cgroup.c 138.0 KB
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/*
 *  Generic process-grouping system.
 *
 *  Based originally on the cpuset system, extracted by Paul Menage
 *  Copyright (C) 2006 Google, Inc
 *
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 *  Notifications support
 *  Copyright (C) 2009 Nokia Corporation
 *  Author: Kirill A. Shutemov
 *
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 *  Copyright notices from the original cpuset code:
 *  --------------------------------------------------
 *  Copyright (C) 2003 BULL SA.
 *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
 *
 *  Portions derived from Patrick Mochel's sysfs code.
 *  sysfs is Copyright (c) 2001-3 Patrick Mochel
 *
 *  2003-10-10 Written by Simon Derr.
 *  2003-10-22 Updates by Stephen Hemminger.
 *  2004 May-July Rework by Paul Jackson.
 *  ---------------------------------------------------
 *
 *  This file is subject to the terms and conditions of the GNU General Public
 *  License.  See the file COPYING in the main directory of the Linux
 *  distribution for more details.
 */

#include <linux/cgroup.h>
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#include <linux/cred.h>
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#include <linux/ctype.h>
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#include <linux/errno.h>
#include <linux/fs.h>
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#include <linux/init_task.h>
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#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
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#include <linux/proc_fs.h>
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#include <linux/rcupdate.h>
#include <linux/sched.h>
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#include <linux/backing-dev.h>
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#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/magic.h>
#include <linux/spinlock.h>
#include <linux/string.h>
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#include <linux/sort.h>
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#include <linux/kmod.h>
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#include <linux/module.h>
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#include <linux/delayacct.h>
#include <linux/cgroupstats.h>
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#include <linux/hash.h>
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#include <linux/namei.h>
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#include <linux/pid_namespace.h>
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#include <linux/idr.h>
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#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
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#include <linux/eventfd.h>
#include <linux/poll.h>
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#include <linux/flex_array.h> /* used in cgroup_attach_proc */
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#include <linux/atomic.h>
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/*
 * cgroup_mutex is the master lock.  Any modification to cgroup or its
 * hierarchy must be performed while holding it.
 *
 * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
 * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
 * release_agent_path and so on.  Modifying requires both cgroup_mutex and
 * cgroup_root_mutex.  Readers can acquire either of the two.  This is to
 * break the following locking order cycle.
 *
 *  A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
 *  B. namespace_sem -> cgroup_mutex
 *
 * B happens only through cgroup_show_options() and using cgroup_root_mutex
 * breaks it.
 */
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static DEFINE_MUTEX(cgroup_mutex);
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static DEFINE_MUTEX(cgroup_root_mutex);
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/*
 * Generate an array of cgroup subsystem pointers. At boot time, this is
 * populated up to CGROUP_BUILTIN_SUBSYS_COUNT, and modular subsystems are
 * registered after that. The mutable section of this array is protected by
 * cgroup_mutex.
 */
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#define SUBSYS(_x) &_x ## _subsys,
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static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
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#include <linux/cgroup_subsys.h>
};

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#define MAX_CGROUP_ROOT_NAMELEN 64

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

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

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

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

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

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

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

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

	/* Hierarchy-specific flags */
	unsigned long flags;
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	/* The path to use for release notifications. */
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	char release_agent_path[PATH_MAX];
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	/* The name for this hierarchy - may be empty */
	char name[MAX_CGROUP_ROOT_NAMELEN];
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};

/*
 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
 * subsystems that are otherwise unattached - it never has more than a
 * single cgroup, and all tasks are part of that cgroup.
 */
static struct cgroupfs_root rootnode;

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/*
 * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
 * cgroup_subsys->use_id != 0.
 */
#define CSS_ID_MAX	(65535)
struct css_id {
	/*
	 * The css to which this ID points. This pointer is set to valid value
	 * after cgroup is populated. If cgroup is removed, this will be NULL.
	 * This pointer is expected to be RCU-safe because destroy()
	 * is called after synchronize_rcu(). But for safe use, css_is_removed()
	 * css_tryget() should be used for avoiding race.
	 */
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	struct cgroup_subsys_state __rcu *css;
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	/*
	 * ID of this css.
	 */
	unsigned short id;
	/*
	 * Depth in hierarchy which this ID belongs to.
	 */
	unsigned short depth;
	/*
	 * ID is freed by RCU. (and lookup routine is RCU safe.)
	 */
	struct rcu_head rcu_head;
	/*
	 * Hierarchy of CSS ID belongs to.
	 */
	unsigned short stack[0]; /* Array of Length (depth+1) */
};

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/*
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 * cgroup_event represents events which userspace want to receive.
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 */
struct cgroup_event {
	/*
	 * Cgroup which the event belongs to.
	 */
	struct cgroup *cgrp;
	/*
	 * Control file which the event associated.
	 */
	struct cftype *cft;
	/*
	 * eventfd to signal userspace about the event.
	 */
	struct eventfd_ctx *eventfd;
	/*
	 * Each of these stored in a list by the cgroup.
	 */
	struct list_head list;
	/*
	 * All fields below needed to unregister event when
	 * userspace closes eventfd.
	 */
	poll_table pt;
	wait_queue_head_t *wqh;
	wait_queue_t wait;
	struct work_struct remove;
};
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/* The list of hierarchy roots */

static LIST_HEAD(roots);
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static int root_count;
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static DEFINE_IDA(hierarchy_ida);
static int next_hierarchy_id;
static DEFINE_SPINLOCK(hierarchy_id_lock);

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/* dummytop is a shorthand for the dummy hierarchy's top cgroup */
#define dummytop (&rootnode.top_cgroup)

/* This flag indicates whether tasks in the fork and exit paths should
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 * check for fork/exit handlers to call. This avoids us having to do
 * extra work in the fork/exit path if none of the subsystems need to
 * be called.
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 */
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static int need_forkexit_callback __read_mostly;
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#ifdef CONFIG_PROVE_LOCKING
int cgroup_lock_is_held(void)
{
	return lockdep_is_held(&cgroup_mutex);
}
#else /* #ifdef CONFIG_PROVE_LOCKING */
int cgroup_lock_is_held(void)
{
	return mutex_is_locked(&cgroup_mutex);
}
#endif /* #else #ifdef CONFIG_PROVE_LOCKING */

EXPORT_SYMBOL_GPL(cgroup_lock_is_held);

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

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

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

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

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

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

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

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/* the list of cgroups eligible for automatic release. Protected by
 * release_list_lock */
static LIST_HEAD(release_list);
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static DEFINE_RAW_SPINLOCK(release_list_lock);
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static void cgroup_release_agent(struct work_struct *work);
static DECLARE_WORK(release_agent_work, cgroup_release_agent);
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static void check_for_release(struct cgroup *cgrp);
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/* Link structure for associating css_set objects with cgroups */
struct cg_cgroup_link {
	/*
	 * List running through cg_cgroup_links associated with a
	 * cgroup, anchored on cgroup->css_sets
	 */
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	struct list_head cgrp_link_list;
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	struct cgroup *cgrp;
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	/*
	 * List running through cg_cgroup_links pointing at a
	 * single css_set object, anchored on css_set->cg_links
	 */
	struct list_head cg_link_list;
	struct css_set *cg;
};

/* The default css_set - used by init and its children prior to any
 * hierarchies being mounted. It contains a pointer to the root state
 * for each subsystem. Also used to anchor the list of css_sets. Not
 * reference-counted, to improve performance when child cgroups
 * haven't been created.
 */

static struct css_set init_css_set;
static struct cg_cgroup_link init_css_set_link;

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static int cgroup_init_idr(struct cgroup_subsys *ss,
			   struct cgroup_subsys_state *css);
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/* css_set_lock protects the list of css_set objects, and the
 * chain of tasks off each css_set.  Nests outside task->alloc_lock
 * due to cgroup_iter_start() */
static DEFINE_RWLOCK(css_set_lock);
static int css_set_count;

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/*
 * hash table for cgroup groups. This improves the performance to find
 * an existing css_set. This hash doesn't (currently) take into
 * account cgroups in empty hierarchies.
 */
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#define CSS_SET_HASH_BITS	7
#define CSS_SET_TABLE_SIZE	(1 << CSS_SET_HASH_BITS)
static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];

static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
{
	int i;
	int index;
	unsigned long tmp = 0UL;

	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
		tmp += (unsigned long)css[i];
	tmp = (tmp >> 16) ^ tmp;

	index = hash_long(tmp, CSS_SET_HASH_BITS);

	return &css_set_table[index];
}

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/* We don't maintain the lists running through each css_set to its
 * task until after the first call to cgroup_iter_start(). This
 * reduces the fork()/exit() overhead for people who have cgroups
 * compiled into their kernel but not actually in use */
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static int use_task_css_set_links __read_mostly;
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static void __put_css_set(struct css_set *cg, int taskexit)
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{
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	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;
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	/*
	 * Ensure that the refcount doesn't hit zero while any readers
	 * can see it. Similar to atomic_dec_and_lock(), but for an
	 * rwlock
	 */
	if (atomic_add_unless(&cg->refcount, -1, 1))
		return;
	write_lock(&css_set_lock);
	if (!atomic_dec_and_test(&cg->refcount)) {
		write_unlock(&css_set_lock);
		return;
	}
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	/* This css_set is dead. unlink it and release cgroup refcounts */
	hlist_del(&cg->hlist);
	css_set_count--;

	list_for_each_entry_safe(link, saved_link, &cg->cg_links,
				 cg_link_list) {
		struct cgroup *cgrp = link->cgrp;
		list_del(&link->cg_link_list);
		list_del(&link->cgrp_link_list);
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		if (atomic_dec_and_test(&cgrp->count) &&
		    notify_on_release(cgrp)) {
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			if (taskexit)
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				set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
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		}
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		kfree(link);
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	}
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	write_unlock(&css_set_lock);
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	kfree_rcu(cg, rcu_head);
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}

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/*
 * refcounted get/put for css_set objects
 */
static inline void get_css_set(struct css_set *cg)
{
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	atomic_inc(&cg->refcount);
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}

static inline void put_css_set(struct css_set *cg)
{
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	__put_css_set(cg, 0);
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}

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static inline void put_css_set_taskexit(struct css_set *cg)
{
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	__put_css_set(cg, 1);
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}

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/*
 * compare_css_sets - helper function for find_existing_css_set().
 * @cg: candidate css_set being tested
 * @old_cg: existing css_set for a task
 * @new_cgrp: cgroup that's being entered by the task
 * @template: desired set of css pointers in css_set (pre-calculated)
 *
 * Returns true if "cg" matches "old_cg" except for the hierarchy
 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
 */
static bool compare_css_sets(struct css_set *cg,
			     struct css_set *old_cg,
			     struct cgroup *new_cgrp,
			     struct cgroup_subsys_state *template[])
{
	struct list_head *l1, *l2;

	if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
		/* Not all subsystems matched */
		return false;
	}

	/*
	 * Compare cgroup pointers in order to distinguish between
	 * different cgroups in heirarchies with no subsystems. We
	 * could get by with just this check alone (and skip the
	 * memcmp above) but on most setups the memcmp check will
	 * avoid the need for this more expensive check on almost all
	 * candidates.
	 */

	l1 = &cg->cg_links;
	l2 = &old_cg->cg_links;
	while (1) {
		struct cg_cgroup_link *cgl1, *cgl2;
		struct cgroup *cg1, *cg2;

		l1 = l1->next;
		l2 = l2->next;
		/* See if we reached the end - both lists are equal length. */
		if (l1 == &cg->cg_links) {
			BUG_ON(l2 != &old_cg->cg_links);
			break;
		} else {
			BUG_ON(l2 == &old_cg->cg_links);
		}
		/* Locate the cgroups associated with these links. */
		cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
		cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
		cg1 = cgl1->cgrp;
		cg2 = cgl2->cgrp;
		/* Hierarchies should be linked in the same order. */
		BUG_ON(cg1->root != cg2->root);

		/*
		 * If this hierarchy is the hierarchy of the cgroup
		 * that's changing, then we need to check that this
		 * css_set points to the new cgroup; if it's any other
		 * hierarchy, then this css_set should point to the
		 * same cgroup as the old css_set.
		 */
		if (cg1->root == new_cgrp->root) {
			if (cg1 != new_cgrp)
				return false;
		} else {
			if (cg1 != cg2)
				return false;
		}
	}
	return true;
}

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/*
 * find_existing_css_set() is a helper for
 * find_css_set(), and checks to see whether an existing
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 * css_set is suitable.
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 *
 * oldcg: the cgroup group that we're using before the cgroup
 * transition
 *
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 * cgrp: the cgroup that we're moving into
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 *
 * template: location in which to build the desired set of subsystem
 * state objects for the new cgroup group
 */
static struct css_set *find_existing_css_set(
	struct css_set *oldcg,
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	struct cgroup *cgrp,
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	struct cgroup_subsys_state *template[])
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{
	int i;
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	struct cgroupfs_root *root = cgrp->root;
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	struct hlist_head *hhead;
	struct hlist_node *node;
	struct css_set *cg;
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	/*
	 * Build the set of subsystem state objects that we want to see in the
	 * new css_set. while subsystems can change globally, the entries here
	 * won't change, so no need for locking.
	 */
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	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
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		if (root->subsys_bits & (1UL << i)) {
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			/* Subsystem is in this hierarchy. So we want
			 * the subsystem state from the new
			 * cgroup */
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			template[i] = cgrp->subsys[i];
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		} else {
			/* Subsystem is not in this hierarchy, so we
			 * don't want to change the subsystem state */
			template[i] = oldcg->subsys[i];
		}
	}

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

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

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

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

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

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

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

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

	struct list_head tmp_cg_links;

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	struct hlist_head *hhead;
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	struct cg_cgroup_link *link;
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	/* First see if we already have a cgroup group that matches
	 * the desired set */
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	read_lock(&css_set_lock);
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	res = find_existing_css_set(oldcg, cgrp, template);
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	if (res)
		get_css_set(res);
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	read_unlock(&css_set_lock);
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	if (res)
		return res;

	res = kmalloc(sizeof(*res), GFP_KERNEL);
	if (!res)
		return NULL;

	/* Allocate all the cg_cgroup_link objects that we'll need */
	if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
		kfree(res);
		return NULL;
	}

