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   1  /*
   2    Trivial Database 2: free list/block handling
   3    Copyright (C) Rusty Russell 2010
   4
   5    This library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 3 of the License, or (at your option) any later version.
   9
  10    This library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with this library; if not, see <http://www.gnu.org/licenses/>.
  17 */
  18 #include "private.h"
  19 #include <ccan/likely/likely.h>
  20 #include <time.h>
  21 #include <assert.h>
  22 #include <limits.h>
  23
  24 /* We have to be able to fit a free record here. */
  25 #define MIN_DATA_LEN    \
  26         (sizeof(struct tdb_free_record) - sizeof(struct tdb_used_record))
  27
  28 static unsigned fls64(uint64_t val)
  29 {
  30 #if HAVE_BUILTIN_CLZL
  31         if (val <= ULONG_MAX) {
  32                 /* This is significantly faster! */
  33                 return val ? sizeof(long) * CHAR_BIT - __builtin_clzl(val) : 0;
  34         } else {
  35 #endif
  36         uint64_t r = 64;
  37
  38         if (!val)
  39                 return 0;
  40         if (!(val & 0xffffffff00000000ull)) {
  41                 val <<= 32;
  42                 r -= 32;
  43         }
  44         if (!(val & 0xffff000000000000ull)) {
  45                 val <<= 16;
  46                 r -= 16;
  47         }
  48         if (!(val & 0xff00000000000000ull)) {
  49                 val <<= 8;
  50                 r -= 8;
  51         }
  52         if (!(val & 0xf000000000000000ull)) {
  53                 val <<= 4;
  54                 r -= 4;
  55         }
  56         if (!(val & 0xc000000000000000ull)) {
  57                 val <<= 2;
  58                 r -= 2;
  59         }
  60         if (!(val & 0x8000000000000000ull)) {
  61                 val <<= 1;
  62                 r -= 1;
  63         }
  64         return r;
  65 #if HAVE_BUILTIN_CLZL
  66         }
  67 #endif
  68 }
  69
  70 /* In which bucket would we find a particular record size? (ignoring header) */
  71 unsigned int size_to_bucket(unsigned int zone_bits, tdb_len_t data_len)
  72 {
  73         unsigned int bucket;
  74
  75         /* We can't have records smaller than this. */
  76         assert(data_len >= MIN_DATA_LEN);
  77
  78         /* Ignoring the header... */
  79         if (data_len - MIN_DATA_LEN <= 64) {
  80                 /* 0 in bucket 0, 8 in bucket 1... 64 in bucket 6. */
  81                 bucket = (data_len - MIN_DATA_LEN) / 8;
  82         } else {
  83                 /* After that we go power of 2. */
  84                 bucket = fls64(data_len - MIN_DATA_LEN) + 2;
  85         }
  86
  87         if (unlikely(bucket > BUCKETS_FOR_ZONE(zone_bits)))
  88                 bucket = BUCKETS_FOR_ZONE(zone_bits);
  89         return bucket;
  90 }
  91
  92 /* Subtract 1-byte tailer and header.  Then round up to next power of 2. */
  93 static unsigned max_zone_bits(struct tdb_context *tdb)
  94 {
  95         return fls64(tdb->map_size-1-sizeof(struct tdb_header)-1) + 1;
  96 }
  97
  98 /* Start by using a random zone to spread the load: returns the offset. */
  99 static uint64_t random_zone(struct tdb_context *tdb)
 100 {
 101         struct free_zone_header zhdr;
 102         tdb_off_t off = sizeof(struct tdb_header);
 103         tdb_len_t half_bits;
 104         uint64_t randbits = 0;
 105         unsigned int i;
 106
 107         for (i = 0; i < 64; i += fls64(RAND_MAX))
 108                 randbits ^= ((uint64_t)random()) << i;
 109
 110         /* FIXME: Does this work?  Test! */
 111         half_bits = max_zone_bits(tdb) - 1;
 112         do {
 113                 /* Pick left or right side (not outside file) */
 114                 if ((randbits & 1)
 115                     && !tdb->methods->oob(tdb, off + (1ULL << half_bits)
 116                                           + sizeof(zhdr), true)) {
 117                         off += 1ULL << half_bits;
 118                 }
 119                 randbits >>= 1;
 120
 121                 if (tdb_read_convert(tdb, off, &zhdr, sizeof(zhdr)) == -1)
 122                         return TDB_OFF_ERR;
 123
 124                 if (zhdr.zone_bits == half_bits)
 125                         return off;
 126
 127                 half_bits--;
