cgroup.c 129.8 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>
#include <linux/slab.h>
#include <linux/spinlock.h>
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#include <linux/rwsem.h>
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#include <linux/string.h>
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#include <linux/sort.h>
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#include <linux/kmod.h>
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#include <linux/delayacct.h>
#include <linux/cgroupstats.h>
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#include <linux/hashtable.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/kthread.h>
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#include <linux/delay.h>
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#include <linux/atomic.h>
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/*
 * pidlists linger the following amount before being destroyed.  The goal
 * is avoiding frequent destruction in the middle of consecutive read calls
 * Expiring in the middle is a performance problem not a correctness one.
 * 1 sec should be enough.
 */
#define CGROUP_PIDLIST_DESTROY_DELAY	HZ

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#define CGROUP_FILE_NAME_MAX		(MAX_CGROUP_TYPE_NAMELEN +	\
					 MAX_CFTYPE_NAME + 2)

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/*
 * cgroup_tree_mutex nests above cgroup_mutex and protects cftypes, file
 * creation/removal and hierarchy changing operations including cgroup
 * creation, removal, css association and controller rebinding.  This outer
 * lock is needed mainly to resolve the circular dependency between kernfs
 * active ref and cgroup_mutex.  cgroup_tree_mutex nests above both.
 */
static DEFINE_MUTEX(cgroup_tree_mutex);

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/*
 * cgroup_mutex is the master lock.  Any modification to cgroup or its
 * hierarchy must be performed while holding it.
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 *
 * css_set_rwsem protects task->cgroups pointer, the list of css_set
 * objects, and the chain of tasks off each css_set.
 *
 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
 * cgroup.h can use them for lockdep annotations.
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 */
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#ifdef CONFIG_PROVE_RCU
DEFINE_MUTEX(cgroup_mutex);
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DECLARE_RWSEM(css_set_rwsem);
EXPORT_SYMBOL_GPL(cgroup_mutex);
EXPORT_SYMBOL_GPL(css_set_rwsem);
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#else
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static DEFINE_MUTEX(cgroup_mutex);
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static DECLARE_RWSEM(css_set_rwsem);
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#endif

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/*
 * Protects cgroup_subsys->release_agent_path.  Modifying it also requires
 * cgroup_mutex.  Reading requires either cgroup_mutex or this spinlock.
 */
static DEFINE_SPINLOCK(release_agent_path_lock);

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#define cgroup_assert_mutexes_or_rcu_locked()				\
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	rcu_lockdep_assert(rcu_read_lock_held() ||			\
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			   lockdep_is_held(&cgroup_tree_mutex) ||	\
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			   lockdep_is_held(&cgroup_mutex),		\
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			   "cgroup_[tree_]mutex or RCU read lock required");
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/*
 * cgroup destruction makes heavy use of work items and there can be a lot
 * of concurrent destructions.  Use a separate workqueue so that cgroup
 * destruction work items don't end up filling up max_active of system_wq
 * which may lead to deadlock.
 */
static struct workqueue_struct *cgroup_destroy_wq;

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/*
 * pidlist destructions need to be flushed on cgroup destruction.  Use a
 * separate workqueue as flush domain.
 */
static struct workqueue_struct *cgroup_pidlist_destroy_wq;

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/* generate an array of cgroup subsystem pointers */
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#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
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static struct cgroup_subsys *cgroup_subsys[] = {
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#include <linux/cgroup_subsys.h>
};
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#undef SUBSYS

/* array of cgroup subsystem names */
#define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
static const char *cgroup_subsys_name[] = {
#include <linux/cgroup_subsys.h>
};
#undef SUBSYS
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/*
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 * The default hierarchy, reserved for the subsystems that are otherwise
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 * unattached - it never has more than a single cgroup, and all tasks are
 * part of that cgroup.
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 */
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struct cgroup_root cgrp_dfl_root;

/*
 * The default hierarchy always exists but is hidden until mounted for the
 * first time.  This is for backward compatibility.
 */
static bool cgrp_dfl_root_visible;
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/* The list of hierarchy roots */

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static LIST_HEAD(cgroup_roots);
static int cgroup_root_count;
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/* hierarchy ID allocation and mapping, protected by cgroup_mutex */
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static DEFINE_IDR(cgroup_hierarchy_idr);
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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
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 * the ascending serial number order on the list.  Protected by
 * cgroup_mutex.
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 */
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static u64 cgroup_serial_nr_next = 1;
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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 struct cftype cgroup_base_files[];

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static void cgroup_put(struct cgroup *cgrp);
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static int rebind_subsystems(struct cgroup_root *dst_root,
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			     unsigned long ss_mask);
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static void cgroup_destroy_css_killed(struct cgroup *cgrp);
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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 cftype cfts[],
			      bool is_add);
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static void cgroup_pidlist_destroy_all(struct cgroup *cgrp);
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/**
 * cgroup_css - obtain a cgroup's css for the specified subsystem
 * @cgrp: the cgroup of interest
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 * @ss: the subsystem of interest (%NULL returns the dummy_css)
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 *
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 * Return @cgrp's css (cgroup_subsys_state) associated with @ss.  This
 * function must be called either under cgroup_mutex or rcu_read_lock() and
 * the caller is responsible for pinning the returned css if it wants to
 * keep accessing it outside the said locks.  This function may return
 * %NULL if @cgrp doesn't have @subsys_id enabled.
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 */
static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
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					      struct cgroup_subsys *ss)
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{
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	if (ss)
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		return rcu_dereference_check(cgrp->subsys[ss->id],
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					lockdep_is_held(&cgroup_tree_mutex) ||
					lockdep_is_held(&cgroup_mutex));
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	else
		return &cgrp->dummy_css;
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}
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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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struct cgroup_subsys_state *seq_css(struct seq_file *seq)
{
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	struct kernfs_open_file *of = seq->private;
	struct cgroup *cgrp = of->kn->parent->priv;
	struct cftype *cft = seq_cft(seq);

	/*
	 * This is open and unprotected implementation of cgroup_css().
	 * seq_css() is only called from a kernfs file operation which has
	 * an active reference on the file.  Because all the subsystem
	 * files are drained before a css is disassociated with a cgroup,
	 * the matching css from the cgroup's subsys table is guaranteed to
	 * be and stay valid until the enclosing operation is complete.
	 */
	if (cft->ss)
		return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
	else
		return &cgrp->dummy_css;
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}
EXPORT_SYMBOL_GPL(seq_css);

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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;
}
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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_css - iterate all css's of a cgroup
 * @css: the iteration cursor
 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
 * @cgrp: the target cgroup to iterate css's of
 *
 * Should be called under cgroup_mutex.
 */
#define for_each_css(css, ssid, cgrp)					\
	for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++)	\
		if (!((css) = rcu_dereference_check(			\
				(cgrp)->subsys[(ssid)],			\
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				lockdep_is_held(&cgroup_tree_mutex) ||	\
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				lockdep_is_held(&cgroup_mutex)))) { }	\
		else

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/**
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 * for_each_subsys - iterate all enabled cgroup subsystems
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 * @ss: the iteration cursor
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 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
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 */
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#define for_each_subsys(ss, ssid)					\
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	for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT &&		\
	     (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
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/* iterate across the hierarchies */
#define for_each_root(root)						\
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	list_for_each_entry((root), &cgroup_roots, root_list)
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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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};

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/*
 * The default css_set - used by init and its children prior to any
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 * 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.
 */
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static struct css_set init_css_set = {
	.refcount		= ATOMIC_INIT(1),
	.cgrp_links		= LIST_HEAD_INIT(init_css_set.cgrp_links),
	.tasks			= LIST_HEAD_INIT(init_css_set.tasks),
	.mg_tasks		= LIST_HEAD_INIT(init_css_set.mg_tasks),
	.mg_preload_node	= LIST_HEAD_INIT(init_css_set.mg_preload_node),
	.mg_node		= LIST_HEAD_INIT(init_css_set.mg_node),
};
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static int css_set_count	= 1;	/* 1 for init_css_set */
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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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{
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	unsigned long key = 0UL;
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	struct cgroup_subsys *ss;
	int i;
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	for_each_subsys(ss, 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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static void put_css_set_locked(struct css_set *cset, bool taskexit)
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{
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	struct cgrp_cset_link *link, *tmp_link;
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	lockdep_assert_held(&css_set_rwsem);

	if (!atomic_dec_and_test(&cset->refcount))
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		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_rwsem */
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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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	kfree_rcu(cset, rcu_head);
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}

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static void put_css_set(struct css_set *cset, bool taskexit)
{
	/*
	 * Ensure that the refcount doesn't hit zero while any readers
	 * can see it. Similar to atomic_dec_and_lock(), but for an
	 * rwlock
	 */
	if (atomic_add_unless(&cset->refcount, -1, 1))
		return;

	down_write(&css_set_rwsem);
	put_css_set_locked(cset, taskexit);
	up_write(&css_set_rwsem);
}

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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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/**
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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)
 *
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 * Returns true if "cset" matches "old_cset" except for the hierarchy
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 * 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 - init css array and find the matching css_set
 * @old_cset: the css_set that we're using before the cgroup transition
 * @cgrp: the cgroup that we're moving into
 * @template: out param for the new set of csses, should be clear on entry
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 */
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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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{
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	struct cgroup_root *root = cgrp->root;
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	struct cgroup_subsys *ss;
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	struct css_set *cset;
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	unsigned long key;
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	int i;
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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_each_subsys(ss, i) {
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		if (root->cgrp.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] = cgroup_css(cgrp, ss);
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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.
574
 */
575
static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
576
{
577
	struct cgrp_cset_link *link;
578
	int i;
579 580 581

	INIT_LIST_HEAD(tmp_links);

582
	for (i = 0; i < count; i++) {
583
		link = kzalloc(sizeof(*link), GFP_KERNEL);
584
		if (!link) {
585
			free_cgrp_cset_links(tmp_links);
586 587
			return -ENOMEM;
		}
588
		list_add(&link->cset_link, tmp_links);
589 590 591 592
	}
	return 0;
}

593 594
/**
 * link_css_set - a helper function to link a css_set to a cgroup
595
 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
596
 * @cset: the css_set to be linked
597 598
 * @cgrp: the destination cgroup
 */
599 600
static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
			 struct cgroup *cgrp)
601
{
602
	struct cgrp_cset_link *link;
603

604 605 606
	BUG_ON(list_empty(tmp_links));
	link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
	link->cset = cset;
607
	link->cgrp = cgrp;
608
	list_move(&link->cset_link, &cgrp->cset_links);
609 610 611 612
	/*
	 * Always add links to the tail of the list so that the list
	 * is sorted by order of hierarchy creation
	 */
613
	list_add_tail(&link->cgrp_link, &cset->cgrp_links);
614 615
}

616 617 618 619 620 621 622
/**
 * find_css_set - return a new css_set with one cgroup updated
 * @old_cset: the baseline css_set
 * @cgrp: the cgroup to be updated
 *
 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
 * substituted into the appropriate hierarchy.
623
 */
624 625
static struct css_set *find_css_set(struct css_set *old_cset,
				    struct cgroup *cgrp)
626
{
627
	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
628
	struct css_set *cset;
629 630
	struct list_head tmp_links;
	struct cgrp_cset_link *link;
631
	unsigned long key;
632

633 634
	lockdep_assert_held(&cgroup_mutex);

635 636
	/* First see if we already have a cgroup group that matches
	 * the desired set */
637
	down_read(&css_set_rwsem);
638 639 640
	cset = find_existing_css_set(old_cset, cgrp, template);
	if (cset)
		get_css_set(cset);
641
	up_read(&css_set_rwsem);
642

643 644
	if (cset)
		return cset;
645

646
	cset = kzalloc(sizeof(*cset), GFP_KERNEL);
647
	if (!cset)
648 649
		return NULL;

650
	/* Allocate all the cgrp_cset_link objects that we'll need */
651
	if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
652
		kfree(cset);
653 654 655
		return NULL;
	}

656
	atomic_set(&cset->refcount, 1);
657
	INIT_LIST_HEAD(&cset->cgrp_links);
658
	INIT_LIST_HEAD(&cset->tasks);
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659
	INIT_LIST_HEAD(&cset->mg_tasks);
660
	INIT_LIST_HEAD(&cset->mg_preload_node);
661
	INIT_LIST_HEAD(&cset->mg_node);
662
	INIT_HLIST_NODE(&cset->hlist);
663 664 665

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

668
	down_write(&css_set_rwsem);
669
	/* Add reference counts and links from the new css_set. */
670
	list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
671
		struct cgroup *c = link->cgrp;
672

673 674
		if (c->root == cgrp->root)
			c = cgrp;
675
		link_css_set(&tmp_links, cset, c);
676
	}
677

678
	BUG_ON(!list_empty(&tmp_links));
679 680

	css_set_count++;
681 682

	/* Add this cgroup group to the hash table */
683 684
	key = css_set_hash(cset->subsys);
	hash_add(css_set_table, &cset->hlist, key);
685

686
	up_write(&css_set_rwsem);
687

688
	return cset;
689 690
}

691
static struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
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692
{
693
	struct cgroup *root_cgrp = kf_root->kn->priv;
T
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695
	return root_cgrp->root;
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696 697
}

698
static int cgroup_init_root_id(struct cgroup_root *root)
699 700 701 702 703
{
	int id;

	lockdep_assert_held(&cgroup_mutex);

704
	id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
705 706 707 708 709 710 711
	if (id < 0)
		return id;

	root->hierarchy_id = id;
	return 0;
}

712
static void cgroup_exit_root_id(struct cgroup_root *root)
713 714 715 716 717 718 719 720 721
{
	lockdep_assert_held(&cgroup_mutex);

	if (root->hierarchy_id) {
		idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
		root->hierarchy_id = 0;
	}
}

722
static void cgroup_free_root(struct cgroup_root *root)
723 724 725 726 727 728 729 730 731 732
{
	if (root) {
		/* hierarhcy ID shoulid already have been released */
		WARN_ON_ONCE(root->hierarchy_id);

		idr_destroy(&root->cgroup_idr);
		kfree(root);
	}
}

733
static void cgroup_destroy_root(struct cgroup_root *root)
734
{
735
	struct cgroup *cgrp = &root->cgrp;
736 737
	struct cgrp_cset_link *link, *tmp_link;

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738 739
	mutex_lock(&cgroup_tree_mutex);
	mutex_lock(&cgroup_mutex);
740

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741
	BUG_ON(atomic_read(&root->nr_cgrps));
742 743 744
	BUG_ON(!list_empty(&cgrp->children));

	/* Rebind all subsystems back to the default hierarchy */
745
	rebind_subsystems(&cgrp_dfl_root, cgrp->subsys_mask);
746 747 748 749 750

	/*
	 * Release all the links from cset_links to this hierarchy's
	 * root cgroup
	 */
751
	down_write(&css_set_rwsem);
752 753 754 755 756 757

	list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
		list_del(&link->cset_link);
		list_del(&link->cgrp_link);
		kfree(link);
	}
758
	up_write(&css_set_rwsem);
759 760 761 762 763 764 765 766 767 768 769

	if (!list_empty(&root->root_list)) {
		list_del(&root->root_list);
		cgroup_root_count--;
	}

	cgroup_exit_root_id(root);

	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&cgroup_tree_mutex);

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	kernfs_destroy_root(root->kf_root);
771 772 773
	cgroup_free_root(root);
}

774 775
/* look up cgroup associated with given css_set on the specified hierarchy */
static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
776
					    struct cgroup_root *root)
777 778 779
{
	struct cgroup *res = NULL;

780 781 782
	lockdep_assert_held(&cgroup_mutex);
	lockdep_assert_held(&css_set_rwsem);

783
	if (cset == &init_css_set) {
784
		res = &root->cgrp;
785
	} else {
786 787 788
		struct cgrp_cset_link *link;

		list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
789
			struct cgroup *c = link->cgrp;
790

791 792 793 794 795 796
			if (c->root == root) {
				res = c;
				break;
			}
		}
	}
797

798 799 800 801
	BUG_ON(!res);
	return res;
}

802 803 804 805 806
/*
 * Return the cgroup for "task" from the given hierarchy. Must be
 * called with cgroup_mutex and css_set_rwsem held.
 */
static struct cgroup *task_cgroup_from_root(struct task_struct *task,
807
					    struct cgroup_root *root)
808 809 810 811 812 813 814 815 816
{
	/*
	 * 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.
	 */
	return cset_cgroup_from_root(task_css_set(task), root);
}

817 818 819 820 821 822
/*
 * 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
823
 * cgroup_attach_task() can increment it again.  Because a count of zero
824 825 826 827 828 829 830 831 832 833 834 835 836
 * 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
837 838
 * to the release agent with the name of the cgroup (path relative to
 * the root of cgroup file system) as the argument.
839 840 841 842
 *
 * 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
843
 * least one task in the system (init, pid == 1), therefore, root cgroup
844
 * always has either children cgroups and/or using tasks.  So we don't
845
 * need a special hack to ensure that root cgroup cannot be deleted.
846 847
 *
 * P.S.  One more locking exception.  RCU is used to guard the
848
 * update of a tasks cgroup pointer by cgroup_attach_task()
849 850
 */

851
static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask);
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852
static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
853
static const struct file_operations proc_cgroupstats_operations;
854

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855 856 857 858 859 860 861 862 863 864 865 866
static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
			      char *buf)
{
	if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
	    !(cgrp->root->flags & CGRP_ROOT_NOPREFIX))
		snprintf(buf, CGROUP_FILE_NAME_MAX, "%s.%s",
			 cft->ss->name, cft->name);
	else
		strncpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
	return buf;
}

867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892
/**
 * cgroup_file_mode - deduce file mode of a control file
 * @cft: the control file in question
 *
 * returns cft->mode if ->mode is not 0
 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
 * returns S_IRUGO if it has only a read handler
 * returns S_IWUSR if it has only a write hander
 */
static umode_t cgroup_file_mode(const struct cftype *cft)
{
	umode_t mode = 0;

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

	if (cft->read_u64 || cft->read_s64 || cft->seq_show)
		mode |= S_IRUGO;

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

	return mode;
}

893 894
static void cgroup_free_fn(struct work_struct *work)
{
895
	struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work);
896

897
	atomic_dec(&cgrp->root->nr_cgrps);
898
	cgroup_pidlist_destroy_all(cgrp);
899

T
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900 901 902 903 904 905 906 907 908 909 910
	if (cgrp->parent) {
		/*
		 * We get a ref to the parent, and put the ref when this
		 * cgroup is being freed, so it's guaranteed that the
		 * parent won't be destroyed before its children.
		 */
		cgroup_put(cgrp->parent);
		kernfs_put(cgrp->kn);
		kfree(cgrp);
	} else {
		/*
911
		 * This is root cgroup's refcnt reaching zero, which
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912 913 914 915
		 * indicates that the root should be released.
		 */
		cgroup_destroy_root(cgrp->root);
	}
916 917 918 919 920 921
}

