text: /*
   * 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.
   */
  
  /*
   * transport.c
   *
   * This file contains the top-level implementation of an RPC RDMA
   * transport.
   *
   * Naming convention: functions beginning with xprt_ are part of the
   * transport switch. All others are RPC RDMA internal.
   */
  
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/seq_file.h>
  #include <linux/sunrpc/addr.h>
  
  #include "xprt_rdma.h"
  
  #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  # define RPCDBG_FACILITY	RPCDBG_TRANS
  #endif
  
  /*
   * tunables
   */
  
  static unsigned int xprt_rdma_slot_table_entries = RPCRDMA_DEF_SLOT_TABLE;
  unsigned int xprt_rdma_max_inline_read = RPCRDMA_DEF_INLINE;
  static unsigned int xprt_rdma_max_inline_write = RPCRDMA_DEF_INLINE;
  static unsigned int xprt_rdma_inline_write_padding;
  unsigned int xprt_rdma_memreg_strategy		= RPCRDMA_FRMR;
  int xprt_rdma_pad_optimize;
  
  #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  
  static unsigned int min_slot_table_size = RPCRDMA_MIN_SLOT_TABLE;
  static unsigned int max_slot_table_size = RPCRDMA_MAX_SLOT_TABLE;
  static unsigned int min_inline_size = RPCRDMA_MIN_INLINE;
  static unsigned int max_inline_size = RPCRDMA_MAX_INLINE;
  static unsigned int zero;
  static unsigned int max_padding = PAGE_SIZE;
  static unsigned int min_memreg = RPCRDMA_BOUNCEBUFFERS;
  static unsigned int max_memreg = RPCRDMA_LAST - 1;
  
  static struct ctl_table_header *sunrpc_table_header;
  
  static struct ctl_table xr_tunables_table[] = {
  	{
  		.procname	= "rdma_slot_table_entries",
  		.data		= &xprt_rdma_slot_table_entries,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec_minmax,
  		.extra1		= &min_slot_table_size,
  		.extra2		= &max_slot_table_size
  	},
  	{
  		.procname	= "rdma_max_inline_read",
  		.data		= &xprt_rdma_max_inline_read,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec_minmax,
  		.extra1		= &min_inline_size,
  		.extra2		= &max_inline_size,
  	},
  	{
  		.procname	= "rdma_max_inline_write",
  		.data		= &xprt_rdma_max_inline_write,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec_minmax,
  		.extra1		= &min_inline_size,
  		.extra2		= &max_inline_size,
  	},
  	{
  		.procname	= "rdma_inline_write_padding",
  		.data		= &xprt_rdma_inline_write_padding,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec_minmax,
  		.extra1		= &zero,
  		.extra2		= &max_padding,
  	},
  	{
  		.procname	= "rdma_memreg_strategy",
  		.data		= &xprt_rdma_memreg_strategy,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec_minmax,
  		.extra1		= &min_memreg,
  		.extra2		= &max_memreg,
  	},
  	{
  		.procname	= "rdma_pad_optimize",
  		.data		= &xprt_rdma_pad_optimize,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec,
  	},
  	{ },
  };
  
  static struct ctl_table sunrpc_table[] = {
  	{
  		.procname	= "sunrpc",
  		.mode		= 0555,
  		.child		= xr_tunables_table
  	},
  	{ },
  };
  
  #endif
  
  static struct rpc_xprt_ops xprt_rdma_procs;	/*forward reference */
  
  static void
  xprt_rdma_format_addresses4(struct rpc_xprt *xprt, struct sockaddr *sap)
  {
  	struct sockaddr_in *sin = (struct sockaddr_in *)sap;
  	char buf[20];
  
  	snprintf(buf, sizeof(buf), "%08x", ntohl(sin->sin_addr.s_addr));
  	xprt->address_strings[RPC_DISPLAY_HEX_ADDR] = kstrdup(buf, GFP_KERNEL);
  
  	xprt->address_strings[RPC_DISPLAY_NETID] = RPCBIND_NETID_RDMA;
  }
  
  static void
  xprt_rdma_format_addresses6(struct rpc_xprt *xprt, struct sockaddr *sap)
  {
  	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
  	char buf[40];
  
