cgroup: make debug an implicit controller on cgroup2

Make debug an implicit controller on cgroup2 which is enabled by
"cgroup_debug" boot param.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Waiman Long <longman@redhat.com>

1 files changed, 56 insertions, 3 deletions

diff --git a/kernel/cgroup/debug.c b/kernel/cgroup/debug.c
index 057d9b07f461..d61e692a5338 100644
--- a/kernel/cgroup/debug.c
+++ b/kernel/cgroup/debug.c
@@ -240,7 +240,7 @@ static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
                 !css_has_online_children(&css->cgroup->self));
 }
 
-static struct cftype debug_files[] =  {
+static struct cftype debug_legacy_files[] =  {
         {
                 .name = "taskcount",
                 .read_u64 = debug_taskcount_read,
@@ -287,9 +287,62 @@ static struct cftype debug_files[] =  {
         { }     /* terminate */
 };
 
+static struct cftype debug_files[] =  {
+        {
+                .name = "taskcount",
+                .read_u64 = debug_taskcount_read,
+        },
+
+        {
+                .name = "current_css_set",
+                .seq_show = current_css_set_read,
+                .flags = CFTYPE_ONLY_ON_ROOT,
+        },
+
+        {
+                .name = "current_css_set_refcount",
+                .read_u64 = current_css_set_refcount_read,
+                .flags = CFTYPE_ONLY_ON_ROOT,
+        },
+
+        {
+                .name = "current_css_set_cg_links",
+                .seq_show = current_css_set_cg_links_read,
+                .flags = CFTYPE_ONLY_ON_ROOT,
+        },
+
+        {
+                .name = "css_links",
+                .seq_show = cgroup_css_links_read,
+        },
+
+        {
+                .name = "csses",
+                .seq_show = cgroup_subsys_states_read,
+        },
+
+        {
+                .name = "masks",
+                .seq_show = cgroup_masks_read,
+        },
+
+        { }     /* terminate */
+};
+
 struct cgroup_subsys debug_cgrp_subsys = {
         .css_alloc      = debug_css_alloc,
         .css_free       = debug_css_free,
-        .legacy_cftypes = debug_files,
-        .dfl_cftypes    = debug_files,
+        .legacy_cftypes = debug_legacy_files,
 };
+
+/*
+ * On v2, debug is an implicit controller enabled by "cgroup_debug" boot
+ * parameter.
+ */
+static int __init enable_cgroup_debug(char *str)
+{
+        debug_cgrp_subsys.dfl_cftypes = debug_files;
+        debug_cgrp_subsys.implicit_on_dfl = true;
+        return 1;
+}
+__setup("cgroup_debug", enable_cgroup_debug);