cpuset.c 76.7 KB
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/*
 *  kernel/cpuset.c
 *
 *  Processor and Memory placement constraints for sets of tasks.
 *
 *  Copyright (C) 2003 BULL SA.
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 *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
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 *
 *  Portions derived from Patrick Mochel's sysfs code.
 *  sysfs is Copyright (c) 2001-3 Patrick Mochel
 *
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 *  2003-10-10 Written by Simon Derr.
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 *  2003-10-22 Updates by Stephen Hemminger.
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 *  2004 May-July Rework by Paul Jackson.
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 *
 *  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>
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#include <linux/mempolicy.h>
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#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>
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#include <linux/rcupdate.h>
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#include <linux/sched.h>
#include <linux/seq_file.h>
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#include <linux/security.h>
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#include <linux/slab.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>
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#include <linux/mutex.h>
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#define CPUSET_SUPER_MAGIC		0x27e0eb
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/*
 * Tracks how many cpusets are currently defined in system.
 * When there is only one cpuset (the root cpuset) we can
 * short circuit some hooks.
 */
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int number_of_cpusets __read_mostly;
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/* 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 */
};

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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 */

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

	struct fmeter fmeter;		/* memory_pressure filter */
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};

/* bits in struct cpuset flags field */
typedef enum {
	CS_CPU_EXCLUSIVE,
	CS_MEM_EXCLUSIVE,
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	CS_MEMORY_MIGRATE,
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	CS_REMOVED,
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	CS_NOTIFY_ON_RELEASE,
	CS_SPREAD_PAGE,
	CS_SPREAD_SLAB,
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} cpuset_flagbits_t;

/* convenient tests for these bits */
static inline int is_cpu_exclusive(const struct cpuset *cs)
{
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	return test_bit(CS_CPU_EXCLUSIVE, &cs->flags);
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}

static inline int is_mem_exclusive(const struct cpuset *cs)
{
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	return test_bit(CS_MEM_EXCLUSIVE, &cs->flags);
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}

static inline int is_removed(const struct cpuset *cs)
{
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	return test_bit(CS_REMOVED, &cs->flags);
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}

static inline int notify_on_release(const struct cpuset *cs)
{
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	return test_bit(CS_NOTIFY_ON_RELEASE, &cs->flags);
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}

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static inline int is_memory_migrate(const struct cpuset *cs)
{
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	return test_bit(CS_MEMORY_MIGRATE, &cs->flags);
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}

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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);
}

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/*
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 * Increment this integer everytime any cpuset changes its
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 * 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.
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 *
 * Since cpuset_mems_generation is guarded by manage_mutex,
 * there is no need to mark it atomic.
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 */
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static int cpuset_mems_generation;
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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;
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static struct super_block *cpuset_sb;
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/*
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 * We have two global cpuset mutexes below.  They can nest.
 * It is ok to first take manage_mutex, then nest callback_mutex.  We also
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 * require taking task_lock() when dereferencing a tasks cpuset pointer.
 * See "The task_lock() exception", at the end of this comment.
 *
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 * 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
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 * and be able to modify cpusets.  It can perform various checks on
 * the cpuset structure first, knowing nothing will change.  It can
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 * also allocate memory while just holding manage_mutex.  While it is
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 * performing these checks, various callback routines can briefly
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 * acquire callback_mutex to query cpusets.  Once it is ready to make
 * the changes, it takes callback_mutex, blocking everyone else.
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 *
 * Calls to the kernel memory allocator can not be made while holding
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 * callback_mutex, as that would risk double tripping on callback_mutex
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 * from one of the callbacks into the cpuset code from within
 * __alloc_pages().
 *
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 * If a task is only holding callback_mutex, then it has read-only
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 * 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.
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 * So in general, code holding manage_mutex or callback_mutex can't rely
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 * on the count field not changing.  However, if the count goes to
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 * zero, then only attach_task(), which holds both mutexes, can
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 * 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).
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 * So code holding manage_mutex or callback_mutex can safely assume that
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 * if the count is zero, it will stay zero.  Similarly, if a task
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 * holds manage_mutex or callback_mutex on a cpuset with zero count, it
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 * knows that the cpuset won't be removed, as cpuset_rmdir() needs
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 * both of those mutexes.
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 *
 * The cpuset_common_file_write handler for operations that modify
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 * the cpuset hierarchy holds manage_mutex across the entire operation,
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 * single threading all such cpuset modifications across the system.
 *
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 * The cpuset_common_file_read() handlers only hold callback_mutex across
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 * 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
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 * (usually) take either mutex.  These are the two most performance
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 * critical pieces of code here.  The exception occurs on cpuset_exit(),
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 * when a task in a notify_on_release cpuset exits.  Then manage_mutex
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 * is taken, and if the cpuset count is zero, a usermode call made
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 * to /sbin/cpuset_release_agent with the name of the cpuset (path
 * relative to the root of cpuset file system) as the argument.
 *
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 * 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
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 * least one task in the system (init), therefore, top_cpuset
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 * 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
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 * so using both mutexes, however there are several performance
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 * critical places that need to reference task->cpuset without the
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 * expense of grabbing a system global mutex.  Therefore except as
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 * 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.
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 *
 * 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().
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 */

