lib/rhashtable.c

   1 /*
   2  * Resizable, Scalable, Concurrent Hash Table
   3  *
   4  * Copyright (c) 2014 Thomas Graf <tgraf@suug.ch>
   5  * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
   6  *
   7  * Based on the following paper:
   8  * https://www.usenix.org/legacy/event/atc11/tech/final_files/Triplett.pdf
   9  *
  10  * Code partially derived from nft_hash
  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/kernel.h>
  18 #include <linux/init.h>
  19 #include <linux/log2.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
  27 #define HASH_DEFAULT_SIZE       64UL
  28 #define HASH_MIN_SIZE           4UL
  29
  30 #define ASSERT_RHT_MUTEX(HT) BUG_ON(!lockdep_rht_mutex_is_held(HT))
  31
  32 #ifdef CONFIG_PROVE_LOCKING
  33 int lockdep_rht_mutex_is_held(const struct rhashtable *ht)
  34 {
  35         return ht->p.mutex_is_held(ht->p.parent);
  36 }
  37 EXPORT_SYMBOL_GPL(lockdep_rht_mutex_is_held);
  38 #endif
  39
  40 static void *rht_obj(const struct rhashtable *ht, const struct rhash_head *he)
  41 {
  42         return (void *) he - ht->p.head_offset;
  43 }
  44
  45 static u32 __hashfn(const struct rhashtable *ht, const void *key,
  46                       u32 len, u32 hsize)
  47 {
  48         u32 h;
  49
  50         h = ht->p.hashfn(key, len, ht->p.hash_rnd);
  51
  52         return h & (hsize - 1);
  53 }
  54
  55 /**
  56  * rhashtable_hashfn - compute hash for key of given length
  57  * @ht:         hash table to compute for
  58  * @key:        pointer to key
  59  * @len:        length of key
  60  *
  61  * Computes the hash value using the hash function provided in the 'hashfn'
  62  * of struct rhashtable_params. The returned value is guaranteed to be
  63  * smaller than the number of buckets in the hash table.
  64  */
  65 u32 rhashtable_hashfn(const struct rhashtable *ht, const void *key, u32 len)
  66 {
  67         struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht);
  68
  69         return __hashfn(ht, key, len, tbl->size);
  70 }
  71 EXPORT_SYMBOL_GPL(rhashtable_hashfn);
  72
  73 static u32 obj_hashfn(const struct rhashtable *ht, const void *ptr, u32 hsize)
  74 {
  75         if (unlikely(!ht->p.key_len)) {
  76                 u32 h;
  77
  78                 h = ht->p.obj_hashfn(ptr, ht->p.hash_rnd);
  79
  80                 return h & (hsize - 1);
  81         }
  82
  83         return __hashfn(ht, ptr + ht->p.key_offset, ht->p.key_len, hsize);
  84 }
  85
  86 /**
  87  * rhashtable_obj_hashfn - compute hash for hashed object
  88  * @ht:         hash table to compute for
  89  * @ptr:        pointer to hashed object
  90  *
  91  * Computes the hash value using the hash function `hashfn` respectively
  92  * 'obj_hashfn' depending on whether the hash table is set up to work with
  93  * a fixed length key. The returned value is guaranteed to be smaller than
  94  * the number of buckets in the hash table.
