text: /*
   *  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 "netns.h"
  
  #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  # define RPCDBG_FACILITY	RPCDBG_CALL
  #endif
  
  #define dprint_status(t)					\
  	dprintk("RPC: %5u %s (status %d)\n", t->tk_pid,		\
  			__func__, t->tk_status)
  
  /*
   * All RPC clients are linked into this list
   */
  
  static DECLARE_WAIT_QUEUE_HEAD(destroy_wait);
  
  
  static void	call_start(struct rpc_task *task);
  static void	call_reserve(struct rpc_task *task);
  static void	call_reserveresult(struct rpc_task *task);
  static void	call_allocate(struct rpc_task *task);
  static void	call_decode(struct rpc_task *task);
  static void	call_bind(struct rpc_task *task);
  static void	call_bind_status(struct rpc_task *task);
  static void	call_transmit(struct rpc_task *task);
  #if defined(CONFIG_SUNRPC_BACKCHANNEL)
  static void	call_bc_transmit(struct rpc_task *task);
  #endif /* CONFIG_SUNRPC_BACKCHANNEL */
  static void	call_status(struct rpc_task *task);
  static void	call_transmit_status(struct rpc_task *task);
  static void	call_refresh(struct rpc_task *task);
  static void	call_refreshresult(struct rpc_task *task);
  static void	call_timeout(struct rpc_task *task);
  static void	call_connect(struct rpc_task *task);
  static void	call_connect_status(struct rpc_task *task);
  
  static __be32	*rpc_encode_header(struct rpc_task *task);
  static __be32	*rpc_verify_header(struct rpc_task *task);
  static int	rpc_ping(struct rpc_clnt *clnt);
  
  static void rpc_register_client(struct rpc_clnt *clnt)
  {
  	struct net *net = rpc_net_ns(clnt);
  	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
  
  	spin_lock(&sn->rpc_client_lock);
  	list_add(&clnt->cl_clients, &sn->all_clients);
  	spin_unlock(&sn->rpc_client_lock);
  }
  
  static void rpc_unregister_client(struct rpc_clnt *clnt)
  {
  	struct net *net = rpc_net_ns(clnt);
  	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
  
  	spin_lock(&sn->rpc_client_lock);
  	list_del(&clnt->cl_clients);
  	spin_unlock(&sn->rpc_client_lock);
  }
  
  static void __rpc_clnt_remove_pipedir(struct rpc_clnt *clnt)
  {
  	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 (atomic_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;
  	int err = 0;
  
  	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 err;
  }
  
  static int __rpc_pipefs_event(struct rpc_clnt *clnt, unsigned long event,
  				struct super_block *sb)
  {
  	int error = 0;
  
  	for (;; clnt = clnt->cl_parent) {
  		if (!rpc_clnt_skip_event(clnt, event))
  			error = __rpc_clnt_handle_event(clnt, event, sb);
  		if (error || clnt == clnt->cl_parent)
  			break;
  	}
  	return error;
  }
  
  static struct rpc_clnt *rpc_get_client_for_event(struct net *net, int event)
  {
  	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
  	struct rpc_clnt *clnt;
  
  	spin_lock(&sn->rpc_client_lock);
  	list_for_each_entry(clnt, &sn->all_clients, cl_clients) {
  		if (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_clnt_debugfs_unregister(clnt);
  	return err;
  }
  
  static DEFINE_IDA(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 *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;
  
  	/* sanity check the name before trying to print it */
  	dprintk("RPC:       creating %s client for %s (xprt %p)\n",
  			program->name, args->servername, xprt);
  
  	err = rpciod_up();
  	if (err)
  		goto out_no_rpciod;
  
  	err = -EINVAL;
  	if (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_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);
  
  	clnt->cl_rtt = &clnt->cl_rtt_default;
  	rpc_init_rtt(&clnt->cl_rtt_default, clnt->cl_timeout->to_initval);
  
  	atomic_set(&clnt->cl_count, 1);
  
  	if (nodename == NULL)
  		nodename = utsname()->nodename;
  	/* save the nodename */
  	rpc_clnt_set_nodename(clnt, nodename);
  
  	err = rpc_client_register(clnt, args->authflavor, args->client_name);
  	if (err)
  		goto out_no_path;
  	if (parent)
  		atomic_inc(&parent->cl_count);
  	return clnt;
  
  out_no_path:
  	rpc_free_iostats(clnt->cl_metrics);
  out_no_stats:
  	rpc_free_clid(clnt);
  out_no_clid:
  	kfree(clnt);
  out_err:
  	rpciod_down();
  out_no_rpciod:
  	xprt_put(xprt);
  	return ERR_PTR(err);
  }
  
  struct rpc_clnt *rpc_create_xprt(struct rpc_create_args *args,
  					struct rpc_xprt *xprt)
  {
  	struct rpc_clnt *clnt = NULL;
  
  	clnt = rpc_new_client(args, xprt, NULL);
  	if (IS_ERR(clnt))
  		return clnt;
  
  	if (!(args->flags & RPC_CLNT_CREATE_NOPING)) {
  		int err = rpc_ping(clnt);
  		if (err != 0) {
  			rpc_shutdown_client(clnt);
  			return ERR_PTR(err);
  		}
  	}
  
  	clnt->cl_softrtry = 1;
  	if (args->flags & RPC_CLNT_CREATE_HARDRTRY)
  		clnt->cl_softrtry = 0;
  
  	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;
  }
  EXPORT_SYMBOL_GPL(rpc_create_xprt);
  
  /**
   * 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];
  
  	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;
  
  	return rpc_create_xprt(args, xprt);
  }
  EXPORT_SYMBOL_GPL(rpc_create);
  
  /*
   * This function clones the RPC client structure. It allows us to share the
   * same transport while varying parameters such as the authentication
   * flavour.
   */
  static struct rpc_clnt *__rpc_clone_client(struct rpc_create_args *args,
  					   struct rpc_clnt *clnt)
  {
  	struct rpc_xprt *xprt;
  	struct rpc_clnt *new;
  	int err;
  
  	err = -ENOMEM;
  	rcu_read_lock();
  	xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
  	rcu_read_unlock();
  	if (xprt == NULL)
  		goto out_err;
  	args->servername = xprt->servername;
  	args->nodename = clnt->cl_nodename;
  
  	new = rpc_new_client(args, xprt, clnt);
  	if (IS_ERR(new)) {
  		err = PTR_ERR(new);
  		goto out_err;
  	}
  
