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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Basic worker thread pool for io_uring
4 *
5 * Copyright (C) 2019 Jens Axboe
6 *
7 */
8#include <linux/kernel.h>
9#include <linux/init.h>
10#include <linux/errno.h>
11#include <linux/sched/signal.h>
12#include <linux/mm.h>
13#include <linux/sched/mm.h>
14#include <linux/percpu.h>
15#include <linux/slab.h>
16#include <linux/kthread.h>
17#include <linux/rculist_nulls.h>
18#include <linux/fs_struct.h>
19#include <linux/task_work.h>
20
21#include "io-wq.h"
22
23#define WORKER_IDLE_TIMEOUT (5 * HZ)
24
25enum {
26 IO_WORKER_F_UP = 1, /* up and active */
27 IO_WORKER_F_RUNNING = 2, /* account as running */
28 IO_WORKER_F_FREE = 4, /* worker on free list */
29 IO_WORKER_F_EXITING = 8, /* worker exiting */
30 IO_WORKER_F_FIXED = 16, /* static idle worker */
31 IO_WORKER_F_BOUND = 32, /* is doing bounded work */
32};
33
34enum {
35 IO_WQ_BIT_EXIT = 0, /* wq exiting */
36 IO_WQ_BIT_CANCEL = 1, /* cancel work on list */
37 IO_WQ_BIT_ERROR = 2, /* error on setup */
38};
39
40enum {
41 IO_WQE_FLAG_STALLED = 1, /* stalled on hash */
42};
43
44/*
45 * One for each thread in a wqe pool
46 */
47struct io_worker {
48 refcount_t ref;
49 unsigned flags;
50 struct hlist_nulls_node nulls_node;
51 struct list_head all_list;
52 struct task_struct *task;
53 struct io_wqe *wqe;
54
55 struct io_wq_work *cur_work;
56 spinlock_t lock;
57
58 struct rcu_head rcu;
59 struct mm_struct *mm;
60 const struct cred *cur_creds;
61 const struct cred *saved_creds;
62 struct files_struct *restore_files;
63 struct fs_struct *restore_fs;
64};
65
66#if BITS_PER_LONG == 64
67#define IO_WQ_HASH_ORDER 6
68#else
69#define IO_WQ_HASH_ORDER 5
70#endif
71
72#define IO_WQ_NR_HASH_BUCKETS (1u << IO_WQ_HASH_ORDER)
73
74struct io_wqe_acct {
75 unsigned nr_workers;
76 unsigned max_workers;
77 atomic_t nr_running;
78};
79
80enum {
81 IO_WQ_ACCT_BOUND,
82 IO_WQ_ACCT_UNBOUND,
83};
84
85/*
86 * Per-node worker thread pool
87 */
88struct io_wqe {
89 struct {
90 spinlock_t lock;
91 struct io_wq_work_list work_list;
92 unsigned long hash_map;
93 unsigned flags;
94 } ____cacheline_aligned_in_smp;
95
96 int node;
97 struct io_wqe_acct acct[2];
98
99 struct hlist_nulls_head free_list;
100 struct list_head all_list;
101
102 struct io_wq *wq;
103 struct io_wq_work *hash_tail[IO_WQ_NR_HASH_BUCKETS];
104};
105
106/*
107 * Per io_wq state
108 */
109struct io_wq {
110 struct io_wqe **wqes;
111 unsigned long state;
112
113 free_work_fn *free_work;
114 io_wq_work_fn *do_work;
115
116 struct task_struct *manager;
117 struct user_struct *user;
118 refcount_t refs;
119 struct completion done;
120
121 refcount_t use_refs;
122};
123
124static bool io_worker_get(struct io_worker *worker)
125{
126 return refcount_inc_not_zero(&worker->ref);
127}
128
129static void io_worker_release(struct io_worker *worker)
130{
131 if (refcount_dec_and_test(&worker->ref))
132 wake_up_process(worker->task);
133}
134
135/*
136 * Note: drops the wqe->lock if returning true! The caller must re-acquire
137 * the lock in that case. Some callers need to restart handling if this
138 * happens, so we can't just re-acquire the lock on behalf of the caller.
139 */
140static bool __io_worker_unuse(struct io_wqe *wqe, struct io_worker *worker)
141{
142 bool dropped_lock = false;
143
144 if (worker->saved_creds) {
145 revert_creds(worker->saved_creds);
146 worker->cur_creds = worker->saved_creds = NULL;
147 }
148
149 if (current->files != worker->restore_files) {
150 __acquire(&wqe->lock);
151 spin_unlock_irq(&wqe->lock);
152 dropped_lock = true;
153
154 task_lock(current);
155 current->files = worker->restore_files;
156 task_unlock(current);
157 }
158
159 if (current->fs != worker->restore_fs)
160 current->fs = worker->restore_fs;
161
162 /*
163 * If we have an active mm, we need to drop the wq lock before unusing
164 * it. If we do, return true and let the caller retry the idle loop.
