Merge tag 'gpio-v4.6-3' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux...

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

/*
 * Copyright (c) 2014 Open Grid Computing, Inc. All rights reserved.
 * 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/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 svcxprt_rdma *rdma_create_xprt(struct svc_serv *, int);
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 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 int svc_rdma_secure_port(struct svc_rqst *);

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,
        .xpo_secure_port = svc_rdma_secure_port,
};

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

#if defined(CONFIG_SUNRPC_BACKCHANNEL)
static struct svc_xprt *svc_rdma_bc_create(struct svc_serv *, struct net *,
                                           struct sockaddr *, int, int);
static void svc_rdma_bc_detach(struct svc_xprt *);
static void svc_rdma_bc_free(struct svc_xprt *);

static struct svc_xprt_ops svc_rdma_bc_ops = {
        .xpo_create = svc_rdma_bc_create,
        .xpo_detach = svc_rdma_bc_detach,
        .xpo_free = svc_rdma_bc_free,
        .xpo_prep_reply_hdr = svc_rdma_prep_reply_hdr,
        .xpo_secure_port = svc_rdma_secure_port,
};

struct svc_xprt_class svc_rdma_bc_class = {
        .xcl_name = "rdma-bc",
        .xcl_owner = THIS_MODULE,
        .xcl_ops = &svc_rdma_bc_ops,
        .xcl_max_payload = (1024 - RPCRDMA_HDRLEN_MIN)
};

static struct svc_xprt *svc_rdma_bc_create(struct svc_serv *serv,
                                           struct net *net,
                                           struct sockaddr *sa, int salen,
                                           int flags)
{
        struct svcxprt_rdma *cma_xprt;
        struct svc_xprt *xprt;

        cma_xprt = rdma_create_xprt(serv, 0);
        if (!cma_xprt)
                return ERR_PTR(-ENOMEM);
        xprt = &cma_xprt->sc_xprt;

        svc_xprt_init(net, &svc_rdma_bc_class, xprt, serv);
        serv->sv_bc_xprt = xprt;

        dprintk("svcrdma: %s(%p)\n", __func__, xprt);
        return xprt;
}

static void svc_rdma_bc_detach(struct svc_xprt *xprt)
{
        dprintk("svcrdma: %s(%p)\n", __func__, xprt);
}

static void svc_rdma_bc_free(struct svc_xprt *xprt)
{
        struct svcxprt_rdma *rdma =
                container_of(xprt, struct svcxprt_rdma, sc_xprt);

        dprintk("svcrdma: %s(%p)\n", __func__, xprt);
        if (xprt)
                kfree(rdma);
}
#endif  /* CONFIG_SUNRPC_BACKCHANNEL */

static struct svc_rdma_op_ctxt *alloc_ctxt(struct svcxprt_rdma *xprt,
                                           gfp_t flags)
{
        struct svc_rdma_op_ctxt *ctxt;

        ctxt = kmalloc(sizeof(*ctxt), flags);
        if (ctxt) {
                ctxt->xprt = xprt;
                INIT_LIST_HEAD(&ctxt->free);
                INIT_LIST_HEAD(&ctxt->dto_q);
        }
        return ctxt;
}

static bool svc_rdma_prealloc_ctxts(struct svcxprt_rdma *xprt)
{
        unsigned int i;

        /* Each RPC/RDMA credit can consume a number of send
         * and receive WQEs. One ctxt is allocated for each.
         */
        i = xprt->sc_sq_depth + xprt->sc_rq_depth;

        while (i--) {
                struct svc_rdma_op_ctxt *ctxt;

                ctxt = alloc_ctxt(xprt, GFP_KERNEL);
                if (!ctxt) {
                        dprintk("svcrdma: No memory for RDMA ctxt\n");
                        return false;
                }
                list_add(&ctxt->free, &xprt->sc_ctxts);
        }
        return true;
}

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

        spin_lock_bh(&xprt->sc_ctxt_lock);
        xprt->sc_ctxt_used++;
        if (list_empty(&xprt->sc_ctxts))
                goto out_empty;

        ctxt = list_first_entry(&xprt->sc_ctxts,
                                struct svc_rdma_op_ctxt, free);
        list_del_init(&ctxt->free);
        spin_unlock_bh(&xprt->sc_ctxt_lock);

out:
        ctxt->count = 0;
        ctxt->frmr = NULL;
        return ctxt;

out_empty:
        /* Either pre-allocation missed the mark, or send
         * queue accounting is broken.
         */
        spin_unlock_bh(&xprt->sc_ctxt_lock);

        ctxt = alloc_ctxt(xprt, GFP_NOIO);
        if (ctxt)
                goto out;

        spin_lock_bh(&xprt->sc_ctxt_lock);
        xprt->sc_ctxt_used--;
        spin_unlock_bh(&xprt->sc_ctxt_lock);
        WARN_ONCE(1, "svcrdma: empty RDMA ctxt list?\n");
        return NULL;
}

