/*
   *  kernel/cpuset.c
   *
   *  Processor and Memory placement constraints for sets of tasks.
   *
   *  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/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/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 CPUSET_SUPER_MAGIC		0x27e0eb

  /*
   * Tracks how many cpusets are currently defined in system.
   * When there is only one cpuset (the root cpuset) we can
   * short circuit some hooks.
   */

  int number_of_cpusets __read_mostly;

  /* See "Frequency meter" comments, below. */
  
  struct fmeter {
  	int cnt;		/* unprocessed events count */
  	int val;		/* most recent output value */
  	time_t time;		/* clock (secs) when val computed */
  	spinlock_t lock;	/* guards read or write of above */
  };

  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 */

  	/*
  	 * Count is atomic so can incr (fork) or decr (exit) without a lock.
  	 */

  	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;
  
  	struct fmeter fmeter;		/* memory_pressure filter */

  };
  
  /* bits in struct cpuset flags field */
  typedef enum {
  	CS_CPU_EXCLUSIVE,
  	CS_MEM_EXCLUSIVE,

  	CS_MEMORY_MIGRATE,

  	CS_REMOVED,

  	CS_NOTIFY_ON_RELEASE,
  	CS_SPREAD_PAGE,
  	CS_SPREAD_SLAB,

  } 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);

  }

  static inline int is_memory_migrate(const struct cpuset *cs)
  {

  	return test_bit(CS_MEMORY_MIGRATE, &cs->flags);

  }

  static inline int is_spread_page(const struct cpuset *cs)
  {
  	return test_bit(CS_SPREAD_PAGE, &cs->flags);
  }
  
  static inline int is_spread_slab(const struct cpuset *cs)
  {
  	return test_bit(CS_SPREAD_SLAB, &cs->flags);
  }

  /*

   * Increment this 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.

   *
   * Since cpuset_mems_generation is guarded by manage_mutex,
   * there is no need to mark it atomic.

   */

  static int cpuset_mems_generation;

  
  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),

  };
  
  static struct vfsmount *cpuset_mount;

  static struct super_block *cpuset_sb;

  
  /*

   * We have two global cpuset mutexes below.  They can nest.
   * It is ok to first take manage_mutex, then nest callback_mutex.  We also

   * require taking task_lock() when dereferencing a tasks cpuset pointer.
   * See "The task_lock() exception", at the end of this comment.
   *

   * A task must hold both mutexes to modify cpusets.  If a task
   * holds manage_mutex, then it blocks others wanting that mutex,
   * ensuring that it is the only task able to also acquire callback_mutex

   * and be able to modify cpusets.  It can perform various checks on
   * the cpuset structure first, knowing nothing will change.  It can

   * also allocate memory while just holding manage_mutex.  While it is

   * performing these checks, various callback routines can briefly

   * acquire callback_mutex to query cpusets.  Once it is ready to make
   * the changes, it takes callback_mutex, blocking everyone else.

   *
   * Calls to the kernel memory allocator can not be made while holding

   * callback_mutex, as that would risk double tripping on callback_mutex

   * from one of the callbacks into the cpuset code from within
   * __alloc_pages().
   *

   * If a task is only holding callback_mutex, then it has read-only

   * access to cpusets.
   *
   * The task_struct fields mems_allowed and mems_generation may only
   * be accessed in the context of that task, so require no locks.
   *
   * Any task can increment and decrement the count field without lock.

   * So in general, code holding manage_mutex or callback_mutex can't rely

   * on the count field not changing.  However, if the count goes to

   * zero, then only attach_task(), which holds both mutexes, 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 cpuset can fork (the other way to increment the count).

   * So code holding manage_mutex or callback_mutex can safely assume that

   * if the count is zero, it will stay zero.  Similarly, if a task

   * holds manage_mutex or callback_mutex on a cpuset with zero count, it

   * knows that the cpuset won't be removed, as cpuset_rmdir() needs

   * both of those mutexes.

   *
   * The cpuset_common_file_write handler for operations that modify

   * the cpuset hierarchy holds manage_mutex across the entire operation,

   * single threading all such cpuset modifications across the system.
   *

   * The cpuset_common_file_read() handlers only hold callback_mutex across

   * small pieces of code, such as when reading out possibly multi-word
   * cpumasks and nodemasks.
   *
   * The fork and exit callbacks cpuset_fork() and cpuset_exit(), don't

   * (usually) take either mutex.  These are the two most performance

   * critical pieces of code here.  The exception occurs on cpuset_exit(),

   * when a task in a notify_on_release cpuset exits.  Then manage_mutex

   * is taken, and if the cpuset count is zero, 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), therefore, top_cpuset

   * always has either children cpusets and/or using tasks.  So we don't
   * need a special hack to ensure that top_cpuset cannot be deleted.
   *
   * The above "Tale of Two Semaphores" would be complete, but for:
   *
   *	The task_lock() exception
   *
   * The need for this exception arises from the action of attach_task(),
   * which overwrites one tasks cpuset pointer with another.  It does

   * so using both mutexes, however there are several performance

   * critical places that need to reference task->cpuset without the

   * expense of grabbing a system global mutex.  Therefore except as

   * noted below, when dereferencing or, as in attach_task(), modifying
   * a tasks cpuset 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 cpuset pointer by attach_task() and the
   * access of task->cpuset->mems_generation via that pointer in
   * the routine cpuset_update_task_memory_state().

   */

  static DEFINE_MUTEX(manage_mutex);
  static DEFINE_MUTEX(callback_mutex);

  
  /*

   * 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 */
  	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
  };
  
  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_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 dentry *d = lookup_one_len(name, parent, strlen(name));

  	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_u.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_u.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) */

  		inc_nlink(inode);

  	} else {
  		return -ENOMEM;
  	}
  
  	root = d_alloc_root(inode);
  	if (!root) {
  		iput(inode);
  		return -ENOMEM;
  	}
  	sb->s_root = root;
  	return 0;
  }

  static int cpuset_get_sb(struct file_system_type *fs_type,
  			 int flags, const char *unused_dev_name,
  			 void *data, struct vfsmount *mnt)

  {

  	return get_sb_single(fs_type, flags, data, cpuset_fill_super, mnt);

  }
  
  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_path.dentry->d_parent->d_fsdata
   *	- the 'cftype' of the file is file->f_path.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 __user *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 manage_mutex 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.
   *

   * The final arg to call_usermodehelper() is 0, which means don't
   * wait.  The separate /sbin/cpuset_release_agent task is forked by
   * call_usermodehelper(), then control in this thread returns here,
   * without waiting for the release agent task.  We don't bother to
   * wait because the caller of this routine has no use for the exit
   * status of the /sbin/cpuset_release_agent task, so no sense holding
   * our caller up for that.
   *

   * When we had only one cpuset mutex, we had to call this

   * without holding it, to avoid deadlock when call_usermodehelper()
   * allocated memory.  With two locks, we could now call this while

   * holding manage_mutex, but we still don't, so as to minimize
   * the time manage_mutex is held.

   */

  static void cpuset_release_agent(const char *pathbuf)

  {
  	char *argv[3], *envp[3];
  	int i;

  	if (!pathbuf)
  		return;

  	i = 0;
  	argv[i++] = "/sbin/cpuset_release_agent";

  	argv[i++] = (char *)pathbuf;

  	argv[i] = NULL;
  
  	i = 0;
  	/* minimal command environment */
  	envp[i++] = "HOME=/";
  	envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
  	envp[i] = NULL;

  	call_usermodehelper(argv[0], argv, envp, 0);
  	kfree(pathbuf);

  }
  
  /*
   * 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, prepare cpuset path in a kmalloc'd
   * buffer, to be returned via ppathbuf, so that the caller can invoke

   * cpuset_release_agent() with it later on, once manage_mutex is dropped.
   * Call here with manage_mutex held.

