cgroup.c 144.5 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
 * populated up to CGROUP_BUILTIN_SUBSYS_COUNT, and modular subsystems are
 * registered after that. The mutable section of this array is protected by
 * cgroup_mutex.
 */
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#define SUBSYS(_x) &_x ## _subsys,
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static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
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#include <linux/cgroup_subsys.h>
};

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#define MAX_CGROUP_ROOT_NAMELEN 64

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

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

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

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

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

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

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

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

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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 {
	ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
};

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

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

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

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

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

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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_bits & (1UL << i)) {
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			/* Subsystem is in this hierarchy. So we want
			 * the subsystem state from the new
			 * cgroup */
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			template[i] = cgrp->subsys[i];
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		} else {
			/* Subsystem is not in this hierarchy, so we
			 * don't want to change the subsystem state */
			template[i] = oldcg->subsys[i];
		}
	}

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

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

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

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

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

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

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

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

	struct list_head tmp_cg_links;

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	struct hlist_head *hhead;
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	struct cg_cgroup_link *link;
658

659 660
	/* First see if we already have a cgroup group that matches
	 * the desired set */
661
	read_lock(&css_set_lock);
662
	res = find_existing_css_set(oldcg, cgrp, template);
663 664
	if (res)
		get_css_set(res);
665
	read_unlock(&css_set_lock);
666 667 668 669 670 671 672 673 674 675 676 677 678 679

	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;
	}

680
	atomic_set(&res->refcount, 1);
681 682
	INIT_LIST_HEAD(&res->cg_links);
	INIT_LIST_HEAD(&res->tasks);
683
	INIT_HLIST_NODE(&res->hlist);
684 685 686 687 688 689 690

	/* 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. */
691 692 693 694 695 696
	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);
	}
697 698 699 700

	BUG_ON(!list_empty(&tmp_cg_links));

	css_set_count++;
701 702 703 704 705

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

706 707 708
	write_unlock(&css_set_lock);

	return res;
709 710
}

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
/*
 * 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;
}

746 747 748 749 750 751 752 753 754 755
/*
 * 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
756
 * cgroup_attach_task() can increment it again.  Because a count of zero
757 758 759 760 761 762 763 764 765 766 767 768 769
 * 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.
772 773 774 775 776 777 778 779 780 781 782
 *
 * 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
783
 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
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 * another.  It does so using cgroup_mutex, however there are
785 786 787
 * 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
788
 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
789 790 791 792
 * 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
793
 * update of a tasks cgroup pointer by cgroup_attach_task()
794 795 796 797 798 799 800 801 802 803
 */

/**
 * 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);
805 806 807 808 809 810 811 812 813 814

/**
 * 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);
816 817 818 819 820 821 822 823

/*
 * 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.
 */

824
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);
826
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
827
static int cgroup_populate_dir(struct cgroup *cgrp);
828
static const struct inode_operations cgroup_dir_inode_operations;
829
static const struct file_operations proc_cgroupstats_operations;
830 831

static struct backing_dev_info cgroup_backing_dev_info = {
832
	.name		= "cgroup",
833
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
834
};
835

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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)
840 841 842 843
{
	struct inode *inode = new_inode(sb);

	if (inode) {
844
		inode->i_ino = get_next_ino();
845
		inode->i_mode = mode;
846 847
		inode->i_uid = current_fsuid();
		inode->i_gid = current_fsgid();
848 849 850 851 852 853
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
	}
	return inode;
}

854 855 856 857
/*
 * Call subsys's pre_destroy handler.
 * This is called before css refcnt check.
 */
858
static int cgroup_call_pre_destroy(struct cgroup *cgrp)
859 860
{
	struct cgroup_subsys *ss;
861 862
	int ret = 0;

863 864 865 866 867 868 869 870 871
	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;
872
		}
873
	}
874

875
	return ret;
876 877
}

878 879 880 881
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)) {
882
		struct cgroup *cgrp = dentry->d_fsdata;
883
		struct cgroup_subsys *ss;
884
		BUG_ON(!(cgroup_is_removed(cgrp)));
885 886 887 888 889 890 891
		/* 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();
892 893 894 895 896

		mutex_lock(&cgroup_mutex);
		/*
		 * Release the subsystem state objects.
		 */
897
		for_each_subsys(cgrp->root, ss)
898
			ss->destroy(cgrp);
899 900 901 902

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

903
		/*
904 905
		 * Drop the active superblock reference that we took when we
		 * created the cgroup
906
		 */
907
		deactivate_super(cgrp->root->sb);
908

909 910 911 912 913 914
		/*
		 * if we're getting rid of the cgroup, refcount should ensure
		 * that there are no pidlists left.
		 */
		BUG_ON(!list_empty(&cgrp->pidlists));

915
		kfree_rcu(cgrp, rcu_head);
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	} else {
		struct cfent *cfe = __d_cfe(dentry);
		struct cgroup *cgrp = dentry->d_parent->d_fsdata;

		WARN_ONCE(!list_empty(&cfe->node) &&
			  cgrp != &cgrp->root->top_cgroup,
			  "cfe still linked for %s\n", cfe->type->name);
		kfree(cfe);
924 925 926 927
	}
	iput(inode);
}

928 929 930 931 932
static int cgroup_delete(const struct dentry *d)
{
	return 1;
}

933 934 935 936 937 938 939 940 941
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);
957
		simple_unlink(cgrp->dentry->d_inode, d);
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		list_del_init(&cfe->node);
		dput(d);

		return 0;
962
	}
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	return -ENOENT;
}

static void cgroup_clear_directory(struct dentry *dir)
{
	struct cgroup *cgrp = __d_cgrp(dir);

	while (!list_empty(&cgrp->files))
		cgroup_rm_file(cgrp, NULL);
972 973 974 975 976 977 978
}

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

981 982
	cgroup_clear_directory(dentry);

N
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	parent = dentry->d_parent;
	spin_lock(&parent->d_lock);
985
	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
986
	list_del_init(&dentry->d_u.d_child);
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987 988
	spin_unlock(&dentry->d_lock);
	spin_unlock(&parent->d_lock);
989 990 991
	remove_dir(dentry);
}

992 993 994 995 996 997
/*
 * 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.
 *
998
 * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
999
 */
1000
static DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
1001

1002
static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
1003
{
1004
	if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
1005 1006 1007
		wake_up_all(&cgroup_rmdir_waitq);
}

1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018
void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
{
	css_get(css);
}

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

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/*
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1020 1021 1022
 * Call with cgroup_mutex held. Drops reference counts on modules, including
 * any duplicate ones that parse_cgroupfs_options took. If this function
 * returns an error, no reference counts are touched.
B
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 */
1024 1025 1026 1027
static int rebind_subsystems(struct cgroupfs_root *root,
			      unsigned long final_bits)
{
	unsigned long added_bits, removed_bits;
1028
	struct cgroup *cgrp = &root->top_cgroup;
1029 1030
	int i;

B
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1031
	BUG_ON(!mutex_is_locked(&cgroup_mutex));
T
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1032
	BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
B
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1034 1035 1036 1037
	removed_bits = root->actual_subsys_bits & ~final_bits;
	added_bits = final_bits & ~root->actual_subsys_bits;
	/* Check that any added subsystems are currently free */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
L
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1038
		unsigned long bit = 1UL << i;
1039 1040 1041
		struct cgroup_subsys *ss = subsys[i];
		if (!(bit & added_bits))
			continue;
B
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1042 1043 1044 1045 1046 1047
		/*
		 * 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);
1048 1049 1050 1051 1052 1053 1054 1055 1056 1057
		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 */
1058
	if (root->number_of_cgroups > 1)
1059 1060 1061 1062 1063 1064 1065 1066
		return -EBUSY;

	/* Process each subsystem */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		unsigned long bit = 1UL << i;
		if (bit & added_bits) {
			/* We're binding this subsystem to this hierarchy */
B
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1067
			BUG_ON(ss == NULL);
1068
			BUG_ON(cgrp->subsys[i]);
1069 1070
			BUG_ON(!dummytop->subsys[i]);
			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1071 1072
			cgrp->subsys[i] = dummytop->subsys[i];
			cgrp->subsys[i]->cgroup = cgrp;
1073
			list_move(&ss->sibling, &root->subsys_list);
1074
			ss->root = root;
1075
			if (ss->bind)
1076
				ss->bind(cgrp);
B
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			/* refcount was already taken, and we're keeping it */
1078 1079
		} else if (bit & removed_bits) {
			/* We're removing this subsystem */
B
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1080
			BUG_ON(ss == NULL);
1081 1082
			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1083
			if (ss->bind)
1084
				ss->bind(dummytop);
1085
			dummytop->subsys[i]->cgroup = dummytop;
1086
			cgrp->subsys[i] = NULL;
1087
			subsys[i]->root = &rootnode;
1088
			list_move(&ss->sibling, &rootnode.subsys_list);
B
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1089 1090
			/* subsystem is now free - drop reference on module */
			module_put(ss->module);
1091 1092
		} else if (bit & final_bits) {
			/* Subsystem state should already exist */
B
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1093
			BUG_ON(ss == NULL);
1094
			BUG_ON(!cgrp->subsys[i]);
B
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1095 1096 1097 1098 1099 1100 1101 1102
			/*
			 * 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
1103 1104
		} else {
			/* Subsystem state shouldn't exist */
1105
			BUG_ON(cgrp->subsys[i]);
1106 1107 1108 1109 1110 1111 1112 1113
		}
	}
	root->subsys_bits = root->actual_subsys_bits = final_bits;
	synchronize_rcu();

	return 0;
}

1114
static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1115
{
1116
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1117 1118
	struct cgroup_subsys *ss;

T
Tejun Heo 已提交
1119
	mutex_lock(&cgroup_root_mutex);
1120 1121 1122 1123
	for_each_subsys(root, ss)
		seq_printf(seq, ",%s", ss->name);
	if (test_bit(ROOT_NOPREFIX, &root->flags))
		seq_puts(seq, ",noprefix");
1124 1125
	if (strlen(root->release_agent_path))
		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1126 1127
	if (clone_children(&root->top_cgroup))
		seq_puts(seq, ",clone_children");
1128 1129
	if (strlen(root->name))
		seq_printf(seq, ",name=%s", root->name);
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	mutex_unlock(&cgroup_root_mutex);
1131 1132 1133 1134 1135 1136
	return 0;
}

struct cgroup_sb_opts {
	unsigned long subsys_bits;
	unsigned long flags;
1137
	char *release_agent;
1138
	bool clone_children;
1139
	char *name;
1140 1141
	/* User explicitly requested empty subsystem */
	bool none;
1142 1143

	struct cgroupfs_root *new_root;
1144

1145 1146
};

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/*
 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
B
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1149 1150 1151
 * 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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1152
 */
B
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1153
static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1154
{
1155 1156
	char *token, *o = data;
	bool all_ss = false, one_ss = false;
1157
	unsigned long mask = (unsigned long)-1;
B
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1158 1159
	int i;
	bool module_pin_failed = false;
1160

B
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1161 1162
	BUG_ON(!mutex_is_locked(&cgroup_mutex));

1163 1164 1165
#ifdef CONFIG_CPUSETS
	mask = ~(1UL << cpuset_subsys_id);
#endif
1166

