1/*
2 * Resizable, Scalable, Concurrent Hash Table
3 *
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>
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#include <linux/atomic.h>
18#include <linux/kernel.h>
19#include <linux/init.h>
20#include <linux/log2.h>
21#include <linux/sched.h>
22#include <linux/rculist.h>
23#include <linux/slab.h>
24#include <linux/vmalloc.h>
25#include <linux/mm.h>
26#include <linux/jhash.h>
27#include <linux/random.h>
28#include <linux/rhashtable.h>
29#include <linux/err.h>
30#include <linux/export.h>
31
32#define HASH_DEFAULT_SIZE 64UL
33#define HASH_MIN_SIZE 4U
34#define BUCKET_LOCKS_PER_CPU 32UL
35
36union nested_table {
37 union nested_table __rcu *table;
38 struct rhash_head __rcu *bucket;
39};
40
41static u32 head_hashfn(struct rhashtable *ht,
42 const struct bucket_table *tbl,
43 const struct rhash_head *he)
44{
45 return rht_head_hashfn(ht, tbl, he, ht->p);
46}
47
48#ifdef CONFIG_PROVE_LOCKING
49#define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
50
51int lockdep_rht_mutex_is_held(struct rhashtable *ht)
52{
53 return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
54}
55EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
56
57int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
58{
59 spinlock_t *lock = rht_bucket_lock(tbl, hash);
60
61 return (debug_locks) ? lockdep_is_held(lock) : 1;
62}
63EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
64#else
65#define ASSERT_RHT_MUTEX(HT)
66#endif
67
68static void nested_table_free(union nested_table *ntbl, unsigned int size)
69{
70 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
71 const unsigned int len = 1 << shift;
72 unsigned int i;
73
74 ntbl = rcu_dereference_raw(ntbl->table);
75 if (!ntbl)
76 return;
77
78 if (size > len) {
79 size >>= shift;
80 for (i = 0; i < len; i++)
81 nested_table_free(ntbl + i, size);
82 }
83
84 kfree(ntbl);
85}
86
87static void nested_bucket_table_free(const struct bucket_table *tbl)
88{
89 unsigned int size = tbl->size >> tbl->nest;
90 unsigned int len = 1 << tbl->nest;
91 union nested_table *ntbl;
92 unsigned int i;
93
94 ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
95
96 for (i = 0; i < len; i++)
97 nested_table_free(ntbl + i, size);
98
99 kfree(ntbl);
100}
101
102static void bucket_table_free(const struct bucket_table *tbl)
103{
104 if (tbl->nest)
105 nested_bucket_table_free(tbl);
106
107 free_bucket_spinlocks(tbl->locks);
108 kvfree(tbl);
109}
110
111static void bucket_table_free_rcu(struct rcu_head *head)
112{
113 bucket_table_free(container_of(head, struct bucket_table, rcu));
114}
115
116static union nested_table *nested_table_alloc(struct rhashtable *ht,
117 union nested_table __rcu **prev,
118 bool leaf)
119{
120 union nested_table *ntbl;
121 int i;
122
123 ntbl = rcu_dereference(*prev);
124 if (ntbl)
125 return ntbl;
126
127 ntbl = kzalloc(PAGE_SIZE, GFP_ATOMIC);
128
129 if (ntbl && leaf) {
130 for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0]); i++)
131 INIT_RHT_NULLS_HEAD(ntbl[i].bucket);
132 }
133
134 rcu_assign_pointer(*prev, ntbl);
135
136 return ntbl;
137}
138
139static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht,
140 size_t nbuckets,
141 gfp_t gfp)
142{
143 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
144 struct bucket_table *tbl;
145 size_t size;
146
147 if (nbuckets < (1 << (shift + 1)))
148 return NULL;
149
150 size = sizeof(*tbl) + sizeof(tbl->buckets[0]);
151
152 tbl = kzalloc(size, gfp);
153 if (!tbl)
154 return NULL;
155
156 if (!nested_table_alloc(ht, (union nested_table __rcu **)tbl->buckets,
157 false)) {
158 kfree(tbl);
159 return NULL;
160 }
161
162 tbl->nest = (ilog2(nbuckets) - 1) % shift + 1;
163
164 return tbl;
165}
166
167static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
168 size_t nbuckets,
169 gfp_t gfp)
170{
171 struct bucket_table *tbl = NULL;
172 size_t size, max_locks;
173 int i;
174
175 size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
176 tbl = kvzalloc(size, gfp);
177
178 size = nbuckets;
