git.ozlabs.org Git - ccan/blob - ccan/tdb2/hash.c

   1  /*
   2    Trivial Database 2: hash handling
   3    Copyright (C) Rusty Russell 2010
   4
   5    This library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 3 of the License, or (at your option) any later version.
   9
  10    This library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with this library; if not, see <http://www.gnu.org/licenses/>.
  17 */
  18 #include "private.h"
  19 #include <assert.h>
  20 #include <ccan/hash/hash.h>
  21
  22 static uint64_t jenkins_hash(const void *key, size_t length, uint64_t seed,
  23                              void *arg)
  24 {
  25         uint64_t ret;
  26         /* hash64_stable assumes lower bits are more important; they are a
  27          * slightly better hash.  We use the upper bits first, so swap them. */
  28         ret = hash64_stable((const unsigned char *)key, length, seed);
  29         return (ret >> 32) | (ret << 32);
  30 }
  31
  32 void tdb_hash_init(struct tdb_context *tdb)
  33 {
  34         tdb->khash = jenkins_hash;
  35         tdb->hash_priv = NULL;
  36 }
  37
  38 uint64_t tdb_hash(struct tdb_context *tdb, const void *ptr, size_t len)
  39 {
  40         return tdb->khash(ptr, len, tdb->hash_seed, tdb->hash_priv);
  41 }
  42
  43 uint64_t hash_record(struct tdb_context *tdb, tdb_off_t off)
  44 {
  45         const struct tdb_used_record *r;
  46         const void *key;
  47         uint64_t klen, hash;
  48
  49         r = tdb_access_read(tdb, off, sizeof(*r), true);
  50         if (TDB_PTR_IS_ERR(r)) {
  51                 tdb->ecode = TDB_PTR_ERR(r);
  52                 /* FIXME */
  53                 return 0;
  54         }
  55
  56         klen = rec_key_length(r);
  57         tdb_access_release(tdb, r);
  58
  59         key = tdb_access_read(tdb, off + sizeof(*r), klen, false);
  60         if (TDB_PTR_IS_ERR(key)) {
  61                 tdb->ecode = TDB_PTR_ERR(key);
  62                 return 0;
  63         }
  64
  65         hash = tdb_hash(tdb, key, klen);
  66         tdb_access_release(tdb, key);
  67         return hash;
  68 }
  69
  70 /* Get bits from a value. */
  71 static uint32_t bits_from(uint64_t val, unsigned start, unsigned num)
  72 {
  73         assert(num <= 32);
  74         return (val >> start) & ((1U << num) - 1);
  75 }
  76
  77 /* We take bits from the top: that way we can lock whole sections of the hash
  78  * by using lock ranges. */
  79 static uint32_t use_bits(struct hash_info *h, unsigned num)
  80 {
  81         h->hash_used += num;
  82         return bits_from(h->h, 64 - h->hash_used, num);
  83 }
  84
  85 static bool key_matches(struct tdb_context *tdb,
  86                         const struct tdb_used_record *rec,
  87                         tdb_off_t off,
  88                         const struct tdb_data *key)
  89 {
  90         bool ret = false;
  91         const char *rkey;
  92
  93         if (rec_key_length(rec) != key->dsize) {
  94                 add_stat(tdb, compare_wrong_keylen, 1);
  95                 return ret;
  96         }
  97
  98         rkey = tdb_access_read(tdb, off + sizeof(*rec), key->dsize, false);
  99         if (TDB_PTR_IS_ERR(rkey)) {
 100                 tdb->ecode = TDB_PTR_ERR(rkey);
 101                 return ret;
 102         }
 103         if (memcmp(rkey, key->dptr, key->dsize) == 0)
 104                 ret = true;
 105         else
 106                 add_stat(tdb, compare_wrong_keycmp, 1);
 107         tdb_access_release(tdb, rkey);
 108         return ret;
 109 }
 110
 111 /* Does entry match? */
 112 static bool match(struct tdb_context *tdb,
 113                   struct hash_info *h,
 114                   const struct tdb_data *key,
 115                   tdb_off_t val,
 116                   struct tdb_used_record *rec)
 117 {
 118         tdb_off_t off;
 119         enum TDB_ERROR ecode;
 120
 121         add_stat(tdb, compares, 1);
 122         /* Desired bucket must match. */
 123         if (h->home_bucket != (val & TDB_OFF_HASH_GROUP_MASK)) {
 124                 add_stat(tdb, compare_wrong_bucket, 1);
 125                 return false;
 126         }
 127
 128         /* Top bits of offset == next bits of hash. */
 129         if (bits_from(val, TDB_OFF_HASH_EXTRA_BIT, TDB_OFF_UPPER_STEAL_EXTRA)
 130             != bits_from(h->h, 64 - h->hash_used - TDB_OFF_UPPER_STEAL_EXTRA,
 131                     TDB_OFF_UPPER_STEAL_EXTRA)) {
 132                 add_stat(tdb, compare_wrong_offsetbits, 1);
 133                 return false;
 134         }
 135
 136         off = val & TDB_OFF_MASK;