165 */
166 if (worker->mm) {
167 if (!dropped_lock) {
168 __acquire(&wqe->lock);
169 spin_unlock_irq(&wqe->lock);
170 dropped_lock = true;
171 }
172 __set_current_state(TASK_RUNNING);
173 kthread_unuse_mm(worker->mm);
174 mmput(worker->mm);
175 worker->mm = NULL;
176 }
177
178 return dropped_lock;
179}
180
181static inline struct io_wqe_acct *io_work_get_acct(struct io_wqe *wqe,
182 struct io_wq_work *work)
183{
184 if (work->flags & IO_WQ_WORK_UNBOUND)
185 return &wqe->acct[IO_WQ_ACCT_UNBOUND];
186
187 return &wqe->acct[IO_WQ_ACCT_BOUND];
188}
189
190static inline struct io_wqe_acct *io_wqe_get_acct(struct io_wqe *wqe,
191 struct io_worker *worker)
192{
193 if (worker->flags & IO_WORKER_F_BOUND)
194 return &wqe->acct[IO_WQ_ACCT_BOUND];
195
196 return &wqe->acct[IO_WQ_ACCT_UNBOUND];
197}
198
199static void io_worker_exit(struct io_worker *worker)
200{
201 struct io_wqe *wqe = worker->wqe;
202 struct io_wqe_acct *acct = io_wqe_get_acct(wqe, worker);
203 unsigned nr_workers;
204
205 /*
206 * If we're not at zero, someone else is holding a brief reference
207 * to the worker. Wait for that to go away.
208 */
209 set_current_state(TASK_INTERRUPTIBLE);
210 if (!refcount_dec_and_test(&worker->ref))
211 schedule();
212 __set_current_state(TASK_RUNNING);
213
214 preempt_disable();
215 current->flags &= ~PF_IO_WORKER;
216 if (worker->flags & IO_WORKER_F_RUNNING)
217 atomic_dec(&acct->nr_running);
218 if (!(worker->flags & IO_WORKER_F_BOUND))
219 atomic_dec(&wqe->wq->user->processes);
220 worker->flags = 0;
221 preempt_enable();
222
223 spin_lock_irq(&wqe->lock);
224 hlist_nulls_del_rcu(&worker->nulls_node);
225 list_del_rcu(&worker->all_list);
226 if (__io_worker_unuse(wqe, worker)) {
227 __release(&wqe->lock);
228 spin_lock_irq(&wqe->lock);
229 }
230 acct->nr_workers--;
231 nr_workers = wqe->acct[IO_WQ_ACCT_BOUND].nr_workers +
232 wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers;
233 spin_unlock_irq(&wqe->lock);
234
235 /* all workers gone, wq exit can proceed */
236 if (!nr_workers && refcount_dec_and_test(&wqe->wq->refs))
237 complete(&wqe->wq->done);
238
239 kfree_rcu(worker, rcu);
240}
241
242static inline bool io_wqe_run_queue(struct io_wqe *wqe)
243 __must_hold(wqe->lock)
244{
245 if (!wq_list_empty(&wqe->work_list) &&
246 !(wqe->flags & IO_WQE_FLAG_STALLED))
247 return true;
248 return false;
249}
250
251/*
252 * Check head of free list for an available worker. If one isn't available,
253 * caller must wake up the wq manager to create one.
254 */
255static bool io_wqe_activate_free_worker(struct io_wqe *wqe)
256 __must_hold(RCU)
257{
258 struct hlist_nulls_node *n;
259 struct io_worker *worker;
260
261 n = rcu_dereference(hlist_nulls_first_rcu(&wqe->free_list));
262 if (is_a_nulls(n))
263 return false;
264
265 worker = hlist_nulls_entry(n, struct io_worker, nulls_node);
266 if (io_worker_get(worker)) {
267 wake_up_process(worker->task);
268 io_worker_release(worker);
269 return true;
270 }
271
272 return false;
273}
274
275/*
276 * We need a worker. If we find a free one, we're good. If not, and we're
277 * below the max number of workers, wake up the manager to create one.
278 */
279static void io_wqe_wake_worker(struct io_wqe *wqe, struct io_wqe_acct *acct)
280{
281 bool ret;
282
283 /*
284 * Most likely an attempt to queue unbounded work on an io_wq that
285 * wasn't setup with any unbounded workers.
