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From: Derrick Stolee <derrickstolee@github.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org, me@ttaylorr.com, newren@gmail.com,
	avarab@gmail.com, mjcheetham@outlook.com, steadmon@google.com,
	Glen Choo <chooglen@google.com>,
	Jonathan Tan <jonathantanmy@google.com>,
	Teng Long <dyroneteng@gmail.com>
Subject: Re: [PATCH v4 08/11] bundle: add flags to verify_bundle(), skip walk
Date: Tue, 11 Oct 2022 15:04:26 -0400	[thread overview]
Message-ID: <d85704ef-97e8-57aa-9711-01d00b74d36e@github.com> (raw)
In-Reply-To: <xmqqk05734kr.fsf@gitster.g>

On 10/10/2022 2:40 PM, Junio C Hamano wrote:
> Derrick Stolee <derrickstolee@github.com> writes:
> 
>> I've been going over the refs code multiple times today trying to
>> fix this "real" culprit, with no luck. I can share this interesting
>> point:
>>
>>  * The initial loop over the bundles tries to apply each, but the
>>    prerequisite objects are not present so we never reach the revision
>>    walk. A refs/bundle/* ref is added via update_ref().
>>
>>  * The second loop over the bundles tries to apply each, but the only
>>    bundle with its prerequisites present also finds the commits as
>>    reachable (this must be where the loose ref cache is populated).
>>    Then, a refs/bundle/* ref is added via update_ref().
>>
>>  * The third loop over the bundles finds a bundle whose prerequisites
>>    are present, but verify_bundle() rejected it because those commits
>>    were not seen from any ref.
>>
>> Other than identifying that issue, I was unable to track down exactly
>> what is happening here or offer a fix. I had considered inserting
>> more cache frees deep in the refs code, but I wasn't sure what effect
>> that would have across the wider system.
> 
> OK.  That certainly is understandable.
> 
> As a comment in the proposed log message that BUNDLE_SKIP_REACHABLE
> bit is a band aid papering over a problem we punted in this series,
> to guide future developers, I think what you wrote is sufficient.
> We do not want them to think that skipping the check is our
> preferred longer term solution and add their own hack to keep
> skipping the check when they resolve "the real culprit".

I have discovered the real culprit, and my expectation was incorrect
about the loose ref cache. The key issue was that I was looking at
this loop:

	i = req_nr;
	while (i && (commit = get_revision(&revs)))
		if (commit->object.flags & PREREQ_MARK)
			i--;

and noticing that only one commit was being visited. I was not 
seeing the actually-important commit. But it wasn't the revision
walk's fault. The loop was terminating because "i" was reaching
zero!

It turns out that verify_bundles() is not clearing the PREREQ_MARK
flag, so multiple runs would incorrectly hit this short-circuit
and terminate the walk early.

I'll replace this patch with the correct fix soon.

Thanks,
-Stolee

  reply	other threads:[~2022-10-11 19:04 UTC|newest]