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 local_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_pd->local_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 = ctxt->xprt;
        int i;

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

        spin_lock_bh(&xprt->sc_ctxt_lock);
        xprt->sc_ctxt_used--;
        list_add(&ctxt->free, &xprt->sc_ctxts);
        spin_unlock_bh(&xprt->sc_ctxt_lock);
}

static void svc_rdma_destroy_ctxts(struct svcxprt_rdma *xprt)
{
        while (!list_empty(&xprt->sc_ctxts)) {
                struct svc_rdma_op_ctxt *ctxt;

                ctxt = list_first_entry(&xprt->sc_ctxts,
                                        struct svc_rdma_op_ctxt, free);
                list_del(&ctxt->free);
                kfree(ctxt);
        }
}

static struct svc_rdma_req_map *alloc_req_map(gfp_t flags)
{
        struct svc_rdma_req_map *map;

        map = kmalloc(sizeof(*map), flags);
        if (map)
                INIT_LIST_HEAD(&map->free);
        return map;
}

static bool svc_rdma_prealloc_maps(struct svcxprt_rdma *xprt)
{
        unsigned int i;

        /* One for each receive buffer on this connection. */
        i = xprt->sc_max_requests;

        while (i--) {
                struct svc_rdma_req_map *map;

                map = alloc_req_map(GFP_KERNEL);
                if (!map) {
                        dprintk("svcrdma: No memory for request map\n");
                        return false;
                }
                list_add(&map->free, &xprt->sc_maps);
        }
        return true;
}

struct svc_rdma_req_map *svc_rdma_get_req_map(struct svcxprt_rdma *xprt)
{
        struct svc_rdma_req_map *map = NULL;

        spin_lock(&xprt->sc_map_lock);
        if (list_empty(&xprt->sc_maps))
                goto out_empty;

        map = list_first_entry(&xprt->sc_maps,
                               struct svc_rdma_req_map, free);
        list_del_init(&map->free);
        spin_unlock(&xprt->sc_map_lock);

out:
        map->count = 0;
        return map;

out_empty:
        spin_unlock(&xprt->sc_map_lock);

        /* Pre-allocation amount was incorrect */
        map = alloc_req_map(GFP_NOIO);
        if (map)
                goto out;

        WARN_ONCE(1, "svcrdma: empty request map list?\n");
        return NULL;
}

void svc_rdma_put_req_map(struct svcxprt_rdma *xprt,
                          struct svc_rdma_req_map *map)
{
        spin_lock(&xprt->sc_map_lock);
        list_add(&map->free, &xprt->sc_maps);
        spin_unlock(&xprt->sc_map_lock);
}

static void svc_rdma_destroy_maps(struct svcxprt_rdma *xprt)
{
        while (!list_empty(&xprt->sc_maps)) {
                struct svc_rdma_req_map *map;

                map = list_first_entry(&xprt->sc_maps,
                                       struct svc_rdma_req_map, free);
                list_del(&map->free);
                kfree(map);
        }
}

/* 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 %s (%d) received for QP=%p\n",
                        ib_event_msg(event->event), 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 %s (%d) received for QP=%p, "
                        "closing transport\n",
                        ib_event_msg(event->event), event->event,
                        event->element.qp);
                set_bit(XPT_CLOSE, &xprt->xpt_flags);
                break;
        }
}

/**
 * svc_rdma_wc_receive - Invoked by RDMA provider for each polled Receive WC
 * @cq:        completion queue
 * @wc:        completed WR
 *
 */
static void svc_rdma_wc_receive(struct ib_cq *cq, struct ib_wc *wc)
{
        struct svcxprt_rdma *xprt = cq->cq_context;
        struct ib_cqe *cqe = wc->wr_cqe;
        struct svc_rdma_op_ctxt *ctxt;

        /* WARNING: Only wc->wr_cqe and wc->status are reliable */
        ctxt = container_of(cqe, struct svc_rdma_op_ctxt, cqe);
        ctxt->wc_status = wc->status;
        svc_rdma_unmap_dma(ctxt);

        if (wc->status != IB_WC_SUCCESS)
                goto flushed;