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

922
	INIT_WORK(&cgrp->destroy_work, cgroup_free_fn);
923
	queue_work(cgroup_destroy_wq, &cgrp->destroy_work);
924 925
}

926 927
static void cgroup_get(struct cgroup *cgrp)
{
T
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928 929 930
	WARN_ON_ONCE(cgroup_is_dead(cgrp));
	WARN_ON_ONCE(atomic_read(&cgrp->refcnt) <= 0);
	atomic_inc(&cgrp->refcnt);
931 932
}

933 934
static void cgroup_put(struct cgroup *cgrp)
{
T
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935 936
	if (!atomic_dec_and_test(&cgrp->refcnt))
		return;
T
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937
	if (WARN_ON_ONCE(cgrp->parent && !cgroup_is_dead(cgrp)))
T
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938
		return;
939

T
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940 941 942 943 944 945 946 947 948 949
	/*
	 * XXX: cgrp->id is only used to look up css's.  As cgroup and
	 * css's lifetimes will be decoupled, it should be made
	 * per-subsystem and moved to css->id so that lookups are
	 * successful until the target css is released.
	 */
	mutex_lock(&cgroup_mutex);
	idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
	mutex_unlock(&cgroup_mutex);
	cgrp->id = -1;
950

T
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951
	call_rcu(&cgrp->rcu_head, cgroup_free_rcu);
952 953
}

954
static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
T
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955
{
T
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956
	char name[CGROUP_FILE_NAME_MAX];
T
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957

T
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958
	lockdep_assert_held(&cgroup_tree_mutex);
T
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959
	kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
T
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960 961
}

962
/**
963
 * cgroup_clear_dir - remove subsys files in a cgroup directory
964
 * @cgrp: target cgroup
965 966
 * @subsys_mask: mask of the subsystem ids whose files should be removed
 */
967
static void cgroup_clear_dir(struct cgroup *cgrp, unsigned long subsys_mask)
T
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968
{
969
	struct cgroup_subsys *ss;
970
	int i;
T
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971

972
	for_each_subsys(ss, i) {
T
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973
		struct cftype *cfts;
974 975

		if (!test_bit(i, &subsys_mask))
976
			continue;
T
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977 978
		list_for_each_entry(cfts, &ss->cfts, node)
			cgroup_addrm_files(cgrp, cfts, false);
979
	}
980 981
}

982
static int rebind_subsystems(struct cgroup_root *dst_root,
983
			     unsigned long ss_mask)
984
{
985
	struct cgroup_subsys *ss;
986
	int ssid, ret;
987

T
Tejun Heo 已提交
988 989
	lockdep_assert_held(&cgroup_tree_mutex);
	lockdep_assert_held(&cgroup_mutex);
B
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990

991 992 993 994 995
	for_each_subsys(ss, ssid) {
		if (!(ss_mask & (1 << ssid)))
			continue;

		/* if @ss is on the dummy_root, we can always move it */
996
		if (ss->root == &cgrp_dfl_root)
997 998 999
			continue;

		/* if @ss has non-root cgroups attached to it, can't move */
1000
		if (!list_empty(&ss->root->cgrp.children))
T
Tejun Heo 已提交
1001
			return -EBUSY;
1002

1003
		/* can't move between two non-dummy roots either */
1004
		if (dst_root != &cgrp_dfl_root)
1005 1006 1007
			return -EBUSY;
	}

T
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1008 1009 1010
	ret = cgroup_populate_dir(&dst_root->cgrp, ss_mask);
	if (ret) {
		if (dst_root != &cgrp_dfl_root)
1011
			return ret;
T
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1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023

		/*
		 * Rebinding back to the default root is not allowed to
		 * fail.  Using both default and non-default roots should
		 * be rare.  Moving subsystems back and forth even more so.
		 * Just warn about it and continue.
		 */
		if (cgrp_dfl_root_visible) {
			pr_warning("cgroup: failed to create files (%d) while rebinding 0x%lx to default root\n",
				   ret, ss_mask);
			pr_warning("cgroup: you may retry by moving them to a different hierarchy and unbinding\n");
		}
1024
	}
1025 1026 1027 1028 1029

	/*
	 * Nothing can fail from this point on.  Remove files for the
	 * removed subsystems and rebind each subsystem.
	 */
1030
	mutex_unlock(&cgroup_mutex);
1031
	for_each_subsys(ss, ssid)
T
Tejun Heo 已提交
1032
		if (ss_mask & (1 << ssid))
1033
			cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
1034
	mutex_lock(&cgroup_mutex);
1035

1036
	for_each_subsys(ss, ssid) {
1037
		struct cgroup_root *src_root;
1038
		struct cgroup_subsys_state *css;
1039

1040 1041
		if (!(ss_mask & (1 << ssid)))
			continue;
1042

1043
		src_root = ss->root;
1044
		css = cgroup_css(&src_root->cgrp, ss);
1045

1046
		WARN_ON(!css || cgroup_css(&dst_root->cgrp, ss));
1047

1048 1049
		RCU_INIT_POINTER(src_root->cgrp.subsys[ssid], NULL);
		rcu_assign_pointer(dst_root->cgrp.subsys[ssid], css);
1050
		ss->root = dst_root;
1051
		css->cgroup = &dst_root->cgrp;
1052

1053 1054
		src_root->cgrp.subsys_mask &= ~(1 << ssid);
		dst_root->cgrp.subsys_mask |= 1 << ssid;
1055

1056 1057
		if (ss->bind)
			ss->bind(css);
1058 1059
	}

T
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1060
	kernfs_activate(dst_root->cgrp.kn);
1061 1062 1063
	return 0;
}

T
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1064 1065
static int cgroup_show_options(struct seq_file *seq,
			       struct kernfs_root *kf_root)
1066
{
1067
	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1068
	struct cgroup_subsys *ss;
T
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1069
	int ssid;
1070

T
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1071
	for_each_subsys(ss, ssid)
1072
		if (root->cgrp.subsys_mask & (1 << ssid))
T
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1073
			seq_printf(seq, ",%s", ss->name);
1074 1075
	if (root->flags & CGRP_ROOT_SANE_BEHAVIOR)
		seq_puts(seq, ",sane_behavior");
1076
	if (root->flags & CGRP_ROOT_NOPREFIX)
1077
		seq_puts(seq, ",noprefix");
1078
	if (root->flags & CGRP_ROOT_XATTR)
A
Aristeu Rozanski 已提交
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		seq_puts(seq, ",xattr");
1080 1081

	spin_lock(&release_agent_path_lock);
1082 1083
	if (strlen(root->release_agent_path))
		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1084 1085
	spin_unlock(&release_agent_path_lock);

1086
	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags))
1087
		seq_puts(seq, ",clone_children");
1088 1089
	if (strlen(root->name))
		seq_printf(seq, ",name=%s", root->name);
1090 1091 1092 1093
	return 0;
}

struct cgroup_sb_opts {
1094
	unsigned long subsys_mask;
1095
	unsigned long flags;
1096
	char *release_agent;
1097
	bool cpuset_clone_children;
1098
	char *name;
1099 1100
	/* User explicitly requested empty subsystem */
	bool none;
1101 1102
};

B
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1103
/*
1104 1105 1106 1107
 * Convert a hierarchy specifier into a bitmask of subsystems and
 * flags. Call with cgroup_mutex held to protect the cgroup_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
1108
 */
B
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1109
static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1110
{
1111 1112
	char *token, *o = data;
	bool all_ss = false, one_ss = false;
1113
	unsigned long mask = (unsigned long)-1;
1114 1115
	struct cgroup_subsys *ss;
	int i;
1116

B
Ben Blum 已提交
1117 1118
	BUG_ON(!mutex_is_locked(&cgroup_mutex));

1119
#ifdef CONFIG_CPUSETS
1120
	mask = ~(1UL << cpuset_cgrp_id);
1121
#endif
1122

1123
	memset(opts, 0, sizeof(*opts));
1124 1125 1126 1127

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
1128
		if (!strcmp(token, "none")) {
1129 1130
			/* Explicitly have no subsystems */
			opts->none = true;
1131 1132 1133 1134 1135 1136 1137 1138 1139
			continue;
		}
		if (!strcmp(token, "all")) {
			/* Mutually exclusive option 'all' + subsystem name */
			if (one_ss)
				return -EINVAL;
			all_ss = true;
			continue;
		}
1140 1141 1142 1143
		if (!strcmp(token, "__DEVEL__sane_behavior")) {
			opts->flags |= CGRP_ROOT_SANE_BEHAVIOR;
			continue;
		}
1144
		if (!strcmp(token, "noprefix")) {
1145
			opts->flags |= CGRP_ROOT_NOPREFIX;
1146 1147 1148
			continue;
		}
		if (!strcmp(token, "clone_children")) {
1149
			opts->cpuset_clone_children = true;
1150 1151
			continue;
		}
A
Aristeu Rozanski 已提交
1152
		if (!strcmp(token, "xattr")) {
1153
			opts->flags |= CGRP_ROOT_XATTR;
A
Aristeu Rozanski 已提交
1154 1155
			continue;
		}
1156
		if (!strncmp(token, "release_agent=", 14)) {
1157 1158 1159
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1160
			opts->release_agent =
1161
				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1162 1163
			if (!opts->release_agent)
				return -ENOMEM;
1164 1165 1166
			continue;
		}
		if (!strncmp(token, "name=", 5)) {
1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183
			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,
1184
					      MAX_CGROUP_ROOT_NAMELEN - 1,
1185 1186 1187
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1188 1189 1190 1191

			continue;
		}

1192
		for_each_subsys(ss, i) {
1193 1194 1195 1196 1197 1198 1199 1200
			if (strcmp(token, ss->name))
				continue;
			if (ss->disabled)
				continue;

			/* Mutually exclusive option 'all' + subsystem name */
			if (all_ss)
				return -EINVAL;
1201
			set_bit(i, &opts->subsys_mask);
1202 1203 1204 1205 1206 1207 1208 1209
			one_ss = true;

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

1210 1211
	/* Consistency checks */

1212 1213 1214
	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");

1215 1216 1217 1218
		if ((opts->flags & (CGRP_ROOT_NOPREFIX | CGRP_ROOT_XATTR)) ||
		    opts->cpuset_clone_children || opts->release_agent ||
		    opts->name) {
			pr_err("cgroup: sane_behavior: noprefix, xattr, clone_children, release_agent and name are not allowed\n");
1219 1220
			return -EINVAL;
		}
T
Tejun Heo 已提交
1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237
	} else {
		/*
		 * If the 'all' option was specified select all the
		 * subsystems, otherwise if 'none', 'name=' and a subsystem
		 * name options were not specified, let's default to 'all'
		 */
		if (all_ss || (!one_ss && !opts->none && !opts->name))
			for_each_subsys(ss, i)
				if (!ss->disabled)
					set_bit(i, &opts->subsys_mask);

		/*
		 * We either have to specify by name or by subsystems. (So
		 * all empty hierarchies must have a name).
		 */
		if (!opts->subsys_mask && !opts->name)
			return -EINVAL;
1238 1239
	}

1240 1241 1242 1243 1244
	/*
	 * Option noprefix was introduced just for backward compatibility
	 * with the old cpuset, so we allow noprefix only if mounting just
	 * the cpuset subsystem.
	 */
1245
	if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
1246 1247
		return -EINVAL;

1248 1249

	/* Can't specify "none" and some subsystems */
1250
	if (opts->subsys_mask && opts->none)
1251 1252
		return -EINVAL;

1253 1254 1255
	return 0;
}

T
Tejun Heo 已提交
1256
static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
1257 1258
{
	int ret = 0;
1259
	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1260
	struct cgroup_sb_opts opts;
1261
	unsigned long added_mask, removed_mask;
1262

1263 1264 1265 1266 1267
	if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) {
		pr_err("cgroup: sane_behavior: remount is not allowed\n");
		return -EINVAL;
	}

T
Tejun Heo 已提交
1268
	mutex_lock(&cgroup_tree_mutex);
1269 1270 1271 1272 1273 1274 1275
	mutex_lock(&cgroup_mutex);

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

1276
	if (opts.subsys_mask != root->cgrp.subsys_mask || opts.release_agent)
1277 1278 1279
		pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
			   task_tgid_nr(current), current->comm);

1280 1281
	added_mask = opts.subsys_mask & ~root->cgrp.subsys_mask;
	removed_mask = root->cgrp.subsys_mask & ~opts.subsys_mask;
1282

B
Ben Blum 已提交
1283
	/* Don't allow flags or name to change at remount */
1284
	if (((opts.flags ^ root->flags) & CGRP_ROOT_OPTION_MASK) ||
B
Ben Blum 已提交
1285
	    (opts.name && strcmp(opts.name, root->name))) {
1286 1287 1288
		pr_err("cgroup: option or name mismatch, new: 0x%lx \"%s\", old: 0x%lx \"%s\"\n",
		       opts.flags & CGRP_ROOT_OPTION_MASK, opts.name ?: "",
		       root->flags & CGRP_ROOT_OPTION_MASK, root->name);
1289 1290 1291 1292
		ret = -EINVAL;
		goto out_unlock;
	}

1293
	/* remounting is not allowed for populated hierarchies */
1294
	if (!list_empty(&root->cgrp.children)) {
1295
		ret = -EBUSY;
1296
		goto out_unlock;
B
Ben Blum 已提交
1297
	}
1298

1299
	ret = rebind_subsystems(root, added_mask);
1300
	if (ret)
1301
		goto out_unlock;
1302

1303
	rebind_subsystems(&cgrp_dfl_root, removed_mask);
1304

1305 1306
	if (opts.release_agent) {
		spin_lock(&release_agent_path_lock);
1307
		strcpy(root->release_agent_path, opts.release_agent);
1308 1309
		spin_unlock(&release_agent_path_lock);
	}
1310
 out_unlock:
1311
	kfree(opts.release_agent);
1312
	kfree(opts.name);
1313
	mutex_unlock(&cgroup_mutex);
T
Tejun Heo 已提交
1314
	mutex_unlock(&cgroup_tree_mutex);
1315 1316 1317
	return ret;
}

1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329
/*
 * 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 mount.
 */
static bool use_task_css_set_links __read_mostly;

static void cgroup_enable_task_cg_lists(void)
{
	struct task_struct *p, *g;

1330
	down_write(&css_set_rwsem);
1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352

	if (use_task_css_set_links)
		goto out_unlock;

	use_task_css_set_links = true;

	/*
	 * 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);
	do_each_thread(g, p) {
		WARN_ON_ONCE(!list_empty(&p->cg_list) ||
			     task_css_set(p) != &init_css_set);

		/*
		 * 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.
1353 1354
		 * Do it while holding siglock so that we don't end up
		 * racing against cgroup_exit().
1355
		 */
1356
		spin_lock_irq(&p->sighand->siglock);
1357 1358 1359 1360 1361 1362
		if (!(p->flags & PF_EXITING)) {
			struct css_set *cset = task_css_set(p);

			list_add(&p->cg_list, &cset->tasks);
			get_css_set(cset);
		}
1363
		spin_unlock_irq(&p->sighand->siglock);
1364 1365 1366
	} while_each_thread(g, p);
	read_unlock(&tasklist_lock);
out_unlock:
1367
	up_write(&css_set_rwsem);
1368 1369
}

1370 1371
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
T
Tejun Heo 已提交
1372
	atomic_set(&cgrp->refcnt, 1);
1373 1374
	INIT_LIST_HEAD(&cgrp->sibling);
	INIT_LIST_HEAD(&cgrp->children);
1375
	INIT_LIST_HEAD(&cgrp->cset_links);
1376
	INIT_LIST_HEAD(&cgrp->release_list);
1377 1378
	INIT_LIST_HEAD(&cgrp->pidlists);
	mutex_init(&cgrp->pidlist_mutex);
T
Tejun Heo 已提交
1379
	cgrp->dummy_css.cgroup = cgrp;
1380
}
1381

1382
static void init_cgroup_root(struct cgroup_root *root,
1383
			     struct cgroup_sb_opts *opts)
1384
{
1385
	struct cgroup *cgrp = &root->cgrp;
1386

1387
	INIT_LIST_HEAD(&root->root_list);
1388
	atomic_set(&root->nr_cgrps, 1);
1389
	cgrp->root = root;
1390
	init_cgroup_housekeeping(cgrp);
1391
	idr_init(&root->cgroup_idr);
1392

1393 1394 1395 1396 1397
	root->flags = opts->flags;
	if (opts->release_agent)
		strcpy(root->release_agent_path, opts->release_agent);
	if (opts->name)
		strcpy(root->name, opts->name);
1398
	if (opts->cpuset_clone_children)
1399
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
1400 1401
}

1402
static int cgroup_setup_root(struct cgroup_root *root, unsigned long ss_mask)
1403 1404
{
	LIST_HEAD(tmp_links);
1405
	struct cgroup *root_cgrp = &root->cgrp;
1406 1407 1408 1409 1410 1411 1412 1413
	struct css_set *cset;
	int i, ret;

	lockdep_assert_held(&cgroup_tree_mutex);
	lockdep_assert_held(&cgroup_mutex);

	ret = idr_alloc(&root->cgroup_idr, root_cgrp, 0, 1, GFP_KERNEL);
	if (ret < 0)
T
Tejun Heo 已提交
1414
		goto out;
1415 1416 1417
	root_cgrp->id = ret;

	/*
1418
	 * We're accessing css_set_count without locking css_set_rwsem here,
1419 1420 1421 1422 1423 1424
	 * but that's OK - it can only be increased by someone holding
	 * cgroup_lock, and that's us. The worst that can happen is that we
	 * have some link structures left over
	 */
	ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
	if (ret)
T
Tejun Heo 已提交
1425
		goto out;
1426

1427
	ret = cgroup_init_root_id(root);
1428
	if (ret)
T
Tejun Heo 已提交
1429
		goto out;
1430

T
Tejun Heo 已提交
1431 1432 1433 1434 1435 1436 1437 1438
	root->kf_root = kernfs_create_root(&cgroup_kf_syscall_ops,
					   KERNFS_ROOT_CREATE_DEACTIVATED,
					   root_cgrp);
	if (IS_ERR(root->kf_root)) {
		ret = PTR_ERR(root->kf_root);
		goto exit_root_id;
	}
	root_cgrp->kn = root->kf_root->kn;
1439 1440 1441

	ret = cgroup_addrm_files(root_cgrp, cgroup_base_files, true);
	if (ret)
T
Tejun Heo 已提交
1442
		goto destroy_root;
1443

