io-wq.c 25.9 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
// SPDX-License-Identifier: GPL-2.0
/*
 * Basic worker thread pool for io_uring
 *
 * Copyright (C) 2019 Jens Axboe
 *
 */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/sched/signal.h>
#include <linux/mm.h>
#include <linux/mmu_context.h>
#include <linux/sched/mm.h>
#include <linux/percpu.h>
#include <linux/slab.h>
#include <linux/kthread.h>
#include <linux/rculist_nulls.h>
19
#include <linux/uaccess.h>
20 21 22 23 24 25 26 27 28 29 30

#include "io-wq.h"

#define WORKER_IDLE_TIMEOUT	(5 * HZ)

enum {
	IO_WORKER_F_UP		= 1,	/* up and active */
	IO_WORKER_F_RUNNING	= 2,	/* account as running */
	IO_WORKER_F_FREE	= 4,	/* worker on free list */
	IO_WORKER_F_EXITING	= 8,	/* worker exiting */
	IO_WORKER_F_FIXED	= 16,	/* static idle worker */
31
	IO_WORKER_F_BOUND	= 32,	/* is doing bounded work */
32 33 34 35 36
};

enum {
	IO_WQ_BIT_EXIT		= 0,	/* wq exiting */
	IO_WQ_BIT_CANCEL	= 1,	/* cancel work on list */
37
	IO_WQ_BIT_ERROR		= 2,	/* error on setup */
38 39 40 41 42 43 44 45 46 47 48 49 50
};

enum {
	IO_WQE_FLAG_STALLED	= 1,	/* stalled on hash */
};

/*
 * One for each thread in a wqe pool
 */
struct io_worker {
	refcount_t ref;
	unsigned flags;
	struct hlist_nulls_node nulls_node;
51
	struct list_head all_list;
52 53 54
	struct task_struct *task;
	wait_queue_head_t wait;
	struct io_wqe *wqe;
55

56
	struct io_wq_work *cur_work;
57
	spinlock_t lock;
58 59 60

	struct rcu_head rcu;
	struct mm_struct *mm;
61
	const struct cred *creds;
62
	struct files_struct *restore_files;
63 64 65 66 67 68 69 70
};

#if BITS_PER_LONG == 64
#define IO_WQ_HASH_ORDER	6
#else
#define IO_WQ_HASH_ORDER	5
#endif

71 72 73 74 75 76 77 78 79 80 81
struct io_wqe_acct {
	unsigned nr_workers;
	unsigned max_workers;
	atomic_t nr_running;
};

enum {
	IO_WQ_ACCT_BOUND,
	IO_WQ_ACCT_UNBOUND,
};

82 83 84 85 86 87 88 89 90 91 92 93
/*
 * Per-node worker thread pool
 */
struct io_wqe {
	struct {
		spinlock_t lock;
		struct list_head work_list;
		unsigned long hash_map;
		unsigned flags;
	} ____cacheline_aligned_in_smp;

	int node;
94
	struct io_wqe_acct acct[2];
95

96 97
	struct hlist_nulls_head free_list;
	struct hlist_nulls_head busy_list;
98
	struct list_head all_list;
99 100 101 102 103 104 105 106 107 108 109 110

	struct io_wq *wq;
};

/*
 * Per io_wq state
  */
struct io_wq {
	struct io_wqe **wqes;
	unsigned long state;
	unsigned nr_wqes;

111 112 113
	get_work_fn *get_work;
	put_work_fn *put_work;

114
	struct task_struct *manager;
115
	struct user_struct *user;
116
	const struct cred *creds;
117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139
	struct mm_struct *mm;
	refcount_t refs;
	struct completion done;
};

static bool io_worker_get(struct io_worker *worker)
{
	return refcount_inc_not_zero(&worker->ref);
}

static void io_worker_release(struct io_worker *worker)
{
	if (refcount_dec_and_test(&worker->ref))
		wake_up_process(worker->task);
}

/*
 * Note: drops the wqe->lock if returning true! The caller must re-acquire
 * the lock in that case. Some callers need to restart handling if this
 * happens, so we can't just re-acquire the lock on behalf of the caller.
 */
static bool __io_worker_unuse(struct io_wqe *wqe, struct io_worker *worker)
{
140 141
	bool dropped_lock = false;

142 143 144 145 146
	if (worker->creds) {
		revert_creds(worker->creds);
		worker->creds = NULL;
	}

147 148 149 150 151 152 153 154 155 156
	if (current->files != worker->restore_files) {
		__acquire(&wqe->lock);
		spin_unlock_irq(&wqe->lock);
		dropped_lock = true;

		task_lock(current);
		current->files = worker->restore_files;
		task_unlock(current);
	}

