cgroup.c 147.7 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/hashtable.h>
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#include <linux/namei.h>
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#include <linux/pid_namespace.h>
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#include <linux/idr.h>
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#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
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#include <linux/eventfd.h>
#include <linux/poll.h>
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#include <linux/flex_array.h> /* used in cgroup_attach_proc */
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#include <linux/kthread.h>
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#include <linux/atomic.h>
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/* css deactivation bias, makes css->refcnt negative to deny new trygets */
#define CSS_DEACT_BIAS		INT_MIN

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/*
 * cgroup_mutex is the master lock.  Any modification to cgroup or its
 * hierarchy must be performed while holding it.
 *
 * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
 * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
 * release_agent_path and so on.  Modifying requires both cgroup_mutex and
 * cgroup_root_mutex.  Readers can acquire either of the two.  This is to
 * break the following locking order cycle.
 *
 *  A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
 *  B. namespace_sem -> cgroup_mutex
 *
 * B happens only through cgroup_show_options() and using cgroup_root_mutex
 * breaks it.
 */
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static DEFINE_MUTEX(cgroup_mutex);
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static DEFINE_MUTEX(cgroup_root_mutex);
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/*
 * Generate an array of cgroup subsystem pointers. At boot time, this is
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 * populated with the built in subsystems, and modular subsystems are
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 * registered after that. The mutable section of this array is protected by
 * cgroup_mutex.
 */
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#define SUBSYS(_x) [_x ## _subsys_id] = &_x ## _subsys,
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#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
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static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
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#include <linux/cgroup_subsys.h>
};

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#define MAX_CGROUP_ROOT_NAMELEN 64

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

	/*
	 * The bitmask of subsystems intended to be attached to this
	 * hierarchy
	 */
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	unsigned long subsys_mask;
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	/* Unique id for this hierarchy. */
	int hierarchy_id;

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	/* The bitmask of subsystems currently attached to this hierarchy */
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	unsigned long actual_subsys_mask;
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	/* A list running through the attached subsystems */
	struct list_head subsys_list;

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

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

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

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

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	/* Hierarchy-specific flags */
	unsigned long flags;
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	/* IDs for cgroups in this hierarchy */
	struct ida cgroup_ida;

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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()
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	 * is called after synchronize_rcu(). But for safe use, css_tryget()
	 * should be used for avoiding race.
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	 */
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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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static int cgroup_destroy_locked(struct cgroup *cgrp);
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static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
			      struct cftype cfts[], bool is_add);
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#ifdef CONFIG_PROVE_LOCKING
int cgroup_lock_is_held(void)
{
	return lockdep_is_held(&cgroup_mutex);
}
#else /* #ifdef CONFIG_PROVE_LOCKING */
int cgroup_lock_is_held(void)
{
	return mutex_is_locked(&cgroup_mutex);
}
#endif /* #else #ifdef CONFIG_PROVE_LOCKING */

EXPORT_SYMBOL_GPL(cgroup_lock_is_held);

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

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

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	return css_unbias_refcnt(v);
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}

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

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

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

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

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/*
 * 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
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static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
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static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
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{
	int i;
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	unsigned long key = 0UL;
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	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
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		key += (unsigned long)css[i];
	key = (key >> 16) ^ key;
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	return key;
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}

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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 */
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	hash_del(&cg->hlist);
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	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_node *node;
	struct css_set *cg;
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	unsigned long key;
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	/*
	 * Build the set of subsystem state objects that we want to see in the
	 * new css_set. while subsystems can change globally, the entries here
	 * won't change, so no need for locking.
	 */
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	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
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		if (root->subsys_mask & (1UL << i)) {
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			/* Subsystem is in this hierarchy. So we want
			 * the subsystem state from the new
			 * cgroup */
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			template[i] = cgrp->subsys[i];
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		} else {
			/* Subsystem is not in this hierarchy, so we
			 * don't want to change the subsystem state */
			template[i] = oldcg->subsys[i];
		}
	}

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	key = css_set_hash(template);
	hash_for_each_possible(css_set_table, cg, node, hlist, key) {
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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(
649
	struct css_set *oldcg, struct cgroup *cgrp)
650 651 652 653 654 655
{
	struct css_set *res;
	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];

	struct list_head tmp_cg_links;

656
	struct cg_cgroup_link *link;
657
	unsigned long key;
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

	/* Add this cgroup group to the hash table */
703 704
	key = css_set_hash(res->subsys);
	hash_add(css_set_table, &res->hlist, key);
705

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 task's cgroup pointer with
L
Li Zefan 已提交
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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's 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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Al Viro 已提交
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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);
827 828
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
			       unsigned long subsys_mask);
829
static const struct inode_operations cgroup_dir_inode_operations;
830
static const struct file_operations proc_cgroupstats_operations;
831 832

static struct backing_dev_info cgroup_backing_dev_info = {
833
	.name		= "cgroup",
834
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
835
};
836

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

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Al Viro 已提交
840
static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
841 842 843 844
{
	struct inode *inode = new_inode(sb);

	if (inode) {
845
		inode->i_ino = get_next_ino();
846
		inode->i_mode = mode;
847 848
		inode->i_uid = current_fsuid();
		inode->i_gid = current_fsgid();
849 850 851 852 853 854 855 856 857 858
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
	}
	return inode;
}

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)) {
859
		struct cgroup *cgrp = dentry->d_fsdata;
860
		struct cgroup_subsys *ss;
861
		BUG_ON(!(cgroup_is_removed(cgrp)));
862 863 864 865 866 867 868
		/* 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();
869 870 871 872 873

		mutex_lock(&cgroup_mutex);
		/*
		 * Release the subsystem state objects.
		 */
874
		for_each_subsys(cgrp->root, ss)
875
			ss->css_free(cgrp);
876 877 878 879

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

880
		/*
881 882
		 * Drop the active superblock reference that we took when we
		 * created the cgroup
883
		 */
884
		deactivate_super(cgrp->root->sb);
885

886 887 888 889 890 891
		/*
		 * if we're getting rid of the cgroup, refcount should ensure
		 * that there are no pidlists left.
		 */
		BUG_ON(!list_empty(&cgrp->pidlists));

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

T
Tejun Heo 已提交
894
		ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id);
895
		kfree_rcu(cgrp, rcu_head);
T
Tejun Heo 已提交
896 897 898
	} else {
		struct cfent *cfe = __d_cfe(dentry);
		struct cgroup *cgrp = dentry->d_parent->d_fsdata;
A
Aristeu Rozanski 已提交
899
		struct cftype *cft = cfe->type;
T
Tejun Heo 已提交
900 901 902 903 904

		WARN_ONCE(!list_empty(&cfe->node) &&
			  cgrp != &cgrp->root->top_cgroup,
			  "cfe still linked for %s\n", cfe->type->name);
		kfree(cfe);
A
Aristeu Rozanski 已提交
905
		simple_xattrs_free(&cft->xattrs);
906 907 908 909
	}
	iput(inode);
}

910 911 912 913 914
static int cgroup_delete(const struct dentry *d)
{
	return 1;
}

915 916 917 918 919 920 921 922 923
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);
}

924
static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
T
Tejun Heo 已提交
925 926 927 928 929 930
{
	struct cfent *cfe;

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

931 932 933 934
	/*
	 * If we're doing cleanup due to failure of cgroup_create(),
	 * the corresponding @cfe may not exist.
	 */
T
Tejun Heo 已提交
935 936 937 938 939 940 941 942
	list_for_each_entry(cfe, &cgrp->files, node) {
		struct dentry *d = cfe->dentry;

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

		dget(d);
		d_delete(d);
943
		simple_unlink(cgrp->dentry->d_inode, d);
T
Tejun Heo 已提交
944 945 946
		list_del_init(&cfe->node);
		dput(d);

947
		break;
948
	}
T
Tejun Heo 已提交
949 950
}

951 952 953 954 955 956 957 958
/**
 * cgroup_clear_directory - selective removal of base and subsystem files
 * @dir: directory containing the files
 * @base_files: true if the base files should be removed
 * @subsys_mask: mask of the subsystem ids whose files should be removed
 */
static void cgroup_clear_directory(struct dentry *dir, bool base_files,
				   unsigned long subsys_mask)
T
Tejun Heo 已提交
959 960
{
	struct cgroup *cgrp = __d_cgrp(dir);
961
	struct cgroup_subsys *ss;
T
Tejun Heo 已提交
962

963 964 965 966 967
	for_each_subsys(cgrp->root, ss) {
		struct cftype_set *set;
		if (!test_bit(ss->subsys_id, &subsys_mask))
			continue;
		list_for_each_entry(set, &ss->cftsets, node)
968
			cgroup_addrm_files(cgrp, NULL, set->cfts, false);
969 970 971 972 973
	}
	if (base_files) {
		while (!list_empty(&cgrp->files))
			cgroup_rm_file(cgrp, NULL);
	}
974 975 976 977 978 979 980
}

/*
 * NOTE : the dentry must have been dget()'ed
 */
static void cgroup_d_remove_dir(struct dentry *dentry)
{
N
Nick Piggin 已提交
981
	struct dentry *parent;
982
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
N
Nick Piggin 已提交
983

984
	cgroup_clear_directory(dentry, true, root->subsys_mask);
985

N
Nick Piggin 已提交
986 987
	parent = dentry->d_parent;
	spin_lock(&parent->d_lock);
988
	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
989
	list_del_init(&dentry->d_u.d_child);
N
Nick Piggin 已提交
990 991
	spin_unlock(&dentry->d_lock);
	spin_unlock(&parent->d_lock);
992 993 994
	remove_dir(dentry);
}

B
Ben Blum 已提交
995
/*
B
Ben Blum 已提交
996 997 998
 * Call with cgroup_mutex held. Drops reference counts on modules, including
 * any duplicate ones that parse_cgroupfs_options took. If this function
 * returns an error, no reference counts are touched.
B
Ben Blum 已提交
999
 */
1000
static int rebind_subsystems(struct cgroupfs_root *root,
1001
			      unsigned long final_subsys_mask)
1002
{
1003
	unsigned long added_mask, removed_mask;
1004
	struct cgroup *cgrp = &root->top_cgroup;
1005 1006
	int i;

B
Ben Blum 已提交
1007
	BUG_ON(!mutex_is_locked(&cgroup_mutex));
T
Tejun Heo 已提交
1008
	BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
B
Ben Blum 已提交
1009

1010 1011
	removed_mask = root->actual_subsys_mask & ~final_subsys_mask;
	added_mask = final_subsys_mask & ~root->actual_subsys_mask;
1012 1013
	/* Check that any added subsystems are currently free */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
L
Li Zefan 已提交
1014
		unsigned long bit = 1UL << i;
1015
		struct cgroup_subsys *ss = subsys[i];
1016
		if (!(bit & added_mask))
1017
			continue;
B
Ben Blum 已提交
1018 1019 1020 1021 1022 1023
		/*
		 * 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);
1024 1025 1026 1027 1028 1029 1030 1031 1032 1033
		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 */
1034
	if (root->number_of_cgroups > 1)
1035 1036 1037 1038 1039 1040
		return -EBUSY;

	/* Process each subsystem */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		unsigned long bit = 1UL << i;
1041
		if (bit & added_mask) {
1042
			/* We're binding this subsystem to this hierarchy */
B
Ben Blum 已提交
1043
			BUG_ON(ss == NULL);
1044
			BUG_ON(cgrp->subsys[i]);
1045 1046
			BUG_ON(!dummytop->subsys[i]);
			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1047 1048
			cgrp->subsys[i] = dummytop->subsys[i];
			cgrp->subsys[i]->cgroup = cgrp;
1049
			list_move(&ss->sibling, &root->subsys_list);
1050
			ss->root = root;
1051
			if (ss->bind)
1052
				ss->bind(cgrp);
B
Ben Blum 已提交
1053
			/* refcount was already taken, and we're keeping it */
1054
		} else if (bit & removed_mask) {
1055
			/* We're removing this subsystem */
B
Ben Blum 已提交
1056
			BUG_ON(ss == NULL);
1057 1058
			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1059
			if (ss->bind)
1060
				ss->bind(dummytop);
1061
			dummytop->subsys[i]->cgroup = dummytop;
1062
			cgrp->subsys[i] = NULL;
1063
			subsys[i]->root = &rootnode;
1064
			list_move(&ss->sibling, &rootnode.subsys_list);
B
Ben Blum 已提交
1065 1066
			/* subsystem is now free - drop reference on module */
			module_put(ss->module);
1067
		} else if (bit & final_subsys_mask) {
1068
			/* Subsystem state should already exist */
B
Ben Blum 已提交
1069
			BUG_ON(ss == NULL);
1070
			BUG_ON(!cgrp->subsys[i]);
B
Ben Blum 已提交
1071 1072 1073 1074 1075 1076 1077 1078
			/*
			 * 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
1079 1080
		} else {
			/* Subsystem state shouldn't exist */
1081
			BUG_ON(cgrp->subsys[i]);
1082 1083
		}
	}
1084
	root->subsys_mask = root->actual_subsys_mask = final_subsys_mask;
1085 1086 1087 1088

	return 0;
}

1089
static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1090
{
1091
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1092 1093
	struct cgroup_subsys *ss;

T
Tejun Heo 已提交
1094
	mutex_lock(&cgroup_root_mutex);
1095 1096 1097 1098
	for_each_subsys(root, ss)
		seq_printf(seq, ",%s", ss->name);
	if (test_bit(ROOT_NOPREFIX, &root->flags))
		seq_puts(seq, ",noprefix");
A
Aristeu Rozanski 已提交
1099 1100
	if (test_bit(ROOT_XATTR, &root->flags))
		seq_puts(seq, ",xattr");
1101 1102
	if (strlen(root->release_agent_path))
		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1103
	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags))
1104
		seq_puts(seq, ",clone_children");
1105 1106
	if (strlen(root->name))
		seq_printf(seq, ",name=%s", root->name);
T
Tejun Heo 已提交
1107
	mutex_unlock(&cgroup_root_mutex);
1108 1109 1110 1111
	return 0;
}

struct cgroup_sb_opts {
1112
	unsigned long subsys_mask;
1113
	unsigned long flags;
1114
	char *release_agent;
1115
	bool cpuset_clone_children;
1116
	char *name;
1117 1118
	/* User explicitly requested empty subsystem */
	bool none;
1119 1120

	struct cgroupfs_root *new_root;
1121

1122 1123
};

