[PATCH 1/2] rcfs core patch

[Srivatsa Vaddagiri <vatsa@in.ibm.com>]

Heavily based on Paul Menage's (inturn cpuset) work. The big difference
is that the patch uses task->nsproxy to group tasks for resource control
purpose (instead of task->containers).

The patch retains the same user interface as Paul Menage's patches. In
particular, you can have multiple hierarchies, each hierarchy giving a 
different composition/view of task-groups.

(Ideally this patch should have been split into 2 or 3 sub-patches, but
will do that on a subsequent version post)

Signed-off-by : Srivatsa Vaddagiri <vatsa@in.ibm.com>
Signed-off-by : Paul Menage <menage@google.com>


---

 linux-2.6.20-vatsa/include/linux/init_task.h |    4 
 linux-2.6.20-vatsa/include/linux/nsproxy.h   |    5 
 linux-2.6.20-vatsa/init/Kconfig              |   22 
 linux-2.6.20-vatsa/init/main.c               |    1 
 linux-2.6.20-vatsa/kernel/Makefile           |    1 


---


diff -puN include/linux/init_task.h~rcfs include/linux/init_task.h
--- linux-2.6.20/include/linux/init_task.h~rcfs	2007-03-01 14:20:47.000000000 +0530
+++ linux-2.6.20-vatsa/include/linux/init_task.h	2007-03-01 14:20:47.000000000 +0530
@@ -71,6 +71,16 @@
 }
 
 extern struct nsproxy init_nsproxy;
+
+#ifdef CONFIG_RCFS
+#define INIT_RCFS(nsproxy) 						\
+	.list 		= LIST_HEAD_INIT(nsproxy.list),			\
+	.ctlr_data 	= {[ 0 ... CONFIG_MAX_RC_SUBSYS-1 ] = NULL },
+#else
+#define INIT_RCFS(nsproxy)
+#endif
+
+
 #define INIT_NSPROXY(nsproxy) {						\
 	.pid_ns		= &init_pid_ns,					\
 	.count		= ATOMIC_INIT(1),				\
@@ -78,6 +88,7 @@ extern struct nsproxy init_nsproxy;
 	.uts_ns		= &init_uts_ns,					\
 	.mnt_ns		= NULL,						\
 	INIT_IPC_NS(ipc_ns)						\
+	INIT_RCFS(nsproxy)						\
 }
 
 #define INIT_SIGHAND(sighand) {						\
diff -puN include/linux/nsproxy.h~rcfs include/linux/nsproxy.h
--- linux-2.6.20/include/linux/nsproxy.h~rcfs	2007-03-01 14:20:47.000000000 +0530
+++ linux-2.6.20-vatsa/include/linux/nsproxy.h	2007-03-01 14:20:47.000000000 +0530
@@ -28,6 +28,10 @@ struct nsproxy {
 	struct ipc_namespace *ipc_ns;
 	struct mnt_namespace *mnt_ns;
 	struct pid_namespace *pid_ns;
+#ifdef CONFIG_RCFS
+	struct list_head list;
+	void *ctlr_data[CONFIG_MAX_RC_SUBSYS];
+#endif
 };
 extern struct nsproxy init_nsproxy;
 
@@ -35,6 +39,12 @@ struct nsproxy *dup_namespaces(struct ns
 int copy_namespaces(int flags, struct task_struct *tsk);
 void get_task_namespaces(struct task_struct *tsk);
 void free_nsproxy(struct nsproxy *ns);
+#ifdef CONFIG_RCFS
+struct nsproxy *find_nsproxy(struct nsproxy *ns);
+int namespaces_init(void);
+#else
+static inline int namespaces_init(void) { return 0;}
+#endif
 
 static inline void put_nsproxy(struct nsproxy *ns)
 {
diff -puN /dev/null include/linux/rcfs.h
--- /dev/null	2006-02-25 03:06:56.000000000 +0530
+++ linux-2.6.20-vatsa/include/linux/rcfs.h	2007-03-01 14:20:47.000000000 +0530
@@ -0,0 +1,72 @@
+#ifndef _LINUX_RCFS_H
+#define _LINUX_RCFS_H
+
+#ifdef CONFIG_RCFS
+
+/* 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 nsproxy *ns, struct cftype *cft,
+			 struct file *file,
+			 char __user *buf, size_t nbytes, loff_t *ppos);
+	ssize_t (*write) (struct nsproxy *ns, struct cftype *cft,
+			  struct file *file,
+			  const char __user *buf, size_t nbytes, loff_t *ppos);
+	int (*release) (struct inode *inode, struct file *file);
+};
+
+/* resource control subsystem type. See Documentation/rcfs.txt for details */
+
+struct rc_subsys {
+	int (*create)(struct rc_subsys *ss, struct nsproxy *ns,
+			 struct nsproxy *parent);
+	void (*destroy)(struct rc_subsys *ss, struct nsproxy *ns);
+	int (*can_attach)(struct rc_subsys *ss, struct nsproxy *ns,
+				 struct task_struct *tsk);
+	void (*attach)(struct rc_subsys *ss, void *new, void *old,
+				 struct task_struct *tsk);
+	int (*populate)(struct rc_subsys *ss, struct dentry *d);
+	int subsys_id;
+	int active;
+
+#define MAX_CONTAINER_TYPE_NAMELEN 32
+	const char *name;
+
+	/* Protected by RCU */
+	int hierarchy;
+
+	struct list_head sibling;
+};
+
+int rc_register_subsys(struct rc_subsys *subsys);
+/* Add a new file to the given container directory. Should only be
+ * called by subsystems from within a populate() method */
+int rcfs_add_file(struct dentry *d, const struct cftype *cft);
+extern int rcfs_init(void);
+
+#else
+
+static inline int rcfs_init(void) { return 0; }
+
+#endif
+
+
+#endif
diff -puN init/Kconfig~rcfs init/Kconfig
--- linux-2.6.20/init/Kconfig~rcfs	2007-03-01 14:20:47.000000000 +0530
+++ linux-2.6.20-vatsa/init/Kconfig	2007-03-01 16:52:50.000000000 +0530
@@ -238,6 +238,28 @@ config IKCONFIG_PROC
 	  This option enables access to the kernel configuration file
 	  through /proc/config.gz.
 
