Adding upstream version 6.6.15.upstream/6.6.15

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

1 files changed, 1361 insertions, 0 deletions

diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
new file mode 100644
index 0000000000..6debf4fd42
--- /dev/null
+++ b/net/sunrpc/sched.c
@@ -0,0 +1,1361 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * linux/net/sunrpc/sched.c
+ *
+ * Scheduling for synchronous and asynchronous RPC requests.
+ *
+ * Copyright (C) 1996 Olaf Kirch, <okir@monad.swb.de>
+ *
+ * TCP NFS related read + write fixes
+ * (C) 1999 Dave Airlie, University of Limerick, Ireland <airlied@linux.ie>
+ */
+
+#include <linux/module.h>
+
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/slab.h>
+#include <linux/mempool.h>
+#include <linux/smp.h>
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+#include <linux/freezer.h>
+#include <linux/sched/mm.h>
+
+#include <linux/sunrpc/clnt.h>
+#include <linux/sunrpc/metrics.h>
+
+#include "sunrpc.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/sunrpc.h>
+
+/*
+ * RPC slabs and memory pools
+ */
+#define RPC_BUFFER_MAXSIZE	(2048)
+#define RPC_BUFFER_POOLSIZE	(8)
+#define RPC_TASK_POOLSIZE	(8)
+static struct kmem_cache	*rpc_task_slabp __read_mostly;
+static struct kmem_cache	*rpc_buffer_slabp __read_mostly;
+static mempool_t	*rpc_task_mempool __read_mostly;
+static mempool_t	*rpc_buffer_mempool __read_mostly;
+
+static void			rpc_async_schedule(struct work_struct *);
+static void			 rpc_release_task(struct rpc_task *task);
+static void __rpc_queue_timer_fn(struct work_struct *);
+
+/*
+ * RPC tasks sit here while waiting for conditions to improve.
+ */
+static struct rpc_wait_queue delay_queue;
+
+/*
+ * rpciod-related stuff
+ */
+struct workqueue_struct *rpciod_workqueue __read_mostly;
+struct workqueue_struct *xprtiod_workqueue __read_mostly;
+EXPORT_SYMBOL_GPL(xprtiod_workqueue);
+
+gfp_t rpc_task_gfp_mask(void)
+{
+	if (current->flags & PF_WQ_WORKER)
+		return GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN;
+	return GFP_KERNEL;
+}
+EXPORT_SYMBOL_GPL(rpc_task_gfp_mask);
+
+bool rpc_task_set_rpc_status(struct rpc_task *task, int rpc_status)
+{
+	if (cmpxchg(&task->tk_rpc_status, 0, rpc_status) == 0)
+		return true;
+	return false;
+}
+
+unsigned long
+rpc_task_timeout(const struct rpc_task *task)
+{
+	unsigned long timeout = READ_ONCE(task->tk_timeout);
+
+	if (timeout != 0) {
+		unsigned long now = jiffies;
+		if (time_before(now, timeout))
+			return timeout - now;
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(rpc_task_timeout);
+
+/*
+ * Disable the timer for a given RPC task. Should be called with
+ * queue->lock and bh_disabled in order to avoid races within
+ * rpc_run_timer().
+ */
+static void
+__rpc_disable_timer(struct rpc_wait_queue *queue, struct rpc_task *task)
+{
+	if (list_empty(&task->u.tk_wait.timer_list))
+		return;
+	task->tk_timeout = 0;
+	list_del(&task->u.tk_wait.timer_list);
+	if (list_empty(&queue->timer_list.list))
+		cancel_delayed_work(&queue->timer_list.dwork);
+}
+
+static void
+rpc_set_queue_timer(struct rpc_wait_queue *queue, unsigned long expires)
+{
+	unsigned long now = jiffies;
+	queue->timer_list.expires = expires;
+	if (time_before_eq(expires, now))
+		expires = 0;
+	else
+		expires -= now;
+	mod_delayed_work(rpciod_workqueue, &queue->timer_list.dwork, expires);
+}
+
+/*
+ * Set up a timer for the current task.
+ */
+static void
+__rpc_add_timer(struct rpc_wait_queue *queue, struct rpc_task *task,
+		unsigned long timeout)
+{
+	task->tk_timeout = timeout;
+	if (list_empty(&queue->timer_list.list) || time_before(timeout, queue->timer_list.expires))
+		rpc_set_queue_timer(queue, timeout);
+	list_add(&task->u.tk_wait.timer_list, &queue->timer_list.list);
+}
+
+static void rpc_set_waitqueue_priority(struct rpc_wait_queue *queue, int priority)
+{
+	if (queue->priority != priority) {
+		queue->priority = priority;
+		queue->nr = 1U << priority;
+	}
+}
+
+static void rpc_reset_waitqueue_priority(struct rpc_wait_queue *queue)
+{
+	rpc_set_waitqueue_priority(queue, queue->maxpriority);
+}
+
+/*
+ * Add a request to a queue list
+ */
+static void
+__rpc_list_enqueue_task(struct list_head *q, struct rpc_task *task)
+{
+	struct rpc_task *t;
+
+	list_for_each_entry(t, q, u.tk_wait.list) {
+		if (t->tk_owner == task->tk_owner) {
+			list_add_tail(&task->u.tk_wait.links,
+					&t->u.tk_wait.links);
+			/* Cache the queue head in task->u.tk_wait.list */
+			task->u.tk_wait.list.next = q;
+			task->u.tk_wait.list.prev = NULL;
+			return;
+		}
+	}
+	INIT_LIST_HEAD(&task->u.tk_wait.links);
+	list_add_tail(&task->u.tk_wait.list, q);
+}
+
+/*
+ * Remove request from a queue list
+ */
+static void
+__rpc_list_dequeue_task(struct rpc_task *task)
+{
+	struct list_head *q;
+	struct rpc_task *t;
+
+	if (task->u.tk_wait.list.prev == NULL) {
+		list_del(&task->u.tk_wait.links);
+		return;
+	}
+	if (!list_empty(&task->u.tk_wait.links)) {
+		t = list_first_entry(&task->u.tk_wait.links,
+				struct rpc_task,
+				u.tk_wait.links);
+		/* Assume __rpc_list_enqueue_task() cached the queue head */
+		q = t->u.tk_wait.list.next;
+		list_add_tail(&t->u.tk_wait.list, q);
+		list_del(&task->u.tk_wait.links);
+	}
+	list_del(&task->u.tk_wait.list);
+}
+
+/*
+ * Add new request to a priority queue.
