cgroup.c 108.5 KB
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/*
 *  Generic process-grouping system.
 *
 *  Based originally on the cpuset system, extracted by Paul Menage
 *  Copyright (C) 2006 Google, Inc
 *
 *  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/ctype.h>
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#include <linux/errno.h>
#include <linux/fs.h>
#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/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/smp_lock.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 <asm/atomic.h>

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static DEFINE_MUTEX(cgroup_mutex);

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/* Generate an array of cgroup subsystem pointers */
#define SUBSYS(_x) &_x ## _subsys,

static struct cgroup_subsys *subsys[] = {
#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.
	 */
	struct cgroup_subsys_state *css;
	/*
	 * 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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/* 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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/* 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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/*
 * 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);
static DEFINE_SPINLOCK(release_list_lock);
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_subsys_init_idr(struct cgroup_subsys *ss);

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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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static void free_css_set_rcu(struct rcu_head *obj)
{
	struct css_set *cg = container_of(obj, struct css_set, rcu_head);
	kfree(cg);
}

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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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	call_rcu(&cg->rcu_head, free_css_set_rcu);
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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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	/* Built the set of subsystem state objects that we want to
	 * see in the new css_set */
	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++;
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	/* Add this cgroup group to the hash table */
	hhead = css_set_hash(res->subsys);
	hlist_add_head(&res->hlist, hhead);

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	write_unlock(&css_set_lock);

	return res;
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}

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/*
 * 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;
}

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/*
 * 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
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 * cgroup_attach_task() can increment it again.  Because a count of zero
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 * means that no tasks are currently attached, therefore there is no
 * way a task attached to that cgroup can fork (the other way to
 * increment the count).  So code holding cgroup_mutex can safely
 * assume that if the count is zero, it will stay zero. Similarly, if
 * a task holds cgroup_mutex on a cgroup with zero count, it
 * knows that the cgroup won't be removed, as cgroup_rmdir()
 * needs that mutex.
 *
 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
 * (usually) take cgroup_mutex.  These are the two most performance
 * critical pieces of code here.  The exception occurs on cgroup_exit(),
 * when a task in a notify_on_release cgroup exits.  Then cgroup_mutex
 * is taken, and if the cgroup count is zero, a usermode call made
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 * to the release agent with the name of the cgroup (path relative to
 * the root of cgroup file system) as the argument.
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 *
 * 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
663
 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
L
Li Zefan 已提交
664
 * another.  It does so using cgroup_mutex, however there are
665 666 667
 * 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
668
 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
669 670 671 672
 * 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
673
 * update of a tasks cgroup pointer by cgroup_attach_task()
674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703
 */

/**
 * cgroup_lock - lock out any changes to cgroup structures
 *
 */
void cgroup_lock(void)
{
	mutex_lock(&cgroup_mutex);
}

/**
 * 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);
}

/*
 * 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.
 */

static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode);
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
704
static int cgroup_populate_dir(struct cgroup *cgrp);
705
static const struct inode_operations cgroup_dir_inode_operations;
706 707 708
static struct file_operations proc_cgroupstats_operations;

static struct backing_dev_info cgroup_backing_dev_info = {
709
	.name		= "cgroup",
710
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
711
};
712

K
KAMEZAWA Hiroyuki 已提交
713 714 715
static int alloc_css_id(struct cgroup_subsys *ss,
			struct cgroup *parent, struct cgroup *child);

716 717 718 719 720 721
static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
{
	struct inode *inode = new_inode(sb);

	if (inode) {
		inode->i_mode = mode;
722 723
		inode->i_uid = current_fsuid();
		inode->i_gid = current_fsgid();
724 725 726 727 728 729
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
	}
	return inode;
}

730 731 732 733
/*
 * Call subsys's pre_destroy handler.
 * This is called before css refcnt check.
 */
734
static int cgroup_call_pre_destroy(struct cgroup *cgrp)
735 736
{
	struct cgroup_subsys *ss;
737 738
	int ret = 0;

739
	for_each_subsys(cgrp->root, ss)
740 741 742 743 744 745
		if (ss->pre_destroy) {
			ret = ss->pre_destroy(ss, cgrp);
			if (ret)
				break;
		}
	return ret;
746 747
}

748 749 750 751 752 753 754
static void free_cgroup_rcu(struct rcu_head *obj)
{
	struct cgroup *cgrp = container_of(obj, struct cgroup, rcu_head);

	kfree(cgrp);
}

755 756 757 758
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)) {
759
		struct cgroup *cgrp = dentry->d_fsdata;
760
		struct cgroup_subsys *ss;
761
		BUG_ON(!(cgroup_is_removed(cgrp)));
762 763 764 765 766 767 768
		/* 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();
769 770 771 772 773

		mutex_lock(&cgroup_mutex);
		/*
		 * Release the subsystem state objects.
		 */
774 775
		for_each_subsys(cgrp->root, ss)
			ss->destroy(ss, cgrp);
776 777 778 779

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

780 781 782 783
		/*
		 * Drop the active superblock reference that we took when we
		 * created the cgroup
		 */
784 785
		deactivate_super(cgrp->root->sb);

786 787 788 789 790 791
		/*
		 * if we're getting rid of the cgroup, refcount should ensure
		 * that there are no pidlists left.
		 */
		BUG_ON(!list_empty(&cgrp->pidlists));

792
		call_rcu(&cgrp->rcu_head, free_cgroup_rcu);
793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844
	}
	iput(inode);
}

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));
	spin_lock(&dcache_lock);
	node = dentry->d_subdirs.next;
	while (node != &dentry->d_subdirs) {
		struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
		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);
			d = dget_locked(d);
			spin_unlock(&dcache_lock);
			d_delete(d);
			simple_unlink(dentry->d_inode, d);
			dput(d);
			spin_lock(&dcache_lock);
		}
		node = dentry->d_subdirs.next;
	}
	spin_unlock(&dcache_lock);
}

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

	spin_lock(&dcache_lock);
	list_del_init(&dentry->d_u.d_child);
	spin_unlock(&dcache_lock);
	remove_dir(dentry);
}

845 846 847 848 849 850
/*
 * 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.
 *
851
 * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
852 853 854
 */
DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);

855
static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
856
{
857
	if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
858 859 860
		wake_up_all(&cgroup_rmdir_waitq);
}

861 862 863 864 865 866 867 868 869 870 871 872
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);
}


873 874 875 876
static int rebind_subsystems(struct cgroupfs_root *root,
			      unsigned long final_bits)
{
	unsigned long added_bits, removed_bits;
877
	struct cgroup *cgrp = &root->top_cgroup;
878 879 880 881 882 883
	int i;

	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
884
		unsigned long bit = 1UL << i;
885 886 887 888 889 890 891 892 893 894 895 896 897
		struct cgroup_subsys *ss = subsys[i];
		if (!(bit & added_bits))
			continue;
		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 */
898
	if (root->number_of_cgroups > 1)
899 900 901 902 903 904 905 906
		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 */
907
			BUG_ON(cgrp->subsys[i]);
908 909
			BUG_ON(!dummytop->subsys[i]);
			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
910
			mutex_lock(&ss->hierarchy_mutex);
911 912
			cgrp->subsys[i] = dummytop->subsys[i];
			cgrp->subsys[i]->cgroup = cgrp;
913
			list_move(&ss->sibling, &root->subsys_list);
914
			ss->root = root;
915
			if (ss->bind)
916
				ss->bind(ss, cgrp);
917
			mutex_unlock(&ss->hierarchy_mutex);
918 919
		} else if (bit & removed_bits) {
			/* We're removing this subsystem */
920 921
			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
922
			mutex_lock(&ss->hierarchy_mutex);
923 924 925
			if (ss->bind)
				ss->bind(ss, dummytop);
			dummytop->subsys[i]->cgroup = dummytop;
926
			cgrp->subsys[i] = NULL;
927
			subsys[i]->root = &rootnode;
928
			list_move(&ss->sibling, &rootnode.subsys_list);
929
			mutex_unlock(&ss->hierarchy_mutex);
930 931
		} else if (bit & final_bits) {
			/* Subsystem state should already exist */
932
			BUG_ON(!cgrp->subsys[i]);
933 934
		} else {
			/* Subsystem state shouldn't exist */
935
			BUG_ON(cgrp->subsys[i]);
936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953
		}
	}
	root->subsys_bits = root->actual_subsys_bits = final_bits;
	synchronize_rcu();

	return 0;
}

static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
	struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info;
	struct cgroup_subsys *ss;

	mutex_lock(&cgroup_mutex);
	for_each_subsys(root, ss)
		seq_printf(seq, ",%s", ss->name);
	if (test_bit(ROOT_NOPREFIX, &root->flags))
		seq_puts(seq, ",noprefix");
954 955
	if (strlen(root->release_agent_path))
		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
956 957
	if (strlen(root->name))
		seq_printf(seq, ",name=%s", root->name);
958 959 960 961 962 963 964
	mutex_unlock(&cgroup_mutex);
	return 0;
}

struct cgroup_sb_opts {
	unsigned long subsys_bits;
	unsigned long flags;
965
	char *release_agent;
966
	char *name;
967 968
	/* User explicitly requested empty subsystem */
	bool none;
969 970

	struct cgroupfs_root *new_root;
971

972 973 974 975 976 977 978 979
};

