tipc: transfer broadcast nacks in link state messages
[cascardo/linux.git] / lib / rhashtable.c
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/slab.h>
23 #include <linux/vmalloc.h>
24 #include <linux/mm.h>
25 #include <linux/jhash.h>
26 #include <linux/random.h>
27 #include <linux/rhashtable.h>
28 #include <linux/err.h>
29 #include <linux/export.h>
30
31 #define HASH_DEFAULT_SIZE       64UL
32 #define HASH_MIN_SIZE           4U
33 #define BUCKET_LOCKS_PER_CPU    32UL
34
35 static u32 head_hashfn(struct rhashtable *ht,
36                        const struct bucket_table *tbl,
37                        const struct rhash_head *he)
38 {
39         return rht_head_hashfn(ht, tbl, he, ht->p);
40 }
41
42 #ifdef CONFIG_PROVE_LOCKING
43 #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
44
45 int lockdep_rht_mutex_is_held(struct rhashtable *ht)
46 {
47         return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
48 }
49 EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
50
51 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
52 {
53         spinlock_t *lock = rht_bucket_lock(tbl, hash);
54
55         return (debug_locks) ? lockdep_is_held(lock) : 1;
56 }
57 EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
58 #else
59 #define ASSERT_RHT_MUTEX(HT)
60 #endif
61
62
63 static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
64                               gfp_t gfp)
65 {
66         unsigned int i, size;
67 #if defined(CONFIG_PROVE_LOCKING)
68         unsigned int nr_pcpus = 2;
69 #else
70         unsigned int nr_pcpus = num_possible_cpus();
71 #endif
72
73         nr_pcpus = min_t(unsigned int, nr_pcpus, 64UL);
74         size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul);
75
76         /* Never allocate more than 0.5 locks per bucket */
77         size = min_t(unsigned int, size, tbl->size >> 1);
78
79         if (sizeof(spinlock_t) != 0) {
80                 tbl->locks = NULL;
81 #ifdef CONFIG_NUMA
82                 if (size * sizeof(spinlock_t) > PAGE_SIZE &&
83                     gfp == GFP_KERNEL)
84                         tbl->locks = vmalloc(size * sizeof(spinlock_t));
85 #endif
86                 if (gfp != GFP_KERNEL)
87                         gfp |= __GFP_NOWARN | __GFP_NORETRY;
88
89                 if (!tbl->locks)
90                         tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
91                                                    gfp);
92                 if (!tbl->locks)
93                         return -ENOMEM;
94                 for (i = 0; i < size; i++)
95                         spin_lock_init(&tbl->locks[i]);
96         }
97         tbl->locks_mask = size - 1;
98
99         return 0;
100 }
101
102 static void bucket_table_free(const struct bucket_table *tbl)
103 {
104         if (tbl)
105                 kvfree(tbl->locks);
106
107         kvfree(tbl);
108 }
109
110 static void bucket_table_free_rcu(struct rcu_head *head)
111 {
112         bucket_table_free(container_of(head, struct bucket_table, rcu));
113 }
114
115 static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
116                                                size_t nbuckets,
117                                                gfp_t gfp)
118 {
119         struct bucket_table *tbl = NULL;
120         size_t size;
121         int i;
122
123         size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
124         if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER) ||
125             gfp != GFP_KERNEL)
126                 tbl = kzalloc(size, gfp | __GFP_NOWARN | __GFP_NORETRY);
127         if (tbl == NULL && gfp == GFP_KERNEL)
128                 tbl = vzalloc(size);
129         if (tbl == NULL)
130                 return NULL;
131
132         tbl->size = nbuckets;
133
134         if (alloc_bucket_locks(ht, tbl, gfp) < 0) {
135                 bucket_table_free(tbl);
136                 return NULL;
137         }
138
139         INIT_LIST_HEAD(&tbl->walkers);
140
141         get_random_bytes(&tbl->hash_rnd, sizeof(tbl->hash_rnd));
142
143         for (i = 0; i < nbuckets; i++)
144                 INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i);
145
146         return tbl;
147 }
148
149 static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
150                                                   struct bucket_table *tbl)
151 {
152         struct bucket_table *new_tbl;
153
154         do {
155                 new_tbl = tbl;
156                 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
157         } while (tbl);
158
159         return new_tbl;
160 }
161
