From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46022) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Voa4n-00037n-GH for qemu-devel@nongnu.org; Thu, 05 Dec 2013 09:38:54 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Voa4i-0002AG-JN for qemu-devel@nongnu.org; Thu, 05 Dec 2013 09:38:49 -0500 Received: from mx1.redhat.com ([209.132.183.28]:16796) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Voa4i-0002AC-B0 for qemu-devel@nongnu.org; Thu, 05 Dec 2013 09:38:44 -0500 Message-ID: <52A08FED.7020305@redhat.com> Date: Thu, 05 Dec 2013 07:38:37 -0700 From: Eric Blake MIME-Version: 1.0 References: <1386077165-19577-1-git-send-email-benoit@irqsave.net> <1386077165-19577-4-git-send-email-benoit@irqsave.net> <529FBEDA.9050409@redhat.com> <20131205142416.GD2892@irqsave.net> In-Reply-To: <20131205142416.GD2892@irqsave.net> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="HnCiuWDjTIvQT7J5Exo3AvGhtCbDtcVcP" Subject: Re: [Qemu-devel] [RFC V3 3/7] qapi: Add skeletton of command to query a drive bs graph. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?UTF-8?B?QmVub8OudCBDYW5ldA==?= Cc: kwolf@redhat.com, famz@redhat.com, jcody@redhat.com, qemu-devel@nongnu.org, armbru@redhat.com, stefanha@redhat.com This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --HnCiuWDjTIvQT7J5Exo3AvGhtCbDtcVcP Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 12/05/2013 07:24 AM, Beno=C3=AEt Canet wrote: >> >> Am I correct that it will be possible to have named nodes that are not= >> currently associated with any device? If so, how do we learn about >> those nodes? Would it be better to have a command that returns an arr= ay >> of structs for all known node roots, with an optional member describin= g >> which device owns that node root? Something like: >=20 > The code have a list of all named nodes but not a list of named nodes r= oots. > Also it's difficult to get the device name for a named node because the= bses don't > have any backward pointers to their parents. > It could be done by recursing into all the blockbackend bs but it's twi= sted. Still worth thinking about how to structure things so we could add it in the future if it turns out to be useful to management, but I can understand why you aren't providing it right away. >=20 > In fact I am wondering if we really need something to spit out the name= d nodes > topology in QMP for the simple reason that the names of the nodes are g= iven by the > management so the management should already know the topology. There's one case where management might not know - if libvirtd gets restarted while in the middle of an operation that was attempting to create a named node, then on restart and reconnection to the monitor, libvirt would want to query to see if the node actually got created or if the command needs to be attempted again. I'm not a fan of write-only interfaces - and making management responsible to track all named nodes with no way to query if qemu actually agrees with the topology that management thinks it has commanded feels like a write-only interface. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --HnCiuWDjTIvQT7J5Exo3AvGhtCbDtcVcP Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.15 (GNU/Linux) Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJSoI/tAAoJEKeha0olJ0Nq12UIAKQ4q05Cr3UMZ5wIu1P+XEJn jn3hSLtQ7KdIMpKkM1cG/1HqCRnzByAPJmJsIYBe1KlUuwhyk+pwXDU5dEIOG6dk nTsJ/6KtZlHd1T0pyXraUY2PmKd1G3toGycwixSYtcC77IvA9AGlXtBftmsWlIrZ 55cbJxkgPj59XqKKki/3X1W8WwcuDdwg0qhs2ImMCovnM5LaNbjf44dyi0EbCWTz ihqETzOO1k8bo1j0TWq0fHFSUB29IPqjXu/tvqSBjQxIwAcmGkYubz1CWbac4kCb gN1GLpun5dtLVNLoB0m3oWnS5KQXZo3rZN/WqreoRPz4VgYaNy5LUlKVIXJUZXk= =MFoo -----END PGP SIGNATURE----- --HnCiuWDjTIvQT7J5Exo3AvGhtCbDtcVcP--