svc_rdma_recvfrom.c

Go to the documentation of this file.

/*
 * 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

/*
 * Replace the pages in the rq_argpages array with the pages from the SGE in
 * the RDMA_RECV completion. The SGL should contain full pages up until the
 * last one.
 */
static void rdma_build_arg_xdr(struct svc_rqst *rqstp,
                   struct svc_rdma_op_ctxt *ctxt,
                   u32 byte_count)
{
    struct page *page;
    u32 bc;
    int sge_no;

    /* Swap the page in the SGE with the page in argpages */
    page = ctxt->pages[0];
    put_page(rqstp->rq_pages[0]);
    rqstp->rq_pages[0] = page;

    /* Set up the XDR head */
    rqstp->rq_arg.head[0].iov_base = page_address(page);
    rqstp->rq_arg.head[0].iov_len = min(byte_count, ctxt->sge[0].length);
    rqstp->rq_arg.len = byte_count;
    rqstp->rq_arg.buflen = byte_count;

    /* Compute bytes past head in the SGL */
    bc = byte_count - rqstp->rq_arg.head[0].iov_len;

    /* If data remains, store it in the pagelist */
    rqstp->rq_arg.page_len = bc;
    rqstp->rq_arg.page_base = 0;
    rqstp->rq_arg.pages = &rqstp->rq_pages[1];
    sge_no = 1;
    while (bc && sge_no < ctxt->count) {
        page = ctxt->pages[sge_no];
        put_page(rqstp->rq_pages[sge_no]);
        rqstp->rq_pages[sge_no] = page;
        bc -= min(bc, ctxt->sge[sge_no].length);
        rqstp->rq_arg.buflen += ctxt->sge[sge_no].length;
        sge_no++;
    }
    rqstp->rq_respages = &rqstp->rq_pages[sge_no];

    /* We should never run out of SGE because the limit is defined to
     * support the max allowed RPC data length
     */
    BUG_ON(bc && (sge_no == ctxt->count));
    BUG_ON((rqstp->rq_arg.head[0].iov_len + rqstp->rq_arg.page_len)
           != byte_count);
    BUG_ON(rqstp->rq_arg.len != byte_count);

    /* If not all pages were used from the SGL, free the remaining ones */
    bc = sge_no;
    while (sge_no < ctxt->count) {
        page = ctxt->pages[sge_no++];
        put_page(page);
    }
    ctxt->count = bc;

    /* Set up tail */
    rqstp->rq_arg.tail[0].iov_base = NULL;
    rqstp->rq_arg.tail[0].iov_len = 0;
}

/* Encode a read-chunk-list as an array of IB SGE
 *
 * Assumptions:
 * - chunk[0]->position points to pages[0] at an offset of 0
 * - pages[] is not physically or virtually contiguous and consists of
 *   PAGE_SIZE elements.
 *
 * Output:
 * - sge array pointing into pages[] array.
 * - chunk_sge array specifying sge index and count for each
 *   chunk in the read list
 *
 */
static int map_read_chunks(struct svcxprt_rdma *xprt,
               struct svc_rqst *rqstp,
               struct svc_rdma_op_ctxt *head,
               struct rpcrdma_msg *rmsgp,
               struct svc_rdma_req_map *rpl_map,
               struct svc_rdma_req_map *chl_map,
               int ch_count,
               int byte_count)
{
    int sge_no;
    int sge_bytes;
    int page_off;
    int page_no;
    int ch_bytes;
    int ch_no;
    struct rpcrdma_read_chunk *ch;

