fs/fscache/operation.c

   1 /* FS-Cache worker operation management routines
   2  *
   3  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  *
  11  * See Documentation/filesystems/caching/operations.txt
  12  */
  13
  14 #define FSCACHE_DEBUG_LEVEL OPERATION
  15 #include <linux/module.h>
  16 #include <linux/seq_file.h>
  17 #include <linux/slab.h>
  18 #include "internal.h"
  19
  20 atomic_t fscache_op_debug_id;
  21 EXPORT_SYMBOL(fscache_op_debug_id);
  22
  23 static void fscache_operation_dummy_cancel(struct fscache_operation *op)
  24 {
  25 }
  26
  27 /**
  28  * fscache_operation_init - Do basic initialisation of an operation
  29  * @op: The operation to initialise
  30  * @release: The release function to assign
  31  *
  32  * Do basic initialisation of an operation.  The caller must still set flags,
  33  * object and processor if needed.
  34  */
  35 void fscache_operation_init(struct fscache_operation *op,
  36                             fscache_operation_processor_t processor,
  37                             fscache_operation_cancel_t cancel,
  38                             fscache_operation_release_t release)
  39 {
  40         INIT_WORK(&op->work, fscache_op_work_func);
  41         atomic_set(&op->usage, 1);
  42         op->state = FSCACHE_OP_ST_INITIALISED;
  43         op->debug_id = atomic_inc_return(&fscache_op_debug_id);
  44         op->processor = processor;
  45         op->cancel = cancel ?: fscache_operation_dummy_cancel;
  46         op->release = release;
  47         INIT_LIST_HEAD(&op->pend_link);
  48         fscache_stat(&fscache_n_op_initialised);
  49 }
  50 EXPORT_SYMBOL(fscache_operation_init);
  51
  52 /**
  53  * fscache_enqueue_operation - Enqueue an operation for processing
  54  * @op: The operation to enqueue
  55  *
  56  * Enqueue an operation for processing by the FS-Cache thread pool.
  57  *
  58  * This will get its own ref on the object.
  59  */
  60 void fscache_enqueue_operation(struct fscache_operation *op)
  61 {
  62         _enter("{OBJ%x OP%x,%u}",
  63                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
  64
  65         ASSERT(list_empty(&op->pend_link));
  66         ASSERT(op->processor != NULL);
  67         ASSERT(fscache_object_is_available(op->object));
  68         ASSERTCMP(atomic_read(&op->usage), >, 0);
  69         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
  70
  71         fscache_stat(&fscache_n_op_enqueue);
  72         switch (op->flags & FSCACHE_OP_TYPE) {
  73         case FSCACHE_OP_ASYNC:
  74                 _debug("queue async");
  75                 atomic_inc(&op->usage);
  76                 if (!queue_work(fscache_op_wq, &op->work))
  77                         fscache_put_operation(op);
  78                 break;
  79         case FSCACHE_OP_MYTHREAD:
  80                 _debug("queue for caller's attention");
  81                 break;
  82         default:
  83                 pr_err("Unexpected op type %lx", op->flags);
  84                 BUG();
  85                 break;
  86         }
  87 }
  88 EXPORT_SYMBOL(fscache_enqueue_operation);
  89
  90 /*
  91  * start an op running
  92  */
  93 static void fscache_run_op(struct fscache_object *object,
  94                            struct fscache_operation *op)
  95 {
  96         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
  97
  98         op->state = FSCACHE_OP_ST_IN_PROGRESS;
  99         object->n_in_progress++;
 100         if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 101                 wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 102         if (op->processor)
 103                 fscache_enqueue_operation(op);
 104         fscache_stat(&fscache_n_op_run);
 105 }
 106
 107 /*
 108  * report an unexpected submission
 109  */
 110 static void fscache_report_unexpected_submission(struct fscache_object *object,
 111                                                  struct fscache_operation *op,
 112                                                  const struct fscache_state *ostate)
 113 {
 114         static bool once_only;
 115         struct fscache_operation *p;
 116         unsigned n;
 117
 118         if (once_only)
 119                 return;
 120         once_only = true;
 121
