git.oblomov.eu Git - git/blob - split-index.c

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