    sge_no = 0;
    page_no = 0;
    page_off = 0;
    ch = (struct rpcrdma_read_chunk *)&rmsgp->rm_body.rm_chunks[0];
    ch_no = 0;
    ch_bytes = ntohl(ch->rc_target.rs_length);
    head->arg.head[0] = rqstp->rq_arg.head[0];
    head->arg.tail[0] = rqstp->rq_arg.tail[0];
    head->arg.pages = &head->pages[head->count];
    head->hdr_count = head->count; /* save count of hdr pages */
    head->arg.page_base = 0;
    head->arg.page_len = ch_bytes;
    head->arg.len = rqstp->rq_arg.len + ch_bytes;
    head->arg.buflen = rqstp->rq_arg.buflen + ch_bytes;
    head->count++;
    chl_map->ch[0].start = 0;
    while (byte_count) {
        rpl_map->sge[sge_no].iov_base =
            page_address(rqstp->rq_arg.pages[page_no]) + page_off;
        sge_bytes = min_t(int, PAGE_SIZE-page_off, ch_bytes);
        rpl_map->sge[sge_no].iov_len = sge_bytes;
        /*
         * Don't bump head->count here because the same page
         * may be used by multiple SGE.
         */
        head->arg.pages[page_no] = rqstp->rq_arg.pages[page_no];
        rqstp->rq_respages = &rqstp->rq_arg.pages[page_no+1];

        byte_count -= sge_bytes;
        ch_bytes -= sge_bytes;
        sge_no++;
        /*
         * If all bytes for this chunk have been mapped to an
         * SGE, move to the next SGE
         */
        if (ch_bytes == 0) {
            chl_map->ch[ch_no].count =
                sge_no - chl_map->ch[ch_no].start;
            ch_no++;
            ch++;
            chl_map->ch[ch_no].start = sge_no;
            ch_bytes = ntohl(ch->rc_target.rs_length);
            /* If bytes remaining account for next chunk */
            if (byte_count) {
                head->arg.page_len += ch_bytes;
                head->arg.len += ch_bytes;
                head->arg.buflen += ch_bytes;
            }
        }
        /*
         * If this SGE consumed all of the page, move to the
         * next page
         */
        if ((sge_bytes + page_off) == PAGE_SIZE) {
            page_no++;
            page_off = 0;
            /*
             * If there are still bytes left to map, bump
             * the page count
             */
            if (byte_count)
                head->count++;
        } else
            page_off += sge_bytes;
    }
    BUG_ON(byte_count != 0);
    return sge_no;
}

/* Map a read-chunk-list to an XDR and fast register the page-list.
 *
 * Assumptions:
 * - chunk[0]   position points to pages[0] at an offset of 0
 * - pages[]    will be made physically contiguous by creating a one-off memory
 *      region using the fastreg verb.
 * - byte_count is # of bytes in read-chunk-list
 * - ch_count   is # of chunks in read-chunk-list
 *
 * Output:
 * - sge array pointing into pages[] array.
 * - chunk_sge array specifying sge index and count for each
 *   chunk in the read list
 */
static int fast_reg_read_chunks(struct svcxprt_rdma *xprt,
                struct svc_rqst *rqstp,
                struct svc_rdma_op_ctxt *head,
                struct rpcrdma_msg *rmsgp,
                struct svc_rdma_req_map *rpl_map,
                struct svc_rdma_req_map *chl_map,
                int ch_count,
                int byte_count)
{
    int page_no;
    int ch_no;
    u32 offset;
    struct rpcrdma_read_chunk *ch;
    struct svc_rdma_fastreg_mr *frmr;
    int ret = 0;

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

    head->frmr = frmr;
    head->arg.head[0] = rqstp->rq_arg.head[0];
    head->arg.tail[0] = rqstp->rq_arg.tail[0];
    head->arg.pages = &head->pages[head->count];
    head->hdr_count = head->count; /* save count of hdr pages */
    head->arg.page_base = 0;
    head->arg.page_len = byte_count;
    head->arg.len = rqstp->rq_arg.len + byte_count;
    head->arg.buflen = rqstp->rq_arg.buflen + byte_count;

    /* Fast register the page list */
    frmr->kva = page_address(rqstp->rq_arg.pages[0]);
    frmr->direction = DMA_FROM_DEVICE;
    frmr->access_flags = (IB_ACCESS_LOCAL_WRITE|IB_ACCESS_REMOTE_WRITE);
    frmr->map_len = byte_count;
    frmr->page_list_len = PAGE_ALIGN(byte_count) >> PAGE_SHIFT;
    for (page_no = 0; page_no < frmr->page_list_len; page_no++) {
        frmr->page_list->page_list[page_no] =
            ib_dma_map_page(xprt->sc_cm_id->device,
                    rqstp->rq_arg.pages[page_no], 0,
                    PAGE_SIZE, DMA_FROM_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);
        head->arg.pages[page_no] = rqstp->rq_arg.pages[page_no];
    }
    head->count += page_no;

