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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 #include <linux/sched/mm.h>
 23 
 24 #include <linux/sunrpc/clnt.h>
 25 
 26 #include "sunrpc.h"
 27 
 28 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 29 #define RPCDBG_FACILITY         RPCDBG_SCHED
 30 #endif
 31 
 32 #define CREATE_TRACE_POINTS
 33 #include <trace/events/sunrpc.h>
 34 
 35 /*
 36  * RPC slabs and memory pools
 37  */
 38 #define RPC_BUFFER_MAXSIZE      (2048)
 39 #define RPC_BUFFER_POOLSIZE     (8)
 40 #define RPC_TASK_POOLSIZE       (8)
 41 static struct kmem_cache        *rpc_task_slabp __read_mostly;
 42 static struct kmem_cache        *rpc_buffer_slabp __read_mostly;
 43 static mempool_t        *rpc_task_mempool __read_mostly;
 44 static mempool_t        *rpc_buffer_mempool __read_mostly;
 45 
 46 static void                     rpc_async_schedule(struct work_struct *);
 47 static void                      rpc_release_task(struct rpc_task *task);
 48 static void __rpc_queue_timer_fn(struct timer_list *t);
 49 
 50 /*
 51  * RPC tasks sit here while waiting for conditions to improve.
 52  */
 53 static struct rpc_wait_queue delay_queue;
 54 
 55 /*
 56  * rpciod-related stuff
 57  */
 58 struct workqueue_struct *rpciod_workqueue __read_mostly;
 59 struct workqueue_struct *xprtiod_workqueue __read_mostly;
 60 
 61 /*
 62  * Disable the timer for a given RPC task. Should be called with
 63  * queue->lock and bh_disabled in order to avoid races within
 64  * rpc_run_timer().
 65  */
 66 static void
 67 __rpc_disable_timer(struct rpc_wait_queue *queue, struct rpc_task *task)
 68 {
 69         if (task->tk_timeout == 0)
 70                 return;
 71         dprintk("RPC: %5u disabling timer\n", task->tk_pid);
 72         task->tk_timeout = 0;
 73         list_del(&task->u.tk_wait.timer_list);
 74         if (list_empty(&queue->timer_list.list))
 75                 del_timer(&queue->timer_list.timer);
 76 }
 77 
 78 static void
 79 rpc_set_queue_timer(struct rpc_wait_queue *queue, unsigned long expires)
 80 {
 81         queue->timer_list.expires = expires;
 82         mod_timer(&queue->timer_list.timer, expires);
 83 }
 84 
 85 /*
 86  * Set up a timer for the current task.
 87  */
 88 static void
 89 __rpc_add_timer(struct rpc_wait_queue *queue, struct rpc_task *task)
 90 {
 91         if (!task->tk_timeout)
 92                 return;
 93 
 94         dprintk("RPC: %5u setting alarm for %u ms\n",
 95                 task->tk_pid, jiffies_to_msecs(task->tk_timeout));
 96 
 97         task->u.tk_wait.expires = jiffies + task->tk_timeout;
 98         if (list_empty(&queue->timer_list.list) || time_before(task->u.tk_wait.expires, queue->timer_list.expires))
 99                 rpc_set_queue_timer(queue, task->u.tk_wait.expires);
100         list_add(&task->u.tk_wait.timer_list, &queue->timer_list.list);
101 }
102 
103 static void rpc_set_waitqueue_priority(struct rpc_wait_queue *queue, int priority)
104 {
105         if (queue->priority != priority) {
106                 queue->priority = priority;
107                 queue->nr = 1U << priority;
108         }
109 }
110 
111 static void rpc_reset_waitqueue_priority(struct rpc_wait_queue *queue)
112 {
113         rpc_set_waitqueue_priority(queue, queue->maxpriority);
114 }
115 
116 /*
117  * Add a request to a queue list
118  */
119 static void
120 __rpc_list_enqueue_task(struct list_head *q, struct rpc_task *task)
121 {
122         struct rpc_task *t;
123 
124         list_for_each_entry(t, q, u.tk_wait.list) {
125                 if (t->tk_owner == task->tk_owner) {
126                         list_add_tail(&task->u.tk_wait.links,
127                                         &t->u.tk_wait.links);
128                         /* Cache the queue head in task->u.tk_wait.list */
129                         task->u.tk_wait.list.next = q;
130                         task->u.tk_wait.list.prev = NULL;
131                         return;
132                 }
133         }
134         INIT_LIST_HEAD(&task->u.tk_wait.links);
135         list_add_tail(&task->u.tk_wait.list, q);
136 }
137 
138 /*
139  * Remove request from a queue list
140  */
141 static void
142 __rpc_list_dequeue_task(struct rpc_task *task)
143 {
144         struct list_head *q;
145         struct rpc_task *t;
146 
147         if (task->u.tk_wait.list.prev == NULL) {
148                 list_del(&task->u.tk_wait.links);
149                 return;
150         }
151         if (!list_empty(&task->u.tk_wait.links)) {
152                 t = list_first_entry(&task->u.tk_wait.links,
153                                 struct rpc_task,
154                                 u.tk_wait.links);
155                 /* Assume __rpc_list_enqueue_task() cached the queue head */
156                 q = t->u.tk_wait.list.next;
157                 list_add_tail(&t->u.tk_wait.list, q);
158                 list_del(&task->u.tk_wait.links);
159         }
160         list_del(&task->u.tk_wait.list);
161 }
162 
163 /*
164  * Add new request to a priority queue.
