Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1593 insertions, 0 deletions

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
new file mode 100644
index 000000000..d05fa7c36
--- /dev/null
+++ b/net/sunrpc/xprt.c
@@ -0,0 +1,1593 @@
+/*
+ *  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 <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_connect_status(struct rpc_task *task);
+static int      __xprt_get_cong(struct rpc_xprt *, struct rpc_task *);
+static void     __xprt_put_cong(struct rpc_xprt *, struct rpc_rqst *);
+static void	 xprt_destroy(struct rpc_xprt *xprt);
+
+static DEFINE_SPINLOCK(xprt_list_lock);
+static LIST_HEAD(xprt_list);
+
+/**
+ * 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.\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);
+			goto out;
+		}
+	}
+	result = -ENOENT;
+
+out:
+	spin_unlock(&xprt_list_lock);
+	return result;
+}
+EXPORT_SYMBOL_GPL(xprt_unregister_transport);
+
+static void
+xprt_class_release(const struct xprt_class *t)
+{
+	module_put(t->owner);
+}
+
+static const struct xprt_class *
+xprt_class_find_by_netid_locked(const char *netid)
+{
+	const struct xprt_class *t;
+	unsigned int i;
+
+	list_for_each_entry(t, &xprt_list, list) {
+		for (i = 0; t->netid[i][0] != '\0'; i++) {
+			if (strcmp(t->netid[i], netid) != 0)
+				continue;
+			if (!try_module_get(t->owner))
+				continue;
+			return t;
+		}
+	}
+	return NULL;
+}
+
+static const struct xprt_class *
+xprt_class_find_by_netid(const char *netid)
+{
+	const struct xprt_class *t;
+
+	spin_lock(&xprt_list_lock);
+	t = xprt_class_find_by_netid_locked(netid);
+	if (!t) {
+		spin_unlock(&xprt_list_lock);
+		request_module("rpc%s", netid);
+		spin_lock(&xprt_list_lock);
+		t = xprt_class_find_by_netid_locked(netid);
+	}
+	spin_unlock(&xprt_list_lock);
+	return t;
+}
+
+/**
+ * xprt_load_transport - load a transport implementation
+ * @netid: transport to load
+ *
+ * Returns:
+ * 0:		transport successfully loaded
+ * -ENOENT:	transport module not available
+ */
+int xprt_load_transport(const char *netid)
+{
+	const struct xprt_class *t;
+
+	t = xprt_class_find_by_netid(netid);
+	if (!t)
+		return -ENOENT;
+	xprt_class_release(t);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xprt_load_transport);
+
+/**
+ * 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;
+	int priority;
+
+	if (test_and_set_bit(XPRT_LOCKED, &xprt->state)) {
+		if (task == xprt->snd_task)
+			return 1;
+		goto out_sleep;
+	}
+	xprt->snd_task = task;
+	if (req != NULL)
+		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 == NULL)
+		priority = RPC_PRIORITY_LOW;
+	else if (!req->rq_ntrans)
+		priority = RPC_PRIORITY_NORMAL;
+	else
+		priority = RPC_PRIORITY_HIGH;
+	rpc_sleep_on_priority(&xprt->sending, task, NULL, priority);
+	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)) {
+		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_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_xprt *xprt, struct rpc_task *task)
+{
+	struct rpc_rqst *req = task->tk_rqstp;
+	int priority;
+
+	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 (__xprt_get_cong(xprt, task)) {
+		xprt->snd_task = task;
+		req->rq_ntrans++;
+		return 1;
+	}
+	xprt_clear_locked(xprt);
+out_sleep:
+	if (req)
+		__xprt_put_cong(xprt, req);
+	dprintk("RPC: %5u failed to lock transport %p\n", task->tk_pid, xprt);
+	task->tk_timeout = 0;
+	task->tk_status = -EAGAIN;
+	if (req == NULL)
+		priority = RPC_PRIORITY_LOW;
+	else if (!req->rq_ntrans)
+		priority = RPC_PRIORITY_NORMAL;
+	else
+		priority = RPC_PRIORITY_HIGH;
+	rpc_sleep_on_priority(&xprt->sending, task, NULL, priority);
+	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(xprt, task);
+	spin_unlock_bh(&xprt->transport_lock);
+	return retval;
+}
+
+static bool __xprt_lock_write_func(struct rpc_task *task, void *data)
+{
+	struct rpc_xprt *xprt = data;
+	struct rpc_rqst *req;
+
+	req = task->tk_rqstp;
+	xprt->snd_task = task;
+	if (req)
+		req->rq_ntrans++;
+	return true;
+}
+
+static void __xprt_lock_write_next(struct rpc_xprt *xprt)
+{
+	if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
+		return;
+
+	if (rpc_wake_up_first_on_wq(xprtiod_workqueue, &xprt->sending,
+				__xprt_lock_write_func, xprt))
+		return;
+	xprt_clear_locked(xprt);
+}
+
+static bool __xprt_lock_write_cong_func(struct rpc_task *task, void *data)
+{
+	struct rpc_xprt *xprt = data;
+	struct rpc_rqst *req;
