On 4/26/19 11:53 AM, Weller, Lennart wrote:
Hello everyone,
To increase my odds of finding an answer I also wanted to ask here.
This is my post from serverfault[1] in verbatim:
While trying to get a cloned disk running from my OS snapshot I run
into the problem that Libvirt cannot see existing images cloned from a
snapshot. Created via:
# rbd -p vmdisks clone vmdisks/coreos_2023@base vmdisks/coreos00.disk
The base image has the one snapshot 'base' and is protected. The cloned
disk is created just fine:
# rbd -p vmdisks info coreos00.disk
rbd image 'coreos00.disk':
size 8.49GiB in 2174 objects
order 22 (4MiB objects)
block_name_prefix: rbd_data.48a99c6b8b4567
format: 2
features: layering
flags:
create_timestamp: Thu Apr 25 14:46:52 2019
parent: vmdisks/coreos_2023@base
overlap: 8.49GiB
I temporarily have Libvirt configured with a rbd pool that uses the
ceph admin user. But I cannot see the cloned disk. Just the parent:
virsh # vol-list --pool rbd_image_root
Name Path
---------------------------------------------------------------------
---------
coreos_2023 vmdisks/coreos_2023
If I try to create the cloned image from within virsh I run into the
following issue:
virsh # vol-clone --pool rbd_image_root coreos_2023 coreos00.disk
error: Failed to clone vol from coreos_2023
error: failed to iterate RBD snapshot coreos_2023@base: Operation not
permitted
Note that this pool uses the Ceph admin user which makes the Operation
not permitted a tad odd.
Am I missing a configuration option here that would allow for the pool
to use clones? I can't find any information on this in the
documentation so far. And the source code of libvirt looks like it
should support both features.
Versions:
Libvirt Machine: Ubuntu 18.04
Compiled against library: libvirt 4.0.0
Using library: libvirt 4.0.0
Using API: QEMU 4.0.0
Running hypervisor: QEMU 2.11.1
Ceph Machine: openSUSE Leap 42.3
Ceph 12.2.5
I wonder if this is a libvirt bug. Looks like it. The error comes from
rbd_diff_iterate() (or rbd_diff_iterate2 if compiled against newer
librbd). Anyway, a callback is passed to the itreate() function and from
librbd code it looks like if the callback returns a negative value then
an error is signalized from the iterate() function. Well, we're passing
a callback that does nothing but return an error. This might be a
possible fix then:
diff --git i/src/storage/storage_backend_rbd.c w/src/storage/storage_backend_rbd.c
index f8c968e682..08f8123678 100644
--- i/src/storage/storage_backend_rbd.c
+++ w/src/storage/storage_backend_rbd.c
@@ -1038,7 +1038,7 @@ virStorageBackendRBDIterateCb(uint64_t offset ATTRIBUTE_UNUSED,
* searching any further.
*/
*(int*) arg = 1;
- return -1;
+ return 0;
}
static int
Can you please give it a try?
Thanks,
Michal