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TOMOYO Linux Cross Reference
Linux/net/sunrpc/sched.c

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  1 /*
  2  * linux/net/sunrpc/sched.c
  3  *
  4  * Scheduling for synchronous and asynchronous RPC requests.
  5  *
  6  * Copyright (C) 1996 Olaf Kirch, <okir@monad.swb.de>
  7  *
  8  * TCP NFS related read + write fixes
  9  * (C) 1999 Dave Airlie, University of Limerick, Ireland <airlied@linux.ie>
 10  */
 11 
 12 #include <linux/module.h>
 13 
 14 #include <linux/sched.h>
 15 #include <linux/interrupt.h>
 16 #include <linux/slab.h>
 17 #include <linux/mempool.h>
 18 #include <linux/smp.h>
 19 #include <linux/spinlock.h>
 20 #include <linux/mutex.h>
 21 #include <linux/freezer.h>
 22 
 23 #include <linux/sunrpc/clnt.h>
 24 
 25 #include "sunrpc.h"
 26 
 27 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 28 #define RPCDBG_FACILITY         RPCDBG_SCHED
 29 #endif
 30 
 31 #define CREATE_TRACE_POINTS
 32 #include <trace/events/sunrpc.h>
 33 
 34 /*
 35  * RPC slabs and memory pools
 36  */
 37 #define RPC_BUFFER_MAXSIZE      (2048)
 38 #define RPC_BUFFER_POOLSIZE     (8)
 39 #define RPC_TASK_POOLSIZE       (8)
 40 static struct kmem_cache        *rpc_task_slabp __read_mostly;
 41 static struct kmem_cache        *rpc_buffer_slabp __read_mostly;
 42 static mempool_t        *rpc_task_mempool __read_mostly;
 43 static mempool_t        *rpc_buffer_mempool __read_mostly;
 44 
 45 static void                     rpc_async_schedule(struct work_struct *);
 46 static void                      rpc_release_task(struct rpc_task *task);
 47 static void __rpc_queue_timer_fn(struct timer_list *t);
 48 
 49 /*
 50  * RPC tasks sit here while waiting for conditions to improve.
 51  */
 52 static struct rpc_wait_queue delay_queue;
 53 
 54 /*
 55  * rpciod-related stuff
 56  */
 57 struct workqueue_struct *rpciod_workqueue __read_mostly;
 58 struct workqueue_struct *xprtiod_workqueue __read_mostly;
 59 
 60 /*
 61  * Disable the timer for a given RPC task. Should be called with
 62  * queue->lock and bh_disabled in order to avoid races within
 63  * rpc_run_timer().
 64  */
 65 static void
 66 __rpc_disable_timer(struct rpc_wait_queue *queue, struct rpc_task *task)
 67 {
 68         if (task->tk_timeout == 0)
 69                 return;
 70         dprintk("RPC: %5u disabling timer\n", task->tk_pid);
 71         task->tk_timeout = 0;
 72         list_del(&task->u.tk_wait.timer_list);
 73         if (list_empty(&queue->timer_list.list))
 74                 del_timer(&queue->timer_list.timer);
 75 }
 76 
 77 static void
 78 rpc_set_queue_timer(struct rpc_wait_queue *queue, unsigned long expires)
 79 {
 80         queue->timer_list.expires = expires;
 81         mod_timer(&queue->timer_list.timer, expires);
 82 }
 83 
 84 /*
 85  * Set up a timer for the current task.
 86  */
 87 static void
 88 __rpc_add_timer(struct rpc_wait_queue *queue, struct rpc_task *task)
 89 {
 90         if (!task->tk_timeout)
 91                 return;
 92 
 93         dprintk("RPC: %5u setting alarm for %u ms\n",
 94                 task->tk_pid, jiffies_to_msecs(task->tk_timeout));
 95 
 96         task->u.tk_wait.expires = jiffies + task->tk_timeout;
 97         if (list_empty(&queue->timer_list.list) || time_before(task->u.tk_wait.expires, queue->timer_list.expires))
 98                 rpc_set_queue_timer(queue, task->u.tk_wait.expires);
 99         list_add(&task->u.tk_wait.timer_list, &queue->timer_list.list);
100 }
101 
102 static void rpc_set_waitqueue_priority(struct rpc_wait_queue *queue, int priority)
103 {
104         if (queue->priority != priority) {
105                 queue->priority = priority;
106                 queue->nr = 1U << priority;
107         }
108 }
109 
110 static void rpc_reset_waitqueue_priority(struct rpc_wait_queue *queue)
111 {
112         rpc_set_waitqueue_priority(queue, queue->maxpriority);
113 }
114 
115 /*
116  * Add a request to a queue list
117  */
118 static void
119 __rpc_list_enqueue_task(struct list_head *q, struct rpc_task *task)
120 {
121         struct rpc_task *t;
122 
123         list_for_each_entry(t, q, u.tk_wait.list) {
124                 if (t->tk_owner == task->tk_owner) {
125                         list_add_tail(&task->u.tk_wait.links,
126                                         &t->u.tk_wait.links);
127                         /* Cache the queue head in task->u.tk_wait.list */
128                         task->u.tk_wait.list.next = q;
129                         task->u.tk_wait.list.prev = NULL;
130                         return;
131                 }
132         }
133         INIT_LIST_HEAD(&task->u.tk_wait.links);
134         list_add_tail(&task->u.tk_wait.list, q);
135 }
136 
137 /*
138  * Remove request from a queue list
139  */
140 static void
141 __rpc_list_dequeue_task(struct rpc_task *task)
142 {
143         struct list_head *q;
144         struct rpc_task *t;
145 
146         if (task->u.tk_wait.list.prev == NULL) {
147                 list_del(&task->u.tk_wait.links);
148                 return;
149         }
150         if (!list_empty(&task->u.tk_wait.links)) {
151                 t = list_first_entry(&task->u.tk_wait.links,
152                                 struct rpc_task,
153                                 u.tk_wait.links);
154                 /* Assume __rpc_list_enqueue_task() cached the queue head */
155                 q = t->u.tk_wait.list.next;
156                 list_add_tail(&t->u.tk_wait.list, q);
157                 list_del(&task->u.tk_wait.links);
158         }
159         list_del(&task->u.tk_wait.list);
160 }
161 
162 /*
163  * Add new request to a priority queue.
