blob: a25444ab2baf8562a2a0d73da30c7ba4cfd41d39 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/fs/mbcache.c
3 * (C) 2001-2002 Andreas Gruenbacher, <a.gruenbacher@computer.org>
4 */
5
6/*
7 * Filesystem Meta Information Block Cache (mbcache)
8 *
9 * The mbcache caches blocks of block devices that need to be located
10 * by their device/block number, as well as by other criteria (such
11 * as the block's contents).
12 *
13 * There can only be one cache entry in a cache per device and block number.
14 * Additional indexes need not be unique in this sense. The number of
15 * additional indexes (=other criteria) can be hardwired at compile time
16 * or specified at cache create time.
17 *
18 * Each cache entry is of fixed size. An entry may be `valid' or `invalid'
19 * in the cache. A valid entry is in the main hash tables of the cache,
20 * and may also be in the lru list. An invalid entry is not in any hashes
21 * or lists.
22 *
23 * A valid cache entry is only in the lru list if no handles refer to it.
24 * Invalid cache entries will be freed when the last handle to the cache
25 * entry is released. Entries that cannot be freed immediately are put
26 * back on the lru list.
27 */
28
29#include <linux/kernel.h>
30#include <linux/module.h>
31
32#include <linux/hash.h>
33#include <linux/fs.h>
34#include <linux/mm.h>
35#include <linux/slab.h>
36#include <linux/sched.h>
37#include <linux/init.h>
38#include <linux/mbcache.h>
39
40
41#ifdef MB_CACHE_DEBUG
42# define mb_debug(f...) do { \
43 printk(KERN_DEBUG f); \
44 printk("\n"); \
45 } while (0)
46#define mb_assert(c) do { if (!(c)) \
47 printk(KERN_ERR "assertion " #c " failed\n"); \
48 } while(0)
49#else
50# define mb_debug(f...) do { } while(0)
51# define mb_assert(c) do { } while(0)
52#endif
53#define mb_error(f...) do { \
54 printk(KERN_ERR f); \
55 printk("\n"); \
56 } while(0)
57
58#define MB_CACHE_WRITER ((unsigned short)~0U >> 1)
59
Adrian Bunk75c96f82005-05-05 16:16:09 -070060static DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -070061
62MODULE_AUTHOR("Andreas Gruenbacher <a.gruenbacher@computer.org>");
63MODULE_DESCRIPTION("Meta block cache (for extended attributes)");
64MODULE_LICENSE("GPL");
65
66EXPORT_SYMBOL(mb_cache_create);
67EXPORT_SYMBOL(mb_cache_shrink);
68EXPORT_SYMBOL(mb_cache_destroy);
69EXPORT_SYMBOL(mb_cache_entry_alloc);
70EXPORT_SYMBOL(mb_cache_entry_insert);
71EXPORT_SYMBOL(mb_cache_entry_release);
72EXPORT_SYMBOL(mb_cache_entry_free);
73EXPORT_SYMBOL(mb_cache_entry_get);
74#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
75EXPORT_SYMBOL(mb_cache_entry_find_first);
76EXPORT_SYMBOL(mb_cache_entry_find_next);
77#endif
78
Linus Torvalds1da177e2005-04-16 15:20:36 -070079/*
80 * Global data: list of all mbcache's, lru list, and a spinlock for
81 * accessing cache data structures on SMP machines. The lru list is
82 * global across all mbcaches.
83 */
84
85static LIST_HEAD(mb_cache_list);
86static LIST_HEAD(mb_cache_lru_list);
87static DEFINE_SPINLOCK(mb_cache_spinlock);
Linus Torvalds1da177e2005-04-16 15:20:36 -070088
Linus Torvalds1da177e2005-04-16 15:20:36 -070089/*
90 * What the mbcache registers as to get shrunk dynamically.
