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

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