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1/*
2 * Resizable, Scalable, Concurrent Hash Table
3 *
4 * Copyright (c) 2015-2016 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>
7 *
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
11 *
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.
15 */
16
17#ifndef _LINUX_RHASHTABLE_H
18#define _LINUX_RHASHTABLE_H
19
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>
29
30/*
31 * The end of the chain is marked with a special nulls marks which has
32 * the following format:
33 *
34 * +-------+-----------------------------------------------------+-+
35 * | Base | Hash |1|
36 * +-------+-----------------------------------------------------+-+
37 *
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)
42 *
43 * The remaining bits of the next pointer remain unused for now.
44 */
45#define RHT_BASE_BITS 4
46#define RHT_HASH_BITS 27
47#define RHT_BASE_SHIFT RHT_HASH_BITS
48
49/* Base bits plus 1 bit for nulls marker */
50#define RHT_HASH_RESERVED_SPACE (RHT_BASE_BITS + 1)
51
52struct rhash_head {
53 struct rhash_head __rcu *next;
54};
55
56struct rhlist_head {
57 struct rhash_head rhead;
58 struct rhlist_head __rcu *next;
59};
60
61/**
62 * struct bucket_table - Table of hash buckets
63 * @size: Number of hash buckets
64 * @rehash: Current bucket being rehashed
65 * @hash_rnd: Random seed to fold into hash
66 * @locks_mask: Mask to apply before accessing locks[]
67 * @locks: Array of spinlocks protecting individual buckets
68 * @walkers: List of active walkers
69 * @rcu: RCU structure for freeing the table
70 * @future_tbl: Table under construction during rehashing
71 * @buckets: size * hash buckets
72 */
73struct bucket_table {
74 unsigned int size;
75 unsigned int rehash;
76 u32 hash_rnd;
77 unsigned int locks_mask;
78 spinlock_t *locks;
79 struct list_head walkers;
80 struct rcu_head rcu;
81
82 struct bucket_table __rcu *future_tbl;
83
84 struct rhash_head __rcu *buckets[] ____cacheline_aligned_in_smp;
85};
86
87/**
88 * struct rhashtable_compare_arg - Key for the function rhashtable_compare
89 * @ht: Hash table
90 * @key: Key to compare against
91 */
92struct rhashtable_compare_arg {
93 struct rhashtable *ht;
94 const void *key;
95};
96
97typedef u32 (*rht_hashfn_t)(const void *data, u32 len, u32 seed);
98typedef u32 (*rht_obj_hashfn_t)(const void *data, u32 len, u32 seed);
99typedef int (*rht_obj_cmpfn_t)(struct rhashtable_compare_arg *arg,
100 const void *obj);
101
102struct rhashtable;
103
104/**
105 * struct rhashtable_params - Hash table construction parameters
106 * @nelem_hint: Hint on number of elements, should be 75% of desired size
107 * @key_len: Length of key
108 * @key_offset: Offset of key in struct to be hashed
109 * @head_offset: Offset of rhash_head in struct to be hashed
110 * @insecure_max_entries: Maximum number of entries (may be exceeded)
111 * @max_size: Maximum size while expanding
112 * @min_size: Minimum size while shrinking
113 * @nulls_base: Base value to generate nulls marker
114 * @insecure_elasticity: Set to true to disable chain length checks
115 * @automatic_shrinking: Enable automatic shrinking of tables
116 * @locks_mul: Number of bucket locks to allocate per cpu (default: 128)
117 * @hashfn: Hash function (default: jhash2 if !(key_len % 4), or jhash)
118 * @obj_hashfn: Function to hash object
119 * @obj_cmpfn: Function to compare key with object
120 */
121struct rhashtable_params {
122 size_t nelem_hint;
123 size_t key_len;
124 size_t key_offset;
125 size_t head_offset;
126 unsigned int insecure_max_entries;
127 unsigned int max_size;
128 unsigned int min_size;
129 u32 nulls_base;
130 bool insecure_elasticity;
131 bool automatic_shrinking;
132 size_t locks_mul;
133 rht_hashfn_t hashfn;
134 rht_obj_hashfn_t obj_hashfn;
135 rht_obj_cmpfn_t obj_cmpfn;
136};
137
138/**
139 * struct rhashtable - Hash table handle
140 * @tbl: Bucket table
141 * @nelems: Number of elements in table
142 * @key_len: Key length for hashfn
143 * @elasticity: Maximum chain length before rehash
144 * @p: Configuration parameters
145 * @rhlist: True if this is an rhltable
146 * @run_work: Deferred worker to expand/shrink asynchronously
147 * @mutex: Mutex to protect current/future table swapping
148 * @lock: Spin lock to protect walker list
149 */
150struct rhashtable {
151 struct bucket_table __rcu *tbl;
152 atomic_t nelems;
153 unsigned int key_len;
154 unsigned int elasticity;
155 struct rhashtable_params p;
156 bool rhlist;
157 struct work_struct run_work;
158 struct mutex mutex;
159 spinlock_t lock;
160};
161
162/**
163 * struct rhltable - Hash table with duplicate objects in a list
164 * @ht: Underlying rhtable
165 */
166struct rhltable {
167 struct rhashtable ht;
168};
169
170/**
171 * struct rhashtable_walker - Hash table walker
172 * @list: List entry on list of walkers
