cgroup.c 139.2 KB
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/*
 *  Generic process-grouping system.
 *
 *  Based originally on the cpuset system, extracted by Paul Menage
 *  Copyright (C) 2006 Google, Inc
 *
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 *  Notifications support
 *  Copyright (C) 2009 Nokia Corporation
 *  Author: Kirill A. Shutemov
 *
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 *  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/cred.h>
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#include <linux/ctype.h>
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#include <linux/errno.h>
#include <linux/fs.h>
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#include <linux/init_task.h>
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#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/module.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/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 <linux/eventfd.h>
#include <linux/poll.h>
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#include <linux/flex_array.h> /* used in cgroup_attach_proc */
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#include <linux/atomic.h>
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/*
 * cgroup_mutex is the master lock.  Any modification to cgroup or its
 * hierarchy must be performed while holding it.
 *
 * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
 * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
 * release_agent_path and so on.  Modifying requires both cgroup_mutex and
 * cgroup_root_mutex.  Readers can acquire either of the two.  This is to
 * break the following locking order cycle.
 *
 *  A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
 *  B. namespace_sem -> cgroup_mutex
 *
 * B happens only through cgroup_show_options() and using cgroup_root_mutex
 * breaks it.
 */
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static DEFINE_MUTEX(cgroup_mutex);
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static DEFINE_MUTEX(cgroup_root_mutex);
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/*
 * Generate an array of cgroup subsystem pointers. At boot time, this is
 * populated up to CGROUP_BUILTIN_SUBSYS_COUNT, and modular subsystems are
 * registered after that. The mutable section of this array is protected by
 * cgroup_mutex.
 */
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#define SUBSYS(_x) &_x ## _subsys,
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static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
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#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.
	 */
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	struct cgroup_subsys_state __rcu *css;
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	/*
	 * 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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/*
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 * cgroup_event represents events which userspace want to receive.
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 */
struct cgroup_event {
	/*
	 * Cgroup which the event belongs to.
	 */
	struct cgroup *cgrp;
	/*
	 * Control file which the event associated.
	 */
	struct cftype *cft;
	/*
	 * eventfd to signal userspace about the event.
	 */
	struct eventfd_ctx *eventfd;
	/*
	 * Each of these stored in a list by the cgroup.
	 */
	struct list_head list;
	/*
	 * All fields below needed to unregister event when
	 * userspace closes eventfd.
	 */
	poll_table pt;
	wait_queue_head_t *wqh;
	wait_queue_t wait;
	struct work_struct remove;
};
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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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static int clone_children(const struct cgroup *cgrp)
{
	return test_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
}

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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);
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static DEFINE_RAW_SPINLOCK(release_list_lock);
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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_init_idr(struct cgroup_subsys *ss,
			   struct cgroup_subsys_state *css);
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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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/* 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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	kfree_rcu(cg, rcu_head);
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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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	/*
	 * Build the set of subsystem state objects that we want to see in the
	 * new css_set. while subsystems can change globally, the entries here
	 * won't change, so no need for locking.
	 */
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	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++;
657 658 659 660 661

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

662 663 664
	write_unlock(&css_set_lock);

	return res;
665 666
}

667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701
/*
 * 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;
}

702 703 704 705 706 707 708 709 710 711
/*
 * 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
712
 * cgroup_attach_task() can increment it again.  Because a count of zero
713 714 715 716 717 718 719 720 721 722 723 724 725
 * 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
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 * to the release agent with the name of the cgroup (path relative to
 * the root of cgroup file system) as the argument.
728 729 730 731 732 733 734 735 736 737 738
 *
 * 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
739
 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
L
Li Zefan 已提交
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 * another.  It does so using cgroup_mutex, however there are
741 742 743
 * 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
744
 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
745 746 747 748
 * 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
749
 * update of a tasks cgroup pointer by cgroup_attach_task()
750 751 752 753 754 755 756 757 758 759
 */

/**
 * cgroup_lock - lock out any changes to cgroup structures
 *
 */
void cgroup_lock(void)
{
	mutex_lock(&cgroup_mutex);
}
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EXPORT_SYMBOL_GPL(cgroup_lock);
761 762 763 764 765 766 767 768 769 770

/**
 * 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);
}
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EXPORT_SYMBOL_GPL(cgroup_unlock);
772 773 774 775 776 777 778 779 780

/*
 * 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);
781
static struct dentry *cgroup_lookup(struct inode *, struct dentry *, struct nameidata *);
782
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
783
static int cgroup_populate_dir(struct cgroup *cgrp);
784
static const struct inode_operations cgroup_dir_inode_operations;
785
static const struct file_operations proc_cgroupstats_operations;
786 787

static struct backing_dev_info cgroup_backing_dev_info = {
788
	.name		= "cgroup",
789
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
790
};
791

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static int alloc_css_id(struct cgroup_subsys *ss,
			struct cgroup *parent, struct cgroup *child);

795 796 797 798 799
static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
{
	struct inode *inode = new_inode(sb);

	if (inode) {
800
		inode->i_ino = get_next_ino();
801
		inode->i_mode = mode;
802 803
		inode->i_uid = current_fsuid();
		inode->i_gid = current_fsgid();
804 805 806 807 808 809
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
	}
	return inode;
}

810 811 812 813
/*
 * Call subsys's pre_destroy handler.
 * This is called before css refcnt check.
 */
814
static int cgroup_call_pre_destroy(struct cgroup *cgrp)
815 816
{
	struct cgroup_subsys *ss;
817 818
	int ret = 0;

819
	for_each_subsys(cgrp->root, ss)
820 821 822
		if (ss->pre_destroy) {
			ret = ss->pre_destroy(ss, cgrp);
			if (ret)
823
				break;
824
		}
825

826
	return ret;
827 828
}

829 830 831 832
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)) {
833
		struct cgroup *cgrp = dentry->d_fsdata;
834
		struct cgroup_subsys *ss;
835
		BUG_ON(!(cgroup_is_removed(cgrp)));
836 837 838 839 840 841 842
		/* 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();
843 844 845 846 847

		mutex_lock(&cgroup_mutex);
		/*
		 * Release the subsystem state objects.
		 */
848 849
		for_each_subsys(cgrp->root, ss)
			ss->destroy(ss, cgrp);
850 851 852 853

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

854 855 856 857
		/*
		 * Drop the active superblock reference that we took when we
		 * created the cgroup
		 */
858 859
		deactivate_super(cgrp->root->sb);

860 861 862 863 864 865
		/*
		 * if we're getting rid of the cgroup, refcount should ensure
		 * that there are no pidlists left.
		 */
		BUG_ON(!list_empty(&cgrp->pidlists));

866
		kfree_rcu(cgrp, rcu_head);
867 868 869 870
	}
	iput(inode);
}

871 872 873 874 875
static int cgroup_delete(const struct dentry *d)
{
	return 1;
}

876 877 878 879 880 881 882 883 884 885 886 887 888 889
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));
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Nick Piggin 已提交
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	spin_lock(&dentry->d_lock);
891 892 893
	node = dentry->d_subdirs.next;
	while (node != &dentry->d_subdirs) {
		struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
N
Nick Piggin 已提交
894 895

		spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
896 897 898 899 900
		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);
901
			dget_dlock(d);
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Nick Piggin 已提交
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			spin_unlock(&d->d_lock);
			spin_unlock(&dentry->d_lock);
904 905 906
			d_delete(d);
			simple_unlink(dentry->d_inode, d);
			dput(d);
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907 908 909
			spin_lock(&dentry->d_lock);
		} else
			spin_unlock(&d->d_lock);
910 911
		node = dentry->d_subdirs.next;
	}
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	spin_unlock(&dentry->d_lock);
913 914 915 916 917 918 919
}

/*
 * NOTE : the dentry must have been dget()'ed
 */
static void cgroup_d_remove_dir(struct dentry *dentry)
{
N
Nick Piggin 已提交
920 921
	struct dentry *parent;

922 923
	cgroup_clear_directory(dentry);

N
Nick Piggin 已提交
924 925
	parent = dentry->d_parent;
	spin_lock(&parent->d_lock);
926
	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
927
	list_del_init(&dentry->d_u.d_child);
N
Nick Piggin 已提交
928 929
	spin_unlock(&dentry->d_lock);
	spin_unlock(&parent->d_lock);
930 931 932
	remove_dir(dentry);
}

933 934 935 936 937 938
/*
 * 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.
 *
939
 * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
940 941 942
 */
DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);

943
static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
944
{
945
	if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
946 947 948
		wake_up_all(&cgroup_rmdir_waitq);
}

949 950 951 952 953 954 955 956 957 958 959
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);
}

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/*
B
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961 962 963
 * Call with cgroup_mutex held. Drops reference counts on modules, including
 * any duplicate ones that parse_cgroupfs_options took. If this function
 * returns an error, no reference counts are touched.
B
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 */
965 966 967 968
static int rebind_subsystems(struct cgroupfs_root *root,
			      unsigned long final_bits)
{
	unsigned long added_bits, removed_bits;
969
	struct cgroup *cgrp = &root->top_cgroup;
970 971
	int i;

B
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	BUG_ON(!mutex_is_locked(&cgroup_mutex));
T
Tejun Heo 已提交
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	BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
B
Ben Blum 已提交
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975 976 977 978
	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
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		unsigned long bit = 1UL << i;
980 981 982
		struct cgroup_subsys *ss = subsys[i];
		if (!(bit & added_bits))
			continue;
B
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983 984 985 986 987 988
		/*
		 * Nobody should tell us to do a subsys that doesn't exist:
		 * parse_cgroupfs_options should catch that case and refcounts
		 * ensure that subsystems won't disappear once selected.
		 */
		BUG_ON(ss == NULL);
989 990 991 992 993 994 995 996 997 998
		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 */
999
	if (root->number_of_cgroups > 1)
1000 1001 1002 1003 1004 1005 1006 1007
		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 */
B
Ben Blum 已提交
1008
			BUG_ON(ss == NULL);
1009
			BUG_ON(cgrp->subsys[i]);
1010 1011
			BUG_ON(!dummytop->subsys[i]);
			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1012
			mutex_lock(&ss->hierarchy_mutex);
1013 1014
			cgrp->subsys[i] = dummytop->subsys[i];
			cgrp->subsys[i]->cgroup = cgrp;
1015
			list_move(&ss->sibling, &root->subsys_list);
1016
			ss->root = root;
1017
			if (ss->bind)
1018
				ss->bind(ss, cgrp);
1019
			mutex_unlock(&ss->hierarchy_mutex);
B
Ben Blum 已提交
1020
			/* refcount was already taken, and we're keeping it */
1021 1022
		} else if (bit & removed_bits) {
			/* We're removing this subsystem */
B
Ben Blum 已提交
1023
			BUG_ON(ss == NULL);
1024 1025
			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1026
			mutex_lock(&ss->hierarchy_mutex);
1027 1028 1029
			if (ss->bind)
				ss->bind(ss, dummytop);
			dummytop->subsys[i]->cgroup = dummytop;
1030
			cgrp->subsys[i] = NULL;
1031
			subsys[i]->root = &rootnode;
1032
			list_move(&ss->sibling, &rootnode.subsys_list);
1033
			mutex_unlock(&ss->hierarchy_mutex);
B
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1034 1035
			/* subsystem is now free - drop reference on module */
			module_put(ss->module);
1036 1037
		} else if (bit & final_bits) {
			/* Subsystem state should already exist */
B
Ben Blum 已提交
1038
			BUG_ON(ss == NULL);
1039
			BUG_ON(!cgrp->subsys[i]);
B
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1040 1041 1042 1043 1044 1045 1046 1047
			/*
			 * a refcount was taken, but we already had one, so
			 * drop the extra reference.
			 */
			module_put(ss->module);
#ifdef CONFIG_MODULE_UNLOAD
			BUG_ON(ss->module && !module_refcount(ss->module));
#endif
1048 1049
		} else {
			/* Subsystem state shouldn't exist */
1050
			BUG_ON(cgrp->subsys[i]);
1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063
		}
	}
	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;

T
Tejun Heo 已提交
1064
	mutex_lock(&cgroup_root_mutex);
1065 1066 1067 1068
	for_each_subsys(root, ss)
		seq_printf(seq, ",%s", ss->name);
	if (test_bit(ROOT_NOPREFIX, &root->flags))
		seq_puts(seq, ",noprefix");
1069 1070
	if (strlen(root->release_agent_path))
		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1071 1072
	if (clone_children(&root->top_cgroup))
		seq_puts(seq, ",clone_children");
1073 1074
	if (strlen(root->name))
		seq_printf(seq, ",name=%s", root->name);
T
Tejun Heo 已提交
1075
	mutex_unlock(&cgroup_root_mutex);
1076 1077 1078 1079 1080 1081
	return 0;
}

struct cgroup_sb_opts {
	unsigned long subsys_bits;
	unsigned long flags;
1082
	char *release_agent;
1083
	bool clone_children;
1084
	char *name;
1085 1086
	/* User explicitly requested empty subsystem */
	bool none;
1087 1088

	struct cgroupfs_root *new_root;
1089

1090 1091
};

B
Ben Blum 已提交
1092 1093
/*
 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
B
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1094 1095 1096
 * with cgroup_mutex held to protect the subsys[] array. This function takes
 * refcounts on subsystems to be used, unless it returns error, in which case
 * no refcounts are taken.
B
Ben Blum 已提交
1097
 */
B
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1098
static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1099
{
1100 1101
	char *token, *o = data;
	bool all_ss = false, one_ss = false;
1102
	unsigned long mask = (unsigned long)-1;
B
Ben Blum 已提交
1103 1104
	int i;
	bool module_pin_failed = false;
1105

B
Ben Blum 已提交
1106 1107
	BUG_ON(!mutex_is_locked(&cgroup_mutex));

1108 1109 1110
#ifdef CONFIG_CPUSETS
	mask = ~(1UL << cpuset_subsys_id);
#endif
1111

