From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53433) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1akvoW-00017P-6z for qemu-devel@nongnu.org; Tue, 29 Mar 2016 11:44:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1akvoV-0001Bz-3S for qemu-devel@nongnu.org; Tue, 29 Mar 2016 11:44:16 -0400 References: <1457578181-27111-1-git-send-email-xiecl.fnst@cn.fujitsu.com> <1457578181-27111-3-git-send-email-xiecl.fnst@cn.fujitsu.com> <56E653E0.9030808@cn.fujitsu.com> <56EA06E0.7000409@cn.fujitsu.com> <56EA7C62.3090000@cn.fujitsu.com> <20160317094831.GA2504@work-vm> <56EA7F39.9060504@cn.fujitsu.com> <56FAA168.9090304@redhat.com> From: Eric Blake Message-ID: <56FAA2C4.3000002@redhat.com> Date: Tue, 29 Mar 2016 09:44:04 -0600 MIME-Version: 1.0 In-Reply-To: <56FAA168.9090304@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="qE1WRajntOmckl8MI3NBjT5LMi2gUA1wC" Subject: Re: [Qemu-devel] [PATCH v12 2/3] quorum: implement bdrv_add_child() and bdrv_del_child() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Max Reitz , Wen Congyang , "Dr. David Alan Gilbert" Cc: Kevin Wolf , Changlong Xie , Alberto Garcia , zhanghailiang , qemu block , Jiang Yunhong , Dong Eddie , qemu devel , Markus Armbruster , Gonglei , Stefan Hajnoczi This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --qE1WRajntOmckl8MI3NBjT5LMi2gUA1wC Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 03/29/2016 09:38 AM, Max Reitz wrote: > On 17.03.2016 10:56, Wen Congyang wrote: >> On 03/17/2016 05:48 PM, Dr. David Alan Gilbert wrote: >=20 > [...] >=20 >>> The children.0 notation is really confusing in the way that Berto >>> describes; I hit this a couple of months ago and it really doesn't >>> make sense. >> >> Do you mean: read from children.1 first, and then read from children.0= in >> fifo mode? Yes, the behavior is very strange. >=20 > So is this intended or is it not? In > http://lists.nongnu.org/archive/html/qemu-block/2016-03/msg00526.html > you said that it is. >=20 > I myself would indeed say it is very strange. If I were a user, I would= > not expect this behavior. And as I developer, I think that how a BDS's > child is used by its parent should solely depend on its role (e.g. > whether it is "children.0" or "children.1"). It sounds like the argument here, and in Max's thread on query-block-node-tree, is that we DO have cases where order matters, and so we need a way for the hot-add operation to explicitly specify where in the list a child is inserted (whether it is being inserted as the new primary image, or explicitly as the last resort, or somewhere in the middle). An optional parameter, that defaults to appending, may be ok, but we definitely need to consider how the order of children is affected by hot-add. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --qE1WRajntOmckl8MI3NBjT5LMi2gUA1wC 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 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJW+qLEAAoJEKeha0olJ0NqNRUH+gLycqjS24kB1LI0LE55ZSN8 B2hpaMmo5uIBX5fw5zbSkzsvwFCp3xiDydl6jTnMQ0H2/c2eKb5xk0X/lHO3NvVm LdOD/VV+8+NEvh/URaOqi0XDfT/GYrB72CBEbWrmqOLI9hZEDstmdt8df5N6jJ9y EcWPOG1NYC7ty2uXDLXGXQwN6tvkTlNNuJ3ptj5uymhh/hE9Pzy/tH/7vouLf8nj ir35+pgXXyA/WGMeYG3DRTyOA1MIVtSkPSlc0fm0uXmouHWf9UbG/GdTliNP7hVz mZY1Pp+GTyD1sc2XG/rRF8B+bPoZxfsNBK2DPI6o6rQBj26HeArFo6yB6Yn9aBA= =1IeE -----END PGP SIGNATURE----- --qE1WRajntOmckl8MI3NBjT5LMi2gUA1wC--