  	/* Turn off autobind on clones */
  	new->cl_autobind = 0;
  	new->cl_softrtry = clnt->cl_softrtry;
  	new->cl_noretranstimeo = clnt->cl_noretranstimeo;
  	new->cl_discrtry = clnt->cl_discrtry;
  	new->cl_chatty = clnt->cl_chatty;
  	return new;
  
  out_err:
  	dprintk("RPC:       %s: returned error %d\n", __func__, 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,
  	};
  	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,
  	};
  	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 *xprt, *old;
  	struct rpc_clnt *parent;
  	int err;
  
  	xprt = xprt_create_transport(args);
  	if (IS_ERR(xprt)) {
  		dprintk("RPC:       failed to create new xprt for clnt %p\n",
  			clnt);
  		return PTR_ERR(xprt);
  	}
  
  	pseudoflavor = clnt->cl_auth->au_flavor;
  
  	old_timeo = clnt->cl_timeout;
  	old = rpc_clnt_set_transport(clnt, xprt, timeout);
  
  	rpc_unregister_client(clnt);
  	__rpc_clnt_remove_pipedir(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_put(old);
  	dprintk("RPC:       replaced xprt for clnt %p\n", clnt);
  	return 0;
  
  out_revert:
  	rpc_clnt_set_transport(clnt, old, old_timeo);
  	clnt->cl_parent = parent;
  	rpc_client_register(clnt, pseudoflavor, NULL);
  	xprt_put(xprt);
  	dprintk("RPC:       failed to switch xprt for clnt %p\n", clnt);
  	return err;
  }
  EXPORT_SYMBOL_GPL(rpc_switch_client_transport);
  
  /*
   * Kill all tasks for the given client.
   * XXX: kill their descendants as well?
   */
  void rpc_killall_tasks(struct rpc_clnt *clnt)
  {
  	struct rpc_task	*rovr;
  
  
  	if (list_empty(&clnt->cl_tasks))
  		return;
  	dprintk("RPC:       killing all tasks for client %p\n", clnt);
  	/*
  	 * Spin lock all_tasks to prevent changes...
  	 */
  	spin_lock(&clnt->cl_lock);
  	list_for_each_entry(rovr, &clnt->cl_tasks, tk_task) {
  		if (!RPC_IS_ACTIVATED(rovr))
  			continue;
  		if (!(rovr->tk_flags & RPC_TASK_KILLED)) {
  			rovr->tk_flags |= RPC_TASK_KILLED;
  			rpc_exit(rovr, -EIO);
  			if (RPC_IS_QUEUED(rovr))
  				rpc_wake_up_queued_task(rovr->tk_waitqueue,
  							rovr);
  		}
  	}
  	spin_unlock(&clnt->cl_lock);
  }
  EXPORT_SYMBOL_GPL(rpc_killall_tasks);
  
  /*
   * Properly shut down an RPC client, terminating all outstanding
   * requests.
   */
  void rpc_shutdown_client(struct rpc_clnt *clnt)
  {
  	might_sleep();
  
  	dprintk_rcu("RPC:       shutting down %s client for %s\n",
  			clnt->cl_program->name,
  			rcu_dereference(clnt->cl_xprt)->servername);
  
  	while (!list_empty(&clnt->cl_tasks)) {
  		rpc_killall_tasks(clnt);
  		wait_event_timeout(destroy_wait,
  			list_empty(&clnt->cl_tasks), 1*HZ);
  	}
  
  	rpc_release_client(clnt);
  }
  EXPORT_SYMBOL_GPL(rpc_shutdown_client);
  
  /*
   * Free an RPC client
   */
  static struct rpc_clnt *
  rpc_free_client(struct rpc_clnt *clnt)
  {
  	struct rpc_clnt *parent = NULL;
  
  	dprintk_rcu("RPC:       destroying %s client for %s\n",
  			clnt->cl_program->name,
  			rcu_dereference(clnt->cl_xprt)->servername);
  	if (clnt->cl_parent != clnt)
  		parent = clnt->cl_parent;
  	rpc_clnt_debugfs_unregister(clnt);
  	rpc_clnt_remove_pipedir(clnt);
  	rpc_unregister_client(clnt);
  	rpc_free_iostats(clnt->cl_metrics);
  	clnt->cl_metrics = NULL;
  	xprt_put(rcu_dereference_raw(clnt->cl_xprt));
  	rpciod_down();
  	rpc_free_clid(clnt);
  	kfree(clnt);
  	return parent;
  }
  
  /*
   * Free an RPC client
   */
  static struct rpc_clnt * 
  rpc_free_auth(struct rpc_clnt *clnt)
  {
  	if (clnt->cl_auth == NULL)
  		return rpc_free_client(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.
  	 */
  	atomic_inc(&clnt->cl_count);
  	rpcauth_release(clnt->cl_auth);
  	clnt->cl_auth = NULL;
  	if (atomic_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)
  {
  	dprintk("RPC:       rpc_release_client(%p)\n", clnt);
  
  	do {
  		if (list_empty(&clnt->cl_tasks))
  			wake_up(&destroy_wait);
  		if (!atomic_dec_and_test(&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,
  	};
  	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);
  
  void rpc_task_release_client(struct rpc_task *task)
  {
  	struct rpc_clnt *clnt = task->tk_client;
  
  	if (clnt != NULL) {
  		/* Remove from client task list */
  		spin_lock(&clnt->cl_lock);
  		list_del(&task->tk_task);
  		spin_unlock(&clnt->cl_lock);
  		task->tk_client = NULL;
  
  		rpc_release_client(clnt);
  	}
  }
  
  static
  void rpc_task_set_client(struct rpc_task *task, struct rpc_clnt *clnt)
  {
  	if (clnt != NULL) {
  		rpc_task_release_client(task);
  		task->tk_client = clnt;
  		atomic_inc(&clnt->cl_count);
  		if (clnt->cl_softrtry)
  			task->tk_flags |= RPC_TASK_SOFT;
  		if (clnt->cl_noretranstimeo)
  			task->tk_flags |= RPC_TASK_NO_RETRANS_TIMEOUT;
  		if (atomic_read(&clnt->cl_swapper))
  			task->tk_flags |= RPC_TASK_SWAPPER;
  		/* Add to the client's list of all tasks */
  		spin_lock(&clnt->cl_lock);
  		list_add_tail(&task->tk_task, &clnt->cl_tasks);
  		spin_unlock(&clnt->cl_lock);
  	}
  }
  
  void rpc_task_reset_client(struct rpc_task *task, struct rpc_clnt *clnt)
  {
  	rpc_task_release_client(task);
  	rpc_task_set_client(task, clnt);
  }
  EXPORT_SYMBOL_GPL(rpc_task_reset_client);
  
  
  static void
  rpc_task_set_rpc_message(struct rpc_task *task, const struct rpc_message *msg)
  {
  	if (msg != NULL) {
  		task->tk_msg.rpc_proc = msg->rpc_proc;
  		task->tk_msg.rpc_argp = msg->rpc_argp;
  		task->tk_msg.rpc_resp = msg->rpc_resp;
  		if (msg->rpc_cred != NULL)
  			task->tk_msg.rpc_cred = get_rpccred(msg->rpc_cred);
  	}
  }
  
  /*
   * Default callback for async RPC calls
   */
  static void
  rpc_default_callback(struct rpc_task *task, void *data)
  {
  }
  
  static const struct rpc_call_ops rpc_default_ops = {
  	.rpc_call_done = rpc_default_callback,
  };
  
