fs/io-wq.c

   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 <uapi/linux/io_uring.h>
  19
  20 #include "io-wq.h"
  21
  22 #define WORKER_IDLE_TIMEOUT     (5 * HZ)
  23
  24 enum {
  25         IO_WORKER_F_UP          = 1,    /* up and active */
  26         IO_WORKER_F_RUNNING     = 2,    /* account as running */
  27         IO_WORKER_F_FREE        = 4,    /* worker on free list */
  28         IO_WORKER_F_BOUND       = 8,    /* is doing bounded work */
  29 };
  30
  31 enum {
  32         IO_WQ_BIT_EXIT          = 0,    /* wq exiting */
  33 };
  34
  35 enum {
  36         IO_ACCT_STALLED_BIT     = 0,    /* stalled on hash */
  37 };
  38
  39 /*
  40  * One for each thread in a wqe pool
  41  */
  42 struct io_worker {
  43         refcount_t ref;
  44         unsigned flags;
  45         struct hlist_nulls_node nulls_node;
  46         struct list_head all_list;
  47         struct task_struct *task;
  48         struct io_wqe *wqe;
  49
  50         struct io_wq_work *cur_work;
  51         struct io_wq_work *next_work;
  52         raw_spinlock_t lock;
  53
  54         struct completion ref_done;
  55
  56         unsigned long create_state;
  57         struct callback_head create_work;
  58         int create_index;
  59
  60         union {
  61                 struct rcu_head rcu;
  62                 struct work_struct work;
  63         };
  64 };
  65
  66 #if BITS_PER_LONG == 64
  67 #define IO_WQ_HASH_ORDER        6
  68 #else
  69 #define IO_WQ_HASH_ORDER        5
  70 #endif
  71
  72 #define IO_WQ_NR_HASH_BUCKETS   (1u << IO_WQ_HASH_ORDER)
  73
  74 struct io_wqe_acct {
  75         unsigned nr_workers;
  76         unsigned max_workers;
  77         int index;
  78         atomic_t nr_running;
  79         raw_spinlock_t lock;
  80         struct io_wq_work_list work_list;
  81         unsigned long flags;
  82 };
  83
  84 enum {
  85         IO_WQ_ACCT_BOUND,
  86         IO_WQ_ACCT_UNBOUND,
  87         IO_WQ_ACCT_NR,
  88 };
  89
  90 /*
  91  * Per-node worker thread pool
  92  */
  93 struct io_wqe {
  94         raw_spinlock_t lock;
  95         struct io_wqe_acct acct[IO_WQ_ACCT_NR];
  96
  97         int node;
  98
  99         struct hlist_nulls_head free_list;
 100         struct list_head all_list;
 101
 102         struct wait_queue_entry wait;
 103
 104         struct io_wq *wq;
 105         struct io_wq_work *hash_tail[IO_WQ_NR_HASH_BUCKETS];
 106
 107         cpumask_var_t cpu_mask;
 108 };
 109
 110 /*
 111  * Per io_wq state
 112   */
 113 struct io_wq {
 114         unsigned long state;
 115
 116         free_work_fn *free_work;
 117         io_wq_work_fn *do_work;
 118
 119         struct io_wq_hash *hash;
 120
 121         atomic_t worker_refs;
 122         struct completion worker_done;
 123
 124         struct hlist_node cpuhp_node;
 125
 126         struct task_struct *task;
 127
 128         struct io_wqe *wqes[];
 129 };
 130
 131 static enum cpuhp_state io_wq_online;
 132
 133 struct io_cb_cancel_data {
 134         work_cancel_fn *fn;
 135         void *data;
 136         int nr_running;
 137         int nr_pending;
 138         bool cancel_all;
 139 };
 140
 141 static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index);
 142 static void io_wqe_dec_running(struct io_worker *worker);
 143 static bool io_acct_cancel_pending_work(struct io_wqe *wqe,
 144                                         struct io_wqe_acct *acct,
 145                                         struct io_cb_cancel_data *match);
 146 static void create_worker_cb(struct callback_head *cb);
 147 static void io_wq_cancel_tw_create(struct io_wq *wq);
 148
 149 static bool io_worker_get(struct io_worker *worker)
 150 {
 151         return refcount_inc_not_zero(&worker->ref);
 152 }
 153
 154 static void io_worker_release(struct io_worker *worker)
 155 {
 156         if (refcount_dec_and_test(&worker->ref))
 157                 complete(&worker->ref_done);
 158 }
 159
 160 static inline struct io_wqe_acct *io_get_acct(struct io_wqe *wqe, bool bound)
 161 {
 162         return &wqe->acct[bound ? IO_WQ_ACCT_BOUND : IO_WQ_ACCT_UNBOUND];
 163 }
 164
 165 static inline struct io_wqe_acct *io_work_get_acct(struct io_wqe *wqe,
 166                                                    struct io_wq_work *work)
 167 {
 168         return io_get_acct(wqe, !(work->flags & IO_WQ_WORK_UNBOUND));
 169 }
 170
 171 static inline struct io_wqe_acct *io_wqe_get_acct(struct io_worker *worker)
 172 {
 173         return io_get_acct(worker->wqe, worker->flags & IO_WORKER_F_BOUND);
 174 }
 175
 176 static void io_worker_ref_put(struct io_wq *wq)
 177 {
 178         if (atomic_dec_and_test(&wq->worker_refs))
 179                 complete(&wq->worker_done);
 180 }
 181
 182 static void io_worker_cancel_cb(struct io_worker *worker)
 183 {
 184         struct io_wqe_acct *acct = io_wqe_get_acct(worker);
 185         struct io_wqe *wqe = worker->wqe;
 186         struct io_wq *wq = wqe->wq;
 187
 188         atomic_dec(&acct->nr_running);
 189         raw_spin_lock(&worker->wqe->lock);
 190         acct->nr_workers--;
 191         raw_spin_unlock(&worker->wqe->lock);
 192         io_worker_ref_put(wq);
 193         clear_bit_unlock(0, &worker->create_state);
 194         io_worker_release(worker);
 195 }
 196
 197 static bool io_task_worker_match(struct callback_head *cb, void *data)
 198 {
 199         struct io_worker *worker;
 200
 201         if (cb->func != create_worker_cb)
 202                 return false;
 203         worker = container_of(cb, struct io_worker, create_work);
 204         return worker == data;
 205 }
 206
 207 static void io_worker_exit(struct io_worker *worker)
 208 {
 209         struct io_wqe *wqe = worker->wqe;
 210         struct io_wq *wq = wqe->wq;
 211
 212         while (1) {
 213                 struct callback_head *cb = task_work_cancel_match(wq->task,
 214                                                 io_task_worker_match, worker);
 215
 216                 if (!cb)
 217                         break;
 218                 io_worker_cancel_cb(worker);
 219         }
 220
 221         io_worker_release(worker);
 222         wait_for_completion(&worker->ref_done);
 223
 224         raw_spin_lock(&wqe->lock);
 225         if (worker->flags & IO_WORKER_F_FREE)
 226                 hlist_nulls_del_rcu(&worker->nulls_node);
 227         list_del_rcu(&worker->all_list);
 228         raw_spin_unlock(&wqe->lock);
 229         io_wqe_dec_running(worker);
 230         worker->flags = 0;
 231         preempt_disable();
 232         current->flags &= ~PF_IO_WORKER;
 233         preempt_enable();
 234
 235         kfree_rcu(worker, rcu);
 236         io_worker_ref_put(wqe->wq);
 237         do_exit(0);
 238 }
 239
 240 static inline bool io_acct_run_queue(struct io_wqe_acct *acct)
 241 {
 242         bool ret = false;
 243
 244         raw_spin_lock(&acct->lock);
 245         if (!wq_list_empty(&acct->work_list) &&
 246             !test_bit(IO_ACCT_STALLED_BIT, &acct->flags))
 247                 ret = true;
 248         raw_spin_unlock(&acct->lock);
 249
 250         return ret;
 251 }
 252
 253 /*
 254  * Check head of free list for an available worker. If one isn't available,
 255  * caller must create one.
