Commit | Line | Data |
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09c434b8 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
f9a61eb4 JK |
2 | #include <linux/spinlock.h> |
3 | #include <linux/slab.h> | |
4 | #include <linux/list.h> | |
5 | #include <linux/list_bl.h> | |
6 | #include <linux/module.h> | |
7 | #include <linux/sched.h> | |
c2f3140f | 8 | #include <linux/workqueue.h> |
7a2508e1 | 9 | #include <linux/mbcache.h> |
f9a61eb4 JK |
10 | |
11 | /* | |
12 | * Mbcache is a simple key-value store. Keys need not be unique, however | |
13 | * key-value pairs are expected to be unique (we use this fact in | |
3dc96bba | 14 | * mb_cache_entry_delete_or_get()). |
f9a61eb4 JK |
15 | * |
16 | * Ext2 and ext4 use this cache for deduplication of extended attribute blocks. | |
dec214d0 TE |
17 | * Ext4 also uses it for deduplication of xattr values stored in inodes. |
18 | * They use hash of data as a key and provide a value that may represent a | |
19 | * block or inode number. That's why keys need not be unique (hash of different | |
20 | * data may be the same). However user provided value always uniquely | |
21 | * identifies a cache entry. | |
f9a61eb4 JK |
22 | * |
23 | * We provide functions for creation and removal of entries, search by key, | |
24 | * and a special "delete entry with given key-value pair" operation. Fixed | |
25 | * size hash table is used for fast key lookups. | |
26 | */ | |
27 | ||
7a2508e1 | 28 | struct mb_cache { |
f9a61eb4 JK |
29 | /* Hash table of entries */ |
30 | struct hlist_bl_head *c_hash; | |
31 | /* log2 of hash table size */ | |
32 | int c_bucket_bits; | |
c2f3140f | 33 | /* Maximum entries in cache to avoid degrading hash too much */ |
132d4e2d | 34 | unsigned long c_max_entries; |
f0c8b462 JK |
35 | /* Protects c_list, c_entry_count */ |
36 | spinlock_t c_list_lock; | |
37 | struct list_head c_list; | |
f9a61eb4 JK |
38 | /* Number of entries in cache */ |
39 | unsigned long c_entry_count; | |
714e5bde | 40 | struct shrinker *c_shrink; |
c2f3140f JK |
41 | /* Work for shrinking when the cache has too many entries */ |
42 | struct work_struct c_shrink_work; | |
f9a61eb4 JK |
43 | }; |
44 | ||
7a2508e1 | 45 | static struct kmem_cache *mb_entry_cache; |
f9a61eb4 | 46 | |
7a2508e1 | 47 | static unsigned long mb_cache_shrink(struct mb_cache *cache, |
132d4e2d | 48 | unsigned long nr_to_scan); |
c2f3140f | 49 | |
dc8d5e56 AG |
50 | static inline struct hlist_bl_head *mb_cache_entry_head(struct mb_cache *cache, |
51 | u32 key) | |
f0c8b462 | 52 | { |
dc8d5e56 | 53 | return &cache->c_hash[hash_32(key, cache->c_bucket_bits)]; |
f0c8b462 JK |
54 | } |
55 | ||
c2f3140f JK |
56 | /* |
57 | * Number of entries to reclaim synchronously when there are too many entries | |
58 | * in cache | |
59 | */ | |
60 | #define SYNC_SHRINK_BATCH 64 | |
61 | ||
f9a61eb4 | 62 | /* |
7a2508e1 | 63 | * mb_cache_entry_create - create entry in cache |
f9a61eb4 JK |
64 | * @cache - cache where the entry should be created |
65 | * @mask - gfp mask with which the entry should be allocated | |
66 | * @key - key of the entry | |
c07dfcb4 TE |
67 | * @value - value of the entry |
