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/rculist.h>
23 #include <linux/slab.h>
24 #include <linux/vmalloc.h>
26 #include <linux/jhash.h>
27 #include <linux/random.h>
28 #include <linux/rhashtable.h>
29 #include <linux/err.h>
30 #include <linux/export.h>
32 #define HASH_DEFAULT_SIZE 64UL
33 #define HASH_MIN_SIZE 4U
34 #define BUCKET_LOCKS_PER_CPU 32UL
37 union nested_table __rcu *table;
38 struct rhash_head __rcu *bucket;
41 static u32 head_hashfn(struct rhashtable *ht,
42 const struct bucket_table *tbl,
43 const struct rhash_head *he)
45 return rht_head_hashfn(ht, tbl, he, ht->p);
48 #ifdef CONFIG_PROVE_LOCKING
49 #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
51 int lockdep_rht_mutex_is_held(struct rhashtable *ht)
53 return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
55 EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
57 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
59 spinlock_t *lock = rht_bucket_lock(tbl, hash);
61 return (debug_locks) ? lockdep_is_held(lock) : 1;
63 EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
65 #define ASSERT_RHT_MUTEX(HT)
68 static void nested_table_free(union nested_table *ntbl, unsigned int size)
70 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
71 const unsigned int len = 1 << shift;
74 ntbl = rcu_dereference_raw(ntbl->table);
80 for (i = 0; i < len; i++)
81 nested_table_free(ntbl + i, size);
87 static void nested_bucket_table_free(const struct bucket_table *tbl)
89 unsigned int size = tbl->size >> tbl->nest;
90 unsigned int len = 1 << tbl->nest;
91 union nested_table *ntbl;
94 ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
96 for (i = 0; i < len; i++)
97 nested_table_free(ntbl + i, size);
102 static void bucket_table_free(const struct bucket_table *tbl)
105 nested_bucket_table_free(tbl);
107 free_bucket_spinlocks(tbl->locks);
111 static void bucket_table_free_rcu(struct rcu_head *head)
113 bucket_table_free(container_of(head, struct bucket_table, rcu));
116 static union nested_table *nested_table_alloc(struct rhashtable *ht,
117 union nested_table __rcu **prev,
120 union nested_table *ntbl;
123 ntbl = rcu_dereference(*prev);
127 ntbl = kzalloc(PAGE_SIZE, GFP_ATOMIC);
130 for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0]); i++)
131 INIT_RHT_NULLS_HEAD(ntbl[i].bucket);
134 rcu_assign_pointer(*prev, ntbl);
139 static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht,
143 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
144 struct bucket_table *tbl;
147 if (nbuckets < (1 << (shift + 1)))
150 size = sizeof(*tbl) + sizeof(tbl->buckets[0]);
152 tbl = kzalloc(size, gfp);
156 if (!nested_table_alloc(ht, (union nested_table __rcu **)tbl->buckets,
162 tbl->nest = (ilog2(nbuckets) - 1) % shift + 1;
167 static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
171 struct bucket_table *tbl = NULL;
172 size_t size, max_locks;
175 size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
176 tbl = kvzalloc(size, gfp);
180 if (tbl == NULL && (gfp & ~__GFP_NOFAIL) != GFP_KERNEL) {
181 tbl = nested_bucket_table_alloc(ht, nbuckets, gfp);
190 max_locks = size >> 1;
192 max_locks = min_t(size_t, max_locks, 1U << tbl->nest);
194 if (alloc_bucket_spinlocks(&tbl->locks, &tbl->locks_mask, max_locks,
195 ht->p.locks_mul, gfp) < 0) {
196 bucket_table_free(tbl);
200 INIT_LIST_HEAD(&tbl->walkers);
202 tbl->hash_rnd = get_random_u32();
204 for (i = 0; i < nbuckets; i++)
205 INIT_RHT_NULLS_HEAD(tbl->buckets[i]);
210 static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
211 struct bucket_table *tbl)
213 struct bucket_table *new_tbl;
