IB/umad: Add support for large RMPP transfers

Add support for sending and receiving large RMPP transfers.  The old
code supports transfers only as large as a single contiguous kernel
memory allocation.  This patch uses linked list of memory buffers when
sending and receiving data to avoid needing contiguous pages for
larger transfers.

  Receive side: copy the arriving MADs in chunks instead of coalescing
  to one large buffer in kernel space.

  Send side: split a multipacket MAD buffer to a list of segments,
  (multipacket_list) and send these using a gather list of size 2.
  Also, save pointer to last sent segment, and retrieve requested
  segments by walking list starting at last sent segment. Finally,
  save pointer to last-acked segment.  When retrying, retrieve
  segments for resending relative to this pointer.  When updating last
  ack, start at this pointer.

Signed-off-by: Jack Morgenstein <jackm@mellanox.co.il>
Signed-off-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/core/mad.c

@@ -31,7 +31,7 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  *
- * $Id: mad.c 2817 2005-07-07 11:29:26Z halr $
+ * $Id: mad.c 5596 2006-03-03 01:00:07Z sean.hefty $
  */
 #include <linux/dma-mapping.h>
 
@@ -765,18 +765,67 @@ out:
 	return ret;
 }
 
-static int get_buf_length(int hdr_len, int data_len)
+static int get_pad_size(int hdr_len, int data_len)
 {
 	int seg_size, pad;
 
 	seg_size = sizeof(struct ib_mad) - hdr_len;
 	if (data_len && seg_size) {
 		pad = seg_size - data_len % seg_size;
-		if (pad == seg_size)
-			pad = 0;
+		return pad == seg_size ? 0 : pad;
 	} else
-		pad = seg_size;
-	return hdr_len + data_len + pad;
+		return seg_size;
+}
+
+static void free_send_rmpp_list(struct ib_mad_send_wr_private *mad_send_wr)
+{
+	struct ib_rmpp_segment *s, *t;
+
+	list_for_each_entry_safe(s, t, &mad_send_wr->rmpp_list, list) {
+		list_del(&s->list);
+		kfree(s);
+	}
+}
+
+static int alloc_send_rmpp_list(struct ib_mad_send_wr_private *send_wr,
+				gfp_t gfp_mask)
+{
+	struct ib_mad_send_buf *send_buf = &send_wr->send_buf;
+	struct ib_rmpp_mad *rmpp_mad = send_buf->mad;
+	struct ib_rmpp_segment *seg = NULL;
+	int left, seg_size, pad;
+
+	send_buf->seg_size = sizeof (struct ib_mad) - send_buf->hdr_len;
+	seg_size = send_buf->seg_size;
+	pad = send_wr->pad;
+
+	/* Allocate data segments. */
+	for (left = send_buf->data_len + pad; left > 0; left -= seg_size) {
+		seg = kmalloc(sizeof (*seg) + seg_size, gfp_mask);
+		if (!seg) {
+			printk(KERN_ERR "alloc_send_rmpp_segs: RMPP mem "
+			       "alloc failed for len %zd, gfp %#x\n",
+			       sizeof (*seg) + seg_size, gfp_mask);
+			free_send_rmpp_list(send_wr);
+			return -ENOMEM;
+		}
+		seg->num = ++send_buf->seg_count;
+		list_add_tail(&seg->list, &send_wr->rmpp_list);
+	}
+
+	/* Zero any padding */
+	if (pad)
+		memset(seg->data + seg_size - pad, 0, pad);
+
+	rmpp_mad->rmpp_hdr.rmpp_version = send_wr->mad_agent_priv->
+					  agent.rmpp_version;
+	rmpp_mad->rmpp_hdr.rmpp_type = IB_MGMT_RMPP_TYPE_DATA;
+	ib_set_rmpp_flags(&rmpp_mad->rmpp_hdr, IB_MGMT_RMPP_FLAG_ACTIVE);
+
+	send_wr->cur_seg = container_of(send_wr->rmpp_list.next,
+					struct ib_rmpp_segment, list);
+	send_wr->last_ack_seg = send_wr->cur_seg;
+	return 0;
 }
 
 struct ib_mad_send_buf * ib_create_send_mad(struct ib_mad_agent *mad_agent,
@@ -787,32 +836,40 @@ struct ib_mad_send_buf * ib_create_send_mad(struct ib_mad_agent *mad_agent,
 {
 	struct ib_mad_agent_private *mad_agent_priv;
 	struct ib_mad_send_wr_private *mad_send_wr;
-	int buf_size;
+	int pad, message_size, ret, size;
 	void *buf;
 
 	mad_agent_priv = container_of(mad_agent, struct ib_mad_agent_private,
 				      agent);
-	buf_size = get_buf_length(hdr_len, data_len);
+	pad = get_pad_size(hdr_len, data_len);
+	message_size = hdr_len + data_len + pad;
 
 	if ((!mad_agent->rmpp_version &&
-	     (rmpp_active || buf_size > sizeof(struct ib_mad))) ||
-	    (!rmpp_active && buf_size > sizeof(struct ib_mad)))
+	     (rmpp_active || message_size > sizeof(struct ib_mad))) ||
+	    (!rmpp_active && message_size > sizeof(struct ib_mad)))
 		return ERR_PTR(-EINVAL);
 
-	buf = kzalloc(sizeof *mad_send_wr + buf_size, gfp_mask);
+	size = rmpp_active ? hdr_len : sizeof(struct ib_mad);
+	buf = kzalloc(sizeof *mad_send_wr + size, gfp_mask);
 	if (!buf)
 		return ERR_PTR(-ENOMEM);
 
