I get this BUG in 5.1-rc1 sometimes when powering off the machine. I suspect my setup erroneously executes two swapoff+cryptsetup close operations simultaneously, so a race condition is triggered. I am using a single swap on a plain dm-crypt device on a MBR partition on a SATA drive. I think the problem is probably related to b56a2d8af9147a4efe4011b60d93779c0461ca97, so CCing the related people. Thanks, Alex.