    /* rq_respages points one past arg pages */
    rqstp->rq_respages = &rqstp->rq_arg.pages[page_no];

    /* Create the reply and chunk maps */
    offset = 0;
    ch = (struct rpcrdma_read_chunk *)&rmsgp->rm_body.rm_chunks[0];
    for (ch_no = 0; ch_no < ch_count; ch_no++) {
        int len = ntohl(ch->rc_target.rs_length);
        rpl_map->sge[ch_no].iov_base = frmr->kva + offset;
        rpl_map->sge[ch_no].iov_len = len;
        chl_map->ch[ch_no].count = 1;
        chl_map->ch[ch_no].start = ch_no;
        offset += len;
        ch++;
    }

    ret = svc_rdma_fastreg(xprt, frmr);
    if (ret)
        goto fatal_err;

    return ch_no;

 fatal_err:
    printk("svcrdma: error fast registering xdr for xprt %p", xprt);
    svc_rdma_put_frmr(xprt, frmr);
    return -EIO;
}

static int rdma_set_ctxt_sge(struct svcxprt_rdma *xprt,
                 struct svc_rdma_op_ctxt *ctxt,
                 struct svc_rdma_fastreg_mr *frmr,
                 struct kvec *vec,
                 u64 *sgl_offset,
                 int count)
{
    int i;
    unsigned long off;

    ctxt->count = count;
    ctxt->direction = DMA_FROM_DEVICE;
    for (i = 0; i < count; i++) {
        ctxt->sge[i].length = 0; /* in case map fails */
        if (!frmr) {
            BUG_ON(!virt_to_page(vec[i].iov_base));
            off = (unsigned long)vec[i].iov_base & ~PAGE_MASK;
            ctxt->sge[i].addr =
                ib_dma_map_page(xprt->sc_cm_id->device,
                        virt_to_page(vec[i].iov_base),
                        off,
                        vec[i].iov_len,
                        DMA_FROM_DEVICE);
            if (ib_dma_mapping_error(xprt->sc_cm_id->device,
                         ctxt->sge[i].addr))
                return -EINVAL;
            ctxt->sge[i].lkey = xprt->sc_dma_lkey;
            atomic_inc(&xprt->sc_dma_used);
        } else {
            ctxt->sge[i].addr = (unsigned long)vec[i].iov_base;
            ctxt->sge[i].lkey = frmr->mr->lkey;
        }
        ctxt->sge[i].length = vec[i].iov_len;
        *sgl_offset = *sgl_offset + vec[i].iov_len;
    }
    return 0;
}

static int rdma_read_max_sge(struct svcxprt_rdma *xprt, int sge_count)
{
    if ((rdma_node_get_transport(xprt->sc_cm_id->device->node_type) ==
         RDMA_TRANSPORT_IWARP) &&
        sge_count > 1)
        return 1;
    else
        return min_t(int, sge_count, xprt->sc_max_sge);
}

