Merge branch 'for-4.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:
 "Nothing too exciting.

   - updates to the pids controller so that pid limit breaches can be
     noticed and monitored from userland.

   - cleanups and non-critical bug fixes"

* 'for-4.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: remove duplicated include from cgroup.c
  cgroup: Use lld instead of ld when printing pids controller events_limit
  cgroup: Add pids controller event when fork fails because of pid limit
  cgroup: allow NULL return from ss->css_alloc()
  cgroup: remove unnecessary 0 check from css_from_id()
  cgroup: fix idr leak for the first cgroup root

1 files changed, 4 insertions, 9 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 75c0ff00aca6..33a2f63d4a10 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -61,7 +61,6 @@
 #include <linux/cpuset.h>
 #include <linux/proc_ns.h>
 #include <linux/nsproxy.h>
-#include <linux/proc_ns.h>
 #include <net/sock.h>
 
 /*
@@ -1160,18 +1159,12 @@ static void cgroup_exit_root_id(struct cgroup_root *root)
 {
         lockdep_assert_held(&cgroup_mutex);
 
-        if (root->hierarchy_id) {
-                idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
-                root->hierarchy_id = 0;
-        }
+        idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
 }
 
 static void cgroup_free_root(struct cgroup_root *root)
 {
         if (root) {
-                /* hierarchy ID should already have been released */
-                WARN_ON_ONCE(root->hierarchy_id);
-
                 idr_destroy(&root->cgroup_idr);
                 kfree(root);
         }
@@ -5146,6 +5139,8 @@ static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
         lockdep_assert_held(&cgroup_mutex);
 
         css = ss->css_alloc(parent_css);
+        if (!css)
+                css = ERR_PTR(-ENOMEM);
         if (IS_ERR(css))
                 return css;
 
@@ -6172,7 +6167,7 @@ struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
 {
         WARN_ON_ONCE(!rcu_read_lock_held());
-        return id > 0 ? idr_find(&ss->css_idr, id) : NULL;
+        return idr_find(&ss->css_idr, id);
 }
 
 /**