cgroup.c 150.8 KB
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/*
 *  Generic process-grouping system.
 *
 *  Based originally on the cpuset system, extracted by Paul Menage
 *  Copyright (C) 2006 Google, Inc
 *
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 *  Notifications support
 *  Copyright (C) 2009 Nokia Corporation
 *  Author: Kirill A. Shutemov
 *
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 *  Copyright notices from the original cpuset code:
 *  --------------------------------------------------
 *  Copyright (C) 2003 BULL SA.
 *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
 *
 *  Portions derived from Patrick Mochel's sysfs code.
 *  sysfs is Copyright (c) 2001-3 Patrick Mochel
 *
 *  2003-10-10 Written by Simon Derr.
 *  2003-10-22 Updates by Stephen Hemminger.
 *  2004 May-July Rework by Paul Jackson.
 *  ---------------------------------------------------
 *
 *  This file is subject to the terms and conditions of the GNU General Public
 *  License.  See the file COPYING in the main directory of the Linux
 *  distribution for more details.
 */

#include <linux/cgroup.h>
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#include <linux/cred.h>
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#include <linux/ctype.h>
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#include <linux/errno.h>
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#include <linux/init_task.h>
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#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
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#include <linux/proc_fs.h>
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#include <linux/rcupdate.h>
#include <linux/sched.h>
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#include <linux/backing-dev.h>
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#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/magic.h>
#include <linux/spinlock.h>
#include <linux/string.h>
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#include <linux/sort.h>
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#include <linux/kmod.h>
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#include <linux/module.h>
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#include <linux/delayacct.h>
#include <linux/cgroupstats.h>
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#include <linux/hashtable.h>
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#include <linux/namei.h>
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#include <linux/pid_namespace.h>
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#include <linux/idr.h>
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#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
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#include <linux/eventfd.h>
#include <linux/poll.h>
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#include <linux/flex_array.h> /* used in cgroup_attach_task */
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#include <linux/kthread.h>
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#include <linux/atomic.h>
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/*
 * cgroup_mutex is the master lock.  Any modification to cgroup or its
 * hierarchy must be performed while holding it.
 *
 * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
 * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
 * release_agent_path and so on.  Modifying requires both cgroup_mutex and
 * cgroup_root_mutex.  Readers can acquire either of the two.  This is to
 * break the following locking order cycle.
 *
 *  A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
 *  B. namespace_sem -> cgroup_mutex
 *
 * B happens only through cgroup_show_options() and using cgroup_root_mutex
 * breaks it.
 */
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#ifdef CONFIG_PROVE_RCU
DEFINE_MUTEX(cgroup_mutex);
EXPORT_SYMBOL_GPL(cgroup_mutex);	/* only for task_subsys_state_check() */
#else
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static DEFINE_MUTEX(cgroup_mutex);
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#endif

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static DEFINE_MUTEX(cgroup_root_mutex);
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/*
 * Generate an array of cgroup subsystem pointers. At boot time, this is
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 * populated with the built in subsystems, and modular subsystems are
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 * registered after that. The mutable section of this array is protected by
 * cgroup_mutex.
 */
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#define SUBSYS(_x) [_x ## _subsys_id] = &_x ## _subsys,
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#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
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static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
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#include <linux/cgroup_subsys.h>
};

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

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/*
 * cgroupfs file entry, pointed to from leaf dentry->d_fsdata.
 */
struct cfent {
	struct list_head		node;
	struct dentry			*dentry;
	struct cftype			*type;
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	/* file xattrs */
	struct simple_xattrs		xattrs;
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};

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

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

static LIST_HEAD(roots);
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static int root_count;
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/*
 * Hierarchy ID allocation and mapping.  It follows the same exclusion
 * rules as other root ops - both cgroup_mutex and cgroup_root_mutex for
 * writes, either for reads.
 */
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static DEFINE_IDR(cgroup_hierarchy_idr);
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/* dummytop is a shorthand for the dummy hierarchy's top cgroup */
#define dummytop (&rootnode.top_cgroup)

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static struct cgroup_name root_cgroup_name = { .name = "/" };

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/*
 * Assign a monotonically increasing serial number to cgroups.  It
 * guarantees cgroups with bigger numbers are newer than those with smaller
 * numbers.  Also, as cgroups are always appended to the parent's
 * ->children list, it guarantees that sibling cgroups are always sorted in
 * the ascending serial number order on the list.
 */
static atomic64_t cgroup_serial_nr_cursor = ATOMIC64_INIT(0);

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/* This flag indicates whether tasks in the fork and exit paths should
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 * check for fork/exit handlers to call. This avoids us having to do
 * extra work in the fork/exit path if none of the subsystems need to
 * be called.
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 */
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static int need_forkexit_callback __read_mostly;
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static void cgroup_offline_fn(struct work_struct *work);
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static int cgroup_destroy_locked(struct cgroup *cgrp);
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static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
			      struct cftype cfts[], bool is_add);
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/* convenient tests for these bits */
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static inline bool cgroup_is_dead(const struct cgroup *cgrp)
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{
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	return test_bit(CGRP_DEAD, &cgrp->flags);
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}

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/**
 * cgroup_is_descendant - test ancestry
 * @cgrp: the cgroup to be tested
 * @ancestor: possible ancestor of @cgrp
 *
 * Test whether @cgrp is a descendant of @ancestor.  It also returns %true
 * if @cgrp == @ancestor.  This function is safe to call as long as @cgrp
 * and @ancestor are accessible.
 */
bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor)
{
	while (cgrp) {
		if (cgrp == ancestor)
			return true;
		cgrp = cgrp->parent;
	}
	return false;
}
EXPORT_SYMBOL_GPL(cgroup_is_descendant);
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static int cgroup_is_releasable(const struct cgroup *cgrp)
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{
	const int bits =
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		(1 << CGRP_RELEASABLE) |
		(1 << CGRP_NOTIFY_ON_RELEASE);
	return (cgrp->flags & bits) == bits;
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}

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

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

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

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static inline struct cgroup *__d_cgrp(struct dentry *dentry)
{
	return dentry->d_fsdata;
}

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static inline struct cfent *__d_cfe(struct dentry *dentry)
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{
	return dentry->d_fsdata;
}

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

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/**
 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
 * @cgrp: the cgroup to be checked for liveness
 *
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 * On success, returns true; the mutex should be later unlocked.  On
 * failure returns false with no lock held.
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 */
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static bool cgroup_lock_live_group(struct cgroup *cgrp)
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{
	mutex_lock(&cgroup_mutex);
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	if (cgroup_is_dead(cgrp)) {
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		mutex_unlock(&cgroup_mutex);
		return false;
	}
	return true;
}

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/* the list of cgroups eligible for automatic release. Protected by
 * release_list_lock */
static LIST_HEAD(release_list);
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static DEFINE_RAW_SPINLOCK(release_list_lock);
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static void cgroup_release_agent(struct work_struct *work);
static DECLARE_WORK(release_agent_work, cgroup_release_agent);
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static void check_for_release(struct cgroup *cgrp);
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/*
 * A cgroup can be associated with multiple css_sets as different tasks may
 * belong to different cgroups on different hierarchies.  In the other
 * direction, a css_set is naturally associated with multiple cgroups.
 * This M:N relationship is represented by the following link structure
 * which exists for each association and allows traversing the associations
 * from both sides.
 */
struct cgrp_cset_link {
	/* the cgroup and css_set this link associates */
	struct cgroup		*cgrp;
	struct css_set		*cset;

	/* list of cgrp_cset_links anchored at cgrp->cset_links */
	struct list_head	cset_link;

	/* list of cgrp_cset_links anchored at css_set->cgrp_links */
	struct list_head	cgrp_link;
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};

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

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/*
 * hash table for cgroup groups. This improves the performance to find
 * an existing css_set. This hash doesn't (currently) take into
 * account cgroups in empty hierarchies.
 */
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#define CSS_SET_HASH_BITS	7
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static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
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static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
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{
	int i;
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	unsigned long key = 0UL;
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	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
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		key += (unsigned long)css[i];
	key = (key >> 16) ^ key;
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	return key;
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}

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/* We don't maintain the lists running through each css_set to its
 * task until after the first call to cgroup_iter_start(). This
 * reduces the fork()/exit() overhead for people who have cgroups
 * compiled into their kernel but not actually in use */
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static int use_task_css_set_links __read_mostly;
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static void __put_css_set(struct css_set *cset, int taskexit)
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{
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	struct cgrp_cset_link *link, *tmp_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
	 */
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	if (atomic_add_unless(&cset->refcount, -1, 1))
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		return;
	write_lock(&css_set_lock);
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	if (!atomic_dec_and_test(&cset->refcount)) {
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		write_unlock(&css_set_lock);
		return;
	}
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	/* This css_set is dead. unlink it and release cgroup refcounts */
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	hash_del(&cset->hlist);
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	css_set_count--;

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	list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
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		struct cgroup *cgrp = link->cgrp;
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		list_del(&link->cset_link);
		list_del(&link->cgrp_link);
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		/* @cgrp can't go away while we're holding css_set_lock */
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		if (list_empty(&cgrp->cset_links) && notify_on_release(cgrp)) {
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			if (taskexit)
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				set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
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		}
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		kfree(link);
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	}
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	write_unlock(&css_set_lock);
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	kfree_rcu(cset, rcu_head);
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}

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

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

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

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/*
 * compare_css_sets - helper function for find_existing_css_set().
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 * @cset: candidate css_set being tested
 * @old_cset: existing css_set for a task
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 * @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".
 */
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static bool compare_css_sets(struct css_set *cset,
			     struct css_set *old_cset,
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			     struct cgroup *new_cgrp,
			     struct cgroup_subsys_state *template[])
{
	struct list_head *l1, *l2;

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	if (memcmp(template, cset->subsys, sizeof(cset->subsys))) {
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		/* 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.
	 */

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	l1 = &cset->cgrp_links;
	l2 = &old_cset->cgrp_links;
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	while (1) {
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		struct cgrp_cset_link *link1, *link2;
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		struct cgroup *cgrp1, *cgrp2;
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		l1 = l1->next;
		l2 = l2->next;
		/* See if we reached the end - both lists are equal length. */
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		if (l1 == &cset->cgrp_links) {
			BUG_ON(l2 != &old_cset->cgrp_links);
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			break;
		} else {
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			BUG_ON(l2 == &old_cset->cgrp_links);
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		}
		/* Locate the cgroups associated with these links. */
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		link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
		link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
		cgrp1 = link1->cgrp;
		cgrp2 = link2->cgrp;
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		/* Hierarchies should be linked in the same order. */
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		BUG_ON(cgrp1->root != cgrp2->root);
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		/*
		 * 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.
		 */
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		if (cgrp1->root == new_cgrp->root) {
			if (cgrp1 != new_cgrp)
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				return false;
		} else {
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			if (cgrp1 != cgrp2)
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				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
 */
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static struct css_set *find_existing_css_set(struct css_set *old_cset,
					struct cgroup *cgrp,
					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 css_set *cset;
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	unsigned long key;
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	/*
	 * Build the set of subsystem state objects that we want to see in the
	 * new css_set. while subsystems can change globally, the entries here
	 * won't change, so no need for locking.
	 */
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	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
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		if (root->subsys_mask & (1UL << i)) {
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			/* Subsystem is in this hierarchy. So we want
			 * the subsystem state from the new
			 * cgroup */
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			template[i] = cgrp->subsys[i];
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		} else {
			/* Subsystem is not in this hierarchy, so we
			 * don't want to change the subsystem state */
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			template[i] = old_cset->subsys[i];
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		}
	}

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	key = css_set_hash(template);
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	hash_for_each_possible(css_set_table, cset, hlist, key) {
		if (!compare_css_sets(cset, old_cset, cgrp, template))
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			continue;

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

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static void free_cgrp_cset_links(struct list_head *links_to_free)
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{
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	struct cgrp_cset_link *link, *tmp_link;
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	list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
		list_del(&link->cset_link);
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		kfree(link);
	}
}

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/**
 * allocate_cgrp_cset_links - allocate cgrp_cset_links
 * @count: the number of links to allocate
 * @tmp_links: list_head the allocated links are put on
 *
 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
 * through ->cset_link.  Returns 0 on success or -errno.
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 */
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static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
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{
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	struct cgrp_cset_link *link;
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	int i;
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	INIT_LIST_HEAD(tmp_links);

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	for (i = 0; i < count; i++) {
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		link = kzalloc(sizeof(*link), GFP_KERNEL);
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		if (!link) {
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			free_cgrp_cset_links(tmp_links);
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			return -ENOMEM;
		}
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		list_add(&link->cset_link, tmp_links);
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	}
	return 0;
}

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/**
 * link_css_set - a helper function to link a css_set to a cgroup
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 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
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 * @cset: the css_set to be linked
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 * @cgrp: the destination cgroup
 */
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static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
			 struct cgroup *cgrp)
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{
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	struct cgrp_cset_link *link;
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	BUG_ON(list_empty(tmp_links));
	link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
	link->cset = cset;
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	link->cgrp = cgrp;
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	list_move(&link->cset_link, &cgrp->cset_links);
613 614 615 616
	/*
	 * Always add links to the tail of the list so that the list
	 * is sorted by order of hierarchy creation
	 */
617
	list_add_tail(&link->cgrp_link, &cset->cgrp_links);
618 619
}

620 621 622 623 624 625 626
/*
 * 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
 */
627 628
static struct css_set *find_css_set(struct css_set *old_cset,
				    struct cgroup *cgrp)
629
{
630
	struct css_set *cset;
631
	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
632 633
	struct list_head tmp_links;
	struct cgrp_cset_link *link;
634
	unsigned long key;
635

636 637
	/* First see if we already have a cgroup group that matches
	 * the desired set */
638
	read_lock(&css_set_lock);
639 640 641
	cset = find_existing_css_set(old_cset, cgrp, template);
	if (cset)
		get_css_set(cset);
642
	read_unlock(&css_set_lock);
643

644 645
	if (cset)
		return cset;
646

647
	cset = kzalloc(sizeof(*cset), GFP_KERNEL);
648
	if (!cset)
649 650
		return NULL;

651 652
	/* Allocate all the cgrp_cset_link objects that we'll need */
	if (allocate_cgrp_cset_links(root_count, &tmp_links) < 0) {
653
		kfree(cset);
654 655 656
		return NULL;
	}

657
	atomic_set(&cset->refcount, 1);
658
	INIT_LIST_HEAD(&cset->cgrp_links);
659 660
	INIT_LIST_HEAD(&cset->tasks);
	INIT_HLIST_NODE(&cset->hlist);
661 662 663

	/* Copy the set of subsystem state objects generated in
	 * find_existing_css_set() */
664
	memcpy(cset->subsys, template, sizeof(cset->subsys));
665 666 667

	write_lock(&css_set_lock);
	/* Add reference counts and links from the new css_set. */
668
	list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
669
		struct cgroup *c = link->cgrp;
670

671 672
		if (c->root == cgrp->root)
			c = cgrp;
673
		link_css_set(&tmp_links, cset, c);
674
	}
675

676
	BUG_ON(!list_empty(&tmp_links));
677 678

	css_set_count++;
679 680

	/* Add this cgroup group to the hash table */
681 682
	key = css_set_hash(cset->subsys);
	hash_add(css_set_table, &cset->hlist, key);
683

684 685
	write_unlock(&css_set_lock);

686
	return cset;
687 688
}

689 690 691 692 693 694 695
/*
 * 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)
{
696
	struct css_set *cset;
697 698 699 700 701 702 703 704 705
	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.
	 */
706 707
	cset = task->cgroups;
	if (cset == &init_css_set) {
708 709
		res = &root->top_cgroup;
	} else {
710 711 712
		struct cgrp_cset_link *link;

		list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
713
			struct cgroup *c = link->cgrp;
714

715 716 717 718 719 720 721 722 723 724 725
			if (c->root == root) {
				res = c;
				break;
			}
		}
	}
	read_unlock(&css_set_lock);
	BUG_ON(!res);
	return res;
}

726 727 728 729 730 731 732 733 734 735
/*
 * 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
736
 * cgroup_attach_task() can increment it again.  Because a count of zero
737 738 739 740 741 742 743 744 745 746 747 748 749
 * means that no tasks are currently attached, therefore there is no
 * way a task attached to that cgroup can fork (the other way to
 * increment the count).  So code holding cgroup_mutex can safely
 * assume that if the count is zero, it will stay zero. Similarly, if
 * a task holds cgroup_mutex on a cgroup with zero count, it
 * knows that the cgroup won't be removed, as cgroup_rmdir()
 * needs that mutex.
 *
 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
 * (usually) take cgroup_mutex.  These are the two most performance
 * critical pieces of code here.  The exception occurs on cgroup_exit(),
 * when a task in a notify_on_release cgroup exits.  Then cgroup_mutex
 * is taken, and if the cgroup count is zero, a usermode call made
L
Li Zefan 已提交
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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.
752 753 754 755 756 757 758 759 760 761 762
 *
 * 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
763
 * cgroup_attach_task(), which overwrites one task's cgroup pointer with
L
Li Zefan 已提交
764
 * another.  It does so using cgroup_mutex, however there are
765 766 767
 * 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
768
 * in cgroup_attach_task(), modifying a task's cgroup pointer we use
769 770 771 772
 * 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
773
 * update of a tasks cgroup pointer by cgroup_attach_task()
774 775 776 777 778 779 780 781 782
 */

/*
 * 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.
 */

783
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
A
Al Viro 已提交
784
static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);
785
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
786 787
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
			       unsigned long subsys_mask);
788
static const struct inode_operations cgroup_dir_inode_operations;
789
static const struct file_operations proc_cgroupstats_operations;
790 791

static struct backing_dev_info cgroup_backing_dev_info = {
792
	.name		= "cgroup",
793
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
794
};
795

K
KAMEZAWA Hiroyuki 已提交
796 797 798
static int alloc_css_id(struct cgroup_subsys *ss,
			struct cgroup *parent, struct cgroup *child);

A
Al Viro 已提交
799
static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
800 801 802 803
{
	struct inode *inode = new_inode(sb);

	if (inode) {
804
		inode->i_ino = get_next_ino();
805
		inode->i_mode = mode;
806 807
		inode->i_uid = current_fsuid();
		inode->i_gid = current_fsgid();
808 809 810 811 812 813
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
	}
	return inode;
}

814 815 816 817 818 819 820 821 822 823 824
static struct cgroup_name *cgroup_alloc_name(struct dentry *dentry)
{
	struct cgroup_name *name;

	name = kmalloc(sizeof(*name) + dentry->d_name.len + 1, GFP_KERNEL);
	if (!name)
		return NULL;
	strcpy(name->name, dentry->d_name.name);
	return name;
}

825 826
static void cgroup_free_fn(struct work_struct *work)
{
827
	struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work);
828 829 830 831 832 833 834 835 836 837 838 839
	struct cgroup_subsys *ss;

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

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

840 841 842 843 844 845 846
	/*
	 * We get a ref to the parent's dentry, and put the ref when
	 * this cgroup is being freed, so it's guaranteed that the
	 * parent won't be destroyed before its children.
	 */
	dput(cgrp->parent->dentry);

847 848
	ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id);

849 850
	/*
	 * Drop the active superblock reference that we took when we
851 852
	 * created the cgroup. This will free cgrp->root, if we are
	 * holding the last reference to @sb.
853 854 855 856 857 858 859 860 861 862 863
	 */
	deactivate_super(cgrp->root->sb);

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

	simple_xattrs_free(&cgrp->xattrs);

864
	kfree(rcu_dereference_raw(cgrp->name));
865 866 867 868 869 870 871
	kfree(cgrp);
}

