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 {
  63         struct fscache_cookie *cookie;
  64
  65         BUG_ON(!def);
  66
  67         _enter("{%s},{%s},%p",
  68                parent ? (char *) parent->def->name : "<no-parent>",
  69                def->name, netfs_data);
  70
  71         fscache_stat(&fscache_n_acquires);
  72
  73         /* if there's no parent cookie, then we don't create one here either */
  74         if (!parent) {
  75                 fscache_stat(&fscache_n_acquires_null);
  76                 _leave(" [no parent]");
  77                 return NULL;
  78         }
  79
  80         /* validate the definition */
  81         BUG_ON(!def->get_key);
  82         BUG_ON(!def->name[0]);
  83
  84         BUG_ON(def->type == FSCACHE_COOKIE_TYPE_INDEX &&
  85                parent->def->type != FSCACHE_COOKIE_TYPE_INDEX);
  86
  87         /* allocate and initialise a cookie */
  88         cookie = kmem_cache_alloc(fscache_cookie_jar, GFP_KERNEL);
  89         if (!cookie) {
  90                 fscache_stat(&fscache_n_acquires_oom);
  91                 _leave(" [ENOMEM]");
  92                 return NULL;
  93         }
  94
  95         atomic_set(&cookie->usage, 1);
  96         atomic_set(&cookie->n_children, 0);
  97
  98         atomic_inc(&parent->usage);
  99         atomic_inc(&parent->n_children);
 100
 101         cookie->def             = def;
 102         cookie->parent          = parent;
 103         cookie->netfs_data      = netfs_data;
 104         cookie->flags           = 0;
 105
 106         /* radix tree insertion won't use the preallocation pool unless it's
 107          * told it may not wait */
 108         INIT_RADIX_TREE(&cookie->stores, GFP_NOFS & ~__GFP_WAIT);
 109
 110         switch (cookie->def->type) {
 111         case FSCACHE_COOKIE_TYPE_INDEX:
 112                 fscache_stat(&fscache_n_cookie_index);
 113                 break;
 114         case FSCACHE_COOKIE_TYPE_DATAFILE:
 115                 fscache_stat(&fscache_n_cookie_data);
 116                 break;
 117         default:
 118                 fscache_stat(&fscache_n_cookie_special);
 119                 break;
 120         }
 121
 122         /* if the object is an index then we need do nothing more here - we
 123          * create indices on disk when we need them as an index may exist in
 124          * multiple caches */
 125         if (cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX) {
 126                 if (fscache_acquire_non_index_cookie(cookie) < 0) {
 127                         atomic_dec(&parent->n_children);
 128                         __fscache_cookie_put(cookie);
 129                         fscache_stat(&fscache_n_acquires_nobufs);
 130                         _leave(" = NULL");
 131                         return NULL;
 132                 }
 133         }
 134
 135         fscache_stat(&fscache_n_acquires_ok);
 136         _leave(" = %p", cookie);
 137         return cookie;
 138 }
 139 EXPORT_SYMBOL(__fscache_acquire_cookie);
 140
 141 /*
 142  * acquire a non-index cookie
 143  * - this must make sure the index chain is instantiated and instantiate the
 144  *   object representation too
 145  */
 146 static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie)
 147 {
 148         struct fscache_object *object;
 149         struct fscache_cache *cache;
 150         uint64_t i_size;
 151         int ret;
 152
 153         _enter("");
 154
 155         cookie->flags = 1 << FSCACHE_COOKIE_UNAVAILABLE;
 156
 157         /* now we need to see whether the backing objects for this cookie yet
 158          * exist, if not there'll be nothing to search */
 159         down_read(&fscache_addremove_sem);
 160
 161         if (list_empty(&fscache_cache_list)) {
 162                 up_read(&fscache_addremove_sem);
 163                 _leave(" = 0 [no caches]");
 164                 return 0;
 165         }
 166
 167         /* select a cache in which to store the object */
 168         cache = fscache_select_cache_for_object(cookie->parent);
 169         if (!cache) {
 170                 up_read(&fscache_addremove_sem);