 122         kdebug("unexpected submission OP%x [OBJ%x %s]",
 123                op->debug_id, object->debug_id, object->state->name);
 124         kdebug("objstate=%s [%s]", object->state->name, ostate->name);
 125         kdebug("objflags=%lx", object->flags);
 126         kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
 127         kdebug("ops=%u inp=%u exc=%u",
 128                object->n_ops, object->n_in_progress, object->n_exclusive);
 129
 130         if (!list_empty(&object->pending_ops)) {
 131                 n = 0;
 132                 list_for_each_entry(p, &object->pending_ops, pend_link) {
 133                         ASSERTCMP(p->object, ==, object);
 134                         kdebug("%p %p", op->processor, op->release);
 135                         n++;
 136                 }
 137
 138                 kdebug("n=%u", n);
 139         }
 140
 141         dump_stack();
 142 }
 143
 144 /*
 145  * submit an exclusive operation for an object
 146  * - other ops are excluded from running simultaneously with this one
 147  * - this gets any extra refs it needs on an op
 148  */
 149 int fscache_submit_exclusive_op(struct fscache_object *object,
 150                                 struct fscache_operation *op)
 151 {
 152         const struct fscache_state *ostate;
 153         unsigned long flags;
 154         int ret;
 155
 156         _enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
 157
 158         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
 159         ASSERTCMP(atomic_read(&op->usage), >, 0);
 160
 161         spin_lock(&object->lock);
 162         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
 163         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
 164         ASSERT(list_empty(&op->pend_link));
 165
 166         ostate = object->state;
 167         smp_rmb();
 168
 169         op->state = FSCACHE_OP_ST_PENDING;
 170         flags = READ_ONCE(object->flags);
 171         if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
 172                 fscache_stat(&fscache_n_op_rejected);
 173                 op->cancel(op);
 174                 op->state = FSCACHE_OP_ST_CANCELLED;
 175                 ret = -ENOBUFS;
 176         } else if (unlikely(fscache_cache_is_broken(object))) {
 177                 op->cancel(op);
 178                 op->state = FSCACHE_OP_ST_CANCELLED;
 179                 ret = -EIO;
 180         } else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
 181                 op->object = object;
 182                 object->n_ops++;
 183                 object->n_exclusive++;  /* reads and writes must wait */
 184
 185                 if (object->n_in_progress > 0) {
 186                         atomic_inc(&op->usage);
 187                         list_add_tail(&op->pend_link, &object->pending_ops);
 188                         fscache_stat(&fscache_n_op_pend);
 189                 } else if (!list_empty(&object->pending_ops)) {
 190                         atomic_inc(&op->usage);
 191                         list_add_tail(&op->pend_link, &object->pending_ops);
 192                         fscache_stat(&fscache_n_op_pend);
 193                         fscache_start_operations(object);
 194                 } else {
 195                         ASSERTCMP(object->n_in_progress, ==, 0);
 196                         fscache_run_op(object, op);
 197                 }
 198
 199                 /* need to issue a new write op after this */
 200                 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 201                 ret = 0;
 202         } else if (flags & BIT(FSCACHE_OBJECT_IS_LOOKED_UP)) {
 203                 op->object = object;
 204                 object->n_ops++;
 205                 object->n_exclusive++;  /* reads and writes must wait */
 206                 atomic_inc(&op->usage);
 207                 list_add_tail(&op->pend_link, &object->pending_ops);
 208                 fscache_stat(&fscache_n_op_pend);
 209                 ret = 0;
 210         } else if (flags & BIT(FSCACHE_OBJECT_KILLED_BY_CACHE)) {
 211                 op->cancel(op);
 212                 op->state = FSCACHE_OP_ST_CANCELLED;
 213                 ret = -ENOBUFS;
 214         } else {
 215                 fscache_report_unexpected_submission(object, op, ostate);
