Bug 1555311
| Summary: | Creating external snapshot will fail after failed hot-plugging operation | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 7 | Reporter: | jiyan <jiyan> |
| Component: | libvirt | Assignee: | Libvirt Maintainers <libvirt-maint> |
| Status: | CLOSED DUPLICATE | QA Contact: | jiyan <jiyan> |
| Severity: | unspecified | Docs Contact: | |
| Priority: | unspecified | ||
| Version: | 7.5 | CC: | dyuan, hhan, jiyan, lmen, pkrempa, rbalakri, xuzhang |
| Target Milestone: | rc | ||
| Target Release: | --- | ||
| Hardware: | x86_64 | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | If docs needed, set a value | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2018-03-15 13:56:44 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
This is an instance of libvirtd breaking the label on a VM if the operation fails for some reason. We have a different instance of this bug when starting two VMs with same disk image which does not support sharing. Closing this as a duplicate. *** This bug has been marked as a duplicate of bug 1524792 *** |
Description of problem: After hot-plugging same qcow2 file which is the source of bootable disk in VM, creating external snapshot will fail. Version-Release number of selected component (if applicable): kernel-3.10.0-860.el7.x86_64 qemu-kvm-rhev-2.10.0-21.el7.x86_64 libvirt-3.9.0-14.el7.x86_64 How reproducible: 100% Steps to Reproduce: Steps: 1. Prepare a shutdown VM with bootable source file as following: # virsh domstate test4 shut off # virsh dumpxml test4 |grep "<disk" -A5 <disk type='file' device='disk'> <driver name='qemu' type='qcow2'/> <source file='/var/lib/libvirt/images/RHEL-7.5-x86_64-latest.qcow2'/> <target dev='hda' bus='ide'/> <address type='drive' controller='0' bus='0' target='0' unit='0'/> </disk> 2. Prepare a xml file, the source file is same with Step-1. # cat test4.xml <disk type='file' device='disk'> <driver name='qemu' type='qcow2'/> <source file='/var/lib/libvirt/images/RHEL-7.5-x86_64-latest.qcow2'/> <target dev='hdb' bus='virtio'/> </disk> 3. Start VM and hot-plug, the error will raise # virsh start test4 Domain test4 started # virsh attach-device test4 test4.xml error: Failed to attach device from test4.xml error: internal error: unable to execute QEMU command '__com.redhat_drive_add': Device 'drive-virtio-disk1' could not be initialized 4. Try to create external snapshot, it will fail # virsh snapshot-create-as test4 t4s1 --disk-only --diskspec hda,snapshot=external,file=/tmp/t4s1 error: internal error: unable to execute QEMU command 'transaction': Failed to lock byte 100 Actual results: As step-4 shows Expected results: Creating snapshot should succeed. Additional info: The error info in step-3 is related to the following bug: Bug 1526313 - Improve QEMU lock error info for hot-plugging same qcow2 image file twice in different target to VM And famz has been checked this issue and provides some debug info as following: https://bugzilla.redhat.com/show_bug.cgi?id=1526313#c6 I find that disabling SELinux will fix the issue. My guess is that the error handling logic in libvirt triggered in step 3 has misconfigured the context of the image or something, as a result, a following locking operation when QEMU tries to create the snapshot is rejected by system security policy: [pid 9863] fcntl(17, F_OFD_SETLK, {l_type=F_RDLCK, l_whence=SEEK_SET, l_start=100, l_len=1}) = -1 EACCES (Permission denied)