Comment 9 for bug 906722

Doesn't look to me like any changes to util-linux are called for here. I think cloud-init should just have a versioned dependency on util-linux (>= 2.20) and call sfdisk with the --no-reread option, since that's what you want. (You know that the disk is always going to be mounted in this case, and that you always want to resize if necessary, so this check doesn't seem to serve any purpose here.)

If that doesn't work for whatever reason, feel free to reopen against util-linux of course.