1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Resizable, Scalable, Concurrent Hash Table
4 *
5 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au>
6 * Copyright (c) 2014-2015 Thomas Graf <tgraf@suug.ch>
7 * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
8 *
9 * Code partially derived from nft_hash
10 * Rewritten with rehash code from br_multicast plus single list
11 * pointer as suggested by Josh Triplett
12 */
13
14 #include <linux/atomic.h>
15 #include <linux/kernel.h>
16 #include <linux/init.h>
17 #include <linux/log2.h>
18 #include <linux/sched.h>
19 #include <linux/rculist.h>
20 #include <linux/slab.h>
21 #include <linux/vmalloc.h>
22 #include <linux/mm.h>
23 #include <linux/jhash.h>
24 #include <linux/random.h>
25 #include <linux/rhashtable.h>
26 #include <linux/err.h>
27 #include <linux/export.h>
28
29 #define HASH_DEFAULT_SIZE 64UL
30 #define HASH_MIN_SIZE 4U
31
32 union nested_table {
33 union nested_table __rcu *table;
34 struct rhash_lock_head __rcu *bucket;
35 };
36
37 static u32 head_hashfn(struct rhashtable *ht,
38 const struct bucket_table *tbl,
39 const struct rhash_head *he)
40 {
41 return rht_head_hashfn(ht, tbl, he, ht->p);
42 }
43
44 #ifdef CONFIG_PROVE_LOCKING
45 #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
46
47 int lockdep_rht_mutex_is_held(struct rhashtable *ht)
48 {
49 return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;
50 }
51 EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
52
53 int lockdep_rht_bucket_is_held(const struct bucket_table *tbl, u32 hash)
54 {
55 if (!debug_locks)
56 return 1;
57 if (unlikely(tbl->nest))
58 return 1;
59 return bit_spin_is_locked(0, (unsigned long *)&tbl->buckets[hash]);
60 }
61 EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);
62 #else
63 #define ASSERT_RHT_MUTEX(HT)
64 #endif
65
66 static inline union nested_table *nested_table_top(
67 const struct bucket_table *tbl)
68 {
69 /* The top-level bucket entry does not need RCU protection
70 * because it's set at the same time as tbl->nest.
71 */
72 return (void *)rcu_dereference_protected(tbl->buckets[0], 1);
73 }
74
75 static void nested_table_free(union nested_table *ntbl, unsigned int size)
76 {
77 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
78 const unsigned int len = 1 << shift;
79 unsigned int i;
80
81 ntbl = rcu_dereference_protected(ntbl->table, 1);
82 if (!ntbl)
83 return;
84
85 if (size > len) {
86 size >>= shift;
87 for (i = 0; i < len; i++)
88 nested_table_free(ntbl + i, size);
89 }
90
91 kfree(ntbl);
92 }
93
94 static void nested_bucket_table_free(const struct bucket_table *tbl)
95 {
96 unsigned int size = tbl->size >> tbl->nest;
97 unsigned int len = 1 << tbl->nest;
98 union nested_table *ntbl;
99 unsigned int i;
100
101 ntbl = nested_table_top(tbl);
102
103 for (i = 0; i < len; i++)
104 nested_table_free(ntbl + i, size);
105
106 kfree(ntbl);
107 }
108
109 static void bucket_table_free(const struct bucket_table *tbl)
110 {
111 if (tbl->nest)
112 nested_bucket_table_free(tbl);
113
114 kvfree(tbl);
115 }
116
117 static void bucket_table_free_rcu(struct rcu_head *head)
118 {
119 bucket_table_free(container_of(head, struct bucket_table, rcu));
120 }
121
122 static union nested_table *nested_table_alloc(struct rhashtable *ht,
123 union nested_table __rcu **prev,
124 bool leaf)
125 {
126 union nested_table *ntbl;
127 int i;
128
129 ntbl = rcu_dereference(*prev);
130 if (ntbl)
131 return ntbl;
132
133 ntbl = alloc_hooks_tag(ht->alloc_tag,
134 kmalloc_noprof(PAGE_SIZE, GFP_ATOMIC|__GFP_ZERO));
135
136 if (ntbl && leaf) {
137 for (i = 0; i < PAGE_SIZE / sizeof(ntbl[0]); i++)
138 INIT_RHT_NULLS_HEAD(ntbl[i].bucket);
139 }
140
141 if (cmpxchg((union nested_table **)prev, NULL, ntbl) == NULL)
142 return ntbl;
143 /* Raced with another thread. */
144 kfree(ntbl);
145 return rcu_dereference(*prev);
146 }
147
148 static struct bucket_table *nested_bucket_table_alloc(struct rhashtable *ht,
149 size_t nbuckets,
150 gfp_t gfp)
151 {
152 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
153 struct bucket_table *tbl;
154 size_t size;
155
156 if (nbuckets < (1 << (shift + 1)))
157 return NULL;
158
159 size = sizeof(*tbl) + sizeof(tbl->buckets[0]);
160
161 tbl = alloc_hooks_tag(ht->alloc_tag,
162 kmalloc_noprof(size, gfp|__GFP_ZERO));
163 if (!tbl)
164 return NULL;
165
166 if (!nested_table_alloc(ht, (union nested_table __rcu **)tbl->buckets,
167 false)) {
168 kfree(tbl);
169 return NULL;
