// SPDX-License-Identifier: GPL-2.0-only

  /*
   *  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/ktime.h>

  #include <linux/sunrpc/clnt.h>

  #include <linux/sunrpc/metrics.h>

  #include <linux/sunrpc/bc_xprt.h>

  #include <linux/rcupdate.h>

  #include <linux/sched/mm.h>

  #include <trace/events/sunrpc.h>

  #include "sunrpc.h"

  /*
   * Local variables
   */

  #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)

  # define RPCDBG_FACILITY	RPCDBG_XPRT
  #endif

  /*
   * Local functions
   */

  static void	 xprt_init(struct rpc_xprt *xprt, struct net *net);

  static __be32	xprt_alloc_xid(struct rpc_xprt *xprt);

  static void	 xprt_destroy(struct rpc_xprt *xprt);

  static DEFINE_SPINLOCK(xprt_list_lock);

  static LIST_HEAD(xprt_list);

  static unsigned long xprt_request_timeout(const struct rpc_rqst *req)
  {
  	unsigned long timeout = jiffies + req->rq_timeout;
  
  	if (time_before(timeout, req->rq_majortimeo))
  		return timeout;
  	return req->rq_majortimeo;
  }

  /**

   * 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;

  	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);

  	result = request_module("xprt%s", transport_name);

  out:
  	return result;
  }
  EXPORT_SYMBOL_GPL(xprt_load_transport);

  static void xprt_clear_locked(struct rpc_xprt *xprt)
  {
  	xprt->snd_task = NULL;
  	if (!test_bit(XPRT_CLOSE_WAIT, &xprt->state)) {
  		smp_mb__before_atomic();
  		clear_bit(XPRT_LOCKED, &xprt->state);
  		smp_mb__after_atomic();
  	} else
  		queue_work(xprtiod_workqueue, &xprt->task_cleanup);
  }

  /**

   * xprt_reserve_xprt - serialize write access to transports
   * @task: task that is requesting access to the transport

   * @xprt: pointer to the target 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_xprt *xprt, struct rpc_task *task)

  {

  	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 (test_bit(XPRT_WRITE_SPACE, &xprt->state))
  		goto out_unlock;

  	xprt->snd_task = task;

  	return 1;

  out_unlock:
  	xprt_clear_locked(xprt);

  out_sleep:

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

  			task->tk_pid, xprt);

  	task->tk_status = -EAGAIN;

  	if  (RPC_IS_SOFT(task))
  		rpc_sleep_on_timeout(&xprt->sending, task, NULL,

  				xprt_request_timeout(req));

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

  	return 0;
  }

  EXPORT_SYMBOL_GPL(xprt_reserve_xprt);

  static bool
  xprt_need_congestion_window_wait(struct rpc_xprt *xprt)
  {
  	return test_bit(XPRT_CWND_WAIT, &xprt->state);
  }
  
  static void
  xprt_set_congestion_window_wait(struct rpc_xprt *xprt)
  {
  	if (!list_empty(&xprt->xmit_queue)) {
  		/* Peek at head of queue to see if it can make progress */
  		if (list_first_entry(&xprt->xmit_queue, struct rpc_rqst,
  					rq_xmit)->rq_cong)
  			return;
  	}
  	set_bit(XPRT_CWND_WAIT, &xprt->state);
  }
  
  static void
  xprt_test_and_clear_congestion_window_wait(struct rpc_xprt *xprt)
  {
  	if (!RPCXPRT_CONGESTED(xprt))
  		clear_bit(XPRT_CWND_WAIT, &xprt->state);
  }

  /*

   * 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.

   * Note that the lock is only granted if we know there are free slots.

   */

  int xprt_reserve_xprt_cong(struct rpc_xprt *xprt, struct rpc_task *task)

  {
  	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 (req == NULL) {
  		xprt->snd_task = task;
  		return 1;
  	}

  	if (test_bit(XPRT_WRITE_SPACE, &xprt->state))
  		goto out_unlock;

  	if (!xprt_need_congestion_window_wait(xprt)) {

  		xprt->snd_task = task;

  		return 1;
  	}

  out_unlock:

  	xprt_clear_locked(xprt);

  out_sleep:

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

  	task->tk_status = -EAGAIN;

  	if (RPC_IS_SOFT(task))
  		rpc_sleep_on_timeout(&xprt->sending, task, NULL,

  				xprt_request_timeout(req));

  	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;

  	if (test_bit(XPRT_LOCKED, &xprt->state) && xprt->snd_task == task)
  		return 1;

  	spin_lock(&xprt->transport_lock);

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

  	spin_unlock(&xprt->transport_lock);

  	return retval;
  }

  static bool __xprt_lock_write_func(struct rpc_task *task, void *data)

  {

  	struct rpc_xprt *xprt = data;

  	xprt->snd_task = task;

  	return true;
  }

  static void __xprt_lock_write_next(struct rpc_xprt *xprt)
  {
  	if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
  		return;

  	if (test_bit(XPRT_WRITE_SPACE, &xprt->state))
  		goto out_unlock;

  	if (rpc_wake_up_first_on_wq(xprtiod_workqueue, &xprt->sending,
  				__xprt_lock_write_func, xprt))

  		return;

  out_unlock:

  	xprt_clear_locked(xprt);

  }

  static void __xprt_lock_write_next_cong(struct rpc_xprt *xprt)
  {
  	if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
  		return;

  	if (test_bit(XPRT_WRITE_SPACE, &xprt->state))
  		goto out_unlock;

  	if (xprt_need_congestion_window_wait(xprt))

  		goto out_unlock;

  	if (rpc_wake_up_first_on_wq(xprtiod_workqueue, &xprt->sending,

  				__xprt_lock_write_func, xprt))

  		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)

  {

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

  	spin_lock(&xprt->transport_lock);

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

  	spin_unlock(&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_rqst *req)

  {

  	if (req->rq_cong)
  		return 1;