  	snprintf(buf, sizeof(buf), "%pi6", &sin6->sin6_addr);
  	xprt->address_strings[RPC_DISPLAY_HEX_ADDR] = kstrdup(buf, GFP_KERNEL);
  
  	xprt->address_strings[RPC_DISPLAY_NETID] = RPCBIND_NETID_RDMA6;
  }
  
  void
  xprt_rdma_format_addresses(struct rpc_xprt *xprt, struct sockaddr *sap)
  {
  	char buf[128];
  
  	switch (sap->sa_family) {
  	case AF_INET:
  		xprt_rdma_format_addresses4(xprt, sap);
  		break;
  	case AF_INET6:
  		xprt_rdma_format_addresses6(xprt, sap);
  		break;
  	default:
  		pr_err("rpcrdma: Unrecognized address family\n");
  		return;
  	}
  
  	(void)rpc_ntop(sap, buf, sizeof(buf));
  	xprt->address_strings[RPC_DISPLAY_ADDR] = kstrdup(buf, GFP_KERNEL);
  
  	snprintf(buf, sizeof(buf), "%u", rpc_get_port(sap));
  	xprt->address_strings[RPC_DISPLAY_PORT] = kstrdup(buf, GFP_KERNEL);
  
  	snprintf(buf, sizeof(buf), "%4hx", rpc_get_port(sap));
  	xprt->address_strings[RPC_DISPLAY_HEX_PORT] = kstrdup(buf, GFP_KERNEL);
  
  	xprt->address_strings[RPC_DISPLAY_PROTO] = "rdma";
  }
  
  void
  xprt_rdma_free_addresses(struct rpc_xprt *xprt)
  {
  	unsigned int i;
  
  	for (i = 0; i < RPC_DISPLAY_MAX; i++)
  		switch (i) {
  		case RPC_DISPLAY_PROTO:
  		case RPC_DISPLAY_NETID:
  			continue;
  		default:
  			kfree(xprt->address_strings[i]);
  		}
  }
  
  void
  rpcrdma_conn_func(struct rpcrdma_ep *ep)
  {
  	schedule_delayed_work(&ep->rep_connect_worker, 0);
  }
  
  void
  rpcrdma_connect_worker(struct work_struct *work)
  {
  	struct rpcrdma_ep *ep =
  		container_of(work, struct rpcrdma_ep, rep_connect_worker.work);
  	struct rpcrdma_xprt *r_xprt =
  		container_of(ep, struct rpcrdma_xprt, rx_ep);
  	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
  
  	spin_lock_bh(&xprt->transport_lock);
  	if (++xprt->connect_cookie == 0)	/* maintain a reserved value */
  		++xprt->connect_cookie;
  	if (ep->rep_connected > 0) {
  		if (!xprt_test_and_set_connected(xprt))
  			xprt_wake_pending_tasks(xprt, 0);
  	} else {
  		if (xprt_test_and_clear_connected(xprt))
  			xprt_wake_pending_tasks(xprt, -ENOTCONN);
  	}
  	spin_unlock_bh(&xprt->transport_lock);
  }
  
  static void
  xprt_rdma_connect_worker(struct work_struct *work)
  {
  	struct rpcrdma_xprt *r_xprt = container_of(work, struct rpcrdma_xprt,
  						   rx_connect_worker.work);
  	struct rpc_xprt *xprt = &r_xprt->rx_xprt;
  	int rc = 0;
  
  	xprt_clear_connected(xprt);
  
  	dprintk("RPC:       %s: %sconnect\n", __func__,
  			r_xprt->rx_ep.rep_connected != 0 ? "re" : "");
  	rc = rpcrdma_ep_connect(&r_xprt->rx_ep, &r_xprt->rx_ia);
  	if (rc)
  		xprt_wake_pending_tasks(xprt, rc);
  
  	dprintk("RPC:       %s: exit\n", __func__);
  	xprt_clear_connecting(xprt);
  }
  
  static void
  xprt_rdma_inject_disconnect(struct rpc_xprt *xprt)
  {
  	struct rpcrdma_xprt *r_xprt = container_of(xprt, struct rpcrdma_xprt,
  						   rx_xprt);
  
  	pr_info("rpcrdma: injecting transport disconnect on xprt=%p\n", xprt);
  	rdma_disconnect(r_xprt->rx_ia.ri_id);
  }
  
