SUNRPC/call_alloc: async tasks mustn't block waiting for memory

[mirror_ubuntu-jammy-kernel.git] / net / sunrpc / clnt.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/net/sunrpc/clnt.c
 *
 *  This file contains the high-level RPC interface.
 *  It is modeled as a finite state machine to support both synchronous
 *  and asynchronous requests.
 *
 *  -   RPC header generation and argument serialization.
 *  -   Credential refresh.
 *  -   TCP connect handling.
 *  -   Retry of operation when it is suspected the operation failed because
 *      of uid squashing on the server, or when the credentials were stale
 *      and need to be refreshed, or when a packet was damaged in transit.
 *      This may be have to be moved to the VFS layer.
 *
 *  Copyright (C) 1992,1993 Rick Sladkey <jrs@world.std.com>
 *  Copyright (C) 1995,1996 Olaf Kirch <okir@monad.swb.de>
 */


#include <linux/module.h>
#include <linux/types.h>
#include <linux/kallsyms.h>
#include <linux/mm.h>
#include <linux/namei.h>
#include <linux/mount.h>
#include <linux/slab.h>
#include <linux/rcupdate.h>
#include <linux/utsname.h>
#include <linux/workqueue.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/un.h>

#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/addr.h>
#include <linux/sunrpc/rpc_pipe_fs.h>
#include <linux/sunrpc/metrics.h>
#include <linux/sunrpc/bc_xprt.h>
#include <trace/events/sunrpc.h>

#include "sunrpc.h"
#include "sysfs.h"
#include "netns.h"

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

/*
 * All RPC clients are linked into this list
 */

static DECLARE_WAIT_QUEUE_HEAD(destroy_wait);


static void     call_start(struct rpc_task *task);
static void     call_reserve(struct rpc_task *task);
static void     call_reserveresult(struct rpc_task *task);
static void     call_allocate(struct rpc_task *task);
static void     call_encode(struct rpc_task *task);
static void     call_decode(struct rpc_task *task);
static void     call_bind(struct rpc_task *task);
static void     call_bind_status(struct rpc_task *task);
static void     call_transmit(struct rpc_task *task);
static void     call_status(struct rpc_task *task);
static void     call_transmit_status(struct rpc_task *task);
static void     call_refresh(struct rpc_task *task);
static void     call_refreshresult(struct rpc_task *task);
static void     call_connect(struct rpc_task *task);
static void     call_connect_status(struct rpc_task *task);

static int      rpc_encode_header(struct rpc_task *task,
                                  struct xdr_stream *xdr);
static int      rpc_decode_header(struct rpc_task *task,
                                  struct xdr_stream *xdr);
static int      rpc_ping(struct rpc_clnt *clnt);
static void     rpc_check_timeout(struct rpc_task *task);

static void rpc_register_client(struct rpc_clnt *clnt)
{
        struct net *net = rpc_net_ns(clnt);
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        spin_lock(&sn->rpc_client_lock);
        list_add(&clnt->cl_clients, &sn->all_clients);
        spin_unlock(&sn->rpc_client_lock);
}

static void rpc_unregister_client(struct rpc_clnt *clnt)
{
        struct net *net = rpc_net_ns(clnt);
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        spin_lock(&sn->rpc_client_lock);
        list_del(&clnt->cl_clients);
        spin_unlock(&sn->rpc_client_lock);
}

static void __rpc_clnt_remove_pipedir(struct rpc_clnt *clnt)
{
        rpc_remove_client_dir(clnt);
}

static void rpc_clnt_remove_pipedir(struct rpc_clnt *clnt)
{
        struct net *net = rpc_net_ns(clnt);
        struct super_block *pipefs_sb;

        pipefs_sb = rpc_get_sb_net(net);
        if (pipefs_sb) {
                __rpc_clnt_remove_pipedir(clnt);
                rpc_put_sb_net(net);
        }
}

static struct dentry *rpc_setup_pipedir_sb(struct super_block *sb,
                                    struct rpc_clnt *clnt)
{
        static uint32_t clntid;
        const char *dir_name = clnt->cl_program->pipe_dir_name;
        char name[15];
        struct dentry *dir, *dentry;

        dir = rpc_d_lookup_sb(sb, dir_name);
        if (dir == NULL) {
                pr_info("RPC: pipefs directory doesn't exist: %s\n", dir_name);
                return dir;
        }
        for (;;) {
                snprintf(name, sizeof(name), "clnt%x", (unsigned int)clntid++);
                name[sizeof(name) - 1] = '\0';
                dentry = rpc_create_client_dir(dir, name, clnt);
                if (!IS_ERR(dentry))
                        break;
                if (dentry == ERR_PTR(-EEXIST))
                        continue;
                printk(KERN_INFO "RPC: Couldn't create pipefs entry"
                                " %s/%s, error %ld\n",
                                dir_name, name, PTR_ERR(dentry));
                break;
        }
        dput(dir);
        return dentry;
}

static int
rpc_setup_pipedir(struct super_block *pipefs_sb, struct rpc_clnt *clnt)
{
        struct dentry *dentry;

        if (clnt->cl_program->pipe_dir_name != NULL) {
                dentry = rpc_setup_pipedir_sb(pipefs_sb, clnt);
                if (IS_ERR(dentry))
                        return PTR_ERR(dentry);
        }
        return 0;
}

static int rpc_clnt_skip_event(struct rpc_clnt *clnt, unsigned long event)
{
        if (clnt->cl_program->pipe_dir_name == NULL)
                return 1;

        switch (event) {
        case RPC_PIPEFS_MOUNT:
                if (clnt->cl_pipedir_objects.pdh_dentry != NULL)
                        return 1;
                if (refcount_read(&clnt->cl_count) == 0)
                        return 1;
                break;
        case RPC_PIPEFS_UMOUNT:
                if (clnt->cl_pipedir_objects.pdh_dentry == NULL)
                        return 1;
                break;
        }
        return 0;
}

static int __rpc_clnt_handle_event(struct rpc_clnt *clnt, unsigned long event,
                                   struct super_block *sb)
{
        struct dentry *dentry;

        switch (event) {
        case RPC_PIPEFS_MOUNT:
                dentry = rpc_setup_pipedir_sb(sb, clnt);
                if (!dentry)
                        return -ENOENT;
                if (IS_ERR(dentry))
                        return PTR_ERR(dentry);
                break;
        case RPC_PIPEFS_UMOUNT:
                __rpc_clnt_remove_pipedir(clnt);
                break;
        default:
                printk(KERN_ERR "%s: unknown event: %ld\n", __func__, event);
                return -ENOTSUPP;
        }
        return 0;
}

static int __rpc_pipefs_event(struct rpc_clnt *clnt, unsigned long event,
                                struct super_block *sb)
{
        int error = 0;

        for (;; clnt = clnt->cl_parent) {
                if (!rpc_clnt_skip_event(clnt, event))
                        error = __rpc_clnt_handle_event(clnt, event, sb);
                if (error || clnt == clnt->cl_parent)
                        break;
        }
        return error;
}

static struct rpc_clnt *rpc_get_client_for_event(struct net *net, int event)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        struct rpc_clnt *clnt;

        spin_lock(&sn->rpc_client_lock);
        list_for_each_entry(clnt, &sn->all_clients, cl_clients) {
                if (rpc_clnt_skip_event(clnt, event))
                        continue;
                spin_unlock(&sn->rpc_client_lock);
                return clnt;
        }
        spin_unlock(&sn->rpc_client_lock);
        return NULL;
}

static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
                            void *ptr)
{
        struct super_block *sb = ptr;
        struct rpc_clnt *clnt;
        int error = 0;

        while ((clnt = rpc_get_client_for_event(sb->s_fs_info, event))) {
                error = __rpc_pipefs_event(clnt, event, sb);
                if (error)
                        break;
        }
        return error;
}

static struct notifier_block rpc_clients_block = {
        .notifier_call  = rpc_pipefs_event,
        .priority       = SUNRPC_PIPEFS_RPC_PRIO,
};

int rpc_clients_notifier_register(void)
{
        return rpc_pipefs_notifier_register(&rpc_clients_block);
}

void rpc_clients_notifier_unregister(void)
{
        return rpc_pipefs_notifier_unregister(&rpc_clients_block);
}

static struct rpc_xprt *rpc_clnt_set_transport(struct rpc_clnt *clnt,
                struct rpc_xprt *xprt,
                const struct rpc_timeout *timeout)
{
        struct rpc_xprt *old;

        spin_lock(&clnt->cl_lock);
        old = rcu_dereference_protected(clnt->cl_xprt,
                        lockdep_is_held(&clnt->cl_lock));

        if (!xprt_bound(xprt))
                clnt->cl_autobind = 1;

        clnt->cl_timeout = timeout;
        rcu_assign_pointer(clnt->cl_xprt, xprt);
        spin_unlock(&clnt->cl_lock);

        return old;
}

static void rpc_clnt_set_nodename(struct rpc_clnt *clnt, const char *nodename)
{
        clnt->cl_nodelen = strlcpy(clnt->cl_nodename,
                        nodename, sizeof(clnt->cl_nodename));
}

static int rpc_client_register(struct rpc_clnt *clnt,
                               rpc_authflavor_t pseudoflavor,
                               const char *client_name)
{
        struct rpc_auth_create_args auth_args = {
                .pseudoflavor = pseudoflavor,
                .target_name = client_name,
        };
        struct rpc_auth *auth;
        struct net *net = rpc_net_ns(clnt);
        struct super_block *pipefs_sb;
        int err;

        rpc_clnt_debugfs_register(clnt);

        pipefs_sb = rpc_get_sb_net(net);
        if (pipefs_sb) {
                err = rpc_setup_pipedir(pipefs_sb, clnt);
                if (err)
                        goto out;
        }

        rpc_register_client(clnt);
        if (pipefs_sb)
                rpc_put_sb_net(net);

        auth = rpcauth_create(&auth_args, clnt);
        if (IS_ERR(auth)) {
                dprintk("RPC:       Couldn't create auth handle (flavor %u)\n",
                                pseudoflavor);
                err = PTR_ERR(auth);
                goto err_auth;
        }
        return 0;
err_auth:
        pipefs_sb = rpc_get_sb_net(net);
        rpc_unregister_client(clnt);
        __rpc_clnt_remove_pipedir(clnt);
out:
        if (pipefs_sb)
                rpc_put_sb_net(net);
        rpc_sysfs_client_destroy(clnt);
        rpc_clnt_debugfs_unregister(clnt);
        return err;
}

static DEFINE_IDA(rpc_clids);

void rpc_cleanup_clids(void)
{
        ida_destroy(&rpc_clids);
}

static int rpc_alloc_clid(struct rpc_clnt *clnt)
{
        int clid;

        clid = ida_simple_get(&rpc_clids, 0, 0, GFP_KERNEL);
        if (clid < 0)
                return clid;
        clnt->cl_clid = clid;
        return 0;
}

static void rpc_free_clid(struct rpc_clnt *clnt)
{
        ida_simple_remove(&rpc_clids, clnt->cl_clid);
}

static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args,
                struct rpc_xprt_switch *xps,
                struct rpc_xprt *xprt,
                struct rpc_clnt *parent)
{
        const struct rpc_program *program = args->program;
        const struct rpc_version *version;
        struct rpc_clnt *clnt = NULL;
        const struct rpc_timeout *timeout;
        const char *nodename = args->nodename;
        int err;

        err = rpciod_up();
        if (err)
                goto out_no_rpciod;

        err = -EINVAL;
        if (args->version >= program->nrvers)
                goto out_err;
        version = program->version[args->version];
        if (version == NULL)
                goto out_err;

        err = -ENOMEM;
        clnt = kzalloc(sizeof(*clnt), GFP_KERNEL);
        if (!clnt)
                goto out_err;
        clnt->cl_parent = parent ? : clnt;

        err = rpc_alloc_clid(clnt);
        if (err)
                goto out_no_clid;