 137         ecode = tdb_read_convert(tdb, off, rec, sizeof(*rec));
 138         if (ecode != TDB_SUCCESS) {
 139                 tdb->ecode = ecode;
 140                 return false;
 141         }
 142
 143         if ((h->h & ((1 << 11)-1)) != rec_hash(rec)) {
 144                 add_stat(tdb, compare_wrong_rechash, 1);
 145                 return false;
 146         }
 147
 148         return key_matches(tdb, rec, off, key);
 149 }
 150
 151 static tdb_off_t hbucket_off(tdb_off_t group_start, unsigned bucket)
 152 {
 153         return group_start
 154                 + (bucket % (1 << TDB_HASH_GROUP_BITS)) * sizeof(tdb_off_t);
 155 }
 156
 157 bool is_subhash(tdb_off_t val)
 158 {
 159         return (val >> TDB_OFF_UPPER_STEAL_SUBHASH_BIT) & 1;
 160 }
 161
 162 /* FIXME: Guess the depth, don't over-lock! */
 163 static tdb_off_t hlock_range(tdb_off_t group, tdb_off_t *size)
 164 {
 165         *size = 1ULL << (64 - (TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS));
 166         return group << (64 - (TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS));
 167 }
 168
 169 static tdb_off_t COLD find_in_chain(struct tdb_context *tdb,
 170                                     struct tdb_data key,
 171                                     tdb_off_t chain,
 172                                     struct hash_info *h,
 173                                     struct tdb_used_record *rec,
 174                                     struct traverse_info *tinfo)
 175 {
 176         tdb_off_t off, next;
 177         enum TDB_ERROR ecode;
 178
 179         /* In case nothing is free, we set these to zero. */
 180         h->home_bucket = h->found_bucket = 0;
 181
 182         for (off = chain; off; off = next) {
 183                 unsigned int i;
 184
 185                 h->group_start = off;
 186                 ecode = tdb_read_convert(tdb, off, h->group, sizeof(h->group));
 187                 if (ecode != TDB_SUCCESS) {
 188                         tdb->ecode = ecode;
 189                         return TDB_OFF_ERR;
 190                 }
 191
 192                 for (i = 0; i < (1 << TDB_HASH_GROUP_BITS); i++) {
 193                         tdb_off_t recoff;
 194                         if (!h->group[i]) {
 195                                 /* Remember this empty bucket. */
 196                                 h->home_bucket = h->found_bucket = i;
 197                                 continue;
 198                         }
 199
 200                         /* We can insert extra bits via add_to_hash
 201                          * empty bucket logic. */
 202                         recoff = h->group[i] & TDB_OFF_MASK;
 203                         ecode = tdb_read_convert(tdb, recoff, rec,
 204                                                  sizeof(*rec));
 205                         if (ecode != TDB_SUCCESS) {
 206                                 tdb->ecode = ecode;
 207                                 return TDB_OFF_ERR;
 208                         }
 209
 210                         if (key_matches(tdb, rec, recoff, &key)) {
 211                                 h->home_bucket = h->found_bucket = i;
 212
 213                                 if (tinfo) {
 214                                         tinfo->levels[tinfo->num_levels]
 215                                                 .hashtable = off;
 216                                         tinfo->levels[tinfo->num_levels]
 217                                                 .total_buckets
 218                                                 = 1 << TDB_HASH_GROUP_BITS;
 219                                         tinfo->levels[tinfo->num_levels].entry
 220                                                 = i;
 221                                         tinfo->num_levels++;
 222                                 }
 223                                 return recoff;
 224                         }
 225                 }
 226                 next = tdb_read_off(tdb, off
 227                                     + offsetof(struct tdb_chain, next));
 228                 if (TDB_OFF_IS_ERR(next)) {
 229                         tdb->ecode = next;
 230                         return TDB_OFF_ERR;
 231                 }
 232                 if (next)
 233                         next += sizeof(struct tdb_used_record);
 234         }
 235         return 0;
 236 }
 237
 238 /* This is the core routine which searches the hashtable for an entry.
 239  * On error, no locks are held and TDB_OFF_ERR is returned.
 240  * Otherwise, hinfo is filled in (and the optional tinfo).
 241  * If not found, the return value is 0.
