multi-pack-index: implement 'expire' subcommand

The 'git multi-pack-index expire' subcommand looks at the existing
mult-pack-index, counts the number of objects referenced in each
pack-file, deletes the pack-fils with no referenced objects, and
rewrites the multi-pack-index to no longer reference those packs.

Refactor the write_midx_file() method to call write_midx_internal()
which now takes an existing 'struct multi_pack_index' and a list
of pack-files to drop (as specified by the names of their pack-
indexes). As we write the new multi-pack-index, we drop those
file names from the list of known pack-files.

The expire_midx_packs() method removes the unreferenced pack-files
after carefully closing the packs to avoid open handles.

Test that a new pack-file that covers the contents of two other
pack-files leads to those pack-files being deleted during the
expire subcommand. Be sure to read the multi-pack-index to ensure
it no longer references those packs.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Derrick Stolee 2019-06-10 16:35:25 -07:00 committed by Junio C Hamano
parent d01bf2e609
commit 19575c7c8e
2 changed files with 129 additions and 10 deletions

119
midx.c
View file

@ -34,6 +34,8 @@
#define MIDX_CHUNK_LARGE_OFFSET_WIDTH (sizeof(uint64_t))
#define MIDX_LARGE_OFFSET_NEEDED 0x80000000
#define PACK_EXPIRED UINT_MAX
static char *get_midx_filename(const char *object_dir)
{
return xstrfmt("%s/pack/multi-pack-index", object_dir);
@ -431,6 +433,7 @@ struct pack_info {
uint32_t orig_pack_int_id;
char *pack_name;
struct packed_git *p;
unsigned expired : 1;
};
static int pack_info_compare(const void *_a, const void *_b)
@ -478,6 +481,7 @@ static void add_pack_to_midx(const char *full_path, size_t full_path_len,
packs->info[packs->nr].pack_name = xstrdup(file_name);
packs->info[packs->nr].orig_pack_int_id = packs->nr;
packs->info[packs->nr].expired = 0;
packs->nr++;
}
}
@ -637,13 +641,17 @@ static size_t write_midx_pack_names(struct hashfile *f,
size_t written = 0;
for (i = 0; i < num_packs; i++) {
size_t writelen = strlen(info[i].pack_name) + 1;
size_t writelen;
if (info[i].expired)
continue;
if (i && strcmp(info[i].pack_name, info[i - 1].pack_name) <= 0)
BUG("incorrect pack-file order: %s before %s",
info[i - 1].pack_name,
info[i].pack_name);
writelen = strlen(info[i].pack_name) + 1;
hashwrite(f, info[i].pack_name, writelen);
written += writelen;
}
@ -725,6 +733,11 @@ static size_t write_midx_object_offsets(struct hashfile *f, int large_offset_nee
for (i = 0; i < nr_objects; i++) {
struct pack_midx_entry *obj = list++;
if (perm[obj->pack_int_id] == PACK_EXPIRED)
BUG("object %s is in an expired pack with int-id %d",
oid_to_hex(&obj->oid),
obj->pack_int_id);
hashwrite_be32(f, perm[obj->pack_int_id]);
if (large_offset_needed && obj->offset >> 31)
@ -771,7 +784,8 @@ static size_t write_midx_large_offsets(struct hashfile *f, uint32_t nr_large_off
return written;
}
int write_midx_file(const char *object_dir)
static int write_midx_internal(const char *object_dir, struct multi_pack_index *m,
struct string_list *packs_to_drop)
{
unsigned char cur_chunk, num_chunks = 0;
char *midx_name;
@ -787,6 +801,8 @@ int write_midx_file(const char *object_dir)
struct pack_midx_entry *entries = NULL;
int large_offsets_needed = 0;
int pack_name_concat_len = 0;
int dropped_packs = 0;
int result = 0;
midx_name = get_midx_filename(object_dir);
if (safe_create_leading_directories(midx_name)) {
@ -795,7 +811,10 @@ int write_midx_file(const char *object_dir)
midx_name);
}
packs.m = load_multi_pack_index(object_dir, 1);
if (m)
packs.m = m;
else
packs.m = load_multi_pack_index(object_dir, 1);
packs.nr = 0;
packs.alloc = packs.m ? packs.m->num_packs : 16;
@ -809,13 +828,14 @@ int write_midx_file(const char *object_dir)
packs.info[packs.nr].orig_pack_int_id = i;
packs.info[packs.nr].pack_name = xstrdup(packs.m->pack_names[i]);
packs.info[packs.nr].p = NULL;
packs.info[packs.nr].expired = 0;
packs.nr++;
}
}
