[PATCH 1/9] Containers (V9): Basic container framework

[menage]

This patch adds the main containers framework - the container
filesystem, and the basic structures for tracking membership and
associating subsystem state objects to tasks.

Signed-off-by: Paul Menage <menage@xxxxxxxxxx>

---
 Documentation/containers.txt     |  524 +++++++++++++++++
 include/linux/container.h        |  198 ++++++
 include/linux/container_subsys.h |   10 
 include/linux/sched.h            |   34 +
 init/Kconfig                     |    3 
 init/main.c                      |    3 
 kernel/Makefile                  |    1 
 kernel/container.c               | 1151 +++++++++++++++++++++++++++++++++++++++
 8 files changed, 1923 insertions(+), 1 deletion(-)

Index: container-2.6.21-rc7-mm1/Documentation/containers.txt
===================================================================
--- /dev/null
+++ container-2.6.21-rc7-mm1/Documentation/containers.txt
@@ -0,0 +1,524 @@
+				CONTAINERS
+				-------
+
+Written by Paul Menage <menage@xxxxxxxxxx> based on Documentation/cpusets.txt
+
+Original copyright statements from cpusets.txt:
+Portions Copyright (C) 2004 BULL SA.
+Portions Copyright (c) 2004-2006 Silicon Graphics, Inc.
+Modified by Paul Jackson <pj@xxxxxxx>
+Modified by Christoph Lameter <clameter@xxxxxxx>
+
+CONTENTS:
+=========
+
+1. Containers
+  1.1 What are containers ?
+  1.2 Why are containers needed ?
+  1.3 How are containers implemented ?
+  1.4 What does notify_on_release do ?
+  1.5 How do I use containers ?
+2. Usage Examples and Syntax
+  2.1 Basic Usage
+  2.2 Attaching processes
+3. Kernel API
+  3.1 Overview
+  3.2 Synchronization
+  3.3 Subsystem API
+4. Questions
+
+1. Containers
+==========
+
+1.1 What are containers ?
+----------------------
+
+Containers provide a mechanism for aggregating/partitioning sets of
+tasks, and all their future children, into hierarchical groups with
+specialized behaviour.
+
+Definitions:
+
+A *container* associates a set of tasks with a set of parameters for one
+or more subsystems.
+
+A *subsystem* is a module that makes use of the task grouping
+facilities provided by containers to treat groups of tasks in
+particular ways. A subsystem is typically a "resource controller" that
+schedules a resource or applies per-container limits, but it may be
+anything that wants to act on a group of processes, e.g. a
+virtualization subsystem.
+
+A *hierarchy* is a set of containers arranged in a tree, such that
+every task in the system is in exactly one of the containers in the
+hierarchy, and a set of subsystems; each subsystem has system-specific
+state attached to each container in the hierarchy.  Each hierarchy has
+an instance of the container virtual filesystem associated with it.
+
+At any one time there may be multiple active hierachies of task
+containers. Each hierarchy is a partition of all tasks in the system.
+
+User level code may create and destroy containers by name in an
+instance of the container virtual file system, specify and query to
+which container a task is assigned, and list the task pids assigned to
+a container. Those creations and assignments only affect the hierarchy
+associated with that instance of the container file system.
+
+On their own, the only use for containers is for simple job
+tracking. The intention is that other subsystems hook into the generic
+container support to provide new attributes for containers, such as
+accounting/limiting the resources which processes in a container can
+access. For example, cpusets (see Documentation/cpusets.txt) allows
+you to associate a set of CPUs and a set of memory nodes with the
+tasks in each container.
+
+1.2 Why are containers needed ?
+----------------------------
+
+There are multiple efforts to provide process aggregations in the
+Linux kernel, mainly for resource tracking purposes. Such efforts
+include cpusets, CKRM/ResGroups, UserBeanCounters, and virtual server
+namespaces. These all require the basic notion of a
+grouping/partitioning of processes, with newly forked processes ending
+in the same group (container) as their parent process.
+
+The kernel container patch provides the minimum essential kernel
+mechanisms required to efficiently implement such groups. It has
+minimal impact on the system fast paths, and provides hooks for
+specific subsystems such as cpusets to provide additional behaviour as
+desired.
+
+Multiple hierarchy support is provided to allow for situations where
+the division of tasks into containers is distinctly different for
+different subsystems - having parallel hierarchies allows each
+hierarchy to be a natural division of tasks, without having to handle
+complex combinations of tasks that would be present if several
+unrelated subsystems needed to be forced into the same tree of
+containers.
+
+At one extreme, each resource controller or subsystem could be in a
+separate hierarchy; at the other extreme, all subsystems
+would be attached to the same hierarchy.
+
+As an example of a scenario (originally proposed by vatsa@xxxxxxxxxx)
+that can benefit from multiple hierarchies, consider a large
+university server with various users - students, professors, system
+tasks etc. The resource planning for this server could be along the
+following lines:
+
+       CPU :           Top cpuset
+                       /       \
+               CPUSet1         CPUSet2
+                  |              |
+               (Profs)         (Students)
+
+               In addition (system tasks) are attached to topcpuset (so
+               that they can run anywhere) with a limit of 20%
+
+       Memory : Professors (50%), students (30%), system (20%)
+
+       Disk : Prof (50%), students (30%), system (20%)
+
+       Network : WWW browsing (20%), Network File System (60%), others (20%)
+                               / \
+                       Prof (15%) students (5%)
+
+Browsers like firefox/lynx go into the WWW network class, while (k)nfsd go
+into NFS network class.
+
+At the same time firefox/lynx will share an appropriate CPU/Memory class
+depending on who launched it (prof/student).
+
+With the ability to classify tasks differently for different resources
+(by putting those resource subsystems in different hierarchies) then
+the admin can easily set up a script which receives exec notifications
+and depending on who is launching the browser he can
+
+       # echo browser_pid > /mnt/<restype>/<userclass>/tasks
+
+With only a single hierarchy, he now would potentially have to create
+a separate container for every browser launched and associate it with
+approp network and other resource class.  This may lead to
+proliferation of such containers.
+
+Also lets say that the administrator would like to give enhanced network
+access temporarily to a student's browser (since it is night and the user
+wants to do online gaming :)  OR give one of the students simulation
+apps enhanced CPU power,
+
+With ability to write pids directly to resource classes, its just a
+matter of :
+
+       # echo pid > /mnt/network/<new_class>/tasks
+       (after some time)
+       # echo pid > /mnt/network/<orig_class>/tasks
+
+Without this ability, he would have to split the container into
+multiple separate ones and then associate the new containers with the
+new resource classes.
+
+
+
+1.3 How are containers implemented ?
+---------------------------------
+
+Containers extends the kernel as follows:
+
+ - Each task in the system has a reference-counted pointer to a
+   css_group.
+
+ - A css_group contains a set of reference-counted pointers to
+   container_subsys_state objects, one for each container subsystem
+   registered in the system. There is no direct link from a task to
+   the container of which it's a member in each hierarchy, but this
+   can be determined by following pointers through the
+   container_subsys_state objects. This is because accessing the
+   subsystem state is something that's expected to happen frequently
+   and in performance-critical code, whereas operations that require a
+   task's actual container assignments (in particular, moving between
+   containers) are less common.
+
+ - A container hierarchy filesystem can be mounted  for browsing and
+   manipulation from user space.
+
+ - You can list all the tasks (by pid) attached to any container.
+
+The implementation of containers requires a few, simple hooks
+into the rest of the kernel, none in performance critical paths:
+
+ - in init/main.c, to initialize the root containers and initial
+   css_group at system boot.
+
+ - in fork and exit, to attach and detach a task from its css_group.
+
+In addition a new file system, of type "container" may be mounted, to
+enable browsing and modifying the containers presently known to the
+kernel.  When mounting a container hierarchy, you may specify a
+comma-separated list of subsystems to mount as the filesystem mount
+options.  By default, mounting the container filesystem attempts to
+mount a hierarchy containing all registered subsystems.
+
+If an active hierarchy with exactly the same set of subsystems already
+exists, it will be reused for the new mount. If no existing hierarchy
+matches, and any of the requested subsystems are in use in an existing
+hierarchy, the mount will fail with -EBUSY. Otherwise, a new hierarchy
+is activated, associated with the requested subsystems.
