/*
   *  linux/net/sunrpc/xprt.c
   *
   *  This is a generic RPC call interface supporting congestion avoidance,
   *  and asynchronous calls.
   *
   *  The interface works like this:
   *
   *  -	When a process places a call, it allocates a request slot if
   *	one is available. Otherwise, it sleeps on the backlog queue
   *	(xprt_reserve).
   *  -	Next, the caller puts together the RPC message, stuffs it into

   *	the request struct, and calls xprt_transmit().
   *  -	xprt_transmit sends the message and installs the caller on the

   *	transport's wait list. At the same time, if a reply is expected,
   *	it installs a timer that is run after the packet's timeout has
   *	expired.

   *  -	When a packet arrives, the data_ready handler walks the list of

   *	pending requests for that transport. If a matching XID is found, the

   *	caller is woken up, and the timer removed.
   *  -	When no reply arrives within the timeout interval, the timer is
   *	fired by the kernel and runs xprt_timer(). It either adjusts the
   *	timeout values (minor timeout) or wakes up the caller with a status
   *	of -ETIMEDOUT.
   *  -	When the caller receives a notification from RPC that a reply arrived,
   *	it should release the RPC slot, and process the reply.
   *	If the call timed out, it may choose to retry the operation by
   *	adjusting the initial timeout value, and simply calling rpc_call
   *	again.
   *
   *  Support for async RPC is done through a set of RPC-specific scheduling
   *  primitives that `transparently' work for processes as well as async
   *  tasks that rely on callbacks.
   *
   *  Copyright (C) 1995-1997, Olaf Kirch <okir@monad.swb.de>

   *
   *  Transport switch API copyright (C) 2005, Chuck Lever <cel@netapp.com>

   */

  #include <linux/module.h>

  #include <linux/types.h>

  #include <linux/interrupt.h>

  #include <linux/workqueue.h>

  #include <linux/net.h>

  #include <linux/sunrpc/clnt.h>

  #include <linux/sunrpc/metrics.h>

  #include "sunrpc.h"

  /*
   * Local variables
   */
  
  #ifdef RPC_DEBUG

  # define RPCDBG_FACILITY	RPCDBG_XPRT
  #endif

  /*
   * Local functions
   */
  static void	xprt_request_init(struct rpc_task *, struct rpc_xprt *);
  static inline void	do_xprt_reserve(struct rpc_task *);

  static void	xprt_connect_status(struct rpc_task *task);

  static int      __xprt_get_cong(struct rpc_xprt *, struct rpc_task *);

  static DEFINE_SPINLOCK(xprt_list_lock);

  static LIST_HEAD(xprt_list);

  /*
   * The transport code maintains an estimate on the maximum number of out-
   * standing RPC requests, using a smoothed version of the congestion
   * avoidance implemented in 44BSD. This is basically the Van Jacobson
   * congestion algorithm: If a retransmit occurs, the congestion window is
   * halved; otherwise, it is incremented by 1/cwnd when
   *
   *	-	a reply is received and
   *	-	a full number of requests are outstanding and
   *	-	the congestion window hasn't been updated recently.
   */
  #define RPC_CWNDSHIFT		(8U)
  #define RPC_CWNDSCALE		(1U << RPC_CWNDSHIFT)
  #define RPC_INITCWND		RPC_CWNDSCALE
  #define RPC_MAXCWND(xprt)	((xprt)->max_reqs << RPC_CWNDSHIFT)
  
  #define RPCXPRT_CONGESTED(xprt) ((xprt)->cong >= (xprt)->cwnd)

  /**

   * xprt_register_transport - register a transport implementation
   * @transport: transport to register
   *
   * If a transport implementation is loaded as a kernel module, it can
   * call this interface to make itself known to the RPC client.
   *
   * Returns:
   * 0:		transport successfully registered
   * -EEXIST:	transport already registered
   * -EINVAL:	transport module being unloaded
   */
  int xprt_register_transport(struct xprt_class *transport)
  {
  	struct xprt_class *t;
  	int result;
  
  	result = -EEXIST;
  	spin_lock(&xprt_list_lock);
  	list_for_each_entry(t, &xprt_list, list) {
  		/* don't register the same transport class twice */

  		if (t->ident == transport->ident)

  			goto out;
  	}

  	list_add_tail(&transport->list, &xprt_list);
  	printk(KERN_INFO "RPC: Registered %s transport module.
  ",
  	       transport->name);
  	result = 0;

  
  out:
  	spin_unlock(&xprt_list_lock);
  	return result;
  }
  EXPORT_SYMBOL_GPL(xprt_register_transport);
  
  /**
   * xprt_unregister_transport - unregister a transport implementation

   * @transport: transport to unregister

   *
   * Returns:
   * 0:		transport successfully unregistered
   * -ENOENT:	transport never registered
   */
  int xprt_unregister_transport(struct xprt_class *transport)
  {
  	struct xprt_class *t;
  	int result;
  
  	result = 0;
  	spin_lock(&xprt_list_lock);
  	list_for_each_entry(t, &xprt_list, list) {
  		if (t == transport) {
  			printk(KERN_INFO
  				"RPC: Unregistered %s transport module.
  ",
  				transport->name);
  			list_del_init(&transport->list);

  			goto out;
  		}
  	}
  	result = -ENOENT;
  
  out:
  	spin_unlock(&xprt_list_lock);
  	return result;
  }
  EXPORT_SYMBOL_GPL(xprt_unregister_transport);
  