170 }
171
172 tbl->nest = (ilog2(nbuckets) - 1) % shift + 1;
173
174 return tbl;
175 }
176
177 static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
178 size_t nbuckets,
179 gfp_t gfp)
180 {
181 struct bucket_table *tbl = NULL;
182 size_t size;
183 int i;
184 static struct lock_class_key __key;
185
186 tbl = alloc_hooks_tag(ht->alloc_tag,
187 kvmalloc_node_noprof(struct_size(tbl, buckets, nbuckets),
188 gfp|__GFP_ZERO, NUMA_NO_NODE));
189
190 size = nbuckets;
191
192 if (tbl == NULL && (gfp & ~__GFP_NOFAIL) != GFP_KERNEL) {
193 tbl = nested_bucket_table_alloc(ht, nbuckets, gfp);
194 nbuckets = 0;
195 }
196
197 if (tbl == NULL)
198 return NULL;
199
200 lockdep_init_map(&tbl->dep_map, "rhashtable_bucket", &__key, 0);
201
202 tbl->size = size;
203
204 rcu_head_init(&tbl->rcu);
205 INIT_LIST_HEAD(&tbl->walkers);
206
207 tbl->hash_rnd = get_random_u32();
208
209 for (i = 0; i < nbuckets; i++)
210 INIT_RHT_NULLS_HEAD(tbl->buckets[i]);
211
212 return tbl;
213 }
214
215 static struct bucket_table *rhashtable_last_table(struct rhashtable *ht,
216 struct bucket_table *tbl)
217 {
218 struct bucket_table *new_tbl;
219
220 do {
221 new_tbl = tbl;
222 tbl = rht_dereference_rcu(tbl->future_tbl, ht);
223 } while (tbl);
224
225 return new_tbl;
226 }
227
228 static int rhashtable_rehash_one(struct rhashtable *ht,
229 struct rhash_lock_head __rcu **bkt,
230 unsigned int old_hash)
231 {
232 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
233 struct bucket_table *new_tbl = rhashtable_last_table(ht, old_tbl);
234 int err = -EAGAIN;
235 struct rhash_head *head, *next, *entry;
236 struct rhash_head __rcu **pprev = NULL;
237 unsigned int new_hash;
238 unsigned long flags;
239
240 if (new_tbl->nest)
241 goto out;
242
243 err = -ENOENT;
244
245 rht_for_each_from(entry, rht_ptr(bkt, old_tbl, old_hash),
246 old_tbl, old_hash) {
247 err = 0;
248 next = rht_dereference_bucket(entry->next, old_tbl, old_hash);
249
250 if (rht_is_a_nulls(next))
251 break;
252
253 pprev = &entry->next;
254 }
255
256 if (err)
257 goto out;
258
259 new_hash = head_hashfn(ht, new_tbl, entry);
260
261 flags = rht_lock_nested(new_tbl, &new_tbl->buckets[new_hash],
262 SINGLE_DEPTH_NESTING);
263
264 head = rht_ptr(new_tbl->buckets + new_hash, new_tbl, new_hash);
265
266 RCU_INIT_POINTER(entry->next, head);
267
268 rht_assign_unlock(new_tbl, &new_tbl->buckets[new_hash], entry, flags);
269
270 if (pprev)
271 rcu_assign_pointer(*pprev, next);
272 else
273 /* Need to preserved the bit lock. */
274 rht_assign_locked(bkt, next);
275
276 out:
277 return err;
278 }
279
280 static int rhashtable_rehash_chain(struct rhashtable *ht,
281 unsigned int old_hash)
282 {
283 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
284 struct rhash_lock_head __rcu **bkt = rht_bucket_var(old_tbl, old_hash);
285 unsigned long flags;
286 int err;
287
288 if (!bkt)
289 return 0;
290 flags = rht_lock(old_tbl, bkt);
291
292 while (!(err = rhashtable_rehash_one(ht, bkt, old_hash)))
293 ;
294
295 if (err == -ENOENT)
296 err = 0;
297 rht_unlock(old_tbl, bkt, flags);
298
299 return err;
300 }
301
302 static int rhashtable_rehash_attach(struct rhashtable *ht,
303 struct bucket_table *old_tbl,
304 struct bucket_table *new_tbl)
305 {
306 /* Make insertions go into the new, empty table right away. Deletions
307 * and lookups will be attempted in both tables until we synchronize.
308 * As cmpxchg() provides strong barriers, we do not need
309 * rcu_assign_pointer().
310 */
311
312 if (cmpxchg((struct bucket_table **)&old_tbl->future_tbl, NULL,
313 new_tbl) != NULL)
314 return -EEXIST;
315
316 return 0;
317 }
318
319 static int rhashtable_rehash_table(struct rhashtable *ht)
320 {
321 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
322 struct bucket_table *new_tbl;
323 struct rhashtable_walker *walker;
324 unsigned int old_hash;
325 int err;
326
327 new_tbl = rht_dereference(old_tbl->future_tbl, ht);
328 if (!new_tbl)
329 return 0;
330
331 for (old_hash = 0; old_hash < old_tbl->size; old_hash++) {
332 err = rhashtable_rehash_chain(ht, old_hash);
333 if (err)
334 return err;
335 cond_resched();
336 }
337
338 /* Publish the new table pointer. */
339 rcu_assign_pointer(ht->tbl, new_tbl);
340
341 spin_lock(&ht->lock);
342 list_for_each_entry(walker, &old_tbl->walkers, list)
343 walker->tbl = NULL;
344
345 /* Wait for readers. All new readers will see the new
346 * table, and thus no references to the old table will
347 * remain.
