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->hash_fn = jenkins_hash;
  35 }
  36
  37 uint64_t tdb_hash(struct tdb_context *tdb, const void *ptr, size_t len)
  38 {
  39         return tdb->hash_fn(ptr, len, tdb->hash_seed, tdb->hash_data);
  40 }
  41
  42 uint64_t hash_record(struct tdb_context *tdb, tdb_off_t off)
  43 {
  44         const struct tdb_used_record *r;
  45         const void *key;
  46         uint64_t klen, hash;
  47
  48         r = tdb_access_read(tdb, off, sizeof(*r), true);
  49         if (TDB_PTR_IS_ERR(r)) {
  50                 /* FIXME */
  51                 return 0;
  52         }
  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 (TDB_PTR_IS_ERR(key)) {
  59                 return 0;
  60         }
  61
  62         hash = tdb_hash(tdb, key, klen);
  63         tdb_access_release(tdb, key);
  64         return hash;
  65 }
  66
  67 /* Get bits from a value. */
  68 static uint32_t bits_from(uint64_t val, unsigned start, unsigned num)
  69 {
  70         assert(num <= 32);
  71         return (val >> start) & ((1U << num) - 1);
  72 }
  73
  74 /* We take bits from the top: that way we can lock whole sections of the hash
  75  * by using lock ranges. */
  76 static uint32_t use_bits(struct hash_info *h, unsigned num)
  77 {
  78         h->hash_used += num;
  79         return bits_from(h->h, 64 - h->hash_used, num);
  80 }
  81
  82 static tdb_bool_err key_matches(struct tdb_context *tdb,
  83                                 const struct tdb_used_record *rec,
  84                                 tdb_off_t off,
  85                                 const struct tdb_data *key)
  86 {
  87         tdb_bool_err ret = false;
  88         const char *rkey;
  89
  90         if (rec_key_length(rec) != key->dsize) {
  91                 add_stat(tdb, compare_wrong_keylen, 1);
  92                 return ret;
  93         }
  94
  95         rkey = tdb_access_read(tdb, off + sizeof(*rec), key->dsize, false);
  96         if (TDB_PTR_IS_ERR(rkey)) {
  97                 return TDB_PTR_ERR(rkey);
  98         }
  99         if (memcmp(rkey, key->dptr, key->dsize) == 0)
 100                 ret = true;
 101         else
 102                 add_stat(tdb, compare_wrong_keycmp, 1);
 103         tdb_access_release(tdb, rkey);
 104         return ret;
 105 }
 106
 107 /* Does entry match? */
 108 static tdb_bool_err match(struct tdb_context *tdb,
 109                           struct hash_info *h,
 110                           const struct tdb_data *key,
 111                           tdb_off_t val,
 112                           struct tdb_used_record *rec)
 113 {
 114         tdb_off_t off;
 115         enum TDB_ERROR ecode;
 116
 117         add_stat(tdb, compares, 1);
 118         /* Desired bucket must match. */
 119         if (h->home_bucket != (val & TDB_OFF_HASH_GROUP_MASK)) {
 120                 add_stat(tdb, compare_wrong_bucket, 1);
 121                 return false;
 122         }
 123
 124         /* Top bits of offset == next bits of hash. */
 125         if (bits_from(val, TDB_OFF_HASH_EXTRA_BIT, TDB_OFF_UPPER_STEAL_EXTRA)
 126             != bits_from(h->h, 64 - h->hash_used - TDB_OFF_UPPER_STEAL_EXTRA,
 127                     TDB_OFF_UPPER_STEAL_EXTRA)) {
 128                 add_stat(tdb, compare_wrong_offsetbits, 1);
 129                 return false;
 130         }
 131
 132         off = val & TDB_OFF_MASK;
 133         ecode = tdb_read_convert(tdb, off, rec, sizeof(*rec));
 134         if (ecode != TDB_SUCCESS) {
 135                 return ecode;
 136         }
 137
 138         if ((h->h & ((1 << 11)-1)) != rec_hash(rec)) {
 139                 add_stat(tdb, compare_wrong_rechash, 1);
 140                 return false;
 141         }
 142
 143         return key_matches(tdb, rec, off, key);
 144 }
 145
 146 static tdb_off_t hbucket_off(tdb_off_t group_start, unsigned bucket)
 147 {
 148         return group_start
 149                 + (bucket % (1 << TDB_HASH_GROUP_BITS)) * sizeof(tdb_off_t);
 150 }
 151
 152 bool is_subhash(tdb_off_t val)
 153 {
 154         return (val >> TDB_OFF_UPPER_STEAL_SUBHASH_BIT) & 1;
 155 }
 156
 157 /* FIXME: Guess the depth, don't over-lock! */
 158 static tdb_off_t hlock_range(tdb_off_t group, tdb_off_t *size)
 159 {
 160         *size = 1ULL << (64 - (TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS));
 161         return group << (64 - (TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS));
 162 }
 163
 164 static tdb_off_t COLD find_in_chain(struct tdb_context *tdb,
 165                                     struct tdb_data key,
 166                                     tdb_off_t chain,
 167                                     struct hash_info *h,
 168                                     struct tdb_used_record *rec,
 169                                     struct traverse_info *tinfo)
 170 {
 171         tdb_off_t off, next;
 172         enum TDB_ERROR ecode;
 173
 174         /* In case nothing is free, we set these to zero. */
 175         h->home_bucket = h->found_bucket = 0;
 176
 177         for (off = chain; off; off = next) {
 178                 unsigned int i;
 179
 180                 h->group_start = off;
 181                 ecode = tdb_read_convert(tdb, off, h->group, sizeof(h->group));
 182                 if (ecode != TDB_SUCCESS) {
 183                         return ecode;
 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                                 return ecode;
 201                         }
 202
 203                         ecode = key_matches(tdb, rec, recoff, &key);
 204                         if (ecode < 0) {
 205                                 return ecode;
 206                         }
 207                         if (ecode == 1) {
 208                                 h->home_bucket = h->found_bucket = i;
 209
 210                                 if (tinfo) {
 211                                         tinfo->levels[tinfo->num_levels]
 212                                                 .hashtable = off;
 213                                         tinfo->levels[tinfo->num_levels]
 214                                                 .total_buckets
 215                                                 = 1 << TDB_HASH_GROUP_BITS;
 216                                         tinfo->levels[tinfo->num_levels].entry
 217                                                 = i;
 218                                         tinfo->num_levels++;
 219                                 }
 220                                 return recoff;
 221                         }
 222                 }
 223                 next = tdb_read_off(tdb, off
 224                                     + offsetof(struct tdb_chain, next));
 225                 if (TDB_OFF_IS_ERR(next)) {
 226                         return next;
 227                 }
 228                 if (next)
 229                         next += sizeof(struct tdb_used_record);
 230         }
 231         return 0;
 232 }
 233
 234 /* This is the core routine which searches the hashtable for an entry.
 235  * On error, no locks are held and -ve is returned.
 236  * Otherwise, hinfo is filled in (and the optional tinfo).
 237  * If not found, the return value is 0.
 238  * If found, the return value is the offset, and *rec is the record. */
 239 tdb_off_t find_and_lock(struct tdb_context *tdb,
 240                         struct tdb_data key,
 241                         int ltype,
 242                         struct hash_info *h,
 243                         struct tdb_used_record *rec,
 244                         struct traverse_info *tinfo)
 245 {
 246         uint32_t i, group;
 247         tdb_off_t hashtable;
 248         enum TDB_ERROR ecode;
 249
 250         h->h = tdb_hash(tdb, key.dptr, key.dsize);
 251         h->hash_used = 0;
 252         group = use_bits(h, TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS);
 253         h->home_bucket = use_bits(h, TDB_HASH_GROUP_BITS);
 254
 255         h->hlock_start = hlock_range(group, &h->hlock_range);
 256         ecode = tdb_lock_hashes(tdb, h->hlock_start, h->hlock_range, ltype,
 257                                 TDB_LOCK_WAIT);
 258         if (ecode != TDB_SUCCESS) {
 259                 return ecode;
 260         }
 261
 262         hashtable = offsetof(struct tdb_header, hashtable);
 263         if (tinfo) {
 264                 tinfo->toplevel_group = group;
 265                 tinfo->num_levels = 1;
 266                 tinfo->levels[0].entry = 0;
 267                 tinfo->levels[0].hashtable = hashtable