+config RCFS
+	bool "Resource control file system support"
+	default n
+	help
+	  This option will let you create and manage resource containers,
+	  which can be used to aggregate multiple processes, e.g. for
+	  the purposes of resource tracking.
+
+	  Say N if unsure
+
+config MAX_RC_SUBSYS
+       int "Number of resource control subsystems to support"
+       depends on RCFS
+       range 1 255
+       default 8
+
+config MAX_RC_HIERARCHIES
+       int "Number of rcfs hierarchies to support"
+       depends on RCFS
+       range 2 255
+       default 4
+
 config CPUSETS
 	bool "Cpuset support"
 	depends on SMP
diff -puN init/main.c~rcfs init/main.c
--- linux-2.6.20/init/main.c~rcfs	2007-03-01 14:20:47.000000000 +0530
+++ linux-2.6.20-vatsa/init/main.c	2007-03-01 14:20:47.000000000 +0530
@@ -52,6 +52,7 @@
 #include <linux/lockdep.h>
 #include <linux/pid_namespace.h>
 #include <linux/device.h>
+#include <linux/rcfs.h>
 
 #include <asm/io.h>
 #include <asm/bugs.h>
@@ -512,6 +513,7 @@ asmlinkage void __init start_kernel(void
 	setup_per_cpu_areas();
 	smp_prepare_boot_cpu();	/* arch-specific boot-cpu hooks */
 
+	namespaces_init();
 	/*
 	 * Set up the scheduler prior starting any interrupts (such as the
 	 * timer interrupt). Full topology setup happens at smp_init()
@@ -608,6 +610,7 @@ asmlinkage void __init start_kernel(void
 #ifdef CONFIG_PROC_FS
 	proc_root_init();
 #endif
+	rcfs_init();
 	cpuset_init();
 	taskstats_init_early();
 	delayacct_init();
diff -puN kernel/Makefile~rcfs kernel/Makefile
--- linux-2.6.20/kernel/Makefile~rcfs	2007-03-01 14:20:47.000000000 +0530
+++ linux-2.6.20-vatsa/kernel/Makefile	2007-03-01 16:52:50.000000000 +0530
@@ -50,6 +50,7 @@ obj-$(CONFIG_RELAY) += relay.o
 obj-$(CONFIG_UTS_NS) += utsname.o
 obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
 obj-$(CONFIG_TASKSTATS) += taskstats.o tsacct.o
+obj-$(CONFIG_RCFS) += rcfs.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
diff -puN kernel/nsproxy.c~rcfs kernel/nsproxy.c
--- linux-2.6.20/kernel/nsproxy.c~rcfs	2007-03-01 14:20:47.000000000 +0530
+++ linux-2.6.20-vatsa/kernel/nsproxy.c	2007-03-01 14:20:47.000000000 +0530
@@ -23,6 +23,11 @@
 
 struct nsproxy init_nsproxy = INIT_NSPROXY(init_nsproxy);
 
+#ifdef CONFIG_RCFS
+static LIST_HEAD(nslisthead);
+static DEFINE_SPINLOCK(nslistlock);
+#endif
+
 static inline void get_nsproxy(struct nsproxy *ns)
 {
 	atomic_inc(&ns->count);
@@ -71,6 +76,12 @@ struct nsproxy *dup_namespaces(struct ns
 			get_pid_ns(ns->pid_ns);
 	}
 
+#ifdef CONFIG_RCFS
+	spin_lock(&nslistlock);
+	list_add(&ns->list, &nslisthead);
+	spin_unlock(&nslistlock);
+#endif
+
 	return ns;
 }
 
