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