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

872 873
	INIT_WORK(&cgrp->destroy_work, cgroup_free_fn);
	schedule_work(&cgrp->destroy_work);
874 875
}

876 877 878 879
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)) {
880
		struct cgroup *cgrp = dentry->d_fsdata;
881

882
		BUG_ON(!(cgroup_is_dead(cgrp)));
883
		call_rcu(&cgrp->rcu_head, cgroup_free_rcu);
T
Tejun Heo 已提交
884 885 886 887 888 889 890
	} else {
		struct cfent *cfe = __d_cfe(dentry);
		struct cgroup *cgrp = dentry->d_parent->d_fsdata;

		WARN_ONCE(!list_empty(&cfe->node) &&
			  cgrp != &cgrp->root->top_cgroup,
			  "cfe still linked for %s\n", cfe->type->name);
L
Li Zefan 已提交
891
		simple_xattrs_free(&cfe->xattrs);
T
Tejun Heo 已提交
892
		kfree(cfe);
893 894 895 896
	}
	iput(inode);
}

897 898 899 900 901
static int cgroup_delete(const struct dentry *d)
{
	return 1;
}

902 903 904 905 906 907 908 909 910
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);
}

911
static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
T
Tejun Heo 已提交
912 913 914 915 916 917
{
	struct cfent *cfe;

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

918 919 920 921
	/*
	 * If we're doing cleanup due to failure of cgroup_create(),
	 * the corresponding @cfe may not exist.
	 */
T
Tejun Heo 已提交
922 923 924 925 926 927 928 929
	list_for_each_entry(cfe, &cgrp->files, node) {
		struct dentry *d = cfe->dentry;

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

		dget(d);
		d_delete(d);
930
		simple_unlink(cgrp->dentry->d_inode, d);
T
Tejun Heo 已提交
931 932 933
		list_del_init(&cfe->node);
		dput(d);

934
		break;
935
	}
T
Tejun Heo 已提交
936 937
}

938 939 940 941 942 943 944 945
/**
 * cgroup_clear_directory - selective removal of base and subsystem files
 * @dir: directory containing the files
 * @base_files: true if the base files should be removed
 * @subsys_mask: mask of the subsystem ids whose files should be removed
 */
static void cgroup_clear_directory(struct dentry *dir, bool base_files,
				   unsigned long subsys_mask)
T
Tejun Heo 已提交
946 947
{
	struct cgroup *cgrp = __d_cgrp(dir);
948
	struct cgroup_subsys *ss;
T
Tejun Heo 已提交
949

950 951 952 953 954
	for_each_subsys(cgrp->root, ss) {
		struct cftype_set *set;
		if (!test_bit(ss->subsys_id, &subsys_mask))
			continue;
		list_for_each_entry(set, &ss->cftsets, node)
955
			cgroup_addrm_files(cgrp, NULL, set->cfts, false);
956 957 958 959 960
	}
	if (base_files) {
		while (!list_empty(&cgrp->files))
			cgroup_rm_file(cgrp, NULL);
	}
961 962 963 964 965 966 967
}

/*
 * NOTE : the dentry must have been dget()'ed
 */
static void cgroup_d_remove_dir(struct dentry *dentry)
{
N
Nick Piggin 已提交
968
	struct dentry *parent;
969
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
N
Nick Piggin 已提交
970

971
	cgroup_clear_directory(dentry, true, root->subsys_mask);
972

N
Nick Piggin 已提交
973 974
	parent = dentry->d_parent;
	spin_lock(&parent->d_lock);
975
	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
976
	list_del_init(&dentry->d_u.d_child);
N
Nick Piggin 已提交
977 978
	spin_unlock(&dentry->d_lock);
	spin_unlock(&parent->d_lock);
979 980 981
	remove_dir(dentry);
}

B
Ben Blum 已提交
982
/*
B
Ben Blum 已提交
983 984 985
 * Call with cgroup_mutex held. Drops reference counts on modules, including
 * any duplicate ones that parse_cgroupfs_options took. If this function
 * returns an error, no reference counts are touched.
B
Ben Blum 已提交
986
 */
987
static int rebind_subsystems(struct cgroupfs_root *root,
988
			      unsigned long final_subsys_mask)
989
{
990
	unsigned long added_mask, removed_mask;
991
	struct cgroup *cgrp = &root->top_cgroup;
992 993
	int i;

B
Ben Blum 已提交
994
	BUG_ON(!mutex_is_locked(&cgroup_mutex));
T
Tejun Heo 已提交
995
	BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
B
Ben Blum 已提交
996

997 998
	removed_mask = root->actual_subsys_mask & ~final_subsys_mask;
	added_mask = final_subsys_mask & ~root->actual_subsys_mask;
999 1000
	/* Check that any added subsystems are currently free */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
L
Li Zefan 已提交
1001
		unsigned long bit = 1UL << i;
1002
		struct cgroup_subsys *ss = subsys[i];
1003
		if (!(bit & added_mask))
1004
			continue;
B
Ben Blum 已提交
1005 1006 1007 1008 1009 1010
		/*
		 * Nobody should tell us to do a subsys that doesn't exist:
		 * parse_cgroupfs_options should catch that case and refcounts
		 * ensure that subsystems won't disappear once selected.
		 */
		BUG_ON(ss == NULL);
1011 1012 1013 1014 1015 1016 1017 1018 1019 1020
		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 */
1021
	if (root->number_of_cgroups > 1)
1022 1023 1024 1025 1026 1027
		return -EBUSY;

	/* Process each subsystem */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		unsigned long bit = 1UL << i;
1028
		if (bit & added_mask) {
1029
			/* We're binding this subsystem to this hierarchy */
B
Ben Blum 已提交
1030
			BUG_ON(ss == NULL);
1031
			BUG_ON(cgrp->subsys[i]);
1032 1033
			BUG_ON(!dummytop->subsys[i]);
			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1034 1035
			cgrp->subsys[i] = dummytop->subsys[i];
			cgrp->subsys[i]->cgroup = cgrp;
1036
			list_move(&ss->sibling, &root->subsys_list);
1037
			ss->root = root;
1038
			if (ss->bind)
1039
				ss->bind(cgrp);
B
Ben Blum 已提交
1040
			/* refcount was already taken, and we're keeping it */
1041
		} else if (bit & removed_mask) {
1042
			/* We're removing this subsystem */
B
Ben Blum 已提交
1043
			BUG_ON(ss == NULL);
1044 1045
			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1046
			if (ss->bind)
1047
				ss->bind(dummytop);
1048
			dummytop->subsys[i]->cgroup = dummytop;
1049
			cgrp->subsys[i] = NULL;
1050
			subsys[i]->root = &rootnode;
1051
			list_move(&ss->sibling, &rootnode.subsys_list);
B
Ben Blum 已提交
1052 1053
			/* subsystem is now free - drop reference on module */
			module_put(ss->module);
1054
		} else if (bit & final_subsys_mask) {
1055
			/* Subsystem state should already exist */
B
Ben Blum 已提交
1056
			BUG_ON(ss == NULL);
1057
			BUG_ON(!cgrp->subsys[i]);
B
Ben Blum 已提交
1058 1059 1060 1061 1062 1063 1064 1065
			/*
			 * a refcount was taken, but we already had one, so
			 * drop the extra reference.
			 */
			module_put(ss->module);
#ifdef CONFIG_MODULE_UNLOAD
			BUG_ON(ss->module && !module_refcount(ss->module));
#endif
1066 1067
		} else {
			/* Subsystem state shouldn't exist */
1068
			BUG_ON(cgrp->subsys[i]);
1069 1070
		}
	}
1071
	root->subsys_mask = root->actual_subsys_mask = final_subsys_mask;
1072 1073 1074 1075

	return 0;
}

1076
static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1077
{
1078
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1079 1080
	struct cgroup_subsys *ss;

T
Tejun Heo 已提交
1081
	mutex_lock(&cgroup_root_mutex);
1082 1083
	for_each_subsys(root, ss)
		seq_printf(seq, ",%s", ss->name);
1084 1085
	if (root->flags & CGRP_ROOT_SANE_BEHAVIOR)
		seq_puts(seq, ",sane_behavior");
1086
	if (root->flags & CGRP_ROOT_NOPREFIX)
1087
		seq_puts(seq, ",noprefix");
1088
	if (root->flags & CGRP_ROOT_XATTR)
A
Aristeu Rozanski 已提交
1089
		seq_puts(seq, ",xattr");
1090 1091
	if (strlen(root->release_agent_path))
		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1092
	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags))
1093
		seq_puts(seq, ",clone_children");
1094 1095
	if (strlen(root->name))
		seq_printf(seq, ",name=%s", root->name);
T
Tejun Heo 已提交
1096
	mutex_unlock(&cgroup_root_mutex);
1097 1098 1099 1100
	return 0;
}

struct cgroup_sb_opts {
1101
	unsigned long subsys_mask;
1102
	unsigned long flags;
1103
	char *release_agent;
1104
	bool cpuset_clone_children;
1105
	char *name;
1106 1107
	/* User explicitly requested empty subsystem */
	bool none;
1108 1109

	struct cgroupfs_root *new_root;
1110

1111 1112
};

B
Ben Blum 已提交
1113 1114
/*
 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
B
Ben Blum 已提交
1115 1116 1117
 * with cgroup_mutex held to protect the subsys[] array. This function takes
 * refcounts on subsystems to be used, unless it returns error, in which case
 * no refcounts are taken.
B
Ben Blum 已提交
1118
 */
B
Ben Blum 已提交
1119
static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1120
{
1121 1122
	char *token, *o = data;
	bool all_ss = false, one_ss = false;
1123
	unsigned long mask = (unsigned long)-1;
B
Ben Blum 已提交
1124 1125
	int i;
	bool module_pin_failed = false;
1126

B
Ben Blum 已提交
1127 1128
	BUG_ON(!mutex_is_locked(&cgroup_mutex));

1129 1130 1131
#ifdef CONFIG_CPUSETS
	mask = ~(1UL << cpuset_subsys_id);
#endif
1132

1133
	memset(opts, 0, sizeof(*opts));
1134 1135 1136 1137

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
1138
		if (!strcmp(token, "none")) {
1139 1140
			/* Explicitly have no subsystems */
			opts->none = true;
1141 1142 1143 1144 1145 1146 1147 1148 1149
			continue;
		}
		if (!strcmp(token, "all")) {
			/* Mutually exclusive option 'all' + subsystem name */
			if (one_ss)
				return -EINVAL;
			all_ss = true;
			continue;
		}
1150 1151 1152 1153
		if (!strcmp(token, "__DEVEL__sane_behavior")) {
			opts->flags |= CGRP_ROOT_SANE_BEHAVIOR;
			continue;
		}
1154
		if (!strcmp(token, "noprefix")) {
1155
			opts->flags |= CGRP_ROOT_NOPREFIX;
1156 1157 1158
			continue;
		}
		if (!strcmp(token, "clone_children")) {
1159
			opts->cpuset_clone_children = true;
1160 1161
			continue;
		}
A
Aristeu Rozanski 已提交
1162
		if (!strcmp(token, "xattr")) {
1163
			opts->flags |= CGRP_ROOT_XATTR;
A
Aristeu Rozanski 已提交
1164 1165
			continue;
		}
1166
		if (!strncmp(token, "release_agent=", 14)) {
1167 1168 1169
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1170
			opts->release_agent =
1171
				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1172 1173
			if (!opts->release_agent)
				return -ENOMEM;
1174 1175 1176
			continue;
		}
		if (!strncmp(token, "name=", 5)) {
1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193
			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,
1194
					      MAX_CGROUP_ROOT_NAMELEN - 1,
1195 1196 1197
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213

			continue;
		}

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

			/* Mutually exclusive option 'all' + subsystem name */
			if (all_ss)
				return -EINVAL;
1214
			set_bit(i, &opts->subsys_mask);
1215 1216 1217 1218 1219 1220 1221 1222 1223 1224
			one_ss = true;

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

	/*
	 * If the 'all' option was specified select all the subsystems,
1225 1226
	 * otherwise if 'none', 'name=' and a subsystem name options
	 * were not specified, let's default to 'all'
1227
	 */
1228
	if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1229 1230 1231 1232 1233 1234
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss == NULL)
				continue;
			if (ss->disabled)
				continue;
1235
			set_bit(i, &opts->subsys_mask);
1236 1237 1238
		}
	}

1239 1240
	/* Consistency checks */

1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254
	if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
		pr_warning("cgroup: sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");

		if (opts->flags & CGRP_ROOT_NOPREFIX) {
			pr_err("cgroup: sane_behavior: noprefix is not allowed\n");
			return -EINVAL;
		}

		if (opts->cpuset_clone_children) {
			pr_err("cgroup: sane_behavior: clone_children is not allowed\n");
			return -EINVAL;
		}
	}

1255 1256 1257 1258 1259
	/*
	 * Option noprefix was introduced just for backward compatibility
	 * with the old cpuset, so we allow noprefix only if mounting just
	 * the cpuset subsystem.
	 */
1260
	if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
1261 1262
		return -EINVAL;

1263 1264

	/* Can't specify "none" and some subsystems */
1265
	if (opts->subsys_mask && opts->none)
1266 1267 1268 1269 1270 1271
		return -EINVAL;

	/*
	 * We either have to specify by name or by subsystems. (So all
	 * empty hierarchies must have a name).
	 */
1272
	if (!opts->subsys_mask && !opts->name)
1273 1274
		return -EINVAL;

B
Ben Blum 已提交
1275 1276 1277 1278 1279 1280
	/*
	 * Grab references on all the modules we'll need, so the subsystems
	 * don't dance around before rebind_subsystems attaches them. This may
	 * take duplicate reference counts on a subsystem that's already used,
	 * but rebind_subsystems handles this case.
	 */
1281
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
B
Ben Blum 已提交
1282 1283
		unsigned long bit = 1UL << i;

1284
		if (!(bit & opts->subsys_mask))
B
Ben Blum 已提交
1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296
			continue;
		if (!try_module_get(subsys[i]->module)) {
			module_pin_failed = true;
			break;
		}
	}
	if (module_pin_failed) {
		/*
		 * oops, one of the modules was going away. this means that we
		 * raced with a module_delete call, and to the user this is
		 * essentially a "subsystem doesn't exist" case.
		 */
1297
		for (i--; i >= 0; i--) {
B
Ben Blum 已提交
1298 1299 1300
			/* drop refcounts only on the ones we took */
			unsigned long bit = 1UL << i;

1301
			if (!(bit & opts->subsys_mask))
B
Ben Blum 已提交
1302 1303 1304 1305 1306 1307
				continue;
			module_put(subsys[i]->module);
		}
		return -ENOENT;
	}

1308 1309 1310
	return 0;
}

1311
static void drop_parsed_module_refcounts(unsigned long subsys_mask)
B
Ben Blum 已提交
1312 1313
{
	int i;
1314
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
B
Ben Blum 已提交
1315 1316
		unsigned long bit = 1UL << i;

1317
		if (!(bit & subsys_mask))
B
Ben Blum 已提交
1318 1319 1320 1321 1322
			continue;
		module_put(subsys[i]->module);
	}
}

1323 1324 1325 1326
static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
	int ret = 0;
	struct cgroupfs_root *root = sb->s_fs_info;
1327
	struct cgroup *cgrp = &root->top_cgroup;
1328
	struct cgroup_sb_opts opts;
1329
	unsigned long added_mask, removed_mask;
1330

1331 1332 1333 1334 1335
	if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) {
		pr_err("cgroup: sane_behavior: remount is not allowed\n");
		return -EINVAL;
	}

1336
	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1337
	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1338
	mutex_lock(&cgroup_root_mutex);
1339 1340 1341 1342 1343 1344

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

1345
	if (opts.subsys_mask != root->actual_subsys_mask || opts.release_agent)
1346 1347 1348
		pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
			   task_tgid_nr(current), current->comm);

1349 1350
	added_mask = opts.subsys_mask & ~root->subsys_mask;
	removed_mask = root->subsys_mask & ~opts.subsys_mask;
1351

B
Ben Blum 已提交
1352 1353 1354
	/* Don't allow flags or name to change at remount */
	if (opts.flags != root->flags ||
	    (opts.name && strcmp(opts.name, root->name))) {
1355
		ret = -EINVAL;
1356
		drop_parsed_module_refcounts(opts.subsys_mask);
1357 1358 1359
		goto out_unlock;
	}

1360 1361 1362 1363 1364 1365 1366
	/*
	 * Clear out the files of subsystems that should be removed, do
	 * this before rebind_subsystems, since rebind_subsystems may
	 * change this hierarchy's subsys_list.
	 */
	cgroup_clear_directory(cgrp->dentry, false, removed_mask);

1367
	ret = rebind_subsystems(root, opts.subsys_mask);
B
Ben Blum 已提交
1368
	if (ret) {
1369 1370
		/* rebind_subsystems failed, re-populate the removed files */
		cgroup_populate_dir(cgrp, false, removed_mask);
1371
		drop_parsed_module_refcounts(opts.subsys_mask);
1372
		goto out_unlock;
B
Ben Blum 已提交
1373
	}
1374

1375
	/* re-populate subsystem files */
1376
	cgroup_populate_dir(cgrp, false, added_mask);
1377

1378 1379
	if (opts.release_agent)
		strcpy(root->release_agent_path, opts.release_agent);
1380
 out_unlock:
1381
	kfree(opts.release_agent);
1382
	kfree(opts.name);
T
Tejun Heo 已提交
1383
	mutex_unlock(&cgroup_root_mutex);
1384
	mutex_unlock(&cgroup_mutex);
1385
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1386 1387 1388
	return ret;
}

1389
static const struct super_operations cgroup_ops = {
1390 1391 1392 1393 1394 1395
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.show_options = cgroup_show_options,
	.remount_fs = cgroup_remount,
};

1396 1397 1398 1399
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
	INIT_LIST_HEAD(&cgrp->sibling);
	INIT_LIST_HEAD(&cgrp->children);
T
Tejun Heo 已提交
1400
	INIT_LIST_HEAD(&cgrp->files);
1401
	INIT_LIST_HEAD(&cgrp->cset_links);
1402
	INIT_LIST_HEAD(&cgrp->release_list);
1403 1404
	INIT_LIST_HEAD(&cgrp->pidlists);
	mutex_init(&cgrp->pidlist_mutex);
1405 1406
	INIT_LIST_HEAD(&cgrp->event_list);
	spin_lock_init(&cgrp->event_list_lock);
A
Aristeu Rozanski 已提交
1407
	simple_xattrs_init(&cgrp->xattrs);
1408
}
1409

1410 1411
static void init_cgroup_root(struct cgroupfs_root *root)
{
1412
	struct cgroup *cgrp = &root->top_cgroup;
1413

1414 1415 1416
	INIT_LIST_HEAD(&root->subsys_list);
	INIT_LIST_HEAD(&root->root_list);
	root->number_of_cgroups = 1;
1417
	cgrp->root = root;
1418
	cgrp->name = &root_cgroup_name;
1419
	init_cgroup_housekeeping(cgrp);
1420 1421
}

1422
static int cgroup_init_root_id(struct cgroupfs_root *root)
1423
{
1424
	int id;
1425

T
Tejun Heo 已提交
1426 1427 1428
	lockdep_assert_held(&cgroup_mutex);
	lockdep_assert_held(&cgroup_root_mutex);

1429 1430 1431 1432 1433
	id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 2, 0, GFP_KERNEL);
	if (id < 0)
		return id;

	root->hierarchy_id = id;
1434 1435 1436 1437 1438
	return 0;
}

static void cgroup_exit_root_id(struct cgroupfs_root *root)
{
T
Tejun Heo 已提交
1439 1440 1441
	lockdep_assert_held(&cgroup_mutex);
	lockdep_assert_held(&cgroup_root_mutex);