165  */
166 static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue,
167                 struct rpc_task *task,
168                 unsigned char queue_priority)
169 {
170         if (unlikely(queue_priority > queue->maxpriority))
171                 queue_priority = queue->maxpriority;
172         __rpc_list_enqueue_task(&queue->tasks[queue_priority], task);
173 }
174 
175 /*
176  * Add new request to wait queue.
177  *
178  * Swapper tasks always get inserted at the head of the queue.
179  * This should avoid many nasty memory deadlocks and hopefully
180  * improve overall performance.
181  * Everyone else gets appended to the queue to ensure proper FIFO behavior.
182  */
183 static void __rpc_add_wait_queue(struct rpc_wait_queue *queue,
184                 struct rpc_task *task,
185                 unsigned char queue_priority)
186 {
187         WARN_ON_ONCE(RPC_IS_QUEUED(task));
188         if (RPC_IS_QUEUED(task))
189                 return;
190 
191         if (RPC_IS_PRIORITY(queue))
192                 __rpc_add_wait_queue_priority(queue, task, queue_priority);
193         else if (RPC_IS_SWAPPER(task))
194                 list_add(&task->u.tk_wait.list, &queue->tasks[0]);
195         else
196                 list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);
197         task->tk_waitqueue = queue;
198         queue->qlen++;
199         /* barrier matches the read in rpc_wake_up_task_queue_locked() */
200         smp_wmb();
201         rpc_set_queued(task);
202 
203         dprintk("RPC: %5u added to queue %p \"%s\"\n",
204                         task->tk_pid, queue, rpc_qname(queue));
205 }
206 
207 /*
208  * Remove request from a priority queue.
209  */
210 static void __rpc_remove_wait_queue_priority(struct rpc_task *task)
211 {
212         __rpc_list_dequeue_task(task);
213 }
214 
215 /*
216  * Remove request from queue.
217  * Note: must be called with spin lock held.
218  */
219 static void __rpc_remove_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *task)
220 {
221         __rpc_disable_timer(queue, task);
222         if (RPC_IS_PRIORITY(queue))
223                 __rpc_remove_wait_queue_priority(task);
224         else
225                 list_del(&task->u.tk_wait.list);
226         queue->qlen--;
227         dprintk("RPC: %5u removed from queue %p \"%s\"\n",
228                         task->tk_pid, queue, rpc_qname(queue));
229 }
230 
231 static void __rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname, unsigned char nr_queues)
232 {
233         int i;
234 
235         spin_lock_init(&queue->lock);
236         for (i = 0; i < ARRAY_SIZE(queue->tasks); i++)
237                 INIT_LIST_HEAD(&queue->tasks[i]);
238         queue->maxpriority = nr_queues - 1;
239         rpc_reset_waitqueue_priority(queue);
240         queue->qlen = 0;
241         timer_setup(&queue->timer_list.timer, __rpc_queue_timer_fn, 0);
242         INIT_LIST_HEAD(&queue->timer_list.list);
243         rpc_assign_waitqueue_name(queue, qname);
244 }
245 
246 void rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname)
247 {
248         __rpc_init_priority_wait_queue(queue, qname, RPC_NR_PRIORITY);
249 }
250 EXPORT_SYMBOL_GPL(rpc_init_priority_wait_queue);
251 
252 void rpc_init_wait_queue(struct rpc_wait_queue *queue, const char *qname)
253 {
254         __rpc_init_priority_wait_queue(queue, qname, 1);
255 }
256 EXPORT_SYMBOL_GPL(rpc_init_wait_queue);
257 
258 void rpc_destroy_wait_queue(struct rpc_wait_queue *queue)
259 {
260         del_timer_sync(&queue->timer_list.timer);
261 }
262 EXPORT_SYMBOL_GPL(rpc_destroy_wait_queue);
263 
264 static int rpc_wait_bit_killable(struct wait_bit_key *key, int mode)
265 {
266         freezable_schedule_unsafe();
267         if (signal_pending_state(mode, current))
268                 return -ERESTARTSYS;
269         return 0;
270 }
271 
272 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG) || IS_ENABLED(CONFIG_TRACEPOINTS)
273 static void rpc_task_set_debuginfo(struct rpc_task *task)
274 {
275         static atomic_t rpc_pid;
276 
277         task->tk_pid = atomic_inc_return(&rpc_pid);
278 }
279 #else
280 static inline void rpc_task_set_debuginfo(struct rpc_task *task)
281 {
282 }
283 #endif
284 
285 static void rpc_set_active(struct rpc_task *task)
286 {
287         rpc_task_set_debuginfo(task);
288         set_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
289         trace_rpc_task_begin(task, NULL);
290 }
291 
292 /*
293  * Mark an RPC call as having completed by clearing the 'active' bit
294  * and then waking up all tasks that were sleeping.