   *
   * This check_for_release() routine is responsible for kmalloc'ing
   * pathbuf.  The above cpuset_release_agent() is responsible for
   * kfree'ing pathbuf.  The caller of these routines is responsible
   * for providing a pathbuf pointer, initialized to NULL, then

   * calling check_for_release() with manage_mutex held and the address
   * of the pathbuf pointer, then dropping manage_mutex, then calling

   * cpuset_release_agent() with pathbuf, as set by check_for_release().

   */

  static void check_for_release(struct cpuset *cs, char **ppathbuf)

  {
  	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)

  			kfree(buf);
  		else
  			*ppathbuf = 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 callback_mutex 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 callback_mutex 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));
  }

  /**
   * cpuset_update_task_memory_state - update task memory placement
   *
   * If the current tasks cpusets mems_allowed changed behind our
   * backs, update current->mems_allowed, mems_generation and task NUMA
   * mempolicy to the new value.

   *

   * Task mempolicy is updated by rebinding it relative to the
   * current->cpuset if a task has its memory placement changed.
   * Do not call this routine if in_interrupt().
   *

   * Call without callback_mutex or task_lock() held.  May be
   * called with or without manage_mutex held.  Thanks in part to
   * 'the_top_cpuset_hack', the tasks cpuset pointer will never
   * be NULL.  This routine also might acquire callback_mutex and

   * current->mm->mmap_sem during call.

   *

   * Reading current->cpuset->mems_generation doesn't need task_lock
   * to guard the current->cpuset derefence, because it is guarded
   * from concurrent freeing of current->cpuset by attach_task(),
   * using RCU.
   *
   * The rcu_dereference() is technically probably not needed,
   * as I don't actually mind if I see a new cpuset pointer but
   * an old value of mems_generation.  However this really only
   * matters on alpha systems using cpusets heavily.  If I dropped
   * that rcu_dereference(), it would save them a memory barrier.
   * For all other arch's, rcu_dereference is a no-op anyway, and for
   * alpha systems not using cpusets, another planned optimization,
   * avoiding the rcu critical section for tasks in the root cpuset
   * which is statically allocated, so can't vanish, will make this
   * irrelevant.  Better to use RCU as intended, than to engage in
   * some cute trick to save a memory barrier that is impossible to
   * test, for alpha systems using cpusets heavily, which might not
   * even exist.

   *
   * This routine is needed to update the per-task mems_allowed data,
   * within the tasks context, when it is trying to allocate memory
   * (in various mm/mempolicy.c routines) and notices that some other
   * task has been modifying its cpuset.

   */

  void cpuset_update_task_memory_state(void)

  {

  	int my_cpusets_mem_gen;

  	struct task_struct *tsk = current;

  	struct cpuset *cs;

  	if (tsk->cpuset == &top_cpuset) {
  		/* Don't need rcu for top_cpuset.  It's never freed. */
  		my_cpusets_mem_gen = top_cpuset.mems_generation;
  	} else {
  		rcu_read_lock();
  		cs = rcu_dereference(tsk->cpuset);
  		my_cpusets_mem_gen = cs->mems_generation;
  		rcu_read_unlock();
  	}

  	if (my_cpusets_mem_gen != tsk->cpuset_mems_generation) {

  		mutex_lock(&callback_mutex);

  		task_lock(tsk);
  		cs = tsk->cpuset;	/* Maybe changed when task not locked */

  		guarantee_online_mems(cs, &tsk->mems_allowed);
  		tsk->cpuset_mems_generation = cs->mems_generation;

  		if (is_spread_page(cs))
  			tsk->flags |= PF_SPREAD_PAGE;
  		else
  			tsk->flags &= ~PF_SPREAD_PAGE;
  		if (is_spread_slab(cs))
  			tsk->flags |= PF_SPREAD_SLAB;
  		else
  			tsk->flags &= ~PF_SPREAD_SLAB;

  		task_unlock(tsk);

  		mutex_unlock(&callback_mutex);

  		mpol_rebind_task(tsk, &tsk->mems_allowed);

  	}
  }
  
  /*
   * 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.  Call holding manage_mutex.

   */
  
  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

   * manage_mutex 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 (cur == &top_cpuset)

  		return 0;

  	par = cur->parent;

  	/* 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;
  }

  /*
   * For a given cpuset cur, partition the system as follows
   * a. All cpus in the parent cpuset's cpus_allowed that are not part of any
   *    exclusive child cpusets
   * b. All cpus in the current cpuset's cpus_allowed that are not part of any
   *    exclusive child cpusets
   * Build these two partitions by calling partition_sched_domains
   *

   * Call with manage_mutex held.  May nest a call to the

   * lock_cpu_hotplug()/unlock_cpu_hotplug() pair.

   * Must not be called holding callback_mutex, because we must
   * not call lock_cpu_hotplug() while holding callback_mutex.

   */

  static void update_cpu_domains(struct cpuset *cur)
  {
  	struct cpuset *c, *par = cur->parent;
  	cpumask_t pspan, cspan;
  
  	if (par == NULL || cpus_empty(cur->cpus_allowed))
  		return;
  
  	/*
  	 * Get all cpus from parent's cpus_allowed not part of exclusive
  	 * children
  	 */
  	pspan = par->cpus_allowed;
  	list_for_each_entry(c, &par->children, sibling) {
  		if (is_cpu_exclusive(c))
  			cpus_andnot(pspan, pspan, c->cpus_allowed);
  	}

  	if (!is_cpu_exclusive(cur)) {

  		cpus_or(pspan, pspan, cur->cpus_allowed);
  		if (cpus_equal(pspan, cur->cpus_allowed))
  			return;
  		cspan = CPU_MASK_NONE;
  	} else {
  		if (cpus_empty(pspan))
  			return;
  		cspan = cur->cpus_allowed;
  		/*
  		 * Get all cpus from current cpuset's cpus_allowed not part
  		 * of exclusive children
  		 */
  		list_for_each_entry(c, &cur->children, sibling) {
  			if (is_cpu_exclusive(c))
  				cpus_andnot(cspan, cspan, c->cpus_allowed);
  		}
  	}
  
  	lock_cpu_hotplug();
  	partition_sched_domains(&pspan, &cspan);
  	unlock_cpu_hotplug();
  }

  /*

   * Call with manage_mutex held.  May take callback_mutex during call.

   */

  static int update_cpumask(struct cpuset *cs, char *buf)
  {
  	struct cpuset trialcs;

  	int retval, cpus_unchanged;

  	/* top_cpuset.cpus_allowed tracks cpu_online_map; it's read-only */
  	if (cs == &top_cpuset)
  		return -EACCES;

  	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)
  		return retval;
  	cpus_unchanged = cpus_equal(cs->cpus_allowed, trialcs.cpus_allowed);

  	mutex_lock(&callback_mutex);

  	cs->cpus_allowed = trialcs.cpus_allowed;

  	mutex_unlock(&callback_mutex);

  	if (is_cpu_exclusive(cs) && !cpus_unchanged)
  		update_cpu_domains(cs);
  	return 0;

  }

  /*

   * cpuset_migrate_mm
   *
   *    Migrate memory region from one set of nodes to another.
   *
   *    Temporarilly set tasks mems_allowed to target nodes of migration,
   *    so that the migration code can allocate pages on these nodes.
   *
   *    Call holding manage_mutex, so our current->cpuset won't change
   *    during this call, as manage_mutex holds off any attach_task()
   *    calls.  Therefore we don't need to take task_lock around the
   *    call to guarantee_online_mems(), as we know no one is changing
   *    our tasks cpuset.
   *
   *    Hold callback_mutex around the two modifications of our tasks
   *    mems_allowed to synchronize with cpuset_mems_allowed().
   *
   *    While the mm_struct we are migrating is typically from some
   *    other task, the task_struct mems_allowed that we are hacking
   *    is for our current task, which must allocate new pages for that
   *    migrating memory region.
   *
   *    We call cpuset_update_task_memory_state() before hacking
   *    our tasks mems_allowed, so that we are assured of being in
   *    sync with our tasks cpuset, and in particular, callbacks to
   *    cpuset_update_task_memory_state() from nested page allocations
   *    won't see any mismatch of our cpuset and task mems_generation
   *    values, so won't overwrite our hacked tasks mems_allowed
   *    nodemask.
   */
  
  static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
  							const nodemask_t *to)
  {
  	struct task_struct *tsk = current;
  
  	cpuset_update_task_memory_state();
  
  	mutex_lock(&callback_mutex);
  	tsk->mems_allowed = *to;
  	mutex_unlock(&callback_mutex);
  
  	do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL);
  
  	mutex_lock(&callback_mutex);
  	guarantee_online_mems(tsk->cpuset, &tsk->mems_allowed);
  	mutex_unlock(&callback_mutex);
  }
  
  /*

   * Handle user request to change the 'mems' memory placement
   * of a cpuset.  Needs to validate the request, update the
   * cpusets mems_allowed and mems_generation, and for each

   * task in the cpuset, rebind any vma mempolicies and if
   * the cpuset is marked 'memory_migrate', migrate the tasks
   * pages to the new memory.