 128         } while (half_bits >= INITIAL_ZONE_BITS);
 129
 130         tdb->ecode = TDB_ERR_CORRUPT;
 131         tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 132                  "random_zone: zone at %llu smaller than %u bits?",
 133                  (long long)off, INITIAL_ZONE_BITS);
 134         return TDB_OFF_ERR;
 135 }
 136
 137 int tdb_zone_init(struct tdb_context *tdb)
 138 {
 139         tdb->zone_off = random_zone(tdb);
 140         if (tdb->zone_off == TDB_OFF_ERR)
 141                 return -1;
 142         if (tdb_read_convert(tdb, tdb->zone_off,
 143                              &tdb->zhdr, sizeof(tdb->zhdr)) == -1)
 144                 return -1;
 145         return 0;
 146 }
 147
 148 /* Where's the header, given a zone size of 1 << zone_bits? */
 149 static tdb_off_t zone_off(tdb_off_t off, unsigned int zone_bits)
 150 {
 151         off -= sizeof(struct tdb_header);
 152         return (off & ~((1ULL << zone_bits) - 1)) + sizeof(struct tdb_header);
 153 }
 154
 155 /* Offset of a given bucket. */
 156 /* FIXME: bucket can be "unsigned" everywhere, or even uint8/16. */
 157 tdb_off_t bucket_off(tdb_off_t zone_off, tdb_off_t bucket)
 158 {
 159         return zone_off
 160                 + sizeof(struct free_zone_header)
 161                 + bucket * sizeof(tdb_off_t);
 162 }
 163
 164 /* Returns free_buckets + 1, or list number to search. */
 165 static tdb_off_t find_free_head(struct tdb_context *tdb, tdb_off_t bucket)
 166 {
 167         tdb_off_t b;
 168
 169         /* Speculatively search for a non-zero bucket. */
 170         b = tdb_find_nonzero_off(tdb, bucket_off(tdb->zone_off, bucket),
 171                                  BUCKETS_FOR_ZONE(tdb->zhdr.zone_bits) + 1
 172                                  - bucket);
 173         return bucket + b;
 174 }
 175
 176 /* Remove from free bucket. */
 177 static int remove_from_list(struct tdb_context *tdb,
 178                             tdb_off_t b_off, struct tdb_free_record *r)
 179 {
 180         tdb_off_t off;
 181
 182         /* Front of list? */
 183         if (r->prev == 0) {
 184                 off = b_off;
 185         } else {
 186                 off = r->prev + offsetof(struct tdb_free_record, next);
 187         }
 188         /* r->prev->next = r->next */
 189         if (tdb_write_off(tdb, off, r->next)) {
 190                 return -1;
 191         }
 192
 193         if (r->next != 0) {
 194                 off = r->next + offsetof(struct tdb_free_record, prev);
 195                 /* r->next->prev = r->prev */
 196                 if (tdb_write_off(tdb, off, r->prev)) {
 197                         return -1;
 198                 }
 199         }
 200         return 0;
 201 }
 202
 203 /* Enqueue in this free bucket. */
 204 static int enqueue_in_free(struct tdb_context *tdb,
 205                            tdb_off_t b_off,
 206                            tdb_off_t off,
 207                            struct tdb_free_record *new)
 208 {
 209         new->prev = 0;
 210         /* new->next = head. */
 211         new->next = tdb_read_off(tdb, b_off);
 212         if (new->next == TDB_OFF_ERR)
 213                 return -1;
 214
 215         if (new->next) {
 216                 /* next->prev = new. */
 217                 if (tdb_write_off(tdb, new->next
 218                                   + offsetof(struct tdb_free_record, prev),
 219                                   off) != 0)
 220                         return -1;
 221         }
 222         /* head = new */
 223         if (tdb_write_off(tdb, b_off, off) != 0)
 224                 return -1;
 225
 226         return tdb_write_convert(tdb, off, new, sizeof(*new));
 227 }
 228
 229 /* List need not be locked. */
 230 int add_free_record(struct tdb_context *tdb,
 231                     unsigned int zone_bits,
 232                     tdb_off_t off, tdb_len_t len_with_header)
 233 {
 234         struct tdb_free_record new;
 235         tdb_off_t b_off;
 236         int ret;
 237
 238         assert(len_with_header >= sizeof(new));
 239         assert(zone_bits < (1 << 6));
 240
 241         new.magic_and_meta = TDB_FREE_MAGIC | zone_bits;
 242         new.data_len = len_with_header - sizeof(struct tdb_used_record);
 243
 244         b_off = bucket_off(zone_off(off, zone_bits),
 245                            size_to_bucket(zone_bits, new.data_len));
