cgroup.c 148.0 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/kthread.h>
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#include <linux/atomic.h>
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/* css deactivation bias, makes css->refcnt negative to deny new trygets */
#define CSS_DEACT_BIAS		INT_MIN

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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
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 * populated with the built in subsystems, and modular subsystems are
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 * registered after that. The mutable section of this array is protected by
 * cgroup_mutex.
 */
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#define SUBSYS(_x) [_x ## _subsys_id] = &_x ## _subsys,
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#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
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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
	 */
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	unsigned long subsys_mask;
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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 */
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	unsigned long actual_subsys_mask;
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	/* 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;

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	/* All cgroups on this root, cgroup_mutex protected */
	struct list_head allcg_list;

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	/* 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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/*
 * cgroupfs file entry, pointed to from leaf dentry->d_fsdata.
 */
struct cfent {
	struct list_head		node;
	struct dentry			*dentry;
	struct cftype			*type;
};

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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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static int css_unbias_refcnt(int refcnt)
{
	return refcnt >= 0 ? refcnt : refcnt - CSS_DEACT_BIAS;
}

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/* the current nr of refs, always >= 0 whether @css is deactivated or not */
static int css_refcnt(struct cgroup_subsys_state *css)
{
	int v = atomic_read(&css->refcnt);

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	return css_unbias_refcnt(v);
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}

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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 {
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	ROOT_NOPREFIX,	/* mounted subsystems have no named prefix */
	ROOT_XATTR,	/* supports extended attributes */
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};

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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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static inline struct cgroup *__d_cgrp(struct dentry *dentry)
{
	return dentry->d_fsdata;
}

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static inline struct cfent *__d_cfe(struct dentry *dentry)
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{
	return dentry->d_fsdata;
}

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

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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_mask & (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;

658
	struct hlist_head *hhead;
659
	struct cg_cgroup_link *link;
660

661 662
	/* First see if we already have a cgroup group that matches
	 * the desired set */
663
	read_lock(&css_set_lock);
664
	res = find_existing_css_set(oldcg, cgrp, template);
665 666
	if (res)
		get_css_set(res);
667
	read_unlock(&css_set_lock);
668 669 670 671 672 673 674 675 676 677 678 679 680 681

	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;
	}

682
	atomic_set(&res->refcount, 1);
683 684
	INIT_LIST_HEAD(&res->cg_links);
	INIT_LIST_HEAD(&res->tasks);
685
	INIT_HLIST_NODE(&res->hlist);
686 687 688 689 690 691 692

	/* 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. */
693 694 695 696 697 698
	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);
	}
699 700 701 702

	BUG_ON(!list_empty(&tmp_cg_links));

	css_set_count++;
703 704 705 706 707

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

708 709 710
	write_unlock(&css_set_lock);

	return res;
711 712
}

713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747
/*
 * 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;
}

748 749 750 751 752 753 754 755 756 757
/*
 * 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
758
 * cgroup_attach_task() can increment it again.  Because a count of zero
759 760 761 762 763 764 765 766 767 768 769 770 771
 * 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
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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.
774 775 776 777 778 779 780 781 782 783 784
 *
 * 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
785
 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
L
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 * another.  It does so using cgroup_mutex, however there are
787 788 789
 * 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
790
 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
791 792 793 794
 * 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
795
 * update of a tasks cgroup pointer by cgroup_attach_task()
796 797 798 799 800 801 802 803 804 805
 */

/**
 * 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);
807 808 809 810 811 812 813 814 815 816

/**
 * 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);
818 819 820 821 822 823 824 825

/*
 * 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.
 */

826
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
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static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);
828
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
829 830
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
			       unsigned long subsys_mask);
831
static const struct inode_operations cgroup_dir_inode_operations;
832
static const struct file_operations proc_cgroupstats_operations;
833 834

static struct backing_dev_info cgroup_backing_dev_info = {
835
	.name		= "cgroup",
836
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
837
};
838

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

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static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
843 844 845 846
{
	struct inode *inode = new_inode(sb);

	if (inode) {
847
		inode->i_ino = get_next_ino();
848
		inode->i_mode = mode;
849 850
		inode->i_uid = current_fsuid();
		inode->i_gid = current_fsgid();
851 852 853 854 855 856
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
	}
	return inode;
}

857 858 859 860
/*
 * Call subsys's pre_destroy handler.
 * This is called before css refcnt check.
 */
861
static int cgroup_call_pre_destroy(struct cgroup *cgrp)
862 863
{
	struct cgroup_subsys *ss;
864 865
	int ret = 0;

866 867 868 869 870 871 872 873 874
	for_each_subsys(cgrp->root, ss) {
		if (!ss->pre_destroy)
			continue;

		ret = ss->pre_destroy(cgrp);
		if (ret) {
			/* ->pre_destroy() failure is being deprecated */
			WARN_ON_ONCE(!ss->__DEPRECATED_clear_css_refs);
			break;
875
		}
876
	}
877

878
	return ret;
879 880
}

881 882 883 884
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)) {
885
		struct cgroup *cgrp = dentry->d_fsdata;
886
		struct cgroup_subsys *ss;
887
		BUG_ON(!(cgroup_is_removed(cgrp)));
888 889 890 891 892 893 894
		/* 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();
895 896 897 898 899

		mutex_lock(&cgroup_mutex);
		/*
		 * Release the subsystem state objects.
		 */
900
		for_each_subsys(cgrp->root, ss)
901
			ss->destroy(cgrp);
902 903 904 905

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

906
		/*
907 908
		 * Drop the active superblock reference that we took when we
		 * created the cgroup
909
		 */
910
		deactivate_super(cgrp->root->sb);
911

912 913 914 915 916 917
		/*
		 * if we're getting rid of the cgroup, refcount should ensure
		 * that there are no pidlists left.
		 */
		BUG_ON(!list_empty(&cgrp->pidlists));

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Aristeu Rozanski 已提交
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		simple_xattrs_free(&cgrp->xattrs);

920
		kfree_rcu(cgrp, rcu_head);
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Tejun Heo 已提交
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	} else {
		struct cfent *cfe = __d_cfe(dentry);
		struct cgroup *cgrp = dentry->d_parent->d_fsdata;
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		struct cftype *cft = cfe->type;
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		WARN_ONCE(!list_empty(&cfe->node) &&
			  cgrp != &cgrp->root->top_cgroup,
			  "cfe still linked for %s\n", cfe->type->name);
		kfree(cfe);
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		simple_xattrs_free(&cft->xattrs);
931 932 933 934
	}
	iput(inode);
}

935 936 937 938 939
static int cgroup_delete(const struct dentry *d)
{
	return 1;
}

940 941 942 943 944 945 946 947 948
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);
}

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static int cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
{
	struct cfent *cfe;

	lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
	lockdep_assert_held(&cgroup_mutex);

	list_for_each_entry(cfe, &cgrp->files, node) {
		struct dentry *d = cfe->dentry;

		if (cft && cfe->type != cft)
			continue;

		dget(d);
		d_delete(d);
964
		simple_unlink(cgrp->dentry->d_inode, d);
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		list_del_init(&cfe->node);
		dput(d);

		return 0;
969
	}
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970 971 972
	return -ENOENT;
}

973 974 975 976 977 978 979 980
/**
 * cgroup_clear_directory - selective removal of base and subsystem files
 * @dir: directory containing the files
 * @base_files: true if the base files should be removed
 * @subsys_mask: mask of the subsystem ids whose files should be removed
 */
static void cgroup_clear_directory(struct dentry *dir, bool base_files,
				   unsigned long subsys_mask)
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{
	struct cgroup *cgrp = __d_cgrp(dir);
983
	struct cgroup_subsys *ss;
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984

985 986 987 988 989 990 991 992 993 994 995
	for_each_subsys(cgrp->root, ss) {
		struct cftype_set *set;
		if (!test_bit(ss->subsys_id, &subsys_mask))
			continue;
		list_for_each_entry(set, &ss->cftsets, node)
			cgroup_rm_file(cgrp, set->cfts);
	}
	if (base_files) {
		while (!list_empty(&cgrp->files))
			cgroup_rm_file(cgrp, NULL);
	}
996 997 998 999 1000 1001 1002
}

/*
 * NOTE : the dentry must have been dget()'ed
 */
static void cgroup_d_remove_dir(struct dentry *dentry)
{
N
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1003
	struct dentry *parent;
1004
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
N
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1005

1006
	cgroup_clear_directory(dentry, true, root->subsys_mask);
1007

N
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1008 1009
	parent = dentry->d_parent;
	spin_lock(&parent->d_lock);
1010
	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1011
	list_del_init(&dentry->d_u.d_child);
N
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1012 1013
	spin_unlock(&dentry->d_lock);
	spin_unlock(&parent->d_lock);
1014 1015 1016
	remove_dir(dentry);
}

1017 1018 1019 1020 1021 1022
/*
 * 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.
 *
1023
 * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
1024
 */
1025
static DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
1026

1027
static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
1028
{
1029
	if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
1030 1031 1032
		wake_up_all(&cgroup_rmdir_waitq);
}

1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043
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);
}

B
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1044
/*
B
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1045 1046 1047
 * 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
Ben Blum 已提交
1048
 */
1049
static int rebind_subsystems(struct cgroupfs_root *root,
1050
			      unsigned long final_subsys_mask)
1051
{
1052
	unsigned long added_mask, removed_mask;
1053
	struct cgroup *cgrp = &root->top_cgroup;
1054 1055
	int i;

B
Ben Blum 已提交
1056
	BUG_ON(!mutex_is_locked(&cgroup_mutex));
T
Tejun Heo 已提交
1057
	BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
B
Ben Blum 已提交
1058

1059 1060
	removed_mask = root->actual_subsys_mask & ~final_subsys_mask;
	added_mask = final_subsys_mask & ~root->actual_subsys_mask;
1061 1062
	/* Check that any added subsystems are currently free */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
L
Li Zefan 已提交
1063
		unsigned long bit = 1UL << i;
1064
		struct cgroup_subsys *ss = subsys[i];
1065
		if (!(bit & added_mask))
1066
			continue;
B
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1067 1068 1069 1070 1071 1072
		/*
		 * 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);
1073 1074 1075 1076 1077 1078 1079 1080 1081 1082
		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 */
1083
	if (root->number_of_cgroups > 1)
1084 1085 1086 1087 1088 1089
		return -EBUSY;

	/* Process each subsystem */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		unsigned long bit = 1UL << i;
1090
		if (bit & added_mask) {
1091
			/* We're binding this subsystem to this hierarchy */
B
Ben Blum 已提交
1092
			BUG_ON(ss == NULL);
1093
			BUG_ON(cgrp->subsys[i]);
1094 1095
			BUG_ON(!dummytop->subsys[i]);
			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1096 1097
			cgrp->subsys[i] = dummytop->subsys[i];
			cgrp->subsys[i]->cgroup = cgrp;
1098
			list_move(&ss->sibling, &root->subsys_list);
1099
			ss->root = root;
1100
			if (ss->bind)
1101
				ss->bind(cgrp);
B
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1102
			/* refcount was already taken, and we're keeping it */
1103
		} else if (bit & removed_mask) {
1104
			/* We're removing this subsystem */
B
Ben Blum 已提交
1105
			BUG_ON(ss == NULL);
1106 1107
			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1108
			if (ss->bind)
1109
				ss->bind(dummytop);
1110
			dummytop->subsys[i]->cgroup = dummytop;
1111
			cgrp->subsys[i] = NULL;
1112
			subsys[i]->root = &rootnode;
1113
			list_move(&ss->sibling, &rootnode.subsys_list);
B
Ben Blum 已提交
1114 1115
			/* subsystem is now free - drop reference on module */
			module_put(ss->module);
1116
		} else if (bit & final_subsys_mask) {
1117
			/* Subsystem state should already exist */
B
Ben Blum 已提交
1118
			BUG_ON(ss == NULL);
1119
			BUG_ON(!cgrp->subsys[i]);
B
Ben Blum 已提交
1120 1121 1122 1123 1124 1125 1126 1127
			/*
			 * 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
1128 1129
		} else {
			/* Subsystem state shouldn't exist */
1130
			BUG_ON(cgrp->subsys[i]);
1131 1132
		}
	}
1133
	root->subsys_mask = root->actual_subsys_mask = final_subsys_mask;
1134 1135 1136 1137 1138
	synchronize_rcu();

	return 0;
}

1139
static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1140
{
1141
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1142 1143
	struct cgroup_subsys *ss;

T
Tejun Heo 已提交
1144
	mutex_lock(&cgroup_root_mutex);
1145 1146 1147 1148
	for_each_subsys(root, ss)
		seq_printf(seq, ",%s", ss->name);
	if (test_bit(ROOT_NOPREFIX, &root->flags))
		seq_puts(seq, ",noprefix");
A
Aristeu Rozanski 已提交
1149 1150
	if (test_bit(ROOT_XATTR, &root->flags))
		seq_puts(seq, ",xattr");
1151 1152
	if (strlen(root->release_agent_path))
		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1153 1154
	if (clone_children(&root->top_cgroup))
		seq_puts(seq, ",clone_children");
1155 1156
	if (strlen(root->name))
		seq_printf(seq, ",name=%s", root->name);
T
Tejun Heo 已提交
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	mutex_unlock(&cgroup_root_mutex);
1158 1159 1160 1161
	return 0;
}

struct cgroup_sb_opts {
1162
	unsigned long subsys_mask;
1163
	unsigned long flags;
1164
	char *release_agent;
1165
	bool clone_children;
1166
	char *name;
1167 1168
	/* User explicitly requested empty subsystem */
	bool none;
1169 1170

	struct cgroupfs_root *new_root;
1171

1172 1173
};