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	atomic_set(&res->refcount, 1);
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	INIT_LIST_HEAD(&res->cg_links);
	INIT_LIST_HEAD(&res->tasks);
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	INIT_HLIST_NODE(&res->hlist);
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	/* Copy the set of subsystem state objects generated in
	 * find_existing_css_set() */
	memcpy(res->subsys, template, sizeof(res->subsys));

	write_lock(&css_set_lock);
	/* Add reference counts and links from the new css_set. */
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	list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
		struct cgroup *c = link->cgrp;
		if (c->root == cgrp->root)
			c = cgrp;
		link_css_set(&tmp_cg_links, res, c);
	}
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	BUG_ON(!list_empty(&tmp_cg_links));

	css_set_count++;
657 658 659 660 661

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

662 663 664
	write_unlock(&css_set_lock);

	return res;
665 666
}

667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701
/*
 * Return the cgroup for "task" from the given hierarchy. Must be
 * called with cgroup_mutex held.
 */
static struct cgroup *task_cgroup_from_root(struct task_struct *task,
					    struct cgroupfs_root *root)
{
	struct css_set *css;
	struct cgroup *res = NULL;

	BUG_ON(!mutex_is_locked(&cgroup_mutex));
	read_lock(&css_set_lock);
	/*
	 * No need to lock the task - since we hold cgroup_mutex the
	 * task can't change groups, so the only thing that can happen
	 * is that it exits and its css is set back to init_css_set.
	 */
	css = task->cgroups;
	if (css == &init_css_set) {
		res = &root->top_cgroup;
	} else {
		struct cg_cgroup_link *link;
		list_for_each_entry(link, &css->cg_links, cg_link_list) {
			struct cgroup *c = link->cgrp;
			if (c->root == root) {
				res = c;
				break;
			}
		}
	}
	read_unlock(&css_set_lock);
	BUG_ON(!res);
	return res;
}

702 703 704 705 706 707 708 709 710 711
/*
 * There is one global cgroup mutex. We also require taking
 * task_lock() when dereferencing a task's cgroup subsys pointers.
 * See "The task_lock() exception", at the end of this comment.
 *
 * A task must hold cgroup_mutex to modify cgroups.
 *
 * Any task can increment and decrement the count field without lock.
 * So in general, code holding cgroup_mutex can't rely on the count
 * field not changing.  However, if the count goes to zero, then only
712
 * cgroup_attach_task() can increment it again.  Because a count of zero
713 714 715 716 717 718 719 720 721 722 723 724 725
 * means that no tasks are currently attached, therefore there is no
 * way a task attached to that cgroup can fork (the other way to
 * increment the count).  So code holding cgroup_mutex can safely
 * assume that if the count is zero, it will stay zero. Similarly, if
 * a task holds cgroup_mutex on a cgroup with zero count, it
 * knows that the cgroup won't be removed, as cgroup_rmdir()
 * needs that mutex.
 *
 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
 * (usually) take cgroup_mutex.  These are the two most performance
 * critical pieces of code here.  The exception occurs on cgroup_exit(),
 * when a task in a notify_on_release cgroup exits.  Then cgroup_mutex
 * is taken, and if the cgroup count is zero, a usermode call made
L
Li Zefan 已提交
726 727
 * to the release agent with the name of the cgroup (path relative to
 * the root of cgroup file system) as the argument.
728 729 730 731 732 733 734 735 736 737 738
 *
 * A cgroup can only be deleted if both its 'count' of using tasks
 * is zero, and its list of 'children' cgroups is empty.  Since all
 * tasks in the system use _some_ cgroup, and since there is always at
 * least one task in the system (init, pid == 1), therefore, top_cgroup
 * always has either children cgroups and/or using tasks.  So we don't
 * need a special hack to ensure that top_cgroup cannot be deleted.
 *
 *	The task_lock() exception
 *
 * The need for this exception arises from the action of
739
 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
L
Li Zefan 已提交
740
 * another.  It does so using cgroup_mutex, however there are
741 742 743
 * several performance critical places that need to reference
 * task->cgroup without the expense of grabbing a system global
 * mutex.  Therefore except as noted below, when dereferencing or, as
744
 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
745 746 747 748
 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
 * the task_struct routinely used for such matters.
 *
 * P.S.  One more locking exception.  RCU is used to guard the
749
 * update of a tasks cgroup pointer by cgroup_attach_task()
750 751 752 753 754 755 756 757 758 759
 */

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

/**
 * cgroup_unlock - release lock on cgroup changes
 *
 * Undo the lock taken in a previous cgroup_lock() call.
 */
void cgroup_unlock(void)
{
	mutex_unlock(&cgroup_mutex);
}
B
Ben Blum 已提交
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EXPORT_SYMBOL_GPL(cgroup_unlock);
772 773 774 775 776 777 778 779

/*
 * 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.
 */

780
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
781
static struct dentry *cgroup_lookup(struct inode *, struct dentry *, struct nameidata *);
782
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
783
static int cgroup_populate_dir(struct cgroup *cgrp);
784
static const struct inode_operations cgroup_dir_inode_operations;
785
static const struct file_operations proc_cgroupstats_operations;
786 787

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

K
KAMEZAWA Hiroyuki 已提交
792 793 794
static int alloc_css_id(struct cgroup_subsys *ss,
			struct cgroup *parent, struct cgroup *child);

A
Al Viro 已提交
795
static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
796 797 798 799
{
	struct inode *inode = new_inode(sb);

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

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

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

826
	return ret;
827 828
}

829 830 831 832
static void cgroup_diput(struct dentry *dentry, struct inode *inode)
{
	/* is dentry a directory ? if so, kfree() associated cgroup */
	if (S_ISDIR(inode->i_mode)) {
833
		struct cgroup *cgrp = dentry->d_fsdata;
834
		struct cgroup_subsys *ss;
835
		BUG_ON(!(cgroup_is_removed(cgrp)));
836 837 838 839 840 841 842
		/* It's possible for external users to be holding css
		 * reference counts on a cgroup; css_put() needs to
		 * be able to access the cgroup after decrementing
		 * the reference count in order to know if it needs to
		 * queue the cgroup to be handled by the release
		 * agent */
		synchronize_rcu();
843 844 845 846 847

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

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

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

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

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

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

876 877 878 879 880 881 882 883 884 885 886 887 888 889
static void remove_dir(struct dentry *d)
{
	struct dentry *parent = dget(d->d_parent);

	d_delete(d);
	simple_rmdir(parent->d_inode, d);
	dput(parent);
}

static void cgroup_clear_directory(struct dentry *dentry)
{
	struct list_head *node;

	BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
N
Nick Piggin 已提交
890
	spin_lock(&dentry->d_lock);
891 892 893
	node = dentry->d_subdirs.next;
	while (node != &dentry->d_subdirs) {
		struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
N
Nick Piggin 已提交
894 895

		spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
896 897 898 899 900
		list_del_init(node);
		if (d->d_inode) {
			/* This should never be called on a cgroup
			 * directory with child cgroups */
			BUG_ON(d->d_inode->i_mode & S_IFDIR);
901
			dget_dlock(d);
N
Nick Piggin 已提交
902 903
			spin_unlock(&d->d_lock);
			spin_unlock(&dentry->d_lock);
904 905 906
			d_delete(d);
			simple_unlink(dentry->d_inode, d);
			dput(d);
N
Nick Piggin 已提交
907 908 909
			spin_lock(&dentry->d_lock);
		} else
			spin_unlock(&d->d_lock);
910 911
		node = dentry->d_subdirs.next;
	}
N
Nick Piggin 已提交
912
	spin_unlock(&dentry->d_lock);
913 914 915 916 917 918 919
}

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

922 923
	cgroup_clear_directory(dentry);

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

933 934 935 936 937 938
/*
 * A queue for waiters to do rmdir() cgroup. A tasks will sleep when
 * cgroup->count == 0 && list_empty(&cgroup->children) && subsys has some
 * reference to css->refcnt. In general, this refcnt is expected to goes down
 * to zero, soon.
 *
939
 * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
940
 */
941
static DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
942

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

949 950 951 952 953 954 955 956 957 958 959
void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
{
	css_get(css);
}

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

B
Ben Blum 已提交
960
/*
B
Ben Blum 已提交
961 962 963
 * Call with cgroup_mutex held. Drops reference counts on modules, including
 * any duplicate ones that parse_cgroupfs_options took. If this function
 * returns an error, no reference counts are touched.
B
Ben Blum 已提交
964
 */
965 966 967 968
static int rebind_subsystems(struct cgroupfs_root *root,
			      unsigned long final_bits)
{
	unsigned long added_bits, removed_bits;
969
	struct cgroup *cgrp = &root->top_cgroup;
970 971
	int i;

B
Ben Blum 已提交
972
	BUG_ON(!mutex_is_locked(&cgroup_mutex));
T
Tejun Heo 已提交
973
	BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
B
Ben Blum 已提交
974

975 976 977 978
	removed_bits = root->actual_subsys_bits & ~final_bits;
	added_bits = final_bits & ~root->actual_subsys_bits;
	/* Check that any added subsystems are currently free */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
L
Li Zefan 已提交
979
		unsigned long bit = 1UL << i;
980 981 982
		struct cgroup_subsys *ss = subsys[i];
		if (!(bit & added_bits))
			continue;
B
Ben Blum 已提交
983 984 985 986 987 988
		/*
		 * Nobody should tell us to do a subsys that doesn't exist:
		 * parse_cgroupfs_options should catch that case and refcounts
		 * ensure that subsystems won't disappear once selected.
		 */
		BUG_ON(ss == NULL);
989 990 991 992 993 994 995 996 997 998
		if (ss->root != &rootnode) {
			/* Subsystem isn't free */
			return -EBUSY;
		}
	}

	/* Currently we don't handle adding/removing subsystems when
	 * any child cgroups exist. This is theoretically supportable
	 * but involves complex error handling, so it's being left until
	 * later */
999
	if (root->number_of_cgroups > 1)
1000 1001 1002 1003 1004 1005 1006 1007
		return -EBUSY;

	/* Process each subsystem */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		unsigned long bit = 1UL << i;
		if (bit & added_bits) {
			/* We're binding this subsystem to this hierarchy */
B
Ben Blum 已提交
1008
			BUG_ON(ss == NULL);
1009
			BUG_ON(cgrp->subsys[i]);
1010 1011
			BUG_ON(!dummytop->subsys[i]);
			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1012
			mutex_lock(&ss->hierarchy_mutex);
1013 1014
			cgrp->subsys[i] = dummytop->subsys[i];
			cgrp->subsys[i]->cgroup = cgrp;
1015
			list_move(&ss->sibling, &root->subsys_list);
1016
			ss->root = root;
1017
			if (ss->bind)
1018
				ss->bind(cgrp);
1019
			mutex_unlock(&ss->hierarchy_mutex);
B
Ben Blum 已提交
1020
			/* refcount was already taken, and we're keeping it */
1021 1022
		} else if (bit & removed_bits) {
			/* We're removing this subsystem */
B
Ben Blum 已提交
1023
			BUG_ON(ss == NULL);
1024 1025
			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1026
			mutex_lock(&ss->hierarchy_mutex);
1027
			if (ss->bind)
1028
				ss->bind(dummytop);
1029
			dummytop->subsys[i]->cgroup = dummytop;
1030
			cgrp->subsys[i] = NULL;
1031
			subsys[i]->root = &rootnode;
1032
			list_move(&ss->sibling, &rootnode.subsys_list);
1033
			mutex_unlock(&ss->hierarchy_mutex);
B
Ben Blum 已提交
1034 1035
			/* subsystem is now free - drop reference on module */
			module_put(ss->module);
1036 1037
		} else if (bit & final_bits) {
			/* Subsystem state should already exist */
B
Ben Blum 已提交
1038
			BUG_ON(ss == NULL);
1039
			BUG_ON(!cgrp->subsys[i]);
B
Ben Blum 已提交
1040 1041 1042 1043 1044 1045 1046 1047
			/*
			 * a refcount was taken, but we already had one, so
			 * drop the extra reference.
			 */
			module_put(ss->module);
#ifdef CONFIG_MODULE_UNLOAD
			BUG_ON(ss->module && !module_refcount(ss->module));
#endif
1048 1049
		} else {
			/* Subsystem state shouldn't exist */
1050
			BUG_ON(cgrp->subsys[i]);
1051 1052 1053 1054 1055 1056 1057 1058
		}
	}
	root->subsys_bits = root->actual_subsys_bits = final_bits;
	synchronize_rcu();

	return 0;
}

1059
static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1060
{
1061
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1062 1063
	struct cgroup_subsys *ss;

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

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

	struct cgroupfs_root *new_root;
1089

1090 1091
};

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

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

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

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

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
1117
		if (!strcmp(token, "none")) {
1118 1119
			/* Explicitly have no subsystems */
			opts->none = true;
1120 1121 1122 1123 1124 1125 1126 1127 1128 1129
			continue;
		}
		if (!strcmp(token, "all")) {
			/* Mutually exclusive option 'all' + subsystem name */
			if (one_ss)
				return -EINVAL;
			all_ss = true;
			continue;
		}
		if (!strcmp(token, "noprefix")) {
1130
			set_bit(ROOT_NOPREFIX, &opts->flags);
1131 1132 1133
			continue;
		}
		if (!strcmp(token, "clone_children")) {
1134
			opts->clone_children = true;
1135 1136 1137
			continue;
		}
		if (!strncmp(token, "release_agent=", 14)) {
1138 1139 1140
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1141
			opts->release_agent =
1142
				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1143 1144
			if (!opts->release_agent)
				return -ENOMEM;
1145 1146 1147
			continue;
		}
		if (!strncmp(token, "name=", 5)) {
1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164
			const char *name = token + 5;
			/* Can't specify an empty name */
			if (!strlen(name))
				return -EINVAL;
			/* Must match [\w.-]+ */
			for (i = 0; i < strlen(name); i++) {
				char c = name[i];
				if (isalnum(c))
					continue;
				if ((c == '.') || (c == '-') || (c == '_'))
					continue;
				return -EINVAL;
			}
			/* Specifying two names is forbidden */
			if (opts->name)
				return -EINVAL;
			opts->name = kstrndup(name,
1165
					      MAX_CGROUP_ROOT_NAMELEN - 1,
1166 1167 1168
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195

			continue;
		}

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

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

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

	/*
	 * If the 'all' option was specified select all the subsystems,
1196 1197
	 * otherwise if 'none', 'name=' and a subsystem name options
	 * were not specified, let's default to 'all'
1198
	 */
1199
	if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1200 1201 1202 1203 1204 1205 1206
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss == NULL)
				continue;
			if (ss->disabled)
				continue;
			set_bit(i, &opts->subsys_bits);
1207 1208 1209
		}
	}

