Merge tag 'riscv-for-linus-4.18-merge_window' of git://git.kernel.org/pub/scm/linux...
[linux-2.6-block.git] / fs / mbcache.c
CommitLineData
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1#include <linux/spinlock.h>
2#include <linux/slab.h>
3#include <linux/list.h>
4#include <linux/list_bl.h>
5#include <linux/module.h>
6#include <linux/sched.h>
c2f3140f 7#include <linux/workqueue.h>
7a2508e1 8#include <linux/mbcache.h>
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9
10/*
11 * Mbcache is a simple key-value store. Keys need not be unique, however
12 * key-value pairs are expected to be unique (we use this fact in
c07dfcb4 13 * mb_cache_entry_delete()).
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14 *
15 * Ext2 and ext4 use this cache for deduplication of extended attribute blocks.
dec214d0
TE
16 * Ext4 also uses it for deduplication of xattr values stored in inodes.
17 * They use hash of data as a key and provide a value that may represent a
18 * block or inode number. That's why keys need not be unique (hash of different
19 * data may be the same). However user provided value always uniquely
20 * identifies a cache entry.
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21 *
22 * We provide functions for creation and removal of entries, search by key,
23 * and a special "delete entry with given key-value pair" operation. Fixed
24 * size hash table is used for fast key lookups.
25 */
26
7a2508e1 27struct mb_cache {
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28 /* Hash table of entries */
29 struct hlist_bl_head *c_hash;
30 /* log2 of hash table size */
31 int c_bucket_bits;
c2f3140f 32 /* Maximum entries in cache to avoid degrading hash too much */
132d4e2d 33 unsigned long c_max_entries;
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34 /* Protects c_list, c_entry_count */
35 spinlock_t c_list_lock;
36 struct list_head c_list;
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37 /* Number of entries in cache */
38 unsigned long c_entry_count;
39 struct shrinker c_shrink;
c2f3140f
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40 /* Work for shrinking when the cache has too many entries */
41 struct work_struct c_shrink_work;
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42};
43
7a2508e1 44static struct kmem_cache *mb_entry_cache;
f9a61eb4 45
7a2508e1 46static unsigned long mb_cache_shrink(struct mb_cache *cache,
132d4e2d 47 unsigned long nr_to_scan);
c2f3140f 48
dc8d5e56
AG
49static inline struct hlist_bl_head *mb_cache_entry_head(struct mb_cache *cache,
50 u32 key)
f0c8b462 51{
dc8d5e56 52 return &cache->c_hash[hash_32(key, cache->c_bucket_bits)];
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53}
54
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55/*
56 * Number of entries to reclaim synchronously when there are too many entries
57 * in cache
58 */
59#define SYNC_SHRINK_BATCH 64
60
f9a61eb4 61/*
7a2508e1 62 * mb_cache_entry_create - create entry in cache
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63 * @cache - cache where the entry should be created
64 * @mask - gfp mask with which the entry should be allocated
65 * @key - key of the entry
c07dfcb4
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66 * @value - value of the entry
67 * @reusable - is the entry reusable by others?
f9a61eb4 68 *
c07dfcb4
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69 * Creates entry in @cache with key @key and value @value. The function returns
70 * -EBUSY if entry with the same key and value already exists in cache.
71 * Otherwise 0 is returned.
