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From: Jonathan Tan <jonathantanmy@google.com>
To: me@ttaylorr.com
Cc: git@vger.kernel.org, peff@peff.net, gitster@pobox.com,
	avarab@gmail.com, Jonathan Tan <jonathantanmy@google.com>
Subject: Re: [PATCH v2 3/8] midx: preliminary support for `--refs-snapshot`
Date: Wed, 22 Sep 2021 16:00:12 -0700	[thread overview]
Message-ID: <20210922230012.2608849-1-jonathantanmy@google.com> (raw)
In-Reply-To: <42f1ae9edeb55d8e1b0c8f2c3110e9c8326a5fc1.1631730270.git.me@ttaylorr.com>

> This approach will cause a problem when multi-pack bitmaps are able to
> be generated from `git repack`, since the reference tips can change
> during the repack. Even though we ignore commits that don't exist in
> the MIDX (when doing a scan of the ref tips), it's possible that a
> commit in the MIDX reaches something that isn't.
> 
> This can happen when a multi-pack index contains some pack which refers
> to loose objects (which by definition aren't included in the multi-pack
> index).
> 
> By taking a snapshot of the references before we start repacking, we can
> close that race window.

I can understand why we want the refs to remain the same both for the
MIDX generation and the MIDX bitmap generation (one reason that comes to
mind is how we select the commits for which to generate bitmaps), but I
don't understand what referring to loose objects has to do with it. I
think that using the same set of refs for MIDX generation and bitmap
generation is a good enough reason to do this, and we don't need to
mention loose objects.

The patch itself looks good.

  parent reply	other threads:[~2021-09-22 23:00 UTC|newest]

