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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);
 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 #ifdef CCAN_TDB2_DEBUG
 154                 if (tdb_read_off(tdb, b_off) != r_off) {
 155                         return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 156                                           "remove_from_list:"
 157                                           " %llu head %llu on list %llu",
 158                                           (long long)r_off,
 159                                           (long long)tdb_read_off(tdb, b_off),
 160                                           (long long)b_off);
 161                 }
 162 #endif
 163                 ecode = tdb_write_off(tdb, b_off, r->next);
 164                 if (ecode != TDB_SUCCESS)
 165                         return ecode;
 166         } else {
 167                 /* r->prev->next = r->next */
 168                 ecode = tdb_write_off(tdb, off, r->next);
 169                 if (ecode != TDB_SUCCESS)
 170                         return ecode;
 171         }
 172
 173         /* If we were the tail, off = &head->prev. */
 174         if (r->next == 0) {
 175                 head = tdb_read_off(tdb, b_off);
 176                 if (TDB_OFF_IS_ERR(head))
 177                         return head;
 178                 off = head + offsetof(struct tdb_free_record, magic_and_prev);
 179         } else {
 180                 /* off = &r->next->prev */
 181                 off = r->next + offsetof(struct tdb_free_record,
 182                                          magic_and_prev);
 183         }
 184
 185 #ifdef CCAN_TDB2_DEBUG
 186         /* *off == r */
 187         if ((tdb_read_off(tdb, off) & TDB_OFF_MASK) != r_off) {
 188                 return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 189                                   "remove_from_list:"
 190                                   " %llu bad prev in list %llu",
 191                                   (long long)r_off, (long long)b_off);
 192         }
 193 #endif
 194         /* r->next->prev = r->prev */
 195         return tdb_write_off(tdb, off, r->magic_and_prev);
 196 }
 197
 198 /* Enqueue in this free bucket. */
 199 static enum TDB_ERROR enqueue_in_free(struct tdb_context *tdb,
 200                                       tdb_off_t b_off,
 201                                       tdb_off_t off,
 202                                       tdb_len_t len)
 203 {
 204         struct tdb_free_record new;
 205         enum TDB_ERROR ecode;
 206         tdb_off_t prev;
 207         uint64_t magic = (TDB_FREE_MAGIC << (64 - TDB_OFF_UPPER_STEAL));
 208
 209         /* We only need to set ftable_and_len; rest is set in enqueue_in_free */
 210         new.ftable_and_len = ((uint64_t)tdb->ftable << (64 - TDB_OFF_UPPER_STEAL))
 211                 | len;
 212
 213         /* new->next = head. */
 214         new.next = tdb_read_off(tdb, b_off);
 215         if (TDB_OFF_IS_ERR(new.next)) {
 216                 return new.next;
 217         }
 218
 219         /* First element?  Prev points to ourselves. */
 220         if (!new.next) {
 221                 new.magic_and_prev = (magic | off);
 222         } else {
 223                 /* new->prev = next->prev */
 224                 prev = tdb_read_off(tdb,
 225                                     new.next + offsetof(struct tdb_free_record,
 226                                                         magic_and_prev));
 227                 new.magic_and_prev = prev;
 228                 if (frec_magic(&new) != TDB_FREE_MAGIC) {
 229                         return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 230                                           "enqueue_in_free: %llu bad head"
 231                                           " prev %llu",
 232                                           (long long)new.next,
 233                                           (long long)prev);
 234                 }
 235                 /* next->prev = new. */
 236                 ecode = tdb_write_off(tdb, new.next
 237                                       + offsetof(struct tdb_free_record,