286 */
287 WARN_ON_ONCE(!acct->max_workers);
288
289 rcu_read_lock();
290 ret = io_wqe_activate_free_worker(wqe);
291 rcu_read_unlock();
292
293 if (!ret && acct->nr_workers < acct->max_workers)
294 wake_up_process(wqe->wq->manager);
295}
296
297static void io_wqe_inc_running(struct io_wqe *wqe, struct io_worker *worker)
298{
299 struct io_wqe_acct *acct = io_wqe_get_acct(wqe, worker);
300
301 atomic_inc(&acct->nr_running);
302}
303
304static void io_wqe_dec_running(struct io_wqe *wqe, struct io_worker *worker)
305 __must_hold(wqe->lock)
306{
307 struct io_wqe_acct *acct = io_wqe_get_acct(wqe, worker);
308
309 if (atomic_dec_and_test(&acct->nr_running) && io_wqe_run_queue(wqe))
310 io_wqe_wake_worker(wqe, acct);
311}
312
313static void io_worker_start(struct io_wqe *wqe, struct io_worker *worker)
314{
315 allow_kernel_signal(SIGINT);
316
317 current->flags |= PF_IO_WORKER;
318
319 worker->flags |= (IO_WORKER_F_UP | IO_WORKER_F_RUNNING);
320 worker->restore_files = current->files;
321 worker->restore_fs = current->fs;
322 io_wqe_inc_running(wqe, worker);
323}
324
325/*
326 * Worker will start processing some work. Move it to the busy list, if
327 * it's currently on the freelist
328 */
329static void __io_worker_busy(struct io_wqe *wqe, struct io_worker *worker,
330 struct io_wq_work *work)
331 __must_hold(wqe->lock)
332{
333 bool worker_bound, work_bound;
334
335 if (worker->flags & IO_WORKER_F_FREE) {
336 worker->flags &= ~IO_WORKER_F_FREE;
337 hlist_nulls_del_init_rcu(&worker->nulls_node);
338 }
339
340 /*
341 * If worker is moving from bound to unbound (or vice versa), then
342 * ensure we update the running accounting.
343 */
344 worker_bound = (worker->flags & IO_WORKER_F_BOUND) != 0;
345 work_bound = (work->flags & IO_WQ_WORK_UNBOUND) == 0;
346 if (worker_bound != work_bound) {
347 io_wqe_dec_running(wqe, worker);
348 if (work_bound) {
349 worker->flags |= IO_WORKER_F_BOUND;
350 wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers--;
351 wqe->acct[IO_WQ_ACCT_BOUND].nr_workers++;
352 atomic_dec(&wqe->wq->user->processes);
353 } else {
354 worker->flags &= ~IO_WORKER_F_BOUND;
355 wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers++;
356 wqe->acct[IO_WQ_ACCT_BOUND].nr_workers--;
357 atomic_inc(&wqe->wq->user->processes);
358 }
359 io_wqe_inc_running(wqe, worker);
360 }
361}
362
363/*
364 * No work, worker going to sleep. Move to freelist, and unuse mm if we
365 * have one attached. Dropping the mm may potentially sleep, so we drop
366 * the lock in that case and return success. Since the caller has to
367 * retry the loop in that case (we changed task state), we don't regrab
368 * the lock if we return success.
369 */
370static bool __io_worker_idle(struct io_wqe *wqe, struct io_worker *worker)
371 __must_hold(wqe->lock)
372{
373 if (!(worker->flags & IO_WORKER_F_FREE)) {
374 worker->flags |= IO_WORKER_F_FREE;
375 hlist_nulls_add_head_rcu(&worker->nulls_node, &wqe->free_list);
376 }
377
378 return __io_worker_unuse(wqe, worker);
379}
380
381static inline unsigned int io_get_work_hash(struct io_wq_work *work)
382{
383 return work->flags >> IO_WQ_HASH_SHIFT;
384}
385
386static struct io_wq_work *io_get_next_work(struct io_wqe *wqe)
387 __must_hold(wqe->lock)
388{
389 struct io_wq_work_node *node, *prev;
390 struct io_wq_work *work, *tail;
391 unsigned int hash;
392
393 wq_list_for_each(node, prev, &wqe->work_list) {
394 work = container_of(node, struct io_wq_work, list);
395
396 /* not hashed, can run anytime */
397 if (!io_wq_is_hashed(work)) {
398 wq_list_del(&wqe->work_list, node, prev);
399 return work;
400 }
401
402 /* hashed, can run if not already running */
403 hash = io_get_work_hash(work);
404 if (!(wqe->hash_map & BIT(hash))) {
405 wqe->hash_map |= BIT(hash);
406 /* all items with this hash lie in [work, tail] */
407 tail = wqe->hash_tail[hash];
408 wqe->hash_tail[hash] = NULL;
409 wq_list_cut(&wqe->work_list, &tail->list, prev);
410 return work;
411 }
412 }
413
414 return NULL;
415}
416
417static void io_wq_switch_mm(struct io_worker *worker, struct io_wq_work *work)
418{
419 if (worker->mm) {
420 kthread_unuse_mm(worker->mm);
421 mmput(worker->mm);
422 worker->mm = NULL;
423 }
424 if (!work->mm)
425 return;
426
427 if (mmget_not_zero(work->mm)) {
428 kthread_use_mm(work->mm);
429 worker->mm = work->mm;
430 /* hang on to this mm */
431 work->mm = NULL;
432 return;
433 }
434
435 /* failed grabbing mm, ensure work gets cancelled */
436 work->flags |= IO_WQ_WORK_CANCEL;
437}
438