173 * @tbl: The table that we were walking over
174 */
175struct rhashtable_walker {
176 struct list_head list;
177 struct bucket_table *tbl;
178};
179
180/**
181 * struct rhashtable_iter - Hash table iterator
182 * @ht: Table to iterate through
183 * @p: Current pointer
184 * @list: Current hash list pointer
185 * @walker: Associated rhashtable walker
186 * @slot: Current slot
187 * @skip: Number of entries to skip in slot
188 */
189struct rhashtable_iter {
190 struct rhashtable *ht;
191 struct rhash_head *p;
192 struct rhlist_head *list;
193 struct rhashtable_walker walker;
194 unsigned int slot;
195 unsigned int skip;
196};
197
198static inline unsigned long rht_marker(const struct rhashtable *ht, u32 hash)
199{
200 return NULLS_MARKER(ht->p.nulls_base + hash);
201}
202
203#define INIT_RHT_NULLS_HEAD(ptr, ht, hash) \
204 ((ptr) = (typeof(ptr)) rht_marker(ht, hash))
205
206static inline bool rht_is_a_nulls(const struct rhash_head *ptr)
207{
208 return ((unsigned long) ptr & 1);
209}
210
211static inline unsigned long rht_get_nulls_value(const struct rhash_head *ptr)
212{
213 return ((unsigned long) ptr) >> 1;
214}
215
216static inline void *rht_obj(const struct rhashtable *ht,
217 const struct rhash_head *he)
218{
219 return (char *)he - ht->p.head_offset;
220}
221
222static inline unsigned int rht_bucket_index(const struct bucket_table *tbl,
223 unsigned int hash)
224{
225 return (hash >> RHT_HASH_RESERVED_SPACE) & (tbl->size - 1);
226}
227
228static inline unsigned int rht_key_hashfn(
229 struct rhashtable *ht, const struct bucket_table *tbl,
230 const void *key, const struct rhashtable_params params)
231{
232 unsigned int hash;
233
234 /* params must be equal to ht->p if it isn't constant. */
235 if (!__builtin_constant_p(params.key_len))
236 hash = ht->p.hashfn(key, ht->key_len, tbl->hash_rnd);
237 else if (params.key_len) {
238 unsigned int key_len = params.key_len;
239
240 if (params.hashfn)
241 hash = params.hashfn(key, key_len, tbl->hash_rnd);
242 else if (key_len & (sizeof(u32) - 1))
243 hash = jhash(key, key_len, tbl->hash_rnd);
244 else
245 hash = jhash2(key, key_len / sizeof(u32),
246 tbl->hash_rnd);
247 } else {
248 unsigned int key_len = ht->p.key_len;
249
250 if (params.hashfn)
251 hash = params.hashfn(key, key_len, tbl->hash_rnd);
252 else
253 hash = jhash(key, key_len, tbl->hash_rnd);
254 }
255
256 return rht_bucket_index(tbl, hash);
257}
258
259static inline unsigned int rht_head_hashfn(
260 struct rhashtable *ht, const struct bucket_table *tbl,
261 const struct rhash_head *he, const struct rhashtable_params params)
262{
263 const char *ptr = rht_obj(ht, he);
264
265 return likely(params.obj_hashfn) ?
266 rht_bucket_index(tbl, params.obj_hashfn(ptr, params.key_len ?:
267 ht->p.key_len,
268 tbl->hash_rnd)) :
269 rht_key_hashfn(ht, tbl, ptr + params.key_offset, params);
270}
271
272/**
273 * rht_grow_above_75 - returns true if nelems > 0.75 * table-size
274 * @ht: hash table
275 * @tbl: current table
276 */
277static inline bool rht_grow_above_75(const struct rhashtable *ht,
278 const struct bucket_table *tbl)
279{
280 /* Expand table when exceeding 75% load */
281 return atomic_read(&ht->nelems) > (tbl->size / 4 * 3) &&
282 (!ht->p.max_size || tbl->size < ht->p.max_size);
283}
284
285/**
286 * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
287 * @ht: hash table
288 * @tbl: current table
289 */
290static inline bool rht_shrink_below_30(const struct rhashtable *ht,
291 const struct bucket_table *tbl)
292{
293 /* Shrink table beneath 30% load */
294 return atomic_read(&ht->nelems) < (tbl->size * 3 / 10) &&
295 tbl->size > ht->p.min_size;
296}
297
298/**
299 * rht_grow_above_100 - returns true if nelems > table-size
300 * @ht: hash table
301 * @tbl: current table
302 */
303static inline bool rht_grow_above_100(const struct rhashtable *ht,
304 const struct bucket_table *tbl)
305{
306 return atomic_read(&ht->nelems) > tbl->size &&
307 (!ht->p.max_size || tbl->size < ht->p.max_size);
308}
309
310/**
311 * rht_grow_above_max - returns true if table is above maximum
312 * @ht: hash table
313 * @tbl: current table
314 */
315static inline bool rht_grow_above_max(const struct rhashtable *ht,
316 const struct bucket_table *tbl)
317{
318 return ht->p.insecure_max_entries &&
319 atomic_read(&ht->nelems) >= ht->p.insecure_max_entries;
320}
321
322/* The bucket lock is selected based on the hash and protects mutations
323 * on a group of hash buckets.
324 *
325 * A maximum of tbl->size/2 bucket locks is allocated. This ensures that
326 * a single lock always covers both buckets which may both contains
327 * entries which link to the same bucket of the old table during resizing.
328 * This allows to simplify the locking as locking the bucket in both
329 * tables during resize always guarantee protection.