  /*
   * xprt_rdma_destroy
   *
   * Destroy the xprt.
   * Free all memory associated with the object, including its own.
   * NOTE: none of the *destroy methods free memory for their top-level
   * objects, even though they may have allocated it (they do free
   * private memory). It's up to the caller to handle it. In this
   * case (RDMA transport), all structure memory is inlined with the
   * struct rpcrdma_xprt.
   */
  static void
  xprt_rdma_destroy(struct rpc_xprt *xprt)
  {
  	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  
  	dprintk("RPC:       %s: called\n", __func__);
  
  	cancel_delayed_work_sync(&r_xprt->rx_connect_worker);
  
  	xprt_clear_connected(xprt);
  
  	rpcrdma_ep_destroy(&r_xprt->rx_ep, &r_xprt->rx_ia);
  	rpcrdma_buffer_destroy(&r_xprt->rx_buf);
  	rpcrdma_ia_close(&r_xprt->rx_ia);
  
  	xprt_rdma_free_addresses(xprt);
  
  	xprt_free(xprt);
  
  	dprintk("RPC:       %s: returning\n", __func__);
  
  	module_put(THIS_MODULE);
  }
  
  static const struct rpc_timeout xprt_rdma_default_timeout = {
  	.to_initval = 60 * HZ,
  	.to_maxval = 60 * HZ,
  };
  
  /**
   * xprt_setup_rdma - Set up transport to use RDMA
   *
   * @args: rpc transport arguments
   */
  static struct rpc_xprt *
  xprt_setup_rdma(struct xprt_create *args)
  {
  	struct rpcrdma_create_data_internal cdata;
  	struct rpc_xprt *xprt;
  	struct rpcrdma_xprt *new_xprt;
  	struct rpcrdma_ep *new_ep;
  	struct sockaddr *sap;
  	int rc;
  
  	if (args->addrlen > sizeof(xprt->addr)) {
  		dprintk("RPC:       %s: address too large\n", __func__);
  		return ERR_PTR(-EBADF);
  	}
  
  	xprt = xprt_alloc(args->net, sizeof(struct rpcrdma_xprt),
  			xprt_rdma_slot_table_entries,
  			xprt_rdma_slot_table_entries);
  	if (xprt == NULL) {
  		dprintk("RPC:       %s: couldn't allocate rpcrdma_xprt\n",
  			__func__);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	/* 60 second timeout, no retries */
  	xprt->timeout = &xprt_rdma_default_timeout;
  	xprt->bind_timeout = RPCRDMA_BIND_TO;
  	xprt->reestablish_timeout = RPCRDMA_INIT_REEST_TO;
  	xprt->idle_timeout = RPCRDMA_IDLE_DISC_TO;
  
  	xprt->resvport = 0;		/* privileged port not needed */
  	xprt->tsh_size = 0;		/* RPC-RDMA handles framing */
  	xprt->ops = &xprt_rdma_procs;
  
  	/*
  	 * Set up RDMA-specific connect data.
  	 */
  
  	sap = (struct sockaddr *)&cdata.addr;
  	memcpy(sap, args->dstaddr, args->addrlen);
  
  	/* Ensure xprt->addr holds valid server TCP (not RDMA)
  	 * address, for any side protocols which peek at it */
  	xprt->prot = IPPROTO_TCP;
  	xprt->addrlen = args->addrlen;
  	memcpy(&xprt->addr, sap, xprt->addrlen);
  
  	if (rpc_get_port(sap))
  		xprt_set_bound(xprt);
  
  	cdata.max_requests = xprt->max_reqs;
  
  	cdata.rsize = RPCRDMA_MAX_SEGS * PAGE_SIZE; /* RDMA write max */
  	cdata.wsize = RPCRDMA_MAX_SEGS * PAGE_SIZE; /* RDMA read max */
  
  	cdata.inline_wsize = xprt_rdma_max_inline_write;
  	if (cdata.inline_wsize > cdata.wsize)
  		cdata.inline_wsize = cdata.wsize;
  
  	cdata.inline_rsize = xprt_rdma_max_inline_read;
  	if (cdata.inline_rsize > cdata.rsize)
  		cdata.inline_rsize = cdata.rsize;
  
  	cdata.padding = xprt_rdma_inline_write_padding;
  
