git.ozlabs.org Git - ccan/blob - junkcode/rusty@rustcorp.com.au-ntdb/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 <limits.h>
  23
  24 static unsigned fls64(uint64_t val)
  25 {
  26         return ilog64(val);
  27 }
  28
  29 /* In which bucket would we find a particular record size? (ignoring header) */
  30 unsigned int size_to_bucket(ntdb_len_t data_len)
  31 {
  32         unsigned int bucket;
  33
  34         /* We can't have records smaller than this. */
  35         assert(data_len >= NTDB_MIN_DATA_LEN);
  36
  37         /* Ignoring the header... */
  38         if (data_len - NTDB_MIN_DATA_LEN <= 64) {
  39                 /* 0 in bucket 0, 8 in bucket 1... 64 in bucket 8. */
  40                 bucket = (data_len - NTDB_MIN_DATA_LEN) / 8;
  41         } else {
  42                 /* After that we go power of 2. */
  43                 bucket = fls64(data_len - NTDB_MIN_DATA_LEN) + 2;
  44         }
  45
  46         if (unlikely(bucket >= NTDB_FREE_BUCKETS))
  47                 bucket = NTDB_FREE_BUCKETS - 1;
  48         return bucket;
  49 }
  50
  51 ntdb_off_t first_ftable(struct ntdb_context *ntdb)
  52 {
  53         return ntdb_read_off(ntdb, offsetof(struct ntdb_header, free_table));
  54 }
  55
  56 ntdb_off_t next_ftable(struct ntdb_context *ntdb, ntdb_off_t ftable)
  57 {
  58         return ntdb_read_off(ntdb, ftable + offsetof(struct ntdb_freetable,next));
  59 }
  60
  61 enum NTDB_ERROR ntdb_ftable_init(struct ntdb_context *ntdb)
  62 {
  63         /* Use reservoir sampling algorithm to select a free list at random. */
  64         unsigned int rnd, max = 0, count = 0;
  65         ntdb_off_t off;
  66
  67         ntdb->ftable_off = off = first_ftable(ntdb);
  68         ntdb->ftable = 0;
  69
  70         while (off) {
  71                 if (NTDB_OFF_IS_ERR(off)) {
  72                         return NTDB_OFF_TO_ERR(off);
  73                 }
  74
  75                 rnd = random();
  76                 if (rnd >= max) {
  77                         ntdb->ftable_off = off;
  78                         ntdb->ftable = count;
  79                         max = rnd;
  80                 }
  81
  82                 off = next_ftable(ntdb, off);
  83                 count++;
  84         }
  85         return NTDB_SUCCESS;
  86 }
  87
  88 /* Offset of a given bucket. */
  89 ntdb_off_t bucket_off(ntdb_off_t ftable_off, unsigned bucket)
  90 {
  91         return ftable_off + offsetof(struct ntdb_freetable, buckets)
  92                 + bucket * sizeof(ntdb_off_t);
  93 }
  94
  95 /* Returns free_buckets + 1, or list number to search, or -ve error. */
  96 static ntdb_off_t find_free_head(struct ntdb_context *ntdb,
  97                                 ntdb_off_t ftable_off,
  98                                 ntdb_off_t bucket)
  99 {
 100         /* Speculatively search for a non-zero bucket. */
 101         return ntdb_find_nonzero_off(ntdb, bucket_off(ftable_off, 0),
 102                                     bucket, NTDB_FREE_BUCKETS);
 103 }
 104
 105 static void check_list(struct ntdb_context *ntdb, ntdb_off_t b_off)
 106 {
 107 #ifdef CCAN_NTDB_DEBUG
 108         ntdb_off_t off, prev = 0, first;
 109         struct ntdb_free_record r;
 110
 111         first = off = (ntdb_read_off(ntdb, b_off) & NTDB_OFF_MASK);
 112         while (off != 0) {
 113                 ntdb_read_convert(ntdb, off, &r, sizeof(r));
 114                 if (frec_magic(&r) != NTDB_FREE_MAGIC)
 115                         abort();
 116                 if (prev && frec_prev(&r) != prev)
 117                         abort();
 118                 prev = off;
 119                 off = r.next;
 120         }
 121
 122         if (first) {
 123                 ntdb_read_convert(ntdb, first, &r, sizeof(r));
 124                 if (frec_prev(&r) != prev)
 125                         abort();
 126         }
 127 #endif
 128 }
 129
 130 /* Remove from free bucket. */
 131 static enum NTDB_ERROR remove_from_list(struct ntdb_context *ntdb,
 132                                        ntdb_off_t b_off, ntdb_off_t r_off,
 133                                        const struct ntdb_free_record *r)
 134 {
 135         ntdb_off_t off, prev_next, head;
 136         enum NTDB_ERROR ecode;
 137
 138         /* Is this only element in list?  Zero out bucket, and we're done. */
 139         if (frec_prev(r) == r_off)
 140                 return ntdb_write_off(ntdb, b_off, 0);
 141
 142         /* off = &r->prev->next */
 143         off = frec_prev(r) + offsetof(struct ntdb_free_record, next);
 144
 145         /* Get prev->next */
 146         prev_next = ntdb_read_off(ntdb, off);
 147         if (NTDB_OFF_IS_ERR(prev_next))
 148                 return NTDB_OFF_TO_ERR(prev_next);
 149
 150         /* If prev->next == 0, we were head: update bucket to point to next. */
 151         if (prev_next == 0) {
 152                 /* We must preserve upper bits. */
