[bug#64260] [PATCH] Use cgroups v2 file system

[Sam Lockart <sam@samlockart.com>]

cgroup v2 is the next generation of the control groups API.
This patch replaces the cgroup v1 file system with the unified
cgroup v2 file system.

cgroup v2 allows for things like containerd/podman to run rootless containers and opens guix system up to running things like Kubernetes.

* gnu/system/file-systems.scm: Use cgroups v2 file system
---
 gnu/system/file-systems.scm | 27 +++++++--------------------
 1 file changed, 7 insertions(+), 20 deletions(-)

diff --git a/gnu/system/file-systems.scm b/gnu/system/file-systems.scm
index 0ff5a0dcf6..59e04bcecf 100644
--- a/gnu/system/file-systems.scm
+++ b/gnu/system/file-systems.scm
@@ -445,26 +445,13 @@ (define %immutable-store
     (flags '(read-only bind-mount no-atime))))
 
 (define %control-groups
-  (let ((parent (file-system
-                  (device "cgroup")
-                  (mount-point "/sys/fs/cgroup")
-                  (type "tmpfs")
-                  (check? #f))))
-    (cons parent
-          (map (lambda (subsystem)
-                 (file-system
-                   (device "cgroup")
-                   (mount-point (string-append "/sys/fs/cgroup/" subsystem))
-                   (type "cgroup")
-                   (check? #f)
-                   (options subsystem)
-                   (create-mount-point? #t)
-
-                   ;; This must be mounted after, and unmounted before the
-                   ;; parent directory.
-                   (dependencies (list parent))))
-               '("cpuset" "cpu" "cpuacct" "memory" "devices" "freezer"
-                 "blkio" "perf_event" "pids")))))
+  ;; The cgroup2 file system.
+  (list (file-system
+           (device "none")
+	   (mount-point "/sys/fs/cgroup")
+	   (type "cgroup2")
+	   (check? #f)
+	   (create-mount-point? #f))))
 
 (define %elogind-file-systems
   ;; We don't use systemd, but these file systems are needed for elogind,
-- 
2.39.2