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         INIT_HLIST_HEAD(&cookie->backing_objects);
  40 }
  41
  42 /*
  43  * request a cookie to represent an object (index, datafile, xattr, etc)
  44  * - parent specifies the parent object
  45  *   - the top level index cookie for each netfs is stored in the fscache_netfs
  46  *     struct upon registration
  47  * - def points to the definition
  48  * - the netfs_data will be passed to the functions pointed to in *def
  49  * - all attached caches will be searched to see if they contain this object
  50  * - index objects aren't stored on disk until there's a dependent file that
  51  *   needs storing
  52  * - other objects are stored in a selected cache immediately, and all the
  53  *   indices forming the path to it are instantiated if necessary
  54  * - we never let on to the netfs about errors
  55  *   - we may set a negative cookie pointer, but that's okay
  56  */
  57 struct fscache_cookie *__fscache_acquire_cookie(
  58         struct fscache_cookie *parent,
  59         const struct fscache_cookie_def *def,
  60         void *netfs_data)
  61 {
  62         struct fscache_cookie *cookie;
  63
  64         BUG_ON(!def);
  65
  66         _enter("{%s},{%s},%p",
  67                parent ? (char *) parent->def->name : "<no-parent>",
  68                def->name, netfs_data);
  69
  70         fscache_stat(&fscache_n_acquires);
  71
  72         /* if there's no parent cookie, then we don't create one here either */
  73         if (!parent) {
  74                 fscache_stat(&fscache_n_acquires_null);
  75                 _leave(" [no parent]");
  76                 return NULL;
  77         }
  78
  79         /* validate the definition */
  80         BUG_ON(!def->get_key);
  81         BUG_ON(!def->name[0]);
  82
  83         BUG_ON(def->type == FSCACHE_COOKIE_TYPE_INDEX &&
  84                parent->def->type != FSCACHE_COOKIE_TYPE_INDEX);
  85
  86         /* allocate and initialise a cookie */
  87         cookie = kmem_cache_alloc(fscache_cookie_jar, GFP_KERNEL);
  88         if (!cookie) {
  89                 fscache_stat(&fscache_n_acquires_oom);
  90                 _leave(" [ENOMEM]");
  91                 return NULL;
  92         }
  93
  94         atomic_set(&cookie->usage, 1);
  95         atomic_set(&cookie->n_children, 0);
  96
  97         atomic_inc(&parent->usage);
  98         atomic_inc(&parent->n_children);
  99
 100         cookie->def             = def;
 101         cookie->parent          = parent;
 102         cookie->netfs_data      = netfs_data;
 103         cookie->flags           = 0;
 104
 105         INIT_RADIX_TREE(&cookie->stores, GFP_NOFS);
 106
 107         switch (cookie->def->type) {
 108         case FSCACHE_COOKIE_TYPE_INDEX:
 109                 fscache_stat(&fscache_n_cookie_index);
 110                 break;
 111         case FSCACHE_COOKIE_TYPE_DATAFILE:
 112                 fscache_stat(&fscache_n_cookie_data);
 113                 break;
 114         default:
 115                 fscache_stat(&fscache_n_cookie_special);
 116                 break;
 117         }
 118
 119         /* if the object is an index then we need do nothing more here - we
 120          * create indices on disk when we need them as an index may exist in
 121          * multiple caches */
 122         if (cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX) {
 123                 if (fscache_acquire_non_index_cookie(cookie) < 0) {
 124                         atomic_dec(&parent->n_children);
 125                         __fscache_cookie_put(cookie);
 126                         fscache_stat(&fscache_n_acquires_nobufs);
 127                         _leave(" = NULL");
 128                         return NULL;
 129                 }
 130         }
 131
 132         fscache_stat(&fscache_n_acquires_ok);
 133         _leave(" = %p", cookie);
 134         return cookie;
 135 }
 136 EXPORT_SYMBOL(__fscache_acquire_cookie);
 137
 138 /*
 139  * acquire a non-index cookie
 140  * - this must make sure the index chain is instantiated and instantiate the
 141  *   object representation too
 142  */
 143 static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie)
 144 {
 145         struct fscache_object *object;
 146         struct fscache_cache *cache;
 147         uint64_t i_size;
 148         int ret;
