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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 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 static void check_list(struct tdb_context *tdb, tdb_off_t b_off)
 107 {
 108 #ifdef CCAN_TDB2_DEBUG
 109         tdb_off_t off, prev = 0, first;
 110         struct tdb_free_record r;
 111
 112         first = off = (tdb_read_off(tdb, b_off) & TDB_OFF_MASK);
 113         while (off != 0) {
 114                 tdb_read_convert(tdb, off, &r, sizeof(r));
 115                 if (frec_magic(&r) != TDB_FREE_MAGIC)
 116                         abort();
 117                 if (prev && frec_prev(&r) != prev)
 118                         abort();
 119                 prev = off;
 120                 off = r.next;
 121         }
 122
 123         if (first) {
 124                 tdb_read_convert(tdb, first, &r, sizeof(r));
 125                 if (frec_prev(&r) != prev)
 126                         abort();
 127         }
 128 #endif
 129 }
 130
 131 /* Remove from free bucket. */
 132 static enum TDB_ERROR remove_from_list(struct tdb_context *tdb,
 133                                        tdb_off_t b_off, tdb_off_t r_off,
 134                                        const struct tdb_free_record *r)
 135 {
 136         tdb_off_t off, prev_next, head;
 137         enum TDB_ERROR ecode;
 138
 139         /* Is this only element in list?  Zero out bucket, and we're done. */
 140         if (frec_prev(r) == r_off)
 141                 return tdb_write_off(tdb, b_off, 0);
 142
 143         /* off = &r->prev->next */
 144         off = frec_prev(r) + offsetof(struct tdb_free_record, next);
 145
 146         /* Get prev->next */
 147         prev_next = tdb_read_off(tdb, off);
 148         if (TDB_OFF_IS_ERR(prev_next))
 149                 return prev_next;
 150
 151         /* If prev->next == 0, we were head: update bucket to point to next. */
 152         if (prev_next == 0) {
 153                 /* We must preserve upper bits. */
 154                 head = tdb_read_off(tdb, b_off);
 155                 if (TDB_OFF_IS_ERR(head))
 156                         return head;
 157
 158                 if ((head & TDB_OFF_MASK) != r_off) {
 159                         return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 160                                           "remove_from_list:"
 161                                           " %llu head %llu on list %llu",
 162                                           (long long)r_off,
 163                                           (long long)head,
 164                                           (long long)b_off);
 165                 }
 166                 head = ((head & ~TDB_OFF_MASK) | r->next);
 167                 ecode = tdb_write_off(tdb, b_off, head);
 168                 if (ecode != TDB_SUCCESS)
 169                         return ecode;
 170         } else {
 171                 /* r->prev->next = r->next */
 172                 ecode = tdb_write_off(tdb, off, r->next);
 173                 if (ecode != TDB_SUCCESS)
 174                         return ecode;
 175         }
 176
 177         /* If we were the tail, off = &head->prev. */
 178         if (r->next == 0) {
 179                 head = tdb_read_off(tdb, b_off);
 180                 if (TDB_OFF_IS_ERR(head))
 181                         return head;
 182                 head &= TDB_OFF_MASK;
 183                 off = head + offsetof(struct tdb_free_record, magic_and_prev);
 184         } else {
 185                 /* off = &r->next->prev */
 186                 off = r->next + offsetof(struct tdb_free_record,
 187                                          magic_and_prev);
 188         }
 189
 190 #ifdef CCAN_TDB2_DEBUG
 191         /* *off == r */
 192         if ((tdb_read_off(tdb, off) & TDB_OFF_MASK) != r_off) {
 193                 return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 194                                   "remove_from_list:"
 195                                   " %llu bad prev in list %llu",
 196                                   (long long)r_off, (long long)b_off);
