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 #ifndef _LINUX_RHASHTABLE_H
18 #define _LINUX_RHASHTABLE_H
20 #include <linux/atomic.h>
21 #include <linux/compiler.h>
22 #include <linux/err.h>
23 #include <linux/errno.h>
24 #include <linux/jhash.h>
25 #include <linux/list_nulls.h>
26 #include <linux/workqueue.h>
27 #include <linux/mutex.h>
28 #include <linux/rcupdate.h>
31 * The end of the chain is marked with a special nulls marks which has
32 * the following format:
34 * +-------+-----------------------------------------------------+-+
36 * +-------+-----------------------------------------------------+-+
38 * Base (4 bits) : Reserved to distinguish between multiple tables.
39 * Specified via &struct rhashtable_params.nulls_base.
40 * Hash (27 bits): Full hash (unmasked) of first element added to bucket
41 * 1 (1 bit) : Nulls marker (always set)
43 * The remaining bits of the next pointer remain unused for now.
45 #define RHT_BASE_BITS 4
46 #define RHT_HASH_BITS 27
47 #define RHT_BASE_SHIFT RHT_HASH_BITS
49 /* Base bits plus 1 bit for nulls marker */
50 #define RHT_HASH_RESERVED_SPACE (RHT_BASE_BITS + 1)
53 struct rhash_head __rcu *next;
57 * struct bucket_table - Table of hash buckets
58 * @size: Number of hash buckets
59 * @rehash: Current bucket being rehashed
60 * @hash_rnd: Random seed to fold into hash
61 * @locks_mask: Mask to apply before accessing locks[]
62 * @locks: Array of spinlocks protecting individual buckets
63 * @walkers: List of active walkers
64 * @rcu: RCU structure for freeing the table
65 * @future_tbl: Table under construction during rehashing
66 * @buckets: size * hash buckets
72 unsigned int locks_mask;
74 struct list_head walkers;
77 struct bucket_table __rcu *future_tbl;
79 struct rhash_head __rcu *buckets[] ____cacheline_aligned_in_smp;
83 * struct rhashtable_compare_arg - Key for the function rhashtable_compare
85 * @key: Key to compare against
87 struct rhashtable_compare_arg {
88 struct rhashtable *ht;
92 typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
93 typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 len, u32 seed);
94 typedef int (*rht_obj_cmpfn_t)(struct rhashtable_compare_arg *arg,
100 * struct rhashtable_params - Hash table construction parameters
101 * @nelem_hint: Hint on number of elements, should be 75% of desired size
102 * @key_len: Length of key
103 * @key_offset: Offset of key in struct to be hashed
104 * @head_offset: Offset of rhash_head in struct to be hashed
105 * @insecure_max_entries: Maximum number of entries (may be exceeded)
106 * @max_size: Maximum size while expanding
107 * @min_size: Minimum size while shrinking
108 * @nulls_base: Base value to generate nulls marker
109 * @insecure_elasticity: Set to true to disable chain length checks
110 * @automatic_shrinking: Enable automatic shrinking of tables
111 * @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
112 * @hashfn: Hash function (default: jhash2 if !(key_len % 4), or jhash)
113 * @obj_hashfn: Function to hash object
114 * @obj_cmpfn: Function to compare key with object
116 struct rhashtable_params {
121 unsigned int insecure_max_entries;
122 unsigned int max_size;
123 unsigned int min_size;
125 bool insecure_elasticity;
126 bool automatic_shrinking;
129 rht_obj_hashfn_t obj_hashfn;
130 rht_obj_cmpfn_t obj_cmpfn;
134 * struct rhashtable - Hash table handle
136 * @key_len: Key length for hashfn
137 * @elasticity: Maximum chain length before rehash
138 * @p: Configuration parameters
139 * @run_work: Deferred worker to expand/shrink asynchronously
140 * @mutex: Mutex to protect current/future table swapping
141 * @lock: Spin lock to protect walker list
142 * @nelems: Number of elements in table
145 struct bucket_table __rcu *tbl;
146 unsigned int key_len;
147 unsigned int elasticity;
148 struct rhashtable_params p;
149 struct work_struct run_work;
156 * struct rhashtable_walker - Hash table walker
157 * @list: List entry on list of walkers
158 * @tbl: The table that we were walking over
