net/sunrpc/xprtrdma/svc_rdma_sendto.c - kernel/msm - Gitiles

 /*
  * Copyright (c) 2005-2006 Network Appliance, Inc. All rights reserved.
  *
  * This software is available to you under a choice of one of two
  * licenses.  You may choose to be licensed under the terms of the GNU
  * General Public License (GPL) Version 2, available from the file
  * COPYING in the main directory of this source tree, or the BSD-type
  * license below:
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  *      Redistributions of source code must retain the above copyright
  *      notice, this list of conditions and the following disclaimer.
  *
  *      Redistributions in binary form must reproduce the above
  *      copyright notice, this list of conditions and the following
  *      disclaimer in the documentation and/or other materials provided
  *      with the distribution.
  *
  *      Neither the name of the Network Appliance, Inc. nor the names of
  *      its contributors may be used to endorse or promote products
  *      derived from this software without specific prior written
  *      permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * Author: Tom Tucker <tom@opengridcomputing.com>
  */

 #include <linux/sunrpc/debug.h>
 #include <linux/sunrpc/rpc_rdma.h>
 #include <linux/spinlock.h>
 #include <asm/unaligned.h>
 #include <rdma/ib_verbs.h>
 #include <rdma/rdma_cm.h>
 #include <linux/sunrpc/svc_rdma.h>

 #define RPCDBG_FACILITY	RPCDBG_SVCXPRT

 /* Encode an XDR as an array of IB SGE
  *
  * Assumptions:
  * - head[0] is physically contiguous.
  * - tail[0] is physically contiguous.
  * - pages[] is not physically or virtually contigous and consists of
  *   PAGE_SIZE elements.
  *
  * Output:
  * SGE[0]              reserved for RCPRDMA header
  * SGE[1]              data from xdr->head[]
  * SGE[2..sge_count-2] data from xdr->pages[]
  * SGE[sge_count-1]    data from xdr->tail.
  *
  */
 static struct ib_sge *xdr_to_sge(struct svcxprt_rdma *xprt,
 				 struct xdr_buf *xdr,
 				 struct ib_sge *sge,
 				 int *sge_count)
 {
 	/* Max we need is the length of the XDR / pagesize + one for
 	 * head + one for tail + one for RPCRDMA header
 	 */
 	int sge_max = (xdr->len+PAGE_SIZE-1) / PAGE_SIZE + 3;
 	int sge_no;
 	u32 byte_count = xdr->len;
 	u32 sge_bytes;
 	u32 page_bytes;
 	int page_off;
 	int page_no;

 	/* Skip the first sge, this is for the RPCRDMA header */
 	sge_no = 1;

 	/* Head SGE */
 	sge[sge_no].addr = ib_dma_map_single(xprt->sc_cm_id->device,
 					     xdr->head[0].iov_base,
 					     xdr->head[0].iov_len,
 					     DMA_TO_DEVICE);
 	sge_bytes = min_t(u32, byte_count, xdr->head[0].iov_len);
 	byte_count -= sge_bytes;
 	sge[sge_no].length = sge_bytes;
 	sge[sge_no].lkey = xprt->sc_phys_mr->lkey;
 	sge_no++;

 	/* pages SGE */
 	page_no = 0;
 	page_bytes = xdr->page_len;
 	page_off = xdr->page_base;
 	while (byte_count && page_bytes) {
 		sge_bytes = min_t(u32, byte_count, (PAGE_SIZE-page_off));
 		sge[sge_no].addr =
 			ib_dma_map_page(xprt->sc_cm_id->device,
 					xdr->pages[page_no], page_off,
 					sge_bytes, DMA_TO_DEVICE);
 		sge_bytes = min(sge_bytes, page_bytes);
 		byte_count -= sge_bytes;
 		page_bytes -= sge_bytes;
 		sge[sge_no].length = sge_bytes;
 		sge[sge_no].lkey = xprt->sc_phys_mr->lkey;

 		sge_no++;
 		page_no++;
 		page_off = 0; /* reset for next time through loop */
 	}

 	/* Tail SGE */
 	if (byte_count && xdr->tail[0].iov_len) {
 		sge[sge_no].addr =
 			ib_dma_map_single(xprt->sc_cm_id->device,
 					  xdr->tail[0].iov_base,
 					  xdr->tail[0].iov_len,
 					  DMA_TO_DEVICE);
 		sge_bytes = min_t(u32, byte_count, xdr->tail[0].iov_len);
 		byte_count -= sge_bytes;
 		sge[sge_no].length = sge_bytes;
 		sge[sge_no].lkey = xprt->sc_phys_mr->lkey;
 		sge_no++;
 	}

 	BUG_ON(sge_no > sge_max);
 	BUG_ON(byte_count != 0);

