Re: [PATCH cgroup/for-4.3 2/3] cgroup: drop cgroup__DEVEL__legacy_files_on_dfl

[Tejun Heo <tj@kernel.org>]

Now that interfaces for the major three controllers - cpu, memory, io
- are shaping up, there's no reason to have an option to force legacy
files to show up on the unified hierarchy for testing.  Drop it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
---
 Documentation/cgroups/unified-hierarchy.txt |    6 -----
 kernel/cgroup.c                             |   30 +---------------------------
 2 files changed, 2 insertions(+), 34 deletions(-)

--- a/Documentation/cgroups/unified-hierarchy.txt
+++ b/Documentation/cgroups/unified-hierarchy.txt
@@ -107,12 +107,6 @@ root of unified hierarchy can be bound t
 allows mixing unified hierarchy with the traditional multiple
 hierarchies in a fully backward compatible way.
 
-For development purposes, the following boot parameter makes all
-controllers to appear on the unified hierarchy whether supported or
-not.
-
- cgroup__DEVEL__legacy_files_on_dfl
-
 A controller can be moved across hierarchies only after the controller
 is no longer referenced in its current hierarchy.  Because per-cgroup
 controller states are destroyed asynchronously and controllers may
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -152,12 +152,6 @@ struct cgroup_root cgrp_dfl_root;
  */
 static bool cgrp_dfl_root_visible;
 
-/*
- * Set by the boot param of the same name and makes subsystems with NULL
- * ->dfl_files to use ->legacy_files on the default hierarchy.
- */
-static bool cgroup_legacy_files_on_dfl;
-
 /* some controllers are not supported in the default hierarchy */
 static unsigned long cgrp_dfl_root_inhibit_ss_mask;
 
@@ -3340,17 +3334,8 @@ int cgroup_add_legacy_cftypes(struct cgr
 {
 	struct cftype *cft;
 
-	/*
-	 * If legacy_flies_on_dfl, we want to show the legacy files on the
-	 * dfl hierarchy but iff the target subsystem hasn't been updated
-	 * for the dfl hierarchy yet.
-	 */
-	if (!cgroup_legacy_files_on_dfl ||
-	    ss->dfl_cftypes != ss->legacy_cftypes) {
-		for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
-			cft->flags |= __CFTYPE_NOT_ON_DFL;
-	}
-
+	for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
+		cft->flags |= __CFTYPE_NOT_ON_DFL;
 	return cgroup_add_cftypes(ss, cfts);
 }
 
@@ -5055,9 +5040,6 @@ int __init cgroup_init(void)
 
 		cgrp_dfl_root.subsys_mask |= 1 << ss->id;
 
-		if (cgroup_legacy_files_on_dfl && !ss->dfl_cftypes)
-			ss->dfl_cftypes = ss->legacy_cftypes;
-
 		if (!ss->dfl_cftypes)
 			cgrp_dfl_root_inhibit_ss_mask |= 1 << ss->id;
 
@@ -5474,14 +5456,6 @@ static int __init cgroup_disable(char *s
 }
 __setup("cgroup_disable=", cgroup_disable);
 
-static int __init cgroup_set_legacy_files_on_dfl(char *str)
-{
-	printk("cgroup: using legacy files on the default hierarchy\n");
-	cgroup_legacy_files_on_dfl = true;
-	return 0;
-}
-__setup("cgroup__DEVEL__legacy_files_on_dfl", cgroup_set_legacy_files_on_dfl);
-
 /**
  * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
  * @dentry: directory dentry of interest