root/fs/fscache/operation.c

DEFINITIONS

1. fscache_operation_dummy_cancel
2. fscache_operation_init
3. fscache_enqueue_operation
4. fscache_run_op
5. fscache_report_unexpected_submission
6. fscache_submit_exclusive_op
7. fscache_submit_op
8. fscache_abort_object
9. fscache_start_operations
10. fscache_cancel_op
11. fscache_cancel_all_ops
12. fscache_op_complete
13. fscache_put_operation
14. fscache_operation_gc
15. fscache_op_work_func

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* FS-Cache worker operation management routines
   3  *
   4  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  *
   7  * See Documentation/filesystems/caching/operations.txt
   8  */
   9 
  10 #define FSCACHE_DEBUG_LEVEL OPERATION
  11 #include <linux/module.h>
  12 #include <linux/seq_file.h>
  13 #include <linux/slab.h>
  14 #include "internal.h"
  15 
  16 atomic_t fscache_op_debug_id;
  17 EXPORT_SYMBOL(fscache_op_debug_id);
  18 
  19 static void fscache_operation_dummy_cancel(struct fscache_operation *op)
  20 {
  21 }
  22 
  23 /**
  24  * fscache_operation_init - Do basic initialisation of an operation
  25  * @op: The operation to initialise
  26  * @release: The release function to assign
  27  *
  28  * Do basic initialisation of an operation.  The caller must still set flags,
  29  * object and processor if needed.
  30  */
  31 void fscache_operation_init(struct fscache_cookie *cookie,
  32                             struct fscache_operation *op,
  33                             fscache_operation_processor_t processor,
  34                             fscache_operation_cancel_t cancel,
  35                             fscache_operation_release_t release)
  36 {
  37         INIT_WORK(&op->work, fscache_op_work_func);
  38         atomic_set(&op->usage, 1);
  39         op->state = FSCACHE_OP_ST_INITIALISED;
  40         op->debug_id = atomic_inc_return(&fscache_op_debug_id);
  41         op->processor = processor;
  42         op->cancel = cancel ?: fscache_operation_dummy_cancel;
  43         op->release = release;
  44         INIT_LIST_HEAD(&op->pend_link);
  45         fscache_stat(&fscache_n_op_initialised);
  46         trace_fscache_op(cookie, op, fscache_op_init);
  47 }
  48 EXPORT_SYMBOL(fscache_operation_init);
  49 
  50 /**
  51  * fscache_enqueue_operation - Enqueue an operation for processing
  52  * @op: The operation to enqueue
  53  *
  54  * Enqueue an operation for processing by the FS-Cache thread pool.
  55  *
  56  * This will get its own ref on the object.
  57  */
  58 void fscache_enqueue_operation(struct fscache_operation *op)
  59 {
  60         struct fscache_cookie *cookie = op->object->cookie;
  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         ASSERTIFCMP(op->state != FSCACHE_OP_ST_IN_PROGRESS,
  70                     op->state, ==,  FSCACHE_OP_ST_CANCELLED);
  71 
  72         fscache_stat(&fscache_n_op_enqueue);
  73         switch (op->flags & FSCACHE_OP_TYPE) {
  74         case FSCACHE_OP_ASYNC:
  75                 trace_fscache_op(cookie, op, fscache_op_enqueue_async);
  76                 _debug("queue async");
  77                 atomic_inc(&op->usage);
  78                 if (!queue_work(fscache_op_wq, &op->work))
  79                         fscache_put_operation(op);
  80                 break;
  81         case FSCACHE_OP_MYTHREAD:
  82                 trace_fscache_op(cookie, op, fscache_op_enqueue_mythread);
  83                 _debug("queue for caller's attention");
  84                 break;
  85         default:
  86                 pr_err("Unexpected op type %lx", op->flags);
  87                 BUG();
  88                 break;
  89         }
  90 }
  91 EXPORT_SYMBOL(fscache_enqueue_operation);
  92 
  93 /*
  94  * start an op running
  95  */
  96 static void fscache_run_op(struct fscache_object *object,
  97                            struct fscache_operation *op)
  98 {
  99         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
 100 
 101         op->state = FSCACHE_OP_ST_IN_PROGRESS;
 102         object->n_in_progress++;
 103         if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 104                 wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 105         if (op->processor)
 106                 fscache_enqueue_operation(op);
 107         else
 108                 trace_fscache_op(object->cookie, op, fscache_op_run);
 109         fscache_stat(&fscache_n_op_run);
 110 }
 111 
 112 /*
 113  * report an unexpected submission
 114  */
 115 static void fscache_report_unexpected_submission(struct fscache_object *object,
