sched.c

Go to the documentation of this file.

/*
 * linux/net/sunrpc/sched.c
 *
 * Scheduling for synchronous and asynchronous RPC requests.
 *
 * Copyright (C) 1996 Olaf Kirch, <[email protected]>
 *
 * TCP NFS related read + write fixes
 * (C) 1999 Dave Airlie, University of Limerick, Ireland <[email protected]>
 */

#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/sunrpc/clnt.h>

#include "sunrpc.h"

#ifdef RPC_DEBUG
#define RPCDBG_FACILITY     RPCDBG_SCHED
#endif

#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(unsigned long ptr);

/*
 * 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;

/*
 * 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 (task->tk_timeout == 0)
        return;
    dprintk("RPC: %5u disabling timer\n", task->tk_pid);
    task->tk_timeout = 0;
    list_del(&task->u.tk_wait.timer_list);
    if (list_empty(&queue->timer_list.list))
        del_timer(&queue->timer_list.timer);
}

static void
rpc_set_queue_timer(struct rpc_wait_queue *queue, unsigned long expires)
{
    queue->timer_list.expires = expires;
    mod_timer(&queue->timer_list.timer, expires);
}

/*
 * Set up a timer for the current task.
 */
static void
__rpc_add_timer(struct rpc_wait_queue *queue, struct rpc_task *task)
{
    if (!task->tk_timeout)
        return;

    dprintk("RPC: %5u setting alarm for %lu ms\n",
            task->tk_pid, task->tk_timeout * 1000 / HZ);

    task->u.tk_wait.expires = jiffies + task->tk_timeout;
    if (list_empty(&queue->timer_list.list) || time_before(task->u.tk_wait.expires, queue->timer_list.expires))
        rpc_set_queue_timer(queue, task->u.tk_wait.expires);
    list_add(&task->u.tk_wait.timer_list, &queue->timer_list.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)
{
    struct list_head *q;
    struct rpc_task *t;

    INIT_LIST_HEAD(&task->u.tk_wait.links);
    q = &queue->tasks[queue_priority];
    if (unlikely(queue_priority > queue->maxpriority))
        q = &queue->tasks[queue->maxpriority];
    list_for_each_entry(t, q, u.tk_wait.list) {
        if (t->tk_owner == task->tk_owner) {
            list_add_tail(&task->u.tk_wait.list, &t->u.tk_wait.links);
            return;
        }
    }
    list_add_tail(&task->u.tk_wait.list, q);
}

/*
 * Add new request to wait queue.
 *
 * Swapper tasks always get inserted at the head of the queue.
 * This should avoid many nasty memory deadlocks and hopefully
 * improve overall performance.
 * Everyone else gets appended to the queue to ensure proper FIFO behavior.
 */
static void __rpc_add_wait_queue(struct rpc_wait_queue *queue,
        struct rpc_task *task,
        unsigned char queue_priority)
{
    BUG_ON (RPC_IS_QUEUED(task));

    if (RPC_IS_PRIORITY(queue))
        __rpc_add_wait_queue_priority(queue, task, queue_priority);
    else if (RPC_IS_SWAPPER(task))
        list_add(&task->u.tk_wait.list, &queue->tasks[0]);
    else
        list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);
    task->tk_waitqueue = queue;
    queue->qlen++;
    rpc_set_queued(task);

    dprintk("RPC: %5u added to queue %p \"%s\"\n",
            task->tk_pid, queue, rpc_qname(queue));
}

/*
 * Remove request from a priority queue.
 */
static void __rpc_remove_wait_queue_priority(struct rpc_task *task)
{
    struct rpc_task *t;

    if (!list_empty(&task->u.tk_wait.links)) {
        t = list_entry(task->u.tk_wait.links.next, struct rpc_task, u.tk_wait.list);
        list_move(&t->u.tk_wait.list, &task->u.tk_wait.list);
        list_splice_init(&task->u.tk_wait.links, &t->u.tk_wait.links);
    }
}

/*
 * 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);
    list_del(&task->u.tk_wait.list);
    queue->qlen--;
    dprintk("RPC: %5u removed from queue %p \"%s\"\n",
            task->tk_pid, queue, rpc_qname(queue));
}

static inline void rpc_set_waitqueue_priority(struct rpc_wait_queue *queue, int priority)
{
    queue->priority = priority;
    queue->count = 1 << (priority * 2);
}

static inline void rpc_set_waitqueue_owner(struct rpc_wait_queue *queue, pid_t pid)
{
    queue->owner = pid;
    queue->nr = RPC_BATCH_COUNT;
}

static inline void rpc_reset_waitqueue_priority(struct rpc_wait_queue *queue)
{
    rpc_set_waitqueue_priority(queue, queue->maxpriority);
    rpc_set_waitqueue_owner(queue, 0);
}