 153                 head = ntdb_read_off(ntdb, b_off);
 154                 if (NTDB_OFF_IS_ERR(head))
 155                         return NTDB_OFF_TO_ERR(head);
 156
 157                 if ((head & NTDB_OFF_MASK) != r_off) {
 158                         return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
 159                                           "remove_from_list:"
 160                                           " %llu head %llu on list %llu",
 161                                           (long long)r_off,
 162                                           (long long)head,
 163                                           (long long)b_off);
 164                 }
 165                 head = ((head & ~NTDB_OFF_MASK) | r->next);
 166                 ecode = ntdb_write_off(ntdb, b_off, head);
 167                 if (ecode != NTDB_SUCCESS)
 168                         return ecode;
 169         } else {
 170                 /* r->prev->next = r->next */
 171                 ecode = ntdb_write_off(ntdb, off, r->next);
 172                 if (ecode != NTDB_SUCCESS)
 173                         return ecode;
 174         }
 175
 176         /* If we were the tail, off = &head->prev. */
 177         if (r->next == 0) {
 178                 head = ntdb_read_off(ntdb, b_off);
 179                 if (NTDB_OFF_IS_ERR(head))
 180                         return NTDB_OFF_TO_ERR(head);
 181                 head &= NTDB_OFF_MASK;
 182                 off = head + offsetof(struct ntdb_free_record, magic_and_prev);
 183         } else {
 184                 /* off = &r->next->prev */
 185                 off = r->next + offsetof(struct ntdb_free_record,
 186                                          magic_and_prev);
 187         }
 188
 189 #ifdef CCAN_NTDB_DEBUG
 190         /* *off == r */
 191         if ((ntdb_read_off(ntdb, off) & NTDB_OFF_MASK) != r_off) {
 192                 return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
 193                                   "remove_from_list:"
 194                                   " %llu bad prev in list %llu",
 195                                   (long long)r_off, (long long)b_off);
 196         }
 197 #endif
 198         /* r->next->prev = r->prev */
 199         return ntdb_write_off(ntdb, off, r->magic_and_prev);
 200 }
 201
 202 /* Enqueue in this free bucket: sets coalesce if we've added 128
 203  * entries to it. */
 204 static enum NTDB_ERROR enqueue_in_free(struct ntdb_context *ntdb,
 205                                       ntdb_off_t b_off,
 206                                       ntdb_off_t off,
 207                                       ntdb_len_t len,
 208                                       bool *coalesce)
 209 {
 210         struct ntdb_free_record new;
 211         enum NTDB_ERROR ecode;
 212         ntdb_off_t prev, head;
 213         uint64_t magic = (NTDB_FREE_MAGIC << (64 - NTDB_OFF_UPPER_STEAL));
 214
 215         head = ntdb_read_off(ntdb, b_off);
 216         if (NTDB_OFF_IS_ERR(head))
 217                 return NTDB_OFF_TO_ERR(head);
 218
 219         /* We only need to set ftable_and_len; rest is set in enqueue_in_free */
 220         new.ftable_and_len = ((uint64_t)ntdb->ftable
 221                               << (64 - NTDB_OFF_UPPER_STEAL))
 222                 | len;
 223
 224         /* new->next = head. */
 225         new.next = (head & NTDB_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 = ntdb_read_off(ntdb,
 233                                     new.next + offsetof(struct ntdb_free_record,
 234                                                         magic_and_prev));
 235                 new.magic_and_prev = prev;
 236                 if (frec_magic(&new) != NTDB_FREE_MAGIC) {
 237                         return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_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 = ntdb_write_off(ntdb, new.next
 245                                       + offsetof(struct ntdb_free_record,
 246                                                  magic_and_prev),
 247                                       off | magic);
 248                 if (ecode != NTDB_SUCCESS) {
 249                         return ecode;
 250                 }
 251
 252 #ifdef CCAN_NTDB_DEBUG
 253                 prev = ntdb_read_off(ntdb, frec_prev(&new)
 254                                     + offsetof(struct ntdb_free_record, next));
 255                 if (prev != 0) {
 256                         return ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
 257                                           "enqueue_in_free:"
 258                                           " %llu bad tail next ptr %llu",
 259                                           (long long)frec_prev(&new)
 260                                           + offsetof(struct ntdb_free_record,
 261                                                      next),
 262                                           (long long)prev);
