From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44350) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wl0li-0005WU-9U for qemu-devel@nongnu.org; Thu, 15 May 2014 14:52:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wl0lc-0000hK-PC for qemu-devel@nongnu.org; Thu, 15 May 2014 14:52:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:30689) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Wl0lc-0000gd-GS for qemu-devel@nongnu.org; Thu, 15 May 2014 14:52:32 -0400 Message-ID: <53750CE9.3060607@redhat.com> Date: Thu, 15 May 2014 12:52:25 -0600 From: Eric Blake MIME-Version: 1.0 References: <50765faa0041d43d22dd14a0128d3b55850571ac.1400123059.git.jcody@redhat.com> <5374E622.4000805@redhat.com> <20140515182203.GL8452@localhost.localdomain> In-Reply-To: <20140515182203.GL8452@localhost.localdomain> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="eI4vA0VksTuljPhQtSOoH25b2fUOG4MTd" Subject: Re: [Qemu-devel] [PATCH 5/5] block: extend block-commit to accept a string for the backing file List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jeff Cody Cc: kwolf@redhat.com, benoit.canet@irqsave.net, pkrempa@redhat.com, famz@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --eI4vA0VksTuljPhQtSOoH25b2fUOG4MTd Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 05/15/2014 12:22 PM, Jeff Cody wrote: >> Hmm - how will this be discoverable by libvirt? Maybe when libvirt is >> doing the 'qemu -m none' probing, it can hotplug a device pointing to >> /dev/null (libvirt _already_ does that to test if add-fd works), and >> intentionally omit a node name. If libvirt then queries the device, a= nd >> sees that the __qemu##000NNNN node-name was auto-assigned, then it can= >> be assumed that this qemu is new enough to provide node-names for ALL >> operations (but that means this series is incomplete unless we add >> node-name support to all remaining block commands, such as block-strea= m, >> drive-mirror, and drive-backup). This part is where I wonder if patch= >> 1/5 should be rebased to be last in the series. >> >=20 > Ah... I had originally planned on submitting separate patches for each > of the block jobs, to make reviewing easier. But your idea on how > libvirt can discover this is a good one, and would mandate changing > those commands all in one series to be effective. So this series will > grow by a few patches. :) >=20 > If libvirt is going to use the autogenerated string format for > decisions, we should also document the string format in the QAPI docs. Adding a new command is much easier to probe for (a single query-commands, which we are already using) than requiring a sequence of operations (hotplug, then query to see if a name was assigned), and probably even more direct (if the standalone command exists, then so does the integrated use of setting backing names). >> >> In short, this new command option allows the equivalent of 'qemu-img >> rebase -u' on a live image. Definitely a needed functionality. >> >=20 > Would it be useful to have a stand-alone QMP command to change the > backing-file, as well? As this stands, it will only change the > backing file if you are also merging data down the chain.=20 >=20 > If you want/need the ability to do a true 'qemu-img rebase -u' on any > given image without other chain modification, that needs a new > command. Yes, I think that's probably a wise idea to provide a dedicated command for just changing the name recorded in a backing file. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --eI4vA0VksTuljPhQtSOoH25b2fUOG4MTd 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 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJTdQzpAAoJEKeha0olJ0NqYX8H/3mwoy1Qf7mbx2MIfemAwuQp WdCUCtTanULPOTs4luTTlatTN/suFCcCcUtP9rstox9memo+kCRKQxiqV3CTQpGI M8kIDApvJWgoWffJ9np7PUuBDV62FNDTp5S7wE47ruhKm8KvbTNyDu3Gwd2bdY5g zUKN1bLrPlKj3b2pY+HgCHQ85QOGpiDcCJOzbFtbw/2Anr9wvwQ0VCMFsEgSptME gX2ABcCvwZxZ6cofZwHJ11UyooWbJf2a7jmulfDNEFA5QoLiNe2krilzcye45E1A 14FRRjKVkzgUyoHqgaPCsmkSg+x3LAU/a0HJ1XE/1xvi2RHgg/pOPRpuhh/Mj78= =hC3B -----END PGP SIGNATURE----- --eI4vA0VksTuljPhQtSOoH25b2fUOG4MTd--