clnt.c

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/*
 *  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 <[email protected]>
 *  Copyright (C) 1995,1996 Olaf Kirch <[email protected]>
 */


#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/utsname.h>
#include <linux/workqueue.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/un.h>
#include <linux/rcupdate.h>

#include <linux/sunrpc/clnt.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 "netns.h"

#ifdef RPC_DEBUG
# define RPCDBG_FACILITY    RPCDBG_CALL
#endif

#define dprint_status(t)                    \
    dprintk("RPC: %5u %s (status %d)\n", t->tk_pid,     \
            __func__, t->tk_status)

/*
 * 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_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);
#if defined(CONFIG_SUNRPC_BACKCHANNEL)
static void call_bc_transmit(struct rpc_task *task);
#endif /* CONFIG_SUNRPC_BACKCHANNEL */
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_timeout(struct rpc_task *task);
static void call_connect(struct rpc_task *task);
static void call_connect_status(struct rpc_task *task);

static __be32   *rpc_encode_header(struct rpc_task *task);
static __be32   *rpc_verify_header(struct rpc_task *task);
static int  rpc_ping(struct rpc_clnt *clnt);

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)
{
    if (clnt->cl_dentry) {
        if (clnt->cl_auth && clnt->cl_auth->au_ops->pipes_destroy)
            clnt->cl_auth->au_ops->pipes_destroy(clnt->cl_auth);
        rpc_remove_client_dir(clnt->cl_dentry);
    }
    clnt->cl_dentry = NULL;
}

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,
                    const char *dir_name)
{
    static uint32_t clntid;
    char name[15];
    struct qstr q = { .name = name };
    struct dentry *dir, *dentry;
    int error;

    dir = rpc_d_lookup_sb(sb, dir_name);
    if (dir == NULL)
        return dir;
    for (;;) {
        q.len = snprintf(name, sizeof(name), "clnt%x", (unsigned int)clntid++);
        name[sizeof(name) - 1] = '\0';
        q.hash = full_name_hash(q.name, q.len);
        dentry = rpc_create_client_dir(dir, &q, clnt);
        if (!IS_ERR(dentry))
            break;
        error = PTR_ERR(dentry);
        if (error != -EEXIST) {
            printk(KERN_INFO "RPC: Couldn't create pipefs entry"
                    " %s/%s, error %d\n",
                    dir_name, name, error);
            break;
        }
    }
    dput(dir);
    return dentry;
}

static int
rpc_setup_pipedir(struct rpc_clnt *clnt, const char *dir_name)
{
    struct net *net = rpc_net_ns(clnt);
    struct super_block *pipefs_sb;
    struct dentry *dentry;

    clnt->cl_dentry = NULL;
    if (dir_name == NULL)
        return 0;
    pipefs_sb = rpc_get_sb_net(net);
    if (!pipefs_sb)
        return 0;
    dentry = rpc_setup_pipedir_sb(pipefs_sb, clnt, dir_name);
    rpc_put_sb_net(net);
    if (IS_ERR(dentry))
        return PTR_ERR(dentry);
    clnt->cl_dentry = dentry;
    return 0;
}

static inline int rpc_clnt_skip_event(struct rpc_clnt *clnt, unsigned long event)
{
    if (((event == RPC_PIPEFS_MOUNT) && clnt->cl_dentry) ||
        ((event == RPC_PIPEFS_UMOUNT) && !clnt->cl_dentry))
        return 1;
    return 0;
}

static int __rpc_clnt_handle_event(struct rpc_clnt *clnt, unsigned long event,
                   struct super_block *sb)
{
    struct dentry *dentry;
    int err = 0;

    switch (event) {
    case RPC_PIPEFS_MOUNT:
        dentry = rpc_setup_pipedir_sb(sb, clnt,
                          clnt->cl_program->pipe_dir_name);
        BUG_ON(dentry == NULL);
        if (IS_ERR(dentry))
            return PTR_ERR(dentry);
        clnt->cl_dentry = dentry;
        if (clnt->cl_auth->au_ops->pipes_create) {
            err = clnt->cl_auth->au_ops->pipes_create(clnt->cl_auth);
            if (err)
                __rpc_clnt_remove_pipedir(clnt);
        }
        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 err;
}

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 (clnt->cl_program->pipe_dir_name == NULL)
            break;
        if (rpc_clnt_skip_event(clnt, event))
            continue;
        if (atomic_inc_not_zero(&clnt->cl_count) == 0)
            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);
        rpc_release_client(clnt);
        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 void rpc_clnt_set_nodename(struct rpc_clnt *clnt, const char *nodename)
{
    clnt->cl_nodelen = strlen(nodename);
    if (clnt->cl_nodelen > UNX_MAXNODENAME)
        clnt->cl_nodelen = UNX_MAXNODENAME;
    memcpy(clnt->cl_nodename, nodename, clnt->cl_nodelen);
}

static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, struct rpc_xprt *xprt)
{
    const struct rpc_program *program = args->program;
    const struct rpc_version *version;
    struct rpc_clnt     *clnt = NULL;
    struct rpc_auth     *auth;
    int err;