 242  * If found, the return value is the offset, and *rec is the record. */
 243 tdb_off_t find_and_lock(struct tdb_context *tdb,
 244                         struct tdb_data key,
 245                         int ltype,
 246                         struct hash_info *h,
 247                         struct tdb_used_record *rec,
 248                         struct traverse_info *tinfo)
 249 {
 250         uint32_t i, group;
 251         tdb_off_t hashtable;
 252         enum TDB_ERROR ecode;
 253
 254         h->h = tdb_hash(tdb, key.dptr, key.dsize);
 255         h->hash_used = 0;
 256         group = use_bits(h, TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS);
 257         h->home_bucket = use_bits(h, TDB_HASH_GROUP_BITS);
 258
 259         h->hlock_start = hlock_range(group, &h->hlock_range);
 260         ecode = tdb_lock_hashes(tdb, h->hlock_start, h->hlock_range, ltype,
 261                                 TDB_LOCK_WAIT);
 262         if (ecode != TDB_SUCCESS) {
 263                 tdb->ecode = ecode;
 264                 return TDB_OFF_ERR;
 265         }
 266
 267         hashtable = offsetof(struct tdb_header, hashtable);
 268         if (tinfo) {
 269                 tinfo->toplevel_group = group;
 270                 tinfo->num_levels = 1;
 271                 tinfo->levels[0].entry = 0;
 272                 tinfo->levels[0].hashtable = hashtable
 273                         + (group << TDB_HASH_GROUP_BITS) * sizeof(tdb_off_t);
 274                 tinfo->levels[0].total_buckets = 1 << TDB_HASH_GROUP_BITS;
 275         }
 276
 277         while (h->hash_used <= 64) {
 278                 /* Read in the hash group. */
 279                 h->group_start = hashtable
 280                         + group * (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
 281
 282                 ecode = tdb_read_convert(tdb, h->group_start, &h->group,
 283                                          sizeof(h->group));
 284                 if (ecode != TDB_SUCCESS) {
 285                         tdb->ecode = ecode;
 286                         goto fail;
 287                 }
 288
 289                 /* Pointer to another hash table?  Go down... */
 290                 if (is_subhash(h->group[h->home_bucket])) {
 291                         hashtable = (h->group[h->home_bucket] & TDB_OFF_MASK)
 292                                 + sizeof(struct tdb_used_record);
 293                         if (tinfo) {
 294                                 /* When we come back, use *next* bucket */
 295                                 tinfo->levels[tinfo->num_levels-1].entry
 296                                         += h->home_bucket + 1;
 297                         }
 298                         group = use_bits(h, TDB_SUBLEVEL_HASH_BITS
 299                                          - TDB_HASH_GROUP_BITS);
 300                         h->home_bucket = use_bits(h, TDB_HASH_GROUP_BITS);
 301                         if (tinfo) {
 302                                 tinfo->levels[tinfo->num_levels].hashtable
 303                                         = hashtable;
 304                                 tinfo->levels[tinfo->num_levels].total_buckets
 305                                         = 1 << TDB_SUBLEVEL_HASH_BITS;
 306                                 tinfo->levels[tinfo->num_levels].entry
 307                                         = group << TDB_HASH_GROUP_BITS;
 308                                 tinfo->num_levels++;
 309                         }
 310                         continue;
 311                 }
 312
 313                 /* It's in this group: search (until 0 or all searched) */
 314                 for (i = 0, h->found_bucket = h->home_bucket;
 315                      i < (1 << TDB_HASH_GROUP_BITS);
 316                      i++, h->found_bucket = ((h->found_bucket+1)
 317                                              % (1 << TDB_HASH_GROUP_BITS))) {
 318                         if (is_subhash(h->group[h->found_bucket]))
 319                                 continue;
 320
 321                         if (!h->group[h->found_bucket])
 322                                 break;
 323
 324                         if (match(tdb, h, &key, h->group[h->found_bucket],
 325                                   rec)) {
 326                                 if (tinfo) {
 327                                         tinfo->levels[tinfo->num_levels-1].entry
 328                                                 += h->found_bucket;
 329                                 }
 330                                 return h->group[h->found_bucket] & TDB_OFF_MASK;
 331                         }
 332                 }
 333                 /* Didn't find it: h indicates where it would go. */
 334                 return 0;
 335         }
 336
 337         return find_in_chain(tdb, key, hashtable, h, rec, tinfo);
 338
 339 fail:
 340         tdb_unlock_hashes(tdb, h->hlock_start, h->hlock_range, ltype);
 341         return TDB_OFF_ERR;
 342 }
 343
 344 /* I wrote a simple test, expanding a hash to 2GB, for the following
 345  * cases:
 346  * 1) Expanding all the buckets at once,
 347  * 2) Expanding the bucket we wanted to place the new entry into.
