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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 <ccan/ilog/ilog.h>
  21 #include <time.h>
  22 #include <assert.h>
  23 #include <limits.h>
  24
  25 static unsigned fls64(uint64_t val)
  26 {
  27         return ilog64(val);
  28 }
  29
  30 /* In which bucket would we find a particular record size? (ignoring header) */
  31 unsigned int size_to_bucket(tdb_len_t data_len)
  32 {
  33         unsigned int bucket;
  34
  35         /* We can't have records smaller than this. */
  36         assert(data_len >= TDB_MIN_DATA_LEN);
  37
  38         /* Ignoring the header... */
  39         if (data_len - TDB_MIN_DATA_LEN <= 64) {
  40                 /* 0 in bucket 0, 8 in bucket 1... 64 in bucket 8. */
  41                 bucket = (data_len - TDB_MIN_DATA_LEN) / 8;
  42         } else {
  43                 /* After that we go power of 2. */
  44                 bucket = fls64(data_len - TDB_MIN_DATA_LEN) + 2;
  45         }
  46
  47         if (unlikely(bucket >= TDB_FREE_BUCKETS))
  48                 bucket = TDB_FREE_BUCKETS - 1;
  49         return bucket;
  50 }
  51
  52 tdb_off_t first_ftable(struct tdb_context *tdb)
  53 {
  54         return tdb_read_off(tdb, offsetof(struct tdb_header, free_table));
  55 }
  56
  57 tdb_off_t next_ftable(struct tdb_context *tdb, tdb_off_t ftable)
  58 {
  59         return tdb_read_off(tdb, ftable + offsetof(struct tdb_freetable,next));
  60 }
  61
  62 int tdb_ftable_init(struct tdb_context *tdb)
  63 {
  64         /* Use reservoir sampling algorithm to select a free list at random. */
  65         unsigned int rnd, max = 0, count = 0;
  66         tdb_off_t off;
  67
  68         tdb->ftable_off = off = first_ftable(tdb);
  69         tdb->ftable = 0;
  70
  71         while (off) {
  72                 if (off == TDB_OFF_ERR)
  73                         return -1;
  74
  75                 rnd = random();
  76                 if (rnd >= max) {
  77                         tdb->ftable_off = off;
  78                         tdb->ftable = count;
  79                         max = rnd;
  80                 }
  81
  82                 off = next_ftable(tdb, off);
  83                 count++;
  84         }
  85         return 0;
  86 }
  87
  88 /* Offset of a given bucket. */
  89 tdb_off_t bucket_off(tdb_off_t ftable_off, unsigned bucket)
  90 {
  91         return ftable_off + offsetof(struct tdb_freetable, buckets)
  92                 + bucket * sizeof(tdb_off_t);
  93 }
  94
  95 /* Returns free_buckets + 1, or list number to search. */
  96 static tdb_off_t find_free_head(struct tdb_context *tdb,
  97                                 tdb_off_t ftable_off,
  98                                 tdb_off_t bucket)
  99 {
 100         /* Speculatively search for a non-zero bucket. */
 101         return tdb_find_nonzero_off(tdb, bucket_off(ftable_off, 0),
 102                                     bucket, TDB_FREE_BUCKETS);
 103 }
 104
 105 /* Remove from free bucket. */
 106 static int remove_from_list(struct tdb_context *tdb,
 107                             tdb_off_t b_off, tdb_off_t r_off,
 108                             const struct tdb_free_record *r)
 109 {
 110         tdb_off_t off;
 111
 112         /* Front of list? */
 113         if (frec_prev(r) == 0) {
 114                 off = b_off;
 115         } else {
 116                 off = frec_prev(r) + offsetof(struct tdb_free_record, next);
 117         }
 118
 119 #ifdef CCAN_TDB2_DEBUG
 120         if (tdb_read_off(tdb, off) != r_off) {
 121                 tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 122                          "remove_from_list: %llu bad prev in list %llu",
 123                          (long long)r_off, (long long)b_off);
 124                 return -1;
 125         }
 126 #endif
 127
 128         /* r->prev->next = r->next */
 129         if (tdb_write_off(tdb, off, r->next)) {
 130                 return -1;
 131         }
 132
 133         if (r->next != 0) {
 134                 off = r->next + offsetof(struct tdb_free_record,magic_and_prev);
 135                 /* r->next->prev = r->prev */
 136
 137 #ifdef CCAN_TDB2_DEBUG
 138                 if (tdb_read_off(tdb, off) & TDB_OFF_MASK != r_off) {
