Merge tag 'tegra-for-4.8-i2c' of git://git.kernel.org/pub/scm/linux/kernel/git/tegra...

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

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 5e8dab5..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);
@@ -6301,6 +6328,16 @@ void cgroup_sk_free(struct sock_cgroup_data *skcd)
 
 /* cgroup namespaces */
 
+static struct ucounts *inc_cgroup_namespaces(struct user_namespace *ns)
+{
+       return inc_ucount(ns, current_euid(), UCOUNT_CGROUP_NAMESPACES);
+}
+
+static void dec_cgroup_namespaces(struct ucounts *ucounts)
+{
+       dec_ucount(ucounts, UCOUNT_CGROUP_NAMESPACES);
+}
+
 static struct cgroup_namespace *alloc_cgroup_ns(void)
 {
        struct cgroup_namespace *new_ns;
@@ -6322,6 +6359,7 @@ static struct cgroup_namespace *alloc_cgroup_ns(void)
 void free_cgroup_ns(struct cgroup_namespace *ns)
 {
        put_css_set(ns->root_cset);
+       dec_cgroup_namespaces(ns->ucounts);
        put_user_ns(ns->user_ns);
        ns_free_inum(&ns->ns);
        kfree(ns);
@@ -6333,6 +6371,7 @@ struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
                                        struct cgroup_namespace *old_ns)
 {
        struct cgroup_namespace *new_ns;
+       struct ucounts *ucounts;
        struct css_set *cset;
 
        BUG_ON(!old_ns);
@@ -6346,6 +6385,10 @@ struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
        if (!ns_capable(user_ns, CAP_SYS_ADMIN))
                return ERR_PTR(-EPERM);
 
+       ucounts = inc_cgroup_namespaces(user_ns);
+       if (!ucounts)
+               return ERR_PTR(-ENOSPC);
+
        /* It is not safe to take cgroup_mutex here */
        spin_lock_irq(&css_set_lock);
        cset = task_css_set(current);
@@ -6355,10 +6398,12 @@ struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
        new_ns = alloc_cgroup_ns();
        if (IS_ERR(new_ns)) {
                put_css_set(cset);
+               dec_cgroup_namespaces(ucounts);
                return new_ns;
        }
 
        new_ns->user_ns = get_user_ns(user_ns);
+       new_ns->ucounts = ucounts;
        new_ns->root_cset = cset;
 
        return new_ns;
@@ -6409,12 +6454,18 @@ static void cgroupns_put(struct ns_common *ns)
        put_cgroup_ns(to_cg_ns(ns));
 }
 
+static struct user_namespace *cgroupns_owner(struct ns_common *ns)
+{
+       return to_cg_ns(ns)->user_ns;
+}
+
 const struct proc_ns_operations cgroupns_operations = {
        .name           = "cgroup",
        .type           = CLONE_NEWCGROUP,
        .get            = cgroupns_get,
        .put            = cgroupns_put,
        .install        = cgroupns_install,
+       .owner          = cgroupns_owner,
 };
 
 static __init int cgroup_namespaces_init(void)