Description of Problem:

The problem is that if a 'tmpfs' file system will be mounted following
suggestions from /usr/src/linux-2.4/Documentation/filesystems/tmpfs.txt,
i.e. 'mount -t tmpfs tmpfs /some/where', then the first field shown by
/proc/mounts will be not "none" and this file system will be printed
twice by the first and third invocations of awk.  Here is a corrected
function which, BTW, is calling awk only once:

halt_get_remaining() {
    awk '$2 ~ /^\/$|^\/proc|^\/dev/{next}
    $3 == "tmpfs" {print $2 ; next}
    /(^#|loopfs|autofs|devfs|^none|^\/dev\/root)/ {next}
    {print $2}' /proc/mounts
}

and here is an alternative implemented only in shell

halt_get_remaining() {
    local mpnt fs type rest all
    while read mpnt fs type rest ; do
        case "$fs" in
            /|/proc*|/dev*) continue ;;
        esac
        if [ "$type"  = tmpfs ] ; then
            echo $fs
            continue
        fi
        all="$mpnt $fs $type"
        case "$all" in
            \#*|*loopfs*|*autofs*|*devfs*|*tmpfs*|none*|/dev/root*) continue ;;
        esac
        echo $fs
    done < /proc/mounts
}

Checks for /dev/root and comment lines are likely superflous, but...
Also likely one check for "$all" can be replaced by separate, simpler, checks
for "$mpnt" and "$type" but this changes somewhat semantics of the original.

The other thing is that if procfs happens to be mounted also in some other
place but /proc, which happens, we likely want to print that as well so
this should really be
    $3 == "tmpfs" || $3 == "procfs {print $2 ; next}
and a similar obvious change in a shell version.