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

   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 enum TDB_ERROR 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 (TDB_OFF_IS_ERR(off)) {
  73                         return off;
  74                 }
  75
  76                 rnd = random();
  77                 if (rnd >= max) {
  78                         tdb->ftable_off = off;
  79                         tdb->ftable = count;
  80                         max = rnd;
  81                 }
  82
  83                 off = next_ftable(tdb, off);
  84                 count++;
  85         }
  86         return TDB_SUCCESS;
  87 }
  88
  89 /* Offset of a given bucket. */
  90 tdb_off_t bucket_off(tdb_off_t ftable_off, unsigned bucket)
  91 {
  92         return ftable_off + offsetof(struct tdb_freetable, buckets)
  93                 + bucket * sizeof(tdb_off_t);
  94 }
  95
  96 /* Returns free_buckets + 1, or list number to search, or -ve error. */
  97 static tdb_off_t find_free_head(struct tdb_context *tdb,
  98                                 tdb_off_t ftable_off,
  99                                 tdb_off_t bucket)
 100 {
 101         /* Speculatively search for a non-zero bucket. */
 102         return tdb_find_nonzero_off(tdb, bucket_off(ftable_off, 0),
 103                                     bucket, TDB_FREE_BUCKETS);
 104 }
 105
 106 /* Remove from free bucket. */
 107 static enum TDB_ERROR remove_from_list(struct tdb_context *tdb,
 108                                        tdb_off_t b_off, tdb_off_t r_off,
 109                                        const struct tdb_free_record *r)
 110 {
 111         tdb_off_t off;
 112         enum TDB_ERROR ecode;
 113
 114         /* Front of list? */
 115         if (frec_prev(r) == 0) {
 116                 off = b_off;
 117         } else {
 118                 off = frec_prev(r) + offsetof(struct tdb_free_record, next);
 119         }
 120
 121 #ifdef CCAN_TDB2_DEBUG
 122         if (tdb_read_off(tdb, off) != r_off) {
 123                 return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 124                                   "remove_from_list:"
 125                                   " %llu bad prev in list %llu",
 126                                   (long long)r_off, (long long)b_off);
 127         }
 128 #endif
 129
 130         /* r->prev->next = r->next */
 131         ecode = tdb_write_off(tdb, off, r->next);
 132         if (ecode != TDB_SUCCESS) {
 133                 return ecode;
 134         }
 135
 136         if (r->next != 0) {
 137                 off = r->next + offsetof(struct tdb_free_record,magic_and_prev);
 138                 /* r->next->prev = r->prev */
 139
 140 #ifdef CCAN_TDB2_DEBUG
 141                 if (tdb_read_off(tdb, off) & TDB_OFF_MASK != r_off) {
 142                         return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 143                                           "remove_from_list:"
 144                                           " %llu bad list %llu",
 145                                           (long long)r_off, (long long)b_off);
 146                 }
 147 #endif
 148
 149                 ecode = tdb_write_off(tdb, off, r->magic_and_prev);
 150                 if (ecode != TDB_SUCCESS) {
 151                         return ecode;
 152                 }
 153         }
 154         return TDB_SUCCESS;
 155 }
 156
 157 /* Enqueue in this free bucket. */
 158 static enum TDB_ERROR enqueue_in_free(struct tdb_context *tdb,
 159                                       tdb_off_t b_off,
 160                                       tdb_off_t off,
 161                                       tdb_len_t len)
 162 {
 163         struct tdb_free_record new;
 164         enum TDB_ERROR ecode;
 165         uint64_t magic = (TDB_FREE_MAGIC << (64 - TDB_OFF_UPPER_STEAL));
 166
 167         /* We only need to set ftable_and_len; rest is set in enqueue_in_free */
 168         new.ftable_and_len = ((uint64_t)tdb->ftable << (64 - TDB_OFF_UPPER_STEAL))
 169                 | len;
 170         /* prev = 0. */
 171         new.magic_and_prev = magic;
 172
 173         /* new->next = head. */
 174         new.next = tdb_read_off(tdb, b_off);
 175         if (TDB_OFF_IS_ERR(new.next)) {
 176                 return new.next;
 177         }
 178
 179         if (new.next) {
 180 #ifdef CCAN_TDB2_DEBUG
 181                 if (tdb_read_off(tdb,
 182                                  new.next + offsetof(struct tdb_free_record,
