cgroup.c 148.0 KB
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/*
 *  Generic process-grouping system.
 *
 *  Based originally on the cpuset system, extracted by Paul Menage
 *  Copyright (C) 2006 Google, Inc
 *
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 *  Notifications support
 *  Copyright (C) 2009 Nokia Corporation
 *  Author: Kirill A. Shutemov
 *
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 *  Copyright notices from the original cpuset code:
 *  --------------------------------------------------
 *  Copyright (C) 2003 BULL SA.
 *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
 *
 *  Portions derived from Patrick Mochel's sysfs code.
 *  sysfs is Copyright (c) 2001-3 Patrick Mochel
 *
 *  2003-10-10 Written by Simon Derr.
 *  2003-10-22 Updates by Stephen Hemminger.
 *  2004 May-July Rework by Paul Jackson.
 *  ---------------------------------------------------
 *
 *  This file is subject to the terms and conditions of the GNU General Public
 *  License.  See the file COPYING in the main directory of the Linux
 *  distribution for more details.
 */

#include <linux/cgroup.h>
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#include <linux/cred.h>
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#include <linux/ctype.h>
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#include <linux/errno.h>
#include <linux/fs.h>
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#include <linux/init_task.h>
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#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
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#include <linux/proc_fs.h>
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#include <linux/rcupdate.h>
#include <linux/sched.h>
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#include <linux/backing-dev.h>
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#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/magic.h>
#include <linux/spinlock.h>
#include <linux/string.h>
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#include <linux/sort.h>
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#include <linux/kmod.h>
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#include <linux/module.h>
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#include <linux/delayacct.h>
#include <linux/cgroupstats.h>
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#include <linux/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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		/*
		 * We may not be holding cgroup_mutex, and if cgrp->count is
		 * dropped to 0 the cgroup can be destroyed at any time, hence
		 * rcu_read_lock is used to keep it alive.
		 */
		rcu_read_lock();
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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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		rcu_read_unlock();
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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);
647 648
}

649 650 651 652 653 654 655 656
/*
 * 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(
657
	struct css_set *oldcg, struct cgroup *cgrp)
658 659 660 661 662 663
{
	struct css_set *res;
	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];

	struct list_head tmp_cg_links;

664
	struct cg_cgroup_link *link;
665
	unsigned long key;
666

667 668
	/* First see if we already have a cgroup group that matches
	 * the desired set */
669
	read_lock(&css_set_lock);
670
	res = find_existing_css_set(oldcg, cgrp, template);
671 672
	if (res)
		get_css_set(res);
673
	read_unlock(&css_set_lock);
674 675 676 677 678 679 680 681 682 683 684 685 686 687

	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;
	}

688
	atomic_set(&res->refcount, 1);
689 690
	INIT_LIST_HEAD(&res->cg_links);
	INIT_LIST_HEAD(&res->tasks);
691
	INIT_HLIST_NODE(&res->hlist);
692 693 694 695 696 697 698

	/* 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. */
699 700 701 702 703 704
	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);
	}
705 706 707 708

	BUG_ON(!list_empty(&tmp_cg_links));

	css_set_count++;
709 710

	/* Add this cgroup group to the hash table */
711 712
	key = css_set_hash(res->subsys);
	hash_add(css_set_table, &res->hlist, key);
713

714 715 716
	write_unlock(&css_set_lock);

	return res;
717 718
}

719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753
/*
 * 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;
}

754 755 756 757 758 759 760 761 762 763
/*
 * 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
764
 * cgroup_attach_task() can increment it again.  Because a count of zero
765 766 767 768 769 770 771 772 773 774 775 776 777
 * 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.
780 781 782 783 784 785 786 787 788 789 790
 *
 * 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
791
 * cgroup_attach_task(), which overwrites one task's cgroup pointer with
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 * another.  It does so using cgroup_mutex, however there are
793 794 795
 * 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
796
 * in cgroup_attach_task(), modifying a task's cgroup pointer we use
797 798 799 800
 * 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
801
 * update of a tasks cgroup pointer by cgroup_attach_task()
802 803 804 805 806 807 808 809 810 811
 */

/**
 * 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);
813 814 815 816 817 818 819 820 821 822

/**
 * 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);
824 825 826 827 828 829 830 831

/*
 * 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.
 */

832
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);
834
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
835 836
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
			       unsigned long subsys_mask);
837
static const struct inode_operations cgroup_dir_inode_operations;
838
static const struct file_operations proc_cgroupstats_operations;
839 840

static struct backing_dev_info cgroup_backing_dev_info = {
841
	.name		= "cgroup",
842
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
843
};
844

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

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static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
849 850 851 852
{
	struct inode *inode = new_inode(sb);

	if (inode) {
853
		inode->i_ino = get_next_ino();
854
		inode->i_mode = mode;
855 856
		inode->i_uid = current_fsuid();
		inode->i_gid = current_fsgid();
857 858 859 860 861 862
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
	}
	return inode;
}

863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902
static void cgroup_free_fn(struct work_struct *work)
{
	struct cgroup *cgrp = container_of(work, struct cgroup, free_work);
	struct cgroup_subsys *ss;

	mutex_lock(&cgroup_mutex);
	/*
	 * Release the subsystem state objects.
	 */
	for_each_subsys(cgrp->root, ss)
		ss->css_free(cgrp);

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

	/*
	 * Drop the active superblock reference that we took when we
	 * created the cgroup
	 */
	deactivate_super(cgrp->root->sb);

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

	simple_xattrs_free(&cgrp->xattrs);

	ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id);
	kfree(cgrp);
}

static void cgroup_free_rcu(struct rcu_head *head)
{
	struct cgroup *cgrp = container_of(head, struct cgroup, rcu_head);

	schedule_work(&cgrp->free_work);
}

903 904 905 906
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)) {
907
		struct cgroup *cgrp = dentry->d_fsdata;
908

909
		BUG_ON(!(cgroup_is_removed(cgrp)));
910
		call_rcu(&cgrp->rcu_head, cgroup_free_rcu);
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	} else {
		struct cfent *cfe = __d_cfe(dentry);
		struct cgroup *cgrp = dentry->d_parent->d_fsdata;
A
Aristeu Rozanski 已提交
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		struct cftype *cft = cfe->type;
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		WARN_ONCE(!list_empty(&cfe->node) &&
			  cgrp != &cgrp->root->top_cgroup,
			  "cfe still linked for %s\n", cfe->type->name);
		kfree(cfe);
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Aristeu Rozanski 已提交
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		simple_xattrs_free(&cft->xattrs);
921 922 923 924
	}
	iput(inode);
}

925 926 927 928 929
static int cgroup_delete(const struct dentry *d)
{
	return 1;
}

930 931 932 933 934 935 936 937 938
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);
}

939
static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
T
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940 941 942 943 944 945
{
	struct cfent *cfe;

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

946 947 948 949
	/*
	 * If we're doing cleanup due to failure of cgroup_create(),
	 * the corresponding @cfe may not exist.
	 */
T
Tejun Heo 已提交
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	list_for_each_entry(cfe, &cgrp->files, node) {
		struct dentry *d = cfe->dentry;

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

		dget(d);
		d_delete(d);
958
		simple_unlink(cgrp->dentry->d_inode, d);
T
Tejun Heo 已提交
959 960 961
		list_del_init(&cfe->node);
		dput(d);

962
		break;
963
	}
T
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964 965
}

966 967 968 969 970 971 972 973
/**
 * 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
974 975
{
	struct cgroup *cgrp = __d_cgrp(dir);
976
	struct cgroup_subsys *ss;
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977

978 979 980 981 982
	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)
983
			cgroup_addrm_files(cgrp, NULL, set->cfts, false);
984 985 986 987 988
	}
	if (base_files) {
		while (!list_empty(&cgrp->files))
			cgroup_rm_file(cgrp, NULL);
	}
989 990 991 992 993 994 995
}

/*
 * NOTE : the dentry must have been dget()'ed
 */
static void cgroup_d_remove_dir(struct dentry *dentry)
{
N
Nick Piggin 已提交
996
	struct dentry *parent;
997
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
N
Nick Piggin 已提交
998

999
	cgroup_clear_directory(dentry, true, root->subsys_mask);
1000

N
Nick Piggin 已提交
1001 1002
	parent = dentry->d_parent;
	spin_lock(&parent->d_lock);
1003
	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1004
	list_del_init(&dentry->d_u.d_child);
N
Nick Piggin 已提交
1005 1006
	spin_unlock(&dentry->d_lock);
	spin_unlock(&parent->d_lock);
1007 1008 1009
	remove_dir(dentry);
}

B
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1010
/*
B
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1011 1012 1013
 * 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
1014
 */
1015
static int rebind_subsystems(struct cgroupfs_root *root,
1016
			      unsigned long final_subsys_mask)
1017
{
1018
	unsigned long added_mask, removed_mask;
1019
	struct cgroup *cgrp = &root->top_cgroup;
1020 1021
	int i;

B
Ben Blum 已提交
1022
	BUG_ON(!mutex_is_locked(&cgroup_mutex));
T
Tejun Heo 已提交
1023
	BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
B
Ben Blum 已提交
1024

1025 1026
	removed_mask = root->actual_subsys_mask & ~final_subsys_mask;
	added_mask = final_subsys_mask & ~root->actual_subsys_mask;
1027 1028
	/* Check that any added subsystems are currently free */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
L
Li Zefan 已提交
1029
		unsigned long bit = 1UL << i;
1030
		struct cgroup_subsys *ss = subsys[i];
1031
		if (!(bit & added_mask))
1032
			continue;
B
Ben Blum 已提交
1033 1034 1035 1036 1037 1038
		/*
		 * 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);
1039 1040 1041 1042 1043 1044 1045 1046 1047 1048
		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 */
1049
	if (root->number_of_cgroups > 1)
1050 1051 1052 1053 1054 1055
		return -EBUSY;

	/* Process each subsystem */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		unsigned long bit = 1UL << i;
1056
		if (bit & added_mask) {
1057
			/* We're binding this subsystem to this hierarchy */
B
Ben Blum 已提交
1058
			BUG_ON(ss == NULL);
1059
			BUG_ON(cgrp->subsys[i]);
1060 1061
			BUG_ON(!dummytop->subsys[i]);
			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1062 1063
			cgrp->subsys[i] = dummytop->subsys[i];
			cgrp->subsys[i]->cgroup = cgrp;
1064
			list_move(&ss->sibling, &root->subsys_list);
1065
			ss->root = root;
1066
			if (ss->bind)
1067
				ss->bind(cgrp);
B
Ben Blum 已提交
1068
			/* refcount was already taken, and we're keeping it */
1069
		} else if (bit & removed_mask) {
1070
			/* We're removing this subsystem */
B
Ben Blum 已提交
1071
			BUG_ON(ss == NULL);
1072 1073
			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1074
			if (ss->bind)
1075
				ss->bind(dummytop);
1076
			dummytop->subsys[i]->cgroup = dummytop;
1077
			cgrp->subsys[i] = NULL;
1078
			subsys[i]->root = &rootnode;
1079
			list_move(&ss->sibling, &rootnode.subsys_list);
B
Ben Blum 已提交
1080 1081
			/* subsystem is now free - drop reference on module */
			module_put(ss->module);
1082
		} else if (bit & final_subsys_mask) {
1083
			/* Subsystem state should already exist */
B
Ben Blum 已提交
1084
			BUG_ON(ss == NULL);
1085
			BUG_ON(!cgrp->subsys[i]);
B
Ben Blum 已提交
1086 1087 1088 1089 1090 1091 1092 1093
			/*
			 * 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
1094 1095
		} else {
			/* Subsystem state shouldn't exist */
1096
			BUG_ON(cgrp->subsys[i]);
1097 1098
		}
	}
1099
	root->subsys_mask = root->actual_subsys_mask = final_subsys_mask;
1100 1101 1102 1103

	return 0;
}

1104
static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1105
{
1106
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1107 1108
	struct cgroup_subsys *ss;

T
Tejun Heo 已提交
1109
	mutex_lock(&cgroup_root_mutex);
1110 1111 1112 1113
	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
1114 1115
	if (test_bit(ROOT_XATTR, &root->flags))
		seq_puts(seq, ",xattr");
1116 1117
	if (strlen(root->release_agent_path))
		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1118
	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags))
1119
		seq_puts(seq, ",clone_children");
1120 1121
	if (strlen(root->name))
		seq_printf(seq, ",name=%s", root->name);
T
Tejun Heo 已提交
1122
	mutex_unlock(&cgroup_root_mutex);
1123 1124 1125 1126
	return 0;
}

struct cgroup_sb_opts {
1127
	unsigned long subsys_mask;
1128
	unsigned long flags;
1129
	char *release_agent;
1130
	bool cpuset_clone_children;
1131
	char *name;
1132 1133
	/* User explicitly requested empty subsystem */
	bool none;
1134 1135

	struct cgroupfs_root *new_root;
1136

1137 1138
};

