svc_rdma_transport.c

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/*
 * Copyright (c) 2005-2007 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/svc_xprt.h>
#include <linux/sunrpc/debug.h>
#include <linux/sunrpc/rpc_rdma.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/workqueue.h>
#include <rdma/ib_verbs.h>
#include <rdma/rdma_cm.h>
#include <linux/sunrpc/svc_rdma.h>
#include <linux/export.h>
#include "xprt_rdma.h"

#define RPCDBG_FACILITY RPCDBG_SVCXPRT

static struct svc_xprt *svc_rdma_create(struct svc_serv *serv,
                    struct net *net,
                    struct sockaddr *sa, int salen,
                    int flags);
static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt);
static void svc_rdma_release_rqst(struct svc_rqst *);
static void dto_tasklet_func(unsigned long data);
static void svc_rdma_detach(struct svc_xprt *xprt);
static void svc_rdma_free(struct svc_xprt *xprt);
static int svc_rdma_has_wspace(struct svc_xprt *xprt);
static void rq_cq_reap(struct svcxprt_rdma *xprt);
static void sq_cq_reap(struct svcxprt_rdma *xprt);

static DECLARE_TASKLET(dto_tasklet, dto_tasklet_func, 0UL);
static DEFINE_SPINLOCK(dto_lock);
static LIST_HEAD(dto_xprt_q);

static struct svc_xprt_ops svc_rdma_ops = {
    .xpo_create = svc_rdma_create,
    .xpo_recvfrom = svc_rdma_recvfrom,
    .xpo_sendto = svc_rdma_sendto,
    .xpo_release_rqst = svc_rdma_release_rqst,
    .xpo_detach = svc_rdma_detach,
    .xpo_free = svc_rdma_free,
    .xpo_prep_reply_hdr = svc_rdma_prep_reply_hdr,
    .xpo_has_wspace = svc_rdma_has_wspace,
    .xpo_accept = svc_rdma_accept,
};

struct svc_xprt_class svc_rdma_class = {
    .xcl_name = "rdma",
    .xcl_owner = THIS_MODULE,
    .xcl_ops = &svc_rdma_ops,
    .xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP,
};

struct svc_rdma_op_ctxt *svc_rdma_get_context(struct svcxprt_rdma *xprt)
{
    struct svc_rdma_op_ctxt *ctxt;

    while (1) {
        ctxt = kmem_cache_alloc(svc_rdma_ctxt_cachep, GFP_KERNEL);
        if (ctxt)
            break;
        schedule_timeout_uninterruptible(msecs_to_jiffies(500));
    }
    ctxt->xprt = xprt;
    INIT_LIST_HEAD(&ctxt->dto_q);
    ctxt->count = 0;
    ctxt->frmr = NULL;
    atomic_inc(&xprt->sc_ctxt_used);
    return ctxt;
}

void svc_rdma_unmap_dma(struct svc_rdma_op_ctxt *ctxt)
{
    struct svcxprt_rdma *xprt = ctxt->xprt;
    int i;
    for (i = 0; i < ctxt->count && ctxt->sge[i].length; i++) {
        /*
         * Unmap the DMA addr in the SGE if the lkey matches
         * the sc_dma_lkey, otherwise, ignore it since it is
         * an FRMR lkey and will be unmapped later when the
         * last WR that uses it completes.
         */
        if (ctxt->sge[i].lkey == xprt->sc_dma_lkey) {
            atomic_dec(&xprt->sc_dma_used);
            ib_dma_unmap_page(xprt->sc_cm_id->device,
                        ctxt->sge[i].addr,
                        ctxt->sge[i].length,
                        ctxt->direction);
        }
    }
}

void svc_rdma_put_context(struct svc_rdma_op_ctxt *ctxt, int free_pages)
{
    struct svcxprt_rdma *xprt;
    int i;

    BUG_ON(!ctxt);
    xprt = ctxt->xprt;
    if (free_pages)
        for (i = 0; i < ctxt->count; i++)
            put_page(ctxt->pages[i]);

    kmem_cache_free(svc_rdma_ctxt_cachep, ctxt);
    atomic_dec(&xprt->sc_ctxt_used);
}

/*
 * Temporary NFS req mappings are shared across all transport
 * instances. These are short lived and should be bounded by the number
 * of concurrent server threads * depth of the SQ.
 */
struct svc_rdma_req_map *svc_rdma_get_req_map(void)
{
    struct svc_rdma_req_map *map;
    while (1) {
        map = kmem_cache_alloc(svc_rdma_map_cachep, GFP_KERNEL);
        if (map)
            break;
        schedule_timeout_uninterruptible(msecs_to_jiffies(500));
    }
    map->count = 0;
    map->frmr = NULL;
    return map;
}

void svc_rdma_put_req_map(struct svc_rdma_req_map *map)
{
    kmem_cache_free(svc_rdma_map_cachep, map);
}

/* ib_cq event handler */
static void cq_event_handler(struct ib_event *event, void *context)
{
    struct svc_xprt *xprt = context;
    dprintk("svcrdma: received CQ event id=%d, context=%p\n",
        event->event, context);
    set_bit(XPT_CLOSE, &xprt->xpt_flags);
}

/* QP event handler */
static void qp_event_handler(struct ib_event *event, void *context)
{
    struct svc_xprt *xprt = context;

    switch (event->event) {
    /* These are considered benign events */
    case IB_EVENT_PATH_MIG:
    case IB_EVENT_COMM_EST:
    case IB_EVENT_SQ_DRAINED:
    case IB_EVENT_QP_LAST_WQE_REACHED:
        dprintk("svcrdma: QP event %d received for QP=%p\n",
            event->event, event->element.qp);
        break;
    /* These are considered fatal events */
    case IB_EVENT_PATH_MIG_ERR:
    case IB_EVENT_QP_FATAL:
    case IB_EVENT_QP_REQ_ERR:
    case IB_EVENT_QP_ACCESS_ERR:
    case IB_EVENT_DEVICE_FATAL:
    default:
        dprintk("svcrdma: QP ERROR event %d received for QP=%p, "
            "closing transport\n",
            event->event, event->element.qp);
        set_bit(XPT_CLOSE, &xprt->xpt_flags);
        break;
    }
}