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static DEFINE_MUTEX(manage_mutex);
static DEFINE_MUTEX(callback_mutex);
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/*
 * 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)
{
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	struct dentry *d = lookup_one_len(name, parent, strlen(name));
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	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) {
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		struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
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		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;
	}
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	list_del_init(&dentry->d_u.d_child);
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	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) */
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		inc_nlink(inode);
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	} else {
		return -ENOMEM;
	}

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

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static int cpuset_get_sb(struct file_system_type *fs_type,
			 int flags, const char *unused_dev_name,
			 void *data, struct vfsmount *mnt)
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{
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	return get_sb_single(fs_type, flags, data, cpuset_fill_super, mnt);
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}

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:
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 *	- 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
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 */

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;
}

/*
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 * Call with manage_mutex held.  Writes path of cpuset into buf.
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 * 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.
 *
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 * 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.
 *
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 * When we had only one cpuset mutex, we had to call this
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 * without holding it, to avoid deadlock when call_usermodehelper()
 * allocated memory.  With two locks, we could now call this while
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 * holding manage_mutex, but we still don't, so as to minimize
 * the time manage_mutex is held.
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 */

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static void cpuset_release_agent(const char *pathbuf)
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{
	char *argv[3], *envp[3];
	int i;

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	if (!pathbuf)
		return;

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	i = 0;
	argv[i++] = "/sbin/cpuset_release_agent";
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	argv[i++] = (char *)pathbuf;
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	argv[i] = NULL;

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

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

/*
 * 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
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 * 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
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 * cpuset_release_agent() with it later on, once manage_mutex is dropped.
 * Call here with manage_mutex held.
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 *
 * 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
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 * calling check_for_release() with manage_mutex held and the address
 * of the pathbuf pointer, then dropping manage_mutex, then calling
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 * cpuset_release_agent() with pathbuf, as set by check_for_release().
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 */

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static void check_for_release(struct cpuset *cs, char **ppathbuf)
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{
	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)
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			kfree(buf);
		else
			*ppathbuf = buf;
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	}
}

/*
 * 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.
 *
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 * Call with callback_mutex held.
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 */

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
584 585 586 587
 * are online, with memory.  If none are online with memory, 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_states[N_HIGH_MEMORY].
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 *
 * One way or another, we guarantee to return some non-empty subset
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 * of node_states[N_HIGH_MEMORY].
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 *
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 * Call with callback_mutex held.
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 */

static void guarantee_online_mems(const struct cpuset *cs, nodemask_t *pmask)
{
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	while (cs && !nodes_intersects(cs->mems_allowed,
					node_states[N_HIGH_MEMORY]))
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		cs = cs->parent;
	if (cs)
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		nodes_and(*pmask, cs->mems_allowed,
					node_states[N_HIGH_MEMORY]);
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	else
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		*pmask = node_states[N_HIGH_MEMORY];
	BUG_ON(!nodes_intersects(*pmask, node_states[N_HIGH_MEMORY]));
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}

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/**
 * 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.
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 *
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 * 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().
 *
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 * 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
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 * current->mm->mmap_sem during call.
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 *
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 * 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.
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 *
 * 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.
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 */

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void cpuset_update_task_memory_state(void)
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{
652
	int my_cpusets_mem_gen;
653
	struct task_struct *tsk = current;
654
	struct cpuset *cs;
655

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	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();
	}
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666
	if (my_cpusets_mem_gen != tsk->cpuset_mems_generation) {
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		mutex_lock(&callback_mutex);
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		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;
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		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;
680
		task_unlock(tsk);
681
		mutex_unlock(&callback_mutex);
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		mpol_rebind_task(tsk, &tsk->mems_allowed);
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	}
}

/*
 * 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
691
 * are only set if the other's are set.  Call holding manage_mutex.
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 */

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
709
 * manage_mutex held.
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 *
 * '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 */
733
	if (cur == &top_cpuset)
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		return 0;

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	par = cur->parent;

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	/* 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;
}

757
/*
758
 * Call with manage_mutex held.  May take callback_mutex during call.
759 760
 */

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static int update_cpumask(struct cpuset *cs, char *buf)
{
	struct cpuset trialcs;
764
	int retval;
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	/* top_cpuset.cpus_allowed tracks cpu_online_map; it's read-only */
	if (cs == &top_cpuset)
		return -EACCES;

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	trialcs = *cs;
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	/*
	 * We allow a cpuset's cpus_allowed to be empty; if it has attached
	 * tasks, we'll catch it later when we validate the change and return
	 * -ENOSPC.
	 */
	if (!buf[0] || (buf[0] == '\n' && !buf[1])) {
		cpus_clear(trialcs.cpus_allowed);
	} else {
		retval = cpulist_parse(buf, trialcs.cpus_allowed);
		if (retval < 0)
			return retval;
	}
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	cpus_and(trialcs.cpus_allowed, trialcs.cpus_allowed, cpu_online_map);
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	/* cpus_allowed cannot be empty for a cpuset with attached tasks. */
	if (atomic_read(&cs->count) && cpus_empty(trialcs.cpus_allowed))
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		return -ENOSPC;
	retval = validate_change(cs, &trialcs);
789 790
	if (retval < 0)
		return retval;
791
	mutex_lock(&callback_mutex);
792
	cs->cpus_allowed = trialcs.cpus_allowed;
793
	mutex_unlock(&callback_mutex);
794
	return 0;
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}

