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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/cpuset.h>
17#include <linux/task_work.h>
18#include <linux/audit.h>
19#include <linux/mmu_context.h>
20#include <uapi/linux/io_uring.h>
21
22#include "io-wq.h"
23#include "slist.h"
24#include "io_uring.h"
25
26#define WORKER_IDLE_TIMEOUT (5 * HZ)
27#define WORKER_INIT_LIMIT 3
28
29enum {
30 IO_WORKER_F_UP = 0, /* up and active */
31 IO_WORKER_F_RUNNING = 1, /* account as running */
32 IO_WORKER_F_FREE = 2, /* worker on free list */
33 IO_WORKER_F_BOUND = 3, /* is doing bounded work */
34};
35
36enum {
37 IO_WQ_BIT_EXIT = 0, /* wq exiting */
38};
39
40enum {
41 IO_ACCT_STALLED_BIT = 0, /* stalled on hash */
42};
43
44/*
45 * One for each thread in a wq pool
46 */
47struct io_worker {
48 refcount_t ref;
49 int create_index;
50 unsigned long flags;
51 struct hlist_nulls_node nulls_node;
52 struct list_head all_list;
53 struct task_struct *task;
54 struct io_wq *wq;
55
56 struct io_wq_work *cur_work;
57 raw_spinlock_t lock;
58
59 struct completion ref_done;
60
61 unsigned long create_state;
62 struct callback_head create_work;
63 int init_retries;
64
65 union {
66 struct rcu_head rcu;
67 struct work_struct work;
68 };
69};
70
71#if BITS_PER_LONG == 64
72#define IO_WQ_HASH_ORDER 6
73#else
74#define IO_WQ_HASH_ORDER 5
75#endif
76
77#define IO_WQ_NR_HASH_BUCKETS (1u << IO_WQ_HASH_ORDER)
78
79struct io_wq_acct {
80 unsigned nr_workers;
81 unsigned max_workers;
82 int index;
83 atomic_t nr_running;
84 raw_spinlock_t lock;
85 struct io_wq_work_list work_list;
86 unsigned long flags;
87};
88
89enum {
90 IO_WQ_ACCT_BOUND,
91 IO_WQ_ACCT_UNBOUND,
92 IO_WQ_ACCT_NR,
93};
94
95/*
96 * Per io_wq state
97 */
98struct io_wq {
99 unsigned long state;
100
101 free_work_fn *free_work;
102 io_wq_work_fn *do_work;
103
104 struct io_wq_hash *hash;
105
106 atomic_t worker_refs;
107 struct completion worker_done;
108
109 struct hlist_node cpuhp_node;
110
111 struct task_struct *task;
112
113 struct io_wq_acct acct[IO_WQ_ACCT_NR];
114
115 /* lock protects access to elements below */
116 raw_spinlock_t lock;
117
118 struct hlist_nulls_head free_list;
119 struct list_head all_list;
120
121 struct wait_queue_entry wait;
122
123 struct io_wq_work *hash_tail[IO_WQ_NR_HASH_BUCKETS];
124
125 cpumask_var_t cpu_mask;
126};
127
128static enum cpuhp_state io_wq_online;
129
130struct io_cb_cancel_data {
131 work_cancel_fn *fn;
132 void *data;
133 int nr_running;
134 int nr_pending;
135 bool cancel_all;
136};
137
138static bool create_io_worker(struct io_wq *wq, int index);
139static void io_wq_dec_running(struct io_worker *worker);
140static bool io_acct_cancel_pending_work(struct io_wq *wq,
141 struct io_wq_acct *acct,
142 struct io_cb_cancel_data *match);
143static void create_worker_cb(struct callback_head *cb);
144static void io_wq_cancel_tw_create(struct io_wq *wq);
145
146static bool io_worker_get(struct io_worker *worker)
147{
148 return refcount_inc_not_zero(&worker->ref);
149}
150
151static void io_worker_release(struct io_worker *worker)
152{
153 if (refcount_dec_and_test(&worker->ref))
154 complete(&worker->ref_done);
155}
156
157static inline struct io_wq_acct *io_get_acct(struct io_wq *wq, bool bound)
158{
159 return &wq->acct[bound ? IO_WQ_ACCT_BOUND : IO_WQ_ACCT_UNBOUND];
160}
161
162static inline struct io_wq_acct *io_work_get_acct(struct io_wq *wq,
163 struct io_wq_work *work)
164{
165 return io_get_acct(wq, !(atomic_read(&work->flags) & IO_WQ_WORK_UNBOUND));
166}
167
168static inline struct io_wq_acct *io_wq_get_acct(struct io_worker *worker)
169{
170 return io_get_acct(worker->wq, test_bit(IO_WORKER_F_BOUND, &worker->flags));
171}
172
173static void io_worker_ref_put(struct io_wq *wq)
174{
175 if (atomic_dec_and_test(&wq->worker_refs))
176 complete(&wq->worker_done);
177}
178
179bool io_wq_worker_stopped(void)
180{
181 struct io_worker *worker = current->worker_private;
182
183 if (WARN_ON_ONCE(!io_wq_current_is_worker()))
184 return true;
185
186 return test_bit(IO_WQ_BIT_EXIT, &worker->wq->state);
187}
188
189static void io_worker_cancel_cb(struct io_worker *worker)
190{
191 struct io_wq_acct *acct = io_wq_get_acct(worker);
192 struct io_wq *wq = worker->wq;
193
194 atomic_dec(&acct->nr_running);
195 raw_spin_lock(&wq->lock);
196 acct->nr_workers--;
197 raw_spin_unlock(&wq->lock);
198 io_worker_ref_put(wq);
199 clear_bit_unlock(0, &worker->create_state);
200 io_worker_release(worker);
201}
202
203static bool io_task_worker_match(struct callback_head *cb, void *data)
204{
205 struct io_worker *worker;
206
207 if (cb->func != create_worker_cb)
208 return false;
209 worker = container_of(cb, struct io_worker, create_work);
210 return worker == data;
211}
212
213static void io_worker_exit(struct io_worker *worker)
214{
215 struct io_wq *wq = worker->wq;
216
217 while (1) {
218 struct callback_head *cb = task_work_cancel_match(wq->task,
219 io_task_worker_match, worker);
220
221 if (!cb)
222 break;
223 io_worker_cancel_cb(worker);
224 }
225
226 io_worker_release(worker);
227 wait_for_completion(&worker->ref_done);
228
229 raw_spin_lock(&wq->lock);
230 if (test_bit(IO_WORKER_F_FREE, &worker->flags))
231 hlist_nulls_del_rcu(&worker->nulls_node);
232 list_del_rcu(&worker->all_list);
233 raw_spin_unlock(&wq->lock);
234 io_wq_dec_running(worker);
235 /*
236 * this worker is a goner, clear ->worker_private to avoid any
237 * inc/dec running calls that could happen as part of exit from
238 * touching 'worker'.
