git.oblomov.eu Git - git/blob - midx.c

   1 #include "cache.h"
   2 #include "csum-file.h"
   3 #include "dir.h"
   4 #include "lockfile.h"
   5 #include "packfile.h"
   6 #include "object-store.h"
   7 #include "packfile.h"
   8 #include "midx.h"
   9
  10 #define MIDX_SIGNATURE 0x4d494458 /* "MIDX" */
  11 #define MIDX_VERSION 1
  12 #define MIDX_BYTE_FILE_VERSION 4
  13 #define MIDX_BYTE_HASH_VERSION 5
  14 #define MIDX_BYTE_NUM_CHUNKS 6
  15 #define MIDX_BYTE_NUM_PACKS 8
  16 #define MIDX_HASH_VERSION 1
  17 #define MIDX_HEADER_SIZE 12
  18 #define MIDX_HASH_LEN 20
  19 #define MIDX_MIN_SIZE (MIDX_HEADER_SIZE + MIDX_HASH_LEN)
  20
  21 #define MIDX_MAX_CHUNKS 3
  22 #define MIDX_CHUNK_ALIGNMENT 4
  23 #define MIDX_CHUNKID_PACKNAMES 0x504e414d /* "PNAM" */
  24 #define MIDX_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
  25 #define MIDX_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
  26 #define MIDX_CHUNKLOOKUP_WIDTH (sizeof(uint32_t) + sizeof(uint64_t))
  27 #define MIDX_CHUNK_FANOUT_SIZE (sizeof(uint32_t) * 256)
  28
  29 static char *get_midx_filename(const char *object_dir)
  30 {
  31         return xstrfmt("%s/pack/multi-pack-index", object_dir);
  32 }
  33
  34 struct multi_pack_index *load_multi_pack_index(const char *object_dir)
  35 {
  36         struct multi_pack_index *m = NULL;
  37         int fd;
  38         struct stat st;
  39         size_t midx_size;
  40         void *midx_map = NULL;
  41         uint32_t hash_version;
  42         char *midx_name = get_midx_filename(object_dir);
  43         uint32_t i;
  44         const char *cur_pack_name;
  45
  46         fd = git_open(midx_name);
  47
  48         if (fd < 0)
  49                 goto cleanup_fail;
  50         if (fstat(fd, &st)) {
  51                 error_errno(_("failed to read %s"), midx_name);
  52                 goto cleanup_fail;
  53         }
  54
  55         midx_size = xsize_t(st.st_size);
  56
  57         if (midx_size < MIDX_MIN_SIZE) {
  58                 error(_("multi-pack-index file %s is too small"), midx_name);
  59                 goto cleanup_fail;
  60         }
  61
  62         FREE_AND_NULL(midx_name);
  63
  64         midx_map = xmmap(NULL, midx_size, PROT_READ, MAP_PRIVATE, fd, 0);
  65
  66         FLEX_ALLOC_MEM(m, object_dir, object_dir, strlen(object_dir));
  67         m->fd = fd;
  68         m->data = midx_map;
  69         m->data_len = midx_size;
  70
  71         m->signature = get_be32(m->data);
  72         if (m->signature != MIDX_SIGNATURE) {
  73                 error(_("multi-pack-index signature 0x%08x does not match signature 0x%08x"),
  74                       m->signature, MIDX_SIGNATURE);
  75                 goto cleanup_fail;
  76         }
  77
  78         m->version = m->data[MIDX_BYTE_FILE_VERSION];
  79         if (m->version != MIDX_VERSION) {
  80                 error(_("multi-pack-index version %d not recognized"),
  81                       m->version);
  82                 goto cleanup_fail;
  83         }
  84
  85         hash_version = m->data[MIDX_BYTE_HASH_VERSION];
  86         if (hash_version != MIDX_HASH_VERSION) {
  87                 error(_("hash version %u does not match"), hash_version);
  88                 goto cleanup_fail;
  89         }
  90         m->hash_len = MIDX_HASH_LEN;
  91
  92         m->num_chunks = m->data[MIDX_BYTE_NUM_CHUNKS];
  93
  94         m->num_packs = get_be32(m->data + MIDX_BYTE_NUM_PACKS);
  95
  96         for (i = 0; i < m->num_chunks; i++) {
  97                 uint32_t chunk_id = get_be32(m->data + MIDX_HEADER_SIZE +
  98                                              MIDX_CHUNKLOOKUP_WIDTH * i);
  99                 uint64_t chunk_offset = get_be64(m->data + MIDX_HEADER_SIZE + 4 +
 100                                                  MIDX_CHUNKLOOKUP_WIDTH * i);
 101
 102                 switch (chunk_id) {
