[ewg] [UPDATE][PATCH] IPoIB-UD 4K MTU patch against 2.6.24 ofed-1.3-git tree

Shirley Ma mashirle at us.ibm.com
Mon Feb 4 10:14:52 PST 2008


I found one one line was out side "for loop" when merging this patch
with current git-tree. This caused UD_POST_RCV_COUNT = 16 wrong. I have
fixed it. This is the updated patch.

Thanks
Shirley


Signed-off-by: Shirley Ma <xma at us.ibm.com>
---

diff -urpN ofed_kernel_a/drivers/infiniband/ulp/ipoib/ipoib.h
ofed_kernel_b/drivers/infiniband/ulp/ipoib/ipoib.h
--- ofed_kernel_a/drivers/infiniband/ulp/ipoib/ipoib.h	2008-02-04
20:09:18.000000000 -0800
+++ ofed_kernel_b/drivers/infiniband/ulp/ipoib/ipoib.h	2008-02-04
20:11:26.000000000 -0800
@@ -56,11 +56,11 @@
 /* constants */
 
 enum {
-	IPOIB_PACKET_SIZE         = 2048,
-	IPOIB_BUF_SIZE 		  = IPOIB_PACKET_SIZE + IB_GRH_BYTES,
-
 	IPOIB_ENCAP_LEN 	  = 4,
 
+ 	IPOIB_UD_HEAD_SIZE	  = IB_GRH_BYTES + IPOIB_ENCAP_LEN,
+ 	IPOIB_UD_RX_SG		  = 2, /* for 4K MTU */ 
+
 	IPOIB_CM_MTU              = 0x10000 - 0x10, /* padding to align header
to 16 */
 	IPOIB_CM_BUF_SIZE         = IPOIB_CM_MTU  + IPOIB_ENCAP_LEN,
 	IPOIB_CM_HEAD_SIZE 	  = IPOIB_CM_BUF_SIZE % PAGE_SIZE,
@@ -141,9 +141,9 @@ struct ipoib_mcast {
 	struct net_device *dev;
 };
 
-struct ipoib_rx_buf {
+struct ipoib_sg_rx_buf {
 	struct sk_buff *skb;
-	u64		mapping;
+	u64		mapping[IPOIB_UD_RX_SG];
 };
 
 struct ipoib_tx_buf {
@@ -337,7 +337,7 @@ struct ipoib_dev_priv {
 
 	struct net_device      *dev;
 	struct ib_recv_wr	rx_wr_draft[UD_POST_RCV_COUNT];
-	struct ib_sge 		sglist_draft[UD_POST_RCV_COUNT];
+	struct ib_sge 		sglist_draft[UD_POST_RCV_COUNT][IPOIB_UD_RX_SG];
 	unsigned int		rx_outst;
 
 	struct napi_struct napi;
@@ -378,7 +378,7 @@ struct ipoib_dev_priv {
 	unsigned int admin_mtu;
 	unsigned int mcast_mtu;
 
-	struct ipoib_rx_buf *rx_ring;
+	struct ipoib_sg_rx_buf *rx_ring;
 
 	spinlock_t           tx_lock;
 	struct ipoib_tx_buf *tx_ring;
@@ -412,6 +412,7 @@ struct ipoib_dev_priv {
 	struct ipoib_ethtool_st etool;
 	struct timer_list poll_timer;
 	struct ib_ah *own_ah;
+ 	int max_ib_mtu;
 };
 
 struct ipoib_ah {
@@ -452,6 +453,19 @@ struct ipoib_neigh {
 	struct list_head    list;
 };
 
+#define IPOIB_UD_MTU(ib_mtu)		(ib_mtu - IPOIB_ENCAP_LEN)
+#define IPOIB_UD_BUF_SIZE(ib_mtu)	(ib_mtu + IB_GRH_BYTES)
+static inline int ipoib_ud_need_sg(int ib_mtu)
+{
+	return (IPOIB_UD_BUF_SIZE(ib_mtu) > PAGE_SIZE) ? 1 : 0;
+}
+static inline void ipoib_sg_dma_unmap_rx(struct ipoib_dev_priv *priv,
+					 u64 mapping[IPOIB_UD_RX_SG])
+{
+	ib_dma_unmap_single(priv->ca, mapping[0], IPOIB_UD_HEAD_SIZE,
DMA_FROM_DEVICE);
+	ib_dma_unmap_single(priv->ca, mapping[1], PAGE_SIZE, DMA_FROM_DEVICE);
+}
+
 /*
  * We stash a pointer to our private neighbour information after our
  * hardware address in neigh->ha.  The ALIGN() expression here makes
diff -urpN ofed_kernel_a/drivers/infiniband/ulp/ipoib/ipoib_ib.c
ofed_kernel_b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
--- ofed_kernel_a/drivers/infiniband/ulp/ipoib/ipoib_ib.c	2008-02-04
20:09:18.000000000 -0800
+++ ofed_kernel_b/drivers/infiniband/ulp/ipoib/ipoib_ib.c	2008-02-04
20:11:26.000000000 -0800
@@ -96,14 +96,82 @@ static void clean_pending_receives(struc
 
