From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47374) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aBkrN-0001XF-CJ for qemu-devel@nongnu.org; Wed, 23 Dec 2015 09:57:51 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aBkrJ-000564-Oy for qemu-devel@nongnu.org; Wed, 23 Dec 2015 09:57:49 -0500 Received: from mail-lf0-x244.google.com ([2a00:1450:4010:c07::244]:35043) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aBkrJ-00055Y-Hx for qemu-devel@nongnu.org; Wed, 23 Dec 2015 09:57:45 -0500 Received: by mail-lf0-x244.google.com with SMTP id z124so14786441lfa.2 for ; Wed, 23 Dec 2015 06:57:44 -0800 (PST) MIME-Version: 1.0 Sender: vase@selfip.ru In-Reply-To: <1450802786-20893-1-git-send-email-kwolf@redhat.com> References: <1450802786-20893-1-git-send-email-kwolf@redhat.com> From: Vasiliy Tolstov Date: Wed, 23 Dec 2015 17:57:28 +0300 Message-ID: Content-Type: text/plain; charset=UTF-8 Subject: Re: [Qemu-devel] [PATCH 00/10] qcow2: Implement image locking List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, mreitz@redhat.com 2015-12-22 19:46 GMT+03:00 Kevin Wolf : > Enough innocent images have died because users called 'qemu-img snapshot' while > the VM was still running. Educating the users doesn't seem to be a working > strategy, so this series adds locking to qcow2 that refuses to access the image > read-write from two processes. > > Eric, this will require a libvirt update to deal with qemu crashes which leave > locked images behind. The simplest thinkable way would be to unconditionally > override the lock in libvirt whenever the option is present. In that case, > libvirt VMs would be protected against concurrent non-libvirt accesses, but not > the other way round. If you want more than that, libvirt would have to check > somehow if it was its own VM that used the image and left the lock behind. I > imagine that can't be too hard either. This breaks ability to create disk only snapshot while vm is running. Or i miss something? -- Vasiliy Tolstov, e-mail: v.tolstov@selfip.ru