+ */
+static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue,
+		struct rpc_task *task,
+		unsigned char queue_priority)
+{
+	if (unlikely(queue_priority > queue->maxpriority))
+		queue_priority = queue->maxpriority;
+	__rpc_list_enqueue_task(&queue->tasks[queue_priority], task);
+}
+
+/*
+ * Add new request to wait queue.
+ */
+static void __rpc_add_wait_queue(struct rpc_wait_queue *queue,
+		struct rpc_task *task,
+		unsigned char queue_priority)
+{
+	INIT_LIST_HEAD(&task->u.tk_wait.timer_list);
+	if (RPC_IS_PRIORITY(queue))
+		__rpc_add_wait_queue_priority(queue, task, queue_priority);
+	else
+		list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);
+	task->tk_waitqueue = queue;
+	queue->qlen++;
+	/* barrier matches the read in rpc_wake_up_task_queue_locked() */
+	smp_wmb();
+	rpc_set_queued(task);
+}
+
+/*
+ * Remove request from a priority queue.
+ */
+static void __rpc_remove_wait_queue_priority(struct rpc_task *task)
+{
+	__rpc_list_dequeue_task(task);
+}
+
+/*
+ * Remove request from queue.
+ * Note: must be called with spin lock held.
+ */
+static void __rpc_remove_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *task)
+{
+	__rpc_disable_timer(queue, task);
+	if (RPC_IS_PRIORITY(queue))
+		__rpc_remove_wait_queue_priority(task);
+	else
+		list_del(&task->u.tk_wait.list);
+	queue->qlen--;
+}
+
+static void __rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname, unsigned char nr_queues)
+{
+	int i;
+
+	spin_lock_init(&queue->lock);
+	for (i = 0; i < ARRAY_SIZE(queue->tasks); i++)
+		INIT_LIST_HEAD(&queue->tasks[i]);
+	queue->maxpriority = nr_queues - 1;
+	rpc_reset_waitqueue_priority(queue);
+	queue->qlen = 0;
+	queue->timer_list.expires = 0;
+	INIT_DELAYED_WORK(&queue->timer_list.dwork, __rpc_queue_timer_fn);
+	INIT_LIST_HEAD(&queue->timer_list.list);
+	rpc_assign_waitqueue_name(queue, qname);
+}
+
+void rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname)
+{
+	__rpc_init_priority_wait_queue(queue, qname, RPC_NR_PRIORITY);
+}
+EXPORT_SYMBOL_GPL(rpc_init_priority_wait_queue);
+
+void rpc_init_wait_queue(struct rpc_wait_queue *queue, const char *qname)
+{
+	__rpc_init_priority_wait_queue(queue, qname, 1);
+}
+EXPORT_SYMBOL_GPL(rpc_init_wait_queue);
+
+void rpc_destroy_wait_queue(struct rpc_wait_queue *queue)
+{
+	cancel_delayed_work_sync(&queue->timer_list.dwork);
+}
+EXPORT_SYMBOL_GPL(rpc_destroy_wait_queue);
+
+static int rpc_wait_bit_killable(struct wait_bit_key *key, int mode)
+{
+	schedule();
+	if (signal_pending_state(mode, current))
+		return -ERESTARTSYS;
+	return 0;
+}
+
+#if IS_ENABLED(CONFIG_SUNRPC_DEBUG) || IS_ENABLED(CONFIG_TRACEPOINTS)
+static void rpc_task_set_debuginfo(struct rpc_task *task)
+{
+	struct rpc_clnt *clnt = task->tk_client;
+
+	/* Might be a task carrying a reverse-direction operation */
+	if (!clnt) {
+		static atomic_t rpc_pid;
+
+		task->tk_pid = atomic_inc_return(&rpc_pid);
+		return;
+	}
+
+	task->tk_pid = atomic_inc_return(&clnt->cl_pid);
+}
+#else
+static inline void rpc_task_set_debuginfo(struct rpc_task *task)
+{
+}
+#endif
+
+static void rpc_set_active(struct rpc_task *task)
+{
+	rpc_task_set_debuginfo(task);
+	set_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
+	trace_rpc_task_begin(task, NULL);
+}
+
+/*
+ * Mark an RPC call as having completed by clearing the 'active' bit
+ * and then waking up all tasks that were sleeping.
+ */
+static int rpc_complete_task(struct rpc_task *task)
+{
+	void *m = &task->tk_runstate;
+	wait_queue_head_t *wq = bit_waitqueue(m, RPC_TASK_ACTIVE);
+	struct wait_bit_key k = __WAIT_BIT_KEY_INITIALIZER(m, RPC_TASK_ACTIVE);
+	unsigned long flags;
+	int ret;
+
+	trace_rpc_task_complete(task, NULL);
+
+	spin_lock_irqsave(&wq->lock, flags);
+	clear_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
+	ret = atomic_dec_and_test(&task->tk_count);
+	if (waitqueue_active(wq))
+		__wake_up_locked_key(wq, TASK_NORMAL, &k);
+	spin_unlock_irqrestore(&wq->lock, flags);
+	return ret;
+}
+
+/*
+ * Allow callers to wait for completion of an RPC call
+ *
+ * Note the use of out_of_line_wait_on_bit() rather than wait_on_bit()
+ * to enforce taking of the wq->lock and hence avoid races with
+ * rpc_complete_task().
