From: Jeff King <peff@peff.net>
To: Taylor Blau <me@ttaylorr.com>
Cc: git@vger.kernel.org, gitster@pobox.com
Subject: Re: [PATCH 6/7] rev-list: let traversal die when --missing is not in use
Date: Fri, 5 Apr 2019 14:41:11 -0400 [thread overview]
Message-ID: <20190405184111.GE2284@sigill.intra.peff.net> (raw)
In-Reply-To: <a3a80b4b2a988eb65d85a5acd54c584d047073c7.1554435033.git.me@ttaylorr.com>
On Thu, Apr 04, 2019 at 08:37:54PM -0700, Taylor Blau wrote:
> 3. have the traversal machinery communicate the failure to the caller,
> so that it can decide how to proceed without re-evaluting the object
> itself.
>
> Of those, I think (3) is probably the best path forward. However, this
> patch does none of them. In the name of expediently fixing the
> regression to a normal "rev-list --objects" that we use for connectivity
> checks, this simply restores the pre-7c0fe330d5 behavior of having the
> traversal die as soon as it fails to load a tree (when --missing is set
> to MA_ERROR, which is the default).
I think this is worth doing, as it restores the earlier behavior. But a
few general thoughts (which I've shared already with you, but for the
benefit of the list):
- actually doing the "communicate failure to the caller" would probably
not be too bad as a single-bit PARSE_FAILED flag in obj->flags. But
it does require the caller understanding which objects the traversal
would try to parse (i.e., rev-list would have to understand that it
is on its own to check blobs, even if they don't have a PARSE_FAILED
flag).
- speaking of blobs, this series does not help rev-list find a
mis-typed or bit-rotted blob at all, because it never opens the
blobs. Does that mean my expectations for rev-list are simply too
high, and that we should be expecting fsck-like checks to catch
these? I dunno.
It would not be too expensive to convert the existing "do we have the
blob" check in rev-list to "do we have it, and is its type correct?".
But obviously finding bitrot would be super-expensive. Which leads me
to...
- there actually _is_ a --verify-objects option, which would check even
blobs for bitrot. It was added long ago in 5a48d24012 (rev-list
--verify-object, 2011-09-01) for use with check_connected(). But it
was deemed too slow for normal use, and ripped out in d21c463d55
(fetch/receive: remove over-pessimistic connectivity check,
2012-03-15).
That last one implies that we're OK relying on the incoming index-pack
to catch these cases (which is going to do a sha1 over each object).
It does seem like we should bother to notice failures when it's _free_
to do so, which is the case with these tree-loading failures. Which is
basically what this patch is doing.
-Peff
next prev parent reply other threads:[~2019-04-05 18:41 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-05 3:37 [PATCH 0/7] harden unexpected object types checks Taylor Blau
2019-04-05 3:37 ` [PATCH 1/7] t: move 'hex2oct' into test-lib-functions.sh Taylor Blau
2019-04-05 3:37 ` [PATCH 2/7] t: introduce tests for unexpected object types Taylor Blau
2019-04-05 10:50 ` SZEDER Gábor
2019-04-05 18:24 ` Jeff King
2019-04-05 18:42 ` SZEDER Gábor
2019-04-05 18:52 ` Jeff King
2019-04-07 21:00 ` Ævar Arnfjörð Bjarmason
2019-04-09 2:29 ` Taylor Blau
2019-04-09 9:14 ` Ævar Arnfjörð Bjarmason
2019-04-10 1:59 ` Taylor Blau
2019-04-08 5:27 ` Junio C Hamano
2019-04-05 19:25 ` Eric Sunshine
2019-04-05 20:53 ` Jeff King
2019-04-06 5:33 ` Taylor Blau
2019-04-08 6:44 ` Junio C Hamano
2019-04-09 2:30 ` Taylor Blau
2019-04-09 3:28 ` Eric Sunshine
2019-04-09 5:08 ` Taylor Blau
2019-04-09 8:02 ` Eric Sunshine
2019-04-10 1:54 ` Taylor Blau
2019-04-06 5:31 ` Taylor Blau
2019-04-05 18:31 ` Jeff King
2019-04-06 5:23 ` Taylor Blau
2019-04-05 3:37 ` [PATCH 3/7] list-objects.c: handle unexpected non-blob entries Taylor Blau
2019-04-05 3:37 ` [PATCH 4/7] list-objects.c: handle unexpected non-tree entries Taylor Blau
2019-04-05 3:37 ` [PATCH 5/7] get_commit_tree(): return NULL for broken tree Taylor Blau
2019-04-05 3:37 ` [PATCH 6/7] rev-list: let traversal die when --missing is not in use Taylor Blau
2019-04-05 18:41 ` Jeff King [this message]
2019-04-06 5:36 ` Taylor Blau
2019-04-07 13:41 ` Jeff King
2019-04-09 2:11 ` Taylor Blau
2019-04-05 3:37 ` [PATCH 7/7] rev-list: detect broken root trees Taylor Blau
2019-04-10 2:13 ` [PATCH v2 0/7] harden unexpected object types checks Taylor Blau
2019-04-10 2:13 ` [PATCH v2 1/7] t: move 'hex2oct' into test-lib-functions.sh Taylor Blau
2019-04-10 2:13 ` [PATCH v2 2/7] t: introduce tests for unexpected object types Taylor Blau
2019-04-10 2:13 ` [PATCH v2 3/7] list-objects.c: handle unexpected non-blob entries Taylor Blau
2019-04-10 2:13 ` [PATCH v2 4/7] list-objects.c: handle unexpected non-tree entries Taylor Blau
2019-04-10 2:13 ` [PATCH v2 5/7] get_commit_tree(): return NULL for broken tree Taylor Blau
2019-04-10 2:13 ` [PATCH v2 6/7] rev-list: let traversal die when --missing is not in use Taylor Blau
2019-04-10 2:13 ` [PATCH v2 7/7] rev-list: detect broken root trees Taylor Blau
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