From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.71) id 1drhln-00064F-6k for mharc-qemu-trivial@gnu.org; Tue, 12 Sep 2017 05:46:15 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52016) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1drhlk-00062c-F7 for qemu-trivial@nongnu.org; Tue, 12 Sep 2017 05:46:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1drhlj-00076F-K0 for qemu-trivial@nongnu.org; Tue, 12 Sep 2017 05:46:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47232) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1drhlf-00074T-04; Tue, 12 Sep 2017 05:46:07 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D0C904E33D; Tue, 12 Sep 2017 09:46:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com D0C904E33D Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=rjones@redhat.com Received: from localhost (ovpn-117-64.ams2.redhat.com [10.36.117.64]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1EB156E1E7; Tue, 12 Sep 2017 09:45:59 +0000 (UTC) Date: Tue, 12 Sep 2017 10:45:59 +0100 From: "Richard W.M. Jones" To: Kevin Wolf Cc: qemu-devel@nongnu.org, armbru@redhat.com, famz@redhat.com, qemu-trivial@nongnu.org, mjt@tls.msk.ru, berrange@redhat.com Message-ID: <20170912094558.GO20914@redhat.com> References: <20170906085006.26983-1-rjones@redhat.com> <20170906101905.GD3753@dhcp-200-186.str.redhat.com> <20170906104451.GM20914@redhat.com> <20170906113845.GE3753@dhcp-200-186.str.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170906113845.GE3753@dhcp-200-186.str.redhat.com> User-Agent: Mutt/1.5.20 (2009-12-10) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Tue, 12 Sep 2017 09:46:04 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-trivial] [PATCH for-2.10] qemu-options: Document the -drive locking parameter. X-BeenThere: qemu-trivial@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 12 Sep 2017 09:46:13 -0000 On Wed, Sep 06, 2017 at 01:38:45PM +0200, Kevin Wolf wrote: > This command line fragment looks correct to me. For me, it seems to > work. I'm starting a first qemu in the background with default locking > options: > > $ x86_64-softmmu/qemu-system-x86_64 -hda /tmp/test.qcow2 > > And then starting a second one with a command line resembling yours: > > $ x86_64-softmmu/qemu-system-x86_64 -device virtio-scsi \ > -drive file=/tmp/test.qcow2,cache=unsafe,format=qcow2,file.locking=off,id=hd0,if=none \ > -device scsi-hd,drive=hd0 The problem is with overlays, where file.locking doesn't propagate to the backing file. Thus: $ qemu-system-x86_64 -drive file=backing,format=raw while in another terminal: $ qemu-img create -b backing -f qcow2 overlay $ qemu-system-x86_64 -drive file=overlay,format=qcow2,file.locking=off qemu-system-x86_64: Failed to get shared "write" lock Is another process using the image? After some experimentation, I came up with this command which works: $ qemu-system-x86_64 -drive file.file.filename=overlay,file.driver=qcow2,file.backing.file.locking=off Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/