162 static int rhashtable_rehash_one(struct rhashtable *ht, unsigned int old_hash)
163 {
164         struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
165         struct bucket_table *new_tbl = rhashtable_last_table(ht,
166                 rht_dereference_rcu(old_tbl->future_tbl, ht));
167         struct rhash_head __rcu **pprev = &old_tbl->buckets[old_hash];
168         int err = -ENOENT;
169         struct rhash_head *head, *next, *entry;
170         spinlock_t *new_bucket_lock;
171         unsigned int new_hash;
172
173         rht_for_each(entry, old_tbl, old_hash) {
174                 err = 0;
175                 next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
176
177                 if (rht_is_a_nulls(next))
178                         break;
179
180                 pprev = &entry->next;
181         }
182
183         if (err)
184                 goto out;
185
186         new_hash = head_hashfn(ht, new_tbl, entry);
187
188         new_bucket_lock = rht_bucket_lock(new_tbl, new_hash);
189
190         spin_lock_nested(new_bucket_lock, SINGLE_DEPTH_NESTING);
191         head = rht_dereference_bucket(new_tbl->buckets[new_hash],
192                                       new_tbl, new_hash);
193
194         RCU_INIT_POINTER(entry->next, head);
195
196         rcu_assign_pointer(new_tbl->buckets[new_hash], entry);
197         spin_unlock(new_bucket_lock);
198
199         rcu_assign_pointer(*pprev, next);
200
201 out:
202         return err;
203 }
204
205 static void rhashtable_rehash_chain(struct rhashtable *ht,
206                                     unsigned int old_hash)
207 {
208         struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
209         spinlock_t *old_bucket_lock;
210
211         old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
212
213         spin_lock_bh(old_bucket_lock);
214         while (!rhashtable_rehash_one(ht, old_hash))
215                 ;
216         old_tbl->rehash++;
217         spin_unlock_bh(old_bucket_lock);
218 }
219
220 static int rhashtable_rehash_attach(struct rhashtable *ht,
221                                     struct bucket_table *old_tbl,
222                                     struct bucket_table *new_tbl)
223 {
224         /* Protect future_tbl using the first bucket lock. */
225         spin_lock_bh(old_tbl->locks);
226
227         /* Did somebody beat us to it? */
228         if (rcu_access_pointer(old_tbl->future_tbl)) {
229                 spin_unlock_bh(old_tbl->locks);
230                 return -EEXIST;
231         }
232
233         /* Make insertions go into the new, empty table right away. Deletions
234          * and lookups will be attempted in both tables until we synchronize.
235          */
236         rcu_assign_pointer(old_tbl->future_tbl, new_tbl);
237
238         spin_unlock_bh(old_tbl->locks);
239
240         return 0;
241 }
242
243 static int rhashtable_rehash_table(struct rhashtable *ht)
244 {
245         struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
246         struct bucket_table *new_tbl;
247         struct rhashtable_walker *walker;
248         unsigned int old_hash;
249
250         new_tbl = rht_dereference(old_tbl->future_tbl, ht);
251         if (!new_tbl)
252                 return 0;
253
254         for (old_hash = 0; old_hash < old_tbl->size; old_hash++)
255                 rhashtable_rehash_chain(ht, old_hash);
256
257         /* Publish the new table pointer. */
258         rcu_assign_pointer(ht->tbl, new_tbl);
259
260         spin_lock(&ht->lock);
261         list_for_each_entry(walker, &old_tbl->walkers, list)
262                 walker->tbl = NULL;
263         spin_unlock(&ht->lock);
264
265         /* Wait for readers. All new readers will see the new
266          * table, and thus no references to the old table will
267          * remain.
268          */
269         call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
270
271         return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
272 }
273
274 /**
275  * rhashtable_expand - Expand hash table while allowing concurrent lookups
276  * @ht:         the hash table to expand
277  *
278  * A secondary bucket array is allocated and the hash entries are migrated.
279  *
280  * This function may only be called in a context where it is safe to call
281  * synchronize_rcu(), e.g. not within a rcu_read_lock() section.
282  *
283  * The caller must ensure that no concurrent resizing occurs by holding
284  * ht->mutex.
285  *
286  * It is valid to have concurrent insertions and deletions protected by per
287  * bucket locks or concurrent RCU protected lookups and traversals.
