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xprt.c

/*
 *  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, 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>

/*
 * 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;
      }

      result = -EINVAL;
      if (try_module_get(THIS_MODULE)) {
            list_add_tail(&transport->list, &xprt_list);
            printk(KERN_INFO "RPC: Registered %s transport module.\n",
                  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.\n",
                        transport->name);
                  list_del_init(&transport->list);
                  module_put(THIS_MODULE);
                  goto out;
            }
      }
      result = -ENOENT;

out:
      spin_unlock(&xprt_list_lock);
      return result;
}
EXPORT_SYMBOL_GPL(xprt_unregister_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_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;
            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\n",
                  task->tk_pid, xprt);
      task->tk_timeout = 0;
      task->tk_status = -EAGAIN;
      if (req && req->rq_ntrans)
            rpc_sleep_on(&xprt->resend, task, NULL, NULL);
      else
            rpc_sleep_on(&xprt->sending, task, NULL, 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\n", task->tk_pid, xprt);
      task->tk_timeout = 0;
      task->tk_status = -EAGAIN;
      if (req && req->rq_ntrans)
            rpc_sleep_on(&xprt->resend, task, NULL, NULL);
      else
            rpc_sleep_on(&xprt->sending, task, NULL, 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\n",
                  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\n",
                  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
 *
 */
void xprt_wait_for_buffer_space(struct rpc_task *task)
{
      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, NULL, NULL);
}
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\n", xprt);
            rpc_wake_up_task(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_rtt *rtt = task->tk_client->cl_rtt;
      struct rpc_rqst *req = task->tk_rqstp;
      unsigned long max_timeout = req->rq_xprt->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)
{
      struct rpc_timeout *to = &req->rq_xprt->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;
      struct rpc_timeout *to = &xprt->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!\n");
            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_disconnect(xprt);
      xprt->ops->close(xprt);
      xprt_release_write(xprt, NULL);
}

/**
 * xprt_disconnect - mark a transport as disconnected
 * @xprt: transport to flag for disconnect
 *
 */
void xprt_disconnect(struct rpc_xprt *xprt)
{
      dprintk("RPC:       disconnected transport %p\n", xprt);
      spin_lock_bh(&xprt->transport_lock);
      xprt_clear_connected(xprt);
      xprt_wake_pending_tasks(xprt, -ENOTCONN);
      spin_unlock_bh(&xprt->transport_lock);
}
EXPORT_SYMBOL_GPL(xprt_disconnect);

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);
      if (xprt_connecting(xprt))
            xprt_release_write(xprt, NULL);
      else
            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\n", task->tk_pid,
                  xprt, (xprt_connected(xprt) ? "is" : "is not"));

      if (!xprt_bound(xprt)) {
            task->tk_status = -EIO;
            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, NULL);
            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\n",
                        task->tk_pid);
            return;
      }

      switch (task->tk_status) {
      case -ECONNREFUSED:
      case -ECONNRESET:
            dprintk("RPC: %5u xprt_connect_status: server %s refused "
                        "connection\n", task->tk_pid,
                        task->tk_client->cl_server);
            break;
      case -ENOTCONN:
            dprintk("RPC: %5u xprt_connect_status: connection broken\n",
                        task->tk_pid);
            break;
      case -ETIMEDOUT:
            dprintk("RPC: %5u xprt_connect_status: connect attempt timed "
                        "out\n", task->tk_pid);
            break;
      default:
            dprintk("RPC: %5u xprt_connect_status: error %d connecting to "
                        "server %s\n", 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\n",
                  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;

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

      task->tk_xprt->stat.recvs++;
      task->tk_rtt = (long)jiffies - req->rq_xtime;

      list_del_init(&req->rq_list);
      /* Ensure all writes are done before we update req->rq_received */
      smp_wmb();
      req->rq_received = req->rq_private_buf.len = copied;
      rpc_wake_up_task(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;

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

      spin_lock(&xprt->transport_lock);
      if (!req->rq_received) {
            if (xprt->ops->timer)
                  xprt->ops->timer(task);
            task->tk_status = -ETIMEDOUT;
      }
      task->tk_timeout = 0;
      rpc_wake_up_task(task);
      spin_unlock(&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\n", task->tk_pid);

      spin_lock_bh(&xprt->transport_lock);
      if (req->rq_received && !req->rq_bytes_sent) {
            err = req->rq_received;
            goto out_unlock;
      }
      if (!xprt->ops->reserve_xprt(task)) {
            err = -EAGAIN;
            goto out_unlock;
      }

      if (!xprt_connected(xprt)) {
            err = -ENOTCONN;
            goto out_unlock;
      }
out_unlock:
      spin_unlock_bh(&xprt->transport_lock);
      return err;
}

void xprt_end_transmit(struct rpc_task *task)
{
      xprt_release_write(task->tk_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)\n", task->tk_pid, req->rq_slen);

      if (!req->rq_received) {
            if (list_empty(&req->rq_list)) {
                  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;

      status = xprt->ops->send_request(task);
      if (status == 0) {
            dprintk("RPC: %5u xmit complete\n", 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_received)
                  rpc_sleep_on(&xprt->pending, task, NULL, xprt_timer);
            spin_unlock_bh(&xprt->transport_lock);
            return;
      }

      /* Note: at this point, task->tk_sleeping has not yet been set,
       *     hence there is no danger of the waking up task being put on
       *     schedq, and being picked up by a parallel run of rpciod().
       */
      task->tk_status = status;
      if (status == -ECONNREFUSED)
            rpc_sleep_on(&xprt->sending, task, NULL, NULL);
}

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\n");
      task->tk_status = -EAGAIN;
      task->tk_timeout = 0;
      rpc_sleep_on(&xprt->backlog, task, NULL, 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 = xprt->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\n", 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 = task->tk_xprt;
      struct rpc_rqst   *req;

      if (!(req = task->tk_rqstp))
            return;
      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);
      xprt->ops->buf_free(req->rq_buffer);
      task->tk_rqstp = NULL;
      if (req->rq_release_snd_buf)
            req->rq_release_snd_buf(req);
      memset(req, 0, sizeof(*req)); /* mark unused */

      dprintk("RPC: %5u release request %p\n", 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_set_timeout - set constant RPC timeout
 * @to: RPC timeout parameters to set up
 * @retr: number of retries
 * @incr: amount of increase after each retry
 *
 */
void xprt_set_timeout(struct rpc_timeout *to, unsigned int retr, unsigned long incr)
{
      to->to_initval   =
      to->to_increment = incr;
      to->to_maxval    = to->to_initval + (incr * retr);
      to->to_retries   = retr;
      to->to_exponential = 0;
}

/**
 * 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\n", args->ident);
      return ERR_PTR(-EIO);

found:
      xprt = t->setup(args);
      if (IS_ERR(xprt)) {
            dprintk("RPC:       xprt_create_transport: failed, %ld\n",
                        -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);
      INIT_WORK(&xprt->task_cleanup, xprt_autoclose);
      init_timer(&xprt->timer);
      xprt->timer.function = xprt_init_autodisconnect;
      xprt->timer.data = (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\n", 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\n", xprt);
      xprt->shutdown = 1;
      del_timer_sync(&xprt->timer);

      /*
       * 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;
}

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