cgroup.c 109.6 KB
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/*
 *  Generic process-grouping system.
 *
 *  Based originally on the cpuset system, extracted by Paul Menage
 *  Copyright (C) 2006 Google, Inc
 *
 *  Copyright notices from the original cpuset code:
 *  --------------------------------------------------
 *  Copyright (C) 2003 BULL SA.
 *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
 *
 *  Portions derived from Patrick Mochel's sysfs code.
 *  sysfs is Copyright (c) 2001-3 Patrick Mochel
 *
 *  2003-10-10 Written by Simon Derr.
 *  2003-10-22 Updates by Stephen Hemminger.
 *  2004 May-July Rework by Paul Jackson.
 *  ---------------------------------------------------
 *
 *  This file is subject to the terms and conditions of the GNU General Public
 *  License.  See the file COPYING in the main directory of the Linux
 *  distribution for more details.
 */

#include <linux/cgroup.h>
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#include <linux/module.h>
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#include <linux/ctype.h>
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#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
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#include <linux/proc_fs.h>
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#include <linux/rcupdate.h>
#include <linux/sched.h>
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#include <linux/backing-dev.h>
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#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/magic.h>
#include <linux/spinlock.h>
#include <linux/string.h>
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#include <linux/sort.h>
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#include <linux/kmod.h>
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#include <linux/delayacct.h>
#include <linux/cgroupstats.h>
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#include <linux/hash.h>
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#include <linux/namei.h>
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#include <linux/smp_lock.h>
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#include <linux/pid_namespace.h>
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#include <linux/idr.h>
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#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
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#include <asm/atomic.h>

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static DEFINE_MUTEX(cgroup_mutex);

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/* Generate an array of cgroup subsystem pointers */
#define SUBSYS(_x) &_x ## _subsys,

static struct cgroup_subsys *subsys[] = {
#include <linux/cgroup_subsys.h>
};

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#define MAX_CGROUP_ROOT_NAMELEN 64

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/*
 * A cgroupfs_root represents the root of a cgroup hierarchy,
 * and may be associated with a superblock to form an active
 * hierarchy
 */
struct cgroupfs_root {
	struct super_block *sb;

	/*
	 * The bitmask of subsystems intended to be attached to this
	 * hierarchy
	 */
	unsigned long subsys_bits;

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	/* Unique id for this hierarchy. */
	int hierarchy_id;

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	/* The bitmask of subsystems currently attached to this hierarchy */
	unsigned long actual_subsys_bits;

	/* A list running through the attached subsystems */
	struct list_head subsys_list;

	/* The root cgroup for this hierarchy */
	struct cgroup top_cgroup;

	/* Tracks how many cgroups are currently defined in hierarchy.*/
	int number_of_cgroups;

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	/* A list running through the active hierarchies */
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	struct list_head root_list;

	/* Hierarchy-specific flags */
	unsigned long flags;
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	/* The path to use for release notifications. */
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	char release_agent_path[PATH_MAX];
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	/* The name for this hierarchy - may be empty */
	char name[MAX_CGROUP_ROOT_NAMELEN];
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};

/*
 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
 * subsystems that are otherwise unattached - it never has more than a
 * single cgroup, and all tasks are part of that cgroup.
 */
static struct cgroupfs_root rootnode;

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/*
 * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
 * cgroup_subsys->use_id != 0.
 */
#define CSS_ID_MAX	(65535)
struct css_id {
	/*
	 * The css to which this ID points. This pointer is set to valid value
	 * after cgroup is populated. If cgroup is removed, this will be NULL.
	 * This pointer is expected to be RCU-safe because destroy()
	 * is called after synchronize_rcu(). But for safe use, css_is_removed()
	 * css_tryget() should be used for avoiding race.
	 */
	struct cgroup_subsys_state *css;
	/*
	 * ID of this css.
	 */
	unsigned short id;
	/*
	 * Depth in hierarchy which this ID belongs to.
	 */
	unsigned short depth;
	/*
	 * ID is freed by RCU. (and lookup routine is RCU safe.)
	 */
	struct rcu_head rcu_head;
	/*
	 * Hierarchy of CSS ID belongs to.
	 */
	unsigned short stack[0]; /* Array of Length (depth+1) */
};


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/* The list of hierarchy roots */

static LIST_HEAD(roots);
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static int root_count;
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static DEFINE_IDA(hierarchy_ida);
static int next_hierarchy_id;
static DEFINE_SPINLOCK(hierarchy_id_lock);

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/* dummytop is a shorthand for the dummy hierarchy's top cgroup */
#define dummytop (&rootnode.top_cgroup)

/* This flag indicates whether tasks in the fork and exit paths should
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 * check for fork/exit handlers to call. This avoids us having to do
 * extra work in the fork/exit path if none of the subsystems need to
 * be called.
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 */
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static int need_forkexit_callback __read_mostly;
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#ifdef CONFIG_PROVE_LOCKING
int cgroup_lock_is_held(void)
{
	return lockdep_is_held(&cgroup_mutex);
}
#else /* #ifdef CONFIG_PROVE_LOCKING */
int cgroup_lock_is_held(void)
{
	return mutex_is_locked(&cgroup_mutex);
}
#endif /* #else #ifdef CONFIG_PROVE_LOCKING */

EXPORT_SYMBOL_GPL(cgroup_lock_is_held);

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/* convenient tests for these bits */
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inline int cgroup_is_removed(const struct cgroup *cgrp)
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{
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	return test_bit(CGRP_REMOVED, &cgrp->flags);
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}

/* bits in struct cgroupfs_root flags field */
enum {
	ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
};

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static int cgroup_is_releasable(const struct cgroup *cgrp)
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{
	const int bits =
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		(1 << CGRP_RELEASABLE) |
		(1 << CGRP_NOTIFY_ON_RELEASE);
	return (cgrp->flags & bits) == bits;
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}

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static int notify_on_release(const struct cgroup *cgrp)
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{
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	return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
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}

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/*
 * for_each_subsys() allows you to iterate on each subsystem attached to
 * an active hierarchy
 */
#define for_each_subsys(_root, _ss) \
list_for_each_entry(_ss, &_root->subsys_list, sibling)

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/* for_each_active_root() allows you to iterate across the active hierarchies */
#define for_each_active_root(_root) \
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list_for_each_entry(_root, &roots, root_list)

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/* the list of cgroups eligible for automatic release. Protected by
 * release_list_lock */
static LIST_HEAD(release_list);
static DEFINE_SPINLOCK(release_list_lock);
static void cgroup_release_agent(struct work_struct *work);
static DECLARE_WORK(release_agent_work, cgroup_release_agent);
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static void check_for_release(struct cgroup *cgrp);
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/* Link structure for associating css_set objects with cgroups */
struct cg_cgroup_link {
	/*
	 * List running through cg_cgroup_links associated with a
	 * cgroup, anchored on cgroup->css_sets
	 */
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	struct list_head cgrp_link_list;
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	struct cgroup *cgrp;
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	/*
	 * List running through cg_cgroup_links pointing at a
	 * single css_set object, anchored on css_set->cg_links
	 */
	struct list_head cg_link_list;
	struct css_set *cg;
};

/* The default css_set - used by init and its children prior to any
 * hierarchies being mounted. It contains a pointer to the root state
 * for each subsystem. Also used to anchor the list of css_sets. Not
 * reference-counted, to improve performance when child cgroups
 * haven't been created.
 */

static struct css_set init_css_set;
static struct cg_cgroup_link init_css_set_link;

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static int cgroup_subsys_init_idr(struct cgroup_subsys *ss);

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/* css_set_lock protects the list of css_set objects, and the
 * chain of tasks off each css_set.  Nests outside task->alloc_lock
 * due to cgroup_iter_start() */
static DEFINE_RWLOCK(css_set_lock);
static int css_set_count;

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/*
 * hash table for cgroup groups. This improves the performance to find
 * an existing css_set. This hash doesn't (currently) take into
 * account cgroups in empty hierarchies.
 */
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#define CSS_SET_HASH_BITS	7
#define CSS_SET_TABLE_SIZE	(1 << CSS_SET_HASH_BITS)
static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];

static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
{
	int i;
	int index;
	unsigned long tmp = 0UL;

	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
		tmp += (unsigned long)css[i];
	tmp = (tmp >> 16) ^ tmp;

	index = hash_long(tmp, CSS_SET_HASH_BITS);

	return &css_set_table[index];
}

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static void free_css_set_rcu(struct rcu_head *obj)
{
	struct css_set *cg = container_of(obj, struct css_set, rcu_head);
	kfree(cg);
}

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/* We don't maintain the lists running through each css_set to its
 * task until after the first call to cgroup_iter_start(). This
 * reduces the fork()/exit() overhead for people who have cgroups
 * compiled into their kernel but not actually in use */
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static int use_task_css_set_links __read_mostly;
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static void __put_css_set(struct css_set *cg, int taskexit)
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{
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	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;
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	/*
	 * Ensure that the refcount doesn't hit zero while any readers
	 * can see it. Similar to atomic_dec_and_lock(), but for an
	 * rwlock
	 */
	if (atomic_add_unless(&cg->refcount, -1, 1))
		return;
	write_lock(&css_set_lock);
	if (!atomic_dec_and_test(&cg->refcount)) {
		write_unlock(&css_set_lock);
		return;
	}
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	/* This css_set is dead. unlink it and release cgroup refcounts */
	hlist_del(&cg->hlist);
	css_set_count--;

	list_for_each_entry_safe(link, saved_link, &cg->cg_links,
				 cg_link_list) {
		struct cgroup *cgrp = link->cgrp;
		list_del(&link->cg_link_list);
		list_del(&link->cgrp_link_list);
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		if (atomic_dec_and_test(&cgrp->count) &&
		    notify_on_release(cgrp)) {
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			if (taskexit)
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				set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
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		}
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		kfree(link);
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	}
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	write_unlock(&css_set_lock);
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	call_rcu(&cg->rcu_head, free_css_set_rcu);
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}

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/*
 * refcounted get/put for css_set objects
 */
static inline void get_css_set(struct css_set *cg)
{
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	atomic_inc(&cg->refcount);
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}

static inline void put_css_set(struct css_set *cg)
{
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	__put_css_set(cg, 0);
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}

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static inline void put_css_set_taskexit(struct css_set *cg)
{
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	__put_css_set(cg, 1);
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}

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/*
 * compare_css_sets - helper function for find_existing_css_set().
 * @cg: candidate css_set being tested
 * @old_cg: existing css_set for a task
 * @new_cgrp: cgroup that's being entered by the task
 * @template: desired set of css pointers in css_set (pre-calculated)
 *
 * Returns true if "cg" matches "old_cg" except for the hierarchy
 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
 */
static bool compare_css_sets(struct css_set *cg,
			     struct css_set *old_cg,
			     struct cgroup *new_cgrp,
			     struct cgroup_subsys_state *template[])
{
	struct list_head *l1, *l2;

	if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
		/* Not all subsystems matched */
		return false;
	}

	/*
	 * Compare cgroup pointers in order to distinguish between
	 * different cgroups in heirarchies with no subsystems. We
	 * could get by with just this check alone (and skip the
	 * memcmp above) but on most setups the memcmp check will
	 * avoid the need for this more expensive check on almost all
	 * candidates.
	 */

	l1 = &cg->cg_links;
	l2 = &old_cg->cg_links;
	while (1) {
		struct cg_cgroup_link *cgl1, *cgl2;
		struct cgroup *cg1, *cg2;

		l1 = l1->next;
		l2 = l2->next;
		/* See if we reached the end - both lists are equal length. */
		if (l1 == &cg->cg_links) {
			BUG_ON(l2 != &old_cg->cg_links);
			break;
		} else {
			BUG_ON(l2 == &old_cg->cg_links);
		}
		/* Locate the cgroups associated with these links. */
		cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
		cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
		cg1 = cgl1->cgrp;
		cg2 = cgl2->cgrp;
		/* Hierarchies should be linked in the same order. */
		BUG_ON(cg1->root != cg2->root);

		/*
		 * If this hierarchy is the hierarchy of the cgroup
		 * that's changing, then we need to check that this
		 * css_set points to the new cgroup; if it's any other
		 * hierarchy, then this css_set should point to the
		 * same cgroup as the old css_set.
		 */
		if (cg1->root == new_cgrp->root) {
			if (cg1 != new_cgrp)
				return false;
		} else {
			if (cg1 != cg2)
				return false;
		}
	}
	return true;
}

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/*
 * find_existing_css_set() is a helper for
 * find_css_set(), and checks to see whether an existing
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 * css_set is suitable.
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 *
 * oldcg: the cgroup group that we're using before the cgroup
 * transition
 *
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 * cgrp: the cgroup that we're moving into
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 *
 * template: location in which to build the desired set of subsystem
 * state objects for the new cgroup group
 */
static struct css_set *find_existing_css_set(
	struct css_set *oldcg,
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	struct cgroup *cgrp,
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	struct cgroup_subsys_state *template[])
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{
	int i;
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	struct cgroupfs_root *root = cgrp->root;
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	struct hlist_head *hhead;
	struct hlist_node *node;
	struct css_set *cg;
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	/* Built the set of subsystem state objects that we want to
	 * see in the new css_set */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
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		if (root->subsys_bits & (1UL << i)) {
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			/* Subsystem is in this hierarchy. So we want
			 * the subsystem state from the new
			 * cgroup */
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			template[i] = cgrp->subsys[i];
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		} else {
			/* Subsystem is not in this hierarchy, so we
			 * don't want to change the subsystem state */
			template[i] = oldcg->subsys[i];
		}
	}

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	hhead = css_set_hash(template);
	hlist_for_each_entry(cg, node, hhead, hlist) {
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		if (!compare_css_sets(cg, oldcg, cgrp, template))
			continue;

		/* This css_set matches what we need */
		return cg;
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	}
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	/* No existing cgroup group matched */
	return NULL;
}

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static void free_cg_links(struct list_head *tmp)
{
	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;

	list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
		list_del(&link->cgrp_link_list);
		kfree(link);
	}
}

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/*
 * allocate_cg_links() allocates "count" cg_cgroup_link structures
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 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
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 * success or a negative error
 */
static int allocate_cg_links(int count, struct list_head *tmp)
{
	struct cg_cgroup_link *link;
	int i;
	INIT_LIST_HEAD(tmp);
	for (i = 0; i < count; i++) {
		link = kmalloc(sizeof(*link), GFP_KERNEL);
		if (!link) {
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			free_cg_links(tmp);
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			return -ENOMEM;
		}
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		list_add(&link->cgrp_link_list, tmp);
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	}
	return 0;
}

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/**
 * link_css_set - a helper function to link a css_set to a cgroup
 * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
 * @cg: the css_set to be linked
 * @cgrp: the destination cgroup
 */
static void link_css_set(struct list_head *tmp_cg_links,
			 struct css_set *cg, struct cgroup *cgrp)
{
	struct cg_cgroup_link *link;

	BUG_ON(list_empty(tmp_cg_links));
	link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
				cgrp_link_list);
	link->cg = cg;
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	link->cgrp = cgrp;
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	atomic_inc(&cgrp->count);
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	list_move(&link->cgrp_link_list, &cgrp->css_sets);
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	/*
	 * Always add links to the tail of the list so that the list
	 * is sorted by order of hierarchy creation
	 */
	list_add_tail(&link->cg_link_list, &cg->cg_links);
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}

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/*
 * find_css_set() takes an existing cgroup group and a
 * cgroup object, and returns a css_set object that's
 * equivalent to the old group, but with the given cgroup
 * substituted into the appropriate hierarchy. Must be called with
 * cgroup_mutex held
 */
static struct css_set *find_css_set(
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	struct css_set *oldcg, struct cgroup *cgrp)
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{
	struct css_set *res;
	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];

	struct list_head tmp_cg_links;

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	struct hlist_head *hhead;
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	struct cg_cgroup_link *link;
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	/* First see if we already have a cgroup group that matches
	 * the desired set */
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	read_lock(&css_set_lock);
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	res = find_existing_css_set(oldcg, cgrp, template);
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	if (res)
		get_css_set(res);
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	read_unlock(&css_set_lock);
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	if (res)
		return res;

	res = kmalloc(sizeof(*res), GFP_KERNEL);
	if (!res)
		return NULL;