164  */
165 static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue,
166                 struct rpc_task *task,
167                 unsigned char queue_priority)
168 {
169         if (unlikely(queue_priority > queue->maxpriority))
170                 queue_priority = queue->maxpriority;
171         __rpc_list_enqueue_task(&queue->tasks[queue_priority], task);
172 }
173 
174 /*
175  * Add new request to wait queue.
176  *
177  * Swapper tasks always get inserted at the head of the queue.
178  * This should avoid many nasty memory deadlocks and hopefully
179  * improve overall performance.
180  * Everyone else gets appended to the queue to ensure proper FIFO behavior.
181  */
182 static void __rpc_add_wait_queue(struct rpc_wait_queue *queue,
183                 struct rpc_task *task,
184                 unsigned char queue_priority)
185 {
186         WARN_ON_ONCE(RPC_IS_QUEUED(task));
187         if (RPC_IS_QUEUED(task))
188                 return;
189 
190         if (RPC_IS_PRIORITY(queue))
191                 __rpc_add_wait_queue_priority(queue, task, queue_priority);
192         else if (RPC_IS_SWAPPER(task))
193                 list_add(&task->u.tk_wait.list, &queue->tasks[0]);
194         else
195                 list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);
196         task->tk_waitqueue = queue;
197         queue->qlen++;
198         /* barrier matches the read in rpc_wake_up_task_queue_locked() */
199         smp_wmb();
200         rpc_set_queued(task);
201 
202         dprintk("RPC: %5u added to queue %p \"%s\"\n",
203                         task->tk_pid, queue, rpc_qname(queue));
204 }
205 
206 /*
207  * Remove request from a priority queue.
208  */
209 static void __rpc_remove_wait_queue_priority(struct rpc_task *task)
210 {
211         __rpc_list_dequeue_task(task);
212 }
213 
214 /*
215  * Remove request from queue.
216  * Note: must be called with spin lock held.
217  */
218 static void __rpc_remove_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *task)
219 {
220         __rpc_disable_timer(queue, task);
221         if (RPC_IS_PRIORITY(queue))
222                 __rpc_remove_wait_queue_priority(task);
223         else
224                 list_del(&task->u.tk_wait.list);
225         queue->qlen--;
226         dprintk("RPC: %5u removed from queue %p \"%s\"\n",
227                         task->tk_pid, queue, rpc_qname(queue));
228 }
229 
230 static void __rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname, unsigned char nr_queues)
231 {
232         int i;
233 
234         spin_lock_init(&queue->lock);
235         for (i = 0; i < ARRAY_SIZE(queue->tasks); i++)
236                 INIT_LIST_HEAD(&queue->tasks[i]);
237         queue->maxpriority = nr_queues - 1;
238         rpc_reset_waitqueue_priority(queue);
239         queue->qlen = 0;
240         timer_setup(&queue->timer_list.timer, __rpc_queue_timer_fn, 0);
241         INIT_LIST_HEAD(&queue->timer_list.list);
242         rpc_assign_waitqueue_name(queue, qname);
243 }
244 
245 void rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname)
246 {
247         __rpc_init_priority_wait_queue(queue, qname, RPC_NR_PRIORITY);
248 }
249 EXPORT_SYMBOL_GPL(rpc_init_priority_wait_queue);
250 
251 void rpc_init_wait_queue(struct rpc_wait_queue *queue, const char *qname)
252 {
253         __rpc_init_priority_wait_queue(queue, qname, 1);
254 }
255 EXPORT_SYMBOL_GPL(rpc_init_wait_queue);
256 
257 void rpc_destroy_wait_queue(struct rpc_wait_queue *queue)
258 {
259         del_timer_sync(&queue->timer_list.timer);
260 }
261 EXPORT_SYMBOL_GPL(rpc_destroy_wait_queue);
262 
263 static int rpc_wait_bit_killable(struct wait_bit_key *key, int mode)
264 {
265         freezable_schedule_unsafe();
266         if (signal_pending_state(mode, current))
267                 return -ERESTARTSYS;
268         return 0;
269 }
270 
271 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG) || IS_ENABLED(CONFIG_TRACEPOINTS)
272 static void rpc_task_set_debuginfo(struct rpc_task *task)
273 {
274         static atomic_t rpc_pid;
275 
276         task->tk_pid = atomic_inc_return(&rpc_pid);
277 }
278 #else
279 static inline void rpc_task_set_debuginfo(struct rpc_task *task)
280 {
281 }
282 #endif
283 
284 static void rpc_set_active(struct rpc_task *task)
285 {
286         rpc_task_set_debuginfo(task);
287         set_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
288         trace_rpc_task_begin(task, NULL);
289 }
290 
291 /*
292  * Mark an RPC call as having completed by clearing the 'active' bit
293  * and then waking up all tasks that were sleeping.
