1 files changed, 54 insertions, 71 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index c4901c19668b..7bb274487c89 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -256,68 +256,7 @@ struct cgroup {
 
 /* cgroup_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", "xattr", "clone_children",
-         *   "release_agent" and "name" are disallowed.
-         *
-         * - When mounting an existing superblock, mount options should
-         *   match.
-         *
-         * - Remount is disallowed.
-         *
-         * - rename(2) is disallowed.
-         *
-         * - "tasks" is removed.  Everything should be at process
-         *   granularity.  Use "cgroup.procs" instead.
-         *
-         * - "cgroup.procs" is not sorted.  pids will be unique unless they
-         *   got recycled inbetween reads.
-         *
-         * - "release_agent" and "notify_on_release" are removed.
-         *   Replacement notification mechanism will be implemented.
-         *
-         * - "cgroup.clone_children" is removed.
-         *
-         * - "cgroup.subtree_populated" is available.  Its value is 0 if
-         *   the cgroup and its descendants contain no task; otherwise, 1.
-         *   The file also generates kernfs notification which can be
-         *   monitored through poll and [di]notify when the value of the
-         *   file changes.
-         *
-         * - If mount is requested with sane_behavior but without any
-         *   subsystem, the default unified hierarchy is mounted.
-         *
-         * - cpuset: tasks will be kept in empty cpusets when hotplug happens
-         *   and take masks of ancestors with non-empty cpus/mems, instead of
-         *   being moved to an ancestor.
-         *
-         * - cpuset: a task can be moved into an empty cpuset, and again it
-         *   takes masks of ancestors.
-         *
-         * - memcg: use_hierarchy is on by default and the cgroup file for
-         *   the flag is not created.
-         *
-         * - blkcg: blk-throttle becomes properly hierarchical.
-         *
-         * - debug: disallowed on the default hierarchy.
-         */
-        CGRP_ROOT_SANE_BEHAVIOR = (1 << 0),
-
+        CGRP_ROOT_SANE_BEHAVIOR = (1 << 0), /* __DEVEL__sane_behavior specified */
         CGRP_ROOT_NOPREFIX      = (1 << 1), /* mounted subsystems have no named prefix */
         CGRP_ROOT_XATTR         = (1 << 2), /* supports extended attributes */
 };
@@ -531,20 +470,64 @@ struct cftype {
 extern struct cgroup_root cgrp_dfl_root;
 extern struct css_set init_css_set;
 
+/**
+ * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
+ * @cgrp: the cgroup of interest
+ *
+ * The default hierarchy is the v2 interface of cgroup and this function
+ * can be used to test whether a cgroup is on the default hierarchy for
+ * cases where a subsystem should behave differnetly depending on the
+ * interface version.
+ *
+ * The set of behaviors which change on the default hierarchy are still
+ * being determined and the mount option is prefixed with __DEVEL__.
+ *
+ * List of changed behaviors:
+ *
+ * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
+ *   and "name" are disallowed.
+ *
+ * - When mounting an existing superblock, mount options should match.
+ *
+ * - Remount is disallowed.
+ *
+ * - rename(2) is disallowed.
+ *
+ * - "tasks" is removed.  Everything should be at process granularity.  Use
+ *   "cgroup.procs" instead.
+ *
+ * - "cgroup.procs" is not sorted.  pids will be unique unless they got
+ *   recycled inbetween reads.
+ *
+ * - "release_agent" and "notify_on_release" are removed.  Replacement
+ *   notification mechanism will be implemented.
+ *
+ * - "cgroup.clone_children" is removed.
+ *
+ * - "cgroup.subtree_populated" is available.  Its value is 0 if the cgroup
+ *   and its descendants contain no task; otherwise, 1.  The file also
+ *   generates kernfs notification which can be monitored through poll and
+ *   [di]notify when the value of the file changes.
+ *
+ * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
+ *   take masks of ancestors with non-empty cpus/mems, instead of being
+ *   moved to an ancestor.
+ *
+ * - cpuset: a task can be moved into an empty cpuset, and again it takes
+ *   masks of ancestors.
+ *
+ * - memcg: use_hierarchy is on by default and the cgroup file for the flag
+ *   is not created.
+ *
+ * - blkcg: blk-throttle becomes properly hierarchical.
+ *
+ * - debug: disallowed on the default hierarchy.
+ */
 static inline bool cgroup_on_dfl(const struct cgroup *cgrp)
 {
         return cgrp->root == &cgrp_dfl_root;
 }
 
-/*
- * See the comment above CGRP_ROOT_SANE_BEHAVIOR for details.  This
- * function can be called as long as @cgrp is accessible.
- */
-static inline bool cgroup_sane_behavior(const struct cgroup *cgrp)
-{
-        return cgrp->root->flags & CGRP_ROOT_SANE_BEHAVIOR;
-}
-
 /* no synchronization, the result can only be used as a hint */
 static inline bool cgroup_has_tasks(struct cgroup *cgrp)
 {