2 * Resizable, Scalable, Concurrent Hash Table
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>
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
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.
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>
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>
31 #define HASH_DEFAULT_SIZE 64UL
32 #define HASH_MIN_SIZE 4U
33 #define BUCKET_LOCKS_PER_CPU 32UL
36 union nested_table __rcu *table;
37 struct rhash_head __rcu *bucket;
40 static u32 head_hashfn(struct rhashtable *ht,
41 const struct bucket_table *tbl,
42 const struct rhash_head *he)
44 return rht_head_hashfn(ht, tbl, he, ht->p);
47 #ifdef CONFIG_PROVE_LOCKING
48 #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
50 int lockdep_rht_mutex_is_held(struct rhashtable *ht)
52 return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
54 EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
56 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
58 spinlock_t *lock = rht_bucket_lock(tbl, hash);
60 return (debug_locks) ? lockdep_is_held(lock) : 1;
62 EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
64 #define ASSERT_RHT_MUTEX(HT)
68 static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
72 #if defined(CONFIG_PROVE_LOCKING)
73 unsigned int nr_pcpus = 2;
75 unsigned int nr_pcpus = num_possible_cpus();
78 nr_pcpus = min_t(unsigned int, nr_pcpus, 64UL);
79 size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul);
81 /* Never allocate more than 0.5 locks per bucket */
82 size = min_t(unsigned int, size, tbl->size >> 1);
85 size = min(size, 1U << tbl->nest);
87 if (sizeof(spinlock_t) != 0) {
90 if (size * sizeof(spinlock_t) > PAGE_SIZE &&
92 tbl->locks = vmalloc(size * sizeof(spinlock_t));
94 if (gfp != GFP_KERNEL)
95 gfp |= __GFP_NOWARN | __GFP_NORETRY;
98 tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
102 for (i = 0; i < size; i++)
103 spin_lock_init(&tbl->locks[i]);
105 tbl->locks_mask = size - 1;
110 static void nested_table_free(union nested_table *ntbl, unsigned int size)
112 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
113 const unsigned int len = 1 << shift;
116 ntbl = rcu_dereference_raw(ntbl->table);
122 for (i = 0; i < len; i++)
123 nested_table_free(ntbl + i, size);
129 static void nested_bucket_table_free(const struct bucket_table *tbl)
131 unsigned int size = tbl->size >> tbl->nest;
132 unsigned int len = 1 << tbl->nest;
133 union nested_table *ntbl;
136 ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
138 for (i = 0; i < len; i++)
139 nested_table_free(ntbl + i, size);
144 static void bucket_table_free(const struct bucket_table *tbl)
147 nested_bucket_table_free(tbl);
153 static void bucket_table_free_rcu(struct rcu_head *head)
155 bucket_table_free(container_of(head, struct bucket_table, rcu));
158 static union nested_table *nested_table_alloc(struct rhashtable *ht,
159 union nested_table __rcu **prev,
160 unsigned int shifted,
163 union nested_table *ntbl;
166 ntbl = rcu_dereference(*prev);
170 ntbl = kzalloc(PAGE_SIZE, GFP_ATOMIC);
172 if (ntbl && shifted) {
173 for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0].bucket); i++)
174 INIT_RHT_NULLS_HEAD(ntbl[i].bucket, ht,
175 (i << shifted) | nhash);
178 rcu_assign_pointer(*prev, ntbl);
183 static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht,
187 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
188 struct bucket_table *tbl;
191 if (nbuckets < (1 << (shift + 1)))
194 size = sizeof(*tbl) + sizeof(tbl->buckets[0]);
196 tbl = kzalloc(size, gfp);
200 if (!nested_table_alloc(ht, (union nested_table __rcu **)tbl->buckets,
206 tbl->nest = (ilog2(nbuckets) - 1) % shift + 1;
211 static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
215 struct bucket_table *tbl = NULL;
219 size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
220 if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER) ||
222 tbl = kzalloc(size, gfp | __GFP_NOWARN | __GFP_NORETRY);