/*
 * Use RDMA_READ to read data from the advertised client buffer into the
 * XDR stream starting at rq_arg.head[0].iov_base.
 * Each chunk in the array
 * contains the following fields:
 * discrim      - '1', This isn't used for data placement
 * position     - The xdr stream offset (the same for every chunk)
 * handle       - RMR for client memory region
 * length       - data transfer length
 * offset       - 64 bit tagged offset in remote memory region
 *
 * On our side, we need to read into a pagelist. The first page immediately
 * follows the RPC header.
 *
 * This function returns:
 * 0 - No error and no read-list found.
 *
 * 1 - Successful read-list processing. The data is not yet in
 * the pagelist and therefore the RPC request must be deferred. The
 * I/O completion will enqueue the transport again and
 * svc_rdma_recvfrom will complete the request.
 *
 * <0 - Error processing/posting read-list.
 *
 * NOTE: The ctxt must not be touched after the last WR has been posted
 * because the I/O completion processing may occur on another
 * processor and free / modify the context. Ne touche pas!
 */
static int rdma_read_xdr(struct svcxprt_rdma *xprt,
             struct rpcrdma_msg *rmsgp,
             struct svc_rqst *rqstp,
             struct svc_rdma_op_ctxt *hdr_ctxt)
{
    struct ib_send_wr read_wr;
    struct ib_send_wr inv_wr;
    int err = 0;
    int ch_no;
    int ch_count;
    int byte_count;
    int sge_count;
    u64 sgl_offset;
    struct rpcrdma_read_chunk *ch;
    struct svc_rdma_op_ctxt *ctxt = NULL;
    struct svc_rdma_req_map *rpl_map;
    struct svc_rdma_req_map *chl_map;

    /* If no read list is present, return 0 */
    ch = svc_rdma_get_read_chunk(rmsgp);
    if (!ch)
        return 0;

    svc_rdma_rcl_chunk_counts(ch, &ch_count, &byte_count);
    if (ch_count > RPCSVC_MAXPAGES)
        return -EINVAL;

    /* Allocate temporary reply and chunk maps */
    rpl_map = svc_rdma_get_req_map();
    chl_map = svc_rdma_get_req_map();

    if (!xprt->sc_frmr_pg_list_len)
        sge_count = map_read_chunks(xprt, rqstp, hdr_ctxt, rmsgp,
                        rpl_map, chl_map, ch_count,
                        byte_count);
    else
        sge_count = fast_reg_read_chunks(xprt, rqstp, hdr_ctxt, rmsgp,
                         rpl_map, chl_map, ch_count,
                         byte_count);
    if (sge_count < 0) {
        err = -EIO;
        goto out;
    }

    sgl_offset = 0;
    ch_no = 0;

    for (ch = (struct rpcrdma_read_chunk *)&rmsgp->rm_body.rm_chunks[0];
         ch->rc_discrim != 0; ch++, ch_no++) {
        u64 rs_offset;
next_sge:
        ctxt = svc_rdma_get_context(xprt);
        ctxt->direction = DMA_FROM_DEVICE;
        ctxt->frmr = hdr_ctxt->frmr;
        ctxt->read_hdr = NULL;
        clear_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
        clear_bit(RDMACTXT_F_FAST_UNREG, &ctxt->flags);

        /* Prepare READ WR */
        memset(&read_wr, 0, sizeof read_wr);
        read_wr.wr_id = (unsigned long)ctxt;
        read_wr.opcode = IB_WR_RDMA_READ;
        ctxt->wr_op = read_wr.opcode;
        read_wr.send_flags = IB_SEND_SIGNALED;
        read_wr.wr.rdma.rkey = ntohl(ch->rc_target.rs_handle);
        xdr_decode_hyper((__be32 *)&ch->rc_target.rs_offset,
                 &rs_offset);
        read_wr.wr.rdma.remote_addr = rs_offset + sgl_offset;
        read_wr.sg_list = ctxt->sge;
        read_wr.num_sge =
            rdma_read_max_sge(xprt, chl_map->ch[ch_no].count);
        err = rdma_set_ctxt_sge(xprt, ctxt, hdr_ctxt->frmr,
                    &rpl_map->sge[chl_map->ch[ch_no].start],
                    &sgl_offset,
                    read_wr.num_sge);
        if (err) {
            svc_rdma_unmap_dma(ctxt);
            svc_rdma_put_context(ctxt, 0);
            goto out;
        }
        if (((ch+1)->rc_discrim == 0) &&
            (read_wr.num_sge == chl_map->ch[ch_no].count)) {
            /*
             * Mark the last RDMA_READ with a bit to
             * indicate all RPC data has been fetched from
             * the client and the RPC needs to be enqueued.
             */
            set_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
            if (hdr_ctxt->frmr) {
                set_bit(RDMACTXT_F_FAST_UNREG, &ctxt->flags);
                /*
                 * Invalidate the local MR used to map the data
                 * sink.
                 */
                if (xprt->sc_dev_caps &
                    SVCRDMA_DEVCAP_READ_W_INV) {
                    read_wr.opcode =
                        IB_WR_RDMA_READ_WITH_INV;
                    ctxt->wr_op = read_wr.opcode;
                    read_wr.ex.invalidate_rkey =
                        ctxt->frmr->mr->lkey;
                } else {
                    /* 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 =
                        hdr_ctxt->frmr->mr->lkey;
                    read_wr.next = &inv_wr;
                }
            }
            ctxt->read_hdr = hdr_ctxt;
        }
        /* Post the read */
        err = svc_rdma_send(xprt, &read_wr);
        if (err) {
            printk(KERN_ERR "svcrdma: Error %d posting RDMA_READ\n",
                   err);
            set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
            svc_rdma_unmap_dma(ctxt);
            svc_rdma_put_context(ctxt, 0);
            goto out;
        }
        atomic_inc(&rdma_stat_read);

