svc_rdma_sendto.c

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/*
 * 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 <[email protected]>
 */

#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 contiguous 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.
 *
 * The max SGE we need is the length of the XDR / pagesize + one for
 * head + one for tail + one for RPCRDMA header. Since RPCSVC_MAXPAGES
 * reserves a page for both the request and the reply header, and this
 * array is only concerned with the reply we are assured that we have
 * on extra page for the RPCRMDA header.
 */
static int fast_reg_xdr(struct svcxprt_rdma *xprt,
            struct xdr_buf *xdr,
            struct svc_rdma_req_map *vec)
{
    int sge_no;
    u32 sge_bytes;
    u32 page_bytes;
    u32 page_off;
    int page_no = 0;
    u8 *frva;
    struct svc_rdma_fastreg_mr *frmr;

    frmr = svc_rdma_get_frmr(xprt);
    if (IS_ERR(frmr))
        return -ENOMEM;
    vec->frmr = frmr;

    /* Skip the RPCRDMA header */
    sge_no = 1;

    /* Map the head. */
    frva = (void *)((unsigned long)(xdr->head[0].iov_base) & PAGE_MASK);
    vec->sge[sge_no].iov_base = xdr->head[0].iov_base;
    vec->sge[sge_no].iov_len = xdr->head[0].iov_len;
    vec->count = 2;
    sge_no++;

    /* Map the XDR head */
    frmr->kva = frva;
    frmr->direction = DMA_TO_DEVICE;
    frmr->access_flags = 0;
    frmr->map_len = PAGE_SIZE;
    frmr->page_list_len = 1;
    page_off = (unsigned long)xdr->head[0].iov_base & ~PAGE_MASK;
    frmr->page_list->page_list[page_no] =
        ib_dma_map_page(xprt->sc_cm_id->device,
                virt_to_page(xdr->head[0].iov_base),
                page_off,
                PAGE_SIZE - page_off,
                DMA_TO_DEVICE);
    if (ib_dma_mapping_error(xprt->sc_cm_id->device,
                 frmr->page_list->page_list[page_no]))
        goto fatal_err;
    atomic_inc(&xprt->sc_dma_used);

    /* Map the XDR page list */
    page_off = xdr->page_base;
    page_bytes = xdr->page_len + page_off;
    if (!page_bytes)
        goto encode_tail;

    /* Map the pages */
    vec->sge[sge_no].iov_base = frva + frmr->map_len + page_off;
    vec->sge[sge_no].iov_len = page_bytes;
    sge_no++;
    while (page_bytes) {
        struct page *page;

        page = xdr->pages[page_no++];
        sge_bytes = min_t(u32, page_bytes, (PAGE_SIZE - page_off));
        page_bytes -= sge_bytes;

        frmr->page_list->page_list[page_no] =
            ib_dma_map_page(xprt->sc_cm_id->device,
                    page, page_off,
                    sge_bytes, DMA_TO_DEVICE);
        if (ib_dma_mapping_error(xprt->sc_cm_id->device,
                     frmr->page_list->page_list[page_no]))
            goto fatal_err;

        atomic_inc(&xprt->sc_dma_used);
        page_off = 0; /* reset for next time through loop */
        frmr->map_len += PAGE_SIZE;
        frmr->page_list_len++;
    }
    vec->count++;

 encode_tail:
    /* Map tail */
    if (0 == xdr->tail[0].iov_len)
        goto done;

    vec->count++;
    vec->sge[sge_no].iov_len = xdr->tail[0].iov_len;

    if (((unsigned long)xdr->tail[0].iov_base & PAGE_MASK) ==
        ((unsigned long)xdr->head[0].iov_base & PAGE_MASK)) {
        /*
         * If head and tail use the same page, we don't need
         * to map it again.
         */
        vec->sge[sge_no].iov_base = xdr->tail[0].iov_base;
    } else {
        void *va;

