This issue was already fixed in released mdadm-4.1. https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/commit/?id=20e8fe52e7190b3ffda127566852eac2eb7fa1f7
Actually there is "mdadm - v4.1-rc1 - 2018-03-22" in Ubuntu 18.04.2. Please update mdadm package to mdadm-4.1.
This issue was already fixed in released mdadm-4.1. https:/ /git.kernel. org/pub/ scm/utils/ mdadm/mdadm. git/commit/ ?id=20e8fe52e71 90b3ffda1275668 52eac2eb7fa1f7
Actually there is "mdadm - v4.1-rc1 - 2018-03-22" in Ubuntu 18.04.2. Please update mdadm package to mdadm-4.1.