-	mad_send_wr = buf + buf_size;
+	mad_send_wr = buf + size;
+	INIT_LIST_HEAD(&mad_send_wr->rmpp_list);
 	mad_send_wr->send_buf.mad = buf;
+	mad_send_wr->send_buf.hdr_len = hdr_len;
+	mad_send_wr->send_buf.data_len = data_len;
+	mad_send_wr->pad = pad;
 
 	mad_send_wr->mad_agent_priv = mad_agent_priv;
-	mad_send_wr->sg_list[0].length = buf_size;
+	mad_send_wr->sg_list[0].length = hdr_len;
 	mad_send_wr->sg_list[0].lkey = mad_agent->mr->lkey;
+	mad_send_wr->sg_list[1].length = sizeof(struct ib_mad) - hdr_len;
+	mad_send_wr->sg_list[1].lkey = mad_agent->mr->lkey;
 
 	mad_send_wr->send_wr.wr_id = (unsigned long) mad_send_wr;
 	mad_send_wr->send_wr.sg_list = mad_send_wr->sg_list;
-	mad_send_wr->send_wr.num_sge = 1;
+	mad_send_wr->send_wr.num_sge = 2;
 	mad_send_wr->send_wr.opcode = IB_WR_SEND;
 	mad_send_wr->send_wr.send_flags = IB_SEND_SIGNALED;
 	mad_send_wr->send_wr.wr.ud.remote_qpn = remote_qpn;
@@ -820,13 +877,11 @@ struct ib_mad_send_buf * ib_create_send_mad(struct ib_mad_agent *mad_agent,
 	mad_send_wr->send_wr.wr.ud.pkey_index = pkey_index;
 
 	if (rmpp_active) {
-		struct ib_rmpp_mad *rmpp_mad = mad_send_wr->send_buf.mad;
-		rmpp_mad->rmpp_hdr.paylen_newwin = cpu_to_be32(hdr_len -
-						   IB_MGMT_RMPP_HDR + data_len);
-		rmpp_mad->rmpp_hdr.rmpp_version = mad_agent->rmpp_version;
-		rmpp_mad->rmpp_hdr.rmpp_type = IB_MGMT_RMPP_TYPE_DATA;
-		ib_set_rmpp_flags(&rmpp_mad->rmpp_hdr,
-				  IB_MGMT_RMPP_FLAG_ACTIVE);
+		ret = alloc_send_rmpp_list(mad_send_wr, gfp_mask);
+		if (ret) {
+			kfree(buf);
+			return ERR_PTR(ret);
+		}
 	}
 
 	mad_send_wr->send_buf.mad_agent = mad_agent;
@@ -835,14 +890,50 @@ struct ib_mad_send_buf * ib_create_send_mad(struct ib_mad_agent *mad_agent,
 }
 EXPORT_SYMBOL(ib_create_send_mad);
 
+void *ib_get_rmpp_segment(struct ib_mad_send_buf *send_buf, int seg_num)
+{
+	struct ib_mad_send_wr_private *mad_send_wr;
+	struct list_head *list;
+
+	mad_send_wr = container_of(send_buf, struct ib_mad_send_wr_private,
+				   send_buf);
+	list = &mad_send_wr->cur_seg->list;
+
+	if (mad_send_wr->cur_seg->num < seg_num) {
+		list_for_each_entry(mad_send_wr->cur_seg, list, list)
+			if (mad_send_wr->cur_seg->num == seg_num)
+				break;
+	} else if (mad_send_wr->cur_seg->num > seg_num) {
+		list_for_each_entry_reverse(mad_send_wr->cur_seg, list, list)
+			if (mad_send_wr->cur_seg->num == seg_num)
+				break;
+	}
+	return mad_send_wr->cur_seg->data;
+}
+EXPORT_SYMBOL(ib_get_rmpp_segment);
+
+static inline void *ib_get_payload(struct ib_mad_send_wr_private *mad_send_wr)
+{
+	if (mad_send_wr->send_buf.seg_count)
+		return ib_get_rmpp_segment(&mad_send_wr->send_buf,
+					   mad_send_wr->seg_num);
+	else
+		return mad_send_wr->send_buf.mad +
+		       mad_send_wr->send_buf.hdr_len;
+}
+
 void ib_free_send_mad(struct ib_mad_send_buf *send_buf)
 {
 	struct ib_mad_agent_private *mad_agent_priv;
+	struct ib_mad_send_wr_private *mad_send_wr;
 
 	mad_agent_priv = container_of(send_buf->mad_agent,
 				      struct ib_mad_agent_private, agent);
-	kfree(send_buf->mad);
+	mad_send_wr = container_of(send_buf, struct ib_mad_send_wr_private,
+				   send_buf);
 
+	free_send_rmpp_list(mad_send_wr);
+	kfree(send_buf->mad);
 	if (atomic_dec_and_test(&mad_agent_priv->refcount))
 		wake_up(&mad_agent_priv->wait);
 }
@@ -865,10 +956,17 @@ int ib_send_mad(struct ib_mad_send_wr_private *mad_send_wr)
 
 	mad_agent = mad_send_wr->send_buf.mad_agent;
 	sge = mad_send_wr->sg_list;
-	sge->addr = dma_map_single(mad_agent->device->dma_device,
-				   mad_send_wr->send_buf.mad, sge->length,
-				   DMA_TO_DEVICE);
-	pci_unmap_addr_set(mad_send_wr, mapping, sge->addr);
+	sge[0].addr = dma_map_single(mad_agent->device->dma_device,
+				     mad_send_wr->send_buf.mad,
+				     sge[0].length,
+				     DMA_TO_DEVICE);
+	pci_unmap_addr_set(mad_send_wr, header_mapping, sge[0].addr);
+
+	sge[1].addr = dma_map_single(mad_agent->device->dma_device,
+				     ib_get_payload(mad_send_wr),
+				     sge[1].length,
+				     DMA_TO_DEVICE);
+	pci_unmap_addr_set(mad_send_wr, payload_mapping, sge[1].addr);
 
 	spin_lock_irqsave(&qp_info->send_queue.lock, flags);
 	if (qp_info->send_queue.count < qp_info->send_queue.max_active) {
@@ -885,11 +983,14 @@ int ib_send_mad(struct ib_mad_send_wr_private *mad_send_wr)
 		list_add_tail(&mad_send_wr->mad_list.list, list);
 	}
 	spin_unlock_irqrestore(&qp_info->send_queue.lock, flags);
-	if (ret)
+	if (ret) {
 		dma_unmap_single(mad_agent->device->dma_device,
-				 pci_unmap_addr(mad_send_wr, mapping),
-				 sge->length, DMA_TO_DEVICE);
-
+				 pci_unmap_addr(mad_send_wr, header_mapping),
+				 sge[0].length, DMA_TO_DEVICE);
+		dma_unmap_single(mad_agent->device->dma_device,
+				 pci_unmap_addr(mad_send_wr, payload_mapping),
+				 sge[1].length, DMA_TO_DEVICE);
+	}
 	return ret;
 }
 