179
180 if (tbl == NULL && (gfp & ~__GFP_NOFAIL) != GFP_KERNEL) {
181 tbl = nested_bucket_table_alloc(ht, nbuckets, gfp);
182 nbuckets = 0;
183 }
184
185 if (tbl == NULL)
186 return NULL;
187
188 tbl->size = size;
189
190 max_locks = size >> 1;
191 if (tbl->nest)
192 max_locks = min_t(size_t, max_locks, 1U << tbl->nest);
193
194 if (alloc_bucket_spinlocks(&tbl->locks, &tbl->locks_mask, max_locks,
195 ht->p.locks_mul, gfp) < 0) {
196 bucket_table_free(tbl);
197 return NULL;
198 }
199
200 INIT_LIST_HEAD(&tbl->walkers);
201
202 tbl->hash_rnd = get_random_u32();
203
204 for (i = 0; i < nbuckets; i++)
205 INIT_RHT_NULLS_HEAD(tbl->buckets[i]);
206
207 return tbl;
208}
209
210static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
211 struct bucket_table *tbl)
212{
213 struct bucket_table *new_tbl;
214
215 do {
216 new_tbl = tbl;
217 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
218 } while (tbl);
219
220 return new_tbl;
221}
222
223static int rhashtable_rehash_one(struct rhashtable *ht, unsigned int old_hash)
224{
225 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
226 struct bucket_table *new_tbl = rhashtable_last_table(ht, old_tbl);
227 struct rhash_head __rcu **pprev = rht_bucket_var(old_tbl, old_hash);
228 int err = -EAGAIN;
229 struct rhash_head *head, *next, *entry;
230 spinlock_t *new_bucket_lock;
231 unsigned int new_hash;
232
233 if (new_tbl->nest)
234 goto out;
235
236 err = -ENOENT;
237
238 rht_for_each(entry, old_tbl, old_hash) {
239 err = 0;
240 next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
241
242 if (rht_is_a_nulls(next))
243 break;
244
245 pprev = &entry->next;
246 }
247
248 if (err)
249 goto out;
250
251 new_hash = head_hashfn(ht, new_tbl, entry);
252
253 new_bucket_lock = rht_bucket_lock(new_tbl, new_hash);
254
255 spin_lock_nested(new_bucket_lock, SINGLE_DEPTH_NESTING);
256 head = rht_dereference_bucket(new_tbl->buckets[new_hash],
257 new_tbl, new_hash);
258
259 RCU_INIT_POINTER(entry->next, head);
260
261 rcu_assign_pointer(new_tbl->buckets[new_hash], entry);
262 spin_unlock(new_bucket_lock);
263
264 rcu_assign_pointer(*pprev, next);
265
266out:
267 return err;
268}
269
270static int rhashtable_rehash_chain(struct rhashtable *ht,
271 unsigned int old_hash)
272{
273 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
274 spinlock_t *old_bucket_lock;
275 int err;
276
277 old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
278
279 spin_lock_bh(old_bucket_lock);
280 while (!(err = rhashtable_rehash_one(ht, old_hash)))
281 ;
282
283 if (err == -ENOENT) {
284 old_tbl->rehash++;
285 err = 0;
286 }
287 spin_unlock_bh(old_bucket_lock);
288
289 return err;
290}
291
292static int rhashtable_rehash_attach(struct rhashtable *ht,
293 struct bucket_table *old_tbl,
294 struct bucket_table *new_tbl)
295{
296 /* Make insertions go into the new, empty table right away. Deletions
297 * and lookups will be attempted in both tables until we synchronize.
298 * As cmpxchg() provides strong barriers, we do not need
299 * rcu_assign_pointer().
300 */
301
302 if (cmpxchg(&old_tbl->future_tbl, NULL, new_tbl) != NULL)
303 return -EEXIST;
304
305 return 0;
306}
307
308static int rhashtable_rehash_table(struct rhashtable *ht)
309{
310 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
311 struct bucket_table *new_tbl;
312 struct rhashtable_walker *walker;
313 unsigned int old_hash;
314 int err;
315
316 new_tbl = rht_dereference(old_tbl->future_tbl, ht);
317 if (!new_tbl)
318 return 0;
319
320 for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
321 err = rhashtable_rehash_chain(ht, old_hash);
322 if (err)
323 return err;
324 cond_resched();
325 }
326
327 /* Publish the new table pointer. */
328 rcu_assign_pointer(ht->tbl, new_tbl);
329
330 spin_lock(&ht->lock);
331 list_for_each_entry(walker, &old_tbl->walkers, list)
332 walker->tbl = NULL;
333 spin_unlock(&ht->lock);
334
335 /* Wait for readers. All new readers will see the new
336 * table, and thus no references to the old table will
337 * remain.
