Commit 3c41382e authored by Michal Koutný's avatar Michal Koutný Committed by Tejun Heo
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cgroup: Disallow mounting v1 hierarchies without controller implementation 



The configs that disable some v1 controllers would still allow mounting
them but with no controller-specific files. (Making such hierarchies
equivalent to named v1 hierarchies.) To achieve behavior consistent with
actual out-compilation of a whole controller, the mounts should treat
respective controllers as non-existent.

Wrap implementation into a helper function, leverage legacy_files to
detect compiled out controllers. The effect is that mounts on v1 would
fail and produce a message like:
  [ 1543.999081] cgroup: Unknown subsys name 'memory'

Signed-off-by: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 659f90f8

kernel/cgroup/cgroup-v1.c

+10 −2
Original line number Diff line number Diff line
@@ -46,6 +46,12 @@ bool cgroup1_ssid_disabled(int ssid) 
	return cgroup_no_v1_mask & (1 << ssid);

}



static bool cgroup1_subsys_absent(struct cgroup_subsys *ss)

{

	/* Check also dfl_cftypes for file-less controllers, i.e. perf_event */

	return ss->legacy_cftypes == NULL && ss->dfl_cftypes;

}



/**

 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'

 * @from: attach to all cgroups of a given task
@@ -932,7 +938,8 @@ int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param) 
		if (ret != -ENOPARAM)

			return ret;

		for_each_subsys(ss, i) {

			if (strcmp(param->key, ss->legacy_name))

			if (strcmp(param->key, ss->legacy_name) ||

			    cgroup1_subsys_absent(ss))

				continue;

			if (!cgroup_ssid_enabled(i) || cgroup1_ssid_disabled(i))

				return invalfc(fc, "Disabled controller '%s'",
@@ -1024,7 +1031,8 @@ static int check_cgroupfs_options(struct fs_context *fc) 
	mask = ~((u16)1 << cpuset_cgrp_id);

#endif

	for_each_subsys(ss, i)

		if (cgroup_ssid_enabled(i) && !cgroup1_ssid_disabled(i))

		if (cgroup_ssid_enabled(i) && !cgroup1_ssid_disabled(i) &&

		    !cgroup1_subsys_absent(ss))

			enabled |= 1 << i;



	ctx->subsys_mask &= enabled;