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19#include <linux/kthread.h>
20#include <linux/slab.h>
21#include <linux/list.h>
22#include <linux/spinlock.h>
23#include <linux/freezer.h>
24#include "async-thread.h"
25
26#define WORK_QUEUED_BIT 0
27#define WORK_DONE_BIT 1
28#define WORK_ORDER_DONE_BIT 2
29#define WORK_HIGH_PRIO_BIT 3
30
31
32
33
34
35struct btrfs_worker_thread {
36
37 struct btrfs_workers *workers;
38
39
40 struct list_head pending;
41 struct list_head prio_pending;
42
43
44 struct list_head worker_list;
45
46
47 struct task_struct *task;
48
49
50 atomic_t num_pending;
51
52
53 atomic_t refs;
54
55 unsigned long sequence;
56
57
58 spinlock_t lock;
59
60
61 int working;
62
63
64 int idle;
65};
66
67static int __btrfs_start_workers(struct btrfs_workers *workers);
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84struct worker_start {
85 struct btrfs_work work;
86 struct btrfs_workers *queue;
87};
88
89static void start_new_worker_func(struct btrfs_work *work)
90{
91 struct worker_start *start;
92 start = container_of(work, struct worker_start, work);
93 __btrfs_start_workers(start->queue);
94 kfree(start);
95}
96
97
98
99
100
101static void check_idle_worker(struct btrfs_worker_thread *worker)
102{
103 if (!worker->idle && atomic_read(&worker->num_pending) <
104 worker->workers->idle_thresh / 2) {
105 unsigned long flags;
106 spin_lock_irqsave(&worker->workers->lock, flags);
107 worker->idle = 1;
108
109
110 if (!list_empty(&worker->worker_list)) {
111 list_move(&worker->worker_list,
112 &worker->workers->idle_list);
113 }
114 spin_unlock_irqrestore(&worker->workers->lock, flags);
115 }
116}
117
118
119
120
121
122static void check_busy_worker(struct btrfs_worker_thread *worker)
123{
124 if (worker->idle && atomic_read(&worker->num_pending) >=
125 worker->workers->idle_thresh) {
126 unsigned long flags;
127 spin_lock_irqsave(&worker->workers->lock, flags);
128 worker->idle = 0;
129
130 if (!list_empty(&worker->worker_list)) {
131 list_move_tail(&worker->worker_list,
132 &worker->workers->worker_list);
133 }
134 spin_unlock_irqrestore(&worker->workers->lock, flags);
135 }
136}
137
138static void check_pending_worker_creates(struct btrfs_worker_thread *worker)
139{
140 struct btrfs_workers *workers = worker->workers;
141 struct worker_start *start;
142 unsigned long flags;
143
144 rmb();
145 if (!workers->atomic_start_pending)
146 return;
147
148 start = kzalloc(sizeof(*start), GFP_NOFS);
149 if (!start)
150 return;
151
152 start->work.func = start_new_worker_func;
153 start->queue = workers;
154
155 spin_lock_irqsave(&workers->lock, flags);
156 if (!workers->atomic_start_pending)
157 goto out;
158
159 workers->atomic_start_pending = 0;
160 if (workers->num_workers + workers->num_workers_starting >=
161 workers->max_workers)
162 goto out;
163
164 workers->num_workers_starting += 1;
165 spin_unlock_irqrestore(&workers->lock, flags);
166 btrfs_queue_worker(workers->atomic_worker_start, &start->work);
167 return;
168
169out:
170 kfree(start);
171 spin_unlock_irqrestore(&workers->lock, flags);
172}
173
174static noinline void run_ordered_completions(struct btrfs_workers *workers,
175 struct btrfs_work *work)
176{
177 if (!workers->ordered)
178 return;
179
180 set_bit(WORK_DONE_BIT, &work->flags);
181
182 spin_lock(&workers->order_lock);
183
184 while (1) {
185 if (!list_empty(&workers->prio_order_list)) {
186 work = list_entry(workers->prio_order_list.next,
187 struct btrfs_work, order_list);
188 } else if (!list_empty(&workers->order_list)) {
189 work = list_entry(workers->order_list.next,
190 struct btrfs_work, order_list);
191 } else {
192 break;
193 }
194 if (!test_bit(WORK_DONE_BIT, &work->flags))
195 break;
196
197
198
199
200
201
202 if (test_and_set_bit(WORK_ORDER_DONE_BIT, &work->flags))