 116                                                  struct fscache_operation *op,
 117                                                  const struct fscache_state *ostate)
 118 {
 119         static bool once_only;
 120         struct fscache_operation *p;
 121         unsigned n;
 122 
 123         if (once_only)
 124                 return;
 125         once_only = true;
 126 
 127         kdebug("unexpected submission OP%x [OBJ%x %s]",
 128                op->debug_id, object->debug_id, object->state->name);
 129         kdebug("objstate=%s [%s]", object->state->name, ostate->name);
 130         kdebug("objflags=%lx", object->flags);
 131         kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
 132         kdebug("ops=%u inp=%u exc=%u",
 133                object->n_ops, object->n_in_progress, object->n_exclusive);
 134 
 135         if (!list_empty(&object->pending_ops)) {
 136                 n = 0;
 137                 list_for_each_entry(p, &object->pending_ops, pend_link) {
 138                         ASSERTCMP(p->object, ==, object);
 139                         kdebug("%p %p", op->processor, op->release);
 140                         n++;
 141                 }
 142 
 143                 kdebug("n=%u", n);
 144         }
 145 
 146         dump_stack();
 147 }
 148 
 149 /*
 150  * submit an exclusive operation for an object
 151  * - other ops are excluded from running simultaneously with this one
 152  * - this gets any extra refs it needs on an op
 153  */
 154 int fscache_submit_exclusive_op(struct fscache_object *object,
 155                                 struct fscache_operation *op)
 156 {
 157         const struct fscache_state *ostate;
 158         unsigned long flags;
 159         int ret;
 160 
 161         _enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
 162 
 163         trace_fscache_op(object->cookie, op, fscache_op_submit_ex);
 164 
 165         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
 166         ASSERTCMP(atomic_read(&op->usage), >, 0);
 167 
 168         spin_lock(&object->lock);
 169         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
 170         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
 171         ASSERT(list_empty(&op->pend_link));
 172 
 173         ostate = object->state;
 174         smp_rmb();
 175 
 176         op->state = FSCACHE_OP_ST_PENDING;
 177         flags = READ_ONCE(object->flags);
 178         if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
 179                 fscache_stat(&fscache_n_op_rejected);
 180                 op->cancel(op);
 181                 op->state = FSCACHE_OP_ST_CANCELLED;
 182                 ret = -ENOBUFS;
 183         } else if (unlikely(fscache_cache_is_broken(object))) {
 184                 op->cancel(op);
 185                 op->state = FSCACHE_OP_ST_CANCELLED;
 186                 ret = -EIO;
 187         } else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
 188                 op->object = object;
 189                 object->n_ops++;
 190                 object->n_exclusive++;  /* reads and writes must wait */
 191 
 192                 if (object->n_in_progress > 0) {
 193                         atomic_inc(&op->usage);
 194                         list_add_tail(&op->pend_link, &object->pending_ops);
 195                         fscache_stat(&fscache_n_op_pend);
 196                 } else if (!list_empty(&object->pending_ops)) {
 197                         atomic_inc(&op->usage);
 198                         list_add_tail(&op->pend_link, &object->pending_ops);
 199                         fscache_stat(&fscache_n_op_pend);
 200                         fscache_start_operations(object);
 201                 } else {
 202                         ASSERTCMP(object->n_in_progress, ==, 0);
 203                         fscache_run_op(object, op);
 204                 }
 205 
 206                 /* need to issue a new write op after this */
 207                 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 208                 ret = 0;
 209         } else if (flags & BIT(FSCACHE_OBJECT_IS_LOOKED_UP)) {
 210                 op->object = object;
 211                 object->n_ops++;
 212                 object->n_exclusive++;  /* reads and writes must wait */
 213                 atomic_inc(&op->usage);
 214                 list_add_tail(&op->pend_link, &object->pending_ops);
 215                 fscache_stat(&fscache_n_op_pend);
 216                 ret = 0;
 217         } else if (flags & BIT(FSCACHE_OBJECT_KILLED_BY_CACHE)) {