  /**
   * 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))
  		goto out;
  
  	rpc_task_set_client(task, task_setup_data->rpc_client);
  	rpc_task_set_rpc_message(task, task_setup_data->rpc_message);
  
  	if (task->tk_action == NULL)
  		rpc_call_start(task);
  
  	atomic_inc(&task->tk_count);
  	rpc_execute(task);
  out:
  	return task;
  }
  EXPORT_SYMBOL_GPL(rpc_run_task);
  
  /**
   * 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)
  /**
   * 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 xdr_buf *xbufp = &req->rq_snd_buf;
  	struct rpc_task_setup task_setup_data = {
  		.callback_ops = &rpc_default_ops,
  		.flags = RPC_TASK_SOFTCONN,
  	};
  
  	dprintk("RPC: rpc_run_bc_task req= %p\n", req);
  	/*
  	 * Create an rpc_task to send the data
  	 */
  	task = rpc_new_task(&task_setup_data);
  	if (IS_ERR(task)) {
  		xprt_free_bc_request(req);
  		goto out;
  	}
  	task->tk_rqstp = req;
  
  	/*
  	 * Set up the xdr_buf length.
  	 * This also indicates that the buffer is XDR encoded already.
  	 */
  	xbufp->len = xbufp->head[0].iov_len + xbufp->page_len +
  			xbufp->tail[0].iov_len;
  
  	task->tk_action = call_bc_transmit;
  	atomic_inc(&task->tk_count);
  	WARN_ON_ONCE(atomic_read(&task->tk_count) != 2);
  	rpc_execute(task);
  
  out:
  	dprintk("RPC: rpc_run_bc_task: task= %p\n", task);
  	return task;
  }
  #endif /* CONFIG_SUNRPC_BACKCHANNEL */
  
  void
  rpc_call_start(struct rpc_task *task)
  {
  	task->tk_action = call_start;
  }
  EXPORT_SYMBOL_GPL(rpc_call_start);
  
  /**
   * 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, int buflen)
  {
  	struct socket *sock;
  	int err;
  
  	err = __sock_create(net, sap->sa_family,
  				SOCK_DGRAM, IPPROTO_UDP, &sock, 1);
  	if (err < 0) {
  		dprintk("RPC:       can't create UDP socket (%d)\n", err);
  		goto out;
  	}
  
  	switch (sap->sa_family) {
  	case AF_INET:
  		err = kernel_bind(sock,
  				(struct sockaddr *)&rpc_inaddr_loopback,
  				sizeof(rpc_inaddr_loopback));
  		break;
  	case AF_INET6:
  		err = kernel_bind(sock,
  				(struct sockaddr *)&rpc_in6addr_loopback,
  				sizeof(rpc_in6addr_loopback));
  		break;
  	default:
  		err = -EAFNOSUPPORT;
  		goto out;
  	}
  	if (err < 0) {
  		dprintk("RPC:       can't bind UDP socket (%d)\n", err);
  		goto out_release;
  	}
  
  	err = kernel_connect(sock, sap, salen, 0);
  	if (err < 0) {
  		dprintk("RPC:       can't connect UDP socket (%d)\n", err);
  		goto out_release;
  	}
  
  	err = kernel_getsockname(sock, buf, &buflen);
  	if (err < 0) {
  		dprintk("RPC:       getsockname failed (%d)\n", err);
  		goto out_release;
  	}
  
  	err = 0;
  	if (buf->sa_family == AF_INET6) {
  		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)buf;
  		sin6->sin6_scope_id = 0;
  	}
  	dprintk("RPC:       %s succeeded\n", __func__);
  
  out_release:
  	sock_release(sock);
  out:
  	return err;
  }
  
  /*
   * Scraping a connected socket failed, so we don't have a useable
   * local address.  Fallback: generate an address that will prevent
   * the server from calling us back.
   *
   * Returns zero and fills in "buf" if successful; otherwise, a
   * negative errno is returned.
   */
  static int rpc_anyaddr(int family, struct sockaddr *buf, size_t buflen)
  {
  	switch (family) {
  	case AF_INET:
  		if (buflen < sizeof(rpc_inaddr_loopback))
  			return -EINVAL;
  		memcpy(buf, &rpc_inaddr_loopback,
  				sizeof(rpc_inaddr_loopback));
  		break;
  	case AF_INET6:
  		if (buflen < sizeof(rpc_in6addr_loopback))
  			return -EINVAL;
  		memcpy(buf, &rpc_in6addr_loopback,
  				sizeof(rpc_in6addr_loopback));
  		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, buflen);
  	put_net(net);
  	if (err != 0)
  		/* Couldn't discover local address, return ANYADDR */
  		return rpc_anyaddr(sap->sa_family, buf, buflen);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(rpc_localaddr);
  
  void
  rpc_setbufsize(struct rpc_clnt *clnt, unsigned int sndsize, unsigned int rcvsize)
  {
  	struct rpc_xprt *xprt;
  
  	rcu_read_lock();
  	xprt = rcu_dereference(clnt->cl_xprt);
  	if (xprt->ops->set_buffer_size)
  		xprt->ops->set_buffer_size(xprt, sndsize, rcvsize);
  	rcu_read_unlock();
  }
  EXPORT_SYMBOL_GPL(rpc_setbufsize);
  
  /**
   * rpc_protocol - Get transport protocol number for an RPC client
   * @clnt: RPC client to query
   *
   */
  int rpc_protocol(struct rpc_clnt *clnt)
  {
  	int protocol;
  
  	rcu_read_lock();
  	protocol = rcu_dereference(clnt->cl_xprt)->prot;
  	rcu_read_unlock();
  	return protocol;
  }
  EXPORT_SYMBOL_GPL(rpc_protocol);
  
  /**
   * 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_get_timeout - Get timeout for transport in units of HZ
   * @clnt: RPC client to query
   */
  unsigned long rpc_get_timeout(struct rpc_clnt *clnt)
  {
  	unsigned long ret;
  
  	rcu_read_lock();
  	ret = rcu_dereference(clnt->cl_xprt)->timeout->to_initval;
  	rcu_read_unlock();
  	return ret;
  }
  EXPORT_SYMBOL_GPL(rpc_get_timeout);
  
  /**
   * 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);
  
  /*
   * Restart an (async) RPC call from the call_prepare state.
   * Usually called from within the exit handler.
   */
  int
  rpc_restart_call_prepare(struct rpc_task *task)
  {
  	if (RPC_ASSASSINATED(task))
  		return 0;
  	task->tk_action = call_start;
  	task->tk_status = 0;
  	if (task->tk_ops->rpc_call_prepare != NULL)
  		task->tk_action = rpc_prepare_task;
  	return 1;
  }
  EXPORT_SYMBOL_GPL(rpc_restart_call_prepare);
  
  /*
   * Restart an (async) RPC call. Usually called from within the
   * exit handler.
   */
  int
  rpc_restart_call(struct rpc_task *task)
  {
  	if (RPC_ASSASSINATED(task))
  		return 0;
  	task->tk_action = call_start;
  	task->tk_status = 0;
  	return 1;
  }
  EXPORT_SYMBOL_GPL(rpc_restart_call);
  
