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7e1e7763 TG |
1 | /* |
2 | * Resizable, Scalable, Concurrent Hash Table | |
3 | * | |
a5ec68e3 | 4 | * Copyright (c) 2014-2015 Thomas Graf <tgraf@suug.ch> |
7e1e7763 TG |
5 | * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net> |
6 | * | |
7 | * Based on the following paper: | |
8 | * https://www.usenix.org/legacy/event/atc11/tech/final_files/Triplett.pdf | |
9 | * | |
10 | * Code partially derived from nft_hash | |
11 | * | |
12 | * This program is free software; you can redistribute it and/or modify | |
13 | * it under the terms of the GNU General Public License version 2 as | |
14 | * published by the Free Software Foundation. | |
15 | */ | |
16 | ||
17 | #include <linux/kernel.h> | |
18 | #include <linux/init.h> | |
19 | #include <linux/log2.h> | |
20 | #include <linux/slab.h> | |
21 | #include <linux/vmalloc.h> | |
22 | #include <linux/mm.h> | |
87545899 | 23 | #include <linux/jhash.h> |
7e1e7763 TG |
24 | #include <linux/random.h> |
25 | #include <linux/rhashtable.h> | |
7e1e7763 TG |
26 | |
27 | #define HASH_DEFAULT_SIZE 64UL | |
28 | #define HASH_MIN_SIZE 4UL | |
97defe1e TG |
29 | #define BUCKET_LOCKS_PER_CPU 128UL |
30 | ||
f89bd6f8 TG |
31 | /* Base bits plus 1 bit for nulls marker */ |
32 | #define HASH_RESERVED_SPACE (RHT_BASE_BITS + 1) | |
33 | ||
97defe1e TG |
34 | enum { |
35 | RHT_LOCK_NORMAL, | |
36 | RHT_LOCK_NESTED, | |
97defe1e TG |
37 | }; |
38 | ||
39 | /* The bucket lock is selected based on the hash and protects mutations | |
40 | * on a group of hash buckets. | |
41 | * | |
a5ec68e3 TG |
42 | * A maximum of tbl->size/2 bucket locks is allocated. This ensures that |
43 | * a single lock always covers both buckets which may both contains | |
44 | * entries which link to the same bucket of the old table during resizing. | |
45 | * This allows to simplify the locking as locking the bucket in both | |
46 | * tables during resize always guarantee protection. | |
47 | * | |
97defe1e TG |
48 | * IMPORTANT: When holding the bucket lock of both the old and new table |
49 | * during expansions and shrinking, the old bucket lock must always be | |
50 | * acquired first. | |
51 | */ | |
52 | static spinlock_t *bucket_lock(const struct bucket_table *tbl, u32 hash) | |
53 | { | |
54 | return &tbl->locks[hash & tbl->locks_mask]; | |
55 | } | |
7e1e7763 | 56 | |
c91eee56 | 57 | static void *rht_obj(const struct rhashtable *ht, const struct rhash_head *he) |
7e1e7763 TG |
58 | { |
59 | return (void *) he - ht->p.head_offset; | |
60 | } | |
7e1e7763 | 61 | |
8d24c0b4 | 62 | static u32 rht_bucket_index(const struct bucket_table *tbl, u32 hash) |
7e1e7763 | 63 | { |
8d24c0b4 | 64 | return hash & (tbl->size - 1); |
7e1e7763 | 65 | } |
7e1e7763 | 66 | |
8d24c0b4 | 67 | static u32 obj_raw_hashfn(const struct rhashtable *ht, const void *ptr) |
7e1e7763 | 68 | { |
8d24c0b4 | 69 | u32 hash; |
7e1e7763 | 70 | |
8d24c0b4 TG |
71 | if (unlikely(!ht->p.key_len)) |
72 | hash = ht->p.obj_hashfn(ptr, ht->p.hash_rnd); | |
73 | else | |
74 | hash = ht->p.hashfn(ptr + ht->p.key_offset, ht->p.key_len, | |
75 | ht->p.hash_rnd); | |
7e1e7763 | 76 | |
f89bd6f8 | 77 | return hash >> HASH_RESERVED_SPACE; |
7e1e7763 TG |
78 | } |
79 | ||
97defe1e | 80 | static u32 key_hashfn(struct rhashtable *ht, const void *key, u32 len) |
7e1e7763 | 81 | { |
c88455ce | 82 | return ht->p.hashfn(key, len, ht->p.hash_rnd) >> HASH_RESERVED_SPACE; |
7e1e7763 | 83 | } |
7e1e7763 TG |
84 | |
85 | static u32 head_hashfn(const struct rhashtable *ht, | |
8d24c0b4 TG |
86 | const struct bucket_table *tbl, |
87 | const struct rhash_head *he) | |
7e1e7763 | 88 | { |
8d24c0b4 | 89 | return rht_bucket_index(tbl, obj_raw_hashfn(ht, rht_obj(ht, he))); |
7e1e7763 TG |
90 | } |
91 | ||
a03eaec0 TG |
92 | #ifdef CONFIG_PROVE_LOCKING |
93 | static void debug_dump_buckets(const struct rhashtable *ht, | |
94 | const struct bucket_table *tbl) | |
95 | { | |
96 | struct rhash_head *he; | |
97 | unsigned int i, hash; | |
98 | ||
99 | for (i = 0; i < tbl->size; i++) { | |
100 | pr_warn(" [Bucket %d] ", i); | |
101 | rht_for_each_rcu(he, tbl, i) { | |
102 | hash = head_hashfn(ht, tbl, he); | |
103 | pr_cont("[hash = %#x, lock = %p] ", | |
104 | hash, bucket_lock(tbl, hash)); | |
105 | } | |
106 | pr_cont("\n"); | |
107 | } | |
108 | ||
109 | } | |
110 | ||
111 | static void debug_dump_table(struct rhashtable *ht, | |
112 | const struct bucket_table *tbl, | |
113 | unsigned int hash) | |
114 | { | |
115 | struct bucket_table *old_tbl, *future_tbl; | |
116 | ||
117 | pr_emerg("BUG: lock for hash %#x in table %p not held\n", | |
118 | hash, tbl); | |
119 | ||
120 | rcu_read_lock(); | |
121 | future_tbl = rht_dereference_rcu(ht->future_tbl, ht); | |
122 | old_tbl = rht_dereference_rcu(ht->tbl, ht); | |
123 | if (future_tbl != old_tbl) { | |
124 | pr_warn("Future table %p (size: %zd)\n", | |
125 | future_tbl, future_tbl->size); | |
126 | debug_dump_buckets(ht, future_tbl); | |
127 | } | |
128 | ||
129 | pr_warn("Table %p (size: %zd)\n", old_tbl, old_tbl->size); | |
130 | debug_dump_buckets(ht, old_tbl); | |
131 | ||
132 | rcu_read_unlock(); | |
133 | } | |
134 | ||
135 | #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT)) | |
136 | #define ASSERT_BUCKET_LOCK(HT, TBL, HASH) \ | |
137 | do { \ | |
138 | if (unlikely(!lockdep_rht_bucket_is_held(TBL, HASH))) { \ | |
139 | debug_dump_table(HT, TBL, HASH); \ | |