 263                 }
 264 #endif
 265         }
 266
 267         /* Update enqueue count, but don't set high bit: see NTDB_OFF_IS_ERR */
 268         if (*coalesce)
 269                 head += (1ULL << (64 - NTDB_OFF_UPPER_STEAL));
 270         head &= ~(NTDB_OFF_MASK | (1ULL << 63));
 271         head |= off;
 272
 273         ecode = ntdb_write_off(ntdb, b_off, head);
 274         if (ecode != NTDB_SUCCESS) {
 275                 return ecode;
 276         }
 277
 278         /* It's time to coalesce if counter wrapped. */
 279         if (*coalesce)
 280                 *coalesce = ((head & ~NTDB_OFF_MASK) == 0);
 281
 282         return ntdb_write_convert(ntdb, off, &new, sizeof(new));
 283 }
 284
 285 static ntdb_off_t ftable_offset(struct ntdb_context *ntdb, unsigned int ftable)
 286 {
 287         ntdb_off_t off;
 288         unsigned int i;
 289
 290         if (likely(ntdb->ftable == ftable))
 291                 return ntdb->ftable_off;
 292
 293         off = first_ftable(ntdb);
 294         for (i = 0; i < ftable; i++) {
 295                 if (NTDB_OFF_IS_ERR(off)) {
 296                         break;
 297                 }
 298                 off = next_ftable(ntdb, 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 ntdb_len_t coalesce(struct ntdb_context *ntdb,
 306                           ntdb_off_t off, ntdb_off_t b_off,
 307                           ntdb_len_t data_len,
 308                           ntdb_off_t *protect)
 309 {
 310         ntdb_off_t end;
 311         struct ntdb_free_record rec;
 312         enum NTDB_ERROR ecode;
 313
 314         ntdb->stats.alloc_coalesce_tried++;
 315         end = off + sizeof(struct ntdb_used_record) + data_len;
 316
 317         while (end < ntdb->file->map_size) {
 318                 const struct ntdb_free_record *r;
 319                 ntdb_off_t nb_off;
 320                 unsigned ftable, bucket;
 321
 322                 r = ntdb_access_read(ntdb, end, sizeof(*r), true);
 323                 if (NTDB_PTR_IS_ERR(r)) {
 324                         ecode = NTDB_PTR_ERR(r);
 325                         goto err;
 326                 }
 327
 328                 if (frec_magic(r) != NTDB_FREE_MAGIC
 329                     || frec_ftable(r) == NTDB_FTABLE_NONE) {
 330                         ntdb_access_release(ntdb, r);
 331                         break;
 332                 }
 333
 334                 ftable = frec_ftable(r);
 335                 bucket = size_to_bucket(frec_len(r));
 336                 nb_off = ftable_offset(ntdb, ftable);
 337                 if (NTDB_OFF_IS_ERR(nb_off)) {
 338                         ntdb_access_release(ntdb, r);
 339                         ecode = NTDB_OFF_TO_ERR(nb_off);
 340                         goto err;
 341                 }
 342                 nb_off = bucket_off(nb_off, bucket);
 343                 ntdb_access_release(ntdb, r);
 344
 345                 /* We may be violating lock order here, so best effort. */
 346                 if (ntdb_lock_free_bucket(ntdb, nb_off, NTDB_LOCK_NOWAIT)
 347                     != NTDB_SUCCESS) {
 348                         ntdb->stats.alloc_coalesce_lockfail++;
 349                         break;
 350                 }
 351
 352                 /* Now we have lock, re-check. */
 353                 ecode = ntdb_read_convert(ntdb, end, &rec, sizeof(rec));
 354                 if (ecode != NTDB_SUCCESS) {
 355                         ntdb_unlock_free_bucket(ntdb, nb_off);
 356                         goto err;
 357                 }
 358
 359                 if (unlikely(frec_magic(&rec) != NTDB_FREE_MAGIC)) {
 360                         ntdb->stats.alloc_coalesce_race++;
 361                         ntdb_unlock_free_bucket(ntdb, nb_off);
 362                         break;
 363                 }
 364
 365                 if (unlikely(frec_ftable(&rec) != ftable)
 366                     || unlikely(size_to_bucket(frec_len(&rec)) != bucket)) {
 367                         ntdb->stats.alloc_coalesce_race++;
 368                         ntdb_unlock_free_bucket(ntdb, nb_off);
 369                         break;
 370                 }
 371
 372                 /* Did we just mess up a record you were hoping to use? */
 373                 if (end == *protect) {
 374                         ntdb->stats.alloc_coalesce_iterate_clash++;
 375                         *protect = NTDB_ERR_TO_OFF(NTDB_ERR_NOEXIST);
 376                 }
 377
 378                 ecode = remove_from_list(ntdb, nb_off, end, &rec);
 379                 check_list(ntdb, nb_off);
 380                 if (ecode != NTDB_SUCCESS) {
 381                         ntdb_unlock_free_bucket(ntdb, nb_off);
 382                         goto err;
 383                 }
 384
 385                 end += sizeof(struct ntdb_used_record) + frec_len(&rec);
 386                 ntdb_unlock_free_bucket(ntdb, nb_off);
 387                 ntdb->stats.alloc_coalesce_num_merged++;