797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845
/*
 * 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);
}

846
/*
847 848 849
 * 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
850 851 852
 * task in the cpuset, rebind any vma mempolicies and if
 * the cpuset is marked 'memory_migrate', migrate the tasks
 * pages to the new memory.
853
 *
854
 * Call with manage_mutex held.  May take callback_mutex during call.
855 856 857
 * 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.
858 859
 */

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static int update_nodemask(struct cpuset *cs, char *buf)
{
	struct cpuset trialcs;
863
	nodemask_t oldmem;
864 865 866
	struct task_struct *g, *p;
	struct mm_struct **mmarray;
	int i, n, ntasks;
867
	int migrate;
868
	int fudge;
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	int retval;

871 872 873 874
	/*
	 * top_cpuset.mems_allowed tracks node_stats[N_HIGH_MEMORY];
	 * it's read-only
	 */
875 876 877
	if (cs == &top_cpuset)
		return -EACCES;

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	trialcs = *cs;
879 880 881 882 883 884 885 886 887 888 889 890

	/*
	 * We allow a cpuset's mems_allowed to be empty; if it has attached
	 * tasks, we'll catch it later when we validate the change and return
	 * -ENOSPC.
	 */
	if (!buf[0] || (buf[0] == '\n' && !buf[1])) {
		nodes_clear(trialcs.mems_allowed);
	} else {
		retval = nodelist_parse(buf, trialcs.mems_allowed);
		if (retval < 0)
			goto done;
891 892 893 894 895 896 897 898
		if (!nodes_intersects(trialcs.mems_allowed,
						node_states[N_HIGH_MEMORY])) {
			/*
			 * error if only memoryless nodes specified.
			 */
			retval = -ENOSPC;
			goto done;
		}
899
	}
900 901 902 903 904 905
	/*
	 * Exclude memoryless nodes.  We know that trialcs.mems_allowed
	 * contains at least one node with memory.
	 */
	nodes_and(trialcs.mems_allowed, trialcs.mems_allowed,
						node_states[N_HIGH_MEMORY]);
906 907 908 909 910
	oldmem = cs->mems_allowed;
	if (nodes_equal(oldmem, trialcs.mems_allowed)) {
		retval = 0;		/* Too easy - nothing to do */
		goto done;
	}
911 912
	/* mems_allowed cannot be empty for a cpuset with attached tasks. */
	if (atomic_read(&cs->count) && nodes_empty(trialcs.mems_allowed)) {
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		retval = -ENOSPC;
		goto done;
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	}
916 917 918 919
	retval = validate_change(cs, &trialcs);
	if (retval < 0)
		goto done;

920
	mutex_lock(&callback_mutex);
921
	cs->mems_allowed = trialcs.mems_allowed;
922
	cs->mems_generation = cpuset_mems_generation++;
923
	mutex_unlock(&callback_mutex);
924

925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943
	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;
944
		read_lock(&tasklist_lock);		/* block fork */
945 946
		if (atomic_read(&cs->count) <= ntasks)
			break;				/* got enough */
947
		read_unlock(&tasklist_lock);		/* try again */
948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968
		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.\n");
			continue;
		}
		if (p->cpuset != cs)
			continue;
		mm = get_task_mm(p);
		if (!mm)
			continue;
		mmarray[n++] = mm;
	} while_each_thread(g, p);
969
	read_unlock(&tasklist_lock);
970 971 972 973 974 975 976 977 978

	/*
	 * 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
979
	 * cpuset manage_mutex, we know that no other rebind effort will
980 981
	 * be contending for the global variable cpuset_being_rebound.
	 * It's ok if we rebind the same mm twice; mpol_rebind_mm()
982
	 * is idempotent.  Also migrate pages in each mm to new nodes.
983
	 */
984
	migrate = is_memory_migrate(cs);
985 986 987 988
	for (i = 0; i < n; i++) {
		struct mm_struct *mm = mmarray[i];

		mpol_rebind_mm(mm, &cs->mems_allowed);
989 990
		if (migrate)
			cpuset_migrate_mm(mm, &oldmem, &cs->mems_allowed);
991 992 993 994 995 996 997
		mmput(mm);
	}

	/* We're done rebinding vma's to this cpusets new mems_allowed. */
	kfree(mmarray);
	set_cpuset_being_rebound(NULL);
	retval = 0;
998
done:
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	return retval;
}

1002
/*
1003
 * Call with manage_mutex held.
1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014
 */

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;
}

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/*
 * 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,
1018 1019
 *				CS_NOTIFY_ON_RELEASE, CS_MEMORY_MIGRATE,
 *				CS_SPREAD_PAGE, CS_SPREAD_SLAB)
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 * cs:	the cpuset to update
 * buf:	the buffer where we read the 0 or 1
1022
 *
1023
 * Call with manage_mutex held.
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 */

static int update_flag(cpuset_flagbits_t bit, struct cpuset *cs, char *buf)
{
	int turning_on;
	struct cpuset trialcs;
1030
	int err;
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	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);
1041 1042
	if (err < 0)
		return err;
1043
	mutex_lock(&callback_mutex);
1044
	cs->flags = trialcs.flags;
1045
	mutex_unlock(&callback_mutex);
1046 1047

	return 0;
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}

1050
/*
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 * Frequency meter - How fast is some event occurring?
1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147
 *
 * 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;
}

