On Fri, Mar 14, 2025 at 1:18 PM Taylor Blau <me@xxxxxxxxxxxx> wrote:
>
> Prepare the reverse index machinery to handle object lookups in an
> incremental MIDX bitmap. These changes are broken out across a few
> functions:
>
> - load_midx_revindex() learns to use the appropriate MIDX filename
> depending on whether the given 'struct multi_pack_index *' is
> incremental or not.
>
> - pack_pos_to_midx() and midx_to_pack_pos() now both take in a global
> object position in the MIDX pseudo-pack order, and finds the
> earliest containing MIDX (similar to midx.c::midx_for_object().
s/finds/find/ ?
>
> - midx_pack_order_cmp() adjusts its call to pack_pos_to_midx() by the
> number of objects in the base (since 'vb - midx->revindx_data' is
> relative to the containing MIDX, and pack_pos_to_midx() expects a
> global position).
>
> Likewise, this function adjusts its output by adding
> m->num_objects_in_base to return a global position out through the
> `*pos` pointer.
>
> Together, these changes are sufficient to use the multi-pack index's
> reverse index format for incremental multi-pack reachability bitmaps.
>
> Signed-off-by: Taylor Blau <me@xxxxxxxxxxxx>
> ---
> pack-bitmap.c | 40 ++++++++++++++++++++++++++++------------
> pack-revindex.c | 34 +++++++++++++++++++++++++---------
> 2 files changed, 53 insertions(+), 21 deletions(-)
>
> diff --git a/pack-bitmap.c b/pack-bitmap.c
> index 6406953d32..c26d85b5db 100644
> --- a/pack-bitmap.c
> +++ b/pack-bitmap.c
> @@ -170,6 +170,15 @@ static struct ewah_bitmap *read_bitmap_1(struct bitmap_index *index)
> return read_bitmap(index->map, index->map_size, &index->map_pos);
> }
>
> +static uint32_t bitmap_non_extended_bits(struct bitmap_index *index)
> +{
> + if (index->midx) {
> + struct multi_pack_index *m = index->midx;
> + return m->num_objects + m->num_objects_in_base;
> + }
> + return index->pack->num_objects;
> +}
> +
> static uint32_t bitmap_num_objects(struct bitmap_index *index)
> {
> if (index->midx)
> @@ -924,7 +933,7 @@ static inline int bitmap_position_extended(struct bitmap_index *bitmap_git,
>
> if (pos < kh_end(positions)) {
> int bitmap_pos = kh_value(positions, pos);
> - return bitmap_pos + bitmap_num_objects(bitmap_git);
> + return bitmap_pos + bitmap_non_extended_bits(bitmap_git);
> }
>
> return -1;
> @@ -992,7 +1001,7 @@ static int ext_index_add_object(struct bitmap_index *bitmap_git,
> bitmap_pos = kh_value(eindex->positions, hash_pos);
> }
>
> - return bitmap_pos + bitmap_num_objects(bitmap_git);
> + return bitmap_pos + bitmap_non_extended_bits(bitmap_git);
> }
>
> struct bitmap_show_data {
> @@ -1342,11 +1351,17 @@ struct ewah_bitmap *pseudo_merge_bitmap_for_commit(struct bitmap_index *bitmap_g
> if (pos < 0 || pos >= bitmap_num_objects(bitmap_git))
> goto done;
>
> + /*
> + * Use bitmap-relative positions instead of offsetting
> + * by bitmap_git->num_objects_in_base because we use
> + * this to find a match in pseudo_merge_for_parents(),
> + * and pseudo-merge groups cannot span multiple bitmap
> + * layers.
