cgroup: implement static_key based cgroup_subsys_enabled() and cgroup_subsys_on_dfl()
Whether a subsys is enabled and attached to the default hierarchy
seldom changes and may be tested in the hot paths. This patch
implements static_key based cgroup_subsys_enabled() and
cgroup_subsys_on_dfl() tests.
The following patches will update the users and remove duplicate
mechanisms.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index eb7ca55..c3a9f1e 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -17,6 +17,7 @@
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/kernfs.h>
+#include <linux/jump_label.h>
#include <linux/cgroup-defs.h>
@@ -50,6 +51,26 @@
#include <linux/cgroup_subsys.h>
#undef SUBSYS
+#define SUBSYS(_x) \
+ extern struct static_key_true _x ## _cgrp_subsys_enabled_key; \
+ extern struct static_key_true _x ## _cgrp_subsys_on_dfl_key;
+#include <linux/cgroup_subsys.h>
+#undef SUBSYS
+
+/**
+ * cgroup_subsys_enabled - fast test on whether a subsys is enabled
+ * @ss: subsystem in question
+ */
+#define cgroup_subsys_enabled(ss) \
+ static_branch_likely(&ss ## _enabled_key)
+
+/**
+ * cgroup_subsys_on_dfl - fast test on whether a subsys is on default hierarchy
+ * @ss: subsystem in question
+ */
+#define cgroup_subsys_on_dfl(ss) \
+ static_branch_likely(&ss ## _on_dfl_key)
+
bool css_has_online_children(struct cgroup_subsys_state *css);
struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup,