cgroups: implement namespace tracking subsystem

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

diff --git a/kernel/ns_cgroup.c b/kernel/ns_cgroup.c
new file mode 100644 (file)
index 0000000..aead4d6
--- /dev/null
+++ b/kernel/ns_cgroup.c
@@ -0,0 +1,100 @@
+/*
+ * ns_cgroup.c - namespace cgroup subsystem
+ *
+ * Copyright 2006, 2007 IBM Corp
+ */
+
+#include <linux/module.h>
+#include <linux/cgroup.h>
+#include <linux/fs.h>
+
+struct ns_cgroup {
+       struct cgroup_subsys_state css;
+       spinlock_t lock;
+};
+
+struct cgroup_subsys ns_subsys;
+
+static inline struct ns_cgroup *cgroup_to_ns(
+               struct cgroup *cgroup)
+{
+       return container_of(cgroup_subsys_state(cgroup, ns_subsys_id),
+                           struct ns_cgroup, css);
+}
+
+int ns_cgroup_clone(struct task_struct *task)
+{
+       return cgroup_clone(task, &ns_subsys);
+}
+
+/*
+ * Rules:
+ *   1. you can only enter a cgroup which is a child of your current
+ *     cgroup
+ *   2. you can only place another process into a cgroup if
+ *     a. you have CAP_SYS_ADMIN
+ *     b. your cgroup is an ancestor of task's destination cgroup
+ *       (hence either you are in the same cgroup as task, or in an
+ *        ancestor cgroup thereof)
+ */
+static int ns_can_attach(struct cgroup_subsys *ss,
+               struct cgroup *new_cgroup, struct task_struct *task)
+{
+       struct cgroup *orig;
+
+       if (current != task) {
+               if (!capable(CAP_SYS_ADMIN))
+                       return -EPERM;
+
+               if (!cgroup_is_descendant(new_cgroup))
+                       return -EPERM;
+       }
+
+       if (atomic_read(&new_cgroup->count) != 0)
+               return -EPERM;
+
+       orig = task_cgroup(task, ns_subsys_id);
+       if (orig && orig != new_cgroup->parent)
+               return -EPERM;
+
+       return 0;
+}
+
+/*
+ * Rules: you can only create a cgroup if
+ *     1. you are capable(CAP_SYS_ADMIN)
+ *     2. the target cgroup is a descendant of your own cgroup
+ */
+static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
+                                               struct cgroup *cgroup)
+{
+       struct ns_cgroup *ns_cgroup;
+
+       if (!capable(CAP_SYS_ADMIN))
+               return ERR_PTR(-EPERM);
+       if (!cgroup_is_descendant(cgroup))
+               return ERR_PTR(-EPERM);
+
+       ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
+       if (!ns_cgroup)
+               return ERR_PTR(-ENOMEM);
+       spin_lock_init(&ns_cgroup->lock);
+       return &ns_cgroup->css;
+}
+
+static void ns_destroy(struct cgroup_subsys *ss,
+                       struct cgroup *cgroup)
+{
+       struct ns_cgroup *ns_cgroup;
+
+       ns_cgroup = cgroup_to_ns(cgroup);
+       kfree(ns_cgroup);
+}
+
+struct cgroup_subsys ns_subsys = {
+       .name = "ns",
+       .can_attach = ns_can_attach,
+       .create = ns_create,
+       .destroy  = ns_destroy,
+       .subsys_id = ns_subsys_id,
+};