/*
 * Data Transfer Operation Tasklet
 *
 * Walks a list of transports with I/O pending, removing entries as
 * they are added to the server's I/O pending list. Two bits indicate
 * if SQ, RQ, or both have I/O pending. The dto_lock is an irqsave
 * spinlock that serializes access to the transport list with the RQ
 * and SQ interrupt handlers.
 */
static void dto_tasklet_func(unsigned long data)
{
    struct svcxprt_rdma *xprt;
    unsigned long flags;

    spin_lock_irqsave(&dto_lock, flags);
    while (!list_empty(&dto_xprt_q)) {
        xprt = list_entry(dto_xprt_q.next,
                  struct svcxprt_rdma, sc_dto_q);
        list_del_init(&xprt->sc_dto_q);
        spin_unlock_irqrestore(&dto_lock, flags);

        rq_cq_reap(xprt);
        sq_cq_reap(xprt);

        svc_xprt_put(&xprt->sc_xprt);
        spin_lock_irqsave(&dto_lock, flags);
    }
    spin_unlock_irqrestore(&dto_lock, flags);
}

/*
 * Receive Queue Completion Handler
 *
 * Since an RQ completion handler is called on interrupt context, we
 * need to defer the handling of the I/O to a tasklet
 */
static void rq_comp_handler(struct ib_cq *cq, void *cq_context)
{
    struct svcxprt_rdma *xprt = cq_context;
    unsigned long flags;

    /* Guard against unconditional flush call for destroyed QP */
    if (atomic_read(&xprt->sc_xprt.xpt_ref.refcount)==0)
        return;

    /*
     * Set the bit regardless of whether or not it's on the list
     * because it may be on the list already due to an SQ
     * completion.
     */
    set_bit(RDMAXPRT_RQ_PENDING, &xprt->sc_flags);

    /*
     * If this transport is not already on the DTO transport queue,
     * add it
     */
    spin_lock_irqsave(&dto_lock, flags);
    if (list_empty(&xprt->sc_dto_q)) {
        svc_xprt_get(&xprt->sc_xprt);
        list_add_tail(&xprt->sc_dto_q, &dto_xprt_q);
    }
    spin_unlock_irqrestore(&dto_lock, flags);

    /* Tasklet does all the work to avoid irqsave locks. */
    tasklet_schedule(&dto_tasklet);
}

/*
 * rq_cq_reap - Process the RQ CQ.
 *
 * Take all completing WC off the CQE and enqueue the associated DTO
 * context on the dto_q for the transport.
 *
 * Note that caller must hold a transport reference.
 */
static void rq_cq_reap(struct svcxprt_rdma *xprt)
{
    int ret;
    struct ib_wc wc;
    struct svc_rdma_op_ctxt *ctxt = NULL;

    if (!test_and_clear_bit(RDMAXPRT_RQ_PENDING, &xprt->sc_flags))
        return;

    ib_req_notify_cq(xprt->sc_rq_cq, IB_CQ_NEXT_COMP);
    atomic_inc(&rdma_stat_rq_poll);

    while ((ret = ib_poll_cq(xprt->sc_rq_cq, 1, &wc)) > 0) {
        ctxt = (struct svc_rdma_op_ctxt *)(unsigned long)wc.wr_id;
        ctxt->wc_status = wc.status;
        ctxt->byte_len = wc.byte_len;
        svc_rdma_unmap_dma(ctxt);
        if (wc.status != IB_WC_SUCCESS) {
            /* Close the transport */
            dprintk("svcrdma: transport closing putting ctxt %p\n", ctxt);
            set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
            svc_rdma_put_context(ctxt, 1);
            svc_xprt_put(&xprt->sc_xprt);
            continue;
        }
        spin_lock_bh(&xprt->sc_rq_dto_lock);
        list_add_tail(&ctxt->dto_q, &xprt->sc_rq_dto_q);
        spin_unlock_bh(&xprt->sc_rq_dto_lock);
        svc_xprt_put(&xprt->sc_xprt);
    }

    if (ctxt)
        atomic_inc(&rdma_stat_rq_prod);

    set_bit(XPT_DATA, &xprt->sc_xprt.xpt_flags);
    /*
     * If data arrived before established event,
     * don't enqueue. This defers RPC I/O until the
     * RDMA connection is complete.
     */
    if (!test_bit(RDMAXPRT_CONN_PENDING, &xprt->sc_flags))
        svc_xprt_enqueue(&xprt->sc_xprt);
}

/*
 * Process a completion context
 */
static void process_context(struct svcxprt_rdma *xprt,
                struct svc_rdma_op_ctxt *ctxt)
{
    svc_rdma_unmap_dma(ctxt);

    switch (ctxt->wr_op) {
    case IB_WR_SEND:
        if (test_bit(RDMACTXT_F_FAST_UNREG, &ctxt->flags))
            svc_rdma_put_frmr(xprt, ctxt->frmr);
        svc_rdma_put_context(ctxt, 1);
        break;

    case IB_WR_RDMA_WRITE:
        svc_rdma_put_context(ctxt, 0);
        break;

    case IB_WR_RDMA_READ:
    case IB_WR_RDMA_READ_WITH_INV:
        if (test_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags)) {
            struct svc_rdma_op_ctxt *read_hdr = ctxt->read_hdr;
            BUG_ON(!read_hdr);
            if (test_bit(RDMACTXT_F_FAST_UNREG, &ctxt->flags))
                svc_rdma_put_frmr(xprt, ctxt->frmr);
            spin_lock_bh(&xprt->sc_rq_dto_lock);
            set_bit(XPT_DATA, &xprt->sc_xprt.xpt_flags);
            list_add_tail(&read_hdr->dto_q,
                      &xprt->sc_read_complete_q);
            spin_unlock_bh(&xprt->sc_rq_dto_lock);
            svc_xprt_enqueue(&xprt->sc_xprt);
        }
        svc_rdma_put_context(ctxt, 0);
        break;

    default:
        printk(KERN_ERR "svcrdma: unexpected completion type, "
               "opcode=%d\n",
               ctxt->wr_op);
        break;
    }
}

/*
 * Send Queue Completion Handler - potentially called on interrupt context.
 *
 * Note that caller must hold a transport reference.
 */
static void sq_cq_reap(struct svcxprt_rdma *xprt)
{
    struct svc_rdma_op_ctxt *ctxt = NULL;
    struct ib_wc wc;
    struct ib_cq *cq = xprt->sc_sq_cq;
    int ret;

    if (!test_and_clear_bit(RDMAXPRT_SQ_PENDING, &xprt->sc_flags))
        return;

    ib_req_notify_cq(xprt->sc_sq_cq, IB_CQ_NEXT_COMP);
    atomic_inc(&rdma_stat_sq_poll);
    while ((ret = ib_poll_cq(cq, 1, &wc)) > 0) {
        if (wc.status != IB_WC_SUCCESS)
            /* Close the transport */
            set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);