B
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1139 1140
/*
 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
B
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1141 1142 1143
 * 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
1144
 */
B
Ben Blum 已提交
1145
static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1146
{
1147 1148
	char *token, *o = data;
	bool all_ss = false, one_ss = false;
1149
	unsigned long mask = (unsigned long)-1;
B
Ben Blum 已提交
1150 1151
	int i;
	bool module_pin_failed = false;
1152

B
Ben Blum 已提交
1153 1154
	BUG_ON(!mutex_is_locked(&cgroup_mutex));

1155 1156 1157
#ifdef CONFIG_CPUSETS
	mask = ~(1UL << cpuset_subsys_id);
#endif
1158

1159
	memset(opts, 0, sizeof(*opts));
1160 1161 1162 1163

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
1164
		if (!strcmp(token, "none")) {
1165 1166
			/* Explicitly have no subsystems */
			opts->none = true;
1167 1168 1169 1170 1171 1172 1173 1174 1175 1176
			continue;
		}
		if (!strcmp(token, "all")) {
			/* Mutually exclusive option 'all' + subsystem name */
			if (one_ss)
				return -EINVAL;
			all_ss = true;
			continue;
		}
		if (!strcmp(token, "noprefix")) {
1177
			set_bit(ROOT_NOPREFIX, &opts->flags);
1178 1179 1180
			continue;
		}
		if (!strcmp(token, "clone_children")) {
1181
			opts->cpuset_clone_children = true;
1182 1183
			continue;
		}
A
Aristeu Rozanski 已提交
1184 1185 1186 1187
		if (!strcmp(token, "xattr")) {
			set_bit(ROOT_XATTR, &opts->flags);
			continue;
		}
1188
		if (!strncmp(token, "release_agent=", 14)) {
1189 1190 1191
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1192
			opts->release_agent =
1193
				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1194 1195
			if (!opts->release_agent)
				return -ENOMEM;
1196 1197 1198
			continue;
		}
		if (!strncmp(token, "name=", 5)) {
1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215
			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,
1216
					      MAX_CGROUP_ROOT_NAMELEN - 1,
1217 1218 1219
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235

			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;
1236
			set_bit(i, &opts->subsys_mask);
1237 1238 1239 1240 1241 1242 1243 1244 1245 1246
			one_ss = true;

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

	/*
	 * If the 'all' option was specified select all the subsystems,
1247 1248
	 * otherwise if 'none', 'name=' and a subsystem name options
	 * were not specified, let's default to 'all'
1249
	 */
1250
	if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1251 1252 1253 1254 1255 1256
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss == NULL)
				continue;
			if (ss->disabled)
				continue;
1257
			set_bit(i, &opts->subsys_mask);
1258 1259 1260
		}
	}

1261 1262
	/* Consistency checks */

1263 1264 1265 1266 1267 1268
	/*
	 * 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) &&
1269
	    (opts->subsys_mask & mask))
1270 1271
		return -EINVAL;

1272 1273

	/* Can't specify "none" and some subsystems */
1274
	if (opts->subsys_mask && opts->none)
1275 1276 1277 1278 1279 1280
		return -EINVAL;

	/*
	 * We either have to specify by name or by subsystems. (So all
	 * empty hierarchies must have a name).
	 */
1281
	if (!opts->subsys_mask && !opts->name)
1282 1283
		return -EINVAL;

B
Ben Blum 已提交
1284 1285 1286 1287 1288 1289
	/*
	 * 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.
	 */
1290
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
B
Ben Blum 已提交
1291 1292
		unsigned long bit = 1UL << i;

1293
		if (!(bit & opts->subsys_mask))
B
Ben Blum 已提交
1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305
			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.
		 */
1306
		for (i--; i >= 0; i--) {
B
Ben Blum 已提交
1307 1308 1309
			/* drop refcounts only on the ones we took */
			unsigned long bit = 1UL << i;

1310
			if (!(bit & opts->subsys_mask))
B
Ben Blum 已提交
1311 1312 1313 1314 1315 1316
				continue;
			module_put(subsys[i]->module);
		}
		return -ENOENT;
	}

1317 1318 1319
	return 0;
}

1320
static void drop_parsed_module_refcounts(unsigned long subsys_mask)
B
Ben Blum 已提交
1321 1322
{
	int i;
1323
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
B
Ben Blum 已提交
1324 1325
		unsigned long bit = 1UL << i;

1326
		if (!(bit & subsys_mask))
B
Ben Blum 已提交
1327 1328 1329 1330 1331
			continue;
		module_put(subsys[i]->module);
	}
}

1332 1333 1334 1335
static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
	int ret = 0;
	struct cgroupfs_root *root = sb->s_fs_info;
1336
	struct cgroup *cgrp = &root->top_cgroup;
1337
	struct cgroup_sb_opts opts;
1338
	unsigned long added_mask, removed_mask;
1339

1340
	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1341
	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1342
	mutex_lock(&cgroup_root_mutex);
1343 1344 1345 1346 1347 1348

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

1349
	if (opts.subsys_mask != root->actual_subsys_mask || opts.release_agent)
1350 1351 1352
		pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
			   task_tgid_nr(current), current->comm);

1353 1354
	added_mask = opts.subsys_mask & ~root->subsys_mask;
	removed_mask = root->subsys_mask & ~opts.subsys_mask;
1355

B
Ben Blum 已提交
1356 1357 1358
	/* Don't allow flags or name to change at remount */
	if (opts.flags != root->flags ||
	    (opts.name && strcmp(opts.name, root->name))) {
1359
		ret = -EINVAL;
1360
		drop_parsed_module_refcounts(opts.subsys_mask);
1361 1362 1363
		goto out_unlock;
	}

1364 1365 1366 1367 1368 1369 1370
	/*
	 * 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);

1371
	ret = rebind_subsystems(root, opts.subsys_mask);
B
Ben Blum 已提交
1372
	if (ret) {
1373 1374
		/* rebind_subsystems failed, re-populate the removed files */
		cgroup_populate_dir(cgrp, false, removed_mask);
1375
		drop_parsed_module_refcounts(opts.subsys_mask);
1376
		goto out_unlock;
B
Ben Blum 已提交
1377
	}
1378

1379
	/* re-populate subsystem files */
1380
	cgroup_populate_dir(cgrp, false, added_mask);
1381

1382 1383
	if (opts.release_agent)
		strcpy(root->release_agent_path, opts.release_agent);
1384
 out_unlock:
1385
	kfree(opts.release_agent);
1386
	kfree(opts.name);
T
Tejun Heo 已提交
1387
	mutex_unlock(&cgroup_root_mutex);
1388
	mutex_unlock(&cgroup_mutex);
1389
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1390 1391 1392
	return ret;
}

1393
static const struct super_operations cgroup_ops = {
1394 1395 1396 1397 1398 1399
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.show_options = cgroup_show_options,
	.remount_fs = cgroup_remount,
};

1400 1401 1402 1403
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
	INIT_LIST_HEAD(&cgrp->sibling);
	INIT_LIST_HEAD(&cgrp->children);
T
Tejun Heo 已提交
1404
	INIT_LIST_HEAD(&cgrp->files);
1405
	INIT_LIST_HEAD(&cgrp->css_sets);
1406
	INIT_LIST_HEAD(&cgrp->allcg_node);
1407
	INIT_LIST_HEAD(&cgrp->release_list);
1408
	INIT_LIST_HEAD(&cgrp->pidlists);
1409
	INIT_WORK(&cgrp->free_work, cgroup_free_fn);
1410
	mutex_init(&cgrp->pidlist_mutex);
1411 1412
	INIT_LIST_HEAD(&cgrp->event_list);
	spin_lock_init(&cgrp->event_list_lock);
A
Aristeu Rozanski 已提交
1413
	simple_xattrs_init(&cgrp->xattrs);
1414
}
1415

1416 1417
static void init_cgroup_root(struct cgroupfs_root *root)
{
1418
	struct cgroup *cgrp = &root->top_cgroup;
1419

1420 1421
	INIT_LIST_HEAD(&root->subsys_list);
	INIT_LIST_HEAD(&root->root_list);
1422
	INIT_LIST_HEAD(&root->allcg_list);
1423
	root->number_of_cgroups = 1;
1424 1425
	cgrp->root = root;
	cgrp->top_cgroup = cgrp;
1426
	init_cgroup_housekeeping(cgrp);
1427
	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1428 1429
}

1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454
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;
}

1455 1456
static int cgroup_test_super(struct super_block *sb, void *data)
{
1457
	struct cgroup_sb_opts *opts = data;
1458 1459
	struct cgroupfs_root *root = sb->s_fs_info;

1460 1461 1462
	/* If we asked for a name then it must match */
	if (opts->name && strcmp(opts->name, root->name))
		return 0;
1463

1464 1465 1466 1467
	/*
	 * If we asked for subsystems (or explicitly for no
	 * subsystems) then they must match
	 */
1468 1469
	if ((opts->subsys_mask || opts->none)
	    && (opts->subsys_mask != root->subsys_mask))
1470 1471 1472 1473 1474
		return 0;

	return 1;
}

1475 1476 1477 1478
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
	struct cgroupfs_root *root;

1479
	if (!opts->subsys_mask && !opts->none)
1480 1481 1482 1483 1484 1485
		return NULL;

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

1486 1487 1488 1489
	if (!init_root_id(root)) {
		kfree(root);
		return ERR_PTR(-ENOMEM);
	}
1490
	init_cgroup_root(root);
1491

1492
	root->subsys_mask = opts->subsys_mask;
1493
	root->flags = opts->flags;
T
Tejun Heo 已提交
1494
	ida_init(&root->cgroup_ida);
1495 1496 1497 1498
	if (opts->release_agent)
		strcpy(root->release_agent_path, opts->release_agent);
	if (opts->name)
		strcpy(root->name, opts->name);
1499 1500
	if (opts->cpuset_clone_children)
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags);
1501 1502 1503
	return root;
}

1504 1505 1506 1507 1508 1509 1510 1511 1512
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
1513
	ida_destroy(&root->cgroup_ida);
1514 1515 1516
	kfree(root);
}

1517 1518 1519
static int cgroup_set_super(struct super_block *sb, void *data)
{
	int ret;
1520 1521 1522 1523 1524 1525
	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;

1526
	BUG_ON(!opts->subsys_mask && !opts->none);
1527 1528 1529 1530 1531

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

1532 1533
	sb->s_fs_info = opts->new_root;
	opts->new_root->sb = sb;
1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544

	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
1545 1546
	static const struct dentry_operations cgroup_dops = {
		.d_iput = cgroup_diput,
1547
		.d_delete = cgroup_delete,
A
Al Viro 已提交
1548 1549
	};

1550 1551 1552 1553 1554 1555 1556 1557 1558 1559
	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);
1560 1561
	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
1562
		return -ENOMEM;
A
Al Viro 已提交
1563 1564
	/* for everything else we want ->d_op set */
	sb->s_d_op = &cgroup_dops;
1565 1566 1567
	return 0;
}

A
Al Viro 已提交
1568
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1569
			 int flags, const char *unused_dev_name,
A
Al Viro 已提交
1570
			 void *data)
1571 1572
{
	struct cgroup_sb_opts opts;
1573
	struct cgroupfs_root *root;
1574 1575
	int ret = 0;
	struct super_block *sb;
1576
	struct cgroupfs_root *new_root;
T
Tejun Heo 已提交
1577
	struct inode *inode;
1578 1579

	/* First find the desired set of subsystems */
B
Ben Blum 已提交
1580
	mutex_lock(&cgroup_mutex);
1581
	ret = parse_cgroupfs_options(data, &opts);
B
Ben Blum 已提交
1582
	mutex_unlock(&cgroup_mutex);
1583 1584
	if (ret)
		goto out_err;
1585

1586 1587 1588 1589 1590 1591 1592
	/*
	 * 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
1593
		goto drop_modules;
1594
	}
1595
	opts.new_root = new_root;
1596

1597
	/* Locate an existing or new sb for this hierarchy */
D
David Howells 已提交
1598
	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
1599
	if (IS_ERR(sb)) {
1600
		ret = PTR_ERR(sb);
1601
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1602
		goto drop_modules;
1603 1604
	}

1605 1606 1607 1608 1609
	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;
1610
		struct cgroup *root_cgrp = &root->top_cgroup;
1611
		struct cgroupfs_root *existing_root;
1612
		const struct cred *cred;
1613
		int i;
1614 1615
		struct hlist_node *node;
		struct css_set *cg;
1616 1617 1618 1619 1620 1621

