fs/fscache/cookie.c

   1 /* netfs cookie management
   2  *
   3  * Copyright (C) 2004-2007 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/netfs-api.txt for more information on
  12  * the netfs API.
  13  */
  14
  15 #define FSCACHE_DEBUG_LEVEL COOKIE
  16 #include <linux/module.h>
  17 #include <linux/slab.h>
  18 #include "internal.h"
  19
  20 struct kmem_cache *fscache_cookie_jar;
  21
  22 static atomic_t fscache_object_debug_id = ATOMIC_INIT(0);
  23
  24 static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie);
  25 static int fscache_alloc_object(struct fscache_cache *cache,
  26                                 struct fscache_cookie *cookie);
  27 static int fscache_attach_object(struct fscache_cookie *cookie,
  28                                  struct fscache_object *object);
  29
  30 /*
  31  * initialise an cookie jar slab element prior to any use
  32  */
  33 void fscache_cookie_init_once(void *_cookie)
  34 {
  35         struct fscache_cookie *cookie = _cookie;
  36
  37         memset(cookie, 0, sizeof(*cookie));
  38         spin_lock_init(&cookie->lock);
  39         spin_lock_init(&cookie->stores_lock);
  40         INIT_HLIST_HEAD(&cookie->backing_objects);
  41 }
  42
  43 /*
  44  * request a cookie to represent an object (index, datafile, xattr, etc)
  45  * - parent specifies the parent object
  46  *   - the top level index cookie for each netfs is stored in the fscache_netfs
  47  *     struct upon registration
  48  * - def points to the definition
  49  * - the netfs_data will be passed to the functions pointed to in *def
  50  * - all attached caches will be searched to see if they contain this object
  51  * - index objects aren't stored on disk until there's a dependent file that
  52  *   needs storing
  53  * - other objects are stored in a selected cache immediately, and all the
  54  *   indices forming the path to it are instantiated if necessary
  55  * - we never let on to the netfs about errors
  56  *   - we may set a negative cookie pointer, but that's okay
  57  */
  58 struct fscache_cookie *__fscache_acquire_cookie(
  59         struct fscache_cookie *parent,
  60         const struct fscache_cookie_def *def,
  61         void *netfs_data,
  62         bool enable)
  63 {
  64         struct fscache_cookie *cookie;
  65
  66         BUG_ON(!def);
  67
  68         _enter("{%s},{%s},%p,%u",
  69                parent ? (char *) parent->def->name : "<no-parent>",
  70                def->name, netfs_data, enable);
  71
  72         fscache_stat(&fscache_n_acquires);
  73
  74         /* if there's no parent cookie, then we don't create one here either */
  75         if (!parent) {
  76                 fscache_stat(&fscache_n_acquires_null);
  77                 _leave(" [no parent]");
  78                 return NULL;
  79         }
  80
  81         /* validate the definition */
  82         BUG_ON(!def->get_key);
  83         BUG_ON(!def->name[0]);
  84
  85         BUG_ON(def->type == FSCACHE_COOKIE_TYPE_INDEX &&
  86                parent->def->type != FSCACHE_COOKIE_TYPE_INDEX);
  87
  88         /* allocate and initialise a cookie */
  89         cookie = kmem_cache_alloc(fscache_cookie_jar, GFP_KERNEL);
  90         if (!cookie) {
  91                 fscache_stat(&fscache_n_acquires_oom);
  92                 _leave(" [ENOMEM]");
  93                 return NULL;
  94         }
  95
  96         atomic_set(&cookie->usage, 1);
  97         atomic_set(&cookie->n_children, 0);
  98
  99         /* We keep the active count elevated until relinquishment to prevent an
 100          * attempt to wake up every time the object operations queue quiesces.
