[PATCH] cpusets - big numa cpu and memory placement

This my cpuset patch, with the following changes in the last two weeks:

 1) Updated to 2.6.8.1-mm1
 2) [Simon Derr <Simon.Derr@bull.net>] Fix new cpuset to begin empty,
    not copied from parent.  Needed to avoid breaking exclusive property.
 3) [Dinakar Guniguntala <dino@in.ibm.com>] Finish initializing top
    cpuset from cpu_possible_map after smp_init() called.
 4) [Paul Jackson <pj@sgi.com>] Check on each call to __alloc_pages()
    if the current tasks cpuset mems_allowed has changed.  Use a cpuset
    generation number, bumped on any cpuset memory placement change,
    to make this check efficient.  Update the tasks mems_allowed from
    its cpuset, if the cpuset has changed.
 5) [Paul Jackson <pj@sgi.com>] If a task is moved to another cpuset,
    then update its cpus_allowed, using set_cpus_allowed().
 6) [Paul Jackson <pj@sgi.com>] Update Documentation/cpusets.txt to
    reflect above changes (4) and (5).

I continue to recommend the following patch for inclusion in your 2.6.9-*mm
series, when that opens.  It provides an important facility for high
performance computing on large systems.  Simon Derr of Bull (France) and
myself are the primary authors.  Erich Focht has indicated that NEC is also
a potential user of this patch on the TX-7 NUMA machines, and that he
"would very much welcome the inclusion of cpusets."

I offer this update to lkml, in order to invite continued feedback.

The one prerequiste patch for this cpuset patch was just posted before this
one.  That was a patch to provide a new bitmap list format, of which
cpusets is the first user.

This patch has been built on top of 2.6.8.1-mm1, for the arch's:

  i386 x86_64 sparc ia64 powerpc-405 powerpc-750 sparc64

with and without CONFIG_CPUSET.  It has been booted and tested on ia64
(sn2_defconfig, SN2 hardware).  The 'alpha' arch also built, except for
what seems to be an unrelated toolchain problem (crosstool ld sigsegv) in
the final link step.

===

Cpusets provide a mechanism for assigning a set of CPUs and Memory Nodes to
a set of tasks.

Cpusets constrain the CPU and Memory placement of tasks to only the
processor and memory resources within a tasks current cpuset.  They form a
nested hierarchy visible in a virtual file system.  These are the essential
hooks, beyond what is already present, required to manage dynamic job
placement on large systems.

Cpusets require small kernel hooks in init, exit, fork, mempolicy,
sched_setaffinity, page_alloc and vmscan.  And they require a "struct
cpuset" pointer, a cpuset_mems_generation, and a "mems_allowed" nodemask_t
(to go along with the "cpus_allowed" cpumask_t that's already there) in
each task struct.

These hooks:
  1) establish and propagate cpusets,
  2) enforce CPU placement in sched_setaffinity,
  3) enforce Memory placement in mbind and sys_set_mempolicy,
  4) restrict page allocation and scanning to mems_allowed, and
  5) restrict migration and set_cpus_allowed to cpus_allowed.

The other required hook, restricting task scheduling to CPUs in a tasks
cpus_allowed mask, is already present.

Cpusets extend the usefulness of, the existing placement support that was
added to Linux 2.6 kernels: sched_setaffinity() for CPU placement, and
mbind() and set_mempolicy() for memory placement.  On smaller or dedicated
use systems, the existing calls are often sufficient.

On larger NUMA systems, running more than one, performance critical, job,
it is necessary to be able to manage jobs in their entirety.  This includes
providing a job with exclusive CPU and memory that no other job can use,
and being able to list all tasks currently in a cpuset.

A given job running within a cpuset, would likely use the existing
placement calls to manage its CPU and memory placement in more detail.

Cpusets are named, nested sets of CPUs and Memory Nodes.  Each cpuset is
represented by a directory in the cpuset virtual file system, normally
mounted at /dev/cpuset.

Each cpuset directory provides the following files, which can be
read and written:

  cpus:
      List of CPUs allowed to tasks in that cpuset.

  mems:
      List of Memory Nodes allowed to tasks in that cpuset.

  tasks:
      List of pid's of tasks in that cpuset.

  cpu_exclusive:
      Flag (0 or 1) - if set, cpuset has exclusive use of
      its CPUs (no sibling or cousin cpuset may overlap CPUs).

  mem_exclusive:
      Flag (0 or 1) - if set, cpuset has exclusive use of
      its Memory Nodes (no sibling or cousin may overlap).

  notify_on_release:
      Flag (0 or 1) - if set, then /sbin/cpuset_release_agent
      will be invoked, with the name (/dev/cpuset relative path)
      of that cpuset in argv[1], when the last user of it (task
      or child cpuset) goes away.  This supports automatic
      cleanup of abandoned cpusets.

In addition one new filetype is added to the /proc file system:

  /proc/<pid>/cpuset:
      For each task (pid), list its cpuset path, relative to the
      root of the cpuset file system.  This file is read-only.

New cpusets are created using 'mkdir' (at the shell or in C).  Old ones are
removed using 'rmdir'.  The above files are accessed using read(2) and
write(2) system calls, or shell commands such as 'cat' and 'echo'.

The CPUs and Memory Nodes in a given cpuset are always a subset of its
parent.  The root cpuset has all possible CPUs and Memory Nodes in the
system.  A cpuset may be exclusive (cpu or memory) only if its parent is
similarly exclusive.

See further Documentation/cpusets.txt, at the top of the following
patch.


/proc interface:

It is useful, when learning and making new uses of cpusets and placement to be
able to see what are the current value of a tasks cpus_allowed and
mems_allowed, which are the actual placement used by the kernel scheduler and
memory allocator.

The cpus_allowed and mems_allowed values are needed by user space apps that
are micromanaging placement, such as when moving an app to a obtained by
that app within its cpuset using sched_setaffinity, mbind and
set_mempolicy.

The cpus_allowed value is also available via the sched_getaffinity system
call.  But since the entire rest of the cpuset API, including the display
of mems_allowed added here, is via an ascii style presentation in /proc and
/dev/cpuset, it is worth the extra couple lines of code to display
cpus_allowed in the same way.

