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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/percpu.h>
13#include <linux/slab.h>
14#include <linux/rculist_nulls.h>
15#include <linux/cpu.h>
16#include <linux/task_work.h>
17#include <linux/audit.h>
18#include <linux/mmu_context.h>
19#include <uapi/linux/io_uring.h>
20
21#include "io-wq.h"
22#include "slist.h"
23#include "io_uring.h"
24
25#define WORKER_IDLE_TIMEOUT (5 * HZ)
26
27enum {
28 IO_WORKER_F_UP = 1, /* up and active */
29 IO_WORKER_F_RUNNING = 2, /* account as running */
30 IO_WORKER_F_FREE = 4, /* worker on free list */
31 IO_WORKER_F_BOUND = 8, /* is doing bounded work */
32};
33
34enum {
35 IO_WQ_BIT_EXIT = 0, /* wq exiting */
36};
37
38enum {
39 IO_ACCT_STALLED_BIT = 0, /* stalled on hash */
40};
41
42/*
43 * One for each thread in a wq pool
44 */
45struct io_worker {
46 refcount_t ref;
47 unsigned flags;
48 struct hlist_nulls_node nulls_node;
49 struct list_head all_list;
50 struct task_struct *task;
51 struct io_wq *wq;
52
53 struct io_wq_work *cur_work;
54 struct io_wq_work *next_work;
55 raw_spinlock_t lock;
56
57 struct completion ref_done;
58
59 unsigned long create_state;
60 struct callback_head create_work;
61 int create_index;
62
63 union {
64 struct rcu_head rcu;
65 struct work_struct work;
66 };
67};
68
69#if BITS_PER_LONG == 64
70#define IO_WQ_HASH_ORDER 6
71#else
72#define IO_WQ_HASH_ORDER 5
73#endif
74
75#define IO_WQ_NR_HASH_BUCKETS (1u << IO_WQ_HASH_ORDER)
76
77struct io_wq_acct {
78 unsigned nr_workers;
79 unsigned max_workers;
80 int index;
81 atomic_t nr_running;
82 raw_spinlock_t lock;
83 struct io_wq_work_list work_list;
84 unsigned long flags;
85};
86
87enum {
88 IO_WQ_ACCT_BOUND,
89 IO_WQ_ACCT_UNBOUND,
90 IO_WQ_ACCT_NR,
91};
92
93/*
94 * Per io_wq state
95 */
96struct io_wq {
97 unsigned long state;
98
99 free_work_fn *free_work;
100 io_wq_work_fn *do_work;
101
102 struct io_wq_hash *hash;
103
104 atomic_t worker_refs;
105 struct completion worker_done;
106
107 struct hlist_node cpuhp_node;
108
109 struct task_struct *task;
110
111 struct io_wq_acct acct[IO_WQ_ACCT_NR];
112
113 /* lock protects access to elements below */
114 raw_spinlock_t lock;
115
116 struct hlist_nulls_head free_list;
117 struct list_head all_list;
118
119 struct wait_queue_entry wait;
120
121 struct io_wq_work *hash_tail[IO_WQ_NR_HASH_BUCKETS];
122
123 cpumask_var_t cpu_mask;
124};
125
126static enum cpuhp_state io_wq_online;
127
128struct io_cb_cancel_data {
129 work_cancel_fn *fn;
130 void *data;
131 int nr_running;
132 int nr_pending;
133 bool cancel_all;
134};
135
136static bool create_io_worker(struct io_wq *wq, int index);
137static void io_wq_dec_running(struct io_worker *worker);
138static bool io_acct_cancel_pending_work(struct io_wq *wq,
139 struct io_wq_acct *acct,
140 struct io_cb_cancel_data *match);
141static void create_worker_cb(struct callback_head *cb);
142static void io_wq_cancel_tw_create(struct io_wq *wq);
143
144static bool io_worker_get(struct io_worker *worker)
145{
146 return refcount_inc_not_zero(&worker->ref);
147}
148
149static void io_worker_release(struct io_worker *worker)
150{
151 if (refcount_dec_and_test(&worker->ref))
152 complete(&worker->ref_done);
153}
154
155static inline struct io_wq_acct *io_get_acct(struct io_wq *wq, bool bound)
156{
157 return &wq->acct[bound ? IO_WQ_ACCT_BOUND : IO_WQ_ACCT_UNBOUND];
158}
159
160static inline struct io_wq_acct *io_work_get_acct(struct io_wq *wq,
161 struct io_wq_work *work)
162{
163 return io_get_acct(wq, !(work->flags & IO_WQ_WORK_UNBOUND));
164}
165
166static inline struct io_wq_acct *io_wq_get_acct(struct io_worker *worker)
167{
168 return io_get_acct(worker->wq, worker->flags & IO_WORKER_F_BOUND);
169}
170
171static void io_worker_ref_put(struct io_wq *wq)
172{
173 if (atomic_dec_and_test(&wq->worker_refs))
174 complete(&wq->worker_done);
175}
176
177bool io_wq_worker_stopped(void)
178{
179 struct io_worker *worker = current->worker_private;
180
181 if (WARN_ON_ONCE(!io_wq_current_is_worker()))
182 return true;
183
184 return test_bit(IO_WQ_BIT_EXIT, &worker->wq->state);
185}
186
187static void io_worker_cancel_cb(struct io_worker *worker)
188{
189 struct io_wq_acct *acct = io_wq_get_acct(worker);
190 struct io_wq *wq = worker->wq;
191
192 atomic_dec(&acct->nr_running);
193 raw_spin_lock(&wq->lock);
194 acct->nr_workers--;
195 raw_spin_unlock(&wq->lock);
196 io_worker_ref_put(wq);
197 clear_bit_unlock(0, &worker->create_state);
198 io_worker_release(worker);
199}
200
201static bool io_task_worker_match(struct callback_head *cb, void *data)
202{
203 struct io_worker *worker;
204
205 if (cb->func != create_worker_cb)
206 return false;
207 worker = container_of(cb, struct io_worker, create_work);
208 return worker == data;
209}
210
211static void io_worker_exit(struct io_worker *worker)
212{
213 struct io_wq *wq = worker->wq;
214
215 while (1) {
216 struct callback_head *cb = task_work_cancel_match(wq->task,
217 io_task_worker_match, worker);
218
219 if (!cb)
220 break;
221 io_worker_cancel_cb(worker);
222 }
223
224 io_worker_release(worker);
225 wait_for_completion(&worker->ref_done);
226
227 raw_spin_lock(&wq->lock);
228 if (worker->flags & IO_WORKER_F_FREE)
229 hlist_nulls_del_rcu(&worker->nulls_node);
230 list_del_rcu(&worker->all_list);
231 raw_spin_unlock(&wq->lock);
232 io_wq_dec_running(worker);
233 /*
234 * this worker is a goner, clear ->worker_private to avoid any
235 * inc/dec running calls that could happen as part of exit from
236 * touching 'worker'.