68 | * @reusable - is the entry reusable by others? | |
f9a61eb4 | 69 | * |
c07dfcb4 TE |
70 | * Creates entry in @cache with key @key and value @value. The function returns |
71 | * -EBUSY if entry with the same key and value already exists in cache. | |
72 | * Otherwise 0 is returned. | |
f9a61eb4 | 73 | */ |
7a2508e1 | 74 | int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key, |
c07dfcb4 | 75 | u64 value, bool reusable) |
f9a61eb4 | 76 | { |
7a2508e1 | 77 | struct mb_cache_entry *entry, *dup; |
f9a61eb4 JK |
78 | struct hlist_bl_node *dup_node; |
79 | struct hlist_bl_head *head; | |
80 | ||
c2f3140f JK |
81 | /* Schedule background reclaim if there are too many entries */ |
82 | if (cache->c_entry_count >= cache->c_max_entries) | |
83 | schedule_work(&cache->c_shrink_work); | |
84 | /* Do some sync reclaim if background reclaim cannot keep up */ | |
85 | if (cache->c_entry_count >= 2*cache->c_max_entries) | |
7a2508e1 | 86 | mb_cache_shrink(cache, SYNC_SHRINK_BATCH); |
c2f3140f | 87 | |
7a2508e1 | 88 | entry = kmem_cache_alloc(mb_entry_cache, mask); |
f9a61eb4 JK |
89 | if (!entry) |
90 | return -ENOMEM; | |
91 | ||
f0c8b462 | 92 | INIT_LIST_HEAD(&entry->e_list); |
5fc4cbd9 JK |
93 | /* |
94 | * We create entry with two references. One reference is kept by the | |
95 | * hash table, the other reference is used to protect us from | |
96 | * mb_cache_entry_delete_or_get() until the entry is fully setup. This | |
97 | * avoids nesting of cache->c_list_lock into hash table bit locks which | |
98 | * is problematic for RT. | |
99 | */ | |
100 | atomic_set(&entry->e_refcnt, 2); | |
f9a61eb4 | 101 | entry->e_key = key; |
c07dfcb4 | 102 | entry->e_value = value; |
a44e84a9 JK |
103 | entry->e_flags = 0; |
104 | if (reusable) | |
105 | set_bit(MBE_REUSABLE_B, &entry->e_flags); | |
dc8d5e56 | 106 | head = mb_cache_entry_head(cache, key); |
f9a61eb4 JK |
107 | hlist_bl_lock(head); |
108 | hlist_bl_for_each_entry(dup, dup_node, head, e_hash_list) { | |
c07dfcb4 | 109 | if (dup->e_key == key && dup->e_value == value) { |
f9a61eb4 | 110 | hlist_bl_unlock(head); |
7a2508e1 | 111 | kmem_cache_free(mb_entry_cache, entry); |
f9a61eb4 JK |
112 | return -EBUSY; |
113 | } | |
114 | } | |
115 | hlist_bl_add_head(&entry->e_hash_list, head); | |
5fc4cbd9 | 116 | hlist_bl_unlock(head); |
f0c8b462 JK |
117 | spin_lock(&cache->c_list_lock); |
118 | list_add_tail(&entry->e_list, &cache->c_list); | |
f9a61eb4 | 119 | cache->c_entry_count++; |
f0c8b462 | 120 | spin_unlock(&cache->c_list_lock); |
5fc4cbd9 | 121 | mb_cache_entry_put(cache, entry); |
f9a61eb4 JK |
122 | |
123 | return 0; | |
124 | } | |
7a2508e1 | 125 | EXPORT_SYMBOL(mb_cache_entry_create); |
f9a61eb4 | 126 | |
307af6c8 | 127 | void __mb_cache_entry_free(struct mb_cache *cache, struct mb_cache_entry *entry) |
f9a61eb4 | 128 | { |
307af6c8 JK |
129 | struct hlist_bl_head *head; |
130 | ||
131 | head = mb_cache_entry_head(cache, entry->e_key); | |
132 | hlist_bl_lock(head); | |
133 | hlist_bl_del(&entry->e_hash_list); | |
134 | hlist_bl_unlock(head); | |
7a2508e1 | 135 | kmem_cache_free(mb_entry_cache, entry); |
f9a61eb4 | 136 | } |
7a2508e1 | 137 | EXPORT_SYMBOL(__mb_cache_entry_free); |