+
+It's not currently possible to bind a new subsystem to an active
+container hierarchy, or to unbind a subsystem from an active container
+hierarchy. This may be possible in future, but is fraught with nasty
+error-recovery issues.
+
+When a container filesystem is unmounted, if there are any
+subcontainers created below the top-level container, that hierarchy
+will remain active even though unmounted; if there are no
+subcontainers then the hierarchy will be deactivated.
+
+No new system calls are added for containers - all support for
+querying and modifying containers is via this container file system.
+
+Each task under /proc has an added file named 'container' displaying,
+for each active hierarchy, the subsystem names and the container name
+as the path relative to the root of the container file system.
+
+Each container is represented by a directory in the container file system
+containing the following files describing that container:
+
+ - tasks: list of tasks (by pid) attached to that container
+ - notify_on_release flag: run /sbin/container_release_agent on exit?
+
+Other subsystems such as cpusets may add additional files in each
+container dir
+
+New containers are created using the mkdir system call or shell
+command.  The properties of a container, such as its flags, are
+modified by writing to the appropriate file in that containers
+directory, as listed above.
+
+The named hierarchical structure of nested containers allows partitioning
+a large system into nested, dynamically changeable, "soft-partitions".
+
+The attachment of each task, automatically inherited at fork by any
+children of that task, to a container allows organizing the work load
+on a system into related sets of tasks.  A task may be re-attached to
+any other container, if allowed by the permissions on the necessary
+container file system directories.
+
+When a task is moved from one container to another, it gets a new
+css_group pointer - if there's an already existing css_group with the
+desired collection of containers then that group is reused, else a new
+css_group is allocated. Note that the current implementation uses a
+linear search to locate an appropriate existing css_group, so isn't
+very efficient. A future version will use a hash table for better
+performance.
+
+The use of a Linux virtual file system (vfs) to represent the
+container hierarchy provides for a familiar permission and name space
+for containers, with a minimum of additional kernel code.
+
+1.4 What does notify_on_release do ?
+------------------------------------
+
+*** notify_on_release is disabled in the current patch set. It may be
+*** reactivated in a future patch in a less-intrusive manner
+
+If the notify_on_release flag is enabled (1) in a container, then
+whenever the last task in the container leaves (exits or attaches to
+some other container) and the last child container of that container
+is removed, then the kernel runs the command specified by the contents
+of the "release_agent" file in that hierarchy's root directory,
+supplying the pathname (relative to the mount point of the container
+file system) of the abandoned container.  This enables automatic
+removal of abandoned containers.  The default value of
+notify_on_release in the root container at system boot is disabled
+(0).  The default value of other containers at creation is the current
+value of their parents notify_on_release setting. The default value of
+a container hierarchy's release_agent path is empty.
+
+1.5 How do I use containers ?
+--------------------------
+
+To start a new job that is to be contained within a container, using
+the "cpuset" container subsystem, the steps are something like:
+
+ 1) mkdir /dev/container
+ 2) mount -t container -ocpuset cpuset /dev/container
+ 3) Create the new container by doing mkdir's and write's (or echo's) in
+    the /dev/container virtual file system.
+ 4) Start a task that will be the "founding father" of the new job.
+ 5) Attach that task to the new container by writing its pid to the
+    /dev/container tasks file for that container.
+ 6) fork, exec or clone the job tasks from this founding father task.
+
+For example, the following sequence of commands will setup a container
+named "Charlie", containing just CPUs 2 and 3, and Memory Node 1,
+and then start a subshell 'sh' in that container:
+
+  mount -t container cpuset -ocpuset /dev/container
+  cd /dev/container
+  mkdir Charlie
+  cd Charlie
+  /bin/echo $$ > tasks
+  sh
+  # The subshell 'sh' is now running in container Charlie
+  # The next line should display '/Charlie'
+  cat /proc/self/container
+
+2. Usage Examples and Syntax
+============================
+
+2.1 Basic Usage
+---------------
+
+Creating, modifying, using the containers can be done through the container
+virtual filesystem.
+
+To mount a container hierarchy will all available subsystems, type:
+# mount -t container xxx /dev/container
+
+The "xxx" is not interpreted by the container code, but will appear in
+/proc/mounts so may be any useful identifying string that you like.
+
+To mount a container hierarchy with just the cpuset and numtasks
+subsystems, type:
+# mount -t container -o cpuset,numtasks hier1 /dev/container
+
+To change the set of subsystems bound to a mounted hierarchy, just
+remount with different options:
+
+# mount -o remount,cpuset,ns  /dev/container
+
+Note that changing the set of subsystems is currently only supported
+when the hierarchy consists of a single (root) container. Supporting
+the ability to arbitrarily bind/unbind subsystems from an existing
+container hierarchy is intended to be implemented in the future.
+
+Then under /dev/container you can find a tree that corresponds to the
+tree of the containers in the system. For instance, /dev/container
+is the container that holds the whole system.
+
+If you want to create a new container under /dev/container:
+# cd /dev/container
+# mkdir my_container
+
+Now you want to do something with this container.
+# cd my_container
+
+In this directory you can find several files:
+# ls
+notify_on_release release_agent tasks
+(plus whatever files are added by the attached subsystems)
+
+Now attach your shell to this container:
+# /bin/echo $$ > tasks
+
+You can also create containers inside your container by using mkdir in this
+directory.
+# mkdir my_sub_cs
+
+To remove a container, just use rmdir:
+# rmdir my_sub_cs
+
+This will fail if the container is in use (has containers inside, or
+has processes attached, or is held alive by other subsystem-specific
+reference).
+
+2.2 Attaching processes
+-----------------------
+
+# /bin/echo PID > tasks
+
+Note that it is PID, not PIDs. You can only attach ONE task at a time.
+If you have several tasks to attach, you have to do it one after another:
+
+# /bin/echo PID1 > tasks
+# /bin/echo PID2 > tasks
+	...
+# /bin/echo PIDn > tasks
+
+3. Kernel API
+=============
+
+3.1 Overview
+------------
+
+Each kernel subsystem that wants to hook into the generic container
+system needs to create a container_subsys object. This contains
+various methods, which are callbacks from the container system, along
+with a subsystem id which will be assigned by the container system.
+
+Other fields in the container_subsys object include:
+
+- subsys_id: a unique array index for the subsystem, indicating which
+  entry in container->subsys[] this subsystem should be
+  managing. Initialized by container_register_subsys(); prior to this
+  it should be initialized to -1
+
+- hierarchy: an index indicating which hierarchy, if any, this
+  subsystem is currently attached to. If this is -1, then the
+  subsystem is not attached to any hierarchy, and all tasks should be
+  considered to be members of the subsystem's top_container. It should
+  be initialized to -1.
+
+- name: should be initialized to a unique subsystem name prior to
+  calling container_register_subsystem. Should be no longer than
+  MAX_CONTAINER_TYPE_NAMELEN
+
+Each container object created by the system has an array of pointers,
+indexed by subsystem id; this pointer is entirely managed by the
+subsystem; the generic container code will never touch this pointer.
+
+3.2 Synchronization
+-------------------
+
+There is a global mutex, container_mutex, used by the container
+system. This should be taken by anything that wants to modify a
+container. It may also be taken to prevent containers from being
+modified, but more specific locks may be more appropriate in that
+situation.
+
+See kernel/container.c for more details.
+
+Subsystems can take/release the container_mutex via the functions
+container_lock()/container_unlock(), and can
+take/release the callback_mutex via the functions
+container_lock()/container_unlock().
+
+Accessing a task's container pointer may be done in the following ways:
+- while holding container_mutex
+- while holding the task's alloc_lock (via task_lock())
+- inside an rcu_read_lock() section via rcu_dereference()
+
+3.3 Subsystem API
+--------------------------
+
+Each subsystem should:
+
+- add an entry in linux/container_subsys.h
+- define a container_subsys object called <name>_subsys
+
+Each subsystem may export the following methods. The only mandatory
+methods are create/destroy. Any others that are null are presumed to
+be successful no-ops.
+
+int create(struct container *cont)
+LL=container_mutex
+
+Called to create a subsystem state object for a container. The
+subsystem should set its subsystem pointer for the passed container,
+returning 0 on success or a negative error code. On success, the
+subsystem pointer should point to a structure of type
+container_subsys_state (typically embedded in a larger
+subsystem-specific object), which will be initialized by the container
+system. Note that this will be called at initialization to create the
+root subsystem state for this subsystem; this case can be identified
+by the passed container object having a NULL parent (since it's the
+root of the hierarchy) and may be an appropriate place for
+initialization code.