 103                         case MIDX_CHUNKID_PACKNAMES:
 104                                 m->chunk_pack_names = m->data + chunk_offset;
 105                                 break;
 106
 107                         case MIDX_CHUNKID_OIDFANOUT:
 108                                 m->chunk_oid_fanout = (uint32_t *)(m->data + chunk_offset);
 109                                 break;
 110
 111                         case MIDX_CHUNKID_OIDLOOKUP:
 112                                 m->chunk_oid_lookup = m->data + chunk_offset;
 113                                 break;
 114
 115                         case 0:
 116                                 die(_("terminating multi-pack-index chunk id appears earlier than expected"));
 117                                 break;
 118
 119                         default:
 120                                 /*
 121                                  * Do nothing on unrecognized chunks, allowing future
 122                                  * extensions to add optional chunks.
 123                                  */
 124                                 break;
 125                 }
 126         }
 127
 128         if (!m->chunk_pack_names)
 129                 die(_("multi-pack-index missing required pack-name chunk"));
 130         if (!m->chunk_oid_fanout)
 131                 die(_("multi-pack-index missing required OID fanout chunk"));
 132         if (!m->chunk_oid_lookup)
 133                 die(_("multi-pack-index missing required OID lookup chunk"));
 134
 135         m->num_objects = ntohl(m->chunk_oid_fanout[255]);
 136
 137         m->pack_names = xcalloc(m->num_packs, sizeof(*m->pack_names));
 138
 139         cur_pack_name = (const char *)m->chunk_pack_names;
 140         for (i = 0; i < m->num_packs; i++) {
 141                 m->pack_names[i] = cur_pack_name;
 142
 143                 cur_pack_name += strlen(cur_pack_name) + 1;
 144
 145                 if (i && strcmp(m->pack_names[i], m->pack_names[i - 1]) <= 0) {
 146                         error(_("multi-pack-index pack names out of order: '%s' before '%s'"),
 147                               m->pack_names[i - 1],
 148                               m->pack_names[i]);
 149                         goto cleanup_fail;
 150                 }
 151         }
 152
 153         return m;
 154
 155 cleanup_fail:
 156         free(m);
 157         free(midx_name);
 158         if (midx_map)
 159                 munmap(midx_map, midx_size);
 160         if (0 <= fd)
 161                 close(fd);
 162         return NULL;
 163 }
 164
 165 static size_t write_midx_header(struct hashfile *f,
 166                                 unsigned char num_chunks,
 167                                 uint32_t num_packs)
 168 {
 169         unsigned char byte_values[4];
 170
 171         hashwrite_be32(f, MIDX_SIGNATURE);
 172         byte_values[0] = MIDX_VERSION;
 173         byte_values[1] = MIDX_HASH_VERSION;
 174         byte_values[2] = num_chunks;
 175         byte_values[3] = 0; /* unused */
 176         hashwrite(f, byte_values, sizeof(byte_values));
 177         hashwrite_be32(f, num_packs);
 178
 179         return MIDX_HEADER_SIZE;
 180 }
 181
 182 struct pack_list {
 183         struct packed_git **list;
 184         char **names;
 185         uint32_t nr;
 186         uint32_t alloc_list;
 187         uint32_t alloc_names;
 188         size_t pack_name_concat_len;
 189 };
 190
 191 static void add_pack_to_midx(const char *full_path, size_t full_path_len,
 192                              const char *file_name, void *data)
 193 {
 194         struct pack_list *packs = (struct pack_list *)data;
 195
 196         if (ends_with(file_name, ".idx")) {
 197                 ALLOC_GROW(packs->list, packs->nr + 1, packs->alloc_list);
 198                 ALLOC_GROW(packs->names, packs->nr + 1, packs->alloc_names);