239 */
240 current->worker_private = NULL;
241
242 kfree_rcu(worker, rcu);
243 io_worker_ref_put(wq);
244 do_exit(0);
245}
246
247static inline bool __io_acct_run_queue(struct io_wq_acct *acct)
248{
249 return !test_bit(IO_ACCT_STALLED_BIT, &acct->flags) &&
250 !wq_list_empty(&acct->work_list);
251}
252
253/*
254 * If there's work to do, returns true with acct->lock acquired. If not,
255 * returns false with no lock held.
256 */
257static inline bool io_acct_run_queue(struct io_wq_acct *acct)
258 __acquires(&acct->lock)
259{
260 raw_spin_lock(&acct->lock);
261 if (__io_acct_run_queue(acct))
262 return true;
263
264 raw_spin_unlock(&acct->lock);
265 return false;
266}
267
268/*
269 * Check head of free list for an available worker. If one isn't available,
270 * caller must create one.
271 */
272static bool io_wq_activate_free_worker(struct io_wq *wq,
273 struct io_wq_acct *acct)
274 __must_hold(RCU)
275{
276 struct hlist_nulls_node *n;
277 struct io_worker *worker;
278
279 /*
280 * Iterate free_list and see if we can find an idle worker to
281 * activate. If a given worker is on the free_list but in the process
282 * of exiting, keep trying.
283 */
284 hlist_nulls_for_each_entry_rcu(worker, n, &wq->free_list, nulls_node) {
285 if (!io_worker_get(worker))
286 continue;
287 if (io_wq_get_acct(worker) != acct) {
288 io_worker_release(worker);
289 continue;
290 }
291 /*
292 * If the worker is already running, it's either already
293 * starting work or finishing work. In either case, if it does
294 * to go sleep, we'll kick off a new task for this work anyway.
295 */
296 wake_up_process(worker->task);
297 io_worker_release(worker);
298 return true;
299 }
300
301 return false;
302}
303
304/*
305 * We need a worker. If we find a free one, we're good. If not, and we're
306 * below the max number of workers, create one.
307 */
308static bool io_wq_create_worker(struct io_wq *wq, struct io_wq_acct *acct)
309{
310 /*
311 * Most likely an attempt to queue unbounded work on an io_wq that
312 * wasn't setup with any unbounded workers.
313 */
314 if (unlikely(!acct->max_workers))
315 pr_warn_once("io-wq is not configured for unbound workers");
316
317 raw_spin_lock(&wq->lock);
318 if (acct->nr_workers >= acct->max_workers) {
319 raw_spin_unlock(&wq->lock);
320 return true;
321 }
322 acct->nr_workers++;
323 raw_spin_unlock(&wq->lock);
324 atomic_inc(&acct->nr_running);
325 atomic_inc(&wq->worker_refs);
326 return create_io_worker(wq, acct->index);
327}
328
329static void io_wq_inc_running(struct io_worker *worker)
330{
331 struct io_wq_acct *acct = io_wq_get_acct(worker);
332
333 atomic_inc(&acct->nr_running);
334}
335
336static void create_worker_cb(struct callback_head *cb)
337{
338 struct io_worker *worker;
339 struct io_wq *wq;
340
341 struct io_wq_acct *acct;
342 bool do_create = false;
343
344 worker = container_of(cb, struct io_worker, create_work);
345 wq = worker->wq;
346 acct = &wq->acct[worker->create_index];
347 raw_spin_lock(&wq->lock);
348
349 if (acct->nr_workers < acct->max_workers) {
350 acct->nr_workers++;
351 do_create = true;
352 }
353 raw_spin_unlock(&wq->lock);
354 if (do_create) {
355 create_io_worker(wq, worker->create_index);
356 } else {
357 atomic_dec(&acct->nr_running);
358 io_worker_ref_put(wq);
359 }
360 clear_bit_unlock(0, &worker->create_state);
361 io_worker_release(worker);
362}
363
364static bool io_queue_worker_create(struct io_worker *worker,
365 struct io_wq_acct *acct,
366 task_work_func_t func)
367{
368 struct io_wq *wq = worker->wq;
369
370 /* raced with exit, just ignore create call */
371 if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
372 goto fail;
373 if (!io_worker_get(worker))
374 goto fail;
375 /*
376 * create_state manages ownership of create_work/index. We should
377 * only need one entry per worker, as the worker going to sleep
378 * will trigger the condition, and waking will clear it once it
379 * runs the task_work.
380 */
381 if (test_bit(0, &worker->create_state) ||
382 test_and_set_bit_lock(0, &worker->create_state))
383 goto fail_release;
384
385 atomic_inc(&wq->worker_refs);
386 init_task_work(&worker->create_work, func);
387 worker->create_index = acct->index;
388 if (!task_work_add(wq->task, &worker->create_work, TWA_SIGNAL)) {
389 /*
390 * EXIT may have been set after checking it above, check after
391 * adding the task_work and remove any creation item if it is
392 * now set. wq exit does that too, but we can have added this
393 * work item after we canceled in io_wq_exit_workers().
