nixos/fileystems: Fix boot fails with encrypted fs

Boot fails when a keyfile is configured for all encrypted filesystems
and no other luks devices are configured. This is because luks support is only
enabled in the initrd, when boot.initrd.luks.devices has entries. When a
fileystem has a keyfile configured though, it is setup by a custom
command, not by boot.initrd.luks.

This commit adds an internal config flag to enable luks support in the
initrd file, even if there are no luks devices configured.

(cherry picked from commit 2000fba561)

nixos/modules/system/boot/luksroot.nix

@@ -235,6 +235,16 @@ in
       '';
     };
 
+    boot.initrd.luks.forceLuksSupportInInitrd = mkOption {
+      type = types.bool;
+      default = false;
+      internal = true;
+      description = ''
+        Whether to configure luks support in the initrd, when no luks
+        devices are configured.
+      '';
+    };
+
     boot.initrd.luks.devices = mkOption {
       default = { };
       example = { "luksroot".device = "/dev/disk/by-uuid/430e9eff-d852-4f68-aa3b-2fa3599ebe08"; };
@@ -417,7 +427,7 @@ in
     };
   };
 
-  config = mkIf (luks.devices != {}) {
+  config = mkIf (luks.devices != {} || luks.forceLuksSupportInInitrd) {
 
     # actually, sbp2 driver is the one enabling the DMA attack, but this needs to be tested
     boot.blacklistedKernelModules = optionals luks.mitigateDMAAttacks

nixos/modules/tasks/encrypted-devices.nix

@@ -61,6 +61,7 @@ in
         devices =
           map (dev: { name = dev.encrypted.label; device = dev.encrypted.blkDev; } ) keylessEncDevs;
         cryptoModules = [ "aes" "sha256" "sha1" "xts" ];
+        forceLuksSupportInInitrd = true;
       };
       postMountCommands =
         concatMapStrings (dev: "cryptsetup luksOpen --key-file ${dev.encrypted.keyFile} ${dev.encrypted.blkDev} ${dev.encrypted.label};\n") keyedEncDevs;