1444
	ret = rebind_subsystems(root, ss_mask);
1445
	if (ret)
T
Tejun Heo 已提交
1446
		goto destroy_root;
1447 1448 1449 1450 1451 1452 1453 1454 1455 1456

	/*
	 * There must be no failure case after here, since rebinding takes
	 * care of subsystems' refcounts, which are explicitly dropped in
	 * the failure exit path.
	 */
	list_add(&root->root_list, &cgroup_roots);
	cgroup_root_count++;

	/*
1457
	 * Link the root cgroup in this hierarchy into all the css_set
1458 1459
	 * objects.
	 */
1460
	down_write(&css_set_rwsem);
1461 1462
	hash_for_each(css_set_table, i, cset, hlist)
		link_css_set(&tmp_links, cset, root_cgrp);
1463
	up_write(&css_set_rwsem);
1464 1465

	BUG_ON(!list_empty(&root_cgrp->children));
1466
	BUG_ON(atomic_read(&root->nr_cgrps) != 1);
1467

T
Tejun Heo 已提交
1468
	kernfs_activate(root_cgrp->kn);
1469
	ret = 0;
T
Tejun Heo 已提交
1470
	goto out;
1471

T
Tejun Heo 已提交
1472 1473 1474 1475
destroy_root:
	kernfs_destroy_root(root->kf_root);
	root->kf_root = NULL;
exit_root_id:
1476
	cgroup_exit_root_id(root);
T
Tejun Heo 已提交
1477
out:
1478 1479 1480 1481
	free_cgrp_cset_links(&tmp_links);
	return ret;
}

A
Al Viro 已提交
1482
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1483
			 int flags, const char *unused_dev_name,
A
Al Viro 已提交
1484
			 void *data)
1485
{
1486
	struct cgroup_root *root;
1487
	struct cgroup_sb_opts opts;
T
Tejun Heo 已提交
1488
	struct dentry *dentry;
1489
	int ret;
1490 1491 1492 1493 1494 1495 1496

	/*
	 * The first time anyone tries to mount a cgroup, enable the list
	 * linking each css_set to its tasks and fix up all existing tasks.
	 */
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();
T
Tejun Heo 已提交
1497
retry:
1498
	mutex_lock(&cgroup_tree_mutex);
B
Ben Blum 已提交
1499
	mutex_lock(&cgroup_mutex);
1500 1501

	/* First find the desired set of subsystems */
1502
	ret = parse_cgroupfs_options(data, &opts);
1503
	if (ret)
1504
		goto out_unlock;
1505

T
Tejun Heo 已提交
1506
	/* look for a matching existing root */
T
Tejun Heo 已提交
1507 1508 1509 1510 1511 1512 1513 1514
	if (!opts.subsys_mask && !opts.none && !opts.name) {
		cgrp_dfl_root_visible = true;
		root = &cgrp_dfl_root;
		cgroup_get(&root->cgrp);
		ret = 0;
		goto out_unlock;
	}

1515
	for_each_root(root) {
T
Tejun Heo 已提交
1516
		bool name_match = false;
1517

1518
		if (root == &cgrp_dfl_root)
1519 1520
			continue;

T
Tejun Heo 已提交
1521 1522 1523 1524 1525 1526 1527 1528 1529 1530
		/*
		 * If we asked for a name then it must match.  Also, if
		 * name matches but sybsys_mask doesn't, we should fail.
		 * Remember whether name matched.
		 */
		if (opts.name) {
			if (strcmp(opts.name, root->name))
				continue;
			name_match = true;
		}
1531

1532
		/*
T
Tejun Heo 已提交
1533 1534
		 * If we asked for subsystems (or explicitly for no
		 * subsystems) then they must match.
1535
		 */
T
Tejun Heo 已提交
1536
		if ((opts.subsys_mask || opts.none) &&
1537
		    (opts.subsys_mask != root->cgrp.subsys_mask)) {
T
Tejun Heo 已提交
1538 1539 1540 1541 1542
			if (!name_match)
				continue;
			ret = -EBUSY;
			goto out_unlock;
		}
1543

1544
		if ((root->flags ^ opts.flags) & CGRP_ROOT_OPTION_MASK) {
1545 1546 1547
			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;
1548
				goto out_unlock;
1549 1550 1551
			} else {
				pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n");
			}
1552
		}
T
Tejun Heo 已提交
1553

T
Tejun Heo 已提交
1554
		/*
1555
		 * A root's lifetime is governed by its root cgroup.  Zero
T
Tejun Heo 已提交
1556 1557 1558 1559 1560
		 * ref indicate that the root is being destroyed.  Wait for
		 * destruction to complete so that the subsystems are free.
		 * We can use wait_queue for the wait but this path is
		 * super cold.  Let's just sleep for a bit and retry.
		 */
1561
		if (!atomic_inc_not_zero(&root->cgrp.refcnt)) {
T
Tejun Heo 已提交
1562 1563
			mutex_unlock(&cgroup_mutex);
			mutex_unlock(&cgroup_tree_mutex);
1564 1565
			kfree(opts.release_agent);
			kfree(opts.name);
T
Tejun Heo 已提交
1566 1567 1568 1569 1570
			msleep(10);
			goto retry;
		}

		ret = 0;
T
Tejun Heo 已提交
1571
		goto out_unlock;
1572 1573
	}

1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586
	/*
	 * No such thing, create a new one.  name= matching without subsys
	 * specification is allowed for already existing hierarchies but we
	 * can't create new one without subsys specification.
	 */
	if (!opts.subsys_mask && !opts.none) {
		ret = -EINVAL;
		goto out_unlock;
	}

	root = kzalloc(sizeof(*root), GFP_KERNEL);
	if (!root) {
		ret = -ENOMEM;
T
Tejun Heo 已提交
1587 1588 1589
		goto out_unlock;
	}

1590 1591
	init_cgroup_root(root, &opts);

T
Tejun Heo 已提交
1592
	ret = cgroup_setup_root(root, opts.subsys_mask);
T
Tejun Heo 已提交
1593 1594 1595
	if (ret)
		cgroup_free_root(root);

1596
out_unlock:
T
Tejun Heo 已提交
1597
	mutex_unlock(&cgroup_mutex);
T
Tejun Heo 已提交
1598
	mutex_unlock(&cgroup_tree_mutex);
1599

1600 1601
	kfree(opts.release_agent);
	kfree(opts.name);
1602

T
Tejun Heo 已提交
1603
	if (ret)
1604
		return ERR_PTR(ret);
T
Tejun Heo 已提交
1605 1606 1607

	dentry = kernfs_mount(fs_type, flags, root->kf_root);
	if (IS_ERR(dentry))
1608
		cgroup_put(&root->cgrp);
T
Tejun Heo 已提交
1609 1610 1611 1612 1613 1614
	return dentry;
}

static void cgroup_kill_sb(struct super_block *sb)
{
	struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
1615
	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
T
Tejun Heo 已提交
1616

1617
	cgroup_put(&root->cgrp);
T
Tejun Heo 已提交
1618
	kernfs_kill_sb(sb);
1619 1620 1621 1622
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
A
Al Viro 已提交
1623
	.mount = cgroup_mount,
1624 1625 1626
	.kill_sb = cgroup_kill_sb,
};

1627 1628
static struct kobject *cgroup_kobj;

1629
/**
1630
 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
1631 1632 1633 1634
 * @task: target task
 * @buf: the buffer to write the path into
 * @buflen: the length of the buffer
 *
1635 1636 1637 1638 1639
 * Determine @task's cgroup on the first (the one with the lowest non-zero
 * hierarchy_id) cgroup hierarchy and copy its path into @buf.  This
 * function grabs cgroup_mutex and shouldn't be used inside locks used by
 * cgroup controller callbacks.
 *
T
Tejun Heo 已提交
1640
 * Return value is the same as kernfs_path().
1641
 */
T
Tejun Heo 已提交
1642
char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
1643
{
1644
	struct cgroup_root *root;
1645
	struct cgroup *cgrp;
T
Tejun Heo 已提交
1646 1647
	int hierarchy_id = 1;
	char *path = NULL;
1648 1649

	mutex_lock(&cgroup_mutex);
1650
	down_read(&css_set_rwsem);
1651

1652 1653
	root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);

1654 1655
	if (root) {
		cgrp = task_cgroup_from_root(task, root);
T
Tejun Heo 已提交
1656
		path = cgroup_path(cgrp, buf, buflen);
1657 1658
	} else {
		/* if no hierarchy exists, everyone is in "/" */
T
Tejun Heo 已提交
1659 1660
		if (strlcpy(buf, "/", buflen) < buflen)
			path = buf;
1661 1662
	}

1663
	up_read(&css_set_rwsem);
1664
	mutex_unlock(&cgroup_mutex);
T
Tejun Heo 已提交
1665
	return path;
1666
}
1667
EXPORT_SYMBOL_GPL(task_cgroup_path);
1668

1669
/* used to track tasks and other necessary states during migration */
1670
struct cgroup_taskset {
1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688
	/* the src and dst cset list running through cset->mg_node */
	struct list_head	src_csets;
	struct list_head	dst_csets;

	/*
	 * Fields for cgroup_taskset_*() iteration.
	 *
	 * Before migration is committed, the target migration tasks are on
	 * ->mg_tasks of the csets on ->src_csets.  After, on ->mg_tasks of
	 * the csets on ->dst_csets.  ->csets point to either ->src_csets
	 * or ->dst_csets depending on whether migration is committed.
	 *
	 * ->cur_csets and ->cur_task point to the current task position
	 * during iteration.
	 */
	struct list_head	*csets;
	struct css_set		*cur_cset;
	struct task_struct	*cur_task;
1689 1690 1691 1692 1693 1694 1695 1696 1697 1698
};

/**
 * 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)
{
1699 1700 1701 1702
	tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
	tset->cur_task = NULL;

	return cgroup_taskset_next(tset);
1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713
}

/**
 * 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)
{
1714 1715
	struct css_set *cset = tset->cur_cset;
	struct task_struct *task = tset->cur_task;
1716

1717 1718 1719 1720 1721 1722
	while (&cset->mg_node != tset->csets) {
		if (!task)
			task = list_first_entry(&cset->mg_tasks,
						struct task_struct, cg_list);
		else
			task = list_next_entry(task, cg_list);
1723

1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734
		if (&task->cg_list != &cset->mg_tasks) {
			tset->cur_cset = cset;
			tset->cur_task = task;
			return task;
		}

		cset = list_next_entry(cset, mg_node);
		task = NULL;
	}

	return NULL;
1735 1736
}

1737
/**
B
Ben Blum 已提交
1738
 * cgroup_task_migrate - move a task from one cgroup to another.
1739 1740 1741
 * @old_cgrp; the cgroup @tsk is being migrated from
 * @tsk: the task being migrated
 * @new_cset: the new css_set @tsk is being attached to
B
Ben Blum 已提交
1742
 *
1743
 * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
B
Ben Blum 已提交
1744
 */
1745 1746 1747
static void cgroup_task_migrate(struct cgroup *old_cgrp,
				struct task_struct *tsk,
				struct css_set *new_cset)
B
Ben Blum 已提交
1748
{
1749
	struct css_set *old_cset;
B
Ben Blum 已提交
1750

1751 1752 1753
	lockdep_assert_held(&cgroup_mutex);
	lockdep_assert_held(&css_set_rwsem);

B
Ben Blum 已提交
1754
	/*
1755 1756 1757
	 * 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
1758
	 */
1759
	WARN_ON_ONCE(tsk->flags & PF_EXITING);
1760
	old_cset = task_css_set(tsk);
B
Ben Blum 已提交
1761

1762
	get_css_set(new_cset);
1763
	rcu_assign_pointer(tsk->cgroups, new_cset);
1764 1765 1766 1767 1768 1769 1770 1771

	/*
	 * Use move_tail so that cgroup_taskset_first() still returns the
	 * leader after migration.  This works because cgroup_migrate()
	 * ensures that the dst_cset of the leader is the first on the
	 * tset's dst_csets list.
	 */
	list_move_tail(&tsk->cg_list, &new_cset->mg_tasks);
B
Ben Blum 已提交
1772 1773

	/*
1774 1775 1776
	 * 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
1777
	 */
1778
	set_bit(CGRP_RELEASABLE, &old_cgrp->flags);
1779
	put_css_set_locked(old_cset, false);
B
Ben Blum 已提交
1780 1781
}

L
Li Zefan 已提交
1782
/**
1783 1784
 * cgroup_migrate_finish - cleanup after attach
 * @preloaded_csets: list of preloaded css_sets
B
Ben Blum 已提交
1785
 *
1786 1787
 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst().  See
 * those functions for details.
B
Ben Blum 已提交
1788
 */
1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913
static void cgroup_migrate_finish(struct list_head *preloaded_csets)
{
	struct css_set *cset, *tmp_cset;

	lockdep_assert_held(&cgroup_mutex);

	down_write(&css_set_rwsem);
	list_for_each_entry_safe(cset, tmp_cset, preloaded_csets, mg_preload_node) {
		cset->mg_src_cgrp = NULL;
		cset->mg_dst_cset = NULL;
		list_del_init(&cset->mg_preload_node);
		put_css_set_locked(cset, false);
	}
	up_write(&css_set_rwsem);
}

/**
 * cgroup_migrate_add_src - add a migration source css_set
 * @src_cset: the source css_set to add
 * @dst_cgrp: the destination cgroup
 * @preloaded_csets: list of preloaded css_sets
 *
 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp.  Pin
 * @src_cset and add it to @preloaded_csets, which should later be cleaned
 * up by cgroup_migrate_finish().
 *
 * This function may be called without holding threadgroup_lock even if the
 * target is a process.  Threads may be created and destroyed but as long
 * as cgroup_mutex is not dropped, no new css_set can be put into play and
 * the preloaded css_sets are guaranteed to cover all migrations.
 */
static void cgroup_migrate_add_src(struct css_set *src_cset,
				   struct cgroup *dst_cgrp,
				   struct list_head *preloaded_csets)
{
	struct cgroup *src_cgrp;

	lockdep_assert_held(&cgroup_mutex);
	lockdep_assert_held(&css_set_rwsem);

	src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);

	/* nothing to do if this cset already belongs to the cgroup */
	if (src_cgrp == dst_cgrp)
		return;

	if (!list_empty(&src_cset->mg_preload_node))
		return;

	WARN_ON(src_cset->mg_src_cgrp);
	WARN_ON(!list_empty(&src_cset->mg_tasks));
	WARN_ON(!list_empty(&src_cset->mg_node));

	src_cset->mg_src_cgrp = src_cgrp;
	get_css_set(src_cset);
	list_add(&src_cset->mg_preload_node, preloaded_csets);
}

/**
 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
 * @dst_cgrp: the destination cgroup
 * @preloaded_csets: list of preloaded source css_sets
 *
 * Tasks are about to be moved to @dst_cgrp and all the source css_sets
 * have been preloaded to @preloaded_csets.  This function looks up and
 * pins all destination css_sets, links each to its source, and put them on
 * @preloaded_csets.
 *
 * This function must be called after cgroup_migrate_add_src() has been
 * called on each migration source css_set.  After migration is performed
 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
 * @preloaded_csets.
 */
static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp,
				      struct list_head *preloaded_csets)
{
	LIST_HEAD(csets);
	struct css_set *src_cset;

	lockdep_assert_held(&cgroup_mutex);

	/* look up the dst cset for each src cset and link it to src */
	list_for_each_entry(src_cset, preloaded_csets, mg_preload_node) {
		struct css_set *dst_cset;

		dst_cset = find_css_set(src_cset, dst_cgrp);
		if (!dst_cset)
			goto err;

		WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
		src_cset->mg_dst_cset = dst_cset;

		if (list_empty(&dst_cset->mg_preload_node))
			list_add(&dst_cset->mg_preload_node, &csets);
		else
			put_css_set(dst_cset, false);
	}

	list_splice(&csets, preloaded_csets);
	return 0;
err:
	cgroup_migrate_finish(&csets);
	return -ENOMEM;
}

/**
 * cgroup_migrate - migrate a process or task to a cgroup
 * @cgrp: the destination cgroup
 * @leader: the leader of the process or the task to migrate
 * @threadgroup: whether @leader points to the whole process or a single task
 *
 * Migrate a process or task denoted by @leader to @cgrp.  If migrating a
 * process, the caller must be holding threadgroup_lock of @leader.  The
 * caller is also responsible for invoking cgroup_migrate_add_src() and
 * cgroup_migrate_prepare_dst() on the targets before invoking this
 * function and following up with cgroup_migrate_finish().
 *
 * As long as a controller's ->can_attach() doesn't fail, this function is
 * guaranteed to succeed.  This means that, excluding ->can_attach()
 * failure, when migrating multiple targets, the success or failure can be
 * decided for all targets by invoking group_migrate_prepare_dst() before
 * actually starting migrating.
 */
static int cgroup_migrate(struct cgroup *cgrp, struct task_struct *leader,
			  bool threadgroup)
B
Ben Blum 已提交
1914
{
1915 1916 1917 1918 1919
	struct cgroup_taskset tset = {
		.src_csets	= LIST_HEAD_INIT(tset.src_csets),
		.dst_csets	= LIST_HEAD_INIT(tset.dst_csets),
		.csets		= &tset.src_csets,
	};
T
Tejun Heo 已提交
1920
	struct cgroup_subsys_state *css, *failed_css = NULL;
1921 1922 1923
	struct css_set *cset, *tmp_cset;
	struct task_struct *task, *tmp_task;
	int i, ret;
B
Ben Blum 已提交
1924

1925 1926 1927 1928 1929
	/*
	 * 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.
	 */
1930
	down_write(&css_set_rwsem);
1931
	rcu_read_lock();
1932
	task = leader;
B
Ben Blum 已提交
1933
	do {
1934 1935
		/* @task either already exited or can't exit until the end */
		if (task->flags & PF_EXITING)
1936
			goto next;
1937

1938 1939 1940 1941
		/* leave @task alone if post_fork() hasn't linked it yet */
		if (list_empty(&task->cg_list))
			goto next;

1942
		cset = task_css_set(task);
1943
		if (!cset->mg_src_cgrp)
1944
			goto next;
1945

1946 1947 1948 1949 1950 1951 1952 1953 1954 1955
		/*
		 * cgroup_taskset_first() must always return the leader.
		 * Take care to avoid disturbing the ordering.
		 */
		list_move_tail(&task->cg_list, &cset->mg_tasks);
		if (list_empty(&cset->mg_node))
			list_add_tail(&cset->mg_node, &tset.src_csets);
		if (list_empty(&cset->mg_dst_cset->mg_node))
			list_move_tail(&cset->mg_dst_cset->mg_node,
				       &tset.dst_csets);
1956
	next:
1957 1958
		if (!threadgroup)
			break;
1959
	} while_each_thread(leader, task);
1960
	rcu_read_unlock();
1961
	up_write(&css_set_rwsem);
B
Ben Blum 已提交
1962