  #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  const char
  *rpc_proc_name(const struct rpc_task *task)
  {
  	const struct rpc_procinfo *proc = task->tk_msg.rpc_proc;
  
  	if (proc) {
  		if (proc->p_name)
  			return proc->p_name;
  		else
  			return "NULL";
  	} else
  		return "no proc";
  }
  #endif
  
  /*
   * 0.  Initial state
   *
   *     Other FSM states can be visited zero or more times, but
   *     this state is visited exactly once for each RPC.
   */
  static void
  call_start(struct rpc_task *task)
  {
  	struct rpc_clnt	*clnt = task->tk_client;
  
  	dprintk("RPC: %5u call_start %s%d proc %s (%s)\n", task->tk_pid,
  			clnt->cl_program->name, clnt->cl_vers,
  			rpc_proc_name(task),
  			(RPC_IS_ASYNC(task) ? "async" : "sync"));
  
  	/* Increment call count */
  	task->tk_msg.rpc_proc->p_count++;
  	clnt->cl_stats->rpccnt++;
  	task->tk_action = call_reserve;
  }
  
  /*
   * 1.	Reserve an RPC call slot
   */
  static void
  call_reserve(struct rpc_task *task)
  {
  	dprint_status(task);
  
  	task->tk_status  = 0;
  	task->tk_action  = call_reserveresult;
  	xprt_reserve(task);
  }
  
  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;
  
  	dprint_status(task);
  
  	/*
  	 * After a call to xprt_reserve(), we must have either
  	 * a request slot or else an error status.
  	 */
  	task->tk_status = 0;
  	if (status >= 0) {
  		if (task->tk_rqstp) {
  			task->tk_action = call_refresh;
  			return;
  		}
  
  		printk(KERN_ERR "%s: status=%d, but no request slot, exiting\n",
  				__func__, status);
  		rpc_exit(task, -EIO);
  		return;
  	}
  
  	/*
  	 * Even though there was an error, we may have acquired
  	 * a request slot somehow.  Make sure not to leak it.
  	 */
  	if (task->tk_rqstp) {
  		printk(KERN_ERR "%s: status=%d, request allocated anyway\n",
  				__func__, status);
  		xprt_release(task);
  	}
  
  	switch (status) {
  	case -ENOMEM:
  		rpc_delay(task, HZ >> 2);
  	case -EAGAIN:	/* woken up; retry */
  		task->tk_action = call_retry_reserve;
  		return;
  	case -EIO:	/* probably a shutdown */
  		break;
  	default:
  		printk(KERN_ERR "%s: unrecognized error %d, exiting\n",
  				__func__, status);
  		break;
  	}
  	rpc_exit(task, status);
  }
  
  /*
   * 1c.	Retry reserving an RPC call slot
   */
  static void
  call_retry_reserve(struct rpc_task *task)
  {
  	dprint_status(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)
  {
  	dprint_status(task);
  
  	task->tk_action = call_refreshresult;
  	task->tk_status = 0;
  	task->tk_client->cl_stats->rpcauthrefresh++;
  	rpcauth_refreshcred(task);
  }
  
  /*
   * 2a.	Process the results of a credential refresh
   */
  static void
  call_refreshresult(struct rpc_task *task)
  {
  	int status = task->tk_status;
  
  	dprint_status(task);
  
  	task->tk_status = 0;
  	task->tk_action = call_refresh;
  	switch (status) {
  	case 0:
  		if (rpcauth_uptodatecred(task)) {
  			task->tk_action = call_allocate;
  			return;
  		}
  		/* Use rate-limiting and a max number of retries if refresh
  		 * had status 0 but failed to update the cred.
  		 */
  	case -ETIMEDOUT:
  		rpc_delay(task, 3*HZ);
  	case -EAGAIN:
  		status = -EACCES;
  	case -EKEYEXPIRED:
  		if (!task->tk_cred_retry)
  			break;
  		task->tk_cred_retry--;
  		dprintk("RPC: %5u %s: retry refresh creds\n",
  				task->tk_pid, __func__);
  		return;
  	}
  	dprintk("RPC: %5u %s: refresh creds failed with error %d\n",
  				task->tk_pid, __func__, status);
  	rpc_exit(task, status);
  }
  
  /*
   * 2b.	Allocate the buffer. For details, see sched.c:rpc_malloc.
   *	(Note: buffer memory is freed in xprt_release).
   */
  static void
  call_allocate(struct rpc_task *task)
  {
  	unsigned int slack = task->tk_rqstp->rq_cred->cr_auth->au_cslack;
  	struct rpc_rqst *req = task->tk_rqstp;
  	struct rpc_xprt *xprt = req->rq_xprt;
  	struct rpc_procinfo *proc = task->tk_msg.rpc_proc;
  
  	dprint_status(task);
  
  	task->tk_status = 0;
  	task->tk_action = call_bind;
  
  	if (req->rq_buffer)
  		return;
  
  	if (proc->p_proc != 0) {
  		BUG_ON(proc->p_arglen == 0);
  		if (proc->p_decode != NULL)
  			BUG_ON(proc->p_replen == 0);
  	}
  
  	/*
  	 * Calculate the size (in quads) of the RPC call
  	 * and reply headers, and convert both values
  	 * to byte sizes.
  	 */
  	req->rq_callsize = RPC_CALLHDRSIZE + (slack << 1) + proc->p_arglen;
  	req->rq_callsize <<= 2;
  	req->rq_rcvsize = RPC_REPHDRSIZE + slack + proc->p_replen;
  	req->rq_rcvsize <<= 2;
  
  	req->rq_buffer = xprt->ops->buf_alloc(task,
  					req->rq_callsize + req->rq_rcvsize);
  	if (req->rq_buffer != NULL)
  		return;
  	xprt_inject_disconnect(xprt);
  
  	dprintk("RPC: %5u rpc_buffer allocation failed\n", task->tk_pid);
  
  	if (RPC_IS_ASYNC(task) || !fatal_signal_pending(current)) {
  		task->tk_action = call_allocate;
  		rpc_delay(task, HZ>>4);
  		return;
  	}
  
  	rpc_exit(task, -ERESTARTSYS);
  }
  
  static inline int
  rpc_task_need_encode(struct rpc_task *task)
  {
  	return task->tk_rqstp->rq_snd_buf.len == 0;
  }
  
  static inline void
  rpc_task_force_reencode(struct rpc_task *task)
  {
  	task->tk_rqstp->rq_snd_buf.len = 0;
  	task->tk_rqstp->rq_bytes_sent = 0;
  }
  
  static inline void
  rpc_xdr_buf_init(struct xdr_buf *buf, void *start, size_t len)
  {
  	buf->head[0].iov_base = start;
  	buf->head[0].iov_len = len;
  	buf->tail[0].iov_len = 0;
  	buf->page_len = 0;
  	buf->flags = 0;
  	buf->len = 0;
  	buf->buflen = len;
  }
  