  	/*
  	 * Create new transport instance, which includes initialized
  	 *  o ia
  	 *  o endpoint
  	 *  o buffers
  	 */
  
  	new_xprt = rpcx_to_rdmax(xprt);
  
  	rc = rpcrdma_ia_open(new_xprt, sap);
  	if (rc)
  		goto out1;
  
  	/*
  	 * initialize and create ep
  	 */
  	new_xprt->rx_data = cdata;
  	new_ep = &new_xprt->rx_ep;
  	new_ep->rep_remote_addr = cdata.addr;
  
  	rc = rpcrdma_ep_create(&new_xprt->rx_ep,
  				&new_xprt->rx_ia, &new_xprt->rx_data);
  	if (rc)
  		goto out2;
  
  	/*
  	 * Allocate pre-registered send and receive buffers for headers and
  	 * any inline data. Also specify any padding which will be provided
  	 * from a preregistered zero buffer.
  	 */
  	rc = rpcrdma_buffer_create(new_xprt);
  	if (rc)
  		goto out3;
  
  	/*
  	 * Register a callback for connection events. This is necessary because
  	 * connection loss notification is async. We also catch connection loss
  	 * when reaping receives.
  	 */
  	INIT_DELAYED_WORK(&new_xprt->rx_connect_worker,
  			  xprt_rdma_connect_worker);
  
  	xprt_rdma_format_addresses(xprt, sap);
  	xprt->max_payload = new_xprt->rx_ia.ri_ops->ro_maxpages(new_xprt);
  	if (xprt->max_payload == 0)
  		goto out4;
  	xprt->max_payload <<= PAGE_SHIFT;
  	dprintk("RPC:       %s: transport data payload maximum: %zu bytes\n",
  		__func__, xprt->max_payload);
  
  	if (!try_module_get(THIS_MODULE))
  		goto out4;
  
  	dprintk("RPC:       %s: %s:%s\n", __func__,
  		xprt->address_strings[RPC_DISPLAY_ADDR],
  		xprt->address_strings[RPC_DISPLAY_PORT]);
  	return xprt;
  
  out4:
  	xprt_rdma_free_addresses(xprt);
  	rc = -EINVAL;
  out3:
  	rpcrdma_ep_destroy(new_ep, &new_xprt->rx_ia);
  out2:
  	rpcrdma_ia_close(&new_xprt->rx_ia);
  out1:
  	xprt_free(xprt);
  	return ERR_PTR(rc);
  }
  
  /**
   * xprt_rdma_close - Close down RDMA connection
   * @xprt: generic transport to be closed
   *
   * Called during transport shutdown reconnect, or device
   * removal. Caller holds the transport's write lock.
   */
  static void
  xprt_rdma_close(struct rpc_xprt *xprt)
  {
  	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  	struct rpcrdma_ep *ep = &r_xprt->rx_ep;
  	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
  
  	dprintk("RPC:       %s: closing xprt %p\n", __func__, xprt);
  
  	if (test_and_clear_bit(RPCRDMA_IAF_REMOVING, &ia->ri_flags)) {
  		xprt_clear_connected(xprt);
  		rpcrdma_ia_remove(ia);
  		return;
  	}
  	if (ep->rep_connected == -ENODEV)
  		return;
  	if (ep->rep_connected > 0)
  		xprt->reestablish_timeout = 0;
  	xprt_disconnect_done(xprt);
  	rpcrdma_ep_disconnect(ep, ia);
  }
  
  static void
  xprt_rdma_set_port(struct rpc_xprt *xprt, u16 port)
  {
  	struct sockaddr_in *sap;
  
  	sap = (struct sockaddr_in *)&xprt->addr;
  	sap->sin_port = htons(port);
  	sap = (struct sockaddr_in *)&rpcx_to_rdmad(xprt).addr;
  	sap->sin_port = htons(port);
  	dprintk("RPC:       %s: %u\n", __func__, port);
  }
  