1112
	memset(opts, 0, sizeof(*opts));
1113 1114 1115 1116

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
1117
		if (!strcmp(token, "none")) {
1118 1119
			/* Explicitly have no subsystems */
			opts->none = true;
1120 1121 1122 1123 1124 1125 1126 1127 1128 1129
			continue;
		}
		if (!strcmp(token, "all")) {
			/* Mutually exclusive option 'all' + subsystem name */
			if (one_ss)
				return -EINVAL;
			all_ss = true;
			continue;
		}
		if (!strcmp(token, "noprefix")) {
1130
			set_bit(ROOT_NOPREFIX, &opts->flags);
1131 1132 1133
			continue;
		}
		if (!strcmp(token, "clone_children")) {
1134
			opts->clone_children = true;
1135 1136 1137
			continue;
		}
		if (!strncmp(token, "release_agent=", 14)) {
1138 1139 1140
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1141
			opts->release_agent =
1142
				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1143 1144
			if (!opts->release_agent)
				return -ENOMEM;
1145 1146 1147
			continue;
		}
		if (!strncmp(token, "name=", 5)) {
1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164
			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,
1165
					      MAX_CGROUP_ROOT_NAMELEN - 1,
1166 1167 1168
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206

			continue;
		}

		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss == NULL)
				continue;
			if (strcmp(token, ss->name))
				continue;
			if (ss->disabled)
				continue;

			/* Mutually exclusive option 'all' + subsystem name */
			if (all_ss)
				return -EINVAL;
			set_bit(i, &opts->subsys_bits);
			one_ss = true;

			break;
		}
		if (i == CGROUP_SUBSYS_COUNT)
			return -ENOENT;
	}

	/*
	 * If the 'all' option was specified select all the subsystems,
	 * otherwise 'all, 'none' and a subsystem name options were not
	 * specified, let's default to 'all'
	 */
	if (all_ss || (!all_ss && !one_ss && !opts->none)) {
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss == NULL)
				continue;
			if (ss->disabled)
				continue;
			set_bit(i, &opts->subsys_bits);
1207 1208 1209
		}
	}

1210 1211
	/* Consistency checks */

1212 1213 1214 1215 1216 1217 1218 1219 1220
	/*
	 * 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;

1221 1222 1223 1224 1225 1226 1227 1228 1229

	/* 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).
	 */
1230
	if (!opts->subsys_bits && !opts->name)
1231 1232
		return -EINVAL;

B
Ben Blum 已提交
1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265
	/*
	 * Grab references on all the modules we'll need, so the subsystems
	 * don't dance around before rebind_subsystems attaches them. This may
	 * take duplicate reference counts on a subsystem that's already used,
	 * but rebind_subsystems handles this case.
	 */
	for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
		unsigned long bit = 1UL << i;

		if (!(bit & opts->subsys_bits))
			continue;
		if (!try_module_get(subsys[i]->module)) {
			module_pin_failed = true;
			break;
		}
	}
	if (module_pin_failed) {
		/*
		 * oops, one of the modules was going away. this means that we
		 * raced with a module_delete call, and to the user this is
		 * essentially a "subsystem doesn't exist" case.
		 */
		for (i--; i >= CGROUP_BUILTIN_SUBSYS_COUNT; i--) {
			/* drop refcounts only on the ones we took */
			unsigned long bit = 1UL << i;

			if (!(bit & opts->subsys_bits))
				continue;
			module_put(subsys[i]->module);
		}
		return -ENOENT;
	}

1266 1267 1268
	return 0;
}

B
Ben Blum 已提交
1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280
static void drop_parsed_module_refcounts(unsigned long subsys_bits)
{
	int i;
	for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
		unsigned long bit = 1UL << i;

		if (!(bit & subsys_bits))
			continue;
		module_put(subsys[i]->module);
	}
}

1281 1282 1283 1284
static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
	int ret = 0;
	struct cgroupfs_root *root = sb->s_fs_info;
1285
	struct cgroup *cgrp = &root->top_cgroup;
1286 1287
	struct cgroup_sb_opts opts;

1288
	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1289
	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1290
	mutex_lock(&cgroup_root_mutex);
1291 1292 1293 1294 1295 1296

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

B
Ben Blum 已提交
1297 1298 1299
	/* Don't allow flags or name to change at remount */
	if (opts.flags != root->flags ||
	    (opts.name && strcmp(opts.name, root->name))) {
1300
		ret = -EINVAL;
B
Ben Blum 已提交
1301
		drop_parsed_module_refcounts(opts.subsys_bits);
1302 1303 1304
		goto out_unlock;
	}

1305
	ret = rebind_subsystems(root, opts.subsys_bits);
B
Ben Blum 已提交
1306 1307
	if (ret) {
		drop_parsed_module_refcounts(opts.subsys_bits);
1308
		goto out_unlock;
B
Ben Blum 已提交
1309
	}
1310 1311

	/* (re)populate subsystem files */
1312
	cgroup_populate_dir(cgrp);
1313

1314 1315
	if (opts.release_agent)
		strcpy(root->release_agent_path, opts.release_agent);
1316
 out_unlock:
1317
	kfree(opts.release_agent);
1318
	kfree(opts.name);
T
Tejun Heo 已提交
1319
	mutex_unlock(&cgroup_root_mutex);
1320
	mutex_unlock(&cgroup_mutex);
1321
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1322 1323 1324
	return ret;
}

1325
static const struct super_operations cgroup_ops = {
1326 1327 1328 1329 1330 1331
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.show_options = cgroup_show_options,
	.remount_fs = cgroup_remount,
};

1332 1333 1334 1335 1336 1337
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);
1338 1339
	INIT_LIST_HEAD(&cgrp->pidlists);
	mutex_init(&cgrp->pidlist_mutex);
1340 1341
	INIT_LIST_HEAD(&cgrp->event_list);
	spin_lock_init(&cgrp->event_list_lock);
1342
}
1343

1344 1345
static void init_cgroup_root(struct cgroupfs_root *root)
{
1346
	struct cgroup *cgrp = &root->top_cgroup;
1347 1348 1349
	INIT_LIST_HEAD(&root->subsys_list);
	INIT_LIST_HEAD(&root->root_list);
	root->number_of_cgroups = 1;
1350 1351
	cgrp->root = root;
	cgrp->top_cgroup = cgrp;
1352
	init_cgroup_housekeeping(cgrp);
1353 1354
}

1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379
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;
}

1380 1381
static int cgroup_test_super(struct super_block *sb, void *data)
{
1382
	struct cgroup_sb_opts *opts = data;
1383 1384
	struct cgroupfs_root *root = sb->s_fs_info;

1385 1386 1387
	/* If we asked for a name then it must match */
	if (opts->name && strcmp(opts->name, root->name))
		return 0;
1388

1389 1390 1391 1392 1393 1394
	/*
	 * 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))
1395 1396 1397 1398 1399
		return 0;

	return 1;
}

1400 1401 1402 1403
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
	struct cgroupfs_root *root;

1404
	if (!opts->subsys_bits && !opts->none)
1405 1406 1407 1408 1409 1410
		return NULL;

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

1411 1412 1413 1414
	if (!init_root_id(root)) {
		kfree(root);
		return ERR_PTR(-ENOMEM);
	}
1415
	init_cgroup_root(root);
1416

1417 1418 1419 1420 1421 1422
	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);
1423 1424
	if (opts->clone_children)
		set_bit(CGRP_CLONE_CHILDREN, &root->top_cgroup.flags);
1425 1426 1427
	return root;
}

1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439
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);
}

1440 1441 1442
static int cgroup_set_super(struct super_block *sb, void *data)
{
	int ret;
1443 1444 1445 1446 1447 1448
	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;

1449
	BUG_ON(!opts->subsys_bits && !opts->none);
1450 1451 1452 1453 1454

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

1455 1456
	sb->s_fs_info = opts->new_root;
	opts->new_root->sb = sb;
1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467

	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)
{
A
Al Viro 已提交
1468 1469
	static const struct dentry_operations cgroup_dops = {
		.d_iput = cgroup_diput,
1470
		.d_delete = cgroup_delete,
A
Al Viro 已提交
1471 1472
	};

1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489
	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;
A
Al Viro 已提交
1490 1491
	/* for everything else we want ->d_op set */
	sb->s_d_op = &cgroup_dops;
1492 1493 1494
	return 0;
}

A
Al Viro 已提交
1495
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1496
			 int flags, const char *unused_dev_name,
A
Al Viro 已提交
1497
			 void *data)
1498 1499
{
	struct cgroup_sb_opts opts;
1500
	struct cgroupfs_root *root;
1501 1502
	int ret = 0;
	struct super_block *sb;
1503
	struct cgroupfs_root *new_root;
T
Tejun Heo 已提交
1504
	struct inode *inode;
1505 1506

	/* First find the desired set of subsystems */
B
Ben Blum 已提交
1507
	mutex_lock(&cgroup_mutex);
1508
	ret = parse_cgroupfs_options(data, &opts);
B
Ben Blum 已提交
1509
	mutex_unlock(&cgroup_mutex);
1510 1511
	if (ret)
		goto out_err;
1512

1513 1514 1515 1516 1517 1518 1519
	/*
	 * 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);
B
Ben Blum 已提交
1520
		goto drop_modules;
1521
	}
1522
	opts.new_root = new_root;
1523

1524 1525
	/* Locate an existing or new sb for this hierarchy */
	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, &opts);
1526
	if (IS_ERR(sb)) {
1527
		ret = PTR_ERR(sb);
1528
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1529
		goto drop_modules;
1530 1531
	}

1532 1533 1534 1535 1536
	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;
1537
		struct cgroup *root_cgrp = &root->top_cgroup;
1538
		struct cgroupfs_root *existing_root;
1539
		const struct cred *cred;
1540
		int i;
1541 1542 1543 1544 1545 1546

		BUG_ON(sb->s_root != NULL);

		ret = cgroup_get_rootdir(sb);
		if (ret)
			goto drop_new_super;
1547
		inode = sb->s_root->d_inode;
1548

1549
		mutex_lock(&inode->i_mutex);
1550
		mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1551
		mutex_lock(&cgroup_root_mutex);
1552

T
Tejun Heo 已提交
1553 1554 1555 1556 1557 1558
		/* Check for name clashes with existing mounts */
		ret = -EBUSY;
		if (strlen(root->name))
			for_each_active_root(existing_root)
				if (!strcmp(existing_root->name, root->name))
					goto unlock_drop;
1559

1560 1561 1562 1563 1564 1565 1566 1567
		/*
		 * 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);
T
Tejun Heo 已提交
1568 1569
		if (ret)
			goto unlock_drop;
1570

1571 1572
		ret = rebind_subsystems(root, root->subsys_bits);
		if (ret == -EBUSY) {
1573
			free_cg_links(&tmp_cg_links);
T
Tejun Heo 已提交
1574
			goto unlock_drop;
1575
		}
B
Ben Blum 已提交
1576 1577 1578 1579 1580
		/*
		 * There must be no failure case after here, since rebinding
		 * takes care of subsystems' refcounts, which are explicitly
		 * dropped in the failure exit path.
		 */
1581 1582 1583 1584 1585

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

		list_add(&root->root_list, &roots);
1586
		root_count++;
1587

1588
		sb->s_root->d_fsdata = root_cgrp;
1589 1590
		root->top_cgroup.dentry = sb->s_root;

1591 1592 1593
		/* Link the top cgroup in this hierarchy into all
		 * the css_set objects */
		write_lock(&css_set_lock);
1594 1595 1596
		for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
			struct hlist_head *hhead = &css_set_table[i];
			struct hlist_node *node;
1597
			struct css_set *cg;
1598

1599 1600
			hlist_for_each_entry(cg, node, hhead, hlist)
				link_css_set(&tmp_cg_links, cg, root_cgrp);
1601
		}
1602 1603 1604 1605
		write_unlock(&css_set_lock);

		free_cg_links(&tmp_cg_links);

1606 1607
		BUG_ON(!list_empty(&root_cgrp->sibling));
		BUG_ON(!list_empty(&root_cgrp->children));
1608 1609
		BUG_ON(root->number_of_cgroups != 1);

1610
		cred = override_creds(&init_cred);
1611
		cgroup_populate_dir(root_cgrp);
1612
		revert_creds(cred);
T
Tejun Heo 已提交
1613
		mutex_unlock(&cgroup_root_mutex);
1614
		mutex_unlock(&cgroup_mutex);
1615
		mutex_unlock(&inode->i_mutex);
1616 1617 1618 1619 1620
	} else {
		/*
		 * We re-used an existing hierarchy - the new root (if
		 * any) is not needed
		 */
1621
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1622 1623
		/* no subsys rebinding, so refcounts don't change */
		drop_parsed_module_refcounts(opts.subsys_bits);
1624 1625
	}

1626 1627
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1628
	return dget(sb->s_root);
1629

T
Tejun Heo 已提交
1630 1631 1632 1633
 unlock_drop:
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&inode->i_mutex);
1634
 drop_new_super:
1635
	deactivate_locked_super(sb);
B
Ben Blum 已提交
1636 1637
 drop_modules:
	drop_parsed_module_refcounts(opts.subsys_bits);
1638 1639 1640
 out_err:
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1641
	return ERR_PTR(ret);
1642 1643 1644 1645
}

static void cgroup_kill_sb(struct super_block *sb) {
	struct cgroupfs_root *root = sb->s_fs_info;
1646
	struct cgroup *cgrp = &root->top_cgroup;
1647
	int ret;
K
KOSAKI Motohiro 已提交
1648 1649
	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;
1650 1651 1652 1653

	BUG_ON(!root);

	BUG_ON(root->number_of_cgroups != 1);
1654 1655
	BUG_ON(!list_empty(&cgrp->children));
	BUG_ON(!list_empty(&cgrp->sibling));
1656 1657

	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1658
	mutex_lock(&cgroup_root_mutex);
1659 1660 1661 1662 1663 1664