 238                                                  magic_and_prev),
 239                                       off | magic);
 240                 if (ecode != TDB_SUCCESS) {
 241                         return ecode;
 242                 }
 243
 244 #ifdef CCAN_TDB2_DEBUG
 245                 prev = tdb_read_off(tdb, frec_prev(&new)
 246                                     + offsetof(struct tdb_free_record, next));
 247                 if (prev != 0) {
 248                         return tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 249                                           "enqueue_in_free:"
 250                                           " %llu bad tail next ptr %llu",
 251                                           (long long)frec_prev(&new)
 252                                           + offsetof(struct tdb_free_record,
 253                                                      next),
 254                                           (long long)prev);
 255                 }
 256 #endif
 257         }
 258         /* head = new */
 259         ecode = tdb_write_off(tdb, b_off, off);
 260         if (ecode != TDB_SUCCESS) {
 261                 return ecode;
 262         }
 263
 264         return tdb_write_convert(tdb, off, &new, sizeof(new));
 265 }
 266
 267 /* List need not be locked. */
 268 enum TDB_ERROR add_free_record(struct tdb_context *tdb,
 269                                tdb_off_t off, tdb_len_t len_with_header,
 270                                enum tdb_lock_flags waitflag)
 271 {
 272         tdb_off_t b_off;
 273         tdb_len_t len;
 274         enum TDB_ERROR ecode;
 275
 276         assert(len_with_header >= sizeof(struct tdb_free_record));
 277
 278         len = len_with_header - sizeof(struct tdb_used_record);
 279
 280         b_off = bucket_off(tdb->ftable_off, size_to_bucket(len));
 281         ecode = tdb_lock_free_bucket(tdb, b_off, waitflag);
 282         if (ecode != TDB_SUCCESS) {
 283                 return ecode;
 284         }
 285
 286         ecode = enqueue_in_free(tdb, b_off, off, len);
 287         check_list(tdb, b_off);
 288         tdb_unlock_free_bucket(tdb, b_off);
 289         return ecode;
 290 }
 291
 292 static size_t adjust_size(size_t keylen, size_t datalen)
 293 {
 294         size_t size = keylen + datalen;
 295
 296         if (size < TDB_MIN_DATA_LEN)
 297                 size = TDB_MIN_DATA_LEN;
 298
 299         /* Round to next uint64_t boundary. */
 300         return (size + (sizeof(uint64_t) - 1ULL)) & ~(sizeof(uint64_t) - 1ULL);
 301 }
 302
 303 /* If we have enough left over to be useful, split that off. */
 304 static size_t record_leftover(size_t keylen, size_t datalen,
 305                               bool want_extra, size_t total_len)
 306 {
 307         ssize_t leftover;
 308
 309         if (want_extra)
 310                 datalen += datalen / 2;
 311         leftover = total_len - adjust_size(keylen, datalen);
 312
 313         if (leftover < (ssize_t)sizeof(struct tdb_free_record))
 314                 return 0;
 315
 316         return leftover;
 317 }
 318
 319 static tdb_off_t ftable_offset(struct tdb_context *tdb, unsigned int ftable)
 320 {
 321         tdb_off_t off;
 322         unsigned int i;
 323
 324         if (likely(tdb->ftable == ftable))
 325                 return tdb->ftable_off;
 326
 327         off = first_ftable(tdb);
 328         for (i = 0; i < ftable; i++) {
 329                 if (TDB_OFF_IS_ERR(off)) {
 330                         break;
 331                 }
 332                 off = next_ftable(tdb, off);
 333         }
 334         return off;
 335 }
 336
 337 /* Note: we unlock the current bucket if fail (-ve), or coalesce (-ve) and
 338  * need to blatt either of the *protect records (which is set to an error). */
 339 static tdb_len_t coalesce(struct tdb_context *tdb,
 340                           tdb_off_t off, tdb_off_t b_off,
 341                           tdb_len_t data_len,
 342                           tdb_off_t *protect1,
 343                           tdb_off_t *protect2)
 344 {
 345         tdb_off_t end;
 346         struct tdb_free_record rec;
 347         enum TDB_ERROR ecode;
 348
 349         tdb->stats.alloc_coalesce_tried++;