+
+	req = task->tk_rqstp;
+	if (req == NULL) {
+		xprt->snd_task = task;
+		return true;
+	}
+	if (__xprt_get_cong(xprt, task)) {
+		xprt->snd_task = task;
+		req->rq_ntrans++;
+		return true;
+	}
+	return false;
+}
+
+static void __xprt_lock_write_next_cong(struct rpc_xprt *xprt)
+{
+	if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
+		return;
+	if (RPCXPRT_CONGESTED(xprt))
+		goto out_unlock;
+	if (rpc_wake_up_first_on_wq(xprtiod_workqueue, &xprt->sending,
+				__xprt_lock_write_cong_func, xprt))
+		return;
+out_unlock:
+	xprt_clear_locked(xprt);
+}
+
+static void xprt_task_clear_bytes_sent(struct rpc_task *task)
+{
+	if (task != NULL) {
+		struct rpc_rqst *req = task->tk_rqstp;
+		if (req != NULL)
+			req->rq_bytes_sent = 0;
+	}
+}
+
+/**
+ * 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_task_clear_bytes_sent(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_task_clear_bytes_sent(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)
+{
+	struct rpc_rqst *req = task->tk_rqstp;
+
+	__xprt_put_cong(req->rq_xprt, req);
+}
+EXPORT_SYMBOL_GPL(xprt_release_rqst_cong);
+
+/**
+ * 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\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
+ * @action: function pointer to be executed after wait
+ *
+ * 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_task *task, rpc_action action)
+{
+	struct rpc_rqst *req = task->tk_rqstp;
+	struct rpc_xprt *xprt = req->rq_xprt;
+
+	task->tk_timeout = RPC_IS_SOFT(task) ? req->rq_timeout : 0;
+	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)
+{
+	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_queued_task_on_wq(xprtiod_workqueue,
+				&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!\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);
+
+	clear_bit(XPRT_CLOSE_WAIT, &xprt->state);
+	xprt->ops->close(xprt);
+	xprt_release_write(xprt, NULL);
+	wake_up_bit(&xprt->state, XPRT_LOCKED);
+}
+
+/**
+ * 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\n", 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(xprtiod_workqueue, &xprt->task_cleanup);
+	xprt_wake_pending_tasks(xprt, -EAGAIN);
+	spin_unlock_bh(&xprt->transport_lock);
+}
+EXPORT_SYMBOL_GPL(xprt_force_disconnect);
+
+/**
+ * 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))
+		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_bh(&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)
+{
+	if (list_empty(&xprt->recv) && 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);
+
+	spin_lock(&xprt->transport_lock);
+	if (!list_empty(&xprt->recv))
+		goto out_abort;
+	/* Reset xprt->last_used to avoid connect/autodisconnect cycling */
+	xprt->last_used = jiffies;
+	if (test_and_set_bit(XPRT_LOCKED, &xprt->state))
+		goto out_abort;
+	spin_unlock(&xprt->transport_lock);
+	queue_work(xprtiod_workqueue, &xprt->task_cleanup);
+	return;
+out_abort:
+	spin_unlock(&xprt->transport_lock);
+}
+
+bool xprt_lock_connect(struct rpc_xprt *xprt,
+		struct rpc_task *task,
+		void *cookie)
+{
+	bool ret = false;
+
+	spin_lock_bh(&xprt->transport_lock);
+	if (!test_bit(XPRT_LOCKED, &xprt->state))
+		goto out;
+	if (xprt->snd_task != task)
+		goto out;
+	xprt_task_clear_bytes_sent(task);
+	xprt->snd_task = cookie;
+	ret = true;
+out:
+	spin_unlock_bh(&xprt->transport_lock);
+	return ret;
+}
+
+void xprt_unlock_connect(struct rpc_xprt *xprt, void *cookie)
+{
+	spin_lock_bh(&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_bh(&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\n", 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_bytes_sent = 0;
+		task->tk_timeout = task->tk_rqstp->rq_timeout;
+		task->tk_rqstp->rq_connect_cookie = xprt->connect_cookie;
+		rpc_sleep_on(&xprt->pending, task, xprt_connect_status);
+
+		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);
+}
+
+static void xprt_connect_status(struct rpc_task *task)
+{
+	switch (task->tk_status) {
+	case 0:
+		dprintk("RPC: %5u xprt_connect_status: connection established\n",
+				task->tk_pid);
+		break;
+	case -ECONNREFUSED:
+	case -ECONNRESET:
+	case -ECONNABORTED:
+	case -ENETUNREACH:
+	case -EHOSTUNREACH:
+	case -EPIPE:
+	case -EAGAIN:
+		dprintk("RPC: %5u xprt_connect_status: retrying\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_rqstp->rq_xprt->servername);
+		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
+ *
+ * Caller holds xprt->recv_lock.