@@ -1860,8 +1961,11 @@ static void ib_mad_send_done_handler(struct ib_mad_port_private *port_priv,
 
 retry:
 	dma_unmap_single(mad_send_wr->send_buf.mad_agent->device->dma_device,
-			 pci_unmap_addr(mad_send_wr, mapping),
+			 pci_unmap_addr(mad_send_wr, header_mapping),
 			 mad_send_wr->sg_list[0].length, DMA_TO_DEVICE);
+	dma_unmap_single(mad_send_wr->send_buf.mad_agent->device->dma_device,
+			 pci_unmap_addr(mad_send_wr, payload_mapping),
+			 mad_send_wr->sg_list[1].length, DMA_TO_DEVICE);
 	queued_send_wr = NULL;
 	spin_lock_irqsave(&send_queue->lock, flags);
 	list_del(&mad_list->list);

drivers/infiniband/core/mad_priv.h

@@ -31,7 +31,7 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  *
- * $Id: mad_priv.h 2730 2005-06-28 16:43:03Z sean.hefty $
+ * $Id: mad_priv.h 5596 2006-03-03 01:00:07Z sean.hefty $
  */
 
 #ifndef __IB_MAD_PRIV_H__
@@ -85,6 +85,12 @@ struct ib_mad_private {
 	} mad;
 } __attribute__ ((packed));
 
+struct ib_rmpp_segment {
+	struct list_head list;
+	u32 num;
+	u8 data[0];
+};
+
 struct ib_mad_agent_private {
 	struct list_head agent_list;
 	struct ib_mad_agent agent;
@@ -119,7 +125,8 @@ struct ib_mad_send_wr_private {
 	struct list_head agent_list;
 	struct ib_mad_agent_private *mad_agent_priv;
 	struct ib_mad_send_buf send_buf;
-	DECLARE_PCI_UNMAP_ADDR(mapping)
+	DECLARE_PCI_UNMAP_ADDR(header_mapping)
+	DECLARE_PCI_UNMAP_ADDR(payload_mapping)
 	struct ib_send_wr send_wr;
 	struct ib_sge sg_list[IB_MAD_SEND_REQ_MAX_SG];
 	__be64 tid;
@@ -130,11 +137,12 @@ struct ib_mad_send_wr_private {
 	enum ib_wc_status status;
 
 	/* RMPP control */
+	struct list_head rmpp_list;
+	struct ib_rmpp_segment *last_ack_seg;
+	struct ib_rmpp_segment *cur_seg;
 	int last_ack;
 	int seg_num;
 	int newwin;
-	int total_seg;
-	int data_offset;
 	int pad;
 };
 

drivers/infiniband/core/mad_rmpp.c

@@ -111,14 +111,14 @@ static int data_offset(u8 mgmt_class)
 		return IB_MGMT_RMPP_HDR;
 }
 
-static void format_ack(struct ib_rmpp_mad *ack,
+static void format_ack(struct ib_mad_send_buf *msg,
 		       struct ib_rmpp_mad *data,
 		       struct mad_rmpp_recv *rmpp_recv)
 {
+	struct ib_rmpp_mad *ack = msg->mad;
 	unsigned long flags;
 
-	memcpy(&ack->mad_hdr, &data->mad_hdr,
-	       data_offset(data->mad_hdr.mgmt_class));
+	memcpy(ack, &data->mad_hdr, msg->hdr_len);
 
 	ack->mad_hdr.method ^= IB_MGMT_METHOD_RESP;
 	ack->rmpp_hdr.rmpp_type = IB_MGMT_RMPP_TYPE_ACK;
@@ -135,16 +135,16 @@ static void ack_recv(struct mad_rmpp_recv *rmpp_recv,
 		     struct ib_mad_recv_wc *recv_wc)
 {
 	struct ib_mad_send_buf *msg;
-	int ret;
+	int ret, hdr_len;
 
+	hdr_len = data_offset(recv_wc->recv_buf.mad->mad_hdr.mgmt_class);
 	msg = ib_create_send_mad(&rmpp_recv->agent->agent, recv_wc->wc->src_qp,
-				 recv_wc->wc->pkey_index, 1, IB_MGMT_RMPP_HDR,
-				 IB_MGMT_RMPP_DATA, GFP_KERNEL);
+				 recv_wc->wc->pkey_index, 1, hdr_len,
+				 0, GFP_KERNEL);
 	if (!msg)
 		return;
 
-	format_ack(msg->mad, (struct ib_rmpp_mad *) recv_wc->recv_buf.mad,
-		   rmpp_recv);
+	format_ack(msg, (struct ib_rmpp_mad *) recv_wc->recv_buf.mad, rmpp_recv);
 	msg->ah = rmpp_recv->ah;
 	ret = ib_post_send_mad(msg, NULL);
 	if (ret)
@@ -156,16 +156,17 @@ static struct ib_mad_send_buf *alloc_response_msg(struct ib_mad_agent *agent,
 {
 	struct ib_mad_send_buf *msg;
 	struct ib_ah *ah;
+	int hdr_len;
 
 	ah = ib_create_ah_from_wc(agent->qp->pd, recv_wc->wc,
 				  recv_wc->recv_buf.grh, agent->port_num);
 	if (IS_ERR(ah))
 		return (void *) ah;
 
+	hdr_len = data_offset(recv_wc->recv_buf.mad->mad_hdr.mgmt_class);
 	msg = ib_create_send_mad(agent, recv_wc->wc->src_qp,
 				 recv_wc->wc->pkey_index, 1,
-				 IB_MGMT_RMPP_HDR, IB_MGMT_RMPP_DATA,
-				 GFP_KERNEL);
+				 hdr_len, 0, GFP_KERNEL);
 	if (IS_ERR(msg))
 		ib_destroy_ah(ah);
 	else
@@ -195,8 +196,7 @@ static void nack_recv(struct ib_mad_agent_private *agent,
 		return;
 
 	rmpp_mad = msg->mad;
-	memcpy(rmpp_mad, recv_wc->recv_buf.mad,
-	       data_offset(recv_wc->recv_buf.mad->mad_hdr.mgmt_class));
+	memcpy(rmpp_mad, recv_wc->recv_buf.mad, msg->hdr_len);
 
 	rmpp_mad->mad_hdr.method ^= IB_MGMT_METHOD_RESP;
 	rmpp_mad->rmpp_hdr.rmpp_version = IB_MGMT_RMPP_VERSION;
@@ -433,44 +433,6 @@ static struct ib_mad_recv_wc * complete_rmpp(struct mad_rmpp_recv *rmpp_recv)
 	return rmpp_wc;
 }
 
