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Date: Tue, 20 Aug 2013 15:57:40 +0100
From: "Daniel P. Berrange" <berrange@redhat.com>
Message-ID: <20130820145740.GA5579@redhat.com>
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Subject: Re: [Qemu-devel] Fwd: [libvirt] virDomainAttachDevice error during
 disk hotplug
Reply-To: "Daniel P. Berrange" <berrange@redhat.com>
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Deepak C Shetty <deepakcs@linux.vnet.ibm.com>, qemu-devel@nongnu.org

On Tue, Aug 20, 2013 at 04:43:48PM +0200, Stefan Hajnoczi wrote:
> On Fri, Aug 16, 2013 at 06:52:32PM +0530, Deepak C Shetty wrote:
> > 2) qemu-img info /var/run/vdsm/3333017d-1278-4bfb-8129-62bded257399
> > image: /var/run/vdsm/3333017d-1278-4bfb-8129-62bded257399
> > file format: qcow2
> > virtual size: 3.8G (4096000000 bytes)
> > disk size: 196K
> > cluster_size: 65536
> > backing file:
> > /rhev/data-center/000065de-04b8-42e2-986c-2de664708be7/11112d24-4cda-4200-8f6d-a1d8362c70fd/images/22224c45-6504-4ea1-bd24-12340017dd32/3333017d-1278-4bfb-8129-62bded257399
> > backing file format: qcow2
> 
> Good, QEMU can parse and read the file.
> 
> > 3) ls -l
> > /rhev/data-center/000065de-04b8-42e2-986c-2de664708be7/11112d24-4cda-4200-8f6d-a1d8362c70fd/images/22224c45-6504-4ea1-bd24-12340017dd32/3333017d-1278-4bfb-8129-62bded257399
> > -r--r-----. 1 vdsm kvm 197120 Aug 10 11:59
> > /rhev/data-center/000065de-04b8-42e2-986c-2de664708be7/11112d24-4cda-4200-8f6d-a1d8362c70fd/images/22224c45-6504-4ea1-bd24-12340017dd32/3333017d-1278-4bfb-8129-62bded257399
> 
> Read-only?
> 
> > 4) libvirtd.log snippets:
> > 
> > 2013-08-10 11:19:41.766+0000: 1103: debug : virDomainAttachDevice:9820 :
> > dom=0x7f92f4003f20, (VM: name=dpk_BR_vm,
> > uuid=9999017d-1278-4bfb-8129-62bded257399), xml=<disk device="disk"
> > snapshot="no" type="file">
> >         <source file="/var/run/vdsm/3333017d-1278-4bfb-8129-62bded257399"/>
> >         <target bus="virtio" dev="vdb"/>
> > <serial>22224c45-6504-4ea1-bd24-12340017dd32</serial>
> >         <driver cache="none" error_policy="stop" io="threads"
> > name="qemu" type="qcow2"/>
> > </disk>
> 
> I see no read-only option.
> 
> Does it work if you make the file read-write instead?

FYI this was solved in libvir-list.

The image file was on tmpfs, which does not support cache=none.

We hit this so often it would be a huge help if QEMU reported a
clearer error message then "Invalid Argument" when trying cache=none
on tmpfs.


Daniel
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