        /* All wc fields are now known to be valid */
        ctxt->byte_len = wc->byte_len;
        spin_lock(&xprt->sc_rq_dto_lock);
        list_add_tail(&ctxt->dto_q, &xprt->sc_rq_dto_q);
        spin_unlock(&xprt->sc_rq_dto_lock);

        set_bit(XPT_DATA, &xprt->sc_xprt.xpt_flags);
        if (test_bit(RDMAXPRT_CONN_PENDING, &xprt->sc_flags))
                goto out;
        svc_xprt_enqueue(&xprt->sc_xprt);
        goto out;

flushed:
        if (wc->status != IB_WC_WR_FLUSH_ERR)
                pr_warn("svcrdma: receive: %s (%u/0x%x)\n",
                        ib_wc_status_msg(wc->status),
                        wc->status, wc->vendor_err);
        set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
        svc_rdma_put_context(ctxt, 1);

out:
        svc_xprt_put(&xprt->sc_xprt);
}

static void svc_rdma_send_wc_common(struct svcxprt_rdma *xprt,
                                    struct ib_wc *wc,
                                    const char *opname)
{
        if (wc->status != IB_WC_SUCCESS)
                goto err;

out:
        atomic_dec(&xprt->sc_sq_count);
        wake_up(&xprt->sc_send_wait);
        return;

err:
        set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
        if (wc->status != IB_WC_WR_FLUSH_ERR)
                pr_err("svcrdma: %s: %s (%u/0x%x)\n",
                       opname, ib_wc_status_msg(wc->status),
                       wc->status, wc->vendor_err);
        goto out;
}

static void svc_rdma_send_wc_common_put(struct ib_cq *cq, struct ib_wc *wc,
                                        const char *opname)
{
        struct svcxprt_rdma *xprt = cq->cq_context;

        svc_rdma_send_wc_common(xprt, wc, opname);
        svc_xprt_put(&xprt->sc_xprt);
}

/**
 * svc_rdma_wc_send - Invoked by RDMA provider for each polled Send WC
 * @cq:        completion queue
 * @wc:        completed WR
 *
 */
void svc_rdma_wc_send(struct ib_cq *cq, struct ib_wc *wc)
{
        struct ib_cqe *cqe = wc->wr_cqe;
        struct svc_rdma_op_ctxt *ctxt;

        svc_rdma_send_wc_common_put(cq, wc, "send");

        ctxt = container_of(cqe, struct svc_rdma_op_ctxt, cqe);
        svc_rdma_unmap_dma(ctxt);
        svc_rdma_put_context(ctxt, 1);
}

/**
 * svc_rdma_wc_write - Invoked by RDMA provider for each polled Write WC
 * @cq:        completion queue
 * @wc:        completed WR
 *
 */
void svc_rdma_wc_write(struct ib_cq *cq, struct ib_wc *wc)
{
        struct ib_cqe *cqe = wc->wr_cqe;
        struct svc_rdma_op_ctxt *ctxt;

        svc_rdma_send_wc_common_put(cq, wc, "write");

        ctxt = container_of(cqe, struct svc_rdma_op_ctxt, cqe);
        svc_rdma_unmap_dma(ctxt);
        svc_rdma_put_context(ctxt, 0);
}

/**
 * svc_rdma_wc_reg - Invoked by RDMA provider for each polled FASTREG WC
 * @cq:        completion queue
 * @wc:        completed WR
 *
 */
void svc_rdma_wc_reg(struct ib_cq *cq, struct ib_wc *wc)
{
        svc_rdma_send_wc_common_put(cq, wc, "fastreg");
}

/**
 * svc_rdma_wc_read - Invoked by RDMA provider for each polled Read WC
 * @cq:        completion queue
 * @wc:        completed WR
 *
 */
void svc_rdma_wc_read(struct ib_cq *cq, struct ib_wc *wc)
{
        struct svcxprt_rdma *xprt = cq->cq_context;
        struct ib_cqe *cqe = wc->wr_cqe;
        struct svc_rdma_op_ctxt *ctxt;

        svc_rdma_send_wc_common(xprt, wc, "read");

        ctxt = container_of(cqe, struct svc_rdma_op_ctxt, cqe);
        svc_rdma_unmap_dma(ctxt);
        svc_rdma_put_frmr(xprt, ctxt->frmr);

        if (test_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags)) {
                struct svc_rdma_op_ctxt *read_hdr;

