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1 | /* |
2 | * Resizable, Scalable, Concurrent Hash Table | |
3 | * | |
4 | * Copyright (c) 2014 Thomas Graf <tgraf@suug.ch> | |
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> | |
23 | #include <linux/hash.h> | |
24 | #include <linux/random.h> | |
25 | #include <linux/rhashtable.h> | |
26 | #include <linux/log2.h> | |
27 | ||
28 | #define HASH_DEFAULT_SIZE 64UL | |
29 | #define HASH_MIN_SIZE 4UL | |
30 | ||
31 | #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT)) | |
32 | ||
33 | #ifdef CONFIG_PROVE_LOCKING | |
34 | int lockdep_rht_mutex_is_held(const struct rhashtable *ht) | |
35 | { | |
36 | return ht->p.mutex_is_held(); | |
37 | } | |
38 | EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held); | |
39 | #endif | |
40 | ||
41 | /** | |
42 | * rht_obj - cast hash head to outer object | |
43 | * @ht: hash table | |
44 | * @he: hashed node | |
45 | */ | |
46 | void *rht_obj(const struct rhashtable *ht, const struct rhash_head *he) | |
47 | { | |
48 | return (void *) he - ht->p.head_offset; | |
49 | } | |
50 | EXPORT_SYMBOL_GPL(rht_obj); | |
51 | ||
52 | static u32 __hashfn(const struct rhashtable *ht, const void *key, | |
53 | u32 len, u32 hsize) | |
54 | { | |
55 | u32 h; | |
56 | ||
57 | h = ht->p.hashfn(key, len, ht->p.hash_rnd); | |
58 | ||
59 | return h & (hsize - 1); | |
60 | } | |
61 | ||
62 | /** | |
63 | * rhashtable_hashfn - compute hash for key of given length | |
64 | * @ht: hash table to compuate for | |
65 | * @key: pointer to key | |
66 | * @len: length of key | |
67 | * | |
68 | * Computes the hash value using the hash function provided in the 'hashfn' | |
69 | * of struct rhashtable_params. The returned value is guaranteed to be | |
70 | * smaller than the number of buckets in the hash table. | |
71 | */ | |
72 | u32 rhashtable_hashfn(const struct rhashtable *ht, const void *key, u32 len) | |
73 | { | |
74 | struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht); | |
75 | ||
76 | return __hashfn(ht, key, len, tbl->size); | |
77 | } | |
78 | EXPORT_SYMBOL_GPL(rhashtable_hashfn); | |
79 | ||
80 | static u32 obj_hashfn(const struct rhashtable *ht, const void *ptr, u32 hsize) | |
81 | { | |
82 | if (unlikely(!ht->p.key_len)) { | |
83 | u32 h; | |
84 | ||
85 | h = ht->p.obj_hashfn(ptr, ht->p.hash_rnd); | |
86 | ||
87 | return h & (hsize - 1); | |
88 | } | |
89 | ||
90 | return __hashfn(ht, ptr + ht->p.key_offset, ht->p.key_len, hsize); | |
91 | } | |
92 | ||
93 | /** | |
94 | * rhashtable_obj_hashfn - compute hash for hashed object | |
95 | * @ht: hash table to compuate for | |
96 | * @ptr: pointer to hashed object | |
97 | * | |
98 | * Computes the hash value using the hash function `hashfn` respectively | |
99 | * 'obj_hashfn' depending on whether the hash table is set up to work with | |
100 | * a fixed length key. The returned value is guaranteed to be smaller than | |
101 | * the number of buckets in the hash table. | |
102 | */ | |
103 | u32 rhashtable_obj_hashfn(const struct rhashtable *ht, void *ptr) | |
104 | { | |
105 | struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht); | |
106 | ||
107 | return obj_hashfn(ht, ptr, tbl->size); | |
108 | } | |
109 | EXPORT_SYMBOL_GPL(rhashtable_obj_hashfn); | |
110 | ||
111 | static u32 head_hashfn(const struct rhashtable *ht, | |
