From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45528) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uzs4W-0003Z6-9D for qemu-devel@nongnu.org; Thu, 18 Jul 2013 13:32:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Uzs4U-0008BS-Un for qemu-devel@nongnu.org; Thu, 18 Jul 2013 13:32:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35657) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uzs4U-0008BD-MA for qemu-devel@nongnu.org; Thu, 18 Jul 2013 13:32:54 -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 r6IHWrWA010106 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 18 Jul 2013 13:32:54 -0400 Message-ID: <51E826C4.6090300@redhat.com> Date: Thu, 18 Jul 2013 11:32:52 -0600 From: Eric Blake MIME-Version: 1.0 References: <1374091462-18391-1-git-send-email-imain@redhat.com> <1374091462-18391-5-git-send-email-imain@redhat.com> <51E82579.20201@redhat.com> In-Reply-To: <51E82579.20201@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="fjQ7MuNeTWimow8B4WscE8rr600hLABAm" Subject: Re: [Qemu-devel] [PATCH V4 4/4] Change default to qcow2 for sync mode none. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: Ian Main , qemu-devel@nongnu.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --fjQ7MuNeTWimow8B4WscE8rr600hLABAm Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 07/18/2013 11:27 AM, Eric Blake wrote: >> if (!has_format) { >> - format =3D mode =3D=3D NEW_IMAGE_MODE_EXISTING ? NULL : bs->d= rv->format_name; >> + format =3D mode =3D=3D NEW_IMAGE_MODE_EXISTING ? NULL : "qcow= 2"; >=20 > Is this the right thing to do? Or should we do: >=20 > if (!has_format) { > if (mode =3D=3D NEW_IMAGE_MODE_EXISTING) { > format =3D NULL; > } else { > format =3D bs->drv->format_name ?: "qcow2"; > } > } >=20 > That is, I think we should default to doing a backup in the format give= n > by the original (what if the original is qed, which also supports > backing files), and only use qcow2 when there is no guidance whatsoever= =2E >=20 > But in practice, I don't care Well, I _DO_ care about one thing - make sure that the qapi-schema.json page accurately documents how this variable is defaulted for callers that don't care about the implications of omitting a format. Or we could simplify life by making 'format' mandatory for drive-backup; it was optional for 'drive-mirror' due to incremental implementation, but for 'drive-backup', we still have the opportunity to do things right from the first release. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --fjQ7MuNeTWimow8B4WscE8rr600hLABAm Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.13 (GNU/Linux) Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJR6CbEAAoJEKeha0olJ0Nq8LMH/3GIHAITj5VJmD/N0t7fa8qh 8JsEnv7Ag2hSKOVYHbAc4nD8wHgTMGwnG2svwSl3NH4EQDnDitDrc8x1AXNXt9mr p9zzl9gmsRWN7Fsa/XzF5Nb/t7+yNwkc7DyLF+c0grrGg56CH3smWrWm7eDUGHgA W/lAze98u3Q4HruyDVvB0GJqpEFAcTwTIzdGAwbYawuj5s61/R3LyUi7yK/dHn0W zIG3kG02KauVJL1RCKXsd62arJLqPOgImtGTOgZmGKmnXmP9P40ejOEVdMgY2I5E PT4lUVBz+l0R3hTJodD3bZGIoMK0npmaJCcSAKTjYPBljzujuUF4kt2oXJBsCXU= =dO3p -----END PGP SIGNATURE----- --fjQ7MuNeTWimow8B4WscE8rr600hLABAm--