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

1665 1666 1667 1668 1669
	/*
	 * Release all the links from css_sets to this hierarchy's
	 * root cgroup
	 */
	write_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
1670 1671 1672

	list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
				 cgrp_link_list) {
1673
		list_del(&link->cg_link_list);
1674
		list_del(&link->cgrp_link_list);
1675 1676 1677 1678
		kfree(link);
	}
	write_unlock(&css_set_lock);

1679 1680 1681 1682
	if (!list_empty(&root->root_list)) {
		list_del(&root->root_list);
		root_count--;
	}
1683

T
Tejun Heo 已提交
1684
	mutex_unlock(&cgroup_root_mutex);
1685 1686 1687
	mutex_unlock(&cgroup_mutex);

	kill_litter_super(sb);
1688
	cgroup_drop_root(root);
1689 1690 1691 1692
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
A
Al Viro 已提交
1693
	.mount = cgroup_mount,
1694 1695 1696
	.kill_sb = cgroup_kill_sb,
};

1697 1698
static struct kobject *cgroup_kobj;

1699
static inline struct cgroup *__d_cgrp(struct dentry *dentry)
1700 1701 1702 1703 1704 1705 1706 1707 1708
{
	return dentry->d_fsdata;
}

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

L
Li Zefan 已提交
1709 1710 1711 1712 1713 1714
/**
 * 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
 *
1715 1716 1717
 * 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.
1718
 */
1719
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1720 1721
{
	char *start;
1722 1723
	struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
						      cgroup_lock_is_held());
1724

1725
	if (!dentry || cgrp == dummytop) {
1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737
		/*
		 * Inactive subsystems have no dentry for their root
		 * cgroup
		 */
		strcpy(buf, "/");
		return 0;
	}

	start = buf + buflen;

	*--start = '\0';
	for (;;) {
1738
		int len = dentry->d_name.len;
1739

1740 1741
		if ((start -= len) < buf)
			return -ENAMETOOLONG;
1742
		memcpy(start, dentry->d_name.name, len);
1743 1744
		cgrp = cgrp->parent;
		if (!cgrp)
1745
			break;
1746 1747 1748

		dentry = rcu_dereference_check(cgrp->dentry,
					       cgroup_lock_is_held());
1749
		if (!cgrp->parent)
1750 1751 1752 1753 1754 1755 1756 1757
			continue;
		if (--start < buf)
			return -ENAMETOOLONG;
		*start = '/';
	}
	memmove(buf, start, buf + buflen - start);
	return 0;
}
B
Ben Blum 已提交
1758
EXPORT_SYMBOL_GPL(cgroup_path);
1759

1760 1761 1762
/*
 * Control Group taskset
 */
1763 1764 1765 1766 1767
struct task_and_cgroup {
	struct task_struct	*task;
	struct cgroup		*cgrp;
};

1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838
struct cgroup_taskset {
	struct task_and_cgroup	single;
	struct flex_array	*tc_array;
	int			tc_array_len;
	int			idx;
	struct cgroup		*cur_cgrp;
};

/**
 * cgroup_taskset_first - reset taskset and return the first task
 * @tset: taskset of interest
 *
 * @tset iteration is initialized and the first task is returned.
 */
struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
{
	if (tset->tc_array) {
		tset->idx = 0;
		return cgroup_taskset_next(tset);
	} else {
		tset->cur_cgrp = tset->single.cgrp;
		return tset->single.task;
	}
}
EXPORT_SYMBOL_GPL(cgroup_taskset_first);

/**
 * cgroup_taskset_next - iterate to the next task in taskset
 * @tset: taskset of interest
 *
 * Return the next task in @tset.  Iteration must have been initialized
 * with cgroup_taskset_first().
 */
struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
{
	struct task_and_cgroup *tc;

	if (!tset->tc_array || tset->idx >= tset->tc_array_len)
		return NULL;

	tc = flex_array_get(tset->tc_array, tset->idx++);
	tset->cur_cgrp = tc->cgrp;
	return tc->task;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_next);

/**
 * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
 * @tset: taskset of interest
 *
 * Return the cgroup for the current (last returned) task of @tset.  This
 * function must be preceded by either cgroup_taskset_first() or
 * cgroup_taskset_next().
 */
struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
{
	return tset->cur_cgrp;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);

/**
 * cgroup_taskset_size - return the number of tasks in taskset
 * @tset: taskset of interest
 */
int cgroup_taskset_size(struct cgroup_taskset *tset)
{
	return tset->tc_array ? tset->tc_array_len : 1;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_size);


B
Ben Blum 已提交
1839 1840 1841 1842 1843
/*
 * cgroup_task_migrate - move a task from one cgroup to another.
 *
 * 'guarantee' is set if the caller promises that a new css_set for the task
 * will already exist. If not set, this function might sleep, and can fail with
1844
 * -ENOMEM. Must be called with cgroup_mutex and threadgroup locked.
B
Ben Blum 已提交
1845 1846 1847 1848 1849 1850 1851 1852
 */
static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
			       struct task_struct *tsk, bool guarantee)
{
	struct css_set *oldcg;
	struct css_set *newcg;

	/*
1853 1854 1855
	 * We are synchronized through threadgroup_lock() against PF_EXITING
	 * setting such that we can't race against cgroup_exit() changing the
	 * css_set to init_css_set and dropping the old one.
B
Ben Blum 已提交
1856
	 */
1857
	WARN_ON_ONCE(tsk->flags & PF_EXITING);
B
Ben Blum 已提交
1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872
	oldcg = tsk->cgroups;

	/* locate or allocate a new css_set for this task. */
	if (guarantee) {
		/* we know the css_set we want already exists. */
		struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
		read_lock(&css_set_lock);
		newcg = find_existing_css_set(oldcg, cgrp, template);
		BUG_ON(!newcg);
		get_css_set(newcg);
		read_unlock(&css_set_lock);
	} else {
		might_sleep();
		/* find_css_set will give us newcg already referenced. */
		newcg = find_css_set(oldcg, cgrp);
1873
		if (!newcg)
B
Ben Blum 已提交
1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897
			return -ENOMEM;
	}

	task_lock(tsk);
	rcu_assign_pointer(tsk->cgroups, newcg);
	task_unlock(tsk);

	/* Update the css_set linked lists if we're using them */
	write_lock(&css_set_lock);
	if (!list_empty(&tsk->cg_list))
		list_move(&tsk->cg_list, &newcg->tasks);
	write_unlock(&css_set_lock);

	/*
	 * We just gained a reference on oldcg by taking it from the task. As
	 * trading it for newcg is protected by cgroup_mutex, we're safe to drop
	 * it here; it will be freed under RCU.
	 */
	put_css_set(oldcg);

	set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
	return 0;
}

L
Li Zefan 已提交
1898 1899 1900 1901
/**
 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
 * @cgrp: the cgroup the task is attaching to
 * @tsk: the task to be attached
1902
 *
1903 1904
 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
 * @tsk during call.
1905
 */
1906
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1907
{
B
Ben Blum 已提交
1908
	int retval;
1909
	struct cgroup_subsys *ss, *failed_ss = NULL;
1910 1911
	struct cgroup *oldcgrp;
	struct cgroupfs_root *root = cgrp->root;
1912
	struct cgroup_taskset tset = { };
1913

1914 1915 1916 1917
	/* @tsk either already exited or can't exit until the end */
	if (tsk->flags & PF_EXITING)
		return -ESRCH;

1918
	/* Nothing to do if the task is already in that cgroup */
1919
	oldcgrp = task_cgroup_from_root(tsk, root);
1920
	if (cgrp == oldcgrp)
1921 1922
		return 0;

1923 1924 1925
	tset.single.task = tsk;
	tset.single.cgrp = oldcgrp;

1926 1927
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
1928
			retval = ss->can_attach(ss, cgrp, &tset);
1929 1930 1931 1932 1933 1934 1935 1936 1937 1938
			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;
			}
1939 1940 1941
		}
	}

B
Ben Blum 已提交
1942 1943
	retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, false);
	if (retval)
1944
		goto out;
1945

1946
	for_each_subsys(root, ss) {
P
Paul Jackson 已提交
1947
		if (ss->attach)
1948
			ss->attach(ss, cgrp, &tset);
1949
	}
B
Ben Blum 已提交
1950

1951
	synchronize_rcu();
1952 1953 1954 1955 1956

	/*
	 * wake up rmdir() waiter. the rmdir should fail since the cgroup
	 * is no longer empty.
	 */
1957
	cgroup_wakeup_rmdir_waiter(cgrp);
1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969
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)
1970
				ss->cancel_attach(ss, cgrp, &tset);
1971 1972 1973
		}
	}
	return retval;
1974 1975
}

1976
/**
M
Michael S. Tsirkin 已提交
1977 1978
 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
 * @from: attach to all cgroups of a given task
1979 1980
 * @tsk: the task to be attached
 */
M
Michael S. Tsirkin 已提交
1981
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
1982 1983 1984 1985 1986 1987
{
	struct cgroupfs_root *root;
	int retval = 0;

	cgroup_lock();
	for_each_active_root(root) {
M
Michael S. Tsirkin 已提交
1988 1989 1990
		struct cgroup *from_cg = task_cgroup_from_root(from, root);

		retval = cgroup_attach_task(from_cg, tsk);
1991 1992 1993 1994 1995 1996 1997
		if (retval)
			break;
	}
	cgroup_unlock();

	return retval;
}
M
Michael S. Tsirkin 已提交
1998
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
1999

2000
/*
B
Ben Blum 已提交
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026
 * cgroup_attach_proc works in two stages, the first of which prefetches all
 * new css_sets needed (to make sure we have enough memory before committing
 * to the move) and stores them in a list of entries of the following type.
 * TODO: possible optimization: use css_set->rcu_head for chaining instead
 */
struct cg_list_entry {
	struct css_set *cg;
	struct list_head links;
};

static bool css_set_check_fetched(struct cgroup *cgrp,
				  struct task_struct *tsk, struct css_set *cg,
				  struct list_head *newcg_list)
{
	struct css_set *newcg;
	struct cg_list_entry *cg_entry;
	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];

	read_lock(&css_set_lock);
	newcg = find_existing_css_set(cg, cgrp, template);
	read_unlock(&css_set_lock);

	/* doesn't exist at all? */
	if (!newcg)
		return false;
	/* see if it's already in the list */
2027 2028
	list_for_each_entry(cg_entry, newcg_list, links)
		if (cg_entry->cg == newcg)
B
Ben Blum 已提交
2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064
			return true;

	/* not found */
	return false;
}

/*
 * Find the new css_set and store it in the list in preparation for moving the
 * given task to the given cgroup. Returns 0 or -ENOMEM.
 */
static int css_set_prefetch(struct cgroup *cgrp, struct css_set *cg,
			    struct list_head *newcg_list)
{
	struct css_set *newcg;
	struct cg_list_entry *cg_entry;

	/* ensure a new css_set will exist for this thread */
	newcg = find_css_set(cg, cgrp);
	if (!newcg)
		return -ENOMEM;
	/* add it to the list */
	cg_entry = kmalloc(sizeof(struct cg_list_entry), GFP_KERNEL);
	if (!cg_entry) {
		put_css_set(newcg);
		return -ENOMEM;
	}
	cg_entry->cg = newcg;
	list_add(&cg_entry->links, newcg_list);
	return 0;
}

/**
 * cgroup_attach_proc - attach all threads in a threadgroup to a cgroup
 * @cgrp: the cgroup to attach to
 * @leader: the threadgroup leader task_struct of the group to be attached
 *
2065 2066
 * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
 * task_lock of each thread in leader's threadgroup individually in turn.
B
Ben Blum 已提交
2067 2068 2069
 */
int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
{
2070
	int retval, i, group_size, nr_migrating_tasks;
B
Ben Blum 已提交
2071 2072 2073 2074 2075 2076
	struct cgroup_subsys *ss, *failed_ss = NULL;
	/* guaranteed to be initialized later, but the compiler needs this */
	struct css_set *oldcg;
	struct cgroupfs_root *root = cgrp->root;
	/* threadgroup list cursor and array */
	struct task_struct *tsk;
2077
	struct task_and_cgroup *tc;
2078
	struct flex_array *group;
2079
	struct cgroup_taskset tset = { };
B
Ben Blum 已提交
2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091
	/*
	 * we need to make sure we have css_sets for all the tasks we're
	 * going to move -before- we actually start moving them, so that in
	 * case we get an ENOMEM we can bail out before making any changes.
	 */
	struct list_head newcg_list;
	struct cg_list_entry *cg_entry, *temp_nobe;

	/*
	 * step 0: in order to do expensive, possibly blocking operations for
	 * every thread, we cannot iterate the thread group list, since it needs
	 * rcu or tasklist locked. instead, build an array of all threads in the
2092 2093
	 * group - group_rwsem prevents new threads from appearing, and if
	 * threads exit, this will just be an over-estimate.
B
Ben Blum 已提交
2094 2095
	 */
	group_size = get_nr_threads(leader);
2096
	/* flex_array supports very large thread-groups better than kmalloc. */
2097
	group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
B
Ben Blum 已提交
2098 2099
	if (!group)
		return -ENOMEM;
2100 2101 2102 2103
	/* pre-allocate to guarantee space while iterating in rcu read-side. */
	retval = flex_array_prealloc(group, 0, group_size - 1, GFP_KERNEL);
	if (retval)
		goto out_free_group_list;
B
Ben Blum 已提交
2104 2105

	/* prevent changes to the threadgroup list while we take a snapshot. */
2106
	read_lock(&tasklist_lock);
B
Ben Blum 已提交
2107 2108 2109 2110 2111 2112 2113 2114
	if (!thread_group_leader(leader)) {
		/*
		 * a race with de_thread from another thread's exec() may strip
		 * us of our leadership, making while_each_thread unsafe to use
		 * on this task. if this happens, there is no choice but to
		 * throw this task away and try again (from cgroup_procs_write);
		 * this is "double-double-toil-and-trouble-check locking".
		 */
2115
		read_unlock(&tasklist_lock);
B
Ben Blum 已提交
2116 2117 2118
		retval = -EAGAIN;
		goto out_free_group_list;
	}
2119