1210 1211
	/* Consistency checks */

1212 1213 1214 1215 1216 1217 1218 1219 1220
	/*
	 * Option noprefix was introduced just for backward compatibility
	 * with the old cpuset, so we allow noprefix only if mounting just
	 * the cpuset subsystem.
	 */
	if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
	    (opts->subsys_bits & mask))
		return -EINVAL;

1221 1222 1223 1224 1225 1226 1227 1228 1229

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

	/*
	 * We either have to specify by name or by subsystems. (So all
	 * empty hierarchies must have a name).
	 */
1230
	if (!opts->subsys_bits && !opts->name)
1231 1232
		return -EINVAL;

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

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

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

1266 1267 1268
	return 0;
}

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

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

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

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

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

1297 1298 1299 1300 1301
	/* See feature-removal-schedule.txt */
	if (opts.subsys_bits != root->actual_subsys_bits || opts.release_agent)
		pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
			   task_tgid_nr(current), current->comm);

B
Ben Blum 已提交
1302 1303 1304
	/* Don't allow flags or name to change at remount */
	if (opts.flags != root->flags ||
	    (opts.name && strcmp(opts.name, root->name))) {
1305
		ret = -EINVAL;
B
Ben Blum 已提交
1306
		drop_parsed_module_refcounts(opts.subsys_bits);
1307 1308 1309
		goto out_unlock;
	}

1310
	ret = rebind_subsystems(root, opts.subsys_bits);
B
Ben Blum 已提交
1311 1312
	if (ret) {
		drop_parsed_module_refcounts(opts.subsys_bits);
1313
		goto out_unlock;
B
Ben Blum 已提交
1314
	}
1315

1316 1317
	/* clear out any existing files and repopulate subsystem files */
	cgroup_clear_directory(cgrp->dentry);
1318
	cgroup_populate_dir(cgrp);
1319

1320 1321
	if (opts.release_agent)
		strcpy(root->release_agent_path, opts.release_agent);
1322
 out_unlock:
1323
	kfree(opts.release_agent);
1324
	kfree(opts.name);
T
Tejun Heo 已提交
1325
	mutex_unlock(&cgroup_root_mutex);
1326
	mutex_unlock(&cgroup_mutex);
1327
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1328 1329 1330
	return ret;
}

1331
static const struct super_operations cgroup_ops = {
1332 1333 1334 1335 1336 1337
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.show_options = cgroup_show_options,
	.remount_fs = cgroup_remount,
};

1338 1339 1340 1341 1342 1343
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
	INIT_LIST_HEAD(&cgrp->sibling);
	INIT_LIST_HEAD(&cgrp->children);
	INIT_LIST_HEAD(&cgrp->css_sets);
	INIT_LIST_HEAD(&cgrp->release_list);
1344 1345
	INIT_LIST_HEAD(&cgrp->pidlists);
	mutex_init(&cgrp->pidlist_mutex);
1346 1347
	INIT_LIST_HEAD(&cgrp->event_list);
	spin_lock_init(&cgrp->event_list_lock);
1348
}
1349

1350 1351
static void init_cgroup_root(struct cgroupfs_root *root)
{
1352
	struct cgroup *cgrp = &root->top_cgroup;
1353 1354 1355
	INIT_LIST_HEAD(&root->subsys_list);
	INIT_LIST_HEAD(&root->root_list);
	root->number_of_cgroups = 1;
1356 1357
	cgrp->root = root;
	cgrp->top_cgroup = cgrp;
1358
	init_cgroup_housekeeping(cgrp);
1359 1360
}

1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385
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;
}

1386 1387
static int cgroup_test_super(struct super_block *sb, void *data)
{
1388
	struct cgroup_sb_opts *opts = data;
1389 1390
	struct cgroupfs_root *root = sb->s_fs_info;

1391 1392 1393
	/* If we asked for a name then it must match */
	if (opts->name && strcmp(opts->name, root->name))
		return 0;
1394

1395 1396 1397 1398 1399 1400
	/*
	 * If we asked for subsystems (or explicitly for no
	 * subsystems) then they must match
	 */
	if ((opts->subsys_bits || opts->none)
	    && (opts->subsys_bits != root->subsys_bits))
1401 1402 1403 1404 1405
		return 0;

	return 1;
}

1406 1407 1408 1409
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
	struct cgroupfs_root *root;

1410
	if (!opts->subsys_bits && !opts->none)
1411 1412 1413 1414 1415 1416
		return NULL;

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

1417 1418 1419 1420
	if (!init_root_id(root)) {
		kfree(root);
		return ERR_PTR(-ENOMEM);
	}
1421
	init_cgroup_root(root);
1422

1423 1424 1425 1426 1427 1428
	root->subsys_bits = opts->subsys_bits;
	root->flags = opts->flags;
	if (opts->release_agent)
		strcpy(root->release_agent_path, opts->release_agent);
	if (opts->name)
		strcpy(root->name, opts->name);
1429 1430
	if (opts->clone_children)
		set_bit(CGRP_CLONE_CHILDREN, &root->top_cgroup.flags);
1431 1432 1433
	return root;
}

1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445
static void cgroup_drop_root(struct cgroupfs_root *root)
{
	if (!root)
		return;

	BUG_ON(!root->hierarchy_id);
	spin_lock(&hierarchy_id_lock);
	ida_remove(&hierarchy_ida, root->hierarchy_id);
	spin_unlock(&hierarchy_id_lock);
	kfree(root);
}

1446 1447 1448
static int cgroup_set_super(struct super_block *sb, void *data)
{
	int ret;
1449 1450 1451 1452 1453 1454
	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;

1455
	BUG_ON(!opts->subsys_bits && !opts->none);
1456 1457 1458 1459 1460

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

1461 1462
	sb->s_fs_info = opts->new_root;
	opts->new_root->sb = sb;
1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473

	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
1474 1475
	static const struct dentry_operations cgroup_dops = {
		.d_iput = cgroup_diput,
1476
		.d_delete = cgroup_delete,
A
Al Viro 已提交
1477 1478
	};

1479 1480 1481 1482 1483 1484 1485 1486 1487 1488
	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);
1489 1490
	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
1491
		return -ENOMEM;
A
Al Viro 已提交
1492 1493
	/* for everything else we want ->d_op set */
	sb->s_d_op = &cgroup_dops;
1494 1495 1496
	return 0;
}

A
Al Viro 已提交
1497
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1498
			 int flags, const char *unused_dev_name,
A
Al Viro 已提交
1499
			 void *data)
1500 1501
{
	struct cgroup_sb_opts opts;
1502
	struct cgroupfs_root *root;
1503 1504
	int ret = 0;
	struct super_block *sb;
1505
	struct cgroupfs_root *new_root;
T
Tejun Heo 已提交
1506
	struct inode *inode;
1507 1508

	/* First find the desired set of subsystems */
B
Ben Blum 已提交
1509
	mutex_lock(&cgroup_mutex);
1510
	ret = parse_cgroupfs_options(data, &opts);
B
Ben Blum 已提交
1511
	mutex_unlock(&cgroup_mutex);
1512 1513
	if (ret)
		goto out_err;
1514

1515 1516 1517 1518 1519 1520 1521
	/*
	 * 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
1522
		goto drop_modules;
1523
	}
1524
	opts.new_root = new_root;
1525

1526 1527
	/* Locate an existing or new sb for this hierarchy */
	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, &opts);
1528
	if (IS_ERR(sb)) {
1529
		ret = PTR_ERR(sb);
1530
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1531
		goto drop_modules;
1532 1533
	}

1534 1535 1536 1537 1538
	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;
1539
		struct cgroup *root_cgrp = &root->top_cgroup;
1540
		struct cgroupfs_root *existing_root;
1541
		const struct cred *cred;
1542
		int i;
1543 1544 1545 1546 1547 1548

		BUG_ON(sb->s_root != NULL);

		ret = cgroup_get_rootdir(sb);
		if (ret)
			goto drop_new_super;
1549
		inode = sb->s_root->d_inode;
1550

1551
		mutex_lock(&inode->i_mutex);
1552
		mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1553
		mutex_lock(&cgroup_root_mutex);
1554

T
Tejun Heo 已提交
1555 1556 1557 1558 1559 1560
		/* 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;
1561

1562 1563 1564 1565 1566 1567 1568 1569
		/*
		 * 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
1570 1571
		if (ret)
			goto unlock_drop;
1572

1573 1574
		ret = rebind_subsystems(root, root->subsys_bits);
		if (ret == -EBUSY) {
1575
			free_cg_links(&tmp_cg_links);
T
Tejun Heo 已提交
1576
			goto unlock_drop;
1577
		}
B
Ben Blum 已提交
1578 1579 1580 1581 1582
		/*
		 * There must be no failure case after here, since rebinding
		 * takes care of subsystems' refcounts, which are explicitly
		 * dropped in the failure exit path.
		 */
1583 1584 1585 1586 1587

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

		list_add(&root->root_list, &roots);
1588
		root_count++;
1589

1590
		sb->s_root->d_fsdata = root_cgrp;
1591 1592
		root->top_cgroup.dentry = sb->s_root;

1593 1594 1595
		/* Link the top cgroup in this hierarchy into all
		 * the css_set objects */
		write_lock(&css_set_lock);
1596 1597 1598
		for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
			struct hlist_head *hhead = &css_set_table[i];
			struct hlist_node *node;
1599
			struct css_set *cg;
1600

1601 1602
			hlist_for_each_entry(cg, node, hhead, hlist)
				link_css_set(&tmp_cg_links, cg, root_cgrp);
1603
		}
1604 1605 1606 1607
		write_unlock(&css_set_lock);

		free_cg_links(&tmp_cg_links);

1608 1609
		BUG_ON(!list_empty(&root_cgrp->sibling));
		BUG_ON(!list_empty(&root_cgrp->children));
1610 1611
		BUG_ON(root->number_of_cgroups != 1);

1612
		cred = override_creds(&init_cred);
1613
		cgroup_populate_dir(root_cgrp);
1614
		revert_creds(cred);
T
Tejun Heo 已提交
1615
		mutex_unlock(&cgroup_root_mutex);
1616
		mutex_unlock(&cgroup_mutex);
1617
		mutex_unlock(&inode->i_mutex);
1618 1619 1620 1621 1622
	} else {
		/*
		 * We re-used an existing hierarchy - the new root (if
		 * any) is not needed
		 */
1623
		cgroup_drop_root(opts.new_root);
B
Ben Blum 已提交
1624 1625
		/* no subsys rebinding, so refcounts don't change */
		drop_parsed_module_refcounts(opts.subsys_bits);
1626 1627
	}

1628 1629
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1630
	return dget(sb->s_root);
1631

T
Tejun Heo 已提交
1632 1633 1634 1635
 unlock_drop:
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&inode->i_mutex);
1636
 drop_new_super:
1637
	deactivate_locked_super(sb);
B
Ben Blum 已提交
1638 1639
 drop_modules:
	drop_parsed_module_refcounts(opts.subsys_bits);
1640 1641 1642
 out_err:
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1643
	return ERR_PTR(ret);
1644 1645 1646 1647
}

static void cgroup_kill_sb(struct super_block *sb) {
	struct cgroupfs_root *root = sb->s_fs_info;
1648
	struct cgroup *cgrp = &root->top_cgroup;
1649
	int ret;
K
KOSAKI Motohiro 已提交
1650 1651
	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;
1652 1653 1654 1655

	BUG_ON(!root);

	BUG_ON(root->number_of_cgroups != 1);
1656 1657
	BUG_ON(!list_empty(&cgrp->children));
	BUG_ON(!list_empty(&cgrp->sibling));
1658 1659

	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1660
	mutex_lock(&cgroup_root_mutex);
1661 1662 1663 1664 1665 1666

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

1667 1668 1669 1670 1671
	/*
	 * Release all the links from css_sets to this hierarchy's
	 * root cgroup
	 */
	write_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
1672 1673 1674

	list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
				 cgrp_link_list) {
1675
		list_del(&link->cg_link_list);
1676
		list_del(&link->cgrp_link_list);
1677 1678 1679 1680
		kfree(link);
	}
	write_unlock(&css_set_lock);

1681 1682 1683 1684
	if (!list_empty(&root->root_list)) {
		list_del(&root->root_list);
		root_count--;
	}
1685

T
Tejun Heo 已提交
1686
	mutex_unlock(&cgroup_root_mutex);
1687 1688 1689
	mutex_unlock(&cgroup_mutex);

	kill_litter_super(sb);
1690
	cgroup_drop_root(root);
1691 1692 1693 1694
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
A
Al Viro 已提交
1695
	.mount = cgroup_mount,
1696 1697 1698
	.kill_sb = cgroup_kill_sb,
};

1699 1700
static struct kobject *cgroup_kobj;

1701
static inline struct cgroup *__d_cgrp(struct dentry *dentry)
1702 1703 1704 1705 1706 1707 1708 1709 1710
{
	return dentry->d_fsdata;
}

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

L
Li Zefan 已提交
1711 1712 1713 1714 1715 1716
/**
 * 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
 *
1717 1718 1719
 * 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.
1720
 */
1721
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1722 1723
{
	char *start;
1724 1725
	struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
						      cgroup_lock_is_held());
1726

1727
	if (!dentry || cgrp == dummytop) {
1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739
		/*
		 * Inactive subsystems have no dentry for their root
		 * cgroup
		 */
		strcpy(buf, "/");
		return 0;
	}

	start = buf + buflen;

	*--start = '\0';
	for (;;) {
1740
		int len = dentry->d_name.len;
1741

1742 1743
		if ((start -= len) < buf)
			return -ENAMETOOLONG;
1744
		memcpy(start, dentry->d_name.name, len);
1745 1746
		cgrp = cgrp->parent;
		if (!cgrp)
1747
			break;
1748 1749 1750

		dentry = rcu_dereference_check(cgrp->dentry,
					       cgroup_lock_is_held());
1751
		if (!cgrp->parent)
1752 1753 1754 1755 1756 1757 1758 1759
			continue;
		if (--start < buf)
			return -ENAMETOOLONG;
		*start = '/';
	}
	memmove(buf, start, buf + buflen - start);
	return 0;
}
B
Ben Blum 已提交
1760
EXPORT_SYMBOL_GPL(cgroup_path);
1761