  /**
   * xprt_rdma_timer - invoked when an RPC times out
   * @xprt: controlling RPC transport
   * @task: RPC task that timed out
   *
   * Invoked when the transport is still connected, but an RPC
   * retransmit timeout occurs.
   *
   * Since RDMA connections don't have a keep-alive, forcibly
   * disconnect and retry to connect. This drives full
   * detection of the network path, and retransmissions of
   * all pending RPCs.
   */
  static void
  xprt_rdma_timer(struct rpc_xprt *xprt, struct rpc_task *task)
  {
  	dprintk("RPC: %5u %s: xprt = %p\n", task->tk_pid, __func__, xprt);
  
  	xprt_force_disconnect(xprt);
  }
  
  static void
  xprt_rdma_connect(struct rpc_xprt *xprt, struct rpc_task *task)
  {
  	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  
  	if (r_xprt->rx_ep.rep_connected != 0) {
  		/* Reconnect */
  		schedule_delayed_work(&r_xprt->rx_connect_worker,
  				      xprt->reestablish_timeout);
  		xprt->reestablish_timeout <<= 1;
  		if (xprt->reestablish_timeout > RPCRDMA_MAX_REEST_TO)
  			xprt->reestablish_timeout = RPCRDMA_MAX_REEST_TO;
  		else if (xprt->reestablish_timeout < RPCRDMA_INIT_REEST_TO)
  			xprt->reestablish_timeout = RPCRDMA_INIT_REEST_TO;
  	} else {
  		schedule_delayed_work(&r_xprt->rx_connect_worker, 0);
  		if (!RPC_IS_ASYNC(task))
  			flush_delayed_work(&r_xprt->rx_connect_worker);
  	}
  }
  
  /* Allocate a fixed-size buffer in which to construct and send the
   * RPC-over-RDMA header for this request.
   */
  static bool
  rpcrdma_get_rdmabuf(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
  		    gfp_t flags)
  {
  	size_t size = RPCRDMA_HDRBUF_SIZE;
  	struct rpcrdma_regbuf *rb;
  
  	if (req->rl_rdmabuf)
  		return true;
  
  	rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, flags);
  	if (IS_ERR(rb))
  		return false;
  
  	r_xprt->rx_stats.hardway_register_count += size;
  	req->rl_rdmabuf = rb;
  	return true;
  }
  
  static bool
  rpcrdma_get_sendbuf(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
  		    size_t size, gfp_t flags)
  {
  	struct rpcrdma_regbuf *rb;
  
  	if (req->rl_sendbuf && rdmab_length(req->rl_sendbuf) >= size)
  		return true;
  
  	rb = rpcrdma_alloc_regbuf(size, DMA_TO_DEVICE, flags);
  	if (IS_ERR(rb))
  		return false;
  
  	rpcrdma_free_regbuf(req->rl_sendbuf);
  	r_xprt->rx_stats.hardway_register_count += size;
  	req->rl_sendbuf = rb;
  	return true;
  }
  
  /* The rq_rcv_buf is used only if a Reply chunk is necessary.
   * The decision to use a Reply chunk is made later in
   * rpcrdma_marshal_req. This buffer is registered at that time.
   *
   * Otherwise, the associated RPC Reply arrives in a separate
   * Receive buffer, arbitrarily chosen by the HCA. The buffer
   * allocated here for the RPC Reply is not utilized in that
   * case. See rpcrdma_inline_fixup.
   *
   * A regbuf is used here to remember the buffer size.
   */
  static bool
  rpcrdma_get_recvbuf(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
  		    size_t size, gfp_t flags)
  {
  	struct rpcrdma_regbuf *rb;
  
  	if (req->rl_recvbuf && rdmab_length(req->rl_recvbuf) >= size)
  		return true;
  
  	rb = rpcrdma_alloc_regbuf(size, DMA_NONE, flags);
  	if (IS_ERR(rb))
  		return false;
  
  	rpcrdma_free_regbuf(req->rl_recvbuf);
  	r_xprt->rx_stats.hardway_register_count += size;
  	req->rl_recvbuf = rb;
  	return true;
  }
  
