split-index.c

   1 #define USE_THE_REPOSITORY_VARIABLE
   2 #define DISABLE_SIGN_COMPARE_WARNINGS
   3
   4 #include "git-compat-util.h"
   5 #include "gettext.h"
   6 #include "hash.h"
   7 #include "mem-pool.h"
   8 #include "read-cache-ll.h"
   9 #include "split-index.h"
  10 #include "strbuf.h"
  11 #include "ewah/ewok.h"
  12
  13 struct split_index *init_split_index(struct index_state *istate)
  14 {
  15         if (!istate->split_index) {
  16                 if (istate->sparse_index)
  17                         die(_("cannot use split index with a sparse index"));
  18
  19                 CALLOC_ARRAY(istate->split_index, 1);
  20                 istate->split_index->refcount = 1;
  21         }
  22         return istate->split_index;
  23 }
  24
  25 int read_link_extension(struct index_state *istate,
  26                          const void *data_, unsigned long sz)
  27 {
  28         const unsigned char *data = data_;
  29         struct split_index *si;
  30         int ret;
  31
  32         if (sz < the_hash_algo->rawsz)
  33                 return error("corrupt link extension (too short)");
  34         si = init_split_index(istate);
  35         oidread(&si->base_oid, data, the_repository->hash_algo);
  36         data += the_hash_algo->rawsz;
  37         sz -= the_hash_algo->rawsz;
  38         if (!sz)
  39                 return 0;
  40         si->delete_bitmap = ewah_new();
  41         ret = ewah_read_mmap(si->delete_bitmap, data, sz);
  42         if (ret < 0)
  43                 return error("corrupt delete bitmap in link extension");
  44         data += ret;
  45         sz -= ret;
  46         si->replace_bitmap = ewah_new();
  47         ret = ewah_read_mmap(si->replace_bitmap, data, sz);
  48         if (ret < 0)
  49                 return error("corrupt replace bitmap in link extension");
  50         if (ret != sz)
  51                 return error("garbage at the end of link extension");
  52         return 0;
  53 }
  54
  55 int write_link_extension(struct strbuf *sb,
  56                          struct index_state *istate)
  57 {
  58         struct split_index *si = istate->split_index;
  59         strbuf_add(sb, si->base_oid.hash, the_hash_algo->rawsz);
  60         if (!si->delete_bitmap && !si->replace_bitmap)
  61                 return 0;
  62         ewah_serialize_strbuf(si->delete_bitmap, sb);
  63         ewah_serialize_strbuf(si->replace_bitmap, sb);
  64         return 0;
  65 }
  66
  67 static void mark_base_index_entries(struct index_state *base)
  68 {
  69         int i;
  70         /*
  71          * To keep track of the shared entries between
  72          * istate->base->cache[] and istate->cache[], base entry
  73          * position is stored in each base entry. All positions start
  74          * from 1 instead of 0, which is reserved to say "this is a new
  75          * entry".
  76          */
  77         for (i = 0; i < base->cache_nr; i++)
  78                 base->cache[i]->index = i + 1;
  79 }
  80
  81 void move_cache_to_base_index(struct index_state *istate)
  82 {
  83         struct split_index *si = istate->split_index;
  84         int i;
  85
  86         /*
  87          * If there was a previous base index, then transfer ownership of allocated
  88          * entries to the parent index.
  89          */
  90         if (si->base &&
  91                 si->base->ce_mem_pool) {
  92
  93                 if (!istate->ce_mem_pool) {
  94                         istate->ce_mem_pool = xmalloc(sizeof(struct mem_pool));
  95                         mem_pool_init(istate->ce_mem_pool, 0);
  96                 }
  97
  98                 mem_pool_combine(istate->ce_mem_pool, istate->split_index->base->ce_mem_pool);
  99         }
 100
 101         if (si->base)
 102                 release_index(si->base);
 103         else
 104                 ALLOC_ARRAY(si->base, 1);
 105
 106         index_state_init(si->base, istate->repo);
 107         si->base->version = istate->version;
 108         /* zero timestamp disables racy test in ce_write_index() */
 109         si->base->timestamp = istate->timestamp;
 110         ALLOC_GROW(si->base->cache, istate->cache_nr, si->base->cache_alloc);
 111         si->base->cache_nr = istate->cache_nr;
 112
 113         /*
 114          * The mem_pool needs to move with the allocated entries.