f9a61eb4 72 */
7a2508e1 73int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key,
c07dfcb4 74 u64 value, bool reusable)
f9a61eb4 75{
7a2508e1 76 struct mb_cache_entry *entry, *dup;
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77 struct hlist_bl_node *dup_node;
78 struct hlist_bl_head *head;
79
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80 /* Schedule background reclaim if there are too many entries */
81 if (cache->c_entry_count >= cache->c_max_entries)
82 schedule_work(&cache->c_shrink_work);
83 /* Do some sync reclaim if background reclaim cannot keep up */
84 if (cache->c_entry_count >= 2*cache->c_max_entries)
7a2508e1 85 mb_cache_shrink(cache, SYNC_SHRINK_BATCH);
c2f3140f 86
7a2508e1 87 entry = kmem_cache_alloc(mb_entry_cache, mask);
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88 if (!entry)
89 return -ENOMEM;
90
f0c8b462 91 INIT_LIST_HEAD(&entry->e_list);
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92 /* One ref for hash, one ref returned */
93 atomic_set(&entry->e_refcnt, 1);
94 entry->e_key = key;
c07dfcb4 95 entry->e_value = value;
6048c64b 96 entry->e_reusable = reusable;
3876bbe2 97 entry->e_referenced = 0;
dc8d5e56 98 head = mb_cache_entry_head(cache, key);
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99 hlist_bl_lock(head);
100 hlist_bl_for_each_entry(dup, dup_node, head, e_hash_list) {
c07dfcb4 101 if (dup->e_key == key && dup->e_value == value) {
f9a61eb4 102 hlist_bl_unlock(head);
7a2508e1 103 kmem_cache_free(mb_entry_cache, entry);
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104 return -EBUSY;
105 }
106 }
107 hlist_bl_add_head(&entry->e_hash_list, head);
108 hlist_bl_unlock(head);
109
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110 spin_lock(&cache->c_list_lock);
111 list_add_tail(&entry->e_list, &cache->c_list);
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112 /* Grab ref for LRU list */
113 atomic_inc(&entry->e_refcnt);
114 cache->c_entry_count++;
f0c8b462 115 spin_unlock(&cache->c_list_lock);
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116
117 return 0;
118}
7a2508e1 119EXPORT_SYMBOL(mb_cache_entry_create);
f9a61eb4 120
7a2508e1 121void __mb_cache_entry_free(struct mb_cache_entry *entry)
f9a61eb4 122{
7a2508e1 123 kmem_cache_free(mb_entry_cache, entry);
f9a61eb4 124}
7a2508e1 125EXPORT_SYMBOL(__mb_cache_entry_free);
f9a61eb4 126
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127static struct mb_cache_entry *__entry_find(struct mb_cache *cache,
128 struct mb_cache_entry *entry,
129 u32 key)
f9a61eb4 130{
7a2508e1 131 struct mb_cache_entry *old_entry = entry;
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132 struct hlist_bl_node *node;
133 struct hlist_bl_head *head;
134
dc8d5e56 135 head = mb_cache_entry_head(cache, key);
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136 hlist_bl_lock(head);
137 if (entry && !hlist_bl_unhashed(&entry->e_hash_list))
138 node = entry->e_hash_list.next;
139 else
140 node = hlist_bl_first(head);
141 while (node) {
7a2508e1 142 entry = hlist_bl_entry(node, struct mb_cache_entry,
f9a61eb4 143 e_hash_list);
6048c64b 144 if (entry->e_key == key && entry->e_reusable) {
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145 atomic_inc(&entry->e_refcnt);
146 goto out;
147 }
148 node = node->next;
149 }
150 entry = NULL;
151out:
152 hlist_bl_unlock(head);
153 if (old_entry)
7a2508e1 154 mb_cache_entry_put(cache, old_entry);
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155
156 return entry;
157}
158
159/*
b649668c 160 * mb_cache_entry_find_first - find the first reusable entry with the given key
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161 * @cache: cache where we should search
162 * @key: key to look for
163 *
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164 * Search in @cache for a reusable entry with key @key. Grabs reference to the
165 * first reusable entry found and returns the entry.
f9a61eb4 166 */
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167struct mb_cache_entry *mb_cache_entry_find_first(struct mb_cache *cache,
168 u32 key)
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169{
170 return __entry_find(cache, NULL, key);
171}
7a2508e1 172EXPORT_SYMBOL(mb_cache_entry_find_first);
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173
174/*
b649668c 175 * mb_cache_entry_find_next - find next reusable entry with the same key
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176 * @cache: cache where we should search
177 * @entry: entry to start search from
178 *
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179 * Finds next reusable entry in the hash chain which has the same key as @entry.