This patch adds the display of these two fields to the 'status' file in the
/proc/<pid> directory of each task.  The fields are only added if
CONFIG_CPUSETS is enabled (which is also needed to define the mems_allowed
field of each task).  The new output lines look like:

  $ tail -2 /proc/1/status
  Cpus_allowed:   ffffffff,ffffffff,ffffffff,ffffffff
  Mems_allowed:   ffffffff,ffffffff


Signed-off-by: Dinakar Guniguntala <dino@in.ibm.com>
Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Simon Derr <simon.derr@bull.net>
Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

5 files changed, 1545 insertions, 1 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index 0ac3efc9d071..d1a273ee6db6 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -18,6 +18,7 @@ obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_PM) += power/
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_COMPAT) += compat.o
+obj-$(CONFIG_CPUSETS) += cpuset.o
 obj-$(CONFIG_IKCONFIG) += configs.o
 obj-$(CONFIG_IKCONFIG_PROC) += configs.o
 obj-$(CONFIG_STOP_MACHINE) += stop_machine.o
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
new file mode 100644
index 000000000000..44c03c666b01
--- /dev/null
+++ b/kernel/cpuset.c
@@ -0,0 +1,1534 @@
+/*
+ *  kernel/cpuset.c
+ *
+ *  Processor and Memory placement constraints for sets of tasks.
+ *
+ *  Copyright (C) 2003 BULL SA.
+ *  Copyright (C) 2004 Silicon Graphics, Inc.
+ *
+ *  Portions derived from Patrick Mochel's sysfs code.
+ *  sysfs is Copyright (c) 2001-3 Patrick Mochel
+ *  Portions Copyright (c) 2004 Silicon Graphics, Inc.
+ *
+ *  2003-10-10 Written by Simon Derr <simon.derr@bull.net>
+ *  2003-10-22 Updates by Stephen Hemminger.
+ *  2004 May-July Rework by Paul Jackson <pj@sgi.com>
+ *
+ *  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/config.h>
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/cpuset.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/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/sched.h>
+#include <linux/seq_file.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 <asm/semaphore.h>
+
+#define CPUSET_SUPER_MAGIC 		0x27e0eb
+
+struct cpuset {
+	unsigned long flags;		/* "unsigned long" so bitops work */
+	cpumask_t cpus_allowed;		/* CPUs allowed to tasks in cpuset */
+	nodemask_t mems_allowed;	/* Memory Nodes allowed to tasks */
+
+	atomic_t count;			/* count tasks using this cpuset */
+
+	/*
+	 * We link our 'sibling' struct into our parents 'children'.
+	 * Our children link their 'sibling' into our 'children'.
+	 */
+	struct list_head sibling;	/* my parents children */
+	struct list_head children;	/* my children */
+
+	struct cpuset *parent;		/* my parent */
+	struct dentry *dentry;		/* cpuset fs entry */
+
+	/*
+	 * Copy of global cpuset_mems_generation as of the most
+	 * recent time this cpuset changed its mems_allowed.
+	 */
+	 int mems_generation;
+};
+
+/* bits in struct cpuset flags field */
+typedef enum {
+	CS_CPU_EXCLUSIVE,
+	CS_MEM_EXCLUSIVE,
+	CS_REMOVED,
+	CS_NOTIFY_ON_RELEASE
+} cpuset_flagbits_t;
+
+/* convenient tests for these bits */
+static inline int is_cpu_exclusive(const struct cpuset *cs)
+{
+	return !!test_bit(CS_CPU_EXCLUSIVE, &cs->flags);
+}
+
+static inline int is_mem_exclusive(const struct cpuset *cs)
+{
+	return !!test_bit(CS_MEM_EXCLUSIVE, &cs->flags);
+}
+
+static inline int is_removed(const struct cpuset *cs)
+{
+	return !!test_bit(CS_REMOVED, &cs->flags);
+}
+
+static inline int notify_on_release(const struct cpuset *cs)
+{
+	return !!test_bit(CS_NOTIFY_ON_RELEASE, &cs->flags);
+}
+
+/*
+ * Increment this atomic integer everytime any cpuset changes its
+ * mems_allowed value.  Users of cpusets can track this generation
+ * number, and avoid having to lock and reload mems_allowed unless
+ * the cpuset they're using changes generation.
+ *
+ * A single, global generation is needed because attach_task() could
+ * reattach a task to a different cpuset, which must not have its
+ * generation numbers aliased with those of that tasks previous cpuset.
+ *
+ * Generations are needed for mems_allowed because one task cannot
+ * modify anothers memory placement.  So we must enable every task,
+ * on every visit to __alloc_pages(), to efficiently check whether
+ * its current->cpuset->mems_allowed has changed, requiring an update
+ * of its current->mems_allowed.
+ */
+static atomic_t cpuset_mems_generation = ATOMIC_INIT(1);
+
+static struct cpuset top_cpuset = {
+	.flags = ((1 << CS_CPU_EXCLUSIVE) | (1 << CS_MEM_EXCLUSIVE)),
+	.cpus_allowed = CPU_MASK_ALL,
+	.mems_allowed = NODE_MASK_ALL,
+	.count = ATOMIC_INIT(0),
+	.sibling = LIST_HEAD_INIT(top_cpuset.sibling),
+	.children = LIST_HEAD_INIT(top_cpuset.children),
+	.parent = NULL,
+	.dentry = NULL,
+	.mems_generation = 0,
+};
+
+static struct vfsmount *cpuset_mount;
+static struct super_block *cpuset_sb = NULL;
+
+/*
+ * cpuset_sem should be held by anyone who is depending on the children
+ * or sibling lists of any cpuset, or performing non-atomic operations
+ * on the flags or *_allowed values of a cpuset, such as raising the
+ * CS_REMOVED flag bit iff it is not already raised, or reading and
+ * conditionally modifying the *_allowed values.  One kernel global
+ * cpuset semaphore should be sufficient - these things don't change
+ * that much.
+ *
+ * The code that modifies cpusets holds cpuset_sem across the entire
+ * operation, from cpuset_common_file_write() down, single threading
+ * all cpuset modifications (except for counter manipulations from
+ * fork and exit) across the system.  This presumes that cpuset
+ * modifications are rare - better kept simple and safe, even if slow.
+ *
+ * The code that reads cpusets, such as in cpuset_common_file_read()
+ * and below, only holds cpuset_sem across small pieces of code, such
+ * as when reading out possibly multi-word cpumasks and nodemasks, as
+ * the risks are less, and the desire for performance a little greater.
+ * The proc_cpuset_show() routine needs to hold cpuset_sem to insure
+ * that no cs->dentry is NULL, as it walks up the cpuset tree to root.
+ *
+ * The hooks from fork and exit, cpuset_fork() and cpuset_exit(), don't
+ * (usually) grab cpuset_sem.  These are the two most performance
+ * critical pieces of code here.  The exception occurs on exit(),
+ * if the last task using a cpuset exits, and the cpuset was marked