        clnt->cl_cred     = get_cred(args->cred);
        clnt->cl_procinfo = version->procs;
        clnt->cl_maxproc  = version->nrprocs;
        clnt->cl_prog     = args->prognumber ? : program->number;
        clnt->cl_vers     = version->number;
        clnt->cl_stats    = program->stats;
        clnt->cl_metrics  = rpc_alloc_iostats(clnt);
        rpc_init_pipe_dir_head(&clnt->cl_pipedir_objects);
        err = -ENOMEM;
        if (clnt->cl_metrics == NULL)
                goto out_no_stats;
        clnt->cl_program  = program;
        INIT_LIST_HEAD(&clnt->cl_tasks);
        spin_lock_init(&clnt->cl_lock);

        timeout = xprt->timeout;
        if (args->timeout != NULL) {
                memcpy(&clnt->cl_timeout_default, args->timeout,
                                sizeof(clnt->cl_timeout_default));
                timeout = &clnt->cl_timeout_default;
        }

        rpc_clnt_set_transport(clnt, xprt, timeout);
        xprt->main = true;
        xprt_iter_init(&clnt->cl_xpi, xps);
        xprt_switch_put(xps);

        clnt->cl_rtt = &clnt->cl_rtt_default;
        rpc_init_rtt(&clnt->cl_rtt_default, clnt->cl_timeout->to_initval);

        refcount_set(&clnt->cl_count, 1);

        if (nodename == NULL)
                nodename = utsname()->nodename;
        /* save the nodename */
        rpc_clnt_set_nodename(clnt, nodename);

        rpc_sysfs_client_setup(clnt, xps, rpc_net_ns(clnt));
        err = rpc_client_register(clnt, args->authflavor, args->client_name);
        if (err)
                goto out_no_path;
        if (parent)
                refcount_inc(&parent->cl_count);

        trace_rpc_clnt_new(clnt, xprt, program->name, args->servername);
        return clnt;

out_no_path:
        rpc_free_iostats(clnt->cl_metrics);
out_no_stats:
        put_cred(clnt->cl_cred);
        rpc_free_clid(clnt);
out_no_clid:
        kfree(clnt);
out_err:
        rpciod_down();
out_no_rpciod:
        xprt_switch_put(xps);
        xprt_put(xprt);
        trace_rpc_clnt_new_err(program->name, args->servername, err);
        return ERR_PTR(err);
}

static struct rpc_clnt *rpc_create_xprt(struct rpc_create_args *args,
                                        struct rpc_xprt *xprt)
{
        struct rpc_clnt *clnt = NULL;
        struct rpc_xprt_switch *xps;

        if (args->bc_xprt && args->bc_xprt->xpt_bc_xps) {
                WARN_ON_ONCE(!(args->protocol & XPRT_TRANSPORT_BC));
                xps = args->bc_xprt->xpt_bc_xps;
                xprt_switch_get(xps);
        } else {
                xps = xprt_switch_alloc(xprt, GFP_KERNEL);
                if (xps == NULL) {
                        xprt_put(xprt);
                        return ERR_PTR(-ENOMEM);
                }
                if (xprt->bc_xprt) {
                        xprt_switch_get(xps);
                        xprt->bc_xprt->xpt_bc_xps = xps;
                }
        }
        clnt = rpc_new_client(args, xps, xprt, NULL);
        if (IS_ERR(clnt))
                return clnt;

        if (!(args->flags & RPC_CLNT_CREATE_NOPING)) {
                int err = rpc_ping(clnt);
                if (err != 0) {
                        rpc_shutdown_client(clnt);
                        return ERR_PTR(err);
                }
        }

        clnt->cl_softrtry = 1;
        if (args->flags & (RPC_CLNT_CREATE_HARDRTRY|RPC_CLNT_CREATE_SOFTERR)) {
                clnt->cl_softrtry = 0;
                if (args->flags & RPC_CLNT_CREATE_SOFTERR)
                        clnt->cl_softerr = 1;
        }

        if (args->flags & RPC_CLNT_CREATE_AUTOBIND)
                clnt->cl_autobind = 1;
        if (args->flags & RPC_CLNT_CREATE_NO_RETRANS_TIMEOUT)
                clnt->cl_noretranstimeo = 1;
        if (args->flags & RPC_CLNT_CREATE_DISCRTRY)
                clnt->cl_discrtry = 1;
        if (!(args->flags & RPC_CLNT_CREATE_QUIET))
                clnt->cl_chatty = 1;

        return clnt;
}

/**
 * rpc_create - create an RPC client and transport with one call
 * @args: rpc_clnt create argument structure
 *
 * Creates and initializes an RPC transport and an RPC client.
 *
 * It can ping the server in order to determine if it is up, and to see if
 * it supports this program and version.  RPC_CLNT_CREATE_NOPING disables
 * this behavior so asynchronous tasks can also use rpc_create.
 */
struct rpc_clnt *rpc_create(struct rpc_create_args *args)
{
        struct rpc_xprt *xprt;
        struct xprt_create xprtargs = {
                .net = args->net,
                .ident = args->protocol,
                .srcaddr = args->saddress,
                .dstaddr = args->address,
                .addrlen = args->addrsize,
                .servername = args->servername,
                .bc_xprt = args->bc_xprt,
        };
        char servername[48];
        struct rpc_clnt *clnt;
        int i;

        if (args->bc_xprt) {
                WARN_ON_ONCE(!(args->protocol & XPRT_TRANSPORT_BC));
                xprt = args->bc_xprt->xpt_bc_xprt;
                if (xprt) {
                        xprt_get(xprt);
                        return rpc_create_xprt(args, xprt);
                }
        }

        if (args->flags & RPC_CLNT_CREATE_INFINITE_SLOTS)
                xprtargs.flags |= XPRT_CREATE_INFINITE_SLOTS;
        if (args->flags & RPC_CLNT_CREATE_NO_IDLE_TIMEOUT)
                xprtargs.flags |= XPRT_CREATE_NO_IDLE_TIMEOUT;
        /*
         * If the caller chooses not to specify a hostname, whip
         * up a string representation of the passed-in address.
         */
        if (xprtargs.servername == NULL) {
                struct sockaddr_un *sun =
                                (struct sockaddr_un *)args->address;
                struct sockaddr_in *sin =
                                (struct sockaddr_in *)args->address;
                struct sockaddr_in6 *sin6 =
                                (struct sockaddr_in6 *)args->address;

                servername[0] = '\0';
                switch (args->address->sa_family) {
                case AF_LOCAL:
                        snprintf(servername, sizeof(servername), "%s",
                                 sun->sun_path);
                        break;
                case AF_INET:
                        snprintf(servername, sizeof(servername), "%pI4",
                                 &sin->sin_addr.s_addr);
                        break;
                case AF_INET6:
                        snprintf(servername, sizeof(servername), "%pI6",
                                 &sin6->sin6_addr);
                        break;
                default:
                        /* caller wants default server name, but
                         * address family isn't recognized. */
                        return ERR_PTR(-EINVAL);
                }
                xprtargs.servername = servername;
        }

        xprt = xprt_create_transport(&xprtargs);
        if (IS_ERR(xprt))
                return (struct rpc_clnt *)xprt;

        /*
         * By default, kernel RPC client connects from a reserved port.
         * CAP_NET_BIND_SERVICE will not be set for unprivileged requesters,
         * but it is always enabled for rpciod, which handles the connect
         * operation.
         */
        xprt->resvport = 1;
        if (args->flags & RPC_CLNT_CREATE_NONPRIVPORT)
                xprt->resvport = 0;
        xprt->reuseport = 0;
        if (args->flags & RPC_CLNT_CREATE_REUSEPORT)
                xprt->reuseport = 1;

        clnt = rpc_create_xprt(args, xprt);
        if (IS_ERR(clnt) || args->nconnect <= 1)
                return clnt;

        for (i = 0; i < args->nconnect - 1; i++) {
                if (rpc_clnt_add_xprt(clnt, &xprtargs, NULL, NULL) < 0)
                        break;
        }
        return clnt;
}
EXPORT_SYMBOL_GPL(rpc_create);

/*
 * This function clones the RPC client structure. It allows us to share the
 * same transport while varying parameters such as the authentication
 * flavour.
 */
static struct rpc_clnt *__rpc_clone_client(struct rpc_create_args *args,
                                           struct rpc_clnt *clnt)
{
        struct rpc_xprt_switch *xps;
        struct rpc_xprt *xprt;
        struct rpc_clnt *new;
        int err;

        err = -ENOMEM;
        rcu_read_lock();
        xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
        xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
        rcu_read_unlock();
        if (xprt == NULL || xps == NULL) {
                xprt_put(xprt);
                xprt_switch_put(xps);
                goto out_err;
        }
        args->servername = xprt->servername;
        args->nodename = clnt->cl_nodename;

        new = rpc_new_client(args, xps, xprt, clnt);
        if (IS_ERR(new))
                return new;

        /* Turn off autobind on clones */
        new->cl_autobind = 0;
        new->cl_softrtry = clnt->cl_softrtry;
        new->cl_softerr = clnt->cl_softerr;
        new->cl_noretranstimeo = clnt->cl_noretranstimeo;
        new->cl_discrtry = clnt->cl_discrtry;
        new->cl_chatty = clnt->cl_chatty;
        new->cl_principal = clnt->cl_principal;
        return new;

out_err:
        trace_rpc_clnt_clone_err(clnt, err);
        return ERR_PTR(err);
}

/**
 * rpc_clone_client - Clone an RPC client structure
 *
 * @clnt: RPC client whose parameters are copied
 *
 * Returns a fresh RPC client or an ERR_PTR.
 */
struct rpc_clnt *rpc_clone_client(struct rpc_clnt *clnt)
{
        struct rpc_create_args args = {
                .program        = clnt->cl_program,
                .prognumber     = clnt->cl_prog,
                .version        = clnt->cl_vers,
                .authflavor     = clnt->cl_auth->au_flavor,
                .cred           = clnt->cl_cred,
        };
        return __rpc_clone_client(&args, clnt);
}
EXPORT_SYMBOL_GPL(rpc_clone_client);

/**
 * rpc_clone_client_set_auth - Clone an RPC client structure and set its auth
 *
 * @clnt: RPC client whose parameters are copied
 * @flavor: security flavor for new client
 *
 * Returns a fresh RPC client or an ERR_PTR.
 */
struct rpc_clnt *
rpc_clone_client_set_auth(struct rpc_clnt *clnt, rpc_authflavor_t flavor)
{
        struct rpc_create_args args = {
                .program        = clnt->cl_program,
                .prognumber     = clnt->cl_prog,
                .version        = clnt->cl_vers,
                .authflavor     = flavor,
                .cred           = clnt->cl_cred,
        };
        return __rpc_clone_client(&args, clnt);
}
EXPORT_SYMBOL_GPL(rpc_clone_client_set_auth);

/**
 * rpc_switch_client_transport: switch the RPC transport on the fly
 * @clnt: pointer to a struct rpc_clnt
 * @args: pointer to the new transport arguments
 * @timeout: pointer to the new timeout parameters
 *
 * This function allows the caller to switch the RPC transport for the
 * rpc_clnt structure 'clnt' to allow it to connect to a mirrored NFS
 * server, for instance.  It assumes that the caller has ensured that
 * there are no active RPC tasks by using some form of locking.
 *
 * Returns zero if "clnt" is now using the new xprt.  Otherwise a
 * negative errno is returned, and "clnt" continues to use the old
 * xprt.
 */
int rpc_switch_client_transport(struct rpc_clnt *clnt,
                struct xprt_create *args,
                const struct rpc_timeout *timeout)
{
        const struct rpc_timeout *old_timeo;
        rpc_authflavor_t pseudoflavor;
        struct rpc_xprt_switch *xps, *oldxps;
        struct rpc_xprt *xprt, *old;
        struct rpc_clnt *parent;
        int err;

        xprt = xprt_create_transport(args);
        if (IS_ERR(xprt))
                return PTR_ERR(xprt);

        xps = xprt_switch_alloc(xprt, GFP_KERNEL);
        if (xps == NULL) {
                xprt_put(xprt);
                return -ENOMEM;
        }

        pseudoflavor = clnt->cl_auth->au_flavor;

        old_timeo = clnt->cl_timeout;
        old = rpc_clnt_set_transport(clnt, xprt, timeout);
        oldxps = xprt_iter_xchg_switch(&clnt->cl_xpi, xps);

        rpc_unregister_client(clnt);
        __rpc_clnt_remove_pipedir(clnt);
        rpc_sysfs_client_destroy(clnt);
        rpc_clnt_debugfs_unregister(clnt);