157 158 159 160 161
	/*
	 * If we have an active mm, we need to drop the wq lock before unusing
	 * it. If we do, return true and let the caller retry the idle loop.
	 */
	if (worker->mm) {
162 163 164 165 166
		if (!dropped_lock) {
			__acquire(&wqe->lock);
			spin_unlock_irq(&wqe->lock);
			dropped_lock = true;
		}
167 168 169 170 171 172 173
		__set_current_state(TASK_RUNNING);
		set_fs(KERNEL_DS);
		unuse_mm(worker->mm);
		mmput(worker->mm);
		worker->mm = NULL;
	}

174
	return dropped_lock;
175 176
}

177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194
static inline struct io_wqe_acct *io_work_get_acct(struct io_wqe *wqe,
						   struct io_wq_work *work)
{
	if (work->flags & IO_WQ_WORK_UNBOUND)
		return &wqe->acct[IO_WQ_ACCT_UNBOUND];

	return &wqe->acct[IO_WQ_ACCT_BOUND];
}

static inline struct io_wqe_acct *io_wqe_get_acct(struct io_wqe *wqe,
						  struct io_worker *worker)
{
	if (worker->flags & IO_WORKER_F_BOUND)
		return &wqe->acct[IO_WQ_ACCT_BOUND];

	return &wqe->acct[IO_WQ_ACCT_UNBOUND];
}

195 196 197
static void io_worker_exit(struct io_worker *worker)
{
	struct io_wqe *wqe = worker->wqe;
198 199
	struct io_wqe_acct *acct = io_wqe_get_acct(wqe, worker);
	unsigned nr_workers;
200 201 202 203 204 205 206 207 208 209 210 211 212

	/*
	 * If we're not at zero, someone else is holding a brief reference
	 * to the worker. Wait for that to go away.
	 */
	set_current_state(TASK_INTERRUPTIBLE);
	if (!refcount_dec_and_test(&worker->ref))
		schedule();
	__set_current_state(TASK_RUNNING);

	preempt_disable();
	current->flags &= ~PF_IO_WORKER;
	if (worker->flags & IO_WORKER_F_RUNNING)
213 214 215
		atomic_dec(&acct->nr_running);
	if (!(worker->flags & IO_WORKER_F_BOUND))
		atomic_dec(&wqe->wq->user->processes);
216 217 218 219 220
	worker->flags = 0;
	preempt_enable();

	spin_lock_irq(&wqe->lock);
	hlist_nulls_del_rcu(&worker->nulls_node);
221
	list_del_rcu(&worker->all_list);
222 223 224 225
	if (__io_worker_unuse(wqe, worker)) {
		__release(&wqe->lock);
		spin_lock_irq(&wqe->lock);
	}
226 227 228
	acct->nr_workers--;
	nr_workers = wqe->acct[IO_WQ_ACCT_BOUND].nr_workers +
			wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers;
229 230 231
	spin_unlock_irq(&wqe->lock);

	/* all workers gone, wq exit can proceed */
232
	if (!nr_workers && refcount_dec_and_test(&wqe->wq->refs))
233 234
		complete(&wqe->wq->done);

235
	kfree_rcu(worker, rcu);
236 237
}

238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255
static inline bool io_wqe_run_queue(struct io_wqe *wqe)
	__must_hold(wqe->lock)
{
	if (!list_empty(&wqe->work_list) && !(wqe->flags & IO_WQE_FLAG_STALLED))
		return true;
	return false;
}

/*
 * Check head of free list for an available worker. If one isn't available,
 * caller must wake up the wq manager to create one.
 */
static bool io_wqe_activate_free_worker(struct io_wqe *wqe)
	__must_hold(RCU)
{
	struct hlist_nulls_node *n;
	struct io_worker *worker;

256
	n = rcu_dereference(hlist_nulls_first_rcu(&wqe->free_list));
257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307
	if (is_a_nulls(n))
		return false;

	worker = hlist_nulls_entry(n, struct io_worker, nulls_node);
	if (io_worker_get(worker)) {
		wake_up(&worker->wait);
		io_worker_release(worker);
		return true;
	}

	return false;
}

/*
 * We need a worker. If we find a free one, we're good. If not, and we're
 * below the max number of workers, wake up the manager to create one.
 */
static void io_wqe_wake_worker(struct io_wqe *wqe, struct io_wqe_acct *acct)
{
	bool ret;

	/*
	 * Most likely an attempt to queue unbounded work on an io_wq that
	 * wasn't setup with any unbounded workers.
	 */
	WARN_ON_ONCE(!acct->max_workers);

	rcu_read_lock();
	ret = io_wqe_activate_free_worker(wqe);
	rcu_read_unlock();

	if (!ret && acct->nr_workers < acct->max_workers)
		wake_up_process(wqe->wq->manager);
}

static void io_wqe_inc_running(struct io_wqe *wqe, struct io_worker *worker)
{
	struct io_wqe_acct *acct = io_wqe_get_acct(wqe, worker);

	atomic_inc(&acct->nr_running);
}

static void io_wqe_dec_running(struct io_wqe *wqe, struct io_worker *worker)
	__must_hold(wqe->lock)
{
	struct io_wqe_acct *acct = io_wqe_get_acct(wqe, worker);

	if (atomic_dec_and_test(&acct->nr_running) && io_wqe_run_queue(wqe))
		io_wqe_wake_worker(wqe, acct);
}