    /* sanity check the name before trying to print it */
    dprintk("RPC:       creating %s client for %s (xprt %p)\n",
            program->name, args->servername, xprt);

    err = rpciod_up();
    if (err)
        goto out_no_rpciod;
    err = -EINVAL;
    if (!xprt)
        goto out_no_xprt;

    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 = clnt;

    rcu_assign_pointer(clnt->cl_xprt, xprt);
    clnt->cl_procinfo = version->procs;
    clnt->cl_maxproc  = version->nrprocs;
    clnt->cl_protname = program->name;
    clnt->cl_prog     = args->prognumber ? : program->number;
    clnt->cl_vers     = version->number;
    clnt->cl_stats    = program->stats;
    clnt->cl_metrics  = rpc_alloc_iostats(clnt);
    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);

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

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

    clnt->cl_rtt = &clnt->cl_rtt_default;
    rpc_init_rtt(&clnt->cl_rtt_default, clnt->cl_timeout->to_initval);
    clnt->cl_principal = NULL;
    if (args->client_name) {
        clnt->cl_principal = kstrdup(args->client_name, GFP_KERNEL);
        if (!clnt->cl_principal)
            goto out_no_principal;
    }

    atomic_set(&clnt->cl_count, 1);

    err = rpc_setup_pipedir(clnt, program->pipe_dir_name);
    if (err < 0)
        goto out_no_path;

    auth = rpcauth_create(args->authflavor, clnt);
    if (IS_ERR(auth)) {
        printk(KERN_INFO "RPC: Couldn't create auth handle (flavor %u)\n",
                args->authflavor);
        err = PTR_ERR(auth);
        goto out_no_auth;
    }

    /* save the nodename */
    rpc_clnt_set_nodename(clnt, utsname()->nodename);
    rpc_register_client(clnt);
    return clnt;

out_no_auth:
    rpc_clnt_remove_pipedir(clnt);
out_no_path:
    kfree(clnt->cl_principal);
out_no_principal:
    rpc_free_iostats(clnt->cl_metrics);
out_no_stats:
    kfree(clnt);
out_err:
    xprt_put(xprt);
out_no_xprt:
    rpciod_down();
out_no_rpciod:
    return ERR_PTR(err);
}

struct rpc_clnt *rpc_create(struct rpc_create_args *args)
{
    struct rpc_xprt *xprt;
    struct rpc_clnt *clnt;
    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];

    /*
     * 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;

    clnt = rpc_new_client(args, xprt);
    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)
        clnt->cl_softrtry = 0;

    if (args->flags & RPC_CLNT_CREATE_AUTOBIND)
        clnt->cl_autobind = 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;
}
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 *xprt;
    struct rpc_clnt *new;
    int err;

    err = -ENOMEM;
    rcu_read_lock();
    xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
    rcu_read_unlock();
    if (xprt == NULL)
        goto out_err;
    args->servername = xprt->servername;

    new = rpc_new_client(args, xprt);
    if (IS_ERR(new)) {
        err = PTR_ERR(new);
        goto out_put;
    }

    atomic_inc(&clnt->cl_count);
    new->cl_parent = clnt;

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

out_put:
    xprt_put(xprt);
out_err:
    dprintk("RPC:       %s: returned error %d\n", __func__, err);
    return ERR_PTR(err);
}

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,
        .client_name    = clnt->cl_principal,
    };
    return __rpc_clone_client(&args, clnt);
}
EXPORT_SYMBOL_GPL(rpc_clone_client);

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,
        .client_name    = clnt->cl_principal,
    };
    return __rpc_clone_client(&args, clnt);
}
EXPORT_SYMBOL_GPL(rpc_clone_client_set_auth);

/*
 * 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;
    dprintk("RPC:       killing all tasks for client %p\n", clnt);
    /*
     * Spin lock all_tasks to prevent changes...
     */
    spin_lock(&clnt->cl_lock);
    list_for_each_entry(rovr, &clnt->cl_tasks, tk_task) {
        if (!RPC_IS_ACTIVATED(rovr))
            continue;
        if (!(rovr->tk_flags & RPC_TASK_KILLED)) {
            rovr->tk_flags |= RPC_TASK_KILLED;
            rpc_exit(rovr, -EIO);
            if (RPC_IS_QUEUED(rovr))
                rpc_wake_up_queued_task(rovr->tk_waitqueue,
                            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)
{
    dprintk_rcu("RPC:       shutting down %s client for %s\n",
            clnt->cl_protname,
            rcu_dereference(clnt->cl_xprt)->servername);

    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(struct rpc_clnt *clnt)
{
    dprintk_rcu("RPC:       destroying %s client for %s\n",
            clnt->cl_protname,
            rcu_dereference(clnt->cl_xprt)->servername);
    if (clnt->cl_parent != clnt)
        rpc_release_client(clnt->cl_parent);
    rpc_unregister_client(clnt);
    rpc_clnt_remove_pipedir(clnt);
    rpc_free_iostats(clnt->cl_metrics);
    kfree(clnt->cl_principal);
    clnt->cl_metrics = NULL;
    xprt_put(rcu_dereference_raw(clnt->cl_xprt));
    rpciod_down();
    kfree(clnt);
}

