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This will be superseded by allowing the full backing chain to be specified in the XML explicitly rather than trying to detect it.
*** This bug has been marked as a duplicate of bug 760547 ***
Description of problem: Recently libvirt can't introspect the backing chain for certain storage technologies, thus the <backingStore> elements are missing for them. And we hope it can support all backing file in backing chain are network disk type. Version-Release number of selected component (if applicable): libvirt-3.9.0-7.el7.x86_64 qemu-kvm-rhev-2.10.0-15.el7.x86_64 How reproducible: 100% Steps to Reproduce: 1. Prepare a guest with iscsi network disk. 2. Create backing file. # qemu-img create -f qcow2 -b iscsi://**IP**:3260/iqn.2003-01.org.linux-iscsi.localhost.x8664:sn.9cba196611e6/0 iscsi://**IP**:3260/iqn.2003-01.org.linux-iscsi.localhost.x8664:sn.a8d92ebb4ece/0 -o backing_fmt=qcow2 3. Check backing chain info. # qemu-img info iscsi://**IP*8:3260/iqn.2003-01.org.linux-iscsi.localhost.x8664:sn.a8d92ebb4ece/0 --backing-chain image: json:{"driver": "qcow2", "file": {"lun": "0", "portal": "**IP**:3260", "driver": "iscsi", "transport": "tcp", "target": "iqn.2003-01.org.linux-iscsi.localhost.x8664:sn.a8d92ebb4ece"}} file format: qcow2 virtual size: 5.0G (5368709120 bytes) disk size: unavailable cluster_size: 65536 backing file: iscsi://**IP**:3260/iqn.2003-01.org.linux-iscsi.localhost.x8664:sn.9cba196611e6/0 backing file format: qcow2 Format specific information: compat: 1.1 lazy refcounts: false refcount bits: 16 corrupt: false image: json:{"driver": "qcow2", "file": {"lun": "0", "portal": "**IP**:3260", "driver": "iscsi", "transport": "tcp", "target": "iqn.2003-01.org.linux-iscsi.localhost.x8664:sn.9cba196611e6"}} file format: qcow2 virtual size: 5.0G (5368709120 bytes) disk size: unavailable cluster_size: 65536 Format specific information: compat: 1.1 lazy refcounts: false refcount bits: 16 corrupt: false 4. Start guest with the last layer and check guest xml. # virsh dumpxml rhel7 | grep disk -A 9 ... <disk type='network' device='disk'> <driver name='qemu' type='qcow2'/> <source protocol='iscsi' name='iqn.2003-01.org.linux-iscsi.localhost.x8664:sn.a8d92ebb4ece/0'> <host name='**IP**' port='3260'/> </source> <target dev='vda' bus='virtio'/> <alias name='virtio-disk1'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/> </disk> ... Actual results: As above step4. Expected results: # virsh dumpxml rhel7 | grep disk -A 9 ... <disk type='network' device='disk'> <driver name='qemu' type='qcow2'/> <source protocol='iscsi' name='iqn.2003-01.org.linux-iscsi.localhost.x8664:sn.a8d92ebb4ece/0'> <host name='**IP**' port='3260'/> <backingStore type='network' index='1'> <format type='qcow2'/> <source protocol='iscsi' name='iqn.2003-01.org.linux-iscsi.localhost.x8664:sn.9cba196611e6/0'> <host name='**IP**' port='3260'/> </source> -- </backingStore> </source> <target dev='vda' bus='virtio'/> <alias name='virtio-disk1'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/> </disk> ... Additional info: