X-Recipient:	archive-cygwin AT delorie DOT com
X-SWARE-Spam-Status:	No, hits=-6.8 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_HI,SPF_HELO_PASS,T_RP_MATCHES_RCVD
X-Spam-Check-By:	sourceware.org
Message-ID:	<4D2783A3.5000008@redhat.com>
Date:	Fri, 07 Jan 2011 14:20:35 -0700
From:	Eric Blake <eblake AT redhat DOT com>
User-Agent:	Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101209 Fedora/3.1.7-0.35.b3pre.fc14 Lightning/1.0b3pre Mnenhy/0.8.3 Thunderbird/3.1.7
MIME-Version:	1.0
To:	cygwin AT cygwin DOT com
Subject:	Re: Strange fstatat / stat behavour on directories causing tar "file changed as we read it" error
References:	<3501944D149644D394474781054F5E98 AT multiplay DOT co DOT uk>
In-Reply-To:	<3501944D149644D394474781054F5E98@multiplay.co.uk>
OpenPGP:	url=http://people.redhat.com/eblake/eblake.gpg
X-IsSubscribed:	yes
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.com>
List-Subscribe:	<mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive:	<http://sourceware.org/ml/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender:	cygwin-owner AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
Delivered-To:	mailing list cygwin AT cygwin DOT com

--------------enig5CF67219E832FC4C37D53547
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

On 01/07/2011 11:21 AM, Steven Hartland wrote:
> It turns out that the value of st_size returned by a call
> to fstatat on a directory can change even though there
> have been no changes at all to said directory or its
> children.

What file system is this on?  Someone else reported the same behavior
for "Samba share on QNX through Virtual PC." - if the problem is limited
to just a subset of (known-buggy) file systems, it would be nicer to
limit the workaround to just those file systems (and have st_size always
return 0 for directories from those systems).

> The attached patch fixes this strange behaviour by ignoring
> size changes for directories as well as correcting the file
> size check to also detect file shrinks as well as growths,
> which seemed very odd.

Thanks for the patch - we'll see if I can get enough free time to apply
it and ship a patched tar, or whether cygwin 1.7.8 with a better
workaround for the issue gets released first (since there was already
talk of getting 1.7.8 complete sometime this month).

>=20
> Is there some "meta data" caching going on in cygwin or
> Windows which causes this very strange behaviour?

Giving us more details about your filesystem would help us answer that
question.

--=20
Eric Blake   eblake AT redhat DOT com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org


--------------enig5CF67219E832FC4C37D53547
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: OpenPGP digital signature
Content-Disposition: attachment; filename="signature.asc"

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.11 (GNU/Linux)
Comment: Public key at http://people.redhat.com/eblake/eblake.gpg
Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org/

iQEcBAEBCAAGBQJNJ4OjAAoJEKeha0olJ0NqLr0H/RckzqrpqsD98sU8IpJUdsJP
kU2/vRNMkBwrXBG/Y/Q/y6ZA4v9KmVcUwuo0hMVRtvnT2txHGG27OjSobj2aUjw+
mjTZSIKWqH1I46HZ6Bki1YzEyMDc0Qk8sZkpdEgUI5cdobVbQIp8rnMcYj9yX63i
D6vXmJsIWMmTkeUr4gltUmAZte10aRyAUr34VV3/fTiO9qSDarM3NKodZE1xYz62
2Gx0hJUDrjrR0I+XlRmwuaM8fU5EH8faGG7gRDKh2u81c6rN8BE3Q2tBllYfFz6d
Eby+jApZQx1T/MDqxZSbo8dBU1VnxmNgDvK6wKftjgf7idHUzwXVJ3eocAbZlrQ=
=gE95
-----END PGP SIGNATURE-----

--------------enig5CF67219E832FC4C37D53547--

- Raw text -