294  */
295 static int rpc_complete_task(struct rpc_task *task)
296 {
297         void *m = &task->tk_runstate;
298         wait_queue_head_t *wq = bit_waitqueue(m, RPC_TASK_ACTIVE);
299         struct wait_bit_key k = __WAIT_BIT_KEY_INITIALIZER(m, RPC_TASK_ACTIVE);
300         unsigned long flags;
301         int ret;
302 
303         trace_rpc_task_complete(task, NULL);
304 
305         spin_lock_irqsave(&wq->lock, flags);
306         clear_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
307         ret = atomic_dec_and_test(&task->tk_count);
308         if (waitqueue_active(wq))
309                 __wake_up_locked_key(wq, TASK_NORMAL, &k);
310         spin_unlock_irqrestore(&wq->lock, flags);
311         return ret;
312 }
313 
314 /*
315  * Allow callers to wait for completion of an RPC call
316  *
317  * Note the use of out_of_line_wait_on_bit() rather than wait_on_bit()
318  * to enforce taking of the wq->lock and hence avoid races with
319  * rpc_complete_task().
320  */
321 int __rpc_wait_for_completion_task(struct rpc_task *task, wait_bit_action_f *action)
322 {
323         if (action == NULL)
324                 action = rpc_wait_bit_killable;
325         return out_of_line_wait_on_bit(&task->tk_runstate, RPC_TASK_ACTIVE,
326                         action, TASK_KILLABLE);
327 }
328 EXPORT_SYMBOL_GPL(__rpc_wait_for_completion_task);
329 
330 /*
331  * Make an RPC task runnable.
332  *
333  * Note: If the task is ASYNC, and is being made runnable after sitting on an
334  * rpc_wait_queue, this must be called with the queue spinlock held to protect
335  * the wait queue operation.
336  * Note the ordering of rpc_test_and_set_running() and rpc_clear_queued(),
337  * which is needed to ensure that __rpc_execute() doesn't loop (due to the
338  * lockless RPC_IS_QUEUED() test) before we've had a chance to test
339  * the RPC_TASK_RUNNING flag.
340  */
341 static void rpc_make_runnable(struct workqueue_struct *wq,
342                 struct rpc_task *task)
343 {
344         bool need_wakeup = !rpc_test_and_set_running(task);
345 
346         rpc_clear_queued(task);
347         if (!need_wakeup)
348                 return;
349         if (RPC_IS_ASYNC(task)) {
350                 INIT_WORK(&task->u.tk_work, rpc_async_schedule);
351                 queue_work(wq, &task->u.tk_work);
352         } else
353                 wake_up_bit(&task->tk_runstate, RPC_TASK_QUEUED);
354 }
355 
356 /*
357  * Prepare for sleeping on a wait queue.
358  * By always appending tasks to the list we ensure FIFO behavior.
359  * NB: An RPC task will only receive interrupt-driven events as long
360  * as it's on a wait queue.
361  */
362 static void __rpc_sleep_on_priority(struct rpc_wait_queue *q,
363                 struct rpc_task *task,
364                 rpc_action action,
365                 unsigned char queue_priority)
366 {
367         dprintk("RPC: %5u sleep_on(queue \"%s\" time %lu)\n",
368                         task->tk_pid, rpc_qname(q), jiffies);
369 
370         trace_rpc_task_sleep(task, q);
371 
372         __rpc_add_wait_queue(q, task, queue_priority);
373 
374         WARN_ON_ONCE(task->tk_callback != NULL);
375         task->tk_callback = action;
376         __rpc_add_timer(q, task);
377 }
378 
379 void rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
380                                 rpc_action action)
381 {
382         /* We shouldn't ever put an inactive task to sleep */
383         WARN_ON_ONCE(!RPC_IS_ACTIVATED(task));
384         if (!RPC_IS_ACTIVATED(task)) {
385                 task->tk_status = -EIO;
386                 rpc_put_task_async(task);
387                 return;
388         }
389 
390         /*
391          * Protect the queue operations.
392          */
393         spin_lock_bh(&q->lock);
394         __rpc_sleep_on_priority(q, task, action, task->tk_priority);
395         spin_unlock_bh(&q->lock);
396 }
397 EXPORT_SYMBOL_GPL(rpc_sleep_on);
398 
399 void rpc_sleep_on_priority(struct rpc_wait_queue *q, struct rpc_task *task,
400                 rpc_action action, int priority)
401 {
402         /* We shouldn't ever put an inactive task to sleep */
403         WARN_ON_ONCE(!RPC_IS_ACTIVATED(task));
404         if (!RPC_IS_ACTIVATED(task)) {
405                 task->tk_status = -EIO;
406                 rpc_put_task_async(task);
407                 return;
408         }
409 
410         /*
411          * Protect the queue operations.
412          */
413         spin_lock_bh(&q->lock);
414         __rpc_sleep_on_priority(q, task, action, priority - RPC_PRIORITY_LOW);
415         spin_unlock_bh(&q->lock);
416 }
417 EXPORT_SYMBOL_GPL(rpc_sleep_on_priority);
418 
419 /**
420  * __rpc_do_wake_up_task_on_wq - wake up a single rpc_task
421  * @wq: workqueue on which to run task
422  * @queue: wait queue
423  * @task: task to be woken up
424  *
425  * Caller must hold queue->lock, and have cleared the task queued flag.