1442
	if (root->hierarchy_id) {
1443
		idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
1444 1445
		root->hierarchy_id = 0;
	}
1446 1447
}

1448 1449
static int cgroup_test_super(struct super_block *sb, void *data)
{
1450
	struct cgroup_sb_opts *opts = data;
1451 1452
	struct cgroupfs_root *root = sb->s_fs_info;

1453 1454 1455
	/* If we asked for a name then it must match */
	if (opts->name && strcmp(opts->name, root->name))
		return 0;
1456

1457 1458 1459 1460
	/*
	 * If we asked for subsystems (or explicitly for no
	 * subsystems) then they must match
	 */
1461 1462
	if ((opts->subsys_mask || opts->none)
	    && (opts->subsys_mask != root->subsys_mask))
1463 1464 1465 1466 1467
		return 0;

	return 1;
}

1468 1469 1470 1471
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
	struct cgroupfs_root *root;

1472
	if (!opts->subsys_mask && !opts->none)
1473 1474 1475 1476 1477 1478 1479
		return NULL;

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

	init_cgroup_root(root);
1480

1481
	root->subsys_mask = opts->subsys_mask;
1482
	root->flags = opts->flags;
T
Tejun Heo 已提交
1483
	ida_init(&root->cgroup_ida);
1484 1485 1486 1487
	if (opts->release_agent)
		strcpy(root->release_agent_path, opts->release_agent);
	if (opts->name)
		strcpy(root->name, opts->name);
1488 1489
	if (opts->cpuset_clone_children)
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags);
1490 1491 1492
	return root;
}

1493
static void cgroup_free_root(struct cgroupfs_root *root)
1494
{
1495 1496 1497
	if (root) {
		/* hierarhcy ID shoulid already have been released */
		WARN_ON_ONCE(root->hierarchy_id);
1498

1499 1500 1501
		ida_destroy(&root->cgroup_ida);
		kfree(root);
	}
1502 1503
}

1504 1505 1506
static int cgroup_set_super(struct super_block *sb, void *data)
{
	int ret;
1507 1508 1509 1510 1511 1512
	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;

1513
	BUG_ON(!opts->subsys_mask && !opts->none);
1514 1515 1516 1517 1518

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

1519 1520
	sb->s_fs_info = opts->new_root;
	opts->new_root->sb = sb;
1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531

	sb->s_blocksize = PAGE_CACHE_SIZE;
	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
	sb->s_magic = CGROUP_SUPER_MAGIC;
	sb->s_op = &cgroup_ops;

	return 0;
}

static int cgroup_get_rootdir(struct super_block *sb)
{
A
Al Viro 已提交
1532 1533
	static const struct dentry_operations cgroup_dops = {
		.d_iput = cgroup_diput,
1534
		.d_delete = cgroup_delete,
A
Al Viro 已提交
1535 1536
	};

1537 1538 1539 1540 1541 1542 1543 1544 1545 1546
	struct inode *inode =
		cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);

	if (!inode)
		return -ENOMEM;

	inode->i_fop = &simple_dir_operations;
	inode->i_op = &cgroup_dir_inode_operations;
	/* directories start off with i_nlink == 2 (for "." entry) */
	inc_nlink(inode);
1547 1548
	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
1549
		return -ENOMEM;
A
Al Viro 已提交
1550 1551
	/* for everything else we want ->d_op set */
	sb->s_d_op = &cgroup_dops;
1552 1553 1554
	return 0;
}

A
Al Viro 已提交
1555
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1556
			 int flags, const char *unused_dev_name,
A
Al Viro 已提交
1557
			 void *data)
1558 1559
{
	struct cgroup_sb_opts opts;
1560
	struct cgroupfs_root *root;
1561 1562
	int ret = 0;
	struct super_block *sb;
1563
	struct cgroupfs_root *new_root;
T
Tejun Heo 已提交
1564
	struct inode *inode;
1565 1566

	/* First find the desired set of subsystems */
B
Ben Blum 已提交
1567
	mutex_lock(&cgroup_mutex);
1568
	ret = parse_cgroupfs_options(data, &opts);
B
Ben Blum 已提交
1569
	mutex_unlock(&cgroup_mutex);
1570 1571
	if (ret)
		goto out_err;
1572

1573 1574 1575 1576 1577 1578 1579
	/*
	 * Allocate a new cgroup root. We may not need it if we're
	 * reusing an existing hierarchy.
	 */
	new_root = cgroup_root_from_opts(&opts);
	if (IS_ERR(new_root)) {
		ret = PTR_ERR(new_root);
B
Ben Blum 已提交
1580
		goto drop_modules;
1581
	}
1582
	opts.new_root = new_root;
1583

1584
	/* Locate an existing or new sb for this hierarchy */
D
David Howells 已提交
1585
	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
1586
	if (IS_ERR(sb)) {
1587
		ret = PTR_ERR(sb);
1588
		cgroup_free_root(opts.new_root);
B
Ben Blum 已提交
1589
		goto drop_modules;
1590 1591
	}

1592 1593 1594 1595
	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 */
1596
		struct list_head tmp_links;
1597
		struct cgroup *root_cgrp = &root->top_cgroup;
1598
		struct cgroupfs_root *existing_root;
1599
		const struct cred *cred;
1600
		int i;
1601
		struct css_set *cset;
1602 1603 1604 1605 1606 1607

		BUG_ON(sb->s_root != NULL);

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

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

T
Tejun Heo 已提交
1614 1615 1616 1617 1618 1619
		/* Check for name clashes with existing mounts */
		ret = -EBUSY;
		if (strlen(root->name))
			for_each_active_root(existing_root)
				if (!strcmp(existing_root->name, root->name))
					goto unlock_drop;
1620

1621 1622 1623 1624 1625 1626 1627
		/*
		 * 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
		 */
1628
		ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
T
Tejun Heo 已提交
1629 1630
		if (ret)
			goto unlock_drop;
1631

1632 1633 1634 1635
		ret = cgroup_init_root_id(root);
		if (ret)
			goto unlock_drop;

1636
		ret = rebind_subsystems(root, root->subsys_mask);
1637
		if (ret == -EBUSY) {
1638
			free_cgrp_cset_links(&tmp_links);
T
Tejun Heo 已提交
1639
			goto unlock_drop;
1640
		}
B
Ben Blum 已提交
1641 1642 1643 1644 1645
		/*
		 * There must be no failure case after here, since rebinding
		 * takes care of subsystems' refcounts, which are explicitly
		 * dropped in the failure exit path.
		 */
1646 1647 1648 1649 1650

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

		list_add(&root->root_list, &roots);
1651
		root_count++;
1652

1653
		sb->s_root->d_fsdata = root_cgrp;
1654 1655
		root->top_cgroup.dentry = sb->s_root;

1656 1657 1658
		/* Link the top cgroup in this hierarchy into all
		 * the css_set objects */
		write_lock(&css_set_lock);
1659
		hash_for_each(css_set_table, i, cset, hlist)
1660
			link_css_set(&tmp_links, cset, root_cgrp);
1661 1662
		write_unlock(&css_set_lock);

1663
		free_cgrp_cset_links(&tmp_links);
1664

1665
		BUG_ON(!list_empty(&root_cgrp->children));
1666 1667
		BUG_ON(root->number_of_cgroups != 1);

1668
		cred = override_creds(&init_cred);
1669
		cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
1670
		revert_creds(cred);
T
Tejun Heo 已提交
1671
		mutex_unlock(&cgroup_root_mutex);
1672
		mutex_unlock(&cgroup_mutex);
1673
		mutex_unlock(&inode->i_mutex);
1674 1675 1676 1677 1678
	} else {
		/*
		 * We re-used an existing hierarchy - the new root (if
		 * any) is not needed
		 */
1679
		cgroup_free_root(opts.new_root);
1680

1681 1682 1683 1684 1685 1686 1687 1688
		if (root->flags != opts.flags) {
			if ((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) {
				pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n");
				ret = -EINVAL;
				goto drop_new_super;
			} else {
				pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n");
			}
1689 1690
		}

B
Ben Blum 已提交
1691
		/* no subsys rebinding, so refcounts don't change */
1692
		drop_parsed_module_refcounts(opts.subsys_mask);
1693 1694
	}

1695 1696
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1697
	return dget(sb->s_root);
1698

T
Tejun Heo 已提交
1699
 unlock_drop:
1700
	cgroup_exit_root_id(root);
T
Tejun Heo 已提交
1701 1702 1703
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&inode->i_mutex);
1704
 drop_new_super:
1705
	deactivate_locked_super(sb);
B
Ben Blum 已提交
1706
 drop_modules:
1707
	drop_parsed_module_refcounts(opts.subsys_mask);
1708 1709 1710
 out_err:
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1711
	return ERR_PTR(ret);
1712 1713 1714 1715
}

static void cgroup_kill_sb(struct super_block *sb) {
	struct cgroupfs_root *root = sb->s_fs_info;
1716
	struct cgroup *cgrp = &root->top_cgroup;
1717
	struct cgrp_cset_link *link, *tmp_link;
1718 1719 1720 1721 1722
	int ret;

	BUG_ON(!root);

	BUG_ON(root->number_of_cgroups != 1);
1723
	BUG_ON(!list_empty(&cgrp->children));
1724 1725

	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1726
	mutex_lock(&cgroup_root_mutex);
1727 1728 1729 1730 1731 1732

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

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

1739 1740 1741
	list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
		list_del(&link->cset_link);
		list_del(&link->cgrp_link);
1742 1743 1744 1745
		kfree(link);
	}
	write_unlock(&css_set_lock);

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

1751 1752
	cgroup_exit_root_id(root);

T
Tejun Heo 已提交
1753
	mutex_unlock(&cgroup_root_mutex);
1754 1755
	mutex_unlock(&cgroup_mutex);

A
Aristeu Rozanski 已提交
1756 1757
	simple_xattrs_free(&cgrp->xattrs);

1758
	kill_litter_super(sb);
1759
	cgroup_free_root(root);
1760 1761 1762 1763
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
A
Al Viro 已提交
1764
	.mount = cgroup_mount,
1765 1766 1767
	.kill_sb = cgroup_kill_sb,
};

1768 1769
static struct kobject *cgroup_kobj;

L
Li Zefan 已提交
1770 1771 1772 1773 1774 1775
/**
 * 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
 *
1776 1777 1778 1779 1780 1781
 * Writes path of cgroup into buf.  Returns 0 on success, -errno on error.
 *
 * We can't generate cgroup path using dentry->d_name, as accessing
 * dentry->name must be protected by irq-unsafe dentry->d_lock or parent
 * inode's i_mutex, while on the other hand cgroup_path() can be called
 * with some irq-safe spinlocks held.
1782
 */
1783
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1784
{
1785
	int ret = -ENAMETOOLONG;
1786
	char *start;
1787

1788 1789 1790
	if (!cgrp->parent) {
		if (strlcpy(buf, "/", buflen) >= buflen)
			return -ENAMETOOLONG;
1791 1792 1793
		return 0;
	}

1794 1795
	start = buf + buflen - 1;
	*start = '\0';
1796

1797
	rcu_read_lock();
1798
	do {
1799 1800 1801 1802
		const char *name = cgroup_name(cgrp);
		int len;

		len = strlen(name);
1803
		if ((start -= len) < buf)
1804 1805
			goto out;
		memcpy(start, name, len);
1806

1807
		if (--start < buf)
1808
			goto out;
1809
		*start = '/';
1810 1811

		cgrp = cgrp->parent;
1812
	} while (cgrp->parent);
1813
	ret = 0;
1814
	memmove(buf, start, buf + buflen - start);
1815 1816 1817
out:
	rcu_read_unlock();
	return ret;
1818
}
B
Ben Blum 已提交
1819
EXPORT_SYMBOL_GPL(cgroup_path);
1820

1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852
/**
 * task_cgroup_path_from_hierarchy - cgroup path of a task on a hierarchy
 * @task: target task
 * @hierarchy_id: the hierarchy to look up @task's cgroup from
 * @buf: the buffer to write the path into
 * @buflen: the length of the buffer
 *
 * Determine @task's cgroup on the hierarchy specified by @hierarchy_id and
 * copy its path into @buf.  This function grabs cgroup_mutex and shouldn't
 * be used inside locks used by cgroup controller callbacks.
 */
int task_cgroup_path_from_hierarchy(struct task_struct *task, int hierarchy_id,
				    char *buf, size_t buflen)
{
	struct cgroupfs_root *root;
	struct cgroup *cgrp = NULL;
	int ret = -ENOENT;

	mutex_lock(&cgroup_mutex);

	root = idr_find(&cgroup_hierarchy_idr, hierarchy_id);
	if (root) {
		cgrp = task_cgroup_from_root(task, root);
		ret = cgroup_path(cgrp, buf, buflen);
	}

	mutex_unlock(&cgroup_mutex);

	return ret;
}
EXPORT_SYMBOL_GPL(task_cgroup_path_from_hierarchy);

1853 1854 1855
/*
 * Control Group taskset
 */
1856 1857 1858
struct task_and_cgroup {
	struct task_struct	*task;
	struct cgroup		*cgrp;
1859
	struct css_set		*cg;
1860 1861
};

1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 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
struct cgroup_taskset {
	struct task_and_cgroup	single;
	struct flex_array	*tc_array;
	int			tc_array_len;
	int			idx;
	struct cgroup		*cur_cgrp;
};

/**
 * cgroup_taskset_first - reset taskset and return the first task
 * @tset: taskset of interest
 *
 * @tset iteration is initialized and the first task is returned.
 */
struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
{
	if (tset->tc_array) {
		tset->idx = 0;
		return cgroup_taskset_next(tset);
	} else {
		tset->cur_cgrp = tset->single.cgrp;
		return tset->single.task;
	}
}
EXPORT_SYMBOL_GPL(cgroup_taskset_first);

/**
 * cgroup_taskset_next - iterate to the next task in taskset
 * @tset: taskset of interest
 *
 * Return the next task in @tset.  Iteration must have been initialized
 * with cgroup_taskset_first().
 */
struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
{
	struct task_and_cgroup *tc;

	if (!tset->tc_array || tset->idx >= tset->tc_array_len)
		return NULL;

	tc = flex_array_get(tset->tc_array, tset->idx++);
	tset->cur_cgrp = tc->cgrp;
	return tc->task;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_next);

/**
 * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
 * @tset: taskset of interest
 *
 * Return the cgroup for the current (last returned) task of @tset.  This
 * function must be preceded by either cgroup_taskset_first() or
 * cgroup_taskset_next().
 */
struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
{
	return tset->cur_cgrp;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);

/**
 * cgroup_taskset_size - return the number of tasks in taskset
 * @tset: taskset of interest
 */
int cgroup_taskset_size(struct cgroup_taskset *tset)
{
	return tset->tc_array ? tset->tc_array_len : 1;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_size);


B
Ben Blum 已提交
1933 1934 1935
/*
 * cgroup_task_migrate - move a task from one cgroup to another.
 *
1936
 * Must be called with cgroup_mutex and threadgroup locked.
B
Ben Blum 已提交
1937
 */
1938 1939 1940
static void cgroup_task_migrate(struct cgroup *old_cgrp,
				struct task_struct *tsk,
				struct css_set *new_cset)
B
Ben Blum 已提交
1941
{
1942
	struct css_set *old_cset;
B
Ben Blum 已提交
1943 1944

	/*
1945 1946 1947
	 * We are synchronized through threadgroup_lock() against PF_EXITING
	 * setting such that we can't race against cgroup_exit() changing the
	 * css_set to init_css_set and dropping the old one.
B
Ben Blum 已提交
1948
	 */
1949
	WARN_ON_ONCE(tsk->flags & PF_EXITING);
1950
	old_cset = tsk->cgroups;
B
Ben Blum 已提交
1951 1952

	task_lock(tsk);
1953
	rcu_assign_pointer(tsk->cgroups, new_cset);
B
Ben Blum 已提交
1954 1955 1956 1957 1958
	task_unlock(tsk);

	/* Update the css_set linked lists if we're using them */
	write_lock(&css_set_lock);
	if (!list_empty(&tsk->cg_list))
1959
		list_move(&tsk->cg_list, &new_cset->tasks);
B
Ben Blum 已提交
1960 1961 1962
	write_unlock(&css_set_lock);

	/*
1963 1964 1965
	 * We just gained a reference on old_cset by taking it from the
	 * task. As trading it for new_cset is protected by cgroup_mutex,
	 * we're safe to drop it here; it will be freed under RCU.
B
Ben Blum 已提交
1966
	 */
1967 1968
	set_bit(CGRP_RELEASABLE, &old_cgrp->flags);
	put_css_set(old_cset);
B
Ben Blum 已提交
1969 1970
}

L
Li Zefan 已提交
1971
/**
1972
 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
B
Ben Blum 已提交
1973
 * @cgrp: the cgroup to attach to
1974 1975
 * @tsk: the task or the leader of the threadgroup to be attached
 * @threadgroup: attach the whole threadgroup?
B
Ben Blum 已提交
1976
 *
1977
 * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
1978
 * task_lock of @tsk or each thread in the threadgroup individually in turn.
B
Ben Blum 已提交
1979
 */
T
Tejun Heo 已提交
1980 1981
static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
			      bool threadgroup)
B
Ben Blum 已提交
1982 1983 1984 1985 1986
{
	int retval, i, group_size;
	struct cgroup_subsys *ss, *failed_ss = NULL;
	struct cgroupfs_root *root = cgrp->root;
	/* threadgroup list cursor and array */
1987
	struct task_struct *leader = tsk;
1988
	struct task_and_cgroup *tc;
1989
	struct flex_array *group;
1990
	struct cgroup_taskset tset = { };
B
Ben Blum 已提交
1991 1992 1993 1994 1995

	/*
	 * step 0: in order to do expensive, possibly blocking operations for
	 * every thread, we cannot iterate the thread group list, since it needs
	 * rcu or tasklist locked. instead, build an array of all threads in the
1996 1997
	 * group - group_rwsem prevents new threads from appearing, and if
	 * threads exit, this will just be an over-estimate.
B
Ben Blum 已提交
1998
	 */
1999 2000 2001 2002
	if (threadgroup)
		group_size = get_nr_threads(tsk);
	else
		group_size = 1;
2003
	/* flex_array supports very large thread-groups better than kmalloc. */
2004
	group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
B
Ben Blum 已提交
2005 2006
	if (!group)
		return -ENOMEM;
2007
	/* pre-allocate to guarantee space while iterating in rcu read-side. */
2008
	retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
2009 2010
	if (retval)
		goto out_free_group_list;
B
Ben Blum 已提交
2011 2012

	i = 0;
2013 2014 2015 2016 2017 2018
	/*
	 * Prevent freeing of tasks while we take a snapshot. Tasks that are
	 * already PF_EXITING could be freed from underneath us unless we
	 * take an rcu_read_lock.
	 */
	rcu_read_lock();
B
Ben Blum 已提交
2019
	do {
2020 2021
		struct task_and_cgroup ent;

2022 2023 2024 2025
		/* @tsk either already exited or can't exit until the end */
		if (tsk->flags & PF_EXITING)
			continue;