 388         }
 389
 390         /* Didn't find any adjacent free? */
 391         if (end == off + sizeof(struct ntdb_used_record) + data_len)
 392                 return 0;
 393
 394         /* Before we expand, check this isn't one you wanted protected? */
 395         if (off == *protect) {
 396                 *protect = NTDB_ERR_TO_OFF(NTDB_ERR_EXISTS);
 397                 ntdb->stats.alloc_coalesce_iterate_clash++;
 398         }
 399
 400         /* OK, expand initial record */
 401         ecode = ntdb_read_convert(ntdb, off, &rec, sizeof(rec));
 402         if (ecode != NTDB_SUCCESS) {
 403                 goto err;
 404         }
 405
 406         if (frec_len(&rec) != data_len) {
 407                 ecode = ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
 408                                    "coalesce: expected data len %zu not %zu",
 409                                    (size_t)data_len, (size_t)frec_len(&rec));
 410                 goto err;
 411         }
 412
 413         ecode = remove_from_list(ntdb, b_off, off, &rec);
 414         check_list(ntdb, b_off);
 415         if (ecode != NTDB_SUCCESS) {
 416                 goto err;
 417         }
 418
 419         /* Try locking violation first.  We don't allow coalesce recursion! */
 420         ecode = add_free_record(ntdb, off, end - off, NTDB_LOCK_NOWAIT, false);
 421         if (ecode != NTDB_SUCCESS) {
 422                 /* Need to drop lock.  Can't rely on anything stable. */
 423                 ntdb->stats.alloc_coalesce_lockfail++;
 424                 *protect = NTDB_ERR_TO_OFF(NTDB_ERR_CORRUPT);
 425
 426                 /* We have to drop this to avoid deadlocks, so make sure record
 427                  * doesn't get coalesced by someone else! */
 428                 rec.ftable_and_len = (NTDB_FTABLE_NONE
 429                                       << (64 - NTDB_OFF_UPPER_STEAL))
 430                         | (end - off - sizeof(struct ntdb_used_record));
 431                 ecode = ntdb_write_off(ntdb,
 432                                       off + offsetof(struct ntdb_free_record,
 433                                                      ftable_and_len),
 434                                       rec.ftable_and_len);
 435                 if (ecode != NTDB_SUCCESS) {
 436                         goto err;
 437                 }
 438
 439                 ntdb_unlock_free_bucket(ntdb, b_off);
 440
 441                 ecode = add_free_record(ntdb, off, end - off, NTDB_LOCK_WAIT,
 442                                         false);
 443                 if (ecode != NTDB_SUCCESS) {
 444                         return NTDB_ERR_TO_OFF(ecode);
 445                 }
 446         } else if (NTDB_OFF_IS_ERR(*protect)) {
 447                 /* For simplicity, we always drop lock if they can't continue */
 448                 ntdb_unlock_free_bucket(ntdb, b_off);
 449         }
 450         ntdb->stats.alloc_coalesce_succeeded++;
 451
 452         /* Return usable length. */
 453         return end - off - sizeof(struct ntdb_used_record);
 454
 455 err:
 456         /* To unify error paths, we *always* unlock bucket on error. */
 457         ntdb_unlock_free_bucket(ntdb, b_off);
 458         return NTDB_ERR_TO_OFF(ecode);
 459 }
 460
 461 /* List is locked: we unlock it. */
 462 static enum NTDB_ERROR coalesce_list(struct ntdb_context *ntdb,
 463                                     ntdb_off_t ftable_off,
 464                                     ntdb_off_t b_off,
 465                                     unsigned int limit)
 466 {
 467         enum NTDB_ERROR ecode;
 468         ntdb_off_t off;
 469
 470         off = ntdb_read_off(ntdb, b_off);
 471         if (NTDB_OFF_IS_ERR(off)) {
 472                 ecode = NTDB_OFF_TO_ERR(off);
 473                 goto unlock_err;
 474         }
 475         /* A little bit of paranoia: counter should be 0. */
 476         off &= NTDB_OFF_MASK;
 477
 478         while (off && limit--) {
 479                 struct ntdb_free_record rec;
 480                 ntdb_len_t coal;
 481                 ntdb_off_t next;
 482
 483                 ecode = ntdb_read_convert(ntdb, off, &rec, sizeof(rec));
 484                 if (ecode != NTDB_SUCCESS)
 485                         goto unlock_err;
 486
 487                 next = rec.next;
 488                 coal = coalesce(ntdb, off, b_off, frec_len(&rec), &next);
 489                 if (NTDB_OFF_IS_ERR(coal)) {
 490                         /* This has already unlocked on error. */
 491                         return NTDB_OFF_TO_ERR(coal);
 492                 }
 493                 if (NTDB_OFF_IS_ERR(next)) {
 494                         /* Coalescing had to unlock, so stop. */
 495                         return NTDB_SUCCESS;
 496                 }
 497                 /* Keep going if we're doing well... */
 498                 limit += size_to_bucket(coal / 16 + NTDB_MIN_DATA_LEN);
 499                 off = next;