330 *
331 * IMPORTANT: When holding the bucket lock of both the old and new table
332 * during expansions and shrinking, the old bucket lock must always be
333 * acquired first.
334 */
335static inline spinlock_t *rht_bucket_lock(const struct bucket_table *tbl,
336 unsigned int hash)
337{
338 return &tbl->locks[hash & tbl->locks_mask];
339}
340
341#ifdef CONFIG_PROVE_LOCKING
342int lockdep_rht_mutex_is_held(struct rhashtable *ht);
343int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash);
344#else
345static inline int lockdep_rht_mutex_is_held(struct rhashtable *ht)
346{
347 return 1;
348}
349
350static inline int lockdep_rht_bucket_is_held(const struct bucket_table *tbl,
351 u32 hash)
352{
353 return 1;
354}
355#endif /* CONFIG_PROVE_LOCKING */
356
357int rhashtable_init(struct rhashtable *ht,
358 const struct rhashtable_params *params);
359int rhltable_init(struct rhltable *hlt,
360 const struct rhashtable_params *params);
361
362void *rhashtable_insert_slow(struct rhashtable *ht, const void *key,
363 struct rhash_head *obj);
364
365void rhashtable_walk_enter(struct rhashtable *ht,
366 struct rhashtable_iter *iter);
367void rhashtable_walk_exit(struct rhashtable_iter *iter);
368int rhashtable_walk_start(struct rhashtable_iter *iter) __acquires(RCU);
369void *rhashtable_walk_next(struct rhashtable_iter *iter);
370void rhashtable_walk_stop(struct rhashtable_iter *iter) __releases(RCU);
371
372void rhashtable_free_and_destroy(struct rhashtable *ht,
373 void (*free_fn)(void *ptr, void *arg),
374 void *arg);
375void rhashtable_destroy(struct rhashtable *ht);
376
377#define rht_dereference(p, ht) \
378 rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
379
380#define rht_dereference_rcu(p, ht) \
381 rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
382
383#define rht_dereference_bucket(p, tbl, hash) \
384 rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
385
386#define rht_dereference_bucket_rcu(p, tbl, hash) \
387 rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
388
389#define rht_entry(tpos, pos, member) \
390 ({ tpos = container_of(pos, typeof(*tpos), member); 1; })
391
392/**
393 * rht_for_each_continue - continue iterating over hash chain
394 * @pos: the &struct rhash_head to use as a loop cursor.
395 * @head: the previous &struct rhash_head to continue from
396 * @tbl: the &struct bucket_table
397 * @hash: the hash value / bucket index
398 */
399#define rht_for_each_continue(pos, head, tbl, hash) \
400 for (pos = rht_dereference_bucket(head, tbl, hash); \
401 !rht_is_a_nulls(pos); \
402 pos = rht_dereference_bucket((pos)->next, tbl, hash))
403
404/**
405 * rht_for_each - iterate over hash chain
406 * @pos: the &struct rhash_head to use as a loop cursor.
407 * @tbl: the &struct bucket_table
408 * @hash: the hash value / bucket index
409 */
410#define rht_for_each(pos, tbl, hash) \
411 rht_for_each_continue(pos, (tbl)->buckets[hash], tbl, hash)
412
413/**
414 * rht_for_each_entry_continue - continue iterating over hash chain
415 * @tpos: the type * to use as a loop cursor.
416 * @pos: the &struct rhash_head to use as a loop cursor.
417 * @head: the previous &struct rhash_head to continue from
418 * @tbl: the &struct bucket_table
419 * @hash: the hash value / bucket index
420 * @member: name of the &struct rhash_head within the hashable struct.
421 */
422#define rht_for_each_entry_continue(tpos, pos, head, tbl, hash, member) \
423 for (pos = rht_dereference_bucket(head, tbl, hash); \
424 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
425 pos = rht_dereference_bucket((pos)->next, tbl, hash))
426
427/**
428 * rht_for_each_entry - iterate over hash chain of given type
429 * @tpos: the type * to use as a loop cursor.
430 * @pos: the &struct rhash_head to use as a loop cursor.
431 * @tbl: the &struct bucket_table
432 * @hash: the hash value / bucket index
433 * @member: name of the &struct rhash_head within the hashable struct.
434 */
435#define rht_for_each_entry(tpos, pos, tbl, hash, member) \
436 rht_for_each_entry_continue(tpos, pos, (tbl)->buckets[hash], \
437 tbl, hash, member)
438
439/**
440 * rht_for_each_entry_safe - safely iterate over hash chain of given type
441 * @tpos: the type * to use as a loop cursor.
442 * @pos: the &struct rhash_head to use as a loop cursor.
443 * @next: the &struct rhash_head to use as next in loop cursor.
444 * @tbl: the &struct bucket_table
445 * @hash: the hash value / bucket index
446 * @member: name of the &struct rhash_head within the hashable struct.
447 *
448 * This hash chain list-traversal primitive allows for the looped code to
449 * remove the loop cursor from the list.
450 */
451#define rht_for_each_entry_safe(tpos, pos, next, tbl, hash, member) \
452 for (pos = rht_dereference_bucket((tbl)->buckets[hash], tbl, hash), \
453 next = !rht_is_a_nulls(pos) ? \
454 rht_dereference_bucket(pos->next, tbl, hash) : NULL; \
455 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
456 pos = next, \
457 next = !rht_is_a_nulls(pos) ? \
458 rht_dereference_bucket(pos->next, tbl, hash) : NULL)
459
460/**
461 * rht_for_each_rcu_continue - continue iterating over rcu hash chain
462 * @pos: the &struct rhash_head to use as a loop cursor.
