commit-graph.c

   1 #include "cache.h"
   2 #include "config.h"
   3 #include "git-compat-util.h"
   4 #include "lockfile.h"
   5 #include "pack.h"
   6 #include "packfile.h"
   7 #include "commit.h"
   8 #include "object.h"
   9 #include "revision.h"
  10 #include "sha1-lookup.h"
  11 #include "commit-graph.h"
  12
  13 #define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
  14 #define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
  15 #define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
  16 #define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
  17 #define GRAPH_CHUNKID_LARGEEDGES 0x45444745 /* "EDGE" */
  18
  19 #define GRAPH_DATA_WIDTH 36
  20
  21 #define GRAPH_VERSION_1 0x1
  22 #define GRAPH_VERSION GRAPH_VERSION_1
  23
  24 #define GRAPH_OID_VERSION_SHA1 1
  25 #define GRAPH_OID_LEN_SHA1 GIT_SHA1_RAWSZ
  26 #define GRAPH_OID_VERSION GRAPH_OID_VERSION_SHA1
  27 #define GRAPH_OID_LEN GRAPH_OID_LEN_SHA1
  28
  29 #define GRAPH_OCTOPUS_EDGES_NEEDED 0x80000000
  30 #define GRAPH_PARENT_MISSING 0x7fffffff
  31 #define GRAPH_EDGE_LAST_MASK 0x7fffffff
  32 #define GRAPH_PARENT_NONE 0x70000000
  33
  34 #define GRAPH_LAST_EDGE 0x80000000
  35
  36 #define GRAPH_FANOUT_SIZE (4 * 256)
  37 #define GRAPH_CHUNKLOOKUP_WIDTH 12
  38 #define GRAPH_MIN_SIZE (5 * GRAPH_CHUNKLOOKUP_WIDTH + GRAPH_FANOUT_SIZE + \
  39                         GRAPH_OID_LEN + 8)
  40
  41
  42 char *get_commit_graph_filename(const char *obj_dir)
  43 {
  44         return xstrfmt("%s/info/commit-graph", obj_dir);
  45 }
  46
  47 static struct commit_graph *alloc_commit_graph(void)
  48 {
  49         struct commit_graph *g = xcalloc(1, sizeof(*g));
  50         g->graph_fd = -1;
  51
  52         return g;
  53 }
  54
  55 struct commit_graph *load_commit_graph_one(const char *graph_file)
  56 {
  57         void *graph_map;
  58         const unsigned char *data, *chunk_lookup;
  59         size_t graph_size;
  60         struct stat st;
  61         uint32_t i;
  62         struct commit_graph *graph;
  63         int fd = git_open(graph_file);
  64         uint64_t last_chunk_offset;
  65         uint32_t last_chunk_id;
  66         uint32_t graph_signature;
  67         unsigned char graph_version, hash_version;
  68
  69         if (fd < 0)
  70                 return NULL;
  71         if (fstat(fd, &st)) {
  72                 close(fd);
  73                 return NULL;
  74         }
  75         graph_size = xsize_t(st.st_size);
  76
  77         if (graph_size < GRAPH_MIN_SIZE) {
  78                 close(fd);
  79                 die("graph file %s is too small", graph_file);
  80         }
  81         graph_map = xmmap(NULL, graph_size, PROT_READ, MAP_PRIVATE, fd, 0);
  82         data = (const unsigned char *)graph_map;
  83
  84         graph_signature = get_be32(data);
  85         if (graph_signature != GRAPH_SIGNATURE) {
  86                 error("graph signature %X does not match signature %X",
  87                       graph_signature, GRAPH_SIGNATURE);
  88                 goto cleanup_fail;
  89         }
  90
  91         graph_version = *(unsigned char*)(data + 4);
  92         if (graph_version != GRAPH_VERSION) {
  93                 error("graph version %X does not match version %X",
  94                       graph_version, GRAPH_VERSION);
  95                 goto cleanup_fail;
  96         }
  97
  98         hash_version = *(unsigned char*)(data + 5);
  99         if (hash_version != GRAPH_OID_VERSION) {
 100                 error("hash version %X does not match version %X",
 101                       hash_version, GRAPH_OID_VERSION);
 102                 goto cleanup_fail;
