system: Introduce 'file-systems' Shepherd service.

* gnu/services/base.scm (file-system-shepherd-services): New procedure.
(file-system-service-type): Use it as the SHEPHERD-ROOT-SERVICE-TYPE
extension.
(user-processes-service-type): Change to take a single 'grace-delay'
parameter.
(user-processes-service): Remove 'file-systems' parameter.  Pass
GRACE-DELAY as the only value for the service.
* gnu/system.scm (essential-services): Adjust accordingly.

gnu/services/base.scm

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2015, 2016, 2017 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015, 2016 Alex Kost <alezost@gmail.com>
 ;;; Copyright © 2015, 2016 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2015 Sou Bunnbu <iyzsong@gmail.com>
@@ -313,13 +313,26 @@ FILE-SYSTEM."
                         #:select (mount-file-system))
                        ,@%default-modules)))))))
 
+(define (file-system-shepherd-services file-systems)
+  "Return the list of Shepherd services for FILE-SYSTEMS."
+  (let* ((file-systems (filter file-system-mount? file-systems)))
+    (define sink
+      (shepherd-service
+       (provision '(file-systems))
+       (requirement (cons* 'root-file-system 'user-file-systems
+                           (map file-system->shepherd-service-name
+                                file-systems)))
+       (documentation "Target for all the initially-mounted file systems")
+       (start #~(const #t))
+       (stop #~(const #f))))
+
+    (cons sink (map file-system-shepherd-service file-systems))))
+
 (define file-system-service-type
   (service-type (name 'file-systems)
                 (extensions
                  (list (service-extension shepherd-root-service-type
-                                          (lambda (file-systems)
+                                          file-system-shepherd-services)
-                                            (filter-map file-system-shepherd-service
-                                                        file-systems)))
                        (service-extension fstab-service-type
                                           identity)))
                 (compose concatenate)
@@ -366,14 +379,11 @@ in KNOWN-MOUNT-POINTS when it is stopped."
 (define user-processes-service-type
   (shepherd-service-type
    'user-processes
-   (match-lambda
+   (lambda (grace-delay)
-     ((requirements grace-delay)
      (shepherd-service
       (documentation "When stopped, terminate all user processes.")
       (provision '(user-processes))
-       (requirement (cons* 'root-file-system 'user-file-systems
+      (requirement '(file-systems))
-                           (map file-system->shepherd-service-name
-                                requirements)))
       (start #~(const #t))
       (stop #~(lambda _
                 (define (kill-except omit signal)
@@ -438,21 +448,20 @@ in KNOWN-MOUNT-POINTS when it is stopped."
 
                 (display "all processes have been terminated\n")
                 #f))
-       (respawn? #f))))))
+      (respawn? #f)))))
 
-(define* (user-processes-service file-systems #:key (grace-delay 4))
+(define* (user-processes-service #:key (grace-delay 4))
   "Return the service that is responsible for terminating all the processes so
 that the root file system can be re-mounted read-only, just before
 rebooting/halting.  Processes still running GRACE-DELAY seconds after SIGTERM
 has been sent are terminated with SIGKILL.
 
-The returned service will depend on 'root-file-system' and on all the shepherd
+The returned service will depend on 'file-systems', meaning that it is
-services corresponding to FILE-SYSTEMS.
+considered started after all the auto-mount file systems have been mounted.
 
 All the services that spawn processes must depend on this one so that they are
 stopped before 'kill' is called."
-  (service user-processes-service-type
+  (service user-processes-service-type grace-delay))
-           (list (filter file-system-mount? file-systems) grace-delay)))
 
 
 ;;;

gnu/system.scm

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2015, 2016, 2017 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>
@@ -293,8 +293,7 @@ a container or that of a \"bare metal\" system."
          (other-fs  (non-boot-file-system-service os))
          (unmount   (user-unmount-service known-fs))
          (swaps     (swap-services os))
-         (procs     (user-processes-service
+         (procs     (user-processes-service))
-                     (service-parameters other-fs)))
          (host-name (host-name-service (operating-system-host-name os)))
          (entries   (operating-system-directory-base-entries
                      os #:container? container?)))