swap on cgd: disklabel: disklabel write (sector 0) size 8192 failed: Read-only file system

[Hugo Silva <hugo%barafranca.com@localhost>]

Hello,

Trying to setup swap on cgd on a 5.1/amd64 Xen domU (following
http://www.netbsd.org/docs/misc/#cgd-swap); Here's what I get:

# cat /etc/cgd/xbd1b
algorithm aes-cbc;
iv-method encblkno1;
keylength 128;
verify_method none;
keygen randomkey;

# cgdconfig cgd0 /dev/xbd1b /etc/cgd/xbd1b
# disklabel -eI cgd0
(change 4.2BSD to swap)
disklabel: disklabel write (sector 0) size 8192 failed: Read-only file
system

in dmesg:
cgd0: error 30 ("read-only filesystem")

What's even stranger is that I can newfs cgd0a..

Thoughts?