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