426  */
427 static void __rpc_do_wake_up_task_on_wq(struct workqueue_struct *wq,
428                 struct rpc_wait_queue *queue,
429                 struct rpc_task *task)
430 {
431         dprintk("RPC: %5u __rpc_wake_up_task (now %lu)\n",
432                         task->tk_pid, jiffies);
433 
434         /* Has the task been executed yet? If not, we cannot wake it up! */
435         if (!RPC_IS_ACTIVATED(task)) {
436                 printk(KERN_ERR "RPC: Inactive task (%p) being woken up!\n", task);
437                 return;
438         }
439 
440         trace_rpc_task_wakeup(task, queue);
441 
442         __rpc_remove_wait_queue(queue, task);
443 
444         rpc_make_runnable(wq, task);
445 
446         dprintk("RPC:       __rpc_wake_up_task done\n");
447 }
448 
449 /*
450  * Wake up a queued task while the queue lock is being held
451  */
452 static struct rpc_task *
453 rpc_wake_up_task_on_wq_queue_action_locked(struct workqueue_struct *wq,
454                 struct rpc_wait_queue *queue, struct rpc_task *task,
455                 bool (*action)(struct rpc_task *, void *), void *data)
456 {
457         if (RPC_IS_QUEUED(task)) {
458                 smp_rmb();
459                 if (task->tk_waitqueue == queue) {
460                         if (action == NULL || action(task, data)) {
461                                 __rpc_do_wake_up_task_on_wq(wq, queue, task);
462                                 return task;
463                         }
464                 }
465         }
466         return NULL;
467 }
468 
469 static void
470 rpc_wake_up_task_on_wq_queue_locked(struct workqueue_struct *wq,
471                 struct rpc_wait_queue *queue, struct rpc_task *task)
472 {
473         rpc_wake_up_task_on_wq_queue_action_locked(wq, queue, task, NULL, NULL);
474 }
475 
476 /*
477  * Wake up a queued task while the queue lock is being held
478  */
479 static void rpc_wake_up_task_queue_locked(struct rpc_wait_queue *queue, struct rpc_task *task)
480 {
481         rpc_wake_up_task_on_wq_queue_locked(rpciod_workqueue, queue, task);
482 }
483 
484 /*
485  * Wake up a task on a specific queue
486  */
487 void rpc_wake_up_queued_task_on_wq(struct workqueue_struct *wq,
488                 struct rpc_wait_queue *queue,
489                 struct rpc_task *task)
490 {
491         if (!RPC_IS_QUEUED(task))
492                 return;
493         spin_lock_bh(&queue->lock);
494         rpc_wake_up_task_on_wq_queue_locked(wq, queue, task);
495         spin_unlock_bh(&queue->lock);
496 }
497 
498 /*
499  * Wake up a task on a specific queue
500  */
501 void rpc_wake_up_queued_task(struct rpc_wait_queue *queue, struct rpc_task *task)
502 {
503         if (!RPC_IS_QUEUED(task))
504                 return;
505         spin_lock_bh(&queue->lock);
506         rpc_wake_up_task_queue_locked(queue, task);
507         spin_unlock_bh(&queue->lock);
508 }
509 EXPORT_SYMBOL_GPL(rpc_wake_up_queued_task);
510 
511 static bool rpc_task_action_set_status(struct rpc_task *task, void *status)
512 {
513         task->tk_status = *(int *)status;
514         return true;
515 }
516 
517 static void
518 rpc_wake_up_task_queue_set_status_locked(struct rpc_wait_queue *queue,
519                 struct rpc_task *task, int status)
520 {
521         rpc_wake_up_task_on_wq_queue_action_locked(rpciod_workqueue, queue,
522                         task, rpc_task_action_set_status, &status);
523 }
524 
525 /**
526  * rpc_wake_up_queued_task_set_status - wake up a task and set task->tk_status
527  * @queue: pointer to rpc_wait_queue
528  * @task: pointer to rpc_task
529  * @status: integer error value
530  *
531  * If @task is queued on @queue, then it is woken up, and @task->tk_status is
532  * set to the value of @status.
533  */
534 void
535 rpc_wake_up_queued_task_set_status(struct rpc_wait_queue *queue,
536                 struct rpc_task *task, int status)
537 {
538         if (!RPC_IS_QUEUED(task))
539                 return;
540         spin_lock_bh(&queue->lock);
541         rpc_wake_up_task_queue_set_status_locked(queue, task, status);
542         spin_unlock_bh(&queue->lock);
543 }
544 
545 /*
546  * Wake up the next task on a priority queue.
547  */
548 static struct rpc_task *__rpc_find_next_queued_priority(struct rpc_wait_queue *queue)
549 {
550         struct list_head *q;
551         struct rpc_task *task;
552 
553         /*
554          * Service a batch of tasks from a single owner.
555          */
556         q = &queue->tasks[queue->priority];
557         if (!list_empty(q) && --queue->nr) {
558                 task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
559                 goto out;
560         }
561 
562         /*
563          * Service the next queue.
564          */
565         do {
566                 if (q == &queue->tasks[0])
567                         q = &queue->tasks[queue->maxpriority];
568                 else
569                         q = q - 1;
570                 if (!list_empty(q)) {
571                         task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
572                         goto new_queue;
573                 }
574         } while (q != &queue->tasks[queue->priority]);
575 
576         rpc_reset_waitqueue_priority(queue);
577         return NULL;
578 
579 new_queue:
580         rpc_set_waitqueue_priority(queue, (unsigned int)(q - &queue->tasks[0]));
581 out:
582         return task;
583 }
584 
585 static struct rpc_task *__rpc_find_next_queued(struct rpc_wait_queue *queue)
586 {
587         if (RPC_IS_PRIORITY(queue))
588                 return __rpc_find_next_queued_priority(queue);
589         if (!list_empty(&queue->tasks[0]))
590                 return list_first_entry(&queue->tasks[0], struct rpc_task, u.tk_wait.list);
591         return NULL;
592 }
593 
594 /*
595  * Wake up the first task on the wait queue.
596  */
597 struct rpc_task *rpc_wake_up_first_on_wq(struct workqueue_struct *wq,
598                 struct rpc_wait_queue *queue,
599                 bool (*func)(struct rpc_task *, void *), void *data)
600 {
601         struct rpc_task *task = NULL;
602 
603         dprintk("RPC:       wake_up_first(%p \"%s\")\n",
604                         queue, rpc_qname(queue));
605         spin_lock_bh(&queue->lock);
606         task = __rpc_find_next_queued(queue);
607         if (task != NULL)
608                 task = rpc_wake_up_task_on_wq_queue_action_locked(wq, queue,
609                                 task, func, data);
610         spin_unlock_bh(&queue->lock);
611 
612         return task;
613 }
614 
615 /*
616  * Wake up the first task on the wait queue.