	/* Allocate all the cg_cgroup_link objects that we'll need */
	if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
		kfree(res);
		return NULL;
	}

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	atomic_set(&res->refcount, 1);
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	INIT_LIST_HEAD(&res->cg_links);
	INIT_LIST_HEAD(&res->tasks);
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	INIT_HLIST_NODE(&res->hlist);
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	/* Copy the set of subsystem state objects generated in
	 * find_existing_css_set() */
	memcpy(res->subsys, template, sizeof(res->subsys));

	write_lock(&css_set_lock);
	/* Add reference counts and links from the new css_set. */
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	list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
		struct cgroup *c = link->cgrp;
		if (c->root == cgrp->root)
			c = cgrp;
		link_css_set(&tmp_cg_links, res, c);
	}
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	BUG_ON(!list_empty(&tmp_cg_links));

	css_set_count++;
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	/* Add this cgroup group to the hash table */
	hhead = css_set_hash(res->subsys);
	hlist_add_head(&res->hlist, hhead);

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	write_unlock(&css_set_lock);

	return res;
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}

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/*
 * Return the cgroup for "task" from the given hierarchy. Must be
 * called with cgroup_mutex held.
 */
static struct cgroup *task_cgroup_from_root(struct task_struct *task,
					    struct cgroupfs_root *root)
{
	struct css_set *css;
	struct cgroup *res = NULL;

	BUG_ON(!mutex_is_locked(&cgroup_mutex));
	read_lock(&css_set_lock);
	/*
	 * No need to lock the task - since we hold cgroup_mutex the
	 * task can't change groups, so the only thing that can happen
	 * is that it exits and its css is set back to init_css_set.
	 */
	css = task->cgroups;
	if (css == &init_css_set) {
		res = &root->top_cgroup;
	} else {
		struct cg_cgroup_link *link;
		list_for_each_entry(link, &css->cg_links, cg_link_list) {
			struct cgroup *c = link->cgrp;
			if (c->root == root) {
				res = c;
				break;
			}
		}
	}
	read_unlock(&css_set_lock);
	BUG_ON(!res);
	return res;
}

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/*
 * There is one global cgroup mutex. We also require taking
 * task_lock() when dereferencing a task's cgroup subsys pointers.
 * See "The task_lock() exception", at the end of this comment.
 *
 * A task must hold cgroup_mutex to modify cgroups.
 *
 * Any task can increment and decrement the count field without lock.
 * So in general, code holding cgroup_mutex can't rely on the count
 * field not changing.  However, if the count goes to zero, then only
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 * cgroup_attach_task() can increment it again.  Because a count of zero
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 * means that no tasks are currently attached, therefore there is no
 * way a task attached to that cgroup can fork (the other way to
 * increment the count).  So code holding cgroup_mutex can safely
 * assume that if the count is zero, it will stay zero. Similarly, if
 * a task holds cgroup_mutex on a cgroup with zero count, it
 * knows that the cgroup won't be removed, as cgroup_rmdir()
 * needs that mutex.
 *
 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
 * (usually) take cgroup_mutex.  These are the two most performance
 * critical pieces of code here.  The exception occurs on cgroup_exit(),
 * when a task in a notify_on_release cgroup exits.  Then cgroup_mutex
 * is taken, and if the cgroup count is zero, a usermode call made
L
Li Zefan 已提交
665 666
 * to the release agent with the name of the cgroup (path relative to
 * the root of cgroup file system) as the argument.
667 668 669 670 671 672 673 674 675 676 677
 *
 * A cgroup can only be deleted if both its 'count' of using tasks
 * is zero, and its list of 'children' cgroups is empty.  Since all
 * tasks in the system use _some_ cgroup, and since there is always at
 * least one task in the system (init, pid == 1), therefore, top_cgroup
 * always has either children cgroups and/or using tasks.  So we don't
 * need a special hack to ensure that top_cgroup cannot be deleted.
 *
 *	The task_lock() exception
 *
 * The need for this exception arises from the action of
678
 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
L
Li Zefan 已提交
679
 * another.  It does so using cgroup_mutex, however there are
680 681 682
 * several performance critical places that need to reference
 * task->cgroup without the expense of grabbing a system global
 * mutex.  Therefore except as noted below, when dereferencing or, as
683
 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
684 685 686 687
 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
 * the task_struct routinely used for such matters.
 *
 * P.S.  One more locking exception.  RCU is used to guard the
688
 * update of a tasks cgroup pointer by cgroup_attach_task()
689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718
 */

/**
 * cgroup_lock - lock out any changes to cgroup structures
 *
 */
void cgroup_lock(void)
{
	mutex_lock(&cgroup_mutex);
}

/**
 * cgroup_unlock - release lock on cgroup changes
 *
 * Undo the lock taken in a previous cgroup_lock() call.
 */
void cgroup_unlock(void)
{
	mutex_unlock(&cgroup_mutex);
}

/*
 * A couple of forward declarations required, due to cyclic reference loop:
 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
 * -> cgroup_mkdir.
 */

static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode);
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
719
static int cgroup_populate_dir(struct cgroup *cgrp);
720
static const struct inode_operations cgroup_dir_inode_operations;
721
static const struct file_operations proc_cgroupstats_operations;
722 723

static struct backing_dev_info cgroup_backing_dev_info = {
724
	.name		= "cgroup",
725
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
726
};
727

K
KAMEZAWA Hiroyuki 已提交
728 729 730
static int alloc_css_id(struct cgroup_subsys *ss,
			struct cgroup *parent, struct cgroup *child);

731 732 733 734 735 736
static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
{
	struct inode *inode = new_inode(sb);

	if (inode) {
		inode->i_mode = mode;
737 738
		inode->i_uid = current_fsuid();
		inode->i_gid = current_fsgid();
739 740 741 742 743 744
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
	}
	return inode;
}

745 746 747 748
/*
 * Call subsys's pre_destroy handler.
 * This is called before css refcnt check.
 */
749
static int cgroup_call_pre_destroy(struct cgroup *cgrp)
750 751
{
	struct cgroup_subsys *ss;
752 753
	int ret = 0;

754
	for_each_subsys(cgrp->root, ss)
755 756 757 758 759 760
		if (ss->pre_destroy) {
			ret = ss->pre_destroy(ss, cgrp);
			if (ret)
				break;
		}
	return ret;
761 762
}

763 764 765 766 767 768 769
static void free_cgroup_rcu(struct rcu_head *obj)
{
	struct cgroup *cgrp = container_of(obj, struct cgroup, rcu_head);

	kfree(cgrp);
}

770 771 772 773
static void cgroup_diput(struct dentry *dentry, struct inode *inode)
{
	/* is dentry a directory ? if so, kfree() associated cgroup */
	if (S_ISDIR(inode->i_mode)) {
774
		struct cgroup *cgrp = dentry->d_fsdata;
775
		struct cgroup_subsys *ss;
776
		BUG_ON(!(cgroup_is_removed(cgrp)));
777 778 779 780 781 782 783
		/* It's possible for external users to be holding css
		 * reference counts on a cgroup; css_put() needs to
		 * be able to access the cgroup after decrementing
		 * the reference count in order to know if it needs to
		 * queue the cgroup to be handled by the release
		 * agent */
		synchronize_rcu();
784 785 786 787 788

		mutex_lock(&cgroup_mutex);
		/*
		 * Release the subsystem state objects.
		 */
789 790
		for_each_subsys(cgrp->root, ss)
			ss->destroy(ss, cgrp);
791 792 793 794

		cgrp->root->number_of_cgroups--;
		mutex_unlock(&cgroup_mutex);

795 796 797 798
		/*
		 * Drop the active superblock reference that we took when we
		 * created the cgroup
		 */
799 800
		deactivate_super(cgrp->root->sb);

801 802 803 804 805 806
		/*
		 * if we're getting rid of the cgroup, refcount should ensure
		 * that there are no pidlists left.
		 */
		BUG_ON(!list_empty(&cgrp->pidlists));

807
		call_rcu(&cgrp->rcu_head, free_cgroup_rcu);
808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859
	}
	iput(inode);
}

static void remove_dir(struct dentry *d)
{
	struct dentry *parent = dget(d->d_parent);

	d_delete(d);
	simple_rmdir(parent->d_inode, d);
	dput(parent);
}

static void cgroup_clear_directory(struct dentry *dentry)
{
	struct list_head *node;

	BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
	spin_lock(&dcache_lock);
	node = dentry->d_subdirs.next;
	while (node != &dentry->d_subdirs) {
		struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
		list_del_init(node);
		if (d->d_inode) {
			/* This should never be called on a cgroup
			 * directory with child cgroups */
			BUG_ON(d->d_inode->i_mode & S_IFDIR);
			d = dget_locked(d);
			spin_unlock(&dcache_lock);
			d_delete(d);
			simple_unlink(dentry->d_inode, d);
			dput(d);
			spin_lock(&dcache_lock);
		}
		node = dentry->d_subdirs.next;
	}
	spin_unlock(&dcache_lock);
}

/*
 * NOTE : the dentry must have been dget()'ed
 */
static void cgroup_d_remove_dir(struct dentry *dentry)
{
	cgroup_clear_directory(dentry);

	spin_lock(&dcache_lock);
	list_del_init(&dentry->d_u.d_child);
	spin_unlock(&dcache_lock);
	remove_dir(dentry);
}

860 861 862 863 864 865
/*
 * A queue for waiters to do rmdir() cgroup. A tasks will sleep when
 * cgroup->count == 0 && list_empty(&cgroup->children) && subsys has some
 * reference to css->refcnt. In general, this refcnt is expected to goes down
 * to zero, soon.
 *
866
 * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
867 868 869
 */
DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);

870
static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
871
{
872
	if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
873 874 875
		wake_up_all(&cgroup_rmdir_waitq);
}

876 877 878 879 880 881 882 883 884 885 886 887
void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
{
	css_get(css);
}

void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
{
	cgroup_wakeup_rmdir_waiter(css->cgroup);
	css_put(css);
}


888 889 890 891
static int rebind_subsystems(struct cgroupfs_root *root,
			      unsigned long final_bits)
{
	unsigned long added_bits, removed_bits;
892
	struct cgroup *cgrp = &root->top_cgroup;
893 894 895 896 897 898
	int i;

	removed_bits = root->actual_subsys_bits & ~final_bits;
	added_bits = final_bits & ~root->actual_subsys_bits;
	/* Check that any added subsystems are currently free */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
L
Li Zefan 已提交
899
		unsigned long bit = 1UL << i;
900 901 902 903 904 905 906 907 908 909 910 911 912
		struct cgroup_subsys *ss = subsys[i];
		if (!(bit & added_bits))
			continue;
		if (ss->root != &rootnode) {
			/* Subsystem isn't free */
			return -EBUSY;
		}
	}

	/* Currently we don't handle adding/removing subsystems when
	 * any child cgroups exist. This is theoretically supportable
	 * but involves complex error handling, so it's being left until
	 * later */
913
	if (root->number_of_cgroups > 1)
914 915 916 917 918 919 920 921
		return -EBUSY;

	/* Process each subsystem */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		unsigned long bit = 1UL << i;
		if (bit & added_bits) {
			/* We're binding this subsystem to this hierarchy */
922
			BUG_ON(cgrp->subsys[i]);
923 924
			BUG_ON(!dummytop->subsys[i]);
			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
925
			mutex_lock(&ss->hierarchy_mutex);
926 927
			cgrp->subsys[i] = dummytop->subsys[i];
			cgrp->subsys[i]->cgroup = cgrp;
928
			list_move(&ss->sibling, &root->subsys_list);
929
			ss->root = root;
930
			if (ss->bind)
931
				ss->bind(ss, cgrp);
932
			mutex_unlock(&ss->hierarchy_mutex);
933 934
		} else if (bit & removed_bits) {
			/* We're removing this subsystem */
935 936
			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
937
			mutex_lock(&ss->hierarchy_mutex);
938 939 940
			if (ss->bind)
				ss->bind(ss, dummytop);
			dummytop->subsys[i]->cgroup = dummytop;
941
			cgrp->subsys[i] = NULL;
942
			subsys[i]->root = &rootnode;
943
			list_move(&ss->sibling, &rootnode.subsys_list);
944
			mutex_unlock(&ss->hierarchy_mutex);
945 946
		} else if (bit & final_bits) {
			/* Subsystem state should already exist */
947
			BUG_ON(!cgrp->subsys[i]);
948 949
		} else {
			/* Subsystem state shouldn't exist */
950
			BUG_ON(cgrp->subsys[i]);
951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968
		}
	}
	root->subsys_bits = root->actual_subsys_bits = final_bits;
	synchronize_rcu();

	return 0;
}

static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
	struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info;
	struct cgroup_subsys *ss;

	mutex_lock(&cgroup_mutex);
	for_each_subsys(root, ss)
		seq_printf(seq, ",%s", ss->name);
	if (test_bit(ROOT_NOPREFIX, &root->flags))
		seq_puts(seq, ",noprefix");
969 970
	if (strlen(root->release_agent_path))
		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
971 972
	if (strlen(root->name))
		seq_printf(seq, ",name=%s", root->name);
973 974 975 976 977 978 979
	mutex_unlock(&cgroup_mutex);
	return 0;
}

struct cgroup_sb_opts {
	unsigned long subsys_bits;
	unsigned long flags;
980
	char *release_agent;
981
	char *name;
982 983
	/* User explicitly requested empty subsystem */
	bool none;
984 985

	struct cgroupfs_root *new_root;
986

987 988 989 990 991 992 993 994
};

/* Convert a hierarchy specifier into a bitmask of subsystems and
 * flags. */
static int parse_cgroupfs_options(char *data,
				     struct cgroup_sb_opts *opts)
{
	char *token, *o = data ?: "all";
995 996 997 998 999
	unsigned long mask = (unsigned long)-1;

#ifdef CONFIG_CPUSETS
	mask = ~(1UL << cpuset_subsys_id);
#endif
1000

1001
	memset(opts, 0, sizeof(*opts));
1002 1003 1004 1005 1006

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
		if (!strcmp(token, "all")) {
1007 1008 1009 1010 1011 1012 1013 1014
			/* Add all non-disabled subsystems */
			int i;
			opts->subsys_bits = 0;
			for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
				struct cgroup_subsys *ss = subsys[i];
				if (!ss->disabled)
					opts->subsys_bits |= 1ul << i;
			}
1015 1016 1017
		} else if (!strcmp(token, "none")) {
			/* Explicitly have no subsystems */
			opts->none = true;
1018 1019
		} else if (!strcmp(token, "noprefix")) {
			set_bit(ROOT_NOPREFIX, &opts->flags);
1020 1021 1022 1023
		} else if (!strncmp(token, "release_agent=", 14)) {
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1024 1025
			opts->release_agent =
				kstrndup(token + 14, PATH_MAX, GFP_KERNEL);
1026 1027
			if (!opts->release_agent)
				return -ENOMEM;
1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050
		} else if (!strncmp(token, "name=", 5)) {
			int i;
			const char *name = token + 5;
			/* Can't specify an empty name */
			if (!strlen(name))
				return -EINVAL;
			/* Must match [\w.-]+ */
			for (i = 0; i < strlen(name); i++) {
				char c = name[i];
				if (isalnum(c))
					continue;
				if ((c == '.') || (c == '-') || (c == '_'))
					continue;
				return -EINVAL;
			}
			/* Specifying two names is forbidden */
			if (opts->name)
				return -EINVAL;
			opts->name = kstrndup(name,
					      MAX_CGROUP_ROOT_NAMELEN,
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1051 1052 1053 1054 1055 1056
		} else {
			struct cgroup_subsys *ss;
			int i;
			for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
				ss = subsys[i];
				if (!strcmp(token, ss->name)) {
1057 1058
					if (!ss->disabled)
						set_bit(i, &opts->subsys_bits);
1059 1060 1061 1062 1063 1064 1065 1066
					break;
				}
			}
			if (i == CGROUP_SUBSYS_COUNT)
				return -ENOENT;
		}
	}

1067 1068
	/* Consistency checks */

1069 1070 1071 1072 1073 1074 1075 1076 1077
	/*
	 * Option noprefix was introduced just for backward compatibility
	 * with the old cpuset, so we allow noprefix only if mounting just
	 * the cpuset subsystem.
	 */
	if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
	    (opts->subsys_bits & mask))
		return -EINVAL;