140 | BUG(); \ | |
141 | } \ | |
142 | } while (0) | |
143 | ||
144 | int lockdep_rht_mutex_is_held(struct rhashtable *ht) | |
145 | { | |
146 | return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1; | |
147 | } | |
148 | EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held); | |
149 | ||
150 | int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash) | |
151 | { | |
152 | spinlock_t *lock = bucket_lock(tbl, hash); | |
153 | ||
154 | return (debug_locks) ? lockdep_is_held(lock) : 1; | |
155 | } | |
156 | EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held); | |
157 | #else | |
158 | #define ASSERT_RHT_MUTEX(HT) | |
159 | #define ASSERT_BUCKET_LOCK(HT, TBL, HASH) | |
160 | #endif | |
161 | ||
162 | ||
b8e1943e TG |
163 | static struct rhash_head __rcu **bucket_tail(struct bucket_table *tbl, u32 n) |
164 | { | |
165 | struct rhash_head __rcu **pprev; | |
166 | ||
167 | for (pprev = &tbl->buckets[n]; | |
f89bd6f8 | 168 | !rht_is_a_nulls(rht_dereference_bucket(*pprev, tbl, n)); |
b8e1943e TG |
169 | pprev = &rht_dereference_bucket(*pprev, tbl, n)->next) |
170 | ; | |
171 | ||
172 | return pprev; | |
173 | } | |
174 | ||
97defe1e TG |
175 | static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl) |
176 | { | |
177 | unsigned int i, size; | |
178 | #if defined(CONFIG_PROVE_LOCKING) | |
179 | unsigned int nr_pcpus = 2; | |
180 | #else | |
181 | unsigned int nr_pcpus = num_possible_cpus(); | |
182 | #endif | |
183 | ||
184 | nr_pcpus = min_t(unsigned int, nr_pcpus, 32UL); | |
185 | size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul); | |
186 | ||
a5ec68e3 TG |
187 | /* Never allocate more than 0.5 locks per bucket */ |
188 | size = min_t(unsigned int, size, tbl->size >> 1); | |
97defe1e TG |
189 | |
190 | if (sizeof(spinlock_t) != 0) { | |
191 | #ifdef CONFIG_NUMA | |
192 | if (size * sizeof(spinlock_t) > PAGE_SIZE) | |
193 | tbl->locks = vmalloc(size * sizeof(spinlock_t)); | |
194 | else | |
195 | #endif | |
196 | tbl->locks = kmalloc_array(size, sizeof(spinlock_t), | |
197 | GFP_KERNEL); | |
198 | if (!tbl->locks) | |
199 | return -ENOMEM; | |
200 | for (i = 0; i < size; i++) | |
201 | spin_lock_init(&tbl->locks[i]); | |
202 | } | |
203 | tbl->locks_mask = size - 1; | |
204 | ||
205 | return 0; | |
206 | } | |
207 | ||
208 | static void bucket_table_free(const struct bucket_table *tbl) | |
209 | { | |
210 | if (tbl) | |
211 | kvfree(tbl->locks); | |
212 | ||
213 | kvfree(tbl); | |
214 | } | |
215 | ||
216 | static struct bucket_table *bucket_table_alloc(struct rhashtable *ht, | |
217 | size_t nbuckets) | |
7e1e7763 TG |
218 | { |
219 | struct bucket_table *tbl; | |
220 | size_t size; | |
f89bd6f8 | 221 | int i; |
7e1e7763 TG |
222 | |
223 | size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]); | |
6eba8224 | 224 | tbl = kzalloc(size, GFP_KERNEL | __GFP_NOWARN); |
7e1e7763 TG |
225 | if (tbl == NULL) |
226 | tbl = vzalloc(size); | |
227 | ||
228 | if (tbl == NULL) | |
229 | return NULL; | |
230 | ||
231 | tbl->size = nbuckets; | |
232 | ||
97defe1e TG |
233 | if (alloc_bucket_locks(ht, tbl) < 0) { |
234 | bucket_table_free(tbl); | |
235 | return NULL; | |
236 | } | |
7e1e7763 | 237 | |
f89bd6f8 TG |
238 | for (i = 0; i < nbuckets; i++) |
239 | INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i); | |
240 | ||
97defe1e | 241 | return tbl; |
7e1e7763 TG |
242 | } |
243 | ||
244 | /** | |
245 | * rht_grow_above_75 - returns true if nelems > 0.75 * table-size | |
246 | * @ht: hash table | |
247 | * @new_size: new table size | |
248 | */ | |
249 | bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size) | |
250 | { | |
251 | /* Expand table when exceeding 75% load */ | |
c0c09bfd YX |
252 | return atomic_read(&ht->nelems) > (new_size / 4 * 3) && |
253 | (ht->p.max_shift && atomic_read(&ht->shift) < ht->p.max_shift); | |
7e1e7763 TG |
254 | } |
255 | EXPORT_SYMBOL_GPL(rht_grow_above_75); | |
256 | ||
257 | /** | |
258 | * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size | |
259 | * @ht: hash table | |
260 | * @new_size: new table size | |
261 | */ | |
262 | bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size) | |
263 | { | |
264 | /* Shrink table beneath 30% load */ | |
c0c09bfd YX |
265 | return atomic_read(&ht->nelems) < (new_size * 3 / 10) && |
266 | (atomic_read(&ht->shift) > ht->p.min_shift); | |
7e1e7763 TG |
267 | } |
268 | EXPORT_SYMBOL_GPL(rht_shrink_below_30); | |
269 | ||
a5ec68e3 TG |
270 | static void lock_buckets(struct bucket_table *new_tbl, |
271 | struct bucket_table *old_tbl, unsigned int hash) | |
272 | __acquires(old_bucket_lock) | |
273 | { | |
274 | spin_lock_bh(bucket_lock(old_tbl, hash)); | |
275 | if (new_tbl != old_tbl) | |
276 | spin_lock_bh_nested(bucket_lock(new_tbl, hash), | |
277 | RHT_LOCK_NESTED); | |
278 | } | |
279 | ||
280 | static void unlock_buckets(struct bucket_table *new_tbl, | |
281 | struct bucket_table *old_tbl, unsigned int hash) | |
282 | __releases(old_bucket_lock) | |
283 | { | |
284 | if (new_tbl != old_tbl) | |
285 | spin_unlock_bh(bucket_lock(new_tbl, hash)); | |
286 | spin_unlock_bh(bucket_lock(old_tbl, hash)); | |
287 | } | |
288 | ||
289 | /** | |
290 | * Unlink entries on bucket which hash to different bucket. | |
291 | * | |
292 | * Returns true if no more work needs to be performed on the bucket. | |
293 | */ | |
a03eaec0 | 294 | static bool hashtable_chain_unzip(struct rhashtable *ht, |