 350         end = off + sizeof(struct tdb_used_record) + data_len;
 351
 352         while (end < tdb->file->map_size) {
 353                 const struct tdb_free_record *r;
 354                 tdb_off_t nb_off;
 355                 unsigned ftable, bucket;
 356
 357                 r = tdb_access_read(tdb, end, sizeof(*r), true);
 358                 if (TDB_PTR_IS_ERR(r)) {
 359                         ecode = TDB_PTR_ERR(r);
 360                         goto err;
 361                 }
 362
 363                 if (frec_magic(r) != TDB_FREE_MAGIC
 364                     || frec_ftable(r) == TDB_FTABLE_NONE) {
 365                         tdb_access_release(tdb, r);
 366                         break;
 367                 }
 368
 369                 ftable = frec_ftable(r);
 370                 bucket = size_to_bucket(frec_len(r));
 371                 nb_off = ftable_offset(tdb, ftable);
 372                 if (TDB_OFF_IS_ERR(nb_off)) {
 373                         tdb_access_release(tdb, r);
 374                         ecode = nb_off;
 375                         goto err;
 376                 }
 377                 nb_off = bucket_off(nb_off, bucket);
 378                 tdb_access_release(tdb, r);
 379
 380                 /* We may be violating lock order here, so best effort. */
 381                 if (tdb_lock_free_bucket(tdb, nb_off, TDB_LOCK_NOWAIT)
 382                     != TDB_SUCCESS) {
 383                         tdb->stats.alloc_coalesce_lockfail++;
 384                         break;
 385                 }
 386
 387                 /* Now we have lock, re-check. */
 388                 ecode = tdb_read_convert(tdb, end, &rec, sizeof(rec));
 389                 if (ecode != TDB_SUCCESS) {
 390                         tdb_unlock_free_bucket(tdb, nb_off);
 391                         goto err;
 392                 }
 393
 394                 if (unlikely(frec_magic(&rec) != TDB_FREE_MAGIC)) {
 395                         tdb->stats.alloc_coalesce_race++;
 396                         tdb_unlock_free_bucket(tdb, nb_off);
 397                         break;
 398                 }
 399
 400                 if (unlikely(frec_ftable(&rec) != ftable)
 401                     || unlikely(size_to_bucket(frec_len(&rec)) != bucket)) {
 402                         tdb->stats.alloc_coalesce_race++;
 403                         tdb_unlock_free_bucket(tdb, nb_off);
 404                         break;
 405                 }
 406
 407                 /* Did we just mess up a record you were hoping to use? */
 408                 if (end == *protect1 || end == *protect2)
 409                         *protect1 = TDB_ERR_NOEXIST;
 410
 411                 ecode = remove_from_list(tdb, nb_off, end, &rec);
 412                 check_list(tdb, nb_off);
 413                 if (ecode != TDB_SUCCESS) {
 414                         tdb_unlock_free_bucket(tdb, nb_off);
 415                         goto err;
 416                 }
 417
 418                 end += sizeof(struct tdb_used_record) + frec_len(&rec);
 419                 tdb_unlock_free_bucket(tdb, nb_off);
 420                 tdb->stats.alloc_coalesce_num_merged++;
 421         }
 422
 423         /* Didn't find any adjacent free? */
 424         if (end == off + sizeof(struct tdb_used_record) + data_len)
 425                 return 0;
 426
 427         /* Before we expand, check this isn't one you wanted protected? */
 428         if (off == *protect1 || off == *protect2)
 429                 *protect1 = TDB_ERR_EXISTS;
 430
 431         /* OK, expand initial record */
 432         ecode = tdb_read_convert(tdb, off, &rec, sizeof(rec));
 433         if (ecode != TDB_SUCCESS) {
 434                 goto err;
 435         }
 436
 437         if (frec_len(&rec) != data_len) {
 438                 ecode = tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 439                                    "coalesce: expected data len %zu not %zu",
 440                                    (size_t)data_len, (size_t)frec_len(&rec));
 441                 goto err;
 442         }
 443
 444         ecode = remove_from_list(tdb, b_off, off, &rec);
 445         check_list(tdb, b_off);
 446         if (ecode != TDB_SUCCESS) {
