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1 | /* |
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 | |
60 | static DECLARE_WAIT_QUEUE_HEAD(mb_cache_queue); |
61 | |
62 | MODULE_AUTHOR("Andreas Gruenbacher <a.gruenbacher@computer.org>"); |
63 | MODULE_DESCRIPTION("Meta block cache (for extended attributes)"); |
64 | MODULE_LICENSE("GPL"); |
65 | |
66 | EXPORT_SYMBOL(mb_cache_create); |
67 | EXPORT_SYMBOL(mb_cache_shrink); |
68 | EXPORT_SYMBOL(mb_cache_destroy); |
69 | EXPORT_SYMBOL(mb_cache_entry_alloc); |
70 | EXPORT_SYMBOL(mb_cache_entry_insert); |
71 | EXPORT_SYMBOL(mb_cache_entry_release); |
72 | EXPORT_SYMBOL(mb_cache_entry_free); |
73 | EXPORT_SYMBOL(mb_cache_entry_get); |
74 | #if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) |
75 | EXPORT_SYMBOL(mb_cache_entry_find_first); |
76 | EXPORT_SYMBOL(mb_cache_entry_find_next); |
77 | #endif |
78 | |
79 | struct 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 |
88 | struct kmem_cache *c_entry_cache; |
89 | 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 | |
100 | static LIST_HEAD(mb_cache_list); |
101 | static LIST_HEAD(mb_cache_lru_list); |
102 | static DEFINE_SPINLOCK(mb_cache_spinlock); |
103 | |
104 | static inline int |
105 | mb_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 | |
118 | static int mb_cache_shrink_fn(int nr_to_scan, gfp_t gfp_mask); |
119 | |
120 | static struct shrinker mb_cache_shrinker = { |
121 | .shrink = mb_cache_shrink_fn, |
122 | .seeks = DEFAULT_SEEKS, |
123 | }; |
124 | |
125 | static 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 | |
132 | static void |
133 | __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 | |
145 | static void |
146 | __mb_cache_entry_forget(struct mb_cache_entry *ce, gfp_t gfp_mask) |
147 | { |
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 | |
164 | static void |
165 | __mb_cache_entry_release_unlock(struct mb_cache_entry *ce) |
166 | __releases(mb_cache_spinlock) |
167 | { |
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; |
182 | forget: |
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 | * |
194 | * @nr_to_scan: Number of objects to scan |
195 | * @gfp_mask: (ignored) |
196 | * |
197 | * Returns the number of objects which are present in the cache. |
198 | */ |
199 | static int |
200 | mb_cache_shrink_fn(int nr_to_scan, gfp_t gfp_mask) |
201 | { |
202 | LIST_HEAD(free_list); |
203 | struct list_head *l, *ltmp; |
204 | int count = 0; |
205 | |
206 | spin_lock(&mb_cache_spinlock); |
207 | list_for_each(l, &mb_cache_list) { |
208 | struct mb_cache *cache = |
209 | list_entry(l, struct mb_cache, c_cache_list); |
210 | mb_debug("cache %s (%d)", cache->c_name, |
211 | atomic_read(&cache->c_entry_count)); |
212 | count += atomic_read(&cache->c_entry_count); |
213 | } |
214 | mb_debug("trying to free %d entries", nr_to_scan); |
215 | if (nr_to_scan == 0) { |
216 | spin_unlock(&mb_cache_spinlock); |
217 | goto out; |
218 | } |
219 | while (nr_to_scan-- && !list_empty(&mb_cache_lru_list)) { |
220 | struct mb_cache_entry *ce = |
221 | list_entry(mb_cache_lru_list.next, |
222 | struct mb_cache_entry, e_lru_list); |