+ */
+int rpc_wait_for_completion_task(struct rpc_task *task)
+{
+	return out_of_line_wait_on_bit(&task->tk_runstate, RPC_TASK_ACTIVE,
+			rpc_wait_bit_killable, TASK_KILLABLE|TASK_FREEZABLE_UNSAFE);
+}
+EXPORT_SYMBOL_GPL(rpc_wait_for_completion_task);
+
+/*
+ * Make an RPC task runnable.
+ *
+ * Note: If the task is ASYNC, and is being made runnable after sitting on an
+ * rpc_wait_queue, this must be called with the queue spinlock held to protect
+ * the wait queue operation.
+ * Note the ordering of rpc_test_and_set_running() and rpc_clear_queued(),
+ * which is needed to ensure that __rpc_execute() doesn't loop (due to the
+ * lockless RPC_IS_QUEUED() test) before we've had a chance to test
+ * the RPC_TASK_RUNNING flag.
+ */
+static void rpc_make_runnable(struct workqueue_struct *wq,
+		struct rpc_task *task)
+{
+	bool need_wakeup = !rpc_test_and_set_running(task);
+
+	rpc_clear_queued(task);
+	if (!need_wakeup)
+		return;
+	if (RPC_IS_ASYNC(task)) {
+		INIT_WORK(&task->u.tk_work, rpc_async_schedule);
+		queue_work(wq, &task->u.tk_work);
+	} else
+		wake_up_bit(&task->tk_runstate, RPC_TASK_QUEUED);
+}
+
+/*
+ * Prepare for sleeping on a wait queue.
+ * By always appending tasks to the list we ensure FIFO behavior.
+ * NB: An RPC task will only receive interrupt-driven events as long
+ * as it's on a wait queue.
+ */
+static void __rpc_do_sleep_on_priority(struct rpc_wait_queue *q,
+		struct rpc_task *task,
+		unsigned char queue_priority)
+{
+	trace_rpc_task_sleep(task, q);
+
+	__rpc_add_wait_queue(q, task, queue_priority);
+}
+
+static void __rpc_sleep_on_priority(struct rpc_wait_queue *q,
+		struct rpc_task *task,
+		unsigned char queue_priority)
+{
+	if (WARN_ON_ONCE(RPC_IS_QUEUED(task)))
+		return;
+	__rpc_do_sleep_on_priority(q, task, queue_priority);
+}
+
+static void __rpc_sleep_on_priority_timeout(struct rpc_wait_queue *q,
+		struct rpc_task *task, unsigned long timeout,
+		unsigned char queue_priority)
+{
+	if (WARN_ON_ONCE(RPC_IS_QUEUED(task)))
+		return;
+	if (time_is_after_jiffies(timeout)) {
+		__rpc_do_sleep_on_priority(q, task, queue_priority);
+		__rpc_add_timer(q, task, timeout);
+	} else
+		task->tk_status = -ETIMEDOUT;
+}
+
+static void rpc_set_tk_callback(struct rpc_task *task, rpc_action action)
+{
+	if (action && !WARN_ON_ONCE(task->tk_callback != NULL))
+		task->tk_callback = action;
+}
+
+static bool rpc_sleep_check_activated(struct rpc_task *task)
+{
+	/* We shouldn't ever put an inactive task to sleep */
+	if (WARN_ON_ONCE(!RPC_IS_ACTIVATED(task))) {
+		task->tk_status = -EIO;
+		rpc_put_task_async(task);
+		return false;
+	}
+	return true;
+}
+
+void rpc_sleep_on_timeout(struct rpc_wait_queue *q, struct rpc_task *task,
+				rpc_action action, unsigned long timeout)
+{
+	if (!rpc_sleep_check_activated(task))
+		return;
+
+	rpc_set_tk_callback(task, action);
+
+	/*
+	 * Protect the queue operations.
+	 */
+	spin_lock(&q->lock);
+	__rpc_sleep_on_priority_timeout(q, task, timeout, task->tk_priority);
+	spin_unlock(&q->lock);
+}
+EXPORT_SYMBOL_GPL(rpc_sleep_on_timeout);
+
+void rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
+				rpc_action action)
+{
+	if (!rpc_sleep_check_activated(task))
+		return;
+
+	rpc_set_tk_callback(task, action);
+
+	WARN_ON_ONCE(task->tk_timeout != 0);
+	/*
+	 * Protect the queue operations.
+	 */
+	spin_lock(&q->lock);
+	__rpc_sleep_on_priority(q, task, task->tk_priority);
+	spin_unlock(&q->lock);
+}
+EXPORT_SYMBOL_GPL(rpc_sleep_on);
+
+void rpc_sleep_on_priority_timeout(struct rpc_wait_queue *q,
+		struct rpc_task *task, unsigned long timeout, int priority)
+{
+	if (!rpc_sleep_check_activated(task))
+		return;
+
+	priority -= RPC_PRIORITY_LOW;
+	/*
+	 * Protect the queue operations.
+	 */
+	spin_lock(&q->lock);
+	__rpc_sleep_on_priority_timeout(q, task, timeout, priority);
+	spin_unlock(&q->lock);
+}
+EXPORT_SYMBOL_GPL(rpc_sleep_on_priority_timeout);
+
+void rpc_sleep_on_priority(struct rpc_wait_queue *q, struct rpc_task *task,
+		int priority)
+{
+	if (!rpc_sleep_check_activated(task))
+		return;
+
+	WARN_ON_ONCE(task->tk_timeout != 0);
+	priority -= RPC_PRIORITY_LOW;
+	/*
+	 * Protect the queue operations.
+	 */
+	spin_lock(&q->lock);
+	__rpc_sleep_on_priority(q, task, priority);
+	spin_unlock(&q->lock);
+}
+EXPORT_SYMBOL_GPL(rpc_sleep_on_priority);
+
+/**
+ * __rpc_do_wake_up_task_on_wq - wake up a single rpc_task
+ * @wq: workqueue on which to run task
+ * @queue: wait queue
+ * @task: task to be woken up
+ *
+ * Caller must hold queue->lock, and have cleared the task queued flag.