f9a61eb4 | 138 | |
3dc96bba JK |
139 | /* |
140 | * mb_cache_entry_wait_unused - wait to be the last user of the entry | |
141 | * | |
142 | * @entry - entry to work on | |
143 | * | |
144 | * Wait to be the last user of the entry. | |
145 | */ | |
146 | void mb_cache_entry_wait_unused(struct mb_cache_entry *entry) | |
147 | { | |
307af6c8 | 148 | wait_var_event(&entry->e_refcnt, atomic_read(&entry->e_refcnt) <= 2); |
3dc96bba JK |
149 | } |
150 | EXPORT_SYMBOL(mb_cache_entry_wait_unused); | |
151 | ||
7a2508e1 JK |
152 | static struct mb_cache_entry *__entry_find(struct mb_cache *cache, |
153 | struct mb_cache_entry *entry, | |
154 | u32 key) | |
f9a61eb4 | 155 | { |
7a2508e1 | 156 | struct mb_cache_entry *old_entry = entry; |
f9a61eb4 JK |
157 | struct hlist_bl_node *node; |
158 | struct hlist_bl_head *head; | |
159 | ||
dc8d5e56 | 160 | head = mb_cache_entry_head(cache, key); |
f9a61eb4 JK |
161 | hlist_bl_lock(head); |
162 | if (entry && !hlist_bl_unhashed(&entry->e_hash_list)) | |
163 | node = entry->e_hash_list.next; | |
164 | else | |
165 | node = hlist_bl_first(head); | |
166 | while (node) { | |
7a2508e1 | 167 | entry = hlist_bl_entry(node, struct mb_cache_entry, |
f9a61eb4 | 168 | e_hash_list); |
a44e84a9 JK |
169 | if (entry->e_key == key && |
170 | test_bit(MBE_REUSABLE_B, &entry->e_flags) && | |
307af6c8 | 171 | atomic_inc_not_zero(&entry->e_refcnt)) |
f9a61eb4 | 172 | goto out; |
f9a61eb4 JK |
173 | node = node->next; |
174 | } | |
175 | entry = NULL; | |
176 | out: | |
177 | hlist_bl_unlock(head); | |
178 | if (old_entry) | |
7a2508e1 | 179 | mb_cache_entry_put(cache, old_entry); |
f9a61eb4 JK |
180 | |
181 | return entry; | |
182 | } | |
183 | ||
184 | /* | |
b649668c | 185 | * mb_cache_entry_find_first - find the first reusable entry with the given key |
f9a61eb4 JK |
186 | * @cache: cache where we should search |
187 | * @key: key to look for | |
188 | * | |
b649668c EB |
189 | * Search in @cache for a reusable entry with key @key. Grabs reference to the |
190 | * first reusable entry found and returns the entry. | |
f9a61eb4 | 191 | */ |
7a2508e1 JK |
192 | struct mb_cache_entry *mb_cache_entry_find_first(struct mb_cache *cache, |
193 | u32 key) | |
f9a61eb4 JK |
194 | { |
195 | return __entry_find(cache, NULL, key); | |
196 | } | |
7a2508e1 | 197 | EXPORT_SYMBOL(mb_cache_entry_find_first); |
f9a61eb4 JK |
198 | |
199 | /* | |
b649668c | 200 | * mb_cache_entry_find_next - find next reusable entry with the same key |
f9a61eb4 JK |
201 | * @cache: cache where we should search |
202 | * @entry: entry to start search from | |
203 | * | |
b649668c EB |
204 | * Finds next reusable entry in the hash chain which has the same key as @entry. |
205 | * If @entry is unhashed (which can happen when deletion of entry races with the | |
206 | * search), finds the first reusable entry in the hash chain. The function drops | |
207 | * reference to @entry and returns with a reference to the found entry. | |
f9a61eb4 | 208 | */ |
7a2508e1 JK |
209 | struct mb_cache_entry *mb_cache_entry_find_next(struct mb_cache *cache, |
210 | struct mb_cache_entry *entry) | |
f9a61eb4 JK |