295  */
296 static int rpc_complete_task(struct rpc_task *task)
297 {
298         void *m = &task->tk_runstate;
299         wait_queue_head_t *wq = bit_waitqueue(m, RPC_TASK_ACTIVE);
300         struct wait_bit_key k = __WAIT_BIT_KEY_INITIALIZER(m, RPC_TASK_ACTIVE);
301         unsigned long flags;
302         int ret;
303 
304         trace_rpc_task_complete(task, NULL);
305 
306         spin_lock_irqsave(&wq->lock, flags);
307         clear_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
308         ret = atomic_dec_and_test(&task->tk_count);
309         if (waitqueue_active(wq))
310                 __wake_up_locked_key(wq, TASK_NORMAL, &k);
311         spin_unlock_irqrestore(&wq->lock, flags);
312         return ret;
313 }
314 
315 /*
316  * Allow callers to wait for completion of an RPC call
317  *
318  * Note the use of out_of_line_wait_on_bit() rather than wait_on_bit()
319  * to enforce taking of the wq->lock and hence avoid races with
320  * rpc_complete_task().
321  */
322 int __rpc_wait_for_completion_task(struct rpc_task *task, wait_bit_action_f *action)
323 {
324         if (action == NULL)
325                 action = rpc_wait_bit_killable;
326         return out_of_line_wait_on_bit(&task->tk_runstate, RPC_TASK_ACTIVE,
327                         action, TASK_KILLABLE);
328 }
329 EXPORT_SYMBOL_GPL(__rpc_wait_for_completion_task);
330 
331 /*
332  * Make an RPC task runnable.
333  *
334  * Note: If the task is ASYNC, and is being made runnable after sitting on an
335  * rpc_wait_queue, this must be called with the queue spinlock held to protect
336  * the wait queue operation.
337  * Note the ordering of rpc_test_and_set_running() and rpc_clear_queued(),
338  * which is needed to ensure that __rpc_execute() doesn't loop (due to the
339  * lockless RPC_IS_QUEUED() test) before we've had a chance to test
340  * the RPC_TASK_RUNNING flag.
341  */
342 static void rpc_make_runnable(struct workqueue_struct *wq,
343                 struct rpc_task *task)
344 {
345         bool need_wakeup = !rpc_test_and_set_running(task);
346 
347         rpc_clear_queued(task);
348         if (!need_wakeup)
349                 return;
350         if (RPC_IS_ASYNC(task)) {
351                 INIT_WORK(&task->u.tk_work, rpc_async_schedule);
352                 queue_work(wq, &task->u.tk_work);
353         } else
354                 wake_up_bit(&task->tk_runstate, RPC_TASK_QUEUED);
355 }
356 
357 /*
358  * Prepare for sleeping on a wait queue.
359  * By always appending tasks to the list we ensure FIFO behavior.
360  * NB: An RPC task will only receive interrupt-driven events as long
361  * as it's on a wait queue.
