linux - kernel/cgroup.c

5446 lines · 143.1 KiB

1	/*
2	* Generic process-grouping system.
3	*
4	* Based originally on the cpuset system, extracted by Paul Menage
5	* Copyright (C) 2006 Google, Inc
6	*
7	* Notifications support
8	* Copyright (C) 2009 Nokia Corporation
9	* Author: Kirill A. Shutemov
10	*
11	* Copyright notices from the original cpuset code:
12	* --------------------------------------------------
13	* Copyright (C) 2003 BULL SA.
14	* Copyright (C) 2004-2006 Silicon Graphics, Inc.
15	*
16	* Portions derived from Patrick Mochel's sysfs code.
17	* sysfs is Copyright (c) 2001-3 Patrick Mochel
18	*
19	* 2003-10-10 Written by Simon Derr.
20	* 2003-10-22 Updates by Stephen Hemminger.
21	* 2004 May-July Rework by Paul Jackson.
22	* ---------------------------------------------------
23	*
24	* This file is subject to the terms and conditions of the GNU General Public
25	* License. See the file COPYING in the main directory of the Linux
26	* distribution for more details.
27	*/
28
29	#include <linux/cgroup.h>
30	#include <linux/cred.h>
31	#include <linux/ctype.h>
32	#include <linux/errno.h>
33	#include <linux/init_task.h>
34	#include <linux/kernel.h>
35	#include <linux/list.h>
36	#include <linux/mm.h>
37	#include <linux/mutex.h>
38	#include <linux/mount.h>
39	#include <linux/pagemap.h>
40	#include <linux/proc_fs.h>
41	#include <linux/rcupdate.h>
42	#include <linux/sched.h>
43	#include <linux/backing-dev.h>
44	#include <linux/seq_file.h>
45	#include <linux/slab.h>
46	#include <linux/magic.h>
47	#include <linux/spinlock.h>
48	#include <linux/string.h>
49	#include <linux/sort.h>
50	#include <linux/kmod.h>
51	#include <linux/module.h>
52	#include <linux/delayacct.h>
53	#include <linux/cgroupstats.h>
54	#include <linux/hashtable.h>
55	#include <linux/namei.h>
56	#include <linux/pid_namespace.h>
57	#include <linux/idr.h>
58	#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
59	#include <linux/eventfd.h>
60	#include <linux/poll.h>
61	#include <linux/flex_array.h> /* used in cgroup_attach_task */
62	#include <linux/kthread.h>
63
64	#include <linux/atomic.h>
65
66	/* css deactivation bias, makes css->refcnt negative to deny new trygets */
67	#define CSS_DEACT_BIAS INT_MIN
68
69	/*
70	* cgroup_mutex is the master lock. Any modification to cgroup or its
71	* hierarchy must be performed while holding it.
72	*
73	* cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
74	* cgroupfs_root of any cgroup hierarchy - subsys list, flags,
75	* release_agent_path and so on. Modifying requires both cgroup_mutex and
76	* cgroup_root_mutex. Readers can acquire either of the two. This is to
77	* break the following locking order cycle.
78	*
79	* A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
80	* B. namespace_sem -> cgroup_mutex
81	*
82	* B happens only through cgroup_show_options() and using cgroup_root_mutex
83	* breaks it.
84	*/
85	#ifdef CONFIG_PROVE_RCU
86	DEFINE_MUTEX(cgroup_mutex);
87	EXPORT_SYMBOL_GPL(cgroup_mutex); /* only for task_subsys_state_check() */
88	#else
89	static DEFINE_MUTEX(cgroup_mutex);
90	#endif
91
92	static DEFINE_MUTEX(cgroup_root_mutex);
93
94	/*
95	* Generate an array of cgroup subsystem pointers. At boot time, this is
96	* populated with the built in subsystems, and modular subsystems are
97	* registered after that. The mutable section of this array is protected by
98	* cgroup_mutex.
99	*/
100	#define SUBSYS(_x) [_x ## _subsys_id] = &_x ## _subsys,
101	#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
102	static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
103	#include <linux/cgroup_subsys.h>
104	};
105
106	/*
107	* The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
108	* subsystems that are otherwise unattached - it never has more than a
109	* single cgroup, and all tasks are part of that cgroup.
110	*/
111	static struct cgroupfs_root rootnode;
112
113	/*
114	* cgroupfs file entry, pointed to from leaf dentry->d_fsdata.
115	*/
116	struct cfent {
117	struct list_head node;
118	struct dentry *dentry;
119	struct cftype *type;
120
121	/* file xattrs */
122	struct simple_xattrs xattrs;
123	};
124
125	/*
126	* CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
127	* cgroup_subsys->use_id != 0.
128	*/
129	#define CSS_ID_MAX (65535)
130	struct css_id {
131	/*
132	* The css to which this ID points. This pointer is set to valid value
133	* after cgroup is populated. If cgroup is removed, this will be NULL.
134	* This pointer is expected to be RCU-safe because destroy()
135	* is called after synchronize_rcu(). But for safe use, css_tryget()
136	* should be used for avoiding race.
137	*/
138	struct cgroup_subsys_state __rcu *css;
139	/*
140	* ID of this css.
141	*/
142	unsigned short id;
143	/*
144	* Depth in hierarchy which this ID belongs to.
145	*/
146	unsigned short depth;
147	/*
148	* ID is freed by RCU. (and lookup routine is RCU safe.)
149	*/
150	struct rcu_head rcu_head;
151	/*
152	* Hierarchy of CSS ID belongs to.
153	*/
154	unsigned short stack[0]; /* Array of Length (depth+1) */
155	};
156
157	/*
158	* cgroup_event represents events which userspace want to receive.
159	*/
160	struct cgroup_event {
161	/*
162	* Cgroup which the event belongs to.
163	*/
164	struct cgroup *cgrp;
165	/*
166	* Control file which the event associated.
167	*/
168	struct cftype *cft;
169	/*
170	* eventfd to signal userspace about the event.
171	*/
172	struct eventfd_ctx *eventfd;
173	/*
174	* Each of these stored in a list by the cgroup.
175	*/
176	struct list_head list;
177	/*
178	* All fields below needed to unregister event when
179	* userspace closes eventfd.
180	*/
181	poll_table pt;
182	wait_queue_head_t *wqh;
183	wait_queue_t wait;
184	struct work_struct remove;
185	};
186
187	/* The list of hierarchy roots */
188
189	static LIST_HEAD(roots);
190	static int root_count;
191
192	static DEFINE_IDA(hierarchy_ida);
193	static int next_hierarchy_id;
194	static DEFINE_SPINLOCK(hierarchy_id_lock);
195
196	/* dummytop is a shorthand for the dummy hierarchy's top cgroup */
197	#define dummytop (&rootnode.top_cgroup)
198
199	static struct cgroup_name root_cgroup_name = { .name = "/" };
200
201	/* This flag indicates whether tasks in the fork and exit paths should
202	* check for fork/exit handlers to call. This avoids us having to do
203	* extra work in the fork/exit path if none of the subsystems need to
204	* be called.
205	*/
206	static int need_forkexit_callback __read_mostly;
207
208	static int cgroup_destroy_locked(struct cgroup *cgrp);
209	static int cgroup_addrm_files(struct cgroup cgrp, struct cgroup_subsys subsys,
210	struct cftype cfts[], bool is_add);
211
212	static int css_unbias_refcnt(int refcnt)
213	{
214	return refcnt >= 0 ? refcnt : refcnt - CSS_DEACT_BIAS;
215	}
216
217	/* the current nr of refs, always >= 0 whether @css is deactivated or not */
218	static int css_refcnt(struct cgroup_subsys_state *css)
219	{
220	int v = atomic_read(&css->refcnt);
221
222	return css_unbias_refcnt(v);
223	}
224
225	/* convenient tests for these bits */
226	inline int cgroup_is_removed(const struct cgroup *cgrp)
227	{
228	return test_bit(CGRP_REMOVED, &cgrp->flags);
229	}
230
231	/**
232	* cgroup_is_descendant - test ancestry
233	* @cgrp: the cgroup to be tested
234	* @ancestor: possible ancestor of @cgrp
235	*
236	* Test whether @cgrp is a descendant of @ancestor. It also returns %true
237	* if @cgrp == @ancestor. This function is safe to call as long as @cgrp
238	* and @ancestor are accessible.
239	*/
240	bool cgroup_is_descendant(struct cgroup cgrp, struct cgroup ancestor)
241	{
242	while (cgrp) {
243	if (cgrp == ancestor)
244	return true;
245	cgrp = cgrp->parent;
246	}
247	return false;
248	}
249	EXPORT_SYMBOL_GPL(cgroup_is_descendant);
250
251	static int cgroup_is_releasable(const struct cgroup *cgrp)
252	{
253	const int bits =
254	(1 << CGRP_RELEASABLE) \|
255	(1 << CGRP_NOTIFY_ON_RELEASE);
256	return (cgrp->flags & bits) == bits;
257	}
258
259	static int notify_on_release(const struct cgroup *cgrp)
260	{
261	return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
262	}
263
264	/*
265	* for_each_subsys() allows you to iterate on each subsystem attached to
266	* an active hierarchy
267	*/
268	#define for_each_subsys(_root, _ss) \
269	list_for_each_entry(_ss, &_root->subsys_list, sibling)
270
271	/* for_each_active_root() allows you to iterate across the active hierarchies */
272	#define for_each_active_root(_root) \
273	list_for_each_entry(_root, &roots, root_list)
274
275	static inline struct cgroup __d_cgrp(struct dentry dentry)
276	{
277	return dentry->d_fsdata;
278	}
279
280	static inline struct cfent __d_cfe(struct dentry dentry)
281	{
282	return dentry->d_fsdata;
283	}
284
285	static inline struct cftype __d_cft(struct dentry dentry)
286	{
287	return __d_cfe(dentry)->type;
288	}
289
290	/**
291	* cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
292	* @cgrp: the cgroup to be checked for liveness
293	*
294	* On success, returns true; the mutex should be later unlocked. On
295	* failure returns false with no lock held.
296	*/
297	static bool cgroup_lock_live_group(struct cgroup *cgrp)
298	{
299	mutex_lock(&cgroup_mutex);
300	if (cgroup_is_removed(cgrp)) {
301	mutex_unlock(&cgroup_mutex);
302	return false;
303	}
304	return true;
305	}
306
307	/* the list of cgroups eligible for automatic release. Protected by
308	* release_list_lock */
309	static LIST_HEAD(release_list);
310	static DEFINE_RAW_SPINLOCK(release_list_lock);
311	static void cgroup_release_agent(struct work_struct *work);
312	static DECLARE_WORK(release_agent_work, cgroup_release_agent);
313	static void check_for_release(struct cgroup *cgrp);
314
315	/* Link structure for associating css_set objects with cgroups */
316	struct cg_cgroup_link {
317	/*
318	* List running through cg_cgroup_links associated with a
319	* cgroup, anchored on cgroup->css_sets
320	*/
321	struct list_head cgrp_link_list;
322	struct cgroup *cgrp;
323	/*
324	* List running through cg_cgroup_links pointing at a
325	* single css_set object, anchored on css_set->cg_links
326	*/
327	struct list_head cg_link_list;
328	struct css_set *cg;
329	};
330
331	/* The default css_set - used by init and its children prior to any
332	* hierarchies being mounted. It contains a pointer to the root state
333	* for each subsystem. Also used to anchor the list of css_sets. Not
334	* reference-counted, to improve performance when child cgroups
335	* haven't been created.
336	*/
337
338	static struct css_set init_css_set;
339	static struct cg_cgroup_link init_css_set_link;
340
341	static int cgroup_init_idr(struct cgroup_subsys *ss,
342	struct cgroup_subsys_state *css);
343
344	/* css_set_lock protects the list of css_set objects, and the
345	* chain of tasks off each css_set. Nests outside task->alloc_lock
346	* due to cgroup_iter_start() */
347	static DEFINE_RWLOCK(css_set_lock);
348	static int css_set_count;
349
350	/*
351	* hash table for cgroup groups. This improves the performance to find
352	* an existing css_set. This hash doesn't (currently) take into
353	* account cgroups in empty hierarchies.
354	*/
355	#define CSS_SET_HASH_BITS 7
356	static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
357
358	static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
359	{
360	int i;
361	unsigned long key = 0UL;
362
363	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
364	key += (unsigned long)css[i];
365	key = (key >> 16) ^ key;
366
367	return key;
368	}
369
370	/* We don't maintain the lists running through each css_set to its
371	* task until after the first call to cgroup_iter_start(). This
372	* reduces the fork()/exit() overhead for people who have cgroups
373	* compiled into their kernel but not actually in use */
374	static int use_task_css_set_links __read_mostly;
375
376	static void __put_css_set(struct css_set *cg, int taskexit)
377	{
378	struct cg_cgroup_link *link;
379	struct cg_cgroup_link *saved_link;
380	/*
381	* Ensure that the refcount doesn't hit zero while any readers
382	* can see it. Similar to atomic_dec_and_lock(), but for an
383	* rwlock
384	*/
385	if (atomic_add_unless(&cg->refcount, -1, 1))
386	return;
387	write_lock(&css_set_lock);
388	if (!atomic_dec_and_test(&cg->refcount)) {
389	write_unlock(&css_set_lock);
390	return;
391	}
392
393	/* This css_set is dead. unlink it and release cgroup refcounts */
394	hash_del(&cg->hlist);
395	css_set_count--;
396
397	list_for_each_entry_safe(link, saved_link, &cg->cg_links,
398	cg_link_list) {
399	struct cgroup *cgrp = link->cgrp;
400	list_del(&link->cg_link_list);
401	list_del(&link->cgrp_link_list);
402
403	/*
404	* We may not be holding cgroup_mutex, and if cgrp->count is
405	* dropped to 0 the cgroup can be destroyed at any time, hence
406	* rcu_read_lock is used to keep it alive.
407	*/
408	rcu_read_lock();
409	if (atomic_dec_and_test(&cgrp->count) &&
410	notify_on_release(cgrp)) {
411	if (taskexit)
412	set_bit(CGRP_RELEASABLE, &cgrp->flags);
413	check_for_release(cgrp);
414	}
415	rcu_read_unlock();
416
417	kfree(link);
418	}
419
420	write_unlock(&css_set_lock);
421	kfree_rcu(cg, rcu_head);
422	}
423
424	/*
425	* refcounted get/put for css_set objects
426	*/
427	static inline void get_css_set(struct css_set *cg)
428	{
429	atomic_inc(&cg->refcount);
430	}
431
432	static inline void put_css_set(struct css_set *cg)
433	{
434	__put_css_set(cg, 0);
435	}
436
437	static inline void put_css_set_taskexit(struct css_set *cg)
438	{
439	__put_css_set(cg, 1);
440	}
441
442	/*
443	* compare_css_sets - helper function for find_existing_css_set().
444	* @cg: candidate css_set being tested
445	* @old_cg: existing css_set for a task
446	* @new_cgrp: cgroup that's being entered by the task
447	* @template: desired set of css pointers in css_set (pre-calculated)
448	*
449	* Returns true if "cg" matches "old_cg" except for the hierarchy
450	* which "new_cgrp" belongs to, for which it should match "new_cgrp".
451	*/
452	static bool compare_css_sets(struct css_set *cg,
453	struct css_set *old_cg,
454	struct cgroup *new_cgrp,
455	struct cgroup_subsys_state *template[])
456	{
457	struct list_head l1, l2;
458
459	if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
460	/* Not all subsystems matched */
461	return false;
462	}
463
464	/*
465	* Compare cgroup pointers in order to distinguish between
466	* different cgroups in heirarchies with no subsystems. We
467	* could get by with just this check alone (and skip the
468	* memcmp above) but on most setups the memcmp check will
469	* avoid the need for this more expensive check on almost all
470	* candidates.
471	*/
472
473	l1 = &cg->cg_links;
474	l2 = &old_cg->cg_links;
475	while (1) {
476	struct cg_cgroup_link cgl1, cgl2;
477	struct cgroup cg1, cg2;
478
479	l1 = l1->next;
480	l2 = l2->next;
481	/* See if we reached the end - both lists are equal length. */
482	if (l1 == &cg->cg_links) {
483	BUG_ON(l2 != &old_cg->cg_links);
484	break;
485	} else {
486	BUG_ON(l2 == &old_cg->cg_links);
487	}
488	/* Locate the cgroups associated with these links. */
489	cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
490	cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
491	cg1 = cgl1->cgrp;
492	cg2 = cgl2->cgrp;
493	/* Hierarchies should be linked in the same order. */
494	BUG_ON(cg1->root != cg2->root);
495
496	/*
497	* If this hierarchy is the hierarchy of the cgroup
498	* that's changing, then we need to check that this
499	* css_set points to the new cgroup; if it's any other
500	* hierarchy, then this css_set should point to the
501	* same cgroup as the old css_set.
502	*/
503	if (cg1->root == new_cgrp->root) {
504	if (cg1 != new_cgrp)
505	return false;
506	} else {
507	if (cg1 != cg2)
508	return false;
509	}
510	}
511	return true;
512	}
513
514	/*
515	* find_existing_css_set() is a helper for
516	* find_css_set(), and checks to see whether an existing
517	* css_set is suitable.
518	*
519	* oldcg: the cgroup group that we're using before the cgroup
520	* transition
521	*
522	* cgrp: the cgroup that we're moving into
523	*
524	* template: location in which to build the desired set of subsystem
525	* state objects for the new cgroup group
526	*/
527	static struct css_set *find_existing_css_set(
528	struct css_set *oldcg,
529	struct cgroup *cgrp,
530	struct cgroup_subsys_state *template[])
531	{
532	int i;
533	struct cgroupfs_root *root = cgrp->root;
534	struct css_set *cg;
535	unsigned long key;
536
537	/*
538	* Build the set of subsystem state objects that we want to see in the
539	* new css_set. while subsystems can change globally, the entries here
540	* won't change, so no need for locking.
541	*/
542	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
543	if (root->subsys_mask & (1UL << i)) {
544	/* Subsystem is in this hierarchy. So we want
545	* the subsystem state from the new
546	* cgroup */
547	template[i] = cgrp->subsys[i];
548	} else {
549	/* Subsystem is not in this hierarchy, so we
550	* don't want to change the subsystem state */
551	template[i] = oldcg->subsys[i];
552	}
553	}
554
555	key = css_set_hash(template);
556	hash_for_each_possible(css_set_table, cg, hlist, key) {
557	if (!compare_css_sets(cg, oldcg, cgrp, template))
558	continue;
559
560	/* This css_set matches what we need */
561	return cg;
562	}
563
564	/* No existing cgroup group matched */
565	return NULL;
566	}
567
568	static void free_cg_links(struct list_head *tmp)
569	{
570	struct cg_cgroup_link *link;
571	struct cg_cgroup_link *saved_link;
572
573	list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
574	list_del(&link->cgrp_link_list);
575	kfree(link);
576	}
577	}
578
579	/*
580	* allocate_cg_links() allocates "count" cg_cgroup_link structures
581	* and chains them on tmp through their cgrp_link_list fields. Returns 0 on
582	* success or a negative error
583	*/
584	static int allocate_cg_links(int count, struct list_head *tmp)
585	{
586	struct cg_cgroup_link *link;
587	int i;
588	INIT_LIST_HEAD(tmp);
589	for (i = 0; i < count; i++) {
590	link = kmalloc(sizeof(*link), GFP_KERNEL);
591	if (!link) {
592	free_cg_links(tmp);
593	return -ENOMEM;
594	}
595	list_add(&link->cgrp_link_list, tmp);
596	}
597	return 0;
598	}
599
600	/**
601	* link_css_set - a helper function to link a css_set to a cgroup
602	* @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
603	* @cg: the css_set to be linked
604	* @cgrp: the destination cgroup
605	*/
606	static void link_css_set(struct list_head *tmp_cg_links,
607	struct css_set cg, struct cgroup cgrp)
608	{
609	struct cg_cgroup_link *link;
610
611	BUG_ON(list_empty(tmp_cg_links));
612	link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
613	cgrp_link_list);
614	link->cg = cg;
615	link->cgrp = cgrp;
616	atomic_inc(&cgrp->count);
617	list_move(&link->cgrp_link_list, &cgrp->css_sets);
618	/*
619	* Always add links to the tail of the list so that the list
620	* is sorted by order of hierarchy creation
621	*/
622	list_add_tail(&link->cg_link_list, &cg->cg_links);
623	}
624
625	/*
626	* find_css_set() takes an existing cgroup group and a
627	* cgroup object, and returns a css_set object that's
628	* equivalent to the old group, but with the given cgroup
629	* substituted into the appropriate hierarchy. Must be called with
630	* cgroup_mutex held
631	*/
632	static struct css_set *find_css_set(
633	struct css_set oldcg, struct cgroup cgrp)
634	{
635	struct css_set *res;
636	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
637
638	struct list_head tmp_cg_links;
639
640	struct cg_cgroup_link *link;
641	unsigned long key;
642
643	/* First see if we already have a cgroup group that matches
644	* the desired set */
645	read_lock(&css_set_lock);
646	res = find_existing_css_set(oldcg, cgrp, template);
647	if (res)
648	get_css_set(res);
649	read_unlock(&css_set_lock);
650
651	if (res)
652	return res;
653
654	res = kmalloc(sizeof(*res), GFP_KERNEL);
655	if (!res)
656	return NULL;
657
658	/* Allocate all the cg_cgroup_link objects that we'll need */
659	if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
660	kfree(res);
661	return NULL;
662	}
663
664	atomic_set(&res->refcount, 1);
665	INIT_LIST_HEAD(&res->cg_links);
666	INIT_LIST_HEAD(&res->tasks);
667	INIT_HLIST_NODE(&res->hlist);
668
669	/* Copy the set of subsystem state objects generated in
670	* find_existing_css_set() */
671	memcpy(res->subsys, template, sizeof(res->subsys));
672
673	write_lock(&css_set_lock);
674	/* Add reference counts and links from the new css_set. */
675	list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
676	struct cgroup *c = link->cgrp;
677	if (c->root == cgrp->root)
678	c = cgrp;
679	link_css_set(&tmp_cg_links, res, c);
680	}
681
682	BUG_ON(!list_empty(&tmp_cg_links));
683
684	css_set_count++;
685
686	/* Add this cgroup group to the hash table */
687	key = css_set_hash(res->subsys);
688	hash_add(css_set_table, &res->hlist, key);
689
690	write_unlock(&css_set_lock);
691
692	return res;
693	}
694
695	/*
696	* Return the cgroup for "task" from the given hierarchy. Must be
697	* called with cgroup_mutex held.
698	*/
699	static struct cgroup task_cgroup_from_root(struct task_struct task,
700	struct cgroupfs_root *root)
701	{
702	struct css_set *css;
703	struct cgroup *res = NULL;
704
705	BUG_ON(!mutex_is_locked(&cgroup_mutex));
706	read_lock(&css_set_lock);
707	/*
708	* No need to lock the task - since we hold cgroup_mutex the
709	* task can't change groups, so the only thing that can happen
710	* is that it exits and its css is set back to init_css_set.