+ */
+struct rpc_rqst *xprt_lookup_rqst(struct rpc_xprt *xprt, __be32 xid)
+{
+	struct rpc_rqst *entry;
+
+	list_for_each_entry(entry, &xprt->recv, rq_list)
+		if (entry->rq_xid == xid) {
+			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\n",
+			ntohl(xid));
+	trace_xprt_lookup_rqst(xprt, xid, -ENOENT);
+	xprt->stat.bad_xids++;
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(xprt_lookup_rqst);
+
+/**
+ * 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 the xprt transport lock.
+ */
+void xprt_pin_rqst(struct rpc_rqst *req)
+{
+	set_bit(RPC_TASK_MSG_RECV, &req->rq_task->tk_runstate);
+}
+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 the xprt transport lock.
+ */
+void xprt_unpin_rqst(struct rpc_rqst *req)
+{
+	struct rpc_task *task = req->rq_task;
+
+	clear_bit(RPC_TASK_MSG_RECV, &task->tk_runstate);
+	if (test_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate))
+		wake_up_bit(&task->tk_runstate, RPC_TASK_MSG_RECV);
+}
+EXPORT_SYMBOL_GPL(xprt_unpin_rqst);
+
+static void xprt_wait_on_pinned_rqst(struct rpc_rqst *req)
+__must_hold(&req->rq_xprt->recv_lock)
+{
+	struct rpc_task *task = req->rq_task;
+
+	if (task && test_bit(RPC_TASK_MSG_RECV, &task->tk_runstate)) {
+		spin_unlock(&req->rq_xprt->recv_lock);
+		set_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate);
+		wait_on_bit(&task->tk_runstate, RPC_TASK_MSG_RECV,
+				TASK_UNINTERRUPTIBLE);
+		clear_bit(RPC_TASK_MSG_RECV_WAIT, &task->tk_runstate);
+		spin_lock(&req->rq_xprt->recv_lock);
+	}
+}
+
+/**
+ * xprt_update_rtt - Update RPC RTT statistics
+ * @task: RPC request that recently completed
+ *
+ * Caller holds xprt->recv_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->recv_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)\n",
+			task->tk_pid, ntohl(req->rq_xid), copied);
+	trace_xprt_complete_rqst(xprt, req->rq_xid, copied);
+
+	xprt->stat.recvs++;
+
+	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;
+
+	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_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;
+	bool ret = false;
+
+	dprintk("RPC: %5u xprt_prepare_transmit\n", task->tk_pid);
+
+	spin_lock_bh(&xprt->transport_lock);
+	if (!req->rq_bytes_sent) {
+		if (req->rq_reply_bytes_recvd) {
+			task->tk_status = req->rq_reply_bytes_recvd;
+			goto out_unlock;
+		}
+		if ((task->tk_flags & RPC_TASK_NO_RETRANS_TIMEOUT)
+		    && xprt_connected(xprt)
+		    && req->rq_connect_cookie == xprt->connect_cookie) {
+			xprt->ops->set_retrans_timeout(task);
+			rpc_sleep_on(&xprt->pending, task, xprt_timer);
+			goto out_unlock;
+		}
+	}
+	if (!xprt->ops->reserve_xprt(xprt, task)) {
+		task->tk_status = -EAGAIN;
+		goto out_unlock;
+	}
+	ret = true;
+out_unlock:
+	spin_unlock_bh(&xprt->transport_lock);
+	return ret;
+}
+
+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;
+	unsigned int connect_cookie;
+	int status;
+
+	dprintk("RPC: %5u xprt_transmit(%u)\n", 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
+			 */
+			/* 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 */
+			spin_lock(&xprt->recv_lock);
+			list_add_tail(&req->rq_list, &xprt->recv);
+			spin_unlock(&xprt->recv_lock);
+			xprt_reset_majortimeo(req);
+			/* Turn off autodisconnect */
+			del_singleshot_timer_sync(&xprt->timer);
+		}
+	} else if (!req->rq_bytes_sent)
+		return;
+
+	connect_cookie = xprt->connect_cookie;
+	status = xprt->ops->send_request(task);
