net/sunrpc/xprtrdma/verbs.c

/*
 * Copyright (c) 2003-2007 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.
 */

/*
 * verbs.c
 *
 * Encapsulates the major functions managing:
 *  o adapters
 *  o endpoints
 *  o connections
 *  o buffer memory
 */

#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/prefetch.h>
#include <linux/sunrpc/addr.h>
#include <asm/bitops.h>

#include "xprt_rdma.h"

/*
 * Globals/Macros
 */

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
# define RPCDBG_FACILITY	RPCDBG_TRANS
#endif

/*
 * internal functions
 */

/*
 * handle replies in tasklet context, using a single, global list
 * rdma tasklet function -- just turn around and call the func
 * for all replies on the list
 */

static DEFINE_SPINLOCK(rpcrdma_tk_lock_g);
static LIST_HEAD(rpcrdma_tasklets_g);

static void
rpcrdma_run_tasklet(unsigned long data)
{
	struct rpcrdma_rep *rep;
	unsigned long flags;

	data = data;
	spin_lock_irqsave(&rpcrdma_tk_lock_g, flags);
	while (!list_empty(&rpcrdma_tasklets_g)) {
		rep = list_entry(rpcrdma_tasklets_g.next,
				 struct rpcrdma_rep, rr_list);
		list_del(&rep->rr_list);
		spin_unlock_irqrestore(&rpcrdma_tk_lock_g, flags);

		rpcrdma_reply_handler(rep);

		spin_lock_irqsave(&rpcrdma_tk_lock_g, flags);
	}
	spin_unlock_irqrestore(&rpcrdma_tk_lock_g, flags);
}

static DECLARE_TASKLET(rpcrdma_tasklet_g, rpcrdma_run_tasklet, 0UL);

static const char * const async_event[] = {
	"CQ error",
	"QP fatal error",
	"QP request error",
	"QP access error",
	"communication established",
	"send queue drained",
	"path migration successful",
	"path mig error",
	"device fatal error",
	"port active",
	"port error",
	"LID change",
	"P_key change",
	"SM change",
	"SRQ error",
	"SRQ limit reached",
	"last WQE reached",
	"client reregister",
	"GID change",
};

#define ASYNC_MSG(status)					\
	((status) < ARRAY_SIZE(async_event) ?			\
		async_event[(status)] : "unknown async error")

static void
rpcrdma_schedule_tasklet(struct list_head *sched_list)
{
	unsigned long flags;

	spin_lock_irqsave(&rpcrdma_tk_lock_g, flags);
	list_splice_tail(sched_list, &rpcrdma_tasklets_g);
	spin_unlock_irqrestore(&rpcrdma_tk_lock_g, flags);
	tasklet_schedule(&rpcrdma_tasklet_g);
}

static void
rpcrdma_qp_async_error_upcall(struct ib_event *event, void *context)
{
	struct rpcrdma_ep *ep = context;

	pr_err("RPC:       %s: %s on device %s ep %p\n",
	       __func__, ASYNC_MSG(event->event),
		event->device->name, context);
	if (ep->rep_connected == 1) {
		ep->rep_connected = -EIO;
		rpcrdma_conn_func(ep);
		wake_up_all(&ep->rep_connect_wait);
	}
}

static void
rpcrdma_cq_async_error_upcall(struct ib_event *event, void *context)
{
	struct rpcrdma_ep *ep = context;

	pr_err("RPC:       %s: %s on device %s ep %p\n",
	       __func__, ASYNC_MSG(event->event),
		event->device->name, context);
	if (ep->rep_connected == 1) {
		ep->rep_connected = -EIO;
		rpcrdma_conn_func(ep);
		wake_up_all(&ep->rep_connect_wait);
	}
}

static const char * const wc_status[] = {
	"success",
	"local length error",
	"local QP operation error",
	"local EE context operation error",
	"local protection error",
	"WR flushed",
	"memory management operation error",
	"bad response error",
	"local access error",
	"remote invalid request error",
	"remote access error",
	"remote operation error",
	"transport retry counter exceeded",
	"RNR retry counter exceeded",
	"local RDD violation error",
	"remove invalid RD request",
	"operation aborted",
	"invalid EE context number",
	"invalid EE context state",
	"fatal error",
	"response timeout error",
	"general error",
};

#define COMPLETION_MSG(status)					\
	((status) < ARRAY_SIZE(wc_status) ?			\
		wc_status[(status)] : "unexpected completion error")

static void
rpcrdma_sendcq_process_wc(struct ib_wc *wc)
{
	/* WARNING: Only wr_id and status are reliable at this point */
	if (wc->wr_id == RPCRDMA_IGNORE_COMPLETION) {
		if (wc->status != IB_WC_SUCCESS &&
		    wc->status != IB_WC_WR_FLUSH_ERR)
			pr_err("RPC:       %s: SEND: %s\n",
			       __func__, COMPLETION_MSG(wc->status));
	} else {
		struct rpcrdma_mw *r;

		r = (struct rpcrdma_mw *)(unsigned long)wc->wr_id;
		r->mw_sendcompletion(wc);
	}
}

static int
rpcrdma_sendcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
{
	struct ib_wc *wcs;
	int budget, count, rc;

	budget = RPCRDMA_WC_BUDGET / RPCRDMA_POLLSIZE;
	do {
		wcs = ep->rep_send_wcs;

		rc = ib_poll_cq(cq, RPCRDMA_POLLSIZE, wcs);
		if (rc <= 0)
			return rc;

		count = rc;
		while (count-- > 0)
			rpcrdma_sendcq_process_wc(wcs++);
	} while (rc == RPCRDMA_POLLSIZE && --budget);
	return 0;
}

/*
 * Handle send, fast_reg_mr, and local_inv completions.
 *
 * Send events are typically suppressed and thus do not result
 * in an upcall. Occasionally one is signaled, however. This
 * prevents the provider's completion queue from wrapping and
 * losing a completion.
 */
static void
rpcrdma_sendcq_upcall(struct ib_cq *cq, void *cq_context)
{
	struct rpcrdma_ep *ep = (struct rpcrdma_ep *)cq_context;
	int rc;

	rc = rpcrdma_sendcq_poll(cq, ep);
	if (rc) {
		dprintk("RPC:       %s: ib_poll_cq failed: %i\n",
			__func__, rc);
		return;
	}

	rc = ib_req_notify_cq(cq,
			IB_CQ_NEXT_COMP | IB_CQ_REPORT_MISSED_EVENTS);
	if (rc == 0)
		return;
	if (rc < 0) {
		dprintk("RPC:       %s: ib_req_notify_cq failed: %i\n",
			__func__, rc);
		return;
	}

	rpcrdma_sendcq_poll(cq, ep);
}

static void
rpcrdma_recvcq_process_wc(struct ib_wc *wc, struct list_head *sched_list)
{
	struct rpcrdma_rep *rep =
			(struct rpcrdma_rep *)(unsigned long)wc->wr_id;