 115          */
 116         si->base->ce_mem_pool = istate->ce_mem_pool;
 117         istate->ce_mem_pool = NULL;
 118
 119         COPY_ARRAY(si->base->cache, istate->cache, istate->cache_nr);
 120         mark_base_index_entries(si->base);
 121         for (i = 0; i < si->base->cache_nr; i++)
 122                 si->base->cache[i]->ce_flags &= ~CE_UPDATE_IN_BASE;
 123 }
 124
 125 static void mark_entry_for_delete(size_t pos, void *data)
 126 {
 127         struct index_state *istate = data;
 128         if (pos >= istate->cache_nr)
 129                 die("position for delete %d exceeds base index size %d",
 130                     (int)pos, istate->cache_nr);
 131         istate->cache[pos]->ce_flags |= CE_REMOVE;
 132         istate->split_index->nr_deletions++;
 133 }
 134
 135 static void replace_entry(size_t pos, void *data)
 136 {
 137         struct index_state *istate = data;
 138         struct split_index *si = istate->split_index;
 139         struct cache_entry *dst, *src;
 140
 141         if (pos >= istate->cache_nr)
 142                 die("position for replacement %d exceeds base index size %d",
 143                     (int)pos, istate->cache_nr);
 144         if (si->nr_replacements >= si->saved_cache_nr)
 145                 die("too many replacements (%d vs %d)",
 146                     si->nr_replacements, si->saved_cache_nr);
 147         dst = istate->cache[pos];
 148         if (dst->ce_flags & CE_REMOVE)
 149                 die("entry %d is marked as both replaced and deleted",
 150                     (int)pos);
 151         src = si->saved_cache[si->nr_replacements];
 152         if (ce_namelen(src))
 153                 die("corrupt link extension, entry %d should have "
 154                     "zero length name", (int)pos);
 155         src->index = pos + 1;
 156         src->ce_flags |= CE_UPDATE_IN_BASE;
 157         src->ce_namelen = dst->ce_namelen;
 158         copy_cache_entry(dst, src);
 159         discard_cache_entry(src);
 160         si->nr_replacements++;
 161 }
 162
 163 void merge_base_index(struct index_state *istate)
 164 {
 165         struct split_index *si = istate->split_index;
 166         unsigned int i;
 167
 168         mark_base_index_entries(si->base);
 169
 170         si->saved_cache     = istate->cache;
 171         si->saved_cache_nr  = istate->cache_nr;
 172         istate->cache_nr    = si->base->cache_nr;
 173         istate->cache       = NULL;
 174         istate->cache_alloc = 0;
 175         ALLOC_GROW(istate->cache, istate->cache_nr, istate->cache_alloc);
 176         COPY_ARRAY(istate->cache, si->base->cache, istate->cache_nr);
 177
 178         si->nr_deletions = 0;
 179         si->nr_replacements = 0;
 180         ewah_each_bit(si->replace_bitmap, replace_entry, istate);
 181         ewah_each_bit(si->delete_bitmap, mark_entry_for_delete, istate);
 182         if (si->nr_deletions)
 183                 remove_marked_cache_entries(istate, 0);
 184
 185         for (i = si->nr_replacements; i < si->saved_cache_nr; i++) {
 186                 if (!ce_namelen(si->saved_cache[i]))
 187                         die("corrupt link extension, entry %d should "
 188                             "have non-zero length name", i);
 189                 add_index_entry(istate, si->saved_cache[i],
 190                                 ADD_CACHE_OK_TO_ADD |
 191                                 ADD_CACHE_KEEP_CACHE_TREE |
 192                                 /*
 193                                  * we may have to replay what
 194                                  * merge-recursive.c:update_stages()
 195                                  * does, which has this flag on
 196                                  */
 197                                 ADD_CACHE_SKIP_DFCHECK);
 198                 si->saved_cache[i] = NULL;
 199         }
 200
 201         ewah_free(si->delete_bitmap);
 202         ewah_free(si->replace_bitmap);
 203         FREE_AND_NULL(si->saved_cache);
 204         si->delete_bitmap  = NULL;
 205         si->replace_bitmap = NULL;
 206         si->saved_cache_nr = 0;
 207 }
 208
 209 /*
 210  * Compare most of the fields in two cache entries, i.e. all except the
 211  * hashmap_entry and the name.
