net/sunrpc/sched.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * linux/net/sunrpc/sched.c
   4  *
   5  * Scheduling for synchronous and asynchronous RPC requests.
   6  *
   7  * Copyright (C) 1996 Olaf Kirch, <okir@monad.swb.de>
   8  *
   9  * TCP NFS related read + write fixes
  10  * (C) 1999 Dave Airlie, University of Limerick, Ireland <airlied@linux.ie>
  11  */
  12
  13 #include <linux/module.h>
  14
  15 #include <linux/sched.h>
  16 #include <linux/interrupt.h>
  17 #include <linux/slab.h>
  18 #include <linux/mempool.h>
  19 #include <linux/smp.h>
  20 #include <linux/spinlock.h>
  21 #include <linux/mutex.h>
  22 #include <linux/freezer.h>
  23 #include <linux/sched/mm.h>
  24
  25 #include <linux/sunrpc/clnt.h>
  26 #include <linux/sunrpc/metrics.h>
  27
  28 #include "sunrpc.h"
  29
  30 #define CREATE_TRACE_POINTS
  31 #include <trace/events/sunrpc.h>
  32
  33 /*
  34  * RPC slabs and memory pools
  35  */
  36 #define RPC_BUFFER_MAXSIZE      (2048)
  37 #define RPC_BUFFER_POOLSIZE     (8)
  38 #define RPC_TASK_POOLSIZE       (8)
  39 static struct kmem_cache        *rpc_task_slabp __read_mostly;
  40 static struct kmem_cache        *rpc_buffer_slabp __read_mostly;
  41 static mempool_t        *rpc_task_mempool __read_mostly;
  42 static mempool_t        *rpc_buffer_mempool __read_mostly;
  43
  44 static void                     rpc_async_schedule(struct work_struct *);
  45 static void                      rpc_release_task(struct rpc_task *task);
  46 static void __rpc_queue_timer_fn(struct work_struct *);
  47
  48 /*
  49  * RPC tasks sit here while waiting for conditions to improve.
  50  */
  51 static struct rpc_wait_queue delay_queue;
  52
  53 /*
  54  * rpciod-related stuff
  55  */
  56 struct workqueue_struct *rpciod_workqueue __read_mostly;
  57 struct workqueue_struct *xprtiod_workqueue __read_mostly;
  58 EXPORT_SYMBOL_GPL(xprtiod_workqueue);
  59
  60 unsigned long
  61 rpc_task_timeout(const struct rpc_task *task)
  62 {
  63         unsigned long timeout = READ_ONCE(task->tk_timeout);
  64
  65         if (timeout != 0) {
  66                 unsigned long now = jiffies;
  67                 if (time_before(now, timeout))
  68                         return timeout - now;
  69         }
  70         return 0;
  71 }
  72 EXPORT_SYMBOL_GPL(rpc_task_timeout);
  73
  74 /*
  75  * Disable the timer for a given RPC task. Should be called with
  76  * queue->lock and bh_disabled in order to avoid races within
  77  * rpc_run_timer().
  78  */
  79 static void
  80 __rpc_disable_timer(struct rpc_wait_queue *queue, struct rpc_task *task)
  81 {
  82         if (list_empty(&task->u.tk_wait.timer_list))
  83                 return;
  84         task->tk_timeout = 0;
  85         list_del(&task->u.tk_wait.timer_list);
  86         if (list_empty(&queue->timer_list.list))
  87                 cancel_delayed_work(&queue->timer_list.dwork);
  88 }
  89
  90 static void
  91 rpc_set_queue_timer(struct rpc_wait_queue *queue, unsigned long expires)
  92 {
  93         unsigned long now = jiffies;
  94         queue->timer_list.expires = expires;
  95         if (time_before_eq(expires, now))
  96                 expires = 0;
  97         else
  98                 expires -= now;
  99         mod_delayed_work(rpciod_workqueue, &queue->timer_list.dwork, expires);
 100 }
 101
 102 /*
 103  * Set up a timer for the current task.
 104  */
 105 static void
 106 __rpc_add_timer(struct rpc_wait_queue *queue, struct rpc_task *task,
 107                 unsigned long timeout)
 108 {
 109         task->tk_timeout = timeout;
 110         if (list_empty(&queue->timer_list.list) || time_before(timeout, queue->timer_list.expires))
 111                 rpc_set_queue_timer(queue, timeout);
 112         list_add(&task->u.tk_wait.timer_list, &queue->timer_list.list);
 113 }
 114
 115 static void rpc_set_waitqueue_priority(struct rpc_wait_queue *queue, int priority)
 116 {
 117         if (queue->priority != priority) {
 118                 queue->priority = priority;
 119                 queue->nr = 1U << priority;
 120         }
 121 }
 122
 123 static void rpc_reset_waitqueue_priority(struct rpc_wait_queue *queue)
 124 {
 125         rpc_set_waitqueue_priority(queue, queue->maxpriority);
 126 }
 127
 128 /*
 129  * Add a request to a queue list
 130  */
 131 static void
 132 __rpc_list_enqueue_task(struct list_head *q, struct rpc_task *task)
 133 {
 134         struct rpc_task *t;
 135
 136         list_for_each_entry(t, q, u.tk_wait.list) {
 137                 if (t->tk_owner == task->tk_owner) {
 138                         list_add_tail(&task->u.tk_wait.links,
 139                                         &t->u.tk_wait.links);
 140                         /* Cache the queue head in task->u.tk_wait.list */
 141                         task->u.tk_wait.list.next = q;
 142                         task->u.tk_wait.list.prev = NULL;
 143                         return;
 144                 }
 145         }
 146         INIT_LIST_HEAD(&task->u.tk_wait.links);
 147         list_add_tail(&task->u.tk_wait.list, q);
 148 }
 149
 150 /*
 151  * Remove request from a queue list
 152  */
 153 static void
 154 __rpc_list_dequeue_task(struct rpc_task *task)
 155 {
 156         struct list_head *q;
 157         struct rpc_task *t;
 158
 159         if (task->u.tk_wait.list.prev == NULL) {
 160                 list_del(&task->u.tk_wait.links);
 161                 return;
 162         }
 163         if (!list_empty(&task->u.tk_wait.links)) {
 164                 t = list_first_entry(&task->u.tk_wait.links,
 165                                 struct rpc_task,
 166                                 u.tk_wait.links);
 167                 /* Assume __rpc_list_enqueue_task() cached the queue head */
 168                 q = t->u.tk_wait.list.next;
 169                 list_add_tail(&t->u.tk_wait.list, q);
 170                 list_del(&task->u.tk_wait.links);
 171         }
 172         list_del(&task->u.tk_wait.list);
 173 }
 174
 175 /*
 176  * Add new request to a priority queue.
