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/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 len
, 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 * @automatic_shrinking: Enable automatic shrinking of tables
108 * @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
109 * @hashfn: Hash function (default: jhash2 if !(key_len % 4), or jhash)
110 * @obj_hashfn: Function to hash object
111 * @obj_cmpfn: Function to compare key with object
113 struct rhashtable_params
{
118 unsigned int max_size
;
119 unsigned int min_size
;
121 bool insecure_elasticity
;
122 bool automatic_shrinking
;
125 rht_obj_hashfn_t obj_hashfn
;
126 rht_obj_cmpfn_t obj_cmpfn
;
130 * struct rhashtable - Hash table handle
132 * @nelems: Number of elements in table
133 * @key_len: Key length for hashfn
134 * @elasticity: Maximum chain length before rehash
135 * @p: Configuration parameters
136 * @run_work: Deferred worker to expand/shrink asynchronously
137 * @mutex: Mutex to protect current/future table swapping
138 * @lock: Spin lock to protect walker list
141 struct bucket_table __rcu
*tbl
;
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
, params
.key_len
?:
248 rht_key_hashfn(ht
, tbl
, ptr
+ params
.key_offset
, params
);
252 * rht_grow_above_75 - returns true if nelems > 0.75 * table-size
254 * @tbl: current table
256 static inline bool rht_grow_above_75(const struct rhashtable
*ht
,
257 const struct bucket_table
*tbl
)
259 /* Expand table when exceeding 75% load */
260 return atomic_read(&ht
->nelems
) > (tbl
->size
/ 4 * 3) &&
261 (!ht
->p
.max_size
|| tbl
->size
< ht
->p
.max_size
);
265 * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
267 * @tbl: current table
269 static inline bool rht_shrink_below_30(const struct rhashtable
*ht
,
270 const struct bucket_table
*tbl
)
272 /* Shrink table beneath 30% load */
273 return atomic_read(&ht
->nelems
) < (tbl
->size
* 3 / 10) &&
274 tbl
->size
> ht
->p
.min_size
;
278 * rht_grow_above_100 - returns true if nelems > table-size
280 * @tbl: current table
282 static inline bool rht_grow_above_100(const struct rhashtable
*ht
,
283 const struct bucket_table
*tbl
)
285 return atomic_read(&ht
->nelems
) > tbl
->size
&&
286 (!ht
->p
.max_size
|| tbl
->size
< ht
->p
.max_size
);
289 /* The bucket lock is selected based on the hash and protects mutations
290 * on a group of hash buckets.
292 * A maximum of tbl->size/2 bucket locks is allocated. This ensures that
293 * a single lock always covers both buckets which may both contains
294 * entries which link to the same bucket of the old table during resizing.
295 * This allows to simplify the locking as locking the bucket in both
296 * tables during resize always guarantee protection.
298 * IMPORTANT: When holding the bucket lock of both the old and new table
299 * during expansions and shrinking, the old bucket lock must always be
302 static inline spinlock_t
*rht_bucket_lock(const struct bucket_table
*tbl
,
305 return &tbl
->locks
[hash
& tbl
->locks_mask
];
308 #ifdef CONFIG_PROVE_LOCKING
309 int lockdep_rht_mutex_is_held(struct rhashtable
*ht
);
310 int lockdep_rht_bucket_is_held(const struct bucket_table
*tbl
, u32 hash
);
312 static inline int lockdep_rht_mutex_is_held(struct rhashtable
*ht
)
317 static inline int lockdep_rht_bucket_is_held(const struct bucket_table
*tbl
,
322 #endif /* CONFIG_PROVE_LOCKING */
324 int rhashtable_init(struct rhashtable
*ht
,
325 const struct rhashtable_params
*params
);
327 int rhashtable_insert_slow(struct rhashtable
*ht
, const void *key
,
328 struct rhash_head
*obj
,
329 struct bucket_table
*old_tbl
);
330 int rhashtable_insert_rehash(struct rhashtable
*ht
);
332 int rhashtable_walk_init(struct rhashtable
*ht
, struct rhashtable_iter
*iter
);
333 void rhashtable_walk_exit(struct rhashtable_iter
*iter
);
334 int rhashtable_walk_start(struct rhashtable_iter
*iter
) __acquires(RCU
);
335 void *rhashtable_walk_next(struct rhashtable_iter
*iter
);
336 void rhashtable_walk_stop(struct rhashtable_iter
*iter
) __releases(RCU
);
338 void rhashtable_free_and_destroy(struct rhashtable
*ht
,
339 void (*free_fn
)(void *ptr
, void *arg
),
341 void rhashtable_destroy(struct rhashtable
*ht
);
343 #define rht_dereference(p, ht) \
344 rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
346 #define rht_dereference_rcu(p, ht) \
347 rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
349 #define rht_dereference_bucket(p, tbl, hash) \
350 rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
352 #define rht_dereference_bucket_rcu(p, tbl, hash) \
353 rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
355 #define rht_entry(tpos, pos, member) \
356 ({ tpos = container_of(pos, typeof(*tpos), member); 1; })
359 * rht_for_each_continue - continue iterating over hash chain
360 * @pos: the &struct rhash_head to use as a loop cursor.
