[PATCH 1/1] containers: implement nsproxy containers subsystem

["Serge E. Hallyn" <serue@us.ibm.com>]

>From 190ea72d213393dd1440643b2b87b5b2128dff87 Mon Sep 17 00:00:00 2001
From: Serge E. Hallyn <serue@us.ibm.com>
Date: Mon, 4 Jun 2007 14:18:52 -0400
Subject: [PATCH 1/1] containers: implement nsproxy containers subsystem

When a task enters a new namespace via a clone() or unshare(), a new
container is created and the task moves into it.  This enables
tracking - and applying resource controls - to virtual servers,
resource jobs, often logins (using per-user namespaces), and in
general any application of per-process namespaces.

This version uses an ida to generate a unique id for auto-created
containers, i.e. those created through container_clone().  After
a container is created, it can be renamed to a more useful name if
so desired.  The original id isn't released until the container is
destroyed.  (This could be fixed at container_rename() if it was
deemed desireable)

There is just one ida for all containers, because an ida per container
to track ids used for child containers would take a great deal of
space, and probably isn't very useful.

Changelog:
	Use an ida to generate unique ids for auto-created containers.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
---
 include/linux/container.h        |    2 +
 include/linux/container_subsys.h |    6 ++
 include/linux/nsproxy.h          |    7 +++
 init/Kconfig                     |    9 ++++
 kernel/Makefile                  |    1 +
 kernel/container.c               |   52 ++++++++++++++++----
 kernel/ns_container.c            |   99 ++++++++++++++++++++++++++++++++++++++
 kernel/nsproxy.c                 |   16 ++++++
 8 files changed, 183 insertions(+), 9 deletions(-)
 create mode 100644 kernel/ns_container.c

diff --git a/include/linux/container.h b/include/linux/container.h
index 37c0bdf..2f8ee47 100644
--- a/include/linux/container.h
+++ b/include/linux/container.h
@@ -87,6 +87,8 @@ struct container {
 	/* Private pointers for each registered subsystem */
 	struct container_subsys_state *subsys[CONTAINER_SUBSYS_COUNT];
 
+	int unique_id;  /* usually -1, set to >=0  in container_clone() */
+
 	struct containerfs_root *root;
 	struct container *top_container;
 
diff --git a/include/linux/container_subsys.h b/include/linux/container_subsys.h
index 8fea7cf..9861751 100644
--- a/include/linux/container_subsys.h
+++ b/include/linux/container_subsys.h
@@ -24,3 +24,9 @@ SUBSYS(debug)
 #endif
 
 /* */
+
+#ifdef CONFIG_CONTAINER_NS
+SUBSYS(ns)
+#endif
+
+/* */
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index 189e0dc..8be975b 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -54,4 +54,11 @@ static inline void exit_task_namespaces(struct task_struct *p)
 		put_nsproxy(ns);
 	}
 }
+
+#ifdef CONFIG_CONTAINER_NS
+int ns_container_clone(struct task_struct *tsk);
+#else
+static inline int ns_container_clone(struct task_struct *tsk) { return 0; }
+#endif
+
 #endif
diff --git a/init/Kconfig b/init/Kconfig
index 5861ad9..d79c505 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -355,6 +355,15 @@ config CONTAINER_CPUACCT
 	  Provides a simple Resource Controller for monitoring the
 	  total CPU consumed by the tasks in a container
 
+config CONTAINER_NS
+        bool "Namespace container subsystem"
+        select CONTAINERS
+        help
+          Provides a simple namespace container subsystem to
+          provide hierarchical naming of sets of namespaces,
+          for instance virtual servers and checkpoint/restart
+          jobs.
+
 config PROC_PID_CPUSET
 	bool "Include legacy /proc/<pid>/cpuset file"
 	depends on CPUSETS
diff --git a/kernel/Makefile b/kernel/Makefile
index f73b3d3..34f2345 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -40,6 +40,7 @@ obj-$(CONFIG_CONTAINERS) += container.o
 obj-$(CONFIG_CONTAINER_DEBUG) += container_debug.o
 obj-$(CONFIG_CPUSETS) += cpuset.o
 obj-$(CONFIG_CONTAINER_CPUACCT) += cpu_acct.o
+obj-$(CONFIG_CONTAINER_NS) += ns_container.o
 obj-$(CONFIG_IKCONFIG) += configs.o
 obj-$(CONFIG_STOP_MACHINE) += stop_machine.o
 obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
diff --git a/kernel/container.c b/kernel/container.c
index 6f80487..0d46d66 100644
--- a/kernel/container.c
+++ b/kernel/container.c
@@ -55,6 +55,7 @@
 #include <linux/time.h>
 #include <linux/backing-dev.h>
 #include <linux/sort.h>
+#include <linux/idr.h>
 
