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From: Taylor Blau <me@ttaylorr.com>
To: Jeff King <peff@peff.net>
Cc: git@vger.kernel.org, "Taylor Blau" <me@ttaylorr.com>,
	"Derrick Stolee" <dstolee@microsoft.com>,
	"Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>
Subject: Re: [PATCH] upload-pack: disable commit graph more gently for shallow traversal
Date: Wed, 11 Sep 2019 22:08:48 -0400	[thread overview]
Message-ID: <20190912020848.GB76228@syl.lan> (raw)
In-Reply-To: <20190912001846.GA31370@sigill.intra.peff.net>

On Wed, Sep 11, 2019 at 08:18:46PM -0400, Jeff King wrote:
> On Wed, Sep 11, 2019 at 08:04:14PM -0400, Jeff King wrote:
>
> > When the client has asked for certain shallow options like
> > "deepen-since", we do a custom rev-list walk that pretends to be
> > shallow. Before doing so, we have to disable the commit-graph, since it
> > is not compatible with the shallow view of the repository. That's
> > handled by 829a321569 (commit-graph: close_commit_graph before shallow
> > walk, 2018-08-20). That commit literally closes and frees our
> > repo->objects->commit_graph struct.
>
> A few notes and curiosities on my patch and this general area.
>
> The test suite passes with my patch both with and without
> GIT_TEST_COMMIT_GRAPH=1. But to my surprise, it also passes if I delete
> the close_commit_graph() line added by 829a321569!
>
> So it's not clear to me whether this whole thing is truly unnecessary
> (and Stolee was just being overly cautious because the code is related
> to shallow-ness, even though it is OK doing a true-parent traversal
> itself), or if we just don't have good test coverage for the case that
> requires it.
>
> If it _is_ necessary, I'm a little worried there are other problems
> lurking. The whole issue is that we've seen and parsed some commits
> before we get to this shallow deepen-since code-path. So just disabling
> commit-graphs isn't enough. Even without them, we might have parsed some
> commits the old-fashioned way and filled in their parent pointers. Is
> that a problem?

I am, too, but I don't think we should hold this patch up which is
obviously improving the situation in the meantime while we figure that
out.

> [snip]

Thanks,
Taylor

  parent reply	other threads:[~2019-09-12  2:08 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-12  0:04 [PATCH] upload-pack: disable commit graph more gently for shallow traversal Jeff King
2019-09-12  0:18 ` Jeff King
2019-09-12  1:11   ` [PATCH] list-objects: don't queue root trees unless revs->tree_objects is set Jeff King
2019-09-12  1:19     ` Jeff King
2019-09-12 12:31     ` Derrick Stolee
2019-09-12 16:52     ` Junio C Hamano
2019-09-12 22:34       ` Jeff King
2019-09-13 18:05         ` Junio C Hamano
2019-09-12  2:08   ` Taylor Blau [this message]
2019-09-12 14:03     ` [PATCH] upload-pack: disable commit graph more gently for shallow traversal Jeff King
2019-09-12  2:07 ` Taylor Blau
2019-09-12 11:06   ` SZEDER Gábor
2019-09-12 14:01     ` Jeff King
2019-09-12 12:46   ` Derrick Stolee
2019-09-12 13:59   ` Jeff King
2019-09-12 12:23 ` Derrick Stolee
2019-09-12 14:23   ` Jeff King
2019-09-12 19:27     ` Derrick Stolee
2019-09-12 14:41 ` [PATCH v2] upload-pack commit graph segfault fix Jeff King
2019-09-12 14:43   ` Jeff King
2019-09-12 14:44   ` [PATCH v2 1/2] commit-graph: bump DIE_ON_LOAD check to actual load-time Jeff King
2019-09-12 19:30     ` Derrick Stolee
2019-09-12 14:44   ` [PATCH v2 2/2] upload-pack: disable commit graph more gently for shallow traversal Jeff King
2019-09-13 13:26     ` Derrick Stolee
2019-09-12 16:56   ` [PATCH v2] upload-pack commit graph segfault fix Taylor Blau

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