348 * We do this inside the locked region so that
349 * rhashtable_walk_stop() can use rcu_head_after_call_rcu()
350 * to check if it should not re-link the table.
351 */
352 call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
353 spin_unlock(&ht->lock);
354
355 return rht_dereference(new_tbl->future_tbl, ht) ? -EAGAIN : 0;
356 }
357
358 static int rhashtable_rehash_alloc(struct rhashtable *ht,
359 struct bucket_table *old_tbl,
360 unsigned int size)
361 {
362 struct bucket_table *new_tbl;
363 int err;
364
365 ASSERT_RHT_MUTEX(ht);
366
367 new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
368 if (new_tbl == NULL)
369 return -ENOMEM;
370
371 err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
372 if (err)
373 bucket_table_free(new_tbl);
374
375 return err;
376 }
377
378 /**
379 * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
380 * @ht: the hash table to shrink
381 *
382 * This function shrinks the hash table to fit, i.e., the smallest
383 * size would not cause it to expand right away automatically.
384 *
385 * The caller must ensure that no concurrent resizing occurs by holding
386 * ht->mutex.
387 *
388 * The caller must ensure that no concurrent table mutations take place.
389 * It is however valid to have concurrent lookups if they are RCU protected.
390 *
391 * It is valid to have concurrent insertions and deletions protected by per
392 * bucket locks or concurrent RCU protected lookups and traversals.
393 */
394 static int rhashtable_shrink(struct rhashtable *ht)
395 {
396 struct bucket_table *old_tbl = rht_dereference(ht->tbl, ht);
397 unsigned int nelems = atomic_read(&ht->nelems);
398 unsigned int size = 0;
399
400 if (nelems)
401 size = roundup_pow_of_two(nelems * 3 / 2);
402 if (size < ht->p.min_size)
403 size = ht->p.min_size;
404
405 if (old_tbl->size <= size)
406 return 0;
407
408 if (rht_dereference(old_tbl->future_tbl, ht))
409 return -EEXIST;
410
411 return rhashtable_rehash_alloc(ht, old_tbl, size);
412 }
413
414 static void rht_deferred_worker(struct work_struct *work)
415 {
416 struct rhashtable *ht;
417 struct bucket_table *tbl;
418 int err = 0;
419
420 ht = container_of(work, struct rhashtable, run_work);
421 mutex_lock(&ht->mutex);
422
423 tbl = rht_dereference(ht->tbl, ht);
424 tbl = rhashtable_last_table(ht, tbl);
425
426 if (rht_grow_above_75(ht, tbl))
427 err = rhashtable_rehash_alloc(ht, tbl, tbl->size * 2);
428 else if (ht->p.automatic_shrinking && rht_shrink_below_30(ht, tbl))
429 err = rhashtable_shrink(ht);
430 else if (tbl->nest)
431 err = rhashtable_rehash_alloc(ht, tbl, tbl->size);
432
433 if (!err || err == -EEXIST) {
434 int nerr;
435
436 nerr = rhashtable_rehash_table(ht);
437 err = err ?: nerr;
438 }
439
440 mutex_unlock(&ht->mutex);
441
442 if (err)
443 schedule_work(&ht->run_work);
444 }
445
446 static int rhashtable_insert_rehash(struct rhashtable *ht,
447 struct bucket_table *tbl)
448 {
449 struct bucket_table *old_tbl;
450 struct bucket_table *new_tbl;
451 unsigned int size;
452 int err;
453
454 old_tbl = rht_dereference_rcu(ht->tbl, ht);
455
456 size = tbl->size;
457
458 err = -EBUSY;
459
460 if (rht_grow_above_75(ht, tbl))
461 size *= 2;
462 /* Do not schedule more than one rehash */
463 else if (old_tbl != tbl)
464 goto fail;
465
466 err = -ENOMEM;
467
468 new_tbl = bucket_table_alloc(ht, size, GFP_ATOMIC | __GFP_NOWARN);
469 if (new_tbl == NULL)
470 goto fail;
471
472 err = rhashtable_rehash_attach(ht, tbl, new_tbl);
473 if (err) {
474 bucket_table_free(new_tbl);
475 if (err == -EEXIST)
476 err = 0;
477 } else
478 schedule_work(&ht->run_work);
479
480 return err;
481
482 fail:
483 /* Do not fail the insert if someone else did a rehash. */
484 if (likely(rcu_access_pointer(tbl->future_tbl)))
485 return 0;
486
487 /* Schedule async rehash to retry allocation in process context. */
488 if (err == -ENOMEM)
489 schedule_work(&ht->run_work);
490
491 return err;
492 }
493
494 static void *rhashtable_lookup_one(struct rhashtable *ht,
495 struct rhash_lock_head __rcu **bkt,
496 struct bucket_table *tbl, unsigned int hash,
497 const void *key, struct rhash_head *obj)
498 {
499 struct rhashtable_compare_arg arg = {
500 .ht = ht,
501 .key = key,
502 };
503 struct rhash_head __rcu **pprev = NULL;
504 struct rhash_head *head;
505 int elasticity;
506
507 elasticity = RHT_ELASTICITY;
508 rht_for_each_from(head, rht_ptr(bkt, tbl, hash), tbl, hash) {
509 struct rhlist_head *list;
510 struct rhlist_head *plist;
511
512 elasticity--;
513 if (!key ||
514 (ht->p.obj_cmpfn ?
