Comment 20 for bug 577239

Guys, make sure what you are seeing is not your machine saving your from data loss. Bug #531240 (root raid_members opened as luks). Especialy if you are only seeing this occasionally/with not all member devices present.

The check to only open /dev/mapper/ is your last hold in preventing data loss by opening a member device (with the same md device UUID and the same filesystem UUID in the raid mirror case).

This seems to pevent cryptsetup to open a raid member device instead of an assembled array.