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7e1e7763 TG |
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> | |
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, | |
37 | RHT_LOCK_NESTED2, | |
38 | }; | |
39 | ||
40 | /* The bucket lock is selected based on the hash and protects mutations | |
41 | * on a group of hash buckets. | |
42 | * | |
43 | * IMPORTANT: When holding the bucket lock of both the old and new table | |
44 | * during expansions and shrinking, the old bucket lock must always be | |
45 | * acquired first. | |
46 | */ | |
47 | static spinlock_t *bucket_lock(const struct bucket_table *tbl, u32 hash) | |
48 | { | |
49 | return &tbl->locks[hash & tbl->locks_mask]; | |
50 | } | |
7e1e7763 TG |
51 | |
52 | #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT)) | |
97defe1e TG |
53 | #define ASSERT_BUCKET_LOCK(TBL, HASH) \ |
54 | BUG_ON(!lockdep_rht_bucket_is_held(TBL, HASH)) | |
7e1e7763 TG |
55 | |
56 | #ifdef CONFIG_PROVE_LOCKING | |
97defe1e | 57 | int lockdep_rht_mutex_is_held(struct rhashtable *ht) |
7e1e7763 | 58 | { |
97defe1e | 59 | return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1; |
7e1e7763 TG |
60 | } |
61 | EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held); | |
88d6ed15 TG |
62 | |
63 | int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash) | |
64 | { | |
97defe1e TG |
65 | spinlock_t *lock = bucket_lock(tbl, hash); |
66 | ||
67 | return (debug_locks) ? lockdep_is_held(lock) : 1; | |
88d6ed15 TG |
68 | } |
69 | EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held); | |
7e1e7763 TG |
70 | #endif |
71 | ||
c91eee56 | 72 | static void *rht_obj(const struct rhashtable *ht, const struct rhash_head *he) |
7e1e7763 TG |
73 | { |
74 | return (void *) he - ht->p.head_offset; | |
75 | } | |
7e1e7763 | 76 | |
8d24c0b4 | 77 | static u32 rht_bucket_index(const struct bucket_table *tbl, u32 hash) |
7e1e7763 | 78 | { |
8d24c0b4 | 79 | return hash & (tbl->size - 1); |
7e1e7763 | 80 | } |
7e1e7763 | 81 | |
8d24c0b4 | 82 | static u32 obj_raw_hashfn(const struct rhashtable *ht, const void *ptr) |
7e1e7763 | 83 | { |
8d24c0b4 | 84 | u32 hash; |
7e1e7763 | 85 | |
8d24c0b4 TG |
86 | if (unlikely(!ht->p.key_len)) |
87 | hash = ht->p.obj_hashfn(ptr, ht->p.hash_rnd); | |
88 | else | |
89 | hash = ht->p.hashfn(ptr + ht->p.key_offset, ht->p.key_len, | |
90 | ht->p.hash_rnd); | |
7e1e7763 | 91 | |
f89bd6f8 | 92 | return hash >> HASH_RESERVED_SPACE; |
7e1e7763 TG |
93 | } |
94 | ||
97defe1e | 95 | static u32 key_hashfn(struct rhashtable *ht, const void *key, u32 len) |
7e1e7763 | 96 | { |
c88455ce | 97 | return ht->p.hashfn(key, len, ht->p.hash_rnd) >> HASH_RESERVED_SPACE; |
7e1e7763 | 98 | } |
7e1e7763 TG |
99 | |
100 | static u32 head_hashfn(const struct rhashtable *ht, | |
8d24c0b4 TG |
101 | const struct bucket_table *tbl, |
102 | const struct rhash_head *he) | |
7e1e7763 | 103 | { |
8d24c0b4 | 104 | return rht_bucket_index(tbl, obj_raw_hashfn(ht, rht_obj(ht, he))); |
7e1e7763 TG |
105 | } |
106 | ||
b8e1943e TG |
107 | static struct rhash_head __rcu **bucket_tail(struct bucket_table *tbl, u32 n) |
108 | { | |
109 | struct rhash_head __rcu **pprev; | |
110 | ||
111 | for (pprev = &tbl->buckets[n]; | |
f89bd6f8 | 112 | !rht_is_a_nulls(rht_dereference_bucket(*pprev, tbl, n)); |
b8e1943e TG |
113 | pprev = &rht_dereference_bucket(*pprev, tbl, n)->next) |
114 | ; | |
115 | ||
116 | return pprev; | |
117 | } | |
118 | ||
97defe1e TG |
119 | static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl) |
120 | { | |
121 | unsigned int i, size; | |
122 | #if defined(CONFIG_PROVE_LOCKING) | |
123 | unsigned int nr_pcpus = 2; | |
124 | #else | |
125 | unsigned int nr_pcpus = num_possible_cpus(); | |
126 | #endif | |
127 | ||
128 | nr_pcpus = min_t(unsigned int, nr_pcpus, 32UL); | |
129 | size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul); | |
130 | ||
131 | /* Never allocate more than one lock per bucket */ | |
132 | size = min_t(unsigned int, size, tbl->size); | |
133 | ||
134 | if (sizeof(spinlock_t) != 0) { | |
135 | #ifdef CONFIG_NUMA | |
136 | if (size * sizeof(spinlock_t) > PAGE_SIZE) | |
137 | tbl->locks = vmalloc(size * sizeof(spinlock_t)); | |
138 | else | |
139 | #endif | |
140 | tbl->locks = kmalloc_array(size, sizeof(spinlock_t), | |
141 | GFP_KERNEL); | |
142 | if (!tbl->locks) | |
143 | return -ENOMEM; | |
144 | for (i = 0; i < size; i++) | |
145 | spin_lock_init(&tbl->locks[i]); | |
146 | } | |
147 | tbl->locks_mask = size - 1; | |
148 | ||
149 | return 0; | |
150 | } | |
151 | ||
152 | static void bucket_table_free(const struct bucket_table *tbl) | |
153 | { | |
154 | if (tbl) | |
155 | kvfree(tbl->locks); | |
156 | ||
157 | kvfree(tbl); | |
158 | } | |
159 | ||
160 | static struct bucket_table *bucket_table_alloc(struct rhashtable *ht, | |
161 | size_t nbuckets) | |
7e1e7763 TG |
162 | { |
163 | struct bucket_table *tbl; | |
164 | size_t size; | |
f89bd6f8 | 165 | int i; |
7e1e7763 TG |
166 | |
167 | size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]); | |
6eba8224 | 168 | tbl = kzalloc(size, GFP_KERNEL | __GFP_NOWARN); |
7e1e7763 TG |
169 | if (tbl == NULL) |
170 | tbl = vzalloc(size); | |
171 | ||