@@ -145,5 +156,44 @@ void free_nsproxy(struct nsproxy *ns)
 		put_ipc_ns(ns->ipc_ns);
 	if (ns->pid_ns)
 		put_pid_ns(ns->pid_ns);
+#ifdef CONFIG_RCFS
+	spin_lock(&nslistlock);
+	list_del(&ns->list);
+	spin_unlock(&nslistlock);
+#endif
 	kfree(ns);
 }
+
+#ifdef CONFIG_RCFS
+struct nsproxy *find_nsproxy(struct nsproxy *target)
+{
+	struct nsproxy *ns;
+	int i = 0;
+
+	spin_lock(&nslistlock);
+	list_for_each_entry(ns, &nslisthead, list) {
+		for (i= 0; i < CONFIG_MAX_RC_SUBSYS; ++i)
+			if (ns->ctlr_data[i] != target->ctlr_data[i])
+				break;
+
+		if (i == CONFIG_MAX_RC_SUBSYS) {
+			/* Found a hit */
+			get_nsproxy(ns);
+			spin_unlock(&nslistlock);
+			return ns;
+		}
+	}
+
+	spin_unlock(&nslistlock);
+
+	ns = dup_namespaces(target);
+	return ns;
+}
+
+int __init namespaces_init(void)
+{
+	list_add(&init_nsproxy.list, &nslisthead);
+
+	return 0;
+}
+#endif
diff -puN /dev/null kernel/rcfs.c
--- /dev/null	2006-02-25 03:06:56.000000000 +0530
+++ linux-2.6.20-vatsa/kernel/rcfs.c	2007-03-01 16:53:24.000000000 +0530
@@ -0,0 +1,1138 @@
+/*
+ *  kernel/rcfs.c
+ *
+ *  Generic resource container 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/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 <linux/nsproxy.h>
+#include <linux/rcfs.h>
+
+#include <asm/uaccess.h>
+#include <asm/atomic.h>
+#include <linux/mutex.h>
+
+#define RCFS_SUPER_MAGIC           0x27e0eb
+
+/* A rcfs_root represents the root of a resource control hierarchy,
+ * and may be associated with a superblock to form an active
+ * hierarchy */
+struct rcfs_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;
+};
+
+static DEFINE_MUTEX(manage_mutex);
+
+/* The set of hierarchies in use */
+static struct rcfs_root rootnode[CONFIG_MAX_RC_HIERARCHIES];
+
+static struct rc_subsys *subsys[CONFIG_MAX_RC_SUBSYS];
+static int subsys_count = 0;
+
+/* for_each_subsys() allows you to act on each subsystem attached to
+ * an active hierarchy */
+#define for_each_subsys(root, _ss) \
+list_for_each_entry(_ss, &root->subsys_list, sibling)
+
+/* Does a container directory have sub-directories under it ? */
+static int dir_empty(struct dentry *dentry)
+{
+	struct dentry *d;
+	int rc = 1;
+
+	spin_lock(&dcache_lock);
+	list_for_each_entry(d, &dentry->d_subdirs, d_u.d_child) {
+		if (S_ISDIR(d->d_inode->i_mode)) {
+			rc = 0;
+			break;
+		}
+	}
+	spin_unlock(&dcache_lock);
+
+	return rc;
+}
+
+static int rebind_subsystems(struct rcfs_root *root, unsigned long final_bits)
+{
+	unsigned long added_bits, removed_bits;
+	int i, hierarchy;
+
+	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 < subsys_count; i++) {
+		unsigned long long bit = 1ull << i;
+		struct rc_subsys *ss = subsys[i];
+
+		if (!(bit & added_bits))
+			continue;
+		if (ss->hierarchy != 0) {
+			/* Subsystem isn't free */
+			return -EBUSY;
+		}
+	}
+
+	/* Currently we don't handle adding/removing subsystems when
+	 * any subdirectories exist. This is theoretically supportable
+	 * but involves complex erro r handling, so it's being left until
+	 * later */
+	/*
+	if (!dir_empty(root->sb->s_root))
+		return -EBUSY;
+	*/
+
+	hierarchy = rootnode - root;
+
+	/* Process each subsystem */
+	for (i = 0; i < subsys_count; i++) {
+		struct rc_subsys *ss = subsys[i];
+		unsigned long bit = 1UL << i;
+		if (bit & added_bits) {
+			/* We're binding this subsystem to this hierarchy */
+			list_add(&ss->sibling, &root->subsys_list);
+			rcu_assign_pointer(ss->hierarchy, hierarchy);
+		} else if (bit & removed_bits) {
+			/* We're removing this subsystem */
+			rcu_assign_pointer(subsys[i]->hierarchy, 0);
+			list_del(&ss->sibling);
+		}
+	}
+	root->subsys_bits = final_bits;
+	synchronize_rcu();	/* needed ? */
+
+	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 rcfs_put_super(struct super_block *sb) {
+
+	struct rcfs_root *root = sb->s_fs_info;
+	int ret;
+
+	mutex_lock(&manage_mutex);
+
+	BUG_ON(!root->subsys_bits);
+
+	/* Rebind all subsystems back to the default hierarchy */
+	ret = rebind_subsystems(root, 0);