 447                 goto err;
 448         }
 449
 450         /* Try locking violation first... */
 451         ecode = add_free_record(tdb, off, end - off, TDB_LOCK_NOWAIT);
 452         if (ecode != TDB_SUCCESS) {
 453                 /* Need to drop lock.  Can't rely on anything stable. */
 454                 *protect1 = TDB_ERR_CORRUPT;
 455
 456                 /* We have to drop this to avoid deadlocks, so make sure record
 457                  * doesn't get coalesced by someone else! */
 458                 rec.ftable_and_len = (TDB_FTABLE_NONE
 459                                       << (64 - TDB_OFF_UPPER_STEAL))
 460                         | (end - off - sizeof(struct tdb_used_record));
 461                 ecode = tdb_write_off(tdb,
 462                                       off + offsetof(struct tdb_free_record,
 463                                                      ftable_and_len),
 464                                       rec.ftable_and_len);
 465                 if (ecode != TDB_SUCCESS) {
 466                         goto err;
 467                 }
 468
 469                 tdb->stats.alloc_coalesce_succeeded++;
 470                 tdb_unlock_free_bucket(tdb, b_off);
 471
 472                 ecode = add_free_record(tdb, off, end - off, TDB_LOCK_WAIT);
 473                 if (ecode != TDB_SUCCESS) {
 474                         return ecode;
 475                 }
 476         } else if (TDB_OFF_IS_ERR(*protect1)) {
 477                 /* For simplicity, we always drop lock if they can't continue */
 478                 tdb_unlock_free_bucket(tdb, b_off);
 479         }
 480
 481         /* Return usable length. */
 482         return end - off - sizeof(struct tdb_used_record);
 483
 484 err:
 485         /* To unify error paths, we *always* unlock bucket on error. */
 486         tdb_unlock_free_bucket(tdb, b_off);
 487         return ecode;
 488 }
 489
 490 /* We need size bytes to put our key and data in. */
 491 static tdb_off_t lock_and_alloc(struct tdb_context *tdb,
 492                                 tdb_off_t ftable_off,
 493                                 tdb_off_t bucket,
 494                                 size_t keylen, size_t datalen,
 495                                 bool want_extra,
 496                                 unsigned magic,
 497                                 unsigned hashlow)
 498 {
 499         tdb_off_t off, b_off,best_off;
 500         struct tdb_free_record best = { 0 };
 501         double multiplier;
 502         bool coalesce_after_best = false; /* Damn GCC warning! */
 503         size_t size = adjust_size(keylen, datalen);
 504         enum TDB_ERROR ecode;
 505
 506         tdb->stats.allocs++;
 507 again:
 508         b_off = bucket_off(ftable_off, bucket);
 509
 510         /* FIXME: Try non-blocking wait first, to measure contention. */
 511         /* Lock this bucket. */
 512         ecode = tdb_lock_free_bucket(tdb, b_off, TDB_LOCK_WAIT);
 513         if (ecode != TDB_SUCCESS) {
 514                 return ecode;
 515         }
 516
 517         best.ftable_and_len = -1ULL;
 518         best_off = 0;
 519
 520         /* Get slack if we're after extra. */
 521         if (want_extra)
 522                 multiplier = 1.5;
 523         else
 524                 multiplier = 1.0;
 525
 526         /* Walk the list to see if any are large enough, getting less fussy
 527          * as we go. */
 528         off = tdb_read_off(tdb, b_off);
 529         if (TDB_OFF_IS_ERR(off)) {
 530                 ecode = off;
 531                 goto unlock_err;
 532         }
 533
 534         while (off) {
 535                 const struct tdb_free_record *r;
 536                 tdb_len_t len, coal;
 537                 tdb_off_t next;
 538
 539                 r = tdb_access_read(tdb, off, sizeof(*r), true);
 540                 if (TDB_PTR_IS_ERR(r)) {
 541                         ecode = TDB_PTR_ERR(r);
 542                         goto unlock_err;
 543                 }
 544
 545                 if (frec_magic(r) != TDB_FREE_MAGIC) {
 546                         ecode = tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
 547                                            "lock_and_alloc:"