 	*sge_count = sge_no;
 	return sge;
 }


 /* Assumptions:
  * - The specified write_len can be represented in sc_max_sge * PAGE_SIZE
  */
 static int send_write(struct svcxprt_rdma *xprt, struct svc_rqst *rqstp,
 		      u32 rmr, u64 to,
 		      u32 xdr_off, int write_len,
 		      struct ib_sge *xdr_sge, int sge_count)
 {
 	struct svc_rdma_op_ctxt *tmp_sge_ctxt;
 	struct ib_send_wr write_wr;
 	struct ib_sge *sge;
 	int xdr_sge_no;
 	int sge_no;
 	int sge_bytes;
 	int sge_off;
 	int bc;
 	struct svc_rdma_op_ctxt *ctxt;
 	int ret = 0;

 	BUG_ON(sge_count > RPCSVC_MAXPAGES);
 	dprintk("svcrdma: RDMA_WRITE rmr=%x, to=%llx, xdr_off=%d, "
 		"write_len=%d, xdr_sge=%p, sge_count=%d\n",
 		rmr, (unsigned long long)to, xdr_off,
 		write_len, xdr_sge, sge_count);

 	ctxt = svc_rdma_get_context(xprt);
 	ctxt->count = 0;
 	tmp_sge_ctxt = svc_rdma_get_context(xprt);
 	sge = tmp_sge_ctxt->sge;

 	/* Find the SGE associated with xdr_off */
 	for (bc = xdr_off, xdr_sge_no = 1; bc && xdr_sge_no < sge_count;
 	     xdr_sge_no++) {
 		if (xdr_sge[xdr_sge_no].length > bc)
 			break;
 		bc -= xdr_sge[xdr_sge_no].length;
 	}

 	sge_off = bc;
 	bc = write_len;
 	sge_no = 0;

 	/* Copy the remaining SGE */
 	while (bc != 0 && xdr_sge_no < sge_count) {
 		sge[sge_no].addr = xdr_sge[xdr_sge_no].addr + sge_off;
 		sge[sge_no].lkey = xdr_sge[xdr_sge_no].lkey;
 		sge_bytes = min((size_t)bc,
 				(size_t)(xdr_sge[xdr_sge_no].length-sge_off));
 		sge[sge_no].length = sge_bytes;

 		sge_off = 0;
 		sge_no++;
 		xdr_sge_no++;
 		bc -= sge_bytes;
 	}

 	BUG_ON(bc != 0);
 	BUG_ON(xdr_sge_no > sge_count);

 	/* Prepare WRITE WR */
 	memset(&write_wr, 0, sizeof write_wr);
 	ctxt->wr_op = IB_WR_RDMA_WRITE;
 	write_wr.wr_id = (unsigned long)ctxt;
 	write_wr.sg_list = &sge[0];
 	write_wr.num_sge = sge_no;
 	write_wr.opcode = IB_WR_RDMA_WRITE;
 	write_wr.send_flags = IB_SEND_SIGNALED;
 	write_wr.wr.rdma.rkey = rmr;
 	write_wr.wr.rdma.remote_addr = to;

 	/* Post It */
 	atomic_inc(&rdma_stat_write);
 	if (svc_rdma_send(xprt, &write_wr)) {
 		svc_rdma_put_context(ctxt, 1);
 		/* Fatal error, close transport */
 		ret = -EIO;
 	}
 	svc_rdma_put_context(tmp_sge_ctxt, 0);
 	return ret;
 }

 static int send_write_chunks(struct svcxprt_rdma *xprt,
 			     struct rpcrdma_msg *rdma_argp,
 			     struct rpcrdma_msg *rdma_resp,
 			     struct svc_rqst *rqstp,
 			     struct ib_sge *sge,
 			     int sge_count)
 {
 	u32 xfer_len = rqstp->rq_res.page_len + rqstp->rq_res.tail[0].iov_len;
 	int write_len;
 	int max_write;
 	u32 xdr_off;
 	int chunk_off;
 	int chunk_no;
 	struct rpcrdma_write_array *arg_ary;
 	struct rpcrdma_write_array *res_ary;
 	int ret;

 	arg_ary = svc_rdma_get_write_array(rdma_argp);
 	if (!arg_ary)
 		return 0;
 	res_ary = (struct rpcrdma_write_array *)
 		&rdma_resp->rm_body.rm_chunks[1];

 	max_write = xprt->sc_max_sge * PAGE_SIZE;

 	/* Write chunks start at the pagelist */
 	for (xdr_off = rqstp->rq_res.head[0].iov_len, chunk_no = 0;
 	     xfer_len && chunk_no < arg_ary->wc_nchunks;
 	     chunk_no++) {
 		struct rpcrdma_segment *arg_ch;
 		u64 rs_offset;

 		arg_ch = &arg_ary->wc_array[chunk_no].wc_target;
 		write_len = min(xfer_len, arg_ch->rs_length);