 197         }
 198 #endif
 199         /* r->next->prev = r->prev */
 200         return tdb_write_off(tdb, off, r->magic_and_prev);
 201 }
 202
 203 /* Enqueue in this free bucket: sets coalesce if we've added 128
 204  * entries to it. */
 205 static enum TDB_ERROR enqueue_in_free(struct tdb_context *tdb,
 206                                       tdb_off_t b_off,
 207                                       tdb_off_t off,
 208                                       tdb_len_t len,
 209                                       bool *coalesce)
 210 {
 211         struct tdb_free_record new;
 212         enum TDB_ERROR ecode;
 213         tdb_off_t prev, head;
 214         uint64_t magic = (TDB_FREE_MAGIC << (64 - TDB_OFF_UPPER_STEAL));
 215
 216         head = tdb_read_off(tdb, b_off);
 217         if (TDB_OFF_IS_ERR(head))
 218                 return head;
 219
 220         /* We only need to set ftable_and_len; rest is set in enqueue_in_free */
 221         new.ftable_and_len = ((uint64_t)tdb->ftable << (64 - TDB_OFF_UPPER_STEAL))
 222                 | len;
 223
 224         /* new->next = head. */
 225         new.next = (head & TDB_OFF_MASK);
 226
 227         /* First element?  Prev points to ourselves. */
 228         if (!new.next) {
 229                 new.magic_and_prev = (magic | off);
 230         } else {
 231                 /* new->prev = next->prev */
 232                 prev = tdb_read_off(tdb,
 233                                     new.next + offsetof(struct tdb_free_record,
 234                                                         magic_and_prev));
 235                 new.magic_and_prev = prev;
 236                 if (frec_magic(&new) != TDB_FREE_MAGIC) {
 237                         return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 238                                           "enqueue_in_free: %llu bad head"
 239                                           " prev %llu",
 240                                           (long long)new.next,
 241                                           (long long)prev);
 242                 }
 243                 /* next->prev = new. */
 244                 ecode = tdb_write_off(tdb, new.next
 245                                       + offsetof(struct tdb_free_record,
 246                                                  magic_and_prev),
 247                                       off | magic);
 248                 if (ecode != TDB_SUCCESS) {
 249                         return ecode;
 250                 }
 251
 252 #ifdef CCAN_TDB2_DEBUG
 253                 prev = tdb_read_off(tdb, frec_prev(&new)
 254                                     + offsetof(struct tdb_free_record, next));
 255                 if (prev != 0) {
 256                         return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 257                                           "enqueue_in_free:"
 258                                           " %llu bad tail next ptr %llu",
 259                                           (long long)frec_prev(&new)
 260                                           + offsetof(struct tdb_free_record,
 261                                                      next),
 262                                           (long long)prev);
 263                 }
 264 #endif
 265         }
 266
 267         /* Update enqueue count, but don't set high bit: see TDB_OFF_IS_ERR */
 268         if (*coalesce)
 269                 head += (1ULL << (64 - TDB_OFF_UPPER_STEAL));
 270         head &= ~(TDB_OFF_MASK | (1ULL << 63));
 271         head |= off;
 272
 273         ecode = tdb_write_off(tdb, b_off, head);
 274         if (ecode != TDB_SUCCESS) {
 275                 return ecode;
 276         }
 277
 278         /* It's time to coalesce if counter wrapped. */
 279         if (*coalesce)
 280                 *coalesce = ((head & ~TDB_OFF_MASK) == 0);
 281
 282         return tdb_write_convert(tdb, off, &new, sizeof(new));
 283 }
 284
 285 static tdb_off_t ftable_offset(struct tdb_context *tdb, unsigned int ftable)
 286 {
 287         tdb_off_t off;
 288         unsigned int i;