160 struct rhashtable_walker {
161 struct list_head list;
162 struct bucket_table *tbl;
166 * struct rhashtable_iter - Hash table iterator, fits into netlink cb
167 * @ht: Table to iterate through
168 * @p: Current pointer
169 * @walker: Associated rhashtable walker
170 * @slot: Current slot
171 * @skip: Number of entries to skip in slot
173 struct rhashtable_iter {
174 struct rhashtable *ht;
175 struct rhash_head *p;
176 struct rhashtable_walker *walker;
181 static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash)
183 return NULLS_MARKER(ht->p.nulls_base + hash);
186 #define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \
187 ((ptr) = (typeof(ptr)) rht_marker(ht, hash))
189 static inline bool rht_is_a_nulls(const struct rhash_head *ptr)
191 return ((unsigned long) ptr & 1);
194 static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr)
196 return ((unsigned long) ptr) >> 1;
199 static inline void *rht_obj(const struct rhashtable *ht,
200 const struct rhash_head *he)
202 return (char *)he - ht->p.head_offset;
205 static inline unsigned int rht_bucket_index(const struct bucket_table *tbl,
208 return (hash >> RHT_HASH_RESERVED_SPACE) & (tbl->size - 1);
211 static inline unsigned int rht_key_hashfn(
212 struct rhashtable *ht, const struct bucket_table *tbl,
213 const void *key, const struct rhashtable_params params)
217 /* params must be equal to ht->p if it isn't constant. */
218 if (!__builtin_constant_p(params.key_len))
219 hash = ht->p.hashfn(key, ht->key_len, tbl->hash_rnd);
220 else if (params.key_len) {
221 unsigned int key_len = params.key_len;
224 hash = params.hashfn(key, key_len, tbl->hash_rnd);
225 else if (key_len & (sizeof(u32) - 1))
226 hash = jhash(key, key_len, tbl->hash_rnd);
228 hash = jhash2(key, key_len / sizeof(u32),
231 unsigned int key_len = ht->p.key_len;
234 hash = params.hashfn(key, key_len, tbl->hash_rnd);
236 hash = jhash(key, key_len, tbl->hash_rnd);
239 return rht_bucket_index(tbl, hash);
242 static inline unsigned int rht_head_hashfn(
243 struct rhashtable *ht, const struct bucket_table *tbl,
244 const struct rhash_head *he, const struct rhashtable_params params)
246 const char *ptr = rht_obj(ht, he);
248 return likely(params.obj_hashfn) ?
249 rht_bucket_index(tbl, params.obj_hashfn(ptr, params.key_len ?:
252 rht_key_hashfn(ht, tbl, ptr + params.key_offset, params);
256 * rht_grow_above_75 - returns true if nelems > 0.75 * table-size
258 * @tbl: current table
260 static inline bool rht_grow_above_75(const struct rhashtable *ht,
261 const struct bucket_table *tbl)
263 /* Expand table when exceeding 75% load */
264 return atomic_read(&ht->nelems) > (tbl->size / 4 * 3) &&
265 (!ht->p.max_size || tbl->size < ht->p.max_size);
269 * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
271 * @tbl: current table
273 static inline bool rht_shrink_below_30(const struct rhashtable *ht,
274 const struct bucket_table *tbl)
276 /* Shrink table beneath 30% load */
277 return atomic_read(&ht->nelems) < (tbl->size * 3 / 10) &&
278 tbl->size > ht->p.min_size;
282 * rht_grow_above_100 - returns true if nelems > table-size
284 * @tbl: current table
286 static inline bool rht_grow_above_100(const struct rhashtable *ht,
287 const struct bucket_table *tbl)
289 return atomic_read(&ht->nelems) > tbl->size &&
290 (!ht->p.max_size || tbl->size < ht->p.max_size);
294 * rht_grow_above_max - returns true if table is above maximum
296 * @tbl: current table
298 static inline bool rht_grow_above_max(const struct rhashtable *ht,
299 const struct bucket_table *tbl)
301 return ht->p.insecure_max_entries &&
302 atomic_read(&ht->nelems) >= ht->p.insecure_max_entries;
305 /* The bucket lock is selected based on the hash and protects mutations
306 * on a group of hash buckets.
308 * A maximum of tbl->size/2 bucket locks is allocated. This ensures that
309 * a single lock always covers both buckets which may both contains
310 * entries which link to the same bucket of the old table during resizing.