1762 1763 1764
/*
 * Control Group taskset
 */
1765 1766 1767
struct task_and_cgroup {
	struct task_struct	*task;
	struct cgroup		*cgrp;
1768
	struct css_set		*cg;
1769 1770
};

1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841
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
1842 1843 1844 1845 1846
/*
 * cgroup_task_migrate - move a task from one cgroup to another.
 *
 * 'guarantee' is set if the caller promises that a new css_set for the task
 * will already exist. If not set, this function might sleep, and can fail with
1847
 * -ENOMEM. Must be called with cgroup_mutex and threadgroup locked.
B
Ben Blum 已提交
1848
 */
1849 1850
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
1851 1852 1853 1854
{
	struct css_set *oldcg;

	/*
1855 1856 1857
	 * 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
1858
	 */
1859
	WARN_ON_ONCE(tsk->flags & PF_EXITING);
B
Ben Blum 已提交
1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881
	oldcg = tsk->cgroups;

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

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

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

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

L
Li Zefan 已提交
1882 1883 1884 1885
/**
 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
 * @cgrp: the cgroup the task is attaching to
 * @tsk: the task to be attached
1886
 *
1887 1888
 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
 * @tsk during call.
1889
 */
1890
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1891
{
1892
	int retval = 0;
1893
	struct cgroup_subsys *ss, *failed_ss = NULL;
1894 1895
	struct cgroup *oldcgrp;
	struct cgroupfs_root *root = cgrp->root;
1896
	struct cgroup_taskset tset = { };
1897
	struct css_set *newcg;
1898

1899 1900 1901
	/* @tsk either already exited or can't exit until the end */
	if (tsk->flags & PF_EXITING)
		return -ESRCH;
1902 1903

	/* Nothing to do if the task is already in that cgroup */
1904
	oldcgrp = task_cgroup_from_root(tsk, root);
1905
	if (cgrp == oldcgrp)
1906 1907
		return 0;

1908 1909 1910
	tset.single.task = tsk;
	tset.single.cgrp = oldcgrp;

1911 1912
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
1913
			retval = ss->can_attach(cgrp, &tset);
1914 1915 1916 1917 1918 1919 1920 1921 1922 1923
			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;
			}
1924 1925 1926
		}
	}

1927 1928 1929
	newcg = find_css_set(tsk->cgroups, cgrp);
	if (!newcg) {
		retval = -ENOMEM;
1930
		goto out;
1931 1932 1933
	}

	cgroup_task_migrate(cgrp, oldcgrp, tsk, newcg);
1934

1935
	for_each_subsys(root, ss) {
P
Paul Jackson 已提交
1936
		if (ss->attach)
1937
			ss->attach(cgrp, &tset);
1938
	}
B
Ben Blum 已提交
1939

1940
	synchronize_rcu();
1941 1942 1943 1944 1945

	/*
	 * wake up rmdir() waiter. the rmdir should fail since the cgroup
	 * is no longer empty.
	 */
1946
	cgroup_wakeup_rmdir_waiter(cgrp);
1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958
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)
1959
				ss->cancel_attach(cgrp, &tset);
1960 1961 1962
		}
	}
	return retval;
1963 1964
}

1965
/**
M
Michael S. Tsirkin 已提交
1966 1967
 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
 * @from: attach to all cgroups of a given task
1968 1969
 * @tsk: the task to be attached
 */
M
Michael S. Tsirkin 已提交
1970
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
1971 1972 1973 1974 1975 1976
{
	struct cgroupfs_root *root;
	int retval = 0;

	cgroup_lock();
	for_each_active_root(root) {
M
Michael S. Tsirkin 已提交
1977 1978 1979
		struct cgroup *from_cg = task_cgroup_from_root(from, root);

		retval = cgroup_attach_task(from_cg, tsk);
1980 1981 1982 1983 1984 1985 1986
		if (retval)
			break;
	}
	cgroup_unlock();

	return retval;
}
M
Michael S. Tsirkin 已提交
1987
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
1988

B
Ben Blum 已提交
1989 1990 1991 1992 1993
/**
 * 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
 *
1994 1995
 * 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
1996
 */
1997
static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
B
Ben Blum 已提交
1998 1999 2000 2001 2002 2003 2004
{
	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;
2005
	struct task_and_cgroup *tc;
2006
	struct flex_array *group;
2007
	struct cgroup_taskset tset = { };
B
Ben Blum 已提交
2008 2009 2010 2011 2012

	/*
	 * 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
2013 2014
	 * 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
2015 2016
	 */
	group_size = get_nr_threads(leader);
2017
	/* flex_array supports very large thread-groups better than kmalloc. */
2018
	group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
B
Ben Blum 已提交
2019 2020
	if (!group)
		return -ENOMEM;
2021 2022 2023 2024
	/* 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
2025 2026 2027

	tsk = leader;
	i = 0;
2028 2029 2030 2031 2032 2033
	/*
	 * 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
2034
	do {
2035 2036
		struct task_and_cgroup ent;

2037 2038 2039 2040
		/* @tsk either already exited or can't exit until the end */
		if (tsk->flags & PF_EXITING)
			continue;

B
Ben Blum 已提交
2041 2042
		/* as per above, nr_threads may decrease, but not increase. */
		BUG_ON(i >= group_size);
2043 2044
		ent.task = tsk;
		ent.cgrp = task_cgroup_from_root(tsk, root);
2045 2046 2047
		/* nothing to do if this task is already in the cgroup */
		if (ent.cgrp == cgrp)
			continue;
2048 2049 2050 2051
		/*
		 * saying GFP_ATOMIC has no effect here because we did prealloc
		 * earlier, but it's good form to communicate our expectations.
		 */
2052
		retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2053
		BUG_ON(retval != 0);
B
Ben Blum 已提交
2054 2055
		i++;
	} while_each_thread(leader, tsk);
2056
	rcu_read_unlock();
B
Ben Blum 已提交
2057 2058
	/* remember the number of threads in the array for later. */
	group_size = i;
2059 2060
	tset.tc_array = group;
	tset.tc_array_len = group_size;
B
Ben Blum 已提交
2061

2062 2063
	/* methods shouldn't be called if no task is actually migrating */
	retval = 0;
2064
	if (!group_size)
2065
		goto out_free_group_list;
2066

B
Ben Blum 已提交
2067 2068 2069 2070 2071
	/*
	 * step 1: check that we can legitimately attach to the cgroup.
	 */
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
2072
			retval = ss->can_attach(cgrp, &tset);
B
Ben Blum 已提交
2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084
			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++) {
2085
		tc = flex_array_get(group, i);
2086 2087 2088 2089
		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
2090 2091 2092 2093
		}
	}

	/*
2094 2095 2096
	 * 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
2097 2098
	 */
	for (i = 0; i < group_size; i++) {
2099
		tc = flex_array_get(group, i);
2100
		cgroup_task_migrate(cgrp, tc->cgrp, tc->task, tc->cg);
B
Ben Blum 已提交
2101 2102 2103 2104
	}
	/* nothing is sensitive to fork() after this point. */

	/*
2105
	 * step 4: do subsystem attach callbacks.
B
Ben Blum 已提交
2106 2107 2108
	 */
	for_each_subsys(root, ss) {
		if (ss->attach)
2109
			ss->attach(cgrp, &tset);
B
Ben Blum 已提交
2110 2111 2112 2113 2114 2115 2116 2117
	}

	/*
	 * step 5: success! and cleanup
	 */
	synchronize_rcu();
	cgroup_wakeup_rmdir_waiter(cgrp);
	retval = 0;
2118 2119 2120 2121 2122 2123 2124 2125
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
2126 2127 2128 2129
	}
out_cancel_attach:
	if (retval) {
		for_each_subsys(root, ss) {
2130
			if (ss == failed_ss)
B
Ben Blum 已提交
2131 2132
				break;
			if (ss->cancel_attach)
2133
				ss->cancel_attach(cgrp, &tset);
B
Ben Blum 已提交
2134 2135 2136
		}
	}
out_free_group_list:
2137
	flex_array_free(group);
B
Ben Blum 已提交
2138 2139 2140 2141 2142
	return retval;
}

/*
 * Find the task_struct of the task to attach by vpid and pass it along to the
2143 2144
 * function to attach either it or all tasks in its threadgroup. Will lock
 * cgroup_mutex and threadgroup; may take task_lock of task.
2145
 */
B
Ben Blum 已提交
2146
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2147 2148
{
	struct task_struct *tsk;
2149
	const struct cred *cred = current_cred(), *tcred;
2150 2151
	int ret;

B
Ben Blum 已提交
2152 2153 2154
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;

2155 2156
retry_find_task:
	rcu_read_lock();
2157
	if (pid) {
2158
		tsk = find_task_by_vpid(pid);
B
Ben Blum 已提交
2159 2160
		if (!tsk) {
			rcu_read_unlock();
2161 2162
			ret= -ESRCH;
			goto out_unlock_cgroup;
2163
		}
B
Ben Blum 已提交
2164 2165 2166 2167
		/*
		 * even if we're attaching all tasks in the thread group, we
		 * only need to check permissions on one of them.
		 */
2168 2169 2170 2171 2172
		tcred = __task_cred(tsk);
		if (cred->euid &&
		    cred->euid != tcred->uid &&
		    cred->euid != tcred->suid) {
			rcu_read_unlock();
2173 2174
			ret = -EACCES;
			goto out_unlock_cgroup;
2175
		}
2176 2177
	} else
		tsk = current;
2178 2179

	if (threadgroup)
2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197
		tsk = tsk->group_leader;
	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
2198
		ret = cgroup_attach_proc(cgrp, tsk);
2199
	} else
B
Ben Blum 已提交
2200
		ret = cgroup_attach_task(cgrp, tsk);
2201 2202
	threadgroup_unlock(tsk);

2203
	put_task_struct(tsk);
2204
out_unlock_cgroup:
B
Ben Blum 已提交
2205
	cgroup_unlock();
2206 2207 2208
	return ret;
}

2209
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
B
Ben Blum 已提交
2210 2211 2212 2213 2214
{
	return attach_task_by_pid(cgrp, pid, false);
}

static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2215
{
2216
	return attach_task_by_pid(cgrp, tgid, true);
2217 2218
}

2219 2220 2221 2222
/**
 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
 * @cgrp: the cgroup to be checked for liveness
 *
2223 2224
 * On success, returns true; the lock should be later released with
 * cgroup_unlock(). On failure returns false with no lock held.
2225
 */
2226
bool cgroup_lock_live_group(struct cgroup *cgrp)
2227 2228 2229 2230 2231 2232 2233 2234
{
	mutex_lock(&cgroup_mutex);
	if (cgroup_is_removed(cgrp)) {
		mutex_unlock(&cgroup_mutex);
		return false;
	}
	return true;
}
B
Ben Blum 已提交
2235
EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2236 2237 2238 2239 2240

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);
2241 2242
	if (strlen(buffer) >= PATH_MAX)
		return -EINVAL;
2243 2244
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
T
Tejun Heo 已提交
2245
	mutex_lock(&cgroup_root_mutex);
2246
	strcpy(cgrp->root->release_agent_path, buffer);
T
Tejun Heo 已提交
2247
	mutex_unlock(&cgroup_root_mutex);
2248
	cgroup_unlock();
2249 2250 2251 2252 2253 2254 2255 2256 2257 2258
	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');
2259
	cgroup_unlock();
2260 2261 2262
	return 0;
}

2263 2264 2265
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64

2266
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2267 2268 2269
				struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *unused_ppos)
2270
{
2271
	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282
	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 */
2283
	if (cft->write_u64) {
K
KOSAKI Motohiro 已提交
2284
		u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2285 2286 2287 2288
		if (*end)
			return -EINVAL;
		retval = cft->write_u64(cgrp, cft, val);
	} else {
K
KOSAKI Motohiro 已提交
2289
		s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2290 2291 2292 2293
		if (*end)
			return -EINVAL;
		retval = cft->write_s64(cgrp, cft, val);
	}
2294 2295 2296 2297 2298
	if (!retval)
		retval = nbytes;
	return retval;
}

2299 2300 2301 2302 2303
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)
{
2304
	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318
	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
2319 2320 2321 2322
	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
		retval = -EFAULT;
		goto out;
	}
2323 2324

	buffer[nbytes] = 0;     /* nul-terminate */
K
KOSAKI Motohiro 已提交
2325
	retval = cft->write_string(cgrp, cft, strstrip(buffer));
2326 2327
	if (!retval)
		retval = nbytes;
L
Li Zefan 已提交
2328
out:
2329 2330 2331 2332 2333
	if (buffer != local_buffer)
		kfree(buffer);
	return retval;
}

2334 2335 2336 2337
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);
2338
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2339

2340
	if (cgroup_is_removed(cgrp))
2341
		return -ENODEV;
2342
	if (cft->write)
2343
		return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2344 2345
	if (cft->write_u64 || cft->write_s64)
		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2346 2347
	if (cft->write_string)
		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2348 2349 2350 2351
	if (cft->trigger) {
		int ret = cft->trigger(cgrp, (unsigned int)cft->private);
		return ret ? ret : nbytes;
	}
2352
	return -EINVAL;
2353 2354
}

2355 2356 2357 2358
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
2359
{
2360
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2361
	u64 val = cft->read_u64(cgrp, cft);
2362 2363 2364 2365 2366
	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);

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

2367 2368 2369 2370 2371
static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
{
2372
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2373 2374 2375 2376 2377 2378
	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);
}

2379 2380 2381 2382
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);
2383
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2384

2385
	if (cgroup_is_removed(cgrp))
2386 2387 2388
		return -ENODEV;

	if (cft->read)
2389
		return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2390 2391
	if (cft->read_u64)
		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2392 2393
	if (cft->read_s64)
		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2394 2395 2396
	return -EINVAL;
}

2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416
/*
 * 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;
2417 2418 2419 2420 2421 2422 2423 2424
	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);
2425 2426
}

2427
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2428 2429 2430 2431 2432 2433
{
	struct seq_file *seq = file->private_data;
	kfree(seq->private);
	return single_release(inode, file);
}

