gnu: system: Add LUKS2 support for the root file system.

* gnu/bootloader/grub.scm (grub-configuration-file): Add 'insmod
luks2'.
* gnu/system/mapped-devices.scm (open-luks-device): Create
'/run/cryptsetup/' directory.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu/bootloader/grub.scm

@@ -415,8 +415,7 @@ menuentry ~s {
           ;; Other type of devices aren't implemented.
           #~()))
     (let ((devices (map crypto-device->cryptomount store-crypto-devices))
-          ;; XXX: Add luks2 when grub 2.06 is packaged.
-          (modules #~(format port "insmod luks~%")))
+          (modules #~(format port "insmod luks~%insmod luks2~%")))
       (if (null? devices)
           devices
           (cons modules devices))))

gnu/system/mapped-devices.scm

@@ -192,7 +192,8 @@ option of @command{guix system}.\n")
   "Return a gexp that maps SOURCE to TARGET as a LUKS device, using
 'cryptsetup'."
   (with-imported-modules (source-module-closure
-                          '((gnu build file-systems)))
+                          '((gnu build file-systems)
+                            (guix build utils))) ;; For mkdir-p
     (match targets
       ((target)
        #~(let ((source #$(if (uuid? source)
@@ -201,7 +202,12 @@ option of @command{guix system}.\n")
            ;; XXX: 'use-modules' should be at the top level.
            (use-modules (rnrs bytevectors) ;bytevector?
                         ((gnu build file-systems)
-                         #:select (find-partition-by-luks-uuid)))
+                         #:select (find-partition-by-luks-uuid))
+                        ((guix build utils) #:select (mkdir-p)))
+
+           ;; Create '/run/cryptsetup/' if it does not exist, as device locking
+           ;; is mandatory for LUKS2.
+           (mkdir-p "/run/cryptsetup/")
 
            ;; Use 'cryptsetup-static', not 'cryptsetup', to avoid pulling the
            ;; whole world inside the initrd (for when we're in an initrd).