394 */
395 if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
396 io_wq_cancel_tw_create(wq);
397 io_worker_ref_put(wq);
398 return true;
399 }
400 io_worker_ref_put(wq);
401 clear_bit_unlock(0, &worker->create_state);
402fail_release:
403 io_worker_release(worker);
404fail:
405 atomic_dec(&acct->nr_running);
406 io_worker_ref_put(wq);
407 return false;
408}
409
410static void io_wq_dec_running(struct io_worker *worker)
411{
412 struct io_wq_acct *acct = io_wq_get_acct(worker);
413 struct io_wq *wq = worker->wq;
414
415 if (!test_bit(IO_WORKER_F_UP, &worker->flags))
416 return;
417
418 if (!atomic_dec_and_test(&acct->nr_running))
419 return;
420 if (!io_acct_run_queue(acct))
421 return;
422
423 raw_spin_unlock(&acct->lock);
424 atomic_inc(&acct->nr_running);
425 atomic_inc(&wq->worker_refs);
426 io_queue_worker_create(worker, acct, create_worker_cb);
427}
428
429/*
430 * Worker will start processing some work. Move it to the busy list, if
431 * it's currently on the freelist
432 */
433static void __io_worker_busy(struct io_wq *wq, struct io_worker *worker)
434{
435 if (test_bit(IO_WORKER_F_FREE, &worker->flags)) {
436 clear_bit(IO_WORKER_F_FREE, &worker->flags);
437 raw_spin_lock(&wq->lock);
438 hlist_nulls_del_init_rcu(&worker->nulls_node);
439 raw_spin_unlock(&wq->lock);
440 }
441}
442
443/*
444 * No work, worker going to sleep. Move to freelist.
445 */
446static void __io_worker_idle(struct io_wq *wq, struct io_worker *worker)
447 __must_hold(wq->lock)
448{
449 if (!test_bit(IO_WORKER_F_FREE, &worker->flags)) {
450 set_bit(IO_WORKER_F_FREE, &worker->flags);
451 hlist_nulls_add_head_rcu(&worker->nulls_node, &wq->free_list);
452 }
453}
454
455static inline unsigned int io_get_work_hash(struct io_wq_work *work)
456{
457 return atomic_read(&work->flags) >> IO_WQ_HASH_SHIFT;
458}
459
460static bool io_wait_on_hash(struct io_wq *wq, unsigned int hash)
461{
462 bool ret = false;
463
464 spin_lock_irq(&wq->hash->wait.lock);
465 if (list_empty(&wq->wait.entry)) {
466 __add_wait_queue(&wq->hash->wait, &wq->wait);
467 if (!test_bit(hash, &wq->hash->map)) {
468 __set_current_state(TASK_RUNNING);
469 list_del_init(&wq->wait.entry);
470 ret = true;
471 }
472 }
473 spin_unlock_irq(&wq->hash->wait.lock);
474 return ret;
475}
476
477static struct io_wq_work *io_get_next_work(struct io_wq_acct *acct,
478 struct io_worker *worker)
479 __must_hold(acct->lock)
480{
481 struct io_wq_work_node *node, *prev;
482 struct io_wq_work *work, *tail;
483 unsigned int stall_hash = -1U;
484 struct io_wq *wq = worker->wq;
485
486 wq_list_for_each(node, prev, &acct->work_list) {
487 unsigned int hash;
488
489 work = container_of(node, struct io_wq_work, list);
490
491 /* not hashed, can run anytime */
492 if (!io_wq_is_hashed(work)) {
493 wq_list_del(&acct->work_list, node, prev);
494 return work;
495 }
496
497 hash = io_get_work_hash(work);
498 /* all items with this hash lie in [work, tail] */
499 tail = wq->hash_tail[hash];
500
501 /* hashed, can run if not already running */
502 if (!test_and_set_bit(hash, &wq->hash->map)) {
503 wq->hash_tail[hash] = NULL;
504 wq_list_cut(&acct->work_list, &tail->list, prev);
505 return work;
506 }
507 if (stall_hash == -1U)
508 stall_hash = hash;
509 /* fast forward to a next hash, for-each will fix up @prev */
510 node = &tail->list;
511 }
512
513 if (stall_hash != -1U) {
514 bool unstalled;
515
516 /*
517 * Set this before dropping the lock to avoid racing with new
518 * work being added and clearing the stalled bit.
519 */
520 set_bit(IO_ACCT_STALLED_BIT, &acct->flags);
521 raw_spin_unlock(&acct->lock);
522 unstalled = io_wait_on_hash(wq, stall_hash);
523 raw_spin_lock(&acct->lock);
524 if (unstalled) {
525 clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
526 if (wq_has_sleeper(&wq->hash->wait))
527 wake_up(&wq->hash->wait);
528 }
529 }
530
531 return NULL;
532}
533
534static void io_assign_current_work(struct io_worker *worker,
535 struct io_wq_work *work)
536{
537 if (work) {
538 io_run_task_work();
539 cond_resched();
540 }
541
542 raw_spin_lock(&worker->lock);
543 worker->cur_work = work;
544 raw_spin_unlock(&worker->lock);
545}
546
547/*
548 * Called with acct->lock held, drops it before returning
549 */
550static void io_worker_handle_work(struct io_wq_acct *acct,
551 struct io_worker *worker)
552 __releases(&acct->lock)
553{
554 struct io_wq *wq = worker->wq;
555 bool do_kill = test_bit(IO_WQ_BIT_EXIT, &wq->state);
556
557 do {
558 struct io_wq_work *work;
559
560 /*
561 * If we got some work, mark us as busy. If we didn't, but
562 * the list isn't empty, it means we stalled on hashed work.