B
Ben Blum 已提交
2120
	tsk = leader;
2121
	i = nr_migrating_tasks = 0;
B
Ben Blum 已提交
2122
	do {
2123 2124
		struct task_and_cgroup ent;

2125 2126 2127 2128
		/* @tsk either already exited or can't exit until the end */
		if (tsk->flags & PF_EXITING)
			continue;

B
Ben Blum 已提交
2129 2130
		/* as per above, nr_threads may decrease, but not increase. */
		BUG_ON(i >= group_size);
2131 2132 2133 2134
		/*
		 * saying GFP_ATOMIC has no effect here because we did prealloc
		 * earlier, but it's good form to communicate our expectations.
		 */
2135 2136 2137
		ent.task = tsk;
		ent.cgrp = task_cgroup_from_root(tsk, root);
		retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2138
		BUG_ON(retval != 0);
B
Ben Blum 已提交
2139
		i++;
2140 2141
		if (ent.cgrp != cgrp)
			nr_migrating_tasks++;
B
Ben Blum 已提交
2142 2143 2144
	} while_each_thread(leader, tsk);
	/* remember the number of threads in the array for later. */
	group_size = i;
2145 2146
	tset.tc_array = group;
	tset.tc_array_len = group_size;
2147
	read_unlock(&tasklist_lock);
B
Ben Blum 已提交
2148

2149 2150 2151
	/* methods shouldn't be called if no task is actually migrating */
	retval = 0;
	if (!nr_migrating_tasks)
2152
		goto out_free_group_list;
2153

B
Ben Blum 已提交
2154 2155 2156 2157 2158
	/*
	 * step 1: check that we can legitimately attach to the cgroup.
	 */
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
2159
			retval = ss->can_attach(ss, cgrp, &tset);
B
Ben Blum 已提交
2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172
			if (retval) {
				failed_ss = ss;
				goto out_cancel_attach;
			}
		}
	}

	/*
	 * step 2: make sure css_sets exist for all threads to be migrated.
	 * we use find_css_set, which allocates a new one if necessary.
	 */
	INIT_LIST_HEAD(&newcg_list);
	for (i = 0; i < group_size; i++) {
2173
		tc = flex_array_get(group, i);
B
Ben Blum 已提交
2174
		/* nothing to do if this task is already in the cgroup */
2175
		if (tc->cgrp == cgrp)
B
Ben Blum 已提交
2176
			continue;
2177 2178 2179 2180 2181
		/*
		 * get old css_set pointer. threadgroup is locked so this is
		 * safe against concurrent cgroup_exit() changing this to
		 * init_css_set.
		 */
2182
		oldcg = tc->task->cgroups;
2183 2184 2185 2186

		/* if we don't already have it in the list get a new one */
		if (!css_set_check_fetched(cgrp, tc->task, oldcg, &newcg_list))
			if (retval = css_set_prefetch(cgrp, oldcg, &newcg_list))
B
Ben Blum 已提交
2187 2188 2189 2190
				goto out_list_teardown;
	}

	/*
2191 2192 2193
	 * step 3: now that we're guaranteed success wrt the css_sets,
	 * proceed to move all tasks to the new cgroup.  There are no
	 * failure cases after here, so this is the commit point.
B
Ben Blum 已提交
2194 2195
	 */
	for (i = 0; i < group_size; i++) {
2196
		tc = flex_array_get(group, i);
B
Ben Blum 已提交
2197
		/* leave current thread as it is if it's already there */
2198
		if (tc->cgrp == cgrp)
B
Ben Blum 已提交
2199
			continue;
2200
		retval = cgroup_task_migrate(cgrp, tc->cgrp, tc->task, true);
2201
		BUG_ON(retval);
B
Ben Blum 已提交
2202 2203 2204 2205
	}
	/* nothing is sensitive to fork() after this point. */

	/*
2206
	 * step 4: do subsystem attach callbacks.
B
Ben Blum 已提交
2207 2208
	 */
	for_each_subsys(root, ss) {
2209 2210
		if (ss->attach)
			ss->attach(ss, cgrp, &tset);
B
Ben Blum 已提交
2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229
	}

	/*
	 * step 5: success! and cleanup
	 */
	synchronize_rcu();
	cgroup_wakeup_rmdir_waiter(cgrp);
	retval = 0;
out_list_teardown:
	/* clean up the list of prefetched css_sets. */
	list_for_each_entry_safe(cg_entry, temp_nobe, &newcg_list, links) {
		list_del(&cg_entry->links);
		put_css_set(cg_entry->cg);
		kfree(cg_entry);
	}
out_cancel_attach:
	/* same deal as in cgroup_attach_task */
	if (retval) {
		for_each_subsys(root, ss) {
2230
			if (ss == failed_ss)
B
Ben Blum 已提交
2231 2232
				break;
			if (ss->cancel_attach)
2233
				ss->cancel_attach(ss, cgrp, &tset);
B
Ben Blum 已提交
2234 2235 2236
		}
	}
out_free_group_list:
2237
	flex_array_free(group);
B
Ben Blum 已提交
2238 2239 2240 2241 2242
	return retval;
}

/*
 * Find the task_struct of the task to attach by vpid and pass it along to the
2243 2244
 * function to attach either it or all tasks in its threadgroup. Will lock
 * cgroup_mutex and threadgroup; may take task_lock of task.
2245
 */
B
Ben Blum 已提交
2246
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2247 2248
{
	struct task_struct *tsk;
2249
	const struct cred *cred = current_cred(), *tcred;
2250 2251
	int ret;

B
Ben Blum 已提交
2252 2253 2254
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;

2255 2256
	if (pid) {
		rcu_read_lock();
2257
		tsk = find_task_by_vpid(pid);
B
Ben Blum 已提交
2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270
		if (!tsk) {
			rcu_read_unlock();
			cgroup_unlock();
			return -ESRCH;
		}
		if (threadgroup) {
			/*
			 * RCU protects this access, since tsk was found in the
			 * tid map. a race with de_thread may cause group_leader
			 * to stop being the leader, but cgroup_attach_proc will
			 * detect it later.
			 */
			tsk = tsk->group_leader;
2271
		}
B
Ben Blum 已提交
2272 2273 2274 2275
		/*
		 * even if we're attaching all tasks in the thread group, we
		 * only need to check permissions on one of them.
		 */
2276 2277 2278 2279 2280
		tcred = __task_cred(tsk);
		if (cred->euid &&
		    cred->euid != tcred->uid &&
		    cred->euid != tcred->suid) {
			rcu_read_unlock();
B
Ben Blum 已提交
2281
			cgroup_unlock();
2282 2283
			return -EACCES;
		}
2284 2285
		get_task_struct(tsk);
		rcu_read_unlock();
2286
	} else {
B
Ben Blum 已提交
2287 2288 2289 2290
		if (threadgroup)
			tsk = current->group_leader;
		else
			tsk = current;
2291 2292 2293
		get_task_struct(tsk);
	}

2294 2295 2296
	threadgroup_lock(tsk);

	if (threadgroup)
B
Ben Blum 已提交
2297
		ret = cgroup_attach_proc(cgrp, tsk);
2298
	else
B
Ben Blum 已提交
2299
		ret = cgroup_attach_task(cgrp, tsk);
2300 2301 2302

	threadgroup_unlock(tsk);

2303
	put_task_struct(tsk);
B
Ben Blum 已提交
2304
	cgroup_unlock();
2305 2306 2307
	return ret;
}

2308
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
B
Ben Blum 已提交
2309 2310 2311 2312 2313
{
	return attach_task_by_pid(cgrp, pid, false);
}

static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2314 2315
{
	int ret;
B
Ben Blum 已提交
2316 2317 2318 2319 2320 2321 2322 2323
	do {
		/*
		 * attach_proc fails with -EAGAIN if threadgroup leadership
		 * changes in the middle of the operation, in which case we need
		 * to find the task_struct for the new leader and start over.
		 */
		ret = attach_task_by_pid(cgrp, tgid, true);
	} while (ret == -EAGAIN);
2324 2325 2326
	return ret;
}

2327 2328 2329 2330
/**
 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
 * @cgrp: the cgroup to be checked for liveness
 *
2331 2332
 * On success, returns true; the lock should be later released with
 * cgroup_unlock(). On failure returns false with no lock held.
2333
 */
2334
bool cgroup_lock_live_group(struct cgroup *cgrp)
2335 2336 2337 2338 2339 2340 2341 2342
{
	mutex_lock(&cgroup_mutex);
	if (cgroup_is_removed(cgrp)) {
		mutex_unlock(&cgroup_mutex);
		return false;
	}
	return true;
}
B
Ben Blum 已提交
2343
EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2344 2345 2346 2347 2348

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);
2349 2350
	if (strlen(buffer) >= PATH_MAX)
		return -EINVAL;
2351 2352
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
T
Tejun Heo 已提交
2353
	mutex_lock(&cgroup_root_mutex);
2354
	strcpy(cgrp->root->release_agent_path, buffer);
T
Tejun Heo 已提交
2355
	mutex_unlock(&cgroup_root_mutex);
2356
	cgroup_unlock();
2357 2358 2359 2360 2361 2362 2363 2364 2365 2366
	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');
2367
	cgroup_unlock();
2368 2369 2370
	return 0;
}

2371 2372 2373
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64

2374
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2375 2376 2377
				struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *unused_ppos)
2378
{
2379
	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390
	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 */
2391
	if (cft->write_u64) {
K
KOSAKI Motohiro 已提交
2392
		u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2393 2394 2395 2396
		if (*end)
			return -EINVAL;
		retval = cft->write_u64(cgrp, cft, val);
	} else {
K
KOSAKI Motohiro 已提交
2397
		s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2398 2399 2400 2401
		if (*end)
			return -EINVAL;
		retval = cft->write_s64(cgrp, cft, val);
	}
2402 2403 2404 2405 2406
	if (!retval)
		retval = nbytes;
	return retval;
}

2407 2408 2409 2410 2411
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)
{
2412
	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426
	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
2427 2428 2429 2430
	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
		retval = -EFAULT;
		goto out;
	}
2431 2432

	buffer[nbytes] = 0;     /* nul-terminate */
K
KOSAKI Motohiro 已提交
2433
	retval = cft->write_string(cgrp, cft, strstrip(buffer));
2434 2435
	if (!retval)
		retval = nbytes;
L
Li Zefan 已提交
2436
out:
2437 2438 2439 2440 2441
	if (buffer != local_buffer)
		kfree(buffer);
	return retval;
}

2442 2443 2444 2445
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);
2446
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2447

2448
	if (cgroup_is_removed(cgrp))
2449
		return -ENODEV;
2450
	if (cft->write)
2451
		return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2452 2453
	if (cft->write_u64 || cft->write_s64)
		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2454 2455
	if (cft->write_string)
		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2456 2457 2458 2459
	if (cft->trigger) {
		int ret = cft->trigger(cgrp, (unsigned int)cft->private);
		return ret ? ret : nbytes;
	}
2460
	return -EINVAL;
2461 2462
}

2463 2464 2465 2466
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
2467
{
2468
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2469
	u64 val = cft->read_u64(cgrp, cft);
2470 2471 2472 2473 2474
	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);

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

2475 2476 2477 2478 2479
static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
{
2480
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2481 2482 2483 2484 2485 2486
	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);
}

2487 2488 2489 2490
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);
2491
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2492

2493
	if (cgroup_is_removed(cgrp))
2494 2495 2496
		return -ENODEV;

	if (cft->read)
2497
		return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2498 2499
	if (cft->read_u64)
		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2500 2501
	if (cft->read_s64)
		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2502 2503 2504
	return -EINVAL;
}

2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524
/*
 * 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;
2525 2526 2527 2528 2529 2530 2531 2532
	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);
2533 2534
}

2535
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2536 2537 2538 2539 2540 2541
{
	struct seq_file *seq = file->private_data;
	kfree(seq->private);
	return single_release(inode, file);
}

2542
static const struct file_operations cgroup_seqfile_operations = {
2543
	.read = seq_read,
2544
	.write = cgroup_file_write,
2545 2546 2547 2548
	.llseek = seq_lseek,
	.release = cgroup_seqfile_release,
};

2549 2550 2551 2552 2553 2554 2555 2556 2557
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);
2558

2559
	if (cft->read_map || cft->read_seq_string) {
2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570
		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)
2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600
		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);
}

2601
static const struct file_operations cgroup_file_operations = {
2602 2603 2604 2605 2606 2607 2608
	.read = cgroup_file_read,
	.write = cgroup_file_write,
	.llseek = generic_file_llseek,
	.open = cgroup_file_open,
	.release = cgroup_file_release,
};

2609
static const struct inode_operations cgroup_dir_inode_operations = {
2610
	.lookup = cgroup_lookup,
2611 2612 2613 2614 2615
	.mkdir = cgroup_mkdir,
	.rmdir = cgroup_rmdir,
	.rename = cgroup_rename,
};

2616 2617 2618 2619 2620 2621 2622 2623
static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
	d_add(dentry, NULL);
	return NULL;
}

2624 2625 2626 2627 2628 2629 2630 2631 2632 2633
/*
 * Check if a file is a control file
 */
static inline struct cftype *__file_cft(struct file *file)
{
	if (file->f_dentry->d_inode->i_fop != &cgroup_file_operations)
		return ERR_PTR(-EINVAL);
	return __d_cft(file->f_dentry);
}

2634 2635 2636
static int cgroup_create_file(struct dentry *dentry, mode_t mode,
				struct super_block *sb)
{
2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656
	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 */
2657
		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
2658 2659 2660 2661 2662 2663 2664 2665 2666 2667
	} else if (S_ISREG(mode)) {
		inode->i_size = 0;
		inode->i_fop = &cgroup_file_operations;
	}
	d_instantiate(dentry, inode);
	dget(dentry);	/* Extra count - pin the dentry in core */
	return 0;
}

