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