        /* Decrement used SQ WR count */
        atomic_dec(&xprt->sc_sq_count);
        wake_up(&xprt->sc_send_wait);

        ctxt = (struct svc_rdma_op_ctxt *)(unsigned long)wc.wr_id;
        if (ctxt)
            process_context(xprt, ctxt);

        svc_xprt_put(&xprt->sc_xprt);
    }

    if (ctxt)
        atomic_inc(&rdma_stat_sq_prod);
}

static void sq_comp_handler(struct ib_cq *cq, void *cq_context)
{
    struct svcxprt_rdma *xprt = cq_context;
    unsigned long flags;

    /* Guard against unconditional flush call for destroyed QP */
    if (atomic_read(&xprt->sc_xprt.xpt_ref.refcount)==0)
        return;

    /*
     * Set the bit regardless of whether or not it's on the list
     * because it may be on the list already due to an RQ
     * completion.
     */
    set_bit(RDMAXPRT_SQ_PENDING, &xprt->sc_flags);

    /*
     * If this transport is not already on the DTO transport queue,
     * add it
     */
    spin_lock_irqsave(&dto_lock, flags);
    if (list_empty(&xprt->sc_dto_q)) {
        svc_xprt_get(&xprt->sc_xprt);
        list_add_tail(&xprt->sc_dto_q, &dto_xprt_q);
    }
    spin_unlock_irqrestore(&dto_lock, flags);

    /* Tasklet does all the work to avoid irqsave locks. */
    tasklet_schedule(&dto_tasklet);
}

static struct svcxprt_rdma *rdma_create_xprt(struct svc_serv *serv,
                         int listener)
{
    struct svcxprt_rdma *cma_xprt = kzalloc(sizeof *cma_xprt, GFP_KERNEL);

    if (!cma_xprt)
        return NULL;
    svc_xprt_init(&init_net, &svc_rdma_class, &cma_xprt->sc_xprt, serv);
    INIT_LIST_HEAD(&cma_xprt->sc_accept_q);
    INIT_LIST_HEAD(&cma_xprt->sc_dto_q);
    INIT_LIST_HEAD(&cma_xprt->sc_rq_dto_q);
    INIT_LIST_HEAD(&cma_xprt->sc_read_complete_q);
    INIT_LIST_HEAD(&cma_xprt->sc_frmr_q);
    init_waitqueue_head(&cma_xprt->sc_send_wait);

    spin_lock_init(&cma_xprt->sc_lock);
    spin_lock_init(&cma_xprt->sc_rq_dto_lock);
    spin_lock_init(&cma_xprt->sc_frmr_q_lock);

    cma_xprt->sc_ord = svcrdma_ord;

    cma_xprt->sc_max_req_size = svcrdma_max_req_size;
    cma_xprt->sc_max_requests = svcrdma_max_requests;
    cma_xprt->sc_sq_depth = svcrdma_max_requests * RPCRDMA_SQ_DEPTH_MULT;
    atomic_set(&cma_xprt->sc_sq_count, 0);
    atomic_set(&cma_xprt->sc_ctxt_used, 0);

    if (listener)
        set_bit(XPT_LISTENER, &cma_xprt->sc_xprt.xpt_flags);

    return cma_xprt;
}

struct page *svc_rdma_get_page(void)
{
    struct page *page;

    while ((page = alloc_page(GFP_KERNEL)) == NULL) {
        /* If we can't get memory, wait a bit and try again */
        printk(KERN_INFO "svcrdma: out of memory...retrying in 1000 "
               "jiffies.\n");
        schedule_timeout_uninterruptible(msecs_to_jiffies(1000));
    }
    return page;
}

int svc_rdma_post_recv(struct svcxprt_rdma *xprt)
{
    struct ib_recv_wr recv_wr, *bad_recv_wr;
    struct svc_rdma_op_ctxt *ctxt;
    struct page *page;
    dma_addr_t pa;
    int sge_no;
    int buflen;
    int ret;

    ctxt = svc_rdma_get_context(xprt);
    buflen = 0;
    ctxt->direction = DMA_FROM_DEVICE;
    for (sge_no = 0; buflen < xprt->sc_max_req_size; sge_no++) {
        BUG_ON(sge_no >= xprt->sc_max_sge);
        page = svc_rdma_get_page();
        ctxt->pages[sge_no] = page;
        pa = ib_dma_map_page(xprt->sc_cm_id->device,
                     page, 0, PAGE_SIZE,
                     DMA_FROM_DEVICE);
        if (ib_dma_mapping_error(xprt->sc_cm_id->device, pa))
            goto err_put_ctxt;
        atomic_inc(&xprt->sc_dma_used);
        ctxt->sge[sge_no].addr = pa;
        ctxt->sge[sge_no].length = PAGE_SIZE;
        ctxt->sge[sge_no].lkey = xprt->sc_dma_lkey;
        ctxt->count = sge_no + 1;
        buflen += PAGE_SIZE;
    }
    recv_wr.next = NULL;
    recv_wr.sg_list = &ctxt->sge[0];
    recv_wr.num_sge = ctxt->count;
    recv_wr.wr_id = (u64)(unsigned long)ctxt;

    svc_xprt_get(&xprt->sc_xprt);
    ret = ib_post_recv(xprt->sc_qp, &recv_wr, &bad_recv_wr);
    if (ret) {
        svc_rdma_unmap_dma(ctxt);
        svc_rdma_put_context(ctxt, 1);
        svc_xprt_put(&xprt->sc_xprt);
    }
    return ret;

 err_put_ctxt:
    svc_rdma_unmap_dma(ctxt);
    svc_rdma_put_context(ctxt, 1);
    return -ENOMEM;
}

/*
 * This function handles the CONNECT_REQUEST event on a listening
 * endpoint. It is passed the cma_id for the _new_ connection. The context in
 * this cma_id is inherited from the listening cma_id and is the svc_xprt
 * structure for the listening endpoint.
 *
 * This function creates a new xprt for the new connection and enqueues it on
 * the accept queue for the listent xprt. When the listen thread is kicked, it
 * will call the recvfrom method on the listen xprt which will accept the new
 * connection.
 */
static void handle_connect_req(struct rdma_cm_id *new_cma_id, size_t client_ird)
{
    struct svcxprt_rdma *listen_xprt = new_cma_id->context;
    struct svcxprt_rdma *newxprt;
    struct sockaddr *sa;

