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1/*
2 * Resizable, Scalable, Concurrent Hash Table
3 *
4 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
5 * Copyright (c) 2014-2015 Thomas Graf <tgraf@suug.ch>
6 * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
7 *
8 * Code partially derived from nft_hash
9 * Rewritten with rehash code from br_multicast plus single list
10 * pointer as suggested by Josh Triplett
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/atomic.h>
18#include <linux/kernel.h>
19#include <linux/init.h>
20#include <linux/log2.h>
21#include <linux/sched.h>
22#include <linux/slab.h>
23#include <linux/vmalloc.h>
24#include <linux/mm.h>
25#include <linux/jhash.h>
26#include <linux/random.h>
27#include <linux/rhashtable.h>
28#include <linux/err.h>
29#include <linux/export.h>
30
31#define HASH_DEFAULT_SIZE 64UL
32#define HASH_MIN_SIZE 4U
33#define BUCKET_LOCKS_PER_CPU 32UL
34
35static u32 head_hashfn(struct rhashtable *ht,
36 const struct bucket_table *tbl,
37 const struct rhash_head *he)
38{
39 return rht_head_hashfn(ht, tbl, he, ht->p);
40}
41
42#ifdef CONFIG_PROVE_LOCKING
43#define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
44
45int lockdep_rht_mutex_is_held(struct rhashtable *ht)
46{
47 return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
48}
49EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
50
51int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
52{
53 spinlock_t *lock = rht_bucket_lock(tbl, hash);
54
55 return (debug_locks) ? lockdep_is_held(lock) : 1;
56}
57EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
58#else
59#define ASSERT_RHT_MUTEX(HT)
60#endif
61
62
63static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
64 gfp_t gfp)
65{
66 unsigned int i, size;
67#if defined(CONFIG_PROVE_LOCKING)
68 unsigned int nr_pcpus = 2;
69#else
70 unsigned int nr_pcpus = num_possible_cpus();
71#endif
72
73 nr_pcpus = min_t(unsigned int, nr_pcpus, 64UL);
74 size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul);
75
76 /* Never allocate more than 0.5 locks per bucket */
77 size = min_t(unsigned int, size, tbl->size >> 1);
78
79 if (sizeof(spinlock_t) != 0) {
80 tbl->locks = NULL;
81#ifdef CONFIG_NUMA
82 if (size * sizeof(spinlock_t) > PAGE_SIZE &&
83 gfp == GFP_KERNEL)
84 tbl->locks = vmalloc(size * sizeof(spinlock_t));
85#endif
86 if (gfp != GFP_KERNEL)
87 gfp |= __GFP_NOWARN | __GFP_NORETRY;
88
89 if (!tbl->locks)
90 tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
91 gfp);
92 if (!tbl->locks)
93 return -ENOMEM;
94 for (i = 0; i < size; i++)
95 spin_lock_init(&tbl->locks[i]);
96 }
97 tbl->locks_mask = size - 1;
98
99 return 0;
100}
101
102static void bucket_table_free(const struct bucket_table *tbl)
103{
104 if (tbl)
105 kvfree(tbl->locks);
106
107 kvfree(tbl);
108}
109
110static void bucket_table_free_rcu(struct rcu_head *head)
111{
112 bucket_table_free(container_of(head, struct bucket_table, rcu));
113}
114
115static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
116 size_t nbuckets,
117 gfp_t gfp)
118{
119 struct bucket_table *tbl = NULL;
120 size_t size;
121 int i;
122
123 size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
124 if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER) ||
125 gfp != GFP_KERNEL)
126 tbl = kzalloc(size, gfp | __GFP_NOWARN | __GFP_NORETRY);
127 if (tbl == NULL && gfp == GFP_KERNEL)
128 tbl = vzalloc(size);
129 if (tbl == NULL)
130 return NULL;
131
132 tbl->size = nbuckets;
133
134 if (alloc_bucket_locks(ht, tbl, gfp) < 0) {
135 bucket_table_free(tbl);
136 return NULL;
137 }