 246         if (tdb_lock_free_bucket(tdb, b_off, TDB_LOCK_WAIT) != 0)
 247                 return -1;
 248
 249         ret = enqueue_in_free(tdb, b_off, off, &new);
 250         tdb_unlock_free_bucket(tdb, b_off);
 251         return ret;
 252 }
 253
 254 /* If we have enough left over to be useful, split that off. */
 255 static int to_used_record(struct tdb_context *tdb,
 256                           unsigned int zone_bits,
 257                           tdb_off_t off,
 258                           tdb_len_t needed,
 259                           tdb_len_t total_len,
 260                           tdb_len_t *actual)
 261 {
 262         struct tdb_used_record used;
 263         tdb_len_t leftover;
 264
 265         leftover = total_len - needed;
 266         if (leftover < sizeof(struct tdb_free_record))
 267                 leftover = 0;
 268
 269         *actual = total_len - leftover;
 270
 271         if (leftover) {
 272                 if (add_free_record(tdb, zone_bits,
 273                                     off + sizeof(used) + *actual,
 274                                     total_len - needed))
 275                         return -1;
 276         }
 277         return 0;
 278 }
 279
 280 /* Note: we unlock the current bucket if we coalesce or fail. */
 281 static int coalesce(struct tdb_context *tdb,
 282                     tdb_off_t zone_off, unsigned zone_bits,
 283                     tdb_off_t off, tdb_off_t b_off, tdb_len_t data_len)
 284 {
 285         struct tdb_free_record pad, *r;
 286         tdb_off_t end = off + sizeof(struct tdb_used_record) + data_len;
 287
 288         while (end < (zone_off + (1ULL << zone_bits))) {
 289                 tdb_off_t nb_off;
 290
 291                 /* FIXME: do tdb_get here and below really win? */
 292                 r = tdb_get(tdb, end, &pad, sizeof(pad));
 293                 if (!r)
 294                         goto err;
 295
 296                 if (frec_magic(r) != TDB_FREE_MAGIC)
 297                         break;
 298
 299                 nb_off = bucket_off(zone_off,
 300                                     size_to_bucket(zone_bits, r->data_len));
 301
 302                 /* We may be violating lock order here, so best effort. */
 303                 if (tdb_lock_free_bucket(tdb, nb_off, TDB_LOCK_NOWAIT) == -1)
 304                         break;
 305
 306                 /* Now we have lock, re-check. */
 307                 r = tdb_get(tdb, end, &pad, sizeof(pad));
 308                 if (!r) {
 309                         tdb_unlock_free_bucket(tdb, nb_off);
 310                         goto err;
 311                 }
 312
 313                 if (unlikely(frec_magic(r) != TDB_FREE_MAGIC)) {
 314                         tdb_unlock_free_bucket(tdb, nb_off);
 315                         break;
 316                 }
 317
 318                 if (remove_from_list(tdb, nb_off, r) == -1) {
 319                         tdb_unlock_free_bucket(tdb, nb_off);
 320                         goto err;
 321                 }
 322
 323                 end += sizeof(struct tdb_used_record) + r->data_len;
 324                 tdb_unlock_free_bucket(tdb, nb_off);
 325         }
 326
 327         /* Didn't find any adjacent free? */
 328         if (end == off + sizeof(struct tdb_used_record) + data_len)
 329                 return 0;
 330
 331         /* OK, expand record */
 332         r = tdb_get(tdb, off, &pad, sizeof(pad));
 333         if (!r)
 334                 goto err;
 335
 336         if (r->data_len != data_len) {
 337                 tdb->ecode = TDB_ERR_CORRUPT;
 338                 tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
 339                          "coalesce: expected data len %llu not %llu\n",
 340                          (long long)data_len, (long long)r->data_len);
 341                 goto err;
 342         }
 343
 344         if (remove_from_list(tdb, b_off, r) == -1)
 345                 goto err;
 346
 347         /* We have to drop this to avoid deadlocks. */
 348         tdb_unlock_free_bucket(tdb, b_off);
 349
 350         if (add_free_record(tdb, zone_bits, off, end - off) == -1)
 351                 return -1;
 352         return 1;
 353
 354 err:
 355         /* To unify error paths, we *always* unlock bucket on error. */