237 */
238 current->worker_private = NULL;
239
240 kfree_rcu(worker, rcu);
241 io_worker_ref_put(wq);
242 do_exit(0);
243}
244
245static inline bool __io_acct_run_queue(struct io_wq_acct *acct)
246{
247 return !test_bit(IO_ACCT_STALLED_BIT, &acct->flags) &&
248 !wq_list_empty(&acct->work_list);
249}
250
251/*
252 * If there's work to do, returns true with acct->lock acquired. If not,
253 * returns false with no lock held.
254 */
255static inline bool io_acct_run_queue(struct io_wq_acct *acct)
256 __acquires(&acct->lock)
257{
258 raw_spin_lock(&acct->lock);
259 if (__io_acct_run_queue(acct))
260 return true;
261
262 raw_spin_unlock(&acct->lock);
263 return false;
264}
265
266/*
267 * Check head of free list for an available worker. If one isn't available,
268 * caller must create one.
269 */
270static bool io_wq_activate_free_worker(struct io_wq *wq,
271 struct io_wq_acct *acct)
272 __must_hold(RCU)
273{
274 struct hlist_nulls_node *n;
275 struct io_worker *worker;
276
277 /*
278 * Iterate free_list and see if we can find an idle worker to
279 * activate. If a given worker is on the free_list but in the process
280 * of exiting, keep trying.
281 */
282 hlist_nulls_for_each_entry_rcu(worker, n, &wq->free_list, nulls_node) {
283 if (!io_worker_get(worker))
284 continue;
285 if (io_wq_get_acct(worker) != acct) {
286 io_worker_release(worker);
287 continue;
288 }
289 /*
290 * If the worker is already running, it's either already
291 * starting work or finishing work. In either case, if it does
292 * to go sleep, we'll kick off a new task for this work anyway.
293 */
294 wake_up_process(worker->task);
295 io_worker_release(worker);
296 return true;
297 }
298
299 return false;
300}
301
302/*
303 * We need a worker. If we find a free one, we're good. If not, and we're
304 * below the max number of workers, create one.
305 */
306static bool io_wq_create_worker(struct io_wq *wq, struct io_wq_acct *acct)
307{
308 /*
309 * Most likely an attempt to queue unbounded work on an io_wq that
310 * wasn't setup with any unbounded workers.
311 */
312 if (unlikely(!acct->max_workers))
313 pr_warn_once("io-wq is not configured for unbound workers");
314
315 raw_spin_lock(&wq->lock);
316 if (acct->nr_workers >= acct->max_workers) {
317 raw_spin_unlock(&wq->lock);
318 return true;
319 }
320 acct->nr_workers++;
321 raw_spin_unlock(&wq->lock);
322 atomic_inc(&acct->nr_running);
323 atomic_inc(&wq->worker_refs);
324 return create_io_worker(wq, acct->index);
325}
326
327static void io_wq_inc_running(struct io_worker *worker)
328{
329 struct io_wq_acct *acct = io_wq_get_acct(worker);
330
331 atomic_inc(&acct->nr_running);
332}
333
334static void create_worker_cb(struct callback_head *cb)
335{
336 struct io_worker *worker;
337 struct io_wq *wq;
338
339 struct io_wq_acct *acct;
340 bool do_create = false;
341
342 worker = container_of(cb, struct io_worker, create_work);
343 wq = worker->wq;
344 acct = &wq->acct[worker->create_index];
345 raw_spin_lock(&wq->lock);
346
347 if (acct->nr_workers < acct->max_workers) {
348 acct->nr_workers++;
349 do_create = true;
350 }
351 raw_spin_unlock(&wq->lock);
352 if (do_create) {
353 create_io_worker(wq, worker->create_index);
354 } else {
355 atomic_dec(&acct->nr_running);
356 io_worker_ref_put(wq);
357 }
358 clear_bit_unlock(0, &worker->create_state);
359 io_worker_release(worker);
360}
361
362static bool io_queue_worker_create(struct io_worker *worker,
363 struct io_wq_acct *acct,
364 task_work_func_t func)
365{
366 struct io_wq *wq = worker->wq;
367
368 /* raced with exit, just ignore create call */
369 if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
370 goto fail;
371 if (!io_worker_get(worker))
372 goto fail;
373 /*
374 * create_state manages ownership of create_work/index. We should
375 * only need one entry per worker, as the worker going to sleep
376 * will trigger the condition, and waking will clear it once it
377 * runs the task_work.
