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Description of problem: wrong backingStore info after blockpull and destroy/start guest Version-Release number of selected component (if applicable): libvirt-1.2.8-3.el7.x86_64 How reproducible: 100% Steps to Reproduce: 1. Prepare a running guest # virsh list Id Name State ---------------------------------------------------- 32 rh7-l running 2. Create four external disk snapshot # for i in 1 2 3 4 ;do virsh snapshot-create-as rh7-l s$i --disk-only --diskspec vda,file=/tmp/rh7-l.s$i;done Domain snapshot s1 created Domain snapshot s2 created Domain snapshot s3 created Domain snapshot s4 created # virsh dumpxml rh7-g .. <disk type='file' device='disk'> <driver name='qemu' type='qcow2' cache='none'/> <source file='/tmp/rh7-l.s4'/> <backingStore type='file' index='1'> <format type='qcow2'/> <source file='/tmp/rh7-l.s3'/> <backingStore type='file' index='2'> <format type='qcow2'/> <source file='/tmp/rh7-l.s2'/> <backingStore type='file' index='3'> <format type='qcow2'/> <source file='/tmp/rh7-l.s1'/> <backingStore type='block' index='4'> <format type='raw'/> <source dev='/dev/vg01/lv01'/> <backingStore/> </backingStore> </backingStore> </backingStore> </backingStore> <target dev='vda' bus='virtio'/> .. #qemu-img info /tmp/rh7-l.s4 --backing-chain rh7-l.s4-> rh7-l.s3->rh7-l.s2->rh7-l.s1->/dev/vg01/lv01 3. Do blockpull from middle to top # virsh blockpull rh7-l vda --base vda[2] --verbose --wait Block Pull: [100 %] Pull complete or # virsh blockpull rh7-l vda --base /tmp/rh7-l.s3 --verbose --wait 4. Check snapshot file backing chain and guest xml #qemu-img info /tmp/rh7-l.s4 --backing-chain rh7-l.s4->rh7-l.s2->rh7-l.s1->/dev/vg01/lv01 # virsh dumpxml rh7-l|grep disk -A 16 <disk type='file' device='disk'> <driver name='qemu' type='qcow2' cache='none'/> <source file='/tmp/rh7-l.s4'/> <backingStore type='file' index='1'> <format type='qcow2'/> <source file='/tmp/rh7-l.s2'/> <backingStore type='file' index='2'> <format type='qcow2'/> <source file='/tmp/rh7-l.s1'/> <backingStore type='block' index='3'> <format type='raw'/> <source dev='/dev/vg01/lv01'/> <backingStore/> </backingStore> </backingStore> </backingStore> <target dev='vda' bus='virtio'/> .. 5. Destroy/start guest then re-check guest xml # virsh destroy rh7-l;virsh start rh7-l; Domain rh7-l destroyed Domain rh7-l started # virsh dumpxml rh7-l .. <disk type='file' device='disk'> <driver name='qemu' type='qcow2' cache='none'/> <source file='/tmp/rh7-l.s4'/> <backingStore type='file' index='1'> <format type='qcow2'/> <source file='/tmp/rh7-l.s3'/> <backingStore type='file' index='2'> <format type='qcow2'/> <source file='/tmp/rh7-l.s2'/> <backingStore type='file' index='3'> <format type='qcow2'/> <source file='/tmp/rh7-l.s1'/> <backingStore type='block' index='4'> <format type='raw'/> <source dev='/dev/vg01/lv01'/> <backingStore/> </backingStore> </backingStore> </backingStore> </backingStore> <target dev='vda' bus='virtio'/> .. 6. Do blockpull again # virsh blockpull rh7-l vda --base vda[1] --verbose --wait error: internal error: Unexpected error: (GenericError) 'Base '/tmp/rh7-l.s3' not found' Actual results: Expected results: /tmp/rh7-l.s3 should not appear in guest xml since it already pull into rh7-l.s4 Additional info:
Fixed upstream: commit fe7ef7b112b3b4d6f9c9edf499a79683fb0b7edb Author: Peter Krempa <pkrempa@redhat.com> Date: Thu Sep 25 17:30:28 2014 +0200 qemu: Always re-detect backing chain Since 363e9a68 we track backing chain metadata when creating snapshots the right way even for the inactive configuration. As we did not yet update other code paths that modify the backing chain (blockpull) the newDef backing chain gets out of sync. After stopping of a VM the new definition gets copied to the next start one. The new VM then has incorrect backing chain info. This patch switches the backing chain detector to always purge the existing backing chain and forces re-detection to avoid this issue until we'll have full backing chain tracking support. v1.2.9-rc1-9-gfe7ef7b