-void ib_coalesce_recv_mad(struct ib_mad_recv_wc *mad_recv_wc, void *buf)
-{
-	struct ib_mad_recv_buf *seg_buf;
-	struct ib_rmpp_mad *rmpp_mad;
-	void *data;
-	int size, len, offset;
-	u8 flags;
-
-	len = mad_recv_wc->mad_len;
-	if (len <= sizeof(struct ib_mad)) {
-		memcpy(buf, mad_recv_wc->recv_buf.mad, len);
-		return;
-	}
-
-	offset = data_offset(mad_recv_wc->recv_buf.mad->mad_hdr.mgmt_class);
-
-	list_for_each_entry(seg_buf, &mad_recv_wc->rmpp_list, list) {
-		rmpp_mad = (struct ib_rmpp_mad *)seg_buf->mad;
-		flags = ib_get_rmpp_flags(&rmpp_mad->rmpp_hdr);
-
-		if (flags & IB_MGMT_RMPP_FLAG_FIRST) {
-			data = rmpp_mad;
-			size = sizeof(*rmpp_mad);
-		} else {
-			data = (void *) rmpp_mad + offset;
-			if (flags & IB_MGMT_RMPP_FLAG_LAST)
-				size = len;
-			else
-				size = sizeof(*rmpp_mad) - offset;
-		}
-
-		memcpy(buf, data, size);
-		len -= size;
-		buf += size;
-	}
-}
-EXPORT_SYMBOL(ib_coalesce_recv_mad);
-
 static struct ib_mad_recv_wc *
 continue_rmpp(struct ib_mad_agent_private *agent,
 	      struct ib_mad_recv_wc *mad_recv_wc)
@@ -570,50 +532,33 @@ start_rmpp(struct ib_mad_agent_private *agent,
 	return mad_recv_wc;
 }
 
-static inline u64 get_seg_addr(struct ib_mad_send_wr_private *mad_send_wr)
-{
-	return mad_send_wr->sg_list[0].addr + mad_send_wr->data_offset +
-	       (sizeof(struct ib_rmpp_mad) - mad_send_wr->data_offset) *
-	       (mad_send_wr->seg_num - 1);
-}
-
 static int send_next_seg(struct ib_mad_send_wr_private *mad_send_wr)
 {
 	struct ib_rmpp_mad *rmpp_mad;
 	int timeout;
-	u32 paylen;
+	u32 paylen = 0;
 
 	rmpp_mad = mad_send_wr->send_buf.mad;
 	ib_set_rmpp_flags(&rmpp_mad->rmpp_hdr, IB_MGMT_RMPP_FLAG_ACTIVE);
-	rmpp_mad->rmpp_hdr.seg_num = cpu_to_be32(mad_send_wr->seg_num);
+	rmpp_mad->rmpp_hdr.seg_num = cpu_to_be32(++mad_send_wr->seg_num);
 
 	if (mad_send_wr->seg_num == 1) {
 		rmpp_mad->rmpp_hdr.rmpp_rtime_flags |= IB_MGMT_RMPP_FLAG_FIRST;
-		paylen = mad_send_wr->total_seg * IB_MGMT_RMPP_DATA -
+		paylen = mad_send_wr->send_buf.seg_count * IB_MGMT_RMPP_DATA -
 			 mad_send_wr->pad;
-		rmpp_mad->rmpp_hdr.paylen_newwin = cpu_to_be32(paylen);
-		mad_send_wr->sg_list[0].length = sizeof(struct ib_rmpp_mad);
-	} else {
-		mad_send_wr->send_wr.num_sge = 2;
-		mad_send_wr->sg_list[0].length = mad_send_wr->data_offset;
-		mad_send_wr->sg_list[1].addr = get_seg_addr(mad_send_wr);
-		mad_send_wr->sg_list[1].length = sizeof(struct ib_rmpp_mad) -
-						 mad_send_wr->data_offset;
-		mad_send_wr->sg_list[1].lkey = mad_send_wr->sg_list[0].lkey;
-		rmpp_mad->rmpp_hdr.paylen_newwin = 0;
 	}
 
-	if (mad_send_wr->seg_num == mad_send_wr->total_seg) {
+	if (mad_send_wr->seg_num == mad_send_wr->send_buf.seg_count) {
 		rmpp_mad->rmpp_hdr.rmpp_rtime_flags |= IB_MGMT_RMPP_FLAG_LAST;
 		paylen = IB_MGMT_RMPP_DATA - mad_send_wr->pad;
-		rmpp_mad->rmpp_hdr.paylen_newwin = cpu_to_be32(paylen);
 	}
+	rmpp_mad->rmpp_hdr.paylen_newwin = cpu_to_be32(paylen);
 
 	/* 2 seconds for an ACK until we can find the packet lifetime */
 	timeout = mad_send_wr->send_buf.timeout_ms;
 	if (!timeout || timeout > 2000)
 		mad_send_wr->timeout = msecs_to_jiffies(2000);
-	mad_send_wr->seg_num++;
+
 	return ib_send_mad(mad_send_wr);
 }
 
@@ -629,7 +574,7 @@ static void abort_send(struct ib_mad_agent_private *agent, __be64 tid,
 	if (!mad_send_wr)
 		goto out;	/* Unmatched send */
 
-	if ((mad_send_wr->last_ack == mad_send_wr->total_seg) ||
+	if ((mad_send_wr->last_ack == mad_send_wr->send_buf.seg_count) ||
 	    (!mad_send_wr->timeout) || (mad_send_wr->status != IB_WC_SUCCESS))
 		goto out;	/* Send is already done */
 
@@ -645,6 +590,18 @@ out:
 	spin_unlock_irqrestore(&agent->lock, flags);
 }
 
+static inline void adjust_last_ack(struct ib_mad_send_wr_private *wr,
+				   int seg_num)
+{
+	struct list_head *list;
+
+	wr->last_ack = seg_num;
+	list = &wr->last_ack_seg->list;
+	list_for_each_entry(wr->last_ack_seg, list, list)
+		if (wr->last_ack_seg->num == seg_num)
+			break;
+}
+
 static void process_rmpp_ack(struct ib_mad_agent_private *agent,
 			     struct ib_mad_recv_wc *mad_recv_wc)
 {
@@ -675,11 +632,12 @@ static void process_rmpp_ack(struct ib_mad_agent_private *agent,
 	if (!mad_send_wr)
 		goto out;	/* Unmatched ACK */
 
-	if ((mad_send_wr->last_ack == mad_send_wr->total_seg) ||
+	if ((mad_send_wr->last_ack == mad_send_wr->send_buf.seg_count) ||
 	    (!mad_send_wr->timeout) || (mad_send_wr->status != IB_WC_SUCCESS))
 		goto out;	/* Send is already done */
 