> + */
> bitmap_set(parents, pos);
> }
>
> - match = pseudo_merge_for_parents(&bitmap_git->pseudo_merges,
> - parents);
> + match = pseudo_merge_for_parents(&bitmap_git->pseudo_merges, parents);
>
> done:
> bitmap_free(parents);
> @@ -1500,7 +1515,8 @@ static void show_extended_objects(struct bitmap_index *bitmap_git,
> for (i = 0; i < eindex->count; ++i) {
> struct object *obj;
>
> - if (!bitmap_get(objects, st_add(bitmap_num_objects(bitmap_git), i)))
> + if (!bitmap_get(objects,
> + st_add(bitmap_non_extended_bits(bitmap_git), i)))
> continue;
>
> obj = eindex->objects[i];
> @@ -1679,7 +1695,7 @@ static void filter_bitmap_exclude_type(struct bitmap_index *bitmap_git,
> * them individually.
> */
> for (i = 0; i < eindex->count; i++) {
> - size_t pos = st_add(i, bitmap_num_objects(bitmap_git));
> + size_t pos = st_add(i, bitmap_non_extended_bits(bitmap_git));
> if (eindex->objects[i]->type == type &&
> bitmap_get(to_filter, pos) &&
> !bitmap_get(tips, pos))
> @@ -1705,7 +1721,7 @@ static unsigned long get_size_by_pos(struct bitmap_index *bitmap_git,
>
> oi.sizep = &size;
>
> - if (pos < bitmap_num_objects(bitmap_git)) {
> + if (pos < bitmap_non_extended_bits(bitmap_git)) {
> struct packed_git *pack;
> off_t ofs;
>
> @@ -1729,7 +1745,7 @@ static unsigned long get_size_by_pos(struct bitmap_index *bitmap_git,
> }
> } else {
> struct eindex *eindex = &bitmap_git->ext_index;
> - struct object *obj = eindex->objects[pos - bitmap_num_objects(bitmap_git)];
> + struct object *obj = eindex->objects[pos - bitmap_non_extended_bits(bitmap_git)];
> if (oid_object_info_extended(bitmap_repo(bitmap_git), &obj->oid,
> &oi, 0) < 0)
> die(_("unable to get size of %s"), oid_to_hex(&obj->oid));
> @@ -1882,7 +1898,7 @@ static void filter_packed_objects_from_bitmap(struct bitmap_index *bitmap_git,
> uint32_t objects_nr;
> size_t i, pos;
>
> - objects_nr = bitmap_num_objects(bitmap_git);
> + objects_nr = bitmap_non_extended_bits(bitmap_git);
> pos = objects_nr / BITS_IN_EWORD;
>
> if (pos > result->word_alloc)
> @@ -2419,7 +2435,7 @@ static uint32_t count_object_type(struct bitmap_index *bitmap_git,
> for (i = 0; i < eindex->count; ++i) {
> if (eindex->objects[i]->type == type &&
> bitmap_get(objects,
> - st_add(bitmap_num_objects(bitmap_git), i)))
> + st_add(bitmap_non_extended_bits(bitmap_git), i)))
> count++;
> }
>
> @@ -2820,7 +2836,7 @@ uint32_t *create_bitmap_mapping(struct bitmap_index *bitmap_git,
> BUG("rebuild_existing_bitmaps: missing required rev-cache "
> "extension");
>
> - num_objects = bitmap_num_objects(bitmap_git);
> + num_objects = bitmap_non_extended_bits(bitmap_git);
> CALLOC_ARRAY(reposition, num_objects);
>
> for (i = 0; i < num_objects; ++i) {
> @@ -2963,7 +2979,7 @@ static off_t get_disk_usage_for_extended(struct bitmap_index *bitmap_git)
> struct object *obj = eindex->objects[i];
>
> if (!bitmap_get(result,
> - st_add(bitmap_num_objects(bitmap_git), i)))
> + st_add(bitmap_non_extended_bits(bitmap_git), i)))
> continue;
>
> if (oid_object_info_extended(bitmap_repo(bitmap_git), &obj->oid,
> diff --git a/pack-revindex.c b/pack-revindex.c
> index d3832478d9..d3faab6a37 100644
> --- a/pack-revindex.c