    /* Create a new transport */
    newxprt = rdma_create_xprt(listen_xprt->sc_xprt.xpt_server, 0);
    if (!newxprt) {
        dprintk("svcrdma: failed to create new transport\n");
        return;
    }
    newxprt->sc_cm_id = new_cma_id;
    new_cma_id->context = newxprt;
    dprintk("svcrdma: Creating newxprt=%p, cm_id=%p, listenxprt=%p\n",
        newxprt, newxprt->sc_cm_id, listen_xprt);

    /* Save client advertised inbound read limit for use later in accept. */
    newxprt->sc_ord = client_ird;

    /* Set the local and remote addresses in the transport */
    sa = (struct sockaddr *)&newxprt->sc_cm_id->route.addr.dst_addr;
    svc_xprt_set_remote(&newxprt->sc_xprt, sa, svc_addr_len(sa));
    sa = (struct sockaddr *)&newxprt->sc_cm_id->route.addr.src_addr;
    svc_xprt_set_local(&newxprt->sc_xprt, sa, svc_addr_len(sa));

    /*
     * Enqueue the new transport on the accept queue of the listening
     * transport
     */
    spin_lock_bh(&listen_xprt->sc_lock);
    list_add_tail(&newxprt->sc_accept_q, &listen_xprt->sc_accept_q);
    spin_unlock_bh(&listen_xprt->sc_lock);

    set_bit(XPT_CONN, &listen_xprt->sc_xprt.xpt_flags);
    svc_xprt_enqueue(&listen_xprt->sc_xprt);
}

/*
 * Handles events generated on the listening endpoint. These events will be
 * either be incoming connect requests or adapter removal  events.
 */
static int rdma_listen_handler(struct rdma_cm_id *cma_id,
                   struct rdma_cm_event *event)
{
    struct svcxprt_rdma *xprt = cma_id->context;
    int ret = 0;

    switch (event->event) {
    case RDMA_CM_EVENT_CONNECT_REQUEST:
        dprintk("svcrdma: Connect request on cma_id=%p, xprt = %p, "
            "event=%d\n", cma_id, cma_id->context, event->event);
        handle_connect_req(cma_id,
                   event->param.conn.initiator_depth);
        break;

    case RDMA_CM_EVENT_ESTABLISHED:
        /* Accept complete */
        dprintk("svcrdma: Connection completed on LISTEN xprt=%p, "
            "cm_id=%p\n", xprt, cma_id);
        break;

    case RDMA_CM_EVENT_DEVICE_REMOVAL:
        dprintk("svcrdma: Device removal xprt=%p, cm_id=%p\n",
            xprt, cma_id);
        if (xprt)
            set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
        break;

    default:
        dprintk("svcrdma: Unexpected event on listening endpoint %p, "
            "event=%d\n", cma_id, event->event);
        break;
    }

    return ret;
}

static int rdma_cma_handler(struct rdma_cm_id *cma_id,
                struct rdma_cm_event *event)
{
    struct svc_xprt *xprt = cma_id->context;
    struct svcxprt_rdma *rdma =
        container_of(xprt, struct svcxprt_rdma, sc_xprt);
    switch (event->event) {
    case RDMA_CM_EVENT_ESTABLISHED:
        /* Accept complete */
        svc_xprt_get(xprt);
        dprintk("svcrdma: Connection completed on DTO xprt=%p, "
            "cm_id=%p\n", xprt, cma_id);
        clear_bit(RDMAXPRT_CONN_PENDING, &rdma->sc_flags);
        svc_xprt_enqueue(xprt);
        break;
    case RDMA_CM_EVENT_DISCONNECTED:
        dprintk("svcrdma: Disconnect on DTO xprt=%p, cm_id=%p\n",
            xprt, cma_id);
        if (xprt) {
            set_bit(XPT_CLOSE, &xprt->xpt_flags);
            svc_xprt_enqueue(xprt);
            svc_xprt_put(xprt);
        }
        break;
    case RDMA_CM_EVENT_DEVICE_REMOVAL:
        dprintk("svcrdma: Device removal cma_id=%p, xprt = %p, "
            "event=%d\n", cma_id, xprt, event->event);
        if (xprt) {
            set_bit(XPT_CLOSE, &xprt->xpt_flags);
            svc_xprt_enqueue(xprt);
        }
        break;
    default:
        dprintk("svcrdma: Unexpected event on DTO endpoint %p, "
            "event=%d\n", cma_id, event->event);
        break;
    }
    return 0;
}

/*
 * Create a listening RDMA service endpoint.
 */
static struct svc_xprt *svc_rdma_create(struct svc_serv *serv,
                    struct net *net,
                    struct sockaddr *sa, int salen,
                    int flags)
{
    struct rdma_cm_id *listen_id;
    struct svcxprt_rdma *cma_xprt;
    struct svc_xprt *xprt;
    int ret;

    dprintk("svcrdma: Creating RDMA socket\n");
    if (sa->sa_family != AF_INET) {
        dprintk("svcrdma: Address family %d is not supported.\n", sa->sa_family);
        return ERR_PTR(-EAFNOSUPPORT);
    }
    cma_xprt = rdma_create_xprt(serv, 1);
    if (!cma_xprt)
        return ERR_PTR(-ENOMEM);
    xprt = &cma_xprt->sc_xprt;

    listen_id = rdma_create_id(rdma_listen_handler, cma_xprt, RDMA_PS_TCP,
                   IB_QPT_RC);
    if (IS_ERR(listen_id)) {
        ret = PTR_ERR(listen_id);
        dprintk("svcrdma: rdma_create_id failed = %d\n", ret);
        goto err0;
    }

    ret = rdma_bind_addr(listen_id, sa);
    if (ret) {
        dprintk("svcrdma: rdma_bind_addr failed = %d\n", ret);
        goto err1;
    }
    cma_xprt->sc_cm_id = listen_id;

    ret = rdma_listen(listen_id, RPCRDMA_LISTEN_BACKLOG);
    if (ret) {
        dprintk("svcrdma: rdma_listen failed = %d\n", ret);
        goto err1;
    }