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

  			req->rq_task->tk_pid, xprt->cong, xprt->cwnd);
  	if (RPCXPRT_CONGESTED(xprt)) {
  		xprt_set_congestion_window_wait(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_test_and_clear_congestion_window_wait(xprt);

  	__xprt_lock_write_next_cong(xprt);

  }

  /**

   * xprt_request_get_cong - Request congestion control credits
   * @xprt: pointer to transport
   * @req: pointer to RPC request
   *
   * Useful for transports that require congestion control.
   */
  bool
  xprt_request_get_cong(struct rpc_xprt *xprt, struct rpc_rqst *req)
  {
  	bool ret = false;
  
  	if (req->rq_cong)
  		return true;

  	spin_lock(&xprt->transport_lock);

  	ret = __xprt_get_cong(xprt, req) != 0;

  	spin_unlock(&xprt->transport_lock);

  	return ret;
  }
  EXPORT_SYMBOL_GPL(xprt_request_get_cong);
  
  /**

   * 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)
  {

  	struct rpc_rqst *req = task->tk_rqstp;
  
  	__xprt_put_cong(req->rq_xprt, req);

  }

  EXPORT_SYMBOL_GPL(xprt_release_rqst_cong);

  static void xprt_clear_congestion_window_wait_locked(struct rpc_xprt *xprt)
  {
  	if (test_and_clear_bit(XPRT_CWND_WAIT, &xprt->state))
  		__xprt_lock_write_next_cong(xprt);
  }

  /*
   * Clear the congestion window wait flag and wake up the next
   * entry on xprt->sending
   */
  static void
  xprt_clear_congestion_window_wait(struct rpc_xprt *xprt)
  {
  	if (test_and_clear_bit(XPRT_CWND_WAIT, &xprt->state)) {

  		spin_lock(&xprt->transport_lock);

  		__xprt_lock_write_next_cong(xprt);

  		spin_unlock(&xprt->transport_lock);

  	}
  }

  /**

   * xprt_adjust_cwnd - adjust transport congestion window

   * @xprt: pointer to xprt

   * @task: recently completed RPC request used to adjust window
   * @result: result code of completed RPC request
   *

   * 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.

   */

  void xprt_adjust_cwnd(struct rpc_xprt *xprt, struct rpc_task *task, int result)

  {

  	struct rpc_rqst *req = task->tk_rqstp;

  	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

   * @xprt: transport

   *
   * Note that we only set the timer for the case of RPC_IS_SOFT(), since
   * we don't in general want to force a socket disconnection due to
   * an incomplete RPC call transmission.

   */

  void xprt_wait_for_buffer_space(struct rpc_xprt *xprt)

  {

  	set_bit(XPRT_WRITE_SPACE, &xprt->state);

  }

  EXPORT_SYMBOL_GPL(xprt_wait_for_buffer_space);

  static bool
  xprt_clear_write_space_locked(struct rpc_xprt *xprt)
  {
  	if (test_and_clear_bit(XPRT_WRITE_SPACE, &xprt->state)) {
  		__xprt_lock_write_next(xprt);
  		dprintk("RPC:       write space: waking waiting task on "
  				"xprt %p
  ", xprt);
  		return true;
  	}
  	return false;
  }

  /**
   * 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.
   */

  bool xprt_write_space(struct rpc_xprt *xprt)

  {

  	bool ret;
  
  	if (!test_bit(XPRT_WRITE_SPACE, &xprt->state))
  		return false;

  	spin_lock(&xprt->transport_lock);

  	ret = xprt_clear_write_space_locked(xprt);

  	spin_unlock(&xprt->transport_lock);

  	return ret;

  }

  EXPORT_SYMBOL_GPL(xprt_write_space);

  static unsigned long xprt_abs_ktime_to_jiffies(ktime_t abstime)
  {
  	s64 delta = ktime_to_ns(ktime_get() - abstime);
  	return likely(delta >= 0) ?
  		jiffies - nsecs_to_jiffies(delta) :
  		jiffies + nsecs_to_jiffies(-delta);
  }
  
  static unsigned long xprt_calc_majortimeo(struct rpc_rqst *req)

  {

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

  	unsigned long majortimeo = req->rq_timeout;

  	if (to->to_exponential)

  		majortimeo <<= to->to_retries;
  	else
  		majortimeo += to->to_increment * to->to_retries;
  	if (majortimeo > to->to_maxval || majortimeo == 0)
  		majortimeo = to->to_maxval;
  	return majortimeo;
  }
  
  static void xprt_reset_majortimeo(struct rpc_rqst *req)
  {
  	req->rq_majortimeo += xprt_calc_majortimeo(req);
  }
  
  static void xprt_init_majortimeo(struct rpc_task *task, struct rpc_rqst *req)
  {
  	unsigned long time_init;
  	struct rpc_xprt *xprt = req->rq_xprt;
  
  	if (likely(xprt && xprt_connected(xprt)))
  		time_init = jiffies;

  	else

  		time_init = xprt_abs_ktime_to_jiffies(task->tk_start);
  	req->rq_timeout = task->tk_client->cl_timeout->to_initval;
  	req->rq_majortimeo = time_init + xprt_calc_majortimeo(req);

  }

  /**
   * 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(&xprt->transport_lock);

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

  		spin_unlock(&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);

  	unsigned int pflags = memalloc_nofs_save();

  	clear_bit(XPRT_CLOSE_WAIT, &xprt->state);

  	xprt->ops->close(xprt);

  	xprt_release_write(xprt, NULL);

  	wake_up_bit(&xprt->state, XPRT_LOCKED);

  	memalloc_nofs_restore(pflags);

  }

  /**

   * 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(&xprt->transport_lock);

  	xprt_clear_connected(xprt);

  	xprt_clear_write_space_locked(xprt);

  	xprt_clear_congestion_window_wait_locked(xprt);

  	xprt_wake_pending_tasks(xprt, -ENOTCONN);

  	spin_unlock(&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(&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(xprtiod_workqueue, &xprt->task_cleanup);

  	else if (xprt->snd_task)
  		rpc_wake_up_queued_task_set_status(&xprt->pending,
  				xprt->snd_task, -ENOTCONN);

  	spin_unlock(&xprt->transport_lock);