1167
	memset(opts, 0, sizeof(*opts));
1168 1169 1170 1171

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
1172
		if (!strcmp(token, "none")) {
1173 1174
			/* Explicitly have no subsystems */
			opts->none = true;
1175 1176 1177 1178 1179 1180 1181 1182 1183 1184
			continue;
		}
		if (!strcmp(token, "all")) {
			/* Mutually exclusive option 'all' + subsystem name */
			if (one_ss)
				return -EINVAL;
			all_ss = true;
			continue;
		}
		if (!strcmp(token, "noprefix")) {
1185
			set_bit(ROOT_NOPREFIX, &opts->flags);
1186 1187 1188
			continue;
		}
		if (!strcmp(token, "clone_children")) {
1189
			opts->clone_children = true;
1190 1191 1192
			continue;
		}
		if (!strncmp(token, "release_agent=", 14)) {
1193 1194 1195
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1196
			opts->release_agent =
1197
				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1198 1199
			if (!opts->release_agent)
				return -ENOMEM;
1200 1201 1202
			continue;
		}
		if (!strncmp(token, "name=", 5)) {
1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219
			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,
1220
					      MAX_CGROUP_ROOT_NAMELEN - 1,
1221 1222 1223
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250

			continue;
		}

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

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

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

	/*
	 * If the 'all' option was specified select all the subsystems,
1251 1252
	 * otherwise if 'none', 'name=' and a subsystem name options
	 * were not specified, let's default to 'all'
1253
	 */
1254
	if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1255 1256 1257 1258 1259 1260 1261
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss == NULL)
				continue;
			if (ss->disabled)
				continue;
			set_bit(i, &opts->subsys_bits);
1262 1263 1264
		}
	}

1265 1266
	/* Consistency checks */

1267 1268 1269 1270 1271 1272 1273 1274 1275
	/*
	 * Option noprefix was introduced just for backward compatibility
	 * with the old cpuset, so we allow noprefix only if mounting just
	 * the cpuset subsystem.
	 */
	if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
	    (opts->subsys_bits & mask))
		return -EINVAL;

1276 1277 1278 1279 1280 1281 1282 1283 1284

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

	/*
	 * We either have to specify by name or by subsystems. (So all
	 * empty hierarchies must have a name).
	 */
1285
	if (!opts->subsys_bits && !opts->name)
1286 1287
		return -EINVAL;

B
Ben Blum 已提交
1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320
	/*
	 * Grab references on all the modules we'll need, so the subsystems
	 * don't dance around before rebind_subsystems attaches them. This may
	 * take duplicate reference counts on a subsystem that's already used,
	 * but rebind_subsystems handles this case.
	 */
	for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
		unsigned long bit = 1UL << i;

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

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

1321 1322 1323
	return 0;
}

B
Ben Blum 已提交
1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335
static void drop_parsed_module_refcounts(unsigned long subsys_bits)
{
	int i;
	for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
		unsigned long bit = 1UL << i;

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

1336 1337 1338 1339
static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
	int ret = 0;
	struct cgroupfs_root *root = sb->s_fs_info;
1340
	struct cgroup *cgrp = &root->top_cgroup;
1341 1342
	struct cgroup_sb_opts opts;

1343
	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1344
	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1345
	mutex_lock(&cgroup_root_mutex);
1346 1347 1348 1349 1350 1351

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

1352 1353 1354 1355 1356
	/* See feature-removal-schedule.txt */
	if (opts.subsys_bits != root->actual_subsys_bits || opts.release_agent)
		pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
			   task_tgid_nr(current), current->comm);

B
Ben Blum 已提交
1357 1358 1359
	/* Don't allow flags or name to change at remount */
	if (opts.flags != root->flags ||
	    (opts.name && strcmp(opts.name, root->name))) {
1360
		ret = -EINVAL;
B
Ben Blum 已提交
1361
		drop_parsed_module_refcounts(opts.subsys_bits);
1362 1363 1364
		goto out_unlock;
	}

1365
	ret = rebind_subsystems(root, opts.subsys_bits);
B
Ben Blum 已提交
1366 1367
	if (ret) {
		drop_parsed_module_refcounts(opts.subsys_bits);
1368
		goto out_unlock;
B
Ben Blum 已提交
1369
	}
1370

1371 1372
	/* clear out any existing files and repopulate subsystem files */
	cgroup_clear_directory(cgrp->dentry);
1373
	cgroup_populate_dir(cgrp);
1374

1375 1376
	if (opts.release_agent)
		strcpy(root->release_agent_path, opts.release_agent);
1377
 out_unlock:
1378
	kfree(opts.release_agent);
1379
	kfree(opts.name);
T
Tejun Heo 已提交
1380
	mutex_unlock(&cgroup_root_mutex);
1381
	mutex_unlock(&cgroup_mutex);
1382
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1383 1384 1385
	return ret;
}

1386
static const struct super_operations cgroup_ops = {
1387 1388 1389 1390 1391 1392
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.show_options = cgroup_show_options,
	.remount_fs = cgroup_remount,
};

1393 1394 1395 1396
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
	INIT_LIST_HEAD(&cgrp->sibling);
	INIT_LIST_HEAD(&cgrp->children);
T
Tejun Heo 已提交
1397
	INIT_LIST_HEAD(&cgrp->files);
1398 1399
	INIT_LIST_HEAD(&cgrp->css_sets);
	INIT_LIST_HEAD(&cgrp->release_list);
1400 1401
	INIT_LIST_HEAD(&cgrp->pidlists);
	mutex_init(&cgrp->pidlist_mutex);
1402 1403
	INIT_LIST_HEAD(&cgrp->event_list);
	spin_lock_init(&cgrp->event_list_lock);
1404
}
1405

1406 1407
static void init_cgroup_root(struct cgroupfs_root *root)
{
1408
	struct cgroup *cgrp = &root->top_cgroup;
1409

1410 1411
	INIT_LIST_HEAD(&root->subsys_list);
	INIT_LIST_HEAD(&root->root_list);
1412
	INIT_LIST_HEAD(&root->allcg_list);
1413
	root->number_of_cgroups = 1;
1414 1415
	cgrp->root = root;
	cgrp->top_cgroup = cgrp;
1416
	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1417
	init_cgroup_housekeeping(cgrp);
1418 1419
}

1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444
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;
}

1445 1446
static int cgroup_test_super(struct super_block *sb, void *data)
{
1447
	struct cgroup_sb_opts *opts = data;
1448 1449
	struct cgroupfs_root *root = sb->s_fs_info;

1450 1451 1452
	/* If we asked for a name then it must match */
	if (opts->name && strcmp(opts->name, root->name))
		return 0;
1453

1454 1455 1456 1457 1458 1459
	/*
	 * If we asked for subsystems (or explicitly for no
	 * subsystems) then they must match
	 */
	if ((opts->subsys_bits || opts->none)
	    && (opts->subsys_bits != root->subsys_bits))
1460 1461 1462 1463 1464
		return 0;

	return 1;
}

1465 1466 1467 1468
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
	struct cgroupfs_root *root;

1469
	if (!opts->subsys_bits && !opts->none)
1470 1471 1472 1473 1474 1475
		return NULL;

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

1476 1477 1478 1479
	if (!init_root_id(root)) {
		kfree(root);
		return ERR_PTR(-ENOMEM);
	}
1480
	init_cgroup_root(root);
1481

1482 1483 1484 1485 1486 1487
	root->subsys_bits = opts->subsys_bits;
	root->flags = opts->flags;
	if (opts->release_agent)
		strcpy(root->release_agent_path, opts->release_agent);
	if (opts->name)
		strcpy(root->name, opts->name);
1488 1489
	if (opts->clone_children)
		set_bit(CGRP_CLONE_CHILDREN, &root->top_cgroup.flags);
1490 1491 1492
	return root;
}

1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504
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);
}

1505 1506 1507
static int cgroup_set_super(struct super_block *sb, void *data)
{
	int ret;
1508 1509 1510 1511 1512 1513
	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;

1514
	BUG_ON(!opts->subsys_bits && !opts->none);
1515 1516 1517 1518 1519

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

1520 1521
	sb->s_fs_info = opts->new_root;
	opts->new_root->sb = sb;
1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532

	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
1533 1534
	static const struct dentry_operations cgroup_dops = {
		.d_iput = cgroup_diput,
1535
		.d_delete = cgroup_delete,
A
Al Viro 已提交
1536 1537
	};

1538 1539 1540 1541 1542 1543 1544 1545 1546 1547
	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);
1548 1549
	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
1550
		return -ENOMEM;
A
Al Viro 已提交
1551 1552
	/* for everything else we want ->d_op set */
	sb->s_d_op = &cgroup_dops;
1553 1554 1555
	return 0;
}

A
Al Viro 已提交
1556
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1557
			 int flags, const char *unused_dev_name,
A
Al Viro 已提交
1558
			 void *data)
1559 1560
{
	struct cgroup_sb_opts opts;
1561
	struct cgroupfs_root *root;
1562 1563
	int ret = 0;
	struct super_block *sb;
1564
	struct cgroupfs_root *new_root;
T
Tejun Heo 已提交
1565
	struct inode *inode;
1566 1567

	/* First find the desired set of subsystems */
B
Ben Blum 已提交
1568
	mutex_lock(&cgroup_mutex);
1569
	ret = parse_cgroupfs_options(data, &opts);
B
Ben Blum 已提交
1570
	mutex_unlock(&cgroup_mutex);
1571 1572
	if (ret)
		goto out_err;
1573

1574 1575 1576 1577 1578 1579 1580
	/*
	 * 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
1581
		goto drop_modules;
1582
	}
1583
	opts.new_root = new_root;
1584

1585
	/* Locate an existing or new sb for this hierarchy */
D
David Howells 已提交
1586
	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
1587
	if (IS_ERR(sb)) {
1588
		ret = PTR_ERR(sb);
1589
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1590
		goto drop_modules;
1591 1592
	}

1593 1594 1595 1596 1597
	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;
1598
		struct cgroup *root_cgrp = &root->top_cgroup;
1599
		struct cgroupfs_root *existing_root;
1600
		const struct cred *cred;
1601
		int i;
1602 1603 1604 1605 1606 1607

		BUG_ON(sb->s_root != NULL);

		ret = cgroup_get_rootdir(sb);
		if (ret)
			goto drop_new_super;
1608
		inode = sb->s_root->d_inode;
1609

1610
		mutex_lock(&inode->i_mutex);
1611
		mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1612
		mutex_lock(&cgroup_root_mutex);
1613

T
Tejun Heo 已提交
1614 1615 1616 1617 1618 1619
		/* 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;
1620

1621 1622 1623 1624 1625 1626 1627 1628
		/*
		 * 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
1629 1630
		if (ret)
			goto unlock_drop;
1631

1632 1633
		ret = rebind_subsystems(root, root->subsys_bits);
		if (ret == -EBUSY) {
1634
			free_cg_links(&tmp_cg_links);
T
Tejun Heo 已提交
1635
			goto unlock_drop;
1636
		}
B
Ben Blum 已提交
1637 1638 1639 1640 1641
		/*
		 * There must be no failure case after here, since rebinding
		 * takes care of subsystems' refcounts, which are explicitly
		 * dropped in the failure exit path.
		 */
1642 1643 1644 1645 1646

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

		list_add(&root->root_list, &roots);
1647
		root_count++;
1648

1649
		sb->s_root->d_fsdata = root_cgrp;
1650 1651
		root->top_cgroup.dentry = sb->s_root;

1652 1653 1654
		/* Link the top cgroup in this hierarchy into all
		 * the css_set objects */
		write_lock(&css_set_lock);
1655 1656 1657
		for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
			struct hlist_head *hhead = &css_set_table[i];
			struct hlist_node *node;
1658
			struct css_set *cg;
1659