617  */
618 struct rpc_task *rpc_wake_up_first(struct rpc_wait_queue *queue,
619                 bool (*func)(struct rpc_task *, void *), void *data)
620 {
621         return rpc_wake_up_first_on_wq(rpciod_workqueue, queue, func, data);
622 }
623 EXPORT_SYMBOL_GPL(rpc_wake_up_first);
624 
625 static bool rpc_wake_up_next_func(struct rpc_task *task, void *data)
626 {
627         return true;
628 }
629 
630 /*
631  * Wake up the next task on the wait queue.
632 */
633 struct rpc_task *rpc_wake_up_next(struct rpc_wait_queue *queue)
634 {
635         return rpc_wake_up_first(queue, rpc_wake_up_next_func, NULL);
636 }
637 EXPORT_SYMBOL_GPL(rpc_wake_up_next);
638 
639 /**
640  * rpc_wake_up - wake up all rpc_tasks
641  * @queue: rpc_wait_queue on which the tasks are sleeping
642  *
643  * Grabs queue->lock
644  */
645 void rpc_wake_up(struct rpc_wait_queue *queue)
646 {
647         struct list_head *head;
648 
649         spin_lock_bh(&queue->lock);
650         head = &queue->tasks[queue->maxpriority];
651         for (;;) {
652                 while (!list_empty(head)) {
653                         struct rpc_task *task;
654                         task = list_first_entry(head,
655                                         struct rpc_task,
656                                         u.tk_wait.list);
657                         rpc_wake_up_task_queue_locked(queue, task);
658                 }
659                 if (head == &queue->tasks[0])
660                         break;
661                 head--;
662         }
663         spin_unlock_bh(&queue->lock);
664 }
665 EXPORT_SYMBOL_GPL(rpc_wake_up);
666 
667 /**
668  * rpc_wake_up_status - wake up all rpc_tasks and set their status value.
669  * @queue: rpc_wait_queue on which the tasks are sleeping
670  * @status: status value to set
671  *
672  * Grabs queue->lock
673  */
674 void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
675 {
676         struct list_head *head;
677 
678         spin_lock_bh(&queue->lock);
679         head = &queue->tasks[queue->maxpriority];
680         for (;;) {
681                 while (!list_empty(head)) {
682                         struct rpc_task *task;
683                         task = list_first_entry(head,
684                                         struct rpc_task,
685                                         u.tk_wait.list);
686                         task->tk_status = status;
687                         rpc_wake_up_task_queue_locked(queue, task);
688                 }
689                 if (head == &queue->tasks[0])
690                         break;
691                 head--;
692         }
693         spin_unlock_bh(&queue->lock);
694 }
695 EXPORT_SYMBOL_GPL(rpc_wake_up_status);
696 
697 static void __rpc_queue_timer_fn(struct timer_list *t)
698 {
699         struct rpc_wait_queue *queue = from_timer(queue, t, timer_list.timer);
700         struct rpc_task *task, *n;
701         unsigned long expires, now, timeo;
702 
703         spin_lock(&queue->lock);
704         expires = now = jiffies;
705         list_for_each_entry_safe(task, n, &queue->timer_list.list, u.tk_wait.timer_list) {
706                 timeo = task->u.tk_wait.expires;
707                 if (time_after_eq(now, timeo)) {
708                         dprintk("RPC: %5u timeout\n", task->tk_pid);
709                         task->tk_status = -ETIMEDOUT;
710                         rpc_wake_up_task_queue_locked(queue, task);
711                         continue;
712                 }
713                 if (expires == now || time_after(expires, timeo))
714                         expires = timeo;
715         }
716         if (!list_empty(&queue->timer_list.list))
717                 rpc_set_queue_timer(queue, expires);
718         spin_unlock(&queue->lock);
719 }
720 
721 static void __rpc_atrun(struct rpc_task *task)
722 {
723         if (task->tk_status == -ETIMEDOUT)
724                 task->tk_status = 0;
725 }
726 
727 /*
728  * Run a task at a later time
729  */
730 void rpc_delay(struct rpc_task *task, unsigned long delay)
731 {
732         task->tk_timeout = delay;
733         rpc_sleep_on(&delay_queue, task, __rpc_atrun);
734 }
735 EXPORT_SYMBOL_GPL(rpc_delay);
736 
737 /*
738  * Helper to call task->tk_ops->rpc_call_prepare
739  */
740 void rpc_prepare_task(struct rpc_task *task)
741 {
742         task->tk_ops->rpc_call_prepare(task, task->tk_calldata);
743 }
744 
745 static void
746 rpc_init_task_statistics(struct rpc_task *task)
747 {
748         /* Initialize retry counters */
749         task->tk_garb_retry = 2;
750         task->tk_cred_retry = 2;
751         task->tk_rebind_retry = 2;
752 
753         /* starting timestamp */
754         task->tk_start = ktime_get();
755 }
756 
757 static void
758 rpc_reset_task_statistics(struct rpc_task *task)
759 {
760         task->tk_timeouts = 0;
761         task->tk_flags &= ~(RPC_CALL_MAJORSEEN|RPC_TASK_KILLED|RPC_TASK_SENT);
762 
763         rpc_init_task_statistics(task);
764 }
765 
766 /*
767  * Helper that calls task->tk_ops->rpc_call_done if it exists
768  */
769 void rpc_exit_task(struct rpc_task *task)
770 {
771         task->tk_action = NULL;
772         if (task->tk_ops->rpc_call_done != NULL) {
773                 task->tk_ops->rpc_call_done(task, task->tk_calldata);
774                 if (task->tk_action != NULL) {
775                         WARN_ON(RPC_ASSASSINATED(task));
776                         /* Always release the RPC slot and buffer memory */
777                         xprt_release(task);
778                         rpc_reset_task_statistics(task);
779                 }
780         }
781 }
782 
783 void rpc_exit(struct rpc_task *task, int status)
784 {
785         task->tk_status = status;
786         task->tk_action = rpc_exit_task;
787         if (RPC_IS_QUEUED(task))
788                 rpc_wake_up_queued_task(task->tk_waitqueue, task);
789 }
790 EXPORT_SYMBOL_GPL(rpc_exit);
791 
792 void rpc_release_calldata(const struct rpc_call_ops *ops, void *calldata)
793 {
794         if (ops->rpc_release != NULL)
795                 ops->rpc_release(calldata);
796 }
797 
798 /*
799  * This is the RPC `scheduler' (or rather, the finite state machine).