/* Convert a hierarchy specifier into a bitmask of subsystems and
 * flags. */
static int parse_cgroupfs_options(char *data,
				     struct cgroup_sb_opts *opts)
{
	char *token, *o = data ?: "all";
980 981 982 983 984
	unsigned long mask = (unsigned long)-1;

#ifdef CONFIG_CPUSETS
	mask = ~(1UL << cpuset_subsys_id);
#endif
985

986
	memset(opts, 0, sizeof(*opts));
987 988 989 990 991

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
		if (!strcmp(token, "all")) {
992 993 994 995 996 997 998 999
			/* Add all non-disabled subsystems */
			int i;
			opts->subsys_bits = 0;
			for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
				struct cgroup_subsys *ss = subsys[i];
				if (!ss->disabled)
					opts->subsys_bits |= 1ul << i;
			}
1000 1001 1002
		} else if (!strcmp(token, "none")) {
			/* Explicitly have no subsystems */
			opts->none = true;
1003 1004
		} else if (!strcmp(token, "noprefix")) {
			set_bit(ROOT_NOPREFIX, &opts->flags);
1005 1006 1007 1008
		} else if (!strncmp(token, "release_agent=", 14)) {
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1009 1010
			opts->release_agent =
				kstrndup(token + 14, PATH_MAX, GFP_KERNEL);
1011 1012
			if (!opts->release_agent)
				return -ENOMEM;
1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035
		} else if (!strncmp(token, "name=", 5)) {
			int i;
			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,
					      MAX_CGROUP_ROOT_NAMELEN,
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1036 1037 1038 1039 1040 1041
		} else {
			struct cgroup_subsys *ss;
			int i;
			for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
				ss = subsys[i];
				if (!strcmp(token, ss->name)) {
1042 1043
					if (!ss->disabled)
						set_bit(i, &opts->subsys_bits);
1044 1045 1046 1047 1048 1049 1050 1051
					break;
				}
			}
			if (i == CGROUP_SUBSYS_COUNT)
				return -ENOENT;
		}
	}

1052 1053
	/* Consistency checks */

1054 1055 1056 1057 1058 1059 1060 1061 1062
	/*
	 * 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;

1063 1064 1065 1066 1067 1068 1069 1070 1071

	/* 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).
	 */
1072
	if (!opts->subsys_bits && !opts->name)
1073 1074 1075 1076 1077 1078 1079 1080 1081
		return -EINVAL;

	return 0;
}

static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
	int ret = 0;
	struct cgroupfs_root *root = sb->s_fs_info;
1082
	struct cgroup *cgrp = &root->top_cgroup;
1083 1084
	struct cgroup_sb_opts opts;

1085
	lock_kernel();
1086
	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099
	mutex_lock(&cgroup_mutex);

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

	/* Don't allow flags to change at remount */
	if (opts.flags != root->flags) {
		ret = -EINVAL;
		goto out_unlock;
	}

1100 1101 1102 1103 1104 1105
	/* Don't allow name to change at remount */
	if (opts.name && strcmp(opts.name, root->name)) {
		ret = -EINVAL;
		goto out_unlock;
	}

1106
	ret = rebind_subsystems(root, opts.subsys_bits);
1107 1108
	if (ret)
		goto out_unlock;
1109 1110

	/* (re)populate subsystem files */
1111
	cgroup_populate_dir(cgrp);
1112

1113 1114
	if (opts.release_agent)
		strcpy(root->release_agent_path, opts.release_agent);
1115
 out_unlock:
1116
	kfree(opts.release_agent);
1117
	kfree(opts.name);
1118
	mutex_unlock(&cgroup_mutex);
1119
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1120
	unlock_kernel();
1121 1122 1123
	return ret;
}

1124
static const struct super_operations cgroup_ops = {
1125 1126 1127 1128 1129 1130
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.show_options = cgroup_show_options,
	.remount_fs = cgroup_remount,
};

1131 1132 1133 1134 1135 1136
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);
1137 1138
	INIT_LIST_HEAD(&cgrp->pidlists);
	mutex_init(&cgrp->pidlist_mutex);
1139
}
1140

1141 1142
static void init_cgroup_root(struct cgroupfs_root *root)
{
1143
	struct cgroup *cgrp = &root->top_cgroup;
1144 1145 1146
	INIT_LIST_HEAD(&root->subsys_list);
	INIT_LIST_HEAD(&root->root_list);
	root->number_of_cgroups = 1;
1147 1148
	cgrp->root = root;
	cgrp->top_cgroup = cgrp;
1149
	init_cgroup_housekeeping(cgrp);
1150 1151
}

1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176
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;
}

1177 1178
static int cgroup_test_super(struct super_block *sb, void *data)
{
1179
	struct cgroup_sb_opts *opts = data;
1180 1181
	struct cgroupfs_root *root = sb->s_fs_info;

1182 1183 1184
	/* If we asked for a name then it must match */
	if (opts->name && strcmp(opts->name, root->name))
		return 0;
1185

1186 1187 1188 1189 1190 1191
	/*
	 * 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))
1192 1193 1194 1195 1196
		return 0;

	return 1;
}

1197 1198 1199 1200
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
	struct cgroupfs_root *root;

1201
	if (!opts->subsys_bits && !opts->none)
1202 1203 1204 1205 1206 1207
		return NULL;

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

1208 1209 1210 1211
	if (!init_root_id(root)) {
		kfree(root);
		return ERR_PTR(-ENOMEM);
	}
1212
	init_cgroup_root(root);
1213

1214 1215 1216 1217 1218 1219 1220 1221 1222
	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);
	return root;
}

1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234
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);
}

1235 1236 1237
static int cgroup_set_super(struct super_block *sb, void *data)
{
	int ret;
1238 1239 1240 1241 1242 1243
	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;

1244
	BUG_ON(!opts->subsys_bits && !opts->none);
1245 1246 1247 1248 1249

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

1250 1251
	sb->s_fs_info = opts->new_root;
	opts->new_root->sb = sb;
1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287

	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)
{
	struct inode *inode =
		cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
	struct dentry *dentry;

	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);
	dentry = d_alloc_root(inode);
	if (!dentry) {
		iput(inode);
		return -ENOMEM;
	}
	sb->s_root = dentry;
	return 0;
}

static int cgroup_get_sb(struct file_system_type *fs_type,
			 int flags, const char *unused_dev_name,
			 void *data, struct vfsmount *mnt)
{
	struct cgroup_sb_opts opts;
1288
	struct cgroupfs_root *root;
1289 1290
	int ret = 0;
	struct super_block *sb;
1291
	struct cgroupfs_root *new_root;
1292 1293 1294

	/* First find the desired set of subsystems */
	ret = parse_cgroupfs_options(data, &opts);
1295 1296
	if (ret)
		goto out_err;
1297

1298 1299 1300 1301 1302 1303 1304 1305
	/*
	 * 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);
		goto out_err;
1306
	}
1307
	opts.new_root = new_root;
1308

1309 1310
	/* Locate an existing or new sb for this hierarchy */
	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, &opts);
1311
	if (IS_ERR(sb)) {
1312
		ret = PTR_ERR(sb);
1313
		cgroup_drop_root(opts.new_root);
1314
		goto out_err;
1315 1316
	}

1317 1318 1319 1320 1321
	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;
1322
		struct cgroup *root_cgrp = &root->top_cgroup;
1323
		struct inode *inode;
1324
		struct cgroupfs_root *existing_root;
1325
		int i;
1326 1327 1328 1329 1330 1331

		BUG_ON(sb->s_root != NULL);

		ret = cgroup_get_rootdir(sb);
		if (ret)
			goto drop_new_super;
1332
		inode = sb->s_root->d_inode;
1333

1334
		mutex_lock(&inode->i_mutex);
1335 1336
		mutex_lock(&cgroup_mutex);

1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348
		if (strlen(root->name)) {
			/* Check for name clashes with existing mounts */
			for_each_active_root(existing_root) {
				if (!strcmp(existing_root->name, root->name)) {
					ret = -EBUSY;
					mutex_unlock(&cgroup_mutex);
					mutex_unlock(&inode->i_mutex);
					goto drop_new_super;
				}
			}
		}

1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362
		/*
		 * 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);
		if (ret) {
			mutex_unlock(&cgroup_mutex);
			mutex_unlock(&inode->i_mutex);
			goto drop_new_super;
		}

1363 1364 1365
		ret = rebind_subsystems(root, root->subsys_bits);
		if (ret == -EBUSY) {
			mutex_unlock(&cgroup_mutex);
1366
			mutex_unlock(&inode->i_mutex);
1367 1368
			free_cg_links(&tmp_cg_links);
			goto drop_new_super;
1369 1370 1371 1372 1373 1374
		}

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

		list_add(&root->root_list, &roots);
1375
		root_count++;
1376

1377
		sb->s_root->d_fsdata = root_cgrp;
1378 1379
		root->top_cgroup.dentry = sb->s_root;