1963
	/* methods shouldn't be called if no task is actually migrating */
1964 1965
	if (list_empty(&tset.src_csets))
		return 0;
1966

1967
	/* check that we can legitimately attach to the cgroup */
T
Tejun Heo 已提交
1968 1969
	for_each_css(css, i, cgrp) {
		if (css->ss->can_attach) {
1970 1971
			ret = css->ss->can_attach(css, &tset);
			if (ret) {
T
Tejun Heo 已提交
1972
				failed_css = css;
B
Ben Blum 已提交
1973 1974 1975 1976 1977 1978
				goto out_cancel_attach;
			}
		}
	}

	/*
1979 1980 1981
	 * Now that we're guaranteed success, 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
1982
	 */
1983
	down_write(&css_set_rwsem);
1984 1985 1986 1987
	list_for_each_entry(cset, &tset.src_csets, mg_node) {
		list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list)
			cgroup_task_migrate(cset->mg_src_cgrp, task,
					    cset->mg_dst_cset);
B
Ben Blum 已提交
1988
	}
1989
	up_write(&css_set_rwsem);
1990

B
Ben Blum 已提交
1991
	/*
1992 1993 1994
	 * Migration is committed, all target tasks are now on dst_csets.
	 * Nothing is sensitive to fork() after this point.  Notify
	 * controllers that migration is complete.
B
Ben Blum 已提交
1995
	 */
1996 1997
	tset.csets = &tset.dst_csets;

T
Tejun Heo 已提交
1998 1999 2000
	for_each_css(css, i, cgrp)
		if (css->ss->attach)
			css->ss->attach(css, &tset);
B
Ben Blum 已提交
2001

2002
	ret = 0;
2003 2004
	goto out_release_tset;

B
Ben Blum 已提交
2005
out_cancel_attach:
2006 2007 2008 2009 2010
	for_each_css(css, i, cgrp) {
		if (css == failed_css)
			break;
		if (css->ss->cancel_attach)
			css->ss->cancel_attach(css, &tset);
B
Ben Blum 已提交
2011
	}
2012 2013 2014 2015
out_release_tset:
	down_write(&css_set_rwsem);
	list_splice_init(&tset.dst_csets, &tset.src_csets);
	list_for_each_entry_safe(cset, tmp_cset, &tset.src_csets, mg_node) {
2016
		list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
2017 2018 2019
		list_del_init(&cset->mg_node);
	}
	up_write(&css_set_rwsem);
2020
	return ret;
B
Ben Blum 已提交
2021 2022
}

2023 2024 2025 2026 2027 2028
/**
 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
 * @dst_cgrp: the cgroup to attach to
 * @leader: the task or the leader of the threadgroup to be attached
 * @threadgroup: attach the whole threadgroup?
 *
2029
 * Call holding cgroup_mutex and threadgroup_lock of @leader.
2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059
 */
static int cgroup_attach_task(struct cgroup *dst_cgrp,
			      struct task_struct *leader, bool threadgroup)
{
	LIST_HEAD(preloaded_csets);
	struct task_struct *task;
	int ret;

	/* look up all src csets */
	down_read(&css_set_rwsem);
	rcu_read_lock();
	task = leader;
	do {
		cgroup_migrate_add_src(task_css_set(task), dst_cgrp,
				       &preloaded_csets);
		if (!threadgroup)
			break;
	} while_each_thread(leader, task);
	rcu_read_unlock();
	up_read(&css_set_rwsem);

	/* prepare dst csets and commit */
	ret = cgroup_migrate_prepare_dst(dst_cgrp, &preloaded_csets);
	if (!ret)
		ret = cgroup_migrate(dst_cgrp, leader, threadgroup);

	cgroup_migrate_finish(&preloaded_csets);
	return ret;
}

B
Ben Blum 已提交
2060 2061
/*
 * Find the task_struct of the task to attach by vpid and pass it along to the
2062
 * function to attach either it or all tasks in its threadgroup. Will lock
2063
 * cgroup_mutex and threadgroup.
2064
 */
B
Ben Blum 已提交
2065
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2066 2067
{
	struct task_struct *tsk;
2068
	const struct cred *cred = current_cred(), *tcred;
2069 2070
	int ret;

B
Ben Blum 已提交
2071 2072 2073
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;

2074 2075
retry_find_task:
	rcu_read_lock();
2076
	if (pid) {
2077
		tsk = find_task_by_vpid(pid);
B
Ben Blum 已提交
2078 2079
		if (!tsk) {
			rcu_read_unlock();
S
SeongJae Park 已提交
2080
			ret = -ESRCH;
2081
			goto out_unlock_cgroup;
2082
		}
B
Ben Blum 已提交
2083 2084 2085 2086
		/*
		 * even if we're attaching all tasks in the thread group, we
		 * only need to check permissions on one of them.
		 */
2087
		tcred = __task_cred(tsk);
2088 2089 2090
		if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
		    !uid_eq(cred->euid, tcred->uid) &&
		    !uid_eq(cred->euid, tcred->suid)) {
2091
			rcu_read_unlock();
2092 2093
			ret = -EACCES;
			goto out_unlock_cgroup;
2094
		}
2095 2096
	} else
		tsk = current;
2097 2098

	if (threadgroup)
2099
		tsk = tsk->group_leader;
2100 2101

	/*
2102
	 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2103 2104 2105
	 * trapped in a cpuset, or RT worker may be born in a cgroup
	 * with no rt_runtime allocated.  Just say no.
	 */
2106
	if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) {
2107 2108 2109 2110 2111
		ret = -EINVAL;
		rcu_read_unlock();
		goto out_unlock_cgroup;
	}

2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128
	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;
		}
2129 2130 2131 2132
	}

	ret = cgroup_attach_task(cgrp, tsk, threadgroup);

2133 2134
	threadgroup_unlock(tsk);

2135
	put_task_struct(tsk);
2136
out_unlock_cgroup:
T
Tejun Heo 已提交
2137
	mutex_unlock(&cgroup_mutex);
2138 2139 2140
	return ret;
}

2141 2142 2143 2144 2145 2146 2147
/**
 * 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)
{
2148
	struct cgroup_root *root;
2149 2150
	int retval = 0;

T
Tejun Heo 已提交
2151
	mutex_lock(&cgroup_mutex);
2152
	for_each_root(root) {
2153 2154
		struct cgroup *from_cgrp;

2155
		if (root == &cgrp_dfl_root)
2156 2157
			continue;

2158 2159 2160
		down_read(&css_set_rwsem);
		from_cgrp = task_cgroup_from_root(from, root);
		up_read(&css_set_rwsem);
2161

L
Li Zefan 已提交
2162
		retval = cgroup_attach_task(from_cgrp, tsk, false);
2163 2164 2165
		if (retval)
			break;
	}
T
Tejun Heo 已提交
2166
	mutex_unlock(&cgroup_mutex);
2167 2168 2169 2170 2171

	return retval;
}
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);

2172 2173
static int cgroup_tasks_write(struct cgroup_subsys_state *css,
			      struct cftype *cft, u64 pid)
B
Ben Blum 已提交
2174
{
2175
	return attach_task_by_pid(css->cgroup, pid, false);
B
Ben Blum 已提交
2176 2177
}

2178 2179
static int cgroup_procs_write(struct cgroup_subsys_state *css,
			      struct cftype *cft, u64 tgid)
2180
{
2181
	return attach_task_by_pid(css->cgroup, tgid, true);
2182 2183
}

2184
static int cgroup_release_agent_write(struct cgroup_subsys_state *css,
2185
				      struct cftype *cft, char *buffer)
2186
{
2187
	struct cgroup_root *root = css->cgroup->root;
2188 2189

	BUILD_BUG_ON(sizeof(root->release_agent_path) < PATH_MAX);
2190
	if (!cgroup_lock_live_group(css->cgroup))
2191
		return -ENODEV;
2192
	spin_lock(&release_agent_path_lock);
2193 2194
	strlcpy(root->release_agent_path, buffer,
		sizeof(root->release_agent_path));
2195
	spin_unlock(&release_agent_path_lock);
T
Tejun Heo 已提交
2196
	mutex_unlock(&cgroup_mutex);
2197 2198 2199
	return 0;
}

2200
static int cgroup_release_agent_show(struct seq_file *seq, void *v)
2201
{
2202
	struct cgroup *cgrp = seq_css(seq)->cgroup;
2203

2204 2205 2206 2207
	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
2208
	mutex_unlock(&cgroup_mutex);
2209 2210 2211
	return 0;
}

2212
static int cgroup_sane_behavior_show(struct seq_file *seq, void *v)
2213
{
2214 2215 2216
	struct cgroup *cgrp = seq_css(seq)->cgroup;

	seq_printf(seq, "%d\n", cgroup_sane_behavior(cgrp));
2217 2218 2219
	return 0;
}

T
Tejun Heo 已提交
2220 2221
static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
				 size_t nbytes, loff_t off)
2222
{
T
Tejun Heo 已提交
2223 2224 2225
	struct cgroup *cgrp = of->kn->parent->priv;
	struct cftype *cft = of->kn->priv;
	struct cgroup_subsys_state *css;
2226
	int ret;
2227

T
Tejun Heo 已提交
2228 2229 2230 2231 2232 2233 2234 2235 2236
	/*
	 * kernfs guarantees that a file isn't deleted with operations in
	 * flight, which means that the matching css is and stays alive and
	 * doesn't need to be pinned.  The RCU locking is not necessary
	 * either.  It's just for the convenience of using cgroup_css().
	 */
	rcu_read_lock();
	css = cgroup_css(cgrp, cft->ss);
	rcu_read_unlock();
2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251

	if (cft->write_string) {
		ret = cft->write_string(css, cft, strstrip(buf));
	} else if (cft->write_u64) {
		unsigned long long v;
		ret = kstrtoull(buf, 0, &v);
		if (!ret)
			ret = cft->write_u64(css, cft, v);
	} else if (cft->write_s64) {
		long long v;
		ret = kstrtoll(buf, 0, &v);
		if (!ret)
			ret = cft->write_s64(css, cft, v);
	} else if (cft->trigger) {
		ret = cft->trigger(css, (unsigned int)cft->private);
2252
	} else {
2253
		ret = -EINVAL;
2254
	}
T
Tejun Heo 已提交
2255

2256
	return ret ?: nbytes;
2257 2258
}

2259
static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
2260
{
T
Tejun Heo 已提交
2261
	return seq_cft(seq)->seq_start(seq, ppos);
2262 2263
}

2264
static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
2265
{
T
Tejun Heo 已提交
2266
	return seq_cft(seq)->seq_next(seq, v, ppos);
2267 2268
}

2269
static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
2270
{
T
Tejun Heo 已提交
2271
	seq_cft(seq)->seq_stop(seq, v);
2272 2273
}

2274
static int cgroup_seqfile_show(struct seq_file *m, void *arg)
2275
{
2276 2277
	struct cftype *cft = seq_cft(m);
	struct cgroup_subsys_state *css = seq_css(m);
2278

2279 2280
	if (cft->seq_show)
		return cft->seq_show(m, arg);
2281

2282
	if (cft->read_u64)
2283 2284 2285 2286 2287 2288
		seq_printf(m, "%llu\n", cft->read_u64(css, cft));
	else if (cft->read_s64)
		seq_printf(m, "%lld\n", cft->read_s64(css, cft));
	else
		return -EINVAL;
	return 0;
2289 2290
}

T
Tejun Heo 已提交
2291 2292 2293 2294
static struct kernfs_ops cgroup_kf_single_ops = {
	.atomic_write_len	= PAGE_SIZE,
	.write			= cgroup_file_write,
	.seq_show		= cgroup_seqfile_show,
2295 2296
};

T
Tejun Heo 已提交
2297 2298 2299 2300 2301 2302 2303 2304
static struct kernfs_ops cgroup_kf_ops = {
	.atomic_write_len	= PAGE_SIZE,
	.write			= cgroup_file_write,
	.seq_start		= cgroup_seqfile_start,
	.seq_next		= cgroup_seqfile_next,
	.seq_stop		= cgroup_seqfile_stop,
	.seq_show		= cgroup_seqfile_show,
};
2305 2306 2307 2308

/*
 * cgroup_rename - Only allow simple rename of directories in place.
 */
T
Tejun Heo 已提交
2309 2310
static int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
			 const char *new_name_str)
2311
{
T
Tejun Heo 已提交
2312 2313
	struct cgroup *cgrp = kn->priv;
	int ret;
2314

T
Tejun Heo 已提交
2315
	if (kernfs_type(kn) != KERNFS_DIR)
2316
		return -ENOTDIR;
T
Tejun Heo 已提交
2317
	if (kn->parent != new_parent)
2318
		return -EIO;
2319

2320 2321 2322 2323 2324 2325 2326
	/*
	 * This isn't a proper migration and its usefulness is very
	 * limited.  Disallow if sane_behavior.
	 */
	if (cgroup_sane_behavior(cgrp))
		return -EPERM;

2327 2328 2329 2330 2331 2332 2333 2334
	/*
	 * We're gonna grab cgroup_tree_mutex which nests outside kernfs
	 * active_ref.  kernfs_rename() doesn't require active_ref
	 * protection.  Break them before grabbing cgroup_tree_mutex.
	 */
	kernfs_break_active_protection(new_parent);
	kernfs_break_active_protection(kn);

T
Tejun Heo 已提交
2335 2336 2337 2338
	mutex_lock(&cgroup_tree_mutex);
	mutex_lock(&cgroup_mutex);

	ret = kernfs_rename(kn, new_parent, new_name_str);
2339

T
Tejun Heo 已提交
2340 2341
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&cgroup_tree_mutex);
2342 2343 2344

	kernfs_unbreak_active_protection(kn);
	kernfs_unbreak_active_protection(new_parent);
T
Tejun Heo 已提交
2345
	return ret;
2346 2347
}

2348
static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
2349
{
T
Tejun Heo 已提交
2350
	char name[CGROUP_FILE_NAME_MAX];
T
Tejun Heo 已提交
2351 2352
	struct kernfs_node *kn;
	struct lock_class_key *key = NULL;
T
Tejun Heo 已提交
2353

T
Tejun Heo 已提交
2354 2355 2356 2357 2358 2359
#ifdef CONFIG_DEBUG_LOCK_ALLOC
	key = &cft->lockdep_key;
#endif
	kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
				  cgroup_file_mode(cft), 0, cft->kf_ops, cft,
				  NULL, false, key);
F
Fengguang Wu 已提交
2360
	return PTR_ERR_OR_ZERO(kn);
2361 2362
}

2363 2364 2365 2366 2367 2368 2369
/**
 * cgroup_addrm_files - add or remove files to a cgroup directory
 * @cgrp: the target cgroup
 * @cfts: array of cftypes to be added
 * @is_add: whether to add or remove
 *
 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
2370 2371 2372
 * For removals, this function never fails.  If addition fails, this
 * function doesn't remove files already added.  The caller is responsible
 * for cleaning up.
2373
 */
2374 2375
static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
			      bool is_add)
2376
{
A
Aristeu Rozanski 已提交
2377
	struct cftype *cft;
2378 2379
	int ret;

T
Tejun Heo 已提交
2380
	lockdep_assert_held(&cgroup_tree_mutex);
T
Tejun Heo 已提交
2381 2382

	for (cft = cfts; cft->name[0] != '\0'; cft++) {
2383
		/* does cft->flags tell us to skip this file on @cgrp? */
T
Tejun Heo 已提交
2384 2385
		if ((cft->flags & CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
			continue;
2386 2387
		if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp))
			continue;
2388 2389 2390 2391 2392
		if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
			continue;
		if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
			continue;

2393
		if (is_add) {
2394
			ret = cgroup_add_file(cgrp, cft);
2395
			if (ret) {
2396
				pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
2397 2398 2399
					cft->name, ret);
				return ret;
			}
2400 2401
		} else {
			cgroup_rm_file(cgrp, cft);
T
Tejun Heo 已提交
2402
		}
2403
	}
2404
	return 0;
2405 2406
}

2407
static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
2408 2409
{
	LIST_HEAD(pending);
2410
	struct cgroup_subsys *ss = cfts[0].ss;
2411
	struct cgroup *root = &ss->root->cgrp;
2412
	struct cgroup_subsys_state *css;
2413
	int ret = 0;
2414

2415
	lockdep_assert_held(&cgroup_tree_mutex);
2416

2417
	/* don't bother if @ss isn't attached */
2418
	if (ss->root == &cgrp_dfl_root)
2419
		return 0;
2420 2421

	/* add/rm files for all cgroups created before */
2422
	css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
2423 2424
		struct cgroup *cgrp = css->cgroup;

2425 2426 2427
		if (cgroup_is_dead(cgrp))
			continue;

2428
		ret = cgroup_addrm_files(cgrp, cfts, is_add);
2429 2430
		if (ret)
			break;
2431
	}
2432 2433 2434

	if (is_add && !ret)
		kernfs_activate(root->kn);
2435
	return ret;
2436 2437
}

2438 2439 2440 2441
static void cgroup_exit_cftypes(struct cftype *cfts)
{
	struct cftype *cft;

T
Tejun Heo 已提交
2442 2443 2444 2445 2446
	for (cft = cfts; cft->name[0] != '\0'; cft++) {
		/* free copy for custom atomic_write_len, see init_cftypes() */
		if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
			kfree(cft->kf_ops);
		cft->kf_ops = NULL;
2447
		cft->ss = NULL;
T
Tejun Heo 已提交
2448
	}
2449 2450
}

T
Tejun Heo 已提交
2451
static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2452 2453 2454
{
	struct cftype *cft;

T
Tejun Heo 已提交
2455 2456 2457
	for (cft = cfts; cft->name[0] != '\0'; cft++) {
		struct kernfs_ops *kf_ops;

T
Tejun Heo 已提交
2458 2459
		WARN_ON(cft->ss || cft->kf_ops);

T
Tejun Heo 已提交
2460 2461 2462 2463 2464 2465 2466 2467 2468 2469 2470 2471 2472 2473 2474 2475 2476 2477 2478
		if (cft->seq_start)
			kf_ops = &cgroup_kf_ops;
		else
			kf_ops = &cgroup_kf_single_ops;

