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-rw-r--r--kernel/cgroup.c49
1 files changed, 48 insertions, 1 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 3a6b77d7ba4a..cd02e99d5d3b 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1037,9 +1037,56 @@ static void cgroup_put(struct cgroup *cgrp)
css_put(&cgrp->self);
}
+/**
+ * cgroup_refresh_child_subsys_mask - update child_subsys_mask
+ * @cgrp: the target cgroup
+ *
+ * On the default hierarchy, a subsystem may request other subsystems to be
+ * enabled together through its ->depends_on mask. In such cases, more
+ * subsystems than specified in "cgroup.subtree_control" may be enabled.
+ *
+ * This function determines which subsystems need to be enabled given the
+ * current @cgrp->subtree_control and records it in
+ * @cgrp->child_subsys_mask. The resulting mask is always a superset of
+ * @cgrp->subtree_control and follows the usual hierarchy rules.
+ */
static void cgroup_refresh_child_subsys_mask(struct cgroup *cgrp)
{
- cgrp->child_subsys_mask = cgrp->subtree_control;
+ struct cgroup *parent = cgroup_parent(cgrp);
+ unsigned int cur_ss_mask = cgrp->subtree_control;
+ struct cgroup_subsys *ss;
+ int ssid;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ if (!cgroup_on_dfl(cgrp)) {
+ cgrp->child_subsys_mask = cur_ss_mask;
+ return;
+ }
+
+ while (true) {
+ unsigned int new_ss_mask = cur_ss_mask;
+
+ for_each_subsys(ss, ssid)
+ if (cur_ss_mask & (1 << ssid))
+ new_ss_mask |= ss->depends_on;
+
+ /*
+ * Mask out subsystems which aren't available. This can
+ * happen only if some depended-upon subsystems were bound
+ * to non-default hierarchies.
+ */
+ if (parent)
+ new_ss_mask &= parent->child_subsys_mask;
+ else
+ new_ss_mask &= cgrp->root->subsys_mask;
+
+ if (new_ss_mask == cur_ss_mask)
+ break;
+ cur_ss_mask = new_ss_mask;
+ }
+
+ cgrp->child_subsys_mask = cur_ss_mask;
}
/**