1380 1381 1382
		/* Link the top cgroup in this hierarchy into all
		 * the css_set objects */
		write_lock(&css_set_lock);
1383 1384 1385
		for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
			struct hlist_head *hhead = &css_set_table[i];
			struct hlist_node *node;
1386
			struct css_set *cg;
1387

1388 1389
			hlist_for_each_entry(cg, node, hhead, hlist)
				link_css_set(&tmp_cg_links, cg, root_cgrp);
1390
		}
1391 1392 1393 1394
		write_unlock(&css_set_lock);

		free_cg_links(&tmp_cg_links);

1395 1396
		BUG_ON(!list_empty(&root_cgrp->sibling));
		BUG_ON(!list_empty(&root_cgrp->children));
1397 1398
		BUG_ON(root->number_of_cgroups != 1);

1399
		cgroup_populate_dir(root_cgrp);
1400
		mutex_unlock(&cgroup_mutex);
1401
		mutex_unlock(&inode->i_mutex);
1402 1403 1404 1405 1406
	} else {
		/*
		 * We re-used an existing hierarchy - the new root (if
		 * any) is not needed
		 */
1407
		cgroup_drop_root(opts.new_root);
1408 1409
	}

1410
	simple_set_mnt(mnt, sb);
1411 1412
	kfree(opts.release_agent);
	kfree(opts.name);
1413
	return 0;
1414 1415

 drop_new_super:
1416
	deactivate_locked_super(sb);
1417 1418 1419 1420
 out_err:
	kfree(opts.release_agent);
	kfree(opts.name);

1421 1422 1423 1424 1425
	return ret;
}

static void cgroup_kill_sb(struct super_block *sb) {
	struct cgroupfs_root *root = sb->s_fs_info;
1426
	struct cgroup *cgrp = &root->top_cgroup;
1427
	int ret;
K
KOSAKI Motohiro 已提交
1428 1429
	struct cg_cgroup_link *link;
	struct cg_cgroup_link *saved_link;
1430 1431 1432 1433

	BUG_ON(!root);

	BUG_ON(root->number_of_cgroups != 1);
1434 1435
	BUG_ON(!list_empty(&cgrp->children));
	BUG_ON(!list_empty(&cgrp->sibling));
1436 1437 1438 1439 1440 1441 1442 1443

	mutex_lock(&cgroup_mutex);

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

1444 1445 1446 1447 1448
	/*
	 * Release all the links from css_sets to this hierarchy's
	 * root cgroup
	 */
	write_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
1449 1450 1451

	list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
				 cgrp_link_list) {
1452
		list_del(&link->cg_link_list);
1453
		list_del(&link->cgrp_link_list);
1454 1455 1456 1457
		kfree(link);
	}
	write_unlock(&css_set_lock);

1458 1459 1460 1461
	if (!list_empty(&root->root_list)) {
		list_del(&root->root_list);
		root_count--;
	}
1462

1463 1464 1465
	mutex_unlock(&cgroup_mutex);

	kill_litter_super(sb);
1466
	cgroup_drop_root(root);
1467 1468 1469 1470 1471 1472 1473 1474
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
	.get_sb = cgroup_get_sb,
	.kill_sb = cgroup_kill_sb,
};

1475
static inline struct cgroup *__d_cgrp(struct dentry *dentry)
1476 1477 1478 1479 1480 1481 1482 1483 1484
{
	return dentry->d_fsdata;
}

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

L
Li Zefan 已提交
1485 1486 1487 1488 1489 1490
/**
 * 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
 *
1491 1492 1493
 * 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.
1494
 */
1495
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1496 1497
{
	char *start;
1498
	struct dentry *dentry = rcu_dereference(cgrp->dentry);
1499

1500
	if (!dentry || cgrp == dummytop) {
1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512
		/*
		 * Inactive subsystems have no dentry for their root
		 * cgroup
		 */
		strcpy(buf, "/");
		return 0;
	}

	start = buf + buflen;

	*--start = '\0';
	for (;;) {
1513
		int len = dentry->d_name.len;
1514 1515
		if ((start -= len) < buf)
			return -ENAMETOOLONG;
1516 1517 1518
		memcpy(start, cgrp->dentry->d_name.name, len);
		cgrp = cgrp->parent;
		if (!cgrp)
1519
			break;
1520
		dentry = rcu_dereference(cgrp->dentry);
1521
		if (!cgrp->parent)
1522 1523 1524 1525 1526 1527 1528 1529 1530
			continue;
		if (--start < buf)
			return -ENAMETOOLONG;
		*start = '/';
	}
	memmove(buf, start, buf + buflen - start);
	return 0;
}

L
Li Zefan 已提交
1531 1532 1533 1534
/**
 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
 * @cgrp: the cgroup the task is attaching to
 * @tsk: the task to be attached
1535
 *
L
Li Zefan 已提交
1536 1537
 * Call holding cgroup_mutex. May take task_lock of
 * the task 'tsk' during call.
1538
 */
1539
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1540 1541 1542
{
	int retval = 0;
	struct cgroup_subsys *ss;
1543
	struct cgroup *oldcgrp;
1544
	struct css_set *cg;
1545
	struct css_set *newcg;
1546
	struct cgroupfs_root *root = cgrp->root;
1547 1548

	/* Nothing to do if the task is already in that cgroup */
1549
	oldcgrp = task_cgroup_from_root(tsk, root);
1550
	if (cgrp == oldcgrp)
1551 1552 1553 1554
		return 0;

	for_each_subsys(root, ss) {
		if (ss->can_attach) {
1555
			retval = ss->can_attach(ss, cgrp, tsk);
P
Paul Jackson 已提交
1556
			if (retval)
1557 1558 1559 1560
				return retval;
		}
	}

1561 1562 1563 1564
	task_lock(tsk);
	cg = tsk->cgroups;
	get_css_set(cg);
	task_unlock(tsk);
1565 1566 1567 1568
	/*
	 * Locate or allocate a new css_set for this task,
	 * based on its final set of cgroups
	 */
1569
	newcg = find_css_set(cg, cgrp);
1570
	put_css_set(cg);
P
Paul Jackson 已提交
1571
	if (!newcg)
1572 1573
		return -ENOMEM;

1574 1575 1576
	task_lock(tsk);
	if (tsk->flags & PF_EXITING) {
		task_unlock(tsk);
1577
		put_css_set(newcg);
1578 1579
		return -ESRCH;
	}
1580
	rcu_assign_pointer(tsk->cgroups, newcg);
1581 1582
	task_unlock(tsk);

1583 1584 1585 1586 1587 1588 1589 1590
	/* Update the css_set linked lists if we're using them */
	write_lock(&css_set_lock);
	if (!list_empty(&tsk->cg_list)) {
		list_del(&tsk->cg_list);
		list_add(&tsk->cg_list, &newcg->tasks);
	}
	write_unlock(&css_set_lock);

1591
	for_each_subsys(root, ss) {
P
Paul Jackson 已提交
1592
		if (ss->attach)
1593
			ss->attach(ss, cgrp, oldcgrp, tsk);
1594
	}
1595
	set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1596
	synchronize_rcu();
1597
	put_css_set(cg);
1598 1599 1600 1601 1602

	/*
	 * wake up rmdir() waiter. the rmdir should fail since the cgroup
	 * is no longer empty.
	 */
1603
	cgroup_wakeup_rmdir_waiter(cgrp);
1604 1605 1606 1607
	return 0;
}

/*
1608 1609
 * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex
 * held. May take task_lock of task
1610
 */
1611
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid)
1612 1613
{
	struct task_struct *tsk;
1614
	const struct cred *cred = current_cred(), *tcred;
1615 1616 1617 1618
	int ret;

	if (pid) {
		rcu_read_lock();
1619
		tsk = find_task_by_vpid(pid);
1620 1621 1622 1623 1624
		if (!tsk || tsk->flags & PF_EXITING) {
			rcu_read_unlock();
			return -ESRCH;
		}

1625 1626 1627 1628 1629
		tcred = __task_cred(tsk);
		if (cred->euid &&
		    cred->euid != tcred->uid &&
		    cred->euid != tcred->suid) {
			rcu_read_unlock();
1630 1631
			return -EACCES;
		}
1632 1633
		get_task_struct(tsk);
		rcu_read_unlock();
1634 1635 1636 1637 1638
	} else {
		tsk = current;
		get_task_struct(tsk);
	}

1639
	ret = cgroup_attach_task(cgrp, tsk);
1640 1641 1642 1643
	put_task_struct(tsk);
	return ret;
}

1644 1645 1646 1647 1648 1649 1650 1651 1652 1653
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
{
	int ret;
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
	ret = attach_task_by_pid(cgrp, pid);
	cgroup_unlock();
	return ret;
}

1654 1655 1656 1657
/**
 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
 * @cgrp: the cgroup to be checked for liveness
 *
1658 1659
 * On success, returns true; the lock should be later released with
 * cgroup_unlock(). On failure returns false with no lock held.
1660
 */
1661
bool cgroup_lock_live_group(struct cgroup *cgrp)
1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677
{
	mutex_lock(&cgroup_mutex);
	if (cgroup_is_removed(cgrp)) {
		mutex_unlock(&cgroup_mutex);
		return false;
	}
	return true;
}

