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_cookie *cookie,
  36                             struct fscache_operation *op,
  37                             fscache_operation_processor_t processor,
  38                             fscache_operation_cancel_t cancel,
  39                             fscache_operation_release_t release)
  40 {
  41         INIT_WORK(&op->work, fscache_op_work_func);
  42         atomic_set(&op->usage, 1);
  43         op->state = FSCACHE_OP_ST_INITIALISED;
  44         op->debug_id = atomic_inc_return(&fscache_op_debug_id);
  45         op->processor = processor;
  46         op->cancel = cancel ?: fscache_operation_dummy_cancel;
  47         op->release = release;
  48         INIT_LIST_HEAD(&op->pend_link);
  49         fscache_stat(&fscache_n_op_initialised);
  50         trace_fscache_op(cookie, op, fscache_op_init);
  51 }
  52 EXPORT_SYMBOL(fscache_operation_init);
  53
  54 /**
  55  * fscache_enqueue_operation - Enqueue an operation for processing
  56  * @op: The operation to enqueue
  57  *
  58  * Enqueue an operation for processing by the FS-Cache thread pool.
  59  *
  60  * This will get its own ref on the object.
  61  */
  62 void fscache_enqueue_operation(struct fscache_operation *op)
  63 {
  64         struct fscache_cookie *cookie = op->object->cookie;
  65
  66         _enter("{OBJ%x OP%x,%u}",
  67                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
  68
  69         ASSERT(list_empty(&op->pend_link));
  70         ASSERT(op->processor != NULL);
  71         ASSERT(fscache_object_is_available(op->object));
  72         ASSERTCMP(atomic_read(&op->usage), >, 0);
  73         ASSERTIFCMP(op->state != FSCACHE_OP_ST_IN_PROGRESS,
  74                     op->state, ==,  FSCACHE_OP_ST_CANCELLED);
  75
  76         fscache_stat(&fscache_n_op_enqueue);
  77         switch (op->flags & FSCACHE_OP_TYPE) {
  78         case FSCACHE_OP_ASYNC:
  79                 trace_fscache_op(cookie, op, fscache_op_enqueue_async);
  80                 _debug("queue async");
  81                 atomic_inc(&op->usage);
  82                 if (!queue_work(fscache_op_wq, &op->work))
  83                         fscache_put_operation(op);
  84                 break;
  85         case FSCACHE_OP_MYTHREAD:
  86                 trace_fscache_op(cookie, op, fscache_op_enqueue_mythread);
  87                 _debug("queue for caller's attention");
  88                 break;
  89         default:
  90                 pr_err("Unexpected op type %lx", op->flags);
  91                 BUG();
  92                 break;
  93         }
  94 }
  95 EXPORT_SYMBOL(fscache_enqueue_operation);
  96
  97 /*
  98  * start an op running
  99  */
 100 static void fscache_run_op(struct fscache_object *object,
 101                            struct fscache_operation *op)
 102 {
 103         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
 104
 105         op->state = FSCACHE_OP_ST_IN_PROGRESS;
 106         object->n_in_progress++;
 107         if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 108                 wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 109         if (op->processor)
 110                 fscache_enqueue_operation(op);
 111         else
 112                 trace_fscache_op(object->cookie, op, fscache_op_run);
 113         fscache_stat(&fscache_n_op_run);
 114 }
 115
 116 /*
 117  * report an unexpected submission
 118  */
 119 static void fscache_report_unexpected_submission(struct fscache_object *object,
 120                                                  struct fscache_operation *op,
 121                                                  const struct fscache_state *ostate)
 122 {
 123         static bool once_only;
 124         struct fscache_operation *p;
 125         unsigned n;
 126
 127         if (once_only)
 128                 return;
 129         once_only = true;
 130
 131         kdebug("unexpected submission OP%x [OBJ%x %s]",
 132                op->debug_id, object->debug_id, object->state->name);
 133         kdebug("objstate=%s [%s]", object->state->name, ostate->name);
 134         kdebug("objflags=%lx", object->flags);
 135         kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
 136         kdebug("ops=%u inp=%u exc=%u",
 137                object->n_ops, object->n_in_progress, object->n_exclusive);
 138
 139         if (!list_empty(&object->pending_ops)) {
 140                 n = 0;
 141                 list_for_each_entry(p, &object->pending_ops, pend_link) {
 142                         ASSERTCMP(p->object, ==, object);
 143                         kdebug("%p %p", op->processor, op->release);
 144                         n++;
 145                 }
 146
 147                 kdebug("n=%u", n);
 148         }
 149
 150         dump_stack();
 151 }
 152
 153 /*
 154  * submit an exclusive operation for an object
