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