 		/* Prepare the response chunk given the length actually
 		 * written */
 		rs_offset = get_unaligned(&(arg_ch->rs_offset));
 		svc_rdma_xdr_encode_array_chunk(res_ary, chunk_no,
 					    arg_ch->rs_handle,
 					    rs_offset,
 					    write_len);
 		chunk_off = 0;
 		while (write_len) {
 			int this_write;
 			this_write = min(write_len, max_write);
 			ret = send_write(xprt, rqstp,
 					 arg_ch->rs_handle,
 					 rs_offset + chunk_off,
 					 xdr_off,
 					 this_write,
 					 sge,
 					 sge_count);
 			if (ret) {
 				dprintk("svcrdma: RDMA_WRITE failed, ret=%d\n",
 					ret);
 				return -EIO;
 			}
 			chunk_off += this_write;
 			xdr_off += this_write;
 			xfer_len -= this_write;
 			write_len -= this_write;
 		}
 	}
 	/* Update the req with the number of chunks actually used */
 	svc_rdma_xdr_encode_write_list(rdma_resp, chunk_no);

 	return rqstp->rq_res.page_len + rqstp->rq_res.tail[0].iov_len;
 }

 static int send_reply_chunks(struct svcxprt_rdma *xprt,
 			     struct rpcrdma_msg *rdma_argp,
 			     struct rpcrdma_msg *rdma_resp,
 			     struct svc_rqst *rqstp,
 			     struct ib_sge *sge,
 			     int sge_count)
 {
 	u32 xfer_len = rqstp->rq_res.len;
 	int write_len;
 	int max_write;
 	u32 xdr_off;
 	int chunk_no;
 	int chunk_off;
 	struct rpcrdma_segment *ch;
 	struct rpcrdma_write_array *arg_ary;
 	struct rpcrdma_write_array *res_ary;
 	int ret;

 	arg_ary = svc_rdma_get_reply_array(rdma_argp);
 	if (!arg_ary)
 		return 0;
 	/* XXX: need to fix when reply lists occur with read-list and or
 	 * write-list */
 	res_ary = (struct rpcrdma_write_array *)
 		&rdma_resp->rm_body.rm_chunks[2];

 	max_write = xprt->sc_max_sge * PAGE_SIZE;

 	/* xdr offset starts at RPC message */
 	for (xdr_off = 0, chunk_no = 0;
 	     xfer_len && chunk_no < arg_ary->wc_nchunks;
 	     chunk_no++) {
 		u64 rs_offset;
 		ch = &arg_ary->wc_array[chunk_no].wc_target;
 		write_len = min(xfer_len, ch->rs_length);


 		/* Prepare the reply chunk given the length actually
 		 * written */
 		rs_offset = get_unaligned(&(ch->rs_offset));
 		svc_rdma_xdr_encode_array_chunk(res_ary, chunk_no,
 					    ch->rs_handle, rs_offset,
 					    write_len);
 		chunk_off = 0;
 		while (write_len) {
 			int this_write;

 			this_write = min(write_len, max_write);
 			ret = send_write(xprt, rqstp,
 					 ch->rs_handle,
 					 rs_offset + chunk_off,
 					 xdr_off,
 					 this_write,
 					 sge,
 					 sge_count);
 			if (ret) {
 				dprintk("svcrdma: RDMA_WRITE failed, ret=%d\n",
 					ret);
 				return -EIO;
 			}
 			chunk_off += this_write;
 			xdr_off += this_write;
 			xfer_len -= this_write;
 			write_len -= this_write;
 		}
 	}
 	/* Update the req with the number of chunks actually used */
 	svc_rdma_xdr_encode_reply_array(res_ary, chunk_no);

 	return rqstp->rq_res.len;
 }

 /* This function prepares the portion of the RPCRDMA message to be
  * sent in the RDMA_SEND. This function is called after data sent via
  * RDMA has already been transmitted. There are three cases:
  * - The RPCRDMA header, RPC header, and payload are all sent in a
  *   single RDMA_SEND. This is the "inline" case.
  * - The RPCRDMA header and some portion of the RPC header and data
  *   are sent via this RDMA_SEND and another portion of the data is
  *   sent via RDMA.
  * - The RPCRDMA header [NOMSG] is sent in this RDMA_SEND and the RPC
  *   header and data are all transmitted via RDMA.
  * In all three cases, this function prepares the RPCRDMA header in
  * sge[0], the 'type' parameter indicates the type to place in the
  * RPCRDMA header, and the 'byte_count' field indicates how much of
  * the XDR to include in this RDMA_SEND.
  */
 static int send_reply(struct svcxprt_rdma *rdma,
 		      struct svc_rqst *rqstp,
 		      struct page *page,
 		      struct rpcrdma_msg *rdma_resp,
 		      struct svc_rdma_op_ctxt *ctxt,
 		      int sge_count,
 		      int byte_count)
 {
 	struct ib_send_wr send_wr;
 	int sge_no;
 	int sge_bytes;
 	int page_no;
 	int ret;