223 if (tbl == NULL && gfp == GFP_KERNEL)
228 if (tbl == NULL && gfp != GFP_KERNEL) {
229 tbl = nested_bucket_table_alloc(ht, nbuckets, gfp);
237 if (alloc_bucket_locks(ht, tbl, gfp) < 0) {
238 bucket_table_free(tbl);
242 INIT_LIST_HEAD(&tbl->walkers);
244 get_random_bytes(&tbl->hash_rnd, sizeof(tbl->hash_rnd));
246 for (i = 0; i < nbuckets; i++)
247 INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i);
252 static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
253 struct bucket_table *tbl)
255 struct bucket_table *new_tbl;
259 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
265 static int rhashtable_rehash_one(struct rhashtable *ht, unsigned int old_hash)
267 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
268 struct bucket_table *new_tbl = rhashtable_last_table(ht,
269 rht_dereference_rcu(old_tbl->future_tbl, ht));
270 struct rhash_head __rcu **pprev = rht_bucket_var(old_tbl, old_hash);
272 struct rhash_head *head, *next, *entry;
273 spinlock_t *new_bucket_lock;
274 unsigned int new_hash;
281 rht_for_each(entry, old_tbl, old_hash) {
283 next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
285 if (rht_is_a_nulls(next))
288 pprev = &entry->next;
294 new_hash = head_hashfn(ht, new_tbl, entry);
296 new_bucket_lock = rht_bucket_lock(new_tbl, new_hash);
298 spin_lock_nested(new_bucket_lock, SINGLE_DEPTH_NESTING);
299 head = rht_dereference_bucket(new_tbl->buckets[new_hash],
302 RCU_INIT_POINTER(entry->next, head);
304 rcu_assign_pointer(new_tbl->buckets[new_hash], entry);
305 spin_unlock(new_bucket_lock);
307 rcu_assign_pointer(*pprev, next);
313 static int rhashtable_rehash_chain(struct rhashtable *ht,
314 unsigned int old_hash)
316 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
317 spinlock_t *old_bucket_lock;
320 old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
322 spin_lock_bh(old_bucket_lock);
323 while (!(err = rhashtable_rehash_one(ht, old_hash)))
326 if (err == -ENOENT) {
330 spin_unlock_bh(old_bucket_lock);
335 static int rhashtable_rehash_attach(struct rhashtable *ht,
336 struct bucket_table *old_tbl,
337 struct bucket_table *new_tbl)
339 /* Protect future_tbl using the first bucket lock. */
340 spin_lock_bh(old_tbl->locks);
342 /* Did somebody beat us to it? */
343 if (rcu_access_pointer(old_tbl->future_tbl)) {
344 spin_unlock_bh(old_tbl->locks);
348 /* Make insertions go into the new, empty table right away. Deletions
349 * and lookups will be attempted in both tables until we synchronize.
351 rcu_assign_pointer(old_tbl->future_tbl, new_tbl);
353 spin_unlock_bh(old_tbl->locks);
358 static int rhashtable_rehash_table(struct rhashtable *ht)
360 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
361 struct bucket_table *new_tbl;
362 struct rhashtable_walker *walker;
363 unsigned int old_hash;
366 new_tbl = rht_dereference(old_tbl->future_tbl, ht);
370 for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
371 err = rhashtable_rehash_chain(ht, old_hash);
376 /* Publish the new table pointer. */
377 rcu_assign_pointer(ht->tbl, new_tbl);
379 spin_lock(&ht->lock);
380 list_for_each_entry(walker, &old_tbl->walkers, list)
382 spin_unlock(&ht->lock);
384 /* Wait for readers. All new readers will see the new
385 * table, and thus no references to the old table will
388 call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
390 return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
393 static int rhashtable_rehash_alloc(struct rhashtable *ht,
394 struct bucket_table *old_tbl,
397 struct bucket_table *new_tbl;
400 ASSERT_RHT_MUTEX(ht);
402 new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
406 err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
408 bucket_table_free(new_tbl);
414 * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
415 * @ht: the hash table to shrink
417 * This function shrinks the hash table to fit, i.e., the smallest
418 * size would not cause it to expand right away automatically.