	/* WARNING: Only wr_id and status are reliable at this point */
	if (wc->status != IB_WC_SUCCESS)
		goto out_fail;

	/* status == SUCCESS means all fields in wc are trustworthy */
	if (wc->opcode != IB_WC_RECV)
		return;

	dprintk("RPC:       %s: rep %p opcode 'recv', length %u: success\n",
		__func__, rep, wc->byte_len);

	rep->rr_len = wc->byte_len;
	ib_dma_sync_single_for_cpu(rep->rr_device,
				   rdmab_addr(rep->rr_rdmabuf),
				   rep->rr_len, DMA_FROM_DEVICE);
	prefetch(rdmab_to_msg(rep->rr_rdmabuf));

out_schedule:
	list_add_tail(&rep->rr_list, sched_list);
	return;
out_fail:
	if (wc->status != IB_WC_WR_FLUSH_ERR)
		pr_err("RPC:       %s: rep %p: %s\n",
		       __func__, rep, COMPLETION_MSG(wc->status));
	rep->rr_len = ~0U;
	goto out_schedule;
}

static int
rpcrdma_recvcq_poll(struct ib_cq *cq, struct rpcrdma_ep *ep)
{
	struct list_head sched_list;
	struct ib_wc *wcs;
	int budget, count, rc;

	INIT_LIST_HEAD(&sched_list);
	budget = RPCRDMA_WC_BUDGET / RPCRDMA_POLLSIZE;
	do {
		wcs = ep->rep_recv_wcs;

		rc = ib_poll_cq(cq, RPCRDMA_POLLSIZE, wcs);
		if (rc <= 0)
			goto out_schedule;

		count = rc;
		while (count-- > 0)
			rpcrdma_recvcq_process_wc(wcs++, &sched_list);
	} while (rc == RPCRDMA_POLLSIZE && --budget);
	rc = 0;

out_schedule:
	rpcrdma_schedule_tasklet(&sched_list);
	return rc;
}

/*
 * Handle receive completions.
 *
 * It is reentrant but processes single events in order to maintain
 * ordering of receives to keep server credits.
 *
 * It is the responsibility of the scheduled tasklet to return
 * recv buffers to the pool. NOTE: this affects synchronization of
 * connection shutdown. That is, the structures required for
 * the completion of the reply handler must remain intact until
 * all memory has been reclaimed.
 */
static void
rpcrdma_recvcq_upcall(struct ib_cq *cq, void *cq_context)
{
	struct rpcrdma_ep *ep = (struct rpcrdma_ep *)cq_context;
	int rc;

	rc = rpcrdma_recvcq_poll(cq, ep);
	if (rc) {
		dprintk("RPC:       %s: ib_poll_cq failed: %i\n",
			__func__, rc);
		return;
	}

	rc = ib_req_notify_cq(cq,
			IB_CQ_NEXT_COMP | IB_CQ_REPORT_MISSED_EVENTS);
	if (rc == 0)
		return;
	if (rc < 0) {
		dprintk("RPC:       %s: ib_req_notify_cq failed: %i\n",
			__func__, rc);
		return;
	}

	rpcrdma_recvcq_poll(cq, ep);
}

static void
rpcrdma_flush_cqs(struct rpcrdma_ep *ep)
{
	struct ib_wc wc;
	LIST_HEAD(sched_list);

	while (ib_poll_cq(ep->rep_attr.recv_cq, 1, &wc) > 0)
		rpcrdma_recvcq_process_wc(&wc, &sched_list);
	if (!list_empty(&sched_list))
		rpcrdma_schedule_tasklet(&sched_list);
	while (ib_poll_cq(ep->rep_attr.send_cq, 1, &wc) > 0)
		rpcrdma_sendcq_process_wc(&wc);
}

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
static const char * const conn[] = {
	"address resolved",
	"address error",
	"route resolved",
	"route error",
	"connect request",
	"connect response",
	"connect error",
	"unreachable",
	"rejected",
	"established",
	"disconnected",
	"device removal",
	"multicast join",
	"multicast error",
	"address change",
	"timewait exit",
};

#define CONNECTION_MSG(status)						\
	((status) < ARRAY_SIZE(conn) ?					\
		conn[(status)] : "unrecognized connection error")
#endif

static int
rpcrdma_conn_upcall(struct rdma_cm_id *id, struct rdma_cm_event *event)
{
	struct rpcrdma_xprt *xprt = id->context;
	struct rpcrdma_ia *ia = &xprt->rx_ia;
	struct rpcrdma_ep *ep = &xprt->rx_ep;
#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
	struct sockaddr *sap = (struct sockaddr *)&ep->rep_remote_addr;
#endif
	struct ib_qp_attr *attr = &ia->ri_qp_attr;
	struct ib_qp_init_attr *iattr = &ia->ri_qp_init_attr;
	int connstate = 0;