  }

  EXPORT_SYMBOL_GPL(xprt_force_disconnect);

  static unsigned int
  xprt_connect_cookie(struct rpc_xprt *xprt)
  {
  	return READ_ONCE(xprt->connect_cookie);
  }
  
  static bool
  xprt_request_retransmit_after_disconnect(struct rpc_task *task)
  {
  	struct rpc_rqst *req = task->tk_rqstp;
  	struct rpc_xprt *xprt = req->rq_xprt;
  
  	return req->rq_connect_cookie != xprt_connect_cookie(xprt) ||
  		!xprt_connected(xprt);
  }

  /**
   * 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(&xprt->transport_lock);

  	if (cookie != xprt->connect_cookie)
  		goto out;

  	if (test_bit(XPRT_CLOSING, &xprt->state))

  		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(xprtiod_workqueue, &xprt->task_cleanup);

  	xprt_wake_pending_tasks(xprt, -EAGAIN);

  out:

  	spin_unlock(&xprt->transport_lock);

  }

  static bool
  xprt_has_timer(const struct rpc_xprt *xprt)
  {
  	return xprt->idle_timeout != 0;
  }
  
  static void
  xprt_schedule_autodisconnect(struct rpc_xprt *xprt)
  	__must_hold(&xprt->transport_lock)
  {

  	xprt->last_used = jiffies;

  	if (RB_EMPTY_ROOT(&xprt->recv_queue) && xprt_has_timer(xprt))

  		mod_timer(&xprt->timer, xprt->last_used + xprt->idle_timeout);
  }

  static void

  xprt_init_autodisconnect(struct timer_list *t)

  {

  	struct rpc_xprt *xprt = from_timer(xprt, t, timer);

  	if (!RB_EMPTY_ROOT(&xprt->recv_queue))

  		return;

  	/* Reset xprt->last_used to avoid connect/autodisconnect cycling */
  	xprt->last_used = jiffies;

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

  		return;

  	queue_work(xprtiod_workqueue, &xprt->task_cleanup);

  }

  bool xprt_lock_connect(struct rpc_xprt *xprt,
  		struct rpc_task *task,
  		void *cookie)
  {
  	bool ret = false;

  	spin_lock(&xprt->transport_lock);

  	if (!test_bit(XPRT_LOCKED, &xprt->state))
  		goto out;
  	if (xprt->snd_task != task)
  		goto out;
  	xprt->snd_task = cookie;
  	ret = true;
  out:

  	spin_unlock(&xprt->transport_lock);

  	return ret;
  }
  
  void xprt_unlock_connect(struct rpc_xprt *xprt, void *cookie)
  {

  	spin_lock(&xprt->transport_lock);

  	if (xprt->snd_task != cookie)
  		goto out;
  	if (!test_bit(XPRT_LOCKED, &xprt->state))
  		goto out;
  	xprt->snd_task =NULL;
  	xprt->ops->release_xprt(xprt, NULL);

  	xprt_schedule_autodisconnect(xprt);

  out:

  	spin_unlock(&xprt->transport_lock);

  	wake_up_bit(&xprt->state, XPRT_LOCKED);

  }

  /**
   * 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_rqstp->rq_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 (test_and_clear_bit(XPRT_CLOSE_WAIT, &xprt->state))
  		xprt->ops->close(xprt);

  	if (!xprt_connected(xprt)) {

  		task->tk_rqstp->rq_connect_cookie = xprt->connect_cookie;

  		rpc_sleep_on_timeout(&xprt->pending, task, NULL,

  				xprt_request_timeout(task->tk_rqstp));

  
  		if (test_bit(XPRT_CLOSING, &xprt->state))
  			return;
  		if (xprt_test_and_set_connecting(xprt))
  			return;

  		/* Race breaker */
  		if (!xprt_connected(xprt)) {
  			xprt->stat.connect_start = jiffies;
  			xprt->ops->connect(xprt, task);
  		} else {
  			xprt_clear_connecting(xprt);
  			task->tk_status = 0;
  			rpc_wake_up_queued_task(&xprt->pending, task);
  		}

  	}

  	xprt_release_write(xprt, task);

  }

  /**
   * xprt_reconnect_delay - compute the wait before scheduling a connect
   * @xprt: transport instance
   *
   */
  unsigned long xprt_reconnect_delay(const struct rpc_xprt *xprt)
  {
  	unsigned long start, now = jiffies;
  
  	start = xprt->stat.connect_start + xprt->reestablish_timeout;
  	if (time_after(start, now))
  		return start - now;
  	return 0;
  }
  EXPORT_SYMBOL_GPL(xprt_reconnect_delay);
  
  /**
   * xprt_reconnect_backoff - compute the new re-establish timeout
   * @xprt: transport instance
   * @init_to: initial reestablish timeout
   *
   */
  void xprt_reconnect_backoff(struct rpc_xprt *xprt, unsigned long init_to)
  {
  	xprt->reestablish_timeout <<= 1;
  	if (xprt->reestablish_timeout > xprt->max_reconnect_timeout)
  		xprt->reestablish_timeout = xprt->max_reconnect_timeout;
  	if (xprt->reestablish_timeout < init_to)
  		xprt->reestablish_timeout = init_to;
  }
  EXPORT_SYMBOL_GPL(xprt_reconnect_backoff);

  enum xprt_xid_rb_cmp {
  	XID_RB_EQUAL,
  	XID_RB_LEFT,
  	XID_RB_RIGHT,
  };
  static enum xprt_xid_rb_cmp
  xprt_xid_cmp(__be32 xid1, __be32 xid2)
  {
  	if (xid1 == xid2)
  		return XID_RB_EQUAL;
  	if ((__force u32)xid1 < (__force u32)xid2)
  		return XID_RB_LEFT;
  	return XID_RB_RIGHT;
  }
  