172 | if (tbl == NULL) | |
173 | return NULL; | |
174 | ||
175 | tbl->size = nbuckets; | |
176 | ||
97defe1e TG |
177 | if (alloc_bucket_locks(ht, tbl) < 0) { |
178 | bucket_table_free(tbl); | |
179 | return NULL; | |
180 | } | |
7e1e7763 | 181 | |
f89bd6f8 TG |
182 | for (i = 0; i < nbuckets; i++) |
183 | INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i); | |
184 | ||
97defe1e | 185 | return tbl; |
7e1e7763 TG |
186 | } |
187 | ||
188 | /** | |
189 | * rht_grow_above_75 - returns true if nelems > 0.75 * table-size | |
190 | * @ht: hash table | |
191 | * @new_size: new table size | |
192 | */ | |
193 | bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size) | |
194 | { | |
195 | /* Expand table when exceeding 75% load */ | |
c0c09bfd YX |
196 | return atomic_read(&ht->nelems) > (new_size / 4 * 3) && |
197 | (ht->p.max_shift && atomic_read(&ht->shift) < ht->p.max_shift); | |
7e1e7763 TG |
198 | } |
199 | EXPORT_SYMBOL_GPL(rht_grow_above_75); | |
200 | ||
201 | /** | |
202 | * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size | |
203 | * @ht: hash table | |
204 | * @new_size: new table size | |
205 | */ | |
206 | bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size) | |
207 | { | |
208 | /* Shrink table beneath 30% load */ | |
c0c09bfd YX |
209 | return atomic_read(&ht->nelems) < (new_size * 3 / 10) && |
210 | (atomic_read(&ht->shift) > ht->p.min_shift); | |
7e1e7763 TG |
211 | } |
212 | EXPORT_SYMBOL_GPL(rht_shrink_below_30); | |
213 | ||
214 | static void hashtable_chain_unzip(const struct rhashtable *ht, | |
215 | const struct bucket_table *new_tbl, | |
97defe1e TG |
216 | struct bucket_table *old_tbl, |
217 | size_t old_hash) | |
7e1e7763 TG |
218 | { |
219 | struct rhash_head *he, *p, *next; | |
97defe1e TG |
220 | spinlock_t *new_bucket_lock, *new_bucket_lock2 = NULL; |
221 | unsigned int new_hash, new_hash2; | |
222 | ||
223 | ASSERT_BUCKET_LOCK(old_tbl, old_hash); | |
7e1e7763 TG |
224 | |
225 | /* Old bucket empty, no work needed. */ | |
97defe1e TG |
226 | p = rht_dereference_bucket(old_tbl->buckets[old_hash], old_tbl, |
227 | old_hash); | |
f89bd6f8 | 228 | if (rht_is_a_nulls(p)) |
7e1e7763 TG |
229 | return; |
230 | ||
97defe1e TG |
231 | new_hash = new_hash2 = head_hashfn(ht, new_tbl, p); |
232 | new_bucket_lock = bucket_lock(new_tbl, new_hash); | |
233 | ||
7e1e7763 TG |
234 | /* Advance the old bucket pointer one or more times until it |
235 | * reaches a node that doesn't hash to the same bucket as the | |
236 | * previous node p. Call the previous node p; | |
237 | */ | |
97defe1e TG |
238 | rht_for_each_continue(he, p->next, old_tbl, old_hash) { |
239 | new_hash2 = head_hashfn(ht, new_tbl, he); | |
240 | if (new_hash != new_hash2) | |
7e1e7763 TG |
241 | break; |
242 | p = he; | |
243 | } | |
97defe1e TG |
244 | rcu_assign_pointer(old_tbl->buckets[old_hash], p->next); |
245 | ||
246 | spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED); | |
247 | ||
248 | /* If we have encountered an entry that maps to a different bucket in | |
249 | * the new table, lock down that bucket as well as we might cut off | |
250 | * the end of the chain. | |
251 | */ | |
252 | new_bucket_lock2 = bucket_lock(new_tbl, new_hash); | |
253 | if (new_bucket_lock != new_bucket_lock2) | |
254 | spin_lock_bh_nested(new_bucket_lock2, RHT_LOCK_NESTED2); | |
7e1e7763 TG |
255 | |
256 | /* Find the subsequent node which does hash to the same | |
257 | * bucket as node P, or NULL if no such node exists. | |
258 | */ | |
f89bd6f8 TG |
259 | INIT_RHT_NULLS_HEAD(next, ht, old_hash); |
260 | if (!rht_is_a_nulls(he)) { | |
97defe1e TG |
261 | rht_for_each_continue(he, he->next, old_tbl, old_hash) { |
262 | if (head_hashfn(ht, new_tbl, he) == new_hash) { | |
7e1e7763 TG |
263 | next = he; |
264 | break; | |
265 | } | |
266 | } | |
267 | } | |
268 | ||
269 | /* Set p's next pointer to that subsequent node pointer, | |
270 | * bypassing the nodes which do not hash to p's bucket | |
271 | */ | |
97defe1e TG |
272 | rcu_assign_pointer(p->next, next); |
273 | ||
274 | if (new_bucket_lock != new_bucket_lock2) | |
275 | spin_unlock_bh(new_bucket_lock2); | |
276 | spin_unlock_bh(new_bucket_lock); | |
277 | } | |
278 | ||
279 | static void link_old_to_new(struct bucket_table *new_tbl, | |
280 | unsigned int new_hash, struct rhash_head *entry) | |
281 | { | |
282 | spinlock_t *new_bucket_lock; | |
283 | ||
284 | new_bucket_lock = bucket_lock(new_tbl, new_hash); | |
285 | ||
286 | spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED); | |
287 | rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), entry); | |
288 | spin_unlock_bh(new_bucket_lock); | |
7e1e7763 TG |
289 | } |
290 | ||
291 | /** | |
292 | * rhashtable_expand - Expand hash table while allowing concurrent lookups | |
293 | * @ht: the hash table to expand | |
7e1e7763 TG |
294 | * |
295 | * A secondary bucket array is allocated and the hash entries are migrated | |
296 | * while keeping them on both lists until the end of the RCU grace period. | |
297 | * | |
298 | * This function may only be called in a context where it is safe to call | |
299 | * synchronize_rcu(), e.g. not within a rcu_read_lock() section. | |
300 | * | |
97defe1e TG |