463 * @head: the previous &struct rhash_head to continue from
464 * @tbl: the &struct bucket_table
465 * @hash: the hash value / bucket index
466 *
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().
470 */
471#define rht_for_each_rcu_continue(pos, head, tbl, hash) \
472 for (({barrier(); }), \
473 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
474 !rht_is_a_nulls(pos); \
475 pos = rcu_dereference_raw(pos->next))
476
477/**
478 * rht_for_each_rcu - iterate over rcu hash chain
479 * @pos: the &struct rhash_head to use as a loop cursor.
480 * @tbl: the &struct bucket_table
481 * @hash: the hash value / bucket index
482 *
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().
486 */
487#define rht_for_each_rcu(pos, tbl, hash) \
488 rht_for_each_rcu_continue(pos, (tbl)->buckets[hash], tbl, hash)
489
490/**
491 * rht_for_each_entry_rcu_continue - continue iterating over rcu hash chain
492 * @tpos: the type * to use as a loop cursor.
493 * @pos: the &struct rhash_head to use as a loop cursor.
494 * @head: the previous &struct rhash_head to continue from
495 * @tbl: the &struct bucket_table
496 * @hash: the hash value / bucket index
497 * @member: name of the &struct rhash_head within the hashable struct.
498 *
499 * This hash chain list-traversal primitive may safely run concurrently with
500 * the _rcu mutation primitives such as rhashtable_insert() as long as the
501 * traversal is guarded by rcu_read_lock().
502 */
503#define rht_for_each_entry_rcu_continue(tpos, pos, head, tbl, hash, member) \
504 for (({barrier(); }), \
505 pos = rht_dereference_bucket_rcu(head, tbl, hash); \
506 (!rht_is_a_nulls(pos)) && rht_entry(tpos, pos, member); \
507 pos = rht_dereference_bucket_rcu(pos->next, tbl, hash))
508
509/**
510 * rht_for_each_entry_rcu - iterate over rcu hash chain of given type
511 * @tpos: the type * to use as a loop cursor.
512 * @pos: the &struct rhash_head to use as a loop cursor.
513 * @tbl: the &struct bucket_table
514 * @hash: the hash value / bucket index
515 * @member: name of the &struct rhash_head within the hashable struct.
516 *
517 * This hash chain list-traversal primitive may safely run concurrently with
518 * the _rcu mutation primitives such as rhashtable_insert() as long as the
519 * traversal is guarded by rcu_read_lock().
520 */
521#define rht_for_each_entry_rcu(tpos, pos, tbl, hash, member) \
522 rht_for_each_entry_rcu_continue(tpos, pos, (tbl)->buckets[hash],\
523 tbl, hash, member)
524
525/**
526 * rhl_for_each_rcu - iterate over rcu hash table list
527 * @pos: the &struct rlist_head to use as a loop cursor.
528 * @list: the head of the list
529 *
530 * This hash chain list-traversal primitive should be used on the
531 * list returned by rhltable_lookup.
532 */
533#define rhl_for_each_rcu(pos, list) \
534 for (pos = list; pos; pos = rcu_dereference_raw(pos->next))
535
536/**
537 * rhl_for_each_entry_rcu - iterate over rcu hash table list of given type
538 * @tpos: the type * to use as a loop cursor.
539 * @pos: the &struct rlist_head to use as a loop cursor.
540 * @list: the head of the list
541 * @member: name of the &struct rlist_head within the hashable struct.
542 *
543 * This hash chain list-traversal primitive should be used on the
544 * list returned by rhltable_lookup.
545 */
546#define rhl_for_each_entry_rcu(tpos, pos, list, member) \
547 for (pos = list; pos && rht_entry(tpos, pos, member); \
548 pos = rcu_dereference_raw(pos->next))
549
550static inline int rhashtable_compare(struct rhashtable_compare_arg *arg,
551 const void *obj)
552{
553 struct rhashtable *ht = arg->ht;
554 const char *ptr = obj;
555
556 return memcmp(ptr + ht->p.key_offset, arg->key, ht->p.key_len);
557}
558
559/* Internal function, do not use. */
560static inline struct rhash_head *__rhashtable_lookup(
561 struct rhashtable *ht, const void *key,
562 const struct rhashtable_params params)
563{
564 struct rhashtable_compare_arg arg = {
565 .ht = ht,
566 .key = key,
567 };
568 const struct bucket_table *tbl;
569 struct rhash_head *he;
570 unsigned int hash;
571
572 tbl = rht_dereference_rcu(ht->tbl, ht);
573restart:
574 hash = rht_key_hashfn(ht, tbl, key, params);
575 rht_for_each_rcu(he, tbl, hash) {
576 if (params.obj_cmpfn ?
577 params.obj_cmpfn(&arg, rht_obj(ht, he)) :
578 rhashtable_compare(&arg, rht_obj(ht, he)))
579 continue;
580 return he;
581 }
582
583 /* Ensure we see any new tables. */
584 smp_rmb();
585
586 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
587 if (unlikely(tbl))
588 goto restart;
589
590 return NULL;
591}
592
593/**
594 * rhashtable_lookup - search hash table
595 * @ht: hash table
596 * @key: the pointer to the key
597 * @params: hash table parameters
598 *
599 * Computes the hash value for the key and traverses the bucket chain looking
600 * for a entry with an identical key. The first matching entry is returned.