308 309 310 311 312 313 314
static void io_worker_start(struct io_wqe *wqe, struct io_worker *worker)
{
	allow_kernel_signal(SIGINT);

	current->flags |= PF_IO_WORKER;

	worker->flags |= (IO_WORKER_F_UP | IO_WORKER_F_RUNNING);
315
	worker->restore_files = current->files;
316
	io_wqe_inc_running(wqe, worker);
317 318 319 320 321 322 323 324 325 326
}

/*
 * Worker will start processing some work. Move it to the busy list, if
 * it's currently on the freelist
 */
static void __io_worker_busy(struct io_wqe *wqe, struct io_worker *worker,
			     struct io_wq_work *work)
	__must_hold(wqe->lock)
{
327 328
	bool worker_bound, work_bound;

329 330 331
	if (worker->flags & IO_WORKER_F_FREE) {
		worker->flags &= ~IO_WORKER_F_FREE;
		hlist_nulls_del_init_rcu(&worker->nulls_node);
332
		hlist_nulls_add_head_rcu(&worker->nulls_node, &wqe->busy_list);
333
	}
334 335 336 337 338

	/*
	 * If worker is moving from bound to unbound (or vice versa), then
	 * ensure we update the running accounting.
	 */
339 340 341
	worker_bound = (worker->flags & IO_WORKER_F_BOUND) != 0;
	work_bound = (work->flags & IO_WQ_WORK_UNBOUND) == 0;
	if (worker_bound != work_bound) {
342 343 344 345 346 347 348 349 350 351 352 353 354 355
		io_wqe_dec_running(wqe, worker);
		if (work_bound) {
			worker->flags |= IO_WORKER_F_BOUND;
			wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers--;
			wqe->acct[IO_WQ_ACCT_BOUND].nr_workers++;
			atomic_dec(&wqe->wq->user->processes);
		} else {
			worker->flags &= ~IO_WORKER_F_BOUND;
			wqe->acct[IO_WQ_ACCT_UNBOUND].nr_workers++;
			wqe->acct[IO_WQ_ACCT_BOUND].nr_workers--;
			atomic_inc(&wqe->wq->user->processes);
		}
		io_wqe_inc_running(wqe, worker);
	 }
356 357 358 359 360 361 362 363 364 365 366 367 368 369 370
}

/*
 * No work, worker going to sleep. Move to freelist, and unuse mm if we
 * have one attached. Dropping the mm may potentially sleep, so we drop
 * the lock in that case and return success. Since the caller has to
 * retry the loop in that case (we changed task state), we don't regrab
 * the lock if we return success.
 */
static bool __io_worker_idle(struct io_wqe *wqe, struct io_worker *worker)
	__must_hold(wqe->lock)
{
	if (!(worker->flags & IO_WORKER_F_FREE)) {
		worker->flags |= IO_WORKER_F_FREE;
		hlist_nulls_del_init_rcu(&worker->nulls_node);
371
		hlist_nulls_add_head_rcu(&worker->nulls_node, &wqe->free_list);
372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403
	}

	return __io_worker_unuse(wqe, worker);
}

static struct io_wq_work *io_get_next_work(struct io_wqe *wqe, unsigned *hash)
	__must_hold(wqe->lock)
{
	struct io_wq_work *work;

	list_for_each_entry(work, &wqe->work_list, list) {
		/* not hashed, can run anytime */
		if (!(work->flags & IO_WQ_WORK_HASHED)) {
			list_del(&work->list);
			return work;
		}

		/* hashed, can run if not already running */
		*hash = work->flags >> IO_WQ_HASH_SHIFT;
		if (!(wqe->hash_map & BIT_ULL(*hash))) {
			wqe->hash_map |= BIT_ULL(*hash);
			list_del(&work->list);
			return work;
		}
	}

	return NULL;
}

static void io_worker_handle_work(struct io_worker *worker)
	__releases(wqe->lock)
{
404
	struct io_wq_work *work, *old_work = NULL, *put_work = NULL;
405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424
	struct io_wqe *wqe = worker->wqe;
	struct io_wq *wq = wqe->wq;

	do {
		unsigned hash = -1U;