112 | const struct rhash_head *he, u32 hsize) | |
113 | { | |
114 | return obj_hashfn(ht, rht_obj(ht, he), hsize); | |
115 | } | |
116 | ||
117 | static struct bucket_table *bucket_table_alloc(size_t nbuckets, gfp_t flags) | |
118 | { | |
119 | struct bucket_table *tbl; | |
120 | size_t size; | |
121 | ||
122 | size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]); | |
123 | tbl = kzalloc(size, flags); | |
124 | if (tbl == NULL) | |
125 | tbl = vzalloc(size); | |
126 | ||
127 | if (tbl == NULL) | |
128 | return NULL; | |
129 | ||
130 | tbl->size = nbuckets; | |
131 | ||
132 | return tbl; | |
133 | } | |
134 | ||
135 | static void bucket_table_free(const struct bucket_table *tbl) | |
136 | { | |
137 | kvfree(tbl); | |
138 | } | |
139 | ||
140 | /** | |
141 | * rht_grow_above_75 - returns true if nelems > 0.75 * table-size | |
142 | * @ht: hash table | |
143 | * @new_size: new table size | |
144 | */ | |
145 | bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size) | |
146 | { | |
147 | /* Expand table when exceeding 75% load */ | |
148 | return ht->nelems > (new_size / 4 * 3); | |
149 | } | |
150 | EXPORT_SYMBOL_GPL(rht_grow_above_75); | |
151 | ||
152 | /** | |
153 | * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size | |
154 | * @ht: hash table | |
155 | * @new_size: new table size | |
156 | */ | |
157 | bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size) | |
158 | { | |
159 | /* Shrink table beneath 30% load */ | |
160 | return ht->nelems < (new_size * 3 / 10); | |
161 | } | |
162 | EXPORT_SYMBOL_GPL(rht_shrink_below_30); | |
163 | ||
164 | static void hashtable_chain_unzip(const struct rhashtable *ht, | |
165 | const struct bucket_table *new_tbl, | |
166 | struct bucket_table *old_tbl, size_t n) | |
167 | { | |
168 | struct rhash_head *he, *p, *next; | |
169 | unsigned int h; | |
170 | ||
171 | /* Old bucket empty, no work needed. */ | |
172 | p = rht_dereference(old_tbl->buckets[n], ht); | |
173 | if (!p) | |
174 | return; | |
175 | ||
176 | /* Advance the old bucket pointer one or more times until it | |
177 | * reaches a node that doesn't hash to the same bucket as the | |
178 | * previous node p. Call the previous node p; | |
179 | */ | |
180 | h = head_hashfn(ht, p, new_tbl->size); | |
181 | rht_for_each(he, p->next, ht) { | |
182 | if (head_hashfn(ht, he, new_tbl->size) != h) | |
183 | break; | |
184 | p = he; | |
185 | } | |
186 | RCU_INIT_POINTER(old_tbl->buckets[n], p->next); | |
187 | ||
188 | /* Find the subsequent node which does hash to the same | |
189 | * bucket as node P, or NULL if no such node exists. | |
190 | */ | |
191 | next = NULL; | |
192 | if (he) { | |
193 | rht_for_each(he, he->next, ht) { | |
194 | if (head_hashfn(ht, he, new_tbl->size) == h) { | |
195 | next = he; | |
196 | break; | |
197 | } | |
198 | } | |
199 | } | |
200 | ||
201 | /* Set p's next pointer to that subsequent node pointer, | |
202 | * bypassing the nodes which do not hash to p's bucket | |
203 | */ | |
204 | RCU_INIT_POINTER(p->next, next); | |
205 | } | |
206 | ||
207 | /** | |
208 | * rhashtable_expand - Expand hash table while allowing concurrent lookups | |
209 | * @ht: the hash table to expand | |
210 | * @flags: allocation flags | |
211 | * | |
212 | * A secondary bucket array is allocated and the hash entries are migrated | |
213 | * while keeping them on both lists until the end of the RCU grace period. | |