		BUG_ON(sb->s_root != NULL);

		ret = cgroup_get_rootdir(sb);
		if (ret)
			goto drop_new_super;
1622
		inode = sb->s_root->d_inode;
1623

1624
		mutex_lock(&inode->i_mutex);
1625
		mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1626
		mutex_lock(&cgroup_root_mutex);
1627

T
Tejun Heo 已提交
1628 1629 1630 1631 1632 1633
		/* 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;
1634

1635 1636 1637 1638 1639 1640 1641 1642
		/*
		 * 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
1643 1644
		if (ret)
			goto unlock_drop;
1645

1646
		ret = rebind_subsystems(root, root->subsys_mask);
1647
		if (ret == -EBUSY) {
1648
			free_cg_links(&tmp_cg_links);
T
Tejun Heo 已提交
1649
			goto unlock_drop;
1650
		}
B
Ben Blum 已提交
1651 1652 1653 1654 1655
		/*
		 * There must be no failure case after here, since rebinding
		 * takes care of subsystems' refcounts, which are explicitly
		 * dropped in the failure exit path.
		 */
1656 1657 1658 1659 1660

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

		list_add(&root->root_list, &roots);
1661
		root_count++;
1662

1663
		sb->s_root->d_fsdata = root_cgrp;
1664 1665
		root->top_cgroup.dentry = sb->s_root;

1666 1667 1668
		/* Link the top cgroup in this hierarchy into all
		 * the css_set objects */
		write_lock(&css_set_lock);
1669 1670
		hash_for_each(css_set_table, i, node, cg, hlist)
			link_css_set(&tmp_cg_links, cg, root_cgrp);
1671 1672 1673 1674
		write_unlock(&css_set_lock);

		free_cg_links(&tmp_cg_links);

1675
		BUG_ON(!list_empty(&root_cgrp->children));
1676 1677
		BUG_ON(root->number_of_cgroups != 1);

1678
		cred = override_creds(&init_cred);
1679
		cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
1680
		revert_creds(cred);
T
Tejun Heo 已提交
1681
		mutex_unlock(&cgroup_root_mutex);
1682
		mutex_unlock(&cgroup_mutex);
1683
		mutex_unlock(&inode->i_mutex);
1684 1685 1686 1687 1688
	} else {
		/*
		 * We re-used an existing hierarchy - the new root (if
		 * any) is not needed
		 */
1689
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1690
		/* no subsys rebinding, so refcounts don't change */
1691
		drop_parsed_module_refcounts(opts.subsys_mask);
1692 1693
	}

1694 1695
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1696
	return dget(sb->s_root);
1697

T
Tejun Heo 已提交
1698 1699 1700 1701
 unlock_drop:
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&inode->i_mutex);
1702
 drop_new_super:
1703
	deactivate_locked_super(sb);
B
Ben Blum 已提交
1704
 drop_modules:
1705
	drop_parsed_module_refcounts(opts.subsys_mask);
1706 1707 1708
 out_err:
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1709
	return ERR_PTR(ret);
1710 1711 1712 1713
}

static void cgroup_kill_sb(struct super_block *sb) {
	struct cgroupfs_root *root = sb->s_fs_info;
1714
	struct cgroup *cgrp = &root->top_cgroup;
1715
	int ret;
K
KOSAKI Motohiro 已提交
1716 1717
	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;
1718 1719 1720 1721

	BUG_ON(!root);

	BUG_ON(root->number_of_cgroups != 1);
1722
	BUG_ON(!list_empty(&cgrp->children));
1723 1724

	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1725
	mutex_lock(&cgroup_root_mutex);
1726 1727 1728 1729 1730 1731

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

1732 1733 1734 1735 1736
	/*
	 * Release all the links from css_sets to this hierarchy's
	 * root cgroup
	 */
	write_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
1737 1738 1739

	list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
				 cgrp_link_list) {
1740
		list_del(&link->cg_link_list);
1741
		list_del(&link->cgrp_link_list);
1742 1743 1744 1745
		kfree(link);
	}
	write_unlock(&css_set_lock);

1746 1747 1748 1749
	if (!list_empty(&root->root_list)) {
		list_del(&root->root_list);
		root_count--;
	}
1750

T
Tejun Heo 已提交
1751
	mutex_unlock(&cgroup_root_mutex);
1752 1753
	mutex_unlock(&cgroup_mutex);

A
Aristeu Rozanski 已提交
1754 1755
	simple_xattrs_free(&cgrp->xattrs);

1756
	kill_litter_super(sb);
1757
	cgroup_drop_root(root);
1758 1759 1760 1761
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
A
Al Viro 已提交
1762
	.mount = cgroup_mount,
1763 1764 1765
	.kill_sb = cgroup_kill_sb,
};

1766 1767
static struct kobject *cgroup_kobj;

L
Li Zefan 已提交
1768 1769 1770 1771 1772 1773
/**
 * 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
 *
1774 1775 1776
 * 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.
1777
 */
1778
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1779
{
1780
	struct dentry *dentry = cgrp->dentry;
1781
	char *start;
1782 1783 1784

	rcu_lockdep_assert(rcu_read_lock_held() || cgroup_lock_is_held(),
			   "cgroup_path() called without proper locking");
1785

1786
	if (cgrp == dummytop) {
1787 1788 1789 1790 1791 1792 1793 1794
		/*
		 * Inactive subsystems have no dentry for their root
		 * cgroup
		 */
		strcpy(buf, "/");
		return 0;
	}

1795
	start = buf + buflen - 1;
1796

1797
	*start = '\0';
1798
	for (;;) {
1799
		int len = dentry->d_name.len;
1800

1801 1802
		if ((start -= len) < buf)
			return -ENAMETOOLONG;
1803
		memcpy(start, dentry->d_name.name, len);
1804 1805
		cgrp = cgrp->parent;
		if (!cgrp)
1806
			break;
1807

1808
		dentry = cgrp->dentry;
1809
		if (!cgrp->parent)
1810 1811 1812 1813 1814 1815 1816 1817
			continue;
		if (--start < buf)
			return -ENAMETOOLONG;
		*start = '/';
	}
	memmove(buf, start, buf + buflen - start);
	return 0;
}
B
Ben Blum 已提交
1818
EXPORT_SYMBOL_GPL(cgroup_path);
1819

1820 1821 1822
/*
 * Control Group taskset
 */
1823 1824 1825
struct task_and_cgroup {
	struct task_struct	*task;
	struct cgroup		*cgrp;
1826
	struct css_set		*cg;
1827 1828
};

1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899
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
1900 1901 1902
/*
 * cgroup_task_migrate - move a task from one cgroup to another.
 *
1903
 * Must be called with cgroup_mutex and threadgroup locked.
B
Ben Blum 已提交
1904
 */
1905 1906
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
1907 1908 1909 1910
{
	struct css_set *oldcg;

	/*
1911 1912 1913
	 * 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
1914
	 */
1915
	WARN_ON_ONCE(tsk->flags & PF_EXITING);
B
Ben Blum 已提交
1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933
	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);
1934
	put_css_set(oldcg);
B
Ben Blum 已提交
1935 1936
}

L
Li Zefan 已提交
1937 1938 1939 1940
/**
 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
 * @cgrp: the cgroup the task is attaching to
 * @tsk: the task to be attached
1941
 *
1942 1943
 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
 * @tsk during call.
1944
 */
1945
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1946
{
1947
	int retval = 0;
1948
	struct cgroup_subsys *ss, *failed_ss = NULL;
1949 1950
	struct cgroup *oldcgrp;
	struct cgroupfs_root *root = cgrp->root;
1951
	struct cgroup_taskset tset = { };
1952
	struct css_set *newcg;
1953

1954 1955 1956
	/* @tsk either already exited or can't exit until the end */
	if (tsk->flags & PF_EXITING)
		return -ESRCH;
1957 1958

	/* Nothing to do if the task is already in that cgroup */
1959
	oldcgrp = task_cgroup_from_root(tsk, root);
1960
	if (cgrp == oldcgrp)
1961 1962
		return 0;

1963 1964 1965
	tset.single.task = tsk;
	tset.single.cgrp = oldcgrp;

1966 1967
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
1968
			retval = ss->can_attach(cgrp, &tset);
1969 1970 1971 1972 1973 1974 1975 1976 1977 1978
			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;
			}
1979 1980 1981
		}
	}

1982 1983 1984
	newcg = find_css_set(tsk->cgroups, cgrp);
	if (!newcg) {
		retval = -ENOMEM;
1985
		goto out;
1986 1987 1988
	}

	cgroup_task_migrate(cgrp, oldcgrp, tsk, newcg);
1989

1990
	for_each_subsys(root, ss) {
P
Paul Jackson 已提交
1991
		if (ss->attach)
1992
			ss->attach(cgrp, &tset);
1993
	}
B
Ben Blum 已提交
1994

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
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)
2007
				ss->cancel_attach(cgrp, &tset);
2008 2009 2010
		}
	}
	return retval;
2011 2012
}

2013
/**
M
Michael S. Tsirkin 已提交
2014 2015
 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
 * @from: attach to all cgroups of a given task
2016 2017
 * @tsk: the task to be attached
 */
M
Michael S. Tsirkin 已提交
2018
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2019 2020 2021 2022 2023 2024
{
	struct cgroupfs_root *root;
	int retval = 0;

	cgroup_lock();
	for_each_active_root(root) {
M
Michael S. Tsirkin 已提交
2025 2026 2027
		struct cgroup *from_cg = task_cgroup_from_root(from, root);

		retval = cgroup_attach_task(from_cg, tsk);
2028 2029 2030 2031 2032 2033 2034
		if (retval)
			break;
	}
	cgroup_unlock();

	return retval;
}
M
Michael S. Tsirkin 已提交
2035
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2036

B
Ben Blum 已提交
2037 2038 2039 2040 2041
/**
 * 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
 *
2042 2043
 * 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
2044
 */
2045
static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
B
Ben Blum 已提交
2046 2047 2048 2049 2050 2051 2052
{
	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;
2053
	struct task_and_cgroup *tc;
2054
	struct flex_array *group;
2055
	struct cgroup_taskset tset = { };
B
Ben Blum 已提交
2056 2057 2058 2059 2060

	/*
	 * 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
2061 2062
	 * 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
2063 2064
	 */
	group_size = get_nr_threads(leader);
2065
	/* flex_array supports very large thread-groups better than kmalloc. */
2066
	group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
B
Ben Blum 已提交
2067 2068
	if (!group)
		return -ENOMEM;
2069 2070 2071 2072
	/* 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
2073 2074 2075

	tsk = leader;
	i = 0;
2076 2077 2078 2079 2080 2081
	/*
	 * 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
2082
	do {
2083 2084
		struct task_and_cgroup ent;

2085 2086 2087 2088
		/* @tsk either already exited or can't exit until the end */
		if (tsk->flags & PF_EXITING)
			continue;

B
Ben Blum 已提交
2089 2090
		/* as per above, nr_threads may decrease, but not increase. */
		BUG_ON(i >= group_size);
2091 2092
		ent.task = tsk;
		ent.cgrp = task_cgroup_from_root(tsk, root);
2093 2094 2095
		/* nothing to do if this task is already in the cgroup */
		if (ent.cgrp == cgrp)
			continue;
2096 2097 2098 2099
		/*
		 * saying GFP_ATOMIC has no effect here because we did prealloc
		 * earlier, but it's good form to communicate our expectations.
		 */
2100
		retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2101
		BUG_ON(retval != 0);
B
Ben Blum 已提交
2102 2103
		i++;
	} while_each_thread(leader, tsk);
2104
	rcu_read_unlock();
B
Ben Blum 已提交
2105 2106
	/* remember the number of threads in the array for later. */
	group_size = i;
2107 2108
	tset.tc_array = group;
	tset.tc_array_len = group_size;
B
Ben Blum 已提交
2109

2110 2111
	/* methods shouldn't be called if no task is actually migrating */
	retval = 0;
2112
	if (!group_size)
2113
		goto out_free_group_list;
2114

B
Ben Blum 已提交
2115 2116 2117 2118 2119
	/*
	 * step 1: check that we can legitimately attach to the cgroup.
	 */
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
2120
			retval = ss->can_attach(cgrp, &tset);
B
Ben Blum 已提交
2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132
			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++) {
2133
		tc = flex_array_get(group, i);
2134 2135 2136 2137
		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
2138 2139 2140 2141
		}
	}