B
Ben Blum 已提交
2026 2027
		/* as per above, nr_threads may decrease, but not increase. */
		BUG_ON(i >= group_size);
2028 2029
		ent.task = tsk;
		ent.cgrp = task_cgroup_from_root(tsk, root);
2030 2031 2032
		/* nothing to do if this task is already in the cgroup */
		if (ent.cgrp == cgrp)
			continue;
2033 2034 2035 2036
		/*
		 * saying GFP_ATOMIC has no effect here because we did prealloc
		 * earlier, but it's good form to communicate our expectations.
		 */
2037
		retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2038
		BUG_ON(retval != 0);
B
Ben Blum 已提交
2039
		i++;
2040 2041 2042

		if (!threadgroup)
			break;
B
Ben Blum 已提交
2043
	} while_each_thread(leader, tsk);
2044
	rcu_read_unlock();
B
Ben Blum 已提交
2045 2046
	/* remember the number of threads in the array for later. */
	group_size = i;
2047 2048
	tset.tc_array = group;
	tset.tc_array_len = group_size;
B
Ben Blum 已提交
2049

2050 2051
	/* methods shouldn't be called if no task is actually migrating */
	retval = 0;
2052
	if (!group_size)
2053
		goto out_free_group_list;
2054

B
Ben Blum 已提交
2055 2056 2057 2058 2059
	/*
	 * step 1: check that we can legitimately attach to the cgroup.
	 */
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
2060
			retval = ss->can_attach(cgrp, &tset);
B
Ben Blum 已提交
2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072
			if (retval) {
				failed_ss = ss;
				goto out_cancel_attach;
			}
		}
	}

	/*
	 * step 2: make sure css_sets exist for all threads to be migrated.
	 * we use find_css_set, which allocates a new one if necessary.
	 */
	for (i = 0; i < group_size; i++) {
2073
		tc = flex_array_get(group, i);
2074 2075 2076 2077
		tc->cg = find_css_set(tc->task->cgroups, cgrp);
		if (!tc->cg) {
			retval = -ENOMEM;
			goto out_put_css_set_refs;
B
Ben Blum 已提交
2078 2079 2080 2081
		}
	}

	/*
2082 2083 2084
	 * step 3: now that we're guaranteed success wrt the css_sets,
	 * proceed to move all tasks to the new cgroup.  There are no
	 * failure cases after here, so this is the commit point.
B
Ben Blum 已提交
2085 2086
	 */
	for (i = 0; i < group_size; i++) {
2087
		tc = flex_array_get(group, i);
2088
		cgroup_task_migrate(tc->cgrp, tc->task, tc->cg);
B
Ben Blum 已提交
2089 2090 2091 2092
	}
	/* nothing is sensitive to fork() after this point. */

	/*
2093
	 * step 4: do subsystem attach callbacks.
B
Ben Blum 已提交
2094 2095 2096
	 */
	for_each_subsys(root, ss) {
		if (ss->attach)
2097
			ss->attach(cgrp, &tset);
B
Ben Blum 已提交
2098 2099 2100 2101 2102 2103
	}

	/*
	 * step 5: success! and cleanup
	 */
	retval = 0;
2104 2105 2106 2107 2108 2109 2110 2111
out_put_css_set_refs:
	if (retval) {
		for (i = 0; i < group_size; i++) {
			tc = flex_array_get(group, i);
			if (!tc->cg)
				break;
			put_css_set(tc->cg);
		}
B
Ben Blum 已提交
2112 2113 2114 2115
	}
out_cancel_attach:
	if (retval) {
		for_each_subsys(root, ss) {
2116
			if (ss == failed_ss)
B
Ben Blum 已提交
2117 2118
				break;
			if (ss->cancel_attach)
2119
				ss->cancel_attach(cgrp, &tset);
B
Ben Blum 已提交
2120 2121 2122
		}
	}
out_free_group_list:
2123
	flex_array_free(group);
B
Ben Blum 已提交
2124 2125 2126 2127 2128
	return retval;
}

/*
 * Find the task_struct of the task to attach by vpid and pass it along to the
2129 2130
 * function to attach either it or all tasks in its threadgroup. Will lock
 * cgroup_mutex and threadgroup; may take task_lock of task.
2131
 */
B
Ben Blum 已提交
2132
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2133 2134
{
	struct task_struct *tsk;
2135
	const struct cred *cred = current_cred(), *tcred;
2136 2137
	int ret;

B
Ben Blum 已提交
2138 2139 2140
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;

2141 2142
retry_find_task:
	rcu_read_lock();
2143
	if (pid) {
2144
		tsk = find_task_by_vpid(pid);
B
Ben Blum 已提交
2145 2146
		if (!tsk) {
			rcu_read_unlock();
2147 2148
			ret= -ESRCH;
			goto out_unlock_cgroup;
2149
		}
B
Ben Blum 已提交
2150 2151 2152 2153
		/*
		 * even if we're attaching all tasks in the thread group, we
		 * only need to check permissions on one of them.
		 */
2154
		tcred = __task_cred(tsk);
2155 2156 2157
		if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
		    !uid_eq(cred->euid, tcred->uid) &&
		    !uid_eq(cred->euid, tcred->suid)) {
2158
			rcu_read_unlock();
2159 2160
			ret = -EACCES;
			goto out_unlock_cgroup;
2161
		}
2162 2163
	} else
		tsk = current;
2164 2165

	if (threadgroup)
2166
		tsk = tsk->group_leader;
2167 2168

	/*
2169
	 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2170 2171 2172
	 * trapped in a cpuset, or RT worker may be born in a cgroup
	 * with no rt_runtime allocated.  Just say no.
	 */
2173
	if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) {
2174 2175 2176 2177 2178
		ret = -EINVAL;
		rcu_read_unlock();
		goto out_unlock_cgroup;
	}

2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195
	get_task_struct(tsk);
	rcu_read_unlock();

	threadgroup_lock(tsk);
	if (threadgroup) {
		if (!thread_group_leader(tsk)) {
			/*
			 * a race with de_thread from another thread's exec()
			 * may strip us of our leadership, if this happens,
			 * there is no choice but to throw this task away and
			 * try again; this is
			 * "double-double-toil-and-trouble-check locking".
			 */
			threadgroup_unlock(tsk);
			put_task_struct(tsk);
			goto retry_find_task;
		}
2196 2197 2198 2199
	}

	ret = cgroup_attach_task(cgrp, tsk, threadgroup);

2200 2201
	threadgroup_unlock(tsk);

2202
	put_task_struct(tsk);
2203
out_unlock_cgroup:
T
Tejun Heo 已提交
2204
	mutex_unlock(&cgroup_mutex);
2205 2206 2207
	return ret;
}

2208 2209 2210 2211 2212 2213 2214 2215 2216 2217
/**
 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
 * @from: attach to all cgroups of a given task
 * @tsk: the task to be attached
 */
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
{
	struct cgroupfs_root *root;
	int retval = 0;

T
Tejun Heo 已提交
2218
	mutex_lock(&cgroup_mutex);
2219 2220 2221 2222 2223 2224 2225
	for_each_active_root(root) {
		struct cgroup *from_cg = task_cgroup_from_root(from, root);

		retval = cgroup_attach_task(from_cg, tsk, false);
		if (retval)
			break;
	}
T
Tejun Heo 已提交
2226
	mutex_unlock(&cgroup_mutex);
2227 2228 2229 2230 2231

	return retval;
}
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);

2232
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
B
Ben Blum 已提交
2233 2234 2235 2236 2237
{
	return attach_task_by_pid(cgrp, pid, false);
}

static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2238
{
2239
	return attach_task_by_pid(cgrp, tgid, true);
2240 2241
}

2242 2243 2244 2245
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);
2246 2247
	if (strlen(buffer) >= PATH_MAX)
		return -EINVAL;
2248 2249
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
T
Tejun Heo 已提交
2250
	mutex_lock(&cgroup_root_mutex);
2251
	strcpy(cgrp->root->release_agent_path, buffer);
T
Tejun Heo 已提交
2252
	mutex_unlock(&cgroup_root_mutex);
T
Tejun Heo 已提交
2253
	mutex_unlock(&cgroup_mutex);
2254 2255 2256 2257 2258 2259 2260 2261 2262 2263
	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');
T
Tejun Heo 已提交
2264
	mutex_unlock(&cgroup_mutex);
2265 2266 2267
	return 0;
}

2268 2269 2270 2271
static int cgroup_sane_behavior_show(struct cgroup *cgrp, struct cftype *cft,
				     struct seq_file *seq)
{
	seq_printf(seq, "%d\n", cgroup_sane_behavior(cgrp));
2272 2273 2274
	return 0;
}

2275 2276 2277
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64

2278
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2279 2280 2281
				struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *unused_ppos)
2282
{
2283
	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294
	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 */
2295
	if (cft->write_u64) {
K
KOSAKI Motohiro 已提交
2296
		u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2297 2298 2299 2300
		if (*end)
			return -EINVAL;
		retval = cft->write_u64(cgrp, cft, val);
	} else {
K
KOSAKI Motohiro 已提交
2301
		s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2302 2303 2304 2305
		if (*end)
			return -EINVAL;
		retval = cft->write_s64(cgrp, cft, val);
	}
2306 2307 2308 2309 2310
	if (!retval)
		retval = nbytes;
	return retval;
}

2311 2312 2313 2314 2315
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)
{
2316
	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330
	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
2331 2332 2333 2334
	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
		retval = -EFAULT;
		goto out;
	}
2335 2336

	buffer[nbytes] = 0;     /* nul-terminate */
K
KOSAKI Motohiro 已提交
2337
	retval = cft->write_string(cgrp, cft, strstrip(buffer));
2338 2339
	if (!retval)
		retval = nbytes;
L
Li Zefan 已提交
2340
out:
2341 2342 2343 2344 2345
	if (buffer != local_buffer)
		kfree(buffer);
	return retval;
}

2346 2347 2348 2349
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);
2350
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2351

2352
	if (cgroup_is_dead(cgrp))
2353
		return -ENODEV;
2354
	if (cft->write)
2355
		return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2356 2357
	if (cft->write_u64 || cft->write_s64)
		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2358 2359
	if (cft->write_string)
		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2360 2361 2362 2363
	if (cft->trigger) {
		int ret = cft->trigger(cgrp, (unsigned int)cft->private);
		return ret ? ret : nbytes;
	}
2364
	return -EINVAL;
2365 2366
}

2367 2368 2369 2370
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
2371
{
2372
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2373
	u64 val = cft->read_u64(cgrp, cft);
2374 2375 2376 2377 2378
	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);

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

2379 2380 2381 2382 2383
static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
{
2384
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2385 2386 2387 2388 2389 2390
	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);
}

2391 2392 2393 2394
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);
2395
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2396

2397
	if (cgroup_is_dead(cgrp))
2398 2399 2400
		return -ENODEV;

	if (cft->read)
2401
		return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2402 2403
	if (cft->read_u64)
		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2404 2405
	if (cft->read_s64)
		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2406 2407 2408
	return -EINVAL;
}

2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428
/*
 * 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;
2429 2430 2431 2432 2433 2434 2435 2436
	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);
2437 2438
}

2439
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2440 2441 2442 2443 2444 2445
{
	struct seq_file *seq = file->private_data;
	kfree(seq->private);
	return single_release(inode, file);
}

2446
static const struct file_operations cgroup_seqfile_operations = {
2447
	.read = seq_read,
2448
	.write = cgroup_file_write,
2449 2450 2451 2452
	.llseek = seq_lseek,
	.release = cgroup_seqfile_release,
};

2453 2454 2455 2456 2457 2458 2459 2460 2461
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);
2462

2463
	if (cft->read_map || cft->read_seq_string) {
2464 2465 2466
		struct cgroup_seqfile_state *state;

		state = kzalloc(sizeof(*state), GFP_USER);
2467 2468
		if (!state)
			return -ENOMEM;
2469

2470 2471 2472 2473 2474 2475 2476
		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)
2477 2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497
		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)
{
2498 2499 2500 2501 2502 2503 2504 2505 2506 2507
	int ret;
	struct cgroup_name *name, *old_name;
	struct cgroup *cgrp;

	/*
	 * It's convinient to use parent dir's i_mutex to protected
	 * cgrp->name.
	 */
	lockdep_assert_held(&old_dir->i_mutex);

2508 2509 2510 2511 2512 2513
	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;
2514 2515 2516

	cgrp = __d_cgrp(old_dentry);

2517 2518 2519 2520 2521 2522 2523
	/*
	 * This isn't a proper migration and its usefulness is very
	 * limited.  Disallow if sane_behavior.
	 */
	if (cgroup_sane_behavior(cgrp))
		return -EPERM;

2524 2525 2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538
	name = cgroup_alloc_name(new_dentry);
	if (!name)
		return -ENOMEM;

	ret = simple_rename(old_dir, old_dentry, new_dir, new_dentry);
	if (ret) {
		kfree(name);
		return ret;
	}

	old_name = cgrp->name;
	rcu_assign_pointer(cgrp->name, name);

	kfree_rcu(old_name, rcu_head);
	return 0;
2539 2540
}

A
Aristeu Rozanski 已提交
2541 2542 2543 2544 2545
static struct simple_xattrs *__d_xattrs(struct dentry *dentry)
{
	if (S_ISDIR(dentry->d_inode->i_mode))
		return &__d_cgrp(dentry)->xattrs;
	else
L
Li Zefan 已提交
2546
		return &__d_cfe(dentry)->xattrs;
A
Aristeu Rozanski 已提交
2547 2548 2549 2550 2551
}

static inline int xattr_enabled(struct dentry *dentry)
{
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
2552
	return root->flags & CGRP_ROOT_XATTR;
A
Aristeu Rozanski 已提交
2553 2554 2555 2556 2557 2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598
}

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

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

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

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

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

2599
static const struct file_operations cgroup_file_operations = {
2600 2601 2602 2603 2604 2605 2606
	.read = cgroup_file_read,
	.write = cgroup_file_write,
	.llseek = generic_file_llseek,
	.open = cgroup_file_open,
	.release = cgroup_file_release,
};

A
Aristeu Rozanski 已提交
2607 2608 2609 2610 2611 2612 2613
static const struct inode_operations cgroup_file_inode_operations = {
	.setxattr = cgroup_setxattr,
	.getxattr = cgroup_getxattr,
	.listxattr = cgroup_listxattr,
	.removexattr = cgroup_removexattr,
};

2614
static const struct inode_operations cgroup_dir_inode_operations = {
2615
	.lookup = cgroup_lookup,
2616 2617 2618
	.mkdir = cgroup_mkdir,
	.rmdir = cgroup_rmdir,
	.rename = cgroup_rename,
A
Aristeu Rozanski 已提交
2619 2620 2621 2622
	.setxattr = cgroup_setxattr,
	.getxattr = cgroup_getxattr,
	.listxattr = cgroup_listxattr,
	.removexattr = cgroup_removexattr,
2623 2624
};

A
Al Viro 已提交
2625
static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
2626 2627 2628 2629 2630 2631 2632
{
	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
	d_add(dentry, NULL);
	return NULL;
}

2633 2634 2635 2636 2637
/*
 * Check if a file is a control file
 */
static inline struct cftype *__file_cft(struct file *file)
{
A
Al Viro 已提交
2638
	if (file_inode(file)->i_fop != &cgroup_file_operations)
2639 2640 2641 2642
		return ERR_PTR(-EINVAL);
	return __d_cft(file->f_dentry);
}

A
Al Viro 已提交
2643
static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2644 2645
				struct super_block *sb)
{
2646 2647 2648 2649 2650 2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662
	struct inode *inode;

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

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

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

		/* start off with i_nlink == 2 (for "." entry) */
		inc_nlink(inode);
T
Tejun Heo 已提交
2663
		inc_nlink(dentry->d_parent->d_inode);
2664

2665 2666 2667 2668 2669 2670 2671 2672 2673
		/*
		 * Control reaches here with cgroup_mutex held.
		 * @inode->i_mutex should nest outside cgroup_mutex but we
		 * want to populate it immediately without releasing
		 * cgroup_mutex.  As @inode isn't visible to anyone else
		 * yet, trylock will always succeed without affecting
		 * lockdep checks.
		 */
		WARN_ON_ONCE(!mutex_trylock(&inode->i_mutex));
2674 2675 2676
	} else if (S_ISREG(mode)) {
		inode->i_size = 0;
		inode->i_fop = &cgroup_file_operations;
A
Aristeu Rozanski 已提交
2677
		inode->i_op = &cgroup_file_inode_operations;
2678 2679 2680 2681 2682 2683
	}
	d_instantiate(dentry, inode);
	dget(dentry);	/* Extra count - pin the dentry in core */
	return 0;
}

L
Li Zefan 已提交
2684 2685 2686 2687 2688 2689 2690 2691 2692
/**
 * cgroup_file_mode - deduce file mode of a control file
 * @cft: the control file in question
 *
 * returns cft->mode if ->mode is not 0
 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
 * returns S_IRUGO if it has only a read handler
 * returns S_IWUSR if it has only a write hander
 */
A
Al Viro 已提交
2693
static umode_t cgroup_file_mode(const struct cftype *cft)
L
Li Zefan 已提交
2694
{
A
Al Viro 已提交
2695
	umode_t mode = 0;
L
Li Zefan 已提交
2696 2697 2698 2699 2700 2701 2702 2703 2704 2705 2706 2707 2708 2709 2710

	if (cft->mode)
		return cft->mode;

	if (cft->read || cft->read_u64 || cft->read_s64 ||
	    cft->read_map || cft->read_seq_string)
		mode |= S_IRUGO;

	if (cft->write || cft->write_u64 || cft->write_s64 ||
	    cft->write_string || cft->trigger)
		mode |= S_IWUSR;

	return mode;
}

T
Tejun Heo 已提交
2711
static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
A
Aristeu Rozanski 已提交
2712
			   struct cftype *cft)
2713
{
2714
	struct dentry *dir = cgrp->dentry;
T
Tejun Heo 已提交
2715
	struct cgroup *parent = __d_cgrp(dir);
2716
	struct dentry *dentry;
T
Tejun Heo 已提交
2717
	struct cfent *cfe;
2718
	int error;
A
Al Viro 已提交
2719
	umode_t mode;
2720
	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2721

2722
	if (subsys && !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
2723 2724 2725 2726
		strcpy(name, subsys->name);
		strcat(name, ".");
	}
	strcat(name, cft->name);
T
Tejun Heo 已提交
2727

2728
	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
T
Tejun Heo 已提交
2729 2730 2731 2732 2733

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

2734
	dentry = lookup_one_len(name, dir, strlen(name));
T
Tejun Heo 已提交
2735
	if (IS_ERR(dentry)) {
2736
		error = PTR_ERR(dentry);
T
Tejun Heo 已提交
2737 2738 2739
		goto out;
	}

2740 2741 2742 2743 2744
	cfe->type = (void *)cft;
	cfe->dentry = dentry;
	dentry->d_fsdata = cfe;
	simple_xattrs_init(&cfe->xattrs);

T
Tejun Heo 已提交
2745 2746 2747 2748 2749 2750 2751 2752 2753
	mode = cgroup_file_mode(cft);
	error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
	if (!error) {
		list_add_tail(&cfe->node, &parent->files);
		cfe = NULL;
	}
	dput(dentry);
out:
	kfree(cfe);
2754 2755 2756
	return error;
}

2757
static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
A
Aristeu Rozanski 已提交
2758
			      struct cftype cfts[], bool is_add)
2759
{
A
Aristeu Rozanski 已提交
2760
	struct cftype *cft;
T
Tejun Heo 已提交
2761 2762 2763
	int err, ret = 0;

	for (cft = cfts; cft->name[0] != '\0'; cft++) {
2764
		/* does cft->flags tell us to skip this file on @cgrp? */
2765 2766
		if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp))
			continue;
2767 2768 2769 2770 2771
		if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
			continue;
		if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
			continue;