 155  * - other ops are excluded from running simultaneously with this one
 156  * - this gets any extra refs it needs on an op
 157  */
 158 int fscache_submit_exclusive_op(struct fscache_object *object,
 159                                 struct fscache_operation *op)
 160 {
 161         const struct fscache_state *ostate;
 162         unsigned long flags;
 163         int ret;
 164
 165         _enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
 166
 167         trace_fscache_op(object->cookie, op, fscache_op_submit_ex);
 168
 169         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
 170         ASSERTCMP(atomic_read(&op->usage), >, 0);
 171
 172         spin_lock(&object->lock);
 173         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
 174         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
 175         ASSERT(list_empty(&op->pend_link));
 176
 177         ostate = object->state;
 178         smp_rmb();
 179
 180         op->state = FSCACHE_OP_ST_PENDING;
 181         flags = READ_ONCE(object->flags);
 182         if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
 183                 fscache_stat(&fscache_n_op_rejected);
 184                 op->cancel(op);
 185                 op->state = FSCACHE_OP_ST_CANCELLED;
 186                 ret = -ENOBUFS;
 187         } else if (unlikely(fscache_cache_is_broken(object))) {
 188                 op->cancel(op);
 189                 op->state = FSCACHE_OP_ST_CANCELLED;
 190                 ret = -EIO;
 191         } else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
 192                 op->object = object;
 193                 object->n_ops++;
 194                 object->n_exclusive++;  /* reads and writes must wait */
 195
 196                 if (object->n_in_progress > 0) {
 197                         atomic_inc(&op->usage);
 198                         list_add_tail(&op->pend_link, &object->pending_ops);
 199                         fscache_stat(&fscache_n_op_pend);
 200                 } else if (!list_empty(&object->pending_ops)) {
 201                         atomic_inc(&op->usage);
 202                         list_add_tail(&op->pend_link, &object->pending_ops);
 203                         fscache_stat(&fscache_n_op_pend);
 204                         fscache_start_operations(object);
 205                 } else {
 206                         ASSERTCMP(object->n_in_progress, ==, 0);
 207                         fscache_run_op(object, op);
 208                 }
 209
 210                 /* need to issue a new write op after this */
 211                 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 212                 ret = 0;
 213         } else if (flags & BIT(FSCACHE_OBJECT_IS_LOOKED_UP)) {
 214                 op->object = object;
 215                 object->n_ops++;
 216                 object->n_exclusive++;  /* reads and writes must wait */
 217                 atomic_inc(&op->usage);
 218                 list_add_tail(&op->pend_link, &object->pending_ops);
 219                 fscache_stat(&fscache_n_op_pend);
 220                 ret = 0;
 221         } else if (flags & BIT(FSCACHE_OBJECT_KILLED_BY_CACHE)) {
 222                 op->cancel(op);
 223                 op->state = FSCACHE_OP_ST_CANCELLED;
 224                 ret = -ENOBUFS;
 225         } else {
 226                 fscache_report_unexpected_submission(object, op, ostate);
 227                 op->cancel(op);
 228                 op->state = FSCACHE_OP_ST_CANCELLED;
 229                 ret = -ENOBUFS;
 230         }
 231
 232         spin_unlock(&object->lock);
 233         return ret;
 234 }
 235
 236 /*
 237  * submit an operation for an object
 238  * - objects may be submitted only in the following states:
 239  *   - during object creation (write ops may be submitted)
 240  *   - whilst the object is active
 241  *   - after an I/O error incurred in one of the two above states (op rejected)
 242  * - this gets any extra refs it needs on an op
 243  */
 244 int fscache_submit_op(struct fscache_object *object,
 245                       struct fscache_operation *op)
 246 {
 247         const struct fscache_state *ostate;
 248         unsigned long flags;
 249         int ret;
 250
 251         _enter("{OBJ%x OP%x},{%u}",
 252                object->debug_id, op->debug_id, atomic_read(&op->usage));
 253
 254         trace_fscache_op(object->cookie, op, fscache_op_submit);
 255
 256         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
 257         ASSERTCMP(atomic_read(&op->usage), >, 0);
 258
 259         spin_lock(&object->lock);
 260         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
 261         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
 262         ASSERT(list_empty(&op->pend_link));
 263
 264         ostate = object->state;
 265         smp_rmb();
 266