1148 1149 1150 1151 1152
/*
 * 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.
 *
1153
 * Call holding manage_mutex.  May take callback_mutex and task_lock of
1154 1155 1156
 * the task 'pid' during call.
 */

1157
static int attach_task(struct cpuset *cs, char *pidbuf, char **ppathbuf)
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{
	pid_t pid;
	struct task_struct *tsk;
	struct cpuset *oldcs;
	cpumask_t cpus;
1163
	nodemask_t from, to;
1164
	struct mm_struct *mm;
1165
	int retval;
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1167
	if (sscanf(pidbuf, "%d", &pid) != 1)
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		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);
1176
		if (!tsk || tsk->flags & PF_EXITING) {
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			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);
	}

1194 1195 1196 1197 1198 1199
	retval = security_task_setscheduler(tsk, 0, NULL);
	if (retval) {
		put_task_struct(tsk);
		return retval;
	}

1200
	mutex_lock(&callback_mutex);
1201

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	task_lock(tsk);
	oldcs = tsk->cpuset;
1204 1205 1206 1207 1208 1209
	/*
	 * 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) {
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		task_unlock(tsk);
1211
		mutex_unlock(&callback_mutex);
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		put_task_struct(tsk);
		return -ESRCH;
	}
	atomic_inc(&cs->count);
1216
	rcu_assign_pointer(tsk->cpuset, cs);
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	task_unlock(tsk);

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

1222 1223 1224
	from = oldcs->mems_allowed;
	to = cs->mems_allowed;

1225
	mutex_unlock(&callback_mutex);
1226 1227 1228 1229

	mm = get_task_mm(tsk);
	if (mm) {
		mpol_rebind_mm(mm, &to);
1230
		if (is_memory_migrate(cs))
1231
			cpuset_migrate_mm(mm, &from, &to);
1232 1233 1234
		mmput(mm);
	}

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	put_task_struct(tsk);
1236
	synchronize_rcu();
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	if (atomic_dec_and_test(&oldcs->count))
1238
		check_for_release(oldcs, ppathbuf);
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	return 0;
}

/* The various types of files and directories in a cpuset file system */

typedef enum {
	FILE_ROOT,
	FILE_DIR,
1247
	FILE_MEMORY_MIGRATE,
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	FILE_CPULIST,
	FILE_MEMLIST,
	FILE_CPU_EXCLUSIVE,
	FILE_MEM_EXCLUSIVE,
	FILE_NOTIFY_ON_RELEASE,
1253 1254
	FILE_MEMORY_PRESSURE_ENABLED,
	FILE_MEMORY_PRESSURE,
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	FILE_SPREAD_PAGE,
	FILE_SPREAD_SLAB,
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	FILE_TASKLIST,
} cpuset_filetype_t;

1260 1261
static ssize_t cpuset_common_file_write(struct file *file,
					const char __user *userbuf,
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					size_t nbytes, loff_t *unused_ppos)
{
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	struct cpuset *cs = __d_cs(file->f_path.dentry->d_parent);
	struct cftype *cft = __d_cft(file->f_path.dentry);
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	cpuset_filetype_t type = cft->private;
	char *buffer;
1268
	char *pathbuf = NULL;
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	int retval = 0;

	/* Crude upper limit on largest legitimate cpulist user might write. */
1272
	if (nbytes > 100 + 6 * max(NR_CPUS, MAX_NUMNODES))
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		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 */

1285
	mutex_lock(&manage_mutex);
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	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;
1308 1309 1310
	case FILE_MEMORY_MIGRATE:
		retval = update_flag(CS_MEMORY_MIGRATE, cs, buffer);
		break;
1311 1312 1313 1314 1315 1316
	case FILE_MEMORY_PRESSURE_ENABLED:
		retval = update_memory_pressure_enabled(cs, buffer);
		break;
	case FILE_MEMORY_PRESSURE:
		retval = -EACCES;
		break;
1317 1318
	case FILE_SPREAD_PAGE:
		retval = update_flag(CS_SPREAD_PAGE, cs, buffer);
1319
		cs->mems_generation = cpuset_mems_generation++;
1320 1321 1322
		break;
	case FILE_SPREAD_SLAB:
		retval = update_flag(CS_SPREAD_SLAB, cs, buffer);
1323
		cs->mems_generation = cpuset_mems_generation++;
1324
		break;
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	case FILE_TASKLIST:
1326
		retval = attach_task(cs, buffer, &pathbuf);
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		break;
	default:
		retval = -EINVAL;
		goto out2;
	}

	if (retval == 0)
		retval = nbytes;
out2:
1336
	mutex_unlock(&manage_mutex);
1337
	cpuset_release_agent(pathbuf);
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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;
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	struct cftype *cft = __d_cft(file->f_path.dentry);
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	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;

1376
	mutex_lock(&callback_mutex);
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	mask = cs->cpus_allowed;
1378
	mutex_unlock(&callback_mutex);
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	return cpulist_scnprintf(page, PAGE_SIZE, mask);
}

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

1387
	mutex_lock(&callback_mutex);
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	mask = cs->mems_allowed;
1389
	mutex_unlock(&callback_mutex);
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	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)
{
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	struct cftype *cft = __d_cft(file->f_path.dentry);
	struct cpuset *cs = __d_cs(file->f_path.dentry->d_parent);
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	cpuset_filetype_t type = cft->private;
	char *page;
	ssize_t retval = 0;
	char *s;