  95  */
  96 u32 rhashtable_obj_hashfn(const struct rhashtable *ht, void *ptr)
  97 {
  98         struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht);
  99
 100         return obj_hashfn(ht, ptr, tbl->size);
 101 }
 102 EXPORT_SYMBOL_GPL(rhashtable_obj_hashfn);
 103
 104 static u32 head_hashfn(const struct rhashtable *ht,
 105                        const struct rhash_head *he, u32 hsize)
 106 {
 107         return obj_hashfn(ht, rht_obj(ht, he), hsize);
 108 }
 109
 110 static struct bucket_table *bucket_table_alloc(size_t nbuckets)
 111 {
 112         struct bucket_table *tbl;
 113         size_t size;
 114
 115         size = sizeof(*tbl) + nbuckets * sizeof(tbl->buckets[0]);
 116         tbl = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
 117         if (tbl == NULL)
 118                 tbl = vzalloc(size);
 119
 120         if (tbl == NULL)
 121                 return NULL;
 122
 123         tbl->size = nbuckets;
 124
 125         return tbl;
 126 }
 127
 128 static void bucket_table_free(const struct bucket_table *tbl)
 129 {
 130         kvfree(tbl);
 131 }
 132
 133 /**
 134  * rht_grow_above_75 - returns true if nelems > 0.75 * table-size
 135  * @ht:         hash table
 136  * @new_size:   new table size
 137  */
 138 bool rht_grow_above_75(const struct rhashtable *ht, size_t new_size)
 139 {
 140         /* Expand table when exceeding 75% load */
 141         return ht->nelems > (new_size / 4 * 3);
 142 }
 143 EXPORT_SYMBOL_GPL(rht_grow_above_75);
 144
 145 /**
 146  * rht_shrink_below_30 - returns true if nelems < 0.3 * table-size
 147  * @ht:         hash table
 148  * @new_size:   new table size
 149  */
 150 bool rht_shrink_below_30(const struct rhashtable *ht, size_t new_size)
 151 {
 152         /* Shrink table beneath 30% load */
 153         return ht->nelems < (new_size * 3 / 10);
 154 }
 155 EXPORT_SYMBOL_GPL(rht_shrink_below_30);
 156
 157 static void hashtable_chain_unzip(const struct rhashtable *ht,
 158                                   const struct bucket_table *new_tbl,
 159                                   struct bucket_table *old_tbl, size_t n)
 160 {
 161         struct rhash_head *he, *p, *next;
 162         unsigned int h;
 163
 164         /* Old bucket empty, no work needed. */
 165         p = rht_dereference(old_tbl->buckets[n], ht);
 166         if (!p)
 167                 return;
 168
 169         /* Advance the old bucket pointer one or more times until it
 170          * reaches a node that doesn't hash to the same bucket as the
 171          * previous node p. Call the previous node p;
 172          */
 173         h = head_hashfn(ht, p, new_tbl->size);
 174         rht_for_each(he, p->next, ht) {
 175                 if (head_hashfn(ht, he, new_tbl->size) != h)
 176                         break;
 177                 p = he;
 178         }
 179         RCU_INIT_POINTER(old_tbl->buckets[n], p->next);
 180
 181         /* Find the subsequent node which does hash to the same
 182          * bucket as node P, or NULL if no such node exists.
 183          */
 184         next = NULL;
 185         if (he) {
 186                 rht_for_each(he, he->next, ht) {
 187                         if (head_hashfn(ht, he, new_tbl->size) == h) {
 188                                 next = he;
 189                                 break;
 190                         }
 191                 }
 192         }
 193
 194         /* Set p's next pointer to that subsequent node pointer,
 195          * bypassing the nodes which do not hash to p's bucket
 196          */
 197         RCU_INIT_POINTER(p->next, next);
 198 }
 199
 200 /**
 201  * rhashtable_expand - Expand hash table while allowing concurrent lookups
 202  * @ht:         the hash table to expand
 203  *
 204  * A secondary bucket array is allocated and the hash entries are migrated
 205  * while keeping them on both lists until the end of the RCU grace period.
 206  *
 207  * This function may only be called in a context where it is safe to call
 208  * synchronize_rcu(), e.g. not within a rcu_read_lock() section.
 209  *
 210  * The caller must ensure that no concurrent table mutations take place.
 211  * It is however valid to have concurrent lookups if they are RCU protected.
 212  */
 213 int rhashtable_expand(struct rhashtable *ht)
 214 {
 215         struct bucket_table *new_tbl, *old_tbl = rht_dereference(ht->tbl, ht);
 216         struct rhash_head *he;
 217         unsigned int i, h;
 218         bool complete;
 219
 220         ASSERT_RHT_MUTEX(ht);
 221
 222         if (ht->p.max_shift && ht->shift >= ht->p.max_shift)
 223                 return 0;
 224
 225         new_tbl = bucket_table_alloc(old_tbl->size * 2);
 226         if (new_tbl == NULL)
 227                 return -ENOMEM;
 228
 229         ht->shift++;
 230
 231         /* For each new bucket, search the corresponding old bucket
 232          * for the first entry that hashes to the new bucket, and
 233          * link the new bucket to that entry. Since all the entries
 234          * which will end up in the new bucket appear in the same
 235          * old bucket, this constructs an entirely valid new hash
 236          * table, but with multiple buckets "zipped" together into a
 237          * single imprecise chain.