+
+void destroy(struct container *cont)
+LL=container_mutex
+
+The container system is about to destroy the passed container; the
+subsystem should do any necessary cleanup
+
+int can_attach(struct container_subsys *ss, struct container *cont,
+	       struct task_struct *task)
+LL=container_mutex
+
+Called prior to moving a task into a container; if the subsystem
+returns an error, this will abort the attach operation.  If a NULL
+task is passed, then a successful result indicates that *any*
+unspecified task can be moved into the container. Note that this isn't
+called on a fork. If this method returns 0 (success) then this should
+remain valid while the caller holds container_mutex.
+
+void attach(struct container_subsys *ss, struct container *cont,
+	    struct container *old_cont, struct task_struct *task)
+LL=container_mutex
+
+
+Called after the task has been attached to the container, to allow any
+post-attachment activity that requires memory allocations or blocking.
+
+void fork(struct container_subsy *ss, struct task_struct *task)
+LL=callback_mutex, maybe read_lock(tasklist_lock)
+
+Called when a task is forked into a container. Also called during
+registration for all existing tasks.
+
+void exit(struct container_subsys *ss, struct task_struct *task)
+LL=callback_mutex
+
+Called during task exit
+
+int populate(struct container_subsys *ss, struct container *cont)
+LL=none
+
+Called after creation of a container to allow a subsystem to populate
+the container directory with file entries.  The subsystem should make
+calls to container_add_file() with objects of type cftype (see
+include/linux/container.h for details).  Note that although this
+method can return an error code, the error code is currently not
+always handled well.
+
+void bind(struct container_subsys *ss, struct container *root)
+LL=callback_mutex
+
+Called when a container subsystem is rebound to a different hierarchy
+and root container. Currently this will only involve movement between
+the default hierarchy (which never has sub-containers) and a hierarchy
+that is being created/destroyed (and hence has no sub-containers).
+
+4. Questions
+============
+
+Q: what's up with this '/bin/echo' ?
+A: bash's builtin 'echo' command does not check calls to write() against
+   errors. If you use it in the container file system, you won't be
+   able to tell whether a command succeeded or failed.
+
+Q: When I attach processes, only the first of the line gets really attached !
+A: We can only return one error code per call to write(). So you should also
+   put only ONE pid.
+
Index: container-2.6.21-rc7-mm1/include/linux/container.h
===================================================================
--- /dev/null
+++ container-2.6.21-rc7-mm1/include/linux/container.h
@@ -0,0 +1,198 @@
+#ifndef _LINUX_CONTAINER_H
+#define _LINUX_CONTAINER_H
+/*
+ *  container interface
+ *
+ *  Copyright (C) 2003 BULL SA
+ *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
+ *
+ */
+
+#include <linux/sched.h>
+#include <linux/kref.h>
+#include <linux/cpumask.h>
+#include <linux/nodemask.h>
+
+#ifdef CONFIG_CONTAINERS
+
+extern int container_init_early(void);
+extern int container_init(void);
+extern void container_init_smp(void);
+
+extern struct file_operations proc_container_operations;
+
+extern void container_lock(void);
+extern void container_unlock(void);
+
+struct containerfs_root;
+
+/* Per-subsystem/per-container state maintained by the system. */
+struct container_subsys_state {
+	/* The container that this subsystem is attached to. Useful
+	 * for subsystems that want to know about the container
+	 * hierarchy structure */
+	struct container *container;
+
+	/* State maintained by the container system to allow
+	 * subsystems to be "busy". Should be accessed via css_get()
+	 * and css_put() */
+
+	atomic_t refcnt;
+};
+
+/*
+ * Call css_get() to hold a reference on the container;
+ *
+ */
+
+static inline void css_get(struct container_subsys_state *css)
+{
+	atomic_inc(&css->refcnt);
+}
+/*
+ * css_put() should be called to release a reference taken by
+ * css_get()
+ */
+
+static inline void css_put(struct container_subsys_state *css)
+{
+	atomic_dec(&css->refcnt);
+}
+
+struct container {
+	unsigned long flags;		/* "unsigned long" so bitops work */
+
+	/* count users of this container. >0 means busy, but doesn't
+	 * necessarily indicate the number of tasks in the
+	 * container */
+	atomic_t count;
+
+	/*
+	 * We link our 'sibling' struct into our parent's 'children'.
+	 * Our children link their 'sibling' into our 'children'.
+	 */
+	struct list_head sibling;	/* my parent's children */
+	struct list_head children;	/* my children */
+
+	struct container *parent;	/* my parent */
+	struct dentry *dentry;	  	/* container fs entry */
+
+	/* Private pointers for each registered subsystem */
+	struct container_subsys_state *subsys[CONTAINER_SUBSYS_COUNT];
+
+	struct containerfs_root *root;
+	struct container *top_container;
+};
+
+/* struct cftype:
+ *
+ * The files in the container filesystem mostly have a very simple read/write
+ * handling, some common function will take care of it. Nevertheless some cases
+ * (read tasks) are special and therefore I define this structure for every
+ * kind of file.
+ *
+ *
+ * When reading/writing to a file:
+ *	- the container to use in file->f_dentry->d_parent->d_fsdata
+ *	- the 'cftype' of the file is file->f_dentry->d_fsdata
+ */
+
+struct inode;
+#define MAX_CFTYPE_NAME 64
+struct cftype {
+	/* By convention, the name should begin with the name of the
+	 * subsystem, followed by a period */
+	char name[MAX_CFTYPE_NAME];
+	int private;
+	int (*open) (struct inode *inode, struct file *file);
+	ssize_t (*read) (struct container *cont, struct cftype *cft,
+			 struct file *file,
+			 char __user *buf, size_t nbytes, loff_t *ppos);
+	u64 (*read_uint) (struct container *cont, struct cftype *cft);
+	ssize_t (*write) (struct container *cont, struct cftype *cft,
+			  struct file *file,
+			  const char __user *buf, size_t nbytes, loff_t *ppos);
+	int (*release) (struct inode *inode, struct file *file);
+};
+
+/* Add a new file to the given container directory. Should only be
+ * called by subsystems from within a populate() method */
+int container_add_file(struct container *cont, const struct cftype *cft);
+
+/* Add a set of new files to the given container directory. Should
+ * only be called by subsystems from within a populate() method */
+int container_add_files(struct container *cont, const struct cftype cft[],
+			int count);
+
+int container_is_removed(const struct container *cont);
+
+int container_path(const struct container *cont, char *buf, int buflen);
+
+/* Return true if the container is a descendant of the current container */
+int container_is_descendant(const struct container *cont);
+
+/* Container subsystem type. See Documentation/containers.txt for details */
+
+struct container_subsys {
+	int (*create)(struct container_subsys *ss,
+		      struct container *cont);
+	void (*destroy)(struct container_subsys *ss, struct container *cont);
+	int (*can_attach)(struct container_subsys *ss,
+			  struct container *cont, struct task_struct *tsk);
+	void (*attach)(struct container_subsys *ss, struct container *cont,
+			struct container *old_cont, struct task_struct *tsk);
+	void (*fork)(struct container_subsys *ss, struct task_struct *task);
+	void (*exit)(struct container_subsys *ss, struct task_struct *task);
+	int (*populate)(struct container_subsys *ss,
+			struct container *cont);
+	void (*bind)(struct container_subsys *ss, struct container *root);
+	int subsys_id;
+	int active;
+	int early_init;
+#define MAX_CONTAINER_TYPE_NAMELEN 32
+	const char *name;
+
+	/* Protected by RCU */
+	struct containerfs_root *root;
+
+	struct list_head sibling;
+
+	void *private;
+};
+
+#define SUBSYS(_x) extern struct container_subsys _x ## _subsys;
+#include <linux/container_subsys.h>
+#undef SUBSYS
+
+static inline struct container_subsys_state *container_subsys_state(
+	struct container *cont, int subsys_id)
+{
+	return cont->subsys[subsys_id];
+}
+
+static inline struct container_subsys_state *task_subsys_state(
+	struct task_struct *task, int subsys_id)
+{
+	return rcu_dereference(task->containers.subsys[subsys_id]);
+}
+
+static inline struct container* task_container(struct task_struct *task,
+					       int subsys_id)
+{
+	return task_subsys_state(task, subsys_id)->container;
+}
+
+int container_path(const struct container *cont, char *buf, int buflen);
+
+#else /* !CONFIG_CONTAINERS */
+
+static inline int container_init_early(void) { return 0; }
+static inline int container_init(void) { return 0; }
+static inline void container_init_smp(void) {}
+
+static inline void container_lock(void) {}
+static inline void container_unlock(void) {}
+
+#endif /* !CONFIG_CONTAINERS */
+
+#endif /* _LINUX_CONTAINER_H */
Index: container-2.6.21-rc7-mm1/include/linux/container_subsys.h
===================================================================
--- /dev/null
+++ container-2.6.21-rc7-mm1/include/linux/container_subsys.h
@@ -0,0 +1,10 @@
+/* Add subsystem definitions of the form SUBSYS(<name>) in this
+ * file. Surround each one by a line of comment markers so that
+ * patches don't collide
+ */
+
+/* */
+
+/* */
+
+/* */
Index: container-2.6.21-rc7-mm1/include/linux/sched.h
===================================================================
--- container-2.6.21-rc7-mm1.orig/include/linux/sched.h
+++ container-2.6.21-rc7-mm1/include/linux/sched.h
@@ -820,6 +820,34 @@ struct uts_namespace;
 
 struct prio_array;
 
+#ifdef CONFIG_CONTAINERS
+
+#define SUBSYS(_x) _x ## _subsys_id,
+enum container_subsys_id {
+#include <linux/container_subsys.h>
+	CONTAINER_SUBSYS_COUNT
+};
+#undef SUBSYS
+
+/* A css_group is a structure holding pointers to a set of
+ * container_subsys_state objects.