 348  * 3) Expanding the most-populated bucket,
 349  *
 350  * I measured the worst/average/best density during this process.
 351  * 1) 3%/16%/30%
 352  * 2) 4%/20%/38%
 353  * 3) 6%/22%/41%
 354  *
 355  * So we figure out the busiest bucket for the moment.
 356  */
 357 static unsigned fullest_bucket(struct tdb_context *tdb,
 358                                const tdb_off_t *group,
 359                                unsigned new_bucket)
 360 {
 361         unsigned counts[1 << TDB_HASH_GROUP_BITS] = { 0 };
 362         unsigned int i, best_bucket;
 363
 364         /* Count the new entry. */
 365         counts[new_bucket]++;
 366         best_bucket = new_bucket;
 367
 368         for (i = 0; i < (1 << TDB_HASH_GROUP_BITS); i++) {
 369                 unsigned this_bucket;
 370
 371                 if (is_subhash(group[i]))
 372                         continue;
 373                 this_bucket = group[i] & TDB_OFF_HASH_GROUP_MASK;
 374                 if (++counts[this_bucket] > counts[best_bucket])
 375                         best_bucket = this_bucket;
 376         }
 377
 378         return best_bucket;
 379 }
 380
 381 static bool put_into_group(tdb_off_t *group,
 382                            unsigned bucket, tdb_off_t encoded)
 383 {
 384         unsigned int i;
 385
 386         for (i = 0; i < (1 << TDB_HASH_GROUP_BITS); i++) {
 387                 unsigned b = (bucket + i) % (1 << TDB_HASH_GROUP_BITS);
 388
 389                 if (group[b] == 0) {
 390                         group[b] = encoded;
 391                         return true;
 392                 }
 393         }
 394         return false;
 395 }
 396
 397 static void force_into_group(tdb_off_t *group,
 398                              unsigned bucket, tdb_off_t encoded)
 399 {
 400         if (!put_into_group(group, bucket, encoded))
 401                 abort();
 402 }
 403
 404 static tdb_off_t encode_offset(tdb_off_t new_off, struct hash_info *h)
 405 {
 406         return h->home_bucket
 407                 | new_off
 408                 | ((uint64_t)bits_from(h->h,
 409                                   64 - h->hash_used - TDB_OFF_UPPER_STEAL_EXTRA,
 410                                   TDB_OFF_UPPER_STEAL_EXTRA)
 411                    << TDB_OFF_HASH_EXTRA_BIT);
 412 }
 413
 414 /* Simply overwrite the hash entry we found before. */
 415 int replace_in_hash(struct tdb_context *tdb,
 416                     struct hash_info *h,
 417                     tdb_off_t new_off)
 418 {
 419         enum TDB_ERROR ecode;
 420
 421         ecode = tdb_write_off(tdb, hbucket_off(h->group_start, h->found_bucket),
 422                               encode_offset(new_off, h));
 423         if (ecode != TDB_SUCCESS) {
 424                 tdb->ecode = ecode;
 425                 return -1;
 426         }
 427         return 0;
 428 }
 429
 430 /* We slot in anywhere that's empty in the chain. */
 431 static int COLD add_to_chain(struct tdb_context *tdb,
 432                              tdb_off_t subhash,
 433                              tdb_off_t new_off)
 434 {
 435         tdb_off_t entry;
 436         enum TDB_ERROR ecode;
 437
 438         entry = tdb_find_zero_off(tdb, subhash, 1<<TDB_HASH_GROUP_BITS);
 439         if (TDB_OFF_IS_ERR(entry)) {
 440                 tdb->ecode = entry;
 441                 return -1;
 442         }
 443
 444         if (entry == 1 << TDB_HASH_GROUP_BITS) {
 445                 tdb_off_t next;
 446
 447                 next = tdb_read_off(tdb, subhash
 448                                     + offsetof(struct tdb_chain, next));
 449                 if (TDB_OFF_IS_ERR(next)) {
 450                         tdb->ecode = next;
 451                         return -1;
 452                 }
 453
 454                 if (!next) {
 455                         next = alloc(tdb, 0, sizeof(struct tdb_chain), 0,
 456                                      TDB_CHAIN_MAGIC, false);
 457                         if (next == TDB_OFF_ERR)
 458                                 return -1;
 459                         ecode = zero_out(tdb,
 460                                          next+sizeof(struct tdb_used_record),
 461                                          sizeof(struct tdb_chain));
 462                         if (ecode != TDB_SUCCESS) {
 463                                 tdb->ecode = ecode;
 464                                 return -1;
 465                         }
 466                         ecode = tdb_write_off(tdb, subhash
 467                                               + offsetof(struct tdb_chain,
 468                                                          next),
 469                                               next);
 470                         if (ecode != TDB_SUCCESS) {