563 * Mark us stalled so we don't keep looking for work when we
564 * can't make progress, any work completion or insertion will
565 * clear the stalled flag.
566 */
567 work = io_get_next_work(acct, worker);
568 if (work) {
569 /*
570 * Make sure cancelation can find this, even before
571 * it becomes the active work. That avoids a window
572 * where the work has been removed from our general
573 * work list, but isn't yet discoverable as the
574 * current work item for this worker.
575 */
576 raw_spin_lock(&worker->lock);
577 worker->cur_work = work;
578 raw_spin_unlock(&worker->lock);
579 }
580
581 raw_spin_unlock(&acct->lock);
582
583 if (!work)
584 break;
585
586 __io_worker_busy(wq, worker);
587
588 io_assign_current_work(worker, work);
589 __set_current_state(TASK_RUNNING);
590
591 /* handle a whole dependent link */
592 do {
593 struct io_wq_work *next_hashed, *linked;
594 unsigned int hash = io_get_work_hash(work);
595
596 next_hashed = wq_next_work(work);
597
598 if (do_kill &&
599 (atomic_read(&work->flags) & IO_WQ_WORK_UNBOUND))
600 atomic_or(IO_WQ_WORK_CANCEL, &work->flags);
601 wq->do_work(work);
602 io_assign_current_work(worker, NULL);
603
604 linked = wq->free_work(work);
605 work = next_hashed;
606 if (!work && linked && !io_wq_is_hashed(linked)) {
607 work = linked;
608 linked = NULL;
609 }
610 io_assign_current_work(worker, work);
611 if (linked)
612 io_wq_enqueue(wq, linked);
613
614 if (hash != -1U && !next_hashed) {
615 /* serialize hash clear with wake_up() */
616 spin_lock_irq(&wq->hash->wait.lock);
617 clear_bit(hash, &wq->hash->map);
618 clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
619 spin_unlock_irq(&wq->hash->wait.lock);
620 if (wq_has_sleeper(&wq->hash->wait))
621 wake_up(&wq->hash->wait);
622 }
623 } while (work);
624
625 if (!__io_acct_run_queue(acct))
626 break;
627 raw_spin_lock(&acct->lock);
628 } while (1);
629}
630
631static int io_wq_worker(void *data)
632{
633 struct io_worker *worker = data;
634 struct io_wq_acct *acct = io_wq_get_acct(worker);
635 struct io_wq *wq = worker->wq;
636 bool exit_mask = false, last_timeout = false;
637 char buf[TASK_COMM_LEN];
638
639 set_mask_bits(&worker->flags, 0,
640 BIT(IO_WORKER_F_UP) | BIT(IO_WORKER_F_RUNNING));
641
642 snprintf(buf, sizeof(buf), "iou-wrk-%d", wq->task->pid);
643 set_task_comm(current, buf);
644
645 while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
646 long ret;
647
648 set_current_state(TASK_INTERRUPTIBLE);
649
650 /*
651 * If we have work to do, io_acct_run_queue() returns with
652 * the acct->lock held. If not, it will drop it.
653 */
654 while (io_acct_run_queue(acct))
655 io_worker_handle_work(acct, worker);
656
657 raw_spin_lock(&wq->lock);
658 /*
659 * Last sleep timed out. Exit if we're not the last worker,
660 * or if someone modified our affinity.
661 */
662 if (last_timeout && (exit_mask || acct->nr_workers > 1)) {
663 acct->nr_workers--;
664 raw_spin_unlock(&wq->lock);
665 __set_current_state(TASK_RUNNING);
666 break;
667 }
668 last_timeout = false;
669 __io_worker_idle(wq, worker);
670 raw_spin_unlock(&wq->lock);
671 if (io_run_task_work())
672 continue;
673 ret = schedule_timeout(WORKER_IDLE_TIMEOUT);
674 if (signal_pending(current)) {
675 struct ksignal ksig;
676
677 if (!get_signal(&ksig))
678 continue;
679 break;
680 }
681 if (!ret) {
682 last_timeout = true;
683 exit_mask = !cpumask_test_cpu(raw_smp_processor_id(),
684 wq->cpu_mask);
685 }
686 }
687
688 if (test_bit(IO_WQ_BIT_EXIT, &wq->state) && io_acct_run_queue(acct))
689 io_worker_handle_work(acct, worker);
690
691 io_worker_exit(worker);
692 return 0;
693}
694
695/*
696 * Called when a worker is scheduled in. Mark us as currently running.
697 */
698void io_wq_worker_running(struct task_struct *tsk)
699{
700 struct io_worker *worker = tsk->worker_private;
701
702 if (!worker)
703 return;
704 if (!test_bit(IO_WORKER_F_UP, &worker->flags))
705 return;
706 if (test_bit(IO_WORKER_F_RUNNING, &worker->flags))
707 return;
708 set_bit(IO_WORKER_F_RUNNING, &worker->flags);
709 io_wq_inc_running(worker);
710}
711
712/*
713 * Called when worker is going to sleep. If there are no workers currently
714 * running and we have work pending, wake up a free one or create a new one.