+ */
+
+struct css_group {
+
+	/* Set of subsystem states, one for each subsystem. NULL for
+	 * subsystems that aren't part of this hierarchy. These
+	 * pointers reduce the number of dereferences required to get
+	 * from a task to its state for a given container, but result
+	 * in increased space usage if tasks are in wildly different
+	 * groupings across different hierarchies. This array is
+	 * immutable after creation */
+	struct container_subsys_state *subsys[CONTAINER_SUBSYS_COUNT];
+
+};
+
+#endif /* CONFIG_CONTAINERS */
+
 struct task_struct {
 	volatile long state;	/* -1 unrunnable, 0 runnable, >0 stopped */
 	struct thread_info *thread_info;
@@ -1072,6 +1100,9 @@ struct task_struct {
 	int cpuset_mems_generation;
 	int cpuset_mem_spread_rotor;
 #endif
+#ifdef CONFIG_CONTAINERS
+	struct css_group containers;
+#endif
 	struct robust_list_head __user *robust_list;
 #ifdef CONFIG_COMPAT
 	struct compat_robust_list_head __user *compat_robust_list;
@@ -1509,7 +1540,8 @@ static inline int thread_group_empty(str
 /*
  * Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring
  * subscriptions and synchronises with wait4().  Also used in procfs.  Also
- * pins the final release of task.io_context.  Also protects ->cpuset.
+ * pins the final release of task.io_context.  Also protects ->cpuset and
+ * ->container.subsys[].
  *
  * Nests both inside and outside of read_lock(&tasklist_lock).
  * It must not be nested with write_lock_irq(&tasklist_lock),
Index: container-2.6.21-rc7-mm1/init/Kconfig
===================================================================
--- container-2.6.21-rc7-mm1.orig/init/Kconfig
+++ container-2.6.21-rc7-mm1/init/Kconfig
@@ -288,6 +288,9 @@ config IKCONFIG_PROC
 	  This option enables access to the kernel configuration file
 	  through /proc/config.gz.
 
+config CONTAINERS
+	bool
+
 config CPUSETS
 	bool "Cpuset support"
 	depends on SMP
Index: container-2.6.21-rc7-mm1/init/main.c
===================================================================
--- container-2.6.21-rc7-mm1.orig/init/main.c
+++ container-2.6.21-rc7-mm1/init/main.c
@@ -39,6 +39,7 @@
 #include <linux/writeback.h>
 #include <linux/cpu.h>
 #include <linux/cpuset.h>
+#include <linux/container.h>
 #include <linux/efi.h>
 #include <linux/tick.h>
 #include <linux/interrupt.h>
@@ -499,6 +500,7 @@ asmlinkage void __init start_kernel(void
 	char * command_line;
 	extern struct kernel_param __start___param[], __stop___param[];
 
+	container_init_early();
 	smp_setup_processor_id();
 
 	/*
@@ -624,6 +626,7 @@ asmlinkage void __init start_kernel(void
 #ifdef CONFIG_PROC_FS
 	proc_root_init();
 #endif
+	container_init();
 	cpuset_init();
 	taskstats_init_early();
 	delayacct_init();
Index: container-2.6.21-rc7-mm1/kernel/Makefile
===================================================================
--- container-2.6.21-rc7-mm1.orig/kernel/Makefile
+++ container-2.6.21-rc7-mm1/kernel/Makefile
@@ -36,6 +36,7 @@ obj-$(CONFIG_PM) += power/
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_KEXEC) += kexec.o
 obj-$(CONFIG_COMPAT) += compat.o
+obj-$(CONFIG_CONTAINERS) += container.o
 obj-$(CONFIG_CPUSETS) += cpuset.o
 obj-$(CONFIG_IKCONFIG) += configs.o
 obj-$(CONFIG_STOP_MACHINE) += stop_machine.o
Index: container-2.6.21-rc7-mm1/kernel/container.c
===================================================================
--- /dev/null
+++ container-2.6.21-rc7-mm1/kernel/container.c
@@ -0,0 +1,1151 @@
+/*
+ *  kernel/container.c
+ *
+ *  Generic process-grouping system.
+ *
+ *  Based originally on the cpuset system, extracted by Paul Menage
+ *  Copyright (C) 2006 Google, Inc
+ *
+ *  Copyright notices from the original cpuset code:
+ *  --------------------------------------------------
+ *  Copyright (C) 2003 BULL SA.
+ *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
+ *
+ *  Portions derived from Patrick Mochel's sysfs code.
+ *  sysfs is Copyright (c) 2001-3 Patrick Mochel
+ *
+ *  2003-10-10 Written by Simon Derr.
+ *  2003-10-22 Updates by Stephen Hemminger.
+ *  2004 May-July Rework by Paul Jackson.
+ *  ---------------------------------------------------
+ *
+ *  This file is subject to the terms and conditions of the GNU General Public
+ *  License.  See the file COPYING in the main directory of the Linux
+ *  distribution for more details.
+ */
+
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/container.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/kmod.h>
+#include <linux/list.h>
+#include <linux/mempolicy.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/pagemap.h>
+#include <linux/proc_fs.h>
+#include <linux/rcupdate.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+#include <linux/security.h>
+#include <linux/slab.h>
+#include <linux/smp_lock.h>
+#include <linux/spinlock.h>
+#include <linux/stat.h>
+#include <linux/string.h>
+#include <linux/time.h>
+#include <linux/backing-dev.h>
+#include <linux/sort.h>
+
+#include <asm/uaccess.h>
+#include <asm/atomic.h>
+#include <linux/mutex.h>
+
+#define CONTAINER_SUPER_MAGIC		0x27e0eb
+
+/* Generate an array of container subsystem pointers */
+#define SUBSYS(_x) &_x ## _subsys,
+
+static struct container_subsys *subsys[] = {
+#include <linux/container_subsys.h>
+};
+
+/* A containerfs_root represents the root of a container hierarchy,
+ * and may be associated with a superblock to form an active
+ * hierarchy */
+struct containerfs_root {
+	struct super_block *sb;
+
+	/* The bitmask of subsystems attached to this hierarchy */
+	unsigned long subsys_bits;
+
+	/* A list running through the attached subsystems */
+	struct list_head subsys_list;
+
+	/* The root container for this hierarchy */
+	struct container top_container;
+
+	/* Tracks how many containers are currently defined in hierarchy.*/
+	int number_of_containers;
+
+	/* A list running through the mounted hierarchies */
+	struct list_head root_list;
+};
+
+
+/* The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
+ * subsystems that are otherwise unattached - it never has more than a
+ * single container, and all tasks are part of that container. */
+
+static struct containerfs_root rootnode;
+
+/* The list of hierarchy roots */
+
+static LIST_HEAD(roots);
+
+/* dummytop is a shorthand for the dummy hierarchy's top container */
+#define dummytop (&rootnode.top_container)
+
+/* This flag indicates whether tasks in the fork and exit paths should
+ * take callback_mutex and check for fork/exit handlers to call. This
+ * avoids us having to do extra work in the fork/exit path if none of the
+ * subsystems need to be called.