+ */
+static void __rpc_do_wake_up_task_on_wq(struct workqueue_struct *wq,
+		struct rpc_wait_queue *queue,
+		struct rpc_task *task)
+{
+	/* Has the task been executed yet? If not, we cannot wake it up! */
+	if (!RPC_IS_ACTIVATED(task)) {
+		printk(KERN_ERR "RPC: Inactive task (%p) being woken up!\n", task);
+		return;
+	}
+
+	trace_rpc_task_wakeup(task, queue);
+
+	__rpc_remove_wait_queue(queue, task);
+
+	rpc_make_runnable(wq, task);
+}
+
+/*
+ * Wake up a queued task while the queue lock is being held
+ */
+static struct rpc_task *
+rpc_wake_up_task_on_wq_queue_action_locked(struct workqueue_struct *wq,
+		struct rpc_wait_queue *queue, struct rpc_task *task,
+		bool (*action)(struct rpc_task *, void *), void *data)
+{
+	if (RPC_IS_QUEUED(task)) {
+		smp_rmb();
+		if (task->tk_waitqueue == queue) {
+			if (action == NULL || action(task, data)) {
+				__rpc_do_wake_up_task_on_wq(wq, queue, task);
+				return task;
+			}
+		}
+	}
+	return NULL;
+}
+
+/*
+ * Wake up a queued task while the queue lock is being held
+ */
+static void rpc_wake_up_task_queue_locked(struct rpc_wait_queue *queue,
+					  struct rpc_task *task)
+{
+	rpc_wake_up_task_on_wq_queue_action_locked(rpciod_workqueue, queue,
+						   task, NULL, NULL);
+}
+
+/*
+ * Wake up a task on a specific queue
+ */
+void rpc_wake_up_queued_task(struct rpc_wait_queue *queue, struct rpc_task *task)
+{
+	if (!RPC_IS_QUEUED(task))
+		return;
+	spin_lock(&queue->lock);
+	rpc_wake_up_task_queue_locked(queue, task);
+	spin_unlock(&queue->lock);
+}
+EXPORT_SYMBOL_GPL(rpc_wake_up_queued_task);
+
+static bool rpc_task_action_set_status(struct rpc_task *task, void *status)
+{
+	task->tk_status = *(int *)status;
+	return true;
+}
+
+static void
+rpc_wake_up_task_queue_set_status_locked(struct rpc_wait_queue *queue,
+		struct rpc_task *task, int status)
+{
+	rpc_wake_up_task_on_wq_queue_action_locked(rpciod_workqueue, queue,
+			task, rpc_task_action_set_status, &status);
+}
+
+/**
+ * rpc_wake_up_queued_task_set_status - wake up a task and set task->tk_status
+ * @queue: pointer to rpc_wait_queue
+ * @task: pointer to rpc_task
+ * @status: integer error value
+ *
+ * If @task is queued on @queue, then it is woken up, and @task->tk_status is
+ * set to the value of @status.
+ */
+void
+rpc_wake_up_queued_task_set_status(struct rpc_wait_queue *queue,
+		struct rpc_task *task, int status)
+{
+	if (!RPC_IS_QUEUED(task))
+		return;
+	spin_lock(&queue->lock);
+	rpc_wake_up_task_queue_set_status_locked(queue, task, status);
+	spin_unlock(&queue->lock);
+}
+
+/*
+ * Wake up the next task on a priority queue.
+ */
+static struct rpc_task *__rpc_find_next_queued_priority(struct rpc_wait_queue *queue)
+{
+	struct list_head *q;
+	struct rpc_task *task;
+
+	/*
+	 * Service the privileged queue.
+	 */
+	q = &queue->tasks[RPC_NR_PRIORITY - 1];
+	if (queue->maxpriority > RPC_PRIORITY_PRIVILEGED && !list_empty(q)) {
+		task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
+		goto out;
+	}
+
+	/*
+	 * Service a batch of tasks from a single owner.
+	 */
+	q = &queue->tasks[queue->priority];
+	if (!list_empty(q) && queue->nr) {
+		queue->nr--;
+		task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
+		goto out;
+	}
+
+	/*
+	 * Service the next queue.
+	 */
+	do {
+		if (q == &queue->tasks[0])
+			q = &queue->tasks[queue->maxpriority];
+		else
+			q = q - 1;
+		if (!list_empty(q)) {
+			task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
+			goto new_queue;
+		}
+	} while (q != &queue->tasks[queue->priority]);
+
+	rpc_reset_waitqueue_priority(queue);
+	return NULL;
+
+new_queue:
+	rpc_set_waitqueue_priority(queue, (unsigned int)(q - &queue->tasks[0]));
+out:
+	return task;
+}
+
+static struct rpc_task *__rpc_find_next_queued(struct rpc_wait_queue *queue)
+{
+	if (RPC_IS_PRIORITY(queue))
+		return __rpc_find_next_queued_priority(queue);
+	if (!list_empty(&queue->tasks[0]))
+		return list_first_entry(&queue->tasks[0], struct rpc_task, u.tk_wait.list);
+	return NULL;
+}
+
+/*
+ * Wake up the first task on the wait queue.
+ */
+struct rpc_task *rpc_wake_up_first_on_wq(struct workqueue_struct *wq,
+		struct rpc_wait_queue *queue,
+		bool (*func)(struct rpc_task *, void *), void *data)
+{
+	struct rpc_task	*task = NULL;
+
+	spin_lock(&queue->lock);
+	task = __rpc_find_next_queued(queue);
+	if (task != NULL)
+		task = rpc_wake_up_task_on_wq_queue_action_locked(wq, queue,
+				task, func, data);
+	spin_unlock(&queue->lock);
+
+	return task;
+}
+
+/*
+ * Wake up the first task on the wait queue.