/*
L
Li Zefan 已提交
2668 2669 2670 2671 2672
 * 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.
2673
 */
2674
static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
L
Li Zefan 已提交
2675
				mode_t mode)
2676 2677 2678 2679
{
	struct dentry *parent;
	int error = 0;

2680 2681
	parent = cgrp->parent->dentry;
	error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
2682
	if (!error) {
2683
		dentry->d_fsdata = cgrp;
2684
		inc_nlink(parent->d_inode);
2685
		rcu_assign_pointer(cgrp->dentry, dentry);
2686 2687 2688 2689 2690 2691 2692
		dget(dentry);
	}
	dput(dentry);

	return error;
}

L
Li Zefan 已提交
2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719
/**
 * 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;
}

2720
int cgroup_add_file(struct cgroup *cgrp,
2721 2722 2723
		       struct cgroup_subsys *subsys,
		       const struct cftype *cft)
{
2724
	struct dentry *dir = cgrp->dentry;
2725 2726
	struct dentry *dentry;
	int error;
L
Li Zefan 已提交
2727
	mode_t mode;
2728 2729

	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2730
	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2731 2732 2733 2734 2735 2736 2737
		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
2738 2739
		mode = cgroup_file_mode(cft);
		error = cgroup_create_file(dentry, mode | S_IFREG,
2740
						cgrp->root->sb);
2741 2742 2743 2744 2745 2746 2747
		if (!error)
			dentry->d_fsdata = (void *)cft;
		dput(dentry);
	} else
		error = PTR_ERR(dentry);
	return error;
}
2748
EXPORT_SYMBOL_GPL(cgroup_add_file);
2749

2750
int cgroup_add_files(struct cgroup *cgrp,
2751 2752 2753 2754 2755 2756
			struct cgroup_subsys *subsys,
			const struct cftype cft[],
			int count)
{
	int i, err;
	for (i = 0; i < count; i++) {
2757
		err = cgroup_add_file(cgrp, subsys, &cft[i]);
2758 2759 2760 2761 2762
		if (err)
			return err;
	}
	return 0;
}
2763
EXPORT_SYMBOL_GPL(cgroup_add_files);
2764

L
Li Zefan 已提交
2765 2766 2767 2768 2769 2770
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2771
int cgroup_task_count(const struct cgroup *cgrp)
2772 2773
{
	int count = 0;
K
KOSAKI Motohiro 已提交
2774
	struct cg_cgroup_link *link;
2775 2776

	read_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
2777
	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2778
		count += atomic_read(&link->cg->refcount);
2779 2780
	}
	read_unlock(&css_set_lock);
2781 2782 2783
	return count;
}

2784 2785 2786 2787
/*
 * Advance a list_head iterator.  The iterator should be positioned at
 * the start of a css_set
 */
2788
static void cgroup_advance_iter(struct cgroup *cgrp,
2789
				struct cgroup_iter *it)
2790 2791 2792 2793 2794 2795 2796 2797
{
	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;
2798
		if (l == &cgrp->css_sets) {
2799 2800 2801
			it->cg_link = NULL;
			return;
		}
2802
		link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2803 2804 2805 2806 2807 2808
		cg = link->cg;
	} while (list_empty(&cg->tasks));
	it->cg_link = l;
	it->task = cg->tasks.next;
}

2809 2810 2811 2812 2813 2814 2815 2816 2817
/*
 * 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.
 */
2818
static void cgroup_enable_task_cg_lists(void)
2819 2820 2821 2822 2823 2824
{
	struct task_struct *p, *g;
	write_lock(&css_set_lock);
	use_task_css_set_links = 1;
	do_each_thread(g, p) {
		task_lock(p);
2825 2826 2827 2828 2829 2830
		/*
		 * 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))
2831 2832 2833 2834 2835 2836
			list_add(&p->cg_list, &p->cgroups->tasks);
		task_unlock(p);
	} while_each_thread(g, p);
	write_unlock(&css_set_lock);
}

2837
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
2838 2839 2840 2841 2842 2843
{
	/*
	 * 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.
	 */
2844 2845 2846
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();

2847
	read_lock(&css_set_lock);
2848 2849
	it->cg_link = &cgrp->css_sets;
	cgroup_advance_iter(cgrp, it);
2850 2851
}

2852
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
2853 2854 2855 2856
					struct cgroup_iter *it)
{
	struct task_struct *res;
	struct list_head *l = it->task;
2857
	struct cg_cgroup_link *link;
2858 2859 2860 2861 2862 2863 2864

	/* 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;
2865 2866
	link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
	if (l == &link->cg->tasks) {
2867 2868
		/* We reached the end of this task list - move on to
		 * the next cg_cgroup_link */
2869
		cgroup_advance_iter(cgrp, it);
2870 2871 2872 2873 2874 2875
	} else {
		it->task = l;
	}
	return res;
}

2876
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
2877 2878 2879 2880
{
	read_unlock(&css_set_lock);
}

2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017
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++) {
3018
			struct task_struct *q = heap->ptrs[i];
3019
			if (i == 0) {
3020 3021
				latest_time = q->start_time;
				latest_task = q;
3022 3023
			}
			/* Process the task per the caller's callback */
3024 3025
			scan->process_task(q, scan);
			put_task_struct(q);
3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040
		}
		/*
		 * 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;
}

3041
/*
3042
 * Stuff for reading the 'tasks'/'procs' files.
3043 3044 3045 3046 3047 3048 3049 3050
 *
 * 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.
 *
 */

3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086
/*
 * 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;
}

3087
/*
3088 3089 3090 3091
 * 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.
3092
 */
3093 3094 3095
/* 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)
3096
{
3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122 3123 3124 3125
	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)) {
3126
		newlist = pidlist_resize(list, dest);
3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137
		if (newlist)
			*p = newlist;
	}
	return dest;
}

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

3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148
/*
 * 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 */
3149 3150
	struct pid_namespace *ns = current->nsproxy->pid_ns;

3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174
	/*
	 * 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) {
			/* 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);
		return l;
	}
	init_rwsem(&l->mutex);
	down_write(&l->mutex);
	l->key.type = type;
3175
	l->key.ns = get_pid_ns(ns);
3176 3177 3178 3179 3180 3181 3182 3183
	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;
}

3184 3185 3186
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
3187 3188
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
3189 3190 3191 3192
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
3193 3194
	struct cgroup_iter it;
	struct task_struct *tsk;
3195 3196 3197 3198 3199 3200 3201 3202 3203
	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);
3204
	array = pidlist_allocate(length);
3205 3206 3207
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
3208 3209
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
3210
		if (unlikely(n == length))
3211
			break;
3212
		/* get tgid or pid for procs or tasks file respectively */
3213 3214 3215 3216
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
3217 3218
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
3219
	}
3220
	cgroup_iter_end(cgrp, &it);
3221 3222 3223
	length = n;
	/* now sort & (if procs) strip out duplicates */
	sort(array, length, sizeof(pid_t), cmppid, NULL);
3224
	if (type == CGROUP_FILE_PROCS)
3225
		length = pidlist_uniq(&array, length);
3226 3227
	l = cgroup_pidlist_find(cgrp, type);
	if (!l) {
3228
		pidlist_free(array);
3229
		return -ENOMEM;
3230
	}
3231
	/* store array, freeing old if necessary - lock already held */
3232
	pidlist_free(l->list);
3233 3234 3235 3236
	l->list = array;
	l->length = length;
	l->use_count++;
	up_write(&l->mutex);
3237
	*lp = l;
3238
	return 0;
3239 3240
}

B
Balbir Singh 已提交
3241
/**
L
Li Zefan 已提交
3242
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
3243 3244 3245
 * @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
3246 3247 3248
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
3249 3250 3251 3252
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
	int ret = -EINVAL;
3253
	struct cgroup *cgrp;
B
Balbir Singh 已提交
3254 3255
	struct cgroup_iter it;
	struct task_struct *tsk;
3256

B
Balbir Singh 已提交
3257
	/*
3258 3259
	 * Validate dentry by checking the superblock operations,
	 * and make sure it's a directory.
B
Balbir Singh 已提交
3260
	 */
3261 3262
	if (dentry->d_sb->s_op != &cgroup_ops ||
	    !S_ISDIR(dentry->d_inode->i_mode))
B
Balbir Singh 已提交
3263 3264 3265
		 goto err;

	ret = 0;
3266
	cgrp = dentry->d_fsdata;
B
Balbir Singh 已提交
3267

3268 3269
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
B
Balbir Singh 已提交
3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288
		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;
		}
	}
3289
	cgroup_iter_end(cgrp, &it);
B
Balbir Singh 已提交
3290 3291 3292 3293 3294

err:
	return ret;
}

3295

3296
/*
3297
 * seq_file methods for the tasks/procs files. The seq_file position is the
3298
 * next pid to display; the seq_file iterator is a pointer to the pid
3299
 * in the cgroup->l->list array.
3300
 */
3301

3302
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3303
{
3304 3305 3306 3307 3308 3309
	/*
	 * 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
	 */
3310
	struct cgroup_pidlist *l = s->private;
3311 3312 3313
	int index = 0, pid = *pos;
	int *iter;

3314
	down_read(&l->mutex);
3315
	if (pid) {
3316
		int end = l->length;
S
Stephen Rothwell 已提交
3317

3318 3319
		while (index < end) {
			int mid = (index + end) / 2;
3320
			if (l->list[mid] == pid) {
3321 3322
				index = mid;
				break;
3323
			} else if (l->list[mid] <= pid)
3324 3325 3326 3327 3328 3329
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
3330
	if (index >= l->length)
3331 3332
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
3333
	iter = l->list + index;
3334 3335 3336 3337
	*pos = *iter;
	return iter;
}

3338
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3339
{
3340 3341
	struct cgroup_pidlist *l = s->private;
	up_read(&l->mutex);
3342 3343
}

3344
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3345
{
3346 3347 3348
	struct cgroup_pidlist *l = s->private;
	pid_t *p = v;
	pid_t *end = l->list + l->length;
3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361
	/*
	 * 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;
	}
}

3362
static int cgroup_pidlist_show(struct seq_file *s, void *v)
3363 3364 3365
{
	return seq_printf(s, "%d\n", *(int *)v);
}
3366

3367 3368 3369 3370 3371 3372 3373 3374 3375
/*
 * 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,
3376 3377
};

3378
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3379
{
3380 3381 3382 3383 3384 3385 3386
	/*
	 * 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);
3387 3388 3389
	down_write(&l->mutex);
	BUG_ON(!l->use_count);
	if (!--l->use_count) {
3390 3391 3392
		/* we're the last user if refcount is 0; remove and free */
		list_del(&l->links);
		mutex_unlock(&l->owner->pidlist_mutex);
3393
		pidlist_free(l->list);
3394 3395 3396 3397
		put_pid_ns(l->key.ns);
		up_write(&l->mutex);
		kfree(l);
		return;
3398
	}
3399
	mutex_unlock(&l->owner->pidlist_mutex);
3400
	up_write(&l->mutex);
3401 3402
}

3403
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3404
{
3405
	struct cgroup_pidlist *l;
3406 3407
	if (!(file->f_mode & FMODE_READ))
		return 0;
3408 3409 3410 3411 3412 3413
	/*
	 * 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);
3414 3415 3416
	return seq_release(inode, file);
}

3417
static const struct file_operations cgroup_pidlist_operations = {
3418 3419 3420
	.read = seq_read,
	.llseek = seq_lseek,
	.write = cgroup_file_write,
3421
	.release = cgroup_pidlist_release,
3422 3423
};

3424
/*
3425 3426 3427
 * 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.
3428
 */
3429
/* helper function for the two below it */
3430
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3431
{
3432
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3433
	struct cgroup_pidlist *l;
3434
	int retval;
3435

3436
	/* Nothing to do for write-only files */
3437 3438 3439
	if (!(file->f_mode & FMODE_READ))
		return 0;

3440
	/* have the array populated */
3441
	retval = pidlist_array_load(cgrp, type, &l);
3442 3443 3444 3445
	if (retval)
		return retval;
	/* configure file information */
	file->f_op = &cgroup_pidlist_operations;
3446

3447
	retval = seq_open(file, &cgroup_pidlist_seq_operations);
3448
	if (retval) {
3449
		cgroup_release_pid_array(l);
3450
		return retval;
3451
	}
3452
	((struct seq_file *)file->private_data)->private = l;
3453 3454
	return 0;
}
3455 3456
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
3457
	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3458 3459 3460
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
3461
	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3462
}
3463

3464
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3465 3466
					    struct cftype *cft)
{
3467
	return notify_on_release(cgrp);
3468 3469
}

3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481
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;
}

3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496
/*
 * Unregister event and free resources.
 *
 * Gets called from workqueue.
 */
static void cgroup_event_remove(struct work_struct *work)
{
	struct cgroup_event *event = container_of(work, struct cgroup_event,
			remove);
	struct cgroup *cgrp = event->cgrp;

	event->cft->unregister_event(cgrp, event->cft, event->eventfd);

	eventfd_ctx_put(event->eventfd);
	kfree(event);
3497
	dput(cgrp->dentry);
3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513
}

