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Merge branch 'mlxsw-fixes'
[karo-tx-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/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
36 union nested_table {
37         union nested_table __rcu *table;
38         struct rhash_head __rcu *bucket;
39 };
40
41 static 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
51 int lockdep_rht_mutex_is_held(struct rhashtable *ht)
52 {
53         return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
54 }
55 EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
56
57 int 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 }
63 EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
64 #else
65 #define ASSERT_RHT_MUTEX(HT)
66 #endif
67
68
69 static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
70                               gfp_t gfp)
71 {
72         unsigned int i, size;
73 #if defined(CONFIG_PROVE_LOCKING)
74         unsigned int nr_pcpus = 2;
75 #else
76         unsigned int nr_pcpus = num_possible_cpus();
77 #endif
78
79         nr_pcpus = min_t(unsigned int, nr_pcpus, 64UL);
80         size = roundup_pow_of_two(nr_pcpus * ht->p.locks_mul);
81
82         /* Never allocate more than 0.5 locks per bucket */
83         size = min_t(unsigned int, size, tbl->size >> 1);
84
85         if (tbl->nest)
86                 size = min(size, 1U << tbl->nest);
87
88         if (sizeof(spinlock_t) != 0) {
89                 if (gfpflags_allow_blocking(gfp))
90                         tbl->locks = kvmalloc(size * sizeof(spinlock_t), gfp);
91                 else
92                         tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
93                                                    gfp);
94                 if (!tbl->locks)
95                         return -ENOMEM;
96                 for (i = 0; i < size; i++)
97                         spin_lock_init(&tbl->locks[i]);
98         }
99         tbl->locks_mask = size - 1;
100
101         return 0;
102 }
103
104 static void nested_table_free(union nested_table *ntbl, unsigned int size)
105 {
106         const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
107         const unsigned int len = 1 << shift;
108         unsigned int i;
109
110         ntbl = rcu_dereference_raw(ntbl->table);
111         if (!ntbl)
112                 return;
113
114         if (size > len) {
115                 size >>= shift;
116                 for (i = 0; i < len; i++)
117                         nested_table_free(ntbl + i, size);
118         }
119
120         kfree(ntbl);
121 }
122
123 static void nested_bucket_table_free(const struct bucket_table *tbl)
124 {
125         unsigned int size = tbl->size >> tbl->nest;
126         unsigned int len = 1 << tbl->nest;
127         union nested_table *ntbl;
128         unsigned int i;
129
130         ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
131
132         for (i = 0; i < len; i++)
133                 nested_table_free(ntbl + i, size);
134
135         kfree(ntbl);
136 }
137
138 static void bucket_table_free(const struct bucket_table *tbl)
139 {
140         if (tbl->nest)
141                 nested_bucket_table_free(tbl);
142
143         kvfree(tbl->locks);
144         kvfree(tbl);
145 }
146
147 static void bucket_table_free_rcu(struct rcu_head *head)
148 {
149         bucket_table_free(container_of(head, struct bucket_table, rcu));
150 }
151
152 static union nested_table *nested_table_alloc(struct rhashtable *ht,
153                                               union nested_table __rcu **prev,
154                                               unsigned int shifted,
155                                               unsigned int nhash)
156 {
157         union nested_table *ntbl;
158         int i;
159
160         ntbl = rcu_dereference(*prev);
161         if (ntbl)
162                 return ntbl;
163
164         ntbl = kzalloc(PAGE_SIZE, GFP_ATOMIC);
165
166         if (ntbl && shifted) {
167                 for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0].bucket); i++)
168                         INIT_RHT_NULLS_HEAD(ntbl[i].bucket, ht,
169                                             (i << shifted) | nhash);
170         }
171
172         rcu_assign_pointer(*prev, ntbl);
173
174         return ntbl;
175 }
176
177 static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht,
178                                                       size_t nbuckets,
179                                                       gfp_t gfp)
180 {
181         const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
182         struct bucket_table *tbl;
183         size_t size;
184
185         if (nbuckets < (1 << (shift + 1)))
186                 return NULL;
187
188         size = sizeof(*tbl) + sizeof(tbl->buckets[0]);
189
190         tbl = kzalloc(size, gfp);
191         if (!tbl)
192                 return NULL;
193
194         if (!nested_table_alloc(ht, (union nested_table __rcu **)tbl->buckets,