338 */
339 call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
340
341 return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
342}
343
344static int rhashtable_rehash_alloc(struct rhashtable *ht,
345 struct bucket_table *old_tbl,
346 unsigned int size)
347{
348 struct bucket_table *new_tbl;
349 int err;
350
351 ASSERT_RHT_MUTEX(ht);
352
353 new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
354 if (new_tbl == NULL)
355 return -ENOMEM;
356
357 err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
358 if (err)
359 bucket_table_free(new_tbl);
360
361 return err;
362}
363
364/**
365 * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
366 * @ht: the hash table to shrink
367 *
368 * This function shrinks the hash table to fit, i.e., the smallest
369 * size would not cause it to expand right away automatically.
370 *
371 * The caller must ensure that no concurrent resizing occurs by holding
372 * ht->mutex.
373 *
374 * The caller must ensure that no concurrent table mutations take place.
375 * It is however valid to have concurrent lookups if they are RCU protected.
376 *
377 * It is valid to have concurrent insertions and deletions protected by per
378 * bucket locks or concurrent RCU protected lookups and traversals.
379 */
380static int rhashtable_shrink(struct rhashtable *ht)
381{
382 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
383 unsigned int nelems = atomic_read(&ht->nelems);
384 unsigned int size = 0;
385
386 if (nelems)
387 size = roundup_pow_of_two(nelems * 3 / 2);
388 if (size < ht->p.min_size)
389 size = ht->p.min_size;
390
391 if (old_tbl->size <= size)
392 return 0;
393
394 if (rht_dereference(old_tbl->future_tbl, ht))
395 return -EEXIST;
396
397 return rhashtable_rehash_alloc(ht, old_tbl, size);
398}
399
400static void rht_deferred_worker(struct work_struct *work)
401{
402 struct rhashtable *ht;
403 struct bucket_table *tbl;
404 int err = 0;
405
406 ht = container_of(work, struct rhashtable, run_work);
407 mutex_lock(&ht->mutex);
408
409 tbl = rht_dereference(ht->tbl, ht);
410 tbl = rhashtable_last_table(ht, tbl);
411
412 if (rht_grow_above_75(ht, tbl))
413 err = rhashtable_rehash_alloc(ht, tbl, tbl->size * 2);
414 else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
415 err = rhashtable_shrink(ht);
416 else if (tbl->nest)
417 err = rhashtable_rehash_alloc(ht, tbl, tbl->size);
418
419 if (!err)
420 err = rhashtable_rehash_table(ht);
421
422 mutex_unlock(&ht->mutex);
423
424 if (err)
425 schedule_work(&ht->run_work);
426}
427
428static int rhashtable_insert_rehash(struct rhashtable *ht,
429 struct bucket_table *tbl)
430{
431 struct bucket_table *old_tbl;
432 struct bucket_table *new_tbl;
433 unsigned int size;
434 int err;
435
436 old_tbl = rht_dereference_rcu(ht->tbl, ht);
437
438 size = tbl->size;
439
440 err = -EBUSY;
441
442 if (rht_grow_above_75(ht, tbl))
443 size *= 2;
444 /* Do not schedule more than one rehash */
445 else if (old_tbl != tbl)
446 goto fail;
447
448 err = -ENOMEM;
449
450 new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC | __GFP_NOWARN);
451 if (new_tbl == NULL)
452 goto fail;
453
454 err = rhashtable_rehash_attach(ht, tbl, new_tbl);
455 if (err) {
456 bucket_table_free(new_tbl);
457 if (err == -EEXIST)
458 err = 0;
459 } else
460 schedule_work(&ht->run_work);
461
462 return err;
463
464fail:
465 /* Do not fail the insert if someone else did a rehash. */
466 if (likely(rcu_access_pointer(tbl->future_tbl)))
467 return 0;
468
469 /* Schedule async rehash to retry allocation in process context. */
470 if (err == -ENOMEM)
471 schedule_work(&ht->run_work);
472
473 return err;
474}
475
476static void *rhashtable_lookup_one(struct rhashtable *ht,
477 struct bucket_table *tbl, unsigned int hash,
478 const void *key, struct rhash_head *obj)
479{
480 struct rhashtable_compare_arg arg = {
481 .ht = ht,
482 .key = key,
483 };
484 struct rhash_head __rcu **pprev;
485 struct rhash_head *head;
486 int elasticity;
487
488 elasticity = RHT_ELASTICITY;
489 pprev = rht_bucket_var(tbl, hash);
490 rht_for_each_continue(head, *pprev, tbl, hash) {
491 struct rhlist_head *list;
492 struct rhlist_head *plist;
493
494 elasticity--;
495 if (!key ||
496 (ht->p.obj_cmpfn ?