  static struct rpc_rqst *
  xprt_request_rb_find(struct rpc_xprt *xprt, __be32 xid)
  {
  	struct rb_node *n = xprt->recv_queue.rb_node;
  	struct rpc_rqst *req;
  
  	while (n != NULL) {
  		req = rb_entry(n, struct rpc_rqst, rq_recv);
  		switch (xprt_xid_cmp(xid, req->rq_xid)) {
  		case XID_RB_LEFT:
  			n = n->rb_left;
  			break;
  		case XID_RB_RIGHT:
  			n = n->rb_right;
  			break;
  		case XID_RB_EQUAL:
  			return req;
  		}
  	}
  	return NULL;
  }
  
  static void
  xprt_request_rb_insert(struct rpc_xprt *xprt, struct rpc_rqst *new)
  {
  	struct rb_node **p = &xprt->recv_queue.rb_node;
  	struct rb_node *n = NULL;
  	struct rpc_rqst *req;
  
  	while (*p != NULL) {
  		n = *p;
  		req = rb_entry(n, struct rpc_rqst, rq_recv);
  		switch(xprt_xid_cmp(new->rq_xid, req->rq_xid)) {
  		case XID_RB_LEFT:
  			p = &n->rb_left;
  			break;
  		case XID_RB_RIGHT:
  			p = &n->rb_right;
  			break;
  		case XID_RB_EQUAL:
  			WARN_ON_ONCE(new != req);
  			return;
  		}
  	}
  	rb_link_node(&new->rq_recv, n, p);
  	rb_insert_color(&new->rq_recv, &xprt->recv_queue);
  }
  
  static void
  xprt_request_rb_remove(struct rpc_xprt *xprt, struct rpc_rqst *req)
  {
  	rb_erase(&req->rq_recv, &xprt->recv_queue);
  }

  /**
   * 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
   *

   * Caller holds xprt->queue_lock.

   */

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

  {

  	struct rpc_rqst *entry;

  	entry = xprt_request_rb_find(xprt, xid);
  	if (entry != NULL) {
  		trace_xprt_lookup_rqst(xprt, xid, 0);
  		entry->rq_rtt = ktime_sub(ktime_get(), entry->rq_xtime);
  		return entry;
  	}

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

  	trace_xprt_lookup_rqst(xprt, xid, -ENOENT);

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

  }

  EXPORT_SYMBOL_GPL(xprt_lookup_rqst);

  static bool
  xprt_is_pinned_rqst(struct rpc_rqst *req)
  {
  	return atomic_read(&req->rq_pin) != 0;
  }

  /**
   * xprt_pin_rqst - Pin a request on the transport receive list
   * @req: Request to pin
   *
   * Caller must ensure this is atomic with the call to xprt_lookup_rqst()

   * so should be holding xprt->queue_lock.

   */
  void xprt_pin_rqst(struct rpc_rqst *req)
  {

  	atomic_inc(&req->rq_pin);

  }

  EXPORT_SYMBOL_GPL(xprt_pin_rqst);

  
  /**
   * xprt_unpin_rqst - Unpin a request on the transport receive list
   * @req: Request to pin
   *

   * Caller should be holding xprt->queue_lock.

   */
  void xprt_unpin_rqst(struct rpc_rqst *req)
  {

  	if (!test_bit(RPC_TASK_MSG_PIN_WAIT, &req->rq_task->tk_runstate)) {
  		atomic_dec(&req->rq_pin);
  		return;
  	}
  	if (atomic_dec_and_test(&req->rq_pin))
  		wake_up_var(&req->rq_pin);

  }

  EXPORT_SYMBOL_GPL(xprt_unpin_rqst);

  
  static void xprt_wait_on_pinned_rqst(struct rpc_rqst *req)

  {

  	wait_var_event(&req->rq_pin, !xprt_is_pinned_rqst(req));

  }

  static bool
  xprt_request_data_received(struct rpc_task *task)
  {
  	return !test_bit(RPC_TASK_NEED_RECV, &task->tk_runstate) &&
  		READ_ONCE(task->tk_rqstp->rq_reply_bytes_recvd) != 0;
  }
  
  static bool
  xprt_request_need_enqueue_receive(struct rpc_task *task, struct rpc_rqst *req)
  {
  	return !test_bit(RPC_TASK_NEED_RECV, &task->tk_runstate) &&
  		READ_ONCE(task->tk_rqstp->rq_reply_bytes_recvd) == 0;
  }
  
  /**
   * xprt_request_enqueue_receive - Add an request to the receive queue
   * @task: RPC task
   *
   */
  void
  xprt_request_enqueue_receive(struct rpc_task *task)
  {
  	struct rpc_rqst *req = task->tk_rqstp;
  	struct rpc_xprt *xprt = req->rq_xprt;
  
  	if (!xprt_request_need_enqueue_receive(task, req))
  		return;

  
  	xprt_request_prepare(task->tk_rqstp);

  	spin_lock(&xprt->queue_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 */

  	xprt_request_rb_insert(xprt, req);

  	set_bit(RPC_TASK_NEED_RECV, &task->tk_runstate);
  	spin_unlock(&xprt->queue_lock);

  	/* Turn off autodisconnect */
  	del_singleshot_timer_sync(&xprt->timer);
  }
  
  /**
   * xprt_request_dequeue_receive_locked - Remove a request from the receive queue
   * @task: RPC task
   *
   * Caller must hold xprt->queue_lock.
   */
  static void
  xprt_request_dequeue_receive_locked(struct rpc_task *task)
  {

  	struct rpc_rqst *req = task->tk_rqstp;

  	if (test_and_clear_bit(RPC_TASK_NEED_RECV, &task->tk_runstate))

  		xprt_request_rb_remove(req->rq_xprt, req);

  }

  /**
   * xprt_update_rtt - Update RPC RTT statistics
   * @task: RPC request that recently completed
   *

   * Caller holds xprt->queue_lock.