 103         }
 104
 105         graph = alloc_commit_graph();
 106
 107         graph->hash_len = GRAPH_OID_LEN;
 108         graph->num_chunks = *(unsigned char*)(data + 6);
 109         graph->graph_fd = fd;
 110         graph->data = graph_map;
 111         graph->data_len = graph_size;
 112
 113         last_chunk_id = 0;
 114         last_chunk_offset = 8;
 115         chunk_lookup = data + 8;
 116         for (i = 0; i < graph->num_chunks; i++) {
 117                 uint32_t chunk_id = get_be32(chunk_lookup + 0);
 118                 uint64_t chunk_offset = get_be64(chunk_lookup + 4);
 119                 int chunk_repeated = 0;
 120
 121                 chunk_lookup += GRAPH_CHUNKLOOKUP_WIDTH;
 122
 123                 if (chunk_offset > graph_size - GIT_MAX_RAWSZ) {
 124                         error("improper chunk offset %08x%08x", (uint32_t)(chunk_offset >> 32),
 125                               (uint32_t)chunk_offset);
 126                         goto cleanup_fail;
 127                 }
 128
 129                 switch (chunk_id) {
 130                 case GRAPH_CHUNKID_OIDFANOUT:
 131                         if (graph->chunk_oid_fanout)
 132                                 chunk_repeated = 1;
 133                         else
 134                                 graph->chunk_oid_fanout = (uint32_t*)(data + chunk_offset);
 135                         break;
 136
 137                 case GRAPH_CHUNKID_OIDLOOKUP:
 138                         if (graph->chunk_oid_lookup)
 139                                 chunk_repeated = 1;
 140                         else
 141                                 graph->chunk_oid_lookup = data + chunk_offset;
 142                         break;
 143
 144                 case GRAPH_CHUNKID_DATA:
 145                         if (graph->chunk_commit_data)
 146                                 chunk_repeated = 1;
 147                         else
 148                                 graph->chunk_commit_data = data + chunk_offset;
 149                         break;
 150
 151                 case GRAPH_CHUNKID_LARGEEDGES:
 152                         if (graph->chunk_large_edges)
 153                                 chunk_repeated = 1;
 154                         else
 155                                 graph->chunk_large_edges = data + chunk_offset;
 156                         break;
 157                 }
 158
 159                 if (chunk_repeated) {
 160                         error("chunk id %08x appears multiple times", chunk_id);
 161                         goto cleanup_fail;
 162                 }
 163
 164                 if (last_chunk_id == GRAPH_CHUNKID_OIDLOOKUP)
 165                 {
 166                         graph->num_commits = (chunk_offset - last_chunk_offset)
 167                                              / graph->hash_len;
 168                 }
 169
 170                 last_chunk_id = chunk_id;
 171                 last_chunk_offset = chunk_offset;
 172         }
 173
 174         return graph;
 175
 176 cleanup_fail:
 177         munmap(graph_map, graph_size);
 178         close(fd);
 179         exit(1);
 180 }
 181
 182 static void write_graph_chunk_fanout(struct hashfile *f,
 183                                      struct commit **commits,
 184                                      int nr_commits)
 185 {
 186         int i, count = 0;
 187         struct commit **list = commits;
 188
 189         /*
 190          * Write the first-level table (the list is sorted,
 191          * but we use a 256-entry lookup to be able to avoid
 192          * having to do eight extra binary search iterations).