 101          */
 102         atomic_set(&cookie->n_active, 1);
 103
 104         atomic_inc(&parent->usage);
 105         atomic_inc(&parent->n_children);
 106
 107         cookie->def             = def;
 108         cookie->parent          = parent;
 109         cookie->netfs_data      = netfs_data;
 110         cookie->flags           = (1 << FSCACHE_COOKIE_NO_DATA_YET);
 111
 112         /* radix tree insertion won't use the preallocation pool unless it's
 113          * told it may not wait */
 114         INIT_RADIX_TREE(&cookie->stores, GFP_NOFS & ~__GFP_WAIT);
 115
 116         switch (cookie->def->type) {
 117         case FSCACHE_COOKIE_TYPE_INDEX:
 118                 fscache_stat(&fscache_n_cookie_index);
 119                 break;
 120         case FSCACHE_COOKIE_TYPE_DATAFILE:
 121                 fscache_stat(&fscache_n_cookie_data);
 122                 break;
 123         default:
 124                 fscache_stat(&fscache_n_cookie_special);
 125                 break;
 126         }
 127
 128         if (enable) {
 129                 /* if the object is an index then we need do nothing more here
 130                  * - we create indices on disk when we need them as an index
 131                  * may exist in multiple caches */
 132                 if (cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX) {
 133                         if (fscache_acquire_non_index_cookie(cookie) == 0) {
 134                                 set_bit(FSCACHE_COOKIE_ENABLED, &cookie->flags);
 135                         } else {
 136                                 atomic_dec(&parent->n_children);
 137                                 __fscache_cookie_put(cookie);
 138                                 fscache_stat(&fscache_n_acquires_nobufs);
 139                                 _leave(" = NULL");
 140                                 return NULL;
 141                         }
 142                 } else {
 143                         set_bit(FSCACHE_COOKIE_ENABLED, &cookie->flags);
 144                 }
 145         }
 146
 147         fscache_stat(&fscache_n_acquires_ok);
 148         _leave(" = %p", cookie);
 149         return cookie;
 150 }
 151 EXPORT_SYMBOL(__fscache_acquire_cookie);
 152
 153 /*
 154  * Enable a cookie to permit it to accept new operations.
 155  */
 156 void __fscache_enable_cookie(struct fscache_cookie *cookie,
 157                              bool (*can_enable)(void *data),
 158                              void *data)
 159 {
 160         _enter("%p", cookie);
 161
 162         wait_on_bit_lock(&cookie->flags, FSCACHE_COOKIE_ENABLEMENT_LOCK,
 163                          TASK_UNINTERRUPTIBLE);
 164
 165         if (test_bit(FSCACHE_COOKIE_ENABLED, &cookie->flags))
 166                 goto out_unlock;
 167
 168         if (can_enable && !can_enable(data)) {
 169                 /* The netfs decided it didn't want to enable after all */
 170         } else if (cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX) {
 171                 /* Wait for outstanding disablement to complete */
 172                 __fscache_wait_on_invalidate(cookie);
 173
 174                 if (fscache_acquire_non_index_cookie(cookie) == 0)
 175                         set_bit(FSCACHE_COOKIE_ENABLED, &cookie->flags);
 176         } else {
 177                 set_bit(FSCACHE_COOKIE_ENABLED, &cookie->flags);
 178         }
 179
 180 out_unlock:
 181         clear_bit_unlock(FSCACHE_COOKIE_ENABLEMENT_LOCK, &cookie->flags);
 182         wake_up_bit(&cookie->flags, FSCACHE_COOKIE_ENABLEMENT_LOCK);
 183 }
 184 EXPORT_SYMBOL(__fscache_enable_cookie);
 185
 186 /*
 187  * acquire a non-index cookie
 188  * - this must make sure the index chain is instantiated and instantiate the
 189  *   object representation too
 190  */
 191 static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie)
 192 {
 193         struct fscache_object *object;
 194         struct fscache_cache *cache;
 195         uint64_t i_size;
 196         int ret;
 197
 198         _enter("");
 199
 200         set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
