in smb_fphelp(): the parent vnode may have already been recycled
since we don't hold a reference to it. Fixes a panic when rebooting
with mdconfig -t vnode devices referring to vnodes on a smbfs mount.
prevent the compiler from optimizing assignments into byte-copy
operations which might make access to the individual fields non-atomic.
Use the individual fields throughout, and don't bother locking them with
Giant: it is no longer needed.
Inspired by: tjr
not to the parent's smbnode, which may be freed during the lifetime
of the child if the mount is forcibly unmounted. umount -f should now
work properly (ie. not panic) on smbfs mounts.