7e1e7763 | 295 | const struct bucket_table *new_tbl, |
97defe1e TG |
296 | struct bucket_table *old_tbl, |
297 | size_t old_hash) | |
7e1e7763 TG |
298 | { |
299 | struct rhash_head *he, *p, *next; | |
97defe1e TG |
300 | unsigned int new_hash, new_hash2; |
301 | ||
a03eaec0 | 302 | ASSERT_BUCKET_LOCK(ht, old_tbl, old_hash); |
7e1e7763 TG |
303 | |
304 | /* Old bucket empty, no work needed. */ | |
97defe1e TG |
305 | p = rht_dereference_bucket(old_tbl->buckets[old_hash], old_tbl, |
306 | old_hash); | |
f89bd6f8 | 307 | if (rht_is_a_nulls(p)) |
a5ec68e3 | 308 | return false; |
7e1e7763 | 309 | |
a5ec68e3 | 310 | new_hash = head_hashfn(ht, new_tbl, p); |
a03eaec0 | 311 | ASSERT_BUCKET_LOCK(ht, new_tbl, new_hash); |
97defe1e | 312 | |
7e1e7763 TG |
313 | /* Advance the old bucket pointer one or more times until it |
314 | * reaches a node that doesn't hash to the same bucket as the | |
315 | * previous node p. Call the previous node p; | |
316 | */ | |
97defe1e TG |
317 | rht_for_each_continue(he, p->next, old_tbl, old_hash) { |
318 | new_hash2 = head_hashfn(ht, new_tbl, he); | |
a03eaec0 | 319 | ASSERT_BUCKET_LOCK(ht, new_tbl, new_hash2); |
a5ec68e3 | 320 | |
97defe1e | 321 | if (new_hash != new_hash2) |
7e1e7763 TG |
322 | break; |
323 | p = he; | |
324 | } | |
97defe1e TG |
325 | rcu_assign_pointer(old_tbl->buckets[old_hash], p->next); |
326 | ||
7e1e7763 TG |
327 | /* Find the subsequent node which does hash to the same |
328 | * bucket as node P, or NULL if no such node exists. | |
329 | */ | |
f89bd6f8 TG |
330 | INIT_RHT_NULLS_HEAD(next, ht, old_hash); |
331 | if (!rht_is_a_nulls(he)) { | |
97defe1e TG |
332 | rht_for_each_continue(he, he->next, old_tbl, old_hash) { |
333 | if (head_hashfn(ht, new_tbl, he) == new_hash) { | |
7e1e7763 TG |
334 | next = he; |
335 | break; | |
336 | } | |
337 | } | |
338 | } | |
339 | ||
340 | /* Set p's next pointer to that subsequent node pointer, | |
341 | * bypassing the nodes which do not hash to p's bucket | |
342 | */ | |
97defe1e TG |
343 | rcu_assign_pointer(p->next, next); |
344 | ||
a5ec68e3 TG |
345 | p = rht_dereference_bucket(old_tbl->buckets[old_hash], old_tbl, |
346 | old_hash); | |
347 | ||
348 | return !rht_is_a_nulls(p); | |
97defe1e TG |
349 | } |
350 | ||
351 | static void link_old_to_new(struct bucket_table *new_tbl, | |
352 | unsigned int new_hash, struct rhash_head *entry) | |
353 | { | |
97defe1e | 354 | rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), entry); |
7e1e7763 TG |
355 | } |
356 | ||
357 | /** | |
358 | * rhashtable_expand - Expand hash table while allowing concurrent lookups | |
359 | * @ht: the hash table to expand | |
7e1e7763 TG |
360 | * |
361 | * A secondary bucket array is allocated and the hash entries are migrated | |
362 | * while keeping them on both lists until the end of the RCU grace period. | |
363 | * | |
364 | * This function may only be called in a context where it is safe to call | |
365 | * synchronize_rcu(), e.g. not within a rcu_read_lock() section. | |
366 | * | |
97defe1e TG |
367 | * The caller must ensure that no concurrent resizing occurs by holding |
368 | * ht->mutex. | |
369 | * | |
370 | * It is valid to have concurrent insertions and deletions protected by per | |
371 | * bucket locks or concurrent RCU protected lookups and traversals. | |
7e1e7763 | 372 | */ |
6eba8224 | 373 | int rhashtable_expand(struct rhashtable *ht) |
7e1e7763 TG |
374 | { |
375 | struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht); | |
376 | struct rhash_head *he; | |
97defe1e TG |
377 | unsigned int new_hash, old_hash; |
378 | bool complete = false; | |
7e1e7763 TG |
379 | |
380 | ASSERT_RHT_MUTEX(ht); | |
381 | ||
97defe1e | 382 | new_tbl = bucket_table_alloc(ht, old_tbl->size * 2); |
7e1e7763 TG |
383 | if (new_tbl == NULL) |
384 | return -ENOMEM; | |
385 | ||
c0c09bfd | 386 | atomic_inc(&ht->shift); |
7e1e7763 | 387 | |
97defe1e TG |
388 | /* Make insertions go into the new, empty table right away. Deletions |
389 | * and lookups will be attempted in both tables until we synchronize. | |
390 | * The synchronize_rcu() guarantees for the new table to be picked up | |
391 | * so no new additions go into the old table while we relink. | |
392 | */ | |
393 | rcu_assign_pointer(ht->future_tbl, new_tbl); | |
394 | synchronize_rcu(); | |
395 | ||
396 | /* For each new bucket, search the corresponding old bucket for the | |
397 | * first entry that hashes to the new bucket, and link the end of | |
398 | * newly formed bucket chain (containing entries added to future | |
399 | * table) to that entry. Since all the entries which will end up in | |
400 | * the new bucket appear in the same old bucket, this constructs an | |
401 | * entirely valid new hash table, but with multiple buckets | |
402 | * "zipped" together into a single imprecise chain. | |
7e1e7763 | 403 | */ |
97defe1e TG |
404 | for (new_hash = 0; new_hash < new_tbl->size; new_hash++) { |
405 | old_hash = rht_bucket_index(old_tbl, new_hash); | |
a5ec68e3 | 406 | lock_buckets(new_tbl, old_tbl, new_hash); |
97defe1e TG |
407 | rht_for_each(he, old_tbl, old_hash) { |
408 | if (head_hashfn(ht, new_tbl, he) == new_hash) { | |
409 | link_old_to_new(new_tbl, new_hash, he); | |
7e1e7763 TG |
410 | break; |
411 | } | |
412 | } | |
a5ec68e3 | 413 | unlock_buckets(new_tbl, old_tbl, new_hash); |
7e1e7763 TG |
414 | } |
415 | ||
416 | /* Publish the new table pointer. Lookups may now traverse | |