  /**
   * xprt_rdma_allocate - allocate transport resources for an RPC
   * @task: RPC task
   *
   * Return values:
   *        0:	Success; rq_buffer points to RPC buffer to use
   *   ENOMEM:	Out of memory, call again later
   *      EIO:	A permanent error occurred, do not retry
   *
   * The RDMA allocate/free functions need the task structure as a place
   * to hide the struct rpcrdma_req, which is necessary for the actual
   * send/recv sequence.
   *
   * xprt_rdma_allocate provides buffers that are already mapped for
   * DMA, and a local DMA lkey is provided for each.
   */
  static int
  xprt_rdma_allocate(struct rpc_task *task)
  {
  	struct rpc_rqst *rqst = task->tk_rqstp;
  	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
  	struct rpcrdma_req *req;
  	gfp_t flags;
  
  	req = rpcrdma_buffer_get(&r_xprt->rx_buf);
  	if (req == NULL)
  		return -ENOMEM;
  
  	flags = RPCRDMA_DEF_GFP;
  	if (RPC_IS_SWAPPER(task))
  		flags = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN;
  
  	if (!rpcrdma_get_rdmabuf(r_xprt, req, flags))
  		goto out_fail;
  	if (!rpcrdma_get_sendbuf(r_xprt, req, rqst->rq_callsize, flags))
  		goto out_fail;
  	if (!rpcrdma_get_recvbuf(r_xprt, req, rqst->rq_rcvsize, flags))
  		goto out_fail;
  
  	dprintk("RPC: %5u %s: send size = %zd, recv size = %zd, req = %p\n",
  		task->tk_pid, __func__, rqst->rq_callsize,
  		rqst->rq_rcvsize, req);
  
  	req->rl_connect_cookie = 0;	/* our reserved value */
  	rpcrdma_set_xprtdata(rqst, req);
  	rqst->rq_buffer = req->rl_sendbuf->rg_base;
  	rqst->rq_rbuffer = req->rl_recvbuf->rg_base;
  	return 0;
  
  out_fail:
  	rpcrdma_buffer_put(req);
  	return -ENOMEM;
  }
  
  /**
   * xprt_rdma_free - release resources allocated by xprt_rdma_allocate
   * @task: RPC task
   *
   * Caller guarantees rqst->rq_buffer is non-NULL.
   */
  static void
  xprt_rdma_free(struct rpc_task *task)
  {
  	struct rpc_rqst *rqst = task->tk_rqstp;
  	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(rqst->rq_xprt);
  	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
  	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
  
  	if (req->rl_backchannel)
  		return;
  
  	dprintk("RPC:       %s: called on 0x%p\n", __func__, req->rl_reply);
  
  	rpcrdma_remove_req(&r_xprt->rx_buf, req);
  	if (!list_empty(&req->rl_registered))
  		ia->ri_ops->ro_unmap_safe(r_xprt, req, !RPC_IS_ASYNC(task));
  	rpcrdma_unmap_sges(ia, req);
  	rpcrdma_buffer_put(req);
  }
  
  /**
   * xprt_rdma_send_request - marshal and send an RPC request
   * @task: RPC task with an RPC message in rq_snd_buf
   *
   * Caller holds the transport's write lock.
   *
   * Return values:
   *        0:	The request has been sent
   * ENOTCONN:	Caller needs to invoke connect logic then call again
   *  ENOBUFS:	Call again later to send the request
   *      EIO:	A permanent error occurred. The request was not sent,
   *		and don't try it again
   *
   * send_request invokes the meat of RPC RDMA. It must do the following:
   *
   *  1.  Marshal the RPC request into an RPC RDMA request, which means
   *	putting a header in front of data, and creating IOVs for RDMA
   *	from those in the request.
   *  2.  In marshaling, detect opportunities for RDMA, and use them.
   *  3.  Post a recv message to set up asynch completion, then send
   *	the request (rpcrdma_ep_post).
   *  4.  No partial sends are possible in the RPC-RDMA protocol (as in UDP).
   */
  static int
  xprt_rdma_send_request(struct rpc_task *task)
  {
  	struct rpc_rqst *rqst = task->tk_rqstp;
  	struct rpc_xprt *xprt = rqst->rq_xprt;
  	struct rpcrdma_req *req = rpcr_to_rdmar(rqst);
  	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  	int rc = 0;
  
