From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Wolf Subject: Re: [tip:tools/kvm] kvm tools, qcow: Fix copy-on-write image corruption Date: Fri, 22 Jul 2011 10:33:33 +0200 Message-ID: <4E2935DD.20005@redhat.com> References: <4E27DEA9.20404@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, levinsasha928@gmail.com, tglx@linutronix.de, linux-tip-commits@vger.kernel.org, kvm-devel To: Pekka Enberg Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Am 22.07.2011 10:21, schrieb Pekka Enberg: > On Thu, 21 Jul 2011, Kevin Wolf wrote: >> Hm, I must have missed this patch on the KVM mailing list... > > It wasn't on the list, sorry. > >> You should also error out before creating a new L2 table as its refcount >> would have to be updated, too. On the other hand, the patch is a bit too >> restrictive, because it applies the check to qcow1 which doesn't even >> have a refcount table. > > Oh, right, I broken QCOW1. > >> I'm not sure if everyone is aware of it, so another hint: Now that you >> can't grow qcow2 any more, you might find it useful to use qemu-img >> create -f qcow2 -o preallocation=metadata, so that all clusters are >> already present and you don't get random failures. > > Yup, I'm aware that you can't grow images anymore. The patch was meant as > a stop-gap measure while I'm hacking on refcount table support. Yeah, I was pretty sure you were aware of _that_, but maybe not everyone knows that metadata preallocation exists. Kevin