301 | * The caller must ensure that no concurrent resizing occurs by holding |
302 | * ht->mutex. | |
303 | * | |
304 | * It is valid to have concurrent insertions and deletions protected by per | |
305 | * bucket locks or concurrent RCU protected lookups and traversals. | |
7e1e7763 | 306 | */ |
6eba8224 | 307 | int rhashtable_expand(struct rhashtable *ht) |
7e1e7763 TG |
308 | { |
309 | struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht); | |
310 | struct rhash_head *he; | |
97defe1e TG |
311 | spinlock_t *old_bucket_lock; |
312 | unsigned int new_hash, old_hash; | |
313 | bool complete = false; | |
7e1e7763 TG |
314 | |
315 | ASSERT_RHT_MUTEX(ht); | |
316 | ||
97defe1e | 317 | new_tbl = bucket_table_alloc(ht, old_tbl->size * 2); |
7e1e7763 TG |
318 | if (new_tbl == NULL) |
319 | return -ENOMEM; | |
320 | ||
c0c09bfd | 321 | atomic_inc(&ht->shift); |
7e1e7763 | 322 | |
97defe1e TG |
323 | /* Make insertions go into the new, empty table right away. Deletions |
324 | * and lookups will be attempted in both tables until we synchronize. | |
325 | * The synchronize_rcu() guarantees for the new table to be picked up | |
326 | * so no new additions go into the old table while we relink. | |
327 | */ | |
328 | rcu_assign_pointer(ht->future_tbl, new_tbl); | |
329 | synchronize_rcu(); | |
330 | ||
331 | /* For each new bucket, search the corresponding old bucket for the | |
332 | * first entry that hashes to the new bucket, and link the end of | |
333 | * newly formed bucket chain (containing entries added to future | |
334 | * table) to that entry. Since all the entries which will end up in | |
335 | * the new bucket appear in the same old bucket, this constructs an | |
336 | * entirely valid new hash table, but with multiple buckets | |
337 | * "zipped" together into a single imprecise chain. | |
7e1e7763 | 338 | */ |
97defe1e TG |
339 | for (new_hash = 0; new_hash < new_tbl->size; new_hash++) { |
340 | old_hash = rht_bucket_index(old_tbl, new_hash); | |
341 | old_bucket_lock = bucket_lock(old_tbl, old_hash); | |
342 | ||
343 | spin_lock_bh(old_bucket_lock); | |
344 | rht_for_each(he, old_tbl, old_hash) { | |
345 | if (head_hashfn(ht, new_tbl, he) == new_hash) { | |
346 | link_old_to_new(new_tbl, new_hash, he); | |
7e1e7763 TG |
347 | break; |
348 | } | |
349 | } | |
97defe1e | 350 | spin_unlock_bh(old_bucket_lock); |
7e1e7763 TG |
351 | } |
352 | ||
353 | /* Publish the new table pointer. Lookups may now traverse | |
0c828f2f HX |
354 | * the new table, but they will not benefit from any |
355 | * additional efficiency until later steps unzip the buckets. | |
7e1e7763 TG |
356 | */ |
357 | rcu_assign_pointer(ht->tbl, new_tbl); | |
358 | ||
359 | /* Unzip interleaved hash chains */ | |
97defe1e | 360 | while (!complete && !ht->being_destroyed) { |
7e1e7763 TG |
361 | /* Wait for readers. All new readers will see the new |
362 | * table, and thus no references to the old table will | |
363 | * remain. | |
364 | */ | |
365 | synchronize_rcu(); | |
366 | ||
367 | /* For each bucket in the old table (each of which | |
368 | * contains items from multiple buckets of the new | |
369 | * table): ... | |
370 | */ | |
371 | complete = true; | |
97defe1e | 372 | for (old_hash = 0; old_hash < old_tbl->size; old_hash++) { |
f89bd6f8 TG |
373 | struct rhash_head *head; |
374 | ||
97defe1e TG |
375 | old_bucket_lock = bucket_lock(old_tbl, old_hash); |
376 | spin_lock_bh(old_bucket_lock); | |
377 | ||
378 | hashtable_chain_unzip(ht, new_tbl, old_tbl, old_hash); | |
f89bd6f8 TG |
379 | head = rht_dereference_bucket(old_tbl->buckets[old_hash], |
380 | old_tbl, old_hash); | |
381 | if (!rht_is_a_nulls(head)) | |
7e1e7763 | 382 | complete = false; |
97defe1e TG |
383 | |
384 | spin_unlock_bh(old_bucket_lock); | |
7e1e7763 | 385 | } |
97defe1e | 386 | } |
7e1e7763 TG |
387 | |
388 | bucket_table_free(old_tbl); | |
389 | return 0; | |
390 | } | |
391 | EXPORT_SYMBOL_GPL(rhashtable_expand); | |
392 | ||
393 | /** | |
394 | * rhashtable_shrink - Shrink hash table while allowing concurrent lookups | |
395 | * @ht: the hash table to shrink | |
7e1e7763 TG |
396 | * |
397 | * This function may only be called in a context where it is safe to call | |
398 | * synchronize_rcu(), e.g. not within a rcu_read_lock() section. | |
399 | * | |
97defe1e TG |
400 | * The caller must ensure that no concurrent resizing occurs by holding |
401 | * ht->mutex. | |
402 | * | |
7e1e7763 TG |
403 | * The caller must ensure that no concurrent table mutations take place. |
404 | * It is however valid to have concurrent lookups if they are RCU protected. | |
97defe1e TG |
405 | * |
406 | * It is valid to have concurrent insertions and deletions protected by per | |
407 | * bucket locks or concurrent RCU protected lookups and traversals. | |
7e1e7763 | 408 | */ |
6eba8224 | 409 | int rhashtable_shrink(struct rhashtable *ht) |
7e1e7763 | 410 | { |
97defe1e TG |
411 | struct bucket_table *new_tbl, *tbl = rht_dereference(ht->tbl, ht); |
412 | spinlock_t *new_bucket_lock, *old_bucket_lock1, *old_bucket_lock2; | |
413 | unsigned int new_hash; | |
7e1e7763 TG |
414 | |
415 | ASSERT_RHT_MUTEX(ht); | |
416 | ||
97defe1e TG |