 238          */
 239         for (i = 0; i < new_tbl->size; i++) {
 240                 h = i & (old_tbl->size - 1);
 241                 rht_for_each(he, old_tbl->buckets[h], ht) {
 242                         if (head_hashfn(ht, he, new_tbl->size) == i) {
 243                                 RCU_INIT_POINTER(new_tbl->buckets[i], he);
 244                                 break;
 245                         }
 246                 }
 247         }
 248
 249         /* Publish the new table pointer. Lookups may now traverse
 250          * the new table, but they will not benefit from any
 251          * additional efficiency until later steps unzip the buckets.
 252          */
 253         rcu_assign_pointer(ht->tbl, new_tbl);
 254
 255         /* Unzip interleaved hash chains */
 256         do {
 257                 /* Wait for readers. All new readers will see the new
 258                  * table, and thus no references to the old table will
 259                  * remain.
 260                  */
 261                 synchronize_rcu();
 262
 263                 /* For each bucket in the old table (each of which
 264                  * contains items from multiple buckets of the new
 265                  * table): ...
 266                  */
 267                 complete = true;
 268                 for (i = 0; i < old_tbl->size; i++) {
 269                         hashtable_chain_unzip(ht, new_tbl, old_tbl, i);
 270                         if (old_tbl->buckets[i] != NULL)
 271                                 complete = false;
 272                 }
 273         } while (!complete);
 274
 275         bucket_table_free(old_tbl);
 276         return 0;
 277 }
 278 EXPORT_SYMBOL_GPL(rhashtable_expand);
 279
 280 /**
 281  * rhashtable_shrink - Shrink hash table while allowing concurrent lookups
 282  * @ht:         the hash table to shrink
 283  *
 284  * This function may only be called in a context where it is safe to call
 285  * synchronize_rcu(), e.g. not within a rcu_read_lock() section.
 286  *
 287  * The caller must ensure that no concurrent table mutations take place.
 288  * It is however valid to have concurrent lookups if they are RCU protected.
 289  */
 290 int rhashtable_shrink(struct rhashtable *ht)
 291 {
 292         struct bucket_table *ntbl, *tbl = rht_dereference(ht->tbl, ht);
 293         struct rhash_head __rcu **pprev;
 294         unsigned int i;
 295
 296         ASSERT_RHT_MUTEX(ht);
 297
 298         if (ht->shift <= ht->p.min_shift)
 299                 return 0;
 300
 301         ntbl = bucket_table_alloc(tbl->size / 2);
 302         if (ntbl == NULL)
 303                 return -ENOMEM;
 304
 305         ht->shift--;
 306
 307         /* Link each bucket in the new table to the first bucket
 308          * in the old table that contains entries which will hash
 309          * to the new bucket.
 310          */
 311         for (i = 0; i < ntbl->size; i++) {
 312                 ntbl->buckets[i] = tbl->buckets[i];
 313
 314                 /* Link each bucket in the new table to the first bucket
 315                  * in the old table that contains entries which will hash
 316                  * to the new bucket.
 317                  */
 318                 for (pprev = &ntbl->buckets[i]; *pprev != NULL;
 319                      pprev = &rht_dereference(*pprev, ht)->next)
 320                         ;
 321                 RCU_INIT_POINTER(*pprev, tbl->buckets[i + ntbl->size]);
 322         }
 323
 324         /* Publish the new, valid hash table */
 325         rcu_assign_pointer(ht->tbl, ntbl);
 326
 327         /* Wait for readers. No new readers will have references to the
 328          * old hash table.
 329          */
 330         synchronize_rcu();
 331
 332         bucket_table_free(tbl);
 333
 334         return 0;
 335 }
 336 EXPORT_SYMBOL_GPL(rhashtable_shrink);
 337
 338 /**
 339  * rhashtable_insert - insert object into hash hash table
 340  * @ht:         hash table
 341  * @obj:        pointer to hash head inside object
 342  *
 343  * Will automatically grow the table via rhashtable_expand() if the the
 344  * grow_decision function specified at rhashtable_init() returns true.
 345  *
 346  * The caller must ensure that no concurrent table mutations occur. It is
 347  * however valid to have concurrent lookups if they are RCU protected.