497 ht->p.obj_cmpfn(&arg, rht_obj(ht, head)) :
498 rhashtable_compare(&arg, rht_obj(ht, head)))) {
499 pprev = &head->next;
500 continue;
501 }
502
503 if (!ht->rhlist)
504 return rht_obj(ht, head);
505
506 list = container_of(obj, struct rhlist_head, rhead);
507 plist = container_of(head, struct rhlist_head, rhead);
508
509 RCU_INIT_POINTER(list->next, plist);
510 head = rht_dereference_bucket(head->next, tbl, hash);
511 RCU_INIT_POINTER(list->rhead.next, head);
512 rcu_assign_pointer(*pprev, obj);
513
514 return NULL;
515 }
516
517 if (elasticity <= 0)
518 return ERR_PTR(-EAGAIN);
519
520 return ERR_PTR(-ENOENT);
521}
522
523static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
524 struct bucket_table *tbl,
525 unsigned int hash,
526 struct rhash_head *obj,
527 void *data)
528{
529 struct rhash_head __rcu **pprev;
530 struct bucket_table *new_tbl;
531 struct rhash_head *head;
532
533 if (!IS_ERR_OR_NULL(data))
534 return ERR_PTR(-EEXIST);
535
536 if (PTR_ERR(data) != -EAGAIN && PTR_ERR(data) != -ENOENT)
537 return ERR_CAST(data);
538
539 new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
540 if (new_tbl)
541 return new_tbl;
542
543 if (PTR_ERR(data) != -ENOENT)
544 return ERR_CAST(data);
545
546 if (unlikely(rht_grow_above_max(ht, tbl)))
547 return ERR_PTR(-E2BIG);
548
549 if (unlikely(rht_grow_above_100(ht, tbl)))
550 return ERR_PTR(-EAGAIN);
551
552 pprev = rht_bucket_insert(ht, tbl, hash);
553 if (!pprev)
554 return ERR_PTR(-ENOMEM);
555
556 head = rht_dereference_bucket(*pprev, tbl, hash);
557
558 RCU_INIT_POINTER(obj->next, head);
559 if (ht->rhlist) {
560 struct rhlist_head *list;
561
562 list = container_of(obj, struct rhlist_head, rhead);
563 RCU_INIT_POINTER(list->next, NULL);
564 }
565
566 rcu_assign_pointer(*pprev, obj);
567
568 atomic_inc(&ht->nelems);
569 if (rht_grow_above_75(ht, tbl))
570 schedule_work(&ht->run_work);
571
572 return NULL;
573}
574
575static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
576 struct rhash_head *obj)
577{
578 struct bucket_table *new_tbl;
579 struct bucket_table *tbl;
580 unsigned int hash;
581 spinlock_t *lock;
582 void *data;
583
584 tbl = rcu_dereference(ht->tbl);
585
586 /* All insertions must grab the oldest table containing
587 * the hashed bucket that is yet to be rehashed.
588 */
589 for (;;) {
590 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
591 lock = rht_bucket_lock(tbl, hash);
592 spin_lock_bh(lock);
593
594 if (tbl->rehash <= hash)
595 break;
596
597 spin_unlock_bh(lock);
598 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
599 }
600
601 data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
602 new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
603 if (PTR_ERR(new_tbl) != -EEXIST)
604 data = ERR_CAST(new_tbl);
605
606 while (!IS_ERR_OR_NULL(new_tbl)) {
607 tbl = new_tbl;
608 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
609 spin_lock_nested(rht_bucket_lock(tbl, hash),
610 SINGLE_DEPTH_NESTING);
611
612 data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
613 new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
614 if (PTR_ERR(new_tbl) != -EEXIST)
615 data = ERR_CAST(new_tbl);
616
617 spin_unlock(rht_bucket_lock(tbl, hash));
618 }
619
620 spin_unlock_bh(lock);
621
622 if (PTR_ERR(data) == -EAGAIN)
623 data = ERR_PTR(rhashtable_insert_rehash(ht, tbl) ?:
624 -EAGAIN);
625
626 return data;
627}
628
629void *rhashtable_insert_slow(struct rhashtable *ht, const void *key,
630 struct rhash_head *obj)
631{
632 void *data;
633
634 do {
635 rcu_read_lock();
636 data = rhashtable_try_insert(ht, key, obj);
637 rcu_read_unlock();
638 } while (PTR_ERR(data) == -EAGAIN);
639
640 return data;
641}
642EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
643
644/**
645 * rhashtable_walk_enter - Initialise an iterator
646 * @ht: Table to walk over
647 * @iter: Hash table Iterator
648 *
649 * This function prepares a hash table walk.
650 *
651 * Note that if you restart a walk after rhashtable_walk_stop you
652 * may see the same object twice. Also, you may miss objects if
653 * there are removals in between rhashtable_walk_stop and the next
654 * call to rhashtable_walk_start.
655 *
656 * For a completely stable walk you should construct your own data
657 * structure outside the hash table.
658 *
659 * This function may be called from any process context, including
660 * non-preemptable context, but cannot be called from softirq or
661 * hardirq context.