800  */
801 static void __rpc_execute(struct rpc_task *task)
802 {
803         struct rpc_wait_queue *queue;
804         int task_is_async = RPC_IS_ASYNC(task);
805         int status = 0;
806 
807         dprintk("RPC: %5u __rpc_execute flags=0x%x\n",
808                         task->tk_pid, task->tk_flags);
809 
810         WARN_ON_ONCE(RPC_IS_QUEUED(task));
811         if (RPC_IS_QUEUED(task))
812                 return;
813 
814         for (;;) {
815                 void (*do_action)(struct rpc_task *);
816 
817                 /*
818                  * Perform the next FSM step or a pending callback.
819                  *
820                  * tk_action may be NULL if the task has been killed.
821                  * In particular, note that rpc_killall_tasks may
822                  * do this at any time, so beware when dereferencing.
823                  */
824                 do_action = task->tk_action;
825                 if (task->tk_callback) {
826                         do_action = task->tk_callback;
827                         task->tk_callback = NULL;
828                 }
829                 if (!do_action)
830                         break;
831                 trace_rpc_task_run_action(task, do_action);
832                 do_action(task);
833 
834                 /*
835                  * Lockless check for whether task is sleeping or not.
836                  */
837                 if (!RPC_IS_QUEUED(task))
838                         continue;
839                 /*
840                  * The queue->lock protects against races with
841                  * rpc_make_runnable().
842                  *
843                  * Note that once we clear RPC_TASK_RUNNING on an asynchronous
844                  * rpc_task, rpc_make_runnable() can assign it to a
845                  * different workqueue. We therefore cannot assume that the
846                  * rpc_task pointer may still be dereferenced.
847                  */
848                 queue = task->tk_waitqueue;
849                 spin_lock_bh(&queue->lock);
850                 if (!RPC_IS_QUEUED(task)) {
851                         spin_unlock_bh(&queue->lock);
852                         continue;
853                 }
854                 rpc_clear_running(task);
855                 spin_unlock_bh(&queue->lock);
856                 if (task_is_async)
857                         return;
858 
859                 /* sync task: sleep here */
860                 dprintk("RPC: %5u sync task going to sleep\n", task->tk_pid);
861                 status = out_of_line_wait_on_bit(&task->tk_runstate,
862                                 RPC_TASK_QUEUED, rpc_wait_bit_killable,
863                                 TASK_KILLABLE);
864                 if (status == -ERESTARTSYS) {
865                         /*
866                          * When a sync task receives a signal, it exits with
867                          * -ERESTARTSYS. In order to catch any callbacks that
868                          * clean up after sleeping on some queue, we don't
869                          * break the loop here, but go around once more.
870                          */
871                         dprintk("RPC: %5u got signal\n", task->tk_pid);
872                         task->tk_flags |= RPC_TASK_KILLED;
873                         rpc_exit(task, -ERESTARTSYS);
874                 }
875                 dprintk("RPC: %5u sync task resuming\n", task->tk_pid);
876         }
877 
878         dprintk("RPC: %5u return %d, status %d\n", task->tk_pid, status,
879                         task->tk_status);
880         /* Release all resources associated with the task */
881         rpc_release_task(task);
882 }
883 
884 /*
885  * User-visible entry point to the scheduler.
886  *
887  * This may be called recursively if e.g. an async NFS task updates
888  * the attributes and finds that dirty pages must be flushed.
889  * NOTE: Upon exit of this function the task is guaranteed to be
890  *       released. In particular note that tk_release() will have
891  *       been called, so your task memory may have been freed.
892  */
893 void rpc_execute(struct rpc_task *task)
894 {
895         bool is_async = RPC_IS_ASYNC(task);
896 
897         rpc_set_active(task);
898         rpc_make_runnable(rpciod_workqueue, task);
899         if (!is_async)
900                 __rpc_execute(task);
901 }
902 
903 static void rpc_async_schedule(struct work_struct *work)
904 {
905         __rpc_execute(container_of(work, struct rpc_task, u.tk_work));
906 }
907 
908 /**
909  * rpc_malloc - allocate RPC buffer resources
910  * @task: RPC task
911  *
912  * A single memory region is allocated, which is split between the
913  * RPC call and RPC reply that this task is being used for. When
914  * this RPC is retired, the memory is released by calling rpc_free.
915  *
916  * To prevent rpciod from hanging, this allocator never sleeps,
917  * returning -ENOMEM and suppressing warning if the request cannot
918  * be serviced immediately. The caller can arrange to sleep in a
919  * way that is safe for rpciod.
920  *
921  * Most requests are 'small' (under 2KiB) and can be serviced from a
922  * mempool, ensuring that NFS reads and writes can always proceed,
923  * and that there is good locality of reference for these buffers.
924  *
925  * In order to avoid memory starvation triggering more writebacks of
926  * NFS requests, we avoid using GFP_KERNEL.