439static void io_wq_switch_creds(struct io_worker *worker,
440 struct io_wq_work *work)
441{
442 const struct cred *old_creds = override_creds(work->creds);
443
444 worker->cur_creds = work->creds;
445 if (worker->saved_creds)
446 put_cred(old_creds); /* creds set by previous switch */
447 else
448 worker->saved_creds = old_creds;
449}
450
451static void io_impersonate_work(struct io_worker *worker,
452 struct io_wq_work *work)
453{
454 if (work->files && current->files != work->files) {
455 task_lock(current);
456 current->files = work->files;
457 task_unlock(current);
458 }
459 if (work->fs && current->fs != work->fs)
460 current->fs = work->fs;
461 if (work->mm != worker->mm)
462 io_wq_switch_mm(worker, work);
463 if (worker->cur_creds != work->creds)
464 io_wq_switch_creds(worker, work);
465 current->signal->rlim[RLIMIT_FSIZE].rlim_cur = work->fsize;
466}
467
468static void io_assign_current_work(struct io_worker *worker,
469 struct io_wq_work *work)
470{
471 if (work) {
472 /* flush pending signals before assigning new work */
473 if (signal_pending(current))
474 flush_signals(current);
475 cond_resched();
476 }
477
478 spin_lock_irq(&worker->lock);
479 worker->cur_work = work;
480 spin_unlock_irq(&worker->lock);
481}
482
483static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work);
484
485static void io_worker_handle_work(struct io_worker *worker)
486 __releases(wqe->lock)
487{
488 struct io_wqe *wqe = worker->wqe;
489 struct io_wq *wq = wqe->wq;
490
491 do {
492 struct io_wq_work *work;
493get_next:
494 /*
495 * If we got some work, mark us as busy. If we didn't, but
496 * the list isn't empty, it means we stalled on hashed work.
497 * Mark us stalled so we don't keep looking for work when we
498 * can't make progress, any work completion or insertion will
499 * clear the stalled flag.
500 */
501 work = io_get_next_work(wqe);
502 if (work)
503 __io_worker_busy(wqe, worker, work);
504 else if (!wq_list_empty(&wqe->work_list))
505 wqe->flags |= IO_WQE_FLAG_STALLED;
506
507 spin_unlock_irq(&wqe->lock);
508 if (!work)
509 break;
510 io_assign_current_work(worker, work);
511
512 /* handle a whole dependent link */
513 do {
514 struct io_wq_work *old_work, *next_hashed, *linked;
515 unsigned int hash = io_get_work_hash(work);
516
517 next_hashed = wq_next_work(work);
518 io_impersonate_work(worker, work);
519 /*
520 * OK to set IO_WQ_WORK_CANCEL even for uncancellable
521 * work, the worker function will do the right thing.
522 */
523 if (test_bit(IO_WQ_BIT_CANCEL, &wq->state))
524 work->flags |= IO_WQ_WORK_CANCEL;
525
526 old_work = work;
527 linked = wq->do_work(work);
528
529 work = next_hashed;
530 if (!work && linked && !io_wq_is_hashed(linked)) {
531 work = linked;
532 linked = NULL;
533 }
534 io_assign_current_work(worker, work);
535 wq->free_work(old_work);
536
537 if (linked)
538 io_wqe_enqueue(wqe, linked);
539
540 if (hash != -1U && !next_hashed) {
541 spin_lock_irq(&wqe->lock);
542 wqe->hash_map &= ~BIT_ULL(hash);
543 wqe->flags &= ~IO_WQE_FLAG_STALLED;
544 /* skip unnecessary unlock-lock wqe->lock */
545 if (!work)
546 goto get_next;
547 spin_unlock_irq(&wqe->lock);
548 }
549 } while (work);
550
551 spin_lock_irq(&wqe->lock);
552 } while (1);
553}
554
555static int io_wqe_worker(void *data)
556{
557 struct io_worker *worker = data;
558 struct io_wqe *wqe = worker->wqe;
559 struct io_wq *wq = wqe->wq;
560
561 io_worker_start(wqe, worker);
562
563 while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
564 set_current_state(TASK_INTERRUPTIBLE);
565loop:
566 spin_lock_irq(&wqe->lock);
567 if (io_wqe_run_queue(wqe)) {
568 __set_current_state(TASK_RUNNING);
569 io_worker_handle_work(worker);
570 goto loop;
571 }
572 /* drops the lock on success, retry */
573 if (__io_worker_idle(wqe, worker)) {
574 __release(&wqe->lock);
575 goto loop;
576 }
577 spin_unlock_irq(&wqe->lock);
578 if (signal_pending(current))
579 flush_signals(current);
580 if (schedule_timeout(WORKER_IDLE_TIMEOUT))
581 continue;
582 /* timed out, exit unless we're the fixed worker */
583 if (test_bit(IO_WQ_BIT_EXIT, &wq->state) ||
584 !(worker->flags & IO_WORKER_F_FIXED))
585 break;
586 }
587
588 if (test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
589 spin_lock_irq(&wqe->lock);
590 if (!wq_list_empty(&wqe->work_list))
591 io_worker_handle_work(worker);
592 else
593 spin_unlock_irq(&wqe->lock);
594 }
595
596 io_worker_exit(worker);
597 return 0;
598}
599
600/*
601 * Called when a worker is scheduled in. Mark us as currently running.