Thread overview: 94+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-22 15:12 [PATCH 0/7] Bundle URIs III: Parse and download from bundle lists Derrick Stolee via GitGitGadget
2022-08-22 15:12 ` [PATCH 1/7] bundle-uri: create bundle_list struct and helpers Derrick Stolee via GitGitGadget
2022-08-22 17:57   ` Junio C Hamano
2022-08-22 15:12 ` [PATCH 2/7] bundle-uri: create base key-value pair parsing Derrick Stolee via GitGitGadget
2022-08-22 18:20   ` Junio C Hamano
2022-08-23 16:29     ` Derrick Stolee
2022-08-31 22:10       ` Jonathan Tan
2022-08-31 22:02   ` Glen Choo
2022-09-01  2:38   ` [PATCH 4/7] bundle-uri: unit test "key=value" parsing Teng Long
2022-08-22 15:12 ` [PATCH 3/7] bundle-uri: create "key=value" line parsing Ævar Arnfjörð Bjarmason via GitGitGadget
2022-08-22 19:17   ` Junio C Hamano
2022-08-23 16:31     ` Derrick Stolee
2022-09-02 23:41   ` Josh Steadmon
2022-08-22 15:12 ` [PATCH 4/7] bundle-uri: unit test "key=value" parsing Ævar Arnfjörð Bjarmason via GitGitGadget
2022-09-01  2:56   ` Teng Long
2022-08-22 15:12 ` [PATCH 5/7] bundle-uri: parse bundle list in config format Derrick Stolee via GitGitGadget
2022-08-22 19:25   ` Junio C Hamano
2022-08-23 16:43     ` Derrick Stolee
2022-08-31 22:18     ` Jonathan Tan
2022-09-01  8:05   ` Teng Long
2022-08-22 15:12 ` [PATCH 6/7] bundle-uri: limit recursion depth for bundle lists Derrick Stolee via GitGitGadget
2022-08-22 15:12 ` [PATCH 7/7] bundle-uri: fetch a list of bundles Derrick Stolee via GitGitGadget
2022-09-02 23:51   ` Josh Steadmon
2022-09-05 12:50   ` Teng Long
2022-09-08 17:10     ` Derrick Stolee
2022-09-09 14:33 ` [PATCH v2 0/9] Bundle URIs III: Parse and download from bundle lists Derrick Stolee via GitGitGadget
2022-09-09 14:33   ` [PATCH v2 1/9] bundle-uri: short-circuit capability parsing Derrick Stolee via GitGitGadget
2022-09-09 17:24     ` Junio C Hamano
2022-09-19 17:55       ` Derrick Stolee
2022-09-09 14:33   ` [PATCH v2 2/9] bundle-uri: use plain string in find_temp_filename() Derrick Stolee via GitGitGadget
2022-09-09 17:56     ` Junio C Hamano
2022-09-19 17:54       ` Derrick Stolee
2022-09-19 18:16         ` Junio C Hamano
2022-09-09 14:33   ` [PATCH v2 3/9] bundle-uri: create bundle_list struct and helpers Derrick Stolee via GitGitGadget
2022-09-09 14:33   ` [PATCH v2 4/9] bundle-uri: create base key-value pair parsing Derrick Stolee via GitGitGadget
2022-09-29 21:49     ` Jonathan Tan
2022-09-09 14:33   ` [PATCH v2 5/9] bundle-uri: create "key=value" line parsing Ævar Arnfjörð Bjarmason via GitGitGadget
2022-09-09 14:33   ` [PATCH v2 6/9] bundle-uri: unit test "key=value" parsing Ævar Arnfjörð Bjarmason via GitGitGadget
2022-09-09 14:33   ` [PATCH v2 7/9] bundle-uri: parse bundle list in config format Derrick Stolee via GitGitGadget
2022-09-09 14:33   ` [PATCH v2 8/9] bundle-uri: limit recursion depth for bundle lists Derrick Stolee via GitGitGadget
2022-09-09 14:33   ` [PATCH v2 9/9] bundle-uri: fetch a list of bundles Derrick Stolee via GitGitGadget
2022-09-29 21:58     ` Jonathan Tan
2022-09-30 12:49       ` Derrick Stolee
2022-09-26 13:19   ` [PATCH v2 0/9] Bundle URIs III: Parse and download from bundle lists Derrick Stolee
2022-09-26 19:10     ` Junio C Hamano
2022-09-29 22:00       ` Jonathan Tan
2022-09-30 13:21         ` Derrick Stolee
2022-10-04 12:34   ` [PATCH v3 " Derrick Stolee via GitGitGadget
2022-10-04 12:34     ` [PATCH v3 1/9] bundle-uri: use plain string in find_temp_filename() Derrick Stolee via GitGitGadget
2022-10-04 12:34     ` [PATCH v3 2/9] bundle-uri: create bundle_list struct and helpers Derrick Stolee via GitGitGadget
2022-10-04 12:34     ` [PATCH v3 3/9] bundle-uri: create base key-value pair parsing Derrick Stolee via GitGitGadget
2022-10-04 12:34     ` [PATCH v3 4/9] bundle-uri: create "key=value" line parsing Ævar Arnfjörð Bjarmason via GitGitGadget
2022-10-04 12:34     ` [PATCH v3 5/9] bundle-uri: unit test "key=value" parsing Ævar Arnfjörð Bjarmason via GitGitGadget
2022-10-04 12:34     ` [PATCH v3 6/9] bundle-uri: parse bundle list in config format Derrick Stolee via GitGitGadget