 	/* Post a recv buffer to handle another request. */
 	ret = svc_rdma_post_recv(rdma);
 	if (ret) {
 		printk(KERN_INFO
 		       "svcrdma: could not post a receive buffer, err=%d."
 		       "Closing transport %p.\n", ret, rdma);
 		set_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags);
 		svc_rdma_put_context(ctxt, 0);
 		return -ENOTCONN;
 	}

 	/* Prepare the context */
 	ctxt->pages[0] = page;
 	ctxt->count = 1;

 	/* Prepare the SGE for the RPCRDMA Header */
 	ctxt->sge[0].addr =
 		ib_dma_map_page(rdma->sc_cm_id->device,
 				page, 0, PAGE_SIZE, DMA_TO_DEVICE);
 	ctxt->direction = DMA_TO_DEVICE;
 	ctxt->sge[0].length = svc_rdma_xdr_get_reply_hdr_len(rdma_resp);
 	ctxt->sge[0].lkey = rdma->sc_phys_mr->lkey;

 	/* Determine how many of our SGE are to be transmitted */
 	for (sge_no = 1; byte_count && sge_no < sge_count; sge_no++) {
 		sge_bytes = min((size_t)ctxt->sge[sge_no].length,
 				(size_t)byte_count);
 		byte_count -= sge_bytes;
 	}
 	BUG_ON(byte_count != 0);

 	/* Save all respages in the ctxt and remove them from the
 	 * respages array. They are our pages until the I/O
 	 * completes.
 	 */
 	for (page_no = 0; page_no < rqstp->rq_resused; page_no++) {
 		ctxt->pages[page_no+1] = rqstp->rq_respages[page_no];
 		ctxt->count++;
 		rqstp->rq_respages[page_no] = NULL;
 	}

 	BUG_ON(sge_no > rdma->sc_max_sge);
 	memset(&send_wr, 0, sizeof send_wr);
 	ctxt->wr_op = IB_WR_SEND;
 	send_wr.wr_id = (unsigned long)ctxt;
 	send_wr.sg_list = ctxt->sge;
 	send_wr.num_sge = sge_no;
 	send_wr.opcode = IB_WR_SEND;
 	send_wr.send_flags =  IB_SEND_SIGNALED;

 	ret = svc_rdma_send(rdma, &send_wr);
 	if (ret)
 		svc_rdma_put_context(ctxt, 1);

 	return ret;
 }

 void svc_rdma_prep_reply_hdr(struct svc_rqst *rqstp)
 {
 }

 /*
  * Return the start of an xdr buffer.
  */
 static void *xdr_start(struct xdr_buf *xdr)
 {
 	return xdr->head[0].iov_base -
 		(xdr->len -
 		 xdr->page_len -
 		 xdr->tail[0].iov_len -
 		 xdr->head[0].iov_len);
 }

 int svc_rdma_sendto(struct svc_rqst *rqstp)
 {
 	struct svc_xprt *xprt = rqstp->rq_xprt;
 	struct svcxprt_rdma *rdma =
 		container_of(xprt, struct svcxprt_rdma, sc_xprt);
 	struct rpcrdma_msg *rdma_argp;
 	struct rpcrdma_msg *rdma_resp;
 	struct rpcrdma_write_array *reply_ary;
 	enum rpcrdma_proc reply_type;
 	int ret;
 	int inline_bytes;
 	struct ib_sge *sge;
 	int sge_count = 0;
 	struct page *res_page;
 	struct svc_rdma_op_ctxt *ctxt;

 	dprintk("svcrdma: sending response for rqstp=%p\n", rqstp);

 	/* Get the RDMA request header. */
 	rdma_argp = xdr_start(&rqstp->rq_arg);

 	/* Build an SGE for the XDR */
 	ctxt = svc_rdma_get_context(rdma);
 	ctxt->direction = DMA_TO_DEVICE;
 	sge = xdr_to_sge(rdma, &rqstp->rq_res, ctxt->sge, &sge_count);

 	inline_bytes = rqstp->rq_res.len;

 	/* Create the RDMA response header */
 	res_page = svc_rdma_get_page();
 	rdma_resp = page_address(res_page);
 	reply_ary = svc_rdma_get_reply_array(rdma_argp);
 	if (reply_ary)
 		reply_type = RDMA_NOMSG;
 	else
 		reply_type = RDMA_MSG;
 	svc_rdma_xdr_encode_reply_header(rdma, rdma_argp,
 					 rdma_resp, reply_type);

 	/* Send any write-chunk data and build resp write-list */
 	ret = send_write_chunks(rdma, rdma_argp, rdma_resp,
 				rqstp, sge, sge_count);
 	if (ret < 0) {
 		printk(KERN_ERR "svcrdma: failed to send write chunks, rc=%d\n",
 		       ret);
 		goto error;
 	}
 	inline_bytes -= ret;

