2 * Resizable, Scalable, Concurrent Hash Table
4 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
5 * Copyright (c) 2014 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/compiler.h>
21 #include <linux/errno.h>
22 #include <linux/jhash.h>
23 #include <linux/list_nulls.h>
24 #include <linux/workqueue.h>
25 #include <linux/mutex.h>
26 #include <linux/rcupdate.h>
29 * The end of the chain is marked with a special nulls marks which has
30 * the following format:
32 * +-------+-----------------------------------------------------+-+
34 * +-------+-----------------------------------------------------+-+
36 * Base (4 bits) : Reserved to distinguish between multiple tables.
37 * Specified via &struct rhashtable_params.nulls_base.
38 * Hash (27 bits): Full hash (unmasked) of first element added to bucket
39 * 1 (1 bit) : Nulls marker (always set)
41 * The remaining bits of the next pointer remain unused for now.
43 #define RHT_BASE_BITS 4
44 #define RHT_HASH_BITS 27
45 #define RHT_BASE_SHIFT RHT_HASH_BITS
47 /* Base bits plus 1 bit for nulls marker */
48 #define RHT_HASH_RESERVED_SPACE (RHT_BASE_BITS + 1)
51 struct rhash_head __rcu
*next
;
55 * struct bucket_table - Table of hash buckets
56 * @size: Number of hash buckets
57 * @rehash: Current bucket being rehashed
58 * @hash_rnd: Random seed to fold into hash
59 * @locks_mask: Mask to apply before accessing locks[]
60 * @locks: Array of spinlocks protecting individual buckets
61 * @walkers: List of active walkers
62 * @rcu: RCU structure for freeing the table
63 * @future_tbl: Table under construction during rehashing
64 * @buckets: size * hash buckets
70 unsigned int locks_mask
;
72 struct list_head walkers
;
75 struct bucket_table __rcu
*future_tbl
;
77 struct rhash_head __rcu
*buckets
[] ____cacheline_aligned_in_smp
;
81 * struct rhashtable_compare_arg - Key for the function rhashtable_compare
83 * @key: Key to compare against
85 struct rhashtable_compare_arg
{
86 struct rhashtable
*ht
;
90 typedef u32 (*rht_hashfn_t
)(const void *data
, u32 len
, u32 seed
);
91 typedef u32 (*rht_obj_hashfn_t
)(const void *data
, u32 seed
);
92 typedef int (*rht_obj_cmpfn_t
)(struct rhashtable_compare_arg
*arg
,
98 * struct rhashtable_params - Hash table construction parameters
99 * @nelem_hint: Hint on number of elements, should be 75% of desired size
100 * @key_len: Length of key
101 * @key_offset: Offset of key in struct to be hashed
102 * @head_offset: Offset of rhash_head in struct to be hashed
103 * @max_size: Maximum size while expanding
104 * @min_size: Minimum size while shrinking
105 * @nulls_base: Base value to generate nulls marker
106 * @insecure_elasticity: Set to true to disable chain length checks
107 * @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
108 * @hashfn: Hash function (default: jhash2 if !(key_len % 4), or jhash)
109 * @obj_hashfn: Function to hash object
110 * @obj_cmpfn: Function to compare key with object
112 struct rhashtable_params
{
117 unsigned int max_size
;
118 unsigned int min_size
;
120 bool insecure_elasticity
;
123 rht_obj_hashfn_t obj_hashfn
;
124 rht_obj_cmpfn_t obj_cmpfn
;
128 * struct rhashtable - Hash table handle
130 * @nelems: Number of elements in table
131 * @key_len: Key length for hashfn
132 * @elasticity: Maximum chain length before rehash
133 * @p: Configuration parameters
134 * @run_work: Deferred worker to expand/shrink asynchronously
135 * @mutex: Mutex to protect current/future table swapping
136 * @lock: Spin lock to protect walker list
137 * @being_destroyed: True if table is set up for destruction
140 struct bucket_table __rcu
*tbl
;
142 bool being_destroyed
;
143 unsigned int key_len
;
144 unsigned int elasticity
;
145 struct rhashtable_params p