288  */
289 static int rhashtable_expand(struct rhashtable *ht)
290 {
291         struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
292         int err;
293
294         ASSERT_RHT_MUTEX(ht);
295
296         old_tbl = rhashtable_last_table(ht, old_tbl);
297
298         new_tbl = bucket_table_alloc(ht, old_tbl->size * 2, GFP_KERNEL);
299         if (new_tbl == NULL)
300                 return -ENOMEM;
301
302         err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
303         if (err)
304                 bucket_table_free(new_tbl);
305
306         return err;
307 }
308
309 /**
310  * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
311  * @ht:         the hash table to shrink
312  *
313  * This function shrinks the hash table to fit, i.e., the smallest
314  * size would not cause it to expand right away automatically.
315  *
316  * The caller must ensure that no concurrent resizing occurs by holding
317  * ht->mutex.
318  *
319  * The caller must ensure that no concurrent table mutations take place.
320  * It is however valid to have concurrent lookups if they are RCU protected.
321  *
322  * It is valid to have concurrent insertions and deletions protected by per
323  * bucket locks or concurrent RCU protected lookups and traversals.
324  */
325 static int rhashtable_shrink(struct rhashtable *ht)
326 {
327         struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
328         unsigned int nelems = atomic_read(&ht->nelems);
329         unsigned int size = 0;
330         int err;
331
332         ASSERT_RHT_MUTEX(ht);
333
334         if (nelems)
335                 size = roundup_pow_of_two(nelems * 3 / 2);
336         if (size < ht->p.min_size)
337                 size = ht->p.min_size;
338
339         if (old_tbl->size <= size)
340                 return 0;
341
342         if (rht_dereference(old_tbl->future_tbl, ht))
343                 return -EEXIST;
344
345         new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
346         if (new_tbl == NULL)
347                 return -ENOMEM;
348
349         err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
350         if (err)
351                 bucket_table_free(new_tbl);
352
353         return err;
354 }
355
356 static void rht_deferred_worker(struct work_struct *work)
357 {
358         struct rhashtable *ht;
359         struct bucket_table *tbl;
360         int err = 0;
361
362         ht = container_of(work, struct rhashtable, run_work);
363         mutex_lock(&ht->mutex);
364
365         tbl = rht_dereference(ht->tbl, ht);
366         tbl = rhashtable_last_table(ht, tbl);
367
368         if (rht_grow_above_75(ht, tbl))
369                 rhashtable_expand(ht);
370         else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
371                 rhashtable_shrink(ht);
372
373         err = rhashtable_rehash_table(ht);
374
375         mutex_unlock(&ht->mutex);
376
377         if (err)
378                 schedule_work(&ht->run_work);
379 }
380
381 static bool rhashtable_check_elasticity(struct rhashtable *ht,
382                                         struct bucket_table *tbl,
383                                         unsigned int hash)
384 {
385         unsigned int elasticity = ht->elasticity;
386         struct rhash_head *head;
387
388         rht_for_each(head, tbl, hash)
389                 if (!--elasticity)
390                         return true;
391
392         return false;
393 }
394
395 int rhashtable_insert_rehash(struct rhashtable *ht,
396                              struct bucket_table *tbl)
397 {
398         struct bucket_table *old_tbl;
399         struct bucket_table *new_tbl;
400         unsigned int size;
401         int err;
402
403         old_tbl = rht_dereference_rcu(ht->tbl, ht);
404
405         size = tbl->size;
406
407         err = -EBUSY;
408
409         if (rht_grow_above_75(ht, tbl))
410                 size *= 2;
411         /* Do not schedule more than one rehash */
412         else if (old_tbl != tbl)
413                 goto fail;
414
415         err = -ENOMEM;
416
417         new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC);
418         if (new_tbl == NULL)
419                 goto fail;
420
421         err = rhashtable_rehash_attach(ht, tbl, new_tbl);
422         if (err) {
423                 bucket_table_free(new_tbl);
424                 if (err == -EEXIST)
425                         err = 0;
426         } else
427                 schedule_work(&ht->run_work);
428
429         return err;
430
431 fail:
432         /* Do not fail the insert if someone else did a rehash. */
433         if (likely(rcu_dereference_raw(tbl->future_tbl)))
434                 return 0;
435
436         /* Schedule async rehash to retry allocation in process context. */
437         if (err == -ENOMEM)