91 */
92
Dave Chinner7f8275d2010-07-19 14:56:17 +100093static int mb_cache_shrink_fn(struct shrinker *shrink, int nr_to_scan, gfp_t gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -070094
Rusty Russell8e1f9362007-07-17 04:03:17 -070095static struct shrinker mb_cache_shrinker = {
96 .shrink = mb_cache_shrink_fn,
97 .seeks = DEFAULT_SEEKS,
98};
Linus Torvalds1da177e2005-04-16 15:20:36 -070099
100static inline int
101__mb_cache_entry_is_hashed(struct mb_cache_entry *ce)
102{
103 return !list_empty(&ce->e_block_list);
104}
105
106
Arjan van de Ven858119e2006-01-14 13:20:43 -0800107static void
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108__mb_cache_entry_unhash(struct mb_cache_entry *ce)
109{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110 if (__mb_cache_entry_is_hashed(ce)) {
111 list_del_init(&ce->e_block_list);
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200112 list_del(&ce->e_index.o_list);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 }
114}
115
116
Arjan van de Ven858119e2006-01-14 13:20:43 -0800117static void
Al Viro27496a82005-10-21 03:20:48 -0400118__mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119{
120 struct mb_cache *cache = ce->e_cache;
121
122 mb_assert(!(ce->e_used || ce->e_queued));
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200123 kmem_cache_free(cache->c_entry_cache, ce);
124 atomic_dec(&cache->c_entry_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700125}
126
127
Arjan van de Ven858119e2006-01-14 13:20:43 -0800128static void
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129__mb_cache_entry_release_unlock(struct mb_cache_entry *ce)
Josh Triplett58f555e2006-09-29 01:59:24 -0700130 __releases(mb_cache_spinlock)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700131{
132 /* Wake up all processes queuing for this cache entry. */
133 if (ce->e_queued)
134 wake_up_all(&mb_cache_queue);
135 if (ce->e_used >= MB_CACHE_WRITER)
136 ce->e_used -= MB_CACHE_WRITER;
137 ce->e_used--;
138 if (!(ce->e_used || ce->e_queued)) {
139 if (!__mb_cache_entry_is_hashed(ce))
140 goto forget;
141 mb_assert(list_empty(&ce->e_lru_list));
142 list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
143 }
144 spin_unlock(&mb_cache_spinlock);
145 return;
146forget:
147 spin_unlock(&mb_cache_spinlock);
148 __mb_cache_entry_forget(ce, GFP_KERNEL);
149}
150
151
152/*
153 * mb_cache_shrink_fn() memory pressure callback
154 *
155 * This function is called by the kernel memory management when memory
156 * gets low.
157 *
Dave Chinner7f8275d2010-07-19 14:56:17 +1000158 * @shrink: (ignored)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 * @nr_to_scan: Number of objects to scan
160 * @gfp_mask: (ignored)
161 *
162 * Returns the number of objects which are present in the cache.
163 */
164static int
Dave Chinner7f8275d2010-07-19 14:56:17 +1000165mb_cache_shrink_fn(struct shrinker *shrink, int nr_to_scan, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166{
167 LIST_HEAD(free_list);
Andreas Gruenbachere566d482010-07-21 19:44:45 +0200168 struct mb_cache *cache;
169 struct mb_cache_entry *entry, *tmp;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700170 int count = 0;
171
Linus Torvalds1da177e2005-04-16 15:20:36 -0700172 mb_debug("trying to free %d entries", nr_to_scan);
Andreas Gruenbachere566d482010-07-21 19:44:45 +0200173 spin_lock(&mb_cache_spinlock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174 while (nr_to_scan-- && !list_empty(&mb_cache_lru_list)) {
175 struct mb_cache_entry *ce =
176 list_entry(mb_cache_lru_list.next,
177 struct mb_cache_entry, e_lru_list);
178 list_move_tail(&ce->e_lru_list, &free_list);
179 __mb_cache_entry_unhash(ce);
180 }
Andreas Gruenbachere566d482010-07-21 19:44:45 +0200181 list_for_each_entry(cache, &mb_cache_list, c_cache_list) {
182 mb_debug("cache %s (%d)", cache->c_name,
183 atomic_read(&cache->c_entry_count));
184 count += atomic_read(&cache->c_entry_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185 }
Andreas Gruenbachere566d482010-07-21 19:44:45 +0200186 spin_unlock(&mb_cache_spinlock);
187 list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) {
188 __mb_cache_entry_forget(entry, gfp_mask);
189 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700190 return (count / 100) * sysctl_vfs_cache_pressure;
191}
192
193
194/*
195 * mb_cache_create() create a new cache
196 *
197 * All entries in one cache are equal size. Cache entries may be from
198 * multiple devices. If this is the first mbcache created, registers
199 * the cache with kernel memory management. Returns NULL if no more
200 * memory was available.