    /*
     * We need to use the address from the cm_id in case the
     * caller specified 0 for the port number.
     */
    sa = (struct sockaddr *)&cma_xprt->sc_cm_id->route.addr.src_addr;
    svc_xprt_set_local(&cma_xprt->sc_xprt, sa, salen);

    return &cma_xprt->sc_xprt;

 err1:
    rdma_destroy_id(listen_id);
 err0:
    kfree(cma_xprt);
    return ERR_PTR(ret);
}

static struct svc_rdma_fastreg_mr *rdma_alloc_frmr(struct svcxprt_rdma *xprt)
{
    struct ib_mr *mr;
    struct ib_fast_reg_page_list *pl;
    struct svc_rdma_fastreg_mr *frmr;

    frmr = kmalloc(sizeof(*frmr), GFP_KERNEL);
    if (!frmr)
        goto err;

    mr = ib_alloc_fast_reg_mr(xprt->sc_pd, RPCSVC_MAXPAGES);
    if (IS_ERR(mr))
        goto err_free_frmr;

    pl = ib_alloc_fast_reg_page_list(xprt->sc_cm_id->device,
                     RPCSVC_MAXPAGES);
    if (IS_ERR(pl))
        goto err_free_mr;

    frmr->mr = mr;
    frmr->page_list = pl;
    INIT_LIST_HEAD(&frmr->frmr_list);
    return frmr;

 err_free_mr:
    ib_dereg_mr(mr);
 err_free_frmr:
    kfree(frmr);
 err:
    return ERR_PTR(-ENOMEM);
}

static void rdma_dealloc_frmr_q(struct svcxprt_rdma *xprt)
{
    struct svc_rdma_fastreg_mr *frmr;

    while (!list_empty(&xprt->sc_frmr_q)) {
        frmr = list_entry(xprt->sc_frmr_q.next,
                  struct svc_rdma_fastreg_mr, frmr_list);
        list_del_init(&frmr->frmr_list);
        ib_dereg_mr(frmr->mr);
        ib_free_fast_reg_page_list(frmr->page_list);
        kfree(frmr);
    }
}

struct svc_rdma_fastreg_mr *svc_rdma_get_frmr(struct svcxprt_rdma *rdma)
{
    struct svc_rdma_fastreg_mr *frmr = NULL;

    spin_lock_bh(&rdma->sc_frmr_q_lock);
    if (!list_empty(&rdma->sc_frmr_q)) {
        frmr = list_entry(rdma->sc_frmr_q.next,
                  struct svc_rdma_fastreg_mr, frmr_list);
        list_del_init(&frmr->frmr_list);
        frmr->map_len = 0;
        frmr->page_list_len = 0;
    }
    spin_unlock_bh(&rdma->sc_frmr_q_lock);
    if (frmr)
        return frmr;

    return rdma_alloc_frmr(rdma);
}

static void frmr_unmap_dma(struct svcxprt_rdma *xprt,
               struct svc_rdma_fastreg_mr *frmr)
{
    int page_no;
    for (page_no = 0; page_no < frmr->page_list_len; page_no++) {
        dma_addr_t addr = frmr->page_list->page_list[page_no];
        if (ib_dma_mapping_error(frmr->mr->device, addr))
            continue;
        atomic_dec(&xprt->sc_dma_used);
        ib_dma_unmap_page(frmr->mr->device, addr, PAGE_SIZE,
                  frmr->direction);
    }
}

void svc_rdma_put_frmr(struct svcxprt_rdma *rdma,
               struct svc_rdma_fastreg_mr *frmr)
{
    if (frmr) {
        frmr_unmap_dma(rdma, frmr);
        spin_lock_bh(&rdma->sc_frmr_q_lock);
        BUG_ON(!list_empty(&frmr->frmr_list));
        list_add(&frmr->frmr_list, &rdma->sc_frmr_q);
        spin_unlock_bh(&rdma->sc_frmr_q_lock);
    }
}

/*
 * This is the xpo_recvfrom function for listening endpoints. Its
 * purpose is to accept incoming connections. The CMA callback handler
 * has already created a new transport and attached it to the new CMA
 * ID.
 *
 * There is a queue of pending connections hung on the listening
 * transport. This queue contains the new svc_xprt structure. This
 * function takes svc_xprt structures off the accept_q and completes
 * the connection.
 */
static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
{
    struct svcxprt_rdma *listen_rdma;
    struct svcxprt_rdma *newxprt = NULL;
    struct rdma_conn_param conn_param;
    struct ib_qp_init_attr qp_attr;
    struct ib_device_attr devattr;
    int uninitialized_var(dma_mr_acc);
    int need_dma_mr;
    int ret;
    int i;

    listen_rdma = container_of(xprt, struct svcxprt_rdma, sc_xprt);
    clear_bit(XPT_CONN, &xprt->xpt_flags);
    /* Get the next entry off the accept list */
    spin_lock_bh(&listen_rdma->sc_lock);
    if (!list_empty(&listen_rdma->sc_accept_q)) {
        newxprt = list_entry(listen_rdma->sc_accept_q.next,
                     struct svcxprt_rdma, sc_accept_q);
        list_del_init(&newxprt->sc_accept_q);
    }
    if (!list_empty(&listen_rdma->sc_accept_q))
        set_bit(XPT_CONN, &listen_rdma->sc_xprt.xpt_flags);
    spin_unlock_bh(&listen_rdma->sc_lock);
    if (!newxprt)
        return NULL;

    dprintk("svcrdma: newxprt from accept queue = %p, cm_id=%p\n",
        newxprt, newxprt->sc_cm_id);

    ret = ib_query_device(newxprt->sc_cm_id->device, &devattr);
    if (ret) {
        dprintk("svcrdma: could not query device attributes on "
            "device %p, rc=%d\n", newxprt->sc_cm_id->device, ret);
        goto errout;
    }

    /* Qualify the transport resource defaults with the
     * capabilities of this particular device */
    newxprt->sc_max_sge = min((size_t)devattr.max_sge,
                  (size_t)RPCSVC_MAXPAGES);
    newxprt->sc_max_requests = min((size_t)devattr.max_qp_wr,
                   (size_t)svcrdma_max_requests);
    newxprt->sc_sq_depth = RPCRDMA_SQ_DEPTH_MULT * newxprt->sc_max_requests;

