From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:46615) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QWbXh-0004Xd-PG for qemu-devel@nongnu.org; Tue, 14 Jun 2011 17:53:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QWbXf-0005fx-Sx for qemu-devel@nongnu.org; Tue, 14 Jun 2011 17:53:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39162) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QWbXf-0005fi-Eb for qemu-devel@nongnu.org; Tue, 14 Jun 2011 17:52:59 -0400 Message-ID: <4DF7D833.7090306@redhat.com> Date: Tue, 14 Jun 2011 15:52:51 -0600 From: Eric Blake MIME-Version: 1.0 References: <4DF762A4.2040503@us.ibm.com> <4DF788AF.3010103@redhat.com> <4DF7BC9F.10506@us.ibm.com> <4DF7C206.2000901@redhat.com> <4DF7D512.5010909@us.ibm.com> In-Reply-To: <4DF7D512.5010909@us.ibm.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enigD9E3EC88D71C6CECE546CCBE" Subject: Re: [Qemu-devel] [libvirt] [PATCH v2] Add support for fd: protocol List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Corey Bryant Cc: libvir-list@redhat.com, Anthony Liguori , qemu-devel@nongnu.org, Tyler C Hicks This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigD9E3EC88D71C6CECE546CCBE Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 06/14/2011 03:39 PM, Corey Bryant wrote: >> Incremental support is fine by me, but we'll need it sooner or later. >=20 > Qemu currently opens the specified copy-on-write file, finds a backing > file name in the opened file's header, opens that backing file, and > repeats. >=20 > So it seems that either a backingN=3D would be needed or a way to map a= > file descriptor to the file name in the header. >=20 > I think the latter is along the lines of what was discussed here with > -blockdev: > http://lists.gnu.org/archive/html/qemu-devel/2011-05/msg02417.html >=20 > Repeating the syntax specified in that thread, you'd have: >=20 > -blockdev id=3Dfoo-base,path=3Dfd:4,format=3Draw > -blockdev id=3Dfoo,path=3Dfd:3,format=3Dqcow2,backing_file=3Dfoo-base >=20 > where id is the file name. This chains the backing files on the comman= d > line. I like it. It scales as deep as we want by adding as many additional -blockdev entries prior to the -drive that uses the nested -blockdevs. --=20 Eric Blake eblake@redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org --------------enigD9E3EC88D71C6CECE546CCBE 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/ iQEcBAEBCAAGBQJN99gzAAoJEKeha0olJ0NqXL0H/3yiD2ftIhDY/NSKxoWOwfQj HrbsFnkvQqt8b5VYE7EJKiPSLXOkOnIZOHQQQQ0cMPlPj947bXOWfpPUvcD4TBjM N/kU68aGH+/lEG/H0obDhML7lHDTWn2ysPgIlEdz5+GciA6mxpfF7EdXJp/JX+ob hspW9M12ro+GHH+iLxtqD6b0ym8RnEYUH3IJKSwztUSFKlOj68AFMt3ZOYXe13ja qbswIzfHbVkucIVBiJxfTrQqQZ4PPcPCKbZyd0bUv/HW9W7QpVbi33VL0NsqqWO8 fam0/JCyhw2blBzmU+rmOmThdTGAlogQRG3k+gUu9O2I4kF8OqA12jc5LWgeues= =3p3f -----END PGP SIGNATURE----- --------------enigD9E3EC88D71C6CECE546CCBE--