378 */
379 if (test_bit(0, &worker->create_state) ||
380 test_and_set_bit_lock(0, &worker->create_state))
381 goto fail_release;
382
383 atomic_inc(&wq->worker_refs);
384 init_task_work(&worker->create_work, func);
385 worker->create_index = acct->index;
386 if (!task_work_add(wq->task, &worker->create_work, TWA_SIGNAL)) {
387 /*
388 * EXIT may have been set after checking it above, check after
389 * adding the task_work and remove any creation item if it is
390 * now set. wq exit does that too, but we can have added this
391 * work item after we canceled in io_wq_exit_workers().
392 */
393 if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
394 io_wq_cancel_tw_create(wq);
395 io_worker_ref_put(wq);
396 return true;
397 }
398 io_worker_ref_put(wq);
399 clear_bit_unlock(0, &worker->create_state);
400fail_release:
401 io_worker_release(worker);
402fail:
403 atomic_dec(&acct->nr_running);
404 io_worker_ref_put(wq);
405 return false;
406}
407
408static void io_wq_dec_running(struct io_worker *worker)
409{
410 struct io_wq_acct *acct = io_wq_get_acct(worker);
411 struct io_wq *wq = worker->wq;
412
413 if (!(worker->flags & IO_WORKER_F_UP))
414 return;
415
416 if (!atomic_dec_and_test(&acct->nr_running))
417 return;
418 if (!io_acct_run_queue(acct))
419 return;
420
421 raw_spin_unlock(&acct->lock);
422 atomic_inc(&acct->nr_running);
423 atomic_inc(&wq->worker_refs);
424 io_queue_worker_create(worker, acct, create_worker_cb);
425}
426
427/*
428 * Worker will start processing some work. Move it to the busy list, if
429 * it's currently on the freelist
430 */
431static void __io_worker_busy(struct io_wq *wq, struct io_worker *worker)
432{
433 if (worker->flags & IO_WORKER_F_FREE) {
434 worker->flags &= ~IO_WORKER_F_FREE;
435 raw_spin_lock(&wq->lock);
436 hlist_nulls_del_init_rcu(&worker->nulls_node);
437 raw_spin_unlock(&wq->lock);
438 }
439}
440
441/*
442 * No work, worker going to sleep. Move to freelist.
443 */
444static void __io_worker_idle(struct io_wq *wq, struct io_worker *worker)
445 __must_hold(wq->lock)
446{
447 if (!(worker->flags & IO_WORKER_F_FREE)) {
448 worker->flags |= IO_WORKER_F_FREE;
449 hlist_nulls_add_head_rcu(&worker->nulls_node, &wq->free_list);
450 }
451}
452
453static inline unsigned int io_get_work_hash(struct io_wq_work *work)
454{
455 return work->flags >> IO_WQ_HASH_SHIFT;
456}
457
458static bool io_wait_on_hash(struct io_wq *wq, unsigned int hash)
459{
460 bool ret = false;
461
462 spin_lock_irq(&wq->hash->wait.lock);
463 if (list_empty(&wq->wait.entry)) {
464 __add_wait_queue(&wq->hash->wait, &wq->wait);
465 if (!test_bit(hash, &wq->hash->map)) {
466 __set_current_state(TASK_RUNNING);
467 list_del_init(&wq->wait.entry);
468 ret = true;
469 }
470 }
471 spin_unlock_irq(&wq->hash->wait.lock);
472 return ret;
473}
474
475static struct io_wq_work *io_get_next_work(struct io_wq_acct *acct,
476 struct io_worker *worker)
477 __must_hold(acct->lock)
478{
479 struct io_wq_work_node *node, *prev;
480 struct io_wq_work *work, *tail;
481 unsigned int stall_hash = -1U;
482 struct io_wq *wq = worker->wq;
483
484 wq_list_for_each(node, prev, &acct->work_list) {
485 unsigned int hash;
486
487 work = container_of(node, struct io_wq_work, list);
488
489 /* not hashed, can run anytime */
490 if (!io_wq_is_hashed(work)) {
491 wq_list_del(&acct->work_list, node, prev);
492 return work;
493 }
494
495 hash = io_get_work_hash(work);
496 /* all items with this hash lie in [work, tail] */
497 tail = wq->hash_tail[hash];
498
499 /* hashed, can run if not already running */
500 if (!test_and_set_bit(hash, &wq->hash->map)) {
501 wq->hash_tail[hash] = NULL;
502 wq_list_cut(&acct->work_list, &tail->list, prev);
503 return work;
504 }
505 if (stall_hash == -1U)
506 stall_hash = hash;
507 /* fast forward to a next hash, for-each will fix up @prev */
508 node = &tail->list;
509 }
510
511 if (stall_hash != -1U) {
512 bool unstalled;
513
514 /*
515 * Set this before dropping the lock to avoid racing with new
516 * work being added and clearing the stalled bit.
517 */
518 set_bit(IO_ACCT_STALLED_BIT, &acct->flags);
519 raw_spin_unlock(&acct->lock);
520 unstalled = io_wait_on_hash(wq, stall_hash);
521 raw_spin_lock(&acct->lock);
522 if (unstalled) {
523 clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
524 if (wq_has_sleeper(&wq->hash->wait))
525 wake_up(&wq->hash->wait);
526 }
527 }
528
529 return NULL;
530}
531
532static void io_assign_current_work(struct io_worker *worker,
533 struct io_wq_work *work)
534{
535 if (work) {
536 io_run_task_work();
537 cond_resched();
538 }
539
540 raw_spin_lock(&worker->lock);
541 worker->cur_work = work;
542 worker->next_work = NULL;
543 raw_spin_unlock(&worker->lock);
544}
545
546/*
547 * Called with acct->lock held, drops it before returning
548 */
549static void io_worker_handle_work(struct io_wq_acct *acct,
550 struct io_worker *worker)
551 __releases(&acct->lock)
552{
553 struct io_wq *wq = worker->wq;
554 bool do_kill = test_bit(IO_WQ_BIT_EXIT, &wq->state);
555
556 do {
557 struct io_wq_work *work;
558
559 /*
560 * If we got some work, mark us as busy. If we didn't, but
561 * the list isn't empty, it means we stalled on hashed work.