715 */
716void io_wq_worker_sleeping(struct task_struct *tsk)
717{
718 struct io_worker *worker = tsk->worker_private;
719
720 if (!worker)
721 return;
722 if (!test_bit(IO_WORKER_F_UP, &worker->flags))
723 return;
724 if (!test_bit(IO_WORKER_F_RUNNING, &worker->flags))
725 return;
726
727 clear_bit(IO_WORKER_F_RUNNING, &worker->flags);
728 io_wq_dec_running(worker);
729}
730
731static void io_init_new_worker(struct io_wq *wq, struct io_worker *worker,
732 struct task_struct *tsk)
733{
734 tsk->worker_private = worker;
735 worker->task = tsk;
736 set_cpus_allowed_ptr(tsk, wq->cpu_mask);
737
738 raw_spin_lock(&wq->lock);
739 hlist_nulls_add_head_rcu(&worker->nulls_node, &wq->free_list);
740 list_add_tail_rcu(&worker->all_list, &wq->all_list);
741 set_bit(IO_WORKER_F_FREE, &worker->flags);
742 raw_spin_unlock(&wq->lock);
743 wake_up_new_task(tsk);
744}
745
746static bool io_wq_work_match_all(struct io_wq_work *work, void *data)
747{
748 return true;
749}
750
751static inline bool io_should_retry_thread(struct io_worker *worker, long err)
752{
753 /*
754 * Prevent perpetual task_work retry, if the task (or its group) is
755 * exiting.
756 */
757 if (fatal_signal_pending(current))
758 return false;
759 if (worker->init_retries++ >= WORKER_INIT_LIMIT)
760 return false;
761
762 switch (err) {
763 case -EAGAIN:
764 case -ERESTARTSYS:
765 case -ERESTARTNOINTR:
766 case -ERESTARTNOHAND:
767 return true;
768 default:
769 return false;
770 }
771}
772
773static void create_worker_cont(struct callback_head *cb)
774{
775 struct io_worker *worker;
776 struct task_struct *tsk;
777 struct io_wq *wq;
778
779 worker = container_of(cb, struct io_worker, create_work);
780 clear_bit_unlock(0, &worker->create_state);
781 wq = worker->wq;
782 tsk = create_io_thread(io_wq_worker, worker, NUMA_NO_NODE);
783 if (!IS_ERR(tsk)) {
784 io_init_new_worker(wq, worker, tsk);
785 io_worker_release(worker);
786 return;
787 } else if (!io_should_retry_thread(worker, PTR_ERR(tsk))) {
788 struct io_wq_acct *acct = io_wq_get_acct(worker);
789
790 atomic_dec(&acct->nr_running);
791 raw_spin_lock(&wq->lock);
792 acct->nr_workers--;
793 if (!acct->nr_workers) {
794 struct io_cb_cancel_data match = {
795 .fn = io_wq_work_match_all,
796 .cancel_all = true,
797 };
798
799 raw_spin_unlock(&wq->lock);
800 while (io_acct_cancel_pending_work(wq, acct, &match))
801 ;
802 } else {
803 raw_spin_unlock(&wq->lock);
804 }
805 io_worker_ref_put(wq);
806 kfree(worker);
807 return;
808 }
809
810 /* re-create attempts grab a new worker ref, drop the existing one */
811 io_worker_release(worker);
812 schedule_work(&worker->work);
813}
814
815static void io_workqueue_create(struct work_struct *work)
816{
817 struct io_worker *worker = container_of(work, struct io_worker, work);
818 struct io_wq_acct *acct = io_wq_get_acct(worker);
819
820 if (!io_queue_worker_create(worker, acct, create_worker_cont))
821 kfree(worker);
822}
823
824static bool create_io_worker(struct io_wq *wq, int index)
825{
826 struct io_wq_acct *acct = &wq->acct[index];
827 struct io_worker *worker;
828 struct task_struct *tsk;
829
830 __set_current_state(TASK_RUNNING);
831
832 worker = kzalloc(sizeof(*worker), GFP_KERNEL);
833 if (!worker) {
834fail:
835 atomic_dec(&acct->nr_running);
836 raw_spin_lock(&wq->lock);
837 acct->nr_workers--;
838 raw_spin_unlock(&wq->lock);
839 io_worker_ref_put(wq);
840 return false;
841 }
842
843 refcount_set(&worker->ref, 1);
844 worker->wq = wq;
845 raw_spin_lock_init(&worker->lock);
846 init_completion(&worker->ref_done);
847
848 if (index == IO_WQ_ACCT_BOUND)
849 set_bit(IO_WORKER_F_BOUND, &worker->flags);
850
851 tsk = create_io_thread(io_wq_worker, worker, NUMA_NO_NODE);
852 if (!IS_ERR(tsk)) {
853 io_init_new_worker(wq, worker, tsk);
854 } else if (!io_should_retry_thread(worker, PTR_ERR(tsk))) {
855 kfree(worker);
856 goto fail;
857 } else {
858 INIT_WORK(&worker->work, io_workqueue_create);
859 schedule_work(&worker->work);
860 }
861
862 return true;
863}
864
865/*
866 * Iterate the passed in list and call the specific function for each
867 * worker that isn't exiting
868 */
869static bool io_wq_for_each_worker(struct io_wq *wq,
870 bool (*func)(struct io_worker *, void *),
871 void *data)
872{
873 struct io_worker *worker;
874 bool ret = false;
875
876 list_for_each_entry_rcu(worker, &wq->all_list, all_list) {
877 if (io_worker_get(worker)) {
878 /* no task if node is/was offline */
879 if (worker->task)
880 ret = func(worker, data);
881 io_worker_release(worker);
882 if (ret)
883 break;
884 }
885 }
886
887 return ret;
888}
889
890static bool io_wq_worker_wake(struct io_worker *worker, void *data)
891{
892 __set_notify_signal(worker->task);
893 wake_up_process(worker->task);
894 return false;
895}
896
897static void io_run_cancel(struct io_wq_work *work, struct io_wq *wq)
898{
899 do {
900 atomic_or(IO_WQ_WORK_CANCEL, &work->flags);
901 wq->do_work(work);
902 work = wq->free_work(work);
903 } while (work);
904}
905
906static void io_wq_insert_work(struct io_wq *wq, struct io_wq_work *work)
907{
908 struct io_wq_acct *acct = io_work_get_acct(wq, work);
909 unsigned int hash;
910 struct io_wq_work *tail;
911
912 if (!io_wq_is_hashed(work)) {
913append:
914 wq_list_add_tail(&work->list, &acct->work_list);
915 return;
916 }
917
918 hash = io_get_work_hash(work);
919 tail = wq->hash_tail[hash];
920 wq->hash_tail[hash] = work;
921 if (!tail)
922 goto append;
923
924 wq_list_add_after(&work->list, &tail->list, &acct->work_list);
925}
926
927static bool io_wq_work_match_item(struct io_wq_work *work, void *data)
928{
929 return work == data;
930}
931
932void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work)
933{
934 struct io_wq_acct *acct = io_work_get_acct(wq, work);
935 unsigned int work_flags = atomic_read(&work->flags);
936 struct io_cb_cancel_data match = {
937 .fn = io_wq_work_match_item,
938 .data = work,
939 .cancel_all = false,
940 };
941 bool do_create;
942
943 /*
944 * If io-wq is exiting for this task, or if the request has explicitly
945 * been marked as one that should not get executed, cancel it here.