		/*
		 * If we got some work, mark us as busy. If we didn't, but
		 * the list isn't empty, it means we stalled on hashed work.
		 * Mark us stalled so we don't keep looking for work when we
		 * can't make progress, any work completion or insertion will
		 * clear the stalled flag.
		 */
		work = io_get_next_work(wqe, &hash);
		if (work)
			__io_worker_busy(wqe, worker, work);
		else if (!list_empty(&wqe->work_list))
			wqe->flags |= IO_WQE_FLAG_STALLED;

		spin_unlock_irq(&wqe->lock);
425 426
		if (put_work && wq->put_work)
			wq->put_work(old_work);
427 428 429
		if (!work)
			break;
next:
430 431 432 433 434 435 436 437
		/* flush any pending signals before assigning new work */
		if (signal_pending(current))
			flush_signals(current);

		spin_lock_irq(&worker->lock);
		worker->cur_work = work;
		spin_unlock_irq(&worker->lock);

438 439 440
		if (work->flags & IO_WQ_WORK_CB)
			work->func(&work);

441 442 443 444 445 446
		if ((work->flags & IO_WQ_WORK_NEEDS_FILES) &&
		    current->files != work->files) {
			task_lock(current);
			current->files = work->files;
			task_unlock(current);
		}
447 448 449 450 451 452
		if ((work->flags & IO_WQ_WORK_NEEDS_USER) && !worker->mm &&
		    wq->mm && mmget_not_zero(wq->mm)) {
			use_mm(wq->mm);
			set_fs(USER_DS);
			worker->mm = wq->mm;
		}
453 454
		if (!worker->creds)
			worker->creds = override_creds(wq->creds);
455 456 457 458 459
		if (test_bit(IO_WQ_BIT_CANCEL, &wq->state))
			work->flags |= IO_WQ_WORK_CANCEL;
		if (worker->mm)
			work->flags |= IO_WQ_WORK_HAS_MM;

460 461 462 463 464
		if (wq->get_work && !(work->flags & IO_WQ_WORK_INTERNAL)) {
			put_work = work;
			wq->get_work(work);
		}

465 466 467
		old_work = work;
		work->func(&work);

468
		spin_lock_irq(&worker->lock);
469
		worker->cur_work = NULL;
470 471 472 473
		spin_unlock_irq(&worker->lock);

		spin_lock_irq(&wqe->lock);

474 475 476 477 478 479
		if (hash != -1U) {
			wqe->hash_map &= ~BIT_ULL(hash);
			wqe->flags &= ~IO_WQE_FLAG_STALLED;
		}
		if (work && work != old_work) {
			spin_unlock_irq(&wqe->lock);
480 481 482 483 484 485

			if (put_work && wq->put_work) {
				wq->put_work(put_work);
				put_work = NULL;
			}

486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553
			/* dependent work not hashed */
			hash = -1U;
			goto next;
		}
	} while (1);
}

static int io_wqe_worker(void *data)
{
	struct io_worker *worker = data;
	struct io_wqe *wqe = worker->wqe;
	struct io_wq *wq = wqe->wq;
	DEFINE_WAIT(wait);

	io_worker_start(wqe, worker);

	while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
		prepare_to_wait(&worker->wait, &wait, TASK_INTERRUPTIBLE);

		spin_lock_irq(&wqe->lock);
		if (io_wqe_run_queue(wqe)) {
			__set_current_state(TASK_RUNNING);
			io_worker_handle_work(worker);
			continue;
		}
		/* drops the lock on success, retry */
		if (__io_worker_idle(wqe, worker)) {
			__release(&wqe->lock);
			continue;
		}
		spin_unlock_irq(&wqe->lock);
		if (signal_pending(current))
			flush_signals(current);
		if (schedule_timeout(WORKER_IDLE_TIMEOUT))
			continue;
		/* timed out, exit unless we're the fixed worker */
		if (test_bit(IO_WQ_BIT_EXIT, &wq->state) ||
		    !(worker->flags & IO_WORKER_F_FIXED))
			break;
	}

	finish_wait(&worker->wait, &wait);

	if (test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
		spin_lock_irq(&wqe->lock);
		if (!list_empty(&wqe->work_list))
			io_worker_handle_work(worker);
		else
			spin_unlock_irq(&wqe->lock);
	}

	io_worker_exit(worker);
	return 0;
}

/*
 * Called when a worker is scheduled in. Mark us as currently running.
 */
void io_wq_worker_running(struct task_struct *tsk)
{
	struct io_worker *worker = kthread_data(tsk);
	struct io_wqe *wqe = worker->wqe;

	if (!(worker->flags & IO_WORKER_F_UP))
		return;
	if (worker->flags & IO_WORKER_F_RUNNING)
		return;
	worker->flags |= IO_WORKER_F_RUNNING;
554
	io_wqe_inc_running(wqe, worker);
555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574
}