+ */
+static int need_forkexit_callback = 0;
+
+/* bits in struct container flags field */
+typedef enum {
+	CONT_REMOVED,
+} container_flagbits_t;
+
+/* convenient tests for these bits */
+inline int container_is_removed(const struct container *cont)
+{
+	return test_bit(CONT_REMOVED, &cont->flags);
+}
+
+/* for_each_subsys() allows you to iterate on each subsystem attached to
+ * an active hierarchy */
+#define for_each_subsys(_root, _ss) \
+list_for_each_entry(_ss, &_root->subsys_list, sibling)
+
+/* for_each_root() allows you to iterate across the active hierarchies */
+#define for_each_root(_root) \
+list_for_each_entry(_root, &roots, root_list)
+
+/*
+ * There is one global container mutex. We also require taking
+ * task_lock() when dereferencing a task's container subsys pointers.
+ * See "The task_lock() exception", at the end of this comment.
+ *
+ * A task must hold container_mutex to modify containers.
+ *
+ * Any task can increment and decrement the count field without lock.
+ * So in general, code holding container_mutex can't rely on the count
+ * field not changing.  However, if the count goes to zero, then only
+ * attach_task() can increment it again.  Because a count of zero
+ * means that no tasks are currently attached, therefore there is no
+ * way a task attached to that container can fork (the other way to
+ * increment the count).  So code holding container_mutex can safely
+ * assume that if the count is zero, it will stay zero. Similarly, if
+ * a task holds container_mutex on a container with zero count, it
+ * knows that the container won't be removed, as container_rmdir()
+ * needs that mutex.
+ *
+ * The container_common_file_write handler for operations that modify
+ * the container hierarchy holds container_mutex across the entire operation,
+ * single threading all such container modifications across the system.
+ *
+ * The fork and exit callbacks container_fork() and container_exit(), don't
+ * (usually) take container_mutex.  These are the two most performance
+ * critical pieces of code here.  The exception occurs on container_exit(),
+ * when a task in a notify_on_release container exits.  Then container_mutex
+ * is taken, and if the container count is zero, a usermode call made
+ * to /sbin/container_release_agent with the name of the container (path
+ * relative to the root of container file system) as the argument.
+ *
+ * A container can only be deleted if both its 'count' of using tasks
+ * is zero, and its list of 'children' containers is empty.  Since all
+ * tasks in the system use _some_ container, and since there is always at
+ * least one task in the system (init, pid == 1), therefore, top_container
+ * always has either children containers and/or using tasks.  So we don't
+ * need a special hack to ensure that top_container cannot be deleted.
+ *
+ *	The task_lock() exception
+ *
+ * The need for this exception arises from the action of
+ * attach_task(), which overwrites one tasks container pointer with
+ * another.  It does so using container_mutexe, however there are
+ * several performance critical places that need to reference
+ * task->container without the expense of grabbing a system global
+ * mutex.  Therefore except as noted below, when dereferencing or, as
+ * in attach_task(), modifying a task'ss container pointer we use
+ * task_lock(), which acts on a spinlock (task->alloc_lock) already in
+ * the task_struct routinely used for such matters.
+ *
+ * P.S.  One more locking exception.  RCU is used to guard the
+ * update of a tasks container pointer by attach_task()
+ */
+
+static DEFINE_MUTEX(container_mutex);
+
+/**
+ * container_lock - lock out any changes to container structures
+ *
+ */
+
+void container_lock(void)
+{
+	mutex_lock(&container_mutex);
+}
+
+/**
+ * container_unlock - release lock on container changes
+ *
+ * Undo the lock taken in a previous container_lock() call.
+ */
+
+void container_unlock(void)
+{
+	mutex_unlock(&container_mutex);
+}
+
+/*
+ * A couple of forward declarations required, due to cyclic reference loop:
+ *  container_mkdir -> container_create -> container_populate_dir -> container_add_file
+ *  -> container_create_file -> container_dir_inode_operations -> container_mkdir.
+ */
+
+static int container_mkdir(struct inode *dir, struct dentry *dentry, int mode);
+static int container_rmdir(struct inode *unused_dir, struct dentry *dentry);
+static int container_populate_dir(struct container *cont);
+static struct inode_operations container_dir_inode_operations;
+
+static struct backing_dev_info container_backing_dev_info = {
+	.ra_pages = 0,		/* No readahead */
+	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
+};
+
+static struct inode *container_new_inode(mode_t mode, struct super_block *sb)
+{
+	struct inode *inode = new_inode(sb);
+
+	if (inode) {
+		inode->i_mode = mode;
+		inode->i_uid = current->fsuid;
+		inode->i_gid = current->fsgid;
+		inode->i_blocks = 0;
+		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+		inode->i_mapping->backing_dev_info = &container_backing_dev_info;
+	}
+	return inode;
+}
+
+static void container_diput(struct dentry *dentry, struct inode *inode)
+{
+	/* is dentry a directory ? if so, kfree() associated container */
+	if (S_ISDIR(inode->i_mode)) {
+		struct container *cont = dentry->d_fsdata;
+		BUG_ON(!(container_is_removed(cont)));
+		kfree(cont);
+	}
+	iput(inode);
+}
+
+static struct dentry_operations container_dops = {
+	.d_iput = container_diput,
+};
+
+static struct dentry *container_get_dentry(struct dentry *parent,
+					   const char *name)
+{
+	struct dentry *d = lookup_one_len(name, parent, strlen(name));
+	if (!IS_ERR(d))
+		d->d_op = &container_dops;
+	return d;
+}
+
+static void remove_dir(struct dentry *d)
+{
+	struct dentry *parent = dget(d->d_parent);
+
+	d_delete(d);
+	simple_rmdir(parent->d_inode, d);
+	dput(parent);
+}
+
+static void container_clear_directory(struct dentry *dentry)
+{
+	struct list_head *node;
+	BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
+	spin_lock(&dcache_lock);
+	node = dentry->d_subdirs.next;
+	while (node != &dentry->d_subdirs) {
+		struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
+		list_del_init(node);
+		if (d->d_inode) {
+			/* This should never be called on a container
+			 * directory with child containers */
+			BUG_ON(d->d_inode->i_mode & S_IFDIR);
+			d = dget_locked(d);
+			spin_unlock(&dcache_lock);
+			d_delete(d);
+			simple_unlink(dentry->d_inode, d);
+			dput(d);
+			spin_lock(&dcache_lock);
+		}
+		node = dentry->d_subdirs.next;
+	}
+	spin_unlock(&dcache_lock);
+}
+
+/*
+ * NOTE : the dentry must have been dget()'ed
+ */
+static void container_d_remove_dir(struct dentry *dentry)
+{
+	container_clear_directory(dentry);
+
+	spin_lock(&dcache_lock);
+	list_del_init(&dentry->d_u.d_child);
+	spin_unlock(&dcache_lock);
+	remove_dir(dentry);
+}
+
+static int rebind_subsystems(struct containerfs_root *root,
+			      unsigned long final_bits)
+{
+	unsigned long added_bits, removed_bits;
+	struct container *cont = &root->top_container;
+	int i;
+
+	removed_bits = root->subsys_bits & ~final_bits;
+	added_bits = final_bits & ~root->subsys_bits;
+	/* Check that any added subsystems are currently free */
+	for (i = 0; i < CONTAINER_SUBSYS_COUNT; i++) {
+		unsigned long long bit = 1ull << i;
+		struct container_subsys *ss = subsys[i];
+		if (!(bit & added_bits))
+			continue;
+		if (ss->root != &rootnode) {
+			/* Subsystem isn't free */
+			return -EBUSY;
+		}
+	}
+
+	/* Currently we don't handle adding/removing subsystems when
+	 * any subcontainers exist. This is theoretically supportable
+	 * but involves complex erro r handling, so it's being left until
+	 * later */
+	if (!list_empty(&cont->children)) {
+		return -EBUSY;
+	}
+
+	/* Process each subsystem */
+	for (i = 0; i < CONTAINER_SUBSYS_COUNT; i++) {
+		struct container_subsys *ss = subsys[i];
+		unsigned long bit = 1UL << i;
+		if (bit & added_bits) {
+			/* We're binding this subsystem to this hierarchy */
+			BUG_ON(cont->subsys[i]);
+			BUG_ON(!dummytop->subsys[i]);
+			BUG_ON(dummytop->subsys[i]->container != dummytop);
+			cont->subsys[i] = dummytop->subsys[i];
+			cont->subsys[i]->container = cont;
+			list_add(&ss->sibling, &root->subsys_list);
+			rcu_assign_pointer(ss->root, root);
+			if (ss->bind)
+				ss->bind(ss, cont);
+
+		} else if (bit & removed_bits) {
+			/* We're removing this subsystem */
+			BUG_ON(cont->subsys[i] != dummytop->subsys[i]);
+			BUG_ON(cont->subsys[i]->container != cont);
+			if (ss->bind)
+				ss->bind(ss, dummytop);
+			dummytop->subsys[i]->container = dummytop;
+			cont->subsys[i] = NULL;
+			rcu_assign_pointer(subsys[i]->root, &rootnode);
+			list_del(&ss->sibling);
+		} else if (bit & final_bits) {
+			/* Subsystem state should already exist */
+			BUG_ON(!cont->subsys[i]);
+		} else {
+			/* Subsystem state shouldn't exist */
+			BUG_ON(cont->subsys[i]);
+		}
+	}
+	root->subsys_bits = final_bits;
+	synchronize_rcu();
+
+	return 0;
+}
+
+/*
+ * Release the last use of a hierarchy.  Will never be called when
+ * there are active subcontainers since each subcontainer bumps the
+ * value of sb->s_active.
