svcrdma: Query device for Fast Reg support during connection setup

[deliverable/linux.git] / net / sunrpc / xprtrdma / svc_rdma_transport.c

/*
 * 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 <tom@opengridcomputing.com>
 */

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

#define RPCDBG_FACILITY RPCDBG_SVCXPRT

static struct svc_xprt *svc_rdma_create(struct svc_serv *serv,
                                        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);

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,
};

/* WR context cache. Created in svc_rdma.c  */
extern struct kmem_cache *svc_rdma_ctxt_cachep;

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;
}

static 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_single(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 request map cache. Created in svc_rdma.c  */
extern struct kmem_cache *svc_rdma_map_cachep;

/*
 * 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);
}

/*
 * 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) {
                ctxt = (struct svc_rdma_op_ctxt *)(unsigned long)wc.wr_id;
                xprt = ctxt->xprt;

                svc_rdma_unmap_dma(ctxt);
                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);

                switch (ctxt->wr_op) {
                case IB_WR_SEND:
                        svc_rdma_put_context(ctxt, 1);
                        break;

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

                case IB_WR_RDMA_READ:
                        if (test_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags)) {
                                struct svc_rdma_op_ctxt *read_hdr = ctxt->read_hdr;
                                BUG_ON(!read_hdr);
                                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, status=%d\n",
                               wc.opcode, wc.status);
                        break;
                }
                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(&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;
        unsigned long 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;
                atomic_inc(&xprt->sc_dma_used);
                pa = ib_dma_map_page(xprt->sc_cm_id->device,
                                     page, 0, PAGE_SIZE,
                                     DMA_FROM_DEVICE);
                ctxt->sge[sge_no].addr = pa;
                ctxt->sge[sge_no].length = PAGE_SIZE;
                ctxt->sge[sge_no].lkey = xprt->sc_phys_mr->lkey;
                buflen += PAGE_SIZE;
        }
        ctxt->count = sge_no;
        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_xprt_put(&xprt->sc_xprt);
                svc_rdma_put_context(ctxt, 1);
        }
        return ret;
}

/*
 * 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);

        /*
         * Can't use svc_xprt_received here because we are not on a
         * rqstp thread
        */
        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.responder_resources);
                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 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");

        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);
        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 (!mr)
                goto err_free_frmr;

        pl = ib_alloc_fast_reg_page_list(xprt->sc_cm_id->device,
                                         RPCSVC_MAXPAGES);
        if (!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_single(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 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        : %d.%d.%d.%d\n"
                "    local_port      : %d\n"
                "    remote_ip       : %d.%d.%d.%d\n"
                "    remote_port     : %d\n"
                "    max_sge         : %d\n"
                "    sq_depth        : %d\n"
                "    max_requests    : %d\n"
                "    ord             : %d\n",
                newxprt,
                NIPQUAD(((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),
                NIPQUAD(((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);
        schedule_work(&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;
}

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

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

        BUG_ON(wr->send_flags != IB_SEND_SIGNALED);
        BUG_ON(((struct svc_rdma_op_ctxt *)(unsigned long)wr->wr_id)->wr_op !=
                wr->opcode);
        /* 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)) {
                        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 0;
                        continue;
                }
                /* Bumped used SQ WR count and post */
                svc_xprt_get(&xprt->sc_xprt);
                ret = ib_post_send(xprt->sc_qp, wr, &bad_wr);
                if (!ret)
                        atomic_inc(&xprt->sc_sq_count);
                else {
                        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);
                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 ib_sge sge;
        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);

        /* Prepare SGE for local address */
        atomic_inc(&xprt->sc_dma_used);
        sge.addr = ib_dma_map_page(xprt->sc_cm_id->device,
                                   p, 0, PAGE_SIZE, DMA_FROM_DEVICE);
        sge.lkey = xprt->sc_phys_mr->lkey;
        sge.length = length;

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

        /* 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 = &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_put_context(ctxt, 1);
        }
}