 218                 op->cancel(op);
 219                 op->state = FSCACHE_OP_ST_CANCELLED;
 220                 ret = -ENOBUFS;
 221         } else {
 222                 fscache_report_unexpected_submission(object, op, ostate);
 223                 op->cancel(op);
 224                 op->state = FSCACHE_OP_ST_CANCELLED;
 225                 ret = -ENOBUFS;
 226         }
 227 
 228         spin_unlock(&object->lock);
 229         return ret;
 230 }
 231 
 232 /*
 233  * submit an operation for an object
 234  * - objects may be submitted only in the following states:
 235  *   - during object creation (write ops may be submitted)
 236  *   - whilst the object is active
 237  *   - after an I/O error incurred in one of the two above states (op rejected)
 238  * - this gets any extra refs it needs on an op
 239  */
 240 int fscache_submit_op(struct fscache_object *object,
 241                       struct fscache_operation *op)
 242 {
 243         const struct fscache_state *ostate;
 244         unsigned long flags;
 245         int ret;
 246 
 247         _enter("{OBJ%x OP%x},{%u}",
 248                object->debug_id, op->debug_id, atomic_read(&op->usage));
 249 
 250         trace_fscache_op(object->cookie, op, fscache_op_submit);
 251 
 252         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
 253         ASSERTCMP(atomic_read(&op->usage), >, 0);
 254 
 255         spin_lock(&object->lock);
 256         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
 257         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
 258         ASSERT(list_empty(&op->pend_link));
 259 
 260         ostate = object->state;
 261         smp_rmb();
 262 
 263         op->state = FSCACHE_OP_ST_PENDING;
 264         flags = READ_ONCE(object->flags);
 265         if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
 266                 fscache_stat(&fscache_n_op_rejected);
 267                 op->cancel(op);
 268                 op->state = FSCACHE_OP_ST_CANCELLED;
 269                 ret = -ENOBUFS;
 270         } else if (unlikely(fscache_cache_is_broken(object))) {
 271                 op->cancel(op);
 272                 op->state = FSCACHE_OP_ST_CANCELLED;
 273                 ret = -EIO;
 274         } else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
 275                 op->object = object;
 276                 object->n_ops++;
 277 
 278                 if (object->n_exclusive > 0) {
 279                         atomic_inc(&op->usage);
 280                         list_add_tail(&op->pend_link, &object->pending_ops);
 281                         fscache_stat(&fscache_n_op_pend);
 282                 } else if (!list_empty(&object->pending_ops)) {
 283                         atomic_inc(&op->usage);
 284                         list_add_tail(&op->pend_link, &object->pending_ops);
 285                         fscache_stat(&fscache_n_op_pend);
 286                         fscache_start_operations(object);
 287                 } else {
 288                         ASSERTCMP(object->n_exclusive, ==, 0);
 289                         fscache_run_op(object, op);
 290                 }
 291                 ret = 0;
 292         } else if (flags & BIT(FSCACHE_OBJECT_IS_LOOKED_UP)) {
 293                 op->object = object;
 294                 object->n_ops++;
 295                 atomic_inc(&op->usage);
 296                 list_add_tail(&op->pend_link, &object->pending_ops);
 297                 fscache_stat(&fscache_n_op_pend);
 298                 ret = 0;
 299         } else if (flags & BIT(FSCACHE_OBJECT_KILLED_BY_CACHE)) {
 300                 op->cancel(op);
 301                 op->state = FSCACHE_OP_ST_CANCELLED;
 302                 ret = -ENOBUFS;
 303         } else {
 304                 fscache_report_unexpected_submission(object, op, ostate);
 305                 ASSERT(!fscache_object_is_active(object));
 306                 op->cancel(op);
 307                 op->state = FSCACHE_OP_ST_CANCELLED;
 308                 ret = -ENOBUFS;
 309         }
 310 
 311         spin_unlock(&object->lock);
 312         return ret;
 313 }
 314 
 315 /*
 316  * queue an object for withdrawal on error, aborting all following asynchronous
 317  * operations
 318  */
 319 void fscache_abort_object(struct fscache_object *object)
 320 {
 321         _enter("{OBJ%x}", object->debug_id);
 322 
 323         fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
 324 }
 325 
 326 /*
 327  * Jump start the operation processing on an object.  The caller must hold
 328  * object->lock.