 177  */
 178 static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue,
 179                 struct rpc_task *task,
 180                 unsigned char queue_priority)
 181 {
 182         if (unlikely(queue_priority > queue->maxpriority))
 183                 queue_priority = queue->maxpriority;
 184         __rpc_list_enqueue_task(&queue->tasks[queue_priority], task);
 185 }
 186
 187 /*
 188  * Add new request to wait queue.
 189  *
 190  * Swapper tasks always get inserted at the head of the queue.
 191  * This should avoid many nasty memory deadlocks and hopefully
 192  * improve overall performance.
 193  * Everyone else gets appended to the queue to ensure proper FIFO behavior.
 194  */
 195 static void __rpc_add_wait_queue(struct rpc_wait_queue *queue,
 196                 struct rpc_task *task,
 197                 unsigned char queue_priority)
 198 {
 199         INIT_LIST_HEAD(&task->u.tk_wait.timer_list);
 200         if (RPC_IS_PRIORITY(queue))
 201                 __rpc_add_wait_queue_priority(queue, task, queue_priority);
 202         else if (RPC_IS_SWAPPER(task))
 203                 list_add(&task->u.tk_wait.list, &queue->tasks[0]);
 204         else
 205                 list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);
 206         task->tk_waitqueue = queue;
 207         queue->qlen++;
 208         /* barrier matches the read in rpc_wake_up_task_queue_locked() */
 209         smp_wmb();
 210         rpc_set_queued(task);
 211 }
 212
 213 /*
 214  * Remove request from a priority queue.
 215  */
 216 static void __rpc_remove_wait_queue_priority(struct rpc_task *task)
 217 {
 218         __rpc_list_dequeue_task(task);
 219 }
 220
 221 /*
 222  * Remove request from queue.
 223  * Note: must be called with spin lock held.
 224  */
 225 static void __rpc_remove_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *task)
 226 {
 227         __rpc_disable_timer(queue, task);
 228         if (RPC_IS_PRIORITY(queue))
 229                 __rpc_remove_wait_queue_priority(task);
 230         else
 231                 list_del(&task->u.tk_wait.list);
 232         queue->qlen--;
 233 }
 234
 235 static void __rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname, unsigned char nr_queues)
 236 {
 237         int i;
 238
 239         spin_lock_init(&queue->lock);
 240         for (i = 0; i < ARRAY_SIZE(queue->tasks); i++)
 241                 INIT_LIST_HEAD(&queue->tasks[i]);
 242         queue->maxpriority = nr_queues - 1;
 243         rpc_reset_waitqueue_priority(queue);
 244         queue->qlen = 0;
 245         queue->timer_list.expires = 0;
 246         INIT_DELAYED_WORK(&queue->timer_list.dwork, __rpc_queue_timer_fn);
 247         INIT_LIST_HEAD(&queue->timer_list.list);
 248         rpc_assign_waitqueue_name(queue, qname);
 249 }
 250
 251 void rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname)
 252 {
 253         __rpc_init_priority_wait_queue(queue, qname, RPC_NR_PRIORITY);
 254 }
 255 EXPORT_SYMBOL_GPL(rpc_init_priority_wait_queue);
 256
 257 void rpc_init_wait_queue(struct rpc_wait_queue *queue, const char *qname)
 258 {
 259         __rpc_init_priority_wait_queue(queue, qname, 1);
 260 }
 261 EXPORT_SYMBOL_GPL(rpc_init_wait_queue);
 262
 263 void rpc_destroy_wait_queue(struct rpc_wait_queue *queue)
 264 {
 265         cancel_delayed_work_sync(&queue->timer_list.dwork);
 266 }
 267 EXPORT_SYMBOL_GPL(rpc_destroy_wait_queue);
 268
 269 static int rpc_wait_bit_killable(struct wait_bit_key *key, int mode)
 270 {
 271         freezable_schedule_unsafe();
 272         if (signal_pending_state(mode, current))
 273                 return -ERESTARTSYS;
 274         return 0;
 275 }
 276
 277 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG) || IS_ENABLED(CONFIG_TRACEPOINTS)
 278 static void rpc_task_set_debuginfo(struct rpc_task *task)
 279 {
 280         static atomic_t rpc_pid;
 281
 282         task->tk_pid = atomic_inc_return(&rpc_pid);
 283 }
 284 #else
 285 static inline void rpc_task_set_debuginfo(struct rpc_task *task)
 286 {
 287 }
 288 #endif
 289
 290 static void rpc_set_active(struct rpc_task *task)
 291 {
 292         rpc_task_set_debuginfo(task);
 293         set_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
 294         trace_rpc_task_begin(task, NULL);
 295 }
 296
 297 /*
 298  * Mark an RPC call as having completed by clearing the 'active' bit
 299  * and then waking up all tasks that were sleeping.
 300  */
 301 static int rpc_complete_task(struct rpc_task *task)
 302 {
 303         void *m = &task->tk_runstate;
 304         wait_queue_head_t *wq = bit_waitqueue(m, RPC_TASK_ACTIVE);
 305         struct wait_bit_key k = __WAIT_BIT_KEY_INITIALIZER(m, RPC_TASK_ACTIVE);
 306         unsigned long flags;
 307         int ret;
 308
 309         trace_rpc_task_complete(task, NULL);
 310
 311         spin_lock_irqsave(&wq->lock, flags);
 312         clear_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
 313         ret = atomic_dec_and_test(&task->tk_count);
 314         if (waitqueue_active(wq))
 315                 __wake_up_locked_key(wq, TASK_NORMAL, &k);
 316         spin_unlock_irqrestore(&wq->lock, flags);
 317         return ret;
 318 }
 319
 320 /*
 321  * Allow callers to wait for completion of an RPC call
 322  *
 323  * Note the use of out_of_line_wait_on_bit() rather than wait_on_bit()
 324  * to enforce taking of the wq->lock and hence avoid races with
 325  * rpc_complete_task().