 201
 202         /* now we need to see whether the backing objects for this cookie yet
 203          * exist, if not there'll be nothing to search */
 204         down_read(&fscache_addremove_sem);
 205
 206         if (list_empty(&fscache_cache_list)) {
 207                 up_read(&fscache_addremove_sem);
 208                 _leave(" = 0 [no caches]");
 209                 return 0;
 210         }
 211
 212         /* select a cache in which to store the object */
 213         cache = fscache_select_cache_for_object(cookie->parent);
 214         if (!cache) {
 215                 up_read(&fscache_addremove_sem);
 216                 fscache_stat(&fscache_n_acquires_no_cache);
 217                 _leave(" = -ENOMEDIUM [no cache]");
 218                 return -ENOMEDIUM;
 219         }
 220
 221         _debug("cache %s", cache->tag->name);
 222
 223         set_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 224
 225         /* ask the cache to allocate objects for this cookie and its parent
 226          * chain */
 227         ret = fscache_alloc_object(cache, cookie);
 228         if (ret < 0) {
 229                 up_read(&fscache_addremove_sem);
 230                 _leave(" = %d", ret);
 231                 return ret;
 232         }
 233
 234         /* pass on how big the object we're caching is supposed to be */
 235         cookie->def->get_attr(cookie->netfs_data, &i_size);
 236
 237         spin_lock(&cookie->lock);
 238         if (hlist_empty(&cookie->backing_objects)) {
 239                 spin_unlock(&cookie->lock);
 240                 goto unavailable;
 241         }
 242
 243         object = hlist_entry(cookie->backing_objects.first,
 244                              struct fscache_object, cookie_link);
 245
 246         fscache_set_store_limit(object, i_size);
 247
 248         /* initiate the process of looking up all the objects in the chain
 249          * (done by fscache_initialise_object()) */
 250         fscache_raise_event(object, FSCACHE_OBJECT_EV_NEW_CHILD);
 251
 252         spin_unlock(&cookie->lock);
 253
 254         /* we may be required to wait for lookup to complete at this point */
 255         if (!fscache_defer_lookup) {
 256                 _debug("non-deferred lookup %p", &cookie->flags);
 257                 wait_on_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP,
 258                             TASK_UNINTERRUPTIBLE);
 259                 _debug("complete");
 260                 if (test_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags))
 261                         goto unavailable;
 262         }
 263
 264         up_read(&fscache_addremove_sem);
 265         _leave(" = 0 [deferred]");
 266         return 0;
 267
 268 unavailable:
 269         up_read(&fscache_addremove_sem);
 270         _leave(" = -ENOBUFS");
 271         return -ENOBUFS;
 272 }
 273
 274 /*
 275  * recursively allocate cache object records for a cookie/cache combination
 276  * - caller must be holding the addremove sem
 277  */
 278 static int fscache_alloc_object(struct fscache_cache *cache,
 279                                 struct fscache_cookie *cookie)
 280 {
 281         struct fscache_object *object;
 282         int ret;
 283
 284         _enter("%p,%p{%s}", cache, cookie, cookie->def->name);
 285
 286         spin_lock(&cookie->lock);
 287         hlist_for_each_entry(object, &cookie->backing_objects,
 288                              cookie_link) {
 289                 if (object->cache == cache)
 290                         goto object_already_extant;
 291         }
 292         spin_unlock(&cookie->lock);
 293
 294         /* ask the cache to allocate an object (we may end up with duplicate
 295          * objects at this stage, but we sort that out later) */
 296         fscache_stat(&fscache_n_cop_alloc_object);
 297         object = cache->ops->alloc_object(cache, cookie);
 298         fscache_stat_d(&fscache_n_cop_alloc_object);
 299         if (IS_ERR(object)) {
 300                 fscache_stat(&fscache_n_object_no_alloc);
 301                 ret = PTR_ERR(object);