 267         op->state = FSCACHE_OP_ST_PENDING;
 268         flags = READ_ONCE(object->flags);
 269         if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
 270                 fscache_stat(&fscache_n_op_rejected);
 271                 op->cancel(op);
 272                 op->state = FSCACHE_OP_ST_CANCELLED;
 273                 ret = -ENOBUFS;
 274         } else if (unlikely(fscache_cache_is_broken(object))) {
 275                 op->cancel(op);
 276                 op->state = FSCACHE_OP_ST_CANCELLED;
 277                 ret = -EIO;
 278         } else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
 279                 op->object = object;
 280                 object->n_ops++;
 281
 282                 if (object->n_exclusive > 0) {
 283                         atomic_inc(&op->usage);
 284                         list_add_tail(&op->pend_link, &object->pending_ops);
 285                         fscache_stat(&fscache_n_op_pend);
 286                 } else if (!list_empty(&object->pending_ops)) {
 287                         atomic_inc(&op->usage);
 288                         list_add_tail(&op->pend_link, &object->pending_ops);
 289                         fscache_stat(&fscache_n_op_pend);
 290                         fscache_start_operations(object);
 291                 } else {
 292                         ASSERTCMP(object->n_exclusive, ==, 0);
 293                         fscache_run_op(object, op);
 294                 }
 295                 ret = 0;
 296         } else if (flags & BIT(FSCACHE_OBJECT_IS_LOOKED_UP)) {
 297                 op->object = object;
 298                 object->n_ops++;
 299                 atomic_inc(&op->usage);
 300                 list_add_tail(&op->pend_link, &object->pending_ops);
 301                 fscache_stat(&fscache_n_op_pend);
 302                 ret = 0;
 303         } else if (flags & BIT(FSCACHE_OBJECT_KILLED_BY_CACHE)) {
 304                 op->cancel(op);
 305                 op->state = FSCACHE_OP_ST_CANCELLED;
 306                 ret = -ENOBUFS;
 307         } else {
 308                 fscache_report_unexpected_submission(object, op, ostate);
 309                 ASSERT(!fscache_object_is_active(object));
 310                 op->cancel(op);
 311                 op->state = FSCACHE_OP_ST_CANCELLED;
 312                 ret = -ENOBUFS;
 313         }
 314
 315         spin_unlock(&object->lock);
 316         return ret;
 317 }
 318
 319 /*
 320  * queue an object for withdrawal on error, aborting all following asynchronous
 321  * operations
 322  */
 323 void fscache_abort_object(struct fscache_object *object)
 324 {
 325         _enter("{OBJ%x}", object->debug_id);
 326
 327         fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
 328 }
 329
 330 /*
 331  * Jump start the operation processing on an object.  The caller must hold
 332  * object->lock.
 333  */
 334 void fscache_start_operations(struct fscache_object *object)
 335 {
 336         struct fscache_operation *op;
 337         bool stop = false;
 338
 339         while (!list_empty(&object->pending_ops) && !stop) {
 340                 op = list_entry(object->pending_ops.next,
 341                                 struct fscache_operation, pend_link);
 342
 343                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
 344                         if (object->n_in_progress > 0)
 345                                 break;
 346                         stop = true;
 347                 }
 348                 list_del_init(&op->pend_link);
 349                 fscache_run_op(object, op);
 350
 351                 /* the pending queue was holding a ref on the object */
 352                 fscache_put_operation(op);
 353         }
 354
 355         ASSERTCMP(object->n_in_progress, <=, object->n_ops);
 356
 357         _debug("woke %d ops on OBJ%x",
 358                object->n_in_progress, object->debug_id);
 359 }
 360
 361 /*
 362  * cancel an operation that's pending on an object
 363  */
 364 int fscache_cancel_op(struct fscache_operation *op,
 365                       bool cancel_in_progress_op)
 366 {
 367         struct fscache_object *object = op->object;
 368         bool put = false;
 369         int ret;
 370
 371         _enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
 372
 373         trace_fscache_op(object->cookie, op, fscache_op_cancel);
 374
 375         ASSERTCMP(op->state, >=, FSCACHE_OP_ST_PENDING);
 376         ASSERTCMP(op->state, !=, FSCACHE_OP_ST_CANCELLED);
 377         ASSERTCMP(atomic_read(&op->usage), >, 0);
 378
 379         spin_lock(&object->lock);
 380
 381         ret = -EBUSY;
 382         if (op->state == FSCACHE_OP_ST_PENDING) {
 383                 ASSERT(!list_empty(&op->pend_link));
 384                 list_del_init(&op->pend_link);
 385                 put = true;
 386
 387                 fscache_stat(&fscache_n_op_cancelled);