1078 1079 1080 1081 1082 1083 1084 1085 1086

	/* Can't specify "none" and some subsystems */
	if (opts->subsys_bits && opts->none)
		return -EINVAL;

	/*
	 * We either have to specify by name or by subsystems. (So all
	 * empty hierarchies must have a name).
	 */
1087
	if (!opts->subsys_bits && !opts->name)
1088 1089 1090 1091 1092 1093 1094 1095 1096
		return -EINVAL;

	return 0;
}

static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
	int ret = 0;
	struct cgroupfs_root *root = sb->s_fs_info;
1097
	struct cgroup *cgrp = &root->top_cgroup;
1098 1099
	struct cgroup_sb_opts opts;

1100
	lock_kernel();
1101
	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114
	mutex_lock(&cgroup_mutex);

	/* See what subsystems are wanted */
	ret = parse_cgroupfs_options(data, &opts);
	if (ret)
		goto out_unlock;

	/* Don't allow flags to change at remount */
	if (opts.flags != root->flags) {
		ret = -EINVAL;
		goto out_unlock;
	}

1115 1116 1117 1118 1119 1120
	/* Don't allow name to change at remount */
	if (opts.name && strcmp(opts.name, root->name)) {
		ret = -EINVAL;
		goto out_unlock;
	}

1121
	ret = rebind_subsystems(root, opts.subsys_bits);
1122 1123
	if (ret)
		goto out_unlock;
1124 1125

	/* (re)populate subsystem files */
1126
	cgroup_populate_dir(cgrp);
1127

1128 1129
	if (opts.release_agent)
		strcpy(root->release_agent_path, opts.release_agent);
1130
 out_unlock:
1131
	kfree(opts.release_agent);
1132
	kfree(opts.name);
1133
	mutex_unlock(&cgroup_mutex);
1134
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1135
	unlock_kernel();
1136 1137 1138
	return ret;
}

1139
static const struct super_operations cgroup_ops = {
1140 1141 1142 1143 1144 1145
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.show_options = cgroup_show_options,
	.remount_fs = cgroup_remount,
};

1146 1147 1148 1149 1150 1151
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
	INIT_LIST_HEAD(&cgrp->sibling);
	INIT_LIST_HEAD(&cgrp->children);
	INIT_LIST_HEAD(&cgrp->css_sets);
	INIT_LIST_HEAD(&cgrp->release_list);
1152 1153
	INIT_LIST_HEAD(&cgrp->pidlists);
	mutex_init(&cgrp->pidlist_mutex);
1154
}
1155

1156 1157
static void init_cgroup_root(struct cgroupfs_root *root)
{
1158
	struct cgroup *cgrp = &root->top_cgroup;
1159 1160 1161
	INIT_LIST_HEAD(&root->subsys_list);
	INIT_LIST_HEAD(&root->root_list);
	root->number_of_cgroups = 1;
1162 1163
	cgrp->root = root;
	cgrp->top_cgroup = cgrp;
1164
	init_cgroup_housekeeping(cgrp);
1165 1166
}

1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191
static bool init_root_id(struct cgroupfs_root *root)
{
	int ret = 0;

	do {
		if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
			return false;
		spin_lock(&hierarchy_id_lock);
		/* Try to allocate the next unused ID */
		ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
					&root->hierarchy_id);
		if (ret == -ENOSPC)
			/* Try again starting from 0 */
			ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
		if (!ret) {
			next_hierarchy_id = root->hierarchy_id + 1;
		} else if (ret != -EAGAIN) {
			/* Can only get here if the 31-bit IDR is full ... */
			BUG_ON(ret);
		}
		spin_unlock(&hierarchy_id_lock);
	} while (ret);
	return true;
}

1192 1193
static int cgroup_test_super(struct super_block *sb, void *data)
{
1194
	struct cgroup_sb_opts *opts = data;
1195 1196
	struct cgroupfs_root *root = sb->s_fs_info;

1197 1198 1199
	/* If we asked for a name then it must match */
	if (opts->name && strcmp(opts->name, root->name))
		return 0;
1200

1201 1202 1203 1204 1205 1206
	/*
	 * If we asked for subsystems (or explicitly for no
	 * subsystems) then they must match
	 */
	if ((opts->subsys_bits || opts->none)
	    && (opts->subsys_bits != root->subsys_bits))
1207 1208 1209 1210 1211
		return 0;

	return 1;
}

1212 1213 1214 1215
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
	struct cgroupfs_root *root;

1216
	if (!opts->subsys_bits && !opts->none)
1217 1218 1219 1220 1221 1222
		return NULL;

	root = kzalloc(sizeof(*root), GFP_KERNEL);
	if (!root)
		return ERR_PTR(-ENOMEM);

1223 1224 1225 1226
	if (!init_root_id(root)) {
		kfree(root);
		return ERR_PTR(-ENOMEM);
	}
1227
	init_cgroup_root(root);
1228

1229 1230 1231 1232 1233 1234 1235 1236 1237
	root->subsys_bits = opts->subsys_bits;
	root->flags = opts->flags;
	if (opts->release_agent)
		strcpy(root->release_agent_path, opts->release_agent);
	if (opts->name)
		strcpy(root->name, opts->name);
	return root;
}

1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249
static void cgroup_drop_root(struct cgroupfs_root *root)
{
	if (!root)
		return;

	BUG_ON(!root->hierarchy_id);
	spin_lock(&hierarchy_id_lock);
	ida_remove(&hierarchy_ida, root->hierarchy_id);
	spin_unlock(&hierarchy_id_lock);
	kfree(root);
}

1250 1251 1252
static int cgroup_set_super(struct super_block *sb, void *data)
{
	int ret;
1253 1254 1255 1256 1257 1258
	struct cgroup_sb_opts *opts = data;

	/* If we don't have a new root, we can't set up a new sb */
	if (!opts->new_root)
		return -EINVAL;

1259
	BUG_ON(!opts->subsys_bits && !opts->none);
1260 1261 1262 1263 1264

	ret = set_anon_super(sb, NULL);
	if (ret)
		return ret;

1265 1266
	sb->s_fs_info = opts->new_root;
	opts->new_root->sb = sb;
1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302

	sb->s_blocksize = PAGE_CACHE_SIZE;
	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
	sb->s_magic = CGROUP_SUPER_MAGIC;
	sb->s_op = &cgroup_ops;

	return 0;
}

static int cgroup_get_rootdir(struct super_block *sb)
{
	struct inode *inode =
		cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
	struct dentry *dentry;

	if (!inode)
		return -ENOMEM;

	inode->i_fop = &simple_dir_operations;
	inode->i_op = &cgroup_dir_inode_operations;
	/* directories start off with i_nlink == 2 (for "." entry) */
	inc_nlink(inode);
	dentry = d_alloc_root(inode);
	if (!dentry) {
		iput(inode);
		return -ENOMEM;
	}
	sb->s_root = dentry;
	return 0;
}

static int cgroup_get_sb(struct file_system_type *fs_type,
			 int flags, const char *unused_dev_name,
			 void *data, struct vfsmount *mnt)
{
	struct cgroup_sb_opts opts;
1303
	struct cgroupfs_root *root;
1304 1305
	int ret = 0;
	struct super_block *sb;
1306
	struct cgroupfs_root *new_root;
1307 1308 1309

	/* First find the desired set of subsystems */
	ret = parse_cgroupfs_options(data, &opts);
1310 1311
	if (ret)
		goto out_err;
1312

1313 1314 1315 1316 1317 1318 1319 1320
	/*
	 * Allocate a new cgroup root. We may not need it if we're
	 * reusing an existing hierarchy.
	 */
	new_root = cgroup_root_from_opts(&opts);
	if (IS_ERR(new_root)) {
		ret = PTR_ERR(new_root);
		goto out_err;
1321
	}
1322
	opts.new_root = new_root;
1323

1324 1325
	/* Locate an existing or new sb for this hierarchy */
	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, &opts);
1326
	if (IS_ERR(sb)) {
1327
		ret = PTR_ERR(sb);
1328
		cgroup_drop_root(opts.new_root);
1329
		goto out_err;
1330 1331
	}

1332 1333 1334 1335 1336
	root = sb->s_fs_info;
	BUG_ON(!root);
	if (root == opts.new_root) {
		/* We used the new root structure, so this is a new hierarchy */
		struct list_head tmp_cg_links;
1337
		struct cgroup *root_cgrp = &root->top_cgroup;
1338
		struct inode *inode;
1339
		struct cgroupfs_root *existing_root;
1340
		int i;
1341 1342 1343 1344 1345 1346

		BUG_ON(sb->s_root != NULL);

		ret = cgroup_get_rootdir(sb);
		if (ret)
			goto drop_new_super;
1347
		inode = sb->s_root->d_inode;
1348

1349
		mutex_lock(&inode->i_mutex);
1350 1351
		mutex_lock(&cgroup_mutex);

1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363
		if (strlen(root->name)) {
			/* Check for name clashes with existing mounts */
			for_each_active_root(existing_root) {
				if (!strcmp(existing_root->name, root->name)) {
					ret = -EBUSY;
					mutex_unlock(&cgroup_mutex);
					mutex_unlock(&inode->i_mutex);
					goto drop_new_super;
				}
			}
		}

1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377
		/*
		 * We're accessing css_set_count without locking
		 * css_set_lock here, but that's OK - it can only be
		 * increased by someone holding cgroup_lock, and
		 * that's us. The worst that can happen is that we
		 * have some link structures left over
		 */
		ret = allocate_cg_links(css_set_count, &tmp_cg_links);
		if (ret) {
			mutex_unlock(&cgroup_mutex);
			mutex_unlock(&inode->i_mutex);
			goto drop_new_super;
		}

1378 1379 1380
		ret = rebind_subsystems(root, root->subsys_bits);
		if (ret == -EBUSY) {
			mutex_unlock(&cgroup_mutex);
1381
			mutex_unlock(&inode->i_mutex);
1382 1383
			free_cg_links(&tmp_cg_links);
			goto drop_new_super;
1384 1385 1386 1387 1388 1389
		}

		/* EBUSY should be the only error here */
		BUG_ON(ret);

		list_add(&root->root_list, &roots);
1390
		root_count++;
1391

1392
		sb->s_root->d_fsdata = root_cgrp;
1393 1394
		root->top_cgroup.dentry = sb->s_root;

1395 1396 1397
		/* Link the top cgroup in this hierarchy into all
		 * the css_set objects */
		write_lock(&css_set_lock);
1398 1399 1400
		for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
			struct hlist_head *hhead = &css_set_table[i];
			struct hlist_node *node;
1401
			struct css_set *cg;
1402

1403 1404
			hlist_for_each_entry(cg, node, hhead, hlist)
				link_css_set(&tmp_cg_links, cg, root_cgrp);
1405
		}
1406 1407 1408 1409
		write_unlock(&css_set_lock);

		free_cg_links(&tmp_cg_links);

1410 1411
		BUG_ON(!list_empty(&root_cgrp->sibling));
		BUG_ON(!list_empty(&root_cgrp->children));
1412 1413
		BUG_ON(root->number_of_cgroups != 1);

1414
		cgroup_populate_dir(root_cgrp);
1415
		mutex_unlock(&cgroup_mutex);
1416
		mutex_unlock(&inode->i_mutex);
1417 1418 1419 1420 1421
	} else {
		/*
		 * We re-used an existing hierarchy - the new root (if
		 * any) is not needed
		 */
1422
		cgroup_drop_root(opts.new_root);
1423 1424
	}

1425
	simple_set_mnt(mnt, sb);
1426 1427
	kfree(opts.release_agent);
	kfree(opts.name);
1428
	return 0;
1429 1430

 drop_new_super:
1431
	deactivate_locked_super(sb);
1432 1433 1434 1435
 out_err:
	kfree(opts.release_agent);
	kfree(opts.name);

1436 1437 1438 1439 1440
	return ret;
}

static void cgroup_kill_sb(struct super_block *sb) {
	struct cgroupfs_root *root = sb->s_fs_info;
1441
	struct cgroup *cgrp = &root->top_cgroup;
1442
	int ret;
K
KOSAKI Motohiro 已提交
1443 1444
	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;
1445 1446 1447 1448

	BUG_ON(!root);

	BUG_ON(root->number_of_cgroups != 1);
1449 1450
	BUG_ON(!list_empty(&cgrp->children));
	BUG_ON(!list_empty(&cgrp->sibling));
1451 1452 1453 1454 1455 1456 1457 1458

	mutex_lock(&cgroup_mutex);

	/* Rebind all subsystems back to the default hierarchy */
	ret = rebind_subsystems(root, 0);
	/* Shouldn't be able to fail ... */
	BUG_ON(ret);

1459 1460 1461 1462 1463
	/*
	 * Release all the links from css_sets to this hierarchy's
	 * root cgroup
	 */
	write_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
1464 1465 1466

	list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
				 cgrp_link_list) {
1467
		list_del(&link->cg_link_list);
1468
		list_del(&link->cgrp_link_list);
1469 1470 1471 1472
		kfree(link);
	}
	write_unlock(&css_set_lock);

1473 1474 1475 1476
	if (!list_empty(&root->root_list)) {
		list_del(&root->root_list);
		root_count--;
	}
1477

1478 1479 1480
	mutex_unlock(&cgroup_mutex);

	kill_litter_super(sb);
1481
	cgroup_drop_root(root);
1482 1483 1484 1485 1486 1487 1488 1489
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
	.get_sb = cgroup_get_sb,
	.kill_sb = cgroup_kill_sb,
};

1490
static inline struct cgroup *__d_cgrp(struct dentry *dentry)
1491 1492 1493 1494 1495 1496 1497 1498 1499
{
	return dentry->d_fsdata;
}

static inline struct cftype *__d_cft(struct dentry *dentry)
{
	return dentry->d_fsdata;
}

L
Li Zefan 已提交
1500 1501 1502 1503 1504 1505
/**
 * cgroup_path - generate the path of a cgroup
 * @cgrp: the cgroup in question
 * @buf: the buffer to write the path into
 * @buflen: the length of the buffer
 *
1506 1507 1508
 * Called with cgroup_mutex held or else with an RCU-protected cgroup
 * reference.  Writes path of cgroup into buf.  Returns 0 on success,
 * -errno on error.
1509
 */
1510
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1511 1512
{
	char *start;
1513
	struct dentry *dentry = rcu_dereference(cgrp->dentry);
1514

1515
	if (!dentry || cgrp == dummytop) {
1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527
		/*
		 * Inactive subsystems have no dentry for their root
		 * cgroup
		 */
		strcpy(buf, "/");
		return 0;
	}

	start = buf + buflen;

	*--start = '\0';
	for (;;) {
1528
		int len = dentry->d_name.len;
1529 1530
		if ((start -= len) < buf)
			return -ENAMETOOLONG;
1531 1532 1533
		memcpy(start, cgrp->dentry->d_name.name, len);
		cgrp = cgrp->parent;
		if (!cgrp)
1534
			break;
1535
		dentry = rcu_dereference(cgrp->dentry);
1536
		if (!cgrp->parent)
1537 1538 1539 1540 1541 1542 1543 1544 1545
			continue;
		if (--start < buf)
			return -ENAMETOOLONG;
		*start = '/';
	}
	memmove(buf, start, buf + buflen - start);
	return 0;
}

L
Li Zefan 已提交
1546 1547 1548 1549
/**
 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
 * @cgrp: the cgroup the task is attaching to
 * @tsk: the task to be attached
1550
 *
L
Li Zefan 已提交
1551 1552
 * Call holding cgroup_mutex. May take task_lock of
 * the task 'tsk' during call.
1553
 */
1554
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1555 1556
{
	int retval = 0;
1557
	struct cgroup_subsys *ss, *failed_ss = NULL;
1558
	struct cgroup *oldcgrp;
1559
	struct css_set *cg;
1560
	struct css_set *newcg;
1561
	struct cgroupfs_root *root = cgrp->root;
1562 1563