> +++ b/pack-revindex.c
> @@ -383,8 +383,14 @@ int load_midx_revindex(struct multi_pack_index *m)
> trace2_data_string("load_midx_revindex", the_repository,
> "source", "rev");
>
> - get_midx_filename_ext(m->repo->hash_algo, &revindex_name, m->object_dir,
> - get_midx_checksum(m), MIDX_EXT_REV);
> + if (m->has_chain)
> + get_split_midx_filename_ext(m->repo->hash_algo, &revindex_name,
> + m->object_dir, get_midx_checksum(m),
> + MIDX_EXT_REV);
> + else
> + get_midx_filename_ext(m->repo->hash_algo, &revindex_name,
> + m->object_dir, get_midx_checksum(m),
> + MIDX_EXT_REV);
>
> ret = load_revindex_from_disk(revindex_name.buf,
> m->num_objects,
> @@ -471,11 +477,15 @@ off_t pack_pos_to_offset(struct packed_git *p, uint32_t pos)
>
> uint32_t pack_pos_to_midx(struct multi_pack_index *m, uint32_t pos)
> {
> + while (m && pos < m->num_objects_in_base)
> + m = m->base_midx;
> + if (!m)
> + BUG("NULL multi-pack-index for object position: %"PRIu32, pos);
> if (!m->revindex_data)
> BUG("pack_pos_to_midx: reverse index not yet loaded");
> - if (m->num_objects <= pos)
> + if (m->num_objects + m->num_objects_in_base <= pos)
> BUG("pack_pos_to_midx: out-of-bounds object at %"PRIu32, pos);
> - return get_be32(m->revindex_data + pos);
> + return get_be32(m->revindex_data + pos - m->num_objects_in_base);
> }
>
> struct midx_pack_key {
> @@ -491,7 +501,8 @@ static int midx_pack_order_cmp(const void *va, const void *vb)
> const struct midx_pack_key *key = va;
> struct multi_pack_index *midx = key->midx;
>
> - uint32_t versus = pack_pos_to_midx(midx, (uint32_t*)vb - (const uint32_t *)midx->revindex_data);
> + size_t pos = (uint32_t *)vb - (const uint32_t *)midx->revindex_data;
> + uint32_t versus = pack_pos_to_midx(midx, pos + midx->num_objects_in_base);
> uint32_t versus_pack = nth_midxed_pack_int_id(midx, versus);
> off_t versus_offset;
>
> @@ -529,9 +540,9 @@ static int midx_key_to_pack_pos(struct multi_pack_index *m,
> {
> uint32_t *found;
>
> - if (key->pack >= m->num_packs)
> + if (key->pack >= m->num_packs + m->num_packs_in_base)
> BUG("MIDX pack lookup out of bounds (%"PRIu32" >= %"PRIu32")",
> - key->pack, m->num_packs);
> + key->pack, m->num_packs + m->num_packs_in_base);
> /*
> * The preferred pack sorts first, so determine its identifier by
> * looking at the first object in pseudo-pack order.
> @@ -551,7 +562,8 @@ static int midx_key_to_pack_pos(struct multi_pack_index *m,
> if (!found)
> return -1;
>
> - *pos = found - m->revindex_data;
> + *pos = (found - m->revindex_data) + m->num_objects_in_base;
> +
> return 0;
> }
>
> @@ -559,9 +571,13 @@ int midx_to_pack_pos(struct multi_pack_index *m, uint32_t at, uint32_t *pos)
> {
> struct midx_pack_key key;
>
> + while (m && at < m->num_objects_in_base)
> + m = m->base_midx;
> + if (!m)
> + BUG("NULL multi-pack-index for object position: %"PRIu32, at);
> if (!m->revindex_data)
> BUG("midx_to_pack_pos: reverse index not yet loaded");
> - if (m->num_objects <= at)
> + if (m->num_objects + m->num_objects_in_base <= at)
> BUG("midx_to_pack_pos: out-of-bounds object at %"PRIu32, at);
>
> key.pack = nth_midxed_pack_int_id(m, at);
> --
> 2.49.0.13.gd0d564685b
>