                read_hdr = ctxt->read_hdr;
                spin_lock(&xprt->sc_rq_dto_lock);
                list_add_tail(&read_hdr->dto_q,
                              &xprt->sc_read_complete_q);
                spin_unlock(&xprt->sc_rq_dto_lock);

                set_bit(XPT_DATA, &xprt->sc_xprt.xpt_flags);
                svc_xprt_enqueue(&xprt->sc_xprt);
        }

        svc_rdma_put_context(ctxt, 0);
        svc_xprt_put(&xprt->sc_xprt);
}

/**
 * svc_rdma_wc_inv - Invoked by RDMA provider for each polled LOCAL_INV WC
 * @cq:        completion queue
 * @wc:        completed WR
 *
 */
void svc_rdma_wc_inv(struct ib_cq *cq, struct ib_wc *wc)
{
        svc_rdma_send_wc_common_put(cq, wc, "localInv");
}

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_LIST_HEAD(&cma_xprt->sc_ctxts);
        INIT_LIST_HEAD(&cma_xprt->sc_maps);
        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);
        spin_lock_init(&cma_xprt->sc_ctxt_lock);
        spin_lock_init(&cma_xprt->sc_map_lock);

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

        return cma_xprt;
}

int svc_rdma_post_recv(struct svcxprt_rdma *xprt, gfp_t flags)
{
        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;
        ctxt->cqe.done = svc_rdma_wc_receive;
        for (sge_no = 0; buflen < xprt->sc_max_req_size; sge_no++) {
                if (sge_no >= xprt->sc_max_sge) {
                        pr_err("svcrdma: Too many sges (%d)\n", sge_no);
                        goto err_put_ctxt;
                }
                page = alloc_page(flags);
                if (!page)
                        goto err_put_ctxt;
                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_pd->local_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_cqe = &ctxt->cqe;

        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;
}

int svc_rdma_repost_recv(struct svcxprt_rdma *xprt, gfp_t flags)
{
        int ret = 0;

        ret = svc_rdma_post_recv(xprt, flags);
        if (ret) {
                pr_err("svcrdma: could not post a receive buffer, err=%d.\n",
                       ret);
                pr_err("svcrdma: closing transport %p.\n", xprt);
                set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
                ret = -ENOTCONN;
        }
        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);

        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 = %s (%d)\n", cma_id, cma_id->context,
                        rdma_event_msg(event->event), 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 = %s (%d)\n", cma_id,
                        rdma_event_msg(event->event), 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 = %s (%d)\n", cma_id, xprt,
                        rdma_event_msg(event->event), event->event);
                if (xprt) {
                        set_bit(XPT_CLOSE, &xprt->xpt_flags);
                        svc_xprt_enqueue(xprt);
                        svc_xprt_put(xprt);
                }
                break;
        default:
                dprintk("svcrdma: Unexpected event on DTO endpoint %p, "
                        "event = %s (%d)\n", cma_id,
                        rdma_event_msg(event->event), 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;
        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);

        listen_id = rdma_create_id(&init_net, 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 scatterlist *sg;
        struct svc_rdma_fastreg_mr *frmr;
        u32 num_sg;

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

        num_sg = min_t(u32, RPCSVC_MAXPAGES, xprt->sc_frmr_pg_list_len);
        mr = ib_alloc_mr(xprt->sc_pd, IB_MR_TYPE_MEM_REG, num_sg);
        if (IS_ERR(mr))
                goto err_free_frmr;

        sg = kcalloc(RPCSVC_MAXPAGES, sizeof(*sg), GFP_KERNEL);
        if (!sg)
                goto err_free_mr;

        sg_init_table(sg, RPCSVC_MAXPAGES);

        frmr->mr = mr;
        frmr->sg = sg;
        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);
                kfree(frmr->sg);
                ib_dereg_mr(frmr->mr);
                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->sg_nents = 0;
        }
        spin_unlock_bh(&rdma->sc_frmr_q_lock);
        if (frmr)
                return frmr;

        return rdma_alloc_frmr(rdma);
}

void svc_rdma_put_frmr(struct svcxprt_rdma *rdma,
                       struct svc_rdma_fastreg_mr *frmr)
{
        if (frmr) {
                ib_dma_unmap_sg(rdma->sc_cm_id->device,
                                frmr->sg, frmr->sg_nents, frmr->direction);
                atomic_dec(&rdma->sc_dma_used);
                spin_lock_bh(&rdma->sc_frmr_q_lock);
                WARN_ON_ONCE(!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 *dev;
        unsigned int i;
        int ret = 0;

        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);

        dev = newxprt->sc_cm_id->device;

