blob: e28f21b95344378aa09ce95771481711870be902 [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
79struct mb_cache {
80 struct list_head c_cache_list;
81 const char *c_name;
82 struct mb_cache_op c_op;
83 atomic_t c_entry_count;
84 int c_bucket_bits;
85#ifndef MB_CACHE_INDEXES_COUNT
86 int c_indexes_count;
87#endif
Christoph Lametere18b8902006-12-06 20:33:20 -080088 struct kmem_cache *c_entry_cache;
Linus Torvalds1da177e2005-04-16 15:20:36 -070089 struct list_head *c_block_hash;
90 struct list_head *c_indexes_hash[0];
91};
92
93
94/*
95 * Global data: list of all mbcache's, lru list, and a spinlock for
96 * accessing cache data structures on SMP machines. The lru list is
97 * global across all mbcaches.
98 */
99
100static LIST_HEAD(mb_cache_list);
101static LIST_HEAD(mb_cache_lru_list);
102static DEFINE_SPINLOCK(mb_cache_spinlock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103
104static inline int
105mb_cache_indexes(struct mb_cache *cache)
106{
107#ifdef MB_CACHE_INDEXES_COUNT
108 return MB_CACHE_INDEXES_COUNT;
109#else
110 return cache->c_indexes_count;
111#endif
112}
113
114/*
115 * What the mbcache registers as to get shrunk dynamically.
116 */
117
Dave Chinner7f8275d2010-07-19 14:56:17 +1000118static int mb_cache_shrink_fn(struct shrinker *shrink, int nr_to_scan, gfp_t gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119
Rusty Russell8e1f9362007-07-17 04:03:17 -0700120static struct shrinker mb_cache_shrinker = {
121 .shrink = mb_cache_shrink_fn,
122 .seeks = DEFAULT_SEEKS,
123};
Linus Torvalds1da177e2005-04-16 15:20:36 -0700124
125static inline int
126__mb_cache_entry_is_hashed(struct mb_cache_entry *ce)
127{
128 return !list_empty(&ce->e_block_list);
129}
130
131
Arjan van de Ven858119e2006-01-14 13:20:43 -0800132static void
Linus Torvalds1da177e2005-04-16 15:20:36 -0700133__mb_cache_entry_unhash(struct mb_cache_entry *ce)
134{
135 int n;
136
137 if (__mb_cache_entry_is_hashed(ce)) {
138 list_del_init(&ce->e_block_list);
139 for (n=0; n<mb_cache_indexes(ce->e_cache); n++)
140 list_del(&ce->e_indexes[n].o_list);
141 }
142}
143
144
Arjan van de Ven858119e2006-01-14 13:20:43 -0800145static void
Al Viro27496a82005-10-21 03:20:48 -0400146__mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147{
148 struct mb_cache *cache = ce->e_cache;
149
150 mb_assert(!(ce->e_used || ce->e_queued));
151 if (cache->c_op.free && cache->c_op.free(ce, gfp_mask)) {
152 /* free failed -- put back on the lru list
153 for freeing later. */
154 spin_lock(&mb_cache_spinlock);
155 list_add(&ce->e_lru_list, &mb_cache_lru_list);
156 spin_unlock(&mb_cache_spinlock);
157 } else {
158 kmem_cache_free(cache->c_entry_cache, ce);
159 atomic_dec(&cache->c_entry_count);
160 }
161}
162
163
Arjan van de Ven858119e2006-01-14 13:20:43 -0800164static void
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165__mb_cache_entry_release_unlock(struct mb_cache_entry *ce)
Josh Triplett58f555e2006-09-29 01:59:24 -0700166 __releases(mb_cache_spinlock)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700167{
168 /* Wake up all processes queuing for this cache entry. */
169 if (ce->e_queued)
170 wake_up_all(&mb_cache_queue);
171 if (ce->e_used >= MB_CACHE_WRITER)
172 ce->e_used -= MB_CACHE_WRITER;
173 ce->e_used--;
174 if (!(ce->e_used || ce->e_queued)) {
175 if (!__mb_cache_entry_is_hashed(ce))
176 goto forget;
177 mb_assert(list_empty(&ce->e_lru_list));
178 list_add_tail(&ce->e_lru_list, &mb_cache_lru_list);
179 }
180 spin_unlock(&mb_cache_spinlock);
181 return;
182forget:
183 spin_unlock(&mb_cache_spinlock);
184 __mb_cache_entry_forget(ce, GFP_KERNEL);
185}
186
187
188/*
189 * mb_cache_shrink_fn() memory pressure callback
190 *
191 * This function is called by the kernel memory management when memory
192 * gets low.
