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[linux-2.6/s3c2410-cpufreq.git] / net / sunrpc / sched.c

/*
 * 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/smp_lock.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>

#include <linux/sunrpc/clnt.h>

#ifdef RPC_DEBUG
#define RPCDBG_FACILITY         RPCDBG_SCHED
#define RPC_TASK_MAGIC_ID       0xf00baa
#endif

/*
 * 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_default_timer(struct rpc_task *task);
static void                     rpc_async_schedule(struct work_struct *);
static void                      rpc_release_task(struct rpc_task *task);

/*
 * 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 inline void
__rpc_disable_timer(struct rpc_task *task)
{
        dprintk("RPC: %5u disabling timer\n", task->tk_pid);
        task->tk_timeout_fn = NULL;
        task->tk_timeout = 0;
}

/*
 * Run a timeout function.
 * We use the callback in order to allow __rpc_wake_up_task()
 * and friends to disable the timer synchronously on SMP systems
 * without calling del_timer_sync(). The latter could cause a
 * deadlock if called while we're holding spinlocks...
 */
static void rpc_run_timer(struct rpc_task *task)
{
        void (*callback)(struct rpc_task *);

        callback = task->tk_timeout_fn;
        task->tk_timeout_fn = NULL;
        if (callback && RPC_IS_QUEUED(task)) {
                dprintk("RPC: %5u running timer\n", task->tk_pid);
                callback(task);
        }
        smp_mb__before_clear_bit();
        clear_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate);
        smp_mb__after_clear_bit();
}

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

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

        if (timer)
                task->tk_timeout_fn = timer;
        else
                task->tk_timeout_fn = __rpc_default_timer;
        set_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate);
        mod_timer(&task->tk_timer, jiffies + task->tk_timeout);
}

/*
 * Delete any timer for the current task. Because we use del_timer_sync(),
 * this function should never be called while holding queue->lock.
 */
static void
rpc_delete_timer(struct rpc_task *task)
{
        if (RPC_IS_QUEUED(task))
                return;
        if (test_and_clear_bit(RPC_TASK_HAS_TIMER, &task->tk_runstate)) {
                del_singleshot_timer_sync(&task->tk_timer);
                dprintk("RPC: %5u deleting timer\n", task->tk_pid);
        }
}

/*
 * Add new request to a priority queue.
 */
static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue, struct rpc_task *task)
{
        struct list_head *q;
        struct rpc_task *t;

        INIT_LIST_HEAD(&task->u.tk_wait.links);
        q = &queue->tasks[task->tk_priority];
        if (unlikely(task->tk_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)
{
        BUG_ON (RPC_IS_QUEUED(task));

        if (RPC_IS_PRIORITY(queue))
                __rpc_add_wait_queue_priority(queue, task);
        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->u.tk_wait.rpc_waitq = 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);
        }
        list_del(&task->u.tk_wait.list);
}

/*
 * Remove request from queue.
 * Note: must be called with spin lock held.
 */
static void __rpc_remove_wait_queue(struct rpc_task *task)
{
        struct rpc_wait_queue *queue;
        queue = task->u.tk_wait.rpc_waitq;

        if (RPC_IS_PRIORITY(queue))
                __rpc_remove_wait_queue_priority(task);
        else
                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);
#ifdef RPC_DEBUG
        queue->name = qname;
#endif
}

void rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname)
{
        __rpc_init_priority_wait_queue(queue, qname, RPC_NR_PRIORITY);
}

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);

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

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

        task->tk_magic = RPC_TASK_MAGIC_ID;
        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)
{
        struct rpc_clnt *clnt;
        if (test_and_set_bit(RPC_TASK_ACTIVE, &task->tk_runstate) != 0)
                return;
        rpc_task_set_debuginfo(task);
        /* Add to global list of all tasks */
        clnt = task->tk_client;
        if (clnt != NULL) {
                spin_lock(&clnt->cl_lock);
                list_add_tail(&task->tk_task, &clnt->cl_tasks);
                spin_unlock(&clnt->cl_lock);
        }
}

/*
 * Mark an RPC call as having completed by clearing the 'active' bit
 */
static void rpc_mark_complete_task(struct rpc_task *task)
{
        smp_mb__before_clear_bit();
        clear_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
        smp_mb__after_clear_bit();
        wake_up_bit(&task->tk_runstate, RPC_TASK_ACTIVE);
}