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);
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
	strcpy(cgrp->root->release_agent_path, buffer);
1678
	cgroup_unlock();
1679 1680 1681 1682 1683 1684 1685 1686 1687 1688
	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');
1689
	cgroup_unlock();
1690 1691 1692
	return 0;
}

1693 1694 1695
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64

1696
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
1697 1698 1699
				struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *unused_ppos)
1700
{
1701
	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712
	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 */
1713
	strstrip(buffer);
1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724
	if (cft->write_u64) {
		u64 val = simple_strtoull(buffer, &end, 0);
		if (*end)
			return -EINVAL;
		retval = cft->write_u64(cgrp, cft, val);
	} else {
		s64 val = simple_strtoll(buffer, &end, 0);
		if (*end)
			return -EINVAL;
		retval = cft->write_s64(cgrp, cft, val);
	}
1725 1726 1727 1728 1729
	if (!retval)
		retval = nbytes;
	return retval;
}

1730 1731 1732 1733 1734
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)
{
1735
	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749
	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
1750 1751 1752 1753
	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
		retval = -EFAULT;
		goto out;
	}
1754 1755 1756 1757 1758 1759

	buffer[nbytes] = 0;     /* nul-terminate */
	strstrip(buffer);
	retval = cft->write_string(cgrp, cft, buffer);
	if (!retval)
		retval = nbytes;
L
Li Zefan 已提交
1760
out:
1761 1762 1763 1764 1765
	if (buffer != local_buffer)
		kfree(buffer);
	return retval;
}

1766 1767 1768 1769
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);
1770
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
1771

1772
	if (cgroup_is_removed(cgrp))
1773
		return -ENODEV;
1774
	if (cft->write)
1775
		return cft->write(cgrp, cft, file, buf, nbytes, ppos);
1776 1777
	if (cft->write_u64 || cft->write_s64)
		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
1778 1779
	if (cft->write_string)
		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
1780 1781 1782 1783
	if (cft->trigger) {
		int ret = cft->trigger(cgrp, (unsigned int)cft->private);
		return ret ? ret : nbytes;
	}
1784
	return -EINVAL;
1785 1786
}

1787 1788 1789 1790
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
1791
{
1792
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
1793
	u64 val = cft->read_u64(cgrp, cft);
1794 1795 1796 1797 1798
	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);

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

1799 1800 1801 1802 1803
static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
{
1804
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
1805 1806 1807 1808 1809 1810
	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);
}

1811 1812 1813 1814
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);
1815
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
1816

1817
	if (cgroup_is_removed(cgrp))
1818 1819 1820
		return -ENODEV;

	if (cft->read)
1821
		return cft->read(cgrp, cft, file, buf, nbytes, ppos);
1822 1823
	if (cft->read_u64)
		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
1824 1825
	if (cft->read_s64)
		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
1826 1827 1828
	return -EINVAL;
}

1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848
/*
 * 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;
1849 1850 1851 1852 1853 1854 1855 1856
	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);
1857 1858
}

1859
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
1860 1861 1862 1863 1864 1865 1866 1867
{
	struct seq_file *seq = file->private_data;
	kfree(seq->private);
	return single_release(inode, file);
}

static struct file_operations cgroup_seqfile_operations = {
	.read = seq_read,
1868
	.write = cgroup_file_write,
1869 1870 1871 1872
	.llseek = seq_lseek,
	.release = cgroup_seqfile_release,
};

1873 1874 1875 1876 1877 1878 1879 1880 1881
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);
1882

1883
	if (cft->read_map || cft->read_seq_string) {
1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894
		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)
1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932
		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);
}

static struct file_operations cgroup_file_operations = {
	.read = cgroup_file_read,
	.write = cgroup_file_write,
	.llseek = generic_file_llseek,
	.open = cgroup_file_open,
	.release = cgroup_file_release,
};

1933
static const struct inode_operations cgroup_dir_inode_operations = {
1934 1935 1936 1937 1938 1939
	.lookup = simple_lookup,
	.mkdir = cgroup_mkdir,
	.rmdir = cgroup_rmdir,
	.rename = cgroup_rename,
};

L
Li Zefan 已提交
1940
static int cgroup_create_file(struct dentry *dentry, mode_t mode,
1941 1942
				struct super_block *sb)
{
A
Al Viro 已提交
1943
	static const struct dentry_operations cgroup_dops = {
1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966
		.d_iput = cgroup_diput,
	};

	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 */
1967
		mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978
	} else if (S_ISREG(mode)) {
		inode->i_size = 0;
		inode->i_fop = &cgroup_file_operations;
	}
	dentry->d_op = &cgroup_dops;
	d_instantiate(dentry, inode);
	dget(dentry);	/* Extra count - pin the dentry in core */
	return 0;
}

/*
L
Li Zefan 已提交
1979 1980 1981 1982 1983
 * 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.
1984
 */
1985
static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
L
Li Zefan 已提交
1986
				mode_t mode)
1987 1988 1989 1990
{
	struct dentry *parent;
	int error = 0;

1991 1992
	parent = cgrp->parent->dentry;
	error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
1993
	if (!error) {
1994
		dentry->d_fsdata = cgrp;
1995
		inc_nlink(parent->d_inode);
1996
		rcu_assign_pointer(cgrp->dentry, dentry);
1997 1998 1999 2000 2001 2002 2003
		dget(dentry);
	}
	dput(dentry);

	return error;
}

L
Li Zefan 已提交
2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030
/**
 * 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
 */
static mode_t cgroup_file_mode(const struct cftype *cft)
{
	mode_t mode = 0;

	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;
}

2031
int cgroup_add_file(struct cgroup *cgrp,
2032 2033 2034
		       struct cgroup_subsys *subsys,
		       const struct cftype *cft)
{
2035
	struct dentry *dir = cgrp->dentry;
2036 2037
	struct dentry *dentry;
	int error;
L
Li Zefan 已提交
2038
	mode_t mode;
2039 2040

	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2041
	if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2042 2043 2044 2045 2046 2047 2048
		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
2049 2050
		mode = cgroup_file_mode(cft);
		error = cgroup_create_file(dentry, mode | S_IFREG,
2051
						cgrp->root->sb);
2052 2053 2054 2055 2056 2057 2058 2059
		if (!error)
			dentry->d_fsdata = (void *)cft;
		dput(dentry);
	} else
		error = PTR_ERR(dentry);
	return error;
}

2060
int cgroup_add_files(struct cgroup *cgrp,
2061 2062 2063 2064 2065 2066
			struct cgroup_subsys *subsys,
			const struct cftype cft[],
			int count)
{
	int i, err;
	for (i = 0; i < count; i++) {
2067
		err = cgroup_add_file(cgrp, subsys, &cft[i]);
2068 2069 2070 2071 2072 2073
		if (err)
			return err;
	}
	return 0;
}

L
Li Zefan 已提交
2074 2075 2076 2077 2078 2079
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2080
int cgroup_task_count(const struct cgroup *cgrp)
2081 2082
{
	int count = 0;
K
KOSAKI Motohiro 已提交
2083
	struct cg_cgroup_link *link;
2084 2085

	read_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
2086
	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2087
		count += atomic_read(&link->cg->refcount);
2088 2089
	}
	read_unlock(&css_set_lock);
2090 2091 2092
	return count;
}

2093 2094 2095 2096
/*
 * Advance a list_head iterator.  The iterator should be positioned at
 * the start of a css_set
 */
2097
static void cgroup_advance_iter(struct cgroup *cgrp,
2098
				struct cgroup_iter *it)
2099 2100 2101 2102 2103 2104 2105 2106
{
	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;
2107
		if (l == &cgrp->css_sets) {
2108 2109 2110
			it->cg_link = NULL;
			return;
		}
2111
		link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2112 2113 2114 2115 2116 2117
		cg = link->cg;
	} while (list_empty(&cg->tasks));
	it->cg_link = l;
	it->task = cg->tasks.next;
}

2118 2119 2120 2121 2122 2123 2124 2125 2126
/*
 * 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().
 *
 * The tasklist_lock is not held here, as do_each_thread() and
 * while_each_thread() are protected by RCU.
 */
2127
static void cgroup_enable_task_cg_lists(void)
2128 2129 2130 2131 2132 2133
{
	struct task_struct *p, *g;
	write_lock(&css_set_lock);
	use_task_css_set_links = 1;
	do_each_thread(g, p) {
		task_lock(p);
2134 2135 2136 2137 2138 2139
		/*
		 * 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))
2140 2141 2142 2143 2144 2145
			list_add(&p->cg_list, &p->cgroups->tasks);
		task_unlock(p);
	} while_each_thread(g, p);
	write_unlock(&css_set_lock);
}

2146
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
2147 2148 2149 2150 2151 2152
{
	/*
	 * 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.
	 */
2153 2154 2155
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();

2156
	read_lock(&css_set_lock);
2157 2158
	it->cg_link = &cgrp->css_sets;
	cgroup_advance_iter(cgrp, it);
2159 2160
}

2161
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
2162 2163 2164 2165
					struct cgroup_iter *it)
{
	struct task_struct *res;
	struct list_head *l = it->task;
2166
	struct cg_cgroup_link *link;
2167 2168 2169 2170 2171 2172 2173