193 *
Dave Chinner7f8275d2010-07-19 14:56:17 +1000194 * @shrink: (ignored)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700195 * @nr_to_scan: Number of objects to scan
196 * @gfp_mask: (ignored)
197 *
198 * Returns the number of objects which are present in the cache.
199 */
200static int
Dave Chinner7f8275d2010-07-19 14:56:17 +1000201mb_cache_shrink_fn(struct shrinker *shrink, int nr_to_scan, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202{
203 LIST_HEAD(free_list);
204 struct list_head *l, *ltmp;
205 int count = 0;
206
207 spin_lock(&mb_cache_spinlock);
208 list_for_each(l, &mb_cache_list) {
209 struct mb_cache *cache =
210 list_entry(l, struct mb_cache, c_cache_list);
211 mb_debug("cache %s (%d)", cache->c_name,
212 atomic_read(&cache->c_entry_count));
213 count += atomic_read(&cache->c_entry_count);
214 }
215 mb_debug("trying to free %d entries", nr_to_scan);
216 if (nr_to_scan == 0) {
217 spin_unlock(&mb_cache_spinlock);
218 goto out;
219 }
220 while (nr_to_scan-- && !list_empty(&mb_cache_lru_list)) {
221 struct mb_cache_entry *ce =
222 list_entry(mb_cache_lru_list.next,
223 struct mb_cache_entry, e_lru_list);
224 list_move_tail(&ce->e_lru_list, &free_list);
225 __mb_cache_entry_unhash(ce);
226 }
227 spin_unlock(&mb_cache_spinlock);
228 list_for_each_safe(l, ltmp, &free_list) {
229 __mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
230 e_lru_list), gfp_mask);
231 }
232out:
233 return (count / 100) * sysctl_vfs_cache_pressure;
234}
235
236
237/*
238 * mb_cache_create() create a new cache
239 *
240 * All entries in one cache are equal size. Cache entries may be from
241 * multiple devices. If this is the first mbcache created, registers
242 * the cache with kernel memory management. Returns NULL if no more
243 * memory was available.
244 *
245 * @name: name of the cache (informal)
246 * @cache_op: contains the callback called when freeing a cache entry
247 * @entry_size: The size of a cache entry, including
248 * struct mb_cache_entry
249 * @indexes_count: number of additional indexes in the cache. Must equal
250 * MB_CACHE_INDEXES_COUNT if the number of indexes is
251 * hardwired.
252 * @bucket_bits: log2(number of hash buckets)
253 */
254struct mb_cache *
255mb_cache_create(const char *name, struct mb_cache_op *cache_op,
256 size_t entry_size, int indexes_count, int bucket_bits)
257{
258 int m=0, n, bucket_count = 1 << bucket_bits;
259 struct mb_cache *cache = NULL;
260
261 if(entry_size < sizeof(struct mb_cache_entry) +
262 indexes_count * sizeof(((struct mb_cache_entry *) 0)->e_indexes[0]))
263 return NULL;
264
265 cache = kmalloc(sizeof(struct mb_cache) +
266 indexes_count * sizeof(struct list_head), GFP_KERNEL);
267 if (!cache)
268 goto fail;
269 cache->c_name = name;
270 cache->c_op.free = NULL;
271 if (cache_op)
272 cache->c_op.free = cache_op->free;
273 atomic_set(&cache->c_entry_count, 0);
274 cache->c_bucket_bits = bucket_bits;
275#ifdef MB_CACHE_INDEXES_COUNT
276 mb_assert(indexes_count == MB_CACHE_INDEXES_COUNT);
277#else
278 cache->c_indexes_count = indexes_count;
279#endif
280 cache->c_block_hash = kmalloc(bucket_count * sizeof(struct list_head),
281 GFP_KERNEL);
282 if (!cache->c_block_hash)
283 goto fail;
284 for (n=0; n<bucket_count; n++)
285 INIT_LIST_HEAD(&cache->c_block_hash[n]);
286 for (m=0; m<indexes_count; m++) {
287 cache->c_indexes_hash[m] = kmalloc(bucket_count *
288 sizeof(struct list_head),
289 GFP_KERNEL);
290 if (!cache->c_indexes_hash[m])
291 goto fail;
292 for (n=0; n<bucket_count; n++)
293 INIT_LIST_HEAD(&cache->c_indexes_hash[m][n]);
294 }
295 cache->c_entry_cache = kmem_cache_create(name, entry_size, 0,
Paul Mundt20c2df82007-07-20 10:11:58 +0900296 SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700297 if (!cache->c_entry_cache)
298 goto fail;
299
300 spin_lock(&mb_cache_spinlock);
301 list_add(&cache->c_cache_list, &mb_cache_list);
302 spin_unlock(&mb_cache_spinlock);
303 return cache;
304
305fail:
306 if (cache) {
307 while (--m >= 0)
308 kfree(cache->c_indexes_hash[m]);
Jesper Juhlf99d49a2005-11-07 01:01:34 -0800309 kfree(cache->c_block_hash);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310 kfree(cache);
311 }
312 return NULL;
313}
314
315
316/*
317 * mb_cache_shrink()
318 *
Alexey Dobriyan7f927fc2006-03-28 01:56:53 -0800319 * Removes all cache entries of a device from the cache. All cache entries
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320 * currently in use cannot be freed, and thus remain in the cache. All others
321 * are freed.