217 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
223 static int rhashtable_rehash_one(struct rhashtable *ht, unsigned int old_hash)
225 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
226 struct bucket_table *new_tbl = rhashtable_last_table(ht, old_tbl);
227 struct rhash_head __rcu **pprev = rht_bucket_var(old_tbl, old_hash);
229 struct rhash_head *head, *next, *entry;
230 spinlock_t *new_bucket_lock;
231 unsigned int new_hash;
238 rht_for_each(entry, old_tbl, old_hash) {
240 next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
242 if (rht_is_a_nulls(next))
245 pprev = &entry->next;
251 new_hash = head_hashfn(ht, new_tbl, entry);
253 new_bucket_lock = rht_bucket_lock(new_tbl, new_hash);
255 spin_lock_nested(new_bucket_lock, SINGLE_DEPTH_NESTING);
256 head = rht_dereference_bucket(new_tbl->buckets[new_hash],
259 RCU_INIT_POINTER(entry->next, head);
261 rcu_assign_pointer(new_tbl->buckets[new_hash], entry);
262 spin_unlock(new_bucket_lock);
264 rcu_assign_pointer(*pprev, next);
270 static int rhashtable_rehash_chain(struct rhashtable *ht,
271 unsigned int old_hash)
273 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
274 spinlock_t *old_bucket_lock;
277 old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
279 spin_lock_bh(old_bucket_lock);
280 while (!(err = rhashtable_rehash_one(ht, old_hash)))
283 if (err == -ENOENT) {
287 spin_unlock_bh(old_bucket_lock);
292 static int rhashtable_rehash_attach(struct rhashtable *ht,
293 struct bucket_table *old_tbl,
294 struct bucket_table *new_tbl)
296 /* Make insertions go into the new, empty table right away. Deletions
297 * and lookups will be attempted in both tables until we synchronize.
298 * As cmpxchg() provides strong barriers, we do not need
299 * rcu_assign_pointer().
302 if (cmpxchg(&old_tbl->future_tbl, NULL, new_tbl) != NULL)
308 static int rhashtable_rehash_table(struct rhashtable *ht)
310 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
311 struct bucket_table *new_tbl;
312 struct rhashtable_walker *walker;
313 unsigned int old_hash;
316 new_tbl = rht_dereference(old_tbl->future_tbl, ht);
320 for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
321 err = rhashtable_rehash_chain(ht, old_hash);
327 /* Publish the new table pointer. */
328 rcu_assign_pointer(ht->tbl, new_tbl);
330 spin_lock(&ht->lock);
331 list_for_each_entry(walker, &old_tbl->walkers, list)
333 spin_unlock(&ht->lock);
335 /* Wait for readers. All new readers will see the new
336 * table, and thus no references to the old table will
339 call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
341 return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
344 static int rhashtable_rehash_alloc(struct rhashtable *ht,
345 struct bucket_table *old_tbl,
348 struct bucket_table *new_tbl;
351 ASSERT_RHT_MUTEX(ht);
353 new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
357 err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
359 bucket_table_free(new_tbl);
365 * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
366 * @ht: the hash table to shrink
368 * This function shrinks the hash table to fit, i.e., the smallest
369 * size would not cause it to expand right away automatically.
371 * The caller must ensure that no concurrent resizing occurs by holding
374 * The caller must ensure that no concurrent table mutations take place.
375 * It is however valid to have concurrent lookups if they are RCU protected.
377 * It is valid to have concurrent insertions and deletions protected by per
378 * bucket locks or concurrent RCU protected lookups and traversals.