2772
		if (is_add) {
2773
			err = cgroup_add_file(cgrp, subsys, cft);
2774 2775 2776
			if (err)
				pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
					cft->name, err);
T
Tejun Heo 已提交
2777
			ret = err;
2778 2779
		} else {
			cgroup_rm_file(cgrp, cft);
T
Tejun Heo 已提交
2780
		}
2781
	}
T
Tejun Heo 已提交
2782
	return ret;
2783 2784
}

2785
static void cgroup_cfts_prepare(void)
2786
	__acquires(&cgroup_mutex)
2787 2788 2789 2790
{
	/*
	 * Thanks to the entanglement with vfs inode locking, we can't walk
	 * the existing cgroups under cgroup_mutex and create files.
2791 2792
	 * Instead, we use cgroup_for_each_descendant_pre() and drop RCU
	 * read lock before calling cgroup_addrm_files().
2793 2794 2795 2796 2797
	 */
	mutex_lock(&cgroup_mutex);
}

static void cgroup_cfts_commit(struct cgroup_subsys *ss,
A
Aristeu Rozanski 已提交
2798
			       struct cftype *cfts, bool is_add)
2799
	__releases(&cgroup_mutex)
2800 2801
{
	LIST_HEAD(pending);
2802
	struct cgroup *cgrp, *root = &ss->root->top_cgroup;
2803
	struct super_block *sb = ss->root->sb;
2804 2805 2806
	struct dentry *prev = NULL;
	struct inode *inode;
	u64 update_upto;
2807 2808

	/* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
2809 2810 2811 2812
	if (!cfts || ss->root == &rootnode ||
	    !atomic_inc_not_zero(&sb->s_active)) {
		mutex_unlock(&cgroup_mutex);
		return;
2813 2814 2815
	}

	/*
2816 2817 2818
	 * All cgroups which are created after we drop cgroup_mutex will
	 * have the updated set of files, so we only need to update the
	 * cgroups created before the current @cgroup_serial_nr_cursor.
2819
	 */
2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843
	update_upto = atomic64_read(&cgroup_serial_nr_cursor);

	mutex_unlock(&cgroup_mutex);

	/* @root always needs to be updated */
	inode = root->dentry->d_inode;
	mutex_lock(&inode->i_mutex);
	mutex_lock(&cgroup_mutex);
	cgroup_addrm_files(root, ss, cfts, is_add);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&inode->i_mutex);

	/* add/rm files for all cgroups created before */
	rcu_read_lock();
	cgroup_for_each_descendant_pre(cgrp, root) {
		if (cgroup_is_dead(cgrp))
			continue;

		inode = cgrp->dentry->d_inode;
		dget(cgrp->dentry);
		rcu_read_unlock();

		dput(prev);
		prev = cgrp->dentry;
2844 2845 2846

		mutex_lock(&inode->i_mutex);
		mutex_lock(&cgroup_mutex);
2847
		if (cgrp->serial_nr <= update_upto && !cgroup_is_dead(cgrp))
2848
			cgroup_addrm_files(cgrp, ss, cfts, is_add);
2849 2850 2851
		mutex_unlock(&cgroup_mutex);
		mutex_unlock(&inode->i_mutex);

2852
		rcu_read_lock();
2853
	}
2854 2855 2856
	rcu_read_unlock();
	dput(prev);
	deactivate_super(sb);
2857 2858 2859 2860 2861 2862 2863 2864 2865 2866 2867 2868 2869 2870 2871 2872
}

/**
 * cgroup_add_cftypes - add an array of cftypes to a subsystem
 * @ss: target cgroup subsystem
 * @cfts: zero-length name terminated array of cftypes
 *
 * Register @cfts to @ss.  Files described by @cfts are created for all
 * existing cgroups to which @ss is attached and all future cgroups will
 * have them too.  This function can be called anytime whether @ss is
 * attached or not.
 *
 * Returns 0 on successful registration, -errno on failure.  Note that this
 * function currently returns 0 as long as @cfts registration is successful
 * even if some file creation attempts on existing cgroups fail.
 */
A
Aristeu Rozanski 已提交
2873
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2874 2875 2876 2877 2878 2879 2880 2881 2882 2883
{
	struct cftype_set *set;

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

	cgroup_cfts_prepare();
	set->cfts = cfts;
	list_add_tail(&set->node, &ss->cftsets);
2884
	cgroup_cfts_commit(ss, cfts, true);
2885 2886 2887 2888 2889

	return 0;
}
EXPORT_SYMBOL_GPL(cgroup_add_cftypes);

2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902
/**
 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
 * @ss: target cgroup subsystem
 * @cfts: zero-length name terminated array of cftypes
 *
 * Unregister @cfts from @ss.  Files described by @cfts are removed from
 * all existing cgroups to which @ss is attached and all future cgroups
 * won't have them either.  This function can be called anytime whether @ss
 * is attached or not.
 *
 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
 * registered with @ss.
 */
A
Aristeu Rozanski 已提交
2903
int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2904 2905 2906 2907 2908 2909 2910
{
	struct cftype_set *set;

	cgroup_cfts_prepare();

	list_for_each_entry(set, &ss->cftsets, node) {
		if (set->cfts == cfts) {
2911 2912
			list_del(&set->node);
			kfree(set);
2913 2914 2915 2916 2917 2918 2919 2920 2921
			cgroup_cfts_commit(ss, cfts, false);
			return 0;
		}
	}

	cgroup_cfts_commit(ss, NULL, false);
	return -ENOENT;
}

L
Li Zefan 已提交
2922 2923 2924 2925 2926 2927
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2928
int cgroup_task_count(const struct cgroup *cgrp)
2929 2930
{
	int count = 0;
2931
	struct cgrp_cset_link *link;
2932 2933

	read_lock(&css_set_lock);
2934 2935
	list_for_each_entry(link, &cgrp->cset_links, cset_link)
		count += atomic_read(&link->cset->refcount);
2936
	read_unlock(&css_set_lock);
2937 2938 2939
	return count;
}

2940 2941 2942 2943
/*
 * Advance a list_head iterator.  The iterator should be positioned at
 * the start of a css_set
 */
2944
static void cgroup_advance_iter(struct cgroup *cgrp, struct cgroup_iter *it)
2945
{
2946 2947
	struct list_head *l = it->cset_link;
	struct cgrp_cset_link *link;
2948
	struct css_set *cset;
2949 2950 2951 2952

	/* Advance to the next non-empty css_set */
	do {
		l = l->next;
2953 2954
		if (l == &cgrp->cset_links) {
			it->cset_link = NULL;
2955 2956
			return;
		}
2957 2958
		link = list_entry(l, struct cgrp_cset_link, cset_link);
		cset = link->cset;
2959
	} while (list_empty(&cset->tasks));
2960
	it->cset_link = l;
2961
	it->task = cset->tasks.next;
2962 2963
}

2964 2965 2966 2967 2968 2969
/*
 * 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().
 */
2970
static void cgroup_enable_task_cg_lists(void)
2971 2972 2973 2974
{
	struct task_struct *p, *g;
	write_lock(&css_set_lock);
	use_task_css_set_links = 1;
2975 2976 2977 2978 2979 2980 2981 2982
	/*
	 * We need tasklist_lock because RCU is not safe against
	 * while_each_thread(). Besides, a forking task that has passed
	 * cgroup_post_fork() without seeing use_task_css_set_links = 1
	 * is not guaranteed to have its child immediately visible in the
	 * tasklist if we walk through it with RCU.
	 */
	read_lock(&tasklist_lock);
2983 2984
	do_each_thread(g, p) {
		task_lock(p);
2985 2986 2987 2988 2989 2990
		/*
		 * 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))
2991 2992 2993
			list_add(&p->cg_list, &p->cgroups->tasks);
		task_unlock(p);
	} while_each_thread(g, p);
2994
	read_unlock(&tasklist_lock);
2995 2996 2997
	write_unlock(&css_set_lock);
}

2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015
/**
 * cgroup_next_sibling - find the next sibling of a given cgroup
 * @pos: the current cgroup
 *
 * This function returns the next sibling of @pos and should be called
 * under RCU read lock.  The only requirement is that @pos is accessible.
 * The next sibling is guaranteed to be returned regardless of @pos's
 * state.
 */
struct cgroup *cgroup_next_sibling(struct cgroup *pos)
{
	struct cgroup *next;

	WARN_ON_ONCE(!rcu_read_lock_held());

	/*
	 * @pos could already have been removed.  Once a cgroup is removed,
	 * its ->sibling.next is no longer updated when its next sibling
3016 3017 3018 3019 3020 3021 3022
	 * changes.  As CGRP_DEAD assertion is serialized and happens
	 * before the cgroup is taken off the ->sibling list, if we see it
	 * unasserted, it's guaranteed that the next sibling hasn't
	 * finished its grace period even if it's already removed, and thus
	 * safe to dereference from this RCU critical section.  If
	 * ->sibling.next is inaccessible, cgroup_is_dead() is guaranteed
	 * to be visible as %true here.
3023
	 */
3024
	if (likely(!cgroup_is_dead(pos))) {
3025 3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047
		next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
		if (&next->sibling != &pos->parent->children)
			return next;
		return NULL;
	}

	/*
	 * Can't dereference the next pointer.  Each cgroup is given a
	 * monotonically increasing unique serial number and always
	 * appended to the sibling list, so the next one can be found by
	 * walking the parent's children until we see a cgroup with higher
	 * serial number than @pos's.
	 *
	 * While this path can be slow, it's taken only when either the
	 * current cgroup is removed or iteration and removal race.
	 */
	list_for_each_entry_rcu(next, &pos->parent->children, sibling)
		if (next->serial_nr > pos->serial_nr)
			return next;
	return NULL;
}
EXPORT_SYMBOL_GPL(cgroup_next_sibling);

3048 3049 3050 3051 3052 3053 3054
/**
 * cgroup_next_descendant_pre - find the next descendant for pre-order walk
 * @pos: the current position (%NULL to initiate traversal)
 * @cgroup: cgroup whose descendants to walk
 *
 * To be used by cgroup_for_each_descendant_pre().  Find the next
 * descendant to visit for pre-order traversal of @cgroup's descendants.
3055 3056 3057 3058 3059
 *
 * While this function requires RCU read locking, it doesn't require the
 * whole traversal to be contained in a single RCU critical section.  This
 * function will return the correct next descendant as long as both @pos
 * and @cgroup are accessible and @pos is a descendant of @cgroup.
3060 3061 3062 3063 3064 3065 3066 3067 3068
 */
struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
					  struct cgroup *cgroup)
{
	struct cgroup *next;

	WARN_ON_ONCE(!rcu_read_lock_held());

	/* if first iteration, pretend we just visited @cgroup */
3069
	if (!pos)
3070 3071 3072 3073 3074 3075 3076 3077
		pos = cgroup;

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

	/* no child, visit my or the closest ancestor's next sibling */
3078
	while (pos != cgroup) {
3079 3080
		next = cgroup_next_sibling(pos);
		if (next)
3081 3082
			return next;
		pos = pos->parent;
3083
	}
3084 3085 3086 3087 3088

	return NULL;
}
EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre);

3089 3090 3091 3092 3093 3094 3095
/**
 * cgroup_rightmost_descendant - return the rightmost descendant of a cgroup
 * @pos: cgroup of interest
 *
 * Return the rightmost descendant of @pos.  If there's no descendant,
 * @pos is returned.  This can be used during pre-order traversal to skip
 * subtree of @pos.
3096 3097 3098 3099 3100
 *
 * While this function requires RCU read locking, it doesn't require the
 * whole traversal to be contained in a single RCU critical section.  This
 * function will return the correct rightmost descendant as long as @pos is
 * accessible.
3101 3102 3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119
 */
struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos)
{
	struct cgroup *last, *tmp;

	WARN_ON_ONCE(!rcu_read_lock_held());

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

	return last;
}
EXPORT_SYMBOL_GPL(cgroup_rightmost_descendant);

3120 3121 3122 3123 3124 3125 3126 3127 3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139
static struct cgroup *cgroup_leftmost_descendant(struct cgroup *pos)
{
	struct cgroup *last;

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

	return last;
}

/**
 * cgroup_next_descendant_post - find the next descendant for post-order walk
 * @pos: the current position (%NULL to initiate traversal)
 * @cgroup: cgroup whose descendants to walk
 *
 * To be used by cgroup_for_each_descendant_post().  Find the next
 * descendant to visit for post-order traversal of @cgroup's descendants.
3140 3141 3142 3143 3144
 *
 * While this function requires RCU read locking, it doesn't require the
 * whole traversal to be contained in a single RCU critical section.  This
 * function will return the correct next descendant as long as both @pos
 * and @cgroup are accessible and @pos is a descendant of @cgroup.
3145 3146 3147 3148 3149 3150 3151 3152 3153 3154 3155 3156 3157 3158 3159
 */
struct cgroup *cgroup_next_descendant_post(struct cgroup *pos,
					   struct cgroup *cgroup)
{
	struct cgroup *next;

	WARN_ON_ONCE(!rcu_read_lock_held());

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

	/* if there's an unvisited sibling, visit its leftmost descendant */
3160 3161
	next = cgroup_next_sibling(pos);
	if (next)
3162 3163 3164 3165 3166 3167 3168 3169
		return cgroup_leftmost_descendant(next);

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

3170
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
3171
	__acquires(css_set_lock)
3172 3173 3174 3175 3176 3177
{
	/*
	 * 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.
	 */
3178 3179 3180
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();

3181
	read_lock(&css_set_lock);
3182
	it->cset_link = &cgrp->cset_links;
3183
	cgroup_advance_iter(cgrp, it);
3184 3185
}

3186
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
3187 3188 3189 3190
					struct cgroup_iter *it)
{
	struct task_struct *res;
	struct list_head *l = it->task;
3191
	struct cgrp_cset_link *link;
3192 3193

	/* If the iterator cg is NULL, we have no tasks */
3194
	if (!it->cset_link)
3195 3196 3197 3198
		return NULL;
	res = list_entry(l, struct task_struct, cg_list);
	/* Advance iterator to find next entry */
	l = l->next;
3199 3200
	link = list_entry(it->cset_link, struct cgrp_cset_link, cset_link);
	if (l == &link->cset->tasks) {
3201 3202
		/* We reached the end of this task list - move on to
		 * the next cg_cgroup_link */
3203
		cgroup_advance_iter(cgrp, it);
3204 3205 3206 3207 3208 3209
	} else {
		it->task = l;
	}
	return res;
}

3210
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
3211
	__releases(css_set_lock)
3212 3213 3214 3215
{
	read_unlock(&css_set_lock);
}

3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335 3336 3337 3338 3339 3340 3341 3342 3343 3344 3345 3346 3347 3348 3349 3350 3351 3352
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++) {
3353
			struct task_struct *q = heap->ptrs[i];
3354
			if (i == 0) {
3355 3356
				latest_time = q->start_time;
				latest_task = q;
3357 3358
			}
			/* Process the task per the caller's callback */
3359 3360
			scan->process_task(q, scan);
			put_task_struct(q);
3361 3362 3363 3364 3365 3366 3367 3368 3369 3370 3371 3372 3373 3374 3375
		}
		/*
		 * 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;
}

3376 3377 3378 3379 3380
static void cgroup_transfer_one_task(struct task_struct *task,
				     struct cgroup_scanner *scan)
{
	struct cgroup *new_cgroup = scan->data;

T
Tejun Heo 已提交
3381
	mutex_lock(&cgroup_mutex);
3382
	cgroup_attach_task(new_cgroup, task, false);
T
Tejun Heo 已提交
3383
	mutex_unlock(&cgroup_mutex);
3384 3385 3386 3387 3388 3389 3390 3391 3392 3393 3394 3395 3396 3397 3398 3399 3400 3401 3402 3403
}

/**
 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
 * @to: cgroup to which the tasks will be moved
 * @from: cgroup in which the tasks currently reside
 */
int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
{
	struct cgroup_scanner scan;

	scan.cg = from;
	scan.test_task = NULL; /* select all tasks in cgroup */
	scan.process_task = cgroup_transfer_one_task;
	scan.heap = NULL;
	scan.data = to;

	return cgroup_scan_tasks(&scan);
}

3404
/*
3405
 * Stuff for reading the 'tasks'/'procs' files.
3406 3407 3408 3409 3410 3411 3412 3413
 *
 * 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.
 *
 */

3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428 3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445
/* which pidlist file are we talking about? */
enum cgroup_filetype {
	CGROUP_FILE_PROCS,
	CGROUP_FILE_TASKS,
};

/*
 * A pidlist is a list of pids that virtually represents the contents of one
 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
 * a pair (one each for procs, tasks) for each pid namespace that's relevant
 * to the cgroup.
 */
struct cgroup_pidlist {
	/*
	 * used to find which pidlist is wanted. doesn't change as long as
	 * this particular list stays in the list.
	*/
	struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
	/* array of xids */
	pid_t *list;
	/* how many elements the above list has */
	int length;
	/* how many files are using the current array */
	int use_count;
	/* each of these stored in a list by its cgroup */
	struct list_head links;
	/* pointer to the cgroup we belong to, for list removal purposes */
	struct cgroup *owner;
	/* protects the other fields */
	struct rw_semaphore mutex;
};

3446 3447 3448 3449 3450 3451 3452 3453 3454 3455 3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466
/*
 * 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);
}

3467
/*
3468
 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3469
 * Returns the number of unique elements.
3470
 */
3471
static int pidlist_uniq(pid_t *list, int length)
3472
{
3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484 3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495 3496 3497 3498 3499 3500 3501
	int src, dest = 1;

	/*
	 * 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:
	return dest;
}

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

3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512
/*
 * 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 */
3513
	struct pid_namespace *ns = task_active_pid_ns(current);
3514

3515 3516 3517 3518 3519 3520 3521 3522 3523 3524 3525 3526 3527 3528 3529 3530
	/*
	 * We can't drop the pidlist_mutex before taking the l->mutex in case
	 * the last ref-holder is trying to remove l from the list at the same
	 * time. Holding the pidlist_mutex precludes somebody taking whichever
	 * list we find out from under us - compare release_pid_array().
	 */
	mutex_lock(&cgrp->pidlist_mutex);
	list_for_each_entry(l, &cgrp->pidlists, links) {
		if (l->key.type == type && l->key.ns == ns) {
			/* make sure l doesn't vanish out from under us */
			down_write(&l->mutex);
			mutex_unlock(&cgrp->pidlist_mutex);
			return l;
		}
	}
	/* entry not found; create a new one */
3531
	l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3532 3533 3534 3535 3536 3537 3538
	if (!l) {
		mutex_unlock(&cgrp->pidlist_mutex);
		return l;
	}
	init_rwsem(&l->mutex);
	down_write(&l->mutex);
	l->key.type = type;
3539
	l->key.ns = get_pid_ns(ns);
3540 3541 3542 3543 3544 3545
	l->owner = cgrp;
	list_add(&l->links, &cgrp->pidlists);
	mutex_unlock(&cgrp->pidlist_mutex);
	return l;
}

3546 3547 3548
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
3549 3550
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
3551 3552 3553 3554
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
3555 3556
	struct cgroup_iter it;
	struct task_struct *tsk;
3557 3558 3559 3560 3561 3562 3563 3564 3565
	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);
3566
	array = pidlist_allocate(length);
3567 3568 3569
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
3570 3571
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
3572
		if (unlikely(n == length))
3573
			break;
3574
		/* get tgid or pid for procs or tasks file respectively */
3575 3576 3577 3578
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
3579 3580
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
3581
	}
3582
	cgroup_iter_end(cgrp, &it);
3583 3584 3585
	length = n;
	/* now sort & (if procs) strip out duplicates */
	sort(array, length, sizeof(pid_t), cmppid, NULL);
3586
	if (type == CGROUP_FILE_PROCS)
3587
		length = pidlist_uniq(array, length);
3588 3589
	l = cgroup_pidlist_find(cgrp, type);
	if (!l) {
3590
		pidlist_free(array);
3591
		return -ENOMEM;
3592
	}
3593
	/* store array, freeing old if necessary - lock already held */
3594
	pidlist_free(l->list);
3595 3596 3597 3598
	l->list = array;
	l->length = length;
	l->use_count++;
	up_write(&l->mutex);
3599
	*lp = l;
3600
	return 0;
3601 3602
}