562 * Mark us stalled so we don't keep looking for work when we
563 * can't make progress, any work completion or insertion will
564 * clear the stalled flag.
565 */
566 work = io_get_next_work(acct, worker);
567 if (work) {
568 /*
569 * Make sure cancelation can find this, even before
570 * it becomes the active work. That avoids a window
571 * where the work has been removed from our general
572 * work list, but isn't yet discoverable as the
573 * current work item for this worker.
574 */
575 raw_spin_lock(&worker->lock);
576 worker->next_work = work;
577 raw_spin_unlock(&worker->lock);
578 }
579
580 raw_spin_unlock(&acct->lock);
581
582 if (!work)
583 break;
584
585 __io_worker_busy(wq, worker);
586
587 io_assign_current_work(worker, work);
588 __set_current_state(TASK_RUNNING);
589
590 /* handle a whole dependent link */
591 do {
592 struct io_wq_work *next_hashed, *linked;
593 unsigned int hash = io_get_work_hash(work);
594
595 next_hashed = wq_next_work(work);
596
597 if (unlikely(do_kill) && (work->flags & IO_WQ_WORK_UNBOUND))
598 work->flags |= IO_WQ_WORK_CANCEL;
599 wq->do_work(work);
600 io_assign_current_work(worker, NULL);
601
602 linked = wq->free_work(work);
603 work = next_hashed;
604 if (!work && linked && !io_wq_is_hashed(linked)) {
605 work = linked;
606 linked = NULL;
607 }
608 io_assign_current_work(worker, work);
609 if (linked)
610 io_wq_enqueue(wq, linked);
611
612 if (hash != -1U && !next_hashed) {
613 /* serialize hash clear with wake_up() */
614 spin_lock_irq(&wq->hash->wait.lock);
615 clear_bit(hash, &wq->hash->map);
616 clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
617 spin_unlock_irq(&wq->hash->wait.lock);
618 if (wq_has_sleeper(&wq->hash->wait))
619 wake_up(&wq->hash->wait);
620 }
621 } while (work);
622
623 if (!__io_acct_run_queue(acct))
624 break;
625 raw_spin_lock(&acct->lock);
626 } while (1);
627}
628
629static int io_wq_worker(void *data)
630{
631 struct io_worker *worker = data;
632 struct io_wq_acct *acct = io_wq_get_acct(worker);
633 struct io_wq *wq = worker->wq;
634 bool exit_mask = false, last_timeout = false;
635 char buf[TASK_COMM_LEN];
636
637 worker->flags |= (IO_WORKER_F_UP | IO_WORKER_F_RUNNING);
638
639 snprintf(buf, sizeof(buf), "iou-wrk-%d", wq->task->pid);
640 set_task_comm(current, buf);
641
642 while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
643 long ret;
644
645 set_current_state(TASK_INTERRUPTIBLE);
646
647 /*
648 * If we have work to do, io_acct_run_queue() returns with
649 * the acct->lock held. If not, it will drop it.
650 */
651 while (io_acct_run_queue(acct))
652 io_worker_handle_work(acct, worker);
653
654 raw_spin_lock(&wq->lock);
655 /*
656 * Last sleep timed out. Exit if we're not the last worker,
657 * or if someone modified our affinity.
658 */
659 if (last_timeout && (exit_mask || acct->nr_workers > 1)) {
660 acct->nr_workers--;
661 raw_spin_unlock(&wq->lock);
662 __set_current_state(TASK_RUNNING);
663 break;
664 }
665 last_timeout = false;
666 __io_worker_idle(wq, worker);
667 raw_spin_unlock(&wq->lock);
668 if (io_run_task_work())
669 continue;
670 ret = schedule_timeout(WORKER_IDLE_TIMEOUT);
671 if (signal_pending(current)) {
672 struct ksignal ksig;
673
674 if (!get_signal(&ksig))
675 continue;
676 break;
677 }
678 if (!ret) {
679 last_timeout = true;
680 exit_mask = !cpumask_test_cpu(raw_smp_processor_id(),
681 wq->cpu_mask);
682 }
683 }
684
685 if (test_bit(IO_WQ_BIT_EXIT, &wq->state) && io_acct_run_queue(acct))
686 io_worker_handle_work(acct, worker);
687
688 io_worker_exit(worker);
689 return 0;
690}
691
692/*
693 * Called when a worker is scheduled in. Mark us as currently running.
694 */
695void io_wq_worker_running(struct task_struct *tsk)
696{
697 struct io_worker *worker = tsk->worker_private;
698
699 if (!worker)
700 return;
701 if (!(worker->flags & IO_WORKER_F_UP))
702 return;
703 if (worker->flags & IO_WORKER_F_RUNNING)
704 return;
705 worker->flags |= IO_WORKER_F_RUNNING;
706 io_wq_inc_running(worker);
707}
708
709/*
710 * Called when worker is going to sleep. If there are no workers currently
711 * running and we have work pending, wake up a free one or create a new one.