 #include <asm/uaccess.h>
 #include <asm/atomic.h>
@@ -64,6 +65,8 @@
 
 static DEFINE_MUTEX(container_mutex);
 
+static struct ida container_ida;
+
 /* Generate an array of container subsystem pointers */
 #define SUBSYS(_x) &_x ## _subsys,
 
@@ -1818,6 +1821,7 @@ static long container_create(struct container *parent, struct dentry *dentry,
 	INIT_LIST_HEAD(&cont->children);
 	INIT_LIST_HEAD(&cont->css_groups);
 	INIT_LIST_HEAD(&cont->release_list);
+	cont->unique_id = -1;
 
 	cont->parent = parent;
 	cont->root = parent->root;
@@ -1941,6 +1945,9 @@ static int container_rmdir(struct inode *unused_dir, struct dentry *dentry)
 	dput(d);
 	root->number_of_containers--;
 
+	if (cont->unique_id != -1)
+		ida_remove(&container_ida, cont->unique_id);
+
 	if (!list_empty(&cont->release_list))
 		list_del(&cont->release_list);
 	set_bit(CONT_RELEASABLE, &parent->flags);
@@ -2040,6 +2047,8 @@ int __init container_init_early(void)
 		if (ss->early_init)
 			container_init_subsys(ss);
 	}
+
+	ida_init(&container_ida);
 	return 0;
 }
 
@@ -2302,12 +2311,6 @@ void container_exit(struct task_struct *tsk, int run_callbacks)
 		put_css_group_taskexit(cg);
 }
 
-static atomic_t namecnt;
-static void get_unused_name(char *buf)
-{
-	sprintf(buf, "node%d", atomic_inc_return(&namecnt));
-}
-
 /**
  * container_clone - duplicate the current container in the hierarchy
  * that the given subsystem is attached to, and move this task into
@@ -2322,6 +2325,7 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
 	struct inode *inode;
 	struct css_group *cg;
 	struct containerfs_root *root;
+	int new_id;
 
 	/* We shouldn't be called by an unregistered subsystem */
 	BUG_ON(!subsys->active);
@@ -2340,6 +2344,19 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
 	}
 	cg = tsk->containers;
 	parent = task_container(tsk, subsys->subsys_id);
+
+	ret = ida_get_new(&container_ida, &new_id);
+	if (ret == -EAGAIN) {
+		if (!ida_pre_get(&container_ida, GFP_KERNEL))
+			return -ENOMEM;
+		ret = ida_get_new(&container_ida, &new_id);
+	}
+	if (ret) {
+		ret = -EBUSY;
+		goto out_no_name;
+	}
+	sprintf(nodename, "node%d", new_id);
+
 	/* Pin the hierarchy */
 	atomic_inc(&parent->root->sb->s_active);
 
@@ -2347,8 +2364,8 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
 	get_css_group(cg);
 	mutex_unlock(&container_mutex);
 
+
 	/* Now do the VFS work to create a container */
-	get_unused_name(nodename);
 	inode = parent->dentry->d_inode;
 
 	/* Hold the parent directory mutex across this operation to
@@ -2403,6 +2420,10 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
 
 	/* All seems fine. Finish by moving the task into the new container */
 	ret = attach_task(child, tsk);
+
+	if (!ret)
+		child->unique_id = new_id;
+
 	mutex_unlock(&container_mutex);
 
  out_release:
@@ -2410,19 +2431,32 @@ int container_clone(struct task_struct *tsk, struct container_subsys *subsys)
 
 	mutex_lock(&container_mutex);
 	put_css_group(cg);
+
+ out_no_name:
 	mutex_unlock(&container_mutex);
 	deactivate_super(parent->root->sb);
 	return ret;
 }
 