420 * The caller must ensure that no concurrent resizing occurs by holding
423 * The caller must ensure that no concurrent table mutations take place.
424 * It is however valid to have concurrent lookups if they are RCU protected.
426 * It is valid to have concurrent insertions and deletions protected by per
427 * bucket locks or concurrent RCU protected lookups and traversals.
429 static int rhashtable_shrink(struct rhashtable *ht)
431 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
432 unsigned int nelems = atomic_read(&ht->nelems);
433 unsigned int size = 0;
436 size = roundup_pow_of_two(nelems * 3 / 2);
437 if (size < ht->p.min_size)
438 size = ht->p.min_size;
440 if (old_tbl->size <= size)
443 if (rht_dereference(old_tbl->future_tbl, ht))
446 return rhashtable_rehash_alloc(ht, old_tbl, size);
449 static void rht_deferred_worker(struct work_struct *work)
451 struct rhashtable *ht;
452 struct bucket_table *tbl;
455 ht = container_of(work, struct rhashtable, run_work);
456 mutex_lock(&ht->mutex);
458 tbl = rht_dereference(ht->tbl, ht);
459 tbl = rhashtable_last_table(ht, tbl);
461 if (rht_grow_above_75(ht, tbl))
462 err = rhashtable_rehash_alloc(ht, tbl, tbl->size * 2);
463 else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
464 err = rhashtable_shrink(ht);
466 err = rhashtable_rehash_alloc(ht, tbl, tbl->size);
469 err = rhashtable_rehash_table(ht);
471 mutex_unlock(&ht->mutex);
474 schedule_work(&ht->run_work);
477 static int rhashtable_insert_rehash(struct rhashtable *ht,
478 struct bucket_table *tbl)
480 struct bucket_table *old_tbl;
481 struct bucket_table *new_tbl;
485 old_tbl = rht_dereference_rcu(ht->tbl, ht);
491 if (rht_grow_above_75(ht, tbl))
493 /* Do not schedule more than one rehash */
494 else if (old_tbl != tbl)
499 new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC);
503 err = rhashtable_rehash_attach(ht, tbl, new_tbl);
505 bucket_table_free(new_tbl);
509 schedule_work(&ht->run_work);
514 /* Do not fail the insert if someone else did a rehash. */
515 if (likely(rcu_dereference_raw(tbl->future_tbl)))
518 /* Schedule async rehash to retry allocation in process context. */
520 schedule_work(&ht->run_work);
525 static void *rhashtable_lookup_one(struct rhashtable *ht,
526 struct bucket_table *tbl, unsigned int hash,
527 const void *key, struct rhash_head *obj)
529 struct rhashtable_compare_arg arg = {
533 struct rhash_head __rcu **pprev;
534 struct rhash_head *head;
537 elasticity = ht->elasticity;
538 pprev = rht_bucket_var(tbl, hash);
539 rht_for_each_continue(head, *pprev, tbl, hash) {
540 struct rhlist_head *list;
541 struct rhlist_head *plist;
546 ht->p.obj_cmpfn(&arg, rht_obj(ht, head)) :
547 rhashtable_compare(&arg, rht_obj(ht, head))))
551 return rht_obj(ht, head);
553 list = container_of(obj, struct rhlist_head, rhead);
554 plist = container_of(head, struct rhlist_head, rhead);
556 RCU_INIT_POINTER(list->next, plist);
557 head = rht_dereference_bucket(head->next, tbl, hash);
558 RCU_INIT_POINTER(list->rhead.next, head);
559 rcu_assign_pointer(*pprev, obj);
565 return ERR_PTR(-EAGAIN);
567 return ERR_PTR(-ENOENT);
570 static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