380 static int rhashtable_shrink(struct rhashtable *ht)
382 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
383 unsigned int nelems = atomic_read(&ht->nelems);
384 unsigned int size = 0;
387 size = roundup_pow_of_two(nelems * 3 / 2);
388 if (size < ht->p.min_size)
389 size = ht->p.min_size;
391 if (old_tbl->size <= size)
394 if (rht_dereference(old_tbl->future_tbl, ht))
397 return rhashtable_rehash_alloc(ht, old_tbl, size);
400 static void rht_deferred_worker(struct work_struct *work)
402 struct rhashtable *ht;
403 struct bucket_table *tbl;
406 ht = container_of(work, struct rhashtable, run_work);
407 mutex_lock(&ht->mutex);
409 tbl = rht_dereference(ht->tbl, ht);
410 tbl = rhashtable_last_table(ht, tbl);
412 if (rht_grow_above_75(ht, tbl))
413 err = rhashtable_rehash_alloc(ht, tbl, tbl->size * 2);
414 else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
415 err = rhashtable_shrink(ht);
417 err = rhashtable_rehash_alloc(ht, tbl, tbl->size);
419 if (!err || err == -EEXIST) {
422 nerr = rhashtable_rehash_table(ht);
426 mutex_unlock(&ht->mutex);
429 schedule_work(&ht->run_work);
432 static int rhashtable_insert_rehash(struct rhashtable *ht,
433 struct bucket_table *tbl)
435 struct bucket_table *old_tbl;
436 struct bucket_table *new_tbl;
440 old_tbl = rht_dereference_rcu(ht->tbl, ht);
446 if (rht_grow_above_75(ht, tbl))
448 /* Do not schedule more than one rehash */
449 else if (old_tbl != tbl)
454 new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC | __GFP_NOWARN);
458 err = rhashtable_rehash_attach(ht, tbl, new_tbl);
460 bucket_table_free(new_tbl);
464 schedule_work(&ht->run_work);
469 /* Do not fail the insert if someone else did a rehash. */
470 if (likely(rcu_access_pointer(tbl->future_tbl)))
473 /* Schedule async rehash to retry allocation in process context. */
475 schedule_work(&ht->run_work);
480 static void *rhashtable_lookup_one(struct rhashtable *ht,
481 struct bucket_table *tbl, unsigned int hash,
482 const void *key, struct rhash_head *obj)
484 struct rhashtable_compare_arg arg = {
488 struct rhash_head __rcu **pprev;
489 struct rhash_head *head;
492 elasticity = RHT_ELASTICITY;
493 pprev = rht_bucket_var(tbl, hash);
494 rht_for_each_continue(head, *pprev, tbl, hash) {
495 struct rhlist_head *list;
496 struct rhlist_head *plist;
501 ht->p.obj_cmpfn(&arg, rht_obj(ht, head)) :
502 rhashtable_compare(&arg, rht_obj(ht, head)))) {
508 return rht_obj(ht, head);
510 list = container_of(obj, struct rhlist_head, rhead);
511 plist = container_of(head, struct rhlist_head, rhead);
513 RCU_INIT_POINTER(list->next, plist);
514 head = rht_dereference_bucket(head->next, tbl, hash);
515 RCU_INIT_POINTER(list->rhead.next, head);
516 rcu_assign_pointer(*pprev, obj);
522 return ERR_PTR(-EAGAIN);
524 return ERR_PTR(-ENOENT);
527 static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
528 struct bucket_table *tbl,
530 struct rhash_head *obj,
533 struct rhash_head __rcu **pprev;
534 struct bucket_table *new_tbl;
535 struct rhash_head *head;
537 if (!IS_ERR_OR_NULL(data))
538 return ERR_PTR(-EEXIST);
540 if (PTR_ERR(data) != -EAGAIN && PTR_ERR(data) != -ENOENT)
541 return ERR_CAST(data);
543 new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
547 if (PTR_ERR(data) != -ENOENT)
548 return ERR_CAST(data);
550 if (unlikely(rht_grow_above_max(ht, tbl)))
551 return ERR_PTR(-E2BIG);
553 if (unlikely(rht_grow_above_100(ht, tbl)))
554 return ERR_PTR(-EAGAIN);
556 pprev = rht_bucket_insert(ht, tbl, hash);
558 return ERR_PTR(-ENOMEM);
560 head = rht_dereference_bucket(*pprev, tbl, hash);
562 RCU_INIT_POINTER(obj->next, head);
564 struct rhlist_head *list;
566 list = container_of(obj, struct rhlist_head, rhead);
567 RCU_INIT_POINTER(list->next, NULL);
570 rcu_assign_pointer(*pprev, obj);
572 atomic_inc(&ht->nelems);
573 if (rht_grow_above_75(ht, tbl))
574 schedule_work(&ht->run_work);
579 static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
580 struct rhash_head *obj)
582 struct bucket_table *new_tbl;
583 struct bucket_table *tbl;
588 tbl = rcu_dereference(ht->tbl);
590 /* All insertions must grab the oldest table containing
591 * the hashed bucket that is yet to be rehashed.