322 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700323 * @bdev: which device's cache entries to shrink
324 */
325void
Andreas Gruenbacher8c52ab42005-07-27 11:45:15 -0700326mb_cache_shrink(struct block_device *bdev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700327{
328 LIST_HEAD(free_list);
329 struct list_head *l, *ltmp;
330
331 spin_lock(&mb_cache_spinlock);
332 list_for_each_safe(l, ltmp, &mb_cache_lru_list) {
333 struct mb_cache_entry *ce =
334 list_entry(l, struct mb_cache_entry, e_lru_list);
335 if (ce->e_bdev == bdev) {
336 list_move_tail(&ce->e_lru_list, &free_list);
337 __mb_cache_entry_unhash(ce);
338 }
339 }
340 spin_unlock(&mb_cache_spinlock);
341 list_for_each_safe(l, ltmp, &free_list) {
342 __mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
343 e_lru_list), GFP_KERNEL);
344 }
345}
346
347
348/*
349 * mb_cache_destroy()
350 *
351 * Shrinks the cache to its minimum possible size (hopefully 0 entries),
352 * and then destroys it. If this was the last mbcache, un-registers the
353 * mbcache from kernel memory management.
354 */
355void
356mb_cache_destroy(struct mb_cache *cache)
357{
358 LIST_HEAD(free_list);
359 struct list_head *l, *ltmp;
360 int n;
361
362 spin_lock(&mb_cache_spinlock);
363 list_for_each_safe(l, ltmp, &mb_cache_lru_list) {
364 struct mb_cache_entry *ce =
365 list_entry(l, struct mb_cache_entry, e_lru_list);
366 if (ce->e_cache == cache) {
367 list_move_tail(&ce->e_lru_list, &free_list);
368 __mb_cache_entry_unhash(ce);
369 }
370 }
371 list_del(&cache->c_cache_list);
372 spin_unlock(&mb_cache_spinlock);
373
374 list_for_each_safe(l, ltmp, &free_list) {
375 __mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
376 e_lru_list), GFP_KERNEL);
377 }
378
379 if (atomic_read(&cache->c_entry_count) > 0) {
380 mb_error("cache %s: %d orphaned entries",
381 cache->c_name,
382 atomic_read(&cache->c_entry_count));
383 }
384
385 kmem_cache_destroy(cache->c_entry_cache);
386
387 for (n=0; n < mb_cache_indexes(cache); n++)
388 kfree(cache->c_indexes_hash[n]);
389 kfree(cache->c_block_hash);
390 kfree(cache);
391}
392
393
394/*
395 * mb_cache_entry_alloc()
396 *
397 * Allocates a new cache entry. The new entry will not be valid initially,
398 * and thus cannot be looked up yet. It should be filled with data, and
399 * then inserted into the cache using mb_cache_entry_insert(). Returns NULL
400 * if no more memory was available.
401 */
402struct mb_cache_entry *
Jan Kara335e92e2008-04-15 14:34:43 -0700403mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700404{
405 struct mb_cache_entry *ce;
406
Jan Kara335e92e2008-04-15 14:34:43 -0700407 ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408 if (ce) {
Ram Guptaf9e83482007-10-25 10:03:28 -0500409 atomic_inc(&cache->c_entry_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700410 INIT_LIST_HEAD(&ce->e_lru_list);
411 INIT_LIST_HEAD(&ce->e_block_list);
412 ce->e_cache = cache;
413 ce->e_used = 1 + MB_CACHE_WRITER;
414 ce->e_queued = 0;
415 }
416 return ce;
417}
418
419
420/*
421 * mb_cache_entry_insert()
422 *
423 * Inserts an entry that was allocated using mb_cache_entry_alloc() into
424 * the cache. After this, the cache entry can be looked up, but is not yet
425 * in the lru list as the caller still holds a handle to it. Returns 0 on
426 * success, or -EBUSY if a cache entry for that device + inode exists
427 * already (this may happen after a failed lookup, but when another process
428 * has inserted the same cache entry in the meantime).
