &tx->tx_ring[tx->tx_head & (ipoib_sendq_size - 1)];
 	tx_req->skb = skb;
-	addr = ib_dma_map_single(priv->ca, skb->data, skb->len, DMA_TO_DEVICE);
-	if (unlikely(ib_dma_mapping_error(priv->ca, addr))) {
-		++dev->stats.tx_errors;
-		dev_kfree_skb_any(skb);
-		return;
-	}
 
-	tx_req->mapping = addr;
+	if (skb_shinfo(skb)->nr_frags) {
+		if (unlikely(ipoib_dma_map_tx(priv->ca, tx_req))) {
+			++dev->stats.tx_errors;
+			dev_kfree_skb_any(skb);
+			return;
+		}
+		rc = post_send_sg(priv, tx, tx->tx_head &
+				  (ipoib_sendq_size - 1),
+				  skb, tx_req->mapping);
+	} else {
+		addr = ib_dma_map_single(priv->ca, skb->data, skb->len,
+					 DMA_TO_DEVICE);
+		if (unlikely(ib_dma_mapping_error(priv->ca, addr))) {
+			++dev->stats.tx_errors;
+			dev_kfree_skb_any(skb);
+			return;
+		}
+
+		tx_req->mapping[0] = addr;
 
-	skb_orphan(skb);
-	skb_dst_drop(skb);
+		skb_orphan(skb);
+		skb_dst_drop(skb);
 
-	rc = post_send(priv, tx, tx->tx_head & (ipoib_sendq_size - 1),
-		       addr, skb->len);
+		rc = post_send(priv, tx, tx->tx_head & (ipoib_sendq_size - 1),
+			       addr, skb->len);
+	}
 	if (unlikely(rc)) {
 		ipoib_warn(priv, "post_send failed, error %d\n", rc);
 		++dev->stats.tx_errors;
-		ib_dma_unmap_single(priv->ca, addr, skb->len, DMA_TO_DEVICE);
+		ipoib_cm_dma_unmap_tx(priv, tx_req);
 		dev_kfree_skb_any(skb);
 	} else {
 		dev->trans_start = jiffies;
@@ -777,7 +843,7 @@ void ipoib_cm_handle_tx_wc(struct net_device *dev, struct ib_wc *wc)
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
 	struct ipoib_cm_tx *tx = wc->qp->qp_context;
 	unsigned int wr_id = wc->wr_id & ~IPOIB_OP_CM;
-	struct ipoib_cm_tx_buf *tx_req;
+	struct ipoib_tx_buf *tx_req;
 	unsigned long flags;
 
 	ipoib_dbg_data(priv, "cm send completion: id %d, status: %d\n",
@@ -791,7 +857,7 @@ void ipoib_cm_handle_tx_wc(struct net_device *dev, struct ib_wc *wc)
 
 	tx_req = &tx->tx_ring[wr_id];
 
-	ib_dma_unmap_single(priv->ca, tx_req->mapping, tx_req->skb->len, DMA_TO_DEVICE);
+	ipoib_cm_dma_unmap_tx(priv, tx_req);
 
 	/* FIXME: is this right? Shouldn't we only increment on success? */
 	++dev->stats.tx_packets;
@@ -1046,6 +1112,9 @@ static struct ib_qp *ipoib_cm_create_tx_qp(struct net_device *dev, struct ipoib_
 
 	struct ib_qp *tx_qp;
 
+	if (dev->features & NETIF_F_SG)
+		attr.cap.max_send_sge = MAX_SKB_FRAGS + 1;
+
 	tx_qp = ib_create_qp(priv->pd, &attr);
 	if (PTR_ERR(tx_qp) == -EINVAL) {
 		ipoib_warn(priv, "can't use GFP_NOIO for QPs on device %s, using GFP_KERNEL\n",
@@ -1180,7 +1249,7 @@ static int ipoib_cm_tx_init(struct ipoib_cm_tx *p, u32 qpn,
 static void ipoib_cm_tx_destroy(struct ipoib_cm_tx *p)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(p->dev);
-	struct ipoib_cm_tx_buf *tx_req;
+	struct ipoib_tx_buf *tx_req;
 	unsigned long begin;
 
 	ipoib_dbg(priv, "Destroy active connection 0x%x head 0x%x tail 0x%x\n",
@@ -1207,8 +1276,7 @@ static void ipoib_cm_tx_destroy(struct ipoib_cm_tx *p)
 
 	while ((int) p->tx_tail - (int) p->tx_head < 0) {
 		tx_req = &p->tx_ring[p->tx_tail & (ipoib_sendq_size - 1)];
-		ib_dma_unmap_single(priv->ca, tx_req->mapping, tx_req->skb->len,
-				    DMA_TO_DEVICE);
+		ipoib_cm_dma_unmap_tx(priv, tx_req);
 		dev_kfree_skb_any(tx_req->skb);
 		++p->tx_tail;
 		netif_tx_lock_bh(p->dev);
@@ -1498,7 +1566,6 @@ static void ipoib_cm_stale_task(struct work_struct *work)
 	spin_unlock_irq(&priv->lock);
 }
 
-
 static ssize_t show_mode(struct device *d, struct device_attribute *attr,
 			 char *buf)
 {

drivers/infiniband/ulp/ipoib/ipoib_ib.c

@@ -263,8 +263,7 @@ static void ipoib_ib_handle_rx_wc(struct net_device *dev, struct ib_wc *wc)
 			   "for buf %d\n", wr_id);
 }
 
-static int ipoib_dma_map_tx(struct ib_device *ca,
-			    struct ipoib_tx_buf *tx_req)
+int ipoib_dma_map_tx(struct ib_device *ca, struct ipoib_tx_buf *tx_req)
 {
 	struct sk_buff *skb = tx_req->skb;
 	u64 *mapping = tx_req->mapping;

drivers/infiniband/ulp/ipoib/ipoib_main.c

@@ -198,7 +198,7 @@ static netdev_features_t ipoib_fix_features(struct net_device *dev, netdev_featu
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
 
 	if (test_bit(IPOIB_FLAG_ADMIN_CM, &priv->flags))
-		features &= ~(NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_TSO);
+		features &= ~(NETIF_F_IP_CSUM | NETIF_F_TSO);
 
 	return features;
 }