Re: Wedges enabled on -current

[Alan Barrett <apb%cequrux.com@localhost>]

On Thu, 21 Aug 2014, Thomas Klausner wrote:
> I have scripts that mount images via vnd + cgd. So far I have been
> using fixed numbers for the vnd and cgd devices I use, making sure I
> don't use them for other purposes.
>
> Now this doesn't work any longer, because as soon as vnd is created, a
> dk device takes over and the vnd cannot be used any longer (busy).
> Same for the cgd. I don't see a way to make these dk* numbers fixed.
>
> What do you propose how to do this from a script after wedges are
> default?

I wrote this shell function, and use things like "$(fixpart wd0a)" 
or "/dev/r$(fixpart wd0a)" instead of just "wd0a" or "/dev/rwd0a". 
I would much prefer it of the old device names continued to work, 
even if dk* names become available as aliases for them.

nl='
' # a newline

# convert from disklabel to wedge device names, if necessary.
# e.g. fixpart wd0a might return dk0.
fixpart()
{
   local diskpart="$1" disk part
   local wedgelist
   local line
   local IFS="${nl}"

   case "${diskpart}" in
   *[0-9][a-z])
       disk="${diskpart%?}"            # e.g. wd0a -> wd0
       part="${diskpart#${disk}}"      # e.g. wd0a -> a
       ;;
   *)
       # already dk*, or an unrecognised name: don't try to change it
       echo "${diskpart}"
       return 0
       ;;
   esac

   wedgelist="$(dkctl "$disk" listwedges)"
   if [ $? = 0 ]; then
       for line in ${wedgelist}; do
           case "${line}" in
           dk*:*/${part}|dk*:*/${part},*)
               echo "${line%%:*}"
               return 0
               ;;
           esac
       done
   fi

   # listwedges failed, or did not include the partition we want.
   # just return the old-style disk and partition
   echo "${disk}${part}"
   return 1
}