 193          */
 194         for (i = 0; i < 256; i++) {
 195                 while (count < nr_commits) {
 196                         if ((*list)->object.oid.hash[0] != i)
 197                                 break;
 198                         count++;
 199                         list++;
 200                 }
 201
 202                 hashwrite_be32(f, count);
 203         }
 204 }
 205
 206 static void write_graph_chunk_oids(struct hashfile *f, int hash_len,
 207                                    struct commit **commits, int nr_commits)
 208 {
 209         struct commit **list = commits;
 210         int count;
 211         for (count = 0; count < nr_commits; count++, list++)
 212                 hashwrite(f, (*list)->object.oid.hash, (int)hash_len);
 213 }
 214
 215 static const unsigned char *commit_to_sha1(size_t index, void *table)
 216 {
 217         struct commit **commits = table;
 218         return commits[index]->object.oid.hash;
 219 }
 220
 221 static void write_graph_chunk_data(struct hashfile *f, int hash_len,
 222                                    struct commit **commits, int nr_commits)
 223 {
 224         struct commit **list = commits;
 225         struct commit **last = commits + nr_commits;
 226         uint32_t num_extra_edges = 0;
 227
 228         while (list < last) {
 229                 struct commit_list *parent;
 230                 int edge_value;
 231                 uint32_t packedDate[2];
 232
 233                 parse_commit(*list);
 234                 hashwrite(f, (*list)->tree->object.oid.hash, hash_len);
 235
 236                 parent = (*list)->parents;
 237
 238                 if (!parent)
 239                         edge_value = GRAPH_PARENT_NONE;
 240                 else {
 241                         edge_value = sha1_pos(parent->item->object.oid.hash,
 242                                               commits,
 243                                               nr_commits,
 244                                               commit_to_sha1);
 245
 246                         if (edge_value < 0)
 247                                 edge_value = GRAPH_PARENT_MISSING;
 248                 }
 249
 250                 hashwrite_be32(f, edge_value);
 251
 252                 if (parent)
 253                         parent = parent->next;
 254
 255                 if (!parent)
 256                         edge_value = GRAPH_PARENT_NONE;
 257                 else if (parent->next)
 258                         edge_value = GRAPH_OCTOPUS_EDGES_NEEDED | num_extra_edges;
 259                 else {
 260                         edge_value = sha1_pos(parent->item->object.oid.hash,
 261                                               commits,
 262                                               nr_commits,
 263                                               commit_to_sha1);
 264                         if (edge_value < 0)
 265                                 edge_value = GRAPH_PARENT_MISSING;
 266                 }
 267
 268                 hashwrite_be32(f, edge_value);
 269
 270                 if (edge_value & GRAPH_OCTOPUS_EDGES_NEEDED) {
 271                         do {
 272                                 num_extra_edges++;
 273                                 parent = parent->next;
 274                         } while (parent);
 275                 }
 276
 277                 if (sizeof((*list)->date) > 4)
 278                         packedDate[0] = htonl(((*list)->date >> 32) & 0x3);
 279                 else
 280                         packedDate[0] = 0;
 281
 282                 packedDate[1] = htonl((*list)->date);
 283                 hashwrite(f, packedDate, 8);
 284
 285                 list++;
 286         }
 287 }
 288
 289 static void write_graph_chunk_large_edges(struct hashfile *f,
 290                                           struct commit **commits,
 291                                           int nr_commits)
 292 {
 293         struct commit **list = commits;
 294         struct commit **last = commits + nr_commits;
 295         struct commit_list *parent;
 296
 297         while (list < last) {
 298                 int num_parents = 0;
 299                 for (parent = (*list)->parents; num_parents < 3 && parent;
 300                      parent = parent->next)
 301                         num_parents++;
 302
 303                 if (num_parents <= 2) {
 304                         list++;
 305                         continue;