 183                                                      magic_and_prev))
 184                     != magic) {
 185                         return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 186                                           "enqueue_in_free: %llu bad head"
 187                                           " prev %llu",
 188                                           (long long)new.next,
 189                                           (long long)b_off);
 190                 }
 191 #endif
 192                 /* next->prev = new. */
 193                 ecode = tdb_write_off(tdb, new.next
 194                                       + offsetof(struct tdb_free_record,
 195                                                  magic_and_prev),
 196                                       off | magic);
 197                 if (ecode != TDB_SUCCESS) {
 198                         return ecode;
 199                 }
 200         }
 201         /* head = new */
 202         ecode = tdb_write_off(tdb, b_off, off);
 203         if (ecode != TDB_SUCCESS) {
 204                 return ecode;
 205         }
 206
 207         return tdb_write_convert(tdb, off, &new, sizeof(new));
 208 }
 209
 210 /* List need not be locked. */
 211 enum TDB_ERROR add_free_record(struct tdb_context *tdb,
 212                                tdb_off_t off, tdb_len_t len_with_header)
 213 {
 214         tdb_off_t b_off;
 215         tdb_len_t len;
 216         enum TDB_ERROR ecode;
 217
 218         assert(len_with_header >= sizeof(struct tdb_free_record));
 219
 220         len = len_with_header - sizeof(struct tdb_used_record);
 221
 222         b_off = bucket_off(tdb->ftable_off, size_to_bucket(len));
 223         ecode = tdb_lock_free_bucket(tdb, b_off, TDB_LOCK_WAIT);
 224         if (ecode != TDB_SUCCESS) {
 225                 return ecode;
 226         }
 227
 228         ecode = enqueue_in_free(tdb, b_off, off, len);
 229         tdb_unlock_free_bucket(tdb, b_off);
 230         return ecode;
 231 }
 232
 233 static size_t adjust_size(size_t keylen, size_t datalen)
 234 {
 235         size_t size = keylen + datalen;
 236
 237         if (size < TDB_MIN_DATA_LEN)
 238                 size = TDB_MIN_DATA_LEN;
 239
 240         /* Round to next uint64_t boundary. */
 241         return (size + (sizeof(uint64_t) - 1ULL)) & ~(sizeof(uint64_t) - 1ULL);
 242 }
 243
 244 /* If we have enough left over to be useful, split that off. */
 245 static size_t record_leftover(size_t keylen, size_t datalen,
 246                               bool want_extra, size_t total_len)
 247 {
 248         ssize_t leftover;
 249
 250         if (want_extra)
 251                 datalen += datalen / 2;
 252         leftover = total_len - adjust_size(keylen, datalen);
 253
 254         if (leftover < (ssize_t)sizeof(struct tdb_free_record))
 255                 return 0;
 256
 257         return leftover;
 258 }
 259
 260 static tdb_off_t ftable_offset(struct tdb_context *tdb, unsigned int ftable)
 261 {
 262         tdb_off_t off;
 263         unsigned int i;
 264
 265         if (likely(tdb->ftable == ftable))
 266                 return tdb->ftable_off;
 267
 268         off = first_ftable(tdb);
 269         for (i = 0; i < ftable; i++) {
 270                 if (TDB_OFF_IS_ERR(off)) {
 271                         break;
 272                 }
 273                 off = next_ftable(tdb, off);
 274         }
 275         return off;
 276 }
 277
 278 /* Note: we unlock the current bucket if we coalesce or fail. */
 279 static tdb_bool_err coalesce(struct tdb_context *tdb,
 280                              tdb_off_t off, tdb_off_t b_off,
 281                              tdb_len_t data_len)
 282 {
 283         tdb_off_t end;
 284         struct tdb_free_record rec;
 285         enum TDB_ERROR ecode;
 286
 287         add_stat(tdb, alloc_coalesce_tried, 1);
 288         end = off + sizeof(struct tdb_used_record) + data_len;
 289
 290         while (end < tdb->map_size) {
 291                 const struct tdb_free_record *r;
 292                 tdb_off_t nb_off;
 293                 unsigned ftable, bucket;
 294
 295                 r = tdb_access_read(tdb, end, sizeof(*r), true);
 296                 if (TDB_PTR_IS_ERR(r)) {
 297                         ecode = TDB_PTR_ERR(r);
 298                         goto err;
 299                 }
 300
 301                 if (frec_magic(r) != TDB_FREE_MAGIC
 302                     || frec_ftable(r) == TDB_FTABLE_NONE) {