	switch (event->event) {
	case RDMA_CM_EVENT_ADDR_RESOLVED:
	case RDMA_CM_EVENT_ROUTE_RESOLVED:
		ia->ri_async_rc = 0;
		complete(&ia->ri_done);
		break;
	case RDMA_CM_EVENT_ADDR_ERROR:
		ia->ri_async_rc = -EHOSTUNREACH;
		dprintk("RPC:       %s: CM address resolution error, ep 0x%p\n",
			__func__, ep);
		complete(&ia->ri_done);
		break;
	case RDMA_CM_EVENT_ROUTE_ERROR:
		ia->ri_async_rc = -ENETUNREACH;
		dprintk("RPC:       %s: CM route resolution error, ep 0x%p\n",
			__func__, ep);
		complete(&ia->ri_done);
		break;
	case RDMA_CM_EVENT_ESTABLISHED:
		connstate = 1;
		ib_query_qp(ia->ri_id->qp, attr,
			    IB_QP_MAX_QP_RD_ATOMIC | IB_QP_MAX_DEST_RD_ATOMIC,
			    iattr);
		dprintk("RPC:       %s: %d responder resources"
			" (%d initiator)\n",
			__func__, attr->max_dest_rd_atomic,
			attr->max_rd_atomic);
		goto connected;
	case RDMA_CM_EVENT_CONNECT_ERROR:
		connstate = -ENOTCONN;
		goto connected;
	case RDMA_CM_EVENT_UNREACHABLE:
		connstate = -ENETDOWN;
		goto connected;
	case RDMA_CM_EVENT_REJECTED:
		connstate = -ECONNREFUSED;
		goto connected;
	case RDMA_CM_EVENT_DISCONNECTED:
		connstate = -ECONNABORTED;
		goto connected;
	case RDMA_CM_EVENT_DEVICE_REMOVAL:
		connstate = -ENODEV;
connected:
		dprintk("RPC:       %s: %sconnected\n",
					__func__, connstate > 0 ? "" : "dis");
		ep->rep_connected = connstate;
		rpcrdma_conn_func(ep);
		wake_up_all(&ep->rep_connect_wait);
		/*FALLTHROUGH*/
	default:
		dprintk("RPC:       %s: %pIS:%u (ep 0x%p): %s\n",
			__func__, sap, rpc_get_port(sap), ep,
			CONNECTION_MSG(event->event));
		break;
	}

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
	if (connstate == 1) {
		int ird = attr->max_dest_rd_atomic;
		int tird = ep->rep_remote_cma.responder_resources;

		pr_info("rpcrdma: connection to %pIS:%u on %s, memreg '%s', %d credits, %d responders%s\n",
			sap, rpc_get_port(sap),
			ia->ri_device->name,
			ia->ri_ops->ro_displayname,
			xprt->rx_buf.rb_max_requests,
			ird, ird < 4 && ird < tird / 2 ? " (low!)" : "");
	} else if (connstate < 0) {
		pr_info("rpcrdma: connection to %pIS:%u closed (%d)\n",
			sap, rpc_get_port(sap), connstate);
	}
#endif

	return 0;
}

static struct rdma_cm_id *
rpcrdma_create_id(struct rpcrdma_xprt *xprt,
			struct rpcrdma_ia *ia, struct sockaddr *addr)
{
	struct rdma_cm_id *id;
	int rc;

	init_completion(&ia->ri_done);

	id = rdma_create_id(rpcrdma_conn_upcall, xprt, RDMA_PS_TCP, IB_QPT_RC);
	if (IS_ERR(id)) {
		rc = PTR_ERR(id);
		dprintk("RPC:       %s: rdma_create_id() failed %i\n",
			__func__, rc);
		return id;
	}

	ia->ri_async_rc = -ETIMEDOUT;
	rc = rdma_resolve_addr(id, NULL, addr, RDMA_RESOLVE_TIMEOUT);
	if (rc) {
		dprintk("RPC:       %s: rdma_resolve_addr() failed %i\n",
			__func__, rc);
		goto out;
	}
	wait_for_completion_interruptible_timeout(&ia->ri_done,
				msecs_to_jiffies(RDMA_RESOLVE_TIMEOUT) + 1);
	rc = ia->ri_async_rc;
	if (rc)
		goto out;

	ia->ri_async_rc = -ETIMEDOUT;
	rc = rdma_resolve_route(id, RDMA_RESOLVE_TIMEOUT);
	if (rc) {
		dprintk("RPC:       %s: rdma_resolve_route() failed %i\n",
			__func__, rc);
		goto out;
	}
	wait_for_completion_interruptible_timeout(&ia->ri_done,
				msecs_to_jiffies(RDMA_RESOLVE_TIMEOUT) + 1);
	rc = ia->ri_async_rc;
	if (rc)
		goto out;

	return id;

out:
	rdma_destroy_id(id);
	return ERR_PTR(rc);
}

/*
 * Drain any cq, prior to teardown.
 */
static void
rpcrdma_clean_cq(struct ib_cq *cq)
{
	struct ib_wc wc;
	int count = 0;

	while (1 == ib_poll_cq(cq, 1, &wc))
		++count;

	if (count)
		dprintk("RPC:       %s: flushed %d events (last 0x%x)\n",
			__func__, count, wc.opcode);
}

/*
 * Exported functions.
 */

/*
 * Open and initialize an Interface Adapter.
 *  o initializes fields of struct rpcrdma_ia, including
 *    interface and provider attributes and protection zone.
 */
int
rpcrdma_ia_open(struct rpcrdma_xprt *xprt, struct sockaddr *addr, int memreg)
{
	int rc, mem_priv;
	struct rpcrdma_ia *ia = &xprt->rx_ia;
	struct ib_device_attr *devattr = &ia->ri_devattr;

	ia->ri_id = rpcrdma_create_id(xprt, ia, addr);
	if (IS_ERR(ia->ri_id)) {
		rc = PTR_ERR(ia->ri_id);
		goto out1;
	}
	ia->ri_device = ia->ri_id->device;

	ia->ri_pd = ib_alloc_pd(ia->ri_device);
	if (IS_ERR(ia->ri_pd)) {
		rc = PTR_ERR(ia->ri_pd);
		dprintk("RPC:       %s: ib_alloc_pd() failed %i\n",
			__func__, rc);
		goto out2;
	}

	rc = ib_query_device(ia->ri_device, devattr);
	if (rc) {
		dprintk("RPC:       %s: ib_query_device failed %d\n",
			__func__, rc);
		goto out3;
	}

	if (devattr->device_cap_flags & IB_DEVICE_LOCAL_DMA_LKEY) {
		ia->ri_have_dma_lkey = 1;
		ia->ri_dma_lkey = ia->ri_device->local_dma_lkey;
	}

	if (memreg == RPCRDMA_FRMR) {
		/* Requires both frmr reg and local dma lkey */
		if (((devattr->device_cap_flags &
		     (IB_DEVICE_MEM_MGT_EXTENSIONS|IB_DEVICE_LOCAL_DMA_LKEY)) !=
		    (IB_DEVICE_MEM_MGT_EXTENSIONS|IB_DEVICE_LOCAL_DMA_LKEY)) ||
		      (devattr->max_fast_reg_page_list_len == 0)) {
			dprintk("RPC:       %s: FRMR registration "
				"not supported by HCA\n", __func__);
			memreg = RPCRDMA_MTHCAFMR;
		}
	}
	if (memreg == RPCRDMA_MTHCAFMR) {
		if (!ia->ri_device->alloc_fmr) {
			dprintk("RPC:       %s: MTHCAFMR registration "
				"not supported by HCA\n", __func__);
			memreg = RPCRDMA_ALLPHYSICAL;
		}
	}