711	*/
712	css = task->cgroups;
713	if (css == &init_css_set) {
714	res = &root->top_cgroup;
715	} else {
716	struct cg_cgroup_link *link;
717	list_for_each_entry(link, &css->cg_links, cg_link_list) {
718	struct cgroup *c = link->cgrp;
719	if (c->root == root) {
720	res = c;
721	break;
722	}
723	}
724	}
725	read_unlock(&css_set_lock);
726	BUG_ON(!res);
727	return res;
728	}
729
730	/*
731	* There is one global cgroup mutex. We also require taking
732	* task_lock() when dereferencing a task's cgroup subsys pointers.
733	* See "The task_lock() exception", at the end of this comment.
734	*
735	* A task must hold cgroup_mutex to modify cgroups.
736	*
737	* Any task can increment and decrement the count field without lock.
738	* So in general, code holding cgroup_mutex can't rely on the count
739	* field not changing. However, if the count goes to zero, then only
740	* cgroup_attach_task() can increment it again. Because a count of zero
741	* means that no tasks are currently attached, therefore there is no
742	* way a task attached to that cgroup can fork (the other way to
743	* increment the count). So code holding cgroup_mutex can safely
744	* assume that if the count is zero, it will stay zero. Similarly, if
745	* a task holds cgroup_mutex on a cgroup with zero count, it
746	* knows that the cgroup won't be removed, as cgroup_rmdir()
747	* needs that mutex.
748	*
749	* The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
750	* (usually) take cgroup_mutex. These are the two most performance
751	* critical pieces of code here. The exception occurs on cgroup_exit(),
752	* when a task in a notify_on_release cgroup exits. Then cgroup_mutex
753	* is taken, and if the cgroup count is zero, a usermode call made
754	* to the release agent with the name of the cgroup (path relative to
755	* the root of cgroup file system) as the argument.
756	*
757	* A cgroup can only be deleted if both its 'count' of using tasks
758	* is zero, and its list of 'children' cgroups is empty. Since all
759	* tasks in the system use _some_ cgroup, and since there is always at
760	* least one task in the system (init, pid == 1), therefore, top_cgroup
761	* always has either children cgroups and/or using tasks. So we don't
762	* need a special hack to ensure that top_cgroup cannot be deleted.
763	*
764	* The task_lock() exception
765	*
766	* The need for this exception arises from the action of
767	* cgroup_attach_task(), which overwrites one task's cgroup pointer with
768	* another. It does so using cgroup_mutex, however there are
769	* several performance critical places that need to reference
770	* task->cgroup without the expense of grabbing a system global
771	* mutex. Therefore except as noted below, when dereferencing or, as
772	* in cgroup_attach_task(), modifying a task's cgroup pointer we use
773	* task_lock(), which acts on a spinlock (task->alloc_lock) already in
774	* the task_struct routinely used for such matters.
775	*
776	* P.S. One more locking exception. RCU is used to guard the
777	* update of a tasks cgroup pointer by cgroup_attach_task()
778	*/
779
780	/*
781	* A couple of forward declarations required, due to cyclic reference loop:
782	* cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
783	* cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
784	* -> cgroup_mkdir.
785	*/
786
787	static int cgroup_mkdir(struct inode dir, struct dentry dentry, umode_t mode);
788	static struct dentry cgroup_lookup(struct inode , struct dentry *, unsigned int);
789	static int cgroup_rmdir(struct inode unused_dir, struct dentry dentry);
790	static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
791	unsigned long subsys_mask);
792	static const struct inode_operations cgroup_dir_inode_operations;
793	static const struct file_operations proc_cgroupstats_operations;
794
795	static struct backing_dev_info cgroup_backing_dev_info = {
796	.name = "cgroup",
797	.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
798	};
799
800	static int alloc_css_id(struct cgroup_subsys *ss,
801	struct cgroup parent, struct cgroup child);
802
803	static struct inode cgroup_new_inode(umode_t mode, struct super_block sb)
804	{
805	struct inode *inode = new_inode(sb);
806
807	if (inode) {
808	inode->i_ino = get_next_ino();
809	inode->i_mode = mode;
810	inode->i_uid = current_fsuid();
811	inode->i_gid = current_fsgid();
812	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
813	inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
814	}
815	return inode;
816	}
817
818	static struct cgroup_name cgroup_alloc_name(struct dentry dentry)
819	{
820	struct cgroup_name *name;
821
822	name = kmalloc(sizeof(*name) + dentry->d_name.len + 1, GFP_KERNEL);
823	if (!name)
824	return NULL;
825	strcpy(name->name, dentry->d_name.name);
826	return name;
827	}
828
829	static void cgroup_free_fn(struct work_struct *work)
830	{
831	struct cgroup *cgrp = container_of(work, struct cgroup, free_work);
832	struct cgroup_subsys *ss;
833
834	mutex_lock(&cgroup_mutex);
835	/*
836	* Release the subsystem state objects.
837	*/
838	for_each_subsys(cgrp->root, ss)
839	ss->css_free(cgrp);
840
841	cgrp->root->number_of_cgroups--;
842	mutex_unlock(&cgroup_mutex);
843
844	/*
845	* We get a ref to the parent's dentry, and put the ref when
846	* this cgroup is being freed, so it's guaranteed that the
847	* parent won't be destroyed before its children.
848	*/
849	dput(cgrp->parent->dentry);
850
851	ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id);
852
853	/*
854	* Drop the active superblock reference that we took when we
855	* created the cgroup. This will free cgrp->root, if we are
856	* holding the last reference to @sb.
857	*/
858	deactivate_super(cgrp->root->sb);
859
860	/*
861	* if we're getting rid of the cgroup, refcount should ensure
862	* that there are no pidlists left.
863	*/
864	BUG_ON(!list_empty(&cgrp->pidlists));
865
866	simple_xattrs_free(&cgrp->xattrs);
867
868	kfree(rcu_dereference_raw(cgrp->name));
869	kfree(cgrp);
870	}
871
872	static void cgroup_free_rcu(struct rcu_head *head)
873	{
874	struct cgroup *cgrp = container_of(head, struct cgroup, rcu_head);
875
876	schedule_work(&cgrp->free_work);
877	}
878
879	static void cgroup_diput(struct dentry dentry, struct inode inode)
880	{
881	/* is dentry a directory ? if so, kfree() associated cgroup */
882	if (S_ISDIR(inode->i_mode)) {
883	struct cgroup *cgrp = dentry->d_fsdata;
884
885	BUG_ON(!(cgroup_is_removed(cgrp)));
886	call_rcu(&cgrp->rcu_head, cgroup_free_rcu);
887	} else {
888	struct cfent *cfe = __d_cfe(dentry);
889	struct cgroup *cgrp = dentry->d_parent->d_fsdata;
890
891	WARN_ONCE(!list_empty(&cfe->node) &&
892	cgrp != &cgrp->root->top_cgroup,
893	"cfe still linked for %s\n", cfe->type->name);
894	simple_xattrs_free(&cfe->xattrs);
895	kfree(cfe);
896	}
897	iput(inode);
898	}
899
900	static int cgroup_delete(const struct dentry *d)
901	{
902	return 1;
903	}
904
905	static void remove_dir(struct dentry *d)
906	{
907	struct dentry *parent = dget(d->d_parent);
908
909	d_delete(d);
910	simple_rmdir(parent->d_inode, d);
911	dput(parent);
912	}
913
914	static void cgroup_rm_file(struct cgroup cgrp, const struct cftype cft)
915	{
916	struct cfent *cfe;
917
918	lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
919	lockdep_assert_held(&cgroup_mutex);
920
921	/*
922	* If we're doing cleanup due to failure of cgroup_create(),
923	* the corresponding @cfe may not exist.
924	*/
925	list_for_each_entry(cfe, &cgrp->files, node) {
926	struct dentry *d = cfe->dentry;
927
928	if (cft && cfe->type != cft)
929	continue;
930
931	dget(d);
932	d_delete(d);
933	simple_unlink(cgrp->dentry->d_inode, d);
934	list_del_init(&cfe->node);
935	dput(d);
936
937	break;
938	}
939	}
940
941	/**
942	* cgroup_clear_directory - selective removal of base and subsystem files
943	* @dir: directory containing the files
944	* @base_files: true if the base files should be removed
945	* @subsys_mask: mask of the subsystem ids whose files should be removed
946	*/
947	static void cgroup_clear_directory(struct dentry *dir, bool base_files,
948	unsigned long subsys_mask)
949	{
950	struct cgroup *cgrp = __d_cgrp(dir);
951	struct cgroup_subsys *ss;
952
953	for_each_subsys(cgrp->root, ss) {
954	struct cftype_set *set;
955	if (!test_bit(ss->subsys_id, &subsys_mask))
956	continue;
957	list_for_each_entry(set, &ss->cftsets, node)
958	cgroup_addrm_files(cgrp, NULL, set->cfts, false);
959	}
960	if (base_files) {
961	while (!list_empty(&cgrp->files))
962	cgroup_rm_file(cgrp, NULL);
963	}
964	}
965
966	/*
967	* NOTE : the dentry must have been dget()'ed
968	*/
969	static void cgroup_d_remove_dir(struct dentry *dentry)
970	{
971	struct dentry *parent;
972	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
973
974	cgroup_clear_directory(dentry, true, root->subsys_mask);
975
976	parent = dentry->d_parent;
977	spin_lock(&parent->d_lock);
978	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
979	list_del_init(&dentry->d_u.d_child);
980	spin_unlock(&dentry->d_lock);
981	spin_unlock(&parent->d_lock);
982	remove_dir(dentry);
983	}
984
985	/*
986	* Call with cgroup_mutex held. Drops reference counts on modules, including
987	* any duplicate ones that parse_cgroupfs_options took. If this function
988	* returns an error, no reference counts are touched.
989	*/
990	static int rebind_subsystems(struct cgroupfs_root *root,
991	unsigned long final_subsys_mask)
992	{
993	unsigned long added_mask, removed_mask;
994	struct cgroup *cgrp = &root->top_cgroup;
995	int i;
996
997	BUG_ON(!mutex_is_locked(&cgroup_mutex));
998	BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
999
1000	removed_mask = root->actual_subsys_mask & ~final_subsys_mask;
1001	added_mask = final_subsys_mask & ~root->actual_subsys_mask;
1002	/* Check that any added subsystems are currently free */
1003	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1004	unsigned long bit = 1UL << i;
1005	struct cgroup_subsys *ss = subsys[i];
1006	if (!(bit & added_mask))
1007	continue;
1008	/*
1009	* Nobody should tell us to do a subsys that doesn't exist:
1010	* parse_cgroupfs_options should catch that case and refcounts
1011	* ensure that subsystems won't disappear once selected.
1012	*/
1013	BUG_ON(ss == NULL);
1014	if (ss->root != &rootnode) {
1015	/* Subsystem isn't free */
1016	return -EBUSY;
1017	}
1018	}
1019
1020	/* Currently we don't handle adding/removing subsystems when
1021	* any child cgroups exist. This is theoretically supportable
1022	* but involves complex error handling, so it's being left until
1023	* later */
1024	if (root->number_of_cgroups > 1)
1025	return -EBUSY;
1026
1027	/* Process each subsystem */
1028	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1029	struct cgroup_subsys *ss = subsys[i];
1030	unsigned long bit = 1UL << i;
1031	if (bit & added_mask) {
1032	/* We're binding this subsystem to this hierarchy */
1033	BUG_ON(ss == NULL);
1034	BUG_ON(cgrp->subsys[i]);
1035	BUG_ON(!dummytop->subsys[i]);
1036	BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1037	cgrp->subsys[i] = dummytop->subsys[i];
1038	cgrp->subsys[i]->cgroup = cgrp;
1039	list_move(&ss->sibling, &root->subsys_list);
1040	ss->root = root;
1041	if (ss->bind)
1042	ss->bind(cgrp);
1043	/* refcount was already taken, and we're keeping it */
1044	} else if (bit & removed_mask) {
1045	/* We're removing this subsystem */
1046	BUG_ON(ss == NULL);
1047	BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
1048	BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1049	if (ss->bind)
1050	ss->bind(dummytop);
1051	dummytop->subsys[i]->cgroup = dummytop;
1052	cgrp->subsys[i] = NULL;
1053	subsys[i]->root = &rootnode;
1054	list_move(&ss->sibling, &rootnode.subsys_list);
1055	/* subsystem is now free - drop reference on module */
1056	module_put(ss->module);
1057	} else if (bit & final_subsys_mask) {
1058	/* Subsystem state should already exist */
1059	BUG_ON(ss == NULL);
1060	BUG_ON(!cgrp->subsys[i]);
1061	/*
1062	* a refcount was taken, but we already had one, so
1063	* drop the extra reference.
1064	*/
1065	module_put(ss->module);
1066	#ifdef CONFIG_MODULE_UNLOAD
1067	BUG_ON(ss->module && !module_refcount(ss->module));
1068	#endif
1069	} else {
1070	/* Subsystem state shouldn't exist */
1071	BUG_ON(cgrp->subsys[i]);
1072	}
1073	}
1074	root->subsys_mask = root->actual_subsys_mask = final_subsys_mask;
1075
1076	return 0;
1077	}
1078
1079	static int cgroup_show_options(struct seq_file seq, struct dentry dentry)
1080	{
1081	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1082	struct cgroup_subsys *ss;
1083
1084	mutex_lock(&cgroup_root_mutex);
1085	for_each_subsys(root, ss)
1086	seq_printf(seq, ",%s", ss->name);
1087	if (root->flags & CGRP_ROOT_SANE_BEHAVIOR)
1088	seq_puts(seq, ",sane_behavior");
1089	if (root->flags & CGRP_ROOT_NOPREFIX)
1090	seq_puts(seq, ",noprefix");
1091	if (root->flags & CGRP_ROOT_XATTR)
1092	seq_puts(seq, ",xattr");
1093	if (strlen(root->release_agent_path))
1094	seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1095	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags))
1096	seq_puts(seq, ",clone_children");
1097	if (strlen(root->name))
1098	seq_printf(seq, ",name=%s", root->name);
1099	mutex_unlock(&cgroup_root_mutex);
1100	return 0;
1101	}
1102
1103	struct cgroup_sb_opts {
1104	unsigned long subsys_mask;
1105	unsigned long flags;
1106	char *release_agent;
1107	bool cpuset_clone_children;
1108	char *name;
1109	/* User explicitly requested empty subsystem */
1110	bool none;
1111
1112	struct cgroupfs_root *new_root;
1113
1114	};
1115
1116	/*
1117	* Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
1118	* with cgroup_mutex held to protect the subsys[] array. This function takes
1119	* refcounts on subsystems to be used, unless it returns error, in which case
1120	* no refcounts are taken.
1121	*/
1122	static int parse_cgroupfs_options(char data, struct cgroup_sb_opts opts)
1123	{
1124	char token, o = data;
1125	bool all_ss = false, one_ss = false;
1126	unsigned long mask = (unsigned long)-1;
1127	int i;
1128	bool module_pin_failed = false;
1129
1130	BUG_ON(!mutex_is_locked(&cgroup_mutex));
1131
1132	#ifdef CONFIG_CPUSETS
1133	mask = ~(1UL << cpuset_subsys_id);
1134	#endif
1135
1136	memset(opts, 0, sizeof(*opts));
1137
1138	while ((token = strsep(&o, ",")) != NULL) {
1139	if (!*token)
1140	return -EINVAL;
1141	if (!strcmp(token, "none")) {
1142	/* Explicitly have no subsystems */
1143	opts->none = true;
1144	continue;
1145	}
1146	if (!strcmp(token, "all")) {
1147	/* Mutually exclusive option 'all' + subsystem name */
1148	if (one_ss)
1149	return -EINVAL;
1150	all_ss = true;
1151	continue;
1152	}
1153	if (!strcmp(token, "__DEVEL__sane_behavior")) {
1154	opts->flags \|= CGRP_ROOT_SANE_BEHAVIOR;
1155	continue;
1156	}
1157	if (!strcmp(token, "noprefix")) {
1158	opts->flags \|= CGRP_ROOT_NOPREFIX;
1159	continue;
1160	}
1161	if (!strcmp(token, "clone_children")) {
1162	opts->cpuset_clone_children = true;
1163	continue;
1164	}
1165	if (!strcmp(token, "xattr")) {
1166	opts->flags \|= CGRP_ROOT_XATTR;
1167	continue;
1168	}
1169	if (!strncmp(token, "release_agent=", 14)) {
1170	/* Specifying two release agents is forbidden */
1171	if (opts->release_agent)
1172	return -EINVAL;
1173	opts->release_agent =
1174	kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1175	if (!opts->release_agent)
1176	return -ENOMEM;
1177	continue;
1178	}
1179	if (!strncmp(token, "name=", 5)) {
1180	const char *name = token + 5;
1181	/* Can't specify an empty name */
1182	if (!strlen(name))
1183	return -EINVAL;
1184	/* Must match [\w.-]+ */
1185	for (i = 0; i < strlen(name); i++) {
1186	char c = name[i];
1187	if (isalnum(c))
1188	continue;
1189	if ((c == '.') \|\| (c == '-') \|\| (c == '_'))
1190	continue;
1191	return -EINVAL;
1192	}
1193	/* Specifying two names is forbidden */
1194	if (opts->name)
1195	return -EINVAL;
1196	opts->name = kstrndup(name,
1197	MAX_CGROUP_ROOT_NAMELEN - 1,
1198	GFP_KERNEL);
1199	if (!opts->name)
1200	return -ENOMEM;
1201
1202	continue;
1203	}
1204
1205	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1206	struct cgroup_subsys *ss = subsys[i];
1207	if (ss == NULL)
1208	continue;
1209	if (strcmp(token, ss->name))
1210	continue;
1211	if (ss->disabled)
1212	continue;
1213
1214	/* Mutually exclusive option 'all' + subsystem name */
1215	if (all_ss)
1216	return -EINVAL;
1217	set_bit(i, &opts->subsys_mask);
1218	one_ss = true;
1219
1220	break;
1221	}
1222	if (i == CGROUP_SUBSYS_COUNT)
1223	return -ENOENT;
1224	}
1225
1226	/*
1227	* If the 'all' option was specified select all the subsystems,
1228	* otherwise if 'none', 'name=' and a subsystem name options
1229	* were not specified, let's default to 'all'
1230	*/
1231	if (all_ss \|\| (!one_ss && !opts->none && !opts->name)) {
1232	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1233	struct cgroup_subsys *ss = subsys[i];
1234	if (ss == NULL)
1235	continue;
1236	if (ss->disabled)
1237	continue;
1238	set_bit(i, &opts->subsys_mask);
1239	}
1240	}
1241
1242	/* Consistency checks */
1243
1244	if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
1245	pr_warning("cgroup: sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
1246
1247	if (opts->flags & CGRP_ROOT_NOPREFIX) {
1248	pr_err("cgroup: sane_behavior: noprefix is not allowed\n");
1249	return -EINVAL;
1250	}
1251
1252	if (opts->cpuset_clone_children) {
1253	pr_err("cgroup: sane_behavior: clone_children is not allowed\n");
1254	return -EINVAL;
1255	}
1256	}
1257
1258	/*
1259	* Option noprefix was introduced just for backward compatibility
1260	* with the old cpuset, so we allow noprefix only if mounting just
1261	* the cpuset subsystem.
1262	*/
1263	if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
1264	return -EINVAL;
1265
1266
1267	/* Can't specify "none" and some subsystems */
1268	if (opts->subsys_mask && opts->none)
1269	return -EINVAL;
1270
1271	/*
1272	* We either have to specify by name or by subsystems. (So all
1273	* empty hierarchies must have a name).
1274	*/
1275	if (!opts->subsys_mask && !opts->name)
1276	return -EINVAL;
1277
1278	/*
1279	* Grab references on all the modules we'll need, so the subsystems
1280	* don't dance around before rebind_subsystems attaches them. This may
1281	* take duplicate reference counts on a subsystem that's already used,
1282	* but rebind_subsystems handles this case.
1283	*/
1284	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1285	unsigned long bit = 1UL << i;
1286
1287	if (!(bit & opts->subsys_mask))
1288	continue;
1289	if (!try_module_get(subsys[i]->module)) {
1290	module_pin_failed = true;
1291	break;
1292	}
1293	}
1294	if (module_pin_failed) {
1295	/*
1296	* oops, one of the modules was going away. this means that we
1297	* raced with a module_delete call, and to the user this is
1298	* essentially a "subsystem doesn't exist" case.
1299	*/
1300	for (i--; i >= 0; i--) {
1301	/* drop refcounts only on the ones we took */
1302	unsigned long bit = 1UL << i;
1303
1304	if (!(bit & opts->subsys_mask))
1305	continue;
1306	module_put(subsys[i]->module);
1307	}
1308	return -ENOENT;
1309	}
1310
1311	return 0;
1312	}
1313
1314	static void drop_parsed_module_refcounts(unsigned long subsys_mask)
1315	{
1316	int i;
1317	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1318	unsigned long bit = 1UL << i;
1319
1320	if (!(bit & subsys_mask))
1321	continue;
1322	module_put(subsys[i]->module);
1323	}
1324	}
1325
1326	static int cgroup_remount(struct super_block sb, int flags, char *data)
1327	{
1328	int ret = 0;
1329	struct cgroupfs_root *root = sb->s_fs_info;
1330	struct cgroup *cgrp = &root->top_cgroup;
1331	struct cgroup_sb_opts opts;
1332	unsigned long added_mask, removed_mask;
1333
1334	if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) {
1335	pr_err("cgroup: sane_behavior: remount is not allowed\n");
1336	return -EINVAL;
1337	}
1338
1339	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1340	mutex_lock(&cgroup_mutex);
1341	mutex_lock(&cgroup_root_mutex);
1342
1343	/* See what subsystems are wanted */
1344	ret = parse_cgroupfs_options(data, &opts);
1345	if (ret)
1346	goto out_unlock;
1347
1348	if (opts.subsys_mask != root->actual_subsys_mask \|\| opts.release_agent)
1349	pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
1350	task_tgid_nr(current), current->comm);
1351
1352	added_mask = opts.subsys_mask & ~root->subsys_mask;
1353	removed_mask = root->subsys_mask & ~opts.subsys_mask;
1354
1355	/* Don't allow flags or name to change at remount */
1356	if (opts.flags != root->flags \|\|
1357	(opts.name && strcmp(opts.name, root->name))) {
1358	ret = -EINVAL;
1359	drop_parsed_module_refcounts(opts.subsys_mask);
1360	goto out_unlock;
1361	}
1362
1363	/*
1364	* Clear out the files of subsystems that should be removed, do
1365	* this before rebind_subsystems, since rebind_subsystems may
1366	* change this hierarchy's subsys_list.
