linux/net/sunrpc/sched.c
Trond Myklebust f42f7c2830 SUNRPC: Fix priority queue fairness
Fix up the priority queue to not batch by owner, but by queue, so that
we allow '1 << priority' elements to be dequeued before switching to
the next priority queue.
The owner field is still used to wake up requests in round robin order
by owner to avoid single processes hogging the RPC layer by loading the
queues.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
2018-09-30 15:35:16 -04:00

1236 lines
31 KiB
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/spinlock.h>
#include <linux/mutex.h>
#include <linux/freezer.h>
#include <linux/sunrpc/clnt.h>
#include "sunrpc.h"
#if IS_ENABLED(CONFIG_SUNRPC_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(struct timer_list *t);
/*
* 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;
/*
* 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 %u ms\n",
task->tk_pid, jiffies_to_msecs(task->tk_timeout));
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);
}
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.
*
* 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)
{
WARN_ON_ONCE(RPC_IS_QUEUED(task));
if (RPC_IS_QUEUED(task))
return;
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++;
/* barrier matches the read in rpc_wake_up_task_queue_locked() */
smp_wmb();
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)
{
__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--;
dprintk("RPC: %5u removed from queue %p \"%s\"\n",
task->tk_pid, queue, rpc_qname(queue));
}
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;
timer_setup(&queue->timer_list.timer, __rpc_queue_timer_fn, 0);
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(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)
{
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)
{
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_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, q);
__rpc_add_wait_queue(q, task, queue_priority);
WARN_ON_ONCE(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 */
WARN_ON_ONCE(!RPC_IS_ACTIVATED(task));
if (!RPC_IS_ACTIVATED(task)) {
task->tk_status = -EIO;
rpc_put_task_async(task);
return;
}
/*
* 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 */
WARN_ON_ONCE(!RPC_IS_ACTIVATED(task));
if (!RPC_IS_ACTIVATED(task)) {
task->tk_status = -EIO;
rpc_put_task_async(task);
return;
}
/*
* 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);
}
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)
{
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, queue);
__rpc_remove_wait_queue(queue, task);
rpc_make_runnable(wq, task);
dprintk("RPC: __rpc_wake_up_task done\n");
}
/*
* 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;
}
static void
rpc_wake_up_task_on_wq_queue_locked(struct workqueue_struct *wq,
struct rpc_wait_queue *queue, struct rpc_task *task)
{
rpc_wake_up_task_on_wq_queue_action_locked(wq, queue, task, NULL, 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_locked(rpciod_workqueue, queue, task);
}
/*
* Wake up a task on a specific queue
*/
void rpc_wake_up_queued_task_on_wq(struct workqueue_struct *wq,
struct rpc_wait_queue *queue,
struct rpc_task *task)
{
if (!RPC_IS_QUEUED(task))
return;
spin_lock_bh(&queue->lock);
rpc_wake_up_task_on_wq_queue_locked(wq, queue, task);
spin_unlock_bh(&queue->lock);
}
/*
* 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_bh(&queue->lock);
rpc_wake_up_task_queue_locked(queue, task);
spin_unlock_bh(&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_bh(&queue->lock);
rpc_wake_up_task_queue_set_status_locked(queue, task, status);
spin_unlock_bh(&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 a batch of tasks from a single owner.
*/
q = &queue->tasks[queue->priority];
if (!list_empty(q) && --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;
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)
task = rpc_wake_up_task_on_wq_queue_action_locked(wq, queue,
task, func, data);
spin_unlock_bh(&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 - 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 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);
/**
* 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 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(struct timer_list *t)
{
struct rpc_wait_queue *queue = from_timer(queue, t, timer_list.timer);
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)
{
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)
{
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);
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;
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))
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);
}
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)
{
bool is_async = RPC_IS_ASYNC(task);
rpc_set_active(task);
rpc_make_runnable(rpciod_workqueue, task);
if (!is_async)
__rpc_execute(task);
}
static void rpc_async_schedule(struct work_struct *work)
{
__rpc_execute(container_of(work, struct rpc_task, u.tk_work));
}
/**
* 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.
*
* In order to avoid memory starvation triggering more writebacks of
* NFS requests, we avoid using GFP_KERNEL.
*/
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 = GFP_NOIO | __GFP_NOWARN;
if (RPC_IS_SWAPPER(task))
gfp = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN;
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 -ENOMEM;
buf->len = size;
dprintk("RPC: %5u allocated buffer of size %zu at %p\n",
task->tk_pid, size, buf);
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;
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;
task->tk_xprt = xprt_get(task_setup_data->rpc_xprt);
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();
flags = RPC_TASK_DYNAMIC;
}
rpc_init_task(task, setup_data);
task->tk_flags |= flags;
dprintk("RPC: allocated task %p\n", task);
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;
rpc_release_calldata(task->tk_ops, task->tk_calldata);
if (tk_flags & RPC_TASK_DYNAMIC) {
dprintk("RPC: %5u freeing task\n", task->tk_pid);
mempool_free(task, rpc_task_mempool);
}
}
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)
{
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);
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.
*/
dprintk("RPC: creating workqueue rpciod\n");
wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
if (!wq)
goto out_failed;
rpciod_workqueue = wq;
/* Note: highpri because network receive is latency sensitive */
wq = alloc_workqueue("xprtiod", WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_HIGHPRI, 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;
dprintk("RPC: destroying workqueue rpciod\n");
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;
}