rdma: SVCRDMA Core Transport Services

This file implements the core transport data management and I/O
path. The I/O path for RDMA involves receiving callbacks on interrupt
context. Since all the svc transport locks are _bh locks we enqueue the
transport on a list, schedule a tasklet to dequeue data indications from
the RDMA completion queue. The tasklet in turn takes _bh locks to
enqueue receive data indications on a list for the transport. The
svc_rdma_recvfrom transport function dequeues data from this list in an
NFSD thread context.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
Acked-by: Neil Brown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 1080 insertions, 0 deletions

diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c
new file mode 100644
index 000000000000..f09444c451bc
--- /dev/null
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -0,0 +1,1080 @@
+/*
+ * 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 rdma_destroy_xprt(struct svcxprt_rdma *xprt);
+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,
+};
+
+static int rdma_bump_context_cache(struct svcxprt_rdma *xprt)
+{
+        int target;
+        int at_least_one = 0;
+        struct svc_rdma_op_ctxt *ctxt;
+
+        target = min(xprt->sc_ctxt_cnt + xprt->sc_ctxt_bump,
+                     xprt->sc_ctxt_max);
+
+        spin_lock_bh(&xprt->sc_ctxt_lock);
+        while (xprt->sc_ctxt_cnt < target) {
+                xprt->sc_ctxt_cnt++;
+                spin_unlock_bh(&xprt->sc_ctxt_lock);
+
+                ctxt = kmalloc(sizeof(*ctxt), GFP_KERNEL);
+
+                spin_lock_bh(&xprt->sc_ctxt_lock);
+                if (ctxt) {
+                        at_least_one = 1;
+                        ctxt->next = xprt->sc_ctxt_head;
+                        xprt->sc_ctxt_head = ctxt;
+                } else {
+                        /* kmalloc failed...give up for now */
+                        xprt->sc_ctxt_cnt--;
+                        break;
+                }
+        }
+        spin_unlock_bh(&xprt->sc_ctxt_lock);
+        dprintk("svcrdma: sc_ctxt_max=%d, sc_ctxt_cnt=%d\n",
+                xprt->sc_ctxt_max, xprt->sc_ctxt_cnt);
+        return at_least_one;
+}
+
+struct svc_rdma_op_ctxt *svc_rdma_get_context(struct svcxprt_rdma *xprt)
+{
+        struct svc_rdma_op_ctxt *ctxt;
+
+        while (1) {
+                spin_lock_bh(&xprt->sc_ctxt_lock);
+                if (unlikely(xprt->sc_ctxt_head == NULL)) {
+                        /* Try to bump my cache. */
+                        spin_unlock_bh(&xprt->sc_ctxt_lock);
+
+                        if (rdma_bump_context_cache(xprt))
+                                continue;
+
+                        printk(KERN_INFO "svcrdma: sleeping waiting for "
+                               "context memory on xprt=%p\n",
+                               xprt);
+                        schedule_timeout_uninterruptible(msecs_to_jiffies(500));
+                        continue;
+                }
+                ctxt = xprt->sc_ctxt_head;
+                xprt->sc_ctxt_head = ctxt->next;
+                spin_unlock_bh(&xprt->sc_ctxt_lock);
+                ctxt->xprt = xprt;
+                INIT_LIST_HEAD(&ctxt->dto_q);
+                ctxt->count = 0;
+                break;
+        }
+        return ctxt;
+}
+
+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]);
+
+        for (i = 0; i < ctxt->count; i++)
+                dma_unmap_single(xprt->sc_cm_id->device->dma_device,
+                                 ctxt->sge[i].addr,
+                                 ctxt->sge[i].length,
+                                 ctxt->direction);
+        spin_lock_bh(&xprt->sc_ctxt_lock);
+        ctxt->next = xprt->sc_ctxt_head;
+        xprt->sc_ctxt_head = ctxt;
+        spin_unlock_bh(&xprt->sc_ctxt_lock);
+}
+
+/* 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);
+
+                if (test_and_clear_bit(RDMAXPRT_RQ_PENDING, &xprt->sc_flags)) {
+                        ib_req_notify_cq(xprt->sc_rq_cq, IB_CQ_NEXT_COMP);
+                        rq_cq_reap(xprt);
+                        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);
+                }
+
+                if (test_and_clear_bit(RDMAXPRT_SQ_PENDING, &xprt->sc_flags)) {
+                        ib_req_notify_cq(xprt->sc_sq_cq, IB_CQ_NEXT_COMP);
+                        sq_cq_reap(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;
+
+        /*
+         * 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))
+                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.