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/*
 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
B
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1176 1177 1178
 * 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
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1179
 */
B
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1180
static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1181
{
1182 1183
	char *token, *o = data;
	bool all_ss = false, one_ss = false;
1184
	unsigned long mask = (unsigned long)-1;
B
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1185 1186
	int i;
	bool module_pin_failed = false;
1187

B
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1188 1189
	BUG_ON(!mutex_is_locked(&cgroup_mutex));

1190 1191 1192
#ifdef CONFIG_CPUSETS
	mask = ~(1UL << cpuset_subsys_id);
#endif
1193

1194
	memset(opts, 0, sizeof(*opts));
1195 1196 1197 1198

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
1199
		if (!strcmp(token, "none")) {
1200 1201
			/* Explicitly have no subsystems */
			opts->none = true;
1202 1203 1204 1205 1206 1207 1208 1209 1210 1211
			continue;
		}
		if (!strcmp(token, "all")) {
			/* Mutually exclusive option 'all' + subsystem name */
			if (one_ss)
				return -EINVAL;
			all_ss = true;
			continue;
		}
		if (!strcmp(token, "noprefix")) {
1212
			set_bit(ROOT_NOPREFIX, &opts->flags);
1213 1214 1215
			continue;
		}
		if (!strcmp(token, "clone_children")) {
1216
			opts->clone_children = true;
1217 1218
			continue;
		}
A
Aristeu Rozanski 已提交
1219 1220 1221 1222
		if (!strcmp(token, "xattr")) {
			set_bit(ROOT_XATTR, &opts->flags);
			continue;
		}
1223
		if (!strncmp(token, "release_agent=", 14)) {
1224 1225 1226
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1227
			opts->release_agent =
1228
				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1229 1230
			if (!opts->release_agent)
				return -ENOMEM;
1231 1232 1233
			continue;
		}
		if (!strncmp(token, "name=", 5)) {
1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250
			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,
1251
					      MAX_CGROUP_ROOT_NAMELEN - 1,
1252 1253 1254
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270

			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;
1271
			set_bit(i, &opts->subsys_mask);
1272 1273 1274 1275 1276 1277 1278 1279 1280 1281
			one_ss = true;

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

	/*
	 * If the 'all' option was specified select all the subsystems,
1282 1283
	 * otherwise if 'none', 'name=' and a subsystem name options
	 * were not specified, let's default to 'all'
1284
	 */
1285
	if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1286 1287 1288 1289 1290 1291
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss == NULL)
				continue;
			if (ss->disabled)
				continue;
1292
			set_bit(i, &opts->subsys_mask);
1293 1294 1295
		}
	}

1296 1297
	/* Consistency checks */

1298 1299 1300 1301 1302 1303
	/*
	 * 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) &&
1304
	    (opts->subsys_mask & mask))
1305 1306
		return -EINVAL;

1307 1308

	/* Can't specify "none" and some subsystems */
1309
	if (opts->subsys_mask && opts->none)
1310 1311 1312 1313 1314 1315
		return -EINVAL;

	/*
	 * We either have to specify by name or by subsystems. (So all
	 * empty hierarchies must have a name).
	 */
1316
	if (!opts->subsys_mask && !opts->name)
1317 1318
		return -EINVAL;

B
Ben Blum 已提交
1319 1320 1321 1322 1323 1324
	/*
	 * 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.
	 */
1325
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
B
Ben Blum 已提交
1326 1327
		unsigned long bit = 1UL << i;

1328
		if (!(bit & opts->subsys_mask))
B
Ben Blum 已提交
1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340
			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.
		 */
1341
		for (i--; i >= 0; i--) {
B
Ben Blum 已提交
1342 1343 1344
			/* drop refcounts only on the ones we took */
			unsigned long bit = 1UL << i;

1345
			if (!(bit & opts->subsys_mask))
B
Ben Blum 已提交
1346 1347 1348 1349 1350 1351
				continue;
			module_put(subsys[i]->module);
		}
		return -ENOENT;
	}

1352 1353 1354
	return 0;
}

1355
static void drop_parsed_module_refcounts(unsigned long subsys_mask)
B
Ben Blum 已提交
1356 1357
{
	int i;
1358
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
B
Ben Blum 已提交
1359 1360
		unsigned long bit = 1UL << i;

1361
		if (!(bit & subsys_mask))
B
Ben Blum 已提交
1362 1363 1364 1365 1366
			continue;
		module_put(subsys[i]->module);
	}
}

1367 1368 1369 1370
static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
	int ret = 0;
	struct cgroupfs_root *root = sb->s_fs_info;
1371
	struct cgroup *cgrp = &root->top_cgroup;
1372
	struct cgroup_sb_opts opts;
1373
	unsigned long added_mask, removed_mask;
1374

1375
	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1376
	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1377
	mutex_lock(&cgroup_root_mutex);
1378 1379 1380 1381 1382 1383

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

1384
	/* See feature-removal-schedule.txt */
1385
	if (opts.subsys_mask != root->actual_subsys_mask || opts.release_agent)
1386 1387 1388
		pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
			   task_tgid_nr(current), current->comm);

1389 1390
	added_mask = opts.subsys_mask & ~root->subsys_mask;
	removed_mask = root->subsys_mask & ~opts.subsys_mask;
1391

B
Ben Blum 已提交
1392 1393 1394
	/* Don't allow flags or name to change at remount */
	if (opts.flags != root->flags ||
	    (opts.name && strcmp(opts.name, root->name))) {
1395
		ret = -EINVAL;
1396
		drop_parsed_module_refcounts(opts.subsys_mask);
1397 1398 1399
		goto out_unlock;
	}

1400
	ret = rebind_subsystems(root, opts.subsys_mask);
B
Ben Blum 已提交
1401
	if (ret) {
1402
		drop_parsed_module_refcounts(opts.subsys_mask);
1403
		goto out_unlock;
B
Ben Blum 已提交
1404
	}
1405

1406
	/* clear out any existing files and repopulate subsystem files */
1407
	cgroup_clear_directory(cgrp->dentry, false, removed_mask);
1408
	/* re-populate subsystem files */
1409
	cgroup_populate_dir(cgrp, false, added_mask);
1410

1411 1412
	if (opts.release_agent)
		strcpy(root->release_agent_path, opts.release_agent);
1413
 out_unlock:
1414
	kfree(opts.release_agent);
1415
	kfree(opts.name);
T
Tejun Heo 已提交
1416
	mutex_unlock(&cgroup_root_mutex);
1417
	mutex_unlock(&cgroup_mutex);
1418
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1419 1420 1421
	return ret;
}

1422
static const struct super_operations cgroup_ops = {
1423 1424 1425 1426 1427 1428
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.show_options = cgroup_show_options,
	.remount_fs = cgroup_remount,
};

1429 1430 1431 1432
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
	INIT_LIST_HEAD(&cgrp->sibling);
	INIT_LIST_HEAD(&cgrp->children);
T
Tejun Heo 已提交
1433
	INIT_LIST_HEAD(&cgrp->files);
1434 1435
	INIT_LIST_HEAD(&cgrp->css_sets);
	INIT_LIST_HEAD(&cgrp->release_list);
1436 1437
	INIT_LIST_HEAD(&cgrp->pidlists);
	mutex_init(&cgrp->pidlist_mutex);
1438 1439
	INIT_LIST_HEAD(&cgrp->event_list);
	spin_lock_init(&cgrp->event_list_lock);
A
Aristeu Rozanski 已提交
1440
	simple_xattrs_init(&cgrp->xattrs);
1441
}
1442

1443 1444
static void init_cgroup_root(struct cgroupfs_root *root)
{
1445
	struct cgroup *cgrp = &root->top_cgroup;
1446

1447 1448
	INIT_LIST_HEAD(&root->subsys_list);
	INIT_LIST_HEAD(&root->root_list);
1449
	INIT_LIST_HEAD(&root->allcg_list);
1450
	root->number_of_cgroups = 1;
1451 1452
	cgrp->root = root;
	cgrp->top_cgroup = cgrp;
1453
	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1454
	init_cgroup_housekeeping(cgrp);
1455 1456
}

1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481
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;
}

1482 1483
static int cgroup_test_super(struct super_block *sb, void *data)
{
1484
	struct cgroup_sb_opts *opts = data;
1485 1486
	struct cgroupfs_root *root = sb->s_fs_info;

1487 1488 1489
	/* If we asked for a name then it must match */
	if (opts->name && strcmp(opts->name, root->name))
		return 0;
1490

1491 1492 1493 1494
	/*
	 * If we asked for subsystems (or explicitly for no
	 * subsystems) then they must match
	 */
1495 1496
	if ((opts->subsys_mask || opts->none)
	    && (opts->subsys_mask != root->subsys_mask))
1497 1498 1499 1500 1501
		return 0;

	return 1;
}

1502 1503 1504 1505
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
	struct cgroupfs_root *root;

1506
	if (!opts->subsys_mask && !opts->none)
1507 1508 1509 1510 1511 1512
		return NULL;

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

1513 1514 1515 1516
	if (!init_root_id(root)) {
		kfree(root);
		return ERR_PTR(-ENOMEM);
	}
1517
	init_cgroup_root(root);
1518

1519
	root->subsys_mask = opts->subsys_mask;
1520 1521 1522 1523 1524
	root->flags = opts->flags;
	if (opts->release_agent)
		strcpy(root->release_agent_path, opts->release_agent);
	if (opts->name)
		strcpy(root->name, opts->name);
1525 1526
	if (opts->clone_children)
		set_bit(CGRP_CLONE_CHILDREN, &root->top_cgroup.flags);
1527 1528 1529
	return root;
}

1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541
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);
}

1542 1543 1544
static int cgroup_set_super(struct super_block *sb, void *data)
{
	int ret;
1545 1546 1547 1548 1549 1550
	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;

1551
	BUG_ON(!opts->subsys_mask && !opts->none);
1552 1553 1554 1555 1556

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

1557 1558
	sb->s_fs_info = opts->new_root;
	opts->new_root->sb = sb;
1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569

	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
1570 1571
	static const struct dentry_operations cgroup_dops = {
		.d_iput = cgroup_diput,
1572
		.d_delete = cgroup_delete,
A
Al Viro 已提交
1573 1574
	};

1575 1576 1577 1578 1579 1580 1581 1582 1583 1584
	struct inode *inode =
		cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);

	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);
1585 1586
	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
1587
		return -ENOMEM;
A
Al Viro 已提交
1588 1589
	/* for everything else we want ->d_op set */
	sb->s_d_op = &cgroup_dops;
1590 1591 1592
	return 0;
}

A
Al Viro 已提交
1593
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1594
			 int flags, const char *unused_dev_name,
A
Al Viro 已提交
1595
			 void *data)
1596 1597
{
	struct cgroup_sb_opts opts;
1598
	struct cgroupfs_root *root;
1599 1600
	int ret = 0;
	struct super_block *sb;
1601
	struct cgroupfs_root *new_root;
T
Tejun Heo 已提交
1602
	struct inode *inode;
1603 1604

	/* First find the desired set of subsystems */
B
Ben Blum 已提交
1605
	mutex_lock(&cgroup_mutex);
1606
	ret = parse_cgroupfs_options(data, &opts);
B
Ben Blum 已提交
1607
	mutex_unlock(&cgroup_mutex);
1608 1609
	if (ret)
		goto out_err;
1610

1611 1612 1613 1614 1615 1616 1617
	/*
	 * 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
1618
		goto drop_modules;
1619
	}
1620
	opts.new_root = new_root;
1621

1622
	/* Locate an existing or new sb for this hierarchy */
D
David Howells 已提交
1623
	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
1624
	if (IS_ERR(sb)) {
1625
		ret = PTR_ERR(sb);
1626
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1627
		goto drop_modules;
1628 1629
	}

1630 1631 1632 1633 1634
	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;
1635
		struct cgroup *root_cgrp = &root->top_cgroup;
1636
		struct cgroupfs_root *existing_root;
1637
		const struct cred *cred;
1638
		int i;
1639 1640 1641 1642 1643 1644

		BUG_ON(sb->s_root != NULL);

		ret = cgroup_get_rootdir(sb);
		if (ret)
			goto drop_new_super;
1645
		inode = sb->s_root->d_inode;
1646

1647
		mutex_lock(&inode->i_mutex);
1648
		mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1649
		mutex_lock(&cgroup_root_mutex);
1650

T
Tejun Heo 已提交
1651 1652 1653 1654 1655 1656
		/* 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;
1657

1658 1659 1660 1661 1662 1663 1664 1665
		/*
		 * 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
1666 1667
		if (ret)
			goto unlock_drop;
1668

1669
		ret = rebind_subsystems(root, root->subsys_mask);
1670
		if (ret == -EBUSY) {
1671
			free_cg_links(&tmp_cg_links);
T
Tejun Heo 已提交
1672
			goto unlock_drop;
1673
		}
B
Ben Blum 已提交
1674 1675 1676 1677 1678
		/*
		 * There must be no failure case after here, since rebinding
		 * takes care of subsystems' refcounts, which are explicitly
		 * dropped in the failure exit path.
		 */
1679 1680 1681 1682 1683

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

		list_add(&root->root_list, &roots);
1684
		root_count++;
1685

1686
		sb->s_root->d_fsdata = root_cgrp;
1687 1688
		root->top_cgroup.dentry = sb->s_root;

1689 1690 1691
		/* Link the top cgroup in this hierarchy into all
		 * the css_set objects */
		write_lock(&css_set_lock);
1692 1693 1694
		for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
			struct hlist_head *hhead = &css_set_table[i];
			struct hlist_node *node;
1695
			struct css_set *cg;
1696