203 break;
204
205 spin_unlock(&workers->order_lock);
206
207 work->ordered_func(work);
208
209
210 spin_lock(&workers->order_lock);
211 list_del(&work->order_list);
212 spin_unlock(&workers->order_lock);
213
214
215
216
217
218 work->ordered_free(work);
219 spin_lock(&workers->order_lock);
220 }
221
222 spin_unlock(&workers->order_lock);
223}
224
225static void put_worker(struct btrfs_worker_thread *worker)
226{
227 if (atomic_dec_and_test(&worker->refs))
228 kfree(worker);
229}
230
231static int try_worker_shutdown(struct btrfs_worker_thread *worker)
232{
233 int freeit = 0;
234
235 spin_lock_irq(&worker->lock);
236 spin_lock(&worker->workers->lock);
237 if (worker->workers->num_workers > 1 &&
238 worker->idle &&
239 !worker->working &&
240 !list_empty(&worker->worker_list) &&
241 list_empty(&worker->prio_pending) &&
242 list_empty(&worker->pending) &&
243 atomic_read(&worker->num_pending) == 0) {
244 freeit = 1;
245 list_del_init(&worker->worker_list);
246 worker->workers->num_workers--;
247 }
248 spin_unlock(&worker->workers->lock);
249 spin_unlock_irq(&worker->lock);
250
251 if (freeit)
252 put_worker(worker);
253 return freeit;
254}
255
256static struct btrfs_work *get_next_work(struct btrfs_worker_thread *worker,
257 struct list_head *prio_head,
258 struct list_head *head)
259{
260 struct btrfs_work *work = NULL;
261 struct list_head *cur = NULL;
262
263 if(!list_empty(prio_head))
264 cur = prio_head->next;
265
266 smp_mb();
267 if (!list_empty(&worker->prio_pending))
268 goto refill;
269
270 if (!list_empty(head))
271 cur = head->next;
272
273 if (cur)
274 goto out;
275
276refill:
277 spin_lock_irq(&worker->lock);
278 list_splice_tail_init(&worker->prio_pending, prio_head);
279 list_splice_tail_init(&worker->pending, head);
280
281 if (!list_empty(prio_head))
282 cur = prio_head->next;
283 else if (!list_empty(head))
284 cur = head->next;
285 spin_unlock_irq(&worker->lock);
286
287 if (!cur)
288 goto out_fail;
289
290out:
291 work = list_entry(cur, struct btrfs_work, list);
292
293out_fail:
294 return work;
295}
296
297
298
299
300static int worker_loop(void *arg)
301{
302 struct btrfs_worker_thread *worker = arg;
303 struct list_head head;
304 struct list_head prio_head;
305 struct btrfs_work *work;
306
307 INIT_LIST_HEAD(&head);
308 INIT_LIST_HEAD(&prio_head);
309
310 do {
311again:
312 while (1) {
313
314
315 work = get_next_work(worker, &prio_head, &head);
316 if (!work)
317 break;
318
319 list_del(&work->list);
320 clear_bit(WORK_QUEUED_BIT, &work->flags);
321
322 work->worker = worker;
323
324 work->func(work);
325
326 atomic_dec(&worker->num_pending);
327
328
329
330
331 run_ordered_completions(worker->workers, work);
332
333 check_pending_worker_creates(worker);
334 cond_resched();
335 }
336
337 spin_lock_irq(&worker->lock);
338 check_idle_worker(worker);
339
340 if (freezing(current)) {
341 worker->working = 0;
342 spin_unlock_irq(&worker->lock);
343 try_to_freeze();
344 } else {
345 spin_unlock_irq(&worker->lock);
346 if (!kthread_should_stop()) {
347 cpu_relax();
348
349
350
351
352 smp_mb();
353 if (!list_empty(&worker->pending) ||
354 !list_empty(&worker->prio_pending))
355 continue;
356
357
358
359
360
361
362
363
364
365 schedule_timeout(1);
366 smp_mb();
367 if (!list_empty(&worker->pending) ||
368 !list_empty(&worker->prio_pending))
369 continue;
370
371 if (kthread_should_stop())
372 break;
373
374
375 spin_lock_irq(&worker->lock);
376 set_current_state(TASK_INTERRUPTIBLE);
377 if (!list_empty(&worker->pending) ||
378 !list_empty(&worker->prio_pending)) {
379 spin_unlock_irq(&worker->lock);
380 set_current_state(TASK_RUNNING);
381 goto again;
382 }
383
384
385
386
387
388 worker->working = 0;
389 spin_unlock_irq(&worker->lock);
390