/*
 * Allow callers to wait for completion of an RPC call
 */
int __rpc_wait_for_completion_task(struct rpc_task *task, int (*action)(void *))
{
        if (action == NULL)
                action = rpc_wait_bit_killable;
        return 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, this must be called with
 * the spinlock held to protect the wait queue operation.
 */
static void rpc_make_runnable(struct rpc_task *task)
{
        BUG_ON(task->tk_timeout_fn);
        rpc_clear_queued(task);
        if (rpc_test_and_set_running(task))
                return;
        /* We might have raced */
        if (RPC_IS_QUEUED(task)) {
                rpc_clear_running(task);
                return;
        }
        if (RPC_IS_ASYNC(task)) {
                int status;

                INIT_WORK(&task->u.tk_work, rpc_async_schedule);
                status = queue_work(task->tk_workqueue, &task->u.tk_work);
                if (status < 0) {
                        printk(KERN_WARNING "RPC: failed to add task to queue: error: %d!\n", status);
                        task->tk_status = status;
                        return;
                }
        } 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(struct rpc_wait_queue *q, struct rpc_task *task,
                        rpc_action action, rpc_action timer)
{
        dprintk("RPC: %5u sleep_on(queue \"%s\" time %lu)\n",
                        task->tk_pid, rpc_qname(q), jiffies);

        if (!RPC_IS_ASYNC(task) && !RPC_IS_ACTIVATED(task)) {
                printk(KERN_ERR "RPC: Inactive synchronous task put to sleep!\n");
                return;
        }

        __rpc_add_wait_queue(q, task);

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

void rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
                                rpc_action action, rpc_action timer)
{
        /* Mark the task as being activated if so needed */
        rpc_set_active(task);

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

/**
 * __rpc_do_wake_up_task - wake up a single rpc_task
 * @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(struct rpc_task *task)
{
        dprintk("RPC: %5u __rpc_wake_up_task (now %lu)\n",
                        task->tk_pid, jiffies);

#ifdef RPC_DEBUG
        BUG_ON(task->tk_magic != RPC_TASK_MAGIC_ID);
#endif
        /* 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;
        }

        __rpc_disable_timer(task);
        __rpc_remove_wait_queue(task);

        rpc_make_runnable(task);

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

/*
 * Wake up the specified task
 */
static void __rpc_wake_up_task(struct rpc_task *task)
{
        if (rpc_start_wakeup(task)) {
                if (RPC_IS_QUEUED(task))
                        __rpc_do_wake_up_task(task);
                rpc_finish_wakeup(task);
        }
}

/*
 * Default timeout handler if none specified by user
 */
static void
__rpc_default_timer(struct rpc_task *task)
{
        dprintk("RPC: %5u timeout (default timer)\n", task->tk_pid);
        task->tk_status = -ETIMEDOUT;
        rpc_wake_up_task(task);
}

/*
 * Wake up the specified task
 */
void rpc_wake_up_task(struct rpc_task *task)
{
        rcu_read_lock_bh();
        if (rpc_start_wakeup(task)) {
                if (RPC_IS_QUEUED(task)) {
                        struct rpc_wait_queue *queue = task->u.tk_wait.rpc_waitq;

                        /* Note: we're already in a bh-safe context */
                        spin_lock(&queue->lock);
                        __rpc_do_wake_up_task(task);
                        spin_unlock(&queue->lock);
                }
                rpc_finish_wakeup(task);
        }
        rcu_read_unlock_bh();
}
EXPORT_SYMBOL_GPL(rpc_wake_up_task);

/*
 * Wake up the next task on a priority queue.
 */
static struct rpc_task * __rpc_wake_up_next_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:
        __rpc_wake_up_task(task);
        return task;
}

/*
 * Wake up the next task on the wait queue.
 */
struct rpc_task * rpc_wake_up_next(struct rpc_wait_queue *queue)
{
        struct rpc_task *task = NULL;

        dprintk("RPC:       wake_up_next(%p \"%s\")\n",
                        queue, rpc_qname(queue));
        rcu_read_lock_bh();
        spin_lock(&queue->lock);
        if (RPC_IS_PRIORITY(queue))
                task = __rpc_wake_up_next_priority(queue);
        else {
                task_for_first(task, &queue->tasks[0])
                        __rpc_wake_up_task(task);
        }
        spin_unlock(&queue->lock);
        rcu_read_unlock_bh();

        return task;
}
EXPORT_SYMBOL_GPL(rpc_wake_up_next);