  /**

   * xprt_load_transport - load a transport implementation
   * @transport_name: transport to load
   *
   * Returns:
   * 0:		transport successfully loaded
   * -ENOENT:	transport module not available
   */
  int xprt_load_transport(const char *transport_name)
  {
  	struct xprt_class *t;
  	char module_name[sizeof t->name + 5];
  	int result;
  
  	result = 0;
  	spin_lock(&xprt_list_lock);
  	list_for_each_entry(t, &xprt_list, list) {
  		if (strcmp(t->name, transport_name) == 0) {
  			spin_unlock(&xprt_list_lock);
  			goto out;
  		}
  	}
  	spin_unlock(&xprt_list_lock);
  	strcpy(module_name, "xprt");
  	strncat(module_name, transport_name, sizeof t->name);
  	result = request_module(module_name);
  out:
  	return result;
  }
  EXPORT_SYMBOL_GPL(xprt_load_transport);
  
  /**

   * xprt_reserve_xprt - serialize write access to transports
   * @task: task that is requesting access to the transport
   *
   * This prevents mixing the payload of separate requests, and prevents
   * transport connects from colliding with writes.  No congestion control
   * is provided.
   */
  int xprt_reserve_xprt(struct rpc_task *task)
  {

  	struct rpc_rqst *req = task->tk_rqstp;

  	struct rpc_xprt	*xprt = req->rq_xprt;

  
  	if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) {
  		if (task == xprt->snd_task)
  			return 1;
  		if (task == NULL)
  			return 0;
  		goto out_sleep;
  	}
  	xprt->snd_task = task;
  	if (req) {
  		req->rq_bytes_sent = 0;
  		req->rq_ntrans++;
  	}
  	return 1;
  
  out_sleep:

  	dprintk("RPC: %5u failed to lock transport %p
  ",

  			task->tk_pid, xprt);
  	task->tk_timeout = 0;
  	task->tk_status = -EAGAIN;
  	if (req && req->rq_ntrans)

  		rpc_sleep_on(&xprt->resend, task, NULL);

  	else

  		rpc_sleep_on(&xprt->sending, task, NULL);

  	return 0;
  }

  EXPORT_SYMBOL_GPL(xprt_reserve_xprt);

  static void xprt_clear_locked(struct rpc_xprt *xprt)
  {
  	xprt->snd_task = NULL;
  	if (!test_bit(XPRT_CLOSE_WAIT, &xprt->state) || xprt->shutdown) {
  		smp_mb__before_clear_bit();
  		clear_bit(XPRT_LOCKED, &xprt->state);
  		smp_mb__after_clear_bit();
  	} else

  		queue_work(rpciod_workqueue, &xprt->task_cleanup);

  }

  /*

   * xprt_reserve_xprt_cong - serialize write access to transports
   * @task: task that is requesting access to the transport
   *
   * Same as xprt_reserve_xprt, but Van Jacobson congestion control is
   * integrated into the decision of whether a request is allowed to be
   * woken up and given access to the transport.

   */

  int xprt_reserve_xprt_cong(struct rpc_task *task)

  {

  	struct rpc_xprt	*xprt = task->tk_xprt;

  	struct rpc_rqst *req = task->tk_rqstp;

  	if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) {

  		if (task == xprt->snd_task)
  			return 1;

  		goto out_sleep;
  	}

  	if (__xprt_get_cong(xprt, task)) {

  		xprt->snd_task = task;
  		if (req) {
  			req->rq_bytes_sent = 0;
  			req->rq_ntrans++;
  		}
  		return 1;
  	}

  	xprt_clear_locked(xprt);

  out_sleep:

  	dprintk("RPC: %5u failed to lock transport %p
  ", task->tk_pid, xprt);

  	task->tk_timeout = 0;
  	task->tk_status = -EAGAIN;
  	if (req && req->rq_ntrans)

  		rpc_sleep_on(&xprt->resend, task, NULL);

  	else

  		rpc_sleep_on(&xprt->sending, task, NULL);

  	return 0;
  }

  EXPORT_SYMBOL_GPL(xprt_reserve_xprt_cong);

  static inline int xprt_lock_write(struct rpc_xprt *xprt, struct rpc_task *task)

  {
  	int retval;

  	spin_lock_bh(&xprt->transport_lock);

  	retval = xprt->ops->reserve_xprt(task);

  	spin_unlock_bh(&xprt->transport_lock);

  	return retval;
  }

  static void __xprt_lock_write_next(struct rpc_xprt *xprt)

  {
  	struct rpc_task *task;

  	struct rpc_rqst *req;
  
  	if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
  		return;
  
  	task = rpc_wake_up_next(&xprt->resend);
  	if (!task) {
  		task = rpc_wake_up_next(&xprt->sending);
  		if (!task)
  			goto out_unlock;
  	}
  
  	req = task->tk_rqstp;
  	xprt->snd_task = task;
  	if (req) {
  		req->rq_bytes_sent = 0;
  		req->rq_ntrans++;
  	}
  	return;
  
  out_unlock:

  	xprt_clear_locked(xprt);