391 if (!kthread_should_stop()) {
392 schedule_timeout(HZ * 120);
393 if (!worker->working &&
394 try_worker_shutdown(worker)) {
395 return 0;
396 }
397 }
398 }
399 __set_current_state(TASK_RUNNING);
400 }
401 } while (!kthread_should_stop());
402 return 0;
403}
404
405
406
407
408void btrfs_stop_workers(struct btrfs_workers *workers)
409{
410 struct list_head *cur;
411 struct btrfs_worker_thread *worker;
412 int can_stop;
413
414 spin_lock_irq(&workers->lock);
415 list_splice_init(&workers->idle_list, &workers->worker_list);
416 while (!list_empty(&workers->worker_list)) {
417 cur = workers->worker_list.next;
418 worker = list_entry(cur, struct btrfs_worker_thread,
419 worker_list);
420
421 atomic_inc(&worker->refs);
422 workers->num_workers -= 1;
423 if (!list_empty(&worker->worker_list)) {
424 list_del_init(&worker->worker_list);
425 put_worker(worker);
426 can_stop = 1;
427 } else
428 can_stop = 0;
429 spin_unlock_irq(&workers->lock);
430 if (can_stop)
431 kthread_stop(worker->task);
432 spin_lock_irq(&workers->lock);
433 put_worker(worker);
434 }
435 spin_unlock_irq(&workers->lock);
436}
437
438
439
440
441void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max,
442 struct btrfs_workers *async_helper)
443{
444 workers->num_workers = 0;
445 workers->num_workers_starting = 0;
446 INIT_LIST_HEAD(&workers->worker_list);
447 INIT_LIST_HEAD(&workers->idle_list);
448 INIT_LIST_HEAD(&workers->order_list);
449 INIT_LIST_HEAD(&workers->prio_order_list);
450 spin_lock_init(&workers->lock);
451 spin_lock_init(&workers->order_lock);
452 workers->max_workers = max;
453 workers->idle_thresh = 32;
454 workers->name = name;
455 workers->ordered = 0;
456 workers->atomic_start_pending = 0;
457 workers->atomic_worker_start = async_helper;
458}
459
460
461
462
463
464static int __btrfs_start_workers(struct btrfs_workers *workers)
465{
466 struct btrfs_worker_thread *worker;
467 int ret = 0;
468
469 worker = kzalloc(sizeof(*worker), GFP_NOFS);
470 if (!worker) {
471 ret = -ENOMEM;
472 goto fail;
473 }
474
475 INIT_LIST_HEAD(&worker->pending);
476 INIT_LIST_HEAD(&worker->prio_pending);
477 INIT_LIST_HEAD(&worker->worker_list);
478 spin_lock_init(&worker->lock);
479
480 atomic_set(&worker->num_pending, 0);
481 atomic_set(&worker->refs, 1);
482 worker->workers = workers;
483 worker->task = kthread_run(worker_loop, worker,
484 "btrfs-%s-%d", workers->name,
485 workers->num_workers + 1);
486 if (IS_ERR(worker->task)) {
487 ret = PTR_ERR(worker->task);
488 kfree(worker);
489 goto fail;
490 }
491 spin_lock_irq(&workers->lock);
492 list_add_tail(&worker->worker_list, &workers->idle_list);
493 worker->idle = 1;
494 workers->num_workers++;
495 workers->num_workers_starting--;
496 WARN_ON(workers->num_workers_starting < 0);
497 spin_unlock_irq(&workers->lock);
498
499 return 0;
500fail:
501 spin_lock_irq(&workers->lock);
502 workers->num_workers_starting--;
503 spin_unlock_irq(&workers->lock);
504 return ret;
505}
506
507int btrfs_start_workers(struct btrfs_workers *workers)
508{
509 spin_lock_irq(&workers->lock);
510 workers->num_workers_starting++;
511 spin_unlock_irq(&workers->lock);
512 return __btrfs_start_workers(workers);
513}
514
515
516
517
518
519
520static struct btrfs_worker_thread *next_worker(struct btrfs_workers *workers)
521{
522 struct btrfs_worker_thread *worker;
523 struct list_head *next;
524 int enforce_min;
525
526 enforce_min = (workers->num_workers + workers->num_workers_starting) <
527 workers->max_workers;
528
529
530
531
532
533
534
535 if (!list_empty(&workers->idle_list)) {
536 next = workers->idle_list.next;
537 worker = list_entry(next, struct btrfs_worker_thread,
538 worker_list);
539 return worker;
540 }
541 if (enforce_min || list_empty(&workers->worker_list))
542 return NULL;
543