/*
 * Called when worker is going to sleep. If there are no workers currently
 * running and we have work pending, wake up a free one or have the manager
 * set one up.
 */
void io_wq_worker_sleeping(struct task_struct *tsk)
{
	struct io_worker *worker = kthread_data(tsk);
	struct io_wqe *wqe = worker->wqe;

	if (!(worker->flags & IO_WORKER_F_UP))
		return;
	if (!(worker->flags & IO_WORKER_F_RUNNING))
		return;

	worker->flags &= ~IO_WORKER_F_RUNNING;

	spin_lock_irq(&wqe->lock);
575
	io_wqe_dec_running(wqe, worker);
576 577 578
	spin_unlock_irq(&wqe->lock);
}

579
static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index)
580
{
581
	struct io_wqe_acct *acct =&wqe->acct[index];
582 583 584 585
	struct io_worker *worker;

	worker = kcalloc_node(1, sizeof(*worker), GFP_KERNEL, wqe->node);
	if (!worker)
586
		return false;
587 588 589 590 591

	refcount_set(&worker->ref, 1);
	worker->nulls_node.pprev = NULL;
	init_waitqueue_head(&worker->wait);
	worker->wqe = wqe;
592
	spin_lock_init(&worker->lock);
593 594

	worker->task = kthread_create_on_node(io_wqe_worker, worker, wqe->node,
595
				"io_wqe_worker-%d/%d", index, wqe->node);
596 597
	if (IS_ERR(worker->task)) {
		kfree(worker);
598
		return false;
599 600 601
	}

	spin_lock_irq(&wqe->lock);
602
	hlist_nulls_add_head_rcu(&worker->nulls_node, &wqe->free_list);
603
	list_add_tail_rcu(&worker->all_list, &wqe->all_list);
604
	worker->flags |= IO_WORKER_F_FREE;
605 606 607
	if (index == IO_WQ_ACCT_BOUND)
		worker->flags |= IO_WORKER_F_BOUND;
	if (!acct->nr_workers && (worker->flags & IO_WORKER_F_BOUND))
608
		worker->flags |= IO_WORKER_F_FIXED;
609
	acct->nr_workers++;
610 611
	spin_unlock_irq(&wqe->lock);

612 613 614
	if (index == IO_WQ_ACCT_UNBOUND)
		atomic_inc(&wq->user->processes);

615
	wake_up_process(worker->task);
616
	return true;
617 618
}

619
static inline bool io_wqe_need_worker(struct io_wqe *wqe, int index)
620 621
	__must_hold(wqe->lock)
{
622
	struct io_wqe_acct *acct = &wqe->acct[index];
623

624
	/* if we have available workers or no work, no need */
625
	if (!hlist_nulls_empty(&wqe->free_list) || !io_wqe_run_queue(wqe))
626 627
		return false;
	return acct->nr_workers < acct->max_workers;
628 629 630 631 632 633 634 635
}

/*
 * Manager thread. Tasked with creating new workers, if we need them.
 */
static int io_wq_manager(void *data)
{
	struct io_wq *wq = data;
636
	int i;
637

638 639 640 641 642 643 644
	/* create fixed workers */
	refcount_set(&wq->refs, wq->nr_wqes);
	for (i = 0; i < wq->nr_wqes; i++) {
		if (create_io_worker(wq, wq->wqes[i], IO_WQ_ACCT_BOUND))
			continue;
		goto err;
	}
645

646 647 648
	complete(&wq->done);

	while (!kthread_should_stop()) {
649 650
		for (i = 0; i < wq->nr_wqes; i++) {
			struct io_wqe *wqe = wq->wqes[i];
651
			bool fork_worker[2] = { false, false };
652 653

			spin_lock_irq(&wqe->lock);
654 655 656 657
			if (io_wqe_need_worker(wqe, IO_WQ_ACCT_BOUND))
				fork_worker[IO_WQ_ACCT_BOUND] = true;
			if (io_wqe_need_worker(wqe, IO_WQ_ACCT_UNBOUND))
				fork_worker[IO_WQ_ACCT_UNBOUND] = true;
658
			spin_unlock_irq(&wqe->lock);
659 660 661 662
			if (fork_worker[IO_WQ_ACCT_BOUND])
				create_io_worker(wq, wqe, IO_WQ_ACCT_BOUND);
			if (fork_worker[IO_WQ_ACCT_UNBOUND])
				create_io_worker(wq, wqe, IO_WQ_ACCT_UNBOUND);
663 664 665 666 667 668
		}
		set_current_state(TASK_INTERRUPTIBLE);
		schedule_timeout(HZ);
	}

	return 0;
669 670 671 672 673 674
err:
	set_bit(IO_WQ_BIT_ERROR, &wq->state);
	set_bit(IO_WQ_BIT_EXIT, &wq->state);
	if (refcount_sub_and_test(wq->nr_wqes - i, &wq->refs))
		complete(&wq->done);
	return 0;
675 676
}

