zfs discuss - Jul 2009 - cannot initialize user accounting information on pool/nfs: Unknown error

After upgrading to b117 and doing a zfs upgrade -a the machine hang.
I pulled the power and booted it again.
Everything seems to work, except zfs userspace on a single filesystem.

Here is some info.

# uname -a
SunOS opensolaris 5.11 snv_117 i86pc i386 i86pc Solaris

# zfs upgrade
This system is currently running ZFS filesystem version 4.

All filesystems are formatted with the current version.

## zfs list pool/nfs
NAME       USED  AVAIL  REFER  MOUNTPOINT
pool/nfs  4,89T  1,49T  4,89T  /data/nfs

# zfs userspace pool/nfs
Initializing accounting information on old filesystem, please wait...
cannot initialize user accounting information on pool/nfs: Unknown error