+ */
+struct rpc_task *rpc_wake_up_first(struct rpc_wait_queue *queue,
+		bool (*func)(struct rpc_task *, void *), void *data)
+{
+	return rpc_wake_up_first_on_wq(rpciod_workqueue, queue, func, data);
+}
+EXPORT_SYMBOL_GPL(rpc_wake_up_first);
+
+static bool rpc_wake_up_next_func(struct rpc_task *task, void *data)
+{
+	return true;
+}
+
+/*
+ * Wake up the next task on the wait queue.
+*/
+struct rpc_task *rpc_wake_up_next(struct rpc_wait_queue *queue)
+{
+	return rpc_wake_up_first(queue, rpc_wake_up_next_func, NULL);
+}
+EXPORT_SYMBOL_GPL(rpc_wake_up_next);
+
+/**
+ * rpc_wake_up_locked - wake up all rpc_tasks
+ * @queue: rpc_wait_queue on which the tasks are sleeping
+ *
+ */
+static void rpc_wake_up_locked(struct rpc_wait_queue *queue)
+{
+	struct rpc_task *task;
+
+	for (;;) {
+		task = __rpc_find_next_queued(queue);
+		if (task == NULL)
+			break;
+		rpc_wake_up_task_queue_locked(queue, task);
+	}
+}
+
+/**
+ * rpc_wake_up - wake up all rpc_tasks
+ * @queue: rpc_wait_queue on which the tasks are sleeping
+ *
+ * Grabs queue->lock
+ */
+void rpc_wake_up(struct rpc_wait_queue *queue)
+{
+	spin_lock(&queue->lock);
+	rpc_wake_up_locked(queue);
+	spin_unlock(&queue->lock);
+}
+EXPORT_SYMBOL_GPL(rpc_wake_up);
+
+/**
+ * rpc_wake_up_status_locked - wake up all rpc_tasks and set their status value.
+ * @queue: rpc_wait_queue on which the tasks are sleeping
+ * @status: status value to set
+ */
+static void rpc_wake_up_status_locked(struct rpc_wait_queue *queue, int status)
+{
+	struct rpc_task *task;
+
+	for (;;) {
+		task = __rpc_find_next_queued(queue);
+		if (task == NULL)
+			break;
+		rpc_wake_up_task_queue_set_status_locked(queue, task, status);
+	}
+}
+
+/**
+ * rpc_wake_up_status - wake up all rpc_tasks and set their status value.
+ * @queue: rpc_wait_queue on which the tasks are sleeping
+ * @status: status value to set
+ *
+ * Grabs queue->lock
+ */
+void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
+{
+	spin_lock(&queue->lock);
+	rpc_wake_up_status_locked(queue, status);
+	spin_unlock(&queue->lock);
+}
+EXPORT_SYMBOL_GPL(rpc_wake_up_status);
+
+static void __rpc_queue_timer_fn(struct work_struct *work)
+{
+	struct rpc_wait_queue *queue = container_of(work,
+			struct rpc_wait_queue,
+			timer_list.dwork.work);
+	struct rpc_task *task, *n;
+	unsigned long expires, now, timeo;
+
+	spin_lock(&queue->lock);
+	expires = now = jiffies;
+	list_for_each_entry_safe(task, n, &queue->timer_list.list, u.tk_wait.timer_list) {
+		timeo = task->tk_timeout;
+		if (time_after_eq(now, timeo)) {
+			trace_rpc_task_timeout(task, task->tk_action);
+			task->tk_status = -ETIMEDOUT;
+			rpc_wake_up_task_queue_locked(queue, task);
+			continue;
+		}
+		if (expires == now || time_after(expires, timeo))
+			expires = timeo;
+	}
+	if (!list_empty(&queue->timer_list.list))
+		rpc_set_queue_timer(queue, expires);
+	spin_unlock(&queue->lock);
+}
+
+static void __rpc_atrun(struct rpc_task *task)
+{
+	if (task->tk_status == -ETIMEDOUT)
+		task->tk_status = 0;
+}
+
+/*
+ * Run a task at a later time
+ */
+void rpc_delay(struct rpc_task *task, unsigned long delay)
+{
+	rpc_sleep_on_timeout(&delay_queue, task, __rpc_atrun, jiffies + delay);
+}
+EXPORT_SYMBOL_GPL(rpc_delay);
+
+/*
+ * Helper to call task->tk_ops->rpc_call_prepare
+ */
+void rpc_prepare_task(struct rpc_task *task)
+{
+	task->tk_ops->rpc_call_prepare(task, task->tk_calldata);
+}
+
+static void
+rpc_init_task_statistics(struct rpc_task *task)
+{
+	/* Initialize retry counters */
+	task->tk_garb_retry = 2;
+	task->tk_cred_retry = 2;
+
+	/* starting timestamp */
+	task->tk_start = ktime_get();
+}
+
+static void
+rpc_reset_task_statistics(struct rpc_task *task)
+{
+	task->tk_timeouts = 0;
+	task->tk_flags &= ~(RPC_CALL_MAJORSEEN|RPC_TASK_SENT);
+	rpc_init_task_statistics(task);
+}
+
+/*
+ * Helper that calls task->tk_ops->rpc_call_done if it exists
+ */
+void rpc_exit_task(struct rpc_task *task)
+{
+	trace_rpc_task_end(task, task->tk_action);
+	task->tk_action = NULL;
+	if (task->tk_ops->rpc_count_stats)
+		task->tk_ops->rpc_count_stats(task, task->tk_calldata);
+	else if (task->tk_client)
+		rpc_count_iostats(task, task->tk_client->cl_metrics);
+	if (task->tk_ops->rpc_call_done != NULL) {
+		trace_rpc_task_call_done(task, task->tk_ops->rpc_call_done);
+		task->tk_ops->rpc_call_done(task, task->tk_calldata);
+		if (task->tk_action != NULL) {
+			/* Always release the RPC slot and buffer memory */
+			xprt_release(task);
