On 04/27/2015 10:08 PM, Shanzhi Yu wrote: >>> Should libvirt post error when try a shallow blockcopy of file without >>> backing file, just as shallow blockcommit? >> I cannot reproduce the error above, could you please post steps to do >> that? or perhaps debug log from libvirt? > > It is easy to reproduce. Suppose live guest xml looks like: > > # virsh dumpxml vm1|grep disk -A 8 > <disk type='file' device='disk'> > <driver name='qemu' type='qcow2'/> > <source file='/var/lib/libvirt/images/raw.1430143276'/> > <backingStore type='file' index='1'> > <format type='raw'/> > <source file='/var/lib/libvirt/images/raw.img'/> > <backingStore/> > </backingStore> > <target dev='vda' bus='virtio'/> > <alias name='virtio-disk0'/> > <address type='pci' domain='0x0000' bus='0x00' slot='0x03' > function='0x0'/> > </disk> > > Then try a shallow blockcommit of file has no backing file > > But a shallow block copy of file which has backing file into a raw file > does not make any sense, right? A shallow block copy of: A <- B into a pre-existing file C, where C starts life with contents identical to A, makes sense. A shallow block copy where _libvirt_ creates C does not make sense. The key is that the moment you use the REUSE_EXTERNAL flag, _you_ are now responsible for providing a valid destination (and anything is supported; libvirt should not get in your way). -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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