        /*
         * A new transport was created.  "clnt" therefore
         * becomes the root of a new cl_parent tree.  clnt's
         * children, if it has any, still point to the old xprt.
         */
        parent = clnt->cl_parent;
        clnt->cl_parent = clnt;

        /*
         * The old rpc_auth cache cannot be re-used.  GSS
         * contexts in particular are between a single
         * client and server.
         */
        err = rpc_client_register(clnt, pseudoflavor, NULL);
        if (err)
                goto out_revert;

        synchronize_rcu();
        if (parent != clnt)
                rpc_release_client(parent);
        xprt_switch_put(oldxps);
        xprt_put(old);
        trace_rpc_clnt_replace_xprt(clnt);
        return 0;

out_revert:
        xps = xprt_iter_xchg_switch(&clnt->cl_xpi, oldxps);
        rpc_clnt_set_transport(clnt, old, old_timeo);
        clnt->cl_parent = parent;
        rpc_client_register(clnt, pseudoflavor, NULL);
        xprt_switch_put(xps);
        xprt_put(xprt);
        trace_rpc_clnt_replace_xprt_err(clnt);
        return err;
}
EXPORT_SYMBOL_GPL(rpc_switch_client_transport);

static
int rpc_clnt_xprt_iter_init(struct rpc_clnt *clnt, struct rpc_xprt_iter *xpi)
{
        struct rpc_xprt_switch *xps;

        rcu_read_lock();
        xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
        rcu_read_unlock();
        if (xps == NULL)
                return -EAGAIN;
        xprt_iter_init_listall(xpi, xps);
        xprt_switch_put(xps);
        return 0;
}

/**
 * rpc_clnt_iterate_for_each_xprt - Apply a function to all transports
 * @clnt: pointer to client
 * @fn: function to apply
 * @data: void pointer to function data
 *
 * Iterates through the list of RPC transports currently attached to the
 * client and applies the function fn(clnt, xprt, data).
 *
 * On error, the iteration stops, and the function returns the error value.
 */
int rpc_clnt_iterate_for_each_xprt(struct rpc_clnt *clnt,
                int (*fn)(struct rpc_clnt *, struct rpc_xprt *, void *),
                void *data)
{
        struct rpc_xprt_iter xpi;
        int ret;

        ret = rpc_clnt_xprt_iter_init(clnt, &xpi);
        if (ret)
                return ret;
        for (;;) {
                struct rpc_xprt *xprt = xprt_iter_get_next(&xpi);

                if (!xprt)
                        break;
                ret = fn(clnt, xprt, data);
                xprt_put(xprt);
                if (ret < 0)
                        break;
        }
        xprt_iter_destroy(&xpi);
        return ret;
}
EXPORT_SYMBOL_GPL(rpc_clnt_iterate_for_each_xprt);

/*
 * Kill all tasks for the given client.
 * XXX: kill their descendants as well?
 */
void rpc_killall_tasks(struct rpc_clnt *clnt)
{
        struct rpc_task *rovr;


        if (list_empty(&clnt->cl_tasks))
                return;

        /*
         * Spin lock all_tasks to prevent changes...
         */
        trace_rpc_clnt_killall(clnt);
        spin_lock(&clnt->cl_lock);
        list_for_each_entry(rovr, &clnt->cl_tasks, tk_task)
                rpc_signal_task(rovr);
        spin_unlock(&clnt->cl_lock);
}
EXPORT_SYMBOL_GPL(rpc_killall_tasks);

/*
 * Properly shut down an RPC client, terminating all outstanding
 * requests.
 */
void rpc_shutdown_client(struct rpc_clnt *clnt)
{
        might_sleep();

        trace_rpc_clnt_shutdown(clnt);

        while (!list_empty(&clnt->cl_tasks)) {
                rpc_killall_tasks(clnt);
                wait_event_timeout(destroy_wait,
                        list_empty(&clnt->cl_tasks), 1*HZ);
        }

        rpc_release_client(clnt);
}
EXPORT_SYMBOL_GPL(rpc_shutdown_client);

/*
 * Free an RPC client
 */
static void rpc_free_client_work(struct work_struct *work)
{
        struct rpc_clnt *clnt = container_of(work, struct rpc_clnt, cl_work);

        trace_rpc_clnt_free(clnt);

        /* These might block on processes that might allocate memory,
         * so they cannot be called in rpciod, so they are handled separately
         * here.
         */
        rpc_sysfs_client_destroy(clnt);
        rpc_clnt_debugfs_unregister(clnt);
        rpc_free_clid(clnt);
        rpc_clnt_remove_pipedir(clnt);
        xprt_put(rcu_dereference_raw(clnt->cl_xprt));

        kfree(clnt);
        rpciod_down();
}
static struct rpc_clnt *
rpc_free_client(struct rpc_clnt *clnt)
{
        struct rpc_clnt *parent = NULL;

        trace_rpc_clnt_release(clnt);
        if (clnt->cl_parent != clnt)
                parent = clnt->cl_parent;
        rpc_unregister_client(clnt);
        rpc_free_iostats(clnt->cl_metrics);
        clnt->cl_metrics = NULL;
        xprt_iter_destroy(&clnt->cl_xpi);
        put_cred(clnt->cl_cred);

        INIT_WORK(&clnt->cl_work, rpc_free_client_work);
        schedule_work(&clnt->cl_work);
        return parent;
}

/*
 * Free an RPC client
 */
static struct rpc_clnt *
rpc_free_auth(struct rpc_clnt *clnt)
{
        /*
         * Note: RPCSEC_GSS may need to send NULL RPC calls in order to
         *       release remaining GSS contexts. This mechanism ensures
         *       that it can do so safely.
         */
        if (clnt->cl_auth != NULL) {
                rpcauth_release(clnt->cl_auth);
                clnt->cl_auth = NULL;
        }
        if (refcount_dec_and_test(&clnt->cl_count))
                return rpc_free_client(clnt);
        return NULL;
}

/*
 * Release reference to the RPC client
 */
void
rpc_release_client(struct rpc_clnt *clnt)
{
        do {
                if (list_empty(&clnt->cl_tasks))
                        wake_up(&destroy_wait);
                if (refcount_dec_not_one(&clnt->cl_count))
                        break;
                clnt = rpc_free_auth(clnt);
        } while (clnt != NULL);
}
EXPORT_SYMBOL_GPL(rpc_release_client);

/**
 * rpc_bind_new_program - bind a new RPC program to an existing client
 * @old: old rpc_client
 * @program: rpc program to set
 * @vers: rpc program version
 *
 * Clones the rpc client and sets up a new RPC program. This is mainly
 * of use for enabling different RPC programs to share the same transport.
 * The Sun NFSv2/v3 ACL protocol can do this.
 */
struct rpc_clnt *rpc_bind_new_program(struct rpc_clnt *old,
                                      const struct rpc_program *program,
                                      u32 vers)
{
        struct rpc_create_args args = {
                .program        = program,
                .prognumber     = program->number,
                .version        = vers,
                .authflavor     = old->cl_auth->au_flavor,
                .cred           = old->cl_cred,
        };
        struct rpc_clnt *clnt;
        int err;

        clnt = __rpc_clone_client(&args, old);
        if (IS_ERR(clnt))
                goto out;
        err = rpc_ping(clnt);
        if (err != 0) {
                rpc_shutdown_client(clnt);
                clnt = ERR_PTR(err);
        }
out:
        return clnt;
}
EXPORT_SYMBOL_GPL(rpc_bind_new_program);

struct rpc_xprt *
rpc_task_get_xprt(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
{
        struct rpc_xprt_switch *xps;

        if (!xprt)
                return NULL;
        rcu_read_lock();
        xps = rcu_dereference(clnt->cl_xpi.xpi_xpswitch);
        atomic_long_inc(&xps->xps_queuelen);
        rcu_read_unlock();
        atomic_long_inc(&xprt->queuelen);

        return xprt;
}

static void
rpc_task_release_xprt(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
{
        struct rpc_xprt_switch *xps;

        atomic_long_dec(&xprt->queuelen);
        rcu_read_lock();
        xps = rcu_dereference(clnt->cl_xpi.xpi_xpswitch);
        atomic_long_dec(&xps->xps_queuelen);
        rcu_read_unlock();

        xprt_put(xprt);
}

void rpc_task_release_transport(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_xprt;

        if (xprt) {
                task->tk_xprt = NULL;
                if (task->tk_client)
                        rpc_task_release_xprt(task->tk_client, xprt);
                else
                        xprt_put(xprt);
        }
}
EXPORT_SYMBOL_GPL(rpc_task_release_transport);

void rpc_task_release_client(struct rpc_task *task)
{
        struct rpc_clnt *clnt = task->tk_client;

        rpc_task_release_transport(task);
        if (clnt != NULL) {
                /* Remove from client task list */
                spin_lock(&clnt->cl_lock);
                list_del(&task->tk_task);
                spin_unlock(&clnt->cl_lock);
                task->tk_client = NULL;

                rpc_release_client(clnt);
        }
}

static struct rpc_xprt *
rpc_task_get_first_xprt(struct rpc_clnt *clnt)
{
        struct rpc_xprt *xprt;

        rcu_read_lock();
        xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
        rcu_read_unlock();
        return rpc_task_get_xprt(clnt, xprt);
}

static struct rpc_xprt *
rpc_task_get_next_xprt(struct rpc_clnt *clnt)
{
        return rpc_task_get_xprt(clnt, xprt_iter_get_next(&clnt->cl_xpi));
}

static
void rpc_task_set_transport(struct rpc_task *task, struct rpc_clnt *clnt)
{
        if (task->tk_xprt &&
                        !(test_bit(XPRT_OFFLINE, &task->tk_xprt->state) &&
                        (task->tk_flags & RPC_TASK_MOVEABLE)))
                return;
        if (task->tk_flags & RPC_TASK_NO_ROUND_ROBIN)
                task->tk_xprt = rpc_task_get_first_xprt(clnt);
        else
                task->tk_xprt = rpc_task_get_next_xprt(clnt);
}

static
void rpc_task_set_client(struct rpc_task *task, struct rpc_clnt *clnt)
{

        if (clnt != NULL) {
                rpc_task_set_transport(task, clnt);
                task->tk_client = clnt;
                refcount_inc(&clnt->cl_count);
                if (clnt->cl_softrtry)
                        task->tk_flags |= RPC_TASK_SOFT;
                if (clnt->cl_softerr)
                        task->tk_flags |= RPC_TASK_TIMEOUT;
                if (clnt->cl_noretranstimeo)
                        task->tk_flags |= RPC_TASK_NO_RETRANS_TIMEOUT;
                if (atomic_read(&clnt->cl_swapper))
                        task->tk_flags |= RPC_TASK_SWAPPER;
                /* Add to the client's list of all tasks */
                spin_lock(&clnt->cl_lock);
                list_add_tail(&task->tk_task, &clnt->cl_tasks);
                spin_unlock(&clnt->cl_lock);
        }
}

static void
rpc_task_set_rpc_message(struct rpc_task *task, const struct rpc_message *msg)
{
        if (msg != NULL) {
                task->tk_msg.rpc_proc = msg->rpc_proc;
                task->tk_msg.rpc_argp = msg->rpc_argp;
                task->tk_msg.rpc_resp = msg->rpc_resp;
                task->tk_msg.rpc_cred = msg->rpc_cred;
                if (!(task->tk_flags & RPC_TASK_CRED_NOREF))
                        get_cred(task->tk_msg.rpc_cred);
        }
}

