Andrew's git / gitweb.git / commit-graph.c
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commit-graph.con commit commit-graph: close under reachability (4f2542b)
   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
  42char *get_commit_graph_filename(const char *obj_dir)
  43{
  44        return xstrfmt("%s/info/commit-graph", obj_dir);
  45}
  46
  47static 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
  55struct 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
 176cleanup_fail:
 177        munmap(graph_map, graph_size);
 178        close(fd);
 179        exit(1);
 180}
 181
 182static 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
 206static 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
 215static 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
 221static 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
 289static 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
 327static 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
 334struct packed_commit_list {
 335        struct commit **list;
 336        int nr;
 337        int alloc;
 338};
 339
 340struct packed_oid_list {
 341        struct object_id *list;
 342        int nr;
 343        int alloc;
 344};
 345
 346static 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
 370static 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
 383static 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
 414void 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}