 268                         + (group << TDB_HASH_GROUP_BITS) * sizeof(tdb_off_t);
 269                 tinfo->levels[0].total_buckets = 1 << TDB_HASH_GROUP_BITS;
 270         }
 271
 272         while (h->hash_used <= 64) {
 273                 /* Read in the hash group. */
 274                 h->group_start = hashtable
 275                         + group * (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
 276
 277                 ecode = tdb_read_convert(tdb, h->group_start, &h->group,
 278                                          sizeof(h->group));
 279                 if (ecode != TDB_SUCCESS) {
 280                         goto fail;
 281                 }
 282
 283                 /* Pointer to another hash table?  Go down... */
 284                 if (is_subhash(h->group[h->home_bucket])) {
 285                         hashtable = (h->group[h->home_bucket] & TDB_OFF_MASK)
 286                                 + sizeof(struct tdb_used_record);
 287                         if (tinfo) {
 288                                 /* When we come back, use *next* bucket */
 289                                 tinfo->levels[tinfo->num_levels-1].entry
 290                                         += h->home_bucket + 1;
 291                         }
 292                         group = use_bits(h, TDB_SUBLEVEL_HASH_BITS
 293                                          - TDB_HASH_GROUP_BITS);
 294                         h->home_bucket = use_bits(h, TDB_HASH_GROUP_BITS);
 295                         if (tinfo) {
 296                                 tinfo->levels[tinfo->num_levels].hashtable
 297                                         = hashtable;
 298                                 tinfo->levels[tinfo->num_levels].total_buckets
 299                                         = 1 << TDB_SUBLEVEL_HASH_BITS;
 300                                 tinfo->levels[tinfo->num_levels].entry
 301                                         = group << TDB_HASH_GROUP_BITS;
 302                                 tinfo->num_levels++;
 303                         }
 304                         continue;
 305                 }
 306
 307                 /* It's in this group: search (until 0 or all searched) */
 308                 for (i = 0, h->found_bucket = h->home_bucket;
 309                      i < (1 << TDB_HASH_GROUP_BITS);
 310                      i++, h->found_bucket = ((h->found_bucket+1)
 311                                              % (1 << TDB_HASH_GROUP_BITS))) {
 312                         tdb_bool_err berr;
 313                         if (is_subhash(h->group[h->found_bucket]))
 314                                 continue;
 315
 316                         if (!h->group[h->found_bucket])
 317                                 break;
 318
 319                         berr = match(tdb, h, &key, h->group[h->found_bucket],
 320                                      rec);
 321                         if (berr < 0) {
 322                                 ecode = berr;
 323                                 goto fail;
 324                         }
 325                         if (berr) {
 326                                 if (tinfo) {
 327                                         tinfo->levels[tinfo->num_levels-1].entry
 328                                                 += h->found_bucket;
 329                                 }
 330                                 return h->group[h->found_bucket] & TDB_OFF_MASK;
 331                         }
 332                 }
 333                 /* Didn't find it: h indicates where it would go. */
 334                 return 0;
 335         }
 336
 337         return find_in_chain(tdb, key, hashtable, h, rec, tinfo);
 338
 339 fail:
 340         tdb_unlock_hashes(tdb, h->hlock_start, h->hlock_range, ltype);
 341         return ecode;
 342 }
 343
 344 /* I wrote a simple test, expanding a hash to 2GB, for the following
 345  * cases:
 346  * 1) Expanding all the buckets at once,
 347  * 2) Expanding the bucket we wanted to place the new entry into.
 348  * 3) Expanding the most-populated bucket,
 349  *
 350  * I measured the worst/average/best density during this process.
 351  * 1) 3%/16%/30%
 352  * 2) 4%/20%/38%
 353  * 3) 6%/22%/41%
 354  *
 355  * So we figure out the busiest bucket for the moment.