 348  */
 349 void rhashtable_insert(struct rhashtable *ht, struct rhash_head *obj)
 350 {
 351         struct bucket_table *tbl = rht_dereference(ht->tbl, ht);
 352         u32 hash;
 353
 354         ASSERT_RHT_MUTEX(ht);
 355
 356         hash = head_hashfn(ht, obj, tbl->size);
 357         RCU_INIT_POINTER(obj->next, tbl->buckets[hash]);
 358         rcu_assign_pointer(tbl->buckets[hash], obj);
 359         ht->nelems++;
 360
 361         if (ht->p.grow_decision && ht->p.grow_decision(ht, tbl->size))
 362                 rhashtable_expand(ht);
 363 }
 364 EXPORT_SYMBOL_GPL(rhashtable_insert);
 365
 366 /**
 367  * rhashtable_remove_pprev - remove object from hash table given previous element
 368  * @ht:         hash table
 369  * @obj:        pointer to hash head inside object
 370  * @pprev:      pointer to previous element
 371  *
 372  * Identical to rhashtable_remove() but caller is alreayd aware of the element
 373  * in front of the element to be deleted. This is in particular useful for
 374  * deletion when combined with walking or lookup.
 375  */
 376 void rhashtable_remove_pprev(struct rhashtable *ht, struct rhash_head *obj,
 377                              struct rhash_head __rcu **pprev)
 378 {
 379         struct bucket_table *tbl = rht_dereference(ht->tbl, ht);
 380
 381         ASSERT_RHT_MUTEX(ht);
 382
 383         RCU_INIT_POINTER(*pprev, obj->next);
 384         ht->nelems--;
 385
 386         if (ht->p.shrink_decision &&
 387             ht->p.shrink_decision(ht, tbl->size))
 388                 rhashtable_shrink(ht);
 389 }
 390 EXPORT_SYMBOL_GPL(rhashtable_remove_pprev);
 391
 392 /**
 393  * rhashtable_remove - remove object from hash table
 394  * @ht:         hash table
 395  * @obj:        pointer to hash head inside object
 396  *
 397  * Since the hash chain is single linked, the removal operation needs to
 398  * walk the bucket chain upon removal. The removal operation is thus
 399  * considerable slow if the hash table is not correctly sized.
 400  *
 401  * Will automatically shrink the table via rhashtable_expand() if the the
 402  * shrink_decision function specified at rhashtable_init() returns true.
 403  *
 404  * The caller must ensure that no concurrent table mutations occur. It is
 405  * however valid to have concurrent lookups if they are RCU protected.
 406  */
 407 bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj)
 408 {
 409         struct bucket_table *tbl = rht_dereference(ht->tbl, ht);
 410         struct rhash_head __rcu **pprev;
 411         struct rhash_head *he;
 412         u32 h;
 413
 414         ASSERT_RHT_MUTEX(ht);
 415
 416         h = head_hashfn(ht, obj, tbl->size);
 417
 418         pprev = &tbl->buckets[h];
 419         rht_for_each(he, tbl->buckets[h], ht) {
 420                 if (he != obj) {
 421                         pprev = &he->next;
 422                         continue;
 423                 }
 424
 425                 rhashtable_remove_pprev(ht, he, pprev);
 426                 return true;
 427         }
 428
 429         return false;
 430 }
 431 EXPORT_SYMBOL_GPL(rhashtable_remove);
 432
 433 /**
 434  * rhashtable_lookup - lookup key in hash table
 435  * @ht:         hash table
 436  * @key:        pointer to key
 437  *
 438  * Computes the hash value for the key and traverses the bucket chain looking
 439  * for a entry with an identical key. The first matching entry is returned.
 440  *
 441  * This lookup function may only be used for fixed key hash table (key_len
 442  * paramter set). It will BUG() if used inappropriately.
 443  *
 444  * Lookups may occur in parallel with hash mutations as long as the lookup is
 445  * guarded by rcu_read_lock(). The caller must take care of this.