  }
  
  static void __xprt_lock_write_next_cong(struct rpc_xprt *xprt)
  {
  	struct rpc_task *task;

  	if (test_and_set_bit(XPRT_LOCKED, &xprt->state))

  		return;

  	if (RPCXPRT_CONGESTED(xprt))

  		goto out_unlock;
  	task = rpc_wake_up_next(&xprt->resend);
  	if (!task) {
  		task = rpc_wake_up_next(&xprt->sending);
  		if (!task)
  			goto out_unlock;
  	}

  	if (__xprt_get_cong(xprt, task)) {

  		struct rpc_rqst *req = task->tk_rqstp;
  		xprt->snd_task = task;
  		if (req) {
  			req->rq_bytes_sent = 0;
  			req->rq_ntrans++;
  		}
  		return;
  	}
  out_unlock:

  	xprt_clear_locked(xprt);

  }

  /**
   * xprt_release_xprt - allow other requests to use a transport
   * @xprt: transport with other tasks potentially waiting
   * @task: task that is releasing access to the transport
   *
   * Note that "task" can be NULL.  No congestion control is provided.

   */

  void xprt_release_xprt(struct rpc_xprt *xprt, struct rpc_task *task)

  {
  	if (xprt->snd_task == task) {

  		xprt_clear_locked(xprt);

  		__xprt_lock_write_next(xprt);
  	}
  }

  EXPORT_SYMBOL_GPL(xprt_release_xprt);

  /**
   * xprt_release_xprt_cong - allow other requests to use a transport
   * @xprt: transport with other tasks potentially waiting
   * @task: task that is releasing access to the transport
   *
   * Note that "task" can be NULL.  Another task is awoken to use the
   * transport if the transport's congestion window allows it.
   */
  void xprt_release_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task)
  {
  	if (xprt->snd_task == task) {

  		xprt_clear_locked(xprt);

  		__xprt_lock_write_next_cong(xprt);
  	}
  }

  EXPORT_SYMBOL_GPL(xprt_release_xprt_cong);

  
  static inline void xprt_release_write(struct rpc_xprt *xprt, struct rpc_task *task)

  {

  	spin_lock_bh(&xprt->transport_lock);

  	xprt->ops->release_xprt(xprt, task);

  	spin_unlock_bh(&xprt->transport_lock);

  }
  
  /*

   * Van Jacobson congestion avoidance. Check if the congestion window
   * overflowed. Put the task to sleep if this is the case.
   */
  static int
  __xprt_get_cong(struct rpc_xprt *xprt, struct rpc_task *task)
  {
  	struct rpc_rqst *req = task->tk_rqstp;
  
  	if (req->rq_cong)
  		return 1;

  	dprintk("RPC: %5u xprt_cwnd_limited cong = %lu cwnd = %lu
  ",

  			task->tk_pid, xprt->cong, xprt->cwnd);
  	if (RPCXPRT_CONGESTED(xprt))
  		return 0;
  	req->rq_cong = 1;
  	xprt->cong += RPC_CWNDSCALE;
  	return 1;
  }
  
  /*
   * Adjust the congestion window, and wake up the next task
   * that has been sleeping due to congestion
   */
  static void
  __xprt_put_cong(struct rpc_xprt *xprt, struct rpc_rqst *req)
  {
  	if (!req->rq_cong)
  		return;
  	req->rq_cong = 0;
  	xprt->cong -= RPC_CWNDSCALE;

  	__xprt_lock_write_next_cong(xprt);

  }

  /**

   * xprt_release_rqst_cong - housekeeping when request is complete
   * @task: RPC request that recently completed
   *
   * Useful for transports that require congestion control.
   */
  void xprt_release_rqst_cong(struct rpc_task *task)
  {
  	__xprt_put_cong(task->tk_xprt, task->tk_rqstp);
  }

  EXPORT_SYMBOL_GPL(xprt_release_rqst_cong);

  
  /**

   * xprt_adjust_cwnd - adjust transport congestion window
   * @task: recently completed RPC request used to adjust window
   * @result: result code of completed RPC request
   *

   * We use a time-smoothed congestion estimator to avoid heavy oscillation.
   */

  void xprt_adjust_cwnd(struct rpc_task *task, int result)

  {

  	struct rpc_rqst *req = task->tk_rqstp;
  	struct rpc_xprt *xprt = task->tk_xprt;
  	unsigned long cwnd = xprt->cwnd;

  	if (result >= 0 && cwnd <= xprt->cong) {
  		/* The (cwnd >> 1) term makes sure
  		 * the result gets rounded properly. */
  		cwnd += (RPC_CWNDSCALE * RPC_CWNDSCALE + (cwnd >> 1)) / cwnd;
  		if (cwnd > RPC_MAXCWND(xprt))
  			cwnd = RPC_MAXCWND(xprt);

  		__xprt_lock_write_next_cong(xprt);

  	} else if (result == -ETIMEDOUT) {
  		cwnd >>= 1;
  		if (cwnd < RPC_CWNDSCALE)
  			cwnd = RPC_CWNDSCALE;
  	}

  	dprintk("RPC:       cong %ld, cwnd was %ld, now %ld
  ",

  			xprt->cong, xprt->cwnd, cwnd);
  	xprt->cwnd = cwnd;