 500         }
 501
 502         /* Now, move those elements to the tail of the list so we get something
 503          * else next time. */
 504         if (off) {
 505                 struct ntdb_free_record oldhrec, newhrec, oldtrec, newtrec;
 506                 ntdb_off_t oldhoff, oldtoff, newtoff;
 507
 508                 /* The record we were up to is the new head. */
 509                 ecode = ntdb_read_convert(ntdb, off, &newhrec, sizeof(newhrec));
 510                 if (ecode != NTDB_SUCCESS)
 511                         goto unlock_err;
 512
 513                 /* Get the new tail. */
 514                 newtoff = frec_prev(&newhrec);
 515                 ecode = ntdb_read_convert(ntdb, newtoff, &newtrec,
 516                                          sizeof(newtrec));
 517                 if (ecode != NTDB_SUCCESS)
 518                         goto unlock_err;
 519
 520                 /* Get the old head. */
 521                 oldhoff = ntdb_read_off(ntdb, b_off);
 522                 if (NTDB_OFF_IS_ERR(oldhoff)) {
 523                         ecode = NTDB_OFF_TO_ERR(oldhoff);
 524                         goto unlock_err;
 525                 }
 526
 527                 /* This could happen if they all coalesced away. */
 528                 if (oldhoff == off)
 529                         goto out;
 530
 531                 ecode = ntdb_read_convert(ntdb, oldhoff, &oldhrec,
 532                                          sizeof(oldhrec));
 533                 if (ecode != NTDB_SUCCESS)
 534                         goto unlock_err;
 535
 536                 /* Get the old tail. */
 537                 oldtoff = frec_prev(&oldhrec);
 538                 ecode = ntdb_read_convert(ntdb, oldtoff, &oldtrec,
 539                                          sizeof(oldtrec));
 540                 if (ecode != NTDB_SUCCESS)
 541                         goto unlock_err;
 542
 543                 /* Old tail's next points to old head. */
 544                 oldtrec.next = oldhoff;
 545
 546                 /* Old head's prev points to old tail. */
 547                 oldhrec.magic_and_prev
 548                         = (NTDB_FREE_MAGIC << (64 - NTDB_OFF_UPPER_STEAL))
 549                         | oldtoff;
 550
 551                 /* New tail's next is 0. */
 552                 newtrec.next = 0;
 553
 554                 /* Write out the modified versions. */
 555                 ecode = ntdb_write_convert(ntdb, oldtoff, &oldtrec,
 556                                           sizeof(oldtrec));
 557                 if (ecode != NTDB_SUCCESS)
 558                         goto unlock_err;
 559
 560                 ecode = ntdb_write_convert(ntdb, oldhoff, &oldhrec,
 561                                           sizeof(oldhrec));
 562                 if (ecode != NTDB_SUCCESS)
 563                         goto unlock_err;
 564
 565                 ecode = ntdb_write_convert(ntdb, newtoff, &newtrec,
 566                                           sizeof(newtrec));
 567                 if (ecode != NTDB_SUCCESS)
 568                         goto unlock_err;
 569
 570                 /* And finally link in new head. */
 571                 ecode = ntdb_write_off(ntdb, b_off, off);
 572                 if (ecode != NTDB_SUCCESS)
 573                         goto unlock_err;
 574         }
 575 out:
 576         ntdb_unlock_free_bucket(ntdb, b_off);
 577         return NTDB_SUCCESS;
 578
 579 unlock_err:
 580         ntdb_unlock_free_bucket(ntdb, b_off);
 581         return ecode;
 582 }
 583
 584 /* List must not be locked if coalesce_ok is set. */
 585 enum NTDB_ERROR add_free_record(struct ntdb_context *ntdb,
 586                                ntdb_off_t off, ntdb_len_t len_with_header,
 587                                enum ntdb_lock_flags waitflag,
 588                                bool coalesce_ok)
 589 {
 590         ntdb_off_t b_off;
 591         ntdb_len_t len;
 592         enum NTDB_ERROR ecode;
 593
 594         assert(len_with_header >= sizeof(struct ntdb_free_record));
 595
 596         len = len_with_header - sizeof(struct ntdb_used_record);
 597
 598         b_off = bucket_off(ntdb->ftable_off, size_to_bucket(len));
 599         ecode = ntdb_lock_free_bucket(ntdb, b_off, waitflag);
 600         if (ecode != NTDB_SUCCESS) {
 601                 return ecode;
 602         }
 603
 604         ecode = enqueue_in_free(ntdb, b_off, off, len, &coalesce_ok);
 605         check_list(ntdb, b_off);
 606
 607         /* Coalescing unlocks free list. */
 608         if (!ecode && coalesce_ok)
 609                 ecode = coalesce_list(ntdb, ntdb->ftable_off, b_off, 2);
 610         else
 611                 ntdb_unlock_free_bucket(ntdb, b_off);
 612         return ecode;
 613 }
 614
 615 static size_t adjust_size(size_t keylen, size_t datalen)
 616 {
 617         size_t size = keylen + datalen;
 618
 619         if (size < NTDB_MIN_DATA_LEN)