211 | { |
212 | return __entry_find(cache, entry, entry->e_key); | |
213 | } | |
7a2508e1 | 214 | EXPORT_SYMBOL(mb_cache_entry_find_next); |
f9a61eb4 | 215 | |
6048c64b | 216 | /* |
c07dfcb4 | 217 | * mb_cache_entry_get - get a cache entry by value (and key) |
6048c64b | 218 | * @cache - cache we work with |
c07dfcb4 TE |
219 | * @key - key |
220 | * @value - value | |
6048c64b AG |
221 | */ |
222 | struct mb_cache_entry *mb_cache_entry_get(struct mb_cache *cache, u32 key, | |
c07dfcb4 | 223 | u64 value) |
6048c64b AG |
224 | { |
225 | struct hlist_bl_node *node; | |
226 | struct hlist_bl_head *head; | |
227 | struct mb_cache_entry *entry; | |
228 | ||
229 | head = mb_cache_entry_head(cache, key); | |
230 | hlist_bl_lock(head); | |
231 | hlist_bl_for_each_entry(entry, node, head, e_hash_list) { | |
307af6c8 JK |
232 | if (entry->e_key == key && entry->e_value == value && |
233 | atomic_inc_not_zero(&entry->e_refcnt)) | |
6048c64b | 234 | goto out; |
6048c64b AG |
235 | } |
236 | entry = NULL; | |
237 | out: | |
238 | hlist_bl_unlock(head); | |
239 | return entry; | |
240 | } | |
241 | EXPORT_SYMBOL(mb_cache_entry_get); | |
242 | ||
3dc96bba JK |
243 | /* mb_cache_entry_delete_or_get - remove a cache entry if it has no users |
244 | * @cache - cache we work with | |
245 | * @key - key | |
246 | * @value - value | |
247 | * | |
248 | * Remove entry from cache @cache with key @key and value @value. The removal | |
249 | * happens only if the entry is unused. The function returns NULL in case the | |
250 | * entry was successfully removed or there's no entry in cache. Otherwise the | |
251 | * function grabs reference of the entry that we failed to delete because it | |
252 | * still has users and return it. | |
253 | */ | |
254 | struct mb_cache_entry *mb_cache_entry_delete_or_get(struct mb_cache *cache, | |
255 | u32 key, u64 value) | |
256 | { | |
3dc96bba JK |
257 | struct mb_cache_entry *entry; |
258 | ||
307af6c8 JK |
259 | entry = mb_cache_entry_get(cache, key, value); |
260 | if (!entry) | |
261 | return NULL; | |
262 | ||
263 | /* | |
264 | * Drop the ref we got from mb_cache_entry_get() and the initial hash | |
265 | * ref if we are the last user | |
266 | */ | |
267 | if (atomic_cmpxchg(&entry->e_refcnt, 2, 0) != 2) | |
268 | return entry; | |
3dc96bba | 269 | |
307af6c8 JK |
270 | spin_lock(&cache->c_list_lock); |
271 | if (!list_empty(&entry->e_list)) | |
272 | list_del_init(&entry->e_list); | |
273 | cache->c_entry_count--; | |
274 | spin_unlock(&cache->c_list_lock); | |
275 | __mb_cache_entry_free(cache, entry); | |
3dc96bba JK |
276 | return NULL; |
277 | } | |
278 | EXPORT_SYMBOL(mb_cache_entry_delete_or_get); | |
279 | ||
7a2508e1 | 280 | /* mb_cache_entry_touch - cache entry got used |
f9a61eb4 JK |
281 | * @cache - cache the entry belongs to |
282 | * @entry - entry that got used | |
283 | * | |
f0c8b462 | 284 | * Marks entry as used to give hit higher chances of surviving in cache. |
f9a61eb4 | 285 | */ |
7a2508e1 JK |
286 | void mb_cache_entry_touch(struct mb_cache *cache, |
287 | struct mb_cache_entry *entry) | |
f9a61eb4 | 288 | { |
a44e84a9 | 289 | set_bit(MBE_REFERENCED_B, &entry->e_flags); |
