From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1JFAbx-0001LT-TG for qemu-devel@nongnu.org; Wed, 16 Jan 2008 10:55:30 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1JFAbx-0001Kj-BN for qemu-devel@nongnu.org; Wed, 16 Jan 2008 10:55:29 -0500 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1JFAbw-0001Kb-Iq for qemu-devel@nongnu.org; Wed, 16 Jan 2008 10:55:28 -0500 Received: from ecfrec.frec.bull.fr ([129.183.4.8]) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1JFAbv-00071c-MG for qemu-devel@nongnu.org; Wed, 16 Jan 2008 10:55:28 -0500 Subject: Re: [kvm-devel] [Qemu-devel] Re: [RFC][PATCH] Modify loop device to be able to manage partitions of the image disk From: Laurent Vivier In-Reply-To: <478E1B57.7090609@codemonkey.ws> References: <120042137328-git-send-email-Laurent.Vivier@bull.net> <20080115182745.GY17783@redhat.com> <1200440406.4602.16.camel@frecb07144> <20080115235438.GB30528@redhat.com> <1200443443.4602.32.camel@frecb07144> <478E1B57.7090609@codemonkey.ws> Date: Wed, 16 Jan 2008 16:55:18 +0100 Message-Id: <1200498918.4687.18.camel@frecb07144> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-0rtG6RwWkELIq7l7rZyE" Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kvm-devel@lists.sourceforge.net --=-0rtG6RwWkELIq7l7rZyE Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Le mercredi 16 janvier 2008 =C3=A0 08:57 -0600, Anthony Liguori a =C3=A9cri= t : > > Le mardi 15 janvier 2008 =C3=A0 23:54 +0000, Daniel P. Berrange a =C3= =A9crit : [...] > >>> 2- I'd like to mount qcow2 or others disk image formats, so perhaps i= t's > >>> easier to modify loop device driver (but perhaps you know another mag= ic > >>> tool ?) > >>> =20 > >> There has been some work in this area wrt to Xen - the DM-Userspace pr= oject > >> had some working code providing a device mapper target calling out to = a=20 > >> userspace daemon to handle non-raw file formats like qcow. I don't > >> know what the state of it is now wrt to upstream kernel / device-mappe= r, > >> or even whether it is more than just 'proof of concept', but the proje= ct > >> page is here with some info: > >> > >> http://wiki.xensource.com/xenwiki/DmUserspace >=20 > FWIW, I still think a userspace block device is the Right Way to support=20 I agree with you, it was my first idea too, but it introduces complexity to manage communications between the kernel part of the driver and the userspace daemon: I don't like complexity. > these sort of things. dm-userspace turned out to be difficult as device=20 > mapper has some rather strict requirements about alignment that some=20 > formats (like qcow) cannot satisfy. >=20 > The loop driver is a terrible base to start from as it does not preserve=20 > data integrity. [...] But everyone already uses loop as it is currently, so why not to add more supported formats for the disk image ? Why do you say it doesn't preserve data integrity ? Regards, Laurent --=20 ----------------- Laurent.Vivier@bull.net ------------------ "La perfection est atteinte non quand il ne reste rien =C3=A0 ajouter mais quand il ne reste rien =C3=A0 enlever." Saint Exup=C3=A9ry --=-0rtG6RwWkELIq7l7rZyE Content-Type: application/pgp-signature; name=signature.asc Content-Description: Ceci est une partie de message =?ISO-8859-1?Q?num=E9riquement?= =?ISO-8859-1?Q?_sign=E9e?= -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQBHjijm9Kffa9pFVzwRAng7AKCxGARVjqpDdDv9wvz6J+MWmDr2jQCfVfHM xQUnkJquC++ATxaBA82NH7c= =9y/q -----END PGP SIGNATURE----- --=-0rtG6RwWkELIq7l7rZyE--