 256  */
 257 static bool io_wqe_activate_free_worker(struct io_wqe *wqe,
 258                                         struct io_wqe_acct *acct)
 259         __must_hold(RCU)
 260 {
 261         struct hlist_nulls_node *n;
 262         struct io_worker *worker;
 263
 264         /*
 265          * Iterate free_list and see if we can find an idle worker to
 266          * activate. If a given worker is on the free_list but in the process
 267          * of exiting, keep trying.
 268          */
 269         hlist_nulls_for_each_entry_rcu(worker, n, &wqe->free_list, nulls_node) {
 270                 if (!io_worker_get(worker))
 271                         continue;
 272                 if (io_wqe_get_acct(worker) != acct) {
 273                         io_worker_release(worker);
 274                         continue;
 275                 }
 276                 if (wake_up_process(worker->task)) {
 277                         io_worker_release(worker);
 278                         return true;
 279                 }
 280                 io_worker_release(worker);
 281         }
 282
 283         return false;
 284 }
 285
 286 /*
 287  * We need a worker. If we find a free one, we're good. If not, and we're
 288  * below the max number of workers, create one.
 289  */
 290 static bool io_wqe_create_worker(struct io_wqe *wqe, struct io_wqe_acct *acct)
 291 {
 292         /*
 293          * Most likely an attempt to queue unbounded work on an io_wq that
 294          * wasn't setup with any unbounded workers.
 295          */
 296         if (unlikely(!acct->max_workers))
 297                 pr_warn_once("io-wq is not configured for unbound workers");
 298
 299         raw_spin_lock(&wqe->lock);
 300         if (acct->nr_workers >= acct->max_workers) {
 301                 raw_spin_unlock(&wqe->lock);
 302                 return true;
 303         }
 304         acct->nr_workers++;
 305         raw_spin_unlock(&wqe->lock);
 306         atomic_inc(&acct->nr_running);
 307         atomic_inc(&wqe->wq->worker_refs);
 308         return create_io_worker(wqe->wq, wqe, acct->index);
 309 }
 310
 311 static void io_wqe_inc_running(struct io_worker *worker)
 312 {
 313         struct io_wqe_acct *acct = io_wqe_get_acct(worker);
 314
 315         atomic_inc(&acct->nr_running);
 316 }
 317
 318 static void create_worker_cb(struct callback_head *cb)
 319 {
 320         struct io_worker *worker;
 321         struct io_wq *wq;
 322         struct io_wqe *wqe;
 323         struct io_wqe_acct *acct;
 324         bool do_create = false;
 325
 326         worker = container_of(cb, struct io_worker, create_work);
 327         wqe = worker->wqe;
 328         wq = wqe->wq;
 329         acct = &wqe->acct[worker->create_index];
 330         raw_spin_lock(&wqe->lock);
 331         if (acct->nr_workers < acct->max_workers) {
 332                 acct->nr_workers++;
 333                 do_create = true;
 334         }
 335         raw_spin_unlock(&wqe->lock);
 336         if (do_create) {
 337                 create_io_worker(wq, wqe, worker->create_index);
 338         } else {
 339                 atomic_dec(&acct->nr_running);
 340                 io_worker_ref_put(wq);
 341         }
 342         clear_bit_unlock(0, &worker->create_state);
 343         io_worker_release(worker);
 344 }
 345
 346 static bool io_queue_worker_create(struct io_worker *worker,
 347                                    struct io_wqe_acct *acct,
 348                                    task_work_func_t func)
 349 {
 350         struct io_wqe *wqe = worker->wqe;
 351         struct io_wq *wq = wqe->wq;
 352
 353         /* raced with exit, just ignore create call */
 354         if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
 355                 goto fail;
 356         if (!io_worker_get(worker))
 357                 goto fail;
 358         /*
 359          * create_state manages ownership of create_work/index. We should
 360          * only need one entry per worker, as the worker going to sleep
 361          * will trigger the condition, and waking will clear it once it
 362          * runs the task_work.
 363          */
 364         if (test_bit(0, &worker->create_state) ||
 365             test_and_set_bit_lock(0, &worker->create_state))
 366                 goto fail_release;
 367
 368         atomic_inc(&wq->worker_refs);
 369         init_task_work(&worker->create_work, func);
 370         worker->create_index = acct->index;
 371         if (!task_work_add(wq->task, &worker->create_work, TWA_SIGNAL)) {
 372                 /*
 373                  * EXIT may have been set after checking it above, check after
 374                  * adding the task_work and remove any creation item if it is
 375                  * now set. wq exit does that too, but we can have added this
 376                  * work item after we canceled in io_wq_exit_workers().