195                                 0, 0)) {
196                 kfree(tbl);
197                 return NULL;
198         }
199
200         tbl->nest = (ilog2(nbuckets) - 1) % shift + 1;
201
202         return tbl;
203 }
204
205 static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
206                                                size_t nbuckets,
207                                                gfp_t gfp)
208 {
209         struct bucket_table *tbl = NULL;
210         size_t size;
211         int i;
212
213         size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
214         if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER) ||
215             gfp != GFP_KERNEL)
216                 tbl = kzalloc(size, gfp | __GFP_NOWARN | __GFP_NORETRY);
217         if (tbl == NULL && gfp == GFP_KERNEL)
218                 tbl = vzalloc(size);
219
220         size = nbuckets;
221
222         if (tbl == NULL && gfp != GFP_KERNEL) {
223                 tbl = nested_bucket_table_alloc(ht, nbuckets, gfp);
224                 nbuckets = 0;
225         }
226         if (tbl == NULL)
227                 return NULL;
228
229         tbl->size = size;
230
231         if (alloc_bucket_locks(ht, tbl, gfp) < 0) {
232                 bucket_table_free(tbl);
233                 return NULL;
234         }
235
236         INIT_LIST_HEAD(&tbl->walkers);
237
238         get_random_bytes(&tbl->hash_rnd, sizeof(tbl->hash_rnd));
239
240         for (i = 0; i < nbuckets; i++)
241                 INIT_RHT_NULLS_HEAD(tbl->buckets[i], ht, i);
242
243         return tbl;
244 }
245
246 static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
247                                                   struct bucket_table *tbl)
248 {
249         struct bucket_table *new_tbl;
250
251         do {
252                 new_tbl = tbl;
253                 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
254         } while (tbl);
255
256         return new_tbl;
257 }
258
259 static int rhashtable_rehash_one(struct rhashtable *ht, unsigned int old_hash)
260 {
261         struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
262         struct bucket_table *new_tbl = rhashtable_last_table(ht,
263                 rht_dereference_rcu(old_tbl->future_tbl, ht));
264         struct rhash_head __rcu **pprev = rht_bucket_var(old_tbl, old_hash);
265         int err = -EAGAIN;
266         struct rhash_head *head, *next, *entry;
267         spinlock_t *new_bucket_lock;
268         unsigned int new_hash;
269
270         if (new_tbl->nest)
271                 goto out;
272
273         err = -ENOENT;
274
275         rht_for_each(entry, old_tbl, old_hash) {
276                 err = 0;
277                 next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
278
279                 if (rht_is_a_nulls(next))
280                         break;
281
282                 pprev = &entry->next;
283         }
284
285         if (err)
286                 goto out;
287
288         new_hash = head_hashfn(ht, new_tbl, entry);
289
290         new_bucket_lock = rht_bucket_lock(new_tbl, new_hash);
291
292         spin_lock_nested(new_bucket_lock, SINGLE_DEPTH_NESTING);
293         head = rht_dereference_bucket(new_tbl->buckets[new_hash],
294                                       new_tbl, new_hash);
295
296         RCU_INIT_POINTER(entry->next, head);
297
298         rcu_assign_pointer(new_tbl->buckets[new_hash], entry);
299         spin_unlock(new_bucket_lock);
300
301         rcu_assign_pointer(*pprev, next);
302
303 out:
304         return err;
305 }
306
307 static int rhashtable_rehash_chain(struct rhashtable *ht,
308                                     unsigned int old_hash)
309 {
310         struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
311         spinlock_t *old_bucket_lock;
312         int err;
313
314         old_bucket_lock = rht_bucket_lock(old_tbl, old_hash);
315
316         spin_lock_bh(old_bucket_lock);
317         while (!(err = rhashtable_rehash_one(ht, old_hash)))
318                 ;
319
320         if (err == -ENOENT) {
321                 old_tbl->rehash++;
322                 err = 0;
323         }
324         spin_unlock_bh(old_bucket_lock);
325
326         return err;
327 }
328
329 static int rhashtable_rehash_attach(struct rhashtable *ht,
330                                     struct bucket_table *old_tbl,
331                                     struct bucket_table *new_tbl)
332 {
333         /* Protect future_tbl using the first bucket lock. */
334         spin_lock_bh(old_tbl->locks);
335
336         /* Did somebody beat us to it? */
337         if (rcu_access_pointer(old_tbl->future_tbl)) {
338                 spin_unlock_bh(old_tbl->locks);
339                 return -EEXIST;
340         }
341
342         /* Make insertions go into the new, empty table right away. Deletions
343          * and lookups will be attempted in both tables until we synchronize.