602 */
603void io_wq_worker_running(struct task_struct *tsk)
604{
605 struct io_worker *worker = kthread_data(tsk);
606 struct io_wqe *wqe = worker->wqe;
607
608 if (!(worker->flags & IO_WORKER_F_UP))
609 return;
610 if (worker->flags & IO_WORKER_F_RUNNING)
611 return;
612 worker->flags |= IO_WORKER_F_RUNNING;
613 io_wqe_inc_running(wqe, worker);
614}
615
616/*
617 * Called when worker is going to sleep. If there are no workers currently
618 * running and we have work pending, wake up a free one or have the manager
619 * set one up.
620 */
621void io_wq_worker_sleeping(struct task_struct *tsk)
622{
623 struct io_worker *worker = kthread_data(tsk);
624 struct io_wqe *wqe = worker->wqe;
625
626 if (!(worker->flags & IO_WORKER_F_UP))
627 return;
628 if (!(worker->flags & IO_WORKER_F_RUNNING))
629 return;
630
631 worker->flags &= ~IO_WORKER_F_RUNNING;
632
633 spin_lock_irq(&wqe->lock);
634 io_wqe_dec_running(wqe, worker);
635 spin_unlock_irq(&wqe->lock);
636}
637
638static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index)
639{
640 struct io_wqe_acct *acct =&wqe->acct[index];
641 struct io_worker *worker;
642
643 worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, wqe->node);
644 if (!worker)
645 return false;
646
647 refcount_set(&worker->ref, 1);
648 worker->nulls_node.pprev = NULL;
649 worker->wqe = wqe;
650 spin_lock_init(&worker->lock);
651
652 worker->task = kthread_create_on_node(io_wqe_worker, worker, wqe->node,
653 "io_wqe_worker-%d/%d", index, wqe->node);
654 if (IS_ERR(worker->task)) {
655 kfree(worker);
656 return false;
657 }
658
659 spin_lock_irq(&wqe->lock);
660 hlist_nulls_add_head_rcu(&worker->nulls_node, &wqe->free_list);
661 list_add_tail_rcu(&worker->all_list, &wqe->all_list);
662 worker->flags |= IO_WORKER_F_FREE;
663 if (index == IO_WQ_ACCT_BOUND)
664 worker->flags |= IO_WORKER_F_BOUND;
665 if (!acct->nr_workers && (worker->flags & IO_WORKER_F_BOUND))
666 worker->flags |= IO_WORKER_F_FIXED;
667 acct->nr_workers++;
668 spin_unlock_irq(&wqe->lock);
669
670 if (index == IO_WQ_ACCT_UNBOUND)
671 atomic_inc(&wq->user->processes);
672
673 wake_up_process(worker->task);
674 return true;
675}
676
677static inline bool io_wqe_need_worker(struct io_wqe *wqe, int index)
678 __must_hold(wqe->lock)
679{
680 struct io_wqe_acct *acct = &wqe->acct[index];
681
682 /* if we have available workers or no work, no need */
683 if (!hlist_nulls_empty(&wqe->free_list) || !io_wqe_run_queue(wqe))
684 return false;
685 return acct->nr_workers < acct->max_workers;
686}
687
688/*
689 * Manager thread. Tasked with creating new workers, if we need them.