 356         tdb_unlock_free_bucket(tdb, b_off);
 357         return -1;
 358 }
 359
 360 /* We need size bytes to put our key and data in. */
 361 static tdb_off_t lock_and_alloc(struct tdb_context *tdb,
 362                                 tdb_off_t zone_off,
 363                                 unsigned zone_bits,
 364                                 tdb_off_t bucket,
 365                                 size_t size,
 366                                 tdb_len_t *actual)
 367 {
 368         tdb_off_t off, b_off,best_off;
 369         struct tdb_free_record pad, best = { 0 }, *r;
 370         double multiplier;
 371
 372 again:
 373         b_off = bucket_off(zone_off, bucket);
 374
 375         /* Lock this bucket. */
 376         if (tdb_lock_free_bucket(tdb, b_off, TDB_LOCK_WAIT) == -1) {
 377                 return TDB_OFF_ERR;
 378         }
 379
 380         best.data_len = -1ULL;
 381         best_off = 0;
 382         /* FIXME: Start with larger multiplier if we're growing. */
 383         multiplier = 1.0;
 384
 385         /* Walk the list to see if any are large enough, getting less fussy
 386          * as we go. */
 387         off = tdb_read_off(tdb, b_off);
 388         if (unlikely(off == TDB_OFF_ERR))
 389                 goto unlock_err;
 390
 391         while (off) {
 392                 /* FIXME: Does tdb_get win anything here? */
 393                 r = tdb_get(tdb, off, &pad, sizeof(*r));
 394                 if (!r)
 395                         goto unlock_err;
 396
 397                 if (frec_magic(r) != TDB_FREE_MAGIC) {
 398                         tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 399                                  "lock_and_alloc: %llu non-free 0x%llx\n",
 400                                  (long long)off, (long long)r->magic_and_meta);
 401                         goto unlock_err;
 402                 }
 403
 404                 if (r->data_len >= size && r->data_len < best.data_len) {
 405                         best_off = off;
 406                         best = *r;
 407                 }
 408
 409                 if (best.data_len < size * multiplier && best_off)
 410                         goto use_best;
 411
 412                 multiplier *= 1.01;
 413
 414                 /* Since we're going slow anyway, try coalescing here. */
 415                 switch (coalesce(tdb, zone_off, zone_bits, off, b_off,
 416                                  r->data_len)) {
 417                 case -1:
 418                         /* This has already unlocked on error. */
 419                         return -1;
 420                 case 1:
 421                         /* This has unlocked list, restart. */
 422                         goto again;
 423                 }
 424                 off = r->next;
 425         }
 426
 427         /* If we found anything at all, use it. */
 428         if (best_off) {
 429         use_best:
 430                 /* We're happy with this size: take it. */
 431                 if (remove_from_list(tdb, b_off, &best) != 0)
 432                         goto unlock_err;
 433                 tdb_unlock_free_bucket(tdb, b_off);
 434
 435                 if (to_used_record(tdb, zone_bits, best_off, size,
 436                                    best.data_len, actual)) {
 437                         return -1;
 438                 }
 439                 return best_off;
 440         }
 441
 442         tdb_unlock_free_bucket(tdb, b_off);
 443         return 0;
 444
 445 unlock_err:
 446         tdb_unlock_free_bucket(tdb, b_off);
 447         return TDB_OFF_ERR;
 448 }
 449
 450 static bool next_zone(struct tdb_context *tdb)
 451 {
 452         tdb_off_t next = tdb->zone_off + (1ULL << tdb->zhdr.zone_bits);
 453
 454         /* We must have a header. */
 455         if (tdb->methods->oob(tdb, next + sizeof(tdb->zhdr), true))
 456                 return false;
 457
 458         tdb->zone_off = next;
 459         return tdb_read_convert(tdb, next, &tdb->zhdr, sizeof(tdb->zhdr)) == 0;
 460 }
 461
 462 /* Offset returned is within current zone (which it may alter). */
 463 static tdb_off_t get_free(struct tdb_context *tdb, size_t size,
 464                           tdb_len_t *actual)
 465 {
 466         tdb_off_t start_zone = tdb->zone_off, off;
 467         bool wrapped = false;
 468