712 */
713void io_wq_worker_sleeping(struct task_struct *tsk)
714{
715 struct io_worker *worker = tsk->worker_private;
716
717 if (!worker)
718 return;
719 if (!(worker->flags & IO_WORKER_F_UP))
720 return;
721 if (!(worker->flags & IO_WORKER_F_RUNNING))
722 return;
723
724 worker->flags &= ~IO_WORKER_F_RUNNING;
725 io_wq_dec_running(worker);
726}
727
728static void io_init_new_worker(struct io_wq *wq, struct io_worker *worker,
729 struct task_struct *tsk)
730{
731 tsk->worker_private = worker;
732 worker->task = tsk;
733 set_cpus_allowed_ptr(tsk, wq->cpu_mask);
734
735 raw_spin_lock(&wq->lock);
736 hlist_nulls_add_head_rcu(&worker->nulls_node, &wq->free_list);
737 list_add_tail_rcu(&worker->all_list, &wq->all_list);
738 worker->flags |= IO_WORKER_F_FREE;
739 raw_spin_unlock(&wq->lock);
740 wake_up_new_task(tsk);
741}
742
743static bool io_wq_work_match_all(struct io_wq_work *work, void *data)
744{
745 return true;
746}
747
748static inline bool io_should_retry_thread(long err)
749{
750 /*
751 * Prevent perpetual task_work retry, if the task (or its group) is
752 * exiting.
753 */
754 if (fatal_signal_pending(current))
755 return false;
756
757 switch (err) {
758 case -EAGAIN:
759 case -ERESTARTSYS:
760 case -ERESTARTNOINTR:
761 case -ERESTARTNOHAND:
762 return true;
763 default:
764 return false;
765 }
766}
767
768static void create_worker_cont(struct callback_head *cb)
769{
770 struct io_worker *worker;
771 struct task_struct *tsk;
772 struct io_wq *wq;
773
774 worker = container_of(cb, struct io_worker, create_work);
775 clear_bit_unlock(0, &worker->create_state);
776 wq = worker->wq;
777 tsk = create_io_thread(io_wq_worker, worker, NUMA_NO_NODE);
778 if (!IS_ERR(tsk)) {
779 io_init_new_worker(wq, worker, tsk);
780 io_worker_release(worker);
781 return;
782 } else if (!io_should_retry_thread(PTR_ERR(tsk))) {
783 struct io_wq_acct *acct = io_wq_get_acct(worker);
784
785 atomic_dec(&acct->nr_running);
786 raw_spin_lock(&wq->lock);
787 acct->nr_workers--;
788 if (!acct->nr_workers) {
789 struct io_cb_cancel_data match = {
790 .fn = io_wq_work_match_all,
791 .cancel_all = true,
792 };
793
794 raw_spin_unlock(&wq->lock);
795 while (io_acct_cancel_pending_work(wq, acct, &match))
796 ;
797 } else {
798 raw_spin_unlock(&wq->lock);
799 }
800 io_worker_ref_put(wq);
801 kfree(worker);
802 return;
803 }
804
805 /* re-create attempts grab a new worker ref, drop the existing one */
806 io_worker_release(worker);
807 schedule_work(&worker->work);
808}
809
810static void io_workqueue_create(struct work_struct *work)
811{
812 struct io_worker *worker = container_of(work, struct io_worker, work);
813 struct io_wq_acct *acct = io_wq_get_acct(worker);
814
815 if (!io_queue_worker_create(worker, acct, create_worker_cont))
816 kfree(worker);
817}
818
819static bool create_io_worker(struct io_wq *wq, int index)
820{
821 struct io_wq_acct *acct = &wq->acct[index];
822 struct io_worker *worker;
823 struct task_struct *tsk;
824
825 __set_current_state(TASK_RUNNING);
826
827 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
828 if (!worker) {
829fail:
830 atomic_dec(&acct->nr_running);
831 raw_spin_lock(&wq->lock);
832 acct->nr_workers--;
833 raw_spin_unlock(&wq->lock);
834 io_worker_ref_put(wq);
835 return false;
836 }
837
838 refcount_set(&worker->ref, 1);
839 worker->wq = wq;
840 raw_spin_lock_init(&worker->lock);
841 init_completion(&worker->ref_done);
842
843 if (index == IO_WQ_ACCT_BOUND)
844 worker->flags |= IO_WORKER_F_BOUND;
845
846 tsk = create_io_thread(io_wq_worker, worker, NUMA_NO_NODE);
847 if (!IS_ERR(tsk)) {
848 io_init_new_worker(wq, worker, tsk);
849 } else if (!io_should_retry_thread(PTR_ERR(tsk))) {
850 kfree(worker);
851 goto fail;
852 } else {
853 INIT_WORK(&worker->work, io_workqueue_create);
854 schedule_work(&worker->work);
855 }
856
857 return true;
858}
859
860/*
861 * Iterate the passed in list and call the specific function for each
862 * worker that isn't exiting
863 */
864static bool io_wq_for_each_worker(struct io_wq *wq,
865 bool (*func)(struct io_worker *, void *),
866 void *data)
867{
868 struct io_worker *worker;
869 bool ret = false;
870
871 list_for_each_entry_rcu(worker, &wq->all_list, all_list) {
872 if (io_worker_get(worker)) {
873 /* no task if node is/was offline */
874 if (worker->task)
875 ret = func(worker, data);
876 io_worker_release(worker);
877 if (ret)
878 break;
879 }
880 }
881
882 return ret;
883}
884
885static bool io_wq_worker_wake(struct io_worker *worker, void *data)
886{
887 __set_notify_signal(worker->task);
888 wake_up_process(worker->task);
889 return false;
890}
891
892static void io_run_cancel(struct io_wq_work *work, struct io_wq *wq)
893{
894 do {
895 work->flags |= IO_WQ_WORK_CANCEL;
896 wq->do_work(work);
897 work = wq->free_work(work);
898 } while (work);
899}
900
901static void io_wq_insert_work(struct io_wq *wq, struct io_wq_work *work)
902{
903 struct io_wq_acct *acct = io_work_get_acct(wq, work);
904 unsigned int hash;
905 struct io_wq_work *tail;
906
907 if (!io_wq_is_hashed(work)) {
908append:
909 wq_list_add_tail(&work->list, &acct->work_list);
910 return;
911 }
912
913 hash = io_get_work_hash(work);
914 tail = wq->hash_tail[hash];
915 wq->hash_tail[hash] = work;
916 if (!tail)
917 goto append;
918
919 wq_list_add_after(&work->list, &tail->list, &acct->work_list);
920}
921
922static bool io_wq_work_match_item(struct io_wq_work *work, void *data)
923{
924 return work == data;
925}
926
927void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work)
928{
929 struct io_wq_acct *acct = io_work_get_acct(wq, work);
930 struct io_cb_cancel_data match;
931 unsigned work_flags = work->flags;
932 bool do_create;
933
934 /*
935 * If io-wq is exiting for this task, or if the request has explicitly
936 * been marked as one that should not get executed, cancel it here.