362  */
363 static void __rpc_sleep_on_priority(struct rpc_wait_queue *q,
364                 struct rpc_task *task,
365                 rpc_action action,
366                 unsigned char queue_priority)
367 {
368         dprintk("RPC: %5u sleep_on(queue \"%s\" time %lu)\n",
369                         task->tk_pid, rpc_qname(q), jiffies);
370 
371         trace_rpc_task_sleep(task, q);
372 
373         __rpc_add_wait_queue(q, task, queue_priority);
374 
375         WARN_ON_ONCE(task->tk_callback != NULL);
376         task->tk_callback = action;
377         __rpc_add_timer(q, task);
378 }
379 
380 void rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
381                                 rpc_action action)
382 {
383         /* We shouldn't ever put an inactive task to sleep */
384         WARN_ON_ONCE(!RPC_IS_ACTIVATED(task));
385         if (!RPC_IS_ACTIVATED(task)) {
386                 task->tk_status = -EIO;
387                 rpc_put_task_async(task);
388                 return;
389         }
390 
391         /*
392          * Protect the queue operations.
393          */
394         spin_lock_bh(&q->lock);
395         __rpc_sleep_on_priority(q, task, action, task->tk_priority);
396         spin_unlock_bh(&q->lock);
397 }
398 EXPORT_SYMBOL_GPL(rpc_sleep_on);
399 
400 void rpc_sleep_on_priority(struct rpc_wait_queue *q, struct rpc_task *task,
401                 rpc_action action, int priority)
402 {
403         /* We shouldn't ever put an inactive task to sleep */
404         WARN_ON_ONCE(!RPC_IS_ACTIVATED(task));
405         if (!RPC_IS_ACTIVATED(task)) {
406                 task->tk_status = -EIO;
407                 rpc_put_task_async(task);
408                 return;
409         }
410 
411         /*
412          * Protect the queue operations.
413          */
414         spin_lock_bh(&q->lock);
415         __rpc_sleep_on_priority(q, task, action, priority - RPC_PRIORITY_LOW);
416         spin_unlock_bh(&q->lock);
417 }
418 EXPORT_SYMBOL_GPL(rpc_sleep_on_priority);
419 
420 /**
421  * __rpc_do_wake_up_task_on_wq - wake up a single rpc_task
422  * @wq: workqueue on which to run task
423  * @queue: wait queue
424  * @task: task to be woken up
425  *
426  * Caller must hold queue->lock, and have cleared the task queued flag.
427  */
428 static void __rpc_do_wake_up_task_on_wq(struct workqueue_struct *wq,
429                 struct rpc_wait_queue *queue,
430                 struct rpc_task *task)
431 {
432         dprintk("RPC: %5u __rpc_wake_up_task (now %lu)\n",
433                         task->tk_pid, jiffies);
434 
435         /* Has the task been executed yet? If not, we cannot wake it up! */
436         if (!RPC_IS_ACTIVATED(task)) {
437                 printk(KERN_ERR "RPC: Inactive task (%p) being woken up!\n", task);
438                 return;
439         }
440 
441         trace_rpc_task_wakeup(task, queue);
442 
443         __rpc_remove_wait_queue(queue, task);
444 
445         rpc_make_runnable(wq, task);
446 
447         dprintk("RPC:       __rpc_wake_up_task done\n");
448 }
449 
450 /*
451  * Wake up a queued task while the queue lock is being held
452  */
453 static struct rpc_task *
454 rpc_wake_up_task_on_wq_queue_action_locked(struct workqueue_struct *wq,
455                 struct rpc_wait_queue *queue, struct rpc_task *task,
456                 bool (*action)(struct rpc_task *, void *), void *data)
457 {
458         if (RPC_IS_QUEUED(task)) {
459                 smp_rmb();
460                 if (task->tk_waitqueue == queue) {
461                         if (action == NULL || action(task, data)) {
462                                 __rpc_do_wake_up_task_on_wq(wq, queue, task);
463                                 return task;
464                         }
465                 }
466         }
467         return NULL;
468 }
469 
470 static void
471 rpc_wake_up_task_on_wq_queue_locked(struct workqueue_struct *wq,
472                 struct rpc_wait_queue *queue, struct rpc_task *task)
473 {
474         rpc_wake_up_task_on_wq_queue_action_locked(wq, queue, task, NULL, NULL);
475 }
476 
477 /*
478  * Wake up a queued task while the queue lock is being held
479  */
480 static void rpc_wake_up_task_queue_locked(struct rpc_wait_queue *queue, struct rpc_task *task)
481 {
482         rpc_wake_up_task_on_wq_queue_locked(rpciod_workqueue, queue, task);
483 }
484 
485 /*
486  * Wake up a task on a specific queue
487  */