690 */
691static int io_wq_manager(void *data)
692{
693 struct io_wq *wq = data;
694 int workers_to_create = num_possible_nodes();
695 int node;
696
697 /* create fixed workers */
698 refcount_set(&wq->refs, workers_to_create);
699 for_each_node(node) {
700 if (!node_online(node))
701 continue;
702 if (!create_io_worker(wq, wq->wqes[node], IO_WQ_ACCT_BOUND))
703 goto err;
704 workers_to_create--;
705 }
706
707 while (workers_to_create--)
708 refcount_dec(&wq->refs);
709
710 complete(&wq->done);
711
712 while (!kthread_should_stop()) {
713 if (current->task_works)
714 task_work_run();
715
716 for_each_node(node) {
717 struct io_wqe *wqe = wq->wqes[node];
718 bool fork_worker[2] = { false, false };
719
720 if (!node_online(node))
721 continue;
722
723 spin_lock_irq(&wqe->lock);
724 if (io_wqe_need_worker(wqe, IO_WQ_ACCT_BOUND))
725 fork_worker[IO_WQ_ACCT_BOUND] = true;
726 if (io_wqe_need_worker(wqe, IO_WQ_ACCT_UNBOUND))
727 fork_worker[IO_WQ_ACCT_UNBOUND] = true;
728 spin_unlock_irq(&wqe->lock);
729 if (fork_worker[IO_WQ_ACCT_BOUND])
730 create_io_worker(wq, wqe, IO_WQ_ACCT_BOUND);
731 if (fork_worker[IO_WQ_ACCT_UNBOUND])
732 create_io_worker(wq, wqe, IO_WQ_ACCT_UNBOUND);
733 }
734 set_current_state(TASK_INTERRUPTIBLE);
735 schedule_timeout(HZ);
736 }
737
738 if (current->task_works)
739 task_work_run();
740
741 return 0;
742err:
743 set_bit(IO_WQ_BIT_ERROR, &wq->state);
744 set_bit(IO_WQ_BIT_EXIT, &wq->state);
745 if (refcount_sub_and_test(workers_to_create, &wq->refs))
746 complete(&wq->done);
747 return 0;
748}
749
750static bool io_wq_can_queue(struct io_wqe *wqe, struct io_wqe_acct *acct,
751 struct io_wq_work *work)
752{
753 bool free_worker;
754
755 if (!(work->flags & IO_WQ_WORK_UNBOUND))
756 return true;
757 if (atomic_read(&acct->nr_running))
758 return true;
759
760 rcu_read_lock();
761 free_worker = !hlist_nulls_empty(&wqe->free_list);
762 rcu_read_unlock();
763 if (free_worker)
764 return true;
765
766 if (atomic_read(&wqe->wq->user->processes) >= acct->max_workers &&
767 !(capable(CAP_SYS_RESOURCE) || capable(CAP_SYS_ADMIN)))
768 return false;
769
770 return true;
771}
772
773static void io_run_cancel(struct io_wq_work *work, struct io_wqe *wqe)
774{
775 struct io_wq *wq = wqe->wq;
776
777 do {
778 struct io_wq_work *old_work = work;
779
780 work->flags |= IO_WQ_WORK_CANCEL;
781 work = wq->do_work(work);
782 wq->free_work(old_work);
783 } while (work);
784}
785
786static void io_wqe_insert_work(struct io_wqe *wqe, struct io_wq_work *work)
787{
788 unsigned int hash;
789 struct io_wq_work *tail;
790
791 if (!io_wq_is_hashed(work)) {
792append:
793 wq_list_add_tail(&work->list, &wqe->work_list);
794 return;
795 }
796
797 hash = io_get_work_hash(work);
798 tail = wqe->hash_tail[hash];
799 wqe->hash_tail[hash] = work;
800 if (!tail)
801 goto append;
802
803 wq_list_add_after(&work->list, &tail->list, &wqe->work_list);
804}
805
806static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work)
807{
808 struct io_wqe_acct *acct = io_work_get_acct(wqe, work);
809 int work_flags;
810 unsigned long flags;
811
812 /*
813 * Do early check to see if we need a new unbound worker, and if we do,
814 * if we're allowed to do so. This isn't 100% accurate as there's a
815 * gap between this check and incrementing the value, but that's OK.
816 * It's close enough to not be an issue, fork() has the same delay.
817 */
818 if (unlikely(!io_wq_can_queue(wqe, acct, work))) {
819 io_run_cancel(work, wqe);
820 return;
821 }
822
823 work_flags = work->flags;
824 spin_lock_irqsave(&wqe->lock, flags);
825 io_wqe_insert_work(wqe, work);
826 wqe->flags &= ~IO_WQE_FLAG_STALLED;
827 spin_unlock_irqrestore(&wqe->lock, flags);
828
829 if ((work_flags & IO_WQ_WORK_CONCURRENT) ||
830 !atomic_read(&acct->nr_running))
831 io_wqe_wake_worker(wqe, acct);
832}
833
834void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work)
835{
836 struct io_wqe *wqe = wq->wqes[numa_node_id()];
837
838 io_wqe_enqueue(wqe, work);
839}
840
841/*
842 * Work items that hash to the same value will not be done in parallel.
843 * Used to limit concurrent writes, generally hashed by inode.