 	for (i = 0; i < priv->rx_outst; ++i) {
 		id = priv->rx_wr_draft[i].wr_id & ~IPOIB_OP_RECV;
-		ib_dma_unmap_single(priv->ca, priv->rx_ring[id].mapping,
-                                            IPOIB_BUF_SIZE,
DMA_FROM_DEVICE);
+		if (ipoib_ud_need_sg(priv->max_ib_mtu))
+			ipoib_sg_dma_unmap_rx(priv,
+					      priv->rx_ring[i].mapping);
+		else
+			ib_dma_unmap_single(priv->ca, priv->rx_ring[id].mapping[0],
+
IPOIB_UD_BUF_SIZE(priv->max_ib_mtu), DMA_FROM_DEVICE);
 		dev_kfree_skb_any(priv->rx_ring[id].skb);
 		priv->rx_ring[id].skb = NULL;
 	}
 	priv->rx_outst = 0;
 }
 
+static void ipoib_ud_skb_put_frags(struct sk_buff *skb, unsigned int
length,
+				   struct sk_buff *toskb)
+{
+ 	unsigned int size;
+ 	skb_frag_t *frag = &skb_shinfo(skb)->frags[0];
+ 
+ 	/* put header into skb */
+ 	size = min(length, (unsigned)IPOIB_UD_HEAD_SIZE);
+ 	skb->tail += size;
+ 	skb->len += size;
+ 	length -= size;
+ 
+ 	if (length == 0) {
+ 		/* don't need this page */
+ 		skb_fill_page_desc(toskb, 0, frag->page, 0, PAGE_SIZE);
+ 		--skb_shinfo(skb)->nr_frags;
+ 	} else {
+ 		size = min(length, (unsigned) PAGE_SIZE);
+ 		frag->size = size;
+ 		skb->data_len += size;
+ 		skb->truesize += size;
+ 		skb->len += size;
+ 		length -= size;
+	}
+}
+ 
+static struct sk_buff *ipoib_sg_alloc_rx_skb(struct net_device *dev,
+ 					     int id, u64 mapping[IPOIB_UD_RX_SG])
+{
+	struct ipoib_dev_priv *priv = netdev_priv(dev);
+	struct page *page;
+	struct sk_buff *skb;
+
+	skb = dev_alloc_skb(IPOIB_UD_HEAD_SIZE);
+ 
+ 	if (unlikely(!skb)) 
+ 		return NULL;
+ 
+ 	mapping[0] = ib_dma_map_single(priv->ca, skb->data,
IPOIB_UD_HEAD_SIZE,
+ 				       DMA_FROM_DEVICE);
+ 	if (unlikely(ib_dma_mapping_error(priv->ca, mapping[0]))) {
+ 		dev_kfree_skb_any(skb);
+ 		return NULL;
+ 	}
+ 
+ 	page = alloc_page(GFP_ATOMIC);
+ 	if (!page)
+ 		goto partial_error;
+ 
+ 	skb_fill_page_desc(skb, 0, page, 0, PAGE_SIZE);
+ 	mapping[1] = ib_dma_map_page(priv->ca,
skb_shinfo(skb)->frags[0].page,
+ 				     0, PAGE_SIZE, DMA_FROM_DEVICE);
+ 	if (unlikely(ib_dma_mapping_error(priv->ca, mapping[1])))
+ 		goto partial_error;
+ 
+ 	priv->rx_ring[id].skb = skb;
+ 	return skb;
+ 
+partial_error:
+	ib_dma_unmap_single(priv->ca, mapping[0], IPOIB_UD_HEAD_SIZE,
DMA_FROM_DEVICE);
+ 	dev_kfree_skb_any(skb);
+ 	return NULL;
+}
+
 static int ipoib_ib_post_receive(struct net_device *dev, int id)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
@@ -111,8 +179,11 @@ static int ipoib_ib_post_receive(struct 
 	int ret = 0;
 	int i = priv->rx_outst;
 