515 ht->p.obj_cmpfn(&arg, rht_obj(ht, head)) :
516 rhashtable_compare(&arg, rht_obj(ht, head)))) {
517 pprev = &head->next;
518 continue;
519 }
520
521 if (!ht->rhlist)
522 return rht_obj(ht, head);
523
524 list = container_of(obj, struct rhlist_head, rhead);
525 plist = container_of(head, struct rhlist_head, rhead);
526
527 RCU_INIT_POINTER(list->next, plist);
528 head = rht_dereference_bucket(head->next, tbl, hash);
529 RCU_INIT_POINTER(list->rhead.next, head);
530 if (pprev)
531 rcu_assign_pointer(*pprev, obj);
532 else
533 /* Need to preserve the bit lock */
534 rht_assign_locked(bkt, obj);
535
536 return NULL;
537 }
538
539 if (elasticity <= 0)
540 return ERR_PTR(-EAGAIN);
541
542 return ERR_PTR(-ENOENT);
543 }
544
545 static struct bucket_table *rhashtable_insert_one(
546 struct rhashtable *ht, struct rhash_lock_head __rcu **bkt,
547 struct bucket_table *tbl, unsigned int hash, struct rhash_head *obj,
548 void *data)
549 {
550 struct bucket_table *new_tbl;
551 struct rhash_head *head;
552
553 if (!IS_ERR_OR_NULL(data))
554 return ERR_PTR(-EEXIST);
555
556 if (PTR_ERR(data) != -EAGAIN && PTR_ERR(data) != -ENOENT)
557 return ERR_CAST(data);
558
559 new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
560 if (new_tbl)
561 return new_tbl;
562
563 if (PTR_ERR(data) != -ENOENT)
564 return ERR_CAST(data);
565
566 if (unlikely(rht_grow_above_max(ht, tbl)))
567 return ERR_PTR(-E2BIG);
568
569 if (unlikely(rht_grow_above_100(ht, tbl)))
570 return ERR_PTR(-EAGAIN);
571
572 head = rht_ptr(bkt, tbl, hash);
573
574 RCU_INIT_POINTER(obj->next, head);
575 if (ht->rhlist) {
576 struct rhlist_head *list;
577
578 list = container_of(obj, struct rhlist_head, rhead);
579 RCU_INIT_POINTER(list->next, NULL);
580 }
581
582 /* bkt is always the head of the list, so it holds
583 * the lock, which we need to preserve
584 */
585 rht_assign_locked(bkt, obj);
586
587 atomic_inc(&ht->nelems);
588 if (rht_grow_above_75(ht, tbl))
589 schedule_work(&ht->run_work);
590
591 return NULL;
592 }
593
594 static void *rhashtable_try_insert(struct rhashtable *ht, const void *key,
595 struct rhash_head *obj)
596 {
597 struct bucket_table *new_tbl;
598 struct bucket_table *tbl;
599 struct rhash_lock_head __rcu **bkt;
600 unsigned long flags;
601 unsigned int hash;
602 void *data;
603
604 new_tbl = rcu_dereference(ht->tbl);
605
606 do {
607 tbl = new_tbl;
608 hash = rht_head_hashfn(ht, tbl, obj, ht->p);
609 if (rcu_access_pointer(tbl->future_tbl))
610 /* Failure is OK */
611 bkt = rht_bucket_var(tbl, hash);
612 else
613 bkt = rht_bucket_insert(ht, tbl, hash);
614 if (bkt == NULL) {
615 new_tbl = rht_dereference_rcu(tbl->future_tbl, ht);
616 data = ERR_PTR(-EAGAIN);
617 } else {
618 flags = rht_lock(tbl, bkt);
619 data = rhashtable_lookup_one(ht, bkt, tbl,
620 hash, key, obj);
621 new_tbl = rhashtable_insert_one(ht, bkt, tbl,
622 hash, obj, data);
623 if (PTR_ERR(new_tbl) != -EEXIST)
624 data = ERR_CAST(new_tbl);
625
626 rht_unlock(tbl, bkt, flags);
627 }
628 } while (!IS_ERR_OR_NULL(new_tbl));
629
630 if (PTR_ERR(data) == -EAGAIN)
631 data = ERR_PTR(rhashtable_insert_rehash(ht, tbl) ?:
632 -EAGAIN);
633
634 return data;
635 }
636
637 void *rhashtable_insert_slow(struct rhashtable *ht, const void *key,
638 struct rhash_head *obj)
639 {
640 void *data;
641
642 do {
643 rcu_read_lock();
644 data = rhashtable_try_insert(ht, key, obj);
645 rcu_read_unlock();
646 } while (PTR_ERR(data) == -EAGAIN);
647
648 return data;
649 }
650 EXPORT_SYMBOL_GPL(rhashtable_insert_slow);
651
652 /**
653 * rhashtable_walk_enter - Initialise an iterator
654 * @ht: Table to walk over
655 * @iter: Hash table Iterator
656 *
657 * This function prepares a hash table walk.