/**
 * 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)
{
        struct rpc_task *task, *next;
        struct list_head *head;

        rcu_read_lock_bh();
        spin_lock(&queue->lock);
        head = &queue->tasks[queue->maxpriority];
        for (;;) {
                list_for_each_entry_safe(task, next, head, u.tk_wait.list)
                        __rpc_wake_up_task(task);
                if (head == &queue->tasks[0])
                        break;
                head--;
        }
        spin_unlock(&queue->lock);
        rcu_read_unlock_bh();
}
EXPORT_SYMBOL_GPL(rpc_wake_up);

/**
 * 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)
{
        struct rpc_task *task, *next;
        struct list_head *head;

        rcu_read_lock_bh();
        spin_lock(&queue->lock);
        head = &queue->tasks[queue->maxpriority];
        for (;;) {
                list_for_each_entry_safe(task, next, head, u.tk_wait.list) {
                        task->tk_status = status;
                        __rpc_wake_up_task(task);
                }
                if (head == &queue->tasks[0])
                        break;
                head--;
        }
        spin_unlock(&queue->lock);
        rcu_read_unlock_bh();
}
EXPORT_SYMBOL_GPL(rpc_wake_up_status);

static void __rpc_atrun(struct rpc_task *task)
{
        rpc_wake_up_task(task);
}

/*
 * 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, NULL, __rpc_atrun);
}
EXPORT_SYMBOL_GPL(rpc_delay);

/*
 * Helper to call task->tk_ops->rpc_call_prepare
 */
static void rpc_prepare_task(struct rpc_task *task)
{
        lock_kernel();
        task->tk_ops->rpc_call_prepare(task, task->tk_calldata);
        unlock_kernel();
}

/*
 * 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) {
                lock_kernel();
                task->tk_ops->rpc_call_done(task, task->tk_calldata);
                unlock_kernel();
                if (task->tk_action != NULL) {
                        WARN_ON(RPC_ASSASSINATED(task));
                        /* Always release the RPC slot and buffer memory */
                        xprt_release(task);
                }
        }
}
EXPORT_SYMBOL_GPL(rpc_exit_task);

void rpc_release_calldata(const struct rpc_call_ops *ops, void *calldata)
{
        if (ops->rpc_release != NULL) {
                lock_kernel();
                ops->rpc_release(calldata);
                unlock_kernel();
        }
}

/*
 * This is the RPC `scheduler' (or rather, the finite state machine).
 */
static void __rpc_execute(struct rpc_task *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 (;;) {
                /*
                 * Garbage collection of pending timers...
                 */
                rpc_delete_timer(task);

                /*
                 * Execute any pending callback.
                 */
                if (RPC_DO_CALLBACK(task)) {
                        /* Define a callback save pointer */
                        void (*save_callback)(struct rpc_task *);

                        /*
                         * If a callback exists, save it, reset it,
                         * call it.
                         * The save is needed to stop from resetting
                         * another callback set within the callback handler
                         * - Dave
                         */
                        save_callback=task->tk_callback;
                        task->tk_callback=NULL;
                        save_callback(task);
                }

                /*
                 * Perform the next FSM step.
                 * tk_action may be NULL when the task has been killed
                 * by someone else.
                 */
                if (!RPC_IS_QUEUED(task)) {
                        if (task->tk_action == NULL)
                                break;
                        task->tk_action(task);
                }

                /*
                 * Lockless check for whether task is sleeping or not.
                 */
                if (!RPC_IS_QUEUED(task))
                        continue;
                rpc_clear_running(task);
                if (RPC_IS_ASYNC(task)) {
                        /* Careful! we may have raced... */
                        if (RPC_IS_QUEUED(task))
                                return;
                        if (rpc_test_and_set_running(task))
                                return;
                        continue;
                }

                /* 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_wake_up_task(task);
                }
                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_set_running(task);
        __rpc_execute(task);
}

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

struct rpc_buffer {
        size_t  len;
        char    data[];
};

/**
 * rpc_malloc - allocate an RPC buffer
 * @task: RPC task that will use this buffer
 * @size: requested byte size
 *
 * To prevent rpciod from hanging, this allocator never sleeps,
 * returning NULL 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.
 *
 * In order to avoid memory starvation triggering more writebacks of
 * NFS requests, we avoid using GFP_KERNEL.
 */
void *rpc_malloc(struct rpc_task *task, size_t size)
{
        struct rpc_buffer *buf;
        gfp_t gfp = RPC_IS_SWAPPER(task) ? GFP_ATOMIC : GFP_NOWAIT;

        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);

/**
 * rpc_free - free buffer allocated via rpc_malloc
 * @buffer: buffer to free
 *
 */
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));
        setup_timer(&task->tk_timer, (void (*)(unsigned long))rpc_run_timer,
                        (unsigned long)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);