 469         while (!wrapped || tdb->zone_off != start_zone) {
 470                 tdb_off_t b;
 471
 472                 /* Shortcut for really huge allocations... */
 473                 if ((size >> tdb->zhdr.zone_bits) != 0)
 474                         continue;
 475
 476                 /* Start at exact size bucket, and search up... */
 477                 b = size_to_bucket(tdb->zhdr.zone_bits, size);
 478                 for (b = find_free_head(tdb, b);
 479                      b <= BUCKETS_FOR_ZONE(tdb->zhdr.zone_bits);
 480                      b += find_free_head(tdb, b + 1)) {
 481                         /* Try getting one from list. */
 482                         off = lock_and_alloc(tdb, tdb->zone_off,
 483                                              tdb->zhdr.zone_bits,
 484                                              b, size, actual);
 485                         if (off == TDB_OFF_ERR)
 486                                 return TDB_OFF_ERR;
 487                         if (off != 0)
 488                                 return off;
 489                         /* Didn't work.  Try next bucket. */
 490                 }
 491
 492                 /* Didn't work, try next zone, if it exists. */
 493                 if (!next_zone(tdb)) {
 494                         wrapped = true;
 495                         tdb->zone_off = sizeof(struct tdb_header);
 496                         if (tdb_read_convert(tdb, tdb->zone_off,
 497                                              &tdb->zhdr, sizeof(tdb->zhdr))) {
 498                                 return TDB_OFF_ERR;
 499                         }
 500                 }
 501         }
 502         return 0;
 503 }
 504
 505 int set_header(struct tdb_context *tdb,
 506                struct tdb_used_record *rec,
 507                uint64_t keylen, uint64_t datalen,
 508                uint64_t actuallen, uint64_t hash,
 509                unsigned int zone_bits)
 510 {
 511         uint64_t keybits = (fls64(keylen) + 1) / 2;
 512
 513         /* Use top bits of hash, so it's independent of hash table size. */
 514         rec->magic_and_meta
 515                 = zone_bits
 516                 | ((hash >> 59) << 6)
 517                 | ((actuallen - (keylen + datalen)) << 11)
 518                 | (keybits << 43)
 519                 | (TDB_MAGIC << 48);
 520         rec->key_and_data_len = (keylen | (datalen << (keybits*2)));
 521
 522         /* Encoding can fail on big values. */
 523         if (rec_key_length(rec) != keylen
 524             || rec_data_length(rec) != datalen
 525             || rec_extra_padding(rec) != actuallen - (keylen + datalen)) {
 526                 tdb->ecode = TDB_ERR_IO;
 527                 tdb->log(tdb, TDB_DEBUG_ERROR, tdb->log_priv,
 528                          "Could not encode k=%llu,d=%llu,a=%llu\n",
 529                          (long long)keylen, (long long)datalen,
 530                          (long long)actuallen);
 531                 return -1;
 532         }
 533         return 0;
 534 }
 535
 536 static bool zones_happy(struct tdb_context *tdb)
 537 {
 538         /* FIXME: look at distribution of zones. */
 539         return true;
 540 }
 541
 542 /* Assume we want buckets up to the comfort factor. */
 543 static tdb_len_t overhead(unsigned int zone_bits)
 544 {
 545         return sizeof(struct free_zone_header)
 546                 + (BUCKETS_FOR_ZONE(zone_bits) + 1) * sizeof(tdb_off_t);
 547 }
 548
 549 /* Expand the database (by adding a zone). */
 550 static int tdb_expand(struct tdb_context *tdb, tdb_len_t size)
 551 {
 552         uint64_t old_size;
 553         tdb_off_t off;
 554         uint8_t zone_bits;
 555         unsigned int num_buckets;
 556         tdb_len_t wanted;
 557         struct free_zone_header zhdr;
 558         bool enlarge_zone;
 559
 560         /* We need room for the record header too. */
 561         wanted = sizeof(struct tdb_used_record) + size;
 562
 563         /* Only one person can expand file at a time. */
 564         if (tdb_lock_expand(tdb, F_WRLCK) != 0)
 565                 return -1;
 566
 567         /* Someone else may have expanded the file, so retry. */
 568         old_size = tdb->map_size;
 569         tdb->methods->oob(tdb, tdb->map_size + 1, true);
 570         if (tdb->map_size != old_size)