 356  */
 357 static unsigned fullest_bucket(struct tdb_context *tdb,
 358                                const tdb_off_t *group,
 359                                unsigned new_bucket)
 360 {
 361         unsigned counts[1 << TDB_HASH_GROUP_BITS] = { 0 };
 362         unsigned int i, best_bucket;
 363
 364         /* Count the new entry. */
 365         counts[new_bucket]++;
 366         best_bucket = new_bucket;
 367
 368         for (i = 0; i < (1 << TDB_HASH_GROUP_BITS); i++) {
 369                 unsigned this_bucket;
 370
 371                 if (is_subhash(group[i]))
 372                         continue;
 373                 this_bucket = group[i] & TDB_OFF_HASH_GROUP_MASK;
 374                 if (++counts[this_bucket] > counts[best_bucket])
 375                         best_bucket = this_bucket;
 376         }
 377
 378         return best_bucket;
 379 }
 380
 381 static bool put_into_group(tdb_off_t *group,
 382                            unsigned bucket, tdb_off_t encoded)
 383 {
 384         unsigned int i;
 385
 386         for (i = 0; i < (1 << TDB_HASH_GROUP_BITS); i++) {
 387                 unsigned b = (bucket + i) % (1 << TDB_HASH_GROUP_BITS);
 388
 389                 if (group[b] == 0) {
 390                         group[b] = encoded;
 391                         return true;
 392                 }
 393         }
 394         return false;
 395 }
 396
 397 static void force_into_group(tdb_off_t *group,
 398                              unsigned bucket, tdb_off_t encoded)
 399 {
 400         if (!put_into_group(group, bucket, encoded))
 401                 abort();
 402 }
 403
 404 static tdb_off_t encode_offset(tdb_off_t new_off, struct hash_info *h)
 405 {
 406         return h->home_bucket
 407                 | new_off
 408                 | ((uint64_t)bits_from(h->h,
 409                                   64 - h->hash_used - TDB_OFF_UPPER_STEAL_EXTRA,
 410                                   TDB_OFF_UPPER_STEAL_EXTRA)
 411                    << TDB_OFF_HASH_EXTRA_BIT);
 412 }
 413
 414 /* Simply overwrite the hash entry we found before. */
 415 enum TDB_ERROR replace_in_hash(struct tdb_context *tdb,
 416                                struct hash_info *h,
 417                                tdb_off_t new_off)
 418 {
 419         return tdb_write_off(tdb, hbucket_off(h->group_start, h->found_bucket),
 420                              encode_offset(new_off, h));
 421 }
 422
 423 /* We slot in anywhere that's empty in the chain. */
 424 static enum TDB_ERROR COLD add_to_chain(struct tdb_context *tdb,
 425                                         tdb_off_t subhash,
 426                                         tdb_off_t new_off)
 427 {
 428         tdb_off_t entry;
 429         enum TDB_ERROR ecode;
 430
 431         entry = tdb_find_zero_off(tdb, subhash, 1<<TDB_HASH_GROUP_BITS);
 432         if (TDB_OFF_IS_ERR(entry)) {
 433                 return entry;
 434         }
 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 (TDB_OFF_IS_ERR(next)) {
 442                         return next;
 443                 }
 444
 445                 if (!next) {
 446                         next = alloc(tdb, 0, sizeof(struct tdb_chain), 0,
 447                                      TDB_CHAIN_MAGIC, false);
 448                         if (TDB_OFF_IS_ERR(next))
 449                                 return next;
 450                         ecode = zero_out(tdb,
 451                                          next+sizeof(struct tdb_used_record),
 452                                          sizeof(struct tdb_chain));
 453                         if (ecode != TDB_SUCCESS) {
 454                                 return ecode;
 455                         }
 456                         ecode = tdb_write_off(tdb, subhash
 457                                               + offsetof(struct tdb_chain,
 458                                                          next),
 459                                               next);
 460                         if (ecode != TDB_SUCCESS) {
 461                                 return ecode;
 462                         }
 463                 }
 464                 return add_to_chain(tdb, next, new_off);
 465         }
 466
 467         return tdb_write_off(tdb, subhash + entry * sizeof(tdb_off_t),
 468                              new_off);
 469 }
 470
 471 /* Add into a newly created subhash. */
 472 static enum TDB_ERROR 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