+			rpc_reset_task_statistics(task);
+		}
+	}
+}
+
+void rpc_signal_task(struct rpc_task *task)
+{
+	struct rpc_wait_queue *queue;
+
+	if (!RPC_IS_ACTIVATED(task))
+		return;
+
+	if (!rpc_task_set_rpc_status(task, -ERESTARTSYS))
+		return;
+	trace_rpc_task_signalled(task, task->tk_action);
+	set_bit(RPC_TASK_SIGNALLED, &task->tk_runstate);
+	smp_mb__after_atomic();
+	queue = READ_ONCE(task->tk_waitqueue);
+	if (queue)
+		rpc_wake_up_queued_task(queue, task);
+}
+
+void rpc_task_try_cancel(struct rpc_task *task, int error)
+{
+	struct rpc_wait_queue *queue;
+
+	if (!rpc_task_set_rpc_status(task, error))
+		return;
+	queue = READ_ONCE(task->tk_waitqueue);
+	if (queue)
+		rpc_wake_up_queued_task(queue, task);
+}
+
+void rpc_exit(struct rpc_task *task, int status)
+{
+	task->tk_status = status;
+	task->tk_action = rpc_exit_task;
+	rpc_wake_up_queued_task(task->tk_waitqueue, task);
+}
+EXPORT_SYMBOL_GPL(rpc_exit);
+
+void rpc_release_calldata(const struct rpc_call_ops *ops, void *calldata)
+{
+	if (ops->rpc_release != NULL)
+		ops->rpc_release(calldata);
+}
+
+static bool xprt_needs_memalloc(struct rpc_xprt *xprt, struct rpc_task *tk)
+{
+	if (!xprt)
+		return false;
+	if (!atomic_read(&xprt->swapper))
+		return false;
+	return test_bit(XPRT_LOCKED, &xprt->state) && xprt->snd_task == tk;
+}
+
+/*
+ * This is the RPC `scheduler' (or rather, the finite state machine).
+ */
+static void __rpc_execute(struct rpc_task *task)
+{
+	struct rpc_wait_queue *queue;
+	int task_is_async = RPC_IS_ASYNC(task);
+	int status = 0;
+	unsigned long pflags = current->flags;
+
+	WARN_ON_ONCE(RPC_IS_QUEUED(task));
+	if (RPC_IS_QUEUED(task))
+		return;
+
+	for (;;) {
+		void (*do_action)(struct rpc_task *);
+
+		/*
+		 * Perform the next FSM step or a pending callback.
+		 *
+		 * tk_action may be NULL if the task has been killed.
+		 */
+		do_action = task->tk_action;
+		/* Tasks with an RPC error status should exit */
+		if (do_action && do_action != rpc_exit_task &&
+		    (status = READ_ONCE(task->tk_rpc_status)) != 0) {
+			task->tk_status = status;
+			do_action = rpc_exit_task;
+		}
+		/* Callbacks override all actions */
+		if (task->tk_callback) {
+			do_action = task->tk_callback;
+			task->tk_callback = NULL;
+		}
+		if (!do_action)
+			break;
+		if (RPC_IS_SWAPPER(task) ||
+		    xprt_needs_memalloc(task->tk_xprt, task))
+			current->flags |= PF_MEMALLOC;
+
+		trace_rpc_task_run_action(task, do_action);
+		do_action(task);
+
+		/*
+		 * Lockless check for whether task is sleeping or not.
+		 */
+		if (!RPC_IS_QUEUED(task)) {
+			cond_resched();
+			continue;
+		}
+
+		/*
+		 * The queue->lock protects against races with
+		 * rpc_make_runnable().
+		 *
+		 * Note that once we clear RPC_TASK_RUNNING on an asynchronous
+		 * rpc_task, rpc_make_runnable() can assign it to a
+		 * different workqueue. We therefore cannot assume that the
+		 * rpc_task pointer may still be dereferenced.
+		 */
+		queue = task->tk_waitqueue;
+		spin_lock(&queue->lock);
+		if (!RPC_IS_QUEUED(task)) {
+			spin_unlock(&queue->lock);
+			continue;
+		}
+		/* Wake up any task that has an exit status */
+		if (READ_ONCE(task->tk_rpc_status) != 0) {
+			rpc_wake_up_task_queue_locked(queue, task);
+			spin_unlock(&queue->lock);
+			continue;
+		}
+		rpc_clear_running(task);
+		spin_unlock(&queue->lock);
+		if (task_is_async)
+			goto out;
+
+		/* sync task: sleep here */
+		trace_rpc_task_sync_sleep(task, task->tk_action);
+		status = out_of_line_wait_on_bit(&task->tk_runstate,
+				RPC_TASK_QUEUED, rpc_wait_bit_killable,
+				TASK_KILLABLE|TASK_FREEZABLE);
+		if (status < 0) {
+			/*
+			 * When a sync task receives a signal, it exits with
+			 * -ERESTARTSYS. In order to catch any callbacks that
+			 * clean up after sleeping on some queue, we don't
+			 * break the loop here, but go around once more.
+			 */
+			rpc_signal_task(task);
+		}
+		trace_rpc_task_sync_wake(task, task->tk_action);
+	}
+
+	/* Release all resources associated with the task */
+	rpc_release_task(task);
+out:
+	current_restore_flags(pflags, PF_MEMALLOC);
+}
+
+/*
+ * User-visible entry point to the scheduler.
+ *
+ * This may be called recursively if e.g. an async NFS task updates
+ * the attributes and finds that dirty pages must be flushed.
+ * NOTE: Upon exit of this function the task is guaranteed to be
+ *	 released. In particular note that tk_release() will have
+ *	 been called, so your task memory may have been freed.