B
Ben Blum 已提交
1124 1125
/*
 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
B
Ben Blum 已提交
1126 1127 1128
 * with cgroup_mutex held to protect the subsys[] array. This function takes
 * refcounts on subsystems to be used, unless it returns error, in which case
 * no refcounts are taken.
B
Ben Blum 已提交
1129
 */
B
Ben Blum 已提交
1130
static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1131
{
1132 1133
	char *token, *o = data;
	bool all_ss = false, one_ss = false;
1134
	unsigned long mask = (unsigned long)-1;
B
Ben Blum 已提交
1135 1136
	int i;
	bool module_pin_failed = false;
1137

B
Ben Blum 已提交
1138 1139
	BUG_ON(!mutex_is_locked(&cgroup_mutex));

1140 1141 1142
#ifdef CONFIG_CPUSETS
	mask = ~(1UL << cpuset_subsys_id);
#endif
1143

1144
	memset(opts, 0, sizeof(*opts));
1145 1146 1147 1148

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
1149
		if (!strcmp(token, "none")) {
1150 1151
			/* Explicitly have no subsystems */
			opts->none = true;
1152 1153 1154 1155 1156 1157 1158 1159 1160 1161
			continue;
		}
		if (!strcmp(token, "all")) {
			/* Mutually exclusive option 'all' + subsystem name */
			if (one_ss)
				return -EINVAL;
			all_ss = true;
			continue;
		}
		if (!strcmp(token, "noprefix")) {
1162
			set_bit(ROOT_NOPREFIX, &opts->flags);
1163 1164 1165
			continue;
		}
		if (!strcmp(token, "clone_children")) {
1166
			opts->cpuset_clone_children = true;
1167 1168
			continue;
		}
A
Aristeu Rozanski 已提交
1169 1170 1171 1172
		if (!strcmp(token, "xattr")) {
			set_bit(ROOT_XATTR, &opts->flags);
			continue;
		}
1173
		if (!strncmp(token, "release_agent=", 14)) {
1174 1175 1176
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1177
			opts->release_agent =
1178
				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1179 1180
			if (!opts->release_agent)
				return -ENOMEM;
1181 1182 1183
			continue;
		}
		if (!strncmp(token, "name=", 5)) {
1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200
			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,
1201
					      MAX_CGROUP_ROOT_NAMELEN - 1,
1202 1203 1204
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220

			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;
1221
			set_bit(i, &opts->subsys_mask);
1222 1223 1224 1225 1226 1227 1228 1229 1230 1231
			one_ss = true;

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

	/*
	 * If the 'all' option was specified select all the subsystems,
1232 1233
	 * otherwise if 'none', 'name=' and a subsystem name options
	 * were not specified, let's default to 'all'
1234
	 */
1235
	if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1236 1237 1238 1239 1240 1241
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss == NULL)
				continue;
			if (ss->disabled)
				continue;
1242
			set_bit(i, &opts->subsys_mask);
1243 1244 1245
		}
	}

1246 1247
	/* Consistency checks */

1248 1249 1250 1251 1252 1253
	/*
	 * 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) &&
1254
	    (opts->subsys_mask & mask))
1255 1256
		return -EINVAL;

1257 1258

	/* Can't specify "none" and some subsystems */
1259
	if (opts->subsys_mask && opts->none)
1260 1261 1262 1263 1264 1265
		return -EINVAL;

	/*
	 * We either have to specify by name or by subsystems. (So all
	 * empty hierarchies must have a name).
	 */
1266
	if (!opts->subsys_mask && !opts->name)
1267 1268
		return -EINVAL;

B
Ben Blum 已提交
1269 1270 1271 1272 1273 1274
	/*
	 * 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.
	 */
1275
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
B
Ben Blum 已提交
1276 1277
		unsigned long bit = 1UL << i;

1278
		if (!(bit & opts->subsys_mask))
B
Ben Blum 已提交
1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290
			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.
		 */
1291
		for (i--; i >= 0; i--) {
B
Ben Blum 已提交
1292 1293 1294
			/* drop refcounts only on the ones we took */
			unsigned long bit = 1UL << i;

1295
			if (!(bit & opts->subsys_mask))
B
Ben Blum 已提交
1296 1297 1298 1299 1300 1301
				continue;
			module_put(subsys[i]->module);
		}
		return -ENOENT;
	}

1302 1303 1304
	return 0;
}

1305
static void drop_parsed_module_refcounts(unsigned long subsys_mask)
B
Ben Blum 已提交
1306 1307
{
	int i;
1308
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
B
Ben Blum 已提交
1309 1310
		unsigned long bit = 1UL << i;

1311
		if (!(bit & subsys_mask))
B
Ben Blum 已提交
1312 1313 1314 1315 1316
			continue;
		module_put(subsys[i]->module);
	}
}

1317 1318 1319 1320
static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
	int ret = 0;
	struct cgroupfs_root *root = sb->s_fs_info;
1321
	struct cgroup *cgrp = &root->top_cgroup;
1322
	struct cgroup_sb_opts opts;
1323
	unsigned long added_mask, removed_mask;
1324

1325
	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1326
	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1327
	mutex_lock(&cgroup_root_mutex);
1328 1329 1330 1331 1332 1333

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

1334
	if (opts.subsys_mask != root->actual_subsys_mask || opts.release_agent)
1335 1336 1337
		pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
			   task_tgid_nr(current), current->comm);

1338 1339
	added_mask = opts.subsys_mask & ~root->subsys_mask;
	removed_mask = root->subsys_mask & ~opts.subsys_mask;
1340

B
Ben Blum 已提交
1341 1342 1343
	/* Don't allow flags or name to change at remount */
	if (opts.flags != root->flags ||
	    (opts.name && strcmp(opts.name, root->name))) {
1344
		ret = -EINVAL;
1345
		drop_parsed_module_refcounts(opts.subsys_mask);
1346 1347 1348
		goto out_unlock;
	}

1349 1350 1351 1352 1353 1354 1355
	/*
	 * Clear out the files of subsystems that should be removed, do
	 * this before rebind_subsystems, since rebind_subsystems may
	 * change this hierarchy's subsys_list.
	 */
	cgroup_clear_directory(cgrp->dentry, false, removed_mask);

1356
	ret = rebind_subsystems(root, opts.subsys_mask);
B
Ben Blum 已提交
1357
	if (ret) {
1358 1359
		/* rebind_subsystems failed, re-populate the removed files */
		cgroup_populate_dir(cgrp, false, removed_mask);
1360
		drop_parsed_module_refcounts(opts.subsys_mask);
1361
		goto out_unlock;
B
Ben Blum 已提交
1362
	}
1363

1364
	/* re-populate subsystem files */
1365
	cgroup_populate_dir(cgrp, false, added_mask);
1366

1367 1368
	if (opts.release_agent)
		strcpy(root->release_agent_path, opts.release_agent);
1369
 out_unlock:
1370
	kfree(opts.release_agent);
1371
	kfree(opts.name);
T
Tejun Heo 已提交
1372
	mutex_unlock(&cgroup_root_mutex);
1373
	mutex_unlock(&cgroup_mutex);
1374
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1375 1376 1377
	return ret;
}

1378
static const struct super_operations cgroup_ops = {
1379 1380 1381 1382 1383 1384
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.show_options = cgroup_show_options,
	.remount_fs = cgroup_remount,
};

1385 1386 1387 1388
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
	INIT_LIST_HEAD(&cgrp->sibling);
	INIT_LIST_HEAD(&cgrp->children);
T
Tejun Heo 已提交
1389
	INIT_LIST_HEAD(&cgrp->files);
1390
	INIT_LIST_HEAD(&cgrp->css_sets);
1391
	INIT_LIST_HEAD(&cgrp->allcg_node);
1392
	INIT_LIST_HEAD(&cgrp->release_list);
1393 1394
	INIT_LIST_HEAD(&cgrp->pidlists);
	mutex_init(&cgrp->pidlist_mutex);
1395 1396
	INIT_LIST_HEAD(&cgrp->event_list);
	spin_lock_init(&cgrp->event_list_lock);
A
Aristeu Rozanski 已提交
1397
	simple_xattrs_init(&cgrp->xattrs);
1398
}
1399

1400 1401
static void init_cgroup_root(struct cgroupfs_root *root)
{
1402
	struct cgroup *cgrp = &root->top_cgroup;
1403

1404 1405
	INIT_LIST_HEAD(&root->subsys_list);
	INIT_LIST_HEAD(&root->root_list);
1406
	INIT_LIST_HEAD(&root->allcg_list);
1407
	root->number_of_cgroups = 1;
1408 1409
	cgrp->root = root;
	cgrp->top_cgroup = cgrp;
1410
	init_cgroup_housekeeping(cgrp);
1411
	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1412 1413
}

1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438
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;
}

1439 1440
static int cgroup_test_super(struct super_block *sb, void *data)
{
1441
	struct cgroup_sb_opts *opts = data;
1442 1443
	struct cgroupfs_root *root = sb->s_fs_info;

1444 1445 1446
	/* If we asked for a name then it must match */
	if (opts->name && strcmp(opts->name, root->name))
		return 0;
1447

1448 1449 1450 1451
	/*
	 * If we asked for subsystems (or explicitly for no
	 * subsystems) then they must match
	 */
1452 1453
	if ((opts->subsys_mask || opts->none)
	    && (opts->subsys_mask != root->subsys_mask))
1454 1455 1456 1457 1458
		return 0;

	return 1;
}

1459 1460 1461 1462
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
	struct cgroupfs_root *root;

1463
	if (!opts->subsys_mask && !opts->none)
1464 1465 1466 1467 1468 1469
		return NULL;

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

1470 1471 1472 1473
	if (!init_root_id(root)) {
		kfree(root);
		return ERR_PTR(-ENOMEM);
	}
1474
	init_cgroup_root(root);
1475

1476
	root->subsys_mask = opts->subsys_mask;
1477
	root->flags = opts->flags;
T
Tejun Heo 已提交
1478
	ida_init(&root->cgroup_ida);
1479 1480 1481 1482
	if (opts->release_agent)
		strcpy(root->release_agent_path, opts->release_agent);
	if (opts->name)
		strcpy(root->name, opts->name);
1483 1484
	if (opts->cpuset_clone_children)
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags);
1485 1486 1487
	return root;
}

1488 1489 1490 1491 1492 1493 1494 1495 1496
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);
T
Tejun Heo 已提交
1497
	ida_destroy(&root->cgroup_ida);
1498 1499 1500
	kfree(root);
}

1501 1502 1503
static int cgroup_set_super(struct super_block *sb, void *data)
{
	int ret;
1504 1505 1506 1507 1508 1509
	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;

1510
	BUG_ON(!opts->subsys_mask && !opts->none);
1511 1512 1513 1514 1515

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

1516 1517
	sb->s_fs_info = opts->new_root;
	opts->new_root->sb = sb;
1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528

	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
1529 1530
	static const struct dentry_operations cgroup_dops = {
		.d_iput = cgroup_diput,
1531
		.d_delete = cgroup_delete,
A
Al Viro 已提交
1532 1533
	};

1534 1535 1536 1537 1538 1539 1540 1541 1542 1543
	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);
1544 1545
	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
1546
		return -ENOMEM;
A
Al Viro 已提交
1547 1548
	/* for everything else we want ->d_op set */
	sb->s_d_op = &cgroup_dops;
1549 1550 1551
	return 0;
}

A
Al Viro 已提交
1552
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1553
			 int flags, const char *unused_dev_name,
A
Al Viro 已提交
1554
			 void *data)
1555 1556
{
	struct cgroup_sb_opts opts;
1557
	struct cgroupfs_root *root;
1558 1559
	int ret = 0;
	struct super_block *sb;
1560
	struct cgroupfs_root *new_root;
T
Tejun Heo 已提交
1561
	struct inode *inode;
1562 1563

	/* First find the desired set of subsystems */
B
Ben Blum 已提交
1564
	mutex_lock(&cgroup_mutex);
1565
	ret = parse_cgroupfs_options(data, &opts);
B
Ben Blum 已提交
1566
	mutex_unlock(&cgroup_mutex);
1567 1568
	if (ret)
		goto out_err;
1569

1570 1571 1572 1573 1574 1575 1576
	/*
	 * 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
1577
		goto drop_modules;
1578
	}
1579
	opts.new_root = new_root;
1580

1581
	/* Locate an existing or new sb for this hierarchy */
D
David Howells 已提交
1582
	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
1583
	if (IS_ERR(sb)) {
1584
		ret = PTR_ERR(sb);
1585
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1586
		goto drop_modules;
1587 1588
	}

1589 1590 1591 1592 1593
	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;
1594
		struct cgroup *root_cgrp = &root->top_cgroup;
1595
		struct cgroupfs_root *existing_root;
1596
		const struct cred *cred;
1597
		int i;
1598 1599
		struct hlist_node *node;
		struct css_set *cg;
1600 1601 1602 1603 1604 1605

		BUG_ON(sb->s_root != NULL);

		ret = cgroup_get_rootdir(sb);
		if (ret)
			goto drop_new_super;
1606
		inode = sb->s_root->d_inode;
1607

1608
		mutex_lock(&inode->i_mutex);
1609
		mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1610
		mutex_lock(&cgroup_root_mutex);
1611

T
Tejun Heo 已提交
1612 1613 1614 1615 1616 1617
		/* 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;
1618