  	__xprt_put_cong(xprt, req);

  }

  EXPORT_SYMBOL_GPL(xprt_adjust_cwnd);

  /**
   * xprt_wake_pending_tasks - wake all tasks on a transport's pending queue
   * @xprt: transport with waiting tasks
   * @status: result code to plant in each task before waking it
   *
   */
  void xprt_wake_pending_tasks(struct rpc_xprt *xprt, int status)
  {
  	if (status < 0)
  		rpc_wake_up_status(&xprt->pending, status);
  	else
  		rpc_wake_up(&xprt->pending);
  }

  EXPORT_SYMBOL_GPL(xprt_wake_pending_tasks);

  /**
   * xprt_wait_for_buffer_space - wait for transport output buffer to clear
   * @task: task to be put to sleep

   * @action: function pointer to be executed after wait

   */

  void xprt_wait_for_buffer_space(struct rpc_task *task, rpc_action action)

  {
  	struct rpc_rqst *req = task->tk_rqstp;
  	struct rpc_xprt *xprt = req->rq_xprt;
  
  	task->tk_timeout = req->rq_timeout;

  	rpc_sleep_on(&xprt->pending, task, action);

  }

  EXPORT_SYMBOL_GPL(xprt_wait_for_buffer_space);

  
  /**
   * xprt_write_space - wake the task waiting for transport output buffer space
   * @xprt: transport with waiting tasks
   *
   * Can be called in a soft IRQ context, so xprt_write_space never sleeps.
   */
  void xprt_write_space(struct rpc_xprt *xprt)
  {
  	if (unlikely(xprt->shutdown))
  		return;
  
  	spin_lock_bh(&xprt->transport_lock);
  	if (xprt->snd_task) {

  		dprintk("RPC:       write space: waking waiting task on "
  				"xprt %p
  ", xprt);

  		rpc_wake_up_queued_task(&xprt->pending, xprt->snd_task);

  	}
  	spin_unlock_bh(&xprt->transport_lock);
  }

  EXPORT_SYMBOL_GPL(xprt_write_space);

  /**
   * xprt_set_retrans_timeout_def - set a request's retransmit timeout
   * @task: task whose timeout is to be set
   *
   * Set a request's retransmit timeout based on the transport's
   * default timeout parameters.  Used by transports that don't adjust
   * the retransmit timeout based on round-trip time estimation.
   */
  void xprt_set_retrans_timeout_def(struct rpc_task *task)
  {
  	task->tk_timeout = task->tk_rqstp->rq_timeout;
  }

  EXPORT_SYMBOL_GPL(xprt_set_retrans_timeout_def);

  
  /*
   * xprt_set_retrans_timeout_rtt - set a request's retransmit timeout
   * @task: task whose timeout is to be set

   *

   * Set a request's retransmit timeout using the RTT estimator.
   */
  void xprt_set_retrans_timeout_rtt(struct rpc_task *task)
  {
  	int timer = task->tk_msg.rpc_proc->p_timer;

  	struct rpc_clnt *clnt = task->tk_client;
  	struct rpc_rtt *rtt = clnt->cl_rtt;

  	struct rpc_rqst *req = task->tk_rqstp;

  	unsigned long max_timeout = clnt->cl_timeout->to_maxval;

  
  	task->tk_timeout = rpc_calc_rto(rtt, timer);
  	task->tk_timeout <<= rpc_ntimeo(rtt, timer) + req->rq_retries;
  	if (task->tk_timeout > max_timeout || task->tk_timeout == 0)
  		task->tk_timeout = max_timeout;
  }

  EXPORT_SYMBOL_GPL(xprt_set_retrans_timeout_rtt);

  static void xprt_reset_majortimeo(struct rpc_rqst *req)
  {

  	const struct rpc_timeout *to = req->rq_task->tk_client->cl_timeout;

  
  	req->rq_majortimeo = req->rq_timeout;
  	if (to->to_exponential)
  		req->rq_majortimeo <<= to->to_retries;
  	else
  		req->rq_majortimeo += to->to_increment * to->to_retries;
  	if (req->rq_majortimeo > to->to_maxval || req->rq_majortimeo == 0)
  		req->rq_majortimeo = to->to_maxval;
  	req->rq_majortimeo += jiffies;
  }

  /**
   * xprt_adjust_timeout - adjust timeout values for next retransmit
   * @req: RPC request containing parameters to use for the adjustment
   *

   */
  int xprt_adjust_timeout(struct rpc_rqst *req)
  {
  	struct rpc_xprt *xprt = req->rq_xprt;

  	const struct rpc_timeout *to = req->rq_task->tk_client->cl_timeout;

  	int status = 0;
  
  	if (time_before(jiffies, req->rq_majortimeo)) {
  		if (to->to_exponential)
  			req->rq_timeout <<= 1;
  		else
  			req->rq_timeout += to->to_increment;
  		if (to->to_maxval && req->rq_timeout >= to->to_maxval)
  			req->rq_timeout = to->to_maxval;
  		req->rq_retries++;

