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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* FS-Cache cache handling
3 *
4 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#define FSCACHE_DEBUG_LEVEL CACHE
9#include <linux/module.h>
10#include <linux/slab.h>
11#include "internal.h"
12
13LIST_HEAD(fscache_cache_list);
14DECLARE_RWSEM(fscache_addremove_sem);
15DECLARE_WAIT_QUEUE_HEAD(fscache_cache_cleared_wq);
16EXPORT_SYMBOL(fscache_cache_cleared_wq);
17
18static LIST_HEAD(fscache_cache_tag_list);
19
20/*
21 * look up a cache tag
22 */
23struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *name)
24{
25 struct fscache_cache_tag *tag, *xtag;
26
27 /* firstly check for the existence of the tag under read lock */
28 down_read(&fscache_addremove_sem);
29
30 list_for_each_entry(tag, &fscache_cache_tag_list, link) {
31 if (strcmp(tag->name, name) == 0) {
32 atomic_inc(&tag->usage);
33 up_read(&fscache_addremove_sem);
34 return tag;
35 }
36 }
37
38 up_read(&fscache_addremove_sem);
39
40 /* the tag does not exist - create a candidate */
41 xtag = kzalloc(sizeof(*xtag) + strlen(name) + 1, GFP_KERNEL);
42 if (!xtag)
43 /* return a dummy tag if out of memory */
44 return ERR_PTR(-ENOMEM);
45
46 atomic_set(&xtag->usage, 1);
47 strcpy(xtag->name, name);
48
49 /* write lock, search again and add if still not present */
50 down_write(&fscache_addremove_sem);
51
52 list_for_each_entry(tag, &fscache_cache_tag_list, link) {
53 if (strcmp(tag->name, name) == 0) {
54 atomic_inc(&tag->usage);
55 up_write(&fscache_addremove_sem);
56 kfree(xtag);
57 return tag;
58 }
59 }
60
61 list_add_tail(&xtag->link, &fscache_cache_tag_list);
62 up_write(&fscache_addremove_sem);
63 return xtag;
64}
65
66/*
67 * release a reference to a cache tag
68 */
69void __fscache_release_cache_tag(struct fscache_cache_tag *tag)
70{
71 if (tag != ERR_PTR(-ENOMEM)) {
72 down_write(&fscache_addremove_sem);
73
74 if (atomic_dec_and_test(&tag->usage))
75 list_del_init(&tag->link);
76 else
77 tag = NULL;
78
79 up_write(&fscache_addremove_sem);
80
81 kfree(tag);
82 }
83}
84
85/*
86 * select a cache in which to store an object
87 * - the cache addremove semaphore must be at least read-locked by the caller
88 * - the object will never be an index
89 */
90struct fscache_cache *fscache_select_cache_for_object(
91 struct fscache_cookie *cookie)
92{
93 struct fscache_cache_tag *tag;
94 struct fscache_object *object;
95 struct fscache_cache *cache;
96
97 _enter("");
98
99 if (list_empty(&fscache_cache_list)) {
100 _leave(" = NULL [no cache]");
101 return NULL;
102 }
103
104 /* we check the parent to determine the cache to use */
105 spin_lock(&cookie->lock);
106
107 /* the first in the parent's backing list should be the preferred
108 * cache */
109 if (!hlist_empty(&cookie->backing_objects)) {
110 object = hlist_entry(cookie->backing_objects.first,
111 struct fscache_object, cookie_link);
112
113 cache = object->cache;
114 if (fscache_object_is_dying(object) ||
115 test_bit(FSCACHE_IOERROR, &cache->flags))
116 cache = NULL;
117
118 spin_unlock(&cookie->lock);
119 _leave(" = %p [parent]", cache);
120 return cache;
121 }
122
123 /* the parent is unbacked */
124 if (cookie->type != FSCACHE_COOKIE_TYPE_INDEX) {
125 /* cookie not an index and is unbacked */
126 spin_unlock(&cookie->lock);
127 _leave(" = NULL [cookie ub,ni]");
128 return NULL;
129 }
130
131 spin_unlock(&cookie->lock);
132
133 if (!cookie->def->select_cache)
134 goto no_preference;
135
136 /* ask the netfs for its preference */
137 tag = cookie->def->select_cache(cookie->parent->netfs_data,
138 cookie->netfs_data);
139 if (!tag)
140 goto no_preference;
141
142 if (tag == ERR_PTR(-ENOMEM)) {
143 _leave(" = NULL [nomem tag]");
144 return NULL;
145 }
146
147 if (!tag->cache) {
148 _leave(" = NULL [unbacked tag]");
149 return NULL;
150 }
151
152 if (test_bit(FSCACHE_IOERROR, &tag->cache->flags))
153 return NULL;
154
155 _leave(" = %p [specific]", tag->cache);
156 return tag->cache;
157
158no_preference:
159 /* netfs has no preference - just select first cache */
160 cache = list_entry(fscache_cache_list.next,
161 struct fscache_cache, link);
162 _leave(" = %p [first]", cache);
163 return cache;
164}
165
166/**
167 * fscache_init_cache - Initialise a cache record
168 * @cache: The cache record to be initialised
169 * @ops: The cache operations to be installed in that record
170 * @idfmt: Format string to define identifier
171 * @...: sprintf-style arguments
172 *
173 * Initialise a record of a cache and fill in the name.