   */
  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 int timer = task->tk_msg.rpc_proc->p_timer;

  	long m = usecs_to_jiffies(ktime_to_us(req->rq_rtt));

  
  	if (timer) {
  		if (req->rq_ntrans == 1)

  			rpc_update_rtt(rtt, timer, m);

  		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 xprt->queue_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);

  	trace_xprt_complete_rqst(xprt, req->rq_xid, copied);

  	xprt->stat.recvs++;

  	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;

  	xprt_request_dequeue_receive_locked(task);

  	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;

  	trace_xprt_timer(xprt, req->rq_xid, task->tk_status);

  	if (!req->rq_reply_bytes_recvd) {

  		if (xprt->ops->timer)

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

  	} else
  		task->tk_status = 0;

  }

  /**

   * xprt_wait_for_reply_request_def - wait for reply
   * @task: pointer to rpc_task
   *
   * 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,
   * and put the task to sleep on the pending queue.
   */
  void xprt_wait_for_reply_request_def(struct rpc_task *task)
  {
  	struct rpc_rqst *req = task->tk_rqstp;

  	rpc_sleep_on_timeout(&req->rq_xprt->pending, task, xprt_timer,

  			xprt_request_timeout(req));

  }
  EXPORT_SYMBOL_GPL(xprt_wait_for_reply_request_def);
  
  /**
   * xprt_wait_for_reply_request_rtt - wait for reply using RTT estimator
   * @task: pointer to rpc_task
   *
   * Set a request's retransmit timeout using the RTT estimator,
   * and put the task to sleep on the pending queue.
   */
  void xprt_wait_for_reply_request_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;

  	unsigned long timeout;

  	timeout = rpc_calc_rto(rtt, timer);
  	timeout <<= rpc_ntimeo(rtt, timer) + req->rq_retries;
  	if (timeout > max_timeout || timeout == 0)
  		timeout = max_timeout;
  	rpc_sleep_on_timeout(&req->rq_xprt->pending, task, xprt_timer,
  			jiffies + timeout);

  }
  EXPORT_SYMBOL_GPL(xprt_wait_for_reply_request_rtt);
  
  /**

   * xprt_request_wait_receive - wait for the reply to an RPC request
   * @task: RPC task about to send a request
   *
   */
  void xprt_request_wait_receive(struct rpc_task *task)
  {
  	struct rpc_rqst *req = task->tk_rqstp;
  	struct rpc_xprt *xprt = req->rq_xprt;
  
  	if (!test_bit(RPC_TASK_NEED_RECV, &task->tk_runstate))
  		return;
  	/*
  	 * Sleep on the pending queue if we're expecting a reply.
  	 * The spinlock ensures atomicity between the test of
  	 * req->rq_reply_bytes_recvd, and the call to rpc_sleep_on().
  	 */
  	spin_lock(&xprt->queue_lock);
  	if (test_bit(RPC_TASK_NEED_RECV, &task->tk_runstate)) {

  		xprt->ops->wait_for_reply_request(task);

  		/*
  		 * Send an extra queue wakeup call if the
  		 * connection was dropped in case the call to
  		 * rpc_sleep_on() raced.
  		 */
  		if (xprt_request_retransmit_after_disconnect(task))
  			rpc_wake_up_queued_task_set_status(&xprt->pending,
  					task, -ENOTCONN);
  	}
  	spin_unlock(&xprt->queue_lock);
  }

  static bool

  xprt_request_need_enqueue_transmit(struct rpc_task *task, struct rpc_rqst *req)
  {

  	return !test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate);

  }
  
  /**
   * xprt_request_enqueue_transmit - queue a task for transmission
   * @task: pointer to rpc_task
   *
   * Add a task to the transmission queue.
   */
  void
  xprt_request_enqueue_transmit(struct rpc_task *task)
  {

  	struct rpc_rqst *pos, *req = task->tk_rqstp;

  	struct rpc_xprt *xprt = req->rq_xprt;
  
  	if (xprt_request_need_enqueue_transmit(task, req)) {

  		req->rq_bytes_sent = 0;

  		spin_lock(&xprt->queue_lock);

  		/*
  		 * Requests that carry congestion control credits are added
  		 * to the head of the list to avoid starvation issues.
  		 */
  		if (req->rq_cong) {
  			xprt_clear_congestion_window_wait(xprt);
  			list_for_each_entry(pos, &xprt->xmit_queue, rq_xmit) {
  				if (pos->rq_cong)
  					continue;
  				/* Note: req is added _before_ pos */
  				list_add_tail(&req->rq_xmit, &pos->rq_xmit);
  				INIT_LIST_HEAD(&req->rq_xmit2);

  				trace_xprt_enq_xmit(task, 1);

  				goto out;
  			}

  		} else if (RPC_IS_SWAPPER(task)) {
  			list_for_each_entry(pos, &xprt->xmit_queue, rq_xmit) {
  				if (pos->rq_cong || pos->rq_bytes_sent)
  					continue;
  				if (RPC_IS_SWAPPER(pos->rq_task))
  					continue;
  				/* Note: req is added _before_ pos */
  				list_add_tail(&req->rq_xmit, &pos->rq_xmit);
  				INIT_LIST_HEAD(&req->rq_xmit2);

  				trace_xprt_enq_xmit(task, 2);

  				goto out;
  			}

  		} else if (!req->rq_seqno) {

  			list_for_each_entry(pos, &xprt->xmit_queue, rq_xmit) {
  				if (pos->rq_task->tk_owner != task->tk_owner)
  					continue;
  				list_add_tail(&req->rq_xmit2, &pos->rq_xmit2);
  				INIT_LIST_HEAD(&req->rq_xmit);

  				trace_xprt_enq_xmit(task, 3);

  				goto out;
  			}

  		}

  		list_add_tail(&req->rq_xmit, &xprt->xmit_queue);