 	/* Send any reply-list data and update resp reply-list */
 	ret = send_reply_chunks(rdma, rdma_argp, rdma_resp,
 				rqstp, sge, sge_count);
 	if (ret < 0) {
 		printk(KERN_ERR "svcrdma: failed to send reply chunks, rc=%d\n",
 		       ret);
 		goto error;
 	}
 	inline_bytes -= ret;

 	ret = send_reply(rdma, rqstp, res_page, rdma_resp, ctxt, sge_count,
 			 inline_bytes);
 	dprintk("svcrdma: send_reply returns %d\n", ret);
 	return ret;
  error:
 	svc_rdma_put_context(ctxt, 0);
 	put_page(res_page);
 	return ret;
 }
	/*
	* Copyright (c) 2005-2006 Network Appliance, Inc. All rights reserved.
	*
	* This software is available to you under a choice of one of two
	* licenses. You may choose to be licensed under the terms of the GNU
	* General Public License (GPL) Version 2, available from the file
	* COPYING in the main directory of this source tree, or the BSD-type
	* license below:
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	*
	* Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	*
	* Redistributions in binary form must reproduce the above
	* copyright notice, this list of conditions and the following
	* disclaimer in the documentation and/or other materials provided
	* with the distribution.
	*
	* Neither the name of the Network Appliance, Inc. nor the names of
	* its contributors may be used to endorse or promote products
	* derived from this software without specific prior written
	* permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*
	* Author: Tom Tucker <tom@opengridcomputing.com>
	*/

	#include <linux/sunrpc/debug.h>
	#include <linux/sunrpc/rpc_rdma.h>
	#include <linux/spinlock.h>
	#include <asm/unaligned.h>
	#include <rdma/ib_verbs.h>
	#include <rdma/rdma_cm.h>
	#include <linux/sunrpc/svc_rdma.h>

	#define RPCDBG_FACILITY RPCDBG_SVCXPRT

	/* Encode an XDR as an array of IB SGE
	*
	* Assumptions:
	* - head[0] is physically contiguous.
	* - tail[0] is physically contiguous.
	* - pages[] is not physically or virtually contigous and consists of
	* PAGE_SIZE elements.
	*
	* Output:
	* SGE[0] reserved for RCPRDMA header
	* SGE[1] data from xdr->head[]
	* SGE[2..sge_count-2] data from xdr->pages[]
	* SGE[sge_count-1] data from xdr->tail.
	*
	*/
	static struct ib_sge xdr_to_sge(struct svcxprt_rdma xprt,
	struct xdr_buf *xdr,
	struct ib_sge *sge,
	int *sge_count)
	{
	/* Max we need is the length of the XDR / pagesize + one for
	* head + one for tail + one for RPCRDMA header
	*/
	int sge_max = (xdr->len+PAGE_SIZE-1) / PAGE_SIZE + 3;
	int sge_no;
	u32 byte_count = xdr->len;
	u32 sge_bytes;
	u32 page_bytes;
	int page_off;
	int page_no;

	/* Skip the first sge, this is for the RPCRDMA header */
	sge_no = 1;

	/* Head SGE */
	sge[sge_no].addr = ib_dma_map_single(xprt->sc_cm_id->device,
	xdr->head[0].iov_base,
	xdr->head[0].iov_len,
	DMA_TO_DEVICE);
	sge_bytes = min_t(u32, byte_count, xdr->head[0].iov_len);
	byte_count -= sge_bytes;
	sge[sge_no].length = sge_bytes;
	sge[sge_no].lkey = xprt->sc_phys_mr->lkey;
	sge_no++;

	/* pages SGE */
	page_no = 0;
	page_bytes = xdr->page_len;
	page_off = xdr->page_base;
	while (byte_count && page_bytes) {
	sge_bytes = min_t(u32, byte_count, (PAGE_SIZE-page_off));
	sge[sge_no].addr =
	ib_dma_map_page(xprt->sc_cm_id->device,
	xdr->pages[page_no], page_off,
	sge_bytes, DMA_TO_DEVICE);
	sge_bytes = min(sge_bytes, page_bytes);
	byte_count -= sge_bytes;
	page_bytes -= sge_bytes;
	sge[sge_no].length = sge_bytes;
	sge[sge_no].lkey = xprt->sc_phys_mr->lkey;

	sge_no++;
	page_no++;
	page_off = 0; /* reset for next time through loop */
	}

	/* Tail SGE */
	if (byte_count && xdr->tail[0].iov_len) {
	sge[sge_no].addr =
	ib_dma_map_single(xprt->sc_cm_id->device,
	xdr->tail[0].iov_base,
	xdr->tail[0].iov_len,
	DMA_TO_DEVICE);
	sge_bytes = min_t(u32, byte_count, xdr->tail[0].iov_len);
	byte_count -= sge_bytes;
	sge[sge_no].length = sge_bytes;
	sge[sge_no].lkey = xprt->sc_phys_mr->lkey;
	sge_no++;
	}