  /*
   * 3.	Encode arguments of an RPC call
   */
  static void
  rpc_xdr_encode(struct rpc_task *task)
  {
  	struct rpc_rqst	*req = task->tk_rqstp;
  	kxdreproc_t	encode;
  	__be32		*p;
  
  	dprint_status(task);
  
  	rpc_xdr_buf_init(&req->rq_snd_buf,
  			 req->rq_buffer,
  			 req->rq_callsize);
  	rpc_xdr_buf_init(&req->rq_rcv_buf,
  			 (char *)req->rq_buffer + req->rq_callsize,
  			 req->rq_rcvsize);
  
  	p = rpc_encode_header(task);
  	if (p == NULL) {
  		printk(KERN_INFO "RPC: couldn't encode RPC header, exit EIO\n");
  		rpc_exit(task, -EIO);
  		return;
  	}
  
  	encode = task->tk_msg.rpc_proc->p_encode;
  	if (encode == NULL)
  		return;
  
  	task->tk_status = rpcauth_wrap_req(task, encode, req, p,
  			task->tk_msg.rpc_argp);
  }
  
  /*
   * 4.	Get the server port number if not yet set
   */
  static void
  call_bind(struct rpc_task *task)
  {
  	struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;
  
  	dprint_status(task);
  
  	task->tk_action = call_connect;
  	if (!xprt_bound(xprt)) {
  		task->tk_action = call_bind_status;
  		task->tk_timeout = xprt->bind_timeout;
  		xprt->ops->rpcbind(task);
  	}
  }
  
  /*
   * 4a.	Sort out bind result
   */
  static void
  call_bind_status(struct rpc_task *task)
  {
  	int status = -EIO;
  
  	if (task->tk_status >= 0) {
  		dprint_status(task);
  		task->tk_status = 0;
  		task->tk_action = call_connect;
  		return;
  	}
  
  	trace_rpc_bind_status(task);
  	switch (task->tk_status) {
  	case -ENOMEM:
  		dprintk("RPC: %5u rpcbind out of memory\n", task->tk_pid);
  		rpc_delay(task, HZ >> 2);
  		goto retry_timeout;
  	case -EACCES:
  		dprintk("RPC: %5u remote rpcbind: RPC program/version "
  				"unavailable\n", task->tk_pid);
  		/* fail immediately if this is an RPC ping */
  		if (task->tk_msg.rpc_proc->p_proc == 0) {
  			status = -EOPNOTSUPP;
  			break;
  		}
  		if (task->tk_rebind_retry == 0)
  			break;
  		task->tk_rebind_retry--;
  		rpc_delay(task, 3*HZ);
  		goto retry_timeout;
  	case -ETIMEDOUT:
  		dprintk("RPC: %5u rpcbind request timed out\n",
  				task->tk_pid);
  		goto retry_timeout;
  	case -EPFNOSUPPORT:
  		/* server doesn't support any rpcbind version we know of */
  		dprintk("RPC: %5u unrecognized remote rpcbind service\n",
  				task->tk_pid);
  		break;
  	case -EPROTONOSUPPORT:
  		dprintk("RPC: %5u remote rpcbind version unavailable, retrying\n",
  				task->tk_pid);
  		goto retry_timeout;
  	case -ECONNREFUSED:		/* connection problems */
  	case -ECONNRESET:
  	case -ECONNABORTED:
  	case -ENOTCONN:
  	case -EHOSTDOWN:
  	case -EHOSTUNREACH:
  	case -ENETUNREACH:
  	case -ENOBUFS:
  	case -EPIPE:
  		dprintk("RPC: %5u remote rpcbind unreachable: %d\n",
  				task->tk_pid, task->tk_status);
  		if (!RPC_IS_SOFTCONN(task)) {
  			rpc_delay(task, 5*HZ);
  			goto retry_timeout;
  		}
  		status = task->tk_status;
  		break;
  	default:
  		dprintk("RPC: %5u unrecognized rpcbind error (%d)\n",
  				task->tk_pid, -task->tk_status);
  	}
  
  	rpc_exit(task, status);
  	return;
  
  retry_timeout:
  	task->tk_status = 0;
  	task->tk_action = call_timeout;
  }
  
  /*
   * 4b.	Connect to the RPC server
   */
  static void
  call_connect(struct rpc_task *task)
  {
  	struct rpc_xprt *xprt = task->tk_rqstp->rq_xprt;
  
  	dprintk("RPC: %5u call_connect xprt %p %s connected\n",
  			task->tk_pid, xprt,
  			(xprt_connected(xprt) ? "is" : "is not"));
  
  	task->tk_action = call_transmit;
  	if (!xprt_connected(xprt)) {
  		task->tk_action = call_connect_status;
  		if (task->tk_status < 0)
  			return;
  		if (task->tk_flags & RPC_TASK_NOCONNECT) {
  			rpc_exit(task, -ENOTCONN);
  			return;
  		}
  		xprt_connect(task);
  	}
  }
  
  /*
   * 4c.	Sort out connect result
   */
  static void
  call_connect_status(struct rpc_task *task)
  {
  	struct rpc_clnt *clnt = task->tk_client;
  	int status = task->tk_status;
  
  	dprint_status(task);
  
  	trace_rpc_connect_status(task, status);
  	task->tk_status = 0;
  	switch (status) {
  	case -ECONNREFUSED:
  	case -ECONNRESET:
  	case -ECONNABORTED:
  	case -ENETUNREACH:
  	case -EHOSTUNREACH:
  	case -EADDRINUSE:
  	case -ENOBUFS:
  	case -EPIPE:
  		if (RPC_IS_SOFTCONN(task))
  			break;
  		/* retry with existing socket, after a delay */
  		rpc_delay(task, 3*HZ);
  	case -EAGAIN:
  		/* Check for timeouts before looping back to call_bind */
  	case -ETIMEDOUT:
  		task->tk_action = call_timeout;
  		return;
  	case 0:
  		clnt->cl_stats->netreconn++;
  		task->tk_action = call_transmit;
  		return;
  	}
  	rpc_exit(task, status);
  }
  
  /*
   * 5.	Transmit the RPC request, and wait for reply
   */
  static void
  call_transmit(struct rpc_task *task)
  {
  	int is_retrans = RPC_WAS_SENT(task);
  
  	dprint_status(task);
  
  	task->tk_action = call_status;
  	if (task->tk_status < 0)
  		return;
  	if (!xprt_prepare_transmit(task))
  		return;
  	task->tk_action = call_transmit_status;
  	/* Encode here so that rpcsec_gss can use correct sequence number. */
  	if (rpc_task_need_encode(task)) {
  		rpc_xdr_encode(task);
  		/* Did the encode result in an error condition? */
  		if (task->tk_status != 0) {
  			/* Was the error nonfatal? */
  			if (task->tk_status == -EAGAIN)
  				rpc_delay(task, HZ >> 4);
  			else
  				rpc_exit(task, task->tk_status);
  			return;
  		}
  	}
  	xprt_transmit(task);
  	if (task->tk_status < 0)
  		return;
  	if (is_retrans)
  		task->tk_client->cl_stats->rpcretrans++;
  	/*
  	 * On success, ensure that we call xprt_end_transmit() before sleeping
  	 * in order to allow access to the socket to other RPC requests.
  	 */
  	call_transmit_status(task);
  	if (rpc_reply_expected(task))
  		return;
  	task->tk_action = rpc_exit_task;
  	rpc_wake_up_queued_task(&task->tk_rqstp->rq_xprt->pending, task);
  }
  