	/* Nothing to do if the task is already in that cgroup */
1564
	oldcgrp = task_cgroup_from_root(tsk, root);
1565
	if (cgrp == oldcgrp)
1566 1567 1568 1569
		return 0;

	for_each_subsys(root, ss) {
		if (ss->can_attach) {
1570
			retval = ss->can_attach(ss, cgrp, tsk, false);
1571 1572 1573 1574 1575 1576 1577 1578 1579 1580
			if (retval) {
				/*
				 * Remember on which subsystem the can_attach()
				 * failed, so that we only call cancel_attach()
				 * against the subsystems whose can_attach()
				 * succeeded. (See below)
				 */
				failed_ss = ss;
				goto out;
			}
1581 1582 1583
		}
	}

1584 1585 1586 1587
	task_lock(tsk);
	cg = tsk->cgroups;
	get_css_set(cg);
	task_unlock(tsk);
1588 1589 1590 1591
	/*
	 * Locate or allocate a new css_set for this task,
	 * based on its final set of cgroups
	 */
1592
	newcg = find_css_set(cg, cgrp);
1593
	put_css_set(cg);
1594 1595 1596 1597
	if (!newcg) {
		retval = -ENOMEM;
		goto out;
	}
1598

1599 1600 1601
	task_lock(tsk);
	if (tsk->flags & PF_EXITING) {
		task_unlock(tsk);
1602
		put_css_set(newcg);
1603 1604
		retval = -ESRCH;
		goto out;
1605
	}
1606
	rcu_assign_pointer(tsk->cgroups, newcg);
1607 1608
	task_unlock(tsk);

1609 1610 1611 1612 1613 1614 1615 1616
	/* Update the css_set linked lists if we're using them */
	write_lock(&css_set_lock);
	if (!list_empty(&tsk->cg_list)) {
		list_del(&tsk->cg_list);
		list_add(&tsk->cg_list, &newcg->tasks);
	}
	write_unlock(&css_set_lock);

1617
	for_each_subsys(root, ss) {
P
Paul Jackson 已提交
1618
		if (ss->attach)
1619
			ss->attach(ss, cgrp, oldcgrp, tsk, false);
1620
	}
1621
	set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1622
	synchronize_rcu();
1623
	put_css_set(cg);
1624 1625 1626 1627 1628

	/*
	 * wake up rmdir() waiter. the rmdir should fail since the cgroup
	 * is no longer empty.
	 */
1629
	cgroup_wakeup_rmdir_waiter(cgrp);
1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645
out:
	if (retval) {
		for_each_subsys(root, ss) {
			if (ss == failed_ss)
				/*
				 * This subsystem was the one that failed the
				 * can_attach() check earlier, so we don't need
				 * to call cancel_attach() against it or any
				 * remaining subsystems.
				 */
				break;
			if (ss->cancel_attach)
				ss->cancel_attach(ss, cgrp, tsk, false);
		}
	}
	return retval;
1646 1647 1648
}

/*
1649 1650
 * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex
 * held. May take task_lock of task
1651
 */
1652
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid)
1653 1654
{
	struct task_struct *tsk;
1655
	const struct cred *cred = current_cred(), *tcred;
1656 1657 1658 1659
	int ret;

	if (pid) {
		rcu_read_lock();
1660
		tsk = find_task_by_vpid(pid);
1661 1662 1663 1664 1665
		if (!tsk || tsk->flags & PF_EXITING) {
			rcu_read_unlock();
			return -ESRCH;
		}

1666 1667 1668 1669 1670
		tcred = __task_cred(tsk);
		if (cred->euid &&
		    cred->euid != tcred->uid &&
		    cred->euid != tcred->suid) {
			rcu_read_unlock();
1671 1672
			return -EACCES;
		}
1673 1674
		get_task_struct(tsk);
		rcu_read_unlock();
1675 1676 1677 1678 1679
	} else {
		tsk = current;
		get_task_struct(tsk);
	}

1680
	ret = cgroup_attach_task(cgrp, tsk);
1681 1682 1683 1684
	put_task_struct(tsk);
	return ret;
}

1685 1686 1687 1688 1689 1690 1691 1692 1693 1694
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
{
	int ret;
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
	ret = attach_task_by_pid(cgrp, pid);
	cgroup_unlock();
	return ret;
}

1695 1696 1697 1698
/**
 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
 * @cgrp: the cgroup to be checked for liveness
 *
1699 1700
 * On success, returns true; the lock should be later released with
 * cgroup_unlock(). On failure returns false with no lock held.
1701
 */
1702
bool cgroup_lock_live_group(struct cgroup *cgrp)
1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718
{
	mutex_lock(&cgroup_mutex);
	if (cgroup_is_removed(cgrp)) {
		mutex_unlock(&cgroup_mutex);
		return false;
	}
	return true;
}

static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
				      const char *buffer)
{
	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
	strcpy(cgrp->root->release_agent_path, buffer);
1719
	cgroup_unlock();
1720 1721 1722 1723 1724 1725 1726 1727 1728 1729
	return 0;
}

static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
				     struct seq_file *seq)
{
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
	seq_puts(seq, cgrp->root->release_agent_path);
	seq_putc(seq, '\n');
1730
	cgroup_unlock();
1731 1732 1733
	return 0;
}

1734 1735 1736
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64

1737
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
1738 1739 1740
				struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *unused_ppos)
1741
{
1742
	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753
	int retval = 0;
	char *end;

	if (!nbytes)
		return -EINVAL;
	if (nbytes >= sizeof(buffer))
		return -E2BIG;
	if (copy_from_user(buffer, userbuf, nbytes))
		return -EFAULT;

	buffer[nbytes] = 0;     /* nul-terminate */
1754
	if (cft->write_u64) {
K
KOSAKI Motohiro 已提交
1755
		u64 val = simple_strtoull(strstrip(buffer), &end, 0);
1756 1757 1758 1759
		if (*end)
			return -EINVAL;
		retval = cft->write_u64(cgrp, cft, val);
	} else {
K
KOSAKI Motohiro 已提交
1760
		s64 val = simple_strtoll(strstrip(buffer), &end, 0);
1761 1762 1763 1764
		if (*end)
			return -EINVAL;
		retval = cft->write_s64(cgrp, cft, val);
	}
1765 1766 1767 1768 1769
	if (!retval)
		retval = nbytes;
	return retval;
}

1770 1771 1772 1773 1774
static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
				   struct file *file,
				   const char __user *userbuf,
				   size_t nbytes, loff_t *unused_ppos)
{
1775
	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789
	int retval = 0;
	size_t max_bytes = cft->max_write_len;
	char *buffer = local_buffer;

	if (!max_bytes)
		max_bytes = sizeof(local_buffer) - 1;
	if (nbytes >= max_bytes)
		return -E2BIG;
	/* Allocate a dynamic buffer if we need one */
	if (nbytes >= sizeof(local_buffer)) {
		buffer = kmalloc(nbytes + 1, GFP_KERNEL);
		if (buffer == NULL)
			return -ENOMEM;
	}
L
Li Zefan 已提交
1790 1791 1792 1793
	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
		retval = -EFAULT;
		goto out;
	}
1794 1795

	buffer[nbytes] = 0;     /* nul-terminate */
K
KOSAKI Motohiro 已提交
1796
	retval = cft->write_string(cgrp, cft, strstrip(buffer));
1797 1798
	if (!retval)
		retval = nbytes;
L
Li Zefan 已提交
1799
out:
1800 1801 1802 1803 1804
	if (buffer != local_buffer)
		kfree(buffer);
	return retval;
}

1805 1806 1807 1808
static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
						size_t nbytes, loff_t *ppos)
{
	struct cftype *cft = __d_cft(file->f_dentry);
1809
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
1810

1811
	if (cgroup_is_removed(cgrp))
1812
		return -ENODEV;
1813
	if (cft->write)
1814
		return cft->write(cgrp, cft, file, buf, nbytes, ppos);
1815 1816
	if (cft->write_u64 || cft->write_s64)
		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
1817 1818
	if (cft->write_string)
		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
1819 1820 1821 1822
	if (cft->trigger) {
		int ret = cft->trigger(cgrp, (unsigned int)cft->private);
		return ret ? ret : nbytes;
	}
1823
	return -EINVAL;
1824 1825
}

1826 1827 1828 1829
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
1830
{
1831
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
1832
	u64 val = cft->read_u64(cgrp, cft);
1833 1834 1835 1836 1837
	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);

	return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
}

1838 1839 1840 1841 1842
static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
{
1843
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
1844 1845 1846 1847 1848 1849
	s64 val = cft->read_s64(cgrp, cft);
	int len = sprintf(tmp, "%lld\n", (long long) val);

	return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
}

1850 1851 1852 1853
static ssize_t cgroup_file_read(struct file *file, char __user *buf,
				   size_t nbytes, loff_t *ppos)
{
	struct cftype *cft = __d_cft(file->f_dentry);
1854
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
1855

1856
	if (cgroup_is_removed(cgrp))
1857 1858 1859
		return -ENODEV;

	if (cft->read)
1860
		return cft->read(cgrp, cft, file, buf, nbytes, ppos);
1861 1862
	if (cft->read_u64)
		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
1863 1864
	if (cft->read_s64)
		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
1865 1866 1867
	return -EINVAL;
}

1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887
/*
 * seqfile ops/methods for returning structured data. Currently just
 * supports string->u64 maps, but can be extended in future.
 */

struct cgroup_seqfile_state {
	struct cftype *cft;
	struct cgroup *cgroup;
};

static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
{
	struct seq_file *sf = cb->state;
	return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
}

static int cgroup_seqfile_show(struct seq_file *m, void *arg)
{
	struct cgroup_seqfile_state *state = m->private;
	struct cftype *cft = state->cft;
1888 1889 1890 1891 1892 1893 1894 1895
	if (cft->read_map) {
		struct cgroup_map_cb cb = {
			.fill = cgroup_map_add,
			.state = m,
		};
		return cft->read_map(state->cgroup, cft, &cb);
	}
	return cft->read_seq_string(state->cgroup, cft, m);
1896 1897
}

1898
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
1899 1900 1901 1902 1903 1904
{
	struct seq_file *seq = file->private_data;
	kfree(seq->private);
	return single_release(inode, file);
}

1905
static const struct file_operations cgroup_seqfile_operations = {
1906
	.read = seq_read,
1907
	.write = cgroup_file_write,
1908 1909 1910 1911
	.llseek = seq_lseek,
	.release = cgroup_seqfile_release,
};

1912 1913 1914 1915 1916 1917 1918 1919 1920
static int cgroup_file_open(struct inode *inode, struct file *file)
{
	int err;
	struct cftype *cft;

	err = generic_file_open(inode, file);
	if (err)
		return err;
	cft = __d_cft(file->f_dentry);
1921

1922
	if (cft->read_map || cft->read_seq_string) {
1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933
		struct cgroup_seqfile_state *state =
			kzalloc(sizeof(*state), GFP_USER);
		if (!state)
			return -ENOMEM;
		state->cft = cft;
		state->cgroup = __d_cgrp(file->f_dentry->d_parent);
		file->f_op = &cgroup_seqfile_operations;
		err = single_open(file, cgroup_seqfile_show, state);
		if (err < 0)
			kfree(state);
	} else if (cft->open)
1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963
		err = cft->open(inode, file);
	else
		err = 0;

	return err;
}

static int cgroup_file_release(struct inode *inode, struct file *file)
{
	struct cftype *cft = __d_cft(file->f_dentry);
	if (cft->release)
		return cft->release(inode, file);
	return 0;
}

/*
 * cgroup_rename - Only allow simple rename of directories in place.
 */
static int cgroup_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);
}

1964
static const struct file_operations cgroup_file_operations = {
1965 1966 1967 1968 1969 1970 1971
	.read = cgroup_file_read,
	.write = cgroup_file_write,
	.llseek = generic_file_llseek,
	.open = cgroup_file_open,
	.release = cgroup_file_release,
};

1972
static const struct inode_operations cgroup_dir_inode_operations = {
1973 1974 1975 1976 1977 1978
	.lookup = simple_lookup,
	.mkdir = cgroup_mkdir,
	.rmdir = cgroup_rmdir,
	.rename = cgroup_rename,
};

L
Li Zefan 已提交
1979
static int cgroup_create_file(struct dentry *dentry, mode_t mode,
1980 1981
				struct super_block *sb)
{
A
Al Viro 已提交
1982
	static const struct dentry_operations cgroup_dops = {
1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
		.d_iput = cgroup_diput,
	};

	struct inode *inode;

	if (!dentry)
		return -ENOENT;
	if (dentry->d_inode)
		return -EEXIST;

	inode = cgroup_new_inode(mode, sb);
	if (!inode)
		return -ENOMEM;

	if (S_ISDIR(mode)) {
		inode->i_op = &cgroup_dir_inode_operations;
		inode->i_fop = &simple_dir_operations;

		/* start off with i_nlink == 2 (for "." entry) */
		inc_nlink(inode);

		/* start with the directory inode held, so that we can
		 * populate it without racing with another mkdir */
2006
		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017
	} else if (S_ISREG(mode)) {
		inode->i_size = 0;
		inode->i_fop = &cgroup_file_operations;
	}
	dentry->d_op = &cgroup_dops;
	d_instantiate(dentry, inode);
	dget(dentry);	/* Extra count - pin the dentry in core */
	return 0;
}

/*
L
Li Zefan 已提交
2018 2019 2020 2021 2022
 * cgroup_create_dir - create a directory for an object.
 * @cgrp: the cgroup we create the directory for. It must have a valid
 *        ->parent field. And we are going to fill its ->dentry field.
 * @dentry: dentry of the new cgroup
 * @mode: mode to set on new directory.
2023
 */
2024
static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
L
Li Zefan 已提交
2025
				mode_t mode)
2026 2027 2028 2029
{
	struct dentry *parent;
	int error = 0;

2030 2031
	parent = cgrp->parent->dentry;
	error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
2032
	if (!error) {
2033
		dentry->d_fsdata = cgrp;
2034
		inc_nlink(parent->d_inode);
2035
		rcu_assign_pointer(cgrp->dentry, dentry);
2036 2037 2038 2039 2040 2041 2042
		dget(dentry);
	}
	dput(dentry);

	return error;
}

L
Li Zefan 已提交
2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069
/**
 * cgroup_file_mode - deduce file mode of a control file
 * @cft: the control file in question
 *
 * returns cft->mode if ->mode is not 0
 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
 * returns S_IRUGO if it has only a read handler
 * returns S_IWUSR if it has only a write hander
 */
static mode_t cgroup_file_mode(const struct cftype *cft)
{
	mode_t mode = 0;

	if (cft->mode)
		return cft->mode;

	if (cft->read || cft->read_u64 || cft->read_s64 ||
	    cft->read_map || cft->read_seq_string)
		mode |= S_IRUGO;

	if (cft->write || cft->write_u64 || cft->write_s64 ||
	    cft->write_string || cft->trigger)
		mode |= S_IWUSR;

	return mode;
}

2070
int cgroup_add_file(struct cgroup *cgrp,
2071 2072 2073
		       struct cgroup_subsys *subsys,
		       const struct cftype *cft)
{
2074
	struct dentry *dir = cgrp->dentry;
2075 2076
	struct dentry *dentry;
	int error;
L
Li Zefan 已提交
2077
	mode_t mode;
2078 2079

	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2080
	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2081 2082 2083 2084 2085 2086 2087
		strcpy(name, subsys->name);
		strcat(name, ".");
	}
	strcat(name, cft->name);
	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
	dentry = lookup_one_len(name, dir, strlen(name));
	if (!IS_ERR(dentry)) {
L
Li Zefan 已提交
2088 2089
		mode = cgroup_file_mode(cft);
		error = cgroup_create_file(dentry, mode | S_IFREG,
2090
						cgrp->root->sb);
2091 2092 2093 2094 2095 2096 2097 2098
		if (!error)
			dentry->d_fsdata = (void *)cft;
		dput(dentry);
	} else
		error = PTR_ERR(dentry);
	return error;
}

2099
int cgroup_add_files(struct cgroup *cgrp,
2100 2101 2102 2103 2104 2105
			struct cgroup_subsys *subsys,
			const struct cftype cft[],
			int count)
{
	int i, err;
	for (i = 0; i < count; i++) {
2106
		err = cgroup_add_file(cgrp, subsys, &cft[i]);
2107 2108 2109 2110 2111 2112
		if (err)
			return err;
	}
	return 0;
}