-/* See if "cont" is a descendant of the current task's container in
- * the appropriate hierarchy */
+/*
+ * See if "cont" is a descendant of the current task's container in
+ * the appropriate hierarchy
+ *
+ * If we are sending in dummytop, then presumably we are creating
+ * the top container in the subsystem.
+ *
+ * Called only by the ns (nsproxy) container.
+ */
 
 int container_is_descendant(const struct container *cont)
 {
 	int ret;
 	struct container *target;
 	int subsys_id;
+
+	if (cont == dummytop)
+		return 1;
+
 	get_first_subsys(cont, NULL, &subsys_id);
 	target = task_container(current, subsys_id);
 	while (cont != target && cont!= cont->top_container) {
diff --git a/kernel/ns_container.c b/kernel/ns_container.c
new file mode 100644
index 0000000..3465716
--- /dev/null
+++ b/kernel/ns_container.c
@@ -0,0 +1,99 @@
+/*
+ * ns_container.c - namespace container subsystem
+ *
+ * Copyright 2006, 2007 IBM Corp
+ */
+
+#include <linux/module.h>
+#include <linux/container.h>
+#include <linux/fs.h>
+
+struct ns_container {
+	struct container_subsys_state css;
+	spinlock_t lock;
+};
+
+struct container_subsys ns_subsys;
+
+static inline struct ns_container *container_to_ns(
+		struct container *container)
+{
+	return container_of(container_subsys_state(container, ns_subsys_id),
+			    struct ns_container, css);
+}
+
+int ns_container_clone(struct task_struct *task)
+{
+	return container_clone(task, &ns_subsys);
+}
+
+/*
+ * Rules:
+ *   1. you can only enter a container which is a child of your current
+ *     container
+ *   2. you can only place another process into a container if
+ *     a. you have CAP_SYS_ADMIN
+ *     b. your container is an ancestor of task's destination container
+ *       (hence either you are in the same container as task, or in an
+ *        ancestor container thereof)
+ */
+static int ns_can_attach(struct container_subsys *ss,
+		struct container *new_container, struct task_struct *task)
+{
+	struct container *orig;
+
+	if (current != task) {
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+
+		if (!container_is_descendant(new_container))
+			return -EPERM;
+	}
+
+	if (atomic_read(&new_container->count) != 0)
+		return -EPERM;
+
+	orig = task_container(task, ns_subsys_id);
+	if (orig && orig != new_container->parent)
+		return -EPERM;
+
+	return 0;
+}
+
+/*
+ * Rules: you can only create a container if
+ *     1. you are capable(CAP_SYS_ADMIN)
+ *     2. the target container is a descendant of your own container
+ */
+static int ns_create(struct container_subsys *ss, struct container *container)
+{
+	struct ns_container *ns_container;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	if (!container_is_descendant(container))
+		return -EPERM;
+
+	ns_container = kzalloc(sizeof(*ns_container), GFP_KERNEL);
+	if (!ns_container) return -ENOMEM;
+	spin_lock_init(&ns_container->lock);
+	container->subsys[ns_subsys.subsys_id] = &ns_container->css;
+	return 0;
+}
+
+static void ns_destroy(struct container_subsys *ss,
+			struct container *container)
+{
+	struct ns_container *ns_container;
+	
+	ns_container = container_to_ns(container);
+	kfree(ns_container);
+}
+
+struct container_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 1bc4b55..afce808 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -124,7 +124,14 @@ int copy_namespaces(int flags, struct task_struct *tsk)
 		goto out;
 	}
 
+	err = ns_container_clone(tsk);
+	if (err) {
+		put_nsproxy(new_ns);
+		goto out;
+	}
+
 	tsk->nsproxy = new_ns;
+
 out:
 	put_nsproxy(old_ns);
 	return err;
@@ -177,6 +184,15 @@ int unshare_nsproxy_namespaces(unsigned long unshare_flags,
 	if (IS_ERR(*new_nsp)) {
 		err = PTR_ERR(*new_nsp);
 		put_nsproxy(old_ns);
+		goto out;
+	}
+
+	err = ns_container_clone(current);
+	if (err) {
+		put_nsproxy(*new_nsp);
+		put_nsproxy(old_ns);
 	}
+
+out:
 	return err;
 }
-- 
1.5.1.1.GIT

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