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 * Invalidate an object. Callable with spinlocks held. 374 */ 375 void __fscache_invalidate(struct fscache_cookie *cookie) 376 { 377 struct fscache_object *object; 378 379 _enter("{%s}", cookie->def->name); 380 381 fscache_stat(&fscache_n_invalidates); 382 383 /* Only permit invalidation of data files. Invalidating an index will 384 * require the caller to release all its attachments to the tree rooted 385 * there, and if it's doing that, it may as well just retire the 386 * cookie. 387 */ 388 ASSERTCMP(cookie->def->type, ==, FSCACHE_COOKIE_TYPE_DATAFILE); 389 390 /* We will be updating the cookie too. */ 391 BUG_ON(!cookie->def->get_aux); 392 393 /* If there's an object, we tell the object state machine to handle the 394 * invalidation on our behalf, otherwise there's nothing to do. 395 */ 396 if (!hlist_empty(&cookie->backing_objects)) { 397 spin_lock(&cookie->lock); 398 399 if (!hlist_empty(&cookie->backing_objects) && 400 !test_and_set_bit(FSCACHE_COOKIE_INVALIDATING, 401 &cookie->flags)) { 402 object = hlist_entry(cookie->backing_objects.first, 403 struct fscache_object, 404 cookie_link); 405 if (object->state < FSCACHE_OBJECT_DYING) 406 fscache_raise_event( 407 object, FSCACHE_OBJECT_EV_INVALIDATE); 408 } 409 410 spin_unlock(&cookie->lock); 411 } 412 413 _leave(""); 414 } 415 EXPORT_SYMBOL(__fscache_invalidate); 416 417 /* 418 * Wait for object invalidation to complete. 419 */ 420 void __fscache_wait_on_invalidate(struct fscache_cookie *cookie) 421 { 422 _enter("%p", cookie); 423 424 wait_on_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING, 425 fscache_wait_bit_interruptible, 426 TASK_UNINTERRUPTIBLE); 427 428 _leave(""); 429 } 430 EXPORT_SYMBOL(__fscache_wait_on_invalidate); 431 432 /* 433 * update the index entries backing a cookie 434 */ 435 void __fscache_update_cookie(struct fscache_cookie *cookie) 436 { 437 struct fscache_object *object; 438 struct hlist_node *_p; 439 440 fscache_stat(&fscache_n_updates); 441 442 if (!cookie) { 443 fscache_stat(&fscache_n_updates_null); 444 _leave(" [no cookie]"); 445 return; 446 } 447 448 _enter("{%s}", cookie->def->name); 449 450 BUG_ON(!cookie->def->get_aux); 451 452 spin_lock(&cookie->lock); 453 454 /* update the index entry on disk in each cache backing this cookie */ 455 hlist_for_each_entry(object, _p, 456 &cookie->backing_objects, cookie_link) { 457 fscache_raise_event(object, FSCACHE_OBJECT_EV_UPDATE); 458 } 459 460 spin_unlock(&cookie->lock); 461 _leave(""); 462 } 463 EXPORT_SYMBOL(__fscache_update_cookie); 464 465 /* 466 * release a cookie back to the cache 467 * - the object will be marked as recyclable on disk if retire is true 468 * - all dependents of this cookie must have already been unregistered 469 * (indices/files/pages) 470 */ 471 void __fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire) 472 { 473 struct fscache_cache *cache; 474 struct fscache_object *object; 475 unsigned long event; 476 477 fscache_stat(&fscache_n_relinquishes); 478 if (retire) 479 fscache_stat(&fscache_n_relinquishes_retire); 480 481 if (!cookie) { 482 fscache_stat(&fscache_n_relinquishes_null); 483 _leave(" [no cookie]"); 484 return; 485 } 486 487 _enter("%p{%s,%p},%d", 488 cookie, cookie->def->name, cookie->netfs_data, retire); 489 490 if (atomic_read(&cookie->n_children) != 0) { 491 printk(KERN_ERR "FS-Cache: Cookie '%s' still has children\n", 492 cookie->def->name); 493 BUG(); 494 } 495 496 /* wait for the cookie to finish being instantiated (or to fail) */ 497 if (test_bit(FSCACHE_COOKIE_CREATING, &cookie->flags)) { 498 fscache_stat(&fscache_n_relinquishes_waitcrt); 499 wait_on_bit(&cookie->flags, FSCACHE_COOKIE_CREATING, 500 fscache_wait_bit, TASK_UNINTERRUPTIBLE); 501 } 502 503 event = retire ? FSCACHE_OBJECT_EV_RETIRE : FSCACHE_OBJECT_EV_RELEASE; 504 505 try_again: 506 spin_lock(&cookie->lock); 507 508 /* break links with all the active objects */ 509 while (!hlist_empty(&cookie->backing_objects)) { 510 int n_reads; 511 object = hlist_entry(cookie->backing_objects.first, 512 struct fscache_object, 513 cookie_link); 514 515 _debug("RELEASE OBJ%x", object->debug_id); 516 517 set_bit(FSCACHE_COOKIE_WAITING_ON_READS, &cookie->flags); 518 n_reads = atomic_read(&object->n_reads); 519 if (n_reads) { 520 int n_ops = object->n_ops; 521 int n_in_progress = object->n_in_progress; 522 spin_unlock(&cookie->lock); 523 printk(KERN_ERR "FS-Cache:" 524 " Cookie '%s' still has %d outstanding reads (%d,%d)\n", 525 cookie->def->name, 526 n_reads, n_ops, n_in_progress); 527 wait_on_bit(&cookie->flags, FSCACHE_COOKIE_WAITING_ON_READS, 528 fscache_wait_bit, TASK_UNINTERRUPTIBLE); 529 printk("Wait finished\n"); 530 goto try_again; 531 } 532 533 /* detach each cache object from the object cookie */ 534 spin_lock(&object->lock); 535 hlist_del_init(&object->cookie_link); 536 537 cache = object->cache; 538 object->cookie = NULL; 539 fscache_raise_event(object, event); 540 spin_unlock(&object->lock); 541 542 if (atomic_dec_and_test(&cookie->usage)) 543 /* the cookie refcount shouldn't be reduced to 0 yet */ 544 BUG(); 545 } 546 547 /* detach pointers back to the netfs */ 548 cookie->netfs_data = NULL; 549 cookie->def = NULL; 550 551 spin_unlock(&cookie->lock); 552 553 if (cookie->parent) { 554 ASSERTCMP(atomic_read(&cookie->parent->usage), >, 0); 555 ASSERTCMP(atomic_read(&cookie->parent->n_children), >, 0); 556 atomic_dec(&cookie->parent->n_children); 557 } 558 559 /* finally dispose of the cookie */ 560 ASSERTCMP(atomic_read(&cookie->usage), >, 0); 561 fscache_cookie_put(cookie); 562 563 _leave(""); 564 } 565 EXPORT_SYMBOL(__fscache_relinquish_cookie); 566 567 /* 568 * destroy a cookie 569 */ 570 void __fscache_cookie_put(struct fscache_cookie *cookie) 571 { 572 struct fscache_cookie *parent; 573 574 _enter("%p", cookie); 575 576 for (;;) { 577 _debug("FREE COOKIE %p", cookie); 578 parent = cookie->parent; 579 BUG_ON(!hlist_empty(&cookie->backing_objects)); 580 kmem_cache_free(fscache_cookie_jar, cookie); 581 582 if (!parent) 583 break; 584 585 cookie = parent; 586 BUG_ON(atomic_read(&cookie->usage) <= 0); 587 if (!atomic_dec_and_test(&cookie->usage)) 588 break; 589 } 590 591 _leave(""); 592 } 593