 171                 fscache_stat(&fscache_n_acquires_no_cache);
 172                 _leave(" = -ENOMEDIUM [no cache]");
 173                 return -ENOMEDIUM;
 174         }
 175
 176         _debug("cache %s", cache->tag->name);
 177
 178         cookie->flags =
 179                 (1 << FSCACHE_COOKIE_LOOKING_UP) |
 180                 (1 << FSCACHE_COOKIE_CREATING) |
 181                 (1 << FSCACHE_COOKIE_NO_DATA_YET);
 182
 183         /* ask the cache to allocate objects for this cookie and its parent
 184          * chain */
 185         ret = fscache_alloc_object(cache, cookie);
 186         if (ret < 0) {
 187                 up_read(&fscache_addremove_sem);
 188                 _leave(" = %d", ret);
 189                 return ret;
 190         }
 191
 192         /* pass on how big the object we're caching is supposed to be */
 193         cookie->def->get_attr(cookie->netfs_data, &i_size);
 194
 195         spin_lock(&cookie->lock);
 196         if (hlist_empty(&cookie->backing_objects)) {
 197                 spin_unlock(&cookie->lock);
 198                 goto unavailable;
 199         }
 200
 201         object = hlist_entry(cookie->backing_objects.first,
 202                              struct fscache_object, cookie_link);
 203
 204         fscache_set_store_limit(object, i_size);
 205
 206         /* initiate the process of looking up all the objects in the chain
 207          * (done by fscache_initialise_object()) */
 208         fscache_enqueue_object(object);
 209
 210         spin_unlock(&cookie->lock);
 211
 212         /* we may be required to wait for lookup to complete at this point */
 213         if (!fscache_defer_lookup) {
 214                 _debug("non-deferred lookup %p", &cookie->flags);
 215                 wait_on_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP,
 216                             fscache_wait_bit, TASK_UNINTERRUPTIBLE);
 217                 _debug("complete");
 218                 if (test_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags))
 219                         goto unavailable;
 220         }
 221
 222         up_read(&fscache_addremove_sem);
 223         _leave(" = 0 [deferred]");
 224         return 0;
 225
 226 unavailable:
 227         up_read(&fscache_addremove_sem);
 228         _leave(" = -ENOBUFS");
 229         return -ENOBUFS;
 230 }
 231
 232 /*
 233  * recursively allocate cache object records for a cookie/cache combination
 234  * - caller must be holding the addremove sem
 235  */
 236 static int fscache_alloc_object(struct fscache_cache *cache,
 237                                 struct fscache_cookie *cookie)
 238 {
 239         struct fscache_object *object;
 240         int ret;
 241
 242         _enter("%p,%p{%s}", cache, cookie, cookie->def->name);
 243
 244         spin_lock(&cookie->lock);
 245         hlist_for_each_entry(object, &cookie->backing_objects,
 246                              cookie_link) {
 247                 if (object->cache == cache)
 248                         goto object_already_extant;
 249         }
 250         spin_unlock(&cookie->lock);
 251
 252         /* ask the cache to allocate an object (we may end up with duplicate
 253          * objects at this stage, but we sort that out later) */
 254         fscache_stat(&fscache_n_cop_alloc_object);
 255         object = cache->ops->alloc_object(cache, cookie);
 256         fscache_stat_d(&fscache_n_cop_alloc_object);
 257         if (IS_ERR(object)) {
 258                 fscache_stat(&fscache_n_object_no_alloc);
 259                 ret = PTR_ERR(object);
 260                 goto error;
 261         }
 262
 263         fscache_stat(&fscache_n_object_alloc);
 264
 265         object->debug_id = atomic_inc_return(&fscache_object_debug_id);
 266
 267         _debug("ALLOC OBJ%x: %s {%lx}",
 268                object->debug_id, cookie->def->name, object->events);
 269
 270         ret = fscache_alloc_object(cache, cookie->parent);
 271         if (ret < 0)
 272                 goto error_put;
 273
 274         /* only attach if we managed to allocate all we needed, otherwise