311 * This allows to simplify the locking as locking the bucket in both
312 * tables during resize always guarantee protection.
314 * IMPORTANT: When holding the bucket lock of both the old and new table
315 * during expansions and shrinking, the old bucket lock must always be
318 static inline spinlock_t *rht_bucket_lock(const struct bucket_table *tbl,
321 return &tbl->locks[hash & tbl->locks_mask];
324 #ifdef CONFIG_PROVE_LOCKING
325 int lockdep_rht_mutex_is_held(struct rhashtable *ht);
326 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
328 static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht)
333 static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl,
338 #endif /* CONFIG_PROVE_LOCKING */
340 int rhashtable_init(struct rhashtable *ht,
341 const struct rhashtable_params *params);
343 struct bucket_table *rhashtable_insert_slow(struct rhashtable *ht,
345 struct rhash_head *obj,
346 struct bucket_table *old_tbl,
348 int rhashtable_insert_rehash(struct rhashtable *ht, struct bucket_table *tbl);
350 int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter);
351 void rhashtable_walk_exit(struct rhashtable_iter *iter);
352 int rhashtable_walk_start(struct rhashtable_iter *iter) __acquires(RCU);
353 void *rhashtable_walk_next(struct rhashtable_iter *iter);
354 void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
356 void rhashtable_free_and_destroy(struct rhashtable *ht,
357 void (*free_fn)(void *ptr, void *arg),
359 void rhashtable_destroy(struct rhashtable *ht);
361 #define rht_dereference(p, ht) \
362 rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
364 #define rht_dereference_rcu(p, ht) \
365 rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
367 #define rht_dereference_bucket(p, tbl, hash) \
368 rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
370 #define rht_dereference_bucket_rcu(p, tbl, hash) \
371 rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
373 #define rht_entry(tpos, pos, member) \
374 ({ tpos = container_of(pos, typeof(*tpos), member); 1; })
377 * rht_for_each_continue - continue iterating over hash chain
378 * @pos: the &struct rhash_head to use as a loop cursor.
379 * @head: the previous &struct rhash_head to continue from
380 * @tbl: the &struct bucket_table
381 * @hash: the hash value / bucket index
383 #define rht_for_each_continue(pos, head, tbl, hash) \
384 for (pos = rht_dereference_bucket(head, tbl, hash); \
385 !rht_is_a_nulls(pos); \
386 pos = rht_dereference_bucket((pos)->next, tbl, hash))
389 * rht_for_each - iterate over hash chain
390 * @pos: the &struct rhash_head to use as a loop cursor.
391 * @tbl: the &struct bucket_table
392 * @hash: the hash value / bucket index
394 #define rht_for_each(pos, tbl, hash) \
395 rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash)
398 * rht_for_each_entry_continue - continue iterating over hash chain
399 * @tpos: the type * to use as a loop cursor.
400 * @pos: the &struct rhash_head to use as a loop cursor.
401 * @head: the previous &struct rhash_head to continue from
402 * @tbl: the &struct bucket_table
403 * @hash: the hash value / bucket index
404 * @member: name of the &struct rhash_head within the hashable struct.
406 #define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
407 for (pos = rht_dereference_bucket(head, tbl, hash); \
408 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
409 pos = rht_dereference_bucket((pos)->next, tbl, hash))
412 * rht_for_each_entry - iterate over hash chain of given type
413 * @tpos: the type * to use as a loop cursor.
414 * @pos: the &struct rhash_head to use as a loop cursor.
415 * @tbl: the &struct bucket_table
416 * @hash: the hash value / bucket index
417 * @member: name of the &struct rhash_head within the hashable struct.
419 #define rht_for_each_entry(tpos, pos, tbl, hash, member) \
420 rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \
424 * rht_for_each_entry_safe - safely iterate over hash chain of given type
425 * @tpos: the type * to use as a loop cursor.
426 * @pos: the &struct rhash_head to use as a loop cursor.
427 * @next: the &struct rhash_head to use as next in loop cursor.
428 * @tbl: the &struct bucket_table
429 * @hash: the hash value / bucket index
430 * @member: name of the &struct rhash_head within the hashable struct.
432 * This hash chain list-traversal primitive allows for the looped code to
433 * remove the loop cursor from the list.