937 */
938 if (test_bit(IO_WQ_BIT_EXIT, &wq->state) ||
939 (work->flags & IO_WQ_WORK_CANCEL)) {
940 io_run_cancel(work, wq);
941 return;
942 }
943
944 raw_spin_lock(&acct->lock);
945 io_wq_insert_work(wq, work);
946 clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
947 raw_spin_unlock(&acct->lock);
948
949 rcu_read_lock();
950 do_create = !io_wq_activate_free_worker(wq, acct);
951 rcu_read_unlock();
952
953 if (do_create && ((work_flags & IO_WQ_WORK_CONCURRENT) ||
954 !atomic_read(&acct->nr_running))) {
955 bool did_create;
956
957 did_create = io_wq_create_worker(wq, acct);
958 if (likely(did_create))
959 return;
960
961 raw_spin_lock(&wq->lock);
962 if (acct->nr_workers) {
963 raw_spin_unlock(&wq->lock);
964 return;
965 }
966 raw_spin_unlock(&wq->lock);
967
968 /* fatal condition, failed to create the first worker */
969 match.fn = io_wq_work_match_item,
970 match.data = work,
971 match.cancel_all = false,
972
973 io_acct_cancel_pending_work(wq, acct, &match);
974 }
975}
976
977/*
978 * Work items that hash to the same value will not be done in parallel.
979 * Used to limit concurrent writes, generally hashed by inode.
980 */
981void io_wq_hash_work(struct io_wq_work *work, void *val)
982{
983 unsigned int bit;
984
985 bit = hash_ptr(val, IO_WQ_HASH_ORDER);
986 work->flags |= (IO_WQ_WORK_HASHED | (bit << IO_WQ_HASH_SHIFT));
987}
988
989static bool __io_wq_worker_cancel(struct io_worker *worker,
990 struct io_cb_cancel_data *match,
991 struct io_wq_work *work)
992{
993 if (work && match->fn(work, match->data)) {
994 work->flags |= IO_WQ_WORK_CANCEL;
995 __set_notify_signal(worker->task);
996 return true;
997 }
998
999 return false;
1000}
1001
1002static bool io_wq_worker_cancel(struct io_worker *worker, void *data)
1003{
1004 struct io_cb_cancel_data *match = data;
1005
1006 /*
1007 * Hold the lock to avoid ->cur_work going out of scope, caller
1008 * may dereference the passed in work.
1009 */
1010 raw_spin_lock(&worker->lock);
1011 if (__io_wq_worker_cancel(worker, match, worker->cur_work) ||
1012 __io_wq_worker_cancel(worker, match, worker->next_work))
1013 match->nr_running++;
1014 raw_spin_unlock(&worker->lock);
1015
1016 return match->nr_running && !match->cancel_all;
1017}
1018
1019static inline void io_wq_remove_pending(struct io_wq *wq,
1020 struct io_wq_work *work,
1021 struct io_wq_work_node *prev)
1022{
1023 struct io_wq_acct *acct = io_work_get_acct(wq, work);
1024 unsigned int hash = io_get_work_hash(work);
1025 struct io_wq_work *prev_work = NULL;
1026
1027 if (io_wq_is_hashed(work) && work == wq->hash_tail[hash]) {
1028 if (prev)
1029 prev_work = container_of(prev, struct io_wq_work, list);
1030 if (prev_work && io_get_work_hash(prev_work) == hash)
1031 wq->hash_tail[hash] = prev_work;
1032 else
1033 wq->hash_tail[hash] = NULL;
1034 }
1035 wq_list_del(&acct->work_list, &work->list, prev);
1036}
1037
1038static bool io_acct_cancel_pending_work(struct io_wq *wq,
1039 struct io_wq_acct *acct,
1040 struct io_cb_cancel_data *match)
1041{
1042 struct io_wq_work_node *node, *prev;
1043 struct io_wq_work *work;
1044
1045 raw_spin_lock(&acct->lock);
1046 wq_list_for_each(node, prev, &acct->work_list) {
1047 work = container_of(node, struct io_wq_work, list);
1048 if (!match->fn(work, match->data))
1049 continue;
1050 io_wq_remove_pending(wq, work, prev);
1051 raw_spin_unlock(&acct->lock);
1052 io_run_cancel(work, wq);
1053 match->nr_pending++;
1054 /* not safe to continue after unlock */
1055 return true;
1056 }
1057 raw_spin_unlock(&acct->lock);
1058
1059 return false;
1060}
1061
1062static void io_wq_cancel_pending_work(struct io_wq *wq,
1063 struct io_cb_cancel_data *match)
1064{
1065 int i;
1066retry:
1067 for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1068 struct io_wq_acct *acct = io_get_acct(wq, i == 0);
1069
1070 if (io_acct_cancel_pending_work(wq, acct, match)) {
1071 if (match->cancel_all)
1072 goto retry;
1073 break;
1074 }
1075 }
1076}
1077
1078static void io_wq_cancel_running_work(struct io_wq *wq,
1079 struct io_cb_cancel_data *match)
1080{
1081 rcu_read_lock();
1082 io_wq_for_each_worker(wq, io_wq_worker_cancel, match);
1083 rcu_read_unlock();
1084}
1085
1086enum io_wq_cancel io_wq_cancel_cb(struct io_wq *wq, work_cancel_fn *cancel,
1087 void *data, bool cancel_all)
1088{
1089 struct io_cb_cancel_data match = {
1090 .fn = cancel,
1091 .data = data,
1092 .cancel_all = cancel_all,
1093 };
1094
1095 /*
1096 * First check pending list, if we're lucky we can just remove it
1097 * from there. CANCEL_OK means that the work is returned as-new,
1098 * no completion will be posted for it.