 388                 op->cancel(op);
 389                 op->state = FSCACHE_OP_ST_CANCELLED;
 390                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 391                         object->n_exclusive--;
 392                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 393                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 394                 ret = 0;
 395         } else if (op->state == FSCACHE_OP_ST_IN_PROGRESS && cancel_in_progress_op) {
 396                 ASSERTCMP(object->n_in_progress, >, 0);
 397                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 398                         object->n_exclusive--;
 399                 object->n_in_progress--;
 400                 if (object->n_in_progress == 0)
 401                         fscache_start_operations(object);
 402
 403                 fscache_stat(&fscache_n_op_cancelled);
 404                 op->cancel(op);
 405                 op->state = FSCACHE_OP_ST_CANCELLED;
 406                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 407                         object->n_exclusive--;
 408                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 409                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 410                 ret = 0;
 411         }
 412
 413         if (put)
 414                 fscache_put_operation(op);
 415         spin_unlock(&object->lock);
 416         _leave(" = %d", ret);
 417         return ret;
 418 }
 419
 420 /*
 421  * Cancel all pending operations on an object
 422  */
 423 void fscache_cancel_all_ops(struct fscache_object *object)
 424 {
 425         struct fscache_operation *op;
 426
 427         _enter("OBJ%x", object->debug_id);
 428
 429         spin_lock(&object->lock);
 430
 431         while (!list_empty(&object->pending_ops)) {
 432                 op = list_entry(object->pending_ops.next,
 433                                 struct fscache_operation, pend_link);
 434                 fscache_stat(&fscache_n_op_cancelled);
 435                 list_del_init(&op->pend_link);
 436
 437                 trace_fscache_op(object->cookie, op, fscache_op_cancel_all);
 438
 439                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
 440                 op->cancel(op);
 441                 op->state = FSCACHE_OP_ST_CANCELLED;
 442
 443                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 444                         object->n_exclusive--;
 445                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 446                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 447                 fscache_put_operation(op);
 448                 cond_resched_lock(&object->lock);
 449         }
 450
 451         spin_unlock(&object->lock);
 452         _leave("");
 453 }
 454
 455 /*
 456  * Record the completion or cancellation of an in-progress operation.
 457  */
 458 void fscache_op_complete(struct fscache_operation *op, bool cancelled)
 459 {
 460         struct fscache_object *object = op->object;
 461
 462         _enter("OBJ%x", object->debug_id);
 463
 464         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
 465         ASSERTCMP(object->n_in_progress, >, 0);
 466         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 467                     object->n_exclusive, >, 0);
 468         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 469                     object->n_in_progress, ==, 1);
 470
 471         spin_lock(&object->lock);
 472
 473         if (!cancelled) {
 474                 trace_fscache_op(object->cookie, op, fscache_op_completed);
 475                 op->state = FSCACHE_OP_ST_COMPLETE;
 476         } else {
 477                 op->cancel(op);
 478                 trace_fscache_op(object->cookie, op, fscache_op_cancelled);
 479                 op->state = FSCACHE_OP_ST_CANCELLED;
 480         }
 481
 482         if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 483                 object->n_exclusive--;
 484         object->n_in_progress--;
 485         if (object->n_in_progress == 0)
 486                 fscache_start_operations(object);
 487
 488         spin_unlock(&object->lock);
 489         _leave("");
 490 }
 491 EXPORT_SYMBOL(fscache_op_complete);
 492
 493 /*
 494  * release an operation
 495  * - queues pending ops if this is the last in-progress op
 496  */
 497 void fscache_put_operation(struct fscache_operation *op)
 498 {
 499         struct fscache_object *object;
 500         struct fscache_cache *cache;
 501
 502         _enter("{OBJ%x OP%x,%d}",
 503                op->object ? op->object->debug_id : 0,
 504                op->debug_id, atomic_read(&op->usage));
 505
 506         ASSERTCMP(atomic_read(&op->usage), >, 0);
 507
 508         if (!atomic_dec_and_test(&op->usage))
 509                 return;
 510
