On Mon, Apr 29, 2019 at 04:39:40PM +0200, Michal Privoznik wrote:
When cloning an RBD volume we try to find a snapshot which is
not different to the image we're trying to clone. This boils down
to calling rbd_diff_iterate() or rbd_diff_iterate2() on systems
with newer ceph. These two are passed a callback -
virStorageBackendRBDIterateCb() which sets @diff to 1 and returns
-1. The idea is to stop iterating as soon as possible (i.e. we're
iterating over a snapshot with some deltas). Unfortunately,
returning a negative value from the callback means that iterate()
function fails and thus we report an error:

 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

Therefore, report an error if and only if it doesn't originates
in the callback.

Reported on libvirt-users list:

https://www.redhat.com/archives/libvirt-users/2019-April/msg00060.html

Signed-off-by: Michal Privoznik <mpriv...@redhat.com>
---

diff to v1:
- Ignore error as suggested by Jason as it allows us to exit iteration
early.

src/storage/storage_backend_rbd.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)


Reviewed-by: Ján Tomko <jto...@redhat.com>

Jano

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