+	root->sb = NULL;
+	sb->s_fs_info = NULL;
+
+	mutex_unlock(&manage_mutex);
+}
+
+static int rcfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
+{
+	struct rcfs_root *root = vfs->mnt_sb->s_fs_info;
+	struct rc_subsys *ss;
+
+	for_each_subsys(root, ss)
+		seq_printf(seq, ",%s", ss->name);
+
+	return 0;
+}
+
+/* Convert a hierarchy specifier into a bitmask. LL=manage_mutex */
+static int parse_rcfs_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 << subsys_count) - 1;
+		} else {
+			struct rc_subsys *ss;
+			int i;
+			for (i = 0; i < subsys_count; i++) {
+				ss = subsys[i];
+				if (!strcmp(token, ss->name)) {
+					*bits |= 1 << i;
+					break;
+				}
+			}
+			if (i == subsys_count)
+				return -ENOENT;
+		}
+	}
+
+	/* We can't have an empty hierarchy */
+	if (!*bits)
+		return -EINVAL;
+
+	return 0;
+}
+
+static struct backing_dev_info rcfs_backing_dev_info = {
+	.ra_pages = 0,		/* No readahead */
+	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
+};
+
+static struct inode *rcfs_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 = &rcfs_backing_dev_info;
+	}
+	return inode;
+}
+
+static struct super_operations rcfs_sb_ops = {
+	.statfs = simple_statfs,
+	.drop_inode = generic_delete_inode,
+	.put_super = rcfs_put_super,
+	.show_options = rcfs_show_options,
+	//.remount_fs = rcfs_remount,
+};
+
+static struct inode_operations rcfs_dir_inode_operations;
+static int rcfs_create_dir(struct nsproxy *ns, struct dentry *dentry,
+				int mode);
+static int rcfs_populate_dir(struct dentry *d);
+static void rcfs_d_remove_dir(struct dentry *dentry);
+
+static int rcfs_fill_super(struct super_block *sb, void *options,
+				int unused_silent)
+{
+	struct inode *inode;
+	struct dentry *root;
+	struct rcfs_root *hroot = options;
+
+	sb->s_blocksize = PAGE_CACHE_SIZE;
+	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
+	sb->s_magic = RCFS_SUPER_MAGIC;
+	sb->s_op = &rcfs_sb_ops;
+
+	inode = rcfs_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 = &rcfs_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;
+	get_task_namespaces(&init_task);
+	root->d_fsdata = init_task.nsproxy;
+	sb->s_fs_info = hroot;
+	hroot->sb = sb;
+
+	return 0;
+}
+
+/* Count the number of tasks in a container. Could be made more
+ * time-efficient but less space-efficient with more linked lists
+ * running through each container and the container_group structures
+ * that referenced it. */
+
+int rcfs_task_count(const struct nsproxy *ns)
+{
+	int count = 0;
+
+	count = atomic_read(&ns->count);
+
+	return count;
+}
+
+/*
+ * Stuff for reading the 'tasks' file.
+ *
+ * Reading this file can return large amounts of data if a container has
+ * *lots* of attached tasks. So it may need several calls to read(),
+ * but we cannot guarantee that the information we produce is correct
+ * unless we produce it entirely atomically.
+ *
+ * Upon tasks file open(), a struct ctr_struct is allocated, that
+ * will have a pointer to an array (also allocated here).  The struct
+ * ctr_struct * is stored in file->private_data.  Its resources will
+ * be freed by release() when the file is closed.  The array is used
+ * to sprintf the PIDs and then used by read().
+ */
+
+/* containers_tasks_read array */
+
+struct ctr_struct {
+	char *buf;
+	int bufsz;
+};
+
+/*
+ * Load into 'pidarray' up to 'npids' of the tasks using container
+ * 'cont'.  Return actual number of pids loaded.  No need to
+ * task_lock(p) when reading out p->container, since we're in an RCU
+ * read section, so the container_group can't go away, and is
+ * immutable after creation.
+ */
+static int pid_array_load(pid_t *pidarray, int npids, struct nsproxy *ns)
+{
+	int n = 0;
+	struct task_struct *g, *p;
+
+	rcu_read_lock();
+	read_lock(&tasklist_lock);
+
+	do_each_thread(g, p) {
+		if (p->nsproxy == ns) {
+			pidarray[n++] = pid_nr(task_pid(p));
+			if (unlikely(n == npids))
+				goto array_full;
+		}
+	} while_each_thread(g, p);
+
+array_full:
+	read_unlock(&tasklist_lock);