 216                 op->cancel(op);
 217                 op->state = FSCACHE_OP_ST_CANCELLED;
 218                 ret = -ENOBUFS;
 219         }
 220
 221         spin_unlock(&object->lock);
 222         return ret;
 223 }
 224
 225 /*
 226  * submit an operation for an object
 227  * - objects may be submitted only in the following states:
 228  *   - during object creation (write ops may be submitted)
 229  *   - whilst the object is active
 230  *   - after an I/O error incurred in one of the two above states (op rejected)
 231  * - this gets any extra refs it needs on an op
 232  */
 233 int fscache_submit_op(struct fscache_object *object,
 234                       struct fscache_operation *op)
 235 {
 236         const struct fscache_state *ostate;
 237         unsigned long flags;
 238         int ret;
 239
 240         _enter("{OBJ%x OP%x},{%u}",
 241                object->debug_id, op->debug_id, atomic_read(&op->usage));
 242
 243         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
 244         ASSERTCMP(atomic_read(&op->usage), >, 0);
 245
 246         spin_lock(&object->lock);
 247         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
 248         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
 249         ASSERT(list_empty(&op->pend_link));
 250
 251         ostate = object->state;
 252         smp_rmb();
 253
 254         op->state = FSCACHE_OP_ST_PENDING;
 255         flags = READ_ONCE(object->flags);
 256         if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
 257                 fscache_stat(&fscache_n_op_rejected);
 258                 op->cancel(op);
 259                 op->state = FSCACHE_OP_ST_CANCELLED;
 260                 ret = -ENOBUFS;
 261         } else if (unlikely(fscache_cache_is_broken(object))) {
 262                 op->cancel(op);
 263                 op->state = FSCACHE_OP_ST_CANCELLED;
 264                 ret = -EIO;
 265         } else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
 266                 op->object = object;
 267                 object->n_ops++;
 268
 269                 if (object->n_exclusive > 0) {
 270                         atomic_inc(&op->usage);
 271                         list_add_tail(&op->pend_link, &object->pending_ops);
 272                         fscache_stat(&fscache_n_op_pend);
 273                 } else if (!list_empty(&object->pending_ops)) {
 274                         atomic_inc(&op->usage);
 275                         list_add_tail(&op->pend_link, &object->pending_ops);
 276                         fscache_stat(&fscache_n_op_pend);
 277                         fscache_start_operations(object);
 278                 } else {
 279                         ASSERTCMP(object->n_exclusive, ==, 0);
 280                         fscache_run_op(object, op);
 281                 }
 282                 ret = 0;
 283         } else if (flags & BIT(FSCACHE_OBJECT_IS_LOOKED_UP)) {
 284                 op->object = object;
 285                 object->n_ops++;
 286                 atomic_inc(&op->usage);
 287                 list_add_tail(&op->pend_link, &object->pending_ops);
 288                 fscache_stat(&fscache_n_op_pend);
 289                 ret = 0;
 290         } else if (flags & BIT(FSCACHE_OBJECT_KILLED_BY_CACHE)) {
 291                 op->cancel(op);
 292                 op->state = FSCACHE_OP_ST_CANCELLED;
 293                 ret = -ENOBUFS;
 294         } else {
 295                 fscache_report_unexpected_submission(object, op, ostate);
 296                 ASSERT(!fscache_object_is_active(object));
 297                 op->cancel(op);
 298                 op->state = FSCACHE_OP_ST_CANCELLED;
 299                 ret = -ENOBUFS;
 300         }
 301
 302         spin_unlock(&object->lock);
 303         return ret;
 304 }
 305
 306 /*
 307  * queue an object for withdrawal on error, aborting all following asynchronous
 308  * operations
 309  */
 310 void fscache_abort_object(struct fscache_object *object)
 311 {
 312         _enter("{OBJ%x}", object->debug_id);
 313
 314         fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
 315 }
 316
 317 /*
 318  * Jump start the operation processing on an object.  The caller must hold
 319  * object->lock.