 303                         tdb_access_release(tdb, r);
 304                         break;
 305                 }
 306
 307                 ftable = frec_ftable(r);
 308                 bucket = size_to_bucket(frec_len(r));
 309                 nb_off = ftable_offset(tdb, ftable);
 310                 if (TDB_OFF_IS_ERR(nb_off)) {
 311                         tdb_access_release(tdb, r);
 312                         ecode = nb_off;
 313                         goto err;
 314                 }
 315                 nb_off = bucket_off(nb_off, bucket);
 316                 tdb_access_release(tdb, r);
 317
 318                 /* We may be violating lock order here, so best effort. */
 319                 if (tdb_lock_free_bucket(tdb, nb_off, TDB_LOCK_NOWAIT)
 320                     != TDB_SUCCESS) {
 321                         add_stat(tdb, alloc_coalesce_lockfail, 1);
 322                         break;
 323                 }
 324
 325                 /* Now we have lock, re-check. */
 326                 ecode = tdb_read_convert(tdb, end, &rec, sizeof(rec));
 327                 if (ecode != TDB_SUCCESS) {
 328                         tdb_unlock_free_bucket(tdb, nb_off);
 329                         goto err;
 330                 }
 331
 332                 if (unlikely(frec_magic(&rec) != TDB_FREE_MAGIC)) {
 333                         add_stat(tdb, alloc_coalesce_race, 1);
 334                         tdb_unlock_free_bucket(tdb, nb_off);
 335                         break;
 336                 }
 337
 338                 if (unlikely(frec_ftable(&rec) != ftable)
 339                     || unlikely(size_to_bucket(frec_len(&rec)) != bucket)) {
 340                         add_stat(tdb, alloc_coalesce_race, 1);
 341                         tdb_unlock_free_bucket(tdb, nb_off);
 342                         break;
 343                 }
 344
 345                 ecode = remove_from_list(tdb, nb_off, end, &rec);
 346                 if (ecode != TDB_SUCCESS) {
 347                         tdb_unlock_free_bucket(tdb, nb_off);
 348                         goto err;
 349                 }
 350
 351                 end += sizeof(struct tdb_used_record) + frec_len(&rec);
 352                 tdb_unlock_free_bucket(tdb, nb_off);
 353                 add_stat(tdb, alloc_coalesce_num_merged, 1);
 354         }
 355
 356         /* Didn't find any adjacent free? */
 357         if (end == off + sizeof(struct tdb_used_record) + data_len)
 358                 return false;
 359
 360         /* OK, expand initial record */
 361         ecode = tdb_read_convert(tdb, off, &rec, sizeof(rec));
 362         if (ecode != TDB_SUCCESS) {
 363                 goto err;
 364         }
 365
 366         if (frec_len(&rec) != data_len) {
 367                 ecode = tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 368                                    "coalesce: expected data len %zu not %zu",
 369                                    (size_t)data_len, (size_t)frec_len(&rec));
 370                 goto err;
 371         }
 372
 373         ecode = remove_from_list(tdb, b_off, off, &rec);
 374         if (ecode != TDB_SUCCESS) {
 375                 goto err;
 376         }
 377
 378         /* We have to drop this to avoid deadlocks, so make sure record
 379          * doesn't get coalesced by someone else! */
 380         rec.ftable_and_len = (TDB_FTABLE_NONE << (64 - TDB_OFF_UPPER_STEAL))
 381                 | (end - off - sizeof(struct tdb_used_record));
 382         ecode = tdb_write_off(tdb, off + offsetof(struct tdb_free_record,
 383                                                   ftable_and_len),
 384                               rec.ftable_and_len);
 385         if (ecode != TDB_SUCCESS) {
 386                 goto err;
 387         }
 388
 389         add_stat(tdb, alloc_coalesce_succeeded, 1);
 390         tdb_unlock_free_bucket(tdb, b_off);
 391
 392         ecode = add_free_record(tdb, off, end - off);
 393         if (ecode != TDB_SUCCESS) {
 394                 return ecode;
 395         }
 396         return true;
 397
 398 err:
 399         /* To unify error paths, we *always* unlock bucket on error. */
 400         tdb_unlock_free_bucket(tdb, b_off);
 401         return ecode;
 402 }
 403
 404 /* We need size bytes to put our key and data in. */
 405 static tdb_off_t lock_and_alloc(struct tdb_context *tdb,
 406                                 tdb_off_t ftable_off,
 407                                 tdb_off_t bucket,