+	rcu_read_unlock();
+	return n;
+}
+
+static int cmppid(const void *a, const void *b)
+{
+	return *(pid_t *)a - *(pid_t *)b;
+}
+
+/*
+ * Convert array 'a' of 'npids' pid_t's to a string of newline separated
+ * decimal pids in 'buf'.  Don't write more than 'sz' chars, but return
+ * count 'cnt' of how many chars would be written if buf were large enough.
+ */
+static int pid_array_to_buf(char *buf, int sz, pid_t *a, int npids)
+{
+	int cnt = 0;
+	int i;
+
+	for (i = 0; i < npids; i++)
+		cnt += snprintf(buf + cnt, max(sz - cnt, 0), "%d\n", a[i]);
+	return cnt;
+}
+
+static inline struct nsproxy *__d_ns(struct dentry *dentry)
+{
+	return dentry->d_fsdata;
+}
+
+
+static inline struct cftype *__d_cft(struct dentry *dentry)
+{
+	return dentry->d_fsdata;
+}
+
+/*
+ * Handle an open on 'tasks' file.  Prepare a buffer listing the
+ * process id's of tasks currently attached to the container being opened.
+ *
+ * Does not require any specific container mutexes, and does not take any.
+ */
+static int rcfs_tasks_open(struct inode *unused, struct file *file)
+{
+	struct nsproxy *ns = __d_ns(file->f_dentry->d_parent);
+	struct ctr_struct *ctr;
+	pid_t *pidarray;
+	int npids;
+	char c;
+
+	if (!(file->f_mode & FMODE_READ))
+		return 0;
+
+	ctr = kmalloc(sizeof(*ctr), GFP_KERNEL);
+	if (!ctr)
+		goto err0;
+
+	/*
+	 * If container gets more users after we read count, we won't have
+	 * enough space - tough.  This race is indistinguishable to the
+	 * caller from the case that the additional container users didn't
+	 * show up until sometime later on.
+	 */
+	npids = rcfs_task_count(ns);
+	pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL);
+	if (!pidarray)
+		goto err1;
+
+	npids = pid_array_load(pidarray, npids, ns);
+	sort(pidarray, npids, sizeof(pid_t), cmppid, NULL);
+
+	/* Call pid_array_to_buf() twice, first just to get bufsz */
+	ctr->bufsz = pid_array_to_buf(&c, sizeof(c), pidarray, npids) + 1;
+	ctr->buf = kmalloc(ctr->bufsz, GFP_KERNEL);
+	if (!ctr->buf)
+		goto err2;
+	ctr->bufsz = pid_array_to_buf(ctr->buf, ctr->bufsz, pidarray, npids);
+
+	kfree(pidarray);
+	file->private_data = ctr;
+	return 0;
+
+err2:
+	kfree(pidarray);
+err1:
+	kfree(ctr);
+err0:
+	return -ENOMEM;
+}
+
+static ssize_t rcfs_tasks_read(struct nsproxy *ns,
+				    struct cftype *cft,
+				    struct file *file, char __user *buf,
+				    size_t nbytes, loff_t *ppos)
+{
+	struct ctr_struct *ctr = file->private_data;
+
+	if (*ppos + nbytes > ctr->bufsz)
+		nbytes = ctr->bufsz - *ppos;
+	if (copy_to_user(buf, ctr->buf + *ppos, nbytes))
+		return -EFAULT;
+	*ppos += nbytes;
+	return nbytes;
+}
+
+static int rcfs_tasks_release(struct inode *unused_inode, struct file *file)
+{
+	struct ctr_struct *ctr;
+
+	if (file->f_mode & FMODE_READ) {
+		ctr = file->private_data;
+		kfree(ctr->buf);
+		kfree(ctr);
+	}
+	return 0;
+}
+/*
+ * Attach task 'tsk' to container 'cont'
+ *
+ * Call holding manage_mutex.  May take callback_mutex and task_lock of
+ * the task 'pid' during call.
+ */
+
+static int attach_task(struct dentry *d, struct task_struct *tsk)
+{
+	int retval = 0;
+	struct rc_subsys *ss;
+	struct rcfs_root *root = d->d_sb->s_fs_info;
+	struct nsproxy *ns = __d_ns(d->d_parent);
+	struct nsproxy *oldns, *newns;
+	struct nsproxy dupns;
+
+	printk ("attaching task %d to %p \n", tsk->pid, ns);
+
+	/* Nothing to do if the task is already in that container */
+	if (tsk->nsproxy == ns)
+		return 0;
+
+	for_each_subsys(root, ss) {
+		if (ss->can_attach) {
+			retval = ss->can_attach(ss, ns, tsk);
+			if (retval) {
+				put_task_struct(tsk);
+				return retval;
+			}
+		}
+	}
+
+	/* Locate or allocate a new container_group for this task,
+	 * based on its final set of containers */
+ 	get_task_namespaces(tsk);
+	oldns = tsk->nsproxy;
+	memcpy(&dupns, oldns, sizeof(dupns));
+	for_each_subsys(root, ss)
+		dupns.ctlr_data[ss->subsys_id] = ns->ctlr_data[ss->subsys_id];
+	newns = find_nsproxy(&dupns);
+	printk ("find_nsproxy returned %p \n", newns);
+	if (!newns) {