1367	*/
1368	cgroup_clear_directory(cgrp->dentry, false, removed_mask);
1369
1370	ret = rebind_subsystems(root, opts.subsys_mask);
1371	if (ret) {
1372	/* rebind_subsystems failed, re-populate the removed files */
1373	cgroup_populate_dir(cgrp, false, removed_mask);
1374	drop_parsed_module_refcounts(opts.subsys_mask);
1375	goto out_unlock;
1376	}
1377
1378	/* re-populate subsystem files */
1379	cgroup_populate_dir(cgrp, false, added_mask);
1380
1381	if (opts.release_agent)
1382	strcpy(root->release_agent_path, opts.release_agent);
1383	out_unlock:
1384	kfree(opts.release_agent);
1385	kfree(opts.name);
1386	mutex_unlock(&cgroup_root_mutex);
1387	mutex_unlock(&cgroup_mutex);
1388	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1389	return ret;
1390	}
1391
1392	static const struct super_operations cgroup_ops = {
1393	.statfs = simple_statfs,
1394	.drop_inode = generic_delete_inode,
1395	.show_options = cgroup_show_options,
1396	.remount_fs = cgroup_remount,
1397	};
1398
1399	static void init_cgroup_housekeeping(struct cgroup *cgrp)
1400	{
1401	INIT_LIST_HEAD(&cgrp->sibling);
1402	INIT_LIST_HEAD(&cgrp->children);
1403	INIT_LIST_HEAD(&cgrp->files);
1404	INIT_LIST_HEAD(&cgrp->css_sets);
1405	INIT_LIST_HEAD(&cgrp->allcg_node);
1406	INIT_LIST_HEAD(&cgrp->release_list);
1407	INIT_LIST_HEAD(&cgrp->pidlists);
1408	INIT_WORK(&cgrp->free_work, cgroup_free_fn);
1409	mutex_init(&cgrp->pidlist_mutex);
1410	INIT_LIST_HEAD(&cgrp->event_list);
1411	spin_lock_init(&cgrp->event_list_lock);
1412	simple_xattrs_init(&cgrp->xattrs);
1413	}
1414
1415	static void init_cgroup_root(struct cgroupfs_root *root)
1416	{
1417	struct cgroup *cgrp = &root->top_cgroup;
1418
1419	INIT_LIST_HEAD(&root->subsys_list);
1420	INIT_LIST_HEAD(&root->root_list);
1421	INIT_LIST_HEAD(&root->allcg_list);
1422	root->number_of_cgroups = 1;
1423	cgrp->root = root;
1424	cgrp->name = &root_cgroup_name;
1425	init_cgroup_housekeeping(cgrp);
1426	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1427	}
1428
1429	static bool init_root_id(struct cgroupfs_root *root)
1430	{
1431	int ret = 0;
1432
1433	do {
1434	if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
1435	return false;
1436	spin_lock(&hierarchy_id_lock);
1437	/* Try to allocate the next unused ID */
1438	ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
1439	&root->hierarchy_id);
1440	if (ret == -ENOSPC)
1441	/* Try again starting from 0 */
1442	ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
1443	if (!ret) {
1444	next_hierarchy_id = root->hierarchy_id + 1;
1445	} else if (ret != -EAGAIN) {
1446	/* Can only get here if the 31-bit IDR is full ... */
1447	BUG_ON(ret);
1448	}
1449	spin_unlock(&hierarchy_id_lock);
1450	} while (ret);
1451	return true;
1452	}
1453
1454	static int cgroup_test_super(struct super_block sb, void data)
1455	{
1456	struct cgroup_sb_opts *opts = data;
1457	struct cgroupfs_root *root = sb->s_fs_info;
1458
1459	/* If we asked for a name then it must match */
1460	if (opts->name && strcmp(opts->name, root->name))
1461	return 0;
1462
1463	/*
1464	* If we asked for subsystems (or explicitly for no
1465	* subsystems) then they must match
1466	*/
1467	if ((opts->subsys_mask \|\| opts->none)
1468	&& (opts->subsys_mask != root->subsys_mask))
1469	return 0;
1470
1471	return 1;
1472	}
1473
1474	static struct cgroupfs_root cgroup_root_from_opts(struct cgroup_sb_opts opts)
1475	{
1476	struct cgroupfs_root *root;
1477
1478	if (!opts->subsys_mask && !opts->none)
1479	return NULL;
1480
1481	root = kzalloc(sizeof(*root), GFP_KERNEL);
1482	if (!root)
1483	return ERR_PTR(-ENOMEM);
1484
1485	if (!init_root_id(root)) {
1486	kfree(root);
1487	return ERR_PTR(-ENOMEM);
1488	}
1489	init_cgroup_root(root);
1490
1491	root->subsys_mask = opts->subsys_mask;
1492	root->flags = opts->flags;
1493	ida_init(&root->cgroup_ida);
1494	if (opts->release_agent)
1495	strcpy(root->release_agent_path, opts->release_agent);
1496	if (opts->name)
1497	strcpy(root->name, opts->name);
1498	if (opts->cpuset_clone_children)
1499	set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags);
1500	return root;
1501	}
1502
1503	static void cgroup_drop_root(struct cgroupfs_root *root)
1504	{
1505	if (!root)
1506	return;
1507
1508	BUG_ON(!root->hierarchy_id);
1509	spin_lock(&hierarchy_id_lock);
1510	ida_remove(&hierarchy_ida, root->hierarchy_id);
1511	spin_unlock(&hierarchy_id_lock);
1512	ida_destroy(&root->cgroup_ida);
1513	kfree(root);
1514	}
1515
1516	static int cgroup_set_super(struct super_block sb, void data)
1517	{
1518	int ret;
1519	struct cgroup_sb_opts *opts = data;
1520
1521	/* If we don't have a new root, we can't set up a new sb */
1522	if (!opts->new_root)
1523	return -EINVAL;
1524
1525	BUG_ON(!opts->subsys_mask && !opts->none);
1526
1527	ret = set_anon_super(sb, NULL);
1528	if (ret)
1529	return ret;
1530
1531	sb->s_fs_info = opts->new_root;
1532	opts->new_root->sb = sb;
1533
1534	sb->s_blocksize = PAGE_CACHE_SIZE;
1535	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
1536	sb->s_magic = CGROUP_SUPER_MAGIC;
1537	sb->s_op = &cgroup_ops;
1538
1539	return 0;
1540	}
1541
1542	static int cgroup_get_rootdir(struct super_block *sb)
1543	{
1544	static const struct dentry_operations cgroup_dops = {
1545	.d_iput = cgroup_diput,
1546	.d_delete = cgroup_delete,
1547	};
1548
1549	struct inode *inode =
1550	cgroup_new_inode(S_IFDIR \| S_IRUGO \| S_IXUGO \| S_IWUSR, sb);
1551
1552	if (!inode)
1553	return -ENOMEM;
1554
1555	inode->i_fop = &simple_dir_operations;
1556	inode->i_op = &cgroup_dir_inode_operations;
1557	/* directories start off with i_nlink == 2 (for "." entry) */
1558	inc_nlink(inode);
1559	sb->s_root = d_make_root(inode);
1560	if (!sb->s_root)
1561	return -ENOMEM;
1562	/* for everything else we want ->d_op set */
1563	sb->s_d_op = &cgroup_dops;
1564	return 0;
1565	}
1566
1567	static struct dentry cgroup_mount(struct file_system_type fs_type,
1568	int flags, const char *unused_dev_name,
1569	void *data)
1570	{
1571	struct cgroup_sb_opts opts;
1572	struct cgroupfs_root *root;
1573	int ret = 0;
1574	struct super_block *sb;
1575	struct cgroupfs_root *new_root;
1576	struct inode *inode;
1577
1578	/* First find the desired set of subsystems */
1579	mutex_lock(&cgroup_mutex);
1580	ret = parse_cgroupfs_options(data, &opts);
1581	mutex_unlock(&cgroup_mutex);
1582	if (ret)
1583	goto out_err;
1584
1585	/*
1586	* Allocate a new cgroup root. We may not need it if we're
1587	* reusing an existing hierarchy.
1588	*/
1589	new_root = cgroup_root_from_opts(&opts);
1590	if (IS_ERR(new_root)) {
1591	ret = PTR_ERR(new_root);
1592	goto drop_modules;
1593	}
1594	opts.new_root = new_root;
1595
1596	/* Locate an existing or new sb for this hierarchy */
1597	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
1598	if (IS_ERR(sb)) {
1599	ret = PTR_ERR(sb);
1600	cgroup_drop_root(opts.new_root);
1601	goto drop_modules;
1602	}
1603
1604	root = sb->s_fs_info;
1605	BUG_ON(!root);
1606	if (root == opts.new_root) {
1607	/* We used the new root structure, so this is a new hierarchy */
1608	struct list_head tmp_cg_links;
1609	struct cgroup *root_cgrp = &root->top_cgroup;
1610	struct cgroupfs_root *existing_root;
1611	const struct cred *cred;
1612	int i;
1613	struct css_set *cg;
1614
1615	BUG_ON(sb->s_root != NULL);
1616
1617	ret = cgroup_get_rootdir(sb);
1618	if (ret)
1619	goto drop_new_super;
1620	inode = sb->s_root->d_inode;
1621
1622	mutex_lock(&inode->i_mutex);
1623	mutex_lock(&cgroup_mutex);
1624	mutex_lock(&cgroup_root_mutex);
1625
1626	/* Check for name clashes with existing mounts */
1627	ret = -EBUSY;
1628	if (strlen(root->name))
1629	for_each_active_root(existing_root)
1630	if (!strcmp(existing_root->name, root->name))
1631	goto unlock_drop;
1632
1633	/*
1634	* We're accessing css_set_count without locking
1635	* css_set_lock here, but that's OK - it can only be
1636	* increased by someone holding cgroup_lock, and
1637	* that's us. The worst that can happen is that we
1638	* have some link structures left over
1639	*/
1640	ret = allocate_cg_links(css_set_count, &tmp_cg_links);
1641	if (ret)
1642	goto unlock_drop;
1643
1644	ret = rebind_subsystems(root, root->subsys_mask);
1645	if (ret == -EBUSY) {
1646	free_cg_links(&tmp_cg_links);
1647	goto unlock_drop;
1648	}
1649	/*
1650	* There must be no failure case after here, since rebinding
1651	* takes care of subsystems' refcounts, which are explicitly
1652	* dropped in the failure exit path.
1653	*/
1654
1655	/* EBUSY should be the only error here */
1656	BUG_ON(ret);
1657
1658	list_add(&root->root_list, &roots);
1659	root_count++;
1660
1661	sb->s_root->d_fsdata = root_cgrp;
1662	root->top_cgroup.dentry = sb->s_root;
1663
1664	/* Link the top cgroup in this hierarchy into all
1665	* the css_set objects */
1666	write_lock(&css_set_lock);
1667	hash_for_each(css_set_table, i, cg, hlist)
1668	link_css_set(&tmp_cg_links, cg, root_cgrp);
1669	write_unlock(&css_set_lock);
1670
1671	free_cg_links(&tmp_cg_links);
1672
1673	BUG_ON(!list_empty(&root_cgrp->children));
1674	BUG_ON(root->number_of_cgroups != 1);
1675
1676	cred = override_creds(&init_cred);
1677	cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
1678	revert_creds(cred);
1679	mutex_unlock(&cgroup_root_mutex);
1680	mutex_unlock(&cgroup_mutex);
1681	mutex_unlock(&inode->i_mutex);
1682	} else {
1683	/*
1684	* We re-used an existing hierarchy - the new root (if
1685	* any) is not needed
1686	*/
1687	cgroup_drop_root(opts.new_root);
1688
1689	if (root->flags != opts.flags) {
1690	if ((root->flags \| opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) {
1691	pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n");
1692	ret = -EINVAL;
1693	goto drop_new_super;
1694	} else {
1695	pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n");
1696	}
1697	}
1698
1699	/* no subsys rebinding, so refcounts don't change */
1700	drop_parsed_module_refcounts(opts.subsys_mask);
1701	}
1702
1703	kfree(opts.release_agent);
1704	kfree(opts.name);
1705	return dget(sb->s_root);
1706
1707	unlock_drop:
1708	mutex_unlock(&cgroup_root_mutex);
1709	mutex_unlock(&cgroup_mutex);
1710	mutex_unlock(&inode->i_mutex);
1711	drop_new_super:
1712	deactivate_locked_super(sb);
1713	drop_modules:
1714	drop_parsed_module_refcounts(opts.subsys_mask);
1715	out_err:
1716	kfree(opts.release_agent);
1717	kfree(opts.name);
1718	return ERR_PTR(ret);
1719	}
1720
1721	static void cgroup_kill_sb(struct super_block *sb) {
1722	struct cgroupfs_root *root = sb->s_fs_info;
1723	struct cgroup *cgrp = &root->top_cgroup;
1724	int ret;
1725	struct cg_cgroup_link *link;
1726	struct cg_cgroup_link *saved_link;
1727
1728	BUG_ON(!root);
1729
1730	BUG_ON(root->number_of_cgroups != 1);
1731	BUG_ON(!list_empty(&cgrp->children));
1732
1733	mutex_lock(&cgroup_mutex);
1734	mutex_lock(&cgroup_root_mutex);
1735
1736	/* Rebind all subsystems back to the default hierarchy */
1737	ret = rebind_subsystems(root, 0);
1738	/* Shouldn't be able to fail ... */
1739	BUG_ON(ret);
1740
1741	/*
1742	* Release all the links from css_sets to this hierarchy's
1743	* root cgroup
1744	*/
1745	write_lock(&css_set_lock);
1746
1747	list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
1748	cgrp_link_list) {
1749	list_del(&link->cg_link_list);
1750	list_del(&link->cgrp_link_list);
1751	kfree(link);
1752	}
1753	write_unlock(&css_set_lock);
1754
1755	if (!list_empty(&root->root_list)) {
1756	list_del(&root->root_list);
1757	root_count--;
1758	}
1759
1760	mutex_unlock(&cgroup_root_mutex);
1761	mutex_unlock(&cgroup_mutex);
1762
1763	simple_xattrs_free(&cgrp->xattrs);
1764
1765	kill_litter_super(sb);
1766	cgroup_drop_root(root);
1767	}
1768
1769	static struct file_system_type cgroup_fs_type = {
1770	.name = "cgroup",
1771	.mount = cgroup_mount,
1772	.kill_sb = cgroup_kill_sb,
1773	};
1774
1775	static struct kobject *cgroup_kobj;
1776
1777	/**
1778	* cgroup_path - generate the path of a cgroup
1779	* @cgrp: the cgroup in question
1780	* @buf: the buffer to write the path into
1781	* @buflen: the length of the buffer
1782	*
1783	* Writes path of cgroup into buf. Returns 0 on success, -errno on error.
1784	*
1785	* We can't generate cgroup path using dentry->d_name, as accessing
1786	* dentry->name must be protected by irq-unsafe dentry->d_lock or parent
1787	* inode's i_mutex, while on the other hand cgroup_path() can be called
1788	* with some irq-safe spinlocks held.
1789	*/
1790	int cgroup_path(const struct cgroup cgrp, char buf, int buflen)
1791	{
1792	int ret = -ENAMETOOLONG;
1793	char *start;
1794
1795	if (!cgrp->parent) {
1796	if (strlcpy(buf, "/", buflen) >= buflen)
1797	return -ENAMETOOLONG;
1798	return 0;
1799	}
1800
1801	start = buf + buflen - 1;
1802	*start = '\0';
1803
1804	rcu_read_lock();
1805	do {
1806	const char *name = cgroup_name(cgrp);
1807	int len;
1808
1809	len = strlen(name);
1810	if ((start -= len) < buf)
1811	goto out;
1812	memcpy(start, name, len);
1813
1814	if (--start < buf)
1815	goto out;
1816	*start = '/';
1817
1818	cgrp = cgrp->parent;
1819	} while (cgrp->parent);
1820	ret = 0;
1821	memmove(buf, start, buf + buflen - start);
1822	out:
1823	rcu_read_unlock();
1824	return ret;
1825	}
1826	EXPORT_SYMBOL_GPL(cgroup_path);
1827
1828	/*
1829	* Control Group taskset
1830	*/
1831	struct task_and_cgroup {
1832	struct task_struct *task;
1833	struct cgroup *cgrp;
1834	struct css_set *cg;
1835	};
1836
1837	struct cgroup_taskset {
1838	struct task_and_cgroup single;
1839	struct flex_array *tc_array;
1840	int tc_array_len;
1841	int idx;
1842	struct cgroup *cur_cgrp;
1843	};
1844
1845	/**
1846	* cgroup_taskset_first - reset taskset and return the first task
1847	* @tset: taskset of interest
1848	*
1849	* @tset iteration is initialized and the first task is returned.
1850	*/
1851	struct task_struct cgroup_taskset_first(struct cgroup_taskset tset)
1852	{
1853	if (tset->tc_array) {
1854	tset->idx = 0;
1855	return cgroup_taskset_next(tset);
1856	} else {
1857	tset->cur_cgrp = tset->single.cgrp;
1858	return tset->single.task;
1859	}
1860	}
1861	EXPORT_SYMBOL_GPL(cgroup_taskset_first);
1862
1863	/**
1864	* cgroup_taskset_next - iterate to the next task in taskset
1865	* @tset: taskset of interest
1866	*
1867	* Return the next task in @tset. Iteration must have been initialized
1868	* with cgroup_taskset_first().
1869	*/
1870	struct task_struct cgroup_taskset_next(struct cgroup_taskset tset)
1871	{
1872	struct task_and_cgroup *tc;
1873
1874	if (!tset->tc_array \|\| tset->idx >= tset->tc_array_len)
1875	return NULL;
1876
1877	tc = flex_array_get(tset->tc_array, tset->idx++);
1878	tset->cur_cgrp = tc->cgrp;
1879	return tc->task;
1880	}
1881	EXPORT_SYMBOL_GPL(cgroup_taskset_next);
1882
1883	/**
1884	* cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
1885	* @tset: taskset of interest
1886	*
1887	* Return the cgroup for the current (last returned) task of @tset. This
1888	* function must be preceded by either cgroup_taskset_first() or
1889	* cgroup_taskset_next().
1890	*/
1891	struct cgroup cgroup_taskset_cur_cgroup(struct cgroup_taskset tset)
1892	{
1893	return tset->cur_cgrp;
1894	}
1895	EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);
1896
1897	/**
1898	* cgroup_taskset_size - return the number of tasks in taskset
1899	* @tset: taskset of interest
1900	*/
1901	int cgroup_taskset_size(struct cgroup_taskset *tset)
1902	{
1903	return tset->tc_array ? tset->tc_array_len : 1;
1904	}
1905	EXPORT_SYMBOL_GPL(cgroup_taskset_size);
1906
1907
1908	/*
1909	* cgroup_task_migrate - move a task from one cgroup to another.
1910	*
1911	* Must be called with cgroup_mutex and threadgroup locked.
1912	*/
1913	static void cgroup_task_migrate(struct cgroup *oldcgrp,
1914	struct task_struct tsk, struct css_set newcg)
1915	{
1916	struct css_set *oldcg;
1917
1918	/*
1919	* We are synchronized through threadgroup_lock() against PF_EXITING
1920	* setting such that we can't race against cgroup_exit() changing the
1921	* css_set to init_css_set and dropping the old one.
1922	*/
1923	WARN_ON_ONCE(tsk->flags & PF_EXITING);
1924	oldcg = tsk->cgroups;
1925
1926	task_lock(tsk);
1927	rcu_assign_pointer(tsk->cgroups, newcg);
1928	task_unlock(tsk);
1929
1930	/* Update the css_set linked lists if we're using them */
1931	write_lock(&css_set_lock);
1932	if (!list_empty(&tsk->cg_list))
1933	list_move(&tsk->cg_list, &newcg->tasks);
1934	write_unlock(&css_set_lock);
1935
1936	/*
1937	* We just gained a reference on oldcg by taking it from the task. As
1938	* trading it for newcg is protected by cgroup_mutex, we're safe to drop
1939	* it here; it will be freed under RCU.
1940	*/
1941	set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1942	put_css_set(oldcg);
1943	}
1944
1945	/**
1946	* cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
1947	* @cgrp: the cgroup to attach to
1948	* @tsk: the task or the leader of the threadgroup to be attached
1949	* @threadgroup: attach the whole threadgroup?
1950	*
1951	* Call holding cgroup_mutex and the group_rwsem of the leader. Will take
1952	* task_lock of @tsk or each thread in the threadgroup individually in turn.
1953	*/
1954	static int cgroup_attach_task(struct cgroup cgrp, struct task_struct tsk,
1955	bool threadgroup)
1956	{
1957	int retval, i, group_size;
1958	struct cgroup_subsys ss, failed_ss = NULL;
1959	struct cgroupfs_root *root = cgrp->root;
1960	/* threadgroup list cursor and array */
1961	struct task_struct *leader = tsk;
1962	struct task_and_cgroup *tc;
1963	struct flex_array *group;
1964	struct cgroup_taskset tset = { };
1965
1966	/*
1967	* step 0: in order to do expensive, possibly blocking operations for
1968	* every thread, we cannot iterate the thread group list, since it needs
1969	* rcu or tasklist locked. instead, build an array of all threads in the
1970	* group - group_rwsem prevents new threads from appearing, and if
1971	* threads exit, this will just be an over-estimate.
1972	*/
1973	if (threadgroup)
1974	group_size = get_nr_threads(tsk);
1975	else
1976	group_size = 1;
1977	/* flex_array supports very large thread-groups better than kmalloc. */
1978	group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
1979	if (!group)
1980	return -ENOMEM;
1981	/* pre-allocate to guarantee space while iterating in rcu read-side. */
1982	retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
1983	if (retval)
1984	goto out_free_group_list;
1985
1986	i = 0;
1987	/*
1988	* Prevent freeing of tasks while we take a snapshot. Tasks that are
1989	* already PF_EXITING could be freed from underneath us unless we
1990	* take an rcu_read_lock.
1991	*/
1992	rcu_read_lock();
1993	do {
1994	struct task_and_cgroup ent;
1995
1996	/* @tsk either already exited or can't exit until the end */
1997	if (tsk->flags & PF_EXITING)
1998	continue;
1999
2000	/* as per above, nr_threads may decrease, but not increase. */
2001	BUG_ON(i >= group_size);
2002	ent.task = tsk;
2003	ent.cgrp = task_cgroup_from_root(tsk, root);
2004	/* nothing to do if this task is already in the cgroup */
2005	if (ent.cgrp == cgrp)
2006	continue;
2007	/*
2008	* saying GFP_ATOMIC has no effect here because we did prealloc
2009	* earlier, but it's good form to communicate our expectations.
2010	*/
2011	retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2012	BUG_ON(retval != 0);
2013	i++;
2014
2015	if (!threadgroup)
2016	break;
2017	} while_each_thread(leader, tsk);
2018	rcu_read_unlock();
2019	/* remember the number of threads in the array for later. */
2020	group_size = i;
2021	tset.tc_array = group;
2022	tset.tc_array_len = group_size;
2023
2024	/* methods shouldn't be called if no task is actually migrating */
2025	retval = 0;
2026	if (!group_size)
2027	goto out_free_group_list;
2028
2029	/*
2030	* step 1: check that we can legitimately attach to the cgroup.
2031	*/
2032	for_each_subsys(root, ss) {
2033	if (ss->can_attach) {
2034	retval = ss->can_attach(cgrp, &tset);
2035	if (retval) {
2036	failed_ss = ss;
2037	goto out_cancel_attach;
2038	}
2039	}
2040	}
2041
2042	/*
2043	* step 2: make sure css_sets exist for all threads to be migrated.