417 | new_tbl = bucket_table_alloc(ht, tbl->size / 2); |
418 | if (new_tbl == NULL) | |
7e1e7763 TG |
419 | return -ENOMEM; |
420 | ||
97defe1e TG |
421 | rcu_assign_pointer(ht->future_tbl, new_tbl); |
422 | synchronize_rcu(); | |
7e1e7763 | 423 | |
97defe1e TG |
424 | /* Link the first entry in the old bucket to the end of the |
425 | * bucket in the new table. As entries are concurrently being | |
426 | * added to the new table, lock down the new bucket. As we | |
427 | * always divide the size in half when shrinking, each bucket | |
428 | * in the new table maps to exactly two buckets in the old | |
429 | * table. | |
430 | * | |
431 | * As removals can occur concurrently on the old table, we need | |
432 | * to lock down both matching buckets in the old table. | |
7e1e7763 | 433 | */ |
97defe1e TG |
434 | for (new_hash = 0; new_hash < new_tbl->size; new_hash++) { |
435 | old_bucket_lock1 = bucket_lock(tbl, new_hash); | |
436 | old_bucket_lock2 = bucket_lock(tbl, new_hash + new_tbl->size); | |
437 | new_bucket_lock = bucket_lock(new_tbl, new_hash); | |
438 | ||
439 | spin_lock_bh(old_bucket_lock1); | |
80ca8c3a TG |
440 | |
441 | /* Depending on the lock per buckets mapping, the bucket in | |
442 | * the lower and upper region may map to the same lock. | |
443 | */ | |
444 | if (old_bucket_lock1 != old_bucket_lock2) { | |
445 | spin_lock_bh_nested(old_bucket_lock2, RHT_LOCK_NESTED); | |
446 | spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED2); | |
447 | } else { | |
448 | spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED); | |
449 | } | |
97defe1e TG |
450 | |
451 | rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), | |
452 | tbl->buckets[new_hash]); | |
453 | rcu_assign_pointer(*bucket_tail(new_tbl, new_hash), | |
454 | tbl->buckets[new_hash + new_tbl->size]); | |
455 | ||
456 | spin_unlock_bh(new_bucket_lock); | |
80ca8c3a TG |
457 | if (old_bucket_lock1 != old_bucket_lock2) |
458 | spin_unlock_bh(old_bucket_lock2); | |
97defe1e | 459 | spin_unlock_bh(old_bucket_lock1); |
7e1e7763 TG |
460 | } |
461 | ||
462 | /* Publish the new, valid hash table */ | |
97defe1e | 463 | rcu_assign_pointer(ht->tbl, new_tbl); |
c0c09bfd | 464 | atomic_dec(&ht->shift); |
7e1e7763 TG |
465 | |
466 | /* Wait for readers. No new readers will have references to the | |
467 | * old hash table. | |
468 | */ | |
469 | synchronize_rcu(); | |
470 | ||
471 | bucket_table_free(tbl); | |
472 | ||
473 | return 0; | |
474 | } | |
475 | EXPORT_SYMBOL_GPL(rhashtable_shrink); | |
476 | ||
97defe1e TG |
477 | static void rht_deferred_worker(struct work_struct *work) |
478 | { | |
479 | struct rhashtable *ht; | |
480 | struct bucket_table *tbl; | |
f2dba9c6 | 481 | struct rhashtable_walker *walker; |
97defe1e | 482 | |
57699a40 | 483 | ht = container_of(work, struct rhashtable, run_work); |
97defe1e | 484 | mutex_lock(&ht->mutex); |
28134a53 HX |
485 | if (ht->being_destroyed) |
486 | goto unlock; | |
487 | ||
97defe1e TG |
488 | tbl = rht_dereference(ht->tbl, ht); |
489 | ||
f2dba9c6 HX |
490 | list_for_each_entry(walker, &ht->walkers, list) |
491 | walker->resize = true; | |
492 | ||
97defe1e TG |
493 | if (ht->p.grow_decision && ht->p.grow_decision(ht, tbl->size)) |
494 | rhashtable_expand(ht); | |
495 | else if (ht->p.shrink_decision && ht->p.shrink_decision(ht, tbl->size)) | |
496 | rhashtable_shrink(ht); | |
497 | ||
28134a53 | 498 | unlock: |
97defe1e TG |
499 | mutex_unlock(&ht->mutex); |
500 | } | |
501 | ||
54c5b7d3 YX |
502 | static void rhashtable_wakeup_worker(struct rhashtable *ht) |
503 | { | |
504 | struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht); | |
505 | struct bucket_table *new_tbl = rht_dereference_rcu(ht->future_tbl, ht); | |
506 | size_t size = tbl->size; | |
507 | ||
508 | /* Only adjust the table if no resizing is currently in progress. */ | |
509 | if (tbl == new_tbl && | |
510 | ((ht->p.grow_decision && ht->p.grow_decision(ht, size)) || | |
511 | (ht->p.shrink_decision && ht->p.shrink_decision(ht, size)))) | |
57699a40 | 512 | schedule_work(&ht->run_work); |
54c5b7d3 YX |
513 | } |
514 | ||
db304854 YX |
515 | static void __rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj, |
516 | struct bucket_table *tbl, u32 hash) | |
517 | { | |
518 | struct rhash_head *head = rht_dereference_bucket(tbl->buckets[hash], | |
519 | tbl, hash); | |
520 | ||
521 | if (rht_is_a_nulls(head)) | |
522 | INIT_RHT_NULLS_HEAD(obj->next, ht, hash); | |
523 | else | |
524 | RCU_INIT_POINTER(obj->next, head); | |
525 | ||
526 | rcu_assign_pointer(tbl->buckets[hash], obj); | |
527 | ||
528 | atomic_inc(&ht->nelems); | |
529 | ||
530 | rhashtable_wakeup_worker(ht); | |
531 | } | |
532 | ||
7e1e7763 | 533 | /** |
db304854 | 534 | * rhashtable_insert - insert object into hash table |
7e1e7763 TG |
535 | * @ht: hash table |
536 | * @obj: pointer to hash head inside object | |
7e1e7763 | 537 | * |
97defe1e TG |
538 | * Will take a per bucket spinlock to protect against mutual mutations |
539 | * on the same bucket. Multiple insertions may occur in parallel unless | |
540 | * they map to the same bucket lock. | |
7e1e7763 | 541 | * |
97defe1e TG |
542 | * It is safe to call this function from atomic context. |
