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         /* radix tree insertion won't use the preallocation pool unless it's
 106          * told it may not wait */
 107         INIT_RADIX_TREE(&cookie->stores, GFP_NOFS & ~__GFP_WAIT);
 108
 109         switch (cookie->def->type) {
 110         case FSCACHE_COOKIE_TYPE_INDEX:
 111                 fscache_stat(&fscache_n_cookie_index);
 112                 break;
 113         case FSCACHE_COOKIE_TYPE_DATAFILE:
 114                 fscache_stat(&fscache_n_cookie_data);
 115                 break;
 116         default:
 117                 fscache_stat(&fscache_n_cookie_special);
 118                 break;
 119         }
 120
 121         /* if the object is an index then we need do nothing more here - we
 122          * create indices on disk when we need them as an index may exist in
 123          * multiple caches */
 124         if (cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX) {
 125                 if (fscache_acquire_non_index_cookie(cookie) < 0) {
 126                         atomic_dec(&parent->n_children);
 127                         __fscache_cookie_put(cookie);
 128                         fscache_stat(&fscache_n_acquires_nobufs);
 129                         _leave(" = NULL");
 130                         return NULL;
 131                 }
 132         }
 133
 134         fscache_stat(&fscache_n_acquires_ok);
 135         _leave(" = %p", cookie);
 136         return cookie;
 137 }
 138 EXPORT_SYMBOL(__fscache_acquire_cookie);
 139
 140 /*
 141  * acquire a non-index cookie
 142  * - this must make sure the index chain is instantiated and instantiate the
 143  *   object representation too
 144  */
 145 static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie)
 146 {
 147         struct fscache_object *object;
 148         struct fscache_cache *cache;
 149         uint64_t i_size;
 150         int ret;
 151
 152         _enter("");
 153
 154         cookie->flags = 1 << FSCACHE_COOKIE_UNAVAILABLE;
 155
 156         /* now we need to see whether the backing objects for this cookie yet
 157          * exist, if not there'll be nothing to search */
 158         down_read(&fscache_addremove_sem);
 159
 160         if (list_empty(&fscache_cache_list)) {
 161                 up_read(&fscache_addremove_sem);
 162                 _leave(" = 0 [no caches]");
 163                 return 0;
 164         }
 165
 166         /* select a cache in which to store the object */
 167         cache = fscache_select_cache_for_object(cookie->parent);
 168         if (!cache) {
 169                 up_read(&fscache_addremove_sem);
 170                 fscache_stat(&fscache_n_acquires_no_cache);
 171                 _leave(" = -ENOMEDIUM [no cache]");
 172                 return -ENOMEDIUM;
 173         }
 174
 175         _debug("cache %s", cache->tag->name);
 176
 177         cookie->flags =
 178                 (1 << FSCACHE_COOKIE_LOOKING_UP) |
 179                 (1 << FSCACHE_COOKIE_CREATING) |
 180                 (1 << FSCACHE_COOKIE_NO_DATA_YET);
 181
 182         /* ask the cache to allocate objects for this cookie and its parent
 183          * chain */
 184         ret = fscache_alloc_object(cache, cookie);
 185         if (ret < 0) {
 186                 up_read(&fscache_addremove_sem);
 187                 _leave(" = %d", ret);
 188                 return ret;
 189         }
 190
 191         /* pass on how big the object we're caching is supposed to be */
 192         cookie->def->get_attr(cookie->netfs_data, &i_size);
 193
 194         spin_lock(&cookie->lock);
 195         if (hlist_empty(&cookie->backing_objects)) {
 196                 spin_unlock(&cookie->lock);
 197                 goto unavailable;
 198         }
 199
 200         object = hlist_entry(cookie->backing_objects.first,
 201                              struct fscache_object, cookie_link);
 202
 203         fscache_set_store_limit(object, i_size);
 204
 205         /* initiate the process of looking up all the objects in the chain
 206          * (done by fscache_initialise_object()) */
 207         fscache_enqueue_object(object);
 208
 209         spin_unlock(&cookie->lock);
 210
 211         /* we may be required to wait for lookup to complete at this point */