+	trace_xprt_transmit(xprt, req->rq_xid, status);
+	if (status != 0) {
+		task->tk_status = status;
+		return;
+	}
+	xprt_inject_disconnect(xprt);
+
+	dprintk("RPC: %5u xmit complete\n", task->tk_pid);
+	task->tk_flags |= RPC_TASK_SENT;
+	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;
+	xprt->stat.sending_u += xprt->sending.qlen;
+	xprt->stat.pending_u += xprt->pending.qlen;
+	spin_unlock_bh(&xprt->transport_lock);
+
+	req->rq_connect_cookie = connect_cookie;
+	if (rpc_reply_expected(task) && !READ_ONCE(req->rq_reply_bytes_recvd)) {
+		/*
+		 * 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->recv_lock);
+		if (!req->rq_reply_bytes_recvd) {
+			rpc_sleep_on(&xprt->pending, task, xprt_timer);
+			/*
+			 * Send an extra queue wakeup call if the
+			 * connection was dropped in case the call to
+			 * rpc_sleep_on() raced.
+			 */
+			if (!xprt_connected(xprt))
+				xprt_wake_pending_tasks(xprt, -ENOTCONN);
+		}
+		spin_unlock(&xprt->recv_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\n");
+		task->tk_status = -ENOMEM;
+		break;
+	case -EAGAIN:
+		xprt_add_backlog(xprt, task);
+		dprintk("RPC:       waiting for request slot\n");
+		/* 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_lock_and_alloc_slot(struct rpc_xprt *xprt, struct rpc_task *task)
+{
+	/* Note: grabbing the xprt_lock_write() ensures that we throttle
+	 * new slot allocation if the transport is congested (i.e. when
+	 * reconnecting a stream transport or when out of socket write
+	 * buffer space).
+	 */
+	if (xprt_lock_write(xprt, task)) {
+		xprt_alloc_slot(xprt, task);
+		xprt_release_write(xprt, task);
+	}
+}
+EXPORT_SYMBOL_GPL(xprt_lock_and_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 __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;
+
+	INIT_LIST_HEAD(&req->rq_list);
+	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_connect_cookie = xprt->connect_cookie - 1;
+	req->rq_bytes_sent = 0;
+	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_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));
+}
+
+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_timeout = 0;
+	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_timeout = 0;
+	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;
+			if (xprt->snd_task == task)
+				xprt_release_write(xprt, task);
+		}
+		return;
+	}
+
+	xprt = req->rq_xprt;
+	if (task->tk_ops->rpc_count_stats != NULL)
+		task->tk_ops->rpc_count_stats(task, task->tk_calldata);
+	else if (task->tk_client)
+		rpc_count_iostats(task, task->tk_client->cl_metrics);
+	spin_lock(&xprt->recv_lock);
+	if (!list_empty(&req->rq_list)) {
+		list_del_init(&req->rq_list);
+		xprt_wait_on_pinned_rqst(req);
+	}
+	spin_unlock(&xprt->recv_lock);
+	spin_lock_bh(&xprt->transport_lock);
+	xprt->ops->release_xprt(xprt, task);
+	if (xprt->ops->release_request)
+		xprt->ops->release_request(task);
+	xprt->last_used = jiffies;
+	xprt_schedule_autodisconnect(xprt);
+	spin_unlock_bh(&xprt->transport_lock);
+	if (req->rq_buffer)
+		xprt->ops->buf_free(task);
+	xprt_inject_disconnect(xprt);
+	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\n", task->tk_pid, req);
+	if (likely(!bc_prealloc(req)))
+		xprt->ops->free_slot(xprt, req);
+	else
+		xprt_free_bc_request(req);
+}
+
+static void xprt_init(struct rpc_xprt *xprt, struct net *net)
+{
+	kref_init(&xprt->kref);
+
+	spin_lock_init(&xprt->transport_lock);
+	spin_lock_init(&xprt->reserve_lock);
+	spin_lock_init(&xprt->recv_lock);