   *

   * Call with manage_mutex held.  May take callback_mutex during call.

   * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
   * lock each such tasks mm->mmap_sem, scan its vma's and rebind
   * their mempolicies to the cpusets new mems_allowed.

   */

  static int update_nodemask(struct cpuset *cs, char *buf)
  {
  	struct cpuset trialcs;

  	nodemask_t oldmem;

  	struct task_struct *g, *p;
  	struct mm_struct **mmarray;
  	int i, n, ntasks;

  	int migrate;

  	int fudge;

  	int retval;

  	/* top_cpuset.mems_allowed tracks node_online_map; it's read-only */
  	if (cs == &top_cpuset)
  		return -EACCES;

  	trialcs = *cs;
  	retval = nodelist_parse(buf, trialcs.mems_allowed);
  	if (retval < 0)

  		goto done;

  	nodes_and(trialcs.mems_allowed, trialcs.mems_allowed, node_online_map);

  	oldmem = cs->mems_allowed;
  	if (nodes_equal(oldmem, trialcs.mems_allowed)) {
  		retval = 0;		/* Too easy - nothing to do */
  		goto done;
  	}

  	if (nodes_empty(trialcs.mems_allowed)) {
  		retval = -ENOSPC;
  		goto done;

  	}

  	retval = validate_change(cs, &trialcs);
  	if (retval < 0)
  		goto done;

  	mutex_lock(&callback_mutex);

  	cs->mems_allowed = trialcs.mems_allowed;

  	cs->mems_generation = cpuset_mems_generation++;

  	mutex_unlock(&callback_mutex);

  	set_cpuset_being_rebound(cs);		/* causes mpol_copy() rebind */
  
  	fudge = 10;				/* spare mmarray[] slots */
  	fudge += cpus_weight(cs->cpus_allowed);	/* imagine one fork-bomb/cpu */
  	retval = -ENOMEM;
  
  	/*
  	 * Allocate mmarray[] to hold mm reference for each task
  	 * in cpuset cs.  Can't kmalloc GFP_KERNEL while holding
  	 * tasklist_lock.  We could use GFP_ATOMIC, but with a
  	 * few more lines of code, we can retry until we get a big
  	 * enough mmarray[] w/o using GFP_ATOMIC.
  	 */
  	while (1) {
  		ntasks = atomic_read(&cs->count);	/* guess */
  		ntasks += fudge;
  		mmarray = kmalloc(ntasks * sizeof(*mmarray), GFP_KERNEL);
  		if (!mmarray)
  			goto done;
  		write_lock_irq(&tasklist_lock);		/* block fork */
  		if (atomic_read(&cs->count) <= ntasks)
  			break;				/* got enough */
  		write_unlock_irq(&tasklist_lock);	/* try again */
  		kfree(mmarray);
  	}
  
  	n = 0;
  
  	/* Load up mmarray[] with mm reference for each task in cpuset. */
  	do_each_thread(g, p) {
  		struct mm_struct *mm;
  
  		if (n >= ntasks) {
  			printk(KERN_WARNING
  				"Cpuset mempolicy rebind incomplete.
  ");
  			continue;
  		}
  		if (p->cpuset != cs)
  			continue;
  		mm = get_task_mm(p);
  		if (!mm)
  			continue;
  		mmarray[n++] = mm;
  	} while_each_thread(g, p);
  	write_unlock_irq(&tasklist_lock);
  
  	/*
  	 * Now that we've dropped the tasklist spinlock, we can
  	 * rebind the vma mempolicies of each mm in mmarray[] to their
  	 * new cpuset, and release that mm.  The mpol_rebind_mm()
  	 * call takes mmap_sem, which we couldn't take while holding
  	 * tasklist_lock.  Forks can happen again now - the mpol_copy()
  	 * cpuset_being_rebound check will catch such forks, and rebind
  	 * their vma mempolicies too.  Because we still hold the global

  	 * cpuset manage_mutex, we know that no other rebind effort will

  	 * be contending for the global variable cpuset_being_rebound.
  	 * It's ok if we rebind the same mm twice; mpol_rebind_mm()

  	 * is idempotent.  Also migrate pages in each mm to new nodes.

  	 */

  	migrate = is_memory_migrate(cs);

  	for (i = 0; i < n; i++) {
  		struct mm_struct *mm = mmarray[i];
  
  		mpol_rebind_mm(mm, &cs->mems_allowed);

  		if (migrate)
  			cpuset_migrate_mm(mm, &oldmem, &cs->mems_allowed);

  		mmput(mm);
  	}
  
  	/* We're done rebinding vma's to this cpusets new mems_allowed. */
  	kfree(mmarray);
  	set_cpuset_being_rebound(NULL);
  	retval = 0;

  done:

  	return retval;
  }
  
  /*

   * Call with manage_mutex held.

   */
  
  static int update_memory_pressure_enabled(struct cpuset *cs, char *buf)
  {
  	if (simple_strtoul(buf, NULL, 10) != 0)
  		cpuset_memory_pressure_enabled = 1;
  	else
  		cpuset_memory_pressure_enabled = 0;
  	return 0;
  }
  
  /*

   * 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_MEMORY_MIGRATE,
   *				CS_SPREAD_PAGE, CS_SPREAD_SLAB)

   * cs:	the cpuset to update
   * buf:	the buffer where we read the 0 or 1

   *

   * Call with manage_mutex held.

   */
  
  static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, char *buf)
  {
  	int turning_on;
  	struct cpuset trialcs;

  	int err, cpu_exclusive_changed;

  
  	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)
  		return err;
  	cpu_exclusive_changed =
  		(is_cpu_exclusive(cs) != is_cpu_exclusive(&trialcs));

  	mutex_lock(&callback_mutex);

  	cs->flags = trialcs.flags;

  	mutex_unlock(&callback_mutex);

  
  	if (cpu_exclusive_changed)
                  update_cpu_domains(cs);
  	return 0;

  }

  /*

   * Frequency meter - How fast is some event occurring?