;
146 struct work_struct run_work
;
152 * struct rhashtable_walker - Hash table walker
153 * @list: List entry on list of walkers
154 * @tbl: The table that we were walking over
156 struct rhashtable_walker
{
157 struct list_head list
;
158 struct bucket_table
*tbl
;
162 * struct rhashtable_iter - Hash table iterator, fits into netlink cb
163 * @ht: Table to iterate through
164 * @p: Current pointer
165 * @walker: Associated rhashtable walker
166 * @slot: Current slot
167 * @skip: Number of entries to skip in slot
169 struct rhashtable_iter
{
170 struct rhashtable
*ht
;
171 struct rhash_head
*p
;
172 struct rhashtable_walker
*walker
;
177 static inline unsigned long rht_marker(const struct rhashtable
*ht
, u32 hash
)
179 return NULLS_MARKER(ht
->p
.nulls_base
+ hash
);
182 #define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \
183 ((ptr) = (typeof(ptr)) rht_marker(ht, hash))
185 static inline bool rht_is_a_nulls(const struct rhash_head
*ptr
)
187 return ((unsigned long) ptr
& 1);
190 static inline unsigned long rht_get_nulls_value(const struct rhash_head
*ptr
)
192 return ((unsigned long) ptr
) >> 1;
195 static inline void *rht_obj(const struct rhashtable
*ht
,
196 const struct rhash_head
*he
)
198 return (char *)he
- ht
->p
.head_offset
;
201 static inline unsigned int rht_bucket_index(const struct bucket_table
*tbl
,
204 return (hash
>> RHT_HASH_RESERVED_SPACE
) & (tbl
->size
- 1);
207 static inline unsigned int rht_key_hashfn(
208 struct rhashtable
*ht
, const struct bucket_table
*tbl
,
209 const void *key
, const struct rhashtable_params params
)
213 /* params must be equal to ht->p if it isn't constant. */
214 if (!__builtin_constant_p(params
.key_len
))
215 hash
= ht
->p
.hashfn(key
, ht
->key_len
, tbl
->hash_rnd
);
216 else if (params
.key_len
) {
217 unsigned int key_len
= params
.key_len
;
220 hash
= params
.hashfn(key
, key_len
, tbl
->hash_rnd
);
221 else if (key_len
& (sizeof(u32
) - 1))
222 hash
= jhash(key
, key_len
, tbl
->hash_rnd
);
224 hash
= jhash2(key
, key_len
/ sizeof(u32
),
227 unsigned int key_len
= ht
->p
.key_len
;
230 hash
= params
.hashfn(key
, key_len
, tbl
->hash_rnd
);
232 hash
= jhash(key
, key_len
, tbl
->hash_rnd
);
235 return rht_bucket_index(tbl
, hash
);
238 static inline unsigned int rht_head_hashfn(
239 struct rhashtable
*ht
, const struct bucket_table
*tbl
,
240 const struct rhash_head
*he
, const struct rhashtable_params params
)
242 const char *ptr
= rht_obj(ht
, he
);
244 return likely(params
.obj_hashfn
) ?
245 rht_bucket_index(tbl
, params
.obj_hashfn(ptr
, tbl
->hash_rnd
)) :
246 rht_key_hashfn(ht
, tbl
, ptr
+ params
.key_offset
, params
);
250 * rht_grow_above_75 - returns true if nelems > 0.75 * table-size
252 * @tbl: current table
254 static inline bool rht_grow_above_75(const struct rhashtable
*ht
,
255 const struct bucket_table
*tbl
)
257 /* Expand table when exceeding 75% load */
258 return atomic_read(&ht
->nelems
) > (tbl
->size
/ 4 * 3) &&
259 (!ht
->p
.max_size
|| tbl
->size
< ht
->p
.max_size
);
263 * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
265 * @tbl: current table
267 static inline bool rht_shrink_below_30(const struct rhashtable
*ht
,
268 const struct bucket_table
*tbl
)
270 /* Shrink table beneath 30% load */
271 return atomic_read(&ht
->nelems
) < (tbl
->size
* 3 / 10) &&
272 tbl
->size
> ht
->p
.min_size
;
276 * rht_grow_above_100 - returns true if nelems > table-size
278 * @tbl: current table
280 static inline bool rht_grow_above_100(const struct rhashtable
*ht
,
281 const struct bucket_table
*tbl
)
283 return atomic_read(&ht
->nelems
) > tbl
->size
;
286 /* The bucket lock is selected based on the hash and protects mutations
287 * on a group of hash buckets.
