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1 | /* 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 | |
17 | LIST_HEAD(fscache_cache_list); |
18 | DECLARE_RWSEM(fscache_addremove_sem); |
19 | DECLARE_WAIT_QUEUE_HEAD(fscache_cache_cleared_wq); |
20 | EXPORT_SYMBOL(fscache_cache_cleared_wq); |
21 | |
22 | static LIST_HEAD(fscache_cache_tag_list); |
23 | |
24 | /* |
25 | * look up a cache tag |
26 | */ |
27 | struct 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 | */ |
73 | void __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 | */ |
94 | struct 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 | |
162 | no_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 | } |
169 | |
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 | */ |
182 | void 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 | |
197 | INIT_WORK(&cache->op_gc, fscache_operation_gc); |
198 | 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 | } |
204 | EXPORT_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 | */ |
217 | int 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 | fscache_objlist_add(ifsdef); |
267 | |
268 | /* add the cache's netfs definition index object to the top level index |
269 | * cookie as a known backing object */ |
270 | spin_lock(&fscache_fsdef_index.lock); |
271 | |
272 | hlist_add_head(&ifsdef->cookie_link, |
273 | &fscache_fsdef_index.backing_objects); |
274 | |
275 | atomic_inc(&fscache_fsdef_index.usage); |
276 | |
277 | /* done */ |
278 | spin_unlock(&fscache_fsdef_index.lock); |
279 | up_write(&fscache_addremove_sem); |
280 | |
281 | printk(KERN_NOTICE "FS-Cache: Cache \"%s\" added (type %s)\n", |
282 | cache->tag->name, cache->ops->name); |
283 | kobject_uevent(cache->kobj, KOBJ_ADD); |
284 | |
285 | _leave(" = 0 [%s]", cache->identifier); |
286 | return 0; |
287 | |
288 | tag_in_use: |
289 | printk(KERN_ERR "FS-Cache: Cache tag '%s' already in use\n", tagname); |
290 | __fscache_release_cache_tag(tag); |
291 | _leave(" = -EXIST"); |
292 | return -EEXIST; |
293 | |
294 | error: |
295 | __fscache_release_cache_tag(tag); |
296 | _leave(" = -EINVAL"); |
297 | return -EINVAL; |
298 | |
299 | nomem: |
300 | _leave(" = -ENOMEM"); |
301 | return -ENOMEM; |
302 | } |
303 | EXPORT_SYMBOL(fscache_add_cache); |
304 | |
305 | /** |
306 | * fscache_io_error - Note a cache I/O error |
307 | * @cache: The record describing the cache |
308 | * |
309 | * Note that an I/O error occurred in a cache and that it should no longer be |
310 | * used for anything. This also reports the error into the kernel log. |
311 | * |
312 | * See Documentation/filesystems/caching/backend-api.txt for a complete |
313 | * description. |
314 | */ |
315 | void fscache_io_error(struct fscache_cache *cache) |
316 | { |
317 | set_bit(FSCACHE_IOERROR, &cache->flags); |
318 | |
319 | printk(KERN_ERR "FS-Cache: Cache %s stopped due to I/O error\n", |
320 | cache->ops->name); |
321 | } |
322 | EXPORT_SYMBOL(fscache_io_error); |
323 | |
324 | /* |
325 | * request withdrawal of all the objects in a cache |
326 | * - all the objects being withdrawn are moved onto the supplied list |
327 | */ |
328 | static void fscache_withdraw_all_objects(struct fscache_cache *cache, |
329 | struct list_head *dying_objects) |
330 | { |
331 | struct fscache_object *object; |
332 | |
333 | spin_lock(&cache->object_list_lock); |
334 | |
335 | while (!list_empty(&cache->object_list)) { |
336 | object = list_entry(cache->object_list.next, |
337 | struct fscache_object, cache_link); |
338 | list_move_tail(&object->cache_link, dying_objects); |
339 | |
340 | _debug("withdraw %p", object->cookie); |
341 | |
342 | spin_lock(&object->lock); |
343 | spin_unlock(&cache->object_list_lock); |
344 | fscache_raise_event(object, FSCACHE_OBJECT_EV_WITHDRAW); |
345 | spin_unlock(&object->lock); |
346 | |
347 | cond_resched(); |
348 | spin_lock(&cache->object_list_lock); |
349 | } |
350 | |
351 | spin_unlock(&cache->object_list_lock); |
352 | } |
353 | |
354 | /** |
355 | * fscache_withdraw_cache - Withdraw a cache from the active service |
356 | * @cache: The record describing the cache |
357 | * |
358 | * Withdraw a cache from service, unbinding all its cache objects from the |
359 | * netfs cookies they're currently representing. |
360 | * |
361 | * See Documentation/filesystems/caching/backend-api.txt for a complete |
362 | * description. |
363 | */ |
364 | void fscache_withdraw_cache(struct fscache_cache *cache) |
365 | { |
366 | LIST_HEAD(dying_objects); |
367 | |
368 | _enter(""); |
369 | |
370 | printk(KERN_NOTICE "FS-Cache: Withdrawing cache \"%s\"\n", |
371 | cache->tag->name); |
372 | |
373 | /* make the cache unavailable for cookie acquisition */ |
374 | if (test_and_set_bit(FSCACHE_CACHE_WITHDRAWN, &cache->flags)) |
375 | BUG(); |
376 | |
377 | down_write(&fscache_addremove_sem); |
378 | list_del_init(&cache->link); |
379 | cache->tag->cache = NULL; |
380 | up_write(&fscache_addremove_sem); |
381 | |
382 | /* make sure all pages pinned by operations on behalf of the netfs are |
383 | * written to disk */ |
384 | fscache_stat(&fscache_n_cop_sync_cache); |
385 | cache->ops->sync_cache(cache); |
386 | fscache_stat_d(&fscache_n_cop_sync_cache); |
387 | |
388 | /* dissociate all the netfs pages backed by this cache from the block |
389 | * mappings in the cache */ |
390 | fscache_stat(&fscache_n_cop_dissociate_pages); |
391 | cache->ops->dissociate_pages(cache); |
392 | fscache_stat_d(&fscache_n_cop_dissociate_pages); |
393 | |
394 | /* we now have to destroy all the active objects pertaining to this |
395 | * cache - which we do by passing them off to thread pool to be |
396 | * disposed of */ |
397 | _debug("destroy"); |
398 | |
399 | fscache_withdraw_all_objects(cache, &dying_objects); |
400 | |
401 | /* wait for all extant objects to finish their outstanding operations |
402 | * and go away */ |
403 | _debug("wait for finish"); |
404 | wait_event(fscache_cache_cleared_wq, |
405 | atomic_read(&cache->object_count) == 0); |
406 | _debug("wait for clearance"); |
407 | wait_event(fscache_cache_cleared_wq, |
408 | list_empty(&cache->object_list)); |
409 | _debug("cleared"); |
410 | ASSERT(list_empty(&dying_objects)); |
411 | |
412 | kobject_put(cache->kobj); |
413 | |
414 | clear_bit(FSCACHE_TAG_RESERVED, &cache->tag->flags); |
415 | fscache_release_cache_tag(cache->tag); |
416 | cache->tag = NULL; |
417 | |
418 | _leave(""); |
419 | } |
420 | EXPORT_SYMBOL(fscache_withdraw_cache); |
421 |
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