138
139 INIT_LIST_HEAD(&tbl->walkers);
140
141 get_random_bytes(&tbl->hash_rnd, sizeof(tbl->hash_rnd));
142
143 for (i = 0; i < nbuckets; i++)
144 INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i);
145
146 return tbl;
147}
148
149static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
150 struct bucket_table *tbl)
151{
152 struct bucket_table *new_tbl;
153
154 do {
155 new_tbl = tbl;
156 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
157 } while (tbl);
158
159 return new_tbl;
160}
161
162static int rhashtable_rehash_one(struct rhashtable *ht, unsigned int old_hash)
163{
164 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
165 struct bucket_table *new_tbl = rhashtable_last_table(ht,
166 rht_dereference_rcu(old_tbl->future_tbl, ht));
167 struct rhash_head __rcu **pprev = &old_tbl->buckets[old_hash];
168 int err = -ENOENT;
169 struct rhash_head *head, *next, *entry;
170 spinlock_t *new_bucket_lock;
171 unsigned int new_hash;
172
173 rht_for_each(entry, old_tbl, old_hash) {
174 err = 0;
175 next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
176
177 if (rht_is_a_nulls(next))
178 break;
179
180 pprev = &entry->next;
181 }
182
183 if (err)
184 goto out;
185
186 new_hash = head_hashfn(ht, new_tbl, entry);
187
188 new_bucket_lock = rht_bucket_lock(new_tbl, new_hash);
189
190 spin_lock_nested(new_bucket_lock, SINGLE_DEPTH_NESTING);
191 head = rht_dereference_bucket(new_tbl->buckets[new_hash],
192 new_tbl, new_hash);
193
194 RCU_INIT_POINTER(entry->next, head);
195
196 rcu_assign_pointer(new_tbl->buckets[new_hash], entry);
197 spin_unlock(new_bucket_lock);
198
199 rcu_assign_pointer(*pprev, next);
200
201out:
202 return err;
203}
204
205static void rhashtable_rehash_chain(struct rhashtable *ht,
206 unsigned int old_hash)
207{
208 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
209 spinlock_t *old_bucket_lock;
210
211 old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
212
213 spin_lock_bh(old_bucket_lock);
214 while (!rhashtable_rehash_one(ht, old_hash))
215 ;
216 old_tbl->rehash++;
217 spin_unlock_bh(old_bucket_lock);
218}
219
220static int rhashtable_rehash_attach(struct rhashtable *ht,
221 struct bucket_table *old_tbl,
222 struct bucket_table *new_tbl)
223{
224 /* Protect future_tbl using the first bucket lock. */
225 spin_lock_bh(old_tbl->locks);
226
227 /* Did somebody beat us to it? */
228 if (rcu_access_pointer(old_tbl->future_tbl)) {
229 spin_unlock_bh(old_tbl->locks);
230 return -EEXIST;
231 }
232
233 /* Make insertions go into the new, empty table right away. Deletions
234 * and lookups will be attempted in both tables until we synchronize.
235 */
236 rcu_assign_pointer(old_tbl->future_tbl, new_tbl);
237
238 spin_unlock_bh(old_tbl->locks);
239
240 return 0;
241}
242
243static int rhashtable_rehash_table(struct rhashtable *ht)
244{
245 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
246 struct bucket_table *new_tbl;
247 struct rhashtable_walker *walker;
248 unsigned int old_hash;
249
250 new_tbl = rht_dereference(old_tbl->future_tbl, ht);
251 if (!new_tbl)
252 return 0;
253
254 for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
255 rhashtable_rehash_chain(ht, old_hash);
256 cond_resched();
257 }
258
259 /* Publish the new table pointer. */
260 rcu_assign_pointer(ht->tbl, new_tbl);
261
262 spin_lock(&ht->lock);
263 list_for_each_entry(walker, &old_tbl->walkers, list)
264 walker->tbl = NULL;
265 spin_unlock(&ht->lock);
266
267 /* Wait for readers. All new readers will see the new
268 * table, and thus no references to the old table will
269 * remain.