214 | * | |
215 | * This function may only be called in a context where it is safe to call | |
216 | * synchronize_rcu(), e.g. not within a rcu_read_lock() section. | |
217 | * | |
218 | * The caller must ensure that no concurrent table mutations take place. | |
219 | * It is however valid to have concurrent lookups if they are RCU protected. | |
220 | */ | |
221 | int rhashtable_expand(struct rhashtable *ht, gfp_t flags) | |
222 | { | |
223 | struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht); | |
224 | struct rhash_head *he; | |
225 | unsigned int i, h; | |
226 | bool complete; | |
227 | ||
228 | ASSERT_RHT_MUTEX(ht); | |
229 | ||
230 | if (ht->p.max_shift && ht->shift >= ht->p.max_shift) | |
231 | return 0; | |
232 | ||
233 | new_tbl = bucket_table_alloc(old_tbl->size * 2, flags); | |
234 | if (new_tbl == NULL) | |
235 | return -ENOMEM; | |
236 | ||
237 | ht->shift++; | |
238 | ||
239 | /* For each new bucket, search the corresponding old bucket | |
240 | * for the first entry that hashes to the new bucket, and | |
241 | * link the new bucket to that entry. Since all the entries | |
242 | * which will end up in the new bucket appear in the same | |
243 | * old bucket, this constructs an entirely valid new hash | |
244 | * table, but with multiple buckets "zipped" together into a | |
245 | * single imprecise chain. | |
246 | */ | |
247 | for (i = 0; i < new_tbl->size; i++) { | |
248 | h = i & (old_tbl->size - 1); | |
249 | rht_for_each(he, old_tbl->buckets[h], ht) { | |
250 | if (head_hashfn(ht, he, new_tbl->size) == i) { | |
251 | RCU_INIT_POINTER(new_tbl->buckets[i], he); | |
252 | break; | |
253 | } | |
254 | } | |
255 | } | |
256 | ||
257 | /* Publish the new table pointer. Lookups may now traverse | |
258 | * the new table, but they will not benefit from any | |
259 | * additional efficiency until later steps unzip the buckets. | |
260 | */ | |
261 | rcu_assign_pointer(ht->tbl, new_tbl); | |
262 | ||
263 | /* Unzip interleaved hash chains */ | |
264 | do { | |
265 | /* Wait for readers. All new readers will see the new | |
266 | * table, and thus no references to the old table will | |
267 | * remain. | |
268 | */ | |
269 | synchronize_rcu(); | |
270 | ||
271 | /* For each bucket in the old table (each of which | |
272 | * contains items from multiple buckets of the new | |
273 | * table): ... | |
274 | */ | |
275 | complete = true; | |
276 | for (i = 0; i < old_tbl->size; i++) { | |
277 | hashtable_chain_unzip(ht, new_tbl, old_tbl, i); | |
278 | if (old_tbl->buckets[i] != NULL) | |
279 | complete = false; | |
280 | } | |
281 | } while (!complete); | |
282 | ||
283 | bucket_table_free(old_tbl); | |
284 | return 0; | |
285 | } | |
286 | EXPORT_SYMBOL_GPL(rhashtable_expand); | |
287 | ||
288 | /** | |
289 | * rhashtable_shrink - Shrink hash table while allowing concurrent lookups | |
290 | * @ht: the hash table to shrink | |
291 | * @flags: allocation flags | |
292 | * | |
293 | * This function may only be called in a context where it is safe to call | |
294 | * synchronize_rcu(), e.g. not within a rcu_read_lock() section. | |
295 | * | |
296 | * The caller must ensure that no concurrent table mutations take place. | |
297 | * It is however valid to have concurrent lookups if they are RCU protected. | |
298 | */ | |