344          */
345         rcu_assign_pointer(old_tbl->future_tbl, new_tbl);
346
347         spin_unlock_bh(old_tbl->locks);
348
349         return 0;
350 }
351
352 static int rhashtable_rehash_table(struct rhashtable *ht)
353 {
354         struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
355         struct bucket_table *new_tbl;
356         struct rhashtable_walker *walker;
357         unsigned int old_hash;
358         int err;
359
360         new_tbl = rht_dereference(old_tbl->future_tbl, ht);
361         if (!new_tbl)
362                 return 0;
363
364         for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
365                 err = rhashtable_rehash_chain(ht, old_hash);
366                 if (err)
367                         return err;
368         }
369
370         /* Publish the new table pointer. */
371         rcu_assign_pointer(ht->tbl, new_tbl);
372
373         spin_lock(&ht->lock);
374         list_for_each_entry(walker, &old_tbl->walkers, list)
375                 walker->tbl = NULL;
376         spin_unlock(&ht->lock);
377
378         /* Wait for readers. All new readers will see the new
379          * table, and thus no references to the old table will
380          * remain.
381          */
382         call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
383
384         return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
385 }
386
387 static int rhashtable_rehash_alloc(struct rhashtable *ht,
388                                    struct bucket_table *old_tbl,
389                                    unsigned int size)
390 {
391         struct bucket_table *new_tbl;
392         int err;
393
394         ASSERT_RHT_MUTEX(ht);
395
396         new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
397         if (new_tbl == NULL)
398                 return -ENOMEM;
399
400         err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
401         if (err)
402                 bucket_table_free(new_tbl);
403
404         return err;
405 }
406
407 /**
408  * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
409  * @ht:         the hash table to shrink
410  *
411  * This function shrinks the hash table to fit, i.e., the smallest
412  * size would not cause it to expand right away automatically.
413  *
414  * The caller must ensure that no concurrent resizing occurs by holding
415  * ht->mutex.
416  *
417  * The caller must ensure that no concurrent table mutations take place.
418  * It is however valid to have concurrent lookups if they are RCU protected.
419  *
420  * It is valid to have concurrent insertions and deletions protected by per
421  * bucket locks or concurrent RCU protected lookups and traversals.
422  */
423 static int rhashtable_shrink(struct rhashtable *ht)
424 {
425         struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
426         unsigned int nelems = atomic_read(&ht->nelems);
427         unsigned int size = 0;
428
429         if (nelems)
430                 size = roundup_pow_of_two(nelems * 3 / 2);
431         if (size < ht->p.min_size)
432                 size = ht->p.min_size;
433
434         if (old_tbl->size <= size)
435                 return 0;
436
437         if (rht_dereference(old_tbl->future_tbl, ht))
438                 return -EEXIST;
439
440         return rhashtable_rehash_alloc(ht, old_tbl, size);
441 }
442
443 static void rht_deferred_worker(struct work_struct *work)
444 {
445         struct rhashtable *ht;
446         struct bucket_table *tbl;
447         int err = 0;
448
449         ht = container_of(work, struct rhashtable, run_work);
450         mutex_lock(&ht->mutex);
451
452         tbl = rht_dereference(ht->tbl, ht);
453         tbl = rhashtable_last_table(ht, tbl);
454
455         if (rht_grow_above_75(ht, tbl))
456                 err = rhashtable_rehash_alloc(ht, tbl, tbl->size * 2);
457         else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
458                 err = rhashtable_shrink(ht);
459         else if (tbl->nest)
460                 err = rhashtable_rehash_alloc(ht, tbl, tbl->size);
461
462         if (!err)
463                 err = rhashtable_rehash_table(ht);
464
465         mutex_unlock(&ht->mutex);
466
467         if (err)
468                 schedule_work(&ht->run_work);
469 }
470
471 static int rhashtable_insert_rehash(struct rhashtable *ht,
472                                     struct bucket_table *tbl)
473 {
474         struct bucket_table *old_tbl;
475         struct bucket_table *new_tbl;
476         unsigned int size;
477         int err;
478
479         old_tbl = rht_dereference_rcu(ht->tbl, ht);
480
481         size = tbl->size;
482
483         err = -EBUSY;
484
485         if (rht_grow_above_75(ht, tbl))
486                 size *= 2;
487         /* Do not schedule more than one rehash */
488         else if (old_tbl != tbl)