	/* 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;
2174 2175
	link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
	if (l == &link->cg->tasks) {
2176 2177
		/* We reached the end of this task list - move on to
		 * the next cg_cgroup_link */
2178
		cgroup_advance_iter(cgrp, it);
2179 2180 2181 2182 2183 2184
	} else {
		it->task = l;
	}
	return res;
}

2185
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
2186 2187 2188 2189
{
	read_unlock(&css_set_lock);
}

2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326
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++) {
2327
			struct task_struct *q = heap->ptrs[i];
2328
			if (i == 0) {
2329 2330
				latest_time = q->start_time;
				latest_task = q;
2331 2332
			}
			/* Process the task per the caller's callback */
2333 2334
			scan->process_task(q, scan);
			put_task_struct(q);
2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349
		}
		/*
		 * 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;
}

2350
/*
2351
 * Stuff for reading the 'tasks'/'procs' files.
2352 2353 2354 2355 2356 2357 2358 2359
 *
 * 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.
 *
 */

2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395
/*
 * 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;
}

2396
/*
2397 2398 2399 2400
 * 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.
2401
 */
2402 2403 2404
/* 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)
2405
{
2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434
	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)) {
2435
		newlist = pidlist_resize(list, dest);
2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446
		if (newlist)
			*p = newlist;
	}
	return dest;
}

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

2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460 2461 2462 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 2493 2494 2495
/*
 * 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 */
	struct pid_namespace *ns = get_pid_ns(current->nsproxy->pid_ns);
	/*
	 * 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) {
			/* found a matching list - drop the extra refcount */
			put_pid_ns(ns);
			/* make sure l doesn't vanish out from under us */
			down_write(&l->mutex);
			mutex_unlock(&cgrp->pidlist_mutex);
			l->use_count++;
			return l;
		}
	}
	/* entry not found; create a new one */
	l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
	if (!l) {
		mutex_unlock(&cgrp->pidlist_mutex);
		put_pid_ns(ns);
		return l;
	}
	init_rwsem(&l->mutex);
	down_write(&l->mutex);
	l->key.type = type;
	l->key.ns = ns;
	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;
}

2496 2497 2498
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
2499 2500
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
2501 2502 2503 2504
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
2505 2506
	struct cgroup_iter it;
	struct task_struct *tsk;
2507 2508 2509 2510 2511 2512 2513 2514 2515
	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);
2516
	array = pidlist_allocate(length);
2517 2518 2519
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
2520 2521
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
2522
		if (unlikely(n == length))
2523
			break;
2524
		/* get tgid or pid for procs or tasks file respectively */
2525 2526 2527 2528
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
2529 2530
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
2531
	}
2532
	cgroup_iter_end(cgrp, &it);
2533 2534 2535
	length = n;
	/* now sort & (if procs) strip out duplicates */
	sort(array, length, sizeof(pid_t), cmppid, NULL);
2536
	if (type == CGROUP_FILE_PROCS)
2537
		length = pidlist_uniq(&array, length);
2538 2539
	l = cgroup_pidlist_find(cgrp, type);
	if (!l) {
2540
		pidlist_free(array);
2541
		return -ENOMEM;
2542
	}
2543
	/* store array, freeing old if necessary - lock already held */
2544
	pidlist_free(l->list);
2545 2546 2547 2548
	l->list = array;
	l->length = length;
	l->use_count++;
	up_write(&l->mutex);
2549
	*lp = l;
2550
	return 0;
2551 2552
}

B
Balbir Singh 已提交
2553
/**
L
Li Zefan 已提交
2554
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
2555 2556 2557
 * @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
2558 2559 2560
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
2561 2562 2563 2564
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
	int ret = -EINVAL;
2565
	struct cgroup *cgrp;
B
Balbir Singh 已提交
2566 2567
	struct cgroup_iter it;
	struct task_struct *tsk;
2568

B
Balbir Singh 已提交
2569
	/*
2570 2571
	 * Validate dentry by checking the superblock operations,
	 * and make sure it's a directory.
B
Balbir Singh 已提交
2572
	 */
2573 2574
	if (dentry->d_sb->s_op != &cgroup_ops ||
	    !S_ISDIR(dentry->d_inode->i_mode))
B
Balbir Singh 已提交
2575 2576 2577
		 goto err;

	ret = 0;
2578
	cgrp = dentry->d_fsdata;
B
Balbir Singh 已提交
2579

2580 2581
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
B
Balbir Singh 已提交
2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600
		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;
		}
	}
2601
	cgroup_iter_end(cgrp, &it);
B
Balbir Singh 已提交
2602 2603 2604 2605 2606

err:
	return ret;
}

2607

2608
/*
2609
 * seq_file methods for the tasks/procs files. The seq_file position is the
2610
 * next pid to display; the seq_file iterator is a pointer to the pid
2611
 * in the cgroup->l->list array.
2612
 */
2613

2614
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
2615
{
2616 2617 2618 2619 2620 2621
	/*
	 * 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
	 */
2622
	struct cgroup_pidlist *l = s->private;
2623 2624 2625
	int index = 0, pid = *pos;
	int *iter;

2626
	down_read(&l->mutex);
2627
	if (pid) {
2628
		int end = l->length;
S
Stephen Rothwell 已提交
2629

2630 2631
		while (index < end) {
			int mid = (index + end) / 2;
2632
			if (l->list[mid] == pid) {
2633 2634
				index = mid;
				break;
2635
			} else if (l->list[mid] <= pid)
2636 2637 2638 2639 2640 2641
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
2642
	if (index >= l->length)
2643 2644
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
2645
	iter = l->list + index;
2646 2647 2648 2649
	*pos = *iter;
	return iter;
}

2650
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
2651
{
2652 2653
	struct cgroup_pidlist *l = s->private;
	up_read(&l->mutex);
2654 2655
}

2656
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
2657
{
2658 2659 2660
	struct cgroup_pidlist *l = s->private;
	pid_t *p = v;
	pid_t *end = l->list + l->length;
2661 2662 2663 2664 2665 2666 2667 2668 2669 2670 2671 2672 2673
	/*
	 * 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;
	}
}

2674
static int cgroup_pidlist_show(struct seq_file *s, void *v)
2675 2676 2677
{
	return seq_printf(s, "%d\n", *(int *)v);
}
2678

2679 2680 2681 2682 2683 2684 2685 2686 2687
/*
 * 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,
2688 2689
};

2690
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
2691
{
2692 2693 2694 2695 2696 2697 2698
	/*
	 * 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);
2699 2700 2701
	down_write(&l->mutex);
	BUG_ON(!l->use_count);
	if (!--l->use_count) {
2702 2703 2704
		/* we're the last user if refcount is 0; remove and free */
		list_del(&l->links);
		mutex_unlock(&l->owner->pidlist_mutex);
2705
		pidlist_free(l->list);
2706 2707 2708 2709
		put_pid_ns(l->key.ns);
		up_write(&l->mutex);
		kfree(l);
		return;
2710
	}
2711
	mutex_unlock(&l->owner->pidlist_mutex);
2712
	up_write(&l->mutex);
2713 2714
}

2715
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
2716
{
2717
	struct cgroup_pidlist *l;
2718 2719
	if (!(file->f_mode & FMODE_READ))
		return 0;
2720 2721 2722 2723 2724 2725
	/*
	 * 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);
2726 2727 2728
	return seq_release(inode, file);
}

2729
static const struct file_operations cgroup_pidlist_operations = {
2730 2731 2732
	.read = seq_read,
	.llseek = seq_lseek,
	.write = cgroup_file_write,
2733
	.release = cgroup_pidlist_release,
2734 2735
};

2736
/*
2737 2738 2739
 * 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.
2740
 */
2741
/* helper function for the two below it */
2742
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
2743
{
2744
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2745
	struct cgroup_pidlist *l;
2746
	int retval;
2747

2748
	/* Nothing to do for write-only files */
2749 2750 2751
	if (!(file->f_mode & FMODE_READ))
		return 0;

2752
	/* have the array populated */
2753
	retval = pidlist_array_load(cgrp, type, &l);
2754 2755 2756 2757
	if (retval)
		return retval;
	/* configure file information */
	file->f_op = &cgroup_pidlist_operations;
2758

2759
	retval = seq_open(file, &cgroup_pidlist_seq_operations);
2760
	if (retval) {
2761
		cgroup_release_pid_array(l);
2762
		return retval;
2763
	}
2764
	((struct seq_file *)file->private_data)->private = l;
2765 2766
	return 0;
}
2767 2768
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
2769
	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
2770 2771 2772
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
2773
	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
2774
}
2775

2776
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
2777 2778
					    struct cftype *cft)
{
2779
	return notify_on_release(cgrp);
2780 2781
}

2782 2783 2784 2785 2786 2787 2788 2789 2790 2791 2792 2793
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;
}