  	} else {
  		req->rq_timeout = to->to_initval;
  		req->rq_retries = 0;
  		xprt_reset_majortimeo(req);
  		/* Reset the RTT counters == "slow start" */

  		spin_lock_bh(&xprt->transport_lock);

  		rpc_init_rtt(req->rq_task->tk_client->cl_rtt, to->to_initval);

  		spin_unlock_bh(&xprt->transport_lock);

  		status = -ETIMEDOUT;
  	}
  
  	if (req->rq_timeout == 0) {
  		printk(KERN_WARNING "xprt_adjust_timeout: rq_timeout = 0!
  ");
  		req->rq_timeout = 5 * HZ;
  	}
  	return status;
  }

  static void xprt_autoclose(struct work_struct *work)

  {

  	struct rpc_xprt *xprt =
  		container_of(work, struct rpc_xprt, task_cleanup);

  	xprt->ops->close(xprt);

  	clear_bit(XPRT_CLOSE_WAIT, &xprt->state);

  	xprt_release_write(xprt, NULL);
  }

  /**

   * xprt_disconnect_done - mark a transport as disconnected

   * @xprt: transport to flag for disconnect
   *

   */

  void xprt_disconnect_done(struct rpc_xprt *xprt)

  {

  	dprintk("RPC:       disconnected transport %p
  ", xprt);

  	spin_lock_bh(&xprt->transport_lock);

  	xprt_clear_connected(xprt);

  	xprt_wake_pending_tasks(xprt, -EAGAIN);

  	spin_unlock_bh(&xprt->transport_lock);

  }

  EXPORT_SYMBOL_GPL(xprt_disconnect_done);

  /**
   * xprt_force_disconnect - force a transport to disconnect
   * @xprt: transport to disconnect
   *
   */
  void xprt_force_disconnect(struct rpc_xprt *xprt)
  {
  	/* Don't race with the test_bit() in xprt_clear_locked() */
  	spin_lock_bh(&xprt->transport_lock);
  	set_bit(XPRT_CLOSE_WAIT, &xprt->state);
  	/* Try to schedule an autoclose RPC call */
  	if (test_and_set_bit(XPRT_LOCKED, &xprt->state) == 0)
  		queue_work(rpciod_workqueue, &xprt->task_cleanup);

  	xprt_wake_pending_tasks(xprt, -EAGAIN);

  	spin_unlock_bh(&xprt->transport_lock);
  }

  /**
   * xprt_conditional_disconnect - force a transport to disconnect
   * @xprt: transport to disconnect
   * @cookie: 'connection cookie'
   *
   * This attempts to break the connection if and only if 'cookie' matches
   * the current transport 'connection cookie'. It ensures that we don't
   * try to break the connection more than once when we need to retransmit
   * a batch of RPC requests.
   *
   */
  void xprt_conditional_disconnect(struct rpc_xprt *xprt, unsigned int cookie)
  {
  	/* Don't race with the test_bit() in xprt_clear_locked() */
  	spin_lock_bh(&xprt->transport_lock);
  	if (cookie != xprt->connect_cookie)
  		goto out;
  	if (test_bit(XPRT_CLOSING, &xprt->state) || !xprt_connected(xprt))
  		goto out;
  	set_bit(XPRT_CLOSE_WAIT, &xprt->state);
  	/* Try to schedule an autoclose RPC call */
  	if (test_and_set_bit(XPRT_LOCKED, &xprt->state) == 0)
  		queue_work(rpciod_workqueue, &xprt->task_cleanup);

  	xprt_wake_pending_tasks(xprt, -EAGAIN);

  out:
  	spin_unlock_bh(&xprt->transport_lock);
  }

  static void
  xprt_init_autodisconnect(unsigned long data)
  {
  	struct rpc_xprt *xprt = (struct rpc_xprt *)data;

  	spin_lock(&xprt->transport_lock);

  	if (!list_empty(&xprt->recv) || xprt->shutdown)
  		goto out_abort;

  	if (test_and_set_bit(XPRT_LOCKED, &xprt->state))

  		goto out_abort;

  	spin_unlock(&xprt->transport_lock);

  	set_bit(XPRT_CONNECTION_CLOSE, &xprt->state);
  	queue_work(rpciod_workqueue, &xprt->task_cleanup);

  	return;
  out_abort:

  	spin_unlock(&xprt->transport_lock);

  }

  /**
   * xprt_connect - schedule a transport connect operation
   * @task: RPC task that is requesting the connect

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

  	dprintk("RPC: %5u xprt_connect xprt %p %s connected
  ", task->tk_pid,

  			xprt, (xprt_connected(xprt) ? "is" : "is not"));

  	if (!xprt_bound(xprt)) {

  		task->tk_status = -EAGAIN;

  		return;
  	}
  	if (!xprt_lock_write(xprt, task))
  		return;
  	if (xprt_connected(xprt))

  		xprt_release_write(xprt, task);
  	else {
  		if (task->tk_rqstp)
  			task->tk_rqstp->rq_bytes_sent = 0;

  		task->tk_timeout = xprt->connect_timeout;

  		rpc_sleep_on(&xprt->pending, task, xprt_connect_status);

  		xprt->stat.connect_start = jiffies;

  		xprt->ops->connect(task);

  	}
  	return;

  }

  static void xprt_connect_status(struct rpc_task *task)