 289
 290         if (likely(tdb->ftable == ftable))
 291                 return tdb->ftable_off;
 292
 293         off = first_ftable(tdb);
 294         for (i = 0; i < ftable; i++) {
 295                 if (TDB_OFF_IS_ERR(off)) {
 296                         break;
 297                 }
 298                 off = next_ftable(tdb, off);
 299         }
 300         return off;
 301 }
 302
 303 /* Note: we unlock the current bucket if fail (-ve), or coalesce (+ve) and
 304  * need to blatt the *protect record (which is set to an error). */
 305 static tdb_len_t coalesce(struct tdb_context *tdb,
 306                           tdb_off_t off, tdb_off_t b_off,
 307                           tdb_len_t data_len,
 308                           tdb_off_t *protect)
 309 {
 310         tdb_off_t end;
 311         struct tdb_free_record rec;
 312         enum TDB_ERROR ecode;
 313
 314         tdb->stats.alloc_coalesce_tried++;
 315         end = off + sizeof(struct tdb_used_record) + data_len;
 316
 317         while (end < tdb->file->map_size) {
 318                 const struct tdb_free_record *r;
 319                 tdb_off_t nb_off;
 320                 unsigned ftable, bucket;
 321
 322                 r = tdb_access_read(tdb, end, sizeof(*r), true);
 323                 if (TDB_PTR_IS_ERR(r)) {
 324                         ecode = TDB_PTR_ERR(r);
 325                         goto err;
 326                 }
 327
 328                 if (frec_magic(r) != TDB_FREE_MAGIC
 329                     || frec_ftable(r) == TDB_FTABLE_NONE) {
 330                         tdb_access_release(tdb, r);
 331                         break;
 332                 }
 333
 334                 ftable = frec_ftable(r);
 335                 bucket = size_to_bucket(frec_len(r));
 336                 nb_off = ftable_offset(tdb, ftable);
 337                 if (TDB_OFF_IS_ERR(nb_off)) {
 338                         tdb_access_release(tdb, r);
 339                         ecode = nb_off;
 340                         goto err;
 341                 }
 342                 nb_off = bucket_off(nb_off, bucket);
 343                 tdb_access_release(tdb, r);
 344
 345                 /* We may be violating lock order here, so best effort. */
 346                 if (tdb_lock_free_bucket(tdb, nb_off, TDB_LOCK_NOWAIT)
 347                     != TDB_SUCCESS) {
 348                         tdb->stats.alloc_coalesce_lockfail++;
 349                         break;
 350                 }
 351
 352                 /* Now we have lock, re-check. */
 353                 ecode = tdb_read_convert(tdb, end, &rec, sizeof(rec));
 354                 if (ecode != TDB_SUCCESS) {
 355                         tdb_unlock_free_bucket(tdb, nb_off);
 356                         goto err;
 357                 }
 358
 359                 if (unlikely(frec_magic(&rec) != TDB_FREE_MAGIC)) {
 360                         tdb->stats.alloc_coalesce_race++;
 361                         tdb_unlock_free_bucket(tdb, nb_off);
 362                         break;
 363                 }
 364
 365                 if (unlikely(frec_ftable(&rec) != ftable)
 366                     || unlikely(size_to_bucket(frec_len(&rec)) != bucket)) {
 367                         tdb->stats.alloc_coalesce_race++;
 368                         tdb_unlock_free_bucket(tdb, nb_off);
 369                         break;
 370                 }
 371
 372                 /* Did we just mess up a record you were hoping to use? */
 373                 if (end == *protect)
 374                         *protect = TDB_ERR_NOEXIST;
 375
 376                 ecode = remove_from_list(tdb, nb_off, end, &rec);
 377                 check_list(tdb, nb_off);
 378                 if (ecode != TDB_SUCCESS) {
 379                         tdb_unlock_free_bucket(tdb, nb_off);
 380                         goto err;
 381                 }
 382
 383                 end += sizeof(struct tdb_used_record) + frec_len(&rec);
 384                 tdb_unlock_free_bucket(tdb, nb_off);
 385                 tdb->stats.alloc_coalesce_num_merged++;
 386         }
 387
