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         struct hlist_node *_n;
 241         int ret;
 242
 243         _enter("%p,%p{%s}", cache, cookie, cookie->def->name);
 244
 245         spin_lock(&cookie->lock);
 246         hlist_for_each_entry(object, _n, &cookie->backing_objects,
 247                              cookie_link) {
 248                 if (object->cache == cache)
 249                         goto object_already_extant;
 250         }
 251         spin_unlock(&cookie->lock);
 252
 253         /* ask the cache to allocate an object (we may end up with duplicate
 254          * objects at this stage, but we sort that out later) */
 255         fscache_stat(&fscache_n_cop_alloc_object);
 256         object = cache->ops->alloc_object(cache, cookie);
 257         fscache_stat_d(&fscache_n_cop_alloc_object);
 258         if (IS_ERR(object)) {
 259                 fscache_stat(&fscache_n_object_no_alloc);
 260                 ret = PTR_ERR(object);
 261                 goto error;
 262         }
 263
 264         fscache_stat(&fscache_n_object_alloc);
 265
 266         object->debug_id = atomic_inc_return(&fscache_object_debug_id);
 267
 268         _debug("ALLOC OBJ%x: %s {%lx}",
 269                object->debug_id, cookie->def->name, object->events);
 270
 271         ret = fscache_alloc_object(cache, cookie->parent);
 272         if (ret < 0)
 273                 goto error_put;
 274
 275         /* only attach if we managed to allocate all we needed, otherwise
 276          * discard the object we just allocated and instead use the one
 277          * attached to the cookie */
 278         if (fscache_attach_object(cookie, object) < 0) {
 279                 fscache_stat(&fscache_n_cop_put_object);
 280                 cache->ops->put_object(object);
 281                 fscache_stat_d(&fscache_n_cop_put_object);
 282         }
 283
 284         _leave(" = 0");
 285         return 0;
 286
 287 object_already_extant:
 288         ret = -ENOBUFS;
 289         if (object->state >= FSCACHE_OBJECT_DYING) {
 290                 spin_unlock(&cookie->lock);
 291                 goto error;
 292         }
 293         spin_unlock(&cookie->lock);
 294         _leave(" = 0 [found]");
 295         return 0;
 296
 297 error_put:
 298         fscache_stat(&fscache_n_cop_put_object);
 299         cache->ops->put_object(object);
 300         fscache_stat_d(&fscache_n_cop_put_object);
 301 error:
 302         _leave(" = %d", ret);
 303         return ret;
 304 }
 305
 306 /*
 307  * attach a cache object to a cookie
 308  */
 309 static int fscache_attach_object(struct fscache_cookie *cookie,
 310                                  struct fscache_object *object)
 311 {
 312         struct fscache_object *p;
 313         struct fscache_cache *cache = object->cache;
 314         struct hlist_node *_n;
 315         int ret;
 316
 317         _enter("{%s},{OBJ%x}", cookie->def->name, object->debug_id);
 318
 319         spin_lock(&cookie->lock);
 320
 321         /* there may be multiple initial creations of this object, but we only
 322          * want one */
 323         ret = -EEXIST;
 324         hlist_for_each_entry(p, _n, &cookie->backing_objects, cookie_link) {
 325                 if (p->cache == object->cache) {
 326                         if (p->state >= FSCACHE_OBJECT_DYING)
 327                                 ret = -ENOBUFS;
 328                         goto cant_attach_object;
 329                 }
 330         }
 331
 332         /* pin the parent object */
 333         spin_lock_nested(&cookie->parent->lock, 1);
 334         hlist_for_each_entry(p, _n, &cookie->parent->backing_objects,
 335                              cookie_link) {
 336                 if (p->cache == object->cache) {
 337                         if (p->state >= FSCACHE_OBJECT_DYING) {
 338                                 ret = -ENOBUFS;
 339                                 spin_unlock(&cookie->parent->lock);
 340                                 goto cant_attach_object;
 341                         }
 342                         object->parent = p;
 343                         spin_lock(&p->lock);
 344                         p->n_children++;
 345                         spin_unlock(&p->lock);
 346                         break;
 347                 }
 348         }
 349         spin_unlock(&cookie->parent->lock);
 350
 351         /* attach to the cache's object list */
 352         if (list_empty(&object->cache_link)) {
 353                 spin_lock(&cache->object_list_lock);
 354                 list_add(&object->cache_link, &cache->object_list);
 355                 spin_unlock(&cache->object_list_lock);
 356         }
 357
 358         /* attach to the cookie */
 359         object->cookie = cookie;
 360         atomic_inc(&cookie->usage);
 361         hlist_add_head(&object->cookie_link, &cookie->backing_objects);
 362
 363         fscache_objlist_add(object);
 364         ret = 0;
 365
 366 cant_attach_object:
 367         spin_unlock(&cookie->lock);
 368         _leave(" = %d", ret);
 369         return ret;
 370 }
 371
 372 /*