 548                                            " %llu non-free 0x%llx",
 549                                            (long long)off,
 550                                            (long long)r->magic_and_prev);
 551                         tdb_access_release(tdb, r);
 552                         goto unlock_err;
 553                 }
 554
 555                 if (frec_len(r) >= size && frec_len(r) < frec_len(&best)) {
 556                         best_off = off;
 557                         best = *r;
 558                         coalesce_after_best = false;
 559                 }
 560
 561                 if (frec_len(&best) <= size * multiplier && best_off) {
 562                         tdb_access_release(tdb, r);
 563                         break;
 564                 }
 565
 566                 multiplier *= 1.01;
 567
 568                 next = r->next;
 569                 len = frec_len(r);
 570                 tdb_access_release(tdb, r);
 571
 572                 /* Since we're going slow anyway, try coalescing here. */
 573                 coal = coalesce(tdb, off, b_off, len, &best_off, &next);
 574                 if (TDB_OFF_IS_ERR(coal)) {
 575                         /* This has already unlocked on error. */
 576                         return coal;
 577                 }
 578                 if (TDB_OFF_IS_ERR(best_off)) {
 579                         /* This has unlocked list, restart. */
 580                         goto again;
 581                 }
 582                 if (coal > 0)
 583                         coalesce_after_best = true;
 584                 off = next;
 585         }
 586
 587         /* If we found anything at all, use it. */
 588         if (best_off) {
 589                 struct tdb_used_record rec;
 590                 size_t leftover;
 591
 592                 /* If we coalesced, we might have change prev/next ptrs. */
 593                 if (coalesce_after_best) {
 594                         ecode = tdb_read_convert(tdb, best_off, &best,
 595                                                  sizeof(best));
 596                         if (ecode != TDB_SUCCESS)
 597                                 goto unlock_err;
 598                 }
 599
 600                 /* We're happy with this size: take it. */
 601                 ecode = remove_from_list(tdb, b_off, best_off, &best);
 602                 check_list(tdb, b_off);
 603                 if (ecode != TDB_SUCCESS) {
 604                         goto unlock_err;
 605                 }
 606
 607                 leftover = record_leftover(keylen, datalen, want_extra,
 608                                            frec_len(&best));
 609
 610                 assert(keylen + datalen + leftover <= frec_len(&best));
 611                 /* We need to mark non-free before we drop lock, otherwise
 612                  * coalesce() could try to merge it! */
 613                 ecode = set_header(tdb, &rec, magic, keylen, datalen,
 614                                    frec_len(&best) - leftover, hashlow);
 615                 if (ecode != TDB_SUCCESS) {
 616                         goto unlock_err;
 617                 }
 618
 619                 ecode = tdb_write_convert(tdb, best_off, &rec, sizeof(rec));
 620                 if (ecode != TDB_SUCCESS) {
 621                         goto unlock_err;
 622                 }
 623
 624                 /* For futureproofing, we put a 0 in any unused space. */
 625                 if (rec_extra_padding(&rec)) {
 626                         ecode = tdb->methods->twrite(tdb, best_off + sizeof(rec)
 627                                                      + keylen + datalen, "", 1);
 628                         if (ecode != TDB_SUCCESS) {
 629                                 goto unlock_err;
 630                         }
 631                 }
 632
 633                 /* Bucket of leftover will be <= current bucket, so nested
 634                  * locking is allowed. */
 635                 if (leftover) {
 636                         tdb->stats.alloc_leftover++;
 637                         ecode = add_free_record(tdb,
 638                                                 best_off + sizeof(rec)