 388         /* Didn't find any adjacent free? */
 389         if (end == off + sizeof(struct tdb_used_record) + data_len)
 390                 return 0;
 391
 392         /* Before we expand, check this isn't one you wanted protected? */
 393         if (off == *protect)
 394                 *protect = TDB_ERR_EXISTS;
 395
 396         /* OK, expand initial record */
 397         ecode = tdb_read_convert(tdb, off, &rec, sizeof(rec));
 398         if (ecode != TDB_SUCCESS) {
 399                 goto err;
 400         }
 401
 402         if (frec_len(&rec) != data_len) {
 403                 ecode = tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 404                                    "coalesce: expected data len %zu not %zu",
 405                                    (size_t)data_len, (size_t)frec_len(&rec));
 406                 goto err;
 407         }
 408
 409         ecode = remove_from_list(tdb, b_off, off, &rec);
 410         check_list(tdb, b_off);
 411         if (ecode != TDB_SUCCESS) {
 412                 goto err;
 413         }
 414
 415         /* Try locking violation first.  We don't allow coalesce recursion! */
 416         ecode = add_free_record(tdb, off, end - off, TDB_LOCK_NOWAIT, false);
 417         if (ecode != TDB_SUCCESS) {
 418                 /* Need to drop lock.  Can't rely on anything stable. */
 419                 *protect = TDB_ERR_CORRUPT;
 420
 421                 /* We have to drop this to avoid deadlocks, so make sure record
 422                  * doesn't get coalesced by someone else! */
 423                 rec.ftable_and_len = (TDB_FTABLE_NONE
 424                                       << (64 - TDB_OFF_UPPER_STEAL))
 425                         | (end - off - sizeof(struct tdb_used_record));
 426                 ecode = tdb_write_off(tdb,
 427                                       off + offsetof(struct tdb_free_record,
 428                                                      ftable_and_len),
 429                                       rec.ftable_and_len);
 430                 if (ecode != TDB_SUCCESS) {
 431                         goto err;
 432                 }
 433
 434                 tdb->stats.alloc_coalesce_succeeded++;
 435                 tdb_unlock_free_bucket(tdb, b_off);
 436
 437                 ecode = add_free_record(tdb, off, end - off, TDB_LOCK_WAIT,
 438                                         false);
 439                 if (ecode != TDB_SUCCESS) {
 440                         return ecode;
 441                 }
 442         } else if (TDB_OFF_IS_ERR(*protect)) {
 443                 /* For simplicity, we always drop lock if they can't continue */
 444                 tdb_unlock_free_bucket(tdb, b_off);
 445         }
 446
 447         /* Return usable length. */
 448         return end - off - sizeof(struct tdb_used_record);
 449
 450 err:
 451         /* To unify error paths, we *always* unlock bucket on error. */
 452         tdb_unlock_free_bucket(tdb, b_off);
 453         return ecode;
 454 }
 455
 456 /* List is locked: we unlock it. */
 457 static enum TDB_ERROR coalesce_list(struct tdb_context *tdb,
 458                                     tdb_off_t ftable_off, tdb_off_t b_off)
 459 {
 460         enum TDB_ERROR ecode;
 461         tdb_off_t off;
 462
 463         off = tdb_read_off(tdb, b_off);
 464         if (TDB_OFF_IS_ERR(off)) {
 465                 ecode = off;
 466                 goto unlock_err;
 467         }
 468         /* A little bit of paranoia */
 469         off &= TDB_OFF_MASK;
 470
 471         while (off) {
 472                 struct tdb_free_record rec;
 473                 tdb_len_t coal;
 474                 tdb_off_t next;
 475
 476                 ecode = tdb_read_convert(tdb, off, &rec, sizeof(rec));
 477                 if (ecode != TDB_SUCCESS)
 478                         goto unlock_err;
 479
 480                 next = rec.next;
 481                 coal = coalesce(tdb, off, b_off, frec_len(&rec), &next);
 482                 if (TDB_OFF_IS_ERR(coal)) {
 483                         /* This has already unlocked on error. */