201 *
202 * @name: name of the cache (informal)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700203 * @bucket_bits: log2(number of hash buckets)
204 */
205struct mb_cache *
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200206mb_cache_create(const char *name, int bucket_bits)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207{
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200208 int n, bucket_count = 1 << bucket_bits;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700209 struct mb_cache *cache = NULL;
210
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200211 cache = kmalloc(sizeof(struct mb_cache), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212 if (!cache)
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200213 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214 cache->c_name = name;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700215 atomic_set(&cache->c_entry_count, 0);
216 cache->c_bucket_bits = bucket_bits;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700217 cache->c_block_hash = kmalloc(bucket_count * sizeof(struct list_head),
218 GFP_KERNEL);
219 if (!cache->c_block_hash)
220 goto fail;
221 for (n=0; n<bucket_count; n++)
222 INIT_LIST_HEAD(&cache->c_block_hash[n]);
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200223 cache->c_index_hash = kmalloc(bucket_count * sizeof(struct list_head),
224 GFP_KERNEL);
225 if (!cache->c_index_hash)
226 goto fail;
227 for (n=0; n<bucket_count; n++)
228 INIT_LIST_HEAD(&cache->c_index_hash[n]);
229 cache->c_entry_cache = kmem_cache_create(name,
230 sizeof(struct mb_cache_entry), 0,
Paul Mundt20c2df82007-07-20 10:11:58 +0900231 SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700232 if (!cache->c_entry_cache)
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200233 goto fail2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700234
Andreas Gruenbacher3a48ee82010-08-16 19:05:23 +0200235 /*
236 * Set an upper limit on the number of cache entries so that the hash
237 * chains won't grow too long.
238 */
239 cache->c_max_entries = bucket_count << 4;
240
Linus Torvalds1da177e2005-04-16 15:20:36 -0700241 spin_lock(&mb_cache_spinlock);
242 list_add(&cache->c_cache_list, &mb_cache_list);
243 spin_unlock(&mb_cache_spinlock);
244 return cache;
245
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200246fail2:
247 kfree(cache->c_index_hash);
248
Linus Torvalds1da177e2005-04-16 15:20:36 -0700249fail:
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200250 kfree(cache->c_block_hash);
251 kfree(cache);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700252 return NULL;
253}
254
255
256/*
257 * mb_cache_shrink()
258 *
Alexey Dobriyan7f927fc2006-03-28 01:56:53 -0800259 * Removes all cache entries of a device from the cache. All cache entries
Linus Torvalds1da177e2005-04-16 15:20:36 -0700260 * currently in use cannot be freed, and thus remain in the cache. All others
261 * are freed.
262 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700263 * @bdev: which device's cache entries to shrink
264 */
265void
Andreas Gruenbacher8c52ab42005-07-27 11:45:15 -0700266mb_cache_shrink(struct block_device *bdev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267{
268 LIST_HEAD(free_list);
269 struct list_head *l, *ltmp;
270
271 spin_lock(&mb_cache_spinlock);
272 list_for_each_safe(l, ltmp, &mb_cache_lru_list) {
273 struct mb_cache_entry *ce =
274 list_entry(l, struct mb_cache_entry, e_lru_list);
275 if (ce->e_bdev == bdev) {
276 list_move_tail(&ce->e_lru_list, &free_list);
277 __mb_cache_entry_unhash(ce);
278 }
279 }
280 spin_unlock(&mb_cache_spinlock);
281 list_for_each_safe(l, ltmp, &free_list) {
282 __mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
283 e_lru_list), GFP_KERNEL);
284 }
285}
286
287
288/*
289 * mb_cache_destroy()
290 *
291 * Shrinks the cache to its minimum possible size (hopefully 0 entries),
292 * and then destroys it. If this was the last mbcache, un-registers the
293 * mbcache from kernel memory management.