543 | * | |
544 | * Will trigger an automatic deferred table resizing if the size grows | |
545 | * beyond the watermark indicated by grow_decision() which can be passed | |
546 | * to rhashtable_init(). | |
7e1e7763 | 547 | */ |
6eba8224 | 548 | void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj) |
7e1e7763 | 549 | { |
97defe1e TG |
550 | struct bucket_table *tbl; |
551 | spinlock_t *lock; | |
552 | unsigned hash; | |
7e1e7763 | 553 | |
97defe1e | 554 | rcu_read_lock(); |
7e1e7763 | 555 | |
97defe1e | 556 | tbl = rht_dereference_rcu(ht->future_tbl, ht); |
8d24c0b4 | 557 | hash = head_hashfn(ht, tbl, obj); |
97defe1e TG |
558 | lock = bucket_lock(tbl, hash); |
559 | ||
560 | spin_lock_bh(lock); | |
db304854 | 561 | __rhashtable_insert(ht, obj, tbl, hash); |
97defe1e | 562 | spin_unlock_bh(lock); |
7e1e7763 | 563 | |
97defe1e | 564 | rcu_read_unlock(); |
7e1e7763 TG |
565 | } |
566 | EXPORT_SYMBOL_GPL(rhashtable_insert); | |
567 | ||
7e1e7763 TG |
568 | /** |
569 | * rhashtable_remove - remove object from hash table | |
570 | * @ht: hash table | |
571 | * @obj: pointer to hash head inside object | |
7e1e7763 TG |
572 | * |
573 | * Since the hash chain is single linked, the removal operation needs to | |
574 | * walk the bucket chain upon removal. The removal operation is thus | |
575 | * considerable slow if the hash table is not correctly sized. | |
576 | * | |
db304854 | 577 | * Will automatically shrink the table via rhashtable_expand() if the |
7e1e7763 TG |
578 | * shrink_decision function specified at rhashtable_init() returns true. |
579 | * | |
580 | * The caller must ensure that no concurrent table mutations occur. It is | |
581 | * however valid to have concurrent lookups if they are RCU protected. | |
582 | */ | |
6eba8224 | 583 | bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj) |
7e1e7763 | 584 | { |
97defe1e | 585 | struct bucket_table *tbl; |
7e1e7763 TG |
586 | struct rhash_head __rcu **pprev; |
587 | struct rhash_head *he; | |
97defe1e TG |
588 | spinlock_t *lock; |
589 | unsigned int hash; | |
fe6a043c | 590 | bool ret = false; |
7e1e7763 | 591 | |
97defe1e TG |
592 | rcu_read_lock(); |
593 | tbl = rht_dereference_rcu(ht->tbl, ht); | |
594 | hash = head_hashfn(ht, tbl, obj); | |
7e1e7763 | 595 | |
97defe1e TG |
596 | lock = bucket_lock(tbl, hash); |
597 | spin_lock_bh(lock); | |
7e1e7763 | 598 | |
97defe1e TG |
599 | restart: |
600 | pprev = &tbl->buckets[hash]; | |
601 | rht_for_each(he, tbl, hash) { | |
7e1e7763 TG |
602 | if (he != obj) { |
603 | pprev = &he->next; | |
604 | continue; | |
605 | } | |
606 | ||
97defe1e | 607 | rcu_assign_pointer(*pprev, obj->next); |
897362e4 | 608 | |
fe6a043c TG |
609 | ret = true; |
610 | break; | |
7e1e7763 TG |
611 | } |
612 | ||
fe6a043c TG |
613 | /* The entry may be linked in either 'tbl', 'future_tbl', or both. |
614 | * 'future_tbl' only exists for a short period of time during | |
615 | * resizing. Thus traversing both is fine and the added cost is | |
616 | * very rare. | |
617 | */ | |
bd6d4db5 | 618 | if (tbl != rht_dereference_rcu(ht->future_tbl, ht)) { |
97defe1e TG |
619 | spin_unlock_bh(lock); |
620 | ||
bd6d4db5 | 621 | tbl = rht_dereference_rcu(ht->future_tbl, ht); |
97defe1e TG |
622 | hash = head_hashfn(ht, tbl, obj); |
623 | ||
624 | lock = bucket_lock(tbl, hash); | |
625 | spin_lock_bh(lock); | |
626 | goto restart; | |
627 | } | |
628 | ||
629 | spin_unlock_bh(lock); | |
fe6a043c TG |
630 | |
631 | if (ret) { | |
632 | atomic_dec(&ht->nelems); | |
633 | rhashtable_wakeup_worker(ht); | |
634 | } | |
635 | ||
97defe1e TG |
636 | rcu_read_unlock(); |
637 | ||
fe6a043c | 638 | return ret; |
7e1e7763 TG |
639 | } |
640 | EXPORT_SYMBOL_GPL(rhashtable_remove); | |
641 | ||
efb975a6 YX |
642 | struct rhashtable_compare_arg { |
643 | struct rhashtable *ht; | |
644 | const void *key; | |
645 | }; | |
646 | ||
647 | static bool rhashtable_compare(void *ptr, void *arg) | |
648 | { | |
649 | struct rhashtable_compare_arg *x = arg; | |
650 | struct rhashtable *ht = x->ht; | |
651 | ||
652 | return !memcmp(ptr + ht->p.key_offset, x->key, ht->p.key_len); | |
653 | } | |
654 | ||
7e1e7763 TG |
655 | /** |
656 | * rhashtable_lookup - lookup key in hash table | |
657 | * @ht: hash table | |
658 | * @key: pointer to key | |
659 | * | |
660 | * Computes the hash value for the key and traverses the bucket chain looking | |
661 | * for a entry with an identical key. The first matching entry is returned. | |
662 | * | |
663 | * This lookup function may only be used for fixed key hash table (key_len | |
db304854 | 664 | * parameter set). It will BUG() if used inappropriately. |
7e1e7763 | 665 | * |
97defe1e | 666 | * Lookups may occur in parallel with hashtable mutations and resizing. |
7e1e7763 | 667 | */ |
97defe1e | 668 | void *rhashtable_lookup(struct rhashtable *ht, const void *key) |
7e1e7763 | 669 | { |
efb975a6 YX |
670 | struct rhashtable_compare_arg arg = { |
671 | .ht = ht, | |
672 | .key = key, | |
673 | }; | |
7e1e7763 TG |
674 | |
675 | BUG_ON(!ht->p.key_len); | |
676 | ||
efb975a6 | 677 | return rhashtable_lookup_compare(ht, key, &rhashtable_compare, &arg); |
7e1e7763 TG |
678 | } |