 329  */
 330 void fscache_start_operations(struct fscache_object *object)
 331 {
 332         struct fscache_operation *op;
 333         bool stop = false;
 334 
 335         while (!list_empty(&object->pending_ops) && !stop) {
 336                 op = list_entry(object->pending_ops.next,
 337                                 struct fscache_operation, pend_link);
 338 
 339                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
 340                         if (object->n_in_progress > 0)
 341                                 break;
 342                         stop = true;
 343                 }
 344                 list_del_init(&op->pend_link);
 345                 fscache_run_op(object, op);
 346 
 347                 /* the pending queue was holding a ref on the object */
 348                 fscache_put_operation(op);
 349         }
 350 
 351         ASSERTCMP(object->n_in_progress, <=, object->n_ops);
 352 
 353         _debug("woke %d ops on OBJ%x",
 354                object->n_in_progress, object->debug_id);
 355 }
 356 
 357 /*
 358  * cancel an operation that's pending on an object
 359  */
 360 int fscache_cancel_op(struct fscache_operation *op,
 361                       bool cancel_in_progress_op)
 362 {
 363         struct fscache_object *object = op->object;
 364         bool put = false;
 365         int ret;
 366 
 367         _enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
 368 
 369         trace_fscache_op(object->cookie, op, fscache_op_cancel);
 370 
 371         ASSERTCMP(op->state, >=, FSCACHE_OP_ST_PENDING);
 372         ASSERTCMP(op->state, !=, FSCACHE_OP_ST_CANCELLED);
 373         ASSERTCMP(atomic_read(&op->usage), >, 0);
 374 
 375         spin_lock(&object->lock);
 376 
 377         ret = -EBUSY;
 378         if (op->state == FSCACHE_OP_ST_PENDING) {
 379                 ASSERT(!list_empty(&op->pend_link));
 380                 list_del_init(&op->pend_link);
 381                 put = true;
 382 
 383                 fscache_stat(&fscache_n_op_cancelled);
 384                 op->cancel(op);
 385                 op->state = FSCACHE_OP_ST_CANCELLED;
 386                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 387                         object->n_exclusive--;
 388                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 389                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 390                 ret = 0;
 391         } else if (op->state == FSCACHE_OP_ST_IN_PROGRESS && cancel_in_progress_op) {
 392                 ASSERTCMP(object->n_in_progress, >, 0);
 393                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 394                         object->n_exclusive--;
 395                 object->n_in_progress--;
 396                 if (object->n_in_progress == 0)
 397                         fscache_start_operations(object);
 398 
 399                 fscache_stat(&fscache_n_op_cancelled);
 400                 op->cancel(op);
 401                 op->state = FSCACHE_OP_ST_CANCELLED;
 402                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 403                         object->n_exclusive--;
 404                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 405                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 406                 ret = 0;
 407         }
 408 
 409         if (put)
 410                 fscache_put_operation(op);
 411         spin_unlock(&object->lock);
 412         _leave(" = %d", ret);
 413         return ret;
 414 }
 415 
 416 /*
 417  * Cancel all pending operations on an object
 418  */
 419 void fscache_cancel_all_ops(struct fscache_object *object)
 420 {
 421         struct fscache_operation *op;
 422 
 423         _enter("OBJ%x", object->debug_id);
 424 
 425         spin_lock(&object->lock);
 426 
 427         while (!list_empty(&object->pending_ops)) {
 428                 op = list_entry(object->pending_ops.next,