+ */
+
+static void container_put_super(struct super_block *sb) {
+
+	struct containerfs_root *root = sb->s_fs_info;
+	struct container *cont = &root->top_container;
+	int ret;
+
+	root->sb = NULL;
+	sb->s_fs_info = NULL;
+
+	mutex_lock(&container_mutex);
+
+	BUG_ON(root->number_of_containers != 1);
+	BUG_ON(!list_empty(&cont->children));
+	BUG_ON(!list_empty(&cont->sibling));
+	BUG_ON(!root->subsys_bits);
+
+	/* Rebind all subsystems back to the default hierarchy */
+	ret = rebind_subsystems(root, 0);
+	BUG_ON(ret);
+
+	kfree(root);
+	mutex_unlock(&container_mutex);
+}
+
+static int container_show_options(struct seq_file *seq, struct vfsmount *vfs)
+{
+	struct containerfs_root *root = vfs->mnt_sb->s_fs_info;
+	struct container_subsys *ss;
+	for_each_subsys(root, ss) {
+		seq_printf(seq, ",%s", ss->name);
+	}
+	return 0;
+}
+
+/* Convert a hierarchy specifier into a bitmask. LL=container_mutex */
+static int parse_containerfs_options(char *opts, unsigned long *bits)
+{
+	char *token, *o = opts ?: "all";
+
+	*bits = 0;
+
+	while ((token = strsep(&o, ",")) != NULL) {
+		if (!*token)
+			return -EINVAL;
+		if (!strcmp(token, "all")) {
+			*bits = (1 << CONTAINER_SUBSYS_COUNT) - 1;
+		} else {
+			struct container_subsys *ss;
+			int i;
+			for (i = 0; i < CONTAINER_SUBSYS_COUNT; i++) {
+				ss = subsys[i];
+				if (!strcmp(token, ss->name)) {
+					*bits |= 1 << i;
+					break;
+				}
+			}
+			if (i == CONTAINER_SUBSYS_COUNT)
+				return -ENOENT;
+		}
+	}
+
+	/* We can't have an empty hierarchy */
+	if (!*bits)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int container_remount(struct super_block *sb, int *flags, char *data)
+{
+	int ret = 0;
+	unsigned long subsys_bits;
+	struct containerfs_root *root = sb->s_fs_info;
+	struct container *cont = &root->top_container;
+
+	mutex_lock(&cont->dentry->d_inode->i_mutex);
+	mutex_lock(&container_mutex);
+
+	/* See what subsystems are wanted */
+	ret = parse_containerfs_options(data, &subsys_bits);
+	if (ret)
+		goto out_unlock;
+
+	ret = rebind_subsystems(root, subsys_bits);
+
+	/* (re)populate subsystem files */
+	if (!ret)
+		container_populate_dir(cont);
+
+ out_unlock:
+	mutex_unlock(&container_mutex);
+	mutex_unlock(&cont->dentry->d_inode->i_mutex);
+	return ret;
+}
+
+static struct super_operations container_ops = {
+	.statfs = simple_statfs,
+	.drop_inode = generic_delete_inode,
+	.put_super = container_put_super,
+	.show_options = container_show_options,
+	.remount_fs = container_remount,
+};
+
+static int container_fill_super(struct super_block *sb, void *options,
+				int unused_silent)
+{
+	struct inode *inode;
+	struct dentry *root;
+	struct containerfs_root *hroot = options;
+
+	sb->s_blocksize = PAGE_CACHE_SIZE;
+	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
+	sb->s_magic = CONTAINER_SUPER_MAGIC;
+	sb->s_op = &container_ops;
+
+	inode = container_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
+	if (!inode)
+		return -ENOMEM;
+
+	inode->i_op = &simple_dir_inode_operations;
+	inode->i_fop = &simple_dir_operations;
+	inode->i_op = &container_dir_inode_operations;
+	/* directories start off with i_nlink == 2 (for "." entry) */
+	inc_nlink(inode);
+
+	root = d_alloc_root(inode);
+	if (!root) {
+		iput(inode);
+		return -ENOMEM;
+	}
+	sb->s_root = root;
+	root->d_fsdata = &hroot->top_container;
+	hroot->top_container.dentry = root;
+
+	sb->s_fs_info = hroot;
+	hroot->sb = sb;
+
+	return 0;
+}
+
+static void init_container_root(struct containerfs_root *root) {
+	struct container *cont = &root->top_container;
+	INIT_LIST_HEAD(&root->subsys_list);
+	root->number_of_containers = 1;
+	cont->root = root;
+	cont->top_container = cont;
+	INIT_LIST_HEAD(&cont->sibling);
+	INIT_LIST_HEAD(&cont->children);
+	list_add(&root->root_list, &roots);
+}
+
+static int container_get_sb(struct file_system_type *fs_type,
+			 int flags, const char *unused_dev_name,
+			 void *data, struct vfsmount *mnt)
+{
+	unsigned long subsys_bits = 0;
+	int ret = 0;
+	struct containerfs_root *root = NULL;
+	int use_existing = 0;
+
+	mutex_lock(&container_mutex);
+
+	/* First find the desired set of resource controllers */
+	ret = parse_containerfs_options(data, &subsys_bits);
+	if (ret)
+		goto out_unlock;
+
+	/* See if we already have a hierarchy containing this set */
+
+	for_each_root(root) {
+		/* We match - use this hieracrchy */
+		if (root->subsys_bits == subsys_bits) {
+			use_existing = 1;
+			break;
+		}
+		/* We clash - fail */
+		if (root->subsys_bits & subsys_bits) {
+			ret = -EBUSY;
+			goto out_unlock;
+		}
+	}
+
+	if (!use_existing) {
+		/* We need a new root */
+		root = kzalloc(sizeof(*root), GFP_KERNEL);
+		if (!root) {
+			ret = -ENOMEM;
+			goto out_unlock;
+		}
+		init_container_root(root);
+	}
+
+	if (!root->sb) {
+		/* We need a new superblock for this container combination */
+		struct container *cont = &root->top_container;
+
+		BUG_ON(root->subsys_bits);
+		ret = get_sb_nodev(fs_type, flags, root,
+				   container_fill_super, mnt);
+		if (ret)
+			goto out_unlock;
+
+		BUG_ON(!list_empty(&cont->sibling));
+		BUG_ON(!list_empty(&cont->children));
+		BUG_ON(root->number_of_containers != 1);
+
+		ret = rebind_subsystems(root, subsys_bits);
+
+		/* It's safe to nest i_mutex inside container_mutex in
+		 * this case, since no-one else can be accessing this
+		 * directory yet */
+		mutex_lock(&cont->dentry->d_inode->i_mutex);
+		container_populate_dir(cont);
+		mutex_unlock(&cont->dentry->d_inode->i_mutex);
+		BUG_ON(ret);
+
+	} else {
+		/* Reuse the existing superblock */
+		ret = simple_set_mnt(mnt, root->sb);
+		if (!ret)
+			atomic_inc(&root->sb->s_active);
+	}
+
+ out_unlock:
+	mutex_unlock(&container_mutex);
+	return ret;
+}
+
+static struct file_system_type container_fs_type = {
+	.name = "container",
+	.get_sb = container_get_sb,
+	.kill_sb = kill_litter_super,
+};
+
+static inline struct container *__d_cont(struct dentry *dentry)
+{
+	return dentry->d_fsdata;
+}
+
+static inline struct cftype *__d_cft(struct dentry *dentry)
+{
+	return dentry->d_fsdata;
+}
+
+/*
+ * Call with container_mutex held.  Writes path of container into buf.