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;
    setup_timer(&queue->timer_list.timer, __rpc_queue_timer_fn, (unsigned long)queue);
    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)
{
    del_timer_sync(&queue->timer_list.timer);
}
EXPORT_SYMBOL_GPL(rpc_destroy_wait_queue);

static int rpc_wait_bit_killable(void *word)
{
    if (fatal_signal_pending(current))
        return -ERESTARTSYS;
    freezable_schedule();
    return 0;
}

#ifdef RPC_DEBUG
static void rpc_task_set_debuginfo(struct rpc_task *task)
{
    static atomic_t rpc_pid;

    task->tk_pid = atomic_inc_return(&rpc_pid);
}
#else
static inline void rpc_task_set_debuginfo(struct rpc_task *task)
{
}
#endif

static void rpc_set_active(struct rpc_task *task)
{
    trace_rpc_task_begin(task->tk_client, task, NULL);

    rpc_task_set_debuginfo(task);
    set_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
}

/*
 * 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->tk_client, 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, int (*action)(void *))
{
    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.
 */
static void rpc_make_runnable(struct rpc_task *task)
{
    rpc_clear_queued(task);
    if (rpc_test_and_set_running(task))
        return;
    if (RPC_IS_ASYNC(task)) {
        INIT_WORK(&task->u.tk_work, rpc_async_schedule);
        queue_work(rpciod_workqueue, &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_sleep_on_priority(struct rpc_wait_queue *q,
        struct rpc_task *task,
        rpc_action action,
        unsigned char queue_priority)
{
    dprintk("RPC: %5u sleep_on(queue \"%s\" time %lu)\n",
            task->tk_pid, rpc_qname(q), jiffies);

    trace_rpc_task_sleep(task->tk_client, task, q);

    __rpc_add_wait_queue(q, task, queue_priority);

    BUG_ON(task->tk_callback != NULL);
    task->tk_callback = action;
    __rpc_add_timer(q, task);
}

void rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
                rpc_action action)
{
    /* We shouldn't ever put an inactive task to sleep */
    BUG_ON(!RPC_IS_ACTIVATED(task));

    /*
     * Protect the queue operations.
     */
    spin_lock_bh(&q->lock);
    __rpc_sleep_on_priority(q, task, action, task->tk_priority);
    spin_unlock_bh(&q->lock);
}
EXPORT_SYMBOL_GPL(rpc_sleep_on);

void rpc_sleep_on_priority(struct rpc_wait_queue *q, struct rpc_task *task,
        rpc_action action, int priority)
{
    /* We shouldn't ever put an inactive task to sleep */
    BUG_ON(!RPC_IS_ACTIVATED(task));

    /*
     * Protect the queue operations.
     */
    spin_lock_bh(&q->lock);
    __rpc_sleep_on_priority(q, task, action, priority - RPC_PRIORITY_LOW);
    spin_unlock_bh(&q->lock);
}

static void __rpc_do_wake_up_task(struct rpc_wait_queue *queue, struct rpc_task *task)
{
    dprintk("RPC: %5u __rpc_wake_up_task (now %lu)\n",
            task->tk_pid, jiffies);

    /* 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->tk_client, task, queue);

    __rpc_remove_wait_queue(queue, task);

    rpc_make_runnable(task);

    dprintk("RPC:       __rpc_wake_up_task done\n");
}

/*
 * 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)
{
    if (RPC_IS_QUEUED(task) && task->tk_waitqueue == queue)
        __rpc_do_wake_up_task(queue, task);
}

/*
 * Tests whether rpc queue is empty
 */
int rpc_queue_empty(struct rpc_wait_queue *queue)
{
    int res;

    spin_lock_bh(&queue->lock);
    res = queue->qlen;
    spin_unlock_bh(&queue->lock);
    return res == 0;
}
EXPORT_SYMBOL_GPL(rpc_queue_empty);

/*
 * Wake up a task on a specific queue
 */
void rpc_wake_up_queued_task(struct rpc_wait_queue *queue, struct rpc_task *task)
{
    spin_lock_bh(&queue->lock);
    rpc_wake_up_task_queue_locked(queue, task);
    spin_unlock_bh(&queue->lock);
}
EXPORT_SYMBOL_GPL(rpc_wake_up_queued_task);