-	priv->sglist_draft[i].addr = priv->rx_ring[id].mapping;
+	priv->sglist_draft[i][0].addr = priv->rx_ring[id].mapping[0];
+	priv->sglist_draft[i][1].addr = priv->rx_ring[id].mapping[1];
+	
 	priv->rx_wr_draft[i].wr_id = id | IPOIB_OP_RECV;
+	
 	if (++priv->rx_outst == UD_POST_RCV_COUNT) {
 		ret = ib_post_recv(priv->qp, priv->rx_wr_draft, &bad_wr);
 
@@ -120,8 +191,13 @@ static int ipoib_ib_post_receive(struct 
 			ipoib_warn(priv, "receive failed for buf %d (%d)\n", id, ret);
 			while (bad_wr) {
 				id = bad_wr->wr_id & ~IPOIB_OP_RECV;
-				ib_dma_unmap_single(priv->ca, priv->rx_ring[id].mapping,
-						    IPOIB_BUF_SIZE, DMA_FROM_DEVICE);
+				if (ipoib_ud_need_sg(priv->max_ib_mtu))
+					ipoib_sg_dma_unmap_rx(priv,
+						      priv->rx_ring[i].mapping);
+				else
+					ib_dma_unmap_single(priv->ca, priv->rx_ring[id].mapping[0],
+							    IPOIB_UD_BUF_SIZE(priv->max_ib_mtu), 
+							    DMA_FROM_DEVICE);
 				dev_kfree_skb_any(priv->rx_ring[id].skb);
 				priv->rx_ring[id].skb = NULL;
 			}
@@ -138,7 +214,7 @@ static int ipoib_alloc_rx_skb(struct net
 	struct sk_buff *skb;
 	u64 addr;
 
-	skb = dev_alloc_skb(IPOIB_BUF_SIZE + 4);
+	skb = dev_alloc_skb(IPOIB_UD_BUF_SIZE(priv->max_ib_mtu) + 4);
 	if (!skb)
 		return -ENOMEM;
 
@@ -149,7 +225,8 @@ static int ipoib_alloc_rx_skb(struct net
 	 */
 	skb_reserve(skb, 4);
 
-	addr = ib_dma_map_single(priv->ca, skb->data, IPOIB_BUF_SIZE,
+	addr = ib_dma_map_single(priv->ca, skb->data,
+				 IPOIB_UD_BUF_SIZE(priv->max_ib_mtu),
 				 DMA_FROM_DEVICE);
 	if (unlikely(ib_dma_mapping_error(priv->ca, addr))) {
 		dev_kfree_skb_any(skb);
@@ -157,7 +234,7 @@ static int ipoib_alloc_rx_skb(struct net
 	}
 
 	priv->rx_ring[id].skb     = skb;
-	priv->rx_ring[id].mapping = addr;
+	priv->rx_ring[id].mapping[0] = addr;
 
 	return 0;
 }
@@ -165,10 +242,15 @@ static int ipoib_alloc_rx_skb(struct net
 static int ipoib_ib_post_receives(struct net_device *dev)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
-	int i;
+	int i, ret;
 
 	for (i = 0; i < ipoib_recvq_size; ++i) {
-		if (ipoib_alloc_rx_skb(dev, i)) {
+		if (ipoib_ud_need_sg(priv->max_ib_mtu)) 
+			ret = !(ipoib_sg_alloc_rx_skb(dev, i,
+						      priv->rx_ring[i].mapping));
+		else
+			ret = ipoib_alloc_rx_skb(dev, i);
+		if (ret) {
 			ipoib_warn(priv, "failed to allocate receive buffer %d\n", i);
 			return -ENOMEM;
 		}
@@ -186,7 +268,7 @@ static void ipoib_ib_handle_rx_wc(struct
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
 	unsigned int wr_id = wc->wr_id & ~IPOIB_OP_RECV;
 	struct sk_buff *skb;
-	u64 addr;
+	u64 mapping[IPOIB_UD_RX_SG];
 
 	ipoib_dbg_data(priv, "recv completion: id %d, status: %d\n",
 		       wr_id, wc->status);
@@ -198,42 +280,74 @@ static void ipoib_ib_handle_rx_wc(struct
 	}
 
 	skb  = priv->rx_ring[wr_id].skb;
-	addr = priv->rx_ring[wr_id].mapping;
 