/*
 * Free an RPC client
 */
static void
rpc_free_auth(struct rpc_clnt *clnt)
{
    if (clnt->cl_auth == NULL) {
        rpc_free_client(clnt);
        return;
    }

    /*
     * 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.
     */
    atomic_inc(&clnt->cl_count);
    rpcauth_release(clnt->cl_auth);
    clnt->cl_auth = NULL;
    if (atomic_dec_and_test(&clnt->cl_count))
        rpc_free_client(clnt);
}

/*
 * Release reference to the RPC client
 */
void
rpc_release_client(struct rpc_clnt *clnt)
{
    dprintk("RPC:       rpc_release_client(%p)\n", clnt);

    if (list_empty(&clnt->cl_tasks))
        wake_up(&destroy_wait);
    if (atomic_dec_and_test(&clnt->cl_count))
        rpc_free_auth(clnt);
}

struct rpc_clnt *rpc_bind_new_program(struct rpc_clnt *old,
                      const struct rpc_program *program,
                      u32 vers)
{
    struct rpc_clnt *clnt;
    const struct rpc_version *version;
    int err;

    BUG_ON(vers >= program->nrvers || !program->version[vers]);
    version = program->version[vers];
    clnt = rpc_clone_client(old);
    if (IS_ERR(clnt))
        goto out;
    clnt->cl_procinfo = version->procs;
    clnt->cl_maxproc  = version->nrprocs;
    clnt->cl_protname = program->name;
    clnt->cl_prog     = program->number;
    clnt->cl_vers     = version->number;
    clnt->cl_stats    = program->stats;
    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);

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

    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
void rpc_task_set_client(struct rpc_task *task, struct rpc_clnt *clnt)
{
    if (clnt != NULL) {
        rpc_task_release_client(task);
        task->tk_client = clnt;
        atomic_inc(&clnt->cl_count);
        if (clnt->cl_softrtry)
            task->tk_flags |= RPC_TASK_SOFT;
        if (sk_memalloc_socks()) {
            struct rpc_xprt *xprt;

            rcu_read_lock();
            xprt = rcu_dereference(clnt->cl_xprt);
            if (xprt->swapper)
                task->tk_flags |= RPC_TASK_SWAPPER;
            rcu_read_unlock();
        }
        /* 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);
    }
}

void rpc_task_reset_client(struct rpc_task *task, struct rpc_clnt *clnt)
{
    rpc_task_release_client(task);
    rpc_task_set_client(task, clnt);
}
EXPORT_SYMBOL_GPL(rpc_task_reset_client);


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;
        if (msg->rpc_cred != NULL)
            task->tk_msg.rpc_cred = get_rpccred(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,
};

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 (IS_ERR(task))
        goto out;

    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);
out:
    return task;
}
EXPORT_SYMBOL_GPL(rpc_run_task);

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;

    BUG_ON(flags & RPC_TASK_ASYNC);

    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);

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)

struct rpc_task *rpc_run_bc_task(struct rpc_rqst *req,
                const struct rpc_call_ops *tk_ops)
{
    struct rpc_task *task;
    struct xdr_buf *xbufp = &req->rq_snd_buf;
    struct rpc_task_setup task_setup_data = {
        .callback_ops = tk_ops,
    };

    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);
    if (IS_ERR(task)) {
        xprt_free_bc_request(req);
        goto out;
    }
    task->tk_rqstp = req;

    /*
     * Set up the xdr_buf length.
     * This also indicates that the buffer is XDR encoded already.
     */
    xbufp->len = xbufp->head[0].iov_len + xbufp->page_len +
            xbufp->tail[0].iov_len;

    task->tk_action = call_bc_transmit;
    atomic_inc(&task->tk_count);
    BUG_ON(atomic_read(&task->tk_count) != 2);
    rpc_execute(task);

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

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

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);

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, int buflen)
{
    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, &buflen);
    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));
    default:
        dprintk("RPC:       %s: address family not supported\n",
            __func__);
        return -EAFNOSUPPORT;
    }
    dprintk("RPC:       %s: succeeded\n", __func__);
    return 0;
}

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, buflen);
    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);

int rpc_protocol(struct rpc_clnt *clnt)
{
    int protocol;

    rcu_read_lock();
    protocol = rcu_dereference(clnt->cl_xprt)->prot;
    rcu_read_unlock();
    return protocol;
}
EXPORT_SYMBOL_GPL(rpc_protocol);

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);

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);

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);

/*
 * 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 (RPC_ASSASSINATED(task))
        return 0;
    task->tk_action = call_start;
    if (task->tk_ops->rpc_call_prepare != NULL)
        task->tk_action = rpc_prepare_task;
    return 1;
}
EXPORT_SYMBOL_GPL(rpc_restart_call_prepare);