294 */
295void
296mb_cache_destroy(struct mb_cache *cache)
297{
298 LIST_HEAD(free_list);
299 struct list_head *l, *ltmp;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700300
301 spin_lock(&mb_cache_spinlock);
302 list_for_each_safe(l, ltmp, &mb_cache_lru_list) {
303 struct mb_cache_entry *ce =
304 list_entry(l, struct mb_cache_entry, e_lru_list);
305 if (ce->e_cache == cache) {
306 list_move_tail(&ce->e_lru_list, &free_list);
307 __mb_cache_entry_unhash(ce);
308 }
309 }
310 list_del(&cache->c_cache_list);
311 spin_unlock(&mb_cache_spinlock);
312
313 list_for_each_safe(l, ltmp, &free_list) {
314 __mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
315 e_lru_list), GFP_KERNEL);
316 }
317
318 if (atomic_read(&cache->c_entry_count) > 0) {
319 mb_error("cache %s: %d orphaned entries",
320 cache->c_name,
321 atomic_read(&cache->c_entry_count));
322 }
323
324 kmem_cache_destroy(cache->c_entry_cache);
325
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200326 kfree(cache->c_index_hash);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700327 kfree(cache->c_block_hash);
328 kfree(cache);
329}
330
Linus Torvalds1da177e2005-04-16 15:20:36 -0700331/*
332 * mb_cache_entry_alloc()
333 *
334 * Allocates a new cache entry. The new entry will not be valid initially,
335 * and thus cannot be looked up yet. It should be filled with data, and
336 * then inserted into the cache using mb_cache_entry_insert(). Returns NULL
337 * if no more memory was available.
338 */
339struct mb_cache_entry *
Jan Kara335e92e2008-04-15 14:34:43 -0700340mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341{
Andreas Gruenbacher3a48ee82010-08-16 19:05:23 +0200342 struct mb_cache_entry *ce = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700343
Andreas Gruenbacher3a48ee82010-08-16 19:05:23 +0200344 if (atomic_read(&cache->c_entry_count) >= cache->c_max_entries) {
345 spin_lock(&mb_cache_spinlock);
346 if (!list_empty(&mb_cache_lru_list)) {
347 ce = list_entry(mb_cache_lru_list.next,
348 struct mb_cache_entry, e_lru_list);
349 list_del_init(&ce->e_lru_list);
350 __mb_cache_entry_unhash(ce);
351 }
352 spin_unlock(&mb_cache_spinlock);
353 }
354 if (!ce) {
355 ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags);
356 if (!ce)
357 return NULL;
Ram Guptaf9e83482007-10-25 10:03:28 -0500358 atomic_inc(&cache->c_entry_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700359 INIT_LIST_HEAD(&ce->e_lru_list);
360 INIT_LIST_HEAD(&ce->e_block_list);
361 ce->e_cache = cache;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700362 ce->e_queued = 0;
363 }
Andreas Gruenbacher3a48ee82010-08-16 19:05:23 +0200364 ce->e_used = 1 + MB_CACHE_WRITER;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700365 return ce;
366}
367
368
369/*
370 * mb_cache_entry_insert()
371 *
372 * Inserts an entry that was allocated using mb_cache_entry_alloc() into
373 * the cache. After this, the cache entry can be looked up, but is not yet
374 * in the lru list as the caller still holds a handle to it. Returns 0 on
375 * success, or -EBUSY if a cache entry for that device + inode exists
376 * already (this may happen after a failed lookup, but when another process
377 * has inserted the same cache entry in the meantime).