1619 1620 1621 1622 1623 1624 1625 1626
		/*
		 * 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
1627 1628
		if (ret)
			goto unlock_drop;
1629

1630
		ret = rebind_subsystems(root, root->subsys_mask);
1631
		if (ret == -EBUSY) {
1632
			free_cg_links(&tmp_cg_links);
T
Tejun Heo 已提交
1633
			goto unlock_drop;
1634
		}
B
Ben Blum 已提交
1635 1636 1637 1638 1639
		/*
		 * There must be no failure case after here, since rebinding
		 * takes care of subsystems' refcounts, which are explicitly
		 * dropped in the failure exit path.
		 */
1640 1641 1642 1643 1644

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

		list_add(&root->root_list, &roots);
1645
		root_count++;
1646

1647
		sb->s_root->d_fsdata = root_cgrp;
1648 1649
		root->top_cgroup.dentry = sb->s_root;

1650 1651 1652
		/* Link the top cgroup in this hierarchy into all
		 * the css_set objects */
		write_lock(&css_set_lock);
1653 1654
		hash_for_each(css_set_table, i, node, cg, hlist)
			link_css_set(&tmp_cg_links, cg, root_cgrp);
1655 1656 1657 1658
		write_unlock(&css_set_lock);

		free_cg_links(&tmp_cg_links);

1659
		BUG_ON(!list_empty(&root_cgrp->children));
1660 1661
		BUG_ON(root->number_of_cgroups != 1);

1662
		cred = override_creds(&init_cred);
1663
		cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
1664
		revert_creds(cred);
T
Tejun Heo 已提交
1665
		mutex_unlock(&cgroup_root_mutex);
1666
		mutex_unlock(&cgroup_mutex);
1667
		mutex_unlock(&inode->i_mutex);
1668 1669 1670 1671 1672
	} else {
		/*
		 * We re-used an existing hierarchy - the new root (if
		 * any) is not needed
		 */
1673
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1674
		/* no subsys rebinding, so refcounts don't change */
1675
		drop_parsed_module_refcounts(opts.subsys_mask);
1676 1677
	}

1678 1679
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1680
	return dget(sb->s_root);
1681

T
Tejun Heo 已提交
1682 1683 1684 1685
 unlock_drop:
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&inode->i_mutex);
1686
 drop_new_super:
1687
	deactivate_locked_super(sb);
B
Ben Blum 已提交
1688
 drop_modules:
1689
	drop_parsed_module_refcounts(opts.subsys_mask);
1690 1691 1692
 out_err:
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1693
	return ERR_PTR(ret);
1694 1695 1696 1697
}

static void cgroup_kill_sb(struct super_block *sb) {
	struct cgroupfs_root *root = sb->s_fs_info;
1698
	struct cgroup *cgrp = &root->top_cgroup;
1699
	int ret;
K
KOSAKI Motohiro 已提交
1700 1701
	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;
1702 1703 1704 1705

	BUG_ON(!root);

	BUG_ON(root->number_of_cgroups != 1);
1706
	BUG_ON(!list_empty(&cgrp->children));
1707 1708

	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1709
	mutex_lock(&cgroup_root_mutex);
1710 1711 1712 1713 1714 1715

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

1716 1717 1718 1719 1720
	/*
	 * Release all the links from css_sets to this hierarchy's
	 * root cgroup
	 */
	write_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
1721 1722 1723

	list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
				 cgrp_link_list) {
1724
		list_del(&link->cg_link_list);
1725
		list_del(&link->cgrp_link_list);
1726 1727 1728 1729
		kfree(link);
	}
	write_unlock(&css_set_lock);

1730 1731 1732 1733
	if (!list_empty(&root->root_list)) {
		list_del(&root->root_list);
		root_count--;
	}
1734

T
Tejun Heo 已提交
1735
	mutex_unlock(&cgroup_root_mutex);
1736 1737
	mutex_unlock(&cgroup_mutex);

A
Aristeu Rozanski 已提交
1738 1739
	simple_xattrs_free(&cgrp->xattrs);

1740
	kill_litter_super(sb);
1741
	cgroup_drop_root(root);
1742 1743 1744 1745
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
A
Al Viro 已提交
1746
	.mount = cgroup_mount,
1747 1748 1749
	.kill_sb = cgroup_kill_sb,
};

1750 1751
static struct kobject *cgroup_kobj;

L
Li Zefan 已提交
1752 1753 1754 1755 1756 1757
/**
 * 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
 *
1758 1759 1760
 * 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.
1761
 */
1762
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1763
{
1764
	struct dentry *dentry = cgrp->dentry;
1765
	char *start;
1766 1767 1768

	rcu_lockdep_assert(rcu_read_lock_held() || cgroup_lock_is_held(),
			   "cgroup_path() called without proper locking");
1769

1770
	if (!dentry || cgrp == dummytop) {
1771 1772 1773 1774 1775 1776 1777 1778
		/*
		 * Inactive subsystems have no dentry for their root
		 * cgroup
		 */
		strcpy(buf, "/");
		return 0;
	}

1779
	start = buf + buflen - 1;
1780

1781
	*start = '\0';
1782
	for (;;) {
1783
		int len = dentry->d_name.len;
1784

1785 1786
		if ((start -= len) < buf)
			return -ENAMETOOLONG;
1787
		memcpy(start, dentry->d_name.name, len);
1788 1789
		cgrp = cgrp->parent;
		if (!cgrp)
1790
			break;
1791

1792
		dentry = cgrp->dentry;
1793
		if (!cgrp->parent)
1794 1795 1796 1797 1798 1799 1800 1801
			continue;
		if (--start < buf)
			return -ENAMETOOLONG;
		*start = '/';
	}
	memmove(buf, start, buf + buflen - start);
	return 0;
}
B
Ben Blum 已提交
1802
EXPORT_SYMBOL_GPL(cgroup_path);
1803

1804 1805 1806
/*
 * Control Group taskset
 */
1807 1808 1809
struct task_and_cgroup {
	struct task_struct	*task;
	struct cgroup		*cgrp;
1810
	struct css_set		*cg;
1811 1812
};

1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 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
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
1884 1885 1886
/*
 * cgroup_task_migrate - move a task from one cgroup to another.
 *
1887
 * Must be called with cgroup_mutex and threadgroup locked.
B
Ben Blum 已提交
1888
 */
1889 1890
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
1891 1892 1893 1894
{
	struct css_set *oldcg;

	/*
1895 1896 1897
	 * 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
1898
	 */
1899
	WARN_ON_ONCE(tsk->flags & PF_EXITING);
B
Ben Blum 已提交
1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917
	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.
	 */
	set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1918
	put_css_set(oldcg);
B
Ben Blum 已提交
1919 1920
}

L
Li Zefan 已提交
1921 1922 1923 1924
/**
 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
 * @cgrp: the cgroup the task is attaching to
 * @tsk: the task to be attached
1925
 *
1926 1927
 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
 * @tsk during call.
1928
 */
1929
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1930
{
1931
	int retval = 0;
1932
	struct cgroup_subsys *ss, *failed_ss = NULL;
1933 1934
	struct cgroup *oldcgrp;
	struct cgroupfs_root *root = cgrp->root;
1935
	struct cgroup_taskset tset = { };
1936
	struct css_set *newcg;
1937

1938 1939 1940
	/* @tsk either already exited or can't exit until the end */
	if (tsk->flags & PF_EXITING)
		return -ESRCH;
1941 1942

	/* Nothing to do if the task is already in that cgroup */
1943
	oldcgrp = task_cgroup_from_root(tsk, root);
1944
	if (cgrp == oldcgrp)
1945 1946
		return 0;

1947 1948 1949
	tset.single.task = tsk;
	tset.single.cgrp = oldcgrp;

1950 1951
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
1952
			retval = ss->can_attach(cgrp, &tset);
1953 1954 1955 1956 1957 1958 1959 1960 1961 1962
			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;
			}
1963 1964 1965
		}
	}

1966 1967 1968
	newcg = find_css_set(tsk->cgroups, cgrp);
	if (!newcg) {
		retval = -ENOMEM;
1969
		goto out;
1970 1971 1972
	}

	cgroup_task_migrate(cgrp, oldcgrp, tsk, newcg);
1973

1974
	for_each_subsys(root, ss) {
P
Paul Jackson 已提交
1975
		if (ss->attach)
1976
			ss->attach(cgrp, &tset);
1977
	}
B
Ben Blum 已提交
1978

1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990
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)
1991
				ss->cancel_attach(cgrp, &tset);
1992 1993 1994
		}
	}
	return retval;
1995 1996
}

1997
/**
M
Michael S. Tsirkin 已提交
1998 1999
 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
 * @from: attach to all cgroups of a given task
2000 2001
 * @tsk: the task to be attached
 */
M
Michael S. Tsirkin 已提交
2002
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2003 2004 2005 2006 2007 2008
{
	struct cgroupfs_root *root;
	int retval = 0;

	cgroup_lock();
	for_each_active_root(root) {
M
Michael S. Tsirkin 已提交
2009 2010 2011
		struct cgroup *from_cg = task_cgroup_from_root(from, root);

		retval = cgroup_attach_task(from_cg, tsk);
2012 2013 2014 2015 2016 2017 2018
		if (retval)
			break;
	}
	cgroup_unlock();

	return retval;
}
M
Michael S. Tsirkin 已提交
2019
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2020

B
Ben Blum 已提交
2021 2022 2023 2024 2025
/**
 * 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
 *
2026 2027
 * 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
2028
 */
2029
static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
B
Ben Blum 已提交
2030 2031 2032 2033 2034 2035 2036
{
	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;
2037
	struct task_and_cgroup *tc;
2038
	struct flex_array *group;
2039
	struct cgroup_taskset tset = { };
B
Ben Blum 已提交
2040 2041 2042 2043 2044

	/*
	 * 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
2045 2046
	 * 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
2047 2048
	 */
	group_size = get_nr_threads(leader);
2049
	/* flex_array supports very large thread-groups better than kmalloc. */
2050
	group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
B
Ben Blum 已提交
2051 2052
	if (!group)
		return -ENOMEM;
2053 2054 2055 2056
	/* 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
2057 2058 2059

	tsk = leader;
	i = 0;
2060 2061 2062 2063 2064 2065
	/*
	 * 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
2066
	do {
2067 2068
		struct task_and_cgroup ent;

2069 2070 2071 2072
		/* @tsk either already exited or can't exit until the end */
		if (tsk->flags & PF_EXITING)
			continue;

B
Ben Blum 已提交
2073 2074
		/* as per above, nr_threads may decrease, but not increase. */
		BUG_ON(i >= group_size);
2075 2076
		ent.task = tsk;
		ent.cgrp = task_cgroup_from_root(tsk, root);
2077 2078 2079
		/* nothing to do if this task is already in the cgroup */
		if (ent.cgrp == cgrp)
			continue;
2080 2081 2082 2083
		/*
		 * saying GFP_ATOMIC has no effect here because we did prealloc
		 * earlier, but it's good form to communicate our expectations.
		 */
2084
		retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2085
		BUG_ON(retval != 0);
B
Ben Blum 已提交
2086 2087
		i++;
	} while_each_thread(leader, tsk);
2088
	rcu_read_unlock();
B
Ben Blum 已提交
2089 2090
	/* remember the number of threads in the array for later. */
	group_size = i;
2091 2092
	tset.tc_array = group;
	tset.tc_array_len = group_size;
B
Ben Blum 已提交
2093

2094 2095
	/* methods shouldn't be called if no task is actually migrating */
	retval = 0;
2096
	if (!group_size)
2097
		goto out_free_group_list;
2098

B
Ben Blum 已提交
2099 2100 2101 2102 2103
	/*
	 * step 1: check that we can legitimately attach to the cgroup.
	 */
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
2104
			retval = ss->can_attach(cgrp, &tset);
B
Ben Blum 已提交
2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116
			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++) {
2117
		tc = flex_array_get(group, i);
2118 2119 2120 2121
		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
2122 2123 2124 2125
		}
	}

	/*
2126 2127 2128
	 * 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
2129 2130
	 */
	for (i = 0; i < group_size; i++) {
2131
		tc = flex_array_get(group, i);
2132
		cgroup_task_migrate(cgrp, tc->cgrp, tc->task, tc->cg);
B
Ben Blum 已提交
2133 2134 2135 2136
	}
	/* nothing is sensitive to fork() after this point. */

	/*
2137
	 * step 4: do subsystem attach callbacks.
B
Ben Blum 已提交
2138 2139 2140
	 */
	for_each_subsys(root, ss) {
		if (ss->attach)
2141
			ss->attach(cgrp, &tset);
B
Ben Blum 已提交
2142 2143 2144 2145 2146 2147
	}

	/*
	 * step 5: success! and cleanup
	 */
	retval = 0;
2148 2149 2150 2151 2152 2153 2154 2155
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
2156 2157 2158 2159
	}
out_cancel_attach:
	if (retval) {
		for_each_subsys(root, ss) {
2160
			if (ss == failed_ss)
B
Ben Blum 已提交
2161 2162
				break;
			if (ss->cancel_attach)
2163
				ss->cancel_attach(cgrp, &tset);
B
Ben Blum 已提交
2164 2165 2166
		}
	}
out_free_group_list:
2167
	flex_array_free(group);
B
Ben Blum 已提交
2168 2169 2170 2171 2172
	return retval;
}

/*
 * Find the task_struct of the task to attach by vpid and pass it along to the
2173 2174
 * function to attach either it or all tasks in its threadgroup. Will lock
 * cgroup_mutex and threadgroup; may take task_lock of task.
2175
 */
B
Ben Blum 已提交
2176
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2177 2178
{
	struct task_struct *tsk;
2179
	const struct cred *cred = current_cred(), *tcred;
2180 2181
	int ret;

B
Ben Blum 已提交
2182 2183 2184
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;