 620                 size = NTDB_MIN_DATA_LEN;
 621
 622         /* Round to next uint64_t boundary. */
 623         return (size + (sizeof(uint64_t) - 1ULL)) & ~(sizeof(uint64_t) - 1ULL);
 624 }
 625
 626 /* If we have enough left over to be useful, split that off. */
 627 static size_t record_leftover(size_t keylen, size_t datalen,
 628                               bool want_extra, size_t total_len)
 629 {
 630         ssize_t leftover;
 631
 632         if (want_extra)
 633                 datalen += datalen / 2;
 634         leftover = total_len - adjust_size(keylen, datalen);
 635
 636         if (leftover < (ssize_t)sizeof(struct ntdb_free_record))
 637                 return 0;
 638
 639         return leftover;
 640 }
 641
 642 /* We need size bytes to put our key and data in. */
 643 static ntdb_off_t lock_and_alloc(struct ntdb_context *ntdb,
 644                                 ntdb_off_t ftable_off,
 645                                 ntdb_off_t bucket,
 646                                 size_t keylen, size_t datalen,
 647                                 bool want_extra,
 648                                 unsigned magic)
 649 {
 650         ntdb_off_t off, b_off,best_off;
 651         struct ntdb_free_record best = { 0 };
 652         double multiplier;
 653         size_t size = adjust_size(keylen, datalen);
 654         enum NTDB_ERROR ecode;
 655
 656         ntdb->stats.allocs++;
 657         b_off = bucket_off(ftable_off, bucket);
 658
 659         /* FIXME: Try non-blocking wait first, to measure contention. */
 660         /* Lock this bucket. */
 661         ecode = ntdb_lock_free_bucket(ntdb, b_off, NTDB_LOCK_WAIT);
 662         if (ecode != NTDB_SUCCESS) {
 663                 return NTDB_ERR_TO_OFF(ecode);
 664         }
 665
 666         best.ftable_and_len = -1ULL;
 667         best_off = 0;
 668
 669         /* Get slack if we're after extra. */
 670         if (want_extra)
 671                 multiplier = 1.5;
 672         else
 673                 multiplier = 1.0;
 674
 675         /* Walk the list to see if any are large enough, getting less fussy
 676          * as we go. */
 677         off = ntdb_read_off(ntdb, b_off);
 678         if (NTDB_OFF_IS_ERR(off)) {
 679                 ecode = NTDB_OFF_TO_ERR(off);
 680                 goto unlock_err;
 681         }
 682         off &= NTDB_OFF_MASK;
 683
 684         while (off) {
 685                 const struct ntdb_free_record *r;
 686                 ntdb_off_t next;
 687
 688                 r = ntdb_access_read(ntdb, off, sizeof(*r), true);
 689                 if (NTDB_PTR_IS_ERR(r)) {
 690                         ecode = NTDB_PTR_ERR(r);
 691                         goto unlock_err;
 692                 }
 693
 694                 if (frec_magic(r) != NTDB_FREE_MAGIC) {
 695                         ecode = ntdb_logerr(ntdb, NTDB_ERR_CORRUPT, NTDB_LOG_ERROR,
 696                                            "lock_and_alloc:"
 697                                            " %llu non-free 0x%llx",
 698                                            (long long)off,
 699                                            (long long)r->magic_and_prev);
 700                         ntdb_access_release(ntdb, r);
 701                         goto unlock_err;
 702                 }
 703
 704                 if (frec_len(r) >= size && frec_len(r) < frec_len(&best)) {
 705                         best_off = off;
 706                         best = *r;
 707                 }
 708
 709                 if (frec_len(&best) <= size * multiplier && best_off) {
 710                         ntdb_access_release(ntdb, r);
 711                         break;
 712                 }
 713
 714                 multiplier *= 1.01;
 715
 716                 next = r->next;
 717                 ntdb_access_release(ntdb, r);
 718                 off = next;
 719         }
 720
 721         /* If we found anything at all, use it. */
 722         if (best_off) {
 723                 struct ntdb_used_record rec;
 724                 size_t leftover;
 725
 726                 /* We're happy with this size: take it. */
 727                 ecode = remove_from_list(ntdb, b_off, best_off, &best);
 728                 check_list(ntdb, b_off);
 729                 if (ecode != NTDB_SUCCESS) {
 730                         goto unlock_err;
 731                 }
 732
 733                 leftover = record_leftover(keylen, datalen, want_extra,
 734                                            frec_len(&best));
 735
 736                 assert(keylen + datalen + leftover <= frec_len(&best));
 737                 /* We need to mark non-free before we drop lock, otherwise
 738                  * coalesce() could try to merge it! */
 739                 ecode = set_header(ntdb, &rec, magic, keylen, datalen,
 740                                    frec_len(&best) - leftover);
 741                 if (ecode != NTDB_SUCCESS) {
 742                         goto unlock_err;