946 */
947 if (test_bit(IO_WQ_BIT_EXIT, &wq->state) ||
948 (work_flags & IO_WQ_WORK_CANCEL)) {
949 io_run_cancel(work, wq);
950 return;
951 }
952
953 raw_spin_lock(&acct->lock);
954 io_wq_insert_work(wq, work);
955 clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
956 raw_spin_unlock(&acct->lock);
957
958 rcu_read_lock();
959 do_create = !io_wq_activate_free_worker(wq, acct);
960 rcu_read_unlock();
961
962 if (do_create && ((work_flags & IO_WQ_WORK_CONCURRENT) ||
963 !atomic_read(&acct->nr_running))) {
964 bool did_create;
965
966 did_create = io_wq_create_worker(wq, acct);
967 if (likely(did_create))
968 return;
969
970 raw_spin_lock(&wq->lock);
971 if (acct->nr_workers) {
972 raw_spin_unlock(&wq->lock);
973 return;
974 }
975 raw_spin_unlock(&wq->lock);
976
977 /* fatal condition, failed to create the first worker */
978 io_acct_cancel_pending_work(wq, acct, &match);
979 }
980}
981
982/*
983 * Work items that hash to the same value will not be done in parallel.
984 * Used to limit concurrent writes, generally hashed by inode.
985 */
986void io_wq_hash_work(struct io_wq_work *work, void *val)
987{
988 unsigned int bit;
989
990 bit = hash_ptr(val, IO_WQ_HASH_ORDER);
991 atomic_or(IO_WQ_WORK_HASHED | (bit << IO_WQ_HASH_SHIFT), &work->flags);
992}
993
994static bool __io_wq_worker_cancel(struct io_worker *worker,
995 struct io_cb_cancel_data *match,
996 struct io_wq_work *work)
997{
998 if (work && match->fn(work, match->data)) {
999 atomic_or(IO_WQ_WORK_CANCEL, &work->flags);
1000 __set_notify_signal(worker->task);
1001 return true;
1002 }
1003
1004 return false;
1005}
1006
1007static bool io_wq_worker_cancel(struct io_worker *worker, void *data)
1008{
1009 struct io_cb_cancel_data *match = data;
1010
1011 /*
1012 * Hold the lock to avoid ->cur_work going out of scope, caller
1013 * may dereference the passed in work.
1014 */
1015 raw_spin_lock(&worker->lock);
1016 if (__io_wq_worker_cancel(worker, match, worker->cur_work))
1017 match->nr_running++;
1018 raw_spin_unlock(&worker->lock);
1019
1020 return match->nr_running && !match->cancel_all;
1021}
1022
1023static inline void io_wq_remove_pending(struct io_wq *wq,
1024 struct io_wq_work *work,
1025 struct io_wq_work_node *prev)
1026{
1027 struct io_wq_acct *acct = io_work_get_acct(wq, work);
1028 unsigned int hash = io_get_work_hash(work);
1029 struct io_wq_work *prev_work = NULL;
1030
1031 if (io_wq_is_hashed(work) && work == wq->hash_tail[hash]) {
1032 if (prev)
1033 prev_work = container_of(prev, struct io_wq_work, list);
1034 if (prev_work && io_get_work_hash(prev_work) == hash)
1035 wq->hash_tail[hash] = prev_work;
1036 else
1037 wq->hash_tail[hash] = NULL;
1038 }
1039 wq_list_del(&acct->work_list, &work->list, prev);
1040}
1041
1042static bool io_acct_cancel_pending_work(struct io_wq *wq,
1043 struct io_wq_acct *acct,
1044 struct io_cb_cancel_data *match)
1045{
1046 struct io_wq_work_node *node, *prev;
1047 struct io_wq_work *work;
1048
1049 raw_spin_lock(&acct->lock);
1050 wq_list_for_each(node, prev, &acct->work_list) {
1051 work = container_of(node, struct io_wq_work, list);
1052 if (!match->fn(work, match->data))
1053 continue;
1054 io_wq_remove_pending(wq, work, prev);
1055 raw_spin_unlock(&acct->lock);
1056 io_run_cancel(work, wq);
1057 match->nr_pending++;
1058 /* not safe to continue after unlock */
1059 return true;
1060 }
1061 raw_spin_unlock(&acct->lock);
1062
1063 return false;
1064}
1065
1066static void io_wq_cancel_pending_work(struct io_wq *wq,
1067 struct io_cb_cancel_data *match)
1068{
1069 int i;
1070retry:
1071 for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1072 struct io_wq_acct *acct = io_get_acct(wq, i == 0);
1073
1074 if (io_acct_cancel_pending_work(wq, acct, match)) {
1075 if (match->cancel_all)
1076 goto retry;
1077 break;
1078 }
1079 }
1080}
1081
1082static void io_wq_cancel_running_work(struct io_wq *wq,
1083 struct io_cb_cancel_data *match)
1084{
1085 rcu_read_lock();
1086 io_wq_for_each_worker(wq, io_wq_worker_cancel, match);
1087 rcu_read_unlock();
1088}
1089
1090enum io_wq_cancel io_wq_cancel_cb(struct io_wq *wq, work_cancel_fn *cancel,
1091 void *data, bool cancel_all)
1092{
1093 struct io_cb_cancel_data match = {
1094 .fn = cancel,
1095 .data = data,
1096 .cancel_all = cancel_all,
1097 };
1098
1099 /*
1100 * First check pending list, if we're lucky we can just remove it
1101 * from there. CANCEL_OK means that the work is returned as-new,
1102 * no completion will be posted for it.