544
545
546
547
548
549
550 next = workers->worker_list.next;
551 worker = list_entry(next, struct btrfs_worker_thread, worker_list);
552 worker->sequence++;
553
554 if (worker->sequence % workers->idle_thresh == 0)
555 list_move_tail(next, &workers->worker_list);
556 return worker;
557}
558
559
560
561
562
563
564static struct btrfs_worker_thread *find_worker(struct btrfs_workers *workers)
565{
566 struct btrfs_worker_thread *worker;
567 unsigned long flags;
568 struct list_head *fallback;
569 int ret;
570
571 spin_lock_irqsave(&workers->lock, flags);
572again:
573 worker = next_worker(workers);
574
575 if (!worker) {
576 if (workers->num_workers + workers->num_workers_starting >=
577 workers->max_workers) {
578 goto fallback;
579 } else if (workers->atomic_worker_start) {
580 workers->atomic_start_pending = 1;
581 goto fallback;
582 } else {
583 workers->num_workers_starting++;
584 spin_unlock_irqrestore(&workers->lock, flags);
585
586 ret = __btrfs_start_workers(workers);
587 spin_lock_irqsave(&workers->lock, flags);
588 if (ret)
589 goto fallback;
590 goto again;
591 }
592 }
593 goto found;
594
595fallback:
596 fallback = NULL;
597
598
599
600
601 if (!list_empty(&workers->worker_list))
602 fallback = workers->worker_list.next;
603 if (!list_empty(&workers->idle_list))
604 fallback = workers->idle_list.next;
605 BUG_ON(!fallback);
606 worker = list_entry(fallback,
607 struct btrfs_worker_thread, worker_list);
608found:
609
610
611
612
613 atomic_inc(&worker->num_pending);
614 spin_unlock_irqrestore(&workers->lock, flags);
615 return worker;
616}
617
618
619
620
621
622
623void btrfs_requeue_work(struct btrfs_work *work)
624{
625 struct btrfs_worker_thread *worker = work->worker;
626 unsigned long flags;
627 int wake = 0;
628
629 if (test_and_set_bit(WORK_QUEUED_BIT, &work->flags))
630 return;
631
632 spin_lock_irqsave(&worker->lock, flags);
633 if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags))
634 list_add_tail(&work->list, &worker->prio_pending);
635 else
636 list_add_tail(&work->list, &worker->pending);
637 atomic_inc(&worker->num_pending);
638
639
640
641
642 if (worker->idle) {
643 spin_lock(&worker->workers->lock);
644 worker->idle = 0;
645 list_move_tail(&worker->worker_list,
646 &worker->workers->worker_list);
647 spin_unlock(&worker->workers->lock);
648 }
649 if (!worker->working) {
650 wake = 1;
651 worker->working = 1;
652 }
653
654 if (wake)
655 wake_up_process(worker->task);
656 spin_unlock_irqrestore(&worker->lock, flags);
657}
658
659void btrfs_set_work_high_prio(struct btrfs_work *work)
660{
661 set_bit(WORK_HIGH_PRIO_BIT, &work->flags);
662}
663
664
665
666
667void btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work)
668{
669 struct btrfs_worker_thread *worker;
670 unsigned long flags;
671 int wake = 0;
672
673
674 if (test_and_set_bit(WORK_QUEUED_BIT, &work->flags))
675 return;
676
677 worker = find_worker(workers);
678 if (workers->ordered) {
679
680
681
682
683 spin_lock(&workers->order_lock);
684 if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags)) {
685 list_add_tail(&work->order_list,
686 &workers->prio_order_list);
687 } else {
688 list_add_tail(&work->order_list, &workers->order_list);
689 }
690 spin_unlock(&workers->order_lock);
691 } else {
692 INIT_LIST_HEAD(&work->order_list);
693 }
694
695 spin_lock_irqsave(&worker->lock, flags);
696
697 if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags))
698 list_add_tail(&work->list, &worker->prio_pending);
699 else
700 list_add_tail(&work->list, &worker->pending);
701 check_busy_worker(worker);
702
703
704
705
706
707 if (!worker->working)
708 wake = 1;
709 worker->working = 1;
710
711 if (wake)
712 wake_up_process(worker->task);
713 spin_unlock_irqrestore(&worker->lock, flags);
714}
715