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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Resizable, Scalable, Concurrent Hash Table4 *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_hash10 * Rewritten with rehash code from br_multicast plus single list11 * pointer as suggested by Josh Triplett12 */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 64UL30#define HASH_MIN_SIZE 4U31 32union nested_table {33 union nested_table __rcu *table;34 struct rhash_lock_head __rcu *bucket;35};36 37static HWJS_SUSPENDS 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_LOCKING45#define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))46 47int lockdep_rht_mutex_is_held(struct rhashtable *ht)48{49 return (debug_locks) ? lockdep_is_held(&ht->mutex) : 1;50}51EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);52 53int 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}61EXPORT_SYMBOL_GPL(lockdep_rht_bucket_is_held);62#else63#define ASSERT_RHT_MUTEX(HT)64#endif65 66static inline union nested_table *nested_table_top(67 const struct bucket_table *tbl)68{69 /* The top-level bucket entry does not need RCU protection70 * because it's set at the same time as tbl->nest.71 */72 return (void *)rcu_dereference_protected(tbl->buckets[0], 1);73}74 75static 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 94static 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 109static 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 117static void bucket_table_free_rcu(struct rcu_head *head)118{119 bucket_table_free(container_of(head, struct bucket_table, rcu));120}121 122static 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 148static 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 177static 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 && !gfpflags_allow_blocking(gfp)) {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 215static 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 228static HWJS_SUSPENDS 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 else273 /* Need to preserved the bit lock. */274 rht_assign_locked(bkt, next);275 276out:277 return err;278}279 280static HWJS_SUSPENDS 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 302static 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. Deletions307 * and lookups will be attempted in both tables until we synchronize.308 * As cmpxchg() provides strong barriers, we do not need309 * 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 319static HWJS_SUSPENDS 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 new346 * table, and thus no references to the old table will347 * remain.348 * We do this inside the locked region so that349 * 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 358static 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 lookups380 * @ht: the hash table to shrink381 *382 * This function shrinks the hash table to fit, i.e., the smallest383 * size would not cause it to expand right away automatically.384 *385 * The caller must ensure that no concurrent resizing occurs by holding386 * 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 per392 * bucket locks or concurrent RCU protected lookups and traversals.393 */394static 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 414static HWJS_SUSPENDS 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 446static HWJS_SUSPENDS 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 } else478 schedule_work(&ht->run_work);479 480 return err;481 482fail: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 494static HWJS_SUSPENDS 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 else533 /* 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 545static HWJS_SUSPENDS 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 holds583 * the lock, which we need to preserve584 */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 594static HWJS_SUSPENDS 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 else613 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 637void *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}650EXPORT_SYMBOL_GPL(rhashtable_insert_slow);651 652/**653 * rhashtable_walk_enter - Initialise an iterator654 * @ht: Table to walk over655 * @iter: Hash table Iterator656 *657 * This function prepares a hash table walk.658 *659 * Note that if you restart a walk after rhashtable_walk_stop you660 * may see the same object twice. Also, you may miss objects if661 * there are removals in between rhashtable_walk_stop and the next662 * call to rhashtable_walk_start.663 *664 * For a completely stable walk you should construct your own data665 * structure outside the hash table.666 *667 * This function may be called from any process context, including668 * non-preemptable context, but cannot be called from softirq or669 * hardirq context.670 *671 * You must call rhashtable_walk_exit after this function returns.672 */673void 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}687EXPORT_SYMBOL_GPL(rhashtable_walk_enter);688 689/**690 * rhashtable_walk_exit - Free an iterator691 * @iter: Hash table Iterator692 *693 * This function frees resources allocated by rhashtable_walk_enter.694 */695void 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}702EXPORT_SYMBOL_GPL(rhashtable_walk_exit);703 704/**705 * rhashtable_walk_start_check - Start a hash table walk706 * @iter: Hash table iterator707 *708 * Start a hash table walk at the