-	if (unlikely(wc->status != IB_WC_SUCCESS)) {
-		if (wc->status != IB_WC_WR_FLUSH_ERR)
-			ipoib_warn(priv, "failed recv event "
-				   "(status=%d, wrid=%d vend_err %x)\n",
-				   wc->status, wr_id, wc->vendor_err);
-		ib_dma_unmap_single(priv->ca, addr,
-				    IPOIB_BUF_SIZE, DMA_FROM_DEVICE);
-		dev_kfree_skb_any(skb);
-		priv->rx_ring[wr_id].skb = NULL;
-		return;
-	}
+	/* duplicate the code here, to omit fast path if need-sg condition
check */
+	if (ipoib_ud_need_sg(priv->max_ib_mtu)) {
+		struct sk_buff *newskb;
+		if (unlikely(wc->status != IB_WC_SUCCESS)) {
+			if (wc->status != IB_WC_WR_FLUSH_ERR)
+				ipoib_warn(priv, "failed recv event "
+					   "(status=%d, wrid=%d vend_err %x)\n",
+					   wc->status, wr_id, wc->vendor_err);
+			ipoib_sg_dma_unmap_rx(priv, priv->rx_ring[wr_id].mapping);
+			dev_kfree_skb_any(skb);
+			priv->rx_ring[wr_id].skb = NULL;
+			return;
+		}
+		/*
+		 * Drop packets that this interface sent, ie multicast packets
+		 * that the HCA has replicated.
+		 */
+		if (wc->slid == priv->local_lid && wc->src_qp == priv->qp->qp_num)
+			goto repost;
+		newskb = ipoib_sg_alloc_rx_skb(dev, wr_id, mapping);
+		if (unlikely(!newskb)) {
+			++dev->stats.rx_dropped;
+			goto repost;
+		}
+		ipoib_dbg_data(priv, "received %d bytes, SLID 0x%04x\n",
+			       wc->byte_len, wc->slid);
+		ipoib_sg_dma_unmap_rx(priv, priv->rx_ring[wr_id].mapping);
+		memcpy(priv->rx_ring[wr_id].mapping, mapping,
+		       IPOIB_UD_RX_SG * sizeof *mapping);
+		ipoib_ud_skb_put_frags(skb, wc->byte_len, newskb);
+	} else {
+		u64 addr = priv->rx_ring[wr_id].mapping[0];
+		if (unlikely(wc->status != IB_WC_SUCCESS)) {
+			if (wc->status != IB_WC_WR_FLUSH_ERR)
+				ipoib_warn(priv, "failed recv event "
+					   "(status=%d, wrid=%d vend_err %x)\n",
+					   wc->status, wr_id, wc->vendor_err);
+			ib_dma_unmap_single(priv->ca, addr,
+					    IPOIB_UD_BUF_SIZE(priv->max_ib_mtu), DMA_FROM_DEVICE);
+			dev_kfree_skb_any(skb);
+			priv->rx_ring[wr_id].skb = NULL;
+			return;
+		}
 
-	/*
-	 * Drop packets that this interface sent, ie multicast packets
-	 * that the HCA has replicated.
-	 */
-	if (unlikely(wc->slid == priv->local_lid && wc->src_qp ==
priv->qp->qp_num))
-		goto repost;
+		/*
+		 * Drop packets that this interface sent, ie multicast packets
+		 * that the HCA has replicated.
+		 */
+		if (unlikely(wc->slid == priv->local_lid && wc->src_qp ==
priv->qp->qp_num))
+			goto repost;
 
-	/*
-	 * If we can't allocate a new RX buffer, dump
-	 * this packet and reuse the old buffer.
-	 */
-	if (unlikely(ipoib_alloc_rx_skb(dev, wr_id))) {
-		++dev->stats.rx_dropped;
-		goto repost;
-	}
+		/*
+		 * If we can't allocate a new RX buffer, dump
+		 * this packet and reuse the old buffer.
+		 */
+		if (unlikely(ipoib_alloc_rx_skb(dev, wr_id))) {
+			++dev->stats.rx_dropped;
+			goto repost;
+		}
 
