@matheusbsbs / matheus-bagliano / commits / 59552fb3e2

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midx: traverse the local MIDX first

When a repository has an alternate object directory configured, callers can traverse through each alternate's MIDX by walking the '->next' pointer. But, when 'prepare_multi_pack_index_one()' loads multiple MIDXs, it places the new ones at the front of this pointer chain, not at the end. This can be confusing for callers such as 'git repack -ad', causing test failures like in t7700.6 with 'GIT_TEST_MULTI_PACK_INDEX=1'. The occurs when dropping a pack known to the local MIDX with alternates configured that have their own MIDX. Since the alternate's MIDX is returned via 'get_multi_pack_index()', 'midx_contains_pack()' returns true (which is correct, since it traverses through the '->next' pointer to find the MIDX in the chain that does contain the requested object). But, we call 'clear_midx_file()' on 'the_repository', which drops the MIDX at the path of the first MIDX in the chain, which (in the case of t7700.6 is the one in the alternate). This patch addresses that by: - placing the local MIDX first in the chain when calling 'prepare_multi_pack_index_one()', and - introducing a new 'get_local_multi_pack_index()', which explicitly returns the repository-local MIDX, if any. Don't impose an additional order on the MIDX's '->next' pointer beyond that the first item in the chain must be local if one exists so that we avoid a quadratic insertion. Likewise, use 'get_local_multi_pack_index()' in 'remove_redundant_pack()' to fix the formerly broken t7700.6 when run with 'GIT_TEST_MULTI_PACK_INDEX=1'. Finally, note that the MIDX ordering invariant is only preserved by the insertion order in 'prepare_packed_git()', which traverses through the ODB's '->next' pointer, meaning we visit the local object store first. This fragility makes this an undesirable long-term solution if more callers are added, but it is acceptable for now since this is the only caller. Helped-by: Jeff King <peff@peff.net> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Taylor Blau committed Aug 28, 2020 at 16:22 UTC 59552fb3e2161648952a8a1240ffef57eff9a262

4 files changed +19 -3

builtin/repack.c

+1 -1

@@ -133,7 +133,7 @@ static void get_non_kept_pack_filenames(struct string_list *fname_list,

133 static void remove_redundant_pack(const char *dir_name, const char *base_name)

134 {

135 struct strbuf buf = STRBUF_INIT;

136 - struct multi_pack_index *m = get_multi_pack_index(the_repository);

136 + struct multi_pack_index *m = get_local_multi_pack_index(the_repository);

137 strbuf_addf(&buf, "%s.pack", base_name);

138 if (m && midx_contains_pack(m, buf.buf))

139 clear_midx_file(the_repository);

midx.c

+6 -2

@@ -402,8 +402,12 @@ int prepare_multi_pack_index_one(struct repository *r, const char *object_dir, i

402 m = load_multi_pack_index(object_dir, local);

403

404 if (m) {

405 - m->next = r->objects->multi_pack_index;

406 - r->objects->multi_pack_index = m;

405 + struct multi_pack_index *mp = r->objects->multi_pack_index;

406 + if (mp) {

407 + m->next = mp->next;

408 + mp->next = m;

409 + } else

410 + r->objects->multi_pack_index = m;

411 return 1;

412 }

413

packfile.c

+11

@@ -1027,6 +1027,17 @@ struct multi_pack_index *get_multi_pack_index(struct repository *r)

1027 return r->objects->multi_pack_index;

1028 }

1029

1030 +struct multi_pack_index *get_local_multi_pack_index(struct repository *r)

1031 +{

1032 + struct multi_pack_index *m = get_multi_pack_index(r);

1033 +

1034 + /* no need to iterate; we always put the local one first (if any) */

1035 + if (m && m->local)

1036 + return m;

1037 +

1038 + return NULL;

1039 +}

1040 +

1041 struct packed_git *get_all_packs(struct repository *r)

1042 {

1043 struct multi_pack_index *m;

packfile.h

@@ -57,6 +57,7 @@ void install_packed_git(struct repository *r, struct packed_git *pack);

57 struct packed_git *get_packed_git(struct repository *r);

58 struct list_head *get_packed_git_mru(struct repository *r);

59 struct multi_pack_index *get_multi_pack_index(struct repository *r);

60 +struct multi_pack_index *get_local_multi_pack_index(struct repository *r);

61 struct packed_git *get_all_packs(struct repository *r);

63 /*