This is the bug fix.

"So to be safe, it's better to run kpartx -d, change the partitions, then again kpartx -a. If old maps lie around and are accidentally used, disaster is likely as they will be referencing the start and end of partitions that no longer exist, resulting in mapping now-unrelated parts of the device."

Reference:
http://backreference.org/2010/09/25/access-partitions-in-non-disk-block-devices-with-kpartx/