1660 1661
			hlist_for_each_entry(cg, node, hhead, hlist)
				link_css_set(&tmp_cg_links, cg, root_cgrp);
1662
		}
1663 1664 1665 1666
		write_unlock(&css_set_lock);

		free_cg_links(&tmp_cg_links);

1667 1668
		BUG_ON(!list_empty(&root_cgrp->sibling));
		BUG_ON(!list_empty(&root_cgrp->children));
1669 1670
		BUG_ON(root->number_of_cgroups != 1);

1671
		cred = override_creds(&init_cred);
1672
		cgroup_populate_dir(root_cgrp);
1673
		revert_creds(cred);
T
Tejun Heo 已提交
1674
		mutex_unlock(&cgroup_root_mutex);
1675
		mutex_unlock(&cgroup_mutex);
1676
		mutex_unlock(&inode->i_mutex);
1677 1678 1679 1680 1681
	} else {
		/*
		 * We re-used an existing hierarchy - the new root (if
		 * any) is not needed
		 */
1682
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1683 1684
		/* no subsys rebinding, so refcounts don't change */
		drop_parsed_module_refcounts(opts.subsys_bits);
1685 1686
	}

1687 1688
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1689
	return dget(sb->s_root);
1690

T
Tejun Heo 已提交
1691 1692 1693 1694
 unlock_drop:
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&inode->i_mutex);
1695
 drop_new_super:
1696
	deactivate_locked_super(sb);
B
Ben Blum 已提交
1697 1698
 drop_modules:
	drop_parsed_module_refcounts(opts.subsys_bits);
1699 1700 1701
 out_err:
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1702
	return ERR_PTR(ret);
1703 1704 1705 1706
}

static void cgroup_kill_sb(struct super_block *sb) {
	struct cgroupfs_root *root = sb->s_fs_info;
1707
	struct cgroup *cgrp = &root->top_cgroup;
1708
	int ret;
K
KOSAKI Motohiro 已提交
1709 1710
	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;
1711 1712 1713 1714

	BUG_ON(!root);

	BUG_ON(root->number_of_cgroups != 1);
1715 1716
	BUG_ON(!list_empty(&cgrp->children));
	BUG_ON(!list_empty(&cgrp->sibling));
1717 1718

	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1719
	mutex_lock(&cgroup_root_mutex);
1720 1721 1722 1723 1724 1725

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

1726 1727 1728 1729 1730
	/*
	 * Release all the links from css_sets to this hierarchy's
	 * root cgroup
	 */
	write_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
1731 1732 1733

	list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
				 cgrp_link_list) {
1734
		list_del(&link->cg_link_list);
1735
		list_del(&link->cgrp_link_list);
1736 1737 1738 1739
		kfree(link);
	}
	write_unlock(&css_set_lock);

1740 1741 1742 1743
	if (!list_empty(&root->root_list)) {
		list_del(&root->root_list);
		root_count--;
	}
1744

T
Tejun Heo 已提交
1745
	mutex_unlock(&cgroup_root_mutex);
1746 1747 1748
	mutex_unlock(&cgroup_mutex);

	kill_litter_super(sb);
1749
	cgroup_drop_root(root);
1750 1751 1752 1753
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
A
Al Viro 已提交
1754
	.mount = cgroup_mount,
1755 1756 1757
	.kill_sb = cgroup_kill_sb,
};

1758 1759
static struct kobject *cgroup_kobj;

L
Li Zefan 已提交
1760 1761 1762 1763 1764 1765
/**
 * 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
 *
1766 1767 1768
 * 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.
1769
 */
1770
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1771 1772
{
	char *start;
1773 1774
	struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
						      cgroup_lock_is_held());
1775

1776
	if (!dentry || cgrp == dummytop) {
1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788
		/*
		 * Inactive subsystems have no dentry for their root
		 * cgroup
		 */
		strcpy(buf, "/");
		return 0;
	}

	start = buf + buflen;

	*--start = '\0';
	for (;;) {
1789
		int len = dentry->d_name.len;
1790

1791 1792
		if ((start -= len) < buf)
			return -ENAMETOOLONG;
1793
		memcpy(start, dentry->d_name.name, len);
1794 1795
		cgrp = cgrp->parent;
		if (!cgrp)
1796
			break;
1797 1798 1799

		dentry = rcu_dereference_check(cgrp->dentry,
					       cgroup_lock_is_held());
1800
		if (!cgrp->parent)
1801 1802 1803 1804 1805 1806 1807 1808
			continue;
		if (--start < buf)
			return -ENAMETOOLONG;
		*start = '/';
	}
	memmove(buf, start, buf + buflen - start);
	return 0;
}
B
Ben Blum 已提交
1809
EXPORT_SYMBOL_GPL(cgroup_path);
1810

1811 1812 1813
/*
 * Control Group taskset
 */
1814 1815 1816
struct task_and_cgroup {
	struct task_struct	*task;
	struct cgroup		*cgrp;
1817
	struct css_set		*cg;
1818 1819
};

1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 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
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
1891 1892 1893 1894 1895
/*
 * 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
1896
 * -ENOMEM. Must be called with cgroup_mutex and threadgroup locked.
B
Ben Blum 已提交
1897
 */
1898 1899
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
1900 1901 1902 1903
{
	struct css_set *oldcg;

	/*
1904 1905 1906
	 * 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
1907
	 */
1908
	WARN_ON_ONCE(tsk->flags & PF_EXITING);
B
Ben Blum 已提交
1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930
	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
1931 1932 1933 1934
/**
 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
 * @cgrp: the cgroup the task is attaching to
 * @tsk: the task to be attached
1935
 *
1936 1937
 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
 * @tsk during call.
1938
 */
1939
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1940
{
1941
	int retval = 0;
1942
	struct cgroup_subsys *ss, *failed_ss = NULL;
1943 1944
	struct cgroup *oldcgrp;
	struct cgroupfs_root *root = cgrp->root;
1945
	struct cgroup_taskset tset = { };
1946
	struct css_set *newcg;
1947

1948 1949 1950
	/* @tsk either already exited or can't exit until the end */
	if (tsk->flags & PF_EXITING)
		return -ESRCH;
1951 1952

	/* Nothing to do if the task is already in that cgroup */
1953
	oldcgrp = task_cgroup_from_root(tsk, root);
1954
	if (cgrp == oldcgrp)
1955 1956
		return 0;

1957 1958 1959
	tset.single.task = tsk;
	tset.single.cgrp = oldcgrp;

1960 1961
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
1962
			retval = ss->can_attach(cgrp, &tset);
1963 1964 1965 1966 1967 1968 1969 1970 1971 1972
			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;
			}
1973 1974 1975
		}
	}

1976 1977 1978
	newcg = find_css_set(tsk->cgroups, cgrp);
	if (!newcg) {
		retval = -ENOMEM;
1979
		goto out;
1980 1981 1982
	}

	cgroup_task_migrate(cgrp, oldcgrp, tsk, newcg);
1983

1984
	for_each_subsys(root, ss) {
P
Paul Jackson 已提交
1985
		if (ss->attach)
1986
			ss->attach(cgrp, &tset);
1987
	}
B
Ben Blum 已提交
1988

1989
	synchronize_rcu();
1990 1991 1992 1993 1994

	/*
	 * wake up rmdir() waiter. the rmdir should fail since the cgroup
	 * is no longer empty.
	 */
1995
	cgroup_wakeup_rmdir_waiter(cgrp);
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
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)
2008
				ss->cancel_attach(cgrp, &tset);
2009 2010 2011
		}
	}
	return retval;
2012 2013
}

2014
/**
M
Michael S. Tsirkin 已提交
2015 2016
 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
 * @from: attach to all cgroups of a given task
2017 2018
 * @tsk: the task to be attached
 */
M
Michael S. Tsirkin 已提交
2019
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2020 2021 2022 2023 2024 2025
{
	struct cgroupfs_root *root;
	int retval = 0;

	cgroup_lock();
	for_each_active_root(root) {
M
Michael S. Tsirkin 已提交
2026 2027 2028
		struct cgroup *from_cg = task_cgroup_from_root(from, root);

		retval = cgroup_attach_task(from_cg, tsk);
2029 2030 2031 2032 2033 2034 2035
		if (retval)
			break;
	}
	cgroup_unlock();

	return retval;
}
M
Michael S. Tsirkin 已提交
2036
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2037

B
Ben Blum 已提交
2038 2039 2040 2041 2042
/**
 * 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
 *
2043 2044
 * 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
2045
 */
2046
static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
B
Ben Blum 已提交
2047 2048 2049 2050 2051 2052 2053
{
	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;
2054
	struct task_and_cgroup *tc;
2055
	struct flex_array *group;
2056
	struct cgroup_taskset tset = { };
B
Ben Blum 已提交
2057 2058 2059 2060 2061

	/*
	 * 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
2062 2063
	 * 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
2064 2065
	 */
	group_size = get_nr_threads(leader);
2066
	/* flex_array supports very large thread-groups better than kmalloc. */
2067
	group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
B
Ben Blum 已提交
2068 2069
	if (!group)
		return -ENOMEM;
2070 2071 2072 2073
	/* 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
2074 2075 2076

	tsk = leader;
	i = 0;
2077 2078 2079 2080 2081 2082
	/*
	 * 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
2083
	do {
2084 2085
		struct task_and_cgroup ent;

2086 2087 2088 2089
		/* @tsk either already exited or can't exit until the end */
		if (tsk->flags & PF_EXITING)
			continue;

B
Ben Blum 已提交
2090 2091
		/* as per above, nr_threads may decrease, but not increase. */
		BUG_ON(i >= group_size);
2092 2093
		ent.task = tsk;
		ent.cgrp = task_cgroup_from_root(tsk, root);
2094 2095 2096
		/* nothing to do if this task is already in the cgroup */
		if (ent.cgrp == cgrp)
			continue;
2097 2098 2099 2100
		/*
		 * saying GFP_ATOMIC has no effect here because we did prealloc
		 * earlier, but it's good form to communicate our expectations.
		 */
2101
		retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2102
		BUG_ON(retval != 0);
B
Ben Blum 已提交
2103 2104
		i++;
	} while_each_thread(leader, tsk);
2105
	rcu_read_unlock();
B
Ben Blum 已提交
2106 2107
	/* remember the number of threads in the array for later. */
	group_size = i;
2108 2109
	tset.tc_array = group;
	tset.tc_array_len = group_size;
B
Ben Blum 已提交
2110

2111 2112
	/* methods shouldn't be called if no task is actually migrating */
	retval = 0;
2113
	if (!group_size)
2114
		goto out_free_group_list;
2115

B
Ben Blum 已提交
2116 2117 2118 2119 2120
	/*
	 * step 1: check that we can legitimately attach to the cgroup.
	 */
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
2121
			retval = ss->can_attach(cgrp, &tset);
B
Ben Blum 已提交
2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133
			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++) {
2134
		tc = flex_array_get(group, i);
2135 2136 2137 2138
		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
2139 2140 2141 2142
		}
	}

	/*
2143 2144 2145
	 * 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
2146 2147
	 */
	for (i = 0; i < group_size; i++) {
2148
		tc = flex_array_get(group, i);
2149
		cgroup_task_migrate(cgrp, tc->cgrp, tc->task, tc->cg);
B
Ben Blum 已提交
2150 2151 2152 2153
	}
	/* nothing is sensitive to fork() after this point. */

