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: <4D2DC23E.5040202@redhat.com> Date: Wed, 12 Jan 2011 08:01:18 -0700 From: Eric Blake 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> <4D2783A3 DOT 5000008 AT redhat DOT com> <4D27C896 DOT 30202 AT cygwin DOT com> <265F601A437E4A03BE8C665BE7470721 AT multiplay DOT co DOT uk> <4D27D66F DOT 8030201 AT cygwin DOT com> <4D28F1AC DOT 1070907 AT laposte DOT net> <20110111095435 DOT GF3413 AT calimero DOT vinschen DOT de> <4D2C7024 DOT 8090507 AT redhat DOT com> <20110112102823 DOT GF6353 AT calimero DOT vinschen DOT de> <20110112104744 DOT GH6353 AT calimero DOT vinschen DOT de> In-Reply-To: <20110112104744.GH6353@calimero.vinschen.de> OpenPGP: url=http://people.redhat.com/eblake/eblake.gpg Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enig02164FA21554370C1D61207A" X-IsSubscribed: yes Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner AT cygwin DOT com Mail-Followup-To: cygwin AT cygwin DOT com Delivered-To: mailing list cygwin AT cygwin DOT com --------------enig02164FA21554370C1D61207A Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 01/12/2011 03:47 AM, Corinna Vinschen wrote: >=20 > On second thought, let's take a step back. >=20 > Actually, directories can change all the time. Why on earth is tar > checking the st_size member of a directory at all? That's a bug IMO. > No application should do that. I understand that a change in the inode > number points to the fact that the directory has been replaced > underfoot, but why should tar be concerned that a directory has changed > its size while it's reading files from it? I mean, even during a tar > backup, there's no reason to expect that files are *not* added or > deleted to a directory by other applications, and these actions may > naturally change the size of the directory. When tar is trying to capture the entire contents of the directory, any modification to that directory (including adding a file to the directory which changes the st_size of the directory) means that tar missed something, so tar emits a warning to tell you about that fact. >=20 > Having said that, I don't think it's correct to change Cygwin here. > It's just a bug in tar. I'm not sure we've established that point yet, but I'll raise the question upstream. But, assuming tar is doing the right thing... > The fact that the directory size changes even > if the content hasn't changed is just a side effect of the OS MO. It > doesn't matter if the directory has actually changed or not. It's not > in the hand of a single application. then cygwin's behavior DOES matter to tar - no other system changes the st_size of a directory without ALSO adding or deleting files within that directory and also updating the st_mtim of the directory; at which point tar is entirely within its rights to complain (the directory changed while trying to read it, so the tar file may be incomplete). Locking st_size at 0 avoids the issue entirely, whether or not upstream tar agrees that checking changes in st_mtim but ignoring changes in st_size would be a more appropriate behavior. --=20 Eric Blake eblake AT redhat DOT com +1-801-349-2682 Libvirt virtualization library http://libvirt.org --------------enig02164FA21554370C1D61207A 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/ iQEcBAEBCAAGBQJNLcI+AAoJEKeha0olJ0Nq8HwH/09QXf6xvV5avB4OcfG1R61U eDV5XFNiohVoGBcU4o7OIFhfJRHpPQXepdjgJYpO3PPVpJeg+QNfnHAT5pb2MfwO xtq6SgEe2VlHZizYmff0GDVH9lK4WQIGT1gtOJTHnkI7CAooXSNMaqfFoLIABpSQ 3Ae03BHhgdSEnPphsn1m2qs0rphUHTV166myIS0AXvORtZaZl0Nb+kMJwrZQb7Nz tENIjJHH6ztlhIwIy3XumbAj8GM3dQ7yuYHJKgnwxYLfByHcO1ncrffj3duh8dAa y1mvg/DUSYUuiJ38diC3WSqOd0VPMrRellx+J3HrZdPubaHzQRv4LUP/5CNLa0E= =aqZ/ -----END PGP SIGNATURE----- --------------enig02164FA21554370C1D61207A--