 377                  */
 378                 if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
 379                         io_wq_cancel_tw_create(wq);
 380                 io_worker_ref_put(wq);
 381                 return true;
 382         }
 383         io_worker_ref_put(wq);
 384         clear_bit_unlock(0, &worker->create_state);
 385 fail_release:
 386         io_worker_release(worker);
 387 fail:
 388         atomic_dec(&acct->nr_running);
 389         io_worker_ref_put(wq);
 390         return false;
 391 }
 392
 393 static void io_wqe_dec_running(struct io_worker *worker)
 394 {
 395         struct io_wqe_acct *acct = io_wqe_get_acct(worker);
 396         struct io_wqe *wqe = worker->wqe;
 397
 398         if (!(worker->flags & IO_WORKER_F_UP))
 399                 return;
 400
 401         if (!atomic_dec_and_test(&acct->nr_running))
 402                 return;
 403         if (!io_acct_run_queue(acct))
 404                 return;
 405
 406         atomic_inc(&acct->nr_running);
 407         atomic_inc(&wqe->wq->worker_refs);
 408         io_queue_worker_create(worker, acct, create_worker_cb);
 409 }
 410
 411 /*
 412  * Worker will start processing some work. Move it to the busy list, if
 413  * it's currently on the freelist
 414  */
 415 static void __io_worker_busy(struct io_wqe *wqe, struct io_worker *worker)
 416 {
 417         if (worker->flags & IO_WORKER_F_FREE) {
 418                 worker->flags &= ~IO_WORKER_F_FREE;
 419                 raw_spin_lock(&wqe->lock);
 420                 hlist_nulls_del_init_rcu(&worker->nulls_node);
 421                 raw_spin_unlock(&wqe->lock);
 422         }
 423 }
 424
 425 /*
 426  * No work, worker going to sleep. Move to freelist, and unuse mm if we
 427  * have one attached. Dropping the mm may potentially sleep, so we drop
 428  * the lock in that case and return success. Since the caller has to
 429  * retry the loop in that case (we changed task state), we don't regrab
 430  * the lock if we return success.
 431  */
 432 static void __io_worker_idle(struct io_wqe *wqe, struct io_worker *worker)
 433         __must_hold(wqe->lock)
 434 {
 435         if (!(worker->flags & IO_WORKER_F_FREE)) {
 436                 worker->flags |= IO_WORKER_F_FREE;
 437                 hlist_nulls_add_head_rcu(&worker->nulls_node, &wqe->free_list);
 438         }
 439 }
 440
 441 static inline unsigned int io_get_work_hash(struct io_wq_work *work)
 442 {
 443         return work->flags >> IO_WQ_HASH_SHIFT;
 444 }
 445
 446 static bool io_wait_on_hash(struct io_wqe *wqe, unsigned int hash)
 447 {
 448         struct io_wq *wq = wqe->wq;
 449         bool ret = false;
 450
 451         spin_lock_irq(&wq->hash->wait.lock);
 452         if (list_empty(&wqe->wait.entry)) {
 453                 __add_wait_queue(&wq->hash->wait, &wqe->wait);
 454                 if (!test_bit(hash, &wq->hash->map)) {
 455                         __set_current_state(TASK_RUNNING);
 456                         list_del_init(&wqe->wait.entry);
 457                         ret = true;
 458                 }
 459         }
 460         spin_unlock_irq(&wq->hash->wait.lock);
 461         return ret;
 462 }
 463
 464 static struct io_wq_work *io_get_next_work(struct io_wqe_acct *acct,
 465                                            struct io_worker *worker)
 466         __must_hold(acct->lock)
 467 {
 468         struct io_wq_work_node *node, *prev;
 469         struct io_wq_work *work, *tail;
 470         unsigned int stall_hash = -1U;
 471         struct io_wqe *wqe = worker->wqe;
 472
 473         wq_list_for_each(node, prev, &acct->work_list) {
 474                 unsigned int hash;
 475
 476                 work = container_of(node, struct io_wq_work, list);
 477
 478                 /* not hashed, can run anytime */
 479                 if (!io_wq_is_hashed(work)) {
 480                         wq_list_del(&acct->work_list, node, prev);
 481                         return work;
 482                 }
 483
 484                 hash = io_get_work_hash(work);
 485                 /* all items with this hash lie in [work, tail] */
 486                 tail = wqe->hash_tail[hash];
 487
 488                 /* hashed, can run if not already running */
 489                 if (!test_and_set_bit(hash, &wqe->wq->hash->map)) {
 490                         wqe->hash_tail[hash] = NULL;
 491                         wq_list_cut(&acct->work_list, &tail->list, prev);
 492                         return work;
 493                 }
 494                 if (stall_hash == -1U)
 495                         stall_hash = hash;
 496                 /* fast forward to a next hash, for-each will fix up @prev */
 497                 node = &tail->list;
 498         }
 499
 500         if (stall_hash != -1U) {
 501                 bool unstalled;
 502
 503                 /*
 504                  * Set this before dropping the lock to avoid racing with new
 505                  * work being added and clearing the stalled bit.
 506                  */
 507                 set_bit(IO_ACCT_STALLED_BIT, &acct->flags);
 508                 raw_spin_unlock(&acct->lock);
 509                 unstalled = io_wait_on_hash(wqe, stall_hash);
 510                 raw_spin_lock(&acct->lock);
 511                 if (unstalled) {
 512                         clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
 513                         if (wq_has_sleeper(&wqe->wq->hash->wait))
 514                                 wake_up(&wqe->wq->hash->wait);
 515                 }
 516         }
 517
 518         return NULL;
 519 }
 520
 521 static bool io_flush_signals(void)
 522 {
 523         if (unlikely(test_thread_flag(TIF_NOTIFY_SIGNAL))) {
 524                 __set_current_state(TASK_RUNNING);
 525                 clear_notify_signal();
 526                 if (task_work_pending(current))
 527                         task_work_run();
 528                 return true;
 529         }
 530         return false;
 531 }
 532
 533 static void io_assign_current_work(struct io_worker *worker,
 534                                    struct io_wq_work *work)
 535 {
 536         if (work) {
 537                 io_flush_signals();
 538                 cond_resched();
 539         }
 540
 541         raw_spin_lock(&worker->lock);
 542         worker->cur_work = work;
 543         worker->next_work = NULL;
 544         raw_spin_unlock(&worker->lock);
 545 }
 546
 547 static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work);
 548
 549 static void io_worker_handle_work(struct io_worker *worker)
 550 {
 551         struct io_wqe_acct *acct = io_wqe_get_acct(worker);
 552         struct io_wqe *wqe = worker->wqe;
 553         struct io_wq *wq = wqe->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                 raw_spin_lock(&acct->lock);
 567                 work = io_get_next_work(acct, worker);
 568                 raw_spin_unlock(&acct->lock);
 569                 if (work) {
 570                         __io_worker_busy(wqe, worker);
 571
 572                         /*
 573                          * Make sure cancelation can find this, even before
 574                          * it becomes the active work. That avoids a window
 575                          * where the work has been removed from our general
 576                          * work list, but isn't yet discoverable as the
 577                          * current work item for this worker.
