OSCL-LXR linux-6.0.1/​net/​sunrpc/​clnt.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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 int  rpc_ping_noreply(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);
         }
     } else if (args->flags & RPC_CLNT_CREATE_CONNECTED) {
         int err = rpc_ping_noreply(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;
     new->cl_max_connect = clnt->cl_max_connect;
     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,
                  void func(struct rpc_xprt_iter *xpi, struct rpc_xprt_switch *xps))
 {
     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;
     func(xpi, xps);
     xprt_switch_put(xps);
     return 0;
 }
 
 static
 int rpc_clnt_xprt_iter_init(struct rpc_clnt *clnt, struct rpc_xprt_iter *xpi)
 {
     return _rpc_clnt_xprt_iter_init(clnt, xpi, xprt_iter_init_listall);
 }
 
 static
 int rpc_clnt_xprt_iter_offline_init(struct rpc_clnt *clnt,
                     struct rpc_xprt_iter *xpi)
 {
     return _rpc_clnt_xprt_iter_init(clnt, xpi, xprt_iter_init_listoffline);
 }
 
 /**
  * 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) {
         if (!(test_bit(XPRT_OFFLINE, &task->tk_xprt->state) &&
               (task->tk_flags & RPC_TASK_MOVEABLE)))
             return;
         xprt_release(task);
         xprt_put(task->tk_xprt);
     }
     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)
 {
     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;
     /* 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 (IS_ERR(task))
         return task;
 
     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);
     if (IS_ERR(task)) {
         xprt_free_bc_request(req);
         return task;
     }
 
     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;
     case -ENOMEM:
         rpc_delay(task, HZ >> 4);
         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);
     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);
     /* Add task to reply queue before transmission to avoid races */
     if (task->tk_status == 0 && rpc_reply_expected(task))
         task->tk_status = xprt_request_enqueue_receive(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_call_rpcerror(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;
     }
 
     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,
                                     true);
                 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 -ENOMEM:
     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 -ENOMEM:
     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 -ENFILE:
     case -ENOBUFS:
     case -ENOMEM:
         rpc_delay(task, HZ>>2);
         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_err;
 
 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 const struct rpc_procinfo rpcproc_null_noreply = {
     .p_encode = rpcproc_encode_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;
 }
 
 static int rpc_ping_noreply(struct rpc_clnt *clnt)
 {
     struct rpc_message msg = {
         .rpc_proc = &rpcproc_null_noreply,
     };
     struct rpc_task_setup task_setup_data = {
         .rpc_client = clnt,
         .rpc_message = &msg,
         .callback_ops = &rpc_null_ops,
         .flags = RPC_TASK_SOFT | RPC_TASK_SOFTCONN | RPC_TASK_NULLCREDS,
     };
     struct rpc_task *task;
     int status;
 
     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;
 }
 
 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_KERNEL);
     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);
     if (IS_ERR(task))
         return PTR_ERR(task);
 
     data->xps->xps_nunique_destaddr_xprts++;
     rpc_put_task(task);
 success:
     return 1;
 }
 EXPORT_SYMBOL_GPL(rpc_clnt_test_and_add_xprt);
 
 static int rpc_clnt_add_xprt_helper(struct rpc_clnt *clnt,
                     struct rpc_xprt *xprt,
                     struct rpc_add_xprt_test *data)
 {
     struct rpc_task *task;
     int status = -EADDRINUSE;
 
     /* Test the connection */
     task = rpc_call_null_helper(clnt, xprt, NULL, 0, NULL, NULL);
     if (IS_ERR(task))
         return PTR_ERR(task);
 
     status = task->tk_status;
     rpc_put_task(task);
 
     if (status < 0)
         return status;
 
     /* rpc_xprt_switch and rpc_xprt are deferrenced by add_xprt_test() */
     data->add_xprt_test(clnt, xprt, data->data);
 
     return 0;
 }
 
 /**
  * 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)
 {
     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;
 
     status = rpc_clnt_add_xprt_helper(clnt, xprt, data);
     if (status < 0)
         goto out_err;
 
     status = 1;
 out_err:
     xprt_put(xprt);
     xprt_switch_put(xps);
     if (status < 0)
         pr_info("RPC:   rpc_clnt_test_xprt failed: %d addr %s not "
             "added\n", status,
             xprt->address_strings[RPC_DISPLAY_ADDR]);
     /* so that rpc_clnt_add_xprt does not call rpc_xprt_switch_add_xprt */
     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);
 