  		INIT_LIST_HEAD(&req->rq_xmit2);

  		trace_xprt_enq_xmit(task, 4);

  out:

  		set_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate);
  		spin_unlock(&xprt->queue_lock);
  	}
  }
  
  /**
   * xprt_request_dequeue_transmit_locked - remove a task from the transmission queue
   * @task: pointer to rpc_task
   *
   * Remove a task from the transmission queue
   * Caller must hold xprt->queue_lock
   */
  static void
  xprt_request_dequeue_transmit_locked(struct rpc_task *task)
  {

  	struct rpc_rqst *req = task->tk_rqstp;
  
  	if (!test_and_clear_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate))
  		return;
  	if (!list_empty(&req->rq_xmit)) {
  		list_del(&req->rq_xmit);
  		if (!list_empty(&req->rq_xmit2)) {
  			struct rpc_rqst *next = list_first_entry(&req->rq_xmit2,
  					struct rpc_rqst, rq_xmit2);
  			list_del(&req->rq_xmit2);
  			list_add_tail(&next->rq_xmit, &next->rq_xprt->xmit_queue);
  		}
  	} else
  		list_del(&req->rq_xmit2);

  }
  
  /**
   * xprt_request_dequeue_transmit - remove a task from the transmission queue
   * @task: pointer to rpc_task
   *
   * Remove a task from the transmission queue
   */
  static void
  xprt_request_dequeue_transmit(struct rpc_task *task)
  {
  	struct rpc_rqst *req = task->tk_rqstp;
  	struct rpc_xprt *xprt = req->rq_xprt;
  
  	spin_lock(&xprt->queue_lock);
  	xprt_request_dequeue_transmit_locked(task);
  	spin_unlock(&xprt->queue_lock);
  }

  /**

   * xprt_request_dequeue_xprt - remove a task from the transmit+receive queue
   * @task: pointer to rpc_task
   *
   * Remove a task from the transmit and receive queues, and ensure that
   * it is not pinned by the receive work item.
   */
  void
  xprt_request_dequeue_xprt(struct rpc_task *task)
  {
  	struct rpc_rqst	*req = task->tk_rqstp;
  	struct rpc_xprt *xprt = req->rq_xprt;
  
  	if (test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate) ||
  	    test_bit(RPC_TASK_NEED_RECV, &task->tk_runstate) ||
  	    xprt_is_pinned_rqst(req)) {
  		spin_lock(&xprt->queue_lock);
  		xprt_request_dequeue_transmit_locked(task);
  		xprt_request_dequeue_receive_locked(task);
  		while (xprt_is_pinned_rqst(req)) {
  			set_bit(RPC_TASK_MSG_PIN_WAIT, &task->tk_runstate);
  			spin_unlock(&xprt->queue_lock);
  			xprt_wait_on_pinned_rqst(req);
  			spin_lock(&xprt->queue_lock);
  			clear_bit(RPC_TASK_MSG_PIN_WAIT, &task->tk_runstate);
  		}
  		spin_unlock(&xprt->queue_lock);
  	}
  }
  
  /**

   * xprt_request_prepare - prepare an encoded request for transport
   * @req: pointer to rpc_rqst
   *
   * Calls into the transport layer to do whatever is needed to prepare
   * the request for transmission or receive.
   */
  void
  xprt_request_prepare(struct rpc_rqst *req)
  {
  	struct rpc_xprt *xprt = req->rq_xprt;
  
  	if (xprt->ops->prepare_request)
  		xprt->ops->prepare_request(req);
  }
  
  /**

   * xprt_request_need_retransmit - Test if a task needs retransmission
   * @task: pointer to rpc_task
   *
   * Test for whether a connection breakage requires the task to retransmit
   */
  bool
  xprt_request_need_retransmit(struct rpc_task *task)
  {
  	return xprt_request_retransmit_after_disconnect(task);
  }
  
  /**

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

   */

  bool xprt_prepare_transmit(struct rpc_task *task)

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

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

  	if (!xprt_lock_write(xprt, task)) {
  		/* Race breaker: someone may have transmitted us */

  		if (!test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate))

  			rpc_wake_up_queued_task_set_status(&xprt->sending,
  					task, 0);
  		return false;

  	}

  	return true;

  }

  void xprt_end_transmit(struct rpc_task *task)

  {

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

  }

  /**

   * xprt_request_transmit - send an RPC request on a transport
   * @req: pointer to request to transmit
   * @snd_task: RPC task that owns the transport lock

   *

   * This performs the transmission of a single request.
   * Note that if the request is not the same as snd_task, then it
   * does need to be pinned.
   * Returns '0' on success.

   */

  static int
  xprt_request_transmit(struct rpc_rqst *req, struct rpc_task *snd_task)

  {

  	struct rpc_xprt *xprt = req->rq_xprt;
  	struct rpc_task *task = req->rq_task;

  	unsigned int connect_cookie;

  	int is_retrans = RPC_WAS_SENT(task);

  	int status;

  	if (!req->rq_bytes_sent) {

  		if (xprt_request_data_received(task)) {
  			status = 0;

  			goto out_dequeue;

  		}

  		/* Verify that our message lies in the RPCSEC_GSS window */

  		if (rpcauth_xmit_need_reencode(task)) {

  			status = -EBADMSG;

  			goto out_dequeue;

  		}

  		if (RPC_SIGNALLED(task)) {
  			status = -ERESTARTSYS;
  			goto out_dequeue;

  		}

  	}

  	/*
  	 * Update req->rq_ntrans before transmitting to avoid races with
  	 * xprt_update_rtt(), which needs to know that it is recording a
  	 * reply to the first transmission.
  	 */
  	req->rq_ntrans++;

  	connect_cookie = xprt->connect_cookie;

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

  	if (status != 0) {

  		req->rq_ntrans--;

  		trace_xprt_transmit(req, status);

  		return status;