	/*
2142 2143 2144
	 * 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
2145 2146
	 */
	for (i = 0; i < group_size; i++) {
2147
		tc = flex_array_get(group, i);
2148
		cgroup_task_migrate(cgrp, tc->cgrp, tc->task, tc->cg);
B
Ben Blum 已提交
2149 2150 2151 2152
	}
	/* nothing is sensitive to fork() after this point. */

	/*
2153
	 * step 4: do subsystem attach callbacks.
B
Ben Blum 已提交
2154 2155 2156
	 */
	for_each_subsys(root, ss) {
		if (ss->attach)
2157
			ss->attach(cgrp, &tset);
B
Ben Blum 已提交
2158 2159 2160 2161 2162 2163
	}

	/*
	 * step 5: success! and cleanup
	 */
	retval = 0;
2164 2165 2166 2167 2168 2169 2170 2171
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
2172 2173 2174 2175
	}
out_cancel_attach:
	if (retval) {
		for_each_subsys(root, ss) {
2176
			if (ss == failed_ss)
B
Ben Blum 已提交
2177 2178
				break;
			if (ss->cancel_attach)
2179
				ss->cancel_attach(cgrp, &tset);
B
Ben Blum 已提交
2180 2181 2182
		}
	}
out_free_group_list:
2183
	flex_array_free(group);
B
Ben Blum 已提交
2184 2185 2186 2187 2188
	return retval;
}

/*
 * Find the task_struct of the task to attach by vpid and pass it along to the
2189 2190
 * function to attach either it or all tasks in its threadgroup. Will lock
 * cgroup_mutex and threadgroup; may take task_lock of task.
2191
 */
B
Ben Blum 已提交
2192
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2193 2194
{
	struct task_struct *tsk;
2195
	const struct cred *cred = current_cred(), *tcred;
2196 2197
	int ret;

B
Ben Blum 已提交
2198 2199 2200
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;

2201 2202
retry_find_task:
	rcu_read_lock();
2203
	if (pid) {
2204
		tsk = find_task_by_vpid(pid);
B
Ben Blum 已提交
2205 2206
		if (!tsk) {
			rcu_read_unlock();
2207 2208
			ret= -ESRCH;
			goto out_unlock_cgroup;
2209
		}
B
Ben Blum 已提交
2210 2211 2212 2213
		/*
		 * even if we're attaching all tasks in the thread group, we
		 * only need to check permissions on one of them.
		 */
2214
		tcred = __task_cred(tsk);
2215 2216 2217
		if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
		    !uid_eq(cred->euid, tcred->uid) &&
		    !uid_eq(cred->euid, tcred->suid)) {
2218
			rcu_read_unlock();
2219 2220
			ret = -EACCES;
			goto out_unlock_cgroup;
2221
		}
2222 2223
	} else
		tsk = current;
2224 2225

	if (threadgroup)
2226
		tsk = tsk->group_leader;
2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238

	/*
	 * 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;
	}

2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255
	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
2256
		ret = cgroup_attach_proc(cgrp, tsk);
2257
	} else
B
Ben Blum 已提交
2258
		ret = cgroup_attach_task(cgrp, tsk);
2259 2260
	threadgroup_unlock(tsk);

2261
	put_task_struct(tsk);
2262
out_unlock_cgroup:
B
Ben Blum 已提交
2263
	cgroup_unlock();
2264 2265 2266
	return ret;
}

2267
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
B
Ben Blum 已提交
2268 2269 2270 2271 2272
{
	return attach_task_by_pid(cgrp, pid, false);
}

static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2273
{
2274
	return attach_task_by_pid(cgrp, tgid, true);
2275 2276
}

2277 2278 2279 2280
/**
 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
 * @cgrp: the cgroup to be checked for liveness
 *
2281 2282
 * On success, returns true; the lock should be later released with
 * cgroup_unlock(). On failure returns false with no lock held.
2283
 */
2284
bool cgroup_lock_live_group(struct cgroup *cgrp)
2285 2286 2287 2288 2289 2290 2291 2292
{
	mutex_lock(&cgroup_mutex);
	if (cgroup_is_removed(cgrp)) {
		mutex_unlock(&cgroup_mutex);
		return false;
	}
	return true;
}
B
Ben Blum 已提交
2293
EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2294 2295 2296 2297 2298

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);
2299 2300
	if (strlen(buffer) >= PATH_MAX)
		return -EINVAL;
2301 2302
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
T
Tejun Heo 已提交
2303
	mutex_lock(&cgroup_root_mutex);
2304
	strcpy(cgrp->root->release_agent_path, buffer);
T
Tejun Heo 已提交
2305
	mutex_unlock(&cgroup_root_mutex);
2306
	cgroup_unlock();
2307 2308 2309 2310 2311 2312 2313 2314 2315 2316
	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');
2317
	cgroup_unlock();
2318 2319 2320
	return 0;
}

2321 2322 2323
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64

2324
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2325 2326 2327
				struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *unused_ppos)
2328
{
2329
	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340
	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 */
2341
	if (cft->write_u64) {
K
KOSAKI Motohiro 已提交
2342
		u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2343 2344 2345 2346
		if (*end)
			return -EINVAL;
		retval = cft->write_u64(cgrp, cft, val);
	} else {
K
KOSAKI Motohiro 已提交
2347
		s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2348 2349 2350 2351
		if (*end)
			return -EINVAL;
		retval = cft->write_s64(cgrp, cft, val);
	}
2352 2353 2354 2355 2356
	if (!retval)
		retval = nbytes;
	return retval;
}

2357 2358 2359 2360 2361
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)
{
2362
	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376
	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
2377 2378 2379 2380
	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
		retval = -EFAULT;
		goto out;
	}
2381 2382

	buffer[nbytes] = 0;     /* nul-terminate */
K
KOSAKI Motohiro 已提交
2383
	retval = cft->write_string(cgrp, cft, strstrip(buffer));
2384 2385
	if (!retval)
		retval = nbytes;
L
Li Zefan 已提交
2386
out:
2387 2388 2389 2390 2391
	if (buffer != local_buffer)
		kfree(buffer);
	return retval;
}

2392 2393 2394 2395
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);
2396
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2397

2398
	if (cgroup_is_removed(cgrp))
2399
		return -ENODEV;
2400
	if (cft->write)
2401
		return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2402 2403
	if (cft->write_u64 || cft->write_s64)
		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2404 2405
	if (cft->write_string)
		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2406 2407 2408 2409
	if (cft->trigger) {
		int ret = cft->trigger(cgrp, (unsigned int)cft->private);
		return ret ? ret : nbytes;
	}
2410
	return -EINVAL;
2411 2412
}

2413 2414 2415 2416
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
2417
{
2418
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2419
	u64 val = cft->read_u64(cgrp, cft);
2420 2421 2422 2423 2424
	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);

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

2425 2426 2427 2428 2429
static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
{
2430
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2431 2432 2433 2434 2435 2436
	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);
}

2437 2438 2439 2440
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);
2441
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2442

2443
	if (cgroup_is_removed(cgrp))
2444 2445 2446
		return -ENODEV;

	if (cft->read)
2447
		return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2448 2449
	if (cft->read_u64)
		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2450 2451
	if (cft->read_s64)
		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2452 2453 2454
	return -EINVAL;
}

2455 2456 2457 2458 2459 2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474
/*
 * 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;
2475 2476 2477 2478 2479 2480 2481 2482
	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);
2483 2484
}

2485
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2486 2487 2488 2489 2490 2491
{
	struct seq_file *seq = file->private_data;
	kfree(seq->private);
	return single_release(inode, file);
}

2492
static const struct file_operations cgroup_seqfile_operations = {
2493
	.read = seq_read,
2494
	.write = cgroup_file_write,
2495 2496 2497 2498
	.llseek = seq_lseek,
	.release = cgroup_seqfile_release,
};

2499 2500 2501 2502 2503 2504 2505 2506 2507
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);
2508

2509
	if (cft->read_map || cft->read_seq_string) {
2510 2511 2512 2513 2514 2515 2516 2517 2518 2519 2520
		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)
2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548 2549 2550
		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
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 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608
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);
}

2609
static const struct file_operations cgroup_file_operations = {
2610 2611 2612 2613 2614 2615 2616
	.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
2617 2618 2619 2620 2621 2622 2623
static const struct inode_operations cgroup_file_inode_operations = {
	.setxattr = cgroup_setxattr,
	.getxattr = cgroup_getxattr,
	.listxattr = cgroup_listxattr,
	.removexattr = cgroup_removexattr,
};

2624
static const struct inode_operations cgroup_dir_inode_operations = {
2625
	.lookup = cgroup_lookup,
2626 2627 2628
	.mkdir = cgroup_mkdir,
	.rmdir = cgroup_rmdir,
	.rename = cgroup_rename,
A
Aristeu Rozanski 已提交
2629 2630 2631 2632
	.setxattr = cgroup_setxattr,
	.getxattr = cgroup_getxattr,
	.listxattr = cgroup_listxattr,
	.removexattr = cgroup_removexattr,
2633 2634
};

A
Al Viro 已提交
2635
static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
2636 2637 2638 2639 2640 2641 2642
{
	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
	d_add(dentry, NULL);
	return NULL;
}

2643 2644 2645 2646 2647
/*
 * Check if a file is a control file
 */
static inline struct cftype *__file_cft(struct file *file)
{
A
Al Viro 已提交
2648
	if (file_inode(file)->i_fop != &cgroup_file_operations)
2649 2650 2651 2652
		return ERR_PTR(-EINVAL);
	return __d_cft(file->f_dentry);
}

A
Al Viro 已提交
2653
static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2654 2655
				struct super_block *sb)
{
2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672
	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
2673
		inc_nlink(dentry->d_parent->d_inode);
2674

2675 2676 2677 2678 2679 2680 2681 2682 2683
		/*
		 * 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));
2684 2685 2686
	} else if (S_ISREG(mode)) {
		inode->i_size = 0;
		inode->i_fop = &cgroup_file_operations;
A
Aristeu Rozanski 已提交
2687
		inode->i_op = &cgroup_file_inode_operations;
2688 2689 2690 2691 2692 2693
	}
	d_instantiate(dentry, inode);
	dget(dentry);	/* Extra count - pin the dentry in core */
	return 0;
}

L
Li Zefan 已提交
2694 2695 2696 2697 2698 2699 2700 2701 2702
/**
 * 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
2703
static umode_t cgroup_file_mode(const struct cftype *cft)
L
Li Zefan 已提交
2704
{
A
Al Viro 已提交
2705
	umode_t mode = 0;
L
Li Zefan 已提交
2706 2707 2708 2709 2710 2711 2712 2713 2714 2715 2716 2717 2718 2719 2720

	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
2721
static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
A
Aristeu Rozanski 已提交
2722
			   struct cftype *cft)
2723
{
2724
	struct dentry *dir = cgrp->dentry;
T
Tejun Heo 已提交
2725
	struct cgroup *parent = __d_cgrp(dir);
2726
	struct dentry *dentry;
T
Tejun Heo 已提交
2727
	struct cfent *cfe;
2728
	int error;
A
Al Viro 已提交
2729
	umode_t mode;
2730
	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2731

A
Aristeu Rozanski 已提交
2732 2733
	simple_xattrs_init(&cft->xattrs);

2734
	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2735 2736 2737 2738
		strcpy(name, subsys->name);
		strcat(name, ".");
	}
	strcat(name, cft->name);
T
Tejun Heo 已提交
2739

2740
	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
T
Tejun Heo 已提交
2741 2742 2743 2744 2745

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

2746
	dentry = lookup_one_len(name, dir, strlen(name));
T
Tejun Heo 已提交
2747
	if (IS_ERR(dentry)) {
2748
		error = PTR_ERR(dentry);
T
Tejun Heo 已提交
2749 2750 2751 2752 2753 2754 2755 2756 2757 2758 2759 2760 2761 2762 2763
		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);
2764 2765 2766
	return error;
}

2767
static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
A
Aristeu Rozanski 已提交
2768
			      struct cftype cfts[], bool is_add)
2769
{
A
Aristeu Rozanski 已提交
2770
	struct cftype *cft;
T
Tejun Heo 已提交
2771 2772 2773
	int err, ret = 0;

	for (cft = cfts; cft->name[0] != '\0'; cft++) {
2774 2775 2776 2777 2778 2779
		/* 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;

2780
		if (is_add) {
2781
			err = cgroup_add_file(cgrp, subsys, cft);
2782 2783 2784
			if (err)
				pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
					cft->name, err);
T
Tejun Heo 已提交
2785
			ret = err;
2786 2787
		} else {
			cgroup_rm_file(cgrp, cft);
T
Tejun Heo 已提交
2788
		}
2789
	}
T
Tejun Heo 已提交
2790
	return ret;
2791 2792
}