1099 *
1100 * Then check if a free (going busy) or busy worker has the work
1101 * currently running. If we find it there, we'll return CANCEL_RUNNING
1102 * as an indication that we attempt to signal cancellation. The
1103 * completion will run normally in this case.
1104 *
1105 * Do both of these while holding the wq->lock, to ensure that
1106 * we'll find a work item regardless of state.
1107 */
1108 io_wq_cancel_pending_work(wq, &match);
1109 if (match.nr_pending && !match.cancel_all)
1110 return IO_WQ_CANCEL_OK;
1111
1112 raw_spin_lock(&wq->lock);
1113 io_wq_cancel_running_work(wq, &match);
1114 raw_spin_unlock(&wq->lock);
1115 if (match.nr_running && !match.cancel_all)
1116 return IO_WQ_CANCEL_RUNNING;
1117
1118 if (match.nr_running)
1119 return IO_WQ_CANCEL_RUNNING;
1120 if (match.nr_pending)
1121 return IO_WQ_CANCEL_OK;
1122 return IO_WQ_CANCEL_NOTFOUND;
1123}
1124
1125static int io_wq_hash_wake(struct wait_queue_entry *wait, unsigned mode,
1126 int sync, void *key)
1127{
1128 struct io_wq *wq = container_of(wait, struct io_wq, wait);
1129 int i;
1130
1131 list_del_init(&wait->entry);
1132
1133 rcu_read_lock();
1134 for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1135 struct io_wq_acct *acct = &wq->acct[i];
1136
1137 if (test_and_clear_bit(IO_ACCT_STALLED_BIT, &acct->flags))
1138 io_wq_activate_free_worker(wq, acct);
1139 }
1140 rcu_read_unlock();
1141 return 1;
1142}
1143
1144struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
1145{
1146 int ret, i;
1147 struct io_wq *wq;
1148
1149 if (WARN_ON_ONCE(!data->free_work || !data->do_work))
1150 return ERR_PTR(-EINVAL);
1151 if (WARN_ON_ONCE(!bounded))
1152 return ERR_PTR(-EINVAL);
1153
1154 wq = kzalloc(sizeof(struct io_wq), GFP_KERNEL);
1155 if (!wq)
1156 return ERR_PTR(-ENOMEM);
1157
1158 refcount_inc(&data->hash->refs);
1159 wq->hash = data->hash;
1160 wq->free_work = data->free_work;
1161 wq->do_work = data->do_work;
1162
1163 ret = -ENOMEM;
1164
1165 if (!alloc_cpumask_var(&wq->cpu_mask, GFP_KERNEL))
1166 goto err;
1167 cpumask_copy(wq->cpu_mask, cpu_possible_mask);
1168 wq->acct[IO_WQ_ACCT_BOUND].max_workers = bounded;
1169 wq->acct[IO_WQ_ACCT_UNBOUND].max_workers =
1170 task_rlimit(current, RLIMIT_NPROC);
1171 INIT_LIST_HEAD(&wq->wait.entry);
1172 wq->wait.func = io_wq_hash_wake;
1173 for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1174 struct io_wq_acct *acct = &wq->acct[i];
1175
1176 acct->index = i;
1177 atomic_set(&acct->nr_running, 0);
1178 INIT_WQ_LIST(&acct->work_list);
1179 raw_spin_lock_init(&acct->lock);
1180 }
1181
1182 raw_spin_lock_init(&wq->lock);
1183 INIT_HLIST_NULLS_HEAD(&wq->free_list, 0);
1184 INIT_LIST_HEAD(&wq->all_list);
1185
1186 wq->task = get_task_struct(data->task);
1187 atomic_set(&wq->worker_refs, 1);
1188 init_completion(&wq->worker_done);
1189 ret = cpuhp_state_add_instance_nocalls(io_wq_online, &wq->cpuhp_node);
1190 if (ret)
1191 goto err;
1192
1193 return wq;
1194err:
1195 io_wq_put_hash(data->hash);
1196 free_cpumask_var(wq->cpu_mask);
1197 kfree(wq);
1198 return ERR_PTR(ret);
1199}
1200
1201static bool io_task_work_match(struct callback_head *cb, void *data)
1202{
1203 struct io_worker *worker;
1204
1205 if (cb->func != create_worker_cb && cb->func != create_worker_cont)
1206 return false;
1207 worker = container_of(cb, struct io_worker, create_work);
1208 return worker->wq == data;
1209}
1210
1211void io_wq_exit_start(struct io_wq *wq)
1212{
1213 set_bit(IO_WQ_BIT_EXIT, &wq->state);
1214}
1215
1216static void io_wq_cancel_tw_create(struct io_wq *wq)
1217{
1218 struct callback_head *cb;
1219
1220 while ((cb = task_work_cancel_match(wq->task, io_task_work_match, wq)) != NULL) {
1221 struct io_worker *worker;
1222
1223 worker = container_of(cb, struct io_worker, create_work);
1224 io_worker_cancel_cb(worker);
1225 /*
1226 * Only the worker continuation helper has worker allocated and
1227 * hence needs freeing.