270 */
271 call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
272
273 return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
274}
275
276/**
277 * rhashtable_expand - Expand hash table while allowing concurrent lookups
278 * @ht: the hash table to expand
279 *
280 * A secondary bucket array is allocated and the hash entries are migrated.
281 *
282 * This function may only be called in a context where it is safe to call
283 * synchronize_rcu(), e.g. not within a rcu_read_lock() section.
284 *
285 * The caller must ensure that no concurrent resizing occurs by holding
286 * ht->mutex.
287 *
288 * It is valid to have concurrent insertions and deletions protected by per
289 * bucket locks or concurrent RCU protected lookups and traversals.
290 */
291static int rhashtable_expand(struct rhashtable *ht)
292{
293 struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
294 int err;
295
296 ASSERT_RHT_MUTEX(ht);
297
298 old_tbl = rhashtable_last_table(ht, old_tbl);
299
300 new_tbl = bucket_table_alloc(ht, old_tbl->size * 2, GFP_KERNEL);
301 if (new_tbl == NULL)
302 return -ENOMEM;
303
304 err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
305 if (err)
306 bucket_table_free(new_tbl);
307
308 return err;
309}
310
311/**
312 * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
313 * @ht: the hash table to shrink
314 *
315 * This function shrinks the hash table to fit, i.e., the smallest
316 * size would not cause it to expand right away automatically.
317 *
318 * The caller must ensure that no concurrent resizing occurs by holding
319 * ht->mutex.
320 *
321 * The caller must ensure that no concurrent table mutations take place.
322 * It is however valid to have concurrent lookups if they are RCU protected.
323 *
324 * It is valid to have concurrent insertions and deletions protected by per
325 * bucket locks or concurrent RCU protected lookups and traversals.
326 */
327static int rhashtable_shrink(struct rhashtable *ht)
328{
329 struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
330 unsigned int nelems = atomic_read(&ht->nelems);
331 unsigned int size = 0;
332 int err;
333
334 ASSERT_RHT_MUTEX(ht);
335
336 if (nelems)
337 size = roundup_pow_of_two(nelems * 3 / 2);
338 if (size < ht->p.min_size)
339 size = ht->p.min_size;
340
341 if (old_tbl->size <= size)
342 return 0;
343
344 if (rht_dereference(old_tbl->future_tbl, ht))
345 return -EEXIST;
346
347 new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
348 if (new_tbl == NULL)
349 return -ENOMEM;
350
351 err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
352 if (err)
353 bucket_table_free(new_tbl);
354
355 return err;
356}
357
358static void rht_deferred_worker(struct work_struct *work)
359{
360 struct rhashtable *ht;
361 struct bucket_table *tbl;
362 int err = 0;
363
364 ht = container_of(work, struct rhashtable, run_work);
365 mutex_lock(&ht->mutex);
366
367 tbl = rht_dereference(ht->tbl, ht);
368 tbl = rhashtable_last_table(ht, tbl);
369
370 if (rht_grow_above_75(ht, tbl))
371 rhashtable_expand(ht);
372 else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
373 rhashtable_shrink(ht);
374
375 err = rhashtable_rehash_table(ht);
376
377 mutex_unlock(&ht->mutex);
378
379 if (err)
380 schedule_work(&ht->run_work);
381}
382
383static int rhashtable_insert_rehash(struct rhashtable *ht,
384 struct bucket_table *tbl)
385{
386 struct bucket_table *old_tbl;
387 struct bucket_table *new_tbl;
388 unsigned int size;
389 int err;
390
391 old_tbl = rht_dereference_rcu(ht->tbl, ht);
392
393 size = tbl->size;