B
Balbir Singh 已提交
3603
/**
L
Li Zefan 已提交
3604
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
3605 3606 3607
 * @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
3608 3609 3610
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
3611 3612 3613 3614
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
	int ret = -EINVAL;
3615
	struct cgroup *cgrp;
B
Balbir Singh 已提交
3616 3617
	struct cgroup_iter it;
	struct task_struct *tsk;
3618

B
Balbir Singh 已提交
3619
	/*
3620 3621
	 * Validate dentry by checking the superblock operations,
	 * and make sure it's a directory.
B
Balbir Singh 已提交
3622
	 */
3623 3624
	if (dentry->d_sb->s_op != &cgroup_ops ||
	    !S_ISDIR(dentry->d_inode->i_mode))
B
Balbir Singh 已提交
3625 3626 3627
		 goto err;

	ret = 0;
3628
	cgrp = dentry->d_fsdata;
B
Balbir Singh 已提交
3629

3630 3631
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
B
Balbir Singh 已提交
3632 3633 3634 3635 3636 3637 3638 3639 3640 3641 3642 3643 3644 3645 3646 3647 3648 3649 3650
		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;
		}
	}
3651
	cgroup_iter_end(cgrp, &it);
B
Balbir Singh 已提交
3652 3653 3654 3655 3656

err:
	return ret;
}

3657

3658
/*
3659
 * seq_file methods for the tasks/procs files. The seq_file position is the
3660
 * next pid to display; the seq_file iterator is a pointer to the pid
3661
 * in the cgroup->l->list array.
3662
 */
3663

3664
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3665
{
3666 3667 3668 3669 3670 3671
	/*
	 * 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
	 */
3672
	struct cgroup_pidlist *l = s->private;
3673 3674 3675
	int index = 0, pid = *pos;
	int *iter;

3676
	down_read(&l->mutex);
3677
	if (pid) {
3678
		int end = l->length;
S
Stephen Rothwell 已提交
3679

3680 3681
		while (index < end) {
			int mid = (index + end) / 2;
3682
			if (l->list[mid] == pid) {
3683 3684
				index = mid;
				break;
3685
			} else if (l->list[mid] <= pid)
3686 3687 3688 3689 3690 3691
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
3692
	if (index >= l->length)
3693 3694
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
3695
	iter = l->list + index;
3696 3697 3698 3699
	*pos = *iter;
	return iter;
}

3700
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3701
{
3702 3703
	struct cgroup_pidlist *l = s->private;
	up_read(&l->mutex);
3704 3705
}

3706
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3707
{
3708 3709 3710
	struct cgroup_pidlist *l = s->private;
	pid_t *p = v;
	pid_t *end = l->list + l->length;
3711 3712 3713 3714 3715 3716 3717 3718 3719 3720 3721 3722 3723
	/*
	 * 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;
	}
}

3724
static int cgroup_pidlist_show(struct seq_file *s, void *v)
3725 3726 3727
{
	return seq_printf(s, "%d\n", *(int *)v);
}
3728

3729 3730 3731 3732 3733 3734 3735 3736 3737
/*
 * 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,
3738 3739
};

3740
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3741
{
3742 3743 3744 3745 3746 3747 3748
	/*
	 * 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);
3749 3750 3751
	down_write(&l->mutex);
	BUG_ON(!l->use_count);
	if (!--l->use_count) {
3752 3753 3754
		/* we're the last user if refcount is 0; remove and free */
		list_del(&l->links);
		mutex_unlock(&l->owner->pidlist_mutex);
3755
		pidlist_free(l->list);
3756 3757 3758 3759
		put_pid_ns(l->key.ns);
		up_write(&l->mutex);
		kfree(l);
		return;
3760
	}
3761
	mutex_unlock(&l->owner->pidlist_mutex);
3762
	up_write(&l->mutex);
3763 3764
}

3765
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3766
{
3767
	struct cgroup_pidlist *l;
3768 3769
	if (!(file->f_mode & FMODE_READ))
		return 0;
3770 3771 3772 3773 3774 3775
	/*
	 * 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);
3776 3777 3778
	return seq_release(inode, file);
}

3779
static const struct file_operations cgroup_pidlist_operations = {
3780 3781 3782
	.read = seq_read,
	.llseek = seq_lseek,
	.write = cgroup_file_write,
3783
	.release = cgroup_pidlist_release,
3784 3785
};

3786
/*
3787 3788 3789
 * 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.
3790
 */
3791
/* helper function for the two below it */
3792
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3793
{
3794
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3795
	struct cgroup_pidlist *l;
3796
	int retval;
3797

3798
	/* Nothing to do for write-only files */
3799 3800 3801
	if (!(file->f_mode & FMODE_READ))
		return 0;

3802
	/* have the array populated */
3803
	retval = pidlist_array_load(cgrp, type, &l);
3804 3805 3806 3807
	if (retval)
		return retval;
	/* configure file information */
	file->f_op = &cgroup_pidlist_operations;
3808

3809
	retval = seq_open(file, &cgroup_pidlist_seq_operations);
3810
	if (retval) {
3811
		cgroup_release_pid_array(l);
3812
		return retval;
3813
	}
3814
	((struct seq_file *)file->private_data)->private = l;
3815 3816
	return 0;
}
3817 3818
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
3819
	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3820 3821 3822
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
3823
	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3824
}
3825

3826
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3827 3828
					    struct cftype *cft)
{
3829
	return notify_on_release(cgrp);
3830 3831
}

3832 3833 3834 3835 3836 3837 3838 3839 3840 3841 3842 3843
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;
}

3844 3845 3846 3847 3848 3849 3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860
/*
 * When dput() is called asynchronously, if umount has been done and
 * then deactivate_super() in cgroup_free_fn() kills the superblock,
 * there's a small window that vfs will see the root dentry with non-zero
 * refcnt and trigger BUG().
 *
 * That's why we hold a reference before dput() and drop it right after.
 */
static void cgroup_dput(struct cgroup *cgrp)
{
	struct super_block *sb = cgrp->root->sb;

	atomic_inc(&sb->s_active);
	dput(cgrp->dentry);
	deactivate_super(sb);
}

3861 3862 3863 3864 3865 3866 3867 3868 3869 3870 3871
/*
 * Unregister event and free resources.
 *
 * Gets called from workqueue.
 */
static void cgroup_event_remove(struct work_struct *work)
{
	struct cgroup_event *event = container_of(work, struct cgroup_event,
			remove);
	struct cgroup *cgrp = event->cgrp;

3872 3873
	remove_wait_queue(event->wqh, &event->wait);

3874 3875
	event->cft->unregister_event(cgrp, event->cft, event->eventfd);

3876 3877 3878
	/* Notify userspace the event is going away. */
	eventfd_signal(event->eventfd, 1);

3879 3880
	eventfd_ctx_put(event->eventfd);
	kfree(event);
3881
	cgroup_dput(cgrp);
3882 3883 3884 3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898
}

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

	if (flags & POLLHUP) {
		/*
3899 3900 3901 3902 3903 3904 3905
		 * If the event has been detached at cgroup removal, we
		 * can simply return knowing the other side will cleanup
		 * for us.
		 *
		 * We can't race against event freeing since the other
		 * side will require wqh->lock via remove_wait_queue(),
		 * which we hold.
3906
		 */
3907 3908 3909 3910 3911 3912 3913 3914 3915 3916
		spin_lock(&cgrp->event_list_lock);
		if (!list_empty(&event->list)) {
			list_del_init(&event->list);
			/*
			 * We are in atomic context, but cgroup_event_remove()
			 * may sleep, so we have to call it in workqueue.
			 */
			schedule_work(&event->remove);
		}
		spin_unlock(&cgrp->event_list_lock);
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
	}

	return 0;
}

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

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

/*
 * Parse input and register new cgroup event handler.
 *
 * Input must be in format '<event_fd> <control_fd> <args>'.
 * Interpretation of args is defined by control file implementation.
 */
static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
				      const char *buffer)
{
	struct cgroup_event *event = NULL;
3942
	struct cgroup *cgrp_cfile;
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
	unsigned int efd, cfd;
	struct file *efile = NULL;
	struct file *cfile = NULL;
	char *endp;
	int ret;

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

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

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

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

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

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

	/* the process need read permission on control file */
A
Al Viro 已提交
3987
	/* AV: shouldn't we check that it's been opened for read instead? */
A
Al Viro 已提交
3988
	ret = inode_permission(file_inode(cfile), MAY_READ);
3989 3990 3991 3992 3993 3994 3995 3996 3997
	if (ret < 0)
		goto fail;

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

3998 3999 4000 4001 4002 4003 4004 4005 4006 4007
	/*
	 * The file to be monitored must be in the same cgroup as
	 * cgroup.event_control is.
	 */
	cgrp_cfile = __d_cgrp(cfile->f_dentry->d_parent);
	if (cgrp_cfile != cgrp) {
		ret = -EINVAL;
		goto fail;
	}

4008 4009 4010 4011 4012 4013 4014 4015 4016 4017
	if (!event->cft->register_event || !event->cft->unregister_event) {
		ret = -EINVAL;
		goto fail;
	}

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

4018
	efile->f_op->poll(efile, &event->pt);
4019

4020 4021 4022 4023 4024 4025 4026
	/*
	 * Events should be removed after rmdir of cgroup directory, but before
	 * destroying subsystem state objects. Let's take reference to cgroup
	 * directory dentry to do that.
	 */
	dget(cgrp->dentry);

4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050
	spin_lock(&cgrp->event_list_lock);
	list_add(&event->list, &cgrp->event_list);
	spin_unlock(&cgrp->event_list_lock);

	fput(cfile);
	fput(efile);

	return 0;

fail:
	if (cfile)
		fput(cfile);

	if (event && event->eventfd && !IS_ERR(event->eventfd))
		eventfd_ctx_put(event->eventfd);

	if (!IS_ERR_OR_NULL(efile))
		fput(efile);

	kfree(event);

	return ret;
}

4051 4052 4053
static u64 cgroup_clone_children_read(struct cgroup *cgrp,
				    struct cftype *cft)
{
4054
	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4055 4056 4057 4058 4059 4060 4061
}

static int cgroup_clone_children_write(struct cgroup *cgrp,
				     struct cftype *cft,
				     u64 val)
{
	if (val)
4062
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4063
	else
4064
		clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4065 4066 4067
	return 0;
}

4068
static struct cftype cgroup_base_files[] = {
4069
	{
4070
		.name = "cgroup.procs",
4071
		.open = cgroup_procs_open,
B
Ben Blum 已提交
4072
		.write_u64 = cgroup_procs_write,
4073
		.release = cgroup_pidlist_release,
B
Ben Blum 已提交
4074
		.mode = S_IRUGO | S_IWUSR,
4075
	},
4076
	{
4077
		.name = "cgroup.event_control",
4078 4079 4080
		.write_string = cgroup_write_event_control,
		.mode = S_IWUGO,
	},
4081 4082
	{
		.name = "cgroup.clone_children",
4083
		.flags = CFTYPE_INSANE,
4084 4085 4086
		.read_u64 = cgroup_clone_children_read,
		.write_u64 = cgroup_clone_children_write,
	},
4087 4088 4089 4090 4091
	{
		.name = "cgroup.sane_behavior",
		.flags = CFTYPE_ONLY_ON_ROOT,
		.read_seq_string = cgroup_sane_behavior_show,
	},
4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 4110 4111

	/*
	 * Historical crazy stuff.  These don't have "cgroup."  prefix and
	 * don't exist if sane_behavior.  If you're depending on these, be
	 * prepared to be burned.
	 */
	{
		.name = "tasks",
		.flags = CFTYPE_INSANE,		/* use "procs" instead */
		.open = cgroup_tasks_open,
		.write_u64 = cgroup_tasks_write,
		.release = cgroup_pidlist_release,
		.mode = S_IRUGO | S_IWUSR,
	},
	{
		.name = "notify_on_release",
		.flags = CFTYPE_INSANE,
		.read_u64 = cgroup_read_notify_on_release,
		.write_u64 = cgroup_write_notify_on_release,
	},
4112 4113
	{
		.name = "release_agent",
4114
		.flags = CFTYPE_INSANE | CFTYPE_ONLY_ON_ROOT,
4115 4116 4117 4118
		.read_seq_string = cgroup_release_agent_show,
		.write_string = cgroup_release_agent_write,
		.max_write_len = PATH_MAX,
	},
T
Tejun Heo 已提交
4119
	{ }	/* terminate */
4120 4121
};

4122 4123 4124 4125 4126 4127 4128 4129
/**
 * cgroup_populate_dir - selectively creation of files in a directory
 * @cgrp: target cgroup
 * @base_files: true if the base files should be added
 * @subsys_mask: mask of the subsystem ids whose files should be added
 */
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
			       unsigned long subsys_mask)
4130 4131 4132 4133
{
	int err;
	struct cgroup_subsys *ss;

4134
	if (base_files) {
4135
		err = cgroup_addrm_files(cgrp, NULL, cgroup_base_files, true);
4136 4137 4138
		if (err < 0)
			return err;
	}
4139

4140
	/* process cftsets of each subsystem */
4141
	for_each_subsys(cgrp->root, ss) {
4142
		struct cftype_set *set;
4143 4144
		if (!test_bit(ss->subsys_id, &subsys_mask))
			continue;
4145

T
Tejun Heo 已提交
4146
		list_for_each_entry(set, &ss->cftsets, node)
4147
			cgroup_addrm_files(cgrp, ss, set->cfts, true);
4148
	}
4149

K
KAMEZAWA Hiroyuki 已提交
4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160
	/* 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);
	}
4161 4162 4163 4164

	return 0;
}

4165 4166 4167 4168 4169
static void css_dput_fn(struct work_struct *work)
{
	struct cgroup_subsys_state *css =
		container_of(work, struct cgroup_subsys_state, dput_work);

4170
	cgroup_dput(css->cgroup);
4171 4172
}

4173 4174 4175 4176 4177 4178 4179 4180
static void css_release(struct percpu_ref *ref)
{
	struct cgroup_subsys_state *css =
		container_of(ref, struct cgroup_subsys_state, refcnt);

	schedule_work(&css->dput_work);
}

4181 4182
static void init_cgroup_css(struct cgroup_subsys_state *css,
			       struct cgroup_subsys *ss,
4183
			       struct cgroup *cgrp)
4184
{
4185
	css->cgroup = cgrp;
4186
	css->flags = 0;
K
KAMEZAWA Hiroyuki 已提交
4187
	css->id = NULL;
4188
	if (cgrp == dummytop)
4189
		css->flags |= CSS_ROOT;
4190 4191
	BUG_ON(cgrp->subsys[ss->subsys_id]);
	cgrp->subsys[ss->subsys_id] = css;
4192 4193

	/*
4194 4195 4196 4197
	 * css holds an extra ref to @cgrp->dentry which is put on the last
	 * css_put().  dput() requires process context, which css_put() may
	 * be called without.  @css->dput_work will be used to invoke
	 * dput() asynchronously from css_put().
4198 4199
	 */
	INIT_WORK(&css->dput_work, css_dput_fn);
4200 4201
}

T
Tejun Heo 已提交
4202 4203
/* invoke ->post_create() on a new CSS and mark it online if successful */
static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
4204
{
T
Tejun Heo 已提交
4205 4206
	int ret = 0;

4207 4208
	lockdep_assert_held(&cgroup_mutex);

4209 4210
	if (ss->css_online)
		ret = ss->css_online(cgrp);
T
Tejun Heo 已提交
4211 4212 4213
	if (!ret)
		cgrp->subsys[ss->subsys_id]->flags |= CSS_ONLINE;
	return ret;
4214 4215 4216 4217 4218 4219 4220 4221 4222 4223 4224 4225 4226
}

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

	lockdep_assert_held(&cgroup_mutex);

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

4227
	if (ss->css_offline)
4228
		ss->css_offline(cgrp);
4229 4230 4231 4232

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

4233
/*
L
Li Zefan 已提交
4234 4235 4236 4237
 * 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
4238
 *
L
Li Zefan 已提交
4239
 * Must be called with the mutex on the parent inode held
4240 4241
 */
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
A
Al Viro 已提交
4242
			     umode_t mode)
4243
{
4244
	struct cgroup *cgrp;
4245
	struct cgroup_name *name;
4246 4247 4248 4249 4250
	struct cgroupfs_root *root = parent->root;
	int err = 0;
	struct cgroup_subsys *ss;
	struct super_block *sb = root->sb;

T
Tejun Heo 已提交
4251
	/* allocate the cgroup and its ID, 0 is reserved for the root */
4252 4253
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
4254 4255
		return -ENOMEM;

4256 4257 4258 4259 4260
	name = cgroup_alloc_name(dentry);
	if (!name)
		goto err_free_cgrp;
	rcu_assign_pointer(cgrp->name, name);

T
Tejun Heo 已提交
4261 4262
	cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);
	if (cgrp->id < 0)
4263
		goto err_free_name;
T
Tejun Heo 已提交
4264

4265 4266 4267 4268 4269 4270 4271 4272 4273
	/*
	 * Only live parents can have children.  Note that the liveliness
	 * check isn't strictly necessary because cgroup_mkdir() and
	 * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
	 * anyway so that locking is contained inside cgroup proper and we
	 * don't get nasty surprises if we ever grow another caller.
	 */
	if (!cgroup_lock_live_group(parent)) {
		err = -ENODEV;
T
Tejun Heo 已提交
4274
		goto err_free_id;
4275 4276
	}

4277 4278 4279 4280 4281 4282 4283
	/* 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);

4284
	init_cgroup_housekeeping(cgrp);
4285

4286 4287 4288
	dentry->d_fsdata = cgrp;
	cgrp->dentry = dentry;

4289 4290
	cgrp->parent = parent;
	cgrp->root = parent->root;
4291

4292 4293 4294
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

4295 4296
	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4297

4298
	for_each_subsys(root, ss) {
4299
		struct cgroup_subsys_state *css;
4300

4301
		css = ss->css_alloc(cgrp);
4302 4303
		if (IS_ERR(css)) {
			err = PTR_ERR(css);
4304
			goto err_free_all;
4305
		}
4306 4307 4308 4309 4310

		err = percpu_ref_init(&css->refcnt, css_release);
		if (err)
			goto err_free_all;

4311
		init_cgroup_css(css, ss, cgrp);
4312

4313 4314 4315
		if (ss->use_id) {
			err = alloc_css_id(ss, parent, cgrp);
			if (err)
4316
				goto err_free_all;
4317
		}
4318 4319
	}

4320 4321 4322 4323 4324
	/*
	 * Create directory.  cgroup_create_file() returns with the new
	 * directory locked on success so that it can be populated without
	 * dropping cgroup_mutex.
	 */
T
Tejun Heo 已提交
4325
	err = cgroup_create_file(dentry, S_IFDIR | mode, sb);
4326
	if (err < 0)
4327
		goto err_free_all;
4328
	lockdep_assert_held(&dentry->d_inode->i_mutex);
4329

4330
	cgrp->serial_nr = atomic64_inc_return(&cgroup_serial_nr_cursor);
4331

4332 4333 4334
	/* allocation complete, commit to creation */
	list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
	root->number_of_cgroups++;
T
Tejun Heo 已提交
4335