0c828f2f HX |
417 | * the new table, but they will not benefit from any |
418 | * additional efficiency until later steps unzip the buckets. | |
7e1e7763 TG |
419 | */ |
420 | rcu_assign_pointer(ht->tbl, new_tbl); | |
421 | ||
422 | /* Unzip interleaved hash chains */ | |
97defe1e | 423 | while (!complete && !ht->being_destroyed) { |
7e1e7763 TG |
424 | /* Wait for readers. All new readers will see the new |
425 | * table, and thus no references to the old table will | |
426 | * remain. | |
427 | */ | |
428 | synchronize_rcu(); | |
429 | ||
430 | /* For each bucket in the old table (each of which | |
431 | * contains items from multiple buckets of the new | |
432 | * table): ... | |
433 | */ | |
434 | complete = true; | |
97defe1e | 435 | for (old_hash = 0; old_hash < old_tbl->size; old_hash++) { |
a5ec68e3 | 436 | lock_buckets(new_tbl, old_tbl, old_hash); |
97defe1e | 437 | |
a5ec68e3 TG |
438 | if (hashtable_chain_unzip(ht, new_tbl, old_tbl, |
439 | old_hash)) | |
7e1e7763 | 440 | complete = false; |
97defe1e | 441 | |
a5ec68e3 | 442 | unlock_buckets(new_tbl, old_tbl, old_hash); |
7e1e7763 | 443 | } |
97defe1e | 444 | } |
7e1e7763 | 445 | |
2af4b529 TG |
446 | synchronize_rcu(); |
447 | ||
7e1e7763 TG |
448 | bucket_table_free(old_tbl); |
449 | return 0; | |
450 | } | |
451 | EXPORT_SYMBOL_GPL(rhashtable_expand); | |
452 | ||
453 | /** | |
454 | * rhashtable_shrink - Shrink hash table while allowing concurrent lookups | |
455 | * @ht: the hash table to shrink | |
7e1e7763 TG |
456 | * |
457 | * This function may only be called in a context where it is safe to call | |
458 | * synchronize_rcu(), e.g. not within a rcu_read_lock() section. | |
459 | * | |
97defe1e TG |
460 | * The caller must ensure that no concurrent resizing occurs by holding |
461 | * ht->mutex. | |
462 | * | |
7e1e7763 TG |
463 | * The caller must ensure that no concurrent table mutations take place. |
464 | * It is however valid to have concurrent lookups if they are RCU protected. | |
97defe1e TG |
465 | * |
466 | * It is valid to have concurrent insertions and deletions protected by per | |
467 | * bucket locks or concurrent RCU protected lookups and traversals. | |
7e1e7763 | 468 | */ |
6eba8224 | 469 | int rhashtable_shrink(struct rhashtable *ht) |
7e1e7763 | 470 | { |
97defe1e | 471 | struct bucket_table *new_tbl, *tbl = rht_dereference(ht->tbl, ht); |
97defe1e | 472 | unsigned int new_hash; |
7e1e7763 TG |
473 | |
474 | ASSERT_RHT_MUTEX(ht); | |
475 | ||
97defe1e TG |
476 | new_tbl = bucket_table_alloc(ht, tbl->size / 2); |
477 | if (new_tbl == NULL) | |
7e1e7763 TG |
478 | return -ENOMEM; |
479 | ||
97defe1e TG |
480 | rcu_assign_pointer(ht->future_tbl, new_tbl); |
481 | synchronize_rcu(); | |
7e1e7763 | 482 | |
97defe1e TG |
483 | /* Link the first entry in the old bucket to the end of the |
484 | * bucket in the new table. As entries are concurrently being | |
485 | * added to the new table, lock down the new bucket. As we | |
486 | * always divide the size in half when shrinking, each bucket | |
487 | * in the new table maps to exactly two buckets in the old | |
488 | * table. | |
7e1e7763 | 489 | */ |
97defe1e | 490 | for (new_hash = 0; new_hash < new_tbl->size; new_hash++) { |
a5ec68e3 | 491 | lock_buckets(new_tbl, tbl, new_hash); |
97defe1e TG |
492 | |
493 | rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), | |
494 | tbl->buckets[new_hash]); | |
495 | rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), | |
496 | tbl->buckets[new_hash + new_tbl->size]); | |
497 | ||
a5ec68e3 | 498 | unlock_buckets(new_tbl, tbl, new_hash); |
7e1e7763 TG |
499 | } |
500 | ||
501 | /* Publish the new, valid hash table */ | |
97defe1e | 502 | rcu_assign_pointer(ht->tbl, new_tbl); |
c0c09bfd | 503 | atomic_dec(&ht->shift); |
7e1e7763 TG |
504 | |
505 | /* Wait for readers. No new readers will have references to the | |
506 | * old hash table. | |
507 | */ | |
508 | synchronize_rcu(); | |
509 | ||
510 | bucket_table_free(tbl); | |
511 | ||
512 | return 0; | |
513 | } | |
514 | EXPORT_SYMBOL_GPL(rhashtable_shrink); | |
515 | ||
97defe1e TG |
516 | static void rht_deferred_worker(struct work_struct *work) |
517 | { | |
518 | struct rhashtable *ht; | |
519 | struct bucket_table *tbl; | |
f2dba9c6 | 520 | struct rhashtable_walker *walker; |
97defe1e | 521 | |
57699a40 | 522 | ht = container_of(work, struct rhashtable, run_work); |
97defe1e | 523 | mutex_lock(&ht->mutex); |
28134a53 HX |
524 | if (ht->being_destroyed) |
525 | goto unlock; | |
526 | ||
97defe1e TG |
527 | tbl = rht_dereference(ht->tbl, ht); |
528 | ||
f2dba9c6 HX |
529 | list_for_each_entry(walker, &ht->walkers, list) |
530 | walker->resize = true; | |
531 | ||
97defe1e TG |
532 | if (ht->p.grow_decision && ht->p.grow_decision(ht, tbl->size)) |
533 | rhashtable_expand(ht); | |
534 | else if (ht->p.shrink_decision && ht->p.shrink_decision(ht, tbl->size)) | |
535 | rhashtable_shrink(ht); | |
536 | ||
28134a53 | 537 | unlock: |
97defe1e TG |
538 | mutex_unlock(&ht->mutex); |
539 | } | |
540 | ||
54c5b7d3 YX |
541 | static void rhashtable_wakeup_worker(struct rhashtable *ht) |
542 | { | |
543 | struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht); | |
544 | struct bucket_table *new_tbl = rht_dereference_rcu(ht->future_tbl, ht); | |
545 | size_t size = tbl->size; | |
546 | ||
547 | /* Only adjust the table if no resizing is currently in progress. */ | |
548 | if (tbl == new_tbl && | |