	/*
2154
	 * step 4: do subsystem attach callbacks.
B
Ben Blum 已提交
2155 2156 2157
	 */
	for_each_subsys(root, ss) {
		if (ss->attach)
2158
			ss->attach(cgrp, &tset);
B
Ben Blum 已提交
2159 2160 2161 2162 2163 2164 2165 2166
	}

	/*
	 * step 5: success! and cleanup
	 */
	synchronize_rcu();
	cgroup_wakeup_rmdir_waiter(cgrp);
	retval = 0;
2167 2168 2169 2170 2171 2172 2173 2174
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
2175 2176 2177 2178
	}
out_cancel_attach:
	if (retval) {
		for_each_subsys(root, ss) {
2179
			if (ss == failed_ss)
B
Ben Blum 已提交
2180 2181
				break;
			if (ss->cancel_attach)
2182
				ss->cancel_attach(cgrp, &tset);
B
Ben Blum 已提交
2183 2184 2185
		}
	}
out_free_group_list:
2186
	flex_array_free(group);
B
Ben Blum 已提交
2187 2188 2189 2190 2191
	return retval;
}

/*
 * Find the task_struct of the task to attach by vpid and pass it along to the
2192 2193
 * function to attach either it or all tasks in its threadgroup. Will lock
 * cgroup_mutex and threadgroup; may take task_lock of task.
2194
 */
B
Ben Blum 已提交
2195
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2196 2197
{
	struct task_struct *tsk;
2198
	const struct cred *cred = current_cred(), *tcred;
2199 2200
	int ret;

B
Ben Blum 已提交
2201 2202 2203
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;

2204 2205
retry_find_task:
	rcu_read_lock();
2206
	if (pid) {
2207
		tsk = find_task_by_vpid(pid);
B
Ben Blum 已提交
2208 2209
		if (!tsk) {
			rcu_read_unlock();
2210 2211
			ret= -ESRCH;
			goto out_unlock_cgroup;
2212
		}
B
Ben Blum 已提交
2213 2214 2215 2216
		/*
		 * even if we're attaching all tasks in the thread group, we
		 * only need to check permissions on one of them.
		 */
2217
		tcred = __task_cred(tsk);
2218 2219 2220
		if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
		    !uid_eq(cred->euid, tcred->uid) &&
		    !uid_eq(cred->euid, tcred->suid)) {
2221
			rcu_read_unlock();
2222 2223
			ret = -EACCES;
			goto out_unlock_cgroup;
2224
		}
2225 2226
	} else
		tsk = current;
2227 2228

	if (threadgroup)
2229
		tsk = tsk->group_leader;
2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241

	/*
	 * 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;
	}

2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258
	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
2259
		ret = cgroup_attach_proc(cgrp, tsk);
2260
	} else
B
Ben Blum 已提交
2261
		ret = cgroup_attach_task(cgrp, tsk);
2262 2263
	threadgroup_unlock(tsk);

2264
	put_task_struct(tsk);
2265
out_unlock_cgroup:
B
Ben Blum 已提交
2266
	cgroup_unlock();
2267 2268 2269
	return ret;
}

2270
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
B
Ben Blum 已提交
2271 2272 2273 2274 2275
{
	return attach_task_by_pid(cgrp, pid, false);
}

static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2276
{
2277
	return attach_task_by_pid(cgrp, tgid, true);
2278 2279
}

2280 2281 2282 2283
/**
 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
 * @cgrp: the cgroup to be checked for liveness
 *
2284 2285
 * On success, returns true; the lock should be later released with
 * cgroup_unlock(). On failure returns false with no lock held.
2286
 */
2287
bool cgroup_lock_live_group(struct cgroup *cgrp)
2288 2289 2290 2291 2292 2293 2294 2295
{
	mutex_lock(&cgroup_mutex);
	if (cgroup_is_removed(cgrp)) {
		mutex_unlock(&cgroup_mutex);
		return false;
	}
	return true;
}
B
Ben Blum 已提交
2296
EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2297 2298 2299 2300 2301

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);
2302 2303
	if (strlen(buffer) >= PATH_MAX)
		return -EINVAL;
2304 2305
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
T
Tejun Heo 已提交
2306
	mutex_lock(&cgroup_root_mutex);
2307
	strcpy(cgrp->root->release_agent_path, buffer);
T
Tejun Heo 已提交
2308
	mutex_unlock(&cgroup_root_mutex);
2309
	cgroup_unlock();
2310 2311 2312 2313 2314 2315 2316 2317 2318 2319
	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');
2320
	cgroup_unlock();
2321 2322 2323
	return 0;
}

2324 2325 2326
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64

2327
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2328 2329 2330
				struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *unused_ppos)
2331
{
2332
	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343
	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 */
2344
	if (cft->write_u64) {
K
KOSAKI Motohiro 已提交
2345
		u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2346 2347 2348 2349
		if (*end)
			return -EINVAL;
		retval = cft->write_u64(cgrp, cft, val);
	} else {
K
KOSAKI Motohiro 已提交
2350
		s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2351 2352 2353 2354
		if (*end)
			return -EINVAL;
		retval = cft->write_s64(cgrp, cft, val);
	}
2355 2356 2357 2358 2359
	if (!retval)
		retval = nbytes;
	return retval;
}

2360 2361 2362 2363 2364
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)
{
2365
	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379
	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
2380 2381 2382 2383
	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
		retval = -EFAULT;
		goto out;
	}
2384 2385

	buffer[nbytes] = 0;     /* nul-terminate */
K
KOSAKI Motohiro 已提交
2386
	retval = cft->write_string(cgrp, cft, strstrip(buffer));
2387 2388
	if (!retval)
		retval = nbytes;
L
Li Zefan 已提交
2389
out:
2390 2391 2392 2393 2394
	if (buffer != local_buffer)
		kfree(buffer);
	return retval;
}

2395 2396 2397 2398
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);
2399
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2400

2401
	if (cgroup_is_removed(cgrp))
2402
		return -ENODEV;
2403
	if (cft->write)
2404
		return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2405 2406
	if (cft->write_u64 || cft->write_s64)
		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2407 2408
	if (cft->write_string)
		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2409 2410 2411 2412
	if (cft->trigger) {
		int ret = cft->trigger(cgrp, (unsigned int)cft->private);
		return ret ? ret : nbytes;
	}
2413
	return -EINVAL;
2414 2415
}

2416 2417 2418 2419
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
2420
{
2421
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2422
	u64 val = cft->read_u64(cgrp, cft);
2423 2424 2425 2426 2427
	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);

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

2428 2429 2430 2431 2432
static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
{
2433
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2434 2435 2436 2437 2438 2439
	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);
}

2440 2441 2442 2443
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);
2444
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2445

2446
	if (cgroup_is_removed(cgrp))
2447 2448 2449
		return -ENODEV;

	if (cft->read)
2450
		return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2451 2452
	if (cft->read_u64)
		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2453 2454
	if (cft->read_s64)
		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2455 2456 2457
	return -EINVAL;
}

2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477
/*
 * 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;
2478 2479 2480 2481 2482 2483 2484 2485
	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);
2486 2487
}

2488
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2489 2490 2491 2492 2493 2494
{
	struct seq_file *seq = file->private_data;
	kfree(seq->private);
	return single_release(inode, file);
}

2495
static const struct file_operations cgroup_seqfile_operations = {
2496
	.read = seq_read,
2497
	.write = cgroup_file_write,
2498 2499 2500 2501
	.llseek = seq_lseek,
	.release = cgroup_seqfile_release,
};

2502 2503 2504 2505 2506 2507 2508 2509 2510
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);
2511

2512
	if (cft->read_map || cft->read_seq_string) {
2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523
		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)
2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553
		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);
}

2554
static const struct file_operations cgroup_file_operations = {
2555 2556 2557 2558 2559 2560 2561
	.read = cgroup_file_read,
	.write = cgroup_file_write,
	.llseek = generic_file_llseek,
	.open = cgroup_file_open,
	.release = cgroup_file_release,
};

2562
static const struct inode_operations cgroup_dir_inode_operations = {
2563
	.lookup = cgroup_lookup,
2564 2565 2566 2567 2568
	.mkdir = cgroup_mkdir,
	.rmdir = cgroup_rmdir,
	.rename = cgroup_rename,
};

A
Al Viro 已提交
2569
static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
2570 2571 2572 2573 2574 2575 2576
{
	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
	d_add(dentry, NULL);
	return NULL;
}

2577 2578 2579 2580 2581 2582 2583 2584 2585 2586
/*
 * 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
2587
static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2588 2589
				struct super_block *sb)
{
2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609
	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 */
2610
		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
2611 2612 2613 2614 2615 2616 2617 2618 2619 2620
	} else if (S_ISREG(mode)) {
		inode->i_size = 0;
		inode->i_fop = &cgroup_file_operations;
	}
	d_instantiate(dentry, inode);
	dget(dentry);	/* Extra count - pin the dentry in core */
	return 0;
}

/*
L
Li Zefan 已提交
2621 2622 2623 2624 2625
 * 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.
2626
 */
2627
static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
A
Al Viro 已提交
2628
				umode_t mode)
2629 2630 2631 2632
{
	struct dentry *parent;
	int error = 0;

2633 2634
	parent = cgrp->parent->dentry;
	error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
2635
	if (!error) {
2636
		dentry->d_fsdata = cgrp;
2637
		inc_nlink(parent->d_inode);
2638
		rcu_assign_pointer(cgrp->dentry, dentry);
2639 2640 2641 2642 2643 2644 2645
		dget(dentry);
	}
	dput(dentry);

	return error;
}

L
Li Zefan 已提交
2646 2647 2648 2649 2650 2651 2652 2653 2654
/**
 * 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
2655
static umode_t cgroup_file_mode(const struct cftype *cft)
L
Li Zefan 已提交
2656
{
A
Al Viro 已提交
2657
	umode_t mode = 0;
L
Li Zefan 已提交
2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672

	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
2673 2674
static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
			   const struct cftype *cft)
2675
{
2676
	struct dentry *dir = cgrp->dentry;
T
Tejun Heo 已提交
2677
	struct cgroup *parent = __d_cgrp(dir);
2678
	struct dentry *dentry;
T
Tejun Heo 已提交
2679
	struct cfent *cfe;
2680
	int error;
A
Al Viro 已提交
2681
	umode_t mode;
2682
	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2683 2684 2685 2686 2687 2688 2689

	/* 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;

2690
	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2691 2692 2693 2694
		strcpy(name, subsys->name);
		strcat(name, ".");
	}
	strcat(name, cft->name);
T
Tejun Heo 已提交
2695

2696
	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
T
Tejun Heo 已提交
2697 2698 2699 2700 2701

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

2702
	dentry = lookup_one_len(name, dir, strlen(name));
T
Tejun Heo 已提交
2703
	if (IS_ERR(dentry)) {
2704
		error = PTR_ERR(dentry);
T
Tejun Heo 已提交
2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719
		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);
2720 2721 2722
	return error;
}

2723 2724
static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
			      const struct cftype cfts[], bool is_add)
2725
{
T
Tejun Heo 已提交
2726 2727 2728 2729
	const struct cftype *cft;
	int err, ret = 0;

	for (cft = cfts; cft->name[0] != '\0'; cft++) {
2730 2731 2732 2733
		if (is_add)
			err = cgroup_add_file(cgrp, subsys, cft);
		else
			err = cgroup_rm_file(cgrp, cft);
T
Tejun Heo 已提交
2734
		if (err) {
2735 2736
			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
2737 2738
			ret = err;
		}
2739
	}
T
Tejun Heo 已提交
2740
	return ret;
2741 2742
}

