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 <[e-mail]>
Acked-by: Neil Brown <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>

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 <[e-mail]>
+ */
+
+#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;
+}