L
Li Zefan 已提交
2113 2114 2115 2116 2117 2118
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2119
int cgroup_task_count(const struct cgroup *cgrp)
2120 2121
{
	int count = 0;
K
KOSAKI Motohiro 已提交
2122
	struct cg_cgroup_link *link;
2123 2124

	read_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
2125
	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2126
		count += atomic_read(&link->cg->refcount);
2127 2128
	}
	read_unlock(&css_set_lock);
2129 2130 2131
	return count;
}

2132 2133 2134 2135
/*
 * Advance a list_head iterator.  The iterator should be positioned at
 * the start of a css_set
 */
2136
static void cgroup_advance_iter(struct cgroup *cgrp,
2137
				struct cgroup_iter *it)
2138 2139 2140 2141 2142 2143 2144 2145
{
	struct list_head *l = it->cg_link;
	struct cg_cgroup_link *link;
	struct css_set *cg;

	/* Advance to the next non-empty css_set */
	do {
		l = l->next;
2146
		if (l == &cgrp->css_sets) {
2147 2148 2149
			it->cg_link = NULL;
			return;
		}
2150
		link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2151 2152 2153 2154 2155 2156
		cg = link->cg;
	} while (list_empty(&cg->tasks));
	it->cg_link = l;
	it->task = cg->tasks.next;
}

2157 2158 2159 2160 2161 2162 2163 2164 2165
/*
 * To reduce the fork() overhead for systems that are not actually
 * using their cgroups capability, we don't maintain the lists running
 * through each css_set to its tasks until we see the list actually
 * used - in other words after the first call to cgroup_iter_start().
 *
 * The tasklist_lock is not held here, as do_each_thread() and
 * while_each_thread() are protected by RCU.
 */
2166
static void cgroup_enable_task_cg_lists(void)
2167 2168 2169 2170 2171 2172
{
	struct task_struct *p, *g;
	write_lock(&css_set_lock);
	use_task_css_set_links = 1;
	do_each_thread(g, p) {
		task_lock(p);
2173 2174 2175 2176 2177 2178
		/*
		 * We should check if the process is exiting, otherwise
		 * it will race with cgroup_exit() in that the list
		 * entry won't be deleted though the process has exited.
		 */
		if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
2179 2180 2181 2182 2183 2184
			list_add(&p->cg_list, &p->cgroups->tasks);
		task_unlock(p);
	} while_each_thread(g, p);
	write_unlock(&css_set_lock);
}

2185
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
2186 2187 2188 2189 2190 2191
{
	/*
	 * The first time anyone tries to iterate across a cgroup,
	 * we need to enable the list linking each css_set to its
	 * tasks, and fix up all existing tasks.
	 */
2192 2193 2194
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();

2195
	read_lock(&css_set_lock);
2196 2197
	it->cg_link = &cgrp->css_sets;
	cgroup_advance_iter(cgrp, it);
2198 2199
}

2200
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
2201 2202 2203 2204
					struct cgroup_iter *it)
{
	struct task_struct *res;
	struct list_head *l = it->task;
2205
	struct cg_cgroup_link *link;
2206 2207 2208 2209 2210 2211 2212

	/* If the iterator cg is NULL, we have no tasks */
	if (!it->cg_link)
		return NULL;
	res = list_entry(l, struct task_struct, cg_list);
	/* Advance iterator to find next entry */
	l = l->next;
2213 2214
	link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
	if (l == &link->cg->tasks) {
2215 2216
		/* We reached the end of this task list - move on to
		 * the next cg_cgroup_link */
2217
		cgroup_advance_iter(cgrp, it);
2218 2219 2220 2221 2222 2223
	} else {
		it->task = l;
	}
	return res;
}

2224
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
2225 2226 2227 2228
{
	read_unlock(&css_set_lock);
}

2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365
static inline int started_after_time(struct task_struct *t1,
				     struct timespec *time,
				     struct task_struct *t2)
{
	int start_diff = timespec_compare(&t1->start_time, time);
	if (start_diff > 0) {
		return 1;
	} else if (start_diff < 0) {
		return 0;
	} else {
		/*
		 * Arbitrarily, if two processes started at the same
		 * time, we'll say that the lower pointer value
		 * started first. Note that t2 may have exited by now
		 * so this may not be a valid pointer any longer, but
		 * that's fine - it still serves to distinguish
		 * between two tasks started (effectively) simultaneously.
		 */
		return t1 > t2;
	}
}

/*
 * This function is a callback from heap_insert() and is used to order
 * the heap.
 * In this case we order the heap in descending task start time.
 */
static inline int started_after(void *p1, void *p2)
{
	struct task_struct *t1 = p1;
	struct task_struct *t2 = p2;
	return started_after_time(t1, &t2->start_time, t2);
}

/**
 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
 * @scan: struct cgroup_scanner containing arguments for the scan
 *
 * Arguments include pointers to callback functions test_task() and
 * process_task().
 * Iterate through all the tasks in a cgroup, calling test_task() for each,
 * and if it returns true, call process_task() for it also.
 * The test_task pointer may be NULL, meaning always true (select all tasks).
 * Effectively duplicates cgroup_iter_{start,next,end}()
 * but does not lock css_set_lock for the call to process_task().
 * The struct cgroup_scanner may be embedded in any structure of the caller's
 * creation.
 * It is guaranteed that process_task() will act on every task that
 * is a member of the cgroup for the duration of this call. This
 * function may or may not call process_task() for tasks that exit
 * or move to a different cgroup during the call, or are forked or
 * move into the cgroup during the call.
 *
 * Note that test_task() may be called with locks held, and may in some
 * situations be called multiple times for the same task, so it should
 * be cheap.
 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
 * pre-allocated and will be used for heap operations (and its "gt" member will
 * be overwritten), else a temporary heap will be used (allocation of which
 * may cause this function to fail).
 */
int cgroup_scan_tasks(struct cgroup_scanner *scan)
{
	int retval, i;
	struct cgroup_iter it;
	struct task_struct *p, *dropped;
	/* Never dereference latest_task, since it's not refcounted */
	struct task_struct *latest_task = NULL;
	struct ptr_heap tmp_heap;
	struct ptr_heap *heap;
	struct timespec latest_time = { 0, 0 };

	if (scan->heap) {
		/* The caller supplied our heap and pre-allocated its memory */
		heap = scan->heap;
		heap->gt = &started_after;
	} else {
		/* We need to allocate our own heap memory */
		heap = &tmp_heap;
		retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
		if (retval)
			/* cannot allocate the heap */
			return retval;
	}

 again:
	/*
	 * Scan tasks in the cgroup, using the scanner's "test_task" callback
	 * to determine which are of interest, and using the scanner's
	 * "process_task" callback to process any of them that need an update.
	 * Since we don't want to hold any locks during the task updates,
	 * gather tasks to be processed in a heap structure.
	 * The heap is sorted by descending task start time.
	 * If the statically-sized heap fills up, we overflow tasks that
	 * started later, and in future iterations only consider tasks that
	 * started after the latest task in the previous pass. This
	 * guarantees forward progress and that we don't miss any tasks.
	 */
	heap->size = 0;
	cgroup_iter_start(scan->cg, &it);
	while ((p = cgroup_iter_next(scan->cg, &it))) {
		/*
		 * Only affect tasks that qualify per the caller's callback,
		 * if he provided one
		 */
		if (scan->test_task && !scan->test_task(p, scan))
			continue;
		/*
		 * Only process tasks that started after the last task
		 * we processed
		 */
		if (!started_after_time(p, &latest_time, latest_task))
			continue;
		dropped = heap_insert(heap, p);
		if (dropped == NULL) {
			/*
			 * The new task was inserted; the heap wasn't
			 * previously full
			 */
			get_task_struct(p);
		} else if (dropped != p) {
			/*
			 * The new task was inserted, and pushed out a
			 * different task
			 */
			get_task_struct(p);
			put_task_struct(dropped);
		}
		/*
		 * Else the new task was newer than anything already in
		 * the heap and wasn't inserted
		 */
	}
	cgroup_iter_end(scan->cg, &it);

	if (heap->size) {
		for (i = 0; i < heap->size; i++) {
2366
			struct task_struct *q = heap->ptrs[i];
2367
			if (i == 0) {
2368 2369
				latest_time = q->start_time;
				latest_task = q;
2370 2371
			}
			/* Process the task per the caller's callback */
2372 2373
			scan->process_task(q, scan);
			put_task_struct(q);
2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388
		}
		/*
		 * If we had to process any tasks at all, scan again
		 * in case some of them were in the middle of forking
		 * children that didn't get processed.
		 * Not the most efficient way to do it, but it avoids
		 * having to take callback_mutex in the fork path
		 */
		goto again;
	}
	if (heap == &tmp_heap)
		heap_free(&tmp_heap);
	return 0;
}

2389
/*
2390
 * Stuff for reading the 'tasks'/'procs' files.
2391 2392 2393 2394 2395 2396 2397 2398
 *
 * Reading this file can return large amounts of data if a cgroup 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.
 *
 */

2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434
/*
 * The following two functions "fix" the issue where there are more pids
 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
 * TODO: replace with a kernel-wide solution to this problem
 */
#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
static void *pidlist_allocate(int count)
{
	if (PIDLIST_TOO_LARGE(count))
		return vmalloc(count * sizeof(pid_t));
	else
		return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
}
static void pidlist_free(void *p)
{
	if (is_vmalloc_addr(p))
		vfree(p);
	else
		kfree(p);
}
static void *pidlist_resize(void *p, int newcount)
{
	void *newlist;
	/* note: if new alloc fails, old p will still be valid either way */
	if (is_vmalloc_addr(p)) {
		newlist = vmalloc(newcount * sizeof(pid_t));
		if (!newlist)
			return NULL;
		memcpy(newlist, p, newcount * sizeof(pid_t));
		vfree(p);
	} else {
		newlist = krealloc(p, newcount * sizeof(pid_t), GFP_KERNEL);
	}
	return newlist;
}

2435
/*
2436 2437 2438 2439
 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
 * If the new stripped list is sufficiently smaller and there's enough memory
 * to allocate a new buffer, will let go of the unneeded memory. Returns the
 * number of unique elements.
2440
 */
2441 2442 2443
/* is the size difference enough that we should re-allocate the array? */
#define PIDLIST_REALLOC_DIFFERENCE(old, new) ((old) - PAGE_SIZE >= (new))
static int pidlist_uniq(pid_t **p, int length)
2444
{
2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473
	int src, dest = 1;
	pid_t *list = *p;
	pid_t *newlist;

	/*
	 * we presume the 0th element is unique, so i starts at 1. trivial
	 * edge cases first; no work needs to be done for either
	 */
	if (length == 0 || length == 1)
		return length;
	/* src and dest walk down the list; dest counts unique elements */
	for (src = 1; src < length; src++) {
		/* find next unique element */
		while (list[src] == list[src-1]) {
			src++;
			if (src == length)
				goto after;
		}
		/* dest always points to where the next unique element goes */
		list[dest] = list[src];
		dest++;
	}
after:
	/*
	 * if the length difference is large enough, we want to allocate a
	 * smaller buffer to save memory. if this fails due to out of memory,
	 * we'll just stay with what we've got.
	 */
	if (PIDLIST_REALLOC_DIFFERENCE(length, dest)) {
2474
		newlist = pidlist_resize(list, dest);
2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485
		if (newlist)
			*p = newlist;
	}
	return dest;
}

static int cmppid(const void *a, const void *b)
{
	return *(pid_t *)a - *(pid_t *)b;
}

2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533
/*
 * find the appropriate pidlist for our purpose (given procs vs tasks)
 * returns with the lock on that pidlist already held, and takes care
 * of the use count, or returns NULL with no locks held if we're out of
 * memory.
 */
static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
						  enum cgroup_filetype type)
{
	struct cgroup_pidlist *l;
	/* don't need task_nsproxy() if we're looking at ourself */
	struct pid_namespace *ns = get_pid_ns(current->nsproxy->pid_ns);
	/*
	 * We can't drop the pidlist_mutex before taking the l->mutex in case
	 * the last ref-holder is trying to remove l from the list at the same
	 * time. Holding the pidlist_mutex precludes somebody taking whichever
	 * list we find out from under us - compare release_pid_array().
	 */
	mutex_lock(&cgrp->pidlist_mutex);
	list_for_each_entry(l, &cgrp->pidlists, links) {
		if (l->key.type == type && l->key.ns == ns) {
			/* found a matching list - drop the extra refcount */
			put_pid_ns(ns);
			/* make sure l doesn't vanish out from under us */
			down_write(&l->mutex);
			mutex_unlock(&cgrp->pidlist_mutex);
			return l;
		}
	}
	/* entry not found; create a new one */
	l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
	if (!l) {
		mutex_unlock(&cgrp->pidlist_mutex);
		put_pid_ns(ns);
		return l;
	}
	init_rwsem(&l->mutex);
	down_write(&l->mutex);
	l->key.type = type;
	l->key.ns = ns;
	l->use_count = 0; /* don't increment here */
	l->list = NULL;
	l->owner = cgrp;
	list_add(&l->links, &cgrp->pidlists);
	mutex_unlock(&cgrp->pidlist_mutex);
	return l;
}

2534 2535 2536
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
2537 2538
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
2539 2540 2541 2542
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
2543 2544
	struct cgroup_iter it;
	struct task_struct *tsk;
2545 2546 2547 2548 2549 2550 2551 2552 2553
	struct cgroup_pidlist *l;

	/*
	 * If cgroup 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 cgroup users didn't
	 * show up until sometime later on.
	 */
	length = cgroup_task_count(cgrp);
2554
	array = pidlist_allocate(length);
2555 2556 2557
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
2558 2559
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
2560
		if (unlikely(n == length))
2561
			break;
2562
		/* get tgid or pid for procs or tasks file respectively */
2563 2564 2565 2566
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
2567 2568
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
2569
	}
2570
	cgroup_iter_end(cgrp, &it);
2571 2572 2573
	length = n;
	/* now sort & (if procs) strip out duplicates */
	sort(array, length, sizeof(pid_t), cmppid, NULL);
2574
	if (type == CGROUP_FILE_PROCS)
2575
		length = pidlist_uniq(&array, length);
2576 2577
	l = cgroup_pidlist_find(cgrp, type);
	if (!l) {
2578
		pidlist_free(array);
2579
		return -ENOMEM;
2580
	}
2581
	/* store array, freeing old if necessary - lock already held */
2582
	pidlist_free(l->list);
2583 2584 2585 2586
	l->list = array;
	l->length = length;
	l->use_count++;
	up_write(&l->mutex);
2587
	*lp = l;
2588
	return 0;
2589 2590
}

B
Balbir Singh 已提交
2591
/**
L
Li Zefan 已提交
2592
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
2593 2594 2595
 * @stats: cgroupstats to fill information into
 * @dentry: A dentry entry belonging to the cgroup for which stats have
 * been requested.
L
Li Zefan 已提交
2596 2597 2598
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
2599 2600 2601 2602
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
	int ret = -EINVAL;
2603
	struct cgroup *cgrp;
B
Balbir Singh 已提交
2604 2605
	struct cgroup_iter it;
	struct task_struct *tsk;
2606

B
Balbir Singh 已提交
2607
	/*
2608 2609
	 * Validate dentry by checking the superblock operations,
	 * and make sure it's a directory.
B
Balbir Singh 已提交
2610
	 */
2611 2612
	if (dentry->d_sb->s_op != &cgroup_ops ||
	    !S_ISDIR(dentry->d_inode->i_mode))
B
Balbir Singh 已提交
2613 2614 2615
		 goto err;

	ret = 0;
2616
	cgrp = dentry->d_fsdata;
B
Balbir Singh 已提交
2617

2618 2619
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
B
Balbir Singh 已提交
2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638
		switch (tsk->state) {
		case TASK_RUNNING:
			stats->nr_running++;
			break;
		case TASK_INTERRUPTIBLE:
			stats->nr_sleeping++;
			break;
		case TASK_UNINTERRUPTIBLE:
			stats->nr_uninterruptible++;
			break;
		case TASK_STOPPED:
			stats->nr_stopped++;
			break;
		default:
			if (delayacct_is_task_waiting_on_io(tsk))
				stats->nr_io_wait++;
			break;
		}
	}
2639
	cgroup_iter_end(cgrp, &it);
B
Balbir Singh 已提交
2640 2641 2642 2643 2644

err:
	return ret;
}

2645

2646
/*
2647
 * seq_file methods for the tasks/procs files. The seq_file position is the
2648
 * next pid to display; the seq_file iterator is a pointer to the pid
2649
 * in the cgroup->l->list array.
2650
 */
2651