 471                                 tdb->ecode = ecode;
 472                                 return -1;
 473                         }
 474                 }
 475                 return add_to_chain(tdb, next, new_off);
 476         }
 477
 478         ecode = tdb_write_off(tdb, subhash + entry * sizeof(tdb_off_t),
 479                               new_off);
 480         if (ecode != TDB_SUCCESS) {
 481                 tdb->ecode = ecode;
 482                 return -1;
 483         }
 484         return 0;
 485 }
 486
 487 /* Add into a newly created subhash. */
 488 static int add_to_subhash(struct tdb_context *tdb, tdb_off_t subhash,
 489                           unsigned hash_used, tdb_off_t val)
 490 {
 491         tdb_off_t off = (val & TDB_OFF_MASK), *group;
 492         struct hash_info h;
 493         unsigned int gnum;
 494         enum TDB_ERROR ecode;
 495
 496         h.hash_used = hash_used;
 497
 498         if (hash_used + TDB_SUBLEVEL_HASH_BITS > 64)
 499                 return add_to_chain(tdb, subhash, off);
 500
 501         h.h = hash_record(tdb, off);
 502         gnum = use_bits(&h, TDB_SUBLEVEL_HASH_BITS-TDB_HASH_GROUP_BITS);
 503         h.group_start = subhash
 504                 + gnum * (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
 505         h.home_bucket = use_bits(&h, TDB_HASH_GROUP_BITS);
 506
 507         group = tdb_access_write(tdb, h.group_start,
 508                                  sizeof(*group) << TDB_HASH_GROUP_BITS, true);
 509         if (TDB_PTR_IS_ERR(group)) {
 510                 tdb->ecode = TDB_PTR_ERR(group);
 511                 return -1;
 512         }
 513         force_into_group(group, h.home_bucket, encode_offset(off, &h));
 514         ecode = tdb_access_commit(tdb, group);
 515         if (ecode != TDB_SUCCESS) {
 516                 tdb->ecode = ecode;
 517                 return -1;
 518         }
 519         return 0;
 520 }
 521
 522 static int expand_group(struct tdb_context *tdb, struct hash_info *h)
 523 {
 524         unsigned bucket, num_vals, i, magic;
 525         size_t subsize;
 526         tdb_off_t subhash;
 527         tdb_off_t vals[1 << TDB_HASH_GROUP_BITS];
 528         enum TDB_ERROR ecode;
 529
 530         /* Attach new empty subhash under fullest bucket. */
 531         bucket = fullest_bucket(tdb, h->group, h->home_bucket);
 532
 533         if (h->hash_used == 64) {
 534                 add_stat(tdb, alloc_chain, 1);
 535                 subsize = sizeof(struct tdb_chain);
 536                 magic = TDB_CHAIN_MAGIC;
 537         } else {
 538                 add_stat(tdb, alloc_subhash, 1);
 539                 subsize = (sizeof(tdb_off_t) << TDB_SUBLEVEL_HASH_BITS);
 540                 magic = TDB_HTABLE_MAGIC;
 541         }
 542
 543         subhash = alloc(tdb, 0, subsize, 0, magic, false);
 544         if (subhash == TDB_OFF_ERR)
 545                 return -1;
 546
 547         ecode = zero_out(tdb, subhash + sizeof(struct tdb_used_record),
 548                          subsize);
 549         if (ecode != TDB_SUCCESS) {
 550                 tdb->ecode = ecode;
 551                 return -1;
 552         }
 553
 554         /* Remove any which are destined for bucket or are in wrong place. */
 555         num_vals = 0;
 556         for (i = 0; i < (1 << TDB_HASH_GROUP_BITS); i++) {
 557                 unsigned home_bucket = h->group[i] & TDB_OFF_HASH_GROUP_MASK;
 558                 if (!h->group[i] || is_subhash(h->group[i]))
 559                         continue;
 560                 if (home_bucket == bucket || home_bucket != i) {
 561                         vals[num_vals++] = h->group[i];
 562                         h->group[i] = 0;
 563                 }
 564         }
 565         /* FIXME: This assert is valid, but we do this during unit test :( */
 566         /* assert(num_vals); */
 567
 568         /* Overwrite expanded bucket with subhash pointer. */
 569         h->group[bucket] = subhash | (1ULL << TDB_OFF_UPPER_STEAL_SUBHASH_BIT);
 570
 571         /* Point to actual contents of record. */
 572         subhash += sizeof(struct tdb_used_record);
 573
 574         /* Put values back. */
 575         for (i = 0; i < num_vals; i++) {
 576                 unsigned this_bucket = vals[i] & TDB_OFF_HASH_GROUP_MASK;
 577
 578                 if (this_bucket == bucket) {
 579                         if (add_to_subhash(tdb, subhash, h->hash_used, vals[i]))
 580                                 return -1;
 581                 } else {
 582                         /* There should be room to put this back. */
 583                         force_into_group(h->group, this_bucket, vals[i]);
 584                 }
 585         }
 586         return 0;
 587 }
 588
 589 int delete_from_hash(struct tdb_context *tdb, struct hash_info *h)
