cgroup: implement CFTYPE_ONLY_ON_DFL

This cftype flag makes the file only appear on the default hierarchy.
This will later be used for cgroup.controllers file.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 69b4939e9f6d..37b6d534b0ca 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2356,6 +2356,8 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
 
         for (cft = cfts; cft->name[0] != '\0'; cft++) {
                 /* does cft->flags tell us to skip this file on @cgrp? */
+                if ((cft->flags & CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
+                        continue;
                 if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp))
                         continue;
                 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)