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
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