679 | EXPORT_SYMBOL_GPL(rhashtable_lookup); | |
680 | ||
681 | /** | |
682 | * rhashtable_lookup_compare - search hash table with compare function | |
683 | * @ht: hash table | |
8d24c0b4 | 684 | * @key: the pointer to the key |
7e1e7763 TG |
685 | * @compare: compare function, must return true on match |
686 | * @arg: argument passed on to compare function | |
687 | * | |
688 | * Traverses the bucket chain behind the provided hash value and calls the | |
689 | * specified compare function for each entry. | |
690 | * | |
97defe1e | 691 | * Lookups may occur in parallel with hashtable mutations and resizing. |
7e1e7763 TG |
692 | * |
693 | * Returns the first entry on which the compare function returned true. | |
694 | */ | |
97defe1e | 695 | void *rhashtable_lookup_compare(struct rhashtable *ht, const void *key, |
7e1e7763 TG |
696 | bool (*compare)(void *, void *), void *arg) |
697 | { | |
97defe1e | 698 | const struct bucket_table *tbl, *old_tbl; |
7e1e7763 | 699 | struct rhash_head *he; |
8d24c0b4 | 700 | u32 hash; |
7e1e7763 | 701 | |
97defe1e TG |
702 | rcu_read_lock(); |
703 | ||
704 | old_tbl = rht_dereference_rcu(ht->tbl, ht); | |
705 | tbl = rht_dereference_rcu(ht->future_tbl, ht); | |
8d24c0b4 | 706 | hash = key_hashfn(ht, key, ht->p.key_len); |
97defe1e TG |
707 | restart: |
708 | rht_for_each_rcu(he, tbl, rht_bucket_index(tbl, hash)) { | |
7e1e7763 TG |
709 | if (!compare(rht_obj(ht, he), arg)) |
710 | continue; | |
97defe1e | 711 | rcu_read_unlock(); |
a4b18cda | 712 | return rht_obj(ht, he); |
7e1e7763 TG |
713 | } |
714 | ||
97defe1e TG |
715 | if (unlikely(tbl != old_tbl)) { |
716 | tbl = old_tbl; | |
717 | goto restart; | |
718 | } | |
719 | rcu_read_unlock(); | |
720 | ||
7e1e7763 TG |
721 | return NULL; |
722 | } | |
723 | EXPORT_SYMBOL_GPL(rhashtable_lookup_compare); | |
724 | ||
db304854 YX |
725 | /** |
726 | * rhashtable_lookup_insert - lookup and insert object into hash table | |
727 | * @ht: hash table | |
728 | * @obj: pointer to hash head inside object | |
729 | * | |
730 | * Locks down the bucket chain in both the old and new table if a resize | |
731 | * is in progress to ensure that writers can't remove from the old table | |
732 | * and can't insert to the new table during the atomic operation of search | |
733 | * and insertion. Searches for duplicates in both the old and new table if | |
734 | * a resize is in progress. | |
735 | * | |
736 | * This lookup function may only be used for fixed key hash table (key_len | |
737 | * parameter set). It will BUG() if used inappropriately. | |
738 | * | |
739 | * It is safe to call this function from atomic context. | |
740 | * | |
741 | * Will trigger an automatic deferred table resizing if the size grows | |
742 | * beyond the watermark indicated by grow_decision() which can be passed | |
743 | * to rhashtable_init(). | |
744 | */ | |
745 | bool rhashtable_lookup_insert(struct rhashtable *ht, struct rhash_head *obj) | |
7a868d1e YX |
746 | { |
747 | struct rhashtable_compare_arg arg = { | |
748 | .ht = ht, | |
749 | .key = rht_obj(ht, obj) + ht->p.key_offset, | |
750 | }; | |
751 | ||
752 | BUG_ON(!ht->p.key_len); | |
753 | ||
754 | return rhashtable_lookup_compare_insert(ht, obj, &rhashtable_compare, | |
755 | &arg); | |
756 | } | |
757 | EXPORT_SYMBOL_GPL(rhashtable_lookup_insert); | |
758 | ||
759 | /** | |
760 | * rhashtable_lookup_compare_insert - search and insert object to hash table | |
761 | * with compare function | |
762 | * @ht: hash table | |
763 | * @obj: pointer to hash head inside object | |
764 | * @compare: compare function, must return true on match | |
765 | * @arg: argument passed on to compare function | |
766 | * | |
767 | * Locks down the bucket chain in both the old and new table if a resize | |
768 | * is in progress to ensure that writers can't remove from the old table | |
769 | * and can't insert to the new table during the atomic operation of search | |
770 | * and insertion. Searches for duplicates in both the old and new table if | |
771 | * a resize is in progress. | |
772 | * | |
773 | * Lookups may occur in parallel with hashtable mutations and resizing. | |
774 | * | |
775 | * Will trigger an automatic deferred table resizing if the size grows | |
776 | * beyond the watermark indicated by grow_decision() which can be passed | |
777 | * to rhashtable_init(). | |
778 | */ | |
779 | bool rhashtable_lookup_compare_insert(struct rhashtable *ht, | |
780 | struct rhash_head *obj, | |
781 | bool (*compare)(void *, void *), | |
782 | void *arg) | |
db304854 YX |
783 | { |
784 | struct bucket_table *new_tbl, *old_tbl; | |
785 | spinlock_t *new_bucket_lock, *old_bucket_lock; | |
786 | u32 new_hash, old_hash; | |
787 | bool success = true; | |
788 | ||
789 | BUG_ON(!ht->p.key_len); | |
790 | ||
791 | rcu_read_lock(); | |
792 | ||
793 | old_tbl = rht_dereference_rcu(ht->tbl, ht); | |
794 | old_hash = head_hashfn(ht, old_tbl, obj); | |
795 | old_bucket_lock = bucket_lock(old_tbl, old_hash); | |
796 | spin_lock_bh(old_bucket_lock); | |
797 | ||
798 | new_tbl = rht_dereference_rcu(ht->future_tbl, ht); | |
799 | new_hash = head_hashfn(ht, new_tbl, obj); | |
800 | new_bucket_lock = bucket_lock(new_tbl, new_hash); | |