+ * Returns 0 on success, -errno on error.
+ */
+
+int container_path(const struct container *cont, char *buf, int buflen)
+{
+	char *start;
+
+	start = buf + buflen;
+
+	*--start = '\0';
+	for (;;) {
+		int len = cont->dentry->d_name.len;
+		if ((start -= len) < buf)
+			return -ENAMETOOLONG;
+		memcpy(start, cont->dentry->d_name.name, len);
+		cont = cont->parent;
+		if (!cont)
+			break;
+		if (!cont->parent)
+			continue;
+		if (--start < buf)
+			return -ENAMETOOLONG;
+		*start = '/';
+	}
+	memmove(buf, start, buf + buflen - start);
+	return 0;
+}
+
+static inline void get_first_subsys(const struct container *cont,
+				    struct container_subsys_state **css,
+				    int *subsys_id) {
+	const struct containerfs_root *root = cont->root;
+	const struct container_subsys *test_ss;
+	BUG_ON(list_empty(&root->subsys_list));
+	test_ss = list_entry(root->subsys_list.next,
+			     struct container_subsys, sibling);
+	if (css) {
+		*css = cont->subsys[test_ss->subsys_id];
+		BUG_ON(!*css);
+	}
+	if (subsys_id)
+		*subsys_id = test_ss->subsys_id;
+}
+
+/* The various types of files and directories in a container file system */
+
+typedef enum {
+	FILE_ROOT,
+	FILE_DIR,
+	FILE_TASKLIST,
+} container_filetype_t;
+
+static ssize_t container_file_write(struct file *file, const char __user *buf,
+						size_t nbytes, loff_t *ppos)
+{
+	struct cftype *cft = __d_cft(file->f_dentry);
+	struct container *cont = __d_cont(file->f_dentry->d_parent);
+	if (!cft)
+		return -ENODEV;
+	if (!cft->write)
+		return -EINVAL;
+
+	return cft->write(cont, cft, file, buf, nbytes, ppos);
+}
+
+static ssize_t container_read_uint(struct container *cont, struct cftype *cft,
+				   struct file *file,
+				   char __user *buf, size_t nbytes,
+				   loff_t *ppos)
+{
+	char tmp[64];
+	u64 val = cft->read_uint(cont, cft);
+	int len = sprintf(tmp, "%llu", val);
+	return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
+}
+
+static ssize_t container_file_read(struct file *file, char __user *buf,
+				   size_t nbytes, loff_t *ppos)
+{
+	struct cftype *cft = __d_cft(file->f_dentry);
+	struct container *cont = __d_cont(file->f_dentry->d_parent);
+	if (!cft)
+		return -ENODEV;
+
+	if (cft->read)
+		return cft->read(cont, cft, file, buf, nbytes, ppos);
+	if (cft->read_uint)
+		return container_read_uint(cont, cft, file, buf, nbytes, ppos);
+	return -EINVAL;
+}
+
+static int container_file_open(struct inode *inode, struct file *file)
+{
+	int err;
+	struct cftype *cft;
+
+	err = generic_file_open(inode, file);
+	if (err)
+		return err;
+
+	cft = __d_cft(file->f_dentry);
+	if (!cft)
+		return -ENODEV;
+	if (cft->open)
+		err = cft->open(inode, file);
+	else
+		err = 0;
+
+	return err;
+}
+
+static int container_file_release(struct inode *inode, struct file *file)
+{
+	struct cftype *cft = __d_cft(file->f_dentry);
+	if (cft->release)
+		return cft->release(inode, file);
+	return 0;
+}
+
+/*
+ * container_rename - Only allow simple rename of directories in place.
+ */
+static int container_rename(struct inode *old_dir, struct dentry *old_dentry,
+			    struct inode *new_dir, struct dentry *new_dentry)
+{
+	if (!S_ISDIR(old_dentry->d_inode->i_mode))
+		return -ENOTDIR;
+	if (new_dentry->d_inode)
+		return -EEXIST;
+	if (old_dir != new_dir)
+		return -EIO;
+	return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
+}
+
+static struct file_operations container_file_operations = {
+	.read = container_file_read,
+	.write = container_file_write,
+	.llseek = generic_file_llseek,
+	.open = container_file_open,
+	.release = container_file_release,
+};
+
+static struct inode_operations container_dir_inode_operations = {
+	.lookup = simple_lookup,
+	.mkdir = container_mkdir,
+	.rmdir = container_rmdir,
+	.rename = container_rename,
+};
+
+static int container_create_file(struct dentry *dentry, int mode, struct super_block *sb)
+{
+	struct inode *inode;
+
+	if (!dentry)
+		return -ENOENT;
+	if (dentry->d_inode)
+		return -EEXIST;
+
+	inode = container_new_inode(mode, sb);
+	if (!inode)
+		return -ENOMEM;
+
+	if (S_ISDIR(mode)) {
+		inode->i_op = &container_dir_inode_operations;
+		inode->i_fop = &simple_dir_operations;
+
+		/* start off with i_nlink == 2 (for "." entry) */
+		inc_nlink(inode);
+
+		/* start with the directory inode held, so that we can
+		 * populate it without racing with another mkdir */
+		mutex_lock(&inode->i_mutex);
+	} else if (S_ISREG(mode)) {
+		inode->i_size = 0;
+		inode->i_fop = &container_file_operations;
+	}
+
+	d_instantiate(dentry, inode);
+	dget(dentry);	/* Extra count - pin the dentry in core */
+	return 0;
+}
+
+/*
+ *	container_create_dir - create a directory for an object.
+ *	cont:	the container we create the directory for.
+ *		It must have a valid ->parent field
+ *		And we are going to fill its ->dentry field.
+ *	name:	The name to give to the container directory. Will be copied.
+ *	mode:	mode to set on new directory.
+ */
+
+static int container_create_dir(struct container *cont, struct dentry *dentry,
+				int mode)
+{
+	struct dentry *parent;
+	int error = 0;
+
+	parent = cont->parent->dentry;
+	if (IS_ERR(dentry))
+		return PTR_ERR(dentry);
+	error = container_create_file(dentry, S_IFDIR | mode, cont->root->sb);
+	if (!error) {
+		dentry->d_fsdata = cont;
+		inc_nlink(parent->d_inode);
+		cont->dentry = dentry;
+	}
+	dput(dentry);
+
+	return error;
+}
+
+int container_add_file(struct container *cont, const struct cftype *cft)
+{
+	struct dentry *dir = cont->dentry;
+	struct dentry *dentry;
+	int error;
+
+	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
+	dentry = container_get_dentry(dir, cft->name);
+	if (!IS_ERR(dentry)) {
+		error = container_create_file(dentry, 0644 | S_IFREG, cont->root->sb);
+		if (!error)
+			dentry->d_fsdata = (void *)cft;
+		dput(dentry);
+	} else
+		error = PTR_ERR(dentry);
+	return error;
+}
+
+int container_add_files(struct container *cont, const struct cftype cft[],
+			int count)
+{
+	int i, err;
+	for (i = 0; i < count; i++) {
+		if ((err = container_add_file(cont, &cft[i])))
+			return err;
+	}
+	return 0;
+}
+
+static int container_populate_dir(struct container *cont)
+{
+	int err;
+	struct container_subsys *ss;
+
+	/* First clear out any existing files */
+	container_clear_directory(cont->dentry);
+
+	for_each_subsys(cont->root, ss) {
+		if (ss->populate && (err = ss->populate(ss, cont)) < 0)
+			return err;
+	}
+
+	return 0;
+}
+
+static void init_container_css(struct container_subsys *ss,
+			       struct container *cont)
+{
+	struct container_subsys_state *css = cont->subsys[ss->subsys_id];
+	css->container = cont;
+	atomic_set(&css->refcnt, 0);
+}
+
+/*
+ *	container_create - create a container
+ *	parent:	container that will be parent of the new container.