571 struct bucket_table *tbl,
573 struct rhash_head *obj,
576 struct rhash_head __rcu **pprev;
577 struct bucket_table *new_tbl;
578 struct rhash_head *head;
580 if (!IS_ERR_OR_NULL(data))
581 return ERR_PTR(-EEXIST);
583 if (PTR_ERR(data) != -EAGAIN && PTR_ERR(data) != -ENOENT)
584 return ERR_CAST(data);
586 new_tbl = rcu_dereference(tbl->future_tbl);
590 if (PTR_ERR(data) != -ENOENT)
591 return ERR_CAST(data);
593 if (unlikely(rht_grow_above_max(ht, tbl)))
594 return ERR_PTR(-E2BIG);
596 if (unlikely(rht_grow_above_100(ht, tbl)))
597 return ERR_PTR(-EAGAIN);
599 pprev = rht_bucket_insert(ht, tbl, hash);
601 return ERR_PTR(-ENOMEM);
603 head = rht_dereference_bucket(*pprev, tbl, hash);
605 RCU_INIT_POINTER(obj->next, head);
607 struct rhlist_head *list;
609 list = container_of(obj, struct rhlist_head, rhead);
610 RCU_INIT_POINTER(list->next, NULL);
613 rcu_assign_pointer(*pprev, obj);
615 atomic_inc(&ht->nelems);
616 if (rht_grow_above_75(ht, tbl))
617 schedule_work(&ht->run_work);
622 static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
623 struct rhash_head *obj)
625 struct bucket_table *new_tbl;
626 struct bucket_table *tbl;
631 tbl = rcu_dereference(ht->tbl);
633 /* All insertions must grab the oldest table containing
634 * the hashed bucket that is yet to be rehashed.
637 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
638 lock = rht_bucket_lock(tbl, hash);
641 if (tbl->rehash <= hash)
644 spin_unlock_bh(lock);
645 tbl = rcu_dereference(tbl->future_tbl);
648 data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
649 new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
650 if (PTR_ERR(new_tbl) != -EEXIST)
651 data = ERR_CAST(new_tbl);
653 while (!IS_ERR_OR_NULL(new_tbl)) {
655 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
656 spin_lock_nested(rht_bucket_lock(tbl, hash),
657 SINGLE_DEPTH_NESTING);
659 data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
660 new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
661 if (PTR_ERR(new_tbl) != -EEXIST)
662 data = ERR_CAST(new_tbl);
664 spin_unlock(rht_bucket_lock(tbl, hash));
667 spin_unlock_bh(lock);
669 if (PTR_ERR(data) == -EAGAIN)
670 data = ERR_PTR(rhashtable_insert_rehash(ht, tbl) ?:
676 void *rhashtable_insert_slow(struct rhashtable *ht, const void *key,
677 struct rhash_head *obj)
683 data = rhashtable_try_insert(ht, key, obj);
685 } while (PTR_ERR(data) == -EAGAIN);
689 EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
692 * rhashtable_walk_enter - Initialise an iterator
693 * @ht: Table to walk over
694 * @iter: Hash table Iterator
696 * This function prepares a hash table walk.
698 * Note that if you restart a walk after rhashtable_walk_stop you
699 * may see the same object twice. Also, you may miss objects if
700 * there are removals in between rhashtable_walk_stop and the next
701 * call to rhashtable_walk_start.
703 * For a completely stable walk you should construct your own data
704 * structure outside the hash table.
706 * This function may sleep so you must not call it from interrupt
707 * context or with spin locks held.
709 * You must call rhashtable_walk_exit after this function returns.