488 void rpc_wake_up_queued_task_on_wq(struct workqueue_struct *wq,
489                 struct rpc_wait_queue *queue,
490                 struct rpc_task *task)
491 {
492         if (!RPC_IS_QUEUED(task))
493                 return;
494         spin_lock_bh(&queue->lock);
495         rpc_wake_up_task_on_wq_queue_locked(wq, queue, task);
496         spin_unlock_bh(&queue->lock);
497 }
498 
499 /*
500  * Wake up a task on a specific queue
501  */
502 void rpc_wake_up_queued_task(struct rpc_wait_queue *queue, struct rpc_task *task)
503 {
504         if (!RPC_IS_QUEUED(task))
505                 return;
506         spin_lock_bh(&queue->lock);
507         rpc_wake_up_task_queue_locked(queue, task);
508         spin_unlock_bh(&queue->lock);
509 }
510 EXPORT_SYMBOL_GPL(rpc_wake_up_queued_task);
511 
512 static bool rpc_task_action_set_status(struct rpc_task *task, void *status)
513 {
514         task->tk_status = *(int *)status;
515         return true;
516 }
517 
518 static void
519 rpc_wake_up_task_queue_set_status_locked(struct rpc_wait_queue *queue,
520                 struct rpc_task *task, int status)
521 {
522         rpc_wake_up_task_on_wq_queue_action_locked(rpciod_workqueue, queue,
523                         task, rpc_task_action_set_status, &status);
524 }
525 
526 /**
527  * rpc_wake_up_queued_task_set_status - wake up a task and set task->tk_status
528  * @queue: pointer to rpc_wait_queue
529  * @task: pointer to rpc_task
530  * @status: integer error value
531  *
532  * If @task is queued on @queue, then it is woken up, and @task->tk_status is
533  * set to the value of @status.
534  */
535 void
536 rpc_wake_up_queued_task_set_status(struct rpc_wait_queue *queue,
537                 struct rpc_task *task, int status)
538 {
539         if (!RPC_IS_QUEUED(task))
540                 return;
541         spin_lock_bh(&queue->lock);
542         rpc_wake_up_task_queue_set_status_locked(queue, task, status);
543         spin_unlock_bh(&queue->lock);
544 }
545 
546 /*
547  * Wake up the next task on a priority queue.
548  */
549 static struct rpc_task *__rpc_find_next_queued_priority(struct rpc_wait_queue *queue)
550 {
551         struct list_head *q;
552         struct rpc_task *task;
553 
554         /*
555          * Service a batch of tasks from a single owner.
556          */
557         q = &queue->tasks[queue->priority];
558         if (!list_empty(q) && --queue->nr) {
559                 task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
560                 goto out;
561         }
562 
563         /*
564          * Service the next queue.
565          */
566         do {
567                 if (q == &queue->tasks[0])
568                         q = &queue->tasks[queue->maxpriority];
569                 else
570                         q = q - 1;
571                 if (!list_empty(q)) {
572                         task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
573                         goto new_queue;
574                 }
575         } while (q != &queue->tasks[queue->priority]);
576 
577         rpc_reset_waitqueue_priority(queue);
578         return NULL;
579 
580 new_queue:
581         rpc_set_waitqueue_priority(queue, (unsigned int)(q - &queue->tasks[0]));
582 out:
583         return task;
584 }
585 
586 static struct rpc_task *__rpc_find_next_queued(struct rpc_wait_queue *queue)
587 {
588         if (RPC_IS_PRIORITY(queue))
589                 return __rpc_find_next_queued_priority(queue);
590         if (!list_empty(&queue->tasks[0]))
591                 return list_first_entry(&queue->tasks[0], struct rpc_task, u.tk_wait.list);
592         return NULL;
593 }
594 
595 /*
596  * Wake up the first task on the wait queue.
597  */
598 struct rpc_task *rpc_wake_up_first_on_wq(struct workqueue_struct *wq,
599                 struct rpc_wait_queue *queue,
600                 bool (*func)(struct rpc_task *, void *), void *data)
601 {
602         struct rpc_task *task = NULL;
603 
604         dprintk("RPC:       wake_up_first(%p \"%s\")\n",
605                         queue, rpc_qname(queue));
606         spin_lock_bh(&queue->lock);
607         task = __rpc_find_next_queued(queue);
608         if (task != NULL)
609                 task = rpc_wake_up_task_on_wq_queue_action_locked(wq, queue,
610                                 task, func, data);
611         spin_unlock_bh(&queue->lock);
612 
613         return task;
614 }
615 
616 /*
617  * Wake up the first task on the wait queue.