 326  */
 327 int __rpc_wait_for_completion_task(struct rpc_task *task, wait_bit_action_f *action)
 328 {
 329         if (action == NULL)
 330                 action = rpc_wait_bit_killable;
 331         return out_of_line_wait_on_bit(&task->tk_runstate, RPC_TASK_ACTIVE,
 332                         action, TASK_KILLABLE);
 333 }
 334 EXPORT_SYMBOL_GPL(__rpc_wait_for_completion_task);
 335
 336 /*
 337  * Make an RPC task runnable.
 338  *
 339  * Note: If the task is ASYNC, and is being made runnable after sitting on an
 340  * rpc_wait_queue, this must be called with the queue spinlock held to protect
 341  * the wait queue operation.
 342  * Note the ordering of rpc_test_and_set_running() and rpc_clear_queued(),
 343  * which is needed to ensure that __rpc_execute() doesn't loop (due to the
 344  * lockless RPC_IS_QUEUED() test) before we've had a chance to test
 345  * the RPC_TASK_RUNNING flag.
 346  */
 347 static void rpc_make_runnable(struct workqueue_struct *wq,
 348                 struct rpc_task *task)
 349 {
 350         bool need_wakeup = !rpc_test_and_set_running(task);
 351
 352         rpc_clear_queued(task);
 353         if (!need_wakeup)
 354                 return;
 355         if (RPC_IS_ASYNC(task)) {
 356                 INIT_WORK(&task->u.tk_work, rpc_async_schedule);
 357                 queue_work(wq, &task->u.tk_work);
 358         } else
 359                 wake_up_bit(&task->tk_runstate, RPC_TASK_QUEUED);
 360 }
 361
 362 /*
 363  * Prepare for sleeping on a wait queue.
 364  * By always appending tasks to the list we ensure FIFO behavior.
 365  * NB: An RPC task will only receive interrupt-driven events as long
 366  * as it's on a wait queue.
 367  */
 368 static void __rpc_do_sleep_on_priority(struct rpc_wait_queue *q,
 369                 struct rpc_task *task,
 370                 unsigned char queue_priority)
 371 {
 372         trace_rpc_task_sleep(task, q);
 373
 374         __rpc_add_wait_queue(q, task, queue_priority);
 375 }
 376
 377 static void __rpc_sleep_on_priority(struct rpc_wait_queue *q,
 378                 struct rpc_task *task,
 379                 unsigned char queue_priority)
 380 {
 381         if (WARN_ON_ONCE(RPC_IS_QUEUED(task)))
 382                 return;
 383         __rpc_do_sleep_on_priority(q, task, queue_priority);
 384 }
 385
 386 static void __rpc_sleep_on_priority_timeout(struct rpc_wait_queue *q,
 387                 struct rpc_task *task, unsigned long timeout,
 388                 unsigned char queue_priority)
 389 {
 390         if (WARN_ON_ONCE(RPC_IS_QUEUED(task)))
 391                 return;
 392         if (time_is_after_jiffies(timeout)) {
 393                 __rpc_do_sleep_on_priority(q, task, queue_priority);
 394                 __rpc_add_timer(q, task, timeout);
 395         } else
 396                 task->tk_status = -ETIMEDOUT;
 397 }
 398
 399 static void rpc_set_tk_callback(struct rpc_task *task, rpc_action action)
 400 {
 401         if (action && !WARN_ON_ONCE(task->tk_callback != NULL))
 402                 task->tk_callback = action;
 403 }
 404
 405 static bool rpc_sleep_check_activated(struct rpc_task *task)
 406 {
 407         /* We shouldn't ever put an inactive task to sleep */
 408         if (WARN_ON_ONCE(!RPC_IS_ACTIVATED(task))) {
 409                 task->tk_status = -EIO;
 410                 rpc_put_task_async(task);
 411                 return false;
 412         }
 413         return true;
 414 }
 415
 416 void rpc_sleep_on_timeout(struct rpc_wait_queue *q, struct rpc_task *task,
 417                                 rpc_action action, unsigned long timeout)
 418 {
 419         if (!rpc_sleep_check_activated(task))
 420                 return;
 421
 422         rpc_set_tk_callback(task, action);
 423
 424         /*
 425          * Protect the queue operations.
 426          */
 427         spin_lock(&q->lock);
 428         __rpc_sleep_on_priority_timeout(q, task, timeout, task->tk_priority);
 429         spin_unlock(&q->lock);
 430 }
 431 EXPORT_SYMBOL_GPL(rpc_sleep_on_timeout);
 432
 433 void rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
 434                                 rpc_action action)
 435 {
 436         if (!rpc_sleep_check_activated(task))
 437                 return;
 438
 439         rpc_set_tk_callback(task, action);
 440
 441         WARN_ON_ONCE(task->tk_timeout != 0);
 442         /*
 443          * Protect the queue operations.
 444          */
 445         spin_lock(&q->lock);
 446         __rpc_sleep_on_priority(q, task, task->tk_priority);
 447         spin_unlock(&q->lock);
 448 }
 449 EXPORT_SYMBOL_GPL(rpc_sleep_on);
 450
 451 void rpc_sleep_on_priority_timeout(struct rpc_wait_queue *q,
 452                 struct rpc_task *task, unsigned long timeout, int priority)
 453 {
 454         if (!rpc_sleep_check_activated(task))
 455                 return;
 456
 457         priority -= RPC_PRIORITY_LOW;
 458         /*
 459          * Protect the queue operations.
 460          */
 461         spin_lock(&q->lock);
 462         __rpc_sleep_on_priority_timeout(q, task, timeout, priority);
 463         spin_unlock(&q->lock);
 464 }
 465 EXPORT_SYMBOL_GPL(rpc_sleep_on_priority_timeout);
 466
 467 void rpc_sleep_on_priority(struct rpc_wait_queue *q, struct rpc_task *task,
 468                 int priority)
 469 {
 470         if (!rpc_sleep_check_activated(task))
 471                 return;
 472
 473         WARN_ON_ONCE(task->tk_timeout != 0);
 474         priority -= RPC_PRIORITY_LOW;
 475         /*
 476          * Protect the queue operations.