438                 schedule_work(&ht->run_work);
439
440         return err;
441 }
442 EXPORT_SYMBOL_GPL(rhashtable_insert_rehash);
443
444 struct bucket_table *rhashtable_insert_slow(struct rhashtable *ht,
445                                             const void *key,
446                                             struct rhash_head *obj,
447                                             struct bucket_table *tbl)
448 {
449         struct rhash_head *head;
450         unsigned int hash;
451         int err;
452
453         tbl = rhashtable_last_table(ht, tbl);
454         hash = head_hashfn(ht, tbl, obj);
455         spin_lock_nested(rht_bucket_lock(tbl, hash), SINGLE_DEPTH_NESTING);
456
457         err = -EEXIST;
458         if (key && rhashtable_lookup_fast(ht, key, ht->p))
459                 goto exit;
460
461         err = -E2BIG;
462         if (unlikely(rht_grow_above_max(ht, tbl)))
463                 goto exit;
464
465         err = -EAGAIN;
466         if (rhashtable_check_elasticity(ht, tbl, hash) ||
467             rht_grow_above_100(ht, tbl))
468                 goto exit;
469
470         err = 0;
471
472         head = rht_dereference_bucket(tbl->buckets[hash], tbl, hash);
473
474         RCU_INIT_POINTER(obj->next, head);
475
476         rcu_assign_pointer(tbl->buckets[hash], obj);
477
478         atomic_inc(&ht->nelems);
479
480 exit:
481         spin_unlock(rht_bucket_lock(tbl, hash));
482
483         if (err == 0)
484                 return NULL;
485         else if (err == -EAGAIN)
486                 return tbl;
487         else
488                 return ERR_PTR(err);
489 }
490 EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
491
492 /**
493  * rhashtable_walk_enter - Initialise an iterator
494  * @ht:         Table to walk over
495  * @iter:       Hash table Iterator
496  *
497  * This function prepares a hash table walk.
498  *
499  * Note that if you restart a walk after rhashtable_walk_stop you
500  * may see the same object twice.  Also, you may miss objects if
501  * there are removals in between rhashtable_walk_stop and the next
502  * call to rhashtable_walk_start.
503  *
504  * For a completely stable walk you should construct your own data
505  * structure outside the hash table.
506  *
507  * This function may sleep so you must not call it from interrupt
508  * context or with spin locks held.
509  *
510  * You must call rhashtable_walk_exit after this function returns.
511  */
512 void rhashtable_walk_enter(struct rhashtable *ht, struct rhashtable_iter *iter)
513 {
514         iter->ht = ht;
515         iter->p = NULL;
516         iter->slot = 0;
517         iter->skip = 0;
518
519         spin_lock(&ht->lock);
520         iter->walker.tbl =
521                 rcu_dereference_protected(ht->tbl, lockdep_is_held(&ht->lock));
522         list_add(&iter->walker.list, &iter->walker.tbl->walkers);
523         spin_unlock(&ht->lock);
524 }
525 EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
526
527 /**
528  * rhashtable_walk_exit - Free an iterator
529  * @iter:       Hash table Iterator
530  *
531  * This function frees resources allocated by rhashtable_walk_init.
532  */
533 void rhashtable_walk_exit(struct rhashtable_iter *iter)
534 {
535         spin_lock(&iter->ht->lock);
536         if (iter->walker.tbl)
537                 list_del(&iter->walker.list);
538         spin_unlock(&iter->ht->lock);
539 }
540 EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
541
542 /**
543  * rhashtable_walk_start - Start a hash table walk
544  * @iter:       Hash table iterator
545  *
546  * Start a hash table walk.  Note that we take the RCU lock in all
547  * cases including when we return an error.  So you must always call
548  * rhashtable_walk_stop to clean up.
549  *
550  * Returns zero if successful.
551  *
552  * Returns -EAGAIN if resize event occured.  Note that the iterator
553  * will rewind back to the beginning and you may use it immediately
554  * by calling rhashtable_walk_next.
555  */
556 int rhashtable_walk_start(struct rhashtable_iter *iter)
557         __acquires(RCU)
558 {
559         struct rhashtable *ht = iter->ht;
560
561         rcu_read_lock();
562
563         spin_lock(&ht->lock);
564         if (iter->walker.tbl)
565                 list_del(&iter->walker.list);
566         spin_unlock(&ht->lock);
567
568         if (!iter->walker.tbl) {
569                 iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht);
570                 return -EAGAIN;
571         }
572
573         return 0;
574 }
575 EXPORT_SYMBOL_GPL(rhashtable_walk_start);
576
577 /**
578  * rhashtable_walk_next - Return the next object and advance the iterator
579  * @iter:       Hash table iterator
580  *
581  * Note that you must call rhashtable_walk_stop when you are finished
582  * with the walk.
