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

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