361 * @head: the previous &struct rhash_head to continue from
362 * @tbl: the &struct bucket_table
363 * @hash: the hash value / bucket index
365 #define rht_for_each_continue(pos, head, tbl, hash) \
366 for (pos = rht_dereference_bucket(head, tbl, hash); \
367 !rht_is_a_nulls(pos); \
368 pos = rht_dereference_bucket((pos)->next, tbl, hash))
371 * rht_for_each - iterate over hash chain
372 * @pos: the &struct rhash_head to use as a loop cursor.
373 * @tbl: the &struct bucket_table
374 * @hash: the hash value / bucket index
376 #define rht_for_each(pos, tbl, hash) \
377 rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash)
380 * rht_for_each_entry_continue - continue iterating over hash chain
381 * @tpos: the type * to use as a loop cursor.
382 * @pos: the &struct rhash_head to use as a loop cursor.
383 * @head: the previous &struct rhash_head to continue from
384 * @tbl: the &struct bucket_table
385 * @hash: the hash value / bucket index
386 * @member: name of the &struct rhash_head within the hashable struct.
388 #define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
389 for (pos = rht_dereference_bucket(head, tbl, hash); \
390 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
391 pos = rht_dereference_bucket((pos)->next, tbl, hash))
394 * rht_for_each_entry - iterate over hash chain of given type
395 * @tpos: the type * to use as a loop cursor.
396 * @pos: the &struct rhash_head to use as a loop cursor.
397 * @tbl: the &struct bucket_table
398 * @hash: the hash value / bucket index
399 * @member: name of the &struct rhash_head within the hashable struct.
401 #define rht_for_each_entry(tpos, pos, tbl, hash, member) \
402 rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \
406 * rht_for_each_entry_safe - safely iterate over hash chain of given type
407 * @tpos: the type * to use as a loop cursor.
408 * @pos: the &struct rhash_head to use as a loop cursor.
409 * @next: the &struct rhash_head to use as next in loop cursor.
410 * @tbl: the &struct bucket_table
411 * @hash: the hash value / bucket index
412 * @member: name of the &struct rhash_head within the hashable struct.
414 * This hash chain list-traversal primitive allows for the looped code to
415 * remove the loop cursor from the list.
417 #define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) \
418 for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \
419 next = !rht_is_a_nulls(pos) ? \
420 rht_dereference_bucket(pos->next, tbl, hash) : NULL; \
421 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
423 next = !rht_is_a_nulls(pos) ? \
424 rht_dereference_bucket(pos->next, tbl, hash) : NULL)
427 * rht_for_each_rcu_continue - continue iterating over rcu hash chain
428 * @pos: the &struct rhash_head to use as a loop cursor.
429 * @head: the previous &struct rhash_head to continue from
430 * @tbl: the &struct bucket_table
431 * @hash: the hash value / bucket index
433 * This hash chain list-traversal primitive may safely run concurrently with
434 * the _rcu mutation primitives such as rhashtable_insert() as long as the
435 * traversal is guarded by rcu_read_lock().
437 #define rht_for_each_rcu_continue(pos, head, tbl, hash) \
438 for (({barrier(); }), \
439 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
440 !rht_is_a_nulls(pos); \
441 pos = rcu_dereference_raw(pos->next))
444 * rht_for_each_rcu - iterate over rcu hash chain
445 * @pos: the &struct rhash_head to use as a loop cursor.
446 * @tbl: the &struct bucket_table
447 * @hash: the hash value / bucket index
449 * This hash chain list-traversal primitive may safely run concurrently with
450 * the _rcu mutation primitives such as rhashtable_insert() as long as the
451 * traversal is guarded by rcu_read_lock().
453 #define rht_for_each_rcu(pos, tbl, hash) \
454 rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash)
457 * rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
458 * @tpos: the type * to use as a loop cursor.
459 * @pos: the &struct rhash_head to use as a loop cursor.
460 * @head: the previous &struct rhash_head to continue from
461 * @tbl: the &struct bucket_table
462 * @hash: the hash value / bucket index
463 * @member: name of the &struct rhash_head within the hashable struct.
