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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
257 /* Publish the new table pointer. */
258 rcu_assign_pointer(ht->tbl, new_tbl);
259
260 spin_lock(&ht->lock);
261 list_for_each_entry(walker, &old_tbl->walkers, list)
262 walker->tbl = NULL;
263 spin_unlock(&ht->lock);
264
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 call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
270
271 return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
272}
273
274/**
275 * rhashtable_expand - Expand hash table while allowing concurrent lookups
276 * @ht: the hash table to expand
277 *
278 * A secondary bucket array is allocated and the hash entries are migrated.
279 *
280 * This function may only be called in a context where it is safe to call
281 * synchronize_rcu(), e.g. not within a rcu_read_lock() section.
282 *
283 * The caller must ensure that no concurrent resizing occurs by holding
284 * ht->mutex.
285 *
286 * It is valid to have concurrent insertions and deletions protected by per
287 * bucket locks or concurrent RCU protected lookups and traversals.
288 */
289static int rhashtable_expand(struct rhashtable *ht)
290{
291 struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
292 int err;
293
294 ASSERT_RHT_MUTEX(ht);
295
296 old_tbl = rhashtable_last_table(ht, old_tbl);
297
298 new_tbl = bucket_table_alloc(ht, old_tbl->size * 2, GFP_KERNEL);
299 if (new_tbl == NULL)
300 return -ENOMEM;
301
302 err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
303 if (err)
304 bucket_table_free(new_tbl);
305
306 return err;
307}
308
309/**
310 * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
311 * @ht: the hash table to shrink
312 *
313 * This function shrinks the hash table to fit, i.e., the smallest
314 * size would not cause it to expand right away automatically.
315 *
316 * The caller must ensure that no concurrent resizing occurs by holding
317 * ht->mutex.
318 *
319 * The caller must ensure that no concurrent table mutations take place.
320 * It is however valid to have concurrent lookups if they are RCU protected.
321 *
322 * It is valid to have concurrent insertions and deletions protected by per
323 * bucket locks or concurrent RCU protected lookups and traversals.
324 */
325static int rhashtable_shrink(struct rhashtable *ht)
326{
327 struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
328 unsigned int nelems = atomic_read(&ht->nelems);
329 unsigned int size = 0;
330 int err;
331
332 ASSERT_RHT_MUTEX(ht);
333
334 if (nelems)
335 size = roundup_pow_of_two(nelems * 3 / 2);
336 if (size < ht->p.min_size)
337 size = ht->p.min_size;
338
339 if (old_tbl->size <= size)
340 return 0;
341
342 if (rht_dereference(old_tbl->future_tbl, ht))
343 return -EEXIST;
344
345 new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
346 if (new_tbl == NULL)
347 return -ENOMEM;
348
349 err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
350 if (err)
351 bucket_table_free(new_tbl);
352
353 return err;
354}
355
356static void rht_deferred_worker(struct work_struct *work)
357{
358 struct rhashtable *ht;
359 struct bucket_table *tbl;
360 int err = 0;
361
362 ht = container_of(work, struct rhashtable, run_work);
363 mutex_lock(&ht->mutex);
364
365 tbl = rht_dereference(ht->tbl, ht);
366 tbl = rhashtable_last_table(ht, tbl);
367
368 if (rht_grow_above_75(ht, tbl))
369 rhashtable_expand(ht);
370 else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
371 rhashtable_shrink(ht);
372
373 err = rhashtable_rehash_table(ht);
374
375 mutex_unlock(&ht->mutex);
376
377 if (err)
378 schedule_work(&ht->run_work);
379}
380
381static int rhashtable_insert_rehash(struct rhashtable *ht,
382 struct bucket_table *tbl)
383{
384 struct bucket_table *old_tbl;
385 struct bucket_table *new_tbl;
386 unsigned int size;
387 int err;
388
389 old_tbl = rht_dereference_rcu(ht->tbl, ht);
390
391 size = tbl->size;
392
393 err = -EBUSY;
394
395 if (rht_grow_above_75(ht, tbl))
396 size *= 2;
397 /* Do not schedule more than one rehash */
398 else if (old_tbl != tbl)
399 goto fail;
400
401 err = -ENOMEM;
402
403 new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC);
404 if (new_tbl == NULL)
405 goto fail;
406
407 err = rhashtable_rehash_attach(ht, tbl, new_tbl);
408 if (err) {
409 bucket_table_free(new_tbl);
410 if (err == -EEXIST)
411 err = 0;
412 } else
413 schedule_work(&ht->run_work);
414
415 return err;
416
417fail:
418 /* Do not fail the insert if someone else did a rehash. */
419 if (likely(rcu_dereference_raw(tbl->future_tbl)))
420 return 0;
421
422 /* Schedule async rehash to retry allocation in process context. */
423 if (err == -ENOMEM)
424 schedule_work(&ht->run_work);
425
426 return err;
427}
428
429static void *rhashtable_lookup_one(struct rhashtable *ht,
430 struct bucket_table *tbl, unsigned int hash,
431 const void *key, struct rhash_head *obj)
432{
433 struct rhashtable_compare_arg arg = {
434 .ht = ht,
435 .key = key,
436 };
437 struct rhash_head __rcu **pprev;
438 struct rhash_head *head;
439 int elasticity;
440
441 elasticity = ht->elasticity;
442 pprev = &tbl->buckets[hash];
443 rht_for_each(head, tbl, hash) {
444 struct rhlist_head *list;
445 struct rhlist_head *plist;
446
447 elasticity--;
448 if (!key ||
449 (ht->p.obj_cmpfn ?