 429                                 struct fscache_operation, pend_link);
 430                 fscache_stat(&fscache_n_op_cancelled);
 431                 list_del_init(&op->pend_link);
 432 
 433                 trace_fscache_op(object->cookie, op, fscache_op_cancel_all);
 434 
 435                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
 436                 op->cancel(op);
 437                 op->state = FSCACHE_OP_ST_CANCELLED;
 438 
 439                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 440                         object->n_exclusive--;
 441                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
 442                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
 443                 fscache_put_operation(op);
 444                 cond_resched_lock(&object->lock);
 445         }
 446 
 447         spin_unlock(&object->lock);
 448         _leave("");
 449 }
 450 
 451 /*
 452  * Record the completion or cancellation of an in-progress operation.
 453  */
 454 void fscache_op_complete(struct fscache_operation *op, bool cancelled)
 455 {
 456         struct fscache_object *object = op->object;
 457 
 458         _enter("OBJ%x", object->debug_id);
 459 
 460         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
 461         ASSERTCMP(object->n_in_progress, >, 0);
 462         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 463                     object->n_exclusive, >, 0);
 464         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
 465                     object->n_in_progress, ==, 1);
 466 
 467         spin_lock(&object->lock);
 468 
 469         if (!cancelled) {
 470                 trace_fscache_op(object->cookie, op, fscache_op_completed);
 471                 op->state = FSCACHE_OP_ST_COMPLETE;
 472         } else {
 473                 op->cancel(op);
 474                 trace_fscache_op(object->cookie, op, fscache_op_cancelled);
 475                 op->state = FSCACHE_OP_ST_CANCELLED;
 476         }
 477 
 478         if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
 479                 object->n_exclusive--;
 480         object->n_in_progress--;
 481         if (object->n_in_progress == 0)
 482                 fscache_start_operations(object);
 483 
 484         spin_unlock(&object->lock);
 485         _leave("");
 486 }
 487 EXPORT_SYMBOL(fscache_op_complete);
 488 
 489 /*
 490  * release an operation
 491  * - queues pending ops if this is the last in-progress op
 492  */
 493 void fscache_put_operation(struct fscache_operation *op)
 494 {
 495         struct fscache_object *object;
 496         struct fscache_cache *cache;
 497 
 498         _enter("{OBJ%x OP%x,%d}",
 499                op->object ? op->object->debug_id : 0,
 500                op->debug_id, atomic_read(&op->usage));
 501 
 502         ASSERTCMP(atomic_read(&op->usage), >, 0);
 503 
 504         if (!atomic_dec_and_test(&op->usage))
 505                 return;
 506 
 507         trace_fscache_op(op->object ? op->object->cookie : NULL, op, fscache_op_put);
 508 
 509         _debug("PUT OP");
 510         ASSERTIFCMP(op->state != FSCACHE_OP_ST_INITIALISED &&
 511                     op->state != FSCACHE_OP_ST_COMPLETE,
 512                     op->state, ==, FSCACHE_OP_ST_CANCELLED);
 513 
 514         fscache_stat(&fscache_n_op_release);
 515 
 516         if (op->release) {
 517                 op->release(op);
 518                 op->release = NULL;
 519         }
 520         op->state = FSCACHE_OP_ST_DEAD;
 521 
 522         object = op->object;
 523         if (likely(object)) {
 524                 if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
 525                         atomic_dec(&object->n_reads);
 526                 if (test_bit(FSCACHE_OP_UNUSE_COOKIE, &op->flags))
 527                         fscache_unuse_cookie(object);
 528 
 529                 /* now... we may get called with the object spinlock held, so we