 477          */
 478         spin_lock(&q->lock);
 479         __rpc_sleep_on_priority(q, task, priority);
 480         spin_unlock(&q->lock);
 481 }
 482 EXPORT_SYMBOL_GPL(rpc_sleep_on_priority);
 483
 484 /**
 485  * __rpc_do_wake_up_task_on_wq - wake up a single rpc_task
 486  * @wq: workqueue on which to run task
 487  * @queue: wait queue
 488  * @task: task to be woken up
 489  *
 490  * Caller must hold queue->lock, and have cleared the task queued flag.
 491  */
 492 static void __rpc_do_wake_up_task_on_wq(struct workqueue_struct *wq,
 493                 struct rpc_wait_queue *queue,
 494                 struct rpc_task *task)
 495 {
 496         /* Has the task been executed yet? If not, we cannot wake it up! */
 497         if (!RPC_IS_ACTIVATED(task)) {
 498                 printk(KERN_ERR "RPC: Inactive task (%p) being woken up!\n", task);
 499                 return;
 500         }
 501
 502         trace_rpc_task_wakeup(task, queue);
 503
 504         __rpc_remove_wait_queue(queue, task);
 505
 506         rpc_make_runnable(wq, task);
 507 }
 508
 509 /*
 510  * Wake up a queued task while the queue lock is being held
 511  */
 512 static struct rpc_task *
 513 rpc_wake_up_task_on_wq_queue_action_locked(struct workqueue_struct *wq,
 514                 struct rpc_wait_queue *queue, struct rpc_task *task,
 515                 bool (*action)(struct rpc_task *, void *), void *data)
 516 {
 517         if (RPC_IS_QUEUED(task)) {
 518                 smp_rmb();
 519                 if (task->tk_waitqueue == queue) {
 520                         if (action == NULL || action(task, data)) {
 521                                 __rpc_do_wake_up_task_on_wq(wq, queue, task);
 522                                 return task;
 523                         }
 524                 }
 525         }
 526         return NULL;
 527 }
 528
 529 /*
 530  * Wake up a queued task while the queue lock is being held
 531  */
 532 static void rpc_wake_up_task_queue_locked(struct rpc_wait_queue *queue,
 533                                           struct rpc_task *task)
 534 {
 535         rpc_wake_up_task_on_wq_queue_action_locked(rpciod_workqueue, queue,
 536                                                    task, NULL, NULL);
 537 }
 538
 539 /*
 540  * Wake up a task on a specific queue
 541  */
 542 void rpc_wake_up_queued_task(struct rpc_wait_queue *queue, struct rpc_task *task)
 543 {
 544         if (!RPC_IS_QUEUED(task))
 545                 return;
 546         spin_lock(&queue->lock);
 547         rpc_wake_up_task_queue_locked(queue, task);
 548         spin_unlock(&queue->lock);
 549 }
 550 EXPORT_SYMBOL_GPL(rpc_wake_up_queued_task);
 551
 552 static bool rpc_task_action_set_status(struct rpc_task *task, void *status)
 553 {
 554         task->tk_status = *(int *)status;
 555         return true;
 556 }
 557
 558 static void
 559 rpc_wake_up_task_queue_set_status_locked(struct rpc_wait_queue *queue,
 560                 struct rpc_task *task, int status)
 561 {
 562         rpc_wake_up_task_on_wq_queue_action_locked(rpciod_workqueue, queue,
 563                         task, rpc_task_action_set_status, &status);
 564 }
 565
 566 /**
 567  * rpc_wake_up_queued_task_set_status - wake up a task and set task->tk_status
 568  * @queue: pointer to rpc_wait_queue
 569  * @task: pointer to rpc_task
 570  * @status: integer error value
 571  *
 572  * If @task is queued on @queue, then it is woken up, and @task->tk_status is
 573  * set to the value of @status.
 574  */
 575 void
 576 rpc_wake_up_queued_task_set_status(struct rpc_wait_queue *queue,
 577                 struct rpc_task *task, int status)
 578 {
 579         if (!RPC_IS_QUEUED(task))
 580                 return;
 581         spin_lock(&queue->lock);
 582         rpc_wake_up_task_queue_set_status_locked(queue, task, status);
 583         spin_unlock(&queue->lock);
 584 }
 585
 586 /*
 587  * Wake up the next task on a priority queue.
 588  */
 589 static struct rpc_task *__rpc_find_next_queued_priority(struct rpc_wait_queue *queue)
 590 {
 591         struct list_head *q;
 592         struct rpc_task *task;
 593
 594         /*
 595          * Service a batch of tasks from a single owner.
 596          */
 597         q = &queue->tasks[queue->priority];
 598         if (!list_empty(q) && --queue->nr) {
 599                 task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
 600                 goto out;
 601         }
 602
 603         /*
 604          * Service the next queue.
 605          */
 606         do {
 607                 if (q == &queue->tasks[0])
 608                         q = &queue->tasks[queue->maxpriority];
 609                 else
 610                         q = q - 1;
 611                 if (!list_empty(q)) {
 612                         task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
 613                         goto new_queue;
 614                 }
 615         } while (q != &queue->tasks[queue->priority]);
 616
 617         rpc_reset_waitqueue_priority(queue);
 618         return NULL;
 619
 620 new_queue:
 621         rpc_set_waitqueue_priority(queue, (unsigned int)(q - &queue->tasks[0]));
 622 out:
 623         return task;
 624 }
 625
 626 static struct rpc_task *__rpc_find_next_queued(struct rpc_wait_queue *queue)
 627 {
 628         if (RPC_IS_PRIORITY(queue))
 629                 return __rpc_find_next_queued_priority(queue);
 630         if (!list_empty(&queue->tasks[0]))
 631                 return list_first_entry(&queue->tasks[0], struct rpc_task, u.tk_wait.list);
 632         return NULL;
 633 }
 634
 635 /*
 636  * Wake up the first task on the wait queue.