2044	* we use find_css_set, which allocates a new one if necessary.
2045	*/
2046	for (i = 0; i < group_size; i++) {
2047	tc = flex_array_get(group, i);
2048	tc->cg = find_css_set(tc->task->cgroups, cgrp);
2049	if (!tc->cg) {
2050	retval = -ENOMEM;
2051	goto out_put_css_set_refs;
2052	}
2053	}
2054
2055	/*
2056	* step 3: now that we're guaranteed success wrt the css_sets,
2057	* proceed to move all tasks to the new cgroup. There are no
2058	* failure cases after here, so this is the commit point.
2059	*/
2060	for (i = 0; i < group_size; i++) {
2061	tc = flex_array_get(group, i);
2062	cgroup_task_migrate(tc->cgrp, tc->task, tc->cg);
2063	}
2064	/* nothing is sensitive to fork() after this point. */
2065
2066	/*
2067	* step 4: do subsystem attach callbacks.
2068	*/
2069	for_each_subsys(root, ss) {
2070	if (ss->attach)
2071	ss->attach(cgrp, &tset);
2072	}
2073
2074	/*
2075	* step 5: success! and cleanup
2076	*/
2077	retval = 0;
2078	out_put_css_set_refs:
2079	if (retval) {
2080	for (i = 0; i < group_size; i++) {
2081	tc = flex_array_get(group, i);
2082	if (!tc->cg)
2083	break;
2084	put_css_set(tc->cg);
2085	}
2086	}
2087	out_cancel_attach:
2088	if (retval) {
2089	for_each_subsys(root, ss) {
2090	if (ss == failed_ss)
2091	break;
2092	if (ss->cancel_attach)
2093	ss->cancel_attach(cgrp, &tset);
2094	}
2095	}
2096	out_free_group_list:
2097	flex_array_free(group);
2098	return retval;
2099	}
2100
2101	/*
2102	* Find the task_struct of the task to attach by vpid and pass it along to the
2103	* function to attach either it or all tasks in its threadgroup. Will lock
2104	* cgroup_mutex and threadgroup; may take task_lock of task.
2105	*/
2106	static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2107	{
2108	struct task_struct *tsk;
2109	const struct cred cred = current_cred(), tcred;
2110	int ret;
2111
2112	if (!cgroup_lock_live_group(cgrp))
2113	return -ENODEV;
2114
2115	retry_find_task:
2116	rcu_read_lock();
2117	if (pid) {
2118	tsk = find_task_by_vpid(pid);
2119	if (!tsk) {
2120	rcu_read_unlock();
2121	ret= -ESRCH;
2122	goto out_unlock_cgroup;
2123	}
2124	/*
2125	* even if we're attaching all tasks in the thread group, we
2126	* only need to check permissions on one of them.
2127	*/
2128	tcred = __task_cred(tsk);
2129	if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
2130	!uid_eq(cred->euid, tcred->uid) &&
2131	!uid_eq(cred->euid, tcred->suid)) {
2132	rcu_read_unlock();
2133	ret = -EACCES;
2134	goto out_unlock_cgroup;
2135	}
2136	} else
2137	tsk = current;
2138
2139	if (threadgroup)
2140	tsk = tsk->group_leader;
2141
2142	/*
2143	* Workqueue threads may acquire PF_NO_SETAFFINITY and become
2144	* trapped in a cpuset, or RT worker may be born in a cgroup
2145	* with no rt_runtime allocated. Just say no.
2146	*/
2147	if (tsk == kthreadd_task \|\| (tsk->flags & PF_NO_SETAFFINITY)) {
2148	ret = -EINVAL;
2149	rcu_read_unlock();
2150	goto out_unlock_cgroup;
2151	}
2152
2153	get_task_struct(tsk);
2154	rcu_read_unlock();
2155
2156	threadgroup_lock(tsk);
2157	if (threadgroup) {
2158	if (!thread_group_leader(tsk)) {
2159	/*
2160	* a race with de_thread from another thread's exec()
2161	* may strip us of our leadership, if this happens,
2162	* there is no choice but to throw this task away and
2163	* try again; this is
2164	* "double-double-toil-and-trouble-check locking".
2165	*/
2166	threadgroup_unlock(tsk);
2167	put_task_struct(tsk);
2168	goto retry_find_task;
2169	}
2170	}
2171
2172	ret = cgroup_attach_task(cgrp, tsk, threadgroup);
2173
2174	threadgroup_unlock(tsk);
2175
2176	put_task_struct(tsk);
2177	out_unlock_cgroup:
2178	mutex_unlock(&cgroup_mutex);
2179	return ret;
2180	}
2181
2182	/**
2183	* cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2184	* @from: attach to all cgroups of a given task
2185	* @tsk: the task to be attached
2186	*/
2187	int cgroup_attach_task_all(struct task_struct from, struct task_struct tsk)
2188	{
2189	struct cgroupfs_root *root;
2190	int retval = 0;
2191
2192	mutex_lock(&cgroup_mutex);
2193	for_each_active_root(root) {
2194	struct cgroup *from_cg = task_cgroup_from_root(from, root);
2195
2196	retval = cgroup_attach_task(from_cg, tsk, false);
2197	if (retval)
2198	break;
2199	}
2200	mutex_unlock(&cgroup_mutex);
2201
2202	return retval;
2203	}
2204	EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2205
2206	static int cgroup_tasks_write(struct cgroup cgrp, struct cftype cft, u64 pid)
2207	{
2208	return attach_task_by_pid(cgrp, pid, false);
2209	}
2210
2211	static int cgroup_procs_write(struct cgroup cgrp, struct cftype cft, u64 tgid)
2212	{
2213	return attach_task_by_pid(cgrp, tgid, true);
2214	}
2215
2216	static int cgroup_release_agent_write(struct cgroup cgrp, struct cftype cft,
2217	const char *buffer)
2218	{
2219	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
2220	if (strlen(buffer) >= PATH_MAX)
2221	return -EINVAL;
2222	if (!cgroup_lock_live_group(cgrp))
2223	return -ENODEV;
2224	mutex_lock(&cgroup_root_mutex);
2225	strcpy(cgrp->root->release_agent_path, buffer);
2226	mutex_unlock(&cgroup_root_mutex);
2227	mutex_unlock(&cgroup_mutex);
2228	return 0;
2229	}
2230
2231	static int cgroup_release_agent_show(struct cgroup cgrp, struct cftype cft,
2232	struct seq_file *seq)
2233	{
2234	if (!cgroup_lock_live_group(cgrp))
2235	return -ENODEV;
2236	seq_puts(seq, cgrp->root->release_agent_path);
2237	seq_putc(seq, '\n');
2238	mutex_unlock(&cgroup_mutex);
2239	return 0;
2240	}
2241
2242	static int cgroup_sane_behavior_show(struct cgroup cgrp, struct cftype cft,
2243	struct seq_file *seq)
2244	{
2245	seq_printf(seq, "%d\n", cgroup_sane_behavior(cgrp));
2246	return 0;
2247	}
2248
2249	/* A buffer size big enough for numbers or short strings */
2250	#define CGROUP_LOCAL_BUFFER_SIZE 64
2251
2252	static ssize_t cgroup_write_X64(struct cgroup cgrp, struct cftype cft,
2253	struct file *file,
2254	const char __user *userbuf,
2255	size_t nbytes, loff_t *unused_ppos)
2256	{
2257	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2258	int retval = 0;
2259	char *end;
2260
2261	if (!nbytes)
2262	return -EINVAL;
2263	if (nbytes >= sizeof(buffer))
2264	return -E2BIG;
2265	if (copy_from_user(buffer, userbuf, nbytes))
2266	return -EFAULT;
2267
2268	buffer[nbytes] = 0; /* nul-terminate */
2269	if (cft->write_u64) {
2270	u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2271	if (*end)
2272	return -EINVAL;
2273	retval = cft->write_u64(cgrp, cft, val);
2274	} else {
2275	s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2276	if (*end)
2277	return -EINVAL;
2278	retval = cft->write_s64(cgrp, cft, val);
2279	}
2280	if (!retval)
2281	retval = nbytes;
2282	return retval;
2283	}
2284
2285	static ssize_t cgroup_write_string(struct cgroup cgrp, struct cftype cft,
2286	struct file *file,
2287	const char __user *userbuf,
2288	size_t nbytes, loff_t *unused_ppos)
2289	{
2290	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2291	int retval = 0;
2292	size_t max_bytes = cft->max_write_len;
2293	char *buffer = local_buffer;
2294
2295	if (!max_bytes)
2296	max_bytes = sizeof(local_buffer) - 1;
2297	if (nbytes >= max_bytes)
2298	return -E2BIG;
2299	/* Allocate a dynamic buffer if we need one */
2300	if (nbytes >= sizeof(local_buffer)) {
2301	buffer = kmalloc(nbytes + 1, GFP_KERNEL);
2302	if (buffer == NULL)
2303	return -ENOMEM;
2304	}
2305	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
2306	retval = -EFAULT;
2307	goto out;
2308	}
2309
2310	buffer[nbytes] = 0; /* nul-terminate */
2311	retval = cft->write_string(cgrp, cft, strstrip(buffer));
2312	if (!retval)
2313	retval = nbytes;
2314	out:
2315	if (buffer != local_buffer)
2316	kfree(buffer);
2317	return retval;
2318	}
2319
2320	static ssize_t cgroup_file_write(struct file file, const char __user buf,
2321	size_t nbytes, loff_t *ppos)
2322	{
2323	struct cftype *cft = __d_cft(file->f_dentry);
2324	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2325
2326	if (cgroup_is_removed(cgrp))
2327	return -ENODEV;
2328	if (cft->write)
2329	return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2330	if (cft->write_u64 \|\| cft->write_s64)
2331	return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2332	if (cft->write_string)
2333	return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2334	if (cft->trigger) {
2335	int ret = cft->trigger(cgrp, (unsigned int)cft->private);
2336	return ret ? ret : nbytes;
2337	}
2338	return -EINVAL;
2339	}
2340
2341	static ssize_t cgroup_read_u64(struct cgroup cgrp, struct cftype cft,
2342	struct file *file,
2343	char __user *buf, size_t nbytes,
2344	loff_t *ppos)
2345	{
2346	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2347	u64 val = cft->read_u64(cgrp, cft);
2348	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
2349
2350	return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2351	}
2352
2353	static ssize_t cgroup_read_s64(struct cgroup cgrp, struct cftype cft,
2354	struct file *file,
2355	char __user *buf, size_t nbytes,
2356	loff_t *ppos)
2357	{
2358	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2359	s64 val = cft->read_s64(cgrp, cft);
2360	int len = sprintf(tmp, "%lld\n", (long long) val);
2361
2362	return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2363	}
2364
2365	static ssize_t cgroup_file_read(struct file file, char __user buf,
2366	size_t nbytes, loff_t *ppos)
2367	{
2368	struct cftype *cft = __d_cft(file->f_dentry);
2369	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2370
2371	if (cgroup_is_removed(cgrp))
2372	return -ENODEV;
2373
2374	if (cft->read)
2375	return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2376	if (cft->read_u64)
2377	return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2378	if (cft->read_s64)
2379	return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2380	return -EINVAL;
2381	}
2382
2383	/*
2384	* seqfile ops/methods for returning structured data. Currently just
2385	* supports string->u64 maps, but can be extended in future.
2386	*/
2387
2388	struct cgroup_seqfile_state {
2389	struct cftype *cft;
2390	struct cgroup *cgroup;
2391	};
2392
2393	static int cgroup_map_add(struct cgroup_map_cb cb, const char key, u64 value)
2394	{
2395	struct seq_file *sf = cb->state;
2396	return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
2397	}
2398
2399	static int cgroup_seqfile_show(struct seq_file m, void arg)
2400	{
2401	struct cgroup_seqfile_state *state = m->private;
2402	struct cftype *cft = state->cft;
2403	if (cft->read_map) {
2404	struct cgroup_map_cb cb = {
2405	.fill = cgroup_map_add,
2406	.state = m,
2407	};
2408	return cft->read_map(state->cgroup, cft, &cb);
2409	}
2410	return cft->read_seq_string(state->cgroup, cft, m);
2411	}
2412
2413	static int cgroup_seqfile_release(struct inode inode, struct file file)
2414	{
2415	struct seq_file *seq = file->private_data;
2416	kfree(seq->private);
2417	return single_release(inode, file);
2418	}
2419
2420	static const struct file_operations cgroup_seqfile_operations = {
2421	.read = seq_read,
2422	.write = cgroup_file_write,
2423	.llseek = seq_lseek,
2424	.release = cgroup_seqfile_release,
2425	};
2426
2427	static int cgroup_file_open(struct inode inode, struct file file)
2428	{
2429	int err;
2430	struct cftype *cft;
2431
2432	err = generic_file_open(inode, file);
2433	if (err)
2434	return err;
2435	cft = __d_cft(file->f_dentry);
2436
2437	if (cft->read_map \|\| cft->read_seq_string) {
2438	struct cgroup_seqfile_state *state =
2439	kzalloc(sizeof(*state), GFP_USER);
2440	if (!state)
2441	return -ENOMEM;
2442	state->cft = cft;
2443	state->cgroup = __d_cgrp(file->f_dentry->d_parent);
2444	file->f_op = &cgroup_seqfile_operations;
2445	err = single_open(file, cgroup_seqfile_show, state);
2446	if (err < 0)
2447	kfree(state);
2448	} else if (cft->open)
2449	err = cft->open(inode, file);
2450	else
2451	err = 0;
2452
2453	return err;
2454	}
2455
2456	static int cgroup_file_release(struct inode inode, struct file file)
2457	{
2458	struct cftype *cft = __d_cft(file->f_dentry);
2459	if (cft->release)
2460	return cft->release(inode, file);
2461	return 0;
2462	}
2463
2464	/*
2465	* cgroup_rename - Only allow simple rename of directories in place.
2466	*/
2467	static int cgroup_rename(struct inode old_dir, struct dentry old_dentry,
2468	struct inode new_dir, struct dentry new_dentry)
2469	{
2470	int ret;
2471	struct cgroup_name name, old_name;
2472	struct cgroup *cgrp;
2473
2474	/*
2475	* It's convinient to use parent dir's i_mutex to protected
2476	* cgrp->name.
2477	*/
2478	lockdep_assert_held(&old_dir->i_mutex);
2479
2480	if (!S_ISDIR(old_dentry->d_inode->i_mode))
2481	return -ENOTDIR;
2482	if (new_dentry->d_inode)
2483	return -EEXIST;
2484	if (old_dir != new_dir)
2485	return -EIO;
2486
2487	cgrp = __d_cgrp(old_dentry);
2488
2489	name = cgroup_alloc_name(new_dentry);
2490	if (!name)
2491	return -ENOMEM;
2492
2493	ret = simple_rename(old_dir, old_dentry, new_dir, new_dentry);
2494	if (ret) {
2495	kfree(name);
2496	return ret;
2497	}
2498
2499	old_name = cgrp->name;
2500	rcu_assign_pointer(cgrp->name, name);
2501
2502	kfree_rcu(old_name, rcu_head);
2503	return 0;
2504	}
2505
2506	static struct simple_xattrs __d_xattrs(struct dentry dentry)
2507	{
2508	if (S_ISDIR(dentry->d_inode->i_mode))
2509	return &__d_cgrp(dentry)->xattrs;
2510	else
2511	return &__d_cfe(dentry)->xattrs;
2512	}
2513
2514	static inline int xattr_enabled(struct dentry *dentry)
2515	{
2516	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
2517	return root->flags & CGRP_ROOT_XATTR;
2518	}
2519
2520	static bool is_valid_xattr(const char *name)
2521	{
2522	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) \|\|
2523	!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN))
2524	return true;
2525	return false;
2526	}
2527
2528	static int cgroup_setxattr(struct dentry dentry, const char name,
2529	const void *val, size_t size, int flags)
2530	{
2531	if (!xattr_enabled(dentry))
2532	return -EOPNOTSUPP;
2533	if (!is_valid_xattr(name))
2534	return -EINVAL;
2535	return simple_xattr_set(__d_xattrs(dentry), name, val, size, flags);
2536	}
2537
2538	static int cgroup_removexattr(struct dentry dentry, const char name)
2539	{
2540	if (!xattr_enabled(dentry))
2541	return -EOPNOTSUPP;
2542	if (!is_valid_xattr(name))
2543	return -EINVAL;
2544	return simple_xattr_remove(__d_xattrs(dentry), name);
2545	}
2546
2547	static ssize_t cgroup_getxattr(struct dentry dentry, const char name,
2548	void *buf, size_t size)
2549	{
2550	if (!xattr_enabled(dentry))
2551	return -EOPNOTSUPP;
2552	if (!is_valid_xattr(name))
2553	return -EINVAL;
2554	return simple_xattr_get(__d_xattrs(dentry), name, buf, size);
2555	}
2556
2557	static ssize_t cgroup_listxattr(struct dentry dentry, char buf, size_t size)
2558	{
2559	if (!xattr_enabled(dentry))
2560	return -EOPNOTSUPP;
2561	return simple_xattr_list(__d_xattrs(dentry), buf, size);
2562	}
2563
2564	static const struct file_operations cgroup_file_operations = {
2565	.read = cgroup_file_read,
2566	.write = cgroup_file_write,
2567	.llseek = generic_file_llseek,
2568	.open = cgroup_file_open,
2569	.release = cgroup_file_release,
2570	};
2571
2572	static const struct inode_operations cgroup_file_inode_operations = {
2573	.setxattr = cgroup_setxattr,
2574	.getxattr = cgroup_getxattr,
2575	.listxattr = cgroup_listxattr,
2576	.removexattr = cgroup_removexattr,
2577	};
2578
2579	static const struct inode_operations cgroup_dir_inode_operations = {
2580	.lookup = cgroup_lookup,
2581	.mkdir = cgroup_mkdir,
2582	.rmdir = cgroup_rmdir,
2583	.rename = cgroup_rename,
2584	.setxattr = cgroup_setxattr,
2585	.getxattr = cgroup_getxattr,
2586	.listxattr = cgroup_listxattr,
2587	.removexattr = cgroup_removexattr,
2588	};
2589
2590	static struct dentry cgroup_lookup(struct inode dir, struct dentry *dentry, unsigned int flags)
2591	{
2592	if (dentry->d_name.len > NAME_MAX)
2593	return ERR_PTR(-ENAMETOOLONG);
2594	d_add(dentry, NULL);
2595	return NULL;
2596	}
2597
2598	/*
2599	* Check if a file is a control file
2600	*/
2601	static inline struct cftype __file_cft(struct file file)
2602	{
2603	if (file_inode(file)->i_fop != &cgroup_file_operations)
2604	return ERR_PTR(-EINVAL);
2605	return __d_cft(file->f_dentry);
2606	}
2607
2608	static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2609	struct super_block *sb)
2610	{
2611	struct inode *inode;
2612
2613	if (!dentry)
2614	return -ENOENT;
2615	if (dentry->d_inode)
2616	return -EEXIST;
2617
2618	inode = cgroup_new_inode(mode, sb);
2619	if (!inode)
2620	return -ENOMEM;
2621
2622	if (S_ISDIR(mode)) {
2623	inode->i_op = &cgroup_dir_inode_operations;
2624	inode->i_fop = &simple_dir_operations;
2625
2626	/* start off with i_nlink == 2 (for "." entry) */
2627	inc_nlink(inode);
2628	inc_nlink(dentry->d_parent->d_inode);
2629
2630	/*
2631	* Control reaches here with cgroup_mutex held.
2632	* @inode->i_mutex should nest outside cgroup_mutex but we
2633	* want to populate it immediately without releasing
2634	* cgroup_mutex. As @inode isn't visible to anyone else
2635	* yet, trylock will always succeed without affecting
2636	* lockdep checks.
2637	*/
2638	WARN_ON_ONCE(!mutex_trylock(&inode->i_mutex));
2639	} else if (S_ISREG(mode)) {
2640	inode->i_size = 0;
2641	inode->i_fop = &cgroup_file_operations;
2642	inode->i_op = &cgroup_file_inode_operations;
2643	}
2644	d_instantiate(dentry, inode);
2645	dget(dentry); /* Extra count - pin the dentry in core */
2646	return 0;
2647	}
2648
2649	/**
2650	* cgroup_file_mode - deduce file mode of a control file
2651	* @cft: the control file in question
2652	*
2653	* returns cft->mode if ->mode is not 0
2654	* returns S_IRUGO\|S_IWUSR if it has both a read and a write handler
2655	* returns S_IRUGO if it has only a read handler
2656	* returns S_IWUSR if it has only a write hander
2657	*/
2658	static umode_t cgroup_file_mode(const struct cftype *cft)
2659	{
2660	umode_t mode = 0;
2661
2662	if (cft->mode)
2663	return cft->mode;
2664
2665	if (cft->read \|\| cft->read_u64 \|\| cft->read_s64 \|\|
2666	cft->read_map \|\| cft->read_seq_string)
2667	mode \|= S_IRUGO;
2668
2669	if (cft->write \|\| cft->write_u64 \|\| cft->write_s64 \|\|
2670	cft->write_string \|\| cft->trigger)
2671	mode \|= S_IWUSR;
2672
2673	return mode;
2674	}
2675
2676	static int cgroup_add_file(struct cgroup cgrp, struct cgroup_subsys subsys,
2677	struct cftype *cft)
2678	{
2679	struct dentry *dir = cgrp->dentry;
2680	struct cgroup *parent = __d_cgrp(dir);
2681	struct dentry *dentry;
2682	struct cfent *cfe;
2683	int error;
2684	umode_t mode;
2685	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2686
2687	if (subsys && !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
2688	strcpy(name, subsys->name);
2689	strcat(name, ".");
2690	}
2691	strcat(name, cft->name);
2692
2693	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
2694
2695	cfe = kzalloc(sizeof(*cfe), GFP_KERNEL);
2696	if (!cfe)
2697	return -ENOMEM;
2698
2699	dentry = lookup_one_len(name, dir, strlen(name));
2700	if (IS_ERR(dentry)) {
2701	error = PTR_ERR(dentry);
2702	goto out;
2703	}
2704
2705	cfe->type = (void *)cft;
2706	cfe->dentry = dentry;
2707	dentry->d_fsdata = cfe;
2708	simple_xattrs_init(&cfe->xattrs);
2709
2710	mode = cgroup_file_mode(cft);
2711	error = cgroup_create_file(dentry, mode \| S_IFREG, cgrp->root->sb);
2712	if (!error) {
2713	list_add_tail(&cfe->node, &parent->files);
2714	cfe = NULL;
2715	}
2716	dput(dentry);
2717	out:
2718	kfree(cfe);
2719	return error;
2720	}
2721
2722	static int cgroup_addrm_files(struct cgroup cgrp, struct cgroup_subsys subsys,
2723	struct cftype cfts[], bool is_add)
2724	{
2725	struct cftype *cft;
2726	int err, ret = 0;
2727
2728	for (cft = cfts; cft->name[0] != '\0'; cft++) {
2729	/* does cft->flags tell us to skip this file on @cgrp? */
2730	if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp))
2731	continue;
2732	if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
2733	continue;
2734	if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
2735	continue;
2736
2737	if (is_add) {
2738	err = cgroup_add_file(cgrp, subsys, cft);
2739	if (err)
2740	pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
2741	cft->name, err);
2742	ret = err;
2743	} else {
2744	cgroup_rm_file(cgrp, cft);
2745	}
2746	}
2747	return ret;
2748	}
2749
2750	static DEFINE_MUTEX(cgroup_cft_mutex);
2751
2752	static void cgroup_cfts_prepare(void)
2753	__acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex)
2754	{
2755	/*
2756	* Thanks to the entanglement with vfs inode locking, we can't walk
2757	* the existing cgroups under cgroup_mutex and create files.