2434
static const struct file_operations cgroup_seqfile_operations = {
2435
	.read = seq_read,
2436
	.write = cgroup_file_write,
2437 2438 2439 2440
	.llseek = seq_lseek,
	.release = cgroup_seqfile_release,
};

2441 2442 2443 2444 2445 2446 2447 2448 2449
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);
2450

2451
	if (cft->read_map || cft->read_seq_string) {
2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462
		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)
2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492
		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);
}

2493
static const struct file_operations cgroup_file_operations = {
2494 2495 2496 2497 2498 2499 2500
	.read = cgroup_file_read,
	.write = cgroup_file_write,
	.llseek = generic_file_llseek,
	.open = cgroup_file_open,
	.release = cgroup_file_release,
};

2501
static const struct inode_operations cgroup_dir_inode_operations = {
2502
	.lookup = cgroup_lookup,
2503 2504 2505 2506 2507
	.mkdir = cgroup_mkdir,
	.rmdir = cgroup_rmdir,
	.rename = cgroup_rename,
};

2508 2509 2510 2511 2512 2513 2514 2515
static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
	d_add(dentry, NULL);
	return NULL;
}

2516 2517 2518 2519 2520 2521 2522 2523 2524 2525
/*
 * Check if a file is a control file
 */
static inline struct cftype *__file_cft(struct file *file)
{
	if (file->f_dentry->d_inode->i_fop != &cgroup_file_operations)
		return ERR_PTR(-EINVAL);
	return __d_cft(file->f_dentry);
}

A
Al Viro 已提交
2526
static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2527 2528
				struct super_block *sb)
{
2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546 2547 2548
	struct inode *inode;

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

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

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

		/* start off with i_nlink == 2 (for "." entry) */
		inc_nlink(inode);

		/* start with the directory inode held, so that we can
		 * populate it without racing with another mkdir */
2549
		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
2550 2551 2552 2553 2554 2555 2556 2557 2558 2559
	} else if (S_ISREG(mode)) {
		inode->i_size = 0;
		inode->i_fop = &cgroup_file_operations;
	}
	d_instantiate(dentry, inode);
	dget(dentry);	/* Extra count - pin the dentry in core */
	return 0;
}

/*
L
Li Zefan 已提交
2560 2561 2562 2563 2564
 * cgroup_create_dir - create a directory for an object.
 * @cgrp: the cgroup we create the directory for. It must have a valid
 *        ->parent field. And we are going to fill its ->dentry field.
 * @dentry: dentry of the new cgroup
 * @mode: mode to set on new directory.
2565
 */
2566
static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
A
Al Viro 已提交
2567
				umode_t mode)
2568 2569 2570 2571
{
	struct dentry *parent;
	int error = 0;

2572 2573
	parent = cgrp->parent->dentry;
	error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
2574
	if (!error) {
2575
		dentry->d_fsdata = cgrp;
2576
		inc_nlink(parent->d_inode);
2577
		rcu_assign_pointer(cgrp->dentry, dentry);
2578 2579 2580 2581 2582 2583 2584
		dget(dentry);
	}
	dput(dentry);

	return error;
}

L
Li Zefan 已提交
2585 2586 2587 2588 2589 2590 2591 2592 2593
/**
 * 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
2594
static umode_t cgroup_file_mode(const struct cftype *cft)
L
Li Zefan 已提交
2595
{
A
Al Viro 已提交
2596
	umode_t mode = 0;
L
Li Zefan 已提交
2597 2598 2599 2600 2601 2602 2603 2604 2605 2606 2607 2608 2609 2610 2611

	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;
}

2612
int cgroup_add_file(struct cgroup *cgrp,
2613 2614 2615
		       struct cgroup_subsys *subsys,
		       const struct cftype *cft)
{
2616
	struct dentry *dir = cgrp->dentry;
2617 2618
	struct dentry *dentry;
	int error;
A
Al Viro 已提交
2619
	umode_t mode;
2620 2621

	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2622
	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2623 2624 2625 2626 2627 2628 2629
		strcpy(name, subsys->name);
		strcat(name, ".");
	}
	strcat(name, cft->name);
	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
	dentry = lookup_one_len(name, dir, strlen(name));
	if (!IS_ERR(dentry)) {
L
Li Zefan 已提交
2630 2631
		mode = cgroup_file_mode(cft);
		error = cgroup_create_file(dentry, mode | S_IFREG,
2632
						cgrp->root->sb);
2633 2634 2635 2636 2637 2638 2639
		if (!error)
			dentry->d_fsdata = (void *)cft;
		dput(dentry);
	} else
		error = PTR_ERR(dentry);
	return error;
}
2640
EXPORT_SYMBOL_GPL(cgroup_add_file);
2641

2642
int cgroup_add_files(struct cgroup *cgrp,
2643 2644 2645 2646 2647 2648
			struct cgroup_subsys *subsys,
			const struct cftype cft[],
			int count)
{
	int i, err;
	for (i = 0; i < count; i++) {
2649
		err = cgroup_add_file(cgrp, subsys, &cft[i]);
2650 2651 2652 2653 2654
		if (err)
			return err;
	}
	return 0;
}
2655
EXPORT_SYMBOL_GPL(cgroup_add_files);
2656

L
Li Zefan 已提交
2657 2658 2659 2660 2661 2662
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2663
int cgroup_task_count(const struct cgroup *cgrp)
2664 2665
{
	int count = 0;
K
KOSAKI Motohiro 已提交
2666
	struct cg_cgroup_link *link;
2667 2668

	read_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
2669
	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2670
		count += atomic_read(&link->cg->refcount);
2671 2672
	}
	read_unlock(&css_set_lock);
2673 2674 2675
	return count;
}

2676 2677 2678 2679
/*
 * Advance a list_head iterator.  The iterator should be positioned at
 * the start of a css_set
 */
2680
static void cgroup_advance_iter(struct cgroup *cgrp,
2681
				struct cgroup_iter *it)
2682 2683 2684 2685 2686 2687 2688 2689
{
	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;
2690
		if (l == &cgrp->css_sets) {
2691 2692 2693
			it->cg_link = NULL;
			return;
		}
2694
		link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2695 2696 2697 2698 2699 2700
		cg = link->cg;
	} while (list_empty(&cg->tasks));
	it->cg_link = l;
	it->task = cg->tasks.next;
}

2701 2702 2703 2704 2705 2706
/*
 * 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().
 */
2707
static void cgroup_enable_task_cg_lists(void)
2708 2709 2710 2711
{
	struct task_struct *p, *g;
	write_lock(&css_set_lock);
	use_task_css_set_links = 1;
2712 2713 2714 2715 2716 2717 2718 2719
	/*
	 * 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);
2720 2721
	do_each_thread(g, p) {
		task_lock(p);
2722 2723 2724 2725 2726 2727
		/*
		 * 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))
2728 2729 2730
			list_add(&p->cg_list, &p->cgroups->tasks);
		task_unlock(p);
	} while_each_thread(g, p);
2731
	read_unlock(&tasklist_lock);
2732 2733 2734
	write_unlock(&css_set_lock);
}

2735
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
2736
	__acquires(css_set_lock)
2737 2738 2739 2740 2741 2742
{
	/*
	 * 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.
	 */
2743 2744 2745
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();

2746
	read_lock(&css_set_lock);
2747 2748
	it->cg_link = &cgrp->css_sets;
	cgroup_advance_iter(cgrp, it);
2749 2750
}

2751
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
2752 2753 2754 2755
					struct cgroup_iter *it)
{
	struct task_struct *res;
	struct list_head *l = it->task;
2756
	struct cg_cgroup_link *link;
2757 2758 2759 2760 2761 2762 2763

	/* 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;
2764 2765
	link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
	if (l == &link->cg->tasks) {
2766 2767
		/* We reached the end of this task list - move on to
		 * the next cg_cgroup_link */
2768
		cgroup_advance_iter(cgrp, it);
2769 2770 2771 2772 2773 2774
	} else {
		it->task = l;
	}
	return res;
}

2775
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
2776
	__releases(css_set_lock)
2777 2778 2779 2780
{
	read_unlock(&css_set_lock);
}

2781 2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806 2807 2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872 2873 2874 2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905 2906 2907 2908 2909 2910 2911 2912 2913 2914 2915 2916 2917
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++) {
2918
			struct task_struct *q = heap->ptrs[i];
2919
			if (i == 0) {
2920 2921
				latest_time = q->start_time;
				latest_task = q;
2922 2923
			}
			/* Process the task per the caller's callback */
2924 2925
			scan->process_task(q, scan);
			put_task_struct(q);
2926 2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940
		}
		/*
		 * 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;
}

2941
/*
2942
 * Stuff for reading the 'tasks'/'procs' files.
2943 2944 2945 2946 2947 2948 2949 2950
 *
 * 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.
 *
 */

2951 2952 2953 2954 2955 2956 2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969 2970 2971 2972 2973 2974 2975 2976 2977 2978 2979 2980 2981 2982
/* 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;
};

2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018
/*
 * 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;
}

3019
/*
3020 3021 3022 3023
 * 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.
3024
 */
3025 3026 3027
/* 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)
3028
{
3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049 3050 3051 3052 3053 3054 3055 3056 3057
	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)) {
3058
		newlist = pidlist_resize(list, dest);
3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069
		if (newlist)
			*p = newlist;
	}
	return dest;
}

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

3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080
/*
 * 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 */
3081 3082
	struct pid_namespace *ns = current->nsproxy->pid_ns;

3083 3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106
	/*
	 * 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;
3107
	l->key.ns = get_pid_ns(ns);
3108 3109 3110 3111 3112 3113 3114 3115
	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;
}

3116 3117 3118
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
3119 3120
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
3121 3122 3123 3124
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
3125 3126
	struct cgroup_iter it;
	struct task_struct *tsk;
3127 3128 3129 3130 3131 3132 3133 3134 3135
	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);
3136
	array = pidlist_allocate(length);
3137 3138 3139
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
3140 3141
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
3142
		if (unlikely(n == length))
3143
			break;
3144
		/* get tgid or pid for procs or tasks file respectively */
3145 3146 3147 3148
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
3149 3150
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
3151
	}
3152
	cgroup_iter_end(cgrp, &it);
3153 3154 3155
	length = n;
	/* now sort & (if procs) strip out duplicates */
	sort(array, length, sizeof(pid_t), cmppid, NULL);
3156
	if (type == CGROUP_FILE_PROCS)
3157
		length = pidlist_uniq(&array, length);
3158 3159
	l = cgroup_pidlist_find(cgrp, type);
	if (!l) {
3160
		pidlist_free(array);
3161
		return -ENOMEM;
3162
	}
3163
	/* store array, freeing old if necessary - lock already held */
3164
	pidlist_free(l->list);
3165 3166 3167 3168
	l->list = array;
	l->length = length;
	l->use_count++;
	up_write(&l->mutex);
3169
	*lp = l;
3170
	return 0;
3171 3172
}

B
Balbir Singh 已提交
3173
/**
L
Li Zefan 已提交
3174
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
3175 3176 3177
 * @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
3178 3179 3180
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
3181 3182 3183 3184
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
	int ret = -EINVAL;
3185
	struct cgroup *cgrp;
B
Balbir Singh 已提交
3186 3187
	struct cgroup_iter it;
	struct task_struct *tsk;
3188

B
Balbir Singh 已提交
3189
	/*
3190 3191
	 * Validate dentry by checking the superblock operations,
	 * and make sure it's a directory.
B
Balbir Singh 已提交
3192
	 */
3193 3194
	if (dentry->d_sb->s_op != &cgroup_ops ||
	    !S_ISDIR(dentry->d_inode->i_mode))
B
Balbir Singh 已提交
3195 3196 3197
		 goto err;

	ret = 0;
3198
	cgrp = dentry->d_fsdata;
B
Balbir Singh 已提交
3199

3200 3201
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
B
Balbir Singh 已提交
3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220
		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;
		}
	}
3221
	cgroup_iter_end(cgrp, &it);
B
Balbir Singh 已提交
3222 3223 3224 3225 3226

err:
	return ret;
}

3227

3228
/*
3229
 * seq_file methods for the tasks/procs files. The seq_file position is the
3230
 * next pid to display; the seq_file iterator is a pointer to the pid
3231
 * in the cgroup->l->list array.
3232
 */
3233

3234
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3235
{
3236 3237 3238 3239 3240 3241
	/*
	 * 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
	 */
3242
	struct cgroup_pidlist *l = s->private;
3243 3244 3245
	int index = 0, pid = *pos;
	int *iter;

3246
	down_read(&l->mutex);
3247
	if (pid) {
3248
		int end = l->length;
S
Stephen Rothwell 已提交
3249

3250 3251
		while (index < end) {
			int mid = (index + end) / 2;
3252
			if (l->list[mid] == pid) {
3253 3254
				index = mid;
				break;
3255
			} else if (l->list[mid] <= pid)
3256 3257 3258 3259 3260 3261
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
3262
	if (index >= l->length)
3263 3264
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
3265
	iter = l->list + index;
3266 3267 3268 3269
	*pos = *iter;
	return iter;
}

3270
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3271
{
3272 3273
	struct cgroup_pidlist *l = s->private;
	up_read(&l->mutex);
3274 3275
}

3276
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3277
{
3278 3279 3280
	struct cgroup_pidlist *l = s->private;
	pid_t *p = v;
	pid_t *end = l->list + l->length;
3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293
	/*
	 * 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;
	}
}

3294
static int cgroup_pidlist_show(struct seq_file *s, void *v)
3295 3296 3297
{
	return seq_printf(s, "%d\n", *(int *)v);
}
3298

3299 3300 3301 3302 3303 3304 3305 3306 3307
/*
 * 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,
3308 3309
};

3310
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3311
{
3312 3313 3314 3315 3316 3317 3318
	/*
	 * 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);
3319 3320 3321
	down_write(&l->mutex);
	BUG_ON(!l->use_count);
	if (!--l->use_count) {
3322 3323 3324
		/* we're the last user if refcount is 0; remove and free */
		list_del(&l->links);
		mutex_unlock(&l->owner->pidlist_mutex);
3325
		pidlist_free(l->list);
3326 3327 3328 3329
		put_pid_ns(l->key.ns);
		up_write(&l->mutex);
		kfree(l);
		return;
3330
	}
3331
	mutex_unlock(&l->owner->pidlist_mutex);
3332
	up_write(&l->mutex);
3333 3334
}