223 | list_move_tail(&ce->e_lru_list, &free_list); |
224 | __mb_cache_entry_unhash(ce); |
225 | } |
226 | spin_unlock(&mb_cache_spinlock); |
227 | list_for_each_safe(l, ltmp, &free_list) { |
228 | __mb_cache_entry_forget(list_entry(l, struct mb_cache_entry, |
229 | e_lru_list), gfp_mask); |
230 | } |
231 | out: |
232 | return (count / 100) * sysctl_vfs_cache_pressure; |
233 | } |
234 | |
235 | |
236 | /* |
237 | * mb_cache_create() create a new cache |
238 | * |
239 | * All entries in one cache are equal size. Cache entries may be from |
240 | * multiple devices. If this is the first mbcache created, registers |
241 | * the cache with kernel memory management. Returns NULL if no more |
242 | * memory was available. |
243 | * |
244 | * @name: name of the cache (informal) |
245 | * @cache_op: contains the callback called when freeing a cache entry |
246 | * @entry_size: The size of a cache entry, including |
247 | * struct mb_cache_entry |
248 | * @indexes_count: number of additional indexes in the cache. Must equal |
249 | * MB_CACHE_INDEXES_COUNT if the number of indexes is |
250 | * hardwired. |
251 | * @bucket_bits: log2(number of hash buckets) |
252 | */ |
253 | struct mb_cache * |
254 | mb_cache_create(const char *name, struct mb_cache_op *cache_op, |
255 | size_t entry_size, int indexes_count, int bucket_bits) |
256 | { |
257 | int m=0, n, bucket_count = 1 << bucket_bits; |
258 | struct mb_cache *cache = NULL; |
259 | |
260 | if(entry_size < sizeof(struct mb_cache_entry) + |
261 | indexes_count * sizeof(((struct mb_cache_entry *) 0)->e_indexes[0])) |
262 | return NULL; |
263 | |
264 | cache = kmalloc(sizeof(struct mb_cache) + |
265 | indexes_count * sizeof(struct list_head), GFP_KERNEL); |
266 | if (!cache) |
267 | goto fail; |
268 | cache->c_name = name; |
269 | cache->c_op.free = NULL; |
270 | if (cache_op) |
271 | cache->c_op.free = cache_op->free; |
272 | atomic_set(&cache->c_entry_count, 0); |
273 | cache->c_bucket_bits = bucket_bits; |
274 | #ifdef MB_CACHE_INDEXES_COUNT |
275 | mb_assert(indexes_count == MB_CACHE_INDEXES_COUNT); |
276 | #else |
277 | cache->c_indexes_count = indexes_count; |
278 | #endif |
279 | cache->c_block_hash = kmalloc(bucket_count * sizeof(struct list_head), |
280 | GFP_KERNEL); |
281 | if (!cache->c_block_hash) |
282 | goto fail; |
283 | for (n=0; n<bucket_count; n++) |
284 | INIT_LIST_HEAD(&cache->c_block_hash[n]); |
285 | for (m=0; m<indexes_count; m++) { |
286 | cache->c_indexes_hash[m] = kmalloc(bucket_count * |
287 | sizeof(struct list_head), |
288 | GFP_KERNEL); |
289 | if (!cache->c_indexes_hash[m]) |
290 | goto fail; |
291 | for (n=0; n<bucket_count; n++) |
292 | INIT_LIST_HEAD(&cache->c_indexes_hash[m][n]); |
293 | } |
294 | cache->c_entry_cache = kmem_cache_create(name, entry_size, 0, |
295 | SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL); |
296 | if (!cache->c_entry_cache) |
297 | goto fail; |
298 | |
299 | spin_lock(&mb_cache_spinlock); |
300 | list_add(&cache->c_cache_list, &mb_cache_list); |
301 | spin_unlock(&mb_cache_spinlock); |
302 | return cache; |
303 | |
304 | fail: |
305 | if (cache) { |
306 | while (--m >= 0) |