current iterator position. Note that we take709 * the RCU lock in all cases including when we return an error. So you must710 * 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 iterator715 * will rewind back to the beginning and you may use it immediately716 * by calling rhashtable_walk_next.717 *718 * rhashtable_walk_start is defined as an inline variant that returns719 * void. This is preferred in cases where the caller would ignore720 * resize events and always continue.721 */722int 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, and747 * 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, and761 * 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 }780found:781 return 0;782}783EXPORT_SYMBOL_GPL(rhashtable_walk_start_check);784 785/**786 * __rhashtable_walk_find_next - Find the next element in a table (or the first787 * one in case of a new walk).788 *789 * @iter: Hash table iterator790 *791 * Returns the found object or NULL when the end of the table is reached.792 *793 * Returns -EAGAIN if resize event occurred.794 */795static 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 827next: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 iterator857 * @iter: Hash table iterator858 *859 * Note that you must call rhashtable_walk_stop when you are finished860 * 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 iterator865 * will rewind back to the beginning and you may continue to use it.866 */867void *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 find887 * next entry from that point.888 */889 iter->skip = 0;890 iter->slot++;891 }892 893 return __rhashtable_walk_find_next(iter);894}895EXPORT_SYMBOL_GPL(rhashtable_walk_next);896 897/**898 * rhashtable_walk_peek - Return the next object but don't advance the iterator899 * @iter: Hash table iterator900 *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 iterator904 * will rewind back to the beginning and you may continue to use it.905 */906void *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 table919 * beyond that last one that was found. Decrement skip so920 * we find the current value. __rhashtable_walk_find_next921 * will restore the original value of skip assuming that922 * the table hasn't changed.923 */924 iter->skip--;925 }926 927 return __rhashtable_walk_find_next(iter);928}929EXPORT_SYMBOL_GPL(rhashtable_walk_peek);930 931/**932 * rhashtable_walk_stop - Finish a hash table walk933 * @iter: Hash table iterator934 *935 * Finish a hash table walk. Does not reset the iterator to the start of the936 * hash table.937 */938void 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 else954 list_add(&iter->walker.list, &tbl->walkers);955 spin_unlock(&ht->lock);956 957out:958 rcu_read_unlock();959}960EXPORT_SYMBOL_GPL(rhashtable_walk_stop);961 962static 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 else970 retsize = max(HASH_DEFAULT_SIZE,971 (unsigned long)params->min_size);972 973 return retsize;974}975 976static 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 table983 * @ht: hash table to be initialized984 * @params: configuration parameters985 *986 * Initializes a new hash table based on the provided configuration987 * parameters. A table can be configured either with a variable or988 * fixed length key:989 *990 * Configuration Example 1: Fixed length keys991 * 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 keys1005 * 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 */1023int 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 the1068 * initial rhashtable allocation. Upon failure, retry with the1069 * 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}1085EXPORT_SYMBOL_GPL(rhashtable_init_noprof);1086 1087/**1088 * rhltable_init - initialize a new hash list table1089 * @hlt: hash list table to be initialized1090 * @params: configuration parameters1091 *1092 * Initializes a new hash list table.1093 *1094 * See documentation for rhashtable_init.1095 */1096int 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}1104EXPORT_SYMBOL_GPL(rhltable_init_noprof);1105 1106static 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 table1127 * @ht: the hash table to destroy1128 * @free_fn: callback to release resources of element1129 * @arg: pointer passed to free_fn1130 *1131 * Stops an eventual async resize. If defined, invokes free_fn for each1132 * element to releasal resources. Please note that RCU protected1133 * readers may still be accessing the elements. Releasing of resources1134 * must occur in a compatible manner. Then frees the bucket array.1135 *1136 * This function will eventually sleep to wait for an async resize1137 * to complete. The caller is responsible that no further write operations1138 * occurs in parallel.1139 */1140void 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);1151restart: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}1176EXPORT_SYMBOL_GPL(rhashtable_free_and_destroy);1177 1178void rhashtable_destroy(struct rhashtable *ht)1179{1180 return rhashtable_free_and_destroy(ht, NULL, NULL);1181}1182EXPORT_SYMBOL_GPL(rhashtable_destroy);1183 1184struct 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}1211EXPORT_SYMBOL_GPL(__rht_bucket_nested);1212 1213struct 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}1222EXPORT_SYMBOL_GPL(rht_bucket_nested);1223 1224struct 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}1251EXPORT_SYMBOL_GPL(rht_bucket_nested_insert);1252