        if (read_wr.num_sge < chl_map->ch[ch_no].count) {
            chl_map->ch[ch_no].count -= read_wr.num_sge;
            chl_map->ch[ch_no].start += read_wr.num_sge;
            goto next_sge;
        }
        sgl_offset = 0;
        err = 1;
    }

 out:
    svc_rdma_put_req_map(rpl_map);
    svc_rdma_put_req_map(chl_map);

    /* Detach arg pages. svc_recv will replenish them */
    for (ch_no = 0; &rqstp->rq_pages[ch_no] < rqstp->rq_respages; ch_no++)
        rqstp->rq_pages[ch_no] = NULL;

    /*
     * Detach res pages. svc_release must see a resused count of
     * zero or it will attempt to put them.
     */
    while (rqstp->rq_resused)
        rqstp->rq_respages[--rqstp->rq_resused] = NULL;

    return err;
}

static int rdma_read_complete(struct svc_rqst *rqstp,
                  struct svc_rdma_op_ctxt *head)
{
    int page_no;
    int ret;

    BUG_ON(!head);

    /* Copy RPC pages */
    for (page_no = 0; page_no < head->count; page_no++) {
        put_page(rqstp->rq_pages[page_no]);
        rqstp->rq_pages[page_no] = head->pages[page_no];
    }
    /* Point rq_arg.pages past header */
    rqstp->rq_arg.pages = &rqstp->rq_pages[head->hdr_count];
    rqstp->rq_arg.page_len = head->arg.page_len;
    rqstp->rq_arg.page_base = head->arg.page_base;

    /* rq_respages starts after the last arg page */
    rqstp->rq_respages = &rqstp->rq_arg.pages[page_no];
    rqstp->rq_resused = 0;

    /* Rebuild rq_arg head and tail. */
    rqstp->rq_arg.head[0] = head->arg.head[0];
    rqstp->rq_arg.tail[0] = head->arg.tail[0];
    rqstp->rq_arg.len = head->arg.len;
    rqstp->rq_arg.buflen = head->arg.buflen;

    /* Free the context */
    svc_rdma_put_context(head, 0);

    /* XXX: What should this be? */
    rqstp->rq_prot = IPPROTO_MAX;
    svc_xprt_copy_addrs(rqstp, rqstp->rq_xprt);

    ret = rqstp->rq_arg.head[0].iov_len
        + rqstp->rq_arg.page_len
        + rqstp->rq_arg.tail[0].iov_len;
    dprintk("svcrdma: deferred read ret=%d, rq_arg.len =%d, "
        "rq_arg.head[0].iov_base=%p, rq_arg.head[0].iov_len = %zd\n",
        ret, rqstp->rq_arg.len, rqstp->rq_arg.head[0].iov_base,
        rqstp->rq_arg.head[0].iov_len);

    return ret;
}

/*
 * Set up the rqstp thread context to point to the RQ buffer. If
 * necessary, pull additional data from the client with an RDMA_READ
 * request.
 */
int svc_rdma_recvfrom(struct svc_rqst *rqstp)
{
    struct svc_xprt *xprt = rqstp->rq_xprt;
    struct svcxprt_rdma *rdma_xprt =
        container_of(xprt, struct svcxprt_rdma, sc_xprt);
    struct svc_rdma_op_ctxt *ctxt = NULL;
    struct rpcrdma_msg *rmsgp;
    int ret = 0;
    int len;