		/*
		 * Ugh... if @cft wants a custom max_write_len, we need to
		 * make a copy of kf_ops to set its atomic_write_len.
		 */
		if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
			kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
			if (!kf_ops) {
				cgroup_exit_cftypes(cfts);
				return -ENOMEM;
			}
			kf_ops->atomic_write_len = cft->max_write_len;
		}

		cft->kf_ops = kf_ops;
2479
		cft->ss = ss;
T
Tejun Heo 已提交
2480 2481 2482
	}

	return 0;
2483 2484
}

2485 2486 2487 2488 2489 2490 2491 2492 2493 2494 2495 2496 2497
static int cgroup_rm_cftypes_locked(struct cftype *cfts)
{
	lockdep_assert_held(&cgroup_tree_mutex);

	if (!cfts || !cfts[0].ss)
		return -ENOENT;

	list_del(&cfts->node);
	cgroup_apply_cftypes(cfts, false);
	cgroup_exit_cftypes(cfts);
	return 0;
}

T
Tejun Heo 已提交
2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509 2510
/**
 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
 * @cfts: zero-length name terminated array of cftypes
 *
 * Unregister @cfts.  Files described by @cfts are removed from all
 * existing cgroups and all future cgroups won't have them either.  This
 * function can be called anytime whether @cfts' subsys is attached or not.
 *
 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
 * registered.
 */
int cgroup_rm_cftypes(struct cftype *cfts)
{
2511
	int ret;
T
Tejun Heo 已提交
2512

2513 2514 2515 2516
	mutex_lock(&cgroup_tree_mutex);
	ret = cgroup_rm_cftypes_locked(cfts);
	mutex_unlock(&cgroup_tree_mutex);
	return ret;
T
Tejun Heo 已提交
2517 2518
}

2519 2520 2521 2522 2523 2524 2525 2526 2527 2528 2529 2530 2531 2532
/**
 * 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
2533
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2534
{
2535
	int ret;
2536

2537 2538 2539
	if (!cfts || cfts[0].name[0] == '\0')
		return 0;

T
Tejun Heo 已提交
2540 2541 2542
	ret = cgroup_init_cftypes(ss, cfts);
	if (ret)
		return ret;
2543

2544 2545
	mutex_lock(&cgroup_tree_mutex);

T
Tejun Heo 已提交
2546
	list_add_tail(&cfts->node, &ss->cfts);
2547
	ret = cgroup_apply_cftypes(cfts, true);
2548
	if (ret)
2549 2550 2551
		cgroup_rm_cftypes_locked(cfts);

	mutex_unlock(&cgroup_tree_mutex);
2552
	return ret;
2553 2554
}

L
Li Zefan 已提交
2555 2556 2557 2558 2559 2560
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2561
static int cgroup_task_count(const struct cgroup *cgrp)
2562 2563
{
	int count = 0;
2564
	struct cgrp_cset_link *link;
2565

2566
	down_read(&css_set_rwsem);
2567 2568
	list_for_each_entry(link, &cgrp->cset_links, cset_link)
		count += atomic_read(&link->cset->refcount);
2569
	up_read(&css_set_rwsem);
2570 2571 2572
	return count;
}

2573
/**
2574 2575 2576
 * css_next_child - find the next child of a given css
 * @pos_css: the current position (%NULL to initiate traversal)
 * @parent_css: css whose children to walk
2577
 *
2578
 * This function returns the next child of @parent_css and should be called
2579 2580 2581
 * under either cgroup_mutex or RCU read lock.  The only requirement is
 * that @parent_css and @pos_css are accessible.  The next sibling is
 * guaranteed to be returned regardless of their states.
2582
 */
2583 2584 2585
struct cgroup_subsys_state *
css_next_child(struct cgroup_subsys_state *pos_css,
	       struct cgroup_subsys_state *parent_css)
2586
{
2587 2588
	struct cgroup *pos = pos_css ? pos_css->cgroup : NULL;
	struct cgroup *cgrp = parent_css->cgroup;
2589 2590
	struct cgroup *next;

T
Tejun Heo 已提交
2591
	cgroup_assert_mutexes_or_rcu_locked();
2592 2593 2594 2595

	/*
	 * @pos could already have been removed.  Once a cgroup is removed,
	 * its ->sibling.next is no longer updated when its next sibling
2596 2597 2598 2599 2600 2601 2602
	 * 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.
2603 2604 2605 2606 2607 2608 2609 2610
	 *
	 * If @pos is dead, its next pointer can't be dereferenced;
	 * however, as each cgroup is given a monotonically increasing
	 * unique serial number and always appended to the sibling list,
	 * 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 slower, it's taken only when either the current
	 * cgroup is removed or iteration and removal race.
2611
	 */
2612 2613 2614
	if (!pos) {
		next = list_entry_rcu(cgrp->children.next, struct cgroup, sibling);
	} else if (likely(!cgroup_is_dead(pos))) {
2615
		next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
2616 2617 2618 2619
	} else {
		list_for_each_entry_rcu(next, &cgrp->children, sibling)
			if (next->serial_nr > pos->serial_nr)
				break;
2620 2621
	}

2622 2623 2624
	if (&next->sibling == &cgrp->children)
		return NULL;

2625
	return cgroup_css(next, parent_css->ss);
2626 2627
}

2628
/**
2629
 * css_next_descendant_pre - find the next descendant for pre-order walk
2630
 * @pos: the current position (%NULL to initiate traversal)
2631
 * @root: css whose descendants to walk
2632
 *
2633
 * To be used by css_for_each_descendant_pre().  Find the next descendant
2634 2635
 * to visit for pre-order traversal of @root's descendants.  @root is
 * included in the iteration and the first node to be visited.
2636
 *
2637 2638 2639 2640
 * While this function requires cgroup_mutex or RCU read locking, it
 * doesn't require the whole traversal to be contained in a single critical
 * section.  This function will return the correct next descendant as long
 * as both @pos and @root are accessible and @pos is a descendant of @root.
2641
 */
2642 2643 2644
struct cgroup_subsys_state *
css_next_descendant_pre(struct cgroup_subsys_state *pos,
			struct cgroup_subsys_state *root)
2645
{
2646
	struct cgroup_subsys_state *next;
2647

T
Tejun Heo 已提交
2648
	cgroup_assert_mutexes_or_rcu_locked();
2649

2650
	/* if first iteration, visit @root */
2651
	if (!pos)
2652
		return root;
2653 2654

	/* visit the first child if exists */
2655
	next = css_next_child(NULL, pos);
2656 2657 2658 2659
	if (next)
		return next;

	/* no child, visit my or the closest ancestor's next sibling */
2660 2661
	while (pos != root) {
		next = css_next_child(pos, css_parent(pos));
2662
		if (next)
2663
			return next;
2664
		pos = css_parent(pos);
2665
	}
2666 2667 2668 2669

	return NULL;
}

2670
/**
2671 2672
 * css_rightmost_descendant - return the rightmost descendant of a css
 * @pos: css of interest
2673
 *
2674 2675
 * Return the rightmost descendant of @pos.  If there's no descendant, @pos
 * is returned.  This can be used during pre-order traversal to skip
2676
 * subtree of @pos.
2677
 *
2678 2679 2680 2681
 * While this function requires cgroup_mutex or RCU read locking, it
 * doesn't require the whole traversal to be contained in a single critical
 * section.  This function will return the correct rightmost descendant as
 * long as @pos is accessible.
2682
 */
2683 2684
struct cgroup_subsys_state *
css_rightmost_descendant(struct cgroup_subsys_state *pos)
2685
{
2686
	struct cgroup_subsys_state *last, *tmp;
2687

T
Tejun Heo 已提交
2688
	cgroup_assert_mutexes_or_rcu_locked();
2689 2690 2691 2692 2693

	do {
		last = pos;
		/* ->prev isn't RCU safe, walk ->next till the end */
		pos = NULL;
2694
		css_for_each_child(tmp, last)
2695 2696 2697 2698 2699 2700
			pos = tmp;
	} while (pos);

	return last;
}

2701 2702
static struct cgroup_subsys_state *
css_leftmost_descendant(struct cgroup_subsys_state *pos)
2703
{
2704
	struct cgroup_subsys_state *last;
2705 2706 2707

	do {
		last = pos;
2708
		pos = css_next_child(NULL, pos);
2709 2710 2711 2712 2713 2714
	} while (pos);

	return last;
}

/**
2715
 * css_next_descendant_post - find the next descendant for post-order walk
2716
 * @pos: the current position (%NULL to initiate traversal)
2717
 * @root: css whose descendants to walk
2718
 *
2719
 * To be used by css_for_each_descendant_post().  Find the next descendant
2720 2721
 * to visit for post-order traversal of @root's descendants.  @root is
 * included in the iteration and the last node to be visited.
2722
 *
2723 2724 2725 2726 2727
 * While this function requires cgroup_mutex or RCU read locking, it
 * doesn't require the whole traversal to be contained in a single 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.
2728
 */
2729 2730 2731
struct cgroup_subsys_state *
css_next_descendant_post(struct cgroup_subsys_state *pos,
			 struct cgroup_subsys_state *root)
2732
{
2733
	struct cgroup_subsys_state *next;
2734

T
Tejun Heo 已提交
2735
	cgroup_assert_mutexes_or_rcu_locked();
2736

2737 2738 2739
	/* if first iteration, visit leftmost descendant which may be @root */
	if (!pos)
		return css_leftmost_descendant(root);
2740

2741 2742 2743 2744
	/* if we visited @root, we're done */
	if (pos == root)
		return NULL;

2745
	/* if there's an unvisited sibling, visit its leftmost descendant */
2746
	next = css_next_child(pos, css_parent(pos));
2747
	if (next)
2748
		return css_leftmost_descendant(next);
2749 2750

	/* no sibling left, visit parent */
2751
	return css_parent(pos);
2752 2753
}

2754
/**
2755
 * css_advance_task_iter - advance a task itererator to the next css_set
2756 2757 2758
 * @it: the iterator to advance
 *
 * Advance @it to the next css_set to walk.
2759
 */
2760
static void css_advance_task_iter(struct css_task_iter *it)
2761 2762 2763 2764 2765 2766 2767 2768
{
	struct list_head *l = it->cset_link;
	struct cgrp_cset_link *link;
	struct css_set *cset;

	/* Advance to the next non-empty css_set */
	do {
		l = l->next;
2769
		if (l == &it->origin_css->cgroup->cset_links) {
2770 2771 2772 2773 2774
			it->cset_link = NULL;
			return;
		}
		link = list_entry(l, struct cgrp_cset_link, cset_link);
		cset = link->cset;
T
Tejun Heo 已提交
2775 2776
	} while (list_empty(&cset->tasks) && list_empty(&cset->mg_tasks));

2777
	it->cset_link = l;
T
Tejun Heo 已提交
2778 2779 2780 2781 2782

	if (!list_empty(&cset->tasks))
		it->task = cset->tasks.next;
	else
		it->task = cset->mg_tasks.next;
2783 2784
}

2785
/**
2786 2787
 * css_task_iter_start - initiate task iteration
 * @css: the css to walk tasks of
2788 2789
 * @it: the task iterator to use
 *
2790 2791 2792 2793
 * Initiate iteration through the tasks of @css.  The caller can call
 * css_task_iter_next() to walk through the tasks until the function
 * returns NULL.  On completion of iteration, css_task_iter_end() must be
 * called.
2794 2795 2796 2797 2798
 *
 * Note that this function acquires a lock which is released when the
 * iteration finishes.  The caller can't sleep while iteration is in
 * progress.
 */
2799 2800
void css_task_iter_start(struct cgroup_subsys_state *css,
			 struct css_task_iter *it)
2801
	__acquires(css_set_rwsem)
2802
{
2803 2804
	/* no one should try to iterate before mounting cgroups */
	WARN_ON_ONCE(!use_task_css_set_links);
2805

2806
	down_read(&css_set_rwsem);
2807

2808 2809
	it->origin_css = css;
	it->cset_link = &css->cgroup->cset_links;
2810

2811
	css_advance_task_iter(it);
2812 2813
}

2814
/**
2815
 * css_task_iter_next - return the next task for the iterator
2816 2817 2818
 * @it: the task iterator being iterated
 *
 * The "next" function for task iteration.  @it should have been
2819 2820
 * initialized via css_task_iter_start().  Returns NULL when the iteration
 * reaches the end.
2821
 */
2822
struct task_struct *css_task_iter_next(struct css_task_iter *it)
2823 2824 2825
{
	struct task_struct *res;
	struct list_head *l = it->task;
T
Tejun Heo 已提交
2826 2827
	struct cgrp_cset_link *link = list_entry(it->cset_link,
					struct cgrp_cset_link, cset_link);
2828 2829

	/* If the iterator cg is NULL, we have no tasks */
2830
	if (!it->cset_link)
2831 2832
		return NULL;
	res = list_entry(l, struct task_struct, cg_list);
T
Tejun Heo 已提交
2833 2834 2835 2836 2837 2838

	/*
	 * Advance iterator to find next entry.  cset->tasks is consumed
	 * first and then ->mg_tasks.  After ->mg_tasks, we move onto the
	 * next cset.
	 */
2839
	l = l->next;
T
Tejun Heo 已提交
2840 2841 2842 2843 2844

	if (l == &link->cset->tasks)
		l = link->cset->mg_tasks.next;

	if (l == &link->cset->mg_tasks)
2845
		css_advance_task_iter(it);
T
Tejun Heo 已提交
2846
	else
2847
		it->task = l;
T
Tejun Heo 已提交
2848

2849 2850 2851
	return res;
}

2852
/**
2853
 * css_task_iter_end - finish task iteration
2854 2855
 * @it: the task iterator to finish
 *
2856
 * Finish task iteration started by css_task_iter_start().
2857
 */
2858
void css_task_iter_end(struct css_task_iter *it)
2859
	__releases(css_set_rwsem)
2860
{
2861
	up_read(&css_set_rwsem);
2862 2863
}

2864 2865 2866 2867
/**
 * 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
2868 2869 2870 2871 2872 2873
 *
 * Locking rules between cgroup_post_fork() and the migration path
 * guarantee that, if a task is forking while being migrated, the new child
 * is guaranteed to be either visible in the source cgroup after the
 * parent's migration is complete or put into the target cgroup.  No task
 * can slip out of migration through forking.
2874 2875 2876
 */
int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
{
2877 2878
	LIST_HEAD(preloaded_csets);
	struct cgrp_cset_link *link;
2879 2880
	struct css_task_iter it;
	struct task_struct *task;
2881 2882 2883 2884 2885 2886 2887 2888 2889
	int ret;

	mutex_lock(&cgroup_mutex);

	/* all tasks in @from are being moved, all csets are source */
	down_read(&css_set_rwsem);
	list_for_each_entry(link, &from->cset_links, cset_link)
		cgroup_migrate_add_src(link->cset, to, &preloaded_csets);
	up_read(&css_set_rwsem);
2890

2891 2892 2893 2894 2895 2896 2897 2898
	ret = cgroup_migrate_prepare_dst(to, &preloaded_csets);
	if (ret)
		goto out_err;

	/*
	 * Migrate tasks one-by-one until @form is empty.  This fails iff
	 * ->can_attach() fails.
	 */
2899 2900 2901 2902 2903 2904 2905 2906
	do {
		css_task_iter_start(&from->dummy_css, &it);
		task = css_task_iter_next(&it);
		if (task)
			get_task_struct(task);
		css_task_iter_end(&it);

		if (task) {
2907
			ret = cgroup_migrate(to, task, false);
2908 2909 2910
			put_task_struct(task);
		}
	} while (task && !ret);
2911 2912 2913
out_err:
	cgroup_migrate_finish(&preloaded_csets);
	mutex_unlock(&cgroup_mutex);
2914
	return ret;
2915 2916
}

2917
/*
2918
 * Stuff for reading the 'tasks'/'procs' files.
2919 2920 2921 2922 2923 2924 2925 2926
 *
 * 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.
 *
 */

2927 2928 2929 2930 2931 2932 2933 2934 2935 2936 2937 2938 2939 2940 2941 2942 2943 2944 2945 2946 2947 2948 2949 2950 2951 2952
/* 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;
	/* 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;
2953 2954
	/* for delayed destruction */
	struct delayed_work destroy_dwork;
2955 2956
};

2957 2958 2959 2960 2961 2962 2963 2964 2965 2966 2967 2968 2969
/*
 * 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);
}
2970

2971 2972 2973 2974 2975 2976 2977 2978
static void pidlist_free(void *p)
{
	if (is_vmalloc_addr(p))
		vfree(p);
	else
		kfree(p);
}

2979 2980 2981 2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005
/*
 * Used to destroy all pidlists lingering waiting for destroy timer.  None
 * should be left afterwards.
 */
static void cgroup_pidlist_destroy_all(struct cgroup *cgrp)
{
	struct cgroup_pidlist *l, *tmp_l;

	mutex_lock(&cgrp->pidlist_mutex);
	list_for_each_entry_safe(l, tmp_l, &cgrp->pidlists, links)
		mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, 0);
	mutex_unlock(&cgrp->pidlist_mutex);

	flush_workqueue(cgroup_pidlist_destroy_wq);
	BUG_ON(!list_empty(&cgrp->pidlists));
}

static void cgroup_pidlist_destroy_work_fn(struct work_struct *work)
{
	struct delayed_work *dwork = to_delayed_work(work);
	struct cgroup_pidlist *l = container_of(dwork, struct cgroup_pidlist,
						destroy_dwork);
	struct cgroup_pidlist *tofree = NULL;

	mutex_lock(&l->owner->pidlist_mutex);

	/*
3006 3007
	 * Destroy iff we didn't get queued again.  The state won't change
	 * as destroy_dwork can only be queued while locked.
3008
	 */
3009
	if (!delayed_work_pending(dwork)) {
3010 3011 3012 3013 3014 3015 3016 3017 3018 3019
		list_del(&l->links);
		pidlist_free(l->list);
		put_pid_ns(l->key.ns);
		tofree = l;
	}

	mutex_unlock(&l->owner->pidlist_mutex);
	kfree(tofree);
}

3020
/*
3021
 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3022
 * Returns the number of unique elements.
3023
 */
3024
static int pidlist_uniq(pid_t *list, int length)
3025
{
3026 3027 3028 3029 3030 3031 3032 3033 3034 3035 3036 3037 3038 3039 3040 3041 3042 3043 3044 3045 3046 3047 3048 3049
	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;
}