 320  */
 321 void fscache_start_operations(struct fscache_object *object)
 322 {
 323         struct fscache_operation *op;
 324         bool stop = false;
 325
 326         while (!list_empty(&object->pending_ops) && !stop) {
 327                 op = list_entry(object->pending_ops.next,
 328                                 struct fscache_operation, pend_link);
 329
 330                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
 331                         if (object->n_in_progress > 0)
 332                                 break;
 333                         stop = true;
 334                 }
 335                 list_del_init(&op->pend_link);
 336                 fscache_run_op(object, op);
 337
 338                 /* the pending queue was holding a ref on the object */
 339                 fscache_put_operation(op);
 340         }
 341
 342         ASSERTCMP(object->n_in_progress, <=, object->n_ops);
 343
 344         _debug("woke %d ops on OBJ%x",
 345                object->n_in_progress, object->debug_id);
 346 }
 347
 348 /*
 349  * cancel an operation that's pending on an object
 350  */
 351 int fscache_cancel_op(struct fscache_operation *op,
 352                       bool cancel_in_progress_op)
 353 {
 354         struct fscache_object *object = op->object;
 355         bool put = false;
 356         int ret;
 357
 358         _enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
 359
 360         ASSERTCMP(op->state, >=, FSCACHE_OP_ST_PENDING);
 361         ASSERTCMP(op->state, !=, FSCACHE_OP_ST_CANCELLED);
 362         ASSERTCMP(atomic_read(&op->usage), >, 0);
 363
 364         spin_lock(&object->lock);
 365
 366         ret = -EBUSY;
 367         if (op->state == FSCACHE_OP_ST_PENDING) {
 368                 ASSERT(!list_empty(&op->pend_link));
 369                 list_del_init(&op->pend_link);
 370                 put = true;
 371
 372                 fscache_stat(&fscache_n_op_cancelled);
 373                 op->cancel(op);
 374                 op->state = FSCACHE_OP_ST_CANCELLED;
 375                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 376                         object->n_exclusive--;
 377                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 378                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 379                 ret = 0;
 380         } else if (op->state == FSCACHE_OP_ST_IN_PROGRESS && cancel_in_progress_op) {
 381                 ASSERTCMP(object->n_in_progress, >, 0);
 382                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 383                         object->n_exclusive--;
 384                 object->n_in_progress--;
 385                 if (object->n_in_progress == 0)
 386                         fscache_start_operations(object);
 387
 388                 fscache_stat(&fscache_n_op_cancelled);
 389                 op->cancel(op);
 390                 op->state = FSCACHE_OP_ST_CANCELLED;
 391                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 392                         object->n_exclusive--;
 393                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 394                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 395                 ret = 0;
 396         }
 397
 398         if (put)
 399                 fscache_put_operation(op);
 400         spin_unlock(&object->lock);
 401         _leave(" = %d", ret);
 402         return ret;
 403 }
 404
 405 /*
 406  * Cancel all pending operations on an object
 407  */
 408 void fscache_cancel_all_ops(struct fscache_object *object)
 409 {
 410         struct fscache_operation *op;
 411
 412         _enter("OBJ%x", object->debug_id);
 413
 414         spin_lock(&object->lock);
 415
 416         while (!list_empty(&object->pending_ops)) {
 417                 op = list_entry(object->pending_ops.next,
 418                                 struct fscache_operation, pend_link);
 419                 fscache_stat(&fscache_n_op_cancelled);
 420                 list_del_init(&op->pend_link);
 421
 422                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
 423                 op->cancel(op);
 424                 op->state = FSCACHE_OP_ST_CANCELLED;
 425
 426                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 427                         object->n_exclusive--;
 428                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 429                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 430                 fscache_put_operation(op);
 431                 cond_resched_lock(&object->lock);
 432         }
 433
 434         spin_unlock(&object->lock);
 435         _leave("");
 436 }
 437
 438 /*
 439  * Record the completion or cancellation of an in-progress operation.
 440  */
 441 void fscache_op_complete(struct fscache_operation *op, bool cancelled)
 442 {
 443         struct fscache_object *object = op->object;
 444
 445         _enter("OBJ%x", object->debug_id);
 446
 447         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
 448         ASSERTCMP(object->n_in_progress, >, 0);
 449         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 450                     object->n_exclusive, >, 0);
 451         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 452                     object->n_in_progress, ==, 1);
 453
 454         spin_lock(&object->lock);
 455
 456         if (!cancelled) {
 457                 op->state = FSCACHE_OP_ST_COMPLETE;
 458         } else {
 459                 op->cancel(op);
 460                 op->state = FSCACHE_OP_ST_CANCELLED;