2743 2744 2745 2746 2747 2748 2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759
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,
2760
			       const struct cftype *cfts, bool is_add)
2761 2762 2763 2764 2765 2766 2767 2768 2769 2770 2771 2772 2773 2774 2775 2776 2777 2778 2779 2780 2781 2782 2783 2784 2785
	__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))
2786
			cgroup_addrm_files(cgrp, ss, cfts, is_add);
2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821
		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.
 */
int cgroup_add_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
{
	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);
2822
	cgroup_cfts_commit(ss, cfts, true);
2823 2824 2825 2826 2827

	return 0;
}
EXPORT_SYMBOL_GPL(cgroup_add_cftypes);

2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858
/**
 * 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.
 */
int cgroup_rm_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
{
	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
2859 2860 2861 2862 2863 2864
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2865
int cgroup_task_count(const struct cgroup *cgrp)
2866 2867
{
	int count = 0;
K
KOSAKI Motohiro 已提交
2868
	struct cg_cgroup_link *link;
2869 2870

	read_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
2871
	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2872
		count += atomic_read(&link->cg->refcount);
2873 2874
	}
	read_unlock(&css_set_lock);
2875 2876 2877
	return count;
}

2878 2879 2880 2881
/*
 * Advance a list_head iterator.  The iterator should be positioned at
 * the start of a css_set
 */
2882
static void cgroup_advance_iter(struct cgroup *cgrp,
2883
				struct cgroup_iter *it)
2884 2885 2886 2887 2888 2889 2890 2891
{
	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;
2892
		if (l == &cgrp->css_sets) {
2893 2894 2895
			it->cg_link = NULL;
			return;
		}
2896
		link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2897 2898 2899 2900 2901 2902
		cg = link->cg;
	} while (list_empty(&cg->tasks));
	it->cg_link = l;
	it->task = cg->tasks.next;
}

2903 2904 2905 2906 2907 2908
/*
 * 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().
 */
2909
static void cgroup_enable_task_cg_lists(void)
2910 2911 2912 2913
{
	struct task_struct *p, *g;
	write_lock(&css_set_lock);
	use_task_css_set_links = 1;
2914 2915 2916 2917 2918 2919 2920 2921
	/*
	 * 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);
2922 2923
	do_each_thread(g, p) {
		task_lock(p);
2924 2925 2926 2927 2928 2929
		/*
		 * 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))
2930 2931 2932
			list_add(&p->cg_list, &p->cgroups->tasks);
		task_unlock(p);
	} while_each_thread(g, p);
2933
	read_unlock(&tasklist_lock);
2934 2935 2936
	write_unlock(&css_set_lock);
}

2937
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
2938
	__acquires(css_set_lock)
2939 2940 2941 2942 2943 2944
{
	/*
	 * 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.
	 */
2945 2946 2947
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();

2948
	read_lock(&css_set_lock);
2949 2950
	it->cg_link = &cgrp->css_sets;
	cgroup_advance_iter(cgrp, it);
2951 2952
}

2953
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
2954 2955 2956 2957
					struct cgroup_iter *it)
{
	struct task_struct *res;
	struct list_head *l = it->task;
2958
	struct cg_cgroup_link *link;
2959 2960 2961 2962 2963 2964 2965

	/* 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;
2966 2967
	link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
	if (l == &link->cg->tasks) {
2968 2969
		/* We reached the end of this task list - move on to
		 * the next cg_cgroup_link */
2970
		cgroup_advance_iter(cgrp, it);
2971 2972 2973 2974 2975 2976
	} else {
		it->task = l;
	}
	return res;
}

2977
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
2978
	__releases(css_set_lock)
2979 2980 2981 2982
{
	read_unlock(&css_set_lock);
}

2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 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
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++) {
3120
			struct task_struct *q = heap->ptrs[i];
3121
			if (i == 0) {
3122 3123
				latest_time = q->start_time;
				latest_task = q;
3124 3125
			}
			/* Process the task per the caller's callback */
3126 3127
			scan->process_task(q, scan);
			put_task_struct(q);
3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142
		}
		/*
		 * 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;
}

3143
/*
3144
 * Stuff for reading the 'tasks'/'procs' files.
3145 3146 3147 3148 3149 3150 3151 3152
 *
 * 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.
 *
 */

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
/* 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;
};

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
/*
 * 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;
}

3221
/*
3222 3223 3224 3225
 * 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.
3226
 */
3227 3228 3229
/* 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)
3230
{
3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259
	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)) {
3260
		newlist = pidlist_resize(list, dest);
3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271
		if (newlist)
			*p = newlist;
	}
	return dest;
}

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

3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282
/*
 * 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 */
3283 3284
	struct pid_namespace *ns = current->nsproxy->pid_ns;

3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308
	/*
	 * 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;
3309
	l->key.ns = get_pid_ns(ns);
3310 3311 3312 3313 3314 3315 3316 3317
	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;
}

3318 3319 3320
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
3321 3322
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
3323 3324 3325 3326
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
3327 3328
	struct cgroup_iter it;
	struct task_struct *tsk;
3329 3330 3331 3332 3333 3334 3335 3336 3337
	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);
3338
	array = pidlist_allocate(length);
3339 3340 3341
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
3342 3343
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
3344
		if (unlikely(n == length))
3345
			break;
3346
		/* get tgid or pid for procs or tasks file respectively */
3347 3348 3349 3350
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
3351 3352
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
3353
	}
3354
	cgroup_iter_end(cgrp, &it);
3355 3356 3357
	length = n;
	/* now sort & (if procs) strip out duplicates */
	sort(array, length, sizeof(pid_t), cmppid, NULL);
3358
	if (type == CGROUP_FILE_PROCS)
3359
		length = pidlist_uniq(&array, length);
3360 3361
	l = cgroup_pidlist_find(cgrp, type);
	if (!l) {
3362
		pidlist_free(array);
3363
		return -ENOMEM;
3364
	}
3365
	/* store array, freeing old if necessary - lock already held */
3366
	pidlist_free(l->list);
3367 3368 3369 3370
	l->list = array;
	l->length = length;
	l->use_count++;
	up_write(&l->mutex);
3371
	*lp = l;
3372
	return 0;
3373 3374
}

B
Balbir Singh 已提交
3375
/**
L
Li Zefan 已提交
3376
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
3377 3378 3379
 * @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
3380 3381 3382
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
3383 3384 3385 3386
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
	int ret = -EINVAL;
3387
	struct cgroup *cgrp;
B
Balbir Singh 已提交
3388 3389
	struct cgroup_iter it;
	struct task_struct *tsk;
3390

B
Balbir Singh 已提交
3391
	/*
3392 3393
	 * Validate dentry by checking the superblock operations,
	 * and make sure it's a directory.
B
Balbir Singh 已提交
3394
	 */
3395 3396
	if (dentry->d_sb->s_op != &cgroup_ops ||
	    !S_ISDIR(dentry->d_inode->i_mode))
B
Balbir Singh 已提交
3397 3398 3399
		 goto err;

	ret = 0;
3400
	cgrp = dentry->d_fsdata;
B
Balbir Singh 已提交
3401

3402 3403
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
B
Balbir Singh 已提交
3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422
		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;
		}
	}
3423
	cgroup_iter_end(cgrp, &it);
B
Balbir Singh 已提交
3424 3425 3426 3427 3428

err:
	return ret;
}

3429

3430
/*
3431
 * seq_file methods for the tasks/procs files. The seq_file position is the
3432
 * next pid to display; the seq_file iterator is a pointer to the pid
3433
 * in the cgroup->l->list array.
3434
 */
3435

3436
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3437
{
3438 3439 3440 3441 3442 3443
	/*
	 * 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
	 */
3444
	struct cgroup_pidlist *l = s->private;
3445 3446 3447
	int index = 0, pid = *pos;
	int *iter;

3448
	down_read(&l->mutex);
3449
	if (pid) {
3450
		int end = l->length;
S
Stephen Rothwell 已提交
3451

3452 3453
		while (index < end) {
			int mid = (index + end) / 2;
3454
			if (l->list[mid] == pid) {
3455 3456
				index = mid;
				break;
3457
			} else if (l->list[mid] <= pid)
3458 3459 3460 3461 3462 3463
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
3464
	if (index >= l->length)
3465 3466
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
3467
	iter = l->list + index;
3468 3469 3470 3471
	*pos = *iter;
	return iter;
}

3472
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3473
{
3474 3475
	struct cgroup_pidlist *l = s->private;
	up_read(&l->mutex);
3476 3477
}

3478
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3479
{
3480 3481 3482
	struct cgroup_pidlist *l = s->private;
	pid_t *p = v;
	pid_t *end = l->list + l->length;
3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495
	/*
	 * 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;
	}
}

3496
static int cgroup_pidlist_show(struct seq_file *s, void *v)
3497 3498 3499
{
	return seq_printf(s, "%d\n", *(int *)v);
}
3500

3501 3502 3503 3504 3505 3506 3507 3508 3509
/*
 * 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,
3510 3511
};

3512
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3513
{
3514 3515 3516 3517 3518 3519 3520
	/*
	 * 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);
3521 3522 3523
	down_write(&l->mutex);
	BUG_ON(!l->use_count);
	if (!--l->use_count) {
3524 3525 3526
		/* we're the last user if refcount is 0; remove and free */
		list_del(&l->links);
		mutex_unlock(&l->owner->pidlist_mutex);
3527
		pidlist_free(l->list);
3528 3529 3530 3531
		put_pid_ns(l->key.ns);
		up_write(&l->mutex);
		kfree(l);
		return;
3532
	}
3533
	mutex_unlock(&l->owner->pidlist_mutex);
3534
	up_write(&l->mutex);
3535 3536
}

3537
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3538
{
3539
	struct cgroup_pidlist *l;
3540 3541
	if (!(file->f_mode & FMODE_READ))
		return 0;
3542 3543 3544 3545 3546 3547
	/*
	 * 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);
3548 3549 3550
	return seq_release(inode, file);
}

3551
static const struct file_operations cgroup_pidlist_operations = {
3552 3553 3554
	.read = seq_read,
	.llseek = seq_lseek,
	.write = cgroup_file_write,
3555
	.release = cgroup_pidlist_release,
3556 3557
};

3558
/*
3559 3560 3561
 * 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.
3562
 */
3563
/* helper function for the two below it */
3564
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3565
{
3566
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3567
	struct cgroup_pidlist *l;
3568
	int retval;
3569

3570
	/* Nothing to do for write-only files */
3571 3572 3573
	if (!(file->f_mode & FMODE_READ))
		return 0;

3574
	/* have the array populated */
3575
	retval = pidlist_array_load(cgrp, type, &l);
3576 3577 3578 3579
	if (retval)
		return retval;
	/* configure file information */
	file->f_op = &cgroup_pidlist_operations;
3580

3581
	retval = seq_open(file, &cgroup_pidlist_seq_operations);
3582
	if (retval) {
3583
		cgroup_release_pid_array(l);
3584
		return retval;
3585
	}
3586
	((struct seq_file *)file->private_data)->private = l;
3587 3588
	return 0;
}
3589 3590
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
3591
	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3592 3593 3594
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
3595
	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3596
}
3597