435 #define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) \
436 for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \
437 next = !rht_is_a_nulls(pos) ? \
438 rht_dereference_bucket(pos->next, tbl, hash) : NULL; \
439 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
441 next = !rht_is_a_nulls(pos) ? \
442 rht_dereference_bucket(pos->next, tbl, hash) : NULL)
445 * rht_for_each_rcu_continue - continue iterating over rcu hash chain
446 * @pos: the &struct rhash_head to use as a loop cursor.
447 * @head: the previous &struct rhash_head to continue from
448 * @tbl: the &struct bucket_table
449 * @hash: the hash value / bucket index
451 * This hash chain list-traversal primitive may safely run concurrently with
452 * the _rcu mutation primitives such as rhashtable_insert() as long as the
453 * traversal is guarded by rcu_read_lock().
455 #define rht_for_each_rcu_continue(pos, head, tbl, hash) \
456 for (({barrier(); }), \
457 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
458 !rht_is_a_nulls(pos); \
459 pos = rcu_dereference_raw(pos->next))
462 * rht_for_each_rcu - iterate over rcu hash chain
463 * @pos: the &struct rhash_head to use as a loop cursor.
464 * @tbl: the &struct bucket_table
465 * @hash: the hash value / bucket index
467 * This hash chain list-traversal primitive may safely run concurrently with
468 * the _rcu mutation primitives such as rhashtable_insert() as long as the
469 * traversal is guarded by rcu_read_lock().
471 #define rht_for_each_rcu(pos, tbl, hash) \
472 rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash)
475 * rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
476 * @tpos: the type * to use as a loop cursor.
477 * @pos: the &struct rhash_head to use as a loop cursor.
478 * @head: the previous &struct rhash_head to continue from
479 * @tbl: the &struct bucket_table
480 * @hash: the hash value / bucket index
481 * @member: name of the &struct rhash_head within the hashable struct.
483 * This hash chain list-traversal primitive may safely run concurrently with
484 * the _rcu mutation primitives such as rhashtable_insert() as long as the
485 * traversal is guarded by rcu_read_lock().
487 #define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
488 for (({barrier(); }), \
489 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
490 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
491 pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
494 * rht_for_each_entry_rcu - iterate over rcu hash chain of given type
495 * @tpos: the type * to use as a loop cursor.
496 * @pos: the &struct rhash_head to use as a loop cursor.
497 * @tbl: the &struct bucket_table
498 * @hash: the hash value / bucket index
499 * @member: name of the &struct rhash_head within the hashable struct.
501 * This hash chain list-traversal primitive may safely run concurrently with
502 * the _rcu mutation primitives such as rhashtable_insert() as long as the
503 * traversal is guarded by rcu_read_lock().
505 #define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \
506 rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
509 static inline int rhashtable_compare(struct rhashtable_compare_arg *arg,
512 struct rhashtable *ht = arg->ht;
513 const char *ptr = obj;
515 return memcmp(ptr + ht->p.key_offset, arg->key, ht->p.key_len);
518 /* Internal function, do not use. */
519 static inline struct rhash_head *__rhashtable_lookup(
520 struct rhashtable *ht, const void *key,
521 const struct rhashtable_params params)
523 struct rhashtable_compare_arg arg = {
527 const struct bucket_table *tbl;
528 struct rhash_head *he;
531 tbl = rht_dereference_rcu(ht->tbl, ht);
533 hash = rht_key_hashfn(ht, tbl, key, params);
534 rht_for_each_rcu(he, tbl, hash) {
535 if (params.obj_cmpfn ?
536 params.obj_cmpfn(&arg, rht_obj(ht, he)) :
537 rhashtable_compare(&arg, rht_obj(ht, he)))
542 /* Ensure we see any new tables. */
545 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
553 * rhashtable_lookup - search hash table
555 * @key: the pointer to the key
556 * @params: hash table parameters
558 * Computes the hash value for the key and traverses the bucket chain looking
559 * for a entry with an identical key. The first matching entry is returned.
561 * This must only be called under the RCU read lock.
563 * Returns the first entry on which the compare function returned true.