-	ipoib_dbg_data(priv, "received %d bytes, SLID 0x%04x\n",
-		       wc->byte_len, wc->slid);
+		ipoib_dbg_data(priv, "received %d bytes, SLID 0x%04x\n",
+			       wc->byte_len, wc->slid);
 
-	ib_dma_unmap_single(priv->ca, addr, IPOIB_BUF_SIZE, DMA_FROM_DEVICE);
+		ib_dma_unmap_single(priv->ca, addr,
IPOIB_UD_BUF_SIZE(priv->max_ib_mtu), DMA_FROM_DEVICE);
 
-	skb_put(skb, wc->byte_len);
+		skb_put(skb, wc->byte_len);
+	}
 	skb_pull(skb, IB_GRH_BYTES);
 
 	skb->protocol = ((struct ipoib_header *) skb->data)->proto;
@@ -827,18 +941,21 @@ int ipoib_ib_dev_stop(struct net_device 
 			 * all our pending work requests.
 			 */
 			for (i = 0; i < ipoib_recvq_size; ++i) {
-				struct ipoib_rx_buf *rx_req;
+				struct ipoib_sg_rx_buf *rx_req;
 
 				rx_req = &priv->rx_ring[i];
-
-				if (rx_req->skb) {
+				if (!rx_req->skb)
+					continue;
+				if (ipoib_ud_need_sg(priv->max_ib_mtu))
+					ipoib_sg_dma_unmap_rx(priv,
+							      priv->rx_ring[i].mapping);
+				else
 					ib_dma_unmap_single(priv->ca,
-							    rx_req->mapping,
-							    IPOIB_BUF_SIZE,
+							    rx_req->mapping[0],
+							    IPOIB_UD_BUF_SIZE(priv->max_ib_mtu),
 							    DMA_FROM_DEVICE);
-					dev_kfree_skb_any(rx_req->skb);
-					rx_req->skb = NULL;
-				}
+				dev_kfree_skb_any(rx_req->skb);
+				rx_req->skb = NULL;
 			}
 
 			goto timeout;
diff -urpN ofed_kernel_a/drivers/infiniband/ulp/ipoib/ipoib_main.c
ofed_kernel_b/drivers/infiniband/ulp/ipoib/ipoib_main.c
--- ofed_kernel_a/drivers/infiniband/ulp/ipoib/ipoib_main.c	2008-02-04
20:09:18.000000000 -0800
+++ ofed_kernel_b/drivers/infiniband/ulp/ipoib/ipoib_main.c	2008-02-04
20:11:26.000000000 -0800
@@ -193,7 +193,7 @@ static int ipoib_change_mtu(struct net_d
 		return 0;
 	}
 
-	if (new_mtu > IPOIB_PACKET_SIZE - IPOIB_ENCAP_LEN)
+	if (new_mtu > IPOIB_UD_MTU(priv->max_ib_mtu))
 		return -EINVAL;
 
 	priv->admin_mtu = new_mtu;
@@ -1007,10 +1007,6 @@ static void ipoib_setup(struct net_devic
 	dev->tx_queue_len 	 = ipoib_sendq_size * 2;
 	dev->features            = NETIF_F_VLAN_CHALLENGED | NETIF_F_LLTX;
 
-	/* MTU will be reset when mcast join happens */
-	dev->mtu 		 = IPOIB_PACKET_SIZE - IPOIB_ENCAP_LEN;
-	priv->mcast_mtu 	 = priv->admin_mtu = dev->mtu;
-
 	memcpy(dev->broadcast, ipv4_bcast_addr, INFINIBAND_ALEN);
 
 	netif_carrier_off(dev);
@@ -1156,6 +1152,7 @@ static struct net_device *ipoib_add_port
 					 struct ib_device *hca, u8 port)
 {
 	struct ipoib_dev_priv *priv;
+	struct ib_port_attr attr;
 	int result = -ENOMEM;
 
 	priv = ipoib_intf_alloc(format);
@@ -1166,6 +1163,18 @@ static struct net_device *ipoib_add_port
 
 	priv->dev->features |= NETIF_F_HIGHDMA;
 
