** Changed in: nova/ussuri
Status: In Progress => Fix Released
** Changed in: nova/victoria
Status: Fix Committed => Fix Released
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https://bugs.launchpad.net/bugs/1885528
Title:
snapshot delete fails on shutdown VM
Status in OpenStack Compute (nova):
Fix Released
Status in OpenStack Compute (nova) queens series:
New
Status in OpenStack Compute (nova) rocky series:
In Progress
Status in OpenStack Compute (nova) stein series:
New
Status in OpenStack Compute (nova) trunk series:
New
Status in OpenStack Compute (nova) ussuri series:
Fix Released
Status in OpenStack Compute (nova) victoria series:
Fix Released
Bug description:
Description:
When we try to delete the last snapshot of a VM in shutdown state, this
snapshot_delete will fail (and be stuck in state error-deleting). When setting
state==available and redeleting the snapshot, the volume will be corrupted and
the VM will never start again. Volumes are stored on NFS.
(for root cause and fix, see the bottom of this post)
To reproduce:
- storage on NFS
- create a VM and some snapshots
- shut down the VM (ie volume is still considered "attached" but vm is no
longer "active")
- delete the last snapshot
Expected Result:
snapshot is deleted, vm still works
Actual result:
The snapshot is stuck on error deleting. After setting the snapshot
state==available and deleting the snapshot again, the volume will be corrupted
and the VM will never start again. (non-existing backing_file in qcow on disk)
Environment:
- openstack version: stein, deployed via kolla-ansible. I suspect this
downloads from git but i don't know the exact version.
- hypervisor: Libvirt + KVM
- storage: NFS
- networking: Neutron with OpenVSwitch
Nova debug Logs:
2020-02-06 12:20:10.713 6 ERROR nova.virt.libvirt.driver
[req-d38b5ec8-afdb-4dfe-af12-0c47598c6a47 6dd1c995b2ea4ddfbeb0685bc52e5fbf
6bebb564667d4a75b9281fd826b32ecf - d
efault default] [instance: 711651a3-8440-42dd-a210-e7e550a8624e] Error
occurred during volume_snapshot_delete, sending error status to Cinder.:
DiskNotFound: No disk at
volume-86c06b12-699c-4b54-8bca-fb92c99a2bf0.63d1585e-eb76-4e8f-bc96-93960e9c9692
2020-02-06 12:20:10.713 6 ERROR nova.virt.libvirt.driver [instance:
711651a3-8440-42dd-a210-e7e550a8624e] Traceback (most recent call last):
2020-02-06 12:20:10.713 6 ERROR nova.virt.libvirt.driver [instance:
711651a3-8440-42dd-a210-e7e550a8624e] File
"/usr/lib/python2.7/site-packages/nova/virt/libvirt/dri
ver.py", line 2726, in volume_snapshot_delete
2020-02-06 12:20:10.713 6 ERROR nova.virt.libvirt.driver [instance:
711651a3-8440-42dd-a210-e7e550a8624e] snapshot_id, delete_info=delete_info)
2020-02-06 12:20:10.713 6 ERROR nova.virt.libvirt.driver [instance:
711651a3-8440-42dd-a210-e7e550a8624e] File
"/usr/lib/python2.7/site-packages/nova/virt/libvirt/dri
ver.py", line 2686, in _volume_snapshot_delete
2020-02-06 12:20:10.713 6 ERROR nova.virt.libvirt.driver [instance:
711651a3-8440-42dd-a210-e7e550a8624e] rebase_base)
2020-02-06 12:20:10.713 6 ERROR nova.virt.libvirt.driver [instance:
711651a3-8440-42dd-a210-e7e550a8624e] File
"/usr/lib/python2.7/site-packages/nova/virt/libvirt/dri
ver.py", line 2519, in _rebase_with_qemu_img
2020-02-06 12:20:10.713 6 ERROR nova.virt.libvirt.driver [instance:
711651a3-8440-42dd-a210-e7e550a8624e] b_file_fmt =
images.qemu_img_info(backing_file).file_forma
t
2020-02-06 12:20:10.713 6 ERROR nova.virt.libvirt.driver [instance:
711651a3-8440-42dd-a210-e7e550a8624e] File
"/usr/lib/python2.7/site-packages/nova/virt/images.py",
line 58, in qemu_img_info
2020-02-06 12:20:10.713 6 ERROR nova.virt.libvirt.driver [instance:
711651a3-8440-42dd-a210-e7e550a8624e] raise
exception.DiskNotFound(location=path)
2020-02-06 12:20:10.713 6 ERROR nova.virt.libvirt.driver [instance:
711651a3-8440-42dd-a210-e7e550a8624e] DiskNotFound: No disk at
volume-86c06b12-699c-4b54-8bca-fb92c9
9a2bf0.63d1585e-eb76-4e8f-bc96-93960e9c9692
2020-02-06 12:20:10.713 6 ERROR nova.virt.libvirt.driver [instance:
711651a3-8440-42dd-a210-e7e550a8624e]
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server
[req-d38b5ec8-afdb-4dfe-af12-0c47598c6a47 6dd1c995b2ea4ddfbeb0685bc52e5fbf
6bebb564667d4a75b9281fd826b32ecf -
default default] Exception during message handling: DiskNotFound: No disk at
volume-86c06b12-699c-4b54-8bca-fb92c99a2bf0.63d1585e-eb76-4e8f-bc96-93960e9c9692
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server Traceback (most
recent call last):
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/oslo_messaging/rpc/server.py", line 166, in
_process_incoming
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server res =
self.dispatcher.dispatch(message)
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/oslo_messaging/rpc/dispatcher.py", line 265,
in dispatch
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server return
self._do_dispatch(endpoint, method, ctxt, args)
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/oslo_messaging/rpc/dispatcher.py", line 194,
in _do_dispatch
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server result =