        /* Map another page for the tail */
        page_off = (unsigned long)xdr->tail[0].iov_base & ~PAGE_MASK;
        va = (void *)((unsigned long)xdr->tail[0].iov_base & PAGE_MASK);
        vec->sge[sge_no].iov_base = frva + frmr->map_len + page_off;

        frmr->page_list->page_list[page_no] =
            ib_dma_map_page(xprt->sc_cm_id->device, virt_to_page(va),
                    page_off,
                    PAGE_SIZE,
                    DMA_TO_DEVICE);
        if (ib_dma_mapping_error(xprt->sc_cm_id->device,
                     frmr->page_list->page_list[page_no]))
            goto fatal_err;
        atomic_inc(&xprt->sc_dma_used);
        frmr->map_len += PAGE_SIZE;
        frmr->page_list_len++;
    }

 done:
    if (svc_rdma_fastreg(xprt, frmr))
        goto fatal_err;

    return 0;

 fatal_err:
    printk("svcrdma: Error fast registering memory for xprt %p\n", xprt);
    vec->frmr = NULL;
    svc_rdma_put_frmr(xprt, frmr);
    return -EIO;
}

static int map_xdr(struct svcxprt_rdma *xprt,
           struct xdr_buf *xdr,
           struct svc_rdma_req_map *vec)
{
    int sge_no;
    u32 sge_bytes;
    u32 page_bytes;
    u32 page_off;
    int page_no;

    BUG_ON(xdr->len !=
           (xdr->head[0].iov_len + xdr->page_len + xdr->tail[0].iov_len));

    if (xprt->sc_frmr_pg_list_len)
        return fast_reg_xdr(xprt, xdr, vec);

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

    /* Head SGE */
    vec->sge[sge_no].iov_base = xdr->head[0].iov_base;
    vec->sge[sge_no].iov_len = xdr->head[0].iov_len;
    sge_no++;

    /* pages SGE */
    page_no = 0;
    page_bytes = xdr->page_len;
    page_off = xdr->page_base;
    while (page_bytes) {
        vec->sge[sge_no].iov_base =
            page_address(xdr->pages[page_no]) + page_off;
        sge_bytes = min_t(u32, page_bytes, (PAGE_SIZE - page_off));
        page_bytes -= sge_bytes;
        vec->sge[sge_no].iov_len = sge_bytes;

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

    /* Tail SGE */
    if (xdr->tail[0].iov_len) {
        vec->sge[sge_no].iov_base = xdr->tail[0].iov_base;
        vec->sge[sge_no].iov_len = xdr->tail[0].iov_len;
        sge_no++;
    }

    dprintk("svcrdma: map_xdr: sge_no %d page_no %d "
        "page_base %u page_len %u head_len %zu tail_len %zu\n",
        sge_no, page_no, xdr->page_base, xdr->page_len,
        xdr->head[0].iov_len, xdr->tail[0].iov_len);

    vec->count = sge_no;
    return 0;
}

static dma_addr_t dma_map_xdr(struct svcxprt_rdma *xprt,
                  struct xdr_buf *xdr,
                  u32 xdr_off, size_t len, int dir)
{
    struct page *page;
    dma_addr_t dma_addr;
    if (xdr_off < xdr->head[0].iov_len) {
        /* This offset is in the head */
        xdr_off += (unsigned long)xdr->head[0].iov_base & ~PAGE_MASK;
        page = virt_to_page(xdr->head[0].iov_base);
    } else {
        xdr_off -= xdr->head[0].iov_len;
        if (xdr_off < xdr->page_len) {
            /* This offset is in the page list */
            page = xdr->pages[xdr_off >> PAGE_SHIFT];
            xdr_off &= ~PAGE_MASK;
        } else {
            /* This offset is in the tail */
            xdr_off -= xdr->page_len;
            xdr_off += (unsigned long)
                xdr->tail[0].iov_base & ~PAGE_MASK;
            page = virt_to_page(xdr->tail[0].iov_base);
        }
    }
    dma_addr = ib_dma_map_page(xprt->sc_cm_id->device, page, xdr_off,
                   min_t(size_t, PAGE_SIZE, len), dir);
    return dma_addr;
}

/* Assumptions:
 * - We are using FRMR
 *     - or -
 * - 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 svc_rdma_req_map *vec)
{
    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;

