We are gradually converting to byte-based interfaces, as they are
easier to reason about than sector-based.  Continue by converting
an internal function (no semantic change), and simplifying its
caller accordingly.
Signed-off-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>