677 678 679 680 681 682 683 684 685 686 687
static bool io_wq_can_queue(struct io_wqe *wqe, struct io_wqe_acct *acct,
			    struct io_wq_work *work)
{
	bool free_worker;

	if (!(work->flags & IO_WQ_WORK_UNBOUND))
		return true;
	if (atomic_read(&acct->nr_running))
		return true;

	rcu_read_lock();
688
	free_worker = !hlist_nulls_empty(&wqe->free_list);
689 690 691 692 693 694 695 696 697 698 699
	rcu_read_unlock();
	if (free_worker)
		return true;

	if (atomic_read(&wqe->wq->user->processes) >= acct->max_workers &&
	    !(capable(CAP_SYS_RESOURCE) || capable(CAP_SYS_ADMIN)))
		return false;

	return true;
}

700 701
static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work)
{
702
	struct io_wqe_acct *acct = io_work_get_acct(wqe, work);
703 704
	unsigned long flags;

705 706 707 708 709 710 711 712 713 714 715 716
	/*
	 * Do early check to see if we need a new unbound worker, and if we do,
	 * if we're allowed to do so. This isn't 100% accurate as there's a
	 * gap between this check and incrementing the value, but that's OK.
	 * It's close enough to not be an issue, fork() has the same delay.
	 */
	if (unlikely(!io_wq_can_queue(wqe, acct, work))) {
		work->flags |= IO_WQ_WORK_CANCEL;
		work->func(&work);
		return;
	}

717 718 719 720 721
	spin_lock_irqsave(&wqe->lock, flags);
	list_add_tail(&work->list, &wqe->work_list);
	wqe->flags &= ~IO_WQE_FLAG_STALLED;
	spin_unlock_irqrestore(&wqe->lock, flags);

722 723
	if (!atomic_read(&acct->nr_running))
		io_wqe_wake_worker(wqe, acct);
724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765
}

void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work)
{
	struct io_wqe *wqe = wq->wqes[numa_node_id()];

	io_wqe_enqueue(wqe, work);
}

/*
 * Enqueue work, hashed by some key. Work items that hash to the same value
 * will not be done in parallel. Used to limit concurrent writes, generally
 * hashed by inode.
 */
void io_wq_enqueue_hashed(struct io_wq *wq, struct io_wq_work *work, void *val)
{
	struct io_wqe *wqe = wq->wqes[numa_node_id()];
	unsigned bit;


	bit = hash_ptr(val, IO_WQ_HASH_ORDER);
	work->flags |= (IO_WQ_WORK_HASHED | (bit << IO_WQ_HASH_SHIFT));
	io_wqe_enqueue(wqe, work);
}

static bool io_wqe_worker_send_sig(struct io_worker *worker, void *data)
{
	send_sig(SIGINT, worker->task, 1);
	return false;
}

/*
 * Iterate the passed in list and call the specific function for each
 * worker that isn't exiting
 */
static bool io_wq_for_each_worker(struct io_wqe *wqe,
				  bool (*func)(struct io_worker *, void *),
				  void *data)
{
	struct io_worker *worker;
	bool ret = false;

766
	list_for_each_entry_rcu(worker, &wqe->all_list, all_list) {
767 768 769 770 771 772 773
		if (io_worker_get(worker)) {
			ret = func(worker, data);
			io_worker_release(worker);
			if (ret)
				break;
		}
	}
774

775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791
	return ret;
}

void io_wq_cancel_all(struct io_wq *wq)
{
	int i;

	set_bit(IO_WQ_BIT_CANCEL, &wq->state);

	/*
	 * Browse both lists, as there's a gap between handing work off
	 * to a worker and the worker putting itself on the busy_list
	 */
	rcu_read_lock();
	for (i = 0; i < wq->nr_wqes; i++) {
		struct io_wqe *wqe = wq->wqes[i];

792
		io_wq_for_each_worker(wqe, io_wqe_worker_send_sig, NULL);
793 794 795 796
	}
	rcu_read_unlock();
}

797 798 799 800 801 802 803 804 805
struct io_cb_cancel_data {
	struct io_wqe *wqe;
	work_cancel_fn *cancel;
	void *caller_data;
};

static bool io_work_cancel(struct io_worker *worker, void *cancel_data)
{
	struct io_cb_cancel_data *data = cancel_data;
806
	unsigned long flags;
807 808 809 810
	bool ret = false;

	/*
	 * Hold the lock to avoid ->cur_work going out of scope, caller
811
	 * may dereference the passed in work.
812
	 */
813
	spin_lock_irqsave(&worker->lock, flags);
814 815 816 817 818
	if (worker->cur_work &&
	    data->cancel(worker->cur_work, data->caller_data)) {
		send_sig(SIGINT, worker->task, 1);
		ret = true;
	}
819
	spin_unlock_irqrestore(&worker->lock, flags);
820 821 822 823 824 825 826 827 828 829 830 831 832 833

	return ret;
}

static enum io_wq_cancel io_wqe_cancel_cb_work(struct io_wqe *wqe,
					       work_cancel_fn *cancel,
					       void *cancel_data)
{
	struct io_cb_cancel_data data = {
		.wqe = wqe,
		.cancel = cancel,
		.caller_data = cancel_data,
	};
	struct io_wq_work *work;
834
	unsigned long flags;
835 836
	bool found = false;