3598
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3599 3600
					    struct cftype *cft)
{
3601
	return notify_on_release(cgrp);
3602 3603
}

3604 3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615
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;
}

3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629 3630
/*
 * 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);
3631
	dput(cgrp->dentry);
3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647
}

/*
 * 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
3648
		__remove_wait_queue(event->wqh, &event->wait);
3649 3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671 3672 3673 3674 3675 3676 3677 3678 3679 3680 3681 3682 3683 3684 3685 3686 3687 3688 3689 3690 3691 3692 3693 3694 3695 3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708 3709 3710 3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723 3724 3725
		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
3726 3727
	/* AV: shouldn't we check that it's been opened for read instead? */
	ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752
	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;
	}

3753 3754 3755 3756 3757 3758 3759
	/*
	 * 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);

3760 3761 3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783
	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;
}

3784 3785 3786 3787 3788 3789 3790 3791 3792 3793 3794 3795 3796 3797 3798 3799 3800
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;
}

3801 3802 3803
/*
 * for the common functions, 'private' gives the type of file
 */
3804 3805
/* for hysterical raisins, we can't put this on the older files */
#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3806 3807 3808 3809
static struct cftype files[] = {
	{
		.name = "tasks",
		.open = cgroup_tasks_open,
3810
		.write_u64 = cgroup_tasks_write,
3811
		.release = cgroup_pidlist_release,
L
Li Zefan 已提交
3812
		.mode = S_IRUGO | S_IWUSR,
3813
	},
3814 3815 3816
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "procs",
		.open = cgroup_procs_open,
B
Ben Blum 已提交
3817
		.write_u64 = cgroup_procs_write,
3818
		.release = cgroup_pidlist_release,
B
Ben Blum 已提交
3819
		.mode = S_IRUGO | S_IWUSR,
3820
	},
3821 3822
	{
		.name = "notify_on_release",
3823
		.read_u64 = cgroup_read_notify_on_release,
3824
		.write_u64 = cgroup_write_notify_on_release,
3825
	},
3826 3827 3828 3829 3830
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "event_control",
		.write_string = cgroup_write_event_control,
		.mode = S_IWUGO,
	},
3831 3832 3833 3834 3835
	{
		.name = "cgroup.clone_children",
		.read_u64 = cgroup_clone_children_read,
		.write_u64 = cgroup_clone_children_write,
	},
3836 3837 3838 3839 3840 3841 3842
	{
		.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
3843
	{ }	/* terminate */
3844 3845
};

3846
static int cgroup_populate_dir(struct cgroup *cgrp)
3847 3848 3849 3850
{
	int err;
	struct cgroup_subsys *ss;

3851
	err = cgroup_addrm_files(cgrp, NULL, files, true);
3852 3853 3854
	if (err < 0)
		return err;

3855
	/* process cftsets of each subsystem */
3856
	for_each_subsys(cgrp->root, ss) {
3857 3858
		struct cftype_set *set;

T
Tejun Heo 已提交
3859
		list_for_each_entry(set, &ss->cftsets, node)
3860
			cgroup_addrm_files(cgrp, ss, set->cfts, true);
3861
	}
3862

K
KAMEZAWA Hiroyuki 已提交
3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873
	/* 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);
	}
3874 3875 3876 3877

	return 0;
}

3878 3879 3880 3881
static void css_dput_fn(struct work_struct *work)
{
	struct cgroup_subsys_state *css =
		container_of(work, struct cgroup_subsys_state, dput_work);
3882 3883
	struct dentry *dentry = css->cgroup->dentry;
	struct super_block *sb = dentry->d_sb;
3884

3885 3886 3887
	atomic_inc(&sb->s_active);
	dput(dentry);
	deactivate_super(sb);
3888 3889
}

3890 3891
static void init_cgroup_css(struct cgroup_subsys_state *css,
			       struct cgroup_subsys *ss,
3892
			       struct cgroup *cgrp)
3893
{
3894
	css->cgroup = cgrp;
P
Paul Menage 已提交
3895
	atomic_set(&css->refcnt, 1);
3896
	css->flags = 0;
K
KAMEZAWA Hiroyuki 已提交
3897
	css->id = NULL;
3898
	if (cgrp == dummytop)
3899
		set_bit(CSS_ROOT, &css->flags);
3900 3901
	BUG_ON(cgrp->subsys[ss->subsys_id]);
	cgrp->subsys[ss->subsys_id] = css;
3902 3903 3904 3905 3906 3907 3908 3909 3910 3911

	/*
	 * 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);
3912 3913 3914
}

/*
L
Li Zefan 已提交
3915 3916 3917 3918
 * 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
3919
 *
L
Li Zefan 已提交
3920
 * Must be called with the mutex on the parent inode held
3921 3922
 */
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
A
Al Viro 已提交
3923
			     umode_t mode)
3924
{
3925
	struct cgroup *cgrp;
3926 3927 3928 3929 3930
	struct cgroupfs_root *root = parent->root;
	int err = 0;
	struct cgroup_subsys *ss;
	struct super_block *sb = root->sb;

3931 3932
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943
		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);

3944
	init_cgroup_housekeeping(cgrp);
3945

3946 3947 3948
	cgrp->parent = parent;
	cgrp->root = parent->root;
	cgrp->top_cgroup = parent->top_cgroup;
3949

3950 3951 3952
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

3953 3954 3955
	if (clone_children(parent))
		set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);

3956
	for_each_subsys(root, ss) {
3957
		struct cgroup_subsys_state *css = ss->create(cgrp);
3958

3959 3960 3961 3962
		if (IS_ERR(css)) {
			err = PTR_ERR(css);
			goto err_destroy;
		}
3963
		init_cgroup_css(css, ss, cgrp);
3964 3965 3966
		if (ss->use_id) {
			err = alloc_css_id(ss, parent, cgrp);
			if (err)
K
KAMEZAWA Hiroyuki 已提交
3967
				goto err_destroy;
3968
		}
K
KAMEZAWA Hiroyuki 已提交
3969
		/* At error, ->destroy() callback has to free assigned ID. */
3970
		if (clone_children(parent) && ss->post_clone)
3971
			ss->post_clone(cgrp);
3972 3973
	}

3974
	list_add(&cgrp->sibling, &cgrp->parent->children);
3975 3976
	root->number_of_cgroups++;

3977
	err = cgroup_create_dir(cgrp, dentry, mode);
3978 3979 3980
	if (err < 0)
		goto err_remove;

3981 3982 3983 3984 3985
	/* 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);

3986
	/* The cgroup directory was pre-locked for us */
3987
	BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
3988

3989 3990
	list_add_tail(&cgrp->allcg_node, &root->allcg_list);

3991
	err = cgroup_populate_dir(cgrp);
3992 3993 3994
	/* If err < 0, we have a half-filled directory - oh well ;) */

	mutex_unlock(&cgroup_mutex);
3995
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
3996 3997 3998 3999 4000

	return 0;

 err_remove:

4001
	list_del(&cgrp->sibling);
4002 4003 4004 4005 4006
	root->number_of_cgroups--;

 err_destroy:

	for_each_subsys(root, ss) {
4007
		if (cgrp->subsys[ss->subsys_id])
4008
			ss->destroy(cgrp);
4009 4010 4011 4012 4013 4014 4015
	}

	mutex_unlock(&cgroup_mutex);

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

4016
	kfree(cgrp);
4017 4018 4019
	return err;
}

4020
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
4021 4022 4023 4024 4025 4026 4027
{
	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);
}

4028 4029 4030 4031 4032 4033 4034 4035 4036
/*
 * 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.
 */
4037
static int cgroup_has_css_refs(struct cgroup *cgrp)
4038 4039
{
	int i;
4040

B
Ben Blum 已提交
4041 4042 4043 4044 4045
	/*
	 * 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.
	 */
4046 4047 4048
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		struct cgroup_subsys_state *css;
4049

B
Ben Blum 已提交
4050 4051
		/* Skip subsystems not present or not in this hierarchy */
		if (ss == NULL || ss->root != cgrp->root)
4052
			continue;
4053

4054
		css = cgrp->subsys[ss->subsys_id];
4055 4056
		/*
		 * When called from check_for_release() it's possible
4057 4058 4059 4060
		 * 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
4061 4062 4063
		 * release agent to be called anyway.
		 */
		if (css && css_refcnt(css) > 1)
4064 4065 4066 4067 4068
			return 1;
	}
	return 0;
}

P
Paul Menage 已提交
4069 4070 4071 4072
/*
 * 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
4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088 4089
 *
 * 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
4090 4091 4092 4093 4094 4095
 */
static int cgroup_clear_css_refs(struct cgroup *cgrp)
{
	struct cgroup_subsys *ss;
	unsigned long flags;
	bool failed = false;
4096

P
Paul Menage 已提交
4097
	local_irq_save(flags);
4098 4099 4100

	/*
	 * Block new css_tryget() by deactivating refcnt.  If all refcnts
4101 4102
	 * for subsystems w/ clear_css_refs set were 1 at the moment of
	 * deactivation, we succeeded.
4103
	 */
P
Paul Menage 已提交
4104 4105
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4106 4107 4108

		WARN_ON(atomic_read(&css->refcnt) < 0);
		atomic_add(CSS_DEACT_BIAS, &css->refcnt);
4109 4110 4111

		if (ss->__DEPRECATED_clear_css_refs)
			failed |= css_refcnt(css) != 1;
P
Paul Menage 已提交
4112
	}
4113 4114 4115 4116 4117 4118

	/*
	 * 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
4119 4120
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4121 4122

		if (!failed) {
P
Paul Menage 已提交
4123
			set_bit(CSS_REMOVED, &css->flags);
4124 4125 4126
			css_put(css);
		} else {
			atomic_sub(CSS_DEACT_BIAS, &css->refcnt);
P
Paul Menage 已提交
4127 4128
		}
	}
4129

P
Paul Menage 已提交
4130 4131 4132 4133
	local_irq_restore(flags);
	return !failed;
}

4134 4135
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
4136
	struct cgroup *cgrp = dentry->d_fsdata;
4137 4138
	struct dentry *d;
	struct cgroup *parent;
4139
	DEFINE_WAIT(wait);
4140
	struct cgroup_event *event, *tmp;
4141
	int ret;
4142 4143

	/* the vfs holds both inode->i_mutex already */
4144
again:
4145
	mutex_lock(&cgroup_mutex);
4146
	if (atomic_read(&cgrp->count) != 0) {
4147 4148 4149
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
4150
	if (!list_empty(&cgrp->children)) {
4151 4152 4153
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
4154
	mutex_unlock(&cgroup_mutex);
L
Li Zefan 已提交
4155

4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166
	/*
	 * 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);

4167
	/*
L
Li Zefan 已提交
4168 4169
	 * Call pre_destroy handlers of subsys. Notify subsystems
	 * that rmdir() request comes.
4170
	 */
4171
	ret = cgroup_call_pre_destroy(cgrp);
4172 4173
	if (ret) {
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4174
		return ret;
4175
	}
4176

4177 4178
	mutex_lock(&cgroup_mutex);
	parent = cgrp->parent;
4179
	if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
4180
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4181 4182 4183
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
4184 4185 4186
	prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
	if (!cgroup_clear_css_refs(cgrp)) {
		mutex_unlock(&cgroup_mutex);
4187 4188 4189 4190 4191 4192
		/*
		 * 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();
4193 4194 4195 4196 4197 4198 4199 4200 4201
		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);
4202