+	if (!ib_query_port(hca, port, &attr))
+		priv->max_ib_mtu = ib_mtu_enum_to_int(attr.max_mtu);
+	else {
+		printk(KERN_WARNING "%s: ib_query_port %d failed\n",
+		       hca->name, port);
+		goto device_init_failed;
+	}
+
+	/* MTU will be reset when mcast join happens */
+	priv->dev->mtu  = IPOIB_UD_MTU(priv->max_ib_mtu);
+	priv->mcast_mtu  = priv->admin_mtu = priv->dev->mtu;
+
 	result = ib_query_pkey(hca, port, 0, &priv->pkey);
 	if (result) {
 		printk(KERN_WARNING "%s: ib_query_pkey port %d failed (ret = %d)\n",
diff -urpN ofed_kernel_a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
ofed_kernel_b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
--- ofed_kernel_a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
2008-02-04 15:31:14.000000000 -0800
+++ ofed_kernel_b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
2008-02-04 20:11:26.000000000 -0800
@@ -567,8 +567,7 @@ void ipoib_mcast_join_task(struct work_s
 		return;
 	}
 
-	priv->mcast_mtu = ib_mtu_enum_to_int(priv->broadcast->mcmember.mtu) -
-		IPOIB_ENCAP_LEN;
+	priv->mcast_mtu =
IPOIB_UD_MTU(ib_mtu_enum_to_int(priv->broadcast->mcmember.mtu));
 
 	if (!ipoib_cm_admin_enabled(dev))
 		dev->mtu = min(priv->mcast_mtu, priv->admin_mtu);
diff -urpN ofed_kernel_a/drivers/infiniband/ulp/ipoib/ipoib_verbs.c
ofed_kernel_b/drivers/infiniband/ulp/ipoib/ipoib_verbs.c
--- ofed_kernel_a/drivers/infiniband/ulp/ipoib/ipoib_verbs.c	2008-02-04
20:09:18.000000000 -0800
+++ ofed_kernel_b/drivers/infiniband/ulp/ipoib/ipoib_verbs.c	2008-02-04
20:11:50.000000000 -0800
@@ -151,7 +151,7 @@ int ipoib_transport_dev_init(struct net_
 			.max_send_wr  = ipoib_sendq_size,
 			.max_recv_wr  = ipoib_recvq_size,
 			.max_send_sge = dev->features & NETIF_F_SG ? MAX_SKB_FRAGS + 1 : 1,
-			.max_recv_sge = 1
+			.max_recv_sge = IPOIB_UD_RX_SG 
 		},
 		.sq_sig_type = IB_SIGNAL_REQ_WR,
 		.qp_type     = IB_QPT_UD,
@@ -225,18 +225,29 @@ int ipoib_transport_dev_init(struct net_
 	priv->tx_wr.opcode 	= IB_WR_SEND;
 	priv->tx_wr.sg_list 	= priv->tx_sge;
 	priv->tx_wr.send_flags 	= IB_SEND_SIGNALED;
-
+	
 	for (i = 0; i < UD_POST_RCV_COUNT; ++i) {
-		priv->sglist_draft[i].length = IPOIB_BUF_SIZE;
-		priv->sglist_draft[i].lkey = priv->mr->lkey;
-
-		priv->rx_wr_draft[i].sg_list = &priv->sglist_draft[i];
-		priv->rx_wr_draft[i].num_sge = 1;
+		priv->sglist_draft[i][0].lkey = priv->mr->lkey;
+		priv->sglist_draft[i][1].lkey = priv->mr->lkey;
+		priv->rx_wr_draft[i].sg_list = &priv->sglist_draft[i][0];
 		if (i < UD_POST_RCV_COUNT - 1)
 			priv->rx_wr_draft[i].next = &priv->rx_wr_draft[i + 1];
 	}
 	priv->rx_wr_draft[i].next = NULL;
 
+	if (ipoib_ud_need_sg(priv->max_ib_mtu)) {
+		for (i = 0; i < UD_POST_RCV_COUNT; ++i) {
+			priv->sglist_draft[i][0].length = IPOIB_UD_HEAD_SIZE;
+			priv->sglist_draft[i][1].length = PAGE_SIZE;
+			priv->rx_wr_draft[i].num_sge = IPOIB_UD_RX_SG;
+		}
+	} else {
+		for (i = 0; i < UD_POST_RCV_COUNT; ++i) {
+			priv->sglist_draft[i][0].length =
IPOIB_UD_BUF_SIZE(priv->max_ib_mtu);
+			priv->rx_wr_draft[i].num_sge = 1;
+		}
+	}
+
 	return 0;
 
 out_free_scq:


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