2758	* Instead, we increment reference on all cgroups and build list of
2759	* them using @cgrp->cft_q_node. Grab cgroup_cft_mutex to ensure
2760	* exclusive access to the field.
2761	*/
2762	mutex_lock(&cgroup_cft_mutex);
2763	mutex_lock(&cgroup_mutex);
2764	}
2765
2766	static void cgroup_cfts_commit(struct cgroup_subsys *ss,
2767	struct cftype *cfts, bool is_add)
2768	__releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
2769	{
2770	LIST_HEAD(pending);
2771	struct cgroup cgrp, n;
2772
2773	/* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
2774	if (cfts && ss->root != &rootnode) {
2775	list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) {
2776	dget(cgrp->dentry);
2777	list_add_tail(&cgrp->cft_q_node, &pending);
2778	}
2779	}
2780
2781	mutex_unlock(&cgroup_mutex);
2782
2783	/*
2784	* All new cgroups will see @cfts update on @ss->cftsets. Add/rm
2785	* files for all cgroups which were created before.
2786	*/
2787	list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {
2788	struct inode *inode = cgrp->dentry->d_inode;
2789
2790	mutex_lock(&inode->i_mutex);
2791	mutex_lock(&cgroup_mutex);
2792	if (!cgroup_is_removed(cgrp))
2793	cgroup_addrm_files(cgrp, ss, cfts, is_add);
2794	mutex_unlock(&cgroup_mutex);
2795	mutex_unlock(&inode->i_mutex);
2796
2797	list_del_init(&cgrp->cft_q_node);
2798	dput(cgrp->dentry);
2799	}
2800
2801	mutex_unlock(&cgroup_cft_mutex);
2802	}
2803
2804	/**
2805	* cgroup_add_cftypes - add an array of cftypes to a subsystem
2806	* @ss: target cgroup subsystem
2807	* @cfts: zero-length name terminated array of cftypes
2808	*
2809	* Register @cfts to @ss. Files described by @cfts are created for all
2810	* existing cgroups to which @ss is attached and all future cgroups will
2811	* have them too. This function can be called anytime whether @ss is
2812	* attached or not.
2813	*
2814	* Returns 0 on successful registration, -errno on failure. Note that this
2815	* function currently returns 0 as long as @cfts registration is successful
2816	* even if some file creation attempts on existing cgroups fail.
2817	*/
2818	int cgroup_add_cftypes(struct cgroup_subsys ss, struct cftype cfts)
2819	{
2820	struct cftype_set *set;
2821
2822	set = kzalloc(sizeof(*set), GFP_KERNEL);
2823	if (!set)
2824	return -ENOMEM;
2825
2826	cgroup_cfts_prepare();
2827	set->cfts = cfts;
2828	list_add_tail(&set->node, &ss->cftsets);
2829	cgroup_cfts_commit(ss, cfts, true);
2830
2831	return 0;
2832	}
2833	EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
2834
2835	/**
2836	* cgroup_rm_cftypes - remove an array of cftypes from a subsystem
2837	* @ss: target cgroup subsystem
2838	* @cfts: zero-length name terminated array of cftypes
2839	*
2840	* Unregister @cfts from @ss. Files described by @cfts are removed from
2841	* all existing cgroups to which @ss is attached and all future cgroups
2842	* won't have them either. This function can be called anytime whether @ss
2843	* is attached or not.
2844	*
2845	* Returns 0 on successful unregistration, -ENOENT if @cfts is not
2846	* registered with @ss.
2847	*/
2848	int cgroup_rm_cftypes(struct cgroup_subsys ss, struct cftype cfts)
2849	{
2850	struct cftype_set *set;
2851
2852	cgroup_cfts_prepare();
2853
2854	list_for_each_entry(set, &ss->cftsets, node) {
2855	if (set->cfts == cfts) {
2856	list_del_init(&set->node);
2857	cgroup_cfts_commit(ss, cfts, false);
2858	return 0;
2859	}
2860	}
2861
2862	cgroup_cfts_commit(ss, NULL, false);
2863	return -ENOENT;
2864	}
2865
2866	/**
2867	* cgroup_task_count - count the number of tasks in a cgroup.
2868	* @cgrp: the cgroup in question
2869	*
2870	* Return the number of tasks in the cgroup.
2871	*/
2872	int cgroup_task_count(const struct cgroup *cgrp)
2873	{
2874	int count = 0;
2875	struct cg_cgroup_link *link;
2876
2877	read_lock(&css_set_lock);
2878	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2879	count += atomic_read(&link->cg->refcount);
2880	}
2881	read_unlock(&css_set_lock);
2882	return count;
2883	}
2884
2885	/*
2886	* Advance a list_head iterator. The iterator should be positioned at
2887	* the start of a css_set
2888	*/
2889	static void cgroup_advance_iter(struct cgroup *cgrp,
2890	struct cgroup_iter *it)
2891	{
2892	struct list_head *l = it->cg_link;
2893	struct cg_cgroup_link *link;
2894	struct css_set *cg;
2895
2896	/* Advance to the next non-empty css_set */
2897	do {
2898	l = l->next;
2899	if (l == &cgrp->css_sets) {
2900	it->cg_link = NULL;
2901	return;
2902	}
2903	link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2904	cg = link->cg;
2905	} while (list_empty(&cg->tasks));
2906	it->cg_link = l;
2907	it->task = cg->tasks.next;
2908	}
2909
2910	/*
2911	* To reduce the fork() overhead for systems that are not actually
2912	* using their cgroups capability, we don't maintain the lists running
2913	* through each css_set to its tasks until we see the list actually
2914	* used - in other words after the first call to cgroup_iter_start().
2915	*/
2916	static void cgroup_enable_task_cg_lists(void)
2917	{
2918	struct task_struct p, g;
2919	write_lock(&css_set_lock);
2920	use_task_css_set_links = 1;
2921	/*
2922	* We need tasklist_lock because RCU is not safe against
2923	* while_each_thread(). Besides, a forking task that has passed
2924	* cgroup_post_fork() without seeing use_task_css_set_links = 1
2925	* is not guaranteed to have its child immediately visible in the
2926	* tasklist if we walk through it with RCU.
2927	*/
2928	read_lock(&tasklist_lock);
2929	do_each_thread(g, p) {
2930	task_lock(p);
2931	/*
2932	* We should check if the process is exiting, otherwise
2933	* it will race with cgroup_exit() in that the list
2934	* entry won't be deleted though the process has exited.
2935	*/
2936	if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
2937	list_add(&p->cg_list, &p->cgroups->tasks);
2938	task_unlock(p);
2939	} while_each_thread(g, p);
2940	read_unlock(&tasklist_lock);
2941	write_unlock(&css_set_lock);
2942	}
2943
2944	/**
2945	* cgroup_next_descendant_pre - find the next descendant for pre-order walk
2946	* @pos: the current position (%NULL to initiate traversal)
2947	* @cgroup: cgroup whose descendants to walk
2948	*
2949	* To be used by cgroup_for_each_descendant_pre(). Find the next
2950	* descendant to visit for pre-order traversal of @cgroup's descendants.
2951	*/
2952	struct cgroup cgroup_next_descendant_pre(struct cgroup pos,
2953	struct cgroup *cgroup)
2954	{
2955	struct cgroup *next;
2956
2957	WARN_ON_ONCE(!rcu_read_lock_held());
2958
2959	/* if first iteration, pretend we just visited @cgroup */
2960	if (!pos)
2961	pos = cgroup;
2962
2963	/* visit the first child if exists */
2964	next = list_first_or_null_rcu(&pos->children, struct cgroup, sibling);
2965	if (next)
2966	return next;
2967
2968	/* no child, visit my or the closest ancestor's next sibling */
2969	while (pos != cgroup) {
2970	next = list_entry_rcu(pos->sibling.next, struct cgroup,
2971	sibling);
2972	if (&next->sibling != &pos->parent->children)
2973	return next;
2974
2975	pos = pos->parent;
2976	}
2977
2978	return NULL;
2979	}
2980	EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre);
2981
2982	/**
2983	* cgroup_rightmost_descendant - return the rightmost descendant of a cgroup
2984	* @pos: cgroup of interest
2985	*
2986	* Return the rightmost descendant of @pos. If there's no descendant,
2987	* @pos is returned. This can be used during pre-order traversal to skip
2988	* subtree of @pos.
2989	*/
2990	struct cgroup cgroup_rightmost_descendant(struct cgroup pos)
2991	{
2992	struct cgroup last, tmp;
2993
2994	WARN_ON_ONCE(!rcu_read_lock_held());
2995
2996	do {
2997	last = pos;
2998	/* ->prev isn't RCU safe, walk ->next till the end */
2999	pos = NULL;
3000	list_for_each_entry_rcu(tmp, &last->children, sibling)
3001	pos = tmp;
3002	} while (pos);
3003
3004	return last;
3005	}
3006	EXPORT_SYMBOL_GPL(cgroup_rightmost_descendant);
3007
3008	static struct cgroup cgroup_leftmost_descendant(struct cgroup pos)
3009	{
3010	struct cgroup *last;
3011
3012	do {
3013	last = pos;
3014	pos = list_first_or_null_rcu(&pos->children, struct cgroup,
3015	sibling);
3016	} while (pos);
3017
3018	return last;
3019	}
3020
3021	/**
3022	* cgroup_next_descendant_post - find the next descendant for post-order walk
3023	* @pos: the current position (%NULL to initiate traversal)
3024	* @cgroup: cgroup whose descendants to walk
3025	*
3026	* To be used by cgroup_for_each_descendant_post(). Find the next
3027	* descendant to visit for post-order traversal of @cgroup's descendants.
3028	*/
3029	struct cgroup cgroup_next_descendant_post(struct cgroup pos,
3030	struct cgroup *cgroup)
3031	{
3032	struct cgroup *next;
3033
3034	WARN_ON_ONCE(!rcu_read_lock_held());
3035
3036	/* if first iteration, visit the leftmost descendant */
3037	if (!pos) {
3038	next = cgroup_leftmost_descendant(cgroup);
3039	return next != cgroup ? next : NULL;
3040	}
3041
3042	/* if there's an unvisited sibling, visit its leftmost descendant */
3043	next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
3044	if (&next->sibling != &pos->parent->children)
3045	return cgroup_leftmost_descendant(next);
3046
3047	/* no sibling left, visit parent */
3048	next = pos->parent;
3049	return next != cgroup ? next : NULL;
3050	}
3051	EXPORT_SYMBOL_GPL(cgroup_next_descendant_post);
3052
3053	void cgroup_iter_start(struct cgroup cgrp, struct cgroup_iter it)
3054	__acquires(css_set_lock)
3055	{
3056	/*
3057	* The first time anyone tries to iterate across a cgroup,
3058	* we need to enable the list linking each css_set to its
3059	* tasks, and fix up all existing tasks.
3060	*/
3061	if (!use_task_css_set_links)
3062	cgroup_enable_task_cg_lists();
3063
3064	read_lock(&css_set_lock);
3065	it->cg_link = &cgrp->css_sets;
3066	cgroup_advance_iter(cgrp, it);
3067	}
3068
3069	struct task_struct cgroup_iter_next(struct cgroup cgrp,
3070	struct cgroup_iter *it)
3071	{
3072	struct task_struct *res;
3073	struct list_head *l = it->task;
3074	struct cg_cgroup_link *link;
3075
3076	/* If the iterator cg is NULL, we have no tasks */
3077	if (!it->cg_link)
3078	return NULL;
3079	res = list_entry(l, struct task_struct, cg_list);
3080	/* Advance iterator to find next entry */
3081	l = l->next;
3082	link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
3083	if (l == &link->cg->tasks) {
3084	/* We reached the end of this task list - move on to
3085	* the next cg_cgroup_link */
3086	cgroup_advance_iter(cgrp, it);
3087	} else {
3088	it->task = l;
3089	}
3090	return res;
3091	}
3092
3093	void cgroup_iter_end(struct cgroup cgrp, struct cgroup_iter it)
3094	__releases(css_set_lock)
3095	{
3096	read_unlock(&css_set_lock);
3097	}
3098
3099	static inline int started_after_time(struct task_struct *t1,
3100	struct timespec *time,
3101	struct task_struct *t2)
3102	{
3103	int start_diff = timespec_compare(&t1->start_time, time);
3104	if (start_diff > 0) {
3105	return 1;
3106	} else if (start_diff < 0) {
3107	return 0;
3108	} else {
3109	/*
3110	* Arbitrarily, if two processes started at the same
3111	* time, we'll say that the lower pointer value
3112	* started first. Note that t2 may have exited by now
3113	* so this may not be a valid pointer any longer, but
3114	* that's fine - it still serves to distinguish
3115	* between two tasks started (effectively) simultaneously.
3116	*/
3117	return t1 > t2;
3118	}
3119	}
3120
3121	/*
3122	* This function is a callback from heap_insert() and is used to order
3123	* the heap.
3124	* In this case we order the heap in descending task start time.
3125	*/
3126	static inline int started_after(void p1, void p2)
3127	{
3128	struct task_struct *t1 = p1;
3129	struct task_struct *t2 = p2;
3130	return started_after_time(t1, &t2->start_time, t2);
3131	}
3132
3133	/**
3134	* cgroup_scan_tasks - iterate though all the tasks in a cgroup
3135	* @scan: struct cgroup_scanner containing arguments for the scan
3136	*
3137	* Arguments include pointers to callback functions test_task() and
3138	* process_task().
3139	* Iterate through all the tasks in a cgroup, calling test_task() for each,
3140	* and if it returns true, call process_task() for it also.
3141	* The test_task pointer may be NULL, meaning always true (select all tasks).
3142	* Effectively duplicates cgroup_iter_{start,next,end}()
3143	* but does not lock css_set_lock for the call to process_task().
3144	* The struct cgroup_scanner may be embedded in any structure of the caller's
3145	* creation.
3146	* It is guaranteed that process_task() will act on every task that
3147	* is a member of the cgroup for the duration of this call. This
3148	* function may or may not call process_task() for tasks that exit
3149	* or move to a different cgroup during the call, or are forked or
3150	* move into the cgroup during the call.
3151	*
3152	* Note that test_task() may be called with locks held, and may in some
3153	* situations be called multiple times for the same task, so it should
3154	* be cheap.
3155	* If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
3156	* pre-allocated and will be used for heap operations (and its "gt" member will
3157	* be overwritten), else a temporary heap will be used (allocation of which
3158	* may cause this function to fail).
3159	*/
3160	int cgroup_scan_tasks(struct cgroup_scanner *scan)
3161	{
3162	int retval, i;
3163	struct cgroup_iter it;
3164	struct task_struct p, dropped;
3165	/* Never dereference latest_task, since it's not refcounted */
3166	struct task_struct *latest_task = NULL;
3167	struct ptr_heap tmp_heap;
3168	struct ptr_heap *heap;
3169	struct timespec latest_time = { 0, 0 };
3170
3171	if (scan->heap) {
3172	/* The caller supplied our heap and pre-allocated its memory */
3173	heap = scan->heap;
3174	heap->gt = &started_after;
3175	} else {
3176	/* We need to allocate our own heap memory */
3177	heap = &tmp_heap;
3178	retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
3179	if (retval)
3180	/* cannot allocate the heap */
3181	return retval;
3182	}
3183
3184	again:
3185	/*
3186	* Scan tasks in the cgroup, using the scanner's "test_task" callback
3187	* to determine which are of interest, and using the scanner's
3188	* "process_task" callback to process any of them that need an update.
3189	* Since we don't want to hold any locks during the task updates,
3190	* gather tasks to be processed in a heap structure.
3191	* The heap is sorted by descending task start time.
3192	* If the statically-sized heap fills up, we overflow tasks that
3193	* started later, and in future iterations only consider tasks that
3194	* started after the latest task in the previous pass. This
3195	* guarantees forward progress and that we don't miss any tasks.
3196	*/
3197	heap->size = 0;
3198	cgroup_iter_start(scan->cg, &it);
3199	while ((p = cgroup_iter_next(scan->cg, &it))) {
3200	/*
3201	* Only affect tasks that qualify per the caller's callback,
3202	* if he provided one
3203	*/
3204	if (scan->test_task && !scan->test_task(p, scan))
3205	continue;
3206	/*
3207	* Only process tasks that started after the last task
3208	* we processed
3209	*/
3210	if (!started_after_time(p, &latest_time, latest_task))
3211	continue;
3212	dropped = heap_insert(heap, p);
3213	if (dropped == NULL) {
3214	/*
3215	* The new task was inserted; the heap wasn't
3216	* previously full
3217	*/
3218	get_task_struct(p);
3219	} else if (dropped != p) {
3220	/*
3221	* The new task was inserted, and pushed out a
3222	* different task
3223	*/
3224	get_task_struct(p);
3225	put_task_struct(dropped);
3226	}
3227	/*
3228	* Else the new task was newer than anything already in
3229	* the heap and wasn't inserted
3230	*/
3231	}
3232	cgroup_iter_end(scan->cg, &it);
3233
3234	if (heap->size) {
3235	for (i = 0; i < heap->size; i++) {
3236	struct task_struct *q = heap->ptrs[i];
3237	if (i == 0) {
3238	latest_time = q->start_time;
3239	latest_task = q;
3240	}
3241	/* Process the task per the caller's callback */
3242	scan->process_task(q, scan);
3243	put_task_struct(q);
3244	}
3245	/*
3246	* If we had to process any tasks at all, scan again
3247	* in case some of them were in the middle of forking
3248	* children that didn't get processed.
3249	* Not the most efficient way to do it, but it avoids
3250	* having to take callback_mutex in the fork path
3251	*/
3252	goto again;
3253	}
3254	if (heap == &tmp_heap)
3255	heap_free(&tmp_heap);
3256	return 0;
3257	}
3258
3259	static void cgroup_transfer_one_task(struct task_struct *task,
3260	struct cgroup_scanner *scan)
3261	{
3262	struct cgroup *new_cgroup = scan->data;
3263
3264	mutex_lock(&cgroup_mutex);
3265	cgroup_attach_task(new_cgroup, task, false);
3266	mutex_unlock(&cgroup_mutex);
3267	}
3268
3269	/**
3270	* cgroup_trasnsfer_tasks - move tasks from one cgroup to another
3271	* @to: cgroup to which the tasks will be moved
3272	* @from: cgroup in which the tasks currently reside
3273	*/
3274	int cgroup_transfer_tasks(struct cgroup to, struct cgroup from)
3275	{
3276	struct cgroup_scanner scan;
3277
3278	scan.cg = from;
3279	scan.test_task = NULL; /* select all tasks in cgroup */
3280	scan.process_task = cgroup_transfer_one_task;
3281	scan.heap = NULL;
3282	scan.data = to;
3283
3284	return cgroup_scan_tasks(&scan);
3285	}
3286
3287	/*
3288	* Stuff for reading the 'tasks'/'procs' files.
3289	*
3290	* Reading this file can return large amounts of data if a cgroup has
3291	* lots of attached tasks. So it may need several calls to read(),
3292	* but we cannot guarantee that the information we produce is correct
3293	* unless we produce it entirely atomically.
3294	*
3295	*/
3296
3297	/* which pidlist file are we talking about? */
3298	enum cgroup_filetype {
3299	CGROUP_FILE_PROCS,
3300	CGROUP_FILE_TASKS,
3301	};
3302
3303	/*
3304	* A pidlist is a list of pids that virtually represents the contents of one
3305	* of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3306	* a pair (one each for procs, tasks) for each pid namespace that's relevant
3307	* to the cgroup.
3308	*/
3309	struct cgroup_pidlist {
3310	/*
3311	* used to find which pidlist is wanted. doesn't change as long as
3312	* this particular list stays in the list.
3313	*/
3314	struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
3315	/* array of xids */
3316	pid_t *list;
3317	/* how many elements the above list has */
3318	int length;
3319	/* how many files are using the current array */
3320	int use_count;
3321	/* each of these stored in a list by its cgroup */
3322	struct list_head links;
3323	/* pointer to the cgroup we belong to, for list removal purposes */
3324	struct cgroup *owner;
3325	/* protects the other fields */
3326	struct rw_semaphore mutex;
3327	};
3328
3329	/*
3330	* The following two functions "fix" the issue where there are more pids
3331	* than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3332	* TODO: replace with a kernel-wide solution to this problem
3333	*/
3334	#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3335	static void *pidlist_allocate(int count)
3336	{
3337	if (PIDLIST_TOO_LARGE(count))
3338	return vmalloc(count * sizeof(pid_t));
3339	else
3340	return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
3341	}
3342	static void pidlist_free(void *p)
3343	{
3344	if (is_vmalloc_addr(p))
3345	vfree(p);
3346	else
3347	kfree(p);
3348	}
3349
3350	/*
3351	* pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3352	* Returns the number of unique elements.
3353	*/
3354	static int pidlist_uniq(pid_t *list, int length)
3355	{
3356	int src, dest = 1;
3357
3358	/*
3359	* we presume the 0th element is unique, so i starts at 1. trivial
3360	* edge cases first; no work needs to be done for either
3361	*/
3362	if (length == 0 \|\| length == 1)
3363	return length;
3364	/* src and dest walk down the list; dest counts unique elements */
3365	for (src = 1; src < length; src++) {
3366	/* find next unique element */
3367	while (list[src] == list[src-1]) {
3368	src++;
3369	if (src == length)
3370	goto after;
3371	}
3372	/* dest always points to where the next unique element goes */
3373	list[dest] = list[src];
3374	dest++;
3375	}
3376	after:
3377	return dest;
3378	}
3379
3380	static int cmppid(const void a, const void b)
3381	{
3382	return (pid_t )a - (pid_t )b;
3383	}
3384
3385	/*
3386	* find the appropriate pidlist for our purpose (given procs vs tasks)
3387	* returns with the lock on that pidlist already held, and takes care
3388	* of the use count, or returns NULL with no locks held if we're out of
3389	* memory.
3390	*/
3391	static struct cgroup_pidlist cgroup_pidlist_find(struct cgroup cgrp,
3392	enum cgroup_filetype type)
3393	{
3394	struct cgroup_pidlist *l;
3395	/* don't need task_nsproxy() if we're looking at ourself */
3396	struct pid_namespace *ns = task_active_pid_ns(current);
3397
3398	/*
3399	* We can't drop the pidlist_mutex before taking the l->mutex in case
3400	* the last ref-holder is trying to remove l from the list at the same
3401	* time. Holding the pidlist_mutex precludes somebody taking whichever
3402	* list we find out from under us - compare release_pid_array().
