1. I'd like to use DM with a new target type. I'm porting our virtualized storage solution from Windows. I've been able to register my target and get callbacks working, but in looking at the dm-raid code, I'm concerned with how tightly coupled it is with the routines in md.c (multiple devices implementation). Is there an expectation that a DM target use the md_xxxx routines?
2. I used dmsetup to create a mapping for a device that my target controls. Is there a way to make the underlying device (e.g. /dev/sdb) not visible to the system? I'm paranoid about external accesses to a LUN that I'm using.