2185 2186
retry_find_task:
	rcu_read_lock();
2187
	if (pid) {
2188
		tsk = find_task_by_vpid(pid);
B
Ben Blum 已提交
2189 2190
		if (!tsk) {
			rcu_read_unlock();
2191 2192
			ret= -ESRCH;
			goto out_unlock_cgroup;
2193
		}
B
Ben Blum 已提交
2194 2195 2196 2197
		/*
		 * even if we're attaching all tasks in the thread group, we
		 * only need to check permissions on one of them.
		 */
2198
		tcred = __task_cred(tsk);
2199 2200 2201
		if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
		    !uid_eq(cred->euid, tcred->uid) &&
		    !uid_eq(cred->euid, tcred->suid)) {
2202
			rcu_read_unlock();
2203 2204
			ret = -EACCES;
			goto out_unlock_cgroup;
2205
		}
2206 2207
	} else
		tsk = current;
2208 2209

	if (threadgroup)
2210
		tsk = tsk->group_leader;
2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222

	/*
	 * 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;
	}

2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239
	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
2240
		ret = cgroup_attach_proc(cgrp, tsk);
2241
	} else
B
Ben Blum 已提交
2242
		ret = cgroup_attach_task(cgrp, tsk);
2243 2244
	threadgroup_unlock(tsk);

2245
	put_task_struct(tsk);
2246
out_unlock_cgroup:
B
Ben Blum 已提交
2247
	cgroup_unlock();
2248 2249 2250
	return ret;
}

2251
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
B
Ben Blum 已提交
2252 2253 2254 2255 2256
{
	return attach_task_by_pid(cgrp, pid, false);
}

static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2257
{
2258
	return attach_task_by_pid(cgrp, tgid, true);
2259 2260
}

2261 2262 2263 2264
/**
 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
 * @cgrp: the cgroup to be checked for liveness
 *
2265 2266
 * On success, returns true; the lock should be later released with
 * cgroup_unlock(). On failure returns false with no lock held.
2267
 */
2268
bool cgroup_lock_live_group(struct cgroup *cgrp)
2269 2270 2271 2272 2273 2274 2275 2276
{
	mutex_lock(&cgroup_mutex);
	if (cgroup_is_removed(cgrp)) {
		mutex_unlock(&cgroup_mutex);
		return false;
	}
	return true;
}
B
Ben Blum 已提交
2277
EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2278 2279 2280 2281 2282

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);
2283 2284
	if (strlen(buffer) >= PATH_MAX)
		return -EINVAL;
2285 2286
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
T
Tejun Heo 已提交
2287
	mutex_lock(&cgroup_root_mutex);
2288
	strcpy(cgrp->root->release_agent_path, buffer);
T
Tejun Heo 已提交
2289
	mutex_unlock(&cgroup_root_mutex);
2290
	cgroup_unlock();
2291 2292 2293 2294 2295 2296 2297 2298 2299 2300
	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');
2301
	cgroup_unlock();
2302 2303 2304
	return 0;
}

2305 2306 2307
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64

2308
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2309 2310 2311
				struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *unused_ppos)
2312
{
2313
	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324
	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 */
2325
	if (cft->write_u64) {
K
KOSAKI Motohiro 已提交
2326
		u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2327 2328 2329 2330
		if (*end)
			return -EINVAL;
		retval = cft->write_u64(cgrp, cft, val);
	} else {
K
KOSAKI Motohiro 已提交
2331
		s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2332 2333 2334 2335
		if (*end)
			return -EINVAL;
		retval = cft->write_s64(cgrp, cft, val);
	}
2336 2337 2338 2339 2340
	if (!retval)
		retval = nbytes;
	return retval;
}

2341 2342 2343 2344 2345
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)
{
2346
	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360
	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
2361 2362 2363 2364
	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
		retval = -EFAULT;
		goto out;
	}
2365 2366

	buffer[nbytes] = 0;     /* nul-terminate */
K
KOSAKI Motohiro 已提交
2367
	retval = cft->write_string(cgrp, cft, strstrip(buffer));
2368 2369
	if (!retval)
		retval = nbytes;
L
Li Zefan 已提交
2370
out:
2371 2372 2373 2374 2375
	if (buffer != local_buffer)
		kfree(buffer);
	return retval;
}

2376 2377 2378 2379
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);
2380
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2381

2382
	if (cgroup_is_removed(cgrp))
2383
		return -ENODEV;
2384
	if (cft->write)
2385
		return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2386 2387
	if (cft->write_u64 || cft->write_s64)
		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2388 2389
	if (cft->write_string)
		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2390 2391 2392 2393
	if (cft->trigger) {
		int ret = cft->trigger(cgrp, (unsigned int)cft->private);
		return ret ? ret : nbytes;
	}
2394
	return -EINVAL;
2395 2396
}

2397 2398 2399 2400
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
2401
{
2402
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2403
	u64 val = cft->read_u64(cgrp, cft);
2404 2405 2406 2407 2408
	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);

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

2409 2410 2411 2412 2413
static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
{
2414
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2415 2416 2417 2418 2419 2420
	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);
}

2421 2422 2423 2424
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);
2425
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2426

2427
	if (cgroup_is_removed(cgrp))
2428 2429 2430
		return -ENODEV;

	if (cft->read)
2431
		return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2432 2433
	if (cft->read_u64)
		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2434 2435
	if (cft->read_s64)
		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2436 2437 2438
	return -EINVAL;
}

2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458
/*
 * 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;
2459 2460 2461 2462 2463 2464 2465 2466
	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);
2467 2468
}

2469
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2470 2471 2472 2473 2474 2475
{
	struct seq_file *seq = file->private_data;
	kfree(seq->private);
	return single_release(inode, file);
}

2476
static const struct file_operations cgroup_seqfile_operations = {
2477
	.read = seq_read,
2478
	.write = cgroup_file_write,
2479 2480 2481 2482
	.llseek = seq_lseek,
	.release = cgroup_seqfile_release,
};

2483 2484 2485 2486 2487 2488 2489 2490 2491
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);
2492

2493
	if (cft->read_map || cft->read_seq_string) {
2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504
		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)
2505 2506 2507 2508 2509 2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534
		err = cft->open(inode, file);
	else
		err = 0;

	return err;
}

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

/*
 * cgroup_rename - Only allow simple rename of directories in place.
 */
static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
			    struct inode *new_dir, struct dentry *new_dentry)
{
	if (!S_ISDIR(old_dentry->d_inode->i_mode))
		return -ENOTDIR;
	if (new_dentry->d_inode)
		return -EEXIST;
	if (old_dir != new_dir)
		return -EIO;
	return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
}

A
Aristeu Rozanski 已提交
2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550 2551 2552 2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592
static struct simple_xattrs *__d_xattrs(struct dentry *dentry)
{
	if (S_ISDIR(dentry->d_inode->i_mode))
		return &__d_cgrp(dentry)->xattrs;
	else
		return &__d_cft(dentry)->xattrs;
}

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

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

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

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

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

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

2593
static const struct file_operations cgroup_file_operations = {
2594 2595 2596 2597 2598 2599 2600
	.read = cgroup_file_read,
	.write = cgroup_file_write,
	.llseek = generic_file_llseek,
	.open = cgroup_file_open,
	.release = cgroup_file_release,
};

A
Aristeu Rozanski 已提交
2601 2602 2603 2604 2605 2606 2607
static const struct inode_operations cgroup_file_inode_operations = {
	.setxattr = cgroup_setxattr,
	.getxattr = cgroup_getxattr,
	.listxattr = cgroup_listxattr,
	.removexattr = cgroup_removexattr,
};

2608
static const struct inode_operations cgroup_dir_inode_operations = {
2609
	.lookup = cgroup_lookup,
2610 2611 2612
	.mkdir = cgroup_mkdir,
	.rmdir = cgroup_rmdir,
	.rename = cgroup_rename,
A
Aristeu Rozanski 已提交
2613 2614 2615 2616
	.setxattr = cgroup_setxattr,
	.getxattr = cgroup_getxattr,
	.listxattr = cgroup_listxattr,
	.removexattr = cgroup_removexattr,
2617 2618
};

A
Al Viro 已提交
2619
static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
2620 2621 2622 2623 2624 2625 2626
{
	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
	d_add(dentry, NULL);
	return NULL;
}

2627 2628 2629 2630 2631 2632 2633 2634 2635 2636
/*
 * 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
2637
static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2638 2639
				struct super_block *sb)
{
2640 2641 2642 2643 2644 2645 2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656
	struct inode *inode;

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

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

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

		/* start off with i_nlink == 2 (for "." entry) */
		inc_nlink(inode);
T
Tejun Heo 已提交
2657
		inc_nlink(dentry->d_parent->d_inode);
2658

2659 2660 2661 2662 2663 2664 2665 2666 2667
		/*
		 * Control reaches here with cgroup_mutex held.
		 * @inode->i_mutex should nest outside cgroup_mutex but we
		 * want to populate it immediately without releasing
		 * cgroup_mutex.  As @inode isn't visible to anyone else
		 * yet, trylock will always succeed without affecting
		 * lockdep checks.
		 */
		WARN_ON_ONCE(!mutex_trylock(&inode->i_mutex));
2668 2669 2670
	} else if (S_ISREG(mode)) {
		inode->i_size = 0;
		inode->i_fop = &cgroup_file_operations;
A
Aristeu Rozanski 已提交
2671
		inode->i_op = &cgroup_file_inode_operations;
2672 2673 2674 2675 2676 2677
	}
	d_instantiate(dentry, inode);
	dget(dentry);	/* Extra count - pin the dentry in core */
	return 0;
}

L
Li Zefan 已提交
2678 2679 2680 2681 2682 2683 2684 2685 2686
/**
 * 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
2687
static umode_t cgroup_file_mode(const struct cftype *cft)
L
Li Zefan 已提交
2688
{
A
Al Viro 已提交
2689
	umode_t mode = 0;
L
Li Zefan 已提交
2690 2691 2692 2693 2694 2695 2696 2697 2698 2699 2700 2701 2702 2703 2704

	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
2705
static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
A
Aristeu Rozanski 已提交
2706
			   struct cftype *cft)
2707
{
2708
	struct dentry *dir = cgrp->dentry;
T
Tejun Heo 已提交
2709
	struct cgroup *parent = __d_cgrp(dir);
2710
	struct dentry *dentry;
T
Tejun Heo 已提交
2711
	struct cfent *cfe;
2712
	int error;
A
Al Viro 已提交
2713
	umode_t mode;
2714
	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2715

A
Aristeu Rozanski 已提交
2716 2717
	simple_xattrs_init(&cft->xattrs);

2718
	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2719 2720 2721 2722
		strcpy(name, subsys->name);
		strcat(name, ".");
	}
	strcat(name, cft->name);
T
Tejun Heo 已提交
2723

2724
	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
T
Tejun Heo 已提交
2725 2726 2727 2728 2729

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

2730
	dentry = lookup_one_len(name, dir, strlen(name));
T
Tejun Heo 已提交
2731
	if (IS_ERR(dentry)) {
2732
		error = PTR_ERR(dentry);
T
Tejun Heo 已提交
2733 2734 2735 2736 2737 2738 2739 2740 2741 2742 2743 2744 2745 2746 2747
		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);
2748 2749 2750
	return error;
}

2751
static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
A
Aristeu Rozanski 已提交
2752
			      struct cftype cfts[], bool is_add)
2753
{
A
Aristeu Rozanski 已提交
2754
	struct cftype *cft;
T
Tejun Heo 已提交
2755 2756 2757
	int err, ret = 0;

	for (cft = cfts; cft->name[0] != '\0'; cft++) {
2758 2759 2760 2761 2762 2763
		/* does cft->flags tell us to skip this file on @cgrp? */
		if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
			continue;
		if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
			continue;

2764
		if (is_add) {
2765
			err = cgroup_add_file(cgrp, subsys, cft);
2766 2767 2768
			if (err)
				pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
					cft->name, err);
T
Tejun Heo 已提交
2769
			ret = err;
2770 2771
		} else {
			cgroup_rm_file(cgrp, cft);
T
Tejun Heo 已提交
2772
		}
2773
	}
T
Tejun Heo 已提交
2774
	return ret;
2775 2776
}

2777 2778 2779 2780 2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793
static DEFINE_MUTEX(cgroup_cft_mutex);

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

static void cgroup_cfts_commit(struct cgroup_subsys *ss,
A
Aristeu Rozanski 已提交
2794
			       struct cftype *cfts, bool is_add)
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
	__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))
2820
			cgroup_addrm_files(cgrp, ss, cfts, is_add);
2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844
		mutex_unlock(&cgroup_mutex);
		mutex_unlock(&inode->i_mutex);

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

	mutex_unlock(&cgroup_cft_mutex);
}

/**
 * cgroup_add_cftypes - add an array of cftypes to a subsystem
 * @ss: target cgroup subsystem
 * @cfts: zero-length name terminated array of cftypes
 *
 * Register @cfts to @ss.  Files described by @cfts are created for all
 * existing cgroups to which @ss is attached and all future cgroups will
 * have them too.  This function can be called anytime whether @ss is
 * attached or not.
 *
 * Returns 0 on successful registration, -errno on failure.  Note that this
 * function currently returns 0 as long as @cfts registration is successful
 * even if some file creation attempts on existing cgroups fail.
 */
A
Aristeu Rozanski 已提交
2845
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2846 2847 2848 2849 2850 2851 2852 2853 2854 2855
{
	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);
2856
	cgroup_cfts_commit(ss, cfts, true);
2857 2858 2859 2860 2861

	return 0;
}
EXPORT_SYMBOL_GPL(cgroup_add_cftypes);