450 ht->p.obj_cmpfn(&arg, rht_obj(ht, head)) :
451 rhashtable_compare(&arg, rht_obj(ht, head))))
452 continue;
453
454 if (!ht->rhlist)
455 return rht_obj(ht, head);
456
457 list = container_of(obj, struct rhlist_head, rhead);
458 plist = container_of(head, struct rhlist_head, rhead);
459
460 RCU_INIT_POINTER(list->next, plist);
461 head = rht_dereference_bucket(head->next, tbl, hash);
462 RCU_INIT_POINTER(list->rhead.next, head);
463 rcu_assign_pointer(*pprev, obj);
464
465 return NULL;
466 }
467
468 if (elasticity <= 0)
469 return ERR_PTR(-EAGAIN);
470
471 return ERR_PTR(-ENOENT);
472}
473
474static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
475 struct bucket_table *tbl,
476 unsigned int hash,
477 struct rhash_head *obj,
478 void *data)
479{
480 struct bucket_table *new_tbl;
481 struct rhash_head *head;
482
483 if (!IS_ERR_OR_NULL(data))
484 return ERR_PTR(-EEXIST);
485
486 if (PTR_ERR(data) != -EAGAIN && PTR_ERR(data) != -ENOENT)
487 return ERR_CAST(data);
488
489 new_tbl = rcu_dereference(tbl->future_tbl);
490 if (new_tbl)
491 return new_tbl;
492
493 if (PTR_ERR(data) != -ENOENT)
494 return ERR_CAST(data);
495
496 if (unlikely(rht_grow_above_max(ht, tbl)))
497 return ERR_PTR(-E2BIG);
498
499 if (unlikely(rht_grow_above_100(ht, tbl)))
500 return ERR_PTR(-EAGAIN);
501
502 head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
503
504 RCU_INIT_POINTER(obj->next, head);
505 if (ht->rhlist) {
506 struct rhlist_head *list;
507
508 list = container_of(obj, struct rhlist_head, rhead);
509 RCU_INIT_POINTER(list->next, NULL);
510 }
511
512 rcu_assign_pointer(tbl->buckets[hash], obj);
513
514 atomic_inc(&ht->nelems);
515 if (rht_grow_above_75(ht, tbl))
516 schedule_work(&ht->run_work);
517
518 return NULL;
519}
520
521static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
522 struct rhash_head *obj)
523{
524 struct bucket_table *new_tbl;
525 struct bucket_table *tbl;
526 unsigned int hash;
527 spinlock_t *lock;
528 void *data;
529
530 tbl = rcu_dereference(ht->tbl);
531
532 /* All insertions must grab the oldest table containing
533 * the hashed bucket that is yet to be rehashed.
534 */
535 for (;;) {
536 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
537 lock = rht_bucket_lock(tbl, hash);
538 spin_lock_bh(lock);
539
540 if (tbl->rehash <= hash)
541 break;
542
543 spin_unlock_bh(lock);
544 tbl = rcu_dereference(tbl->future_tbl);
545 }
546
547 data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
548 new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
549 if (PTR_ERR(new_tbl) != -EEXIST)
550 data = ERR_CAST(new_tbl);
551
552 while (!IS_ERR_OR_NULL(new_tbl)) {
553 tbl = new_tbl;
554 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
555 spin_lock_nested(rht_bucket_lock(tbl, hash),
556 SINGLE_DEPTH_NESTING);
557
558 data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
559 new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
560 if (PTR_ERR(new_tbl) != -EEXIST)
561 data = ERR_CAST(new_tbl);
562
563 spin_unlock(rht_bucket_lock(tbl, hash));
564 }
565
566 spin_unlock_bh(lock);
567
568 if (PTR_ERR(data) == -EAGAIN)
569 data = ERR_PTR(rhashtable_insert_rehash(ht, tbl) ?:
570 -EAGAIN);
571
572 return data;
573}
574
575void *rhashtable_insert_slow(struct rhashtable *ht, const void *key,
576 struct rhash_head *obj)
577{
578 void *data;
579
580 do {
581 rcu_read_lock();
582 data = rhashtable_try_insert(ht, key, obj);
583 rcu_read_unlock();
584 } while (PTR_ERR(data) == -EAGAIN);
585
586 return data;
587}
588EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
589
590/**
591 * rhashtable_walk_enter - Initialise an iterator
592 * @ht: Table to walk over
593 * @iter: Hash table Iterator
594 *
595 * This function prepares a hash table walk.