429 *
430 * @bdev: device the cache entry belongs to
431 * @block: block number
432 * @keys: array of additional keys. There must be indexes_count entries
433 * in the array (as specified when creating the cache).
434 */
435int
436mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev,
437 sector_t block, unsigned int keys[])
438{
439 struct mb_cache *cache = ce->e_cache;
440 unsigned int bucket;
441 struct list_head *l;
442 int error = -EBUSY, n;
443
444 bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
445 cache->c_bucket_bits);
446 spin_lock(&mb_cache_spinlock);
447 list_for_each_prev(l, &cache->c_block_hash[bucket]) {
448 struct mb_cache_entry *ce =
449 list_entry(l, struct mb_cache_entry, e_block_list);
450 if (ce->e_bdev == bdev && ce->e_block == block)
451 goto out;
452 }
453 __mb_cache_entry_unhash(ce);
454 ce->e_bdev = bdev;
455 ce->e_block = block;
456 list_add(&ce->e_block_list, &cache->c_block_hash[bucket]);
457 for (n=0; n<mb_cache_indexes(cache); n++) {
458 ce->e_indexes[n].o_key = keys[n];
459 bucket = hash_long(keys[n], cache->c_bucket_bits);
460 list_add(&ce->e_indexes[n].o_list,
461 &cache->c_indexes_hash[n][bucket]);
462 }
463 error = 0;
464out:
465 spin_unlock(&mb_cache_spinlock);
466 return error;
467}
468
469
470/*
471 * mb_cache_entry_release()
472 *
473 * Release a handle to a cache entry. When the last handle to a cache entry
474 * is released it is either freed (if it is invalid) or otherwise inserted
475 * in to the lru list.
476 */
477void
478mb_cache_entry_release(struct mb_cache_entry *ce)
479{
480 spin_lock(&mb_cache_spinlock);
481 __mb_cache_entry_release_unlock(ce);
482}
483
484
485/*
486 * mb_cache_entry_free()
487 *
488 * This is equivalent to the sequence mb_cache_entry_takeout() --
489 * mb_cache_entry_release().
490 */
491void
492mb_cache_entry_free(struct mb_cache_entry *ce)
493{
494 spin_lock(&mb_cache_spinlock);
495 mb_assert(list_empty(&ce->e_lru_list));
496 __mb_cache_entry_unhash(ce);
497 __mb_cache_entry_release_unlock(ce);
498}
499
500
501/*
502 * mb_cache_entry_get()
503 *
504 * Get a cache entry by device / block number. (There can only be one entry
505 * in the cache per device and block.) Returns NULL if no such cache entry
506 * exists. The returned cache entry is locked for exclusive access ("single
507 * writer").
508 */
509struct mb_cache_entry *
510mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev,
511 sector_t block)
512{
513 unsigned int bucket;
514 struct list_head *l;
515 struct mb_cache_entry *ce;
516
517 bucket = hash_long((unsigned long)bdev + (block & 0xffffffff),
518 cache->c_bucket_bits);
519 spin_lock(&mb_cache_spinlock);
520 list_for_each(l, &cache->c_block_hash[bucket]) {
521 ce = list_entry(l, struct mb_cache_entry, e_block_list);
522 if (ce->e_bdev == bdev && ce->e_block == block) {
523 DEFINE_WAIT(wait);
524
525 if (!list_empty(&ce->e_lru_list))
526 list_del_init(&ce->e_lru_list);
527
528 while (ce->e_used > 0) {
529 ce->e_queued++;
530 prepare_to_wait(&mb_cache_queue, &wait,
531 TASK_UNINTERRUPTIBLE);
532 spin_unlock(&mb_cache_spinlock);
533 schedule();
534 spin_lock(&mb_cache_spinlock);
535 ce->e_queued--;
536 }
537 finish_wait(&mb_cache_queue, &wait);
538 ce->e_used += 1 + MB_CACHE_WRITER;
539
540 if (!__mb_cache_entry_is_hashed(ce)) {
541 __mb_cache_entry_release_unlock(ce);
542 return NULL;
543 }
544 goto cleanup;
545 }
546 }
547 ce = NULL;
548
549cleanup:
550 spin_unlock(&mb_cache_spinlock);
551 return ce;
552}
553
554#if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0)
555
556static struct mb_cache_entry *
557__mb_cache_entry_find(struct list_head *l, struct list_head *head,
558 int index, struct block_device *bdev, unsigned int key)
559{
560 while (l != head) {
561 struct mb_cache_entry *ce =
562 list_entry(l, struct mb_cache_entry,
