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