1697 1698
			hlist_for_each_entry(cg, node, hhead, hlist)
				link_css_set(&tmp_cg_links, cg, root_cgrp);
1699
		}
1700 1701 1702 1703
		write_unlock(&css_set_lock);

		free_cg_links(&tmp_cg_links);

1704 1705
		BUG_ON(!list_empty(&root_cgrp->sibling));
		BUG_ON(!list_empty(&root_cgrp->children));
1706 1707
		BUG_ON(root->number_of_cgroups != 1);

1708
		cred = override_creds(&init_cred);
1709
		cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
1710
		revert_creds(cred);
T
Tejun Heo 已提交
1711
		mutex_unlock(&cgroup_root_mutex);
1712
		mutex_unlock(&cgroup_mutex);
1713
		mutex_unlock(&inode->i_mutex);
1714 1715 1716 1717 1718
	} else {
		/*
		 * We re-used an existing hierarchy - the new root (if
		 * any) is not needed
		 */
1719
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1720
		/* no subsys rebinding, so refcounts don't change */
1721
		drop_parsed_module_refcounts(opts.subsys_mask);
1722 1723
	}

1724 1725
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1726
	return dget(sb->s_root);
1727

T
Tejun Heo 已提交
1728 1729 1730 1731
 unlock_drop:
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&inode->i_mutex);
1732
 drop_new_super:
1733
	deactivate_locked_super(sb);
B
Ben Blum 已提交
1734
 drop_modules:
1735
	drop_parsed_module_refcounts(opts.subsys_mask);
1736 1737 1738
 out_err:
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1739
	return ERR_PTR(ret);
1740 1741 1742 1743
}

static void cgroup_kill_sb(struct super_block *sb) {
	struct cgroupfs_root *root = sb->s_fs_info;
1744
	struct cgroup *cgrp = &root->top_cgroup;
1745
	int ret;
K
KOSAKI Motohiro 已提交
1746 1747
	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;
1748 1749 1750 1751

	BUG_ON(!root);

	BUG_ON(root->number_of_cgroups != 1);
1752 1753
	BUG_ON(!list_empty(&cgrp->children));
	BUG_ON(!list_empty(&cgrp->sibling));
1754 1755

	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1756
	mutex_lock(&cgroup_root_mutex);
1757 1758 1759 1760 1761 1762

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

1763 1764 1765 1766 1767
	/*
	 * Release all the links from css_sets to this hierarchy's
	 * root cgroup
	 */
	write_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
1768 1769 1770

	list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
				 cgrp_link_list) {
1771
		list_del(&link->cg_link_list);
1772
		list_del(&link->cgrp_link_list);
1773 1774 1775 1776
		kfree(link);
	}
	write_unlock(&css_set_lock);

1777 1778 1779 1780
	if (!list_empty(&root->root_list)) {
		list_del(&root->root_list);
		root_count--;
	}
1781

T
Tejun Heo 已提交
1782
	mutex_unlock(&cgroup_root_mutex);
1783 1784
	mutex_unlock(&cgroup_mutex);

A
Aristeu Rozanski 已提交
1785 1786
	simple_xattrs_free(&cgrp->xattrs);

1787
	kill_litter_super(sb);
1788
	cgroup_drop_root(root);
1789 1790 1791 1792
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
A
Al Viro 已提交
1793
	.mount = cgroup_mount,
1794 1795 1796
	.kill_sb = cgroup_kill_sb,
};

1797 1798
static struct kobject *cgroup_kobj;

L
Li Zefan 已提交
1799 1800 1801 1802 1803 1804
/**
 * 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
 *
1805 1806 1807
 * 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.
1808
 */
1809
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1810 1811
{
	char *start;
1812 1813
	struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
						      cgroup_lock_is_held());
1814

1815
	if (!dentry || cgrp == dummytop) {
1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827
		/*
		 * Inactive subsystems have no dentry for their root
		 * cgroup
		 */
		strcpy(buf, "/");
		return 0;
	}

	start = buf + buflen;

	*--start = '\0';
	for (;;) {
1828
		int len = dentry->d_name.len;
1829

1830 1831
		if ((start -= len) < buf)
			return -ENAMETOOLONG;
1832
		memcpy(start, dentry->d_name.name, len);
1833 1834
		cgrp = cgrp->parent;
		if (!cgrp)
1835
			break;
1836 1837 1838

		dentry = rcu_dereference_check(cgrp->dentry,
					       cgroup_lock_is_held());
1839
		if (!cgrp->parent)
1840 1841 1842 1843 1844 1845 1846 1847
			continue;
		if (--start < buf)
			return -ENAMETOOLONG;
		*start = '/';
	}
	memmove(buf, start, buf + buflen - start);
	return 0;
}
B
Ben Blum 已提交
1848
EXPORT_SYMBOL_GPL(cgroup_path);
1849

1850 1851 1852
/*
 * Control Group taskset
 */
1853 1854 1855
struct task_and_cgroup {
	struct task_struct	*task;
	struct cgroup		*cgrp;
1856
	struct css_set		*cg;
1857 1858
};

1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929
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
1930 1931 1932 1933 1934
/*
 * 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
1935
 * -ENOMEM. Must be called with cgroup_mutex and threadgroup locked.
B
Ben Blum 已提交
1936
 */
1937 1938
static void cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
				struct task_struct *tsk, struct css_set *newcg)
B
Ben Blum 已提交
1939 1940 1941 1942
{
	struct css_set *oldcg;

	/*
1943 1944 1945
	 * 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
1946
	 */
1947
	WARN_ON_ONCE(tsk->flags & PF_EXITING);
B
Ben Blum 已提交
1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969
	oldcg = tsk->cgroups;

	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);
}

L
Li Zefan 已提交
1970 1971 1972 1973
/**
 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
 * @cgrp: the cgroup the task is attaching to
 * @tsk: the task to be attached
1974
 *
1975 1976
 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
 * @tsk during call.
1977
 */
1978
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1979
{
1980
	int retval = 0;
1981
	struct cgroup_subsys *ss, *failed_ss = NULL;
1982 1983
	struct cgroup *oldcgrp;
	struct cgroupfs_root *root = cgrp->root;
1984
	struct cgroup_taskset tset = { };
1985
	struct css_set *newcg;
1986

1987 1988 1989
	/* @tsk either already exited or can't exit until the end */
	if (tsk->flags & PF_EXITING)
		return -ESRCH;
1990 1991

	/* Nothing to do if the task is already in that cgroup */
1992
	oldcgrp = task_cgroup_from_root(tsk, root);
1993
	if (cgrp == oldcgrp)
1994 1995
		return 0;

1996 1997 1998
	tset.single.task = tsk;
	tset.single.cgrp = oldcgrp;

1999 2000
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
2001
			retval = ss->can_attach(cgrp, &tset);
2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
			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;
			}
2012 2013 2014
		}
	}

2015 2016 2017
	newcg = find_css_set(tsk->cgroups, cgrp);
	if (!newcg) {
		retval = -ENOMEM;
2018
		goto out;
2019 2020 2021
	}

	cgroup_task_migrate(cgrp, oldcgrp, tsk, newcg);
2022

2023
	for_each_subsys(root, ss) {
P
Paul Jackson 已提交
2024
		if (ss->attach)
2025
			ss->attach(cgrp, &tset);
2026
	}
B
Ben Blum 已提交
2027

2028
	synchronize_rcu();
2029 2030 2031 2032 2033

	/*
	 * wake up rmdir() waiter. the rmdir should fail since the cgroup
	 * is no longer empty.
	 */
2034
	cgroup_wakeup_rmdir_waiter(cgrp);
2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046
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)
2047
				ss->cancel_attach(cgrp, &tset);
2048 2049 2050
		}
	}
	return retval;
2051 2052
}

2053
/**
M
Michael S. Tsirkin 已提交
2054 2055
 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
 * @from: attach to all cgroups of a given task
2056 2057
 * @tsk: the task to be attached
 */
M
Michael S. Tsirkin 已提交
2058
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2059 2060 2061 2062 2063 2064
{
	struct cgroupfs_root *root;
	int retval = 0;

	cgroup_lock();
	for_each_active_root(root) {
M
Michael S. Tsirkin 已提交
2065 2066 2067
		struct cgroup *from_cg = task_cgroup_from_root(from, root);

		retval = cgroup_attach_task(from_cg, tsk);
2068 2069 2070 2071 2072 2073 2074
		if (retval)
			break;
	}
	cgroup_unlock();

	return retval;
}
M
Michael S. Tsirkin 已提交
2075
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2076

B
Ben Blum 已提交
2077 2078 2079 2080 2081
/**
 * 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
 *
2082 2083
 * 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
2084
 */
2085
static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
B
Ben Blum 已提交
2086 2087 2088 2089 2090 2091 2092
{
	int retval, i, group_size;
	struct cgroup_subsys *ss, *failed_ss = NULL;
	/* guaranteed to be initialized later, but the compiler needs this */
	struct cgroupfs_root *root = cgrp->root;
	/* threadgroup list cursor and array */
	struct task_struct *tsk;
2093
	struct task_and_cgroup *tc;
2094
	struct flex_array *group;
2095
	struct cgroup_taskset tset = { };
B
Ben Blum 已提交
2096 2097 2098 2099 2100

	/*
	 * 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
2101 2102
	 * 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
2103 2104
	 */
	group_size = get_nr_threads(leader);
2105
	/* flex_array supports very large thread-groups better than kmalloc. */
2106
	group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
B
Ben Blum 已提交
2107 2108
	if (!group)
		return -ENOMEM;
2109 2110 2111 2112
	/* 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
2113 2114 2115

	tsk = leader;
	i = 0;
2116 2117 2118 2119 2120 2121
	/*
	 * Prevent freeing of tasks while we take a snapshot. Tasks that are
	 * already PF_EXITING could be freed from underneath us unless we
	 * take an rcu_read_lock.
	 */
	rcu_read_lock();
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
		ent.task = tsk;
		ent.cgrp = task_cgroup_from_root(tsk, root);
2133 2134 2135
		/* nothing to do if this task is already in the cgroup */
		if (ent.cgrp == cgrp)
			continue;
2136 2137 2138 2139
		/*
		 * saying GFP_ATOMIC has no effect here because we did prealloc
		 * earlier, but it's good form to communicate our expectations.
		 */
2140
		retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2141
		BUG_ON(retval != 0);
B
Ben Blum 已提交
2142 2143
		i++;
	} while_each_thread(leader, tsk);
2144
	rcu_read_unlock();
B
Ben Blum 已提交
2145 2146
	/* remember the number of threads in the array for later. */
	group_size = i;
2147 2148
	tset.tc_array = group;
	tset.tc_array_len = group_size;
B
Ben Blum 已提交
2149

2150 2151
	/* methods shouldn't be called if no task is actually migrating */
	retval = 0;
2152
	if (!group_size)
2153
		goto out_free_group_list;
2154

B
Ben Blum 已提交
2155 2156 2157 2158 2159
	/*
	 * step 1: check that we can legitimately attach to the cgroup.
	 */
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
2160
			retval = ss->can_attach(cgrp, &tset);
B
Ben Blum 已提交
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.
	 */
	for (i = 0; i < group_size; i++) {
2173
		tc = flex_array_get(group, i);
2174 2175 2176 2177
		tc->cg = find_css_set(tc->task->cgroups, cgrp);
		if (!tc->cg) {
			retval = -ENOMEM;
			goto out_put_css_set_refs;
B
Ben Blum 已提交
2178 2179 2180 2181
		}
	}

	/*
2182 2183 2184
	 * 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
2185 2186
	 */
	for (i = 0; i < group_size; i++) {
2187
		tc = flex_array_get(group, i);
2188
		cgroup_task_migrate(cgrp, tc->cgrp, tc->task, tc->cg);
B
Ben Blum 已提交
2189 2190 2191 2192
	}
	/* nothing is sensitive to fork() after this point. */

	/*
2193
	 * step 4: do subsystem attach callbacks.
B
Ben Blum 已提交
2194 2195 2196
	 */
	for_each_subsys(root, ss) {
		if (ss->attach)
2197
			ss->attach(cgrp, &tset);
B
Ben Blum 已提交
2198 2199 2200 2201 2202 2203 2204 2205
	}

	/*
	 * step 5: success! and cleanup
	 */
	synchronize_rcu();
	cgroup_wakeup_rmdir_waiter(cgrp);
	retval = 0;
2206 2207 2208 2209 2210 2211 2212 2213
out_put_css_set_refs:
	if (retval) {
		for (i = 0; i < group_size; i++) {
			tc = flex_array_get(group, i);
			if (!tc->cg)
				break;
			put_css_set(tc->cg);
		}
B
Ben Blum 已提交
2214 2215 2216 2217
	}
out_cancel_attach:
	if (retval) {
		for_each_subsys(root, ss) {
2218
			if (ss == failed_ss)
B
Ben Blum 已提交
2219 2220
				break;
			if (ss->cancel_attach)
2221
				ss->cancel_attach(cgrp, &tset);
B
Ben Blum 已提交
2222 2223 2224
		}
	}
out_free_group_list:
2225
	flex_array_free(group);
B
Ben Blum 已提交
2226 2227 2228 2229 2230
	return retval;
}

/*
 * Find the task_struct of the task to attach by vpid and pass it along to the
2231 2232
 * function to attach either it or all tasks in its threadgroup. Will lock
 * cgroup_mutex and threadgroup; may take task_lock of task.
2233
 */
B
Ben Blum 已提交
2234
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2235 2236
{
	struct task_struct *tsk;
2237
	const struct cred *cred = current_cred(), *tcred;
2238 2239
	int ret;