801 | if (unlikely(old_tbl != new_tbl)) | |
802 | spin_lock_bh_nested(new_bucket_lock, RHT_LOCK_NESTED); | |
803 | ||
7a868d1e YX |
804 | if (rhashtable_lookup_compare(ht, rht_obj(ht, obj) + ht->p.key_offset, |
805 | compare, arg)) { | |
db304854 YX |
806 | success = false; |
807 | goto exit; | |
808 | } | |
809 | ||
810 | __rhashtable_insert(ht, obj, new_tbl, new_hash); | |
811 | ||
812 | exit: | |
813 | if (unlikely(old_tbl != new_tbl)) | |
814 | spin_unlock_bh(new_bucket_lock); | |
815 | spin_unlock_bh(old_bucket_lock); | |
816 | ||
817 | rcu_read_unlock(); | |
818 | ||
819 | return success; | |
820 | } | |
7a868d1e | 821 | EXPORT_SYMBOL_GPL(rhashtable_lookup_compare_insert); |
db304854 | 822 | |
f2dba9c6 HX |
823 | /** |
824 | * rhashtable_walk_init - Initialise an iterator | |
825 | * @ht: Table to walk over | |
826 | * @iter: Hash table Iterator | |
827 | * | |
828 | * This function prepares a hash table walk. | |
829 | * | |
830 | * Note that if you restart a walk after rhashtable_walk_stop you | |
831 | * may see the same object twice. Also, you may miss objects if | |
832 | * there are removals in between rhashtable_walk_stop and the next | |
833 | * call to rhashtable_walk_start. | |
834 | * | |
835 | * For a completely stable walk you should construct your own data | |
836 | * structure outside the hash table. | |
837 | * | |
838 | * This function may sleep so you must not call it from interrupt | |
839 | * context or with spin locks held. | |
840 | * | |
841 | * You must call rhashtable_walk_exit if this function returns | |
842 | * successfully. | |
843 | */ | |
844 | int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter) | |
845 | { | |
846 | iter->ht = ht; | |
847 | iter->p = NULL; | |
848 | iter->slot = 0; | |
849 | iter->skip = 0; | |
850 | ||
851 | iter->walker = kmalloc(sizeof(*iter->walker), GFP_KERNEL); | |
852 | if (!iter->walker) | |
853 | return -ENOMEM; | |
854 | ||
855 | mutex_lock(&ht->mutex); | |
856 | list_add(&iter->walker->list, &ht->walkers); | |
857 | mutex_unlock(&ht->mutex); | |
858 | ||
859 | return 0; | |
860 | } | |
861 | EXPORT_SYMBOL_GPL(rhashtable_walk_init); | |
862 | ||
863 | /** | |
864 | * rhashtable_walk_exit - Free an iterator | |
865 | * @iter: Hash table Iterator | |
866 | * | |
867 | * This function frees resources allocated by rhashtable_walk_init. | |
868 | */ | |
869 | void rhashtable_walk_exit(struct rhashtable_iter *iter) | |
870 | { | |
871 | mutex_lock(&iter->ht->mutex); | |
872 | list_del(&iter->walker->list); | |
873 | mutex_unlock(&iter->ht->mutex); | |
874 | kfree(iter->walker); | |
875 | } | |
876 | EXPORT_SYMBOL_GPL(rhashtable_walk_exit); | |
877 | ||
878 | /** | |
879 | * rhashtable_walk_start - Start a hash table walk | |
880 | * @iter: Hash table iterator | |
881 | * | |
882 | * Start a hash table walk. Note that we take the RCU lock in all | |
883 | * cases including when we return an error. So you must always call | |
884 | * rhashtable_walk_stop to clean up. | |
885 | * | |
886 | * Returns zero if successful. | |
887 | * | |
888 | * Returns -EAGAIN if resize event occured. Note that the iterator | |
889 | * will rewind back to the beginning and you may use it immediately | |
890 | * by calling rhashtable_walk_next. | |
891 | */ | |
892 | int rhashtable_walk_start(struct rhashtable_iter *iter) | |
893 | { | |
894 | rcu_read_lock(); | |
895 | ||
896 | if (iter->walker->resize) { | |
897 | iter->slot = 0; | |
898 | iter->skip = 0; | |
899 | iter->walker->resize = false; | |
900 | return -EAGAIN; | |
901 | } | |
902 | ||
903 | return 0; | |
904 | } | |
905 | EXPORT_SYMBOL_GPL(rhashtable_walk_start); | |
906 | ||
907 | /** | |
908 | * rhashtable_walk_next - Return the next object and advance the iterator | |
909 | * @iter: Hash table iterator | |
910 | * | |
911 | * Note that you must call rhashtable_walk_stop when you are finished | |
912 | * with the walk. | |
913 | * | |
914 | * Returns the next object or NULL when the end of the table is reached. | |
915 | * | |
916 | * Returns -EAGAIN if resize event occured. Note that the iterator | |
917 | * will rewind back to the beginning and you may continue to use it. | |
918 | */ | |
919 | void *rhashtable_walk_next(struct rhashtable_iter *iter) | |
920 | { | |
921 | const struct bucket_table *tbl; | |
922 | struct rhashtable *ht = iter->ht; | |
923 | struct rhash_head *p = iter->p; | |
924 | void *obj = NULL; | |
925 | ||
926 | tbl = rht_dereference_rcu(ht->tbl, ht); | |
927 | ||
928 | if (p) { | |
929 | p = rht_dereference_bucket_rcu(p->next, tbl, iter->slot); | |
930 | goto next; | |
931 | } | |
932 | ||
933 | for (; iter->slot < tbl->size; iter->slot++) { | |
934 | int skip = iter->skip; | |
935 | ||
936 | rht_for_each_rcu(p, tbl, iter->slot) { | |
937 | if (!skip) | |
938 | break; | |
939 | skip--; | |
940 | } | |
941 | ||
942 | next: | |
943 | if (!rht_is_a_nulls(p)) { | |
944 | iter->skip++; | |
945 | iter->p = p; | |
946 | obj = rht_obj(ht, p); | |
947 | goto out; | |
948 | } | |
949 | ||
950 | iter->skip = 0; | |
951 | } | |
952 | ||
953 | iter->p = NULL; | |
954 | ||
955 | out: | |
956 | if (iter->walker->resize) { | |
957 | iter->p = NULL; | |