  	if (!xprt_connected(xprt))
  		goto drop_connection;
  
  	/* On retransmit, remove any previously registered chunks */
  	if (unlikely(!list_empty(&req->rl_registered)))
  		r_xprt->rx_ia.ri_ops->ro_unmap_safe(r_xprt, req, false);
  
  	rc = rpcrdma_marshal_req(rqst);
  	if (rc < 0)
  		goto failed_marshal;
  
  	if (req->rl_reply == NULL) 		/* e.g. reconnection */
  		rpcrdma_recv_buffer_get(req);
  
  	/* Must suppress retransmit to maintain credits */
  	if (req->rl_connect_cookie == xprt->connect_cookie)
  		goto drop_connection;
  	req->rl_connect_cookie = xprt->connect_cookie;
  
  	if (rpcrdma_ep_post(&r_xprt->rx_ia, &r_xprt->rx_ep, req))
  		goto drop_connection;
  
  	rqst->rq_xmit_bytes_sent += rqst->rq_snd_buf.len;
  	rqst->rq_bytes_sent = 0;
  	return 0;
  
  failed_marshal:
  	if (rc != -ENOTCONN)
  		return rc;
  drop_connection:
  	xprt_disconnect_done(xprt);
  	return -ENOTCONN;	/* implies disconnect */
  }
  
  void xprt_rdma_print_stats(struct rpc_xprt *xprt, struct seq_file *seq)
  {
  	struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
  	long idle_time = 0;
  
  	if (xprt_connected(xprt))
  		idle_time = (long)(jiffies - xprt->last_used) / HZ;
  
  	seq_puts(seq, "\txprt:\trdma ");
  	seq_printf(seq, "%u %lu %lu %lu %ld %lu %lu %lu %llu %llu ",
  		   0,	/* need a local port? */
  		   xprt->stat.bind_count,
  		   xprt->stat.connect_count,
  		   xprt->stat.connect_time,
  		   idle_time,
  		   xprt->stat.sends,
  		   xprt->stat.recvs,
  		   xprt->stat.bad_xids,
  		   xprt->stat.req_u,
  		   xprt->stat.bklog_u);
  	seq_printf(seq, "%lu %lu %lu %llu %llu %llu %llu %lu %lu %lu %lu ",
  		   r_xprt->rx_stats.read_chunk_count,
  		   r_xprt->rx_stats.write_chunk_count,
  		   r_xprt->rx_stats.reply_chunk_count,
  		   r_xprt->rx_stats.total_rdma_request,
  		   r_xprt->rx_stats.total_rdma_reply,
  		   r_xprt->rx_stats.pullup_copy_count,
  		   r_xprt->rx_stats.fixup_copy_count,
  		   r_xprt->rx_stats.hardway_register_count,
  		   r_xprt->rx_stats.failed_marshal_count,
  		   r_xprt->rx_stats.bad_reply_count,
  		   r_xprt->rx_stats.nomsg_call_count);
  	seq_printf(seq, "%lu %lu %lu %lu\n",
  		   r_xprt->rx_stats.mrs_recovered,
  		   r_xprt->rx_stats.mrs_orphaned,
  		   r_xprt->rx_stats.mrs_allocated,
  		   r_xprt->rx_stats.local_inv_needed);
  }
  