B
Ben Blum 已提交
2240 2241 2242
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;

2243 2244
retry_find_task:
	rcu_read_lock();
2245
	if (pid) {
2246
		tsk = find_task_by_vpid(pid);
B
Ben Blum 已提交
2247 2248
		if (!tsk) {
			rcu_read_unlock();
2249 2250
			ret= -ESRCH;
			goto out_unlock_cgroup;
2251
		}
B
Ben Blum 已提交
2252 2253 2254 2255
		/*
		 * even if we're attaching all tasks in the thread group, we
		 * only need to check permissions on one of them.
		 */
2256
		tcred = __task_cred(tsk);
2257 2258 2259
		if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
		    !uid_eq(cred->euid, tcred->uid) &&
		    !uid_eq(cred->euid, tcred->suid)) {
2260
			rcu_read_unlock();
2261 2262
			ret = -EACCES;
			goto out_unlock_cgroup;
2263
		}
2264 2265
	} else
		tsk = current;
2266 2267

	if (threadgroup)
2268
		tsk = tsk->group_leader;
2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280

	/*
	 * Workqueue threads may acquire PF_THREAD_BOUND and become
	 * trapped in a cpuset, or RT worker may be born in a cgroup
	 * with no rt_runtime allocated.  Just say no.
	 */
	if (tsk == kthreadd_task || (tsk->flags & PF_THREAD_BOUND)) {
		ret = -EINVAL;
		rcu_read_unlock();
		goto out_unlock_cgroup;
	}

2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297
	get_task_struct(tsk);
	rcu_read_unlock();

	threadgroup_lock(tsk);
	if (threadgroup) {
		if (!thread_group_leader(tsk)) {
			/*
			 * a race with de_thread from another thread's exec()
			 * may strip us of our leadership, if this happens,
			 * there is no choice but to throw this task away and
			 * try again; this is
			 * "double-double-toil-and-trouble-check locking".
			 */
			threadgroup_unlock(tsk);
			put_task_struct(tsk);
			goto retry_find_task;
		}
B
Ben Blum 已提交
2298
		ret = cgroup_attach_proc(cgrp, tsk);
2299
	} else
B
Ben Blum 已提交
2300
		ret = cgroup_attach_task(cgrp, tsk);
2301 2302
	threadgroup_unlock(tsk);

2303
	put_task_struct(tsk);
2304
out_unlock_cgroup:
B
Ben Blum 已提交
2305
	cgroup_unlock();
2306 2307 2308
	return ret;
}

2309
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
B
Ben Blum 已提交
2310 2311 2312 2313 2314
{
	return attach_task_by_pid(cgrp, pid, false);
}

static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2315
{
2316
	return attach_task_by_pid(cgrp, tgid, true);
2317 2318
}

2319 2320 2321 2322
/**
 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
 * @cgrp: the cgroup to be checked for liveness
 *
2323 2324
 * On success, returns true; the lock should be later released with
 * cgroup_unlock(). On failure returns false with no lock held.
2325
 */
2326
bool cgroup_lock_live_group(struct cgroup *cgrp)
2327 2328 2329 2330 2331 2332 2333 2334
{
	mutex_lock(&cgroup_mutex);
	if (cgroup_is_removed(cgrp)) {
		mutex_unlock(&cgroup_mutex);
		return false;
	}
	return true;
}
B
Ben Blum 已提交
2335
EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2336 2337 2338 2339 2340

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);
2341 2342
	if (strlen(buffer) >= PATH_MAX)
		return -EINVAL;
2343 2344
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
T
Tejun Heo 已提交
2345
	mutex_lock(&cgroup_root_mutex);
2346
	strcpy(cgrp->root->release_agent_path, buffer);
T
Tejun Heo 已提交
2347
	mutex_unlock(&cgroup_root_mutex);
2348
	cgroup_unlock();
2349 2350 2351 2352 2353 2354 2355 2356 2357 2358
	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');
2359
	cgroup_unlock();
2360 2361 2362
	return 0;
}

2363 2364 2365
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64

2366
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2367 2368 2369
				struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *unused_ppos)
2370
{
2371
	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382
	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 */
2383
	if (cft->write_u64) {
K
KOSAKI Motohiro 已提交
2384
		u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2385 2386 2387 2388
		if (*end)
			return -EINVAL;
		retval = cft->write_u64(cgrp, cft, val);
	} else {
K
KOSAKI Motohiro 已提交
2389
		s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2390 2391 2392 2393
		if (*end)
			return -EINVAL;
		retval = cft->write_s64(cgrp, cft, val);
	}
2394 2395 2396 2397 2398
	if (!retval)
		retval = nbytes;
	return retval;
}

2399 2400 2401 2402 2403
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)
{
2404
	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418
	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
2419 2420 2421 2422
	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
		retval = -EFAULT;
		goto out;
	}
2423 2424

	buffer[nbytes] = 0;     /* nul-terminate */
K
KOSAKI Motohiro 已提交
2425
	retval = cft->write_string(cgrp, cft, strstrip(buffer));
2426 2427
	if (!retval)
		retval = nbytes;
L
Li Zefan 已提交
2428
out:
2429 2430 2431 2432 2433
	if (buffer != local_buffer)
		kfree(buffer);
	return retval;
}

2434 2435 2436 2437
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);
2438
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2439

2440
	if (cgroup_is_removed(cgrp))
2441
		return -ENODEV;
2442
	if (cft->write)
2443
		return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2444 2445
	if (cft->write_u64 || cft->write_s64)
		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2446 2447
	if (cft->write_string)
		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2448 2449 2450 2451
	if (cft->trigger) {
		int ret = cft->trigger(cgrp, (unsigned int)cft->private);
		return ret ? ret : nbytes;
	}
2452
	return -EINVAL;
2453 2454
}

2455 2456 2457 2458
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
2459
{
2460
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2461
	u64 val = cft->read_u64(cgrp, cft);
2462 2463 2464 2465 2466
	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);

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

2467 2468 2469 2470 2471
static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
{
2472
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2473 2474 2475 2476 2477 2478
	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);
}

2479 2480 2481 2482
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);
2483
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2484

2485
	if (cgroup_is_removed(cgrp))
2486 2487 2488
		return -ENODEV;

	if (cft->read)
2489
		return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2490 2491
	if (cft->read_u64)
		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2492 2493
	if (cft->read_s64)
		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2494 2495 2496
	return -EINVAL;
}

2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516
/*
 * 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;
2517 2518 2519 2520 2521 2522 2523 2524
	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);
2525 2526
}

2527
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2528 2529 2530 2531 2532 2533
{
	struct seq_file *seq = file->private_data;
	kfree(seq->private);
	return single_release(inode, file);
}

2534
static const struct file_operations cgroup_seqfile_operations = {
2535
	.read = seq_read,
2536
	.write = cgroup_file_write,
2537 2538 2539 2540
	.llseek = seq_lseek,
	.release = cgroup_seqfile_release,
};

2541 2542 2543 2544 2545 2546 2547 2548 2549
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);
2550

2551
	if (cft->read_map || cft->read_seq_string) {
2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562
		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)
2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592
		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);
}

A
Aristeu Rozanski 已提交
2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615 2616 2617 2618 2619 2620 2621 2622 2623 2624 2625 2626 2627 2628 2629 2630 2631 2632 2633 2634 2635 2636 2637 2638 2639 2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650
static struct simple_xattrs *__d_xattrs(struct dentry *dentry)
{
	if (S_ISDIR(dentry->d_inode->i_mode))
		return &__d_cgrp(dentry)->xattrs;
	else
		return &__d_cft(dentry)->xattrs;
}

static inline int xattr_enabled(struct dentry *dentry)
{
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
	return test_bit(ROOT_XATTR, &root->flags);
}

static bool is_valid_xattr(const char *name)
{
	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
	    !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN))
		return true;
	return false;
}

static int cgroup_setxattr(struct dentry *dentry, const char *name,
			   const void *val, size_t size, int flags)
{
	if (!xattr_enabled(dentry))
		return -EOPNOTSUPP;
	if (!is_valid_xattr(name))
		return -EINVAL;
	return simple_xattr_set(__d_xattrs(dentry), name, val, size, flags);
}

static int cgroup_removexattr(struct dentry *dentry, const char *name)
{
	if (!xattr_enabled(dentry))
		return -EOPNOTSUPP;
	if (!is_valid_xattr(name))
		return -EINVAL;
	return simple_xattr_remove(__d_xattrs(dentry), name);
}

static ssize_t cgroup_getxattr(struct dentry *dentry, const char *name,
			       void *buf, size_t size)
{
	if (!xattr_enabled(dentry))
		return -EOPNOTSUPP;
	if (!is_valid_xattr(name))
		return -EINVAL;
	return simple_xattr_get(__d_xattrs(dentry), name, buf, size);
}

static ssize_t cgroup_listxattr(struct dentry *dentry, char *buf, size_t size)
{
	if (!xattr_enabled(dentry))
		return -EOPNOTSUPP;
	return simple_xattr_list(__d_xattrs(dentry), buf, size);
}

2651
static const struct file_operations cgroup_file_operations = {
2652 2653 2654 2655 2656 2657 2658
	.read = cgroup_file_read,
	.write = cgroup_file_write,
	.llseek = generic_file_llseek,
	.open = cgroup_file_open,
	.release = cgroup_file_release,
};

A
Aristeu Rozanski 已提交
2659 2660 2661 2662 2663 2664 2665
static const struct inode_operations cgroup_file_inode_operations = {
	.setxattr = cgroup_setxattr,
	.getxattr = cgroup_getxattr,
	.listxattr = cgroup_listxattr,
	.removexattr = cgroup_removexattr,
};

2666
static const struct inode_operations cgroup_dir_inode_operations = {
2667
	.lookup = cgroup_lookup,
2668 2669 2670
	.mkdir = cgroup_mkdir,
	.rmdir = cgroup_rmdir,
	.rename = cgroup_rename,
A
Aristeu Rozanski 已提交
2671 2672 2673 2674
	.setxattr = cgroup_setxattr,
	.getxattr = cgroup_getxattr,
	.listxattr = cgroup_listxattr,
	.removexattr = cgroup_removexattr,
2675 2676
};

A
Al Viro 已提交
2677
static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
2678 2679 2680 2681 2682 2683 2684
{
	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
	d_add(dentry, NULL);
	return NULL;
}

2685 2686 2687 2688 2689 2690 2691 2692 2693 2694
/*
 * 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);
}

A
Al Viro 已提交
2695
static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2696 2697
				struct super_block *sb)
{
2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717
	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 */
2718
		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
2719 2720 2721
	} else if (S_ISREG(mode)) {
		inode->i_size = 0;
		inode->i_fop = &cgroup_file_operations;
A
Aristeu Rozanski 已提交
2722
		inode->i_op = &cgroup_file_inode_operations;
2723 2724 2725 2726 2727 2728 2729
	}
	d_instantiate(dentry, inode);
	dget(dentry);	/* Extra count - pin the dentry in core */
	return 0;
}

/*
L
Li Zefan 已提交
2730 2731 2732 2733 2734
 * 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.
2735
 */
2736
static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
A
Al Viro 已提交
2737
				umode_t mode)
2738 2739 2740 2741
{
	struct dentry *parent;
	int error = 0;

2742 2743
	parent = cgrp->parent->dentry;
	error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
2744
	if (!error) {
2745
		dentry->d_fsdata = cgrp;
2746
		inc_nlink(parent->d_inode);
2747
		rcu_assign_pointer(cgrp->dentry, dentry);
2748 2749 2750 2751 2752 2753 2754
		dget(dentry);
	}
	dput(dentry);

	return error;
}

L
Li Zefan 已提交
2755 2756 2757 2758 2759 2760 2761 2762 2763
/**
 * 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
 */
A
Al Viro 已提交
2764
static umode_t cgroup_file_mode(const struct cftype *cft)
L
Li Zefan 已提交
2765
{
A
Al Viro 已提交
2766
	umode_t mode = 0;
L
Li Zefan 已提交
2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781

	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;
}

T
Tejun Heo 已提交
2782
static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
A
Aristeu Rozanski 已提交
2783
			   struct cftype *cft)
2784
{
2785
	struct dentry *dir = cgrp->dentry;
T
Tejun Heo 已提交
2786
	struct cgroup *parent = __d_cgrp(dir);
2787
	struct dentry *dentry;
T
Tejun Heo 已提交
2788
	struct cfent *cfe;
2789
	int error;
A
Al Viro 已提交
2790
	umode_t mode;
2791
	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2792

A
Aristeu Rozanski 已提交
2793 2794
	simple_xattrs_init(&cft->xattrs);

2795 2796 2797 2798 2799 2800
	/* does @cft->flags tell us to skip creation on @cgrp? */
	if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
		return 0;
	if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
		return 0;

2801
	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2802 2803 2804 2805
		strcpy(name, subsys->name);
		strcat(name, ".");
	}
	strcat(name, cft->name);
T
Tejun Heo 已提交
2806

2807
	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
T
Tejun Heo 已提交
2808 2809 2810 2811 2812

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

2813
	dentry = lookup_one_len(name, dir, strlen(name));
T
Tejun Heo 已提交
2814
	if (IS_ERR(dentry)) {
2815
		error = PTR_ERR(dentry);
T
Tejun Heo 已提交
2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830
		goto out;
	}

	mode = cgroup_file_mode(cft);
	error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
	if (!error) {
		cfe->type = (void *)cft;
		cfe->dentry = dentry;
		dentry->d_fsdata = cfe;
		list_add_tail(&cfe->node, &parent->files);
		cfe = NULL;
	}
	dput(dentry);
out:
	kfree(cfe);
2831 2832 2833
	return error;
}