837
	spin_lock_irqsave(&wqe->lock, flags);
838 839 840 841 842 843 844
	list_for_each_entry(work, &wqe->work_list, list) {
		if (cancel(work, cancel_data)) {
			list_del(&work->list);
			found = true;
			break;
		}
	}
845
	spin_unlock_irqrestore(&wqe->lock, flags);
846 847 848 849 850 851 852 853

	if (found) {
		work->flags |= IO_WQ_WORK_CANCEL;
		work->func(&work);
		return IO_WQ_CANCEL_OK;
	}

	rcu_read_lock();
854
	found = io_wq_for_each_worker(wqe, io_work_cancel, &data);
855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875
	rcu_read_unlock();
	return found ? IO_WQ_CANCEL_RUNNING : IO_WQ_CANCEL_NOTFOUND;
}

enum io_wq_cancel io_wq_cancel_cb(struct io_wq *wq, work_cancel_fn *cancel,
				  void *data)
{
	enum io_wq_cancel ret = IO_WQ_CANCEL_NOTFOUND;
	int i;

	for (i = 0; i < wq->nr_wqes; i++) {
		struct io_wqe *wqe = wq->wqes[i];

		ret = io_wqe_cancel_cb_work(wqe, cancel, data);
		if (ret != IO_WQ_CANCEL_NOTFOUND)
			break;
	}

	return ret;
}

876 877 878
static bool io_wq_worker_cancel(struct io_worker *worker, void *data)
{
	struct io_wq_work *work = data;
879 880
	unsigned long flags;
	bool ret = false;
881

882 883 884 885
	if (worker->cur_work != work)
		return false;

	spin_lock_irqsave(&worker->lock, flags);
886 887
	if (worker->cur_work == work) {
		send_sig(SIGINT, worker->task, 1);
888
		ret = true;
889
	}
890
	spin_unlock_irqrestore(&worker->lock, flags);
891

892
	return ret;
893 894 895 896 897 898
}

static enum io_wq_cancel io_wqe_cancel_work(struct io_wqe *wqe,
					    struct io_wq_work *cwork)
{
	struct io_wq_work *work;
899
	unsigned long flags;
900 901 902 903 904 905 906 907 908
	bool found = false;

	cwork->flags |= IO_WQ_WORK_CANCEL;

	/*
	 * First check pending list, if we're lucky we can just remove it
	 * from there. CANCEL_OK means that the work is returned as-new,
	 * no completion will be posted for it.
	 */
909
	spin_lock_irqsave(&wqe->lock, flags);
910 911 912 913 914 915 916
	list_for_each_entry(work, &wqe->work_list, list) {
		if (work == cwork) {
			list_del(&work->list);
			found = true;
			break;
		}
	}
917
	spin_unlock_irqrestore(&wqe->lock, flags);
918 919 920 921 922 923 924 925 926 927 928 929 930 931

	if (found) {
		work->flags |= IO_WQ_WORK_CANCEL;
		work->func(&work);
		return IO_WQ_CANCEL_OK;
	}

	/*
	 * Now check if a free (going busy) or busy worker has the work
	 * currently running. If we find it there, we'll return CANCEL_RUNNING
	 * as an indication that we attempte to signal cancellation. The
	 * completion will run normally in this case.
	 */
	rcu_read_lock();
932
	found = io_wq_for_each_worker(wqe, io_wq_worker_cancel, cwork);
933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980
	rcu_read_unlock();
	return found ? IO_WQ_CANCEL_RUNNING : IO_WQ_CANCEL_NOTFOUND;
}

enum io_wq_cancel io_wq_cancel_work(struct io_wq *wq, struct io_wq_work *cwork)
{
	enum io_wq_cancel ret = IO_WQ_CANCEL_NOTFOUND;
	int i;

	for (i = 0; i < wq->nr_wqes; i++) {
		struct io_wqe *wqe = wq->wqes[i];

		ret = io_wqe_cancel_work(wqe, cwork);
		if (ret != IO_WQ_CANCEL_NOTFOUND)
			break;
	}

	return ret;
}

struct io_wq_flush_data {
	struct io_wq_work work;
	struct completion done;
};

static void io_wq_flush_func(struct io_wq_work **workptr)
{
	struct io_wq_work *work = *workptr;
	struct io_wq_flush_data *data;

	data = container_of(work, struct io_wq_flush_data, work);
	complete(&data->done);
}