658 *
659 * Note that if you restart a walk after rhashtable_walk_stop you
660 * may see the same object twice. Also, you may miss objects if
661 * there are removals in between rhashtable_walk_stop and the next
662 * call to rhashtable_walk_start.
663 *
664 * For a completely stable walk you should construct your own data
665 * structure outside the hash table.
666 *
667 * This function may be called from any process context, including
668 * non-preemptable context, but cannot be called from softirq or
669 * hardirq context.
670 *
671 * You must call rhashtable_walk_exit after this function returns.
672 */
673 void rhashtable_walk_enter(struct rhashtable *ht, struct rhashtable_iter *iter)
674 {
675 iter->ht = ht;
676 iter->p = NULL;
677 iter->slot = 0;
678 iter->skip = 0;
679 iter->end_of_table = 0;
680
681 spin_lock(&ht->lock);
682 iter->walker.tbl =
683 rcu_dereference_protected(ht->tbl, lockdep_is_held(&ht->lock));
684 list_add(&iter->walker.list, &iter->walker.tbl->walkers);
685 spin_unlock(&ht->lock);
686 }
687 EXPORT_SYMBOL_GPL(rhashtable_walk_enter);
688
689 /**
690 * rhashtable_walk_exit - Free an iterator
691 * @iter: Hash table Iterator
692 *
693 * This function frees resources allocated by rhashtable_walk_enter.
694 */
695 void rhashtable_walk_exit(struct rhashtable_iter *iter)
696 {
697 spin_lock(&iter->ht->lock);
698 if (iter->walker.tbl)
699 list_del(&iter->walker.list);
700 spin_unlock(&iter->ht->lock);
701 }
702 EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
703
704 /**
705 * rhashtable_walk_start_check - Start a hash table walk
706 * @iter: Hash table iterator
707 *
708 * Start a hash table walk at the current iterator position. Note that we take
709 * the RCU lock in all cases including when we return an error. So you must
710 * always call rhashtable_walk_stop to clean up.
711 *
712 * Returns zero if successful.
713 *
714 * Returns -EAGAIN if resize event occurred. Note that the iterator
715 * will rewind back to the beginning and you may use it immediately
716 * by calling rhashtable_walk_next.
717 *
718 * rhashtable_walk_start is defined as an inline variant that returns
719 * void. This is preferred in cases where the caller would ignore
720 * resize events and always continue.
721 */
722 int rhashtable_walk_start_check(struct rhashtable_iter *iter)
723 __acquires(RCU)
724 {
725 struct rhashtable *ht = iter->ht;
726 bool rhlist = ht->rhlist;
727
728 rcu_read_lock();
729
730 spin_lock(&ht->lock);
731 if (iter->walker.tbl)
732 list_del(&iter->walker.list);
733 spin_unlock(&ht->lock);
734
735 if (iter->end_of_table)
736 return 0;
737 if (!iter->walker.tbl) {
738 iter->walker.tbl = rht_dereference_rcu(ht->tbl, ht);
739 iter->slot = 0;
740 iter->skip = 0;
741 return -EAGAIN;
742 }
743
744 if (iter->p && !rhlist) {
745 /*
746 * We need to validate that 'p' is still in the table, and
747 * if so, update 'skip'
748 */
749 struct rhash_head *p;
750 int skip = 0;
751 rht_for_each_rcu(p, iter->walker.tbl, iter->slot) {
752 skip++;
753 if (p == iter->p) {
754 iter->skip = skip;
755 goto found;
756 }
757 }
758 iter->p = NULL;
759 } else if (iter->p && rhlist) {
760 /* Need to validate that 'list' is still in the table, and
761 * if so, update 'skip' and 'p'.
762 */
763 struct rhash_head *p;
764 struct rhlist_head *list;
765 int skip = 0;
766 rht_for_each_rcu(p, iter->walker.tbl, iter->slot) {
767 for (list = container_of(p, struct rhlist_head, rhead);
768 list;
769 list = rcu_dereference(list->next)) {
770 skip++;
771 if (list == iter->list) {
772 iter->p = p;
773 iter->skip = skip;
774 goto found;
775 }
776 }
777 }
778 iter->p = NULL;
779 }
780 found:
781 return 0;
782 }
783 EXPORT_SYMBOL_GPL(rhashtable_walk_start_check);
784
785 /**
786 * __rhashtable_walk_find_next - Find the next element in a table (or the first
787 * one in case of a new walk).
788 *
789 * @iter: Hash table iterator
790 *
791 * Returns the found object or NULL when the end of the table is reached.
792 *
793 * Returns -EAGAIN if resize event occurred.