 212         if (!fscache_defer_lookup) {
 213                 _debug("non-deferred lookup %p", &cookie->flags);
 214                 wait_on_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP,
 215                             fscache_wait_bit, TASK_UNINTERRUPTIBLE);
 216                 _debug("complete");
 217                 if (test_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags))
 218                         goto unavailable;
 219         }
 220
 221         up_read(&fscache_addremove_sem);
 222         _leave(" = 0 [deferred]");
 223         return 0;
 224
 225 unavailable:
 226         up_read(&fscache_addremove_sem);
 227         _leave(" = -ENOBUFS");
 228         return -ENOBUFS;
 229 }
 230
 231 /*
 232  * recursively allocate cache object records for a cookie/cache combination
 233  * - caller must be holding the addremove sem
 234  */
 235 static int fscache_alloc_object(struct fscache_cache *cache,
 236                                 struct fscache_cookie *cookie)
 237 {
 238         struct fscache_object *object;
 239         struct hlist_node *_n;
 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, _n, &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         struct hlist_node *_n;
 314         int ret;
 315
 316         _enter("{%s},{OBJ%x}", cookie->def->name, object->debug_id);
 317
 318         spin_lock(&cookie->lock);
 319
 320         /* there may be multiple initial creations of this object, but we only
 321          * want one */
 322         ret = -EEXIST;
 323         hlist_for_each_entry(p, _n, &cookie->backing_objects, cookie_link) {
 324                 if (p->cache == object->cache) {
 325                         if (p->state >= FSCACHE_OBJECT_DYING)
 326                                 ret = -ENOBUFS;
 327                         goto cant_attach_object;
 328                 }
 329         }
 330
 331         /* pin the parent object */
 332         spin_lock_nested(&cookie->parent->lock, 1);
 333         hlist_for_each_entry(p, _n, &cookie->parent->backing_objects,
 334                              cookie_link) {
 335                 if (p->cache == object->cache) {
 336                         if (p->state >= FSCACHE_OBJECT_DYING) {
 337                                 ret = -ENOBUFS;
 338                                 spin_unlock(&cookie->parent->lock);
 339                                 goto cant_attach_object;
 340                         }
 341                         object->parent = p;
 342                         spin_lock(&p->lock);
 343                         p->n_children++;
 344                         spin_unlock(&p->lock);
 345                         break;
 346                 }
 347         }
 348         spin_unlock(&cookie->parent->lock);
 349
 350         /* attach to the cache's object list */
 351         if (list_empty(&object->cache_link)) {
 352                 spin_lock(&cache->object_list_lock);
 353                 list_add(&object->cache_link, &cache->object_list);
 354                 spin_unlock(&cache->object_list_lock);
 355         }
 356
 357         /* attach to the cookie */
 358         object->cookie = cookie;
 359         atomic_inc(&cookie->usage);
 360         hlist_add_head(&object->cookie_link, &cookie->backing_objects);
 361
 362         fscache_objlist_add(object);
 363         ret = 0;
 364
 365 cant_attach_object:
 366         spin_unlock(&cookie->lock);
 367         _leave(" = %d", ret);
 368         return ret;
 369 }
 370
 371 /*
 372  * update the index entries backing a cookie
 373  */
 374 void __fscache_update_cookie(struct fscache_cookie *cookie)
 375 {
 376         struct fscache_object *object;
 377         struct hlist_node *_p;
 378
 379         fscache_stat(&fscache_n_updates);
 380
 381         if (!cookie) {
 382                 fscache_stat(&fscache_n_updates_null);
 383                 _leave(" [no cookie]");
 384                 return;
 385         }
 386
 387         _enter("{%s}", cookie->def->name);
 388
 389         BUG_ON(!cookie->def->get_aux);
 390
 391         spin_lock(&cookie->lock);
 392
 393         /* update the index entry on disk in each cache backing this cookie */
 394         hlist_for_each_entry(object, _p,
 395                              &cookie->backing_objects, cookie_link) {
