From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:40750) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TGshB-0000YI-FO for qemu-devel@nongnu.org; Wed, 26 Sep 2012 10:34:42 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TGsh1-0001oh-Qy for qemu-devel@nongnu.org; Wed, 26 Sep 2012 10:34:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50322) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TGsh1-0001oQ-Io for qemu-devel@nongnu.org; Wed, 26 Sep 2012 10:34:27 -0400 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q8QEYQBR024960 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 26 Sep 2012 10:34:26 -0400 Message-ID: <50631267.8060404@redhat.com> Date: Wed, 26 Sep 2012 08:34:15 -0600 From: Eric Blake MIME-Version: 1.0 References: <75bbfc268498ae3733d7ffb896ab0852527d5b11.1348589526.git.jcody@redhat.com> <50630D94.9000605@redhat.com> <5063104A.7080604@redhat.com> In-Reply-To: <5063104A.7080604@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enigB3C1B3BD88A976157D0422CF" Subject: Re: [Qemu-devel] [PATCH v2 5/7] QAPI: add command for live block commit, 'block-commit' List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: jcody@redhat.com Cc: Kevin Wolf , pbonzini@redhat.com, qemu-devel@nongnu.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigB3C1B3BD88A976157D0422CF Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable On 09/26/2012 08:25 AM, Jeff Cody wrote: >>> +# @top: #optional The file name of the backing image within the i= mage chain, >>> +# which contains the topmost data to be committed= down. >>> +# If not specified, this is one layer below the a= ctive >>> +# layer (i.e. active->backing_hd). >> >> Why isn't active the default any more? I know, we don't support it yet= , >> but long term this is what makes most sense as a default. >> >=20 > Eric had a similar question, and asked if anyone had any preference - > this was my response: >=20 > --- >=20 > I guess I don't have a strong preference either - I originally had it > the other way, but then that meant the default in the current > implementation was actually an error. >=20 > Also, I assumed (danger!) that the most common use of commit would be a= > snapshot, followed by a commit of active->backing_hd. With that > assumption, it seemed like a sane default. Actually, I envision my personal use case to be: Take a snapshot, do an experiment in the guest (such as install a questionable package), and then either roll back to the snapshot (experiment failed) or commit the active (experiment worked, no need to have a snapshot any more); either way, taking the snapshot created a new temporary file name, and after I make my decision on whether to commit or discard the snapshot, I want to get back to the original file name. Since the snapshot effectively created a temporary file name, I'd rather not have to know the name of that temporary file just to pass it to an explicit 'top' argument when committing the active layer. Having to specify 'top' to avoid an error when not committing the active layer is not as bad as getting the defaults wrong for when we do add support for committing the active layer. > --- >=20 > I can certainly revert back to having the active layer be the top, if > that is the preference. Given that it has been asked again, I'd say yes, go ahead and revert to the behavior of defaulting 'top' to the active layer. --=20 Eric Blake eblake@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --------------enigB3C1B3BD88A976157D0422CF Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Mozilla - http://www.enigmail.net/ iQEcBAEBCAAGBQJQYxJtAAoJEKeha0olJ0NqmHUH/jsPFgdlPjKqPFiA8UwlRw+i yoUO+mCx7yw2bT/J/Tq4AvxqVyhZNfUeGKNcyT/6DStI7pTlghSJKdjKH5jlyLdh R4fx44i8+896kB+eL+UhhGjF+MhoM4l3bDXnnsSo9on2OQRhoyHx7A9HWmCwf2L+ i3MyK8gAGSY3FpUyLjsq6ynv42/U1Ap4dYB4kGuKzi3VahYqqLPx0PVCdNBr3+2z L0UyaY8rxHU8yLS3lEvt28AwZOmAbeMzmMKjdiaQBh+JKKkwfA1DCC+41ZTEsTcX sEhd93HArgtNxlypl44binHRghdyK6GDU+PPMhrpQrhElEs6gAQNlhtP0Dk4+6Q= =VS27 -----END PGP SIGNATURE----- --------------enigB3C1B3BD88A976157D0422CF--