 637  */
 638 struct rpc_task *rpc_wake_up_first_on_wq(struct workqueue_struct *wq,
 639                 struct rpc_wait_queue *queue,
 640                 bool (*func)(struct rpc_task *, void *), void *data)
 641 {
 642         struct rpc_task *task = NULL;
 643
 644         spin_lock(&queue->lock);
 645         task = __rpc_find_next_queued(queue);
 646         if (task != NULL)
 647                 task = rpc_wake_up_task_on_wq_queue_action_locked(wq, queue,
 648                                 task, func, data);
 649         spin_unlock(&queue->lock);
 650
 651         return task;
 652 }
 653
 654 /*
 655  * Wake up the first task on the wait queue.
 656  */
 657 struct rpc_task *rpc_wake_up_first(struct rpc_wait_queue *queue,
 658                 bool (*func)(struct rpc_task *, void *), void *data)
 659 {
 660         return rpc_wake_up_first_on_wq(rpciod_workqueue, queue, func, data);
 661 }
 662 EXPORT_SYMBOL_GPL(rpc_wake_up_first);
 663
 664 static bool rpc_wake_up_next_func(struct rpc_task *task, void *data)
 665 {
 666         return true;
 667 }
 668
 669 /*
 670  * Wake up the next task on the wait queue.
 671 */
 672 struct rpc_task *rpc_wake_up_next(struct rpc_wait_queue *queue)
 673 {
 674         return rpc_wake_up_first(queue, rpc_wake_up_next_func, NULL);
 675 }
 676 EXPORT_SYMBOL_GPL(rpc_wake_up_next);
 677
 678 /**
 679  * rpc_wake_up_locked - wake up all rpc_tasks
 680  * @queue: rpc_wait_queue on which the tasks are sleeping
 681  *
 682  */
 683 static void rpc_wake_up_locked(struct rpc_wait_queue *queue)
 684 {
 685         struct rpc_task *task;
 686
 687         for (;;) {
 688                 task = __rpc_find_next_queued(queue);
 689                 if (task == NULL)
 690                         break;
 691                 rpc_wake_up_task_queue_locked(queue, task);
 692         }
 693 }
 694
 695 /**
 696  * rpc_wake_up - wake up all rpc_tasks
 697  * @queue: rpc_wait_queue on which the tasks are sleeping
 698  *
 699  * Grabs queue->lock
 700  */
 701 void rpc_wake_up(struct rpc_wait_queue *queue)
 702 {
 703         spin_lock(&queue->lock);
 704         rpc_wake_up_locked(queue);
 705         spin_unlock(&queue->lock);
 706 }
 707 EXPORT_SYMBOL_GPL(rpc_wake_up);
 708
 709 /**
 710  * rpc_wake_up_status_locked - wake up all rpc_tasks and set their status value.
 711  * @queue: rpc_wait_queue on which the tasks are sleeping
 712  * @status: status value to set
 713  */
 714 static void rpc_wake_up_status_locked(struct rpc_wait_queue *queue, int status)
 715 {
 716         struct rpc_task *task;
 717
 718         for (;;) {
 719                 task = __rpc_find_next_queued(queue);
 720                 if (task == NULL)
 721                         break;
 722                 rpc_wake_up_task_queue_set_status_locked(queue, task, status);
 723         }
 724 }
 725
 726 /**
 727  * rpc_wake_up_status - wake up all rpc_tasks and set their status value.
 728  * @queue: rpc_wait_queue on which the tasks are sleeping
 729  * @status: status value to set
 730  *
 731  * Grabs queue->lock
 732  */
 733 void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
 734 {
 735         spin_lock(&queue->lock);
 736         rpc_wake_up_status_locked(queue, status);
 737         spin_unlock(&queue->lock);
 738 }
 739 EXPORT_SYMBOL_GPL(rpc_wake_up_status);
 740
 741 static void __rpc_queue_timer_fn(struct work_struct *work)
 742 {
 743         struct rpc_wait_queue *queue = container_of(work,
 744                         struct rpc_wait_queue,
 745                         timer_list.dwork.work);
 746         struct rpc_task *task, *n;
 747         unsigned long expires, now, timeo;
 748
 749         spin_lock(&queue->lock);
 750         expires = now = jiffies;
 751         list_for_each_entry_safe(task, n, &queue->timer_list.list, u.tk_wait.timer_list) {
 752                 timeo = task->tk_timeout;
 753                 if (time_after_eq(now, timeo)) {
 754                         trace_rpc_task_timeout(task, task->tk_action);
 755                         task->tk_status = -ETIMEDOUT;
 756                         rpc_wake_up_task_queue_locked(queue, task);
 757                         continue;
 758                 }
 759                 if (expires == now || time_after(expires, timeo))
 760                         expires = timeo;
 761         }
 762         if (!list_empty(&queue->timer_list.list))
 763                 rpc_set_queue_timer(queue, expires);
 764         spin_unlock(&queue->lock);
 765 }
 766
 767 static void __rpc_atrun(struct rpc_task *task)
 768 {
 769         if (task->tk_status == -ETIMEDOUT)
 770                 task->tk_status = 0;
 771 }
 772
 773 /*
 774  * Run a task at a later time
 775  */
 776 void rpc_delay(struct rpc_task *task, unsigned long delay)
 777 {
 778         rpc_sleep_on_timeout(&delay_queue, task, __rpc_atrun, jiffies + delay);
 779 }
 780 EXPORT_SYMBOL_GPL(rpc_delay);
 781
 782 /*
 783  * Helper to call task->tk_ops->rpc_call_prepare
 784  */
 785 void rpc_prepare_task(struct rpc_task *task)
 786 {
 787         task->tk_ops->rpc_call_prepare(task, task->tk_calldata);
 788 }
 789
 790 static void
 791 rpc_init_task_statistics(struct rpc_task *task)
 792 {
 793         /* Initialize retry counters */
 794         task->tk_garb_retry = 2;
 795         task->tk_cred_retry = 2;
 796         task->tk_rebind_retry = 2;
 797
 798         /* starting timestamp */
 799         task->tk_start = ktime_get();
 800 }
 801
 802 static void
 803 rpc_reset_task_statistics(struct rpc_task *task)
 804 {
 805         task->tk_timeouts = 0;
 806         task->tk_flags &= ~(RPC_CALL_MAJORSEEN|RPC_TASK_SENT);
 807         rpc_init_task_statistics(task);
 808 }
 809
 810 /*
 811  * Helper that calls task->tk_ops->rpc_call_done if it exists
 812  */
 813 void rpc_exit_task(struct rpc_task *task)
 814 {
 815         trace_rpc_task_end(task, task->tk_action);
 816         task->tk_action = NULL;
 817         if (task->tk_ops->rpc_count_stats)