 199
 200                 packs->list[packs->nr] = add_packed_git(full_path,
 201                                                         full_path_len,
 202                                                         0);
 203
 204                 if (!packs->list[packs->nr]) {
 205                         warning(_("failed to add packfile '%s'"),
 206                                 full_path);
 207                         return;
 208                 }
 209
 210                 if (open_pack_index(packs->list[packs->nr])) {
 211                         warning(_("failed to open pack-index '%s'"),
 212                                 full_path);
 213                         close_pack(packs->list[packs->nr]);
 214                         FREE_AND_NULL(packs->list[packs->nr]);
 215                         return;
 216                 }
 217
 218                 packs->names[packs->nr] = xstrdup(file_name);
 219                 packs->pack_name_concat_len += strlen(file_name) + 1;
 220                 packs->nr++;
 221         }
 222 }
 223
 224 struct pack_pair {
 225         uint32_t pack_int_id;
 226         char *pack_name;
 227 };
 228
 229 static int pack_pair_compare(const void *_a, const void *_b)
 230 {
 231         struct pack_pair *a = (struct pack_pair *)_a;
 232         struct pack_pair *b = (struct pack_pair *)_b;
 233         return strcmp(a->pack_name, b->pack_name);
 234 }
 235
 236 static void sort_packs_by_name(char **pack_names, uint32_t nr_packs, uint32_t *perm)
 237 {
 238         uint32_t i;
 239         struct pack_pair *pairs;
 240
 241         ALLOC_ARRAY(pairs, nr_packs);
 242
 243         for (i = 0; i < nr_packs; i++) {
 244                 pairs[i].pack_int_id = i;
 245                 pairs[i].pack_name = pack_names[i];
 246         }
 247
 248         QSORT(pairs, nr_packs, pack_pair_compare);
 249
 250         for (i = 0; i < nr_packs; i++) {
 251                 pack_names[i] = pairs[i].pack_name;
 252                 perm[pairs[i].pack_int_id] = i;
 253         }
 254
 255         free(pairs);
 256 }
 257
 258 struct pack_midx_entry {
 259         struct object_id oid;
 260         uint32_t pack_int_id;
 261         time_t pack_mtime;
 262         uint64_t offset;
 263 };
 264
 265 static int midx_oid_compare(const void *_a, const void *_b)
 266 {
 267         const struct pack_midx_entry *a = (const struct pack_midx_entry *)_a;
 268         const struct pack_midx_entry *b = (const struct pack_midx_entry *)_b;
 269         int cmp = oidcmp(&a->oid, &b->oid);
 270
 271         if (cmp)
 272                 return cmp;
 273
 274         if (a->pack_mtime > b->pack_mtime)
 275                 return -1;
 276         else if (a->pack_mtime < b->pack_mtime)
 277                 return 1;
 278
 279         return a->pack_int_id - b->pack_int_id;
 280 }
 281
 282 static void fill_pack_entry(uint32_t pack_int_id,
 283                             struct packed_git *p,
 284                             uint32_t cur_object,
 285                             struct pack_midx_entry *entry)
 286 {
 287         if (!nth_packed_object_oid(&entry->oid, p, cur_object))
 288                 die(_("failed to locate object %d in packfile"), cur_object);
 289
 290         entry->pack_int_id = pack_int_id;
 291         entry->pack_mtime = p->mtime;
 292
 293         entry->offset = nth_packed_object_offset(p, cur_object);
 294 }
 295
 296 /*
 297  * It is possible to artificially get into a state where there are many
 298  * duplicate copies of objects. That can create high memory pressure if
 299  * we are to create a list of all objects before de-duplication. To reduce
 300  * this memory pressure without a significant performance drop, automatically
 301  * group objects by the first byte of their object id. Use the IDX fanout
 302  * tables to group the data, copy to a local array, then sort.