 639                                                 + frec_len(&best) - leftover,
 640                                                 leftover, TDB_LOCK_WAIT);
 641                         if (ecode != TDB_SUCCESS) {
 642                                 best_off = ecode;
 643                         }
 644                 }
 645                 tdb_unlock_free_bucket(tdb, b_off);
 646
 647                 return best_off;
 648         }
 649
 650         tdb_unlock_free_bucket(tdb, b_off);
 651         return 0;
 652
 653 unlock_err:
 654         tdb_unlock_free_bucket(tdb, b_off);
 655         return ecode;
 656 }
 657
 658 /* Get a free block from current free list, or 0 if none, -ve on error. */
 659 static tdb_off_t get_free(struct tdb_context *tdb,
 660                           size_t keylen, size_t datalen, bool want_extra,
 661                           unsigned magic, unsigned hashlow)
 662 {
 663         tdb_off_t off, ftable_off;
 664         tdb_off_t start_b, b, ftable;
 665         bool wrapped = false;
 666
 667         /* If they are growing, add 50% to get to higher bucket. */
 668         if (want_extra)
 669                 start_b = size_to_bucket(adjust_size(keylen,
 670                                                      datalen + datalen / 2));
 671         else
 672                 start_b = size_to_bucket(adjust_size(keylen, datalen));
 673
 674         ftable_off = tdb->ftable_off;
 675         ftable = tdb->ftable;
 676         while (!wrapped || ftable_off != tdb->ftable_off) {
 677                 /* Start at exact size bucket, and search up... */
 678                 for (b = find_free_head(tdb, ftable_off, start_b);
 679                      b < TDB_FREE_BUCKETS;
 680                      b = find_free_head(tdb, ftable_off, b + 1)) {
 681                         /* Try getting one from list. */
 682                         off = lock_and_alloc(tdb, ftable_off,
 683                                              b, keylen, datalen, want_extra,
 684                                              magic, hashlow);
 685                         if (TDB_OFF_IS_ERR(off))
 686                                 return off;
 687                         if (off != 0) {
 688                                 if (b == start_b)
 689                                         tdb->stats.alloc_bucket_exact++;
 690                                 if (b == TDB_FREE_BUCKETS - 1)
 691                                         tdb->stats.alloc_bucket_max++;
 692                                 /* Worked?  Stay using this list. */
 693                                 tdb->ftable_off = ftable_off;
 694                                 tdb->ftable = ftable;
 695                                 return off;
 696                         }
 697                         /* Didn't work.  Try next bucket. */
 698                 }
 699
 700                 if (TDB_OFF_IS_ERR(b)) {
 701                         return b;
 702                 }
 703
 704                 /* Hmm, try next table. */
 705                 ftable_off = next_ftable(tdb, ftable_off);
 706                 if (TDB_OFF_IS_ERR(ftable_off)) {
 707                         return ftable_off;
 708                 }
 709                 ftable++;
 710
 711                 if (ftable_off == 0) {
 712                         wrapped = true;
 713                         ftable_off = first_ftable(tdb);
 714                         if (TDB_OFF_IS_ERR(ftable_off)) {
 715                                 return ftable_off;
 716                         }
 717                         ftable = 0;
 718                 }
 719         }
 720
 721         return 0;
 722 }
 723
 724 enum TDB_ERROR set_header(struct tdb_context *tdb,
 725                           struct tdb_used_record *rec,
 726                           unsigned magic, uint64_t keylen, uint64_t datalen,
 727                           uint64_t actuallen, unsigned hashlow)
 728 {
 729         uint64_t keybits = (fls64(keylen) + 1) / 2;
 730
 731         /* Use bottom bits of hash, so it's independent of hash table size. */
 732         rec->magic_and_meta = (hashlow & ((1 << 11)-1))
 733                 | ((actuallen - (keylen + datalen)) << 11)
 734                 | (keybits << 43)