565 static inline void *rhashtable_lookup(
566 struct rhashtable *ht, const void *key,
567 const struct rhashtable_params params)
569 struct rhash_head *he = __rhashtable_lookup(ht, key, params);
571 return he ? rht_obj(ht, he) : NULL;
575 * rhashtable_lookup_fast - search hash table, without RCU read lock
577 * @key: the pointer to the key
578 * @params: hash table parameters
580 * Computes the hash value for the key and traverses the bucket chain looking
581 * for a entry with an identical key. The first matching entry is returned.
583 * Only use this function when you have other mechanisms guaranteeing
584 * that the object won't go away after the RCU read lock is released.
586 * Returns the first entry on which the compare function returned true.
588 static inline void *rhashtable_lookup_fast(
589 struct rhashtable *ht, const void *key,
590 const struct rhashtable_params params)
595 obj = rhashtable_lookup(ht, key, params);
601 /* Internal function, please use rhashtable_insert_fast() instead. This
602 * function returns the existing element already in hashes in there is a clash,
603 * otherwise it returns an error via ERR_PTR().
605 static inline void *__rhashtable_insert_fast(
606 struct rhashtable *ht, const void *key, struct rhash_head *obj,
607 const struct rhashtable_params params)
609 struct rhashtable_compare_arg arg = {
613 struct bucket_table *tbl, *new_tbl;
614 struct rhash_head *head;
616 unsigned int elasticity;
624 tbl = rht_dereference_rcu(ht->tbl, ht);
626 /* All insertions must grab the oldest table containing
627 * the hashed bucket that is yet to be rehashed.
630 hash = rht_head_hashfn(ht, tbl, obj, params);
631 lock = rht_bucket_lock(tbl, hash);
634 if (tbl->rehash <= hash)
637 spin_unlock_bh(lock);
638 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
641 new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
642 if (unlikely(new_tbl)) {
643 tbl = rhashtable_insert_slow(ht, key, obj, new_tbl, &data);
644 if (!IS_ERR_OR_NULL(tbl))
655 if (unlikely(rht_grow_above_max(ht, tbl)))
658 if (unlikely(rht_grow_above_100(ht, tbl))) {
660 spin_unlock_bh(lock);
661 err = rhashtable_insert_rehash(ht, tbl);
670 elasticity = ht->elasticity;
671 rht_for_each(head, tbl, hash) {
673 unlikely(!(params.obj_cmpfn ?
674 params.obj_cmpfn(&arg, rht_obj(ht, head)) :
675 rhashtable_compare(&arg, rht_obj(ht, head))))) {
676 data = rht_obj(ht, head);
683 head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
685 RCU_INIT_POINTER(obj->next, head);
687 rcu_assign_pointer(tbl->buckets[hash], obj);
689 atomic_inc(&ht->nelems);
690 if (rht_grow_above_75(ht, tbl))
691 schedule_work(&ht->run_work);
694 spin_unlock_bh(lock);
697 return err ? ERR_PTR(err) : data;
701 * rhashtable_insert_fast - insert object into hash table
703 * @obj: pointer to hash head inside object
704 * @params: hash table parameters
706 * Will take a per bucket spinlock to protect against mutual mutations
707 * on the same bucket. Multiple insertions may occur in parallel unless
708 * they map to the same bucket lock.
710 * It is safe to call this function from atomic context.
712 * Will trigger an automatic deferred table resizing if the size grows
713 * beyond the watermark indicated by grow_decision() which can be passed
714 * to rhashtable_init().
716 static inline int rhashtable_insert_fast(
717 struct rhashtable *ht, struct rhash_head *obj,
718 const struct rhashtable_params params)
722 ret = __rhashtable_insert_fast(ht, NULL, obj, params);
726 return ret == NULL ? 0 : -EEXIST;
730 * rhashtable_lookup_insert_fast - lookup and insert object into hash table
732 * @obj: pointer to hash head inside object
733 * @params: hash table parameters
735 * Locks down the bucket chain in both the old and new table if a resize
736 * is in progress to ensure that writers can't remove from the old table
737 * and can't insert to the new table during the atomic operation of search
738 * and insertion. Searches for duplicates in both the old and new table if
739 * a resize is in progress.
741 * This lookup function may only be used for fixed key hash table (key_len
742 * parameter set). It will BUG() if used inappropriately.
744 * It is safe to call this function from atomic context.
746 * Will trigger an automatic deferred table resizing if the size grows
747 * beyond the watermark indicated by grow_decision() which can be passed
748 * to rhashtable_init().