 818                 task->tk_ops->rpc_count_stats(task, task->tk_calldata);
 819         else if (task->tk_client)
 820                 rpc_count_iostats(task, task->tk_client->cl_metrics);
 821         if (task->tk_ops->rpc_call_done != NULL) {
 822                 task->tk_ops->rpc_call_done(task, task->tk_calldata);
 823                 if (task->tk_action != NULL) {
 824                         /* Always release the RPC slot and buffer memory */
 825                         xprt_release(task);
 826                         rpc_reset_task_statistics(task);
 827                 }
 828         }
 829 }
 830
 831 void rpc_signal_task(struct rpc_task *task)
 832 {
 833         struct rpc_wait_queue *queue;
 834
 835         if (!RPC_IS_ACTIVATED(task))
 836                 return;
 837
 838         trace_rpc_task_signalled(task, task->tk_action);
 839         set_bit(RPC_TASK_SIGNALLED, &task->tk_runstate);
 840         smp_mb__after_atomic();
 841         queue = READ_ONCE(task->tk_waitqueue);
 842         if (queue)
 843                 rpc_wake_up_queued_task_set_status(queue, task, -ERESTARTSYS);
 844 }
 845
 846 void rpc_exit(struct rpc_task *task, int status)
 847 {
 848         task->tk_status = status;
 849         task->tk_action = rpc_exit_task;
 850         rpc_wake_up_queued_task(task->tk_waitqueue, task);
 851 }
 852 EXPORT_SYMBOL_GPL(rpc_exit);
 853
 854 void rpc_release_calldata(const struct rpc_call_ops *ops, void *calldata)
 855 {
 856         if (ops->rpc_release != NULL)
 857                 ops->rpc_release(calldata);
 858 }
 859
 860 /*
 861  * This is the RPC `scheduler' (or rather, the finite state machine).
 862  */
 863 static void __rpc_execute(struct rpc_task *task)
 864 {
 865         struct rpc_wait_queue *queue;
 866         int task_is_async = RPC_IS_ASYNC(task);
 867         int status = 0;
 868
 869         WARN_ON_ONCE(RPC_IS_QUEUED(task));
 870         if (RPC_IS_QUEUED(task))
 871                 return;
 872
 873         for (;;) {
 874                 void (*do_action)(struct rpc_task *);
 875
 876                 /*
 877                  * Perform the next FSM step or a pending callback.
 878                  *
 879                  * tk_action may be NULL if the task has been killed.
 880                  * In particular, note that rpc_killall_tasks may
 881                  * do this at any time, so beware when dereferencing.
 882                  */
 883                 do_action = task->tk_action;
 884                 if (task->tk_callback) {
 885                         do_action = task->tk_callback;
 886                         task->tk_callback = NULL;
 887                 }
 888                 if (!do_action)
 889                         break;
 890                 trace_rpc_task_run_action(task, do_action);
 891                 do_action(task);
 892
 893                 /*
 894                  * Lockless check for whether task is sleeping or not.
 895                  */
 896                 if (!RPC_IS_QUEUED(task))
 897                         continue;
 898
 899                 /*
 900                  * Signalled tasks should exit rather than sleep.
 901                  */
 902                 if (RPC_SIGNALLED(task)) {
 903                         task->tk_rpc_status = -ERESTARTSYS;
 904                         rpc_exit(task, -ERESTARTSYS);
 905                 }
 906
 907                 /*
 908                  * The queue->lock protects against races with
 909                  * rpc_make_runnable().
 910                  *
 911                  * Note that once we clear RPC_TASK_RUNNING on an asynchronous
 912                  * rpc_task, rpc_make_runnable() can assign it to a
 913                  * different workqueue. We therefore cannot assume that the
 914                  * rpc_task pointer may still be dereferenced.
 915                  */
 916                 queue = task->tk_waitqueue;
 917                 spin_lock(&queue->lock);
 918                 if (!RPC_IS_QUEUED(task)) {
 919                         spin_unlock(&queue->lock);
 920                         continue;
 921                 }
 922                 rpc_clear_running(task);
 923                 spin_unlock(&queue->lock);
 924                 if (task_is_async)
 925                         return;
 926
 927                 /* sync task: sleep here */
 928                 trace_rpc_task_sync_sleep(task, task->tk_action);
 929                 status = out_of_line_wait_on_bit(&task->tk_runstate,
 930                                 RPC_TASK_QUEUED, rpc_wait_bit_killable,
 931                                 TASK_KILLABLE);
 932                 if (status < 0) {
 933                         /*
 934                          * When a sync task receives a signal, it exits with
 935                          * -ERESTARTSYS. In order to catch any callbacks that
 936                          * clean up after sleeping on some queue, we don't
 937                          * break the loop here, but go around once more.
 938                          */
 939                         trace_rpc_task_signalled(task, task->tk_action);
 940                         set_bit(RPC_TASK_SIGNALLED, &task->tk_runstate);
 941                         task->tk_rpc_status = -ERESTARTSYS;
 942                         rpc_exit(task, -ERESTARTSYS);
 943                 }
 944                 trace_rpc_task_sync_wake(task, task->tk_action);
 945         }
 946
 947         /* Release all resources associated with the task */
 948         rpc_release_task(task);
 949 }
 950
 951 /*
 952  * User-visible entry point to the scheduler.
 953  *
 954  * This may be called recursively if e.g. an async NFS task updates
 955  * the attributes and finds that dirty pages must be flushed.
 956  * NOTE: Upon exit of this function the task is guaranteed to be
 957  *       released. In particular note that tk_release() will have
 958  *       been called, so your task memory may have been freed.