   *
   * These routines manage a digitally filtered, constant time based,
   * event frequency meter.  There are four routines:
   *   fmeter_init() - initialize a frequency meter.
   *   fmeter_markevent() - called each time the event happens.
   *   fmeter_getrate() - returns the recent rate of such events.
   *   fmeter_update() - internal routine used to update fmeter.
   *
   * A common data structure is passed to each of these routines,
   * which is used to keep track of the state required to manage the
   * frequency meter and its digital filter.
   *
   * The filter works on the number of events marked per unit time.
   * The filter is single-pole low-pass recursive (IIR).  The time unit
   * is 1 second.  Arithmetic is done using 32-bit integers scaled to
   * simulate 3 decimal digits of precision (multiplied by 1000).
   *
   * With an FM_COEF of 933, and a time base of 1 second, the filter
   * has a half-life of 10 seconds, meaning that if the events quit
   * happening, then the rate returned from the fmeter_getrate()
   * will be cut in half each 10 seconds, until it converges to zero.
   *
   * It is not worth doing a real infinitely recursive filter.  If more
   * than FM_MAXTICKS ticks have elapsed since the last filter event,
   * just compute FM_MAXTICKS ticks worth, by which point the level
   * will be stable.
   *
   * Limit the count of unprocessed events to FM_MAXCNT, so as to avoid
   * arithmetic overflow in the fmeter_update() routine.
   *
   * Given the simple 32 bit integer arithmetic used, this meter works
   * best for reporting rates between one per millisecond (msec) and
   * one per 32 (approx) seconds.  At constant rates faster than one
   * per msec it maxes out at values just under 1,000,000.  At constant
   * rates between one per msec, and one per second it will stabilize
   * to a value N*1000, where N is the rate of events per second.
   * At constant rates between one per second and one per 32 seconds,
   * it will be choppy, moving up on the seconds that have an event,
   * and then decaying until the next event.  At rates slower than
   * about one in 32 seconds, it decays all the way back to zero between
   * each event.
   */
  
  #define FM_COEF 933		/* coefficient for half-life of 10 secs */
  #define FM_MAXTICKS ((time_t)99) /* useless computing more ticks than this */
  #define FM_MAXCNT 1000000	/* limit cnt to avoid overflow */
  #define FM_SCALE 1000		/* faux fixed point scale */
  
  /* Initialize a frequency meter */
  static void fmeter_init(struct fmeter *fmp)
  {
  	fmp->cnt = 0;
  	fmp->val = 0;
  	fmp->time = 0;
  	spin_lock_init(&fmp->lock);
  }
  
  /* Internal meter update - process cnt events and update value */
  static void fmeter_update(struct fmeter *fmp)
  {
  	time_t now = get_seconds();
  	time_t ticks = now - fmp->time;
  
  	if (ticks == 0)
  		return;
  
  	ticks = min(FM_MAXTICKS, ticks);
  	while (ticks-- > 0)
  		fmp->val = (FM_COEF * fmp->val) / FM_SCALE;
  	fmp->time = now;
  
  	fmp->val += ((FM_SCALE - FM_COEF) * fmp->cnt) / FM_SCALE;
  	fmp->cnt = 0;
  }
  
  /* Process any previous ticks, then bump cnt by one (times scale). */
  static void fmeter_markevent(struct fmeter *fmp)
  {
  	spin_lock(&fmp->lock);
  	fmeter_update(fmp);
  	fmp->cnt = min(FM_MAXCNT, fmp->cnt + FM_SCALE);
  	spin_unlock(&fmp->lock);
  }
  
  /* Process any previous ticks, then return current value. */
  static int fmeter_getrate(struct fmeter *fmp)
  {
  	int val;
  
  	spin_lock(&fmp->lock);
  	fmeter_update(fmp);
  	val = fmp->val;
  	spin_unlock(&fmp->lock);
  	return val;
  }
  
  /*

   * Attack task specified by pid in 'pidbuf' to cpuset 'cs', possibly
   * writing the path of the old cpuset in 'ppathbuf' if it needs to be
   * notified on release.
   *

   * Call holding manage_mutex.  May take callback_mutex and task_lock of

   * the task 'pid' during call.
   */

  static int attach_task(struct cpuset *cs, char *pidbuf, char **ppathbuf)

  {
  	pid_t pid;
  	struct task_struct *tsk;
  	struct cpuset *oldcs;
  	cpumask_t cpus;

  	nodemask_t from, to;

  	struct mm_struct *mm;

  	int retval;

  	if (sscanf(pidbuf, "%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 || 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);
  	}

  	retval = security_task_setscheduler(tsk, 0, NULL);
  	if (retval) {
  		put_task_struct(tsk);
  		return retval;
  	}

  	mutex_lock(&callback_mutex);

  	task_lock(tsk);
  	oldcs = tsk->cpuset;

  	/*
  	 * After getting 'oldcs' cpuset ptr, be sure still not exiting.
  	 * If 'oldcs' might be the top_cpuset due to the_top_cpuset_hack
  	 * then fail this attach_task(), to avoid breaking top_cpuset.count.
  	 */
  	if (tsk->flags & PF_EXITING) {

  		task_unlock(tsk);

  		mutex_unlock(&callback_mutex);

  		put_task_struct(tsk);
  		return -ESRCH;
  	}
  	atomic_inc(&cs->count);

  	rcu_assign_pointer(tsk->cpuset, cs);

  	task_unlock(tsk);
  
  	guarantee_online_cpus(cs, &cpus);
  	set_cpus_allowed(tsk, cpus);

  	from = oldcs->mems_allowed;
  	to = cs->mems_allowed;

  	mutex_unlock(&callback_mutex);

  
  	mm = get_task_mm(tsk);
  	if (mm) {
  		mpol_rebind_mm(mm, &to);

  		if (is_memory_migrate(cs))

  			cpuset_migrate_mm(mm, &from, &to);

  		mmput(mm);
  	}

  	put_task_struct(tsk);

  	synchronize_rcu();

  	if (atomic_dec_and_test(&oldcs->count))

  		check_for_release(oldcs, ppathbuf);

  	return 0;
  }
  
  /* The various types of files and directories in a cpuset file system */
  
  typedef enum {
  	FILE_ROOT,
  	FILE_DIR,

  	FILE_MEMORY_MIGRATE,

  	FILE_CPULIST,
  	FILE_MEMLIST,
  	FILE_CPU_EXCLUSIVE,
  	FILE_MEM_EXCLUSIVE,
  	FILE_NOTIFY_ON_RELEASE,

  	FILE_MEMORY_PRESSURE_ENABLED,
  	FILE_MEMORY_PRESSURE,

  	FILE_SPREAD_PAGE,
  	FILE_SPREAD_SLAB,

  	FILE_TASKLIST,
  } cpuset_filetype_t;

  static ssize_t cpuset_common_file_write(struct file *file,
  					const char __user *userbuf,

  					size_t nbytes, loff_t *unused_ppos)
  {

  	struct cpuset *cs = __d_cs(file->f_path.dentry->d_parent);
  	struct cftype *cft = __d_cft(file->f_path.dentry);

  	cpuset_filetype_t type = cft->private;
  	char *buffer;

  	char *pathbuf = NULL;

  	int retval = 0;
  
  	/* Crude upper limit on largest legitimate cpulist user might write. */

  	if (nbytes > 100 + 6 * max(NR_CPUS, MAX_NUMNODES))

  		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);

  
  	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_MEMORY_MIGRATE:
  		retval = update_flag(CS_MEMORY_MIGRATE, cs, buffer);
  		break;

  	case FILE_MEMORY_PRESSURE_ENABLED:
  		retval = update_memory_pressure_enabled(cs, buffer);
  		break;
  	case FILE_MEMORY_PRESSURE:
  		retval = -EACCES;
  		break;

  	case FILE_SPREAD_PAGE:
  		retval = update_flag(CS_SPREAD_PAGE, cs, buffer);

  		cs->mems_generation = cpuset_mems_generation++;

  		break;
  	case FILE_SPREAD_SLAB:
  		retval = update_flag(CS_SPREAD_SLAB, cs, buffer);

  		cs->mems_generation = cpuset_mems_generation++;

  		break;

  	case FILE_TASKLIST:

  		retval = attach_task(cs, buffer, &pathbuf);

  		break;
  	default:
  		retval = -EINVAL;
  		goto out2;
  	}
  
  	if (retval == 0)
  		retval = nbytes;
  out2:

  	mutex_unlock(&manage_mutex);

  	cpuset_release_agent(pathbuf);

  out1:
  	kfree(buffer);
  	return retval;
  }
  
  static ssize_t cpuset_file_write(struct file *file, const char __user *buf,
  						size_t nbytes, loff_t *ppos)
  {
  	ssize_t retval = 0;

  	struct cftype *cft = __d_cft(file->f_path.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;

  	mutex_lock(&callback_mutex);

  	mask = cs->cpus_allowed;

  	mutex_unlock(&callback_mutex);

  
  	return cpulist_scnprintf(page, PAGE_SIZE, mask);
  }
  
  static int cpuset_sprintf_memlist(char *page, struct cpuset *cs)
  {
  	nodemask_t mask;

  	mutex_lock(&callback_mutex);

  	mask = cs->mems_allowed;

  	mutex_unlock(&callback_mutex);

