Bug 735457
| Summary: | libvirt should not leave stale snapshot metadata behind after domain disappears | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 6 | Reporter: | Eric Blake <eblake> |
| Component: | libvirt | Assignee: | Eric Blake <eblake> |
| Status: | CLOSED ERRATA | QA Contact: | Virtualization Bugs <virt-bugs> |
| Severity: | unspecified | Docs Contact: | |
| Priority: | unspecified | ||
| Version: | 6.2 | CC: | ajia, dyuan, mzhan, nzhang, rwu, veillard, whuang, xhu |
| Target Milestone: | rc | ||
| Target Release: | --- | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Whiteboard: | |||
| Fixed In Version: | libvirt-0.9.4-13.el6 | Doc Type: | Bug Fix |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2011-12-06 11:28:10 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | |||
| Bug Blocks: | 638510, 747120 | ||
|
Description
Eric Blake
2011-09-02 17:25:14 UTC
Getting this fixed is a prereq to bug 638510 support for live snapshots via the snapshot_blkdev qemu monitor command. Since this patch proposes blocking undefine only if metadata is present, it also becomes important to identify when metadata is present, as well as to delete metadata without affecting snapshot contents. Additionally, it becomes important to be able to redefine metadata to the state that it was before deletion, so that snapshot hierarchy can be preserved across transient domain restart or migrated between machines. I'm lumping all of those fixes into this bug. Upstream series ending in this commit:
commit e2fb96d92b4b986a2b5732416f7bfd302a848970
Author: Eric Blake <eblake>
Date: Fri Aug 12 13:23:09 2011 -0600
snapshot: prevent migration from stranding snapshot data
Migration is another case of stranding metadata. And since
snapshot metadata is arbitrarily large, there's no way to
shoehorn it into the migration cookie of migration v3.
Two additional patches make it so that 'virsh snapshot-create dom --no-metadata' will print out the just-generated snapshot name rather than failing (however, directly using the first of these two patches would be an incompatible API change, so it can't be back-ported as-is): https://www.redhat.com/archives/libvir-list/2011-September/msg00390.html I posted the followup patches for the --no-metadata improvement, although I'm not yet sure whether they belong to this BZ or a new one: http://post-office.corp.redhat.com/archives/rhvirt-patches/2011-September/msg00307.html Hmm, I realized that -12 fails to remove snapshot metadata for transient domains as documented; since my patches to date focused only on persistent domains. I'm not sure whether to split that into another BZ or move this one back to assigned. Pulling back to ASSIGNED while waiting for three more upstream patches to be approved: https://www.redhat.com/archives/libvir-list/2011-September/msg00860.html Verify it with libvirt-0.9.4-13.el6.x86_64 1. define a persistent domain named "snap"with qcow2 disks 2. create a snapshot for domain snap # virsh snapshot-create snap 3. virsh # snapshot-list snap Name Creation Time State ------------------------------------------------------------ 1317020538 2011-09-26 15:02:18 +0800 shutoff 4.virsh # undefine snap error: Failed to undefine domain snap error: Requested operation is not valid: cannot delete inactive domain with 1 snapshots 5. virsh undefine --snapshots-metadata snap Domain snap has been undefined 4. check snapshot metadata (no metadata) # ls /var/lib/libvirt/qemu/snapshot/snap 5. define a new domain with the same name, but different UUID 6. check snapshot for domain test: # virsh snapshot-list snap Name Creation Time State --------------------------------------------------------- This patch series introduced a typo in the user-visible error message: http://post-office.corp.redhat.com/archives/rhvirt-patches/2011-October/msg00233.html These issues have been resolved on rhel6 beta(2.6.32-193.el6.x86_64) with libvirt-0.9.4-16.el6.x86_64, so move the bug to VERIFIED status.
The following are some details:
# qemu-img create -f qcow2 /var/lib/libvirt/images/foo.img 10M
Formatting '/var/lib/libvirt/images/foo.img', fmt=qcow2 size=10485760 encryption=off cluster_size=65536
# qemu-img info /var/lib/libvirt/images/foo.img
image: /var/lib/libvirt/images/foo.img
file format: qcow2
virtual size: 10M (10485760 bytes)
disk size: 140K
cluster_size: 65536
$ cat > /root/demo.xml <<EOF
<domain type='qemu'>
<name>demo</name>
<memory>219200</memory>
<vcpu>1</vcpu>
<os>
<type arch='x86_64'>hvm</type>
<boot dev='cdrom'/>
</os>
<devices>
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2'/>
<source file='/var/lib/libvirt/images/foo.img'/>
<target dev='vda' bus='virtio'/>
</disk>
<input type='mouse' bus='ps2'/>
<graphics type='spice' autoport='yes' listen='0.0.0.0'/>
</devices>
</domain>
EOF
# virsh define /root/demo.xml
Domain demo defined from /root/demo.xml
# virsh snapshot-list demo
Name Creation Time State
------------------------------------------------------------
# cat > /root/snap.xml <<EOF
<domainsnapshot>
<state>shutoff</state>
</domainsnapshot>
EOF
# virsh snapshot-create demo /root/snap.xml
Domain snapshot 1318054922 created from '/root/snap.xml'
# virsh snapshot-list demo
Name Creation Time State
------------------------------------------------------------
1318054922 2011-10-08 14:22:02 +0800 shutoff
# virsh snapshot-list demo --parent
Name Creation Time State Parent
------------------------------------------------------------
1318054922 2011-10-08 14:22:02 +0800 shutoff
# virsh snapshot-list demo --roots
Name Creation Time State
------------------------------------------------------------
1318054922 2011-10-08 14:22:02 +0800 shutoff
# virsh snapshot-list demo --parent --roots
error: --parent and --roots are mutually exclusive
Notes, without typo issue for 'exclusive' words.
# ls /var/lib/libvirt/qemu/snapshot/demo/1318054922.xml
/var/lib/libvirt/qemu/snapshot/demo/1318054922.xml
# virsh undefine demo
error: Failed to undefine domain demo
error: Requested operation is not valid: cannot delete inactive domain with 1 snapshots
Notes, this is a expected behaviour.
# ls /var/lib/libvirt/qemu/snapshot/demo/1318054922.xml
/var/lib/libvirt/qemu/snapshot/demo/1318054922.xml
Notes, snapshot metadata still exists, this is a expected result.
# virsh undefine --snapshots-metadata demo
Domain demo has been undefined
# ls /var/lib/libvirt/qemu/snapshot/demo/1318054922.xml
ls: cannot access /var/lib/libvirt/qemu/snapshot/demo/1318054922.xml: No such file or directory
Notes, everything is okay now.
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. http://rhn.redhat.com/errata/RHBA-2011-1513.html |