Taylor Blau wrote:
> A subsequent patch will teach `want_object_in_pack()` to set its
> `*found_pack` and `*found_offset` poitners to NULL when the provided
s/poitners/pointers
> pack does not pass the `is_pack_valid()` check.
>
> The `--stdin-packs` mode of `pack-objects` is not quite prepared to
> handle this. To prepare it for this change, do the following two things:
>
> - Ensure provided packs pass the `is_pack_valid()` check when
> collecting the caller-provided packs into the "included" and
> "excluded" lists.
>
Is the 'is_pack_valid()' check happening for the "excluded" packs? It looks
like you only added it for the packs in the "included" list in this patch.
> - Gracefully handle any _invalid_ packs being passed to
> `want_object_in_pack()`.
>
> Calling `is_pack_valid()` early on makes it substantially less likely
> that we will have to deal with a pack going away, since we'll have an
> open file descriptor on its contents much earlier.
>
> But even packs with open descriptors can become invalid in the future if
> we (a) hit our open descriptor limit, forcing us to close some open
> packs, and (b) one of those just-closed packs has gone away in the
> meantime.
>
> `add_object_entry_from_pack()` depends on having a non-NULL
> `*found_pack`, since it passes that pointer to `packed_object_info()`,
> meaning that we would SEGV if the pointer became NULL (like we propose
> to do in `want_object_in_pack()` in the following patch).
>
> But avoiding calling `packed_object_info()` entirely is OK, too, since
> its only purpose is to identify which objects in the included packs are
> commits, so that they can form the tips of the advisory traversal used
> to discover the object namehashes.
>
> Failing to do this means that at worst we will produce lower-quality
> deltas, but it does not prevent us from generating the pack as long as
> we can find a copy of each object from the disappearing pack in some
> other part of the repository.
>
The rest of this makes sense and (as far as I can tell) lines up with the
implementation below.
> Co-authored-by: Victoria Dye <vdye@xxxxxxxxxx>
> Signed-off-by: Taylor Blau <me@xxxxxxxxxxxx>
> ---
> builtin/pack-objects.c | 35 ++++++++++++++++++++---------------
> 1 file changed, 20 insertions(+), 15 deletions(-)
>
> diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
> index ec3193fd95..ffeaecd1d8 100644
> --- a/builtin/pack-objects.c
> +++ b/builtin/pack-objects.c
> @@ -3201,10 +3201,8 @@ static int add_object_entry_from_pack(const struct object_id *oid,
> uint32_t pos,
> void *_data)
> {
> - struct rev_info *revs = _data;
> - struct object_info oi = OBJECT_INFO_INIT;
> off_t ofs;
> - enum object_type type;
> + enum object_type type = OBJ_NONE;
>
> display_progress(progress_state, ++nr_seen);
>
> @@ -3215,20 +3213,25 @@ static int add_object_entry_from_pack(const struct object_id *oid,
> if (!want_object_in_pack(oid, 0, &p, &ofs))
> return 0;
>
> - oi.typep = &type;
> - if (packed_object_info(the_repository, p, ofs, &oi) < 0)
> - die(_("could not get type of object %s in pack %s"),
> - oid_to_hex(oid), p->pack_name);
> - else if (type == OBJ_COMMIT) {
> - /*
> - * commits in included packs are used as starting points for the
> - * subsequent revision walk
> - */
> - add_pending_oid(revs, NULL, oid, 0);
> + if (p) {
> + struct rev_info *revs = _data;
> + struct object_info oi = OBJECT_INFO_INIT;
> +
> + oi.typep = &type;
> + if (packed_object_info(the_repository, p, ofs, &oi) < 0) {
> + die(_("could not get type of object %s in pack %s"),
> + oid_to_hex(oid), p->pack_name);
> + } else if (type == OBJ_COMMIT) {
> + /*
> + * commits in included packs are used as starting points for the
> + * subsequent revision walk
> + */
> + add_pending_oid(revs, NULL, oid, 0);
> + }
> +
> + stdin_packs_found_nr++;
> }
>
> - stdin_packs_found_nr++;
> -
> create_object_entry(oid, type, 0, 0, 0, p, ofs);
>
> return 0;
> @@ -3346,6 +3349,8 @@ static void read_packs_list_from_stdin(void)
> struct packed_git *p = item->util;
> if (!p)
> die(_("could not find pack '%s'"), item->string);
> + if (!is_pack_valid(p))
> + die(_("packfile %s cannot be accessed"), p->pack_name);
> }
>
> /*