927  */
928 int rpc_malloc(struct rpc_task *task)
929 {
930         struct rpc_rqst *rqst = task->tk_rqstp;
931         size_t size = rqst->rq_callsize + rqst->rq_rcvsize;
932         struct rpc_buffer *buf;
933         gfp_t gfp = GFP_NOIO | __GFP_NOWARN;
934 
935         if (RPC_IS_SWAPPER(task))
936                 gfp = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN;
937 
938         size += sizeof(struct rpc_buffer);
939         if (size <= RPC_BUFFER_MAXSIZE)
940                 buf = mempool_alloc(rpc_buffer_mempool, gfp);
941         else
942                 buf = kmalloc(size, gfp);
943 
944         if (!buf)
945                 return -ENOMEM;
946 
947         buf->len = size;
948         dprintk("RPC: %5u allocated buffer of size %zu at %p\n",
949                         task->tk_pid, size, buf);
950         rqst->rq_buffer = buf->data;
951         rqst->rq_rbuffer = (char *)rqst->rq_buffer + rqst->rq_callsize;
952         return 0;
953 }
954 EXPORT_SYMBOL_GPL(rpc_malloc);
955 
956 /**
957  * rpc_free - free RPC buffer resources allocated via rpc_malloc
958  * @task: RPC task
959  *
960  */
961 void rpc_free(struct rpc_task *task)
962 {
963         void *buffer = task->tk_rqstp->rq_buffer;
964         size_t size;
965         struct rpc_buffer *buf;
966 
967         buf = container_of(buffer, struct rpc_buffer, data);
968         size = buf->len;
969 
970         dprintk("RPC:       freeing buffer of size %zu at %p\n",
971                         size, buf);
972 
973         if (size <= RPC_BUFFER_MAXSIZE)
974                 mempool_free(buf, rpc_buffer_mempool);
975         else
976                 kfree(buf);
977 }
978 EXPORT_SYMBOL_GPL(rpc_free);
979 
980 /*
981  * Creation and deletion of RPC task structures
982  */
983 static void rpc_init_task(struct rpc_task *task, const struct rpc_task_setup *task_setup_data)
984 {
985         memset(task, 0, sizeof(*task));
986         atomic_set(&task->tk_count, 1);
987         task->tk_flags  = task_setup_data->flags;
988         task->tk_ops = task_setup_data->callback_ops;
989         task->tk_calldata = task_setup_data->callback_data;
990         INIT_LIST_HEAD(&task->tk_task);
991 
992         task->tk_priority = task_setup_data->priority - RPC_PRIORITY_LOW;
993         task->tk_owner = current->tgid;
994 
995         /* Initialize workqueue for async tasks */
996         task->tk_workqueue = task_setup_data->workqueue;
997 
998         task->tk_xprt = xprt_get(task_setup_data->rpc_xprt);
999 
1000         task->tk_op_cred = get_rpccred(task_setup_data->rpc_op_cred);
1001 
1002         if (task->tk_ops->rpc_call_prepare != NULL)
1003                 task->tk_action = rpc_prepare_task;
1004 
1005         rpc_init_task_statistics(task);
1006 
1007         dprintk("RPC:       new task initialized, procpid %u\n",
1008                                 task_pid_nr(current));
1009 }
1010 
1011 static struct rpc_task *
1012 rpc_alloc_task(void)
1013 {
1014         return (struct rpc_task *)mempool_alloc(rpc_task_mempool, GFP_NOIO);
1015 }
1016 
1017 /*
1018  * Create a new task for the specified client.
1019  */
1020 struct rpc_task *rpc_new_task(const struct rpc_task_setup *setup_data)
1021 {
1022         struct rpc_task *task = setup_data->task;
1023         unsigned short flags = 0;
1024 
1025         if (task == NULL) {
1026                 task = rpc_alloc_task();
1027                 flags = RPC_TASK_DYNAMIC;
1028         }
1029 
1030         rpc_init_task(task, setup_data);
1031         task->tk_flags |= flags;
1032         dprintk("RPC:       allocated task %p\n", task);
1033         return task;
1034 }
1035 
1036 /*
1037  * rpc_free_task - release rpc task and perform cleanups
1038  *
1039  * Note that we free up the rpc_task _after_ rpc_release_calldata()
1040  * in order to work around a workqueue dependency issue.
1041  *
1042  * Tejun Heo states:
1043  * "Workqueue currently considers two work items to be the same if they're
1044  * on the same address and won't execute them concurrently - ie. it
1045  * makes a work item which is queued again while being executed wait
1046  * for the previous execution to complete.
1047  *
1048  * If a work function frees the work item, and then waits for an event
1049  * which should be performed by another work item and *that* work item
1050  * recycles the freed work item, it can create a false dependency loop.
1051  * There really is no reliable way to detect this short of verifying
1052  * every memory free."
