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