2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874
/**
 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
 * @ss: target cgroup subsystem
 * @cfts: zero-length name terminated array of cftypes
 *
 * Unregister @cfts from @ss.  Files described by @cfts are removed from
 * all existing cgroups to which @ss is attached and all future cgroups
 * won't have them either.  This function can be called anytime whether @ss
 * is attached or not.
 *
 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
 * registered with @ss.
 */
A
Aristeu Rozanski 已提交
2875
int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892
{
	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
2893 2894 2895 2896 2897 2898
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2899
int cgroup_task_count(const struct cgroup *cgrp)
2900 2901
{
	int count = 0;
K
KOSAKI Motohiro 已提交
2902
	struct cg_cgroup_link *link;
2903 2904

	read_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
2905
	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2906
		count += atomic_read(&link->cg->refcount);
2907 2908
	}
	read_unlock(&css_set_lock);
2909 2910 2911
	return count;
}

2912 2913 2914 2915
/*
 * Advance a list_head iterator.  The iterator should be positioned at
 * the start of a css_set
 */
2916
static void cgroup_advance_iter(struct cgroup *cgrp,
2917
				struct cgroup_iter *it)
2918 2919 2920 2921 2922 2923 2924 2925
{
	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;
2926
		if (l == &cgrp->css_sets) {
2927 2928 2929
			it->cg_link = NULL;
			return;
		}
2930
		link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2931 2932 2933 2934 2935 2936
		cg = link->cg;
	} while (list_empty(&cg->tasks));
	it->cg_link = l;
	it->task = cg->tasks.next;
}

2937 2938 2939 2940 2941 2942
/*
 * 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().
 */
2943
static void cgroup_enable_task_cg_lists(void)
2944 2945 2946 2947
{
	struct task_struct *p, *g;
	write_lock(&css_set_lock);
	use_task_css_set_links = 1;
2948 2949 2950 2951 2952 2953 2954 2955
	/*
	 * 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);
2956 2957
	do_each_thread(g, p) {
		task_lock(p);
2958 2959 2960 2961 2962 2963
		/*
		 * 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))
2964 2965 2966
			list_add(&p->cg_list, &p->cgroups->tasks);
		task_unlock(p);
	} while_each_thread(g, p);
2967
	read_unlock(&tasklist_lock);
2968 2969 2970
	write_unlock(&css_set_lock);
}

2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011
/**
 * cgroup_next_descendant_pre - find the next descendant for pre-order walk
 * @pos: the current position (%NULL to initiate traversal)
 * @cgroup: cgroup whose descendants to walk
 *
 * To be used by cgroup_for_each_descendant_pre().  Find the next
 * descendant to visit for pre-order traversal of @cgroup's descendants.
 */
struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
					  struct cgroup *cgroup)
{
	struct cgroup *next;

	WARN_ON_ONCE(!rcu_read_lock_held());

	/* if first iteration, pretend we just visited @cgroup */
	if (!pos) {
		if (list_empty(&cgroup->children))
			return NULL;
		pos = cgroup;
	}

	/* visit the first child if exists */
	next = list_first_or_null_rcu(&pos->children, struct cgroup, sibling);
	if (next)
		return next;

	/* no child, visit my or the closest ancestor's next sibling */
	do {
		next = list_entry_rcu(pos->sibling.next, struct cgroup,
				      sibling);
		if (&next->sibling != &pos->parent->children)
			return next;

		pos = pos->parent;
	} while (pos != cgroup);

	return NULL;
}
EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre);

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
/**
 * cgroup_rightmost_descendant - return the rightmost descendant of a cgroup
 * @pos: cgroup of interest
 *
 * Return the rightmost descendant of @pos.  If there's no descendant,
 * @pos is returned.  This can be used during pre-order traversal to skip
 * subtree of @pos.
 */
struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos)
{
	struct cgroup *last, *tmp;

	WARN_ON_ONCE(!rcu_read_lock_held());

	do {
		last = pos;
		/* ->prev isn't RCU safe, walk ->next till the end */
		pos = NULL;
		list_for_each_entry_rcu(tmp, &last->children, sibling)
			pos = tmp;
	} while (pos);

	return last;
}
EXPORT_SYMBOL_GPL(cgroup_rightmost_descendant);

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
static struct cgroup *cgroup_leftmost_descendant(struct cgroup *pos)
{
	struct cgroup *last;

	do {
		last = pos;
		pos = list_first_or_null_rcu(&pos->children, struct cgroup,
					     sibling);
	} while (pos);

	return last;
}

/**
 * cgroup_next_descendant_post - find the next descendant for post-order walk
 * @pos: the current position (%NULL to initiate traversal)
 * @cgroup: cgroup whose descendants to walk
 *
 * To be used by cgroup_for_each_descendant_post().  Find the next
 * descendant to visit for post-order traversal of @cgroup's descendants.
 */
struct cgroup *cgroup_next_descendant_post(struct cgroup *pos,
					   struct cgroup *cgroup)
{
	struct cgroup *next;

	WARN_ON_ONCE(!rcu_read_lock_held());

	/* if first iteration, visit the leftmost descendant */
	if (!pos) {
		next = cgroup_leftmost_descendant(cgroup);
		return next != cgroup ? next : NULL;
	}

	/* if there's an unvisited sibling, visit its leftmost descendant */
	next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
	if (&next->sibling != &pos->parent->children)
		return cgroup_leftmost_descendant(next);

	/* no sibling left, visit parent */
	next = pos->parent;
	return next != cgroup ? next : NULL;
}
EXPORT_SYMBOL_GPL(cgroup_next_descendant_post);

3083
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
3084
	__acquires(css_set_lock)
3085 3086 3087 3088 3089 3090
{
	/*
	 * 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.
	 */
3091 3092 3093
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();

3094
	read_lock(&css_set_lock);
3095 3096
	it->cg_link = &cgrp->css_sets;
	cgroup_advance_iter(cgrp, it);
3097 3098
}

3099
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
3100 3101 3102 3103
					struct cgroup_iter *it)
{
	struct task_struct *res;
	struct list_head *l = it->task;
3104
	struct cg_cgroup_link *link;
3105 3106 3107 3108 3109 3110 3111

	/* 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;
3112 3113
	link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
	if (l == &link->cg->tasks) {
3114 3115
		/* We reached the end of this task list - move on to
		 * the next cg_cgroup_link */
3116
		cgroup_advance_iter(cgrp, it);
3117 3118 3119 3120 3121 3122
	} else {
		it->task = l;
	}
	return res;
}

3123
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
3124
	__releases(css_set_lock)
3125 3126 3127 3128
{
	read_unlock(&css_set_lock);
}

3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142 3143 3144 3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159 3160 3161 3162 3163 3164 3165 3166 3167 3168 3169 3170 3171 3172 3173 3174 3175 3176 3177 3178 3179 3180 3181 3182 3183 3184 3185 3186 3187 3188 3189 3190 3191 3192 3193 3194 3195 3196 3197 3198 3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 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 3260 3261 3262 3263 3264 3265
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++) {
3266
			struct task_struct *q = heap->ptrs[i];
3267
			if (i == 0) {
3268 3269
				latest_time = q->start_time;
				latest_task = q;
3270 3271
			}
			/* Process the task per the caller's callback */
3272 3273
			scan->process_task(q, scan);
			put_task_struct(q);
3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288
		}
		/*
		 * 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;
}

3289
/*
3290
 * Stuff for reading the 'tasks'/'procs' files.
3291 3292 3293 3294 3295 3296 3297 3298
 *
 * 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.
 *
 */

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

3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366
/*
 * 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;
}

3367
/*
3368 3369 3370 3371
 * 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.
3372
 */
3373 3374 3375
/* 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)
3376
{
3377 3378 3379 3380 3381 3382 3383 3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405
	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)) {
3406
		newlist = pidlist_resize(list, dest);
3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417
		if (newlist)
			*p = newlist;
	}
	return dest;
}

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

3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428
/*
 * 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 */
3429
	struct pid_namespace *ns = task_active_pid_ns(current);
3430

3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452 3453 3454
	/*
	 * 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;
3455
	l->key.ns = get_pid_ns(ns);
3456 3457 3458 3459 3460 3461 3462 3463
	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;
}

3464 3465 3466
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
3467 3468
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
3469 3470 3471 3472
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
3473 3474
	struct cgroup_iter it;
	struct task_struct *tsk;
3475 3476 3477 3478 3479 3480 3481 3482 3483
	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);
3484
	array = pidlist_allocate(length);
3485 3486 3487
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
3488 3489
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
3490
		if (unlikely(n == length))
3491
			break;
3492
		/* get tgid or pid for procs or tasks file respectively */
3493 3494 3495 3496
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
3497 3498
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
3499
	}
3500
	cgroup_iter_end(cgrp, &it);
3501 3502 3503
	length = n;
	/* now sort & (if procs) strip out duplicates */
	sort(array, length, sizeof(pid_t), cmppid, NULL);
3504
	if (type == CGROUP_FILE_PROCS)
3505
		length = pidlist_uniq(&array, length);
3506 3507
	l = cgroup_pidlist_find(cgrp, type);
	if (!l) {
3508
		pidlist_free(array);
3509
		return -ENOMEM;
3510
	}
3511
	/* store array, freeing old if necessary - lock already held */
3512
	pidlist_free(l->list);
3513 3514 3515 3516
	l->list = array;
	l->length = length;
	l->use_count++;
	up_write(&l->mutex);
3517
	*lp = l;
3518
	return 0;
3519 3520
}

B
Balbir Singh 已提交
3521
/**
L
Li Zefan 已提交
3522
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
3523 3524 3525
 * @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
3526 3527 3528
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
3529 3530 3531 3532
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
	int ret = -EINVAL;
3533
	struct cgroup *cgrp;
B
Balbir Singh 已提交
3534 3535
	struct cgroup_iter it;
	struct task_struct *tsk;
3536

B
Balbir Singh 已提交
3537
	/*
3538 3539
	 * Validate dentry by checking the superblock operations,
	 * and make sure it's a directory.
B
Balbir Singh 已提交
3540
	 */
3541 3542
	if (dentry->d_sb->s_op != &cgroup_ops ||
	    !S_ISDIR(dentry->d_inode->i_mode))
B
Balbir Singh 已提交
3543 3544 3545
		 goto err;

	ret = 0;
3546
	cgrp = dentry->d_fsdata;
B
Balbir Singh 已提交
3547

3548 3549
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
B
Balbir Singh 已提交
3550 3551 3552 3553 3554 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568
		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;
		}
	}
3569
	cgroup_iter_end(cgrp, &it);
B
Balbir Singh 已提交
3570 3571 3572 3573 3574

err:
	return ret;
}

3575

3576
/*
3577
 * seq_file methods for the tasks/procs files. The seq_file position is the
3578
 * next pid to display; the seq_file iterator is a pointer to the pid
3579
 * in the cgroup->l->list array.
3580
 */
3581

3582
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3583
{
3584 3585 3586 3587 3588 3589
	/*
	 * 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
	 */
3590
	struct cgroup_pidlist *l = s->private;
3591 3592 3593
	int index = 0, pid = *pos;
	int *iter;

3594
	down_read(&l->mutex);
3595
	if (pid) {
3596
		int end = l->length;
S
Stephen Rothwell 已提交
3597

3598 3599
		while (index < end) {
			int mid = (index + end) / 2;
3600
			if (l->list[mid] == pid) {
3601 3602
				index = mid;
				break;
3603
			} else if (l->list[mid] <= pid)
3604 3605 3606 3607 3608 3609
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
3610
	if (index >= l->length)
3611 3612
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
3613
	iter = l->list + index;
3614 3615 3616 3617
	*pos = *iter;
	return iter;
}

3618
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3619
{
3620 3621
	struct cgroup_pidlist *l = s->private;
	up_read(&l->mutex);
3622 3623
}

3624
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3625
{
3626 3627 3628
	struct cgroup_pidlist *l = s->private;
	pid_t *p = v;
	pid_t *end = l->list + l->length;
3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641
	/*
	 * 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;
	}
}

3642
static int cgroup_pidlist_show(struct seq_file *s, void *v)
3643 3644 3645
{
	return seq_printf(s, "%d\n", *(int *)v);
}
3646

3647 3648 3649 3650 3651 3652 3653 3654 3655
/*
 * 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,
3656 3657
};

3658
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3659
{
3660 3661 3662 3663 3664 3665 3666
	/*
	 * 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);
3667 3668 3669
	down_write(&l->mutex);
	BUG_ON(!l->use_count);
	if (!--l->use_count) {
3670 3671 3672
		/* we're the last user if refcount is 0; remove and free */
		list_del(&l->links);
		mutex_unlock(&l->owner->pidlist_mutex);
3673
		pidlist_free(l->list);
3674 3675 3676 3677
		put_pid_ns(l->key.ns);
		up_write(&l->mutex);
		kfree(l);
		return;
3678
	}
3679
	mutex_unlock(&l->owner->pidlist_mutex);
3680
	up_write(&l->mutex);
3681 3682
}

3683
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3684
{
3685
	struct cgroup_pidlist *l;
3686 3687
	if (!(file->f_mode & FMODE_READ))
		return 0;
3688 3689 3690 3691 3692 3693
	/*
	 * 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);
3694 3695 3696
	return seq_release(inode, file);
}

3697
static const struct file_operations cgroup_pidlist_operations = {
3698 3699 3700
	.read = seq_read,
	.llseek = seq_lseek,
	.write = cgroup_file_write,
3701
	.release = cgroup_pidlist_release,
3702 3703
};

3704
/*
3705 3706 3707
 * 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.
3708
 */
3709
/* helper function for the two below it */
3710
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3711
{
3712
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3713
	struct cgroup_pidlist *l;
3714
	int retval;
3715

3716
	/* Nothing to do for write-only files */
3717 3718 3719
	if (!(file->f_mode & FMODE_READ))
		return 0;

3720
	/* have the array populated */
3721
	retval = pidlist_array_load(cgrp, type, &l);
3722 3723 3724 3725
	if (retval)
		return retval;
	/* configure file information */
	file->f_op = &cgroup_pidlist_operations;
3726

3727
	retval = seq_open(file, &cgroup_pidlist_seq_operations);
3728
	if (retval) {
3729
		cgroup_release_pid_array(l);
3730
		return retval;
3731
	}
3732
	((struct seq_file *)file->private_data)->private = l;
3733 3734
	return 0;
}
3735 3736
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
3737
	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3738 3739 3740
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
3741
	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3742
}
3743