 303  *
 304  * Copy only the de-duplicated entries (selected by most-recent modified time
 305  * of a packfile containing the object).
 306  */
 307 static struct pack_midx_entry *get_sorted_entries(struct packed_git **p,
 308                                                   uint32_t *perm,
 309                                                   uint32_t nr_packs,
 310                                                   uint32_t *nr_objects)
 311 {
 312         uint32_t cur_fanout, cur_pack, cur_object;
 313         uint32_t alloc_fanout, alloc_objects, total_objects = 0;
 314         struct pack_midx_entry *entries_by_fanout = NULL;
 315         struct pack_midx_entry *deduplicated_entries = NULL;
 316
 317         for (cur_pack = 0; cur_pack < nr_packs; cur_pack++)
 318                 total_objects += p[cur_pack]->num_objects;
 319
 320         /*
 321          * As we de-duplicate by fanout value, we expect the fanout
 322          * slices to be evenly distributed, with some noise. Hence,
 323          * allocate slightly more than one 256th.
 324          */
 325         alloc_objects = alloc_fanout = total_objects > 3200 ? total_objects / 200 : 16;
 326
 327         ALLOC_ARRAY(entries_by_fanout, alloc_fanout);
 328         ALLOC_ARRAY(deduplicated_entries, alloc_objects);
 329         *nr_objects = 0;
 330
 331         for (cur_fanout = 0; cur_fanout < 256; cur_fanout++) {
 332                 uint32_t nr_fanout = 0;
 333
 334                 for (cur_pack = 0; cur_pack < nr_packs; cur_pack++) {
 335                         uint32_t start = 0, end;
 336
 337                         if (cur_fanout)
 338                                 start = get_pack_fanout(p[cur_pack], cur_fanout - 1);
 339                         end = get_pack_fanout(p[cur_pack], cur_fanout);
 340
 341                         for (cur_object = start; cur_object < end; cur_object++) {
 342                                 ALLOC_GROW(entries_by_fanout, nr_fanout + 1, alloc_fanout);
 343                                 fill_pack_entry(perm[cur_pack], p[cur_pack], cur_object, &entries_by_fanout[nr_fanout]);
 344                                 nr_fanout++;
 345                         }
 346                 }
 347
 348                 QSORT(entries_by_fanout, nr_fanout, midx_oid_compare);
 349
 350                 /*
 351                  * The batch is now sorted by OID and then mtime (descending).
 352                  * Take only the first duplicate.
 353                  */
 354                 for (cur_object = 0; cur_object < nr_fanout; cur_object++) {
 355                         if (cur_object && !oidcmp(&entries_by_fanout[cur_object - 1].oid,
 356                                                   &entries_by_fanout[cur_object].oid))
 357                                 continue;
 358
 359                         ALLOC_GROW(deduplicated_entries, *nr_objects + 1, alloc_objects);
 360                         memcpy(&deduplicated_entries[*nr_objects],
 361                                &entries_by_fanout[cur_object],
 362                                sizeof(struct pack_midx_entry));
 363                         (*nr_objects)++;
 364                 }
 365         }
 366
 367         free(entries_by_fanout);
 368         return deduplicated_entries;
 369 }
 370
 371 static size_t write_midx_pack_names(struct hashfile *f,
 372                                     char **pack_names,
 373                                     uint32_t num_packs)
 374 {
 375         uint32_t i;
 376         unsigned char padding[MIDX_CHUNK_ALIGNMENT];
 377         size_t written = 0;
 378
 379         for (i = 0; i < num_packs; i++) {
 380                 size_t writelen = strlen(pack_names[i]) + 1;
 381
 382                 if (i && strcmp(pack_names[i], pack_names[i - 1]) <= 0)
 383                         BUG("incorrect pack-file order: %s before %s",
 384                             pack_names[i - 1],
 385                             pack_names[i]);
 386
 387                 hashwrite(f, pack_names[i], writelen);
 388                 written += writelen;
 389         }
 390
 391         /* add padding to be aligned */
 392         i = MIDX_CHUNK_ALIGNMENT - (written % MIDX_CHUNK_ALIGNMENT);
 393         if (i < MIDX_CHUNK_ALIGNMENT) {
 394                 memset(padding, 0, sizeof(padding));
 395                 hashwrite(f, padding, i);
 396                 written += i;
 397         }
 398
 399         return written;
 400 }
 401
 402 static size_t write_midx_oid_fanout(struct hashfile *f,
 403                                     struct pack_midx_entry *objects,
 404                                     uint32_t nr_objects)
 405 {
 406         struct pack_midx_entry *list = objects;
 407         struct pack_midx_entry *last = objects + nr_objects;
 408         uint32_t count = 0;
 409         uint32_t i;
 410
 411         /*
 412         * Write the first-level table (the list is sorted,
 413         * but we use a 256-entry lookup to be able to avoid
 414         * having to do eight extra binary search iterations).
