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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // 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);
 
 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)
 {
     freezable_schedule_unsafe();
     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, wait_bit_action_f *action)
 {
     if (action == NULL)
         action = rpc_wait_bit_killable;
     return out_of_line_wait_on_bit(&task->tk_runstate, RPC_TASK_ACTIVE,
             action, TASK_KILLABLE);
 }
 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;
     task->tk_rebind_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;
 
     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_set_status(queue, task, -ERESTARTSYS);
 }
 
 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.
          * In particular, note that rpc_killall_tasks may
          * do this at any time, so beware when dereferencing.
          */
         do_action = task->tk_action;
         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;
         }
 
         /*
          * Signalled tasks should exit rather than sleep.
          */
         if (RPC_SIGNALLED(task)) {
             task->tk_rpc_status = -ERESTARTSYS;
             rpc_exit(task, -ERESTARTSYS);
         }
 
         /*
          * 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;
         }
         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);
         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.
              */
             trace_rpc_task_signalled(task, task->tk_action);
             set_bit(RPC_TASK_SIGNALLED, &task->tk_runstate);
             task->tk_rpc_status = -ERESTARTSYS;
             rpc_exit(task, -ERESTARTSYS);
         }
         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;
 }

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