	BUG_ON(sge_no > sge_max);
	BUG_ON(byte_count != 0);

	*sge_count = sge_no;
	return sge;
	}


	/* Assumptions:
	* - The specified write_len can be represented in sc_max_sge * PAGE_SIZE
	*/
	static int send_write(struct svcxprt_rdma xprt, struct svc_rqst rqstp,
	u32 rmr, u64 to,
	u32 xdr_off, int write_len,
	struct ib_sge *xdr_sge, int sge_count)
	{
	struct svc_rdma_op_ctxt *tmp_sge_ctxt;
	struct ib_send_wr write_wr;
	struct ib_sge *sge;
	int xdr_sge_no;
	int sge_no;
	int sge_bytes;
	int sge_off;
	int bc;
	struct svc_rdma_op_ctxt *ctxt;
	int ret = 0;

	BUG_ON(sge_count > RPCSVC_MAXPAGES);
	dprintk("svcrdma: RDMA_WRITE rmr=%x, to=%llx, xdr_off=%d, "
	"write_len=%d, xdr_sge=%p, sge_count=%d\n",
	rmr, (unsigned long long)to, xdr_off,
	write_len, xdr_sge, sge_count);

	ctxt = svc_rdma_get_context(xprt);
	ctxt->count = 0;
	tmp_sge_ctxt = svc_rdma_get_context(xprt);
	sge = tmp_sge_ctxt->sge;

	/* Find the SGE associated with xdr_off */
	for (bc = xdr_off, xdr_sge_no = 1; bc && xdr_sge_no < sge_count;
	xdr_sge_no++) {
	if (xdr_sge[xdr_sge_no].length > bc)
	break;
	bc -= xdr_sge[xdr_sge_no].length;
	}

	sge_off = bc;
	bc = write_len;
	sge_no = 0;

	/* Copy the remaining SGE */
	while (bc != 0 && xdr_sge_no < sge_count) {
	sge[sge_no].addr = xdr_sge[xdr_sge_no].addr + sge_off;
	sge[sge_no].lkey = xdr_sge[xdr_sge_no].lkey;
	sge_bytes = min((size_t)bc,
	(size_t)(xdr_sge[xdr_sge_no].length-sge_off));
	sge[sge_no].length = sge_bytes;

	sge_off = 0;
	sge_no++;
	xdr_sge_no++;
	bc -= sge_bytes;
	}

	BUG_ON(bc != 0);
	BUG_ON(xdr_sge_no > sge_count);

	/* Prepare WRITE WR */
	memset(&write_wr, 0, sizeof write_wr);
	ctxt->wr_op = IB_WR_RDMA_WRITE;
	write_wr.wr_id = (unsigned long)ctxt;
	write_wr.sg_list = &sge[0];
	write_wr.num_sge = sge_no;
	write_wr.opcode = IB_WR_RDMA_WRITE;
	write_wr.send_flags = IB_SEND_SIGNALED;
	write_wr.wr.rdma.rkey = rmr;
	write_wr.wr.rdma.remote_addr = to;

	/* Post It */
	atomic_inc(&rdma_stat_write);
	if (svc_rdma_send(xprt, &write_wr)) {
	svc_rdma_put_context(ctxt, 1);
	/* Fatal error, close transport */
	ret = -EIO;
	}
	svc_rdma_put_context(tmp_sge_ctxt, 0);
	return ret;
	}

	static int send_write_chunks(struct svcxprt_rdma *xprt,
	struct rpcrdma_msg *rdma_argp,
	struct rpcrdma_msg *rdma_resp,
	struct svc_rqst *rqstp,
	struct ib_sge *sge,
	int sge_count)
	{
	u32 xfer_len = rqstp->rq_res.page_len + rqstp->rq_res.tail[0].iov_len;
	int write_len;
	int max_write;
	u32 xdr_off;
	int chunk_off;
	int chunk_no;
	struct rpcrdma_write_array *arg_ary;
	struct rpcrdma_write_array *res_ary;
	int ret;

	arg_ary = svc_rdma_get_write_array(rdma_argp);
	if (!arg_ary)
	return 0;
	res_ary = (struct rpcrdma_write_array *)
	&rdma_resp->rm_body.rm_chunks[1];

	max_write = xprt->sc_max_sge * PAGE_SIZE;

	/* Write chunks start at the pagelist */
	for (xdr_off = rqstp->rq_res.head[0].iov_len, chunk_no = 0;
	xfer_len && chunk_no < arg_ary->wc_nchunks;
	chunk_no++) {
	struct rpcrdma_segment *arg_ch;
	u64 rs_offset;

	arg_ch = &arg_ary->wc_array[chunk_no].wc_target;
	write_len = min(xfer_len, arg_ch->rs_length);