/*
 * Default callback for async RPC calls
 */
static void
rpc_default_callback(struct rpc_task *task, void *data)
{
}

static const struct rpc_call_ops rpc_default_ops = {
        .rpc_call_done = rpc_default_callback,
};

/**
 * rpc_run_task - Allocate a new RPC task, then run rpc_execute against it
 * @task_setup_data: pointer to task initialisation data
 */
struct rpc_task *rpc_run_task(const struct rpc_task_setup *task_setup_data)
{
        struct rpc_task *task;

        task = rpc_new_task(task_setup_data);

        if (!RPC_IS_ASYNC(task))
                task->tk_flags |= RPC_TASK_CRED_NOREF;

        rpc_task_set_client(task, task_setup_data->rpc_client);
        rpc_task_set_rpc_message(task, task_setup_data->rpc_message);

        if (task->tk_action == NULL)
                rpc_call_start(task);

        atomic_inc(&task->tk_count);
        rpc_execute(task);
        return task;
}
EXPORT_SYMBOL_GPL(rpc_run_task);

/**
 * rpc_call_sync - Perform a synchronous RPC call
 * @clnt: pointer to RPC client
 * @msg: RPC call parameters
 * @flags: RPC call flags
 */
int rpc_call_sync(struct rpc_clnt *clnt, const struct rpc_message *msg, int flags)
{
        struct rpc_task *task;
        struct rpc_task_setup task_setup_data = {
                .rpc_client = clnt,
                .rpc_message = msg,
                .callback_ops = &rpc_default_ops,
                .flags = flags,
        };
        int status;

        WARN_ON_ONCE(flags & RPC_TASK_ASYNC);
        if (flags & RPC_TASK_ASYNC) {
                rpc_release_calldata(task_setup_data.callback_ops,
                        task_setup_data.callback_data);
                return -EINVAL;
        }

        task = rpc_run_task(&task_setup_data);
        if (IS_ERR(task))
                return PTR_ERR(task);
        status = task->tk_status;
        rpc_put_task(task);
        return status;
}
EXPORT_SYMBOL_GPL(rpc_call_sync);

/**
 * rpc_call_async - Perform an asynchronous RPC call
 * @clnt: pointer to RPC client
 * @msg: RPC call parameters
 * @flags: RPC call flags
 * @tk_ops: RPC call ops
 * @data: user call data
 */
int
rpc_call_async(struct rpc_clnt *clnt, const struct rpc_message *msg, int flags,
               const struct rpc_call_ops *tk_ops, void *data)
{
        struct rpc_task *task;
        struct rpc_task_setup task_setup_data = {
                .rpc_client = clnt,
                .rpc_message = msg,
                .callback_ops = tk_ops,
                .callback_data = data,
                .flags = flags|RPC_TASK_ASYNC,
        };

        task = rpc_run_task(&task_setup_data);
        if (IS_ERR(task))
                return PTR_ERR(task);
        rpc_put_task(task);
        return 0;
}
EXPORT_SYMBOL_GPL(rpc_call_async);

#if defined(CONFIG_SUNRPC_BACKCHANNEL)
static void call_bc_encode(struct rpc_task *task);

/**
 * rpc_run_bc_task - Allocate a new RPC task for backchannel use, then run
 * rpc_execute against it
 * @req: RPC request
 */
struct rpc_task *rpc_run_bc_task(struct rpc_rqst *req)
{
        struct rpc_task *task;
        struct rpc_task_setup task_setup_data = {
                .callback_ops = &rpc_default_ops,
                .flags = RPC_TASK_SOFTCONN |
                        RPC_TASK_NO_RETRANS_TIMEOUT,
        };

        dprintk("RPC: rpc_run_bc_task req= %p\n", req);
        /*
         * Create an rpc_task to send the data
         */
        task = rpc_new_task(&task_setup_data);
        xprt_init_bc_request(req, task);

        task->tk_action = call_bc_encode;
        atomic_inc(&task->tk_count);
        WARN_ON_ONCE(atomic_read(&task->tk_count) != 2);
        rpc_execute(task);

        dprintk("RPC: rpc_run_bc_task: task= %p\n", task);
        return task;
}
#endif /* CONFIG_SUNRPC_BACKCHANNEL */

/**
 * rpc_prepare_reply_pages - Prepare to receive a reply data payload into pages
 * @req: RPC request to prepare
 * @pages: vector of struct page pointers
 * @base: offset in first page where receive should start, in bytes
 * @len: expected size of the upper layer data payload, in bytes
 * @hdrsize: expected size of upper layer reply header, in XDR words
 *
 */
void rpc_prepare_reply_pages(struct rpc_rqst *req, struct page **pages,
                             unsigned int base, unsigned int len,
                             unsigned int hdrsize)
{
        hdrsize += RPC_REPHDRSIZE + req->rq_cred->cr_auth->au_ralign;

        xdr_inline_pages(&req->rq_rcv_buf, hdrsize << 2, pages, base, len);
        trace_rpc_xdr_reply_pages(req->rq_task, &req->rq_rcv_buf);
}
EXPORT_SYMBOL_GPL(rpc_prepare_reply_pages);

void
rpc_call_start(struct rpc_task *task)
{
        task->tk_action = call_start;
}
EXPORT_SYMBOL_GPL(rpc_call_start);

/**
 * rpc_peeraddr - extract remote peer address from clnt's xprt
 * @clnt: RPC client structure
 * @buf: target buffer
 * @bufsize: length of target buffer
 *
 * Returns the number of bytes that are actually in the stored address.
 */
size_t rpc_peeraddr(struct rpc_clnt *clnt, struct sockaddr *buf, size_t bufsize)
{
        size_t bytes;
        struct rpc_xprt *xprt;

        rcu_read_lock();
        xprt = rcu_dereference(clnt->cl_xprt);

        bytes = xprt->addrlen;
        if (bytes > bufsize)
                bytes = bufsize;
        memcpy(buf, &xprt->addr, bytes);
        rcu_read_unlock();

        return bytes;
}
EXPORT_SYMBOL_GPL(rpc_peeraddr);

/**
 * rpc_peeraddr2str - return remote peer address in printable format
 * @clnt: RPC client structure
 * @format: address format
 *
 * NB: the lifetime of the memory referenced by the returned pointer is
 * the same as the rpc_xprt itself.  As long as the caller uses this
 * pointer, it must hold the RCU read lock.
 */
const char *rpc_peeraddr2str(struct rpc_clnt *clnt,
                             enum rpc_display_format_t format)
{
        struct rpc_xprt *xprt;

        xprt = rcu_dereference(clnt->cl_xprt);

        if (xprt->address_strings[format] != NULL)
                return xprt->address_strings[format];
        else
                return "unprintable";
}
EXPORT_SYMBOL_GPL(rpc_peeraddr2str);

static const struct sockaddr_in rpc_inaddr_loopback = {
        .sin_family             = AF_INET,
        .sin_addr.s_addr        = htonl(INADDR_ANY),
};

static const struct sockaddr_in6 rpc_in6addr_loopback = {
        .sin6_family            = AF_INET6,
        .sin6_addr              = IN6ADDR_ANY_INIT,
};

/*
 * Try a getsockname() on a connected datagram socket.  Using a
 * connected datagram socket prevents leaving a socket in TIME_WAIT.
 * This conserves the ephemeral port number space.
 *
 * Returns zero and fills in "buf" if successful; otherwise, a
 * negative errno is returned.
 */
static int rpc_sockname(struct net *net, struct sockaddr *sap, size_t salen,
                        struct sockaddr *buf)
{
        struct socket *sock;
        int err;

        err = __sock_create(net, sap->sa_family,
                                SOCK_DGRAM, IPPROTO_UDP, &sock, 1);
        if (err < 0) {
                dprintk("RPC:       can't create UDP socket (%d)\n", err);
                goto out;
        }

        switch (sap->sa_family) {
        case AF_INET:
                err = kernel_bind(sock,
                                (struct sockaddr *)&rpc_inaddr_loopback,
                                sizeof(rpc_inaddr_loopback));
                break;
        case AF_INET6:
                err = kernel_bind(sock,
                                (struct sockaddr *)&rpc_in6addr_loopback,
                                sizeof(rpc_in6addr_loopback));
                break;
        default:
                err = -EAFNOSUPPORT;
                goto out;
        }
        if (err < 0) {
                dprintk("RPC:       can't bind UDP socket (%d)\n", err);
                goto out_release;
        }

        err = kernel_connect(sock, sap, salen, 0);
        if (err < 0) {
                dprintk("RPC:       can't connect UDP socket (%d)\n", err);
                goto out_release;
        }

        err = kernel_getsockname(sock, buf);
        if (err < 0) {
                dprintk("RPC:       getsockname failed (%d)\n", err);
                goto out_release;
        }

        err = 0;
        if (buf->sa_family == AF_INET6) {
                struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)buf;
                sin6->sin6_scope_id = 0;
        }
        dprintk("RPC:       %s succeeded\n", __func__);

out_release:
        sock_release(sock);
out:
        return err;
}

/*
 * Scraping a connected socket failed, so we don't have a useable
 * local address.  Fallback: generate an address that will prevent
 * the server from calling us back.
 *
 * Returns zero and fills in "buf" if successful; otherwise, a
 * negative errno is returned.
 */
static int rpc_anyaddr(int family, struct sockaddr *buf, size_t buflen)
{
        switch (family) {
        case AF_INET:
                if (buflen < sizeof(rpc_inaddr_loopback))
                        return -EINVAL;
                memcpy(buf, &rpc_inaddr_loopback,
                                sizeof(rpc_inaddr_loopback));
                break;
        case AF_INET6:
                if (buflen < sizeof(rpc_in6addr_loopback))
                        return -EINVAL;
                memcpy(buf, &rpc_in6addr_loopback,
                                sizeof(rpc_in6addr_loopback));
                break;
        default:
                dprintk("RPC:       %s: address family not supported\n",
                        __func__);
                return -EAFNOSUPPORT;
        }
        dprintk("RPC:       %s: succeeded\n", __func__);
        return 0;
}

/**
 * rpc_localaddr - discover local endpoint address for an RPC client
 * @clnt: RPC client structure
 * @buf: target buffer
 * @buflen: size of target buffer, in bytes
 *
 * Returns zero and fills in "buf" and "buflen" if successful;
 * otherwise, a negative errno is returned.
 *
 * This works even if the underlying transport is not currently connected,
 * or if the upper layer never previously provided a source address.
 *
 * The result of this function call is transient: multiple calls in
 * succession may give different results, depending on how local
 * networking configuration changes over time.
 */
int rpc_localaddr(struct rpc_clnt *clnt, struct sockaddr *buf, size_t buflen)
{
        struct sockaddr_storage address;
        struct sockaddr *sap = (struct sockaddr *)&address;
        struct rpc_xprt *xprt;
        struct net *net;
        size_t salen;
        int err;

        rcu_read_lock();
        xprt = rcu_dereference(clnt->cl_xprt);
        salen = xprt->addrlen;
        memcpy(sap, &xprt->addr, salen);
        net = get_net(xprt->xprt_net);
        rcu_read_unlock();

        rpc_set_port(sap, 0);
        err = rpc_sockname(net, sap, salen, buf);
        put_net(net);
        if (err != 0)
                /* Couldn't discover local address, return ANYADDR */
                return rpc_anyaddr(sap->sa_family, buf, buflen);
        return 0;
}
EXPORT_SYMBOL_GPL(rpc_localaddr);

void
rpc_setbufsize(struct rpc_clnt *clnt, unsigned int sndsize, unsigned int rcvsize)
{
        struct rpc_xprt *xprt;

        rcu_read_lock();
        xprt = rcu_dereference(clnt->cl_xprt);
        if (xprt->ops->set_buffer_size)
                xprt->ops->set_buffer_size(xprt, sndsize, rcvsize);
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(rpc_setbufsize);