2794 2795 2796
/*
 * for the common functions, 'private' gives the type of file
 */
2797 2798
/* for hysterical raisins, we can't put this on the older files */
#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
2799 2800 2801 2802
static struct cftype files[] = {
	{
		.name = "tasks",
		.open = cgroup_tasks_open,
2803
		.write_u64 = cgroup_tasks_write,
2804
		.release = cgroup_pidlist_release,
L
Li Zefan 已提交
2805
		.mode = S_IRUGO | S_IWUSR,
2806
	},
2807 2808 2809 2810 2811 2812 2813
	{
		.name = CGROUP_FILE_GENERIC_PREFIX "procs",
		.open = cgroup_procs_open,
		/* .write_u64 = cgroup_procs_write, TODO */
		.release = cgroup_pidlist_release,
		.mode = S_IRUGO,
	},
2814 2815
	{
		.name = "notify_on_release",
2816
		.read_u64 = cgroup_read_notify_on_release,
2817
		.write_u64 = cgroup_write_notify_on_release,
2818 2819 2820 2821 2822
	},
};

static struct cftype cft_release_agent = {
	.name = "release_agent",
2823 2824 2825
	.read_seq_string = cgroup_release_agent_show,
	.write_string = cgroup_release_agent_write,
	.max_write_len = PATH_MAX,
2826 2827
};

2828
static int cgroup_populate_dir(struct cgroup *cgrp)
2829 2830 2831 2832 2833
{
	int err;
	struct cgroup_subsys *ss;

	/* First clear out any existing files */
2834
	cgroup_clear_directory(cgrp->dentry);
2835

2836
	err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));
2837 2838 2839
	if (err < 0)
		return err;

2840 2841
	if (cgrp == cgrp->top_cgroup) {
		if ((err = cgroup_add_file(cgrp, NULL, &cft_release_agent)) < 0)
2842 2843 2844
			return err;
	}

2845 2846
	for_each_subsys(cgrp->root, ss) {
		if (ss->populate && (err = ss->populate(ss, cgrp)) < 0)
2847 2848
			return err;
	}
K
KAMEZAWA Hiroyuki 已提交
2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859
	/* 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);
	}
2860 2861 2862 2863 2864 2865

	return 0;
}

static void init_cgroup_css(struct cgroup_subsys_state *css,
			       struct cgroup_subsys *ss,
2866
			       struct cgroup *cgrp)
2867
{
2868
	css->cgroup = cgrp;
P
Paul Menage 已提交
2869
	atomic_set(&css->refcnt, 1);
2870
	css->flags = 0;
K
KAMEZAWA Hiroyuki 已提交
2871
	css->id = NULL;
2872
	if (cgrp == dummytop)
2873
		set_bit(CSS_ROOT, &css->flags);
2874 2875
	BUG_ON(cgrp->subsys[ss->subsys_id]);
	cgrp->subsys[ss->subsys_id] = css;
2876 2877
}

2878 2879 2880 2881 2882 2883 2884 2885
static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
{
	/* We need to take each hierarchy_mutex in a consistent order */
	int i;

	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		if (ss->root == root)
2886
			mutex_lock(&ss->hierarchy_mutex);
2887 2888 2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900
	}
}

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];
		if (ss->root == root)
			mutex_unlock(&ss->hierarchy_mutex);
	}
}

2901
/*
L
Li Zefan 已提交
2902 2903 2904 2905
 * 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
2906
 *
L
Li Zefan 已提交
2907
 * Must be called with the mutex on the parent inode held
2908 2909
 */
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
L
Li Zefan 已提交
2910
			     mode_t mode)
2911
{
2912
	struct cgroup *cgrp;
2913 2914 2915 2916 2917
	struct cgroupfs_root *root = parent->root;
	int err = 0;
	struct cgroup_subsys *ss;
	struct super_block *sb = root->sb;

2918 2919
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
2920 2921 2922 2923 2924 2925 2926 2927 2928 2929 2930
		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);

2931
	init_cgroup_housekeeping(cgrp);
2932

2933 2934 2935
	cgrp->parent = parent;
	cgrp->root = parent->root;
	cgrp->top_cgroup = parent->top_cgroup;
2936

2937 2938 2939
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

2940
	for_each_subsys(root, ss) {
2941
		struct cgroup_subsys_state *css = ss->create(ss, cgrp);
2942 2943 2944 2945
		if (IS_ERR(css)) {
			err = PTR_ERR(css);
			goto err_destroy;
		}
2946
		init_cgroup_css(css, ss, cgrp);
K
KAMEZAWA Hiroyuki 已提交
2947 2948 2949 2950
		if (ss->use_id)
			if (alloc_css_id(ss, parent, cgrp))
				goto err_destroy;
		/* At error, ->destroy() callback has to free assigned ID. */
2951 2952
	}

2953
	cgroup_lock_hierarchy(root);
2954
	list_add(&cgrp->sibling, &cgrp->parent->children);
2955
	cgroup_unlock_hierarchy(root);
2956 2957
	root->number_of_cgroups++;

2958
	err = cgroup_create_dir(cgrp, dentry, mode);
2959 2960 2961 2962
	if (err < 0)
		goto err_remove;

	/* The cgroup directory was pre-locked for us */
2963
	BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
2964

2965
	err = cgroup_populate_dir(cgrp);
2966 2967 2968
	/* If err < 0, we have a half-filled directory - oh well ;) */

	mutex_unlock(&cgroup_mutex);
2969
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
2970 2971 2972 2973 2974

	return 0;

 err_remove:

2975
	cgroup_lock_hierarchy(root);
2976
	list_del(&cgrp->sibling);
2977
	cgroup_unlock_hierarchy(root);
2978 2979 2980 2981 2982
	root->number_of_cgroups--;

 err_destroy:

	for_each_subsys(root, ss) {
2983 2984
		if (cgrp->subsys[ss->subsys_id])
			ss->destroy(ss, cgrp);
2985 2986 2987 2988 2989 2990 2991
	}

	mutex_unlock(&cgroup_mutex);

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

2992
	kfree(cgrp);
2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003
	return err;
}

static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
	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);
}

3004
static int cgroup_has_css_refs(struct cgroup *cgrp)
3005 3006 3007
{
	/* Check the reference count on each subsystem. Since we
	 * already established that there are no tasks in the
P
Paul Menage 已提交
3008
	 * cgroup, if the css refcount is also 1, then there should
3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019
	 * 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;
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		struct cgroup_subsys_state *css;
		/* Skip subsystems not in this hierarchy */
3020
		if (ss->root != cgrp->root)
3021
			continue;
3022
		css = cgrp->subsys[ss->subsys_id];
3023 3024 3025 3026 3027 3028
		/* 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
3029
		if (css && (atomic_read(&css->refcnt) > 1))
3030 3031 3032 3033 3034
			return 1;
	}
	return 0;
}

P
Paul Menage 已提交
3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049
/*
 * 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;
3050
		while (1) {
P
Paul Menage 已提交
3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063
			/* 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
			 */
3064 3065 3066 3067
			if (atomic_cmpxchg(&css->refcnt, refcnt, 0) == refcnt)
				break;
			cpu_relax();
		}
P
Paul Menage 已提交
3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082 3083 3084 3085 3086 3087
	}
 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;
}

3088 3089
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
3090
	struct cgroup *cgrp = dentry->d_fsdata;
3091 3092
	struct dentry *d;
	struct cgroup *parent;
3093 3094
	DEFINE_WAIT(wait);
	int ret;
3095 3096

	/* the vfs holds both inode->i_mutex already */
3097
again:
3098
	mutex_lock(&cgroup_mutex);
3099
	if (atomic_read(&cgrp->count) != 0) {
3100 3101 3102
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
3103
	if (!list_empty(&cgrp->children)) {
3104 3105 3106
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
3107
	mutex_unlock(&cgroup_mutex);
L
Li Zefan 已提交
3108

3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119
	/*
	 * 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);

3120
	/*
L
Li Zefan 已提交
3121 3122
	 * Call pre_destroy handlers of subsys. Notify subsystems
	 * that rmdir() request comes.
3123
	 */
3124
	ret = cgroup_call_pre_destroy(cgrp);
3125 3126
	if (ret) {
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
3127
		return ret;
3128
	}
3129

3130 3131
	mutex_lock(&cgroup_mutex);
	parent = cgrp->parent;
3132
	if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
3133
		clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
3134 3135 3136
		mutex_unlock(&cgroup_mutex);
		return -EBUSY;
	}
3137 3138 3139
	prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
	if (!cgroup_clear_css_refs(cgrp)) {
		mutex_unlock(&cgroup_mutex);
3140 3141 3142 3143 3144 3145
		/*
		 * 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();
3146 3147 3148 3149 3150 3151 3152 3153 3154
		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);
3155

3156
	spin_lock(&release_list_lock);
3157 3158 3159
	set_bit(CGRP_REMOVED, &cgrp->flags);
	if (!list_empty(&cgrp->release_list))
		list_del(&cgrp->release_list);
3160
	spin_unlock(&release_list_lock);
3161 3162 3163

	cgroup_lock_hierarchy(cgrp->root);
	/* delete this cgroup from parent->children */
3164
	list_del(&cgrp->sibling);
3165 3166
	cgroup_unlock_hierarchy(cgrp->root);

3167 3168
	spin_lock(&cgrp->dentry->d_lock);
	d = dget(cgrp->dentry);
3169 3170 3171 3172 3173
	spin_unlock(&d->d_lock);

	cgroup_d_remove_dir(d);
	dput(d);

3174
	set_bit(CGRP_RELEASABLE, &parent->flags);
3175 3176
	check_for_release(parent);