489                 goto fail;
490
491         err = -ENOMEM;
492
493         new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC);
494         if (new_tbl == NULL)
495                 goto fail;
496
497         err = rhashtable_rehash_attach(ht, tbl, new_tbl);
498         if (err) {
499                 bucket_table_free(new_tbl);
500                 if (err == -EEXIST)
501                         err = 0;
502         } else
503                 schedule_work(&ht->run_work);
504
505         return err;
506
507 fail:
508         /* Do not fail the insert if someone else did a rehash. */
509         if (likely(rcu_dereference_raw(tbl->future_tbl)))
510                 return 0;
511
512         /* Schedule async rehash to retry allocation in process context. */
513         if (err == -ENOMEM)
514                 schedule_work(&ht->run_work);
515
516         return err;
517 }
518
519 static void *rhashtable_lookup_one(struct rhashtable *ht,
520                                    struct bucket_table *tbl, unsigned int hash,
521                                    const void *key, struct rhash_head *obj)
522 {
523         struct rhashtable_compare_arg arg = {
524                 .ht = ht,
525                 .key = key,
526         };
527         struct rhash_head __rcu **pprev;
528         struct rhash_head *head;
529         int elasticity;
530
531         elasticity = RHT_ELASTICITY;
532         pprev = rht_bucket_var(tbl, hash);
533         rht_for_each_continue(head, *pprev, tbl, hash) {
534                 struct rhlist_head *list;
535                 struct rhlist_head *plist;
536
537                 elasticity--;
538                 if (!key ||
539                     (ht->p.obj_cmpfn ?
540                      ht->p.obj_cmpfn(&arg, rht_obj(ht, head)) :
541                      rhashtable_compare(&arg, rht_obj(ht, head))))
542                         continue;
543
544                 if (!ht->rhlist)
545                         return rht_obj(ht, head);
546
547                 list = container_of(obj, struct rhlist_head, rhead);
548                 plist = container_of(head, struct rhlist_head, rhead);
549
550                 RCU_INIT_POINTER(list->next, plist);
551                 head = rht_dereference_bucket(head->next, tbl, hash);
552                 RCU_INIT_POINTER(list->rhead.next, head);
553                 rcu_assign_pointer(*pprev, obj);
554
555                 return NULL;
556         }
557
558         if (elasticity <= 0)
559                 return ERR_PTR(-EAGAIN);
560
561         return ERR_PTR(-ENOENT);
562 }
563
564 static struct bucket_table *rhashtable_insert_one(struct rhashtable *ht,
565                                                   struct bucket_table *tbl,
566                                                   unsigned int hash,
567                                                   struct rhash_head *obj,
568                                                   void *data)
569 {
570         struct rhash_head __rcu **pprev;
571         struct bucket_table *new_tbl;
572         struct rhash_head *head;
573
574         if (!IS_ERR_OR_NULL(data))
575                 return ERR_PTR(-EEXIST);
576
577         if (PTR_ERR(data) != -EAGAIN && PTR_ERR(data) != -ENOENT)
578                 return ERR_CAST(data);
579
580         new_tbl = rcu_dereference(tbl->future_tbl);
581         if (new_tbl)
582                 return new_tbl;
583
584         if (PTR_ERR(data) != -ENOENT)
585                 return ERR_CAST(data);
586
587         if (unlikely(rht_grow_above_max(ht, tbl)))
588                 return ERR_PTR(-E2BIG);
589
590         if (unlikely(rht_grow_above_100(ht, tbl)))
591                 return ERR_PTR(-EAGAIN);
592
593         pprev = rht_bucket_insert(ht, tbl, hash);
594         if (!pprev)
595                 return ERR_PTR(-ENOMEM);
596
597         head = rht_dereference_bucket(*pprev, tbl, hash);
598
599         RCU_INIT_POINTER(obj->next, head);
600         if (ht->rhlist) {
601                 struct rhlist_head *list;
602
603                 list = container_of(obj, struct rhlist_head, rhead);
604                 RCU_INIT_POINTER(list->next, NULL);
605         }
606
607         rcu_assign_pointer(*pprev, obj);
608
609         atomic_inc(&ht->nelems);
610         if (rht_grow_above_75(ht, tbl))
611                 schedule_work(&ht->run_work);
612
613         return NULL;
614 }
615
616 static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
617                                    struct rhash_head *obj)
618 {
619         struct bucket_table *new_tbl;
620         struct bucket_table *tbl;
621         unsigned int hash;
622         spinlock_t *lock;
623         void *data;
624
625         tbl = rcu_dereference(ht->tbl);
626
627         /* All insertions must grab the oldest table containing
628          * the hashed bucket that is yet to be rehashed.