/*
 * Doesn't wait for previously queued work to finish. When this completes,
 * it just means that previously queued work was started.
 */
void io_wq_flush(struct io_wq *wq)
{
	struct io_wq_flush_data data;
	int i;

	for (i = 0; i < wq->nr_wqes; i++) {
		struct io_wqe *wqe = wq->wqes[i];

		init_completion(&data.done);
		INIT_IO_WORK(&data.work, io_wq_flush_func);
981
		data.work.flags |= IO_WQ_WORK_INTERNAL;
982 983 984 985 986
		io_wqe_enqueue(wqe, &data.work);
		wait_for_completion(&data.done);
	}
}

987
struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002
{
	int ret = -ENOMEM, i, node;
	struct io_wq *wq;

	wq = kcalloc(1, sizeof(*wq), GFP_KERNEL);
	if (!wq)
		return ERR_PTR(-ENOMEM);

	wq->nr_wqes = num_online_nodes();
	wq->wqes = kcalloc(wq->nr_wqes, sizeof(struct io_wqe *), GFP_KERNEL);
	if (!wq->wqes) {
		kfree(wq);
		return ERR_PTR(-ENOMEM);
	}

1003 1004
	wq->get_work = data->get_work;
	wq->put_work = data->put_work;
1005

1006
	/* caller must already hold a reference to this */
1007
	wq->user = data->user;
1008
	wq->creds = data->creds;
1009

1010 1011 1012 1013 1014 1015 1016 1017 1018
	i = 0;
	for_each_online_node(node) {
		struct io_wqe *wqe;

		wqe = kcalloc_node(1, sizeof(struct io_wqe), GFP_KERNEL, node);
		if (!wqe)
			break;
		wq->wqes[i] = wqe;
		wqe->node = node;
1019 1020
		wqe->acct[IO_WQ_ACCT_BOUND].max_workers = bounded;
		atomic_set(&wqe->acct[IO_WQ_ACCT_BOUND].nr_running, 0);
1021
		if (wq->user) {
1022 1023 1024 1025
			wqe->acct[IO_WQ_ACCT_UNBOUND].max_workers =
					task_rlimit(current, RLIMIT_NPROC);
		}
		atomic_set(&wqe->acct[IO_WQ_ACCT_UNBOUND].nr_running, 0);
1026 1027 1028 1029
		wqe->node = node;
		wqe->wq = wq;
		spin_lock_init(&wqe->lock);
		INIT_LIST_HEAD(&wqe->work_list);
1030 1031
		INIT_HLIST_NULLS_HEAD(&wqe->free_list, 0);
		INIT_HLIST_NULLS_HEAD(&wqe->busy_list, 1);
1032
		INIT_LIST_HEAD(&wqe->all_list);
1033 1034 1035 1036 1037 1038 1039 1040 1041 1042

		i++;
	}

	init_completion(&wq->done);

	if (i != wq->nr_wqes)
		goto err;

	/* caller must have already done mmgrab() on this mm */
1043
	wq->mm = data->mm;
1044 1045 1046 1047

	wq->manager = kthread_create(io_wq_manager, wq, "io_wq_manager");
	if (!IS_ERR(wq->manager)) {
		wake_up_process(wq->manager);
1048 1049 1050 1051 1052 1053
		wait_for_completion(&wq->done);
		if (test_bit(IO_WQ_BIT_ERROR, &wq->state)) {
			ret = -ENOMEM;
			goto err;
		}
		reinit_completion(&wq->done);
1054 1055 1056 1057 1058
		return wq;
	}

	ret = PTR_ERR(wq->manager);
	complete(&wq->done);
1059 1060 1061 1062 1063
err:
	for (i = 0; i < wq->nr_wqes; i++)
		kfree(wq->wqes[i]);
	kfree(wq->wqes);
	kfree(wq);
1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076
	return ERR_PTR(ret);
}

static bool io_wq_worker_wake(struct io_worker *worker, void *data)
{
	wake_up_process(worker->task);
	return false;
}

void io_wq_destroy(struct io_wq *wq)
{
	int i;

1077 1078
	set_bit(IO_WQ_BIT_EXIT, &wq->state);
	if (wq->manager)
1079 1080 1081 1082 1083 1084 1085 1086
		kthread_stop(wq->manager);

	rcu_read_lock();
	for (i = 0; i < wq->nr_wqes; i++) {
		struct io_wqe *wqe = wq->wqes[i];

		if (!wqe)
			continue;
1087
		io_wq_for_each_worker(wqe, io_wq_worker_wake, NULL);
1088 1089 1090 1091 1092 1093 1094 1095 1096 1097
	}
	rcu_read_unlock();

	wait_for_completion(&wq->done);

	for (i = 0; i < wq->nr_wqes; i++)
		kfree(wq->wqes[i]);
	kfree(wq->wqes);
	kfree(wq);
}