 139                         tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 140                                    "remove_from_list: %llu bad list %llu",
 141                                    (long long)r_off, (long long)b_off);
 142                         return -1;
 143                 }
 144 #endif
 145
 146                 if (tdb_write_off(tdb, off, r->magic_and_prev)) {
 147                         return -1;
 148                 }
 149         }
 150         return 0;
 151 }
 152
 153 /* Enqueue in this free bucket. */
 154 static int enqueue_in_free(struct tdb_context *tdb,
 155                            tdb_off_t b_off,
 156                            tdb_off_t off,
 157                            tdb_len_t len)
 158 {
 159         struct tdb_free_record new;
 160         uint64_t magic = (TDB_FREE_MAGIC << (64 - TDB_OFF_UPPER_STEAL));
 161
 162         /* We only need to set ftable_and_len; rest is set in enqueue_in_free */
 163         new.ftable_and_len = ((uint64_t)tdb->ftable << (64 - TDB_OFF_UPPER_STEAL))
 164                 | len;
 165         /* prev = 0. */
 166         new.magic_and_prev = magic;
 167
 168         /* new->next = head. */
 169         new.next = tdb_read_off(tdb, b_off);
 170         if (new.next == TDB_OFF_ERR)
 171                 return -1;
 172
 173         if (new.next) {
 174 #ifdef CCAN_TDB2_DEBUG
 175                 if (tdb_read_off(tdb,
 176                                  new.next + offsetof(struct tdb_free_record,
 177                                                      magic_and_prev))
 178                     != magic) {
 179                         tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 180                                    "enqueue_in_free: %llu bad head"
 181                                    " prev %llu",
 182                                    (long long)new.next, (long long)b_off);
 183                         return -1;
 184                 }
 185 #endif
 186                 /* next->prev = new. */
 187                 if (tdb_write_off(tdb, new.next
 188                                   + offsetof(struct tdb_free_record,
 189                                              magic_and_prev),
 190                                   off | magic) != 0)
 191                         return -1;
 192         }
 193         /* head = new */
 194         if (tdb_write_off(tdb, b_off, off) != 0)
 195                 return -1;
 196
 197         return tdb_write_convert(tdb, off, &new, sizeof(new));
 198 }
 199
 200 /* List need not be locked. */
 201 int add_free_record(struct tdb_context *tdb,
 202                     tdb_off_t off, tdb_len_t len_with_header)
 203 {
 204         tdb_off_t b_off;
 205         tdb_len_t len;
 206         int ret;
 207         enum TDB_ERROR ecode;
 208
 209         assert(len_with_header >= sizeof(struct tdb_free_record));
 210
 211         len = len_with_header - sizeof(struct tdb_used_record);
 212
 213         b_off = bucket_off(tdb->ftable_off, size_to_bucket(len));
 214         ecode = tdb_lock_free_bucket(tdb, b_off, TDB_LOCK_WAIT);
 215         if (ecode != TDB_SUCCESS) {
 216                 tdb->ecode = ecode;
 217                 return -1;
 218         }
 219
 220         ret = enqueue_in_free(tdb, b_off, off, len);
 221         tdb_unlock_free_bucket(tdb, b_off);
 222         return ret;
 223 }
 224
 225 static size_t adjust_size(size_t keylen, size_t datalen)
 226 {
 227         size_t size = keylen + datalen;
 228
 229         if (size < TDB_MIN_DATA_LEN)
 230                 size = TDB_MIN_DATA_LEN;
 231
 232         /* Round to next uint64_t boundary. */
 233         return (size + (sizeof(uint64_t) - 1ULL)) & ~(sizeof(uint64_t) - 1ULL);
 234 }
 235
 236 /* If we have enough left over to be useful, split that off. */
 237 static size_t record_leftover(size_t keylen, size_t datalen,
 238                               bool want_extra, size_t total_len)
 239 {
 240         ssize_t leftover;
 241
 242         if (want_extra)
 243                 datalen += datalen / 2;
 244         leftover = total_len - adjust_size(keylen, datalen);
 245
 246         if (leftover < (ssize_t)sizeof(struct tdb_free_record))
 247                 return 0;
 248
 249         return leftover;