	/* Prepare the response chunk given the length actually
	* written */
	rs_offset = get_unaligned(&(arg_ch->rs_offset));
	svc_rdma_xdr_encode_array_chunk(res_ary, chunk_no,
	arg_ch->rs_handle,
	rs_offset,
	write_len);
	chunk_off = 0;
	while (write_len) {
	int this_write;
	this_write = min(write_len, max_write);
	ret = send_write(xprt, rqstp,
	arg_ch->rs_handle,
	rs_offset + chunk_off,
	xdr_off,
	this_write,
	sge,
	sge_count);
	if (ret) {
	dprintk("svcrdma: RDMA_WRITE failed, ret=%d\n",
	ret);
	return -EIO;
	}
	chunk_off += this_write;
	xdr_off += this_write;
	xfer_len -= this_write;
	write_len -= this_write;
	}
	}
	/* Update the req with the number of chunks actually used */
	svc_rdma_xdr_encode_write_list(rdma_resp, chunk_no);

	return rqstp->rq_res.page_len + rqstp->rq_res.tail[0].iov_len;
	}

	static int send_reply_chunks(struct svcxprt_rdma *xprt,
	struct rpcrdma_msg *rdma_argp,
	struct rpcrdma_msg *rdma_resp,
	struct svc_rqst *rqstp,
	struct ib_sge *sge,
	int sge_count)
	{
	u32 xfer_len = rqstp->rq_res.len;
	int write_len;
	int max_write;
	u32 xdr_off;
	int chunk_no;
	int chunk_off;
	struct rpcrdma_segment *ch;
	struct rpcrdma_write_array *arg_ary;
	struct rpcrdma_write_array *res_ary;
	int ret;

	arg_ary = svc_rdma_get_reply_array(rdma_argp);
	if (!arg_ary)
	return 0;
	/* XXX: need to fix when reply lists occur with read-list and or
	* write-list */
	res_ary = (struct rpcrdma_write_array *)
	&rdma_resp->rm_body.rm_chunks[2];

	max_write = xprt->sc_max_sge * PAGE_SIZE;

	/* xdr offset starts at RPC message */
	for (xdr_off = 0, chunk_no = 0;
	xfer_len && chunk_no < arg_ary->wc_nchunks;
	chunk_no++) {
	u64 rs_offset;
	ch = &arg_ary->wc_array[chunk_no].wc_target;
	write_len = min(xfer_len, ch->rs_length);


	/* Prepare the reply chunk given the length actually
	* written */
	rs_offset = get_unaligned(&(ch->rs_offset));
	svc_rdma_xdr_encode_array_chunk(res_ary, chunk_no,
	ch->rs_handle, rs_offset,
	write_len);
	chunk_off = 0;
	while (write_len) {
	int this_write;

	this_write = min(write_len, max_write);
	ret = send_write(xprt, rqstp,
	ch->rs_handle,
	rs_offset + chunk_off,
	xdr_off,
	this_write,
	sge,
	sge_count);
	if (ret) {
	dprintk("svcrdma: RDMA_WRITE failed, ret=%d\n",
	ret);
	return -EIO;
	}
	chunk_off += this_write;
	xdr_off += this_write;
	xfer_len -= this_write;
	write_len -= this_write;
	}
	}
	/* Update the req with the number of chunks actually used */
	svc_rdma_xdr_encode_reply_array(res_ary, chunk_no);

	return rqstp->rq_res.len;
	}

	/* This function prepares the portion of the RPCRDMA message to be
	* sent in the RDMA_SEND. This function is called after data sent via
	* RDMA has already been transmitted. There are three cases:
	* - The RPCRDMA header, RPC header, and payload are all sent in a
	* single RDMA_SEND. This is the "inline" case.
	* - The RPCRDMA header and some portion of the RPC header and data
	* are sent via this RDMA_SEND and another portion of the data is
	* sent via RDMA.
	* - The RPCRDMA header [NOMSG] is sent in this RDMA_SEND and the RPC
	* header and data are all transmitted via RDMA.
	* In all three cases, this function prepares the RPCRDMA header in
	* sge[0], the 'type' parameter indicates the type to place in the
	* RPCRDMA header, and the 'byte_count' field indicates how much of
	* the XDR to include in this RDMA_SEND.
	*/
	static int send_reply(struct svcxprt_rdma *rdma,
	struct svc_rqst *rqstp,
	struct page *page,
	struct rpcrdma_msg *rdma_resp,
	struct svc_rdma_op_ctxt *ctxt,
	int sge_count,
	int byte_count)
	{
	struct ib_send_wr send_wr;
	int sge_no;
	int sge_bytes;
	int page_no;
	int ret;

	/* Post a recv buffer to handle another request. */
	ret = svc_rdma_post_recv(rdma);
	if (ret) {
	printk(KERN_INFO
	"svcrdma: could not post a receive buffer, err=%d."
	"Closing transport %p.\n", ret, rdma);
	set_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags);
	svc_rdma_put_context(ctxt, 0);
	return -ENOTCONN;
	}