 149
 150         _enter("");
 151
 152         cookie->flags = 1 << FSCACHE_COOKIE_UNAVAILABLE;
 153
 154         /* now we need to see whether the backing objects for this cookie yet
 155          * exist, if not there'll be nothing to search */
 156         down_read(&fscache_addremove_sem);
 157
 158         if (list_empty(&fscache_cache_list)) {
 159                 up_read(&fscache_addremove_sem);
 160                 _leave(" = 0 [no caches]");
 161                 return 0;
 162         }
 163
 164         /* select a cache in which to store the object */
 165         cache = fscache_select_cache_for_object(cookie->parent);
 166         if (!cache) {
 167                 up_read(&fscache_addremove_sem);
 168                 fscache_stat(&fscache_n_acquires_no_cache);
 169                 _leave(" = -ENOMEDIUM [no cache]");
 170                 return -ENOMEDIUM;
 171         }
 172
 173         _debug("cache %s", cache->tag->name);
 174
 175         cookie->flags =
 176                 (1 << FSCACHE_COOKIE_LOOKING_UP) |
 177                 (1 << FSCACHE_COOKIE_CREATING) |
 178                 (1 << FSCACHE_COOKIE_NO_DATA_YET);
 179
 180         /* ask the cache to allocate objects for this cookie and its parent
 181          * chain */
 182         ret = fscache_alloc_object(cache, cookie);
 183         if (ret < 0) {
 184                 up_read(&fscache_addremove_sem);
 185                 _leave(" = %d", ret);
 186                 return ret;
 187         }
 188
 189         /* pass on how big the object we're caching is supposed to be */
 190         cookie->def->get_attr(cookie->netfs_data, &i_size);
 191
 192         spin_lock(&cookie->lock);
 193         if (hlist_empty(&cookie->backing_objects)) {
 194                 spin_unlock(&cookie->lock);
 195                 goto unavailable;
 196         }
 197
 198         object = hlist_entry(cookie->backing_objects.first,
 199                              struct fscache_object, cookie_link);
 200
 201         fscache_set_store_limit(object, i_size);
 202
 203         /* initiate the process of looking up all the objects in the chain
 204          * (done by fscache_initialise_object()) */
 205         fscache_enqueue_object(object);
 206
 207         spin_unlock(&cookie->lock);
 208
 209         /* we may be required to wait for lookup to complete at this point */
 210         if (!fscache_defer_lookup) {
 211                 _debug("non-deferred lookup %p", &cookie->flags);
 212                 wait_on_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP,
 213                             fscache_wait_bit, TASK_UNINTERRUPTIBLE);
 214                 _debug("complete");
 215                 if (test_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags))
 216                         goto unavailable;
 217         }
 218
 219         up_read(&fscache_addremove_sem);
 220         _leave(" = 0 [deferred]");
 221         return 0;
 222
 223 unavailable:
 224         up_read(&fscache_addremove_sem);
 225         _leave(" = -ENOBUFS");
 226         return -ENOBUFS;
 227 }
 228
 229 /*
 230  * recursively allocate cache object records for a cookie/cache combination
 231  * - caller must be holding the addremove sem
 232  */
 233 static int fscache_alloc_object(struct fscache_cache *cache,
 234                                 struct fscache_cookie *cookie)
 235 {
 236         struct fscache_object *object;
 237         struct hlist_node *_n;
 238         int ret;
 239
 240         _enter("%p,%p{%s}", cache, cookie, cookie->def->name);
 241
 242         spin_lock(&cookie->lock);
 243         hlist_for_each_entry(object, _n, &cookie->backing_objects,
 244                              cookie_link) {
 245                 if (object->cache == cache)
 246                         goto object_already_extant;
 247         }
 248         spin_unlock(&cookie->lock);
 249
 250         /* ask the cache to allocate an object (we may end up with duplicate
 251          * objects at this stage, but we sort that out later) */
 252         object = cache->ops->alloc_object(cache, cookie);
 253         if (IS_ERR(object)) {
 254                 fscache_stat(&fscache_n_object_no_alloc);
 255                 ret = PTR_ERR(object);
 256                 goto error;
 257         }
 258
 259         fscache_stat(&fscache_n_object_alloc);
 260