629          */
630         for (;;) {
631                 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
632                 lock = rht_bucket_lock(tbl, hash);
633                 spin_lock_bh(lock);
634
635                 if (tbl->rehash <= hash)
636                         break;
637
638                 spin_unlock_bh(lock);
639                 tbl = rcu_dereference(tbl->future_tbl);
640         }
641
642         data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
643         new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
644         if (PTR_ERR(new_tbl) != -EEXIST)
645                 data = ERR_CAST(new_tbl);
646
647         while (!IS_ERR_OR_NULL(new_tbl)) {
648                 tbl = new_tbl;
649                 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
650                 spin_lock_nested(rht_bucket_lock(tbl, hash),
651                                  SINGLE_DEPTH_NESTING);
652
653                 data = rhashtable_lookup_one(ht, tbl, hash, key, obj);
654                 new_tbl = rhashtable_insert_one(ht, tbl, hash, obj, data);
655                 if (PTR_ERR(new_tbl) != -EEXIST)
656                         data = ERR_CAST(new_tbl);
657
658                 spin_unlock(rht_bucket_lock(tbl, hash));
659         }
660
661         spin_unlock_bh(lock);
662
663         if (PTR_ERR(data) == -EAGAIN)
664                 data = ERR_PTR(rhashtable_insert_rehash(ht, tbl) ?:
665                                -EAGAIN);
666
667         return data;
668 }
669
670 void *rhashtable_insert_slow(struct rhashtable *ht, const void *key,
671                              struct rhash_head *obj)
672 {
673         void *data;
674
675         do {
676                 rcu_read_lock();
677                 data = rhashtable_try_insert(ht, key, obj);
678                 rcu_read_unlock();
679         } while (PTR_ERR(data) == -EAGAIN);
680
681         return data;
682 }
683 EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
684
685 /**
686  * rhashtable_walk_enter - Initialise an iterator
687  * @ht:         Table to walk over
688  * @iter:       Hash table Iterator
689  *
690  * This function prepares a hash table walk.
691  *
692  * Note that if you restart a walk after rhashtable_walk_stop you
693  * may see the same object twice.  Also, you may miss objects if
694  * there are removals in between rhashtable_walk_stop and the next
695  * call to rhashtable_walk_start.
696  *
697  * For a completely stable walk you should construct your own data
698  * structure outside the hash table.
699  *
700  * This function may sleep so you must not call it from interrupt
701  * context or with spin locks held.
702  *
703  * You must call rhashtable_walk_exit after this function returns.
704  */
705 void rhashtable_walk_enter(struct rhashtable *ht, struct rhashtable_iter *iter)
706 {
707         iter->ht = ht;
708         iter->p = NULL;
709         iter->slot = 0;
710         iter->skip = 0;
711
712         spin_lock(&ht->lock);
713         iter->walker.tbl =
714                 rcu_dereference_protected(ht->tbl, lockdep_is_held(&ht->lock));
715         list_add(&iter->walker.list, &iter->walker.tbl->walkers);
716         spin_unlock(&ht->lock);
717 }
718 EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
719
720 /**
721  * rhashtable_walk_exit - Free an iterator
722  * @iter:       Hash table Iterator
723  *
724  * This function frees resources allocated by rhashtable_walk_init.
725  */
726 void rhashtable_walk_exit(struct rhashtable_iter *iter)
727 {
728         spin_lock(&iter->ht->lock);
729         if (iter->walker.tbl)
730                 list_del(&iter->walker.list);
731         spin_unlock(&iter->ht->lock);
732 }
733 EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
734
735 /**
736  * rhashtable_walk_start - Start a hash table walk
737  * @iter:       Hash table iterator
738  *
739  * Start a hash table walk.  Note that we take the RCU lock in all
740  * cases including when we return an error.  So you must always call
741  * rhashtable_walk_stop to clean up.