 275          * discard the object we just allocated and instead use the one
 276          * attached to the cookie */
 277         if (fscache_attach_object(cookie, object) < 0) {
 278                 fscache_stat(&fscache_n_cop_put_object);
 279                 cache->ops->put_object(object);
 280                 fscache_stat_d(&fscache_n_cop_put_object);
 281         }
 282
 283         _leave(" = 0");
 284         return 0;
 285
 286 object_already_extant:
 287         ret = -ENOBUFS;
 288         if (object->state >= FSCACHE_OBJECT_DYING) {
 289                 spin_unlock(&cookie->lock);
 290                 goto error;
 291         }
 292         spin_unlock(&cookie->lock);
 293         _leave(" = 0 [found]");
 294         return 0;
 295
 296 error_put:
 297         fscache_stat(&fscache_n_cop_put_object);
 298         cache->ops->put_object(object);
 299         fscache_stat_d(&fscache_n_cop_put_object);
 300 error:
 301         _leave(" = %d", ret);
 302         return ret;
 303 }
 304
 305 /*
 306  * attach a cache object to a cookie
 307  */
 308 static int fscache_attach_object(struct fscache_cookie *cookie,
 309                                  struct fscache_object *object)
 310 {
 311         struct fscache_object *p;
 312         struct fscache_cache *cache = object->cache;
 313         int ret;
 314
 315         _enter("{%s},{OBJ%x}", cookie->def->name, object->debug_id);
 316
 317         spin_lock(&cookie->lock);
 318
 319         /* there may be multiple initial creations of this object, but we only
 320          * want one */
 321         ret = -EEXIST;
 322         hlist_for_each_entry(p, &cookie->backing_objects, cookie_link) {
 323                 if (p->cache == object->cache) {
 324                         if (p->state >= FSCACHE_OBJECT_DYING)
 325                                 ret = -ENOBUFS;
 326                         goto cant_attach_object;
 327                 }
 328         }
 329
 330         /* pin the parent object */
 331         spin_lock_nested(&cookie->parent->lock, 1);
 332         hlist_for_each_entry(p, &cookie->parent->backing_objects,
 333                              cookie_link) {
 334                 if (p->cache == object->cache) {
 335                         if (p->state >= FSCACHE_OBJECT_DYING) {
 336                                 ret = -ENOBUFS;
 337                                 spin_unlock(&cookie->parent->lock);
 338                                 goto cant_attach_object;
 339                         }
 340                         object->parent = p;
 341                         spin_lock(&p->lock);
 342                         p->n_children++;
 343                         spin_unlock(&p->lock);
 344                         break;
 345                 }
 346         }
 347         spin_unlock(&cookie->parent->lock);
 348
 349         /* attach to the cache's object list */
 350         if (list_empty(&object->cache_link)) {
 351                 spin_lock(&cache->object_list_lock);
 352                 list_add(&object->cache_link, &cache->object_list);
 353                 spin_unlock(&cache->object_list_lock);
 354         }
 355
 356         /* attach to the cookie */
 357         object->cookie = cookie;
 358         atomic_inc(&cookie->usage);
 359         hlist_add_head(&object->cookie_link, &cookie->backing_objects);
 360
 361         fscache_objlist_add(object);
 362         ret = 0;
 363
 364 cant_attach_object:
 365         spin_unlock(&cookie->lock);
 366         _leave(" = %d", ret);
 367         return ret;
 368 }
 369
 370 /*
 371  * Invalidate an object.  Callable with spinlocks held.
 372  */
 373 void __fscache_invalidate(struct fscache_cookie *cookie)
 374 {
 375         struct fscache_object *object;
 376
 377         _enter("{%s}", cookie->def->name);
 378
 379         fscache_stat(&fscache_n_invalidates);
 380
 381         /* Only permit invalidation of data files.  Invalidating an index will
 382          * require the caller to release all its attachments to the tree rooted
 383          * there, and if it's doing that, it may as well just retire the
 384          * cookie.