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-11  3:32 [PATCH 0/8] repack: introduce `--write-midx` Taylor Blau
2021-09-11  3:32 ` [PATCH 1/8] midx: expose 'write_midx_file_only()' publicly Taylor Blau
2021-09-11  5:00   ` Junio C Hamano
2021-09-11 16:17     ` Taylor Blau
2021-09-11 10:07   ` Ævar Arnfjörð Bjarmason
2021-09-11 16:21     ` Taylor Blau
2021-09-11  3:32 ` [PATCH 2/8] builtin/multi-pack-index.c: support --stdin-packs mode Taylor Blau
2021-09-11 10:05   ` Ævar Arnfjörð Bjarmason
2021-09-11 16:25     ` Taylor Blau
2021-09-11 16:28       ` Taylor Blau
2021-09-12  2:08       ` Eric Sunshine
2021-09-12  2:21         ` Taylor Blau
2021-09-12 15:15           ` Ævar Arnfjörð Bjarmason
2021-09-12 22:30             ` Junio C Hamano
2021-09-12 22:32               ` Ævar Arnfjörð Bjarmason
2021-09-14 19:02       ` Jeff King
2021-09-14 23:48         ` Taylor Blau
2021-09-15  1:55           ` Eric Sunshine
2021-09-11  3:32 ` [PATCH 3/8] midx: preliminary support for `--refs-snapshot` Taylor Blau
2021-09-11  3:32 ` [PATCH 4/8] builtin/repack.c: keep track of existing packs unconditionally Taylor Blau
2021-09-11  3:32 ` [PATCH 5/8] builtin/repack.c: extract showing progress to a variable Taylor Blau
2021-09-11  3:32 ` [PATCH 6/8] builtin/repack.c: support writing a MIDX while repacking Taylor Blau
2021-09-11  3:32 ` [PATCH 7/8] builtin/repack.c: make largest pack preferred Taylor Blau
2021-09-11 10:17   ` Ævar Arnfjörð Bjarmason
2021-09-11 16:35     ` Taylor Blau
2021-09-11  3:32 ` [PATCH 8/8] builtin/repack.c: pass `--refs-snapshot` when writing bitmaps Taylor Blau
2021-09-11 10:27   ` Ævar Arnfjörð Bjarmason
2021-09-11 11:19     ` Ævar Arnfjörð Bjarmason
2021-09-11 16:51       ` Taylor Blau
2021-09-14 18:55         ` Jeff King
2021-09-14 23:34           ` Taylor Blau
2021-09-14 23:56             ` Ævar Arnfjörð Bjarmason
2021-09-15  4:31               ` Taylor Blau
2021-09-11 16:49     ` Taylor Blau
2021-09-15 18:24 ` [PATCH v2 0/8] repack: introduce `--write-midx` Taylor Blau
2021-09-15 18:24   ` [PATCH v2 1/8] midx: expose `write_midx_file_only()` publicly Taylor Blau
2021-09-22 23:14     ` Jonathan Tan
2021-09-23  3:09       ` Taylor Blau
2021-09-15 18:24   ` [PATCH v2 2/8] builtin/multi-pack-index.c: support `--stdin-packs` mode Taylor Blau
2021-09-22 22:29     ` Josh Steadmon
2021-09-23  2:03       ` Taylor Blau
2021-09-22 23:11     ` Jonathan Tan
2021-09-23  2:06       ` Taylor Blau
2021-09-15 18:24   ` [PATCH v2 3/8] midx: preliminary support for `--refs-snapshot` Taylor Blau
2021-09-22 22:34     ` Josh Steadmon
2021-09-23  2:08       ` Taylor Blau
2021-09-22 23:00     ` Jonathan Tan [this message]
2021-09-23  2:18       ` Taylor Blau
2021-09-15 18:24   ` [PATCH v2 4/8] builtin/repack.c: keep track of existing packs unconditionally Taylor Blau
2021-09-22 22:56     ` Jonathan Tan
2021-09-23  2:59       ` Taylor Blau
2021-09-15 18:24   ` [PATCH v2 5/8] builtin/repack.c: extract showing progress to a variable Taylor Blau
2021-09-15 18:24   ` [PATCH v2 6/8] builtin/repack.c: support writing a MIDX while repacking Taylor Blau
2021-09-22 22:39     ` Jonathan Tan
2021-09-23  2:40       ` Taylor Blau
2021-09-15 18:24   ` [PATCH v2 7/8] builtin/repack.c: make largest pack preferred Taylor Blau
2021-09-15 18:24   ` [PATCH v2 8/8] builtin/repack.c: pass `--refs-snapshot` when writing bitmaps Taylor Blau
2021-09-24 18:22     ` Jonathan Tan
2021-10-01 22:38       ` Taylor Blau
2021-09-15 19:22   ` [PATCH v2 0/8] repack: introduce `--write-midx` Junio C Hamano
2021-09-15 19:29     ` Junio C Hamano
2021-09-15 21:19       ` Taylor Blau
2021-09-16 22:16         ` Junio C Hamano
2021-09-29  1:54   ` [PATCH v3 0/9] " Taylor Blau
2021-09-29  1:55     ` [PATCH v3 1/9] midx: expose `write_midx_file_only()` publicly Taylor Blau
2021-09-29  1:55     ` [PATCH v3 2/9] builtin/multi-pack-index.c: support `--stdin-packs` mode Taylor Blau
2021-09-29  1:55     ` [PATCH v3 3/9] midx: preliminary support for `--refs-snapshot` Taylor Blau
2021-09-29  1:55     ` [PATCH v3 4/9] builtin/repack.c: keep track of existing packs unconditionally Taylor Blau
2021-09-29  1:55     ` [PATCH v3 5/9] builtin/repack.c: rename variables that deal with non-kept packs Taylor Blau
2021-09-29  1:55     ` [PATCH v3 6/9] builtin/repack.c: extract showing progress to a variable Taylor Blau
2021-09-29  1:55     ` [PATCH v3 7/9] builtin/repack.c: support writing a MIDX while repacking Taylor Blau
2021-09-29  1:55     ` [PATCH v3 8/9] builtin/repack.c: make largest pack preferred Taylor Blau
2021-09-29  1:55     ` [PATCH v3 9/9] builtin/repack.c: pass `--refs-snapshot` when writing bitmaps Taylor Blau
2021-09-29  4:24     ` [PATCH v3 0/9] repack: introduce `--write-midx` Junio C Hamano
2021-10-01 20:01     ` Jonathan Tan
2021-10-01 22:40       ` Taylor Blau

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