742  *
743  * Returns zero if successful.
744  *
745  * Returns -EAGAIN if resize event occured.  Note that the iterator
746  * will rewind back to the beginning and you may use it immediately
747  * by calling rhashtable_walk_next.
748  */
749 int rhashtable_walk_start(struct rhashtable_iter *iter)
750         __acquires(RCU)
751 {
752         struct rhashtable *ht = iter->ht;
753
754         rcu_read_lock();
755
756         spin_lock(&ht->lock);
757         if (iter->walker.tbl)
758                 list_del(&iter->walker.list);
759         spin_unlock(&ht->lock);
760
761         if (!iter->walker.tbl) {
762                 iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht);
763                 return -EAGAIN;
764         }
765
766         return 0;
767 }
768 EXPORT_SYMBOL_GPL(rhashtable_walk_start);
769
770 /**
771  * rhashtable_walk_next - Return the next object and advance the iterator
772  * @iter:       Hash table iterator
773  *
774  * Note that you must call rhashtable_walk_stop when you are finished
775  * with the walk.
776  *
777  * Returns the next object or NULL when the end of the table is reached.
778  *
779  * Returns -EAGAIN if resize event occured.  Note that the iterator
780  * will rewind back to the beginning and you may continue to use it.
781  */
782 void *rhashtable_walk_next(struct rhashtable_iter *iter)
783 {
784         struct bucket_table *tbl = iter->walker.tbl;
785         struct rhlist_head *list = iter->list;
786         struct rhashtable *ht = iter->ht;
787         struct rhash_head *p = iter->p;
788         bool rhlist = ht->rhlist;
789
790         if (p) {
791                 if (!rhlist || !(list = rcu_dereference(list->next))) {
792                         p = rcu_dereference(p->next);
793                         list = container_of(p, struct rhlist_head, rhead);
794                 }
795                 goto next;
796         }
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
819 next:
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         }
841
842         return NULL;
843 }
844 EXPORT_SYMBOL_GPL(rhashtable_walk_next);
845
846 /**
847  * rhashtable_walk_stop - Finish a hash table walk
848  * @iter:       Hash table iterator
849  *
850  * Finish a hash table walk.
851  */
852 void rhashtable_walk_stop(struct rhashtable_iter *iter)
853         __releases(RCU)
854 {
855         struct rhashtable *ht;
856         struct bucket_table *tbl = iter->walker.tbl;
857
858         if (!tbl)
859                 goto out;
860
861         ht = iter->ht;
862
863         spin_lock(&ht->lock);
864         if (tbl->rehash < tbl->size)
865                 list_add(&iter->walker.list, &tbl->walkers);
866         else
867                 iter->walker.tbl = NULL;
868         spin_unlock(&ht->lock);
869
870         iter->p = NULL;
871
872 out:
873         rcu_read_unlock();
874 }
875 EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
876
877 static size_t rounded_hashtable_size(const struct rhashtable_params *params)
878 {
879         return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
880                    (unsigned long)params->min_size);
881 }
882
883 static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
884 {
885         return jhash2(key, length, seed);
886 }
887
888 /**
889  * rhashtable_init - initialize a new hash table
890  * @ht:         hash table to be initialized
891  * @params:     configuration parameters
892  *
893  * Initializes a new hash table based on the provided configuration
894  * parameters. A table can be configured either with a variable or
895  * fixed length key:
896  *
897  * Configuration Example 1: Fixed length keys
898  * struct test_obj {
899  *      int                     key;
900  *      void *                  my_member;
901  *      struct rhash_head       node;
902  * };
903  *
904  * struct rhashtable_params params = {
905  *      .head_offset = offsetof(struct test_obj, node),
906  *      .key_offset = offsetof(struct test_obj, key),
907  *      .key_len = sizeof(int),
908  *      .hashfn = jhash,
909  *      .nulls_base = (1U << RHT_BASE_SHIFT),
910  * };
911  *
912  * Configuration Example 2: Variable length keys
913  * struct test_obj {
914  *      [...]
