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David Howells955d0092009-04-03 16:42:38 +01001/* 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.
David Howellsccc4fc32009-04-03 16:42:38 +010010 *
11 * See Documentation/filesystems/caching/netfs-api.txt for more information on
12 * the netfs API.
David Howells955d0092009-04-03 16:42:38 +010013 */
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
David Howellsccc4fc32009-04-03 16:42:38 +010022static 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
David Howells955d0092009-04-03 16:42:38 +010030/*
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);
David Howells1bccf512009-11-19 18:11:25 +000039 spin_lock_init(&cookie->stores_lock);
David Howells955d0092009-04-03 16:42:38 +010040 INIT_HLIST_HEAD(&cookie->backing_objects);
41}
42
43/*
David Howellsccc4fc32009-04-03 16:42:38 +010044 * 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
David Howellsb34df792009-11-19 18:11:14 +0000106 /* 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);
David Howellsccc4fc32009-04-03 16:42:38 +0100109
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) */
David Howells52bd75f2009-11-19 18:11:08 +0000255 fscache_stat(&fscache_n_cop_alloc_object);
David Howellsccc4fc32009-04-03 16:42:38 +0100256 object = cache->ops->alloc_object(cache, cookie);
David Howells52bd75f2009-11-19 18:11:08 +0000257 fscache_stat_d(&fscache_n_cop_alloc_object);
David Howellsccc4fc32009-04-03 16:42:38 +0100258 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 */
David Howells52bd75f2009-11-19 18:11:08 +0000278 if (fscache_attach_object(cookie, object) < 0) {
279 fscache_stat(&fscache_n_cop_put_object);
David Howellsccc4fc32009-04-03 16:42:38 +0100280 cache->ops->put_object(object);
David Howells52bd75f2009-11-19 18:11:08 +0000281 fscache_stat_d(&fscache_n_cop_put_object);
282 }
David Howellsccc4fc32009-04-03 16:42:38 +0100283
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:
David Howells52bd75f2009-11-19 18:11:08 +0000298 fscache_stat(&fscache_n_cop_put_object);
David Howellsccc4fc32009-04-03 16:42:38 +0100299 cache->ops->put_object(object);
David Howells52bd75f2009-11-19 18:11:08 +0000300 fscache_stat_d(&fscache_n_cop_put_object);
David Howellsccc4fc32009-04-03 16:42:38 +0100301error:
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);
David Howells4fbf4292009-11-19 18:11:04 +0000362
363 fscache_objlist_add(object);
David Howellsccc4fc32009-04-03 16:42:38 +0100364 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);
David Howells2175bb02009-11-19 18:11:38 +0000418 if (retire)
419 fscache_stat(&fscache_n_relinquishes_retire);
David Howellsccc4fc32009-04-03 16:42:38 +0100420
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
David Howellsccc4fc32009-04-03 16:42:38 +0100445 spin_lock(&cookie->lock);
446
David Howellsccc4fc32009-04-03 16:42:38 +0100447 /* 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
David Howells7e311a22009-11-19 18:11:11 +0000469 /* detach pointers back to the netfs */
470 cookie->netfs_data = NULL;
471 cookie->def = NULL;
472
David Howellsccc4fc32009-04-03 16:42:38 +0100473 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/*
David Howells955d0092009-04-03 16:42:38 +0100490 * 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}