1228 */
1229 if (cb->func == create_worker_cont)
1230 kfree(worker);
1231 }
1232}
1233
1234static void io_wq_exit_workers(struct io_wq *wq)
1235{
1236 if (!wq->task)
1237 return;
1238
1239 io_wq_cancel_tw_create(wq);
1240
1241 rcu_read_lock();
1242 io_wq_for_each_worker(wq, io_wq_worker_wake, NULL);
1243 rcu_read_unlock();
1244 io_worker_ref_put(wq);
1245 wait_for_completion(&wq->worker_done);
1246
1247 spin_lock_irq(&wq->hash->wait.lock);
1248 list_del_init(&wq->wait.entry);
1249 spin_unlock_irq(&wq->hash->wait.lock);
1250
1251 put_task_struct(wq->task);
1252 wq->task = NULL;
1253}
1254
1255static void io_wq_destroy(struct io_wq *wq)
1256{
1257 struct io_cb_cancel_data match = {
1258 .fn = io_wq_work_match_all,
1259 .cancel_all = true,
1260 };
1261
1262 cpuhp_state_remove_instance_nocalls(io_wq_online, &wq->cpuhp_node);
1263 io_wq_cancel_pending_work(wq, &match);
1264 free_cpumask_var(wq->cpu_mask);
1265 io_wq_put_hash(wq->hash);
1266 kfree(wq);
1267}
1268
1269void io_wq_put_and_exit(struct io_wq *wq)
1270{
1271 WARN_ON_ONCE(!test_bit(IO_WQ_BIT_EXIT, &wq->state));
1272
1273 io_wq_exit_workers(wq);
1274 io_wq_destroy(wq);
1275}
1276
1277struct online_data {
1278 unsigned int cpu;
1279 bool online;
1280};
1281
1282static bool io_wq_worker_affinity(struct io_worker *worker, void *data)
1283{
1284 struct online_data *od = data;
1285
1286 if (od->online)
1287 cpumask_set_cpu(od->cpu, worker->wq->cpu_mask);
1288 else
1289 cpumask_clear_cpu(od->cpu, worker->wq->cpu_mask);
1290 return false;
1291}
1292
1293static int __io_wq_cpu_online(struct io_wq *wq, unsigned int cpu, bool online)
1294{
1295 struct online_data od = {
1296 .cpu = cpu,
1297 .online = online
1298 };
1299
1300 rcu_read_lock();
1301 io_wq_for_each_worker(wq, io_wq_worker_affinity, &od);
1302 rcu_read_unlock();
1303 return 0;
1304}
1305
1306static int io_wq_cpu_online(unsigned int cpu, struct hlist_node *node)
1307{
1308 struct io_wq *wq = hlist_entry_safe(node, struct io_wq, cpuhp_node);
1309
1310 return __io_wq_cpu_online(wq, cpu, true);
1311}
1312
1313static int io_wq_cpu_offline(unsigned int cpu, struct hlist_node *node)
1314{
1315 struct io_wq *wq = hlist_entry_safe(node, struct io_wq, cpuhp_node);
1316
1317 return __io_wq_cpu_online(wq, cpu, false);
1318}
1319
1320int io_wq_cpu_affinity(struct io_uring_task *tctx, cpumask_var_t mask)
1321{
1322 if (!tctx || !tctx->io_wq)
1323 return -EINVAL;
1324
1325 rcu_read_lock();
1326 if (mask)
1327 cpumask_copy(tctx->io_wq->cpu_mask, mask);
1328 else
1329 cpumask_copy(tctx->io_wq->cpu_mask, cpu_possible_mask);
1330 rcu_read_unlock();
1331
1332 return 0;
1333}
1334
1335/*
1336 * Set max number of unbounded workers, returns old value. If new_count is 0,
1337 * then just return the old value.
1338 */
1339int io_wq_max_workers(struct io_wq *wq, int *new_count)
1340{
1341 struct io_wq_acct *acct;
1342 int prev[IO_WQ_ACCT_NR];
1343 int i;
1344
1345 BUILD_BUG_ON((int) IO_WQ_ACCT_BOUND != (int) IO_WQ_BOUND);
1346 BUILD_BUG_ON((int) IO_WQ_ACCT_UNBOUND != (int) IO_WQ_UNBOUND);
1347 BUILD_BUG_ON((int) IO_WQ_ACCT_NR != 2);
1348
1349 for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1350 if (new_count[i] > task_rlimit(current, RLIMIT_NPROC))
1351 new_count[i] = task_rlimit(current, RLIMIT_NPROC);
1352 }
1353
1354 for (i = 0; i < IO_WQ_ACCT_NR; i++)
1355 prev[i] = 0;
1356
1357 rcu_read_lock();
1358
1359 raw_spin_lock(&wq->lock);
1360 for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1361 acct = &wq->acct[i];
1362 prev[i] = max_t(int, acct->max_workers, prev[i]);
1363 if (new_count[i])
1364 acct->max_workers = new_count[i];
1365 }
1366 raw_spin_unlock(&wq->lock);
1367 rcu_read_unlock();
1368
1369 for (i = 0; i < IO_WQ_ACCT_NR; i++)
1370 new_count[i] = prev[i];
1371
1372 return 0;
1373}
1374
1375static __init int io_wq_init(void)
1376{
1377 int ret;
1378
1379 ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "io-wq/online",
1380 io_wq_cpu_online, io_wq_cpu_offline);
1381 if (ret < 0)
1382 return ret;
1383 io_wq_online = ret;
1384 return 0;
1385}
1386subsys_initcall(io_wq_init);