601 *
602 * This must only be called under the RCU read lock.
603 *
604 * Returns the first entry on which the compare function returned true.
605 */
606static inline void *rhashtable_lookup(
607 struct rhashtable *ht, const void *key,
608 const struct rhashtable_params params)
609{
610 struct rhash_head *he = __rhashtable_lookup(ht, key, params);
611
612 return he ? rht_obj(ht, he) : NULL;
613}
614
615/**
616 * rhashtable_lookup_fast - search hash table, without RCU read lock
617 * @ht: hash table
618 * @key: the pointer to the key
619 * @params: hash table parameters
620 *
621 * Computes the hash value for the key and traverses the bucket chain looking
622 * for a entry with an identical key. The first matching entry is returned.
623 *
624 * Only use this function when you have other mechanisms guaranteeing
625 * that the object won't go away after the RCU read lock is released.
626 *
627 * Returns the first entry on which the compare function returned true.
628 */
629static inline void *rhashtable_lookup_fast(
630 struct rhashtable *ht, const void *key,
631 const struct rhashtable_params params)
632{
633 void *obj;
634
635 rcu_read_lock();
636 obj = rhashtable_lookup(ht, key, params);
637 rcu_read_unlock();
638
639 return obj;
640}
641
642/**
643 * rhltable_lookup - search hash list table
644 * @hlt: hash table
645 * @key: the pointer to the key
646 * @params: hash table parameters
647 *
648 * Computes the hash value for the key and traverses the bucket chain looking
649 * for a entry with an identical key. All matching entries are returned
650 * in a list.
651 *
652 * This must only be called under the RCU read lock.
653 *
654 * Returns the list of entries that match the given key.
655 */
656static inline struct rhlist_head *rhltable_lookup(
657 struct rhltable *hlt, const void *key,
658 const struct rhashtable_params params)
659{
660 struct rhash_head *he = __rhashtable_lookup(&hlt->ht, key, params);
661
662 return he ? container_of(he, struct rhlist_head, rhead) : NULL;
663}
664
665/* Internal function, please use rhashtable_insert_fast() instead. This
666 * function returns the existing element already in hashes in there is a clash,
667 * otherwise it returns an error via ERR_PTR().
668 */
669static inline void *__rhashtable_insert_fast(
670 struct rhashtable *ht, const void *key, struct rhash_head *obj,
671 const struct rhashtable_params params, bool rhlist)
672{
673 struct rhashtable_compare_arg arg = {
674 .ht = ht,
675 .key = key,
676 };
677 struct rhash_head __rcu **pprev;
678 struct bucket_table *tbl;
679 struct rhash_head *head;
680 spinlock_t *lock;
681 unsigned int hash;
682 int elasticity;
683 void *data;
684
685 rcu_read_lock();
686
687 tbl = rht_dereference_rcu(ht->tbl, ht);
688 hash = rht_head_hashfn(ht, tbl, obj, params);
689 lock = rht_bucket_lock(tbl, hash);
690 spin_lock_bh(lock);
691
692 if (unlikely(rht_dereference_bucket(tbl->future_tbl, tbl, hash))) {
693slow_path:
694 spin_unlock_bh(lock);
695 rcu_read_unlock();
696 return rhashtable_insert_slow(ht, key, obj);
697 }
698
699 elasticity = ht->elasticity;
700 pprev = &tbl->buckets[hash];
701 rht_for_each(head, tbl, hash) {
702 struct rhlist_head *plist;
703 struct rhlist_head *list;
704
705 elasticity--;
706 if (!key ||
707 (params.obj_cmpfn ?
708 params.obj_cmpfn(&arg, rht_obj(ht, head)) :
709 rhashtable_compare(&arg, rht_obj(ht, head))))
710 continue;
711
712 data = rht_obj(ht, head);
713
714 if (!rhlist)
715 goto out;
716
717
718 list = container_of(obj, struct rhlist_head, rhead);
719 plist = container_of(head, struct rhlist_head, rhead);
720
721 RCU_INIT_POINTER(list->next, plist);
722 head = rht_dereference_bucket(head->next, tbl, hash);
723 RCU_INIT_POINTER(list->rhead.next, head);
724 rcu_assign_pointer(*pprev, obj);
725
726 goto good;
727 }
728
729 if (elasticity <= 0)
730 goto slow_path;
731
732 data = ERR_PTR(-E2BIG);
733 if (unlikely(rht_grow_above_max(ht, tbl)))
734 goto out;
735
736 if (unlikely(rht_grow_above_100(ht, tbl)))
737 goto slow_path;
738
739 head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
740
741 RCU_INIT_POINTER(obj->next, head);
742 if (rhlist) {
743 struct rhlist_head *list;
744
745 list = container_of(obj, struct rhlist_head, rhead);
746 RCU_INIT_POINTER(list->next, NULL);
747 }
748
749 rcu_assign_pointer(tbl->buckets[hash], obj);
750
751 atomic_inc(&ht->nelems);
752 if (rht_grow_above_75(ht, tbl))
753 schedule_work(&ht->run_work);
754
755good:
756 data = NULL;
757
758out:
759 spin_unlock_bh(lock);
760 rcu_read_unlock();
761
762 return data;
763}
764
765/**
766 * rhashtable_insert_fast - insert object into hash table
767 * @ht: hash table
768 * @obj: pointer to hash head inside object
769 * @params: hash table parameters
770 *
771 * Will take a per bucket spinlock to protect against mutual mutations
772 * on the same bucket. Multiple insertions may occur in parallel unless
773 * they map to the same bucket lock.