1053  *
1054  */
1055 static void rpc_free_task(struct rpc_task *task)
1056 {
1057         unsigned short tk_flags = task->tk_flags;
1058 
1059         put_rpccred(task->tk_op_cred);
1060         rpc_release_calldata(task->tk_ops, task->tk_calldata);
1061 
1062         if (tk_flags & RPC_TASK_DYNAMIC) {
1063                 dprintk("RPC: %5u freeing task\n", task->tk_pid);
1064                 mempool_free(task, rpc_task_mempool);
1065         }
1066 }
1067 
1068 static void rpc_async_release(struct work_struct *work)
1069 {
1070         rpc_free_task(container_of(work, struct rpc_task, u.tk_work));
1071 }
1072 
1073 static void rpc_release_resources_task(struct rpc_task *task)
1074 {
1075         xprt_release(task);
1076         if (task->tk_msg.rpc_cred) {
1077                 put_cred(task->tk_msg.rpc_cred);
1078                 task->tk_msg.rpc_cred = NULL;
1079         }
1080         rpc_task_release_client(task);
1081 }
1082 
1083 static void rpc_final_put_task(struct rpc_task *task,
1084                 struct workqueue_struct *q)
1085 {
1086         if (q != NULL) {
1087                 INIT_WORK(&task->u.tk_work, rpc_async_release);
1088                 queue_work(q, &task->u.tk_work);
1089         } else
1090                 rpc_free_task(task);
1091 }
1092 
1093 static void rpc_do_put_task(struct rpc_task *task, struct workqueue_struct *q)
1094 {
1095         if (atomic_dec_and_test(&task->tk_count)) {
1096                 rpc_release_resources_task(task);
1097                 rpc_final_put_task(task, q);
1098         }
1099 }
1100 
1101 void rpc_put_task(struct rpc_task *task)
1102 {
1103         rpc_do_put_task(task, NULL);
1104 }
1105 EXPORT_SYMBOL_GPL(rpc_put_task);
1106 
1107 void rpc_put_task_async(struct rpc_task *task)
1108 {
1109         rpc_do_put_task(task, task->tk_workqueue);
1110 }
1111 EXPORT_SYMBOL_GPL(rpc_put_task_async);
1112 
1113 static void rpc_release_task(struct rpc_task *task)
1114 {
1115         dprintk("RPC: %5u release task\n", task->tk_pid);
1116 
1117         WARN_ON_ONCE(RPC_IS_QUEUED(task));
1118 
1119         rpc_release_resources_task(task);
1120 
1121         /*
1122          * Note: at this point we have been removed from rpc_clnt->cl_tasks,
1123          * so it should be safe to use task->tk_count as a test for whether
1124          * or not any other processes still hold references to our rpc_task.
1125          */
1126         if (atomic_read(&task->tk_count) != 1 + !RPC_IS_ASYNC(task)) {
1127                 /* Wake up anyone who may be waiting for task completion */
1128                 if (!rpc_complete_task(task))
1129                         return;
1130         } else {
1131                 if (!atomic_dec_and_test(&task->tk_count))
1132                         return;
1133         }
1134         rpc_final_put_task(task, task->tk_workqueue);
1135 }
1136 
1137 int rpciod_up(void)
1138 {
1139         return try_module_get(THIS_MODULE) ? 0 : -EINVAL;
1140 }
1141 
1142 void rpciod_down(void)
1143 {
1144         module_put(THIS_MODULE);
1145 }
1146 
1147 /*
1148  * Start up the rpciod workqueue.
1149  */
1150 static int rpciod_start(void)
1151 {
1152         struct workqueue_struct *wq;
1153 
1154         /*
1155          * Create the rpciod thread and wait for it to start.
1156          */
1157         dprintk("RPC:       creating workqueue rpciod\n");
1158         wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
1159         if (!wq)
1160                 goto out_failed;
1161         rpciod_workqueue = wq;
1162         /* Note: highpri because network receive is latency sensitive */
1163         wq = alloc_workqueue("xprtiod", WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_HIGHPRI, 0);
1164         if (!wq)
1165                 goto free_rpciod;
1166         xprtiod_workqueue = wq;
1167         return 1;
1168 free_rpciod:
1169         wq = rpciod_workqueue;
1170         rpciod_workqueue = NULL;
1171         destroy_workqueue(wq);
1172 out_failed:
1173         return 0;
1174 }
1175 
1176 static void rpciod_stop(void)
1177 {
1178         struct workqueue_struct *wq = NULL;
1179 
1180         if (rpciod_workqueue == NULL)
1181                 return;
1182         dprintk("RPC:       destroying workqueue rpciod\n");
1183 
1184         wq = rpciod_workqueue;
1185         rpciod_workqueue = NULL;
1186         destroy_workqueue(wq);
1187         wq = xprtiod_workqueue;
1188         xprtiod_workqueue = NULL;
1189         destroy_workqueue(wq);
1190 }
1191 
1192 void
1193 rpc_destroy_mempool(void)
1194 {
1195         rpciod_stop();
1196         mempool_destroy(rpc_buffer_mempool);
1197         mempool_destroy(rpc_task_mempool);
1198         kmem_cache_destroy(rpc_task_slabp);
1199         kmem_cache_destroy(rpc_buffer_slabp);
1200         rpc_destroy_wait_queue(&delay_queue);
1201 }
1202 
1203 int
1204 rpc_init_mempool(void)
1205 {
1206         /*
1207          * The following is not strictly a mempool initialisation,
1208          * but there is no harm in doing it here
1209          */
1210         rpc_init_wait_queue(&delay_queue, "delayq");
1211         if (!rpciod_start())
1212                 goto err_nomem;
1213 
1214         rpc_task_slabp = kmem_cache_create("rpc_tasks",
1215                                              sizeof(struct rpc_task),
1216                                              0, SLAB_HWCACHE_ALIGN,
1217                                              NULL);
1218         if (!rpc_task_slabp)
1219                 goto err_nomem;
1220         rpc_buffer_slabp = kmem_cache_create("rpc_buffers",
1221                                              RPC_BUFFER_MAXSIZE,
1222                                              0, SLAB_HWCACHE_ALIGN,
1223                                              NULL);
1224         if (!rpc_buffer_slabp)
1225                 goto err_nomem;
1226         rpc_task_mempool = mempool_create_slab_pool(RPC_TASK_POOLSIZE,
1227                                                     rpc_task_slabp);
1228         if (!rpc_task_mempool)
1229                 goto err_nomem;
1230         rpc_buffer_mempool = mempool_create_slab_pool(RPC_BUFFER_POOLSIZE,
1231                                                       rpc_buffer_slabp);
1232         if (!rpc_buffer_mempool)
1233                 goto err_nomem;
1234         return 0;
1235 err_nomem:
1236         rpc_destroy_mempool();
1237         return -ENOMEM;
1238 }
1239 

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