 578                          */
 579                         raw_spin_lock(&worker->lock);
 580                         worker->next_work = work;
 581                         raw_spin_unlock(&worker->lock);
 582                 } else {
 583                         break;
 584                 }
 585                 io_assign_current_work(worker, work);
 586                 __set_current_state(TASK_RUNNING);
 587
 588                 /* handle a whole dependent link */
 589                 do {
 590                         struct io_wq_work *next_hashed, *linked;
 591                         unsigned int hash = io_get_work_hash(work);
 592
 593                         next_hashed = wq_next_work(work);
 594
 595                         if (unlikely(do_kill) && (work->flags & IO_WQ_WORK_UNBOUND))
 596                                 work->flags |= IO_WQ_WORK_CANCEL;
 597                         wq->do_work(work);
 598                         io_assign_current_work(worker, NULL);
 599
 600                         linked = wq->free_work(work);
 601                         work = next_hashed;
 602                         if (!work && linked && !io_wq_is_hashed(linked)) {
 603                                 work = linked;
 604                                 linked = NULL;
 605                         }
 606                         io_assign_current_work(worker, work);
 607                         if (linked)
 608                                 io_wqe_enqueue(wqe, linked);
 609
 610                         if (hash != -1U && !next_hashed) {
 611                                 /* serialize hash clear with wake_up() */
 612                                 spin_lock_irq(&wq->hash->wait.lock);
 613                                 clear_bit(hash, &wq->hash->map);
 614                                 clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
 615                                 spin_unlock_irq(&wq->hash->wait.lock);
 616                                 if (wq_has_sleeper(&wq->hash->wait))
 617                                         wake_up(&wq->hash->wait);
 618                         }
 619                 } while (work);
 620         } while (1);
 621 }
 622
 623 static int io_wqe_worker(void *data)
 624 {
 625         struct io_worker *worker = data;
 626         struct io_wqe_acct *acct = io_wqe_get_acct(worker);
 627         struct io_wqe *wqe = worker->wqe;
 628         struct io_wq *wq = wqe->wq;
 629         bool last_timeout = false;
 630         char buf[TASK_COMM_LEN];
 631
 632         worker->flags |= (IO_WORKER_F_UP | IO_WORKER_F_RUNNING);
 633
 634         snprintf(buf, sizeof(buf), "iou-wrk-%d", wq->task->pid);
 635         set_task_comm(current, buf);
 636
 637         audit_alloc_kernel(current);
 638
 639         while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
 640                 long ret;
 641
 642                 set_current_state(TASK_INTERRUPTIBLE);
 643                 while (io_acct_run_queue(acct))
 644                         io_worker_handle_work(worker);
 645
 646                 raw_spin_lock(&wqe->lock);
 647                 /* timed out, exit unless we're the last worker */
 648                 if (last_timeout && acct->nr_workers > 1) {
 649                         acct->nr_workers--;
 650                         raw_spin_unlock(&wqe->lock);
 651                         __set_current_state(TASK_RUNNING);
 652                         break;
 653                 }
 654                 last_timeout = false;
 655                 __io_worker_idle(wqe, worker);
 656                 raw_spin_unlock(&wqe->lock);
 657                 if (io_flush_signals())
 658                         continue;
 659                 ret = schedule_timeout(WORKER_IDLE_TIMEOUT);
 660                 if (signal_pending(current)) {
 661                         struct ksignal ksig;
 662
 663                         if (!get_signal(&ksig))
 664                                 continue;
 665                         break;
 666                 }
 667                 last_timeout = !ret;
 668         }
 669
 670         if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
 671                 io_worker_handle_work(worker);
 672
 673         audit_free(current);
 674         io_worker_exit(worker);
 675         return 0;
 676 }
 677
 678 /*
 679  * Called when a worker is scheduled in. Mark us as currently running.
 680  */
 681 void io_wq_worker_running(struct task_struct *tsk)
 682 {
 683         struct io_worker *worker = tsk->worker_private;
 684
 685         if (!worker)
 686                 return;
 687         if (!(worker->flags & IO_WORKER_F_UP))
 688                 return;
 689         if (worker->flags & IO_WORKER_F_RUNNING)
 690                 return;
 691         worker->flags |= IO_WORKER_F_RUNNING;
 692         io_wqe_inc_running(worker);
 693 }
 694
 695 /*
 696  * Called when worker is going to sleep. If there are no workers currently
 697  * running and we have work pending, wake up a free one or create a new one.
 698  */
 699 void io_wq_worker_sleeping(struct task_struct *tsk)
 700 {
 701         struct io_worker *worker = tsk->worker_private;
 702
 703         if (!worker)
 704                 return;
 705         if (!(worker->flags & IO_WORKER_F_UP))
 706                 return;
 707         if (!(worker->flags & IO_WORKER_F_RUNNING))
 708                 return;
 709
 710         worker->flags &= ~IO_WORKER_F_RUNNING;
 711         io_wqe_dec_running(worker);
 712 }
 713
 714 static void io_init_new_worker(struct io_wqe *wqe, struct io_worker *worker,
 715                                struct task_struct *tsk)
 716 {
 717         tsk->worker_private = worker;
 718         worker->task = tsk;
 719         set_cpus_allowed_ptr(tsk, wqe->cpu_mask);
 720         tsk->flags |= PF_NO_SETAFFINITY;
 721
 722         raw_spin_lock(&wqe->lock);
 723         hlist_nulls_add_head_rcu(&worker->nulls_node, &wqe->free_list);
 724         list_add_tail_rcu(&worker->all_list, &wqe->all_list);
 725         worker->flags |= IO_WORKER_F_FREE;
 726         raw_spin_unlock(&wqe->lock);
 727         wake_up_new_task(tsk);
 728 }
 729
 730 static bool io_wq_work_match_all(struct io_wq_work *work, void *data)
 731 {
 732         return true;
 733 }
 734
 735 static inline bool io_should_retry_thread(long err)
 736 {
 737         /*
 738          * Prevent perpetual task_work retry, if the task (or its group) is
 739          * exiting.