 530                  * complete the cleanup here only if we can immediately acquire the
 531                  * lock, and defer it otherwise */
 532                 if (!spin_trylock(&object->lock)) {
 533                         _debug("defer put");
 534                         fscache_stat(&fscache_n_op_deferred_release);
 535 
 536                         cache = object->cache;
 537                         spin_lock(&cache->op_gc_list_lock);
 538                         list_add_tail(&op->pend_link, &cache->op_gc_list);
 539                         spin_unlock(&cache->op_gc_list_lock);
 540                         schedule_work(&cache->op_gc);
 541                         _leave(" [defer]");
 542                         return;
 543                 }
 544 
 545                 ASSERTCMP(object->n_ops, >, 0);
 546                 object->n_ops--;
 547                 if (object->n_ops == 0)
 548                         fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 549 
 550                 spin_unlock(&object->lock);
 551         }
 552 
 553         kfree(op);
 554         _leave(" [done]");
 555 }
 556 EXPORT_SYMBOL(fscache_put_operation);
 557 
 558 /*
 559  * garbage collect operations that have had their release deferred
 560  */
 561 void fscache_operation_gc(struct work_struct *work)
 562 {
 563         struct fscache_operation *op;
 564         struct fscache_object *object;
 565         struct fscache_cache *cache =
 566                 container_of(work, struct fscache_cache, op_gc);
 567         int count = 0;
 568 
 569         _enter("");
 570 
 571         do {
 572                 spin_lock(&cache->op_gc_list_lock);
 573                 if (list_empty(&cache->op_gc_list)) {
 574                         spin_unlock(&cache->op_gc_list_lock);
 575                         break;
 576                 }
 577 
 578                 op = list_entry(cache->op_gc_list.next,
 579                                 struct fscache_operation, pend_link);
 580                 list_del(&op->pend_link);
 581                 spin_unlock(&cache->op_gc_list_lock);
 582 
 583                 object = op->object;
 584                 trace_fscache_op(object->cookie, op, fscache_op_gc);
 585 
 586                 spin_lock(&object->lock);
 587 
 588                 _debug("GC DEFERRED REL OBJ%x OP%x",
 589                        object->debug_id, op->debug_id);
 590                 fscache_stat(&fscache_n_op_gc);
 591 
 592                 ASSERTCMP(atomic_read(&op->usage), ==, 0);
 593                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_DEAD);
 594 
 595                 ASSERTCMP(object->n_ops, >, 0);
 596                 object->n_ops--;
 597                 if (object->n_ops == 0)
 598                         fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
 599 
 600                 spin_unlock(&object->lock);
 601                 kfree(op);
 602 
 603         } while (count++ < 20);
 604 
 605         if (!list_empty(&cache->op_gc_list))
 606                 schedule_work(&cache->op_gc);
 607 
 608         _leave("");
 609 }
 610 
 611 /*
 612  * execute an operation using fs_op_wq to provide processing context -
 613  * the caller holds a ref to this object, so we don't need to hold one
 614  */
 615 void fscache_op_work_func(struct work_struct *work)
 616 {
 617         struct fscache_operation *op =
 618                 container_of(work, struct fscache_operation, work);
 619         unsigned long start;
 620 
 621         _enter("{OBJ%x OP%x,%d}",
 622                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 623 
 624         trace_fscache_op(op->object->cookie, op, fscache_op_work);
 625 
 626         ASSERT(op->processor != NULL);
 627         start = jiffies;
 628         op->processor(op);
 629         fscache_hist(fscache_ops_histogram, start);
 630         fscache_put_operation(op);
 631 
 632         _leave("");
 633 }