 385          */
 386         ASSERTCMP(cookie->def->type, ==, FSCACHE_COOKIE_TYPE_DATAFILE);
 387
 388         /* We will be updating the cookie too. */
 389         BUG_ON(!cookie->def->get_aux);
 390
 391         /* If there's an object, we tell the object state machine to handle the
 392          * invalidation on our behalf, otherwise there's nothing to do.
 393          */
 394         if (!hlist_empty(&cookie->backing_objects)) {
 395                 spin_lock(&cookie->lock);
 396
 397                 if (!hlist_empty(&cookie->backing_objects) &&
 398                     !test_and_set_bit(FSCACHE_COOKIE_INVALIDATING,
 399                                       &cookie->flags)) {
 400                         object = hlist_entry(cookie->backing_objects.first,
 401                                              struct fscache_object,
 402                                              cookie_link);
 403                         if (object->state < FSCACHE_OBJECT_DYING)
 404                                 fscache_raise_event(
 405                                         object, FSCACHE_OBJECT_EV_INVALIDATE);
 406                 }
 407
 408                 spin_unlock(&cookie->lock);
 409         }
 410
 411         _leave("");
 412 }
 413 EXPORT_SYMBOL(__fscache_invalidate);
 414
 415 /*
 416  * Wait for object invalidation to complete.
 417  */
 418 void __fscache_wait_on_invalidate(struct fscache_cookie *cookie)
 419 {
 420         _enter("%p", cookie);
 421
 422         wait_on_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING,
 423                     fscache_wait_bit_interruptible,
 424                     TASK_UNINTERRUPTIBLE);
 425
 426         _leave("");
 427 }
 428 EXPORT_SYMBOL(__fscache_wait_on_invalidate);
 429
 430 /*
 431  * update the index entries backing a cookie
 432  */
 433 void __fscache_update_cookie(struct fscache_cookie *cookie)
 434 {
 435         struct fscache_object *object;
 436
 437         fscache_stat(&fscache_n_updates);
 438
 439         if (!cookie) {
 440                 fscache_stat(&fscache_n_updates_null);
 441                 _leave(" [no cookie]");
 442                 return;
 443         }
 444
 445         _enter("{%s}", cookie->def->name);
 446
 447         BUG_ON(!cookie->def->get_aux);
 448
 449         spin_lock(&cookie->lock);
 450
 451         /* update the index entry on disk in each cache backing this cookie */
 452         hlist_for_each_entry(object,
 453                              &cookie->backing_objects, cookie_link) {
 454                 fscache_raise_event(object, FSCACHE_OBJECT_EV_UPDATE);
 455         }
 456
 457         spin_unlock(&cookie->lock);
 458         _leave("");
 459 }
 460 EXPORT_SYMBOL(__fscache_update_cookie);
 461
 462 /*
 463  * release a cookie back to the cache
 464  * - the object will be marked as recyclable on disk if retire is true
 465  * - all dependents of this cookie must have already been unregistered
 466  *   (indices/files/pages)
 467  */
 468 void __fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
 469 {
 470         struct fscache_cache *cache;
 471         struct fscache_object *object;
 472         unsigned long event;
 473
 474         fscache_stat(&fscache_n_relinquishes);
 475         if (retire)
 476                 fscache_stat(&fscache_n_relinquishes_retire);
 477
 478         if (!cookie) {
 479                 fscache_stat(&fscache_n_relinquishes_null);
 480                 _leave(" [no cookie]");
 481                 return;
 482         }
 483
 484         _enter("%p{%s,%p},%d",
 485                cookie, cookie->def->name, cookie->netfs_data, retire);
 486
 487         if (atomic_read(&cookie->n_children) != 0) {
 488                 printk(KERN_ERR "FS-Cache: Cookie '%s' still has children\n",
 489                        cookie->def->name);
 490                 BUG();
 491         }
 492
 493         /* wait for the cookie to finish being instantiated (or to fail) */