 261         object->debug_id = atomic_inc_return(&fscache_object_debug_id);
 262
 263         _debug("ALLOC OBJ%x: %s {%lx}",
 264                object->debug_id, cookie->def->name, object->events);
 265
 266         ret = fscache_alloc_object(cache, cookie->parent);
 267         if (ret < 0)
 268                 goto error_put;
 269
 270         /* only attach if we managed to allocate all we needed, otherwise
 271          * discard the object we just allocated and instead use the one
 272          * attached to the cookie */
 273         if (fscache_attach_object(cookie, object) < 0)
 274                 cache->ops->put_object(object);
 275
 276         _leave(" = 0");
 277         return 0;
 278
 279 object_already_extant:
 280         ret = -ENOBUFS;
 281         if (object->state >= FSCACHE_OBJECT_DYING) {
 282                 spin_unlock(&cookie->lock);
 283                 goto error;
 284         }
 285         spin_unlock(&cookie->lock);
 286         _leave(" = 0 [found]");
 287         return 0;
 288
 289 error_put:
 290         cache->ops->put_object(object);
 291 error:
 292         _leave(" = %d", ret);
 293         return ret;
 294 }
 295
 296 /*
 297  * attach a cache object to a cookie
 298  */
 299 static int fscache_attach_object(struct fscache_cookie *cookie,
 300                                  struct fscache_object *object)
 301 {
 302         struct fscache_object *p;
 303         struct fscache_cache *cache = object->cache;
 304         struct hlist_node *_n;
 305         int ret;
 306
 307         _enter("{%s},{OBJ%x}", cookie->def->name, object->debug_id);
 308
 309         spin_lock(&cookie->lock);
 310
 311         /* there may be multiple initial creations of this object, but we only
 312          * want one */
 313         ret = -EEXIST;
 314         hlist_for_each_entry(p, _n, &cookie->backing_objects, cookie_link) {
 315                 if (p->cache == object->cache) {
 316                         if (p->state >= FSCACHE_OBJECT_DYING)
 317                                 ret = -ENOBUFS;
 318                         goto cant_attach_object;
 319                 }
 320         }
 321
 322         /* pin the parent object */
 323         spin_lock_nested(&cookie->parent->lock, 1);
 324         hlist_for_each_entry(p, _n, &cookie->parent->backing_objects,
 325                              cookie_link) {
 326                 if (p->cache == object->cache) {
 327                         if (p->state >= FSCACHE_OBJECT_DYING) {
 328                                 ret = -ENOBUFS;
 329                                 spin_unlock(&cookie->parent->lock);
 330                                 goto cant_attach_object;
 331                         }
 332                         object->parent = p;
 333                         spin_lock(&p->lock);
 334                         p->n_children++;
 335                         spin_unlock(&p->lock);
 336                         break;
 337                 }
 338         }
 339         spin_unlock(&cookie->parent->lock);
 340
 341         /* attach to the cache's object list */
 342         if (list_empty(&object->cache_link)) {
 343                 spin_lock(&cache->object_list_lock);
 344                 list_add(&object->cache_link, &cache->object_list);
 345                 spin_unlock(&cache->object_list_lock);
 346         }
 347
 348         /* attach to the cookie */
 349         object->cookie = cookie;
 350         atomic_inc(&cookie->usage);
 351         hlist_add_head(&object->cookie_link, &cookie->backing_objects);
 352         ret = 0;
 353
 354 cant_attach_object:
 355         spin_unlock(&cookie->lock);
 356         _leave(" = %d", ret);
 357         return ret;
 358 }
 359
 360 /*
 361  * update the index entries backing a cookie
 362  */
 363 void __fscache_update_cookie(struct fscache_cookie *cookie)
 364 {
 365         struct fscache_object *object;
 366         struct hlist_node *_p;
 367
 368         fscache_stat(&fscache_n_updates);
 369
 370         if (!cookie) {
 371                 fscache_stat(&fscache_n_updates_null);
 372                 _leave(" [no cookie]");
 373                 return;
 374         }
 375
 376         _enter("{%s}", cookie->def->name);
 377
 378         BUG_ON(!cookie->def->get_aux);
 379
 380         spin_lock(&cookie->lock);
 381
 382         /* update the index entry on disk in each cache backing this cookie */