 306                 }
 307
 308                 /* Since num_parents > 2, this initializer is safe. */
 309                 for (parent = (*list)->parents->next; parent; parent = parent->next) {
 310                         int edge_value = sha1_pos(parent->item->object.oid.hash,
 311                                                   commits,
 312                                                   nr_commits,
 313                                                   commit_to_sha1);
 314
 315                         if (edge_value < 0)
 316                                 edge_value = GRAPH_PARENT_MISSING;
 317                         else if (!parent->next)
 318                                 edge_value |= GRAPH_LAST_EDGE;
 319
 320                         hashwrite_be32(f, edge_value);
 321                 }
 322
 323                 list++;
 324         }
 325 }
 326
 327 static int commit_compare(const void *_a, const void *_b)
 328 {
 329         const struct object_id *a = (const struct object_id *)_a;
 330         const struct object_id *b = (const struct object_id *)_b;
 331         return oidcmp(a, b);
 332 }
 333
 334 struct packed_commit_list {
 335         struct commit **list;
 336         int nr;
 337         int alloc;
 338 };
 339
 340 struct packed_oid_list {
 341         struct object_id *list;
 342         int nr;
 343         int alloc;
 344 };
 345
 346 static int add_packed_commits(const struct object_id *oid,
 347                               struct packed_git *pack,
 348                               uint32_t pos,
 349                               void *data)
 350 {
 351         struct packed_oid_list *list = (struct packed_oid_list*)data;
 352         enum object_type type;
 353         off_t offset = nth_packed_object_offset(pack, pos);
 354         struct object_info oi = OBJECT_INFO_INIT;
 355
 356         oi.typep = &type;
 357         if (packed_object_info(pack, offset, &oi) < 0)
 358                 die("unable to get type of object %s", oid_to_hex(oid));
 359
 360         if (type != OBJ_COMMIT)
 361                 return 0;
 362
 363         ALLOC_GROW(list->list, list->nr + 1, list->alloc);
 364         oidcpy(&(list->list[list->nr]), oid);
 365         list->nr++;
 366
 367         return 0;
 368 }
 369
 370 static void add_missing_parents(struct packed_oid_list *oids, struct commit *commit)
 371 {
 372         struct commit_list *parent;
 373         for (parent = commit->parents; parent; parent = parent->next) {
 374                 if (!(parent->item->object.flags & UNINTERESTING)) {
 375                         ALLOC_GROW(oids->list, oids->nr + 1, oids->alloc);
 376                         oidcpy(&oids->list[oids->nr], &(parent->item->object.oid));
 377                         oids->nr++;
 378                         parent->item->object.flags |= UNINTERESTING;
 379                 }
 380         }
 381 }
 382
 383 static void close_reachable(struct packed_oid_list *oids)
 384 {
 385         int i;
 386         struct commit *commit;
 387
 388         for (i = 0; i < oids->nr; i++) {
 389                 commit = lookup_commit(&oids->list[i]);
 390                 if (commit)
 391                         commit->object.flags |= UNINTERESTING;
 392         }
 393
 394         /*
 395          * As this loop runs, oids->nr may grow, but not more
 396          * than the number of missing commits in the reachable
 397          * closure.
 398          */
 399         for (i = 0; i < oids->nr; i++) {
 400                 commit = lookup_commit(&oids->list[i]);
 401
 402                 if (commit && !parse_commit(commit))
 403                         add_missing_parents(oids, commit);
 404         }
 405
 406         for (i = 0; i < oids->nr; i++) {
 407                 commit = lookup_commit(&oids->list[i]);
 408
 409                 if (commit)
 410                         commit->object.flags &= ~UNINTERESTING;
 411         }
 412 }
 413
 414 void write_commit_graph(const char *obj_dir)
 415 {
 416         struct packed_oid_list oids;
 417         struct packed_commit_list commits;
 418         struct hashfile *f;
 419         uint32_t i, count_distinct = 0;
 420         char *graph_name;
 421         int fd;
 422         struct lock_file lk = LOCK_INIT;
 423         uint32_t chunk_ids[5];
 424         uint64_t chunk_offsets[5];
 425         int num_chunks;
 426         int num_extra_edges;
 427         struct commit_list *parent;
 428
 429         oids.nr = 0;