 735                 | ((uint64_t)magic << 48);
 736         rec->key_and_data_len = (keylen | (datalen << (keybits*2)));
 737
 738         /* Encoding can fail on big values. */
 739         if (rec_key_length(rec) != keylen
 740             || rec_data_length(rec) != datalen
 741             || rec_extra_padding(rec) != actuallen - (keylen + datalen)) {
 742                 return tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
 743                                   "Could not encode k=%llu,d=%llu,a=%llu",
 744                                   (long long)keylen, (long long)datalen,
 745                                   (long long)actuallen);
 746         }
 747         return TDB_SUCCESS;
 748 }
 749
 750 /* Expand the database. */
 751 static enum TDB_ERROR tdb_expand(struct tdb_context *tdb, tdb_len_t size)
 752 {
 753         uint64_t old_size, rec_size, map_size;
 754         tdb_len_t wanted;
 755         enum TDB_ERROR ecode;
 756
 757         /* Need to hold a hash lock to expand DB: transactions rely on it. */
 758         if (!(tdb->flags & TDB_NOLOCK)
 759             && !tdb->file->allrecord_lock.count && !tdb_has_hash_locks(tdb)) {
 760                 return tdb_logerr(tdb, TDB_ERR_LOCK, TDB_LOG_ERROR,
 761                                   "tdb_expand: must hold lock during expand");
 762         }
 763
 764         /* Only one person can expand file at a time. */
 765         ecode = tdb_lock_expand(tdb, F_WRLCK);
 766         if (ecode != TDB_SUCCESS) {
 767                 return ecode;
 768         }
 769
 770         /* Someone else may have expanded the file, so retry. */
 771         old_size = tdb->file->map_size;
 772         tdb->methods->oob(tdb, tdb->file->map_size + 1, true);
 773         if (tdb->file->map_size != old_size) {
 774                 tdb_unlock_expand(tdb, F_WRLCK);
 775                 return TDB_SUCCESS;
 776         }
 777
 778         /* limit size in order to avoid using up huge amounts of memory for
 779          * in memory tdbs if an oddball huge record creeps in */
 780         if (size > 100 * 1024) {
 781                 rec_size = size * 2;
 782         } else {
 783                 rec_size = size * 100;
 784         }
 785
 786         /* always make room for at least rec_size more records, and at
 787            least 25% more space. if the DB is smaller than 100MiB,
 788            otherwise grow it by 10% only. */
 789         if (old_size > 100 * 1024 * 1024) {
 790                 map_size = old_size / 10;
 791         } else {
 792                 map_size = old_size / 4;
 793         }
 794
 795         if (map_size > rec_size) {
 796                 wanted = map_size;
 797         } else {
 798                 wanted = rec_size;
 799         }
 800
 801         /* We need room for the record header too. */
 802         wanted = adjust_size(0, sizeof(struct tdb_used_record) + wanted);
 803
 804         ecode = tdb->methods->expand_file(tdb, wanted);
 805         if (ecode != TDB_SUCCESS) {
 806                 tdb_unlock_expand(tdb, F_WRLCK);
 807                 return ecode;
 808         }
 809
 810         /* We need to drop this lock before adding free record. */
 811         tdb_unlock_expand(tdb, F_WRLCK);
 812
 813         tdb->stats.expands++;
 814         return add_free_record(tdb, old_size, wanted, TDB_LOCK_WAIT);
 815 }
 816
 817 /* This won't fail: it will expand the database if it has to. */
 818 tdb_off_t alloc(struct tdb_context *tdb, size_t keylen, size_t datalen,
 819                 uint64_t hash, unsigned magic, bool growing)
 820 {
 821         tdb_off_t off;
 822
 823         /* We can't hold pointers during this: we could unmap! */
 824         assert(!tdb->direct_access);
 825
 826         for (;;) {
 827                 enum TDB_ERROR ecode;
 828                 off = get_free(tdb, keylen, datalen, growing, magic, hash);
 829                 if (likely(off != 0))
 830                         break;
 831
 832                 ecode = tdb_expand(tdb, adjust_size(keylen, datalen));
 833                 if (ecode != TDB_SUCCESS) {
 834                         return ecode;
 835                 }
 836         }
 837
 838         return off;
 839 }