/*
 * Gets called on POLLHUP on eventfd when user closes it.
 *
 * Called with wqh->lock held and interrupts disabled.
 */
static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
		int sync, void *key)
{
	struct cgroup_event *event = container_of(wait,
			struct cgroup_event, wait);
	struct cgroup *cgrp = event->cgrp;
	unsigned long flags = (unsigned long)key;

	if (flags & POLLHUP) {
C
Changli Gao 已提交
3514
		__remove_wait_queue(event->wqh, &event->wait);
3515 3516 3517 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 3546 3547 3548 3549 3550 3551 3552 3553 3554 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584 3585 3586 3587 3588 3589 3590 3591
		spin_lock(&cgrp->event_list_lock);
		list_del(&event->list);
		spin_unlock(&cgrp->event_list_lock);
		/*
		 * We are in atomic context, but cgroup_event_remove() may
		 * sleep, so we have to call it in workqueue.
		 */
		schedule_work(&event->remove);
	}

	return 0;
}

static void cgroup_event_ptable_queue_proc(struct file *file,
		wait_queue_head_t *wqh, poll_table *pt)
{
	struct cgroup_event *event = container_of(pt,
			struct cgroup_event, pt);

	event->wqh = wqh;
	add_wait_queue(wqh, &event->wait);
}

/*
 * Parse input and register new cgroup event handler.
 *
 * Input must be in format '<event_fd> <control_fd> <args>'.
 * Interpretation of args is defined by control file implementation.
 */
static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
				      const char *buffer)
{
	struct cgroup_event *event = NULL;
	unsigned int efd, cfd;
	struct file *efile = NULL;
	struct file *cfile = NULL;
	char *endp;
	int ret;

	efd = simple_strtoul(buffer, &endp, 10);
	if (*endp != ' ')
		return -EINVAL;
	buffer = endp + 1;

	cfd = simple_strtoul(buffer, &endp, 10);
	if ((*endp != ' ') && (*endp != '\0'))
		return -EINVAL;
	buffer = endp + 1;

	event = kzalloc(sizeof(*event), GFP_KERNEL);
	if (!event)
		return -ENOMEM;
	event->cgrp = cgrp;
	INIT_LIST_HEAD(&event->list);
	init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
	init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
	INIT_WORK(&event->remove, cgroup_event_remove);

	efile = eventfd_fget(efd);
	if (IS_ERR(efile)) {
		ret = PTR_ERR(efile);
		goto fail;
	}

	event->eventfd = eventfd_ctx_fileget(efile);
	if (IS_ERR(event->eventfd)) {
		ret = PTR_ERR(event->eventfd);
		goto fail;
	}

	cfile = fget(cfd);
	if (!cfile) {
		ret = -EBADF;
		goto fail;
	}

	/* the process need read permission on control file */
A
Al Viro 已提交
3592 3593
	/* AV: shouldn't we check that it's been opened for read instead? */
	ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618
	if (ret < 0)
		goto fail;

	event->cft = __file_cft(cfile);
	if (IS_ERR(event->cft)) {
		ret = PTR_ERR(event->cft);
		goto fail;
	}

	if (!event->cft->register_event || !event->cft->unregister_event) {
		ret = -EINVAL;
		goto fail;
	}

	ret = event->cft->register_event(cgrp, event->cft,
			event->eventfd, buffer);
	if (ret)
		goto fail;

	if (efile->f_op->poll(efile, &event->pt) & POLLHUP) {
		event->cft->unregister_event(cgrp, event->cft, event->eventfd);
		ret = 0;
		goto fail;
	}

3619 3620 3621 3622 3623 3624 3625
	/*
	 * Events should be removed after rmdir of cgroup directory, but before
	 * destroying subsystem state objects. Let's take reference to cgroup
	 * directory dentry to do that.
	 */
	dget(cgrp->dentry);

3626 3627 3628 3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649
	spin_lock(&cgrp->event_list_lock);
	list_add(&event->list, &cgrp->event_list);
	spin_unlock(&cgrp->event_list_lock);

	fput(cfile);
	fput(efile);

	return 0;

fail:
	if (cfile)
		fput(cfile);

	if (event && event->eventfd && !IS_ERR(event->eventfd))
		eventfd_ctx_put(event->eventfd);

	if (!IS_ERR_OR_NULL(efile))
		fput(efile);

	kfree(event);

	return ret;
}

3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666
static u64 cgroup_clone_children_read(struct cgroup *cgrp,
				    struct cftype *cft)
{
	return clone_children(cgrp);
}

static int cgroup_clone_children_write(struct cgroup *cgrp,
				     struct cftype *cft,
				     u64 val)
{
	if (val)
		set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
	else
		clear_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
	return 0;
}

3667 3668 3669
/*
 * for the common functions, 'private' gives the type of file
 */
3670 3671
/* for hysterical raisins, we can't put this on the older files */
#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3672 3673 3674 3675
static struct cftype files[] = {
	{
		.name = "tasks",
		.open = cgroup_tasks_open,
3676
		.write_u64 = cgroup_tasks_write,
3677
		.release = cgroup_pidlist_release,
L
Li Zefan 已提交
3678
		.mode = S_IRUGO | S_IWUSR,
3679
	},
3680 3681 3682
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "procs",
		.open = cgroup_procs_open,
B
Ben Blum 已提交
3683
		.write_u64 = cgroup_procs_write,
3684
		.release = cgroup_pidlist_release,
B
Ben Blum 已提交
3685
		.mode = S_IRUGO | S_IWUSR,
3686
	},
3687 3688
	{
		.name = "notify_on_release",
3689
		.read_u64 = cgroup_read_notify_on_release,
3690
		.write_u64 = cgroup_write_notify_on_release,
3691
	},
3692 3693 3694 3695 3696
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "event_control",
		.write_string = cgroup_write_event_control,
		.mode = S_IWUGO,
	},
3697 3698 3699 3700 3701
	{
		.name = "cgroup.clone_children",
		.read_u64 = cgroup_clone_children_read,
		.write_u64 = cgroup_clone_children_write,
	},
3702 3703 3704 3705
};

static struct cftype cft_release_agent = {
	.name = "release_agent",
3706 3707 3708
	.read_seq_string = cgroup_release_agent_show,
	.write_string = cgroup_release_agent_write,
	.max_write_len = PATH_MAX,
3709 3710
};

3711
static int cgroup_populate_dir(struct cgroup *cgrp)
3712 3713 3714 3715 3716
{
	int err;
	struct cgroup_subsys *ss;

	/* First clear out any existing files */
3717
	cgroup_clear_directory(cgrp->dentry);
3718

3719
	err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));
3720 3721 3722
	if (err < 0)
		return err;

3723 3724
	if (cgrp == cgrp->top_cgroup) {
		if ((err = cgroup_add_file(cgrp, NULL, &cft_release_agent)) < 0)
3725 3726 3727
			return err;
	}

3728 3729
	for_each_subsys(cgrp->root, ss) {
		if (ss->populate && (err = ss->populate(ss, cgrp)) < 0)
3730 3731
			return err;
	}
K
KAMEZAWA Hiroyuki 已提交
3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742
	/* 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);
	}
3743 3744 3745 3746 3747 3748

	return 0;
}

static void init_cgroup_css(struct cgroup_subsys_state *css,
			       struct cgroup_subsys *ss,
3749
			       struct cgroup *cgrp)
3750
{
3751
	css->cgroup = cgrp;
P
Paul Menage 已提交
3752
	atomic_set(&css->refcnt, 1);
3753
	css->flags = 0;
K
KAMEZAWA Hiroyuki 已提交
3754
	css->id = NULL;
3755
	if (cgrp == dummytop)
3756
		set_bit(CSS_ROOT, &css->flags);
3757 3758
	BUG_ON(cgrp->subsys[ss->subsys_id]);
	cgrp->subsys[ss->subsys_id] = css;
3759 3760
}

3761 3762 3763 3764 3765
static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
{
	/* We need to take each hierarchy_mutex in a consistent order */
	int i;

B
Ben Blum 已提交
3766 3767 3768 3769
	/*
	 * No worry about a race with rebind_subsystems that might mess up the
	 * locking order, since both parties are under cgroup_mutex.
	 */
3770 3771
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
B
Ben Blum 已提交
3772 3773
		if (ss == NULL)
			continue;
3774
		if (ss->root == root)
3775
			mutex_lock(&ss->hierarchy_mutex);
3776 3777 3778 3779 3780 3781 3782 3783 3784
	}
}

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];
B
Ben Blum 已提交
3785 3786
		if (ss == NULL)
			continue;
3787 3788 3789 3790 3791
		if (ss->root == root)
			mutex_unlock(&ss->hierarchy_mutex);
	}
}

3792
/*
L
Li Zefan 已提交
3793 3794 3795 3796
 * 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
3797
 *
L
Li Zefan 已提交
3798
 * Must be called with the mutex on the parent inode held
3799 3800
 */
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
L
Li Zefan 已提交
3801
			     mode_t mode)
3802
{
3803
	struct cgroup *cgrp;
3804 3805 3806 3807 3808
	struct cgroupfs_root *root = parent->root;
	int err = 0;
	struct cgroup_subsys *ss;
	struct super_block *sb = root->sb;

3809 3810
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821
		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);

3822
	init_cgroup_housekeeping(cgrp);
3823

3824 3825 3826
	cgrp->parent = parent;
	cgrp->root = parent->root;
	cgrp->top_cgroup = parent->top_cgroup;
3827

3828 3829 3830
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

3831 3832 3833
	if (clone_children(parent))
		set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);

3834
	for_each_subsys(root, ss) {
3835
		struct cgroup_subsys_state *css = ss->create(ss, cgrp);
3836

3837 3838 3839 3840
		if (IS_ERR(css)) {
			err = PTR_ERR(css);
			goto err_destroy;
		}
3841
		init_cgroup_css(css, ss, cgrp);
3842 3843 3844
		if (ss->use_id) {
			err = alloc_css_id(ss, parent, cgrp);
			if (err)
K
KAMEZAWA Hiroyuki 已提交
3845
				goto err_destroy;
3846
		}
K
KAMEZAWA Hiroyuki 已提交
3847
		/* At error, ->destroy() callback has to free assigned ID. */
3848 3849
		if (clone_children(parent) && ss->post_clone)
			ss->post_clone(ss, cgrp);
3850 3851
	}

3852
	cgroup_lock_hierarchy(root);
3853
	list_add(&cgrp->sibling, &cgrp->parent->children);
3854
	cgroup_unlock_hierarchy(root);
3855 3856
	root->number_of_cgroups++;

3857
	err = cgroup_create_dir(cgrp, dentry, mode);
3858 3859 3860 3861
	if (err < 0)
		goto err_remove;

	/* The cgroup directory was pre-locked for us */
3862
	BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
3863

3864
	err = cgroup_populate_dir(cgrp);
3865 3866 3867
	/* If err < 0, we have a half-filled directory - oh well ;) */

	mutex_unlock(&cgroup_mutex);
3868
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
3869 3870 3871 3872 3873

	return 0;

 err_remove:

3874
	cgroup_lock_hierarchy(root);
3875
	list_del(&cgrp->sibling);
3876
	cgroup_unlock_hierarchy(root);
3877 3878 3879 3880 3881
	root->number_of_cgroups--;

 err_destroy:

	for_each_subsys(root, ss) {
3882 3883
		if (cgrp->subsys[ss->subsys_id])
			ss->destroy(ss, cgrp);
3884 3885 3886 3887 3888 3889 3890
	}

	mutex_unlock(&cgroup_mutex);

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

3891
	kfree(cgrp);
3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902
	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);
}

3903
static int cgroup_has_css_refs(struct cgroup *cgrp)
3904 3905 3906
{
	/* Check the reference count on each subsystem. Since we
	 * already established that there are no tasks in the
P
Paul Menage 已提交
3907
	 * cgroup, if the css refcount is also 1, then there should
3908 3909 3910 3911 3912 3913 3914
	 * 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;
B
Ben Blum 已提交
3915 3916 3917 3918 3919
	/*
	 * We won't need to lock the subsys array, because the subsystems
	 * we're concerned about aren't going anywhere since our cgroup root
	 * has a reference on them.
	 */
3920 3921 3922
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		struct cgroup_subsys_state *css;
B
Ben Blum 已提交
3923 3924
		/* Skip subsystems not present or not in this hierarchy */
		if (ss == NULL || ss->root != cgrp->root)
3925
			continue;
3926
		css = cgrp->subsys[ss->subsys_id];
3927 3928 3929 3930 3931 3932
		/* 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
3933
		if (css && (atomic_read(&css->refcnt) > 1))
3934 3935 3936 3937 3938
			return 1;
	}
	return 0;
}

P
Paul Menage 已提交
3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953
/*
 * 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;
3954
		while (1) {
P
Paul Menage 已提交
3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967
			/* 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
			 */
3968 3969 3970 3971
			if (atomic_cmpxchg(&css->refcnt, refcnt, 0) == refcnt)
				break;
			cpu_relax();
		}
P
Paul Menage 已提交
3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991
	}
 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;
}

3992 3993
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
3994
	struct cgroup *cgrp = dentry->d_fsdata;
3995 3996
	struct dentry *d;
	struct cgroup *parent;
3997
	DEFINE_WAIT(wait);
3998
	struct cgroup_event *event, *tmp;
3999
	int ret;
4000 4001

	/* the vfs holds both inode->i_mutex already */
4002
again:
4003
	mutex_lock(&cgroup_mutex);
4004
	if (atomic_read(&cgrp->count) != 0) {
4005 4006 4007
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
4008
	if (!list_empty(&cgrp->children)) {
4009 4010 4011
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
4012
	mutex_unlock(&cgroup_mutex);
L
Li Zefan 已提交
4013

4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024
	/*
	 * 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);

4025
	/*
L
Li Zefan 已提交
4026 4027
	 * Call pre_destroy handlers of subsys. Notify subsystems
	 * that rmdir() request comes.
4028
	 */
4029
	ret = cgroup_call_pre_destroy(cgrp);
4030 4031
	if (ret) {
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4032
		return ret;
4033
	}
4034

4035 4036
	mutex_lock(&cgroup_mutex);
	parent = cgrp->parent;
4037
	if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
4038
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4039 4040 4041
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
4042 4043 4044
	prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
	if (!cgroup_clear_css_refs(cgrp)) {
		mutex_unlock(&cgroup_mutex);
4045 4046 4047 4048 4049 4050
		/*
		 * 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();
4051 4052 4053 4054 4055 4056 4057 4058 4059
		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);
4060