  	}

  	if (is_retrans)
  		task->tk_client->cl_stats->rpcretrans++;

  	xprt_inject_disconnect(xprt);

  	task->tk_flags |= RPC_TASK_SENT;

  	spin_lock(&xprt->transport_lock);

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

  	xprt->stat.sending_u += xprt->sending.qlen;
  	xprt->stat.pending_u += xprt->pending.qlen;

  	spin_unlock(&xprt->transport_lock);

  	req->rq_connect_cookie = connect_cookie;

  out_dequeue:

  	trace_xprt_transmit(req, status);

  	xprt_request_dequeue_transmit(task);

  	rpc_wake_up_queued_task_set_status(&xprt->sending, task, status);
  	return status;
  }
  
  /**
   * xprt_transmit - send an RPC request on a transport
   * @task: controlling RPC task
   *
   * Attempts to drain the transmit queue. On exit, either the transport
   * signalled an error that needs to be handled before transmission can
   * resume, or @task finished transmitting, and detected that it already
   * received a reply.
   */
  void
  xprt_transmit(struct rpc_task *task)
  {
  	struct rpc_rqst *next, *req = task->tk_rqstp;
  	struct rpc_xprt	*xprt = req->rq_xprt;
  	int status;
  
  	spin_lock(&xprt->queue_lock);
  	while (!list_empty(&xprt->xmit_queue)) {
  		next = list_first_entry(&xprt->xmit_queue,
  				struct rpc_rqst, rq_xmit);
  		xprt_pin_rqst(next);
  		spin_unlock(&xprt->queue_lock);
  		status = xprt_request_transmit(next, task);
  		if (status == -EBADMSG && next != req)
  			status = 0;
  		cond_resched();
  		spin_lock(&xprt->queue_lock);
  		xprt_unpin_rqst(next);
  		if (status == 0) {
  			if (!xprt_request_data_received(task) ||
  			    test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate))
  				continue;

  		} else if (test_bit(RPC_TASK_NEED_XMIT, &task->tk_runstate))

  			task->tk_status = status;
  		break;
  	}
  	spin_unlock(&xprt->queue_lock);

  }

  static void xprt_add_backlog(struct rpc_xprt *xprt, struct rpc_task *task)
  {
  	set_bit(XPRT_CONGESTED, &xprt->state);
  	rpc_sleep_on(&xprt->backlog, task, NULL);
  }
  
  static void xprt_wake_up_backlog(struct rpc_xprt *xprt)
  {
  	if (rpc_wake_up_next(&xprt->backlog) == NULL)
  		clear_bit(XPRT_CONGESTED, &xprt->state);
  }
  
  static bool xprt_throttle_congested(struct rpc_xprt *xprt, struct rpc_task *task)
  {
  	bool ret = false;
  
  	if (!test_bit(XPRT_CONGESTED, &xprt->state))
  		goto out;
  	spin_lock(&xprt->reserve_lock);
  	if (test_bit(XPRT_CONGESTED, &xprt->state)) {
  		rpc_sleep_on(&xprt->backlog, task, NULL);
  		ret = true;
  	}
  	spin_unlock(&xprt->reserve_lock);
  out:
  	return ret;
  }

  static struct rpc_rqst *xprt_dynamic_alloc_slot(struct rpc_xprt *xprt)

  {
  	struct rpc_rqst *req = ERR_PTR(-EAGAIN);

  	if (xprt->num_reqs >= xprt->max_reqs)

  		goto out;

  	++xprt->num_reqs;

  	spin_unlock(&xprt->reserve_lock);
  	req = kzalloc(sizeof(struct rpc_rqst), GFP_NOFS);
  	spin_lock(&xprt->reserve_lock);

  	if (req != NULL)
  		goto out;

  	--xprt->num_reqs;

  	req = ERR_PTR(-ENOMEM);
  out:
  	return req;
  }
  
  static bool xprt_dynamic_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)
  {

  	if (xprt->num_reqs > xprt->min_reqs) {
  		--xprt->num_reqs;

  		kfree(req);
  		return true;
  	}
  	return false;
  }

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

  {

  	struct rpc_rqst *req;

  	spin_lock(&xprt->reserve_lock);

  	if (!list_empty(&xprt->free)) {

  		req = list_entry(xprt->free.next, struct rpc_rqst, rq_list);
  		list_del(&req->rq_list);
  		goto out_init_req;
  	}

  	req = xprt_dynamic_alloc_slot(xprt);

  	if (!IS_ERR(req))
  		goto out_init_req;
  	switch (PTR_ERR(req)) {
  	case -ENOMEM:

  		dprintk("RPC:       dynamic allocation of request slot "
  				"failed! Retrying
  ");

  		task->tk_status = -ENOMEM;

  		break;
  	case -EAGAIN:

  		xprt_add_backlog(xprt, task);

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

  		/* fall through */

  	default:
  		task->tk_status = -EAGAIN;

  	}

  	spin_unlock(&xprt->reserve_lock);

  	return;
  out_init_req:

  	xprt->stat.max_slots = max_t(unsigned int, xprt->stat.max_slots,
  				     xprt->num_reqs);

  	spin_unlock(&xprt->reserve_lock);

  	task->tk_status = 0;
  	task->tk_rqstp = req;

  }
  EXPORT_SYMBOL_GPL(xprt_alloc_slot);

  void xprt_free_slot(struct rpc_xprt *xprt, struct rpc_rqst *req)

  {

  	spin_lock(&xprt->reserve_lock);

  	if (!xprt_dynamic_free_slot(xprt, req)) {
  		memset(req, 0, sizeof(*req));	/* mark unused */
  		list_add(&req->rq_list, &xprt->free);
  	}

  	xprt_wake_up_backlog(xprt);

  	spin_unlock(&xprt->reserve_lock);
  }

  EXPORT_SYMBOL_GPL(xprt_free_slot);

  static void xprt_free_all_slots(struct rpc_xprt *xprt)
  {
  	struct rpc_rqst *req;
  	while (!list_empty(&xprt->free)) {
  		req = list_first_entry(&xprt->free, struct rpc_rqst, rq_list);
  		list_del(&req->rq_list);
  		kfree(req);
  	}
  }

  struct rpc_xprt *xprt_alloc(struct net *net, size_t size,
  		unsigned int num_prealloc,
  		unsigned int max_alloc)