299 | int rhashtable_shrink(struct rhashtable *ht, gfp_t flags) | |
300 | { | |
301 | struct bucket_table *ntbl, *tbl = rht_dereference(ht->tbl, ht); | |
302 | struct rhash_head __rcu **pprev; | |
303 | unsigned int i; | |
304 | ||
305 | ASSERT_RHT_MUTEX(ht); | |
306 | ||
307 | if (tbl->size <= HASH_MIN_SIZE) | |
308 | return 0; | |
309 | ||
310 | ntbl = bucket_table_alloc(tbl->size / 2, flags); | |
311 | if (ntbl == NULL) | |
312 | return -ENOMEM; | |
313 | ||
314 | ht->shift--; | |
315 | ||
316 | /* Link each bucket in the new table to the first bucket | |
317 | * in the old table that contains entries which will hash | |
318 | * to the new bucket. | |
319 | */ | |
320 | for (i = 0; i < ntbl->size; i++) { | |
321 | ntbl->buckets[i] = tbl->buckets[i]; | |
322 | ||
323 | /* Link each bucket in the new table to the first bucket | |
324 | * in the old table that contains entries which will hash | |
325 | * to the new bucket. | |
326 | */ | |
327 | for (pprev = &ntbl->buckets[i]; *pprev != NULL; | |
328 | pprev = &rht_dereference(*pprev, ht)->next) | |
329 | ; | |
330 | RCU_INIT_POINTER(*pprev, tbl->buckets[i + ntbl->size]); | |
331 | } | |
332 | ||
333 | /* Publish the new, valid hash table */ | |
334 | rcu_assign_pointer(ht->tbl, ntbl); | |
335 | ||
336 | /* Wait for readers. No new readers will have references to the | |
337 | * old hash table. | |
338 | */ | |
339 | synchronize_rcu(); | |
340 | ||
341 | bucket_table_free(tbl); | |
342 | ||
343 | return 0; | |
344 | } | |
345 | EXPORT_SYMBOL_GPL(rhashtable_shrink); | |
346 | ||
347 | /** | |
348 | * rhashtable_insert - insert object into hash hash table | |
349 | * @ht: hash table | |
350 | * @obj: pointer to hash head inside object | |
351 | * @flags: allocation flags (table expansion) | |
352 | * | |
353 | * Will automatically grow the table via rhashtable_expand() if the the | |
354 | * grow_decision function specified at rhashtable_init() returns true. | |
355 | * | |
356 | * The caller must ensure that no concurrent table mutations occur. It is | |
357 | * however valid to have concurrent lookups if they are RCU protected. | |
358 | */ | |
359 | void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj, | |
360 | gfp_t flags) | |
361 | { | |
362 | struct bucket_table *tbl = rht_dereference(ht->tbl, ht); | |
363 | u32 hash; | |
364 | ||
365 | ASSERT_RHT_MUTEX(ht); | |
366 | ||
367 | hash = head_hashfn(ht, obj, tbl->size); | |
368 | RCU_INIT_POINTER(obj->next, tbl->buckets[hash]); | |
369 | rcu_assign_pointer(tbl->buckets[hash], obj); | |
370 | ht->nelems++; | |
371 | ||
372 | if (ht->p.grow_decision && ht->p.grow_decision(ht, tbl->size)) | |
373 | rhashtable_expand(ht, flags); | |
374 | } | |
375 | EXPORT_SYMBOL_GPL(rhashtable_insert); | |
376 | ||
377 | /** | |
378 | * rhashtable_remove_pprev - remove object from hash table given previous element | |
379 | * @ht: hash table | |
380 | * @obj: pointer to hash head inside object | |
381 | * @pprev: pointer to previous element | |
382 | * @flags: allocation flags (table expansion) | |
383 | * | |
384 | * Identical to rhashtable_remove() but caller is alreayd aware of the element | |
385 | * in front of the element to be deleted. This is in particular useful for | |
386 | * deletion when combined with walking or lookup. | |
387 | */ | |
388 | void rhashtable_remove_pprev(struct rhashtable *ht, struct rhash_head *obj, | |