f9a61eb4 | 290 | } |
7a2508e1 | 291 | EXPORT_SYMBOL(mb_cache_entry_touch); |
f9a61eb4 | 292 | |
7a2508e1 JK |
293 | static unsigned long mb_cache_count(struct shrinker *shrink, |
294 | struct shrink_control *sc) | |
f9a61eb4 | 295 | { |
714e5bde | 296 | struct mb_cache *cache = shrink->private_data; |
f9a61eb4 JK |
297 | |
298 | return cache->c_entry_count; | |
299 | } | |
300 | ||
301 | /* Shrink number of entries in cache */ | |
7a2508e1 | 302 | static unsigned long mb_cache_shrink(struct mb_cache *cache, |
132d4e2d | 303 | unsigned long nr_to_scan) |
f9a61eb4 | 304 | { |
7a2508e1 | 305 | struct mb_cache_entry *entry; |
132d4e2d | 306 | unsigned long shrunk = 0; |
f9a61eb4 | 307 | |
f0c8b462 JK |
308 | spin_lock(&cache->c_list_lock); |
309 | while (nr_to_scan-- && !list_empty(&cache->c_list)) { | |
310 | entry = list_first_entry(&cache->c_list, | |
7a2508e1 | 311 | struct mb_cache_entry, e_list); |
307af6c8 | 312 | /* Drop initial hash reference if there is no user */ |
a44e84a9 | 313 | if (test_bit(MBE_REFERENCED_B, &entry->e_flags) || |
307af6c8 | 314 | atomic_cmpxchg(&entry->e_refcnt, 1, 0) != 1) { |
a44e84a9 | 315 | clear_bit(MBE_REFERENCED_B, &entry->e_flags); |
918b7306 | 316 | list_move_tail(&entry->e_list, &cache->c_list); |
f0c8b462 JK |
317 | continue; |
318 | } | |
319 | list_del_init(&entry->e_list); | |
f9a61eb4 | 320 | cache->c_entry_count--; |
f0c8b462 | 321 | spin_unlock(&cache->c_list_lock); |
307af6c8 JK |
322 | __mb_cache_entry_free(cache, entry); |
323 | shrunk++; | |
f9a61eb4 | 324 | cond_resched(); |
f0c8b462 | 325 | spin_lock(&cache->c_list_lock); |
f9a61eb4 | 326 | } |
f0c8b462 | 327 | spin_unlock(&cache->c_list_lock); |
f9a61eb4 JK |
328 | |
329 | return shrunk; | |
330 | } | |
331 | ||
7a2508e1 JK |
332 | static unsigned long mb_cache_scan(struct shrinker *shrink, |
333 | struct shrink_control *sc) | |
c2f3140f | 334 | { |
714e5bde | 335 | struct mb_cache *cache = shrink->private_data; |
132d4e2d | 336 | return mb_cache_shrink(cache, sc->nr_to_scan); |
c2f3140f JK |
337 | } |
338 | ||
339 | /* We shrink 1/X of the cache when we have too many entries in it */ | |
340 | #define SHRINK_DIVISOR 16 | |
341 | ||
7a2508e1 | 342 | static void mb_cache_shrink_worker(struct work_struct *work) |
c2f3140f | 343 | { |
7a2508e1 JK |
344 | struct mb_cache *cache = container_of(work, struct mb_cache, |
345 | c_shrink_work); | |
346 | mb_cache_shrink(cache, cache->c_max_entries / SHRINK_DIVISOR); | |
c2f3140f JK |
347 | } |
348 | ||
f9a61eb4 | 349 | /* |
7a2508e1 | 350 | * mb_cache_create - create cache |
f9a61eb4 JK |
351 | * @bucket_bits: log2 of the hash table size |
352 | * | |
353 | * Create cache for keys with 2^bucket_bits hash entries. | |
354 | */ | |
7a2508e1 | 355 | struct mb_cache *mb_cache_create(int bucket_bits) |
f9a61eb4 | 356 | { |
7a2508e1 | 357 | struct mb_cache *cache; |
132d4e2d EB |
358 | unsigned long bucket_count = 1UL << bucket_bits; |
359 | unsigned long i; | |
f9a61eb4 | 360 | |
7a2508e1 | 361 | cache = kzalloc(sizeof(struct mb_cache), GFP_KERNEL); |
f9a61eb4 JK |
362 | if (!cache) |
363 | goto err_out; | |
364 | cache->c_bucket_bits = bucket_bits; | |
