cgroup: introduce cgroup_subsys->legacy_name

This allows cgroup subsystems to use a different name on the unified
hierarchy.  cgroup_subsys->name is used on the unified hierarchy,
->legacy_name elsewhere.  If ->legacy_name is not explicitly set, it's
automatically set to ->name and the userland visible behavior remains
unchanged.

v2: Make parse_cgroupfs_options() only consider ->legacy_name as mount
    options are used only on legacy hierarchies.  Suggested by Li
    Zefan.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: cgroups@vger.kernel.org

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 8f5770a..7d0bb53 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -434,6 +434,9 @@ struct cgroup_subsys {
 	int id;
 	const char *name;
 
+	/* optional, initialized automatically during boot if not set */
+	const char *legacy_name;
+
 	/* link to parent, protected by cgroup_lock() */
 	struct cgroup_root *root;