3050 3051 3052 3053 3054 3055 3056 3057 3058 3059 3060 3061 3062 3063 3064 3065 3066 3067 3068 3069 3070 3071 3072 3073 3074 3075 3076 3077 3078 3079 3080 3081 3082
/*
 * The two pid files - task and cgroup.procs - guaranteed that the result
 * is sorted, which forced this whole pidlist fiasco.  As pid order is
 * different per namespace, each namespace needs differently sorted list,
 * making it impossible to use, for example, single rbtree of member tasks
 * sorted by task pointer.  As pidlists can be fairly large, allocating one
 * per open file is dangerous, so cgroup had to implement shared pool of
 * pidlists keyed by cgroup and namespace.
 *
 * All this extra complexity was caused by the original implementation
 * committing to an entirely unnecessary property.  In the long term, we
 * want to do away with it.  Explicitly scramble sort order if
 * sane_behavior so that no such expectation exists in the new interface.
 *
 * Scrambling is done by swapping every two consecutive bits, which is
 * non-identity one-to-one mapping which disturbs sort order sufficiently.
 */
static pid_t pid_fry(pid_t pid)
{
	unsigned a = pid & 0x55555555;
	unsigned b = pid & 0xAAAAAAAA;

	return (a << 1) | (b >> 1);
}

static pid_t cgroup_pid_fry(struct cgroup *cgrp, pid_t pid)
{
	if (cgroup_sane_behavior(cgrp))
		return pid_fry(pid);
	else
		return pid;
}

3083 3084 3085 3086 3087
static int cmppid(const void *a, const void *b)
{
	return *(pid_t *)a - *(pid_t *)b;
}

3088 3089 3090 3091 3092
static int fried_cmppid(const void *a, const void *b)
{
	return pid_fry(*(pid_t *)a) - pid_fry(*(pid_t *)b);
}

T
Tejun Heo 已提交
3093 3094 3095 3096 3097 3098 3099 3100 3101 3102 3103 3104 3105 3106 3107
static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
						  enum cgroup_filetype type)
{
	struct cgroup_pidlist *l;
	/* don't need task_nsproxy() if we're looking at ourself */
	struct pid_namespace *ns = task_active_pid_ns(current);

	lockdep_assert_held(&cgrp->pidlist_mutex);

	list_for_each_entry(l, &cgrp->pidlists, links)
		if (l->key.type == type && l->key.ns == ns)
			return l;
	return NULL;
}

3108 3109 3110 3111 3112 3113
/*
 * 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.
 */
T
Tejun Heo 已提交
3114 3115
static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
						enum cgroup_filetype type)
3116 3117
{
	struct cgroup_pidlist *l;
3118

T
Tejun Heo 已提交
3119 3120 3121 3122 3123 3124
	lockdep_assert_held(&cgrp->pidlist_mutex);

	l = cgroup_pidlist_find(cgrp, type);
	if (l)
		return l;

3125
	/* entry not found; create a new one */
3126
	l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
T
Tejun Heo 已提交
3127
	if (!l)
3128
		return l;
T
Tejun Heo 已提交
3129

3130
	INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
3131
	l->key.type = type;
T
Tejun Heo 已提交
3132 3133
	/* don't need task_nsproxy() if we're looking at ourself */
	l->key.ns = get_pid_ns(task_active_pid_ns(current));
3134 3135 3136 3137 3138
	l->owner = cgrp;
	list_add(&l->links, &cgrp->pidlists);
	return l;
}

3139 3140 3141
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
3142 3143
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
3144 3145 3146 3147
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
3148
	struct css_task_iter it;
3149
	struct task_struct *tsk;
3150 3151
	struct cgroup_pidlist *l;

3152 3153
	lockdep_assert_held(&cgrp->pidlist_mutex);

3154 3155 3156 3157 3158 3159 3160
	/*
	 * 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);
3161
	array = pidlist_allocate(length);
3162 3163 3164
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
3165 3166
	css_task_iter_start(&cgrp->dummy_css, &it);
	while ((tsk = css_task_iter_next(&it))) {
3167
		if (unlikely(n == length))
3168
			break;
3169
		/* get tgid or pid for procs or tasks file respectively */
3170 3171 3172 3173
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
3174 3175
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
3176
	}
3177
	css_task_iter_end(&it);
3178 3179
	length = n;
	/* now sort & (if procs) strip out duplicates */
3180 3181 3182 3183
	if (cgroup_sane_behavior(cgrp))
		sort(array, length, sizeof(pid_t), fried_cmppid, NULL);
	else
		sort(array, length, sizeof(pid_t), cmppid, NULL);
3184
	if (type == CGROUP_FILE_PROCS)
3185
		length = pidlist_uniq(array, length);
T
Tejun Heo 已提交
3186 3187

	l = cgroup_pidlist_find_create(cgrp, type);
3188
	if (!l) {
T
Tejun Heo 已提交
3189
		mutex_unlock(&cgrp->pidlist_mutex);
3190
		pidlist_free(array);
3191
		return -ENOMEM;
3192
	}
T
Tejun Heo 已提交
3193 3194

	/* store array, freeing old if necessary */
3195
	pidlist_free(l->list);
3196 3197
	l->list = array;
	l->length = length;
3198
	*lp = l;
3199
	return 0;
3200 3201
}

B
Balbir Singh 已提交
3202
/**
L
Li Zefan 已提交
3203
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
3204 3205 3206
 * @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
3207 3208 3209
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
3210 3211 3212
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
T
Tejun Heo 已提交
3213
	struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
3214
	struct cgroup *cgrp;
3215
	struct css_task_iter it;
B
Balbir Singh 已提交
3216
	struct task_struct *tsk;
3217

T
Tejun Heo 已提交
3218 3219 3220 3221 3222
	/* it should be kernfs_node belonging to cgroupfs and is a directory */
	if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
	    kernfs_type(kn) != KERNFS_DIR)
		return -EINVAL;

3223 3224
	mutex_lock(&cgroup_mutex);

B
Balbir Singh 已提交
3225
	/*
T
Tejun Heo 已提交
3226 3227 3228
	 * We aren't being called from kernfs and there's no guarantee on
	 * @kn->priv's validity.  For this and css_tryget_from_dir(),
	 * @kn->priv is RCU safe.  Let's do the RCU dancing.
B
Balbir Singh 已提交
3229
	 */
T
Tejun Heo 已提交
3230 3231
	rcu_read_lock();
	cgrp = rcu_dereference(kn->priv);
3232
	if (!cgrp || cgroup_is_dead(cgrp)) {
T
Tejun Heo 已提交
3233
		rcu_read_unlock();
3234
		mutex_unlock(&cgroup_mutex);
T
Tejun Heo 已提交
3235 3236
		return -ENOENT;
	}
3237
	rcu_read_unlock();
B
Balbir Singh 已提交
3238

3239 3240
	css_task_iter_start(&cgrp->dummy_css, &it);
	while ((tsk = css_task_iter_next(&it))) {
B
Balbir Singh 已提交
3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259
		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;
		}
	}
3260
	css_task_iter_end(&it);
B
Balbir Singh 已提交
3261

3262
	mutex_unlock(&cgroup_mutex);
T
Tejun Heo 已提交
3263
	return 0;
B
Balbir Singh 已提交
3264 3265
}

3266

3267
/*
3268
 * seq_file methods for the tasks/procs files. The seq_file position is the
3269
 * next pid to display; the seq_file iterator is a pointer to the pid
3270
 * in the cgroup->l->list array.
3271
 */
3272

3273
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3274
{
3275 3276 3277 3278 3279 3280
	/*
	 * 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
	 */
T
Tejun Heo 已提交
3281
	struct kernfs_open_file *of = s->private;
3282
	struct cgroup *cgrp = seq_css(s)->cgroup;
3283
	struct cgroup_pidlist *l;
3284
	enum cgroup_filetype type = seq_cft(s)->private;
3285
	int index = 0, pid = *pos;
3286 3287 3288 3289 3290
	int *iter, ret;

	mutex_lock(&cgrp->pidlist_mutex);

	/*
3291
	 * !NULL @of->priv indicates that this isn't the first start()
3292
	 * after open.  If the matching pidlist is around, we can use that.
3293
	 * Look for it.  Note that @of->priv can't be used directly.  It
3294 3295
	 * could already have been destroyed.
	 */
3296 3297
	if (of->priv)
		of->priv = cgroup_pidlist_find(cgrp, type);
3298 3299 3300 3301 3302

	/*
	 * Either this is the first start() after open or the matching
	 * pidlist has been destroyed inbetween.  Create a new one.
	 */
3303 3304 3305
	if (!of->priv) {
		ret = pidlist_array_load(cgrp, type,
					 (struct cgroup_pidlist **)&of->priv);
3306 3307 3308
		if (ret)
			return ERR_PTR(ret);
	}
3309
	l = of->priv;
3310 3311

	if (pid) {
3312
		int end = l->length;
S
Stephen Rothwell 已提交
3313

3314 3315
		while (index < end) {
			int mid = (index + end) / 2;
3316
			if (cgroup_pid_fry(cgrp, l->list[mid]) == pid) {
3317 3318
				index = mid;
				break;
3319
			} else if (cgroup_pid_fry(cgrp, l->list[mid]) <= pid)
3320 3321 3322 3323 3324 3325
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
3326
	if (index >= l->length)
3327 3328
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
3329
	iter = l->list + index;
3330
	*pos = cgroup_pid_fry(cgrp, *iter);
3331 3332 3333
	return iter;
}

3334
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3335
{
T
Tejun Heo 已提交
3336
	struct kernfs_open_file *of = s->private;
3337
	struct cgroup_pidlist *l = of->priv;
3338

3339 3340
	if (l)
		mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
3341
				 CGROUP_PIDLIST_DESTROY_DELAY);
3342
	mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
3343 3344
}

3345
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3346
{
T
Tejun Heo 已提交
3347
	struct kernfs_open_file *of = s->private;
3348
	struct cgroup_pidlist *l = of->priv;
3349 3350
	pid_t *p = v;
	pid_t *end = l->list + l->length;
3351 3352 3353 3354 3355 3356 3357 3358
	/*
	 * Advance to the next pid in the array. If this goes off the
	 * end, we're done
	 */
	p++;
	if (p >= end) {
		return NULL;
	} else {
3359
		*pos = cgroup_pid_fry(seq_css(s)->cgroup, *p);
3360 3361 3362 3363
		return p;
	}
}

3364
static int cgroup_pidlist_show(struct seq_file *s, void *v)
3365 3366 3367
{
	return seq_printf(s, "%d\n", *(int *)v);
}
3368

3369 3370 3371 3372 3373 3374 3375 3376 3377
/*
 * 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,
3378 3379
};

3380 3381
static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
					 struct cftype *cft)
3382
{
3383
	return notify_on_release(css->cgroup);
3384 3385
}

3386 3387
static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
					  struct cftype *cft, u64 val)
3388
{
3389
	clear_bit(CGRP_RELEASABLE, &css->cgroup->flags);
3390
	if (val)
3391
		set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
3392
	else
3393
		clear_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
3394 3395 3396
	return 0;
}

3397 3398
static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
				      struct cftype *cft)
3399
{
3400
	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
3401 3402
}

3403 3404
static int cgroup_clone_children_write(struct cgroup_subsys_state *css,
				       struct cftype *cft, u64 val)
3405 3406
{
	if (val)
3407
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
3408
	else
3409
		clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
3410 3411 3412
	return 0;
}

3413
static struct cftype cgroup_base_files[] = {
3414
	{
3415
		.name = "cgroup.procs",
3416 3417 3418 3419
		.seq_start = cgroup_pidlist_start,
		.seq_next = cgroup_pidlist_next,
		.seq_stop = cgroup_pidlist_stop,
		.seq_show = cgroup_pidlist_show,
3420
		.private = CGROUP_FILE_PROCS,
B
Ben Blum 已提交
3421 3422
		.write_u64 = cgroup_procs_write,
		.mode = S_IRUGO | S_IWUSR,
3423
	},
3424 3425
	{
		.name = "cgroup.clone_children",
3426
		.flags = CFTYPE_INSANE,
3427 3428 3429
		.read_u64 = cgroup_clone_children_read,
		.write_u64 = cgroup_clone_children_write,
	},
3430 3431 3432
	{
		.name = "cgroup.sane_behavior",
		.flags = CFTYPE_ONLY_ON_ROOT,
3433
		.seq_show = cgroup_sane_behavior_show,
3434
	},
3435 3436 3437 3438 3439 3440 3441 3442 3443

	/*
	 * 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 */
3444 3445 3446 3447
		.seq_start = cgroup_pidlist_start,
		.seq_next = cgroup_pidlist_next,
		.seq_stop = cgroup_pidlist_stop,
		.seq_show = cgroup_pidlist_show,
3448
		.private = CGROUP_FILE_TASKS,
3449 3450 3451 3452 3453 3454 3455 3456 3457
		.write_u64 = cgroup_tasks_write,
		.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,
	},
3458 3459
	{
		.name = "release_agent",
3460
		.flags = CFTYPE_INSANE | CFTYPE_ONLY_ON_ROOT,
3461
		.seq_show = cgroup_release_agent_show,
3462
		.write_string = cgroup_release_agent_write,
3463
		.max_write_len = PATH_MAX - 1,
3464
	},
T
Tejun Heo 已提交
3465
	{ }	/* terminate */
3466 3467
};

3468
/**
3469
 * cgroup_populate_dir - create subsys files in a cgroup directory
3470 3471
 * @cgrp: target cgroup
 * @subsys_mask: mask of the subsystem ids whose files should be added
3472 3473
 *
 * On failure, no file is added.
3474
 */
3475
static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
3476 3477
{
	struct cgroup_subsys *ss;
3478
	int i, ret = 0;
3479

3480
	/* process cftsets of each subsystem */
3481
	for_each_subsys(ss, i) {
T
Tejun Heo 已提交
3482
		struct cftype *cfts;
3483 3484

		if (!test_bit(i, &subsys_mask))
3485
			continue;
3486

T
Tejun Heo 已提交
3487 3488
		list_for_each_entry(cfts, &ss->cfts, node) {
			ret = cgroup_addrm_files(cgrp, cfts, true);
3489 3490 3491
			if (ret < 0)
				goto err;
		}
3492 3493
	}
	return 0;
3494 3495 3496
err:
	cgroup_clear_dir(cgrp, subsys_mask);
	return ret;
3497 3498
}

3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520
/*
 * css destruction is four-stage process.
 *
 * 1. Destruction starts.  Killing of the percpu_ref is initiated.
 *    Implemented in kill_css().
 *
 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
 *    and thus css_tryget() is guaranteed to fail, the css can be offlined
 *    by invoking offline_css().  After offlining, the base ref is put.
 *    Implemented in css_killed_work_fn().
 *
 * 3. When the percpu_ref reaches zero, the only possible remaining
 *    accessors are inside RCU read sections.  css_release() schedules the
 *    RCU callback.
 *
 * 4. After the grace period, the css can be freed.  Implemented in
 *    css_free_work_fn().
 *
 * It is actually hairier because both step 2 and 4 require process context
 * and thus involve punting to css->destroy_work adding two additional
 * steps to the already complex sequence.
 */
3521
static void css_free_work_fn(struct work_struct *work)
3522 3523
{
	struct cgroup_subsys_state *css =
3524
		container_of(work, struct cgroup_subsys_state, destroy_work);
3525
	struct cgroup *cgrp = css->cgroup;
3526

3527 3528 3529
	if (css->parent)
		css_put(css->parent);

3530
	css->ss->css_free(css);
T
Tejun Heo 已提交
3531
	cgroup_put(cgrp);
3532 3533
}

3534
static void css_free_rcu_fn(struct rcu_head *rcu_head)
3535 3536
{
	struct cgroup_subsys_state *css =
3537
		container_of(rcu_head, struct cgroup_subsys_state, rcu_head);
3538

3539
	INIT_WORK(&css->destroy_work, css_free_work_fn);
3540
	queue_work(cgroup_destroy_wq, &css->destroy_work);
3541 3542
}

3543 3544 3545 3546 3547
static void css_release(struct percpu_ref *ref)
{
	struct cgroup_subsys_state *css =
		container_of(ref, struct cgroup_subsys_state, refcnt);

3548
	RCU_INIT_POINTER(css->cgroup->subsys[css->ss->id], NULL);
3549
	call_rcu(&css->rcu_head, css_free_rcu_fn);
3550 3551
}

3552 3553
static void init_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss,
		     struct cgroup *cgrp)
3554
{
3555
	css->cgroup = cgrp;
3556
	css->ss = ss;
3557
	css->flags = 0;
3558 3559

	if (cgrp->parent)
3560
		css->parent = cgroup_css(cgrp->parent, ss);
3561
	else
3562
		css->flags |= CSS_ROOT;
3563

3564
	BUG_ON(cgroup_css(cgrp, ss));
3565 3566
}

3567
/* invoke ->css_online() on a new CSS and mark it online if successful */
3568
static int online_css(struct cgroup_subsys_state *css)
3569
{
3570
	struct cgroup_subsys *ss = css->ss;
T
Tejun Heo 已提交
3571 3572
	int ret = 0;

T
Tejun Heo 已提交
3573
	lockdep_assert_held(&cgroup_tree_mutex);
3574 3575
	lockdep_assert_held(&cgroup_mutex);

3576
	if (ss->css_online)
3577
		ret = ss->css_online(css);
3578
	if (!ret) {
3579
		css->flags |= CSS_ONLINE;
3580
		css->cgroup->nr_css++;
3581
		rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
3582
	}
T
Tejun Heo 已提交
3583
	return ret;
3584 3585
}

3586
/* if the CSS is online, invoke ->css_offline() on it and mark it offline */
3587
static void offline_css(struct cgroup_subsys_state *css)
3588
{
3589
	struct cgroup_subsys *ss = css->ss;
3590

T
Tejun Heo 已提交
3591
	lockdep_assert_held(&cgroup_tree_mutex);
3592 3593 3594 3595 3596
	lockdep_assert_held(&cgroup_mutex);

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

3597
	if (ss->css_offline)
3598
		ss->css_offline(css);
3599

3600
	css->flags &= ~CSS_ONLINE;
3601
	css->cgroup->nr_css--;
3602
	RCU_INIT_POINTER(css->cgroup->subsys[ss->id], css);
3603 3604
}

3605 3606 3607 3608 3609 3610 3611 3612 3613 3614 3615 3616 3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629 3630 3631
/**
 * create_css - create a cgroup_subsys_state
 * @cgrp: the cgroup new css will be associated with
 * @ss: the subsys of new css
 *
 * Create a new css associated with @cgrp - @ss pair.  On success, the new
 * css is online and installed in @cgrp with all interface files created.
 * Returns 0 on success, -errno on failure.
 */
static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss)
{
	struct cgroup *parent = cgrp->parent;
	struct cgroup_subsys_state *css;
	int err;

	lockdep_assert_held(&cgroup_mutex);

	css = ss->css_alloc(cgroup_css(parent, ss));
	if (IS_ERR(css))
		return PTR_ERR(css);

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

	init_css(css, ss, cgrp);

3632
	err = cgroup_populate_dir(cgrp, 1 << ss->id);
3633 3634 3635 3636 3637 3638 3639
	if (err)
		goto err_free;

	err = online_css(css);
	if (err)
		goto err_free;

3640
	cgroup_get(cgrp);
3641 3642
	css_get(css->parent);