  /*
   * 5a.	Handle cleanup after a transmission
   */
  static void
  call_transmit_status(struct rpc_task *task)
  {
  	task->tk_action = call_status;
  
  	/*
  	 * Common case: success.  Force the compiler to put this
  	 * test first.
  	 */
  	if (task->tk_status == 0) {
  		xprt_end_transmit(task);
  		rpc_task_force_reencode(task);
  		return;
  	}
  
  	switch (task->tk_status) {
  	case -EAGAIN:
  	case -ENOBUFS:
  		break;
  	default:
  		dprint_status(task);
  		xprt_end_transmit(task);
  		rpc_task_force_reencode(task);
  		break;
  		/*
  		 * Special cases: if we've been waiting on the
  		 * socket's write_space() callback, or if the
  		 * socket just returned a connection error,
  		 * then hold onto the transport lock.
  		 */
  	case -ECONNREFUSED:
  	case -EHOSTDOWN:
  	case -EHOSTUNREACH:
  	case -ENETUNREACH:
  	case -EPERM:
  		if (RPC_IS_SOFTCONN(task)) {
  			xprt_end_transmit(task);
  			rpc_exit(task, task->tk_status);
  			break;
  		}
  	case -ECONNRESET:
  	case -ECONNABORTED:
  	case -EADDRINUSE:
  	case -ENOTCONN:
  	case -EPIPE:
  		rpc_task_force_reencode(task);
  	}
  }
  
  #if defined(CONFIG_SUNRPC_BACKCHANNEL)
  /*
   * 5b.	Send the backchannel RPC reply.  On error, drop the reply.  In
   * addition, disconnect on connectivity errors.
   */
  static void
  call_bc_transmit(struct rpc_task *task)
  {
  	struct rpc_rqst *req = task->tk_rqstp;
  
  	if (!xprt_prepare_transmit(task))
  		goto out_retry;
  
  	if (task->tk_status < 0) {
  		printk(KERN_NOTICE "RPC: Could not send backchannel reply "
  			"error: %d\n", task->tk_status);
  		goto out_done;
  	}
  	if (req->rq_connect_cookie != req->rq_xprt->connect_cookie)
  		req->rq_bytes_sent = 0;
  
  	xprt_transmit(task);
  
  	if (task->tk_status == -EAGAIN)
  		goto out_nospace;
  
  	xprt_end_transmit(task);
  	dprint_status(task);
  	switch (task->tk_status) {
  	case 0:
  		/* Success */
  	case -EHOSTDOWN:
  	case -EHOSTUNREACH:
  	case -ENETUNREACH:
  	case -ECONNRESET:
  	case -ECONNREFUSED:
  	case -EADDRINUSE:
  	case -ENOTCONN:
  	case -EPIPE:
  		break;
  	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.
  		 */
  		WARN_ON_ONCE(task->tk_status == -EAGAIN);
  		printk(KERN_NOTICE "RPC: Could not send backchannel reply "
  			"error: %d\n", task->tk_status);
  		break;
  	}
  	rpc_wake_up_queued_task(&req->rq_xprt->pending, task);
  out_done:
  	task->tk_action = rpc_exit_task;
  	return;
  out_nospace:
  	req->rq_connect_cookie = req->rq_xprt->connect_cookie;
  out_retry:
  	task->tk_status = 0;
  }
  #endif /* CONFIG_SUNRPC_BACKCHANNEL */
  
  /*
   * 6.	Sort out the RPC call status
   */
  static void
  call_status(struct rpc_task *task)
  {
  	struct rpc_clnt	*clnt = task->tk_client;
  	struct rpc_rqst	*req = task->tk_rqstp;
  	int		status;
  
  	if (req->rq_reply_bytes_recvd > 0 && !req->rq_bytes_sent)
  		task->tk_status = req->rq_reply_bytes_recvd;
  
  	dprint_status(task);
  
  	status = task->tk_status;
  	if (status >= 0) {
  		task->tk_action = call_decode;
  		return;
  	}
  
  	trace_rpc_call_status(task);
  	task->tk_status = 0;
  	switch(status) {
  	case -EHOSTDOWN:
  	case -EHOSTUNREACH:
  	case -ENETUNREACH:
  	case -EPERM:
  		if (RPC_IS_SOFTCONN(task)) {
  			rpc_exit(task, status);
  			break;
  		}
  		/*
  		 * Delay any retries for 3 seconds, then handle as if it
  		 * were a timeout.
  		 */
  		rpc_delay(task, 3*HZ);
  	case -ETIMEDOUT:
  		task->tk_action = call_timeout;
  		if (!(task->tk_flags & RPC_TASK_NO_RETRANS_TIMEOUT)
  		    && task->tk_client->cl_discrtry)
  			xprt_conditional_disconnect(req->rq_xprt,
  					req->rq_connect_cookie);
  		break;
  	case -ECONNREFUSED:
  	case -ECONNRESET:
  	case -ECONNABORTED:
  		rpc_force_rebind(clnt);
  	case -EADDRINUSE:
  		rpc_delay(task, 3*HZ);
  	case -EPIPE:
  	case -ENOTCONN:
  		task->tk_action = call_bind;
  		break;
  	case -ENOBUFS:
  		rpc_delay(task, HZ>>2);
  	case -EAGAIN:
  		task->tk_action = call_transmit;
  		break;
  	case -EIO:
  		/* shutdown or soft timeout */
  		rpc_exit(task, status);
  		break;
  	default:
  		if (clnt->cl_chatty)
  			printk("%s: RPC call returned error %d\n",
  			       clnt->cl_program->name, -status);
  		rpc_exit(task, status);
  	}
  }
  
  /*
   * 6a.	Handle RPC timeout
   * 	We do not release the request slot, so we keep using the
   *	same XID for all retransmits.
   */
  static void
  call_timeout(struct rpc_task *task)
  {
  	struct rpc_clnt	*clnt = task->tk_client;
  
  	if (xprt_adjust_timeout(task->tk_rqstp) == 0) {
  		dprintk("RPC: %5u call_timeout (minor)\n", task->tk_pid);
  		goto retry;
  	}
  
  	dprintk("RPC: %5u call_timeout (major)\n", task->tk_pid);
  	task->tk_timeouts++;
  
  	if (RPC_IS_SOFTCONN(task)) {
  		rpc_exit(task, -ETIMEDOUT);
  		return;
  	}
  	if (RPC_IS_SOFT(task)) {
  		if (clnt->cl_chatty) {
  			rcu_read_lock();
  			printk(KERN_NOTICE "%s: server %s not responding, timed out\n",
  				clnt->cl_program->name,
  				rcu_dereference(clnt->cl_xprt)->servername);
  			rcu_read_unlock();
  		}
  		if (task->tk_flags & RPC_TASK_TIMEOUT)
  			rpc_exit(task, -ETIMEDOUT);
  		else
  			rpc_exit(task, -EIO);
  		return;
  	}
  