394
395 err = -EBUSY;
396
397 if (rht_grow_above_75(ht, tbl))
398 size *= 2;
399 /* Do not schedule more than one rehash */
400 else if (old_tbl != tbl)
401 goto fail;
402
403 err = -ENOMEM;
404
405 new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC);
406 if (new_tbl == NULL)
407 goto fail;
408
409 err = rhashtable_rehash_attach(ht, tbl, new_tbl);
410 if (err) {
411 bucket_table_free(new_tbl);
412 if (err == -EEXIST)
413 err = 0;
414 } else
415 schedule_work(&ht->run_work);
416
417 return err;
418
419fail:
420 /* Do not fail the insert if someone else did a rehash. */
421 if (likely(rcu_dereference_raw(tbl->future_tbl)))
422 return 0;
423
424 /* Schedule async rehash to retry allocation in process context. */
425 if (err == -ENOMEM)
426 schedule_work(&ht->run_work);
427
428 return err;
429}
430
431static void *rhashtable_lookup_one(struct rhashtable *ht,
432 struct bucket_table *tbl, unsigned int hash,
433 const void *key, struct rhash_head *obj)
434{
435 struct rhashtable_compare_arg arg = {
436 .ht = ht,
437 .key = key,
438 };
439 struct rhash_head __rcu **pprev;
440 struct rhash_head *head;
441 int elasticity;
442
443 elasticity = ht->elasticity;
444 pprev = &tbl->buckets[hash];
445 rht_for_each(head, tbl, hash) {
446 struct rhlist_head *list;
447 struct rhlist_head *plist;
448
449 elasticity--;
450 if (!key ||
451 (ht->p.obj_cmpfn ?
452 ht->p.obj_cmpfn(&arg, rht_obj(ht, head)) :
453 rhashtable_compare(&arg, rht_obj(ht, head)))) {
454 pprev = &head->next;
455 continue;
456 }
457
458 if (!ht->rhlist)
459 return rht_obj(ht, head);
460
461 list = container_of(obj, struct rhlist_head, rhead);
462 plist = container_of(head, struct rhlist_head, rhead);
463
464 RCU_INIT_POINTER(list->next, plist);
465 head = rht_dereference_bucket(head->next, tbl, hash);
466 RCU_INIT_POINTER(list->rhead.next, head);
467 rcu_assign_pointer(*pprev, obj);
468
469 return NULL;
470 }
471
472 if (elasticity <= 0)
473 return ERR_PTR(-EAGAIN);
474
475 return ERR_PTR(-ENOENT);
476}
477
478static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
479 struct bucket_table *tbl,
480 unsigned int hash,
481 struct rhash_head *obj,
482 void *data)
483{
484 struct bucket_table *new_tbl;
485 struct rhash_head *head;
486
487 if (!IS_ERR_OR_NULL(data))
488 return ERR_PTR(-EEXIST);
489
490 if (PTR_ERR(data) != -EAGAIN && PTR_ERR(data) != -ENOENT)
491 return ERR_CAST(data);
492
493 new_tbl = rcu_dereference(tbl->future_tbl);
494 if (new_tbl)
495 return new_tbl;
496
497 if (PTR_ERR(data) != -ENOENT)
498 return ERR_CAST(data);
499
500 if (unlikely(rht_grow_above_max(ht, tbl)))
501 return ERR_PTR(-E2BIG);
502
503 if (unlikely(rht_grow_above_100(ht, tbl)))
504 return ERR_PTR(-EAGAIN);
505
506 head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
507
508 RCU_INIT_POINTER(obj->next, head);
509 if (ht->rhlist) {
510 struct rhlist_head *list;
511
512 list = container_of(obj, struct rhlist_head, rhead);
513 RCU_INIT_POINTER(list->next, NULL);
514 }
515
516 rcu_assign_pointer(tbl->buckets[hash], obj);
517
518 atomic_inc(&ht->nelems);
519 if (rht_grow_above_75(ht, tbl))
520 schedule_work(&ht->run_work);
521
522 return NULL;
523}
524
525static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
526 struct rhash_head *obj)
527{
528 struct bucket_table *new_tbl;
529 struct bucket_table *tbl;
530 unsigned int hash;
531 spinlock_t *lock;
532 void *data;
533
534 tbl = rcu_dereference(ht->tbl);
535
536 /* All insertions must grab the oldest table containing
537 * the hashed bucket that is yet to be rehashed.