    BUG_ON(vec->count > RPCSVC_MAXPAGES);
    dprintk("svcrdma: RDMA_WRITE rmr=%x, to=%llx, xdr_off=%d, "
        "write_len=%d, vec->sge=%p, vec->count=%lu\n",
        rmr, (unsigned long long)to, xdr_off,
        write_len, vec->sge, vec->count);

    ctxt = svc_rdma_get_context(xprt);
    ctxt->direction = DMA_TO_DEVICE;
    sge = ctxt->sge;

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

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

    /* Copy the remaining SGE */
    while (bc != 0) {
        sge_bytes = min_t(size_t,
              bc, vec->sge[xdr_sge_no].iov_len-sge_off);
        sge[sge_no].length = sge_bytes;
        if (!vec->frmr) {
            sge[sge_no].addr =
                dma_map_xdr(xprt, &rqstp->rq_res, xdr_off,
                        sge_bytes, DMA_TO_DEVICE);
            xdr_off += sge_bytes;
            if (ib_dma_mapping_error(xprt->sc_cm_id->device,
                         sge[sge_no].addr))
                goto err;
            atomic_inc(&xprt->sc_dma_used);
            sge[sge_no].lkey = xprt->sc_dma_lkey;
        } else {
            sge[sge_no].addr = (unsigned long)
                vec->sge[xdr_sge_no].iov_base + sge_off;
            sge[sge_no].lkey = vec->frmr->mr->lkey;
        }
        ctxt->count++;
        ctxt->frmr = vec->frmr;
        sge_off = 0;
        sge_no++;
        xdr_sge_no++;
        BUG_ON(xdr_sge_no > vec->count);
        bc -= sge_bytes;
    }

    /* 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))
        goto err;
    return 0;
 err:
    svc_rdma_unmap_dma(ctxt);
    svc_rdma_put_frmr(xprt, vec->frmr);
    svc_rdma_put_context(ctxt, 0);
    /* Fatal error, close transport */
    return -EIO;
}

static int send_write_chunks(struct svcxprt_rdma *xprt,
                 struct rpcrdma_msg *rdma_argp,
                 struct rpcrdma_msg *rdma_resp,
                 struct svc_rqst *rqstp,
                 struct svc_rdma_req_map *vec)
{
    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];

    if (vec->frmr)
        max_write = vec->frmr->map_len;
    else
        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, ntohl(arg_ch->rs_length));

        /* Prepare the response chunk given the length actually
         * written */
        xdr_decode_hyper((__be32 *)&arg_ch->rs_offset, &rs_offset);
        svc_rdma_xdr_encode_array_chunk(res_ary, chunk_no,
                        arg_ch->rs_handle,
                        arg_ch->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,
                     ntohl(arg_ch->rs_handle),
                     rs_offset + chunk_off,
                     xdr_off,
                     this_write,
                     vec);
            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 svc_rdma_req_map *vec)
{
    u32 xfer_len = rqstp->rq_res.len;
    int write_len;
    int max_write;
    u32 xdr_off;
    int chunk_no;
    int chunk_off;
    int nchunks;
    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];

    if (vec->frmr)
        max_write = vec->frmr->map_len;
    else
        max_write = xprt->sc_max_sge * PAGE_SIZE;

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

        /* Prepare the reply chunk given the length actually
         * written */
        xdr_decode_hyper((__be32 *)&ch->rs_offset, &rs_offset);
        svc_rdma_xdr_encode_array_chunk(res_ary, chunk_no,
                        ch->rs_handle, ch->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,
                     ntohl(ch->rs_handle),
                     rs_offset + chunk_off,
                     xdr_off,
                     this_write,
                     vec);
            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. NB: The offset of the payload
 * to send is zero in the XDR.
 */
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,
              struct svc_rdma_req_map *vec,
              int byte_count)
{
    struct ib_send_wr send_wr;
    struct ib_send_wr inv_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_frmr(rdma, vec->frmr);
        svc_rdma_put_context(ctxt, 0);
        return -ENOTCONN;
    }

    /* Prepare the context */
    ctxt->pages[0] = page;
    ctxt->count = 1;
    ctxt->frmr = vec->frmr;
    if (vec->frmr)
        set_bit(RDMACTXT_F_FAST_UNREG, &ctxt->flags);
    else
        clear_bit(RDMACTXT_F_FAST_UNREG, &ctxt->flags);

