From: Haiyng Tan <haiyangtand@gmail.com>
To: git@vger.kernel.org, chiyutianyi@gmail.com
Cc: ps@pks.im, jonathantanmy@google.com
Subject: Re: An endless loop fetching issue with partial clone, alternates and commit graph
Date: Tue, 14 Jun 2022 15:25:13 +0800 [thread overview]
Message-ID: <CANe9W27GVn-w1WSZNTxh5SKEMzHGEZQCF48vmbvMi4AUEg12yQ@mail.gmail.com> (raw)
On Mon, 13 Jun 2022 00:17:07 +0800, Han Xin wrote:
> We found an issue that could create an endless loop where alternates
> objects are used improperly.
>
> While do fetching in a partial cloned repository with a commit graph,
> deref_without_lazy_fetch_extended() will call lookup_commit_in_graph()
> to find the commit object. We can found the code in commit-graph.c:
>
> struct commit *lookup_commit_in_graph(struct repository *repo, const struct object_id *id)
> {
> …
> if (!search_commit_pos_in_graph(id, repo->objects->commit_graph, &pos))
> return NULL;
> if (!repo_has_object_file(repo, id))
> return NULL;
> If we found the object in the commit graph, but missing it in the repository,
> we will go into an endless loop:
> git fetch -> deref_without_lazy_fetch_extended() ->
> lookup_commit_in_graph() -> repo_has_object_file() ->
> promisor_remote_get_direct() -> fetch_objects() ->
> git fetch
>
> I know that the reason for this issue is due to improper use of
> alternates, we can ensure that objects will not be lost by maintaining
> all the references. But shouldn't we do something about this unusual
> usage, it will cause a fetch bombardment of the remote git service.
>
> We can reproduce this issue with the following test case, it will
> generate a lot of git processes, please be careful to stop it.
> ———————————————————————————
> #!/bin/sh
>
> test_description='test for an endless loop fetching’
>
> GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
> export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
>
> . ./test-lib.sh
>
> test_expect_success 'setup’ ‘
> git init --bare dest.git &&
> test_commit one &&
> git checkout -b testbranch &&
> test_commit two &&
> git push dest.git --all
> '
>
> test_expect_success 'prepare a alternates repository without testbranch' '
> git clone -b $GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME dest.git alternates &&
> oid=$(git -C alternates rev-parse refs/remotes/origin/testbranch) &&
> git -C alternates update-ref -d refs/remotes/origin/testbranch &&
> git -C alternates gc --prune=now
> '
>
> test_expect_success 'prepare a repository with commit-graph' '
> git init source &&
> echo "$(pwd)/dest.git/objects" >source/.git/objects/info/alternates &&
> git -C source remote add origin "$(pwd)/dest.git" &&
> git -C source config remote.origin.promisor true &&
> git -C source config remote.origin.partialclonefilter blob:none &&
> git -C source fetch origin &&
> (
> cd source &&
> test_commit three &&
> git -c gc.writeCommitGraph=true gc
> )
> '
>
> test_expect_success 'change alternates' '
> echo "$(pwd)/alternates/.git/objects" >source/.git/objects/info/alternates &&
> # this will bring an endless loop fetching
> git -C source fetch origin $oid
> '
>
> test_done
>
> ------------------------------------------------------
>
> Thanks
> -Han Xin
I think it's caused by using lazy-fetch in deref_without_lazy_fetch_extended().
