panic: mdconfig on an iso file mounted on smbfs

[Donn Miller]

Please see the attached gdb file.  I get this panic if I have a samba 
filesystem mounted via mount_smbfs, where an iso file resides.  When I 
try to use mdconfig on the file, I get an immediate panic.  The exact 
mdconfig command issued is:

mount -a -t vnode -f /smbfs/sol-9-u3-x86-v1.iso -u 0

output of mount command:

/dev/ad0s4a on / (ufs, local)
devfs on /dev (devfs, local)
/dev/ad0s4d on /tmp (ufs, local, soft-updates)
/dev/ad0s4f on /usr (ufs, local, soft-updates)
/dev/ad0s4e on /var (ufs, local, soft-updates)
procfs on /proc (procfs, local)
/dev/ad0s2 on /windows (ntfs, local)
//GUEST at DONN/BACKUPS on /smbfs (smbfs)

If I copy the ISO to a local filesystem, and run mdconfig, the mdconfig 
command succeeds, and doesn't result in a panic.