-	if (seg_num > mad_send_wr->total_seg || seg_num > mad_send_wr->newwin) {
+	if (seg_num > mad_send_wr->send_buf.seg_count ||
+	    seg_num > mad_send_wr->newwin) {
 		spin_unlock_irqrestore(&agent->lock, flags);
 		abort_send(agent, rmpp_mad->mad_hdr.tid,
 			   IB_MGMT_RMPP_STATUS_S2B);
@@ -691,11 +649,11 @@ static void process_rmpp_ack(struct ib_mad_agent_private *agent,
 		goto out;	/* Old ACK */
 
 	if (seg_num > mad_send_wr->last_ack) {
-		mad_send_wr->last_ack = seg_num;
+		adjust_last_ack(mad_send_wr, seg_num);
 		mad_send_wr->retries = mad_send_wr->send_buf.retries;
 	}
 	mad_send_wr->newwin = newwin;
-	if (mad_send_wr->last_ack == mad_send_wr->total_seg) {
+	if (mad_send_wr->last_ack == mad_send_wr->send_buf.seg_count) {
 		/* If no response is expected, the ACK completes the send */
 		if (!mad_send_wr->send_buf.timeout_ms) {
 			struct ib_mad_send_wc wc;
@@ -714,7 +672,7 @@ static void process_rmpp_ack(struct ib_mad_agent_private *agent,
 					     mad_send_wr->send_buf.timeout_ms);
 	} else if (mad_send_wr->refcount == 1 &&
 		   mad_send_wr->seg_num < mad_send_wr->newwin &&
-		   mad_send_wr->seg_num <= mad_send_wr->total_seg) {
+		   mad_send_wr->seg_num < mad_send_wr->send_buf.seg_count) {
 		/* Send failure will just result in a timeout/retry */
 		ret = send_next_seg(mad_send_wr);
 		if (ret)
@@ -838,31 +796,19 @@ out:
 int ib_send_rmpp_mad(struct ib_mad_send_wr_private *mad_send_wr)
 {
 	struct ib_rmpp_mad *rmpp_mad;
-	int i, total_len, ret;
+	int ret;
 
 	rmpp_mad = mad_send_wr->send_buf.mad;
 	if (!(ib_get_rmpp_flags(&rmpp_mad->rmpp_hdr) &
 	      IB_MGMT_RMPP_FLAG_ACTIVE))
 		return IB_RMPP_RESULT_UNHANDLED;
 
-	if (rmpp_mad->rmpp_hdr.rmpp_type != IB_MGMT_RMPP_TYPE_DATA)
+	if (rmpp_mad->rmpp_hdr.rmpp_type != IB_MGMT_RMPP_TYPE_DATA) {
+		mad_send_wr->seg_num = 1;
 		return IB_RMPP_RESULT_INTERNAL;
+	}
 
-	if (mad_send_wr->send_wr.num_sge > 1)
-		return -EINVAL;		/* TODO: support num_sge > 1 */
-
-	mad_send_wr->seg_num = 1;
 	mad_send_wr->newwin = 1;
-	mad_send_wr->data_offset = data_offset(rmpp_mad->mad_hdr.mgmt_class);
-
-	total_len = 0;
-	for (i = 0; i < mad_send_wr->send_wr.num_sge; i++)
-		total_len += mad_send_wr->send_wr.sg_list[i].length;
-
-        mad_send_wr->total_seg = (total_len - mad_send_wr->data_offset) /
-			(sizeof(struct ib_rmpp_mad) - mad_send_wr->data_offset);
-	mad_send_wr->pad = total_len - IB_MGMT_RMPP_HDR -
-			   be32_to_cpu(rmpp_mad->rmpp_hdr.paylen_newwin);
 
 	/* We need to wait for the final ACK even if there isn't a response */
 	mad_send_wr->refcount += (mad_send_wr->timeout == 0);
@@ -893,14 +839,14 @@ int ib_process_rmpp_send_wc(struct ib_mad_send_wr_private *mad_send_wr,
 	if (!mad_send_wr->timeout)
 		return IB_RMPP_RESULT_PROCESSED; /* Response received */
 
-	if (mad_send_wr->last_ack == mad_send_wr->total_seg) {
+	if (mad_send_wr->last_ack == mad_send_wr->send_buf.seg_count) {
 		mad_send_wr->timeout =
 			msecs_to_jiffies(mad_send_wr->send_buf.timeout_ms);
 		return IB_RMPP_RESULT_PROCESSED; /* Send done */
 	}
 
-	if (mad_send_wr->seg_num > mad_send_wr->newwin ||
-	    mad_send_wr->seg_num > mad_send_wr->total_seg)
+	if (mad_send_wr->seg_num == mad_send_wr->newwin ||
+	    mad_send_wr->seg_num == mad_send_wr->send_buf.seg_count)
 		return IB_RMPP_RESULT_PROCESSED; /* Wait for ACK */
 
 	ret = send_next_seg(mad_send_wr);
@@ -921,10 +867,12 @@ int ib_retry_rmpp(struct ib_mad_send_wr_private *mad_send_wr)
 	      IB_MGMT_RMPP_FLAG_ACTIVE))
 		return IB_RMPP_RESULT_UNHANDLED; /* RMPP not active */
 
-	if (mad_send_wr->last_ack == mad_send_wr->total_seg)
+	if (mad_send_wr->last_ack == mad_send_wr->send_buf.seg_count)
 		return IB_RMPP_RESULT_PROCESSED;
 
-	mad_send_wr->seg_num = mad_send_wr->last_ack + 1;
+	mad_send_wr->seg_num = mad_send_wr->last_ack;
+	mad_send_wr->cur_seg = mad_send_wr->last_ack_seg;
+
 	ret = send_next_seg(mad_send_wr);
 	if (ret)
 		return IB_RMPP_RESULT_PROCESSED;

drivers/infiniband/core/user_mad.c

@@ -31,7 +31,7 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  *
- * $Id: user_mad.c 4010 2005-11-09 23:11:56Z roland $
+ * $Id: user_mad.c 5596 2006-03-03 01:00:07Z sean.hefty $
  */
 
 #include <linux/module.h>
@@ -121,6 +121,7 @@ struct ib_umad_file {
 
 struct ib_umad_packet {
 	struct ib_mad_send_buf *msg;
+	struct ib_mad_recv_wc  *recv_wc;
 	struct list_head   list;
 	int		   length;
 	struct ib_user_mad mad;
@@ -176,31 +177,32 @@ static int queue_packet(struct ib_umad_file *file,
 	return ret;
 }
 