538 */
539 for (;;) {
540 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
541 lock = rht_bucket_lock(tbl, hash);
542 spin_lock_bh(lock);
543
544 if (tbl->rehash <= hash)
545 break;
546
547 spin_unlock_bh(lock);
548 tbl = rcu_dereference(tbl->future_tbl);
549 }
550
551 data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
552 new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
553 if (PTR_ERR(new_tbl) != -EEXIST)
554 data = ERR_CAST(new_tbl);
555
556 while (!IS_ERR_OR_NULL(new_tbl)) {
557 tbl = new_tbl;
558 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
559 spin_lock_nested(rht_bucket_lock(tbl, hash),
560 SINGLE_DEPTH_NESTING);
561
562 data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
563 new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
564 if (PTR_ERR(new_tbl) != -EEXIST)
565 data = ERR_CAST(new_tbl);
566
567 spin_unlock(rht_bucket_lock(tbl, hash));
568 }
569
570 spin_unlock_bh(lock);
571
572 if (PTR_ERR(data) == -EAGAIN)
573 data = ERR_PTR(rhashtable_insert_rehash(ht, tbl) ?:
574 -EAGAIN);
575
576 return data;
577}
578
579void *rhashtable_insert_slow(struct rhashtable *ht, const void *key,
580 struct rhash_head *obj)
581{
582 void *data;
583
584 do {
585 rcu_read_lock();
586 data = rhashtable_try_insert(ht, key, obj);
587 rcu_read_unlock();
588 } while (PTR_ERR(data) == -EAGAIN);
589
590 return data;
591}
592EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
593
594/**
595 * rhashtable_walk_enter - Initialise an iterator
596 * @ht: Table to walk over
597 * @iter: Hash table Iterator
598 *
599 * This function prepares a hash table walk.
600 *
601 * Note that if you restart a walk after rhashtable_walk_stop you
602 * may see the same object twice. Also, you may miss objects if
603 * there are removals in between rhashtable_walk_stop and the next
604 * call to rhashtable_walk_start.
605 *
606 * For a completely stable walk you should construct your own data
607 * structure outside the hash table.
608 *
609 * This function may sleep so you must not call it from interrupt
610 * context or with spin locks held.
611 *
612 * You must call rhashtable_walk_exit after this function returns.
613 */
614void rhashtable_walk_enter(struct rhashtable *ht, struct rhashtable_iter *iter)
615{
616 iter->ht = ht;
617 iter->p = NULL;
618 iter->slot = 0;
619 iter->skip = 0;
620
621 spin_lock(&ht->lock);
622 iter->walker.tbl =
623 rcu_dereference_protected(ht->tbl, lockdep_is_held(&ht->lock));
624 list_add(&iter->walker.list, &iter->walker.tbl->walkers);
625 spin_unlock(&ht->lock);
626}
627EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
628
629/**
630 * rhashtable_walk_exit - Free an iterator
631 * @iter: Hash table Iterator
632 *
633 * This function frees resources allocated by rhashtable_walk_init.
634 */
635void rhashtable_walk_exit(struct rhashtable_iter *iter)
636{
637 spin_lock(&iter->ht->lock);
638 if (iter->walker.tbl)
639 list_del(&iter->walker.list);
640 spin_unlock(&iter->ht->lock);
641}
642EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
643
644/**
645 * rhashtable_walk_start - Start a hash table walk
646 * @iter: Hash table iterator
647 *
648 * Start a hash table walk. Note that we take the RCU lock in all
649 * cases including when we return an error. So you must always call
650 * rhashtable_walk_stop to clean up.