 212  */
 213 static int compare_ce_content(struct cache_entry *a, struct cache_entry *b)
 214 {
 215         const unsigned int ondisk_flags = CE_STAGEMASK | CE_VALID |
 216                                           CE_EXTENDED_FLAGS;
 217         unsigned int ce_flags = a->ce_flags;
 218         unsigned int base_flags = b->ce_flags;
 219         int ret;
 220
 221         /* only on-disk flags matter */
 222         a->ce_flags &= ondisk_flags;
 223         b->ce_flags &= ondisk_flags;
 224         ret = memcmp(&a->ce_stat_data, &b->ce_stat_data,
 225                      offsetof(struct cache_entry, name) -
 226                      offsetof(struct cache_entry, oid)) ||
 227                 !oideq(&a->oid, &b->oid);
 228         a->ce_flags = ce_flags;
 229         b->ce_flags = base_flags;
 230
 231         return ret;
 232 }
 233
 234 void prepare_to_write_split_index(struct index_state *istate)
 235 {
 236         struct split_index *si = init_split_index(istate);
 237         struct cache_entry **entries = NULL, *ce;
 238         int i, nr_entries = 0, nr_alloc = 0;
 239
 240         si->delete_bitmap = ewah_new();
 241         si->replace_bitmap = ewah_new();
 242
 243         if (si->base) {
 244                 /* Go through istate->cache[] and mark CE_MATCHED to
 245                  * entry with positive index. We'll go through
 246                  * base->cache[] later to delete all entries in base
 247                  * that are not marked with either CE_MATCHED or
 248                  * CE_UPDATE_IN_BASE. If istate->cache[i] is a
 249                  * duplicate, deduplicate it.
 250                  */
 251                 for (i = 0; i < istate->cache_nr; i++) {
 252                         struct cache_entry *base;
 253                         ce = istate->cache[i];
 254                         if (!ce->index) {
 255                                 /*
 256                                  * During simple update index operations this
 257                                  * is a cache entry that is not present in
 258                                  * the shared index.  It will be added to the
 259                                  * split index.
 260                                  *
 261                                  * However, it might also represent a file
 262                                  * that already has a cache entry in the
 263                                  * shared index, but a new index has just
 264                                  * been constructed by unpack_trees(), and
 265                                  * this entry now refers to different content
 266                                  * than what was recorded in the original
 267                                  * index, e.g. during 'read-tree -m HEAD^' or
 268                                  * 'checkout HEAD^'.  In this case the
 269                                  * original entry in the shared index will be
 270                                  * marked as deleted, and this entry will be
 271                                  * added to the split index.
 272                                  */
 273                                 continue;
 274                         }
 275                         if (ce->index > si->base->cache_nr) {
 276                                 BUG("ce refers to a shared ce at %d, which is beyond the shared index size %d",
 277                                     ce->index, si->base->cache_nr);
 278                         }
 279                         ce->ce_flags |= CE_MATCHED; /* or "shared" */
 280                         base = si->base->cache[ce->index - 1];
 281                         if (ce == base) {
 282                                 /* The entry is present in the shared index. */
 283                                 if (ce->ce_flags & CE_UPDATE_IN_BASE) {
 284                                         /*
 285                                          * Already marked for inclusion in
 286                                          * the split index, either because
 287                                          * the corresponding file was
 288                                          * modified and the cached stat data
 289                                          * was refreshed, or because there
 290                                          * is already a replacement entry in
 291                                          * the split index.