 446  */
 447 void *rhashtable_lookup(const struct rhashtable *ht, const void *key)
 448 {
 449         const struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht);
 450         struct rhash_head *he;
 451         u32 h;
 452
 453         BUG_ON(!ht->p.key_len);
 454
 455         h = __hashfn(ht, key, ht->p.key_len, tbl->size);
 456         rht_for_each_rcu(he, tbl->buckets[h], ht) {
 457                 if (memcmp(rht_obj(ht, he) + ht->p.key_offset, key,
 458                            ht->p.key_len))
 459                         continue;
 460                 return (void *) he - ht->p.head_offset;
 461         }
 462
 463         return NULL;
 464 }
 465 EXPORT_SYMBOL_GPL(rhashtable_lookup);
 466
 467 /**
 468  * rhashtable_lookup_compare - search hash table with compare function
 469  * @ht:         hash table
 470  * @hash:       hash value of desired entry
 471  * @compare:    compare function, must return true on match
 472  * @arg:        argument passed on to compare function
 473  *
 474  * Traverses the bucket chain behind the provided hash value and calls the
 475  * specified compare function for each entry.
 476  *
 477  * Lookups may occur in parallel with hash mutations as long as the lookup is
 478  * guarded by rcu_read_lock(). The caller must take care of this.
 479  *
 480  * Returns the first entry on which the compare function returned true.
 481  */
 482 void *rhashtable_lookup_compare(const struct rhashtable *ht, u32 hash,
 483                                 bool (*compare)(void *, void *), void *arg)
 484 {
 485         const struct bucket_table *tbl = rht_dereference_rcu(ht->tbl, ht);
 486         struct rhash_head *he;
 487
 488         if (unlikely(hash >= tbl->size))
 489                 return NULL;
 490
 491         rht_for_each_rcu(he, tbl->buckets[hash], ht) {
 492                 if (!compare(rht_obj(ht, he), arg))
 493                         continue;
 494                 return (void *) he - ht->p.head_offset;
 495         }
 496
 497         return NULL;
 498 }
 499 EXPORT_SYMBOL_GPL(rhashtable_lookup_compare);
 500
 501 static size_t rounded_hashtable_size(struct rhashtable_params *params)
 502 {
 503         return max(roundup_pow_of_two(params->nelem_hint * 4 / 3),
 504                    1UL << params->min_shift);
 505 }
 506
 507 /**
 508  * rhashtable_init - initialize a new hash table
 509  * @ht:         hash table to be initialized
 510  * @params:     configuration parameters
 511  *
 512  * Initializes a new hash table based on the provided configuration
 513  * parameters. A table can be configured either with a variable or
 514  * fixed length key:
 515  *
 516  * Configuration Example 1: Fixed length keys
 517  * struct test_obj {
 518  *      int                     key;
 519  *      void *                  my_member;
 520  *      struct rhash_head       node;
 521  * };
 522  *
 523  * struct rhashtable_params params = {
 524  *      .head_offset = offsetof(struct test_obj, node),
 525  *      .key_offset = offsetof(struct test_obj, key),
 526  *      .key_len = sizeof(int),
 527  *      .hashfn = jhash,
 528  * #ifdef CONFIG_PROVE_LOCKING
 529  *      .mutex_is_held = &my_mutex_is_held,
 530  * #endif
 531  * };
 532  *
 533  * Configuration Example 2: Variable length keys
 534  * struct test_obj {
 535  *      [...]
 536  *      struct rhash_head       node;
 537  * };
 538  *
 539  * u32 my_hash_fn(const void *data, u32 seed)
 540  * {
 541  *      struct test_obj *obj = data;
 542  *
 543  *      return [... hash ...];
 544  * }
 545  *
 546  * struct rhashtable_params params = {
 547  *      .head_offset = offsetof(struct test_obj, node),
 548  *      .hashfn = jhash,
 549  *      .obj_hashfn = my_hash_fn,
 550  * #ifdef CONFIG_PROVE_LOCKING
 551  *      .mutex_is_held = &my_mutex_is_held,
 552  * #endif
 553  * };
 554  */
 555 int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params)
 556 {
 557         struct bucket_table *tbl;
 558         size_t size;
 559
 560         size = HASH_DEFAULT_SIZE;
 561
 562         if ((params->key_len && !params->hashfn) ||
 563             (!params->key_len && !params->obj_hashfn))
 564                 return -EINVAL;
 565
 566         params->min_shift = max_t(size_t, params->min_shift,
 567                                   ilog2(HASH_MIN_SIZE));
 568
 569         if (params->nelem_hint)
 570                 size = rounded_hashtable_size(params);
 571
 572         tbl = bucket_table_alloc(size);
 573         if (tbl == NULL)
 574                 return -ENOMEM;
 575
 576         memset(ht, 0, sizeof(*ht));
 577         ht->shift = ilog2(tbl->size);
 578         memcpy(&ht->p, params, sizeof(*params));
 579         RCU_INIT_POINTER(ht->tbl, tbl);
 580
 581         if (!ht->p.hash_rnd)
 582                 get_random_bytes(&ht->p.hash_rnd, sizeof(ht->p.hash_rnd));
 583
 584         return 0;
 585 }
 586 EXPORT_SYMBOL_GPL(rhashtable_init);
 587
 588 /**
 589  * rhashtable_destroy - destroy hash table
 590  * @ht:         the hash table to destroy
 591  *
 592  * Frees the bucket array. This function is not rcu safe, therefore the caller
 593  * has to make sure that no resizing may happen by unpublishing the hashtable
 594  * and waiting for the quiescent cycle before releasing the bucket array.