Verified on libvirt-1.2.8-5.el7.x86_64 and qemu-kvm-rhev-2.1.2-1.el7.x86_64 Steps: 1. Create 4 external disk only snapshots # for i in s1 s2 s3 s4; do virsh snapshot-create-as qe-con $i --disk-only --diskspec vda,file=/tmp/qe-con.$i; done Domain snapshot s1 created Domain snapshot s2 created Domain snapshot s3 created Domain snapshot s4 created # virsh snapshot-list qe-con Name Creation Time State ------------------------------------------------------------ s1 2014-10-11 14:42:10 +0800 disk-snapshot s2 2014-10-11 14:42:10 +0800 disk-snapshot s3 2014-10-11 14:42:11 +0800 disk-snapshot s4 2014-10-11 14:42:11 +0800 disk-snapshot 2. check the xml # virsh dumpxml qe-con | grep disk -a16 <disk type='file' device='disk'> <driver name='qemu' type='qcow2' cache='none'/> <source file='/tmp/qe-con.s4'/> <backingStore type='file' index='1'> <format type='qcow2'/> <source file='/tmp/qe-con.s3'/> <backingStore type='file' index='2'> <format type='qcow2'/> <source file='/tmp/qe-con.s2'/> <backingStore type='file' index='3'> <format type='qcow2'/> <source file='/tmp/qe-con.s1'/> <backingStore type='file' index='4'> <format type='qcow2'/> <source file='/var/lib/libvirt/images/qe-con.qcow2'/> <backingStore/> </backingStore> </backingStore> </backingStore> </backingStore> <target dev='vda' bus='virtio'/> <alias name='virtio-disk0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/> </disk> 3. check the image chain # qemu-img info /tmp/qe-con.s4 --backing-chain image: /tmp/qe-con.s4 file format: qcow2 virtual size: 5.0G (5368709120 bytes) disk size: 3.3M cluster_size: 65536 backing file: /tmp/qe-con.s3 backing file format: qcow2 Format specific information: compat: 1.1 lazy refcounts: false image: /tmp/qe-con.s3 file format: qcow2 virtual size: 5.0G (5368709120 bytes) disk size: 196K cluster_size: 65536 backing file: /tmp/qe-con.s2 backing file format: qcow2 Format specific information: compat: 1.1 lazy refcounts: false image: /tmp/qe-con.s2 file format: qcow2 virtual size: 5.0G (5368709120 bytes) disk size: 196K cluster_size: 65536 backing file: /tmp/qe-con.s1 backing file format: qcow2 Format specific information: compat: 1.1 lazy refcounts: false image: /tmp/qe-con.s1 file format: qcow2 virtual size: 5.0G (5368709120 bytes) disk size: 196K cluster_size: 65536 backing file: /var/lib/libvirt/images/qe-con.qcow2 backing file format: qcow2 Format specific information: compat: 1.1 lazy refcounts: false image: /var/lib/libvirt/images/qe-con.qcow2 file format: qcow2 virtual size: 5.0G (5368709120 bytes) disk size: 1.2G cluster_size: 65536 Format specific information: compat: 1.1 lazy refcounts: false 4. do blockpull # virsh blockpull qe-con vda --base /tmp/qe-con.s2 --verbose --wait Block Pull: [100 %] Pull complete 5. check the image chain again # qemu-img info /tmp/qe-con.s4 --backing-chainimage: /tmp/qe-con.s4 file format: qcow2 virtual size: 5.0G (5368709120 bytes) disk size: 3.4M cluster_size: 65536 backing file: /tmp/qe-con.s2 backing file format: qcow2 Format specific information: compat: 1.1 lazy refcounts: false image: /tmp/qe-con.s2 file format: qcow2 virtual size: 5.0G (5368709120 bytes) disk size: 196K cluster_size: 65536 backing file: /tmp/qe-con.s1 backing file format: qcow2 Format specific information: compat: 1.1 lazy refcounts: false image: /tmp/qe-con.s1 file format: qcow2 virtual size: 5.0G (5368709120 bytes) disk size: 196K cluster_size: 65536 backing file: /var/lib/libvirt/images/qe-con.qcow2 backing file format: qcow2 Format specific information: compat: 1.1 lazy refcounts: false image: /var/lib/libvirt/images/qe-con.qcow2 file format: qcow2 virtual size: 5.0G (5368709120 bytes) disk size: 1.2G cluster_size: 65536 Format specific information: compat: 1.1 lazy refcounts: false 6. check xml # virsh dumpxml qe-con | grep disk -a16 <disk type='file' device='disk'> <driver name='qemu' type='qcow2' cache='none'/> <source file='/tmp/qe-con.s4'/> <backingStore type='file' index='1'> <format type='qcow2'/> <source file='/tmp/qe-con.s2'/> <backingStore type='file' index='2'> <format type='qcow2'/> <source file='/tmp/qe-con.s1'/> <backingStore type='file' index='3'> <format type='qcow2'/> <source file='/var/lib/libvirt/images/qe-con.qcow2'/> <backingStore/> </backingStore> </backingStore> </backingStore> <target dev='vda' bus='virtio'/> <alias name='virtio-disk0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/> </disk> 7. destroy/start the domain and check xml again # virsh destroy qe-con; virsh start qe-con Domain qe-con destroyed Domain qe-con started # virsh dumpxml qe-con | grep disk -a16 <disk type='file' device='disk'> <driver name='qemu' type='qcow2' cache='none'/> <source file='/tmp/qe-con.s4'/> <backingStore type='file' index='1'> <format type='qcow2'/> <source file='/tmp/qe-con.s2'/> <backingStore type='file' index='2'> <format type='qcow2'/> <source file='/tmp/qe-con.s1'/> <backingStore type='file' index='3'> <format type='qcow2'/> <source file='/var/lib/libvirt/images/qe-con.qcow2'/> <backingStore/> </backingStore> </backingStore> </backingStore> <target dev='vda' bus='virtio'/> <alias name='virtio-disk0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/> </disk> Since the results are as expected, I'd like to set it to verified
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://rhn.redhat.com/errata/RHSA-2015-0323.html