    /*
     * Limit ORD based on client limit, local device limit, and
     * configured svcrdma limit.
     */
    newxprt->sc_ord = min_t(size_t, devattr.max_qp_rd_atom, newxprt->sc_ord);
    newxprt->sc_ord = min_t(size_t, svcrdma_ord, newxprt->sc_ord);

    newxprt->sc_pd = ib_alloc_pd(newxprt->sc_cm_id->device);
    if (IS_ERR(newxprt->sc_pd)) {
        dprintk("svcrdma: error creating PD for connect request\n");
        goto errout;
    }
    newxprt->sc_sq_cq = ib_create_cq(newxprt->sc_cm_id->device,
                     sq_comp_handler,
                     cq_event_handler,
                     newxprt,
                     newxprt->sc_sq_depth,
                     0);
    if (IS_ERR(newxprt->sc_sq_cq)) {
        dprintk("svcrdma: error creating SQ CQ for connect request\n");
        goto errout;
    }
    newxprt->sc_rq_cq = ib_create_cq(newxprt->sc_cm_id->device,
                     rq_comp_handler,
                     cq_event_handler,
                     newxprt,
                     newxprt->sc_max_requests,
                     0);
    if (IS_ERR(newxprt->sc_rq_cq)) {
        dprintk("svcrdma: error creating RQ CQ for connect request\n");
        goto errout;
    }

    memset(&qp_attr, 0, sizeof qp_attr);
    qp_attr.event_handler = qp_event_handler;
    qp_attr.qp_context = &newxprt->sc_xprt;
    qp_attr.cap.max_send_wr = newxprt->sc_sq_depth;
    qp_attr.cap.max_recv_wr = newxprt->sc_max_requests;
    qp_attr.cap.max_send_sge = newxprt->sc_max_sge;
    qp_attr.cap.max_recv_sge = newxprt->sc_max_sge;
    qp_attr.sq_sig_type = IB_SIGNAL_REQ_WR;
    qp_attr.qp_type = IB_QPT_RC;
    qp_attr.send_cq = newxprt->sc_sq_cq;
    qp_attr.recv_cq = newxprt->sc_rq_cq;
    dprintk("svcrdma: newxprt->sc_cm_id=%p, newxprt->sc_pd=%p\n"
        "    cm_id->device=%p, sc_pd->device=%p\n"
        "    cap.max_send_wr = %d\n"
        "    cap.max_recv_wr = %d\n"
        "    cap.max_send_sge = %d\n"
        "    cap.max_recv_sge = %d\n",
        newxprt->sc_cm_id, newxprt->sc_pd,
        newxprt->sc_cm_id->device, newxprt->sc_pd->device,
        qp_attr.cap.max_send_wr,
        qp_attr.cap.max_recv_wr,
        qp_attr.cap.max_send_sge,
        qp_attr.cap.max_recv_sge);

    ret = rdma_create_qp(newxprt->sc_cm_id, newxprt->sc_pd, &qp_attr);
    if (ret) {
        /*
         * XXX: This is a hack. We need a xx_request_qp interface
         * that will adjust the qp_attr's with a best-effort
         * number
         */
        qp_attr.cap.max_send_sge -= 2;
        qp_attr.cap.max_recv_sge -= 2;
        ret = rdma_create_qp(newxprt->sc_cm_id, newxprt->sc_pd,
                     &qp_attr);
        if (ret) {
            dprintk("svcrdma: failed to create QP, ret=%d\n", ret);
            goto errout;
        }
        newxprt->sc_max_sge = qp_attr.cap.max_send_sge;
        newxprt->sc_max_sge = qp_attr.cap.max_recv_sge;
        newxprt->sc_sq_depth = qp_attr.cap.max_send_wr;
        newxprt->sc_max_requests = qp_attr.cap.max_recv_wr;
    }
    newxprt->sc_qp = newxprt->sc_cm_id->qp;

    /*
     * Use the most secure set of MR resources based on the
     * transport type and available memory management features in
     * the device. Here's the table implemented below:
     *
     *      Fast    Global  DMA Remote WR
     *      Reg LKEY    MR  Access
     *      Sup'd   Sup'd   Needed  Needed
     *
     * IWARP    N   N   Y   Y
     *      N   Y   Y   Y
     *      Y   N   Y   N
     *      Y   Y   N   -
     *
     * IB       N   N   Y   N
     *      N   Y   N   -
     *      Y   N   Y   N
     *      Y   Y   N   -
     *
     * NB:  iWARP requires remote write access for the data sink
     *  of an RDMA_READ. IB does not.
     */
    if (devattr.device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS) {
        newxprt->sc_frmr_pg_list_len =
            devattr.max_fast_reg_page_list_len;
        newxprt->sc_dev_caps |= SVCRDMA_DEVCAP_FAST_REG;
    }

    /*
     * Determine if a DMA MR is required and if so, what privs are required
     */
    switch (rdma_node_get_transport(newxprt->sc_cm_id->device->node_type)) {
    case RDMA_TRANSPORT_IWARP:
        newxprt->sc_dev_caps |= SVCRDMA_DEVCAP_READ_W_INV;
        if (!(newxprt->sc_dev_caps & SVCRDMA_DEVCAP_FAST_REG)) {
            need_dma_mr = 1;
            dma_mr_acc =
                (IB_ACCESS_LOCAL_WRITE |
                 IB_ACCESS_REMOTE_WRITE);
        } else if (!(devattr.device_cap_flags & IB_DEVICE_LOCAL_DMA_LKEY)) {
            need_dma_mr = 1;
            dma_mr_acc = IB_ACCESS_LOCAL_WRITE;
        } else
            need_dma_mr = 0;
        break;
    case RDMA_TRANSPORT_IB:
        if (!(devattr.device_cap_flags & IB_DEVICE_LOCAL_DMA_LKEY)) {
            need_dma_mr = 1;
            dma_mr_acc = IB_ACCESS_LOCAL_WRITE;
        } else
            need_dma_mr = 0;
        break;
    default:
        goto errout;
    }

    /* Create the DMA MR if needed, otherwise, use the DMA LKEY */
    if (need_dma_mr) {
        /* Register all of physical memory */
        newxprt->sc_phys_mr =
            ib_get_dma_mr(newxprt->sc_pd, dma_mr_acc);
        if (IS_ERR(newxprt->sc_phys_mr)) {
            dprintk("svcrdma: Failed to create DMA MR ret=%d\n",
                ret);
            goto errout;
        }
        newxprt->sc_dma_lkey = newxprt->sc_phys_mr->lkey;
    } else
        newxprt->sc_dma_lkey =
            newxprt->sc_cm_id->device->local_dma_lkey;

    /* Post receive buffers */
    for (i = 0; i < newxprt->sc_max_requests; i++) {
        ret = svc_rdma_post_recv(newxprt);
        if (ret) {
            dprintk("svcrdma: failure posting receive buffers\n");
            goto errout;
        }
    }

    /* Swap out the handler */
    newxprt->sc_cm_id->event_handler = rdma_cma_handler;

    /*
     * Arm the CQs for the SQ and RQ before accepting so we can't
     * miss the first message
     */
    ib_req_notify_cq(newxprt->sc_sq_cq, IB_CQ_NEXT_COMP);
    ib_req_notify_cq(newxprt->sc_rq_cq, IB_CQ_NEXT_COMP);

    /* Accept Connection */
    set_bit(RDMAXPRT_CONN_PENDING, &newxprt->sc_flags);
    memset(&conn_param, 0, sizeof conn_param);
    conn_param.responder_resources = 0;
    conn_param.initiator_depth = newxprt->sc_ord;
    ret = rdma_accept(newxprt->sc_cm_id, &conn_param);
    if (ret) {
        dprintk("svcrdma: failed to accept new connection, ret=%d\n",
               ret);
        goto errout;
    }

    dprintk("svcrdma: new connection %p accepted with the following "
        "attributes:\n"
        "    local_ip        : %pI4\n"
        "    local_port      : %d\n"
        "    remote_ip       : %pI4\n"
        "    remote_port     : %d\n"
        "    max_sge         : %d\n"
        "    sq_depth        : %d\n"
        "    max_requests    : %d\n"
        "    ord             : %d\n",
        newxprt,
        &((struct sockaddr_in *)&newxprt->sc_cm_id->
             route.addr.src_addr)->sin_addr.s_addr,
        ntohs(((struct sockaddr_in *)&newxprt->sc_cm_id->
               route.addr.src_addr)->sin_port),
        &((struct sockaddr_in *)&newxprt->sc_cm_id->
             route.addr.dst_addr)->sin_addr.s_addr,
        ntohs(((struct sockaddr_in *)&newxprt->sc_cm_id->
               route.addr.dst_addr)->sin_port),
        newxprt->sc_max_sge,
        newxprt->sc_sq_depth,
        newxprt->sc_max_requests,
        newxprt->sc_ord);

    return &newxprt->sc_xprt;

 errout:
    dprintk("svcrdma: failure accepting new connection rc=%d.\n", ret);
    /* Take a reference in case the DTO handler runs */
    svc_xprt_get(&newxprt->sc_xprt);
    if (newxprt->sc_qp && !IS_ERR(newxprt->sc_qp))
        ib_destroy_qp(newxprt->sc_qp);
    rdma_destroy_id(newxprt->sc_cm_id);
    /* This call to put will destroy the transport */
    svc_xprt_put(&newxprt->sc_xprt);
    return NULL;
}

static void svc_rdma_release_rqst(struct svc_rqst *rqstp)
{
}

/*
 * When connected, an svc_xprt has at least two references:
 *
 * - A reference held by the cm_id between the ESTABLISHED and
 *   DISCONNECTED events. If the remote peer disconnected first, this
 *   reference could be gone.
 *
 * - A reference held by the svc_recv code that called this function
 *   as part of close processing.
 *
 * At a minimum one references should still be held.
 */
static void svc_rdma_detach(struct svc_xprt *xprt)
{
    struct svcxprt_rdma *rdma =
        container_of(xprt, struct svcxprt_rdma, sc_xprt);
    dprintk("svc: svc_rdma_detach(%p)\n", xprt);

    /* Disconnect and flush posted WQE */
    rdma_disconnect(rdma->sc_cm_id);
}

static void __svc_rdma_free(struct work_struct *work)
{
    struct svcxprt_rdma *rdma =
        container_of(work, struct svcxprt_rdma, sc_work);
    dprintk("svcrdma: svc_rdma_free(%p)\n", rdma);

    /* We should only be called from kref_put */
    BUG_ON(atomic_read(&rdma->sc_xprt.xpt_ref.refcount) != 0);

    /*
     * Destroy queued, but not processed read completions. Note
     * that this cleanup has to be done before destroying the
     * cm_id because the device ptr is needed to unmap the dma in
     * svc_rdma_put_context.
     */
    while (!list_empty(&rdma->sc_read_complete_q)) {
        struct svc_rdma_op_ctxt *ctxt;
        ctxt = list_entry(rdma->sc_read_complete_q.next,
                  struct svc_rdma_op_ctxt,
                  dto_q);
        list_del_init(&ctxt->dto_q);
        svc_rdma_put_context(ctxt, 1);
    }

    /* Destroy queued, but not processed recv completions */
    while (!list_empty(&rdma->sc_rq_dto_q)) {
        struct svc_rdma_op_ctxt *ctxt;
        ctxt = list_entry(rdma->sc_rq_dto_q.next,
                  struct svc_rdma_op_ctxt,
                  dto_q);
        list_del_init(&ctxt->dto_q);
        svc_rdma_put_context(ctxt, 1);
    }

    /* Warn if we leaked a resource or under-referenced */
    WARN_ON(atomic_read(&rdma->sc_ctxt_used) != 0);
    WARN_ON(atomic_read(&rdma->sc_dma_used) != 0);

    /* De-allocate fastreg mr */
    rdma_dealloc_frmr_q(rdma);

    /* Destroy the QP if present (not a listener) */
    if (rdma->sc_qp && !IS_ERR(rdma->sc_qp))
        ib_destroy_qp(rdma->sc_qp);

    if (rdma->sc_sq_cq && !IS_ERR(rdma->sc_sq_cq))
        ib_destroy_cq(rdma->sc_sq_cq);

    if (rdma->sc_rq_cq && !IS_ERR(rdma->sc_rq_cq))
        ib_destroy_cq(rdma->sc_rq_cq);

    if (rdma->sc_phys_mr && !IS_ERR(rdma->sc_phys_mr))
        ib_dereg_mr(rdma->sc_phys_mr);

    if (rdma->sc_pd && !IS_ERR(rdma->sc_pd))
        ib_dealloc_pd(rdma->sc_pd);