 590 {
 591         unsigned int i, num_movers = 0;
 592         tdb_off_t movers[1 << TDB_HASH_GROUP_BITS];
 593         enum TDB_ERROR ecode;
 594
 595         h->group[h->found_bucket] = 0;
 596         for (i = 1; i < (1 << TDB_HASH_GROUP_BITS); i++) {
 597                 unsigned this_bucket;
 598
 599                 this_bucket = (h->found_bucket+i) % (1 << TDB_HASH_GROUP_BITS);
 600                 /* Empty bucket?  We're done. */
 601                 if (!h->group[this_bucket])
 602                         break;
 603
 604                 /* Ignore subhashes. */
 605                 if (is_subhash(h->group[this_bucket]))
 606                         continue;
 607
 608                 /* If this one is not happy where it is, we'll move it. */
 609                 if ((h->group[this_bucket] & TDB_OFF_HASH_GROUP_MASK)
 610                     != this_bucket) {
 611                         movers[num_movers++] = h->group[this_bucket];
 612                         h->group[this_bucket] = 0;
 613                 }
 614         }
 615
 616         /* Put back the ones we erased. */
 617         for (i = 0; i < num_movers; i++) {
 618                 force_into_group(h->group, movers[i] & TDB_OFF_HASH_GROUP_MASK,
 619                                  movers[i]);
 620         }
 621
 622         /* Now we write back the hash group */
 623         ecode = tdb_write_convert(tdb, h->group_start,
 624                                   h->group, sizeof(h->group));
 625         if (ecode != TDB_SUCCESS) {
 626                 tdb->ecode = ecode;
 627                 return -1;
 628         }
 629         return 0;
 630 }
 631
 632 int add_to_hash(struct tdb_context *tdb, struct hash_info *h, tdb_off_t new_off)
 633 {
 634         enum TDB_ERROR ecode;
 635
 636         /* We hit an empty bucket during search?  That's where it goes. */
 637         if (!h->group[h->found_bucket]) {
 638                 h->group[h->found_bucket] = encode_offset(new_off, h);
 639                 /* Write back the modified group. */
 640                 ecode = tdb_write_convert(tdb, h->group_start,
 641                                           h->group, sizeof(h->group));
 642                 if (ecode != TDB_SUCCESS) {
 643                         tdb->ecode = ecode;
 644                         return -1;
 645                 }
 646                 return 0;
 647         }
 648
 649         if (h->hash_used > 64)
 650                 return add_to_chain(tdb, h->group_start, new_off);
 651
 652         /* We're full.  Expand. */
 653         if (expand_group(tdb, h) == -1)
 654                 return -1;
 655
 656         if (is_subhash(h->group[h->home_bucket])) {
 657                 /* We were expanded! */
 658                 tdb_off_t hashtable;
 659                 unsigned int gnum;
 660
 661                 /* Write back the modified group. */
 662                 ecode = tdb_write_convert(tdb, h->group_start, h->group,
 663                                           sizeof(h->group));
 664                 if (ecode != TDB_SUCCESS) {
 665                         tdb->ecode = ecode;
 666                         return -1;
 667                 }
 668
 669                 /* Move hashinfo down a level. */
 670                 hashtable = (h->group[h->home_bucket] & TDB_OFF_MASK)
 671                         + sizeof(struct tdb_used_record);
 672                 gnum = use_bits(h,TDB_SUBLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS);
 673                 h->home_bucket = use_bits(h, TDB_HASH_GROUP_BITS);
 674                 h->group_start = hashtable
 675                         + gnum * (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
 676                 ecode = tdb_read_convert(tdb, h->group_start, &h->group,
 677                                          sizeof(h->group));
 678                 if (ecode != TDB_SUCCESS) {
 679                         tdb->ecode = ecode;
 680                         return -1;
 681                 }
 682         }
 683
 684         /* Expanding the group must have made room if it didn't choose this
 685          * bucket. */
 686         if (put_into_group(h->group, h->home_bucket, encode_offset(new_off,h))){
 687                 ecode = tdb_write_convert(tdb, h->group_start,
 688                                           h->group, sizeof(h->group));
 689                 if (ecode != TDB_SUCCESS) {
 690                         tdb->ecode = ecode;
 691                         return -1;
 692                 }
 693                 return 0;
 694         }
 695
 696         /* This can happen if all hashes in group (and us) dropped into same
 697          * group in subhash. */
 698         return add_to_hash(tdb, h, new_off);
 699 }
 700