594 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
595 lock = rht_bucket_lock(tbl, hash);
598 if (tbl->rehash <= hash)
601 spin_unlock_bh(lock);
602 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
605 data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
606 new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
607 if (PTR_ERR(new_tbl) != -EEXIST)
608 data = ERR_CAST(new_tbl);
610 while (!IS_ERR_OR_NULL(new_tbl)) {
612 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
613 spin_lock_nested(rht_bucket_lock(tbl, hash),
614 SINGLE_DEPTH_NESTING);
616 data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
617 new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
618 if (PTR_ERR(new_tbl) != -EEXIST)
619 data = ERR_CAST(new_tbl);
621 spin_unlock(rht_bucket_lock(tbl, hash));
624 spin_unlock_bh(lock);
626 if (PTR_ERR(data) == -EAGAIN)
627 data = ERR_PTR(rhashtable_insert_rehash(ht, tbl) ?:
633 void *rhashtable_insert_slow(struct rhashtable *ht, const void *key,
634 struct rhash_head *obj)
640 data = rhashtable_try_insert(ht, key, obj);
642 } while (PTR_ERR(data) == -EAGAIN);
646 EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
649 * rhashtable_walk_enter - Initialise an iterator
650 * @ht: Table to walk over
651 * @iter: Hash table Iterator
653 * This function prepares a hash table walk.
655 * Note that if you restart a walk after rhashtable_walk_stop you
656 * may see the same object twice. Also, you may miss objects if
657 * there are removals in between rhashtable_walk_stop and the next
658 * call to rhashtable_walk_start.
660 * For a completely stable walk you should construct your own data
661 * structure outside the hash table.
663 * This function may be called from any process context, including
664 * non-preemptable context, but cannot be called from softirq or
667 * You must call rhashtable_walk_exit after this function returns.
669 void rhashtable_walk_enter(struct rhashtable *ht, struct rhashtable_iter *iter)
675 iter->end_of_table = 0;
677 spin_lock(&ht->lock);
679 rcu_dereference_protected(ht->tbl, lockdep_is_held(&ht->lock));
680 list_add(&iter->walker.list, &iter->walker.tbl->walkers);
681 spin_unlock(&ht->lock);
683 EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
686 * rhashtable_walk_exit - Free an iterator
687 * @iter: Hash table Iterator
689 * This function frees resources allocated by rhashtable_walk_enter.
691 void rhashtable_walk_exit(struct rhashtable_iter *iter)
693 spin_lock(&iter->ht->lock);
694 if (iter->walker.tbl)
695 list_del(&iter->walker.list);
696 spin_unlock(&iter->ht->lock);
698 EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
701 * rhashtable_walk_start_check - Start a hash table walk
702 * @iter: Hash table iterator
704 * Start a hash table walk at the current iterator position. Note that we take
705 * the RCU lock in all cases including when we return an error. So you must
706 * always call rhashtable_walk_stop to clean up.
708 * Returns zero if successful.
710 * Returns -EAGAIN if resize event occured. Note that the iterator
711 * will rewind back to the beginning and you may use it immediately
712 * by calling rhashtable_walk_next.
714 * rhashtable_walk_start is defined as an inline variant that returns
715 * void. This is preferred in cases where the caller would ignore
716 * resize events and always continue.
718 int rhashtable_walk_start_check(struct rhashtable_iter *iter)
721 struct rhashtable *ht = iter->ht;
722 bool rhlist = ht->rhlist;
726 spin_lock(&ht->lock);
727 if (iter->walker.tbl)
728 list_del(&iter->walker.list);
729 spin_unlock(&ht->lock);
731 if (iter->end_of_table)
733 if (!iter->walker.tbl) {
734 iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht);
740 if (iter->p && !rhlist) {
742 * We need to validate that 'p' is still in the table, and
743 * if so, update 'skip'
745 struct rhash_head *p;
747 rht_for_each_rcu(p, iter->walker.tbl, iter->slot) {
755 } else if (iter->p && rhlist) {
756 /* Need to validate that 'list' is still in the table, and
757 * if so, update 'skip' and 'p'.