 302                 goto error;
 303         }
 304
 305         fscache_stat(&fscache_n_object_alloc);
 306
 307         object->debug_id = atomic_inc_return(&fscache_object_debug_id);
 308
 309         _debug("ALLOC OBJ%x: %s {%lx}",
 310                object->debug_id, cookie->def->name, object->events);
 311
 312         ret = fscache_alloc_object(cache, cookie->parent);
 313         if (ret < 0)
 314                 goto error_put;
 315
 316         /* only attach if we managed to allocate all we needed, otherwise
 317          * discard the object we just allocated and instead use the one
 318          * attached to the cookie */
 319         if (fscache_attach_object(cookie, object) < 0) {
 320                 fscache_stat(&fscache_n_cop_put_object);
 321                 cache->ops->put_object(object);
 322                 fscache_stat_d(&fscache_n_cop_put_object);
 323         }
 324
 325         _leave(" = 0");
 326         return 0;
 327
 328 object_already_extant:
 329         ret = -ENOBUFS;
 330         if (fscache_object_is_dead(object)) {
 331                 spin_unlock(&cookie->lock);
 332                 goto error;
 333         }
 334         spin_unlock(&cookie->lock);
 335         _leave(" = 0 [found]");
 336         return 0;
 337
 338 error_put:
 339         fscache_stat(&fscache_n_cop_put_object);
 340         cache->ops->put_object(object);
 341         fscache_stat_d(&fscache_n_cop_put_object);
 342 error:
 343         _leave(" = %d", ret);
 344         return ret;
 345 }
 346
 347 /*
 348  * attach a cache object to a cookie
 349  */
 350 static int fscache_attach_object(struct fscache_cookie *cookie,
 351                                  struct fscache_object *object)
 352 {
 353         struct fscache_object *p;
 354         struct fscache_cache *cache = object->cache;
 355         int ret;
 356
 357         _enter("{%s},{OBJ%x}", cookie->def->name, object->debug_id);
 358
 359         spin_lock(&cookie->lock);
 360
 361         /* there may be multiple initial creations of this object, but we only
 362          * want one */
 363         ret = -EEXIST;
 364         hlist_for_each_entry(p, &cookie->backing_objects, cookie_link) {
 365                 if (p->cache == object->cache) {
 366                         if (fscache_object_is_dying(p))
 367                                 ret = -ENOBUFS;
 368                         goto cant_attach_object;
 369                 }
 370         }
 371
 372         /* pin the parent object */
 373         spin_lock_nested(&cookie->parent->lock, 1);
 374         hlist_for_each_entry(p, &cookie->parent->backing_objects,
 375                              cookie_link) {
 376                 if (p->cache == object->cache) {
 377                         if (fscache_object_is_dying(p)) {
 378                                 ret = -ENOBUFS;
 379                                 spin_unlock(&cookie->parent->lock);
 380                                 goto cant_attach_object;
 381                         }
 382                         object->parent = p;
 383                         spin_lock(&p->lock);
 384                         p->n_children++;
 385                         spin_unlock(&p->lock);
 386                         break;
 387                 }
 388         }
 389         spin_unlock(&cookie->parent->lock);
 390
 391         /* attach to the cache's object list */
 392         if (list_empty(&object->cache_link)) {
 393                 spin_lock(&cache->object_list_lock);
 394                 list_add(&object->cache_link, &cache->object_list);
 395                 spin_unlock(&cache->object_list_lock);
 396         }
 397
 398         /* attach to the cookie */
 399         object->cookie = cookie;
 400         atomic_inc(&cookie->usage);
 401         hlist_add_head(&object->cookie_link, &cookie->backing_objects);
 402
 403         fscache_objlist_add(object);
 404         ret = 0;
 405
 406 cant_attach_object:
 407         spin_unlock(&cookie->lock);
 408         _leave(" = %d", ret);
 409         return ret;
 410 }
 411
 412 /*
 413  * Invalidate an object.  Callable with spinlocks held.