 408                                 size_t keylen, size_t datalen,
 409                                 bool want_extra,
 410                                 unsigned magic,
 411                                 unsigned hashlow)
 412 {
 413         tdb_off_t off, b_off,best_off;
 414         struct tdb_free_record best = { 0 };
 415         double multiplier;
 416         size_t size = adjust_size(keylen, datalen);
 417         enum TDB_ERROR ecode;
 418
 419         add_stat(tdb, allocs, 1);
 420 again:
 421         b_off = bucket_off(ftable_off, bucket);
 422
 423         /* FIXME: Try non-blocking wait first, to measure contention. */
 424         /* Lock this bucket. */
 425         ecode = tdb_lock_free_bucket(tdb, b_off, TDB_LOCK_WAIT);
 426         if (ecode != TDB_SUCCESS) {
 427                 return ecode;
 428         }
 429
 430         best.ftable_and_len = -1ULL;
 431         best_off = 0;
 432
 433         /* Get slack if we're after extra. */
 434         if (want_extra)
 435                 multiplier = 1.5;
 436         else
 437                 multiplier = 1.0;
 438
 439         /* Walk the list to see if any are large enough, getting less fussy
 440          * as we go. */
 441         off = tdb_read_off(tdb, b_off);
 442         if (TDB_OFF_IS_ERR(off)) {
 443                 ecode = off;
 444                 goto unlock_err;
 445         }
 446
 447         while (off) {
 448                 const struct tdb_free_record *r;
 449                 tdb_len_t len;
 450                 tdb_off_t next;
 451                 int coal;
 452
 453                 r = tdb_access_read(tdb, off, sizeof(*r), true);
 454                 if (TDB_PTR_IS_ERR(r)) {
 455                         ecode = TDB_PTR_ERR(r);
 456                         goto unlock_err;
 457                 }
 458
 459                 if (frec_magic(r) != TDB_FREE_MAGIC) {
 460                         tdb_access_release(tdb, r);
 461                         ecode = tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 462                                            "lock_and_alloc:"
 463                                            " %llu non-free 0x%llx",
 464                                            (long long)off,
 465                                            (long long)r->magic_and_prev);
 466                         goto unlock_err;
 467                 }
 468
 469                 if (frec_len(r) >= size && frec_len(r) < frec_len(&best)) {
 470                         best_off = off;
 471                         best = *r;
 472                 }
 473
 474                 if (frec_len(&best) < size * multiplier && best_off) {
 475                         tdb_access_release(tdb, r);
 476                         break;
 477                 }
 478
 479                 multiplier *= 1.01;
 480
 481                 next = r->next;
 482                 len = frec_len(r);
 483                 tdb_access_release(tdb, r);
 484
 485                 /* Since we're going slow anyway, try coalescing here. */
 486                 coal = coalesce(tdb, off, b_off, len);
 487                 if (coal == 1) {
 488                         /* This has unlocked list, restart. */
 489                         goto again;
 490                 }
 491                 if (coal < 0) {
 492                         /* This has already unlocked on error. */
 493                         return coal;
 494                 }
 495                 off = next;
 496         }
 497
 498         /* If we found anything at all, use it. */
 499         if (best_off) {
 500                 struct tdb_used_record rec;
 501                 size_t leftover;
 502
 503                 /* We're happy with this size: take it. */
 504                 ecode = remove_from_list(tdb, b_off, best_off, &best);
 505                 if (ecode != TDB_SUCCESS) {
 506                         goto unlock_err;
 507                 }
 508
 509                 leftover = record_leftover(keylen, datalen, want_extra,
 510                                            frec_len(&best));
 511
 512                 assert(keylen + datalen + leftover <= frec_len(&best));
 513                 /* We need to mark non-free before we drop lock, otherwise
 514                  * coalesce() could try to merge it! */
 515                 ecode = set_header(tdb, &rec, magic, keylen, datalen,
 516                                    frec_len(&best) - leftover, hashlow);
 517                 if (ecode != TDB_SUCCESS) {