2022-10-04 12:34     ` [PATCH v3 7/9] bundle-uri: limit recursion depth for bundle lists Derrick Stolee via GitGitGadget
2022-10-04 12:34     ` [PATCH v3 8/9] bundle-uri: fetch a list of bundles Derrick Stolee via GitGitGadget
2022-10-04 21:44       ` Jonathan Tan
2022-10-07 13:29         ` Derrick Stolee
2022-10-04 12:34     ` [PATCH v3 9/9] bundle-uri: suppress stderr from remote-https Derrick Stolee via GitGitGadget
2022-10-10 16:04     ` [PATCH v4 00/11] Bundle URIs III: Parse and download from bundle lists Derrick Stolee via GitGitGadget
2022-10-10 16:04       ` [PATCH v4 01/11] bundle-uri: use plain string in find_temp_filename() Derrick Stolee via GitGitGadget
2022-10-10 16:04       ` [PATCH v4 02/11] bundle-uri: create bundle_list struct and helpers Derrick Stolee via GitGitGadget
2022-10-10 16:04       ` [PATCH v4 03/11] bundle-uri: create base key-value pair parsing Derrick Stolee via GitGitGadget
2022-10-10 16:04       ` [PATCH v4 04/11] bundle-uri: create "key=value" line parsing Ævar Arnfjörð Bjarmason via GitGitGadget
2022-10-10 16:04       ` [PATCH v4 05/11] bundle-uri: unit test "key=value" parsing Ævar Arnfjörð Bjarmason via GitGitGadget
2022-10-10 16:04       ` [PATCH v4 06/11] bundle-uri: parse bundle list in config format Derrick Stolee via GitGitGadget
2022-10-10 16:04       ` [PATCH v4 07/11] bundle-uri: limit recursion depth for bundle lists Derrick Stolee via GitGitGadget
2022-10-10 16:04       ` [PATCH v4 08/11] bundle: add flags to verify_bundle(), skip walk Derrick Stolee via GitGitGadget
2022-10-10 17:27         ` Junio C Hamano
2022-10-10 18:13           ` Derrick Stolee
2022-10-10 18:40             ` Junio C Hamano
2022-10-11 19:04               ` Derrick Stolee [this message]
2022-10-10 16:04       ` [PATCH v4 09/11] bundle-uri: fetch a list of bundles Derrick Stolee via GitGitGadget
2022-10-10 16:04       ` [PATCH v4 10/11] bundle-uri: quiet failed unbundlings Derrick Stolee via GitGitGadget
2022-10-10 16:04       ` [PATCH v4 11/11] bundle-uri: suppress stderr from remote-https Derrick Stolee via GitGitGadget
2022-10-12 12:52       ` [PATCH v5 00/12] Bundle URIs III: Parse and download from bundle lists Derrick Stolee via GitGitGadget
2022-10-12 12:52         ` [PATCH v5 01/12] bundle-uri: use plain string in find_temp_filename() Derrick Stolee via GitGitGadget
2022-10-12 12:52         ` [PATCH v5 02/12] bundle-uri: create bundle_list struct and helpers Derrick Stolee via GitGitGadget
2022-10-12 12:52         ` [PATCH v5 03/12] bundle-uri: create base key-value pair parsing Derrick Stolee via GitGitGadget
2022-10-12 12:52         ` [PATCH v5 04/12] bundle-uri: create "key=value" line parsing Ævar Arnfjörð Bjarmason via GitGitGadget
2022-10-12 12:52         ` [PATCH v5 05/12] bundle-uri: unit test "key=value" parsing Ævar Arnfjörð Bjarmason via GitGitGadget
2022-10-12 12:52         ` [PATCH v5 06/12] bundle-uri: parse bundle list in config format Derrick Stolee via GitGitGadget
2022-10-12 12:52         ` [PATCH v5 07/12] bundle-uri: limit recursion depth for bundle lists Derrick Stolee via GitGitGadget
2022-10-12 12:52         ` [PATCH v5 08/12] bundle: properly clear all revision flags Derrick Stolee via GitGitGadget
2022-10-12 16:17           ` Junio C Hamano
2022-10-12 12:52         ` [PATCH v5 09/12] bundle-uri: fetch a list of bundles Derrick Stolee via GitGitGadget
2022-10-26 19:06           ` Junio C Hamano
2022-10-12 12:52         ` [PATCH v5 10/12] bundle: add flags to verify_bundle() Derrick Stolee via GitGitGadget
2022-10-12 12:52         ` [PATCH v5 11/12] bundle-uri: quiet failed unbundlings Derrick Stolee via GitGitGadget
2022-10-12 16:32           ` Junio C Hamano
2022-10-12 12:52         ` [PATCH v5 12/12] bundle-uri: suppress stderr from remote-https Derrick Stolee via GitGitGadget
2022-10-26 18:54           ` Junio C Hamano
2022-10-26 14:34         ` [PATCH v5 00/12] Bundle URIs III: Parse and download from bundle lists Derrick Stolee
2022-10-26 16:06           ` Junio C Hamano

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