 571                 goto success;
 572
 573         /* zone bits tailer char is protected by EXPAND lock. */
 574         if (tdb->methods->read(tdb, old_size - 1, &zone_bits, 1) == -1)
 575                 goto fail;
 576
 577         /* If zones aren't working well, add larger zone if possible. */
 578         enlarge_zone = !zones_happy(tdb);
 579
 580         /* New zone can be between zone_bits or larger if we're on the right
 581          * boundary. */
 582         for (;;) {
 583                 /* Does this fit the allocation comfortably? */
 584                 if ((1ULL << zone_bits) >= overhead(zone_bits) + wanted) {
 585                         /* Only let enlarge_zone enlarge us once. */
 586                         if (!enlarge_zone)
 587                                 break;
 588                         enlarge_zone = false;
 589                 }
 590                 if ((old_size - 1 - sizeof(struct tdb_header))
 591                     & (1 << zone_bits))
 592                         break;
 593                 zone_bits++;
 594         }
 595
 596         zhdr.zone_bits = zone_bits;
 597         num_buckets = BUCKETS_FOR_ZONE(zone_bits);
 598
 599         if (tdb->methods->expand_file(tdb, 1ULL << zone_bits) == -1)
 600                 goto fail;
 601
 602         /* Write new tailer. */
 603         if (tdb->methods->write(tdb, tdb->map_size - 1, &zone_bits, 1) == -1)
 604                 goto fail;
 605
 606         /* Write new zone header (just before old tailer). */
 607         off = old_size - 1;
 608         if (tdb_write_convert(tdb, off, &zhdr, sizeof(zhdr)) == -1)
 609                 goto fail;
 610
 611         /* Now write empty buckets. */
 612         off += sizeof(zhdr);
 613         if (zero_out(tdb, off, (num_buckets+1) * sizeof(tdb_off_t)) == -1)
 614                 goto fail;
 615         off += (num_buckets+1) * sizeof(tdb_off_t);
 616
 617         /* Now add the rest as our free record. */
 618         if (add_free_record(tdb, zone_bits, off, tdb->map_size-1-off) == -1)
 619                 goto fail;
 620
 621         /* Try allocating from this zone now. */
 622         tdb->zone_off = old_size - 1;
 623         tdb->zhdr = zhdr;
 624
 625 success:
 626         tdb_unlock_expand(tdb, F_WRLCK);
 627         return 0;
 628
 629 fail:
 630         tdb_unlock_expand(tdb, F_WRLCK);
 631         return -1;
 632 }
 633
 634 static tdb_len_t adjust_size(size_t keylen, size_t datalen, bool growing)
 635 {
 636         tdb_len_t size = keylen + datalen;
 637
 638         if (size < MIN_DATA_LEN)
 639                 size = MIN_DATA_LEN;
 640
 641         /* Overallocate if this is coming from an enlarging store. */
 642         if (growing)
 643                 size += datalen / 2;
 644
 645         /* Round to next uint64_t boundary. */
 646         return (size + (sizeof(uint64_t) - 1ULL)) & ~(sizeof(uint64_t) - 1ULL);
 647 }
 648
 649 /* This won't fail: it will expand the database if it has to. */
 650 tdb_off_t alloc(struct tdb_context *tdb, size_t keylen, size_t datalen,
 651                 uint64_t hash, bool growing)
 652 {
 653         tdb_off_t off;
 654         tdb_len_t size, actual;
 655         struct tdb_used_record rec;
 656
 657         /* We don't want header to change during this! */
 658         assert(tdb->header_uptodate);
 659
 660         size = adjust_size(keylen, datalen, growing);
 661
 662 again:
 663         off = get_free(tdb, size, &actual);
 664         if (unlikely(off == TDB_OFF_ERR))
 665                 return off;
 666
 667         if (unlikely(off == 0)) {
 668                 if (tdb_expand(tdb, size) == -1)
 669                         return TDB_OFF_ERR;
 670                 goto again;
 671         }
 672
 673         /* Some supergiant values can't be encoded. */
 674         /* FIXME: Check before, and limit actual in get_free. */
 675         if (set_header(tdb, &rec, keylen, datalen, actual, hash,
 676                        tdb->zhdr.zone_bits) != 0) {
 677                 add_free_record(tdb, tdb->zhdr.zone_bits, off,
 678                                 sizeof(rec) + actual);
 679                 return TDB_OFF_ERR;
 680         }
 681
 682         if (tdb_write_convert(tdb, off, &rec, sizeof(rec)) != 0)
 683                 return TDB_OFF_ERR;
 684
 685         return off;
 686 }