774 *
775 * It is safe to call this function from atomic context.
776 *
777 * Will trigger an automatic deferred table resizing if the size grows
778 * beyond the watermark indicated by grow_decision() which can be passed
779 * to rhashtable_init().
780 */
781static inline int rhashtable_insert_fast(
782 struct rhashtable *ht, struct rhash_head *obj,
783 const struct rhashtable_params params)
784{
785 void *ret;
786
787 ret = __rhashtable_insert_fast(ht, NULL, obj, params, false);
788 if (IS_ERR(ret))
789 return PTR_ERR(ret);
790
791 return ret == NULL ? 0 : -EEXIST;
792}
793
794/**
795 * rhltable_insert_key - insert object into hash list table
796 * @hlt: hash list table
797 * @key: the pointer to the key
798 * @list: pointer to hash list head inside object
799 * @params: hash table parameters
800 *
801 * Will take a per bucket spinlock to protect against mutual mutations
802 * on the same bucket. Multiple insertions may occur in parallel unless
803 * they map to the same bucket lock.
804 *
805 * It is safe to call this function from atomic context.
806 *
807 * Will trigger an automatic deferred table resizing if the size grows
808 * beyond the watermark indicated by grow_decision() which can be passed
809 * to rhashtable_init().
810 */
811static inline int rhltable_insert_key(
812 struct rhltable *hlt, const void *key, struct rhlist_head *list,
813 const struct rhashtable_params params)
814{
815 return PTR_ERR(__rhashtable_insert_fast(&hlt->ht, key, &list->rhead,
816 params, true));
817}
818
819/**
820 * rhltable_insert - insert object into hash list table
821 * @hlt: hash list table
822 * @list: pointer to hash list head inside object
823 * @params: hash table parameters
824 *
825 * Will take a per bucket spinlock to protect against mutual mutations
826 * on the same bucket. Multiple insertions may occur in parallel unless
827 * they map to the same bucket lock.
828 *
829 * It is safe to call this function from atomic context.
830 *
831 * Will trigger an automatic deferred table resizing if the size grows
832 * beyond the watermark indicated by grow_decision() which can be passed
833 * to rhashtable_init().
834 */
835static inline int rhltable_insert(
836 struct rhltable *hlt, struct rhlist_head *list,
837 const struct rhashtable_params params)
838{
839 const char *key = rht_obj(&hlt->ht, &list->rhead);
840
841 key += params.key_offset;
842
843 return rhltable_insert_key(hlt, key, list, params);
844}
845
846/**
847 * rhashtable_lookup_insert_fast - lookup and insert object into hash table
848 * @ht: hash table
849 * @obj: pointer to hash head inside object
850 * @params: hash table parameters
851 *
852 * Locks down the bucket chain in both the old and new table if a resize
853 * is in progress to ensure that writers can't remove from the old table
854 * and can't insert to the new table during the atomic operation of search
855 * and insertion. Searches for duplicates in both the old and new table if
856 * a resize is in progress.
857 *
858 * This lookup function may only be used for fixed key hash table (key_len
859 * parameter set). It will BUG() if used inappropriately.
860 *
861 * It is safe to call this function from atomic context.
862 *
863 * Will trigger an automatic deferred table resizing if the size grows
864 * beyond the watermark indicated by grow_decision() which can be passed
865 * to rhashtable_init().
866 */
867static inline int rhashtable_lookup_insert_fast(
868 struct rhashtable *ht, struct rhash_head *obj,
869 const struct rhashtable_params params)
870{
871 const char *key = rht_obj(ht, obj);
872 void *ret;
873
874 BUG_ON(ht->p.obj_hashfn);
875
876 ret = __rhashtable_insert_fast(ht, key + ht->p.key_offset, obj, params,
877 false);
878 if (IS_ERR(ret))
879 return PTR_ERR(ret);
880
881 return ret == NULL ? 0 : -EEXIST;
882}
883
884/**
885 * rhashtable_lookup_insert_key - search and insert object to hash table
886 * with explicit key
887 * @ht: hash table
888 * @key: key
889 * @obj: pointer to hash head inside object
890 * @params: hash table parameters
891 *
892 * Locks down the bucket chain in both the old and new table if a resize
893 * is in progress to ensure that writers can't remove from the old table
894 * and can't insert to the new table during the atomic operation of search
895 * and insertion. Searches for duplicates in both the old and new table if
896 * a resize is in progress.
897 *
898 * Lookups may occur in parallel with hashtable mutations and resizing.
899 *
900 * Will trigger an automatic deferred table resizing if the size grows
901 * beyond the watermark indicated by grow_decision() which can be passed
902 * to rhashtable_init().
903 *
904 * Returns zero on success.