 494         if (test_bit(FSCACHE_COOKIE_CREATING, &cookie->flags)) {
 495                 fscache_stat(&fscache_n_relinquishes_waitcrt);
 496                 wait_on_bit(&cookie->flags, FSCACHE_COOKIE_CREATING,
 497                             fscache_wait_bit, TASK_UNINTERRUPTIBLE);
 498         }
 499
 500         event = retire ? FSCACHE_OBJECT_EV_RETIRE : FSCACHE_OBJECT_EV_RELEASE;
 501
 502 try_again:
 503         spin_lock(&cookie->lock);
 504
 505         /* break links with all the active objects */
 506         while (!hlist_empty(&cookie->backing_objects)) {
 507                 int n_reads;
 508                 object = hlist_entry(cookie->backing_objects.first,
 509                                      struct fscache_object,
 510                                      cookie_link);
 511
 512                 _debug("RELEASE OBJ%x", object->debug_id);
 513
 514                 set_bit(FSCACHE_COOKIE_WAITING_ON_READS, &cookie->flags);
 515                 n_reads = atomic_read(&object->n_reads);
 516                 if (n_reads) {
 517                         int n_ops = object->n_ops;
 518                         int n_in_progress = object->n_in_progress;
 519                         spin_unlock(&cookie->lock);
 520                         printk(KERN_ERR "FS-Cache:"
 521                                " Cookie '%s' still has %d outstanding reads (%d,%d)\n",
 522                                cookie->def->name,
 523                                n_reads, n_ops, n_in_progress);
 524                         wait_on_bit(&cookie->flags, FSCACHE_COOKIE_WAITING_ON_READS,
 525                                     fscache_wait_bit, TASK_UNINTERRUPTIBLE);
 526                         printk("Wait finished\n");
 527                         goto try_again;
 528                 }
 529
 530                 /* detach each cache object from the object cookie */
 531                 spin_lock(&object->lock);
 532                 hlist_del_init(&object->cookie_link);
 533
 534                 cache = object->cache;
 535                 object->cookie = NULL;
 536                 fscache_raise_event(object, event);
 537                 spin_unlock(&object->lock);
 538
 539                 if (atomic_dec_and_test(&cookie->usage))
 540                         /* the cookie refcount shouldn't be reduced to 0 yet */
 541                         BUG();
 542         }
 543
 544         /* detach pointers back to the netfs */
 545         cookie->netfs_data      = NULL;
 546         cookie->def             = NULL;
 547
 548         spin_unlock(&cookie->lock);
 549
 550         if (cookie->parent) {
 551                 ASSERTCMP(atomic_read(&cookie->parent->usage), >, 0);
 552                 ASSERTCMP(atomic_read(&cookie->parent->n_children), >, 0);
 553                 atomic_dec(&cookie->parent->n_children);
 554         }
 555
 556         /* finally dispose of the cookie */
 557         ASSERTCMP(atomic_read(&cookie->usage), >, 0);
 558         fscache_cookie_put(cookie);
 559
 560         _leave("");
 561 }
 562 EXPORT_SYMBOL(__fscache_relinquish_cookie);
 563
 564 /*
 565  * destroy a cookie
 566  */
 567 void __fscache_cookie_put(struct fscache_cookie *cookie)
 568 {
 569         struct fscache_cookie *parent;
 570
 571         _enter("%p", cookie);
 572
 573         for (;;) {
 574                 _debug("FREE COOKIE %p", cookie);
 575                 parent = cookie->parent;
 576                 BUG_ON(!hlist_empty(&cookie->backing_objects));
 577                 kmem_cache_free(fscache_cookie_jar, cookie);
 578
 579                 if (!parent)
 580                         break;
 581
 582                 cookie = parent;
 583                 BUG_ON(atomic_read(&cookie->usage) <= 0);
 584                 if (!atomic_dec_and_test(&cookie->usage))
 585                         break;
 586         }
 587
 588         _leave("");
 589 }