549 | ((ht->p.grow_decision && ht->p.grow_decision(ht, size)) || | |
550 | (ht->p.shrink_decision && ht->p.shrink_decision(ht, size)))) | |
57699a40 | 551 | schedule_work(&ht->run_work); |
54c5b7d3 YX |
552 | } |
553 | ||
db304854 YX |
554 | static void __rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj, |
555 | struct bucket_table *tbl, u32 hash) | |
556 | { | |
557 | struct rhash_head *head = rht_dereference_bucket(tbl->buckets[hash], | |
558 | tbl, hash); | |
559 | ||
560 | if (rht_is_a_nulls(head)) | |
561 | INIT_RHT_NULLS_HEAD(obj->next, ht, hash); | |
562 | else | |
563 | RCU_INIT_POINTER(obj->next, head); | |
564 | ||
565 | rcu_assign_pointer(tbl->buckets[hash], obj); | |
566 | ||
567 | atomic_inc(&ht->nelems); | |
568 | ||
569 | rhashtable_wakeup_worker(ht); | |
570 | } | |
571 | ||
7e1e7763 | 572 | /** |
db304854 | 573 | * rhashtable_insert - insert object into hash table |
7e1e7763 TG |
574 | * @ht: hash table |
575 | * @obj: pointer to hash head inside object | |
7e1e7763 | 576 | * |
97defe1e TG |
577 | * Will take a per bucket spinlock to protect against mutual mutations |
578 | * on the same bucket. Multiple insertions may occur in parallel unless | |
579 | * they map to the same bucket lock. | |
7e1e7763 | 580 | * |
97defe1e TG |
581 | * It is safe to call this function from atomic context. |
582 | * | |
583 | * Will trigger an automatic deferred table resizing if the size grows | |
584 | * beyond the watermark indicated by grow_decision() which can be passed | |
585 | * to rhashtable_init(). | |
7e1e7763 | 586 | */ |
6eba8224 | 587 | void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj) |
7e1e7763 | 588 | { |
a5ec68e3 | 589 | struct bucket_table *tbl, *old_tbl; |
97defe1e | 590 | unsigned hash; |
7e1e7763 | 591 | |
97defe1e | 592 | rcu_read_lock(); |
7e1e7763 | 593 | |
97defe1e | 594 | tbl = rht_dereference_rcu(ht->future_tbl, ht); |
a5ec68e3 | 595 | old_tbl = rht_dereference_rcu(ht->tbl, ht); |
8d24c0b4 | 596 | hash = head_hashfn(ht, tbl, obj); |
97defe1e | 597 | |
a5ec68e3 | 598 | lock_buckets(tbl, old_tbl, hash); |
db304854 | 599 | __rhashtable_insert(ht, obj, tbl, hash); |
a5ec68e3 | 600 | unlock_buckets(tbl, old_tbl, hash); |
7e1e7763 | 601 | |
97defe1e | 602 | rcu_read_unlock(); |
7e1e7763 TG |
603 | } |
604 | EXPORT_SYMBOL_GPL(rhashtable_insert); | |
605 | ||
7e1e7763 TG |
606 | /** |
607 | * rhashtable_remove - remove object from hash table | |
608 | * @ht: hash table | |
609 | * @obj: pointer to hash head inside object | |
7e1e7763 TG |
610 | * |
611 | * Since the hash chain is single linked, the removal operation needs to | |
612 | * walk the bucket chain upon removal. The removal operation is thus | |
613 | * considerable slow if the hash table is not correctly sized. | |
614 | * | |
db304854 | 615 | * Will automatically shrink the table via rhashtable_expand() if the |
7e1e7763 TG |
616 | * shrink_decision function specified at rhashtable_init() returns true. |
617 | * | |
618 | * The caller must ensure that no concurrent table mutations occur. It is | |
619 | * however valid to have concurrent lookups if they are RCU protected. | |
620 | */ | |
6eba8224 | 621 | bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj) |
7e1e7763 | 622 | { |
a5ec68e3 | 623 | struct bucket_table *tbl, *new_tbl, *old_tbl; |
7e1e7763 TG |
624 | struct rhash_head __rcu **pprev; |
625 | struct rhash_head *he; | |
a5ec68e3 | 626 | unsigned int hash, new_hash; |
fe6a043c | 627 | bool ret = false; |
7e1e7763 | 628 | |
97defe1e | 629 | rcu_read_lock(); |
a5ec68e3 TG |
630 | tbl = old_tbl = rht_dereference_rcu(ht->tbl, ht); |
631 | new_tbl = rht_dereference_rcu(ht->future_tbl, ht); | |
632 | new_hash = head_hashfn(ht, new_tbl, obj); | |
7e1e7763 | 633 | |
a5ec68e3 | 634 | lock_buckets(new_tbl, old_tbl, new_hash); |
97defe1e | 635 | restart: |
a5ec68e3 | 636 | hash = rht_bucket_index(tbl, new_hash); |
97defe1e TG |
637 | pprev = &tbl->buckets[hash]; |
638 | rht_for_each(he, tbl, hash) { | |
7e1e7763 TG |
639 | if (he != obj) { |
640 | pprev = &he->next; | |
641 | continue; | |
642 | } | |
643 | ||
97defe1e | 644 | rcu_assign_pointer(*pprev, obj->next); |
897362e4 | 645 | |
fe6a043c TG |
646 | ret = true; |
647 | break; | |
7e1e7763 TG |
648 | } |
649 | ||
fe6a043c TG |
650 | /* The entry may be linked in either 'tbl', 'future_tbl', or both. |
651 | * 'future_tbl' only exists for a short period of time during | |
652 | * resizing. Thus traversing both is fine and the added cost is | |
653 | * very rare. | |
654 | */ | |
a5ec68e3 TG |
655 | if (tbl != new_tbl) { |
656 | tbl = new_tbl; | |
97defe1e TG |
657 | goto restart; |
658 | } | |
659 | ||
a5ec68e3 | 660 | unlock_buckets(new_tbl, old_tbl, new_hash); |
fe6a043c TG |
661 | |
662 | if (ret) { | |
663 | atomic_dec(&ht->nelems); | |
664 | rhashtable_wakeup_worker(ht); | |
665 | } | |
666 | ||
97defe1e TG |
667 | rcu_read_unlock(); |
668 | ||
fe6a043c | 669 | return ret; |
7e1e7763 TG |
670 | } |
671 | EXPORT_SYMBOL_GPL(rhashtable_remove); | |
672 | ||
efb975a6 YX |
673 | struct rhashtable_compare_arg { |
674 | struct rhashtable *ht; | |
675 | const void *key; | |
676 | }; | |
677 | ||
678 | static bool rhashtable_compare(void *ptr, void *arg) | |
679 | { | |
680 | struct rhashtable_compare_arg *x = arg; | |
681 | struct rhashtable *ht = x->ht; | |
682 | ||
683 | return !memcmp(ptr + ht->p.key_offset, x->key, ht->p.key_len); | |
684 | } | |
685 | ||
