Commit a0ab1453 authored by Michal Koutný's avatar Michal Koutný Committed by Tejun Heo
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cgroup: Print message when /proc/cgroups is read on v2-only system 



As a followup to commits 6c292092 ("cgroup: replace
unified-hierarchy.txt with a proper cgroup v2 documentation") and
ab031252 ("cgroup: Show # of subsystem CSSes in cgroup.stat"),
add a runtime message to users who read status of controllers in
/proc/cgroups on v2-only system. The detection is based on a)
no controllers are attached to v1, b) default hierarchy is mounted (the
latter is for setups that never mount v2 but read /proc/cgroups upon
boot when controllers default to v2, so that this code may be backported
to older kernels).

Signed-off-by: default avatarMichal Koutný <mkoutny@suse.com>
Acked-by: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 77bbb259

kernel/cgroup/cgroup-internal.h

+1 −0
Original line number Diff line number Diff line
@@ -168,6 +168,7 @@ struct cgroup_mgctx { 


extern struct cgroup_subsys *cgroup_subsys[];

extern struct list_head cgroup_roots;

extern bool cgrp_dfl_visible;



/* iterate across the hierarchies */

#define for_each_root(root)						\

kernel/cgroup/cgroup-v1.c

+7 −0
Original line number Diff line number Diff line
@@ -673,6 +673,7 @@ struct cftype cgroup1_base_files[] = { 
int proc_cgroupstats_show(struct seq_file *m, void *v)

{

	struct cgroup_subsys *ss;

	bool cgrp_v1_visible = false;

	int i;



	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
@@ -684,12 +685,18 @@ int proc_cgroupstats_show(struct seq_file *m, void *v) 
	for_each_subsys(ss, i) {

		if (cgroup1_subsys_absent(ss))

			continue;

		cgrp_v1_visible |= ss->root != &cgrp_dfl_root;



		seq_printf(m, "%s\t%d\t%d\t%d\n",

			   ss->legacy_name, ss->root->hierarchy_id,

			   atomic_read(&ss->root->nr_cgrps),

			   cgroup_ssid_enabled(i));

	}



	if (cgrp_dfl_visible && !cgrp_v1_visible)

		pr_info_once("/proc/cgroups lists only v1 controllers, use cgroup.controllers of root cgroup for v2 info\n");





	return 0;

}

kernel/cgroup/cgroup.c

+1 −1
Original line number Diff line number Diff line
@@ -171,7 +171,7 @@ EXPORT_SYMBOL_GPL(cgrp_dfl_root); 
 * The default hierarchy always exists but is hidden until mounted for the

 * first time.  This is for backward compatibility.

 */

static bool cgrp_dfl_visible;

bool cgrp_dfl_visible;



/* some controllers are not supported in the default hierarchy */

static u16 cgrp_dfl_inhibit_ss_mask;