618  */
619 struct rpc_task *rpc_wake_up_first(struct rpc_wait_queue *queue,
620                 bool (*func)(struct rpc_task *, void *), void *data)
621 {
622         return rpc_wake_up_first_on_wq(rpciod_workqueue, queue, func, data);
623 }
624 EXPORT_SYMBOL_GPL(rpc_wake_up_first);
625 
626 static bool rpc_wake_up_next_func(struct rpc_task *task, void *data)
627 {
628         return true;
629 }
630 
631 /*
632  * Wake up the next task on the wait queue.
633 */
634 struct rpc_task *rpc_wake_up_next(struct rpc_wait_queue *queue)
635 {
636         return rpc_wake_up_first(queue, rpc_wake_up_next_func, NULL);
637 }
638 EXPORT_SYMBOL_GPL(rpc_wake_up_next);
639 
640 /**
641  * rpc_wake_up - wake up all rpc_tasks
642  * @queue: rpc_wait_queue on which the tasks are sleeping
643  *
644  * Grabs queue->lock
645  */
646 void rpc_wake_up(struct rpc_wait_queue *queue)
647 {
648         struct list_head *head;
649 
650         spin_lock_bh(&queue->lock);
651         head = &queue->tasks[queue->maxpriority];
652         for (;;) {
653                 while (!list_empty(head)) {
654                         struct rpc_task *task;
655                         task = list_first_entry(head,
656                                         struct rpc_task,
657                                         u.tk_wait.list);
658                         rpc_wake_up_task_queue_locked(queue, task);
659                 }
660                 if (head == &queue->tasks[0])
661                         break;
662                 head--;
663         }
664         spin_unlock_bh(&queue->lock);
665 }
666 EXPORT_SYMBOL_GPL(rpc_wake_up);
667 
668 /**
669  * rpc_wake_up_status - wake up all rpc_tasks and set their status value.
670  * @queue: rpc_wait_queue on which the tasks are sleeping
671  * @status: status value to set
672  *
673  * Grabs queue->lock
674  */
675 void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
676 {
677         struct list_head *head;
678 
679         spin_lock_bh(&queue->lock);
680         head = &queue->tasks[queue->maxpriority];
681         for (;;) {
682                 while (!list_empty(head)) {
683                         struct rpc_task *task;
684                         task = list_first_entry(head,
685                                         struct rpc_task,
686                                         u.tk_wait.list);
687                         task->tk_status = status;
688                         rpc_wake_up_task_queue_locked(queue, task);
689                 }
690                 if (head == &queue->tasks[0])
691                         break;
692                 head--;
693         }
694         spin_unlock_bh(&queue->lock);
695 }
696 EXPORT_SYMBOL_GPL(rpc_wake_up_status);
697 
698 static void __rpc_queue_timer_fn(struct timer_list *t)
699 {
700         struct rpc_wait_queue *queue = from_timer(queue, t, timer_list.timer);
701         struct rpc_task *task, *n;
702         unsigned long expires, now, timeo;
703 
704         spin_lock(&queue->lock);
705         expires = now = jiffies;
706         list_for_each_entry_safe(task, n, &queue->timer_list.list, u.tk_wait.timer_list) {
707                 timeo = task->u.tk_wait.expires;
708                 if (time_after_eq(now, timeo)) {
709                         dprintk("RPC: %5u timeout\n", task->tk_pid);
710                         task->tk_status = -ETIMEDOUT;
711                         rpc_wake_up_task_queue_locked(queue, task);
712                         continue;
713                 }
714                 if (expires == now || time_after(expires, timeo))
715                         expires = timeo;
716         }
717         if (!list_empty(&queue->timer_list.list))
718                 rpc_set_queue_timer(queue, expires);
719         spin_unlock(&queue->lock);
720 }
721 
722 static void __rpc_atrun(struct rpc_task *task)
723 {
724         if (task->tk_status == -ETIMEDOUT)
725                 task->tk_status = 0;
726 }
727 
728 /*
729  * Run a task at a later time
730  */
731 void rpc_delay(struct rpc_task *task, unsigned long delay)
732 {
733         task->tk_timeout = delay;
734         rpc_sleep_on(&delay_queue, task, __rpc_atrun);
735 }
736 EXPORT_SYMBOL_GPL(rpc_delay);
737 
738 /*
739  * Helper to call task->tk_ops->rpc_call_prepare
740  */
741 void rpc_prepare_task(struct rpc_task *task)
742 {
743         task->tk_ops->rpc_call_prepare(task, task->tk_calldata);
744 }
745 
746 static void
747 rpc_init_task_statistics(struct rpc_task *task)