 250 }
 251
 252 static tdb_off_t ftable_offset(struct tdb_context *tdb, unsigned int ftable)
 253 {
 254         tdb_off_t off;
 255         unsigned int i;
 256
 257         if (likely(tdb->ftable == ftable))
 258                 return tdb->ftable_off;
 259
 260         off = first_ftable(tdb);
 261         for (i = 0; i < ftable; i++)
 262                 off = next_ftable(tdb, off);
 263         return off;
 264 }
 265
 266 /* Note: we unlock the current bucket if we coalesce or fail. */
 267 static int coalesce(struct tdb_context *tdb,
 268                     tdb_off_t off, tdb_off_t b_off, tdb_len_t data_len)
 269 {
 270         tdb_off_t end;
 271         struct tdb_free_record rec;
 272
 273         add_stat(tdb, alloc_coalesce_tried, 1);
 274         end = off + sizeof(struct tdb_used_record) + data_len;
 275
 276         while (end < tdb->map_size) {
 277                 const struct tdb_free_record *r;
 278                 tdb_off_t nb_off;
 279                 unsigned ftable, bucket;
 280
 281                 r = tdb_access_read(tdb, end, sizeof(*r), true);
 282                 if (!r)
 283                         goto err;
 284
 285                 if (frec_magic(r) != TDB_FREE_MAGIC
 286                     || frec_ftable(r) == TDB_FTABLE_NONE) {
 287                         tdb_access_release(tdb, r);
 288                         break;
 289                 }
 290
 291                 ftable = frec_ftable(r);
 292                 bucket = size_to_bucket(frec_len(r));
 293                 nb_off = bucket_off(ftable_offset(tdb, ftable), bucket);
 294                 tdb_access_release(tdb, r);
 295
 296                 /* We may be violating lock order here, so best effort. */
 297                 if (tdb_lock_free_bucket(tdb, nb_off, TDB_LOCK_NOWAIT)
 298                     != TDB_SUCCESS) {
 299                         add_stat(tdb, alloc_coalesce_lockfail, 1);
 300                         break;
 301                 }
 302
 303                 /* Now we have lock, re-check. */
 304                 if (tdb_read_convert(tdb, end, &rec, sizeof(rec))) {
 305                         tdb_unlock_free_bucket(tdb, nb_off);
 306                         goto err;
 307                 }
 308
 309                 if (unlikely(frec_magic(&rec) != TDB_FREE_MAGIC)) {
 310                         add_stat(tdb, alloc_coalesce_race, 1);
 311                         tdb_unlock_free_bucket(tdb, nb_off);
 312                         break;
 313                 }
 314
 315                 if (unlikely(frec_ftable(&rec) != ftable)
 316                     || unlikely(size_to_bucket(frec_len(&rec)) != bucket)) {
 317                         add_stat(tdb, alloc_coalesce_race, 1);
 318                         tdb_unlock_free_bucket(tdb, nb_off);
 319                         break;
 320                 }
 321
 322                 if (remove_from_list(tdb, nb_off, end, &rec) == -1) {
 323                         tdb_unlock_free_bucket(tdb, nb_off);
 324                         goto err;
 325                 }
 326
 327                 end += sizeof(struct tdb_used_record) + frec_len(&rec);
 328                 tdb_unlock_free_bucket(tdb, nb_off);
 329                 add_stat(tdb, alloc_coalesce_num_merged, 1);
 330         }
 331
 332         /* Didn't find any adjacent free? */
 333         if (end == off + sizeof(struct tdb_used_record) + data_len)
 334                 return 0;
 335
 336         /* OK, expand initial record */
 337         if (tdb_read_convert(tdb, off, &rec, sizeof(rec)))
 338                 goto err;
 339
 340         if (frec_len(&rec) != data_len) {
 341                 tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 342                            "coalesce: expected data len %zu not %zu",
 343                            (size_t)data_len, (size_t)frec_len(&rec));
 344                 goto err;
 345         }
 346
 347         if (remove_from_list(tdb, b_off, off, &rec) == -1)
 348                 goto err;
 349
 350         /* We have to drop this to avoid deadlocks, so make sure record
 351          * doesn't get coalesced by someone else! */
 352         rec.ftable_and_len = (TDB_FTABLE_NONE << (64 - TDB_OFF_UPPER_STEAL))