 373  * update the index entries backing a cookie
 374  */
 375 void __fscache_update_cookie(struct fscache_cookie *cookie)
 376 {
 377         struct fscache_object *object;
 378         struct hlist_node *_p;
 379
 380         fscache_stat(&fscache_n_updates);
 381
 382         if (!cookie) {
 383                 fscache_stat(&fscache_n_updates_null);
 384                 _leave(" [no cookie]");
 385                 return;
 386         }
 387
 388         _enter("{%s}", cookie->def->name);
 389
 390         BUG_ON(!cookie->def->get_aux);
 391
 392         spin_lock(&cookie->lock);
 393
 394         /* update the index entry on disk in each cache backing this cookie */
 395         hlist_for_each_entry(object, _p,
 396                              &cookie->backing_objects, cookie_link) {
 397                 fscache_raise_event(object, FSCACHE_OBJECT_EV_UPDATE);
 398         }
 399
 400         spin_unlock(&cookie->lock);
 401         _leave("");
 402 }
 403 EXPORT_SYMBOL(__fscache_update_cookie);
 404
 405 /*
 406  * release a cookie back to the cache
 407  * - the object will be marked as recyclable on disk if retire is true
 408  * - all dependents of this cookie must have already been unregistered
 409  *   (indices/files/pages)
 410  */
 411 void __fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
 412 {
 413         struct fscache_cache *cache;
 414         struct fscache_object *object;
 415         unsigned long event;
 416
 417         fscache_stat(&fscache_n_relinquishes);
 418         if (retire)
 419                 fscache_stat(&fscache_n_relinquishes_retire);
 420
 421         if (!cookie) {
 422                 fscache_stat(&fscache_n_relinquishes_null);
 423                 _leave(" [no cookie]");
 424                 return;
 425         }
 426
 427         _enter("%p{%s,%p},%d",
 428                cookie, cookie->def->name, cookie->netfs_data, retire);
 429
 430         if (atomic_read(&cookie->n_children) != 0) {
 431                 printk(KERN_ERR "FS-Cache: Cookie '%s' still has children\n",
 432                        cookie->def->name);
 433                 BUG();
 434         }
 435
 436         /* wait for the cookie to finish being instantiated (or to fail) */
 437         if (test_bit(FSCACHE_COOKIE_CREATING, &cookie->flags)) {
 438                 fscache_stat(&fscache_n_relinquishes_waitcrt);
 439                 wait_on_bit(&cookie->flags, FSCACHE_COOKIE_CREATING,
 440                             fscache_wait_bit, TASK_UNINTERRUPTIBLE);
 441         }
 442
 443         event = retire ? FSCACHE_OBJECT_EV_RETIRE : FSCACHE_OBJECT_EV_RELEASE;
 444
 445         spin_lock(&cookie->lock);
 446
 447         /* break links with all the active objects */
 448         while (!hlist_empty(&cookie->backing_objects)) {
 449                 object = hlist_entry(cookie->backing_objects.first,
 450                                      struct fscache_object,
 451                                      cookie_link);
 452
 453                 _debug("RELEASE OBJ%x", object->debug_id);
 454
 455                 /* detach each cache object from the object cookie */
 456                 spin_lock(&object->lock);
 457                 hlist_del_init(&object->cookie_link);
 458
 459                 cache = object->cache;
 460                 object->cookie = NULL;
 461                 fscache_raise_event(object, event);
 462                 spin_unlock(&object->lock);
 463
 464                 if (atomic_dec_and_test(&cookie->usage))
 465                         /* the cookie refcount shouldn't be reduced to 0 yet */
 466                         BUG();
 467         }
 468
 469         /* detach pointers back to the netfs */
 470         cookie->netfs_data      = NULL;
 471         cookie->def             = NULL;
 472
 473         spin_unlock(&cookie->lock);
 474
 475         if (cookie->parent) {
 476                 ASSERTCMP(atomic_read(&cookie->parent->usage), >, 0);
 477                 ASSERTCMP(atomic_read(&cookie->parent->n_children), >, 0);
 478                 atomic_dec(&cookie->parent->n_children);
 479         }
 480
 481         /* finally dispose of the cookie */
 482         ASSERTCMP(atomic_read(&cookie->usage), >, 0);
 483         fscache_cookie_put(cookie);
 484
 485         _leave("");
 486 }
 487 EXPORT_SYMBOL(__fscache_relinquish_cookie);
 488
 489 /*
 490  * destroy a cookie
 491  */
 492 void __fscache_cookie_put(struct fscache_cookie *cookie)
 493 {
 494         struct fscache_cookie *parent;
 495
 496         _enter("%p", cookie);
 497
 498         for (;;) {
 499                 _debug("FREE COOKIE %p", cookie);
 500                 parent = cookie->parent;
 501                 BUG_ON(!hlist_empty(&cookie->backing_objects));
 502                 kmem_cache_free(fscache_cookie_jar, cookie);
 503
 504                 if (!parent)
 505                         break;
 506
 507                 cookie = parent;
 508                 BUG_ON(atomic_read(&cookie->usage) <= 0);
 509                 if (!atomic_dec_and_test(&cookie->usage))
 510                         break;
 511         }
 512
 513         _leave("");
 514 }