Commit 5f2e6734 authored Nov 06, 2017 by Roman Gushchin Committed by Tejun Heo Nov 06, 2017

cgroup: export list of cgroups v2 features using sysfs



The active development of cgroups v2 sometimes leads to a creation
of interfaces, which are not turned on by default (to provide
backward compatibility). It's handy to know from userspace, which
cgroup v2 features are supported without calculating it based
on the kernel version. So, let's export the list of such features
using /sys/kernel/cgroup/features pseudo-file.

The list is hardcoded and has to be extended when new functionality
is added. Each feature is printed on a new line.

Example:
  $ cat /sys/kernel/cgroup/features
  nsdelegate

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: kernel-team@fb.com
Signed-off-by: Tejun Heo <tj@kernel.org>

parent 01ee6cfb

kernel/cgroup/cgroup.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -5877,8 +5877,16 @@ static ssize_t delegate_show(struct kobject kobj, struct kobj_attribute attr,
		}
		static struct kobj_attribute cgroup_delegate_attr = __ATTR_RO(delegate);

		static ssize_t features_show(struct kobject kobj, struct kobj_attribute attr,
		char *buf)
		{
		return snprintf(buf, PAGE_SIZE, "nsdelegate\n");
		}
		static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features);

		static struct attribute *cgroup_sysfs_attrs[] = {
		&cgroup_delegate_attr.attr,
		&cgroup_features_attr.attr,
		NULL,
		};

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