3643 3644
	cgrp->subsys_mask |= 1 << ss->id;

3645 3646 3647 3648 3649 3650 3651 3652 3653 3654 3655 3656 3657 3658 3659 3660 3661
	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;
	}

	return 0;

err_free:
	percpu_ref_cancel_init(&css->refcnt);
	ss->css_free(css);
	return err;
}

T
Tejun Heo 已提交
3662
/**
L
Li Zefan 已提交
3663 3664
 * cgroup_create - create a cgroup
 * @parent: cgroup that will be parent of the new cgroup
T
Tejun Heo 已提交
3665
 * @name: name of the new cgroup
T
Tejun Heo 已提交
3666
 * @mode: mode to set on new cgroup
3667
 */
T
Tejun Heo 已提交
3668
static long cgroup_create(struct cgroup *parent, const char *name,
T
Tejun Heo 已提交
3669
			  umode_t mode)
3670
{
3671
	struct cgroup *cgrp;
3672
	struct cgroup_root *root = parent->root;
3673
	int ssid, err;
3674
	struct cgroup_subsys *ss;
T
Tejun Heo 已提交
3675
	struct kernfs_node *kn;
3676

T
Tejun Heo 已提交
3677 3678 3679 3680 3681 3682 3683
	/*
	 * XXX: The default hierarchy isn't fully implemented yet.  Block
	 * !root cgroup creation on it for now.
	 */
	if (root == &cgrp_dfl_root)
		return -EINVAL;

T
Tejun Heo 已提交
3684
	/* allocate the cgroup and its ID, 0 is reserved for the root */
3685 3686
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
3687 3688
		return -ENOMEM;

T
Tejun Heo 已提交
3689 3690
	mutex_lock(&cgroup_tree_mutex);

3691 3692 3693 3694 3695 3696 3697 3698 3699
	/*
	 * 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
3700
		goto err_unlock_tree;
3701 3702 3703 3704 3705 3706 3707 3708 3709 3710
	}

	/*
	 * Temporarily set the pointer to NULL, so idr_find() won't return
	 * a half-baked cgroup.
	 */
	cgrp->id = idr_alloc(&root->cgroup_idr, NULL, 1, 0, GFP_KERNEL);
	if (cgrp->id < 0) {
		err = -ENOMEM;
		goto err_unlock;
3711 3712
	}

3713
	init_cgroup_housekeeping(cgrp);
3714

3715
	cgrp->parent = parent;
3716
	cgrp->dummy_css.parent = &parent->dummy_css;
3717
	cgrp->root = parent->root;
3718

3719 3720 3721
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

3722 3723
	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3724

T
Tejun Heo 已提交
3725
	/* create the directory */
T
Tejun Heo 已提交
3726
	kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
T
Tejun Heo 已提交
3727 3728
	if (IS_ERR(kn)) {
		err = PTR_ERR(kn);
3729
		goto err_free_id;
T
Tejun Heo 已提交
3730 3731
	}
	cgrp->kn = kn;
3732

3733 3734 3735 3736 3737 3738
	/*
	 * This extra ref will be put in cgroup_free_fn() and guarantees
	 * that @cgrp->kn is always accessible.
	 */
	kernfs_get(kn);

3739
	cgrp->serial_nr = cgroup_serial_nr_next++;
3740

3741 3742
	/* allocation complete, commit to creation */
	list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
3743
	atomic_inc(&root->nr_cgrps);
3744
	cgroup_get(parent);
3745

3746 3747 3748 3749
	/*
	 * @cgrp is now fully operational.  If something fails after this
	 * point, it'll be released via the normal destruction path.
	 */
3750 3751
	idr_replace(&root->cgroup_idr, cgrp, cgrp->id);

3752
	err = cgroup_addrm_files(cgrp, cgroup_base_files, true);
3753 3754 3755
	if (err)
		goto err_destroy;

3756
	/* let's create and online css's */
T
Tejun Heo 已提交
3757
	for_each_subsys(ss, ssid) {
3758
		if (root->cgrp.subsys_mask & (1 << ssid)) {
T
Tejun Heo 已提交
3759 3760 3761 3762
			err = create_css(cgrp, ss);
			if (err)
				goto err_destroy;
		}
3763
	}
3764

T
Tejun Heo 已提交
3765 3766
	kernfs_activate(kn);

3767
	mutex_unlock(&cgroup_mutex);
T
Tejun Heo 已提交
3768
	mutex_unlock(&cgroup_tree_mutex);
3769 3770 3771

	return 0;

T
Tejun Heo 已提交
3772
err_free_id:
3773
	idr_remove(&root->cgroup_idr, cgrp->id);
3774 3775
err_unlock:
	mutex_unlock(&cgroup_mutex);
T
Tejun Heo 已提交
3776 3777
err_unlock_tree:
	mutex_unlock(&cgroup_tree_mutex);
3778
	kfree(cgrp);
3779
	return err;
3780 3781 3782 3783

err_destroy:
	cgroup_destroy_locked(cgrp);
	mutex_unlock(&cgroup_mutex);
T
Tejun Heo 已提交
3784
	mutex_unlock(&cgroup_tree_mutex);
3785
	return err;
3786 3787
}

T
Tejun Heo 已提交
3788 3789
static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
			umode_t mode)
3790
{
T
Tejun Heo 已提交
3791
	struct cgroup *parent = parent_kn->priv;
3792
	int ret;
3793

3794 3795 3796 3797 3798 3799 3800 3801 3802 3803 3804 3805 3806 3807
	/*
	 * cgroup_create() grabs cgroup_tree_mutex which nests outside
	 * kernfs active_ref and cgroup_create() already synchronizes
	 * properly against removal through cgroup_lock_live_group().
	 * Break it before calling cgroup_create().
	 */
	cgroup_get(parent);
	kernfs_break_active_protection(parent_kn);

	ret = cgroup_create(parent, name, mode);

	kernfs_unbreak_active_protection(parent_kn);
	cgroup_put(parent);
	return ret;
3808 3809
}

3810 3811 3812 3813 3814
/*
 * This is called when the refcnt of a css is confirmed to be killed.
 * css_tryget() is now guaranteed to fail.
 */
static void css_killed_work_fn(struct work_struct *work)
3815
{
3816 3817 3818
	struct cgroup_subsys_state *css =
		container_of(work, struct cgroup_subsys_state, destroy_work);
	struct cgroup *cgrp = css->cgroup;
3819

T
Tejun Heo 已提交
3820
	mutex_lock(&cgroup_tree_mutex);
3821 3822
	mutex_lock(&cgroup_mutex);

3823 3824 3825 3826 3827 3828
	/*
	 * css_tryget() is guaranteed to fail now.  Tell subsystems to
	 * initate destruction.
	 */
	offline_css(css);

3829 3830 3831 3832 3833
	/*
	 * If @cgrp is marked dead, it's waiting for refs of all css's to
	 * be disabled before proceeding to the second phase of cgroup
	 * destruction.  If we are the last one, kick it off.
	 */
3834
	if (!cgrp->nr_css && cgroup_is_dead(cgrp))
3835 3836 3837
		cgroup_destroy_css_killed(cgrp);

	mutex_unlock(&cgroup_mutex);
T
Tejun Heo 已提交
3838
	mutex_unlock(&cgroup_tree_mutex);
3839 3840 3841 3842 3843 3844 3845 3846 3847

	/*
	 * Put the css refs from kill_css().  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.
	 */
	css_put(css);
3848 3849
}

3850 3851
/* css kill confirmation processing requires process context, bounce */
static void css_killed_ref_fn(struct percpu_ref *ref)
3852 3853 3854 3855
{
	struct cgroup_subsys_state *css =
		container_of(ref, struct cgroup_subsys_state, refcnt);

3856
	INIT_WORK(&css->destroy_work, css_killed_work_fn);
3857
	queue_work(cgroup_destroy_wq, &css->destroy_work);
3858 3859
}

3860
static void __kill_css(struct cgroup_subsys_state *css)
T
Tejun Heo 已提交
3861
{
3862 3863
	lockdep_assert_held(&cgroup_tree_mutex);

T
Tejun Heo 已提交
3864 3865 3866 3867
	/*
	 * This must happen before css is disassociated with its cgroup.
	 * See seq_css() for details.
	 */
3868
	cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
3869

T
Tejun Heo 已提交
3870 3871 3872 3873 3874 3875 3876 3877 3878 3879 3880 3881 3882 3883 3884 3885 3886
	/*
	 * Killing would put the base ref, but we need to keep it alive
	 * until after ->css_offline().
	 */
	css_get(css);

	/*
	 * 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.
	 */
	percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
3887 3888
}

3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909 3910
/**
 * kill_css - destroy a css
 * @css: css to destroy
 *
 * This function initiates destruction of @css by removing cgroup interface
 * files and putting its base reference.  ->css_offline() will be invoked
 * asynchronously once css_tryget() is guaranteed to fail and when the
 * reference count reaches zero, @css will be released.
 */
static void kill_css(struct cgroup_subsys_state *css)
{
	struct cgroup *cgrp = css->cgroup;

	lockdep_assert_held(&cgroup_tree_mutex);

	/* if already killed, noop */
	if (cgrp->subsys_mask & (1 << css->ss->id)) {
		cgrp->subsys_mask &= ~(1 << css->ss->id);
		__kill_css(css);
	}
}

3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934
/**
 * 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.
 */
3935 3936
static int cgroup_destroy_locked(struct cgroup *cgrp)
	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
3937
{
3938
	struct cgroup *child;
T
Tejun Heo 已提交
3939
	struct cgroup_subsys_state *css;
3940
	bool empty;
T
Tejun Heo 已提交
3941
	int ssid;
3942

T
Tejun Heo 已提交
3943
	lockdep_assert_held(&cgroup_tree_mutex);
3944 3945
	lockdep_assert_held(&cgroup_mutex);

3946
	/*
3947
	 * css_set_rwsem synchronizes access to ->cset_links and prevents
3948
	 * @cgrp from being removed while put_css_set() is in progress.
3949
	 */
3950
	down_read(&css_set_rwsem);
3951
	empty = list_empty(&cgrp->cset_links);
3952
	up_read(&css_set_rwsem);
3953
	if (!empty)
3954
		return -EBUSY;
L
Li Zefan 已提交
3955

3956 3957 3958 3959 3960 3961 3962 3963 3964 3965 3966 3967 3968 3969 3970 3971
	/*
	 * Make sure there's no live children.  We can't test ->children
	 * emptiness as dead children linger on it while being destroyed;
	 * otherwise, "rmdir parent/child parent" may fail with -EBUSY.
	 */
	empty = true;
	rcu_read_lock();
	list_for_each_entry_rcu(child, &cgrp->children, sibling) {
		empty = cgroup_is_dead(child);
		if (!empty)
			break;
	}
	rcu_read_unlock();
	if (!empty)
		return -EBUSY;

3972 3973 3974 3975 3976 3977 3978 3979 3980
	/*
	 * 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 css_next_child() to
	 * resume iteration after dropping RCU read lock.  See
	 * css_next_child() for details.
	 */
	set_bit(CGRP_DEAD, &cgrp->flags);

3981
	/*
T
Tejun Heo 已提交
3982 3983
	 * Initiate massacre of all css's.  cgroup_destroy_css_killed()
	 * will be invoked to perform the rest of destruction once the
3984 3985
	 * percpu refs of all css's are confirmed to be killed.  This
	 * involves removing the subsystem's files, drop cgroup_mutex.
3986
	 */
3987
	mutex_unlock(&cgroup_mutex);
T
Tejun Heo 已提交
3988 3989
	for_each_css(css, ssid, cgrp)
		kill_css(css);
3990
	mutex_lock(&cgroup_mutex);
3991 3992 3993 3994 3995 3996 3997 3998

	/* 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);

	/*
3999 4000 4001 4002 4003 4004 4005 4006
	 * If @cgrp has css's attached, the second stage of cgroup
	 * destruction is kicked off from css_killed_work_fn() after the
	 * refs of all attached css's are killed.  If @cgrp doesn't have
	 * any css, we kick it off here.
	 */
	if (!cgrp->nr_css)
		cgroup_destroy_css_killed(cgrp);

T
Tejun Heo 已提交
4007 4008 4009
	/* remove @cgrp directory along with the base files */
	mutex_unlock(&cgroup_mutex);

4010
	/*
T
Tejun Heo 已提交
4011 4012 4013 4014 4015
	 * There are two control paths which try to determine cgroup from
	 * dentry without going through kernfs - cgroupstats_build() and
	 * css_tryget_from_dir().  Those are supported by RCU protecting
	 * clearing of cgrp->kn->priv backpointer, which should happen
	 * after all files under it have been removed.
4016
	 */
4017
	kernfs_remove(cgrp->kn);	/* @cgrp has an extra ref on its kn */
T
Tejun Heo 已提交
4018 4019
	RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL);

4020
	mutex_lock(&cgroup_mutex);
4021

4022 4023 4024
	return 0;
};

4025
/**
4026
 * cgroup_destroy_css_killed - the second step of cgroup destruction
4027 4028 4029
 * @work: cgroup->destroy_free_work
 *
 * This function is invoked from a work item for a cgroup which is being
4030 4031 4032
 * destroyed after all css's are offlined and performs the rest of
 * destruction.  This is the second step of destruction described in the
 * comment above cgroup_destroy_locked().
4033
 */
4034
static void cgroup_destroy_css_killed(struct cgroup *cgrp)
4035 4036 4037
{
	struct cgroup *parent = cgrp->parent;

T
Tejun Heo 已提交
4038
	lockdep_assert_held(&cgroup_tree_mutex);
4039
	lockdep_assert_held(&cgroup_mutex);
4040

4041
	/* delete this cgroup from parent->children */
4042
	list_del_rcu(&cgrp->sibling);
4043

4044
	cgroup_put(cgrp);
4045

4046
	set_bit(CGRP_RELEASABLE, &parent->flags);
4047
	check_for_release(parent);
4048 4049
}

T
Tejun Heo 已提交
4050
static int cgroup_rmdir(struct kernfs_node *kn)
4051
{
T
Tejun Heo 已提交
4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062
	struct cgroup *cgrp = kn->priv;
	int ret = 0;

	/*
	 * This is self-destruction but @kn can't be removed while this
	 * callback is in progress.  Let's break active protection.  Once
	 * the protection is broken, @cgrp can be destroyed at any point.
	 * Pin it so that it stays accessible.
	 */
	cgroup_get(cgrp);
	kernfs_break_active_protection(kn);
4063

T
Tejun Heo 已提交
4064
	mutex_lock(&cgroup_tree_mutex);
4065
	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
4066 4067 4068 4069 4070 4071 4072 4073

	/*
	 * @cgrp might already have been destroyed while we're trying to
	 * grab the mutexes.
	 */
	if (!cgroup_is_dead(cgrp))
		ret = cgroup_destroy_locked(cgrp);

4074
	mutex_unlock(&cgroup_mutex);
T
Tejun Heo 已提交
4075
	mutex_unlock(&cgroup_tree_mutex);
4076

T
Tejun Heo 已提交
4077 4078
	kernfs_unbreak_active_protection(kn);
	cgroup_put(cgrp);
4079 4080 4081
	return ret;
}

T
Tejun Heo 已提交
4082 4083 4084 4085 4086 4087 4088 4089
static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
	.remount_fs		= cgroup_remount,
	.show_options		= cgroup_show_options,
	.mkdir			= cgroup_mkdir,
	.rmdir			= cgroup_rmdir,
	.rename			= cgroup_rename,
};

4090
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4091 4092
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
4093 4094

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4095

T
Tejun Heo 已提交
4096
	mutex_lock(&cgroup_tree_mutex);
4097 4098
	mutex_lock(&cgroup_mutex);

T
Tejun Heo 已提交
4099
	INIT_LIST_HEAD(&ss->cfts);
4100

4101 4102 4103
	/* Create the root cgroup state for this subsystem */
	ss->root = &cgrp_dfl_root;
	css = ss->css_alloc(cgroup_css(&cgrp_dfl_root.cgrp, ss));
4104 4105
	/* We don't handle early failures gracefully */
	BUG_ON(IS_ERR(css));
4106
	init_css(css, ss, &cgrp_dfl_root.cgrp);
4107

L
Li Zefan 已提交
4108
	/* Update the init_css_set to contain a subsys
4109
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
4110
	 * newly registered, all tasks and hence the
4111
	 * init_css_set is in the subsystem's root cgroup. */
4112
	init_css_set.subsys[ss->id] = css;
4113 4114 4115

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

L
Li Zefan 已提交
4116 4117 4118 4119 4120
	/* 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));

4121
	BUG_ON(online_css(css));
4122

4123
	cgrp_dfl_root.cgrp.subsys_mask |= 1 << ss->id;
4124

4125
	mutex_unlock(&cgroup_mutex);
T
Tejun Heo 已提交
4126
	mutex_unlock(&cgroup_tree_mutex);
4127 4128
}

4129
/**
L
Li Zefan 已提交
4130 4131 4132 4133
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
4134 4135 4136
 */
int __init cgroup_init_early(void)
{
T
Tejun Heo 已提交
4137 4138
	static struct cgroup_sb_opts __initdata opts =
		{ .flags = CGRP_ROOT_SANE_BEHAVIOR };
4139
	struct cgroup_subsys *ss;
4140
	int i;
4141

4142
	init_cgroup_root(&cgrp_dfl_root, &opts);
4143
	RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
4144

T
Tejun Heo 已提交
4145
	for_each_subsys(ss, i) {
4146
		WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
4147 4148
		     "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
		     i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
4149
		     ss->id, ss->name);
4150 4151 4152
		WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
		     "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);

4153
		ss->id = i;
4154
		ss->name = cgroup_subsys_name[i];
4155 4156 4157 4158 4159 4160 4161 4162

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

/**
L
Li Zefan 已提交
4163 4164 4165 4166
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
4167 4168 4169
 */
int __init cgroup_init(void)
{
4170
	struct cgroup_subsys *ss;
4171
	unsigned long key;
4172
	int ssid, err;
4173

T
Tejun Heo 已提交
4174
	BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
4175

4176
	mutex_lock(&cgroup_tree_mutex);
T
Tejun Heo 已提交
4177 4178
	mutex_lock(&cgroup_mutex);

4179 4180 4181 4182
	/* Add init_css_set to the hash table */
	key = css_set_hash(init_css_set.subsys);
	hash_add(css_set_table, &init_css_set.hlist, key);

4183
	BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0));
4184

T
Tejun Heo 已提交
4185
	mutex_unlock(&cgroup_mutex);
4186
	mutex_unlock(&cgroup_tree_mutex);
T
Tejun Heo 已提交
4187

4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199
	for_each_subsys(ss, ssid) {
		if (!ss->early_init)
			cgroup_init_subsys(ss);

