From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50771) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b06gD-0004BJ-64 for qemu-devel@nongnu.org; Tue, 10 May 2016 08:22:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1b06gA-0007JZ-QA for qemu-devel@nongnu.org; Tue, 10 May 2016 08:22:23 -0400 Date: Tue, 10 May 2016 13:22:09 +0100 From: "Daniel P. Berrange" Message-ID: <20160510122209.GJ13377@redhat.com> Reply-To: "Daniel P. Berrange" References: <20160510091422.GG4921@noname.str.redhat.com> <20160510092338.GG13377@redhat.com> <20160510093514.GH4921@noname.str.redhat.com> <20160510094310.GH13377@redhat.com> <20160510100706.GJ4921@noname.str.redhat.com> <20160510101612.GY1683@redhat.com> <20160510110849.GK4921@noname.str.redhat.com> <20160510114615.GZ1683@redhat.com> <20160510120102.GM4921@noname.str.redhat.com> <20160510121130.GA1683@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20160510121130.GA1683@redhat.com> Subject: Re: [Qemu-devel] [PATCH v4 00/27] block: Lock images when opening List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Richard W.M. Jones" Cc: Kevin Wolf , Fam Zheng , qemu-block@nongnu.org, Jeff Cody , Markus Armbruster , qemu-devel@nongnu.org, stefanha@redhat.com, pbonzini@redhat.com, den@openvz.org, Max Reitz , John Snow On Tue, May 10, 2016 at 01:11:30PM +0100, Richard W.M. Jones wrote: > At no point did I say that it was safe to use libguestfs on live VMs > or that you would always get consistent data out. > > But the fact that it can fail is understood, the chance of failure is > really tiny (it has literally only happened twice that I've read > corrupted data, in years of daily use), and the operation is very > useful. > > So I think this patch series should either not lock r/o VMs, or should > add a nolock flag to override the locking (which libguestfs will > always use). If QEMU locks r/o disks, then libvirt would likely end up setting the "nolock" flag unconditionally too, in order to avoid breaking libguestfs and other application usage of libvirt. Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|