+ */
+void rpc_execute(struct rpc_task *task)
+{
+	bool is_async = RPC_IS_ASYNC(task);
+
+	rpc_set_active(task);
+	rpc_make_runnable(rpciod_workqueue, task);
+	if (!is_async) {
+		unsigned int pflags = memalloc_nofs_save();
+		__rpc_execute(task);
+		memalloc_nofs_restore(pflags);
+	}
+}
+
+static void rpc_async_schedule(struct work_struct *work)
+{
+	unsigned int pflags = memalloc_nofs_save();
+
+	__rpc_execute(container_of(work, struct rpc_task, u.tk_work));
+	memalloc_nofs_restore(pflags);
+}
+
+/**
+ * rpc_malloc - allocate RPC buffer resources
+ * @task: RPC task
+ *
+ * A single memory region is allocated, which is split between the
+ * RPC call and RPC reply that this task is being used for. When
+ * this RPC is retired, the memory is released by calling rpc_free.
+ *
+ * To prevent rpciod from hanging, this allocator never sleeps,
+ * returning -ENOMEM and suppressing warning if the request cannot
+ * be serviced immediately. The caller can arrange to sleep in a
+ * way that is safe for rpciod.
+ *
+ * Most requests are 'small' (under 2KiB) and can be serviced from a
+ * mempool, ensuring that NFS reads and writes can always proceed,
+ * and that there is good locality of reference for these buffers.
+ */
+int rpc_malloc(struct rpc_task *task)
+{
+	struct rpc_rqst *rqst = task->tk_rqstp;
+	size_t size = rqst->rq_callsize + rqst->rq_rcvsize;
+	struct rpc_buffer *buf;
+	gfp_t gfp = rpc_task_gfp_mask();
+
+	size += sizeof(struct rpc_buffer);
+	if (size <= RPC_BUFFER_MAXSIZE) {
+		buf = kmem_cache_alloc(rpc_buffer_slabp, gfp);
+		/* Reach for the mempool if dynamic allocation fails */
+		if (!buf && RPC_IS_ASYNC(task))
+			buf = mempool_alloc(rpc_buffer_mempool, GFP_NOWAIT);
+	} else
+		buf = kmalloc(size, gfp);
+
+	if (!buf)
+		return -ENOMEM;
+
+	buf->len = size;
+	rqst->rq_buffer = buf->data;
+	rqst->rq_rbuffer = (char *)rqst->rq_buffer + rqst->rq_callsize;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(rpc_malloc);
+
+/**
+ * rpc_free - free RPC buffer resources allocated via rpc_malloc
+ * @task: RPC task
+ *
+ */
+void rpc_free(struct rpc_task *task)
+{
+	void *buffer = task->tk_rqstp->rq_buffer;
+	size_t size;
+	struct rpc_buffer *buf;
+
+	buf = container_of(buffer, struct rpc_buffer, data);
+	size = buf->len;
+
+	if (size <= RPC_BUFFER_MAXSIZE)
+		mempool_free(buf, rpc_buffer_mempool);
+	else
+		kfree(buf);
+}
+EXPORT_SYMBOL_GPL(rpc_free);
+
+/*
+ * Creation and deletion of RPC task structures
+ */
+static void rpc_init_task(struct rpc_task *task, const struct rpc_task_setup *task_setup_data)
+{
+	memset(task, 0, sizeof(*task));
+	atomic_set(&task->tk_count, 1);
+	task->tk_flags  = task_setup_data->flags;
+	task->tk_ops = task_setup_data->callback_ops;
+	task->tk_calldata = task_setup_data->callback_data;
+	INIT_LIST_HEAD(&task->tk_task);
+
+	task->tk_priority = task_setup_data->priority - RPC_PRIORITY_LOW;
+	task->tk_owner = current->tgid;
+
+	/* Initialize workqueue for async tasks */
+	task->tk_workqueue = task_setup_data->workqueue;
+
+	task->tk_xprt = rpc_task_get_xprt(task_setup_data->rpc_client,
+			xprt_get(task_setup_data->rpc_xprt));
+
+	task->tk_op_cred = get_rpccred(task_setup_data->rpc_op_cred);
+
+	if (task->tk_ops->rpc_call_prepare != NULL)
+		task->tk_action = rpc_prepare_task;
+
+	rpc_init_task_statistics(task);
+}
+
+static struct rpc_task *rpc_alloc_task(void)
+{
+	struct rpc_task *task;
+
+	task = kmem_cache_alloc(rpc_task_slabp, rpc_task_gfp_mask());
+	if (task)
+		return task;
+	return mempool_alloc(rpc_task_mempool, GFP_NOWAIT);
+}
+
+/*
+ * Create a new task for the specified client.
+ */
+struct rpc_task *rpc_new_task(const struct rpc_task_setup *setup_data)
+{
+	struct rpc_task	*task = setup_data->task;
+	unsigned short flags = 0;
+
+	if (task == NULL) {
+		task = rpc_alloc_task();
+		if (task == NULL) {
+			rpc_release_calldata(setup_data->callback_ops,
+					     setup_data->callback_data);
+			return ERR_PTR(-ENOMEM);
+		}
+		flags = RPC_TASK_DYNAMIC;
+	}
+
+	rpc_init_task(task, setup_data);
+	task->tk_flags |= flags;
+	return task;
+}
+
+/*
+ * rpc_free_task - release rpc task and perform cleanups
+ *
+ * Note that we free up the rpc_task _after_ rpc_release_calldata()
+ * in order to work around a workqueue dependency issue.
+ *
+ * Tejun Heo states:
+ * "Workqueue currently considers two work items to be the same if they're
+ * on the same address and won't execute them concurrently - ie. it
+ * makes a work item which is queued again while being executed wait
+ * for the previous execution to complete.
+ *
+ * If a work function frees the work item, and then waits for an event
+ * which should be performed by another work item and *that* work item
+ * recycles the freed work item, it can create a false dependency loop.
+ * There really is no reliable way to detect this short of verifying
+ * every memory free."