 484                         return coal;
 485                 }
 486                 if (TDB_OFF_IS_ERR(next)) {
 487                         /* Coalescing had to unlock, so stop. */
 488                         return TDB_SUCCESS;
 489                 }
 490                 off = next;
 491         }
 492
 493         tdb_unlock_free_bucket(tdb, b_off);
 494         return TDB_SUCCESS;
 495
 496 unlock_err:
 497         tdb_unlock_free_bucket(tdb, b_off);
 498         return ecode;
 499 }
 500
 501 /* List must not be locked if coalesce_ok is set. */
 502 enum TDB_ERROR add_free_record(struct tdb_context *tdb,
 503                                tdb_off_t off, tdb_len_t len_with_header,
 504                                enum tdb_lock_flags waitflag,
 505                                bool coalesce)
 506 {
 507         tdb_off_t b_off;
 508         tdb_len_t len;
 509         enum TDB_ERROR ecode;
 510
 511         assert(len_with_header >= sizeof(struct tdb_free_record));
 512
 513         len = len_with_header - sizeof(struct tdb_used_record);
 514
 515         b_off = bucket_off(tdb->ftable_off, size_to_bucket(len));
 516         ecode = tdb_lock_free_bucket(tdb, b_off, waitflag);
 517         if (ecode != TDB_SUCCESS) {
 518                 return ecode;
 519         }
 520
 521         ecode = enqueue_in_free(tdb, b_off, off, len, &coalesce);
 522         check_list(tdb, b_off);
 523
 524         /* Coalescing unlocks free list. */
 525         if (!ecode && coalesce)
 526                 ecode = coalesce_list(tdb, tdb->ftable_off, b_off);
 527         else
 528                 tdb_unlock_free_bucket(tdb, b_off);
 529         return ecode;
 530 }
 531
 532 static size_t adjust_size(size_t keylen, size_t datalen)
 533 {
 534         size_t size = keylen + datalen;
 535
 536         if (size < TDB_MIN_DATA_LEN)
 537                 size = TDB_MIN_DATA_LEN;
 538
 539         /* Round to next uint64_t boundary. */
 540         return (size + (sizeof(uint64_t) - 1ULL)) & ~(sizeof(uint64_t) - 1ULL);
 541 }
 542
 543 /* If we have enough left over to be useful, split that off. */
 544 static size_t record_leftover(size_t keylen, size_t datalen,
 545                               bool want_extra, size_t total_len)
 546 {
 547         ssize_t leftover;
 548
 549         if (want_extra)
 550                 datalen += datalen / 2;
 551         leftover = total_len - adjust_size(keylen, datalen);
 552
 553         if (leftover < (ssize_t)sizeof(struct tdb_free_record))
 554                 return 0;
 555
 556         return leftover;
 557 }
 558
 559 /* We need size bytes to put our key and data in. */
 560 static tdb_off_t lock_and_alloc(struct tdb_context *tdb,
 561                                 tdb_off_t ftable_off,
 562                                 tdb_off_t bucket,
 563                                 size_t keylen, size_t datalen,
 564                                 bool want_extra,
 565                                 unsigned magic,
 566                                 unsigned hashlow)
 567 {
 568         tdb_off_t off, b_off,best_off;
 569         struct tdb_free_record best = { 0 };
 570         double multiplier;
 571         size_t size = adjust_size(keylen, datalen);
 572         enum TDB_ERROR ecode;
 573
 574         tdb->stats.allocs++;
 575         b_off = bucket_off(ftable_off, bucket);
 576
 577         /* FIXME: Try non-blocking wait first, to measure contention. */
 578         /* Lock this bucket. */
 579         ecode = tdb_lock_free_bucket(tdb, b_off, TDB_LOCK_WAIT);
 580         if (ecode != TDB_SUCCESS) {
 581                 return ecode;
 582         }
 583
 584         best.ftable_and_len = -1ULL;
 585         best_off = 0;
 586
 587         /* Get slack if we're after extra. */
 588         if (want_extra)
 589                 multiplier = 1.5;
 590         else
 591                 multiplier = 1.0;
 592
 593         /* Walk the list to see if any are large enough, getting less fussy
 594          * as we go. */
 595         off = tdb_read_off(tdb, b_off);
 596         if (TDB_OFF_IS_ERR(off)) {