 595  */
 596 void rhashtable_destroy(const struct rhashtable *ht)
 597 {
 598         bucket_table_free(ht->tbl);
 599 }
 600 EXPORT_SYMBOL_GPL(rhashtable_destroy);
 601
 602 /**************************************************************************
 603  * Self Test
 604  **************************************************************************/
 605
 606 #ifdef CONFIG_TEST_RHASHTABLE
 607
 608 #define TEST_HT_SIZE    8
 609 #define TEST_ENTRIES    2048
 610 #define TEST_PTR        ((void *) 0xdeadbeef)
 611 #define TEST_NEXPANDS   4
 612
 613 #ifdef CONFIG_PROVE_LOCKING
 614 static int test_mutex_is_held(void *parent)
 615 {
 616         return 1;
 617 }
 618 #endif
 619
 620 struct test_obj {
 621         void                    *ptr;
 622         int                     value;
 623         struct rhash_head       node;
 624 };
 625
 626 static int __init test_rht_lookup(struct rhashtable *ht)
 627 {
 628         unsigned int i;
 629
 630         for (i = 0; i < TEST_ENTRIES * 2; i++) {
 631                 struct test_obj *obj;
 632                 bool expected = !(i % 2);
 633                 u32 key = i;
 634
 635                 obj = rhashtable_lookup(ht, &key);
 636
 637                 if (expected && !obj) {
 638                         pr_warn("Test failed: Could not find key %u\n", key);
 639                         return -ENOENT;
 640                 } else if (!expected && obj) {
 641                         pr_warn("Test failed: Unexpected entry found for key %u\n",
 642                                 key);
 643                         return -EEXIST;
 644                 } else if (expected && obj) {
 645                         if (obj->ptr != TEST_PTR || obj->value != i) {
 646                                 pr_warn("Test failed: Lookup value mismatch %p!=%p, %u!=%u\n",
 647                                         obj->ptr, TEST_PTR, obj->value, i);
 648                                 return -EINVAL;
 649                         }
 650                 }
 651         }
 652
 653         return 0;
 654 }
 655
 656 static void test_bucket_stats(struct rhashtable *ht, bool quiet)
 657 {
 658         unsigned int cnt, rcu_cnt, i, total = 0;
 659         struct test_obj *obj;
 660         struct bucket_table *tbl;
 661
 662         tbl = rht_dereference_rcu(ht->tbl, ht);
 663         for (i = 0; i < tbl->size; i++) {
 664                 rcu_cnt = cnt = 0;
 665
 666                 if (!quiet)
 667                         pr_info(" [%#4x/%zu]", i, tbl->size);
 668
 669                 rht_for_each_entry_rcu(obj, tbl->buckets[i], node) {
 670                         cnt++;
 671                         total++;
 672                         if (!quiet)
 673                                 pr_cont(" [%p],", obj);
 674                 }
 675
 676                 rht_for_each_entry_rcu(obj, tbl->buckets[i], node)
 677                         rcu_cnt++;
 678
 679                 if (rcu_cnt != cnt)
 680                         pr_warn("Test failed: Chain count mismach %d != %d",
 681                                 cnt, rcu_cnt);
 682
 683                 if (!quiet)
 684                         pr_cont("\n  [%#x] first element: %p, chain length: %u\n",
 685                                 i, tbl->buckets[i], cnt);
 686         }
 687
 688         pr_info("  Traversal complete: counted=%u, nelems=%zu, entries=%d\n",
 689                 total, ht->nelems, TEST_ENTRIES);
 690
 691         if (total != ht->nelems || total != TEST_ENTRIES)
 692                 pr_warn("Test failed: Total count mismatch ^^^");
 693 }
 694
 695 static int __init test_rhashtable(struct rhashtable *ht)