3335
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3336
{
3337
	struct cgroup_pidlist *l;
3338 3339
	if (!(file->f_mode & FMODE_READ))
		return 0;
3340 3341 3342 3343 3344 3345
	/*
	 * 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);
3346 3347 3348
	return seq_release(inode, file);
}

3349
static const struct file_operations cgroup_pidlist_operations = {
3350 3351 3352
	.read = seq_read,
	.llseek = seq_lseek,
	.write = cgroup_file_write,
3353
	.release = cgroup_pidlist_release,
3354 3355
};

3356
/*
3357 3358 3359
 * 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.
3360
 */
3361
/* helper function for the two below it */
3362
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3363
{
3364
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3365
	struct cgroup_pidlist *l;
3366
	int retval;
3367

3368
	/* Nothing to do for write-only files */
3369 3370 3371
	if (!(file->f_mode & FMODE_READ))
		return 0;

3372
	/* have the array populated */
3373
	retval = pidlist_array_load(cgrp, type, &l);
3374 3375 3376 3377
	if (retval)
		return retval;
	/* configure file information */
	file->f_op = &cgroup_pidlist_operations;
3378

3379
	retval = seq_open(file, &cgroup_pidlist_seq_operations);
3380
	if (retval) {
3381
		cgroup_release_pid_array(l);
3382
		return retval;
3383
	}
3384
	((struct seq_file *)file->private_data)->private = l;
3385 3386
	return 0;
}
3387 3388
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
3389
	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3390 3391 3392
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
3393
	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3394
}
3395

3396
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3397 3398
					    struct cftype *cft)
{
3399
	return notify_on_release(cgrp);
3400 3401
}

3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413
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;
}

3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428
/*
 * Unregister event and free resources.
 *
 * Gets called from workqueue.
 */
static void cgroup_event_remove(struct work_struct *work)
{
	struct cgroup_event *event = container_of(work, struct cgroup_event,
			remove);
	struct cgroup *cgrp = event->cgrp;

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

	eventfd_ctx_put(event->eventfd);
	kfree(event);
3429
	dput(cgrp->dentry);
3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445
}

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

	if (flags & POLLHUP) {
C
Changli Gao 已提交
3446
		__remove_wait_queue(event->wqh, &event->wait);
3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521 3522 3523
		spin_lock(&cgrp->event_list_lock);
		list_del(&event->list);
		spin_unlock(&cgrp->event_list_lock);
		/*
		 * We are in atomic context, but cgroup_event_remove() may
		 * sleep, so we have to call it in workqueue.
		 */
		schedule_work(&event->remove);
	}

	return 0;
}

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

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

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

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

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

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

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

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

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

	/* the process need read permission on control file */
A
Al Viro 已提交
3524 3525
	/* AV: shouldn't we check that it's been opened for read instead? */
	ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3526 3527 3528 3529 3530 3531 3532 3533 3534 3535 3536 3537 3538 3539 3540 3541 3542 3543 3544 3545 3546 3547 3548 3549 3550
	if (ret < 0)
		goto fail;

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

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

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

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

3551 3552 3553 3554 3555 3556 3557
	/*
	 * 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);

3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576 3577 3578 3579 3580 3581
	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;
}

3582 3583 3584 3585 3586 3587 3588 3589 3590 3591 3592 3593 3594 3595 3596 3597 3598
static u64 cgroup_clone_children_read(struct cgroup *cgrp,
				    struct cftype *cft)
{
	return clone_children(cgrp);
}

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

3599 3600 3601
/*
 * for the common functions, 'private' gives the type of file
 */
3602 3603
/* for hysterical raisins, we can't put this on the older files */
#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3604 3605 3606 3607
static struct cftype files[] = {
	{
		.name = "tasks",
		.open = cgroup_tasks_open,
3608
		.write_u64 = cgroup_tasks_write,
3609
		.release = cgroup_pidlist_release,
L
Li Zefan 已提交
3610
		.mode = S_IRUGO | S_IWUSR,
3611
	},
3612 3613 3614
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "procs",
		.open = cgroup_procs_open,
B
Ben Blum 已提交
3615
		.write_u64 = cgroup_procs_write,
3616
		.release = cgroup_pidlist_release,
B
Ben Blum 已提交
3617
		.mode = S_IRUGO | S_IWUSR,
3618
	},
3619 3620
	{
		.name = "notify_on_release",
3621
		.read_u64 = cgroup_read_notify_on_release,
3622
		.write_u64 = cgroup_write_notify_on_release,
3623
	},
3624 3625 3626 3627 3628
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "event_control",
		.write_string = cgroup_write_event_control,
		.mode = S_IWUGO,
	},
3629 3630 3631 3632 3633
	{
		.name = "cgroup.clone_children",
		.read_u64 = cgroup_clone_children_read,
		.write_u64 = cgroup_clone_children_write,
	},
3634 3635 3636 3637
};

static struct cftype cft_release_agent = {
	.name = "release_agent",
3638 3639 3640
	.read_seq_string = cgroup_release_agent_show,
	.write_string = cgroup_release_agent_write,
	.max_write_len = PATH_MAX,
3641 3642
};

3643
static int cgroup_populate_dir(struct cgroup *cgrp)
3644 3645 3646 3647
{
	int err;
	struct cgroup_subsys *ss;

3648
	err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));
3649 3650 3651
	if (err < 0)
		return err;

3652 3653
	if (cgrp == cgrp->top_cgroup) {
		if ((err = cgroup_add_file(cgrp, NULL, &cft_release_agent)) < 0)
3654 3655 3656
			return err;
	}

3657 3658
	for_each_subsys(cgrp->root, ss) {
		if (ss->populate && (err = ss->populate(ss, cgrp)) < 0)
3659 3660
			return err;
	}
K
KAMEZAWA Hiroyuki 已提交
3661 3662 3663 3664 3665 3666 3667 3668 3669 3670 3671
	/* 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);
	}
3672 3673 3674 3675 3676 3677

	return 0;
}

static void init_cgroup_css(struct cgroup_subsys_state *css,
			       struct cgroup_subsys *ss,
3678
			       struct cgroup *cgrp)
3679
{
3680
	css->cgroup = cgrp;
P
Paul Menage 已提交
3681
	atomic_set(&css->refcnt, 1);
3682
	css->flags = 0;
K
KAMEZAWA Hiroyuki 已提交
3683
	css->id = NULL;
3684
	if (cgrp == dummytop)
3685
		set_bit(CSS_ROOT, &css->flags);
3686 3687
	BUG_ON(cgrp->subsys[ss->subsys_id]);
	cgrp->subsys[ss->subsys_id] = css;
3688 3689
}

3690 3691 3692 3693 3694
static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
{
	/* We need to take each hierarchy_mutex in a consistent order */
	int i;

B
Ben Blum 已提交
3695 3696 3697 3698
	/*
	 * No worry about a race with rebind_subsystems that might mess up the
	 * locking order, since both parties are under cgroup_mutex.
	 */
3699 3700
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
B
Ben Blum 已提交
3701 3702
		if (ss == NULL)
			continue;
3703
		if (ss->root == root)
3704
			mutex_lock(&ss->hierarchy_mutex);
3705 3706 3707 3708 3709 3710 3711 3712 3713
	}
}

static void cgroup_unlock_hierarchy(struct cgroupfs_root *root)
{
	int i;

	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
B
Ben Blum 已提交
3714 3715
		if (ss == NULL)
			continue;
3716 3717 3718 3719 3720
		if (ss->root == root)
			mutex_unlock(&ss->hierarchy_mutex);
	}
}

3721
/*
L
Li Zefan 已提交
3722 3723 3724 3725
 * 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
3726
 *
L
Li Zefan 已提交
3727
 * Must be called with the mutex on the parent inode held
3728 3729
 */
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
A
Al Viro 已提交
3730
			     umode_t mode)
3731
{
3732
	struct cgroup *cgrp;
3733 3734 3735 3736 3737
	struct cgroupfs_root *root = parent->root;
	int err = 0;
	struct cgroup_subsys *ss;
	struct super_block *sb = root->sb;

3738 3739
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750
		return -ENOMEM;

	/* Grab a reference on the superblock so the hierarchy doesn't
	 * get deleted on unmount if there are child cgroups.  This
	 * can be done outside cgroup_mutex, since the sb can't
	 * disappear while someone has an open control file on the
	 * fs */
	atomic_inc(&sb->s_active);

	mutex_lock(&cgroup_mutex);

3751
	init_cgroup_housekeeping(cgrp);
3752

3753 3754 3755
	cgrp->parent = parent;
	cgrp->root = parent->root;
	cgrp->top_cgroup = parent->top_cgroup;
3756

3757 3758 3759
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

3760 3761 3762
	if (clone_children(parent))
		set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);

3763
	for_each_subsys(root, ss) {
3764
		struct cgroup_subsys_state *css = ss->create(cgrp);
3765

3766 3767 3768 3769
		if (IS_ERR(css)) {
			err = PTR_ERR(css);
			goto err_destroy;
		}
3770
		init_cgroup_css(css, ss, cgrp);
3771 3772 3773
		if (ss->use_id) {
			err = alloc_css_id(ss, parent, cgrp);
			if (err)
K
KAMEZAWA Hiroyuki 已提交
3774
				goto err_destroy;
3775
		}
K
KAMEZAWA Hiroyuki 已提交
3776
		/* At error, ->destroy() callback has to free assigned ID. */
3777
		if (clone_children(parent) && ss->post_clone)
3778
			ss->post_clone(cgrp);
3779 3780
	}

3781
	cgroup_lock_hierarchy(root);
3782
	list_add(&cgrp->sibling, &cgrp->parent->children);
3783
	cgroup_unlock_hierarchy(root);
3784 3785
	root->number_of_cgroups++;

3786
	err = cgroup_create_dir(cgrp, dentry, mode);
3787 3788 3789 3790
	if (err < 0)
		goto err_remove;

	/* The cgroup directory was pre-locked for us */
3791
	BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
3792

3793
	err = cgroup_populate_dir(cgrp);
3794 3795 3796
	/* If err < 0, we have a half-filled directory - oh well ;) */

	mutex_unlock(&cgroup_mutex);
3797
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
3798 3799 3800 3801 3802

	return 0;

 err_remove:

3803
	cgroup_lock_hierarchy(root);
3804
	list_del(&cgrp->sibling);
3805
	cgroup_unlock_hierarchy(root);
3806 3807 3808 3809 3810
	root->number_of_cgroups--;

 err_destroy:

	for_each_subsys(root, ss) {
3811
		if (cgrp->subsys[ss->subsys_id])
3812
			ss->destroy(cgrp);
3813 3814 3815 3816 3817 3818 3819
	}

	mutex_unlock(&cgroup_mutex);

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

3820
	kfree(cgrp);
3821 3822 3823
	return err;
}

3824
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3825 3826 3827 3828 3829 3830 3831
{
	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);
}

3832
static int cgroup_has_css_refs(struct cgroup *cgrp)
3833 3834 3835
{
	/* Check the reference count on each subsystem. Since we
	 * already established that there are no tasks in the
P
Paul Menage 已提交
3836
	 * cgroup, if the css refcount is also 1, then there should
3837 3838 3839 3840 3841 3842 3843
	 * be no outstanding references, so the subsystem is safe to
	 * destroy. We scan across all subsystems rather than using
	 * the per-hierarchy linked list of mounted subsystems since
	 * we can be called via check_for_release() with no
	 * synchronization other than RCU, and the subsystem linked
	 * list isn't RCU-safe */
	int i;
B
Ben Blum 已提交
3844 3845 3846 3847 3848
	/*
	 * 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.
	 */
3849 3850 3851
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		struct cgroup_subsys_state *css;
B
Ben Blum 已提交
3852 3853
		/* Skip subsystems not present or not in this hierarchy */
		if (ss == NULL || ss->root != cgrp->root)
3854
			continue;
3855
		css = cgrp->subsys[ss->subsys_id];
3856 3857 3858 3859 3860 3861
		/* When called from check_for_release() it's possible
		 * that by this point the cgroup has been removed
		 * and the css deleted. But a false-positive doesn't
		 * matter, since it can only happen if the cgroup
		 * has been deleted and hence no longer needs the
		 * release agent to be called anyway. */
P
Paul Menage 已提交
3862
		if (css && (atomic_read(&css->refcnt) > 1))
3863 3864 3865 3866 3867
			return 1;
	}
	return 0;
}

P
Paul Menage 已提交
3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882
/*
 * Atomically mark all (or else none) of the cgroup's CSS objects as
 * CSS_REMOVED. Return true on success, or false if the cgroup has
 * busy subsystems. Call with cgroup_mutex held
 */

static int cgroup_clear_css_refs(struct cgroup *cgrp)
{
	struct cgroup_subsys *ss;
	unsigned long flags;
	bool failed = false;
	local_irq_save(flags);
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
		int refcnt;
3883
		while (1) {
P
Paul Menage 已提交
3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896
			/* We can only remove a CSS with a refcnt==1 */
			refcnt = atomic_read(&css->refcnt);
			if (refcnt > 1) {
				failed = true;
				goto done;
			}
			BUG_ON(!refcnt);
			/*
			 * Drop the refcnt to 0 while we check other
			 * subsystems. This will cause any racing
			 * css_tryget() to spin until we set the
			 * CSS_REMOVED bits or abort
			 */
3897 3898 3899 3900
			if (atomic_cmpxchg(&css->refcnt, refcnt, 0) == refcnt)
				break;
			cpu_relax();
		}
P
Paul Menage 已提交
3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920
	}
 done:
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
		if (failed) {
			/*
			 * Restore old refcnt if we previously managed
			 * to clear it from 1 to 0
			 */
			if (!atomic_read(&css->refcnt))
				atomic_set(&css->refcnt, 1);
		} else {
			/* Commit the fact that the CSS is removed */
			set_bit(CSS_REMOVED, &css->flags);
		}
	}
	local_irq_restore(flags);
	return !failed;
}

3921 3922
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
3923
	struct cgroup *cgrp = dentry->d_fsdata;
3924 3925
	struct dentry *d;
	struct cgroup *parent;
3926
	DEFINE_WAIT(wait);
3927
	struct cgroup_event *event, *tmp;
3928
	int ret;
3929 3930

