[bug#29409] Remove hugetlb control group on ARM32.

[Mathieu Othacehe]

Hi Tobias, Danny and Ludo,

Thanks for your answers!

> Indeed.  So actually we can probably remove it altogether.
>
> We could simply do that and keep the definition around for when we need
> it.
>
> Thoughts?

Seems ok to me.

I also proposed a patch to move %control-groups from %base-file-systems
to %elogind-file-systems.

WDYT ?

Thanks,

Mathieu

>From a531af25b3cffeb70e5681ef70ced564378f2db7 Mon Sep 17 00:00:00 2001
From: Mathieu Othacehe <address@hidden>
Date: Fri, 22 Dec 2017 08:42:29 +0100
Subject: [PATCH 1/2] file-systems: Do not mount hugetlb cgroup filesystem.

On ARM32 without LPAE support, hugetlb control group is not supported.
As it is not needed by elogind, remove it for all platforms.

* gnu/system/file-systems.scm (%control-groups): Remove hugetlb from control
  groups platforms.
---
 gnu/system/file-systems.scm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gnu/system/file-systems.scm b/gnu/system/file-systems.scm
index 27734e892..9de465167 100644
--- a/gnu/system/file-systems.scm
+++ b/gnu/system/file-systems.scm
@@ -279,7 +279,7 @@ TARGET in the other system."
                    ;; parent directory.
                    (dependencies (list parent))))
                '("cpuset" "cpu" "cpuacct" "memory" "devices" "freezer"
-                 "blkio" "perf_event" "hugetlb")))))
+                 "blkio" "perf_event")))))
 
 (define %elogind-file-systems
   ;; We don't use systemd, but these file systems are needed for elogind,
-- 
2.15.0

>From 4a28602843a661989c687086af009481dab05eed Mon Sep 17 00:00:00 2001
From: Mathieu Othacehe <address@hidden>
Date: Fri, 22 Dec 2017 08:43:24 +0100
Subject: [PATCH 2/2] file-systems: Move %control-groups from
 %base-file-systems to %elogind-file-systems.

* gnu/system/file-systems.scm (%base-file-systems): Move %control-groups from
here, to ...
(%elogind-file-systems): ... here.
---
 gnu/system/file-systems.scm | 63 +++++++++++++++++++++++----------------------
 1 file changed, 32 insertions(+), 31 deletions(-)

diff --git a/gnu/system/file-systems.scm b/gnu/system/file-systems.scm
index 9de465167..7f5afb00f 100644
--- a/gnu/system/file-systems.scm
+++ b/gnu/system/file-systems.scm
@@ -284,41 +284,42 @@ TARGET in the other system."
 (define %elogind-file-systems
   ;; We don't use systemd, but these file systems are needed for elogind,
   ;; which was extracted from systemd.
-  (list (file-system
-          (device "none")
-          (mount-point "/run/systemd")
-          (type "tmpfs")
-          (check? #f)
-          (flags '(no-suid no-dev no-exec))
-          (options "mode=0755")
-          (create-mount-point? #t))
-        (file-system
-          (device "none")
-          (mount-point "/run/user")
-          (type "tmpfs")
-          (check? #f)
-          (flags '(no-suid no-dev no-exec))
-          (options "mode=0755")
-          (create-mount-point? #t))
-        ;; Elogind uses cgroups to organize processes, allowing it to map PIDs
-        ;; to sessions.  Elogind's cgroup hierarchy isn't associated with any
-        ;; resource controller ("subsystem").
-        (file-system
-          (device "cgroup")
-          (mount-point "/sys/fs/cgroup/elogind")
-          (type "cgroup")
-          (check? #f)
-          (options "none,name=elogind")
-          (create-mount-point? #t)
-          (dependencies (list (car %control-groups))))))
+  (append
+   (list (file-system
+           (device "none")
+           (mount-point "/run/systemd")
+           (type "tmpfs")
+           (check? #f)
+           (flags '(no-suid no-dev no-exec))
+           (options "mode=0755")
+           (create-mount-point? #t))
+         (file-system
+           (device "none")
+           (mount-point "/run/user")
+           (type "tmpfs")
+           (check? #f)
+           (flags '(no-suid no-dev no-exec))
+           (options "mode=0755")
+           (create-mount-point? #t))
+         ;; Elogind uses cgroups to organize processes, allowing it to map PIDs
+         ;; to sessions.  Elogind's cgroup hierarchy isn't associated with any
+         ;; resource controller ("subsystem").
+         (file-system
+           (device "cgroup")
+           (mount-point "/sys/fs/cgroup/elogind")
+           (type "cgroup")
+           (check? #f)
+           (options "none,name=elogind")
+           (create-mount-point? #t)
+           (dependencies (list (car %control-groups)))))
+   %control-groups))
 
 (define %base-file-systems
   ;; List of basic file systems to be mounted.  Note that /proc and /sys are
   ;; currently mounted by the initrd.
-  (append (list %pseudo-terminal-file-system
-                %shared-memory-file-system
-                %immutable-store)
-          %control-groups))
+  (list %pseudo-terminal-file-system
+        %shared-memory-file-system
+        %immutable-store))
 
 ;; File systems for Linux containers differ from %base-file-systems in that
 ;; they impose additional restrictions such as no-exec or need different
-- 
2.15.0