711 void rhashtable_walk_enter(struct rhashtable *ht, struct rhashtable_iter *iter)
718 spin_lock(&ht->lock);
720 rcu_dereference_protected(ht->tbl, lockdep_is_held(&ht->lock));
721 list_add(&iter->walker.list, &iter->walker.tbl->walkers);
722 spin_unlock(&ht->lock);
724 EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
727 * rhashtable_walk_exit - Free an iterator
728 * @iter: Hash table Iterator
730 * This function frees resources allocated by rhashtable_walk_init.
732 void rhashtable_walk_exit(struct rhashtable_iter *iter)
734 spin_lock(&iter->ht->lock);
735 if (iter->walker.tbl)
736 list_del(&iter->walker.list);
737 spin_unlock(&iter->ht->lock);
739 EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
742 * rhashtable_walk_start - Start a hash table walk
743 * @iter: Hash table iterator
745 * Start a hash table walk. Note that we take the RCU lock in all
746 * cases including when we return an error. So you must always call
747 * rhashtable_walk_stop to clean up.
749 * Returns zero if successful.
751 * Returns -EAGAIN if resize event occured. Note that the iterator
752 * will rewind back to the beginning and you may use it immediately
753 * by calling rhashtable_walk_next.
755 int rhashtable_walk_start(struct rhashtable_iter *iter)
758 struct rhashtable *ht = iter->ht;
762 spin_lock(&ht->lock);
763 if (iter->walker.tbl)
764 list_del(&iter->walker.list);
765 spin_unlock(&ht->lock);
767 if (!iter->walker.tbl) {
768 iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht);
774 EXPORT_SYMBOL_GPL(rhashtable_walk_start);
777 * rhashtable_walk_next - Return the next object and advance the iterator
778 * @iter: Hash table iterator
780 * Note that you must call rhashtable_walk_stop when you are finished
783 * Returns the next object or NULL when the end of the table is reached.
785 * Returns -EAGAIN if resize event occured. Note that the iterator
786 * will rewind back to the beginning and you may continue to use it.
788 void *rhashtable_walk_next(struct rhashtable_iter *iter)
790 struct bucket_table *tbl = iter->walker.tbl;
791 struct rhlist_head *list = iter->list;
792 struct rhashtable *ht = iter->ht;
793 struct rhash_head *p = iter->p;
794 bool rhlist = ht->rhlist;
797 if (!rhlist || !(list = rcu_dereference(list->next))) {
798 p = rcu_dereference(p->next);
799 list = container_of(p, struct rhlist_head, rhead);
804 for (; iter->slot < tbl->size; iter->slot++) {
805 int skip = iter->skip;
807 rht_for_each_rcu(p, tbl, iter->slot) {
809 list = container_of(p, struct rhlist_head,
815 list = rcu_dereference(list->next);
826 if (!rht_is_a_nulls(p)) {
830 return rht_obj(ht, rhlist ? &list->rhead : p);
838 /* Ensure we see any new tables. */
841 iter->walker.tbl = rht_dereference_rcu(tbl->future_tbl, ht);
842 if (iter->walker.tbl) {
845 return ERR_PTR(-EAGAIN);
850 EXPORT_SYMBOL_GPL(rhashtable_walk_next);
853 * rhashtable_walk_stop - Finish a hash table walk
854 * @iter: Hash table iterator
856 * Finish a hash table walk.
