blob: e21985bbb1fb00eedb38b6d5e7f829952c3eb066 [file] [log] [blame]
David Howells0e04d4c2009-04-03 16:42:37 +01001/* FS-Cache cache handling
2 *
3 * Copyright (C) 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
12#define FSCACHE_DEBUG_LEVEL CACHE
13#include <linux/module.h>
14#include <linux/slab.h>
15#include "internal.h"
16
17LIST_HEAD(fscache_cache_list);
18DECLARE_RWSEM(fscache_addremove_sem);
David Howells4c515dd2009-04-03 16:42:37 +010019DECLARE_WAIT_QUEUE_HEAD(fscache_cache_cleared_wq);
20EXPORT_SYMBOL(fscache_cache_cleared_wq);
David Howells0e04d4c2009-04-03 16:42:37 +010021
22static LIST_HEAD(fscache_cache_tag_list);
23
24/*
25 * look up a cache tag
26 */
27struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *name)
28{
29 struct fscache_cache_tag *tag, *xtag;
30
31 /* firstly check for the existence of the tag under read lock */
32 down_read(&fscache_addremove_sem);
33
34 list_for_each_entry(tag, &fscache_cache_tag_list, link) {
35 if (strcmp(tag->name, name) == 0) {
36 atomic_inc(&tag->usage);
37 up_read(&fscache_addremove_sem);
38 return tag;
39 }
40 }
41
42 up_read(&fscache_addremove_sem);
43
44 /* the tag does not exist - create a candidate */
45 xtag = kzalloc(sizeof(*xtag) + strlen(name) + 1, GFP_KERNEL);
46 if (!xtag)
47 /* return a dummy tag if out of memory */
48 return ERR_PTR(-ENOMEM);
49
50 atomic_set(&xtag->usage, 1);
51 strcpy(xtag->name, name);
52
53 /* write lock, search again and add if still not present */
54 down_write(&fscache_addremove_sem);
55
56 list_for_each_entry(tag, &fscache_cache_tag_list, link) {
57 if (strcmp(tag->name, name) == 0) {
58 atomic_inc(&tag->usage);
59 up_write(&fscache_addremove_sem);
60 kfree(xtag);
61 return tag;
62 }
63 }
64
65 list_add_tail(&xtag->link, &fscache_cache_tag_list);
66 up_write(&fscache_addremove_sem);
67 return xtag;
68}
69
70/*
71 * release a reference to a cache tag
72 */
73void __fscache_release_cache_tag(struct fscache_cache_tag *tag)
74{
75 if (tag != ERR_PTR(-ENOMEM)) {
76 down_write(&fscache_addremove_sem);
77
78 if (atomic_dec_and_test(&tag->usage))
79 list_del_init(&tag->link);
80 else
81 tag = NULL;
82
83 up_write(&fscache_addremove_sem);
84
85 kfree(tag);
86 }
87}
88
89/*
90 * select a cache in which to store an object
91 * - the cache addremove semaphore must be at least read-locked by the caller
92 * - the object will never be an index
93 */
94struct fscache_cache *fscache_select_cache_for_object(
95 struct fscache_cookie *cookie)
96{
97 struct fscache_cache_tag *tag;
98 struct fscache_object *object;
99 struct fscache_cache *cache;
100
101 _enter("");
102
103 if (list_empty(&fscache_cache_list)) {
104 _leave(" = NULL [no cache]");
105 return NULL;
106 }
107
108 /* we check the parent to determine the cache to use */
109 spin_lock(&cookie->lock);
110
111 /* the first in the parent's backing list should be the preferred
112 * cache */
113 if (!hlist_empty(&cookie->backing_objects)) {
114 object = hlist_entry(cookie->backing_objects.first,
115 struct fscache_object, cookie_link);
116
117 cache = object->cache;
118 if (object->state >= FSCACHE_OBJECT_DYING ||
119 test_bit(FSCACHE_IOERROR, &cache->flags))
120 cache = NULL;
121
122 spin_unlock(&cookie->lock);
123 _leave(" = %p [parent]", cache);
124 return cache;
125 }
126
127 /* the parent is unbacked */
128 if (cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX) {
129 /* cookie not an index and is unbacked */
130 spin_unlock(&cookie->lock);
131 _leave(" = NULL [cookie ub,ni]");
132 return NULL;
133 }
134
135 spin_unlock(&cookie->lock);
136
137 if (!cookie->def->select_cache)
138 goto no_preference;
139
140 /* ask the netfs for its preference */
141 tag = cookie->def->select_cache(cookie->parent->netfs_data,
142 cookie->netfs_data);
143 if (!tag)
144 goto no_preference;
145
146 if (tag == ERR_PTR(-ENOMEM)) {
147 _leave(" = NULL [nomem tag]");
148 return NULL;
149 }
150
151 if (!tag->cache) {
152 _leave(" = NULL [unbacked tag]");
153 return NULL;
154 }
155
156 if (test_bit(FSCACHE_IOERROR, &tag->cache->flags))
157 return NULL;
158
159 _leave(" = %p [specific]", tag->cache);
160 return tag->cache;
161
162no_preference:
163 /* netfs has no preference - just select first cache */
164 cache = list_entry(fscache_cache_list.next,
165 struct fscache_cache, link);
166 _leave(" = %p [first]", cache);
167 return cache;
168}
David Howells4c515dd2009-04-03 16:42:37 +0100169
170/**
171 * fscache_init_cache - Initialise a cache record
172 * @cache: The cache record to be initialised
173 * @ops: The cache operations to be installed in that record
174 * @idfmt: Format string to define identifier
175 * @...: sprintf-style arguments
176 *
177 * Initialise a record of a cache and fill in the name.