307 | kfree(cache->c_indexes_hash[m]); |
308 | kfree(cache->c_block_hash); |
309 | kfree(cache); |
310 | } |
311 | return NULL; |
312 | } |
313 | |
314 | |
315 | /* |
316 | * mb_cache_shrink() |
317 | * |
318 | * Removes all cache entries of a device from the cache. All cache entries |
319 | * currently in use cannot be freed, and thus remain in the cache. All others |
320 | * are freed. |
321 | * |
322 | * @bdev: which device's cache entries to shrink |
323 | */ |
324 | void |
325 | mb_cache_shrink(struct block_device *bdev) |
326 | { |
327 | LIST_HEAD(free_list); |
328 | struct list_head *l, *ltmp; |
329 | |
330 | spin_lock(&mb_cache_spinlock); |
331 | list_for_each_safe(l, ltmp, &mb_cache_lru_list) { |
332 | struct mb_cache_entry *ce = |
333 | list_entry(l, struct mb_cache_entry, e_lru_list); |
334 | if (ce->e_bdev == bdev) { |
335 | list_move_tail(&ce->e_lru_list, &free_list); |
336 | __mb_cache_entry_unhash(ce); |
337 | } |
338 | } |
339 | spin_unlock(&mb_cache_spinlock); |
340 | list_for_each_safe(l, ltmp, &free_list) { |
341 | __mb_cache_entry_forget(list_entry(l, struct mb_cache_entry, |
342 | e_lru_list), GFP_KERNEL); |
343 | } |
344 | } |
345 | |
346 | |
347 | /* |
348 | * mb_cache_destroy() |
349 | * |
350 | * Shrinks the cache to its minimum possible size (hopefully 0 entries), |
351 | * and then destroys it. If this was the last mbcache, un-registers the |
352 | * mbcache from kernel memory management. |
353 | */ |
354 | void |
355 | mb_cache_destroy(struct mb_cache *cache) |
356 | { |
357 | LIST_HEAD(free_list); |
358 | struct list_head *l, *ltmp; |
359 | int n; |
360 | |
361 | spin_lock(&mb_cache_spinlock); |
362 | list_for_each_safe(l, ltmp, &mb_cache_lru_list) { |
363 | struct mb_cache_entry *ce = |
364 | list_entry(l, struct mb_cache_entry, e_lru_list); |
365 | if (ce->e_cache == cache) { |
366 | list_move_tail(&ce->e_lru_list, &free_list); |
367 | __mb_cache_entry_unhash(ce); |
368 | } |
369 | } |
370 | list_del(&cache->c_cache_list); |
371 | spin_unlock(&mb_cache_spinlock); |
372 | |
373 | list_for_each_safe(l, ltmp, &free_list) { |
374 | __mb_cache_entry_forget(list_entry(l, struct mb_cache_entry, |
375 | e_lru_list), GFP_KERNEL); |
376 | } |
377 | |
378 | if (atomic_read(&cache->c_entry_count) > 0) { |
379 | mb_error("cache %s: %d orphaned entries", |
380 | cache->c_name, |
381 | atomic_read(&cache->c_entry_count)); |
382 | } |
383 | |
384 | kmem_cache_destroy(cache->c_entry_cache); |
385 | |
386 | for (n=0; n < mb_cache_indexes(cache); n++) |
387 | kfree(cache->c_indexes_hash[n]); |
388 | kfree(cache->c_block_hash); |
389 | kfree(cache); |
390 | } |
391 | |
392 | |
393 | /* |
394 | * mb_cache_entry_alloc() |
395 | * |
396 | * Allocates a new cache entry. The new entry will not be valid initially, |
397 | * and thus cannot be looked up yet. It should be filled with data, and |
398 | * then inserted into the cache using mb_cache_entry_insert(). Returns NULL |
399 | * if no more memory was available. |
400 | */ |
401 | struct mb_cache_entry * |
402 | mb_cache_entry_alloc(struct mb_cache *cache, gfp_t gfp_flags) |
403 | { |
404 | struct mb_cache_entry *ce; |