794 */
795 static void *__rhashtable_walk_find_next(struct rhashtable_iter *iter)
796 {
797 struct bucket_table *tbl = iter->walker.tbl;
798 struct rhlist_head *list = iter->list;
799 struct rhashtable *ht = iter->ht;
800 struct rhash_head *p = iter->p;
801 bool rhlist = ht->rhlist;
802
803 if (!tbl)
804 return NULL;
805
806 for (; iter->slot < tbl->size; iter->slot++) {
807 int skip = iter->skip;
808
809 rht_for_each_rcu(p, tbl, iter->slot) {
810 if (rhlist) {
811 list = container_of(p, struct rhlist_head,
812 rhead);
813 do {
814 if (!skip)
815 goto next;
816 skip--;
817 list = rcu_dereference(list->next);
818 } while (list);
819
820 continue;
821 }
822 if (!skip)
823 break;
824 skip--;
825 }
826
827 next:
828 if (!rht_is_a_nulls(p)) {
829 iter->skip++;
830 iter->p = p;
831 iter->list = list;
832 return rht_obj(ht, rhlist ? &list->rhead : p);
833 }
834
835 iter->skip = 0;
836 }
837
838 iter->p = NULL;
839
840 /* Ensure we see any new tables. */
841 smp_rmb();
842
843 iter->walker.tbl = rht_dereference_rcu(tbl->future_tbl, ht);
844 if (iter->walker.tbl) {
845 iter->slot = 0;
846 iter->skip = 0;
847 return ERR_PTR(-EAGAIN);
848 } else {
849 iter->end_of_table = true;
850 }
851
852 return NULL;
853 }
854
855 /**
856 * rhashtable_walk_next - Return the next object and advance the iterator
857 * @iter: Hash table iterator
858 *
859 * Note that you must call rhashtable_walk_stop when you are finished
860 * with the walk.
861 *
862 * Returns the next object or NULL when the end of the table is reached.
863 *
864 * Returns -EAGAIN if resize event occurred. Note that the iterator
865 * will rewind back to the beginning and you may continue to use it.
866 */
867 void *rhashtable_walk_next(struct rhashtable_iter *iter)
868 {
869 struct rhlist_head *list = iter->list;
870 struct rhashtable *ht = iter->ht;
871 struct rhash_head *p = iter->p;
872 bool rhlist = ht->rhlist;
873
874 if (p) {
875 if (!rhlist || !(list = rcu_dereference(list->next))) {
876 p = rcu_dereference(p->next);
877 list = container_of(p, struct rhlist_head, rhead);
878 }
879 if (!rht_is_a_nulls(p)) {
880 iter->skip++;
881 iter->p = p;
882 iter->list = list;
883 return rht_obj(ht, rhlist ? &list->rhead : p);
884 }
885
886 /* At the end of this slot, switch to next one and then find
887 * next entry from that point.
888 */
889 iter->skip = 0;
890 iter->slot++;
891 }
892
893 return __rhashtable_walk_find_next(iter);
894 }
895 EXPORT_SYMBOL_GPL(rhashtable_walk_next);
896
897 /**
898 * rhashtable_walk_peek - Return the next object but don't advance the iterator
899 * @iter: Hash table iterator
900 *
901 * Returns the next object or NULL when the end of the table is reached.
902 *
903 * Returns -EAGAIN if resize event occurred. Note that the iterator
904 * will rewind back to the beginning and you may continue to use it.
905 */
906 void *rhashtable_walk_peek(struct rhashtable_iter *iter)
907 {
908 struct rhlist_head *list = iter->list;
909 struct rhashtable *ht = iter->ht;
910 struct rhash_head *p = iter->p;
911
912 if (p)
913 return rht_obj(ht, ht->rhlist ? &list->rhead : p);
914
915 /* No object found in current iter, find next one in the table. */
916
917 if (iter->skip) {
918 /* A nonzero skip value points to the next entry in the table
919 * beyond that last one that was found. Decrement skip so
920 * we find the current value. __rhashtable_walk_find_next
921 * will restore the original value of skip assuming that
922 * the table hasn't changed.
923 */
924 iter->skip--;
925 }
926
927 return __rhashtable_walk_find_next(iter);
928 }
929 EXPORT_SYMBOL_GPL(rhashtable_walk_peek);
930
931 /**
932 * rhashtable_walk_stop - Finish a hash table walk
933 * @iter: Hash table iterator
934 *
935 * Finish a hash table walk. Does not reset the iterator to the start of the
936 * hash table.