    /* Prepare the SGE for the RPCRDMA Header */
    ctxt->sge[0].lkey = rdma->sc_dma_lkey;
    ctxt->sge[0].length = svc_rdma_xdr_get_reply_hdr_len(rdma_resp);
    ctxt->sge[0].addr =
        ib_dma_map_page(rdma->sc_cm_id->device, page, 0,
                ctxt->sge[0].length, DMA_TO_DEVICE);
    if (ib_dma_mapping_error(rdma->sc_cm_id->device, ctxt->sge[0].addr))
        goto err;
    atomic_inc(&rdma->sc_dma_used);

    ctxt->direction = DMA_TO_DEVICE;

    /* Map the payload indicated by 'byte_count' */
    for (sge_no = 1; byte_count && sge_no < vec->count; sge_no++) {
        int xdr_off = 0;
        sge_bytes = min_t(size_t, vec->sge[sge_no].iov_len, byte_count);
        byte_count -= sge_bytes;
        if (!vec->frmr) {
            ctxt->sge[sge_no].addr =
                dma_map_xdr(rdma, &rqstp->rq_res, xdr_off,
                        sge_bytes, DMA_TO_DEVICE);
            xdr_off += sge_bytes;
            if (ib_dma_mapping_error(rdma->sc_cm_id->device,
                         ctxt->sge[sge_no].addr))
                goto err;
            atomic_inc(&rdma->sc_dma_used);
            ctxt->sge[sge_no].lkey = rdma->sc_dma_lkey;
        } else {
            ctxt->sge[sge_no].addr = (unsigned long)
                vec->sge[sge_no].iov_base;
            ctxt->sge[sge_no].lkey = vec->frmr->mr->lkey;
        }
        ctxt->sge[sge_no].length = 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;
        /*
         * If there are more pages than SGE, terminate SGE
         * list so that svc_rdma_unmap_dma doesn't attempt to
         * unmap garbage.
         */
        if (page_no+1 >= sge_no)
            ctxt->sge[page_no+1].length = 0;
    }
    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;
    if (vec->frmr) {
        /* Prepare INVALIDATE WR */
        memset(&inv_wr, 0, sizeof inv_wr);
        inv_wr.opcode = IB_WR_LOCAL_INV;
        inv_wr.send_flags = IB_SEND_SIGNALED;
        inv_wr.ex.invalidate_rkey =
            vec->frmr->mr->lkey;
        send_wr.next = &inv_wr;
    }

    ret = svc_rdma_send(rdma, &send_wr);
    if (ret)
        goto err;

    return 0;

 err:
    svc_rdma_unmap_dma(ctxt);
    svc_rdma_put_frmr(rdma, vec->frmr);
    svc_rdma_put_context(ctxt, 1);
    return -EIO;
}

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 page *res_page;
    struct svc_rdma_op_ctxt *ctxt;
    struct svc_rdma_req_map *vec;

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

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

    /* Build an req vec for the XDR */
    ctxt = svc_rdma_get_context(rdma);
    ctxt->direction = DMA_TO_DEVICE;
    vec = svc_rdma_get_req_map();
    ret = map_xdr(rdma, &rqstp->rq_res, vec);
    if (ret)
        goto err0;
    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, vec);
    if (ret < 0) {
        printk(KERN_ERR "svcrdma: failed to send write chunks, rc=%d\n",
               ret);
        goto err1;
    }
    inline_bytes -= ret;

    /* Send any reply-list data and update resp reply-list */
    ret = send_reply_chunks(rdma, rdma_argp, rdma_resp,
                rqstp, vec);
    if (ret < 0) {
        printk(KERN_ERR "svcrdma: failed to send reply chunks, rc=%d\n",
               ret);
        goto err1;
    }
    inline_bytes -= ret;

    ret = send_reply(rdma, rqstp, res_page, rdma_resp, ctxt, vec,
             inline_bytes);
    svc_rdma_put_req_map(vec);
    dprintk("svcrdma: send_reply returns %d\n", ret);
    return ret;

 err1:
    put_page(res_page);
 err0:
    svc_rdma_put_req_map(vec);
    svc_rdma_put_context(ctxt, 0);
    return ret;
}