2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809
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
2810
			       struct cftype *cfts, bool is_add)
2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835
	__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))
2836
			cgroup_addrm_files(cgrp, ss, cfts, is_add);
2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860
		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
2861
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2862 2863 2864 2865 2866 2867 2868 2869 2870 2871
{
	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);
2872
	cgroup_cfts_commit(ss, cfts, true);
2873 2874 2875 2876 2877

	return 0;
}
EXPORT_SYMBOL_GPL(cgroup_add_cftypes);

2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890
/**
 * 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
2891
int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908
{
	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
2909 2910 2911 2912 2913 2914
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2915
int cgroup_task_count(const struct cgroup *cgrp)
2916 2917
{
	int count = 0;
K
KOSAKI Motohiro 已提交
2918
	struct cg_cgroup_link *link;
2919 2920

	read_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
2921
	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2922
		count += atomic_read(&link->cg->refcount);
2923 2924
	}
	read_unlock(&css_set_lock);
2925 2926 2927
	return count;
}

2928 2929 2930 2931
/*
 * Advance a list_head iterator.  The iterator should be positioned at
 * the start of a css_set
 */
2932
static void cgroup_advance_iter(struct cgroup *cgrp,
2933
				struct cgroup_iter *it)
2934 2935 2936 2937 2938 2939 2940 2941
{
	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;
2942
		if (l == &cgrp->css_sets) {
2943 2944 2945
			it->cg_link = NULL;
			return;
		}
2946
		link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2947 2948 2949 2950 2951 2952
		cg = link->cg;
	} while (list_empty(&cg->tasks));
	it->cg_link = l;
	it->task = cg->tasks.next;
}

2953 2954 2955 2956 2957 2958
/*
 * 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().
 */
2959
static void cgroup_enable_task_cg_lists(void)
2960 2961 2962 2963
{
	struct task_struct *p, *g;
	write_lock(&css_set_lock);
	use_task_css_set_links = 1;
2964 2965 2966 2967 2968 2969 2970 2971
	/*
	 * 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);
2972 2973
	do_each_thread(g, p) {
		task_lock(p);
2974 2975 2976 2977 2978 2979
		/*
		 * 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))
2980 2981 2982
			list_add(&p->cg_list, &p->cgroups->tasks);
		task_unlock(p);
	} while_each_thread(g, p);
2983
	read_unlock(&tasklist_lock);
2984 2985 2986
	write_unlock(&css_set_lock);
}

2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027
/**
 * 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);

3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053
/**
 * 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);

3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098
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);

3099
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
3100
	__acquires(css_set_lock)
3101 3102 3103 3104 3105 3106
{
	/*
	 * 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.
	 */
3107 3108 3109
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();

3110
	read_lock(&css_set_lock);
3111 3112
	it->cg_link = &cgrp->css_sets;
	cgroup_advance_iter(cgrp, it);
3113 3114
}

3115
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
3116 3117 3118 3119
					struct cgroup_iter *it)
{
	struct task_struct *res;
	struct list_head *l = it->task;
3120
	struct cg_cgroup_link *link;
3121 3122 3123 3124 3125 3126 3127

	/* 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;
3128 3129
	link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
	if (l == &link->cg->tasks) {
3130 3131
		/* We reached the end of this task list - move on to
		 * the next cg_cgroup_link */
3132
		cgroup_advance_iter(cgrp, it);
3133 3134 3135 3136 3137 3138
	} else {
		it->task = l;
	}
	return res;
}

3139
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
3140
	__releases(css_set_lock)
3141 3142 3143 3144
{
	read_unlock(&css_set_lock);
}

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 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281
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++) {
3282
			struct task_struct *q = heap->ptrs[i];
3283
			if (i == 0) {
3284 3285
				latest_time = q->start_time;
				latest_task = q;
3286 3287
			}
			/* Process the task per the caller's callback */
3288 3289
			scan->process_task(q, scan);
			put_task_struct(q);
3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304
		}
		/*
		 * 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;
}

3305
/*
3306
 * Stuff for reading the 'tasks'/'procs' files.
3307 3308 3309 3310 3311 3312 3313 3314
 *
 * 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.
 *
 */

3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346
/* 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;
};

3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382
/*
 * 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;
}

3383
/*
3384 3385 3386 3387
 * 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.
3388
 */
3389 3390 3391
/* 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)
3392
{
3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421
	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)) {
3422
		newlist = pidlist_resize(list, dest);
3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433
		if (newlist)
			*p = newlist;
	}
	return dest;
}

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

3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444
/*
 * 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 */
3445
	struct pid_namespace *ns = task_active_pid_ns(current);
3446

3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470
	/*
	 * 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;
3471
	l->key.ns = get_pid_ns(ns);
3472 3473 3474 3475 3476 3477 3478 3479
	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;
}

3480 3481 3482
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
3483 3484
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
3485 3486 3487 3488
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
3489 3490
	struct cgroup_iter it;
	struct task_struct *tsk;
3491 3492 3493 3494 3495 3496 3497 3498 3499
	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);
3500
	array = pidlist_allocate(length);
3501 3502 3503
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
3504 3505
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
3506
		if (unlikely(n == length))
3507
			break;
3508
		/* get tgid or pid for procs or tasks file respectively */
3509 3510 3511 3512
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
3513 3514
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
3515
	}
3516
	cgroup_iter_end(cgrp, &it);
3517 3518 3519
	length = n;
	/* now sort & (if procs) strip out duplicates */
	sort(array, length, sizeof(pid_t), cmppid, NULL);
3520
	if (type == CGROUP_FILE_PROCS)
3521
		length = pidlist_uniq(&array, length);
3522 3523
	l = cgroup_pidlist_find(cgrp, type);
	if (!l) {
3524
		pidlist_free(array);
3525
		return -ENOMEM;
3526
	}
3527
	/* store array, freeing old if necessary - lock already held */
3528
	pidlist_free(l->list);
3529 3530 3531 3532
	l->list = array;
	l->length = length;
	l->use_count++;
	up_write(&l->mutex);
3533
	*lp = l;
3534
	return 0;
3535 3536
}

B
Balbir Singh 已提交
3537
/**
L
Li Zefan 已提交
3538
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
3539 3540 3541
 * @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
3542 3543 3544
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
3545 3546 3547 3548
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
	int ret = -EINVAL;
3549
	struct cgroup *cgrp;
B
Balbir Singh 已提交
3550 3551
	struct cgroup_iter it;
	struct task_struct *tsk;
3552

B
Balbir Singh 已提交
3553
	/*
3554 3555
	 * Validate dentry by checking the superblock operations,
	 * and make sure it's a directory.
B
Balbir Singh 已提交
3556
	 */
3557 3558
	if (dentry->d_sb->s_op != &cgroup_ops ||
	    !S_ISDIR(dentry->d_inode->i_mode))
B
Balbir Singh 已提交
3559 3560 3561
		 goto err;

	ret = 0;
3562
	cgrp = dentry->d_fsdata;
B
Balbir Singh 已提交
3563

3564 3565
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
B
Balbir Singh 已提交
3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581 3582 3583 3584
		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;
		}
	}
3585
	cgroup_iter_end(cgrp, &it);
B
Balbir Singh 已提交
3586 3587 3588 3589 3590

err:
	return ret;
}

3591

3592
/*
3593
 * seq_file methods for the tasks/procs files. The seq_file position is the
3594
 * next pid to display; the seq_file iterator is a pointer to the pid
3595
 * in the cgroup->l->list array.
3596
 */
3597

3598
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3599
{
3600 3601 3602 3603 3604 3605
	/*
	 * 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
	 */
3606
	struct cgroup_pidlist *l = s->private;
3607 3608 3609
	int index = 0, pid = *pos;
	int *iter;

3610
	down_read(&l->mutex);
3611
	if (pid) {
3612
		int end = l->length;
S
Stephen Rothwell 已提交
3613

3614 3615
		while (index < end) {
			int mid = (index + end) / 2;
3616
			if (l->list[mid] == pid) {
3617 3618
				index = mid;
				break;
3619
			} else if (l->list[mid] <= pid)
3620 3621 3622 3623 3624 3625
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
3626
	if (index >= l->length)
3627 3628
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
3629
	iter = l->list + index;
3630 3631 3632 3633
	*pos = *iter;
	return iter;
}

3634
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3635
{
3636 3637
	struct cgroup_pidlist *l = s->private;
	up_read(&l->mutex);
3638 3639
}

3640
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3641
{
3642 3643 3644
	struct cgroup_pidlist *l = s->private;
	pid_t *p = v;
	pid_t *end = l->list + l->length;
3645 3646 3647 3648 3649 3650 3651 3652 3653 3654 3655 3656 3657
	/*
	 * 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;
	}
}

3658
static int cgroup_pidlist_show(struct seq_file *s, void *v)
3659 3660 3661
{
	return seq_printf(s, "%d\n", *(int *)v);
}
3662

3663 3664 3665 3666 3667 3668 3669 3670 3671
/*
 * 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,
3672 3673
};

3674
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3675
{
3676 3677 3678 3679 3680 3681 3682
	/*
	 * 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);
3683 3684 3685
	down_write(&l->mutex);
	BUG_ON(!l->use_count);
	if (!--l->use_count) {
3686 3687 3688
		/* we're the last user if refcount is 0; remove and free */
		list_del(&l->links);
		mutex_unlock(&l->owner->pidlist_mutex);
3689
		pidlist_free(l->list);
3690 3691 3692 3693
		put_pid_ns(l->key.ns);
		up_write(&l->mutex);
		kfree(l);
		return;
3694
	}
3695
	mutex_unlock(&l->owner->pidlist_mutex);
3696
	up_write(&l->mutex);
3697 3698
}

3699
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3700
{
3701
	struct cgroup_pidlist *l;
3702 3703
	if (!(file->f_mode & FMODE_READ))
		return 0;
3704 3705 3706 3707 3708 3709
	/*
	 * 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);
3710 3711 3712
	return seq_release(inode, file);
}

3713
static const struct file_operations cgroup_pidlist_operations = {
3714 3715 3716
	.read = seq_read,
	.llseek = seq_lseek,
	.write = cgroup_file_write,
3717
	.release = cgroup_pidlist_release,
3718 3719
};

3720
/*
3721 3722 3723
 * 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.
3724
 */
3725
/* helper function for the two below it */
3726
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3727
{
3728
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3729
	struct cgroup_pidlist *l;
3730
	int retval;
3731

3732
	/* Nothing to do for write-only files */
3733 3734 3735
	if (!(file->f_mode & FMODE_READ))
		return 0;

3736
	/* have the array populated */
3737
	retval = pidlist_array_load(cgrp, type, &l);
3738 3739 3740 3741
	if (retval)
		return retval;
	/* configure file information */
	file->f_op = &cgroup_pidlist_operations;
3742

3743
	retval = seq_open(file, &cgroup_pidlist_seq_operations);
3744
	if (retval) {
3745
		cgroup_release_pid_array(l);
3746
		return retval;
3747
	}
3748
	((struct seq_file *)file->private_data)->private = l;
3749 3750
	return 0;
}
3751 3752
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
3753
	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3754 3755 3756
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
3757
	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3758
}
3759

3760
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3761 3762
					    struct cftype *cft)
{
3763
	return notify_on_release(cgrp);
3764 3765
}

3766 3767 3768 3769 3770 3771 3772 3773 3774 3775 3776 3777
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;
}

3778 3779 3780 3781 3782 3783 3784 3785 3786 3787 3788
/*
 * 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;

3789 3790
	remove_wait_queue(event->wqh, &event->wait);

3791 3792
	event->cft->unregister_event(cgrp, event->cft, event->eventfd);

3793 3794 3795
	/* Notify userspace the event is going away. */
	eventfd_signal(event->eventfd, 1);

3796 3797
	eventfd_ctx_put(event->eventfd);
	kfree(event);
3798
	dput(cgrp->dentry);
3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815
}

/*
 * 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) {
		/*
3816 3817 3818 3819 3820 3821 3822
		 * If the event has been detached at cgroup removal, we
		 * can simply return knowing the other side will cleanup
		 * for us.
		 *
		 * We can't race against event freeing since the other
		 * side will require wqh->lock via remove_wait_queue(),
		 * which we hold.
3823
		 */
3824 3825 3826 3827 3828 3829 3830 3831 3832 3833
		spin_lock(&cgrp->event_list_lock);
		if (!list_empty(&event->list)) {
			list_del_init(&event->list);
			/*
			 * We are in atomic context, but cgroup_event_remove()
			 * may sleep, so we have to call it in workqueue.
			 */
			schedule_work(&event->remove);
		}
		spin_unlock(&cgrp->event_list_lock);
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
	}