  
  	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_path.dentry);
  	struct cpuset *cs = __d_cs(file->f_path.dentry->d_parent);

  	cpuset_filetype_t type = cft->private;
  	char *page;
  	ssize_t retval = 0;
  	char *s;

  
  	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;

  	case FILE_MEMORY_MIGRATE:
  		*s++ = is_memory_migrate(cs) ? '1' : '0';
  		break;

  	case FILE_MEMORY_PRESSURE_ENABLED:
  		*s++ = cpuset_memory_pressure_enabled ? '1' : '0';
  		break;
  	case FILE_MEMORY_PRESSURE:
  		s += sprintf(s, "%d", fmeter_getrate(&cs->fmeter));
  		break;

  	case FILE_SPREAD_PAGE:
  		*s++ = is_spread_page(cs) ? '1' : '0';
  		break;
  	case FILE_SPREAD_SLAB:
  		*s++ = is_spread_slab(cs) ? '1' : '0';
  		break;

  	default:
  		retval = -EINVAL;
  		goto out;
  	}
  	*s++ = '
  ';

  	retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page);

  out:
  	free_page((unsigned long)page);
  	return retval;
  }
  
  static ssize_t cpuset_file_read(struct file *file, char __user *buf, size_t nbytes,
  								loff_t *ppos)
  {
  	ssize_t retval = 0;

  	struct cftype *cft = __d_cft(file->f_path.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_path.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_path.dentry);

  	if (cft->release)
  		return cft->release(inode, file);
  	return 0;
  }

  /*
   * cpuset_rename - Only allow simple rename of directories in place.
   */
  static int cpuset_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 const 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,

  	.rename = cpuset_rename,

  };
  
  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) */

  		inc_nlink(inode);

  	} 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;

  		inc_nlink(parent->d_inode);

  		cs->dentry = dentry;
  	}
  	dput(dentry);
  
  	return error;
  }
  
  static int cpuset_add_file(struct dentry *dir, const struct cftype *cft)
  {
  	struct dentry *dentry;
  	int error;

  	mutex_lock(&dir->d_inode->i_mutex);

  	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);

  	mutex_unlock(&dir->d_inode->i_mutex);

  	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.  No need to task_lock(p)
   * when reading out p->cpuset, as we don't really care if it changes
   * on the next cycle, and we are not going to try to dereference it.

   */

  static 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
  ", a[i]);
  	return cnt;
  }

  /*
   * Handle an open on 'tasks' file.  Prepare a buffer listing the
   * process id's of tasks currently attached to the cpuset being opened.
   *

   * Does not require any specific cpuset mutexes, and does not take any.

   */

  static int cpuset_tasks_open(struct inode *unused, struct file *file)
  {

  	struct cpuset *cs = __d_cs(file->f_path.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 struct cftype cft_memory_migrate = {
  	.name = "memory_migrate",
  	.private = FILE_MEMORY_MIGRATE,
  };

  static struct cftype cft_memory_pressure_enabled = {
  	.name = "memory_pressure_enabled",
  	.private = FILE_MEMORY_PRESSURE_ENABLED,
  };
  
  static struct cftype cft_memory_pressure = {
  	.name = "memory_pressure",
  	.private = FILE_MEMORY_PRESSURE,
  };

  static struct cftype cft_spread_page = {
  	.name = "memory_spread_page",
  	.private = FILE_SPREAD_PAGE,
  };
  
  static struct cftype cft_spread_slab = {
  	.name = "memory_spread_slab",
  	.private = FILE_SPREAD_SLAB,
  };

  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_memory_migrate)) < 0)
  		return err;

  	if ((err = cpuset_add_file(cs_dentry, &cft_memory_pressure)) < 0)
  		return err;

  	if ((err = cpuset_add_file(cs_dentry, &cft_spread_page)) < 0)
  		return err;
  	if ((err = cpuset_add_file(cs_dentry, &cft_spread_slab)) < 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 mutex 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;

  	mutex_lock(&manage_mutex);

  	cpuset_update_task_memory_state();

  	cs->flags = 0;
  	if (notify_on_release(parent))
  		set_bit(CS_NOTIFY_ON_RELEASE, &cs->flags);

  	if (is_spread_page(parent))
  		set_bit(CS_SPREAD_PAGE, &cs->flags);
  	if (is_spread_slab(parent))
  		set_bit(CS_SPREAD_SLAB, &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);

  	cs->mems_generation = cpuset_mems_generation++;

  	fmeter_init(&cs->fmeter);

  
  	cs->parent = parent;

  	mutex_lock(&callback_mutex);

  	list_add(&cs->sibling, &cs->parent->children);

  	number_of_cpusets++;

  	mutex_unlock(&callback_mutex);

  
  	err = cpuset_create_dir(cs, name, mode);
  	if (err < 0)
  		goto err;
  
  	/*

  	 * Release manage_mutex before cpuset_populate_dir() because it

  	 * will down() this new directory's i_mutex and if we race with

  	 * another mkdir, we might deadlock.
  	 */

  	mutex_unlock(&manage_mutex);

  
  	err = cpuset_populate_dir(cs->dentry);
  	/* If err < 0, we have a half-filled directory - oh well ;) */
  	return 0;
  err:
  	list_del(&cs->sibling);

  	mutex_unlock(&manage_mutex);

  	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_mutex already */

  	return cpuset_create(c_parent, dentry->d_name.name, mode | S_IFDIR);
  }

  /*
   * Locking note on the strange update_flag() call below:
   *
   * If the cpuset being removed is marked cpu_exclusive, then simulate
   * turning cpu_exclusive off, which will call update_cpu_domains().
   * The lock_cpu_hotplug() call in update_cpu_domains() must not be
   * made while holding callback_mutex.  Elsewhere the kernel nests
   * callback_mutex inside lock_cpu_hotplug() calls.  So the reverse
   * nesting would risk an ABBA deadlock.
   */

  static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry)
  {
  	struct cpuset *cs = dentry->d_fsdata;
  	struct dentry *d;
  	struct cpuset *parent;

  	char *pathbuf = NULL;

  	/* the vfs holds both inode->i_mutex already */

  	mutex_lock(&manage_mutex);

  	cpuset_update_task_memory_state();

  	if (atomic_read(&cs->count) > 0) {

  		mutex_unlock(&manage_mutex);

  		return -EBUSY;
  	}
  	if (!list_empty(&cs->children)) {

  		mutex_unlock(&manage_mutex);

  		return -EBUSY;
  	}

  	if (is_cpu_exclusive(cs)) {
  		int retval = update_flag(CS_CPU_EXCLUSIVE, cs, "0");
  		if (retval < 0) {
  			mutex_unlock(&manage_mutex);
  			return retval;
  		}
  	}

  	parent = cs->parent;

  	mutex_lock(&callback_mutex);

  	set_bit(CS_REMOVED, &cs->flags);
  	list_del(&cs->sibling);	/* delete my sibling from parent->children */

  	spin_lock(&cs->dentry->d_lock);

  	d = dget(cs->dentry);
  	cs->dentry = NULL;
  	spin_unlock(&d->d_lock);
  	cpuset_d_remove_dir(d);
  	dput(d);

  	number_of_cpusets--;

  	mutex_unlock(&callback_mutex);

  	if (list_empty(&parent->children))
  		check_for_release(parent, &pathbuf);

  	mutex_unlock(&manage_mutex);

  	cpuset_release_agent(pathbuf);

  	return 0;
  }

  /*
   * cpuset_init_early - just enough so that the calls to
   * cpuset_update_task_memory_state() in early init code
   * are harmless.
   */
  
  int __init cpuset_init_early(void)
  {
  	struct task_struct *tsk = current;
  
  	tsk->cpuset = &top_cpuset;

  	tsk->cpuset->mems_generation = cpuset_mems_generation++;

