+#define MAX_CGROUP_ROOT_NAMELEN 64
+
+/* cgroupfs_root->flags */
+enum {
+ /*
+ * Unfortunately, cgroup core and various controllers are riddled
+ * with idiosyncrasies and pointless options. The following flag,
+ * when set, will force sane behavior - some options are forced on,
+ * others are disallowed, and some controllers will change their
+ * hierarchical or other behaviors.
+ *
+ * The set of behaviors affected by this flag are still being
+ * determined and developed and the mount option for this flag is
+ * prefixed with __DEVEL__. The prefix will be dropped once we
+ * reach the point where all behaviors are compatible with the
+ * planned unified hierarchy, which will automatically turn on this
+ * flag.
+ *
+ * The followings are the behaviors currently affected this flag.
+ *
+ * - Mount options "noprefix" and "clone_children" are disallowed.
+ * Also, cgroupfs file cgroup.clone_children is not created.
+ *
+ * - When mounting an existing superblock, mount options should
+ * match.
+ *
+ * - Remount is disallowed.
+ *
+ * - memcg: use_hierarchy is on by default and the cgroup file for
+ * the flag is not created.
+ *
+ * The followings are planned changes.
+ *
+ * - release_agent will be disallowed once replacement notification
+ * mechanism is implemented.
+ */
+ CGRP_ROOT_SANE_BEHAVIOR = (1 << 0),
+
+ CGRP_ROOT_NOPREFIX = (1 << 1), /* mounted subsystems have no named prefix */
+ CGRP_ROOT_XATTR = (1 << 2), /* supports extended attributes */
+};
+
+/*
+ * A cgroupfs_root represents the root of a cgroup hierarchy, and may be
+ * associated with a superblock to form an active hierarchy. This is
+ * internal to cgroup core. Don't access directly from controllers.
+ */
+struct cgroupfs_root {
+ struct super_block *sb;
+
+ /*
+ * The bitmask of subsystems intended to be attached to this
+ * hierarchy
+ */
+ unsigned long subsys_mask;
+
+ /* Unique id for this hierarchy. */
+ int hierarchy_id;
+
+ /* The bitmask of subsystems currently attached to this hierarchy */
+ unsigned long actual_subsys_mask;
+
+ /* A list running through the attached subsystems */
+ struct list_head subsys_list;
+
+ /* The root cgroup for this hierarchy */
+ struct cgroup top_cgroup;
+
+ /* Tracks how many cgroups are currently defined in hierarchy.*/
+ int number_of_cgroups;
+
+ /* A list running through the active hierarchies */
+ struct list_head root_list;
+
+ /* All cgroups on this root, cgroup_mutex protected */
+ struct list_head allcg_list;
+
+ /* Hierarchy-specific flags */
+ unsigned long flags;
+
+ /* IDs for cgroups in this hierarchy */
+ struct ida cgroup_ida;
+
+ /* The path to use for release notifications. */
+ char release_agent_path[PATH_MAX];
+
+ /* The name for this hierarchy - may be empty */
+ char name[MAX_CGROUP_ROOT_NAMELEN];
+};
+