596 *
597 * Note that if you restart a walk after rhashtable_walk_stop you
598 * may see the same object twice. Also, you may miss objects if
599 * there are removals in between rhashtable_walk_stop and the next
600 * call to rhashtable_walk_start.
601 *
602 * For a completely stable walk you should construct your own data
603 * structure outside the hash table.
604 *
605 * This function may sleep so you must not call it from interrupt
606 * context or with spin locks held.
607 *
608 * You must call rhashtable_walk_exit after this function returns.
609 */
610void rhashtable_walk_enter(struct rhashtable *ht, struct rhashtable_iter *iter)
611{
612 iter->ht = ht;
613 iter->p = NULL;
614 iter->slot = 0;
615 iter->skip = 0;
616
617 spin_lock(&ht->lock);
618 iter->walker.tbl =
619 rcu_dereference_protected(ht->tbl, lockdep_is_held(&ht->lock));
620 list_add(&iter->walker.list, &iter->walker.tbl->walkers);
621 spin_unlock(&ht->lock);
622}
623EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
624
625/**
626 * rhashtable_walk_exit - Free an iterator
627 * @iter: Hash table Iterator
628 *
629 * This function frees resources allocated by rhashtable_walk_init.
630 */
631void rhashtable_walk_exit(struct rhashtable_iter *iter)
632{
633 spin_lock(&iter->ht->lock);
634 if (iter->walker.tbl)
635 list_del(&iter->walker.list);
636 spin_unlock(&iter->ht->lock);
637}
638EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
639
640/**
641 * rhashtable_walk_start - Start a hash table walk
642 * @iter: Hash table iterator
643 *
644 * Start a hash table walk. Note that we take the RCU lock in all
645 * cases including when we return an error. So you must always call
646 * rhashtable_walk_stop to clean up.
647 *
648 * Returns zero if successful.
649 *
650 * Returns -EAGAIN if resize event occured. Note that the iterator
651 * will rewind back to the beginning and you may use it immediately
652 * by calling rhashtable_walk_next.
653 */
654int rhashtable_walk_start(struct rhashtable_iter *iter)
655 __acquires(RCU)
656{
657 struct rhashtable *ht = iter->ht;
658
659 rcu_read_lock();
660
661 spin_lock(&ht->lock);
662 if (iter->walker.tbl)
663 list_del(&iter->walker.list);
664 spin_unlock(&ht->lock);
665
666 if (!iter->walker.tbl) {
667 iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht);
668 return -EAGAIN;
669 }
670
671 return 0;
672}
673EXPORT_SYMBOL_GPL(rhashtable_walk_start);
674
675/**
676 * rhashtable_walk_next - Return the next object and advance the iterator
677 * @iter: Hash table iterator
678 *
679 * Note that you must call rhashtable_walk_stop when you are finished
680 * with the walk.
681 *
682 * Returns the next object or NULL when the end of the table is reached.
683 *
684 * Returns -EAGAIN if resize event occured. Note that the iterator
685 * will rewind back to the beginning and you may continue to use it.