 414  */
 415 void __fscache_invalidate(struct fscache_cookie *cookie)
 416 {
 417         struct fscache_object *object;
 418
 419         _enter("{%s}", cookie->def->name);
 420
 421         fscache_stat(&fscache_n_invalidates);
 422
 423         /* Only permit invalidation of data files.  Invalidating an index will
 424          * require the caller to release all its attachments to the tree rooted
 425          * there, and if it's doing that, it may as well just retire the
 426          * cookie.
 427          */
 428         ASSERTCMP(cookie->def->type, ==, FSCACHE_COOKIE_TYPE_DATAFILE);
 429
 430         /* We will be updating the cookie too. */
 431         BUG_ON(!cookie->def->get_aux);
 432
 433         /* If there's an object, we tell the object state machine to handle the
 434          * invalidation on our behalf, otherwise there's nothing to do.
 435          */
 436         if (!hlist_empty(&cookie->backing_objects)) {
 437                 spin_lock(&cookie->lock);
 438
 439                 if (fscache_cookie_enabled(cookie) &&
 440                     !hlist_empty(&cookie->backing_objects) &&
 441                     !test_and_set_bit(FSCACHE_COOKIE_INVALIDATING,
 442                                       &cookie->flags)) {
 443                         object = hlist_entry(cookie->backing_objects.first,
 444                                              struct fscache_object,
 445                                              cookie_link);
 446                         if (fscache_object_is_live(object))
 447                                 fscache_raise_event(
 448                                         object, FSCACHE_OBJECT_EV_INVALIDATE);
 449                 }
 450
 451                 spin_unlock(&cookie->lock);
 452         }
 453
 454         _leave("");
 455 }
 456 EXPORT_SYMBOL(__fscache_invalidate);
 457
 458 /*
 459  * Wait for object invalidation to complete.
 460  */
 461 void __fscache_wait_on_invalidate(struct fscache_cookie *cookie)
 462 {
 463         _enter("%p", cookie);
 464
 465         wait_on_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING,
 466                     TASK_UNINTERRUPTIBLE);
 467
 468         _leave("");
 469 }
 470 EXPORT_SYMBOL(__fscache_wait_on_invalidate);
 471
 472 /*
 473  * update the index entries backing a cookie
 474  */
 475 void __fscache_update_cookie(struct fscache_cookie *cookie)
 476 {
 477         struct fscache_object *object;
 478
 479         fscache_stat(&fscache_n_updates);
 480
 481         if (!cookie) {
 482                 fscache_stat(&fscache_n_updates_null);
 483                 _leave(" [no cookie]");
 484                 return;
 485         }
 486
 487         _enter("{%s}", cookie->def->name);
 488
 489         BUG_ON(!cookie->def->get_aux);
 490
 491         spin_lock(&cookie->lock);
 492
 493         if (fscache_cookie_enabled(cookie)) {
 494                 /* update the index entry on disk in each cache backing this
 495                  * cookie.
 496                  */
 497                 hlist_for_each_entry(object,
 498                                      &cookie->backing_objects, cookie_link) {
 499                         fscache_raise_event(object, FSCACHE_OBJECT_EV_UPDATE);
 500                 }
 501         }
 502
 503         spin_unlock(&cookie->lock);
 504         _leave("");
 505 }
 506 EXPORT_SYMBOL(__fscache_update_cookie);
 507
 508 /*
 509  * Disable a cookie to stop it from accepting new requests from the netfs.
