services: file-systems: Include 'user-file-systems' service.

Previously the KNOWN-FS value used in 'essential-services' would be
incomplete: it would lack all the file systems provided by services that
extend 'file-system-service-type' (/sys/fs/cgroup,
/proc/sys/fs/binfmt_misc, etc.)  Consequently, upon shutdown,
'user-processes' would unmount these file systems before their
corresponding service had been stopped; when their corresponding (e.g.,
'file-system-/proc/sys/fs/binfmt_misc') was stopped, its 'umount' call
would fail.

This was harmless in practice, but this patch makes sure things work as
intended and file systems are unmounted in the right order.

* gnu/services/base.scm (file-system-shepherd-services): Instantiate
'user-file-systems' Shepherd service from here.
(user-unmount-service-type, user-unmount-service): Remove.
* gnu/system.scm (essential-services): Remove call to 'user-unmount-service'.
* gnu/system/install.scm (cow-store-service-type): Adjust comment.

gnu/services/base.scm

@@ -55,7 +55,6 @@
   #:export (fstab-service-type
             root-file-system-service
             file-system-service-type
-            user-unmount-service
             swap-service
             user-processes-service-type
             host-name-service
@@ -464,29 +463,10 @@ FILE-SYSTEM."
        (start #~(const #t))
        (stop #~(const #f))))
 
-    (cons sink (map file-system-shepherd-service file-systems))))
+    (define known-mount-points
+      (map file-system-mount-point file-systems))
 
-(define file-system-service-type
+    (define user-unmount
-  (service-type (name 'file-systems)
-                (extensions
-                 (list (service-extension shepherd-root-service-type
-                                          file-system-shepherd-services)
-                       (service-extension fstab-service-type
-                                          identity)
-
-                       ;; Have 'user-processes' depend on 'file-systems'.
-                       (service-extension user-processes-service-type
-                                          (const '(file-systems)))))
-                (compose concatenate)
-                (extend append)
-                (description
-                 "Provide Shepherd services to mount and unmount the given
-file systems, as well as corresponding @file{/etc/fstab} entries.")))
-
-(define user-unmount-service-type
-  (shepherd-service-type
-   'user-file-systems
-   (lambda (known-mount-points)
       (shepherd-service
        (documentation "Unmount manually-mounted file systems.")
        (provision '(user-file-systems))
@@ -509,12 +489,28 @@ file systems, as well as corresponding @file{/etc/fstab} entries.")))
                                    (format #t "failed to unmount '~a': ~a~%"
                                            mount-point (strerror errno))))))
                            (filter (negate known?) (mount-points)))
-                #f))))))
+                 #f))))
+
+    (cons* sink user-unmount
+           (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
+                                          file-system-shepherd-services)
+                       (service-extension fstab-service-type
+                                          identity)
+
+                       ;; Have 'user-processes' depend on 'file-systems'.
+                       (service-extension user-processes-service-type
+                                          (const '(file-systems)))))
+                (compose concatenate)
+                (extend append)
+                (description
+                 "Provide Shepherd services to mount and unmount the given
+file systems, as well as corresponding @file{/etc/fstab} entries.")))
 
-(define (user-unmount-service known-mount-points)
-  "Return a service whose sole purpose is to unmount file systems not listed
-in KNOWN-MOUNT-POINTS when it is stopped."
-  (service user-unmount-service-type known-mount-points))
 
 
 ;;;

gnu/system.scm

@@ -453,7 +453,6 @@ a container or that of a \"bare metal\" system."
   (let* ((mappings  (device-mapping-services os))
          (root-fs   (root-file-system-service))
          (other-fs  (non-boot-file-system-service os))
-         (unmount   (user-unmount-service known-fs))
          (swaps     (swap-services os))
          (procs     (service user-processes-service-type))
          (host-name (host-name-service (operating-system-host-name os)))
@@ -478,7 +477,7 @@ a container or that of a \"bare metal\" system."
            (service fstab-service-type '())
            (session-environment-service
             (operating-system-environment-variables os))
-           host-name procs root-fs unmount
+           host-name procs root-fs
            (service setuid-program-service-type
                     (operating-system-setuid-programs os))
            (service profile-service-type

gnu/system/install.scm

@@ -133,7 +133,7 @@ the given target.")
       (stop #~(lambda (target)
                 ;; Delete the temporary directory, but leave everything
                 ;; mounted as there may still be processes using it since
-                ;; 'user-processes' doesn't depend on us.  The 'user-unmount'
+                ;; 'user-processes' doesn't depend on us.  The 'user-file-systems'
                 ;; service will unmount TARGET eventually.
                 (delete-file-recursively
                  (string-append target #$%backing-directory))))))))