178 *
179 * See Documentation/filesystems/caching/backend-api.txt for a complete
180 * description.
181 */
182void fscache_init_cache(struct fscache_cache *cache,
183 const struct fscache_cache_ops *ops,
184 const char *idfmt,
185 ...)
186{
187 va_list va;
188
189 memset(cache, 0, sizeof(*cache));
190
191 cache->ops = ops;
192
193 va_start(va, idfmt);
194 vsnprintf(cache->identifier, sizeof(cache->identifier), idfmt, va);
195 va_end(va);
196
David Howells952efe72009-04-03 16:42:39 +0100197 INIT_WORK(&cache->op_gc, fscache_operation_gc);
David Howells4c515dd2009-04-03 16:42:37 +0100198 INIT_LIST_HEAD(&cache->link);
199 INIT_LIST_HEAD(&cache->object_list);
200 INIT_LIST_HEAD(&cache->op_gc_list);
201 spin_lock_init(&cache->object_list_lock);
202 spin_lock_init(&cache->op_gc_list_lock);
203}
204EXPORT_SYMBOL(fscache_init_cache);
205
206/**
207 * fscache_add_cache - Declare a cache as being open for business
208 * @cache: The record describing the cache
209 * @ifsdef: The record of the cache object describing the top-level index
210 * @tagname: The tag describing this cache
211 *
212 * Add a cache to the system, making it available for netfs's to use.
213 *
214 * See Documentation/filesystems/caching/backend-api.txt for a complete
215 * description.
216 */
217int fscache_add_cache(struct fscache_cache *cache,
218 struct fscache_object *ifsdef,
219 const char *tagname)
220{
221 struct fscache_cache_tag *tag;
222
223 BUG_ON(!cache->ops);
224 BUG_ON(!ifsdef);
225
226 cache->flags = 0;
227 ifsdef->event_mask = ULONG_MAX & ~(1 << FSCACHE_OBJECT_EV_CLEARED);
228 ifsdef->state = FSCACHE_OBJECT_ACTIVE;
229
230 if (!tagname)
231 tagname = cache->identifier;
232
233 BUG_ON(!tagname[0]);
234
235 _enter("{%s.%s},,%s", cache->ops->name, cache->identifier, tagname);
236
237 /* we use the cache tag to uniquely identify caches */
238 tag = __fscache_lookup_cache_tag(tagname);
239 if (IS_ERR(tag))
240 goto nomem;
241
242 if (test_and_set_bit(FSCACHE_TAG_RESERVED, &tag->flags))
243 goto tag_in_use;
244
245 cache->kobj = kobject_create_and_add(tagname, fscache_root);
246 if (!cache->kobj)
247 goto error;
248
249 ifsdef->cookie = &fscache_fsdef_index;
250 ifsdef->cache = cache;
251 cache->fsdef = ifsdef;
252
253 down_write(&fscache_addremove_sem);
254
255 tag->cache = cache;
256 cache->tag = tag;
257
258 /* add the cache to the list */
259 list_add(&cache->link, &fscache_cache_list);
260
261 /* add the cache's netfs definition index object to the cache's
262 * list */
263 spin_lock(&cache->object_list_lock);
264 list_add_tail(&ifsdef->cache_link, &cache->object_list);
265 spin_unlock(&cache->object_list_lock);
266
267 /* add the cache's netfs definition index object to the top level index
268 * cookie as a known backing object */
269 spin_lock(&fscache_fsdef_index.lock);
270
271 hlist_add_head(&ifsdef->cookie_link,
272 &fscache_fsdef_index.backing_objects);
273
274 atomic_inc(&fscache_fsdef_index.usage);
275
276 /* done */
277 spin_unlock(&fscache_fsdef_index.lock);
278 up_write(&fscache_addremove_sem);
279
280 printk(KERN_NOTICE "FS-Cache: Cache \"%s\" added (type %s)\n",
281 cache->tag->name, cache->ops->name);
282 kobject_uevent(cache->kobj, KOBJ_ADD);
283
284 _leave(" = 0 [%s]", cache->identifier);
285 return 0;
286
287tag_in_use:
288 printk(KERN_ERR "FS-Cache: Cache tag '%s' already in use\n", tagname);
289 __fscache_release_cache_tag(tag);
290 _leave(" = -EXIST");
291 return -EEXIST;
292
293error:
294 __fscache_release_cache_tag(tag);
295 _leave(" = -EINVAL");
296 return -EINVAL;
297
298nomem:
299 _leave(" = -ENOMEM");
300 return -ENOMEM;
301}
302EXPORT_SYMBOL(fscache_add_cache);
303
304/**
305 * fscache_io_error - Note a cache I/O error
306 * @cache: The record describing the cache
307 *
308 * Note that an I/O error occurred in a cache and that it should no longer be
309 * used for anything. This also reports the error into the kernel log.