759 struct rhash_head *p;
760 struct rhlist_head *list;
762 rht_for_each_rcu(p, iter->walker.tbl, iter->slot) {
763 for (list = container_of(p, struct rhlist_head, rhead);
765 list = rcu_dereference(list->next)) {
767 if (list == iter->list) {
779 EXPORT_SYMBOL_GPL(rhashtable_walk_start_check);
782 * __rhashtable_walk_find_next - Find the next element in a table (or the first
783 * one in case of a new walk).
785 * @iter: Hash table iterator
787 * Returns the found object or NULL when the end of the table is reached.
789 * Returns -EAGAIN if resize event occurred.
791 static void *__rhashtable_walk_find_next(struct rhashtable_iter *iter)
793 struct bucket_table *tbl = iter->walker.tbl;
794 struct rhlist_head *list = iter->list;
795 struct rhashtable *ht = iter->ht;
796 struct rhash_head *p = iter->p;
797 bool rhlist = ht->rhlist;
802 for (; iter->slot < tbl->size; iter->slot++) {
803 int skip = iter->skip;
805 rht_for_each_rcu(p, tbl, iter->slot) {
807 list = container_of(p, struct rhlist_head,
813 list = rcu_dereference(list->next);
824 if (!rht_is_a_nulls(p)) {
828 return rht_obj(ht, rhlist ? &list->rhead : p);
836 /* Ensure we see any new tables. */
839 iter->walker.tbl = rht_dereference_rcu(tbl->future_tbl, ht);
840 if (iter->walker.tbl) {
843 return ERR_PTR(-EAGAIN);
845 iter->end_of_table = true;
852 * rhashtable_walk_next - Return the next object and advance the iterator
853 * @iter: Hash table iterator
855 * Note that you must call rhashtable_walk_stop when you are finished
858 * Returns the next object or NULL when the end of the table is reached.
860 * Returns -EAGAIN if resize event occurred. Note that the iterator
861 * will rewind back to the beginning and you may continue to use it.
863 void *rhashtable_walk_next(struct rhashtable_iter *iter)
865 struct rhlist_head *list = iter->list;
866 struct rhashtable *ht = iter->ht;
867 struct rhash_head *p = iter->p;
868 bool rhlist = ht->rhlist;
871 if (!rhlist || !(list = rcu_dereference(list->next))) {
872 p = rcu_dereference(p->next);
873 list = container_of(p, struct rhlist_head, rhead);
875 if (!rht_is_a_nulls(p)) {
879 return rht_obj(ht, rhlist ? &list->rhead : p);
882 /* At the end of this slot, switch to next one and then find
883 * next entry from that point.
889 return __rhashtable_walk_find_next(iter);
891 EXPORT_SYMBOL_GPL(rhashtable_walk_next);
894 * rhashtable_walk_peek - Return the next object but don't advance the iterator
895 * @iter: Hash table iterator
897 * Returns the next object or NULL when the end of the table is reached.
899 * Returns -EAGAIN if resize event occurred. Note that the iterator
900 * will rewind back to the beginning and you may continue to use it.
902 void *rhashtable_walk_peek(struct rhashtable_iter *iter)
904 struct rhlist_head *list = iter->list;
905 struct rhashtable *ht = iter->ht;
906 struct rhash_head *p = iter->p;
909 return rht_obj(ht, ht->rhlist ? &list->rhead : p);
911 /* No object found in current iter, find next one in the table. */
914 /* A nonzero skip value points to the next entry in the table
915 * beyond that last one that was found. Decrement skip so
916 * we find the current value. __rhashtable_walk_find_next
917 * will restore the original value of skip assuming that
918 * the table hasn't changed.
