From: Neil Brown <neilb@cse.unsw.edu.au>

If programs like mount use /proc/partitions to find filesystems based on
labels, then surely we want md devices in there as they often contain
filesystems.

If the problem is that mount-by-label takes forever with removable media
then surely the "right" approch is the following patch, and then actually
set this flag on the "floppy.c" device.  (It is already set for ide-floppy
and sd devices).