+ * notify_on_release.  In that case, the cpuset_sem is taken, the
+ * path to the released cpuset calculated, and a usermode call made
+ * to /sbin/cpuset_release_agent with the name of the cpuset (path
+ * relative to the root of cpuset file system) as the argument.
+ *
+ * A cpuset can only be deleted if both its 'count' of using tasks is
+ * zero, and its list of 'children' cpusets is empty.  Since all tasks
+ * in the system use _some_ cpuset, and since there is always at least
+ * one task in the system (init, pid == 1), therefore, top_cpuset
+ * always has either children cpusets and/or using tasks.  So no need
+ * for any special hack to ensure that top_cpuset cannot be deleted.
+ */
+
+static DECLARE_MUTEX(cpuset_sem);
+
+/*
+ * A couple of forward declarations required, due to cyclic reference loop:
+ *  cpuset_mkdir -> cpuset_create -> cpuset_populate_dir -> cpuset_add_file
+ *  -> cpuset_create_file -> cpuset_dir_inode_operations -> cpuset_mkdir.
+ */
+
+static int cpuset_mkdir(struct inode *dir, struct dentry *dentry, int mode);
+static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry);
+
+static struct backing_dev_info cpuset_backing_dev_info = {
+	.ra_pages = 0,		/* No readahead */
+	.memory_backed = 1,	/* Does not contribute to dirty memory */
+};
+
+static struct inode *cpuset_new_inode(mode_t mode)
+{
+	struct inode *inode = new_inode(cpuset_sb);
+
+	if (inode) {
+		inode->i_mode = mode;
+		inode->i_uid = current->fsuid;
+		inode->i_gid = current->fsgid;
+		inode->i_blksize = PAGE_CACHE_SIZE;
+		inode->i_blocks = 0;
+		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+		inode->i_mapping->backing_dev_info = &cpuset_backing_dev_info;
+	}
+	return inode;
+}
+
+static void cpuset_diput(struct dentry *dentry, struct inode *inode)
+{
+	/* is dentry a directory ? if so, kfree() associated cpuset */
+	if (S_ISDIR(inode->i_mode)) {
+		struct cpuset *cs = dentry->d_fsdata;
+		BUG_ON(!(is_removed(cs)));
+		kfree(cs);
+	}
+	iput(inode);
+}
+
+static struct dentry_operations cpuset_dops = {
+	.d_iput = cpuset_diput,
+};
+
+static struct dentry *cpuset_get_dentry(struct dentry *parent, const char *name)
+{
+	struct qstr qstr;
+	struct dentry *d;
+
+	qstr.name = name;
+	qstr.len = strlen(name);
+	qstr.hash = full_name_hash(name, qstr.len);
+	d = lookup_hash(&qstr, parent);
+	if (!IS_ERR(d))
+		d->d_op = &cpuset_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);
+}
+
+/*
+ * NOTE : the dentry must have been dget()'ed
+ */
+static void cpuset_d_remove_dir(struct dentry *dentry)
+{
+	struct list_head *node;
+
+	spin_lock(&dcache_lock);
+	node = dentry->d_subdirs.next;
+	while (node != &dentry->d_subdirs) {
+		struct dentry *d = list_entry(node, struct dentry, d_child);
+		list_del_init(node);
+		if (d->d_inode) {
+			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;
+	}
+	list_del_init(&dentry->d_child);
+	spin_unlock(&dcache_lock);
+	remove_dir(dentry);
+}
+
+static struct super_operations cpuset_ops = {
+	.statfs = simple_statfs,
+	.drop_inode = generic_delete_inode,
+};
+
+static int cpuset_fill_super(struct super_block *sb, void *unused_data,
+							int unused_silent)
+{
+	struct inode *inode;
+	struct dentry *root;
+
+	sb->s_blocksize = PAGE_CACHE_SIZE;
+	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
+	sb->s_magic = CPUSET_SUPER_MAGIC;
+	sb->s_op = &cpuset_ops;
+	cpuset_sb = sb;
+
+	inode = cpuset_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR);
+	if (inode) {
+		inode->i_op = &simple_dir_inode_operations;
+		inode->i_fop = &simple_dir_operations;
+		/* directories start off with i_nlink == 2 (for "." entry) */
+		inode->i_nlink++;
+	} else {
+		return -ENOMEM;
+	}
+
+	root = d_alloc_root(inode);
+	if (!root) {
+		iput(inode);
+		return -ENOMEM;
+	}
+	sb->s_root = root;
+	return 0;
+}
+
+static struct super_block *cpuset_get_sb(struct file_system_type *fs_type,
+					int flags, const char *unused_dev_name,
+					void *data)
+{
+	return get_sb_single(fs_type, flags, data, cpuset_fill_super);
+}
+
+static struct file_system_type cpuset_fs_type = {
+	.name = "cpuset",
+	.get_sb = cpuset_get_sb,
+	.kill_sb = kill_litter_super,
+};
+
+/* struct cftype:
+ *
+ * The files in the cpuset 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 cpuset to use in file->f_dentry->d_parent->d_fsdata
+ *	- the 'cftype' of the file is file->f_dentry->d_fsdata
+ */
+
+struct cftype {
+	char *name;
+	int private;
+	int (*open) (struct inode *inode, struct file *file);
+	ssize_t (*read) (struct file *file, char __user *buf, size_t nbytes,
+							loff_t *ppos);
+	int (*write) (struct file *file, const char *buf, size_t nbytes,
+							loff_t *ppos);
+	int (*release) (struct inode *inode, struct file *file);
+};
+
+static inline struct cpuset *__d_cs(struct dentry *dentry)
+{
+	return dentry->d_fsdata;
+}
+
+static inline struct cftype *__d_cft(struct dentry *dentry)
+{
+	return dentry->d_fsdata;
+}
+
+/*
+ * Call with cpuset_sem held.  Writes path of cpuset into buf.
+ * Returns 0 on success, -errno on error.
+ */
+
+static int cpuset_path(const struct cpuset *cs, char *buf, int buflen)
+{
+	char *start;
+
+	start = buf + buflen;
+
+	*--start = '\0';
+	for (;;) {
+		int len = cs->dentry->d_name.len;
+		if ((start -= len) < buf)
+			return -ENAMETOOLONG;
+		memcpy(start, cs->dentry->d_name.name, len);
+		cs = cs->parent;
+		if (!cs)
+			break;
+		if (!cs->parent)
+			continue;
+		if (--start < buf)
+			return -ENAMETOOLONG;
+		*start = '/';
+	}
+	memmove(buf, start, buf + buflen - start);
+	return 0;
+}
+
+/*
+ * Notify userspace when a cpuset is released, by running
+ * /sbin/cpuset_release_agent with the name of the cpuset (path
+ * relative to the root of cpuset file system) as the argument.
+ *
+ * Most likely, this user command will try to rmdir this cpuset.
+ *
+ * This races with the possibility that some other task will be
+ * attached to this cpuset before it is removed, or that some other
+ * user task will 'mkdir' a child cpuset of this cpuset.  That's ok.
+ * The presumed 'rmdir' will fail quietly if this cpuset is no longer
+ * unused, and this cpuset will be reprieved from its death sentence,
+ * to continue to serve a useful existence.  Next time it's released,
+ * we will get notified again, if it still has 'notify_on_release' set.
+ *
+ * Note final arg to call_usermodehelper() is 0 - that means