+static int data_offset(u8 mgmt_class)
+{
+	if (mgmt_class == IB_MGMT_CLASS_SUBN_ADM)
+		return IB_MGMT_SA_HDR;
+	else if ((mgmt_class >= IB_MGMT_CLASS_VENDOR_RANGE2_START) &&
+		 (mgmt_class <= IB_MGMT_CLASS_VENDOR_RANGE2_END))
+		return IB_MGMT_VENDOR_HDR;
+	else
+		return IB_MGMT_RMPP_HDR;
+}
+
 static void send_handler(struct ib_mad_agent *agent,
 			 struct ib_mad_send_wc *send_wc)
 {
 	struct ib_umad_file *file = agent->context;
-	struct ib_umad_packet *timeout;
 	struct ib_umad_packet *packet = send_wc->send_buf->context[0];
 
 	ib_destroy_ah(packet->msg->ah);
 	ib_free_send_mad(packet->msg);
 
 	if (send_wc->status == IB_WC_RESP_TIMEOUT_ERR) {
-		timeout = kzalloc(sizeof *timeout + IB_MGMT_MAD_HDR, GFP_KERNEL);
-		if (!timeout)
-			goto out;
-
-		timeout->length 	= IB_MGMT_MAD_HDR;
-		timeout->mad.hdr.id 	= packet->mad.hdr.id;
-		timeout->mad.hdr.status = ETIMEDOUT;
-		memcpy(timeout->mad.data, packet->mad.data,
-		       sizeof (struct ib_mad_hdr));
-
-		if (queue_packet(file, agent, timeout))
-			kfree(timeout);
+		packet->length = IB_MGMT_MAD_HDR;
+		packet->mad.hdr.status = ETIMEDOUT;
+		if (!queue_packet(file, agent, packet))
+			return;
 	}
-out:
 	kfree(packet);
 }
 
@@ -209,22 +211,20 @@ static void recv_handler(struct ib_mad_agent *agent,
 {
 	struct ib_umad_file *file = agent->context;
 	struct ib_umad_packet *packet;
-	int length;
 
 	if (mad_recv_wc->wc->status != IB_WC_SUCCESS)
-		goto out;
+		goto err1;
 
-	length = mad_recv_wc->mad_len;
-	packet = kzalloc(sizeof *packet + length, GFP_KERNEL);
+	packet = kzalloc(sizeof *packet, GFP_KERNEL);
 	if (!packet)
-		goto out;
+		goto err1;
 
-	packet->length = length;
-
-	ib_coalesce_recv_mad(mad_recv_wc, packet->mad.data);
+	packet->length = mad_recv_wc->mad_len;
+	packet->recv_wc = mad_recv_wc;
 
 	packet->mad.hdr.status    = 0;
-	packet->mad.hdr.length    = length + sizeof (struct ib_user_mad);
+	packet->mad.hdr.length    = sizeof (struct ib_user_mad) +
+				    mad_recv_wc->mad_len;
 	packet->mad.hdr.qpn 	  = cpu_to_be32(mad_recv_wc->wc->src_qp);
 	packet->mad.hdr.lid 	  = cpu_to_be16(mad_recv_wc->wc->slid);
 	packet->mad.hdr.sl  	  = mad_recv_wc->wc->sl;
@@ -240,12 +240,79 @@ static void recv_handler(struct ib_mad_agent *agent,
 	}
 
 	if (queue_packet(file, agent, packet))
-		kfree(packet);
+		goto err2;
+	return;
 
-out:
+err2:
+	kfree(packet);
+err1:
 	ib_free_recv_mad(mad_recv_wc);
 }
 
+static ssize_t copy_recv_mad(char __user *buf, struct ib_umad_packet *packet,
+			     size_t count)
+{
+	struct ib_mad_recv_buf *recv_buf;
+	int left, seg_payload, offset, max_seg_payload;
+
+	/* We need enough room to copy the first (or only) MAD segment. */
+	recv_buf = &packet->recv_wc->recv_buf;
+	if ((packet->length <= sizeof (*recv_buf->mad) &&
+	     count < sizeof (packet->mad) + packet->length) ||
+	    (packet->length > sizeof (*recv_buf->mad) &&
+	     count < sizeof (packet->mad) + sizeof (*recv_buf->mad)))
+		return -EINVAL;
+
+	if (copy_to_user(buf, &packet->mad, sizeof (packet->mad)))
+		return -EFAULT;
+
+	buf += sizeof (packet->mad);
+	seg_payload = min_t(int, packet->length, sizeof (*recv_buf->mad));
+	if (copy_to_user(buf, recv_buf->mad, seg_payload))
+		return -EFAULT;
+
+	if (seg_payload < packet->length) {
+		/*
+		 * Multipacket RMPP MAD message. Copy remainder of message.
+		 * Note that last segment may have a shorter payload.
+		 */
+		if (count < sizeof (packet->mad) + packet->length) {
+			/*
+			 * The buffer is too small, return the first RMPP segment,
+			 * which includes the RMPP message length.
+			 */
+			return -ENOSPC;
+		}
+		offset = data_offset(recv_buf->mad->mad_hdr.mgmt_class);
+		max_seg_payload = sizeof (struct ib_mad) - offset;
+
+		for (left = packet->length - seg_payload, buf += seg_payload;
+		     left; left -= seg_payload, buf += seg_payload) {
+			recv_buf = container_of(recv_buf->list.next,
+						struct ib_mad_recv_buf, list);
+			seg_payload = min(left, max_seg_payload);
+			if (copy_to_user(buf, ((void *) recv_buf->mad) + offset,
+					 seg_payload))
+				return -EFAULT;
+		}
+	}
+	return sizeof (packet->mad) + packet->length;
+}
+
+static ssize_t copy_send_mad(char __user *buf, struct ib_umad_packet *packet,
+			     size_t count)
+{
+	ssize_t size = sizeof (packet->mad) + packet->length;
+
+	if (count < size)
+		return -EINVAL;
+
+	if (copy_to_user(buf, &packet->mad, size))
+		return -EFAULT;
+
+	return size;
+}
+
 static ssize_t ib_umad_read(struct file *filp, char __user *buf,
 			    size_t count, loff_t *pos)
 {
@@ -253,7 +320,7 @@ static ssize_t ib_umad_read(struct file *filp, char __user *buf,
 	struct ib_umad_packet *packet;
 	ssize_t ret;
 