3403	*/
3404	mutex_lock(&cgrp->pidlist_mutex);
3405	list_for_each_entry(l, &cgrp->pidlists, links) {
3406	if (l->key.type == type && l->key.ns == ns) {
3407	/* make sure l doesn't vanish out from under us */
3408	down_write(&l->mutex);
3409	mutex_unlock(&cgrp->pidlist_mutex);
3410	return l;
3411	}
3412	}
3413	/* entry not found; create a new one */
3414	l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3415	if (!l) {
3416	mutex_unlock(&cgrp->pidlist_mutex);
3417	return l;
3418	}
3419	init_rwsem(&l->mutex);
3420	down_write(&l->mutex);
3421	l->key.type = type;
3422	l->key.ns = get_pid_ns(ns);
3423	l->use_count = 0; /* don't increment here */
3424	l->list = NULL;
3425	l->owner = cgrp;
3426	list_add(&l->links, &cgrp->pidlists);
3427	mutex_unlock(&cgrp->pidlist_mutex);
3428	return l;
3429	}
3430
3431	/*
3432	* Load a cgroup's pidarray with either procs' tgids or tasks' pids
3433	*/
3434	static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
3435	struct cgroup_pidlist **lp)
3436	{
3437	pid_t *array;
3438	int length;
3439	int pid, n = 0; /* used for populating the array */
3440	struct cgroup_iter it;
3441	struct task_struct *tsk;
3442	struct cgroup_pidlist *l;
3443
3444	/*
3445	* If cgroup gets more users after we read count, we won't have
3446	* enough space - tough. This race is indistinguishable to the
3447	* caller from the case that the additional cgroup users didn't
3448	* show up until sometime later on.
3449	*/
3450	length = cgroup_task_count(cgrp);
3451	array = pidlist_allocate(length);
3452	if (!array)
3453	return -ENOMEM;
3454	/* now, populate the array */
3455	cgroup_iter_start(cgrp, &it);
3456	while ((tsk = cgroup_iter_next(cgrp, &it))) {
3457	if (unlikely(n == length))
3458	break;
3459	/* get tgid or pid for procs or tasks file respectively */
3460	if (type == CGROUP_FILE_PROCS)
3461	pid = task_tgid_vnr(tsk);
3462	else
3463	pid = task_pid_vnr(tsk);
3464	if (pid > 0) /* make sure to only use valid results */
3465	array[n++] = pid;
3466	}
3467	cgroup_iter_end(cgrp, &it);
3468	length = n;
3469	/* now sort & (if procs) strip out duplicates */
3470	sort(array, length, sizeof(pid_t), cmppid, NULL);
3471	if (type == CGROUP_FILE_PROCS)
3472	length = pidlist_uniq(array, length);
3473	l = cgroup_pidlist_find(cgrp, type);
3474	if (!l) {
3475	pidlist_free(array);
3476	return -ENOMEM;
3477	}
3478	/* store array, freeing old if necessary - lock already held */
3479	pidlist_free(l->list);
3480	l->list = array;
3481	l->length = length;
3482	l->use_count++;
3483	up_write(&l->mutex);
3484	*lp = l;
3485	return 0;
3486	}
3487
3488	/**
3489	* cgroupstats_build - build and fill cgroupstats
3490	* @stats: cgroupstats to fill information into
3491	* @dentry: A dentry entry belonging to the cgroup for which stats have
3492	* been requested.
3493	*
3494	* Build and fill cgroupstats so that taskstats can export it to user
3495	* space.
3496	*/
3497	int cgroupstats_build(struct cgroupstats stats, struct dentry dentry)
3498	{
3499	int ret = -EINVAL;
3500	struct cgroup *cgrp;
3501	struct cgroup_iter it;
3502	struct task_struct *tsk;
3503
3504	/*
3505	* Validate dentry by checking the superblock operations,
3506	* and make sure it's a directory.
3507	*/
3508	if (dentry->d_sb->s_op != &cgroup_ops \|\|
3509	!S_ISDIR(dentry->d_inode->i_mode))
3510	goto err;
3511
3512	ret = 0;
3513	cgrp = dentry->d_fsdata;
3514
3515	cgroup_iter_start(cgrp, &it);
3516	while ((tsk = cgroup_iter_next(cgrp, &it))) {
3517	switch (tsk->state) {
3518	case TASK_RUNNING:
3519	stats->nr_running++;
3520	break;
3521	case TASK_INTERRUPTIBLE:
3522	stats->nr_sleeping++;
3523	break;
3524	case TASK_UNINTERRUPTIBLE:
3525	stats->nr_uninterruptible++;
3526	break;
3527	case TASK_STOPPED:
3528	stats->nr_stopped++;
3529	break;
3530	default:
3531	if (delayacct_is_task_waiting_on_io(tsk))
3532	stats->nr_io_wait++;
3533	break;
3534	}
3535	}
3536	cgroup_iter_end(cgrp, &it);
3537
3538	err:
3539	return ret;
3540	}
3541
3542
3543	/*
3544	* seq_file methods for the tasks/procs files. The seq_file position is the
3545	* next pid to display; the seq_file iterator is a pointer to the pid
3546	* in the cgroup->l->list array.
3547	*/
3548
3549	static void cgroup_pidlist_start(struct seq_file s, loff_t *pos)
3550	{
3551	/*
3552	* Initially we receive a position value that corresponds to
3553	* one more than the last pid shown (or 0 on the first call or
3554	* after a seek to the start). Use a binary-search to find the
3555	* next pid to display, if any
3556	*/
3557	struct cgroup_pidlist *l = s->private;
3558	int index = 0, pid = *pos;
3559	int *iter;
3560
3561	down_read(&l->mutex);
3562	if (pid) {
3563	int end = l->length;
3564
3565	while (index < end) {
3566	int mid = (index + end) / 2;
3567	if (l->list[mid] == pid) {
3568	index = mid;
3569	break;
3570	} else if (l->list[mid] <= pid)
3571	index = mid + 1;
3572	else
3573	end = mid;
3574	}
3575	}
3576	/* If we're off the end of the array, we're done */
3577	if (index >= l->length)
3578	return NULL;
3579	/* Update the abstract position to be the actual pid that we found */
3580	iter = l->list + index;
3581	pos = iter;
3582	return iter;
3583	}
3584
3585	static void cgroup_pidlist_stop(struct seq_file s, void v)
3586	{
3587	struct cgroup_pidlist *l = s->private;
3588	up_read(&l->mutex);
3589	}
3590
3591	static void cgroup_pidlist_next(struct seq_file s, void v, loff_t pos)
3592	{
3593	struct cgroup_pidlist *l = s->private;
3594	pid_t *p = v;
3595	pid_t *end = l->list + l->length;
3596	/*
3597	* Advance to the next pid in the array. If this goes off the
3598	* end, we're done
3599	*/
3600	p++;
3601	if (p >= end) {
3602	return NULL;
3603	} else {
3604	pos = p;
3605	return p;
3606	}
3607	}
3608
3609	static int cgroup_pidlist_show(struct seq_file s, void v)
3610	{
3611	return seq_printf(s, "%d\n", (int )v);
3612	}
3613
3614	/*
3615	* seq_operations functions for iterating on pidlists through seq_file -
3616	* independent of whether it's tasks or procs
3617	*/
3618	static const struct seq_operations cgroup_pidlist_seq_operations = {
3619	.start = cgroup_pidlist_start,
3620	.stop = cgroup_pidlist_stop,
3621	.next = cgroup_pidlist_next,
3622	.show = cgroup_pidlist_show,
3623	};
3624
3625	static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3626	{
3627	/*
3628	* the case where we're the last user of this particular pidlist will
3629	* have us remove it from the cgroup's list, which entails taking the
3630	* mutex. since in pidlist_find the pidlist->lock depends on cgroup->
3631	* pidlist_mutex, we have to take pidlist_mutex first.
3632	*/
3633	mutex_lock(&l->owner->pidlist_mutex);
3634	down_write(&l->mutex);
3635	BUG_ON(!l->use_count);
3636	if (!--l->use_count) {
3637	/* we're the last user if refcount is 0; remove and free */
3638	list_del(&l->links);
3639	mutex_unlock(&l->owner->pidlist_mutex);
3640	pidlist_free(l->list);
3641	put_pid_ns(l->key.ns);
3642	up_write(&l->mutex);
3643	kfree(l);
3644	return;
3645	}
3646	mutex_unlock(&l->owner->pidlist_mutex);
3647	up_write(&l->mutex);
3648	}
3649
3650	static int cgroup_pidlist_release(struct inode inode, struct file file)
3651	{
3652	struct cgroup_pidlist *l;
3653	if (!(file->f_mode & FMODE_READ))
3654	return 0;
3655	/*
3656	* the seq_file will only be initialized if the file was opened for
3657	* reading; hence we check if it's not null only in that case.
3658	*/
3659	l = ((struct seq_file *)file->private_data)->private;
3660	cgroup_release_pid_array(l);
3661	return seq_release(inode, file);
3662	}
3663
3664	static const struct file_operations cgroup_pidlist_operations = {
3665	.read = seq_read,
3666	.llseek = seq_lseek,
3667	.write = cgroup_file_write,
3668	.release = cgroup_pidlist_release,
3669	};
3670
3671	/*
3672	* The following functions handle opens on a file that displays a pidlist
3673	* (tasks or procs). Prepare an array of the process/thread IDs of whoever's
3674	* in the cgroup.
3675	*/
3676	/* helper function for the two below it */
3677	static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3678	{
3679	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3680	struct cgroup_pidlist *l;
3681	int retval;
3682
3683	/* Nothing to do for write-only files */
3684	if (!(file->f_mode & FMODE_READ))
3685	return 0;
3686
3687	/* have the array populated */
3688	retval = pidlist_array_load(cgrp, type, &l);
3689	if (retval)
3690	return retval;
3691	/* configure file information */
3692	file->f_op = &cgroup_pidlist_operations;
3693
3694	retval = seq_open(file, &cgroup_pidlist_seq_operations);
3695	if (retval) {
3696	cgroup_release_pid_array(l);
3697	return retval;
3698	}
3699	((struct seq_file *)file->private_data)->private = l;
3700	return 0;
3701	}
3702	static int cgroup_tasks_open(struct inode unused, struct file file)
3703	{
3704	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3705	}
3706	static int cgroup_procs_open(struct inode unused, struct file file)
3707	{
3708	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3709	}
3710
3711	static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3712	struct cftype *cft)
3713	{
3714	return notify_on_release(cgrp);
3715	}
3716
3717	static int cgroup_write_notify_on_release(struct cgroup *cgrp,
3718	struct cftype *cft,
3719	u64 val)
3720	{
3721	clear_bit(CGRP_RELEASABLE, &cgrp->flags);
3722	if (val)
3723	set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3724	else
3725	clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3726	return 0;
3727	}
3728
3729	/*
3730	* Unregister event and free resources.
3731	*
3732	* Gets called from workqueue.
3733	*/
3734	static void cgroup_event_remove(struct work_struct *work)
3735	{
3736	struct cgroup_event *event = container_of(work, struct cgroup_event,
3737	remove);
3738	struct cgroup *cgrp = event->cgrp;
3739
3740	remove_wait_queue(event->wqh, &event->wait);
3741
3742	event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3743
3744	/* Notify userspace the event is going away. */
3745	eventfd_signal(event->eventfd, 1);
3746
3747	eventfd_ctx_put(event->eventfd);
3748	kfree(event);
3749	dput(cgrp->dentry);
3750	}
3751
3752	/*
3753	* Gets called on POLLHUP on eventfd when user closes it.
3754	*
3755	* Called with wqh->lock held and interrupts disabled.
3756	*/
3757	static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
3758	int sync, void *key)
3759	{
3760	struct cgroup_event *event = container_of(wait,
3761	struct cgroup_event, wait);
3762	struct cgroup *cgrp = event->cgrp;
3763	unsigned long flags = (unsigned long)key;
3764
3765	if (flags & POLLHUP) {
3766	/*
3767	* If the event has been detached at cgroup removal, we
3768	* can simply return knowing the other side will cleanup
3769	* for us.
3770	*
3771	* We can't race against event freeing since the other
3772	* side will require wqh->lock via remove_wait_queue(),
3773	* which we hold.
3774	*/
3775	spin_lock(&cgrp->event_list_lock);
3776	if (!list_empty(&event->list)) {
3777	list_del_init(&event->list);
3778	/*
3779	* We are in atomic context, but cgroup_event_remove()
3780	* may sleep, so we have to call it in workqueue.
3781	*/
3782	schedule_work(&event->remove);
3783	}
3784	spin_unlock(&cgrp->event_list_lock);
3785	}
3786
3787	return 0;
3788	}
3789
3790	static void cgroup_event_ptable_queue_proc(struct file *file,
3791	wait_queue_head_t wqh, poll_table pt)
3792	{
3793	struct cgroup_event *event = container_of(pt,
3794	struct cgroup_event, pt);
3795
3796	event->wqh = wqh;
3797	add_wait_queue(wqh, &event->wait);
3798	}
3799
3800	/*
3801	* Parse input and register new cgroup event handler.
3802	*
3803	* Input must be in format '<event_fd> <control_fd> <args>'.
3804	* Interpretation of args is defined by control file implementation.
3805	*/
3806	static int cgroup_write_event_control(struct cgroup cgrp, struct cftype cft,
3807	const char *buffer)
3808	{
3809	struct cgroup_event *event = NULL;
3810	struct cgroup *cgrp_cfile;
3811	unsigned int efd, cfd;
3812	struct file *efile = NULL;
3813	struct file *cfile = NULL;
3814	char *endp;
3815	int ret;
3816
3817	efd = simple_strtoul(buffer, &endp, 10);
3818	if (*endp != ' ')
3819	return -EINVAL;
3820	buffer = endp + 1;
3821
3822	cfd = simple_strtoul(buffer, &endp, 10);
3823	if ((endp != ' ') && (endp != '\0'))
3824	return -EINVAL;
3825	buffer = endp + 1;
3826
3827	event = kzalloc(sizeof(*event), GFP_KERNEL);
3828	if (!event)
3829	return -ENOMEM;
3830	event->cgrp = cgrp;
3831	INIT_LIST_HEAD(&event->list);
3832	init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
3833	init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
3834	INIT_WORK(&event->remove, cgroup_event_remove);
3835
3836	efile = eventfd_fget(efd);
3837	if (IS_ERR(efile)) {
3838	ret = PTR_ERR(efile);
3839	goto fail;
3840	}
3841
3842	event->eventfd = eventfd_ctx_fileget(efile);
3843	if (IS_ERR(event->eventfd)) {
3844	ret = PTR_ERR(event->eventfd);
3845	goto fail;
3846	}
3847
3848	cfile = fget(cfd);
3849	if (!cfile) {
3850	ret = -EBADF;
3851	goto fail;
3852	}
3853
3854	/* the process need read permission on control file */
3855	/* AV: shouldn't we check that it's been opened for read instead? */
3856	ret = inode_permission(file_inode(cfile), MAY_READ);
3857	if (ret < 0)
3858	goto fail;
3859
3860	event->cft = __file_cft(cfile);
3861	if (IS_ERR(event->cft)) {
3862	ret = PTR_ERR(event->cft);
3863	goto fail;
3864	}
3865
3866	/*
3867	* The file to be monitored must be in the same cgroup as
3868	* cgroup.event_control is.
3869	*/
3870	cgrp_cfile = __d_cgrp(cfile->f_dentry->d_parent);
3871	if (cgrp_cfile != cgrp) {
3872	ret = -EINVAL;
3873	goto fail;
3874	}
3875
3876	if (!event->cft->register_event \|\| !event->cft->unregister_event) {
3877	ret = -EINVAL;
3878	goto fail;
3879	}
3880
3881	ret = event->cft->register_event(cgrp, event->cft,
3882	event->eventfd, buffer);
3883	if (ret)
3884	goto fail;
3885
3886	efile->f_op->poll(efile, &event->pt);
3887
3888	/*
3889	* Events should be removed after rmdir of cgroup directory, but before
3890	* destroying subsystem state objects. Let's take reference to cgroup
3891	* directory dentry to do that.
3892	*/
3893	dget(cgrp->dentry);
3894
3895	spin_lock(&cgrp->event_list_lock);
3896	list_add(&event->list, &cgrp->event_list);
3897	spin_unlock(&cgrp->event_list_lock);
3898
3899	fput(cfile);
3900	fput(efile);
3901
3902	return 0;
3903
3904	fail:
3905	if (cfile)
3906	fput(cfile);
3907
3908	if (event && event->eventfd && !IS_ERR(event->eventfd))
3909	eventfd_ctx_put(event->eventfd);
3910
3911	if (!IS_ERR_OR_NULL(efile))
3912	fput(efile);
3913
3914	kfree(event);
3915
3916	return ret;
3917	}
3918
3919	static u64 cgroup_clone_children_read(struct cgroup *cgrp,
3920	struct cftype *cft)
3921	{
3922	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3923	}
3924
3925	static int cgroup_clone_children_write(struct cgroup *cgrp,
3926	struct cftype *cft,
3927	u64 val)
3928	{
3929	if (val)
3930	set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3931	else
3932	clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3933	return 0;
3934	}
3935
3936	/*
3937	* for the common functions, 'private' gives the type of file
3938	*/
3939	/* for hysterical raisins, we can't put this on the older files */
3940	#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3941	static struct cftype files[] = {
3942	{
3943	.name = "tasks",
3944	.open = cgroup_tasks_open,
3945	.write_u64 = cgroup_tasks_write,
3946	.release = cgroup_pidlist_release,
3947	.mode = S_IRUGO \| S_IWUSR,
3948	},
3949	{
3950	.name = CGROUP_FILE_GENERIC_PREFIX "procs",
3951	.open = cgroup_procs_open,
3952	.write_u64 = cgroup_procs_write,
3953	.release = cgroup_pidlist_release,
3954	.mode = S_IRUGO \| S_IWUSR,
3955	},
3956	{
3957	.name = "notify_on_release",
3958	.read_u64 = cgroup_read_notify_on_release,
3959	.write_u64 = cgroup_write_notify_on_release,
3960	},
3961	{
3962	.name = CGROUP_FILE_GENERIC_PREFIX "event_control",
3963	.write_string = cgroup_write_event_control,
3964	.mode = S_IWUGO,
3965	},
3966	{
3967	.name = "cgroup.clone_children",
3968	.flags = CFTYPE_INSANE,
3969	.read_u64 = cgroup_clone_children_read,
3970	.write_u64 = cgroup_clone_children_write,
3971	},
3972	{
3973	.name = "cgroup.sane_behavior",
3974	.flags = CFTYPE_ONLY_ON_ROOT,
3975	.read_seq_string = cgroup_sane_behavior_show,
3976	},
3977	{
3978	.name = "release_agent",
3979	.flags = CFTYPE_ONLY_ON_ROOT,
3980	.read_seq_string = cgroup_release_agent_show,
3981	.write_string = cgroup_release_agent_write,
3982	.max_write_len = PATH_MAX,
3983	},
3984	{ } /* terminate */
3985	};
3986
3987	/**
3988	* cgroup_populate_dir - selectively creation of files in a directory
3989	* @cgrp: target cgroup
3990	* @base_files: true if the base files should be added
3991	* @subsys_mask: mask of the subsystem ids whose files should be added
3992	*/
3993	static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
3994	unsigned long subsys_mask)
3995	{
3996	int err;
3997	struct cgroup_subsys *ss;
3998
3999	if (base_files) {
4000	err = cgroup_addrm_files(cgrp, NULL, files, true);
4001	if (err < 0)
4002	return err;
4003	}
4004
4005	/* process cftsets of each subsystem */
4006	for_each_subsys(cgrp->root, ss) {
4007	struct cftype_set *set;
4008	if (!test_bit(ss->subsys_id, &subsys_mask))
4009	continue;
4010
4011	list_for_each_entry(set, &ss->cftsets, node)
4012	cgroup_addrm_files(cgrp, ss, set->cfts, true);
4013	}
4014
4015	/* This cgroup is ready now */
4016	for_each_subsys(cgrp->root, ss) {
4017	struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4018	/*
4019	* Update id->css pointer and make this css visible from
4020	* CSS ID functions. This pointer will be dereferened
4021	* from RCU-read-side without locks.
4022	*/
4023	if (css->id)
4024	rcu_assign_pointer(css->id->css, css);
4025	}
4026
4027	return 0;
4028	}
4029
4030	static void css_dput_fn(struct work_struct *work)
4031	{
4032	struct cgroup_subsys_state *css =
4033	container_of(work, struct cgroup_subsys_state, dput_work);
4034	struct dentry *dentry = css->cgroup->dentry;
4035	struct super_block *sb = dentry->d_sb;
4036
4037	atomic_inc(&sb->s_active);
4038	dput(dentry);
4039	deactivate_super(sb);
4040	}
4041
4042	static void init_cgroup_css(struct cgroup_subsys_state *css,
4043	struct cgroup_subsys *ss,
4044	struct cgroup *cgrp)
4045	{
4046	css->cgroup = cgrp;
4047	atomic_set(&css->refcnt, 1);
4048	css->flags = 0;
4049	css->id = NULL;
4050	if (cgrp == dummytop)
4051	css->flags \|= CSS_ROOT;
4052	BUG_ON(cgrp->subsys[ss->subsys_id]);
4053	cgrp->subsys[ss->subsys_id] = css;
4054
4055	/*
4056	* css holds an extra ref to @cgrp->dentry which is put on the last
4057	* css_put(). dput() requires process context, which css_put() may
4058	* be called without. @css->dput_work will be used to invoke
4059	* dput() asynchronously from css_put().
4060	*/
4061	INIT_WORK(&css->dput_work, css_dput_fn);
4062	}
4063
4064	/* invoke ->post_create() on a new CSS and mark it online if successful */
4065	static int online_css(struct cgroup_subsys ss, struct cgroup cgrp)
4066	{
4067	int ret = 0;
4068
4069	lockdep_assert_held(&cgroup_mutex);
4070
4071	if (ss->css_online)
4072	ret = ss->css_online(cgrp);
4073	if (!ret)
4074	cgrp->subsys[ss->subsys_id]->flags \|= CSS_ONLINE;
4075	return ret;
4076	}
4077
4078	/* if the CSS is online, invoke ->pre_destory() on it and mark it offline */
4079	static void offline_css(struct cgroup_subsys ss, struct cgroup cgrp)
4080	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4081	{
4082	struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4083
4084	lockdep_assert_held(&cgroup_mutex);
4085
4086	if (!(css->flags & CSS_ONLINE))
4087	return;
4088
4089	if (ss->css_offline)
4090	ss->css_offline(cgrp);
4091
4092	cgrp->subsys[ss->subsys_id]->flags &= ~CSS_ONLINE;
4093	}
4094
4095	/*
4096	* cgroup_create - create a cgroup
4097	* @parent: cgroup that will be parent of the new cgroup
4098	* @dentry: dentry of the new cgroup
4099	* @mode: mode to set on new inode
4100	*
4101	* Must be called with the mutex on the parent inode held
4102	*/
4103	static long cgroup_create(struct cgroup parent, struct dentry dentry,
4104	umode_t mode)
4105	{
4106	struct cgroup *cgrp;
4107	struct cgroup_name *name;
4108	struct cgroupfs_root *root = parent->root;
4109	int err = 0;
4110	struct cgroup_subsys *ss;
4111	struct super_block *sb = root->sb;
4112
4113	/* allocate the cgroup and its ID, 0 is reserved for the root */
4114	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
4115	if (!cgrp)
4116	return -ENOMEM;
4117
4118	name = cgroup_alloc_name(dentry);
4119	if (!name)
4120	goto err_free_cgrp;
4121	rcu_assign_pointer(cgrp->name, name);
4122
4123	cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);
4124	if (cgrp->id < 0)
4125	goto err_free_name;
4126
4127	/*
4128	* Only live parents can have children. Note that the liveliness
4129	* check isn't strictly necessary because cgroup_mkdir() and
4130	* cgroup_rmdir() are fully synchronized by i_mutex; however, do it
4131	* anyway so that locking is contained inside cgroup proper and we
4132	* don't get nasty surprises if we ever grow another caller.