465 * This hash chain list-traversal primitive may safely run concurrently with
466 * the _rcu mutation primitives such as rhashtable_insert() as long as the
467 * traversal is guarded by rcu_read_lock().
469 #define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
470 for (({barrier(); }), \
471 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
472 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
473 pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
476 * rht_for_each_entry_rcu - iterate over rcu hash chain of given type
477 * @tpos: the type * to use as a loop cursor.
478 * @pos: the &struct rhash_head to use as a loop cursor.
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(tpos, pos, tbl, hash, member) \
488 rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
491 static inline int rhashtable_compare(struct rhashtable_compare_arg
*arg
,
494 struct rhashtable
*ht
= arg
->ht
;
495 const char *ptr
= obj
;
497 return memcmp(ptr
+ ht
->p
.key_offset
, arg
->key
, ht
->p
.key_len
);
501 * rhashtable_lookup_fast - search hash table, inlined version
503 * @key: the pointer to the key
504 * @params: hash table parameters
506 * Computes the hash value for the key and traverses the bucket chain looking
507 * for a entry with an identical key. The first matching entry is returned.
509 * Returns the first entry on which the compare function returned true.
511 static inline void *rhashtable_lookup_fast(
512 struct rhashtable
*ht
, const void *key
,
513 const struct rhashtable_params params
)
515 struct rhashtable_compare_arg arg
= {
519 const struct bucket_table
*tbl
;
520 struct rhash_head
*he
;
525 tbl
= rht_dereference_rcu(ht
->tbl
, ht
);
527 hash
= rht_key_hashfn(ht
, tbl
, key
, params
);
528 rht_for_each_rcu(he
, tbl
, hash
) {
529 if (params
.obj_cmpfn
?
530 params
.obj_cmpfn(&arg
, rht_obj(ht
, he
)) :
531 rhashtable_compare(&arg
, rht_obj(ht
, he
)))
534 return rht_obj(ht
, he
);
537 /* Ensure we see any new tables. */
540 tbl
= rht_dereference_rcu(tbl
->future_tbl
, ht
);
548 /* Internal function, please use rhashtable_insert_fast() instead */
549 static inline int __rhashtable_insert_fast(
550 struct rhashtable
*ht
, const void *key
, struct rhash_head
*obj
,
551 const struct rhashtable_params params
)
553 struct rhashtable_compare_arg arg
= {
557 struct bucket_table
*tbl
, *new_tbl
;
558 struct rhash_head
*head
;
560 unsigned int elasticity
;
567 tbl
= rht_dereference_rcu(ht
->tbl
, ht
);
569 /* All insertions must grab the oldest table containing
570 * the hashed bucket that is yet to be rehashed.
573 hash
= rht_head_hashfn(ht
, tbl
, obj
, params
);
574 lock
= rht_bucket_lock(tbl
, hash
);
577 if (tbl
->rehash
<= hash
)
580 spin_unlock_bh(lock
);
581 tbl
= rht_dereference_rcu(tbl
->future_tbl
, ht
);
584 new_tbl
= rht_dereference_rcu(tbl
->future_tbl
, ht
);
585 if (unlikely(new_tbl
)) {
586 err
= rhashtable_insert_slow(ht
, key
, obj
, new_tbl
);
592 if (unlikely(rht_grow_above_100(ht
, tbl
))) {
594 spin_unlock_bh(lock
);
595 err
= rhashtable_insert_rehash(ht
);
604 elasticity
= ht
->elasticity
;
605 rht_for_each(head
, tbl
, hash
) {
607 unlikely(!(params
.obj_cmpfn
?
608 params
.obj_cmpfn(&arg
, rht_obj(ht
, head
)) :
609 rhashtable_compare(&arg
, rht_obj(ht
, head
)))))
617 head
= rht_dereference_bucket(tbl
->buckets
[hash
], tbl
, hash
);
619 RCU_INIT_POINTER(obj
->next
, head
);
621 rcu_assign_pointer(tbl
->buckets
[hash
], obj
);
623 atomic_inc(&ht
->nelems
);
624 if (rht_grow_above_75(ht
, tbl
))
625 schedule_work(&ht
->run_work
);
628 spin_unlock_bh(lock
);
635 * rhashtable_insert_fast - insert object into hash table
637 * @obj: pointer to hash head inside object
638 * @params: hash table parameters
640 * Will take a per bucket spinlock to protect against mutual mutations
641 * on the same bucket. Multiple insertions may occur in parallel unless
642 * they map to the same bucket lock.
644 * It is safe to call this function from atomic context.
646 * Will trigger an automatic deferred table resizing if the size grows
647 * beyond the watermark indicated by grow_decision() which can be passed
648 * to rhashtable_init().