T
Tejun Heo 已提交
4336 4337
	/* each css holds a ref to the cgroup's dentry */
	for_each_subsys(root, ss)
4338
		dget(dentry);
4339

4340 4341 4342
	/* hold a ref to the parent's dentry */
	dget(parent->dentry);

T
Tejun Heo 已提交
4343 4344 4345 4346 4347
	/* creation succeeded, notify subsystems */
	for_each_subsys(root, ss) {
		err = online_css(ss, cgrp);
		if (err)
			goto err_destroy;
4348 4349 4350 4351 4352 4353 4354 4355 4356

		if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
		    parent->parent) {
			pr_warning("cgroup: %s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
				   current->comm, current->pid, ss->name);
			if (!strcmp(ss->name, "memory"))
				pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
			ss->warned_broken_hierarchy = true;
		}
4357 4358
	}

4359
	err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
4360 4361
	if (err)
		goto err_destroy;
4362 4363

	mutex_unlock(&cgroup_mutex);
4364
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
4365 4366 4367

	return 0;

4368
err_free_all:
4369
	for_each_subsys(root, ss) {
4370 4371 4372 4373
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];

		if (css) {
			percpu_ref_cancel_init(&css->refcnt);
4374
			ss->css_free(cgrp);
4375
		}
4376 4377 4378 4379
	}
	mutex_unlock(&cgroup_mutex);
	/* Release the reference count that we took on the superblock */
	deactivate_super(sb);
T
Tejun Heo 已提交
4380 4381
err_free_id:
	ida_simple_remove(&root->cgroup_ida, cgrp->id);
4382 4383
err_free_name:
	kfree(rcu_dereference_raw(cgrp->name));
4384
err_free_cgrp:
4385
	kfree(cgrp);
4386
	return err;
4387 4388 4389 4390 4391 4392

err_destroy:
	cgroup_destroy_locked(cgrp);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&dentry->d_inode->i_mutex);
	return err;
4393 4394
}

4395
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
4396 4397 4398 4399 4400 4401 4402
{
	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);
}

4403 4404 4405 4406 4407 4408 4409 4410 4411 4412 4413 4414 4415 4416 4417 4418 4419 4420 4421 4422 4423 4424 4425 4426 4427 4428 4429 4430 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444
static void cgroup_css_killed(struct cgroup *cgrp)
{
	if (!atomic_dec_and_test(&cgrp->css_kill_cnt))
		return;

	/* percpu ref's of all css's are killed, kick off the next step */
	INIT_WORK(&cgrp->destroy_work, cgroup_offline_fn);
	schedule_work(&cgrp->destroy_work);
}

static void css_ref_killed_fn(struct percpu_ref *ref)
{
	struct cgroup_subsys_state *css =
		container_of(ref, struct cgroup_subsys_state, refcnt);

	cgroup_css_killed(css->cgroup);
}

/**
 * cgroup_destroy_locked - the first stage of cgroup destruction
 * @cgrp: cgroup to be destroyed
 *
 * css's make use of percpu refcnts whose killing latency shouldn't be
 * exposed to userland and are RCU protected.  Also, cgroup core needs to
 * guarantee that css_tryget() won't succeed by the time ->css_offline() is
 * invoked.  To satisfy all the requirements, destruction is implemented in
 * the following two steps.
 *
 * s1. Verify @cgrp can be destroyed and mark it dying.  Remove all
 *     userland visible parts and start killing the percpu refcnts of
 *     css's.  Set up so that the next stage will be kicked off once all
 *     the percpu refcnts are confirmed to be killed.
 *
 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
 *     rest of destruction.  Once all cgroup references are gone, the
 *     cgroup is RCU-freed.
 *
 * This function implements s1.  After this step, @cgrp is gone as far as
 * the userland is concerned and a new cgroup with the same name may be
 * created.  As cgroup doesn't care about the names internally, this
 * doesn't cause any problem.
 */
4445 4446
static int cgroup_destroy_locked(struct cgroup *cgrp)
	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4447
{
4448
	struct dentry *d = cgrp->dentry;
4449
	struct cgroup_event *event, *tmp;
4450
	struct cgroup_subsys *ss;
4451
	bool empty;
4452

4453 4454 4455
	lockdep_assert_held(&d->d_inode->i_mutex);
	lockdep_assert_held(&cgroup_mutex);

4456
	/*
T
Tejun Heo 已提交
4457 4458
	 * css_set_lock synchronizes access to ->cset_links and prevents
	 * @cgrp from being removed while __put_css_set() is in progress.
4459 4460
	 */
	read_lock(&css_set_lock);
T
Tejun Heo 已提交
4461
	empty = list_empty(&cgrp->cset_links) && list_empty(&cgrp->children);
4462 4463
	read_unlock(&css_set_lock);
	if (!empty)
4464
		return -EBUSY;
L
Li Zefan 已提交
4465

4466
	/*
4467 4468 4469 4470 4471 4472 4473 4474 4475 4476 4477 4478 4479
	 * Block new css_tryget() by killing css refcnts.  cgroup core
	 * guarantees that, by the time ->css_offline() is invoked, no new
	 * css reference will be given out via css_tryget().  We can't
	 * simply call percpu_ref_kill() and proceed to offlining css's
	 * because percpu_ref_kill() doesn't guarantee that the ref is seen
	 * as killed on all CPUs on return.
	 *
	 * Use percpu_ref_kill_and_confirm() to get notifications as each
	 * css is confirmed to be seen as killed on all CPUs.  The
	 * notification callback keeps track of the number of css's to be
	 * killed and schedules cgroup_offline_fn() to perform the rest of
	 * destruction once the percpu refs of all css's are confirmed to
	 * be killed.
4480
	 */
4481
	atomic_set(&cgrp->css_kill_cnt, 1);
4482 4483
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4484

4485 4486 4487 4488 4489 4490 4491 4492
		/*
		 * Killing would put the base ref, but we need to keep it
		 * alive until after ->css_offline.
		 */
		percpu_ref_get(&css->refcnt);

		atomic_inc(&cgrp->css_kill_cnt);
		percpu_ref_kill_and_confirm(&css->refcnt, css_ref_killed_fn);
4493
	}
4494
	cgroup_css_killed(cgrp);
4495 4496 4497 4498 4499 4500 4501 4502

	/*
	 * Mark @cgrp dead.  This prevents further task migration and child
	 * creation by disabling cgroup_lock_live_group().  Note that
	 * CGRP_DEAD assertion is depended upon by cgroup_next_sibling() to
	 * resume iteration after dropping RCU read lock.  See
	 * cgroup_next_sibling() for details.
	 */
4503
	set_bit(CGRP_DEAD, &cgrp->flags);
4504

4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 4519 4520 4521 4522 4523 4524 4525 4526 4527 4528 4529
	/* CGRP_DEAD is set, remove from ->release_list for the last time */
	raw_spin_lock(&release_list_lock);
	if (!list_empty(&cgrp->release_list))
		list_del_init(&cgrp->release_list);
	raw_spin_unlock(&release_list_lock);

	/*
	 * Remove @cgrp directory.  The removal puts the base ref but we
	 * aren't quite done with @cgrp yet, so hold onto it.
	 */
	dget(d);
	cgroup_d_remove_dir(d);

	/*
	 * Unregister events and notify userspace.
	 * Notify userspace about cgroup removing only after rmdir of cgroup
	 * directory to avoid race between userspace and kernelspace.
	 */
	spin_lock(&cgrp->event_list_lock);
	list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
		list_del_init(&event->list);
		schedule_work(&event->remove);
	}
	spin_unlock(&cgrp->event_list_lock);

4530 4531 4532
	return 0;
};

4533 4534 4535 4536 4537 4538 4539 4540 4541 4542
/**
 * cgroup_offline_fn - the second step of cgroup destruction
 * @work: cgroup->destroy_free_work
 *
 * This function is invoked from a work item for a cgroup which is being
 * destroyed after the percpu refcnts of all css's are guaranteed to be
 * seen as killed on all CPUs, and performs the rest of destruction.  This
 * is the second step of destruction described in the comment above
 * cgroup_destroy_locked().
 */
4543 4544 4545 4546 4547 4548 4549 4550 4551
static void cgroup_offline_fn(struct work_struct *work)
{
	struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work);
	struct cgroup *parent = cgrp->parent;
	struct dentry *d = cgrp->dentry;
	struct cgroup_subsys *ss;

	mutex_lock(&cgroup_mutex);

4552 4553 4554 4555
	/*
	 * css_tryget() is guaranteed to fail now.  Tell subsystems to
	 * initate destruction.
	 */
4556
	for_each_subsys(cgrp->root, ss)
4557
		offline_css(ss, cgrp);
4558 4559

	/*
4560 4561 4562 4563 4564
	 * Put the css refs from cgroup_destroy_locked().  Each css holds
	 * an extra reference to the cgroup's dentry and cgroup removal
	 * proceeds regardless of css refs.  On the last put of each css,
	 * whenever that may be, the extra dentry ref is put so that dentry
	 * destruction happens only after all css's are released.
4565
	 */
T
Tejun Heo 已提交
4566 4567
	for_each_subsys(cgrp->root, ss)
		css_put(cgrp->subsys[ss->subsys_id]);
4568

4569
	/* delete this cgroup from parent->children */
4570
	list_del_rcu(&cgrp->sibling);
4571

4572 4573
	dput(d);

4574
	set_bit(CGRP_RELEASABLE, &parent->flags);
4575 4576
	check_for_release(parent);

4577
	mutex_unlock(&cgroup_mutex);
4578 4579
}

4580 4581 4582 4583 4584 4585 4586 4587 4588 4589 4590
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
	int ret;

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

	return ret;
}

4591 4592 4593 4594 4595 4596 4597 4598 4599 4600 4601 4602 4603 4604
static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
{
	INIT_LIST_HEAD(&ss->cftsets);

	/*
	 * base_cftset is embedded in subsys itself, no need to worry about
	 * deregistration.
	 */
	if (ss->base_cftypes) {
		ss->base_cftset.cfts = ss->base_cftypes;
		list_add_tail(&ss->base_cftset.node, &ss->cftsets);
	}
}

4605
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4606 4607
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
4608 4609

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4610

4611 4612
	mutex_lock(&cgroup_mutex);

4613 4614 4615
	/* init base cftset */
	cgroup_init_cftsets(ss);

4616
	/* Create the top cgroup state for this subsystem */
4617
	list_add(&ss->sibling, &rootnode.subsys_list);
4618
	ss->root = &rootnode;
4619
	css = ss->css_alloc(dummytop);
4620 4621 4622 4623
	/* We don't handle early failures gracefully */
	BUG_ON(IS_ERR(css));
	init_cgroup_css(css, ss, dummytop);

L
Li Zefan 已提交
4624
	/* Update the init_css_set to contain a subsys
4625
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
4626 4627
	 * newly registered, all tasks and hence the
	 * init_css_set is in the subsystem's top cgroup. */
4628
	init_css_set.subsys[ss->subsys_id] = css;
4629 4630 4631

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

L
Li Zefan 已提交
4632 4633 4634 4635 4636
	/* 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));

T
Tejun Heo 已提交
4637
	BUG_ON(online_css(ss, dummytop));
4638

4639 4640
	mutex_unlock(&cgroup_mutex);

4641 4642 4643 4644 4645 4646 4647 4648 4649 4650
	/* this function shouldn't be used with modular subsystems, since they
	 * need to register a subsys_id, among other things */
	BUG_ON(ss->module);
}

/**
 * cgroup_load_subsys: load and register a modular subsystem at runtime
 * @ss: the subsystem to load
 *
 * This function should be called in a modular subsystem's initcall. If the
T
Thomas Weber 已提交
4651
 * subsystem is built as a module, it will be assigned a new subsys_id and set
4652 4653 4654 4655 4656 4657
 * up for use. If the subsystem is built-in anyway, work is delegated to the
 * simpler cgroup_init_subsys.
 */
int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
{
	struct cgroup_subsys_state *css;
4658
	int i, ret;
4659
	struct hlist_node *tmp;
4660
	struct css_set *cset;
4661
	unsigned long key;
4662 4663 4664

	/* check name and function validity */
	if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
4665
	    ss->css_alloc == NULL || ss->css_free == NULL)
4666 4667 4668 4669 4670 4671 4672 4673 4674 4675 4676 4677 4678 4679 4680 4681
		return -EINVAL;

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

	/*
	 * an optionally modular subsystem is built-in: we want to do nothing,
	 * since cgroup_init_subsys will have already taken care of it.
	 */
	if (ss->module == NULL) {
4682
		/* a sanity check */
4683 4684 4685 4686
		BUG_ON(subsys[ss->subsys_id] != ss);
		return 0;
	}

4687 4688 4689
	/* init base cftset */
	cgroup_init_cftsets(ss);

4690
	mutex_lock(&cgroup_mutex);
4691
	subsys[ss->subsys_id] = ss;
4692 4693

	/*
4694 4695 4696
	 * no ss->css_alloc seems to need anything important in the ss
	 * struct, so this can happen first (i.e. before the rootnode
	 * attachment).
4697
	 */
4698
	css = ss->css_alloc(dummytop);
4699 4700
	if (IS_ERR(css)) {
		/* failure case - need to deassign the subsys[] slot. */
4701
		subsys[ss->subsys_id] = NULL;
4702 4703 4704 4705 4706 4707 4708 4709 4710 4711 4712
		mutex_unlock(&cgroup_mutex);
		return PTR_ERR(css);
	}

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

	/* our new subsystem will be attached to the dummy hierarchy. */
	init_cgroup_css(css, ss, dummytop);
	/* init_idr must be after init_cgroup_css because it sets css->id. */
	if (ss->use_id) {
4713 4714 4715
		ret = cgroup_init_idr(ss, css);
		if (ret)
			goto err_unload;
4716 4717 4718 4719 4720 4721 4722 4723 4724 4725 4726
	}

	/*
	 * Now we need to entangle the css into the existing css_sets. unlike
	 * in cgroup_init_subsys, there are now multiple css_sets, so each one
	 * will need a new pointer to it; done by iterating the css_set_table.
	 * furthermore, modifying the existing css_sets will corrupt the hash
	 * table state, so each changed css_set will need its hash recomputed.
	 * this is all done under the css_set_lock.
	 */
	write_lock(&css_set_lock);
4727
	hash_for_each_safe(css_set_table, i, tmp, cset, hlist) {
4728
		/* skip entries that we already rehashed */
4729
		if (cset->subsys[ss->subsys_id])
4730 4731
			continue;
		/* remove existing entry */
4732
		hash_del(&cset->hlist);
4733
		/* set new value */
4734
		cset->subsys[ss->subsys_id] = css;
4735
		/* recompute hash and restore entry */
4736 4737
		key = css_set_hash(cset->subsys);
		hash_add(css_set_table, &cset->hlist, key);
4738 4739 4740
	}
	write_unlock(&css_set_lock);

T
Tejun Heo 已提交
4741 4742 4743
	ret = online_css(ss, dummytop);
	if (ret)
		goto err_unload;
4744

4745 4746 4747
	/* success! */
	mutex_unlock(&cgroup_mutex);
	return 0;
4748 4749 4750 4751 4752 4753

err_unload:
	mutex_unlock(&cgroup_mutex);
	/* @ss can't be mounted here as try_module_get() would fail */
	cgroup_unload_subsys(ss);
	return ret;
4754
}
4755
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4756

B
Ben Blum 已提交
4757 4758 4759 4760 4761 4762 4763 4764 4765 4766
/**
 * cgroup_unload_subsys: unload a modular subsystem
 * @ss: the subsystem to unload
 *
 * This function should be called in a modular subsystem's exitcall. When this
 * function is invoked, the refcount on the subsystem's module will be 0, so
 * the subsystem will not be attached to any hierarchy.
 */
void cgroup_unload_subsys(struct cgroup_subsys *ss)
{
4767
	struct cgrp_cset_link *link;
B
Ben Blum 已提交
4768 4769 4770 4771 4772 4773 4774 4775 4776 4777 4778

	BUG_ON(ss->module == NULL);

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

	mutex_lock(&cgroup_mutex);
4779

4780
	offline_css(ss, dummytop);
4781

T
Tejun Heo 已提交
4782
	if (ss->use_id)
4783 4784
		idr_destroy(&ss->idr);

B
Ben Blum 已提交
4785 4786 4787 4788
	/* deassign the subsys_id */
	subsys[ss->subsys_id] = NULL;

	/* remove subsystem from rootnode's list of subsystems */
4789
	list_del_init(&ss->sibling);
B
Ben Blum 已提交
4790 4791 4792 4793 4794 4795

	/*
	 * disentangle the css from all css_sets attached to the dummytop. as
	 * in loading, we need to pay our respects to the hashtable gods.
	 */
	write_lock(&css_set_lock);
4796 4797
	list_for_each_entry(link, &dummytop->cset_links, cset_link) {
		struct css_set *cset = link->cset;
4798
		unsigned long key;
B
Ben Blum 已提交
4799

4800 4801 4802 4803
		hash_del(&cset->hlist);
		cset->subsys[ss->subsys_id] = NULL;
		key = css_set_hash(cset->subsys);
		hash_add(css_set_table, &cset->hlist, key);
B
Ben Blum 已提交
4804 4805 4806 4807
	}
	write_unlock(&css_set_lock);

	/*
4808 4809 4810 4811
	 * remove subsystem's css from the dummytop and free it - need to
	 * free before marking as null because ss->css_free needs the
	 * cgrp->subsys pointer to find their state. note that this also
	 * takes care of freeing the css_id.
B
Ben Blum 已提交
4812
	 */
4813
	ss->css_free(dummytop);
B
Ben Blum 已提交
4814 4815 4816 4817 4818 4819
	dummytop->subsys[ss->subsys_id] = NULL;

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

4820
/**
L
Li Zefan 已提交
4821 4822 4823 4824
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
4825 4826 4827 4828
 */
int __init cgroup_init_early(void)
{
	int i;
4829
	atomic_set(&init_css_set.refcount, 1);
4830
	INIT_LIST_HEAD(&init_css_set.cgrp_links);
4831
	INIT_LIST_HEAD(&init_css_set.tasks);
4832
	INIT_HLIST_NODE(&init_css_set.hlist);
4833
	css_set_count = 1;
4834
	init_cgroup_root(&rootnode);
4835 4836 4837
	root_count = 1;
	init_task.cgroups = &init_css_set;

4838 4839 4840 4841
	init_cgrp_cset_link.cset = &init_css_set;
	init_cgrp_cset_link.cgrp = dummytop;
	list_add(&init_cgrp_cset_link.cset_link, &rootnode.top_cgroup.cset_links);
	list_add(&init_cgrp_cset_link.cgrp_link, &init_css_set.cgrp_links);
4842

4843
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4844 4845
		struct cgroup_subsys *ss = subsys[i];

4846 4847 4848 4849
		/* at bootup time, we don't worry about modular subsystems */
		if (!ss || ss->module)
			continue;

4850 4851
		BUG_ON(!ss->name);
		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4852 4853
		BUG_ON(!ss->css_alloc);
		BUG_ON(!ss->css_free);
4854
		if (ss->subsys_id != i) {
D
Diego Calleja 已提交
4855
			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4856 4857 4858 4859 4860 4861 4862 4863 4864 4865 4866
			       ss->name, ss->subsys_id);
			BUG();
		}

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

/**
L
Li Zefan 已提交
4867 4868 4869 4870
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
4871 4872 4873 4874 4875
 */
int __init cgroup_init(void)
{
	int err;
	int i;
4876
	unsigned long key;
4877 4878 4879 4880

	err = bdi_init(&cgroup_backing_dev_info);
	if (err)
		return err;
4881

4882
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4883
		struct cgroup_subsys *ss = subsys[i];
4884 4885 4886 4887