	/*
	 * Optionally obtain an underlying physical identity mapping in
	 * order to do a memory window-based bind. This base registration
	 * is protected from remote access - that is enabled only by binding
	 * for the specific bytes targeted during each RPC operation, and
	 * revoked after the corresponding completion similar to a storage
	 * adapter.
	 */
	switch (memreg) {
	case RPCRDMA_FRMR:
		ia->ri_ops = &rpcrdma_frwr_memreg_ops;
		break;
	case RPCRDMA_ALLPHYSICAL:
		ia->ri_ops = &rpcrdma_physical_memreg_ops;
		mem_priv = IB_ACCESS_LOCAL_WRITE |
				IB_ACCESS_REMOTE_WRITE |
				IB_ACCESS_REMOTE_READ;
		goto register_setup;
	case RPCRDMA_MTHCAFMR:
		ia->ri_ops = &rpcrdma_fmr_memreg_ops;
		if (ia->ri_have_dma_lkey)
			break;
		mem_priv = IB_ACCESS_LOCAL_WRITE;
	register_setup:
		ia->ri_bind_mem = ib_get_dma_mr(ia->ri_pd, mem_priv);
		if (IS_ERR(ia->ri_bind_mem)) {
			printk(KERN_ALERT "%s: ib_get_dma_mr for "
				"phys register failed with %lX\n",
				__func__, PTR_ERR(ia->ri_bind_mem));
			rc = -ENOMEM;
			goto out3;
		}
		break;
	default:
		printk(KERN_ERR "RPC: Unsupported memory "
				"registration mode: %d\n", memreg);
		rc = -ENOMEM;
		goto out3;
	}
	dprintk("RPC:       %s: memory registration strategy is '%s'\n",
		__func__, ia->ri_ops->ro_displayname);

	rwlock_init(&ia->ri_qplock);
	return 0;

out3:
	ib_dealloc_pd(ia->ri_pd);
	ia->ri_pd = NULL;
out2:
	rdma_destroy_id(ia->ri_id);
	ia->ri_id = NULL;
out1:
	return rc;
}

/*
 * Clean up/close an IA.
 *   o if event handles and PD have been initialized, free them.
 *   o close the IA
 */
void
rpcrdma_ia_close(struct rpcrdma_ia *ia)
{
	int rc;

	dprintk("RPC:       %s: entering\n", __func__);
	if (ia->ri_bind_mem != NULL) {
		rc = ib_dereg_mr(ia->ri_bind_mem);
		dprintk("RPC:       %s: ib_dereg_mr returned %i\n",
			__func__, rc);
	}

	if (ia->ri_id != NULL && !IS_ERR(ia->ri_id)) {
		if (ia->ri_id->qp)
			rdma_destroy_qp(ia->ri_id);
		rdma_destroy_id(ia->ri_id);
		ia->ri_id = NULL;
	}

	/* If the pd is still busy, xprtrdma missed freeing a resource */
	if (ia->ri_pd && !IS_ERR(ia->ri_pd))
		WARN_ON(ib_dealloc_pd(ia->ri_pd));
}

/*
 * Create unconnected endpoint.
 */
int
rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia,
				struct rpcrdma_create_data_internal *cdata)
{
	struct ib_device_attr *devattr = &ia->ri_devattr;
	struct ib_cq *sendcq, *recvcq;
	int rc, err;

	/* check provider's send/recv wr limits */
	if (cdata->max_requests > devattr->max_qp_wr)
		cdata->max_requests = devattr->max_qp_wr;

	ep->rep_attr.event_handler = rpcrdma_qp_async_error_upcall;
	ep->rep_attr.qp_context = ep;
	ep->rep_attr.srq = NULL;
	ep->rep_attr.cap.max_send_wr = cdata->max_requests;
	rc = ia->ri_ops->ro_open(ia, ep, cdata);
	if (rc)
		return rc;
	ep->rep_attr.cap.max_recv_wr = cdata->max_requests;
	ep->rep_attr.cap.max_send_sge = (cdata->padding ? 4 : 2);
	ep->rep_attr.cap.max_recv_sge = 1;
	ep->rep_attr.cap.max_inline_data = 0;
	ep->rep_attr.sq_sig_type = IB_SIGNAL_REQ_WR;
	ep->rep_attr.qp_type = IB_QPT_RC;
	ep->rep_attr.port_num = ~0;

	if (cdata->padding) {
		ep->rep_padbuf = rpcrdma_alloc_regbuf(ia, cdata->padding,
						      GFP_KERNEL);
		if (IS_ERR(ep->rep_padbuf))
			return PTR_ERR(ep->rep_padbuf);
	} else
		ep->rep_padbuf = NULL;

	dprintk("RPC:       %s: requested max: dtos: send %d recv %d; "
		"iovs: send %d recv %d\n",
		__func__,
		ep->rep_attr.cap.max_send_wr,
		ep->rep_attr.cap.max_recv_wr,
		ep->rep_attr.cap.max_send_sge,
		ep->rep_attr.cap.max_recv_sge);

	/* set trigger for requesting send completion */
	ep->rep_cqinit = ep->rep_attr.cap.max_send_wr/2 - 1;
	if (ep->rep_cqinit > RPCRDMA_MAX_UNSIGNALED_SENDS)
		ep->rep_cqinit = RPCRDMA_MAX_UNSIGNALED_SENDS;
	else if (ep->rep_cqinit <= 2)
		ep->rep_cqinit = 0;
	INIT_CQCOUNT(ep);
	init_waitqueue_head(&ep->rep_connect_wait);
	INIT_DELAYED_WORK(&ep->rep_connect_worker, rpcrdma_connect_worker);

	sendcq = ib_create_cq(ia->ri_device, rpcrdma_sendcq_upcall,
			      rpcrdma_cq_async_error_upcall, ep,
			      ep->rep_attr.cap.max_send_wr + 1, 0);
	if (IS_ERR(sendcq)) {
		rc = PTR_ERR(sendcq);
		dprintk("RPC:       %s: failed to create send CQ: %i\n",
			__func__, rc);
		goto out1;
	}