289 * A maximum of tbl->size/2 bucket locks is allocated. This ensures that
290 * a single lock always covers both buckets which may both contains
291 * entries which link to the same bucket of the old table during resizing.
292 * This allows to simplify the locking as locking the bucket in both
293 * tables during resize always guarantee protection.
295 * IMPORTANT: When holding the bucket lock of both the old and new table
296 * during expansions and shrinking, the old bucket lock must always be
299 static inline spinlock_t
*rht_bucket_lock(const struct bucket_table
*tbl
,
302 return &tbl
->locks
[hash
& tbl
->locks_mask
];
305 #ifdef CONFIG_PROVE_LOCKING
306 int lockdep_rht_mutex_is_held(struct rhashtable
*ht
);
307 int lockdep_rht_bucket_is_held(const struct bucket_table
*tbl
, u32 hash
);
309 static inline int lockdep_rht_mutex_is_held(struct rhashtable
*ht
)
314 static inline int lockdep_rht_bucket_is_held(const struct bucket_table
*tbl
,
319 #endif /* CONFIG_PROVE_LOCKING */
321 int rhashtable_init(struct rhashtable
*ht
,
322 const struct rhashtable_params
*params
);
324 int rhashtable_insert_slow(struct rhashtable
*ht
, const void *key
,
325 struct rhash_head
*obj
,
326 struct bucket_table
*old_tbl
);
327 int rhashtable_insert_rehash(struct rhashtable
*ht
);
329 int rhashtable_walk_init(struct rhashtable
*ht
, struct rhashtable_iter
*iter
);
330 void rhashtable_walk_exit(struct rhashtable_iter
*iter
);
331 int rhashtable_walk_start(struct rhashtable_iter
*iter
) __acquires(RCU
);
332 void *rhashtable_walk_next(struct rhashtable_iter
*iter
);
333 void rhashtable_walk_stop(struct rhashtable_iter
*iter
) __releases(RCU
);
335 void rhashtable_destroy(struct rhashtable
*ht
);
337 #define rht_dereference(p, ht) \
338 rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
340 #define rht_dereference_rcu(p, ht) \
341 rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
343 #define rht_dereference_bucket(p, tbl, hash) \
344 rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
346 #define rht_dereference_bucket_rcu(p, tbl, hash) \
347 rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
349 #define rht_entry(tpos, pos, member) \
350 ({ tpos = container_of(pos, typeof(*tpos), member); 1; })
353 * rht_for_each_continue - continue iterating over hash chain
354 * @pos: the &struct rhash_head to use as a loop cursor.
355 * @head: the previous &struct rhash_head to continue from
356 * @tbl: the &struct bucket_table
357 * @hash: the hash value / bucket index
359 #define rht_for_each_continue(pos, head, tbl, hash) \
360 for (pos = rht_dereference_bucket(head, tbl, hash); \
361 !rht_is_a_nulls(pos); \
362 pos = rht_dereference_bucket((pos)->next, tbl, hash))
365 * rht_for_each - iterate over hash chain
366 * @pos: the &struct rhash_head to use as a loop cursor.
367 * @tbl: the &struct bucket_table
368 * @hash: the hash value / bucket index
370 #define rht_for_each(pos, tbl, hash) \
371 rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash)
374 * rht_for_each_entry_continue - continue iterating over hash chain
375 * @tpos: the type * to use as a loop cursor.
376 * @pos: the &struct rhash_head to use as a loop cursor.
377 * @head: the previous &struct rhash_head to continue from
378 * @tbl: the &struct bucket_table
379 * @hash: the hash value / bucket index
380 * @member: name of the &struct rhash_head within the hashable struct.
