From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41053) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZ1NA-00019q-KE for qemu-devel@nongnu.org; Mon, 07 Sep 2015 14:42:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZZ1N9-0002D9-I8 for qemu-devel@nongnu.org; Mon, 07 Sep 2015 14:42:32 -0400 References: <1437414365-11881-1-git-send-email-mreitz@redhat.com> <55E70F9B.20309@redhat.com> <55ED2655.1040405@cn.fujitsu.com> From: Max Reitz Message-ID: <55EDDA8E.6060900@redhat.com> Date: Mon, 7 Sep 2015 20:42:22 +0200 MIME-Version: 1.0 In-Reply-To: <55ED2655.1040405@cn.fujitsu.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="AirLWD3Ec7BKC6DVww9FJI8xOt8lPHIIS" Subject: Re: [Qemu-devel] [PATCH v4 00/38] blockdev: BlockBackend and media List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Wen Congyang , Eric Blake , qemu-block@nongnu.org Cc: Kevin Wolf , Alberto Garcia , qemu-devel@nongnu.org, Markus Armbruster , Stefan Hajnoczi , John Snow This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --AirLWD3Ec7BKC6DVww9FJI8xOt8lPHIIS Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 07.09.2015 07:53, Wen Congyang wrote: > On 09/02/2015 11:02 PM, Eric Blake wrote: >> On 07/20/2015 11:45 AM, Max Reitz wrote: >>> First of all: Thank you, Eric and Berto, for reviewing v3! And thank >>> you, Fam, for at least having a peek at it and being confident enough= to >>> base a series of your own on it. :-) >>> >>> This series reworks a lot regarding BlockBackend and media. Basically= , >>> it allows empty BlockBackends, that is BBs without a BDS tree. >>> >>> Before this series, empty drives are represented by a BlockBackend wi= th >>> an empty BDS attached to it (a BDS with a NULL driver). However, now = we >>> have BlockBackends, thus an empty drive should be represented by a >>> BlockBackend without any BDS tree attached to it. This is what this >>> series does. >> >> We've obviously missed 2.4; but now that 2.5 is open, are there plans = to >> get this series in sooner rather than later? Wen's work on dynamicall= y >> adding/deleting children from a quorum would benefit from the ability = to >> create a BDS without an associated BB, which in turn would help the CO= LO >> work. >> >=20 > This feature is very useful for COLO. COLO needs the following: > 1. adding/deleting children from a quorum dynamically > 2. allow references for backing files >=20 > The BDS without BB only can be created by the monitor command blockdev-= add. > How to create it in the command line? Right now: Not at all. Of course it would be possible to add a new command line parameter ("-blockdev"? "-bds"?) or option to drive ("backend=3Doff" or whatever), but right now I didn't see a need for that= =2E This series uses this so you can add a new medium for e.g. a CD drive at runtime. The backends remains attached to the drive, and you swap out the BDS tree. Thus, there was no need to add a medium via the command lin= e. Furthermore, often runtime configuration is a subset of command line configuration, i.e. you can always start the VM paused, invoke some QMP commands, and then continue the VM. Therefore I don't know whether we really need the ability to add BB-less BDS trees via the command line. Max --AirLWD3Ec7BKC6DVww9FJI8xOt8lPHIIS Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBCAAGBQJV7dqOAAoJEDuxQgLoOKytKZ4H/j4HXtccgq5HR/Inw4CJGW/F 2mcyJJlbPPV4tjFy0QObRC7ta8wWG0EHpmKkGgZEP99PbWNqNwGzg162C/EXhxvd z3LaoRWuuRBbii8UjCT5osOyTAhi0x7hjijTyEzGKMVKnBW5cSpvM/7xXkvxwbKj KAjbD//ZXLzMP144HEkI3MIC7vyrk5Nwp7odHvYy9JaRiugt4trVrliuPBc8nmlR CRcQrCDJHg/iY6iLI/GMDw7kVtu5ZFj7cpTe/whKry1D6W5O2P3mRz3pOnOqrI81 ZAGN1GxiNcP+sHvgkMVjTXhvqaRE8pypOzhaUM5uPMbunWtSmWCTsnyMIApx1K8= =1riy -----END PGP SIGNATURE----- --AirLWD3Ec7BKC6DVww9FJI8xOt8lPHIIS--