/**
 * rpc_net_ns - Get the network namespace for this RPC client
 * @clnt: RPC client to query
 *
 */
struct net *rpc_net_ns(struct rpc_clnt *clnt)
{
        struct net *ret;

        rcu_read_lock();
        ret = rcu_dereference(clnt->cl_xprt)->xprt_net;
        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL_GPL(rpc_net_ns);

/**
 * rpc_max_payload - Get maximum payload size for a transport, in bytes
 * @clnt: RPC client to query
 *
 * For stream transports, this is one RPC record fragment (see RFC
 * 1831), as we don't support multi-record requests yet.  For datagram
 * transports, this is the size of an IP packet minus the IP, UDP, and
 * RPC header sizes.
 */
size_t rpc_max_payload(struct rpc_clnt *clnt)
{
        size_t ret;

        rcu_read_lock();
        ret = rcu_dereference(clnt->cl_xprt)->max_payload;
        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL_GPL(rpc_max_payload);

/**
 * rpc_max_bc_payload - Get maximum backchannel payload size, in bytes
 * @clnt: RPC client to query
 */
size_t rpc_max_bc_payload(struct rpc_clnt *clnt)
{
        struct rpc_xprt *xprt;
        size_t ret;

        rcu_read_lock();
        xprt = rcu_dereference(clnt->cl_xprt);
        ret = xprt->ops->bc_maxpayload(xprt);
        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL_GPL(rpc_max_bc_payload);

unsigned int rpc_num_bc_slots(struct rpc_clnt *clnt)
{
        struct rpc_xprt *xprt;
        unsigned int ret;

        rcu_read_lock();
        xprt = rcu_dereference(clnt->cl_xprt);
        ret = xprt->ops->bc_num_slots(xprt);
        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL_GPL(rpc_num_bc_slots);

/**
 * rpc_force_rebind - force transport to check that remote port is unchanged
 * @clnt: client to rebind
 *
 */
void rpc_force_rebind(struct rpc_clnt *clnt)
{
        if (clnt->cl_autobind) {
                rcu_read_lock();
                xprt_clear_bound(rcu_dereference(clnt->cl_xprt));
                rcu_read_unlock();
        }
}
EXPORT_SYMBOL_GPL(rpc_force_rebind);

static int
__rpc_restart_call(struct rpc_task *task, void (*action)(struct rpc_task *))
{
        task->tk_status = 0;
        task->tk_rpc_status = 0;
        task->tk_action = action;
        return 1;
}

/*
 * Restart an (async) RPC call. Usually called from within the
 * exit handler.
 */
int
rpc_restart_call(struct rpc_task *task)
{
        return __rpc_restart_call(task, call_start);
}
EXPORT_SYMBOL_GPL(rpc_restart_call);

/*
 * Restart an (async) RPC call from the call_prepare state.
 * Usually called from within the exit handler.
 */
int
rpc_restart_call_prepare(struct rpc_task *task)
{
        if (task->tk_ops->rpc_call_prepare != NULL)
                return __rpc_restart_call(task, rpc_prepare_task);
        return rpc_restart_call(task);
}
EXPORT_SYMBOL_GPL(rpc_restart_call_prepare);

const char
*rpc_proc_name(const struct rpc_task *task)
{
        const struct rpc_procinfo *proc = task->tk_msg.rpc_proc;

        if (proc) {
                if (proc->p_name)
                        return proc->p_name;
                else
                        return "NULL";
        } else
                return "no proc";
}

static void
__rpc_call_rpcerror(struct rpc_task *task, int tk_status, int rpc_status)
{
        trace_rpc_call_rpcerror(task, tk_status, rpc_status);
        task->tk_rpc_status = rpc_status;
        rpc_exit(task, tk_status);
}

static void
rpc_call_rpcerror(struct rpc_task *task, int status)
{
        __rpc_call_rpcerror(task, status, status);
}

/*
 * 0.  Initial state
 *
 *     Other FSM states can be visited zero or more times, but
 *     this state is visited exactly once for each RPC.
 */
static void
call_start(struct rpc_task *task)
{
        struct rpc_clnt *clnt = task->tk_client;
        int idx = task->tk_msg.rpc_proc->p_statidx;

        trace_rpc_request(task);

        /* Increment call count (version might not be valid for ping) */
        if (clnt->cl_program->version[clnt->cl_vers])
                clnt->cl_program->version[clnt->cl_vers]->counts[idx]++;
        clnt->cl_stats->rpccnt++;
        task->tk_action = call_reserve;
        rpc_task_set_transport(task, clnt);
}

/*
 * 1.   Reserve an RPC call slot
 */
static void
call_reserve(struct rpc_task *task)
{
        task->tk_status  = 0;
        task->tk_action  = call_reserveresult;
        xprt_reserve(task);
}

static void call_retry_reserve(struct rpc_task *task);

/*
 * 1b.  Grok the result of xprt_reserve()
 */
static void
call_reserveresult(struct rpc_task *task)
{
        int status = task->tk_status;

        /*
         * After a call to xprt_reserve(), we must have either
         * a request slot or else an error status.
         */
        task->tk_status = 0;
        if (status >= 0) {
                if (task->tk_rqstp) {
                        task->tk_action = call_refresh;
                        return;
                }

                rpc_call_rpcerror(task, -EIO);
                return;
        }

        switch (status) {
        case -ENOMEM:
                rpc_delay(task, HZ >> 2);
                fallthrough;
        case -EAGAIN:   /* woken up; retry */
                task->tk_action = call_retry_reserve;
                return;
        default:
                rpc_call_rpcerror(task, status);
        }
}

/*
 * 1c.  Retry reserving an RPC call slot
 */
static void
call_retry_reserve(struct rpc_task *task)
{
        task->tk_status  = 0;
        task->tk_action  = call_reserveresult;
        xprt_retry_reserve(task);
}

/*
 * 2.   Bind and/or refresh the credentials
 */
static void
call_refresh(struct rpc_task *task)
{
        task->tk_action = call_refreshresult;
        task->tk_status = 0;
        task->tk_client->cl_stats->rpcauthrefresh++;
        rpcauth_refreshcred(task);
}

/*
 * 2a.  Process the results of a credential refresh
 */
static void
call_refreshresult(struct rpc_task *task)
{
        int status = task->tk_status;

        task->tk_status = 0;
        task->tk_action = call_refresh;
        switch (status) {
        case 0:
                if (rpcauth_uptodatecred(task)) {
                        task->tk_action = call_allocate;
                        return;
                }
                /* Use rate-limiting and a max number of retries if refresh
                 * had status 0 but failed to update the cred.
                 */
                fallthrough;
        case -ETIMEDOUT:
                rpc_delay(task, 3*HZ);
                fallthrough;
        case -EAGAIN:
                status = -EACCES;
                fallthrough;
        case -EKEYEXPIRED:
                if (!task->tk_cred_retry)
                        break;
                task->tk_cred_retry--;
                trace_rpc_retry_refresh_status(task);
                return;
        }
        trace_rpc_refresh_status(task);
        rpc_call_rpcerror(task, status);
}

/*
 * 2b.  Allocate the buffer. For details, see sched.c:rpc_malloc.
 *      (Note: buffer memory is freed in xprt_release).
 */
static void
call_allocate(struct rpc_task *task)
{
        const struct rpc_auth *auth = task->tk_rqstp->rq_cred->cr_auth;
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_xprt *xprt = req->rq_xprt;
        const struct rpc_procinfo *proc = task->tk_msg.rpc_proc;
        int status;

        task->tk_status = 0;
        task->tk_action = call_encode;

        if (req->rq_buffer)
                return;

        if (proc->p_proc != 0) {
                BUG_ON(proc->p_arglen == 0);
                if (proc->p_decode != NULL)
                        BUG_ON(proc->p_replen == 0);
        }

        /*
         * Calculate the size (in quads) of the RPC call
         * and reply headers, and convert both values
         * to byte sizes.
         */
        req->rq_callsize = RPC_CALLHDRSIZE + (auth->au_cslack << 1) +
                           proc->p_arglen;
        req->rq_callsize <<= 2;
        /*
         * Note: the reply buffer must at minimum allocate enough space
         * for the 'struct accepted_reply' from RFC5531.
         */
        req->rq_rcvsize = RPC_REPHDRSIZE + auth->au_rslack + \
                        max_t(size_t, proc->p_replen, 2);
        req->rq_rcvsize <<= 2;

        status = xprt->ops->buf_alloc(task);
        trace_rpc_buf_alloc(task, status);
        if (status == 0)
                return;
        if (status != -ENOMEM) {
                rpc_call_rpcerror(task, status);
                return;
        }

        if (RPC_IS_ASYNC(task) || !fatal_signal_pending(current)) {
                task->tk_action = call_allocate;
                rpc_delay(task, HZ>>4);
                return;
        }

        rpc_call_rpcerror(task, -ERESTARTSYS);
}

static int
rpc_task_need_encode(struct rpc_task *task)
{
        return test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate) == 0 &&
                (!(task->tk_flags & RPC_TASK_SENT) ||
                 !(task->tk_flags & RPC_TASK_NO_RETRANS_TIMEOUT) ||
                 xprt_request_need_retransmit(task));
}

static void
rpc_xdr_encode(struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;
        struct xdr_stream xdr;

        xdr_buf_init(&req->rq_snd_buf,
                     req->rq_buffer,
                     req->rq_callsize);
        xdr_buf_init(&req->rq_rcv_buf,
                     req->rq_rbuffer,
                     req->rq_rcvsize);

        req->rq_reply_bytes_recvd = 0;
        req->rq_snd_buf.head[0].iov_len = 0;
        xdr_init_encode(&xdr, &req->rq_snd_buf,
                        req->rq_snd_buf.head[0].iov_base, req);
        xdr_free_bvec(&req->rq_snd_buf);
        if (rpc_encode_header(task, &xdr))
                return;

        task->tk_status = rpcauth_wrap_req(task, &xdr);
}

/*
 * 3.   Encode arguments of an RPC call
 */
static void
call_encode(struct rpc_task *task)
{
        if (!rpc_task_need_encode(task))
                goto out;

        /* Dequeue task from the receive queue while we're encoding */
        xprt_request_dequeue_xprt(task);
        /* Encode here so that rpcsec_gss can use correct sequence number. */
        rpc_xdr_encode(task);
        /* Did the encode result in an error condition? */
        if (task->tk_status != 0) {
                /* Was the error nonfatal? */
                switch (task->tk_status) {
                case -EAGAIN:
                case -ENOMEM:
                        rpc_delay(task, HZ >> 4);
                        break;
                case -EKEYEXPIRED:
                        if (!task->tk_cred_retry) {
                                rpc_exit(task, task->tk_status);
                        } else {
                                task->tk_action = call_refresh;
                                task->tk_cred_retry--;
                                trace_rpc_retry_refresh_status(task);
                        }
                        break;
                default:
                        rpc_call_rpcerror(task, task->tk_status);
                }
                return;
        }

        /* Add task to reply queue before transmission to avoid races */
        if (rpc_reply_expected(task))
                xprt_request_enqueue_receive(task);
        xprt_request_enqueue_transmit(task);
out:
        task->tk_action = call_transmit;
        /* Check that the connection is OK */
        if (!xprt_bound(task->tk_xprt))
                task->tk_action = call_bind;
        else if (!xprt_connected(task->tk_xprt))
                task->tk_action = call_connect;
}

/*
 * Helpers to check if the task was already transmitted, and
 * to take action when that is the case.
 */
static bool
rpc_task_transmitted(struct rpc_task *task)
{
        return !test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate);
}

static void
rpc_task_handle_transmitted(struct rpc_task *task)
{
        xprt_end_transmit(task);
        task->tk_action = call_transmit_status;
}

