From: Jonathan Tan <jonathantanmy@google.com>
To: me@ttaylorr.com
Cc: jonathantanmy@google.com, git@vger.kernel.org, gitster@pobox.com,
stolee@gmail.com
Subject: Re: [PATCH v3 3/9] pack-revindex.c: instrument loading on-disk reverse index
Date: Mon, 24 Jan 2022 09:53:22 -0800 [thread overview]
Message-ID: <20220124175322.2433200-1-jonathantanmy@google.com> (raw)
In-Reply-To: <YenfyK8wE5VXuHoo@nand.local>
Taylor Blau <me@ttaylorr.com> writes:
> On Thu, Jan 20, 2022 at 10:15:45AM -0800, Jonathan Tan wrote:
> > Taylor Blau <me@ttaylorr.com> writes:
> > > In a subsequent commit, we'll use the MIDX's new 'RIDX' chunk as a
> > > source for the reverse index's data. But it will be useful for tests to
> > > be able to determine whether the reverse index was loaded from the
> > > separate .rev file, or from a chunk within the MIDX.
> >
> > As for this patch and all subsequent patches, we (at $DAYJOB) discussed
> > during our Review Club the idea of not supporting .rev files altogether.
> > Firstly, because of this bug, we cannot fully trust .rev files anymore.
> > And even if we decided to trust it (or to trust it after some
> > verification step that I can't think of), that file would only be useful
> > for a short time until a regularly scheduled maintenance step
> > regenerates the bitmaps anyway.
>
> I assume that you're talking about MIDX .rev files here, not the usual
> packfile ones which are only related in the sense that they follow the
> same file format, but are otherwise distinct.
Ah, yes - sorry for the lack of clarity.
> We could drop support for the MIDX .rev files, but I do not think it is
> a very good idea. There are tagged versions of Git which have .rev files
> out in the wild, so suddenly dropping support for them would mean that
> existing repositories would no longer be able to read their multi-pack
> bitmaps after upgrading to a version of Git which doesn't include
> support for separate .rev files.
>
> So there are some backwards compatibility concerns there, and I think
> that that alone means we can't do it.
>
> In order to maintain good test coverage of the soon-to-be deprecated
> external MIDX .rev files, this patch series adds some additional testing
> knobs to make sure that we're thoroughly exercising both cases.
>
> It's somewhat unfortunate that we are stuck with on-disk .rev files for
> MIDXs, since it opened the door for this bug to manifest itself. But I
> am not comfortable getting rid of them at this point.
Thanks for this explanation of your viewpoint. I still think that it's
fine to drop support for reading something that a tagged and released
version of Git has created, since it is a potentially wrong cache (and
does not contain any new information), but what I can do is to review
the rest of this patch set assuming that we want to keep support for the
on-disk MIDX .rev files, so I'll do that. This way, if we decide to keep
support for these files, I would be happy to see this patch set merged.
next prev parent reply other threads:[~2022-01-24 17:53 UTC|newest]
Thread overview: 87+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-08 19:26 [PATCH 0/2] midx: prevent bitmap corruption when permuting pack order Taylor Blau
2021-12-08 19:26 ` [PATCH 1/2] t5326: demonstrate bitmap corruption after permutation Taylor Blau
2021-12-08 19:26 ` [PATCH 2/2] midx.c: make changing the preferred pack safe Taylor Blau
2021-12-08 19:30 ` [PATCH 0/2] midx: prevent bitmap corruption when permuting pack order Derrick Stolee
2021-12-08 19:55 ` Jeff King
2021-12-10 18:36 ` Taylor Blau
2021-12-10 22:31 ` Taylor Blau
2021-12-11 1:39 ` Taylor Blau
2021-12-13 14:00 ` Derrick Stolee
2021-12-13 14:31 ` Taylor Blau
2021-12-14 1:55 ` [PATCH v2 0/8] " Taylor Blau
2021-12-14 1:55 ` [PATCH v2 1/8] t5326: demonstrate bitmap corruption after permutation Taylor Blau
2021-12-14 1:55 ` [PATCH v2 2/8] midx.c: make changing the preferred pack safe Taylor Blau
2021-12-14 1:55 ` [PATCH v2 3/8] pack-revindex.c: instrument loading on-disk reverse index Taylor Blau
2021-12-14 1:55 ` [PATCH v2 4/8] t5326: drop unnecessary setup Taylor Blau
2021-12-14 1:55 ` [PATCH v2 5/8] t5326: extract `test_rev_exists` Taylor Blau