  	if (!(task->tk_flags & RPC_CALL_MAJORSEEN)) {
  		task->tk_flags |= RPC_CALL_MAJORSEEN;
  		if (clnt->cl_chatty) {
  			rcu_read_lock();
  			printk(KERN_NOTICE "%s: server %s not responding, still trying\n",
  			clnt->cl_program->name,
  			rcu_dereference(clnt->cl_xprt)->servername);
  			rcu_read_unlock();
  		}
  	}
  	rpc_force_rebind(clnt);
  	/*
  	 * Did our request time out due to an RPCSEC_GSS out-of-sequence
  	 * event? RFC2203 requires the server to drop all such requests.
  	 */
  	rpcauth_invalcred(task);
  
  retry:
  	task->tk_action = call_bind;
  	task->tk_status = 0;
  }
  
  /*
   * 7.	Decode the RPC reply
   */
  static void
  call_decode(struct rpc_task *task)
  {
  	struct rpc_clnt	*clnt = task->tk_client;
  	struct rpc_rqst	*req = task->tk_rqstp;
  	kxdrdproc_t	decode = task->tk_msg.rpc_proc->p_decode;
  	__be32		*p;
  
  	dprint_status(task);
  
  	if (task->tk_flags & RPC_CALL_MAJORSEEN) {
  		if (clnt->cl_chatty) {
  			rcu_read_lock();
  			printk(KERN_NOTICE "%s: server %s OK\n",
  				clnt->cl_program->name,
  				rcu_dereference(clnt->cl_xprt)->servername);
  			rcu_read_unlock();
  		}
  		task->tk_flags &= ~RPC_CALL_MAJORSEEN;
  	}
  
  	/*
  	 * Ensure that we see all writes made by xprt_complete_rqst()
  	 * before it changed req->rq_reply_bytes_recvd.
  	 */
  	smp_rmb();
  	req->rq_rcv_buf.len = req->rq_private_buf.len;
  
  	/* Check that the softirq receive buffer is valid */
  	WARN_ON(memcmp(&req->rq_rcv_buf, &req->rq_private_buf,
  				sizeof(req->rq_rcv_buf)) != 0);
  
  	if (req->rq_rcv_buf.len < 12) {
  		if (!RPC_IS_SOFT(task)) {
  			task->tk_action = call_bind;
  			goto out_retry;
  		}
  		dprintk("RPC:       %s: too small RPC reply size (%d bytes)\n",
  				clnt->cl_program->name, task->tk_status);
  		task->tk_action = call_timeout;
  		goto out_retry;
  	}
  
  	p = rpc_verify_header(task);
  	if (IS_ERR(p)) {
  		if (p == ERR_PTR(-EAGAIN))
  			goto out_retry;
  		return;
  	}
  
  	task->tk_action = rpc_exit_task;
  
  	if (decode) {
  		task->tk_status = rpcauth_unwrap_resp(task, decode, req, p,
  						      task->tk_msg.rpc_resp);
  	}
  	dprintk("RPC: %5u call_decode result %d\n", task->tk_pid,
  			task->tk_status);
  	return;
  out_retry:
  	task->tk_status = 0;
  	/* Note: rpc_verify_header() may have freed the RPC slot */
  	if (task->tk_rqstp == req) {
  		req->rq_reply_bytes_recvd = req->rq_rcv_buf.len = 0;
  		if (task->tk_client->cl_discrtry)
  			xprt_conditional_disconnect(req->rq_xprt,
  					req->rq_connect_cookie);
  	}
  }
  
  static __be32 *
  rpc_encode_header(struct rpc_task *task)
  {
  	struct rpc_clnt *clnt = task->tk_client;
  	struct rpc_rqst	*req = task->tk_rqstp;
  	__be32		*p = req->rq_svec[0].iov_base;
  
  	/* FIXME: check buffer size? */
  
  	p = xprt_skip_transport_header(req->rq_xprt, p);
  	*p++ = req->rq_xid;		/* XID */
  	*p++ = htonl(RPC_CALL);		/* CALL */
  	*p++ = htonl(RPC_VERSION);	/* RPC version */
  	*p++ = htonl(clnt->cl_prog);	/* program number */
  	*p++ = htonl(clnt->cl_vers);	/* program version */
  	*p++ = htonl(task->tk_msg.rpc_proc->p_proc);	/* procedure */
  	p = rpcauth_marshcred(task, p);
  	req->rq_slen = xdr_adjust_iovec(&req->rq_svec[0], p);
  	return p;
  }
  
  static __be32 *
  rpc_verify_header(struct rpc_task *task)
  {
  	struct rpc_clnt *clnt = task->tk_client;
  	struct kvec *iov = &task->tk_rqstp->rq_rcv_buf.head[0];
  	int len = task->tk_rqstp->rq_rcv_buf.len >> 2;
  	__be32	*p = iov->iov_base;
  	u32 n;
  	int error = -EACCES;
  
  	if ((task->tk_rqstp->rq_rcv_buf.len & 3) != 0) {
  		/* RFC-1014 says that the representation of XDR data must be a
  		 * multiple of four bytes
  		 * - if it isn't pointer subtraction in the NFS client may give
  		 *   undefined results
  		 */
  		dprintk("RPC: %5u %s: XDR representation not a multiple of"
  		       " 4 bytes: 0x%x\n", task->tk_pid, __func__,
  		       task->tk_rqstp->rq_rcv_buf.len);
  		error = -EIO;
  		goto out_err;
  	}
  	if ((len -= 3) < 0)
  		goto out_overflow;
  
  	p += 1; /* skip XID */
  	if ((n = ntohl(*p++)) != RPC_REPLY) {
  		dprintk("RPC: %5u %s: not an RPC reply: %x\n",
  			task->tk_pid, __func__, n);
  		error = -EIO;
  		goto out_garbage;
  	}
  