/*
 * 4.   Get the server port number if not yet set
 */
static void
call_bind(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;

        if (rpc_task_transmitted(task)) {
                rpc_task_handle_transmitted(task);
                return;
        }

        if (xprt_bound(xprt)) {
                task->tk_action = call_connect;
                return;
        }

        task->tk_action = call_bind_status;
        if (!xprt_prepare_transmit(task))
                return;

        xprt->ops->rpcbind(task);
}

/*
 * 4a.  Sort out bind result
 */
static void
call_bind_status(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;
        int status = -EIO;

        if (rpc_task_transmitted(task)) {
                rpc_task_handle_transmitted(task);
                return;
        }

        if (task->tk_status >= 0)
                goto out_next;
        if (xprt_bound(xprt)) {
                task->tk_status = 0;
                goto out_next;
        }

        switch (task->tk_status) {
        case -ENOMEM:
                rpc_delay(task, HZ >> 2);
                goto retry_timeout;
        case -EACCES:
                trace_rpcb_prog_unavail_err(task);
                /* fail immediately if this is an RPC ping */
                if (task->tk_msg.rpc_proc->p_proc == 0) {
                        status = -EOPNOTSUPP;
                        break;
                }
                if (task->tk_rebind_retry == 0)
                        break;
                task->tk_rebind_retry--;
                rpc_delay(task, 3*HZ);
                goto retry_timeout;
        case -ENOBUFS:
                rpc_delay(task, HZ >> 2);
                goto retry_timeout;
        case -EAGAIN:
                goto retry_timeout;
        case -ETIMEDOUT:
                trace_rpcb_timeout_err(task);
                goto retry_timeout;
        case -EPFNOSUPPORT:
                /* server doesn't support any rpcbind version we know of */
                trace_rpcb_bind_version_err(task);
                break;
        case -EPROTONOSUPPORT:
                trace_rpcb_bind_version_err(task);
                goto retry_timeout;
        case -ECONNREFUSED:             /* connection problems */
        case -ECONNRESET:
        case -ECONNABORTED:
        case -ENOTCONN:
        case -EHOSTDOWN:
        case -ENETDOWN:
        case -EHOSTUNREACH:
        case -ENETUNREACH:
        case -EPIPE:
                trace_rpcb_unreachable_err(task);
                if (!RPC_IS_SOFTCONN(task)) {
                        rpc_delay(task, 5*HZ);
                        goto retry_timeout;
                }
                status = task->tk_status;
                break;
        default:
                trace_rpcb_unrecognized_err(task);
        }

        rpc_call_rpcerror(task, status);
        return;
out_next:
        task->tk_action = call_connect;
        return;
retry_timeout:
        task->tk_status = 0;
        task->tk_action = call_bind;
        rpc_check_timeout(task);
}

/*
 * 4b.  Connect to the RPC server
 */
static void
call_connect(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;

        if (rpc_task_transmitted(task)) {
                rpc_task_handle_transmitted(task);
                return;
        }

        if (xprt_connected(xprt)) {
                task->tk_action = call_transmit;
                return;
        }

        task->tk_action = call_connect_status;
        if (task->tk_status < 0)
                return;
        if (task->tk_flags & RPC_TASK_NOCONNECT) {
                rpc_call_rpcerror(task, -ENOTCONN);
                return;
        }
        if (!xprt_prepare_transmit(task))
                return;
        xprt_connect(task);
}

/*
 * 4c.  Sort out connect result
 */
static void
call_connect_status(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;
        struct rpc_clnt *clnt = task->tk_client;
        int status = task->tk_status;

        if (rpc_task_transmitted(task)) {
                rpc_task_handle_transmitted(task);
                return;
        }

        trace_rpc_connect_status(task);

        if (task->tk_status == 0) {
                clnt->cl_stats->netreconn++;
                goto out_next;
        }
        if (xprt_connected(xprt)) {
                task->tk_status = 0;
                goto out_next;
        }

        task->tk_status = 0;
        switch (status) {
        case -ECONNREFUSED:
                /* A positive refusal suggests a rebind is needed. */
                if (RPC_IS_SOFTCONN(task))
                        break;
                if (clnt->cl_autobind) {
                        rpc_force_rebind(clnt);
                        goto out_retry;
                }
                fallthrough;
        case -ECONNRESET:
        case -ECONNABORTED:
        case -ENETDOWN:
        case -ENETUNREACH:
        case -EHOSTUNREACH:
        case -EPIPE:
        case -EPROTO:
                xprt_conditional_disconnect(task->tk_rqstp->rq_xprt,
                                            task->tk_rqstp->rq_connect_cookie);
                if (RPC_IS_SOFTCONN(task))
                        break;
                /* retry with existing socket, after a delay */
                rpc_delay(task, 3*HZ);
                fallthrough;
        case -EADDRINUSE:
        case -ENOTCONN:
        case -EAGAIN:
        case -ETIMEDOUT:
                if (!(task->tk_flags & RPC_TASK_NO_ROUND_ROBIN) &&
                    (task->tk_flags & RPC_TASK_MOVEABLE) &&
                    test_bit(XPRT_REMOVE, &xprt->state)) {
                        struct rpc_xprt *saved = task->tk_xprt;
                        struct rpc_xprt_switch *xps;

                        rcu_read_lock();
                        xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
                        rcu_read_unlock();
                        if (xps->xps_nxprts > 1) {
                                long value;

                                xprt_release(task);
                                value = atomic_long_dec_return(&xprt->queuelen);
                                if (value == 0)
                                        rpc_xprt_switch_remove_xprt(xps, saved);
                                xprt_put(saved);
                                task->tk_xprt = NULL;
                                task->tk_action = call_start;
                        }
                        xprt_switch_put(xps);
                        if (!task->tk_xprt)
                                return;
                }
                goto out_retry;
        case -ENOBUFS:
                rpc_delay(task, HZ >> 2);
                goto out_retry;
        }
        rpc_call_rpcerror(task, status);
        return;
out_next:
        task->tk_action = call_transmit;
        return;
out_retry:
        /* Check for timeouts before looping back to call_bind */
        task->tk_action = call_bind;
        rpc_check_timeout(task);
}

/*
 * 5.   Transmit the RPC request, and wait for reply
 */
static void
call_transmit(struct rpc_task *task)
{
        if (rpc_task_transmitted(task)) {
                rpc_task_handle_transmitted(task);
                return;
        }

        task->tk_action = call_transmit_status;
        if (!xprt_prepare_transmit(task))
                return;
        task->tk_status = 0;
        if (test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate)) {
                if (!xprt_connected(task->tk_xprt)) {
                        task->tk_status = -ENOTCONN;
                        return;
                }
                xprt_transmit(task);
        }
        xprt_end_transmit(task);
}

/*
 * 5a.  Handle cleanup after a transmission
 */
static void
call_transmit_status(struct rpc_task *task)
{
        task->tk_action = call_status;

        /*
         * Common case: success.  Force the compiler to put this
         * test first.
         */
        if (rpc_task_transmitted(task)) {
                task->tk_status = 0;
                xprt_request_wait_receive(task);
                return;
        }

        switch (task->tk_status) {
        default:
                break;
        case -EBADMSG:
                task->tk_status = 0;
                task->tk_action = call_encode;
                break;
                /*
                 * Special cases: if we've been waiting on the
                 * socket's write_space() callback, or if the
                 * socket just returned a connection error,
                 * then hold onto the transport lock.
                 */
        case -ENOBUFS:
                rpc_delay(task, HZ>>2);
                fallthrough;
        case -EBADSLT:
        case -EAGAIN:
                task->tk_action = call_transmit;
                task->tk_status = 0;
                break;
        case -ECONNREFUSED:
        case -EHOSTDOWN:
        case -ENETDOWN:
        case -EHOSTUNREACH:
        case -ENETUNREACH:
        case -EPERM:
                if (RPC_IS_SOFTCONN(task)) {
                        if (!task->tk_msg.rpc_proc->p_proc)
                                trace_xprt_ping(task->tk_xprt,
                                                task->tk_status);
                        rpc_call_rpcerror(task, task->tk_status);
                        return;
                }
                fallthrough;
        case -ECONNRESET:
        case -ECONNABORTED:
        case -EADDRINUSE:
        case -ENOTCONN:
        case -EPIPE:
                task->tk_action = call_bind;
                task->tk_status = 0;
                break;
        }
        rpc_check_timeout(task);
}

#if defined(CONFIG_SUNRPC_BACKCHANNEL)
static void call_bc_transmit(struct rpc_task *task);
static void call_bc_transmit_status(struct rpc_task *task);

static void
call_bc_encode(struct rpc_task *task)
{
        xprt_request_enqueue_transmit(task);
        task->tk_action = call_bc_transmit;
}

/*
 * 5b.  Send the backchannel RPC reply.  On error, drop the reply.  In
 * addition, disconnect on connectivity errors.
 */
static void
call_bc_transmit(struct rpc_task *task)
{
        task->tk_action = call_bc_transmit_status;
        if (test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate)) {
                if (!xprt_prepare_transmit(task))
                        return;
                task->tk_status = 0;
                xprt_transmit(task);
        }
        xprt_end_transmit(task);
}

static void
call_bc_transmit_status(struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;

        if (rpc_task_transmitted(task))
                task->tk_status = 0;

        switch (task->tk_status) {
        case 0:
                /* Success */
        case -ENETDOWN:
        case -EHOSTDOWN:
        case -EHOSTUNREACH:
        case -ENETUNREACH:
        case -ECONNRESET:
        case -ECONNREFUSED:
        case -EADDRINUSE:
        case -ENOTCONN:
        case -EPIPE:
                break;
        case -ENOBUFS:
                rpc_delay(task, HZ>>2);
                fallthrough;
        case -EBADSLT:
        case -EAGAIN:
                task->tk_status = 0;
                task->tk_action = call_bc_transmit;
                return;
        case -ETIMEDOUT:
                /*
                 * Problem reaching the server.  Disconnect and let the
                 * forechannel reestablish the connection.  The server will
                 * have to retransmit the backchannel request and we'll
                 * reprocess it.  Since these ops are idempotent, there's no
                 * need to cache our reply at this time.
                 */
                printk(KERN_NOTICE "RPC: Could not send backchannel reply "
                        "error: %d\n", task->tk_status);
                xprt_conditional_disconnect(req->rq_xprt,
                        req->rq_connect_cookie);
                break;
        default:
                /*
                 * We were unable to reply and will have to drop the
                 * request.  The server should reconnect and retransmit.
                 */
                printk(KERN_NOTICE "RPC: Could not send backchannel reply "
                        "error: %d\n", task->tk_status);
                break;
        }
        task->tk_action = rpc_exit_task;
}
#endif /* CONFIG_SUNRPC_BACKCHANNEL */