  static int
  xprt_rdma_enable_swap(struct rpc_xprt *xprt)
  {
  	return 0;
  }
  
  static void
  xprt_rdma_disable_swap(struct rpc_xprt *xprt)
  {
  }
  
  /*
   * Plumbing for rpc transport switch and kernel module
   */
  
  static struct rpc_xprt_ops xprt_rdma_procs = {
  	.reserve_xprt		= xprt_reserve_xprt_cong,
  	.release_xprt		= xprt_release_xprt_cong, /* sunrpc/xprt.c */
  	.alloc_slot		= xprt_alloc_slot,
  	.release_request	= xprt_release_rqst_cong,       /* ditto */
  	.set_retrans_timeout	= xprt_set_retrans_timeout_def, /* ditto */
  	.timer			= xprt_rdma_timer,
  	.rpcbind		= rpcb_getport_async,	/* sunrpc/rpcb_clnt.c */
  	.set_port		= xprt_rdma_set_port,
  	.connect		= xprt_rdma_connect,
  	.buf_alloc		= xprt_rdma_allocate,
  	.buf_free		= xprt_rdma_free,
  	.send_request		= xprt_rdma_send_request,
  	.close			= xprt_rdma_close,
  	.destroy		= xprt_rdma_destroy,
  	.print_stats		= xprt_rdma_print_stats,
  	.enable_swap		= xprt_rdma_enable_swap,
  	.disable_swap		= xprt_rdma_disable_swap,
  	.inject_disconnect	= xprt_rdma_inject_disconnect,
  #if defined(CONFIG_SUNRPC_BACKCHANNEL)
  	.bc_setup		= xprt_rdma_bc_setup,
  	.bc_up			= xprt_rdma_bc_up,
  	.bc_maxpayload		= xprt_rdma_bc_maxpayload,
  	.bc_free_rqst		= xprt_rdma_bc_free_rqst,
  	.bc_destroy		= xprt_rdma_bc_destroy,
  #endif
  };
  
  static struct xprt_class xprt_rdma = {
  	.list			= LIST_HEAD_INIT(xprt_rdma.list),
  	.name			= "rdma",
  	.owner			= THIS_MODULE,
  	.ident			= XPRT_TRANSPORT_RDMA,
  	.setup			= xprt_setup_rdma,
  };
  
  void xprt_rdma_cleanup(void)
  {
  	int rc;
  
  	dprintk("RPCRDMA Module Removed, deregister RPC RDMA transport\n");
  #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  	if (sunrpc_table_header) {
  		unregister_sysctl_table(sunrpc_table_header);
  		sunrpc_table_header = NULL;
  	}
  #endif
  	rc = xprt_unregister_transport(&xprt_rdma);
  	if (rc)
  		dprintk("RPC:       %s: xprt_unregister returned %i\n",
  			__func__, rc);
  
  	rpcrdma_destroy_wq();
  
  	rc = xprt_unregister_transport(&xprt_rdma_bc);
  	if (rc)
  		dprintk("RPC:       %s: xprt_unregister(bc) returned %i\n",
  			__func__, rc);
  }
  
  int xprt_rdma_init(void)
  {
  	int rc;
  
  	rc = rpcrdma_alloc_wq();
  	if (rc)
  		return rc;
  
  	rc = xprt_register_transport(&xprt_rdma);
  	if (rc) {
  		rpcrdma_destroy_wq();
  		return rc;
  	}
  
  	rc = xprt_register_transport(&xprt_rdma_bc);
  	if (rc) {
  		xprt_unregister_transport(&xprt_rdma);
  		rpcrdma_destroy_wq();
  		return rc;
  	}
  
  	dprintk("RPCRDMA Module Init, register RPC RDMA transport\n");
  
  	dprintk("Defaults:\n");
  	dprintk("\tSlots %d\n"
  		"\tMaxInlineRead %d\n\tMaxInlineWrite %d\n",
  		xprt_rdma_slot_table_entries,
  		xprt_rdma_max_inline_read, xprt_rdma_max_inline_write);
  	dprintk("\tPadding %d\n\tMemreg %d\n",
  		xprt_rdma_inline_write_padding, xprt_rdma_memreg_strategy);
  
  #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  	if (!sunrpc_table_header)
  		sunrpc_table_header = register_sysctl_table(sunrpc_table);
  #endif
  	return 0;
  }
  