405 | |
406 | ce = kmem_cache_alloc(cache->c_entry_cache, gfp_flags); |
407 | if (ce) { |
408 | atomic_inc(&cache->c_entry_count); |
409 | INIT_LIST_HEAD(&ce->e_lru_list); |
410 | INIT_LIST_HEAD(&ce->e_block_list); |
411 | ce->e_cache = cache; |
412 | ce->e_used = 1 + MB_CACHE_WRITER; |
413 | ce->e_queued = 0; |
414 | } |
415 | return ce; |
416 | } |
417 | |
418 | |
419 | /* |
420 | * mb_cache_entry_insert() |
421 | * |
422 | * Inserts an entry that was allocated using mb_cache_entry_alloc() into |
423 | * the cache. After this, the cache entry can be looked up, but is not yet |
424 | * in the lru list as the caller still holds a handle to it. Returns 0 on |
425 | * success, or -EBUSY if a cache entry for that device + inode exists |
426 | * already (this may happen after a failed lookup, but when another process |
427 | * has inserted the same cache entry in the meantime). |
428 | * |
429 | * @bdev: device the cache entry belongs to |
430 | * @block: block number |
431 | * @keys: array of additional keys. There must be indexes_count entries |
432 | * in the array (as specified when creating the cache). |
433 | */ |
434 | int |
435 | mb_cache_entry_insert(struct mb_cache_entry *ce, struct block_device *bdev, |
436 | sector_t block, unsigned int keys[]) |
437 | { |
438 | struct mb_cache *cache = ce->e_cache; |
439 | unsigned int bucket; |
440 | struct list_head *l; |
441 | int error = -EBUSY, n; |
442 | |
443 | bucket = hash_long((unsigned long)bdev + (block & 0xffffffff), |
444 | cache->c_bucket_bits); |
445 | spin_lock(&mb_cache_spinlock); |
446 | list_for_each_prev(l, &cache->c_block_hash[bucket]) { |
447 | struct mb_cache_entry *ce = |
448 | list_entry(l, struct mb_cache_entry, e_block_list); |
449 | if (ce->e_bdev == bdev && ce->e_block == block) |
450 | goto out; |
451 | } |
452 | __mb_cache_entry_unhash(ce); |
453 | ce->e_bdev = bdev; |
454 | ce->e_block = block; |
455 | list_add(&ce->e_block_list, &cache->c_block_hash[bucket]); |
456 | for (n=0; n<mb_cache_indexes(cache); n++) { |
457 | ce->e_indexes[n].o_key = keys[n]; |
458 | bucket = hash_long(keys[n], cache->c_bucket_bits); |
459 | list_add(&ce->e_indexes[n].o_list, |
460 | &cache->c_indexes_hash[n][bucket]); |
461 | } |
462 | error = 0; |
463 | out: |
464 | spin_unlock(&mb_cache_spinlock); |
465 | return error; |
466 | } |
467 | |
468 | |
469 | /* |
470 | * mb_cache_entry_release() |
471 | * |
472 | * Release a handle to a cache entry. When the last handle to a cache entry |
473 | * is released it is either freed (if it is invalid) or otherwise inserted |
474 | * in to the lru list. |
475 | */ |
476 | void |
477 | mb_cache_entry_release(struct mb_cache_entry *ce) |
478 | { |
479 | spin_lock(&mb_cache_spinlock); |
480 | __mb_cache_entry_release_unlock(ce); |
481 | } |
482 | |
483 | |
484 | /* |
485 | * mb_cache_entry_free() |
486 | * |
487 | * This is equivalent to the sequence mb_cache_entry_takeout() -- |
488 | * mb_cache_entry_release(). |
489 | */ |
490 | void |
491 | mb_cache_entry_free(struct mb_cache_entry *ce) |
492 | { |
493 | spin_lock(&mb_cache_spinlock); |
494 | mb_assert(list_empty(&ce->e_lru_list)); |