686 */
687void *rhashtable_walk_next(struct rhashtable_iter *iter)
688{
689 struct bucket_table *tbl = iter->walker.tbl;
690 struct rhlist_head *list = iter->list;
691 struct rhashtable *ht = iter->ht;
692 struct rhash_head *p = iter->p;
693 bool rhlist = ht->rhlist;
694
695 if (p) {
696 if (!rhlist || !(list = rcu_dereference(list->next))) {
697 p = rcu_dereference(p->next);
698 list = container_of(p, struct rhlist_head, rhead);
699 }
700 goto next;
701 }
702
703 for (; iter->slot < tbl->size; iter->slot++) {
704 int skip = iter->skip;
705
706 rht_for_each_rcu(p, tbl, iter->slot) {
707 if (rhlist) {
708 list = container_of(p, struct rhlist_head,
709 rhead);
710 do {
711 if (!skip)
712 goto next;
713 skip--;
714 list = rcu_dereference(list->next);
715 } while (list);
716
717 continue;
718 }
719 if (!skip)
720 break;
721 skip--;
722 }
723
724next:
725 if (!rht_is_a_nulls(p)) {
726 iter->skip++;
727 iter->p = p;
728 iter->list = list;
729 return rht_obj(ht, rhlist ? &list->rhead : p);
730 }
731
732 iter->skip = 0;
733 }
734
735 iter->p = NULL;
736
737 /* Ensure we see any new tables. */
738 smp_rmb();
739
740 iter->walker.tbl = rht_dereference_rcu(tbl->future_tbl, ht);
741 if (iter->walker.tbl) {
742 iter->slot = 0;
743 iter->skip = 0;
744 return ERR_PTR(-EAGAIN);
745 }
746
747 return NULL;
748}
749EXPORT_SYMBOL_GPL(rhashtable_walk_next);
750
751/**
752 * rhashtable_walk_stop - Finish a hash table walk
753 * @iter: Hash table iterator
754 *
755 * Finish a hash table walk.
756 */
757void rhashtable_walk_stop(struct rhashtable_iter *iter)
758 __releases(RCU)
759{
760 struct rhashtable *ht;
761 struct bucket_table *tbl = iter->walker.tbl;
762
763 if (!tbl)
764 goto out;
765
766 ht = iter->ht;
767
768 spin_lock(&ht->lock);
769 if (tbl->rehash < tbl->size)
770 list_add(&iter->walker.list, &tbl->walkers);
771 else
772 iter->walker.tbl = NULL;
773 spin_unlock(&ht->lock);
774
775 iter->p = NULL;
776
777out:
778 rcu_read_unlock();
779}
780EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
781
782static size_t rounded_hashtable_size(const struct rhashtable_params *params)
783{
784 return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
785 (unsigned long)params->min_size);
786}
787
788static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
789{
790 return jhash2(key, length, seed);
791}
792
793/**
794 * rhashtable_init - initialize a new hash table
795 * @ht: hash table to be initialized
796 * @params: configuration parameters
797 *
798 * Initializes a new hash table based on the provided configuration
799 * parameters. A table can be configured either with a variable or
800 * fixed length key:
801 *
802 * Configuration Example 1: Fixed length keys
803 * struct test_obj {
804 * int key;
805 * void * my_member;
806 * struct rhash_head node;
807 * };
808 *
809 * struct rhashtable_params params = {
810 * .head_offset = offsetof(struct test_obj, node),
811 * .key_offset = offsetof(struct test_obj, key),
812 * .key_len = sizeof(int),
813 * .hashfn = jhash,
814 * .nulls_base = (1U << RHT_BASE_SHIFT),
815 * };
816 *
817 * Configuration Example 2: Variable length keys
818 * struct test_obj {
819 * [...]
820 * struct rhash_head node;
821 * };
822 *
823 * u32 my_hash_fn(const void *data, u32 len, u32 seed)
824 * {
825 * struct test_obj *obj = data;
826 *
827 * return [... hash ...];
828 * }
829 *
830 * struct rhashtable_params params = {
831 * .head_offset = offsetof(struct test_obj, node),
832 * .hashfn = jhash,
833 * .obj_hashfn = my_hash_fn,
834 * };
835 */
836int rhashtable_init(struct rhashtable *ht,
837 const struct rhashtable_params *params)
838{
839 struct bucket_table *tbl;
840 size_t size;
841
842 size = HASH_DEFAULT_SIZE;
843
844 if ((!params->key_len && !params->obj_hashfn) ||
845 (params->obj_hashfn && !params->obj_cmpfn))
846 return -EINVAL;
847
848 if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
849 return -EINVAL;
850
851 memset(ht, 0, sizeof(*ht));
852 mutex_init(&ht->mutex);
853 spin_lock_init(&ht->lock);
854 memcpy(&ht->p, params, sizeof(*params));
855
856 if (params->min_size)
857 ht->p.min_size = roundup_pow_of_two(params->min_size);
858
859 if (params->max_size)
860 ht->p.max_size = rounddown_pow_of_two(params->max_size);
861
862 if (params->insecure_max_entries)
863 ht->p.insecure_max_entries =
864 rounddown_pow_of_two(params->insecure_max_entries);
865 else
866 ht->p.insecure_max_entries = ht->p.max_size * 2;
867
868 ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);
869
870 if (params->nelem_hint)
871 size = rounded_hashtable_size(&ht->p);
872
873 /* The maximum (not average) chain length grows with the
874 * size of the hash table, at a rate of (log N)/(log log N).