174 *
175 * See Documentation/filesystems/caching/backend-api.rst for a complete
176 * description.
177 */
178void fscache_init_cache(struct fscache_cache *cache,
179 const struct fscache_cache_ops *ops,
180 const char *idfmt,
181 ...)
182{
183 va_list va;
184
185 memset(cache, 0, sizeof(*cache));
186
187 cache->ops = ops;
188
189 va_start(va, idfmt);
190 vsnprintf(cache->identifier, sizeof(cache->identifier), idfmt, va);
191 va_end(va);
192
193 INIT_WORK(&cache->op_gc, fscache_operation_gc);
194 INIT_LIST_HEAD(&cache->link);
195 INIT_LIST_HEAD(&cache->object_list);
196 INIT_LIST_HEAD(&cache->op_gc_list);
197 spin_lock_init(&cache->object_list_lock);
198 spin_lock_init(&cache->op_gc_list_lock);
199}
200EXPORT_SYMBOL(fscache_init_cache);
201
202/**
203 * fscache_add_cache - Declare a cache as being open for business
204 * @cache: The record describing the cache
205 * @ifsdef: The record of the cache object describing the top-level index
206 * @tagname: The tag describing this cache
207 *
208 * Add a cache to the system, making it available for netfs's to use.
209 *
210 * See Documentation/filesystems/caching/backend-api.rst for a complete
211 * description.
212 */
213int fscache_add_cache(struct fscache_cache *cache,
214 struct fscache_object *ifsdef,
215 const char *tagname)
216{
217 struct fscache_cache_tag *tag;
218
219 ASSERTCMP(ifsdef->cookie, ==, &fscache_fsdef_index);
220 BUG_ON(!cache->ops);
221 BUG_ON(!ifsdef);
222
223 cache->flags = 0;
224 ifsdef->event_mask =
225 ((1 << NR_FSCACHE_OBJECT_EVENTS) - 1) &
226 ~(1 << FSCACHE_OBJECT_EV_CLEARED);
227 __set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &ifsdef->flags);
228
229 if (!tagname)
230 tagname = cache->identifier;
231
232 BUG_ON(!tagname[0]);
233
234 _enter("{%s.%s},,%s", cache->ops->name, cache->identifier, tagname);
235
236 /* we use the cache tag to uniquely identify caches */
237 tag = __fscache_lookup_cache_tag(tagname);
238 if (IS_ERR(tag))
239 goto nomem;
240
241 if (test_and_set_bit(FSCACHE_TAG_RESERVED, &tag->flags))
242 goto tag_in_use;
243
244 cache->kobj = kobject_create_and_add(tagname, fscache_root);
245 if (!cache->kobj)
246 goto error;
247
248 ifsdef->cache = cache;
249 cache->fsdef = ifsdef;
250
251 down_write(&fscache_addremove_sem);
252
253 tag->cache = cache;
254 cache->tag = tag;
255
256 /* add the cache to the list */
257 list_add(&cache->link, &fscache_cache_list);
258
259 /* add the cache's netfs definition index object to the cache's
260 * list */
261 spin_lock(&cache->object_list_lock);
262 list_add_tail(&ifsdef->cache_link, &cache->object_list);
263 spin_unlock(&cache->object_list_lock);
264 fscache_objlist_add(ifsdef);
265
266 /* add the cache's netfs definition index object to the top level index
267 * cookie as a known backing object */
268 spin_lock(&fscache_fsdef_index.lock);
269
270 hlist_add_head(&ifsdef->cookie_link,
271 &fscache_fsdef_index.backing_objects);
272
273 atomic_inc(&fscache_fsdef_index.usage);
274
275 /* done */
276 spin_unlock(&fscache_fsdef_index.lock);
277 up_write(&fscache_addremove_sem);
278
279 pr_notice("Cache \"%s\" added (type %s)\n",
280 cache->tag->name, cache->ops->name);
281 kobject_uevent(cache->kobj, KOBJ_ADD);
282
283 _leave(" = 0 [%s]", cache->identifier);
284 return 0;
285
286tag_in_use:
287 pr_err("Cache tag '%s' already in use\n", tagname);
288 __fscache_release_cache_tag(tag);
289 _leave(" = -EXIST");
290 return -EEXIST;
291
292error:
293 __fscache_release_cache_tag(tag);
294 _leave(" = -EINVAL");
295 return -EINVAL;
296
297nomem:
298 _leave(" = -ENOMEM");
299 return -ENOMEM;
300}
301EXPORT_SYMBOL(fscache_add_cache);
302
303/**
304 * fscache_io_error - Note a cache I/O error
305 * @cache: The record describing the cache
306 *
307 * Note that an I/O error occurred in a cache and that it should no longer be
308 * used for anything. This also reports the error into the kernel log.