 959  */
 960 void rpc_execute(struct rpc_task *task)
 961 {
 962         bool is_async = RPC_IS_ASYNC(task);
 963
 964         rpc_set_active(task);
 965         rpc_make_runnable(rpciod_workqueue, task);
 966         if (!is_async)
 967                 __rpc_execute(task);
 968 }
 969
 970 static void rpc_async_schedule(struct work_struct *work)
 971 {
 972         unsigned int pflags = memalloc_nofs_save();
 973
 974         __rpc_execute(container_of(work, struct rpc_task, u.tk_work));
 975         memalloc_nofs_restore(pflags);
 976 }
 977
 978 /**
 979  * rpc_malloc - allocate RPC buffer resources
 980  * @task: RPC task
 981  *
 982  * A single memory region is allocated, which is split between the
 983  * RPC call and RPC reply that this task is being used for. When
 984  * this RPC is retired, the memory is released by calling rpc_free.
 985  *
 986  * To prevent rpciod from hanging, this allocator never sleeps,
 987  * returning -ENOMEM and suppressing warning if the request cannot
 988  * be serviced immediately. The caller can arrange to sleep in a
 989  * way that is safe for rpciod.
 990  *
 991  * Most requests are 'small' (under 2KiB) and can be serviced from a
 992  * mempool, ensuring that NFS reads and writes can always proceed,
 993  * and that there is good locality of reference for these buffers.
 994  */
 995 int rpc_malloc(struct rpc_task *task)
 996 {
 997         struct rpc_rqst *rqst = task->tk_rqstp;
 998         size_t size = rqst->rq_callsize + rqst->rq_rcvsize;
 999         struct rpc_buffer *buf;
1000         gfp_t gfp = GFP_NOFS;
1001
1002         if (RPC_IS_SWAPPER(task))
1003                 gfp = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN;
1004
1005         size += sizeof(struct rpc_buffer);
1006         if (size <= RPC_BUFFER_MAXSIZE)
1007                 buf = mempool_alloc(rpc_buffer_mempool, gfp);
1008         else
1009                 buf = kmalloc(size, gfp);
1010
1011         if (!buf)
1012                 return -ENOMEM;
1013
1014         buf->len = size;
1015         rqst->rq_buffer = buf->data;
1016         rqst->rq_rbuffer = (char *)rqst->rq_buffer + rqst->rq_callsize;
1017         return 0;
1018 }
1019 EXPORT_SYMBOL_GPL(rpc_malloc);
1020
1021 /**
1022  * rpc_free - free RPC buffer resources allocated via rpc_malloc
1023  * @task: RPC task
1024  *
1025  */
1026 void rpc_free(struct rpc_task *task)
1027 {
1028         void *buffer = task->tk_rqstp->rq_buffer;
1029         size_t size;
1030         struct rpc_buffer *buf;
1031
1032         buf = container_of(buffer, struct rpc_buffer, data);
1033         size = buf->len;
1034
1035         if (size <= RPC_BUFFER_MAXSIZE)
1036                 mempool_free(buf, rpc_buffer_mempool);
1037         else
1038                 kfree(buf);
1039 }
1040 EXPORT_SYMBOL_GPL(rpc_free);
1041
1042 /*
1043  * Creation and deletion of RPC task structures
1044  */
1045 static void rpc_init_task(struct rpc_task *task, const struct rpc_task_setup *task_setup_data)
1046 {
1047         memset(task, 0, sizeof(*task));
1048         atomic_set(&task->tk_count, 1);
1049         task->tk_flags  = task_setup_data->flags;
1050         task->tk_ops = task_setup_data->callback_ops;
1051         task->tk_calldata = task_setup_data->callback_data;
1052         INIT_LIST_HEAD(&task->tk_task);
1053
1054         task->tk_priority = task_setup_data->priority - RPC_PRIORITY_LOW;
1055         task->tk_owner = current->tgid;
1056
1057         /* Initialize workqueue for async tasks */
1058         task->tk_workqueue = task_setup_data->workqueue;
1059
1060         task->tk_xprt = rpc_task_get_xprt(task_setup_data->rpc_client,
1061                         xprt_get(task_setup_data->rpc_xprt));
1062
1063         task->tk_op_cred = get_rpccred(task_setup_data->rpc_op_cred);
1064
1065         if (task->tk_ops->rpc_call_prepare != NULL)
1066                 task->tk_action = rpc_prepare_task;
1067
1068         rpc_init_task_statistics(task);
1069 }
1070
1071 static struct rpc_task *
1072 rpc_alloc_task(void)
1073 {
1074         return (struct rpc_task *)mempool_alloc(rpc_task_mempool, GFP_NOFS);
1075 }
1076
1077 /*
1078  * Create a new task for the specified client.
1079  */
1080 struct rpc_task *rpc_new_task(const struct rpc_task_setup *setup_data)
1081 {
1082         struct rpc_task *task = setup_data->task;
1083         unsigned short flags = 0;
1084
1085         if (task == NULL) {
1086                 task = rpc_alloc_task();
1087                 flags = RPC_TASK_DYNAMIC;
1088         }
1089
1090         rpc_init_task(task, setup_data);
1091         task->tk_flags |= flags;
1092         return task;
1093 }
1094
1095 /*
1096  * rpc_free_task - release rpc task and perform cleanups
1097  *
1098  * Note that we free up the rpc_task _after_ rpc_release_calldata()
1099  * in order to work around a workqueue dependency issue.
1100  *
1101  * Tejun Heo states:
1102  * "Workqueue currently considers two work items to be the same if they're
1103  * on the same address and won't execute them concurrently - ie. it
1104  * makes a work item which is queued again while being executed wait
1105  * for the previous execution to complete.
1106  *
1107  * If a work function frees the work item, and then waits for an event
1108  * which should be performed by another work item and *that* work item
1109  * recycles the freed work item, it can create a false dependency loop.
1110  * There really is no reliable way to detect this short of verifying
1111  * every memory free."