389 | struct rhash_head **pprev, gfp_t flags) | |
390 | { | |
391 | struct bucket_table *tbl = rht_dereference(ht->tbl, ht); | |
392 | ||
393 | ASSERT_RHT_MUTEX(ht); | |
394 | ||
395 | RCU_INIT_POINTER(*pprev, obj->next); | |
396 | ht->nelems--; | |
397 | ||
398 | if (ht->p.shrink_decision && | |
399 | ht->p.shrink_decision(ht, tbl->size)) | |
400 | rhashtable_shrink(ht, flags); | |
401 | } | |
402 | EXPORT_SYMBOL_GPL(rhashtable_remove_pprev); | |
403 | ||
404 | /** | |
405 | * rhashtable_remove - remove object from hash table | |
406 | * @ht: hash table | |
407 | * @obj: pointer to hash head inside object | |
408 | * @flags: allocation flags (table expansion) | |
409 | * | |
410 | * Since the hash chain is single linked, the removal operation needs to | |
411 | * walk the bucket chain upon removal. The removal operation is thus | |
412 | * considerable slow if the hash table is not correctly sized. | |
413 | * | |
414 | * Will automatically shrink the table via rhashtable_expand() if the the | |
415 | * shrink_decision function specified at rhashtable_init() returns true. | |
416 | * | |
417 | * The caller must ensure that no concurrent table mutations occur. It is | |
418 | * however valid to have concurrent lookups if they are RCU protected. | |
419 | */ | |
420 | bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj, | |
421 | gfp_t flags) | |
422 | { | |
423 | struct bucket_table *tbl = rht_dereference(ht->tbl, ht); | |
424 | struct rhash_head __rcu **pprev; | |
425 | struct rhash_head *he; | |
426 | u32 h; | |
427 | ||
428 | ASSERT_RHT_MUTEX(ht); | |
429 | ||
430 | h = head_hashfn(ht, obj, tbl->size); | |
431 | ||
432 | pprev = &tbl->buckets[h]; | |
433 | rht_for_each(he, tbl->buckets[h], ht) { | |
434 | if (he != obj) { | |
435 | pprev = &he->next; | |
436 | continue; | |
437 | } | |
438 | ||
439 | rhashtable_remove_pprev(ht, he, pprev, flags); | |
440 | return true; | |
441 | } | |
442 | ||
443 | return false; | |
444 | } | |
445 | EXPORT_SYMBOL_GPL(rhashtable_remove); | |
446 | ||
447 | /** | |
448 | * rhashtable_lookup - lookup key in hash table | |
449 | * @ht: hash table | |
450 | * @key: pointer to key | |
451 | * | |
452 | * Computes the hash value for the key and traverses the bucket chain looking | |
453 | * for a entry with an identical key. The first matching entry is returned. | |
454 | * | |
455 | * This lookup function may only be used for fixed key hash table (key_len | |
456 | * paramter set). It will BUG() if used inappropriately. | |
457 | * | |
458 | * Lookups may occur in parallel with hash mutations as long as the lookup is | |
459 | * guarded by rcu_read_lock(). The caller must take care of this. | |
460 | */ | |
461 | void *rhashtable_lookup(const struct rhashtable *ht, const void *key) | |
462 | { | |
463 | const struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht); | |
464 | struct rhash_head *he; | |
465 | u32 h; | |
466 | ||
467 | BUG_ON(!ht->p.key_len); | |
468 | ||
469 | h = __hashfn(ht, key, ht->p.key_len, tbl->size); | |
470 | rht_for_each_rcu(he, tbl->buckets[h], ht) { | |
471 | if (memcmp(rht_obj(ht, he) + ht->p.key_offset, key, | |
472 | ht->p.key_len)) | |
473 | continue; | |
474 | return (void *) he - ht->p.head_offset; | |
475 | } | |
476 | ||
477 | return NULL; | |
478 | } | |
479 | EXPORT_SYMBOL_GPL(rhashtable_lookup); | |
