[bug#70542] [PATCH 2/4] services: base: Use requirements to delay some file-systems

[Richard Sent]

Add a mechanism to only require a subset of file-system entries during early
Shepherd initialization. Any file-system with additional Shepherd service
requirements (e.g. networking) will be brought up after 'file-systems is
provisioned.

* gnu/services/base.scm (file-system-shepherd-service): Splice
file-system-requirements into the Shepherd service requirement list.
* gnu/services/base.scm (file-system-shepherd-services): Provision
'file-system when file-systems that satisfy initial-file-system?  are started.

Change-Id: I7b1336ee970f4320f7431bef187e66f34f0d718c
---
 gnu/services/base.scm | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/gnu/services/base.scm b/gnu/services/base.scm
index 3f912225a0..af92b700b4 100644
--- a/gnu/services/base.scm
+++ b/gnu/services/base.scm
@@ -403,6 +403,7 @@ (define (file-system-shepherd-service file-system)
         (create? (file-system-create-mount-point? file-system))
         (mount?  (file-system-mount? file-system))
         (dependencies (file-system-dependencies file-system))
+        (requirements (file-system-requirements file-system))
         (packages (file-system-packages (list file-system))))
     (and (or mount? create?)
          (with-imported-modules (source-module-closure
@@ -411,7 +412,8 @@ (define (file-system-shepherd-service file-system)
             (provision (list (file-system->shepherd-service-name file-system)))
             (requirement `(root-file-system
                            udev
-                           ,@(map dependency->shepherd-service-name 
dependencies)))
+                           ,@(map dependency->shepherd-service-name 
dependencies)
+                           ,@requirements))
             (documentation "Check, mount, and unmount the given file system.")
             (start #~(lambda args
                        #$(if create?
@@ -460,12 +462,22 @@ (define (file-system-shepherd-services file-systems)
                                  (or (file-system-mount? x)
                                      (file-system-create-mount-point? x)))
                                file-systems)))
+
+    (define (initial-file-system? file-system)
+      "Return #t if the file system should be mounted initially or #f."
+      ;; File systems with additional Shepherd requirements (e.g. networking)
+      ;; should not be considered initial. Those requirements likely rely on
+      ;; 'file-systems being provisioned.
+      (null? (file-system-requirements file-system)))
+
     (define sink
       (shepherd-service
        (provision '(file-systems))
        (requirement (cons* 'root-file-system 'user-file-systems
                            (map file-system->shepherd-service-name
-                                file-systems)))
+                                ;; Only file systems considered initial should
+                                ;; be required to provision 'file-systems.
+                                (filter initial-file-system? file-systems))))
        (documentation "Target for all the initially-mounted file systems")
        (start #~(const #t))
        (stop #~(const #f))))
-- 
2.41.0