pack-bitmap-write.c: gracefully fail to write non-closed bitmaps

The set of objects covered by a bitmap must be closed under
reachability, since it must be the case that there is a valid bit
position assigned for every possible reachable object (otherwise the
bitmaps would be incomplete).

Pack bitmaps are never written from 'git repack' unless repacking
all-into-one, and so we never write non-closed bitmaps (except in the
case of partial clones where we aren't guaranteed to have all objects).

But multi-pack bitmaps change this, since it isn't known whether the
set of objects in the MIDX is closed under reachability until walking
them. Plumb through a bit that is set when a reachable object isn't
found.

As soon as a reachable object isn't found in the set of objects to
include in the bitmap, bitmap_writer_build() knows that the set is not
closed, and so it now fails gracefully.

A test is added in t0410 to trigger a bitmap write without full
reachability closure by removing local copies of some reachable objects
from a promisor remote.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
pull/1115/head
Taylor Blau 1 year ago committed by Junio C Hamano
parent fa95666a40
commit 3ba3d0621b
  1. 3
      builtin/pack-objects.c
  2. 76
      pack-bitmap-write.c
  3. 2
      pack-bitmap.h
  4. 9
      t/t0410-partial-clone.sh

@ -1256,7 +1256,8 @@ static void write_pack_file(void)
bitmap_writer_show_progress(progress);
bitmap_writer_select_commits(indexed_commits, indexed_commits_nr, -1);
bitmap_writer_build(&to_pack);
if (bitmap_writer_build(&to_pack) < 0)
die(_("failed to write bitmap index"));
bitmap_writer_finish(written_list, nr_written,
tmpname.buf, write_bitmap_options);
write_bitmap_index = 0;