		/*
		 * cftype registration needs kmalloc and can't be done
		 * during early_init.  Register base cftypes separately.
		 */
		if (ss->base_cftypes)
			WARN_ON(cgroup_add_cftypes(ss, ss->base_cftypes));
	}

4200
	cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
T
Tejun Heo 已提交
4201 4202
	if (!cgroup_kobj)
		return -ENOMEM;
4203

4204
	err = register_filesystem(&cgroup_fs_type);
4205 4206
	if (err < 0) {
		kobject_put(cgroup_kobj);
T
Tejun Heo 已提交
4207
		return err;
4208
	}
4209

L
Li Zefan 已提交
4210
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
T
Tejun Heo 已提交
4211
	return 0;
4212
}
4213

4214 4215 4216 4217 4218
static int __init cgroup_wq_init(void)
{
	/*
	 * There isn't much point in executing destruction path in
	 * parallel.  Good chunk is serialized with cgroup_mutex anyway.
4219
	 * Use 1 for @max_active.
4220 4221 4222 4223
	 *
	 * We would prefer to do this in cgroup_init() above, but that
	 * is called before init_workqueues(): so leave this until after.
	 */
4224
	cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
4225
	BUG_ON(!cgroup_destroy_wq);
4226 4227 4228 4229 4230 4231 4232 4233 4234

	/*
	 * Used to destroy pidlists and separate to serve as flush domain.
	 * Cap @max_active to 1 too.
	 */
	cgroup_pidlist_destroy_wq = alloc_workqueue("cgroup_pidlist_destroy",
						    0, 1);
	BUG_ON(!cgroup_pidlist_destroy_wq);

4235 4236 4237 4238
	return 0;
}
core_initcall(cgroup_wq_init);

4239 4240 4241 4242 4243 4244 4245
/*
 * proc_cgroup_show()
 *  - Print task's cgroup paths into seq_file, one line for each hierarchy
 *  - Used for /proc/<pid>/cgroup.
 */

/* TODO: Use a proper seq_file iterator */
4246
int proc_cgroup_show(struct seq_file *m, void *v)
4247 4248 4249
{
	struct pid *pid;
	struct task_struct *tsk;
T
Tejun Heo 已提交
4250
	char *buf, *path;
4251
	int retval;
4252
	struct cgroup_root *root;
4253 4254

	retval = -ENOMEM;
T
Tejun Heo 已提交
4255
	buf = kmalloc(PATH_MAX, GFP_KERNEL);
4256 4257 4258 4259 4260 4261 4262 4263 4264 4265 4266 4267
	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);
4268
	down_read(&css_set_rwsem);
4269

4270
	for_each_root(root) {
4271
		struct cgroup_subsys *ss;
4272
		struct cgroup *cgrp;
T
Tejun Heo 已提交
4273
		int ssid, count = 0;
4274

T
Tejun Heo 已提交
4275
		if (root == &cgrp_dfl_root && !cgrp_dfl_root_visible)
4276 4277
			continue;

4278
		seq_printf(m, "%d:", root->hierarchy_id);
T
Tejun Heo 已提交
4279
		for_each_subsys(ss, ssid)
4280
			if (root->cgrp.subsys_mask & (1 << ssid))
T
Tejun Heo 已提交
4281
				seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4282 4283 4284
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
4285
		seq_putc(m, ':');
4286
		cgrp = task_cgroup_from_root(tsk, root);
T
Tejun Heo 已提交
4287 4288 4289
		path = cgroup_path(cgrp, buf, PATH_MAX);
		if (!path) {
			retval = -ENAMETOOLONG;
4290
			goto out_unlock;
T
Tejun Heo 已提交
4291 4292
		}
		seq_puts(m, path);
4293 4294 4295 4296
		seq_putc(m, '\n');
	}

out_unlock:
4297
	up_read(&css_set_rwsem);
4298 4299 4300 4301 4302 4303 4304 4305 4306 4307 4308
	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)
{
4309
	struct cgroup_subsys *ss;
4310 4311
	int i;

4312
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
B
Ben Blum 已提交
4313 4314 4315 4316 4317
	/*
	 * 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.
	 */
4318
	mutex_lock(&cgroup_mutex);
4319 4320

	for_each_subsys(ss, i)
4321 4322
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
4323
			   atomic_read(&ss->root->nr_cgrps), !ss->disabled);
4324

4325 4326 4327 4328 4329 4330
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
4331
	return single_open(file, proc_cgroupstats_show, NULL);
4332 4333
}

4334
static const struct file_operations proc_cgroupstats_operations = {
4335 4336 4337 4338 4339 4340
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

4341
/**
4342
 * cgroup_fork - initialize cgroup related fields during copy_process()
L
Li Zefan 已提交
4343
 * @child: pointer to task_struct of forking parent process.
4344
 *
4345 4346 4347
 * A task is associated with the init_css_set until cgroup_post_fork()
 * attaches it to the parent's css_set.  Empty cg_list indicates that
 * @child isn't holding reference to its css_set.
4348 4349 4350
 */
void cgroup_fork(struct task_struct *child)
{
4351
	RCU_INIT_POINTER(child->cgroups, &init_css_set);
4352
	INIT_LIST_HEAD(&child->cg_list);
4353 4354
}

4355
/**
L
Li Zefan 已提交
4356 4357 4358
 * cgroup_post_fork - called on a new task after adding it to the task list
 * @child: the task in question
 *
4359 4360 4361
 * 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
4362
 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
4363
 * list.
L
Li Zefan 已提交
4364
 */
4365 4366
void cgroup_post_fork(struct task_struct *child)
{
4367
	struct cgroup_subsys *ss;
4368 4369
	int i;

4370
	/*
4371 4372 4373 4374 4375 4376 4377 4378 4379 4380 4381 4382 4383 4384 4385 4386 4387 4388 4389
	 * This may race against cgroup_enable_task_cg_links().  As that
	 * function sets use_task_css_set_links before grabbing
	 * tasklist_lock and we just went through tasklist_lock to add
	 * @child, it's guaranteed that either we see the set
	 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
	 * @child during its iteration.
	 *
	 * If we won the race, @child is associated with %current's
	 * css_set.  Grabbing css_set_rwsem guarantees both that the
	 * association is stable, and, on completion of the parent's
	 * migration, @child is visible in the source of migration or
	 * already in the destination cgroup.  This guarantee is necessary
	 * when implementing operations which need to migrate all tasks of
	 * a cgroup to another.
	 *
	 * Note that if we lose to cgroup_enable_task_cg_links(), @child
	 * will remain in init_css_set.  This is safe because all tasks are
	 * in the init_css_set before cg_links is enabled and there's no
	 * operation which transfers all tasks out of init_css_set.
4390
	 */
4391
	if (use_task_css_set_links) {
4392 4393
		struct css_set *cset;

4394
		down_write(&css_set_rwsem);
4395
		cset = task_css_set(current);
4396 4397 4398 4399 4400
		if (list_empty(&child->cg_list)) {
			rcu_assign_pointer(child->cgroups, cset);
			list_add(&child->cg_list, &cset->tasks);
			get_css_set(cset);
		}
4401
		up_write(&css_set_rwsem);
4402
	}
4403 4404 4405 4406 4407 4408 4409

	/*
	 * 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) {
T
Tejun Heo 已提交
4410
		for_each_subsys(ss, i)
4411 4412 4413
			if (ss->fork)
				ss->fork(child);
	}
4414
}
4415

4416 4417 4418
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
4419
 * @run_callback: run exit callbacks?
4420 4421 4422 4423 4424 4425 4426 4427 4428
 *
 * 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.
 *
4429 4430 4431 4432 4433 4434 4435
 * We 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.  No need to bother with
 * init_css_set refcnting.  init_css_set never goes away and we can't race
 * with migration path - either PF_EXITING is visible to migration path or
 * @tsk never got on the tasklist.
4436 4437 4438
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
4439
	struct cgroup_subsys *ss;
4440
	struct css_set *cset;
4441
	bool put_cset = false;
4442
	int i;
4443 4444

	/*
4445 4446
	 * Unlink from @tsk from its css_set.  As migration path can't race
	 * with us, we can check cg_list without grabbing css_set_rwsem.
4447 4448
	 */
	if (!list_empty(&tsk->cg_list)) {
4449
		down_write(&css_set_rwsem);
4450
		list_del_init(&tsk->cg_list);
4451
		up_write(&css_set_rwsem);
4452
		put_cset = true;
4453 4454
	}

4455
	/* Reassign the task to the init_css_set. */
4456 4457
	cset = task_css_set(tsk);
	RCU_INIT_POINTER(tsk->cgroups, &init_css_set);
4458 4459

	if (run_callbacks && need_forkexit_callback) {
T
Tejun Heo 已提交
4460 4461
		/* see cgroup_post_fork() for details */
		for_each_subsys(ss, i) {
4462
			if (ss->exit) {
4463 4464
				struct cgroup_subsys_state *old_css = cset->subsys[i];
				struct cgroup_subsys_state *css = task_css(tsk, i);
4465

4466
				ss->exit(css, old_css, tsk);
4467 4468 4469 4470
			}
		}
	}

4471 4472
	if (put_cset)
		put_css_set(cset, true);
4473
}
4474

4475
static void check_for_release(struct cgroup *cgrp)
4476
{
4477
	if (cgroup_is_releasable(cgrp) &&
T
Tejun Heo 已提交
4478
	    list_empty(&cgrp->cset_links) && list_empty(&cgrp->children)) {
4479 4480
		/*
		 * Control Group is currently removeable. If it's not
4481
		 * already queued for a userspace notification, queue
4482 4483
		 * it now
		 */
4484
		int need_schedule_work = 0;
4485

4486
		raw_spin_lock(&release_list_lock);
4487
		if (!cgroup_is_dead(cgrp) &&
4488 4489
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
4490 4491
			need_schedule_work = 1;
		}
4492
		raw_spin_unlock(&release_list_lock);
4493 4494 4495 4496 4497 4498 4499 4500 4501 4502 4503 4504 4505 4506 4507 4508 4509 4510 4511 4512 4513 4514 4515 4516 4517 4518 4519 4520 4521 4522 4523 4524
		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);
4525
	raw_spin_lock(&release_list_lock);
4526 4527 4528
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
T
Tejun Heo 已提交
4529
		char *pathbuf = NULL, *agentbuf = NULL, *path;
4530
		struct cgroup *cgrp = list_entry(release_list.next,
4531 4532
						    struct cgroup,
						    release_list);
4533
		list_del_init(&cgrp->release_list);
4534
		raw_spin_unlock(&release_list_lock);
T
Tejun Heo 已提交
4535
		pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
4536 4537
		if (!pathbuf)
			goto continue_free;
T
Tejun Heo 已提交
4538 4539
		path = cgroup_path(cgrp, pathbuf, PATH_MAX);
		if (!path)
4540 4541 4542 4543
			goto continue_free;
		agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
		if (!agentbuf)
			goto continue_free;
4544 4545

		i = 0;
4546
		argv[i++] = agentbuf;
T
Tejun Heo 已提交
4547
		argv[i++] = path;
4548 4549 4550 4551 4552 4553 4554 4555 4556 4557 4558 4559 4560 4561
		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);
4562 4563 4564
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
4565
		raw_spin_lock(&release_list_lock);
4566
	}
4567
	raw_spin_unlock(&release_list_lock);
4568 4569
	mutex_unlock(&cgroup_mutex);
}
4570 4571 4572

static int __init cgroup_disable(char *str)
{
4573
	struct cgroup_subsys *ss;
4574
	char *token;
4575
	int i;
4576 4577 4578 4579

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;
4580

T
Tejun Heo 已提交
4581
		for_each_subsys(ss, i) {
4582 4583 4584 4585 4586 4587 4588 4589 4590 4591 4592
			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
4593

4594
/**
4595
 * css_tryget_from_dir - get corresponding css from the dentry of a cgroup dir
4596 4597
 * @dentry: directory dentry of interest
 * @ss: subsystem of interest
4598
 *
4599 4600 4601
 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
 * to get the corresponding css and return it.  If such css doesn't exist
 * or can't be pinned, an ERR_PTR value is returned.
S
Stephane Eranian 已提交
4602
 */
4603 4604
struct cgroup_subsys_state *css_tryget_from_dir(struct dentry *dentry,
						struct cgroup_subsys *ss)
S
Stephane Eranian 已提交
4605
{
T
Tejun Heo 已提交
4606 4607
	struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
	struct cgroup_subsys_state *css = NULL;
S
Stephane Eranian 已提交
4608
	struct cgroup *cgrp;
4609

4610
	/* is @dentry a cgroup dir? */
T
Tejun Heo 已提交
4611 4612
	if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
	    kernfs_type(kn) != KERNFS_DIR)
S
Stephane Eranian 已提交
4613 4614
		return ERR_PTR(-EBADF);

4615 4616
	rcu_read_lock();

T
Tejun Heo 已提交
4617 4618 4619 4620 4621 4622 4623 4624
	/*
	 * This path doesn't originate from kernfs and @kn could already
	 * have been or be removed at any point.  @kn->priv is RCU
	 * protected for this access.  See destroy_locked() for details.
	 */
	cgrp = rcu_dereference(kn->priv);
	if (cgrp)
		css = cgroup_css(cgrp, ss);
4625 4626 4627 4628 4629 4630

	if (!css || !css_tryget(css))
		css = ERR_PTR(-ENOENT);

	rcu_read_unlock();
	return css;
S
Stephane Eranian 已提交
4631 4632
}

4633 4634 4635 4636 4637 4638 4639 4640 4641 4642 4643 4644
/**
 * css_from_id - lookup css by id
 * @id: the cgroup id
 * @ss: cgroup subsys to be looked into
 *
 * Returns the css if there's valid one with @id, otherwise returns NULL.
 * Should be called under rcu_read_lock().
 */
struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
{
	struct cgroup *cgrp;

T
Tejun Heo 已提交
4645
	cgroup_assert_mutexes_or_rcu_locked();
4646 4647 4648

	cgrp = idr_find(&ss->root->cgroup_idr, id);
	if (cgrp)
4649
		return cgroup_css(cgrp, ss);
4650
	return NULL;
S
Stephane Eranian 已提交
4651 4652
}

4653
#ifdef CONFIG_CGROUP_DEBUG
4654 4655
static struct cgroup_subsys_state *
debug_css_alloc(struct cgroup_subsys_state *parent_css)
4656 4657 4658 4659 4660 4661 4662 4663 4664
{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

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

	return css;
}

4665
static void debug_css_free(struct cgroup_subsys_state *css)
4666
{
4667
	kfree(css);
4668 4669
}

4670 4671
static u64 debug_taskcount_read(struct cgroup_subsys_state *css,
				struct cftype *cft)
4672
{
4673
	return cgroup_task_count(css->cgroup);
4674 4675
}

4676 4677
static u64 current_css_set_read(struct cgroup_subsys_state *css,
				struct cftype *cft)
4678 4679 4680 4681
{
	return (u64)(unsigned long)current->cgroups;
}

4682
static u64 current_css_set_refcount_read(struct cgroup_subsys_state *css,
L
Li Zefan 已提交
4683
					 struct cftype *cft)
4684 4685 4686 4687
{
	u64 count;

	rcu_read_lock();
4688
	count = atomic_read(&task_css_set(current)->refcount);
4689 4690 4691 4692
	rcu_read_unlock();
	return count;
}

4693
static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
4694
{
4695
	struct cgrp_cset_link *link;
4696
	struct css_set *cset;
T
Tejun Heo 已提交
4697 4698 4699 4700 4701
	char *name_buf;

	name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
	if (!name_buf)
		return -ENOMEM;
4702

4703
	down_read(&css_set_rwsem);
4704
	rcu_read_lock();
4705
	cset = rcu_dereference(current->cgroups);
4706
	list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
4707 4708
		struct cgroup *c = link->cgrp;

T
Tejun Heo 已提交
4709
		cgroup_name(c, name_buf, NAME_MAX + 1);
4710
		seq_printf(seq, "Root %d group %s\n",
T
Tejun Heo 已提交
4711
			   c->root->hierarchy_id, name_buf);
4712 4713
	}
	rcu_read_unlock();
4714
	up_read(&css_set_rwsem);
T
Tejun Heo 已提交
4715
	kfree(name_buf);
4716 4717 4718 4719
	return 0;
}

#define MAX_TASKS_SHOWN_PER_CSS 25
4720
static int cgroup_css_links_read(struct seq_file *seq, void *v)
4721
{
4722
	struct cgroup_subsys_state *css = seq_css(seq);
4723
	struct cgrp_cset_link *link;
4724

4725
	down_read(&css_set_rwsem);
4726
	list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
4727
		struct css_set *cset = link->cset;
4728 4729
		struct task_struct *task;
		int count = 0;
T
Tejun Heo 已提交
4730

4731
		seq_printf(seq, "css_set %p\n", cset);
T
Tejun Heo 已提交
4732

4733
		list_for_each_entry(task, &cset->tasks, cg_list) {
T
Tejun Heo 已提交
4734 4735 4736 4737 4738 4739 4740 4741 4742
			if (count++ > MAX_TASKS_SHOWN_PER_CSS)
				goto overflow;
			seq_printf(seq, "  task %d\n", task_pid_vnr(task));
		}

		list_for_each_entry(task, &cset->mg_tasks, cg_list) {
			if (count++ > MAX_TASKS_SHOWN_PER_CSS)
				goto overflow;
			seq_printf(seq, "  task %d\n", task_pid_vnr(task));
4743
		}
T
Tejun Heo 已提交
4744 4745 4746
		continue;
	overflow:
		seq_puts(seq, "  ...\n");
4747
	}
4748
	up_read(&css_set_rwsem);
4749 4750 4751
	return 0;
}

4752
static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
4753
{
4754
	return test_bit(CGRP_RELEASABLE, &css->cgroup->flags);
4755 4756 4757 4758 4759 4760 4761 4762 4763 4764 4765 4766 4767 4768 4769 4770 4771 4772
}

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,
	},

4773 4774
	{
		.name = "current_css_set_cg_links",
4775
		.seq_show = current_css_set_cg_links_read,
4776 4777 4778 4779
	},

	{
		.name = "cgroup_css_links",
4780
		.seq_show = cgroup_css_links_read,
4781 4782
	},

4783 4784 4785 4786 4787
	{
		.name = "releasable",
		.read_u64 = releasable_read,
	},

4788 4789
	{ }	/* terminate */
};
4790

4791
struct cgroup_subsys debug_cgrp_subsys = {
4792 4793
	.css_alloc = debug_css_alloc,
	.css_free = debug_css_free,
4794
	.base_cftypes = debug_files,
4795 4796
};
#endif /* CONFIG_CGROUP_DEBUG */