In lookup_commit_in_graph(), lazy-fetch is initiated by
repo_has_object_file() used.
has_object() should be used, it's no-lazy-fetch.
next reply other threads:[~2022-06-14 7:25 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-14 7:25 Haiyng Tan [this message]
2022-06-15 2:18 ` An endless loop fetching issue with partial clone, alternates and commit graph Taylor Blau
2022-06-16 3:38 ` [RFC PATCH 0/2] " Han Xin
2022-06-16 3:38 ` [RFC PATCH 1/2] commit-graph.c: add "flags" to lookup_commit_in_graph() Han Xin
2022-06-16 3:38 ` [RFC PATCH 2/2] fetch-pack.c: pass "oi_flags" " Han Xin
2022-06-17 21:47 ` [RFC PATCH 0/2] Re: An endless loop fetching issue with partial clone, alternates and commit graph Jonathan Tan
2022-06-18 3:01 ` [PATCH v1] commit-graph.c: no lazy fetch in lookup_commit_in_graph() Han Xin
2022-06-20 7:07 ` Patrick Steinhardt
2022-06-20 8:53 ` [External] " 欣韩
2022-06-20 9:05 ` Patrick Steinhardt
2022-06-21 18:23 ` Jonathan Tan
2022-06-22 3:17 ` Han Xin
2022-06-24 5:27 ` [PATCH v2 0/2] " Han Xin
2022-06-24 5:27 ` [PATCH v2 1/2] test-lib.sh: add limited processes to test-lib Han Xin
2022-06-24 16:03 ` Junio C Hamano
2022-06-25 1:35 ` Han Xin
2022-06-27 12:22 ` Junio C Hamano
2022-06-24 5:27 ` [PATCH v2 2/2] commit-graph.c: no lazy fetch in lookup_commit_in_graph() Han Xin
2022-06-24 16:56 ` Junio C Hamano
2022-06-25 2:25 ` Han Xin
2022-06-25 2:31 ` Han Xin
2022-06-28 2:02 ` [PATCH v3 0/2] " Han Xin
2022-06-28 2:02 ` [PATCH v3 1/2] test-lib.sh: add limited processes to test-lib Han Xin
2022-06-28 2:02 ` [PATCH v3 2/2] commit-graph.c: no lazy fetch in lookup_commit_in_graph() Han Xin
2022-06-28 7:49 ` Ævar Arnfjörð Bjarmason
2022-06-28 17:36 ` Junio C Hamano
2022-06-30 12:21 ` Johannes Schindelin
2022-06-30 13:43 ` Ævar Arnfjörð Bjarmason
2022-06-30 15:40 ` Junio C Hamano
2022-06-30 18:47 ` Ævar Arnfjörð Bjarmason
2022-07-01 19:31 ` Johannes Schindelin
2022-07-01 20:47 ` Junio C Hamano
2022-06-29 2:08 ` Han Xin
2022-06-30 17:37 ` test name conflict + js/ci-github-workflow-markup regression (was: [PATCH v3 0/2] no lazy fetch in lookup_commit_in_graph()) Ævar Arnfjörð Bjarmason
2022-07-01 1:34 ` [PATCH v4 0/1] no lazy fetch in lookup_commit_in_graph() Han Xin
2022-07-01 1:34 ` [PATCH v4 1/1] commit-graph.c: " Han Xin
2022-07-09 12:23 ` Michael J Gruber
2022-07-11 15:09 ` Jeff King
2022-07-11 20:17 ` Junio C Hamano
2022-07-12 1:52 ` [External] " Han Xin
2022-07-12 5:23 ` Junio C Hamano
2022-07-12 5:32 ` Han Xin
2022-07-12 6:37 ` [External] " Jeff King
2022-07-12 14:19 ` Junio C Hamano
2022-07-12 6:50 ` [PATCH v5 0/1] " Han Xin
2022-07-12 6:50 ` [PATCH v5 1/1] commit-graph.c: " Han Xin
2022-07-12 9:50 ` Ævar Arnfjörð Bjarmason
2022-07-13 1:26 ` Han Xin
2022-07-12 6:58 ` [PATCH v5 0/1] " Jeff King
2022-07-12 8:01 ` [PATCH v1] t5330: remove run_with_limited_processses() Han Xin
-- strict thread matches above, loose matches on Subject: below --
2022-06-12 16:17 An endless loop fetching issue with partial clone, alternates and commit graph Han Xin
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