cgroup: unexport cgroup_css() and remove __file_cft()

Now that cgroup_event is made memcg specific, the temporarily exported
functions are no longer necessary.  Unexport cgroup_css() and remove
__file_cft() which doesn't have any user left.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

include/linux/cgroup.h

@@ -883,11 +883,6 @@ unsigned short css_id(struct cgroup_subsys_state *css);
 struct cgroup_subsys_state *css_from_dir(struct dentry *dentry,
 					 struct cgroup_subsys *ss);
 
-/* XXX: temporary */
-struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
-				       struct cgroup_subsys *ss);
-struct cftype *__file_cft(struct file *file);
-
 #else /* !CONFIG_CGROUPS */
 
 static inline int cgroup_init_early(void) { return 0; }

kernel/cgroup.c

@@ -202,8 +202,8 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
  * keep accessing it outside the said locks.  This function may return
  * %NULL if @cgrp doesn't have @subsys_id enabled.
  */
-struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
-				       struct cgroup_subsys *ss)
+static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
+					      struct cgroup_subsys *ss)
 {
 	if (ss)
 		return rcu_dereference_check(cgrp->subsys[ss->subsys_id],
@@ -2625,16 +2625,6 @@ static const struct inode_operations cgroup_dir_inode_operations = {
 	.removexattr = cgroup_removexattr,
 };
 
-/*
- * Check if a file is a control file
- */
-struct cftype *__file_cft(struct file *file)
-{
-	if (file_inode(file)->i_fop != &cgroup_file_operations)
-		return ERR_PTR(-EINVAL);
-	return __d_cft(file->f_dentry);
-}
-
 static int cgroup_create_file(struct dentry *dentry, umode_t mode,
 				struct super_block *sb)
 {