	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;
3859
	struct cgroup *cgrp_cfile;
3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903
	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
3904
	/* AV: shouldn't we check that it's been opened for read instead? */
A
Al Viro 已提交
3905
	ret = inode_permission(file_inode(cfile), MAY_READ);
3906 3907 3908 3909 3910 3911 3912 3913 3914
	if (ret < 0)
		goto fail;

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

3915 3916 3917 3918 3919 3920 3921 3922 3923 3924
	/*
	 * The file to be monitored must be in the same cgroup as
	 * cgroup.event_control is.
	 */
	cgrp_cfile = __d_cgrp(cfile->f_dentry->d_parent);
	if (cgrp_cfile != cgrp) {
		ret = -EINVAL;
		goto fail;
	}

3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940
	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;
	}

3941 3942 3943 3944 3945 3946 3947
	/*
	 * 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);

3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971
	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;
}

3972 3973 3974
static u64 cgroup_clone_children_read(struct cgroup *cgrp,
				    struct cftype *cft)
{
3975
	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3976 3977 3978 3979 3980 3981 3982
}

static int cgroup_clone_children_write(struct cgroup *cgrp,
				     struct cftype *cft,
				     u64 val)
{
	if (val)
3983
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3984
	else
3985
		clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3986 3987 3988
	return 0;
}

3989 3990 3991
/*
 * for the common functions, 'private' gives the type of file
 */
3992 3993
/* for hysterical raisins, we can't put this on the older files */
#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3994 3995 3996 3997
static struct cftype files[] = {
	{
		.name = "tasks",
		.open = cgroup_tasks_open,
3998
		.write_u64 = cgroup_tasks_write,
3999
		.release = cgroup_pidlist_release,
L
Li Zefan 已提交
4000
		.mode = S_IRUGO | S_IWUSR,
4001
	},
4002 4003 4004
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "procs",
		.open = cgroup_procs_open,
B
Ben Blum 已提交
4005
		.write_u64 = cgroup_procs_write,
4006
		.release = cgroup_pidlist_release,
B
Ben Blum 已提交
4007
		.mode = S_IRUGO | S_IWUSR,
4008
	},
4009 4010
	{
		.name = "notify_on_release",
4011
		.read_u64 = cgroup_read_notify_on_release,
4012
		.write_u64 = cgroup_write_notify_on_release,
4013
	},
4014 4015 4016 4017 4018
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "event_control",
		.write_string = cgroup_write_event_control,
		.mode = S_IWUGO,
	},
4019 4020 4021 4022 4023
	{
		.name = "cgroup.clone_children",
		.read_u64 = cgroup_clone_children_read,
		.write_u64 = cgroup_clone_children_write,
	},
4024 4025 4026 4027 4028 4029 4030
	{
		.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
4031
	{ }	/* terminate */
4032 4033
};

4034 4035 4036 4037 4038 4039 4040 4041
/**
 * 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)
4042 4043 4044 4045
{
	int err;
	struct cgroup_subsys *ss;

4046 4047 4048 4049 4050
	if (base_files) {
		err = cgroup_addrm_files(cgrp, NULL, files, true);
		if (err < 0)
			return err;
	}
4051

4052
	/* process cftsets of each subsystem */
4053
	for_each_subsys(cgrp->root, ss) {
4054
		struct cftype_set *set;
4055 4056
		if (!test_bit(ss->subsys_id, &subsys_mask))
			continue;
4057

T
Tejun Heo 已提交
4058
		list_for_each_entry(set, &ss->cftsets, node)
4059
			cgroup_addrm_files(cgrp, ss, set->cfts, true);
4060
	}
4061

K
KAMEZAWA Hiroyuki 已提交
4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072
	/* 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);
	}
4073 4074 4075 4076

	return 0;
}

4077 4078 4079 4080
static void css_dput_fn(struct work_struct *work)
{
	struct cgroup_subsys_state *css =
		container_of(work, struct cgroup_subsys_state, dput_work);
4081 4082
	struct dentry *dentry = css->cgroup->dentry;
	struct super_block *sb = dentry->d_sb;
4083

4084 4085 4086
	atomic_inc(&sb->s_active);
	dput(dentry);
	deactivate_super(sb);
4087 4088
}

4089 4090
static void init_cgroup_css(struct cgroup_subsys_state *css,
			       struct cgroup_subsys *ss,
4091
			       struct cgroup *cgrp)
4092
{
4093
	css->cgroup = cgrp;
P
Paul Menage 已提交
4094
	atomic_set(&css->refcnt, 1);
4095
	css->flags = 0;
K
KAMEZAWA Hiroyuki 已提交
4096
	css->id = NULL;
4097
	if (cgrp == dummytop)
4098
		css->flags |= CSS_ROOT;
4099 4100
	BUG_ON(cgrp->subsys[ss->subsys_id]);
	cgrp->subsys[ss->subsys_id] = css;
4101 4102

	/*
4103 4104 4105 4106
	 * 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().
4107 4108
	 */
	INIT_WORK(&css->dput_work, css_dput_fn);
4109 4110
}

T
Tejun Heo 已提交
4111 4112
/* invoke ->post_create() on a new CSS and mark it online if successful */
static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
4113
{
T
Tejun Heo 已提交
4114 4115
	int ret = 0;

4116 4117
	lockdep_assert_held(&cgroup_mutex);

4118 4119
	if (ss->css_online)
		ret = ss->css_online(cgrp);
T
Tejun Heo 已提交
4120 4121 4122
	if (!ret)
		cgrp->subsys[ss->subsys_id]->flags |= CSS_ONLINE;
	return ret;
4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136
}

/* 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;

	/*
4137
	 * css_offline() should be called with cgroup_mutex unlocked.  See
4138 4139 4140 4141
	 * 3fa59dfbc3 ("cgroup: fix potential deadlock in pre_destroy") for
	 * details.  This temporary unlocking should go away once
	 * cgroup_mutex is unexported from controllers.
	 */
4142
	if (ss->css_offline) {
4143
		mutex_unlock(&cgroup_mutex);
4144
		ss->css_offline(cgrp);
4145 4146 4147 4148 4149 4150
		mutex_lock(&cgroup_mutex);
	}

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

4151
/*
L
Li Zefan 已提交
4152 4153 4154 4155
 * 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
4156
 *
L
Li Zefan 已提交
4157
 * Must be called with the mutex on the parent inode held
4158 4159
 */
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
A
Al Viro 已提交
4160
			     umode_t mode)
4161
{
4162
	struct cgroup *cgrp;
4163 4164 4165 4166 4167
	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
4168
	/* allocate the cgroup and its ID, 0 is reserved for the root */
4169 4170
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
4171 4172
		return -ENOMEM;

T
Tejun Heo 已提交
4173 4174 4175 4176
	cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);
	if (cgrp->id < 0)
		goto err_free_cgrp;

4177 4178 4179 4180 4181 4182 4183 4184 4185
	/*
	 * 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
4186
		goto err_free_id;
4187 4188
	}

4189 4190 4191 4192 4193 4194 4195
	/* 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);

4196
	init_cgroup_housekeeping(cgrp);
4197

4198 4199 4200
	dentry->d_fsdata = cgrp;
	cgrp->dentry = dentry;

4201 4202 4203
	cgrp->parent = parent;
	cgrp->root = parent->root;
	cgrp->top_cgroup = parent->top_cgroup;
4204

4205 4206 4207
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

4208 4209
	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4210

4211
	for_each_subsys(root, ss) {
4212
		struct cgroup_subsys_state *css;
4213

4214
		css = ss->css_alloc(cgrp);
4215 4216
		if (IS_ERR(css)) {
			err = PTR_ERR(css);
4217
			goto err_free_all;
4218
		}
4219
		init_cgroup_css(css, ss, cgrp);
4220 4221 4222
		if (ss->use_id) {
			err = alloc_css_id(ss, parent, cgrp);
			if (err)
4223
				goto err_free_all;
4224
		}
4225 4226
	}

4227 4228 4229 4230 4231
	/*
	 * 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
4232
	err = cgroup_create_file(dentry, S_IFDIR | mode, sb);
4233
	if (err < 0)
4234
		goto err_free_all;
4235
	lockdep_assert_held(&dentry->d_inode->i_mutex);
4236

4237 4238 4239 4240
	/* allocation complete, commit to creation */
	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
4241

T
Tejun Heo 已提交
4242 4243
	/* each css holds a ref to the cgroup's dentry */
	for_each_subsys(root, ss)
4244
		dget(dentry);
4245

T
Tejun Heo 已提交
4246 4247 4248 4249 4250
	/* creation succeeded, notify subsystems */
	for_each_subsys(root, ss) {
		err = online_css(ss, cgrp);
		if (err)
			goto err_destroy;
4251 4252 4253 4254 4255 4256 4257 4258 4259

		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;
		}
4260 4261
	}

4262
	err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
4263 4264
	if (err)
		goto err_destroy;
4265 4266

	mutex_unlock(&cgroup_mutex);
4267
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
4268 4269 4270

	return 0;

4271
err_free_all:
4272
	for_each_subsys(root, ss) {
4273
		if (cgrp->subsys[ss->subsys_id])
4274
			ss->css_free(cgrp);
4275 4276 4277 4278
	}
	mutex_unlock(&cgroup_mutex);
	/* Release the reference count that we took on the superblock */
	deactivate_super(sb);
T
Tejun Heo 已提交
4279 4280
err_free_id:
	ida_simple_remove(&root->cgroup_ida, cgrp->id);
4281
err_free_cgrp:
4282
	kfree(cgrp);
4283
	return err;
4284 4285 4286 4287 4288 4289

err_destroy:
	cgroup_destroy_locked(cgrp);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&dentry->d_inode->i_mutex);
	return err;
4290 4291
}

4292
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
4293 4294 4295 4296 4297 4298 4299
{
	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);
}

4300 4301 4302 4303 4304 4305 4306 4307 4308
/*
 * 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.
 */
4309
static int cgroup_has_css_refs(struct cgroup *cgrp)
4310 4311
{
	int i;
4312

B
Ben Blum 已提交
4313 4314 4315 4316 4317
	/*
	 * 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.
	 */
4318 4319 4320
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		struct cgroup_subsys_state *css;
4321

B
Ben Blum 已提交
4322 4323
		/* Skip subsystems not present or not in this hierarchy */
		if (ss == NULL || ss->root != cgrp->root)
4324
			continue;
4325

4326
		css = cgrp->subsys[ss->subsys_id];
4327 4328
		/*
		 * When called from check_for_release() it's possible
4329 4330 4331 4332
		 * 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
4333 4334 4335
		 * release agent to be called anyway.
		 */
		if (css && css_refcnt(css) > 1)
4336 4337 4338 4339 4340
			return 1;
	}
	return 0;
}

4341 4342
static int cgroup_destroy_locked(struct cgroup *cgrp)
	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4343
{
4344 4345
	struct dentry *d = cgrp->dentry;
	struct cgroup *parent = cgrp->parent;
4346
	DEFINE_WAIT(wait);
4347
	struct cgroup_event *event, *tmp;
4348
	struct cgroup_subsys *ss;
4349
	LIST_HEAD(tmp_list);
4350

4351 4352 4353 4354
	lockdep_assert_held(&d->d_inode->i_mutex);
	lockdep_assert_held(&cgroup_mutex);

	if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children))
4355
		return -EBUSY;
L
Li Zefan 已提交
4356

4357
	/*
4358 4359 4360 4361
	 * 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.
4362
	 */
4363 4364
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4365

4366 4367
		WARN_ON(atomic_read(&css->refcnt) < 0);
		atomic_add(CSS_DEACT_BIAS, &css->refcnt);
4368
	}
4369
	set_bit(CGRP_REMOVED, &cgrp->flags);
4370

4371
	/* tell subsystems to initate destruction */
4372
	for_each_subsys(cgrp->root, ss)
4373
		offline_css(ss, cgrp);
4374 4375 4376 4377 4378 4379 4380 4381

	/*
	 * 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
4382 4383
	for_each_subsys(cgrp->root, ss)
		css_put(cgrp->subsys[ss->subsys_id]);
4384

4385
	raw_spin_lock(&release_list_lock);
4386
	if (!list_empty(&cgrp->release_list))
4387
		list_del_init(&cgrp->release_list);
4388
	raw_spin_unlock(&release_list_lock);
4389 4390

	/* delete this cgroup from parent->children */
4391
	list_del_rcu(&cgrp->sibling);
4392 4393
	list_del_init(&cgrp->allcg_node);

4394
	dget(d);
4395 4396 4397
	cgroup_d_remove_dir(d);
	dput(d);