2652
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
2653
{
2654 2655 2656 2657 2658 2659
	/*
	 * Initially we receive a position value that corresponds to
	 * one more than the last pid shown (or 0 on the first call or
	 * after a seek to the start). Use a binary-search to find the
	 * next pid to display, if any
	 */
2660
	struct cgroup_pidlist *l = s->private;
2661 2662 2663
	int index = 0, pid = *pos;
	int *iter;

2664
	down_read(&l->mutex);
2665
	if (pid) {
2666
		int end = l->length;
S
Stephen Rothwell 已提交
2667

2668 2669
		while (index < end) {
			int mid = (index + end) / 2;
2670
			if (l->list[mid] == pid) {
2671 2672
				index = mid;
				break;
2673
			} else if (l->list[mid] <= pid)
2674 2675 2676 2677 2678 2679
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
2680
	if (index >= l->length)
2681 2682
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
2683
	iter = l->list + index;
2684 2685 2686 2687
	*pos = *iter;
	return iter;
}

2688
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
2689
{
2690 2691
	struct cgroup_pidlist *l = s->private;
	up_read(&l->mutex);
2692 2693
}

2694
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
2695
{
2696 2697 2698
	struct cgroup_pidlist *l = s->private;
	pid_t *p = v;
	pid_t *end = l->list + l->length;
2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711
	/*
	 * Advance to the next pid in the array. If this goes off the
	 * end, we're done
	 */
	p++;
	if (p >= end) {
		return NULL;
	} else {
		*pos = *p;
		return p;
	}
}

2712
static int cgroup_pidlist_show(struct seq_file *s, void *v)
2713 2714 2715
{
	return seq_printf(s, "%d\n", *(int *)v);
}
2716

2717 2718 2719 2720 2721 2722 2723 2724 2725
/*
 * seq_operations functions for iterating on pidlists through seq_file -
 * independent of whether it's tasks or procs
 */
static const struct seq_operations cgroup_pidlist_seq_operations = {
	.start = cgroup_pidlist_start,
	.stop = cgroup_pidlist_stop,
	.next = cgroup_pidlist_next,
	.show = cgroup_pidlist_show,
2726 2727
};

2728
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
2729
{
2730 2731 2732 2733 2734 2735 2736
	/*
	 * the case where we're the last user of this particular pidlist will
	 * have us remove it from the cgroup's list, which entails taking the
	 * mutex. since in pidlist_find the pidlist->lock depends on cgroup->
	 * pidlist_mutex, we have to take pidlist_mutex first.
	 */
	mutex_lock(&l->owner->pidlist_mutex);
2737 2738 2739
	down_write(&l->mutex);
	BUG_ON(!l->use_count);
	if (!--l->use_count) {
2740 2741 2742
		/* we're the last user if refcount is 0; remove and free */
		list_del(&l->links);
		mutex_unlock(&l->owner->pidlist_mutex);
2743
		pidlist_free(l->list);
2744 2745 2746 2747
		put_pid_ns(l->key.ns);
		up_write(&l->mutex);
		kfree(l);
		return;
2748
	}
2749
	mutex_unlock(&l->owner->pidlist_mutex);
2750
	up_write(&l->mutex);
2751 2752
}

2753
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
2754
{
2755
	struct cgroup_pidlist *l;
2756 2757
	if (!(file->f_mode & FMODE_READ))
		return 0;
2758 2759 2760 2761 2762 2763
	/*
	 * the seq_file will only be initialized if the file was opened for
	 * reading; hence we check if it's not null only in that case.
	 */
	l = ((struct seq_file *)file->private_data)->private;
	cgroup_release_pid_array(l);
2764 2765 2766
	return seq_release(inode, file);
}

2767
static const struct file_operations cgroup_pidlist_operations = {
2768 2769 2770
	.read = seq_read,
	.llseek = seq_lseek,
	.write = cgroup_file_write,
2771
	.release = cgroup_pidlist_release,
2772 2773
};

2774
/*
2775 2776 2777
 * The following functions handle opens on a file that displays a pidlist
 * (tasks or procs). Prepare an array of the process/thread IDs of whoever's
 * in the cgroup.
2778
 */
2779
/* helper function for the two below it */
2780
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
2781
{
2782
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2783
	struct cgroup_pidlist *l;
2784
	int retval;
2785

2786
	/* Nothing to do for write-only files */
2787 2788 2789
	if (!(file->f_mode & FMODE_READ))
		return 0;

2790
	/* have the array populated */
2791
	retval = pidlist_array_load(cgrp, type, &l);
2792 2793 2794 2795
	if (retval)
		return retval;
	/* configure file information */
	file->f_op = &cgroup_pidlist_operations;
2796

2797
	retval = seq_open(file, &cgroup_pidlist_seq_operations);
2798
	if (retval) {
2799
		cgroup_release_pid_array(l);
2800
		return retval;
2801
	}
2802
	((struct seq_file *)file->private_data)->private = l;
2803 2804
	return 0;
}
2805 2806
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
2807
	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
2808 2809 2810
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
2811
	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
2812
}
2813

2814
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
2815 2816
					    struct cftype *cft)
{
2817
	return notify_on_release(cgrp);
2818 2819
}

2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831
static int cgroup_write_notify_on_release(struct cgroup *cgrp,
					  struct cftype *cft,
					  u64 val)
{
	clear_bit(CGRP_RELEASABLE, &cgrp->flags);
	if (val)
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
	else
		clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
	return 0;
}

2832 2833 2834
/*
 * for the common functions, 'private' gives the type of file
 */
2835 2836
/* for hysterical raisins, we can't put this on the older files */
#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
2837 2838 2839 2840
static struct cftype files[] = {
	{
		.name = "tasks",
		.open = cgroup_tasks_open,
2841
		.write_u64 = cgroup_tasks_write,
2842
		.release = cgroup_pidlist_release,
L
Li Zefan 已提交
2843
		.mode = S_IRUGO | S_IWUSR,
2844
	},
2845 2846 2847 2848 2849 2850 2851
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "procs",
		.open = cgroup_procs_open,
		/* .write_u64 = cgroup_procs_write, TODO */
		.release = cgroup_pidlist_release,
		.mode = S_IRUGO,
	},
2852 2853
	{
		.name = "notify_on_release",
2854
		.read_u64 = cgroup_read_notify_on_release,
2855
		.write_u64 = cgroup_write_notify_on_release,
2856 2857 2858 2859 2860
	},
};

static struct cftype cft_release_agent = {
	.name = "release_agent",
2861 2862 2863
	.read_seq_string = cgroup_release_agent_show,
	.write_string = cgroup_release_agent_write,
	.max_write_len = PATH_MAX,
2864 2865
};

2866
static int cgroup_populate_dir(struct cgroup *cgrp)
2867 2868 2869 2870 2871
{
	int err;
	struct cgroup_subsys *ss;

	/* First clear out any existing files */
2872
	cgroup_clear_directory(cgrp->dentry);
2873

2874
	err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));
2875 2876 2877
	if (err < 0)
		return err;

2878 2879
	if (cgrp == cgrp->top_cgroup) {
		if ((err = cgroup_add_file(cgrp, NULL, &cft_release_agent)) < 0)
2880 2881 2882
			return err;
	}

2883 2884
	for_each_subsys(cgrp->root, ss) {
		if (ss->populate && (err = ss->populate(ss, cgrp)) < 0)
2885 2886
			return err;
	}
K
KAMEZAWA Hiroyuki 已提交
2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897
	/* This cgroup is ready now */
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
		/*
		 * Update id->css pointer and make this css visible from
		 * CSS ID functions. This pointer will be dereferened
		 * from RCU-read-side without locks.
		 */
		if (css->id)
			rcu_assign_pointer(css->id->css, css);
	}
2898 2899 2900 2901 2902 2903

	return 0;
}

static void init_cgroup_css(struct cgroup_subsys_state *css,
			       struct cgroup_subsys *ss,
2904
			       struct cgroup *cgrp)
2905
{
2906
	css->cgroup = cgrp;
P
Paul Menage 已提交
2907
	atomic_set(&css->refcnt, 1);
2908
	css->flags = 0;
K
KAMEZAWA Hiroyuki 已提交
2909
	css->id = NULL;
2910
	if (cgrp == dummytop)
2911
		set_bit(CSS_ROOT, &css->flags);
2912 2913
	BUG_ON(cgrp->subsys[ss->subsys_id]);
	cgrp->subsys[ss->subsys_id] = css;
2914 2915
}

2916 2917 2918 2919 2920 2921 2922 2923
static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
{
	/* We need to take each hierarchy_mutex in a consistent order */
	int i;

	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		if (ss->root == root)
2924
			mutex_lock(&ss->hierarchy_mutex);
2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938
	}
}

static void cgroup_unlock_hierarchy(struct cgroupfs_root *root)
{
	int i;

	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		if (ss->root == root)
			mutex_unlock(&ss->hierarchy_mutex);
	}
}

2939
/*
L
Li Zefan 已提交
2940 2941 2942 2943
 * cgroup_create - create a cgroup
 * @parent: cgroup that will be parent of the new cgroup
 * @dentry: dentry of the new cgroup
 * @mode: mode to set on new inode
2944
 *
L
Li Zefan 已提交
2945
 * Must be called with the mutex on the parent inode held
2946 2947
 */
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
L
Li Zefan 已提交
2948
			     mode_t mode)
2949
{
2950
	struct cgroup *cgrp;
2951 2952 2953 2954 2955
	struct cgroupfs_root *root = parent->root;
	int err = 0;
	struct cgroup_subsys *ss;
	struct super_block *sb = root->sb;

2956 2957
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968
		return -ENOMEM;

	/* Grab a reference on the superblock so the hierarchy doesn't
	 * get deleted on unmount if there are child cgroups.  This
	 * can be done outside cgroup_mutex, since the sb can't
	 * disappear while someone has an open control file on the
	 * fs */
	atomic_inc(&sb->s_active);

	mutex_lock(&cgroup_mutex);

2969
	init_cgroup_housekeeping(cgrp);
2970

2971 2972 2973
	cgrp->parent = parent;
	cgrp->root = parent->root;
	cgrp->top_cgroup = parent->top_cgroup;
2974

2975 2976 2977
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

2978
	for_each_subsys(root, ss) {
2979
		struct cgroup_subsys_state *css = ss->create(ss, cgrp);
2980

2981 2982 2983 2984
		if (IS_ERR(css)) {
			err = PTR_ERR(css);
			goto err_destroy;
		}
2985
		init_cgroup_css(css, ss, cgrp);
2986 2987 2988
		if (ss->use_id) {
			err = alloc_css_id(ss, parent, cgrp);
			if (err)
K
KAMEZAWA Hiroyuki 已提交
2989
				goto err_destroy;
2990
		}
K
KAMEZAWA Hiroyuki 已提交
2991
		/* At error, ->destroy() callback has to free assigned ID. */
2992 2993
	}

2994
	cgroup_lock_hierarchy(root);
2995
	list_add(&cgrp->sibling, &cgrp->parent->children);
2996
	cgroup_unlock_hierarchy(root);
2997 2998
	root->number_of_cgroups++;

2999
	err = cgroup_create_dir(cgrp, dentry, mode);
3000 3001 3002 3003
	if (err < 0)
		goto err_remove;

	/* The cgroup directory was pre-locked for us */
3004
	BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
3005

3006
	err = cgroup_populate_dir(cgrp);
3007 3008 3009
	/* If err < 0, we have a half-filled directory - oh well ;) */

	mutex_unlock(&cgroup_mutex);
3010
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
3011 3012 3013 3014 3015

	return 0;

 err_remove:

3016
	cgroup_lock_hierarchy(root);
3017
	list_del(&cgrp->sibling);
3018
	cgroup_unlock_hierarchy(root);
3019 3020 3021 3022 3023
	root->number_of_cgroups--;

 err_destroy:

	for_each_subsys(root, ss) {
3024 3025
		if (cgrp->subsys[ss->subsys_id])
			ss->destroy(ss, cgrp);
3026 3027 3028 3029 3030 3031 3032
	}

	mutex_unlock(&cgroup_mutex);

	/* Release the reference count that we took on the superblock */
	deactivate_super(sb);

3033
	kfree(cgrp);
3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044
	return err;
}

static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
	struct cgroup *c_parent = dentry->d_parent->d_fsdata;

	/* the vfs holds inode->i_mutex already */
	return cgroup_create(c_parent, dentry, mode | S_IFDIR);
}

3045
static int cgroup_has_css_refs(struct cgroup *cgrp)
3046 3047 3048
{
	/* Check the reference count on each subsystem. Since we
	 * already established that there are no tasks in the
P
Paul Menage 已提交
3049
	 * cgroup, if the css refcount is also 1, then there should
3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060
	 * be no outstanding references, so the subsystem is safe to
	 * destroy. We scan across all subsystems rather than using
	 * the per-hierarchy linked list of mounted subsystems since
	 * we can be called via check_for_release() with no
	 * synchronization other than RCU, and the subsystem linked
	 * list isn't RCU-safe */
	int i;
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		struct cgroup_subsys_state *css;
		/* Skip subsystems not in this hierarchy */
3061
		if (ss->root != cgrp->root)
3062
			continue;
3063
		css = cgrp->subsys[ss->subsys_id];
3064 3065 3066 3067 3068 3069
		/* When called from check_for_release() it's possible
		 * that by this point the cgroup has been removed
		 * and the css deleted. But a false-positive doesn't
		 * matter, since it can only happen if the cgroup
		 * has been deleted and hence no longer needs the
		 * release agent to be called anyway. */
P
Paul Menage 已提交
3070
		if (css && (atomic_read(&css->refcnt) > 1))
3071 3072 3073 3074 3075
			return 1;
	}
	return 0;
}

P
Paul Menage 已提交
3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090
/*
 * Atomically mark all (or else none) of the cgroup's CSS objects as
 * CSS_REMOVED. Return true on success, or false if the cgroup has
 * busy subsystems. Call with cgroup_mutex held
 */

static int cgroup_clear_css_refs(struct cgroup *cgrp)
{
	struct cgroup_subsys *ss;
	unsigned long flags;
	bool failed = false;
	local_irq_save(flags);
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
		int refcnt;
3091
		while (1) {
P
Paul Menage 已提交
3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104
			/* We can only remove a CSS with a refcnt==1 */
			refcnt = atomic_read(&css->refcnt);
			if (refcnt > 1) {
				failed = true;
				goto done;
			}
			BUG_ON(!refcnt);
			/*
			 * Drop the refcnt to 0 while we check other
			 * subsystems. This will cause any racing
			 * css_tryget() to spin until we set the
			 * CSS_REMOVED bits or abort
			 */
3105 3106 3107 3108
			if (atomic_cmpxchg(&css->refcnt, refcnt, 0) == refcnt)
				break;
			cpu_relax();
		}
P
Paul Menage 已提交
3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125 3126 3127 3128
	}
 done:
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
		if (failed) {
			/*
			 * Restore old refcnt if we previously managed
			 * to clear it from 1 to 0
			 */
			if (!atomic_read(&css->refcnt))
				atomic_set(&css->refcnt, 1);
		} else {
			/* Commit the fact that the CSS is removed */
			set_bit(CSS_REMOVED, &css->flags);
		}
	}
	local_irq_restore(flags);
	return !failed;
}

3129 3130
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
3131
	struct cgroup *cgrp = dentry->d_fsdata;
3132 3133
	struct dentry *d;
	struct cgroup *parent;
3134 3135
	DEFINE_WAIT(wait);
	int ret;
3136 3137

	/* the vfs holds both inode->i_mutex already */
3138
again:
3139
	mutex_lock(&cgroup_mutex);
3140
	if (atomic_read(&cgrp->count) != 0) {
3141 3142 3143
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
3144
	if (!list_empty(&cgrp->children)) {
3145 3146 3147
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
3148
	mutex_unlock(&cgroup_mutex);
L
Li Zefan 已提交
3149