382 #define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
383 for (pos = rht_dereference_bucket(head, tbl, hash); \
384 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
385 pos = rht_dereference_bucket((pos)->next, tbl, hash))
388 * rht_for_each_entry - iterate over hash chain of given type
389 * @tpos: the type * to use as a loop cursor.
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
393 * @member: name of the &struct rhash_head within the hashable struct.
395 #define rht_for_each_entry(tpos, pos, tbl, hash, member) \
396 rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \
400 * rht_for_each_entry_safe - safely iterate over hash chain of given type
401 * @tpos: the type * to use as a loop cursor.
402 * @pos: the &struct rhash_head to use as a loop cursor.
403 * @next: the &struct rhash_head to use as next in loop cursor.
404 * @tbl: the &struct bucket_table
405 * @hash: the hash value / bucket index
406 * @member: name of the &struct rhash_head within the hashable struct.
408 * This hash chain list-traversal primitive allows for the looped code to
409 * remove the loop cursor from the list.
411 #define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) \
412 for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \
413 next = !rht_is_a_nulls(pos) ? \
414 rht_dereference_bucket(pos->next, tbl, hash) : NULL; \
415 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
417 next = !rht_is_a_nulls(pos) ? \
418 rht_dereference_bucket(pos->next, tbl, hash) : NULL)
421 * rht_for_each_rcu_continue - continue iterating over rcu hash chain
422 * @pos: the &struct rhash_head to use as a loop cursor.
423 * @head: the previous &struct rhash_head to continue from
424 * @tbl: the &struct bucket_table
425 * @hash: the hash value / bucket index
427 * This hash chain list-traversal primitive may safely run concurrently with
428 * the _rcu mutation primitives such as rhashtable_insert() as long as the
429 * traversal is guarded by rcu_read_lock().
431 #define rht_for_each_rcu_continue(pos, head, tbl, hash) \
432 for (({barrier(); }), \
433 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
434 !rht_is_a_nulls(pos); \
435 pos = rcu_dereference_raw(pos->next))
438 * rht_for_each_rcu - iterate over rcu hash chain
439 * @pos: the &struct rhash_head to use as a loop cursor.
440 * @tbl: the &struct bucket_table
441 * @hash: the hash value / bucket index
443 * This hash chain list-traversal primitive may safely run concurrently with
444 * the _rcu mutation primitives such as rhashtable_insert() as long as the
445 * traversal is guarded by rcu_read_lock().
447 #define rht_for_each_rcu(pos, tbl, hash) \
448 rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash)
451 * rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
452 * @tpos: the type * to use as a loop cursor.
453 * @pos: the &struct rhash_head to use as a loop cursor.
454 * @head: the previous &struct rhash_head to continue from
455 * @tbl: the &struct bucket_table
456 * @hash: the hash value / bucket index
457 * @member: name of the &struct rhash_head within the hashable struct.
459 * This hash chain list-traversal primitive may safely run concurrently with
460 * the _rcu mutation primitives such as rhashtable_insert() as long as the
461 * traversal is guarded by rcu_read_lock().
463 #define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
464 for (({barrier(); }), \
465 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
466 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
467 pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
470 * rht_for_each_entry_rcu - iterate over rcu hash chain of given type
471 * @tpos: the type * to use as a loop cursor.
472 * @pos: the &struct rhash_head to use as a loop cursor.
473 * @tbl: the &struct bucket_table
474 * @hash: the hash value / bucket index
475 * @member: name of the &struct rhash_head within the hashable struct.
477 * This hash chain list-traversal primitive may safely run concurrently with
478 * the _rcu mutation primitives such as rhashtable_insert() as long as the
479 * traversal is guarded by rcu_read_lock().
481 #define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \
482 rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
485 static inline int rhashtable_compare(struct rhashtable_compare_arg
*arg
,
488 struct rhashtable
*ht
= arg
->ht
;
489 const char *ptr
= obj
;
491 return memcmp(ptr
+ ht
->p
.key_offset
, arg
->key
, ht
->p
.key_len
);
495 * rhashtable_lookup_fast - search hash table, inlined version
497 * @key: the pointer to the key
498 * @params: hash table parameters
500 * Computes the hash value for the key and traverses the bucket chain looking
501 * for a entry with an identical key. The first matching entry is returned.