937 */
938 void rhashtable_walk_stop(struct rhashtable_iter *iter)
939 __releases(RCU)
940 {
941 struct rhashtable *ht;
942 struct bucket_table *tbl = iter->walker.tbl;
943
944 if (!tbl)
945 goto out;
946
947 ht = iter->ht;
948
949 spin_lock(&ht->lock);
950 if (rcu_head_after_call_rcu(&tbl->rcu, bucket_table_free_rcu))
951 /* This bucket table is being freed, don't re-link it. */
952 iter->walker.tbl = NULL;
953 else
954 list_add(&iter->walker.list, &tbl->walkers);
955 spin_unlock(&ht->lock);
956
957 out:
958 rcu_read_unlock();
959 }
960 EXPORT_SYMBOL_GPL(rhashtable_walk_stop);
961
962 static size_t rounded_hashtable_size(const struct rhashtable_params *params)
963 {
964 size_t retsize;
965
966 if (params->nelem_hint)
967 retsize = max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
968 (unsigned long)params->min_size);
969 else
970 retsize = max(HASH_DEFAULT_SIZE,
971 (unsigned long)params->min_size);
972
973 return retsize;
974 }
975
976 static u32 rhashtable_jhash2(const void *key, u32 length, u32 seed)
977 {
978 return jhash2(key, length, seed);
979 }
980
981 /**
982 * rhashtable_init - initialize a new hash table
983 * @ht: hash table to be initialized
984 * @params: configuration parameters
985 *
986 * Initializes a new hash table based on the provided configuration
987 * parameters. A table can be configured either with a variable or
988 * fixed length key:
989 *
990 * Configuration Example 1: Fixed length keys
991 * struct test_obj {
992 * int key;
993 * void * my_member;
994 * struct rhash_head node;
995 * };
996 *
997 * struct rhashtable_params params = {
998 * .head_offset = offsetof(struct test_obj, node),
999 * .key_offset = offsetof(struct test_obj, key),
1000 * .key_len = sizeof(int),
1001 * .hashfn = jhash,
1002 * };
1003 *
1004 * Configuration Example 2: Variable length keys
1005 * struct test_obj {
1006 * [...]
1007 * struct rhash_head node;
1008 * };
1009 *
1010 * u32 my_hash_fn(const void *data, u32 len, u32 seed)
1011 * {
1012 * struct test_obj *obj = data;
1013 *
1014 * return [... hash ...];
1015 * }
1016 *
1017 * struct rhashtable_params params = {
1018 * .head_offset = offsetof(struct test_obj, node),
1019 * .hashfn = jhash,
1020 * .obj_hashfn = my_hash_fn,
1021 * };
1022 */
1023 int rhashtable_init_noprof(struct rhashtable *ht,
1024 const struct rhashtable_params *params)
1025 {
1026 struct bucket_table *tbl;
1027 size_t size;
1028
1029 if ((!params->key_len && !params->obj_hashfn) ||
1030 (params->obj_hashfn && !params->obj_cmpfn))
1031 return -EINVAL;
1032
1033 memset(ht, 0, sizeof(*ht));
1034 mutex_init(&ht->mutex);
1035 spin_lock_init(&ht->lock);
1036 memcpy(&ht->p, params, sizeof(*params));
1037
1038 alloc_tag_record(ht->alloc_tag);
1039
1040 if (params->min_size)
1041 ht->p.min_size = roundup_pow_of_two(params->min_size);
1042
1043 /* Cap total entries at 2^31 to avoid nelems overflow. */
1044 ht->max_elems = 1u << 31;
1045
1046 if (params->max_size) {
1047 ht->p.max_size = rounddown_pow_of_two(params->max_size);
1048 if (ht->p.max_size < ht->max_elems / 2)
1049 ht->max_elems = ht->p.max_size * 2;
1050 }
1051
1052 ht->p.min_size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
1053
1054 size = rounded_hashtable_size(&ht->p);
1055
1056 ht->key_len = ht->p.key_len;
1057 if (!params->hashfn) {
1058 ht->p.hashfn = jhash;
1059
1060 if (!(ht->key_len & (sizeof(u32) - 1))) {
1061 ht->key_len /= sizeof(u32);
1062 ht->p.hashfn = rhashtable_jhash2;
1063 }
1064 }
1065
1066 /*
1067 * This is api initialization and thus we need to guarantee the
1068 * initial rhashtable allocation. Upon failure, retry with the
1069 * smallest possible size with __GFP_NOFAIL semantics.
1070 */
1071 tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
1072 if (unlikely(tbl == NULL)) {
1073 size = max_t(u16, ht->p.min_size, HASH_MIN_SIZE);
1074 tbl = bucket_table_alloc(ht, size, GFP_KERNEL | __GFP_NOFAIL);
1075 }
1076
1077 atomic_set(&ht->nelems, 0);
1078
1079 RCU_INIT_POINTER(ht->tbl, tbl);
1080
1081 INIT_WORK(&ht->run_work, rht_deferred_worker);
1082
1083 return 0;
1084 }
1085 EXPORT_SYMBOL_GPL(rhashtable_init_noprof);
1086
1087 /**
1088 * rhltable_init - initialize a new hash list table
1089 * @hlt: hash list table to be initialized
1090 * @params: configuration parameters
1091 *
1092 * Initializes a new hash list table.
1093 *
1094 * See documentation for rhashtable_init.
1095 */
1096 int rhltable_init_noprof(struct rhltable *hlt, const struct rhashtable_params *params)
1097 {
1098 int err;
1099
1100 err = rhashtable_init_noprof(&hlt->ht, params);
1101 hlt->ht.rhlist = true;
1102 return err;
1103 }
1104 EXPORT_SYMBOL_GPL(rhltable_init_noprof);
1105
1106 static void rhashtable_free_one(struct rhashtable *ht, struct rhash_head *obj,
1107 void (*free_fn)(void *ptr, void *arg),
1108 void *arg)
1109 {
1110 struct rhlist_head *list;
1111
1112 if (!ht->rhlist) {
1113 free_fn(rht_obj(ht, obj), arg);
1114 return;
1115 }
1116
1117 list = container_of(obj, struct rhlist_head, rhead);
1118 do {
1119 obj = &list->rhead;
1120 list = rht_dereference(list->next, ht);
1121 free_fn(rht_obj(ht, obj), arg);
1122 } while (list);
1123 }
1124
1125 /**
1126 * rhashtable_free_and_destroy - free elements and destroy hash table
1127 * @ht: the hash table to destroy
1128 * @free_fn: callback to release resources of element
1129 * @arg: pointer passed to free_fn
1130 *
1131 * Stops an eventual async resize. If defined, invokes free_fn for each
1132 * element to releasal resources. Please note that RCU protected
1133 * readers may still be accessing the elements. Releasing of resources
1134 * must occur in a compatible manner. Then frees the bucket array.
