cgroup: misc preps for kernfs conversion

* Un-inline seq_css().  After kernfs conversion, the function will
  need to dereference internal data structures.

* Add cgroup_get/put_root() and replace direct super_block->s_active
  manipulatinos with them.  These will be converted to kernfs_root
  refcnting.

* Add cgroup_get/put() and replace dget/put() on cgrp->dentry with
  them.  These will be converted to kernfs refcnting.

* Update current_css_set_cg_links_read() to use cgroup_name() instead
  of reaching into the dentry name.  The end result is the same.

These changes don't make functional differences but will make
transition to kernfs easier.

v2: Rebased on top of 0ab02ca8f887 ("cgroup: protect modifications to
    cgroup_idr with cgroup_mutex").

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

1 files changed, 2 insertions, 6 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 06f577764414..523277871913 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -516,18 +516,14 @@ static inline ino_t cgroup_ino(struct cgroup *cgrp)
 		return 0;
 }
 
-static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)
-{
-	struct cgroup_open_file *of = seq->private;
-	return of->cfe->css;
-}
-
 static inline struct cftype *seq_cft(struct seq_file *seq)
 {
 	struct cgroup_open_file *of = seq->private;
 	return of->cfe->type;
 }
 
+struct cgroup_subsys_state *seq_css(struct seq_file *seq);
+
 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
 int cgroup_rm_cftypes(struct cftype *cfts);