 740          */
 741         if (fatal_signal_pending(current))
 742                 return false;
 743
 744         switch (err) {
 745         case -EAGAIN:
 746         case -ERESTARTSYS:
 747         case -ERESTARTNOINTR:
 748         case -ERESTARTNOHAND:
 749                 return true;
 750         default:
 751                 return false;
 752         }
 753 }
 754
 755 static void create_worker_cont(struct callback_head *cb)
 756 {
 757         struct io_worker *worker;
 758         struct task_struct *tsk;
 759         struct io_wqe *wqe;
 760
 761         worker = container_of(cb, struct io_worker, create_work);
 762         clear_bit_unlock(0, &worker->create_state);
 763         wqe = worker->wqe;
 764         tsk = create_io_thread(io_wqe_worker, worker, wqe->node);
 765         if (!IS_ERR(tsk)) {
 766                 io_init_new_worker(wqe, worker, tsk);
 767                 io_worker_release(worker);
 768                 return;
 769         } else if (!io_should_retry_thread(PTR_ERR(tsk))) {
 770                 struct io_wqe_acct *acct = io_wqe_get_acct(worker);
 771
 772                 atomic_dec(&acct->nr_running);
 773                 raw_spin_lock(&wqe->lock);
 774                 acct->nr_workers--;
 775                 if (!acct->nr_workers) {
 776                         struct io_cb_cancel_data match = {
 777                                 .fn             = io_wq_work_match_all,
 778                                 .cancel_all     = true,
 779                         };
 780
 781                         raw_spin_unlock(&wqe->lock);
 782                         while (io_acct_cancel_pending_work(wqe, acct, &match))
 783                                 ;
 784                 } else {
 785                         raw_spin_unlock(&wqe->lock);
 786                 }
 787                 io_worker_ref_put(wqe->wq);
 788                 kfree(worker);
 789                 return;
 790         }
 791
 792         /* re-create attempts grab a new worker ref, drop the existing one */
 793         io_worker_release(worker);
 794         schedule_work(&worker->work);
 795 }
 796
 797 static void io_workqueue_create(struct work_struct *work)
 798 {
 799         struct io_worker *worker = container_of(work, struct io_worker, work);
 800         struct io_wqe_acct *acct = io_wqe_get_acct(worker);
 801
 802         if (!io_queue_worker_create(worker, acct, create_worker_cont))
 803                 kfree(worker);
 804 }
 805
 806 static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index)
 807 {
 808         struct io_wqe_acct *acct = &wqe->acct[index];
 809         struct io_worker *worker;
 810         struct task_struct *tsk;
 811
 812         __set_current_state(TASK_RUNNING);
 813
 814         worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, wqe->node);
 815         if (!worker) {
 816 fail:
 817                 atomic_dec(&acct->nr_running);
 818                 raw_spin_lock(&wqe->lock);
 819                 acct->nr_workers--;
 820                 raw_spin_unlock(&wqe->lock);
 821                 io_worker_ref_put(wq);
 822                 return false;
 823         }
 824
 825         refcount_set(&worker->ref, 1);
 826         worker->wqe = wqe;
 827         raw_spin_lock_init(&worker->lock);
 828         init_completion(&worker->ref_done);
 829
 830         if (index == IO_WQ_ACCT_BOUND)
 831                 worker->flags |= IO_WORKER_F_BOUND;
 832
 833         tsk = create_io_thread(io_wqe_worker, worker, wqe->node);
 834         if (!IS_ERR(tsk)) {
 835                 io_init_new_worker(wqe, worker, tsk);
 836         } else if (!io_should_retry_thread(PTR_ERR(tsk))) {
 837                 kfree(worker);
 838                 goto fail;
 839         } else {
 840                 INIT_WORK(&worker->work, io_workqueue_create);
 841                 schedule_work(&worker->work);
 842         }
 843
 844         return true;
 845 }
 846
 847 /*
 848  * Iterate the passed in list and call the specific function for each
 849  * worker that isn't exiting
 850  */
 851 static bool io_wq_for_each_worker(struct io_wqe *wqe,
 852                                   bool (*func)(struct io_worker *, void *),
 853                                   void *data)
 854 {
 855         struct io_worker *worker;
 856         bool ret = false;
 857
 858         list_for_each_entry_rcu(worker, &wqe->all_list, all_list) {
 859                 if (io_worker_get(worker)) {
 860                         /* no task if node is/was offline */
 861                         if (worker->task)
 862                                 ret = func(worker, data);
 863                         io_worker_release(worker);
 864                         if (ret)
 865                                 break;
 866                 }
 867         }
 868
 869         return ret;
 870 }
 871
 872 static bool io_wq_worker_wake(struct io_worker *worker, void *data)
 873 {
 874         set_notify_signal(worker->task);
 875         wake_up_process(worker->task);
 876         return false;
 877 }
 878
 879 static void io_run_cancel(struct io_wq_work *work, struct io_wqe *wqe)
 880 {
 881         struct io_wq *wq = wqe->wq;
 882
 883         do {
 884                 work->flags |= IO_WQ_WORK_CANCEL;
 885                 wq->do_work(work);
 886                 work = wq->free_work(work);
 887         } while (work);
 888 }
 889
 890 static void io_wqe_insert_work(struct io_wqe *wqe, struct io_wq_work *work)
 891 {
 892         struct io_wqe_acct *acct = io_work_get_acct(wqe, work);
 893         unsigned int hash;
 894         struct io_wq_work *tail;
 895
 896         if (!io_wq_is_hashed(work)) {
 897 append:
 898                 wq_list_add_tail(&work->list, &acct->work_list);
 899                 return;
 900         }
 901
 902         hash = io_get_work_hash(work);
 903         tail = wqe->hash_tail[hash];
 904         wqe->hash_tail[hash] = work;
 905         if (!tail)
 906                 goto append;
 907
 908         wq_list_add_after(&work->list, &tail->list, &acct->work_list);
 909 }
 910
 911 static bool io_wq_work_match_item(struct io_wq_work *work, void *data)
 912 {
 913         return work == data;
 914 }
 915
 916 static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work)
 917 {
 918         struct io_wqe_acct *acct = io_work_get_acct(wqe, work);
 919         struct io_cb_cancel_data match;
 920         unsigned work_flags = work->flags;
 921         bool do_create;
 922
 923         /*
 924          * If io-wq is exiting for this task, or if the request has explicitly
 925          * been marked as one that should not get executed, cancel it here.