750 static inline int rhashtable_lookup_insert_fast(
751 struct rhashtable *ht, struct rhash_head *obj,
752 const struct rhashtable_params params)
754 const char *key = rht_obj(ht, obj);
757 BUG_ON(ht->p.obj_hashfn);
759 ret = __rhashtable_insert_fast(ht, key + ht->p.key_offset, obj, params);
763 return ret == NULL ? 0 : -EEXIST;
767 * rhashtable_lookup_insert_key - search and insert object to hash table
771 * @obj: pointer to hash head inside object
772 * @params: hash table parameters
774 * Locks down the bucket chain in both the old and new table if a resize
775 * is in progress to ensure that writers can't remove from the old table
776 * and can't insert to the new table during the atomic operation of search
777 * and insertion. Searches for duplicates in both the old and new table if
778 * a resize is in progress.
780 * Lookups may occur in parallel with hashtable mutations and resizing.
782 * Will trigger an automatic deferred table resizing if the size grows
783 * beyond the watermark indicated by grow_decision() which can be passed
784 * to rhashtable_init().
786 * Returns zero on success.
788 static inline int rhashtable_lookup_insert_key(
789 struct rhashtable *ht, const void *key, struct rhash_head *obj,
790 const struct rhashtable_params params)
794 BUG_ON(!ht->p.obj_hashfn || !key);
796 ret = __rhashtable_insert_fast(ht, key, obj, params);
800 return ret == NULL ? 0 : -EEXIST;
804 * rhashtable_lookup_get_insert_key - lookup and insert object into hash table
806 * @obj: pointer to hash head inside object
807 * @params: hash table parameters
808 * @data: pointer to element data already in hashes
810 * Just like rhashtable_lookup_insert_key(), but this function returns the
811 * object if it exists, NULL if it does not and the insertion was successful,
812 * and an ERR_PTR otherwise.
814 static inline void *rhashtable_lookup_get_insert_key(
815 struct rhashtable *ht, const void *key, struct rhash_head *obj,
816 const struct rhashtable_params params)
818 BUG_ON(!ht->p.obj_hashfn || !key);
820 return __rhashtable_insert_fast(ht, key, obj, params);
823 /* Internal function, please use rhashtable_remove_fast() instead */
824 static inline int __rhashtable_remove_fast(
825 struct rhashtable *ht, struct bucket_table *tbl,
826 struct rhash_head *obj, const struct rhashtable_params params)
828 struct rhash_head __rcu **pprev;
829 struct rhash_head *he;
834 hash = rht_head_hashfn(ht, tbl, obj, params);
835 lock = rht_bucket_lock(tbl, hash);
839 pprev = &tbl->buckets[hash];
840 rht_for_each(he, tbl, hash) {
846 rcu_assign_pointer(*pprev, obj->next);
851 spin_unlock_bh(lock);
857 * rhashtable_remove_fast - remove object from hash table
859 * @obj: pointer to hash head inside object
860 * @params: hash table parameters
862 * Since the hash chain is single linked, the removal operation needs to
863 * walk the bucket chain upon removal. The removal operation is thus
864 * considerable slow if the hash table is not correctly sized.
866 * Will automatically shrink the table via rhashtable_expand() if the
867 * shrink_decision function specified at rhashtable_init() returns true.
869 * Returns zero on success, -ENOENT if the entry could not be found.
871 static inline int rhashtable_remove_fast(
872 struct rhashtable *ht, struct rhash_head *obj,
873 const struct rhashtable_params params)
875 struct bucket_table *tbl;
880 tbl = rht_dereference_rcu(ht->tbl, ht);
882 /* Because we have already taken (and released) the bucket
883 * lock in old_tbl, if we find that future_tbl is not yet
884 * visible then that guarantees the entry to still be in
885 * the old tbl if it exists.
887 while ((err = __rhashtable_remove_fast(ht, tbl, obj, params)) &&
888 (tbl = rht_dereference_rcu(tbl->future_tbl, ht)))
894 atomic_dec(&ht->nelems);
895 if (unlikely(ht->p.automatic_shrinking &&
896 rht_shrink_below_30(ht, tbl)))
897 schedule_work(&ht->run_work);
905 #endif /* _LINUX_RHASHTABLE_H */