	/* the vfs holds both inode->i_mutex already */
3931
again:
3932
	mutex_lock(&cgroup_mutex);
3933
	if (atomic_read(&cgrp->count) != 0) {
3934 3935 3936
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
3937
	if (!list_empty(&cgrp->children)) {
3938 3939 3940
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
3941
	mutex_unlock(&cgroup_mutex);
L
Li Zefan 已提交
3942

3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953
	/*
	 * In general, subsystem has no css->refcnt after pre_destroy(). But
	 * in racy cases, subsystem may have to get css->refcnt after
	 * pre_destroy() and it makes rmdir return with -EBUSY. This sometimes
	 * make rmdir return -EBUSY too often. To avoid that, we use waitqueue
	 * for cgroup's rmdir. CGRP_WAIT_ON_RMDIR is for synchronizing rmdir
	 * and subsystem's reference count handling. Please see css_get/put
	 * and css_tryget() and cgroup_wakeup_rmdir_waiter() implementation.
	 */
	set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);

3954
	/*
L
Li Zefan 已提交
3955 3956
	 * Call pre_destroy handlers of subsys. Notify subsystems
	 * that rmdir() request comes.
3957
	 */
3958
	ret = cgroup_call_pre_destroy(cgrp);
3959 3960
	if (ret) {
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
3961
		return ret;
3962
	}
3963

3964 3965
	mutex_lock(&cgroup_mutex);
	parent = cgrp->parent;
3966
	if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
3967
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
3968 3969 3970
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
3971 3972 3973
	prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
	if (!cgroup_clear_css_refs(cgrp)) {
		mutex_unlock(&cgroup_mutex);
3974 3975 3976 3977 3978 3979
		/*
		 * Because someone may call cgroup_wakeup_rmdir_waiter() before
		 * prepare_to_wait(), we need to check this flag.
		 */
		if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))
			schedule();
3980 3981 3982 3983 3984 3985 3986 3987 3988
		finish_wait(&cgroup_rmdir_waitq, &wait);
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
		if (signal_pending(current))
			return -EINTR;
		goto again;
	}
	/* NO css_tryget() can success after here. */
	finish_wait(&cgroup_rmdir_waitq, &wait);
	clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
3989

3990
	raw_spin_lock(&release_list_lock);
3991 3992
	set_bit(CGRP_REMOVED, &cgrp->flags);
	if (!list_empty(&cgrp->release_list))
3993
		list_del_init(&cgrp->release_list);
3994
	raw_spin_unlock(&release_list_lock);
3995 3996 3997

	cgroup_lock_hierarchy(cgrp->root);
	/* delete this cgroup from parent->children */
3998
	list_del_init(&cgrp->sibling);
3999 4000
	cgroup_unlock_hierarchy(cgrp->root);

4001
	d = dget(cgrp->dentry);
4002 4003 4004 4005

	cgroup_d_remove_dir(d);
	dput(d);

4006
	set_bit(CGRP_RELEASABLE, &parent->flags);
4007 4008
	check_for_release(parent);

4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022
	/*
	 * Unregister events and notify userspace.
	 * Notify userspace about cgroup removing only after rmdir of cgroup
	 * directory to avoid race between userspace and kernelspace
	 */
	spin_lock(&cgrp->event_list_lock);
	list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
		list_del(&event->list);
		remove_wait_queue(event->wqh, &event->wait);
		eventfd_signal(event->eventfd, 1);
		schedule_work(&event->remove);
	}
	spin_unlock(&cgrp->event_list_lock);

4023 4024 4025 4026
	mutex_unlock(&cgroup_mutex);
	return 0;
}

4027
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4028 4029
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
4030 4031

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4032 4033

	/* Create the top cgroup state for this subsystem */
4034
	list_add(&ss->sibling, &rootnode.subsys_list);
4035
	ss->root = &rootnode;
4036
	css = ss->create(dummytop);
4037 4038 4039 4040
	/* We don't handle early failures gracefully */
	BUG_ON(IS_ERR(css));
	init_cgroup_css(css, ss, dummytop);

L
Li Zefan 已提交
4041
	/* Update the init_css_set to contain a subsys
4042
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
4043 4044 4045
	 * newly registered, all tasks and hence the
	 * init_css_set is in the subsystem's top cgroup. */
	init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
4046 4047 4048

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

L
Li Zefan 已提交
4049 4050 4051 4052 4053
	/* 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));

4054
	mutex_init(&ss->hierarchy_mutex);
4055
	lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
4056
	ss->active = 1;
4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067

	/* 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
4068
 * subsystem is built as a module, it will be assigned a new subsys_id and set
4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124
 * up for use. If the subsystem is built-in anyway, work is delegated to the
 * simpler cgroup_init_subsys.
 */
int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
{
	int i;
	struct cgroup_subsys_state *css;

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

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

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

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

	/*
	 * no ss->create seems to need anything important in the ss struct, so
	 * this can happen first (i.e. before the rootnode attachment).
	 */
4125
	css = ss->create(dummytop);
4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142
	if (IS_ERR(css)) {
		/* failure case - need to deassign the subsys[] slot. */
		subsys[i] = NULL;
		mutex_unlock(&cgroup_mutex);
		return PTR_ERR(css);
	}

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

	/* our new subsystem will be attached to the dummy hierarchy. */
	init_cgroup_css(css, ss, dummytop);
	/* init_idr must be after init_cgroup_css because it sets css->id. */
	if (ss->use_id) {
		int ret = cgroup_init_idr(ss, css);
		if (ret) {
			dummytop->subsys[ss->subsys_id] = NULL;
4143
			ss->destroy(dummytop);
4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185
			subsys[i] = NULL;
			mutex_unlock(&cgroup_mutex);
			return ret;
		}
	}

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

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

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

	/* success! */
	mutex_unlock(&cgroup_mutex);
	return 0;
4186
}
4187
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4188

B
Ben Blum 已提交
4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213 4214 4215 4216
/**
 * cgroup_unload_subsys: unload a modular subsystem
 * @ss: the subsystem to unload
 *
 * This function should be called in a modular subsystem's exitcall. When this
 * function is invoked, the refcount on the subsystem's module will be 0, so
 * the subsystem will not be attached to any hierarchy.
 */
void cgroup_unload_subsys(struct cgroup_subsys *ss)
{
	struct cg_cgroup_link *link;
	struct hlist_head *hhead;

	BUG_ON(ss->module == NULL);

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

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

	/* remove subsystem from rootnode's list of subsystems */
4217
	list_del_init(&ss->sibling);
B
Ben Blum 已提交
4218 4219 4220 4221 4222 4223 4224 4225 4226 4227 4228 4229 4230 4231 4232 4233 4234 4235 4236 4237 4238 4239 4240

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

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

	/*
	 * remove subsystem's css from the dummytop and free it - need to free
	 * before marking as null because ss->destroy needs the cgrp->subsys
	 * pointer to find their state. note that this also takes care of
	 * freeing the css_id.
	 */
4241
	ss->destroy(dummytop);
B
Ben Blum 已提交
4242 4243 4244 4245 4246 4247
	dummytop->subsys[ss->subsys_id] = NULL;

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

4248
/**
L
Li Zefan 已提交
4249 4250 4251 4252
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
4253 4254 4255 4256
 */
int __init cgroup_init_early(void)
{
	int i;
4257
	atomic_set(&init_css_set.refcount, 1);
4258 4259
	INIT_LIST_HEAD(&init_css_set.cg_links);
	INIT_LIST_HEAD(&init_css_set.tasks);
4260
	INIT_HLIST_NODE(&init_css_set.hlist);
4261
	css_set_count = 1;
4262
	init_cgroup_root(&rootnode);
4263 4264 4265 4266
	root_count = 1;
	init_task.cgroups = &init_css_set;

	init_css_set_link.cg = &init_css_set;
4267
	init_css_set_link.cgrp = dummytop;
4268
	list_add(&init_css_set_link.cgrp_link_list,
4269 4270 4271
		 &rootnode.top_cgroup.css_sets);
	list_add(&init_css_set_link.cg_link_list,
		 &init_css_set.cg_links);
4272

4273 4274 4275
	for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
		INIT_HLIST_HEAD(&css_set_table[i]);

B
Ben Blum 已提交
4276 4277
	/* at bootup time, we don't worry about modular subsystems */
	for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4278 4279 4280 4281 4282 4283 4284
		struct cgroup_subsys *ss = subsys[i];

		BUG_ON(!ss->name);
		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
		BUG_ON(!ss->create);
		BUG_ON(!ss->destroy);
		if (ss->subsys_id != i) {
D
Diego Calleja 已提交
4285
			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4286 4287 4288 4289 4290 4291 4292 4293 4294 4295 4296
			       ss->name, ss->subsys_id);
			BUG();
		}

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

/**
L
Li Zefan 已提交
4297 4298 4299 4300
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
4301 4302 4303 4304 4305
 */
int __init cgroup_init(void)
{
	int err;
	int i;
4306
	struct hlist_head *hhead;
4307 4308 4309 4310

	err = bdi_init(&cgroup_backing_dev_info);
	if (err)
		return err;
4311

B
Ben Blum 已提交
4312 4313
	/* at bootup time, we don't worry about modular subsystems */
	for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4314 4315 4316
		struct cgroup_subsys *ss = subsys[i];
		if (!ss->early_init)
			cgroup_init_subsys(ss);
K
KAMEZAWA Hiroyuki 已提交
4317
		if (ss->use_id)
4318
			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4319 4320
	}

4321 4322 4323
	/* Add init_css_set to the hash table */
	hhead = css_set_hash(init_css_set.subsys);
	hlist_add_head(&init_css_set.hlist, hhead);
4324
	BUG_ON(!init_root_id(&rootnode));
4325 4326 4327 4328 4329 4330 4331

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

4332
	err = register_filesystem(&cgroup_fs_type);
4333 4334
	if (err < 0) {
		kobject_put(cgroup_kobj);
4335
		goto out;
4336
	}
4337

L
Li Zefan 已提交
4338
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4339

4340
out:
4341 4342 4343
	if (err)
		bdi_destroy(&cgroup_backing_dev_info);

4344 4345
	return err;
}
4346

4347 4348 4349 4350 4351 4352
/*
 * 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,
4353
 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4354 4355 4356 4357 4358 4359 4360 4361 4362 4363 4364 4365 4366 4367 4368 4369 4370 4371 4372 4373 4374 4375 4376 4377 4378 4379 4380 4381 4382
 *    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);

4383
	for_each_active_root(root) {
4384
		struct cgroup_subsys *ss;
4385
		struct cgroup *cgrp;
4386 4387
		int count = 0;

4388
		seq_printf(m, "%d:", root->hierarchy_id);
4389 4390
		for_each_subsys(root, ss)
			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4391 4392 4393
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
4394
		seq_putc(m, ':');
4395
		cgrp = task_cgroup_from_root(tsk, root);
4396
		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4397 4398 4399 4400 4401 4402 4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417
		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);
}

4418
const struct file_operations proc_cgroup_operations = {
4419 4420 4421 4422 4423 4424 4425 4426 4427 4428 4429
	.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;

4430
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
B
Ben Blum 已提交
4431 4432 4433 4434 4435
	/*
	 * 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.
	 */
4436 4437 4438
	mutex_lock(&cgroup_mutex);
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
B
Ben Blum 已提交
4439 4440
		if (ss == NULL)
			continue;
4441 4442
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
4443
			   ss->root->number_of_cgroups, !ss->disabled);
4444 4445 4446 4447 4448 4449 4450
	}
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
4451
	return single_open(file, proc_cgroupstats_show, NULL);
4452 4453
}

4454
static const struct file_operations proc_cgroupstats_operations = {
4455 4456 4457 4458 4459 4460
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

4461 4462
/**
 * cgroup_fork - attach newly forked task to its parents cgroup.
L
Li Zefan 已提交
4463
 * @child: pointer to task_struct of forking parent process.
4464 4465 4466 4467 4468
 *
 * 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
4469 4470 4471 4472 4473 4474 4475 4476 4477 4478 4479
 * it was not made under the protection of RCU, cgroup_mutex or
 * threadgroup_change_begin(), so it might no longer be a valid
 * cgroup pointer.  cgroup_attach_task() might have already changed
 * current->cgroups, allowing the previously referenced cgroup
 * group to be removed and freed.
 *
 * Outside the pointer validity we also need to process the css_set
 * inheritance between threadgoup_change_begin() and
 * threadgoup_change_end(), this way there is no leak in any process
 * wide migration performed by cgroup_attach_proc() that could otherwise
 * miss a thread because it is too early or too late in the fork stage.
4480 4481 4482 4483 4484 4485
 *
 * 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)
{
4486 4487 4488 4489 4490 4491
	/*
	 * We don't need to task_lock() current because current->cgroups
	 * can't be changed concurrently here. The parent obviously hasn't
	 * exited and called cgroup_exit(), and we are synchronized against
	 * cgroup migration through threadgroup_change_begin().
	 */
4492 4493 4494
	child->cgroups = current->cgroups;
	get_css_set(child->cgroups);
	INIT_LIST_HEAD(&child->cg_list);
4495 4496 4497
}

/**
L
Li Zefan 已提交
4498 4499 4500 4501 4502 4503
 * cgroup_fork_callbacks - run fork callbacks
 * @child: the new task
 *
 * Called on a new task very soon before adding it to the
 * tasklist. No need to take any locks since no-one can
 * be operating on this task.
4504 4505 4506 4507 4508
 */
void cgroup_fork_callbacks(struct task_struct *child)
{
	if (need_forkexit_callback) {
		int i;
B
Ben Blum 已提交
4509 4510 4511 4512 4513 4514
		/*
		 * forkexit callbacks are only supported for builtin
		 * subsystems, and the builtin section of the subsys array is
		 * immutable, so we don't need to lock the subsys array here.
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4515 4516
			struct cgroup_subsys *ss = subsys[i];
			if (ss->fork)
4517
				ss->fork(child);
4518 4519 4520 4521
		}
	}
}