 926          */
 927         if (test_bit(IO_WQ_BIT_EXIT, &wqe->wq->state) ||
 928             (work->flags & IO_WQ_WORK_CANCEL)) {
 929                 io_run_cancel(work, wqe);
 930                 return;
 931         }
 932
 933         raw_spin_lock(&acct->lock);
 934         io_wqe_insert_work(wqe, work);
 935         clear_bit(IO_ACCT_STALLED_BIT, &acct->flags);
 936         raw_spin_unlock(&acct->lock);
 937
 938         raw_spin_lock(&wqe->lock);
 939         rcu_read_lock();
 940         do_create = !io_wqe_activate_free_worker(wqe, acct);
 941         rcu_read_unlock();
 942
 943         raw_spin_unlock(&wqe->lock);
 944
 945         if (do_create && ((work_flags & IO_WQ_WORK_CONCURRENT) ||
 946             !atomic_read(&acct->nr_running))) {
 947                 bool did_create;
 948
 949                 did_create = io_wqe_create_worker(wqe, acct);
 950                 if (likely(did_create))
 951                         return;
 952
 953                 raw_spin_lock(&wqe->lock);
 954                 if (acct->nr_workers) {
 955                         raw_spin_unlock(&wqe->lock);
 956                         return;
 957                 }
 958                 raw_spin_unlock(&wqe->lock);
 959
 960                 /* fatal condition, failed to create the first worker */
 961                 match.fn                = io_wq_work_match_item,
 962                 match.data              = work,
 963                 match.cancel_all        = false,
 964
 965                 io_acct_cancel_pending_work(wqe, acct, &match);
 966         }
 967 }
 968
 969 void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work)
 970 {
 971         struct io_wqe *wqe = wq->wqes[numa_node_id()];
 972
 973         io_wqe_enqueue(wqe, work);
 974 }
 975
 976 /*
 977  * Work items that hash to the same value will not be done in parallel.
 978  * Used to limit concurrent writes, generally hashed by inode.
 979  */
 980 void io_wq_hash_work(struct io_wq_work *work, void *val)
 981 {
 982         unsigned int bit;
 983
 984         bit = hash_ptr(val, IO_WQ_HASH_ORDER);
 985         work->flags |= (IO_WQ_WORK_HASHED | (bit << IO_WQ_HASH_SHIFT));
 986 }
 987
 988 static bool __io_wq_worker_cancel(struct io_worker *worker,
 989                                   struct io_cb_cancel_data *match,
 990                                   struct io_wq_work *work)
 991 {
 992         if (work && match->fn(work, match->data)) {
 993                 work->flags |= IO_WQ_WORK_CANCEL;
 994                 set_notify_signal(worker->task);
 995                 return true;
 996         }
 997
 998         return false;
 999 }
1000
1001 static bool io_wq_worker_cancel(struct io_worker *worker, void *data)
1002 {
1003         struct io_cb_cancel_data *match = data;
1004
1005         /*
1006          * Hold the lock to avoid ->cur_work going out of scope, caller
1007          * may dereference the passed in work.
1008          */
1009         raw_spin_lock(&worker->lock);
1010         if (__io_wq_worker_cancel(worker, match, worker->cur_work) ||
1011             __io_wq_worker_cancel(worker, match, worker->next_work))
1012                 match->nr_running++;
1013         raw_spin_unlock(&worker->lock);
1014
1015         return match->nr_running && !match->cancel_all;
1016 }
1017
1018 static inline void io_wqe_remove_pending(struct io_wqe *wqe,
1019                                          struct io_wq_work *work,
1020                                          struct io_wq_work_node *prev)
1021 {
1022         struct io_wqe_acct *acct = io_work_get_acct(wqe, work);
1023         unsigned int hash = io_get_work_hash(work);
1024         struct io_wq_work *prev_work = NULL;
1025
1026         if (io_wq_is_hashed(work) && work == wqe->hash_tail[hash]) {
1027                 if (prev)
1028                         prev_work = container_of(prev, struct io_wq_work, list);
1029                 if (prev_work && io_get_work_hash(prev_work) == hash)
1030                         wqe->hash_tail[hash] = prev_work;
1031                 else
1032                         wqe->hash_tail[hash] = NULL;
1033         }
1034         wq_list_del(&acct->work_list, &work->list, prev);
1035 }
1036
1037 static bool io_acct_cancel_pending_work(struct io_wqe *wqe,
1038                                         struct io_wqe_acct *acct,
1039                                         struct io_cb_cancel_data *match)
1040 {
1041         struct io_wq_work_node *node, *prev;
1042         struct io_wq_work *work;
1043
1044         raw_spin_lock(&acct->lock);
1045         wq_list_for_each(node, prev, &acct->work_list) {
1046                 work = container_of(node, struct io_wq_work, list);
1047                 if (!match->fn(work, match->data))
1048                         continue;
1049                 io_wqe_remove_pending(wqe, work, prev);
1050                 raw_spin_unlock(&acct->lock);
1051                 io_run_cancel(work, wqe);
1052                 match->nr_pending++;
1053                 /* not safe to continue after unlock */
1054                 return true;
1055         }
1056         raw_spin_unlock(&acct->lock);
1057
1058         return false;
1059 }
1060
1061 static void io_wqe_cancel_pending_work(struct io_wqe *wqe,
1062                                        struct io_cb_cancel_data *match)
1063 {
1064         int i;
1065 retry:
1066         for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1067                 struct io_wqe_acct *acct = io_get_acct(wqe, i == 0);
1068
1069                 if (io_acct_cancel_pending_work(wqe, acct, match)) {
1070                         if (match->cancel_all)
1071                                 goto retry;
1072                         break;
1073                 }
1074         }
1075 }
1076
1077 static void io_wqe_cancel_running_work(struct io_wqe *wqe,
1078                                        struct io_cb_cancel_data *match)
1079 {
1080         rcu_read_lock();
1081         io_wq_for_each_worker(wqe, io_wq_worker_cancel, match);
1082         rcu_read_unlock();
1083 }
1084
1085 enum io_wq_cancel io_wq_cancel_cb(struct io_wq *wq, work_cancel_fn *cancel,
1086                                   void *data, bool cancel_all)
1087 {
1088         struct io_cb_cancel_data match = {
1089                 .fn             = cancel,
1090                 .data           = data,
1091                 .cancel_all     = cancel_all,
1092         };
1093         int node;
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 wqe->lock, to ensure that
1106          * we'll find a work item regardless of state.