480 | ||
481 | /** | |
482 | * rhashtable_lookup_compare - search hash table with compare function | |
483 | * @ht: hash table | |
484 | * @hash: hash value of desired entry | |
485 | * @compare: compare function, must return true on match | |
486 | * @arg: argument passed on to compare function | |
487 | * | |
488 | * Traverses the bucket chain behind the provided hash value and calls the | |
489 | * specified compare function for each entry. | |
490 | * | |
491 | * Lookups may occur in parallel with hash mutations as long as the lookup is | |
492 | * guarded by rcu_read_lock(). The caller must take care of this. | |
493 | * | |
494 | * Returns the first entry on which the compare function returned true. | |
495 | */ | |
496 | void *rhashtable_lookup_compare(const struct rhashtable *ht, u32 hash, | |
497 | bool (*compare)(void *, void *), void *arg) | |
498 | { | |
499 | const struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht); | |
500 | struct rhash_head *he; | |
501 | ||
502 | if (unlikely(hash >= tbl->size)) | |
503 | return NULL; | |
504 | ||
505 | rht_for_each_rcu(he, tbl->buckets[hash], ht) { | |
506 | if (!compare(rht_obj(ht, he), arg)) | |
507 | continue; | |
508 | return (void *) he - ht->p.head_offset; | |
509 | } | |
510 | ||
511 | return NULL; | |
512 | } | |
513 | EXPORT_SYMBOL_GPL(rhashtable_lookup_compare); | |
514 | ||
515 | static size_t rounded_hashtable_size(unsigned int nelem) | |
516 | { | |
517 | return max(roundup_pow_of_two(nelem * 4 / 3), HASH_MIN_SIZE); | |
518 | } | |
519 | ||
520 | /** | |
521 | * rhashtable_init - initialize a new hash table | |
522 | * @ht: hash table to be initialized | |
523 | * @params: configuration parameters | |
524 | * | |
525 | * Initializes a new hash table based on the provided configuration | |
526 | * parameters. A table can be configured either with a variable or | |
527 | * fixed length key: | |
528 | * | |
529 | * Configuration Example 1: Fixed length keys | |
530 | * struct test_obj { | |
531 | * int key; | |
532 | * void * my_member; | |
533 | * struct rhash_head node; | |
534 | * }; | |
535 | * | |
536 | * struct rhashtable_params params = { | |
537 | * .head_offset = offsetof(struct test_obj, node), | |
538 | * .key_offset = offsetof(struct test_obj, key), | |
539 | * .key_len = sizeof(int), | |
540 | * .hashfn = arch_fast_hash, | |
541 | * .mutex_is_held = &my_mutex_is_held, | |
542 | * }; | |
543 | * | |
544 | * Configuration Example 2: Variable length keys | |
545 | * struct test_obj { | |
546 | * [...] | |
547 | * struct rhash_head node; | |
548 | * }; | |
549 | * | |
550 | * u32 my_hash_fn(const void *data, u32 seed) | |
551 | * { | |
552 | * struct test_obj *obj = data; | |
553 | * | |
554 | * return [... hash ...]; | |
555 | * } | |
556 | * | |
557 | * struct rhashtable_params params = { | |
558 | * .head_offset = offsetof(struct test_obj, node), | |
559 | * .hashfn = arch_fast_hash, | |
560 | * .obj_hashfn = my_hash_fn, | |
561 | * .mutex_is_held = &my_mutex_is_held, | |
562 | * }; | |
563 | */ | |
564 | int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params) | |
565 | { | |
566 | struct bucket_table *tbl; | |
567 | size_t size; | |
568 | ||
569 | size = HASH_DEFAULT_SIZE; | |
570 | ||
571 | if ((params->key_len && !params->hashfn) || | |
572 | (!params->key_len && !params->obj_hashfn)) | |