1404
	if (!(page = (char *)__get_free_page(GFP_TEMPORARY)))
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		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;
1425 1426 1427
	case FILE_MEMORY_MIGRATE:
		*s++ = is_memory_migrate(cs) ? '1' : '0';
		break;
1428 1429 1430 1431 1432 1433
	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;
1434 1435 1436 1437 1438 1439
	case FILE_SPREAD_PAGE:
		*s++ = is_spread_page(cs) ? '1' : '0';
		break;
	case FILE_SPREAD_SLAB:
		*s++ = is_spread_slab(cs) ? '1' : '0';
		break;
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	default:
		retval = -EINVAL;
		goto out;
	}
	*s++ = '\n';

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	retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page);
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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;
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	struct cftype *cft = __d_cft(file->f_path.dentry);
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	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;

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	cft = __d_cft(file->f_path.dentry);
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	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)
{
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	struct cftype *cft = __d_cft(file->f_path.dentry);
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	if (cft->release)
		return cft->release(inode, file);
	return 0;
}

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/*
 * 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);
}

1512
static const struct file_operations cpuset_file_operations = {
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	.read = cpuset_file_read,
	.write = cpuset_file_write,
	.llseek = generic_file_llseek,
	.open = cpuset_file_open,
	.release = cpuset_file_release,
};

1520
static const struct inode_operations cpuset_dir_inode_operations = {
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	.lookup = simple_lookup,
	.mkdir = cpuset_mkdir,
	.rmdir = cpuset_rmdir,
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	.rename = cpuset_rename,
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};

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) */
1545
		inc_nlink(inode);
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	} 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.
1558
 *	cs:	the cpuset we create the directory for.
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 *		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;
1578
		inc_nlink(parent->d_inode);
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		cs->dentry = dentry;
	}
	dput(dentry);

	return error;
}

static int cpuset_add_file(struct dentry *dir, const struct cftype *cft)
{
	struct dentry *dentry;
	int error;

1591
	mutex_lock(&dir->d_inode->i_mutex);
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	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);
1600
	mutex_unlock(&dir->d_inode->i_mutex);
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	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'.
1628 1629 1630
 * 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.
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 */
1632
static int pid_array_load(pid_t *pidarray, int npids, struct cpuset *cs)
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{
	int n = 0;
	struct task_struct *g, *p;

	read_lock(&tasklist_lock);

	do_each_thread(g, p) {
		if (p->cpuset == cs) {
1641
			pidarray[n++] = p->pid;
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			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;
}

1672 1673 1674 1675
/*
 * Handle an open on 'tasks' file.  Prepare a buffer listing the
 * process id's of tasks currently attached to the cpuset being opened.
 *
1676
 * Does not require any specific cpuset mutexes, and does not take any.
1677
 */
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static int cpuset_tasks_open(struct inode *unused, struct file *file)
{
J
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	struct cpuset *cs = __d_cs(file->f_path.dentry->d_parent);
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1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730
	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;

1731
	return simple_read_from_buffer(buf, nbytes, ppos, ctr->buf, ctr->bufsz);
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1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782
}

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,
};

1783 1784 1785 1786 1787
static struct cftype cft_memory_migrate = {
	.name = "memory_migrate",
	.private = FILE_MEMORY_MIGRATE,
};

1788 1789 1790 1791 1792 1793 1794 1795 1796 1797
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,
};

1798 1799 1800 1801 1802 1803 1804 1805 1806 1807
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,
};

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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;
1822 1823
	if ((err = cpuset_add_file(cs_dentry, &cft_memory_migrate)) < 0)
		return err;
1824 1825
	if ((err = cpuset_add_file(cs_dentry, &cft_memory_pressure)) < 0)
		return err;
1826 1827 1828 1829
	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;
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	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
 *
1841
 *	Must be called with the mutex on the parent inode held
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 */

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;

1853
	mutex_lock(&manage_mutex);
1854
	cpuset_update_task_memory_state();
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	cs->flags = 0;
	if (notify_on_release(parent))
		set_bit(CS_NOTIFY_ON_RELEASE, &cs->flags);
1858 1859 1860 1861
	if (is_spread_page(parent))
		set_bit(CS_SPREAD_PAGE, &cs->flags);
	if (is_spread_slab(parent))
		set_bit(CS_SPREAD_SLAB, &cs->flags);
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	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);
1867
	cs->mems_generation = cpuset_mems_generation++;
1868
	fmeter_init(&cs->fmeter);
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	cs->parent = parent;

1872
	mutex_lock(&callback_mutex);
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	list_add(&cs->sibling, &cs->parent->children);
1874
	number_of_cpusets++;
1875
	mutex_unlock(&callback_mutex);
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	err = cpuset_create_dir(cs, name, mode);
	if (err < 0)
		goto err;

	/*
1882
	 * Release manage_mutex before cpuset_populate_dir() because it
1883
	 * will down() this new directory's i_mutex and if we race with
L
Linus Torvalds 已提交
1884 1885
	 * another mkdir, we might deadlock.
	 */
1886
	mutex_unlock(&manage_mutex);
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	err = cpuset_populate_dir(cs->dentry);
	/* If err < 0, we have a half-filled directory - oh well ;) */
	return 0;
err:
	list_del(&cs->sibling);
1893
	mutex_unlock(&manage_mutex);
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1894 1895 1896 1897 1898 1899 1900 1901
	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;