 597                 ecode = off;
 598                 goto unlock_err;
 599         }
 600         off &= TDB_OFF_MASK;
 601
 602         while (off) {
 603                 const struct tdb_free_record *r;
 604                 tdb_len_t len;
 605                 tdb_off_t next;
 606
 607                 r = tdb_access_read(tdb, off, sizeof(*r), true);
 608                 if (TDB_PTR_IS_ERR(r)) {
 609                         ecode = TDB_PTR_ERR(r);
 610                         goto unlock_err;
 611                 }
 612
 613                 if (frec_magic(r) != TDB_FREE_MAGIC) {
 614                         ecode = tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 615                                            "lock_and_alloc:"
 616                                            " %llu non-free 0x%llx",
 617                                            (long long)off,
 618                                            (long long)r->magic_and_prev);
 619                         tdb_access_release(tdb, r);
 620                         goto unlock_err;
 621                 }
 622
 623                 if (frec_len(r) >= size && frec_len(r) < frec_len(&best)) {
 624                         best_off = off;
 625                         best = *r;
 626                 }
 627
 628                 if (frec_len(&best) <= size * multiplier && best_off) {
 629                         tdb_access_release(tdb, r);
 630                         break;
 631                 }
 632
 633                 multiplier *= 1.01;
 634
 635                 next = r->next;
 636                 len = frec_len(r);
 637                 tdb_access_release(tdb, r);
 638                 off = next;
 639         }
 640
 641         /* If we found anything at all, use it. */
 642         if (best_off) {
 643                 struct tdb_used_record rec;
 644                 size_t leftover;
 645
 646                 /* We're happy with this size: take it. */
 647                 ecode = remove_from_list(tdb, b_off, best_off, &best);
 648                 check_list(tdb, b_off);
 649                 if (ecode != TDB_SUCCESS) {
 650                         goto unlock_err;
 651                 }
 652
 653                 leftover = record_leftover(keylen, datalen, want_extra,
 654                                            frec_len(&best));
 655
 656                 assert(keylen + datalen + leftover <= frec_len(&best));
 657                 /* We need to mark non-free before we drop lock, otherwise
 658                  * coalesce() could try to merge it! */
 659                 ecode = set_header(tdb, &rec, magic, keylen, datalen,
 660                                    frec_len(&best) - leftover, hashlow);
 661                 if (ecode != TDB_SUCCESS) {
 662                         goto unlock_err;
 663                 }
 664
 665                 ecode = tdb_write_convert(tdb, best_off, &rec, sizeof(rec));
 666                 if (ecode != TDB_SUCCESS) {
 667                         goto unlock_err;
 668                 }
 669
 670                 /* For futureproofing, we put a 0 in any unused space. */
 671                 if (rec_extra_padding(&rec)) {
 672                         ecode = tdb->methods->twrite(tdb, best_off + sizeof(rec)
 673                                                      + keylen + datalen, "", 1);
 674                         if (ecode != TDB_SUCCESS) {
 675                                 goto unlock_err;
 676                         }
 677                 }
 678
 679                 /* Bucket of leftover will be <= current bucket, so nested
 680                  * locking is allowed. */
 681                 if (leftover) {
 682                         tdb->stats.alloc_leftover++;
 683                         ecode = add_free_record(tdb,
 684                                                 best_off + sizeof(rec)
 685                                                 + frec_len(&best) - leftover,
 686                                                 leftover, TDB_LOCK_WAIT, false);
 687                         if (ecode != TDB_SUCCESS) {
 688                                 best_off = ecode;