/*
 * Restart an (async) RPC call. Usually called from within the
 * exit handler.
 */
int
rpc_restart_call(struct rpc_task *task)
{
    if (RPC_ASSASSINATED(task))
        return 0;
    task->tk_action = call_start;
    return 1;
}
EXPORT_SYMBOL_GPL(rpc_restart_call);

#ifdef RPC_DEBUG
static 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";
}
#endif

/*
 * 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;

    dprintk("RPC: %5u call_start %s%d proc %s (%s)\n", task->tk_pid,
            clnt->cl_protname, clnt->cl_vers,
            rpc_proc_name(task),
            (RPC_IS_ASYNC(task) ? "async" : "sync"));

    /* Increment call count */
    task->tk_msg.rpc_proc->p_count++;
    clnt->cl_stats->rpccnt++;
    task->tk_action = call_reserve;
}

/*
 * 1.   Reserve an RPC call slot
 */
static void
call_reserve(struct rpc_task *task)
{
    dprint_status(task);

    task->tk_status  = 0;
    task->tk_action  = call_reserveresult;
    xprt_reserve(task);
}

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

    dprint_status(task);

    /*
     * 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;
        }

        printk(KERN_ERR "%s: status=%d, but no request slot, exiting\n",
                __func__, status);
        rpc_exit(task, -EIO);
        return;
    }

    /*
     * Even though there was an error, we may have acquired
     * a request slot somehow.  Make sure not to leak it.
     */
    if (task->tk_rqstp) {
        printk(KERN_ERR "%s: status=%d, request allocated anyway\n",
                __func__, status);
        xprt_release(task);
    }

    switch (status) {
    case -ENOMEM:
        rpc_delay(task, HZ >> 2);
    case -EAGAIN:   /* woken up; retry */
        task->tk_action = call_reserve;
        return;
    case -EIO:  /* probably a shutdown */
        break;
    default:
        printk(KERN_ERR "%s: unrecognized error %d, exiting\n",
                __func__, status);
        break;
    }
    rpc_exit(task, status);
}

/*
 * 2.   Bind and/or refresh the credentials
 */
static void
call_refresh(struct rpc_task *task)
{
    dprint_status(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;

    dprint_status(task);

    task->tk_status = 0;
    task->tk_action = call_refresh;
    switch (status) {
    case 0:
        if (rpcauth_uptodatecred(task))
            task->tk_action = call_allocate;
        return;
    case -ETIMEDOUT:
        rpc_delay(task, 3*HZ);
    case -EAGAIN:
        status = -EACCES;
        if (!task->tk_cred_retry)
            break;
        task->tk_cred_retry--;
        dprintk("RPC: %5u %s: retry refresh creds\n",
                task->tk_pid, __func__);
        return;
    }
    dprintk("RPC: %5u %s: refresh creds failed with error %d\n",
                task->tk_pid, __func__, status);
    rpc_exit(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)
{
    unsigned int slack = task->tk_rqstp->rq_cred->cr_auth->au_cslack;
    struct rpc_rqst *req = task->tk_rqstp;
    struct rpc_xprt *xprt = task->tk_xprt;
    struct rpc_procinfo *proc = task->tk_msg.rpc_proc;

    dprint_status(task);

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

    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 + (slack << 1) + proc->p_arglen;
    req->rq_callsize <<= 2;
    req->rq_rcvsize = RPC_REPHDRSIZE + slack + proc->p_replen;
    req->rq_rcvsize <<= 2;

    req->rq_buffer = xprt->ops->buf_alloc(task,
                    req->rq_callsize + req->rq_rcvsize);
    if (req->rq_buffer != NULL)
        return;

    dprintk("RPC: %5u rpc_buffer allocation failed\n", task->tk_pid);

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

    rpc_exit(task, -ERESTARTSYS);
}

static inline int
rpc_task_need_encode(struct rpc_task *task)
{
    return task->tk_rqstp->rq_snd_buf.len == 0;
}

static inline void
rpc_task_force_reencode(struct rpc_task *task)
{
    task->tk_rqstp->rq_snd_buf.len = 0;
    task->tk_rqstp->rq_bytes_sent = 0;
}

static inline void
rpc_xdr_buf_init(struct xdr_buf *buf, void *start, size_t len)
{
    buf->head[0].iov_base = start;
    buf->head[0].iov_len = len;
    buf->tail[0].iov_len = 0;
    buf->page_len = 0;
    buf->flags = 0;
    buf->len = 0;
    buf->buflen = len;
}

