/*
         * This function is used while updating css associations and thus
-        * can't test the csses directly.  Use ->child_subsys_mask.
+        * can't test the csses directly.  Use ->subtree_ss_mask.
         */
        while (cgroup_parent(cgrp) &&
-              !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ss->id)))
+              !(cgroup_parent(cgrp)->subtree_ss_mask & (1 << ss->id)))
                cgrp = cgroup_parent(cgrp);
 
        return cgroup_css(cgrp, ss);
 }
 
 /**
- * cgroup_calc_child_subsys_mask - calculate child_subsys_mask
+ * cgroup_calc_subtree_ss_mask - calculate subtree_ss_mask
  * @cgrp: the target cgroup
  * @subtree_control: the new subtree_control mask to consider
  *
  * @subtree_control is to be applied to @cgrp.  The returned mask is always
  * a superset of @subtree_control and follows the usual hierarchy rules.
  */
-static unsigned long cgroup_calc_child_subsys_mask(struct cgroup *cgrp,
-                                                 unsigned long subtree_control)
+static unsigned long cgroup_calc_subtree_ss_mask(struct cgroup *cgrp,
+                                                unsigned long subtree_control)
 {
        struct cgroup *parent = cgroup_parent(cgrp);
        unsigned long cur_ss_mask = subtree_control;
                 * to non-default hierarchies.
                 */
                if (parent)
-                       new_ss_mask &= parent->child_subsys_mask;
+                       new_ss_mask &= parent->subtree_ss_mask;
                else
                        new_ss_mask &= cgrp->root->subsys_mask;
 
 }
 
 /**
- * cgroup_refresh_child_subsys_mask - update child_subsys_mask
+ * cgroup_refresh_subtree_ss_mask - update subtree_ss_mask
  * @cgrp: the target cgroup
  *
- * Update @cgrp->child_subsys_mask according to the current
- * @cgrp->subtree_control using cgroup_calc_child_subsys_mask().
+ * Update @cgrp->subtree_ss_mask according to the current
+ * @cgrp->subtree_control using cgroup_calc_subtree_ss_mask().
  */
-static void cgroup_refresh_child_subsys_mask(struct cgroup *cgrp)
+static void cgroup_refresh_subtree_ss_mask(struct cgroup *cgrp)
 {
-       cgrp->child_subsys_mask =
-               cgroup_calc_child_subsys_mask(cgrp, cgrp->subtree_control);
+       cgrp->subtree_ss_mask =
+               cgroup_calc_subtree_ss_mask(cgrp, cgrp->subtree_control);
 }
 
 /**
 
                src_root->subsys_mask &= ~(1 << ssid);
                scgrp->subtree_control &= ~(1 << ssid);
-               cgroup_refresh_child_subsys_mask(scgrp);
+               cgroup_refresh_subtree_ss_mask(scgrp);
 
                /* default hierarchy doesn't enable controllers by default */
                dst_root->subsys_mask |= 1 << ssid;
                        static_branch_enable(cgroup_subsys_on_dfl_key[ssid]);
                } else {
                        dcgrp->subtree_control |= 1 << ssid;
-                       cgroup_refresh_child_subsys_mask(dcgrp);
+                       cgroup_refresh_subtree_ss_mask(dcgrp);
                        static_branch_disable(cgroup_subsys_on_dfl_key[ssid]);
                }
 
        lockdep_assert_held(&cgroup_mutex);
 
        /*
-        * Except for the root, child_subsys_mask must be zero for a cgroup
+        * Except for the root, subtree_ss_mask must be zero for a cgroup
         * with tasks so that child cgroups don't compete against tasks.
         */
        if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && cgroup_parent(dst_cgrp) &&
-           dst_cgrp->child_subsys_mask)
+           dst_cgrp->subtree_ss_mask)
                return -EBUSY;
 
        /* look up the dst cset for each src cset and link it to src */
  * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
  * @cgrp: root of the subtree to update csses for
  *
- * @cgrp's child_subsys_mask has changed and its subtree's (self excluded)
+ * @cgrp's subtree_ss_mask has changed and its subtree's (self excluded)
  * css associations need to be updated accordingly.  This function looks up
  * all css_sets which are attached to the subtree, creates the matching
  * updated css_sets and migrates the tasks to the new ones.
        css_for_each_descendant_pre(css, cgroup_css(cgrp, NULL)) {
                struct cgrp_cset_link *link;
 
-               /* self is not affected by child_subsys_mask change */
+               /* self is not affected by subtree_ss_mask change */
                if (css->cgroup == cgrp)
                        continue;
 
         * depending on subsystem dependencies.
         */
        old_sc = cgrp->subtree_control;
-       old_ss = cgrp->child_subsys_mask;
+       old_ss = cgrp->subtree_ss_mask;
        new_sc = (old_sc | enable) & ~disable;
-       new_ss = cgroup_calc_child_subsys_mask(cgrp, new_sc);
+       new_ss = cgroup_calc_subtree_ss_mask(cgrp, new_sc);
 
        css_enable = ~old_ss & new_ss;
        css_disable = old_ss & ~new_ss;
        }
 
        cgrp->subtree_control = new_sc;
-       cgrp->child_subsys_mask = new_ss;
+       cgrp->subtree_ss_mask = new_ss;
 
        /*
         * Create new csses or make the existing ones visible.  A css is
 
 err_undo_css:
        cgrp->subtree_control = old_sc;
-       cgrp->child_subsys_mask = old_ss;
+       cgrp->subtree_ss_mask = old_ss;
 
        for_each_subsys(ss, ssid) {
                if (!(enable & (1 << ssid)))
 
        /* let's create and online css's */
        for_each_subsys(ss, ssid) {
-               if (parent->child_subsys_mask & (1 << ssid)) {
+               if (parent->subtree_ss_mask & (1 << ssid)) {
                        ret = create_css(cgrp, ss,
                                         parent->subtree_control & (1 << ssid));
                        if (ret)
         */
        if (!cgroup_on_dfl(cgrp)) {
                cgrp->subtree_control = parent->subtree_control;
-               cgroup_refresh_child_subsys_mask(cgrp);
+               cgroup_refresh_subtree_ss_mask(cgrp);
        }
 
        kernfs_activate(kn);