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'.

1 files changed, 9 insertions, 3 deletions

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.