  {
  	struct rpc_xprt *xprt;

  	struct rpc_rqst *req;
  	int i;

  
  	xprt = kzalloc(size, GFP_KERNEL);
  	if (xprt == NULL)
  		goto out;

  	xprt_init(xprt, net);
  
  	for (i = 0; i < num_prealloc; i++) {
  		req = kzalloc(sizeof(struct rpc_rqst), GFP_KERNEL);
  		if (!req)

  			goto out_free;

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

  	if (max_alloc > num_prealloc)
  		xprt->max_reqs = max_alloc;
  	else
  		xprt->max_reqs = num_prealloc;
  	xprt->min_reqs = num_prealloc;

  	xprt->num_reqs = num_prealloc;

  
  	return xprt;
  
  out_free:

  	xprt_free(xprt);

  out:
  	return NULL;
  }
  EXPORT_SYMBOL_GPL(xprt_alloc);

  void xprt_free(struct rpc_xprt *xprt)
  {

  	put_net(xprt->xprt_net);

  	xprt_free_all_slots(xprt);

  	kfree_rcu(xprt, rcu);

  }
  EXPORT_SYMBOL_GPL(xprt_free);

  static void
  xprt_init_connect_cookie(struct rpc_rqst *req, struct rpc_xprt *xprt)
  {
  	req->rq_connect_cookie = xprt_connect_cookie(xprt) - 1;
  }

  static __be32
  xprt_alloc_xid(struct rpc_xprt *xprt)
  {
  	__be32 xid;
  
  	spin_lock(&xprt->reserve_lock);
  	xid = (__force __be32)xprt->xid++;
  	spin_unlock(&xprt->reserve_lock);
  	return xid;
  }
  
  static void
  xprt_init_xid(struct rpc_xprt *xprt)
  {
  	xprt->xid = prandom_u32();
  }
  
  static void
  xprt_request_init(struct rpc_task *task)
  {
  	struct rpc_xprt *xprt = task->tk_xprt;
  	struct rpc_rqst	*req = task->tk_rqstp;

  	req->rq_task	= task;
  	req->rq_xprt    = xprt;
  	req->rq_buffer  = NULL;
  	req->rq_xid	= xprt_alloc_xid(xprt);

  	xprt_init_connect_cookie(req, xprt);

  	req->rq_snd_buf.len = 0;
  	req->rq_snd_buf.buflen = 0;
  	req->rq_rcv_buf.len = 0;
  	req->rq_rcv_buf.buflen = 0;

  	req->rq_snd_buf.bvec = NULL;
  	req->rq_rcv_buf.bvec = NULL;

  	req->rq_release_snd_buf = NULL;

  	xprt_init_majortimeo(task, req);

  	dprintk("RPC: %5u reserved req %p xid %08x
  ", task->tk_pid,
  			req, ntohl(req->rq_xid));
  }
  
  static void
  xprt_do_reserve(struct rpc_xprt *xprt, struct rpc_task *task)
  {
  	xprt->ops->alloc_slot(xprt, task);
  	if (task->tk_rqstp != NULL)
  		xprt_request_init(task);
  }

  /**
   * xprt_reserve - allocate an RPC request slot
   * @task: RPC task requesting a slot allocation
   *

   * If the transport is marked as being congested, or 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 = 0;
  	if (task->tk_rqstp != NULL)
  		return;

  	task->tk_status = -EAGAIN;

  	if (!xprt_throttle_congested(xprt, task))

  		xprt_do_reserve(xprt, task);

  }
  
  /**
   * xprt_retry_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.
   * Note that the only difference with xprt_reserve is that we now
   * ignore the value of the XPRT_CONGESTED flag.
   */
  void xprt_retry_reserve(struct rpc_task *task)
  {

  	struct rpc_xprt *xprt = task->tk_xprt;

  
  	task->tk_status = 0;
  	if (task->tk_rqstp != NULL)
  		return;

  	task->tk_status = -EAGAIN;

  	xprt_do_reserve(xprt, task);

  }

  /**
   * 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 = task->tk_rqstp;

  	if (req == NULL) {
  		if (task->tk_client) {

  			xprt = task->tk_xprt;

  			xprt_release_write(xprt, task);

  		}

  		return;

  	}

  	xprt = req->rq_xprt;

  	xprt_request_dequeue_xprt(task);

  	spin_lock(&xprt->transport_lock);

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

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

  	xprt_schedule_autodisconnect(xprt);

  	spin_unlock(&xprt->transport_lock);

  	if (req->rq_buffer)

  		xprt->ops->buf_free(task);

  	xprt_inject_disconnect(xprt);

  	xdr_free_bvec(&req->rq_rcv_buf);

  	xdr_free_bvec(&req->rq_snd_buf);

  	if (req->rq_cred != NULL)
  		put_rpccred(req->rq_cred);

  	task->tk_rqstp = NULL;

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

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

  	if (likely(!bc_prealloc(req)))

  		xprt->ops->free_slot(xprt, req);

  	else

  		xprt_free_bc_request(req);

  }

  #ifdef CONFIG_SUNRPC_BACKCHANNEL
  void
  xprt_init_bc_request(struct rpc_rqst *req, struct rpc_task *task)
  {
  	struct xdr_buf *xbufp = &req->rq_snd_buf;
  
  	task->tk_rqstp = req;
  	req->rq_task = task;
  	xprt_init_connect_cookie(req, req->rq_xprt);
  	/*
  	 * 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;

  }
  #endif

  static void xprt_init(struct rpc_xprt *xprt, struct net *net)

  {

  	kref_init(&xprt->kref);