+ */
+static void rq_cq_reap(struct svcxprt_rdma *xprt)
+{
+        int ret;
+        struct ib_wc wc;
+        struct svc_rdma_op_ctxt *ctxt = NULL;
+
+        atomic_inc(&rdma_stat_rq_poll);
+
+        spin_lock_bh(&xprt->sc_rq_dto_lock);
+        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;
+                if (wc.status != IB_WC_SUCCESS) {
+                        /* Close the transport */
+                        set_bit(XPT_CLOSE, &xprt->sc_xprt.xpt_flags);
+                        svc_rdma_put_context(ctxt, 1);
+                        continue;
+                }
+                list_add_tail(&ctxt->dto_q, &xprt->sc_rq_dto_q);
+        }
+        spin_unlock_bh(&xprt->sc_rq_dto_lock);
+
+        if (ctxt)
+                atomic_inc(&rdma_stat_rq_prod);
+}
+
+/*
+ * Send Queue Completion Handler - potentially called on interrupt context.
+ */
+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;
+
+        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;
+
+                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:
+                case IB_WR_RDMA_WRITE:
+                        svc_rdma_put_context(ctxt, 1);
+                        break;
+
+                case IB_WR_RDMA_READ:
+                        if (test_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags)) {
+                                set_bit(XPT_DATA, &xprt->sc_xprt.xpt_flags);
+                                set_bit(RDMACTXT_F_READ_DONE, &ctxt->flags);
+                                spin_lock_bh(&xprt->sc_read_complete_lock);
+                                list_add_tail(&ctxt->dto_q,
+                                              &xprt->sc_read_complete_q);
+                                spin_unlock_bh(&xprt->sc_read_complete_lock);
+                                svc_xprt_enqueue(&xprt->sc_xprt);
+                        }
+                        break;
+
+                default:
+                        printk(KERN_ERR "svcrdma: unexpected completion type, "
+                               "opcode=%d, status=%d\n",
+                               wc.opcode, wc.status);
+                        break;
+                }
+        }
+
+        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;
+
+        /*
+         * 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))
+                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 void create_context_cache(struct svcxprt_rdma *xprt,
+                                 int ctxt_count, int ctxt_bump, int ctxt_max)
+{
+        struct svc_rdma_op_ctxt *ctxt;
+        int i;
+
+        xprt->sc_ctxt_max = ctxt_max;
+        xprt->sc_ctxt_bump = ctxt_bump;
+        xprt->sc_ctxt_cnt = 0;
+        xprt->sc_ctxt_head = NULL;
+        for (i = 0; i < ctxt_count; i++) {
+                ctxt = kmalloc(sizeof(*ctxt), GFP_KERNEL);
+                if (ctxt) {
+                        ctxt->next = xprt->sc_ctxt_head;
+                        xprt->sc_ctxt_head = ctxt;
+                        xprt->sc_ctxt_cnt++;
+                }
+        }
+}
+
+static void destroy_context_cache(struct svc_rdma_op_ctxt *ctxt)
+{
+        struct svc_rdma_op_ctxt *next;
+        if (!ctxt)
+                return;
+
+        do {
+                next = ctxt->next;
+                kfree(ctxt);
+                ctxt = next;
+        } while (next);
+}
+
+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_waitqueue_head(&cma_xprt->sc_send_wait);
+
+        spin_lock_init(&cma_xprt->sc_lock);
+        spin_lock_init(&cma_xprt->sc_read_complete_lock);
+        spin_lock_init(&cma_xprt->sc_ctxt_lock);
+        spin_lock_init(&cma_xprt->sc_rq_dto_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);
+
+        if (!listener) {
+                int reqs = cma_xprt->sc_max_requests;
+                create_context_cache(cma_xprt,
+                                     reqs << 1, /* starting size */
+                                     reqs,      /* bump amount */
+                                     reqs +
+                                     cma_xprt->sc_sq_depth +
+                                     RPCRDMA_MAX_THREADS + 1); /* max */
+                if (!cma_xprt->sc_ctxt_head) {
+                        kfree(cma_xprt);
+                        return NULL;
+                }
+                clear_bit(XPT_LISTENER, &cma_xprt->sc_xprt.xpt_flags);
+        } else
+                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;
+                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;
+
+        ret = ib_post_recv(xprt->sc_qp, &recv_wr, &bad_recv_wr);
+        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)
+{
+        struct svcxprt_rdma *listen_xprt = new_cma_id->context;
+        struct svcxprt_rdma *newxprt;
+
+        /* 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);
+
+        /*
+         * 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);
+                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 */
+                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);
+                }
+                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)) {
+                rdma_destroy_xprt(cma_xprt);
+                dprintk("svcrdma: rdma_create_id failed = %ld\n",
+                        PTR_ERR(listen_id));
+                return (void *)listen_id;