495 | __mb_cache_entry_unhash(ce); |
496 | __mb_cache_entry_release_unlock(ce); |
497 | } |
498 | |
499 | |
500 | /* |
501 | * mb_cache_entry_get() |
502 | * |
503 | * Get a cache entry by device / block number. (There can only be one entry |
504 | * in the cache per device and block.) Returns NULL if no such cache entry |
505 | * exists. The returned cache entry is locked for exclusive access ("single |
506 | * writer"). |
507 | */ |
508 | struct mb_cache_entry * |
509 | mb_cache_entry_get(struct mb_cache *cache, struct block_device *bdev, |
510 | sector_t block) |
511 | { |
512 | unsigned int bucket; |
513 | struct list_head *l; |
514 | struct mb_cache_entry *ce; |
515 | |
516 | bucket = hash_long((unsigned long)bdev + (block & 0xffffffff), |
517 | cache->c_bucket_bits); |
518 | spin_lock(&mb_cache_spinlock); |
519 | list_for_each(l, &cache->c_block_hash[bucket]) { |
520 | ce = list_entry(l, struct mb_cache_entry, e_block_list); |
521 | if (ce->e_bdev == bdev && ce->e_block == block) { |
522 | DEFINE_WAIT(wait); |
523 | |
524 | if (!list_empty(&ce->e_lru_list)) |
525 | list_del_init(&ce->e_lru_list); |
526 | |
527 | while (ce->e_used > 0) { |
528 | ce->e_queued++; |
529 | prepare_to_wait(&mb_cache_queue, &wait, |
530 | TASK_UNINTERRUPTIBLE); |
531 | spin_unlock(&mb_cache_spinlock); |
532 | schedule(); |
533 | spin_lock(&mb_cache_spinlock); |
534 | ce->e_queued--; |
535 | } |
536 | finish_wait(&mb_cache_queue, &wait); |
537 | ce->e_used += 1 + MB_CACHE_WRITER; |
538 | |
539 | if (!__mb_cache_entry_is_hashed(ce)) { |
540 | __mb_cache_entry_release_unlock(ce); |
541 | return NULL; |
542 | } |
543 | goto cleanup; |
544 | } |
545 | } |
546 | ce = NULL; |
547 | |
548 | cleanup: |
549 | spin_unlock(&mb_cache_spinlock); |
550 | return ce; |
551 | } |
552 | |
553 | #if !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) |
554 | |
555 | static struct mb_cache_entry * |
556 | __mb_cache_entry_find(struct list_head *l, struct list_head *head, |
557 | int index, struct block_device *bdev, unsigned int key) |
558 | { |
559 | while (l != head) { |
560 | struct mb_cache_entry *ce = |
561 | list_entry(l, struct mb_cache_entry, |
562 | e_indexes[index].o_list); |
563 | if (ce->e_bdev == bdev && ce->e_indexes[index].o_key == key) { |
564 | DEFINE_WAIT(wait); |
565 | |
566 | if (!list_empty(&ce->e_lru_list)) |
567 | list_del_init(&ce->e_lru_list); |
568 | |
569 | /* Incrementing before holding the lock gives readers |
570 | priority over writers. */ |
571 | ce->e_used++; |
572 | while (ce->e_used >= MB_CACHE_WRITER) { |
573 | ce->e_queued++; |
574 | prepare_to_wait(&mb_cache_queue, &wait, |
575 | TASK_UNINTERRUPTIBLE); |
576 | spin_unlock(&mb_cache_spinlock); |
577 | schedule(); |
578 | spin_lock(&mb_cache_spinlock); |
579 | ce->e_queued--; |
580 | } |
581 | finish_wait(&mb_cache_queue, &wait); |
582 | |
583 | if (!__mb_cache_entry_is_hashed(ce)) { |
584 | __mb_cache_entry_release_unlock(ce); |
585 | spin_lock(&mb_cache_spinlock); |
586 | return ERR_PTR(-EAGAIN); |
587 | } |
588 | return ce; |
589 | } |
590 | l = l->next; |
591 | } |
592 | return NULL; |
593 | } |
594 | |
595 | |
596 | /* |
