This file is not exact for all linux.
At least my fedora19 is "/sys/fs/selinux/enforce".
And IMHO, @cevich @liyangfnst  I think just leaving it failed is ok:
1.It seems that you have not got a good way to let selinux pass for floppy(not force selinux off).
2.We can look it as a bug: selinux do not consider floppy type(my guess :) ).