Re: [libvirt] [PATCH v1] qemu-migration: Disallow migration of read only disk

On 08/11/2016 08:57 AM, Corey S McQuay wrote: > On 08/10/2016 09:16 AM, Koniszewski, Pawel wrote: > >>> -----Original Message----- >>> From: libvir-list-bounces(a)redhat.com [mailto:libvir-list- >>> bounces(a)redhat.com] On Behalf Of Corey S. McQuay >>> Sent: Friday, August 5, 2016 8:34 PM >>> To: jjherne(a)linux.vnet.ibm.com; libvir-list(a)redhat.com >>> Cc: Corey S. McQuay <csmcquay(a)linux.vnet.ibm.com&gt; >>> Subject: [libvirt] [PATCH v1] qemu-migration: Disallow migration of >>> read only >>> disk >>> >>> From: "Corey S. McQuay" <csmcquay(a)linux.vnet.ibm.com&gt; >>> >>> Currently Libvirt allows attempts to migrate read only disks. Qemu >>> cannot >>> handle this as read only disks cannot be written to on the >>> destination system. >>> The end result is a cryptic error message and a failed migration. >>> >>> This patch causes migration to fail earlier and provides a meaningful >>> error >>> message stating that migrating read only disks is not supported. >> What will happen if read-only disk is copied to destination prior to >> migration start? Currently such scenario works, will it still work >> with this code? > Based on our testing, pre-copying a read only disk image to the > destination system has no effect on the outcome of attempting to migrate > a non-shared read only disk. I'm not sure what scenario you are > referring to but here is what we tried: > > Relevant guest xml: > <disk type='file' device='cdrom'> > <driver name='qemu' type='raw' cache='writethrough'/> > <source file='/disk-images/guest.iso'/> > <backingStore/> > <target dev='sdz' bus='scsi'/> > <readonly/> > <alias name='scsi0-0-0-0'/> > <address type='drive' controller='0' bus='0' target='0' unit='0'/> > </disk> > > The disk image exists at /disk-images/guest.iso on the source. Before > migration we copied the image to the same path on the destination > system. Then we attempted migration: > > virsh migrate --live --copy-storage-all --migrate-disks sdz > --verbose kvm1 qemu+ssh://dstHost/system tcp://dstHost > > The error message we get is: > > error: internal error: info migration reply was missing return status > > Running journalctl shows additional information: > > Aug 10 16:02:16 collin-kvm libvirtd[41616]: operation failed: migration > of disk sdz failed. > > I'm pretty sure this patch does not stop the user from doing anything > that works today. But if your scenario is different from ours in some > way please let us know and we'll do some more testing. Pawel, Thanks for taking a look. Does Corey's reply address your concerns?