-	if (count < sizeof (struct ib_user_mad) + sizeof (struct ib_mad))
+	if (count < sizeof (struct ib_user_mad))
 		return -EINVAL;
 
 	spin_lock_irq(&file->recv_lock);
@@ -276,28 +343,44 @@ static ssize_t ib_umad_read(struct file *filp, char __user *buf,
 
 	spin_unlock_irq(&file->recv_lock);
 
-	if (count < packet->length + sizeof (struct ib_user_mad)) {
-		/* Return length needed (and first RMPP segment) if too small */
-		if (copy_to_user(buf, &packet->mad,
-				 sizeof (struct ib_user_mad) + sizeof (struct ib_mad)))
-			ret = -EFAULT;
-		else
-			ret = -ENOSPC;
-	} else if (copy_to_user(buf, &packet->mad,
-				packet->length + sizeof (struct ib_user_mad)))
-		ret = -EFAULT;
+	if (packet->recv_wc)
+		ret = copy_recv_mad(buf, packet, count);
 	else
-		ret = packet->length + sizeof (struct ib_user_mad);
+		ret = copy_send_mad(buf, packet, count);
+
 	if (ret < 0) {
 		/* Requeue packet */
 		spin_lock_irq(&file->recv_lock);
 		list_add(&packet->list, &file->recv_list);
 		spin_unlock_irq(&file->recv_lock);
-	} else
+	} else {
+		if (packet->recv_wc)
+			ib_free_recv_mad(packet->recv_wc);
 		kfree(packet);
+	}
 	return ret;
 }
 
+static int copy_rmpp_mad(struct ib_mad_send_buf *msg, const char __user *buf)
+{
+	int left, seg;
+
+	/* Copy class specific header */
+	if ((msg->hdr_len > IB_MGMT_RMPP_HDR) &&
+	    copy_from_user(msg->mad + IB_MGMT_RMPP_HDR, buf + IB_MGMT_RMPP_HDR,
+			   msg->hdr_len - IB_MGMT_RMPP_HDR))
+		return -EFAULT;
+
+	/* All headers are in place.  Copy data segments. */
+	for (seg = 1, left = msg->data_len, buf += msg->hdr_len; left > 0;
+	     seg++, left -= msg->seg_size, buf += msg->seg_size) {
+		if (copy_from_user(ib_get_rmpp_segment(msg, seg), buf,
+				   min(left, msg->seg_size)))
+			return -EFAULT;
+	}
+	return 0;
+}
+
 static ssize_t ib_umad_write(struct file *filp, const char __user *buf,
 			     size_t count, loff_t *pos)
 {
@@ -309,14 +392,12 @@ static ssize_t ib_umad_write(struct file *filp, const char __user *buf,
 	struct ib_rmpp_mad *rmpp_mad;
 	u8 method;
 	__be64 *tid;
-	int ret, length, hdr_len, copy_offset;
-	int rmpp_active, has_rmpp_header;
+	int ret, data_len, hdr_len, copy_offset, rmpp_active;
 
 	if (count < sizeof (struct ib_user_mad) + IB_MGMT_RMPP_HDR)
 		return -EINVAL;
 
-	length = count - sizeof (struct ib_user_mad);
-	packet = kmalloc(sizeof *packet + IB_MGMT_RMPP_HDR, GFP_KERNEL);
+	packet = kzalloc(sizeof *packet + IB_MGMT_RMPP_HDR, GFP_KERNEL);
 	if (!packet)
 		return -ENOMEM;
 
@@ -363,35 +444,25 @@ static ssize_t ib_umad_write(struct file *filp, const char __user *buf,
 	if (rmpp_mad->mad_hdr.mgmt_class == IB_MGMT_CLASS_SUBN_ADM) {
 		hdr_len = IB_MGMT_SA_HDR;
 		copy_offset = IB_MGMT_RMPP_HDR;
-		has_rmpp_header = 1;
+		rmpp_active = ib_get_rmpp_flags(&rmpp_mad->rmpp_hdr) &
+			      IB_MGMT_RMPP_FLAG_ACTIVE;
 	} else if (rmpp_mad->mad_hdr.mgmt_class >= IB_MGMT_CLASS_VENDOR_RANGE2_START &&
 		   rmpp_mad->mad_hdr.mgmt_class <= IB_MGMT_CLASS_VENDOR_RANGE2_END) {
-			hdr_len = IB_MGMT_VENDOR_HDR;
-			copy_offset = IB_MGMT_RMPP_HDR;
-			has_rmpp_header = 1;
+		hdr_len = IB_MGMT_VENDOR_HDR;
+		copy_offset = IB_MGMT_RMPP_HDR;
+		rmpp_active = ib_get_rmpp_flags(&rmpp_mad->rmpp_hdr) &
+			      IB_MGMT_RMPP_FLAG_ACTIVE;
 	} else {
 		hdr_len = IB_MGMT_MAD_HDR;
 		copy_offset = IB_MGMT_MAD_HDR;
-		has_rmpp_header = 0;
-	}
-
-	if (has_rmpp_header)
-		rmpp_active = ib_get_rmpp_flags(&rmpp_mad->rmpp_hdr) &
-			      IB_MGMT_RMPP_FLAG_ACTIVE;
-	else
 		rmpp_active = 0;
-
-	/* Validate that the management class can support RMPP */
-	if (rmpp_active && !agent->rmpp_version) {
-		ret = -EINVAL;
-		goto err_ah;
 	}
 
+	data_len = count - sizeof (struct ib_user_mad) - hdr_len;
 	packet->msg = ib_create_send_mad(agent,
 					 be32_to_cpu(packet->mad.hdr.qpn),
-					 0, rmpp_active,
-					 hdr_len, length - hdr_len,
-					 GFP_KERNEL);
+					 0, rmpp_active, hdr_len,
+					 data_len, GFP_KERNEL);
 	if (IS_ERR(packet->msg)) {
 		ret = PTR_ERR(packet->msg);
 		goto err_ah;
@@ -402,14 +473,21 @@ static ssize_t ib_umad_write(struct file *filp, const char __user *buf,
 	packet->msg->retries 	= packet->mad.hdr.retries;
 	packet->msg->context[0] = packet;
 