 479         h.hash_used = hash_used;
 480
 481         if (hash_used + TDB_SUBLEVEL_HASH_BITS > 64)
 482                 return add_to_chain(tdb, subhash, off);
 483
 484         h.h = hash_record(tdb, off);
 485         gnum = use_bits(&h, TDB_SUBLEVEL_HASH_BITS-TDB_HASH_GROUP_BITS);
 486         h.group_start = subhash
 487                 + gnum * (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
 488         h.home_bucket = use_bits(&h, TDB_HASH_GROUP_BITS);
 489
 490         group = tdb_access_write(tdb, h.group_start,
 491                                  sizeof(*group) << TDB_HASH_GROUP_BITS, true);
 492         if (TDB_PTR_IS_ERR(group)) {
 493                 return TDB_PTR_ERR(group);
 494         }
 495         force_into_group(group, h.home_bucket, encode_offset(off, &h));
 496         return tdb_access_commit(tdb, group);
 497 }
 498
 499 static enum TDB_ERROR expand_group(struct tdb_context *tdb, struct hash_info *h)
 500 {
 501         unsigned bucket, num_vals, i, magic;
 502         size_t subsize;
 503         tdb_off_t subhash;
 504         tdb_off_t vals[1 << TDB_HASH_GROUP_BITS];
 505         enum TDB_ERROR ecode;
 506
 507         /* Attach new empty subhash under fullest bucket. */
 508         bucket = fullest_bucket(tdb, h->group, h->home_bucket);
 509
 510         if (h->hash_used == 64) {
 511                 add_stat(tdb, alloc_chain, 1);
 512                 subsize = sizeof(struct tdb_chain);
 513                 magic = TDB_CHAIN_MAGIC;
 514         } else {
 515                 add_stat(tdb, alloc_subhash, 1);
 516                 subsize = (sizeof(tdb_off_t) << TDB_SUBLEVEL_HASH_BITS);
 517                 magic = TDB_HTABLE_MAGIC;
 518         }
 519
 520         subhash = alloc(tdb, 0, subsize, 0, magic, false);
 521         if (TDB_OFF_IS_ERR(subhash)) {
 522                 return subhash;
 523         }
 524
 525         ecode = zero_out(tdb, subhash + sizeof(struct tdb_used_record),
 526                          subsize);
 527         if (ecode != TDB_SUCCESS) {
 528                 return ecode;
 529         }
 530
 531         /* Remove any which are destined for bucket or are in wrong place. */
 532         num_vals = 0;
 533         for (i = 0; i < (1 << TDB_HASH_GROUP_BITS); i++) {
 534                 unsigned home_bucket = h->group[i] & TDB_OFF_HASH_GROUP_MASK;
 535                 if (!h->group[i] || is_subhash(h->group[i]))
 536                         continue;
 537                 if (home_bucket == bucket || home_bucket != i) {
 538                         vals[num_vals++] = h->group[i];
 539                         h->group[i] = 0;
 540                 }
 541         }
 542         /* FIXME: This assert is valid, but we do this during unit test :( */
 543         /* assert(num_vals); */
 544
 545         /* Overwrite expanded bucket with subhash pointer. */
 546         h->group[bucket] = subhash | (1ULL << TDB_OFF_UPPER_STEAL_SUBHASH_BIT);
 547
 548         /* Point to actual contents of record. */
 549         subhash += sizeof(struct tdb_used_record);
 550
 551         /* Put values back. */
 552         for (i = 0; i < num_vals; i++) {
 553                 unsigned this_bucket = vals[i] & TDB_OFF_HASH_GROUP_MASK;
 554
 555                 if (this_bucket == bucket) {
 556                         ecode = add_to_subhash(tdb, subhash, h->hash_used,
 557                                                vals[i]);
 558                         if (ecode != TDB_SUCCESS)
 559                                 return ecode;
 560                 } else {
 561                         /* There should be room to put this back. */
 562                         force_into_group(h->group, this_bucket, vals[i]);
 563                 }
 564         }
 565         return TDB_SUCCESS;
 566 }
 567
 568 enum TDB_ERROR delete_from_hash(struct tdb_context *tdb, struct hash_info *h)
 569 {
 570         unsigned int i, num_movers = 0;
 571         tdb_off_t movers[1 << TDB_HASH_GROUP_BITS];
 572
 573         h->group[h->found_bucket] = 0;
 574         for (i = 1; i < (1 << TDB_HASH_GROUP_BITS); i++) {
 575                 unsigned this_bucket;
 576
 577                 this_bucket = (h->found_bucket+i) % (1 << TDB_HASH_GROUP_BITS);
 578                 /* Empty bucket?  We're done. */
 579                 if (!h->group[this_bucket])
 580                         break;
 581
 582                 /* Ignore subhashes. */
 583                 if (is_subhash(h->group[this_bucket]))