1902
	/* the vfs holds inode->i_mutex already */
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	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;
1911
	char *pathbuf = NULL;
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1912

1913
	/* the vfs holds both inode->i_mutex already */
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1914

1915
	mutex_lock(&manage_mutex);
1916
	cpuset_update_task_memory_state();
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1917
	if (atomic_read(&cs->count) > 0) {
1918
		mutex_unlock(&manage_mutex);
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		return -EBUSY;
	}
	if (!list_empty(&cs->children)) {
1922
		mutex_unlock(&manage_mutex);
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		return -EBUSY;
	}
	parent = cs->parent;
1926
	mutex_lock(&callback_mutex);
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	set_bit(CS_REMOVED, &cs->flags);
	list_del(&cs->sibling);	/* delete my sibling from parent->children */
1929
	spin_lock(&cs->dentry->d_lock);
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	d = dget(cs->dentry);
	cs->dentry = NULL;
	spin_unlock(&d->d_lock);
	cpuset_d_remove_dir(d);
	dput(d);
1935
	number_of_cpusets--;
1936
	mutex_unlock(&callback_mutex);
1937 1938
	if (list_empty(&parent->children))
		check_for_release(parent, &pathbuf);
1939
	mutex_unlock(&manage_mutex);
1940
	cpuset_release_agent(pathbuf);
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	return 0;
}

1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954
/*
 * 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;
1955
	tsk->cpuset->mems_generation = cpuset_mems_generation++;
1956 1957 1958
	return 0;
}

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/**
 * 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;

1973
	fmeter_init(&top_cpuset.fmeter);
1974
	top_cpuset.mems_generation = cpuset_mems_generation++;
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	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;
1990
	inc_nlink(root->d_inode);
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	top_cpuset.dentry = root;
	root->d_inode->i_op = &cpuset_dir_inode_operations;
1993
	number_of_cpusets = 1;
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	err = cpuset_populate_dir(root);
1995 1996 1997
	/* memory_pressure_enabled is in root cpuset only */
	if (err == 0)
		err = cpuset_add_file(root, &cft_memory_pressure_enabled);
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out:
	return err;
}

2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038
/*
 * 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
2039 2040 2041
 * cpu_online_map and node_states[N_HIGH_MEMORY].  Force the top cpuset to
 * track what's online after any CPU or memory node hotplug or unplug
 * event.
2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060
 *
 * 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;
2061
	top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
2062 2063 2064 2065 2066

	mutex_unlock(&callback_mutex);
	mutex_unlock(&manage_mutex);
}

2067 2068 2069 2070 2071 2072
/*
 * 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.
 *
2073 2074
 * This routine ensures that top_cpuset.cpus_allowed tracks
 * cpu_online_map on each CPU hotplug (cpuhp) event.
2075 2076 2077 2078 2079
 */

static int cpuset_handle_cpuhp(struct notifier_block *nb,
				unsigned long phase, void *cpu)
{
2080 2081 2082
	if (phase == CPU_DYING || phase == CPU_DYING_FROZEN)
		return NOTIFY_DONE;

2083
	common_cpu_mem_hotplug_unplug();
2084 2085 2086
	return 0;
}

2087
#ifdef CONFIG_MEMORY_HOTPLUG
2088
/*
2089 2090 2091
 * Keep top_cpuset.mems_allowed tracking node_states[N_HIGH_MEMORY].
 * Call this routine anytime after you change
 * node_states[N_HIGH_MEMORY].
2092 2093 2094
 * See also the previous routine cpuset_handle_cpuhp().
 */

A
Al Viro 已提交
2095
void cpuset_track_online_nodes(void)
2096
{
2097
	common_cpu_mem_hotplug_unplug();
2098 2099 2100
}
#endif

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/**
 * 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;
2110
	top_cpuset.mems_allowed = node_states[N_HIGH_MEMORY];
2111 2112

	hotcpu_notifier(cpuset_handle_cpuhp, 0);
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}

/**
 * cpuset_fork - attach newly forked task to its parents cpuset.
2117
 * @tsk: pointer to task_struct of forking parent process.
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 *
2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130
 * 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.
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 **/

2133
void cpuset_fork(struct task_struct *child)
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2134
{
2135 2136 2137 2138
	task_lock(current);
	child->cpuset = current->cpuset;
	atomic_inc(&child->cpuset->count);
	task_unlock(current);
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}

/**
 * cpuset_exit - detach cpuset from exiting task
 * @tsk: pointer to task_struct of exiting process
 *
 * Description: Detach cpuset from @tsk and release it.
 *
2147
 * Note that cpusets marked notify_on_release force every task in
2148
 * them to take the global manage_mutex mutex when exiting.
2149 2150 2151 2152 2153
 * 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
2154 2155
 * 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
2156 2157
 * any other task to nuke the cpuset immediately, via cpuset_rmdir().
 *
2158 2159 2160
 * 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().
2161
 *
2162
 * the_top_cpuset_hack:
2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193
 *
 *    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 ;).
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 **/

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

2200
	task_lock(current);
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2201
	cs = tsk->cpuset;
2202
	tsk->cpuset = &top_cpuset;	/* the_top_cpuset_hack - see above */
2203
	task_unlock(current);
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2204

