Merge branch 'sg/split-index-test' into maint
[git] / 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 }