 584                         continue;
 585
 586                 /* If this one is not happy where it is, we'll move it. */
 587                 if ((h->group[this_bucket] & TDB_OFF_HASH_GROUP_MASK)
 588                     != this_bucket) {
 589                         movers[num_movers++] = h->group[this_bucket];
 590                         h->group[this_bucket] = 0;
 591                 }
 592         }
 593
 594         /* Put back the ones we erased. */
 595         for (i = 0; i < num_movers; i++) {
 596                 force_into_group(h->group, movers[i] & TDB_OFF_HASH_GROUP_MASK,
 597                                  movers[i]);
 598         }
 599
 600         /* Now we write back the hash group */
 601         return tdb_write_convert(tdb, h->group_start,
 602                                  h->group, sizeof(h->group));
 603 }
 604
 605 enum TDB_ERROR add_to_hash(struct tdb_context *tdb, struct hash_info *h,
 606                            tdb_off_t new_off)
 607 {
 608         enum TDB_ERROR ecode;
 609
 610         /* We hit an empty bucket during search?  That's where it goes. */
 611         if (!h->group[h->found_bucket]) {
 612                 h->group[h->found_bucket] = encode_offset(new_off, h);
 613                 /* Write back the modified group. */
 614                 return tdb_write_convert(tdb, h->group_start,
 615                                          h->group, sizeof(h->group));
 616         }
 617
 618         if (h->hash_used > 64)
 619                 return add_to_chain(tdb, h->group_start, new_off);
 620
 621         /* We're full.  Expand. */
 622         ecode = expand_group(tdb, h);
 623         if (ecode != TDB_SUCCESS) {
 624                 return ecode;
 625         }
 626
 627         if (is_subhash(h->group[h->home_bucket])) {
 628                 /* We were expanded! */
 629                 tdb_off_t hashtable;
 630                 unsigned int gnum;
 631
 632                 /* Write back the modified group. */
 633                 ecode = tdb_write_convert(tdb, h->group_start, h->group,
 634                                           sizeof(h->group));
 635                 if (ecode != TDB_SUCCESS) {
 636                         return ecode;
 637                 }
 638
 639                 /* Move hashinfo down a level. */
 640                 hashtable = (h->group[h->home_bucket] & TDB_OFF_MASK)
 641                         + sizeof(struct tdb_used_record);
 642                 gnum = use_bits(h,TDB_SUBLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS);
 643                 h->home_bucket = use_bits(h, TDB_HASH_GROUP_BITS);
 644                 h->group_start = hashtable
 645                         + gnum * (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
 646                 ecode = tdb_read_convert(tdb, h->group_start, &h->group,
 647                                          sizeof(h->group));
 648                 if (ecode != TDB_SUCCESS) {
 649                         return ecode;
 650                 }
 651         }
 652
 653         /* Expanding the group must have made room if it didn't choose this
 654          * bucket. */
 655         if (put_into_group(h->group, h->home_bucket, encode_offset(new_off,h))){
 656                 return tdb_write_convert(tdb, h->group_start,
 657                                          h->group, sizeof(h->group));
 658         }
 659
 660         /* This can happen if all hashes in group (and us) dropped into same
 661          * group in subhash. */
 662         return add_to_hash(tdb, h, new_off);
 663 }
 664
 665 /* Traverse support: returns offset of record, or 0 or -ve error. */
 666 static tdb_off_t iterate_hash(struct tdb_context *tdb,
 667                               struct traverse_info *tinfo)
 668 {
 669         tdb_off_t off, val, i;
 670         struct traverse_level *tlevel;
 671
 672         tlevel = &tinfo->levels[tinfo->num_levels-1];
 673
 674 again:
 675         for (i = tdb_find_nonzero_off(tdb, tlevel->hashtable,
 676                                       tlevel->entry, tlevel->total_buckets);
 677              i != tlevel->total_buckets;
 678              i = tdb_find_nonzero_off(tdb, tlevel->hashtable,
 679                                       i+1, tlevel->total_buckets)) {
 680                 if (TDB_OFF_IS_ERR(i)) {
 681                         return i;
 682                 }
 683
 684                 val = tdb_read_off(tdb, tlevel->hashtable+sizeof(tdb_off_t)*i);