 353                 | (end - off - sizeof(struct tdb_used_record));
 354         if (tdb_write_off(tdb, off + offsetof(struct tdb_free_record,
 355                                               ftable_and_len),
 356                           rec.ftable_and_len) != 0)
 357                 goto err;
 358
 359         add_stat(tdb, alloc_coalesce_succeeded, 1);
 360         tdb_unlock_free_bucket(tdb, b_off);
 361
 362         if (add_free_record(tdb, off, end - off) == -1)
 363                 return -1;
 364         return 1;
 365
 366 err:
 367         /* To unify error paths, we *always* unlock bucket on error. */
 368         tdb_unlock_free_bucket(tdb, b_off);
 369         return -1;
 370 }
 371
 372 /* We need size bytes to put our key and data in. */
 373 static tdb_off_t lock_and_alloc(struct tdb_context *tdb,
 374                                 tdb_off_t ftable_off,
 375                                 tdb_off_t bucket,
 376                                 size_t keylen, size_t datalen,
 377                                 bool want_extra,
 378                                 unsigned magic,
 379                                 unsigned hashlow)
 380 {
 381         tdb_off_t off, b_off,best_off;
 382         struct tdb_free_record best = { 0 };
 383         double multiplier;
 384         size_t size = adjust_size(keylen, datalen);
 385         enum TDB_ERROR ecode;
 386
 387         add_stat(tdb, allocs, 1);
 388 again:
 389         b_off = bucket_off(ftable_off, bucket);
 390
 391         /* FIXME: Try non-blocking wait first, to measure contention. */
 392         /* Lock this bucket. */
 393         ecode = tdb_lock_free_bucket(tdb, b_off, TDB_LOCK_WAIT);
 394         if (ecode != TDB_SUCCESS) {
 395                 tdb->ecode = ecode;
 396                 return TDB_OFF_ERR;
 397         }
 398
 399         best.ftable_and_len = -1ULL;
 400         best_off = 0;
 401
 402         /* Get slack if we're after extra. */
 403         if (want_extra)
 404                 multiplier = 1.5;
 405         else
 406                 multiplier = 1.0;
 407
 408         /* Walk the list to see if any are large enough, getting less fussy
 409          * as we go. */
 410         off = tdb_read_off(tdb, b_off);
 411         if (unlikely(off == TDB_OFF_ERR))
 412                 goto unlock_err;
 413
 414         while (off) {
 415                 const struct tdb_free_record *r;
 416                 tdb_len_t len;
 417                 tdb_off_t next;
 418
 419                 r = tdb_access_read(tdb, off, sizeof(*r), true);
 420                 if (!r)
 421                         goto unlock_err;
 422
 423                 if (frec_magic(r) != TDB_FREE_MAGIC) {
 424                         tdb_access_release(tdb, r);
 425                         tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 426                                  "lock_and_alloc: %llu non-free 0x%llx",
 427                                  (long long)off, (long long)r->magic_and_prev);
 428                         goto unlock_err;
 429                 }
 430
 431                 if (frec_len(r) >= size && frec_len(r) < frec_len(&best)) {
 432                         best_off = off;
 433                         best = *r;
 434                 }
 435
 436                 if (frec_len(&best) < size * multiplier && best_off) {
 437                         tdb_access_release(tdb, r);
 438                         break;
 439                 }
 440
 441                 multiplier *= 1.01;
 442
 443                 next = r->next;
 444                 len = frec_len(r);
 445                 tdb_access_release(tdb, r);
 446
 447                 /* Since we're going slow anyway, try coalescing here. */
 448                 switch (coalesce(tdb, off, b_off, len)) {
 449                 case -1:
 450                         /* This has already unlocked on error. */
 451                         return -1;
 452                 case 1:
 453                         /* This has unlocked list, restart. */
 454                         goto again;
 455                 }
 456                 off = next;
 457         }
 458
 459         /* If we found anything at all, use it. */
 460         if (best_off) {
 461                 struct tdb_used_record rec;