905 */
906static inline int rhashtable_lookup_insert_key(
907 struct rhashtable *ht, const void *key, struct rhash_head *obj,
908 const struct rhashtable_params params)
909{
910 void *ret;
911
912 BUG_ON(!ht->p.obj_hashfn || !key);
913
914 ret = __rhashtable_insert_fast(ht, key, obj, params, false);
915 if (IS_ERR(ret))
916 return PTR_ERR(ret);
917
918 return ret == NULL ? 0 : -EEXIST;
919}
920
921/**
922 * rhashtable_lookup_get_insert_key - lookup and insert object into hash table
923 * @ht: hash table
924 * @obj: pointer to hash head inside object
925 * @params: hash table parameters
926 * @data: pointer to element data already in hashes
927 *
928 * Just like rhashtable_lookup_insert_key(), but this function returns the
929 * object if it exists, NULL if it does not and the insertion was successful,
930 * and an ERR_PTR otherwise.
931 */
932static inline void *rhashtable_lookup_get_insert_key(
933 struct rhashtable *ht, const void *key, struct rhash_head *obj,
934 const struct rhashtable_params params)
935{
936 BUG_ON(!ht->p.obj_hashfn || !key);
937
938 return __rhashtable_insert_fast(ht, key, obj, params, false);
939}
940
941/* Internal function, please use rhashtable_remove_fast() instead */
942static inline int __rhashtable_remove_fast_one(
943 struct rhashtable *ht, struct bucket_table *tbl,
944 struct rhash_head *obj, const struct rhashtable_params params,
945 bool rhlist)
946{
947 struct rhash_head __rcu **pprev;
948 struct rhash_head *he;
949 spinlock_t * lock;
950 unsigned int hash;
951 int err = -ENOENT;
952
953 hash = rht_head_hashfn(ht, tbl, obj, params);
954 lock = rht_bucket_lock(tbl, hash);
955
956 spin_lock_bh(lock);
957
958 pprev = &tbl->buckets[hash];
959 rht_for_each(he, tbl, hash) {
960 struct rhlist_head *list;
961
962 list = container_of(he, struct rhlist_head, rhead);
963
964 if (he != obj) {
965 struct rhlist_head __rcu **lpprev;
966
967 pprev = &he->next;
968
969 if (!rhlist)
970 continue;
971
972 do {
973 lpprev = &list->next;
974 list = rht_dereference_bucket(list->next,
975 tbl, hash);
976 } while (list && obj != &list->rhead);
977
978 if (!list)
979 continue;
980
981 list = rht_dereference_bucket(list->next, tbl, hash);
982 RCU_INIT_POINTER(*lpprev, list);
983 err = 0;
984 break;
985 }
986
987 obj = rht_dereference_bucket(obj->next, tbl, hash);
988 err = 1;
989
990 if (rhlist) {
991 list = rht_dereference_bucket(list->next, tbl, hash);
992 if (list) {
993 RCU_INIT_POINTER(list->rhead.next, obj);
994 obj = &list->rhead;
995 err = 0;
996 }
997 }
998
999 rcu_assign_pointer(*pprev, obj);
1000 break;
1001 }
1002
1003 spin_unlock_bh(lock);
1004
1005 if (err > 0) {
1006 atomic_dec(&ht->nelems);
1007 if (unlikely(ht->p.automatic_shrinking &&
1008 rht_shrink_below_30(ht, tbl)))
1009 schedule_work(&ht->run_work);
1010 err = 0;
1011 }
1012
1013 return err;
1014}
1015
1016/* Internal function, please use rhashtable_remove_fast() instead */
1017static inline int __rhashtable_remove_fast(
1018 struct rhashtable *ht, struct rhash_head *obj,
1019 const struct rhashtable_params params, bool rhlist)
1020{
1021 struct bucket_table *tbl;
1022 int err;
1023
1024 rcu_read_lock();
1025
1026 tbl = rht_dereference_rcu(ht->tbl, ht);
1027
1028 /* Because we have already taken (and released) the bucket
1029 * lock in old_tbl, if we find that future_tbl is not yet
1030 * visible then that guarantees the entry to still be in
1031 * the old tbl if it exists.
1032 */
1033 while ((err = __rhashtable_remove_fast_one(ht, tbl, obj, params,
1034 rhlist)) &&
1035 (tbl = rht_dereference_rcu(tbl->future_tbl, ht)))
1036 ;
1037
1038 rcu_read_unlock();
1039
1040 return err;
1041}
1042
1043/**
1044 * rhashtable_remove_fast - remove object from hash table
1045 * @ht: hash table
1046 * @obj: pointer to hash head inside object
1047 * @params: hash table parameters
1048 *
1049 * Since the hash chain is single linked, the removal operation needs to
1050 * walk the bucket chain upon removal. The removal operation is thus
1051 * considerable slow if the hash table is not correctly sized.
1052 *
1053 * Will automatically shrink the table via rhashtable_expand() if the
1054 * shrink_decision function specified at rhashtable_init() returns true.
1055 *
1056 * Returns zero on success, -ENOENT if the entry could not be found.
1057 */
1058static inline int rhashtable_remove_fast(
1059 struct rhashtable *ht, struct rhash_head *obj,
1060 const struct rhashtable_params params)
1061{
1062 return __rhashtable_remove_fast(ht, obj, params, false);
1063}
1064
1065/**
1066 * rhltable_remove - remove object from hash list table
1067 * @hlt: hash list table
1068 * @list: pointer to hash list head inside object
1069 * @params: hash table parameters
1070 *
1071 * Since the hash chain is single linked, the removal operation needs to
1072 * walk the bucket chain upon removal. The removal operation is thus
1073 * considerable slow if the hash table is not correctly sized.
1074 *
1075 * Will automatically shrink the table via rhashtable_expand() if the
1076 * shrink_decision function specified at rhashtable_init() returns true.