 518                         goto unlock_err;
 519                 }
 520
 521                 ecode = tdb_write_convert(tdb, best_off, &rec, sizeof(rec));
 522                 if (ecode != TDB_SUCCESS) {
 523                         goto unlock_err;
 524                 }
 525
 526                 /* For futureproofing, we put a 0 in any unused space. */
 527                 if (rec_extra_padding(&rec)) {
 528                         ecode = tdb->methods->twrite(tdb, best_off + sizeof(rec)
 529                                                      + keylen + datalen, "", 1);
 530                         if (ecode != TDB_SUCCESS) {
 531                                 goto unlock_err;
 532                         }
 533                 }
 534
 535                 /* Bucket of leftover will be <= current bucket, so nested
 536                  * locking is allowed. */
 537                 if (leftover) {
 538                         add_stat(tdb, alloc_leftover, 1);
 539                         ecode = add_free_record(tdb,
 540                                                 best_off + sizeof(rec)
 541                                                 + frec_len(&best) - leftover,
 542                                                 leftover);
 543                         if (ecode != TDB_SUCCESS) {
 544                                 best_off = ecode;
 545                         }
 546                 }
 547                 tdb_unlock_free_bucket(tdb, b_off);
 548
 549                 return best_off;
 550         }
 551
 552         tdb_unlock_free_bucket(tdb, b_off);
 553         return 0;
 554
 555 unlock_err:
 556         tdb_unlock_free_bucket(tdb, b_off);
 557         return ecode;
 558 }
 559
 560 /* Get a free block from current free list, or 0 if none, -ve on error. */
 561 static tdb_off_t get_free(struct tdb_context *tdb,
 562                           size_t keylen, size_t datalen, bool want_extra,
 563                           unsigned magic, unsigned hashlow)
 564 {
 565         tdb_off_t off, ftable_off;
 566         tdb_off_t start_b, b, ftable;
 567         bool wrapped = false;
 568
 569         /* If they are growing, add 50% to get to higher bucket. */
 570         if (want_extra)
 571                 start_b = size_to_bucket(adjust_size(keylen,
 572                                                      datalen + datalen / 2));
 573         else
 574                 start_b = size_to_bucket(adjust_size(keylen, datalen));
 575
 576         ftable_off = tdb->ftable_off;
 577         ftable = tdb->ftable;
 578         while (!wrapped || ftable_off != tdb->ftable_off) {
 579                 /* Start at exact size bucket, and search up... */
 580                 for (b = find_free_head(tdb, ftable_off, start_b);
 581                      b < TDB_FREE_BUCKETS;
 582                      b = find_free_head(tdb, ftable_off, b + 1)) {
 583                         /* Try getting one from list. */
 584                         off = lock_and_alloc(tdb, ftable_off,
 585                                              b, keylen, datalen, want_extra,
 586                                              magic, hashlow);
 587                         if (TDB_OFF_IS_ERR(off))
 588                                 return off;
 589                         if (off != 0) {
 590                                 if (b == start_b)
 591                                         add_stat(tdb, alloc_bucket_exact, 1);
 592                                 if (b == TDB_FREE_BUCKETS - 1)
 593                                         add_stat(tdb, alloc_bucket_max, 1);
 594                                 /* Worked?  Stay using this list. */
 595                                 tdb->ftable_off = ftable_off;
 596                                 tdb->ftable = ftable;
 597                                 return off;
 598                         }
 599                         /* Didn't work.  Try next bucket. */
 600                 }
 601
 602                 if (TDB_OFF_IS_ERR(b)) {
 603                         return b;
 604                 }
 605
 606                 /* Hmm, try next table. */
 607                 ftable_off = next_ftable(tdb, ftable_off);
 608                 if (TDB_OFF_IS_ERR(ftable_off)) {
 609                         return ftable_off;
 610                 }
 611                 ftable++;
 612
 613                 if (ftable_off == 0) {
 614                         wrapped = true;
 615                         ftable_off = first_ftable(tdb);