844 */
845void io_wq_hash_work(struct io_wq_work *work, void *val)
846{
847 unsigned int bit;
848
849 bit = hash_ptr(val, IO_WQ_HASH_ORDER);
850 work->flags |= (IO_WQ_WORK_HASHED | (bit << IO_WQ_HASH_SHIFT));
851}
852
853static bool io_wqe_worker_send_sig(struct io_worker *worker, void *data)
854{
855 send_sig(SIGINT, worker->task, 1);
856 return false;
857}
858
859/*
860 * Iterate the passed in list and call the specific function for each
861 * worker that isn't exiting
862 */
863static bool io_wq_for_each_worker(struct io_wqe *wqe,
864 bool (*func)(struct io_worker *, void *),
865 void *data)
866{
867 struct io_worker *worker;
868 bool ret = false;
869
870 list_for_each_entry_rcu(worker, &wqe->all_list, all_list) {
871 if (io_worker_get(worker)) {
872 /* no task if node is/was offline */
873 if (worker->task)
874 ret = func(worker, data);
875 io_worker_release(worker);
876 if (ret)
877 break;
878 }
879 }
880
881 return ret;
882}
883
884void io_wq_cancel_all(struct io_wq *wq)
885{
886 int node;
887
888 set_bit(IO_WQ_BIT_CANCEL, &wq->state);
889
890 rcu_read_lock();
891 for_each_node(node) {
892 struct io_wqe *wqe = wq->wqes[node];
893
894 io_wq_for_each_worker(wqe, io_wqe_worker_send_sig, NULL);
895 }
896 rcu_read_unlock();
897}
898
899struct io_cb_cancel_data {
900 work_cancel_fn *fn;
901 void *data;
902 int nr_running;
903 int nr_pending;
904 bool cancel_all;
905};
906
907static bool io_wq_worker_cancel(struct io_worker *worker, void *data)
908{
909 struct io_cb_cancel_data *match = data;
910 unsigned long flags;
911
912 /*
913 * Hold the lock to avoid ->cur_work going out of scope, caller
914 * may dereference the passed in work.
915 */
916 spin_lock_irqsave(&worker->lock, flags);
917 if (worker->cur_work &&
918 !(worker->cur_work->flags & IO_WQ_WORK_NO_CANCEL) &&
919 match->fn(worker->cur_work, match->data)) {
920 send_sig(SIGINT, worker->task, 1);
921 match->nr_running++;
922 }
923 spin_unlock_irqrestore(&worker->lock, flags);
924
925 return match->nr_running && !match->cancel_all;
926}
927
928static inline void io_wqe_remove_pending(struct io_wqe *wqe,
929 struct io_wq_work *work,
930 struct io_wq_work_node *prev)
931{
932 unsigned int hash = io_get_work_hash(work);
933 struct io_wq_work *prev_work = NULL;
934
935 if (io_wq_is_hashed(work) && work == wqe->hash_tail[hash]) {
936 if (prev)
937 prev_work = container_of(prev, struct io_wq_work, list);
938 if (prev_work && io_get_work_hash(prev_work) == hash)
939 wqe->hash_tail[hash] = prev_work;
940 else
941 wqe->hash_tail[hash] = NULL;
942 }
943 wq_list_del(&wqe->work_list, &work->list, prev);
944}
945
946static void io_wqe_cancel_pending_work(struct io_wqe *wqe,
947 struct io_cb_cancel_data *match)
948{
949 struct io_wq_work_node *node, *prev;
950 struct io_wq_work *work;
951 unsigned long flags;
952
953retry:
954 spin_lock_irqsave(&wqe->lock, flags);
955 wq_list_for_each(node, prev, &wqe->work_list) {
956 work = container_of(node, struct io_wq_work, list);
957 if (!match->fn(work, match->data))
958 continue;
959 io_wqe_remove_pending(wqe, work, prev);
960 spin_unlock_irqrestore(&wqe->lock, flags);
961 io_run_cancel(work, wqe);
962 match->nr_pending++;
963 if (!match->cancel_all)
964 return;
965
966 /* not safe to continue after unlock */
967 goto retry;
968 }
969 spin_unlock_irqrestore(&wqe->lock, flags);
970}
971
972static void io_wqe_cancel_running_work(struct io_wqe *wqe,
973 struct io_cb_cancel_data *match)
974{
975 rcu_read_lock();
976 io_wq_for_each_worker(wqe, io_wq_worker_cancel, match);
977 rcu_read_unlock();
978}
979
980enum io_wq_cancel io_wq_cancel_cb(struct io_wq *wq, work_cancel_fn *cancel,
981 void *data, bool cancel_all)
982{
983 struct io_cb_cancel_data match = {
984 .fn = cancel,
985 .data = data,
986 .cancel_all = cancel_all,
987 };
988 int node;
989
990 /*
991 * First check pending list, if we're lucky we can just remove it
992 * from there. CANCEL_OK means that the work is returned as-new,
993 * no completion will be posted for it.
994 */
995 for_each_node(node) {
996 struct io_wqe *wqe = wq->wqes[node];
997
998 io_wqe_cancel_pending_work(wqe, &match);
999 if (match.nr_pending && !match.cancel_all)
1000 return IO_WQ_CANCEL_OK;
1001 }
1002
1003 /*
1004 * Now check if a free (going busy) or busy worker has the work
1005 * currently running. If we find it there, we'll return CANCEL_RUNNING
1006 * as an indication that we attempt to signal cancellation. The
1007 * completion will run normally in this case.