1107          */
1108         for_each_node(node) {
1109                 struct io_wqe *wqe = wq->wqes[node];
1110
1111                 io_wqe_cancel_pending_work(wqe, &match);
1112                 if (match.nr_pending && !match.cancel_all)
1113                         return IO_WQ_CANCEL_OK;
1114
1115                 raw_spin_lock(&wqe->lock);
1116                 io_wqe_cancel_running_work(wqe, &match);
1117                 raw_spin_unlock(&wqe->lock);
1118                 if (match.nr_running && !match.cancel_all)
1119                         return IO_WQ_CANCEL_RUNNING;
1120         }
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
1129 static int io_wqe_hash_wake(struct wait_queue_entry *wait, unsigned mode,
1130                             int sync, void *key)
1131 {
1132         struct io_wqe *wqe = container_of(wait, struct io_wqe, 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_wqe_acct *acct = &wqe->acct[i];
1140
1141                 if (test_and_clear_bit(IO_ACCT_STALLED_BIT, &acct->flags))
1142                         io_wqe_activate_free_worker(wqe, acct);
1143         }
1144         rcu_read_unlock();
1145         return 1;
1146 }
1147
1148 struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
1149 {
1150         int ret, node, 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(struct_size(wq, wqes, nr_node_ids), GFP_KERNEL);
1159         if (!wq)
1160                 return ERR_PTR(-ENOMEM);
1161         ret = cpuhp_state_add_instance_nocalls(io_wq_online, &wq->cpuhp_node);
1162         if (ret)
1163                 goto err_wq;
1164
1165         refcount_inc(&data->hash->refs);
1166         wq->hash = data->hash;
1167         wq->free_work = data->free_work;
1168         wq->do_work = data->do_work;
1169
1170         ret = -ENOMEM;
1171         for_each_node(node) {
1172                 struct io_wqe *wqe;
1173                 int alloc_node = node;
1174
1175                 if (!node_online(alloc_node))
1176                         alloc_node = NUMA_NO_NODE;
1177                 wqe = kzalloc_node(sizeof(struct io_wqe), GFP_KERNEL, alloc_node);
1178                 if (!wqe)
1179                         goto err;
1180                 if (!alloc_cpumask_var(&wqe->cpu_mask, GFP_KERNEL))
1181                         goto err;
1182                 cpumask_copy(wqe->cpu_mask, cpumask_of_node(node));
1183                 wq->wqes[node] = wqe;
1184                 wqe->node = alloc_node;
1185                 wqe->acct[IO_WQ_ACCT_BOUND].max_workers = bounded;
1186                 wqe->acct[IO_WQ_ACCT_UNBOUND].max_workers =
1187                                         task_rlimit(current, RLIMIT_NPROC);
1188                 INIT_LIST_HEAD(&wqe->wait.entry);
1189                 wqe->wait.func = io_wqe_hash_wake;
1190                 for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1191                         struct io_wqe_acct *acct = &wqe->acct[i];
1192
1193                         acct->index = i;
1194                         atomic_set(&acct->nr_running, 0);
1195                         INIT_WQ_LIST(&acct->work_list);
1196                         raw_spin_lock_init(&acct->lock);
1197                 }
1198                 wqe->wq = wq;
1199                 raw_spin_lock_init(&wqe->lock);
1200                 INIT_HLIST_NULLS_HEAD(&wqe->free_list, 0);
1201                 INIT_LIST_HEAD(&wqe->all_list);
1202         }
1203
1204         wq->task = get_task_struct(data->task);
1205         atomic_set(&wq->worker_refs, 1);
1206         init_completion(&wq->worker_done);
1207         return wq;
1208 err:
1209         io_wq_put_hash(data->hash);
1210         cpuhp_state_remove_instance_nocalls(io_wq_online, &wq->cpuhp_node);
1211         for_each_node(node) {
1212                 if (!wq->wqes[node])
1213                         continue;
1214                 free_cpumask_var(wq->wqes[node]->cpu_mask);
1215                 kfree(wq->wqes[node]);
1216         }
1217 err_wq:
1218         kfree(wq);
1219         return ERR_PTR(ret);
1220 }
1221
1222 static bool io_task_work_match(struct callback_head *cb, void *data)
1223 {
1224         struct io_worker *worker;
1225
1226         if (cb->func != create_worker_cb && cb->func != create_worker_cont)
1227                 return false;
1228         worker = container_of(cb, struct io_worker, create_work);
1229         return worker->wqe->wq == data;
1230 }
1231
1232 void io_wq_exit_start(struct io_wq *wq)
1233 {
1234         set_bit(IO_WQ_BIT_EXIT, &wq->state);
1235 }
1236
1237 static void io_wq_cancel_tw_create(struct io_wq *wq)
1238 {
1239         struct callback_head *cb;
1240
1241         while ((cb = task_work_cancel_match(wq->task, io_task_work_match, wq)) != NULL) {
1242                 struct io_worker *worker;
1243
1244                 worker = container_of(cb, struct io_worker, create_work);
1245                 io_worker_cancel_cb(worker);
1246         }
1247 }
1248
1249 static void io_wq_exit_workers(struct io_wq *wq)
1250 {
1251         int node;
1252
1253         if (!wq->task)
1254                 return;
1255
1256         io_wq_cancel_tw_create(wq);
1257
1258         rcu_read_lock();
1259         for_each_node(node) {
1260                 struct io_wqe *wqe = wq->wqes[node];
1261
1262                 io_wq_for_each_worker(wqe, io_wq_worker_wake, NULL);
1263         }