+ *	name:		name of the new container. Will be strcpy'ed.
+ *	mode:		mode to set on new inode
+ *
+ *	Must be called with the mutex on the parent inode held
+ */
+
+static long container_create(struct container *parent, struct dentry *dentry,
+			     int mode)
+{
+	struct container *cont;
+	struct containerfs_root *root = parent->root;
+	int err = 0;
+	struct container_subsys *ss;
+	struct super_block *sb = root->sb;
+
+	cont = kzalloc(sizeof(*cont), GFP_KERNEL);
+	if (!cont)
+		return -ENOMEM;
+
+	/* Grab a reference on the superblock so the hierarchy doesn't
+	 * get deleted on unmount if there are child containers.  This
+	 * can be done outside container_mutex, since the sb can't
+	 * disappear while someone has an open control file on the
+	 * fs */
+	atomic_inc(&sb->s_active);
+
+	mutex_lock(&container_mutex);
+
+	cont->flags = 0;
+	INIT_LIST_HEAD(&cont->sibling);
+	INIT_LIST_HEAD(&cont->children);
+
+	cont->parent = parent;
+	cont->root = parent->root;
+	cont->top_container = parent->top_container;
+
+	for_each_subsys(root, ss) {
+		err = ss->create(ss, cont);
+		if (err) goto err_destroy;
+		init_container_css(ss, cont);
+	}
+
+	list_add(&cont->sibling, &cont->parent->children);
+	root->number_of_containers++;
+
+	err = container_create_dir(cont, dentry, mode);
+	if (err < 0)
+		goto err_remove;
+
+	/* The container directory was pre-locked for us */
+	BUG_ON(!mutex_is_locked(&cont->dentry->d_inode->i_mutex));
+
+	err = container_populate_dir(cont);
+	/* If err < 0, we have a half-filled directory - oh well ;) */
+
+	mutex_unlock(&container_mutex);
+	mutex_unlock(&cont->dentry->d_inode->i_mutex);
+
+	return 0;
+
+ err_remove:
+
+	list_del(&cont->sibling);
+	root->number_of_containers--;
+
+ err_destroy:
+
+	for_each_subsys(root, ss) {
+		if (cont->subsys[ss->subsys_id])
+			ss->destroy(ss, cont);
+	}
+
+	mutex_unlock(&container_mutex);
+
+	/* Release the reference count that we took on the superblock */
+	deactivate_super(sb);
+
+	kfree(cont);
+	return err;
+}
+
+static int container_mkdir(struct inode *dir, struct dentry *dentry, int mode)
+{
+	struct container *c_parent = dentry->d_parent->d_fsdata;
+
+	/* the vfs holds inode->i_mutex already */
+	return container_create(c_parent, dentry, mode | S_IFDIR);
+}
+
+static int container_rmdir(struct inode *unused_dir, struct dentry *dentry)
+{
+	struct container *cont = dentry->d_fsdata;
+	struct dentry *d;
+	struct container *parent;
+	struct container_subsys *ss;
+	struct super_block *sb;
+	struct containerfs_root *root;
+	int css_busy = 0;
+
+	/* the vfs holds both inode->i_mutex already */
+
+	mutex_lock(&container_mutex);
+	if (atomic_read(&cont->count) != 0) {
+		mutex_unlock(&container_mutex);
+		return -EBUSY;
+	}
+	if (!list_empty(&cont->children)) {
+		mutex_unlock(&container_mutex);
+		return -EBUSY;
+	}
+
+	parent = cont->parent;
+	root = cont->root;
+	sb = root->sb;
+
+	/* Check the reference count on each subsystem. Since we
+	 * already established that there are no tasks in the
+	 * container, if the css refcount is also 0, then there should
+	 * be no outstanding references, so the subsystem is safe to
+	 * destroy */
+	for_each_subsys(root, ss) {
+		struct container_subsys_state *css;
+		css = cont->subsys[ss->subsys_id];
+		if (atomic_read(&css->refcnt)) {
+			css_busy = 1;
+			break;
+		}
+	}
+	if (css_busy) {
+		mutex_unlock(&container_mutex);
+		return -EBUSY;
+	}
+
+	for_each_subsys(root, ss) {
+		if (cont->subsys[ss->subsys_id])
+			ss->destroy(ss, cont);
+	}
+
+	set_bit(CONT_REMOVED, &cont->flags);
+	/* delete my sibling from parent->children */
+	list_del(&cont->sibling);
+	spin_lock(&cont->dentry->d_lock);
+	d = dget(cont->dentry);
+	cont->dentry = NULL;
+	spin_unlock(&d->d_lock);
+
+	container_d_remove_dir(d);
+	dput(d);
+	root->number_of_containers--;
+
+	mutex_unlock(&container_mutex);
+	/* Drop the active superblock reference that we took when we
+	 * created the container */
+	deactivate_super(sb);
+	return 0;
+}
+
+static void container_init_subsys(struct container_subsys *ss) {
+	int retval;
+	struct task_struct *g, *p;
+	struct container_subsys_state *css;
+	printk(KERN_ERR "Initializing container subsys %s\n", ss->name);
+
+	/* Create the top container state for this subsystem */
+	ss->root = &rootnode;
+	retval = ss->create(ss, dummytop);
+	BUG_ON(retval);
+	BUG_ON(!dummytop->subsys[ss->subsys_id]);
+	init_container_css(ss, dummytop);
+	css = dummytop->subsys[ss->subsys_id];
+
+	/* Update all tasks to contain a subsys pointer to this state
+	 * - since the subsystem is newly registered, all tasks are in
+	 * the subsystem's top container. */
+
+ 	/* If this subsystem requested that it be notified with fork
+ 	 * events, we should send it one now for every process in the
+ 	 * system */
+
+	read_lock(&tasklist_lock);
+	init_task.containers.subsys[ss->subsys_id] = css;
+	if (ss->fork)
+		ss->fork(ss, &init_task);
+
+	do_each_thread(g, p) {
+		printk(KERN_INFO "Setting task %p css to %p (%d)\n", css, p, p->pid);
+		p->containers.subsys[ss->subsys_id] = css;
+		if (ss->fork)
+			ss->fork(ss, p);
+	} while_each_thread(g, p);
+	read_unlock(&tasklist_lock);
+
+	need_forkexit_callback |= ss->fork || ss->exit;
+
+	ss->active = 1;
+}
+
+/**
+ * container_init_early - initialize containers at system boot, and
+ * initialize any subsystems that request early init.
+ *
+ **/
+
+int __init container_init_early(void)
+{
+	int i;
+	init_container_root(&rootnode);
+
+	for (i = 0; i < CONTAINER_SUBSYS_COUNT; i++) {
+		struct container_subsys *ss = subsys[i];
+
+		BUG_ON(!ss->name);
+		BUG_ON(strlen(ss->name) > MAX_CONTAINER_TYPE_NAMELEN);
+		BUG_ON(!ss->create);
+		BUG_ON(!ss->destroy);
+		if (ss->subsys_id != i) {
+			printk(KERN_ERR "Subsys %s id == %d\n",
+			       ss->name, ss->subsys_id);
+			BUG();
+		}
+
+		if (ss->early_init)
+			container_init_subsys(ss);
+	}
+	return 0;
+}
+
+/**
+ * container_init - register container filesystem and /proc file, and
+ * initialize any subsystems that didn't request early init.
+ **/
+
+int __init container_init(void)
+{
+	int err;
+	int i;
+
+	for (i = 0; i < CONTAINER_SUBSYS_COUNT; i++) {
+		struct container_subsys *ss = subsys[i];
+		if (!ss->early_init)
+			container_init_subsys(ss);
+	}
+
+	err = register_filesystem(&container_fs_type);
+	if (err < 0)
+		goto out;
+
+out:
+	return err;
+}

--
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