  	if ((n = ntohl(*p++)) != RPC_MSG_ACCEPTED) {
  		if (--len < 0)
  			goto out_overflow;
  		switch ((n = ntohl(*p++))) {
  		case RPC_AUTH_ERROR:
  			break;
  		case RPC_MISMATCH:
  			dprintk("RPC: %5u %s: RPC call version mismatch!\n",
  				task->tk_pid, __func__);
  			error = -EPROTONOSUPPORT;
  			goto out_err;
  		default:
  			dprintk("RPC: %5u %s: RPC call rejected, "
  				"unknown error: %x\n",
  				task->tk_pid, __func__, n);
  			error = -EIO;
  			goto out_err;
  		}
  		if (--len < 0)
  			goto out_overflow;
  		switch ((n = ntohl(*p++))) {
  		case RPC_AUTH_REJECTEDCRED:
  		case RPC_AUTH_REJECTEDVERF:
  		case RPCSEC_GSS_CREDPROBLEM:
  		case RPCSEC_GSS_CTXPROBLEM:
  			if (!task->tk_cred_retry)
  				break;
  			task->tk_cred_retry--;
  			dprintk("RPC: %5u %s: retry stale creds\n",
  					task->tk_pid, __func__);
  			rpcauth_invalcred(task);
  			/* Ensure we obtain a new XID! */
  			xprt_release(task);
  			task->tk_action = call_reserve;
  			goto out_retry;
  		case RPC_AUTH_BADCRED:
  		case RPC_AUTH_BADVERF:
  			/* possibly garbled cred/verf? */
  			if (!task->tk_garb_retry)
  				break;
  			task->tk_garb_retry--;
  			dprintk("RPC: %5u %s: retry garbled creds\n",
  					task->tk_pid, __func__);
  			task->tk_action = call_bind;
  			goto out_retry;
  		case RPC_AUTH_TOOWEAK:
  			rcu_read_lock();
  			printk(KERN_NOTICE "RPC: server %s requires stronger "
  			       "authentication.\n",
  			       rcu_dereference(clnt->cl_xprt)->servername);
  			rcu_read_unlock();
  			break;
  		default:
  			dprintk("RPC: %5u %s: unknown auth error: %x\n",
  					task->tk_pid, __func__, n);
  			error = -EIO;
  		}
  		dprintk("RPC: %5u %s: call rejected %d\n",
  				task->tk_pid, __func__, n);
  		goto out_err;
  	}
  	p = rpcauth_checkverf(task, p);
  	if (IS_ERR(p)) {
  		error = PTR_ERR(p);
  		dprintk("RPC: %5u %s: auth check failed with %d\n",
  				task->tk_pid, __func__, error);
  		goto out_garbage;		/* bad verifier, retry */
  	}
  	len = p - (__be32 *)iov->iov_base - 1;
  	if (len < 0)
  		goto out_overflow;
  	switch ((n = ntohl(*p++))) {
  	case RPC_SUCCESS:
  		return p;
  	case RPC_PROG_UNAVAIL:
  		dprintk_rcu("RPC: %5u %s: program %u is unsupported "
  				"by server %s\n", task->tk_pid, __func__,
  				(unsigned int)clnt->cl_prog,
  				rcu_dereference(clnt->cl_xprt)->servername);
  		error = -EPFNOSUPPORT;
  		goto out_err;
  	case RPC_PROG_MISMATCH:
  		dprintk_rcu("RPC: %5u %s: program %u, version %u unsupported "
  				"by server %s\n", task->tk_pid, __func__,
  				(unsigned int)clnt->cl_prog,
  				(unsigned int)clnt->cl_vers,
  				rcu_dereference(clnt->cl_xprt)->servername);
  		error = -EPROTONOSUPPORT;
  		goto out_err;
  	case RPC_PROC_UNAVAIL:
  		dprintk_rcu("RPC: %5u %s: proc %s unsupported by program %u, "
  				"version %u on server %s\n",
  				task->tk_pid, __func__,
  				rpc_proc_name(task),
  				clnt->cl_prog, clnt->cl_vers,
  				rcu_dereference(clnt->cl_xprt)->servername);
  		error = -EOPNOTSUPP;
  		goto out_err;
  	case RPC_GARBAGE_ARGS:
  		dprintk("RPC: %5u %s: server saw garbage\n",
  				task->tk_pid, __func__);
  		break;			/* retry */
  	default:
  		dprintk("RPC: %5u %s: server accept status: %x\n",
  				task->tk_pid, __func__, n);
  		/* Also retry */
  	}
  
  out_garbage:
  	clnt->cl_stats->rpcgarbage++;
  	if (task->tk_garb_retry) {
  		task->tk_garb_retry--;
  		dprintk("RPC: %5u %s: retrying\n",
  				task->tk_pid, __func__);
  		task->tk_action = call_bind;
  out_retry:
  		return ERR_PTR(-EAGAIN);
  	}
  out_err:
  	rpc_exit(task, error);
  	dprintk("RPC: %5u %s: call failed with error %d\n", task->tk_pid,
  			__func__, error);
  	return ERR_PTR(error);
  out_overflow:
  	dprintk("RPC: %5u %s: server reply was truncated.\n", task->tk_pid,
  			__func__);
  	goto out_garbage;
  }
  
  static void rpcproc_encode_null(void *rqstp, struct xdr_stream *xdr, void *obj)
  {
  }
  
  static int rpcproc_decode_null(void *rqstp, struct xdr_stream *xdr, void *obj)
  {
  	return 0;
  }
  
  static struct rpc_procinfo rpcproc_null = {
  	.p_encode = rpcproc_encode_null,
  	.p_decode = rpcproc_decode_null,
  };
  
  static int rpc_ping(struct rpc_clnt *clnt)
  {
  	struct rpc_message msg = {
  		.rpc_proc = &rpcproc_null,
  	};
  	int err;
  	msg.rpc_cred = authnull_ops.lookup_cred(NULL, NULL, 0);
  	err = rpc_call_sync(clnt, &msg, RPC_TASK_SOFT | RPC_TASK_SOFTCONN);
  	put_rpccred(msg.rpc_cred);
  	return err;
  }
  
  struct rpc_task *rpc_call_null(struct rpc_clnt *clnt, struct rpc_cred *cred, int flags)
  {
  	struct rpc_message msg = {
  		.rpc_proc = &rpcproc_null,
  		.rpc_cred = cred,
  	};
  	struct rpc_task_setup task_setup_data = {
  		.rpc_client = clnt,
  		.rpc_message = &msg,
  		.callback_ops = &rpc_default_ops,
  		.flags = flags,
  	};
  	return rpc_run_task(&task_setup_data);
  }
  EXPORT_SYMBOL_GPL(rpc_call_null);
  
  #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, task->tk_timeout, 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)
  int
  rpc_clnt_swap_activate(struct rpc_clnt *clnt)
  {
  	int ret = 0;
  	struct rpc_xprt	*xprt;
  
  	if (atomic_inc_return(&clnt->cl_swapper) == 1) {
  retry:
  		rcu_read_lock();
  		xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
  		rcu_read_unlock();
  		if (!xprt) {
  			/*
  			 * If we didn't get a reference, then we likely are
  			 * racing with a migration event. Wait for a grace
  			 * period and try again.
  			 */
  			synchronize_rcu();
  			goto retry;
  		}
  
  		ret = xprt_enable_swap(xprt);
  		xprt_put(xprt);
  	}
  	return ret;
  }
  EXPORT_SYMBOL_GPL(rpc_clnt_swap_activate);
  
  void
  rpc_clnt_swap_deactivate(struct rpc_clnt *clnt)
  {
  	struct rpc_xprt	*xprt;
  
  	if (atomic_dec_if_positive(&clnt->cl_swapper) == 0) {
  retry:
  		rcu_read_lock();
  		xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
  		rcu_read_unlock();
  		if (!xprt) {
  			/*
  			 * If we didn't get a reference, then we likely are
  			 * racing with a migration event. Wait for a grace
  			 * period and try again.
  			 */
  			synchronize_rcu();
  			goto retry;
  		}
  
  		xprt_disable_swap(xprt);
  		xprt_put(xprt);
  	}
  }
  EXPORT_SYMBOL_GPL(rpc_clnt_swap_deactivate);
  #endif /* CONFIG_SUNRPC_SWAP */
  