+ *
+ */
+static void rpc_free_task(struct rpc_task *task)
+{
+	unsigned short tk_flags = task->tk_flags;
+
+	put_rpccred(task->tk_op_cred);
+	rpc_release_calldata(task->tk_ops, task->tk_calldata);
+
+	if (tk_flags & RPC_TASK_DYNAMIC)
+		mempool_free(task, rpc_task_mempool);
+}
+
+static void rpc_async_release(struct work_struct *work)
+{
+	unsigned int pflags = memalloc_nofs_save();
+
+	rpc_free_task(container_of(work, struct rpc_task, u.tk_work));
+	memalloc_nofs_restore(pflags);
+}
+
+static void rpc_release_resources_task(struct rpc_task *task)
+{
+	xprt_release(task);
+	if (task->tk_msg.rpc_cred) {
+		if (!(task->tk_flags & RPC_TASK_CRED_NOREF))
+			put_cred(task->tk_msg.rpc_cred);
+		task->tk_msg.rpc_cred = NULL;
+	}
+	rpc_task_release_client(task);
+}
+
+static void rpc_final_put_task(struct rpc_task *task,
+		struct workqueue_struct *q)
+{
+	if (q != NULL) {
+		INIT_WORK(&task->u.tk_work, rpc_async_release);
+		queue_work(q, &task->u.tk_work);
+	} else
+		rpc_free_task(task);
+}
+
+static void rpc_do_put_task(struct rpc_task *task, struct workqueue_struct *q)
+{
+	if (atomic_dec_and_test(&task->tk_count)) {
+		rpc_release_resources_task(task);
+		rpc_final_put_task(task, q);
+	}
+}
+
+void rpc_put_task(struct rpc_task *task)
+{
+	rpc_do_put_task(task, NULL);
+}
+EXPORT_SYMBOL_GPL(rpc_put_task);
+
+void rpc_put_task_async(struct rpc_task *task)
+{
+	rpc_do_put_task(task, task->tk_workqueue);
+}
+EXPORT_SYMBOL_GPL(rpc_put_task_async);
+
+static void rpc_release_task(struct rpc_task *task)
+{
+	WARN_ON_ONCE(RPC_IS_QUEUED(task));
+
+	rpc_release_resources_task(task);
+
+	/*
+	 * Note: at this point we have been removed from rpc_clnt->cl_tasks,
+	 * so it should be safe to use task->tk_count as a test for whether
+	 * or not any other processes still hold references to our rpc_task.
+	 */
+	if (atomic_read(&task->tk_count) != 1 + !RPC_IS_ASYNC(task)) {
+		/* Wake up anyone who may be waiting for task completion */
+		if (!rpc_complete_task(task))
+			return;
+	} else {
+		if (!atomic_dec_and_test(&task->tk_count))
+			return;
+	}
+	rpc_final_put_task(task, task->tk_workqueue);
+}
+
+int rpciod_up(void)
+{
+	return try_module_get(THIS_MODULE) ? 0 : -EINVAL;
+}
+
+void rpciod_down(void)
+{
+	module_put(THIS_MODULE);
+}
+
+/*
+ * Start up the rpciod workqueue.
+ */
+static int rpciod_start(void)
+{
+	struct workqueue_struct *wq;
+
+	/*
+	 * Create the rpciod thread and wait for it to start.
+	 */
+	wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
+	if (!wq)
+		goto out_failed;
+	rpciod_workqueue = wq;
+	wq = alloc_workqueue("xprtiod", WQ_UNBOUND | WQ_MEM_RECLAIM, 0);
+	if (!wq)
+		goto free_rpciod;
+	xprtiod_workqueue = wq;
+	return 1;
+free_rpciod:
+	wq = rpciod_workqueue;
+	rpciod_workqueue = NULL;
+	destroy_workqueue(wq);
+out_failed:
+	return 0;
+}
+
+static void rpciod_stop(void)
+{
+	struct workqueue_struct *wq = NULL;
+
+	if (rpciod_workqueue == NULL)
+		return;
+
+	wq = rpciod_workqueue;
+	rpciod_workqueue = NULL;
+	destroy_workqueue(wq);
+	wq = xprtiod_workqueue;
+	xprtiod_workqueue = NULL;
+	destroy_workqueue(wq);
+}
+
+void
+rpc_destroy_mempool(void)
+{
+	rpciod_stop();
+	mempool_destroy(rpc_buffer_mempool);
+	mempool_destroy(rpc_task_mempool);
+	kmem_cache_destroy(rpc_task_slabp);
+	kmem_cache_destroy(rpc_buffer_slabp);
+	rpc_destroy_wait_queue(&delay_queue);
+}
+
+int
+rpc_init_mempool(void)
+{
+	/*
+	 * The following is not strictly a mempool initialisation,
+	 * but there is no harm in doing it here
+	 */
+	rpc_init_wait_queue(&delay_queue, "delayq");
+	if (!rpciod_start())
+		goto err_nomem;
+
+	rpc_task_slabp = kmem_cache_create("rpc_tasks",
+					     sizeof(struct rpc_task),
+					     0, SLAB_HWCACHE_ALIGN,
+					     NULL);
+	if (!rpc_task_slabp)
+		goto err_nomem;
+	rpc_buffer_slabp = kmem_cache_create("rpc_buffers",
+					     RPC_BUFFER_MAXSIZE,
+					     0, SLAB_HWCACHE_ALIGN,
+					     NULL);
+	if (!rpc_buffer_slabp)
+		goto err_nomem;
+	rpc_task_mempool = mempool_create_slab_pool(RPC_TASK_POOLSIZE,
+						    rpc_task_slabp);
+	if (!rpc_task_mempool)
+		goto err_nomem;
+	rpc_buffer_mempool = mempool_create_slab_pool(RPC_BUFFER_POOLSIZE,
+						      rpc_buffer_slabp);
+	if (!rpc_buffer_mempool)
+		goto err_nomem;
+	return 0;
+err_nomem:
+	rpc_destroy_mempool();
+	return -ENOMEM;
+}