@ -125,15 +125,20 @@ static inline void push_bitmapped_commit(struct commit *commit)
writer.selected_nr++;
}
static uint32_t find_object_pos(const struct object_id *oid)
static uint32_t find_object_pos(const struct object_id *oid, int *found)
{
struct object_entry *entry = packlist_find(writer.to_pack, oid);
if (!entry) {
die("Failed to write bitmap index. Packfile doesn't have full closure "
if (found)
*found = 0;
warning("Failed to write bitmap index. Packfile doesn't have full closure "
"(object %s is missing)", oid_to_hex(oid));
return 0;
}
if (found)
*found = 1;
return oe_in_pack_pos(writer.to_pack, entry);
}
@ -331,9 +336,10 @@ static void bitmap_builder_clear(struct bitmap_builder *bb)
bb->commits_nr = bb->commits_alloc = 0;
}
static void fill_bitmap_tree(struct bitmap *bitmap,
struct tree *tree)
static int fill_bitmap_tree(struct bitmap *bitmap,
struct tree *tree)
{
int found;
uint32_t pos;
struct tree_desc desc;
struct name_entry entry;
@ -342,9 +348,11 @@ static void fill_bitmap_tree(struct bitmap *bitmap,
* If our bit is already set, then there is nothing to do. Both this
* tree and all of its children will be set.
*/
pos = find_object_pos(&tree->object.oid);
pos = find_object_pos(&tree->object.oid, &found);
if (!found)
return -1;
if (bitmap_get(bitmap, pos))
return;
return 0;
bitmap_set(bitmap, pos);
if (parse_tree(tree) < 0)
@ -355,11 +363,15 @@ static void fill_bitmap_tree(struct bitmap *bitmap,
while (tree_entry(&desc, &entry)) {
switch (object_type(entry.mode)) {
case OBJ_TREE:
fill_bitmap_tree(bitmap,
lookup_tree(the_repository, &entry.oid));
if (fill_bitmap_tree(bitmap,
lookup_tree(the_repository, &entry.oid)) < 0)
return -1;
break;
case OBJ_BLOB:
bitmap_set(bitmap, find_object_pos(&entry.oid));
pos = find_object_pos(&entry.oid, &found);
if (!found)
return -1;
bitmap_set(bitmap, pos);
break;
default:
/* Gitlink, etc; not reachable */
@ -368,15 +380,18 @@ static void fill_bitmap_tree(struct bitmap *bitmap,
}
free_tree_buffer(tree);
return 0;
}
static void fill_bitmap_commit(struct bb_commit *ent,
struct commit *commit,
struct prio_queue *queue,
struct prio_queue *tree_queue,
struct bitmap_index *old_bitmap,
const uint32_t *mapping)
static int fill_bitmap_commit(struct bb_commit *ent,
struct commit *commit,
struct prio_queue *queue,
struct prio_queue *tree_queue,
struct bitmap_index *old_bitmap,
const uint32_t *mapping)
{
int found;
uint32_t pos;
if (!ent->bitmap)
ent->bitmap = bitmap_new();
@ -401,11 +416,16 @@ static void fill_bitmap_commit(struct bb_commit *ent,
* Mark ourselves and queue our tree. The commit
* walk ensures we cover all parents.
*/
bitmap_set(ent->bitmap, find_object_pos(&c->object.oid));
pos = find_object_pos(&c->object.oid, &found);
if (!found)
return -1;
bitmap_set(ent->bitmap, pos);
prio_queue_put(tree_queue, get_commit_tree(c));
for (p = c->parents; p; p = p->next) {
int pos = find_object_pos(&p->item->object.oid);
pos = find_object_pos(&p->item->object.oid, &found);
if (!found)
return -1;
if (!bitmap_get(ent->bitmap, pos)) {
bitmap_set(ent->bitmap, pos);
prio_queue_put(queue, p->item);
@ -413,8 +433,12 @@ static void fill_bitmap_commit(struct bb_commit *ent,
}
}
while (tree_queue->nr)
fill_bitmap_tree(ent->bitmap, prio_queue_get(tree_queue));
while (tree_queue->nr) {
if (fill_bitmap_tree(ent->bitmap,
prio_queue_get(tree_queue)) < 0)
return -1;
}
return 0;
}
static void store_selected(struct bb_commit *ent, struct commit *commit)
@ -432,7 +456,7 @@ static void store_selected(struct bb_commit *ent, struct commit *commit)
kh_value(writer.bitmaps, hash_pos) = stored;
}
void bitmap_writer_build(struct packing_data *to_pack)
int bitmap_writer_build(struct packing_data *to_pack)
{
struct bitmap_builder bb;
size_t i;
@ -441,6 +465,7 @@ void bitmap_writer_build(struct packing_data *to_pack)
struct prio_queue tree_queue = { NULL };
struct bitmap_index *old_bitmap;
uint32_t *mapping;
int closed = 1; /* until proven otherwise */
writer.bitmaps = kh_init_oid_map();
writer.to_pack = to_pack;
@ -463,8 +488,11 @@ void bitmap_writer_build(struct packing_data *to_pack)
struct commit *child;
int reused = 0;
fill_bitmap_commit(ent, commit, &queue, &tree_queue,
old_bitmap, mapping);
if (fill_bitmap_commit(ent, commit, &queue, &tree_queue,
old_bitmap, mapping) < 0) {
closed = 0;
break;
}
if (ent->selected) {
store_selected(ent, commit);
@ -499,7 +527,9 @@ void bitmap_writer_build(struct packing_data *to_pack)
stop_progress(&writer.progress);
compute_xor_offsets();
if (closed)
compute_xor_offsets();
return closed ? 0 : -1;
}
/**

@ -87,7 +87,7 @@ struct ewah_bitmap *bitmap_for_commit(struct bitmap_index *bitmap_git,
struct commit *commit);
void bitmap_writer_select_commits(struct commit **indexed_commits,
unsigned int indexed_commits_nr, int max_bitmaps);
void bitmap_writer_build(struct packing_data *to_pack);
int bitmap_writer_build(struct packing_data *to_pack);
void bitmap_writer_finish(struct pack_idx_entry **index,
uint32_t index_nr,
const char *filename,

@ -536,7 +536,13 @@ test_expect_success 'gc does not repack promisor objects if there are none' '
repack_and_check () {
rm -rf repo2 &&
cp -r repo repo2 &&
git -C repo2 repack $1 -d &&
if test x"$1" = "x--must-fail"
then
shift
test_must_fail git -C repo2 repack $1 -d
else
git -C repo2 repack $1 -d
fi &&
git -C repo2 fsck &&
git -C repo2 cat-file -e $2 &&
@ -561,6 +567,7 @@ test_expect_success 'repack -d does not irreversibly delete promisor objects' '
printf "$THREE\n" | pack_as_from_promisor &&
delete_object repo "$ONE" &&
repack_and_check --must-fail -ab "$TWO" "$THREE" &&
repack_and_check -a "$TWO" "$THREE" &&
repack_and_check -A "$TWO" "$THREE" &&
repack_and_check -l "$TWO" "$THREE"

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