+ * don't wait.  Since we are holding the global cpuset_sem here,
+ * and we are asking another thread (started from keventd) to rmdir a
+ * cpuset, we can't wait - or we'd deadlock with the removing thread
+ * on cpuset_sem.
+ */
+
+static int cpuset_release_agent(char *cpuset_str)
+{
+	char *argv[3], *envp[3];
+	int i;
+
+	i = 0;
+	argv[i++] = "/sbin/cpuset_release_agent";
+	argv[i++] = cpuset_str;
+	argv[i] = NULL;
+
+	i = 0;
+	/* minimal command environment */
+	envp[i++] = "HOME=/";
+	envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
+	envp[i] = NULL;
+
+	return call_usermodehelper(argv[0], argv, envp, 0);
+}
+
+/*
+ * Either cs->count of using tasks transitioned to zero, or the
+ * cs->children list of child cpusets just became empty.  If this
+ * cs is notify_on_release() and now both the user count is zero and
+ * the list of children is empty, send notice to user land.
+ */
+
+static void check_for_release(struct cpuset *cs)
+{
+	if (notify_on_release(cs) && atomic_read(&cs->count) == 0 &&
+	    list_empty(&cs->children)) {
+		char *buf;
+
+		buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+		if (!buf)
+			return;
+		if (cpuset_path(cs, buf, PAGE_SIZE) < 0)
+			goto out;
+		cpuset_release_agent(buf);
+out:
+		kfree(buf);
+	}
+}
+
+/*
+ * Return in *pmask the portion of a cpusets's cpus_allowed that
+ * are online.  If none are online, walk up the cpuset hierarchy
+ * until we find one that does have some online cpus.  If we get
+ * all the way to the top and still haven't found any online cpus,
+ * return cpu_online_map.  Or if passed a NULL cs from an exit'ing
+ * task, return cpu_online_map.
+ *
+ * One way or another, we guarantee to return some non-empty subset
+ * of cpu_online_map.
+ *
+ * Call with cpuset_sem held.
+ */
+
+static void guarantee_online_cpus(const struct cpuset *cs, cpumask_t *pmask)
+{
+	while (cs && !cpus_intersects(cs->cpus_allowed, cpu_online_map))
+		cs = cs->parent;
+	if (cs)
+		cpus_and(*pmask, cs->cpus_allowed, cpu_online_map);
+	else
+		*pmask = cpu_online_map;
+	BUG_ON(!cpus_intersects(*pmask, cpu_online_map));
+}
+
+/*
+ * Return in *pmask the portion of a cpusets's mems_allowed that
+ * are online.  If none are online, walk up the cpuset hierarchy
+ * until we find one that does have some online mems.  If we get
+ * all the way to the top and still haven't found any online mems,
+ * return node_online_map.
+ *
+ * One way or another, we guarantee to return some non-empty subset
+ * of node_online_map.
+ *
+ * Call with cpuset_sem held.
+ */
+
+static void guarantee_online_mems(const struct cpuset *cs, nodemask_t *pmask)
+{
+	while (cs && !nodes_intersects(cs->mems_allowed, node_online_map))
+		cs = cs->parent;
+	if (cs)
+		nodes_and(*pmask, cs->mems_allowed, node_online_map);
+	else
+		*pmask = node_online_map;
+	BUG_ON(!nodes_intersects(*pmask, node_online_map));
+}
+
+/*
+ * is_cpuset_subset(p, q) - Is cpuset p a subset of cpuset q?
+ *
+ * One cpuset is a subset of another if all its allowed CPUs and
+ * Memory Nodes are a subset of the other, and its exclusive flags
+ * are only set if the other's are set.
+ */
+
+static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
+{
+	return	cpus_subset(p->cpus_allowed, q->cpus_allowed) &&
+		nodes_subset(p->mems_allowed, q->mems_allowed) &&
+		is_cpu_exclusive(p) <= is_cpu_exclusive(q) &&
+		is_mem_exclusive(p) <= is_mem_exclusive(q);
+}
+
+/*
+ * validate_change() - Used to validate that any proposed cpuset change
+ *		       follows the structural rules for cpusets.
+ *
+ * If we replaced the flag and mask values of the current cpuset
+ * (cur) with those values in the trial cpuset (trial), would
+ * our various subset and exclusive rules still be valid?  Presumes
+ * cpuset_sem held.
+ *
+ * 'cur' is the address of an actual, in-use cpuset.  Operations
+ * such as list traversal that depend on the actual address of the
+ * cpuset in the list must use cur below, not trial.
+ *
+ * 'trial' is the address of bulk structure copy of cur, with
+ * perhaps one or more of the fields cpus_allowed, mems_allowed,
+ * or flags changed to new, trial values.
+ *
+ * Return 0 if valid, -errno if not.
+ */
+
+static int validate_change(const struct cpuset *cur, const struct cpuset *trial)
+{
+	struct cpuset *c, *par;
+
+	/* Each of our child cpusets must be a subset of us */
+	list_for_each_entry(c, &cur->children, sibling) {
+		if (!is_cpuset_subset(c, trial))
+			return -EBUSY;
+	}
+
+	/* Remaining checks don't apply to root cpuset */
+	if ((par = cur->parent) == NULL)
+		return 0;
+
+	/* We must be a subset of our parent cpuset */
+	if (!is_cpuset_subset(trial, par))
+		return -EACCES;
+
+	/* If either I or some sibling (!= me) is exclusive, we can't overlap */
+	list_for_each_entry(c, &par->children, sibling) {
+		if ((is_cpu_exclusive(trial) || is_cpu_exclusive(c)) &&
+		    c != cur &&
+		    cpus_intersects(trial->cpus_allowed, c->cpus_allowed))
+			return -EINVAL;
+		if ((is_mem_exclusive(trial) || is_mem_exclusive(c)) &&
+		    c != cur &&
+		    nodes_intersects(trial->mems_allowed, c->mems_allowed))
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int update_cpumask(struct cpuset *cs, char *buf)
+{
+	struct cpuset trialcs;
+	int retval;
+
+	trialcs = *cs;
+	retval = cpulist_parse(buf, trialcs.cpus_allowed);
+	if (retval < 0)
+		return retval;
+	cpus_and(trialcs.cpus_allowed, trialcs.cpus_allowed, cpu_online_map);
+	if (cpus_empty(trialcs.cpus_allowed))
+		return -ENOSPC;
+	retval = validate_change(cs, &trialcs);
+	if (retval == 0)
+		cs->cpus_allowed = trialcs.cpus_allowed;
+	return retval;
+}
+
+static int update_nodemask(struct cpuset *cs, char *buf)
+{
+	struct cpuset trialcs;
+	int retval;
+
+	trialcs = *cs;
+	retval = nodelist_parse(buf, trialcs.mems_allowed);
+	if (retval < 0)
+		return retval;
+	nodes_and(trialcs.mems_allowed, trialcs.mems_allowed, node_online_map);
+	if (nodes_empty(trialcs.mems_allowed))
+		return -ENOSPC;
+	retval = validate_change(cs, &trialcs);
+	if (retval == 0) {
+		cs->mems_allowed = trialcs.mems_allowed;
+		atomic_inc(&cpuset_mems_generation);
+		cs->mems_generation = atomic_read(&cpuset_mems_generation);
+	}
+	return retval;
+}
+
+/*
+ * update_flag - read a 0 or a 1 in a file and update associated flag
+ * bit:	the bit to update (CS_CPU_EXCLUSIVE, CS_MEM_EXCLUSIVE,
+ *						CS_NOTIFY_ON_RELEASE)
