From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49255) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1X1czv-0006qs-CY for qemu-devel@nongnu.org; Mon, 30 Jun 2014 10:56:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1X1czm-0002VK-Jv for qemu-devel@nongnu.org; Mon, 30 Jun 2014 10:55:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:27371) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1X1czm-0002Uu-Ap for qemu-devel@nongnu.org; Mon, 30 Jun 2014 10:55:50 -0400 Date: Mon, 30 Jun 2014 16:55:46 +0200 From: Kevin Wolf Message-ID: <20140630145546.GC23599@noname.str.redhat.com> References: <82eecb42a9dfcdf06f2dbf4fceece75baa3bd917.1403723847.git.jcody@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <82eecb42a9dfcdf06f2dbf4fceece75baa3bd917.1403723847.git.jcody@redhat.com> Subject: Re: [Qemu-devel] [PATCH v7 for 2.1 2/4] 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: benoit.canet@irqsave.net, pkrempa@redhat.com, famz@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com Am 25.06.2014 um 21:40 hat Jeff Cody geschrieben: > On some image chains, QEMU may not always be able to resolve the > filenames properly, when updating the backing file of an image > after a block commit. > > For instance, certain relative pathnames may fail, or drives may > have been specified originally by file descriptor (e.g. /dev/fd/???), > or a relative protocol pathname may have been used. > > In these instances, QEMU may lack the information to be able to make > the correct choice, but the user or management layer most likely does > have that knowledge. > > With this extension to the block-commit api, the user is able to change > the backing file of the overlay image as part of the block-commit > operation. > > This allows the change to be 'safe', in the sense that if the attempt > to write the overlay image metadata fails, then the block-commit > operation returns failure, without disrupting the guest. > > If the commit top is the active layer, then specifying the backing > file string will be treated as an error (there is no overlay image > to modify in that case). > > If a backing file string is not specified in the command, the backing > file string to use is determined in the same manner as it was > previously. > > Reviewed-by: Eric Blake > Signed-off-by: Jeff Cody Reviewed-by: Kevin Wolf