cgroup: keep track of number of descent cgroups

Keep track of the number of online and dying descent cgroups.

This data will be used later to add an ability to control cgroup
hierarchy (limit the depth and the number of descent cgroups)
and display hierarchy stats.

Signed-off-by: Roman Gushchin <guro@fb.com>
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: kernel-team@fb.com
Cc: cgroups@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

1 files changed, 17 insertions, 2 deletions

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 85f6a112344b..cfdbb1e780de 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4408,9 +4408,15 @@ static void css_release_work_fn(struct work_struct *work)
                 if (ss->css_released)
                         ss->css_released(css);
         } else {
+                struct cgroup *tcgrp;
+
                 /* cgroup release path */
                 trace_cgroup_release(cgrp);
 
+                for (tcgrp = cgroup_parent(cgrp); tcgrp;
+                     tcgrp = cgroup_parent(tcgrp))
+                        tcgrp->nr_dying_descendants--;
+
                 cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
                 cgrp->id = -1;
 
@@ -4609,9 +4615,13 @@ static struct cgroup *cgroup_create(struct cgroup *parent)
         cgrp->root = root;
         cgrp->level = level;
 
-        for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp))
+        for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
                 cgrp->ancestor_ids[tcgrp->level] = tcgrp->id;
 
+                if (tcgrp != cgrp)
+                        tcgrp->nr_descendants++;
+        }
+
         if (notify_on_release(parent))
                 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
 
@@ -4817,7 +4827,7 @@ static void kill_css(struct cgroup_subsys_state *css)
 static int cgroup_destroy_locked(struct cgroup *cgrp)
         __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
 {
-        struct cgroup *parent = cgroup_parent(cgrp);
+        struct cgroup *tcgrp, *parent = cgroup_parent(cgrp);
         struct cgroup_subsys_state *css;
         struct cgrp_cset_link *link;
         int ssid;
@@ -4865,6 +4875,11 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
         if (parent && cgroup_is_threaded(cgrp))
                 parent->nr_threaded_children--;
 
+        for (tcgrp = cgroup_parent(cgrp); tcgrp; tcgrp = cgroup_parent(tcgrp)) {
+                tcgrp->nr_descendants--;
+                tcgrp->nr_dying_descendants++;
+        }
+
         cgroup1_check_for_release(cgroup_parent(cgrp));
 
         /* put the base reference */