 685                 if (TDB_OFF_IS_ERR(val)) {
 686                         return val;
 687                 }
 688
 689                 off = val & TDB_OFF_MASK;
 690
 691                 /* This makes the delete-all-in-traverse case work
 692                  * (and simplifies our logic a little). */
 693                 if (off == tinfo->prev)
 694                         continue;
 695
 696                 tlevel->entry = i;
 697
 698                 if (!is_subhash(val)) {
 699                         /* Found one. */
 700                         tinfo->prev = off;
 701                         return off;
 702                 }
 703
 704                 /* When we come back, we want the next one */
 705                 tlevel->entry++;
 706                 tinfo->num_levels++;
 707                 tlevel++;
 708                 tlevel->hashtable = off + sizeof(struct tdb_used_record);
 709                 tlevel->entry = 0;
 710                 /* Next level is a chain? */
 711                 if (unlikely(tinfo->num_levels == TDB_MAX_LEVELS + 1))
 712                         tlevel->total_buckets = (1 << TDB_HASH_GROUP_BITS);
 713                 else
 714                         tlevel->total_buckets = (1 << TDB_SUBLEVEL_HASH_BITS);
 715                 goto again;
 716         }
 717
 718         /* Nothing there? */
 719         if (tinfo->num_levels == 1)
 720                 return 0;
 721
 722         /* Handle chained entries. */
 723         if (unlikely(tinfo->num_levels == TDB_MAX_LEVELS + 1)) {
 724                 tlevel->hashtable = tdb_read_off(tdb, tlevel->hashtable
 725                                                  + offsetof(struct tdb_chain,
 726                                                             next));
 727                 if (TDB_OFF_IS_ERR(tlevel->hashtable)) {
 728                         return tlevel->hashtable;
 729                 }
 730                 if (tlevel->hashtable) {
 731                         tlevel->hashtable += sizeof(struct tdb_used_record);
 732                         tlevel->entry = 0;
 733                         goto again;
 734                 }
 735         }
 736
 737         /* Go back up and keep searching. */
 738         tinfo->num_levels--;
 739         tlevel--;
 740         goto again;
 741 }
 742
 743 /* Return success if we find something, TDB_ERR_NOEXIST if none. */
 744 enum TDB_ERROR next_in_hash(struct tdb_context *tdb,
 745                             struct traverse_info *tinfo,
 746                             TDB_DATA *kbuf, size_t *dlen)
 747 {
 748         const unsigned group_bits = TDB_TOPLEVEL_HASH_BITS-TDB_HASH_GROUP_BITS;
 749         tdb_off_t hl_start, hl_range, off;
 750         enum TDB_ERROR ecode;
 751
 752         while (tinfo->toplevel_group < (1 << group_bits)) {
 753                 hl_start = (tdb_off_t)tinfo->toplevel_group
 754                         << (64 - group_bits);
 755                 hl_range = 1ULL << group_bits;
 756                 ecode = tdb_lock_hashes(tdb, hl_start, hl_range, F_RDLCK,
 757                                         TDB_LOCK_WAIT);
 758                 if (ecode != TDB_SUCCESS) {
 759                         return ecode;
 760                 }
 761
 762                 off = iterate_hash(tdb, tinfo);
 763                 if (off) {
 764                         struct tdb_used_record rec;
 765
 766                         if (TDB_OFF_IS_ERR(off)) {
 767                                 ecode = off;
 768                                 goto fail;
 769                         }
 770
 771                         ecode = tdb_read_convert(tdb, off, &rec, sizeof(rec));
 772                         if (ecode != TDB_SUCCESS) {
 773                                 goto fail;
 774                         }
 775                         if (rec_magic(&rec) != TDB_USED_MAGIC) {
 776                                 ecode = tdb_logerr(tdb, TDB_ERR_CORRUPT,
 777                                                    TDB_LOG_ERROR,
 778                                                    "next_in_hash:"
 779                                                    " corrupt record at %llu",
 780                                                    (long long)off);
 781                                 goto fail;
 782                         }
 783
 784                         kbuf->dsize = rec_key_length(&rec);
 785
 786                         /* They want data as well? */
 787                         if (dlen) {
