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authorDavid Howells <dhowells@redhat.com>2009-04-03 11:42:37 -0400
committerDavid Howells <dhowells@redhat.com>2009-04-03 11:42:37 -0400
commit4c515dd47ab41be3f89e757d441661795470b376 (patch)
tree22b1959663cf77ecd60125ef112b87f1ee4fa6ef /fs/fscache/cache.c
parent0e04d4cefcf4d8fbbdb2c50e93ad541582933fd2 (diff)
FS-Cache: Add cache management
Implement the entry points by which a cache backend may initialise, add, declare an error upon and withdraw a cache. Further, an object is created in sysfs under which each cache added will get an object created: /sys/fs/fscache/<cachetag>/ All of this is described in Documentation/filesystems/caching/backend-api.txt added by a previous patch. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
Diffstat (limited to 'fs/fscache/cache.c')
-rw-r--r--fs/fscache/cache.c249
1 files changed, 249 insertions, 0 deletions
diff --git a/fs/fscache/cache.c b/fs/fscache/cache.c
index 1a28df36dd93..355172f785fb 100644
--- a/fs/fscache/cache.c
+++ b/fs/fscache/cache.c
@@ -16,6 +16,8 @@
16 16
17LIST_HEAD(fscache_cache_list); 17LIST_HEAD(fscache_cache_list);
18DECLARE_RWSEM(fscache_addremove_sem); 18DECLARE_RWSEM(fscache_addremove_sem);
19DECLARE_WAIT_QUEUE_HEAD(fscache_cache_cleared_wq);
20EXPORT_SYMBOL(fscache_cache_cleared_wq);
19 21
20static LIST_HEAD(fscache_cache_tag_list); 22static LIST_HEAD(fscache_cache_tag_list);
21 23
@@ -164,3 +166,250 @@ no_preference:
164 _leave(" = %p [first]", cache); 166 _leave(" = %p [first]", cache);
165 return cache; 167 return cache;
166} 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 */
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
197 INIT_WORK(&cache->op_gc, NULL);
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}
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);