 689                         }
 690                 }
 691                 tdb_unlock_free_bucket(tdb, b_off);
 692
 693                 return best_off;
 694         }
 695
 696         tdb_unlock_free_bucket(tdb, b_off);
 697         return 0;
 698
 699 unlock_err:
 700         tdb_unlock_free_bucket(tdb, b_off);
 701         return ecode;
 702 }
 703
 704 /* Get a free block from current free list, or 0 if none, -ve on error. */
 705 static tdb_off_t get_free(struct tdb_context *tdb,
 706                           size_t keylen, size_t datalen, bool want_extra,
 707                           unsigned magic, unsigned hashlow)
 708 {
 709         tdb_off_t off, ftable_off;
 710         tdb_off_t start_b, b, ftable;
 711         bool wrapped = false;
 712
 713         /* If they are growing, add 50% to get to higher bucket. */
 714         if (want_extra)
 715                 start_b = size_to_bucket(adjust_size(keylen,
 716                                                      datalen + datalen / 2));
 717         else
 718                 start_b = size_to_bucket(adjust_size(keylen, datalen));
 719
 720         ftable_off = tdb->ftable_off;
 721         ftable = tdb->ftable;
 722         while (!wrapped || ftable_off != tdb->ftable_off) {
 723                 /* Start at exact size bucket, and search up... */
 724                 for (b = find_free_head(tdb, ftable_off, start_b);
 725                      b < TDB_FREE_BUCKETS;
 726                      b = find_free_head(tdb, ftable_off, b + 1)) {
 727                         /* Try getting one from list. */
 728                         off = lock_and_alloc(tdb, ftable_off,
 729                                              b, keylen, datalen, want_extra,
 730                                              magic, hashlow);
 731                         if (TDB_OFF_IS_ERR(off))
 732                                 return off;
 733                         if (off != 0) {
 734                                 if (b == start_b)
 735                                         tdb->stats.alloc_bucket_exact++;
 736                                 if (b == TDB_FREE_BUCKETS - 1)
 737                                         tdb->stats.alloc_bucket_max++;
 738                                 /* Worked?  Stay using this list. */
 739                                 tdb->ftable_off = ftable_off;
 740                                 tdb->ftable = ftable;
 741                                 return off;
 742                         }
 743                         /* Didn't work.  Try next bucket. */
 744                 }
 745
 746                 if (TDB_OFF_IS_ERR(b)) {
 747                         return b;
 748                 }
 749
 750                 /* Hmm, try next table. */
 751                 ftable_off = next_ftable(tdb, ftable_off);
 752                 if (TDB_OFF_IS_ERR(ftable_off)) {
 753                         return ftable_off;
 754                 }
 755                 ftable++;
 756
 757                 if (ftable_off == 0) {
 758                         wrapped = true;
 759                         ftable_off = first_ftable(tdb);
 760                         if (TDB_OFF_IS_ERR(ftable_off)) {
 761                                 return ftable_off;
 762                         }
 763                         ftable = 0;
 764                 }
 765         }
 766
 767         return 0;
 768 }
 769
 770 enum TDB_ERROR set_header(struct tdb_context *tdb,
 771                           struct tdb_used_record *rec,
 772                           unsigned magic, uint64_t keylen, uint64_t datalen,
 773                           uint64_t actuallen, unsigned hashlow)
 774 {
 775         uint64_t keybits = (fls64(keylen) + 1) / 2;
 776
 777         /* Use bottom bits of hash, so it's independent of hash table size. */
 778         rec->magic_and_meta = (hashlow & ((1 << 11)-1))
 779                 | ((actuallen - (keylen + datalen)) << 11)
 780                 | (keybits << 43)
 781                 | ((uint64_t)magic << 48);
 782         rec->key_and_data_len = (keylen | (datalen << (keybits*2)));