651 *
652 * Returns zero if successful.
653 *
654 * Returns -EAGAIN if resize event occured. Note that the iterator
655 * will rewind back to the beginning and you may use it immediately
656 * by calling rhashtable_walk_next.
657 */
658int rhashtable_walk_start(struct rhashtable_iter *iter)
659 __acquires(RCU)
660{
661 struct rhashtable *ht = iter->ht;
662
663 rcu_read_lock();
664
665 spin_lock(&ht->lock);
666 if (iter->walker.tbl)
667 list_del(&iter->walker.list);
668 spin_unlock(&ht->lock);
669
670 if (!iter->walker.tbl) {
671 iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht);
672 return -EAGAIN;
673 }
674
675 return 0;
676}
677EXPORT_SYMBOL_GPL(rhashtable_walk_start);
678
679/**
680 * rhashtable_walk_next - Return the next object and advance the iterator
681 * @iter: Hash table iterator
682 *
683 * Note that you must call rhashtable_walk_stop when you are finished
684 * with the walk.
685 *
686 * Returns the next object or NULL when the end of the table is reached.
687 *
688 * Returns -EAGAIN if resize event occured. Note that the iterator
689 * will rewind back to the beginning and you may continue to use it.
690 */
691void *rhashtable_walk_next(struct rhashtable_iter *iter)
692{
693 struct bucket_table *tbl = iter->walker.tbl;
694 struct rhlist_head *list = iter->list;
695 struct rhashtable *ht = iter->ht;
696 struct rhash_head *p = iter->p;
697 bool rhlist = ht->rhlist;
698
699 if (p) {
700 if (!rhlist || !(list = rcu_dereference(list->next))) {
701 p = rcu_dereference(p->next);
702 list = container_of(p, struct rhlist_head, rhead);
703 }
704 goto next;
705 }
706
707 for (; iter->slot < tbl->size; iter->slot++) {
708 int skip = iter->skip;
709
710 rht_for_each_rcu(p, tbl, iter->slot) {
711 if (rhlist) {
712 list = container_of(p, struct rhlist_head,
713 rhead);
714 do {
715 if (!skip)
716 goto next;
717 skip--;
718 list = rcu_dereference(list->next);
719 } while (list);
720
721 continue;
722 }
723 if (!skip)
724 break;
725 skip--;
726 }
727
728next:
729 if (!rht_is_a_nulls(p)) {
730 iter->skip++;
731 iter->p = p;
732 iter->list = list;
733 return rht_obj(ht, rhlist ? &list->rhead : p);
734 }
735
736 iter->skip = 0;
737 }
738
739 iter->p = NULL;
740
741 /* Ensure we see any new tables. */
742 smp_rmb();
743
744 iter->walker.tbl = rht_dereference_rcu(tbl->future_tbl, ht);
745 if (iter->walker.tbl) {
746 iter->slot = 0;
747 iter->skip = 0;
748 return ERR_PTR(-EAGAIN);
749 }
750
751 return NULL;
752}
753EXPORT_SYMBOL_GPL(rhashtable_walk_next);
754
755/**
756 * rhashtable_walk_stop - Finish a hash table walk
757 * @iter: Hash table iterator
758 *
759 * Finish a hash table walk.