 415         */
 416         for (i = 0; i < 256; i++) {
 417                 struct pack_midx_entry *next = list;
 418
 419                 while (next < last && next->oid.hash[0] == i) {
 420                         count++;
 421                         next++;
 422                 }
 423
 424                 hashwrite_be32(f, count);
 425                 list = next;
 426         }
 427
 428         return MIDX_CHUNK_FANOUT_SIZE;
 429 }
 430
 431 static size_t write_midx_oid_lookup(struct hashfile *f, unsigned char hash_len,
 432                                     struct pack_midx_entry *objects,
 433                                     uint32_t nr_objects)
 434 {
 435         struct pack_midx_entry *list = objects;
 436         uint32_t i;
 437         size_t written = 0;
 438
 439         for (i = 0; i < nr_objects; i++) {
 440                 struct pack_midx_entry *obj = list++;
 441
 442                 if (i < nr_objects - 1) {
 443                         struct pack_midx_entry *next = list;
 444                         if (oidcmp(&obj->oid, &next->oid) >= 0)
 445                                 BUG("OIDs not in order: %s >= %s",
 446                                     oid_to_hex(&obj->oid),
 447                                     oid_to_hex(&next->oid));
 448                 }
 449
 450                 hashwrite(f, obj->oid.hash, (int)hash_len);
 451                 written += hash_len;
 452         }
 453
 454         return written;
 455 }
 456
 457 int write_midx_file(const char *object_dir)
 458 {
 459         unsigned char cur_chunk, num_chunks = 0;
 460         char *midx_name;
 461         uint32_t i;
 462         struct hashfile *f = NULL;
 463         struct lock_file lk;
 464         struct pack_list packs;
 465         uint32_t *pack_perm = NULL;
 466         uint64_t written = 0;
 467         uint32_t chunk_ids[MIDX_MAX_CHUNKS + 1];
 468         uint64_t chunk_offsets[MIDX_MAX_CHUNKS + 1];
 469         uint32_t nr_entries;
 470         struct pack_midx_entry *entries = NULL;
 471
 472         midx_name = get_midx_filename(object_dir);
 473         if (safe_create_leading_directories(midx_name)) {
 474                 UNLEAK(midx_name);
 475                 die_errno(_("unable to create leading directories of %s"),
 476                           midx_name);
 477         }
 478
 479         packs.nr = 0;
 480         packs.alloc_list = 16;
 481         packs.alloc_names = 16;
 482         packs.list = NULL;
 483         packs.pack_name_concat_len = 0;
 484         ALLOC_ARRAY(packs.list, packs.alloc_list);
 485         ALLOC_ARRAY(packs.names, packs.alloc_names);
 486
 487         for_each_file_in_pack_dir(object_dir, add_pack_to_midx, &packs);
 488
 489         if (packs.pack_name_concat_len % MIDX_CHUNK_ALIGNMENT)
 490                 packs.pack_name_concat_len += MIDX_CHUNK_ALIGNMENT -
 491                                               (packs.pack_name_concat_len % MIDX_CHUNK_ALIGNMENT);
 492
 493         ALLOC_ARRAY(pack_perm, packs.nr);
 494         sort_packs_by_name(packs.names, packs.nr, pack_perm);
 495
 496         entries = get_sorted_entries(packs.list, pack_perm, packs.nr, &nr_entries);
 497
 498         hold_lock_file_for_update(&lk, midx_name, LOCK_DIE_ON_ERROR);
 499         f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
 500         FREE_AND_NULL(midx_name);
 501
 502         cur_chunk = 0;
 503         num_chunks = 3;
 504
 505         written = write_midx_header(f, num_chunks, packs.nr);