for_each_file_in_pack_dir(object_dir, add_pack_to_midx, &packs);
if (packs.m && packs.nr == packs.m->num_packs)
if (packs.m && packs.nr == packs.m->num_packs && !packs_to_drop)
goto cleanup;
entries = get_sorted_entries(packs.m, packs.info, packs.nr, &nr_entries);
@ -829,6 +849,34 @@ int write_midx_file(const char *object_dir)
QSORT(packs.info, packs.nr, pack_info_compare);
if (packs_to_drop && packs_to_drop->nr) {
int drop_index = 0;
int missing_drops = 0;
for (i = 0; i < packs.nr && drop_index < packs_to_drop->nr; i++) {
int cmp = strcmp(packs.info[i].pack_name,
packs_to_drop->items[drop_index].string);
if (!cmp) {
drop_index++;
packs.info[i].expired = 1;
} else if (cmp > 0) {
error(_("did not see pack-file %s to drop"),
packs_to_drop->items[drop_index].string);
drop_index++;
missing_drops++;
i--;
} else {
packs.info[i].expired = 0;
}
}
if (missing_drops) {
result = 1;
goto cleanup;
}
}
/*
* pack_perm stores a permutation between pack-int-ids from the
* previous multi-pack-index to the new one we are writing:
@ -837,11 +885,18 @@ int write_midx_file(const char *object_dir)
*/
ALLOC_ARRAY(pack_perm, packs.nr);
for (i = 0; i < packs.nr; i++) {
pack_perm[packs.info[i].orig_pack_int_id] = i;
if (packs.info[i].expired) {
dropped_packs++;
pack_perm[packs.info[i].orig_pack_int_id] = PACK_EXPIRED;
} else {
pack_perm[packs.info[i].orig_pack_int_id] = i - dropped_packs;
}
}
for (i = 0; i < packs.nr; i++)
pack_name_concat_len += strlen(packs.info[i].pack_name) + 1;
for (i = 0; i < packs.nr; i++) {
if (!packs.info[i].expired)
pack_name_concat_len += strlen(packs.info[i].pack_name) + 1;
}
if (pack_name_concat_len % MIDX_CHUNK_ALIGNMENT)
pack_name_concat_len += MIDX_CHUNK_ALIGNMENT -
@ -857,7 +912,7 @@ int write_midx_file(const char *object_dir)
cur_chunk = 0;
num_chunks = large_offsets_needed ? 5 : 4;
written = write_midx_header(f, num_chunks, packs.nr);
written = write_midx_header(f, num_chunks, packs.nr - dropped_packs);
chunk_ids[cur_chunk] = MIDX_CHUNKID_PACKNAMES;
chunk_offsets[cur_chunk] = written + (num_chunks + 1) * MIDX_CHUNKLOOKUP_WIDTH;
@ -958,7 +1013,12 @@ int write_midx_file(const char *object_dir)
free(entries);
free(pack_perm);
free(midx_name);
return 0;
return result;
}
int write_midx_file(const char *object_dir)
{
return write_midx_internal(object_dir, NULL, NULL);
}
void clear_midx_file(struct repository *r)
@ -1125,5 +1185,44 @@ int verify_midx_file(struct repository *r, const char *object_dir)
int expire_midx_packs(struct repository *r, const char *object_dir)
{
return 0;
uint32_t i, *count, result = 0;
struct string_list packs_to_drop = STRING_LIST_INIT_DUP;
struct multi_pack_index *m = load_multi_pack_index(object_dir, 1);
if (!m)
return 0;
count = xcalloc(m->num_packs, sizeof(uint32_t));
for (i = 0; i < m->num_objects; i++) {
int pack_int_id = nth_midxed_pack_int_id(m, i);
count[pack_int_id]++;
}
for (i = 0; i < m->num_packs; i++) {
char *pack_name;
if (count[i])
continue;
if (prepare_midx_pack(r, m, i))
continue;
if (m->packs[i]->pack_keep)
continue;
pack_name = xstrdup(m->packs[i]->pack_name);
close_pack(m->packs[i]);
string_list_insert(&packs_to_drop, m->pack_names[i]);
unlink_pack_path(pack_name, 0);
free(pack_name);
}
free(count);
if (packs_to_drop.nr)
result = write_midx_internal(object_dir, m, &packs_to_drop);
string_list_clear(&packs_to_drop, 0);
return result;
}

View file

@ -412,4 +412,24 @@ test_expect_success 'expire does not remove any packs' '
)
'
test_expect_success 'expire removes unreferenced packs' '
(
cd dup &&
git pack-objects --revs .git/objects/pack/pack-combined <<-EOF &&
refs/heads/A
^refs/heads/C
EOF
git multi-pack-index write &&
ls .git/objects/pack | grep -v -e pack-[AB] >expect &&
git multi-pack-index expire &&
ls .git/objects/pack >actual &&
test_cmp expect actual &&
ls .git/objects/pack/ | grep idx >expect-idx &&
test-tool read-midx .git/objects | grep idx >actual-midx &&
test_cmp expect-idx actual-midx &&
git multi-pack-index verify &&
git fsck
)
'
test_done