4061
	raw_spin_lock(&release_list_lock);
4062 4063
	set_bit(CGRP_REMOVED, &cgrp->flags);
	if (!list_empty(&cgrp->release_list))
4064
		list_del_init(&cgrp->release_list);
4065
	raw_spin_unlock(&release_list_lock);
4066 4067 4068

	cgroup_lock_hierarchy(cgrp->root);
	/* delete this cgroup from parent->children */
4069
	list_del_init(&cgrp->sibling);
4070 4071
	cgroup_unlock_hierarchy(cgrp->root);

4072
	d = dget(cgrp->dentry);
4073 4074 4075 4076

	cgroup_d_remove_dir(d);
	dput(d);

4077
	set_bit(CGRP_RELEASABLE, &parent->flags);
4078 4079
	check_for_release(parent);

4080 4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093
	/*
	 * Unregister events and notify userspace.
	 * Notify userspace about cgroup removing only after rmdir of cgroup
	 * directory to avoid race between userspace and kernelspace
	 */
	spin_lock(&cgrp->event_list_lock);
	list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
		list_del(&event->list);
		remove_wait_queue(event->wqh, &event->wait);
		eventfd_signal(event->eventfd, 1);
		schedule_work(&event->remove);
	}
	spin_unlock(&cgrp->event_list_lock);

4094 4095 4096 4097
	mutex_unlock(&cgroup_mutex);
	return 0;
}

4098
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4099 4100
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
4101 4102

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4103 4104

	/* Create the top cgroup state for this subsystem */
4105
	list_add(&ss->sibling, &rootnode.subsys_list);
4106 4107 4108 4109 4110 4111
	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
4112
	/* Update the init_css_set to contain a subsys
4113
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
4114 4115 4116
	 * 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];
4117 4118 4119

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

L
Li Zefan 已提交
4120 4121 4122 4123 4124
	/* 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));

4125
	mutex_init(&ss->hierarchy_mutex);
4126
	lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
4127
	ss->active = 1;
4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138

	/* this function shouldn't be used with modular subsystems, since they
	 * need to register a subsys_id, among other things */
	BUG_ON(ss->module);
}

/**
 * cgroup_load_subsys: load and register a modular subsystem at runtime
 * @ss: the subsystem to load
 *
 * This function should be called in a modular subsystem's initcall. If the
T
Thomas Weber 已提交
4139
 * subsystem is built as a module, it will be assigned a new subsys_id and set
4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 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 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 4212 4213 4214 4215 4216 4217 4218 4219 4220 4221 4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253 4254 4255 4256
 * up for use. If the subsystem is built-in anyway, work is delegated to the
 * simpler cgroup_init_subsys.
 */
int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
{
	int i;
	struct cgroup_subsys_state *css;

	/* check name and function validity */
	if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
	    ss->create == NULL || ss->destroy == NULL)
		return -EINVAL;

	/*
	 * we don't support callbacks in modular subsystems. this check is
	 * before the ss->module check for consistency; a subsystem that could
	 * be a module should still have no callbacks even if the user isn't
	 * compiling it as one.
	 */
	if (ss->fork || ss->exit)
		return -EINVAL;

	/*
	 * an optionally modular subsystem is built-in: we want to do nothing,
	 * since cgroup_init_subsys will have already taken care of it.
	 */
	if (ss->module == NULL) {
		/* a few sanity checks */
		BUG_ON(ss->subsys_id >= CGROUP_BUILTIN_SUBSYS_COUNT);
		BUG_ON(subsys[ss->subsys_id] != ss);
		return 0;
	}

	/*
	 * need to register a subsys id before anything else - for example,
	 * init_cgroup_css needs it.
	 */
	mutex_lock(&cgroup_mutex);
	/* find the first empty slot in the array */
	for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
		if (subsys[i] == NULL)
			break;
	}
	if (i == CGROUP_SUBSYS_COUNT) {
		/* maximum number of subsystems already registered! */
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
	/* assign ourselves the subsys_id */
	ss->subsys_id = i;
	subsys[i] = ss;

	/*
	 * no ss->create seems to need anything important in the ss struct, so
	 * this can happen first (i.e. before the rootnode attachment).
	 */
	css = ss->create(ss, dummytop);
	if (IS_ERR(css)) {
		/* failure case - need to deassign the subsys[] slot. */
		subsys[i] = NULL;
		mutex_unlock(&cgroup_mutex);
		return PTR_ERR(css);
	}

	list_add(&ss->sibling, &rootnode.subsys_list);
	ss->root = &rootnode;

	/* our new subsystem will be attached to the dummy hierarchy. */
	init_cgroup_css(css, ss, dummytop);
	/* init_idr must be after init_cgroup_css because it sets css->id. */
	if (ss->use_id) {
		int ret = cgroup_init_idr(ss, css);
		if (ret) {
			dummytop->subsys[ss->subsys_id] = NULL;
			ss->destroy(ss, dummytop);
			subsys[i] = NULL;
			mutex_unlock(&cgroup_mutex);
			return ret;
		}
	}

	/*
	 * Now we need to entangle the css into the existing css_sets. unlike
	 * in cgroup_init_subsys, there are now multiple css_sets, so each one
	 * will need a new pointer to it; done by iterating the css_set_table.
	 * furthermore, modifying the existing css_sets will corrupt the hash
	 * table state, so each changed css_set will need its hash recomputed.
	 * this is all done under the css_set_lock.
	 */
	write_lock(&css_set_lock);
	for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
		struct css_set *cg;
		struct hlist_node *node, *tmp;
		struct hlist_head *bucket = &css_set_table[i], *new_bucket;

		hlist_for_each_entry_safe(cg, node, tmp, bucket, hlist) {
			/* skip entries that we already rehashed */
			if (cg->subsys[ss->subsys_id])
				continue;
			/* remove existing entry */
			hlist_del(&cg->hlist);
			/* set new value */
			cg->subsys[ss->subsys_id] = css;
			/* recompute hash and restore entry */
			new_bucket = css_set_hash(cg->subsys);
			hlist_add_head(&cg->hlist, new_bucket);
		}
	}
	write_unlock(&css_set_lock);

	mutex_init(&ss->hierarchy_mutex);
	lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
	ss->active = 1;

	/* success! */
	mutex_unlock(&cgroup_mutex);
	return 0;
4257
}
4258
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4259

B
Ben Blum 已提交
4260 4261 4262 4263 4264 4265 4266 4267 4268 4269 4270 4271 4272 4273 4274 4275 4276 4277 4278 4279 4280 4281 4282 4283 4284 4285 4286 4287
/**
 * cgroup_unload_subsys: unload a modular subsystem
 * @ss: the subsystem to unload
 *
 * This function should be called in a modular subsystem's exitcall. When this
 * function is invoked, the refcount on the subsystem's module will be 0, so
 * the subsystem will not be attached to any hierarchy.
 */
void cgroup_unload_subsys(struct cgroup_subsys *ss)
{
	struct cg_cgroup_link *link;
	struct hlist_head *hhead;

	BUG_ON(ss->module == NULL);

	/*
	 * we shouldn't be called if the subsystem is in use, and the use of
	 * try_module_get in parse_cgroupfs_options should ensure that it
	 * doesn't start being used while we're killing it off.
	 */
	BUG_ON(ss->root != &rootnode);

	mutex_lock(&cgroup_mutex);
	/* deassign the subsys_id */
	BUG_ON(ss->subsys_id < CGROUP_BUILTIN_SUBSYS_COUNT);
	subsys[ss->subsys_id] = NULL;

	/* remove subsystem from rootnode's list of subsystems */
4288
	list_del_init(&ss->sibling);
B
Ben Blum 已提交
4289 4290 4291 4292 4293 4294 4295 4296 4297 4298 4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316 4317 4318

	/*
	 * disentangle the css from all css_sets attached to the dummytop. as
	 * in loading, we need to pay our respects to the hashtable gods.
	 */
	write_lock(&css_set_lock);
	list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {
		struct css_set *cg = link->cg;

		hlist_del(&cg->hlist);
		BUG_ON(!cg->subsys[ss->subsys_id]);
		cg->subsys[ss->subsys_id] = NULL;
		hhead = css_set_hash(cg->subsys);
		hlist_add_head(&cg->hlist, hhead);
	}
	write_unlock(&css_set_lock);

	/*
	 * remove subsystem's css from the dummytop and free it - need to free
	 * before marking as null because ss->destroy needs the cgrp->subsys
	 * pointer to find their state. note that this also takes care of
	 * freeing the css_id.
	 */
	ss->destroy(ss, dummytop);
	dummytop->subsys[ss->subsys_id] = NULL;

	mutex_unlock(&cgroup_mutex);
}
EXPORT_SYMBOL_GPL(cgroup_unload_subsys);

4319
/**
L
Li Zefan 已提交
4320 4321 4322 4323
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
4324 4325 4326 4327
 */
int __init cgroup_init_early(void)
{
	int i;
4328
	atomic_set(&init_css_set.refcount, 1);
4329 4330
	INIT_LIST_HEAD(&init_css_set.cg_links);
	INIT_LIST_HEAD(&init_css_set.tasks);
4331
	INIT_HLIST_NODE(&init_css_set.hlist);
4332
	css_set_count = 1;
4333
	init_cgroup_root(&rootnode);
4334 4335 4336 4337
	root_count = 1;
	init_task.cgroups = &init_css_set;

	init_css_set_link.cg = &init_css_set;
4338
	init_css_set_link.cgrp = dummytop;
4339
	list_add(&init_css_set_link.cgrp_link_list,
4340 4341 4342
		 &rootnode.top_cgroup.css_sets);
	list_add(&init_css_set_link.cg_link_list,
		 &init_css_set.cg_links);
4343

4344 4345 4346
	for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
		INIT_HLIST_HEAD(&css_set_table[i]);

B
Ben Blum 已提交
4347 4348
	/* at bootup time, we don't worry about modular subsystems */
	for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4349 4350 4351 4352 4353 4354 4355
		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
4356
			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367
			       ss->name, ss->subsys_id);
			BUG();
		}

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

/**
L
Li Zefan 已提交
4368 4369 4370 4371
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
4372 4373 4374 4375 4376
 */
int __init cgroup_init(void)
{
	int err;
	int i;
4377
	struct hlist_head *hhead;
4378 4379 4380 4381

	err = bdi_init(&cgroup_backing_dev_info);
	if (err)
		return err;
4382

B
Ben Blum 已提交
4383 4384
	/* at bootup time, we don't worry about modular subsystems */
	for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4385 4386 4387
		struct cgroup_subsys *ss = subsys[i];
		if (!ss->early_init)
			cgroup_init_subsys(ss);
K
KAMEZAWA Hiroyuki 已提交
4388
		if (ss->use_id)
4389
			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4390 4391
	}

4392 4393 4394
	/* Add init_css_set to the hash table */
	hhead = css_set_hash(init_css_set.subsys);
	hlist_add_head(&init_css_set.hlist, hhead);
4395
	BUG_ON(!init_root_id(&rootnode));
4396 4397 4398 4399 4400 4401 4402

	cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
	if (!cgroup_kobj) {
		err = -ENOMEM;
		goto out;
	}

4403
	err = register_filesystem(&cgroup_fs_type);
4404 4405
	if (err < 0) {
		kobject_put(cgroup_kobj);
4406
		goto out;
4407
	}
4408

L
Li Zefan 已提交
4409
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4410

4411
out:
4412 4413 4414
	if (err)
		bdi_destroy(&cgroup_backing_dev_info);

4415 4416
	return err;
}
4417

4418 4419 4420 4421 4422 4423
/*
 * 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,
4424
 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453
 *    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);

4454
	for_each_active_root(root) {
4455
		struct cgroup_subsys *ss;
4456
		struct cgroup *cgrp;
4457 4458
		int count = 0;

4459
		seq_printf(m, "%d:", root->hierarchy_id);
4460 4461
		for_each_subsys(root, ss)
			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4462 4463 4464
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
4465
		seq_putc(m, ':');
4466
		cgrp = task_cgroup_from_root(tsk, root);
4467
		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4468 4469 4470 4471 4472 4473 4474 4475 4476 4477 4478 4479 4480 4481 4482 4483 4484 4485 4486 4487 4488
		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);
}

4489
const struct file_operations proc_cgroup_operations = {
4490 4491 4492 4493 4494 4495 4496 4497 4498 4499 4500
	.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;

4501
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
B
Ben Blum 已提交
4502 4503 4504 4505 4506
	/*
	 * ideally we don't want subsystems moving around while we do this.
	 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
	 * subsys/hierarchy state.
	 */
4507 4508 4509
	mutex_lock(&cgroup_mutex);
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
B
Ben Blum 已提交
4510 4511
		if (ss == NULL)
			continue;
4512 4513
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
4514
			   ss->root->number_of_cgroups, !ss->disabled);
4515 4516 4517 4518 4519 4520 4521
	}
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
4522
	return single_open(file, proc_cgroupstats_show, NULL);
4523 4524
}

4525
static const struct file_operations proc_cgroupstats_operations = {
4526 4527 4528 4529 4530 4531
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

4532 4533
/**
 * cgroup_fork - attach newly forked task to its parents cgroup.
L
Li Zefan 已提交
4534
 * @child: pointer to task_struct of forking parent process.
4535 4536 4537 4538 4539
 *
 * 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
4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550
 * it was not made under the protection of RCU, cgroup_mutex or
 * threadgroup_change_begin(), so it might no longer be a valid
 * cgroup pointer.  cgroup_attach_task() might have already changed
 * current->cgroups, allowing the previously referenced cgroup
 * group to be removed and freed.
 *
 * Outside the pointer validity we also need to process the css_set
 * inheritance between threadgoup_change_begin() and
 * threadgoup_change_end(), this way there is no leak in any process
 * wide migration performed by cgroup_attach_proc() that could otherwise
 * miss a thread because it is too early or too late in the fork stage.
4551 4552 4553 4554 4555 4556
 *
 * 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)
{
4557 4558 4559 4560 4561 4562
	/*
	 * We don't need to task_lock() current because current->cgroups
	 * can't be changed concurrently here. The parent obviously hasn't
	 * exited and called cgroup_exit(), and we are synchronized against
	 * cgroup migration through threadgroup_change_begin().
	 */
4563 4564 4565
	child->cgroups = current->cgroups;
	get_css_set(child->cgroups);
	INIT_LIST_HEAD(&child->cg_list);
4566 4567 4568
}