2834
static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
A
Aristeu Rozanski 已提交
2835
			      struct cftype cfts[], bool is_add)
2836
{
A
Aristeu Rozanski 已提交
2837
	struct cftype *cft;
T
Tejun Heo 已提交
2838 2839 2840
	int err, ret = 0;

	for (cft = cfts; cft->name[0] != '\0'; cft++) {
2841 2842 2843 2844
		if (is_add)
			err = cgroup_add_file(cgrp, subsys, cft);
		else
			err = cgroup_rm_file(cgrp, cft);
T
Tejun Heo 已提交
2845
		if (err) {
2846 2847
			pr_warning("cgroup_addrm_files: failed to %s %s, err=%d\n",
				   is_add ? "add" : "remove", cft->name, err);
T
Tejun Heo 已提交
2848 2849
			ret = err;
		}
2850
	}
T
Tejun Heo 已提交
2851
	return ret;
2852 2853
}

2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870
static DEFINE_MUTEX(cgroup_cft_mutex);

static void cgroup_cfts_prepare(void)
	__acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex)
{
	/*
	 * Thanks to the entanglement with vfs inode locking, we can't walk
	 * the existing cgroups under cgroup_mutex and create files.
	 * Instead, we increment reference on all cgroups and build list of
	 * them using @cgrp->cft_q_node.  Grab cgroup_cft_mutex to ensure
	 * exclusive access to the field.
	 */
	mutex_lock(&cgroup_cft_mutex);
	mutex_lock(&cgroup_mutex);
}

static void cgroup_cfts_commit(struct cgroup_subsys *ss,
A
Aristeu Rozanski 已提交
2871
			       struct cftype *cfts, bool is_add)
2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896
	__releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
{
	LIST_HEAD(pending);
	struct cgroup *cgrp, *n;

	/* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
	if (cfts && ss->root != &rootnode) {
		list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) {
			dget(cgrp->dentry);
			list_add_tail(&cgrp->cft_q_node, &pending);
		}
	}

	mutex_unlock(&cgroup_mutex);

	/*
	 * All new cgroups will see @cfts update on @ss->cftsets.  Add/rm
	 * files for all cgroups which were created before.
	 */
	list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {
		struct inode *inode = cgrp->dentry->d_inode;

		mutex_lock(&inode->i_mutex);
		mutex_lock(&cgroup_mutex);
		if (!cgroup_is_removed(cgrp))
2897
			cgroup_addrm_files(cgrp, ss, cfts, is_add);
2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917 2918 2919 2920 2921
		mutex_unlock(&cgroup_mutex);
		mutex_unlock(&inode->i_mutex);

		list_del_init(&cgrp->cft_q_node);
		dput(cgrp->dentry);
	}

	mutex_unlock(&cgroup_cft_mutex);
}

/**
 * cgroup_add_cftypes - add an array of cftypes to a subsystem
 * @ss: target cgroup subsystem
 * @cfts: zero-length name terminated array of cftypes
 *
 * Register @cfts to @ss.  Files described by @cfts are created for all
 * existing cgroups to which @ss is attached and all future cgroups will
 * have them too.  This function can be called anytime whether @ss is
 * attached or not.
 *
 * Returns 0 on successful registration, -errno on failure.  Note that this
 * function currently returns 0 as long as @cfts registration is successful
 * even if some file creation attempts on existing cgroups fail.
 */
A
Aristeu Rozanski 已提交
2922
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2923 2924 2925 2926 2927 2928 2929 2930 2931 2932
{
	struct cftype_set *set;

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

	cgroup_cfts_prepare();
	set->cfts = cfts;
	list_add_tail(&set->node, &ss->cftsets);
2933
	cgroup_cfts_commit(ss, cfts, true);
2934 2935 2936 2937 2938

	return 0;
}
EXPORT_SYMBOL_GPL(cgroup_add_cftypes);

2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951
/**
 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
 * @ss: target cgroup subsystem
 * @cfts: zero-length name terminated array of cftypes
 *
 * Unregister @cfts from @ss.  Files described by @cfts are removed from
 * all existing cgroups to which @ss is attached and all future cgroups
 * won't have them either.  This function can be called anytime whether @ss
 * is attached or not.
 *
 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
 * registered with @ss.
 */
A
Aristeu Rozanski 已提交
2952
int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969
{
	struct cftype_set *set;

	cgroup_cfts_prepare();

	list_for_each_entry(set, &ss->cftsets, node) {
		if (set->cfts == cfts) {
			list_del_init(&set->node);
			cgroup_cfts_commit(ss, cfts, false);
			return 0;
		}
	}

	cgroup_cfts_commit(ss, NULL, false);
	return -ENOENT;
}

L
Li Zefan 已提交
2970 2971 2972 2973 2974 2975
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2976
int cgroup_task_count(const struct cgroup *cgrp)
2977 2978
{
	int count = 0;
K
KOSAKI Motohiro 已提交
2979
	struct cg_cgroup_link *link;
2980 2981

	read_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
2982
	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2983
		count += atomic_read(&link->cg->refcount);
2984 2985
	}
	read_unlock(&css_set_lock);
2986 2987 2988
	return count;
}

2989 2990 2991 2992
/*
 * Advance a list_head iterator.  The iterator should be positioned at
 * the start of a css_set
 */
2993
static void cgroup_advance_iter(struct cgroup *cgrp,
2994
				struct cgroup_iter *it)
2995 2996 2997 2998 2999 3000 3001 3002
{
	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;
3003
		if (l == &cgrp->css_sets) {
3004 3005 3006
			it->cg_link = NULL;
			return;
		}
3007
		link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
3008 3009 3010 3011 3012 3013
		cg = link->cg;
	} while (list_empty(&cg->tasks));
	it->cg_link = l;
	it->task = cg->tasks.next;
}

3014 3015 3016 3017 3018 3019
/*
 * 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().
 */
3020
static void cgroup_enable_task_cg_lists(void)
3021 3022 3023 3024
{
	struct task_struct *p, *g;
	write_lock(&css_set_lock);
	use_task_css_set_links = 1;
3025 3026 3027 3028 3029 3030 3031 3032
	/*
	 * We need tasklist_lock because RCU is not safe against
	 * while_each_thread(). Besides, a forking task that has passed
	 * cgroup_post_fork() without seeing use_task_css_set_links = 1
	 * is not guaranteed to have its child immediately visible in the
	 * tasklist if we walk through it with RCU.
	 */
	read_lock(&tasklist_lock);
3033 3034
	do_each_thread(g, p) {
		task_lock(p);
3035 3036 3037 3038 3039 3040
		/*
		 * 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))
3041 3042 3043
			list_add(&p->cg_list, &p->cgroups->tasks);
		task_unlock(p);
	} while_each_thread(g, p);
3044
	read_unlock(&tasklist_lock);
3045 3046 3047
	write_unlock(&css_set_lock);
}

3048
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
3049
	__acquires(css_set_lock)
3050 3051 3052 3053 3054 3055
{
	/*
	 * 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.
	 */
3056 3057 3058
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();

3059
	read_lock(&css_set_lock);
3060 3061
	it->cg_link = &cgrp->css_sets;
	cgroup_advance_iter(cgrp, it);
3062 3063
}

3064
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
3065 3066 3067 3068
					struct cgroup_iter *it)
{
	struct task_struct *res;
	struct list_head *l = it->task;
3069
	struct cg_cgroup_link *link;
3070 3071 3072 3073 3074 3075 3076

	/* 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;
3077 3078
	link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
	if (l == &link->cg->tasks) {
3079 3080
		/* We reached the end of this task list - move on to
		 * the next cg_cgroup_link */
3081
		cgroup_advance_iter(cgrp, it);
3082 3083 3084 3085 3086 3087
	} else {
		it->task = l;
	}
	return res;
}

3088
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
3089
	__releases(css_set_lock)
3090 3091 3092 3093
{
	read_unlock(&css_set_lock);
}

3094 3095 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 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230
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++) {
3231
			struct task_struct *q = heap->ptrs[i];
3232
			if (i == 0) {
3233 3234
				latest_time = q->start_time;
				latest_task = q;
3235 3236
			}
			/* Process the task per the caller's callback */
3237 3238
			scan->process_task(q, scan);
			put_task_struct(q);
3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253
		}
		/*
		 * 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;
}

3254
/*
3255
 * Stuff for reading the 'tasks'/'procs' files.
3256 3257 3258 3259 3260 3261 3262 3263
 *
 * 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.
 *
 */

3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295
/* which pidlist file are we talking about? */
enum cgroup_filetype {
	CGROUP_FILE_PROCS,
	CGROUP_FILE_TASKS,
};

/*
 * A pidlist is a list of pids that virtually represents the contents of one
 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
 * a pair (one each for procs, tasks) for each pid namespace that's relevant
 * to the cgroup.
 */
struct cgroup_pidlist {
	/*
	 * used to find which pidlist is wanted. doesn't change as long as
	 * this particular list stays in the list.
	*/
	struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
	/* array of xids */
	pid_t *list;
	/* how many elements the above list has */
	int length;
	/* how many files are using the current array */
	int use_count;
	/* each of these stored in a list by its cgroup */
	struct list_head links;
	/* pointer to the cgroup we belong to, for list removal purposes */
	struct cgroup *owner;
	/* protects the other fields */
	struct rw_semaphore mutex;
};

3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331
/*
 * 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;
}

3332
/*
3333 3334 3335 3336
 * 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.
3337
 */
3338 3339 3340
/* 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)
3341
{
3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370
	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)) {
3371
		newlist = pidlist_resize(list, dest);
3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382
		if (newlist)
			*p = newlist;
	}
	return dest;
}

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

3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393
/*
 * 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 */
3394 3395
	struct pid_namespace *ns = current->nsproxy->pid_ns;

3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419
	/*
	 * 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;
3420
	l->key.ns = get_pid_ns(ns);
3421 3422 3423 3424 3425 3426 3427 3428
	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;
}

3429 3430 3431
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
3432 3433
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
3434 3435 3436 3437
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
3438 3439
	struct cgroup_iter it;
	struct task_struct *tsk;
3440 3441 3442 3443 3444 3445 3446 3447 3448
	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);
3449
	array = pidlist_allocate(length);
3450 3451 3452
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
3453 3454
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
3455
		if (unlikely(n == length))
3456
			break;
3457
		/* get tgid or pid for procs or tasks file respectively */
3458 3459 3460 3461
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
3462 3463
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
3464
	}
3465
	cgroup_iter_end(cgrp, &it);
3466 3467 3468
	length = n;
	/* now sort & (if procs) strip out duplicates */
	sort(array, length, sizeof(pid_t), cmppid, NULL);
3469
	if (type == CGROUP_FILE_PROCS)
3470
		length = pidlist_uniq(&array, length);
3471 3472
	l = cgroup_pidlist_find(cgrp, type);
	if (!l) {
3473
		pidlist_free(array);
3474
		return -ENOMEM;
3475
	}
3476
	/* store array, freeing old if necessary - lock already held */
3477
	pidlist_free(l->list);
3478 3479 3480 3481
	l->list = array;
	l->length = length;
	l->use_count++;
	up_write(&l->mutex);
3482
	*lp = l;
3483
	return 0;
3484 3485
}

B
Balbir Singh 已提交
3486
/**
L
Li Zefan 已提交
3487
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
3488 3489 3490
 * @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
3491 3492 3493
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
3494 3495 3496 3497
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
	int ret = -EINVAL;
3498
	struct cgroup *cgrp;
B
Balbir Singh 已提交
3499 3500
	struct cgroup_iter it;
	struct task_struct *tsk;
3501

B
Balbir Singh 已提交
3502
	/*
3503 3504
	 * Validate dentry by checking the superblock operations,
	 * and make sure it's a directory.
B
Balbir Singh 已提交
3505
	 */
3506 3507
	if (dentry->d_sb->s_op != &cgroup_ops ||
	    !S_ISDIR(dentry->d_inode->i_mode))
B
Balbir Singh 已提交
3508 3509 3510
		 goto err;

	ret = 0;
3511
	cgrp = dentry->d_fsdata;
B
Balbir Singh 已提交
3512

3513 3514
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
B
Balbir Singh 已提交
3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532 3533
		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;
		}
	}
3534
	cgroup_iter_end(cgrp, &it);
B
Balbir Singh 已提交
3535 3536 3537 3538 3539

err:
	return ret;
}

3540

3541
/*
3542
 * seq_file methods for the tasks/procs files. The seq_file position is the
3543
 * next pid to display; the seq_file iterator is a pointer to the pid
3544
 * in the cgroup->l->list array.
3545
 */
3546

3547
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3548
{
3549 3550 3551 3552 3553 3554
	/*
	 * 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
	 */
3555
	struct cgroup_pidlist *l = s->private;
3556 3557 3558
	int index = 0, pid = *pos;
	int *iter;

3559
	down_read(&l->mutex);
3560
	if (pid) {
3561
		int end = l->length;
S
Stephen Rothwell 已提交
3562

3563 3564
		while (index < end) {
			int mid = (index + end) / 2;
3565
			if (l->list[mid] == pid) {
3566 3567
				index = mid;
				break;
3568
			} else if (l->list[mid] <= pid)
3569 3570 3571 3572 3573 3574
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
3575
	if (index >= l->length)
3576 3577
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
3578
	iter = l->list + index;
3579 3580 3581 3582
	*pos = *iter;
	return iter;
}

