From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44842) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cj6pl-0001SK-Vb for qemu-devel@nongnu.org; Wed, 01 Mar 2017 11:10:34 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cj6pi-0002fH-F0 for qemu-devel@nongnu.org; Wed, 01 Mar 2017 11:10:33 -0500 Date: Thu, 2 Mar 2017 00:10:23 +0800 From: Fam Zheng Message-ID: <20170301161023.GA17634@lemon.lan> References: <20170301081504.23595-1-famz@redhat.com> <20170301094917.GA4799@noname.redhat.com> <20170301123913.GA26744@lemon.lan> <20170301151626.GB4799@noname.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170301151626.GB4799@noname.redhat.com> Subject: Re: [Qemu-devel] [PATCH RFC] block: Tolerate existing writers on read only BdrvChild List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: qemu-devel@nongnu.org, Max Reitz , qemu-block@nongnu.org On Wed, 03/01 16:16, Kevin Wolf wrote: > > I'm not sure about this because: 1) this is intrusive from a user PoV, many > > scripts and upper layer tools will stop working; > > Are you sure? I don't expect user scripts or even proper management > tools to use qemu-io on running VMs. I do expect that some users are > using 'convert -s' with running VMs despite our recommendation against > it. > > If they are aware that they're doing something that works only in the > right circumstances, then breaking it isn't nice. But my gut feeling is > that most of them don't know about the implications of accessing a live > image. In this case breaking their use case and making them think about > whether they want to add something like a --force option sounds like a > good thing because they aren't caught by surprise when things go wrong > eventually. Yes, the use case is poor for qcow2, and your points stand there. But image locking will be at the posix level, which has a wider range of users. I cannot draw the same conclusion on raw images as easily.