180 * If @entry is unhashed (which can happen when deletion of entry races with the
181 * search), finds the first reusable entry in the hash chain. The function drops
182 * reference to @entry and returns with a reference to the found entry.
f9a61eb4 183 */
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184struct mb_cache_entry *mb_cache_entry_find_next(struct mb_cache *cache,
185 struct mb_cache_entry *entry)
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186{
187 return __entry_find(cache, entry, entry->e_key);
188}
7a2508e1 189EXPORT_SYMBOL(mb_cache_entry_find_next);
f9a61eb4 190
6048c64b 191/*
c07dfcb4 192 * mb_cache_entry_get - get a cache entry by value (and key)
6048c64b 193 * @cache - cache we work with
c07dfcb4
TE
194 * @key - key
195 * @value - value
6048c64b
AG
196 */
197struct mb_cache_entry *mb_cache_entry_get(struct mb_cache *cache, u32 key,
c07dfcb4 198 u64 value)
6048c64b
AG
199{
200 struct hlist_bl_node *node;
201 struct hlist_bl_head *head;
202 struct mb_cache_entry *entry;
203
204 head = mb_cache_entry_head(cache, key);
205 hlist_bl_lock(head);
206 hlist_bl_for_each_entry(entry, node, head, e_hash_list) {
c07dfcb4 207 if (entry->e_key == key && entry->e_value == value) {
6048c64b
AG
208 atomic_inc(&entry->e_refcnt);
209 goto out;
210 }
211 }
212 entry = NULL;
213out:
214 hlist_bl_unlock(head);
215 return entry;
216}
217EXPORT_SYMBOL(mb_cache_entry_get);
218
c07dfcb4 219/* mb_cache_entry_delete - remove a cache entry
f9a61eb4 220 * @cache - cache we work with
c07dfcb4
TE
221 * @key - key
222 * @value - value
f9a61eb4 223 *
c07dfcb4 224 * Remove entry from cache @cache with key @key and value @value.
f9a61eb4 225 */
c07dfcb4 226void mb_cache_entry_delete(struct mb_cache *cache, u32 key, u64 value)
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227{
228 struct hlist_bl_node *node;
229 struct hlist_bl_head *head;
7a2508e1 230 struct mb_cache_entry *entry;
f9a61eb4 231
dc8d5e56 232 head = mb_cache_entry_head(cache, key);
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233 hlist_bl_lock(head);
234 hlist_bl_for_each_entry(entry, node, head, e_hash_list) {
c07dfcb4 235 if (entry->e_key == key && entry->e_value == value) {
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236 /* We keep hash list reference to keep entry alive */
237 hlist_bl_del_init(&entry->e_hash_list);
238 hlist_bl_unlock(head);
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239 spin_lock(&cache->c_list_lock);
240 if (!list_empty(&entry->e_list)) {
241 list_del_init(&entry->e_list);
9ee93ba3
JB
242 if (!WARN_ONCE(cache->c_entry_count == 0,
243 "mbcache: attempt to decrement c_entry_count past zero"))
244 cache->c_entry_count--;
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245 atomic_dec(&entry->e_refcnt);
246 }
f0c8b462 247 spin_unlock(&cache->c_list_lock);
7a2508e1 248 mb_cache_entry_put(cache, entry);
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249 return;
250 }
251 }
252 hlist_bl_unlock(head);
253}
c07dfcb4 254EXPORT_SYMBOL(mb_cache_entry_delete);
f9a61eb4 255
7a2508e1 256/* mb_cache_entry_touch - cache entry got used
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257 * @cache - cache the entry belongs to
258 * @entry - entry that got used
259 *
f0c8b462 260 * Marks entry as used to give hit higher chances of surviving in cache.