3744
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3745 3746
					    struct cftype *cft)
{
3747
	return notify_on_release(cgrp);
3748 3749
}

3750 3751 3752 3753 3754 3755 3756 3757 3758 3759 3760 3761
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;
}

3762 3763 3764 3765 3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776
/*
 * 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);
3777
	dput(cgrp->dentry);
3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788 3789 3790 3791 3792 3793
}

/*
 * 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
3794
		__remove_wait_queue(event->wqh, &event->wait);
3795
		spin_lock(&cgrp->event_list_lock);
3796
		list_del_init(&event->list);
3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816 3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843 3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871
		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
3872 3873
	/* AV: shouldn't we check that it's been opened for read instead? */
	ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898
	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;
	}

3899 3900 3901 3902 3903 3904 3905
	/*
	 * 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);

3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929
	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;
}

3930 3931 3932
static u64 cgroup_clone_children_read(struct cgroup *cgrp,
				    struct cftype *cft)
{
3933
	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3934 3935 3936 3937 3938 3939 3940
}

static int cgroup_clone_children_write(struct cgroup *cgrp,
				     struct cftype *cft,
				     u64 val)
{
	if (val)
3941
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3942
	else
3943
		clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3944 3945 3946
	return 0;
}

3947 3948 3949
/*
 * for the common functions, 'private' gives the type of file
 */
3950 3951
/* for hysterical raisins, we can't put this on the older files */
#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3952 3953 3954 3955
static struct cftype files[] = {
	{
		.name = "tasks",
		.open = cgroup_tasks_open,
3956
		.write_u64 = cgroup_tasks_write,
3957
		.release = cgroup_pidlist_release,
L
Li Zefan 已提交
3958
		.mode = S_IRUGO | S_IWUSR,
3959
	},
3960 3961 3962
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "procs",
		.open = cgroup_procs_open,
B
Ben Blum 已提交
3963
		.write_u64 = cgroup_procs_write,
3964
		.release = cgroup_pidlist_release,
B
Ben Blum 已提交
3965
		.mode = S_IRUGO | S_IWUSR,
3966
	},
3967 3968
	{
		.name = "notify_on_release",
3969
		.read_u64 = cgroup_read_notify_on_release,
3970
		.write_u64 = cgroup_write_notify_on_release,
3971
	},
3972 3973 3974 3975 3976
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "event_control",
		.write_string = cgroup_write_event_control,
		.mode = S_IWUGO,
	},
3977 3978 3979 3980 3981
	{
		.name = "cgroup.clone_children",
		.read_u64 = cgroup_clone_children_read,
		.write_u64 = cgroup_clone_children_write,
	},
3982 3983 3984 3985 3986 3987 3988
	{
		.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
3989
	{ }	/* terminate */
3990 3991
};

3992 3993 3994 3995 3996 3997 3998 3999
/**
 * cgroup_populate_dir - selectively creation of files in a directory
 * @cgrp: target cgroup
 * @base_files: true if the base files should be added
 * @subsys_mask: mask of the subsystem ids whose files should be added
 */
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
			       unsigned long subsys_mask)
4000 4001 4002 4003
{
	int err;
	struct cgroup_subsys *ss;

4004 4005 4006 4007 4008
	if (base_files) {
		err = cgroup_addrm_files(cgrp, NULL, files, true);
		if (err < 0)
			return err;
	}
4009

4010
	/* process cftsets of each subsystem */
4011
	for_each_subsys(cgrp->root, ss) {
4012
		struct cftype_set *set;
4013 4014
		if (!test_bit(ss->subsys_id, &subsys_mask))
			continue;
4015

T
Tejun Heo 已提交
4016
		list_for_each_entry(set, &ss->cftsets, node)
4017
			cgroup_addrm_files(cgrp, ss, set->cfts, true);
4018
	}
4019

K
KAMEZAWA Hiroyuki 已提交
4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030
	/* 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);
	}
4031 4032 4033 4034

	return 0;
}

4035 4036 4037 4038
static void css_dput_fn(struct work_struct *work)
{
	struct cgroup_subsys_state *css =
		container_of(work, struct cgroup_subsys_state, dput_work);
4039 4040
	struct dentry *dentry = css->cgroup->dentry;
	struct super_block *sb = dentry->d_sb;
4041

4042 4043 4044
	atomic_inc(&sb->s_active);
	dput(dentry);
	deactivate_super(sb);
4045 4046
}

4047 4048
static void init_cgroup_css(struct cgroup_subsys_state *css,
			       struct cgroup_subsys *ss,
4049
			       struct cgroup *cgrp)
4050
{
4051
	css->cgroup = cgrp;
P
Paul Menage 已提交
4052
	atomic_set(&css->refcnt, 1);
4053
	css->flags = 0;
K
KAMEZAWA Hiroyuki 已提交
4054
	css->id = NULL;
4055
	if (cgrp == dummytop)
4056
		css->flags |= CSS_ROOT;
4057 4058
	BUG_ON(cgrp->subsys[ss->subsys_id]);
	cgrp->subsys[ss->subsys_id] = css;
4059 4060

	/*
4061 4062 4063 4064
	 * 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().
4065 4066
	 */
	INIT_WORK(&css->dput_work, css_dput_fn);
4067 4068
}

T
Tejun Heo 已提交
4069 4070
/* invoke ->post_create() on a new CSS and mark it online if successful */
static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
4071
{
T
Tejun Heo 已提交
4072 4073
	int ret = 0;

4074 4075
	lockdep_assert_held(&cgroup_mutex);

4076 4077
	if (ss->css_online)
		ret = ss->css_online(cgrp);
T
Tejun Heo 已提交
4078 4079 4080
	if (!ret)
		cgrp->subsys[ss->subsys_id]->flags |= CSS_ONLINE;
	return ret;
4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093 4094
}

/* if the CSS is online, invoke ->pre_destory() on it and mark it offline */
static void offline_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
{
	struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];

	lockdep_assert_held(&cgroup_mutex);

	if (!(css->flags & CSS_ONLINE))
		return;

	/*
4095
	 * css_offline() should be called with cgroup_mutex unlocked.  See
4096 4097 4098 4099
	 * 3fa59dfbc3 ("cgroup: fix potential deadlock in pre_destroy") for
	 * details.  This temporary unlocking should go away once
	 * cgroup_mutex is unexported from controllers.
	 */
4100
	if (ss->css_offline) {
4101
		mutex_unlock(&cgroup_mutex);
4102
		ss->css_offline(cgrp);
4103 4104 4105 4106 4107 4108
		mutex_lock(&cgroup_mutex);
	}

	cgrp->subsys[ss->subsys_id]->flags &= ~CSS_ONLINE;
}

4109
/*
L
Li Zefan 已提交
4110 4111 4112 4113
 * 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
4114
 *
L
Li Zefan 已提交
4115
 * Must be called with the mutex on the parent inode held
4116 4117
 */
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
A
Al Viro 已提交
4118
			     umode_t mode)
4119
{
4120
	struct cgroup *cgrp;
4121 4122 4123 4124 4125
	struct cgroupfs_root *root = parent->root;
	int err = 0;
	struct cgroup_subsys *ss;
	struct super_block *sb = root->sb;

T
Tejun Heo 已提交
4126
	/* allocate the cgroup and its ID, 0 is reserved for the root */
4127 4128
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
4129 4130
		return -ENOMEM;

T
Tejun Heo 已提交
4131 4132 4133 4134
	cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);
	if (cgrp->id < 0)
		goto err_free_cgrp;

4135 4136 4137 4138 4139 4140 4141 4142 4143
	/*
	 * Only live parents can have children.  Note that the liveliness
	 * check isn't strictly necessary because cgroup_mkdir() and
	 * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
	 * anyway so that locking is contained inside cgroup proper and we
	 * don't get nasty surprises if we ever grow another caller.
	 */
	if (!cgroup_lock_live_group(parent)) {
		err = -ENODEV;
T
Tejun Heo 已提交
4144
		goto err_free_id;
4145 4146
	}

4147 4148 4149 4150 4151 4152 4153
	/* 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);

4154
	init_cgroup_housekeeping(cgrp);
4155

4156 4157 4158
	cgrp->parent = parent;
	cgrp->root = parent->root;
	cgrp->top_cgroup = parent->top_cgroup;
4159

4160 4161 4162
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

4163 4164
	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4165

4166
	for_each_subsys(root, ss) {
4167
		struct cgroup_subsys_state *css;
4168

4169
		css = ss->css_alloc(cgrp);
4170 4171
		if (IS_ERR(css)) {
			err = PTR_ERR(css);
4172
			goto err_free_all;
4173
		}
4174
		init_cgroup_css(css, ss, cgrp);
4175 4176 4177
		if (ss->use_id) {
			err = alloc_css_id(ss, parent, cgrp);
			if (err)
4178
				goto err_free_all;
4179
		}
4180 4181
	}

4182 4183 4184 4185 4186
	/*
	 * Create directory.  cgroup_create_file() returns with the new
	 * directory locked on success so that it can be populated without
	 * dropping cgroup_mutex.
	 */
T
Tejun Heo 已提交
4187
	err = cgroup_create_file(dentry, S_IFDIR | mode, sb);
4188
	if (err < 0)
4189
		goto err_free_all;
4190
	lockdep_assert_held(&dentry->d_inode->i_mutex);
4191

4192
	/* allocation complete, commit to creation */
T
Tejun Heo 已提交
4193
	dentry->d_fsdata = cgrp;
4194
	cgrp->dentry = dentry;
4195 4196 4197
	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
	list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
	root->number_of_cgroups++;
T
Tejun Heo 已提交
4198

T
Tejun Heo 已提交
4199 4200
	/* each css holds a ref to the cgroup's dentry */
	for_each_subsys(root, ss)
4201
		dget(dentry);
4202

T
Tejun Heo 已提交
4203 4204 4205 4206 4207
	/* creation succeeded, notify subsystems */
	for_each_subsys(root, ss) {
		err = online_css(ss, cgrp);
		if (err)
			goto err_destroy;
4208 4209 4210 4211 4212 4213 4214 4215 4216

		if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
		    parent->parent) {
			pr_warning("cgroup: %s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
				   current->comm, current->pid, ss->name);
			if (!strcmp(ss->name, "memory"))
				pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
			ss->warned_broken_hierarchy = true;
		}
4217 4218
	}

4219
	err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
4220 4221
	if (err)
		goto err_destroy;
4222 4223

	mutex_unlock(&cgroup_mutex);
4224
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
4225 4226 4227

	return 0;

4228
err_free_all:
4229
	for_each_subsys(root, ss) {
4230
		if (cgrp->subsys[ss->subsys_id])
4231
			ss->css_free(cgrp);
4232 4233 4234 4235
	}
	mutex_unlock(&cgroup_mutex);
	/* Release the reference count that we took on the superblock */
	deactivate_super(sb);
T
Tejun Heo 已提交
4236 4237
err_free_id:
	ida_simple_remove(&root->cgroup_ida, cgrp->id);
4238
err_free_cgrp:
4239
	kfree(cgrp);
4240
	return err;
4241 4242 4243 4244 4245 4246

err_destroy:
	cgroup_destroy_locked(cgrp);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&dentry->d_inode->i_mutex);
	return err;
4247 4248
}

4249
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
4250 4251 4252 4253 4254 4255 4256
{
	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);
}

4257 4258 4259 4260 4261 4262 4263 4264 4265
/*
 * 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.
 */
4266
static int cgroup_has_css_refs(struct cgroup *cgrp)
4267 4268
{
	int i;
4269

B
Ben Blum 已提交
4270 4271 4272 4273 4274
	/*
	 * 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.
	 */
4275 4276 4277
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		struct cgroup_subsys_state *css;
4278

B
Ben Blum 已提交
4279 4280
		/* Skip subsystems not present or not in this hierarchy */
		if (ss == NULL || ss->root != cgrp->root)
4281
			continue;
4282

4283
		css = cgrp->subsys[ss->subsys_id];
4284 4285
		/*
		 * When called from check_for_release() it's possible
4286 4287 4288 4289
		 * 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
4290 4291 4292
		 * release agent to be called anyway.
		 */
		if (css && css_refcnt(css) > 1)
4293 4294 4295 4296 4297
			return 1;
	}
	return 0;
}

4298 4299
static int cgroup_destroy_locked(struct cgroup *cgrp)
	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4300
{
4301 4302
	struct dentry *d = cgrp->dentry;
	struct cgroup *parent = cgrp->parent;
4303
	DEFINE_WAIT(wait);
4304
	struct cgroup_event *event, *tmp;
4305
	struct cgroup_subsys *ss;
4306
	LIST_HEAD(tmp_list);
4307

4308 4309 4310 4311
	lockdep_assert_held(&d->d_inode->i_mutex);
	lockdep_assert_held(&cgroup_mutex);

	if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children))
4312
		return -EBUSY;
L
Li Zefan 已提交
4313

4314
	/*
4315 4316 4317 4318
	 * Block new css_tryget() by deactivating refcnt and mark @cgrp
	 * removed.  This makes future css_tryget() and child creation
	 * attempts fail thus maintaining the removal conditions verified
	 * above.
4319
	 */
4320 4321
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4322

4323 4324
		WARN_ON(atomic_read(&css->refcnt) < 0);
		atomic_add(CSS_DEACT_BIAS, &css->refcnt);
4325
	}
4326
	set_bit(CGRP_REMOVED, &cgrp->flags);
4327

4328
	/* tell subsystems to initate destruction */
4329
	for_each_subsys(cgrp->root, ss)
4330
		offline_css(ss, cgrp);
4331 4332 4333 4334 4335 4336 4337 4338