 616                         if (TDB_OFF_IS_ERR(ftable_off)) {
 617                                 return ftable_off;
 618                         }
 619                         ftable = 0;
 620                 }
 621         }
 622
 623         return 0;
 624 }
 625
 626 enum TDB_ERROR set_header(struct tdb_context *tdb,
 627                           struct tdb_used_record *rec,
 628                           unsigned magic, uint64_t keylen, uint64_t datalen,
 629                           uint64_t actuallen, unsigned hashlow)
 630 {
 631         uint64_t keybits = (fls64(keylen) + 1) / 2;
 632
 633         /* Use bottom bits of hash, so it's independent of hash table size. */
 634         rec->magic_and_meta = (hashlow & ((1 << 11)-1))
 635                 | ((actuallen - (keylen + datalen)) << 11)
 636                 | (keybits << 43)
 637                 | ((uint64_t)magic << 48);
 638         rec->key_and_data_len = (keylen | (datalen << (keybits*2)));
 639
 640         /* Encoding can fail on big values. */
 641         if (rec_key_length(rec) != keylen
 642             || rec_data_length(rec) != datalen
 643             || rec_extra_padding(rec) != actuallen - (keylen + datalen)) {
 644                 return tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
 645                                   "Could not encode k=%llu,d=%llu,a=%llu",
 646                                   (long long)keylen, (long long)datalen,
 647                                   (long long)actuallen);
 648         }
 649         return TDB_SUCCESS;
 650 }
 651
 652 /* Expand the database. */
 653 static enum TDB_ERROR tdb_expand(struct tdb_context *tdb, tdb_len_t size)
 654 {
 655         uint64_t old_size;
 656         tdb_len_t wanted;
 657         enum TDB_ERROR ecode;
 658
 659         /* We need room for the record header too. */
 660         wanted = sizeof(struct tdb_used_record) + size;
 661
 662         /* Need to hold a hash lock to expand DB: transactions rely on it. */
 663         if (!(tdb->flags & TDB_NOLOCK)
 664             && !tdb->allrecord_lock.count && !tdb_has_hash_locks(tdb)) {
 665                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 666                                   "tdb_expand: must hold lock during expand");
 667         }
 668
 669         /* always make room for at least 100 more records, and at
 670            least 25% more space. */
 671         if (size * TDB_EXTENSION_FACTOR > tdb->map_size / 4)
 672                 wanted = size * TDB_EXTENSION_FACTOR;
 673         else
 674                 wanted = tdb->map_size / 4;
 675         wanted = adjust_size(0, wanted);
 676
 677         /* Only one person can expand file at a time. */
 678         ecode = tdb_lock_expand(tdb, F_WRLCK);
 679         if (ecode != TDB_SUCCESS) {
 680                 return ecode;
 681         }
 682
 683         /* Someone else may have expanded the file, so retry. */
 684         old_size = tdb->map_size;
 685         tdb->methods->oob(tdb, tdb->map_size + 1, true);
 686         if (tdb->map_size != old_size) {
 687                 tdb_unlock_expand(tdb, F_WRLCK);
 688                 return TDB_SUCCESS;
 689         }
 690
 691         ecode = tdb->methods->expand_file(tdb, wanted);
 692         if (ecode != TDB_SUCCESS) {
 693                 tdb_unlock_expand(tdb, F_WRLCK);
 694                 return ecode;
 695         }
 696
 697         /* We need to drop this lock before adding free record. */
 698         tdb_unlock_expand(tdb, F_WRLCK);
 699
 700         add_stat(tdb, expands, 1);
 701         return add_free_record(tdb, old_size, wanted);
 702 }
 703
 704 /* This won't fail: it will expand the database if it has to. */
 705 tdb_off_t alloc(struct tdb_context *tdb, size_t keylen, size_t datalen,
 706                 uint64_t hash, unsigned magic, bool growing)
 707 {
 708         tdb_off_t off;
 709
 710         /* We can't hold pointers during this: we could unmap! */
 711         assert(!tdb->direct_access);
 712
 713         for (;;) {
 714                 enum TDB_ERROR ecode;
 715                 off = get_free(tdb, keylen, datalen, growing, magic, hash);
 716                 if (likely(off != 0))
 717                         break;
 718
 719                 ecode = tdb_expand(tdb, adjust_size(keylen, datalen));
 720                 if (ecode != TDB_SUCCESS) {
 721                         return ecode;
 722                 }
 723         }
 724
 725         return off;
 726 }