/*
 * 3.   Encode arguments of an RPC call
 */
static void
rpc_xdr_encode(struct rpc_task *task)
{
    struct rpc_rqst *req = task->tk_rqstp;
    kxdreproc_t encode;
    __be32      *p;

    dprint_status(task);

    rpc_xdr_buf_init(&req->rq_snd_buf,
             req->rq_buffer,
             req->rq_callsize);
    rpc_xdr_buf_init(&req->rq_rcv_buf,
             (char *)req->rq_buffer + req->rq_callsize,
             req->rq_rcvsize);

    p = rpc_encode_header(task);
    if (p == NULL) {
        printk(KERN_INFO "RPC: couldn't encode RPC header, exit EIO\n");
        rpc_exit(task, -EIO);
        return;
    }

    encode = task->tk_msg.rpc_proc->p_encode;
    if (encode == NULL)
        return;

    task->tk_status = rpcauth_wrap_req(task, encode, req, p,
            task->tk_msg.rpc_argp);
}

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

    dprint_status(task);

    task->tk_action = call_connect;
    if (!xprt_bound(xprt)) {
        task->tk_action = call_bind_status;
        task->tk_timeout = xprt->bind_timeout;
        xprt->ops->rpcbind(task);
    }
}

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

    if (task->tk_status >= 0) {
        dprint_status(task);
        task->tk_status = 0;
        task->tk_action = call_connect;
        return;
    }

    trace_rpc_bind_status(task);
    switch (task->tk_status) {
    case -ENOMEM:
        dprintk("RPC: %5u rpcbind out of memory\n", task->tk_pid);
        rpc_delay(task, HZ >> 2);
        goto retry_timeout;
    case -EACCES:
        dprintk("RPC: %5u remote rpcbind: RPC program/version "
                "unavailable\n", task->tk_pid);
        /* 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 -ETIMEDOUT:
        dprintk("RPC: %5u rpcbind request timed out\n",
                task->tk_pid);
        goto retry_timeout;
    case -EPFNOSUPPORT:
        /* server doesn't support any rpcbind version we know of */
        dprintk("RPC: %5u unrecognized remote rpcbind service\n",
                task->tk_pid);
        break;
    case -EPROTONOSUPPORT:
        dprintk("RPC: %5u remote rpcbind version unavailable, retrying\n",
                task->tk_pid);
        task->tk_status = 0;
        task->tk_action = call_bind;
        return;
    case -ECONNREFUSED:     /* connection problems */
    case -ECONNRESET:
    case -ENOTCONN:
    case -EHOSTDOWN:
    case -EHOSTUNREACH:
    case -ENETUNREACH:
    case -EPIPE:
        dprintk("RPC: %5u remote rpcbind unreachable: %d\n",
                task->tk_pid, task->tk_status);
        if (!RPC_IS_SOFTCONN(task)) {
            rpc_delay(task, 5*HZ);
            goto retry_timeout;
        }
        status = task->tk_status;
        break;
    default:
        dprintk("RPC: %5u unrecognized rpcbind error (%d)\n",
                task->tk_pid, -task->tk_status);
    }

    rpc_exit(task, status);
    return;

retry_timeout:
    task->tk_action = call_timeout;
}

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

    dprintk("RPC: %5u call_connect xprt %p %s connected\n",
            task->tk_pid, xprt,
            (xprt_connected(xprt) ? "is" : "is not"));

    task->tk_action = call_transmit;
    if (!xprt_connected(xprt)) {
        task->tk_action = call_connect_status;
        if (task->tk_status < 0)
            return;
        xprt_connect(task);
    }
}

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

    dprint_status(task);

    task->tk_status = 0;
    if (status >= 0 || status == -EAGAIN) {
        clnt->cl_stats->netreconn++;
        task->tk_action = call_transmit;
        return;
    }

    trace_rpc_connect_status(task, status);
    switch (status) {
        /* if soft mounted, test if we've timed out */
    case -ETIMEDOUT:
        task->tk_action = call_timeout;
        break;
    default:
        rpc_exit(task, -EIO);
    }
}

/*
 * 5.   Transmit the RPC request, and wait for reply
 */
static void
call_transmit(struct rpc_task *task)
{
    dprint_status(task);

    task->tk_action = call_status;
    if (task->tk_status < 0)
        return;
    task->tk_status = xprt_prepare_transmit(task);
    if (task->tk_status != 0)
        return;
    task->tk_action = call_transmit_status;
    /* Encode here so that rpcsec_gss can use correct sequence number. */
    if (rpc_task_need_encode(task)) {
        BUG_ON(task->tk_rqstp->rq_bytes_sent != 0);
        rpc_xdr_encode(task);
        /* Did the encode result in an error condition? */
        if (task->tk_status != 0) {
            /* Was the error nonfatal? */
            if (task->tk_status == -EAGAIN)
                rpc_delay(task, HZ >> 4);
            else
                rpc_exit(task, task->tk_status);
            return;
        }
    }
    xprt_transmit(task);
    if (task->tk_status < 0)
        return;
    /*
     * On success, ensure that we call xprt_end_transmit() before sleeping
     * in order to allow access to the socket to other RPC requests.
     */
    call_transmit_status(task);
    if (rpc_reply_expected(task))
        return;
    task->tk_action = rpc_exit_task;
    rpc_wake_up_queued_task(&task->tk_xprt->pending, 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 (task->tk_status == 0) {
        xprt_end_transmit(task);
        rpc_task_force_reencode(task);
        return;
    }

    switch (task->tk_status) {
    case -EAGAIN:
        break;
    default:
        dprint_status(task);
        xprt_end_transmit(task);
        rpc_task_force_reencode(task);
        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 -ECONNREFUSED:
    case -EHOSTDOWN:
    case -EHOSTUNREACH:
    case -ENETUNREACH:
        if (RPC_IS_SOFTCONN(task)) {
            xprt_end_transmit(task);
            rpc_exit(task, task->tk_status);
            break;
        }
    case -ECONNRESET:
    case -ENOTCONN:
    case -EPIPE:
        rpc_task_force_reencode(task);
    }
}