662 *
663 * You must call rhashtable_walk_exit after this function returns.
664 */
665void rhashtable_walk_enter(struct rhashtable *ht, struct rhashtable_iter *iter)
666{
667 iter->ht = ht;
668 iter->p = NULL;
669 iter->slot = 0;
670 iter->skip = 0;
671 iter->end_of_table = 0;
672
673 spin_lock(&ht->lock);
674 iter->walker.tbl =
675 rcu_dereference_protected(ht->tbl, lockdep_is_held(&ht->lock));
676 list_add(&iter->walker.list, &iter->walker.tbl->walkers);
677 spin_unlock(&ht->lock);
678}
679EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
680
681/**
682 * rhashtable_walk_exit - Free an iterator
683 * @iter: Hash table Iterator
684 *
685 * This function frees resources allocated by rhashtable_walk_enter.
686 */
687void rhashtable_walk_exit(struct rhashtable_iter *iter)
688{
689 spin_lock(&iter->ht->lock);
690 if (iter->walker.tbl)
691 list_del(&iter->walker.list);
692 spin_unlock(&iter->ht->lock);
693}
694EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
695
696/**
697 * rhashtable_walk_start_check - Start a hash table walk
698 * @iter: Hash table iterator
699 *
700 * Start a hash table walk at the current iterator position. Note that we take
701 * the RCU lock in all cases including when we return an error. So you must
702 * always call rhashtable_walk_stop to clean up.
703 *
704 * Returns zero if successful.
705 *
706 * Returns -EAGAIN if resize event occured. Note that the iterator
707 * will rewind back to the beginning and you may use it immediately
708 * by calling rhashtable_walk_next.
709 *
710 * rhashtable_walk_start is defined as an inline variant that returns
711 * void. This is preferred in cases where the caller would ignore
712 * resize events and always continue.
713 */
714int rhashtable_walk_start_check(struct rhashtable_iter *iter)
715 __acquires(RCU)
716{
717 struct rhashtable *ht = iter->ht;
718 bool rhlist = ht->rhlist;
719
720 rcu_read_lock();
721
722 spin_lock(&ht->lock);
723 if (iter->walker.tbl)
724 list_del(&iter->walker.list);
725 spin_unlock(&ht->lock);
726
727 if (iter->end_of_table)
728 return 0;
729 if (!iter->walker.tbl) {
730 iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht);
731 iter->slot = 0;
732 iter->skip = 0;
733 return -EAGAIN;
734 }
735
736 if (iter->p && !rhlist) {
737 /*
738 * We need to validate that 'p' is still in the table, and
739 * if so, update 'skip'
740 */
741 struct rhash_head *p;
742 int skip = 0;
743 rht_for_each_rcu(p, iter->walker.tbl, iter->slot) {
744 skip++;
745 if (p == iter->p) {
746 iter->skip = skip;
747 goto found;
748 }
749 }
750 iter->p = NULL;
751 } else if (iter->p && rhlist) {
752 /* Need to validate that 'list' is still in the table, and
753 * if so, update 'skip' and 'p'.
754 */
755 struct rhash_head *p;
756 struct rhlist_head *list;
757 int skip = 0;
758 rht_for_each_rcu(p, iter->walker.tbl, iter->slot) {
759 for (list = container_of(p, struct rhlist_head, rhead);
760 list;
761 list = rcu_dereference(list->next)) {
762 skip++;
763 if (list == iter->list) {
764 iter->p = p;
765 iter->skip = skip;
766 goto found;
767 }
768 }
769 }
770 iter->p = NULL;
771 }
772found:
773 return 0;
774}
775EXPORT_SYMBOL_GPL(rhashtable_walk_start_check);
776
777/**
778 * __rhashtable_walk_find_next - Find the next element in a table (or the first
779 * one in case of a new walk).
780 *
781 * @iter: Hash table iterator
782 *
783 * Returns the found object or NULL when the end of the table is reached.
784 *
785 * Returns -EAGAIN if resize event occurred.
