file-systems: Remove 'title' field and add <file-system-label>.

The 'title' field was easily overlooked and was an endless source of
confusion.  Now, the value of the 'device' field is self-contained.

* gnu/system/file-systems.scm (<file-system>): Change constructor name
to '%file-system'.
[title]: Remove.
(<file-system-label>): New record type with printer.
(report-deprecation, device-expression)
(process-file-system-declaration, file-system): New macros.
(file-system-title): New procedure.
(file-system->spec, spec->file-system): Adjust to handle
<file-system-label>.
* gnu/system.scm (bootable-kernel-arguments): Add case for
'file-system-label?'.
(read-boot-parameters): Likewise.
(mapped-device-user): Avoid 'file-system-title'.
(fs->boot-device): Remove.
(operating-system-boot-parameters): Use 'file-system-device' instead of
'fs->boot-device'.
(device->sexp): Add case for 'file-system-label?'.
* gnu/bootloader/grub.scm (grub-root-search): Add case for
'file-system-label?'.
* gnu/system/examples/bare-bones.tmpl,
gnu/system/examples/beaglebone-black.tmpl,
gnu/system/examples/lightweight-desktop.tmpl,
gnu/system/examples/vm-image.tmpl: Remove uses of 'title'.
* gnu/system/vm.scm (virtualized-operating-system): Remove uses of
'file-system-title'.
* guix/scripts/system.scm (check-file-system-availability): Likewise,
and adjust fix-it hint.
(check-initrd-modules)[file-system-/dev]: Likewise.
* gnu/build/file-systems.scm (canonicalize-device-spec): Remove 'title'
parameter.
[canonical-title]: Remove.
Match on SPEC's type rather than on CANONICAL-TITLE.
(mount-file-system): Adjust caller.
* gnu/build/linux-boot.scm (boot-system): Interpret ROOT here.
* gnu/services/base.scm (file-system->fstab-entry): Remove use of
'file-system-title'.
* doc/guix.texi (File Systems): Remove documentation of the 'title'
field.  Rewrite documentation of 'device' and document
'file-system-label'.

2 files changed, 23 insertions, 43 deletions

diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm
index 145b3b14e7..3dd7358fd3 100644
--- a/gnu/build/file-systems.scm
+++ b/gnu/build/file-systems.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2016, 2017 David Craven <david@craven.ch>
 ;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
 ;;;
@@ -473,17 +473,9 @@ were found."
   (find-partition luks-partition-uuid-predicate))
 
 
-(define* (canonicalize-device-spec spec #:optional (title 'any))
-  "Return the device name corresponding to SPEC.  TITLE is a symbol, one of
-the following:
-
-  • 'device', in which case SPEC is known to designate a device node--e.g.,
-     \"/dev/sda1\";
-  • 'label', in which case SPEC is known to designate a partition label--e.g.,
-     \"my-root-part\";
-  • 'uuid', in which case SPEC must be a UUID designating a partition;
-  • 'any', in which case SPEC can be anything.
-"
+(define (canonicalize-device-spec spec)
+  "Return the device name corresponding to SPEC, which can be a <uuid>, a
+<file-system-label>, or a string (typically a /dev file name)."
   (define max-trials
     ;; Number of times we retry partition label resolution, 1 second per
     ;; trial.  Note: somebody reported a delay of 16 seconds (!) before their
@@ -491,19 +483,6 @@ the following:
     ;; this long.
     20)
 
-  (define canonical-title
-    ;; The realm of canonicalization.
-    (if (eq? title 'any)
-        (if (string? spec)
-            ;; The "--root=SPEC" kernel command-line option always provides a
-            ;; string, but the string can represent a device, a UUID, or a
-            ;; label.  So check for all three.
-            (cond ((string-prefix? "/" spec) 'device)
-                  ((string->uuid spec) 'uuid)
-                  (else 'label))
-            'uuid)
-        title))
-
   (define (resolve find-partition spec fmt)
     (let loop ((count 0))
       (let ((device (find-partition spec)))
@@ -518,23 +497,19 @@ the following:
                   (sleep 1)
                   (loop (+ 1 count))))))))
 
-  (case canonical-title
-    ((device)
+  (match spec
+    ((? string?)
      ;; Nothing to do.
      spec)
-    ((label)
+    ((? file-system-label?)
      ;; Resolve the label.
-     (resolve find-partition-by-label spec identity))
-    ((uuid)
+     (resolve find-partition-by-label
+              (file-system-label->string spec)
+              identity))
+    ((? uuid?)
      (resolve find-partition-by-uuid
-              (cond ((string? spec)
-                     (string->uuid spec))
-                    ((uuid? spec)
-                     (uuid-bytevector spec))
-                    (else spec))
-              uuid->string))
-    (else
-     (error "unknown device title" title))))
+              (uuid-bytevector spec)
+              uuid->string))))
 
 (define (check-file-system device type)
   "Run a file system check of TYPE on DEVICE."
@@ -615,8 +590,7 @@ run a file system check."
                                 "")))))
   (let ((type        (file-system-type fs))
         (options     (file-system-options fs))
-        (source      (canonicalize-device-spec (file-system-device fs)
-                                               (file-system-title fs)))
+        (source      (canonicalize-device-spec (file-system-device fs)))
         (mount-point (string-append root "/"
                                     (file-system-mount-point fs)))
         (flags       (mount-flags->bit-mask (file-system-flags fs))))
diff --git a/gnu/build/linux-boot.scm b/gnu/build/linux-boot.scm
index 18d87260a9..44b3506284 100644
--- a/gnu/build/linux-boot.scm
+++ b/gnu/build/linux-boot.scm
@@ -507,9 +507,15 @@ upon error."
            (error "pre-mount actions failed")))
 
        (if root
-           (mount-root-file-system (canonicalize-device-spec root)
-                                   root-fs-type
-                                   #:volatile-root? volatile-root?)
+           ;; The "--root=SPEC" kernel command-line option always provides a
+           ;; string, but the string can represent a device, a UUID, or a
+           ;; label.  So check for all three.
+           (let ((root (cond ((string-prefix? "/" root) root)
+                             ((uuid root) => identity)
+                             (else (file-system-label root)))))
+             (mount-root-file-system (canonicalize-device-spec root)
+                                     root-fs-type
+                                     #:volatile-root? volatile-root?))
            (mount "none" "/root" "tmpfs"))
 
        ;; Mount the specified file systems.