#if defined(CONFIG_SUNRPC_BACKCHANNEL)
/*
 * 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)
{
    struct rpc_rqst *req = task->tk_rqstp;

    BUG_ON(task->tk_status != 0);
    task->tk_status = xprt_prepare_transmit(task);
    if (task->tk_status == -EAGAIN) {
        /*
         * Could not reserve the transport. Try again after the
         * transport is released.
         */
        task->tk_status = 0;
        task->tk_action = call_bc_transmit;
        return;
    }

    task->tk_action = rpc_exit_task;
    if (task->tk_status < 0) {
        printk(KERN_NOTICE "RPC: Could not send backchannel reply "
            "error: %d\n", task->tk_status);
        return;
    }

    xprt_transmit(task);
    xprt_end_transmit(task);
    dprint_status(task);
    switch (task->tk_status) {
    case 0:
        /* Success */
        break;
    case -EHOSTDOWN:
    case -EHOSTUNREACH:
    case -ENETUNREACH:
    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(task->tk_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.
         */
        BUG_ON(task->tk_status == -EAGAIN);
        printk(KERN_NOTICE "RPC: Could not send backchannel reply "
            "error: %d\n", task->tk_status);
        break;
    }
    rpc_wake_up_queued_task(&req->rq_xprt->pending, 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;
    struct rpc_rqst *req = task->tk_rqstp;
    int     status;

    if (req->rq_reply_bytes_recvd > 0 && !req->rq_bytes_sent)
        task->tk_status = req->rq_reply_bytes_recvd;

    dprint_status(task);

    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 -EHOSTUNREACH:
    case -ENETUNREACH:
        /*
         * Delay any retries for 3 seconds, then handle as if it
         * were a timeout.
         */
        rpc_delay(task, 3*HZ);
    case -ETIMEDOUT:
        task->tk_action = call_timeout;
        if (task->tk_client->cl_discrtry)
            xprt_conditional_disconnect(task->tk_xprt,
                    req->rq_connect_cookie);
        break;
    case -ECONNRESET:
    case -ECONNREFUSED:
        rpc_force_rebind(clnt);
        rpc_delay(task, 3*HZ);
    case -EPIPE:
    case -ENOTCONN:
        task->tk_action = call_bind;
        break;
    case -EAGAIN:
        task->tk_action = call_transmit;
        break;
    case -EIO:
        /* shutdown or soft timeout */
        rpc_exit(task, status);
        break;
    default:
        if (clnt->cl_chatty)
            printk("%s: RPC call returned error %d\n",
                   clnt->cl_protname, -status);
        rpc_exit(task, status);
    }
}

/*
 * 6a.  Handle RPC timeout
 *  We do not release the request slot, so we keep using the
 *  same XID for all retransmits.
 */
static void
call_timeout(struct rpc_task *task)
{
    struct rpc_clnt *clnt = task->tk_client;

    if (xprt_adjust_timeout(task->tk_rqstp) == 0) {
        dprintk("RPC: %5u call_timeout (minor)\n", task->tk_pid);
        goto retry;
    }

    dprintk("RPC: %5u call_timeout (major)\n", task->tk_pid);
    task->tk_timeouts++;

    if (RPC_IS_SOFTCONN(task)) {
        rpc_exit(task, -ETIMEDOUT);
        return;
    }
    if (RPC_IS_SOFT(task)) {
        if (clnt->cl_chatty) {
            rcu_read_lock();
            printk(KERN_NOTICE "%s: server %s not responding, timed out\n",
                clnt->cl_protname,
                rcu_dereference(clnt->cl_xprt)->servername);
            rcu_read_unlock();
        }
        if (task->tk_flags & RPC_TASK_TIMEOUT)
            rpc_exit(task, -ETIMEDOUT);
        else
            rpc_exit(task, -EIO);
        return;
    }

    if (!(task->tk_flags & RPC_CALL_MAJORSEEN)) {
        task->tk_flags |= RPC_CALL_MAJORSEEN;
        if (clnt->cl_chatty) {
            rcu_read_lock();
            printk(KERN_NOTICE "%s: server %s not responding, still trying\n",
            clnt->cl_protname,
            rcu_dereference(clnt->cl_xprt)->servername);
            rcu_read_unlock();
        }
    }
    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);

retry:
    clnt->cl_stats->rpcretrans++;
    task->tk_action = call_bind;
    task->tk_status = 0;
}

