From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50869) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z5XP0-0005eu-69 for qemu-devel@nongnu.org; Thu, 18 Jun 2015 06:50:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z5XOw-0008MI-QA for qemu-devel@nongnu.org; Thu, 18 Jun 2015 06:50:34 -0400 Date: Thu, 18 Jun 2015 11:50:25 +0100 From: Stefan Hajnoczi Message-ID: <20150618105025.GC25387@stefanha-thinkpad.redhat.com> References: <1434617361-17778-1-git-send-email-wency@cn.fujitsu.com> <1434617361-17778-5-git-send-email-wency@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="5QAgd0e35j3NYeGe" Content-Disposition: inline In-Reply-To: <1434617361-17778-5-git-send-email-wency@cn.fujitsu.com> Subject: Re: [Qemu-devel] [PATCH COLO-Block v6 04/16] block: Parse "backing_reference" option to reference existing BDS List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Wen Congyang Cc: Kevin Wolf , Fam Zheng , Lai Jiangshan , qemu block , Jiang Yunhong , Dong Eddie , qemu devel , Max Reitz , Gonglei , Stefan Hajnoczi , Paolo Bonzini , Yang Hongyang , "Dr. David Alan Gilbert" , zhanghailiang --5QAgd0e35j3NYeGe Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Jun 18, 2015 at 04:49:09PM +0800, Wen Congyang wrote: > Usage: > -drive file=3Dxxx,id=3DY, \ > -drive file=3Dxxxx,id=3DX,backing_reference.drive_id=3DY,backing_referenc= e.hidden-disk.* >=20 > It will create such backing chain: > {virtio-blk dev 'Y'} = {virtio-blk dev 'X'} > | = | > | = | > v = v >=20 > [base] <- [mid] <- ( Y ) <----------------- (hidden target) <-------= -------- ( X ) >=20 > v ^ > v ^ > v ^ > v ^ > >>>> drive-backup sync=3Dnone >>>> >=20 > X's backing file is hidden-disk, and hidden-disk's backing file is Y. > Disk Y may be opened or reopened in read-write mode, so A block backup > job is automatically created: source is Y and target is hidden disk. > Active disk X, hidden disk, and Y are all on the same AioContext. The command-line option name confused me. I expected "backing_reference" t= o result in: Y <- X The backup block job and hidden target makes this option more than just referencing the backing device. The name "backing.backup-reference" is clearer to me, but I think Kevin might have more idea for you on this patch. --5QAgd0e35j3NYeGe Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJVgqJxAAoJEJykq7OBq3PIWn4H/10MpgqbZYD3IuOLln0qYg/K d2EeqR+DDNYgPyXp+jFI5wHQRfiCbEncpif+/a7Ojk+FuIQNlOhM1qnrQ2N/fRJx LT4FeheJEQkvpQAfgqpYfhtGouLUKXXhuekbvlJkK2x5iX/YNl3Dd9NvOObe+mEW XlHev2BuRkrKGOucYFSmBbShC2P2XsY0p6NgApjABMmqe9fE8giL/jFMI52KN4g0 uSKdV96f/mLji3ecIYwh/+Rzc34tnhLjSV5yNzfKeuTHlYpEK9XoKTfbAoFJLLs3 GVWt/Ce1mIIskgRPd73N5jDofTYRFGr4+4um75gZCeqxyif7SjFHQZdQnmIqFAs= =FejN -----END PGP SIGNATURE----- --5QAgd0e35j3NYeGe--