 701 /* Traverse support: returns offset of record, or 0 or TDB_OFF_ERR. */
 702 static tdb_off_t iterate_hash(struct tdb_context *tdb,
 703                               struct traverse_info *tinfo)
 704 {
 705         tdb_off_t off, val, i;
 706         struct traverse_level *tlevel;
 707
 708         tlevel = &tinfo->levels[tinfo->num_levels-1];
 709
 710 again:
 711         for (i = tdb_find_nonzero_off(tdb, tlevel->hashtable,
 712                                       tlevel->entry, tlevel->total_buckets);
 713              i != tlevel->total_buckets;
 714              i = tdb_find_nonzero_off(tdb, tlevel->hashtable,
 715                                       i+1, tlevel->total_buckets)) {
 716                 if (TDB_OFF_IS_ERR(i)) {
 717                         tdb->ecode = i;
 718                         return TDB_OFF_ERR;
 719                 }
 720
 721                 val = tdb_read_off(tdb, tlevel->hashtable+sizeof(tdb_off_t)*i);
 722                 if (TDB_OFF_IS_ERR(val)) {
 723                         tdb->ecode = val;
 724                         return TDB_OFF_ERR;
 725                 }
 726
 727                 off = val & TDB_OFF_MASK;
 728
 729                 /* This makes the delete-all-in-traverse case work
 730                  * (and simplifies our logic a little). */
 731                 if (off == tinfo->prev)
 732                         continue;
 733
 734                 tlevel->entry = i;
 735
 736                 if (!is_subhash(val)) {
 737                         /* Found one. */
 738                         tinfo->prev = off;
 739                         return off;
 740                 }
 741
 742                 /* When we come back, we want the next one */
 743                 tlevel->entry++;
 744                 tinfo->num_levels++;
 745                 tlevel++;
 746                 tlevel->hashtable = off + sizeof(struct tdb_used_record);
 747                 tlevel->entry = 0;
 748                 /* Next level is a chain? */
 749                 if (unlikely(tinfo->num_levels == TDB_MAX_LEVELS + 1))
 750                         tlevel->total_buckets = (1 << TDB_HASH_GROUP_BITS);
 751                 else
 752                         tlevel->total_buckets = (1 << TDB_SUBLEVEL_HASH_BITS);
 753                 goto again;
 754         }
 755
 756         /* Nothing there? */
 757         if (tinfo->num_levels == 1)
 758                 return 0;
 759
 760         /* Handle chained entries. */
 761         if (unlikely(tinfo->num_levels == TDB_MAX_LEVELS + 1)) {
 762                 tlevel->hashtable = tdb_read_off(tdb, tlevel->hashtable
 763                                                  + offsetof(struct tdb_chain,
 764                                                             next));
 765                 if (TDB_OFF_IS_ERR(tlevel->hashtable)) {
 766                         tdb->ecode = tlevel->hashtable;
 767                         return TDB_OFF_ERR;
 768                 }
 769                 if (tlevel->hashtable) {
 770                         tlevel->hashtable += sizeof(struct tdb_used_record);
 771                         tlevel->entry = 0;
 772                         goto again;
 773                 }
 774         }
 775
 776         /* Go back up and keep searching. */
 777         tinfo->num_levels--;
 778         tlevel--;
 779         goto again;
 780 }
 781
 782 /* Return 1 if we find something, 0 if not, -1 on error. */
 783 int next_in_hash(struct tdb_context *tdb,
 784                  struct traverse_info *tinfo,
 785                  TDB_DATA *kbuf, size_t *dlen)
 786 {
 787         const unsigned group_bits = TDB_TOPLEVEL_HASH_BITS-TDB_HASH_GROUP_BITS;
 788         tdb_off_t hl_start, hl_range, off;
 789         enum TDB_ERROR ecode;
 790
 791         while (tinfo->toplevel_group < (1 << group_bits)) {
 792                 hl_start = (tdb_off_t)tinfo->toplevel_group
 793                         << (64 - group_bits);
 794                 hl_range = 1ULL << group_bits;
 795                 ecode = tdb_lock_hashes(tdb, hl_start, hl_range, F_RDLCK,
 796                                         TDB_LOCK_WAIT);
 797                 if (ecode != TDB_SUCCESS) {
 798                         tdb->ecode = ecode;
 799                         return -1;
 800                 }
 801
 802                 off = iterate_hash(tdb, tinfo);
 803                 if (off) {
 804                         struct tdb_used_record rec;
 805
 806                         ecode = tdb_read_convert(tdb, off, &rec, sizeof(rec));
 807                         if (ecode != TDB_SUCCESS) {
 808                                 tdb->ecode = ecode;
 809                                 tdb_unlock_hashes(tdb,
 810                                                   hl_start, hl_range, F_RDLCK);