/*
 * 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;
    kxdrdproc_t decode = task->tk_msg.rpc_proc->p_decode;
    __be32      *p;

    dprint_status(task);

    if (task->tk_flags & RPC_CALL_MAJORSEEN) {
        if (clnt->cl_chatty) {
            rcu_read_lock();
            printk(KERN_NOTICE "%s: server %s OK\n",
                clnt->cl_protname,
                rcu_dereference(clnt->cl_xprt)->servername);
            rcu_read_unlock();
        }
        task->tk_flags &= ~RPC_CALL_MAJORSEEN;
    }

    /*
     * 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;

    /* 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);

    if (req->rq_rcv_buf.len < 12) {
        if (!RPC_IS_SOFT(task)) {
            task->tk_action = call_bind;
            clnt->cl_stats->rpcretrans++;
            goto out_retry;
        }
        dprintk("RPC:       %s: too small RPC reply size (%d bytes)\n",
                clnt->cl_protname, task->tk_status);
        task->tk_action = call_timeout;
        goto out_retry;
    }

    p = rpc_verify_header(task);
    if (IS_ERR(p)) {
        if (p == ERR_PTR(-EAGAIN))
            goto out_retry;
        return;
    }

    task->tk_action = rpc_exit_task;

    if (decode) {
        task->tk_status = rpcauth_unwrap_resp(task, decode, req, p,
                              task->tk_msg.rpc_resp);
    }
    dprintk("RPC: %5u call_decode result %d\n", task->tk_pid,
            task->tk_status);
    return;
out_retry:
    task->tk_status = 0;
    /* Note: rpc_verify_header() may have freed the RPC slot */
    if (task->tk_rqstp == req) {
        req->rq_reply_bytes_recvd = req->rq_rcv_buf.len = 0;
        if (task->tk_client->cl_discrtry)
            xprt_conditional_disconnect(task->tk_xprt,
                    req->rq_connect_cookie);
    }
}

static __be32 *
rpc_encode_header(struct rpc_task *task)
{
    struct rpc_clnt *clnt = task->tk_client;
    struct rpc_rqst *req = task->tk_rqstp;
    __be32      *p = req->rq_svec[0].iov_base;

    /* FIXME: check buffer size? */

    p = xprt_skip_transport_header(task->tk_xprt, p);
    *p++ = req->rq_xid;     /* XID */
    *p++ = htonl(RPC_CALL);     /* CALL */
    *p++ = htonl(RPC_VERSION);  /* RPC version */
    *p++ = htonl(clnt->cl_prog);    /* program number */
    *p++ = htonl(clnt->cl_vers);    /* program version */
    *p++ = htonl(task->tk_msg.rpc_proc->p_proc);    /* procedure */
    p = rpcauth_marshcred(task, p);
    req->rq_slen = xdr_adjust_iovec(&req->rq_svec[0], p);
    return p;
}

static __be32 *
rpc_verify_header(struct rpc_task *task)
{
    struct rpc_clnt *clnt = task->tk_client;
    struct kvec *iov = &task->tk_rqstp->rq_rcv_buf.head[0];
    int len = task->tk_rqstp->rq_rcv_buf.len >> 2;
    __be32  *p = iov->iov_base;
    u32 n;
    int error = -EACCES;

    if ((task->tk_rqstp->rq_rcv_buf.len & 3) != 0) {
        /* 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
         */
        dprintk("RPC: %5u %s: XDR representation not a multiple of"
               " 4 bytes: 0x%x\n", task->tk_pid, __func__,
               task->tk_rqstp->rq_rcv_buf.len);
        goto out_eio;
    }
    if ((len -= 3) < 0)
        goto out_overflow;

    p += 1; /* skip XID */
    if ((n = ntohl(*p++)) != RPC_REPLY) {
        dprintk("RPC: %5u %s: not an RPC reply: %x\n",
            task->tk_pid, __func__, n);
        goto out_garbage;
    }