923 return __rhashtable_walk_find_next(iter);
925 EXPORT_SYMBOL_GPL(rhashtable_walk_peek);
928 * rhashtable_walk_stop - Finish a hash table walk
929 * @iter: Hash table iterator
931 * Finish a hash table walk. Does not reset the iterator to the start of the
934 void rhashtable_walk_stop(struct rhashtable_iter *iter)
937 struct rhashtable *ht;
938 struct bucket_table *tbl = iter->walker.tbl;
945 spin_lock(&ht->lock);
946 if (tbl->rehash < tbl->size)
947 list_add(&iter->walker.list, &tbl->walkers);
949 iter->walker.tbl = NULL;
950 spin_unlock(&ht->lock);
955 EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
957 static size_t rounded_hashtable_size(const struct rhashtable_params *params)
961 if (params->nelem_hint)
962 retsize = max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
963 (unsigned long)params->min_size);
965 retsize = max(HASH_DEFAULT_SIZE,
966 (unsigned long)params->min_size);
971 static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
973 return jhash2(key, length, seed);
977 * rhashtable_init - initialize a new hash table
978 * @ht: hash table to be initialized
979 * @params: configuration parameters
981 * Initializes a new hash table based on the provided configuration
982 * parameters. A table can be configured either with a variable or
985 * Configuration Example 1: Fixed length keys
989 * struct rhash_head node;
992 * struct rhashtable_params params = {
993 * .head_offset = offsetof(struct test_obj, node),
994 * .key_offset = offsetof(struct test_obj, key),
995 * .key_len = sizeof(int),
999 * Configuration Example 2: Variable length keys
1002 * struct rhash_head node;
1005 * u32 my_hash_fn(const void *data, u32 len, u32 seed)
1007 * struct test_obj *obj = data;
1009 * return [... hash ...];
1012 * struct rhashtable_params params = {
1013 * .head_offset = offsetof(struct test_obj, node),
1015 * .obj_hashfn = my_hash_fn,
1018 int rhashtable_init(struct rhashtable *ht,
1019 const struct rhashtable_params *params)
1021 struct bucket_table *tbl;
1024 if ((!params->key_len && !params->obj_hashfn) ||
1025 (params->obj_hashfn && !params->obj_cmpfn))
1028 memset(ht, 0, sizeof(*ht));
1029 mutex_init(&ht->mutex);
1030 spin_lock_init(&ht->lock);
1031 memcpy(&ht->p, params, sizeof(*params));
1033 if (params->min_size)
1034 ht->p.min_size = roundup_pow_of_two(params->min_size);
1036 /* Cap total entries at 2^31 to avoid nelems overflow. */
1037 ht->max_elems = 1u << 31;
1039 if (params->max_size) {
1040 ht->p.max_size = rounddown_pow_of_two(params->max_size);
1041 if (ht->p.max_size < ht->max_elems / 2)
1042 ht->max_elems = ht->p.max_size * 2;
1045 ht->p.min_size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
1047 size = rounded_hashtable_size(&ht->p);
1049 if (params->locks_mul)
1050 ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
1052 ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
1054 ht->key_len = ht->p.key_len;
1055 if (!params->hashfn) {
1056 ht->p.hashfn = jhash;
1058 if (!(ht->key_len & (sizeof(u32) - 1))) {
1059 ht->key_len /= sizeof(u32);
1060 ht->p.hashfn = rhashtable_jhash2;
1065 * This is api initialization and thus we need to guarantee the
1066 * initial rhashtable allocation. Upon failure, retry with the
1067 * smallest possible size with __GFP_NOFAIL semantics.
1069 tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
1070 if (unlikely(tbl == NULL)) {
1071 size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
1072 tbl = bucket_table_alloc(ht, size, GFP_KERNEL | __GFP_NOFAIL);
1075 atomic_set(&ht->nelems, 0);
1077 RCU_INIT_POINTER(ht->tbl, tbl);
1079 INIT_WORK(&ht->run_work, rht_deferred_worker);
1083 EXPORT_SYMBOL_GPL(rhashtable_init);
1086 * rhltable_init - initialize a new hash list table
1087 * @hlt: hash list table to be initialized
1088 * @params: configuration parameters
1090 * Initializes a new hash list table.
1092 * See documentation for rhashtable_init.