func(ctxt, **new_args)
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/oslo_messaging/rpc/server.py", line 229, in
inner
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server return
func(*args, **kwargs)
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/nova/exception_wrapper.py", line 79, in
wrapped
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server function_name,
call_dict, binary, tb)
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server
self.force_reraise()
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in
force_reraise
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server
six.reraise(self.type_, self.value, self.tb)
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/nova/exception_wrapper.py", line 69, in
wrapped
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server return f(self,
context, *args, **kw)
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/nova/compute/manager.py", line 3686, in
volume_snapshot_delete
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server snapshot_id,
delete_info)
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 2734, in
volume_snapshot_delete
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server context,
snapshot_id, 'error_deleting')
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 220, in __exit__
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server
self.force_reraise()
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/oslo_utils/excutils.py", line 196, in
force_reraise
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server
six.reraise(self.type_, self.value, self.tb)
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 2726, in
volume_snapshot_delete
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server snapshot_id,
delete_info=delete_info)
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 2686, in
_volume_snapshot_delete
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server rebase_base)
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 2519, in
_rebase_with_qemu_img
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server b_file_fmt =
images.qemu_img_info(backing_file).file_format
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server File
"/usr/lib/python2.7/site-packages/nova/virt/images.py", line 58, in
qemu_img_info
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server raise
exception.DiskNotFound(location=path)
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server DiskNotFound: No
disk at
volume-86c06b12-699c-4b54-8bca-fb92c99a2bf0.63d1585e-eb76-4e8f-bc96-93960e9c9692
2020-02-06 12:20:10.780 6 ERROR oslo_messaging.rpc.server
Root Cause:
When you look at the first line in the debug log: "No disk at
volume-volid.snapid", you will notice that this is a relative path. When the
code does an `os.path.exists("volume-volid.snapid")` this will obviously fail
(as nova has a cwd="/") and the volumes are stored under
"/usr/lib/nova/mnt/xxxxx/". If an absolute path were used, the code would be
much happier :)
Code path:
- cinder->snapshot_delete
- In remotefs.py (called for nfs): if volume is attached -> call nova
snapshot_delete
- nova-> snapshot_delete: If snapshot_to_merge == active -> do rebase
- if VM is not active: call _rebase_with_qemu_img (virt/libvirt/driver.py)
- rebase_base/backing_file is now usually a relative file (depends on
wether qemu_img_info is called with json or human and can also depend on the
cwd). In all instances i saw, this was a relative path. When
_rebase_with_qemu_img calls images.qemu_img_info(backing_file), this will fail
unless supplied with and absolute path (first line in qemu_img_info does an
os.path.exists which will obviously fail on a relative path). This will cause
the snapshot delete to fail.
Potential, cinder_based fix:
In cinder, qemu_img_info is typically wrapped to always convert the
backing_file to a relative path. In the code there are typically 2 variables:
backing_file (relative) and backing_path(absolute). The code then decides when
to use what variable:
Patch:
--- /usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py.orig
2020-06-22 14:48:09.760186268 +0000
+++ /usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py
2020-06-25 15:26:42.344963030 +0000
@@ -2515,8 +2515,10 @@
# If the rebased image is going to have a backing file then
# explicitly set the backing file format to avoid any security
# concerns related to file format auto detection.
- backing_file = rebase_base
- b_file_fmt = images.qemu_img_info(backing_file).file_format
+ backing_file = os.path.basename(rebase_base) # relative path
+ volume_path = os.path.dirname(active_disk_object.source_path)
+ backing_path = os.path.join(volume_path, backing_file) #
absolute
+ b_file_fmt = images.qemu_img_info(backing_path).file_format
qemu_img_extra_arg = ['-F', b_file_fmt]
qemu_img_extra_arg.append(active_disk_object.source_path)
Note:
We've only been able to test on Stein. However based on a code analysis of
the current code in git, this bug is probably still present.
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