		/* at bootup time, we don't worry about modular subsystems */
		if (!ss || ss->module)
			continue;
4888 4889
		if (!ss->early_init)
			cgroup_init_subsys(ss);
K
KAMEZAWA Hiroyuki 已提交
4890
		if (ss->use_id)
4891
			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4892 4893
	}

4894
	/* Add init_css_set to the hash table */
4895 4896
	key = css_set_hash(init_css_set.subsys);
	hash_add(css_set_table, &init_css_set.hlist, key);
4897 4898

	/* allocate id for the dummy hierarchy */
T
Tejun Heo 已提交
4899 4900 4901
	mutex_lock(&cgroup_mutex);
	mutex_lock(&cgroup_root_mutex);

4902
	BUG_ON(cgroup_init_root_id(&rootnode));
4903

T
Tejun Heo 已提交
4904 4905 4906
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);

4907 4908 4909 4910 4911 4912
	cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
	if (!cgroup_kobj) {
		err = -ENOMEM;
		goto out;
	}

4913
	err = register_filesystem(&cgroup_fs_type);
4914 4915
	if (err < 0) {
		kobject_put(cgroup_kobj);
4916
		goto out;
4917
	}
4918

L
Li Zefan 已提交
4919
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4920

4921
out:
4922 4923 4924
	if (err)
		bdi_destroy(&cgroup_backing_dev_info);

4925 4926
	return err;
}
4927

4928 4929 4930 4931 4932 4933
/*
 * 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,
4934
 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4935 4936 4937 4938 4939 4940
 *    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 */
4941
int proc_cgroup_show(struct seq_file *m, void *v)
4942 4943 4944 4945 4946 4947 4948 4949 4950 4951 4952 4953 4954 4955 4956 4957 4958 4959 4960 4961 4962 4963
{
	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);

4964
	for_each_active_root(root) {
4965
		struct cgroup_subsys *ss;
4966
		struct cgroup *cgrp;
4967 4968
		int count = 0;

4969
		seq_printf(m, "%d:", root->hierarchy_id);
4970 4971
		for_each_subsys(root, ss)
			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4972 4973 4974
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
4975
		seq_putc(m, ':');
4976
		cgrp = task_cgroup_from_root(tsk, root);
4977
		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4978 4979 4980 4981 4982 4983 4984 4985 4986 4987 4988 4989 4990 4991 4992 4993 4994 4995 4996 4997
		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;
}

/* Display information about each subsystem and each hierarchy */
static int proc_cgroupstats_show(struct seq_file *m, void *v)
{
	int i;

4998
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
B
Ben Blum 已提交
4999 5000 5001 5002 5003
	/*
	 * ideally we don't want subsystems moving around while we do this.
	 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
	 * subsys/hierarchy state.
	 */
5004 5005 5006
	mutex_lock(&cgroup_mutex);
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
B
Ben Blum 已提交
5007 5008
		if (ss == NULL)
			continue;
5009 5010
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
5011
			   ss->root->number_of_cgroups, !ss->disabled);
5012 5013 5014 5015 5016 5017 5018
	}
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
5019
	return single_open(file, proc_cgroupstats_show, NULL);
5020 5021
}

5022
static const struct file_operations proc_cgroupstats_operations = {
5023 5024 5025 5026 5027 5028
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

5029 5030
/**
 * cgroup_fork - attach newly forked task to its parents cgroup.
L
Li Zefan 已提交
5031
 * @child: pointer to task_struct of forking parent process.
5032 5033 5034 5035 5036
 *
 * 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
5037 5038 5039 5040
 * it was not made under the protection of RCU or cgroup_mutex, so
 * might no longer be a valid cgroup pointer.  cgroup_attach_task() might
 * have already changed current->cgroups, allowing the previously
 * referenced cgroup group to be removed and freed.
5041 5042 5043 5044 5045 5046
 *
 * 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)
{
5047
	task_lock(current);
5048 5049
	child->cgroups = current->cgroups;
	get_css_set(child->cgroups);
5050
	task_unlock(current);
5051
	INIT_LIST_HEAD(&child->cg_list);
5052 5053
}

5054
/**
L
Li Zefan 已提交
5055 5056 5057
 * cgroup_post_fork - called on a new task after adding it to the task list
 * @child: the task in question
 *
5058 5059 5060 5061 5062
 * Adds the task to the list running through its css_set if necessary and
 * call the subsystem fork() callbacks.  Has to be after the task is
 * visible on the task list in case we race with the first call to
 * cgroup_iter_start() - to guarantee that the new task ends up on its
 * list.
L
Li Zefan 已提交
5063
 */
5064 5065
void cgroup_post_fork(struct task_struct *child)
{
5066 5067
	int i;

5068 5069 5070 5071 5072 5073 5074 5075 5076 5077 5078
	/*
	 * use_task_css_set_links is set to 1 before we walk the tasklist
	 * under the tasklist_lock and we read it here after we added the child
	 * to the tasklist under the tasklist_lock as well. If the child wasn't
	 * yet in the tasklist when we walked through it from
	 * cgroup_enable_task_cg_lists(), then use_task_css_set_links value
	 * should be visible now due to the paired locking and barriers implied
	 * by LOCK/UNLOCK: it is written before the tasklist_lock unlock
	 * in cgroup_enable_task_cg_lists() and read here after the tasklist_lock
	 * lock on fork.
	 */
5079 5080
	if (use_task_css_set_links) {
		write_lock(&css_set_lock);
5081 5082
		task_lock(child);
		if (list_empty(&child->cg_list))
5083
			list_add(&child->cg_list, &child->cgroups->tasks);
5084
		task_unlock(child);
5085 5086
		write_unlock(&css_set_lock);
	}
5087 5088 5089 5090 5091 5092 5093

	/*
	 * Call ss->fork().  This must happen after @child is linked on
	 * css_set; otherwise, @child might change state between ->fork()
	 * and addition to css_set.
	 */
	if (need_forkexit_callback) {
5094 5095 5096 5097 5098 5099 5100 5101 5102
		/*
		 * fork/exit callbacks are supported only for builtin
		 * subsystems, and the builtin section of the subsys
		 * array is immutable, so we don't need to lock the
		 * subsys array here. On the other hand, modular section
		 * of the array can be freed at module unload, so we
		 * can't touch that.
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
5103 5104 5105 5106 5107 5108
			struct cgroup_subsys *ss = subsys[i];

			if (ss->fork)
				ss->fork(child);
		}
	}
5109
}
5110

5111 5112 5113
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
5114
 * @run_callback: run exit callbacks?
5115 5116 5117 5118 5119 5120 5121 5122 5123 5124 5125 5126 5127 5128 5129 5130 5131 5132 5133 5134 5135 5136 5137 5138 5139 5140 5141 5142
 *
 * 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,
5143 5144
 *    which wards off any cgroup_attach_task() attempts, or task is a failed
 *    fork, never visible to cgroup_attach_task.
5145 5146 5147
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
5148
	struct css_set *cset;
5149
	int i;
5150 5151 5152 5153 5154 5155 5156 5157 5158

	/*
	 * 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))
5159
			list_del_init(&tsk->cg_list);
5160 5161 5162
		write_unlock(&css_set_lock);
	}

5163 5164
	/* Reassign the task to the init_css_set. */
	task_lock(tsk);
5165
	cset = tsk->cgroups;
5166
	tsk->cgroups = &init_css_set;
5167 5168

	if (run_callbacks && need_forkexit_callback) {
5169 5170 5171 5172 5173
		/*
		 * fork/exit callbacks are supported only for builtin
		 * subsystems, see cgroup_post_fork() for details.
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
5174
			struct cgroup_subsys *ss = subsys[i];
5175

5176 5177
			if (ss->exit) {
				struct cgroup *old_cgrp =
5178
					rcu_dereference_raw(cset->subsys[i])->cgroup;
5179
				struct cgroup *cgrp = task_cgroup(tsk, i);
5180
				ss->exit(cgrp, old_cgrp, tsk);
5181 5182 5183
			}
		}
	}
5184
	task_unlock(tsk);
5185

5186
	put_css_set_taskexit(cset);
5187
}
5188

5189
static void check_for_release(struct cgroup *cgrp)
5190
{
5191
	if (cgroup_is_releasable(cgrp) &&
T
Tejun Heo 已提交
5192
	    list_empty(&cgrp->cset_links) && list_empty(&cgrp->children)) {
5193 5194
		/*
		 * Control Group is currently removeable. If it's not
5195
		 * already queued for a userspace notification, queue
5196 5197
		 * it now
		 */
5198
		int need_schedule_work = 0;
5199

5200
		raw_spin_lock(&release_list_lock);
5201
		if (!cgroup_is_dead(cgrp) &&
5202 5203
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
5204 5205
			need_schedule_work = 1;
		}
5206
		raw_spin_unlock(&release_list_lock);
5207 5208 5209 5210 5211 5212 5213 5214 5215 5216 5217 5218 5219 5220 5221 5222 5223 5224 5225 5226 5227 5228 5229 5230 5231 5232 5233 5234 5235 5236 5237 5238
		if (need_schedule_work)
			schedule_work(&release_agent_work);
	}
}

/*
 * 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);
5239
	raw_spin_lock(&release_list_lock);
5240 5241 5242
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
5243
		char *pathbuf = NULL, *agentbuf = NULL;
5244
		struct cgroup *cgrp = list_entry(release_list.next,
5245 5246
						    struct cgroup,
						    release_list);
5247
		list_del_init(&cgrp->release_list);
5248
		raw_spin_unlock(&release_list_lock);
5249
		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
5250 5251 5252 5253 5254 5255 5256
		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;
5257 5258

		i = 0;
5259 5260
		argv[i++] = agentbuf;
		argv[i++] = pathbuf;
5261 5262 5263 5264 5265 5266 5267 5268 5269 5270 5271 5272 5273 5274
		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);
5275 5276 5277
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
5278
		raw_spin_lock(&release_list_lock);
5279
	}
5280
	raw_spin_unlock(&release_list_lock);
5281 5282
	mutex_unlock(&cgroup_mutex);
}
5283 5284 5285 5286 5287 5288 5289 5290 5291

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

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;
5292
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
5293 5294
			struct cgroup_subsys *ss = subsys[i];

5295 5296 5297 5298 5299 5300 5301 5302
			/*
			 * cgroup_disable, being at boot time, can't
			 * know about module subsystems, so we don't
			 * worry about them.
			 */
			if (!ss || ss->module)
				continue;

5303 5304 5305 5306 5307 5308 5309 5310 5311 5312 5313
			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
5314 5315 5316 5317 5318

/*
 * Functons for CSS ID.
 */

5319
/* to get ID other than 0, this should be called when !cgroup_is_dead() */
K
KAMEZAWA Hiroyuki 已提交
5320 5321
unsigned short css_id(struct cgroup_subsys_state *css)
{
5322 5323 5324 5325 5326 5327 5328
	struct css_id *cssid;

	/*
	 * This css_id() can return correct value when somone has refcnt
	 * on this or this is under rcu_read_lock(). Once css->id is allocated,
	 * it's unchanged until freed.
	 */
5329
	cssid = rcu_dereference_raw(css->id);
K
KAMEZAWA Hiroyuki 已提交
5330 5331 5332 5333 5334

	if (cssid)
		return cssid->id;
	return 0;
}
B
Ben Blum 已提交
5335
EXPORT_SYMBOL_GPL(css_id);
K
KAMEZAWA Hiroyuki 已提交
5336

5337 5338 5339 5340 5341 5342
/**
 *  css_is_ancestor - test "root" css is an ancestor of "child"
 * @child: the css to be tested.
 * @root: the css supporsed to be an ancestor of the child.
 *
 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
5343
 * this function reads css->id, the caller must hold rcu_read_lock().
5344 5345 5346 5347 5348 5349
 * But, considering usual usage, the csses should be valid objects after test.
 * Assuming that the caller will do some action to the child if this returns
 * returns true, the caller must take "child";s reference count.
 * If "child" is valid object and this returns true, "root" is valid, too.
 */

K
KAMEZAWA Hiroyuki 已提交
5350
bool css_is_ancestor(struct cgroup_subsys_state *child,
5351
		    const struct cgroup_subsys_state *root)
K
KAMEZAWA Hiroyuki 已提交
5352
{
5353 5354
	struct css_id *child_id;
	struct css_id *root_id;
K
KAMEZAWA Hiroyuki 已提交
5355

5356
	child_id  = rcu_dereference(child->id);
5357 5358
	if (!child_id)
		return false;
5359
	root_id = rcu_dereference(root->id);
5360 5361 5362 5363 5364 5365 5366
	if (!root_id)
		return false;
	if (child_id->depth < root_id->depth)
		return false;
	if (child_id->stack[root_id->depth] != root_id->id)
		return false;
	return true;
K
KAMEZAWA Hiroyuki 已提交
5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379
}

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);
5380
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5381
	idr_remove(&ss->idr, id->id);
5382
	spin_unlock(&ss->id_lock);
5383
	kfree_rcu(id, rcu_head);
K
KAMEZAWA Hiroyuki 已提交
5384
}
B
Ben Blum 已提交
5385
EXPORT_SYMBOL_GPL(free_css_id);
K
KAMEZAWA Hiroyuki 已提交
5386 5387 5388 5389 5390 5391 5392 5393 5394

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

static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
{
	struct css_id *newid;
T
Tejun Heo 已提交
5395
	int ret, size;
K
KAMEZAWA Hiroyuki 已提交
5396 5397 5398 5399 5400 5401 5402

	BUG_ON(!ss->use_id);

	size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
	newid = kzalloc(size, GFP_KERNEL);
	if (!newid)
		return ERR_PTR(-ENOMEM);
T
Tejun Heo 已提交
5403 5404

	idr_preload(GFP_KERNEL);
5405
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5406
	/* Don't use 0. allocates an ID of 1-65535 */
T
Tejun Heo 已提交
5407
	ret = idr_alloc(&ss->idr, newid, 1, CSS_ID_MAX + 1, GFP_NOWAIT);
5408
	spin_unlock(&ss->id_lock);
T
Tejun Heo 已提交
5409
	idr_preload_end();
K
KAMEZAWA Hiroyuki 已提交
5410 5411

	/* Returns error when there are no free spaces for new ID.*/
T
Tejun Heo 已提交
5412
	if (ret < 0)
K
KAMEZAWA Hiroyuki 已提交
5413 5414
		goto err_out;

T
Tejun Heo 已提交
5415
	newid->id = ret;
K
KAMEZAWA Hiroyuki 已提交
5416 5417 5418 5419
	newid->depth = depth;
	return newid;
err_out:
	kfree(newid);
T
Tejun Heo 已提交
5420
	return ERR_PTR(ret);
K
KAMEZAWA Hiroyuki 已提交
5421 5422 5423

}

5424 5425
static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
					    struct cgroup_subsys_state *rootcss)
K
KAMEZAWA Hiroyuki 已提交
5426 5427 5428
{
	struct css_id *newid;

5429
	spin_lock_init(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5430 5431 5432 5433 5434 5435 5436 5437 5438 5439 5440 5441 5442 5443 5444 5445 5446
	idr_init(&ss->idr);

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

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

static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
			struct cgroup *child)
{
	int subsys_id, i, depth = 0;
	struct cgroup_subsys_state *parent_css, *child_css;
5447
	struct css_id *child_id, *parent_id;
K
KAMEZAWA Hiroyuki 已提交
5448 5449 5450 5451 5452

	subsys_id = ss->subsys_id;
	parent_css = parent->subsys[subsys_id];
	child_css = child->subsys[subsys_id];
	parent_id = parent_css->id;
5453
	depth = parent_id->depth + 1;
K
KAMEZAWA Hiroyuki 已提交
5454 5455 5456 5457 5458 5459 5460 5461 5462 5463 5464 5465 5466 5467 5468 5469 5470 5471 5472 5473 5474 5475 5476 5477 5478 5479 5480 5481 5482 5483 5484 5485 5486 5487 5488 5489 5490

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

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

	return 0;
}

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

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

	if (unlikely(!cssid))
		return NULL;

	return rcu_dereference(cssid->css);
}
B
Ben Blum 已提交
5491
EXPORT_SYMBOL_GPL(css_lookup);
K
KAMEZAWA Hiroyuki 已提交
5492

S
Stephane Eranian 已提交
5493 5494 5495 5496 5497 5498 5499 5500 5501
/*
 * get corresponding css from file open on cgroupfs directory
 */
struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
{
	struct cgroup *cgrp;
	struct inode *inode;
	struct cgroup_subsys_state *css;

A
Al Viro 已提交
5502
	inode = file_inode(f);
S
Stephane Eranian 已提交
5503 5504 5505 5506 5507 5508 5509 5510 5511 5512 5513 5514 5515
	/* check in cgroup filesystem dir */
	if (inode->i_op != &cgroup_dir_inode_operations)
		return ERR_PTR(-EBADF);

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

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

5516
#ifdef CONFIG_CGROUP_DEBUG
5517
static struct cgroup_subsys_state *debug_css_alloc(struct cgroup *cont)
5518 5519 5520 5521 5522 5523 5524 5525 5526
{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

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

	return css;
}

5527
static void debug_css_free(struct cgroup *cont)
5528 5529 5530 5531 5532 5533 5534 5535 5536 5537 5538 5539 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 5551 5552
{
	kfree(cont->subsys[debug_subsys_id]);
}

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;
}

5553 5554 5555 5556
static int current_css_set_cg_links_read(struct cgroup *cont,
					 struct cftype *cft,
					 struct seq_file *seq)
{
5557
	struct cgrp_cset_link *link;
5558
	struct css_set *cset;
5559 5560 5561

	read_lock(&css_set_lock);
	rcu_read_lock();
5562
	cset = rcu_dereference(current->cgroups);
5563
	list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
5564 5565 5566 5567 5568 5569 5570
		struct cgroup *c = link->cgrp;
		const char *name;

		if (c->dentry)
			name = c->dentry->d_name.name;
		else
			name = "?";
5571 5572
		seq_printf(seq, "Root %d group %s\n",
			   c->root->hierarchy_id, name);
5573 5574 5575 5576 5577 5578 5579 5580 5581 5582 5583
	}
	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)
{
5584
	struct cgrp_cset_link *link;
5585 5586

	read_lock(&css_set_lock);
5587 5588
	list_for_each_entry(link, &cont->cset_links, cset_link) {
		struct css_set *cset = link->cset;
5589 5590
		struct task_struct *task;
		int count = 0;
5591 5592
		seq_printf(seq, "css_set %p\n", cset);
		list_for_each_entry(task, &cset->tasks, cg_list) {
5593 5594 5595 5596 5597 5598 5599 5600 5601 5602 5603 5604 5605
			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;
}

5606 5607 5608 5609 5610 5611 5612 5613 5614 5615 5616 5617 5618 5619 5620 5621 5622 5623 5624 5625 5626
static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
{
	return test_bit(CGRP_RELEASABLE, &cgrp->flags);
}

static struct cftype debug_files[] =  {
	{
		.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,
	},

5627 5628 5629 5630 5631 5632 5633 5634 5635 5636
	{
		.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,
	},

5637 5638 5639 5640 5641
	{
		.name = "releasable",
		.read_u64 = releasable_read,
	},

5642 5643
	{ }	/* terminate */
};
5644 5645 5646

struct cgroup_subsys debug_subsys = {
	.name = "debug",
5647 5648
	.css_alloc = debug_css_alloc,
	.css_free = debug_css_free,
5649
	.subsys_id = debug_subsys_id,
5650
	.base_cftypes = debug_files,
5651 5652
};
#endif /* CONFIG_CGROUP_DEBUG */