1077 *
1078 * Returns zero on success, -ENOENT if the entry could not be found.
1079 */
1080static inline int rhltable_remove(
1081 struct rhltable *hlt, struct rhlist_head *list,
1082 const struct rhashtable_params params)
1083{
1084 return __rhashtable_remove_fast(&hlt->ht, &list->rhead, params, true);
1085}
1086
1087/* Internal function, please use rhashtable_replace_fast() instead */
1088static inline int __rhashtable_replace_fast(
1089 struct rhashtable *ht, struct bucket_table *tbl,
1090 struct rhash_head *obj_old, struct rhash_head *obj_new,
1091 const struct rhashtable_params params)
1092{
1093 struct rhash_head __rcu **pprev;
1094 struct rhash_head *he;
1095 spinlock_t *lock;
1096 unsigned int hash;
1097 int err = -ENOENT;
1098
1099 /* Minimally, the old and new objects must have same hash
1100 * (which should mean identifiers are the same).
1101 */
1102 hash = rht_head_hashfn(ht, tbl, obj_old, params);
1103 if (hash != rht_head_hashfn(ht, tbl, obj_new, params))
1104 return -EINVAL;
1105
1106 lock = rht_bucket_lock(tbl, hash);
1107
1108 spin_lock_bh(lock);
1109
1110 pprev = &tbl->buckets[hash];
1111 rht_for_each(he, tbl, hash) {
1112 if (he != obj_old) {
1113 pprev = &he->next;
1114 continue;
1115 }
1116
1117 rcu_assign_pointer(obj_new->next, obj_old->next);
1118 rcu_assign_pointer(*pprev, obj_new);
1119 err = 0;
1120 break;
1121 }
1122
1123 spin_unlock_bh(lock);
1124
1125 return err;
1126}
1127
1128/**
1129 * rhashtable_replace_fast - replace an object in hash table
1130 * @ht: hash table
1131 * @obj_old: pointer to hash head inside object being replaced
1132 * @obj_new: pointer to hash head inside object which is new
1133 * @params: hash table parameters
1134 *
1135 * Replacing an object doesn't affect the number of elements in the hash table
1136 * or bucket, so we don't need to worry about shrinking or expanding the
1137 * table here.
1138 *
1139 * Returns zero on success, -ENOENT if the entry could not be found,
1140 * -EINVAL if hash is not the same for the old and new objects.
1141 */
1142static inline int rhashtable_replace_fast(
1143 struct rhashtable *ht, struct rhash_head *obj_old,
1144 struct rhash_head *obj_new,
1145 const struct rhashtable_params params)
1146{
1147 struct bucket_table *tbl;
1148 int err;
1149
1150 rcu_read_lock();
1151
1152 tbl = rht_dereference_rcu(ht->tbl, ht);
1153
1154 /* Because we have already taken (and released) the bucket
1155 * lock in old_tbl, if we find that future_tbl is not yet
1156 * visible then that guarantees the entry to still be in
1157 * the old tbl if it exists.
1158 */
1159 while ((err = __rhashtable_replace_fast(ht, tbl, obj_old,
1160 obj_new, params)) &&
1161 (tbl = rht_dereference_rcu(tbl->future_tbl, ht)))
1162 ;
1163
1164 rcu_read_unlock();
1165
1166 return err;
1167}
1168
1169/* Obsolete function, do not use in new code. */
1170static inline int rhashtable_walk_init(struct rhashtable *ht,
1171 struct rhashtable_iter *iter, gfp_t gfp)
1172{
1173 rhashtable_walk_enter(ht, iter);
1174 return 0;
1175}
1176
1177/**
1178 * rhltable_walk_enter - Initialise an iterator
1179 * @hlt: Table to walk over
1180 * @iter: Hash table Iterator
1181 *
1182 * This function prepares a hash table walk.
1183 *
1184 * Note that if you restart a walk after rhashtable_walk_stop you
1185 * may see the same object twice. Also, you may miss objects if
1186 * there are removals in between rhashtable_walk_stop and the next
1187 * call to rhashtable_walk_start.
1188 *
1189 * For a completely stable walk you should construct your own data
1190 * structure outside the hash table.
1191 *
1192 * This function may sleep so you must not call it from interrupt
1193 * context or with spin locks held.
1194 *
1195 * You must call rhashtable_walk_exit after this function returns.
1196 */
1197static inline void rhltable_walk_enter(struct rhltable *hlt,
1198 struct rhashtable_iter *iter)
1199{
1200 return rhashtable_walk_enter(&hlt->ht, iter);
1201}
1202
1203/**
1204 * rhltable_free_and_destroy - free elements and destroy hash list table
1205 * @hlt: the hash list table to destroy
1206 * @free_fn: callback to release resources of element
1207 * @arg: pointer passed to free_fn
1208 *
1209 * See documentation for rhashtable_free_and_destroy.
1210 */
1211static inline void rhltable_free_and_destroy(struct rhltable *hlt,
1212 void (*free_fn)(void *ptr,
1213 void *arg),
1214 void *arg)
1215{
1216 return rhashtable_free_and_destroy(&hlt->ht, free_fn, arg);
1217}
1218
1219static inline void rhltable_destroy(struct rhltable *hlt)
1220{
1221 return rhltable_free_and_destroy(hlt, NULL, NULL);
1222}
1223
1224#endif /* _LINUX_RHASHTABLE_H */