 430         oids.alloc = approximate_object_count() / 4;
 431
 432         if (oids.alloc < 1024)
 433                 oids.alloc = 1024;
 434         ALLOC_ARRAY(oids.list, oids.alloc);
 435
 436         for_each_packed_object(add_packed_commits, &oids, 0);
 437         close_reachable(&oids);
 438
 439         QSORT(oids.list, oids.nr, commit_compare);
 440
 441         count_distinct = 1;
 442         for (i = 1; i < oids.nr; i++) {
 443                 if (oidcmp(&oids.list[i-1], &oids.list[i]))
 444                         count_distinct++;
 445         }
 446
 447         if (count_distinct >= GRAPH_PARENT_MISSING)
 448                 die(_("the commit graph format cannot write %d commits"), count_distinct);
 449
 450         commits.nr = 0;
 451         commits.alloc = count_distinct;
 452         ALLOC_ARRAY(commits.list, commits.alloc);
 453
 454         num_extra_edges = 0;
 455         for (i = 0; i < oids.nr; i++) {
 456                 int num_parents = 0;
 457                 if (i > 0 && !oidcmp(&oids.list[i-1], &oids.list[i]))
 458                         continue;
 459
 460                 commits.list[commits.nr] = lookup_commit(&oids.list[i]);
 461                 parse_commit(commits.list[commits.nr]);
 462
 463                 for (parent = commits.list[commits.nr]->parents;
 464                      parent; parent = parent->next)
 465                         num_parents++;
 466
 467                 if (num_parents > 2)
 468                         num_extra_edges += num_parents - 1;
 469
 470                 commits.nr++;
 471         }
 472         num_chunks = num_extra_edges ? 4 : 3;
 473
 474         if (commits.nr >= GRAPH_PARENT_MISSING)
 475                 die(_("too many commits to write graph"));
 476
 477         graph_name = get_commit_graph_filename(obj_dir);
 478         fd = hold_lock_file_for_update(&lk, graph_name, 0);
 479
 480         if (fd < 0) {
 481                 struct strbuf folder = STRBUF_INIT;
 482                 strbuf_addstr(&folder, graph_name);
 483                 strbuf_setlen(&folder, strrchr(folder.buf, '/') - folder.buf);
 484
 485                 if (mkdir(folder.buf, 0777) < 0)
 486                         die_errno(_("cannot mkdir %s"), folder.buf);
 487                 strbuf_release(&folder);
 488
 489                 fd = hold_lock_file_for_update(&lk, graph_name, LOCK_DIE_ON_ERROR);
 490
 491                 if (fd < 0)
 492                         die_errno("unable to create '%s'", graph_name);
 493         }
 494
 495         f = hashfd(lk.tempfile->fd, lk.tempfile->filename.buf);
 496
 497         hashwrite_be32(f, GRAPH_SIGNATURE);
 498
 499         hashwrite_u8(f, GRAPH_VERSION);
 500         hashwrite_u8(f, GRAPH_OID_VERSION);
 501         hashwrite_u8(f, num_chunks);
 502         hashwrite_u8(f, 0); /* unused padding byte */
 503
 504         chunk_ids[0] = GRAPH_CHUNKID_OIDFANOUT;
 505         chunk_ids[1] = GRAPH_CHUNKID_OIDLOOKUP;
 506         chunk_ids[2] = GRAPH_CHUNKID_DATA;
 507         if (num_extra_edges)
 508                 chunk_ids[3] = GRAPH_CHUNKID_LARGEEDGES;
 509         else
 510                 chunk_ids[3] = 0;
 511         chunk_ids[4] = 0;
 512
 513         chunk_offsets[0] = 8 + (num_chunks + 1) * GRAPH_CHUNKLOOKUP_WIDTH;
 514         chunk_offsets[1] = chunk_offsets[0] + GRAPH_FANOUT_SIZE;
 515         chunk_offsets[2] = chunk_offsets[1] + GRAPH_OID_LEN * commits.nr;
 516         chunk_offsets[3] = chunk_offsets[2] + (GRAPH_OID_LEN + 16) * commits.nr;
 517         chunk_offsets[4] = chunk_offsets[3] + 4 * num_extra_edges;
 518
 519         for (i = 0; i <= num_chunks; i++) {
 520                 uint32_t chunk_write[3];
 521
 522                 chunk_write[0] = htonl(chunk_ids[i]);
 523                 chunk_write[1] = htonl(chunk_offsets[i] >> 32);
 524                 chunk_write[2] = htonl(chunk_offsets[i] & 0xffffffff);
 525                 hashwrite(f, chunk_write, 12);
 526         }
 527
 528         write_graph_chunk_fanout(f, commits.list, commits.nr);
 529         write_graph_chunk_oids(f, GRAPH_OID_LEN, commits.list, commits.nr);
 530         write_graph_chunk_data(f, GRAPH_OID_LEN, commits.list, commits.nr);
 531         write_graph_chunk_large_edges(f, commits.list, commits.nr);
 532
 533         finalize_hashfile(f, NULL, CSUM_HASH_IN_STREAM | CSUM_FSYNC);
 534         commit_lock_file(&lk);
 535
 536         free(oids.list);
 537         oids.alloc = 0;
 538         oids.nr = 0;
 539 }