3177 3178 3179 3180
	mutex_unlock(&cgroup_mutex);
	return 0;
}

3181
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
3182 3183
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
3184 3185

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
3186 3187

	/* Create the top cgroup state for this subsystem */
3188
	list_add(&ss->sibling, &rootnode.subsys_list);
3189 3190 3191 3192 3193 3194
	ss->root = &rootnode;
	css = ss->create(ss, dummytop);
	/* We don't handle early failures gracefully */
	BUG_ON(IS_ERR(css));
	init_cgroup_css(css, ss, dummytop);

L
Li Zefan 已提交
3195
	/* Update the init_css_set to contain a subsys
3196
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
3197 3198 3199
	 * 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];
3200 3201 3202

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

L
Li Zefan 已提交
3203 3204 3205 3206 3207
	/* 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));

3208
	mutex_init(&ss->hierarchy_mutex);
3209
	lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
3210 3211 3212 3213
	ss->active = 1;
}

/**
L
Li Zefan 已提交
3214 3215 3216 3217
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
3218 3219 3220 3221
 */
int __init cgroup_init_early(void)
{
	int i;
3222
	atomic_set(&init_css_set.refcount, 1);
3223 3224
	INIT_LIST_HEAD(&init_css_set.cg_links);
	INIT_LIST_HEAD(&init_css_set.tasks);
3225
	INIT_HLIST_NODE(&init_css_set.hlist);
3226
	css_set_count = 1;
3227
	init_cgroup_root(&rootnode);
3228 3229 3230 3231
	root_count = 1;
	init_task.cgroups = &init_css_set;

	init_css_set_link.cg = &init_css_set;
3232
	init_css_set_link.cgrp = dummytop;
3233
	list_add(&init_css_set_link.cgrp_link_list,
3234 3235 3236
		 &rootnode.top_cgroup.css_sets);
	list_add(&init_css_set_link.cg_link_list,
		 &init_css_set.cg_links);
3237

3238 3239 3240
	for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
		INIT_HLIST_HEAD(&css_set_table[i]);

3241 3242 3243 3244 3245 3246 3247 3248
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		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
3249
			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260
			       ss->name, ss->subsys_id);
			BUG();
		}

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

/**
L
Li Zefan 已提交
3261 3262 3263 3264
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
3265 3266 3267 3268 3269
 */
int __init cgroup_init(void)
{
	int err;
	int i;
3270
	struct hlist_head *hhead;
3271 3272 3273 3274

	err = bdi_init(&cgroup_backing_dev_info);
	if (err)
		return err;
3275 3276 3277 3278 3279

	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		if (!ss->early_init)
			cgroup_init_subsys(ss);
K
KAMEZAWA Hiroyuki 已提交
3280 3281
		if (ss->use_id)
			cgroup_subsys_init_idr(ss);
3282 3283
	}

3284 3285 3286
	/* Add init_css_set to the hash table */
	hhead = css_set_hash(init_css_set.subsys);
	hlist_add_head(&init_css_set.hlist, hhead);
3287
	BUG_ON(!init_root_id(&rootnode));
3288 3289 3290 3291
	err = register_filesystem(&cgroup_fs_type);
	if (err < 0)
		goto out;

L
Li Zefan 已提交
3292
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
3293

3294
out:
3295 3296 3297
	if (err)
		bdi_destroy(&cgroup_backing_dev_info);

3298 3299
	return err;
}
3300

3301 3302 3303 3304 3305 3306
/*
 * 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,
3307
 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336
 *    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);

3337
	for_each_active_root(root) {
3338
		struct cgroup_subsys *ss;
3339
		struct cgroup *cgrp;
3340 3341
		int count = 0;

3342
		seq_printf(m, "%d:", root->hierarchy_id);
3343 3344
		for_each_subsys(root, ss)
			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
3345 3346 3347
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
3348
		seq_putc(m, ':');
3349
		cgrp = task_cgroup_from_root(tsk, root);
3350
		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
3351 3352 3353 3354 3355 3356 3357 3358 3359 3360 3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382 3383
		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);
}

struct file_operations proc_cgroup_operations = {
	.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;

3384
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
3385 3386 3387
	mutex_lock(&cgroup_mutex);
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
3388 3389
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
3390
			   ss->root->number_of_cgroups, !ss->disabled);
3391 3392 3393 3394 3395 3396 3397
	}
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
3398
	return single_open(file, proc_cgroupstats_show, NULL);
3399 3400 3401 3402 3403 3404 3405 3406 3407
}

static struct file_operations proc_cgroupstats_operations = {
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

3408 3409
/**
 * cgroup_fork - attach newly forked task to its parents cgroup.
L
Li Zefan 已提交
3410
 * @child: pointer to task_struct of forking parent process.
3411 3412 3413 3414 3415 3416
 *
 * 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
 * it was not made under the protection of RCU or cgroup_mutex, so
3417
 * might no longer be a valid cgroup pointer.  cgroup_attach_task() might
3418 3419
 * have already changed current->cgroups, allowing the previously
 * referenced cgroup group to be removed and freed.
3420 3421 3422 3423 3424 3425
 *
 * 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)
{
3426 3427 3428 3429 3430
	task_lock(current);
	child->cgroups = current->cgroups;
	get_css_set(child->cgroups);
	task_unlock(current);
	INIT_LIST_HEAD(&child->cg_list);
3431 3432 3433
}

/**
L
Li Zefan 已提交
3434 3435 3436 3437 3438 3439
 * 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.
3440 3441 3442 3443 3444 3445 3446 3447 3448 3449 3450 3451 3452
 */
void cgroup_fork_callbacks(struct task_struct *child)
{
	if (need_forkexit_callback) {
		int i;
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss->fork)
				ss->fork(ss, child);
		}
	}
}

3453
/**
L
Li Zefan 已提交
3454 3455 3456 3457 3458 3459 3460 3461
 * 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.
 */
3462 3463 3464 3465
void cgroup_post_fork(struct task_struct *child)
{
	if (use_task_css_set_links) {
		write_lock(&css_set_lock);
3466
		task_lock(child);
3467 3468
		if (list_empty(&child->cg_list))
			list_add(&child->cg_list, &child->cgroups->tasks);
3469
		task_unlock(child);
3470 3471 3472
		write_unlock(&css_set_lock);
	}
}
3473 3474 3475
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
3476
 * @run_callback: run exit callbacks?
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
 *
 * 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,
3505 3506
 *    which wards off any cgroup_attach_task() attempts, or task is a failed
 *    fork, never visible to cgroup_attach_task.
3507 3508 3509 3510
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
	int i;
3511
	struct css_set *cg;
3512 3513 3514 3515 3516 3517 3518 3519

	if (run_callbacks && need_forkexit_callback) {
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss->exit)
				ss->exit(ss, tsk);
		}
	}
3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530 3531 3532

	/*
	 * 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))
			list_del(&tsk->cg_list);
		write_unlock(&css_set_lock);
	}

3533 3534
	/* Reassign the task to the init_css_set. */
	task_lock(tsk);
3535 3536
	cg = tsk->cgroups;
	tsk->cgroups = &init_css_set;
3537
	task_unlock(tsk);
3538
	if (cg)
3539
		put_css_set_taskexit(cg);
3540
}
3541 3542

/**
L
Li Zefan 已提交
3543 3544 3545
 * cgroup_clone - clone the cgroup the given subsystem is attached to
 * @tsk: the task to be moved
 * @subsys: the given subsystem
3546
 * @nodename: the name for the new cgroup
L
Li Zefan 已提交
3547 3548 3549 3550
 *
 * Duplicate the current cgroup in the hierarchy that the given
 * subsystem is attached to, and move this task into the new
 * child.
3551
 */
3552 3553
int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
							char *nodename)
3554 3555 3556 3557 3558 3559 3560 3561 3562 3563 3564 3565 3566 3567 3568 3569 3570 3571 3572 3573 3574 3575 3576
{
	struct dentry *dentry;
	int ret = 0;
	struct cgroup *parent, *child;
	struct inode *inode;
	struct css_set *cg;
	struct cgroupfs_root *root;
	struct cgroup_subsys *ss;

	/* We shouldn't be called by an unregistered subsystem */
	BUG_ON(!subsys->active);

	/* First figure out what hierarchy and cgroup we're dealing
	 * with, and pin them so we can drop cgroup_mutex */
	mutex_lock(&cgroup_mutex);
 again:
	root = subsys->root;
	if (root == &rootnode) {
		mutex_unlock(&cgroup_mutex);
		return 0;
	}

	/* Pin the hierarchy */
3577
	if (!atomic_inc_not_zero(&root->sb->s_active)) {
3578 3579 3580 3581
		/* We race with the final deactivate_super() */
		mutex_unlock(&cgroup_mutex);
		return 0;
	}
3582

3583
	/* Keep the cgroup alive */
3584 3585 3586
	task_lock(tsk);
	parent = task_cgroup(tsk, subsys->subsys_id);
	cg = tsk->cgroups;
3587
	get_css_set(cg);
3588
	task_unlock(tsk);
3589

3590 3591 3592 3593 3594 3595 3596 3597 3598 3599 3600
	mutex_unlock(&cgroup_mutex);