 811                                 return -1;
 812                         }
 813                         if (rec_magic(&rec) != TDB_USED_MAGIC) {
 814                                 tdb_logerr(tdb, TDB_ERR_CORRUPT,
 815                                            TDB_LOG_ERROR,
 816                                            "next_in_hash:"
 817                                            " corrupt record at %llu",
 818                                            (long long)off);
 819                                 return -1;
 820                         }
 821
 822                         kbuf->dsize = rec_key_length(&rec);
 823
 824                         /* They want data as well? */
 825                         if (dlen) {
 826                                 *dlen = rec_data_length(&rec);
 827                                 kbuf->dptr = tdb_alloc_read(tdb,
 828                                                             off + sizeof(rec),
 829                                                             kbuf->dsize
 830                                                             + *dlen);
 831                         } else {
 832                                 kbuf->dptr = tdb_alloc_read(tdb,
 833                                                             off + sizeof(rec),
 834                                                             kbuf->dsize);
 835                         }
 836                         tdb_unlock_hashes(tdb, hl_start, hl_range, F_RDLCK);
 837                         if (TDB_PTR_IS_ERR(kbuf->dptr)) {
 838                                 tdb->ecode = TDB_PTR_ERR(kbuf->dptr);
 839                                 return -1;
 840                         }
 841                         return 1;
 842                 }
 843
 844                 tdb_unlock_hashes(tdb, hl_start, hl_range, F_RDLCK);
 845
 846                 tinfo->toplevel_group++;
 847                 tinfo->levels[0].hashtable
 848                         += (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
 849                 tinfo->levels[0].entry = 0;
 850         }
 851         return 0;
 852 }
 853
 854 /* Return 1 if we find something, 0 if not, -1 on error. */
 855 int first_in_hash(struct tdb_context *tdb,
 856                   struct traverse_info *tinfo,
 857                   TDB_DATA *kbuf, size_t *dlen)
 858 {
 859         tinfo->prev = 0;
 860         tinfo->toplevel_group = 0;
 861         tinfo->num_levels = 1;
 862         tinfo->levels[0].hashtable = offsetof(struct tdb_header, hashtable);
 863         tinfo->levels[0].entry = 0;
 864         tinfo->levels[0].total_buckets = (1 << TDB_HASH_GROUP_BITS);
 865
 866         return next_in_hash(tdb, tinfo, kbuf, dlen);
 867 }
 868
 869 /* Even if the entry isn't in this hash bucket, you'd have to lock this
 870  * bucket to find it. */
 871 static int chainlock(struct tdb_context *tdb, const TDB_DATA *key,
 872                      int ltype, enum tdb_lock_flags waitflag,
 873                      const char *func)
 874 {
 875         enum TDB_ERROR ecode;
 876         uint64_t h = tdb_hash(tdb, key->dptr, key->dsize);
 877         tdb_off_t lockstart, locksize;
 878         unsigned int group, gbits;
 879
 880         gbits = TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS;
 881         group = bits_from(h, 64 - gbits, gbits);
 882
 883         lockstart = hlock_range(group, &locksize);
 884
 885         ecode = tdb_lock_hashes(tdb, lockstart, locksize, ltype, waitflag);
 886         tdb_trace_1rec(tdb, func, *key);
 887         if (ecode != TDB_SUCCESS) {
 888                 tdb->ecode = ecode;
 889                 return -1;
 890         }
 891         return 0;
 892 }
 893
 894 /* lock/unlock one hash chain. This is meant to be used to reduce
 895    contention - it cannot guarantee how many records will be locked */
 896 int tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
 897 {
 898         return chainlock(tdb, &key, F_WRLCK, TDB_LOCK_WAIT, "tdb_chainlock");
 899 }
 900
 901 int tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
 902 {
 903         uint64_t h = tdb_hash(tdb, key.dptr, key.dsize);
 904         tdb_off_t lockstart, locksize;
 905         unsigned int group, gbits;
 906         enum TDB_ERROR ecode;
 907
 908         gbits = TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS;
 909         group = bits_from(h, 64 - gbits, gbits);
 910
 911         lockstart = hlock_range(group, &locksize);
 912
 913         tdb_trace_1rec(tdb, "tdb_chainunlock", key);
 914         ecode = tdb_unlock_hashes(tdb, lockstart, locksize, F_WRLCK);
 915         if (ecode != TDB_SUCCESS) {
 916                 tdb->ecode = ecode;
 917                 return -1;
 918         }
 919         return 0;
 920 }