1135 *
1136 * This function will eventually sleep to wait for an async resize
1137 * to complete. The caller is responsible that no further write operations
1138 * occurs in parallel.
1139 */
1140 void rhashtable_free_and_destroy(struct rhashtable *ht,
1141 void (*free_fn)(void *ptr, void *arg),
1142 void *arg)
1143 {
1144 struct bucket_table *tbl, *next_tbl;
1145 unsigned int i;
1146
1147 cancel_work_sync(&ht->run_work);
1148
1149 mutex_lock(&ht->mutex);
1150 tbl = rht_dereference(ht->tbl, ht);
1151 restart:
1152 if (free_fn) {
1153 for (i = 0; i < tbl->size; i++) {
1154 struct rhash_head *pos, *next;
1155
1156 cond_resched();
1157 for (pos = rht_ptr_exclusive(rht_bucket(tbl, i)),
1158 next = !rht_is_a_nulls(pos) ?
1159 rht_dereference(pos->next, ht) : NULL;
1160 !rht_is_a_nulls(pos);
1161 pos = next,
1162 next = !rht_is_a_nulls(pos) ?
1163 rht_dereference(pos->next, ht) : NULL)
1164 rhashtable_free_one(ht, pos, free_fn, arg);
1165 }
1166 }
1167
1168 next_tbl = rht_dereference(tbl->future_tbl, ht);
1169 bucket_table_free(tbl);
1170 if (next_tbl) {
1171 tbl = next_tbl;
1172 goto restart;
1173 }
1174 mutex_unlock(&ht->mutex);
1175 }
1176 EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);
1177
1178 void rhashtable_destroy(struct rhashtable *ht)
1179 {
1180 return rhashtable_free_and_destroy(ht, NULL, NULL);
1181 }
1182 EXPORT_SYMBOL_GPL(rhashtable_destroy);
1183
1184 struct rhash_lock_head __rcu **__rht_bucket_nested(
1185 const struct bucket_table *tbl, unsigned int hash)
1186 {
1187 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1188 unsigned int index = hash & ((1 << tbl->nest) - 1);
1189 unsigned int size = tbl->size >> tbl->nest;
1190 unsigned int subhash = hash;
1191 union nested_table *ntbl;
1192
1193 ntbl = nested_table_top(tbl);
1194 ntbl = rht_dereference_bucket_rcu(ntbl[index].table, tbl, hash);
1195 subhash >>= tbl->nest;
1196
1197 while (ntbl && size > (1 << shift)) {
1198 index = subhash & ((1 << shift) - 1);
1199 ntbl = rht_dereference_bucket_rcu(ntbl[index].table,
1200 tbl, hash);
1201 size >>= shift;
1202 subhash >>= shift;
1203 }
1204
1205 if (!ntbl)
1206 return NULL;
1207
1208 return &ntbl[subhash].bucket;
1209
1210 }
1211 EXPORT_SYMBOL_GPL(__rht_bucket_nested);
1212
1213 struct rhash_lock_head __rcu **rht_bucket_nested(
1214 const struct bucket_table *tbl, unsigned int hash)
1215 {
1216 static struct rhash_lock_head __rcu *rhnull;
1217
1218 if (!rhnull)
1219 INIT_RHT_NULLS_HEAD(rhnull);
1220 return __rht_bucket_nested(tbl, hash) ?: &rhnull;
1221 }
1222 EXPORT_SYMBOL_GPL(rht_bucket_nested);
1223
1224 struct rhash_lock_head __rcu **rht_bucket_nested_insert(
1225 struct rhashtable *ht, struct bucket_table *tbl, unsigned int hash)
1226 {
1227 const unsigned int shift = PAGE_SHIFT - ilog2(sizeof(void *));
1228 unsigned int index = hash & ((1 << tbl->nest) - 1);
1229 unsigned int size = tbl->size >> tbl->nest;
1230 union nested_table *ntbl;
1231
1232 ntbl = nested_table_top(tbl);
1233 hash >>= tbl->nest;
1234 ntbl = nested_table_alloc(ht, &ntbl[index].table,
1235 size <= (1 << shift));
1236
1237 while (ntbl && size > (1 << shift)) {
1238 index = hash & ((1 << shift) - 1);
1239 size >>= shift;
1240 hash >>= shift;
1241 ntbl = nested_table_alloc(ht, &ntbl[index].table,
1242 size <= (1 << shift));
1243 }
1244
1245 if (!ntbl)
1246 return NULL;
1247
1248 return &ntbl[hash].bucket;
1249
1250 }
1251 EXPORT_SYMBOL_GPL(rht_bucket_nested_insert);
1252
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