        /* Initialize retry counters */
        task->tk_garb_retry = 2;
        task->tk_cred_retry = 2;

        task->tk_priority = task_setup_data->priority - RPC_PRIORITY_LOW;
        task->tk_owner = current->tgid;

        /* Initialize workqueue for async tasks */
        task->tk_workqueue = rpciod_workqueue;

        task->tk_client = task_setup_data->rpc_client;
        if (task->tk_client != NULL) {
                kref_get(&task->tk_client->cl_kref);
                if (task->tk_client->cl_softrtry)
                        task->tk_flags |= RPC_TASK_SOFT;
        }

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

        if (task_setup_data->rpc_message != NULL) {
                memcpy(&task->tk_msg, task_setup_data->rpc_message, sizeof(task->tk_msg));
                /* Bind the user cred */
                if (task->tk_msg.rpc_cred != NULL)
                        rpcauth_holdcred(task);
                else
                        rpcauth_bindcred(task);
                if (task->tk_action == NULL)
                        rpc_call_start(task);
        }

        /* starting timestamp */
        task->tk_start = jiffies;

        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_NOFS);
}

static void rpc_free_task(struct rcu_head *rcu)
{
        struct rpc_task *task = container_of(rcu, struct rpc_task, u.tk_rcu);
        dprintk("RPC: %5u freeing task\n", task->tk_pid);
        mempool_free(task, rpc_task_mempool);
}

/*
 * 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)
                        goto out;
                flags = RPC_TASK_DYNAMIC;
        }

        rpc_init_task(task, setup_data);

        task->tk_flags |= flags;
        dprintk("RPC:       allocated task %p\n", task);
out:
        return task;
}


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

        if (!atomic_dec_and_test(&task->tk_count))
                return;
        /* Release resources */
        if (task->tk_rqstp)
                xprt_release(task);
        if (task->tk_msg.rpc_cred)
                rpcauth_unbindcred(task);
        if (task->tk_client) {
                rpc_release_client(task->tk_client);
                task->tk_client = NULL;
        }
        if (task->tk_flags & RPC_TASK_DYNAMIC)
                call_rcu_bh(&task->u.tk_rcu, rpc_free_task);
        rpc_release_calldata(tk_ops, calldata);
}
EXPORT_SYMBOL_GPL(rpc_put_task);

static void rpc_release_task(struct rpc_task *task)
{
#ifdef RPC_DEBUG
        BUG_ON(task->tk_magic != RPC_TASK_MAGIC_ID);
#endif
        dprintk("RPC: %5u release task\n", task->tk_pid);

        if (!list_empty(&task->tk_task)) {
                struct rpc_clnt *clnt = task->tk_client;
                /* Remove from client task list */
                spin_lock(&clnt->cl_lock);
                list_del(&task->tk_task);
                spin_unlock(&clnt->cl_lock);
        }
        BUG_ON (RPC_IS_QUEUED(task));

        /* Synchronously delete any running timer */
        rpc_delete_timer(task);

#ifdef RPC_DEBUG
        task->tk_magic = 0;
#endif
        /* Wake up anyone who is waiting for task completion */
        rpc_mark_complete_task(task);

        rpc_put_task(task);
}

/*
 * Kill all tasks for the given client.
 * XXX: kill their descendants as well?
 */
void rpc_killall_tasks(struct rpc_clnt *clnt)
{
        struct rpc_task *rovr;


        if (list_empty(&clnt->cl_tasks))
                return;
        dprintk("RPC:       killing all tasks for client %p\n", clnt);
        /*
         * Spin lock all_tasks to prevent changes...
         */
        spin_lock(&clnt->cl_lock);
        list_for_each_entry(rovr, &clnt->cl_tasks, tk_task) {
                if (! RPC_IS_ACTIVATED(rovr))
                        continue;
                if (!(rovr->tk_flags & RPC_TASK_KILLED)) {
                        rovr->tk_flags |= RPC_TASK_KILLED;
                        rpc_exit(rovr, -EIO);
                        rpc_wake_up_task(rovr);
                }
        }
        spin_unlock(&clnt->cl_lock);
}
EXPORT_SYMBOL_GPL(rpc_killall_tasks);

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 = create_workqueue("rpciod");
        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);
}

int
rpc_init_mempool(void)
{
        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;
        if (!rpciod_start())
                goto err_nomem;
        /*
         * The following is not strictly a mempool initialisation,
         * but there is no harm in doing it here
         */
        rpc_init_wait_queue(&delay_queue, "delayq");
        return 0;
err_nomem:
        rpc_destroy_mempool();
        return -ENOMEM;
}