 292                                          * Nothing more to do here.
 293                                          */
 294                                 } else if (!ce_uptodate(ce) &&
 295                                            is_racy_timestamp(istate, ce)) {
 296                                         /*
 297                                          * A racily clean cache entry stored
 298                                          * only in the shared index: it must
 299                                          * be added to the split index, so
 300                                          * the subsequent do_write_index()
 301                                          * can smudge its stat data.
 302                                          */
 303                                         ce->ce_flags |= CE_UPDATE_IN_BASE;
 304                                 } else {
 305                                         /*
 306                                          * The entry is only present in the
 307                                          * shared index and it was not
 308                                          * refreshed.
 309                                          * Just leave it there.
 310                                          */
 311                                 }
 312                                 continue;
 313                         }
 314                         if (ce->ce_namelen != base->ce_namelen ||
 315                             strcmp(ce->name, base->name)) {
 316                                 ce->index = 0;
 317                                 continue;
 318                         }
 319                         /*
 320                          * This is the copy of a cache entry that is present
 321                          * in the shared index, created by unpack_trees()
 322                          * while it constructed a new index.
 323                          */
 324                         if (ce->ce_flags & CE_UPDATE_IN_BASE) {
 325                                 /*
 326                                  * Already marked for inclusion in the split
 327                                  * index, either because the corresponding
 328                                  * file was modified and the cached stat data
 329                                  * was refreshed, or because the original
 330                                  * entry already had a replacement entry in
 331                                  * the split index.
 332                                  * Nothing to do.
 333                                  */
 334                         } else if (!ce_uptodate(ce) &&
 335                                    is_racy_timestamp(istate, ce)) {
 336                                 /*
 337                                  * A copy of a racily clean cache entry from
 338                                  * the shared index.  It must be added to
 339                                  * the split index, so the subsequent
 340                                  * do_write_index() can smudge its stat data.
 341                                  */
 342                                 ce->ce_flags |= CE_UPDATE_IN_BASE;
 343                         } else {
 344                                 /*
 345                                  * Thoroughly compare the cached data to see
 346                                  * whether it should be marked for inclusion
 347                                  * in the split index.
 348                                  *
 349                                  * This comparison might be unnecessary, as
 350                                  * code paths modifying the cached data do
 351                                  * set CE_UPDATE_IN_BASE as well.
 352                                  */
 353                                 if (compare_ce_content(ce, base))
 354                                         ce->ce_flags |= CE_UPDATE_IN_BASE;
 355                         }
 356                         discard_cache_entry(base);
 357                         si->base->cache[ce->index - 1] = ce;
 358                 }
 359                 for (i = 0; i < si->base->cache_nr; i++) {
 360                         ce = si->base->cache[i];
 361                         if ((ce->ce_flags & CE_REMOVE) ||
 362                             !(ce->ce_flags & CE_MATCHED))
 363                                 ewah_set(si->delete_bitmap, i);
 364                         else if (ce->ce_flags & CE_UPDATE_IN_BASE) {
 365                                 ewah_set(si->replace_bitmap, i);
 366                                 ce->ce_flags |= CE_STRIP_NAME;
 367                                 ALLOC_GROW(entries, nr_entries+1, nr_alloc);
 368                                 entries[nr_entries++] = ce;
 369                         }
 370                         if (is_null_oid(&ce->oid))
 371                                 istate->drop_cache_tree = 1;