786 */
787static void *__rhashtable_walk_find_next(struct rhashtable_iter *iter)
788{
789 struct bucket_table *tbl = iter->walker.tbl;
790 struct rhlist_head *list = iter->list;
791 struct rhashtable *ht = iter->ht;
792 struct rhash_head *p = iter->p;
793 bool rhlist = ht->rhlist;
794
795 if (!tbl)
796 return NULL;
797
798 for (; iter->slot < tbl->size; iter->slot++) {
799 int skip = iter->skip;
800
801 rht_for_each_rcu(p, tbl, iter->slot) {
802 if (rhlist) {
803 list = container_of(p, struct rhlist_head,
804 rhead);
805 do {
806 if (!skip)
807 goto next;
808 skip--;
809 list = rcu_dereference(list->next);
810 } while (list);
811
812 continue;
813 }
814 if (!skip)
815 break;
816 skip--;
817 }
818
819next:
820 if (!rht_is_a_nulls(p)) {
821 iter->skip++;
822 iter->p = p;
823 iter->list = list;
824 return rht_obj(ht, rhlist ? &list->rhead : p);
825 }
826
827 iter->skip = 0;
828 }
829
830 iter->p = NULL;
831
832 /* Ensure we see any new tables. */
833 smp_rmb();
834
835 iter->walker.tbl = rht_dereference_rcu(tbl->future_tbl, ht);
836 if (iter->walker.tbl) {
837 iter->slot = 0;
838 iter->skip = 0;
839 return ERR_PTR(-EAGAIN);
840 } else {
841 iter->end_of_table = true;
842 }
843
844 return NULL;
845}
846
847/**
848 * rhashtable_walk_next - Return the next object and advance the iterator
849 * @iter: Hash table iterator
850 *
851 * Note that you must call rhashtable_walk_stop when you are finished
852 * with the walk.
853 *
854 * Returns the next object or NULL when the end of the table is reached.
855 *
856 * Returns -EAGAIN if resize event occurred. Note that the iterator
857 * will rewind back to the beginning and you may continue to use it.
858 */
859void *rhashtable_walk_next(struct rhashtable_iter *iter)
860{
861 struct rhlist_head *list = iter->list;
862 struct rhashtable *ht = iter->ht;
863 struct rhash_head *p = iter->p;
864 bool rhlist = ht->rhlist;
865
866 if (p) {
867 if (!rhlist || !(list = rcu_dereference(list->next))) {
868 p = rcu_dereference(p->next);
869 list = container_of(p, struct rhlist_head, rhead);
870 }
871 if (!rht_is_a_nulls(p)) {
872 iter->skip++;
873 iter->p = p;
874 iter->list = list;
875 return rht_obj(ht, rhlist ? &list->rhead : p);
876 }
877
878 /* At the end of this slot, switch to next one and then find
879 * next entry from that point.
880 */
881 iter->skip = 0;
882 iter->slot++;
883 }
884
885 return __rhashtable_walk_find_next(iter);
886}
887EXPORT_SYMBOL_GPL(rhashtable_walk_next);
888
889/**
890 * rhashtable_walk_peek - Return the next object but don't advance the iterator
891 * @iter: Hash table iterator
892 *
893 * Returns the next object or NULL when the end of the table is reached.
894 *
895 * Returns -EAGAIN if resize event occurred. Note that the iterator
896 * will rewind back to the beginning and you may continue to use it.
897 */
898void *rhashtable_walk_peek(struct rhashtable_iter *iter)
899{
900 struct rhlist_head *list = iter->list;
901 struct rhashtable *ht = iter->ht;
902 struct rhash_head *p = iter->p;
903
904 if (p)
905 return rht_obj(ht, ht->rhlist ? &list->rhead : p);
906
907 /* No object found in current iter, find next one in the table. */
908
909 if (iter->skip) {
910 /* A nonzero skip value points to the next entry in the table
911 * beyond that last one that was found. Decrement skip so
912 * we find the current value. __rhashtable_walk_find_next
913 * will restore the original value of skip assuming that
914 * the table hasn't changed.
915 */
916 iter->skip--;
917 }
918
919 return __rhashtable_walk_find_next(iter);
920}
921EXPORT_SYMBOL_GPL(rhashtable_walk_peek);
922
923/**
924 * rhashtable_walk_stop - Finish a hash table walk
925 * @iter: Hash table iterator
926 *
927 * Finish a hash table walk. Does not reset the iterator to the start of the
928 * hash table.
929 */
930void rhashtable_walk_stop(struct rhashtable_iter *iter)
931 __releases(RCU)
932{
933 struct rhashtable *ht;
934 struct bucket_table *tbl = iter->walker.tbl;
935
936 if (!tbl)
937 goto out;
938
939 ht = iter->ht;
940
941 spin_lock(&ht->lock);
942 if (tbl->rehash < tbl->size)
943 list_add(&iter->walker.list, &tbl->walkers);
944 else
945 iter->walker.tbl = NULL;
946 spin_unlock(&ht->lock);
947
948out:
949 rcu_read_unlock();
950}
951EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
952
953static size_t rounded_hashtable_size(const struct rhashtable_params *params)
954{
955 size_t retsize;
956
957 if (params->nelem_hint)
958 retsize = max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
959 (unsigned long)params->min_size);
960 else
961 retsize = max(HASH_DEFAULT_SIZE,
962 (unsigned long)params->min_size);
963
964 return retsize;
965}
966
967static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
968{
969 return jhash2(key, length, seed);
970}
971
972/**
973 * rhashtable_init - initialize a new hash table
974 * @ht: hash table to be initialized
975 * @params: configuration parameters
976 *
977 * Initializes a new hash table based on the provided configuration
978 * parameters. A table can be configured either with a variable or
979 * fixed length key:
980 *
981 * Configuration Example 1: Fixed length keys
982 * struct test_obj {
983 * int key;
984 * void * my_member;
985 * struct rhash_head node;
986 * };
987 *
988 * struct rhashtable_params params = {
989 * .head_offset = offsetof(struct test_obj, node),
990 * .key_offset = offsetof(struct test_obj, key),
991 * .key_len = sizeof(int),
992 * .hashfn = jhash,
993 * };
994 *
995 * Configuration Example 2: Variable length keys
996 * struct test_obj {
997 * [...]