1264         rcu_read_unlock();
1265         io_worker_ref_put(wq);
1266         wait_for_completion(&wq->worker_done);
1267
1268         for_each_node(node) {
1269                 spin_lock_irq(&wq->hash->wait.lock);
1270                 list_del_init(&wq->wqes[node]->wait.entry);
1271                 spin_unlock_irq(&wq->hash->wait.lock);
1272         }
1273         put_task_struct(wq->task);
1274         wq->task = NULL;
1275 }
1276
1277 static void io_wq_destroy(struct io_wq *wq)
1278 {
1279         int node;
1280
1281         cpuhp_state_remove_instance_nocalls(io_wq_online, &wq->cpuhp_node);
1282
1283         for_each_node(node) {
1284                 struct io_wqe *wqe = wq->wqes[node];
1285                 struct io_cb_cancel_data match = {
1286                         .fn             = io_wq_work_match_all,
1287                         .cancel_all     = true,
1288                 };
1289                 io_wqe_cancel_pending_work(wqe, &match);
1290                 free_cpumask_var(wqe->cpu_mask);
1291                 kfree(wqe);
1292         }
1293         io_wq_put_hash(wq->hash);
1294         kfree(wq);
1295 }
1296
1297 void io_wq_put_and_exit(struct io_wq *wq)
1298 {
1299         WARN_ON_ONCE(!test_bit(IO_WQ_BIT_EXIT, &wq->state));
1300
1301         io_wq_exit_workers(wq);
1302         io_wq_destroy(wq);
1303 }
1304
1305 struct online_data {
1306         unsigned int cpu;
1307         bool online;
1308 };
1309
1310 static bool io_wq_worker_affinity(struct io_worker *worker, void *data)
1311 {
1312         struct online_data *od = data;
1313
1314         if (od->online)
1315                 cpumask_set_cpu(od->cpu, worker->wqe->cpu_mask);
1316         else
1317                 cpumask_clear_cpu(od->cpu, worker->wqe->cpu_mask);
1318         return false;
1319 }
1320
1321 static int __io_wq_cpu_online(struct io_wq *wq, unsigned int cpu, bool online)
1322 {
1323         struct online_data od = {
1324                 .cpu = cpu,
1325                 .online = online
1326         };
1327         int i;
1328
1329         rcu_read_lock();
1330         for_each_node(i)
1331                 io_wq_for_each_worker(wq->wqes[i], io_wq_worker_affinity, &od);
1332         rcu_read_unlock();
1333         return 0;
1334 }
1335
1336 static int io_wq_cpu_online(unsigned int cpu, struct hlist_node *node)
1337 {
1338         struct io_wq *wq = hlist_entry_safe(node, struct io_wq, cpuhp_node);
1339
1340         return __io_wq_cpu_online(wq, cpu, true);
1341 }
1342
1343 static int io_wq_cpu_offline(unsigned int cpu, struct hlist_node *node)
1344 {
1345         struct io_wq *wq = hlist_entry_safe(node, struct io_wq, cpuhp_node);
1346
1347         return __io_wq_cpu_online(wq, cpu, false);
1348 }
1349
1350 int io_wq_cpu_affinity(struct io_wq *wq, cpumask_var_t mask)
1351 {
1352         int i;
1353
1354         rcu_read_lock();
1355         for_each_node(i) {
1356                 struct io_wqe *wqe = wq->wqes[i];
1357
1358                 if (mask)
1359                         cpumask_copy(wqe->cpu_mask, mask);
1360                 else
1361                         cpumask_copy(wqe->cpu_mask, cpumask_of_node(i));
1362         }
1363         rcu_read_unlock();
1364         return 0;
1365 }
1366
1367 /*
1368  * Set max number of unbounded workers, returns old value. If new_count is 0,
1369  * then just return the old value.
1370  */
1371 int io_wq_max_workers(struct io_wq *wq, int *new_count)
1372 {
1373         int prev[IO_WQ_ACCT_NR];
1374         bool first_node = true;
1375         int i, node;
1376
1377         BUILD_BUG_ON((int) IO_WQ_ACCT_BOUND   != (int) IO_WQ_BOUND);
1378         BUILD_BUG_ON((int) IO_WQ_ACCT_UNBOUND != (int) IO_WQ_UNBOUND);
1379         BUILD_BUG_ON((int) IO_WQ_ACCT_NR      != 2);
1380
1381         for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1382                 if (new_count[i] > task_rlimit(current, RLIMIT_NPROC))
1383                         new_count[i] = task_rlimit(current, RLIMIT_NPROC);
1384         }
1385
1386         for (i = 0; i < IO_WQ_ACCT_NR; i++)
1387                 prev[i] = 0;
1388
1389         rcu_read_lock();
1390         for_each_node(node) {
1391                 struct io_wqe *wqe = wq->wqes[node];
1392                 struct io_wqe_acct *acct;
1393
1394                 raw_spin_lock(&wqe->lock);
1395                 for (i = 0; i < IO_WQ_ACCT_NR; i++) {
1396                         acct = &wqe->acct[i];
1397                         if (first_node)
1398                                 prev[i] = max_t(int, acct->max_workers, prev[i]);
1399                         if (new_count[i])
1400                                 acct->max_workers = new_count[i];
1401                 }
1402                 raw_spin_unlock(&wqe->lock);
1403                 first_node = false;
1404         }
1405         rcu_read_unlock();
1406
1407         for (i = 0; i < IO_WQ_ACCT_NR; i++)
1408                 new_count[i] = prev[i];
1409
1410         return 0;
1411 }
1412
1413 static __init int io_wq_init(void)
1414 {
1415         int ret;
1416
1417         ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "io-wq/online",
1418                                         io_wq_cpu_online, io_wq_cpu_offline);
1419         if (ret < 0)
1420                 return ret;
1421         io_wq_online = ret;
1422         return 0;
1423 }
1424 subsys_initcall(io_wq_init);