  	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;

  	fmeter_init(&top_cpuset.fmeter);

  	top_cpuset.mems_generation = 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!
  ");
  		err = PTR_ERR(cpuset_mount);
  		cpuset_mount = NULL;
  		goto out;
  	}
  	root = cpuset_mount->mnt_sb->s_root;
  	root->d_fsdata = &top_cpuset;

  	inc_nlink(root->d_inode);

  	top_cpuset.dentry = root;
  	root->d_inode->i_op = &cpuset_dir_inode_operations;

  	number_of_cpusets = 1;

  	err = cpuset_populate_dir(root);

  	/* memory_pressure_enabled is in root cpuset only */
  	if (err == 0)
  		err = cpuset_add_file(root, &cft_memory_pressure_enabled);

  out:
  	return err;
  }

  /*
   * If common_cpu_mem_hotplug_unplug(), below, unplugs any CPUs
   * or memory nodes, we need to walk over the cpuset hierarchy,
   * removing that CPU or node from all cpusets.  If this removes the
   * last CPU or node from a cpuset, then the guarantee_online_cpus()
   * or guarantee_online_mems() code will use that emptied cpusets
   * parent online CPUs or nodes.  Cpusets that were already empty of
   * CPUs or nodes are left empty.
   *
   * This routine is intentionally inefficient in a couple of regards.
   * It will check all cpusets in a subtree even if the top cpuset of
   * the subtree has no offline CPUs or nodes.  It checks both CPUs and
   * nodes, even though the caller could have been coded to know that
   * only one of CPUs or nodes needed to be checked on a given call.
   * This was done to minimize text size rather than cpu cycles.
   *
   * Call with both manage_mutex and callback_mutex held.
   *
   * Recursive, on depth of cpuset subtree.
   */
  
  static void guarantee_online_cpus_mems_in_subtree(const struct cpuset *cur)
  {
  	struct cpuset *c;
  
  	/* Each of our child cpusets mems must be online */
  	list_for_each_entry(c, &cur->children, sibling) {
  		guarantee_online_cpus_mems_in_subtree(c);
  		if (!cpus_empty(c->cpus_allowed))
  			guarantee_online_cpus(c, &c->cpus_allowed);
  		if (!nodes_empty(c->mems_allowed))
  			guarantee_online_mems(c, &c->mems_allowed);
  	}
  }
  
  /*
   * The cpus_allowed and mems_allowed nodemasks in the top_cpuset track
   * cpu_online_map and node_online_map.  Force the top cpuset to track
   * whats online after any CPU or memory node hotplug or unplug event.
   *
   * To ensure that we don't remove a CPU or node from the top cpuset
   * that is currently in use by a child cpuset (which would violate
   * the rule that cpusets must be subsets of their parent), we first
   * call the recursive routine guarantee_online_cpus_mems_in_subtree().
   *
   * Since there are two callers of this routine, one for CPU hotplug
   * events and one for memory node hotplug events, we could have coded
   * two separate routines here.  We code it as a single common routine
   * in order to minimize text size.
   */
  
  static void common_cpu_mem_hotplug_unplug(void)
  {
  	mutex_lock(&manage_mutex);
  	mutex_lock(&callback_mutex);
  
  	guarantee_online_cpus_mems_in_subtree(&top_cpuset);
  	top_cpuset.cpus_allowed = cpu_online_map;
  	top_cpuset.mems_allowed = node_online_map;
  
  	mutex_unlock(&callback_mutex);
  	mutex_unlock(&manage_mutex);
  }

  /*
   * The top_cpuset tracks what CPUs and Memory Nodes are online,
   * period.  This is necessary in order to make cpusets transparent
   * (of no affect) on systems that are actively using CPU hotplug
   * but making no active use of cpusets.
   *

   * This routine ensures that top_cpuset.cpus_allowed tracks
   * cpu_online_map on each CPU hotplug (cpuhp) event.

   */

  static int cpuset_handle_cpuhp(struct notifier_block *nb,
  				unsigned long phase, void *cpu)
  {

  	common_cpu_mem_hotplug_unplug();

  	return 0;
  }

  #ifdef CONFIG_MEMORY_HOTPLUG

  /*
   * Keep top_cpuset.mems_allowed tracking node_online_map.
   * Call this routine anytime after you change node_online_map.
   * See also the previous routine cpuset_handle_cpuhp().
   */

  void cpuset_track_online_nodes(void)

  {

  	common_cpu_mem_hotplug_unplug();

  }
  #endif

  /**
   * 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;

  
  	hotcpu_notifier(cpuset_handle_cpuhp, 0);

  }
  
  /**
   * cpuset_fork - attach newly forked task to its parents cpuset.

   * @tsk: pointer to task_struct of forking parent process.

   *

   * Description: A task inherits its parent's cpuset at fork().
   *
   * A pointer to the shared cpuset was automatically copied in fork.c
   * by dup_task_struct().  However, we ignore that copy, since it was
   * not made under the protection of task_lock(), so might no longer be
   * a valid cpuset pointer.  attach_task() might have already changed
   * current->cpuset, allowing the previously referenced cpuset to
   * be removed and freed.  Instead, we task_lock(current) and copy
   * its present value of current->cpuset for our freshly forked child.
   *
   * At the point that cpuset_fork() is called, 'current' is the parent
   * task, and the passed argument 'child' points to the child task.

   **/

  void cpuset_fork(struct task_struct *child)

  {

  	task_lock(current);
  	child->cpuset = current->cpuset;
  	atomic_inc(&child->cpuset->count);
  	task_unlock(current);

  }
  
  /**
   * cpuset_exit - detach cpuset from exiting task
   * @tsk: pointer to task_struct of exiting process
   *
   * Description: Detach cpuset from @tsk and release it.
   *

   * Note that cpusets marked notify_on_release force every task in

   * them to take the global manage_mutex mutex when exiting.

   * This could impact scaling on very large systems.  Be reluctant to
   * use notify_on_release cpusets where very high task exit scaling
   * is required on large systems.
   *
   * Don't even think about derefencing 'cs' after the cpuset use count

   * goes to zero, except inside a critical section guarded by manage_mutex
   * or callback_mutex.   Otherwise a zero cpuset use count is a license to

   * any other task to nuke the cpuset immediately, via cpuset_rmdir().
   *

   * This routine has to take manage_mutex, not callback_mutex, because
   * it is holding that mutex while calling check_for_release(),
   * which calls kmalloc(), so can't be called holding callback_mutex().

   *
   * We don't need to task_lock() this reference to tsk->cpuset,
   * because tsk is already marked PF_EXITING, so attach_task() won't

   * mess with it, or task is a failed fork, never visible to attach_task.

   *

   * the_top_cpuset_hack:

   *
   *    Set the exiting tasks cpuset to the root cpuset (top_cpuset).
   *
   *    Don't leave a task unable to allocate memory, as that is an
   *    accident waiting to happen should someone add a callout in
   *    do_exit() after the cpuset_exit() call that might allocate.
   *    If a task tries to allocate memory with an invalid cpuset,
   *    it will oops in cpuset_update_task_memory_state().
   *
   *    We call cpuset_exit() while the task is still competent to
   *    handle notify_on_release(), then leave the task attached to
   *    the root cpuset (top_cpuset) for the remainder of its exit.
   *
   *    To do this properly, we would increment the reference count on
   *    top_cpuset, and near the very end of the kernel/exit.c do_exit()
   *    code we would add a second cpuset function call, to drop that
   *    reference.  This would just create an unnecessary hot spot on
   *    the top_cpuset reference count, to no avail.
   *
   *    Normally, holding a reference to a cpuset without bumping its
   *    count is unsafe.   The cpuset could go away, or someone could
   *    attach us to a different cpuset, decrementing the count on
   *    the first cpuset that we never incremented.  But in this case,
   *    top_cpuset isn't going away, and either task has PF_EXITING set,
   *    which wards off any attach_task() attempts, or task is a failed
   *    fork, never visible to attach_task.
   *
   *    Another way to do this would be to set the cpuset pointer
   *    to NULL here, and check in cpuset_update_task_memory_state()
   *    for a NULL pointer.  This hack avoids that NULL check, for no
   *    cost (other than this way too long comment ;).