3583
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3584
{
3585 3586
	struct cgroup_pidlist *l = s->private;
	up_read(&l->mutex);
3587 3588
}

3589
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3590
{
3591 3592 3593
	struct cgroup_pidlist *l = s->private;
	pid_t *p = v;
	pid_t *end = l->list + l->length;
3594 3595 3596 3597 3598 3599 3600 3601 3602 3603 3604 3605 3606
	/*
	 * 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;
	}
}

3607
static int cgroup_pidlist_show(struct seq_file *s, void *v)
3608 3609 3610
{
	return seq_printf(s, "%d\n", *(int *)v);
}
3611

3612 3613 3614 3615 3616 3617 3618 3619 3620
/*
 * 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,
3621 3622
};

3623
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3624
{
3625 3626 3627 3628 3629 3630 3631
	/*
	 * 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);
3632 3633 3634
	down_write(&l->mutex);
	BUG_ON(!l->use_count);
	if (!--l->use_count) {
3635 3636 3637
		/* we're the last user if refcount is 0; remove and free */
		list_del(&l->links);
		mutex_unlock(&l->owner->pidlist_mutex);
3638
		pidlist_free(l->list);
3639 3640 3641 3642
		put_pid_ns(l->key.ns);
		up_write(&l->mutex);
		kfree(l);
		return;
3643
	}
3644
	mutex_unlock(&l->owner->pidlist_mutex);
3645
	up_write(&l->mutex);
3646 3647
}

3648
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3649
{
3650
	struct cgroup_pidlist *l;
3651 3652
	if (!(file->f_mode & FMODE_READ))
		return 0;
3653 3654 3655 3656 3657 3658
	/*
	 * 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);
3659 3660 3661
	return seq_release(inode, file);
}

3662
static const struct file_operations cgroup_pidlist_operations = {
3663 3664 3665
	.read = seq_read,
	.llseek = seq_lseek,
	.write = cgroup_file_write,
3666
	.release = cgroup_pidlist_release,
3667 3668
};

3669
/*
3670 3671 3672
 * 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.
3673
 */
3674
/* helper function for the two below it */
3675
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3676
{
3677
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3678
	struct cgroup_pidlist *l;
3679
	int retval;
3680

3681
	/* Nothing to do for write-only files */
3682 3683 3684
	if (!(file->f_mode & FMODE_READ))
		return 0;

3685
	/* have the array populated */
3686
	retval = pidlist_array_load(cgrp, type, &l);
3687 3688 3689 3690
	if (retval)
		return retval;
	/* configure file information */
	file->f_op = &cgroup_pidlist_operations;
3691

3692
	retval = seq_open(file, &cgroup_pidlist_seq_operations);
3693
	if (retval) {
3694
		cgroup_release_pid_array(l);
3695
		return retval;
3696
	}
3697
	((struct seq_file *)file->private_data)->private = l;
3698 3699
	return 0;
}
3700 3701
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
3702
	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3703 3704 3705
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
3706
	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3707
}
3708

3709
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3710 3711
					    struct cftype *cft)
{
3712
	return notify_on_release(cgrp);
3713 3714
}

3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725 3726
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;
}

3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741
/*
 * 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);
3742
	dput(cgrp->dentry);
3743 3744 3745 3746 3747 3748 3749 3750 3751 3752 3753 3754 3755 3756 3757 3758
}

/*
 * 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
3759
		__remove_wait_queue(event->wqh, &event->wait);
3760 3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835 3836
		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
3837 3838
	/* AV: shouldn't we check that it's been opened for read instead? */
	ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863
	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;
	}

3864 3865 3866 3867 3868 3869 3870
	/*
	 * 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);

3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894
	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;
}

3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911
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;
}

3912 3913 3914
/*
 * for the common functions, 'private' gives the type of file
 */
3915 3916
/* for hysterical raisins, we can't put this on the older files */
#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3917 3918 3919 3920
static struct cftype files[] = {
	{
		.name = "tasks",
		.open = cgroup_tasks_open,
3921
		.write_u64 = cgroup_tasks_write,
3922
		.release = cgroup_pidlist_release,
L
Li Zefan 已提交
3923
		.mode = S_IRUGO | S_IWUSR,
3924
	},
3925 3926 3927
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "procs",
		.open = cgroup_procs_open,
B
Ben Blum 已提交
3928
		.write_u64 = cgroup_procs_write,
3929
		.release = cgroup_pidlist_release,
B
Ben Blum 已提交
3930
		.mode = S_IRUGO | S_IWUSR,
3931
	},
3932 3933
	{
		.name = "notify_on_release",
3934
		.read_u64 = cgroup_read_notify_on_release,
3935
		.write_u64 = cgroup_write_notify_on_release,
3936
	},
3937 3938 3939 3940 3941
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "event_control",
		.write_string = cgroup_write_event_control,
		.mode = S_IWUGO,
	},
3942 3943 3944 3945 3946
	{
		.name = "cgroup.clone_children",
		.read_u64 = cgroup_clone_children_read,
		.write_u64 = cgroup_clone_children_write,
	},
3947 3948 3949 3950 3951 3952 3953
	{
		.name = "release_agent",
		.flags = CFTYPE_ONLY_ON_ROOT,
		.read_seq_string = cgroup_release_agent_show,
		.write_string = cgroup_release_agent_write,
		.max_write_len = PATH_MAX,
	},
T
Tejun Heo 已提交
3954
	{ }	/* terminate */
3955 3956
};

3957 3958 3959 3960 3961 3962 3963 3964
/**
 * cgroup_populate_dir - selectively creation of files in a directory
 * @cgrp: target cgroup
 * @base_files: true if the base files should be added
 * @subsys_mask: mask of the subsystem ids whose files should be added
 */
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
			       unsigned long subsys_mask)
3965 3966 3967 3968
{
	int err;
	struct cgroup_subsys *ss;

3969 3970 3971 3972 3973
	if (base_files) {
		err = cgroup_addrm_files(cgrp, NULL, files, true);
		if (err < 0)
			return err;
	}
3974

3975
	/* process cftsets of each subsystem */
3976
	for_each_subsys(cgrp->root, ss) {
3977
		struct cftype_set *set;
3978 3979
		if (!test_bit(ss->subsys_id, &subsys_mask))
			continue;
3980

T
Tejun Heo 已提交
3981
		list_for_each_entry(set, &ss->cftsets, node)
3982
			cgroup_addrm_files(cgrp, ss, set->cfts, true);
3983
	}
3984

K
KAMEZAWA Hiroyuki 已提交
3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995
	/* 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);
	}
3996 3997 3998 3999

	return 0;
}

4000 4001 4002 4003
static void css_dput_fn(struct work_struct *work)
{
	struct cgroup_subsys_state *css =
		container_of(work, struct cgroup_subsys_state, dput_work);
4004 4005
	struct dentry *dentry = css->cgroup->dentry;
	struct super_block *sb = dentry->d_sb;
4006

4007 4008 4009
	atomic_inc(&sb->s_active);
	dput(dentry);
	deactivate_super(sb);
4010 4011
}

4012 4013
static void init_cgroup_css(struct cgroup_subsys_state *css,
			       struct cgroup_subsys *ss,
4014
			       struct cgroup *cgrp)
4015
{
4016
	css->cgroup = cgrp;
P
Paul Menage 已提交
4017
	atomic_set(&css->refcnt, 1);
4018
	css->flags = 0;
K
KAMEZAWA Hiroyuki 已提交
4019
	css->id = NULL;
4020
	if (cgrp == dummytop)
4021
		set_bit(CSS_ROOT, &css->flags);
4022 4023
	BUG_ON(cgrp->subsys[ss->subsys_id]);
	cgrp->subsys[ss->subsys_id] = css;
4024 4025 4026 4027 4028 4029 4030 4031 4032 4033

	/*
	 * If !clear_css_refs, css holds an extra ref to @cgrp->dentry
	 * which is put on the last css_put().  dput() requires process
	 * context, which css_put() may be called without.  @css->dput_work
	 * will be used to invoke dput() asynchronously from css_put().
	 */
	INIT_WORK(&css->dput_work, css_dput_fn);
	if (ss->__DEPRECATED_clear_css_refs)
		set_bit(CSS_CLEAR_CSS_REFS, &css->flags);
4034 4035 4036
}

/*
L
Li Zefan 已提交
4037 4038 4039 4040
 * 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
4041
 *
L
Li Zefan 已提交
4042
 * Must be called with the mutex on the parent inode held
4043 4044
 */
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
A
Al Viro 已提交
4045
			     umode_t mode)
4046
{
4047
	struct cgroup *cgrp;
4048 4049 4050 4051 4052
	struct cgroupfs_root *root = parent->root;
	int err = 0;
	struct cgroup_subsys *ss;
	struct super_block *sb = root->sb;

4053 4054
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065
		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);

4066
	init_cgroup_housekeeping(cgrp);
4067

4068 4069 4070
	cgrp->parent = parent;
	cgrp->root = parent->root;
	cgrp->top_cgroup = parent->top_cgroup;
4071

4072 4073 4074
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

4075 4076 4077
	if (clone_children(parent))
		set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);

4078
	for_each_subsys(root, ss) {
4079
		struct cgroup_subsys_state *css;
4080

4081
		css = ss->create(cgrp);
4082 4083 4084 4085
		if (IS_ERR(css)) {
			err = PTR_ERR(css);
			goto err_destroy;
		}
4086
		init_cgroup_css(css, ss, cgrp);
4087 4088 4089
		if (ss->use_id) {
			err = alloc_css_id(ss, parent, cgrp);
			if (err)
K
KAMEZAWA Hiroyuki 已提交
4090
				goto err_destroy;
4091
		}
K
KAMEZAWA Hiroyuki 已提交
4092
		/* At error, ->destroy() callback has to free assigned ID. */
4093
		if (clone_children(parent) && ss->post_clone)
4094
			ss->post_clone(cgrp);
4095 4096 4097 4098 4099 4100 4101 4102 4103

		if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
		    parent->parent) {
			pr_warning("cgroup: %s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
				   current->comm, current->pid, ss->name);
			if (!strcmp(ss->name, "memory"))
				pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
			ss->warned_broken_hierarchy = true;
		}
4104 4105
	}

4106
	list_add(&cgrp->sibling, &cgrp->parent->children);
4107 4108
	root->number_of_cgroups++;

4109
	err = cgroup_create_dir(cgrp, dentry, mode);
4110 4111 4112
	if (err < 0)
		goto err_remove;

4113 4114 4115 4116 4117
	/* If !clear_css_refs, each css holds a ref to the cgroup's dentry */
	for_each_subsys(root, ss)
		if (!ss->__DEPRECATED_clear_css_refs)
			dget(dentry);

4118
	/* The cgroup directory was pre-locked for us */
4119
	BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
4120

4121 4122
	list_add_tail(&cgrp->allcg_node, &root->allcg_list);

4123
	err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
4124 4125 4126
	/* If err < 0, we have a half-filled directory - oh well ;) */

	mutex_unlock(&cgroup_mutex);
4127
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
4128 4129 4130 4131 4132

	return 0;

 err_remove:

4133
	list_del(&cgrp->sibling);
4134 4135 4136 4137 4138
	root->number_of_cgroups--;

 err_destroy:

	for_each_subsys(root, ss) {
4139
		if (cgrp->subsys[ss->subsys_id])
4140
			ss->destroy(cgrp);
4141 4142 4143 4144 4145 4146 4147
	}

	mutex_unlock(&cgroup_mutex);

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

4148
	kfree(cgrp);
4149 4150 4151
	return err;
}

4152
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
4153 4154 4155 4156 4157 4158 4159
{
	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);
}

4160 4161 4162 4163 4164 4165 4166 4167 4168
/*
 * Check the reference count on each subsystem. Since we already
 * established that there are no tasks in the cgroup, if the css refcount
 * is also 1, then there should 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.
 */
4169
static int cgroup_has_css_refs(struct cgroup *cgrp)
4170 4171
{
	int i;
4172

B
Ben Blum 已提交
4173 4174 4175 4176 4177
	/*
	 * 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.
	 */
4178 4179 4180
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		struct cgroup_subsys_state *css;
4181

B
Ben Blum 已提交
4182 4183
		/* Skip subsystems not present or not in this hierarchy */
		if (ss == NULL || ss->root != cgrp->root)
4184
			continue;
4185

4186
		css = cgrp->subsys[ss->subsys_id];
4187 4188
		/*
		 * When called from check_for_release() it's possible
4189 4190 4191 4192
		 * 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
4193 4194 4195
		 * release agent to be called anyway.
		 */
		if (css && css_refcnt(css) > 1)
4196 4197 4198 4199 4200
			return 1;
	}
	return 0;
}

P
Paul Menage 已提交
4201 4202 4203 4204
/*
 * 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
4205 4206 4207 4208 4209 4210 4211 4212 4213 4214 4215 4216 4217 4218 4219 4220 4221
 *
 * Depending on whether a subsys has __DEPRECATED_clear_css_refs set or
 * not, cgroup removal behaves differently.
 *
 * If clear is set, css refcnt for the subsystem should be zero before
 * cgroup removal can be committed.  This is implemented by
 * CGRP_WAIT_ON_RMDIR and retry logic around ->pre_destroy(), which may be
 * called multiple times until all css refcnts reach zero and is allowed to
 * veto removal on any invocation.  This behavior is deprecated and will be
 * removed as soon as the existing user (memcg) is updated.
 *
 * If clear is not set, each css holds an extra reference to the cgroup's
 * dentry and cgroup removal proceeds regardless of css refs.
 * ->pre_destroy() will be called at least once and is not allowed to fail.
 * On the last put of each css, whenever that may be, the extra dentry ref
 * is put so that dentry destruction happens only after all css's are
 * released.
P
Paul Menage 已提交
4222 4223 4224 4225 4226 4227
 */
static int cgroup_clear_css_refs(struct cgroup *cgrp)
{
	struct cgroup_subsys *ss;
	unsigned long flags;
	bool failed = false;
4228