915  *      struct rhash_head       node;
916  * };
917  *
918  * u32 my_hash_fn(const void *data, u32 len, u32 seed)
919  * {
920  *      struct test_obj *obj = data;
921  *
922  *      return [... hash ...];
923  * }
924  *
925  * struct rhashtable_params params = {
926  *      .head_offset = offsetof(struct test_obj, node),
927  *      .hashfn = jhash,
928  *      .obj_hashfn = my_hash_fn,
929  * };
930  */
931 int rhashtable_init(struct rhashtable *ht,
932                     const struct rhashtable_params *params)
933 {
934         struct bucket_table *tbl;
935         size_t size;
936
937         size = HASH_DEFAULT_SIZE;
938
939         if ((!params->key_len && !params->obj_hashfn) ||
940             (params->obj_hashfn && !params->obj_cmpfn))
941                 return -EINVAL;
942
943         if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT))
944                 return -EINVAL;
945
946         memset(ht, 0, sizeof(*ht));
947         mutex_init(&ht->mutex);
948         spin_lock_init(&ht->lock);
949         memcpy(&ht->p, params, sizeof(*params));
950
951         if (params->min_size)
952                 ht->p.min_size = roundup_pow_of_two(params->min_size);
953
954         /* Cap total entries at 2^31 to avoid nelems overflow. */
955         ht->max_elems = 1u << 31;
956
957         if (params->max_size) {
958                 ht->p.max_size = rounddown_pow_of_two(params->max_size);
959                 if (ht->p.max_size < ht->max_elems / 2)
960                         ht->max_elems = ht->p.max_size * 2;
961         }
962
963         ht->p.min_size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
964
965         if (params->nelem_hint)
966                 size = rounded_hashtable_size(&ht->p);
967
968         if (params->locks_mul)
969                 ht->p.locks_mul = roundup_pow_of_two(params->locks_mul);
970         else
971                 ht->p.locks_mul = BUCKET_LOCKS_PER_CPU;
972
973         ht->key_len = ht->p.key_len;
974         if (!params->hashfn) {
975                 ht->p.hashfn = jhash;
976
977                 if (!(ht->key_len & (sizeof(u32) - 1))) {
978                         ht->key_len /= sizeof(u32);
979                         ht->p.hashfn = rhashtable_jhash2;
980                 }
981         }
982
983         tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
984         if (tbl == NULL)
985                 return -ENOMEM;
986
987         atomic_set(&ht->nelems, 0);
988
989         RCU_INIT_POINTER(ht->tbl, tbl);
990
991         INIT_WORK(&ht->run_work, rht_deferred_worker);
992
993         return 0;
994 }
995 EXPORT_SYMBOL_GPL(rhashtable_init);
996
997 /**
998  * rhltable_init - initialize a new hash list table
999  * @hlt:        hash list table to be initialized
1000  * @params:     configuration parameters
1001  *
1002  * Initializes a new hash list table.
1003  *
1004  * See documentation for rhashtable_init.
1005  */
1006 int rhltable_init(struct rhltable *hlt, const struct rhashtable_params *params)
1007 {
1008         int err;
1009
1010         /* No rhlist NULLs marking for now. */
1011         if (params->nulls_base)
1012                 return -EINVAL;
1013
1014         err = rhashtable_init(&hlt->ht, params);
1015         hlt->ht.rhlist = true;
1016         return err;
1017 }
1018 EXPORT_SYMBOL_GPL(rhltable_init);
1019
1020 static void rhashtable_free_one(struct rhashtable *ht, struct rhash_head *obj,
1021                                 void (*free_fn)(void *ptr, void *arg),
1022                                 void *arg)
1023 {
1024         struct rhlist_head *list;
1025
1026         if (!ht->rhlist) {
1027                 free_fn(rht_obj(ht, obj), arg);
1028                 return;
1029         }
1030
1031         list = container_of(obj, struct rhlist_head, rhead);
1032         do {
1033                 obj = &list->rhead;
1034                 list = rht_dereference(list->next, ht);
1035                 free_fn(rht_obj(ht, obj), arg);
1036         } while (list);
1037 }
1038
1039 /**
1040  * rhashtable_free_and_destroy - free elements and destroy hash table
1041  * @ht:         the hash table to destroy
1042  * @free_fn:    callback to release resources of element
1043  * @arg:        pointer passed to free_fn
1044  *
1045  * Stops an eventual async resize. If defined, invokes free_fn for each
1046  * element to releasal resources. Please note that RCU protected
1047  * readers may still be accessing the elements. Releasing of resources
1048  * must occur in a compatible manner. Then frees the bucket array.