7e1e7763 TG |
686 | /** |
687 | * rhashtable_lookup - lookup key in hash table | |
688 | * @ht: hash table | |
689 | * @key: pointer to key | |
690 | * | |
691 | * Computes the hash value for the key and traverses the bucket chain looking | |
692 | * for a entry with an identical key. The first matching entry is returned. | |
693 | * | |
694 | * This lookup function may only be used for fixed key hash table (key_len | |
db304854 | 695 | * parameter set). It will BUG() if used inappropriately. |
7e1e7763 | 696 | * |
97defe1e | 697 | * Lookups may occur in parallel with hashtable mutations and resizing. |
7e1e7763 | 698 | */ |
97defe1e | 699 | void *rhashtable_lookup(struct rhashtable *ht, const void *key) |
7e1e7763 | 700 | { |
efb975a6 YX |
701 | struct rhashtable_compare_arg arg = { |
702 | .ht = ht, | |
703 | .key = key, | |
704 | }; | |
7e1e7763 TG |
705 | |
706 | BUG_ON(!ht->p.key_len); | |
707 | ||
efb975a6 | 708 | return rhashtable_lookup_compare(ht, key, &rhashtable_compare, &arg); |
7e1e7763 TG |
709 | } |
710 | EXPORT_SYMBOL_GPL(rhashtable_lookup); | |
711 | ||
712 | /** | |
713 | * rhashtable_lookup_compare - search hash table with compare function | |
714 | * @ht: hash table | |
8d24c0b4 | 715 | * @key: the pointer to the key |
7e1e7763 TG |
716 | * @compare: compare function, must return true on match |
717 | * @arg: argument passed on to compare function | |
718 | * | |
719 | * Traverses the bucket chain behind the provided hash value and calls the | |
720 | * specified compare function for each entry. | |
721 | * | |
97defe1e | 722 | * Lookups may occur in parallel with hashtable mutations and resizing. |
7e1e7763 TG |
723 | * |
724 | * Returns the first entry on which the compare function returned true. | |
725 | */ | |
97defe1e | 726 | void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key, |
7e1e7763 TG |
727 | bool (*compare)(void *, void *), void *arg) |
728 | { | |
97defe1e | 729 | const struct bucket_table *tbl, *old_tbl; |
7e1e7763 | 730 | struct rhash_head *he; |
8d24c0b4 | 731 | u32 hash; |
7e1e7763 | 732 | |
97defe1e TG |
733 | rcu_read_lock(); |
734 | ||
735 | old_tbl = rht_dereference_rcu(ht->tbl, ht); | |
736 | tbl = rht_dereference_rcu(ht->future_tbl, ht); | |
8d24c0b4 | 737 | hash = key_hashfn(ht, key, ht->p.key_len); |
97defe1e TG |
738 | restart: |
739 | rht_for_each_rcu(he, tbl, rht_bucket_index(tbl, hash)) { | |
7e1e7763 TG |
740 | if (!compare(rht_obj(ht, he), arg)) |
741 | continue; | |
97defe1e | 742 | rcu_read_unlock(); |
a4b18cda | 743 | return rht_obj(ht, he); |
7e1e7763 TG |
744 | } |
745 | ||
97defe1e TG |
746 | if (unlikely(tbl != old_tbl)) { |
747 | tbl = old_tbl; | |
748 | goto restart; | |
749 | } | |
750 | rcu_read_unlock(); | |
751 | ||
7e1e7763 TG |
752 | return NULL; |
753 | } | |
754 | EXPORT_SYMBOL_GPL(rhashtable_lookup_compare); | |
755 | ||
db304854 YX |
756 | /** |
757 | * rhashtable_lookup_insert - lookup and insert object into hash table | |
758 | * @ht: hash table | |
759 | * @obj: pointer to hash head inside object | |
760 | * | |
761 | * Locks down the bucket chain in both the old and new table if a resize | |
762 | * is in progress to ensure that writers can't remove from the old table | |
763 | * and can't insert to the new table during the atomic operation of search | |
764 | * and insertion. Searches for duplicates in both the old and new table if | |
765 | * a resize is in progress. | |
766 | * | |
767 | * This lookup function may only be used for fixed key hash table (key_len | |
768 | * parameter set). It will BUG() if used inappropriately. | |
769 | * | |
770 | * It is safe to call this function from atomic context. | |
771 | * | |
772 | * Will trigger an automatic deferred table resizing if the size grows | |
773 | * beyond the watermark indicated by grow_decision() which can be passed | |
774 | * to rhashtable_init(). | |
775 | */ | |
776 | bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj) | |
7a868d1e YX |
777 | { |
778 | struct rhashtable_compare_arg arg = { | |
779 | .ht = ht, | |
780 | .key = rht_obj(ht, obj) + ht->p.key_offset, | |
781 | }; | |
782 | ||
783 | BUG_ON(!ht->p.key_len); | |
784 | ||
785 | return rhashtable_lookup_compare_insert(ht, obj, &rhashtable_compare, | |
786 | &arg); | |
787 | } | |
788 | EXPORT_SYMBOL_GPL(rhashtable_lookup_insert); | |
789 | ||
790 | /** | |
791 | * rhashtable_lookup_compare_insert - search and insert object to hash table | |
792 | * with compare function | |
793 | * @ht: hash table | |
794 | * @obj: pointer to hash head inside object | |
795 | * @compare: compare function, must return true on match | |
796 | * @arg: argument passed on to compare function | |
797 | * | |
798 | * Locks down the bucket chain in both the old and new table if a resize | |
799 | * is in progress to ensure that writers can't remove from the old table | |
800 | * and can't insert to the new table during the atomic operation of search | |
801 | * and insertion. Searches for duplicates in both the old and new table if | |
802 | * a resize is in progress. | |
803 | * | |
804 | * Lookups may occur in parallel with hashtable mutations and resizing. | |
805 | * | |
806 | * Will trigger an automatic deferred table resizing if the size grows | |
807 | * beyond the watermark indicated by grow_decision() which can be passed | |
808 | * to rhashtable_init(). | |
809 | */ | |
810 | bool rhashtable_lookup_compare_insert(struct rhashtable *ht, | |