P
Paul Menage 已提交
4229
	local_irq_save(flags);
4230 4231 4232

	/*
	 * Block new css_tryget() by deactivating refcnt.  If all refcnts
4233 4234
	 * for subsystems w/ clear_css_refs set were 1 at the moment of
	 * deactivation, we succeeded.
4235
	 */
P
Paul Menage 已提交
4236 4237
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4238 4239 4240

		WARN_ON(atomic_read(&css->refcnt) < 0);
		atomic_add(CSS_DEACT_BIAS, &css->refcnt);
4241 4242 4243

		if (ss->__DEPRECATED_clear_css_refs)
			failed |= css_refcnt(css) != 1;
P
Paul Menage 已提交
4244
	}
4245 4246 4247 4248 4249 4250

	/*
	 * If succeeded, set REMOVED and put all the base refs; otherwise,
	 * restore refcnts to positive values.  Either way, all in-progress
	 * css_tryget() will be released.
	 */
P
Paul Menage 已提交
4251 4252
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4253 4254

		if (!failed) {
P
Paul Menage 已提交
4255
			set_bit(CSS_REMOVED, &css->flags);
4256 4257 4258
			css_put(css);
		} else {
			atomic_sub(CSS_DEACT_BIAS, &css->refcnt);
P
Paul Menage 已提交
4259 4260
		}
	}
4261

P
Paul Menage 已提交
4262 4263 4264 4265
	local_irq_restore(flags);
	return !failed;
}

4266 4267
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
4268
	struct cgroup *cgrp = dentry->d_fsdata;
4269 4270
	struct dentry *d;
	struct cgroup *parent;
4271
	DEFINE_WAIT(wait);
4272
	struct cgroup_event *event, *tmp;
4273
	int ret;
4274 4275

	/* the vfs holds both inode->i_mutex already */
4276
again:
4277
	mutex_lock(&cgroup_mutex);
4278
	if (atomic_read(&cgrp->count) != 0) {
4279 4280 4281
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
4282
	if (!list_empty(&cgrp->children)) {
4283 4284 4285
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
4286
	mutex_unlock(&cgroup_mutex);
L
Li Zefan 已提交
4287

4288 4289 4290 4291 4292 4293 4294 4295 4296 4297 4298
	/*
	 * 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);

4299
	/*
L
Li Zefan 已提交
4300 4301
	 * Call pre_destroy handlers of subsys. Notify subsystems
	 * that rmdir() request comes.
4302
	 */
4303
	ret = cgroup_call_pre_destroy(cgrp);
4304 4305
	if (ret) {
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4306
		return ret;
4307
	}
4308

4309 4310
	mutex_lock(&cgroup_mutex);
	parent = cgrp->parent;
4311
	if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
4312
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4313 4314 4315
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
4316 4317 4318
	prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
	if (!cgroup_clear_css_refs(cgrp)) {
		mutex_unlock(&cgroup_mutex);
4319 4320 4321 4322 4323 4324
		/*
		 * 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();
4325 4326 4327 4328 4329 4330 4331 4332 4333
		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);
4334

4335
	raw_spin_lock(&release_list_lock);
4336 4337
	set_bit(CGRP_REMOVED, &cgrp->flags);
	if (!list_empty(&cgrp->release_list))
4338
		list_del_init(&cgrp->release_list);
4339
	raw_spin_unlock(&release_list_lock);
4340 4341

	/* delete this cgroup from parent->children */
4342
	list_del_init(&cgrp->sibling);
4343

4344 4345
	list_del_init(&cgrp->allcg_node);

4346
	d = dget(cgrp->dentry);
4347 4348 4349 4350

	cgroup_d_remove_dir(d);
	dput(d);

4351
	set_bit(CGRP_RELEASABLE, &parent->flags);
4352 4353
	check_for_release(parent);

4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367
	/*
	 * 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);

4368 4369 4370 4371
	mutex_unlock(&cgroup_mutex);
	return 0;
}

4372 4373 4374 4375 4376 4377 4378 4379 4380 4381 4382 4383 4384 4385
static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
{
	INIT_LIST_HEAD(&ss->cftsets);

	/*
	 * base_cftset is embedded in subsys itself, no need to worry about
	 * deregistration.
	 */
	if (ss->base_cftypes) {
		ss->base_cftset.cfts = ss->base_cftypes;
		list_add_tail(&ss->base_cftset.node, &ss->cftsets);
	}
}

4386
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4387 4388
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
4389 4390

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4391

4392 4393 4394
	/* init base cftset */
	cgroup_init_cftsets(ss);

4395
	/* Create the top cgroup state for this subsystem */
4396
	list_add(&ss->sibling, &rootnode.subsys_list);
4397
	ss->root = &rootnode;
4398
	css = ss->create(dummytop);
4399 4400 4401 4402
	/* We don't handle early failures gracefully */
	BUG_ON(IS_ERR(css));
	init_cgroup_css(css, ss, dummytop);

L
Li Zefan 已提交
4403
	/* Update the init_css_set to contain a subsys
4404
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
4405 4406 4407
	 * 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];
4408 4409 4410

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

L
Li Zefan 已提交
4411 4412 4413 4414 4415
	/* 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));

4416
	ss->active = 1;
4417 4418 4419 4420 4421 4422 4423 4424 4425 4426 4427

	/* 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
4428
 * subsystem is built as a module, it will be assigned a new subsys_id and set
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 4454 4455
 * 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) {
4456
		/* a sanity check */
4457 4458 4459 4460
		BUG_ON(subsys[ss->subsys_id] != ss);
		return 0;
	}

4461 4462 4463
	/* init base cftset */
	cgroup_init_cftsets(ss);

4464
	mutex_lock(&cgroup_mutex);
4465
	subsys[ss->subsys_id] = ss;
4466 4467 4468 4469 4470

	/*
	 * no ss->create seems to need anything important in the ss struct, so
	 * this can happen first (i.e. before the rootnode attachment).
	 */
4471
	css = ss->create(dummytop);
4472 4473
	if (IS_ERR(css)) {
		/* failure case - need to deassign the subsys[] slot. */
4474
		subsys[ss->subsys_id] = NULL;
4475 4476 4477 4478 4479 4480 4481 4482 4483 4484 4485 4486 4487 4488
		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;
4489
			ss->destroy(dummytop);
4490
			subsys[ss->subsys_id] = NULL;
4491 4492 4493 4494 4495 4496 4497 4498 4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 4519 4520 4521 4522 4523 4524 4525 4526 4527 4528 4529
			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);

	ss->active = 1;

	/* success! */
	mutex_unlock(&cgroup_mutex);
	return 0;
4530
}
4531
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4532

B
Ben Blum 已提交
4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559
/**
 * 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 */
	subsys[ss->subsys_id] = NULL;

	/* remove subsystem from rootnode's list of subsystems */
4560
	list_del_init(&ss->sibling);
B
Ben Blum 已提交
4561 4562 4563 4564 4565 4566 4567 4568 4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579 4580 4581 4582 4583

	/*
	 * 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.
	 */
4584
	ss->destroy(dummytop);
B
Ben Blum 已提交
4585 4586 4587 4588 4589 4590
	dummytop->subsys[ss->subsys_id] = NULL;

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

4591
/**
L
Li Zefan 已提交
4592 4593 4594 4595
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
4596 4597 4598 4599
 */
int __init cgroup_init_early(void)
{
	int i;
4600
	atomic_set(&init_css_set.refcount, 1);
4601 4602
	INIT_LIST_HEAD(&init_css_set.cg_links);
	INIT_LIST_HEAD(&init_css_set.tasks);
4603
	INIT_HLIST_NODE(&init_css_set.hlist);
4604
	css_set_count = 1;
4605
	init_cgroup_root(&rootnode);
4606 4607 4608 4609
	root_count = 1;
	init_task.cgroups = &init_css_set;

	init_css_set_link.cg = &init_css_set;
4610
	init_css_set_link.cgrp = dummytop;
4611
	list_add(&init_css_set_link.cgrp_link_list,
4612 4613 4614
		 &rootnode.top_cgroup.css_sets);
	list_add(&init_css_set_link.cg_link_list,
		 &init_css_set.cg_links);
4615

4616 4617 4618
	for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
		INIT_HLIST_HEAD(&css_set_table[i]);

4619
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4620 4621
		struct cgroup_subsys *ss = subsys[i];

4622 4623 4624 4625
		/* at bootup time, we don't worry about modular subsystems */
		if (!ss || ss->module)
			continue;

4626 4627 4628 4629 4630
		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
4631
			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4632 4633 4634 4635 4636 4637 4638 4639 4640 4641 4642
			       ss->name, ss->subsys_id);
			BUG();
		}

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

/**
L
Li Zefan 已提交
4643 4644 4645 4646
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
4647 4648 4649 4650 4651
 */
int __init cgroup_init(void)
{
	int err;
	int i;
4652
	struct hlist_head *hhead;
4653 4654 4655 4656

	err = bdi_init(&cgroup_backing_dev_info);
	if (err)
		return err;
4657

4658
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4659
		struct cgroup_subsys *ss = subsys[i];
4660 4661 4662 4663

		/* at bootup time, we don't worry about modular subsystems */
		if (!ss || ss->module)
			continue;
4664 4665
		if (!ss->early_init)
			cgroup_init_subsys(ss);
K
KAMEZAWA Hiroyuki 已提交
4666
		if (ss->use_id)
4667
			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4668 4669
	}

4670 4671 4672
	/* Add init_css_set to the hash table */
	hhead = css_set_hash(init_css_set.subsys);
	hlist_add_head(&init_css_set.hlist, hhead);
4673
	BUG_ON(!init_root_id(&rootnode));
4674 4675 4676 4677 4678 4679 4680

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

4681
	err = register_filesystem(&cgroup_fs_type);
4682 4683
	if (err < 0) {
		kobject_put(cgroup_kobj);
4684
		goto out;
4685
	}
4686

L
Li Zefan 已提交
4687
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4688

4689
out:
4690 4691 4692
	if (err)
		bdi_destroy(&cgroup_backing_dev_info);

4693 4694
	return err;
}
4695

4696 4697 4698 4699 4700 4701
/*
 * 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,
4702
 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4703 4704 4705 4706 4707 4708 4709 4710 4711 4712 4713 4714 4715 4716 4717 4718 4719 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729 4730 4731
 *    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);

4732
	for_each_active_root(root) {
4733
		struct cgroup_subsys *ss;
4734
		struct cgroup *cgrp;
4735 4736
		int count = 0;

4737
		seq_printf(m, "%d:", root->hierarchy_id);
4738 4739
		for_each_subsys(root, ss)
			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4740 4741 4742
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
4743
		seq_putc(m, ':');
4744
		cgrp = task_cgroup_from_root(tsk, root);
4745
		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4746 4747 4748 4749 4750 4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761 4762 4763 4764 4765 4766
		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);
}

4767
const struct file_operations proc_cgroup_operations = {
4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778
	.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;

4779
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
B
Ben Blum 已提交
4780 4781 4782 4783 4784
	/*
	 * 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.
	 */
4785 4786 4787
	mutex_lock(&cgroup_mutex);
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
B
Ben Blum 已提交
4788 4789
		if (ss == NULL)
			continue;
4790 4791
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
4792
			   ss->root->number_of_cgroups, !ss->disabled);
4793 4794 4795 4796 4797 4798 4799
	}
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
4800
	return single_open(file, proc_cgroupstats_show, NULL);
4801 4802
}

4803
static const struct file_operations proc_cgroupstats_operations = {
4804 4805 4806 4807 4808 4809
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

4810 4811
/**
 * cgroup_fork - attach newly forked task to its parents cgroup.
L
Li Zefan 已提交
4812
 * @child: pointer to task_struct of forking parent process.
4813 4814 4815 4816 4817
 *
 * 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
4818 4819 4820 4821 4822 4823 4824 4825 4826 4827 4828
 * 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.
4829 4830 4831 4832 4833 4834
 *
 * 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)
{
4835 4836 4837 4838 4839 4840
	/*
	 * 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().
	 */
4841 4842 4843
	child->cgroups = current->cgroups;
	get_css_set(child->cgroups);
	INIT_LIST_HEAD(&child->cg_list);
4844 4845
}

4846
/**
L
Li Zefan 已提交
4847 4848 4849
 * cgroup_post_fork - called on a new task after adding it to the task list
 * @child: the task in question
 *
4850 4851 4852 4853 4854
 * Adds the task to the list running through its css_set if necessary and
 * call the subsystem fork() callbacks.  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.
L
Li Zefan 已提交
4855
 */
4856 4857
void cgroup_post_fork(struct task_struct *child)
{
4858 4859
	int i;