	rc = ib_req_notify_cq(sendcq, IB_CQ_NEXT_COMP);
	if (rc) {
		dprintk("RPC:       %s: ib_req_notify_cq failed: %i\n",
			__func__, rc);
		goto out2;
	}

	recvcq = ib_create_cq(ia->ri_device, rpcrdma_recvcq_upcall,
			      rpcrdma_cq_async_error_upcall, ep,
			      ep->rep_attr.cap.max_recv_wr + 1, 0);
	if (IS_ERR(recvcq)) {
		rc = PTR_ERR(recvcq);
		dprintk("RPC:       %s: failed to create recv CQ: %i\n",
			__func__, rc);
		goto out2;
	}

	rc = ib_req_notify_cq(recvcq, IB_CQ_NEXT_COMP);
	if (rc) {
		dprintk("RPC:       %s: ib_req_notify_cq failed: %i\n",
			__func__, rc);
		ib_destroy_cq(recvcq);
		goto out2;
	}

	ep->rep_attr.send_cq = sendcq;
	ep->rep_attr.recv_cq = recvcq;

	/* Initialize cma parameters */

	/* RPC/RDMA does not use private data */
	ep->rep_remote_cma.private_data = NULL;
	ep->rep_remote_cma.private_data_len = 0;

	/* Client offers RDMA Read but does not initiate */
	ep->rep_remote_cma.initiator_depth = 0;
	if (devattr->max_qp_rd_atom > 32)	/* arbitrary but <= 255 */
		ep->rep_remote_cma.responder_resources = 32;
	else
		ep->rep_remote_cma.responder_resources =
						devattr->max_qp_rd_atom;

	ep->rep_remote_cma.retry_count = 7;
	ep->rep_remote_cma.flow_control = 0;
	ep->rep_remote_cma.rnr_retry_count = 0;

	return 0;

out2:
	err = ib_destroy_cq(sendcq);
	if (err)
		dprintk("RPC:       %s: ib_destroy_cq returned %i\n",
			__func__, err);
out1:
	rpcrdma_free_regbuf(ia, ep->rep_padbuf);
	return rc;
}

/*
 * rpcrdma_ep_destroy
 *
 * Disconnect and destroy endpoint. After this, the only
 * valid operations on the ep are to free it (if dynamically
 * allocated) or re-create it.
 */
void
rpcrdma_ep_destroy(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia)
{
	int rc;

	dprintk("RPC:       %s: entering, connected is %d\n",
		__func__, ep->rep_connected);

	cancel_delayed_work_sync(&ep->rep_connect_worker);

	if (ia->ri_id->qp) {
		rpcrdma_ep_disconnect(ep, ia);
		rdma_destroy_qp(ia->ri_id);
		ia->ri_id->qp = NULL;
	}

	rpcrdma_free_regbuf(ia, ep->rep_padbuf);

	rpcrdma_clean_cq(ep->rep_attr.recv_cq);
	rc = ib_destroy_cq(ep->rep_attr.recv_cq);
	if (rc)
		dprintk("RPC:       %s: ib_destroy_cq returned %i\n",
			__func__, rc);

	rpcrdma_clean_cq(ep->rep_attr.send_cq);
	rc = ib_destroy_cq(ep->rep_attr.send_cq);
	if (rc)
		dprintk("RPC:       %s: ib_destroy_cq returned %i\n",
			__func__, rc);
}

/*
 * Connect unconnected endpoint.
 */
int
rpcrdma_ep_connect(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia)
{
	struct rdma_cm_id *id, *old;
	int rc = 0;
	int retry_count = 0;

	if (ep->rep_connected != 0) {
		struct rpcrdma_xprt *xprt;
retry:
		dprintk("RPC:       %s: reconnecting...\n", __func__);

		rpcrdma_ep_disconnect(ep, ia);
		rpcrdma_flush_cqs(ep);

		xprt = container_of(ia, struct rpcrdma_xprt, rx_ia);
		id = rpcrdma_create_id(xprt, ia,
				(struct sockaddr *)&xprt->rx_data.addr);
		if (IS_ERR(id)) {
			rc = -EHOSTUNREACH;
			goto out;
		}
		/* TEMP TEMP TEMP - fail if new device:
		 * Deregister/remarshal *all* requests!
		 * Close and recreate adapter, pd, etc!
		 * Re-determine all attributes still sane!
		 * More stuff I haven't thought of!
		 * Rrrgh!
		 */
		if (ia->ri_device != id->device) {
			printk("RPC:       %s: can't reconnect on "
				"different device!\n", __func__);
			rdma_destroy_id(id);
			rc = -ENETUNREACH;
			goto out;
		}
		/* END TEMP */
		rc = rdma_create_qp(id, ia->ri_pd, &ep->rep_attr);
		if (rc) {
			dprintk("RPC:       %s: rdma_create_qp failed %i\n",
				__func__, rc);
			rdma_destroy_id(id);
			rc = -ENETUNREACH;
			goto out;
		}

		write_lock(&ia->ri_qplock);
		old = ia->ri_id;
		ia->ri_id = id;
		write_unlock(&ia->ri_qplock);

		rdma_destroy_qp(old);
		rdma_destroy_id(old);
	} else {
		dprintk("RPC:       %s: connecting...\n", __func__);
		rc = rdma_create_qp(ia->ri_id, ia->ri_pd, &ep->rep_attr);
		if (rc) {
			dprintk("RPC:       %s: rdma_create_qp failed %i\n",
				__func__, rc);
			/* do not update ep->rep_connected */
			return -ENETUNREACH;
		}
	}

	ep->rep_connected = 0;

	rc = rdma_connect(ia->ri_id, &ep->rep_remote_cma);
	if (rc) {
		dprintk("RPC:       %s: rdma_connect() failed with %i\n",
				__func__, rc);
		goto out;
	}

	wait_event_interruptible(ep->rep_connect_wait, ep->rep_connected != 0);