 743                 }
 744
 745                 ecode = ntdb_write_convert(ntdb, best_off, &rec, sizeof(rec));
 746                 if (ecode != NTDB_SUCCESS) {
 747                         goto unlock_err;
 748                 }
 749
 750                 /* For futureproofing, we put a 0 in any unused space. */
 751                 if (rec_extra_padding(&rec)) {
 752                         ecode = ntdb->io->twrite(ntdb, best_off + sizeof(rec)
 753                                                 + keylen + datalen, "", 1);
 754                         if (ecode != NTDB_SUCCESS) {
 755                                 goto unlock_err;
 756                         }
 757                 }
 758
 759                 /* Bucket of leftover will be <= current bucket, so nested
 760                  * locking is allowed. */
 761                 if (leftover) {
 762                         ntdb->stats.alloc_leftover++;
 763                         ecode = add_free_record(ntdb,
 764                                                 best_off + sizeof(rec)
 765                                                 + frec_len(&best) - leftover,
 766                                                 leftover, NTDB_LOCK_WAIT, false);
 767                         if (ecode != NTDB_SUCCESS) {
 768                                 best_off = NTDB_ERR_TO_OFF(ecode);
 769                         }
 770                 }
 771                 ntdb_unlock_free_bucket(ntdb, b_off);
 772
 773                 return best_off;
 774         }
 775
 776         ntdb_unlock_free_bucket(ntdb, b_off);
 777         return 0;
 778
 779 unlock_err:
 780         ntdb_unlock_free_bucket(ntdb, b_off);
 781         return NTDB_ERR_TO_OFF(ecode);
 782 }
 783
 784 /* Get a free block from current free list, or 0 if none, -ve on error. */
 785 static ntdb_off_t get_free(struct ntdb_context *ntdb,
 786                           size_t keylen, size_t datalen, bool want_extra,
 787                           unsigned magic)
 788 {
 789         ntdb_off_t off, ftable_off;
 790         ntdb_off_t start_b, b, ftable;
 791         bool wrapped = false;
 792
 793         /* If they are growing, add 50% to get to higher bucket. */
 794         if (want_extra)
 795                 start_b = size_to_bucket(adjust_size(keylen,
 796                                                      datalen + datalen / 2));
 797         else
 798                 start_b = size_to_bucket(adjust_size(keylen, datalen));
 799
 800         ftable_off = ntdb->ftable_off;
 801         ftable = ntdb->ftable;
 802         while (!wrapped || ftable_off != ntdb->ftable_off) {
 803                 /* Start at exact size bucket, and search up... */
 804                 for (b = find_free_head(ntdb, ftable_off, start_b);
 805                      b < NTDB_FREE_BUCKETS;
 806                      b = find_free_head(ntdb, ftable_off, b + 1)) {
 807                         /* Try getting one from list. */
 808                         off = lock_and_alloc(ntdb, ftable_off,
 809                                              b, keylen, datalen, want_extra,
 810                                              magic);
 811                         if (NTDB_OFF_IS_ERR(off))
 812                                 return off;
 813                         if (off != 0) {
 814                                 if (b == start_b)
 815                                         ntdb->stats.alloc_bucket_exact++;
 816                                 if (b == NTDB_FREE_BUCKETS - 1)
 817                                         ntdb->stats.alloc_bucket_max++;
 818                                 /* Worked?  Stay using this list. */
 819                                 ntdb->ftable_off = ftable_off;
 820                                 ntdb->ftable = ftable;
 821                                 return off;
 822                         }
 823                         /* Didn't work.  Try next bucket. */
 824                 }
 825
 826                 if (NTDB_OFF_IS_ERR(b)) {
 827                         return b;
 828                 }
 829
 830                 /* Hmm, try next table. */
 831                 ftable_off = next_ftable(ntdb, ftable_off);
 832                 if (NTDB_OFF_IS_ERR(ftable_off)) {
 833                         return ftable_off;
 834                 }
 835                 ftable++;
 836
 837                 if (ftable_off == 0) {
 838                         wrapped = true;
 839                         ftable_off = first_ftable(ntdb);
 840                         if (NTDB_OFF_IS_ERR(ftable_off)) {
 841                                 return ftable_off;
 842                         }
 843                         ftable = 0;
 844                 }
 845         }
 846
 847         return 0;
 848 }
 849
 850 enum NTDB_ERROR set_header(struct ntdb_context *ntdb,
 851                           struct ntdb_used_record *rec,
 852                           unsigned magic, uint64_t keylen, uint64_t datalen,