/*
 * 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 a batch of tasks from a single owner.
     */
    q = &queue->tasks[queue->priority];
    if (!list_empty(q)) {
        task = list_entry(q->next, struct rpc_task, u.tk_wait.list);
        if (queue->owner == task->tk_owner) {
            if (--queue->nr)
                goto out;
            list_move_tail(&task->u.tk_wait.list, q);
        }
        /*
         * Check if we need to switch queues.
         */
        if (--queue->count)
            goto new_owner;
    }

    /*
     * 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_entry(q->next, 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]));
new_owner:
    rpc_set_waitqueue_owner(queue, task->tk_owner);
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(struct rpc_wait_queue *queue,
        bool (*func)(struct rpc_task *, void *), void *data)
{
    struct rpc_task *task = NULL;

    dprintk("RPC:       wake_up_first(%p \"%s\")\n",
            queue, rpc_qname(queue));
    spin_lock_bh(&queue->lock);
    task = __rpc_find_next_queued(queue);
    if (task != NULL) {
        if (func(task, data))
            rpc_wake_up_task_queue_locked(queue, task);
        else
            task = NULL;
    }
    spin_unlock_bh(&queue->lock);

    return task;
}
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);

void rpc_wake_up(struct rpc_wait_queue *queue)
{
    struct list_head *head;

    spin_lock_bh(&queue->lock);
    head = &queue->tasks[queue->maxpriority];
    for (;;) {
        while (!list_empty(head)) {
            struct rpc_task *task;
            task = list_first_entry(head,
                    struct rpc_task,
                    u.tk_wait.list);
            rpc_wake_up_task_queue_locked(queue, task);
        }
        if (head == &queue->tasks[0])
            break;
        head--;
    }
    spin_unlock_bh(&queue->lock);
}
EXPORT_SYMBOL_GPL(rpc_wake_up);

void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
{
    struct list_head *head;

    spin_lock_bh(&queue->lock);
    head = &queue->tasks[queue->maxpriority];
    for (;;) {
        while (!list_empty(head)) {
            struct rpc_task *task;
            task = list_first_entry(head,
                    struct rpc_task,
                    u.tk_wait.list);
            task->tk_status = status;
            rpc_wake_up_task_queue_locked(queue, task);
        }
        if (head == &queue->tasks[0])
            break;
        head--;
    }
    spin_unlock_bh(&queue->lock);
}
EXPORT_SYMBOL_GPL(rpc_wake_up_status);

static void __rpc_queue_timer_fn(unsigned long ptr)
{
    struct rpc_wait_queue *queue = (struct rpc_wait_queue *)ptr;
    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->u.tk_wait.expires;
        if (time_after_eq(now, timeo)) {
            dprintk("RPC: %5u timeout\n", task->tk_pid);
            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)
{
    task->tk_status = 0;
}

/*
 * Run a task at a later time
 */
void rpc_delay(struct rpc_task *task, unsigned long delay)
{
    task->tk_timeout = delay;
    rpc_sleep_on(&delay_queue, task, __rpc_atrun);
}
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_KILLED|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)
{
    task->tk_action = NULL;
    if (task->tk_ops->rpc_call_done != NULL) {
        task->tk_ops->rpc_call_done(task, task->tk_calldata);
        if (task->tk_action != NULL) {
            WARN_ON(RPC_ASSASSINATED(task));
            /* Always release the RPC slot and buffer memory */
            xprt_release(task);
            rpc_reset_task_statistics(task);
        }
    }
}

void rpc_exit(struct rpc_task *task, int status)
{
    task->tk_status = status;
    task->tk_action = rpc_exit_task;
    if (RPC_IS_QUEUED(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);
}

/*
 * 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;

    dprintk("RPC: %5u __rpc_execute flags=0x%x\n",
            task->tk_pid, task->tk_flags);

    BUG_ON(RPC_IS_QUEUED(task));

    for (;;) {
        void (*do_action)(struct rpc_task *);

        /*
         * Execute any pending callback first.
         */
        do_action = task->tk_callback;
        task->tk_callback = NULL;
        if (do_action == NULL) {
            /*
             * Perform the next FSM step.
             * 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 (do_action == NULL)
                break;
        }
        trace_rpc_task_run_action(task->tk_client, task, task->tk_action);
        do_action(task);

        /*
         * Lockless check for whether task is sleeping or not.
         */
        if (!RPC_IS_QUEUED(task))
            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_bh(&queue->lock);
        if (!RPC_IS_QUEUED(task)) {
            spin_unlock_bh(&queue->lock);
            continue;
        }
        rpc_clear_running(task);
        spin_unlock_bh(&queue->lock);
        if (task_is_async)
            return;