958 | iter->slot = 0; | |
959 | iter->skip = 0; | |
960 | iter->walker->resize = false; | |
961 | return ERR_PTR(-EAGAIN); | |
962 | } | |
963 | ||
964 | return obj; | |
965 | } | |
966 | EXPORT_SYMBOL_GPL(rhashtable_walk_next); | |
967 | ||
968 | /** | |
969 | * rhashtable_walk_stop - Finish a hash table walk | |
970 | * @iter: Hash table iterator | |
971 | * | |
972 | * Finish a hash table walk. | |
973 | */ | |
974 | void rhashtable_walk_stop(struct rhashtable_iter *iter) | |
975 | { | |
976 | rcu_read_unlock(); | |
977 | iter->p = NULL; | |
978 | } | |
979 | EXPORT_SYMBOL_GPL(rhashtable_walk_stop); | |
980 | ||
94000176 | 981 | static size_t rounded_hashtable_size(struct rhashtable_params *params) |
7e1e7763 | 982 | { |
94000176 YX |
983 | return max(roundup_pow_of_two(params->nelem_hint * 4 / 3), |
984 | 1UL << params->min_shift); | |
7e1e7763 TG |
985 | } |
986 | ||
987 | /** | |
988 | * rhashtable_init - initialize a new hash table | |
989 | * @ht: hash table to be initialized | |
990 | * @params: configuration parameters | |
991 | * | |
992 | * Initializes a new hash table based on the provided configuration | |
993 | * parameters. A table can be configured either with a variable or | |
994 | * fixed length key: | |
995 | * | |
996 | * Configuration Example 1: Fixed length keys | |
997 | * struct test_obj { | |
998 | * int key; | |
999 | * void * my_member; | |
1000 | * struct rhash_head node; | |
1001 | * }; | |
1002 | * | |
1003 | * struct rhashtable_params params = { | |
1004 | * .head_offset = offsetof(struct test_obj, node), | |
1005 | * .key_offset = offsetof(struct test_obj, key), | |
1006 | * .key_len = sizeof(int), | |
87545899 | 1007 | * .hashfn = jhash, |
f89bd6f8 | 1008 | * .nulls_base = (1U << RHT_BASE_SHIFT), |
7e1e7763 TG |
1009 | * }; |
1010 | * | |
1011 | * Configuration Example 2: Variable length keys | |
1012 | * struct test_obj { | |
1013 | * [...] | |
1014 | * struct rhash_head node; | |
1015 | * }; | |
1016 | * | |
1017 | * u32 my_hash_fn(const void *data, u32 seed) | |
1018 | * { | |
1019 | * struct test_obj *obj = data; | |
1020 | * | |
1021 | * return [... hash ...]; | |
1022 | * } | |
1023 | * | |
1024 | * struct rhashtable_params params = { | |
1025 | * .head_offset = offsetof(struct test_obj, node), | |
87545899 | 1026 | * .hashfn = jhash, |
7e1e7763 | 1027 | * .obj_hashfn = my_hash_fn, |
7e1e7763 TG |
1028 | * }; |
1029 | */ | |
1030 | int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params) | |
1031 | { | |
1032 | struct bucket_table *tbl; | |
1033 | size_t size; | |
1034 | ||
1035 | size = HASH_DEFAULT_SIZE; | |
1036 | ||
1037 | if ((params->key_len && !params->hashfn) || | |
1038 | (!params->key_len && !params->obj_hashfn)) | |
1039 | return -EINVAL; | |
1040 | ||
f89bd6f8 TG |
1041 | if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT)) |
1042 | return -EINVAL; | |
1043 | ||
94000176 YX |
1044 | params->min_shift = max_t(size_t, params->min_shift, |
1045 | ilog2(HASH_MIN_SIZE)); | |
1046 | ||
7e1e7763 | 1047 | if (params->nelem_hint) |
94000176 | 1048 | size = rounded_hashtable_size(params); |
7e1e7763 | 1049 | |
97defe1e TG |
1050 | memset(ht, 0, sizeof(*ht)); |
1051 | mutex_init(&ht->mutex); | |
1052 | memcpy(&ht->p, params, sizeof(*params)); | |
f2dba9c6 | 1053 | INIT_LIST_HEAD(&ht->walkers); |
97defe1e TG |
1054 | |
1055 | if (params->locks_mul) | |
1056 | ht->p.locks_mul = roundup_pow_of_two(params->locks_mul); | |
1057 | else | |
1058 | ht->p.locks_mul = BUCKET_LOCKS_PER_CPU; | |
1059 | ||
1060 | tbl = bucket_table_alloc(ht, size); | |
7e1e7763 TG |
1061 | if (tbl == NULL) |
1062 | return -ENOMEM; | |
1063 | ||
545a148e | 1064 | atomic_set(&ht->nelems, 0); |
c0c09bfd | 1065 | atomic_set(&ht->shift, ilog2(tbl->size)); |
7e1e7763 | 1066 | RCU_INIT_POINTER(ht->tbl, tbl); |
97defe1e | 1067 | RCU_INIT_POINTER(ht->future_tbl, tbl); |
7e1e7763 TG |
1068 | |
1069 | if (!ht->p.hash_rnd) | |
1070 | get_random_bytes(&ht->p.hash_rnd, sizeof(ht->p.hash_rnd)); | |
1071 | ||
97defe1e | 1072 | if (ht->p.grow_decision || ht->p.shrink_decision) |
57699a40 | 1073 | INIT_WORK(&ht->run_work, rht_deferred_worker); |
97defe1e | 1074 | |
7e1e7763 TG |
1075 | return 0; |
1076 | } | |
1077 | EXPORT_SYMBOL_GPL(rhashtable_init); | |
1078 | ||
1079 | /** | |
1080 | * rhashtable_destroy - destroy hash table | |
1081 | * @ht: the hash table to destroy | |
1082 | * | |
ae82ddcf PNA |
1083 | * Frees the bucket array. This function is not rcu safe, therefore the caller |
1084 | * has to make sure that no resizing may happen by unpublishing the hashtable | |
1085 | * and waiting for the quiescent cycle before releasing the bucket array. | |
7e1e7763 | 1086 | */ |
97defe1e | 1087 | void rhashtable_destroy(struct rhashtable *ht) |
7e1e7763 | 1088 | { |
97defe1e TG |
1089 | ht->being_destroyed = true; |
1090 | ||
57699a40 YX |
1091 | if (ht->p.grow_decision || ht->p.shrink_decision) |
1092 | cancel_work_sync(&ht->run_work); | |
97defe1e | 1093 | |
57699a40 | 1094 | mutex_lock(&ht->mutex); |
97defe1e | 1095 | bucket_table_free(rht_dereference(ht->tbl, ht)); |
97defe1e | 1096 | mutex_unlock(&ht->mutex); |
7e1e7763 TG |
1097 | } |
1098 | EXPORT_SYMBOL_GPL(rhashtable_destroy); |