 396                 fscache_raise_event(object, FSCACHE_OBJECT_EV_UPDATE);
 397         }
 398
 399         spin_unlock(&cookie->lock);
 400         _leave("");
 401 }
 402 EXPORT_SYMBOL(__fscache_update_cookie);
 403
 404 /*
 405  * release a cookie back to the cache
 406  * - the object will be marked as recyclable on disk if retire is true
 407  * - all dependents of this cookie must have already been unregistered
 408  *   (indices/files/pages)
 409  */
 410 void __fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
 411 {
 412         struct fscache_cache *cache;
 413         struct fscache_object *object;
 414         unsigned long event;
 415
 416         fscache_stat(&fscache_n_relinquishes);
 417
 418         if (!cookie) {
 419                 fscache_stat(&fscache_n_relinquishes_null);
 420                 _leave(" [no cookie]");
 421                 return;
 422         }
 423
 424         _enter("%p{%s,%p},%d",
 425                cookie, cookie->def->name, cookie->netfs_data, retire);
 426
 427         if (atomic_read(&cookie->n_children) != 0) {
 428                 printk(KERN_ERR "FS-Cache: Cookie '%s' still has children\n",
 429                        cookie->def->name);
 430                 BUG();
 431         }
 432
 433         /* wait for the cookie to finish being instantiated (or to fail) */
 434         if (test_bit(FSCACHE_COOKIE_CREATING, &cookie->flags)) {
 435                 fscache_stat(&fscache_n_relinquishes_waitcrt);
 436                 wait_on_bit(&cookie->flags, FSCACHE_COOKIE_CREATING,
 437                             fscache_wait_bit, TASK_UNINTERRUPTIBLE);
 438         }
 439
 440         event = retire ? FSCACHE_OBJECT_EV_RETIRE : FSCACHE_OBJECT_EV_RELEASE;
 441
 442         spin_lock(&cookie->lock);
 443
 444         /* break links with all the active objects */
 445         while (!hlist_empty(&cookie->backing_objects)) {
 446                 object = hlist_entry(cookie->backing_objects.first,
 447                                      struct fscache_object,
 448                                      cookie_link);
 449
 450                 _debug("RELEASE OBJ%x", object->debug_id);
 451
 452                 /* detach each cache object from the object cookie */
 453                 spin_lock(&object->lock);
 454                 hlist_del_init(&object->cookie_link);
 455
 456                 cache = object->cache;
 457                 object->cookie = NULL;
 458                 fscache_raise_event(object, event);
 459                 spin_unlock(&object->lock);
 460
 461                 if (atomic_dec_and_test(&cookie->usage))
 462                         /* the cookie refcount shouldn't be reduced to 0 yet */
 463                         BUG();
 464         }
 465
 466         /* detach pointers back to the netfs */
 467         cookie->netfs_data      = NULL;
 468         cookie->def             = NULL;
 469
 470         spin_unlock(&cookie->lock);
 471
 472         if (cookie->parent) {
 473                 ASSERTCMP(atomic_read(&cookie->parent->usage), >, 0);
 474                 ASSERTCMP(atomic_read(&cookie->parent->n_children), >, 0);
 475                 atomic_dec(&cookie->parent->n_children);
 476         }
 477
 478         /* finally dispose of the cookie */
 479         ASSERTCMP(atomic_read(&cookie->usage), >, 0);
 480         fscache_cookie_put(cookie);
 481
 482         _leave("");
 483 }
 484 EXPORT_SYMBOL(__fscache_relinquish_cookie);
 485
 486 /*
 487  * destroy a cookie
 488  */
 489 void __fscache_cookie_put(struct fscache_cookie *cookie)
 490 {
 491         struct fscache_cookie *parent;
 492
 493         _enter("%p", cookie);
 494
 495         for (;;) {
 496                 _debug("FREE COOKIE %p", cookie);
 497                 parent = cookie->parent;
 498                 BUG_ON(!hlist_empty(&cookie->backing_objects));
 499                 kmem_cache_free(fscache_cookie_jar, cookie);
 500
 501                 if (!parent)
 502                         break;
 503
 504                 cookie = parent;
 505                 BUG_ON(atomic_read(&cookie->usage) <= 0);
 506                 if (!atomic_dec_and_test(&cookie->usage))
 507                         break;
 508         }
 509
 510         _leave("");
 511 }