650 static inline int rhashtable_insert_fast(
651 struct rhashtable
*ht
, struct rhash_head
*obj
,
652 const struct rhashtable_params params
)
654 return __rhashtable_insert_fast(ht
, NULL
, obj
, params
);
658 * rhashtable_lookup_insert_fast - lookup and insert object into hash table
660 * @obj: pointer to hash head inside object
661 * @params: hash table parameters
663 * Locks down the bucket chain in both the old and new table if a resize
664 * is in progress to ensure that writers can't remove from the old table
665 * and can't insert to the new table during the atomic operation of search
666 * and insertion. Searches for duplicates in both the old and new table if
667 * a resize is in progress.
669 * This lookup function may only be used for fixed key hash table (key_len
670 * parameter set). It will BUG() if used inappropriately.
672 * It is safe to call this function from atomic context.
674 * Will trigger an automatic deferred table resizing if the size grows
675 * beyond the watermark indicated by grow_decision() which can be passed
676 * to rhashtable_init().
678 static inline int rhashtable_lookup_insert_fast(
679 struct rhashtable
*ht
, struct rhash_head
*obj
,
680 const struct rhashtable_params params
)
682 const char *key
= rht_obj(ht
, obj
);
684 BUG_ON(ht
->p
.obj_hashfn
);
686 return __rhashtable_insert_fast(ht
, key
+ ht
->p
.key_offset
, obj
,
691 * rhashtable_lookup_insert_key - search and insert object to hash table
695 * @obj: pointer to hash head inside object
696 * @params: hash table parameters
698 * Locks down the bucket chain in both the old and new table if a resize
699 * is in progress to ensure that writers can't remove from the old table
700 * and can't insert to the new table during the atomic operation of search
701 * and insertion. Searches for duplicates in both the old and new table if
702 * a resize is in progress.
704 * Lookups may occur in parallel with hashtable mutations and resizing.
706 * Will trigger an automatic deferred table resizing if the size grows
707 * beyond the watermark indicated by grow_decision() which can be passed
708 * to rhashtable_init().
710 * Returns zero on success.
712 static inline int rhashtable_lookup_insert_key(
713 struct rhashtable
*ht
, const void *key
, struct rhash_head
*obj
,
714 const struct rhashtable_params params
)
716 BUG_ON(!ht
->p
.obj_hashfn
|| !key
);
718 return __rhashtable_insert_fast(ht
, key
, obj
, params
);
721 /* Internal function, please use rhashtable_remove_fast() instead */
722 static inline int __rhashtable_remove_fast(
723 struct rhashtable
*ht
, struct bucket_table
*tbl
,
724 struct rhash_head
*obj
, const struct rhashtable_params params
)
726 struct rhash_head __rcu
**pprev
;
727 struct rhash_head
*he
;
732 hash
= rht_head_hashfn(ht
, tbl
, obj
, params
);
733 lock
= rht_bucket_lock(tbl
, hash
);
737 pprev
= &tbl
->buckets
[hash
];
738 rht_for_each(he
, tbl
, hash
) {
744 rcu_assign_pointer(*pprev
, obj
->next
);
749 spin_unlock_bh(lock
);
755 * rhashtable_remove_fast - remove object from hash table
757 * @obj: pointer to hash head inside object
758 * @params: hash table parameters
760 * Since the hash chain is single linked, the removal operation needs to
761 * walk the bucket chain upon removal. The removal operation is thus
762 * considerable slow if the hash table is not correctly sized.
764 * Will automatically shrink the table via rhashtable_expand() if the
765 * shrink_decision function specified at rhashtable_init() returns true.
767 * Returns zero on success, -ENOENT if the entry could not be found.
769 static inline int rhashtable_remove_fast(
770 struct rhashtable
*ht
, struct rhash_head
*obj
,
771 const struct rhashtable_params params
)
773 struct bucket_table
*tbl
;
778 tbl
= rht_dereference_rcu(ht
->tbl
, ht
);
780 /* Because we have already taken (and released) the bucket
781 * lock in old_tbl, if we find that future_tbl is not yet
782 * visible then that guarantees the entry to still be in
783 * the old tbl if it exists.
785 while ((err
= __rhashtable_remove_fast(ht
, tbl
, obj
, params
)) &&
786 (tbl
= rht_dereference_rcu(tbl
->future_tbl
, ht
)))
792 atomic_dec(&ht
->nelems
);
793 if (unlikely(ht
->p
.automatic_shrinking
&&
794 rht_shrink_below_30(ht
, tbl
)))
795 schedule_work(&ht
->run_work
);
803 #endif /* _LINUX_RHASHTABLE_H */