760 */
761void rhashtable_walk_stop(struct rhashtable_iter *iter)
762 __releases(RCU)
763{
764 struct rhashtable *ht;
765 struct bucket_table *tbl = iter->walker.tbl;
766
767 if (!tbl)
768 goto out;
769
770 ht = iter->ht;
771
772 spin_lock(&ht->lock);
773 if (tbl->rehash < tbl->size)
774 list_add(&iter->walker.list, &tbl->walkers);
775 else
776 iter->walker.tbl = NULL;
777 spin_unlock(&ht->lock);
778
779 iter->p = NULL;
780
781out:
782 rcu_read_unlock();
783}
784EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
785
786static size_t rounded_hashtable_size(const struct rhashtable_params *params)
787{
788 size_t retsize;
789
790 if (params->nelem_hint)
791 retsize = max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
792 (unsigned long)params->min_size);
793 else
794 retsize = max(HASH_DEFAULT_SIZE,
795 (unsigned long)params->min_size);
796
797 return retsize;
798}
799
800static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
801{
802 return jhash2(key, length, seed);
803}
804
805/**
806 * rhashtable_init - initialize a new hash table
807 * @ht: hash table to be initialized
808 * @params: configuration parameters
809 *
810 * Initializes a new hash table based on the provided configuration
811 * parameters. A table can be configured either with a variable or
812 * fixed length key:
813 *
814 * Configuration Example 1: Fixed length keys
815 * struct test_obj {
816 * int key;
817 * void * my_member;
818 * struct rhash_head node;
819 * };
820 *
821 * struct rhashtable_params params = {
822 * .head_offset = offsetof(struct test_obj, node),
823 * .key_offset = offsetof(struct test_obj, key),
824 * .key_len = sizeof(int),
825 * .hashfn = jhash,
826 * .nulls_base = (1U << RHT_BASE_SHIFT),
827 * };
828 *
829 * Configuration Example 2: Variable length keys
830 * struct test_obj {
831 * [...]
832 * struct rhash_head node;
833 * };
834 *
835 * u32 my_hash_fn(const void *data, u32 len, u32 seed)
836 * {
837 * struct test_obj *obj = data;
838 *
839 * return [... hash ...];
840 * }
841 *
842 * struct rhashtable_params params = {
843 * .head_offset = offsetof(struct test_obj, node),
844 * .hashfn = jhash,
845 * .obj_hashfn = my_hash_fn,
846 * };
847 */
848int rhashtable_init(struct rhashtable *ht,
849 const struct rhashtable_params *params)
850{
851 struct bucket_table *tbl;
852 size_t size;
853
854 if ((!params->key_len && !params->obj_hashfn) ||
855 (params->obj_hashfn && !params->obj_cmpfn))
856 return -EINVAL;
857
858 if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
859 return -EINVAL;
860
861 memset(ht, 0, sizeof(*ht));
862 mutex_init(&ht->mutex);
863 spin_lock_init(&ht->lock);
864 memcpy(&ht->p, params, sizeof(*params));
865
866 if (params->min_size)
867 ht->p.min_size = roundup_pow_of_two(params->min_size);
868
869 if (params->max_size)
870 ht->p.max_size = rounddown_pow_of_two(params->max_size);
871
872 if (params->insecure_max_entries)
873 ht->p.insecure_max_entries =
874 rounddown_pow_of_two(params->insecure_max_entries);
875 else
876 ht->p.insecure_max_entries = ht->p.max_size * 2;
877
878 ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);
879
880 size = rounded_hashtable_size(&ht->p);
881
882 /* The maximum (not average) chain length grows with the
883 * size of the hash table, at a rate of (log N)/(log log N).
884 * The value of 16 is selected so that even if the hash
885 * table grew to 2^32 you would not expect the maximum
886 * chain length to exceed it unless we are under attack
887 * (or extremely unlucky).
888 *
889 * As this limit is only to detect attacks, we don't need
890 * to set it to a lower value as you'd need the chain
891 * length to vastly exceed 16 to have any real effect
892 * on the system.