503 * Returns the first entry on which the compare function returned true.
505 static inline void *rhashtable_lookup_fast(
506 struct rhashtable
*ht
, const void *key
,
507 const struct rhashtable_params params
)
509 struct rhashtable_compare_arg arg
= {
513 const struct bucket_table
*tbl
;
514 struct rhash_head
*he
;
519 tbl
= rht_dereference_rcu(ht
->tbl
, ht
);
521 hash
= rht_key_hashfn(ht
, tbl
, key
, params
);
522 rht_for_each_rcu(he
, tbl
, hash
) {
523 if (params
.obj_cmpfn
?
524 params
.obj_cmpfn(&arg
, rht_obj(ht
, he
)) :
525 rhashtable_compare(&arg
, rht_obj(ht
, he
)))
528 return rht_obj(ht
, he
);
531 /* Ensure we see any new tables. */
534 tbl
= rht_dereference_rcu(tbl
->future_tbl
, ht
);
542 static inline int __rhashtable_insert_fast(
543 struct rhashtable
*ht
, const void *key
, struct rhash_head
*obj
,
544 const struct rhashtable_params params
)
546 struct rhashtable_compare_arg arg
= {
550 struct bucket_table
*tbl
, *new_tbl
;
551 struct rhash_head
*head
;
553 unsigned int elasticity
;
560 tbl
= rht_dereference_rcu(ht
->tbl
, ht
);
562 /* All insertions must grab the oldest table containing
563 * the hashed bucket that is yet to be rehashed.
566 hash
= rht_head_hashfn(ht
, tbl
, obj
, params
);
567 lock
= rht_bucket_lock(tbl
, hash
);
570 if (tbl
->rehash
<= hash
)
573 spin_unlock_bh(lock
);
574 tbl
= rht_dereference_rcu(tbl
->future_tbl
, ht
);
577 new_tbl
= rht_dereference_rcu(tbl
->future_tbl
, ht
);
578 if (unlikely(new_tbl
)) {
579 err
= rhashtable_insert_slow(ht
, key
, obj
, new_tbl
);
585 if (unlikely(rht_grow_above_100(ht
, tbl
))) {
587 spin_unlock_bh(lock
);
588 err
= rhashtable_insert_rehash(ht
);
597 elasticity
= ht
->elasticity
;
598 rht_for_each(head
, tbl
, hash
) {
600 unlikely(!(params
.obj_cmpfn
?
601 params
.obj_cmpfn(&arg
, rht_obj(ht
, head
)) :
602 rhashtable_compare(&arg
, rht_obj(ht
, head
)))))
610 head
= rht_dereference_bucket(tbl
->buckets
[hash
], tbl
, hash
);
612 RCU_INIT_POINTER(obj
->next
, head
);
614 rcu_assign_pointer(tbl
->buckets
[hash
], obj
);
616 atomic_inc(&ht
->nelems
);
617 if (rht_grow_above_75(ht
, tbl
))
618 schedule_work(&ht
->run_work
);
621 spin_unlock_bh(lock
);
628 * rhashtable_insert_fast - insert object into hash table
630 * @obj: pointer to hash head inside object
631 * @params: hash table parameters
633 * Will take a per bucket spinlock to protect against mutual mutations
634 * on the same bucket. Multiple insertions may occur in parallel unless
635 * they map to the same bucket lock.
637 * It is safe to call this function from atomic context.
639 * Will trigger an automatic deferred table resizing if the size grows
640 * beyond the watermark indicated by grow_decision() which can be passed
641 * to rhashtable_init().
643 static inline int rhashtable_insert_fast(
644 struct rhashtable
*ht
, struct rhash_head
*obj
,
645 const struct rhashtable_params params
)
647 return __rhashtable_insert_fast(ht
, NULL
, obj
, params
);
651 * rhashtable_lookup_insert_fast - lookup and insert object into hash table
653 * @obj: pointer to hash head inside object
654 * @params: hash table parameters
656 * Locks down the bucket chain in both the old and new table if a resize
657 * is in progress to ensure that writers can't remove from the old table
658 * and can't insert to the new table during the atomic operation of search
659 * and insertion. Searches for duplicates in both the old and new table if
660 * a resize is in progress.
