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