  {
  	struct rpc_xprt	*xprt = task->tk_xprt;

  	if (task->tk_status == 0) {

  		xprt->stat.connect_count++;
  		xprt->stat.connect_time += (long)jiffies - xprt->stat.connect_start;

  		dprintk("RPC: %5u xprt_connect_status: connection established
  ",

  				task->tk_pid);
  		return;
  	}

  	switch (task->tk_status) {

  	case -EAGAIN:
  		dprintk("RPC: %5u xprt_connect_status: retrying
  ", task->tk_pid);

  		break;

  	case -ETIMEDOUT:

  		dprintk("RPC: %5u xprt_connect_status: connect attempt timed "
  				"out
  ", task->tk_pid);

  		break;
  	default:

  		dprintk("RPC: %5u xprt_connect_status: error %d connecting to "
  				"server %s
  ", task->tk_pid, -task->tk_status,
  				task->tk_client->cl_server);

  		xprt_release_write(xprt, task);
  		task->tk_status = -EIO;

  	}

  }

  /**
   * xprt_lookup_rqst - find an RPC request corresponding to an XID
   * @xprt: transport on which the original request was transmitted
   * @xid: RPC XID of incoming reply
   *

   */

  struct rpc_rqst *xprt_lookup_rqst(struct rpc_xprt *xprt, __be32 xid)

  {
  	struct list_head *pos;

  
  	list_for_each(pos, &xprt->recv) {
  		struct rpc_rqst *entry = list_entry(pos, struct rpc_rqst, rq_list);

  		if (entry->rq_xid == xid)
  			return entry;

  	}

  
  	dprintk("RPC:       xprt_lookup_rqst did not find xid %08x
  ",
  			ntohl(xid));

  	xprt->stat.bad_xids++;
  	return NULL;

  }

  EXPORT_SYMBOL_GPL(xprt_lookup_rqst);

  /**

   * xprt_update_rtt - update an RPC client's RTT state after receiving a reply
   * @task: RPC request that recently completed
   *
   */
  void xprt_update_rtt(struct rpc_task *task)
  {
  	struct rpc_rqst *req = task->tk_rqstp;
  	struct rpc_rtt *rtt = task->tk_client->cl_rtt;
  	unsigned timer = task->tk_msg.rpc_proc->p_timer;
  
  	if (timer) {
  		if (req->rq_ntrans == 1)
  			rpc_update_rtt(rtt, timer,
  					(long)jiffies - req->rq_xtime);
  		rpc_set_timeo(rtt, timer, req->rq_ntrans - 1);
  	}
  }

  EXPORT_SYMBOL_GPL(xprt_update_rtt);

  
  /**

   * xprt_complete_rqst - called when reply processing is complete

   * @task: RPC request that recently completed

   * @copied: actual number of bytes received from the transport
   *

   * Caller holds transport lock.

   */

  void xprt_complete_rqst(struct rpc_task *task, int copied)

  {

  	struct rpc_rqst *req = task->tk_rqstp;

  	struct rpc_xprt *xprt = req->rq_xprt;

  	dprintk("RPC: %5u xid %08x complete (%d bytes received)
  ",
  			task->tk_pid, ntohl(req->rq_xid), copied);

  	xprt->stat.recvs++;

  	task->tk_rtt = (long)jiffies - req->rq_xtime;

  	list_del_init(&req->rq_list);

  	req->rq_private_buf.len = copied;

  	/* Ensure all writes are done before we update */
  	/* req->rq_reply_bytes_recvd */

  	smp_wmb();

  	req->rq_reply_bytes_recvd = copied;

  	rpc_wake_up_queued_task(&xprt->pending, task);

  }

  EXPORT_SYMBOL_GPL(xprt_complete_rqst);

  static void xprt_timer(struct rpc_task *task)

  {

  	struct rpc_rqst *req = task->tk_rqstp;

  	struct rpc_xprt *xprt = req->rq_xprt;

  	if (task->tk_status != -ETIMEDOUT)
  		return;

  	dprintk("RPC: %5u xprt_timer
  ", task->tk_pid);

  	spin_lock_bh(&xprt->transport_lock);

  	if (!req->rq_reply_bytes_recvd) {

  		if (xprt->ops->timer)
  			xprt->ops->timer(task);

  	} else
  		task->tk_status = 0;
  	spin_unlock_bh(&xprt->transport_lock);

  }

  /**
   * xprt_prepare_transmit - reserve the transport before sending a request
   * @task: RPC task about to send a request
   *

   */

  int xprt_prepare_transmit(struct rpc_task *task)

  {
  	struct rpc_rqst	*req = task->tk_rqstp;
  	struct rpc_xprt	*xprt = req->rq_xprt;
  	int err = 0;

  	dprintk("RPC: %5u xprt_prepare_transmit
  ", task->tk_pid);

  	spin_lock_bh(&xprt->transport_lock);

  	if (req->rq_reply_bytes_recvd && !req->rq_bytes_sent) {
  		err = req->rq_reply_bytes_recvd;

  		goto out_unlock;
  	}

  	if (!xprt->ops->reserve_xprt(task))

  		err = -EAGAIN;

  out_unlock:

  	spin_unlock_bh(&xprt->transport_lock);

  	return err;
  }

  void xprt_end_transmit(struct rpc_task *task)