4203
	raw_spin_lock(&release_list_lock);
4204 4205
	set_bit(CGRP_REMOVED, &cgrp->flags);
	if (!list_empty(&cgrp->release_list))
4206
		list_del_init(&cgrp->release_list);
4207
	raw_spin_unlock(&release_list_lock);
4208 4209

	/* delete this cgroup from parent->children */
4210
	list_del_init(&cgrp->sibling);
4211

4212 4213
	list_del_init(&cgrp->allcg_node);

4214
	d = dget(cgrp->dentry);
4215 4216 4217 4218

	cgroup_d_remove_dir(d);
	dput(d);

4219
	set_bit(CGRP_RELEASABLE, &parent->flags);
4220 4221
	check_for_release(parent);

4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235
	/*
	 * 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);

4236 4237 4238 4239
	mutex_unlock(&cgroup_mutex);
	return 0;
}

4240 4241 4242 4243 4244 4245 4246 4247 4248 4249 4250 4251 4252 4253
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);
	}
}

4254
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4255 4256
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
4257 4258

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4259

4260 4261 4262
	/* init base cftset */
	cgroup_init_cftsets(ss);

4263
	/* Create the top cgroup state for this subsystem */
4264
	list_add(&ss->sibling, &rootnode.subsys_list);
4265
	ss->root = &rootnode;
4266
	css = ss->create(dummytop);
4267 4268 4269 4270
	/* We don't handle early failures gracefully */
	BUG_ON(IS_ERR(css));
	init_cgroup_css(css, ss, dummytop);

L
Li Zefan 已提交
4271
	/* Update the init_css_set to contain a subsys
4272
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
4273 4274 4275
	 * 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];
4276 4277 4278

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

L
Li Zefan 已提交
4279 4280 4281 4282 4283
	/* 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));

4284
	ss->active = 1;
4285 4286 4287 4288 4289 4290 4291 4292 4293 4294 4295

	/* 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
4296
 * subsystem is built as a module, it will be assigned a new subsys_id and set
4297 4298 4299 4300 4301 4302 4303 4304 4305 4306 4307 4308 4309 4310 4311 4312 4313 4314 4315 4316 4317 4318 4319 4320 4321 4322 4323 4324 4325 4326 4327 4328 4329
 * up for use. If the subsystem is built-in anyway, work is delegated to the
 * simpler cgroup_init_subsys.
 */
int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
{
	int i;
	struct cgroup_subsys_state *css;

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

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

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

4330 4331 4332
	/* init base cftset */
	cgroup_init_cftsets(ss);

4333 4334 4335 4336 4337 4338 4339 4340 4341 4342 4343 4344 4345 4346 4347 4348 4349 4350 4351 4352 4353 4354 4355
	/*
	 * need to register a subsys id before anything else - for example,
	 * init_cgroup_css needs it.
	 */
	mutex_lock(&cgroup_mutex);
	/* find the first empty slot in the array */
	for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
		if (subsys[i] == NULL)
			break;
	}
	if (i == CGROUP_SUBSYS_COUNT) {
		/* maximum number of subsystems already registered! */
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
	/* assign ourselves the subsys_id */
	ss->subsys_id = i;
	subsys[i] = ss;

	/*
	 * no ss->create seems to need anything important in the ss struct, so
	 * this can happen first (i.e. before the rootnode attachment).
	 */
4356
	css = ss->create(dummytop);
4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373
	if (IS_ERR(css)) {
		/* failure case - need to deassign the subsys[] slot. */
		subsys[i] = NULL;
		mutex_unlock(&cgroup_mutex);
		return PTR_ERR(css);
	}

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

	/* our new subsystem will be attached to the dummy hierarchy. */
	init_cgroup_css(css, ss, dummytop);
	/* init_idr must be after init_cgroup_css because it sets css->id. */
	if (ss->use_id) {
		int ret = cgroup_init_idr(ss, css);
		if (ret) {
			dummytop->subsys[ss->subsys_id] = NULL;
4374
			ss->destroy(dummytop);
4375 4376 4377 4378 4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389 4390 4391 4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414
			subsys[i] = NULL;
			mutex_unlock(&cgroup_mutex);
			return ret;
		}
	}

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

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

	ss->active = 1;

	/* success! */
	mutex_unlock(&cgroup_mutex);
	return 0;
4415
}
4416
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4417

B
Ben Blum 已提交
4418 4419 4420 4421 4422 4423 4424 4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445
/**
 * cgroup_unload_subsys: unload a modular subsystem
 * @ss: the subsystem to unload
 *
 * This function should be called in a modular subsystem's exitcall. When this
 * function is invoked, the refcount on the subsystem's module will be 0, so
 * the subsystem will not be attached to any hierarchy.
 */
void cgroup_unload_subsys(struct cgroup_subsys *ss)
{
	struct cg_cgroup_link *link;
	struct hlist_head *hhead;

	BUG_ON(ss->module == NULL);

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

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

	/* remove subsystem from rootnode's list of subsystems */
4446
	list_del_init(&ss->sibling);
B
Ben Blum 已提交
4447 4448 4449 4450 4451 4452 4453 4454 4455 4456 4457 4458 4459 4460 4461 4462 4463 4464 4465 4466 4467 4468 4469

	/*
	 * 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.
	 */
4470
	ss->destroy(dummytop);
B
Ben Blum 已提交
4471 4472 4473 4474 4475 4476
	dummytop->subsys[ss->subsys_id] = NULL;

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

4477
/**
L
Li Zefan 已提交
4478 4479 4480 4481
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
4482 4483 4484 4485
 */
int __init cgroup_init_early(void)
{
	int i;
4486
	atomic_set(&init_css_set.refcount, 1);
4487 4488
	INIT_LIST_HEAD(&init_css_set.cg_links);
	INIT_LIST_HEAD(&init_css_set.tasks);
4489
	INIT_HLIST_NODE(&init_css_set.hlist);
4490
	css_set_count = 1;
4491
	init_cgroup_root(&rootnode);
4492 4493 4494 4495
	root_count = 1;
	init_task.cgroups = &init_css_set;

	init_css_set_link.cg = &init_css_set;
4496
	init_css_set_link.cgrp = dummytop;
4497
	list_add(&init_css_set_link.cgrp_link_list,
4498 4499 4500
		 &rootnode.top_cgroup.css_sets);
	list_add(&init_css_set_link.cg_link_list,
		 &init_css_set.cg_links);
4501

4502 4503 4504
	for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
		INIT_HLIST_HEAD(&css_set_table[i]);

B
Ben Blum 已提交
4505 4506
	/* at bootup time, we don't worry about modular subsystems */
	for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4507 4508 4509 4510 4511 4512 4513
		struct cgroup_subsys *ss = subsys[i];

		BUG_ON(!ss->name);
		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
		BUG_ON(!ss->create);
		BUG_ON(!ss->destroy);
		if (ss->subsys_id != i) {
D
Diego Calleja 已提交
4514
			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4515 4516 4517 4518 4519 4520 4521 4522 4523 4524 4525
			       ss->name, ss->subsys_id);
			BUG();
		}

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

/**
L
Li Zefan 已提交
4526 4527 4528 4529
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
4530 4531 4532 4533 4534
 */
int __init cgroup_init(void)
{
	int err;
	int i;
4535
	struct hlist_head *hhead;
4536 4537 4538 4539

	err = bdi_init(&cgroup_backing_dev_info);
	if (err)
		return err;
4540

B
Ben Blum 已提交
4541 4542
	/* at bootup time, we don't worry about modular subsystems */
	for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4543 4544 4545
		struct cgroup_subsys *ss = subsys[i];
		if (!ss->early_init)
			cgroup_init_subsys(ss);
K
KAMEZAWA Hiroyuki 已提交
4546
		if (ss->use_id)
4547
			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4548 4549
	}

4550 4551 4552
	/* Add init_css_set to the hash table */
	hhead = css_set_hash(init_css_set.subsys);
	hlist_add_head(&init_css_set.hlist, hhead);
4553
	BUG_ON(!init_root_id(&rootnode));
4554 4555 4556 4557 4558 4559 4560

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

4561
	err = register_filesystem(&cgroup_fs_type);
4562 4563
	if (err < 0) {
		kobject_put(cgroup_kobj);
4564
		goto out;
4565
	}
4566

L
Li Zefan 已提交
4567
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4568

4569
out:
4570 4571 4572
	if (err)
		bdi_destroy(&cgroup_backing_dev_info);

4573 4574
	return err;
}
4575

4576 4577 4578 4579 4580 4581
/*
 * 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,
4582
 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601 4602 4603 4604 4605 4606 4607 4608 4609 4610 4611
 *    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);

4612
	for_each_active_root(root) {
4613
		struct cgroup_subsys *ss;
4614
		struct cgroup *cgrp;
4615 4616
		int count = 0;

4617
		seq_printf(m, "%d:", root->hierarchy_id);
4618 4619
		for_each_subsys(root, ss)
			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4620 4621 4622
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
4623
		seq_putc(m, ':');
4624
		cgrp = task_cgroup_from_root(tsk, root);
4625
		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4626 4627 4628 4629 4630 4631 4632 4633 4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644 4645 4646
		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);
}

4647
const struct file_operations proc_cgroup_operations = {
4648 4649 4650 4651 4652 4653 4654 4655 4656 4657 4658
	.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;

4659
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
B
Ben Blum 已提交
4660 4661 4662 4663 4664
	/*
	 * 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.
	 */
4665 4666 4667
	mutex_lock(&cgroup_mutex);
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
B
Ben Blum 已提交
4668 4669
		if (ss == NULL)
			continue;
4670 4671
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
4672
			   ss->root->number_of_cgroups, !ss->disabled);
4673 4674 4675 4676 4677 4678 4679
	}
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
4680
	return single_open(file, proc_cgroupstats_show, NULL);
4681 4682
}

4683
static const struct file_operations proc_cgroupstats_operations = {
4684 4685 4686 4687 4688 4689
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

4690 4691
/**
 * cgroup_fork - attach newly forked task to its parents cgroup.
L
Li Zefan 已提交
4692
 * @child: pointer to task_struct of forking parent process.
4693 4694 4695 4696 4697
 *
 * 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
4698 4699 4700 4701 4702 4703 4704 4705 4706 4707 4708
 * 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.
4709 4710 4711 4712 4713 4714
 *
 * 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)
{
4715 4716 4717 4718 4719 4720
	/*
	 * 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().
	 */
4721 4722 4723
	child->cgroups = current->cgroups;
	get_css_set(child->cgroups);
	INIT_LIST_HEAD(&child->cg_list);
4724 4725 4726
}

/**
L
Li Zefan 已提交
4727 4728 4729 4730 4731 4732
 * cgroup_fork_callbacks - run fork callbacks
 * @child: the new task
 *
 * Called on a new task very soon before adding it to the
 * tasklist. No need to take any locks since no-one can
 * be operating on this task.
4733 4734 4735 4736 4737
 */
void cgroup_fork_callbacks(struct task_struct *child)
{
	if (need_forkexit_callback) {
		int i;
B
Ben Blum 已提交
4738 4739 4740 4741 4742 4743
		/*
		 * forkexit callbacks are only supported for builtin
		 * subsystems, and the builtin section of the subsys array is
		 * immutable, so we don't need to lock the subsys array here.
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4744 4745
			struct cgroup_subsys *ss = subsys[i];
			if (ss->fork)
4746
				ss->fork(child);
4747 4748 4749 4750
		}
	}
}

