From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: Jonathan Tan <jonathantanmy@google.com>, git@vger.kernel.org
Subject: Re: [PATCH 2/2] index-pack: prefetch missing REF_DELTA bases
Date: Thu, 16 May 2019 10:43:03 +0900 [thread overview]
Message-ID: <xmqqk1er5g48.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <20190515231617.GA1395@sigill.intra.peff.net> (Jeff King's message of "Wed, 15 May 2019 19:16:18 -0400")
Jeff King <peff@peff.net> writes:
> I agree that the current implementation (and probably any sane
> implementation) would not send us a delta if we have not provided any
> haves. But this does mean that a malicious server could send a client
> into an infinite loop.
>
> Pretty unlikely, but should we put some kind of circuit-breaker into the
> client to ensure this?
That's a pretty good point. Would it be suffice to have a new
option to tell index-pack that fattens a thin pack and unpack-objects
that expands objects in a small incoming packfile into loose objects
that they are forbidden from on-demand fatching during this invocation,
as it is an error for the packfile they are digesting to depend on a
lazy objects?
> I dunno. Maybe we should just ignore it. It's a fundamental issue with
> partial clones that we're going to have to fetch extra junk here anyway,
Would it be an option not to ask for a thin pack in the first place?
> If we're willing to modify the format, one thing we _could_ do is have
> the server communicate the expectations for each base. I.e., introduce a
> new THIN_DELTA type that behaves exactly as a REF_DELTA, but with the
> extra 1-bit of knowledge that the server knows it is not including the
> base in the pack. I'm not sure how painful that retro-fitting would be.
> It would need at least a new capability and options to pack-objects and
> index-pack. We might be tight on bits in the packfile type field.
The type field is tight, but I wonder how much such a new
representation would help. Unless the receiving end blindly trusts
what the sender says, there needs to be a logic to detect cyclic
dependencies while following such a delta chain to lazy-fill
promised objects on the receiving end anyway, no?
next prev parent reply other threads:[~2019-05-16 1:50 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-14 21:10 [PATCH 0/2] Partial clone fix: handling received REF_DELTA Jonathan Tan
2019-05-14 21:10 ` [PATCH 1/2] t5616: refactor packfile replacement Jonathan Tan
2019-05-15 8:36 ` Johannes Schindelin
2019-05-15 18:22 ` Jonathan Tan
2019-05-14 21:10 ` [PATCH 2/2] index-pack: prefetch missing REF_DELTA bases Jonathan Tan
2019-05-15 8:46 ` Johannes Schindelin
2019-05-15 18:28 ` Jonathan Tan
2019-05-17 18:33 ` Johannes Schindelin
2019-05-15 23:16 ` Jeff King
2019-05-16 1:43 ` Junio C Hamano [this message]
2019-05-16 4:04 ` Jeff King
2019-05-16 18:26 ` Jonathan Tan
2019-05-16 21:12 ` Jeff King
2019-05-16 21:30 ` Jonathan Tan
2019-05-16 21:42 ` Jeff King
2019-05-16 23:15 ` Jonathan Tan
2019-05-17 1:09 ` Jeff King
2019-05-17 1:22 ` Jeff King
2019-05-17 4:39 ` Jeff King
2019-05-17 4:42 ` Jeff King
2019-05-17 7:20 ` Duy Nguyen
2019-05-17 8:55 ` Jeff King
2019-05-18 11:39 ` Duy Nguyen
2019-05-20 23:04 ` Nicolas Pitre
2019-05-21 21:20 ` Jeff King
2019-06-03 22:23 ` Jonathan Nieder
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