2021-12-20 18:33 ` Derrick Stolee
2022-01-04 15:33 ` Taylor Blau
2021-12-14 1:55 ` [PATCH v2 6/8] t5326: move tests to t/lib-bitmap.sh Taylor Blau
2021-12-14 1:55 ` [PATCH v2 7/8] t/lib-bitmap.sh: parameterize tests over reverse index source Taylor Blau
2021-12-14 1:55 ` [PATCH v2 8/8] midx: read `RIDX` chunk when present Taylor Blau
2021-12-20 18:42 ` Derrick Stolee
2022-01-04 15:21 ` Taylor Blau
2021-12-15 19:46 ` [PATCH v2 0/8] midx: prevent bitmap corruption when permuting pack order Junio C Hamano
2021-12-15 21:37 ` Taylor Blau
2021-12-15 22:17 ` Junio C Hamano
2021-12-15 22:55 ` Junio C Hamano
2021-12-20 18:51 ` Derrick Stolee
2021-12-20 19:52 ` Taylor Blau
2021-12-20 20:09 ` Derrick Stolee
2021-12-15 22:58 ` Junio C Hamano
2021-12-15 23:01 ` Taylor Blau
2022-01-04 18:15 ` [PATCH v3 0/9] " Taylor Blau
2022-01-04 18:15 ` [PATCH v3 1/9] t5326: demonstrate bitmap corruption after permutation Taylor Blau
2022-01-20 17:55 ` Jonathan Tan
2022-01-20 22:11 ` Taylor Blau
2022-01-20 22:41 ` Junio C Hamano
2022-01-20 22:46 ` Taylor Blau
2022-01-24 17:40 ` Jonathan Tan
2022-01-04 18:15 ` [PATCH v3 2/9] midx.c: make changing the preferred pack safe Taylor Blau
2022-01-14 21:35 ` Junio C Hamano
2022-01-14 21:43 ` Junio C Hamano
2022-01-15 0:59 ` Taylor Blau
2022-01-15 6:27 ` Junio C Hamano
2022-01-20 18:08 ` Jonathan Tan
2022-01-20 22:13 ` Taylor Blau
2022-01-04 18:15 ` [PATCH v3 3/9] pack-revindex.c: instrument loading on-disk reverse index Taylor Blau
2022-01-20 18:15 ` Jonathan Tan
2022-01-20 22:18 ` Taylor Blau
2022-01-24 17:53 ` Jonathan Tan [this message]
2022-01-04 18:15 ` [PATCH v3 4/9] t5326: drop unnecessary setup Taylor Blau
2022-01-04 18:15 ` [PATCH v3 5/9] t5326: extract `test_rev_exists` Taylor Blau
2022-01-04 18:15 ` [PATCH v3 6/9] t5326: move tests to t/lib-bitmap.sh Taylor Blau
2022-01-04 18:15 ` [PATCH v3 7/9] t/lib-bitmap.sh: parameterize tests over reverse index source Taylor Blau
2022-01-24 19:15 ` Jonathan Tan
2022-01-25 21:40 ` Taylor Blau
2022-01-26 21:00 ` Jonathan Tan
2022-01-04 18:16 ` [PATCH v3 8/9] midx: read `RIDX` chunk when present Taylor Blau
2022-01-24 19:27 ` Jonathan Tan
2022-01-25 21:45 ` Taylor Blau
2022-01-26 21:28 ` Jonathan Tan
2022-01-04 18:16 ` [PATCH v3 9/9] pack-bitmap.c: gracefully fallback after opening pack/MIDX Taylor Blau
2022-01-24 19:29 ` Jonathan Tan
2022-01-25 21:46 ` Taylor Blau
2022-01-25 22:40 ` [PATCH v4 0/9] midx: prevent bitmap corruption when permuting pack order Taylor Blau
2022-01-25 22:41 ` [PATCH v4 1/9] t5326: demonstrate bitmap corruption after permutation Taylor Blau
2022-01-26 15:01 ` Ævar Arnfjörð Bjarmason
2022-01-26 20:18 ` Taylor Blau
2022-01-25 22:41 ` [PATCH v4 2/9] midx.c: make changing the preferred pack safe Taylor Blau
2022-01-25 22:41 ` [PATCH v4 3/9] pack-revindex.c: instrument loading on-disk reverse index Taylor Blau
2022-01-26 15:03 ` Ævar Arnfjörð Bjarmason
2022-01-25 22:41 ` [PATCH v4 4/9] t5326: drop unnecessary setup Taylor Blau
2022-01-25 22:41 ` [PATCH v4 5/9] t5326: extract `test_rev_exists` Taylor Blau
2022-01-26 15:04 ` Ævar Arnfjörð Bjarmason
2022-01-26 20:19 ` Taylor Blau
2022-01-25 22:41 ` [PATCH v4 6/9] t5326: move tests to t/lib-bitmap.sh Taylor Blau
2022-01-25 22:41 ` [PATCH v4 7/9] t/lib-bitmap.sh: parameterize tests over reverse index source Taylor Blau
2022-01-25 22:41 ` [PATCH v4 8/9] midx: read `RIDX` chunk when present Taylor Blau
2022-01-26 15:10 ` Ævar Arnfjörð Bjarmason
2022-01-26 20:23 ` Taylor Blau
2022-01-25 22:41 ` [PATCH v4 9/9] pack-bitmap.c: gracefully fallback after opening pack/MIDX Taylor Blau
2022-01-26 15:08 ` Ævar Arnfjörð Bjarmason
2022-01-26 17:50 ` [PATCH v4 0/9] midx: prevent bitmap corruption when permuting pack order Ævar Arnfjörð Bjarmason
2022-01-26 20:24 ` Taylor Blau
2022-01-27 17:15 ` Jonathan Tan
2022-02-24 22:50 ` Taylor Blau
2022-01-27 14:13 ` Derrick Stolee
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220124175322.2433200-1-jonathantanmy@google.com \
--to=jonathantanmy@google.com \
--cc=git@vger.kernel.org \
--cc=gitster@pobox.com \
--cc=me@ttaylorr.com \
--cc=stolee@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).