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