From: Jonathan Nieder <jrnieder@gmail.com>
To: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Cc: git@vger.kernel.org, me@ttaylorr.com, peff@peff.net,
gitster@pobox.com, abhishekkumar8222@gmail.com,
Derrick Stolee <stolee@gmail.com>,
Taylor Blau <ttaylorr@github.com>,
Derrick Stolee <derrickstolee@github.com>,
Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH v2 2/6] commit-graph: always parse before commit_graph_data_at()
Date: Tue, 2 Feb 2021 17:08:15 -0800 [thread overview]
Message-ID: <YBn3fxFe978Up5Ly@google.com> (raw)
In-Reply-To: <454b183b9ba502da7f40dc36aaa95cc3d12b5c2f.1612234883.git.gitgitgadget@gmail.com>
Derrick Stolee wrote:
> There is a subtle failure happening when computing corrected commit
> dates with --split enabled. It requires a base layer needing the
> generation_data_overflow chunk. Then, the next layer on top
> erroneously thinks it needs an overflow chunk due to a bug leading
> to recalculating all reachable generation numbers. The output of
> the failure is
>
> BUG: commit-graph.c:1912: expected to write 8 bytes to
> chunk 47444f56, but wrote 0 instead
At Google, we're running into a commit-graph issue that appears to
have also arrived as part of this last week's rollout. This one is a
bit worse --- it is reproducible for affected users and stops them
from being able to do day-to-day development:
$ git pull
remote: Finding sources: 100% (33/33)
remote: Total 33 (delta 18), reused 33 (delta 18)
Unpacking objects: 100% (33/33), 27.44 KiB | 460.00 KiB/s, done.
From https://example.com/path/to/repo
05ba0d775..279e4e6d0 master -> origin/master
BUG: commit-reach.c:64: bad generation skip 29e3 > 628 at 62abdabd1be00ebadbf73061ecf72b35042338e3
error: merge died of signal 6
"git commit-graph verify" agrees that the generation numbers are wrong:
$ git commit-graph verify
commit-graph generation for commit 4290b2214cdf50263118322735347d151715a272 is 3 != 1586
Verifying commits in commit graph: 100% (1/1), done.
commit-graph generation for commit b6c73a8472c7cb503cce0668849150a4b4329230 is 1576 != 10724
Verifying commits in commit graph: 100% (10/10), done.
Verifying commits in commit graph: 100% (88/88), done.
Verifying commits in commit graph: 100% (208/208), done.
Verifying commits in commit graph: 100% (592/592), done.
Verifying commits in commit graph: 100% (1567/1567), done.
Verifying commits in commit graph: 100% (8358/8358), done.
We have some examples of repositories that were corrupted this way,
but we didn't catch them in the act of corruption --- it started
happening to several users with this release so we immediately rolled
back.
Questions:
- is this likely to be due to the same cause, or is it orthogonal?
- what is the recommended way to recover from this state? "git fsck"
shows the repositories to have no problems. "git help commit-graph"
doesn't show a command for users to use; is
`rm -fr .git/objects/info/commit-graphs/` the recommended recovery
command?
- is there configuration or a patch we can roll out to help affected
users recover from this state?
Thanks,
Jonathan
next prev parent reply other threads:[~2021-02-03 1:09 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-01 17:15 [PATCH 0/5] Generation Number v2: Fix a tricky split graph bug Derrick Stolee via GitGitGadget
2021-02-01 17:15 ` [PATCH 1/5] commit-graph: use repo_parse_commit Derrick Stolee via GitGitGadget
2021-02-01 17:32 ` Taylor Blau
2021-02-01 17:15 ` [PATCH 2/5] commit-graph: always parse before commit_graph_data_at() Derrick Stolee via GitGitGadget
2021-02-01 18:44 ` Junio C Hamano
2021-02-01 17:15 ` [PATCH 3/5] commit-graph: validate layers for generation data Derrick Stolee via GitGitGadget
2021-02-01 17:39 ` Taylor Blau
2021-02-01 18:10 ` Derrick Stolee
2021-02-01 17:15 ` [PATCH 4/5] commit-graph: be extra careful about mixed generations Derrick Stolee via GitGitGadget
2021-02-01 18:04 ` Taylor Blau
2021-02-01 18:13 ` Derrick Stolee
2021-02-01 18:55 ` Junio C Hamano
2021-02-01 17:15 ` [PATCH 5/5] commit-graph: prepare commit graph Derrick Stolee via GitGitGadget
2021-02-01 18:25 ` Taylor Blau
2021-02-02 3:01 ` [PATCH v2 0/6] Generation Number v2: Fix a tricky split graph bug Derrick Stolee via GitGitGadget
2021-02-02 3:01 ` [PATCH v2 1/6] commit-graph: use repo_parse_commit Derrick Stolee via GitGitGadget
2021-02-02 3:01 ` [PATCH v2 2/6] commit-graph: always parse before commit_graph_data_at() Derrick Stolee via GitGitGadget
2021-02-03 1:08 ` Jonathan Nieder [this message]
2021-02-03 1:35 ` Derrick Stolee
2021-02-03 1:48 ` Jonathan Nieder
2021-02-03 3:07 ` Derrick Stolee
2021-02-03 15:34 ` Taylor Blau
2021-02-03 17:37 ` Eric Sunshine
2021-02-03 18:41 ` Junio C Hamano
2021-02-03 21:08 ` Taylor Blau
2021-02-03 2:06 ` Junio C Hamano
2021-02-03 3:09 ` Derrick Stolee
2021-02-07 19:04 ` SZEDER Gábor
2021-02-07 20:12 ` Junio C Hamano
2021-02-08 2:01 ` Derrick Stolee
2021-02-08 5:55 ` Junio C Hamano
2021-02-02 3:01 ` [PATCH v2 3/6] commit-graph: validate layers for generation data Derrick Stolee via GitGitGadget
2021-02-02 3:01 ` [PATCH v2 4/6] commit-graph: compute generations separately Derrick Stolee via GitGitGadget
2021-02-02 3:01 ` [PATCH v2 5/6] commit-graph: be extra careful about mixed generations Derrick Stolee via GitGitGadget
2021-02-02 3:01 ` [PATCH v2 6/6] commit-graph: prepare commit graph Derrick Stolee via GitGitGadget
2021-02-02 3:08 ` [PATCH v2 0/6] Generation Number v2: Fix a tricky split graph bug Taylor Blau
2021-02-11 4:44 ` Abhishek Kumar
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