 383         hlist_for_each_entry(object, _p,
 384                              &cookie->backing_objects, cookie_link) {
 385                 fscache_raise_event(object, FSCACHE_OBJECT_EV_UPDATE);
 386         }
 387
 388         spin_unlock(&cookie->lock);
 389         _leave("");
 390 }
 391 EXPORT_SYMBOL(__fscache_update_cookie);
 392
 393 /*
 394  * release a cookie back to the cache
 395  * - the object will be marked as recyclable on disk if retire is true
 396  * - all dependents of this cookie must have already been unregistered
 397  *   (indices/files/pages)
 398  */
 399 void __fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
 400 {
 401         struct fscache_cache *cache;
 402         struct fscache_object *object;
 403         unsigned long event;
 404
 405         fscache_stat(&fscache_n_relinquishes);
 406
 407         if (!cookie) {
 408                 fscache_stat(&fscache_n_relinquishes_null);
 409                 _leave(" [no cookie]");
 410                 return;
 411         }
 412
 413         _enter("%p{%s,%p},%d",
 414                cookie, cookie->def->name, cookie->netfs_data, retire);
 415
 416         if (atomic_read(&cookie->n_children) != 0) {
 417                 printk(KERN_ERR "FS-Cache: Cookie '%s' still has children\n",
 418                        cookie->def->name);
 419                 BUG();
 420         }
 421
 422         /* wait for the cookie to finish being instantiated (or to fail) */
 423         if (test_bit(FSCACHE_COOKIE_CREATING, &cookie->flags)) {
 424                 fscache_stat(&fscache_n_relinquishes_waitcrt);
 425                 wait_on_bit(&cookie->flags, FSCACHE_COOKIE_CREATING,
 426                             fscache_wait_bit, TASK_UNINTERRUPTIBLE);
 427         }
 428
 429         event = retire ? FSCACHE_OBJECT_EV_RETIRE : FSCACHE_OBJECT_EV_RELEASE;
 430
 431         /* detach pointers back to the netfs */
 432         spin_lock(&cookie->lock);
 433
 434         cookie->netfs_data      = NULL;
 435         cookie->def             = NULL;
 436
 437         /* break links with all the active objects */
 438         while (!hlist_empty(&cookie->backing_objects)) {
 439                 object = hlist_entry(cookie->backing_objects.first,
 440                                      struct fscache_object,
 441                                      cookie_link);
 442
 443                 _debug("RELEASE OBJ%x", object->debug_id);
 444
 445                 /* detach each cache object from the object cookie */
 446                 spin_lock(&object->lock);
 447                 hlist_del_init(&object->cookie_link);
 448
 449                 cache = object->cache;
 450                 object->cookie = NULL;
 451                 fscache_raise_event(object, event);
 452                 spin_unlock(&object->lock);
 453
 454                 if (atomic_dec_and_test(&cookie->usage))
 455                         /* the cookie refcount shouldn't be reduced to 0 yet */
 456                         BUG();
 457         }
 458
 459         spin_unlock(&cookie->lock);
 460
 461         if (cookie->parent) {
 462                 ASSERTCMP(atomic_read(&cookie->parent->usage), >, 0);
 463                 ASSERTCMP(atomic_read(&cookie->parent->n_children), >, 0);
 464                 atomic_dec(&cookie->parent->n_children);
 465         }
 466
 467         /* finally dispose of the cookie */
 468         ASSERTCMP(atomic_read(&cookie->usage), >, 0);
 469         fscache_cookie_put(cookie);
 470
 471         _leave("");
 472 }
 473 EXPORT_SYMBOL(__fscache_relinquish_cookie);
 474
 475 /*
 476  * destroy a cookie
 477  */
 478 void __fscache_cookie_put(struct fscache_cookie *cookie)
 479 {
 480         struct fscache_cookie *parent;
 481
 482         _enter("%p", cookie);
 483
 484         for (;;) {
 485                 _debug("FREE COOKIE %p", cookie);
 486                 parent = cookie->parent;
 487                 BUG_ON(!hlist_empty(&cookie->backing_objects));
 488                 kmem_cache_free(fscache_cookie_jar, cookie);
 489
 490                 if (!parent)
 491                         break;
 492
 493                 cookie = parent;
 494                 BUG_ON(atomic_read(&cookie->usage) <= 0);
 495                 if (!atomic_dec_and_test(&cookie->usage))
 496                         break;
 497         }
 498
 499         _leave("");
 500 }