+ * cs:	the cpuset to update
+ * buf:	the buffer where we read the 0 or 1
+ */
+
+static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, char *buf)
+{
+	int turning_on;
+	struct cpuset trialcs;
+	int err;
+
+	turning_on = (simple_strtoul(buf, NULL, 10) != 0);
+
+	trialcs = *cs;
+	if (turning_on)
+		set_bit(bit, &trialcs.flags);
+	else
+		clear_bit(bit, &trialcs.flags);
+
+	err = validate_change(cs, &trialcs);
+	if (err == 0) {
+		if (turning_on)
+			set_bit(bit, &cs->flags);
+		else
+			clear_bit(bit, &cs->flags);
+	}
+	return err;
+}
+
+static int attach_task(struct cpuset *cs, char *buf)
+{
+	pid_t pid;
+	struct task_struct *tsk;
+	struct cpuset *oldcs;
+	cpumask_t cpus;
+
+	if (sscanf(buf, "%d", &pid) != 1)
+		return -EIO;
+	if (cpus_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
+		return -ENOSPC;
+
+	if (pid) {
+		read_lock(&tasklist_lock);
+
+		tsk = find_task_by_pid(pid);
+		if (!tsk) {
+			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);
+	}
+
+	task_lock(tsk);
+	oldcs = tsk->cpuset;
+	if (!oldcs) {
+		task_unlock(tsk);
+		put_task_struct(tsk);
+		return -ESRCH;
+	}
+	atomic_inc(&cs->count);
+	tsk->cpuset = cs;
+	task_unlock(tsk);
+
+	guarantee_online_cpus(cs, &cpus);
+	set_cpus_allowed(tsk, cpus);
+
+	put_task_struct(tsk);
+	if (atomic_dec_and_test(&oldcs->count))
+		check_for_release(oldcs);
+	return 0;
+}
+
+/* The various types of files and directories in a cpuset file system */
+
+typedef enum {
+	FILE_ROOT,
+	FILE_DIR,
+	FILE_CPULIST,
+	FILE_MEMLIST,
+	FILE_CPU_EXCLUSIVE,
+	FILE_MEM_EXCLUSIVE,
+	FILE_NOTIFY_ON_RELEASE,
+	FILE_TASKLIST,
+} cpuset_filetype_t;
+
+static ssize_t cpuset_common_file_write(struct file *file, const char *userbuf,
+					size_t nbytes, loff_t *unused_ppos)
+{
+	struct cpuset *cs = __d_cs(file->f_dentry->d_parent);
+	struct cftype *cft = __d_cft(file->f_dentry);
+	cpuset_filetype_t type = cft->private;
+	char *buffer;
+	int retval = 0;
+
+	/* Crude upper limit on largest legitimate cpulist user might write. */
+	if (nbytes > 100 + 6 * NR_CPUS)
+		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 */
+
+	down(&cpuset_sem);
+
+	if (is_removed(cs)) {
+		retval = -ENODEV;
+		goto out2;
+	}
+
+	switch (type) {
+	case FILE_CPULIST:
+		retval = update_cpumask(cs, buffer);
+		break;
+	case FILE_MEMLIST:
+		retval = update_nodemask(cs, buffer);
+		break;
+	case FILE_CPU_EXCLUSIVE:
+		retval = update_flag(CS_CPU_EXCLUSIVE, cs, buffer);
+		break;
+	case FILE_MEM_EXCLUSIVE:
+		retval = update_flag(CS_MEM_EXCLUSIVE, cs, buffer);
+		break;
+	case FILE_NOTIFY_ON_RELEASE:
+		retval = update_flag(CS_NOTIFY_ON_RELEASE, cs, buffer);
+		break;
+	case FILE_TASKLIST:
+		retval = attach_task(cs, buffer);
+		break;
+	default:
+		retval = -EINVAL;
+		goto out2;
+	}
+
+	if (retval == 0)
+		retval = nbytes;
+out2:
+	up(&cpuset_sem);
+out1:
+	kfree(buffer);
+	return retval;
+}
+
+static ssize_t cpuset_file_write(struct file *file, const char *buf,
+						size_t nbytes, loff_t *ppos)
+{
+	ssize_t retval = 0;
+	struct cftype *cft = __d_cft(file->f_dentry);
+	if (!cft)
+		return -ENODEV;
+
+	/* special function ? */
+	if (cft->write)
+		retval = cft->write(file, buf, nbytes, ppos);
+	else
+		retval = cpuset_common_file_write(file, buf, nbytes, ppos);
+
+	return retval;
+}
+
+/*
+ * These ascii lists should be read in a single call, by using a user
+ * buffer large enough to hold the entire map.  If read in smaller
+ * chunks, there is no guarantee of atomicity.  Since the display format
+ * used, list of ranges of sequential numbers, is variable length,
+ * and since these maps can change value dynamically, one could read
+ * gibberish by doing partial reads while a list was changing.
+ * A single large read to a buffer that crosses a page boundary is
+ * ok, because the result being copied to user land is not recomputed
+ * across a page fault.
+ */
+
+static int cpuset_sprintf_cpulist(char *page, struct cpuset *cs)
+{
+	cpumask_t mask;
+
+	down(&cpuset_sem);
+	mask = cs->cpus_allowed;
+	up(&cpuset_sem);
+
+	return cpulist_scnprintf(page, PAGE_SIZE, mask);
+}
+
+static int cpuset_sprintf_memlist(char *page, struct cpuset *cs)
+{
+	nodemask_t mask;
+
+	down(&cpuset_sem);
+	mask = cs->mems_allowed;
+	up(&cpuset_sem);
+
+	return nodelist_scnprintf(page, PAGE_SIZE, mask);
+}
+
+static ssize_t cpuset_common_file_read(struct file *file, char __user *buf,
+				size_t nbytes, loff_t *ppos)
+{
+	struct cftype *cft = __d_cft(file->f_dentry);
+	struct cpuset *cs = __d_cs(file->f_dentry->d_parent);
+	cpuset_filetype_t type = cft->private;
+	char *page;
+	ssize_t retval = 0;
+	char *s;
+	char *start;
+	size_t n;
+
+	if (!(page = (char *)__get_free_page(GFP_KERNEL)))
+		return -ENOMEM;
+
+	s = page;
+
+	switch (type) {
+	case FILE_CPULIST:
+		s += cpuset_sprintf_cpulist(s, cs);
+		break;
+	case FILE_MEMLIST:
+		s += cpuset_sprintf_memlist(s, cs);
+		break;
+	case FILE_CPU_EXCLUSIVE:
+		*s++ = is_cpu_exclusive(cs) ? '1' : '0';
+		break;
+	case FILE_MEM_EXCLUSIVE:
+		*s++ = is_mem_exclusive(cs) ? '1' : '0';
+		break;
+	case FILE_NOTIFY_ON_RELEASE:
+		*s++ = notify_on_release(cs) ? '1' : '0';
+		break;
+	default:
+		retval = -EINVAL;
+		goto out;
+	}
+	*s++ = '\n';
+	*s = '\0';
+
+	start = page + *ppos;
+	n = s - start;
+	retval = n - copy_to_user(buf, start, min(n, nbytes));
+	*ppos += retval;
+out:
+	free_page((unsigned long)page);
+	return retval;
+}
+
+static ssize_t cpuset_file_read(struct file *file, char *buf, size_t nbytes,
+								loff_t *ppos)
+{
+	ssize_t retval = 0;
+	struct cftype *cft = __d_cft(file->f_dentry);
+	if (!cft)
+		return -ENODEV;
+
+	/* special function ? */
+	if (cft->read)
+		retval = cft->read(file, buf, nbytes, ppos);
+	else
+		retval = cpuset_common_file_read(file, buf, nbytes, ppos);
+
+	return retval;
+}
+
+static int cpuset_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 cpuset_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;
+}
+
+static struct file_operations cpuset_file_operations = {
+	.read = cpuset_file_read,
+	.write = cpuset_file_write,
+	.llseek = generic_file_llseek,
+	.open = cpuset_file_open,
+	.release = cpuset_file_release,
+};
+
+static struct inode_operations cpuset_dir_inode_operations = {
+	.lookup = simple_lookup,
+	.mkdir = cpuset_mkdir,
+	.rmdir = cpuset_rmdir,
+};
+
+static int cpuset_create_file(struct dentry *dentry, int mode)
+{
+	struct inode *inode;
+
+	if (!dentry)