	/*
	 * Check state. A non-peer reject indicates no listener
	 * (ECONNREFUSED), which may be a transient state. All
	 * others indicate a transport condition which has already
	 * undergone a best-effort.
	 */
	if (ep->rep_connected == -ECONNREFUSED &&
	    ++retry_count <= RDMA_CONNECT_RETRY_MAX) {
		dprintk("RPC:       %s: non-peer_reject, retry\n", __func__);
		goto retry;
	}
	if (ep->rep_connected <= 0) {
		/* Sometimes, the only way to reliably connect to remote
		 * CMs is to use same nonzero values for ORD and IRD. */
		if (retry_count++ <= RDMA_CONNECT_RETRY_MAX + 1 &&
		    (ep->rep_remote_cma.responder_resources == 0 ||
		     ep->rep_remote_cma.initiator_depth !=
				ep->rep_remote_cma.responder_resources)) {
			if (ep->rep_remote_cma.responder_resources == 0)
				ep->rep_remote_cma.responder_resources = 1;
			ep->rep_remote_cma.initiator_depth =
				ep->rep_remote_cma.responder_resources;
			goto retry;
		}
		rc = ep->rep_connected;
	} else {
		dprintk("RPC:       %s: connected\n", __func__);
	}

out:
	if (rc)
		ep->rep_connected = rc;
	return rc;
}

/*
 * rpcrdma_ep_disconnect
 *
 * This is separate from destroy to facilitate the ability
 * to reconnect without recreating the endpoint.
 *
 * This call is not reentrant, and must not be made in parallel
 * on the same endpoint.
 */
void
rpcrdma_ep_disconnect(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia)
{
	int rc;

	rpcrdma_flush_cqs(ep);
	rc = rdma_disconnect(ia->ri_id);
	if (!rc) {
		/* returns without wait if not connected */
		wait_event_interruptible(ep->rep_connect_wait,
							ep->rep_connected != 1);
		dprintk("RPC:       %s: after wait, %sconnected\n", __func__,
			(ep->rep_connected == 1) ? "still " : "dis");
	} else {
		dprintk("RPC:       %s: rdma_disconnect %i\n", __func__, rc);
		ep->rep_connected = rc;
	}
}

static struct rpcrdma_req *
rpcrdma_create_req(struct rpcrdma_xprt *r_xprt)
{
	struct rpcrdma_req *req;

	req = kzalloc(sizeof(*req), GFP_KERNEL);
	if (req == NULL)
		return ERR_PTR(-ENOMEM);

	req->rl_buffer = &r_xprt->rx_buf;
	return req;
}

static struct rpcrdma_rep *
rpcrdma_create_rep(struct rpcrdma_xprt *r_xprt)
{
	struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
	struct rpcrdma_rep *rep;
	int rc;

	rc = -ENOMEM;
	rep = kzalloc(sizeof(*rep), GFP_KERNEL);
	if (rep == NULL)
		goto out;

	rep->rr_rdmabuf = rpcrdma_alloc_regbuf(ia, cdata->inline_rsize,
					       GFP_KERNEL);
	if (IS_ERR(rep->rr_rdmabuf)) {
		rc = PTR_ERR(rep->rr_rdmabuf);
		goto out_free;
	}

	rep->rr_device = ia->ri_device;
	rep->rr_rxprt = r_xprt;
	return rep;

out_free:
	kfree(rep);
out:
	return ERR_PTR(rc);
}

int
rpcrdma_buffer_create(struct rpcrdma_xprt *r_xprt)
{
	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
	struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
	char *p;
	size_t len;
	int i, rc;

	buf->rb_max_requests = cdata->max_requests;
	spin_lock_init(&buf->rb_lock);

	/* Need to allocate:
	 *   1.  arrays for send and recv pointers
	 *   2.  arrays of struct rpcrdma_req to fill in pointers
	 *   3.  array of struct rpcrdma_rep for replies
	 * Send/recv buffers in req/rep need to be registered
	 */
	len = buf->rb_max_requests *
		(sizeof(struct rpcrdma_req *) + sizeof(struct rpcrdma_rep *));

	p = kzalloc(len, GFP_KERNEL);
	if (p == NULL) {
		dprintk("RPC:       %s: req_t/rep_t/pad kzalloc(%zd) failed\n",
			__func__, len);
		rc = -ENOMEM;
		goto out;
	}
	buf->rb_pool = p;	/* for freeing it later */

	buf->rb_send_bufs = (struct rpcrdma_req **) p;
	p = (char *) &buf->rb_send_bufs[buf->rb_max_requests];
	buf->rb_recv_bufs = (struct rpcrdma_rep **) p;
	p = (char *) &buf->rb_recv_bufs[buf->rb_max_requests];

	rc = ia->ri_ops->ro_init(r_xprt);
	if (rc)
		goto out;

	for (i = 0; i < buf->rb_max_requests; i++) {
		struct rpcrdma_req *req;
		struct rpcrdma_rep *rep;

		req = rpcrdma_create_req(r_xprt);
		if (IS_ERR(req)) {
			dprintk("RPC:       %s: request buffer %d alloc"
				" failed\n", __func__, i);
			rc = PTR_ERR(req);
			goto out;
		}
		buf->rb_send_bufs[i] = req;

		rep = rpcrdma_create_rep(r_xprt);
		if (IS_ERR(rep)) {
			dprintk("RPC:       %s: reply buffer %d alloc failed\n",
				__func__, i);
			rc = PTR_ERR(rep);
			goto out;
		}
		buf->rb_recv_bufs[i] = rep;
	}

	return 0;
out:
	rpcrdma_buffer_destroy(buf);
	return rc;
}

static void
rpcrdma_destroy_rep(struct rpcrdma_ia *ia, struct rpcrdma_rep *rep)
{
	if (!rep)
		return;

	rpcrdma_free_regbuf(ia, rep->rr_rdmabuf);
	kfree(rep);
}

static void
rpcrdma_destroy_req(struct rpcrdma_ia *ia, struct rpcrdma_req *req)
{
	if (!req)
		return;

	rpcrdma_free_regbuf(ia, req->rl_sendbuf);
	rpcrdma_free_regbuf(ia, req->rl_rdmabuf);
	kfree(req);
}

void
rpcrdma_buffer_destroy(struct rpcrdma_buffer *buf)
{
	struct rpcrdma_ia *ia = rdmab_to_ia(buf);
	int i;