        /* Qualify the transport resource defaults with the
         * capabilities of this particular device */
        newxprt->sc_max_sge = min((size_t)dev->attrs.max_sge,
                                  (size_t)RPCSVC_MAXPAGES);
        newxprt->sc_max_sge_rd = min_t(size_t, dev->attrs.max_sge_rd,
                                       RPCSVC_MAXPAGES);
        newxprt->sc_max_req_size = svcrdma_max_req_size;
        newxprt->sc_max_requests = min_t(u32, dev->attrs.max_qp_wr,
                                         svcrdma_max_requests);
        newxprt->sc_max_bc_requests = min_t(u32, dev->attrs.max_qp_wr,
                                            svcrdma_max_bc_requests);
        newxprt->sc_rq_depth = newxprt->sc_max_requests +
                               newxprt->sc_max_bc_requests;
        newxprt->sc_sq_depth = RPCRDMA_SQ_DEPTH_MULT * newxprt->sc_rq_depth;

        if (!svc_rdma_prealloc_ctxts(newxprt))
                goto errout;
        if (!svc_rdma_prealloc_maps(newxprt))
                goto errout;

        /*
         * Limit ORD based on client limit, local device limit, and
         * configured svcrdma limit.
         */
        newxprt->sc_ord = min_t(size_t, dev->attrs.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(dev);
        if (IS_ERR(newxprt->sc_pd)) {
                dprintk("svcrdma: error creating PD for connect request\n");
                goto errout;
        }
        newxprt->sc_sq_cq = ib_alloc_cq(dev, newxprt, newxprt->sc_sq_depth,
                                        0, IB_POLL_SOFTIRQ);
        if (IS_ERR(newxprt->sc_sq_cq)) {
                dprintk("svcrdma: error creating SQ CQ for connect request\n");
                goto errout;
        }
        newxprt->sc_rq_cq = ib_alloc_cq(dev, newxprt, newxprt->sc_rq_depth,
                                        0, IB_POLL_SOFTIRQ);
        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_rq_depth;
        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,
                dev, 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) {
                dprintk("svcrdma: failed to create QP, ret=%d\n", ret);
                goto errout;
        }
        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.
         */
        newxprt->sc_reader = rdma_read_chunk_lcl;
        if (dev->attrs.device_cap_flags & IB_DEVICE_MEM_MGT_EXTENSIONS) {
                newxprt->sc_frmr_pg_list_len =
                        dev->attrs.max_fast_reg_page_list_len;
                newxprt->sc_dev_caps |= SVCRDMA_DEVCAP_FAST_REG;
                newxprt->sc_reader = rdma_read_chunk_frmr;
        }

        /*
         * Determine if a DMA MR is required and if so, what privs are required
         */
        if (!rdma_protocol_iwarp(dev, newxprt->sc_cm_id->port_num) &&
            !rdma_ib_or_roce(dev, newxprt->sc_cm_id->port_num))
                goto errout;

        if (rdma_protocol_iwarp(dev, newxprt->sc_cm_id->port_num))
                newxprt->sc_dev_caps |= SVCRDMA_DEVCAP_READ_W_INV;

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

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

        /* 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"
                "    max_sge_rd      : %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_max_sge_rd,
                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);
        struct svc_xprt *xprt = &rdma->sc_xprt;

        dprintk("svcrdma: %s(%p)\n", __func__, rdma);

        /* We should only be called from kref_put */
        if (atomic_read(&xprt->xpt_ref.refcount) != 0)
                pr_err("svcrdma: sc_xprt still in use? (%d)\n",
                       atomic_read(&xprt->xpt_ref.refcount));

        /*
         * 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 */
        if (rdma->sc_ctxt_used != 0)
                pr_err("svcrdma: ctxt still in use? (%d)\n",
                       rdma->sc_ctxt_used);
        if (atomic_read(&rdma->sc_dma_used) != 0)
                pr_err("svcrdma: dma still in use? (%d)\n",
                       atomic_read(&rdma->sc_dma_used));

        /* Final put of backchannel client transport */
        if (xprt->xpt_bc_xprt) {
                xprt_put(xprt->xpt_bc_xprt);
                xprt->xpt_bc_xprt = NULL;
        }

        rdma_dealloc_frmr_q(rdma);
        svc_rdma_destroy_ctxts(rdma);
        svc_rdma_destroy_maps(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_free_cq(rdma->sc_sq_cq);

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

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

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

static int svc_rdma_secure_port(struct svc_rqst *rqstp)
{
        return 1;
}

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;

        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);

                        /* 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;
}