+		return -ENOENT;
+	if (dentry->d_inode)
+		return -EEXIST;
+
+	inode = cpuset_new_inode(mode);
+	if (!inode)
+		return -ENOMEM;
+
+	if (S_ISDIR(mode)) {
+		inode->i_op = &cpuset_dir_inode_operations;
+		inode->i_fop = &simple_dir_operations;
+
+		/* start off with i_nlink == 2 (for "." entry) */
+		inode->i_nlink++;
+	} else if (S_ISREG(mode)) {
+		inode->i_size = 0;
+		inode->i_fop = &cpuset_file_operations;
+	}
+
+	d_instantiate(dentry, inode);
+	dget(dentry);	/* Extra count - pin the dentry in core */
+	return 0;
+}
+
+/*
+ *	cpuset_create_dir - create a directory for an object.
+ *	cs: 	the cpuset 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 cpuset directory. Will be copied.
+ *	mode:	mode to set on new directory.
+ */
+
+static int cpuset_create_dir(struct cpuset *cs, const char *name, int mode)
+{
+	struct dentry *dentry = NULL;
+	struct dentry *parent;
+	int error = 0;
+
+	parent = cs->parent->dentry;
+	dentry = cpuset_get_dentry(parent, name);
+	if (IS_ERR(dentry))
+		return PTR_ERR(dentry);
+	error = cpuset_create_file(dentry, S_IFDIR | mode);
+	if (!error) {
+		dentry->d_fsdata = cs;
+		parent->d_inode->i_nlink++;
+		cs->dentry = dentry;
+	}
+	dput(dentry);
+
+	return error;
+}
+
+static int cpuset_add_file(struct dentry *dir, const struct cftype *cft)
+{
+	struct dentry *dentry;
+	int error;
+
+	down(&dir->d_inode->i_sem);
+	dentry = cpuset_get_dentry(dir, cft->name);
+	if (!IS_ERR(dentry)) {
+		error = cpuset_create_file(dentry, 0644 | S_IFREG);
+		if (!error)
+			dentry->d_fsdata = (void *)cft;
+		dput(dentry);
+	} else
+		error = PTR_ERR(dentry);
+	up(&dir->d_inode->i_sem);
+	return error;
+}
+
+/*
+ * Stuff for reading the 'tasks' file.
+ *
+ * Reading this file can return large amounts of data if a cpuset 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().
+ */
+
+/* cpusets_tasks_read array */
+
+struct ctr_struct {
+	char *buf;
+	int bufsz;
+};
+
+/*
+ * Load into 'pidarray' up to 'npids' of the tasks using cpuset 'cs'.
+ * Return actual number of pids loaded.
+ */
+static inline int pid_array_load(pid_t *pidarray, int npids, struct cpuset *cs)
+{
+	int n = 0;
+	struct task_struct *g, *p;
+
+	read_lock(&tasklist_lock);
+
+	do_each_thread(g, p) {
+		if (p->cpuset == cs) {
+			pidarray[n++] = p->pid;
+			if (unlikely(n == npids))
+				goto array_full;
+		}
+	} while_each_thread(g, p);
+
+array_full:
+	read_unlock(&tasklist_lock);
+	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 int cpuset_tasks_open(struct inode *unused, struct file *file)
+{
+	struct cpuset *cs = __d_cs(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 cpuset 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 cpuset users didn't
+	 * show up until sometime later on.
+	 */
+	npids = atomic_read(&cs->count);
+	pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL);
+	if (!pidarray)
+		goto err1;
+
+	npids = pid_array_load(pidarray, npids, cs);
+	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 cpuset_tasks_read(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 cpuset_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;
+}
+
+/*
+ * for the common functions, 'private' gives the type of file
+ */
+
+static struct cftype cft_tasks = {
+	.name = "tasks",
+	.open = cpuset_tasks_open,
+	.read = cpuset_tasks_read,
+	.release = cpuset_tasks_release,
+	.private = FILE_TASKLIST,
+};
+
+static struct cftype cft_cpus = {
+	.name = "cpus",
+	.private = FILE_CPULIST,
+};
+
+static struct cftype cft_mems = {
+	.name = "mems",
+	.private = FILE_MEMLIST,
+};
+
+static struct cftype cft_cpu_exclusive = {
+	.name = "cpu_exclusive",
+	.private = FILE_CPU_EXCLUSIVE,
+};
+
+static struct cftype cft_mem_exclusive = {
+	.name = "mem_exclusive",
+	.private = FILE_MEM_EXCLUSIVE,
+};
+
+static struct cftype cft_notify_on_release = {
+	.name = "notify_on_release",
+	.private = FILE_NOTIFY_ON_RELEASE,
+};
+
+static int cpuset_populate_dir(struct dentry *cs_dentry)
+{
+	int err;
+
+	if ((err = cpuset_add_file(cs_dentry, &cft_cpus)) < 0)
+		return err;
+	if ((err = cpuset_add_file(cs_dentry, &cft_mems)) < 0)
+		return err;
+	if ((err = cpuset_add_file(cs_dentry, &cft_cpu_exclusive)) < 0)
+		return err;
+	if ((err = cpuset_add_file(cs_dentry, &cft_mem_exclusive)) < 0)
+		return err;
+	if ((err = cpuset_add_file(cs_dentry, &cft_notify_on_release)) < 0)
+		return err;
+	if ((err = cpuset_add_file(cs_dentry, &cft_tasks)) < 0)
+		return err;
+	return 0;
+}
+
+/*
+ *	cpuset_create - create a cpuset
+ *	parent:	cpuset that will be parent of the new cpuset.
+ *	name:		name of the new cpuset. Will be strcpy'ed.
+ *	mode:		mode to set on new inode
+ *
+ *	Must be called with the semaphore on the parent inode held
+ */
+
+static long cpuset_create(struct cpuset *parent, const char *name, int mode)
+{
+	struct cpuset *cs;
+	int err;
+
+	cs = kmalloc(sizeof(*cs), GFP_KERNEL);
+	if (!cs)
+		return -ENOMEM;
+
+	down(&cpuset_sem);
+	cs->flags = 0;
+	if (notify_on_release(parent))
+		set_bit(CS_NOTIFY_ON_RELEASE, &cs->flags);
+	cs->cpus_allowed = CPU_MASK_NONE;
+	cs->mems_allowed = NODE_MASK_NONE;
+	atomic_set(&cs->count, 0);
+	INIT_LIST_HEAD(&cs->sibling);
+	INIT_LIST_HEAD(&cs->children);
+	atomic_inc(&cpuset_mems_generation);
+	cs->mems_generation = atomic_read(&cpuset_mems_generation);
+
+	cs->parent = parent;
+
+	list_add(&cs->sibling, &cs->parent->children);
+
+	err = cpuset_create_dir(cs, name, mode);
+	if (err < 0)
+		goto err;
+
+	/*
+	 * Release cpuset_sem before cpuset_populate_dir() because it
+	 * will down() this new directory's i_sem and if we race with
+	 * another mkdir, we might deadlock.
+	 */
+	up(&cpuset_sem);
+
+	err = cpuset_populate_dir(cs->dentry);
+	/* If err < 0, we have a half-filled directory - oh well ;) */
+	return 0;
+err:
+	list_del(&cs->sibling);
+	up(&cpuset_sem);
+	kfree(cs);
+	return err;
+}
+
+static int cpuset_mkdir(struct inode *dir, struct dentry *dentry, int mode)
+{
+	struct cpuset *c_parent = dentry->d_parent->d_fsdata;
+
+	/* the vfs holds inode->i_sem already */
+	return cpuset_create(c_parent, dentry->d_name.name, mode | S_IFDIR);
+}
+
+static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry)
+{
+	struct cpuset *cs = dentry->d_fsdata;
+	struct dentry *d;
+	struct cpuset *parent;
+
+	/* the vfs holds both inode->i_sem already */
+
+	down(&cpuset_sem);
+	if (atomic_read(&cs->count) > 0) {
+		up(&cpuset_sem);