893 */
894 if (!params->insecure_elasticity)
895 ht->elasticity = 16;
896
897 if (params->locks_mul)
898 ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
899 else
900 ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
901
902 ht->key_len = ht->p.key_len;
903 if (!params->hashfn) {
904 ht->p.hashfn = jhash;
905
906 if (!(ht->key_len & (sizeof(u32) - 1))) {
907 ht->key_len /= sizeof(u32);
908 ht->p.hashfn = rhashtable_jhash2;
909 }
910 }
911
912 tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
913 if (tbl == NULL)
914 return -ENOMEM;
915
916 atomic_set(&ht->nelems, 0);
917
918 RCU_INIT_POINTER(ht->tbl, tbl);
919
920 INIT_WORK(&ht->run_work, rht_deferred_worker);
921
922 return 0;
923}
924EXPORT_SYMBOL_GPL(rhashtable_init);
925
926/**
927 * rhltable_init - initialize a new hash list table
928 * @hlt: hash list table to be initialized
929 * @params: configuration parameters
930 *
931 * Initializes a new hash list table.
932 *
933 * See documentation for rhashtable_init.
934 */
935int rhltable_init(struct rhltable *hlt, const struct rhashtable_params *params)
936{
937 int err;
938
939 /* No rhlist NULLs marking for now. */
940 if (params->nulls_base)
941 return -EINVAL;
942
943 err = rhashtable_init(&hlt->ht, params);
944 hlt->ht.rhlist = true;
945 return err;
946}
947EXPORT_SYMBOL_GPL(rhltable_init);
948
949static void rhashtable_free_one(struct rhashtable *ht, struct rhash_head *obj,
950 void (*free_fn)(void *ptr, void *arg),
951 void *arg)
952{
953 struct rhlist_head *list;
954
955 if (!ht->rhlist) {
956 free_fn(rht_obj(ht, obj), arg);
957 return;
958 }
959
960 list = container_of(obj, struct rhlist_head, rhead);
961 do {
962 obj = &list->rhead;
963 list = rht_dereference(list->next, ht);
964 free_fn(rht_obj(ht, obj), arg);
965 } while (list);
966}
967
968/**
969 * rhashtable_free_and_destroy - free elements and destroy hash table
970 * @ht: the hash table to destroy
971 * @free_fn: callback to release resources of element
972 * @arg: pointer passed to free_fn
973 *
974 * Stops an eventual async resize. If defined, invokes free_fn for each
975 * element to releasal resources. Please note that RCU protected
976 * readers may still be accessing the elements. Releasing of resources
977 * must occur in a compatible manner. Then frees the bucket array.
978 *
979 * This function will eventually sleep to wait for an async resize
980 * to complete. The caller is responsible that no further write operations
981 * occurs in parallel.
982 */
983void rhashtable_free_and_destroy(struct rhashtable *ht,
984 void (*free_fn)(void *ptr, void *arg),
985 void *arg)
986{
987 const struct bucket_table *tbl;
988 unsigned int i;
989
990 cancel_work_sync(&ht->run_work);
991
992 mutex_lock(&ht->mutex);
993 tbl = rht_dereference(ht->tbl, ht);
994 if (free_fn) {
995 for (i = 0; i < tbl->size; i++) {
996 struct rhash_head *pos, *next;
997
998 cond_resched();
999 for (pos = rht_dereference(tbl->buckets[i], ht),
1000 next = !rht_is_a_nulls(pos) ?
1001 rht_dereference(pos->next, ht) : NULL;
1002 !rht_is_a_nulls(pos);
1003 pos = next,
1004 next = !rht_is_a_nulls(pos) ?
1005 rht_dereference(pos->next, ht) : NULL)
1006 rhashtable_free_one(ht, pos, free_fn, arg);
1007 }
1008 }
1009
1010 bucket_table_free(tbl);
1011 mutex_unlock(&ht->mutex);
1012}
1013EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);
1014
1015void rhashtable_destroy(struct rhashtable *ht)
1016{
1017 return rhashtable_free_and_destroy(ht, NULL, NULL);
1018}
1019EXPORT_SYMBOL_GPL(rhashtable_destroy);
1020
generated by cgit at 2024-05-18 18:17:39 (GMT)