378 *
379 * @bdev: device the cache entry belongs to
380 * @block: block number
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200381 * @key: lookup key
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382 */
383int
384mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200385 sector_t block, unsigned int key)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386{
387 struct mb_cache *cache = ce->e_cache;
388 unsigned int bucket;
389 struct list_head *l;
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200390 int error = -EBUSY;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700391
392 bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
393 cache->c_bucket_bits);
394 spin_lock(&mb_cache_spinlock);
395 list_for_each_prev(l, &cache->c_block_hash[bucket]) {
396 struct mb_cache_entry *ce =
397 list_entry(l, struct mb_cache_entry, e_block_list);
398 if (ce->e_bdev == bdev && ce->e_block == block)
399 goto out;
400 }
401 __mb_cache_entry_unhash(ce);
402 ce->e_bdev = bdev;
403 ce->e_block = block;
404 list_add(&ce->e_block_list, &cache->c_block_hash[bucket]);
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200405 ce->e_index.o_key = key;
406 bucket = hash_long(key, cache->c_bucket_bits);
407 list_add(&ce->e_index.o_list, &cache->c_index_hash[bucket]);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408 error = 0;
409out:
410 spin_unlock(&mb_cache_spinlock);
411 return error;
412}
413
414
415/*
416 * mb_cache_entry_release()
417 *
418 * Release a handle to a cache entry. When the last handle to a cache entry
419 * is released it is either freed (if it is invalid) or otherwise inserted
420 * in to the lru list.
421 */
422void
423mb_cache_entry_release(struct mb_cache_entry *ce)
424{
425 spin_lock(&mb_cache_spinlock);
426 __mb_cache_entry_release_unlock(ce);
427}
428
429
430/*
431 * mb_cache_entry_free()
432 *
433 * This is equivalent to the sequence mb_cache_entry_takeout() --
434 * mb_cache_entry_release().
435 */
436void
437mb_cache_entry_free(struct mb_cache_entry *ce)
438{
439 spin_lock(&mb_cache_spinlock);
440 mb_assert(list_empty(&ce->e_lru_list));
441 __mb_cache_entry_unhash(ce);
442 __mb_cache_entry_release_unlock(ce);
443}
444
445
446/*
447 * mb_cache_entry_get()
448 *
449 * Get a cache entry by device / block number. (There can only be one entry
450 * in the cache per device and block.) Returns NULL if no such cache entry
451 * exists. The returned cache entry is locked for exclusive access ("single
452 * writer").
453 */
454struct mb_cache_entry *
455mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
456 sector_t block)
457{
458 unsigned int bucket;
459 struct list_head *l;
460 struct mb_cache_entry *ce;
461
462 bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
463 cache->c_bucket_bits);
464 spin_lock(&mb_cache_spinlock);
465 list_for_each(l, &cache->c_block_hash[bucket]) {
466 ce = list_entry(l, struct mb_cache_entry, e_block_list);
467 if (ce->e_bdev == bdev && ce->e_block == block) {
468 DEFINE_WAIT(wait);
469
470 if (!list_empty(&ce->e_lru_list))
471 list_del_init(&ce->e_lru_list);
472
473 while (ce->e_used > 0) {
474 ce->e_queued++;
475 prepare_to_wait(&mb_cache_queue, &wait,
476 TASK_UNINTERRUPTIBLE);
477 spin_unlock(&mb_cache_spinlock);
478 schedule();
479 spin_lock(&mb_cache_spinlock);
480 ce->e_queued--;
481 }
482 finish_wait(&mb_cache_queue, &wait);
483 ce->e_used += 1 + MB_CACHE_WRITER;
484
485 if (!__mb_cache_entry_is_hashed(ce)) {
486 __mb_cache_entry_release_unlock(ce);
487 return NULL;
488 }
489 goto cleanup;
490 }
491 }
492 ce = NULL;
493
494cleanup:
495 spin_unlock(&mb_cache_spinlock);
496 return ce;
497}
498
499#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
500
501static struct mb_cache_entry *
502__mb_cache_entry_find(struct list_head *l, struct list_head *head,
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200503 struct block_device *bdev, unsigned int key)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700504{
505 while (l != head) {
506 struct mb_cache_entry *ce =
