On a system running the Debian testing distribution, I recently upgraded the systemd package from 215-18 to 220-7. The system now fails to open the swap device (/dev/sda7) on boot with the following message:

systemd-cryptsetup[23252]: crypt_load() failed on device /dev/sda7.
systemd-cryptsetup[23252]: Failed to activate: Invalid argument

The device is configured as a plain (non-LUKS) device using a keyfile with the following line in /etc/cryptsetup:

sda7_crypt /dev/sda7 /sda7_crypt.keyfile discard,hash=ripemd160

I tracked the issue down to a change in commit 7376e83528 at line 408 which now causes systemd-cryptsetup to fail rather than retry as plain for devices of unspecified type. Since there is no mention of this change in Bug 66396, I assume the change was inadvertent. If the change was intentional, I would highly suggest documenting it as a breaking change for system administrators in the upgrade notes.

Thanks,
Kevin