f9a61eb4 261 */
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262void mb_cache_entry_touch(struct mb_cache *cache,
263 struct mb_cache_entry *entry)
f9a61eb4 264{
dc8d5e56 265 entry->e_referenced = 1;
f9a61eb4 266}
7a2508e1 267EXPORT_SYMBOL(mb_cache_entry_touch);
f9a61eb4 268
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269static unsigned long mb_cache_count(struct shrinker *shrink,
270 struct shrink_control *sc)
f9a61eb4 271{
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272 struct mb_cache *cache = container_of(shrink, struct mb_cache,
273 c_shrink);
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274
275 return cache->c_entry_count;
276}
277
278/* Shrink number of entries in cache */
7a2508e1 279static unsigned long mb_cache_shrink(struct mb_cache *cache,
132d4e2d 280 unsigned long nr_to_scan)
f9a61eb4 281{
7a2508e1 282 struct mb_cache_entry *entry;
f9a61eb4 283 struct hlist_bl_head *head;
132d4e2d 284 unsigned long shrunk = 0;
f9a61eb4 285
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286 spin_lock(&cache->c_list_lock);
287 while (nr_to_scan-- && !list_empty(&cache->c_list)) {
288 entry = list_first_entry(&cache->c_list,
7a2508e1 289 struct mb_cache_entry, e_list);
dc8d5e56
AG
290 if (entry->e_referenced) {
291 entry->e_referenced = 0;
918b7306 292 list_move_tail(&entry->e_list, &cache->c_list);
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293 continue;
294 }
295 list_del_init(&entry->e_list);
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296 cache->c_entry_count--;
297 /*
298 * We keep LRU list reference so that entry doesn't go away
299 * from under us.
300 */
f0c8b462 301 spin_unlock(&cache->c_list_lock);
dc8d5e56 302 head = mb_cache_entry_head(cache, entry->e_key);
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303 hlist_bl_lock(head);
304 if (!hlist_bl_unhashed(&entry->e_hash_list)) {
305 hlist_bl_del_init(&entry->e_hash_list);
306 atomic_dec(&entry->e_refcnt);
307 }
308 hlist_bl_unlock(head);
7a2508e1 309 if (mb_cache_entry_put(cache, entry))
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310 shrunk++;
311 cond_resched();
f0c8b462 312 spin_lock(&cache->c_list_lock);
f9a61eb4 313 }
f0c8b462 314 spin_unlock(&cache->c_list_lock);
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315
316 return shrunk;
317}
318
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319static unsigned long mb_cache_scan(struct shrinker *shrink,
320 struct shrink_control *sc)
c2f3140f 321{
7a2508e1 322 struct mb_cache *cache = container_of(shrink, struct mb_cache,
c2f3140f 323 c_shrink);
132d4e2d 324 return mb_cache_shrink(cache, sc->nr_to_scan);
c2f3140f
JK
325}
326
327/* We shrink 1/X of the cache when we have too many entries in it */
328#define SHRINK_DIVISOR 16
329
7a2508e1 330static void mb_cache_shrink_worker(struct work_struct *work)
c2f3140f 331{
7a2508e1
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332 struct mb_cache *cache = container_of(work, struct mb_cache,
333 c_shrink_work);
334 mb_cache_shrink(cache, cache->c_max_entries / SHRINK_DIVISOR);
c2f3140f
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335}
336
f9a61eb4 337/*
7a2508e1 338 * mb_cache_create - create cache
f9a61eb4
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339 * @bucket_bits: log2 of the hash table size
340 *
341 * Create cache for keys with 2^bucket_bits hash entries.