310 *
311 * See Documentation/filesystems/caching/backend-api.txt for a complete
312 * description.
313 */
314void fscache_io_error(struct fscache_cache *cache)
315{
316 set_bit(FSCACHE_IOERROR, &cache->flags);
317
318 printk(KERN_ERR "FS-Cache: Cache %s stopped due to I/O error\n",
319 cache->ops->name);
320}
321EXPORT_SYMBOL(fscache_io_error);
322
323/*
324 * request withdrawal of all the objects in a cache
325 * - all the objects being withdrawn are moved onto the supplied list
326 */
327static void fscache_withdraw_all_objects(struct fscache_cache *cache,
328 struct list_head *dying_objects)
329{
330 struct fscache_object *object;
331
332 spin_lock(&cache->object_list_lock);
333
334 while (!list_empty(&cache->object_list)) {
335 object = list_entry(cache->object_list.next,
336 struct fscache_object, cache_link);
337 list_move_tail(&object->cache_link, dying_objects);
338
339 _debug("withdraw %p", object->cookie);
340
341 spin_lock(&object->lock);
342 spin_unlock(&cache->object_list_lock);
343 fscache_raise_event(object, FSCACHE_OBJECT_EV_WITHDRAW);
344 spin_unlock(&object->lock);
345
346 cond_resched();
347 spin_lock(&cache->object_list_lock);
348 }
349
350 spin_unlock(&cache->object_list_lock);
351}
352
353/**
354 * fscache_withdraw_cache - Withdraw a cache from the active service
355 * @cache: The record describing the cache
356 *
357 * Withdraw a cache from service, unbinding all its cache objects from the
358 * netfs cookies they're currently representing.
359 *
360 * See Documentation/filesystems/caching/backend-api.txt for a complete
361 * description.
362 */
363void fscache_withdraw_cache(struct fscache_cache *cache)
364{
365 LIST_HEAD(dying_objects);
366
367 _enter("");
368
369 printk(KERN_NOTICE "FS-Cache: Withdrawing cache \"%s\"\n",
370 cache->tag->name);
371
372 /* make the cache unavailable for cookie acquisition */
373 if (test_and_set_bit(FSCACHE_CACHE_WITHDRAWN, &cache->flags))
374 BUG();
375
376 down_write(&fscache_addremove_sem);
377 list_del_init(&cache->link);
378 cache->tag->cache = NULL;
379 up_write(&fscache_addremove_sem);
380
381 /* make sure all pages pinned by operations on behalf of the netfs are
382 * written to disk */
383 cache->ops->sync_cache(cache);
384
385 /* dissociate all the netfs pages backed by this cache from the block
386 * mappings in the cache */
387 cache->ops->dissociate_pages(cache);
388
389 /* we now have to destroy all the active objects pertaining to this
390 * cache - which we do by passing them off to thread pool to be
391 * disposed of */
392 _debug("destroy");
393
394 fscache_withdraw_all_objects(cache, &dying_objects);
395
396 /* wait for all extant objects to finish their outstanding operations
397 * and go away */
398 _debug("wait for finish");
399 wait_event(fscache_cache_cleared_wq,
400 atomic_read(&cache->object_count) == 0);
401 _debug("wait for clearance");
402 wait_event(fscache_cache_cleared_wq,
403 list_empty(&cache->object_list));
404 _debug("cleared");
405 ASSERT(list_empty(&dying_objects));
406
407 kobject_put(cache->kobj);
408
409 clear_bit(FSCACHE_TAG_RESERVED, &cache->tag->flags);
410 fscache_release_cache_tag(cache->tag);
411 cache->tag = NULL;
412
413 _leave("");
414}
415EXPORT_SYMBOL(fscache_withdraw_cache);