1103 *
1104 * Then check if a free (going busy) or busy worker has the work
1105 * currently running. If we find it there, we'll return CANCEL_RUNNING
1106 * as an indication that we attempt to signal cancellation. The
1107 * completion will run normally in this case.
1108 *
1109 * Do both of these while holding the wq->lock, to ensure that
1110 * we'll find a work item regardless of state.
1111 */
1112 io_wq_cancel_pending_work(wq, &match);
1113 if (match.nr_pending && !match.cancel_all)
1114 return IO_WQ_CANCEL_OK;
1115
1116 raw_spin_lock(&wq->lock);
1117 io_wq_cancel_running_work(wq, &match);
1118 raw_spin_unlock(&wq->lock);
1119 if (match.nr_running && !match.cancel_all)
1120 return IO_WQ_CANCEL_RUNNING;
1121
1122 if (match.nr_running)
1123 return IO_WQ_CANCEL_RUNNING;
1124 if (match.nr_pending)
1125 return IO_WQ_CANCEL_OK;
1126 return IO_WQ_CANCEL_NOTFOUND;
1127}
1128
1129static int io_wq_hash_wake(struct wait_queue_entry *wait, unsigned mode,
1130 int sync, void *key)
1131{
1132 struct io_wq *wq = container_of(wait, struct io_wq, wait);
1133 int i;
1134
1135 list_del_init(&wait->entry);
1136
1137 rcu_read_lock();
1138 for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1139 struct io_wq_acct *acct = &wq->acct[i];
1140
1141 if (test_and_clear_bit(IO_ACCT_STALLED_BIT, &acct->flags))
1142 io_wq_activate_free_worker(wq, acct);
1143 }
1144 rcu_read_unlock();
1145 return 1;
1146}
1147
1148struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
1149{
1150 int ret, i;
1151 struct io_wq *wq;
1152
1153 if (WARN_ON_ONCE(!data->free_work || !data->do_work))
1154 return ERR_PTR(-EINVAL);
1155 if (WARN_ON_ONCE(!bounded))
1156 return ERR_PTR(-EINVAL);
1157
1158 wq = kzalloc(sizeof(struct io_wq), GFP_KERNEL);
1159 if (!wq)
1160 return ERR_PTR(-ENOMEM);
1161
1162 refcount_inc(&data->hash->refs);
1163 wq->hash = data->hash;
1164 wq->free_work = data->free_work;
1165 wq->do_work = data->do_work;
1166
1167 ret = -ENOMEM;
1168
1169 if (!alloc_cpumask_var(&wq->cpu_mask, GFP_KERNEL))
1170 goto err;
1171 cpuset_cpus_allowed(data->task, wq->cpu_mask);
1172 wq->acct[IO_WQ_ACCT_BOUND].max_workers = bounded;
1173 wq->acct[IO_WQ_ACCT_UNBOUND].max_workers =
1174 task_rlimit(current, RLIMIT_NPROC);
1175 INIT_LIST_HEAD(&wq->wait.entry);
1176 wq->wait.func = io_wq_hash_wake;
1177 for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1178 struct io_wq_acct *acct = &wq->acct[i];
1179
1180 acct->index = i;
1181 atomic_set(&acct->nr_running, 0);
1182 INIT_WQ_LIST(&acct->work_list);
1183 raw_spin_lock_init(&acct->lock);
1184 }
1185
1186 raw_spin_lock_init(&wq->lock);
1187 INIT_HLIST_NULLS_HEAD(&wq->free_list, 0);
1188 INIT_LIST_HEAD(&wq->all_list);
1189
1190 wq->task = get_task_struct(data->task);
1191 atomic_set(&wq->worker_refs, 1);
1192 init_completion(&wq->worker_done);
1193 ret = cpuhp_state_add_instance_nocalls(io_wq_online, &wq->cpuhp_node);
1194 if (ret)
1195 goto err;
1196
1197 return wq;
1198err:
1199 io_wq_put_hash(data->hash);
1200 free_cpumask_var(wq->cpu_mask);
1201 kfree(wq);
1202 return ERR_PTR(ret);
1203}
1204
1205static bool io_task_work_match(struct callback_head *cb, void *data)
1206{
1207 struct io_worker *worker;
1208
1209 if (cb->func != create_worker_cb && cb->func != create_worker_cont)
1210 return false;
1211 worker = container_of(cb, struct io_worker, create_work);
1212 return worker->wq == data;
1213}
1214
1215void io_wq_exit_start(struct io_wq *wq)
1216{
1217 set_bit(IO_WQ_BIT_EXIT, &wq->state);
1218}
1219
1220static void io_wq_cancel_tw_create(struct io_wq *wq)
1221{
1222 struct callback_head *cb;
1223
1224 while ((cb = task_work_cancel_match(wq->task, io_task_work_match, wq)) != NULL) {
1225 struct io_worker *worker;
1226
1227 worker = container_of(cb, struct io_worker, create_work);
1228 io_worker_cancel_cb(worker);
1229 /*
1230 * Only the worker continuation helper has worker allocated and
1231 * hence needs freeing.