+		put_nsproxy(tsk->nsproxy);
+		put_task_struct(tsk);
+		return -ENOMEM;
+	}
+
+	task_lock(tsk);	/* Needed ? */
+	rcu_assign_pointer(tsk->nsproxy, newns);
+	task_unlock(tsk);
+
+	for_each_subsys(root, ss) {
+		if (ss->attach)
+			ss->attach(ss, newns, oldns, tsk);
+	}
+
+	synchronize_rcu();
+	put_nsproxy(oldns);
+	return 0;
+}
+
+
+/*
+ * Attach task with pid 'pid' to container 'cont'. Call with
+ * manage_mutex, may take callback_mutex and task_lock of task
+ *
+ */
+
+static int attach_task_by_pid(struct dentry *d, char *pidbuf)
+{
+	pid_t pid;
+	struct task_struct *tsk;
+	int ret;
+
+	if (sscanf(pidbuf, "%d", &pid) != 1)
+		return -EIO;
+
+	if (pid) {
+		read_lock(&tasklist_lock);
+
+		tsk = find_task_by_pid(pid);
+		if (!tsk || tsk->flags & PF_EXITING) {
+			read_unlock(&tasklist_lock);
+			return -ESRCH;
+		}
+
+		get_task_struct(tsk);
+		read_unlock(&tasklist_lock);
+
+		if ((current->euid) && (current->euid != tsk->uid)
+		    && (current->euid != tsk->suid)) {
+			put_task_struct(tsk);
+			return -EACCES;
+		}
+	} else {
+		tsk = current;
+		get_task_struct(tsk);
+	}
+
+	ret = attach_task(d, tsk);
+	put_task_struct(tsk);
+	return ret;
+}
+
+/* The various types of files and directories in a container file system */
+
+typedef enum {
+	FILE_ROOT,
+	FILE_DIR,
+	FILE_TASKLIST,
+} rcfs_filetype_t;
+
+static ssize_t rcfs_common_file_write(struct nsproxy *ns, struct cftype *cft,
+					   struct file *file,
+					   const char __user *userbuf,
+					   size_t nbytes, loff_t *unused_ppos)
+{
+	rcfs_filetype_t type = cft->private;
+	char *buffer;
+	int retval = 0;
+
+	if (nbytes >= PATH_MAX)
+		return -E2BIG;
+
+	/* +1 for nul-terminator */
+	if ((buffer = kmalloc(nbytes + 1, GFP_KERNEL)) == 0)
+		return -ENOMEM;
+
+	if (copy_from_user(buffer, userbuf, nbytes)) {
+		retval = -EFAULT;
+		goto out1;
+	}
+	buffer[nbytes] = 0;	/* nul-terminate */
+
+	mutex_lock(&manage_mutex);
+
+	ns = __d_ns(file->f_dentry);
+	if (!ns) {
+		retval = -ENODEV;
+		goto out2;
+	}
+
+	switch (type) {
+	case FILE_TASKLIST:
+		retval = attach_task_by_pid(file->f_dentry, buffer);
+		break;
+	default:
+		retval = -EINVAL;
+		goto out2;
+	}
+
+	if (retval == 0)
+		retval = nbytes;
+out2:
+	mutex_unlock(&manage_mutex);
+out1:
+	kfree(buffer);
+	return retval;
+}
+
+static struct cftype cft_tasks = {
+	.name = "tasks",
+	.open = rcfs_tasks_open,
+	.read = rcfs_tasks_read,
+	.write = rcfs_common_file_write,
+	.release = rcfs_tasks_release,
+	.private = FILE_TASKLIST,
+};
+
+static ssize_t rcfs_file_write(struct file *file, const char __user *buf,
+						size_t nbytes, loff_t *ppos)
+{
+	struct cftype *cft = __d_cft(file->f_dentry);
+	struct nsproxy *ns = __d_ns(file->f_dentry->d_parent);
+	if (!cft)
+		return -ENODEV;
+	if (!cft->write)
+		return -EINVAL;
+
+	return cft->write(ns, cft, file, buf, nbytes, ppos);
+}
+
+static ssize_t rcfs_file_read(struct file *file, char __user *buf,
+				   size_t nbytes, loff_t *ppos)
+{
+	struct cftype *cft = __d_cft(file->f_dentry);
+	struct nsproxy *ns = __d_ns(file->f_dentry->d_parent);
+	if (!cft)
+		return -ENODEV;
+	if (!cft->read)
+		return -EINVAL;
+
+	return cft->read(ns, cft, file, buf, nbytes, ppos);
+}
+
+static int rcfs_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 rcfs_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;
+}
+
+/*
+ *	rcfs_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 rcfs_create(struct nsproxy *parent, struct dentry *dentry,
+			     int mode)
+{
+	struct rcfs_root *root = dentry->d_sb->s_fs_info;
+	int err = 0;
+	struct rc_subsys *ss;
+	struct super_block *sb = dentry->d_sb;
+	struct nsproxy *ns;
+
+	ns = dup_namespaces(parent);
+	if (!ns)
+		return -ENOMEM;
+
+	printk ("rcfs_create: ns = %p \n", ns);
+
+	/* 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 manage_mutex, since the sb can't
+	 * disappear while someone has an open control file on the
+	 * fs */
+	atomic_inc(&sb->s_active);
+
+	mutex_lock(&manage_mutex);
+
+	for_each_subsys(root, ss) {