573 | return -EINVAL; | |
574 | ||
575 | if (params->nelem_hint) | |
576 | size = rounded_hashtable_size(params->nelem_hint); | |
577 | ||
578 | tbl = bucket_table_alloc(size, GFP_KERNEL); | |
579 | if (tbl == NULL) | |
580 | return -ENOMEM; | |
581 | ||
582 | memset(ht, 0, sizeof(*ht)); | |
583 | ht->shift = ilog2(tbl->size); | |
584 | memcpy(&ht->p, params, sizeof(*params)); | |
585 | RCU_INIT_POINTER(ht->tbl, tbl); | |
586 | ||
587 | if (!ht->p.hash_rnd) | |
588 | get_random_bytes(&ht->p.hash_rnd, sizeof(ht->p.hash_rnd)); | |
589 | ||
590 | return 0; | |
591 | } | |
592 | EXPORT_SYMBOL_GPL(rhashtable_init); | |
593 | ||
594 | /** | |
595 | * rhashtable_destroy - destroy hash table | |
596 | * @ht: the hash table to destroy | |
597 | * | |
598 | * Frees the bucket array. | |
599 | */ | |
600 | void rhashtable_destroy(const struct rhashtable *ht) | |
601 | { | |
602 | const struct bucket_table *tbl = rht_dereference(ht->tbl, ht); | |
603 | ||
604 | bucket_table_free(tbl); | |
605 | } | |
606 | EXPORT_SYMBOL_GPL(rhashtable_destroy); | |
607 | ||
608 | /************************************************************************** | |
609 | * Self Test | |
610 | **************************************************************************/ | |
611 | ||
612 | #ifdef CONFIG_TEST_RHASHTABLE | |
613 | ||
614 | #define TEST_HT_SIZE 8 | |
615 | #define TEST_ENTRIES 2048 | |
616 | #define TEST_PTR ((void *) 0xdeadbeef) | |
617 | #define TEST_NEXPANDS 4 | |
618 | ||
619 | static int test_mutex_is_held(void) | |
620 | { | |
621 | return 1; | |
622 | } | |
623 | ||
624 | struct test_obj { | |
625 | void *ptr; | |
626 | int value; | |
627 | struct rhash_head node; | |
628 | }; | |
629 | ||
630 | static int __init test_rht_lookup(struct rhashtable *ht) | |
631 | { | |
632 | unsigned int i; | |
633 | ||
634 | for (i = 0; i < TEST_ENTRIES * 2; i++) { | |
635 | struct test_obj *obj; | |
636 | bool expected = !(i % 2); | |
637 | u32 key = i; | |
638 | ||
639 | obj = rhashtable_lookup(ht, &key); | |
640 | ||
641 | if (expected && !obj) { | |
642 | pr_warn("Test failed: Could not find key %u\n", key); | |
643 | return -ENOENT; | |
644 | } else if (!expected && obj) { | |
645 | pr_warn("Test failed: Unexpected entry found for key %u\n", | |
646 | key); | |
647 | return -EEXIST; | |
648 | } else if (expected && obj) { | |
649 | if (obj->ptr != TEST_PTR || obj->value != i) { | |
650 | pr_warn("Test failed: Lookup value mismatch %p!=%p, %u!=%u\n", | |
651 | obj->ptr, TEST_PTR, obj->value, i); | |
652 | return -EINVAL; | |
653 | } | |
654 | } | |
655 | } | |
656 | ||
657 | return 0; | |
658 | } | |
659 | ||
660 | static void test_bucket_stats(struct rhashtable *ht, | |
661 | struct bucket_table *tbl, | |
662 | bool quiet) | |
663 | { | |
664 | unsigned int cnt, i, total = 0; | |
665 | struct test_obj *obj; | |
666 | ||
667 | for (i = 0; i < tbl->size; i++) { | |
668 | cnt = 0; | |
669 | ||
670 | if (!quiet) | |
671 | pr_info(" [%#4x/%zu]", i, tbl->size); | |
672 | ||
673 | rht_for_each_entry_rcu(obj, tbl->buckets[i], node) { | |
674 | cnt++; | |
675 | total++; | |
676 | if (!quiet) | |
677 | pr_cont(" [%p],", obj); | |
678 | } | |
679 | ||
680 | if (!quiet) | |
681 | pr_cont("\n [%#x] first element: %p, chain length: %u\n", | |
682 | i, tbl->buckets[i], cnt); | |
683 | } | |
684 | ||