3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160
	/*
	 * In general, subsystem has no css->refcnt after pre_destroy(). But
	 * in racy cases, subsystem may have to get css->refcnt after
	 * pre_destroy() and it makes rmdir return with -EBUSY. This sometimes
	 * make rmdir return -EBUSY too often. To avoid that, we use waitqueue
	 * for cgroup's rmdir. CGRP_WAIT_ON_RMDIR is for synchronizing rmdir
	 * and subsystem's reference count handling. Please see css_get/put
	 * and css_tryget() and cgroup_wakeup_rmdir_waiter() implementation.
	 */
	set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);

3161
	/*
L
Li Zefan 已提交
3162 3163
	 * Call pre_destroy handlers of subsys. Notify subsystems
	 * that rmdir() request comes.
3164
	 */
3165
	ret = cgroup_call_pre_destroy(cgrp);
3166 3167
	if (ret) {
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
3168
		return ret;
3169
	}
3170

3171 3172
	mutex_lock(&cgroup_mutex);
	parent = cgrp->parent;
3173
	if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
3174
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
3175 3176 3177
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
3178 3179 3180
	prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
	if (!cgroup_clear_css_refs(cgrp)) {
		mutex_unlock(&cgroup_mutex);
3181 3182 3183 3184 3185 3186
		/*
		 * Because someone may call cgroup_wakeup_rmdir_waiter() before
		 * prepare_to_wait(), we need to check this flag.
		 */
		if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))
			schedule();
3187 3188 3189 3190 3191 3192 3193 3194 3195
		finish_wait(&cgroup_rmdir_waitq, &wait);
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
		if (signal_pending(current))
			return -EINTR;
		goto again;
	}
	/* NO css_tryget() can success after here. */
	finish_wait(&cgroup_rmdir_waitq, &wait);
	clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
3196

3197
	spin_lock(&release_list_lock);
3198 3199 3200
	set_bit(CGRP_REMOVED, &cgrp->flags);
	if (!list_empty(&cgrp->release_list))
		list_del(&cgrp->release_list);
3201
	spin_unlock(&release_list_lock);
3202 3203 3204

	cgroup_lock_hierarchy(cgrp->root);
	/* delete this cgroup from parent->children */
3205
	list_del(&cgrp->sibling);
3206 3207
	cgroup_unlock_hierarchy(cgrp->root);

3208 3209
	spin_lock(&cgrp->dentry->d_lock);
	d = dget(cgrp->dentry);
3210 3211 3212 3213 3214
	spin_unlock(&d->d_lock);

	cgroup_d_remove_dir(d);
	dput(d);

3215
	set_bit(CGRP_RELEASABLE, &parent->flags);
3216 3217
	check_for_release(parent);

3218 3219 3220 3221
	mutex_unlock(&cgroup_mutex);
	return 0;
}

3222
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
3223 3224
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
3225 3226

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
3227 3228

	/* Create the top cgroup state for this subsystem */
3229
	list_add(&ss->sibling, &rootnode.subsys_list);
3230 3231 3232 3233 3234 3235
	ss->root = &rootnode;
	css = ss->create(ss, dummytop);
	/* We don't handle early failures gracefully */
	BUG_ON(IS_ERR(css));
	init_cgroup_css(css, ss, dummytop);

L
Li Zefan 已提交
3236
	/* Update the init_css_set to contain a subsys
3237
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
3238 3239 3240
	 * newly registered, all tasks and hence the
	 * init_css_set is in the subsystem's top cgroup. */
	init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
3241 3242 3243

	need_forkexit_callback |= ss->fork || ss->exit;

L
Li Zefan 已提交
3244 3245 3246 3247 3248
	/* At system boot, before all subsystems have been
	 * registered, no tasks have been forked, so we don't
	 * need to invoke fork callbacks here. */
	BUG_ON(!list_empty(&init_task.tasks));

3249
	mutex_init(&ss->hierarchy_mutex);
3250
	lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
3251 3252 3253 3254
	ss->active = 1;
}

/**
L
Li Zefan 已提交
3255 3256 3257 3258
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
3259 3260 3261 3262
 */
int __init cgroup_init_early(void)
{
	int i;
3263
	atomic_set(&init_css_set.refcount, 1);
3264 3265
	INIT_LIST_HEAD(&init_css_set.cg_links);
	INIT_LIST_HEAD(&init_css_set.tasks);
3266
	INIT_HLIST_NODE(&init_css_set.hlist);
3267
	css_set_count = 1;
3268
	init_cgroup_root(&rootnode);
3269 3270 3271 3272
	root_count = 1;
	init_task.cgroups = &init_css_set;

	init_css_set_link.cg = &init_css_set;
3273
	init_css_set_link.cgrp = dummytop;
3274
	list_add(&init_css_set_link.cgrp_link_list,
3275 3276 3277
		 &rootnode.top_cgroup.css_sets);
	list_add(&init_css_set_link.cg_link_list,
		 &init_css_set.cg_links);
3278

3279 3280 3281
	for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
		INIT_HLIST_HEAD(&css_set_table[i]);

3282 3283 3284 3285 3286 3287 3288 3289
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];

		BUG_ON(!ss->name);
		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
		BUG_ON(!ss->create);
		BUG_ON(!ss->destroy);
		if (ss->subsys_id != i) {
D
Diego Calleja 已提交
3290
			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301
			       ss->name, ss->subsys_id);
			BUG();
		}

		if (ss->early_init)
			cgroup_init_subsys(ss);
	}
	return 0;
}

/**
L
Li Zefan 已提交
3302 3303 3304 3305
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
3306 3307 3308 3309 3310
 */
int __init cgroup_init(void)
{
	int err;
	int i;
3311
	struct hlist_head *hhead;
3312 3313 3314 3315

	err = bdi_init(&cgroup_backing_dev_info);
	if (err)
		return err;
3316 3317 3318 3319 3320

	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		if (!ss->early_init)
			cgroup_init_subsys(ss);
K
KAMEZAWA Hiroyuki 已提交
3321 3322
		if (ss->use_id)
			cgroup_subsys_init_idr(ss);
3323 3324
	}

3325 3326 3327
	/* Add init_css_set to the hash table */
	hhead = css_set_hash(init_css_set.subsys);
	hlist_add_head(&init_css_set.hlist, hhead);
3328
	BUG_ON(!init_root_id(&rootnode));
3329 3330 3331 3332
	err = register_filesystem(&cgroup_fs_type);
	if (err < 0)
		goto out;

L
Li Zefan 已提交
3333
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
3334

3335
out:
3336 3337 3338
	if (err)
		bdi_destroy(&cgroup_backing_dev_info);

3339 3340
	return err;
}
3341

3342 3343 3344 3345 3346 3347
/*
 * proc_cgroup_show()
 *  - Print task's cgroup paths into seq_file, one line for each hierarchy
 *  - Used for /proc/<pid>/cgroup.
 *  - No need to task_lock(tsk) on this tsk->cgroup reference, as it
 *    doesn't really matter if tsk->cgroup changes after we read it,
3348
 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377
 *    anyway.  No need to check that tsk->cgroup != NULL, thanks to
 *    the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
 *    cgroup to top_cgroup.
 */

/* TODO: Use a proper seq_file iterator */
static int proc_cgroup_show(struct seq_file *m, void *v)
{
	struct pid *pid;
	struct task_struct *tsk;
	char *buf;
	int retval;
	struct cgroupfs_root *root;

	retval = -ENOMEM;
	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!buf)
		goto out;

	retval = -ESRCH;
	pid = m->private;
	tsk = get_pid_task(pid, PIDTYPE_PID);
	if (!tsk)
		goto out_free;

	retval = 0;

	mutex_lock(&cgroup_mutex);

3378
	for_each_active_root(root) {
3379
		struct cgroup_subsys *ss;
3380
		struct cgroup *cgrp;
3381 3382
		int count = 0;

3383
		seq_printf(m, "%d:", root->hierarchy_id);
3384 3385
		for_each_subsys(root, ss)
			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
3386 3387 3388
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
3389
		seq_putc(m, ':');
3390
		cgrp = task_cgroup_from_root(tsk, root);
3391
		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412
		if (retval < 0)
			goto out_unlock;
		seq_puts(m, buf);
		seq_putc(m, '\n');
	}

out_unlock:
	mutex_unlock(&cgroup_mutex);
	put_task_struct(tsk);
out_free:
	kfree(buf);
out:
	return retval;
}

static int cgroup_open(struct inode *inode, struct file *file)
{
	struct pid *pid = PROC_I(inode)->pid;
	return single_open(file, proc_cgroup_show, pid);
}

3413
const struct file_operations proc_cgroup_operations = {
3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424
	.open		= cgroup_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

/* Display information about each subsystem and each hierarchy */
static int proc_cgroupstats_show(struct seq_file *m, void *v)
{
	int i;

3425
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
3426 3427 3428
	mutex_lock(&cgroup_mutex);
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
3429 3430
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
3431
			   ss->root->number_of_cgroups, !ss->disabled);
3432 3433 3434 3435 3436 3437 3438
	}
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
3439
	return single_open(file, proc_cgroupstats_show, NULL);
3440 3441
}

3442
static const struct file_operations proc_cgroupstats_operations = {
3443 3444 3445 3446 3447 3448
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

3449 3450
/**
 * cgroup_fork - attach newly forked task to its parents cgroup.
L
Li Zefan 已提交
3451
 * @child: pointer to task_struct of forking parent process.
3452 3453 3454 3455 3456 3457
 *
 * Description: A task inherits its parent's cgroup at fork().
 *
 * A pointer to the shared css_set was automatically copied in
 * fork.c by dup_task_struct().  However, we ignore that copy, since
 * it was not made under the protection of RCU or cgroup_mutex, so
3458
 * might no longer be a valid cgroup pointer.  cgroup_attach_task() might
3459 3460
 * have already changed current->cgroups, allowing the previously
 * referenced cgroup group to be removed and freed.
3461 3462 3463 3464 3465 3466
 *
 * At the point that cgroup_fork() is called, 'current' is the parent
 * task, and the passed argument 'child' points to the child task.
 */
void cgroup_fork(struct task_struct *child)
{
3467 3468 3469 3470 3471
	task_lock(current);
	child->cgroups = current->cgroups;
	get_css_set(child->cgroups);
	task_unlock(current);
	INIT_LIST_HEAD(&child->cg_list);
3472 3473 3474
}

/**
L
Li Zefan 已提交
3475 3476 3477 3478 3479 3480
 * cgroup_fork_callbacks - run fork callbacks
 * @child: the new task
 *
 * Called on a new task very soon before adding it to the
 * tasklist. No need to take any locks since no-one can
 * be operating on this task.
3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493
 */
void cgroup_fork_callbacks(struct task_struct *child)
{
	if (need_forkexit_callback) {
		int i;
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss->fork)
				ss->fork(ss, child);
		}
	}
}

3494
/**
L
Li Zefan 已提交
3495 3496 3497 3498 3499 3500 3501 3502
 * cgroup_post_fork - called on a new task after adding it to the task list
 * @child: the task in question
 *
 * Adds the task to the list running through its css_set if necessary.
 * Has to be after the task is visible on the task list in case we race
 * with the first call to cgroup_iter_start() - to guarantee that the
 * new task ends up on its list.
 */
3503 3504 3505 3506
void cgroup_post_fork(struct task_struct *child)
{
	if (use_task_css_set_links) {
		write_lock(&css_set_lock);
3507
		task_lock(child);
3508 3509
		if (list_empty(&child->cg_list))
			list_add(&child->cg_list, &child->cgroups->tasks);
3510
		task_unlock(child);
3511 3512 3513
		write_unlock(&css_set_lock);
	}
}
3514 3515 3516
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
3517
 * @run_callback: run exit callbacks?
3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545
 *
 * Description: Detach cgroup from @tsk and release it.
 *
 * Note that cgroups marked notify_on_release force every task in
 * them to take the global cgroup_mutex mutex when exiting.
 * This could impact scaling on very large systems.  Be reluctant to
 * use notify_on_release cgroups where very high task exit scaling
 * is required on large systems.
 *
 * the_top_cgroup_hack:
 *
 *    Set the exiting tasks cgroup to the root cgroup (top_cgroup).
 *
 *    We call cgroup_exit() while the task is still competent to
 *    handle notify_on_release(), then leave the task attached to the
 *    root cgroup in each hierarchy for the remainder of its exit.
 *
 *    To do this properly, we would increment the reference count on
 *    top_cgroup, and near the very end of the kernel/exit.c do_exit()
 *    code we would add a second cgroup function call, to drop that
 *    reference.  This would just create an unnecessary hot spot on
 *    the top_cgroup reference count, to no avail.
 *
 *    Normally, holding a reference to a cgroup without bumping its
 *    count is unsafe.   The cgroup could go away, or someone could
 *    attach us to a different cgroup, decrementing the count on
 *    the first cgroup that we never incremented.  But in this case,
 *    top_cgroup isn't going away, and either task has PF_EXITING set,
3546 3547
 *    which wards off any cgroup_attach_task() attempts, or task is a failed
 *    fork, never visible to cgroup_attach_task.
3548 3549 3550 3551
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
	int i;
3552
	struct css_set *cg;
3553 3554 3555 3556 3557 3558 3559 3560

	if (run_callbacks && need_forkexit_callback) {
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss->exit)
				ss->exit(ss, tsk);
		}
	}
3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573

	/*
	 * Unlink from the css_set task list if necessary.
	 * Optimistically check cg_list before taking
	 * css_set_lock
	 */
	if (!list_empty(&tsk->cg_list)) {
		write_lock(&css_set_lock);
		if (!list_empty(&tsk->cg_list))
			list_del(&tsk->cg_list);
		write_unlock(&css_set_lock);
	}

3574 3575
	/* Reassign the task to the init_css_set. */
	task_lock(tsk);
3576 3577
	cg = tsk->cgroups;
	tsk->cgroups = &init_css_set;
3578
	task_unlock(tsk);
3579
	if (cg)
3580
		put_css_set_taskexit(cg);
3581
}
3582 3583

/**
L
Li Zefan 已提交
3584 3585 3586
 * cgroup_clone - clone the cgroup the given subsystem is attached to
 * @tsk: the task to be moved
 * @subsys: the given subsystem
3587
 * @nodename: the name for the new cgroup
L
Li Zefan 已提交
3588 3589 3590 3591
 *
 * Duplicate the current cgroup in the hierarchy that the given
 * subsystem is attached to, and move this task into the new
 * child.
3592
 */
3593 3594
int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
							char *nodename)
3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617
{
	struct dentry *dentry;
	int ret = 0;
	struct cgroup *parent, *child;
	struct inode *inode;
	struct css_set *cg;
	struct cgroupfs_root *root;
	struct cgroup_subsys *ss;

	/* We shouldn't be called by an unregistered subsystem */
	BUG_ON(!subsys->active);

	/* First figure out what hierarchy and cgroup we're dealing
	 * with, and pin them so we can drop cgroup_mutex */
	mutex_lock(&cgroup_mutex);
 again:
	root = subsys->root;
	if (root == &rootnode) {
		mutex_unlock(&cgroup_mutex);
		return 0;
	}

	/* Pin the hierarchy */
3618
	if (!atomic_inc_not_zero(&root->sb->s_active)) {
3619 3620 3621 3622
		/* We race with the final deactivate_super() */
		mutex_unlock(&cgroup_mutex);
		return 0;
	}
3623

3624
	/* Keep the cgroup alive */
3625 3626 3627
	task_lock(tsk);
	parent = task_cgroup(tsk, subsys->subsys_id);
	cg = tsk->cgroups;
3628
	get_css_set(cg);
3629
	task_unlock(tsk);
3630

3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641
	mutex_unlock(&cgroup_mutex);

	/* Now do the VFS work to create a cgroup */
	inode = parent->dentry->d_inode;

	/* Hold the parent directory mutex across this operation to
	 * stop anyone else deleting the new cgroup */
	mutex_lock(&inode->i_mutex);
	dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));
	if (IS_ERR(dentry)) {
		printk(KERN_INFO
D
Diego Calleja 已提交
3642
		       "cgroup: Couldn't allocate dentry for %s: %ld\n", nodename,
3643 3644 3645 3646 3647 3648
		       PTR_ERR(dentry));
		ret = PTR_ERR(dentry);
		goto out_release;
	}