2205
	if (notify_on_release(cs)) {
2206 2207
		char *pathbuf = NULL;

2208
		mutex_lock(&manage_mutex);
2209
		if (atomic_dec_and_test(&cs->count))
2210
			check_for_release(cs, &pathbuf);
2211
		mutex_unlock(&manage_mutex);
2212
		cpuset_release_agent(pathbuf);
2213 2214
	} else {
		atomic_dec(&cs->count);
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	}
}

/**
 * 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.
 **/

2228
cpumask_t cpuset_cpus_allowed(struct task_struct *tsk)
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2229 2230 2231
{
	cpumask_t mask;

2232
	mutex_lock(&callback_mutex);
2233
	task_lock(tsk);
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2234
	guarantee_online_cpus(tsk->cpuset, &mask);
2235
	task_unlock(tsk);
2236
	mutex_unlock(&callback_mutex);
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2237 2238 2239 2240 2241 2242 2243 2244 2245

	return mask;
}

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

2246 2247 2248 2249 2250 2251
/**
 * 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
2252
 * subset of node_states[N_HIGH_MEMORY], even if this means going outside the
2253 2254 2255 2256 2257 2258 2259
 * tasks cpuset.
 **/

nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
{
	nodemask_t mask;

2260
	mutex_lock(&callback_mutex);
2261 2262 2263
	task_lock(tsk);
	guarantee_online_mems(tsk->cpuset, &mask);
	task_unlock(tsk);
2264
	mutex_unlock(&callback_mutex);
2265 2266 2267 2268

	return mask;
}

2269 2270 2271 2272
/**
 * cpuset_zonelist_valid_mems_allowed - check zonelist vs. curremt mems_allowed
 * @zl: the zonelist to be checked
 *
L
Linus Torvalds 已提交
2273 2274 2275 2276 2277 2278 2279
 * 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++) {
2280
		int nid = zone_to_nid(zl->zones[i]);
L
Linus Torvalds 已提交
2281 2282 2283 2284 2285 2286 2287

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

2288 2289
/*
 * nearest_exclusive_ancestor() - Returns the nearest mem_exclusive
2290
 * ancestor to the specified cpuset.  Call holding callback_mutex.
2291 2292 2293 2294 2295 2296 2297 2298 2299 2300
 * 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;
}

2301
/**
2302
 * cpuset_zone_allowed_softwall - Can we allocate on zone z's memory node?
2303
 * @z: is this zone on an allowed node?
2304
 * @gfp_mask: memory allocation flags
2305
 *
2306 2307
 * If we're in interrupt, yes, we can always allocate.  If
 * __GFP_THISNODE is set, yes, we can always allocate.  If zone
2308 2309 2310
 * 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.
2311 2312
 * If the task has been OOM killed and has access to memory reserves
 * as specified by the TIF_MEMDIE flag, yes.
2313 2314
 * Otherwise, no.
 *
2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328
 * 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'.
 *
2329
 * GFP_USER allocations are marked with the __GFP_HARDWALL bit,
2330 2331
 * and do not allow allocations outside the current tasks cpuset
 * unless the task has been OOM killed as is marked TIF_MEMDIE.
2332
 * GFP_KERNEL allocations are not so marked, so can escape to the
2333
 * nearest enclosing mem_exclusive ancestor cpuset.
2334
 *
2335 2336 2337 2338 2339 2340 2341
 * 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.
2342
 *
2343
 * The first call here from mm/page_alloc:get_page_from_freelist()
2344 2345 2346
 * 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).
2347 2348 2349 2350 2351 2352
 *
 * 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:
2353 2354
 *	in_interrupt - any node ok (current task context irrelevant)
 *	GFP_ATOMIC   - any node ok
2355
 *	TIF_MEMDIE   - any node ok
2356 2357
 *	GFP_KERNEL   - any node in enclosing mem_exclusive cpuset ok
 *	GFP_USER     - only nodes in current tasks mems allowed ok.
2358 2359
 *
 * Rule:
2360
 *    Don't call cpuset_zone_allowed_softwall if you can't sleep, unless you
2361 2362
 *    pass in the __GFP_HARDWALL flag set in gfp_flag, which disables
 *    the code that might scan up ancestor cpusets and sleep.
2363
 */
2364

2365
int __cpuset_zone_allowed_softwall(struct zone *z, gfp_t gfp_mask)
L
Linus Torvalds 已提交
2366
{
2367 2368
	int node;			/* node that zone z is on */
	const struct cpuset *cs;	/* current cpuset ancestors */
2369
	int allowed;			/* is allocation in zone z allowed? */
2370

2371
	if (in_interrupt() || (gfp_mask & __GFP_THISNODE))
2372
		return 1;
2373
	node = zone_to_nid(z);
2374
	might_sleep_if(!(gfp_mask & __GFP_HARDWALL));
2375 2376
	if (node_isset(node, current->mems_allowed))
		return 1;
2377 2378 2379 2380 2381 2382
	/*
	 * Allow tasks that have access to memory reserves because they have
	 * been OOM killed to get memory anywhere.
	 */
	if (unlikely(test_thread_flag(TIF_MEMDIE)))
		return 1;
2383 2384 2385
	if (gfp_mask & __GFP_HARDWALL)	/* If hardwall request, stop here */
		return 0;