 511         trace_fscache_op(op->object ? op->object->cookie : NULL, op, fscache_op_put);
 512
 513         _debug("PUT OP");
 514         ASSERTIFCMP(op->state != FSCACHE_OP_ST_INITIALISED &&
 515                     op->state != FSCACHE_OP_ST_COMPLETE,
 516                     op->state, ==, FSCACHE_OP_ST_CANCELLED);
 517
 518         fscache_stat(&fscache_n_op_release);
 519
 520         if (op->release) {
 521                 op->release(op);
 522                 op->release = NULL;
 523         }
 524         op->state = FSCACHE_OP_ST_DEAD;
 525
 526         object = op->object;
 527         if (likely(object)) {
 528                 if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
 529                         atomic_dec(&object->n_reads);
 530                 if (test_bit(FSCACHE_OP_UNUSE_COOKIE, &op->flags))
 531                         fscache_unuse_cookie(object);
 532
 533                 /* now... we may get called with the object spinlock held, so we
 534                  * complete the cleanup here only if we can immediately acquire the
 535                  * lock, and defer it otherwise */
 536                 if (!spin_trylock(&object->lock)) {
 537                         _debug("defer put");
 538                         fscache_stat(&fscache_n_op_deferred_release);
 539
 540                         cache = object->cache;
 541                         spin_lock(&cache->op_gc_list_lock);
 542                         list_add_tail(&op->pend_link, &cache->op_gc_list);
 543                         spin_unlock(&cache->op_gc_list_lock);
 544                         schedule_work(&cache->op_gc);
 545                         _leave(" [defer]");
 546                         return;
 547                 }
 548
 549                 ASSERTCMP(object->n_ops, >, 0);
 550                 object->n_ops--;
 551                 if (object->n_ops == 0)
 552                         fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 553
 554                 spin_unlock(&object->lock);
 555         }
 556
 557         kfree(op);
 558         _leave(" [done]");
 559 }
 560 EXPORT_SYMBOL(fscache_put_operation);
 561
 562 /*
 563  * garbage collect operations that have had their release deferred
 564  */
 565 void fscache_operation_gc(struct work_struct *work)
 566 {
 567         struct fscache_operation *op;
 568         struct fscache_object *object;
 569         struct fscache_cache *cache =
 570                 container_of(work, struct fscache_cache, op_gc);
 571         int count = 0;
 572
 573         _enter("");
 574
 575         do {
 576                 spin_lock(&cache->op_gc_list_lock);
 577                 if (list_empty(&cache->op_gc_list)) {
 578                         spin_unlock(&cache->op_gc_list_lock);
 579                         break;
 580                 }
 581
 582                 op = list_entry(cache->op_gc_list.next,
 583                                 struct fscache_operation, pend_link);
 584                 list_del(&op->pend_link);
 585                 spin_unlock(&cache->op_gc_list_lock);
 586
 587                 object = op->object;
 588                 trace_fscache_op(object->cookie, op, fscache_op_gc);
 589
 590                 spin_lock(&object->lock);
 591
 592                 _debug("GC DEFERRED REL OBJ%x OP%x",
 593                        object->debug_id, op->debug_id);
 594                 fscache_stat(&fscache_n_op_gc);
 595
 596                 ASSERTCMP(atomic_read(&op->usage), ==, 0);
 597                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_DEAD);
 598
 599                 ASSERTCMP(object->n_ops, >, 0);
 600                 object->n_ops--;
 601                 if (object->n_ops == 0)
 602                         fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 603
 604                 spin_unlock(&object->lock);
 605                 kfree(op);
 606
 607         } while (count++ < 20);
 608
 609         if (!list_empty(&cache->op_gc_list))
 610                 schedule_work(&cache->op_gc);
 611
 612         _leave("");
 613 }
 614
 615 /*
 616  * execute an operation using fs_op_wq to provide processing context -
 617  * the caller holds a ref to this object, so we don't need to hold one
 618  */
 619 void fscache_op_work_func(struct work_struct *work)
 620 {
 621         struct fscache_operation *op =
 622                 container_of(work, struct fscache_operation, work);
 623         unsigned long start;
 624
 625         _enter("{OBJ%x OP%x,%d}",
 626                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 627
 628         trace_fscache_op(op->object->cookie, op, fscache_op_work);
 629
 630         ASSERT(op->processor != NULL);
 631         start = jiffies;
 632         op->processor(op);
 633         fscache_hist(fscache_ops_histogram, start);
 634         fscache_put_operation(op);
 635
 636         _leave("");
 637 }