+
+	INIT_LIST_HEAD(&xprt->free);
+	INIT_LIST_HEAD(&xprt->recv);
+#if defined(CONFIG_SUNRPC_BACKCHANNEL)
+	spin_lock_init(&xprt->bc_pa_lock);
+	INIT_LIST_HEAD(&xprt->bc_pa_list);
+#endif /* CONFIG_SUNRPC_BACKCHANNEL */
+	INIT_LIST_HEAD(&xprt->xprt_switch);
+
+	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_priority_wait_queue(&xprt->sending, "xprt_sending");
+	rpc_init_priority_wait_queue(&xprt->backlog, "xprt_backlog");
+
+	xprt_init_xid(xprt);
+
+	xprt->xprt_net = get_net(net);
+}
+
+/**
+ * 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 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);
+	dprintk("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));
+		goto out;
+	}
+	if (args->flags & XPRT_CREATE_NO_IDLE_TIMEOUT)
+		xprt->idle_timeout = 0;
+	INIT_WORK(&xprt->task_cleanup, xprt_autoclose);
+	if (xprt_has_timer(xprt))
+		timer_setup(&xprt->timer, xprt_init_autodisconnect, 0);
+	else
+		timer_setup(&xprt->timer, NULL, 0);
+
+	if (strlen(args->servername) > RPC_MAXNETNAMELEN) {
+		xprt_destroy(xprt);
+		return ERR_PTR(-EINVAL);
+	}
+	xprt->servername = kstrdup(args->servername, GFP_KERNEL);
+	if (xprt->servername == NULL) {
+		xprt_destroy(xprt);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	rpc_xprt_debugfs_register(xprt);
+
+	dprintk("RPC:       created transport %p with %u slots\n", xprt,
+			xprt->max_reqs);
+out:
+	return xprt;
+}
+
+static void xprt_destroy_cb(struct work_struct *work)
+{
+	struct rpc_xprt *xprt =
+		container_of(work, struct rpc_xprt, task_cleanup);
+
+	rpc_xprt_debugfs_unregister(xprt);
+	rpc_destroy_wait_queue(&xprt->binding);
+	rpc_destroy_wait_queue(&xprt->pending);
+	rpc_destroy_wait_queue(&xprt->sending);
+	rpc_destroy_wait_queue(&xprt->backlog);
+	kfree(xprt->servername);
+	/*
+	 * Tear down transport state and free the rpc_xprt
+	 */
+	xprt->ops->destroy(xprt);
+}
+
+/**
+ * xprt_destroy - destroy an RPC transport, killing off all requests.
+ * @xprt: transport to destroy
+ *
+ */
+static void xprt_destroy(struct rpc_xprt *xprt)
+{
+	dprintk("RPC:       destroying transport %p\n", xprt);
+
+	/*
+	 * Exclude transport connect/disconnect handlers and autoclose
+	 */
+	wait_on_bit_lock(&xprt->state, XPRT_LOCKED, TASK_UNINTERRUPTIBLE);
+
+	/*
+	 * xprt_schedule_autodisconnect() can run after XPRT_LOCKED
+	 * is cleared.  We use ->transport_lock to ensure the mod_timer()
+	 * can only run *before* del_time_sync(), never after.
+	 */
+	spin_lock(&xprt->transport_lock);
+	del_timer_sync(&xprt->timer);
+	spin_unlock(&xprt->transport_lock);
+
+	/*
+	 * Destroy sockets etc from the system workqueue so they can
+	 * safely flush receive work running on rpciod.
+	 */
+	INIT_WORK(&xprt->task_cleanup, xprt_destroy_cb);
+	schedule_work(&xprt->task_cleanup);
+}
+
+static void xprt_destroy_kref(struct kref *kref)
+{
+	xprt_destroy(container_of(kref, struct rpc_xprt, kref));
+}
+
+/**
+ * xprt_get - return a reference to an RPC transport.
+ * @xprt: pointer to the transport
+ *
+ */
+struct rpc_xprt *xprt_get(struct rpc_xprt *xprt)
+{
+	if (xprt != NULL && kref_get_unless_zero(&xprt->kref))
+		return xprt;
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(xprt_get);
+
+/**
+ * xprt_put - release a reference to an RPC transport.
+ * @xprt: pointer to the transport
+ *
+ */
+void xprt_put(struct rpc_xprt *xprt)
+{
+	if (xprt != NULL)
+		kref_put(&xprt->kref, xprt_destroy_kref);
+}
+EXPORT_SYMBOL_GPL(xprt_put);