c2f3140f | 365 | cache->c_max_entries = bucket_count << 4; |
f0c8b462 JK |
366 | INIT_LIST_HEAD(&cache->c_list); |
367 | spin_lock_init(&cache->c_list_lock); | |
6da2ec56 KC |
368 | cache->c_hash = kmalloc_array(bucket_count, |
369 | sizeof(struct hlist_bl_head), | |
370 | GFP_KERNEL); | |
f9a61eb4 JK |
371 | if (!cache->c_hash) { |
372 | kfree(cache); | |
373 | goto err_out; | |
374 | } | |
375 | for (i = 0; i < bucket_count; i++) | |
376 | INIT_HLIST_BL_HEAD(&cache->c_hash[i]); | |
377 | ||
714e5bde QZ |
378 | cache->c_shrink = shrinker_alloc(0, "mbcache-shrinker"); |
379 | if (!cache->c_shrink) { | |
8913f343 CY |
380 | kfree(cache->c_hash); |
381 | kfree(cache); | |
382 | goto err_out; | |
383 | } | |
f9a61eb4 | 384 | |
714e5bde QZ |
385 | cache->c_shrink->count_objects = mb_cache_count; |
386 | cache->c_shrink->scan_objects = mb_cache_scan; | |
387 | cache->c_shrink->private_data = cache; | |
388 | ||
389 | shrinker_register(cache->c_shrink); | |
390 | ||
7a2508e1 | 391 | INIT_WORK(&cache->c_shrink_work, mb_cache_shrink_worker); |
c2f3140f | 392 | |
f9a61eb4 JK |
393 | return cache; |
394 | ||
395 | err_out: | |
f9a61eb4 JK |
396 | return NULL; |
397 | } | |
7a2508e1 | 398 | EXPORT_SYMBOL(mb_cache_create); |
f9a61eb4 JK |
399 | |
400 | /* | |
7a2508e1 | 401 | * mb_cache_destroy - destroy cache |
f9a61eb4 JK |
402 | * @cache: the cache to destroy |
403 | * | |
404 | * Free all entries in cache and cache itself. Caller must make sure nobody | |
405 | * (except shrinker) can reach @cache when calling this. | |
406 | */ | |
7a2508e1 | 407 | void mb_cache_destroy(struct mb_cache *cache) |
f9a61eb4 | 408 | { |
7a2508e1 | 409 | struct mb_cache_entry *entry, *next; |
f9a61eb4 | 410 | |
714e5bde | 411 | shrinker_free(cache->c_shrink); |
f9a61eb4 JK |
412 | |
413 | /* | |
414 | * We don't bother with any locking. Cache must not be used at this | |
415 | * point. | |
416 | */ | |
f0c8b462 | 417 | list_for_each_entry_safe(entry, next, &cache->c_list, e_list) { |
f0c8b462 | 418 | list_del(&entry->e_list); |
f9a61eb4 | 419 | WARN_ON(atomic_read(&entry->e_refcnt) != 1); |
7a2508e1 | 420 | mb_cache_entry_put(cache, entry); |
f9a61eb4 JK |
421 | } |
422 | kfree(cache->c_hash); | |
423 | kfree(cache); | |
f9a61eb4 | 424 | } |
7a2508e1 | 425 | EXPORT_SYMBOL(mb_cache_destroy); |
f9a61eb4 | 426 | |
7a2508e1 | 427 | static int __init mbcache_init(void) |
f9a61eb4 | 428 | { |
7a2508e1 JK |
429 | mb_entry_cache = kmem_cache_create("mbcache", |
430 | sizeof(struct mb_cache_entry), 0, | |
f9a61eb4 | 431 | SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD, NULL); |
21d0f4fa EB |
432 | if (!mb_entry_cache) |
433 | return -ENOMEM; | |
f9a61eb4 JK |
434 | return 0; |
435 | } | |
436 | ||
7a2508e1 | 437 | static void __exit mbcache_exit(void) |
f9a61eb4 | 438 | { |
7a2508e1 | 439 | kmem_cache_destroy(mb_entry_cache); |
f9a61eb4 JK |
440 | } |
441 | ||
7a2508e1 JK |
442 | module_init(mbcache_init) |
443 | module_exit(mbcache_exit) | |
f9a61eb4 JK |
444 | |
445 | MODULE_AUTHOR("Jan Kara <jack@suse.cz>"); | |
446 | MODULE_DESCRIPTION("Meta block cache (for extended attributes)"); | |
447 | MODULE_LICENSE("GPL"); |