 510  */
 511 void __fscache_disable_cookie(struct fscache_cookie *cookie, bool invalidate)
 512 {
 513         struct fscache_object *object;
 514         bool awaken = false;
 515
 516         _enter("%p,%u", cookie, invalidate);
 517
 518         ASSERTCMP(atomic_read(&cookie->n_active), >, 0);
 519
 520         if (atomic_read(&cookie->n_children) != 0) {
 521                 pr_err("Cookie '%s' still has children\n",
 522                        cookie->def->name);
 523                 BUG();
 524         }
 525
 526         wait_on_bit_lock(&cookie->flags, FSCACHE_COOKIE_ENABLEMENT_LOCK,
 527                          TASK_UNINTERRUPTIBLE);
 528         if (!test_and_clear_bit(FSCACHE_COOKIE_ENABLED, &cookie->flags))
 529                 goto out_unlock_enable;
 530
 531         /* If the cookie is being invalidated, wait for that to complete first
 532          * so that we can reuse the flag.
 533          */
 534         __fscache_wait_on_invalidate(cookie);
 535
 536         /* Dispose of the backing objects */
 537         set_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags);
 538
 539         spin_lock(&cookie->lock);
 540         if (!hlist_empty(&cookie->backing_objects)) {
 541                 hlist_for_each_entry(object, &cookie->backing_objects, cookie_link) {
 542                         if (invalidate)
 543                                 set_bit(FSCACHE_OBJECT_RETIRED, &object->flags);
 544                         fscache_raise_event(object, FSCACHE_OBJECT_EV_KILL);
 545                 }
 546         } else {
 547                 if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
 548                         awaken = true;
 549         }
 550         spin_unlock(&cookie->lock);
 551         if (awaken)
 552                 wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 553
 554         /* Wait for cessation of activity requiring access to the netfs (when
 555          * n_active reaches 0).  This makes sure outstanding reads and writes
 556          * have completed.
 557          */
 558         if (!atomic_dec_and_test(&cookie->n_active))
 559                 wait_on_atomic_t(&cookie->n_active, fscache_wait_atomic_t,
 560                                  TASK_UNINTERRUPTIBLE);
 561
 562         /* Reset the cookie state if it wasn't relinquished */
 563         if (!test_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags)) {
 564                 atomic_inc(&cookie->n_active);
 565                 set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 566         }
 567
 568 out_unlock_enable:
 569         clear_bit_unlock(FSCACHE_COOKIE_ENABLEMENT_LOCK, &cookie->flags);
 570         wake_up_bit(&cookie->flags, FSCACHE_COOKIE_ENABLEMENT_LOCK);
 571         _leave("");
 572 }
 573 EXPORT_SYMBOL(__fscache_disable_cookie);
 574
 575 /*
 576  * release a cookie back to the cache
 577  * - the object will be marked as recyclable on disk if retire is true
 578  * - all dependents of this cookie must have already been unregistered
 579  *   (indices/files/pages)
 580  */
 581 void __fscache_relinquish_cookie(struct fscache_cookie *cookie, bool retire)
 582 {
 583         fscache_stat(&fscache_n_relinquishes);
 584         if (retire)
 585                 fscache_stat(&fscache_n_relinquishes_retire);
 586
 587         if (!cookie) {
 588                 fscache_stat(&fscache_n_relinquishes_null);
 589                 _leave(" [no cookie]");
 590                 return;
 591         }
 592
 593         _enter("%p{%s,%p,%d},%d",
 594                cookie, cookie->def->name, cookie->netfs_data,
 595                atomic_read(&cookie->n_active), retire);
 596
 597         /* No further netfs-accessing operations on this cookie permitted */
 598         set_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags);
 599
 600         __fscache_disable_cookie(cookie, retire);
 601
 602         /* Clear pointers back to the netfs */
 603         cookie->netfs_data      = NULL;
 604         cookie->def             = NULL;
 605         BUG_ON(cookie->stores.rnode);
 606
