[gentoo-user] Trouble on first install with LUKS & BtrFS

[Diagon]

I've done a basically vanilla install (*) of gentoo hardened with disks prepared at luks/btrfs.  I've used `genkernel --btrfs --luks all`.  I am getting the following error when trying to boot the system and arrive at the point of unlocking a disk (note the spaces, "on ... failed"):

   device-mapper: reload ioctl on <spaces> failed: No such file or directory

Dropping into the initramfs and trying `cryptsetup open`, I get the same error, though `cryptsetup isLuks` is responding positively.

Does anyone have any suggestions on how I might proceed?

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(*) Almost.  I'm actually using two LUKS disks continaing a BtrFS RAID-1.  So I'm using a patch: https://bugs.gentoo.org/694778