[PATCH] IB/ipoib: Add handling of skb with many frags

[Hans Westgaard Ry <hans.westgaard.ry@oracle.com>]

IPoIB converts skb-fragments to sge adding 1 extra sge when offloading
is enabled. Current codepath assumes that the max number of sge a device
support is at least MAX_SKB_FRAGS+1, there is no interaction with upper
layers to limit number of fragments in an skb if a device suports fewer
sge. The assumptions also lead to requesting a fixed number ot sge when
IPoIB creates queue-pairs with scatter/gather enabled.

A fallback/slowpath is implemented using skb_linearize to
handle cases where the conversion would result in more sges than supported.

Signed-off-by: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
Reviewed-by: Håkon Bugge <haakon.bugge@oracle.com>
Reviewed-by: Wei Lin Guay <wei.lin.guay@oracle.com>
---
 drivers/infiniband/ulp/ipoib/ipoib_cm.c    | 4 +++-
 drivers/infiniband/ulp/ipoib/ipoib_ib.c    | 9 +++++++++
 drivers/infiniband/ulp/ipoib/ipoib_verbs.c | 4 +++-
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
index 917e46e..0a2bd43 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
@@ -1031,7 +1031,9 @@ 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;
+		attr.cap.max_send_sge = min_t(u32,
+					      priv->ca->attrs.max_sge,
+					      MAX_SKB_FRAGS + 1);
 
 	tx_qp = ib_create_qp(priv->pd, &attr);
 	if (PTR_ERR(tx_qp) == -EINVAL) {
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_ib.c b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
index 5ea0c14..b4f2240 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_ib.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
@@ -541,6 +541,15 @@ void ipoib_send(struct net_device *dev, struct sk_buff *skb,
 	int hlen, rc;
 	void *phead;
 
+	if (skb_shinfo(skb)->nr_frags >= priv->ca->attrs.max_sge) {
+		if (skb_linearize(skb) != 0) {
+			ipoib_warn(priv, "skb could not be linearized\n");
+			++dev->stats.tx_dropped;
+			++dev->stats.tx_errors;
+			dev_kfree_skb_any(skb);
+			return;
+		}
+	}
 	if (skb_is_gso(skb)) {
 		hlen = skb_transport_offset(skb) + tcp_hdrlen(skb);
 		phead = skb->data;
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_verbs.c b/drivers/infiniband/ulp/ipoib/ipoib_verbs.c
index d48c5ba..62f8ec3 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_verbs.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_verbs.c
@@ -206,7 +206,9 @@ int ipoib_transport_dev_init(struct net_device *dev, struct ib_device *ca)
 		init_attr.create_flags |= IB_QP_CREATE_NETIF_QP;
 
 	if (dev->features & NETIF_F_SG)
-		init_attr.cap.max_send_sge = MAX_SKB_FRAGS + 1;
+		init_attr.cap.max_send_sge = min_t(u32,
+						   priv->ca->attrs.max_sge,
+						   MAX_SKB_FRAGS + 1);
 
 	priv->qp = ib_create_qp(priv->pd, &init_attr);
 	if (IS_ERR(priv->qp)) {
-- 
2.4.3