4133	*/
4134	if (!cgroup_lock_live_group(parent)) {
4135	err = -ENODEV;
4136	goto err_free_id;
4137	}
4138
4139	/* Grab a reference on the superblock so the hierarchy doesn't
4140	* get deleted on unmount if there are child cgroups. This
4141	* can be done outside cgroup_mutex, since the sb can't
4142	* disappear while someone has an open control file on the
4143	* fs */
4144	atomic_inc(&sb->s_active);
4145
4146	init_cgroup_housekeeping(cgrp);
4147
4148	dentry->d_fsdata = cgrp;
4149	cgrp->dentry = dentry;
4150
4151	cgrp->parent = parent;
4152	cgrp->root = parent->root;
4153
4154	if (notify_on_release(parent))
4155	set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
4156
4157	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
4158	set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4159
4160	for_each_subsys(root, ss) {
4161	struct cgroup_subsys_state *css;
4162
4163	css = ss->css_alloc(cgrp);
4164	if (IS_ERR(css)) {
4165	err = PTR_ERR(css);
4166	goto err_free_all;
4167	}
4168	init_cgroup_css(css, ss, cgrp);
4169	if (ss->use_id) {
4170	err = alloc_css_id(ss, parent, cgrp);
4171	if (err)
4172	goto err_free_all;
4173	}
4174	}
4175
4176	/*
4177	* Create directory. cgroup_create_file() returns with the new
4178	* directory locked on success so that it can be populated without
4179	* dropping cgroup_mutex.
4180	*/
4181	err = cgroup_create_file(dentry, S_IFDIR \| mode, sb);
4182	if (err < 0)
4183	goto err_free_all;
4184	lockdep_assert_held(&dentry->d_inode->i_mutex);
4185
4186	/* allocation complete, commit to creation */
4187	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
4188	list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
4189	root->number_of_cgroups++;
4190
4191	/* each css holds a ref to the cgroup's dentry */
4192	for_each_subsys(root, ss)
4193	dget(dentry);
4194
4195	/* hold a ref to the parent's dentry */
4196	dget(parent->dentry);
4197
4198	/* creation succeeded, notify subsystems */
4199	for_each_subsys(root, ss) {
4200	err = online_css(ss, cgrp);
4201	if (err)
4202	goto err_destroy;
4203
4204	if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
4205	parent->parent) {
4206	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",
4207	current->comm, current->pid, ss->name);
4208	if (!strcmp(ss->name, "memory"))
4209	pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
4210	ss->warned_broken_hierarchy = true;
4211	}
4212	}
4213
4214	err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
4215	if (err)
4216	goto err_destroy;
4217
4218	mutex_unlock(&cgroup_mutex);
4219	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
4220
4221	return 0;
4222
4223	err_free_all:
4224	for_each_subsys(root, ss) {
4225	if (cgrp->subsys[ss->subsys_id])
4226	ss->css_free(cgrp);
4227	}
4228	mutex_unlock(&cgroup_mutex);
4229	/* Release the reference count that we took on the superblock */
4230	deactivate_super(sb);
4231	err_free_id:
4232	ida_simple_remove(&root->cgroup_ida, cgrp->id);
4233	err_free_name:
4234	kfree(rcu_dereference_raw(cgrp->name));
4235	err_free_cgrp:
4236	kfree(cgrp);
4237	return err;
4238
4239	err_destroy:
4240	cgroup_destroy_locked(cgrp);
4241	mutex_unlock(&cgroup_mutex);
4242	mutex_unlock(&dentry->d_inode->i_mutex);
4243	return err;
4244	}
4245
4246	static int cgroup_mkdir(struct inode dir, struct dentry dentry, umode_t mode)
4247	{
4248	struct cgroup *c_parent = dentry->d_parent->d_fsdata;
4249
4250	/* the vfs holds inode->i_mutex already */
4251	return cgroup_create(c_parent, dentry, mode \| S_IFDIR);
4252	}
4253
4254	static int cgroup_destroy_locked(struct cgroup *cgrp)
4255	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4256	{
4257	struct dentry *d = cgrp->dentry;
4258	struct cgroup *parent = cgrp->parent;
4259	struct cgroup_event event, tmp;
4260	struct cgroup_subsys *ss;
4261
4262	lockdep_assert_held(&d->d_inode->i_mutex);
4263	lockdep_assert_held(&cgroup_mutex);
4264
4265	if (atomic_read(&cgrp->count) \|\| !list_empty(&cgrp->children))
4266	return -EBUSY;
4267
4268	/*
4269	* Block new css_tryget() by deactivating refcnt and mark @cgrp
4270	* removed. This makes future css_tryget() and child creation
4271	* attempts fail thus maintaining the removal conditions verified
4272	* above.
4273	*/
4274	for_each_subsys(cgrp->root, ss) {
4275	struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4276
4277	WARN_ON(atomic_read(&css->refcnt) < 0);
4278	atomic_add(CSS_DEACT_BIAS, &css->refcnt);
4279	}
4280	set_bit(CGRP_REMOVED, &cgrp->flags);
4281
4282	/* tell subsystems to initate destruction */
4283	for_each_subsys(cgrp->root, ss)
4284	offline_css(ss, cgrp);
4285
4286	/*
4287	* Put all the base refs. Each css holds an extra reference to the
4288	* cgroup's dentry and cgroup removal proceeds regardless of css
4289	* refs. On the last put of each css, whenever that may be, the
4290	* extra dentry ref is put so that dentry destruction happens only
4291	* after all css's are released.
4292	*/
4293	for_each_subsys(cgrp->root, ss)
4294	css_put(cgrp->subsys[ss->subsys_id]);
4295
4296	raw_spin_lock(&release_list_lock);
4297	if (!list_empty(&cgrp->release_list))
4298	list_del_init(&cgrp->release_list);
4299	raw_spin_unlock(&release_list_lock);
4300
4301	/* delete this cgroup from parent->children */
4302	list_del_rcu(&cgrp->sibling);
4303	list_del_init(&cgrp->allcg_node);
4304
4305	dget(d);
4306	cgroup_d_remove_dir(d);
4307	dput(d);
4308
4309	set_bit(CGRP_RELEASABLE, &parent->flags);
4310	check_for_release(parent);
4311
4312	/*
4313	* Unregister events and notify userspace.
4314	* Notify userspace about cgroup removing only after rmdir of cgroup
4315	* directory to avoid race between userspace and kernelspace.
4316	*/
4317	spin_lock(&cgrp->event_list_lock);
4318	list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
4319	list_del_init(&event->list);
4320	schedule_work(&event->remove);
4321	}
4322	spin_unlock(&cgrp->event_list_lock);
4323
4324	return 0;
4325	}
4326
4327	static int cgroup_rmdir(struct inode unused_dir, struct dentry dentry)
4328	{
4329	int ret;
4330
4331	mutex_lock(&cgroup_mutex);
4332	ret = cgroup_destroy_locked(dentry->d_fsdata);
4333	mutex_unlock(&cgroup_mutex);
4334
4335	return ret;
4336	}
4337
4338	static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
4339	{
4340	INIT_LIST_HEAD(&ss->cftsets);
4341
4342	/*
4343	* base_cftset is embedded in subsys itself, no need to worry about
4344	* deregistration.
4345	*/
4346	if (ss->base_cftypes) {
4347	ss->base_cftset.cfts = ss->base_cftypes;
4348	list_add_tail(&ss->base_cftset.node, &ss->cftsets);
4349	}
4350	}
4351
4352	static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4353	{
4354	struct cgroup_subsys_state *css;
4355
4356	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4357
4358	mutex_lock(&cgroup_mutex);
4359
4360	/* init base cftset */
4361	cgroup_init_cftsets(ss);
4362
4363	/* Create the top cgroup state for this subsystem */
4364	list_add(&ss->sibling, &rootnode.subsys_list);
4365	ss->root = &rootnode;
4366	css = ss->css_alloc(dummytop);
4367	/* We don't handle early failures gracefully */
4368	BUG_ON(IS_ERR(css));
4369	init_cgroup_css(css, ss, dummytop);
4370
4371	/* Update the init_css_set to contain a subsys
4372	* pointer to this state - since the subsystem is
4373	* newly registered, all tasks and hence the
4374	* init_css_set is in the subsystem's top cgroup. */
4375	init_css_set.subsys[ss->subsys_id] = css;
4376
4377	need_forkexit_callback \|= ss->fork \|\| ss->exit;
4378
4379	/* At system boot, before all subsystems have been
4380	* registered, no tasks have been forked, so we don't
4381	* need to invoke fork callbacks here. */
4382	BUG_ON(!list_empty(&init_task.tasks));
4383
4384	BUG_ON(online_css(ss, dummytop));
4385
4386	mutex_unlock(&cgroup_mutex);
4387
4388	/* this function shouldn't be used with modular subsystems, since they
4389	* need to register a subsys_id, among other things */
4390	BUG_ON(ss->module);
4391	}
4392
4393	/**
4394	* cgroup_load_subsys: load and register a modular subsystem at runtime
4395	* @ss: the subsystem to load
4396	*
4397	* This function should be called in a modular subsystem's initcall. If the
4398	* subsystem is built as a module, it will be assigned a new subsys_id and set
4399	* up for use. If the subsystem is built-in anyway, work is delegated to the
4400	* simpler cgroup_init_subsys.
4401	*/
4402	int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
4403	{
4404	struct cgroup_subsys_state *css;
4405	int i, ret;
4406	struct hlist_node *tmp;
4407	struct css_set *cg;
4408	unsigned long key;
4409
4410	/* check name and function validity */
4411	if (ss->name == NULL \|\| strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN \|\|
4412	ss->css_alloc == NULL \|\| ss->css_free == NULL)
4413	return -EINVAL;
4414
4415	/*
4416	* we don't support callbacks in modular subsystems. this check is
4417	* before the ss->module check for consistency; a subsystem that could
4418	* be a module should still have no callbacks even if the user isn't
4419	* compiling it as one.
4420	*/
4421	if (ss->fork \|\| ss->exit)
4422	return -EINVAL;
4423
4424	/*
4425	* an optionally modular subsystem is built-in: we want to do nothing,
4426	* since cgroup_init_subsys will have already taken care of it.
4427	*/
4428	if (ss->module == NULL) {
4429	/* a sanity check */
4430	BUG_ON(subsys[ss->subsys_id] != ss);
4431	return 0;
4432	}
4433
4434	/* init base cftset */
4435	cgroup_init_cftsets(ss);
4436
4437	mutex_lock(&cgroup_mutex);
4438	subsys[ss->subsys_id] = ss;
4439
4440	/*
4441	* no ss->css_alloc seems to need anything important in the ss
4442	* struct, so this can happen first (i.e. before the rootnode
4443	* attachment).
4444	*/
4445	css = ss->css_alloc(dummytop);
4446	if (IS_ERR(css)) {
4447	/* failure case - need to deassign the subsys[] slot. */
4448	subsys[ss->subsys_id] = NULL;
4449	mutex_unlock(&cgroup_mutex);
4450	return PTR_ERR(css);
4451	}
4452
4453	list_add(&ss->sibling, &rootnode.subsys_list);
4454	ss->root = &rootnode;
4455
4456	/* our new subsystem will be attached to the dummy hierarchy. */
4457	init_cgroup_css(css, ss, dummytop);
4458	/* init_idr must be after init_cgroup_css because it sets css->id. */
4459	if (ss->use_id) {
4460	ret = cgroup_init_idr(ss, css);
4461	if (ret)
4462	goto err_unload;
4463	}
4464
4465	/*
4466	* Now we need to entangle the css into the existing css_sets. unlike
4467	* in cgroup_init_subsys, there are now multiple css_sets, so each one
4468	* will need a new pointer to it; done by iterating the css_set_table.
4469	* furthermore, modifying the existing css_sets will corrupt the hash
4470	* table state, so each changed css_set will need its hash recomputed.
4471	* this is all done under the css_set_lock.
4472	*/
4473	write_lock(&css_set_lock);
4474	hash_for_each_safe(css_set_table, i, tmp, cg, hlist) {
4475	/* skip entries that we already rehashed */
4476	if (cg->subsys[ss->subsys_id])
4477	continue;
4478	/* remove existing entry */
4479	hash_del(&cg->hlist);
4480	/* set new value */
4481	cg->subsys[ss->subsys_id] = css;
4482	/* recompute hash and restore entry */
4483	key = css_set_hash(cg->subsys);
4484	hash_add(css_set_table, &cg->hlist, key);
4485	}
4486	write_unlock(&css_set_lock);
4487
4488	ret = online_css(ss, dummytop);
4489	if (ret)
4490	goto err_unload;
4491
4492	/* success! */
4493	mutex_unlock(&cgroup_mutex);
4494	return 0;
4495
4496	err_unload:
4497	mutex_unlock(&cgroup_mutex);
4498	/* @ss can't be mounted here as try_module_get() would fail */
4499	cgroup_unload_subsys(ss);
4500	return ret;
4501	}
4502	EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4503
4504	/**
4505	* cgroup_unload_subsys: unload a modular subsystem
4506	* @ss: the subsystem to unload
4507	*
4508	* This function should be called in a modular subsystem's exitcall. When this
4509	* function is invoked, the refcount on the subsystem's module will be 0, so
4510	* the subsystem will not be attached to any hierarchy.
4511	*/
4512	void cgroup_unload_subsys(struct cgroup_subsys *ss)
4513	{
4514	struct cg_cgroup_link *link;
4515
4516	BUG_ON(ss->module == NULL);
4517
4518	/*
4519	* we shouldn't be called if the subsystem is in use, and the use of
4520	* try_module_get in parse_cgroupfs_options should ensure that it
4521	* doesn't start being used while we're killing it off.
4522	*/
4523	BUG_ON(ss->root != &rootnode);
4524
4525	mutex_lock(&cgroup_mutex);
4526
4527	offline_css(ss, dummytop);
4528
4529	if (ss->use_id)
4530	idr_destroy(&ss->idr);
4531
4532	/* deassign the subsys_id */
4533	subsys[ss->subsys_id] = NULL;
4534
4535	/* remove subsystem from rootnode's list of subsystems */
4536	list_del_init(&ss->sibling);
4537
4538	/*
4539	* disentangle the css from all css_sets attached to the dummytop. as
4540	* in loading, we need to pay our respects to the hashtable gods.
4541	*/
4542	write_lock(&css_set_lock);
4543	list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {
4544	struct css_set *cg = link->cg;
4545	unsigned long key;
4546
4547	hash_del(&cg->hlist);
4548	cg->subsys[ss->subsys_id] = NULL;
4549	key = css_set_hash(cg->subsys);
4550	hash_add(css_set_table, &cg->hlist, key);
4551	}
4552	write_unlock(&css_set_lock);
4553
4554	/*
4555	* remove subsystem's css from the dummytop and free it - need to
4556	* free before marking as null because ss->css_free needs the
4557	* cgrp->subsys pointer to find their state. note that this also
4558	* takes care of freeing the css_id.
4559	*/
4560	ss->css_free(dummytop);
4561	dummytop->subsys[ss->subsys_id] = NULL;
4562
4563	mutex_unlock(&cgroup_mutex);
4564	}
4565	EXPORT_SYMBOL_GPL(cgroup_unload_subsys);
4566
4567	/**
4568	* cgroup_init_early - cgroup initialization at system boot
4569	*
4570	* Initialize cgroups at system boot, and initialize any
4571	* subsystems that request early init.
4572	*/
4573	int __init cgroup_init_early(void)
4574	{
4575	int i;
4576	atomic_set(&init_css_set.refcount, 1);
4577	INIT_LIST_HEAD(&init_css_set.cg_links);
4578	INIT_LIST_HEAD(&init_css_set.tasks);
4579	INIT_HLIST_NODE(&init_css_set.hlist);
4580	css_set_count = 1;
4581	init_cgroup_root(&rootnode);
4582	root_count = 1;
4583	init_task.cgroups = &init_css_set;
4584
4585	init_css_set_link.cg = &init_css_set;
4586	init_css_set_link.cgrp = dummytop;
4587	list_add(&init_css_set_link.cgrp_link_list,
4588	&rootnode.top_cgroup.css_sets);
4589	list_add(&init_css_set_link.cg_link_list,
4590	&init_css_set.cg_links);
4591
4592	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4593	struct cgroup_subsys *ss = subsys[i];
4594
4595	/* at bootup time, we don't worry about modular subsystems */
4596	if (!ss \|\| ss->module)
4597	continue;
4598
4599	BUG_ON(!ss->name);
4600	BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4601	BUG_ON(!ss->css_alloc);
4602	BUG_ON(!ss->css_free);
4603	if (ss->subsys_id != i) {
4604	printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4605	ss->name, ss->subsys_id);
4606	BUG();
4607	}
4608
4609	if (ss->early_init)
4610	cgroup_init_subsys(ss);
4611	}
4612	return 0;
4613	}
4614
4615	/**
4616	* cgroup_init - cgroup initialization
4617	*
4618	* Register cgroup filesystem and /proc file, and initialize
4619	* any subsystems that didn't request early init.
4620	*/
4621	int __init cgroup_init(void)
4622	{
4623	int err;
4624	int i;
4625	unsigned long key;
4626
4627	err = bdi_init(&cgroup_backing_dev_info);
4628	if (err)
4629	return err;
4630
4631	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4632	struct cgroup_subsys *ss = subsys[i];
4633
4634	/* at bootup time, we don't worry about modular subsystems */
4635	if (!ss \|\| ss->module)
4636	continue;
4637	if (!ss->early_init)
4638	cgroup_init_subsys(ss);
4639	if (ss->use_id)
4640	cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4641	}
4642
4643	/* Add init_css_set to the hash table */
4644	key = css_set_hash(init_css_set.subsys);
4645	hash_add(css_set_table, &init_css_set.hlist, key);
4646	BUG_ON(!init_root_id(&rootnode));
4647
4648	cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
4649	if (!cgroup_kobj) {
4650	err = -ENOMEM;
4651	goto out;
4652	}
4653
4654	err = register_filesystem(&cgroup_fs_type);
4655	if (err < 0) {
4656	kobject_put(cgroup_kobj);
4657	goto out;
4658	}
4659
4660	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4661
4662	out:
4663	if (err)
4664	bdi_destroy(&cgroup_backing_dev_info);
4665
4666	return err;
4667	}
4668
4669	/*
4670	* proc_cgroup_show()
4671	* - Print task's cgroup paths into seq_file, one line for each hierarchy
4672	* - Used for /proc/<pid>/cgroup.
4673	* - No need to task_lock(tsk) on this tsk->cgroup reference, as it
4674	* doesn't really matter if tsk->cgroup changes after we read it,
4675	* and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4676	* anyway. No need to check that tsk->cgroup != NULL, thanks to
4677	* the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
4678	* cgroup to top_cgroup.
4679	*/
4680
4681	/* TODO: Use a proper seq_file iterator */
4682	int proc_cgroup_show(struct seq_file m, void v)
4683	{
4684	struct pid *pid;
4685	struct task_struct *tsk;
4686	char *buf;
4687	int retval;
4688	struct cgroupfs_root *root;
4689
4690	retval = -ENOMEM;
4691	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4692	if (!buf)
4693	goto out;
4694
4695	retval = -ESRCH;
4696	pid = m->private;
4697	tsk = get_pid_task(pid, PIDTYPE_PID);
4698	if (!tsk)
4699	goto out_free;
4700
4701	retval = 0;
4702
4703	mutex_lock(&cgroup_mutex);
4704
4705	for_each_active_root(root) {
4706	struct cgroup_subsys *ss;
4707	struct cgroup *cgrp;
4708	int count = 0;
4709
4710	seq_printf(m, "%d:", root->hierarchy_id);
4711	for_each_subsys(root, ss)
4712	seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4713	if (strlen(root->name))
4714	seq_printf(m, "%sname=%s", count ? "," : "",
4715	root->name);
4716	seq_putc(m, ':');
4717	cgrp = task_cgroup_from_root(tsk, root);
4718	retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4719	if (retval < 0)
4720	goto out_unlock;
4721	seq_puts(m, buf);
4722	seq_putc(m, '\n');
4723	}
4724
4725	out_unlock:
4726	mutex_unlock(&cgroup_mutex);
4727	put_task_struct(tsk);
4728	out_free:
4729	kfree(buf);
4730	out:
4731	return retval;
4732	}
4733
4734	/* Display information about each subsystem and each hierarchy */
4735	static int proc_cgroupstats_show(struct seq_file m, void v)
4736	{
4737	int i;
4738
4739	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
4740	/*
4741	* ideally we don't want subsystems moving around while we do this.
4742	* cgroup_mutex is also necessary to guarantee an atomic snapshot of
4743	* subsys/hierarchy state.
4744	*/
4745	mutex_lock(&cgroup_mutex);
4746	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4747	struct cgroup_subsys *ss = subsys[i];
4748	if (ss == NULL)
4749	continue;
4750	seq_printf(m, "%s\t%d\t%d\t%d\n",
4751	ss->name, ss->root->hierarchy_id,
4752	ss->root->number_of_cgroups, !ss->disabled);
4753	}
4754	mutex_unlock(&cgroup_mutex);
4755	return 0;
4756	}
4757
4758	static int cgroupstats_open(struct inode inode, struct file file)
4759	{
4760	return single_open(file, proc_cgroupstats_show, NULL);
4761	}
4762
4763	static const struct file_operations proc_cgroupstats_operations = {
4764	.open = cgroupstats_open,
4765	.read = seq_read,
4766	.llseek = seq_lseek,
4767	.release = single_release,
4768	};
4769
4770	/**
4771	* cgroup_fork - attach newly forked task to its parents cgroup.
4772	* @child: pointer to task_struct of forking parent process.
4773	*
4774	* Description: A task inherits its parent's cgroup at fork().