1112  *
1113  */
1114 static void rpc_free_task(struct rpc_task *task)
1115 {
1116         unsigned short tk_flags = task->tk_flags;
1117
1118         put_rpccred(task->tk_op_cred);
1119         rpc_release_calldata(task->tk_ops, task->tk_calldata);
1120
1121         if (tk_flags & RPC_TASK_DYNAMIC)
1122                 mempool_free(task, rpc_task_mempool);
1123 }
1124
1125 static void rpc_async_release(struct work_struct *work)
1126 {
1127         unsigned int pflags = memalloc_nofs_save();
1128
1129         rpc_free_task(container_of(work, struct rpc_task, u.tk_work));
1130         memalloc_nofs_restore(pflags);
1131 }
1132
1133 static void rpc_release_resources_task(struct rpc_task *task)
1134 {
1135         xprt_release(task);
1136         if (task->tk_msg.rpc_cred) {
1137                 if (!(task->tk_flags & RPC_TASK_CRED_NOREF))
1138                         put_cred(task->tk_msg.rpc_cred);
1139                 task->tk_msg.rpc_cred = NULL;
1140         }
1141         rpc_task_release_client(task);
1142 }
1143
1144 static void rpc_final_put_task(struct rpc_task *task,
1145                 struct workqueue_struct *q)
1146 {
1147         if (q != NULL) {
1148                 INIT_WORK(&task->u.tk_work, rpc_async_release);
1149                 queue_work(q, &task->u.tk_work);
1150         } else
1151                 rpc_free_task(task);
1152 }
1153
1154 static void rpc_do_put_task(struct rpc_task *task, struct workqueue_struct *q)
1155 {
1156         if (atomic_dec_and_test(&task->tk_count)) {
1157                 rpc_release_resources_task(task);
1158                 rpc_final_put_task(task, q);
1159         }
1160 }
1161
1162 void rpc_put_task(struct rpc_task *task)
1163 {
1164         rpc_do_put_task(task, NULL);
1165 }
1166 EXPORT_SYMBOL_GPL(rpc_put_task);
1167
1168 void rpc_put_task_async(struct rpc_task *task)
1169 {
1170         rpc_do_put_task(task, task->tk_workqueue);
1171 }
1172 EXPORT_SYMBOL_GPL(rpc_put_task_async);
1173
1174 static void rpc_release_task(struct rpc_task *task)
1175 {
1176         WARN_ON_ONCE(RPC_IS_QUEUED(task));
1177
1178         rpc_release_resources_task(task);
1179
1180         /*
1181          * Note: at this point we have been removed from rpc_clnt->cl_tasks,
1182          * so it should be safe to use task->tk_count as a test for whether
1183          * or not any other processes still hold references to our rpc_task.
1184          */
1185         if (atomic_read(&task->tk_count) != 1 + !RPC_IS_ASYNC(task)) {
1186                 /* Wake up anyone who may be waiting for task completion */
1187                 if (!rpc_complete_task(task))
1188                         return;
1189         } else {
1190                 if (!atomic_dec_and_test(&task->tk_count))
1191                         return;
1192         }
1193         rpc_final_put_task(task, task->tk_workqueue);
1194 }
1195
1196 int rpciod_up(void)
1197 {
1198         return try_module_get(THIS_MODULE) ? 0 : -EINVAL;
1199 }
1200
1201 void rpciod_down(void)
1202 {
1203         module_put(THIS_MODULE);
1204 }
1205
1206 /*
1207  * Start up the rpciod workqueue.
1208  */
1209 static int rpciod_start(void)
1210 {
1211         struct workqueue_struct *wq;
1212
1213         /*
1214          * Create the rpciod thread and wait for it to start.
1215          */
1216         wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
1217         if (!wq)
1218                 goto out_failed;
1219         rpciod_workqueue = wq;
1220         /* Note: highpri because network receive is latency sensitive */
1221         wq = alloc_workqueue("xprtiod", WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_HIGHPRI, 0);
1222         if (!wq)
1223                 goto free_rpciod;
1224         xprtiod_workqueue = wq;
1225         return 1;
1226 free_rpciod:
1227         wq = rpciod_workqueue;
1228         rpciod_workqueue = NULL;
1229         destroy_workqueue(wq);
1230 out_failed:
1231         return 0;
1232 }
1233
1234 static void rpciod_stop(void)
1235 {
1236         struct workqueue_struct *wq = NULL;
1237
1238         if (rpciod_workqueue == NULL)
1239                 return;
1240
1241         wq = rpciod_workqueue;
1242         rpciod_workqueue = NULL;
1243         destroy_workqueue(wq);
1244         wq = xprtiod_workqueue;
1245         xprtiod_workqueue = NULL;
1246         destroy_workqueue(wq);
1247 }
1248
1249 void
1250 rpc_destroy_mempool(void)
1251 {
1252         rpciod_stop();
1253         mempool_destroy(rpc_buffer_mempool);
1254         mempool_destroy(rpc_task_mempool);
1255         kmem_cache_destroy(rpc_task_slabp);
1256         kmem_cache_destroy(rpc_buffer_slabp);
1257         rpc_destroy_wait_queue(&delay_queue);
1258 }
1259
1260 int
1261 rpc_init_mempool(void)
1262 {
1263         /*
1264          * The following is not strictly a mempool initialisation,
1265          * but there is no harm in doing it here
1266          */
1267         rpc_init_wait_queue(&delay_queue, "delayq");
1268         if (!rpciod_start())
1269                 goto err_nomem;
1270
1271         rpc_task_slabp = kmem_cache_create("rpc_tasks",
1272                                              sizeof(struct rpc_task),
1273                                              0, SLAB_HWCACHE_ALIGN,
1274                                              NULL);
1275         if (!rpc_task_slabp)
1276                 goto err_nomem;
1277         rpc_buffer_slabp = kmem_cache_create("rpc_buffers",
1278                                              RPC_BUFFER_MAXSIZE,
1279                                              0, SLAB_HWCACHE_ALIGN,
1280                                              NULL);
1281         if (!rpc_buffer_slabp)
1282                 goto err_nomem;
1283         rpc_task_mempool = mempool_create_slab_pool(RPC_TASK_POOLSIZE,
1284                                                     rpc_task_slabp);
1285         if (!rpc_task_mempool)
1286                 goto err_nomem;
1287         rpc_buffer_mempool = mempool_create_slab_pool(RPC_BUFFER_POOLSIZE,
1288                                                       rpc_buffer_slabp);
1289         if (!rpc_buffer_mempool)
1290                 goto err_nomem;
1291         return 0;
1292 err_nomem:
1293         rpc_destroy_mempool();
1294         return -ENOMEM;
1295 }