1232 */
1233 if (cb->func == create_worker_cont)
1234 kfree(worker);
1235 }
1236}
1237
1238static void io_wq_exit_workers(struct io_wq *wq)
1239{
1240 if (!wq->task)
1241 return;
1242
1243 io_wq_cancel_tw_create(wq);
1244
1245 rcu_read_lock();
1246 io_wq_for_each_worker(wq, io_wq_worker_wake, NULL);
1247 rcu_read_unlock();
1248 io_worker_ref_put(wq);
1249 wait_for_completion(&wq->worker_done);
1250
1251 spin_lock_irq(&wq->hash->wait.lock);
1252 list_del_init(&wq->wait.entry);
1253 spin_unlock_irq(&wq->hash->wait.lock);
1254
1255 put_task_struct(wq->task);
1256 wq->task = NULL;
1257}
1258
1259static void io_wq_destroy(struct io_wq *wq)
1260{
1261 struct io_cb_cancel_data match = {
1262 .fn = io_wq_work_match_all,
1263 .cancel_all = true,
1264 };
1265
1266 cpuhp_state_remove_instance_nocalls(io_wq_online, &wq->cpuhp_node);
1267 io_wq_cancel_pending_work(wq, &match);
1268 free_cpumask_var(wq->cpu_mask);
1269 io_wq_put_hash(wq->hash);
1270 kfree(wq);
1271}
1272
1273void io_wq_put_and_exit(struct io_wq *wq)
1274{
1275 WARN_ON_ONCE(!test_bit(IO_WQ_BIT_EXIT, &wq->state));
1276
1277 io_wq_exit_workers(wq);
1278 io_wq_destroy(wq);
1279}
1280
1281struct online_data {
1282 unsigned int cpu;
1283 bool online;
1284};
1285
1286static bool io_wq_worker_affinity(struct io_worker *worker, void *data)
1287{
1288 struct online_data *od = data;
1289
1290 if (od->online)
1291 cpumask_set_cpu(od->cpu, worker->wq->cpu_mask);
1292 else
1293 cpumask_clear_cpu(od->cpu, worker->wq->cpu_mask);
1294 return false;
1295}
1296
1297static int __io_wq_cpu_online(struct io_wq *wq, unsigned int cpu, bool online)
1298{
1299 struct online_data od = {
1300 .cpu = cpu,
1301 .online = online
1302 };
1303
1304 rcu_read_lock();
1305 io_wq_for_each_worker(wq, io_wq_worker_affinity, &od);
1306 rcu_read_unlock();
1307 return 0;
1308}
1309
1310static int io_wq_cpu_online(unsigned int cpu, struct hlist_node *node)
1311{
1312 struct io_wq *wq = hlist_entry_safe(node, struct io_wq, cpuhp_node);
1313
1314 return __io_wq_cpu_online(wq, cpu, true);
1315}
1316
1317static int io_wq_cpu_offline(unsigned int cpu, struct hlist_node *node)
1318{
1319 struct io_wq *wq = hlist_entry_safe(node, struct io_wq, cpuhp_node);
1320
1321 return __io_wq_cpu_online(wq, cpu, false);
1322}
1323
1324int io_wq_cpu_affinity(struct io_uring_task *tctx, cpumask_var_t mask)
1325{
1326 cpumask_var_t allowed_mask;
1327 int ret = 0;
1328
1329 if (!tctx || !tctx->io_wq)
1330 return -EINVAL;
1331
1332 if (!alloc_cpumask_var(&allowed_mask, GFP_KERNEL))
1333 return -ENOMEM;
1334
1335 rcu_read_lock();
1336 cpuset_cpus_allowed(tctx->io_wq->task, allowed_mask);
1337 if (mask) {
1338 if (cpumask_subset(mask, allowed_mask))
1339 cpumask_copy(tctx->io_wq->cpu_mask, mask);
1340 else
1341 ret = -EINVAL;
1342 } else {
1343 cpumask_copy(tctx->io_wq->cpu_mask, allowed_mask);
1344 }
1345 rcu_read_unlock();
1346
1347 free_cpumask_var(allowed_mask);
1348 return ret;
1349}
1350
1351/*
1352 * Set max number of unbounded workers, returns old value. If new_count is 0,
1353 * then just return the old value.
1354 */
1355int io_wq_max_workers(struct io_wq *wq, int *new_count)
1356{
1357 struct io_wq_acct *acct;
1358 int prev[IO_WQ_ACCT_NR];
1359 int i;
1360
1361 BUILD_BUG_ON((int) IO_WQ_ACCT_BOUND != (int) IO_WQ_BOUND);
1362 BUILD_BUG_ON((int) IO_WQ_ACCT_UNBOUND != (int) IO_WQ_UNBOUND);
1363 BUILD_BUG_ON((int) IO_WQ_ACCT_NR != 2);
1364
1365 for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1366 if (new_count[i] > task_rlimit(current, RLIMIT_NPROC))
1367 new_count[i] = task_rlimit(current, RLIMIT_NPROC);
1368 }
1369
1370 for (i = 0; i < IO_WQ_ACCT_NR; i++)
1371 prev[i] = 0;
1372
1373 rcu_read_lock();
1374
1375 raw_spin_lock(&wq->lock);
1376 for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1377 acct = &wq->acct[i];
1378 prev[i] = max_t(int, acct->max_workers, prev[i]);
1379 if (new_count[i])
1380 acct->max_workers = new_count[i];
1381 }
1382 raw_spin_unlock(&wq->lock);
1383 rcu_read_unlock();
1384
1385 for (i = 0; i < IO_WQ_ACCT_NR; i++)
1386 new_count[i] = prev[i];
1387
1388 return 0;
1389}
1390
1391static __init int io_wq_init(void)
1392{
1393 int ret;
1394
1395 ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "io-wq/online",
1396 io_wq_cpu_online, io_wq_cpu_offline);
1397 if (ret < 0)
1398 return ret;
1399 io_wq_online = ret;
1400 return 0;
1401}
1402subsys_initcall(io_wq_init);