[PATCH 01/10] * gnu/system.scm (<boot-parameters>): Add 'store-device' and 'store-fs-mount-point'.

[cmmarusich@gmail.com]

From: Chris Marusich <cmmarusich@gmail.com>

In a future commit, we will restructure the grub.cfg generation logic to use
this information, to enable the implementation of 'guix system
switch-generation' and 'guix system roll-back'.
---
 gnu/system.scm | 58 +++++++++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 49 insertions(+), 9 deletions(-)

diff --git a/gnu/system.scm b/gnu/system.scm
index 38ae8f1..ff84b63 100644
--- a/gnu/system.scm
+++ b/gnu/system.scm
@@ -2,6 +2,7 @@
 ;;; Copyright © 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2015, 2016 Alex Kost <alezost@gmail.com>
+;;; Copyright © 2016 Chris Marusich <cmmarusich@gmail.com>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -99,6 +100,8 @@
             boot-parameters?
             boot-parameters-label
             boot-parameters-root-device
+            boot-parameters-store-device
+            boot-parameters-store-fs-mount-point
             boot-parameters-kernel
             boot-parameters-kernel-arguments
             boot-parameters-initrd
@@ -750,17 +753,25 @@ listed in OS.  The C library expects to find it under
 this file is the reconstruction of GRUB menu entries for old configurations."
   (mlet %store-monad ((initrd   (operating-system-initrd-file os))
                       (root ->  (operating-system-root-file-system os))
+                      (store -> (operating-system-store-file-system os))
                       (label -> (kernel->grub-label
                                  (operating-system-kernel os))))
-    (gexp->file "parameters"
-                #~(boot-parameters (version 0)
-                                   (label #$label)
-                                   (root-device #$(file-system-device root))
-                                   (kernel #$(operating-system-kernel-file os))
-                                   (kernel-arguments
-                                    #$(operating-system-kernel-arguments os))
-                                   (initrd #$initrd))
-                #:set-load-path? #f)))
+    (gexp->file
+     "parameters"
+     #~(boot-parameters (version 1)
+                        (label #$label)
+                        (root-device #$(file-system-device root))
+                        (store-device
+                         #$(case (file-system-title store)
+                             ((uuid) (file-system-device store))
+                             ((label) (file-system-device store))
+                             (else #f)))
+                        (store-fs-mount-point #$(file-system-mount-point store))
+                        (kernel #$(operating-system-kernel-file os))
+                        (kernel-arguments
+                         #$(operating-system-kernel-arguments os))
+                        (initrd #$initrd))
+     #:set-load-path? #f)))
 
 \f
 ;;;
@@ -770,7 +781,16 @@ this file is the reconstruction of GRUB menu entries for old configurations."
 (define-record-type* <boot-parameters>
   boot-parameters make-boot-parameters boot-parameters?
   (label            boot-parameters-label)
+  ;; Because we will use the 'store-device' to create the GRUB search command,
+  ;; the 'store-device' has slightly different semantics than 'root-device'.
+  ;; The 'store-device' can be a file system uuid, a file system label, or #f,
+  ;; but it cannot be a device path such as "/dev/sda3", since GRUB would not
+  ;; understand that.  The 'root-device', on the other hand, corresponds
+  ;; exactly to the device field of the <file-system> object representing the
+  ;; OS's root file system, so it might be a device path like "/dev/sda3".
   (root-device      boot-parameters-root-device)
+  (store-device     boot-parameters-store-device)
+  (store-fs-mount-point boot-parameters-store-fs-mount-point)
   (kernel           boot-parameters-kernel)
   (kernel-arguments boot-parameters-kernel-arguments)
   (initrd           boot-parameters-initrd))
@@ -786,6 +806,10 @@ this file is the reconstruction of GRUB menu entries for old configurations."
      (boot-parameters
       (label label)
       (root-device root)
+      ;; For backwards compatibility, we assume the store device and the
+      ;; root device are the same.
+      (store-device root)
+      (store-fs-mount-point "/")
 
       ;; In the past, we would store the directory name of the kernel instead
       ;; of the absolute file name of its image.  Detect that and correct it.
@@ -805,6 +829,22 @@ this file is the reconstruction of GRUB menu entries for old configurations."
           (string-append directory file))
          (('initrd (? string? file))
           file)))))
+    (('boot-parameters ('version 1)
+                       ('label label)
+                       ('root-device root)
+                       ('store-device store)
+                       ('store-fs-mount-point store-fs-mount-point)
+                       ('kernel linux)
+                       ('kernel-arguments arguments)
+                       ('initrd initrd))
+     (boot-parameters
+      (label label)
+      (root-device root)
+      (store-device store)
+      (store-fs-mount-point store-fs-mount-point)
+      (kernel linux)
+      (kernel-arguments arguments)
+      (initrd initrd)))
     (x                                            ;unsupported format
      (warning (_ "unrecognized boot parameters for '~a'~%")
               system)
-- 
2.9.2