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200507 list_entry(l, struct mb_cache_entry, e_index.o_list);
508 if (ce->e_bdev == bdev && ce->e_index.o_key == key) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509 DEFINE_WAIT(wait);
510
511 if (!list_empty(&ce->e_lru_list))
512 list_del_init(&ce->e_lru_list);
513
514 /* Incrementing before holding the lock gives readers
515 priority over writers. */
516 ce->e_used++;
517 while (ce->e_used >= MB_CACHE_WRITER) {
518 ce->e_queued++;
519 prepare_to_wait(&mb_cache_queue, &wait,
520 TASK_UNINTERRUPTIBLE);
521 spin_unlock(&mb_cache_spinlock);
522 schedule();
523 spin_lock(&mb_cache_spinlock);
524 ce->e_queued--;
525 }
526 finish_wait(&mb_cache_queue, &wait);
527
528 if (!__mb_cache_entry_is_hashed(ce)) {
529 __mb_cache_entry_release_unlock(ce);
530 spin_lock(&mb_cache_spinlock);
531 return ERR_PTR(-EAGAIN);
532 }
533 return ce;
534 }
535 l = l->next;
536 }
537 return NULL;
538}
539
540
541/*
542 * mb_cache_entry_find_first()
543 *
544 * Find the first cache entry on a given device with a certain key in
545 * an additional index. Additonal matches can be found with
546 * mb_cache_entry_find_next(). Returns NULL if no match was found. The
547 * returned cache entry is locked for shared access ("multiple readers").
548 *
549 * @cache: the cache to search
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550 * @bdev: the device the cache entry should belong to
551 * @key: the key in the index
552 */
553struct mb_cache_entry *
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200554mb_cache_entry_find_first(struct mb_cache *cache, struct block_device *bdev,
555 unsigned int key)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700556{
557 unsigned int bucket = hash_long(key, cache->c_bucket_bits);
558 struct list_head *l;
559 struct mb_cache_entry *ce;
560
Linus Torvalds1da177e2005-04-16 15:20:36 -0700561 spin_lock(&mb_cache_spinlock);
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200562 l = cache->c_index_hash[bucket].next;
563 ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700564 spin_unlock(&mb_cache_spinlock);
565 return ce;
566}
567
568
569/*
570 * mb_cache_entry_find_next()
571 *
572 * Find the next cache entry on a given device with a certain key in an
573 * additional index. Returns NULL if no match could be found. The previous
574 * entry is atomatically released, so that mb_cache_entry_find_next() can
575 * be called like this:
576 *
577 * entry = mb_cache_entry_find_first();
578 * while (entry) {
579 * ...
580 * entry = mb_cache_entry_find_next(entry, ...);
581 * }
582 *
583 * @prev: The previous match
Linus Torvalds1da177e2005-04-16 15:20:36 -0700584 * @bdev: the device the cache entry should belong to
585 * @key: the key in the index
586 */
587struct mb_cache_entry *
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200588mb_cache_entry_find_next(struct mb_cache_entry *prev,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589 struct block_device *bdev, unsigned int key)
590{
591 struct mb_cache *cache = prev->e_cache;
592 unsigned int bucket = hash_long(key, cache->c_bucket_bits);
593 struct list_head *l;
594 struct mb_cache_entry *ce;
595
Linus Torvalds1da177e2005-04-16 15:20:36 -0700596 spin_lock(&mb_cache_spinlock);
Andreas Gruenbacher2aec7c52010-07-19 18:19:41 +0200597 l = prev->e_index.o_list.next;
598 ce = __mb_cache_entry_find(l, &cache->c_index_hash[bucket], bdev, key);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700599 __mb_cache_entry_release_unlock(prev);
600 return ce;
601}
602
603#endif /* !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) */
604
605static int __init init_mbcache(void)
606{
Rusty Russell8e1f9362007-07-17 04:03:17 -0700607 register_shrinker(&mb_cache_shrinker);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700608 return 0;
609}
610
611static void __exit exit_mbcache(void)
612{
Rusty Russell8e1f9362007-07-17 04:03:17 -0700613 unregister_shrinker(&mb_cache_shrinker);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700614}
615
616module_init(init_mbcache)
617module_exit(exit_mbcache)
618