858 void rhashtable_walk_stop(struct rhashtable_iter *iter)
861 struct rhashtable *ht;
862 struct bucket_table *tbl = iter->walker.tbl;
869 spin_lock(&ht->lock);
870 if (tbl->rehash < tbl->size)
871 list_add(&iter->walker.list, &tbl->walkers);
873 iter->walker.tbl = NULL;
874 spin_unlock(&ht->lock);
881 EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
883 static size_t rounded_hashtable_size(const struct rhashtable_params *params)
885 return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
886 (unsigned long)params->min_size);
889 static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
891 return jhash2(key, length, seed);
895 * rhashtable_init - initialize a new hash table
896 * @ht: hash table to be initialized
897 * @params: configuration parameters
899 * Initializes a new hash table based on the provided configuration
900 * parameters. A table can be configured either with a variable or
903 * Configuration Example 1: Fixed length keys
907 * struct rhash_head node;
910 * struct rhashtable_params params = {
911 * .head_offset = offsetof(struct test_obj, node),
912 * .key_offset = offsetof(struct test_obj, key),
913 * .key_len = sizeof(int),
915 * .nulls_base = (1U << RHT_BASE_SHIFT),
918 * Configuration Example 2: Variable length keys
921 * struct rhash_head node;
924 * u32 my_hash_fn(const void *data, u32 len, u32 seed)
926 * struct test_obj *obj = data;
928 * return [... hash ...];
931 * struct rhashtable_params params = {
932 * .head_offset = offsetof(struct test_obj, node),
934 * .obj_hashfn = my_hash_fn,
937 int rhashtable_init(struct rhashtable *ht,
938 const struct rhashtable_params *params)
940 struct bucket_table *tbl;
943 size = HASH_DEFAULT_SIZE;
945 if ((!params->key_len && !params->obj_hashfn) ||
946 (params->obj_hashfn && !params->obj_cmpfn))
949 if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
952 memset(ht, 0, sizeof(*ht));
953 mutex_init(&ht->mutex);
954 spin_lock_init(&ht->lock);
955 memcpy(&ht->p, params, sizeof(*params));
957 if (params->min_size)
958 ht->p.min_size = roundup_pow_of_two(params->min_size);
960 if (params->max_size)
961 ht->p.max_size = rounddown_pow_of_two(params->max_size);
963 if (params->insecure_max_entries)
964 ht->p.insecure_max_entries =
965 rounddown_pow_of_two(params->insecure_max_entries);
967 ht->p.insecure_max_entries = ht->p.max_size * 2;
969 ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);
971 if (params->nelem_hint)
972 size = rounded_hashtable_size(&ht->p);
974 /* The maximum (not average) chain length grows with the
975 * size of the hash table, at a rate of (log N)/(log log N).
976 * The value of 16 is selected so that even if the hash
977 * table grew to 2^32 you would not expect the maximum
978 * chain length to exceed it unless we are under attack
979 * (or extremely unlucky).
981 * As this limit is only to detect attacks, we don't need
982 * to set it to a lower value as you'd need the chain
983 * length to vastly exceed 16 to have any real effect
986 if (!params->insecure_elasticity)
989 if (params->locks_mul)
990 ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
992 ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
994 ht->key_len = ht->p.key_len;
995 if (!params->hashfn) {
996 ht->p.hashfn = jhash;
998 if (!(ht->key_len & (sizeof(u32) - 1))) {
999 ht->key_len /= sizeof(u32);
1000 ht->p.hashfn = rhashtable_jhash2;
1004 tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
1008 atomic_set(&ht->nelems, 0);
1010 RCU_INIT_POINTER(ht->tbl, tbl);
1012 INIT_WORK(&ht->run_work, rht_deferred_worker);
1016 EXPORT_SYMBOL_GPL(rhashtable_init);
1019 * rhltable_init - initialize a new hash list table
1020 * @hlt: hash list table to be initialized
1021 * @params: configuration parameters
1023 * Initializes a new hash list table.
1025 * See documentation for rhashtable_init.