	/*
	 * Put all the base refs.  Each css holds an extra reference to the
	 * cgroup's dentry and cgroup removal proceeds regardless of css
	 * refs.  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.
	 */
T
Tejun Heo 已提交
4339 4340
	for_each_subsys(cgrp->root, ss)
		css_put(cgrp->subsys[ss->subsys_id]);
4341

4342
	raw_spin_lock(&release_list_lock);
4343
	if (!list_empty(&cgrp->release_list))
4344
		list_del_init(&cgrp->release_list);
4345
	raw_spin_unlock(&release_list_lock);
4346 4347

	/* delete this cgroup from parent->children */
4348
	list_del_rcu(&cgrp->sibling);
4349 4350
	list_del_init(&cgrp->allcg_node);

4351
	dget(d);
4352 4353 4354
	cgroup_d_remove_dir(d);
	dput(d);

4355
	set_bit(CGRP_RELEASABLE, &parent->flags);
4356 4357
	check_for_release(parent);

4358 4359 4360
	/*
	 * Unregister events and notify userspace.
	 * Notify userspace about cgroup removing only after rmdir of cgroup
4361 4362 4363 4364
	 * directory to avoid race between userspace and kernelspace. Use
	 * a temporary list to avoid a deadlock with cgroup_event_wake(). Since
	 * cgroup_event_wake() is called with the wait queue head locked,
	 * remove_wait_queue() cannot be called while holding event_list_lock.
4365 4366
	 */
	spin_lock(&cgrp->event_list_lock);
4367 4368 4369
	list_splice_init(&cgrp->event_list, &tmp_list);
	spin_unlock(&cgrp->event_list_lock);
	list_for_each_entry_safe(event, tmp, &tmp_list, list) {
4370
		list_del_init(&event->list);
4371 4372 4373 4374 4375
		remove_wait_queue(event->wqh, &event->wait);
		eventfd_signal(event->eventfd, 1);
		schedule_work(&event->remove);
	}

4376 4377 4378
	return 0;
}

4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
	int ret;

	mutex_lock(&cgroup_mutex);
	ret = cgroup_destroy_locked(dentry->d_fsdata);
	mutex_unlock(&cgroup_mutex);

	return ret;
}

4390 4391 4392 4393 4394 4395 4396 4397 4398 4399 4400 4401 4402 4403
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);
	}
}

4404
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4405 4406
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
4407 4408

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4409

4410 4411
	mutex_lock(&cgroup_mutex);

4412 4413 4414
	/* init base cftset */
	cgroup_init_cftsets(ss);

4415
	/* Create the top cgroup state for this subsystem */
4416
	list_add(&ss->sibling, &rootnode.subsys_list);
4417
	ss->root = &rootnode;
4418
	css = ss->css_alloc(dummytop);
4419 4420 4421 4422
	/* We don't handle early failures gracefully */
	BUG_ON(IS_ERR(css));
	init_cgroup_css(css, ss, dummytop);

L
Li Zefan 已提交
4423
	/* Update the init_css_set to contain a subsys
4424
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
4425 4426
	 * newly registered, all tasks and hence the
	 * init_css_set is in the subsystem's top cgroup. */
4427
	init_css_set.subsys[ss->subsys_id] = css;
4428 4429 4430

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

L
Li Zefan 已提交
4431 4432 4433 4434 4435
	/* 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));

4436
	ss->active = 1;
T
Tejun Heo 已提交
4437
	BUG_ON(online_css(ss, dummytop));
4438

4439 4440
	mutex_unlock(&cgroup_mutex);

4441 4442 4443 4444 4445 4446 4447 4448 4449 4450
	/* 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
4451
 * subsystem is built as a module, it will be assigned a new subsys_id and set
4452 4453 4454 4455 4456 4457
 * 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)
{
	struct cgroup_subsys_state *css;
4458
	int i, ret;
4459 4460 4461
	struct hlist_node *node, *tmp;
	struct css_set *cg;
	unsigned long key;
4462 4463 4464

	/* check name and function validity */
	if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
4465
	    ss->css_alloc == NULL || ss->css_free == NULL)
4466 4467 4468 4469 4470 4471 4472 4473 4474 4475 4476 4477 4478 4479 4480 4481
		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) {
4482
		/* a sanity check */
4483 4484 4485 4486
		BUG_ON(subsys[ss->subsys_id] != ss);
		return 0;
	}

4487 4488 4489
	/* init base cftset */
	cgroup_init_cftsets(ss);

4490
	mutex_lock(&cgroup_mutex);
4491
	subsys[ss->subsys_id] = ss;
4492 4493

	/*
4494 4495 4496
	 * no ss->css_alloc seems to need anything important in the ss
	 * struct, so this can happen first (i.e. before the rootnode
	 * attachment).
4497
	 */
4498
	css = ss->css_alloc(dummytop);
4499 4500
	if (IS_ERR(css)) {
		/* failure case - need to deassign the subsys[] slot. */
4501
		subsys[ss->subsys_id] = NULL;
4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512
		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) {
4513 4514 4515
		ret = cgroup_init_idr(ss, css);
		if (ret)
			goto err_unload;
4516 4517 4518 4519 4520 4521 4522 4523 4524 4525 4526
	}

	/*
	 * 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);
4527 4528 4529 4530 4531 4532 4533 4534 4535 4536 4537
	hash_for_each_safe(css_set_table, i, node, tmp, cg, hlist) {
		/* skip entries that we already rehashed */
		if (cg->subsys[ss->subsys_id])
			continue;
		/* remove existing entry */
		hash_del(&cg->hlist);
		/* set new value */
		cg->subsys[ss->subsys_id] = css;
		/* recompute hash and restore entry */
		key = css_set_hash(cg->subsys);
		hash_add(css_set_table, node, key);
4538 4539 4540 4541
	}
	write_unlock(&css_set_lock);

	ss->active = 1;
T
Tejun Heo 已提交
4542 4543 4544
	ret = online_css(ss, dummytop);
	if (ret)
		goto err_unload;
4545

4546 4547 4548
	/* success! */
	mutex_unlock(&cgroup_mutex);
	return 0;
4549 4550 4551 4552 4553 4554

err_unload:
	mutex_unlock(&cgroup_mutex);
	/* @ss can't be mounted here as try_module_get() would fail */
	cgroup_unload_subsys(ss);
	return ret;
4555
}
4556
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4557

B
Ben Blum 已提交
4558 4559 4560 4561 4562 4563 4564 4565 4566 4567 4568 4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579
/**
 * 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;

	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);
4580

4581
	offline_css(ss, dummytop);
4582 4583 4584 4585 4586 4587 4588
	ss->active = 0;

	if (ss->use_id) {
		idr_remove_all(&ss->idr);
		idr_destroy(&ss->idr);
	}

B
Ben Blum 已提交
4589 4590 4591 4592
	/* deassign the subsys_id */
	subsys[ss->subsys_id] = NULL;

	/* remove subsystem from rootnode's list of subsystems */
4593
	list_del_init(&ss->sibling);
B
Ben Blum 已提交
4594 4595 4596 4597 4598 4599 4600 4601

	/*
	 * 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;
4602
		unsigned long key;
B
Ben Blum 已提交
4603

4604
		hash_del(&cg->hlist);
B
Ben Blum 已提交
4605
		cg->subsys[ss->subsys_id] = NULL;
4606 4607
		key = css_set_hash(cg->subsys);
		hash_add(css_set_table, &cg->hlist, key);
B
Ben Blum 已提交
4608 4609 4610 4611
	}
	write_unlock(&css_set_lock);

	/*
4612 4613 4614 4615
	 * remove subsystem's css from the dummytop and free it - need to
	 * free before marking as null because ss->css_free needs the
	 * cgrp->subsys pointer to find their state. note that this also
	 * takes care of freeing the css_id.
B
Ben Blum 已提交
4616
	 */
4617
	ss->css_free(dummytop);
B
Ben Blum 已提交
4618 4619 4620 4621 4622 4623
	dummytop->subsys[ss->subsys_id] = NULL;

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

4624
/**
L
Li Zefan 已提交
4625 4626 4627 4628
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
4629 4630 4631 4632
 */
int __init cgroup_init_early(void)
{
	int i;
4633
	atomic_set(&init_css_set.refcount, 1);
4634 4635
	INIT_LIST_HEAD(&init_css_set.cg_links);
	INIT_LIST_HEAD(&init_css_set.tasks);
4636
	INIT_HLIST_NODE(&init_css_set.hlist);
4637
	css_set_count = 1;
4638
	init_cgroup_root(&rootnode);
4639 4640 4641 4642
	root_count = 1;
	init_task.cgroups = &init_css_set;

	init_css_set_link.cg = &init_css_set;
4643
	init_css_set_link.cgrp = dummytop;
4644
	list_add(&init_css_set_link.cgrp_link_list,
4645 4646 4647
		 &rootnode.top_cgroup.css_sets);
	list_add(&init_css_set_link.cg_link_list,
		 &init_css_set.cg_links);
4648

4649
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4650 4651
		struct cgroup_subsys *ss = subsys[i];

4652 4653 4654 4655
		/* at bootup time, we don't worry about modular subsystems */
		if (!ss || ss->module)
			continue;

4656 4657
		BUG_ON(!ss->name);
		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4658 4659
		BUG_ON(!ss->css_alloc);
		BUG_ON(!ss->css_free);
4660
		if (ss->subsys_id != i) {
D
Diego Calleja 已提交
4661
			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4662 4663 4664 4665 4666 4667 4668 4669 4670 4671 4672
			       ss->name, ss->subsys_id);
			BUG();
		}

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

/**
L
Li Zefan 已提交
4673 4674 4675 4676
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
4677 4678 4679 4680 4681
 */
int __init cgroup_init(void)
{
	int err;
	int i;
4682
	unsigned long key;
4683 4684 4685 4686

	err = bdi_init(&cgroup_backing_dev_info);
	if (err)
		return err;
4687

4688
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4689
		struct cgroup_subsys *ss = subsys[i];
4690 4691 4692 4693

		/* at bootup time, we don't worry about modular subsystems */
		if (!ss || ss->module)
			continue;
4694 4695
		if (!ss->early_init)
			cgroup_init_subsys(ss);
K
KAMEZAWA Hiroyuki 已提交
4696
		if (ss->use_id)
4697
			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4698 4699
	}

4700
	/* Add init_css_set to the hash table */
4701 4702
	key = css_set_hash(init_css_set.subsys);
	hash_add(css_set_table, &init_css_set.hlist, key);
4703
	BUG_ON(!init_root_id(&rootnode));
4704 4705 4706 4707 4708 4709 4710

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

4711
	err = register_filesystem(&cgroup_fs_type);
4712 4713
	if (err < 0) {
		kobject_put(cgroup_kobj);
4714
		goto out;
4715
	}
4716

L
Li Zefan 已提交
4717
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4718

4719
out:
4720 4721 4722
	if (err)
		bdi_destroy(&cgroup_backing_dev_info);

4723 4724
	return err;
}
4725

4726 4727 4728 4729 4730 4731
/*
 * 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,
4732
 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4733 4734 4735 4736 4737 4738 4739 4740 4741 4742 4743 4744 4745 4746 4747 4748 4749 4750 4751 4752 4753 4754 4755 4756 4757 4758 4759 4760 4761
 *    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);

4762
	for_each_active_root(root) {
4763
		struct cgroup_subsys *ss;
4764
		struct cgroup *cgrp;
4765 4766
		int count = 0;

4767
		seq_printf(m, "%d:", root->hierarchy_id);
4768 4769
		for_each_subsys(root, ss)
			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4770 4771 4772
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
4773
		seq_putc(m, ':');
4774
		cgrp = task_cgroup_from_root(tsk, root);
4775
		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786 4787 4788 4789 4790 4791 4792 4793 4794 4795 4796
		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);
}

4797
const struct file_operations proc_cgroup_operations = {
4798 4799 4800 4801 4802 4803 4804 4805 4806 4807 4808
	.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;

4809
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
B
Ben Blum 已提交
4810 4811 4812 4813 4814
	/*
	 * 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.
	 */
4815 4816 4817
	mutex_lock(&cgroup_mutex);
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
B
Ben Blum 已提交
4818 4819
		if (ss == NULL)
			continue;
4820 4821
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
4822
			   ss->root->number_of_cgroups, !ss->disabled);
4823 4824 4825 4826 4827 4828 4829
	}
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
4830
	return single_open(file, proc_cgroupstats_show, NULL);
4831 4832
}

4833
static const struct file_operations proc_cgroupstats_operations = {
4834 4835 4836 4837 4838 4839
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

4840 4841
/**
 * cgroup_fork - attach newly forked task to its parents cgroup.
L
Li Zefan 已提交
4842
 * @child: pointer to task_struct of forking parent process.
4843 4844 4845 4846 4847
 *
 * 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
4848 4849 4850 4851
 * it was not made under the protection of RCU or cgroup_mutex, so
 * 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.
4852 4853 4854 4855 4856 4857
 *
 * 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)
{
4858
	task_lock(current);
4859 4860
	child->cgroups = current->cgroups;
	get_css_set(child->cgroups);
4861
	task_unlock(current);
4862
	INIT_LIST_HEAD(&child->cg_list);
4863 4864
}

4865
/**
L
Li Zefan 已提交
4866 4867 4868
 * cgroup_post_fork - called on a new task after adding it to the task list
 * @child: the task in question
 *
4869 4870 4871 4872 4873
 * Adds the task to the list running through its css_set if necessary and
 * call the subsystem fork() callbacks.  Has to be after the task is
 * visible on the task list in case we race with the first call to
 * cgroup_iter_start() - to guarantee that the new task ends up on its
 * list.
L
Li Zefan 已提交
4874
 */
4875 4876
void cgroup_post_fork(struct task_struct *child)
{
4877 4878
	int i;