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

    spin_lock_bh(&rdma_xprt->sc_rq_dto_lock);
    if (!list_empty(&rdma_xprt->sc_read_complete_q)) {
        ctxt = list_entry(rdma_xprt->sc_read_complete_q.next,
                  struct svc_rdma_op_ctxt,
                  dto_q);
        list_del_init(&ctxt->dto_q);
    }
    if (ctxt) {
        spin_unlock_bh(&rdma_xprt->sc_rq_dto_lock);
        return rdma_read_complete(rqstp, ctxt);
    }

    if (!list_empty(&rdma_xprt->sc_rq_dto_q)) {
        ctxt = list_entry(rdma_xprt->sc_rq_dto_q.next,
                  struct svc_rdma_op_ctxt,
                  dto_q);
        list_del_init(&ctxt->dto_q);
    } else {
        atomic_inc(&rdma_stat_rq_starve);
        clear_bit(XPT_DATA, &xprt->xpt_flags);
        ctxt = NULL;
    }
    spin_unlock_bh(&rdma_xprt->sc_rq_dto_lock);
    if (!ctxt) {
        /* This is the EAGAIN path. The svc_recv routine will
         * return -EAGAIN, the nfsd thread will go to call into
         * svc_recv again and we shouldn't be on the active
         * transport list
         */
        if (test_bit(XPT_CLOSE, &xprt->xpt_flags))
            goto close_out;

        BUG_ON(ret);
        goto out;
    }
    dprintk("svcrdma: processing ctxt=%p on xprt=%p, rqstp=%p, status=%d\n",
        ctxt, rdma_xprt, rqstp, ctxt->wc_status);
    BUG_ON(ctxt->wc_status != IB_WC_SUCCESS);
    atomic_inc(&rdma_stat_recv);

    /* Build up the XDR from the receive buffers. */
    rdma_build_arg_xdr(rqstp, ctxt, ctxt->byte_len);

    /* Decode the RDMA header. */
    len = svc_rdma_xdr_decode_req(&rmsgp, rqstp);
    rqstp->rq_xprt_hlen = len;

    /* If the request is invalid, reply with an error */
    if (len < 0) {
        if (len == -ENOSYS)
            svc_rdma_send_error(rdma_xprt, rmsgp, ERR_VERS);
        goto close_out;
    }

    /* Read read-list data. */
    ret = rdma_read_xdr(rdma_xprt, rmsgp, rqstp, ctxt);
    if (ret > 0) {
        /* read-list posted, defer until data received from client. */
        goto defer;
    }
    if (ret < 0) {
        /* Post of read-list failed, free context. */
        svc_rdma_put_context(ctxt, 1);
        return 0;
    }

    ret = rqstp->rq_arg.head[0].iov_len
        + rqstp->rq_arg.page_len
        + rqstp->rq_arg.tail[0].iov_len;
    svc_rdma_put_context(ctxt, 0);
 out:
    dprintk("svcrdma: ret = %d, rq_arg.len =%d, "
        "rq_arg.head[0].iov_base=%p, rq_arg.head[0].iov_len = %zd\n",
        ret, rqstp->rq_arg.len,
        rqstp->rq_arg.head[0].iov_base,
        rqstp->rq_arg.head[0].iov_len);
    rqstp->rq_prot = IPPROTO_MAX;
    svc_xprt_copy_addrs(rqstp, xprt);
    return ret;

 close_out:
    if (ctxt)
        svc_rdma_put_context(ctxt, 1);
    dprintk("svcrdma: transport %p is closing\n", xprt);
    /*
     * Set the close bit and enqueue it. svc_recv will see the
     * close bit and call svc_xprt_delete
     */
    set_bit(XPT_CLOSE, &xprt->xpt_flags);
defer:
    return 0;
}