583  *
584  * Returns the next object or NULL when the end of the table is reached.
585  *
586  * Returns -EAGAIN if resize event occured.  Note that the iterator
587  * will rewind back to the beginning and you may continue to use it.
588  */
589 void *rhashtable_walk_next(struct rhashtable_iter *iter)
590 {
591         struct bucket_table *tbl = iter->walker.tbl;
592         struct rhashtable *ht = iter->ht;
593         struct rhash_head *p = iter->p;
594
595         if (p) {
596                 p = rht_dereference_bucket_rcu(p->next, tbl, iter->slot);
597                 goto next;
598         }
599
600         for (; iter->slot < tbl->size; iter->slot++) {
601                 int skip = iter->skip;
602
603                 rht_for_each_rcu(p, tbl, iter->slot) {
604                         if (!skip)
605                                 break;
606                         skip--;
607                 }
608
609 next:
610                 if (!rht_is_a_nulls(p)) {
611                         iter->skip++;
612                         iter->p = p;
613                         return rht_obj(ht, p);
614                 }
615
616                 iter->skip = 0;
617         }
618
619         iter->p = NULL;
620
621         /* Ensure we see any new tables. */
622         smp_rmb();
623
624         iter->walker.tbl = rht_dereference_rcu(tbl->future_tbl, ht);
625         if (iter->walker.tbl) {
626                 iter->slot = 0;
627                 iter->skip = 0;
628                 return ERR_PTR(-EAGAIN);
629         }
630
631         return NULL;
632 }
633 EXPORT_SYMBOL_GPL(rhashtable_walk_next);
634
635 /**
636  * rhashtable_walk_stop - Finish a hash table walk
637  * @iter:       Hash table iterator
638  *
639  * Finish a hash table walk.
640  */
641 void rhashtable_walk_stop(struct rhashtable_iter *iter)
642         __releases(RCU)
643 {
644         struct rhashtable *ht;
645         struct bucket_table *tbl = iter->walker.tbl;
646
647         if (!tbl)
648                 goto out;
649
650         ht = iter->ht;
651
652         spin_lock(&ht->lock);
653         if (tbl->rehash < tbl->size)
654                 list_add(&iter->walker.list, &tbl->walkers);
655         else
656                 iter->walker.tbl = NULL;
657         spin_unlock(&ht->lock);
658
659         iter->p = NULL;
660
661 out:
662         rcu_read_unlock();
663 }
664 EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
665
666 static size_t rounded_hashtable_size(const struct rhashtable_params *params)
667 {
668         return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
669                    (unsigned long)params->min_size);
670 }
671
672 static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
673 {
674         return jhash2(key, length, seed);
675 }
676
677 /**
678  * rhashtable_init - initialize a new hash table
679  * @ht:         hash table to be initialized
680  * @params:     configuration parameters
681  *
682  * Initializes a new hash table based on the provided configuration
683  * parameters. A table can be configured either with a variable or
684  * fixed length key:
685  *
686  * Configuration Example 1: Fixed length keys
687  * struct test_obj {
688  *      int                     key;
689  *      void *                  my_member;
690  *      struct rhash_head       node;
691  * };
692  *
693  * struct rhashtable_params params = {
694  *      .head_offset = offsetof(struct test_obj, node),
695  *      .key_offset = offsetof(struct test_obj, key),
696  *      .key_len = sizeof(int),
697  *      .hashfn = jhash,
698  *      .nulls_base = (1U << RHT_BASE_SHIFT),
699  * };
700  *
701  * Configuration Example 2: Variable length keys
702  * struct test_obj {
703  *      [...]