1027 int rhltable_init(struct rhltable *hlt, const struct rhashtable_params *params)
1031 /* No rhlist NULLs marking for now. */
1032 if (params->nulls_base)
1035 err = rhashtable_init(&hlt->ht, params);
1036 hlt->ht.rhlist = true;
1039 EXPORT_SYMBOL_GPL(rhltable_init);
1041 static void rhashtable_free_one(struct rhashtable *ht, struct rhash_head *obj,
1042 void (*free_fn)(void *ptr, void *arg),
1045 struct rhlist_head *list;
1048 free_fn(rht_obj(ht, obj), arg);
1052 list = container_of(obj, struct rhlist_head, rhead);
1055 list = rht_dereference(list->next, ht);
1056 free_fn(rht_obj(ht, obj), arg);
1061 * rhashtable_free_and_destroy - free elements and destroy hash table
1062 * @ht: the hash table to destroy
1063 * @free_fn: callback to release resources of element
1064 * @arg: pointer passed to free_fn
1066 * Stops an eventual async resize. If defined, invokes free_fn for each
1067 * element to releasal resources. Please note that RCU protected
1068 * readers may still be accessing the elements. Releasing of resources
1069 * must occur in a compatible manner. Then frees the bucket array.
1071 * This function will eventually sleep to wait for an async resize
1072 * to complete. The caller is responsible that no further write operations
1073 * occurs in parallel.
1075 void rhashtable_free_and_destroy(struct rhashtable *ht,
1076 void (*free_fn)(void *ptr, void *arg),
1079 struct bucket_table *tbl;
1082 cancel_work_sync(&ht->run_work);
1084 mutex_lock(&ht->mutex);
1085 tbl = rht_dereference(ht->tbl, ht);
1087 for (i = 0; i < tbl->size; i++) {
1088 struct rhash_head *pos, *next;
1090 for (pos = rht_dereference(*rht_bucket(tbl, i), ht),
1091 next = !rht_is_a_nulls(pos) ?
1092 rht_dereference(pos->next, ht) : NULL;
1093 !rht_is_a_nulls(pos);
1095 next = !rht_is_a_nulls(pos) ?
1096 rht_dereference(pos->next, ht) : NULL)
1097 rhashtable_free_one(ht, pos, free_fn, arg);
1101 bucket_table_free(tbl);
1102 mutex_unlock(&ht->mutex);
1104 EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);
1106 void rhashtable_destroy(struct rhashtable *ht)
1108 return rhashtable_free_and_destroy(ht, NULL, NULL);
1110 EXPORT_SYMBOL_GPL(rhashtable_destroy);
1112 struct rhash_head __rcu **rht_bucket_nested(const struct bucket_table *tbl,
1115 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1116 static struct rhash_head __rcu *rhnull =
1117 (struct rhash_head __rcu *)NULLS_MARKER(0);
1118 unsigned int index = hash & ((1 << tbl->nest) - 1);
1119 unsigned int size = tbl->size >> tbl->nest;
1120 unsigned int subhash = hash;
1121 union nested_table *ntbl;
1123 ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
1124 ntbl = rht_dereference_bucket_rcu(ntbl[index].table, tbl, hash);
1125 subhash >>= tbl->nest;
1127 while (ntbl && size > (1 << shift)) {
1128 index = subhash & ((1 << shift) - 1);
1129 ntbl = rht_dereference_bucket_rcu(ntbl[index].table,
1138 return &ntbl[subhash].bucket;
1141 EXPORT_SYMBOL_GPL(rht_bucket_nested);
1143 struct rhash_head __rcu **rht_bucket_nested_insert(struct rhashtable *ht,
1144 struct bucket_table *tbl,
1147 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1148 unsigned int index = hash & ((1 << tbl->nest) - 1);
1149 unsigned int size = tbl->size >> tbl->nest;
1150 union nested_table *ntbl;
1151 unsigned int shifted;
1154 ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
1157 shifted = tbl->nest;
1158 ntbl = nested_table_alloc(ht, &ntbl[index].table,
1159 size <= (1 << shift) ? shifted : 0, nhash);
1161 while (ntbl && size > (1 << shift)) {
1162 index = hash & ((1 << shift) - 1);
1165 nhash |= index << shifted;
1167 ntbl = nested_table_alloc(ht, &ntbl[index].table,
1168 size <= (1 << shift) ? shifted : 0,
1175 return &ntbl[hash].bucket;
1178 EXPORT_SYMBOL_GPL(rht_bucket_nested_insert);