  {

  	xprt_release_write(task->tk_rqstp->rq_xprt, task);

  }

  /**
   * xprt_transmit - send an RPC request on a transport
   * @task: controlling RPC task
   *
   * We have to copy the iovec because sendmsg fiddles with its contents.
   */
  void xprt_transmit(struct rpc_task *task)

  {

  	struct rpc_rqst	*req = task->tk_rqstp;
  	struct rpc_xprt	*xprt = req->rq_xprt;

  	int status;

  	dprintk("RPC: %5u xprt_transmit(%u)
  ", task->tk_pid, req->rq_slen);

  	if (!req->rq_reply_bytes_recvd) {

  		if (list_empty(&req->rq_list) && rpc_reply_expected(task)) {
  			/*
  			 * Add to the list only if we're expecting a reply
  			 */

  			spin_lock_bh(&xprt->transport_lock);

  			/* Update the softirq receive buffer */
  			memcpy(&req->rq_private_buf, &req->rq_rcv_buf,
  					sizeof(req->rq_private_buf));
  			/* Add request to the receive list */
  			list_add_tail(&req->rq_list, &xprt->recv);

  			spin_unlock_bh(&xprt->transport_lock);

  			xprt_reset_majortimeo(req);

  			/* Turn off autodisconnect */
  			del_singleshot_timer_sync(&xprt->timer);

  		}
  	} else if (!req->rq_bytes_sent)
  		return;

  	req->rq_connect_cookie = xprt->connect_cookie;

  	req->rq_xtime = jiffies;

  	status = xprt->ops->send_request(task);

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

  	dprintk("RPC: %5u xmit complete
  ", task->tk_pid);
  	spin_lock_bh(&xprt->transport_lock);

  	xprt->ops->set_retrans_timeout(task);

  	xprt->stat.sends++;
  	xprt->stat.req_u += xprt->stat.sends - xprt->stat.recvs;
  	xprt->stat.bklog_u += xprt->backlog.qlen;

  	/* Don't race with disconnect */
  	if (!xprt_connected(xprt))
  		task->tk_status = -ENOTCONN;

  	else if (!req->rq_reply_bytes_recvd && rpc_reply_expected(task)) {

  		/*
  		 * Sleep on the pending queue since
  		 * we're expecting a reply.
  		 */

  		rpc_sleep_on(&xprt->pending, task, xprt_timer);

  	}

  	spin_unlock_bh(&xprt->transport_lock);

  }

  static inline void do_xprt_reserve(struct rpc_task *task)

  {
  	struct rpc_xprt	*xprt = task->tk_xprt;
  
  	task->tk_status = 0;
  	if (task->tk_rqstp)
  		return;
  	if (!list_empty(&xprt->free)) {
  		struct rpc_rqst	*req = list_entry(xprt->free.next, struct rpc_rqst, rq_list);
  		list_del_init(&req->rq_list);
  		task->tk_rqstp = req;
  		xprt_request_init(task, xprt);
  		return;
  	}

  	dprintk("RPC:       waiting for request slot
  ");

  	task->tk_status = -EAGAIN;
  	task->tk_timeout = 0;

  	rpc_sleep_on(&xprt->backlog, task, NULL);

  }

  /**
   * xprt_reserve - allocate an RPC request slot
   * @task: RPC task requesting a slot allocation
   *
   * If no more slots are available, place the task on the transport's
   * backlog queue.
   */
  void xprt_reserve(struct rpc_task *task)

  {
  	struct rpc_xprt	*xprt = task->tk_xprt;
  
  	task->tk_status = -EIO;

  	spin_lock(&xprt->reserve_lock);
  	do_xprt_reserve(task);
  	spin_unlock(&xprt->reserve_lock);

  }

  static inline __be32 xprt_alloc_xid(struct rpc_xprt *xprt)

  {
  	return xprt->xid++;
  }
  
  static inline void xprt_init_xid(struct rpc_xprt *xprt)
  {

  	xprt->xid = net_random();

  }

  static void xprt_request_init(struct rpc_task *task, struct rpc_xprt *xprt)

  {
  	struct rpc_rqst	*req = task->tk_rqstp;

  	req->rq_timeout = task->tk_client->cl_timeout->to_initval;

  	req->rq_task	= task;
  	req->rq_xprt    = xprt;

  	req->rq_buffer  = NULL;

  	req->rq_xid     = xprt_alloc_xid(xprt);

  	req->rq_release_snd_buf = NULL;

  	xprt_reset_majortimeo(req);

  	dprintk("RPC: %5u reserved req %p xid %08x
  ", task->tk_pid,

  			req, ntohl(req->rq_xid));
  }

  /**
   * xprt_release - release an RPC request slot
   * @task: task which is finished with the slot
   *

   */

  void xprt_release(struct rpc_task *task)

  {

  	struct rpc_xprt	*xprt;

  	struct rpc_rqst	*req;

  	int is_bc_request;

  
  	if (!(req = task->tk_rqstp))
  		return;

