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 20struct kmem_cache *fscache_cookie_jar; 21 22static atomic_t fscache_object_debug_id = ATOMIC_INIT(0); 23 24static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie); 25static int fscache_alloc_object(struct fscache_cache *cache, 26 struct fscache_cookie *cookie); 27static 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 */ 33void 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 */ 58struct 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} 139EXPORT_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 */ 146static 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 226unavailable: 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 */ 236static 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 287object_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 297error_put: 298 fscache_stat(&fscache_n_cop_put_object); 299 cache->ops->put_object(object); 300 fscache_stat_d(&fscache_n_cop_put_object); 301error: 302 _leave(" = %d", ret); 303 return ret; 304} 305 306/* 307 * attach a cache object to a cookie 308 */ 309static 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 366cant_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 */ 375void __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} 403EXPORT_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 */ 411void __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} 487EXPORT_SYMBOL(__fscache_relinquish_cookie); 488 489/* 490 * destroy a cookie 491 */ 492void __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} 515