   **/
  
  void cpuset_exit(struct task_struct *tsk)
  {
  	struct cpuset *cs;

  	cs = tsk->cpuset;

  	tsk->cpuset = &top_cpuset;	/* the_top_cpuset_hack - see above */

  	if (notify_on_release(cs)) {

  		char *pathbuf = NULL;

  		mutex_lock(&manage_mutex);

  		if (atomic_dec_and_test(&cs->count))

  			check_for_release(cs, &pathbuf);

  		mutex_unlock(&manage_mutex);

  		cpuset_release_agent(pathbuf);

  	} else {
  		atomic_dec(&cs->count);

  	}
  }
  
  /**
   * 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.
   **/

  cpumask_t cpuset_cpus_allowed(struct task_struct *tsk)

  {
  	cpumask_t mask;

  	mutex_lock(&callback_mutex);

  	task_lock(tsk);

  	guarantee_online_cpus(tsk->cpuset, &mask);

  	task_unlock(tsk);

  	mutex_unlock(&callback_mutex);

  
  	return mask;
  }
  
  void cpuset_init_current_mems_allowed(void)
  {
  	current->mems_allowed = NODE_MASK_ALL;
  }

  /**

   * cpuset_mems_allowed - return mems_allowed mask from a tasks cpuset.
   * @tsk: pointer to task_struct from which to obtain cpuset->mems_allowed.
   *
   * Description: Returns the nodemask_t mems_allowed of the cpuset
   * attached to the specified @tsk.  Guaranteed to return some non-empty
   * subset of node_online_map, even if this means going outside the
   * tasks cpuset.
   **/
  
  nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
  {
  	nodemask_t mask;

  	mutex_lock(&callback_mutex);

  	task_lock(tsk);
  	guarantee_online_mems(tsk->cpuset, &mask);
  	task_unlock(tsk);

  	mutex_unlock(&callback_mutex);

  
  	return mask;
  }
  
  /**

   * cpuset_zonelist_valid_mems_allowed - check zonelist vs. curremt mems_allowed
   * @zl: the zonelist to be checked
   *

   * 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 = zone_to_nid(zl->zones[i]);

  
  		if (node_isset(nid, current->mems_allowed))
  			return 1;
  	}
  	return 0;
  }

  /*
   * nearest_exclusive_ancestor() - Returns the nearest mem_exclusive

   * ancestor to the specified cpuset.  Call holding callback_mutex.

   * If no ancestor is mem_exclusive (an unusual configuration), then
   * returns the root cpuset.
   */
  static const struct cpuset *nearest_exclusive_ancestor(const struct cpuset *cs)
  {
  	while (!is_mem_exclusive(cs) && cs->parent)
  		cs = cs->parent;
  	return cs;
  }

  /**

   * cpuset_zone_allowed_softwall - Can we allocate on zone z's memory node?

   * @z: is this zone on an allowed node?

   * @gfp_mask: memory allocation flags

   *

   * If we're in interrupt, yes, we can always allocate.  If
   * __GFP_THISNODE is set, yes, we can always allocate.  If zone

   * z's node is in our tasks mems_allowed, yes.  If it's not a
   * __GFP_HARDWALL request and this zone's nodes is in the nearest
   * mem_exclusive cpuset ancestor to this tasks cpuset, yes.
   * Otherwise, no.
   *

   * If __GFP_HARDWALL is set, cpuset_zone_allowed_softwall()
   * reduces to cpuset_zone_allowed_hardwall().  Otherwise,
   * cpuset_zone_allowed_softwall() might sleep, and might allow a zone
   * from an enclosing cpuset.
   *
   * cpuset_zone_allowed_hardwall() only handles the simpler case of
   * hardwall cpusets, and never sleeps.
   *
   * The __GFP_THISNODE placement logic is really handled elsewhere,
   * by forcibly using a zonelist starting at a specified node, and by
   * (in get_page_from_freelist()) refusing to consider the zones for
   * any node on the zonelist except the first.  By the time any such
   * calls get to this routine, we should just shut up and say 'yes'.
   *

   * GFP_USER allocations are marked with the __GFP_HARDWALL bit,
   * and do not allow allocations outside the current tasks cpuset.
   * GFP_KERNEL allocations are not so marked, so can escape to the

   * nearest enclosing mem_exclusive ancestor cpuset.

   *

   * Scanning up parent cpusets requires callback_mutex.  The
   * __alloc_pages() routine only calls here with __GFP_HARDWALL bit
   * _not_ set if it's a GFP_KERNEL allocation, and all nodes in the
   * current tasks mems_allowed came up empty on the first pass over
   * the zonelist.  So only GFP_KERNEL allocations, if all nodes in the
   * cpuset are short of memory, might require taking the callback_mutex
   * mutex.

   *

   * The first call here from mm/page_alloc:get_page_from_freelist()

   * has __GFP_HARDWALL set in gfp_mask, enforcing hardwall cpusets,
   * so no allocation on a node outside the cpuset is allowed (unless
   * in interrupt, of course).

   *
   * The second pass through get_page_from_freelist() doesn't even call
   * here for GFP_ATOMIC calls.  For those calls, the __alloc_pages()
   * variable 'wait' is not set, and the bit ALLOC_CPUSET is not set
   * in alloc_flags.  That logic and the checks below have the combined
   * affect that:

   *	in_interrupt - any node ok (current task context irrelevant)
   *	GFP_ATOMIC   - any node ok
   *	GFP_KERNEL   - any node in enclosing mem_exclusive cpuset ok
   *	GFP_USER     - only nodes in current tasks mems allowed ok.

   *
   * Rule:

   *    Don't call cpuset_zone_allowed_softwall if you can't sleep, unless you

   *    pass in the __GFP_HARDWALL flag set in gfp_flag, which disables
   *    the code that might scan up ancestor cpusets and sleep.

   */

  int __cpuset_zone_allowed_softwall(struct zone *z, gfp_t gfp_mask)

  {

  	int node;			/* node that zone z is on */
  	const struct cpuset *cs;	/* current cpuset ancestors */

  	int allowed;			/* is allocation in zone z allowed? */

  	if (in_interrupt() || (gfp_mask & __GFP_THISNODE))

  		return 1;

  	node = zone_to_nid(z);

  	might_sleep_if(!(gfp_mask & __GFP_HARDWALL));

  	if (node_isset(node, current->mems_allowed))
  		return 1;
  	if (gfp_mask & __GFP_HARDWALL)	/* If hardwall request, stop here */
  		return 0;

  	if (current->flags & PF_EXITING) /* Let dying task have memory */
  		return 1;

  	/* Not hardwall and node outside mems_allowed: scan up cpusets */

  	mutex_lock(&callback_mutex);

  	task_lock(current);
  	cs = nearest_exclusive_ancestor(current->cpuset);
  	task_unlock(current);

  	allowed = node_isset(node, cs->mems_allowed);

  	mutex_unlock(&callback_mutex);

  	return allowed;