/**
L
Li Zefan 已提交
4569 4570 4571 4572 4573 4574
 * 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.
4575 4576 4577 4578 4579
 */
void cgroup_fork_callbacks(struct task_struct *child)
{
	if (need_forkexit_callback) {
		int i;
B
Ben Blum 已提交
4580 4581 4582 4583 4584 4585
		/*
		 * forkexit callbacks are only supported for builtin
		 * subsystems, and the builtin section of the subsys array is
		 * immutable, so we don't need to lock the subsys array here.
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4586 4587 4588 4589 4590 4591 4592
			struct cgroup_subsys *ss = subsys[i];
			if (ss->fork)
				ss->fork(ss, child);
		}
	}
}

4593
/**
L
Li Zefan 已提交
4594 4595 4596 4597 4598 4599 4600 4601
 * 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.
 */
4602 4603 4604 4605
void cgroup_post_fork(struct task_struct *child)
{
	if (use_task_css_set_links) {
		write_lock(&css_set_lock);
4606
		task_lock(child);
4607 4608
		if (list_empty(&child->cg_list))
			list_add(&child->cg_list, &child->cgroups->tasks);
4609
		task_unlock(child);
4610 4611 4612
		write_unlock(&css_set_lock);
	}
}
4613 4614 4615
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
4616
 * @run_callback: run exit callbacks?
4617 4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644
 *
 * 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,
4645 4646
 *    which wards off any cgroup_attach_task() attempts, or task is a failed
 *    fork, never visible to cgroup_attach_task.
4647 4648 4649
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
4650
	struct css_set *cg;
4651
	int i;
4652 4653 4654 4655 4656 4657 4658 4659 4660

	/*
	 * 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))
4661
			list_del_init(&tsk->cg_list);
4662 4663 4664
		write_unlock(&css_set_lock);
	}

4665 4666
	/* Reassign the task to the init_css_set. */
	task_lock(tsk);
4667 4668
	cg = tsk->cgroups;
	tsk->cgroups = &init_css_set;
4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680 4681 4682 4683 4684

	if (run_callbacks && need_forkexit_callback) {
		/*
		 * modular subsystems can't use callbacks, so no need to lock
		 * the subsys array
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss->exit) {
				struct cgroup *old_cgrp =
					rcu_dereference_raw(cg->subsys[i])->cgroup;
				struct cgroup *cgrp = task_cgroup(tsk, i);
				ss->exit(ss, cgrp, old_cgrp, tsk);
			}
		}
	}
4685
	task_unlock(tsk);
4686

4687
	if (cg)
4688
		put_css_set_taskexit(cg);
4689
}
4690

L
Li Zefan 已提交
4691
/**
4692
 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
L
Li Zefan 已提交
4693
 * @cgrp: the cgroup in question
4694
 * @task: the task in question
L
Li Zefan 已提交
4695
 *
4696 4697
 * See if @cgrp is a descendant of @task's cgroup in the appropriate
 * hierarchy.
4698 4699 4700 4701 4702 4703
 *
 * If we are sending in dummytop, then presumably we are creating
 * the top cgroup in the subsystem.
 *
 * Called only by the ns (nsproxy) cgroup.
 */
4704
int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
4705 4706 4707 4708
{
	int ret;
	struct cgroup *target;

4709
	if (cgrp == dummytop)
4710 4711
		return 1;

4712
	target = task_cgroup_from_root(task, cgrp->root);
4713 4714 4715
	while (cgrp != target && cgrp!= cgrp->top_cgroup)
		cgrp = cgrp->parent;
	ret = (cgrp == target);
4716 4717
	return ret;
}
4718

4719
static void check_for_release(struct cgroup *cgrp)
4720 4721 4722
{
	/* All of these checks rely on RCU to keep the cgroup
	 * structure alive */
4723 4724
	if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
	    && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
4725 4726 4727 4728
		/* Control Group is currently removeable. If it's not
		 * already queued for a userspace notification, queue
		 * it now */
		int need_schedule_work = 0;
4729
		raw_spin_lock(&release_list_lock);
4730 4731 4732
		if (!cgroup_is_removed(cgrp) &&
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
4733 4734
			need_schedule_work = 1;
		}
4735
		raw_spin_unlock(&release_list_lock);
4736 4737 4738 4739 4740
		if (need_schedule_work)
			schedule_work(&release_agent_work);
	}
}

4741 4742
/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css, int count)
4743
{
4744
	struct cgroup *cgrp = css->cgroup;
4745
	int val;
4746
	rcu_read_lock();
4747
	val = atomic_sub_return(count, &css->refcnt);
4748
	if (val == 1) {
4749 4750 4751 4752
		if (notify_on_release(cgrp)) {
			set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
		}
4753
		cgroup_wakeup_rmdir_waiter(cgrp);
4754 4755
	}
	rcu_read_unlock();
4756
	WARN_ON_ONCE(val < 1);
4757
}
B
Ben Blum 已提交
4758
EXPORT_SYMBOL_GPL(__css_put);
4759 4760 4761 4762 4763 4764 4765 4766 4767 4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786

/*
 * 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);
4787
	raw_spin_lock(&release_list_lock);
4788 4789 4790
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
4791
		char *pathbuf = NULL, *agentbuf = NULL;
4792
		struct cgroup *cgrp = list_entry(release_list.next,
4793 4794
						    struct cgroup,
						    release_list);
4795
		list_del_init(&cgrp->release_list);
4796
		raw_spin_unlock(&release_list_lock);
4797
		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4798 4799 4800 4801 4802 4803 4804
		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;
4805 4806

		i = 0;
4807 4808
		argv[i++] = agentbuf;
		argv[i++] = pathbuf;
4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822
		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);
4823 4824 4825
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
4826
		raw_spin_lock(&release_list_lock);
4827
	}
4828
	raw_spin_unlock(&release_list_lock);
4829 4830
	mutex_unlock(&cgroup_mutex);
}
4831 4832 4833 4834 4835 4836 4837 4838 4839

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

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;
B
Ben Blum 已提交
4840 4841 4842 4843 4844
		/*
		 * cgroup_disable, being at boot time, can't know about module
		 * subsystems, so we don't worry about them.
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4845 4846 4847 4848 4849 4850 4851 4852 4853 4854 4855 4856 4857
			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
4858 4859 4860 4861 4862 4863 4864 4865 4866 4867

/*
 * 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)
{
4868 4869 4870 4871 4872 4873 4874
	struct css_id *cssid;

	/*
	 * This css_id() can return correct value when somone has refcnt
	 * on this or this is under rcu_read_lock(). Once css->id is allocated,
	 * it's unchanged until freed.
	 */
4875
	cssid = rcu_dereference_check(css->id, atomic_read(&css->refcnt));
K
KAMEZAWA Hiroyuki 已提交
4876 4877 4878 4879 4880

	if (cssid)
		return cssid->id;
	return 0;
}
B
Ben Blum 已提交
4881
EXPORT_SYMBOL_GPL(css_id);
K
KAMEZAWA Hiroyuki 已提交
4882 4883 4884

unsigned short css_depth(struct cgroup_subsys_state *css)
{
4885 4886
	struct css_id *cssid;

4887
	cssid = rcu_dereference_check(css->id, atomic_read(&css->refcnt));
K
KAMEZAWA Hiroyuki 已提交
4888 4889 4890 4891 4892

	if (cssid)
		return cssid->depth;
	return 0;
}
B
Ben Blum 已提交
4893
EXPORT_SYMBOL_GPL(css_depth);
K
KAMEZAWA Hiroyuki 已提交
4894

4895 4896 4897 4898 4899 4900 4901 4902 4903 4904 4905 4906 4907
/**
 *  css_is_ancestor - test "root" css is an ancestor of "child"
 * @child: the css to be tested.
 * @root: the css supporsed to be an ancestor of the child.
 *
 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
 * this function reads css->id, this use rcu_dereference() and rcu_read_lock().
 * But, considering usual usage, the csses should be valid objects after test.
 * Assuming that the caller will do some action to the child if this returns
 * returns true, the caller must take "child";s reference count.
 * If "child" is valid object and this returns true, "root" is valid, too.
 */

K
KAMEZAWA Hiroyuki 已提交
4908
bool css_is_ancestor(struct cgroup_subsys_state *child,
4909
		    const struct cgroup_subsys_state *root)
K
KAMEZAWA Hiroyuki 已提交
4910
{
4911 4912 4913
	struct css_id *child_id;
	struct css_id *root_id;
	bool ret = true;
K
KAMEZAWA Hiroyuki 已提交
4914

4915 4916 4917 4918 4919 4920 4921 4922 4923 4924
	rcu_read_lock();
	child_id  = rcu_dereference(child->id);
	root_id = rcu_dereference(root->id);
	if (!child_id
	    || !root_id
	    || (child_id->depth < root_id->depth)
	    || (child_id->stack[root_id->depth] != root_id->id))
		ret = false;
	rcu_read_unlock();
	return ret;
K
KAMEZAWA Hiroyuki 已提交
4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937
}

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);
4938
	write_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
4939
	idr_remove(&ss->idr, id->id);
4940
	write_unlock(&ss->id_lock);
4941
	kfree_rcu(id, rcu_head);
K
KAMEZAWA Hiroyuki 已提交
4942
}
B
Ben Blum 已提交
4943
EXPORT_SYMBOL_GPL(free_css_id);
K
KAMEZAWA Hiroyuki 已提交
4944 4945 4946 4947 4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960 4961 4962 4963 4964 4965

/*
 * 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;
	}
4966
	write_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
4967 4968
	/* Don't use 0. allocates an ID of 1-65535 */
	error = idr_get_new_above(&ss->idr, newid, 1, &myid);
4969
	write_unlock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983

	/* 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;
4984
	write_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
4985
	idr_remove(&ss->idr, myid);
4986
	write_unlock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
4987 4988 4989 4990 4991 4992
err_out:
	kfree(newid);
	return ERR_PTR(error);

}

4993 4994
static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
					    struct cgroup_subsys_state *rootcss)
K
KAMEZAWA Hiroyuki 已提交
4995 4996 4997
{
	struct css_id *newid;

4998
	rwlock_init(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
4999 5000 5001 5002 5003 5004 5005 5006 5007 5008 5009 5010 5011 5012 5013 5014 5015
	idr_init(&ss->idr);

	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;
5016
	struct css_id *child_id, *parent_id;
K
KAMEZAWA Hiroyuki 已提交
5017 5018 5019 5020 5021

	subsys_id = ss->subsys_id;
	parent_css = parent->subsys[subsys_id];
	child_css = child->subsys[subsys_id];
	parent_id = parent_css->id;
5022
	depth = parent_id->depth + 1;
K
KAMEZAWA Hiroyuki 已提交
5023 5024 5025 5026 5027 5028 5029 5030 5031 5032 5033 5034 5035 5036 5037 5038 5039 5040 5041 5042 5043 5044 5045 5046 5047 5048 5049 5050 5051 5052 5053 5054 5055 5056 5057 5058 5059

	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);
}
B
Ben Blum 已提交
5060
EXPORT_SYMBOL_GPL(css_lookup);
K
KAMEZAWA Hiroyuki 已提交
5061 5062 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 5074 5075 5076 5077 5078 5079 5080 5081 5082 5083 5084 5085 5086 5087 5088 5089 5090 5091 5092

/**
 * 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().
		 */
5093
		read_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5094
		tmp = idr_get_next(&ss->idr, &tmpid);
5095
		read_unlock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5096 5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107 5108 5109 5110 5111

		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;
}

S
Stephane Eranian 已提交
5112 5113 5114 5115 5116 5117 5118 5119 5120 5121 5122 5123 5124 5125 5126 5127 5128 5129 5130 5131 5132 5133 5134
/*
 * get corresponding css from file open on cgroupfs directory
 */
struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
{
	struct cgroup *cgrp;
	struct inode *inode;
	struct cgroup_subsys_state *css;

	inode = f->f_dentry->d_inode;
	/* check in cgroup filesystem dir */
	if (inode->i_op != &cgroup_dir_inode_operations)
		return ERR_PTR(-EBADF);

	if (id < 0 || id >= CGROUP_SUBSYS_COUNT)
		return ERR_PTR(-EINVAL);

	/* get cgroup */
	cgrp = __d_cgrp(f->f_dentry);
	css = cgrp->subsys[id];
	return css ? css : ERR_PTR(-ENOENT);
}

5135 5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147 5148 5149 5150 5151 5152 5153 5154 5155 5156 5157 5158 5159 5160 5161 5162 5163 5164 5165 5166 5167 5168 5169 5170 5171 5172 5173 5174 5175 5176 5177
#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;
}

5178 5179 5180 5181 5182 5183 5184 5185 5186 5187 5188 5189 5190 5191 5192 5193 5194 5195
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 = "?";
5196 5197
		seq_printf(seq, "Root %d group %s\n",
			   c->root->hierarchy_id, name);
5198 5199 5200 5201 5202 5203 5204 5205 5206 5207 5208 5209 5210 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230
	}
	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;
}

5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244 5245 5246 5247 5248 5249 5250 5251 5252 5253 5254 5255
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,
	},

5256 5257 5258 5259 5260 5261 5262 5263 5264 5265
	{
		.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,
	},

5266 5267 5268 5269 5270 5271 5272 5273 5274 5275 5276 5277 5278 5279 5280 5281 5282 5283 5284 5285
	{
		.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 */