/*
 * 6.   Sort out the RPC call status
 */
static void
call_status(struct rpc_task *task)
{
        struct rpc_clnt *clnt = task->tk_client;
        int             status;

        if (!task->tk_msg.rpc_proc->p_proc)
                trace_xprt_ping(task->tk_xprt, task->tk_status);

        status = task->tk_status;
        if (status >= 0) {
                task->tk_action = call_decode;
                return;
        }

        trace_rpc_call_status(task);
        task->tk_status = 0;
        switch(status) {
        case -EHOSTDOWN:
        case -ENETDOWN:
        case -EHOSTUNREACH:
        case -ENETUNREACH:
        case -EPERM:
                if (RPC_IS_SOFTCONN(task))
                        goto out_exit;
                /*
                 * Delay any retries for 3 seconds, then handle as if it
                 * were a timeout.
                 */
                rpc_delay(task, 3*HZ);
                fallthrough;
        case -ETIMEDOUT:
                break;
        case -ECONNREFUSED:
        case -ECONNRESET:
        case -ECONNABORTED:
        case -ENOTCONN:
                rpc_force_rebind(clnt);
                break;
        case -EADDRINUSE:
                rpc_delay(task, 3*HZ);
                fallthrough;
        case -EPIPE:
        case -EAGAIN:
                break;
        case -EIO:
                /* shutdown or soft timeout */
                goto out_exit;
        default:
                if (clnt->cl_chatty)
                        printk("%s: RPC call returned error %d\n",
                               clnt->cl_program->name, -status);
                goto out_exit;
        }
        task->tk_action = call_encode;
        if (status != -ECONNRESET && status != -ECONNABORTED)
                rpc_check_timeout(task);
        return;
out_exit:
        rpc_call_rpcerror(task, status);
}

static bool
rpc_check_connected(const struct rpc_rqst *req)
{
        /* No allocated request or transport? return true */
        if (!req || !req->rq_xprt)
                return true;
        return xprt_connected(req->rq_xprt);
}

static void
rpc_check_timeout(struct rpc_task *task)
{
        struct rpc_clnt *clnt = task->tk_client;

        if (RPC_SIGNALLED(task)) {
                rpc_call_rpcerror(task, -ERESTARTSYS);
                return;
        }

        if (xprt_adjust_timeout(task->tk_rqstp) == 0)
                return;

        trace_rpc_timeout_status(task);
        task->tk_timeouts++;

        if (RPC_IS_SOFTCONN(task) && !rpc_check_connected(task->tk_rqstp)) {
                rpc_call_rpcerror(task, -ETIMEDOUT);
                return;
        }

        if (RPC_IS_SOFT(task)) {
                /*
                 * Once a "no retrans timeout" soft tasks (a.k.a NFSv4) has
                 * been sent, it should time out only if the transport
                 * connection gets terminally broken.
                 */
                if ((task->tk_flags & RPC_TASK_NO_RETRANS_TIMEOUT) &&
                    rpc_check_connected(task->tk_rqstp))
                        return;

                if (clnt->cl_chatty) {
                        pr_notice_ratelimited(
                                "%s: server %s not responding, timed out\n",
                                clnt->cl_program->name,
                                task->tk_xprt->servername);
                }
                if (task->tk_flags & RPC_TASK_TIMEOUT)
                        rpc_call_rpcerror(task, -ETIMEDOUT);
                else
                        __rpc_call_rpcerror(task, -EIO, -ETIMEDOUT);
                return;
        }

        if (!(task->tk_flags & RPC_CALL_MAJORSEEN)) {
                task->tk_flags |= RPC_CALL_MAJORSEEN;
                if (clnt->cl_chatty) {
                        pr_notice_ratelimited(
                                "%s: server %s not responding, still trying\n",
                                clnt->cl_program->name,
                                task->tk_xprt->servername);
                }
        }
        rpc_force_rebind(clnt);
        /*
         * Did our request time out due to an RPCSEC_GSS out-of-sequence
         * event? RFC2203 requires the server to drop all such requests.
         */
        rpcauth_invalcred(task);
}

/*
 * 7.   Decode the RPC reply
 */
static void
call_decode(struct rpc_task *task)
{
        struct rpc_clnt *clnt = task->tk_client;
        struct rpc_rqst *req = task->tk_rqstp;
        struct xdr_stream xdr;
        int err;

        if (!task->tk_msg.rpc_proc->p_decode) {
                task->tk_action = rpc_exit_task;
                return;
        }

        if (task->tk_flags & RPC_CALL_MAJORSEEN) {
                if (clnt->cl_chatty) {
                        pr_notice_ratelimited("%s: server %s OK\n",
                                clnt->cl_program->name,
                                task->tk_xprt->servername);
                }
                task->tk_flags &= ~RPC_CALL_MAJORSEEN;
        }

        /*
         * Did we ever call xprt_complete_rqst()? If not, we should assume
         * the message is incomplete.
         */
        err = -EAGAIN;
        if (!req->rq_reply_bytes_recvd)
                goto out;

        /* Ensure that we see all writes made by xprt_complete_rqst()
         * before it changed req->rq_reply_bytes_recvd.
         */
        smp_rmb();

        req->rq_rcv_buf.len = req->rq_private_buf.len;
        trace_rpc_xdr_recvfrom(task, &req->rq_rcv_buf);

        /* Check that the softirq receive buffer is valid */
        WARN_ON(memcmp(&req->rq_rcv_buf, &req->rq_private_buf,
                                sizeof(req->rq_rcv_buf)) != 0);

        xdr_init_decode(&xdr, &req->rq_rcv_buf,
                        req->rq_rcv_buf.head[0].iov_base, req);
        err = rpc_decode_header(task, &xdr);
out:
        switch (err) {
        case 0:
                task->tk_action = rpc_exit_task;
                task->tk_status = rpcauth_unwrap_resp(task, &xdr);
                return;
        case -EAGAIN:
                task->tk_status = 0;
                if (task->tk_client->cl_discrtry)
                        xprt_conditional_disconnect(req->rq_xprt,
                                                    req->rq_connect_cookie);
                task->tk_action = call_encode;
                rpc_check_timeout(task);
                break;
        case -EKEYREJECTED:
                task->tk_action = call_reserve;
                rpc_check_timeout(task);
                rpcauth_invalcred(task);
                /* Ensure we obtain a new XID if we retry! */
                xprt_release(task);
        }
}

static int
rpc_encode_header(struct rpc_task *task, struct xdr_stream *xdr)
{
        struct rpc_clnt *clnt = task->tk_client;
        struct rpc_rqst *req = task->tk_rqstp;
        __be32 *p;
        int error;

        error = -EMSGSIZE;
        p = xdr_reserve_space(xdr, RPC_CALLHDRSIZE << 2);
        if (!p)
                goto out_fail;
        *p++ = req->rq_xid;
        *p++ = rpc_call;
        *p++ = cpu_to_be32(RPC_VERSION);
        *p++ = cpu_to_be32(clnt->cl_prog);
        *p++ = cpu_to_be32(clnt->cl_vers);
        *p   = cpu_to_be32(task->tk_msg.rpc_proc->p_proc);

        error = rpcauth_marshcred(task, xdr);
        if (error < 0)
                goto out_fail;
        return 0;
out_fail:
        trace_rpc_bad_callhdr(task);
        rpc_call_rpcerror(task, error);
        return error;
}

static noinline int
rpc_decode_header(struct rpc_task *task, struct xdr_stream *xdr)
{
        struct rpc_clnt *clnt = task->tk_client;
        int error;
        __be32 *p;

        /* RFC-1014 says that the representation of XDR data must be a
         * multiple of four bytes
         * - if it isn't pointer subtraction in the NFS client may give
         *   undefined results
         */
        if (task->tk_rqstp->rq_rcv_buf.len & 3)
                goto out_unparsable;

        p = xdr_inline_decode(xdr, 3 * sizeof(*p));
        if (!p)
                goto out_unparsable;
        p++;    /* skip XID */
        if (*p++ != rpc_reply)
                goto out_unparsable;
        if (*p++ != rpc_msg_accepted)
                goto out_msg_denied;

        error = rpcauth_checkverf(task, xdr);
        if (error)
                goto out_verifier;

        p = xdr_inline_decode(xdr, sizeof(*p));
        if (!p)
                goto out_unparsable;
        switch (*p) {
        case rpc_success:
                return 0;
        case rpc_prog_unavail:
                trace_rpc__prog_unavail(task);
                error = -EPFNOSUPPORT;
                goto out_err;
        case rpc_prog_mismatch:
                trace_rpc__prog_mismatch(task);
                error = -EPROTONOSUPPORT;
                goto out_err;
        case rpc_proc_unavail:
                trace_rpc__proc_unavail(task);
                error = -EOPNOTSUPP;
                goto out_err;
        case rpc_garbage_args:
        case rpc_system_err:
                trace_rpc__garbage_args(task);
                error = -EIO;
                break;
        default:
                goto out_unparsable;
        }

out_garbage:
        clnt->cl_stats->rpcgarbage++;
        if (task->tk_garb_retry) {
                task->tk_garb_retry--;
                task->tk_action = call_encode;
                return -EAGAIN;
        }
out_err:
        rpc_call_rpcerror(task, error);
        return error;

out_unparsable:
        trace_rpc__unparsable(task);
        error = -EIO;
        goto out_garbage;

out_verifier:
        trace_rpc_bad_verifier(task);
        goto out_garbage;

out_msg_denied:
        error = -EACCES;
        p = xdr_inline_decode(xdr, sizeof(*p));
        if (!p)
                goto out_unparsable;
        switch (*p++) {
        case rpc_auth_error:
                break;
        case rpc_mismatch:
                trace_rpc__mismatch(task);
                error = -EPROTONOSUPPORT;
                goto out_err;
        default:
                goto out_unparsable;
        }

        p = xdr_inline_decode(xdr, sizeof(*p));
        if (!p)
                goto out_unparsable;
        switch (*p++) {
        case rpc_autherr_rejectedcred:
        case rpc_autherr_rejectedverf:
        case rpcsec_gsserr_credproblem:
        case rpcsec_gsserr_ctxproblem:
                if (!task->tk_cred_retry)
                        break;
                task->tk_cred_retry--;
                trace_rpc__stale_creds(task);
                return -EKEYREJECTED;
        case rpc_autherr_badcred:
        case rpc_autherr_badverf:
                /* possibly garbled cred/verf? */
                if (!task->tk_garb_retry)
                        break;
                task->tk_garb_retry--;
                trace_rpc__bad_creds(task);
                task->tk_action = call_encode;
                return -EAGAIN;
        case rpc_autherr_tooweak:
                trace_rpc__auth_tooweak(task);
                pr_warn("RPC: server %s requires stronger authentication.\n",
                        task->tk_xprt->servername);
                break;
        default:
                goto out_unparsable;
        }
        goto out_err;
}

static void rpcproc_encode_null(struct rpc_rqst *rqstp, struct xdr_stream *xdr,
                const void *obj)
{
}

static int rpcproc_decode_null(struct rpc_rqst *rqstp, struct xdr_stream *xdr,
                void *obj)
{
        return 0;
}

static const struct rpc_procinfo rpcproc_null = {
        .p_encode = rpcproc_encode_null,
        .p_decode = rpcproc_decode_null,
};

static void
rpc_null_call_prepare(struct rpc_task *task, void *data)
{
        task->tk_flags &= ~RPC_TASK_NO_RETRANS_TIMEOUT;
        rpc_call_start(task);
}

static const struct rpc_call_ops rpc_null_ops = {
        .rpc_call_prepare = rpc_null_call_prepare,
        .rpc_call_done = rpc_default_callback,
};

static
struct rpc_task *rpc_call_null_helper(struct rpc_clnt *clnt,
                struct rpc_xprt *xprt, struct rpc_cred *cred, int flags,
                const struct rpc_call_ops *ops, void *data)
{
        struct rpc_message msg = {
                .rpc_proc = &rpcproc_null,
        };
        struct rpc_task_setup task_setup_data = {
                .rpc_client = clnt,
                .rpc_xprt = xprt,
                .rpc_message = &msg,
                .rpc_op_cred = cred,
                .callback_ops = ops ?: &rpc_null_ops,
                .callback_data = data,
                .flags = flags | RPC_TASK_SOFT | RPC_TASK_SOFTCONN |
                         RPC_TASK_NULLCREDS,
        };

        return rpc_run_task(&task_setup_data);
}

struct rpc_task *rpc_call_null(struct rpc_clnt *clnt, struct rpc_cred *cred, int flags)
{
        return rpc_call_null_helper(clnt, NULL, cred, flags, NULL, NULL);
}
EXPORT_SYMBOL_GPL(rpc_call_null);

static int rpc_ping(struct rpc_clnt *clnt)
{
        struct rpc_task *task;
        int status;

        task = rpc_call_null_helper(clnt, NULL, NULL, 0, NULL, NULL);
        if (IS_ERR(task))
                return PTR_ERR(task);
        status = task->tk_status;
        rpc_put_task(task);
        return status;
}

struct rpc_cb_add_xprt_calldata {
        struct rpc_xprt_switch *xps;
        struct rpc_xprt *xprt;
};

static void rpc_cb_add_xprt_done(struct rpc_task *task, void *calldata)
{
        struct rpc_cb_add_xprt_calldata *data = calldata;

        if (task->tk_status == 0)
                rpc_xprt_switch_add_xprt(data->xps, data->xprt);
}

static void rpc_cb_add_xprt_release(void *calldata)
{
        struct rpc_cb_add_xprt_calldata *data = calldata;

        xprt_put(data->xprt);
        xprt_switch_put(data->xps);
        kfree(data);
}

static const struct rpc_call_ops rpc_cb_add_xprt_call_ops = {
        .rpc_call_prepare = rpc_null_call_prepare,
        .rpc_call_done = rpc_cb_add_xprt_done,
        .rpc_release = rpc_cb_add_xprt_release,
};