4398
	set_bit(CGRP_RELEASABLE, &parent->flags);
4399 4400
	check_for_release(parent);

4401 4402 4403
	/*
	 * Unregister events and notify userspace.
	 * Notify userspace about cgroup removing only after rmdir of cgroup
4404
	 * directory to avoid race between userspace and kernelspace.
4405 4406
	 */
	spin_lock(&cgrp->event_list_lock);
4407
	list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
4408
		list_del_init(&event->list);
4409 4410
		schedule_work(&event->remove);
	}
4411
	spin_unlock(&cgrp->event_list_lock);
4412

4413 4414 4415
	return 0;
}

4416 4417 4418 4419 4420 4421 4422 4423 4424 4425 4426
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;
}

4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440
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);
	}
}

4441
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4442 4443
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
4444 4445

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4446

4447 4448
	mutex_lock(&cgroup_mutex);

4449 4450 4451
	/* init base cftset */
	cgroup_init_cftsets(ss);

4452
	/* Create the top cgroup state for this subsystem */
4453
	list_add(&ss->sibling, &rootnode.subsys_list);
4454
	ss->root = &rootnode;
4455
	css = ss->css_alloc(dummytop);
4456 4457 4458 4459
	/* We don't handle early failures gracefully */
	BUG_ON(IS_ERR(css));
	init_cgroup_css(css, ss, dummytop);

L
Li Zefan 已提交
4460
	/* Update the init_css_set to contain a subsys
4461
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
4462 4463
	 * newly registered, all tasks and hence the
	 * init_css_set is in the subsystem's top cgroup. */
4464
	init_css_set.subsys[ss->subsys_id] = css;
4465 4466 4467

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

L
Li Zefan 已提交
4468 4469 4470 4471 4472
	/* 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));

4473
	ss->active = 1;
T
Tejun Heo 已提交
4474
	BUG_ON(online_css(ss, dummytop));
4475

4476 4477
	mutex_unlock(&cgroup_mutex);

4478 4479 4480 4481 4482 4483 4484 4485 4486 4487
	/* 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
4488
 * subsystem is built as a module, it will be assigned a new subsys_id and set
4489 4490 4491 4492 4493 4494
 * 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;
4495
	int i, ret;
4496 4497 4498
	struct hlist_node *node, *tmp;
	struct css_set *cg;
	unsigned long key;
4499 4500 4501

	/* check name and function validity */
	if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
4502
	    ss->css_alloc == NULL || ss->css_free == NULL)
4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518
		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) {
4519
		/* a sanity check */
4520 4521 4522 4523
		BUG_ON(subsys[ss->subsys_id] != ss);
		return 0;
	}

4524 4525 4526
	/* init base cftset */
	cgroup_init_cftsets(ss);

4527
	mutex_lock(&cgroup_mutex);
4528
	subsys[ss->subsys_id] = ss;
4529 4530

	/*
4531 4532 4533
	 * no ss->css_alloc seems to need anything important in the ss
	 * struct, so this can happen first (i.e. before the rootnode
	 * attachment).
4534
	 */
4535
	css = ss->css_alloc(dummytop);
4536 4537
	if (IS_ERR(css)) {
		/* failure case - need to deassign the subsys[] slot. */
4538
		subsys[ss->subsys_id] = NULL;
4539 4540 4541 4542 4543 4544 4545 4546 4547 4548 4549
		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) {
4550 4551 4552
		ret = cgroup_init_idr(ss, css);
		if (ret)
			goto err_unload;
4553 4554 4555 4556 4557 4558 4559 4560 4561 4562 4563
	}

	/*
	 * 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);
4564 4565 4566 4567 4568 4569 4570 4571 4572 4573 4574
	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);
4575 4576 4577 4578
	}
	write_unlock(&css_set_lock);

	ss->active = 1;
T
Tejun Heo 已提交
4579 4580 4581
	ret = online_css(ss, dummytop);
	if (ret)
		goto err_unload;
4582

4583 4584 4585
	/* success! */
	mutex_unlock(&cgroup_mutex);
	return 0;
4586 4587 4588 4589 4590 4591

err_unload:
	mutex_unlock(&cgroup_mutex);
	/* @ss can't be mounted here as try_module_get() would fail */
	cgroup_unload_subsys(ss);
	return ret;
4592
}
4593
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4594

B
Ben Blum 已提交
4595 4596 4597 4598 4599 4600 4601 4602 4603 4604 4605 4606 4607 4608 4609 4610 4611 4612 4613 4614 4615 4616
/**
 * 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);
4617

4618
	offline_css(ss, dummytop);
4619 4620
	ss->active = 0;

T
Tejun Heo 已提交
4621
	if (ss->use_id)
4622 4623
		idr_destroy(&ss->idr);

B
Ben Blum 已提交
4624 4625 4626 4627
	/* deassign the subsys_id */
	subsys[ss->subsys_id] = NULL;

	/* remove subsystem from rootnode's list of subsystems */
4628
	list_del_init(&ss->sibling);
B
Ben Blum 已提交
4629 4630 4631 4632 4633 4634 4635 4636

	/*
	 * 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;
4637
		unsigned long key;
B
Ben Blum 已提交
4638

4639
		hash_del(&cg->hlist);
B
Ben Blum 已提交
4640
		cg->subsys[ss->subsys_id] = NULL;
4641 4642
		key = css_set_hash(cg->subsys);
		hash_add(css_set_table, &cg->hlist, key);
B
Ben Blum 已提交
4643 4644 4645 4646
	}
	write_unlock(&css_set_lock);

	/*
4647 4648 4649 4650
	 * 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
4651
	 */
4652
	ss->css_free(dummytop);
B
Ben Blum 已提交
4653 4654 4655 4656 4657 4658
	dummytop->subsys[ss->subsys_id] = NULL;

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

4659
/**
L
Li Zefan 已提交
4660 4661 4662 4663
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
4664 4665 4666 4667
 */
int __init cgroup_init_early(void)
{
	int i;
4668
	atomic_set(&init_css_set.refcount, 1);
4669 4670
	INIT_LIST_HEAD(&init_css_set.cg_links);
	INIT_LIST_HEAD(&init_css_set.tasks);
4671
	INIT_HLIST_NODE(&init_css_set.hlist);
4672
	css_set_count = 1;
4673
	init_cgroup_root(&rootnode);
4674 4675 4676 4677
	root_count = 1;
	init_task.cgroups = &init_css_set;

	init_css_set_link.cg = &init_css_set;
4678
	init_css_set_link.cgrp = dummytop;
4679
	list_add(&init_css_set_link.cgrp_link_list,
4680 4681 4682
		 &rootnode.top_cgroup.css_sets);
	list_add(&init_css_set_link.cg_link_list,
		 &init_css_set.cg_links);
4683

4684
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4685 4686
		struct cgroup_subsys *ss = subsys[i];

4687 4688 4689 4690
		/* at bootup time, we don't worry about modular subsystems */
		if (!ss || ss->module)
			continue;

4691 4692
		BUG_ON(!ss->name);
		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4693 4694
		BUG_ON(!ss->css_alloc);
		BUG_ON(!ss->css_free);
4695
		if (ss->subsys_id != i) {
D
Diego Calleja 已提交
4696
			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4697 4698 4699 4700 4701 4702 4703 4704 4705 4706 4707
			       ss->name, ss->subsys_id);
			BUG();
		}

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

/**
L
Li Zefan 已提交
4708 4709 4710 4711
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
4712 4713 4714 4715 4716
 */
int __init cgroup_init(void)
{
	int err;
	int i;
4717
	unsigned long key;
4718 4719 4720 4721

	err = bdi_init(&cgroup_backing_dev_info);
	if (err)
		return err;
4722

4723
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4724
		struct cgroup_subsys *ss = subsys[i];
4725 4726 4727 4728

		/* at bootup time, we don't worry about modular subsystems */
		if (!ss || ss->module)
			continue;
4729 4730
		if (!ss->early_init)
			cgroup_init_subsys(ss);
K
KAMEZAWA Hiroyuki 已提交
4731
		if (ss->use_id)
4732
			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4733 4734
	}

4735
	/* Add init_css_set to the hash table */
4736 4737
	key = css_set_hash(init_css_set.subsys);
	hash_add(css_set_table, &init_css_set.hlist, key);
4738
	BUG_ON(!init_root_id(&rootnode));
4739 4740 4741 4742 4743 4744 4745

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

4746
	err = register_filesystem(&cgroup_fs_type);
4747 4748
	if (err < 0) {
		kobject_put(cgroup_kobj);
4749
		goto out;
4750
	}
4751

L
Li Zefan 已提交
4752
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4753

4754
out:
4755 4756 4757
	if (err)
		bdi_destroy(&cgroup_backing_dev_info);

4758 4759
	return err;
}
4760

4761 4762 4763 4764 4765 4766
/*
 * 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,
4767
 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778 4779 4780 4781 4782 4783 4784 4785 4786 4787 4788 4789 4790 4791 4792 4793 4794 4795 4796
 *    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);

4797
	for_each_active_root(root) {
4798
		struct cgroup_subsys *ss;
4799
		struct cgroup *cgrp;
4800 4801
		int count = 0;

4802
		seq_printf(m, "%d:", root->hierarchy_id);
4803 4804
		for_each_subsys(root, ss)
			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4805 4806 4807
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
4808
		seq_putc(m, ':');
4809
		cgrp = task_cgroup_from_root(tsk, root);
4810
		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822 4823 4824 4825 4826 4827 4828 4829 4830 4831
		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);
}

4832
const struct file_operations proc_cgroup_operations = {
4833 4834 4835 4836 4837 4838 4839 4840 4841 4842 4843
	.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;

4844
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
B
Ben Blum 已提交
4845 4846 4847 4848 4849
	/*
	 * 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.
	 */
4850 4851 4852
	mutex_lock(&cgroup_mutex);
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
B
Ben Blum 已提交
4853 4854
		if (ss == NULL)
			continue;
4855 4856
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
4857
			   ss->root->number_of_cgroups, !ss->disabled);
4858 4859 4860 4861 4862 4863 4864
	}
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
4865
	return single_open(file, proc_cgroupstats_show, NULL);
4866 4867
}

4868
static const struct file_operations proc_cgroupstats_operations = {
4869 4870 4871 4872 4873 4874
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

4875 4876
/**
 * cgroup_fork - attach newly forked task to its parents cgroup.
L
Li Zefan 已提交
4877
 * @child: pointer to task_struct of forking parent process.
4878 4879 4880 4881 4882
 *
 * 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
4883 4884 4885 4886
 * 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.
4887 4888 4889 4890 4891 4892
 *
 * 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)
{
4893
	task_lock(current);
4894 4895
	child->cgroups = current->cgroups;
	get_css_set(child->cgroups);
4896
	task_unlock(current);
4897
	INIT_LIST_HEAD(&child->cg_list);
4898 4899
}

4900
/**
L
Li Zefan 已提交
4901 4902 4903
 * cgroup_post_fork - called on a new task after adding it to the task list
 * @child: the task in question
 *
4904 4905 4906 4907 4908
 * 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
4909
 */
4910 4911
void cgroup_post_fork(struct task_struct *child)
{
4912 4913
	int i;

4914 4915 4916 4917 4918 4919 4920 4921 4922 4923 4924
	/*
	 * 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.
	 */
4925 4926
	if (use_task_css_set_links) {
		write_lock(&css_set_lock);
4927 4928
		task_lock(child);
		if (list_empty(&child->cg_list))
4929
			list_add(&child->cg_list, &child->cgroups->tasks);
4930
		task_unlock(child);
4931 4932
		write_unlock(&css_set_lock);
	}
4933 4934 4935 4936 4937 4938 4939 4940 4941 4942 4943 4944 4945 4946 4947 4948 4949 4950 4951 4952 4953 4954

	/*
	 * 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);
		}
	}
4955
}
4956

4957 4958 4959
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
4960
 * @run_callback: run exit callbacks?
4961 4962 4963 4964 4965 4966 4967 4968 4969 4970 4971 4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985 4986 4987 4988
 *
 * 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,
4989 4990
 *    which wards off any cgroup_attach_task() attempts, or task is a failed
 *    fork, never visible to cgroup_attach_task.
4991 4992 4993
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
4994
	struct css_set *cg;
4995
	int i;
4996 4997 4998 4999 5000 5001 5002 5003 5004

	/*
	 * 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))
5005
			list_del_init(&tsk->cg_list);
5006 5007 5008
		write_unlock(&css_set_lock);
	}

