xprtrdma: Spread reply processing over more CPUs

[mirror_ubuntu-bionic-kernel.git] / net / sunrpc / xprtrdma / transport.c

/*
 * Copyright (c) 2014-2017 Oracle.  All rights reserved.
 * 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 <linux/smp.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 const struct rpc_xprt_ops xprt_rdma_procs;

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;
        xdr_buf_init(&req->rl_hdrbuf, rb->rg_base, rdmab_length(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_cpu = smp_processor_id();
        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);

        if (test_bit(RPCRDMA_REQ_F_BACKCHANNEL, &req->rl_flags))
                return;

        dprintk("RPC:       %s: called on 0x%p\n", __func__, req->rl_reply);

        if (test_bit(RPCRDMA_REQ_F_PENDING, &req->rl_flags))
                rpcrdma_release_rqst(r_xprt, 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_sync(r_xprt,
                                                    &req->rl_registered);

        rc = rpcrdma_marshal_req(r_xprt, 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;

        set_bit(RPCRDMA_REQ_F_PENDING, &req->rl_flags);
        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 %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,
                   r_xprt->rx_stats.empty_sendctx_q,
                   r_xprt->rx_stats.reply_waits_for_send);
}

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 const 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;
}