811 | struct rhash_head *obj, | |
812 | bool (*compare)(void *, void *), | |
813 | void *arg) | |
db304854 YX |
814 | { |
815 | struct bucket_table *new_tbl, *old_tbl; | |
a5ec68e3 | 816 | u32 new_hash; |
db304854 YX |
817 | bool success = true; |
818 | ||
819 | BUG_ON(!ht->p.key_len); | |
820 | ||
821 | rcu_read_lock(); | |
db304854 | 822 | old_tbl = rht_dereference_rcu(ht->tbl, ht); |
db304854 YX |
823 | new_tbl = rht_dereference_rcu(ht->future_tbl, ht); |
824 | new_hash = head_hashfn(ht, new_tbl, obj); | |
a5ec68e3 TG |
825 | |
826 | lock_buckets(new_tbl, old_tbl, new_hash); | |
db304854 | 827 | |
7a868d1e YX |
828 | if (rhashtable_lookup_compare(ht, rht_obj(ht, obj) + ht->p.key_offset, |
829 | compare, arg)) { | |
db304854 YX |
830 | success = false; |
831 | goto exit; | |
832 | } | |
833 | ||
834 | __rhashtable_insert(ht, obj, new_tbl, new_hash); | |
835 | ||
836 | exit: | |
a5ec68e3 | 837 | unlock_buckets(new_tbl, old_tbl, new_hash); |
db304854 YX |
838 | rcu_read_unlock(); |
839 | ||
840 | return success; | |
841 | } | |
7a868d1e | 842 | EXPORT_SYMBOL_GPL(rhashtable_lookup_compare_insert); |
db304854 | 843 | |
f2dba9c6 HX |
844 | /** |
845 | * rhashtable_walk_init - Initialise an iterator | |
846 | * @ht: Table to walk over | |
847 | * @iter: Hash table Iterator | |
848 | * | |
849 | * This function prepares a hash table walk. | |
850 | * | |
851 | * Note that if you restart a walk after rhashtable_walk_stop you | |
852 | * may see the same object twice. Also, you may miss objects if | |
853 | * there are removals in between rhashtable_walk_stop and the next | |
854 | * call to rhashtable_walk_start. | |
855 | * | |
856 | * For a completely stable walk you should construct your own data | |
857 | * structure outside the hash table. | |
858 | * | |
859 | * This function may sleep so you must not call it from interrupt | |
860 | * context or with spin locks held. | |
861 | * | |
862 | * You must call rhashtable_walk_exit if this function returns | |
863 | * successfully. | |
864 | */ | |
865 | int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter) | |
866 | { | |
867 | iter->ht = ht; | |
868 | iter->p = NULL; | |
869 | iter->slot = 0; | |
870 | iter->skip = 0; | |
871 | ||
872 | iter->walker = kmalloc(sizeof(*iter->walker), GFP_KERNEL); | |
873 | if (!iter->walker) | |
874 | return -ENOMEM; | |
875 | ||
876 | mutex_lock(&ht->mutex); | |
877 | list_add(&iter->walker->list, &ht->walkers); | |
878 | mutex_unlock(&ht->mutex); | |
879 | ||
880 | return 0; | |
881 | } | |
882 | EXPORT_SYMBOL_GPL(rhashtable_walk_init); | |
883 | ||
884 | /** | |
885 | * rhashtable_walk_exit - Free an iterator | |
886 | * @iter: Hash table Iterator | |
887 | * | |
888 | * This function frees resources allocated by rhashtable_walk_init. | |
889 | */ | |
890 | void rhashtable_walk_exit(struct rhashtable_iter *iter) | |
891 | { | |
892 | mutex_lock(&iter->ht->mutex); | |
893 | list_del(&iter->walker->list); | |
894 | mutex_unlock(&iter->ht->mutex); | |
895 | kfree(iter->walker); | |
896 | } | |
897 | EXPORT_SYMBOL_GPL(rhashtable_walk_exit); | |
898 | ||
899 | /** | |
900 | * rhashtable_walk_start - Start a hash table walk | |
901 | * @iter: Hash table iterator | |
902 | * | |
903 | * Start a hash table walk. Note that we take the RCU lock in all | |
904 | * cases including when we return an error. So you must always call | |
905 | * rhashtable_walk_stop to clean up. | |
906 | * | |
907 | * Returns zero if successful. | |
908 | * | |
909 | * Returns -EAGAIN if resize event occured. Note that the iterator | |
910 | * will rewind back to the beginning and you may use it immediately | |
911 | * by calling rhashtable_walk_next. | |
912 | */ | |
913 | int rhashtable_walk_start(struct rhashtable_iter *iter) | |
914 | { | |
915 | rcu_read_lock(); | |
916 | ||
917 | if (iter->walker->resize) { | |
918 | iter->slot = 0; | |
919 | iter->skip = 0; | |
920 | iter->walker->resize = false; | |
921 | return -EAGAIN; | |
922 | } | |
923 | ||
924 | return 0; | |
925 | } | |
926 | EXPORT_SYMBOL_GPL(rhashtable_walk_start); | |
927 | ||
928 | /** | |
929 | * rhashtable_walk_next - Return the next object and advance the iterator | |
930 | * @iter: Hash table iterator | |
931 | * | |
932 | * Note that you must call rhashtable_walk_stop when you are finished | |
933 | * with the walk. | |
934 | * | |
935 | * Returns the next object or NULL when the end of the table is reached. | |
936 | * | |
937 | * Returns -EAGAIN if resize event occured. Note that the iterator | |
938 | * will rewind back to the beginning and you may continue to use it. | |
939 | */ | |
940 | void *rhashtable_walk_next(struct rhashtable_iter *iter) | |
941 | { | |
942 | const struct bucket_table *tbl; | |
943 | struct rhashtable *ht = iter->ht; | |
944 | struct rhash_head *p = iter->p; | |
945 | void *obj = NULL; | |
946 | ||
947 | tbl = rht_dereference_rcu(ht->tbl, ht); | |
948 | ||
949 | if (p) { | |
950 | p = rht_dereference_bucket_rcu(p->next, tbl, iter->slot); | |
951 | goto next; | |
952 | } | |
953 | ||
954 | for (; iter->slot < tbl->size; iter->slot++) { | |
955 | int skip = iter->skip; | |
956 | ||
957 | rht_for_each_rcu(p, tbl, iter->slot) { | |
958 | if (!skip) | |
959 | break; | |
960 | skip--; | |
961 | } | |
962 | ||
963 | next: | |
964 | if (!rht_is_a_nulls(p)) { | |
965 | iter->skip++; | |
966 | iter->p = p; | |
967 | obj = rht_obj(ht, p); | |