	/* clean up in reverse order from create
	 *   1.  recv mr memory (mr free, then kfree)
	 *   2.  send mr memory (mr free, then kfree)
	 *   3.  MWs
	 */
	dprintk("RPC:       %s: entering\n", __func__);

	for (i = 0; i < buf->rb_max_requests; i++) {
		if (buf->rb_recv_bufs)
			rpcrdma_destroy_rep(ia, buf->rb_recv_bufs[i]);
		if (buf->rb_send_bufs)
			rpcrdma_destroy_req(ia, buf->rb_send_bufs[i]);
	}

	ia->ri_ops->ro_destroy(buf);

	kfree(buf->rb_pool);
}

struct rpcrdma_mw *
rpcrdma_get_mw(struct rpcrdma_xprt *r_xprt)
{
	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
	struct rpcrdma_mw *mw = NULL;

	spin_lock(&buf->rb_mwlock);
	if (!list_empty(&buf->rb_mws)) {
		mw = list_first_entry(&buf->rb_mws,
				      struct rpcrdma_mw, mw_list);
		list_del_init(&mw->mw_list);
	}
	spin_unlock(&buf->rb_mwlock);

	if (!mw)
		pr_err("RPC:       %s: no MWs available\n", __func__);
	return mw;
}

void
rpcrdma_put_mw(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mw *mw)
{
	struct rpcrdma_buffer *buf = &r_xprt->rx_buf;

	spin_lock(&buf->rb_mwlock);
	list_add_tail(&mw->mw_list, &buf->rb_mws);
	spin_unlock(&buf->rb_mwlock);
}

static void
rpcrdma_buffer_put_sendbuf(struct rpcrdma_req *req, struct rpcrdma_buffer *buf)
{
	buf->rb_send_bufs[--buf->rb_send_index] = req;
	req->rl_niovs = 0;
	if (req->rl_reply) {
		buf->rb_recv_bufs[--buf->rb_recv_index] = req->rl_reply;
		req->rl_reply = NULL;
	}
}

/*
 * Get a set of request/reply buffers.
 *
 * Reply buffer (if needed) is attached to send buffer upon return.
 * Rule:
 *    rb_send_index and rb_recv_index MUST always be pointing to the
 *    *next* available buffer (non-NULL). They are incremented after
 *    removing buffers, and decremented *before* returning them.
 */
struct rpcrdma_req *
rpcrdma_buffer_get(struct rpcrdma_buffer *buffers)
{
	struct rpcrdma_req *req;
	unsigned long flags;

	spin_lock_irqsave(&buffers->rb_lock, flags);

	if (buffers->rb_send_index == buffers->rb_max_requests) {
		spin_unlock_irqrestore(&buffers->rb_lock, flags);
		dprintk("RPC:       %s: out of request buffers\n", __func__);
		return ((struct rpcrdma_req *)NULL);
	}

	req = buffers->rb_send_bufs[buffers->rb_send_index];
	if (buffers->rb_send_index < buffers->rb_recv_index) {
		dprintk("RPC:       %s: %d extra receives outstanding (ok)\n",
			__func__,
			buffers->rb_recv_index - buffers->rb_send_index);
		req->rl_reply = NULL;
	} else {
		req->rl_reply = buffers->rb_recv_bufs[buffers->rb_recv_index];
		buffers->rb_recv_bufs[buffers->rb_recv_index++] = NULL;
	}
	buffers->rb_send_bufs[buffers->rb_send_index++] = NULL;

	spin_unlock_irqrestore(&buffers->rb_lock, flags);
	return req;
}

/*
 * Put request/reply buffers back into pool.
 * Pre-decrement counter/array index.
 */
void
rpcrdma_buffer_put(struct rpcrdma_req *req)
{
	struct rpcrdma_buffer *buffers = req->rl_buffer;
	unsigned long flags;

	spin_lock_irqsave(&buffers->rb_lock, flags);
	rpcrdma_buffer_put_sendbuf(req, buffers);
	spin_unlock_irqrestore(&buffers->rb_lock, flags);
}

/*
 * Recover reply buffers from pool.
 * This happens when recovering from error conditions.
 * Post-increment counter/array index.
 */
void
rpcrdma_recv_buffer_get(struct rpcrdma_req *req)
{
	struct rpcrdma_buffer *buffers = req->rl_buffer;
	unsigned long flags;

	spin_lock_irqsave(&buffers->rb_lock, flags);
	if (buffers->rb_recv_index < buffers->rb_max_requests) {
		req->rl_reply = buffers->rb_recv_bufs[buffers->rb_recv_index];
		buffers->rb_recv_bufs[buffers->rb_recv_index++] = NULL;
	}
	spin_unlock_irqrestore(&buffers->rb_lock, flags);
}

/*
 * Put reply buffers back into pool when not attached to
 * request. This happens in error conditions.
 */
void
rpcrdma_recv_buffer_put(struct rpcrdma_rep *rep)
{
	struct rpcrdma_buffer *buffers = &rep->rr_rxprt->rx_buf;
	unsigned long flags;

	spin_lock_irqsave(&buffers->rb_lock, flags);
	buffers->rb_recv_bufs[--buffers->rb_recv_index] = rep;
	spin_unlock_irqrestore(&buffers->rb_lock, flags);
}

/*
 * Wrappers for internal-use kmalloc memory registration, used by buffer code.
 */

void
rpcrdma_mapping_error(struct rpcrdma_mr_seg *seg)
{
	dprintk("RPC:       map_one: offset %p iova %llx len %zu\n",
		seg->mr_offset,
		(unsigned long long)seg->mr_dma, seg->mr_dmalen);
}

static int
rpcrdma_register_internal(struct rpcrdma_ia *ia, void *va, int len,
				struct ib_mr **mrp, struct ib_sge *iov)
{
	struct ib_phys_buf ipb;
	struct ib_mr *mr;
	int rc;

	/*
	 * All memory passed here was kmalloc'ed, therefore phys-contiguous.
	 */
	iov->addr = ib_dma_map_single(ia->ri_device,
			va, len, DMA_BIDIRECTIONAL);
	if (ib_dma_mapping_error(ia->ri_device, iov->addr))
		return -ENOMEM;

	iov->length = len;

	if (ia->ri_have_dma_lkey) {
		*mrp = NULL;
		iov->lkey = ia->ri_dma_lkey;
		return 0;
	} else if (ia->ri_bind_mem != NULL) {
		*mrp = NULL;
		iov->lkey = ia->ri_bind_mem->lkey;
		return 0;
	}

	ipb.addr = iov->addr;
	ipb.size = iov->length;
	mr = ib_reg_phys_mr(ia->ri_pd, &ipb, 1,
			IB_ACCESS_LOCAL_WRITE, &iov->addr);

	dprintk("RPC:       %s: phys convert: 0x%llx "
			"registered 0x%llx length %d\n",
			__func__, (unsigned long long)ipb.addr,
			(unsigned long long)iov->addr, len);

	if (IS_ERR(mr)) {
		*mrp = NULL;
		rc = PTR_ERR(mr);
		dprintk("RPC:       %s: failed with %i\n", __func__, rc);
	} else {
		*mrp = mr;
		iov->lkey = mr->lkey;
		rc = 0;
	}

	return rc;
}

static int
rpcrdma_deregister_internal(struct rpcrdma_ia *ia,
				struct ib_mr *mr, struct ib_sge *iov)
{
	int rc;

	ib_dma_unmap_single(ia->ri_device,
			    iov->addr, iov->length, DMA_BIDIRECTIONAL);

	if (NULL == mr)
		return 0;

	rc = ib_dereg_mr(mr);
	if (rc)
		dprintk("RPC:       %s: ib_dereg_mr failed %i\n", __func__, rc);
	return rc;
}