 506
 507         chunk_ids[cur_chunk] = MIDX_CHUNKID_PACKNAMES;
 508         chunk_offsets[cur_chunk] = written + (num_chunks + 1) * MIDX_CHUNKLOOKUP_WIDTH;
 509
 510         cur_chunk++;
 511         chunk_ids[cur_chunk] = MIDX_CHUNKID_OIDFANOUT;
 512         chunk_offsets[cur_chunk] = chunk_offsets[cur_chunk - 1] + packs.pack_name_concat_len;
 513
 514         cur_chunk++;
 515         chunk_ids[cur_chunk] = MIDX_CHUNKID_OIDLOOKUP;
 516         chunk_offsets[cur_chunk] = chunk_offsets[cur_chunk - 1] + MIDX_CHUNK_FANOUT_SIZE;
 517
 518         cur_chunk++;
 519         chunk_ids[cur_chunk] = 0;
 520         chunk_offsets[cur_chunk] = chunk_offsets[cur_chunk - 1] + nr_entries * MIDX_HASH_LEN;
 521
 522         for (i = 0; i <= num_chunks; i++) {
 523                 if (i && chunk_offsets[i] < chunk_offsets[i - 1])
 524                         BUG("incorrect chunk offsets: %"PRIu64" before %"PRIu64,
 525                             chunk_offsets[i - 1],
 526                             chunk_offsets[i]);
 527
 528                 if (chunk_offsets[i] % MIDX_CHUNK_ALIGNMENT)
 529                         BUG("chunk offset %"PRIu64" is not properly aligned",
 530                             chunk_offsets[i]);
 531
 532                 hashwrite_be32(f, chunk_ids[i]);
 533                 hashwrite_be32(f, chunk_offsets[i] >> 32);
 534                 hashwrite_be32(f, chunk_offsets[i]);
 535
 536                 written += MIDX_CHUNKLOOKUP_WIDTH;
 537         }
 538
 539         for (i = 0; i < num_chunks; i++) {
 540                 if (written != chunk_offsets[i])
 541                         BUG("incorrect chunk offset (%"PRIu64" != %"PRIu64") for chunk id %"PRIx32,
 542                             chunk_offsets[i],
 543                             written,
 544                             chunk_ids[i]);
 545
 546                 switch (chunk_ids[i]) {
 547                         case MIDX_CHUNKID_PACKNAMES:
 548                                 written += write_midx_pack_names(f, packs.names, packs.nr);
 549                                 break;
 550
 551                         case MIDX_CHUNKID_OIDFANOUT:
 552                                 written += write_midx_oid_fanout(f, entries, nr_entries);
 553                                 break;
 554
 555                         case MIDX_CHUNKID_OIDLOOKUP:
 556                                 written += write_midx_oid_lookup(f, MIDX_HASH_LEN, entries, nr_entries);
 557                                 break;
 558
 559                         default:
 560                                 BUG("trying to write unknown chunk id %"PRIx32,
 561                                     chunk_ids[i]);
 562                 }
 563         }
 564
 565         if (written != chunk_offsets[num_chunks])
 566                 BUG("incorrect final offset %"PRIu64" != %"PRIu64,
 567                     written,
 568                     chunk_offsets[num_chunks]);
 569
 570         finalize_hashfile(f, NULL, CSUM_FSYNC | CSUM_HASH_IN_STREAM);
 571         commit_lock_file(&lk);
 572
 573         for (i = 0; i < packs.nr; i++) {
 574                 if (packs.list[i]) {
 575                         close_pack(packs.list[i]);
 576                         free(packs.list[i]);
 577                 }
 578                 free(packs.names[i]);
 579         }
 580
 581         free(packs.list);
 582         free(packs.names);
 583         free(entries);
 584         return 0;
 585 }