563 e_indexes[index].o_list);
564 if (ce->e_bdev == bdev && ce->e_indexes[index].o_key == key) {
565 DEFINE_WAIT(wait);
566
567 if (!list_empty(&ce->e_lru_list))
568 list_del_init(&ce->e_lru_list);
569
570 /* Incrementing before holding the lock gives readers
571 priority over writers. */
572 ce->e_used++;
573 while (ce->e_used >= MB_CACHE_WRITER) {
574 ce->e_queued++;
575 prepare_to_wait(&mb_cache_queue, &wait,
576 TASK_UNINTERRUPTIBLE);
577 spin_unlock(&mb_cache_spinlock);
578 schedule();
579 spin_lock(&mb_cache_spinlock);
580 ce->e_queued--;
581 }
582 finish_wait(&mb_cache_queue, &wait);
583
584 if (!__mb_cache_entry_is_hashed(ce)) {
585 __mb_cache_entry_release_unlock(ce);
586 spin_lock(&mb_cache_spinlock);
587 return ERR_PTR(-EAGAIN);
588 }
589 return ce;
590 }
591 l = l->next;
592 }
593 return NULL;
594}
595
596
597/*
598 * mb_cache_entry_find_first()
599 *
600 * Find the first cache entry on a given device with a certain key in
601 * an additional index. Additonal matches can be found with
602 * mb_cache_entry_find_next(). Returns NULL if no match was found. The
603 * returned cache entry is locked for shared access ("multiple readers").
604 *
605 * @cache: the cache to search
606 * @index: the number of the additonal index to search (0<=index<indexes_count)
607 * @bdev: the device the cache entry should belong to
608 * @key: the key in the index
609 */
610struct mb_cache_entry *
611mb_cache_entry_find_first(struct mb_cache *cache, int index,
612 struct block_device *bdev, unsigned int key)
613{
614 unsigned int bucket = hash_long(key, cache->c_bucket_bits);
615 struct list_head *l;
616 struct mb_cache_entry *ce;
617
618 mb_assert(index < mb_cache_indexes(cache));
619 spin_lock(&mb_cache_spinlock);
620 l = cache->c_indexes_hash[index][bucket].next;
621 ce = __mb_cache_entry_find(l, &cache->c_indexes_hash[index][bucket],
622 index, bdev, key);
623 spin_unlock(&mb_cache_spinlock);
624 return ce;
625}
626
627
628/*
629 * mb_cache_entry_find_next()
630 *
631 * Find the next cache entry on a given device with a certain key in an
632 * additional index. Returns NULL if no match could be found. The previous
633 * entry is atomatically released, so that mb_cache_entry_find_next() can
634 * be called like this:
635 *
636 * entry = mb_cache_entry_find_first();
637 * while (entry) {
638 * ...
639 * entry = mb_cache_entry_find_next(entry, ...);
640 * }
641 *
642 * @prev: The previous match
643 * @index: the number of the additonal index to search (0<=index<indexes_count)
644 * @bdev: the device the cache entry should belong to
645 * @key: the key in the index
646 */
647struct mb_cache_entry *
648mb_cache_entry_find_next(struct mb_cache_entry *prev, int index,
649 struct block_device *bdev, unsigned int key)
650{
651 struct mb_cache *cache = prev->e_cache;
652 unsigned int bucket = hash_long(key, cache->c_bucket_bits);
653 struct list_head *l;
654 struct mb_cache_entry *ce;
655
656 mb_assert(index < mb_cache_indexes(cache));
657 spin_lock(&mb_cache_spinlock);
658 l = prev->e_indexes[index].o_list.next;
659 ce = __mb_cache_entry_find(l, &cache->c_indexes_hash[index][bucket],
660 index, bdev, key);
661 __mb_cache_entry_release_unlock(prev);
662 return ce;
663}
664
665#endif /* !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) */
666
667static int __init init_mbcache(void)
668{
Rusty Russell8e1f9362007-07-17 04:03:17 -0700669 register_shrinker(&mb_cache_shrinker);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700670 return 0;
671}
672
673static void __exit exit_mbcache(void)
674{
Rusty Russell8e1f9362007-07-17 04:03:17 -0700675 unregister_shrinker(&mb_cache_shrinker);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700676}
677
678module_init(init_mbcache)
679module_exit(exit_mbcache)
680