cgroup: make hierarchy iterators deal with cgroup_subsys_state instead of cgroup

cgroup is currently in the process of transitioning to using css
(cgroup_subsys_state) as the primary handle instead of cgroup in
subsystem API.  For hierarchy iterators, this is beneficial because

* In most cases, css is the only thing subsystems care about anyway.

* On the planned unified hierarchy, iterations for different
  subsystems will need to skip over different subtrees of the
  hierarchy depending on which subsystems are enabled on each cgroup.
  Passing around css makes it unnecessary to explicitly specify the
  subsystem in question as css is intersection between cgroup and
  subsystem

* For the planned unified hierarchy, css's would need to be created
  and destroyed dynamically independent from cgroup hierarchy.  Having
  cgroup core manage css iteration makes enforcing deref rules a lot
  easier.

Most subsystem conversions are straight-forward.  Noteworthy changes
are

* blkio: cgroup_to_blkcg() is no longer used.  Removed.

* freezer: cgroup_freezer() is no longer used.  Removed.

* devices: cgroup_to_devcgroup() is no longer used.  Removed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>

1 files changed, 10 insertions, 15 deletions

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 19613ba51444..98ca48d9ceb4 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -50,11 +50,6 @@ static inline struct freezer *css_freezer(struct cgroup_subsys_state *css)
         return css ? container_of(css, struct freezer, css) : NULL;
 }
 
-static inline struct freezer *cgroup_freezer(struct cgroup *cgroup)
-{
-        return css_freezer(cgroup_css(cgroup, freezer_subsys_id));
-}
-
 static inline struct freezer *task_freezer(struct task_struct *task)
 {
         return css_freezer(task_css(task, freezer_subsys_id));
@@ -120,7 +115,7 @@ static int freezer_css_online(struct cgroup_subsys_state *css)
         /*
          * The following double locking and freezing state inheritance
          * guarantee that @cgroup can never escape ancestors' freezing
-         * states.  See cgroup_for_each_descendant_pre() for details.
+         * states.  See css_for_each_descendant_pre() for details.
          */
         if (parent)
                 spin_lock_irq(&parent->lock);
@@ -262,7 +257,7 @@ out:
 static void update_if_frozen(struct cgroup_subsys_state *css)
 {
         struct freezer *freezer = css_freezer(css);
-        struct cgroup *pos;
+        struct cgroup_subsys_state *pos;
         struct cgroup_iter it;
         struct task_struct *task;
 
@@ -275,8 +270,8 @@ static void update_if_frozen(struct cgroup_subsys_state *css)
                 goto out_unlock;
 
         /* are all (live) children frozen? */
-        cgroup_for_each_child(pos, css->cgroup) {
-                struct freezer *child = cgroup_freezer(pos);
+        css_for_each_child(pos, css) {
+                struct freezer *child = css_freezer(pos);
 
                 if ((child->state & CGROUP_FREEZER_ONLINE) &&
                     !(child->state & CGROUP_FROZEN))
@@ -309,13 +304,13 @@ out_unlock:
 static int freezer_read(struct cgroup_subsys_state *css, struct cftype *cft,
                         struct seq_file *m)
 {
-        struct cgroup *pos;
+        struct cgroup_subsys_state *pos;
 
         rcu_read_lock();
 
         /* update states bottom-up */
-        cgroup_for_each_descendant_post(pos, css->cgroup)
-                update_if_frozen(cgroup_css(pos, freezer_subsys_id));
+        css_for_each_descendant_post(pos, css)
+                update_if_frozen(pos);
         update_if_frozen(css);
 
         rcu_read_unlock();
@@ -396,7 +391,7 @@ static void freezer_apply_state(struct freezer *freezer, bool freeze,
  */
 static void freezer_change_state(struct freezer *freezer, bool freeze)
 {
-        struct cgroup *pos;
+        struct cgroup_subsys_state *pos;
 
         /* update @freezer */
         spin_lock_irq(&freezer->lock);
@@ -409,8 +404,8 @@ static void freezer_change_state(struct freezer *freezer, bool freeze)
          * CGROUP_FREEZING_PARENT.
          */
         rcu_read_lock();
-        cgroup_for_each_descendant_pre(pos, freezer->css.cgroup) {
-                struct freezer *pos_f = cgroup_freezer(pos);
+        css_for_each_descendant_pre(pos, &freezer->css) {
+                struct freezer *pos_f = css_freezer(pos);
                 struct freezer *parent = parent_freezer(pos_f);
 
                 /*