748 {
749         /* Initialize retry counters */
750         task->tk_garb_retry = 2;
751         task->tk_cred_retry = 2;
752         task->tk_rebind_retry = 2;
753 
754         /* starting timestamp */
755         task->tk_start = ktime_get();
756 }
757 
758 static void
759 rpc_reset_task_statistics(struct rpc_task *task)
760 {
761         task->tk_timeouts = 0;
762         task->tk_flags &= ~(RPC_CALL_MAJORSEEN|RPC_TASK_KILLED|RPC_TASK_SENT);
763 
764         rpc_init_task_statistics(task);
765 }
766 
767 /*
768  * Helper that calls task->tk_ops->rpc_call_done if it exists
769  */
770 void rpc_exit_task(struct rpc_task *task)
771 {
772         task->tk_action = NULL;
773         if (task->tk_ops->rpc_call_done != NULL) {
774                 task->tk_ops->rpc_call_done(task, task->tk_calldata);
775                 if (task->tk_action != NULL) {
776                         WARN_ON(RPC_ASSASSINATED(task));
777                         /* Always release the RPC slot and buffer memory */
778                         xprt_release(task);
779                         rpc_reset_task_statistics(task);
780                 }
781         }
782 }
783 
784 void rpc_exit(struct rpc_task *task, int status)
785 {
786         task->tk_status = status;
787         task->tk_action = rpc_exit_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         unsigned int pflags = memalloc_nofs_save();
906 
907         __rpc_execute(container_of(work, struct rpc_task, u.tk_work));
908         memalloc_nofs_restore(pflags);
909 }
910 
911 /**
912  * rpc_malloc - allocate RPC buffer resources
913  * @task: RPC task
914  *
915  * A single memory region is allocated, which is split between the
916  * RPC call and RPC reply that this task is being used for. When
917  * this RPC is retired, the memory is released by calling rpc_free.
918  *
919  * To prevent rpciod from hanging, this allocator never sleeps,
920  * returning -ENOMEM and suppressing warning if the request cannot
921  * be serviced immediately. The caller can arrange to sleep in a
922  * way that is safe for rpciod.
923  *
924  * Most requests are 'small' (under 2KiB) and can be serviced from a
925  * mempool, ensuring that NFS reads and writes can always proceed,
926  * and that there is good locality of reference for these buffers.
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_NOFS;
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_NOFS);
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         unsigned int pflags = memalloc_nofs_save();
1071 
1072         rpc_free_task(container_of(work, struct rpc_task, u.tk_work));
1073         memalloc_nofs_restore(pflags);
1074 }
1075 
1076 static void rpc_release_resources_task(struct rpc_task *task)
1077 {
1078         xprt_release(task);
1079         if (task->tk_msg.rpc_cred) {
1080                 put_cred(task->tk_msg.rpc_cred);
1081                 task->tk_msg.rpc_cred = NULL;
1082         }
1083         rpc_task_release_client(task);
1084 }
1085 
1086 static void rpc_final_put_task(struct rpc_task *task,
1087                 struct workqueue_struct *q)
1088 {
1089         if (q != NULL) {
1090                 INIT_WORK(&task->u.tk_work, rpc_async_release);
1091                 queue_work(q, &task->u.tk_work);
1092         } else
1093                 rpc_free_task(task);
1094 }
1095 
1096 static void rpc_do_put_task(struct rpc_task *task, struct workqueue_struct *q)
1097 {
1098         if (atomic_dec_and_test(&task->tk_count)) {
1099                 rpc_release_resources_task(task);
1100                 rpc_final_put_task(task, q);
1101         }
1102 }
1103 
1104 void rpc_put_task(struct rpc_task *task)
1105 {
1106         rpc_do_put_task(task, NULL);
1107 }
1108 EXPORT_SYMBOL_GPL(rpc_put_task);
1109 
1110 void rpc_put_task_async(struct rpc_task *task)
1111 {
1112         rpc_do_put_task(task, task->tk_workqueue);
1113 }
1114 EXPORT_SYMBOL_GPL(rpc_put_task_async);
1115 
1116 static void rpc_release_task(struct rpc_task *task)
1117 {
1118         dprintk("RPC: %5u release task\n", task->tk_pid);
1119 
1120         WARN_ON_ONCE(RPC_IS_QUEUED(task));
1121 
1122         rpc_release_resources_task(task);
1123 
1124         /*
1125          * Note: at this point we have been removed from rpc_clnt->cl_tasks,
1126          * so it should be safe to use task->tk_count as a test for whether
1127          * or not any other processes still hold references to our rpc_task.