	/* Prepare the context */
	ctxt->pages[0] = page;
	ctxt->count = 1;

	/* Prepare the SGE for the RPCRDMA Header */
	ctxt->sge[0].addr =
	ib_dma_map_page(rdma->sc_cm_id->device,
	page, 0, PAGE_SIZE, DMA_TO_DEVICE);
	ctxt->direction = DMA_TO_DEVICE;
	ctxt->sge[0].length = svc_rdma_xdr_get_reply_hdr_len(rdma_resp);
	ctxt->sge[0].lkey = rdma->sc_phys_mr->lkey;

	/* Determine how many of our SGE are to be transmitted */
	for (sge_no = 1; byte_count && sge_no < sge_count; sge_no++) {
	sge_bytes = min((size_t)ctxt->sge[sge_no].length,
	(size_t)byte_count);
	byte_count -= sge_bytes;
	}
	BUG_ON(byte_count != 0);

	/* Save all respages in the ctxt and remove them from the
	* respages array. They are our pages until the I/O
	* completes.
	*/
	for (page_no = 0; page_no < rqstp->rq_resused; page_no++) {
	ctxt->pages[page_no+1] = rqstp->rq_respages[page_no];
	ctxt->count++;
	rqstp->rq_respages[page_no] = NULL;
	}

	BUG_ON(sge_no > rdma->sc_max_sge);
	memset(&send_wr, 0, sizeof send_wr);
	ctxt->wr_op = IB_WR_SEND;
	send_wr.wr_id = (unsigned long)ctxt;
	send_wr.sg_list = ctxt->sge;
	send_wr.num_sge = sge_no;
	send_wr.opcode = IB_WR_SEND;
	send_wr.send_flags = IB_SEND_SIGNALED;

	ret = svc_rdma_send(rdma, &send_wr);
	if (ret)
	svc_rdma_put_context(ctxt, 1);

	return ret;
	}

	void svc_rdma_prep_reply_hdr(struct svc_rqst *rqstp)
	{
	}

	/*
	* Return the start of an xdr buffer.
	*/
	static void xdr_start(struct xdr_buf xdr)
	{
	return xdr->head[0].iov_base -
	(xdr->len -
	xdr->page_len -
	xdr->tail[0].iov_len -
	xdr->head[0].iov_len);
	}

	int svc_rdma_sendto(struct svc_rqst *rqstp)
	{
	struct svc_xprt *xprt = rqstp->rq_xprt;
	struct svcxprt_rdma *rdma =
	container_of(xprt, struct svcxprt_rdma, sc_xprt);
	struct rpcrdma_msg *rdma_argp;
	struct rpcrdma_msg *rdma_resp;
	struct rpcrdma_write_array *reply_ary;
	enum rpcrdma_proc reply_type;
	int ret;
	int inline_bytes;
	struct ib_sge *sge;
	int sge_count = 0;
	struct page *res_page;
	struct svc_rdma_op_ctxt *ctxt;

	dprintk("svcrdma: sending response for rqstp=%p\n", rqstp);

	/* Get the RDMA request header. */
	rdma_argp = xdr_start(&rqstp->rq_arg);

	/* Build an SGE for the XDR */
	ctxt = svc_rdma_get_context(rdma);
	ctxt->direction = DMA_TO_DEVICE;
	sge = xdr_to_sge(rdma, &rqstp->rq_res, ctxt->sge, &sge_count);

	inline_bytes = rqstp->rq_res.len;

	/* Create the RDMA response header */
	res_page = svc_rdma_get_page();
	rdma_resp = page_address(res_page);
	reply_ary = svc_rdma_get_reply_array(rdma_argp);
	if (reply_ary)
	reply_type = RDMA_NOMSG;
	else
	reply_type = RDMA_MSG;
	svc_rdma_xdr_encode_reply_header(rdma, rdma_argp,
	rdma_resp, reply_type);

	/* Send any write-chunk data and build resp write-list */
	ret = send_write_chunks(rdma, rdma_argp, rdma_resp,
	rqstp, sge, sge_count);
	if (ret < 0) {
	printk(KERN_ERR "svcrdma: failed to send write chunks, rc=%d\n",
	ret);
	goto error;
	}
	inline_bytes -= ret;

	/* Send any reply-list data and update resp reply-list */
	ret = send_reply_chunks(rdma, rdma_argp, rdma_resp,
	rqstp, sge, sge_count);
	if (ret < 0) {
	printk(KERN_ERR "svcrdma: failed to send reply chunks, rc=%d\n",
	ret);
	goto error;
	}
	inline_bytes -= ret;

	ret = send_reply(rdma, rqstp, res_page, rdma_resp, ctxt, sge_count,
	inline_bytes);
	dprintk("svcrdma: send_reply returns %d\n", ret);
	return ret;
	error:
	svc_rdma_put_context(ctxt, 0);
	put_page(res_page);
	return ret;
	}