875 * The value of 16 is selected so that even if the hash
876 * table grew to 2^32 you would not expect the maximum
877 * chain length to exceed it unless we are under attack
878 * (or extremely unlucky).
879 *
880 * As this limit is only to detect attacks, we don't need
881 * to set it to a lower value as you'd need the chain
882 * length to vastly exceed 16 to have any real effect
883 * on the system.
884 */
885 if (!params->insecure_elasticity)
886 ht->elasticity = 16;
887
888 if (params->locks_mul)
889 ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
890 else
891 ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
892
893 ht->key_len = ht->p.key_len;
894 if (!params->hashfn) {
895 ht->p.hashfn = jhash;
896
897 if (!(ht->key_len & (sizeof(u32) - 1))) {
898 ht->key_len /= sizeof(u32);
899 ht->p.hashfn = rhashtable_jhash2;
900 }
901 }
902
903 tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
904 if (tbl == NULL)
905 return -ENOMEM;
906
907 atomic_set(&ht->nelems, 0);
908
909 RCU_INIT_POINTER(ht->tbl, tbl);
910
911 INIT_WORK(&ht->run_work, rht_deferred_worker);
912
913 return 0;
914}
915EXPORT_SYMBOL_GPL(rhashtable_init);
916
917/**
918 * rhltable_init - initialize a new hash list table
919 * @hlt: hash list table to be initialized
920 * @params: configuration parameters
921 *
922 * Initializes a new hash list table.
923 *
924 * See documentation for rhashtable_init.
925 */
926int rhltable_init(struct rhltable *hlt, const struct rhashtable_params *params)
927{
928 int err;
929
930 /* No rhlist NULLs marking for now. */
931 if (params->nulls_base)
932 return -EINVAL;
933
934 err = rhashtable_init(&hlt->ht, params);
935 hlt->ht.rhlist = true;
936 return err;
937}
938EXPORT_SYMBOL_GPL(rhltable_init);
939
940static void rhashtable_free_one(struct rhashtable *ht, struct rhash_head *obj,
941 void (*free_fn)(void *ptr, void *arg),
942 void *arg)
943{
944 struct rhlist_head *list;
945
946 if (!ht->rhlist) {
947 free_fn(rht_obj(ht, obj), arg);
948 return;
949 }
950
951 list = container_of(obj, struct rhlist_head, rhead);
952 do {
953 obj = &list->rhead;
954 list = rht_dereference(list->next, ht);
955 free_fn(rht_obj(ht, obj), arg);
956 } while (list);
957}
958
959/**
960 * rhashtable_free_and_destroy - free elements and destroy hash table
961 * @ht: the hash table to destroy
962 * @free_fn: callback to release resources of element
963 * @arg: pointer passed to free_fn
964 *
965 * Stops an eventual async resize. If defined, invokes free_fn for each
966 * element to releasal resources. Please note that RCU protected
967 * readers may still be accessing the elements. Releasing of resources
968 * must occur in a compatible manner. Then frees the bucket array.
969 *
970 * This function will eventually sleep to wait for an async resize
971 * to complete. The caller is responsible that no further write operations
972 * occurs in parallel.
973 */
974void rhashtable_free_and_destroy(struct rhashtable *ht,
975 void (*free_fn)(void *ptr, void *arg),
976 void *arg)
977{
978 const struct bucket_table *tbl;
979 unsigned int i;
980
981 cancel_work_sync(&ht->run_work);
982
983 mutex_lock(&ht->mutex);
984 tbl = rht_dereference(ht->tbl, ht);
985 if (free_fn) {
986 for (i = 0; i < tbl->size; i++) {
987 struct rhash_head *pos, *next;
988
989 for (pos = rht_dereference(tbl->buckets[i], ht),
990 next = !rht_is_a_nulls(pos) ?
991 rht_dereference(pos->next, ht) : NULL;
992 !rht_is_a_nulls(pos);
993 pos = next,
994 next = !rht_is_a_nulls(pos) ?
995 rht_dereference(pos->next, ht) : NULL)
996 rhashtable_free_one(ht, pos, free_fn, arg);
997 }
998 }
999
1000 bucket_table_free(tbl);
1001 mutex_unlock(&ht->mutex);
1002}
1003EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);
1004
1005void rhashtable_destroy(struct rhashtable *ht)
1006{
1007 return rhashtable_free_and_destroy(ht, NULL, NULL);
1008}
1009EXPORT_SYMBOL_GPL(rhashtable_destroy);