  
  	/* Preallocated backchannel request? */
  	is_bc_request = bc_prealloc(req);
  
  	xprt = req->rq_xprt;

  	rpc_count_iostats(task);

  	spin_lock_bh(&xprt->transport_lock);

  	xprt->ops->release_xprt(xprt, task);

  	if (xprt->ops->release_request)
  		xprt->ops->release_request(task);

  	if (!list_empty(&req->rq_list))
  		list_del(&req->rq_list);
  	xprt->last_used = jiffies;

  	if (list_empty(&xprt->recv))

  		mod_timer(&xprt->timer,

  				xprt->last_used + xprt->idle_timeout);

  	spin_unlock_bh(&xprt->transport_lock);

  	if (!bc_prealloc(req))
  		xprt->ops->buf_free(req->rq_buffer);

  	task->tk_rqstp = NULL;

  	if (req->rq_release_snd_buf)
  		req->rq_release_snd_buf(req);

  
  	/*
  	 * Early exit if this is a backchannel preallocated request.
  	 * There is no need to have it added to the RPC slot list.
  	 */
  	if (is_bc_request)
  		return;

  	memset(req, 0, sizeof(*req));	/* mark unused */

  	dprintk("RPC: %5u release request %p
  ", task->tk_pid, req);

  	spin_lock(&xprt->reserve_lock);

  	list_add(&req->rq_list, &xprt->free);

  	rpc_wake_up_next(&xprt->backlog);

  	spin_unlock(&xprt->reserve_lock);

  }

  /**

   * xprt_create_transport - create an RPC transport

   * @args: rpc transport creation arguments

   *
   */

  struct rpc_xprt *xprt_create_transport(struct xprt_create *args)

  {

  	struct rpc_xprt	*xprt;
  	struct rpc_rqst	*req;

  	struct xprt_class *t;

  	spin_lock(&xprt_list_lock);
  	list_for_each_entry(t, &xprt_list, list) {

  		if (t->ident == args->ident) {

  			spin_unlock(&xprt_list_lock);
  			goto found;
  		}

  	}

  	spin_unlock(&xprt_list_lock);

  	printk(KERN_ERR "RPC: transport (%d) not supported
  ", args->ident);

  	return ERR_PTR(-EIO);
  
  found:
  	xprt = t->setup(args);

  	if (IS_ERR(xprt)) {

  		dprintk("RPC:       xprt_create_transport: failed, %ld
  ",

  				-PTR_ERR(xprt));
  		return xprt;

  	}

  	kref_init(&xprt->kref);

  	spin_lock_init(&xprt->transport_lock);
  	spin_lock_init(&xprt->reserve_lock);
  
  	INIT_LIST_HEAD(&xprt->free);
  	INIT_LIST_HEAD(&xprt->recv);

  #if defined(CONFIG_NFS_V4_1)
  	spin_lock_init(&xprt->bc_pa_lock);
  	INIT_LIST_HEAD(&xprt->bc_pa_list);
  #endif /* CONFIG_NFS_V4_1 */

  	INIT_WORK(&xprt->task_cleanup, xprt_autoclose);

  	setup_timer(&xprt->timer, xprt_init_autodisconnect,
  			(unsigned long)xprt);

  	xprt->last_used = jiffies;
  	xprt->cwnd = RPC_INITCWND;

  	xprt->bind_index = 0;

  
  	rpc_init_wait_queue(&xprt->binding, "xprt_binding");
  	rpc_init_wait_queue(&xprt->pending, "xprt_pending");
  	rpc_init_wait_queue(&xprt->sending, "xprt_sending");
  	rpc_init_wait_queue(&xprt->resend, "xprt_resend");
  	rpc_init_priority_wait_queue(&xprt->backlog, "xprt_backlog");
  
  	/* initialize free list */
  	for (req = &xprt->slot[xprt->max_reqs-1]; req >= &xprt->slot[0]; req--)
  		list_add(&req->rq_list, &xprt->free);
  
  	xprt_init_xid(xprt);

  	dprintk("RPC:       created transport %p with %u slots
  ", xprt,

  			xprt->max_reqs);
  
  	return xprt;
  }

  /**
   * xprt_destroy - destroy an RPC transport, killing off all requests.

   * @kref: kref for the transport to destroy

   *

   */

  static void xprt_destroy(struct kref *kref)

  {

  	struct rpc_xprt *xprt = container_of(kref, struct rpc_xprt, kref);

  	dprintk("RPC:       destroying transport %p
  ", xprt);

  	xprt->shutdown = 1;
  	del_timer_sync(&xprt->timer);

  	rpc_destroy_wait_queue(&xprt->binding);
  	rpc_destroy_wait_queue(&xprt->pending);
  	rpc_destroy_wait_queue(&xprt->sending);
  	rpc_destroy_wait_queue(&xprt->resend);
  	rpc_destroy_wait_queue(&xprt->backlog);

  	/*
  	 * Tear down transport state and free the rpc_xprt
  	 */

  	xprt->ops->destroy(xprt);

  }

  /**
   * xprt_put - release a reference to an RPC transport.
   * @xprt: pointer to the transport
   *
   */
  void xprt_put(struct rpc_xprt *xprt)
  {
  	kref_put(&xprt->kref, xprt_destroy);
  }
  
  /**
   * xprt_get - return a reference to an RPC transport.
   * @xprt: pointer to the transport
   *
   */
  struct rpc_xprt *xprt_get(struct rpc_xprt *xprt)
  {
  	kref_get(&xprt->kref);
  	return xprt;

  }