2386 2387 2388
	if (current->flags & PF_EXITING) /* Let dying task have memory */
		return 1;

2389
	/* Not hardwall and node outside mems_allowed: scan up cpusets */
2390
	mutex_lock(&callback_mutex);
2391 2392 2393 2394 2395

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

2396
	allowed = node_isset(node, cs->mems_allowed);
2397
	mutex_unlock(&callback_mutex);
2398
	return allowed;
L
Linus Torvalds 已提交
2399 2400
}

2401 2402 2403 2404 2405 2406 2407
/*
 * 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
2408 2409 2410
 * z's node is in our tasks mems_allowed, yes.   If the task has been
 * OOM killed and has access to memory reserves as specified by the
 * TIF_MEMDIE flag, yes.  Otherwise, no.
2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433
 *
 * 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;
D
Daniel Walker 已提交
2434 2435 2436 2437 2438 2439
	/*
	 * Allow tasks that have access to memory reserves because they have
	 * been OOM killed to get memory anywhere.
	 */
	if (unlikely(test_thread_flag(TIF_MEMDIE)))
		return 1;
2440 2441 2442
	return 0;
}

P
Paul Jackson 已提交
2443 2444 2445
/**
 * cpuset_lock - lock out any changes to cpuset structures
 *
2446
 * The out of memory (oom) code needs to mutex_lock cpusets
P
Paul Jackson 已提交
2447
 * from being changed while it scans the tasklist looking for a
2448
 * task in an overlapping cpuset.  Expose callback_mutex via this
P
Paul Jackson 已提交
2449 2450
 * cpuset_lock() routine, so the oom code can lock it, before
 * locking the task list.  The tasklist_lock is a spinlock, so
2451
 * must be taken inside callback_mutex.
P
Paul Jackson 已提交
2452 2453 2454 2455
 */

void cpuset_lock(void)
{
2456
	mutex_lock(&callback_mutex);
P
Paul Jackson 已提交
2457 2458 2459 2460 2461 2462 2463 2464 2465 2466
}

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

void cpuset_unlock(void)
{
2467
	mutex_unlock(&callback_mutex);
P
Paul Jackson 已提交
2468 2469
}

2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507
/**
 * 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);

2508
/**
2509 2510 2511 2512 2513 2514 2515 2516
 * cpuset_mems_allowed_intersects - Does @tsk1's mems_allowed intersect @tsk2's?
 * @tsk1: pointer to task_struct of some task.
 * @tsk2: pointer to task_struct of some other task.
 *
 * Description: Return true if @tsk1's mems_allowed intersects the
 * mems_allowed of @tsk2.  Used by the OOM killer to determine if
 * one of the task's memory usage might impact the memory available
 * to the other.
2517 2518
 **/

2519 2520
int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
				   const struct task_struct *tsk2)
2521
{
2522
	return nodes_intersects(tsk1->mems_allowed, tsk2->mems_allowed);
2523 2524
}

2525 2526 2527 2528 2529 2530
/*
 * 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.
 */

2531
int cpuset_memory_pressure_enabled __read_mostly;
2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560

/**
 * 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);
}

L
Linus Torvalds 已提交
2561 2562 2563 2564
/*
 * proc_cpuset_show()
 *  - Print tasks cpuset path into seq_file.
 *  - Used for /proc/<pid>/cpuset.
2565 2566
 *  - 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,
2567
 *    and we take manage_mutex, keeping attach_task() from changing it
2568 2569 2570
 *    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.
L
Linus Torvalds 已提交
2571 2572 2573
 */
static int proc_cpuset_show(struct seq_file *m, void *v)
{
2574
	struct pid *pid;
L
Linus Torvalds 已提交
2575 2576
	struct task_struct *tsk;
	char *buf;
2577
	int retval;
L
Linus Torvalds 已提交
2578

2579
	retval = -ENOMEM;
L
Linus Torvalds 已提交
2580 2581
	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!buf)
2582 2583 2584
		goto out;

	retval = -ESRCH;
2585 2586
	pid = m->private;
	tsk = get_pid_task(pid, PIDTYPE_PID);
2587 2588
	if (!tsk)
		goto out_free;
L
Linus Torvalds 已提交
2589

2590
	retval = -EINVAL;
2591
	mutex_lock(&manage_mutex);
2592

2593
	retval = cpuset_path(tsk->cpuset, buf, PAGE_SIZE);
L
Linus Torvalds 已提交
2594
	if (retval < 0)
2595
		goto out_unlock;
L
Linus Torvalds 已提交
2596 2597
	seq_puts(m, buf);
	seq_putc(m, '\n');
2598
out_unlock:
2599
	mutex_unlock(&manage_mutex);
2600 2601
	put_task_struct(tsk);
out_free:
L
Linus Torvalds 已提交
2602
	kfree(buf);
2603
out:
L
Linus Torvalds 已提交
2604 2605 2606 2607 2608
	return retval;
}

static int cpuset_open(struct inode *inode, struct file *file)
{
2609 2610
	struct pid *pid = PROC_I(inode)->pid;
	return single_open(file, proc_cpuset_show, pid);
L
Linus Torvalds 已提交
2611 2612
}

2613
const struct file_operations proc_cpuset_operations = {
L
Linus Torvalds 已提交
2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630
	.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;
}