1094 int rhltable_init(struct rhltable *hlt, const struct rhashtable_params *params)
1098 err = rhashtable_init(&hlt->ht, params);
1099 hlt->ht.rhlist = true;
1102 EXPORT_SYMBOL_GPL(rhltable_init);
1104 static void rhashtable_free_one(struct rhashtable *ht, struct rhash_head *obj,
1105 void (*free_fn)(void *ptr, void *arg),
1108 struct rhlist_head *list;
1111 free_fn(rht_obj(ht, obj), arg);
1115 list = container_of(obj, struct rhlist_head, rhead);
1118 list = rht_dereference(list->next, ht);
1119 free_fn(rht_obj(ht, obj), arg);
1124 * rhashtable_free_and_destroy - free elements and destroy hash table
1125 * @ht: the hash table to destroy
1126 * @free_fn: callback to release resources of element
1127 * @arg: pointer passed to free_fn
1129 * Stops an eventual async resize. If defined, invokes free_fn for each
1130 * element to releasal resources. Please note that RCU protected
1131 * readers may still be accessing the elements. Releasing of resources
1132 * must occur in a compatible manner. Then frees the bucket array.
1134 * This function will eventually sleep to wait for an async resize
1135 * to complete. The caller is responsible that no further write operations
1136 * occurs in parallel.
1138 void rhashtable_free_and_destroy(struct rhashtable *ht,
1139 void (*free_fn)(void *ptr, void *arg),
1142 struct bucket_table *tbl, *next_tbl;
1145 cancel_work_sync(&ht->run_work);
1147 mutex_lock(&ht->mutex);
1148 tbl = rht_dereference(ht->tbl, ht);
1151 for (i = 0; i < tbl->size; i++) {
1152 struct rhash_head *pos, *next;
1155 for (pos = rht_dereference(*rht_bucket(tbl, i), ht),
1156 next = !rht_is_a_nulls(pos) ?
1157 rht_dereference(pos->next, ht) : NULL;
1158 !rht_is_a_nulls(pos);
1160 next = !rht_is_a_nulls(pos) ?
1161 rht_dereference(pos->next, ht) : NULL)
1162 rhashtable_free_one(ht, pos, free_fn, arg);
1166 next_tbl = rht_dereference(tbl->future_tbl, ht);
1167 bucket_table_free(tbl);
1172 mutex_unlock(&ht->mutex);
1174 EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);
1176 void rhashtable_destroy(struct rhashtable *ht)
1178 return rhashtable_free_and_destroy(ht, NULL, NULL);
1180 EXPORT_SYMBOL_GPL(rhashtable_destroy);
1182 struct rhash_head __rcu **rht_bucket_nested(const struct bucket_table *tbl,
1185 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1186 static struct rhash_head __rcu *rhnull;
1187 unsigned int index = hash & ((1 << tbl->nest) - 1);
1188 unsigned int size = tbl->size >> tbl->nest;
1189 unsigned int subhash = hash;
1190 union nested_table *ntbl;
1192 ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
1193 ntbl = rht_dereference_bucket_rcu(ntbl[index].table, tbl, hash);
1194 subhash >>= tbl->nest;
1196 while (ntbl && size > (1 << shift)) {
1197 index = subhash & ((1 << shift) - 1);
1198 ntbl = rht_dereference_bucket_rcu(ntbl[index].table,
1206 INIT_RHT_NULLS_HEAD(rhnull);
1210 return &ntbl[subhash].bucket;
1213 EXPORT_SYMBOL_GPL(rht_bucket_nested);
1215 struct rhash_head __rcu **rht_bucket_nested_insert(struct rhashtable *ht,
1216 struct bucket_table *tbl,
1219 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1220 unsigned int index = hash & ((1 << tbl->nest) - 1);
1221 unsigned int size = tbl->size >> tbl->nest;
1222 union nested_table *ntbl;
1224 ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
1226 ntbl = nested_table_alloc(ht, &ntbl[index].table,
1227 size <= (1 << shift));
1229 while (ntbl && size > (1 << shift)) {
1230 index = hash & ((1 << shift) - 1);
1233 ntbl = nested_table_alloc(ht, &ntbl[index].table,
1234 size <= (1 << shift));
1240 return &ntbl[hash].bucket;
1243 EXPORT_SYMBOL_GPL(rht_bucket_nested_insert);