 462                 size_t leftover;
 463
 464                 /* We're happy with this size: take it. */
 465                 if (remove_from_list(tdb, b_off, best_off, &best) != 0)
 466                         goto unlock_err;
 467
 468                 leftover = record_leftover(keylen, datalen, want_extra,
 469                                            frec_len(&best));
 470
 471                 assert(keylen + datalen + leftover <= frec_len(&best));
 472                 /* We need to mark non-free before we drop lock, otherwise
 473                  * coalesce() could try to merge it! */
 474                 if (set_header(tdb, &rec, magic, keylen, datalen,
 475                                frec_len(&best) - leftover, hashlow) != 0)
 476                         goto unlock_err;
 477
 478                 if (tdb_write_convert(tdb, best_off, &rec, sizeof(rec)) != 0)
 479                         goto unlock_err;
 480
 481                 /* Bucket of leftover will be <= current bucket, so nested
 482                  * locking is allowed. */
 483                 if (leftover) {
 484                         add_stat(tdb, alloc_leftover, 1);
 485                         if (add_free_record(tdb,
 486                                             best_off + sizeof(rec)
 487                                             + frec_len(&best) - leftover,
 488                                             leftover))
 489                                 best_off = TDB_OFF_ERR;
 490                 }
 491                 tdb_unlock_free_bucket(tdb, b_off);
 492
 493                 return best_off;
 494         }
 495
 496         tdb_unlock_free_bucket(tdb, b_off);
 497         return 0;
 498
 499 unlock_err:
 500         tdb_unlock_free_bucket(tdb, b_off);
 501         return TDB_OFF_ERR;
 502 }
 503
 504 /* Get a free block from current free list, or 0 if none. */
 505 static tdb_off_t get_free(struct tdb_context *tdb,
 506                           size_t keylen, size_t datalen, bool want_extra,
 507                           unsigned magic, unsigned hashlow)
 508 {
 509         tdb_off_t off, ftable_off;
 510         unsigned start_b, b, ftable;
 511         bool wrapped = false;
 512
 513         /* If they are growing, add 50% to get to higher bucket. */
 514         if (want_extra)
 515                 start_b = size_to_bucket(adjust_size(keylen,
 516                                                      datalen + datalen / 2));
 517         else
 518                 start_b = size_to_bucket(adjust_size(keylen, datalen));
 519
 520         ftable_off = tdb->ftable_off;
 521         ftable = tdb->ftable;
 522         while (!wrapped || ftable_off != tdb->ftable_off) {
 523                 /* Start at exact size bucket, and search up... */
 524                 for (b = find_free_head(tdb, ftable_off, start_b);
 525                      b < TDB_FREE_BUCKETS;
 526                      b = find_free_head(tdb, ftable_off, b + 1)) {
 527                         /* Try getting one from list. */
 528                         off = lock_and_alloc(tdb, ftable_off,
 529                                              b, keylen, datalen, want_extra,
 530                                              magic, hashlow);
 531                         if (off == TDB_OFF_ERR)
 532                                 return TDB_OFF_ERR;
 533                         if (off != 0) {
 534                                 if (b == start_b)
 535                                         add_stat(tdb, alloc_bucket_exact, 1);
 536                                 if (b == TDB_FREE_BUCKETS - 1)
 537                                         add_stat(tdb, alloc_bucket_max, 1);
 538                                 /* Worked?  Stay using this list. */
 539                                 tdb->ftable_off = ftable_off;
 540                                 tdb->ftable = ftable;
 541                                 return off;
 542                         }
 543                         /* Didn't work.  Try next bucket. */
 544                 }
 545
 546                 /* Hmm, try next table. */
 547                 ftable_off = next_ftable(tdb, ftable_off);
 548                 ftable++;
 549
 550                 if (ftable_off == 0) {