4860 4861 4862 4863 4864 4865 4866 4867 4868 4869 4870
	/*
	 * use_task_css_set_links is set to 1 before we walk the tasklist
	 * under the tasklist_lock and we read it here after we added the child
	 * to the tasklist under the tasklist_lock as well. If the child wasn't
	 * yet in the tasklist when we walked through it from
	 * cgroup_enable_task_cg_lists(), then use_task_css_set_links value
	 * should be visible now due to the paired locking and barriers implied
	 * by LOCK/UNLOCK: it is written before the tasklist_lock unlock
	 * in cgroup_enable_task_cg_lists() and read here after the tasklist_lock
	 * lock on fork.
	 */
4871 4872
	if (use_task_css_set_links) {
		write_lock(&css_set_lock);
4873 4874 4875 4876 4877 4878 4879 4880 4881 4882 4883
		if (list_empty(&child->cg_list)) {
			/*
			 * It's safe to use child->cgroups without task_lock()
			 * here because we are protected through
			 * threadgroup_change_begin() against concurrent
			 * css_set change in cgroup_task_migrate(). Also
			 * the task can't exit at that point until
			 * wake_up_new_task() is called, so we are protected
			 * against cgroup_exit() setting child->cgroup to
			 * init_css_set.
			 */
4884
			list_add(&child->cg_list, &child->cgroups->tasks);
4885
		}
4886 4887
		write_unlock(&css_set_lock);
	}
4888 4889 4890 4891 4892 4893 4894 4895 4896 4897 4898 4899 4900 4901 4902 4903 4904 4905 4906 4907 4908 4909

	/*
	 * Call ss->fork().  This must happen after @child is linked on
	 * css_set; otherwise, @child might change state between ->fork()
	 * and addition to css_set.
	 */
	if (need_forkexit_callback) {
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];

			/*
			 * fork/exit callbacks are supported only for
			 * builtin subsystems and we don't need further
			 * synchronization as they never go away.
			 */
			if (!ss || ss->module)
				continue;

			if (ss->fork)
				ss->fork(child);
		}
	}
4910
}
4911

4912 4913 4914
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
4915
 * @run_callback: run exit callbacks?
4916 4917 4918 4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943
 *
 * 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,
4944 4945
 *    which wards off any cgroup_attach_task() attempts, or task is a failed
 *    fork, never visible to cgroup_attach_task.
4946 4947 4948
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
4949
	struct css_set *cg;
4950
	int i;
4951 4952 4953 4954 4955 4956 4957 4958 4959

	/*
	 * 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))
4960
			list_del_init(&tsk->cg_list);
4961 4962 4963
		write_unlock(&css_set_lock);
	}

4964 4965
	/* Reassign the task to the init_css_set. */
	task_lock(tsk);
4966 4967
	cg = tsk->cgroups;
	tsk->cgroups = &init_css_set;
4968 4969

	if (run_callbacks && need_forkexit_callback) {
4970
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4971
			struct cgroup_subsys *ss = subsys[i];
4972 4973 4974 4975 4976

			/* modular subsystems can't use callbacks */
			if (!ss || ss->module)
				continue;

4977 4978 4979 4980
			if (ss->exit) {
				struct cgroup *old_cgrp =
					rcu_dereference_raw(cg->subsys[i])->cgroup;
				struct cgroup *cgrp = task_cgroup(tsk, i);
4981
				ss->exit(cgrp, old_cgrp, tsk);
4982 4983 4984
			}
		}
	}
4985
	task_unlock(tsk);
4986

4987
	if (cg)
4988
		put_css_set_taskexit(cg);
4989
}
4990

L
Li Zefan 已提交
4991
/**
4992
 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
L
Li Zefan 已提交
4993
 * @cgrp: the cgroup in question
4994
 * @task: the task in question
L
Li Zefan 已提交
4995
 *
4996 4997
 * See if @cgrp is a descendant of @task's cgroup in the appropriate
 * hierarchy.
4998 4999 5000 5001 5002 5003
 *
 * If we are sending in dummytop, then presumably we are creating
 * the top cgroup in the subsystem.
 *
 * Called only by the ns (nsproxy) cgroup.
 */
5004
int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
5005 5006 5007 5008
{
	int ret;
	struct cgroup *target;

5009
	if (cgrp == dummytop)
5010 5011
		return 1;

5012
	target = task_cgroup_from_root(task, cgrp->root);
5013 5014 5015
	while (cgrp != target && cgrp!= cgrp->top_cgroup)
		cgrp = cgrp->parent;
	ret = (cgrp == target);
5016 5017
	return ret;
}
5018

5019
static void check_for_release(struct cgroup *cgrp)
5020 5021 5022
{
	/* All of these checks rely on RCU to keep the cgroup
	 * structure alive */
5023 5024
	if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
	    && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
5025 5026 5027 5028
		/* Control Group is currently removeable. If it's not
		 * already queued for a userspace notification, queue
		 * it now */
		int need_schedule_work = 0;
5029
		raw_spin_lock(&release_list_lock);
5030 5031 5032
		if (!cgroup_is_removed(cgrp) &&
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
5033 5034
			need_schedule_work = 1;
		}
5035
		raw_spin_unlock(&release_list_lock);
5036 5037 5038 5039 5040
		if (need_schedule_work)
			schedule_work(&release_agent_work);
	}
}

5041
/* Caller must verify that the css is not for root cgroup */
5042 5043 5044 5045 5046 5047 5048 5049 5050 5051 5052 5053 5054 5055 5056 5057
bool __css_tryget(struct cgroup_subsys_state *css)
{
	do {
		int v = css_refcnt(css);

		if (atomic_cmpxchg(&css->refcnt, v, v + 1) == v)
			return true;
		cpu_relax();
	} while (!test_bit(CSS_REMOVED, &css->flags));

	return false;
}
EXPORT_SYMBOL_GPL(__css_tryget);

/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css)
5058
{
5059
	struct cgroup *cgrp = css->cgroup;
5060
	int v;
5061

5062
	rcu_read_lock();
5063 5064 5065
	v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));

	switch (v) {
5066
	case 1:
5067 5068 5069 5070
		if (notify_on_release(cgrp)) {
			set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
		}
5071
		cgroup_wakeup_rmdir_waiter(cgrp);
5072 5073 5074 5075 5076
		break;
	case 0:
		if (!test_bit(CSS_CLEAR_CSS_REFS, &css->flags))
			schedule_work(&css->dput_work);
		break;
5077 5078 5079
	}
	rcu_read_unlock();
}
B
Ben Blum 已提交
5080
EXPORT_SYMBOL_GPL(__css_put);
5081 5082 5083 5084 5085 5086 5087 5088 5089 5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107 5108

/*
 * 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);
5109
	raw_spin_lock(&release_list_lock);
5110 5111 5112
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
5113
		char *pathbuf = NULL, *agentbuf = NULL;
5114
		struct cgroup *cgrp = list_entry(release_list.next,
5115 5116
						    struct cgroup,
						    release_list);
5117
		list_del_init(&cgrp->release_list);
5118
		raw_spin_unlock(&release_list_lock);
5119
		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
5120 5121 5122 5123 5124 5125 5126
		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;
5127 5128

		i = 0;
5129 5130
		argv[i++] = agentbuf;
		argv[i++] = pathbuf;
5131 5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142 5143 5144
		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);
5145 5146 5147
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
5148
		raw_spin_lock(&release_list_lock);
5149
	}
5150
	raw_spin_unlock(&release_list_lock);
5151 5152
	mutex_unlock(&cgroup_mutex);
}
5153 5154 5155 5156 5157 5158 5159 5160 5161

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

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;
5162
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
5163 5164
			struct cgroup_subsys *ss = subsys[i];

5165 5166 5167 5168 5169 5170 5171 5172
			/*
			 * cgroup_disable, being at boot time, can't
			 * know about module subsystems, so we don't
			 * worry about them.
			 */
			if (!ss || ss->module)
				continue;

5173 5174 5175 5176 5177 5178 5179 5180 5181 5182 5183
			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
5184 5185 5186 5187 5188 5189 5190 5191 5192 5193

/*
 * 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)
{
5194 5195 5196 5197 5198 5199 5200
	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.
	 */
5201
	cssid = rcu_dereference_check(css->id, css_refcnt(css));
K
KAMEZAWA Hiroyuki 已提交
5202 5203 5204 5205 5206

	if (cssid)
		return cssid->id;
	return 0;
}
B
Ben Blum 已提交
5207
EXPORT_SYMBOL_GPL(css_id);
K
KAMEZAWA Hiroyuki 已提交
5208 5209 5210

unsigned short css_depth(struct cgroup_subsys_state *css)
{
5211 5212
	struct css_id *cssid;

5213
	cssid = rcu_dereference_check(css->id, css_refcnt(css));
K
KAMEZAWA Hiroyuki 已提交
5214 5215 5216 5217 5218

	if (cssid)
		return cssid->depth;
	return 0;
}
B
Ben Blum 已提交
5219
EXPORT_SYMBOL_GPL(css_depth);
K
KAMEZAWA Hiroyuki 已提交
5220

5221 5222 5223 5224 5225 5226
/**
 *  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
5227
 * this function reads css->id, the caller must hold rcu_read_lock().
5228 5229 5230 5231 5232 5233
 * 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
5234
bool css_is_ancestor(struct cgroup_subsys_state *child,
5235
		    const struct cgroup_subsys_state *root)
K
KAMEZAWA Hiroyuki 已提交
5236
{
5237 5238
	struct css_id *child_id;
	struct css_id *root_id;
K
KAMEZAWA Hiroyuki 已提交
5239

5240
	child_id  = rcu_dereference(child->id);
5241 5242
	if (!child_id)
		return false;
5243
	root_id = rcu_dereference(root->id);
5244 5245 5246 5247 5248 5249 5250
	if (!root_id)
		return false;
	if (child_id->depth < root_id->depth)
		return false;
	if (child_id->stack[root_id->depth] != root_id->id)
		return false;
	return true;
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KAMEZAWA Hiroyuki 已提交
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}

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);
5264
	spin_lock(&ss->id_lock);
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KAMEZAWA Hiroyuki 已提交
5265
	idr_remove(&ss->idr, id->id);
5266
	spin_unlock(&ss->id_lock);
5267
	kfree_rcu(id, rcu_head);
K
KAMEZAWA Hiroyuki 已提交
5268
}
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Ben Blum 已提交
5269
EXPORT_SYMBOL_GPL(free_css_id);
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KAMEZAWA Hiroyuki 已提交
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/*
 * 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;
	}
5292
	spin_lock(&ss->id_lock);
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KAMEZAWA Hiroyuki 已提交
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	/* Don't use 0. allocates an ID of 1-65535 */
	error = idr_get_new_above(&ss->idr, newid, 1, &myid);
5295
	spin_unlock(&ss->id_lock);
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KAMEZAWA Hiroyuki 已提交
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	/* 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;
5310
	spin_lock(&ss->id_lock);
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KAMEZAWA Hiroyuki 已提交
5311
	idr_remove(&ss->idr, myid);
5312
	spin_unlock(&ss->id_lock);
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5313 5314 5315 5316 5317 5318
err_out:
	kfree(newid);
	return ERR_PTR(error);

}

5319 5320
static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
					    struct cgroup_subsys_state *rootcss)
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KAMEZAWA Hiroyuki 已提交
5321 5322 5323
{
	struct css_id *newid;

5324
	spin_lock_init(&ss->id_lock);
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KAMEZAWA Hiroyuki 已提交
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	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;
5342
	struct css_id *child_id, *parent_id;
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KAMEZAWA Hiroyuki 已提交
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	subsys_id = ss->subsys_id;
	parent_css = parent->subsys[subsys_id];
	child_css = child->subsys[subsys_id];
	parent_id = parent_css->id;
5348
	depth = parent_id->depth + 1;
K
KAMEZAWA Hiroyuki 已提交
5349 5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383 5384 5385

	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
5386
EXPORT_SYMBOL_GPL(css_lookup);
K
KAMEZAWA Hiroyuki 已提交
5387 5388 5389 5390 5391 5392 5393 5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411

/**
 * 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);
5412 5413
	WARN_ON_ONCE(!rcu_read_lock_held());

K
KAMEZAWA Hiroyuki 已提交
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	/* fill start point for scan */
	tmpid = id;
	while (1) {
		/*
		 * scan next entry from bitmap(tree), tmpid is updated after
		 * idr_get_next().
		 */
		tmp = idr_get_next(&ss->idr, &tmpid);
		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
5437 5438 5439 5440 5441 5442 5443 5444 5445 5446 5447 5448 5449 5450 5451 5452 5453 5454 5455 5456 5457 5458 5459
/*
 * 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);
}

5460
#ifdef CONFIG_CGROUP_DEBUG
5461
static struct cgroup_subsys_state *debug_create(struct cgroup *cont)
5462 5463 5464 5465 5466 5467 5468 5469 5470
{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

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

	return css;
}

5471
static void debug_destroy(struct cgroup *cont)
5472 5473 5474 5475 5476 5477 5478 5479 5480 5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496 5497 5498 5499 5500 5501
{
	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;
}

5502 5503 5504 5505 5506 5507 5508 5509 5510 5511 5512 5513 5514 5515 5516 5517 5518 5519
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 = "?";
5520 5521
		seq_printf(seq, "Root %d group %s\n",
			   c->root->hierarchy_id, name);
5522 5523 5524 5525 5526 5527 5528 5529 5530 5531 5532 5533 5534 5535 5536 5537 5538 5539 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551 5552 5553 5554
	}
	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;
}

5555 5556 5557 5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574 5575 5576 5577 5578 5579
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,
	},

5580 5581 5582 5583 5584 5585 5586 5587 5588 5589
	{
		.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,
	},

5590 5591 5592 5593 5594
	{
		.name = "releasable",
		.read_u64 = releasable_read,
	},

5595 5596
	{ }	/* terminate */
};
5597 5598 5599 5600 5601 5602

struct cgroup_subsys debug_subsys = {
	.name = "debug",
	.create = debug_create,
	.destroy = debug_destroy,
	.subsys_id = debug_subsys_id,
5603
	.base_cftypes = debug_files,
5604 5605
};
#endif /* CONFIG_CGROUP_DEBUG */