cgroups: implement namespace tracking subsystem
When a task enters a new namespace via a clone() or unshare(), a new cgroup
is created and the task moves into it.
This version names cgroups which are automatically created using
cgroup_clone() as "node_<pid>" where pid is the pid of the unsharing or
cloned process. (Thanks Pavel for the idea) This is safe because if the
process unshares again, it will create
/cgroups/(...)/node_<pid>/node_<pid>
The only possibilities (AFAICT) for a -EEXIST on unshare are
1. pid wraparound
2. a process fails an unshare, then tries again.
Case 1 is unlikely enough that I ignore it (at least for now). In case 2, the
node_<pid> will be empty and can be rmdir'ed to make the subsequent unshare()
succeed.
Changelog:
Name cloned cgroups as "node_<pid>".
[clg@fr.ibm.com: fix order of cgroup subsystems in init/Kconfig]
Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
index cbadc3b..651ff08 100644
--- a/include/linux/cgroup_subsys.h
+++ b/include/linux/cgroup_subsys.h
@@ -24,3 +24,9 @@
#endif
/* */
+
+#ifdef CONFIG_CGROUP_NS
+SUBSYS(ns)
+#endif
+
+/* */
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index 033a648..f1eca68 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -55,4 +55,11 @@
put_nsproxy(ns);
}
}
+
+#ifdef CONFIG_CGROUP_NS
+int ns_cgroup_clone(struct task_struct *tsk);
+#else
+static inline int ns_cgroup_clone(struct task_struct *tsk) { return 0; }
+#endif
+
#endif
diff --git a/init/Kconfig b/init/Kconfig
index 6687f80..0007d1b 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -288,6 +288,22 @@
Say N if unsure
+config CGROUP_NS
+ bool "Namespace cgroup subsystem"
+ depends on CGROUPS
+ help
+ Provides a simple namespace cgroup subsystem to
+ provide hierarchical naming of sets of namespaces,
+ for instance virtual servers and checkpoint/restart
+ jobs.
+
+config CGROUP_CPUACCT
+ bool "Simple CPU accounting cgroup subsystem"
+ depends on CGROUPS
+ help
+ Provides a simple Resource Controller for monitoring the
+ total CPU consumed by the tasks in a cgroup
+
config CPUSETS
bool "Cpuset support"
depends on SMP && CGROUPS
@@ -345,13 +361,6 @@
depends on CPUSETS
default y
-config CGROUP_CPUACCT
- bool "Simple CPU accounting cgroup subsystem"
- depends on CGROUPS
- help
- Provides a simple Resource Controller for monitoring the
- total CPU consumed by the tasks in a cgroup
-
config RELAY
bool "Kernel->user space relay support (formerly relayfs)"
help
diff --git a/kernel/Makefile b/kernel/Makefile
index a50a6de..32b2d8b 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -40,6 +40,7 @@
obj-$(CONFIG_CGROUP_DEBUG) += cgroup_debug.o
obj-$(CONFIG_CPUSETS) += cpuset.o
obj-$(CONFIG_CGROUP_CPUACCT) += cpu_acct.o
+obj-$(CONFIG_CGROUP_NS) += ns_cgroup.o
obj-$(CONFIG_IKCONFIG) += configs.o
obj-$(CONFIG_STOP_MACHINE) += stop_machine.o
obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
diff --git a/kernel/ns_cgroup.c b/kernel/ns_cgroup.c
new file mode 100644
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,
+};
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 049e7c0..ac99837 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -156,7 +156,14 @@
goto out;
}
+ err = ns_cgroup_clone(tsk);
+ if (err) {
+ put_nsproxy(new_ns);
+ goto out;
+ }
+
tsk->nsproxy = new_ns;
+
out:
put_nsproxy(old_ns);
return err;
@@ -196,8 +203,16 @@
*new_nsp = create_new_namespaces(unshare_flags, current,
new_fs ? new_fs : current->fs);
- if (IS_ERR(*new_nsp))
+ if (IS_ERR(*new_nsp)) {
err = PTR_ERR(*new_nsp);
+ goto out;
+ }
+
+ err = ns_cgroup_clone(current);
+ if (err)
+ put_nsproxy(*new_nsp);
+
+out:
return err;
}