309 *
310 * See Documentation/filesystems/caching/backend-api.rst for a complete
311 * description.
312 */
313void fscache_io_error(struct fscache_cache *cache)
314{
315 if (!test_and_set_bit(FSCACHE_IOERROR, &cache->flags))
316 pr_err("Cache '%s' stopped due to I/O error\n",
317 cache->ops->name);
318}
319EXPORT_SYMBOL(fscache_io_error);
320
321/*
322 * request withdrawal of all the objects in a cache
323 * - all the objects being withdrawn are moved onto the supplied list
324 */
325static void fscache_withdraw_all_objects(struct fscache_cache *cache,
326 struct list_head *dying_objects)
327{
328 struct fscache_object *object;
329
330 while (!list_empty(&cache->object_list)) {
331 spin_lock(&cache->object_list_lock);
332
333 if (!list_empty(&cache->object_list)) {
334 object = list_entry(cache->object_list.next,
335 struct fscache_object, cache_link);
336 list_move_tail(&object->cache_link, dying_objects);
337
338 _debug("withdraw %p", object->cookie);
339
340 /* This must be done under object_list_lock to prevent
341 * a race with fscache_drop_object().
342 */
343 fscache_raise_event(object, FSCACHE_OBJECT_EV_KILL);
344 }
345
346 spin_unlock(&cache->object_list_lock);
347 cond_resched();
348 }
349}
350
351/**
352 * fscache_withdraw_cache - Withdraw a cache from the active service
353 * @cache: The record describing the cache
354 *
355 * Withdraw a cache from service, unbinding all its cache objects from the
356 * netfs cookies they're currently representing.
357 *
358 * See Documentation/filesystems/caching/backend-api.rst for a complete
359 * description.
360 */
361void fscache_withdraw_cache(struct fscache_cache *cache)
362{
363 LIST_HEAD(dying_objects);
364
365 _enter("");
366
367 pr_notice("Withdrawing cache \"%s\"\n",
368 cache->tag->name);
369
370 /* make the cache unavailable for cookie acquisition */
371 if (test_and_set_bit(FSCACHE_CACHE_WITHDRAWN, &cache->flags))
372 BUG();
373
374 down_write(&fscache_addremove_sem);
375 list_del_init(&cache->link);
376 cache->tag->cache = NULL;
377 up_write(&fscache_addremove_sem);
378
379 /* make sure all pages pinned by operations on behalf of the netfs are
380 * written to disk */
381 fscache_stat(&fscache_n_cop_sync_cache);
382 cache->ops->sync_cache(cache);
383 fscache_stat_d(&fscache_n_cop_sync_cache);
384
385 /* dissociate all the netfs pages backed by this cache from the block
386 * mappings in the cache */
387 fscache_stat(&fscache_n_cop_dissociate_pages);
388 cache->ops->dissociate_pages(cache);
389 fscache_stat_d(&fscache_n_cop_dissociate_pages);
390
391 /* we now have to destroy all the active objects pertaining to this
392 * cache - which we do by passing them off to thread pool to be
393 * disposed of */
394 _debug("destroy");
395
396 fscache_withdraw_all_objects(cache, &dying_objects);
397
398 /* wait for all extant objects to finish their outstanding operations
399 * and go away */
400 _debug("wait for finish");
401 wait_event(fscache_cache_cleared_wq,
402 atomic_read(&cache->object_count) == 0);
403 _debug("wait for clearance");
404 wait_event(fscache_cache_cleared_wq,
405 list_empty(&cache->object_list));
406 _debug("cleared");
407 ASSERT(list_empty(&dying_objects));
408
409 kobject_put(cache->kobj);
410
411 clear_bit(FSCACHE_TAG_RESERVED, &cache->tag->flags);
412 fscache_release_cache_tag(cache->tag);
413 cache->tag = NULL;
414
415 _leave("");
416}
417EXPORT_SYMBOL(fscache_withdraw_cache);