 783
 784         /* Encoding can fail on big values. */
 785         if (rec_key_length(rec) != keylen
 786             || rec_data_length(rec) != datalen
 787             || rec_extra_padding(rec) != actuallen - (keylen + datalen)) {
 788                 return tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
 789                                   "Could not encode k=%llu,d=%llu,a=%llu",
 790                                   (long long)keylen, (long long)datalen,
 791                                   (long long)actuallen);
 792         }
 793         return TDB_SUCCESS;
 794 }
 795
 796 /* Expand the database. */
 797 static enum TDB_ERROR tdb_expand(struct tdb_context *tdb, tdb_len_t size)
 798 {
 799         uint64_t old_size, rec_size, map_size;
 800         tdb_len_t wanted;
 801         enum TDB_ERROR ecode;
 802
 803         /* Need to hold a hash lock to expand DB: transactions rely on it. */
 804         if (!(tdb->flags & TDB_NOLOCK)
 805             && !tdb->file->allrecord_lock.count && !tdb_has_hash_locks(tdb)) {
 806                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 807                                   "tdb_expand: must hold lock during expand");
 808         }
 809
 810         /* Only one person can expand file at a time. */
 811         ecode = tdb_lock_expand(tdb, F_WRLCK);
 812         if (ecode != TDB_SUCCESS) {
 813                 return ecode;
 814         }
 815
 816         /* Someone else may have expanded the file, so retry. */
 817         old_size = tdb->file->map_size;
 818         tdb->methods->oob(tdb, tdb->file->map_size + 1, true);
 819         if (tdb->file->map_size != old_size) {
 820                 tdb_unlock_expand(tdb, F_WRLCK);
 821                 return TDB_SUCCESS;
 822         }
 823
 824         /* limit size in order to avoid using up huge amounts of memory for
 825          * in memory tdbs if an oddball huge record creeps in */
 826         if (size > 100 * 1024) {
 827                 rec_size = size * 2;
 828         } else {
 829                 rec_size = size * 100;
 830         }
 831
 832         /* always make room for at least rec_size more records, and at
 833            least 25% more space. if the DB is smaller than 100MiB,
 834            otherwise grow it by 10% only. */
 835         if (old_size > 100 * 1024 * 1024) {
 836                 map_size = old_size / 10;
 837         } else {
 838                 map_size = old_size / 4;
 839         }
 840
 841         if (map_size > rec_size) {
 842                 wanted = map_size;
 843         } else {
 844                 wanted = rec_size;
 845         }
 846
 847         /* We need room for the record header too. */
 848         wanted = adjust_size(0, sizeof(struct tdb_used_record) + wanted);
 849
 850         ecode = tdb->methods->expand_file(tdb, wanted);
 851         if (ecode != TDB_SUCCESS) {
 852                 tdb_unlock_expand(tdb, F_WRLCK);
 853                 return ecode;
 854         }
 855
 856         /* We need to drop this lock before adding free record. */
 857         tdb_unlock_expand(tdb, F_WRLCK);
 858
 859         tdb->stats.expands++;
 860         return add_free_record(tdb, old_size, wanted, TDB_LOCK_WAIT, true);
 861 }
 862
 863 /* This won't fail: it will expand the database if it has to. */
 864 tdb_off_t alloc(struct tdb_context *tdb, size_t keylen, size_t datalen,
 865                 uint64_t hash, unsigned magic, bool growing)
 866 {
 867         tdb_off_t off;
 868
 869         /* We can't hold pointers during this: we could unmap! */
 870         assert(!tdb->direct_access);
 871
 872         for (;;) {
 873                 enum TDB_ERROR ecode;
 874                 off = get_free(tdb, keylen, datalen, growing, magic, hash);
 875                 if (likely(off != 0))
 876                         break;
 877
 878                 ecode = tdb_expand(tdb, adjust_size(keylen, datalen));
 879                 if (ecode != TDB_SUCCESS) {
 880                         return ecode;
 881                 }
 882         }
 883
 884         return off;
 885 }