+		err = ss->create(ss, ns, parent);
+		if (err) {
+			printk ("%s create failed \n", ss->name);
+			goto err_destroy;
+		}
+	}
+
+	err = rcfs_create_dir(ns, dentry, mode);
+	if (err < 0)
+		goto err_destroy;
+
+	/* The container directory was pre-locked for us */
+	BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
+
+	err = rcfs_populate_dir(dentry);
+	/* If err < 0, we have a half-filled directory - oh well ;) */
+
+	mutex_unlock(&manage_mutex);
+	mutex_unlock(&dentry->d_inode->i_mutex);
+
+	return 0;
+
+err_destroy:
+
+	for_each_subsys(root, ss)
+		ss->destroy(ss, ns);
+
+	mutex_unlock(&manage_mutex);
+
+	/* Release the reference count that we took on the superblock */
+	deactivate_super(sb);
+
+	free_nsproxy(ns);
+	return err;
+}
+
+static int rcfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
+{
+	struct nsproxy *ns_parent = dentry->d_parent->d_fsdata;
+
+	printk ("rcfs_mkdir : parent_nsproxy = %p (%p) \n", ns_parent, dentry->d_fsdata);
+
+	/* the vfs holds inode->i_mutex already */
+	return rcfs_create(ns_parent, dentry, mode | S_IFDIR);
+}
+
+static int rcfs_rmdir(struct inode *unused_dir, struct dentry *dentry)
+{
+	struct nsproxy *ns = dentry->d_fsdata;
+	struct dentry *d;
+	struct rc_subsys *ss;
+	struct super_block *sb = dentry->d_sb;
+	struct rcfs_root *root = dentry->d_sb->s_fs_info;
+
+	/* the vfs holds both inode->i_mutex already */
+
+	mutex_lock(&manage_mutex);
+
+	if (atomic_read(&ns->count) > 1) {
+		mutex_unlock(&manage_mutex);
+		return -EBUSY;
+	}
+
+	if (!dir_empty(dentry)) {
+		mutex_unlock(&manage_mutex);
+		return -EBUSY;
+	}
+
+	for_each_subsys(root, ss)
+		ss->destroy(ss, ns);
+
+	spin_lock(&dentry->d_lock);
+	d = dget(dentry);
+	spin_unlock(&d->d_lock);
+
+	rcfs_d_remove_dir(d);
+	dput(d);
+
+	mutex_unlock(&manage_mutex);
+	/* Drop the active superblock reference that we took when we
+	 * created the container */
+	deactivate_super(sb);
+	return 0;
+}
+
+static struct file_operations rcfs_file_operations = {
+	.read = rcfs_file_read,
+	.write = rcfs_file_write,
+	.llseek = generic_file_llseek,
+	.open = rcfs_file_open,
+	.release = rcfs_file_release,
+};
+
+static struct inode_operations rcfs_dir_inode_operations = {
+	.lookup = simple_lookup,
+	.mkdir = rcfs_mkdir,
+	.rmdir = rcfs_rmdir,
+	//.rename = rcfs_rename,
+};
+
+static int rcfs_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 = rcfs_new_inode(mode, sb);
+	if (!inode)
+		return -ENOMEM;
+
+	if (S_ISDIR(mode)) {
+		inode->i_op = &rcfs_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 = &rcfs_file_operations;
+	}
+
+	d_instantiate(dentry, inode);
+	dget(dentry);	/* Extra count - pin the dentry in core */
+	return 0;
+}
+
+/*
+ *	rcfs_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 rcfs_create_dir(struct nsproxy *ns, struct dentry *dentry,
+				int mode)
+{
+	struct dentry *parent;
+	int error = 0;
+
+	parent = dentry->d_parent;
+	if (IS_ERR(dentry))
+		return PTR_ERR(dentry);
+	error = rcfs_create_file(dentry, S_IFDIR | mode, dentry->d_sb);
+	if (!error) {
+		dentry->d_fsdata = ns;
+		inc_nlink(parent->d_inode);
+	}
+	dput(dentry);
+
+	return error;
+}
+
+static void rcfs_diput(struct dentry *dentry, struct inode *inode)
+{
+	/* is dentry a directory ? if so, kfree() associated container */
+	if (S_ISDIR(inode->i_mode)) {
+		struct nsproxy *ns = dentry->d_fsdata;
+
+		free_nsproxy(ns);
+		dentry->d_fsdata = NULL;
+	}
+	iput(inode);
+}
+
+static struct dentry_operations rcfs_dops = {
+	.d_iput = rcfs_diput,
+};
+
+static struct dentry *rcfs_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 = &rcfs_dops;
+	return d;
+}
+
+int rcfs_add_file(struct dentry *dir, const struct cftype *cft)
+{
+	struct dentry *dentry;
+	int error;
+
+	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
+	dentry = rcfs_get_dentry(dir, cft->name);
+	if (!IS_ERR(dentry)) {
+		error = rcfs_create_file(dentry, 0644 | S_IFREG, dir->d_sb);
+		if (!error)
+			dentry->d_fsdata = (void *)cft;
+		dput(dentry);
+	} else
+		error = PTR_ERR(dentry);