    /* Destroy the CM ID */
    rdma_destroy_id(rdma->sc_cm_id);

    kfree(rdma);
}

static void svc_rdma_free(struct svc_xprt *xprt)
{
    struct svcxprt_rdma *rdma =
        container_of(xprt, struct svcxprt_rdma, sc_xprt);
    INIT_WORK(&rdma->sc_work, __svc_rdma_free);
    queue_work(svc_rdma_wq, &rdma->sc_work);
}

static int svc_rdma_has_wspace(struct svc_xprt *xprt)
{
    struct svcxprt_rdma *rdma =
        container_of(xprt, struct svcxprt_rdma, sc_xprt);

    /*
     * If there are fewer SQ WR available than required to send a
     * simple response, return false.
     */
    if ((rdma->sc_sq_depth - atomic_read(&rdma->sc_sq_count) < 3))
        return 0;

    /*
     * ...or there are already waiters on the SQ,
     * return false.
     */
    if (waitqueue_active(&rdma->sc_send_wait))
        return 0;

    /* Otherwise return true. */
    return 1;
}

/*
 * Attempt to register the kvec representing the RPC memory with the
 * device.
 *
 * Returns:
 *  NULL : The device does not support fastreg or there were no more
 *         fastreg mr.
 *  frmr : The kvec register request was successfully posted.
 *    <0 : An error was encountered attempting to register the kvec.
 */
int svc_rdma_fastreg(struct svcxprt_rdma *xprt,
             struct svc_rdma_fastreg_mr *frmr)
{
    struct ib_send_wr fastreg_wr;
    u8 key;

    /* Bump the key */
    key = (u8)(frmr->mr->lkey & 0x000000FF);
    ib_update_fast_reg_key(frmr->mr, ++key);

    /* Prepare FASTREG WR */
    memset(&fastreg_wr, 0, sizeof fastreg_wr);
    fastreg_wr.opcode = IB_WR_FAST_REG_MR;
    fastreg_wr.send_flags = IB_SEND_SIGNALED;
    fastreg_wr.wr.fast_reg.iova_start = (unsigned long)frmr->kva;
    fastreg_wr.wr.fast_reg.page_list = frmr->page_list;
    fastreg_wr.wr.fast_reg.page_list_len = frmr->page_list_len;
    fastreg_wr.wr.fast_reg.page_shift = PAGE_SHIFT;
    fastreg_wr.wr.fast_reg.length = frmr->map_len;
    fastreg_wr.wr.fast_reg.access_flags = frmr->access_flags;
    fastreg_wr.wr.fast_reg.rkey = frmr->mr->lkey;
    return svc_rdma_send(xprt, &fastreg_wr);
}

int svc_rdma_send(struct svcxprt_rdma *xprt, struct ib_send_wr *wr)
{
    struct ib_send_wr *bad_wr, *n_wr;
    int wr_count;
    int i;
    int ret;

    if (test_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags))
        return -ENOTCONN;

    BUG_ON(wr->send_flags != IB_SEND_SIGNALED);
    wr_count = 1;
    for (n_wr = wr->next; n_wr; n_wr = n_wr->next)
        wr_count++;

    /* If the SQ is full, wait until an SQ entry is available */
    while (1) {
        spin_lock_bh(&xprt->sc_lock);
        if (xprt->sc_sq_depth < atomic_read(&xprt->sc_sq_count) + wr_count) {
            spin_unlock_bh(&xprt->sc_lock);
            atomic_inc(&rdma_stat_sq_starve);

            /* See if we can opportunistically reap SQ WR to make room */
            sq_cq_reap(xprt);

            /* Wait until SQ WR available if SQ still full */
            wait_event(xprt->sc_send_wait,
                   atomic_read(&xprt->sc_sq_count) <
                   xprt->sc_sq_depth);
            if (test_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags))
                return -ENOTCONN;
            continue;
        }
        /* Take a transport ref for each WR posted */
        for (i = 0; i < wr_count; i++)
            svc_xprt_get(&xprt->sc_xprt);

        /* Bump used SQ WR count and post */
        atomic_add(wr_count, &xprt->sc_sq_count);
        ret = ib_post_send(xprt->sc_qp, wr, &bad_wr);
        if (ret) {
            set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
            atomic_sub(wr_count, &xprt->sc_sq_count);
            for (i = 0; i < wr_count; i ++)
                svc_xprt_put(&xprt->sc_xprt);
            dprintk("svcrdma: failed to post SQ WR rc=%d, "
                   "sc_sq_count=%d, sc_sq_depth=%d\n",
                   ret, atomic_read(&xprt->sc_sq_count),
                   xprt->sc_sq_depth);
        }
        spin_unlock_bh(&xprt->sc_lock);
        if (ret)
            wake_up(&xprt->sc_send_wait);
        break;
    }
    return ret;
}

void svc_rdma_send_error(struct svcxprt_rdma *xprt, struct rpcrdma_msg *rmsgp,
             enum rpcrdma_errcode err)
{
    struct ib_send_wr err_wr;
    struct page *p;
    struct svc_rdma_op_ctxt *ctxt;
    u32 *va;
    int length;
    int ret;

    p = svc_rdma_get_page();
    va = page_address(p);

    /* XDR encode error */
    length = svc_rdma_xdr_encode_error(xprt, rmsgp, err, va);

    ctxt = svc_rdma_get_context(xprt);
    ctxt->direction = DMA_FROM_DEVICE;
    ctxt->count = 1;
    ctxt->pages[0] = p;

    /* Prepare SGE for local address */
    ctxt->sge[0].addr = ib_dma_map_page(xprt->sc_cm_id->device,
                        p, 0, length, DMA_FROM_DEVICE);
    if (ib_dma_mapping_error(xprt->sc_cm_id->device, ctxt->sge[0].addr)) {
        put_page(p);
        svc_rdma_put_context(ctxt, 1);
        return;
    }
    atomic_inc(&xprt->sc_dma_used);
    ctxt->sge[0].lkey = xprt->sc_dma_lkey;
    ctxt->sge[0].length = length;

    /* Prepare SEND WR */
    memset(&err_wr, 0, sizeof err_wr);
    ctxt->wr_op = IB_WR_SEND;
    err_wr.wr_id = (unsigned long)ctxt;
    err_wr.sg_list = ctxt->sge;
    err_wr.num_sge = 1;
    err_wr.opcode = IB_WR_SEND;
    err_wr.send_flags = IB_SEND_SIGNALED;

    /* Post It */
    ret = svc_rdma_send(xprt, &err_wr);
    if (ret) {
        dprintk("svcrdma: Error %d posting send for protocol error\n",
            ret);
        svc_rdma_unmap_dma(ctxt);
        svc_rdma_put_context(ctxt, 1);
    }
}