1049  *
1050  * This function will eventually sleep to wait for an async resize
1051  * to complete. The caller is responsible that no further write operations
1052  * occurs in parallel.
1053  */
1054 void rhashtable_free_and_destroy(struct rhashtable *ht,
1055                                  void (*free_fn)(void *ptr, void *arg),
1056                                  void *arg)
1057 {
1058         struct bucket_table *tbl;
1059         unsigned int i;
1060
1061         cancel_work_sync(&ht->run_work);
1062
1063         mutex_lock(&ht->mutex);
1064         tbl = rht_dereference(ht->tbl, ht);
1065         if (free_fn) {
1066                 for (i = 0; i < tbl->size; i++) {
1067                         struct rhash_head *pos, *next;
1068
1069                         for (pos = rht_dereference(*rht_bucket(tbl, i), ht),
1070                              next = !rht_is_a_nulls(pos) ?
1071                                         rht_dereference(pos->next, ht) : NULL;
1072                              !rht_is_a_nulls(pos);
1073                              pos = next,
1074                              next = !rht_is_a_nulls(pos) ?
1075                                         rht_dereference(pos->next, ht) : NULL)
1076                                 rhashtable_free_one(ht, pos, free_fn, arg);
1077                 }
1078         }
1079
1080         bucket_table_free(tbl);
1081         mutex_unlock(&ht->mutex);
1082 }
1083 EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);
1084
1085 void rhashtable_destroy(struct rhashtable *ht)
1086 {
1087         return rhashtable_free_and_destroy(ht, NULL, NULL);
1088 }
1089 EXPORT_SYMBOL_GPL(rhashtable_destroy);
1090
1091 struct rhash_head __rcu **rht_bucket_nested(const struct bucket_table *tbl,
1092                                             unsigned int hash)
1093 {
1094         const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1095         static struct rhash_head __rcu *rhnull =
1096                 (struct rhash_head __rcu *)NULLS_MARKER(0);
1097         unsigned int index = hash & ((1 << tbl->nest) - 1);
1098         unsigned int size = tbl->size >> tbl->nest;
1099         unsigned int subhash = hash;
1100         union nested_table *ntbl;
1101
1102         ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
1103         ntbl = rht_dereference_bucket_rcu(ntbl[index].table, tbl, hash);
1104         subhash >>= tbl->nest;
1105
1106         while (ntbl && size > (1 << shift)) {
1107                 index = subhash & ((1 << shift) - 1);
1108                 ntbl = rht_dereference_bucket_rcu(ntbl[index].table,
1109                                                   tbl, hash);
1110                 size >>= shift;
1111                 subhash >>= shift;
1112         }
1113
1114         if (!ntbl)
1115                 return &rhnull;
1116
1117         return &ntbl[subhash].bucket;
1118
1119 }
1120 EXPORT_SYMBOL_GPL(rht_bucket_nested);
1121
1122 struct rhash_head __rcu **rht_bucket_nested_insert(struct rhashtable *ht,
1123                                                    struct bucket_table *tbl,
1124                                                    unsigned int hash)
1125 {
1126         const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1127         unsigned int index = hash & ((1 << tbl->nest) - 1);
1128         unsigned int size = tbl->size >> tbl->nest;
1129         union nested_table *ntbl;
1130         unsigned int shifted;
1131         unsigned int nhash;
1132
1133         ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
1134         hash >>= tbl->nest;
1135         nhash = index;
1136         shifted = tbl->nest;
1137         ntbl = nested_table_alloc(ht, &ntbl[index].table,
1138                                   size <= (1 << shift) ? shifted : 0, nhash);
1139
1140         while (ntbl && size > (1 << shift)) {
1141                 index = hash & ((1 << shift) - 1);
1142                 size >>= shift;
1143                 hash >>= shift;
1144                 nhash |= index << shifted;
1145                 shifted += shift;
1146                 ntbl = nested_table_alloc(ht, &ntbl[index].table,
1147                                           size <= (1 << shift) ? shifted : 0,
1148                                           nhash);
1149         }
1150
1151         if (!ntbl)
1152                 return NULL;
1153
1154         return &ntbl[hash].bucket;
1155
1156 }
1157 EXPORT_SYMBOL_GPL(rht_bucket_nested_insert);