 372                 }
 373         }
 374
 375         for (i = 0; i < istate->cache_nr; i++) {
 376                 ce = istate->cache[i];
 377                 if ((!si->base || !ce->index) && !(ce->ce_flags & CE_REMOVE)) {
 378                         assert(!(ce->ce_flags & CE_STRIP_NAME));
 379                         ALLOC_GROW(entries, nr_entries+1, nr_alloc);
 380                         entries[nr_entries++] = ce;
 381                 }
 382                 ce->ce_flags &= ~CE_MATCHED;
 383         }
 384
 385         /*
 386          * take cache[] out temporarily, put entries[] in its place
 387          * for writing
 388          */
 389         si->saved_cache = istate->cache;
 390         si->saved_cache_nr = istate->cache_nr;
 391         istate->cache = entries;
 392         istate->cache_nr = nr_entries;
 393 }
 394
 395 void finish_writing_split_index(struct index_state *istate)
 396 {
 397         struct split_index *si = init_split_index(istate);
 398
 399         ewah_free(si->delete_bitmap);
 400         ewah_free(si->replace_bitmap);
 401         si->delete_bitmap = NULL;
 402         si->replace_bitmap = NULL;
 403         free(istate->cache);
 404         istate->cache = si->saved_cache;
 405         istate->cache_nr = si->saved_cache_nr;
 406 }
 407
 408 void discard_split_index(struct index_state *istate)
 409 {
 410         struct split_index *si = istate->split_index;
 411         if (!si)
 412                 return;
 413         istate->split_index = NULL;
 414         si->refcount--;
 415         if (si->refcount)
 416                 return;
 417         if (si->base) {
 418                 discard_index(si->base);
 419                 free(si->base);
 420         }
 421         free(si);
 422 }
 423
 424 void save_or_free_index_entry(struct index_state *istate, struct cache_entry *ce)
 425 {
 426         if (ce->index &&
 427             istate->split_index &&
 428             istate->split_index->base &&
 429             ce->index <= istate->split_index->base->cache_nr &&
 430             ce == istate->split_index->base->cache[ce->index - 1])
 431                 ce->ce_flags |= CE_REMOVE;
 432         else
 433                 discard_cache_entry(ce);
 434 }
 435
 436 void replace_index_entry_in_base(struct index_state *istate,
 437                                  struct cache_entry *old_entry,
 438                                  struct cache_entry *new_entry)
 439 {
 440         if (old_entry->index &&
 441             istate->split_index &&
 442             istate->split_index->base &&
 443             old_entry->index <= istate->split_index->base->cache_nr) {
 444                 new_entry->index = old_entry->index;
 445                 if (old_entry != istate->split_index->base->cache[new_entry->index - 1])
 446                         discard_cache_entry(istate->split_index->base->cache[new_entry->index - 1]);
 447                 istate->split_index->base->cache[new_entry->index - 1] = new_entry;
 448         }
 449 }
 450
 451 void add_split_index(struct index_state *istate)
 452 {
 453         if (!istate->split_index) {
 454                 init_split_index(istate);
 455                 istate->cache_changed |= SPLIT_INDEX_ORDERED;
 456         }
 457 }
 458
 459 void remove_split_index(struct index_state *istate)
 460 {
 461         if (istate->split_index) {
 462                 if (istate->split_index->base) {
 463                         /*
 464                          * When removing the split index, we need to move
 465                          * ownership of the mem_pool associated with the
 466                          * base index to the main index. There may be cache entries
 467                          * allocated from the base's memory pool that are shared with
 468                          * the_index.cache[].
 469                          */
 470                         mem_pool_combine(istate->ce_mem_pool,
 471                                          istate->split_index->base->ce_mem_pool);
 472
 473                         /*
 474                          * The split index no longer owns the mem_pool backing
 475                          * its cache array. As we are discarding this index,
 476                          * mark the index as having no cache entries, so it
 477                          * will not attempt to clean up the cache entries or
 478                          * validate them.
 479                          */
 480                         istate->split_index->base->cache_nr = 0;
 481                 }
 482
 483                 /*
 484                  * We can discard the split index because its
 485                  * memory pool has been incorporated into the
 486                  * memory pool associated with the the_index.
 487                  */
 488                 discard_split_index(istate);
 489
 490                 istate->cache_changed |= SOMETHING_CHANGED;
 491         }
 492 }