662 * This lookup function may only be used for fixed key hash table (key_len
663 * parameter set). It will BUG() if used inappropriately.
665 * It is safe to call this function from atomic context.
667 * Will trigger an automatic deferred table resizing if the size grows
668 * beyond the watermark indicated by grow_decision() which can be passed
669 * to rhashtable_init().
671 static inline int rhashtable_lookup_insert_fast(
672 struct rhashtable
*ht
, struct rhash_head
*obj
,
673 const struct rhashtable_params params
)
675 const char *key
= rht_obj(ht
, obj
);
677 BUG_ON(ht
->p
.obj_hashfn
);
679 return __rhashtable_insert_fast(ht
, key
+ ht
->p
.key_offset
, obj
,
684 * rhashtable_lookup_insert_key - search and insert object to hash table
688 * @obj: pointer to hash head inside object
689 * @params: hash table parameters
691 * Locks down the bucket chain in both the old and new table if a resize
692 * is in progress to ensure that writers can't remove from the old table
693 * and can't insert to the new table during the atomic operation of search
694 * and insertion. Searches for duplicates in both the old and new table if
695 * a resize is in progress.
697 * Lookups may occur in parallel with hashtable mutations and resizing.
699 * Will trigger an automatic deferred table resizing if the size grows
700 * beyond the watermark indicated by grow_decision() which can be passed
701 * to rhashtable_init().
703 * Returns zero on success.
705 static inline int rhashtable_lookup_insert_key(
706 struct rhashtable
*ht
, const void *key
, struct rhash_head
*obj
,
707 const struct rhashtable_params params
)
709 BUG_ON(!ht
->p
.obj_hashfn
|| !key
);
711 return __rhashtable_insert_fast(ht
, key
, obj
, params
);
714 static inline int __rhashtable_remove_fast(
715 struct rhashtable
*ht
, struct bucket_table
*tbl
,
716 struct rhash_head
*obj
, const struct rhashtable_params params
)
718 struct rhash_head __rcu
**pprev
;
719 struct rhash_head
*he
;
724 hash
= rht_head_hashfn(ht
, tbl
, obj
, params
);
725 lock
= rht_bucket_lock(tbl
, hash
);
729 pprev
= &tbl
->buckets
[hash
];
730 rht_for_each(he
, tbl
, hash
) {
736 rcu_assign_pointer(*pprev
, obj
->next
);
741 spin_unlock_bh(lock
);
747 * rhashtable_remove_fast - remove object from hash table
749 * @obj: pointer to hash head inside object
750 * @params: hash table parameters
752 * Since the hash chain is single linked, the removal operation needs to
753 * walk the bucket chain upon removal. The removal operation is thus
754 * considerable slow if the hash table is not correctly sized.
756 * Will automatically shrink the table via rhashtable_expand() if the
757 * shrink_decision function specified at rhashtable_init() returns true.
759 * Returns zero on success, -ENOENT if the entry could not be found.
761 static inline int rhashtable_remove_fast(
762 struct rhashtable
*ht
, struct rhash_head
*obj
,
763 const struct rhashtable_params params
)
765 struct bucket_table
*tbl
;
770 tbl
= rht_dereference_rcu(ht
->tbl
, ht
);
772 /* Because we have already taken (and released) the bucket
773 * lock in old_tbl, if we find that future_tbl is not yet
774 * visible then that guarantees the entry to still be in
775 * the old tbl if it exists.
777 while ((err
= __rhashtable_remove_fast(ht
, tbl
, obj
, params
)) &&
778 (tbl
= rht_dereference_rcu(tbl
->future_tbl
, ht
)))
784 atomic_dec(&ht
->nelems
);
785 if (rht_shrink_below_30(ht
, tbl
))
786 schedule_work(&ht
->run_work
);
794 #endif /* _LINUX_RHASHTABLE_H */