	/* Now do the VFS work to create a cgroup */
	inode = parent->dentry->d_inode;

	/* Hold the parent directory mutex across this operation to
	 * stop anyone else deleting the new cgroup */
	mutex_lock(&inode->i_mutex);
	dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));
	if (IS_ERR(dentry)) {
		printk(KERN_INFO
D
Diego Calleja 已提交
3601
		       "cgroup: Couldn't allocate dentry for %s: %ld\n", nodename,
3602 3603 3604 3605 3606 3607
		       PTR_ERR(dentry));
		ret = PTR_ERR(dentry);
		goto out_release;
	}

	/* Create the cgroup directory, which also creates the cgroup */
3608
	ret = vfs_mkdir(inode, dentry, 0755);
3609
	child = __d_cgrp(dentry);
3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625
	dput(dentry);
	if (ret) {
		printk(KERN_INFO
		       "Failed to create cgroup %s: %d\n", nodename,
		       ret);
		goto out_release;
	}

	/* The cgroup now exists. Retake cgroup_mutex and check
	 * that we're still in the same state that we thought we
	 * were. */
	mutex_lock(&cgroup_mutex);
	if ((root != subsys->root) ||
	    (parent != task_cgroup(tsk, subsys->subsys_id))) {
		/* Aargh, we raced ... */
		mutex_unlock(&inode->i_mutex);
3626
		put_css_set(cg);
3627

3628
		deactivate_super(root->sb);
3629 3630 3631 3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644
		/* The cgroup is still accessible in the VFS, but
		 * we're not going to try to rmdir() it at this
		 * point. */
		printk(KERN_INFO
		       "Race in cgroup_clone() - leaking cgroup %s\n",
		       nodename);
		goto again;
	}

	/* do any required auto-setup */
	for_each_subsys(root, ss) {
		if (ss->post_clone)
			ss->post_clone(ss, child);
	}

	/* All seems fine. Finish by moving the task into the new cgroup */
3645
	ret = cgroup_attach_task(child, tsk);
3646 3647 3648 3649
	mutex_unlock(&cgroup_mutex);

 out_release:
	mutex_unlock(&inode->i_mutex);
3650 3651

	mutex_lock(&cgroup_mutex);
3652
	put_css_set(cg);
3653
	mutex_unlock(&cgroup_mutex);
3654
	deactivate_super(root->sb);
3655 3656 3657
	return ret;
}

L
Li Zefan 已提交
3658
/**
3659
 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
L
Li Zefan 已提交
3660
 * @cgrp: the cgroup in question
3661
 * @task: the task in question
L
Li Zefan 已提交
3662
 *
3663 3664
 * See if @cgrp is a descendant of @task's cgroup in the appropriate
 * hierarchy.
3665 3666 3667 3668 3669 3670
 *
 * If we are sending in dummytop, then presumably we are creating
 * the top cgroup in the subsystem.
 *
 * Called only by the ns (nsproxy) cgroup.
 */
3671
int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
3672 3673 3674 3675
{
	int ret;
	struct cgroup *target;

3676
	if (cgrp == dummytop)
3677 3678
		return 1;

3679
	target = task_cgroup_from_root(task, cgrp->root);
3680 3681 3682
	while (cgrp != target && cgrp!= cgrp->top_cgroup)
		cgrp = cgrp->parent;
	ret = (cgrp == target);
3683 3684
	return ret;
}
3685

3686
static void check_for_release(struct cgroup *cgrp)
3687 3688 3689
{
	/* All of these checks rely on RCU to keep the cgroup
	 * structure alive */
3690 3691
	if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
	    && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
3692 3693 3694 3695 3696
		/* Control Group is currently removeable. If it's not
		 * already queued for a userspace notification, queue
		 * it now */
		int need_schedule_work = 0;
		spin_lock(&release_list_lock);
3697 3698 3699
		if (!cgroup_is_removed(cgrp) &&
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
3700 3701 3702 3703 3704 3705 3706 3707 3708 3709
			need_schedule_work = 1;
		}
		spin_unlock(&release_list_lock);
		if (need_schedule_work)
			schedule_work(&release_agent_work);
	}
}

void __css_put(struct cgroup_subsys_state *css)
{
3710
	struct cgroup *cgrp = css->cgroup;
3711
	rcu_read_lock();
3712 3713 3714 3715 3716
	if (atomic_dec_return(&css->refcnt) == 1) {
		if (notify_on_release(cgrp)) {
			set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
		}
3717
		cgroup_wakeup_rmdir_waiter(cgrp);
3718 3719 3720 3721 3722 3723 3724 3725 3726 3727 3728 3729 3730 3731 3732 3733 3734 3735 3736 3737 3738 3739 3740 3741 3742 3743 3744 3745 3746 3747 3748 3749 3750 3751 3752
	}
	rcu_read_unlock();
}

/*
 * 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);
	spin_lock(&release_list_lock);
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
3753
		char *pathbuf = NULL, *agentbuf = NULL;
3754
		struct cgroup *cgrp = list_entry(release_list.next,
3755 3756
						    struct cgroup,
						    release_list);
3757
		list_del_init(&cgrp->release_list);
3758 3759
		spin_unlock(&release_list_lock);
		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
3760 3761 3762 3763 3764 3765 3766
		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;
3767 3768

		i = 0;
3769 3770
		argv[i++] = agentbuf;
		argv[i++] = pathbuf;
3771 3772 3773 3774 3775 3776 3777 3778 3779 3780 3781 3782 3783 3784
		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);
3785 3786 3787
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
3788 3789 3790 3791 3792
		spin_lock(&release_list_lock);
	}
	spin_unlock(&release_list_lock);
	mutex_unlock(&cgroup_mutex);
}
3793 3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807 3808 3809 3810 3811 3812 3813 3814 3815 3816

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

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;

		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			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
3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828 3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843

/*
 * 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)
{
	struct css_id *cssid = rcu_dereference(css->id);

	if (cssid)
		return cssid->id;
	return 0;
}

unsigned short css_depth(struct cgroup_subsys_state *css)
{
	struct css_id *cssid = rcu_dereference(css->id);

	if (cssid)
		return cssid->depth;
	return 0;
}

bool css_is_ancestor(struct cgroup_subsys_state *child,
3844
		    const struct cgroup_subsys_state *root)
K
KAMEZAWA Hiroyuki 已提交
3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910 3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954 3955 3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971 3972 3973 3974 3975 3976 3977 3978 3979 3980 3981 3982 3983 3984 3985 3986 3987 3988 3989 3990 3991 3992 3993 3994 3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045
{
	struct css_id *child_id = rcu_dereference(child->id);
	struct css_id *root_id = rcu_dereference(root->id);

	if (!child_id || !root_id || (child_id->depth < root_id->depth))
		return false;
	return child_id->stack[root_id->depth] == root_id->id;
}

static void __free_css_id_cb(struct rcu_head *head)
{
	struct css_id *id;

	id = container_of(head, struct css_id, rcu_head);
	kfree(id);
}

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);
	spin_lock(&ss->id_lock);
	idr_remove(&ss->idr, id->id);
	spin_unlock(&ss->id_lock);
	call_rcu(&id->rcu_head, __free_css_id_cb);
}

/*
 * 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;
	}
	spin_lock(&ss->id_lock);
	/* Don't use 0. allocates an ID of 1-65535 */
	error = idr_get_new_above(&ss->idr, newid, 1, &myid);
	spin_unlock(&ss->id_lock);

	/* 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;
	spin_lock(&ss->id_lock);
	idr_remove(&ss->idr, myid);
	spin_unlock(&ss->id_lock);
err_out:
	kfree(newid);
	return ERR_PTR(error);

}

static int __init cgroup_subsys_init_idr(struct cgroup_subsys *ss)
{
	struct css_id *newid;
	struct cgroup_subsys_state *rootcss;

	spin_lock_init(&ss->id_lock);
	idr_init(&ss->idr);

	rootcss = init_css_set.subsys[ss->subsys_id];
	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;
	struct css_id *child_id, *parent_id = NULL;

	subsys_id = ss->subsys_id;
	parent_css = parent->subsys[subsys_id];
	child_css = child->subsys[subsys_id];
	depth = css_depth(parent_css) + 1;
	parent_id = parent_css->id;

	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);
}

/**
 * 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);
	/* fill start point for scan */
	tmpid = id;
	while (1) {
		/*
		 * scan next entry from bitmap(tree), tmpid is updated after
		 * idr_get_next().
		 */
		spin_lock(&ss->id_lock);
		tmp = idr_get_next(&ss->idr, &tmpid);
		spin_unlock(&ss->id_lock);

		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;
}

4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088
#ifdef CONFIG_CGROUP_DEBUG
static struct cgroup_subsys_state *debug_create(struct cgroup_subsys *ss,
						   struct cgroup *cont)
{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

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

	return css;
}

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

4089 4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105 4106
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 = "?";
4107 4108
		seq_printf(seq, "Root %d group %s\n",
			   c->root->hierarchy_id, name);
4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141
	}
	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;
}

4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166
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,
	},

4167 4168 4169 4170 4171 4172 4173 4174 4175 4176
	{
		.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,
	},

4177 4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196
	{
		.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 */