1128          */
1129         if (atomic_read(&task->tk_count) != 1 + !RPC_IS_ASYNC(task)) {
1130                 /* Wake up anyone who may be waiting for task completion */
1131                 if (!rpc_complete_task(task))
1132                         return;
1133         } else {
1134                 if (!atomic_dec_and_test(&task->tk_count))
1135                         return;
1136         }
1137         rpc_final_put_task(task, task->tk_workqueue);
1138 }
1139 
1140 int rpciod_up(void)
1141 {
1142         return try_module_get(THIS_MODULE) ? 0 : -EINVAL;
1143 }
1144 
1145 void rpciod_down(void)
1146 {
1147         module_put(THIS_MODULE);
1148 }
1149 
1150 /*
1151  * Start up the rpciod workqueue.
1152  */
1153 static int rpciod_start(void)
1154 {
1155         struct workqueue_struct *wq;
1156 
1157         /*
1158          * Create the rpciod thread and wait for it to start.
1159          */
1160         dprintk("RPC:       creating workqueue rpciod\n");
1161         wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
1162         if (!wq)
1163                 goto out_failed;
1164         rpciod_workqueue = wq;
1165         /* Note: highpri because network receive is latency sensitive */
1166         wq = alloc_workqueue("xprtiod", WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_HIGHPRI, 0);
1167         if (!wq)
1168                 goto free_rpciod;
1169         xprtiod_workqueue = wq;
1170         return 1;
1171 free_rpciod:
1172         wq = rpciod_workqueue;
1173         rpciod_workqueue = NULL;
1174         destroy_workqueue(wq);
1175 out_failed:
1176         return 0;
1177 }
1178 
1179 static void rpciod_stop(void)
1180 {
1181         struct workqueue_struct *wq = NULL;
1182 
1183         if (rpciod_workqueue == NULL)
1184                 return;
1185         dprintk("RPC:       destroying workqueue rpciod\n");
1186 
1187         wq = rpciod_workqueue;
1188         rpciod_workqueue = NULL;
1189         destroy_workqueue(wq);
1190         wq = xprtiod_workqueue;
1191         xprtiod_workqueue = NULL;
1192         destroy_workqueue(wq);
1193 }
1194 
1195 void
1196 rpc_destroy_mempool(void)
1197 {
1198         rpciod_stop();
1199         mempool_destroy(rpc_buffer_mempool);
1200         mempool_destroy(rpc_task_mempool);
1201         kmem_cache_destroy(rpc_task_slabp);
1202         kmem_cache_destroy(rpc_buffer_slabp);
1203         rpc_destroy_wait_queue(&delay_queue);
1204 }
1205 
1206 int
1207 rpc_init_mempool(void)
1208 {
1209         /*
1210          * The following is not strictly a mempool initialisation,
1211          * but there is no harm in doing it here
1212          */
1213         rpc_init_wait_queue(&delay_queue, "delayq");
1214         if (!rpciod_start())
1215                 goto err_nomem;
1216 
1217         rpc_task_slabp = kmem_cache_create("rpc_tasks",
1218                                              sizeof(struct rpc_task),
1219                                              0, SLAB_HWCACHE_ALIGN,
1220                                              NULL);
1221         if (!rpc_task_slabp)
1222                 goto err_nomem;
1223         rpc_buffer_slabp = kmem_cache_create("rpc_buffers",
1224                                              RPC_BUFFER_MAXSIZE,
1225                                              0, SLAB_HWCACHE_ALIGN,
1226                                              NULL);
1227         if (!rpc_buffer_slabp)
1228                 goto err_nomem;
1229         rpc_task_mempool = mempool_create_slab_pool(RPC_TASK_POOLSIZE,
1230                                                     rpc_task_slabp);
1231         if (!rpc_task_mempool)
1232                 goto err_nomem;
1233         rpc_buffer_mempool = mempool_create_slab_pool(RPC_BUFFER_POOLSIZE,
1234                                                       rpc_buffer_slabp);
1235         if (!rpc_buffer_mempool)
1236                 goto err_nomem;
1237         return 0;
1238 err_nomem:
1239         rpc_destroy_mempool();
1240         return -ENOMEM;
1241 }
1242 

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