	/* Create the cgroup directory, which also creates the cgroup */
3649
	ret = vfs_mkdir(inode, dentry, 0755);
3650
	child = __d_cgrp(dentry);
3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666
	dput(dentry);
	if (ret) {
		printk(KERN_INFO
		       "Failed to create cgroup %s: %d\n", nodename,
		       ret);
		goto out_release;
	}

	/* The cgroup now exists. Retake cgroup_mutex and check
	 * that we're still in the same state that we thought we
	 * were. */
	mutex_lock(&cgroup_mutex);
	if ((root != subsys->root) ||
	    (parent != task_cgroup(tsk, subsys->subsys_id))) {
		/* Aargh, we raced ... */
		mutex_unlock(&inode->i_mutex);
3667
		put_css_set(cg);
3668

3669
		deactivate_super(root->sb);
3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685
		/* The cgroup is still accessible in the VFS, but
		 * we're not going to try to rmdir() it at this
		 * point. */
		printk(KERN_INFO
		       "Race in cgroup_clone() - leaking cgroup %s\n",
		       nodename);
		goto again;
	}

	/* do any required auto-setup */
	for_each_subsys(root, ss) {
		if (ss->post_clone)
			ss->post_clone(ss, child);
	}

	/* All seems fine. Finish by moving the task into the new cgroup */
3686
	ret = cgroup_attach_task(child, tsk);
3687 3688 3689 3690
	mutex_unlock(&cgroup_mutex);

 out_release:
	mutex_unlock(&inode->i_mutex);
3691 3692

	mutex_lock(&cgroup_mutex);
3693
	put_css_set(cg);
3694
	mutex_unlock(&cgroup_mutex);
3695
	deactivate_super(root->sb);
3696 3697 3698
	return ret;
}

L
Li Zefan 已提交
3699
/**
3700
 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
L
Li Zefan 已提交
3701
 * @cgrp: the cgroup in question
3702
 * @task: the task in question
L
Li Zefan 已提交
3703
 *
3704 3705
 * See if @cgrp is a descendant of @task's cgroup in the appropriate
 * hierarchy.
3706 3707 3708 3709 3710 3711
 *
 * If we are sending in dummytop, then presumably we are creating
 * the top cgroup in the subsystem.
 *
 * Called only by the ns (nsproxy) cgroup.
 */
3712
int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
3713 3714 3715 3716
{
	int ret;
	struct cgroup *target;

3717
	if (cgrp == dummytop)
3718 3719
		return 1;

3720
	target = task_cgroup_from_root(task, cgrp->root);
3721 3722 3723
	while (cgrp != target && cgrp!= cgrp->top_cgroup)
		cgrp = cgrp->parent;
	ret = (cgrp == target);
3724 3725
	return ret;
}
3726

3727
static void check_for_release(struct cgroup *cgrp)
3728 3729 3730
{
	/* All of these checks rely on RCU to keep the cgroup
	 * structure alive */
3731 3732
	if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
	    && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
3733 3734 3735 3736 3737
		/* Control Group is currently removeable. If it's not
		 * already queued for a userspace notification, queue
		 * it now */
		int need_schedule_work = 0;
		spin_lock(&release_list_lock);
3738 3739 3740
		if (!cgroup_is_removed(cgrp) &&
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
3741 3742 3743 3744 3745 3746 3747 3748
			need_schedule_work = 1;
		}
		spin_unlock(&release_list_lock);
		if (need_schedule_work)
			schedule_work(&release_agent_work);
	}
}

3749 3750
/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css, int count)
3751
{
3752
	struct cgroup *cgrp = css->cgroup;
3753
	int val;
3754
	rcu_read_lock();
3755
	val = atomic_sub_return(count, &css->refcnt);
3756
	if (val == 1) {
3757 3758 3759 3760
		if (notify_on_release(cgrp)) {
			set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
		}
3761
		cgroup_wakeup_rmdir_waiter(cgrp);
3762 3763
	}
	rcu_read_unlock();
3764
	WARN_ON_ONCE(val < 1);
3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797
}

/*
 * Notify userspace when a cgroup is released, by running the
 * configured release agent with the name of the cgroup (path
 * relative to the root of cgroup file system) as the argument.
 *
 * Most likely, this user command will try to rmdir this cgroup.
 *
 * This races with the possibility that some other task will be
 * attached to this cgroup before it is removed, or that some other
 * user task will 'mkdir' a child cgroup of this cgroup.  That's ok.
 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
 * unused, and this cgroup will be reprieved from its death sentence,
 * to continue to serve a useful existence.  Next time it's released,
 * we will get notified again, if it still has 'notify_on_release' set.
 *
 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
 * means only wait until the task is successfully execve()'d.  The
 * separate 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 release agent
 * task, so no sense holding our caller up for that.
 */
static void cgroup_release_agent(struct work_struct *work)
{
	BUG_ON(work != &release_agent_work);
	mutex_lock(&cgroup_mutex);
	spin_lock(&release_list_lock);
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
3798
		char *pathbuf = NULL, *agentbuf = NULL;
3799
		struct cgroup *cgrp = list_entry(release_list.next,
3800 3801
						    struct cgroup,
						    release_list);
3802
		list_del_init(&cgrp->release_list);
3803 3804
		spin_unlock(&release_list_lock);
		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
3805 3806 3807 3808 3809 3810 3811
		if (!pathbuf)
			goto continue_free;
		if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
			goto continue_free;
		agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
		if (!agentbuf)
			goto continue_free;
3812 3813

		i = 0;
3814 3815
		argv[i++] = agentbuf;
		argv[i++] = pathbuf;
3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829
		argv[i] = NULL;

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

		/* Drop the lock while we invoke the usermode helper,
		 * since the exec could involve hitting disk and hence
		 * be a slow process */
		mutex_unlock(&cgroup_mutex);
		call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
		mutex_lock(&cgroup_mutex);
3830 3831 3832
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
3833 3834 3835 3836 3837
		spin_lock(&release_list_lock);
	}
	spin_unlock(&release_list_lock);
	mutex_unlock(&cgroup_mutex);
}
3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861

static int __init cgroup_disable(char *str)
{
	int i;
	char *token;

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;

		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];

			if (!strcmp(token, ss->name)) {
				ss->disabled = 1;
				printk(KERN_INFO "Disabling %s control group"
					" subsystem\n", ss->name);
				break;
			}
		}
	}
	return 1;
}
__setup("cgroup_disable=", cgroup_disable);
K
KAMEZAWA Hiroyuki 已提交
3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888

/*
 * Functons for CSS ID.
 */

/*
 *To get ID other than 0, this should be called when !cgroup_is_removed().
 */
unsigned short css_id(struct cgroup_subsys_state *css)
{
	struct css_id *cssid = rcu_dereference(css->id);

	if (cssid)
		return cssid->id;
	return 0;
}

unsigned short css_depth(struct cgroup_subsys_state *css)
{
	struct css_id *cssid = rcu_dereference(css->id);

	if (cssid)
		return cssid->depth;
	return 0;
}

bool css_is_ancestor(struct cgroup_subsys_state *child,
3889
		    const struct cgroup_subsys_state *root)
K
KAMEZAWA Hiroyuki 已提交
3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088 4089 4090
{
	struct css_id *child_id = rcu_dereference(child->id);
	struct css_id *root_id = rcu_dereference(root->id);

	if (!child_id || !root_id || (child_id->depth < root_id->depth))
		return false;
	return child_id->stack[root_id->depth] == root_id->id;
}

static void __free_css_id_cb(struct rcu_head *head)
{
	struct css_id *id;

	id = container_of(head, struct css_id, rcu_head);
	kfree(id);
}

void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
{
	struct css_id *id = css->id;
	/* When this is called before css_id initialization, id can be NULL */
	if (!id)
		return;

	BUG_ON(!ss->use_id);

	rcu_assign_pointer(id->css, NULL);
	rcu_assign_pointer(css->id, NULL);
	spin_lock(&ss->id_lock);
	idr_remove(&ss->idr, id->id);
	spin_unlock(&ss->id_lock);
	call_rcu(&id->rcu_head, __free_css_id_cb);
}

/*
 * This is called by init or create(). Then, calls to this function are
 * always serialized (By cgroup_mutex() at create()).
 */

static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
{
	struct css_id *newid;
	int myid, error, size;

	BUG_ON(!ss->use_id);

	size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
	newid = kzalloc(size, GFP_KERNEL);
	if (!newid)
		return ERR_PTR(-ENOMEM);
	/* get id */
	if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
		error = -ENOMEM;
		goto err_out;
	}
	spin_lock(&ss->id_lock);
	/* Don't use 0. allocates an ID of 1-65535 */
	error = idr_get_new_above(&ss->idr, newid, 1, &myid);
	spin_unlock(&ss->id_lock);

	/* Returns error when there are no free spaces for new ID.*/
	if (error) {
		error = -ENOSPC;
		goto err_out;
	}
	if (myid > CSS_ID_MAX)
		goto remove_idr;

	newid->id = myid;
	newid->depth = depth;
	return newid;
remove_idr:
	error = -ENOSPC;
	spin_lock(&ss->id_lock);
	idr_remove(&ss->idr, myid);
	spin_unlock(&ss->id_lock);
err_out:
	kfree(newid);
	return ERR_PTR(error);

}

static int __init cgroup_subsys_init_idr(struct cgroup_subsys *ss)
{
	struct css_id *newid;
	struct cgroup_subsys_state *rootcss;

	spin_lock_init(&ss->id_lock);
	idr_init(&ss->idr);

	rootcss = init_css_set.subsys[ss->subsys_id];
	newid = get_new_cssid(ss, 0);
	if (IS_ERR(newid))
		return PTR_ERR(newid);

	newid->stack[0] = newid->id;
	newid->css = rootcss;
	rootcss->id = newid;
	return 0;
}

static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
			struct cgroup *child)
{
	int subsys_id, i, depth = 0;
	struct cgroup_subsys_state *parent_css, *child_css;
	struct css_id *child_id, *parent_id = NULL;

	subsys_id = ss->subsys_id;
	parent_css = parent->subsys[subsys_id];
	child_css = child->subsys[subsys_id];
	depth = css_depth(parent_css) + 1;
	parent_id = parent_css->id;

	child_id = get_new_cssid(ss, depth);
	if (IS_ERR(child_id))
		return PTR_ERR(child_id);

	for (i = 0; i < depth; i++)
		child_id->stack[i] = parent_id->stack[i];
	child_id->stack[depth] = child_id->id;
	/*
	 * child_id->css pointer will be set after this cgroup is available
	 * see cgroup_populate_dir()
	 */
	rcu_assign_pointer(child_css->id, child_id);

	return 0;
}

/**
 * css_lookup - lookup css by id
 * @ss: cgroup subsys to be looked into.
 * @id: the id
 *
 * Returns pointer to cgroup_subsys_state if there is valid one with id.
 * NULL if not. Should be called under rcu_read_lock()
 */
struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
{
	struct css_id *cssid = NULL;

	BUG_ON(!ss->use_id);
	cssid = idr_find(&ss->idr, id);

	if (unlikely(!cssid))
		return NULL;

	return rcu_dereference(cssid->css);
}

/**
 * css_get_next - lookup next cgroup under specified hierarchy.
 * @ss: pointer to subsystem
 * @id: current position of iteration.
 * @root: pointer to css. search tree under this.
 * @foundid: position of found object.
 *
 * Search next css under the specified hierarchy of rootid. Calling under
 * rcu_read_lock() is necessary. Returns NULL if it reaches the end.
 */
struct cgroup_subsys_state *
css_get_next(struct cgroup_subsys *ss, int id,
	     struct cgroup_subsys_state *root, int *foundid)
{
	struct cgroup_subsys_state *ret = NULL;
	struct css_id *tmp;
	int tmpid;
	int rootid = css_id(root);
	int depth = css_depth(root);

	if (!rootid)
		return NULL;

	BUG_ON(!ss->use_id);
	/* fill start point for scan */
	tmpid = id;
	while (1) {
		/*
		 * scan next entry from bitmap(tree), tmpid is updated after
		 * idr_get_next().
		 */
		spin_lock(&ss->id_lock);
		tmp = idr_get_next(&ss->idr, &tmpid);
		spin_unlock(&ss->id_lock);

		if (!tmp)
			break;
		if (tmp->depth >= depth && tmp->stack[depth] == rootid) {
			ret = rcu_dereference(tmp->css);
			if (ret) {
				*foundid = tmpid;
				break;
			}
		}
		/* continue to scan from next id */
		tmpid = tmpid + 1;
	}
	return ret;
}

4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133
#ifdef CONFIG_CGROUP_DEBUG
static struct cgroup_subsys_state *debug_create(struct cgroup_subsys *ss,
						   struct cgroup *cont)
{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

	if (!css)
		return ERR_PTR(-ENOMEM);

	return css;
}

static void debug_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
{
	kfree(cont->subsys[debug_subsys_id]);
}

static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
{
	return atomic_read(&cont->count);
}

static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft)
{
	return cgroup_task_count(cont);
}

static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
{
	return (u64)(unsigned long)current->cgroups;
}

static u64 current_css_set_refcount_read(struct cgroup *cont,
					   struct cftype *cft)
{
	u64 count;

	rcu_read_lock();
	count = atomic_read(&current->cgroups->refcount);
	rcu_read_unlock();
	return count;
}

4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151
static int current_css_set_cg_links_read(struct cgroup *cont,
					 struct cftype *cft,
					 struct seq_file *seq)
{
	struct cg_cgroup_link *link;
	struct css_set *cg;

	read_lock(&css_set_lock);
	rcu_read_lock();
	cg = rcu_dereference(current->cgroups);
	list_for_each_entry(link, &cg->cg_links, cg_link_list) {
		struct cgroup *c = link->cgrp;
		const char *name;

		if (c->dentry)
			name = c->dentry->d_name.name;
		else
			name = "?";
4152 4153
		seq_printf(seq, "Root %d group %s\n",
			   c->root->hierarchy_id, name);
4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186
	}
	rcu_read_unlock();
	read_unlock(&css_set_lock);
	return 0;
}

#define MAX_TASKS_SHOWN_PER_CSS 25
static int cgroup_css_links_read(struct cgroup *cont,
				 struct cftype *cft,
				 struct seq_file *seq)
{
	struct cg_cgroup_link *link;

	read_lock(&css_set_lock);
	list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
		struct css_set *cg = link->cg;
		struct task_struct *task;
		int count = 0;
		seq_printf(seq, "css_set %p\n", cg);
		list_for_each_entry(task, &cg->tasks, cg_list) {
			if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
				seq_puts(seq, "  ...\n");
				break;
			} else {
				seq_printf(seq, "  task %d\n",
					   task_pid_vnr(task));
			}
		}
	}
	read_unlock(&css_set_lock);
	return 0;
}

4187 4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211
static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
{
	return test_bit(CGRP_RELEASABLE, &cgrp->flags);
}

static struct cftype debug_files[] =  {
	{
		.name = "cgroup_refcount",
		.read_u64 = cgroup_refcount_read,
	},
	{
		.name = "taskcount",
		.read_u64 = debug_taskcount_read,
	},

	{
		.name = "current_css_set",
		.read_u64 = current_css_set_read,
	},

	{
		.name = "current_css_set_refcount",
		.read_u64 = current_css_set_refcount_read,
	},

4212 4213 4214 4215 4216 4217 4218 4219 4220 4221
	{
		.name = "current_css_set_cg_links",
		.read_seq_string = current_css_set_cg_links_read,
	},

	{
		.name = "cgroup_css_links",
		.read_seq_string = cgroup_css_links_read,
	},

4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240 4241
	{
		.name = "releasable",
		.read_u64 = releasable_read,
	},
};

static int debug_populate(struct cgroup_subsys *ss, struct cgroup *cont)
{
	return cgroup_add_files(cont, ss, debug_files,
				ARRAY_SIZE(debug_files));
}

struct cgroup_subsys debug_subsys = {
	.name = "debug",
	.create = debug_create,
	.destroy = debug_destroy,
	.populate = debug_populate,
	.subsys_id = debug_subsys_id,
};
#endif /* CONFIG_CGROUP_DEBUG */