1008 */
1009 for_each_node(node) {
1010 struct io_wqe *wqe = wq->wqes[node];
1011
1012 io_wqe_cancel_running_work(wqe, &match);
1013 if (match.nr_running && !match.cancel_all)
1014 return IO_WQ_CANCEL_RUNNING;
1015 }
1016
1017 if (match.nr_running)
1018 return IO_WQ_CANCEL_RUNNING;
1019 if (match.nr_pending)
1020 return IO_WQ_CANCEL_OK;
1021 return IO_WQ_CANCEL_NOTFOUND;
1022}
1023
1024static bool io_wq_io_cb_cancel_data(struct io_wq_work *work, void *data)
1025{
1026 return work == data;
1027}
1028
1029enum io_wq_cancel io_wq_cancel_work(struct io_wq *wq, struct io_wq_work *cwork)
1030{
1031 return io_wq_cancel_cb(wq, io_wq_io_cb_cancel_data, (void *)cwork, false);
1032}
1033
1034struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
1035{
1036 int ret = -ENOMEM, node;
1037 struct io_wq *wq;
1038
1039 if (WARN_ON_ONCE(!data->free_work || !data->do_work))
1040 return ERR_PTR(-EINVAL);
1041
1042 wq = kzalloc(sizeof(*wq), GFP_KERNEL);
1043 if (!wq)
1044 return ERR_PTR(-ENOMEM);
1045
1046 wq->wqes = kcalloc(nr_node_ids, sizeof(struct io_wqe *), GFP_KERNEL);
1047 if (!wq->wqes) {
1048 kfree(wq);
1049 return ERR_PTR(-ENOMEM);
1050 }
1051
1052 wq->free_work = data->free_work;
1053 wq->do_work = data->do_work;
1054
1055 /* caller must already hold a reference to this */
1056 wq->user = data->user;
1057
1058 for_each_node(node) {
1059 struct io_wqe *wqe;
1060 int alloc_node = node;
1061
1062 if (!node_online(alloc_node))
1063 alloc_node = NUMA_NO_NODE;
1064 wqe = kzalloc_node(sizeof(struct io_wqe), GFP_KERNEL, alloc_node);
1065 if (!wqe)
1066 goto err;
1067 wq->wqes[node] = wqe;
1068 wqe->node = alloc_node;
1069 wqe->acct[IO_WQ_ACCT_BOUND].max_workers = bounded;
1070 atomic_set(&wqe->acct[IO_WQ_ACCT_BOUND].nr_running, 0);
1071 if (wq->user) {
1072 wqe->acct[IO_WQ_ACCT_UNBOUND].max_workers =
1073 task_rlimit(current, RLIMIT_NPROC);
1074 }
1075 atomic_set(&wqe->acct[IO_WQ_ACCT_UNBOUND].nr_running, 0);
1076 wqe->wq = wq;
1077 spin_lock_init(&wqe->lock);
1078 INIT_WQ_LIST(&wqe->work_list);
1079 INIT_HLIST_NULLS_HEAD(&wqe->free_list, 0);
1080 INIT_LIST_HEAD(&wqe->all_list);
1081 }
1082
1083 init_completion(&wq->done);
1084
1085 wq->manager = kthread_create(io_wq_manager, wq, "io_wq_manager");
1086 if (!IS_ERR(wq->manager)) {
1087 wake_up_process(wq->manager);
1088 wait_for_completion(&wq->done);
1089 if (test_bit(IO_WQ_BIT_ERROR, &wq->state)) {
1090 ret = -ENOMEM;
1091 goto err;
1092 }
1093 refcount_set(&wq->use_refs, 1);
1094 reinit_completion(&wq->done);
1095 return wq;
1096 }
1097
1098 ret = PTR_ERR(wq->manager);
1099 complete(&wq->done);
1100err:
1101 for_each_node(node)
1102 kfree(wq->wqes[node]);
1103 kfree(wq->wqes);
1104 kfree(wq);
1105 return ERR_PTR(ret);
1106}
1107
1108bool io_wq_get(struct io_wq *wq, struct io_wq_data *data)
1109{
1110 if (data->free_work != wq->free_work || data->do_work != wq->do_work)
1111 return false;
1112
1113 return refcount_inc_not_zero(&wq->use_refs);
1114}
1115
1116static bool io_wq_worker_wake(struct io_worker *worker, void *data)
1117{
1118 wake_up_process(worker->task);
1119 return false;
1120}
1121
1122static void __io_wq_destroy(struct io_wq *wq)
1123{
1124 int node;
1125
1126 set_bit(IO_WQ_BIT_EXIT, &wq->state);
1127 if (wq->manager)
1128 kthread_stop(wq->manager);
1129
1130 rcu_read_lock();
1131 for_each_node(node)
1132 io_wq_for_each_worker(wq->wqes[node], io_wq_worker_wake, NULL);
1133 rcu_read_unlock();
1134
1135 wait_for_completion(&wq->done);
1136
1137 for_each_node(node)
1138 kfree(wq->wqes[node]);
1139 kfree(wq->wqes);
1140 kfree(wq);
1141}
1142
1143void io_wq_destroy(struct io_wq *wq)
1144{
1145 if (refcount_dec_and_test(&wq->use_refs))
1146 __io_wq_destroy(wq);
1147}
1148
1149struct task_struct *io_wq_get_task(struct io_wq *wq)
1150{
1151 return wq->manager;
1152}