998 * struct rhash_head node;
999 * };
1000 *
1001 * u32 my_hash_fn(const void *data, u32 len, u32 seed)
1002 * {
1003 * struct test_obj *obj = data;
1004 *
1005 * return [... hash ...];
1006 * }
1007 *
1008 * struct rhashtable_params params = {
1009 * .head_offset = offsetof(struct test_obj, node),
1010 * .hashfn = jhash,
1011 * .obj_hashfn = my_hash_fn,
1012 * };
1013 */
1014int rhashtable_init(struct rhashtable *ht,
1015 const struct rhashtable_params *params)
1016{
1017 struct bucket_table *tbl;
1018 size_t size;
1019
1020 if ((!params->key_len && !params->obj_hashfn) ||
1021 (params->obj_hashfn && !params->obj_cmpfn))
1022 return -EINVAL;
1023
1024 memset(ht, 0, sizeof(*ht));
1025 mutex_init(&ht->mutex);
1026 spin_lock_init(&ht->lock);
1027 memcpy(&ht->p, params, sizeof(*params));
1028
1029 if (params->min_size)
1030 ht->p.min_size = roundup_pow_of_two(params->min_size);
1031
1032 /* Cap total entries at 2^31 to avoid nelems overflow. */
1033 ht->max_elems = 1u << 31;
1034
1035 if (params->max_size) {
1036 ht->p.max_size = rounddown_pow_of_two(params->max_size);
1037 if (ht->p.max_size < ht->max_elems / 2)
1038 ht->max_elems = ht->p.max_size * 2;
1039 }
1040
1041 ht->p.min_size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
1042
1043 size = rounded_hashtable_size(&ht->p);
1044
1045 if (params->locks_mul)
1046 ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
1047 else
1048 ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
1049
1050 ht->key_len = ht->p.key_len;
1051 if (!params->hashfn) {
1052 ht->p.hashfn = jhash;
1053
1054 if (!(ht->key_len & (sizeof(u32) - 1))) {
1055 ht->key_len /= sizeof(u32);
1056 ht->p.hashfn = rhashtable_jhash2;
1057 }
1058 }
1059
1060 /*
1061 * This is api initialization and thus we need to guarantee the
1062 * initial rhashtable allocation. Upon failure, retry with the
1063 * smallest possible size with __GFP_NOFAIL semantics.
1064 */
1065 tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
1066 if (unlikely(tbl == NULL)) {
1067 size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
1068 tbl = bucket_table_alloc(ht, size, GFP_KERNEL | __GFP_NOFAIL);
1069 }
1070
1071 atomic_set(&ht->nelems, 0);
1072
1073 RCU_INIT_POINTER(ht->tbl, tbl);
1074
1075 INIT_WORK(&ht->run_work, rht_deferred_worker);
1076
1077 return 0;
1078}
1079EXPORT_SYMBOL_GPL(rhashtable_init);
1080
1081/**
1082 * rhltable_init - initialize a new hash list table
1083 * @hlt: hash list table to be initialized
1084 * @params: configuration parameters
1085 *
1086 * Initializes a new hash list table.
1087 *
1088 * See documentation for rhashtable_init.
1089 */
1090int rhltable_init(struct rhltable *hlt, const struct rhashtable_params *params)
1091{
1092 int err;
1093
1094 err = rhashtable_init(&hlt->ht, params);
1095 hlt->ht.rhlist = true;
1096 return err;
1097}
1098EXPORT_SYMBOL_GPL(rhltable_init);
1099
1100static void rhashtable_free_one(struct rhashtable *ht, struct rhash_head *obj,
1101 void (*free_fn)(void *ptr, void *arg),
1102 void *arg)
1103{
1104 struct rhlist_head *list;
1105
1106 if (!ht->rhlist) {
1107 free_fn(rht_obj(ht, obj), arg);
1108 return;
1109 }
1110
1111 list = container_of(obj, struct rhlist_head, rhead);
1112 do {
1113 obj = &list->rhead;
1114 list = rht_dereference(list->next, ht);
1115 free_fn(rht_obj(ht, obj), arg);
1116 } while (list);
1117}
1118
1119/**
1120 * rhashtable_free_and_destroy - free elements and destroy hash table
1121 * @ht: the hash table to destroy
1122 * @free_fn: callback to release resources of element
1123 * @arg: pointer passed to free_fn
1124 *
1125 * Stops an eventual async resize. If defined, invokes free_fn for each
1126 * element to releasal resources. Please note that RCU protected
1127 * readers may still be accessing the elements. Releasing of resources
1128 * must occur in a compatible manner. Then frees the bucket array.