 551                         wrapped = true;
 552                         ftable_off = first_ftable(tdb);
 553                         ftable = 0;
 554                 }
 555         }
 556
 557         return 0;
 558 }
 559
 560 int set_header(struct tdb_context *tdb,
 561                struct tdb_used_record *rec,
 562                unsigned magic, uint64_t keylen, uint64_t datalen,
 563                uint64_t actuallen, unsigned hashlow)
 564 {
 565         uint64_t keybits = (fls64(keylen) + 1) / 2;
 566
 567         /* Use bottom bits of hash, so it's independent of hash table size. */
 568         rec->magic_and_meta = (hashlow & ((1 << 11)-1))
 569                 | ((actuallen - (keylen + datalen)) << 11)
 570                 | (keybits << 43)
 571                 | ((uint64_t)magic << 48);
 572         rec->key_and_data_len = (keylen | (datalen << (keybits*2)));
 573
 574         /* Encoding can fail on big values. */
 575         if (rec_key_length(rec) != keylen
 576             || rec_data_length(rec) != datalen
 577             || rec_extra_padding(rec) != actuallen - (keylen + datalen)) {
 578                 tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
 579                          "Could not encode k=%llu,d=%llu,a=%llu",
 580                          (long long)keylen, (long long)datalen,
 581                          (long long)actuallen);
 582                 return -1;
 583         }
 584         return 0;
 585 }
 586
 587 /* Expand the database. */
 588 static int tdb_expand(struct tdb_context *tdb, tdb_len_t size)
 589 {
 590         uint64_t old_size;
 591         tdb_len_t wanted;
 592         enum TDB_ERROR ecode;
 593
 594         /* We need room for the record header too. */
 595         wanted = sizeof(struct tdb_used_record) + size;
 596
 597         /* Need to hold a hash lock to expand DB: transactions rely on it. */
 598         if (!(tdb->flags & TDB_NOLOCK)
 599             && !tdb->allrecord_lock.count && !tdb_has_hash_locks(tdb)) {
 600                 tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 601                            "tdb_expand: must hold lock during expand");
 602                 return -1;
 603         }
 604
 605         /* always make room for at least 100 more records, and at
 606            least 25% more space. */
 607         if (size * TDB_EXTENSION_FACTOR > tdb->map_size / 4)
 608                 wanted = size * TDB_EXTENSION_FACTOR;
 609         else
 610                 wanted = tdb->map_size / 4;
 611         wanted = adjust_size(0, wanted);
 612
 613         /* Only one person can expand file at a time. */
 614         ecode = tdb_lock_expand(tdb, F_WRLCK);
 615         if (ecode != TDB_SUCCESS) {
 616                 tdb->ecode = ecode;
 617                 return -1;
 618         }
 619
 620         /* Someone else may have expanded the file, so retry. */
 621         old_size = tdb->map_size;
 622         tdb->methods->oob(tdb, tdb->map_size + 1, true);
 623         if (tdb->map_size != old_size) {
 624                 tdb_unlock_expand(tdb, F_WRLCK);
 625                 return 0;
 626         }
 627
 628         if (tdb->methods->expand_file(tdb, wanted) == -1) {
 629                 tdb_unlock_expand(tdb, F_WRLCK);
 630                 return -1;
 631         }
 632
 633         /* We need to drop this lock before adding free record. */
 634         tdb_unlock_expand(tdb, F_WRLCK);
 635
 636         add_stat(tdb, expands, 1);
 637         return add_free_record(tdb, old_size, wanted);
 638 }
 639
 640 /* This won't fail: it will expand the database if it has to. */
 641 tdb_off_t alloc(struct tdb_context *tdb, size_t keylen, size_t datalen,
 642                 uint64_t hash, unsigned magic, bool growing)
 643 {
 644         tdb_off_t off;
 645
 646         /* We can't hold pointers during this: we could unmap! */
 647         assert(!tdb->direct_access);
 648
 649         for (;;) {
 650                 off = get_free(tdb, keylen, datalen, growing, magic, hash);
 651                 if (likely(off != 0))
 652                         break;
 653
 654                 if (tdb_expand(tdb, adjust_size(keylen, datalen)))
 655                         return TDB_OFF_ERR;
 656         }
 657
 658         return off;
 659 }