 607         if (cookie->parent) {
 608                 ASSERTCMP(atomic_read(&cookie->parent->usage), >, 0);
 609                 ASSERTCMP(atomic_read(&cookie->parent->n_children), >, 0);
 610                 atomic_dec(&cookie->parent->n_children);
 611         }
 612
 613         /* Dispose of the netfs's link to the cookie */
 614         ASSERTCMP(atomic_read(&cookie->usage), >, 0);
 615         fscache_cookie_put(cookie);
 616
 617         _leave("");
 618 }
 619 EXPORT_SYMBOL(__fscache_relinquish_cookie);
 620
 621 /*
 622  * destroy a cookie
 623  */
 624 void __fscache_cookie_put(struct fscache_cookie *cookie)
 625 {
 626         struct fscache_cookie *parent;
 627
 628         _enter("%p", cookie);
 629
 630         for (;;) {
 631                 _debug("FREE COOKIE %p", cookie);
 632                 parent = cookie->parent;
 633                 BUG_ON(!hlist_empty(&cookie->backing_objects));
 634                 kmem_cache_free(fscache_cookie_jar, cookie);
 635
 636                 if (!parent)
 637                         break;
 638
 639                 cookie = parent;
 640                 BUG_ON(atomic_read(&cookie->usage) <= 0);
 641                 if (!atomic_dec_and_test(&cookie->usage))
 642                         break;
 643         }
 644
 645         _leave("");
 646 }
 647
 648 /*
 649  * check the consistency between the netfs inode and the backing cache
 650  *
 651  * NOTE: it only serves no-index type
 652  */
 653 int __fscache_check_consistency(struct fscache_cookie *cookie)
 654 {
 655         struct fscache_operation *op;
 656         struct fscache_object *object;
 657         bool wake_cookie = false;
 658         int ret;
 659
 660         _enter("%p,", cookie);
 661
 662         ASSERTCMP(cookie->def->type, ==, FSCACHE_COOKIE_TYPE_DATAFILE);
 663
 664         if (fscache_wait_for_deferred_lookup(cookie) < 0)
 665                 return -ERESTARTSYS;
 666
 667         if (hlist_empty(&cookie->backing_objects))
 668                 return 0;
 669
 670         op = kzalloc(sizeof(*op), GFP_NOIO | __GFP_NOMEMALLOC | __GFP_NORETRY);
 671         if (!op)
 672                 return -ENOMEM;
 673
 674         fscache_operation_init(op, NULL, NULL);
 675         op->flags = FSCACHE_OP_MYTHREAD |
 676                 (1 << FSCACHE_OP_WAITING) |
 677                 (1 << FSCACHE_OP_UNUSE_COOKIE);
 678
 679         spin_lock(&cookie->lock);
 680
 681         if (!fscache_cookie_enabled(cookie) ||
 682             hlist_empty(&cookie->backing_objects))
 683                 goto inconsistent;
 684         object = hlist_entry(cookie->backing_objects.first,
 685                              struct fscache_object, cookie_link);
 686         if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
 687                 goto inconsistent;
 688
 689         op->debug_id = atomic_inc_return(&fscache_op_debug_id);
 690
 691         __fscache_use_cookie(cookie);
 692         if (fscache_submit_op(object, op) < 0)
 693                 goto submit_failed;
 694
 695         /* the work queue now carries its own ref on the object */
 696         spin_unlock(&cookie->lock);
 697
 698         ret = fscache_wait_for_operation_activation(object, op,
 699                                                     NULL, NULL, NULL);
 700         if (ret == 0) {
 701                 /* ask the cache to honour the operation */
 702                 ret = object->cache->ops->check_consistency(op);
 703                 fscache_op_complete(op, false);
 704         } else if (ret == -ENOBUFS) {
 705                 ret = 0;
 706         }
 707
 708         fscache_put_operation(op);
 709         _leave(" = %d", ret);
 710         return ret;
 711
 712 submit_failed:
 713         wake_cookie = __fscache_unuse_cookie(cookie);
 714 inconsistent:
 715         spin_unlock(&cookie->lock);
 716         if (wake_cookie)
 717                 __fscache_wake_unused_cookie(cookie);
 718         kfree(op);
 719         _leave(" = -ESTALE");
 720         return -ESTALE;
 721 }
 722 EXPORT_SYMBOL(__fscache_check_consistency);