/**
 * rpcrdma_alloc_regbuf - kmalloc and register memory for SEND/RECV buffers
 * @ia: controlling rpcrdma_ia
 * @size: size of buffer to be allocated, in bytes
 * @flags: GFP flags
 *
 * Returns pointer to private header of an area of internally
 * registered memory, or an ERR_PTR. The registered buffer follows
 * the end of the private header.
 *
 * xprtrdma uses a regbuf for posting an outgoing RDMA SEND, or for
 * receiving the payload of RDMA RECV operations. regbufs are not
 * used for RDMA READ/WRITE operations, thus are registered only for
 * LOCAL access.
 */
struct rpcrdma_regbuf *
rpcrdma_alloc_regbuf(struct rpcrdma_ia *ia, size_t size, gfp_t flags)
{
	struct rpcrdma_regbuf *rb;
	int rc;

	rc = -ENOMEM;
	rb = kmalloc(sizeof(*rb) + size, flags);
	if (rb == NULL)
		goto out;

	rb->rg_size = size;
	rb->rg_owner = NULL;
	rc = rpcrdma_register_internal(ia, rb->rg_base, size,
				       &rb->rg_mr, &rb->rg_iov);
	if (rc)
		goto out_free;

	return rb;

out_free:
	kfree(rb);
out:
	return ERR_PTR(rc);
}

/**
 * rpcrdma_free_regbuf - deregister and free registered buffer
 * @ia: controlling rpcrdma_ia
 * @rb: regbuf to be deregistered and freed
 */
void
rpcrdma_free_regbuf(struct rpcrdma_ia *ia, struct rpcrdma_regbuf *rb)
{
	if (rb) {
		rpcrdma_deregister_internal(ia, rb->rg_mr, &rb->rg_iov);
		kfree(rb);
	}
}

/*
 * Prepost any receive buffer, then post send.
 *
 * Receive buffer is donated to hardware, reclaimed upon recv completion.
 */
int
rpcrdma_ep_post(struct rpcrdma_ia *ia,
		struct rpcrdma_ep *ep,
		struct rpcrdma_req *req)
{
	struct ib_send_wr send_wr, *send_wr_fail;
	struct rpcrdma_rep *rep = req->rl_reply;
	int rc;

	if (rep) {
		rc = rpcrdma_ep_post_recv(ia, ep, rep);
		if (rc)
			goto out;
		req->rl_reply = NULL;
	}

	send_wr.next = NULL;
	send_wr.wr_id = RPCRDMA_IGNORE_COMPLETION;
	send_wr.sg_list = req->rl_send_iov;
	send_wr.num_sge = req->rl_niovs;
	send_wr.opcode = IB_WR_SEND;
	if (send_wr.num_sge == 4)	/* no need to sync any pad (constant) */
		ib_dma_sync_single_for_device(ia->ri_device,
					      req->rl_send_iov[3].addr,
					      req->rl_send_iov[3].length,
					      DMA_TO_DEVICE);
	ib_dma_sync_single_for_device(ia->ri_device,
				      req->rl_send_iov[1].addr,
				      req->rl_send_iov[1].length,
				      DMA_TO_DEVICE);
	ib_dma_sync_single_for_device(ia->ri_device,
				      req->rl_send_iov[0].addr,
				      req->rl_send_iov[0].length,
				      DMA_TO_DEVICE);

	if (DECR_CQCOUNT(ep) > 0)
		send_wr.send_flags = 0;
	else { /* Provider must take a send completion every now and then */
		INIT_CQCOUNT(ep);
		send_wr.send_flags = IB_SEND_SIGNALED;
	}

	rc = ib_post_send(ia->ri_id->qp, &send_wr, &send_wr_fail);
	if (rc)
		dprintk("RPC:       %s: ib_post_send returned %i\n", __func__,
			rc);
out:
	return rc;
}

/*
 * (Re)post a receive buffer.
 */
int
rpcrdma_ep_post_recv(struct rpcrdma_ia *ia,
		     struct rpcrdma_ep *ep,
		     struct rpcrdma_rep *rep)
{
	struct ib_recv_wr recv_wr, *recv_wr_fail;
	int rc;

	recv_wr.next = NULL;
	recv_wr.wr_id = (u64) (unsigned long) rep;
	recv_wr.sg_list = &rep->rr_rdmabuf->rg_iov;
	recv_wr.num_sge = 1;

	ib_dma_sync_single_for_cpu(ia->ri_device,
				   rdmab_addr(rep->rr_rdmabuf),
				   rdmab_length(rep->rr_rdmabuf),
				   DMA_BIDIRECTIONAL);

	rc = ib_post_recv(ia->ri_id->qp, &recv_wr, &recv_wr_fail);

	if (rc)
		dprintk("RPC:       %s: ib_post_recv returned %i\n", __func__,
			rc);
	return rc;
}

/* How many chunk list items fit within our inline buffers?
 */
unsigned int
rpcrdma_max_segments(struct rpcrdma_xprt *r_xprt)
{
	struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
	int bytes, segments;

	bytes = min_t(unsigned int, cdata->inline_wsize, cdata->inline_rsize);
	bytes -= RPCRDMA_HDRLEN_MIN;
	if (bytes < sizeof(struct rpcrdma_segment) * 2) {
		pr_warn("RPC:       %s: inline threshold too small\n",
			__func__);
		return 0;
	}

	segments = 1 << (fls(bytes / sizeof(struct rpcrdma_segment)) - 1);
	dprintk("RPC:       %s: max chunk list size = %d segments\n",
		__func__, segments);
	return segments;
}