4775	*
4776	* A pointer to the shared css_set was automatically copied in
4777	* fork.c by dup_task_struct(). However, we ignore that copy, since
4778	* it was not made under the protection of RCU or cgroup_mutex, so
4779	* might no longer be a valid cgroup pointer. cgroup_attach_task() might
4780	* have already changed current->cgroups, allowing the previously
4781	* referenced cgroup group to be removed and freed.
4782	*
4783	* At the point that cgroup_fork() is called, 'current' is the parent
4784	* task, and the passed argument 'child' points to the child task.
4785	*/
4786	void cgroup_fork(struct task_struct *child)
4787	{
4788	task_lock(current);
4789	child->cgroups = current->cgroups;
4790	get_css_set(child->cgroups);
4791	task_unlock(current);
4792	INIT_LIST_HEAD(&child->cg_list);
4793	}
4794
4795	/**
4796	* cgroup_post_fork - called on a new task after adding it to the task list
4797	* @child: the task in question
4798	*
4799	* Adds the task to the list running through its css_set if necessary and
4800	* call the subsystem fork() callbacks. Has to be after the task is
4801	* visible on the task list in case we race with the first call to
4802	* cgroup_iter_start() - to guarantee that the new task ends up on its
4803	* list.
4804	*/
4805	void cgroup_post_fork(struct task_struct *child)
4806	{
4807	int i;
4808
4809	/*
4810	* use_task_css_set_links is set to 1 before we walk the tasklist
4811	* under the tasklist_lock and we read it here after we added the child
4812	* to the tasklist under the tasklist_lock as well. If the child wasn't
4813	* yet in the tasklist when we walked through it from
4814	* cgroup_enable_task_cg_lists(), then use_task_css_set_links value
4815	* should be visible now due to the paired locking and barriers implied
4816	* by LOCK/UNLOCK: it is written before the tasklist_lock unlock
4817	* in cgroup_enable_task_cg_lists() and read here after the tasklist_lock
4818	* lock on fork.
4819	*/
4820	if (use_task_css_set_links) {
4821	write_lock(&css_set_lock);
4822	task_lock(child);
4823	if (list_empty(&child->cg_list))
4824	list_add(&child->cg_list, &child->cgroups->tasks);
4825	task_unlock(child);
4826	write_unlock(&css_set_lock);
4827	}
4828
4829	/*
4830	* Call ss->fork(). This must happen after @child is linked on
4831	* css_set; otherwise, @child might change state between ->fork()
4832	* and addition to css_set.
4833	*/
4834	if (need_forkexit_callback) {
4835	/*
4836	* fork/exit callbacks are supported only for builtin
4837	* subsystems, and the builtin section of the subsys
4838	* array is immutable, so we don't need to lock the
4839	* subsys array here. On the other hand, modular section
4840	* of the array can be freed at module unload, so we
4841	* can't touch that.
4842	*/
4843	for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4844	struct cgroup_subsys *ss = subsys[i];
4845
4846	if (ss->fork)
4847	ss->fork(child);
4848	}
4849	}
4850	}
4851
4852	/**
4853	* cgroup_exit - detach cgroup from exiting task
4854	* @tsk: pointer to task_struct of exiting process
4855	* @run_callback: run exit callbacks?
4856	*
4857	* Description: Detach cgroup from @tsk and release it.
4858	*
4859	* Note that cgroups marked notify_on_release force every task in
4860	* them to take the global cgroup_mutex mutex when exiting.
4861	* This could impact scaling on very large systems. Be reluctant to
4862	* use notify_on_release cgroups where very high task exit scaling
4863	* is required on large systems.
4864	*
4865	* the_top_cgroup_hack:
4866	*
4867	* Set the exiting tasks cgroup to the root cgroup (top_cgroup).
4868	*
4869	* We call cgroup_exit() while the task is still competent to
4870	* handle notify_on_release(), then leave the task attached to the
4871	* root cgroup in each hierarchy for the remainder of its exit.
4872	*
4873	* To do this properly, we would increment the reference count on
4874	* top_cgroup, and near the very end of the kernel/exit.c do_exit()
4875	* code we would add a second cgroup function call, to drop that
4876	* reference. This would just create an unnecessary hot spot on
4877	* the top_cgroup reference count, to no avail.
4878	*
4879	* Normally, holding a reference to a cgroup without bumping its
4880	* count is unsafe. The cgroup could go away, or someone could
4881	* attach us to a different cgroup, decrementing the count on
4882	* the first cgroup that we never incremented. But in this case,
4883	* top_cgroup isn't going away, and either task has PF_EXITING set,
4884	* which wards off any cgroup_attach_task() attempts, or task is a failed
4885	* fork, never visible to cgroup_attach_task.
4886	*/
4887	void cgroup_exit(struct task_struct *tsk, int run_callbacks)
4888	{
4889	struct css_set *cg;
4890	int i;
4891
4892	/*
4893	* Unlink from the css_set task list if necessary.
4894	* Optimistically check cg_list before taking
4895	* css_set_lock
4896	*/
4897	if (!list_empty(&tsk->cg_list)) {
4898	write_lock(&css_set_lock);
4899	if (!list_empty(&tsk->cg_list))
4900	list_del_init(&tsk->cg_list);
4901	write_unlock(&css_set_lock);
4902	}
4903
4904	/* Reassign the task to the init_css_set. */
4905	task_lock(tsk);
4906	cg = tsk->cgroups;
4907	tsk->cgroups = &init_css_set;
4908
4909	if (run_callbacks && need_forkexit_callback) {
4910	/*
4911	* fork/exit callbacks are supported only for builtin
4912	* subsystems, see cgroup_post_fork() for details.
4913	*/
4914	for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4915	struct cgroup_subsys *ss = subsys[i];
4916
4917	if (ss->exit) {
4918	struct cgroup *old_cgrp =
4919	rcu_dereference_raw(cg->subsys[i])->cgroup;
4920	struct cgroup *cgrp = task_cgroup(tsk, i);
4921	ss->exit(cgrp, old_cgrp, tsk);
4922	}
4923	}
4924	}
4925	task_unlock(tsk);
4926
4927	put_css_set_taskexit(cg);
4928	}
4929
4930	static void check_for_release(struct cgroup *cgrp)
4931	{
4932	/* All of these checks rely on RCU to keep the cgroup
4933	* structure alive */
4934	if (cgroup_is_releasable(cgrp) &&
4935	!atomic_read(&cgrp->count) && list_empty(&cgrp->children)) {
4936	/*
4937	* Control Group is currently removeable. If it's not
4938	* already queued for a userspace notification, queue
4939	* it now
4940	*/
4941	int need_schedule_work = 0;
4942
4943	raw_spin_lock(&release_list_lock);
4944	if (!cgroup_is_removed(cgrp) &&
4945	list_empty(&cgrp->release_list)) {
4946	list_add(&cgrp->release_list, &release_list);
4947	need_schedule_work = 1;
4948	}
4949	raw_spin_unlock(&release_list_lock);
4950	if (need_schedule_work)
4951	schedule_work(&release_agent_work);
4952	}
4953	}
4954
4955	/* Caller must verify that the css is not for root cgroup */
4956	bool __css_tryget(struct cgroup_subsys_state *css)
4957	{
4958	while (true) {
4959	int t, v;
4960
4961	v = css_refcnt(css);
4962	t = atomic_cmpxchg(&css->refcnt, v, v + 1);
4963	if (likely(t == v))
4964	return true;
4965	else if (t < 0)
4966	return false;
4967	cpu_relax();
4968	}
4969	}
4970	EXPORT_SYMBOL_GPL(__css_tryget);
4971
4972	/* Caller must verify that the css is not for root cgroup */
4973	void __css_put(struct cgroup_subsys_state *css)
4974	{
4975	int v;
4976
4977	v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));
4978	if (v == 0)
4979	schedule_work(&css->dput_work);
4980	}
4981	EXPORT_SYMBOL_GPL(__css_put);
4982
4983	/*
4984	* Notify userspace when a cgroup is released, by running the
4985	* configured release agent with the name of the cgroup (path
4986	* relative to the root of cgroup file system) as the argument.
4987	*
4988	* Most likely, this user command will try to rmdir this cgroup.
4989	*
4990	* This races with the possibility that some other task will be
4991	* attached to this cgroup before it is removed, or that some other
4992	* user task will 'mkdir' a child cgroup of this cgroup. That's ok.
4993	* The presumed 'rmdir' will fail quietly if this cgroup is no longer
4994	* unused, and this cgroup will be reprieved from its death sentence,
4995	* to continue to serve a useful existence. Next time it's released,
4996	* we will get notified again, if it still has 'notify_on_release' set.
4997	*
4998	* The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
4999	* means only wait until the task is successfully execve()'d. The
5000	* separate release agent task is forked by call_usermodehelper(),
5001	* then control in this thread returns here, without waiting for the
5002	* release agent task. We don't bother to wait because the caller of
5003	* this routine has no use for the exit status of the release agent
5004	* task, so no sense holding our caller up for that.
5005	*/
5006	static void cgroup_release_agent(struct work_struct *work)
5007	{
5008	BUG_ON(work != &release_agent_work);
5009	mutex_lock(&cgroup_mutex);
5010	raw_spin_lock(&release_list_lock);
5011	while (!list_empty(&release_list)) {
5012	char argv[3], envp[3];
5013	int i;
5014	char pathbuf = NULL, agentbuf = NULL;
5015	struct cgroup *cgrp = list_entry(release_list.next,
5016	struct cgroup,
5017	release_list);
5018	list_del_init(&cgrp->release_list);
5019	raw_spin_unlock(&release_list_lock);
5020	pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
5021	if (!pathbuf)
5022	goto continue_free;
5023	if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
5024	goto continue_free;
5025	agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
5026	if (!agentbuf)
5027	goto continue_free;
5028
5029	i = 0;
5030	argv[i++] = agentbuf;
5031	argv[i++] = pathbuf;
5032	argv[i] = NULL;
5033
5034	i = 0;
5035	/* minimal command environment */
5036	envp[i++] = "HOME=/";
5037	envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
5038	envp[i] = NULL;
5039
5040	/* Drop the lock while we invoke the usermode helper,
5041	* since the exec could involve hitting disk and hence
5042	* be a slow process */
5043	mutex_unlock(&cgroup_mutex);
5044	call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
5045	mutex_lock(&cgroup_mutex);
5046	continue_free:
5047	kfree(pathbuf);
5048	kfree(agentbuf);
5049	raw_spin_lock(&release_list_lock);
5050	}
5051	raw_spin_unlock(&release_list_lock);
5052	mutex_unlock(&cgroup_mutex);
5053	}
5054
5055	static int __init cgroup_disable(char *str)
5056	{
5057	int i;
5058	char *token;
5059
5060	while ((token = strsep(&str, ",")) != NULL) {
5061	if (!*token)
5062	continue;
5063	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
5064	struct cgroup_subsys *ss = subsys[i];
5065
5066	/*
5067	* cgroup_disable, being at boot time, can't
5068	* know about module subsystems, so we don't
5069	* worry about them.
5070	*/
5071	if (!ss \|\| ss->module)
5072	continue;
5073
5074	if (!strcmp(token, ss->name)) {
5075	ss->disabled = 1;
5076	printk(KERN_INFO "Disabling %s control group"
5077	" subsystem\n", ss->name);
5078	break;
5079	}
5080	}
5081	}
5082	return 1;
5083	}
5084	__setup("cgroup_disable=", cgroup_disable);
5085
5086	/*
5087	* Functons for CSS ID.
5088	*/
5089
5090	/*
5091	*To get ID other than 0, this should be called when !cgroup_is_removed().
5092	*/
5093	unsigned short css_id(struct cgroup_subsys_state *css)
5094	{
5095	struct css_id *cssid;
5096
5097	/*
5098	* This css_id() can return correct value when somone has refcnt
5099	* on this or this is under rcu_read_lock(). Once css->id is allocated,
5100	* it's unchanged until freed.
5101	*/
5102	cssid = rcu_dereference_check(css->id, css_refcnt(css));
5103
5104	if (cssid)
5105	return cssid->id;
5106	return 0;
5107	}
5108	EXPORT_SYMBOL_GPL(css_id);
5109
5110	unsigned short css_depth(struct cgroup_subsys_state *css)
5111	{
5112	struct css_id *cssid;
5113
5114	cssid = rcu_dereference_check(css->id, css_refcnt(css));
5115
5116	if (cssid)
5117	return cssid->depth;
5118	return 0;
5119	}
5120	EXPORT_SYMBOL_GPL(css_depth);
5121
5122	/**
5123	* css_is_ancestor - test "root" css is an ancestor of "child"
5124	* @child: the css to be tested.
5125	* @root: the css supporsed to be an ancestor of the child.
5126	*
5127	* Returns true if "root" is an ancestor of "child" in its hierarchy. Because
5128	* this function reads css->id, the caller must hold rcu_read_lock().
5129	* But, considering usual usage, the csses should be valid objects after test.
5130	* Assuming that the caller will do some action to the child if this returns
5131	* returns true, the caller must take "child";s reference count.
5132	* If "child" is valid object and this returns true, "root" is valid, too.
5133	*/
5134
5135	bool css_is_ancestor(struct cgroup_subsys_state *child,
5136	const struct cgroup_subsys_state *root)
5137	{
5138	struct css_id *child_id;
5139	struct css_id *root_id;
5140
5141	child_id = rcu_dereference(child->id);
5142	if (!child_id)
5143	return false;
5144	root_id = rcu_dereference(root->id);
5145	if (!root_id)
5146	return false;
5147	if (child_id->depth < root_id->depth)
5148	return false;
5149	if (child_id->stack[root_id->depth] != root_id->id)
5150	return false;
5151	return true;
5152	}
5153
5154	void free_css_id(struct cgroup_subsys ss, struct cgroup_subsys_state css)
5155	{
5156	struct css_id *id = css->id;
5157	/* When this is called before css_id initialization, id can be NULL */
5158	if (!id)
5159	return;
5160
5161	BUG_ON(!ss->use_id);
5162
5163	rcu_assign_pointer(id->css, NULL);
5164	rcu_assign_pointer(css->id, NULL);
5165	spin_lock(&ss->id_lock);
5166	idr_remove(&ss->idr, id->id);
5167	spin_unlock(&ss->id_lock);
5168	kfree_rcu(id, rcu_head);
5169	}
5170	EXPORT_SYMBOL_GPL(free_css_id);
5171
5172	/*
5173	* This is called by init or create(). Then, calls to this function are
5174	* always serialized (By cgroup_mutex() at create()).
5175	*/
5176
5177	static struct css_id get_new_cssid(struct cgroup_subsys ss, int depth)
5178	{
5179	struct css_id *newid;
5180	int ret, size;
5181
5182	BUG_ON(!ss->use_id);
5183
5184	size = sizeof(newid) + sizeof(unsigned short) (depth + 1);
5185	newid = kzalloc(size, GFP_KERNEL);
5186	if (!newid)
5187	return ERR_PTR(-ENOMEM);
5188
5189	idr_preload(GFP_KERNEL);
5190	spin_lock(&ss->id_lock);
5191	/* Don't use 0. allocates an ID of 1-65535 */
5192	ret = idr_alloc(&ss->idr, newid, 1, CSS_ID_MAX + 1, GFP_NOWAIT);
5193	spin_unlock(&ss->id_lock);
5194	idr_preload_end();
5195
5196	/* Returns error when there are no free spaces for new ID.*/
5197	if (ret < 0)
5198	goto err_out;
5199
5200	newid->id = ret;
5201	newid->depth = depth;
5202	return newid;
5203	err_out:
5204	kfree(newid);
5205	return ERR_PTR(ret);
5206
5207	}
5208
5209	static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
5210	struct cgroup_subsys_state *rootcss)
5211	{
5212	struct css_id *newid;
5213
5214	spin_lock_init(&ss->id_lock);
5215	idr_init(&ss->idr);
5216
5217	newid = get_new_cssid(ss, 0);
5218	if (IS_ERR(newid))
5219	return PTR_ERR(newid);
5220
5221	newid->stack[0] = newid->id;
5222	newid->css = rootcss;
5223	rootcss->id = newid;
5224	return 0;
5225	}
5226
5227	static int alloc_css_id(struct cgroup_subsys ss, struct cgroup parent,
5228	struct cgroup *child)
5229	{
5230	int subsys_id, i, depth = 0;
5231	struct cgroup_subsys_state parent_css, child_css;
5232	struct css_id child_id, parent_id;
5233
5234	subsys_id = ss->subsys_id;
5235	parent_css = parent->subsys[subsys_id];
5236	child_css = child->subsys[subsys_id];
5237	parent_id = parent_css->id;
5238	depth = parent_id->depth + 1;
5239
5240	child_id = get_new_cssid(ss, depth);
5241	if (IS_ERR(child_id))
5242	return PTR_ERR(child_id);
5243
5244	for (i = 0; i < depth; i++)
5245	child_id->stack[i] = parent_id->stack[i];
5246	child_id->stack[depth] = child_id->id;
5247	/*
5248	* child_id->css pointer will be set after this cgroup is available
5249	* see cgroup_populate_dir()
5250	*/
5251	rcu_assign_pointer(child_css->id, child_id);
5252
5253	return 0;
5254	}
5255
5256	/**
5257	* css_lookup - lookup css by id
5258	* @ss: cgroup subsys to be looked into.
5259	* @id: the id
5260	*
5261	* Returns pointer to cgroup_subsys_state if there is valid one with id.
5262	* NULL if not. Should be called under rcu_read_lock()
5263	*/
5264	struct cgroup_subsys_state css_lookup(struct cgroup_subsys ss, int id)
5265	{
5266	struct css_id *cssid = NULL;
5267
5268	BUG_ON(!ss->use_id);
5269	cssid = idr_find(&ss->idr, id);
5270
5271	if (unlikely(!cssid))
5272	return NULL;
5273
5274	return rcu_dereference(cssid->css);
5275	}
5276	EXPORT_SYMBOL_GPL(css_lookup);
5277
5278	/*
5279	* get corresponding css from file open on cgroupfs directory
5280	*/
5281	struct cgroup_subsys_state cgroup_css_from_dir(struct file f, int id)
5282	{
5283	struct cgroup *cgrp;
5284	struct inode *inode;
5285	struct cgroup_subsys_state *css;
5286
5287	inode = file_inode(f);
5288	/* check in cgroup filesystem dir */
5289	if (inode->i_op != &cgroup_dir_inode_operations)
5290	return ERR_PTR(-EBADF);
5291
5292	if (id < 0 \|\| id >= CGROUP_SUBSYS_COUNT)
5293	return ERR_PTR(-EINVAL);
5294
5295	/* get cgroup */
5296	cgrp = __d_cgrp(f->f_dentry);
5297	css = cgrp->subsys[id];
5298	return css ? css : ERR_PTR(-ENOENT);
5299	}
5300
5301	#ifdef CONFIG_CGROUP_DEBUG
5302	static struct cgroup_subsys_state debug_css_alloc(struct cgroup cont)
5303	{
5304	struct cgroup_subsys_state css = kzalloc(sizeof(css), GFP_KERNEL);
5305
5306	if (!css)
5307	return ERR_PTR(-ENOMEM);
5308
5309	return css;
5310	}
5311
5312	static void debug_css_free(struct cgroup *cont)
5313	{
5314	kfree(cont->subsys[debug_subsys_id]);
5315	}
5316
5317	static u64 cgroup_refcount_read(struct cgroup cont, struct cftype cft)
5318	{
5319	return atomic_read(&cont->count);
5320	}
5321
5322	static u64 debug_taskcount_read(struct cgroup cont, struct cftype cft)
5323	{
5324	return cgroup_task_count(cont);
5325	}
5326
5327	static u64 current_css_set_read(struct cgroup cont, struct cftype cft)
5328	{
5329	return (u64)(unsigned long)current->cgroups;
5330	}
5331
5332	static u64 current_css_set_refcount_read(struct cgroup *cont,
5333	struct cftype *cft)
5334	{
5335	u64 count;
5336
5337	rcu_read_lock();
5338	count = atomic_read(&current->cgroups->refcount);
5339	rcu_read_unlock();
5340	return count;
5341	}
5342
5343	static int current_css_set_cg_links_read(struct cgroup *cont,
5344	struct cftype *cft,
5345	struct seq_file *seq)
5346	{
5347	struct cg_cgroup_link *link;
5348	struct css_set *cg;
5349
5350	read_lock(&css_set_lock);
5351	rcu_read_lock();
5352	cg = rcu_dereference(current->cgroups);
5353	list_for_each_entry(link, &cg->cg_links, cg_link_list) {
5354	struct cgroup *c = link->cgrp;
5355	const char *name;
5356
5357	if (c->dentry)
5358	name = c->dentry->d_name.name;
5359	else
5360	name = "?";
5361	seq_printf(seq, "Root %d group %s\n",
5362	c->root->hierarchy_id, name);
5363	}
5364	rcu_read_unlock();
5365	read_unlock(&css_set_lock);
5366	return 0;
5367	}
5368
5369	#define MAX_TASKS_SHOWN_PER_CSS 25
5370	static int cgroup_css_links_read(struct cgroup *cont,
5371	struct cftype *cft,
5372	struct seq_file *seq)
5373	{
5374	struct cg_cgroup_link *link;
5375
5376	read_lock(&css_set_lock);
5377	list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
5378	struct css_set *cg = link->cg;
5379	struct task_struct *task;
5380	int count = 0;
5381	seq_printf(seq, "css_set %p\n", cg);
5382	list_for_each_entry(task, &cg->tasks, cg_list) {
5383	if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
5384	seq_puts(seq, " ...\n");
5385	break;
5386	} else {
5387	seq_printf(seq, " task %d\n",
5388	task_pid_vnr(task));
5389	}
5390	}
5391	}
5392	read_unlock(&css_set_lock);
5393	return 0;
5394	}
5395
5396	static u64 releasable_read(struct cgroup cgrp, struct cftype cft)
5397	{
5398	return test_bit(CGRP_RELEASABLE, &cgrp->flags);
5399	}
5400
5401	static struct cftype debug_files[] = {
5402	{
5403	.name = "cgroup_refcount",
5404	.read_u64 = cgroup_refcount_read,
5405	},
5406	{
5407	.name = "taskcount",
5408	.read_u64 = debug_taskcount_read,
5409	},
5410
5411	{
5412	.name = "current_css_set",
5413	.read_u64 = current_css_set_read,
5414	},
5415
5416	{
5417	.name = "current_css_set_refcount",
5418	.read_u64 = current_css_set_refcount_read,
5419	},
5420
5421	{
5422	.name = "current_css_set_cg_links",
5423	.read_seq_string = current_css_set_cg_links_read,
5424	},
5425
5426	{
5427	.name = "cgroup_css_links",
5428	.read_seq_string = cgroup_css_links_read,
5429	},
5430
5431	{
5432	.name = "releasable",
5433	.read_u64 = releasable_read,
5434	},
5435
5436	{ } /* terminate */
5437	};
5438
5439	struct cgroup_subsys debug_subsys = {
5440	.name = "debug",
5441	.css_alloc = debug_css_alloc,
5442	.css_free = debug_css_free,
5443	.subsys_id = debug_subsys_id,
5444	.base_cftypes = debug_files,
5445	};
5446	#endif /* CONFIG_CGROUP_DEBUG */