4751
/**
L
Li Zefan 已提交
4752 4753 4754 4755 4756 4757 4758 4759
 * cgroup_post_fork - called on a new task after adding it to the task list
 * @child: the task in question
 *
 * Adds the task to the list running through its css_set if necessary.
 * Has to be after the task is visible on the task list in case we race
 * with the first call to cgroup_iter_start() - to guarantee that the
 * new task ends up on its list.
 */
4760 4761
void cgroup_post_fork(struct task_struct *child)
{
4762 4763 4764 4765 4766 4767 4768 4769 4770 4771 4772
	/*
	 * 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.
	 */
4773 4774
	if (use_task_css_set_links) {
		write_lock(&css_set_lock);
4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785
		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.
			 */
4786
			list_add(&child->cg_list, &child->cgroups->tasks);
4787
		}
4788 4789 4790
		write_unlock(&css_set_lock);
	}
}
4791 4792 4793
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
4794
 * @run_callback: run exit callbacks?
4795 4796 4797 4798 4799 4800 4801 4802 4803 4804 4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822
 *
 * 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,
4823 4824
 *    which wards off any cgroup_attach_task() attempts, or task is a failed
 *    fork, never visible to cgroup_attach_task.
4825 4826 4827
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
4828
	struct css_set *cg;
4829
	int i;
4830 4831 4832 4833 4834 4835 4836 4837 4838

	/*
	 * 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))
4839
			list_del_init(&tsk->cg_list);
4840 4841 4842
		write_unlock(&css_set_lock);
	}

4843 4844
	/* Reassign the task to the init_css_set. */
	task_lock(tsk);
4845 4846
	cg = tsk->cgroups;
	tsk->cgroups = &init_css_set;
4847 4848 4849 4850 4851 4852 4853 4854 4855 4856 4857 4858

	if (run_callbacks && need_forkexit_callback) {
		/*
		 * modular subsystems can't use callbacks, so no need to lock
		 * the subsys array
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss->exit) {
				struct cgroup *old_cgrp =
					rcu_dereference_raw(cg->subsys[i])->cgroup;
				struct cgroup *cgrp = task_cgroup(tsk, i);
4859
				ss->exit(cgrp, old_cgrp, tsk);
4860 4861 4862
			}
		}
	}
4863
	task_unlock(tsk);
4864

4865
	if (cg)
4866
		put_css_set_taskexit(cg);
4867
}
4868

L
Li Zefan 已提交
4869
/**
4870
 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
L
Li Zefan 已提交
4871
 * @cgrp: the cgroup in question
4872
 * @task: the task in question
L
Li Zefan 已提交
4873
 *
4874 4875
 * See if @cgrp is a descendant of @task's cgroup in the appropriate
 * hierarchy.
4876 4877 4878 4879 4880 4881
 *
 * If we are sending in dummytop, then presumably we are creating
 * the top cgroup in the subsystem.
 *
 * Called only by the ns (nsproxy) cgroup.
 */
4882
int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
4883 4884 4885 4886
{
	int ret;
	struct cgroup *target;

4887
	if (cgrp == dummytop)
4888 4889
		return 1;

4890
	target = task_cgroup_from_root(task, cgrp->root);
4891 4892 4893
	while (cgrp != target && cgrp!= cgrp->top_cgroup)
		cgrp = cgrp->parent;
	ret = (cgrp == target);
4894 4895
	return ret;
}
4896

4897
static void check_for_release(struct cgroup *cgrp)
4898 4899 4900
{
	/* All of these checks rely on RCU to keep the cgroup
	 * structure alive */
4901 4902
	if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
	    && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
4903 4904 4905 4906
		/* Control Group is currently removeable. If it's not
		 * already queued for a userspace notification, queue
		 * it now */
		int need_schedule_work = 0;
4907
		raw_spin_lock(&release_list_lock);
4908 4909 4910
		if (!cgroup_is_removed(cgrp) &&
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
4911 4912
			need_schedule_work = 1;
		}
4913
		raw_spin_unlock(&release_list_lock);
4914 4915 4916 4917 4918
		if (need_schedule_work)
			schedule_work(&release_agent_work);
	}
}

4919
/* Caller must verify that the css is not for root cgroup */
4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932 4933 4934 4935
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)
4936
{
4937
	struct cgroup *cgrp = css->cgroup;
4938
	int v;
4939

4940
	rcu_read_lock();
4941 4942 4943
	v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));

	switch (v) {
4944
	case 1:
4945 4946 4947 4948
		if (notify_on_release(cgrp)) {
			set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
		}
4949
		cgroup_wakeup_rmdir_waiter(cgrp);
4950 4951 4952 4953 4954
		break;
	case 0:
		if (!test_bit(CSS_CLEAR_CSS_REFS, &css->flags))
			schedule_work(&css->dput_work);
		break;
4955 4956 4957
	}
	rcu_read_unlock();
}
B
Ben Blum 已提交
4958
EXPORT_SYMBOL_GPL(__css_put);
4959 4960 4961 4962 4963 4964 4965 4966 4967 4968 4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985 4986

/*
 * 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);
4987
	raw_spin_lock(&release_list_lock);
4988 4989 4990
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
4991
		char *pathbuf = NULL, *agentbuf = NULL;
4992
		struct cgroup *cgrp = list_entry(release_list.next,
4993 4994
						    struct cgroup,
						    release_list);
4995
		list_del_init(&cgrp->release_list);
4996
		raw_spin_unlock(&release_list_lock);
4997
		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4998 4999 5000 5001 5002 5003 5004
		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;
5005 5006

		i = 0;
5007 5008
		argv[i++] = agentbuf;
		argv[i++] = pathbuf;
5009 5010 5011 5012 5013 5014 5015 5016 5017 5018 5019 5020 5021 5022
		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);
5023 5024 5025
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
5026
		raw_spin_lock(&release_list_lock);
5027
	}
5028
	raw_spin_unlock(&release_list_lock);
5029 5030
	mutex_unlock(&cgroup_mutex);
}
5031 5032 5033 5034 5035 5036 5037 5038 5039

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

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;
B
Ben Blum 已提交
5040 5041 5042 5043 5044
		/*
		 * cgroup_disable, being at boot time, can't know about module
		 * subsystems, so we don't worry about them.
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
5045 5046 5047 5048 5049 5050 5051 5052 5053 5054 5055 5056 5057
			struct cgroup_subsys *ss = subsys[i];

			if (!strcmp(token, ss->name)) {
				ss->disabled = 1;
				printk(KERN_INFO "Disabling %s control group"
					" subsystem\n", ss->name);
				break;
			}
		}
	}
	return 1;
}
__setup("cgroup_disable=", cgroup_disable);
K
KAMEZAWA Hiroyuki 已提交
5058 5059 5060 5061 5062 5063 5064 5065 5066 5067

/*
 * 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)
{
5068 5069 5070 5071 5072 5073 5074
	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.
	 */
5075
	cssid = rcu_dereference_check(css->id, css_refcnt(css));
K
KAMEZAWA Hiroyuki 已提交
5076 5077 5078 5079 5080

	if (cssid)
		return cssid->id;
	return 0;
}
B
Ben Blum 已提交
5081
EXPORT_SYMBOL_GPL(css_id);
K
KAMEZAWA Hiroyuki 已提交
5082 5083 5084

unsigned short css_depth(struct cgroup_subsys_state *css)
{
5085 5086
	struct css_id *cssid;

5087
	cssid = rcu_dereference_check(css->id, css_refcnt(css));
K
KAMEZAWA Hiroyuki 已提交
5088 5089 5090 5091 5092

	if (cssid)
		return cssid->depth;
	return 0;
}
B
Ben Blum 已提交
5093
EXPORT_SYMBOL_GPL(css_depth);
K
KAMEZAWA Hiroyuki 已提交
5094

5095 5096 5097 5098 5099 5100
/**
 *  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
5101
 * this function reads css->id, the caller must hold rcu_read_lock().
5102 5103 5104 5105 5106 5107
 * 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
5108
bool css_is_ancestor(struct cgroup_subsys_state *child,
5109
		    const struct cgroup_subsys_state *root)
K
KAMEZAWA Hiroyuki 已提交
5110
{
5111 5112
	struct css_id *child_id;
	struct css_id *root_id;
K
KAMEZAWA Hiroyuki 已提交
5113

5114
	child_id  = rcu_dereference(child->id);
5115 5116
	if (!child_id)
		return false;
5117
	root_id = rcu_dereference(root->id);
5118 5119 5120 5121 5122 5123 5124
	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;
K
KAMEZAWA Hiroyuki 已提交
5125 5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136 5137
}

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);
5138
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5139
	idr_remove(&ss->idr, id->id);
5140
	spin_unlock(&ss->id_lock);
5141
	kfree_rcu(id, rcu_head);
K
KAMEZAWA Hiroyuki 已提交
5142
}
B
Ben Blum 已提交
5143
EXPORT_SYMBOL_GPL(free_css_id);
K
KAMEZAWA Hiroyuki 已提交
5144 5145 5146 5147 5148 5149 5150 5151 5152 5153 5154 5155 5156 5157 5158 5159 5160 5161 5162 5163 5164 5165

/*
 * 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;
	}
5166
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5167 5168
	/* Don't use 0. allocates an ID of 1-65535 */
	error = idr_get_new_above(&ss->idr, newid, 1, &myid);
5169
	spin_unlock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5170 5171 5172 5173 5174 5175 5176 5177 5178 5179 5180 5181 5182 5183

	/* 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;
5184
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5185
	idr_remove(&ss->idr, myid);
5186
	spin_unlock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5187 5188 5189 5190 5191 5192
err_out:
	kfree(newid);
	return ERR_PTR(error);

}

5193 5194
static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
					    struct cgroup_subsys_state *rootcss)
K
KAMEZAWA Hiroyuki 已提交
5195 5196 5197
{
	struct css_id *newid;

5198
	spin_lock_init(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5199 5200 5201 5202 5203 5204 5205 5206 5207 5208 5209 5210 5211 5212 5213 5214 5215
	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;
5216
	struct css_id *child_id, *parent_id;
K
KAMEZAWA Hiroyuki 已提交
5217 5218 5219 5220 5221

	subsys_id = ss->subsys_id;
	parent_css = parent->subsys[subsys_id];
	child_css = child->subsys[subsys_id];
	parent_id = parent_css->id;
5222
	depth = parent_id->depth + 1;
K
KAMEZAWA Hiroyuki 已提交
5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238 5239 5240 5241 5242 5243 5244 5245 5246 5247 5248 5249 5250 5251 5252 5253 5254 5255 5256 5257 5258 5259

	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);
}
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Ben Blum 已提交
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EXPORT_SYMBOL_GPL(css_lookup);
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KAMEZAWA Hiroyuki 已提交
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/**
 * 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);
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	WARN_ON_ONCE(!rcu_read_lock_held());

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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;
}

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Stephane Eranian 已提交
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/*
 * 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);
}

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#ifdef CONFIG_CGROUP_DEBUG
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static struct cgroup_subsys_state *debug_create(struct cgroup *cont)
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{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

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

	return css;
}

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static void debug_destroy(struct cgroup *cont)
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{
	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;
}

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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 = "?";
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		seq_printf(seq, "Root %d group %s\n",
			   c->root->hierarchy_id, name);
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	}
	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;
}

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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,
	},

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	{
		.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,
	},

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	{
		.name = "releasable",
		.read_u64 = releasable_read,
	},

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