+		return -EBUSY;
+	}
+	if (!list_empty(&cs->children)) {
+		up(&cpuset_sem);
+		return -EBUSY;
+	}
+	spin_lock(&cs->dentry->d_lock);
+	parent = cs->parent;
+	set_bit(CS_REMOVED, &cs->flags);
+	list_del(&cs->sibling);	/* delete my sibling from parent->children */
+	if (list_empty(&parent->children))
+		check_for_release(parent);
+	d = dget(cs->dentry);
+	cs->dentry = NULL;
+	spin_unlock(&d->d_lock);
+	cpuset_d_remove_dir(d);
+	dput(d);
+	up(&cpuset_sem);
+	return 0;
+}
+
+/**
+ * cpuset_init - initialize cpusets at system boot
+ *
+ * Description: Initialize top_cpuset and the cpuset internal file system,
+ **/
+
+int __init cpuset_init(void)
+{
+	struct dentry *root;
+	int err;
+
+	top_cpuset.cpus_allowed = CPU_MASK_ALL;
+	top_cpuset.mems_allowed = NODE_MASK_ALL;
+
+	atomic_inc(&cpuset_mems_generation);
+	top_cpuset.mems_generation = atomic_read(&cpuset_mems_generation);
+
+	init_task.cpuset = &top_cpuset;
+
+	err = register_filesystem(&cpuset_fs_type);
+	if (err < 0)
+		goto out;
+	cpuset_mount = kern_mount(&cpuset_fs_type);
+	if (IS_ERR(cpuset_mount)) {
+		printk(KERN_ERR "cpuset: could not mount!\n");
+		err = PTR_ERR(cpuset_mount);
+		cpuset_mount = NULL;
+		goto out;
+	}
+	root = cpuset_mount->mnt_sb->s_root;
+	root->d_fsdata = &top_cpuset;
+	root->d_inode->i_nlink++;
+	top_cpuset.dentry = root;
+	root->d_inode->i_op = &cpuset_dir_inode_operations;
+	err = cpuset_populate_dir(root);
+out:
+	return err;
+}
+
+/**
+ * cpuset_init_smp - initialize cpus_allowed
+ *
+ * Description: Finish top cpuset after cpu, node maps are initialized
+ **/
+
+void __init cpuset_init_smp(void)
+{
+	top_cpuset.cpus_allowed = cpu_online_map;
+	top_cpuset.mems_allowed = node_online_map;
+}
+
+/**
+ * cpuset_fork - attach newly forked task to its parents cpuset.
+ * @p: pointer to task_struct of forking parent process.
+ *
+ * Description: By default, on fork, a task inherits its
+ * parents cpuset.  The pointer to the shared cpuset is
+ * automatically copied in fork.c by dup_task_struct().
+ * This cpuset_fork() routine need only increment the usage
+ * counter in that cpuset.
+ **/
+
+void cpuset_fork(struct task_struct *tsk)
+{
+	atomic_inc(&tsk->cpuset->count);
+}
+
+/**
+ * cpuset_exit - detach cpuset from exiting task
+ * @tsk: pointer to task_struct of exiting process
+ *
+ * Description: Detach cpuset from @tsk and release it.
+ *
+ **/
+
+void cpuset_exit(struct task_struct *tsk)
+{
+	struct cpuset *cs;
+
+	task_lock(tsk);
+	cs = tsk->cpuset;
+	tsk->cpuset = NULL;
+	task_unlock(tsk);
+
+	if (atomic_dec_and_test(&cs->count)) {
+		down(&cpuset_sem);
+		check_for_release(cs);
+		up(&cpuset_sem);
+	}
+}
+
+/**
+ * cpuset_cpus_allowed - return cpus_allowed mask from a tasks cpuset.
+ * @tsk: pointer to task_struct from which to obtain cpuset->cpus_allowed.
+ *
+ * Description: Returns the cpumask_t cpus_allowed of the cpuset
+ * attached to the specified @tsk.  Guaranteed to return some non-empty
+ * subset of cpu_online_map, even if this means going outside the
+ * tasks cpuset.
+ **/
+
+const cpumask_t cpuset_cpus_allowed(const struct task_struct *tsk)
+{
+	cpumask_t mask;
+
+	down(&cpuset_sem);
+	task_lock((struct task_struct *)tsk);
+	guarantee_online_cpus(tsk->cpuset, &mask);
+	task_unlock((struct task_struct *)tsk);
+	up(&cpuset_sem);
+
+	return mask;
+}
+
+void cpuset_init_current_mems_allowed(void)
+{
+	current->mems_allowed = NODE_MASK_ALL;
+}
+
+/*
+ * If the current tasks cpusets mems_allowed changed behind our backs,
+ * update current->mems_allowed and mems_generation to the new value.
+ * Do not call this routine if in_interrupt().
+ */
+
+void cpuset_update_current_mems_allowed()
+{
+	struct cpuset *cs = current->cpuset;
+
+	if (!cs)
+		return;		/* task is exiting */
+	if (current->cpuset_mems_generation != cs->mems_generation) {
+		down(&cpuset_sem);
+		guarantee_online_mems(cs, &current->mems_allowed);
+		current->cpuset_mems_generation = cs->mems_generation;
+		up(&cpuset_sem);
+	}
+}
+
+void cpuset_restrict_to_mems_allowed(unsigned long *nodes)
+{
+	bitmap_and(nodes, nodes, nodes_addr(current->mems_allowed),
+							MAX_NUMNODES);
+}
+
+/*
+ * Are any of the nodes on zonelist zl allowed in current->mems_allowed?
+ */
+int cpuset_zonelist_valid_mems_allowed(struct zonelist *zl)
+{
+	int i;
+
+	for (i = 0; zl->zones[i]; i++) {
+		int nid = zl->zones[i]->zone_pgdat->node_id;
+
+		if (node_isset(nid, current->mems_allowed))
+			return 1;
+	}
+	return 0;
+}
+
+/*
+ * Is 'current' valid, and is zone z allowed in current->mems_allowed?
+ */
+int cpuset_zone_allowed(struct zone *z)
+{
+	return in_interrupt() ||
+		node_isset(z->zone_pgdat->node_id, current->mems_allowed);
+}
+
+/*
+ * proc_cpuset_show()
+ *  - Print tasks cpuset path into seq_file.
+ *  - Used for /proc/<pid>/cpuset.
+ */
+
+static int proc_cpuset_show(struct seq_file *m, void *v)
+{
+	struct cpuset *cs;
+	struct task_struct *tsk;
+	char *buf;
+	int retval = 0;
+
+	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	tsk = m->private;
+	down(&cpuset_sem);
+	task_lock(tsk);
+	cs = tsk->cpuset;
+	task_unlock(tsk);
+	if (!cs) {
+		retval = -EINVAL;
+		goto out;
+	}
+
+	retval = cpuset_path(cs, buf, PAGE_SIZE);
+	if (retval < 0)
+		goto out;
+	seq_puts(m, buf);
+	seq_putc(m, '\n');
+out:
+	up(&cpuset_sem);
+	kfree(buf);
+	return retval;
+}
+
+static int cpuset_open(struct inode *inode, struct file *file)
+{
+	struct task_struct *tsk = PROC_I(inode)->task;
+	return single_open(file, proc_cpuset_show, tsk);
+}
+
+struct file_operations proc_cpuset_operations = {
+	.open		= cpuset_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
+/* Display task cpus_allowed, mems_allowed in /proc/<pid>/status file. */
+char *cpuset_task_status_allowed(struct task_struct *task, char *buffer)
+{
+	buffer += sprintf(buffer, "Cpus_allowed:\t");
+	buffer += cpumask_scnprintf(buffer, PAGE_SIZE, task->cpus_allowed);
+	buffer += sprintf(buffer, "\n");
+	buffer += sprintf(buffer, "Mems_allowed:\t");
+	buffer += nodemask_scnprintf(buffer, PAGE_SIZE, task->mems_allowed);
+	buffer += sprintf(buffer, "\n");
+	return buffer;
+}
diff --git a/kernel/exit.c b/kernel/exit.c
index ae320758b2f5..6dd4ebe1dd90 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -25,6 +25,7 @@
 #include <linux/mount.h>
 #include <linux/proc_fs.h>
 #include <linux/mempolicy.h>
+#include <linux/cpuset.h>
 #include <linux/syscalls.h>
 