5009 5010
	/* Reassign the task to the init_css_set. */
	task_lock(tsk);
5011 5012
	cg = tsk->cgroups;
	tsk->cgroups = &init_css_set;
5013 5014

	if (run_callbacks && need_forkexit_callback) {
5015
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
5016
			struct cgroup_subsys *ss = subsys[i];
5017 5018 5019 5020 5021

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

5022 5023 5024 5025
			if (ss->exit) {
				struct cgroup *old_cgrp =
					rcu_dereference_raw(cg->subsys[i])->cgroup;
				struct cgroup *cgrp = task_cgroup(tsk, i);
5026
				ss->exit(cgrp, old_cgrp, tsk);
5027 5028 5029
			}
		}
	}
5030
	task_unlock(tsk);
5031

5032
	put_css_set_taskexit(cg);
5033
}
5034

L
Li Zefan 已提交
5035
/**
5036
 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
L
Li Zefan 已提交
5037
 * @cgrp: the cgroup in question
5038
 * @task: the task in question
L
Li Zefan 已提交
5039
 *
5040 5041
 * See if @cgrp is a descendant of @task's cgroup in the appropriate
 * hierarchy.
5042 5043 5044 5045 5046 5047
 *
 * If we are sending in dummytop, then presumably we are creating
 * the top cgroup in the subsystem.
 *
 * Called only by the ns (nsproxy) cgroup.
 */
5048
int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
5049 5050 5051 5052
{
	int ret;
	struct cgroup *target;

5053
	if (cgrp == dummytop)
5054 5055
		return 1;

5056
	target = task_cgroup_from_root(task, cgrp->root);
5057 5058 5059
	while (cgrp != target && cgrp!= cgrp->top_cgroup)
		cgrp = cgrp->parent;
	ret = (cgrp == target);
5060 5061
	return ret;
}
5062

5063
static void check_for_release(struct cgroup *cgrp)
5064 5065 5066
{
	/* All of these checks rely on RCU to keep the cgroup
	 * structure alive */
5067 5068
	if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
	    && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
5069 5070 5071 5072
		/* Control Group is currently removeable. If it's not
		 * already queued for a userspace notification, queue
		 * it now */
		int need_schedule_work = 0;
5073
		raw_spin_lock(&release_list_lock);
5074 5075 5076
		if (!cgroup_is_removed(cgrp) &&
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
5077 5078
			need_schedule_work = 1;
		}
5079
		raw_spin_unlock(&release_list_lock);
5080 5081 5082 5083 5084
		if (need_schedule_work)
			schedule_work(&release_agent_work);
	}
}

5085
/* Caller must verify that the css is not for root cgroup */
5086 5087
bool __css_tryget(struct cgroup_subsys_state *css)
{
T
Tejun Heo 已提交
5088 5089
	while (true) {
		int t, v;
5090

T
Tejun Heo 已提交
5091 5092 5093
		v = css_refcnt(css);
		t = atomic_cmpxchg(&css->refcnt, v, v + 1);
		if (likely(t == v))
5094
			return true;
T
Tejun Heo 已提交
5095 5096
		else if (t < 0)
			return false;
5097
		cpu_relax();
T
Tejun Heo 已提交
5098
	}
5099 5100 5101 5102 5103
}
EXPORT_SYMBOL_GPL(__css_tryget);

/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css)
5104
{
5105
	struct cgroup *cgrp = css->cgroup;
5106
	int v;
5107

5108
	rcu_read_lock();
5109 5110 5111
	v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));

	switch (v) {
5112
	case 1:
5113 5114 5115 5116
		if (notify_on_release(cgrp)) {
			set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
		}
5117 5118
		break;
	case 0:
5119
		schedule_work(&css->dput_work);
5120
		break;
5121 5122 5123
	}
	rcu_read_unlock();
}
B
Ben Blum 已提交
5124
EXPORT_SYMBOL_GPL(__css_put);
5125 5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142 5143 5144 5145 5146 5147 5148 5149 5150 5151 5152

/*
 * 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);
5153
	raw_spin_lock(&release_list_lock);
5154 5155 5156
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
5157
		char *pathbuf = NULL, *agentbuf = NULL;
5158
		struct cgroup *cgrp = list_entry(release_list.next,
5159 5160
						    struct cgroup,
						    release_list);
5161
		list_del_init(&cgrp->release_list);
5162
		raw_spin_unlock(&release_list_lock);
5163
		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
5164 5165 5166 5167 5168 5169 5170
		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;
5171 5172

		i = 0;
5173 5174
		argv[i++] = agentbuf;
		argv[i++] = pathbuf;
5175 5176 5177 5178 5179 5180 5181 5182 5183 5184 5185 5186 5187 5188
		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);
5189 5190 5191
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
5192
		raw_spin_lock(&release_list_lock);
5193
	}
5194
	raw_spin_unlock(&release_list_lock);
5195 5196
	mutex_unlock(&cgroup_mutex);
}
5197 5198 5199 5200 5201 5202 5203 5204 5205

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

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;
5206
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
5207 5208
			struct cgroup_subsys *ss = subsys[i];

5209 5210 5211 5212 5213 5214 5215 5216
			/*
			 * cgroup_disable, being at boot time, can't
			 * know about module subsystems, so we don't
			 * worry about them.
			 */
			if (!ss || ss->module)
				continue;

5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227
			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
5228 5229 5230 5231 5232 5233 5234 5235 5236 5237

/*
 * 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)
{
5238 5239 5240 5241 5242 5243 5244
	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.
	 */
5245
	cssid = rcu_dereference_check(css->id, css_refcnt(css));
K
KAMEZAWA Hiroyuki 已提交
5246 5247 5248 5249 5250

	if (cssid)
		return cssid->id;
	return 0;
}
B
Ben Blum 已提交
5251
EXPORT_SYMBOL_GPL(css_id);
K
KAMEZAWA Hiroyuki 已提交
5252 5253 5254

unsigned short css_depth(struct cgroup_subsys_state *css)
{
5255 5256
	struct css_id *cssid;

5257
	cssid = rcu_dereference_check(css->id, css_refcnt(css));
K
KAMEZAWA Hiroyuki 已提交
5258 5259 5260 5261 5262

	if (cssid)
		return cssid->depth;
	return 0;
}
B
Ben Blum 已提交
5263
EXPORT_SYMBOL_GPL(css_depth);
K
KAMEZAWA Hiroyuki 已提交
5264

5265 5266 5267 5268 5269 5270
/**
 *  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
5271
 * this function reads css->id, the caller must hold rcu_read_lock().
5272 5273 5274 5275 5276 5277
 * 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
5278
bool css_is_ancestor(struct cgroup_subsys_state *child,
5279
		    const struct cgroup_subsys_state *root)
K
KAMEZAWA Hiroyuki 已提交
5280
{
5281 5282
	struct css_id *child_id;
	struct css_id *root_id;
K
KAMEZAWA Hiroyuki 已提交
5283

5284
	child_id  = rcu_dereference(child->id);
5285 5286
	if (!child_id)
		return false;
5287
	root_id = rcu_dereference(root->id);
5288 5289 5290 5291 5292 5293 5294
	if (!root_id)
		return false;
	if (child_id->depth < root_id->depth)
		return false;
	if (child_id->stack[root_id->depth] != root_id->id)
		return false;
	return true;
K
KAMEZAWA Hiroyuki 已提交
5295 5296 5297 5298 5299 5300 5301 5302 5303 5304 5305 5306 5307
}

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);
5308
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5309
	idr_remove(&ss->idr, id->id);
5310
	spin_unlock(&ss->id_lock);
5311
	kfree_rcu(id, rcu_head);
K
KAMEZAWA Hiroyuki 已提交
5312
}
B
Ben Blum 已提交
5313
EXPORT_SYMBOL_GPL(free_css_id);
K
KAMEZAWA Hiroyuki 已提交
5314 5315 5316 5317 5318 5319 5320 5321 5322

/*
 * 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;
T
Tejun Heo 已提交
5323
	int ret, size;
K
KAMEZAWA Hiroyuki 已提交
5324 5325 5326 5327 5328 5329 5330

	BUG_ON(!ss->use_id);

	size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
	newid = kzalloc(size, GFP_KERNEL);
	if (!newid)
		return ERR_PTR(-ENOMEM);
T
Tejun Heo 已提交
5331 5332

	idr_preload(GFP_KERNEL);
5333
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5334
	/* Don't use 0. allocates an ID of 1-65535 */
T
Tejun Heo 已提交
5335
	ret = idr_alloc(&ss->idr, newid, 1, CSS_ID_MAX + 1, GFP_NOWAIT);
5336
	spin_unlock(&ss->id_lock);
T
Tejun Heo 已提交
5337
	idr_preload_end();
K
KAMEZAWA Hiroyuki 已提交
5338 5339

	/* Returns error when there are no free spaces for new ID.*/
T
Tejun Heo 已提交
5340
	if (ret < 0)
K
KAMEZAWA Hiroyuki 已提交
5341 5342
		goto err_out;

T
Tejun Heo 已提交
5343
	newid->id = ret;
K
KAMEZAWA Hiroyuki 已提交
5344 5345 5346 5347
	newid->depth = depth;
	return newid;
err_out:
	kfree(newid);
T
Tejun Heo 已提交
5348
	return ERR_PTR(ret);
K
KAMEZAWA Hiroyuki 已提交
5349 5350 5351

}

5352 5353
static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
					    struct cgroup_subsys_state *rootcss)
K
KAMEZAWA Hiroyuki 已提交
5354 5355 5356
{
	struct css_id *newid;

5357
	spin_lock_init(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374
	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;
5375
	struct css_id *child_id, *parent_id;
K
KAMEZAWA Hiroyuki 已提交
5376 5377 5378 5379 5380

	subsys_id = ss->subsys_id;
	parent_css = parent->subsys[subsys_id];
	child_css = child->subsys[subsys_id];
	parent_id = parent_css->id;
5381
	depth = parent_id->depth + 1;
K
KAMEZAWA Hiroyuki 已提交
5382 5383 5384 5385 5386 5387 5388 5389 5390 5391 5392 5393 5394 5395 5396 5397 5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410 5411 5412 5413 5414 5415 5416 5417 5418

	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
5419
EXPORT_SYMBOL_GPL(css_lookup);
K
KAMEZAWA Hiroyuki 已提交
5420 5421 5422 5423 5424 5425 5426 5427 5428 5429 5430 5431 5432 5433 5434 5435 5436 5437 5438 5439 5440 5441 5442 5443 5444

/**
 * 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);
5445 5446
	WARN_ON_ONCE(!rcu_read_lock_held());

K
KAMEZAWA Hiroyuki 已提交
5447 5448 5449 5450 5451 5452 5453 5454 5455 5456 5457 5458 5459 5460 5461 5462 5463 5464 5465 5466 5467 5468 5469
	/* 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
5470 5471 5472 5473 5474 5475 5476 5477 5478
/*
 * 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;

A
Al Viro 已提交
5479
	inode = file_inode(f);
S
Stephane Eranian 已提交
5480 5481 5482 5483 5484 5485 5486 5487 5488 5489 5490 5491 5492
	/* 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);
}

5493
#ifdef CONFIG_CGROUP_DEBUG
5494
static struct cgroup_subsys_state *debug_css_alloc(struct cgroup *cont)
5495 5496 5497 5498 5499 5500 5501 5502 5503
{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

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

	return css;
}

5504
static void debug_css_free(struct cgroup *cont)
5505 5506 5507 5508 5509 5510 5511 5512 5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528 5529 5530 5531 5532 5533 5534
{
	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;
}

5535 5536 5537 5538 5539 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551 5552
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 = "?";
5553 5554
		seq_printf(seq, "Root %d group %s\n",
			   c->root->hierarchy_id, name);
5555 5556 5557 5558 5559 5560 5561 5562 5563 5564 5565 5566 5567 5568 5569 5570 5571 5572 5573 5574 5575 5576 5577 5578 5579 5580 5581 5582 5583 5584 5585 5586 5587
	}
	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;
}

5588 5589 5590 5591 5592 5593 5594 5595 5596 5597 5598 5599 5600 5601 5602 5603 5604 5605 5606 5607 5608 5609 5610 5611 5612
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,
	},

5613 5614 5615 5616 5617 5618 5619 5620 5621 5622
	{
		.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,
	},

5623 5624 5625 5626 5627
	{
		.name = "releasable",
		.read_u64 = releasable_read,
	},

5628 5629
	{ }	/* terminate */
};
5630 5631 5632

struct cgroup_subsys debug_subsys = {
	.name = "debug",
5633 5634
	.css_alloc = debug_css_alloc,
	.css_free = debug_css_free,
5635
	.subsys_id = debug_subsys_id,
5636
	.base_cftypes = debug_files,
5637 5638
};
#endif /* CONFIG_CGROUP_DEBUG */