[pve-devel] [PATCH storage 2/4] rbd: detect linked clones/base volumes correctly

[Fabian Grünbichler]

since the rbd images themselves are named differently than
the volumes in our config files, we need to recreate this
information from the parent relation in the ceph metadata,
otherwise list_images() might return wrong volume names/IDs

since list_images is used by PVE::Storage::vdisk_free() to
check for children still referencing a base image, because
of the wrong volume id RBDPlugin->parse_volname() does not
detect the base image of linked clones and the check fails.
this is thankfully mitigated by the protected status of the
base snapshot, but creates a rather confusing error message.

scenario (VM 701 is a linked clone of template VM 700):

$ qm config 700 | grep virtio0:
virtio0: ceph_qemu:base-700-disk-1,size=2G
$ qm config 701 | grep virtio0:
virtio0: ceph_qemu:base-700-disk-1/vm-701-disk-1,size=2G

before (pvesm list reports wrong volume ID, check fails):

$ pvesm list ceph_qemu
ceph_qemu:base-700-disk-1   raw 2147483648 700
ceph_qemu:vm-701-disk-1     raw 2147483648 701
$ pvesm free ceph_qemu:base-700-disk-1
snap_unprotect: can't unprotect; at least 1 child(ren) in pool rbd
rbd unprotect base-700-disk-1 snap '__base__' error: snap_unprotect: can't unprotect; at least 1 child(ren) in pool rbd

after (correct volume ID, check works as intended):

$ pvesm list ceph_qemu
ceph_qemu:base-700-disk-1                   raw 2147483648 700
ceph_qemu:base-700-disk-1/vm-701-disk-1     raw 2147483648 701
$ pvesm free ceph_qemu:base-700-disk-1
base volume 'base-700-disk-1' is still in use (use by 'base-700-disk-1/vm-701-disk-1')
---
 PVE/Storage/RBDPlugin.pm | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/PVE/Storage/RBDPlugin.pm b/PVE/Storage/RBDPlugin.pm
index 9833ca6..e953e03 100644
--- a/PVE/Storage/RBDPlugin.pm
+++ b/PVE/Storage/RBDPlugin.pm
@@ -492,6 +492,11 @@ sub list_images {
         foreach my $image (keys %$dat) {
 
             my $volname = $dat->{$image}->{name};
+	    my $parent = $dat->{$image}->{parent};
+
+	    if ($parent && $parent =~ m/^(base-\d+-\S+)\@__base__$/) {
+		$volname = "$1/$volname";
+	    }
 
             my $volid = "$storeid:$volname";
 
-- 
2.1.4