+	return error;
+}
+
+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 rcfs_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 rcfs_d_remove_dir(struct dentry *dentry)
+{
+	rcfs_clear_directory(dentry);
+
+	spin_lock(&dcache_lock);
+	list_del_init(&dentry->d_u.d_child);
+	spin_unlock(&dcache_lock);
+	remove_dir(dentry);
+}
+
+static int rcfs_populate_dir(struct dentry *d)
+{
+	int err;
+	struct rc_subsys *ss;
+	struct rcfs_root *root = d->d_sb->s_fs_info;
+
+	/* First clear out any existing files */
+	rcfs_clear_directory(d);
+
+	if ((err = rcfs_add_file(d, &cft_tasks)) < 0)
+		return err;
+
+	for_each_subsys(root, ss)
+		if (ss->populate && (err = ss->populate(ss, d)) < 0)
+			return err;
+
+	return 0;
+}
+
+static int rcfs_get_sb(struct file_system_type *fs_type,
+                         int flags, const char *unused_dev_name,
+                         void *data, struct vfsmount *mnt)
+{
+	int i;
+	unsigned long subsys_bits = 0;
+	int ret = 0;
+	struct rcfs_root *root = NULL;
+
+	mutex_lock(&manage_mutex);
+
+	/* First find the desired set of resource controllers */
+	ret = parse_rcfs_options(data, &subsys_bits);
+	if (ret)
+		goto out_unlock;
+
+	/* See if we already have a hierarchy containing this set */
+
+	for (i = 0; i < CONFIG_MAX_RC_HIERARCHIES; i++) {
+		root = &rootnode[i];
+		/* We match - use this hieracrchy */
+		if (root->subsys_bits == subsys_bits) break;
+		/* We clash - fail */
+		if (root->subsys_bits & subsys_bits) {
+			ret = -EBUSY;
+			goto out_unlock;
+		}
+	}
+
+	if (i == CONFIG_MAX_RC_HIERARCHIES) {
+		/* No existing hierarchy matched this set - but we
+		 * know that all the subsystems are free */
+		for (i = 0; i < CONFIG_MAX_RC_HIERARCHIES; i++) {
+			root = &rootnode[i];
+			if (!root->sb && !root->subsys_bits) break;
+		}
+	}
+
+	if (i == CONFIG_MAX_RC_HIERARCHIES) {
+		ret = -ENOSPC;
+		goto out_unlock;
+	}
+
+	if (!root->sb) {
+		BUG_ON(root->subsys_bits);
+		ret = get_sb_nodev(fs_type, flags, root,
+				   rcfs_fill_super, mnt);
+		if (ret)
+			goto out_unlock;
+
+		ret = rebind_subsystems(root, subsys_bits);
+		BUG_ON(ret);
+
+		/* It's safe to nest i_mutex inside manage_mutex in
+		 * this case, since no-one else can be accessing this
+		 * directory yet */
+		mutex_lock(&root->sb->s_root->d_inode->i_mutex);
+		rcfs_populate_dir(root->sb->s_root);
+		mutex_unlock(&root->sb->s_root->d_inode->i_mutex);
+
+	} else {
+		/* Reuse the existing superblock */
+		ret = simple_set_mnt(mnt, root->sb);
+		if (!ret)
+			atomic_inc(&root->sb->s_active);
+	}
+
+out_unlock:
+	mutex_unlock(&manage_mutex);
+	return ret;
+}
+
+static struct file_system_type rcfs_type = {
+	.name = "rcfs",
+	.get_sb = rcfs_get_sb,
+	.kill_sb = kill_litter_super,
+};
+
+int __init rcfs_init(void)
+{
+	int i, err;
+
+	for (i=0; i < CONFIG_MAX_RC_HIERARCHIES; ++i)
+		INIT_LIST_HEAD(&rootnode[i].subsys_list);
+
+	err = register_filesystem(&rcfs_type);
+
+	return err;
+}
+
+int rc_register_subsys(struct rc_subsys *new_subsys)
+{
+	int retval = 0;
+	int i;
+	int ss_id;
+
+	BUG_ON(new_subsys->hierarchy);
+	BUG_ON(new_subsys->active);
+
+	mutex_lock(&manage_mutex);
+
+	if (subsys_count == CONFIG_MAX_RC_SUBSYS) {
+		retval = -ENOSPC;
+		goto out;
+	}
+
+	/* Sanity check the subsystem */
+	if (!new_subsys->name ||
+	    (strlen(new_subsys->name) > MAX_CONTAINER_TYPE_NAMELEN) ||
+	    !new_subsys->create || !new_subsys->destroy) {
+		retval = -EINVAL;
+		goto out;
+	}
+
+	/* Check this isn't a duplicate */
+	for (i = 0; i < subsys_count; i++) {
+		if (!strcmp(subsys[i]->name, new_subsys->name)) {
+			retval = -EEXIST;
+			goto out;
+		}
+	}
+
+	/* Create the top container state for this subsystem */
+	ss_id = new_subsys->subsys_id = subsys_count;
+	retval = new_subsys->create(new_subsys, &init_nsproxy, NULL);
+	if (retval) {
+		new_subsys->subsys_id = -1;
+		goto out;
+	}
+
+	subsys[subsys_count++] = new_subsys;
+	new_subsys->active = 1;
+out:
+ 	mutex_unlock(&manage_mutex);
+ 	return retval;
+}
+
_
	
-- 
Regards,
vatsa