342 */
7a2508e1 343struct mb_cache *mb_cache_create(int bucket_bits)
f9a61eb4 344{
7a2508e1 345 struct mb_cache *cache;
132d4e2d
EB
346 unsigned long bucket_count = 1UL << bucket_bits;
347 unsigned long i;
f9a61eb4 348
7a2508e1 349 cache = kzalloc(sizeof(struct mb_cache), GFP_KERNEL);
f9a61eb4
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350 if (!cache)
351 goto err_out;
352 cache->c_bucket_bits = bucket_bits;
c2f3140f 353 cache->c_max_entries = bucket_count << 4;
f0c8b462
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354 INIT_LIST_HEAD(&cache->c_list);
355 spin_lock_init(&cache->c_list_lock);
6da2ec56
KC
356 cache->c_hash = kmalloc_array(bucket_count,
357 sizeof(struct hlist_bl_head),
358 GFP_KERNEL);
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359 if (!cache->c_hash) {
360 kfree(cache);
361 goto err_out;
362 }
363 for (i = 0; i < bucket_count; i++)
364 INIT_HLIST_BL_HEAD(&cache->c_hash[i]);
365
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366 cache->c_shrink.count_objects = mb_cache_count;
367 cache->c_shrink.scan_objects = mb_cache_scan;
f9a61eb4 368 cache->c_shrink.seeks = DEFAULT_SEEKS;
8913f343
CY
369 if (register_shrinker(&cache->c_shrink)) {
370 kfree(cache->c_hash);
371 kfree(cache);
372 goto err_out;
373 }
f9a61eb4 374
7a2508e1 375 INIT_WORK(&cache->c_shrink_work, mb_cache_shrink_worker);
c2f3140f 376
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377 return cache;
378
379err_out:
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380 return NULL;
381}
7a2508e1 382EXPORT_SYMBOL(mb_cache_create);
f9a61eb4
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383
384/*
7a2508e1 385 * mb_cache_destroy - destroy cache
f9a61eb4
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386 * @cache: the cache to destroy
387 *
388 * Free all entries in cache and cache itself. Caller must make sure nobody
389 * (except shrinker) can reach @cache when calling this.
390 */
7a2508e1 391void mb_cache_destroy(struct mb_cache *cache)
f9a61eb4 392{
7a2508e1 393 struct mb_cache_entry *entry, *next;
f9a61eb4
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394
395 unregister_shrinker(&cache->c_shrink);
396
397 /*
398 * We don't bother with any locking. Cache must not be used at this
399 * point.
400 */
f0c8b462 401 list_for_each_entry_safe(entry, next, &cache->c_list, e_list) {
f9a61eb4
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402 if (!hlist_bl_unhashed(&entry->e_hash_list)) {
403 hlist_bl_del_init(&entry->e_hash_list);
404 atomic_dec(&entry->e_refcnt);
405 } else
406 WARN_ON(1);
f0c8b462 407 list_del(&entry->e_list);
f9a61eb4 408 WARN_ON(atomic_read(&entry->e_refcnt) != 1);
7a2508e1 409 mb_cache_entry_put(cache, entry);
f9a61eb4
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410 }
411 kfree(cache->c_hash);
412 kfree(cache);
f9a61eb4 413}
7a2508e1 414EXPORT_SYMBOL(mb_cache_destroy);
f9a61eb4 415
7a2508e1 416static int __init mbcache_init(void)
f9a61eb4 417{
7a2508e1
JK
418 mb_entry_cache = kmem_cache_create("mbcache",
419 sizeof(struct mb_cache_entry), 0,
f9a61eb4 420 SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL);
21d0f4fa
EB
421 if (!mb_entry_cache)
422 return -ENOMEM;
f9a61eb4
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423 return 0;
424}
425
7a2508e1 426static void __exit mbcache_exit(void)
f9a61eb4 427{
7a2508e1 428 kmem_cache_destroy(mb_entry_cache);
f9a61eb4
JK
429}
430
7a2508e1
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431module_init(mbcache_init)
432module_exit(mbcache_exit)
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433
434MODULE_AUTHOR("Jan Kara <jack@suse.cz>");
435MODULE_DESCRIPTION("Meta block cache (for extended attributes)");
436MODULE_LICENSE("GPL");