 #include <asm/uaccess.h>
@@ -820,6 +821,7 @@ fastcall NORET_TYPE void do_exit(long code)
 	__exit_fs(tsk);
 	exit_namespace(tsk);
 	exit_thread();
+	cpuset_exit(tsk);
 	exit_keys(tsk);
 
 	if (group_dead && tsk->signal->leader)
diff --git a/kernel/fork.c b/kernel/fork.c
index 8b00a09f598a..19a56e20f3c1 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -29,6 +29,7 @@
 #include <linux/mman.h>
 #include <linux/fs.h>
 #include <linux/cpu.h>
+#include <linux/cpuset.h>
 #include <linux/security.h>
 #include <linux/swap.h>
 #include <linux/syscalls.h>
@@ -1069,6 +1070,8 @@ static task_t *copy_process(unsigned long clone_flags,
 	if (unlikely(p->ptrace & PT_PTRACED))
 		__ptrace_link(p, current->parent);
 
+	cpuset_fork(p);
+
 	attach_pid(p, PIDTYPE_PID, p->pid);
 	attach_pid(p, PIDTYPE_TGID, p->tgid);
 	if (thread_group_leader(p)) {
diff --git a/kernel/sched.c b/kernel/sched.c
index 56bc8d9a9bda..2b4530eaa3c7 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -40,6 +40,7 @@
 #include <linux/timer.h>
 #include <linux/rcupdate.h>
 #include <linux/cpu.h>
+#include <linux/cpuset.h>
 #include <linux/percpu.h>
 #include <linux/kthread.h>
 #include <linux/seq_file.h>
@@ -3539,6 +3540,7 @@ long sched_setaffinity(pid_t pid, cpumask_t new_mask)
 {
 	task_t *p;
 	int retval;
+	cpumask_t cpus_allowed;
 
 	lock_cpu_hotplug();
 	read_lock(&tasklist_lock);
@@ -3563,6 +3565,8 @@ long sched_setaffinity(pid_t pid, cpumask_t new_mask)
 			!capable(CAP_SYS_NICE))
 		goto out_unlock;
 
+	cpus_allowed = cpuset_cpus_allowed(p);
+	cpus_and(new_mask, new_mask, cpus_allowed);
 	retval = set_cpus_allowed(p, new_mask);
 
 out_unlock:
@@ -4240,7 +4244,7 @@ static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *tsk)
 
 	/* No more Mr. Nice Guy. */
 	if (dest_cpu == NR_CPUS) {
-		cpus_setall(tsk->cpus_allowed);
+		tsk->cpus_allowed = cpuset_cpus_allowed(tsk);
 		dest_cpu = any_online_cpu(tsk->cpus_allowed);
 
 		/*