4879 4880 4881 4882 4883 4884 4885 4886 4887 4888 4889
	/*
	 * 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.
	 */
4890 4891
	if (use_task_css_set_links) {
		write_lock(&css_set_lock);
4892 4893
		task_lock(child);
		if (list_empty(&child->cg_list))
4894
			list_add(&child->cg_list, &child->cgroups->tasks);
4895
		task_unlock(child);
4896 4897
		write_unlock(&css_set_lock);
	}
4898 4899 4900 4901 4902 4903 4904 4905 4906 4907 4908 4909 4910 4911 4912 4913 4914 4915 4916 4917 4918 4919

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

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

			if (ss->fork)
				ss->fork(child);
		}
	}
4920
}
4921

4922 4923 4924
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
4925
 * @run_callback: run exit callbacks?
4926 4927 4928 4929 4930 4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944 4945 4946 4947 4948 4949 4950 4951 4952 4953
 *
 * 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,
4954 4955
 *    which wards off any cgroup_attach_task() attempts, or task is a failed
 *    fork, never visible to cgroup_attach_task.
4956 4957 4958
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
4959
	struct css_set *cg;
4960
	int i;
4961 4962 4963 4964 4965 4966 4967 4968 4969

	/*
	 * 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))
4970
			list_del_init(&tsk->cg_list);
4971 4972 4973
		write_unlock(&css_set_lock);
	}

4974 4975
	/* Reassign the task to the init_css_set. */
	task_lock(tsk);
4976 4977
	cg = tsk->cgroups;
	tsk->cgroups = &init_css_set;
4978 4979

	if (run_callbacks && need_forkexit_callback) {
4980
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4981
			struct cgroup_subsys *ss = subsys[i];
4982 4983 4984 4985 4986

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

4987 4988 4989 4990
			if (ss->exit) {
				struct cgroup *old_cgrp =
					rcu_dereference_raw(cg->subsys[i])->cgroup;
				struct cgroup *cgrp = task_cgroup(tsk, i);
4991
				ss->exit(cgrp, old_cgrp, tsk);
4992 4993 4994
			}
		}
	}
4995
	task_unlock(tsk);
4996

4997
	put_css_set_taskexit(cg);
4998
}
4999

L
Li Zefan 已提交
5000
/**
5001
 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
L
Li Zefan 已提交
5002
 * @cgrp: the cgroup in question
5003
 * @task: the task in question
L
Li Zefan 已提交
5004
 *
5005 5006
 * See if @cgrp is a descendant of @task's cgroup in the appropriate
 * hierarchy.
5007 5008 5009 5010 5011 5012
 *
 * If we are sending in dummytop, then presumably we are creating
 * the top cgroup in the subsystem.
 *
 * Called only by the ns (nsproxy) cgroup.
 */
5013
int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
5014 5015 5016 5017
{
	int ret;
	struct cgroup *target;

5018
	if (cgrp == dummytop)
5019 5020
		return 1;

5021
	target = task_cgroup_from_root(task, cgrp->root);
5022 5023 5024
	while (cgrp != target && cgrp!= cgrp->top_cgroup)
		cgrp = cgrp->parent;
	ret = (cgrp == target);
5025 5026
	return ret;
}
5027

5028
static void check_for_release(struct cgroup *cgrp)
5029 5030 5031
{
	/* All of these checks rely on RCU to keep the cgroup
	 * structure alive */
5032 5033
	if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
	    && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
5034 5035 5036 5037
		/* Control Group is currently removeable. If it's not
		 * already queued for a userspace notification, queue
		 * it now */
		int need_schedule_work = 0;
5038
		raw_spin_lock(&release_list_lock);
5039 5040 5041
		if (!cgroup_is_removed(cgrp) &&
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
5042 5043
			need_schedule_work = 1;
		}
5044
		raw_spin_unlock(&release_list_lock);
5045 5046 5047 5048 5049
		if (need_schedule_work)
			schedule_work(&release_agent_work);
	}
}

5050
/* Caller must verify that the css is not for root cgroup */
5051 5052
bool __css_tryget(struct cgroup_subsys_state *css)
{
T
Tejun Heo 已提交
5053 5054
	while (true) {
		int t, v;
5055

T
Tejun Heo 已提交
5056 5057 5058
		v = css_refcnt(css);
		t = atomic_cmpxchg(&css->refcnt, v, v + 1);
		if (likely(t == v))
5059
			return true;
T
Tejun Heo 已提交
5060 5061
		else if (t < 0)
			return false;
5062
		cpu_relax();
T
Tejun Heo 已提交
5063
	}
5064 5065 5066 5067 5068
}
EXPORT_SYMBOL_GPL(__css_tryget);

/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css)
5069
{
5070
	struct cgroup *cgrp = css->cgroup;
5071
	int v;
5072

5073
	rcu_read_lock();
5074 5075 5076
	v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));

	switch (v) {
5077
	case 1:
5078 5079 5080 5081
		if (notify_on_release(cgrp)) {
			set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
		}
5082 5083
		break;
	case 0:
5084
		schedule_work(&css->dput_work);
5085
		break;
5086 5087 5088
	}
	rcu_read_unlock();
}
B
Ben Blum 已提交
5089
EXPORT_SYMBOL_GPL(__css_put);
5090 5091 5092 5093 5094 5095 5096 5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 5117

/*
 * 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);
5118
	raw_spin_lock(&release_list_lock);
5119 5120 5121
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
5122
		char *pathbuf = NULL, *agentbuf = NULL;
5123
		struct cgroup *cgrp = list_entry(release_list.next,
5124 5125
						    struct cgroup,
						    release_list);
5126
		list_del_init(&cgrp->release_list);
5127
		raw_spin_unlock(&release_list_lock);
5128
		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
5129 5130 5131 5132 5133 5134 5135
		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;
5136 5137

		i = 0;
5138 5139
		argv[i++] = agentbuf;
		argv[i++] = pathbuf;
5140 5141 5142 5143 5144 5145 5146 5147 5148 5149 5150 5151 5152 5153
		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);
5154 5155 5156
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
5157
		raw_spin_lock(&release_list_lock);
5158
	}
5159
	raw_spin_unlock(&release_list_lock);
5160 5161
	mutex_unlock(&cgroup_mutex);
}
5162 5163 5164 5165 5166 5167 5168 5169 5170

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

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;
5171
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
5172 5173
			struct cgroup_subsys *ss = subsys[i];

5174 5175 5176 5177 5178 5179 5180 5181
			/*
			 * cgroup_disable, being at boot time, can't
			 * know about module subsystems, so we don't
			 * worry about them.
			 */
			if (!ss || ss->module)
				continue;

5182 5183 5184 5185 5186 5187 5188 5189 5190 5191 5192
			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
5193 5194 5195 5196 5197 5198 5199 5200 5201 5202

/*
 * 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)
{
5203 5204 5205 5206 5207 5208 5209
	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.
	 */
5210
	cssid = rcu_dereference_check(css->id, css_refcnt(css));
K
KAMEZAWA Hiroyuki 已提交
5211 5212 5213 5214 5215

	if (cssid)
		return cssid->id;
	return 0;
}
B
Ben Blum 已提交
5216
EXPORT_SYMBOL_GPL(css_id);
K
KAMEZAWA Hiroyuki 已提交
5217 5218 5219

unsigned short css_depth(struct cgroup_subsys_state *css)
{
5220 5221
	struct css_id *cssid;

5222
	cssid = rcu_dereference_check(css->id, css_refcnt(css));
K
KAMEZAWA Hiroyuki 已提交
5223 5224 5225 5226 5227

	if (cssid)
		return cssid->depth;
	return 0;
}
B
Ben Blum 已提交
5228
EXPORT_SYMBOL_GPL(css_depth);
K
KAMEZAWA Hiroyuki 已提交
5229

5230 5231 5232 5233 5234 5235
/**
 *  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
5236
 * this function reads css->id, the caller must hold rcu_read_lock().
5237 5238 5239 5240 5241 5242
 * 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
5243
bool css_is_ancestor(struct cgroup_subsys_state *child,
5244
		    const struct cgroup_subsys_state *root)
K
KAMEZAWA Hiroyuki 已提交
5245
{
5246 5247
	struct css_id *child_id;
	struct css_id *root_id;
K
KAMEZAWA Hiroyuki 已提交
5248

5249
	child_id  = rcu_dereference(child->id);
5250 5251
	if (!child_id)
		return false;
5252
	root_id = rcu_dereference(root->id);
5253 5254 5255 5256 5257 5258 5259
	if (!root_id)
		return false;
	if (child_id->depth < root_id->depth)
		return false;
	if (child_id->stack[root_id->depth] != root_id->id)
		return false;
	return true;
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KAMEZAWA Hiroyuki 已提交
5260 5261 5262 5263 5264 5265 5266 5267 5268 5269 5270 5271 5272
}

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);
5273
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5274
	idr_remove(&ss->idr, id->id);
5275
	spin_unlock(&ss->id_lock);
5276
	kfree_rcu(id, rcu_head);
K
KAMEZAWA Hiroyuki 已提交
5277
}
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5278
EXPORT_SYMBOL_GPL(free_css_id);
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KAMEZAWA Hiroyuki 已提交
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/*
 * This is called by init or create(). Then, calls to this function are
 * always serialized (By cgroup_mutex() at create()).
 */

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

	BUG_ON(!ss->use_id);

	size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
	newid = kzalloc(size, GFP_KERNEL);
	if (!newid)
		return ERR_PTR(-ENOMEM);
	/* get id */
	if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
		error = -ENOMEM;
		goto err_out;
	}
5301
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
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	/* Don't use 0. allocates an ID of 1-65535 */
	error = idr_get_new_above(&ss->idr, newid, 1, &myid);
5304
	spin_unlock(&ss->id_lock);
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KAMEZAWA Hiroyuki 已提交
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	/* Returns error when there are no free spaces for new ID.*/
	if (error) {
		error = -ENOSPC;
		goto err_out;
	}
	if (myid > CSS_ID_MAX)
		goto remove_idr;

	newid->id = myid;
	newid->depth = depth;
	return newid;
remove_idr:
	error = -ENOSPC;
5319
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5320
	idr_remove(&ss->idr, myid);
5321
	spin_unlock(&ss->id_lock);
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err_out:
	kfree(newid);
	return ERR_PTR(error);

}

5328 5329
static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
					    struct cgroup_subsys_state *rootcss)
K
KAMEZAWA Hiroyuki 已提交
5330 5331 5332
{
	struct css_id *newid;

5333
	spin_lock_init(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
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	idr_init(&ss->idr);

	newid = get_new_cssid(ss, 0);
	if (IS_ERR(newid))
		return PTR_ERR(newid);

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

static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
			struct cgroup *child)
{
	int subsys_id, i, depth = 0;
	struct cgroup_subsys_state *parent_css, *child_css;
5351
	struct css_id *child_id, *parent_id;
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KAMEZAWA Hiroyuki 已提交
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	subsys_id = ss->subsys_id;
	parent_css = parent->subsys[subsys_id];
	child_css = child->subsys[subsys_id];
	parent_id = parent_css->id;
5357
	depth = parent_id->depth + 1;
K
KAMEZAWA Hiroyuki 已提交
5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383 5384 5385 5386 5387 5388 5389 5390 5391 5392 5393 5394

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

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

	return 0;
}

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

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

	if (unlikely(!cssid))
		return NULL;

	return rcu_dereference(cssid->css);
}
B
Ben Blum 已提交
5395
EXPORT_SYMBOL_GPL(css_lookup);
K
KAMEZAWA Hiroyuki 已提交
5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418 5419 5420

/**
 * 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);
5421 5422
	WARN_ON_ONCE(!rcu_read_lock_held());

K
KAMEZAWA Hiroyuki 已提交
5423 5424 5425 5426 5427 5428 5429 5430 5431 5432 5433 5434 5435 5436 5437 5438 5439 5440 5441 5442 5443 5444 5445
	/* fill start point for scan */
	tmpid = id;
	while (1) {
		/*
		 * scan next entry from bitmap(tree), tmpid is updated after
		 * idr_get_next().
		 */
		tmp = idr_get_next(&ss->idr, &tmpid);
		if (!tmp)
			break;
		if (tmp->depth >= depth && tmp->stack[depth] == rootid) {
			ret = rcu_dereference(tmp->css);
			if (ret) {
				*foundid = tmpid;
				break;
			}
		}
		/* continue to scan from next id */
		tmpid = tmpid + 1;
	}
	return ret;
}

S
Stephane Eranian 已提交
5446 5447 5448 5449 5450 5451 5452 5453 5454 5455 5456 5457 5458 5459 5460 5461 5462 5463 5464 5465 5466 5467 5468
/*
 * 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);
}

5469
#ifdef CONFIG_CGROUP_DEBUG
5470
static struct cgroup_subsys_state *debug_css_alloc(struct cgroup *cont)
5471 5472 5473 5474 5475 5476 5477 5478 5479
{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

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

	return css;
}

5480
static void debug_css_free(struct cgroup *cont)
5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492 5493 5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505 5506 5507 5508 5509 5510
{
	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;
}

5511 5512 5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528
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 = "?";
5529 5530
		seq_printf(seq, "Root %d group %s\n",
			   c->root->hierarchy_id, name);
5531 5532 5533 5534 5535 5536 5537 5538 5539 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551 5552 5553 5554 5555 5556 5557 5558 5559 5560 5561 5562 5563
	}
	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;
}

5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574 5575 5576 5577 5578 5579 5580 5581 5582 5583 5584 5585 5586 5587 5588
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,
	},

5589 5590 5591 5592 5593 5594 5595 5596 5597 5598
	{
		.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,
	},

5599 5600 5601 5602 5603
	{
		.name = "releasable",
		.read_u64 = releasable_read,
	},

5604 5605
	{ }	/* terminate */
};
5606 5607 5608

struct cgroup_subsys debug_subsys = {
	.name = "debug",
5609 5610
	.css_alloc = debug_css_alloc,
	.css_free = debug_css_free,
5611
	.subsys_id = debug_subsys_id,
5612
	.base_cftypes = debug_files,
5613 5614
};
#endif /* CONFIG_CGROUP_DEBUG */