704  *      struct rhash_head       node;
705  * };
706  *
707  * u32 my_hash_fn(const void *data, u32 len, u32 seed)
708  * {
709  *      struct test_obj *obj = data;
710  *
711  *      return [... hash ...];
712  * }
713  *
714  * struct rhashtable_params params = {
715  *      .head_offset = offsetof(struct test_obj, node),
716  *      .hashfn = jhash,
717  *      .obj_hashfn = my_hash_fn,
718  * };
719  */
720 int rhashtable_init(struct rhashtable *ht,
721                     const struct rhashtable_params *params)
722 {
723         struct bucket_table *tbl;
724         size_t size;
725
726         size = HASH_DEFAULT_SIZE;
727
728         if ((!params->key_len && !params->obj_hashfn) ||
729             (params->obj_hashfn && !params->obj_cmpfn))
730                 return -EINVAL;
731
732         if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
733                 return -EINVAL;
734
735         memset(ht, 0, sizeof(*ht));
736         mutex_init(&ht->mutex);
737         spin_lock_init(&ht->lock);
738         memcpy(&ht->p, params, sizeof(*params));
739
740         if (params->min_size)
741                 ht->p.min_size = roundup_pow_of_two(params->min_size);
742
743         if (params->max_size)
744                 ht->p.max_size = rounddown_pow_of_two(params->max_size);
745
746         if (params->insecure_max_entries)
747                 ht->p.insecure_max_entries =
748                         rounddown_pow_of_two(params->insecure_max_entries);
749         else
750                 ht->p.insecure_max_entries = ht->p.max_size * 2;
751
752         ht->p.min_size = max(ht->p.min_size, HASH_MIN_SIZE);
753
754         if (params->nelem_hint)
755                 size = rounded_hashtable_size(&ht->p);
756
757         /* The maximum (not average) chain length grows with the
758          * size of the hash table, at a rate of (log N)/(log log N).
759          * The value of 16 is selected so that even if the hash
760          * table grew to 2^32 you would not expect the maximum
761          * chain length to exceed it unless we are under attack
762          * (or extremely unlucky).
763          *
764          * As this limit is only to detect attacks, we don't need
765          * to set it to a lower value as you'd need the chain
766          * length to vastly exceed 16 to have any real effect
767          * on the system.
768          */
769         if (!params->insecure_elasticity)
770                 ht->elasticity = 16;
771
772         if (params->locks_mul)
773                 ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
774         else
775                 ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
776
777         ht->key_len = ht->p.key_len;
778         if (!params->hashfn) {
779                 ht->p.hashfn = jhash;
780
781                 if (!(ht->key_len & (sizeof(u32) - 1))) {
782                         ht->key_len /= sizeof(u32);
783                         ht->p.hashfn = rhashtable_jhash2;
784                 }
785         }
786
787         tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
788         if (tbl == NULL)
789                 return -ENOMEM;
790
791         atomic_set(&ht->nelems, 0);
792
793         RCU_INIT_POINTER(ht->tbl, tbl);
794
795         INIT_WORK(&ht->run_work, rht_deferred_worker);
796
797         return 0;
798 }
799 EXPORT_SYMBOL_GPL(rhashtable_init);
800
801 /**
802  * rhashtable_free_and_destroy - free elements and destroy hash table
803  * @ht:         the hash table to destroy
804  * @free_fn:    callback to release resources of element
805  * @arg:        pointer passed to free_fn
806  *
807  * Stops an eventual async resize. If defined, invokes free_fn for each
808  * element to releasal resources. Please note that RCU protected
809  * readers may still be accessing the elements. Releasing of resources
810  * must occur in a compatible manner. Then frees the bucket array.
811  *
812  * This function will eventually sleep to wait for an async resize
813  * to complete. The caller is responsible that no further write operations
814  * occurs in parallel.
815  */
816 void rhashtable_free_and_destroy(struct rhashtable *ht,
817                                  void (*free_fn)(void *ptr, void *arg),
818                                  void *arg)
819 {
820         const struct bucket_table *tbl;
821         unsigned int i;
822
823         cancel_work_sync(&ht->run_work);
824
825         mutex_lock(&ht->mutex);
826         tbl = rht_dereference(ht->tbl, ht);
827         if (free_fn) {
828                 for (i = 0; i < tbl->size; i++) {
829                         struct rhash_head *pos, *next;
830
831                         for (pos = rht_dereference(tbl->buckets[i], ht),
832                              next = !rht_is_a_nulls(pos) ?
833                                         rht_dereference(pos->next, ht) : NULL;
834                              !rht_is_a_nulls(pos);
835                              pos = next,
836                              next = !rht_is_a_nulls(pos) ?
837                                         rht_dereference(pos->next, ht) : NULL)
838                                 free_fn(rht_obj(ht, pos), arg);
839                 }
840         }
841
842         bucket_table_free(tbl);
843         mutex_unlock(&ht->mutex);
844 }
845 EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);
846
847 void rhashtable_destroy(struct rhashtable *ht)
848 {
849         return rhashtable_free_and_destroy(ht, NULL, NULL);
850 }
851 EXPORT_SYMBOL_GPL(rhashtable_destroy);