968 | goto out; | |
969 | } | |
970 | ||
971 | iter->skip = 0; | |
972 | } | |
973 | ||
974 | iter->p = NULL; | |
975 | ||
976 | out: | |
977 | if (iter->walker->resize) { | |
978 | iter->p = NULL; | |
979 | iter->slot = 0; | |
980 | iter->skip = 0; | |
981 | iter->walker->resize = false; | |
982 | return ERR_PTR(-EAGAIN); | |
983 | } | |
984 | ||
985 | return obj; | |
986 | } | |
987 | EXPORT_SYMBOL_GPL(rhashtable_walk_next); | |
988 | ||
989 | /** | |
990 | * rhashtable_walk_stop - Finish a hash table walk | |
991 | * @iter: Hash table iterator | |
992 | * | |
993 | * Finish a hash table walk. | |
994 | */ | |
995 | void rhashtable_walk_stop(struct rhashtable_iter *iter) | |
996 | { | |
997 | rcu_read_unlock(); | |
998 | iter->p = NULL; | |
999 | } | |
1000 | EXPORT_SYMBOL_GPL(rhashtable_walk_stop); | |
1001 | ||
94000176 | 1002 | static size_t rounded_hashtable_size(struct rhashtable_params *params) |
7e1e7763 | 1003 | { |
94000176 YX |
1004 | return max(roundup_pow_of_two(params->nelem_hint * 4 / 3), |
1005 | 1UL << params->min_shift); | |
7e1e7763 TG |
1006 | } |
1007 | ||
1008 | /** | |
1009 | * rhashtable_init - initialize a new hash table | |
1010 | * @ht: hash table to be initialized | |
1011 | * @params: configuration parameters | |
1012 | * | |
1013 | * Initializes a new hash table based on the provided configuration | |
1014 | * parameters. A table can be configured either with a variable or | |
1015 | * fixed length key: | |
1016 | * | |
1017 | * Configuration Example 1: Fixed length keys | |
1018 | * struct test_obj { | |
1019 | * int key; | |
1020 | * void * my_member; | |
1021 | * struct rhash_head node; | |
1022 | * }; | |
1023 | * | |
1024 | * struct rhashtable_params params = { | |
1025 | * .head_offset = offsetof(struct test_obj, node), | |
1026 | * .key_offset = offsetof(struct test_obj, key), | |
1027 | * .key_len = sizeof(int), | |
87545899 | 1028 | * .hashfn = jhash, |
f89bd6f8 | 1029 | * .nulls_base = (1U << RHT_BASE_SHIFT), |
7e1e7763 TG |
1030 | * }; |
1031 | * | |
1032 | * Configuration Example 2: Variable length keys | |
1033 | * struct test_obj { | |
1034 | * [...] | |
1035 | * struct rhash_head node; | |
1036 | * }; | |
1037 | * | |
1038 | * u32 my_hash_fn(const void *data, u32 seed) | |
1039 | * { | |
1040 | * struct test_obj *obj = data; | |
1041 | * | |
1042 | * return [... hash ...]; | |
1043 | * } | |
1044 | * | |
1045 | * struct rhashtable_params params = { | |
1046 | * .head_offset = offsetof(struct test_obj, node), | |
87545899 | 1047 | * .hashfn = jhash, |
7e1e7763 | 1048 | * .obj_hashfn = my_hash_fn, |
7e1e7763 TG |
1049 | * }; |
1050 | */ | |
1051 | int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params) | |
1052 | { | |
1053 | struct bucket_table *tbl; | |
1054 | size_t size; | |
1055 | ||
1056 | size = HASH_DEFAULT_SIZE; | |
1057 | ||
1058 | if ((params->key_len && !params->hashfn) || | |
1059 | (!params->key_len && !params->obj_hashfn)) | |
1060 | return -EINVAL; | |
1061 | ||
f89bd6f8 TG |
1062 | if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT)) |
1063 | return -EINVAL; | |
1064 | ||
94000176 YX |
1065 | params->min_shift = max_t(size_t, params->min_shift, |
1066 | ilog2(HASH_MIN_SIZE)); | |
1067 | ||
7e1e7763 | 1068 | if (params->nelem_hint) |
94000176 | 1069 | size = rounded_hashtable_size(params); |
7e1e7763 | 1070 | |
97defe1e TG |
1071 | memset(ht, 0, sizeof(*ht)); |
1072 | mutex_init(&ht->mutex); | |
1073 | memcpy(&ht->p, params, sizeof(*params)); | |
f2dba9c6 | 1074 | INIT_LIST_HEAD(&ht->walkers); |
97defe1e TG |
1075 | |
1076 | if (params->locks_mul) | |
1077 | ht->p.locks_mul = roundup_pow_of_two(params->locks_mul); | |
1078 | else | |
1079 | ht->p.locks_mul = BUCKET_LOCKS_PER_CPU; | |
1080 | ||
1081 | tbl = bucket_table_alloc(ht, size); | |
7e1e7763 TG |
1082 | if (tbl == NULL) |
1083 | return -ENOMEM; | |
1084 | ||
545a148e | 1085 | atomic_set(&ht->nelems, 0); |
c0c09bfd | 1086 | atomic_set(&ht->shift, ilog2(tbl->size)); |
7e1e7763 | 1087 | RCU_INIT_POINTER(ht->tbl, tbl); |
97defe1e | 1088 | RCU_INIT_POINTER(ht->future_tbl, tbl); |
7e1e7763 TG |
1089 | |
1090 | if (!ht->p.hash_rnd) | |
1091 | get_random_bytes(&ht->p.hash_rnd, sizeof(ht->p.hash_rnd)); | |
1092 | ||
97defe1e | 1093 | if (ht->p.grow_decision || ht->p.shrink_decision) |
57699a40 | 1094 | INIT_WORK(&ht->run_work, rht_deferred_worker); |
97defe1e | 1095 | |
7e1e7763 TG |
1096 | return 0; |
1097 | } | |
1098 | EXPORT_SYMBOL_GPL(rhashtable_init); | |
1099 | ||
1100 | /** | |
1101 | * rhashtable_destroy - destroy hash table | |
1102 | * @ht: the hash table to destroy | |
1103 | * | |
ae82ddcf PNA |
1104 | * Frees the bucket array. This function is not rcu safe, therefore the caller |
1105 | * has to make sure that no resizing may happen by unpublishing the hashtable | |
1106 | * and waiting for the quiescent cycle before releasing the bucket array. | |
7e1e7763 | 1107 | */ |
97defe1e | 1108 | void rhashtable_destroy(struct rhashtable *ht) |
7e1e7763 | 1109 | { |
97defe1e TG |
1110 | ht->being_destroyed = true; |
1111 | ||
57699a40 YX |
1112 | if (ht->p.grow_decision || ht->p.shrink_decision) |
1113 | cancel_work_sync(&ht->run_work); | |
97defe1e | 1114 | |
57699a40 | 1115 | mutex_lock(&ht->mutex); |
97defe1e | 1116 | bucket_table_free(rht_dereference(ht->tbl, ht)); |
97defe1e | 1117 | mutex_unlock(&ht->mutex); |
7e1e7763 TG |
1118 | } |
1119 | EXPORT_SYMBOL_GPL(rhashtable_destroy); |