    if ((n = ntohl(*p++)) != RPC_MSG_ACCEPTED) {
        if (--len < 0)
            goto out_overflow;
        switch ((n = ntohl(*p++))) {
        case RPC_AUTH_ERROR:
            break;
        case RPC_MISMATCH:
            dprintk("RPC: %5u %s: RPC call version mismatch!\n",
                task->tk_pid, __func__);
            error = -EPROTONOSUPPORT;
            goto out_err;
        default:
            dprintk("RPC: %5u %s: RPC call rejected, "
                "unknown error: %x\n",
                task->tk_pid, __func__, n);
            goto out_eio;
        }
        if (--len < 0)
            goto out_overflow;
        switch ((n = ntohl(*p++))) {
        case RPC_AUTH_REJECTEDCRED:
        case RPC_AUTH_REJECTEDVERF:
        case RPCSEC_GSS_CREDPROBLEM:
        case RPCSEC_GSS_CTXPROBLEM:
            if (!task->tk_cred_retry)
                break;
            task->tk_cred_retry--;
            dprintk("RPC: %5u %s: retry stale creds\n",
                    task->tk_pid, __func__);
            rpcauth_invalcred(task);
            /* Ensure we obtain a new XID! */
            xprt_release(task);
            task->tk_action = call_reserve;
            goto out_retry;
        case RPC_AUTH_BADCRED:
        case RPC_AUTH_BADVERF:
            /* possibly garbled cred/verf? */
            if (!task->tk_garb_retry)
                break;
            task->tk_garb_retry--;
            dprintk("RPC: %5u %s: retry garbled creds\n",
                    task->tk_pid, __func__);
            task->tk_action = call_bind;
            goto out_retry;
        case RPC_AUTH_TOOWEAK:
            rcu_read_lock();
            printk(KERN_NOTICE "RPC: server %s requires stronger "
                   "authentication.\n",
                   rcu_dereference(clnt->cl_xprt)->servername);
            rcu_read_unlock();
            break;
        default:
            dprintk("RPC: %5u %s: unknown auth error: %x\n",
                    task->tk_pid, __func__, n);
            error = -EIO;
        }
        dprintk("RPC: %5u %s: call rejected %d\n",
                task->tk_pid, __func__, n);
        goto out_err;
    }
    if (!(p = rpcauth_checkverf(task, p))) {
        dprintk("RPC: %5u %s: auth check failed\n",
                task->tk_pid, __func__);
        goto out_garbage;       /* bad verifier, retry */
    }
    len = p - (__be32 *)iov->iov_base - 1;
    if (len < 0)
        goto out_overflow;
    switch ((n = ntohl(*p++))) {
    case RPC_SUCCESS:
        return p;
    case RPC_PROG_UNAVAIL:
        dprintk_rcu("RPC: %5u %s: program %u is unsupported "
                "by server %s\n", task->tk_pid, __func__,
                (unsigned int)clnt->cl_prog,
                rcu_dereference(clnt->cl_xprt)->servername);
        error = -EPFNOSUPPORT;
        goto out_err;
    case RPC_PROG_MISMATCH:
        dprintk_rcu("RPC: %5u %s: program %u, version %u unsupported "
                "by server %s\n", task->tk_pid, __func__,
                (unsigned int)clnt->cl_prog,
                (unsigned int)clnt->cl_vers,
                rcu_dereference(clnt->cl_xprt)->servername);
        error = -EPROTONOSUPPORT;
        goto out_err;
    case RPC_PROC_UNAVAIL:
        dprintk_rcu("RPC: %5u %s: proc %s unsupported by program %u, "
                "version %u on server %s\n",
                task->tk_pid, __func__,
                rpc_proc_name(task),
                clnt->cl_prog, clnt->cl_vers,
                rcu_dereference(clnt->cl_xprt)->servername);
        error = -EOPNOTSUPP;
        goto out_err;
    case RPC_GARBAGE_ARGS:
        dprintk("RPC: %5u %s: server saw garbage\n",
                task->tk_pid, __func__);
        break;          /* retry */
    default:
        dprintk("RPC: %5u %s: server accept status: %x\n",
                task->tk_pid, __func__, n);
        /* Also retry */
    }

out_garbage:
    clnt->cl_stats->rpcgarbage++;
    if (task->tk_garb_retry) {
        task->tk_garb_retry--;
        dprintk("RPC: %5u %s: retrying\n",
                task->tk_pid, __func__);
        task->tk_action = call_bind;
out_retry:
        return ERR_PTR(-EAGAIN);
    }
out_eio:
    error = -EIO;
out_err:
    rpc_exit(task, error);
    dprintk("RPC: %5u %s: call failed with error %d\n", task->tk_pid,
            __func__, error);
    return ERR_PTR(error);
out_overflow:
    dprintk("RPC: %5u %s: server reply was truncated.\n", task->tk_pid,
            __func__);
    goto out_garbage;
}

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

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

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

static int rpc_ping(struct rpc_clnt *clnt)
{
    struct rpc_message msg = {
        .rpc_proc = &rpcproc_null,
    };
    int err;
    msg.rpc_cred = authnull_ops.lookup_cred(NULL, NULL, 0);
    err = rpc_call_sync(clnt, &msg, RPC_TASK_SOFT | RPC_TASK_SOFTCONN);
    put_rpccred(msg.rpc_cred);
    return err;
}

struct rpc_task *rpc_call_null(struct rpc_clnt *clnt, struct rpc_cred *cred, int flags)
{
    struct rpc_message msg = {
        .rpc_proc = &rpcproc_null,
        .rpc_cred = cred,
    };
    struct rpc_task_setup task_setup_data = {
        .rpc_client = clnt,
        .rpc_message = &msg,
        .callback_ops = &rpc_default_ops,
        .flags = flags,
    };
    return rpc_run_task(&task_setup_data);
}
EXPORT_SYMBOL_GPL(rpc_call_null);

#ifdef RPC_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, task->tk_timeout, task->tk_ops,
        clnt->cl_protname, 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