/**
 * rpc_clnt_test_and_add_xprt - Test and add a new transport to a rpc_clnt
 * @clnt: pointer to struct rpc_clnt
 * @xps: pointer to struct rpc_xprt_switch,
 * @xprt: pointer struct rpc_xprt
 * @dummy: unused
 */
int rpc_clnt_test_and_add_xprt(struct rpc_clnt *clnt,
                struct rpc_xprt_switch *xps, struct rpc_xprt *xprt,
                void *dummy)
{
        struct rpc_cb_add_xprt_calldata *data;
        struct rpc_task *task;

        if (xps->xps_nunique_destaddr_xprts + 1 > clnt->cl_max_connect) {
                rcu_read_lock();
                pr_warn("SUNRPC: reached max allowed number (%d) did not add "
                        "transport to server: %s\n", clnt->cl_max_connect,
                        rpc_peeraddr2str(clnt, RPC_DISPLAY_ADDR));
                rcu_read_unlock();
                return -EINVAL;
        }

        data = kmalloc(sizeof(*data), GFP_NOFS);
        if (!data)
                return -ENOMEM;
        data->xps = xprt_switch_get(xps);
        data->xprt = xprt_get(xprt);
        if (rpc_xprt_switch_has_addr(data->xps, (struct sockaddr *)&xprt->addr)) {
                rpc_cb_add_xprt_release(data);
                goto success;
        }

        task = rpc_call_null_helper(clnt, xprt, NULL, RPC_TASK_ASYNC,
                        &rpc_cb_add_xprt_call_ops, data);
        data->xps->xps_nunique_destaddr_xprts++;
        rpc_put_task(task);
success:
        return 1;
}
EXPORT_SYMBOL_GPL(rpc_clnt_test_and_add_xprt);

/**
 * rpc_clnt_setup_test_and_add_xprt()
 *
 * This is an rpc_clnt_add_xprt setup() function which returns 1 so:
 *   1) caller of the test function must dereference the rpc_xprt_switch
 *   and the rpc_xprt.
 *   2) test function must call rpc_xprt_switch_add_xprt, usually in
 *   the rpc_call_done routine.
 *
 * Upon success (return of 1), the test function adds the new
 * transport to the rpc_clnt xprt switch
 *
 * @clnt: struct rpc_clnt to get the new transport
 * @xps:  the rpc_xprt_switch to hold the new transport
 * @xprt: the rpc_xprt to test
 * @data: a struct rpc_add_xprt_test pointer that holds the test function
 *        and test function call data
 */
int rpc_clnt_setup_test_and_add_xprt(struct rpc_clnt *clnt,
                                     struct rpc_xprt_switch *xps,
                                     struct rpc_xprt *xprt,
                                     void *data)
{
        struct rpc_task *task;
        struct rpc_add_xprt_test *xtest = (struct rpc_add_xprt_test *)data;
        int status = -EADDRINUSE;

        xprt = xprt_get(xprt);
        xprt_switch_get(xps);

        if (rpc_xprt_switch_has_addr(xps, (struct sockaddr *)&xprt->addr))
                goto out_err;

        /* Test the connection */
        task = rpc_call_null_helper(clnt, xprt, NULL, 0, NULL, NULL);
        if (IS_ERR(task)) {
                status = PTR_ERR(task);
                goto out_err;
        }
        status = task->tk_status;
        rpc_put_task(task);

        if (status < 0)
                goto out_err;

        /* rpc_xprt_switch and rpc_xprt are deferrenced by add_xprt_test() */
        xtest->add_xprt_test(clnt, xprt, xtest->data);

        xprt_put(xprt);
        xprt_switch_put(xps);

        /* so that rpc_clnt_add_xprt does not call rpc_xprt_switch_add_xprt */
        return 1;
out_err:
        xprt_put(xprt);
        xprt_switch_put(xps);
        pr_info("RPC:   rpc_clnt_test_xprt failed: %d addr %s not added\n",
                status, xprt->address_strings[RPC_DISPLAY_ADDR]);
        return status;
}
EXPORT_SYMBOL_GPL(rpc_clnt_setup_test_and_add_xprt);

/**
 * rpc_clnt_add_xprt - Add a new transport to a rpc_clnt
 * @clnt: pointer to struct rpc_clnt
 * @xprtargs: pointer to struct xprt_create
 * @setup: callback to test and/or set up the connection
 * @data: pointer to setup function data
 *
 * Creates a new transport using the parameters set in args and
 * adds it to clnt.
 * If ping is set, then test that connectivity succeeds before
 * adding the new transport.
 *
 */
int rpc_clnt_add_xprt(struct rpc_clnt *clnt,
                struct xprt_create *xprtargs,
                int (*setup)(struct rpc_clnt *,
                        struct rpc_xprt_switch *,
                        struct rpc_xprt *,
                        void *),
                void *data)
{
        struct rpc_xprt_switch *xps;
        struct rpc_xprt *xprt;
        unsigned long connect_timeout;
        unsigned long reconnect_timeout;
        unsigned char resvport, reuseport;
        int ret = 0, ident;

        rcu_read_lock();
        xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
        xprt = xprt_iter_xprt(&clnt->cl_xpi);
        if (xps == NULL || xprt == NULL) {
                rcu_read_unlock();
                xprt_switch_put(xps);
                return -EAGAIN;
        }
        resvport = xprt->resvport;
        reuseport = xprt->reuseport;
        connect_timeout = xprt->connect_timeout;
        reconnect_timeout = xprt->max_reconnect_timeout;
        ident = xprt->xprt_class->ident;
        rcu_read_unlock();

        if (!xprtargs->ident)
                xprtargs->ident = ident;
        xprt = xprt_create_transport(xprtargs);
        if (IS_ERR(xprt)) {
                ret = PTR_ERR(xprt);
                goto out_put_switch;
        }
        xprt->resvport = resvport;
        xprt->reuseport = reuseport;
        if (xprt->ops->set_connect_timeout != NULL)
                xprt->ops->set_connect_timeout(xprt,
                                connect_timeout,
                                reconnect_timeout);

        rpc_xprt_switch_set_roundrobin(xps);
        if (setup) {
                ret = setup(clnt, xps, xprt, data);
                if (ret != 0)
                        goto out_put_xprt;
        }
        rpc_xprt_switch_add_xprt(xps, xprt);
out_put_xprt:
        xprt_put(xprt);
out_put_switch:
        xprt_switch_put(xps);
        return ret;
}
EXPORT_SYMBOL_GPL(rpc_clnt_add_xprt);

struct connect_timeout_data {
        unsigned long connect_timeout;
        unsigned long reconnect_timeout;
};

static int
rpc_xprt_set_connect_timeout(struct rpc_clnt *clnt,
                struct rpc_xprt *xprt,
                void *data)
{
        struct connect_timeout_data *timeo = data;

        if (xprt->ops->set_connect_timeout)
                xprt->ops->set_connect_timeout(xprt,
                                timeo->connect_timeout,
                                timeo->reconnect_timeout);
        return 0;
}

void
rpc_set_connect_timeout(struct rpc_clnt *clnt,
                unsigned long connect_timeout,
                unsigned long reconnect_timeout)
{
        struct connect_timeout_data timeout = {
                .connect_timeout = connect_timeout,
                .reconnect_timeout = reconnect_timeout,
        };
        rpc_clnt_iterate_for_each_xprt(clnt,
                        rpc_xprt_set_connect_timeout,
                        &timeout);
}
EXPORT_SYMBOL_GPL(rpc_set_connect_timeout);

void rpc_clnt_xprt_switch_put(struct rpc_clnt *clnt)
{
        rcu_read_lock();
        xprt_switch_put(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(rpc_clnt_xprt_switch_put);

void rpc_clnt_xprt_switch_add_xprt(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
{
        rcu_read_lock();
        rpc_xprt_switch_add_xprt(rcu_dereference(clnt->cl_xpi.xpi_xpswitch),
                                 xprt);
        rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(rpc_clnt_xprt_switch_add_xprt);

bool rpc_clnt_xprt_switch_has_addr(struct rpc_clnt *clnt,
                                   const struct sockaddr *sap)
{
        struct rpc_xprt_switch *xps;
        bool ret;

        rcu_read_lock();
        xps = rcu_dereference(clnt->cl_xpi.xpi_xpswitch);
        ret = rpc_xprt_switch_has_addr(xps, sap);
        rcu_read_unlock();
        return ret;
}
EXPORT_SYMBOL_GPL(rpc_clnt_xprt_switch_has_addr);

#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
static void rpc_show_header(void)
{
        printk(KERN_INFO "-pid- flgs status -client- --rqstp- "
                "-timeout ---ops--\n");
}

static void rpc_show_task(const struct rpc_clnt *clnt,
                          const struct rpc_task *task)
{
        const char *rpc_waitq = "none";

        if (RPC_IS_QUEUED(task))
                rpc_waitq = rpc_qname(task->tk_waitqueue);

        printk(KERN_INFO "%5u %04x %6d %8p %8p %8ld %8p %sv%u %s a:%ps q:%s\n",
                task->tk_pid, task->tk_flags, task->tk_status,
                clnt, task->tk_rqstp, rpc_task_timeout(task), task->tk_ops,
                clnt->cl_program->name, clnt->cl_vers, rpc_proc_name(task),
                task->tk_action, rpc_waitq);
}

void rpc_show_tasks(struct net *net)
{
        struct rpc_clnt *clnt;
        struct rpc_task *task;
        int header = 0;
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        spin_lock(&sn->rpc_client_lock);
        list_for_each_entry(clnt, &sn->all_clients, cl_clients) {
                spin_lock(&clnt->cl_lock);
                list_for_each_entry(task, &clnt->cl_tasks, tk_task) {
                        if (!header) {
                                rpc_show_header();
                                header++;
                        }
                        rpc_show_task(clnt, task);
                }
                spin_unlock(&clnt->cl_lock);
        }
        spin_unlock(&sn->rpc_client_lock);
}
#endif

#if IS_ENABLED(CONFIG_SUNRPC_SWAP)
static int
rpc_clnt_swap_activate_callback(struct rpc_clnt *clnt,
                struct rpc_xprt *xprt,
                void *dummy)
{
        return xprt_enable_swap(xprt);
}

int
rpc_clnt_swap_activate(struct rpc_clnt *clnt)
{
        if (atomic_inc_return(&clnt->cl_swapper) == 1)
                return rpc_clnt_iterate_for_each_xprt(clnt,
                                rpc_clnt_swap_activate_callback, NULL);
        return 0;
}
EXPORT_SYMBOL_GPL(rpc_clnt_swap_activate);

static int
rpc_clnt_swap_deactivate_callback(struct rpc_clnt *clnt,
                struct rpc_xprt *xprt,
                void *dummy)
{
        xprt_disable_swap(xprt);
        return 0;
}

void
rpc_clnt_swap_deactivate(struct rpc_clnt *clnt)
{
        if (atomic_dec_if_positive(&clnt->cl_swapper) == 0)
                rpc_clnt_iterate_for_each_xprt(clnt,
                                rpc_clnt_swap_deactivate_callback, NULL);
}
EXPORT_SYMBOL_GPL(rpc_clnt_swap_deactivate);
#endif /* CONFIG_SUNRPC_SWAP */