 static int rpc_xprt_probe_trunked(struct rpc_clnt *clnt,
                   struct rpc_xprt *xprt,
                   struct rpc_add_xprt_test *data)
 {
     struct rpc_xprt_switch *xps;
     struct rpc_xprt *main_xprt;
     int status = 0;
 
     xprt_get(xprt);
 
     rcu_read_lock();
     main_xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
     xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
     status = rpc_cmp_addr_port((struct sockaddr *)&xprt->addr,
                    (struct sockaddr *)&main_xprt->addr);
     rcu_read_unlock();
     xprt_put(main_xprt);
     if (status || !test_bit(XPRT_OFFLINE, &xprt->state))
         goto out;
 
     status = rpc_clnt_add_xprt_helper(clnt, xprt, data);
 out:
     xprt_put(xprt);
     xprt_switch_put(xps);
     return status;
 }
 
 /* rpc_clnt_probe_trunked_xprt -- probe offlined transport for session trunking
  * @clnt rpc_clnt structure
  *
  * For each offlined transport found in the rpc_clnt structure call
  * the function rpc_xprt_probe_trunked() which will determine if this
  * transport still belongs to the trunking group.
  */
 void rpc_clnt_probe_trunked_xprts(struct rpc_clnt *clnt,
                   struct rpc_add_xprt_test *data)
 {
     struct rpc_xprt_iter xpi;
     int ret;
 
     ret = rpc_clnt_xprt_iter_offline_init(clnt, &xpi);
     if (ret)
         return;
     for (;;) {
         struct rpc_xprt *xprt = xprt_iter_get_next(&xpi);
 
         if (!xprt)
             break;
         ret = rpc_xprt_probe_trunked(clnt, xprt, data);
         xprt_put(xprt);
         if (ret < 0)
             break;
         xprt_iter_rewind(&xpi);
     }
     xprt_iter_destroy(&xpi);
 }
 EXPORT_SYMBOL_GPL(rpc_clnt_probe_trunked_xprts);
 
 static int rpc_xprt_offline(struct rpc_clnt *clnt,
                 struct rpc_xprt *xprt,
                 void *data)
 {
     struct rpc_xprt *main_xprt;
     struct rpc_xprt_switch *xps;
     int err = 0;
 
     xprt_get(xprt);
 
     rcu_read_lock();
     main_xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
     xps = xprt_switch_get(rcu_dereference(clnt->cl_xpi.xpi_xpswitch));
     err = rpc_cmp_addr_port((struct sockaddr *)&xprt->addr,
                 (struct sockaddr *)&main_xprt->addr);
     rcu_read_unlock();
     xprt_put(main_xprt);
     if (err)
         goto out;
 
     if (wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_KILLABLE)) {
         err = -EINTR;
         goto out;
     }
     xprt_set_offline_locked(xprt, xps);
 
     xprt_release_write(xprt, NULL);
 out:
     xprt_put(xprt);
     xprt_switch_put(xps);
     return err;
 }
 
 /* rpc_clnt_manage_trunked_xprts -- offline trunked transports
  * @clnt rpc_clnt structure
  *
  * For each active transport found in the rpc_clnt structure call
  * the function rpc_xprt_offline() which will identify trunked transports
  * and will mark them offline.
  */
 void rpc_clnt_manage_trunked_xprts(struct rpc_clnt *clnt)
 {
     rpc_clnt_iterate_for_each_xprt(clnt, rpc_xprt_offline, NULL);
 }
 EXPORT_SYMBOL_GPL(rpc_clnt_manage_trunked_xprts);
 
 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_set_online(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
 {
     struct rpc_xprt_switch *xps;
 
     rcu_read_lock();
     xps = rcu_dereference(clnt->cl_xpi.xpi_xpswitch);
     rcu_read_unlock();
     xprt_set_online_locked(xprt, xps);
 }
 
 void rpc_clnt_xprt_switch_add_xprt(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
 {
     if (rpc_clnt_xprt_switch_has_addr(clnt,
         (const struct sockaddr *)&xprt->addr)) {
         return rpc_clnt_xprt_set_online(clnt, 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);
 
 void rpc_clnt_xprt_switch_remove_xprt(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
 {
     struct rpc_xprt_switch *xps;
 
     rcu_read_lock();
     xps = rcu_dereference(clnt->cl_xpi.xpi_xpswitch);
     rpc_xprt_switch_remove_xprt(rcu_dereference(clnt->cl_xpi.xpi_xpswitch),
                     xprt, 0);
     xps->xps_nunique_destaddr_xprts--;
     rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(rpc_clnt_xprt_switch_remove_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)
 {
     while (clnt != clnt->cl_parent)
         clnt = clnt->cl_parent;
     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 */