597 | * mb_cache_entry_find_first() |
598 | * |
599 | * Find the first cache entry on a given device with a certain key in |
600 | * an additional index. Additonal matches can be found with |
601 | * mb_cache_entry_find_next(). Returns NULL if no match was found. The |
602 | * returned cache entry is locked for shared access ("multiple readers"). |
603 | * |
604 | * @cache: the cache to search |
605 | * @index: the number of the additonal index to search (0<=index<indexes_count) |
606 | * @bdev: the device the cache entry should belong to |
607 | * @key: the key in the index |
608 | */ |
609 | struct mb_cache_entry * |
610 | mb_cache_entry_find_first(struct mb_cache *cache, int index, |
611 | struct block_device *bdev, unsigned int key) |
612 | { |
613 | unsigned int bucket = hash_long(key, cache->c_bucket_bits); |
614 | struct list_head *l; |
615 | struct mb_cache_entry *ce; |
616 | |
617 | mb_assert(index < mb_cache_indexes(cache)); |
618 | spin_lock(&mb_cache_spinlock); |
619 | l = cache->c_indexes_hash[index][bucket].next; |
620 | ce = __mb_cache_entry_find(l, &cache->c_indexes_hash[index][bucket], |
621 | index, bdev, key); |
622 | spin_unlock(&mb_cache_spinlock); |
623 | return ce; |
624 | } |
625 | |
626 | |
627 | /* |
628 | * mb_cache_entry_find_next() |
629 | * |
630 | * Find the next cache entry on a given device with a certain key in an |
631 | * additional index. Returns NULL if no match could be found. The previous |
632 | * entry is atomatically released, so that mb_cache_entry_find_next() can |
633 | * be called like this: |
634 | * |
635 | * entry = mb_cache_entry_find_first(); |
636 | * while (entry) { |
637 | * ... |
638 | * entry = mb_cache_entry_find_next(entry, ...); |
639 | * } |
640 | * |
641 | * @prev: The previous match |
642 | * @index: the number of the additonal index to search (0<=index<indexes_count) |
643 | * @bdev: the device the cache entry should belong to |
644 | * @key: the key in the index |
645 | */ |
646 | struct mb_cache_entry * |
647 | mb_cache_entry_find_next(struct mb_cache_entry *prev, int index, |
648 | struct block_device *bdev, unsigned int key) |
649 | { |
650 | struct mb_cache *cache = prev->e_cache; |
651 | unsigned int bucket = hash_long(key, cache->c_bucket_bits); |
652 | struct list_head *l; |
653 | struct mb_cache_entry *ce; |
654 | |
655 | mb_assert(index < mb_cache_indexes(cache)); |
656 | spin_lock(&mb_cache_spinlock); |
657 | l = prev->e_indexes[index].o_list.next; |
658 | ce = __mb_cache_entry_find(l, &cache->c_indexes_hash[index][bucket], |
659 | index, bdev, key); |
660 | __mb_cache_entry_release_unlock(prev); |
661 | return ce; |
662 | } |
663 | |
664 | #endif /* !defined(MB_CACHE_INDEXES_COUNT) || (MB_CACHE_INDEXES_COUNT > 0) */ |
665 | |
666 | static int __init init_mbcache(void) |
667 | { |
668 | register_shrinker(&mb_cache_shrinker); |
669 | return 0; |
670 | } |
671 | |
672 | static void __exit exit_mbcache(void) |
673 | { |
674 | unregister_shrinker(&mb_cache_shrinker); |
675 | } |
676 | |
677 | module_init(init_mbcache) |
678 | module_exit(exit_mbcache) |
679 | |
680 |
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