1129 *
1130 * This function will eventually sleep to wait for an async resize
1131 * to complete. The caller is responsible that no further write operations
1132 * occurs in parallel.
1133 */
1134void rhashtable_free_and_destroy(struct rhashtable *ht,
1135 void (*free_fn)(void *ptr, void *arg),
1136 void *arg)
1137{
1138 struct bucket_table *tbl, *next_tbl;
1139 unsigned int i;
1140
1141 cancel_work_sync(&ht->run_work);
1142
1143 mutex_lock(&ht->mutex);
1144 tbl = rht_dereference(ht->tbl, ht);
1145restart:
1146 if (free_fn) {
1147 for (i = 0; i < tbl->size; i++) {
1148 struct rhash_head *pos, *next;
1149
1150 cond_resched();
1151 for (pos = rht_dereference(*rht_bucket(tbl, i), ht),
1152 next = !rht_is_a_nulls(pos) ?
1153 rht_dereference(pos->next, ht) : NULL;
1154 !rht_is_a_nulls(pos);
1155 pos = next,
1156 next = !rht_is_a_nulls(pos) ?
1157 rht_dereference(pos->next, ht) : NULL)
1158 rhashtable_free_one(ht, pos, free_fn, arg);
1159 }
1160 }
1161
1162 next_tbl = rht_dereference(tbl->future_tbl, ht);
1163 bucket_table_free(tbl);
1164 if (next_tbl) {
1165 tbl = next_tbl;
1166 goto restart;
1167 }
1168 mutex_unlock(&ht->mutex);
1169}
1170EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);
1171
1172void rhashtable_destroy(struct rhashtable *ht)
1173{
1174 return rhashtable_free_and_destroy(ht, NULL, NULL);
1175}
1176EXPORT_SYMBOL_GPL(rhashtable_destroy);
1177
1178struct rhash_head __rcu **rht_bucket_nested(const struct bucket_table *tbl,
1179 unsigned int hash)
1180{
1181 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1182 static struct rhash_head __rcu *rhnull;
1183 unsigned int index = hash & ((1 << tbl->nest) - 1);
1184 unsigned int size = tbl->size >> tbl->nest;
1185 unsigned int subhash = hash;
1186 union nested_table *ntbl;
1187
1188 ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
1189 ntbl = rht_dereference_bucket_rcu(ntbl[index].table, tbl, hash);
1190 subhash >>= tbl->nest;
1191
1192 while (ntbl && size > (1 << shift)) {
1193 index = subhash & ((1 << shift) - 1);
1194 ntbl = rht_dereference_bucket_rcu(ntbl[index].table,
1195 tbl, hash);
1196 size >>= shift;
1197 subhash >>= shift;
1198 }
1199
1200 if (!ntbl) {
1201 if (!rhnull)
1202 INIT_RHT_NULLS_HEAD(rhnull);
1203 return &rhnull;
1204 }
1205
1206 return &ntbl[subhash].bucket;
1207
1208}
1209EXPORT_SYMBOL_GPL(rht_bucket_nested);
1210
1211struct rhash_head __rcu **rht_bucket_nested_insert(struct rhashtable *ht,
1212 struct bucket_table *tbl,
1213 unsigned int hash)
1214{
1215 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1216 unsigned int index = hash & ((1 << tbl->nest) - 1);
1217 unsigned int size = tbl->size >> tbl->nest;
1218 union nested_table *ntbl;
1219
1220 ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
1221 hash >>= tbl->nest;
1222 ntbl = nested_table_alloc(ht, &ntbl[index].table,
1223 size <= (1 << shift));
1224
1225 while (ntbl && size > (1 << shift)) {
1226 index = hash & ((1 << shift) - 1);
1227 size >>= shift;
1228 hash >>= shift;
1229 ntbl = nested_table_alloc(ht, &ntbl[index].table,
1230 size <= (1 << shift));
1231 }
1232
1233 if (!ntbl)
1234 return NULL;
1235
1236 return &ntbl[hash].bucket;
1237
1238}
1239EXPORT_SYMBOL_GPL(rht_bucket_nested_insert);
1240