4522
/**
L
Li Zefan 已提交
4523 4524 4525 4526 4527 4528 4529 4530
 * cgroup_post_fork - called on a new task after adding it to the task list
 * @child: the task in question
 *
 * Adds the task to the list running through its css_set if necessary.
 * Has to be after the task is visible on the task list in case we race
 * with the first call to cgroup_iter_start() - to guarantee that the
 * new task ends up on its list.
 */
4531 4532
void cgroup_post_fork(struct task_struct *child)
{
4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543
	/*
	 * 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.
	 */
4544 4545
	if (use_task_css_set_links) {
		write_lock(&css_set_lock);
4546 4547 4548 4549 4550 4551 4552 4553 4554 4555 4556
		if (list_empty(&child->cg_list)) {
			/*
			 * It's safe to use child->cgroups without task_lock()
			 * here because we are protected through
			 * threadgroup_change_begin() against concurrent
			 * css_set change in cgroup_task_migrate(). Also
			 * the task can't exit at that point until
			 * wake_up_new_task() is called, so we are protected
			 * against cgroup_exit() setting child->cgroup to
			 * init_css_set.
			 */
4557
			list_add(&child->cg_list, &child->cgroups->tasks);
4558
		}
4559 4560 4561
		write_unlock(&css_set_lock);
	}
}
4562 4563 4564
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
4565
 * @run_callback: run exit callbacks?
4566 4567 4568 4569 4570 4571 4572 4573 4574 4575 4576 4577 4578 4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589 4590 4591 4592 4593
 *
 * 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,
4594 4595
 *    which wards off any cgroup_attach_task() attempts, or task is a failed
 *    fork, never visible to cgroup_attach_task.
4596 4597 4598
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
4599
	struct css_set *cg;
4600
	int i;
4601 4602 4603 4604 4605 4606 4607 4608 4609

	/*
	 * 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))
4610
			list_del_init(&tsk->cg_list);
4611 4612 4613
		write_unlock(&css_set_lock);
	}

4614 4615
	/* Reassign the task to the init_css_set. */
	task_lock(tsk);
4616 4617
	cg = tsk->cgroups;
	tsk->cgroups = &init_css_set;
4618 4619 4620 4621 4622 4623 4624 4625 4626 4627 4628 4629

	if (run_callbacks && need_forkexit_callback) {
		/*
		 * modular subsystems can't use callbacks, so no need to lock
		 * the subsys array
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss->exit) {
				struct cgroup *old_cgrp =
					rcu_dereference_raw(cg->subsys[i])->cgroup;
				struct cgroup *cgrp = task_cgroup(tsk, i);
4630
				ss->exit(cgrp, old_cgrp, tsk);
4631 4632 4633
			}
		}
	}
4634
	task_unlock(tsk);
4635

4636
	if (cg)
4637
		put_css_set_taskexit(cg);
4638
}
4639

L
Li Zefan 已提交
4640
/**
4641
 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
L
Li Zefan 已提交
4642
 * @cgrp: the cgroup in question
4643
 * @task: the task in question
L
Li Zefan 已提交
4644
 *
4645 4646
 * See if @cgrp is a descendant of @task's cgroup in the appropriate
 * hierarchy.
4647 4648 4649 4650 4651 4652
 *
 * If we are sending in dummytop, then presumably we are creating
 * the top cgroup in the subsystem.
 *
 * Called only by the ns (nsproxy) cgroup.
 */
4653
int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
4654 4655 4656 4657
{
	int ret;
	struct cgroup *target;

4658
	if (cgrp == dummytop)
4659 4660
		return 1;

4661
	target = task_cgroup_from_root(task, cgrp->root);
4662 4663 4664
	while (cgrp != target && cgrp!= cgrp->top_cgroup)
		cgrp = cgrp->parent;
	ret = (cgrp == target);
4665 4666
	return ret;
}
4667

4668
static void check_for_release(struct cgroup *cgrp)
4669 4670 4671
{
	/* All of these checks rely on RCU to keep the cgroup
	 * structure alive */
4672 4673
	if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
	    && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
4674 4675 4676 4677
		/* Control Group is currently removeable. If it's not
		 * already queued for a userspace notification, queue
		 * it now */
		int need_schedule_work = 0;
4678
		raw_spin_lock(&release_list_lock);
4679 4680 4681
		if (!cgroup_is_removed(cgrp) &&
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
4682 4683
			need_schedule_work = 1;
		}
4684
		raw_spin_unlock(&release_list_lock);
4685 4686 4687 4688 4689
		if (need_schedule_work)
			schedule_work(&release_agent_work);
	}
}

4690 4691
/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css, int count)
4692
{
4693
	struct cgroup *cgrp = css->cgroup;
4694
	int val;
4695
	rcu_read_lock();
4696
	val = atomic_sub_return(count, &css->refcnt);
4697
	if (val == 1) {
4698 4699 4700 4701
		if (notify_on_release(cgrp)) {
			set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
		}
4702
		cgroup_wakeup_rmdir_waiter(cgrp);
4703 4704
	}
	rcu_read_unlock();
4705
	WARN_ON_ONCE(val < 1);
4706
}
B
Ben Blum 已提交
4707
EXPORT_SYMBOL_GPL(__css_put);
4708 4709 4710 4711 4712 4713 4714 4715 4716 4717 4718 4719 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729 4730 4731 4732 4733 4734 4735

/*
 * 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);
4736
	raw_spin_lock(&release_list_lock);
4737 4738 4739
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
4740
		char *pathbuf = NULL, *agentbuf = NULL;
4741
		struct cgroup *cgrp = list_entry(release_list.next,
4742 4743
						    struct cgroup,
						    release_list);
4744
		list_del_init(&cgrp->release_list);
4745
		raw_spin_unlock(&release_list_lock);
4746
		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4747 4748 4749 4750 4751 4752 4753
		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;
4754 4755

		i = 0;
4756 4757
		argv[i++] = agentbuf;
		argv[i++] = pathbuf;
4758 4759 4760 4761 4762 4763 4764 4765 4766 4767 4768 4769 4770 4771
		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);
4772 4773 4774
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
4775
		raw_spin_lock(&release_list_lock);
4776
	}
4777
	raw_spin_unlock(&release_list_lock);
4778 4779
	mutex_unlock(&cgroup_mutex);
}
4780 4781 4782 4783 4784 4785 4786 4787 4788

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

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;
B
Ben Blum 已提交
4789 4790 4791 4792 4793
		/*
		 * cgroup_disable, being at boot time, can't know about module
		 * subsystems, so we don't worry about them.
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4794 4795 4796 4797 4798 4799 4800 4801 4802 4803 4804 4805 4806
			struct cgroup_subsys *ss = subsys[i];

			if (!strcmp(token, ss->name)) {
				ss->disabled = 1;
				printk(KERN_INFO "Disabling %s control group"
					" subsystem\n", ss->name);
				break;
			}
		}
	}
	return 1;
}
__setup("cgroup_disable=", cgroup_disable);
K
KAMEZAWA Hiroyuki 已提交
4807 4808 4809 4810 4811 4812 4813 4814 4815 4816

/*
 * 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)
{
4817 4818 4819 4820 4821 4822 4823
	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.
	 */
4824
	cssid = rcu_dereference_check(css->id, atomic_read(&css->refcnt));
K
KAMEZAWA Hiroyuki 已提交
4825 4826 4827 4828 4829

	if (cssid)
		return cssid->id;
	return 0;
}
B
Ben Blum 已提交
4830
EXPORT_SYMBOL_GPL(css_id);
K
KAMEZAWA Hiroyuki 已提交
4831 4832 4833

unsigned short css_depth(struct cgroup_subsys_state *css)
{
4834 4835
	struct css_id *cssid;

4836
	cssid = rcu_dereference_check(css->id, atomic_read(&css->refcnt));
K
KAMEZAWA Hiroyuki 已提交
4837 4838 4839 4840 4841

	if (cssid)
		return cssid->depth;
	return 0;
}
B
Ben Blum 已提交
4842
EXPORT_SYMBOL_GPL(css_depth);
K
KAMEZAWA Hiroyuki 已提交
4843

4844 4845 4846 4847 4848 4849 4850 4851 4852 4853 4854 4855 4856
/**
 *  css_is_ancestor - test "root" css is an ancestor of "child"
 * @child: the css to be tested.
 * @root: the css supporsed to be an ancestor of the child.
 *
 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
 * this function reads css->id, this use rcu_dereference() and rcu_read_lock().
 * But, considering usual usage, the csses should be valid objects after test.
 * Assuming that the caller will do some action to the child if this returns
 * returns true, the caller must take "child";s reference count.
 * If "child" is valid object and this returns true, "root" is valid, too.
 */

K
KAMEZAWA Hiroyuki 已提交
4857
bool css_is_ancestor(struct cgroup_subsys_state *child,
4858
		    const struct cgroup_subsys_state *root)
K
KAMEZAWA Hiroyuki 已提交
4859
{
4860 4861 4862
	struct css_id *child_id;
	struct css_id *root_id;
	bool ret = true;
K
KAMEZAWA Hiroyuki 已提交
4863

4864 4865 4866 4867 4868 4869 4870 4871 4872 4873
	rcu_read_lock();
	child_id  = rcu_dereference(child->id);
	root_id = rcu_dereference(root->id);
	if (!child_id
	    || !root_id
	    || (child_id->depth < root_id->depth)
	    || (child_id->stack[root_id->depth] != root_id->id))
		ret = false;
	rcu_read_unlock();
	return ret;
K
KAMEZAWA Hiroyuki 已提交
4874 4875 4876 4877 4878 4879 4880 4881 4882 4883 4884 4885 4886
}

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);
4887
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
4888
	idr_remove(&ss->idr, id->id);
4889
	spin_unlock(&ss->id_lock);
4890
	kfree_rcu(id, rcu_head);
K
KAMEZAWA Hiroyuki 已提交
4891
}
B
Ben Blum 已提交
4892
EXPORT_SYMBOL_GPL(free_css_id);
K
KAMEZAWA Hiroyuki 已提交
4893 4894 4895 4896 4897 4898 4899 4900 4901 4902 4903 4904 4905 4906 4907 4908 4909 4910 4911 4912 4913 4914

/*
 * This is called by init or create(). Then, calls to this function are
 * always serialized (By cgroup_mutex() at create()).
 */

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

	BUG_ON(!ss->use_id);

	size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
	newid = kzalloc(size, GFP_KERNEL);
	if (!newid)
		return ERR_PTR(-ENOMEM);
	/* get id */
	if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
		error = -ENOMEM;
		goto err_out;
	}
4915
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
4916 4917
	/* Don't use 0. allocates an ID of 1-65535 */
	error = idr_get_new_above(&ss->idr, newid, 1, &myid);
4918
	spin_unlock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
4919 4920 4921 4922 4923 4924 4925 4926 4927 4928 4929 4930 4931 4932

	/* Returns error when there are no free spaces for new ID.*/
	if (error) {
		error = -ENOSPC;
		goto err_out;
	}
	if (myid > CSS_ID_MAX)
		goto remove_idr;

	newid->id = myid;
	newid->depth = depth;
	return newid;
remove_idr:
	error = -ENOSPC;
4933
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
4934
	idr_remove(&ss->idr, myid);
4935
	spin_unlock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
4936 4937 4938 4939 4940 4941
err_out:
	kfree(newid);
	return ERR_PTR(error);

}

4942 4943
static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
					    struct cgroup_subsys_state *rootcss)
K
KAMEZAWA Hiroyuki 已提交
4944 4945 4946
{
	struct css_id *newid;

4947
	spin_lock_init(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960 4961 4962 4963 4964
	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;
4965
	struct css_id *child_id, *parent_id;
K
KAMEZAWA Hiroyuki 已提交
4966 4967 4968 4969 4970

	subsys_id = ss->subsys_id;
	parent_css = parent->subsys[subsys_id];
	child_css = child->subsys[subsys_id];
	parent_id = parent_css->id;
4971
	depth = parent_id->depth + 1;
K
KAMEZAWA Hiroyuki 已提交
4972 4973 4974 4975 4976 4977 4978 4979 4980 4981 4982 4983 4984 4985 4986 4987 4988 4989 4990 4991 4992 4993 4994 4995 4996 4997 4998 4999 5000 5001 5002 5003 5004 5005 5006 5007 5008

	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
5009
EXPORT_SYMBOL_GPL(css_lookup);
K
KAMEZAWA Hiroyuki 已提交
5010 5011 5012 5013 5014 5015 5016 5017 5018 5019 5020 5021 5022 5023 5024 5025 5026 5027 5028 5029 5030 5031 5032 5033 5034

/**
 * 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);
5035 5036
	WARN_ON_ONCE(!rcu_read_lock_held());

K
KAMEZAWA Hiroyuki 已提交
5037 5038 5039 5040 5041 5042 5043 5044 5045 5046 5047 5048 5049 5050 5051 5052 5053 5054 5055 5056 5057 5058 5059
	/* 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
5060 5061 5062 5063 5064 5065 5066 5067 5068 5069 5070 5071 5072 5073 5074 5075 5076 5077 5078 5079 5080 5081 5082
/*
 * get corresponding css from file open on cgroupfs directory
 */
struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
{
	struct cgroup *cgrp;
	struct inode *inode;
	struct cgroup_subsys_state *css;

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

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

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

5083
#ifdef CONFIG_CGROUP_DEBUG
5084
static struct cgroup_subsys_state *debug_create(struct cgroup *cont)
5085 5086 5087 5088 5089 5090 5091 5092 5093
{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

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

	return css;
}

5094
static void debug_destroy(struct cgroup *cont)
5095 5096 5097 5098 5099 5100 5101 5102 5103 5104 5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 5117 5118 5119 5120 5121 5122 5123 5124
{
	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;
}

5125 5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142
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 = "?";
5143 5144
		seq_printf(seq, "Root %d group %s\n",
			   c->root->hierarchy_id, name);
5145 5146 5147 5148 5149 5150 5151 5152 5153 5154 5155 5156 5157 5158 5159 5160 5161 5162 5163 5164 5165 5166 5167 5168 5169 5170 5171 5172 5173 5174 5175 5176 5177
	}
	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;
}

5178 5179 5180 5181 5182 5183 5184 5185 5186 5187 5188 5189 5190 5191 5192 5193 5194 5195 5196 5197 5198 5199 5200 5201 5202
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,
	},

5203 5204 5205 5206 5207 5208 5209 5210 5211 5212
	{
		.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,
	},

5213 5214 5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232
	{
		.name = "releasable",
		.read_u64 = releasable_read,
	},
};

static int debug_populate(struct cgroup_subsys *ss, struct cgroup *cont)
{
	return cgroup_add_files(cont, ss, debug_files,
				ARRAY_SIZE(debug_files));
}

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