 853                           uint64_t actuallen)
 854 {
 855         uint64_t keybits = (fls64(keylen) + 1) / 2;
 856
 857         rec->magic_and_meta = ((actuallen - (keylen + datalen)) << 11)
 858                 | (keybits << 43)
 859                 | ((uint64_t)magic << 48);
 860         rec->key_and_data_len = (keylen | (datalen << (keybits*2)));
 861
 862         /* Encoding can fail on big values. */
 863         if (rec_key_length(rec) != keylen
 864             || rec_data_length(rec) != datalen
 865             || rec_extra_padding(rec) != actuallen - (keylen + datalen)) {
 866                 return ntdb_logerr(ntdb, NTDB_ERR_IO, NTDB_LOG_ERROR,
 867                                   "Could not encode k=%llu,d=%llu,a=%llu",
 868                                   (long long)keylen, (long long)datalen,
 869                                   (long long)actuallen);
 870         }
 871         return NTDB_SUCCESS;
 872 }
 873
 874 /* You need 'size', this tells you how much you should expand by. */
 875 ntdb_off_t ntdb_expand_adjust(ntdb_off_t map_size, ntdb_off_t size)
 876 {
 877         ntdb_off_t new_size, top_size;
 878
 879         /* limit size in order to avoid using up huge amounts of memory for
 880          * in memory tdbs if an oddball huge record creeps in */
 881         if (size > 100 * 1024) {
 882                 top_size = map_size + size * 2;
 883         } else {
 884                 top_size = map_size + size * 100;
 885         }
 886
 887         /* always make room for at least top_size more records, and at
 888            least 25% more space. if the DB is smaller than 100MiB,
 889            otherwise grow it by 10% only. */
 890         if (map_size > 100 * 1024 * 1024) {
 891                 new_size = map_size * 1.10;
 892         } else {
 893                 new_size = map_size * 1.25;
 894         }
 895
 896         if (new_size < top_size)
 897                 new_size = top_size;
 898
 899         /* We always make the file a multiple of transaction page
 900          * size.  This guarantees that the transaction recovery area
 901          * is always aligned, otherwise the transaction code can overwrite
 902          * itself. */
 903         new_size = (new_size + NTDB_PGSIZE-1) & ~(NTDB_PGSIZE-1);
 904         return new_size - map_size;
 905 }
 906
 907 /* Expand the database. */
 908 static enum NTDB_ERROR ntdb_expand(struct ntdb_context *ntdb, ntdb_len_t size)
 909 {
 910         uint64_t old_size;
 911         ntdb_len_t wanted;
 912         enum NTDB_ERROR ecode;
 913
 914         /* Need to hold a hash lock to expand DB: transactions rely on it. */
 915         if (!(ntdb->flags & NTDB_NOLOCK)
 916             && !ntdb->file->allrecord_lock.count && !ntdb_has_hash_locks(ntdb)) {
 917                 return ntdb_logerr(ntdb, NTDB_ERR_LOCK, NTDB_LOG_ERROR,
 918                                   "ntdb_expand: must hold lock during expand");
 919         }
 920
 921         /* Only one person can expand file at a time. */
 922         ecode = ntdb_lock_expand(ntdb, F_WRLCK);
 923         if (ecode != NTDB_SUCCESS) {
 924                 return ecode;
 925         }
 926
 927         /* Someone else may have expanded the file, so retry. */
 928         old_size = ntdb->file->map_size;
 929         ntdb_oob(ntdb, ntdb->file->map_size, 1, true);
 930         if (ntdb->file->map_size != old_size) {
 931                 ntdb_unlock_expand(ntdb, F_WRLCK);
 932                 return NTDB_SUCCESS;
 933         }
 934
 935         /* We need room for the record header too. */
 936         size = adjust_size(0, sizeof(struct ntdb_used_record) + size);
 937         /* Overallocate. */
 938         wanted = ntdb_expand_adjust(old_size, size);
 939
 940         ecode = ntdb->io->expand_file(ntdb, wanted);
 941         if (ecode != NTDB_SUCCESS) {
 942                 ntdb_unlock_expand(ntdb, F_WRLCK);
 943                 return ecode;
 944         }
 945
 946         /* We need to drop this lock before adding free record. */
 947         ntdb_unlock_expand(ntdb, F_WRLCK);
 948
 949         ntdb->stats.expands++;
 950         return add_free_record(ntdb, old_size, wanted, NTDB_LOCK_WAIT, true);
 951 }
 952
 953 /* This won't fail: it will expand the database if it has to. */
 954 ntdb_off_t alloc(struct ntdb_context *ntdb, size_t keylen, size_t datalen,
 955                  unsigned magic, bool growing)
 956 {
 957         ntdb_off_t off;
 958
 959         for (;;) {
 960                 enum NTDB_ERROR ecode;
 961                 off = get_free(ntdb, keylen, datalen, growing, magic);
 962                 if (likely(off != 0))
 963                         break;
 964
 965                 ecode = ntdb_expand(ntdb, adjust_size(keylen, datalen));
 966                 if (ecode != NTDB_SUCCESS) {
 967                         return NTDB_ERR_TO_OFF(ecode);
 968                 }
 969         }
 970
 971         return off;
 972 }