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