 696 {
 697         struct bucket_table *tbl;
 698         struct test_obj *obj, *next;
 699         int err;
 700         unsigned int i;
 701
 702         /*
 703          * Insertion Test:
 704          * Insert TEST_ENTRIES into table with all keys even numbers
 705          */
 706         pr_info("  Adding %d keys\n", TEST_ENTRIES);
 707         for (i = 0; i < TEST_ENTRIES; i++) {
 708                 struct test_obj *obj;
 709
 710                 obj = kzalloc(sizeof(*obj), GFP_KERNEL);
 711                 if (!obj) {
 712                         err = -ENOMEM;
 713                         goto error;
 714                 }
 715
 716                 obj->ptr = TEST_PTR;
 717                 obj->value = i * 2;
 718
 719                 rhashtable_insert(ht, &obj->node);
 720         }
 721
 722         rcu_read_lock();
 723         test_bucket_stats(ht, true);
 724         test_rht_lookup(ht);
 725         rcu_read_unlock();
 726
 727         for (i = 0; i < TEST_NEXPANDS; i++) {
 728                 pr_info("  Table expansion iteration %u...\n", i);
 729                 rhashtable_expand(ht);
 730
 731                 rcu_read_lock();
 732                 pr_info("  Verifying lookups...\n");
 733                 test_rht_lookup(ht);
 734                 rcu_read_unlock();
 735         }
 736
 737         for (i = 0; i < TEST_NEXPANDS; i++) {
 738                 pr_info("  Table shrinkage iteration %u...\n", i);
 739                 rhashtable_shrink(ht);
 740
 741                 rcu_read_lock();
 742                 pr_info("  Verifying lookups...\n");
 743                 test_rht_lookup(ht);
 744                 rcu_read_unlock();
 745         }
 746
 747         rcu_read_lock();
 748         test_bucket_stats(ht, true);
 749         rcu_read_unlock();
 750
 751         pr_info("  Deleting %d keys\n", TEST_ENTRIES);
 752         for (i = 0; i < TEST_ENTRIES; i++) {
 753                 u32 key = i * 2;
 754
 755                 obj = rhashtable_lookup(ht, &key);
 756                 BUG_ON(!obj);
 757
 758                 rhashtable_remove(ht, &obj->node);
 759                 kfree(obj);
 760         }
 761
 762         return 0;
 763
 764 error:
 765         tbl = rht_dereference_rcu(ht->tbl, ht);
 766         for (i = 0; i < tbl->size; i++)
 767                 rht_for_each_entry_safe(obj, next, tbl->buckets[i], ht, node)
 768                         kfree(obj);
 769
 770         return err;
 771 }
 772
 773 static int __init test_rht_init(void)
 774 {
 775         struct rhashtable ht;
 776         struct rhashtable_params params = {
 777                 .nelem_hint = TEST_HT_SIZE,
 778                 .head_offset = offsetof(struct test_obj, node),
 779                 .key_offset = offsetof(struct test_obj, value),
 780                 .key_len = sizeof(int),
 781                 .hashfn = jhash,
 782 #ifdef CONFIG_PROVE_LOCKING
 783                 .mutex_is_held = &test_mutex_is_held,
 784 #endif
 785                 .grow_decision = rht_grow_above_75,
 786                 .shrink_decision = rht_shrink_below_30,
 787         };
 788         int err;
 789
 790         pr_info("Running resizable hashtable tests...\n");
 791
 792         err = rhashtable_init(&ht, &params);
 793         if (err < 0) {
 794                 pr_warn("Test failed: Unable to initialize hashtable: %d\n",
 795                         err);
 796                 return err;
 797         }
 798
 799         err = test_rhashtable(&ht);
 800
 801         rhashtable_destroy(&ht);
 802
 803         return err;
 804 }
 805
 806 subsys_initcall(test_rht_init);
 807
 808 #endif /* CONFIG_TEST_RHASHTABLE */