 461         }
 462
 463         if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 464                 object->n_exclusive--;
 465         object->n_in_progress--;
 466         if (object->n_in_progress == 0)
 467                 fscache_start_operations(object);
 468
 469         spin_unlock(&object->lock);
 470         _leave("");
 471 }
 472 EXPORT_SYMBOL(fscache_op_complete);
 473
 474 /*
 475  * release an operation
 476  * - queues pending ops if this is the last in-progress op
 477  */
 478 void fscache_put_operation(struct fscache_operation *op)
 479 {
 480         struct fscache_object *object;
 481         struct fscache_cache *cache;
 482
 483         _enter("{OBJ%x OP%x,%d}",
 484                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 485
 486         ASSERTCMP(atomic_read(&op->usage), >, 0);
 487
 488         if (!atomic_dec_and_test(&op->usage))
 489                 return;
 490
 491         _debug("PUT OP");
 492         ASSERTIFCMP(op->state != FSCACHE_OP_ST_INITIALISED &&
 493                     op->state != FSCACHE_OP_ST_COMPLETE,
 494                     op->state, ==, FSCACHE_OP_ST_CANCELLED);
 495
 496         fscache_stat(&fscache_n_op_release);
 497
 498         if (op->release) {
 499                 op->release(op);
 500                 op->release = NULL;
 501         }
 502         op->state = FSCACHE_OP_ST_DEAD;
 503
 504         object = op->object;
 505         if (likely(object)) {
 506                 if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
 507                         atomic_dec(&object->n_reads);
 508                 if (test_bit(FSCACHE_OP_UNUSE_COOKIE, &op->flags))
 509                         fscache_unuse_cookie(object);
 510
 511                 /* now... we may get called with the object spinlock held, so we
 512                  * complete the cleanup here only if we can immediately acquire the
 513                  * lock, and defer it otherwise */
 514                 if (!spin_trylock(&object->lock)) {
 515                         _debug("defer put");
 516                         fscache_stat(&fscache_n_op_deferred_release);
 517
 518                         cache = object->cache;
 519                         spin_lock(&cache->op_gc_list_lock);
 520                         list_add_tail(&op->pend_link, &cache->op_gc_list);
 521                         spin_unlock(&cache->op_gc_list_lock);
 522                         schedule_work(&cache->op_gc);
 523                         _leave(" [defer]");
 524                         return;
 525                 }
 526
 527                 ASSERTCMP(object->n_ops, >, 0);
 528                 object->n_ops--;
 529                 if (object->n_ops == 0)
 530                         fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 531
 532                 spin_unlock(&object->lock);
 533         }
 534
 535         kfree(op);
 536         _leave(" [done]");
 537 }
 538 EXPORT_SYMBOL(fscache_put_operation);
 539
 540 /*
 541  * garbage collect operations that have had their release deferred
 542  */
 543 void fscache_operation_gc(struct work_struct *work)
 544 {
 545         struct fscache_operation *op;
 546         struct fscache_object *object;
 547         struct fscache_cache *cache =
 548                 container_of(work, struct fscache_cache, op_gc);
 549         int count = 0;
 550
 551         _enter("");
 552
 553         do {
 554                 spin_lock(&cache->op_gc_list_lock);
 555                 if (list_empty(&cache->op_gc_list)) {
 556                         spin_unlock(&cache->op_gc_list_lock);
 557                         break;
 558                 }
 559
 560                 op = list_entry(cache->op_gc_list.next,
 561                                 struct fscache_operation, pend_link);
 562                 list_del(&op->pend_link);
 563                 spin_unlock(&cache->op_gc_list_lock);
 564
 565                 object = op->object;
 566                 spin_lock(&object->lock);
 567
 568                 _debug("GC DEFERRED REL OBJ%x OP%x",
 569                        object->debug_id, op->debug_id);
 570                 fscache_stat(&fscache_n_op_gc);
 571
 572                 ASSERTCMP(atomic_read(&op->usage), ==, 0);
 573                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_DEAD);
 574
 575                 ASSERTCMP(object->n_ops, >, 0);
 576                 object->n_ops--;
 577                 if (object->n_ops == 0)
 578                         fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 579
 580                 spin_unlock(&object->lock);
 581                 kfree(op);
 582
 583         } while (count++ < 20);
 584
 585         if (!list_empty(&cache->op_gc_list))
 586                 schedule_work(&cache->op_gc);
 587
 588         _leave("");
 589 }
 590
 591 /*
 592  * execute an operation using fs_op_wq to provide processing context -
 593  * the caller holds a ref to this object, so we don't need to hold one
 594  */
 595 void fscache_op_work_func(struct work_struct *work)
 596 {
 597         struct fscache_operation *op =
 598                 container_of(work, struct fscache_operation, work);
 599         unsigned long start;
 600
 601         _enter("{OBJ%x OP%x,%d}",
 602                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 603
 604         ASSERT(op->processor != NULL);
 605         start = jiffies;
 606         op->processor(op);
 607         fscache_hist(fscache_ops_histogram, start);
 608         fscache_put_operation(op);
 609
 610         _leave("");
 611 }