        /* sync task: sleep here */
        dprintk("RPC: %5u sync task going to sleep\n", task->tk_pid);
        status = out_of_line_wait_on_bit(&task->tk_runstate,
                RPC_TASK_QUEUED, rpc_wait_bit_killable,
                TASK_KILLABLE);
        if (status == -ERESTARTSYS) {
            /*
             * 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.
             */
            dprintk("RPC: %5u got signal\n", task->tk_pid);
            task->tk_flags |= RPC_TASK_KILLED;
            rpc_exit(task, -ERESTARTSYS);
        }
        rpc_set_running(task);
        dprintk("RPC: %5u sync task resuming\n", task->tk_pid);
    }

    dprintk("RPC: %5u return %d, status %d\n", task->tk_pid, status,
            task->tk_status);
    /* Release all resources associated with the task */
    rpc_release_task(task);
}

/*
 * 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)
{
    rpc_set_active(task);
    rpc_make_runnable(task);
    if (!RPC_IS_ASYNC(task))
        __rpc_execute(task);
}

static void rpc_async_schedule(struct work_struct *work)
{
    current->flags |= PF_FSTRANS;
    __rpc_execute(container_of(work, struct rpc_task, u.tk_work));
    current->flags &= ~PF_FSTRANS;
}

void *rpc_malloc(struct rpc_task *task, size_t size)
{
    struct rpc_buffer *buf;
    gfp_t gfp = GFP_NOWAIT;

    if (RPC_IS_SWAPPER(task))
        gfp |= __GFP_MEMALLOC;

    size += sizeof(struct rpc_buffer);
    if (size <= RPC_BUFFER_MAXSIZE)
        buf = mempool_alloc(rpc_buffer_mempool, gfp);
    else
        buf = kmalloc(size, gfp);

    if (!buf)
        return NULL;

    buf->len = size;
    dprintk("RPC: %5u allocated buffer of size %zu at %p\n",
            task->tk_pid, size, buf);
    return &buf->data;
}
EXPORT_SYMBOL_GPL(rpc_malloc);

void rpc_free(void *buffer)
{
    size_t size;
    struct rpc_buffer *buf;

    if (!buffer)
        return;

    buf = container_of(buffer, struct rpc_buffer, data);
    size = buf->len;

    dprintk("RPC:       freeing buffer of size %zu at %p\n",
            size, buf);

    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;

    if (task->tk_ops->rpc_call_prepare != NULL)
        task->tk_action = rpc_prepare_task;

    rpc_init_task_statistics(task);

    dprintk("RPC:       new task initialized, procpid %u\n",
                task_pid_nr(current));
}

static struct rpc_task *
rpc_alloc_task(void)
{
    return (struct rpc_task *)mempool_alloc(rpc_task_mempool, GFP_NOIO);
}

/*
 * 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;
    dprintk("RPC:       allocated task %p\n", task);
    return task;
}

static void rpc_free_task(struct rpc_task *task)
{
    const struct rpc_call_ops *tk_ops = task->tk_ops;
    void *calldata = task->tk_calldata;

    if (task->tk_flags & RPC_TASK_DYNAMIC) {
        dprintk("RPC: %5u freeing task\n", task->tk_pid);
        mempool_free(task, rpc_task_mempool);
    }
    rpc_release_calldata(tk_ops, calldata);
}

static void rpc_async_release(struct work_struct *work)
{
    rpc_free_task(container_of(work, struct rpc_task, u.tk_work));
}

static void rpc_release_resources_task(struct rpc_task *task)
{
    if (task->tk_rqstp)
        xprt_release(task);
    if (task->tk_msg.rpc_cred) {
        put_rpccred(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)
{
    dprintk("RPC: %5u release task\n", task->tk_pid);

    BUG_ON (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.
     */
    dprintk("RPC:       creating workqueue rpciod\n");
    wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM, 1);
    rpciod_workqueue = wq;
    return rpciod_workqueue != NULL;
}

static void rpciod_stop(void)
{
    struct workqueue_struct *wq = NULL;

    if (rpciod_workqueue == NULL)
        return;
    dprintk("RPC:       destroying workqueue rpciod\n");

    wq = rpciod_workqueue;
    rpciod_workqueue = NULL;
    destroy_workqueue(wq);
}

void
rpc_destroy_mempool(void)
{
    rpciod_stop();
    if (rpc_buffer_mempool)
        mempool_destroy(rpc_buffer_mempool);
    if (rpc_task_mempool)
        mempool_destroy(rpc_task_mempool);
    if (rpc_task_slabp)
        kmem_cache_destroy(rpc_task_slabp);
    if (rpc_buffer_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;
}