685 | pr_info(" Traversal complete: counted=%u, nelems=%zu, entries=%d\n", | |
686 | total, ht->nelems, TEST_ENTRIES); | |
687 | } | |
688 | ||
689 | static int __init test_rhashtable(struct rhashtable *ht) | |
690 | { | |
691 | struct bucket_table *tbl; | |
692 | struct test_obj *obj, *next; | |
693 | int err; | |
694 | unsigned int i; | |
695 | ||
696 | /* | |
697 | * Insertion Test: | |
698 | * Insert TEST_ENTRIES into table with all keys even numbers | |
699 | */ | |
700 | pr_info(" Adding %d keys\n", TEST_ENTRIES); | |
701 | for (i = 0; i < TEST_ENTRIES; i++) { | |
702 | struct test_obj *obj; | |
703 | ||
704 | obj = kzalloc(sizeof(*obj), GFP_KERNEL); | |
705 | if (!obj) { | |
706 | err = -ENOMEM; | |
707 | goto error; | |
708 | } | |
709 | ||
710 | obj->ptr = TEST_PTR; | |
711 | obj->value = i * 2; | |
712 | ||
713 | rhashtable_insert(ht, &obj->node, GFP_KERNEL); | |
714 | } | |
715 | ||
716 | rcu_read_lock(); | |
717 | tbl = rht_dereference_rcu(ht->tbl, ht); | |
718 | test_bucket_stats(ht, tbl, true); | |
719 | test_rht_lookup(ht); | |
720 | rcu_read_unlock(); | |
721 | ||
722 | for (i = 0; i < TEST_NEXPANDS; i++) { | |
723 | pr_info(" Table expansion iteration %u...\n", i); | |
724 | rhashtable_expand(ht, GFP_KERNEL); | |
725 | ||
726 | rcu_read_lock(); | |
727 | pr_info(" Verifying lookups...\n"); | |
728 | test_rht_lookup(ht); | |
729 | rcu_read_unlock(); | |
730 | } | |
731 | ||
732 | for (i = 0; i < TEST_NEXPANDS; i++) { | |
733 | pr_info(" Table shrinkage iteration %u...\n", i); | |
734 | rhashtable_shrink(ht, GFP_KERNEL); | |
735 | ||
736 | rcu_read_lock(); | |
737 | pr_info(" Verifying lookups...\n"); | |
738 | test_rht_lookup(ht); | |
739 | rcu_read_unlock(); | |
740 | } | |
741 | ||
742 | pr_info(" Deleting %d keys\n", TEST_ENTRIES); | |
743 | for (i = 0; i < TEST_ENTRIES; i++) { | |
744 | u32 key = i * 2; | |
745 | ||
746 | obj = rhashtable_lookup(ht, &key); | |
747 | BUG_ON(!obj); | |
748 | ||
749 | rhashtable_remove(ht, &obj->node, GFP_KERNEL); | |
750 | kfree(obj); | |
751 | } | |
752 | ||
753 | return 0; | |
754 | ||
755 | error: | |
756 | tbl = rht_dereference_rcu(ht->tbl, ht); | |
757 | for (i = 0; i < tbl->size; i++) | |
758 | rht_for_each_entry_safe(obj, next, tbl->buckets[i], ht, node) | |
759 | kfree(obj); | |
760 | ||
761 | return err; | |
762 | } | |
763 | ||
764 | static int __init test_rht_init(void) | |
765 | { | |
766 | struct rhashtable ht; | |
767 | struct rhashtable_params params = { | |
768 | .nelem_hint = TEST_HT_SIZE, | |
769 | .head_offset = offsetof(struct test_obj, node), | |
770 | .key_offset = offsetof(struct test_obj, value), | |
771 | .key_len = sizeof(int), | |
772 | .hashfn = arch_fast_hash, | |
773 | .mutex_is_held = &test_mutex_is_held, | |
774 | .grow_decision = rht_grow_above_75, | |
775 | .shrink_decision = rht_shrink_below_30, | |
776 | }; | |
777 | int err; | |
778 | ||
779 | pr_info("Running resizable hashtable tests...\n"); | |
780 | ||
781 | err = rhashtable_init(&ht, ¶ms); | |
782 | if (err < 0) { | |
783 | pr_warn("Test failed: Unable to initialize hashtable: %d\n", | |
784 | err); | |
785 | return err; | |
786 | } | |
787 | ||
788 | err = test_rhashtable(&ht); | |
789 | ||
790 | rhashtable_destroy(&ht); | |
791 | ||
792 | return err; | |
793 | } | |
794 | ||
795 | subsys_initcall(test_rht_init); | |
796 | ||
797 | #endif /* CONFIG_TEST_RHASHTABLE */ |