 788                                 *dlen = rec_data_length(&rec);
 789                                 kbuf->dptr = tdb_alloc_read(tdb,
 790                                                             off + sizeof(rec),
 791                                                             kbuf->dsize
 792                                                             + *dlen);
 793                         } else {
 794                                 kbuf->dptr = tdb_alloc_read(tdb,
 795                                                             off + sizeof(rec),
 796                                                             kbuf->dsize);
 797                         }
 798                         tdb_unlock_hashes(tdb, hl_start, hl_range, F_RDLCK);
 799                         if (TDB_PTR_IS_ERR(kbuf->dptr)) {
 800                                 return TDB_PTR_ERR(kbuf->dptr);
 801                         }
 802                         return TDB_SUCCESS;
 803                 }
 804
 805                 tdb_unlock_hashes(tdb, hl_start, hl_range, F_RDLCK);
 806
 807                 tinfo->toplevel_group++;
 808                 tinfo->levels[0].hashtable
 809                         += (sizeof(tdb_off_t) << TDB_HASH_GROUP_BITS);
 810                 tinfo->levels[0].entry = 0;
 811         }
 812         return TDB_ERR_NOEXIST;
 813
 814 fail:
 815         tdb_unlock_hashes(tdb, hl_start, hl_range, F_RDLCK);
 816         return ecode;
 817
 818 }
 819
 820 enum TDB_ERROR first_in_hash(struct tdb_context *tdb,
 821                              struct traverse_info *tinfo,
 822                              TDB_DATA *kbuf, size_t *dlen)
 823 {
 824         tinfo->prev = 0;
 825         tinfo->toplevel_group = 0;
 826         tinfo->num_levels = 1;
 827         tinfo->levels[0].hashtable = offsetof(struct tdb_header, hashtable);
 828         tinfo->levels[0].entry = 0;
 829         tinfo->levels[0].total_buckets = (1 << TDB_HASH_GROUP_BITS);
 830
 831         return next_in_hash(tdb, tinfo, kbuf, dlen);
 832 }
 833
 834 /* Even if the entry isn't in this hash bucket, you'd have to lock this
 835  * bucket to find it. */
 836 static enum TDB_ERROR chainlock(struct tdb_context *tdb, const TDB_DATA *key,
 837                                 int ltype, enum tdb_lock_flags waitflag,
 838                                 const char *func)
 839 {
 840         enum TDB_ERROR ecode;
 841         uint64_t h = tdb_hash(tdb, key->dptr, key->dsize);
 842         tdb_off_t lockstart, locksize;
 843         unsigned int group, gbits;
 844
 845         gbits = TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS;
 846         group = bits_from(h, 64 - gbits, gbits);
 847
 848         lockstart = hlock_range(group, &locksize);
 849
 850         ecode = tdb_lock_hashes(tdb, lockstart, locksize, ltype, waitflag);
 851         tdb_trace_1rec(tdb, func, *key);
 852         return ecode;
 853 }
 854
 855 /* lock/unlock one hash chain. This is meant to be used to reduce
 856    contention - it cannot guarantee how many records will be locked */
 857 enum TDB_ERROR tdb_chainlock(struct tdb_context *tdb, TDB_DATA key)
 858 {
 859         return tdb->last_error = chainlock(tdb, &key, F_WRLCK, TDB_LOCK_WAIT,
 860                                            "tdb_chainlock");
 861 }
 862
 863 void tdb_chainunlock(struct tdb_context *tdb, TDB_DATA key)
 864 {
 865         uint64_t h = tdb_hash(tdb, key.dptr, key.dsize);
 866         tdb_off_t lockstart, locksize;
 867         unsigned int group, gbits;
 868
 869         gbits = TDB_TOPLEVEL_HASH_BITS - TDB_HASH_GROUP_BITS;
 870         group = bits_from(h, 64 - gbits, gbits);
 871
 872         lockstart = hlock_range(group, &locksize);
 873
 874         tdb_trace_1rec(tdb, "tdb_chainunlock", key);
 875         tdb_unlock_hashes(tdb, lockstart, locksize, F_WRLCK);
 876 }
 877
 878 enum TDB_ERROR tdb_chainlock_read(struct tdb_context *tdb, TDB_DATA key)
 879 {
 880         return tdb->last_error = chainlock(tdb, &key, F_RDLCK, TDB_LOCK_WAIT,
 881                                            "tdb_chainlock_read");
 882 }
 883
 884 void tdb_chainunlock_read(struct tdb_context *tdb, TDB_DATA key)
 885 {
 886         uint64_t h = tdb_hash(tdb, key.dptr, key.dsize);
 887         tdb_off_t lockstart, locksize;
 888         unsigned int group, gbits;
 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_read", key);
 896         tdb_unlock_hashes(tdb, lockstart, locksize, F_RDLCK);
 897 }