  }

  /*
   * cpuset_zone_allowed_hardwall - Can we allocate on zone z's memory node?
   * @z: is this zone on an allowed node?
   * @gfp_mask: memory allocation flags
   *
   * If we're in interrupt, yes, we can always allocate.
   * If __GFP_THISNODE is set, yes, we can always allocate.  If zone
   * z's node is in our tasks mems_allowed, yes.   Otherwise, no.
   *
   * The __GFP_THISNODE placement logic is really handled elsewhere,
   * by forcibly using a zonelist starting at a specified node, and by
   * (in get_page_from_freelist()) refusing to consider the zones for
   * any node on the zonelist except the first.  By the time any such
   * calls get to this routine, we should just shut up and say 'yes'.
   *
   * Unlike the cpuset_zone_allowed_softwall() variant, above,
   * this variant requires that the zone be in the current tasks
   * mems_allowed or that we're in interrupt.  It does not scan up the
   * cpuset hierarchy for the nearest enclosing mem_exclusive cpuset.
   * It never sleeps.
   */
  
  int __cpuset_zone_allowed_hardwall(struct zone *z, gfp_t gfp_mask)
  {
  	int node;			/* node that zone z is on */
  
  	if (in_interrupt() || (gfp_mask & __GFP_THISNODE))
  		return 1;
  	node = zone_to_nid(z);
  	if (node_isset(node, current->mems_allowed))
  		return 1;
  	return 0;
  }

  /**

   * cpuset_lock - lock out any changes to cpuset structures
   *

   * The out of memory (oom) code needs to mutex_lock cpusets

   * from being changed while it scans the tasklist looking for a

   * task in an overlapping cpuset.  Expose callback_mutex via this

   * cpuset_lock() routine, so the oom code can lock it, before
   * locking the task list.  The tasklist_lock is a spinlock, so

   * must be taken inside callback_mutex.

   */
  
  void cpuset_lock(void)
  {

  	mutex_lock(&callback_mutex);

  }
  
  /**
   * cpuset_unlock - release lock on cpuset changes
   *
   * Undo the lock taken in a previous cpuset_lock() call.
   */
  
  void cpuset_unlock(void)
  {

  	mutex_unlock(&callback_mutex);

  }
  
  /**

   * cpuset_mem_spread_node() - On which node to begin search for a page
   *
   * If a task is marked PF_SPREAD_PAGE or PF_SPREAD_SLAB (as for
   * tasks in a cpuset with is_spread_page or is_spread_slab set),
   * and if the memory allocation used cpuset_mem_spread_node()
   * to determine on which node to start looking, as it will for
   * certain page cache or slab cache pages such as used for file
   * system buffers and inode caches, then instead of starting on the
   * local node to look for a free page, rather spread the starting
   * node around the tasks mems_allowed nodes.
   *
   * We don't have to worry about the returned node being offline
   * because "it can't happen", and even if it did, it would be ok.
   *
   * The routines calling guarantee_online_mems() are careful to
   * only set nodes in task->mems_allowed that are online.  So it
   * should not be possible for the following code to return an
   * offline node.  But if it did, that would be ok, as this routine
   * is not returning the node where the allocation must be, only
   * the node where the search should start.  The zonelist passed to
   * __alloc_pages() will include all nodes.  If the slab allocator
   * is passed an offline node, it will fall back to the local node.
   * See kmem_cache_alloc_node().
   */
  
  int cpuset_mem_spread_node(void)
  {
  	int node;
  
  	node = next_node(current->cpuset_mem_spread_rotor, current->mems_allowed);
  	if (node == MAX_NUMNODES)
  		node = first_node(current->mems_allowed);
  	current->cpuset_mem_spread_rotor = node;
  	return node;
  }
  EXPORT_SYMBOL_GPL(cpuset_mem_spread_node);
  
  /**

   * cpuset_excl_nodes_overlap - Do we overlap @p's mem_exclusive ancestors?
   * @p: pointer to task_struct of some other task.
   *
   * Description: Return true if the nearest mem_exclusive ancestor
   * cpusets of tasks @p and current overlap.  Used by oom killer to
   * determine if task @p's memory usage might impact the memory
   * available to the current task.
   *

   * Call while holding callback_mutex.

   **/
  
  int cpuset_excl_nodes_overlap(const struct task_struct *p)
  {
  	const struct cpuset *cs1, *cs2;	/* my and p's cpuset ancestors */

  	int overlap = 1;		/* do cpusets overlap? */

  	task_lock(current);
  	if (current->flags & PF_EXITING) {
  		task_unlock(current);
  		goto done;
  	}
  	cs1 = nearest_exclusive_ancestor(current->cpuset);
  	task_unlock(current);
  
  	task_lock((struct task_struct *)p);
  	if (p->flags & PF_EXITING) {
  		task_unlock((struct task_struct *)p);
  		goto done;
  	}
  	cs2 = nearest_exclusive_ancestor(p->cpuset);
  	task_unlock((struct task_struct *)p);

  	overlap = nodes_intersects(cs1->mems_allowed, cs2->mems_allowed);
  done:

  	return overlap;
  }

  /*

   * Collection of memory_pressure is suppressed unless
   * this flag is enabled by writing "1" to the special
   * cpuset file 'memory_pressure_enabled' in the root cpuset.
   */

  int cpuset_memory_pressure_enabled __read_mostly;

  
  /**
   * cpuset_memory_pressure_bump - keep stats of per-cpuset reclaims.
   *
   * Keep a running average of the rate of synchronous (direct)
   * page reclaim efforts initiated by tasks in each cpuset.
   *
   * This represents the rate at which some task in the cpuset
   * ran low on memory on all nodes it was allowed to use, and
   * had to enter the kernels page reclaim code in an effort to
   * create more free memory by tossing clean pages or swapping
   * or writing dirty pages.
   *
   * Display to user space in the per-cpuset read-only file
   * "memory_pressure".  Value displayed is an integer
   * representing the recent rate of entry into the synchronous
   * (direct) page reclaim by any task attached to the cpuset.
   **/
  
  void __cpuset_memory_pressure_bump(void)
  {
  	struct cpuset *cs;
  
  	task_lock(current);
  	cs = current->cpuset;
  	fmeter_markevent(&cs->fmeter);
  	task_unlock(current);
  }
  
  /*

   * proc_cpuset_show()
   *  - Print tasks cpuset path into seq_file.
   *  - Used for /proc/<pid>/cpuset.

   *  - No need to task_lock(tsk) on this tsk->cpuset reference, as it
   *    doesn't really matter if tsk->cpuset changes after we read it,

   *    and we take manage_mutex, keeping attach_task() from changing it

   *    anyway.  No need to check that tsk->cpuset != NULL, thanks to
   *    the_top_cpuset_hack in cpuset_exit(), which sets an exiting tasks
   *    cpuset to top_cpuset.

   */

  static int proc_cpuset_show(struct seq_file *m, void *v)
  {

  	struct pid *pid;

  	struct task_struct *tsk;
  	char *buf;

  	int retval;

  	retval = -ENOMEM;

  	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
  	if (!buf)

  		goto out;
  
  	retval = -ESRCH;

  	pid = m->private;
  	tsk = get_pid_task(pid, PIDTYPE_PID);

  	if (!tsk)
  		goto out_free;

  	retval = -EINVAL;

  	mutex_lock(&manage_mutex);

  	retval = cpuset_path(tsk->cpuset, buf, PAGE_SIZE);

  	if (retval < 0)

  		goto out_unlock;

  	seq_puts(m, buf);
  	seq_putc(m, '
  ');

  out_unlock:

  	mutex_unlock(&manage_mutex);

  	put_task_struct(tsk);
  out_free:

  	kfree(buf);

  out:

  	return retval;
  }
  
  static int cpuset_open(struct inode *inode, struct file *file)
  {

  	struct pid *pid = PROC_I(inode)->pid;
  	return single_open(file, proc_cpuset_show, pid);

  }

  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, "
  ");
  	buffer += sprintf(buffer, "Mems_allowed:\t");
  	buffer += nodemask_scnprintf(buffer, PAGE_SIZE, task->mems_allowed);
  	buffer += sprintf(buffer, "
  ");
  	return buffer;
  }