-	/* Copy MAD headers (RMPP header in place) */
+	/* Copy MAD header.  Any RMPP header is already in place. */
 	memcpy(packet->msg->mad, packet->mad.data, IB_MGMT_MAD_HDR);
-	/* Now, copy rest of message from user into send buffer */
-	if (copy_from_user(packet->msg->mad + copy_offset,
-			   buf + sizeof (struct ib_user_mad) + copy_offset,
-			   length - copy_offset)) {
-		ret = -EFAULT;
-		goto err_msg;
+	buf += sizeof (struct ib_user_mad);
+
+	if (!rmpp_active) {
+		if (copy_from_user(packet->msg->mad + copy_offset,
+				   buf + copy_offset,
+				   hdr_len + data_len - copy_offset)) {
+			ret = -EFAULT;
+			goto err_msg;
+		}
+	} else {
+		ret = copy_rmpp_mad(packet->msg, buf);
+		if (ret)
+			goto err_msg;
 	}
 
 	/*
@@ -433,18 +511,14 @@ static ssize_t ib_umad_write(struct file *filp, const char __user *buf,
 		goto err_msg;
 
 	up_read(&file->port->mutex);
-
 	return count;
 
 err_msg:
 	ib_free_send_mad(packet->msg);
-
 err_ah:
 	ib_destroy_ah(ah);
-
 err_up:
 	up_read(&file->port->mutex);
-
 err:
 	kfree(packet);
 	return ret;
@@ -627,8 +701,11 @@ static int ib_umad_close(struct inode *inode, struct file *filp)
 	already_dead = file->agents_dead;
 	file->agents_dead = 1;
 
-	list_for_each_entry_safe(packet, tmp, &file->recv_list, list)
+	list_for_each_entry_safe(packet, tmp, &file->recv_list, list) {
+		if (packet->recv_wc)
+			ib_free_recv_mad(packet->recv_wc);
 		kfree(packet);
+	}
 
 	list_del(&file->port_list);
 

include/rdma/ib_mad.h

@@ -33,7 +33,7 @@
  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  *
- * $Id: ib_mad.h 2775 2005-07-02 13:42:12Z halr $
+ * $Id: ib_mad.h 5596 2006-03-03 01:00:07Z sean.hefty $
  */
 
 #if !defined( IB_MAD_H )
@@ -208,15 +208,23 @@ struct ib_class_port_info
 /**
  * ib_mad_send_buf - MAD data buffer and work request for sends.
  * @next: A pointer used to chain together MADs for posting.
- * @mad: References an allocated MAD data buffer.
+ * @mad: References an allocated MAD data buffer for MADs that do not have
+ *   RMPP active.  For MADs using RMPP, references the common and management
+ *   class specific headers.
  * @mad_agent: MAD agent that allocated the buffer.
  * @ah: The address handle to use when sending the MAD.
  * @context: User-controlled context fields.
+ * @hdr_len: Indicates the size of the data header of the MAD.  This length
+ *   includes the common MAD, RMPP, and class specific headers.
+ * @data_len: Indicates the total size of user-transferred data.
+ * @seg_count: The number of RMPP segments allocated for this send.
+ * @seg_size: Size of each RMPP segment.
  * @timeout_ms: Time to wait for a response.
  * @retries: Number of times to retry a request for a response.
  *
  * Users are responsible for initializing the MAD buffer itself, with the
- * exception of specifying the payload length field in any RMPP MAD.
+ * exception of any RMPP header.  Additional segment buffer space allocated
+ * beyond data_len is padding.
  */
 struct ib_mad_send_buf {
 	struct ib_mad_send_buf	*next;
@@ -224,6 +232,10 @@ struct ib_mad_send_buf {
 	struct ib_mad_agent	*mad_agent;
 	struct ib_ah		*ah;
 	void			*context[2];
+	int			hdr_len;
+	int			data_len;
+	int			seg_count;
+	int			seg_size;
 	int			timeout_ms;
 	int			retries;
 };
@@ -299,7 +311,7 @@ typedef void (*ib_mad_snoop_handler)(struct ib_mad_agent *mad_agent,
  * @mad_recv_wc: Received work completion information on the received MAD.
  *
  * MADs received in response to a send request operation will be handed to
- * the user after the send operation completes.  All data buffers given
+ * the user before the send operation completes.  All data buffers given
  * to registered agents through this routine are owned by the receiving
  * client, except for snooping agents.  Clients snooping MADs should not
  * modify the data referenced by @mad_recv_wc.
@@ -485,17 +497,6 @@ int ib_unregister_mad_agent(struct ib_mad_agent *mad_agent);
 int ib_post_send_mad(struct ib_mad_send_buf *send_buf,
 		     struct ib_mad_send_buf **bad_send_buf);
 
-/**
- * ib_coalesce_recv_mad - Coalesces received MAD data into a single buffer.
- * @mad_recv_wc: Work completion information for a received MAD.
- * @buf: User-provided data buffer to receive the coalesced buffers.  The
- *   referenced buffer should be at least the size of the mad_len specified
- *   by @mad_recv_wc.
- *
- * This call copies a chain of received MAD segments into a single data buffer,
- * removing duplicated headers.
- */
-void ib_coalesce_recv_mad(struct ib_mad_recv_wc *mad_recv_wc, void *buf);
 
 /**
  * ib_free_recv_mad - Returns data buffers used to receive a MAD.
@@ -590,9 +591,10 @@ int ib_process_mad_wc(struct ib_mad_agent *mad_agent,
  * with an initialized work request structure.  Users may modify the returned
  * MAD data buffer before posting the send.
  *
- * The returned data buffer will be cleared.  Users are responsible for
- * initializing the common MAD and any class specific headers.  If @rmpp_active
- * is set, the RMPP header will be initialized for sending.
+ * The returned MAD header, class specific headers, and any padding will be
+ * cleared.  Users are responsible for initializing the common MAD header,
+ * any class specific header, and MAD data area.
+ * If @rmpp_active is set, the RMPP header will be initialized for sending.
  */
 struct ib_mad_send_buf * ib_create_send_mad(struct ib_mad_agent *mad_agent,
 					    u32 remote_qpn, u16 pkey_index,
@@ -600,6 +602,16 @@ struct ib_mad_send_buf * ib_create_send_mad(struct ib_mad_agent *mad_agent,
 					    int hdr_len, int data_len,
 					    gfp_t gfp_mask);
 
+/**
+ * ib_get_rmpp_segment - returns the data buffer for a given RMPP segment.
+ * @send_buf: Previously allocated send data buffer.
+ * @seg_num: number of segment to return
+ *
+ * This routine returns a pointer to the data buffer of an RMPP MAD.
+ * Users must provide synchronization to @send_buf around this call.
+ */
+void *ib_get_rmpp_segment(struct ib_mad_send_buf *send_buf, int seg_num);
+
 /**
  * ib_free_send_mad - Returns data buffers used to send a MAD.
  * @send_buf: Previously allocated send data buffer.