+        }
+        ret = rdma_bind_addr(listen_id, sa);
+        if (ret) {
+                rdma_destroy_xprt(cma_xprt);
+                rdma_destroy_id(listen_id);
+                dprintk("svcrdma: rdma_bind_addr failed = %d\n", ret);
+                return ERR_PTR(ret);
+        }
+        cma_xprt->sc_cm_id = listen_id;
+
+        ret = rdma_listen(listen_id, RPCRDMA_LISTEN_BACKLOG);
+        if (ret) {
+                rdma_destroy_id(listen_id);
+                rdma_destroy_xprt(cma_xprt);
+                dprintk("svcrdma: rdma_listen failed = %d\n", ret);
+        }
+
+        /*
+         * 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;
+}
+
+/*
+ * 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;
+        struct sockaddr *sa;
+        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;
+
+        newxprt->sc_ord =  min((size_t)devattr.max_qp_rd_atom,
+                               (size_t)svcrdma_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;
+
+        /* Register all of physical memory */
+        newxprt->sc_phys_mr = ib_get_dma_mr(newxprt->sc_pd,
+                                            IB_ACCESS_LOCAL_WRITE |
+                                            IB_ACCESS_REMOTE_WRITE);
+        if (IS_ERR(newxprt->sc_phys_mr)) {
+                dprintk("svcrdma: Failed to create DMA MR ret=%d\n", ret);
+                goto errout;
+        }
+
+        /* 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;
+
+        /* 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);
+
+        /* 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));
+
+        ib_req_notify_cq(newxprt->sc_sq_cq, IB_CQ_NEXT_COMP);
+        ib_req_notify_cq(newxprt->sc_rq_cq, IB_CQ_NEXT_COMP);
+        return &newxprt->sc_xprt;
+
+ errout:
+        dprintk("svcrdma: failure accepting new connection rc=%d.\n", ret);
+        rdma_destroy_id(newxprt->sc_cm_id);
+        rdma_destroy_xprt(newxprt);
+        return NULL;
+}
+
+/*
+ * Post an RQ WQE to the RQ when the rqst is being released. This
+ * effectively returns an RQ credit to the client. The rq_xprt_ctxt
+ * will be null if the request is deferred due to an RDMA_READ or the
+ * transport had no data ready (EAGAIN). Note that an RPC deferred in
+ * svc_process will still return the credit, this is because the data
+ * is copied and no longer consume a WQE/WC.
+ */
+static void svc_rdma_release_rqst(struct svc_rqst *rqstp)
+{
+        int err;
+        struct svcxprt_rdma *rdma =
+                container_of(rqstp->rq_xprt, struct svcxprt_rdma, sc_xprt);
+        if (rqstp->rq_xprt_ctxt) {
+                BUG_ON(rqstp->rq_xprt_ctxt != rdma);
+                err = svc_rdma_post_recv(rdma);
+                if (err)
+                        dprintk("svcrdma: failed to post an RQ WQE error=%d\n",
+                                err);
+        }
+        rqstp->rq_xprt_ctxt = NULL;
+}
+
+/* Disable data ready events for this connection */
+static void svc_rdma_detach(struct svc_xprt *xprt)
+{
+        struct svcxprt_rdma *rdma =
+                container_of(xprt, struct svcxprt_rdma, sc_xprt);
+        unsigned long flags;
+
+        dprintk("svc: svc_rdma_detach(%p)\n", xprt);
+        /*
+         * Shutdown the connection. This will ensure we don't get any
+         * more events from the provider.
+         */
+        rdma_disconnect(rdma->sc_cm_id);
+        rdma_destroy_id(rdma->sc_cm_id);
+
+        /* We may already be on the DTO list */
+        spin_lock_irqsave(&dto_lock, flags);
+        if (!list_empty(&rdma->sc_dto_q))
+                list_del_init(&rdma->sc_dto_q);
+        spin_unlock_irqrestore(&dto_lock, flags);
+}
+
+static void svc_rdma_free(struct svc_xprt *xprt)
+{
+        struct svcxprt_rdma *rdma = (struct svcxprt_rdma *)xprt;
+        dprintk("svcrdma: svc_rdma_free(%p)\n", rdma);
+        rdma_destroy_xprt(rdma);
+        kfree(rdma);
+}
+
+static void rdma_destroy_xprt(struct svcxprt_rdma *xprt)
+{
+        if (xprt->sc_qp && !IS_ERR(xprt->sc_qp))
+                ib_destroy_qp(xprt->sc_qp);
+
+        if (xprt->sc_sq_cq && !IS_ERR(xprt->sc_sq_cq))
+                ib_destroy_cq(xprt->sc_sq_cq);
+
+        if (xprt->sc_rq_cq && !IS_ERR(xprt->sc_rq_cq))
+                ib_destroy_cq(xprt->sc_rq_cq);
+
+        if (xprt->sc_phys_mr && !IS_ERR(xprt->sc_phys_mr))
+                ib_dereg_mr(xprt->sc_phys_mr);
+
+        if (xprt->sc_pd && !IS_ERR(xprt->sc_pd))
+                ib_dealloc_pd(xprt->sc_pd);
+
+        destroy_context_cache(xprt->sc_ctxt_head);
+}
+
+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 0;
+
+        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 reap some SQ WR */
+                        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);
+                        continue;
+                }
+                /* Bumped used SQ WR count and post */
+                ret = ib_post_send(xprt->sc_qp, wr, &bad_wr);
+                if (!ret)
+                        atomic_inc(&xprt->sc_sq_count);
+                else
+                        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;
+}
+
+int 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 */
+        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 posting send = %d\n", ret);
+                svc_rdma_put_context(ctxt, 1);
+        }
+
+        return ret;
+}