Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm...

[cascardo/linux.git] / kernel / cgroup.c

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index d650433..4406615 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3446,9 +3446,28 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
         * Except for the root, subtree_control must be zero for a cgroup
         * with tasks so that child cgroups don't compete against tasks.
         */
-       if (enable && cgroup_parent(cgrp) && !list_empty(&cgrp->cset_links)) {
-               ret = -EBUSY;
-               goto out_unlock;
+       if (enable && cgroup_parent(cgrp)) {
+               struct cgrp_cset_link *link;
+
+               /*
+                * Because namespaces pin csets too, @cgrp->cset_links
+                * might not be empty even when @cgrp is empty.  Walk and
+                * verify each cset.
+                */
+               spin_lock_irq(&css_set_lock);
+
+               ret = 0;
+               list_for_each_entry(link, &cgrp->cset_links, cset_link) {
+                       if (css_set_populated(link->cset)) {
+                               ret = -EBUSY;
+                               break;
+                       }
+               }
+
+               spin_unlock_irq(&css_set_lock);
+
+               if (ret)
+                       goto out_unlock;
        }
 
        /* save and update control masks and prepare csses */
@@ -3899,7 +3918,9 @@ void cgroup_file_notify(struct cgroup_file *cfile)
  * cgroup_task_count - count the number of tasks in a cgroup.
  * @cgrp: the cgroup in question
  *
- * Return the number of tasks in the cgroup.
+ * Return the number of tasks in the cgroup.  The returned number can be
+ * higher than the actual number of tasks due to css_set references from
+ * namespace roots and temporary usages.
  */
 static int cgroup_task_count(const struct cgroup *cgrp)
 {
@@ -5606,6 +5627,12 @@ int __init cgroup_init(void)
        BUG_ON(cgroup_init_cftypes(NULL, cgroup_dfl_base_files));
        BUG_ON(cgroup_init_cftypes(NULL, cgroup_legacy_base_files));
 
+       /*
+        * The latency of the synchronize_sched() is too high for cgroups,
+        * avoid it at the cost of forcing all readers into the slow path.
+        */
+       rcu_sync_enter_start(&cgroup_threadgroup_rwsem.rss);
+
        get_user_ns(init_cgroup_ns.user_ns);
 
        mutex_lock(&cgroup_mutex);
@@ -6270,6 +6297,12 @@ void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
        if (cgroup_sk_alloc_disabled)
                return;
 
+       /* Socket clone path */
+       if (skcd->val) {
+               cgroup_get(sock_cgroup_ptr(skcd));
+               return;
+       }
+
        rcu_read_lock();
 
        while (true) {