Loading...
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/fs.h>
34#include <linux/init_task.h>
35#include <linux/kernel.h>
36#include <linux/list.h>
37#include <linux/mm.h>
38#include <linux/mutex.h>
39#include <linux/mount.h>
40#include <linux/pagemap.h>
41#include <linux/proc_fs.h>
42#include <linux/rcupdate.h>
43#include <linux/sched.h>
44#include <linux/backing-dev.h>
45#include <linux/seq_file.h>
46#include <linux/slab.h>
47#include <linux/magic.h>
48#include <linux/spinlock.h>
49#include <linux/string.h>
50#include <linux/sort.h>
51#include <linux/kmod.h>
52#include <linux/module.h>
53#include <linux/delayacct.h>
54#include <linux/cgroupstats.h>
55#include <linux/hash.h>
56#include <linux/namei.h>
57#include <linux/pid_namespace.h>
58#include <linux/idr.h>
59#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
60#include <linux/eventfd.h>
61#include <linux/poll.h>
62#include <linux/flex_array.h> /* used in cgroup_attach_proc */
63#include <linux/kthread.h>
64
65#include <linux/atomic.h>
66
67/* css deactivation bias, makes css->refcnt negative to deny new trygets */
68#define CSS_DEACT_BIAS INT_MIN
69
70/*
71 * cgroup_mutex is the master lock. Any modification to cgroup or its
72 * hierarchy must be performed while holding it.
73 *
74 * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
75 * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
76 * release_agent_path and so on. Modifying requires both cgroup_mutex and
77 * cgroup_root_mutex. Readers can acquire either of the two. This is to
78 * break the following locking order cycle.
79 *
80 * A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
81 * B. namespace_sem -> cgroup_mutex
82 *
83 * B happens only through cgroup_show_options() and using cgroup_root_mutex
84 * breaks it.
85 */
86static DEFINE_MUTEX(cgroup_mutex);
87static DEFINE_MUTEX(cgroup_root_mutex);
88
89/*
90 * Generate an array of cgroup subsystem pointers. At boot time, this is
91 * populated up to CGROUP_BUILTIN_SUBSYS_COUNT, and modular subsystems are
92 * registered after that. The mutable section of this array is protected by
93 * cgroup_mutex.
94 */
95#define SUBSYS(_x) &_x ## _subsys,
96static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
97#include <linux/cgroup_subsys.h>
98};
99
100#define MAX_CGROUP_ROOT_NAMELEN 64
101
102/*
103 * A cgroupfs_root represents the root of a cgroup hierarchy,
104 * and may be associated with a superblock to form an active
105 * hierarchy
106 */
107struct cgroupfs_root {
108 struct super_block *sb;
109
110 /*
111 * The bitmask of subsystems intended to be attached to this
112 * hierarchy
113 */
114 unsigned long subsys_bits;
115
116 /* Unique id for this hierarchy. */
117 int hierarchy_id;
118
119 /* The bitmask of subsystems currently attached to this hierarchy */
120 unsigned long actual_subsys_bits;
121
122 /* A list running through the attached subsystems */
123 struct list_head subsys_list;
124
125 /* The root cgroup for this hierarchy */
126 struct cgroup top_cgroup;
127
128 /* Tracks how many cgroups are currently defined in hierarchy.*/
129 int number_of_cgroups;
130
131 /* A list running through the active hierarchies */
132 struct list_head root_list;
133
134 /* All cgroups on this root, cgroup_mutex protected */
135 struct list_head allcg_list;
136
137 /* Hierarchy-specific flags */
138 unsigned long flags;
139
140 /* The path to use for release notifications. */
141 char release_agent_path[PATH_MAX];
142
143 /* The name for this hierarchy - may be empty */
144 char name[MAX_CGROUP_ROOT_NAMELEN];
145};
146
147/*
148 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
149 * subsystems that are otherwise unattached - it never has more than a
150 * single cgroup, and all tasks are part of that cgroup.
151 */
152static struct cgroupfs_root rootnode;
153
154/*
155 * cgroupfs file entry, pointed to from leaf dentry->d_fsdata.
156 */
157struct cfent {
158 struct list_head node;
159 struct dentry *dentry;
160 struct cftype *type;
161};
162
163/*
164 * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
165 * cgroup_subsys->use_id != 0.
166 */
167#define CSS_ID_MAX (65535)
168struct css_id {
169 /*
170 * The css to which this ID points. This pointer is set to valid value
171 * after cgroup is populated. If cgroup is removed, this will be NULL.
172 * This pointer is expected to be RCU-safe because destroy()
173 * is called after synchronize_rcu(). But for safe use, css_is_removed()
174 * css_tryget() should be used for avoiding race.
175 */
176 struct cgroup_subsys_state __rcu *css;
177 /*
178 * ID of this css.
179 */
180 unsigned short id;
181 /*
182 * Depth in hierarchy which this ID belongs to.
183 */
184 unsigned short depth;
185 /*
186 * ID is freed by RCU. (and lookup routine is RCU safe.)
187 */
188 struct rcu_head rcu_head;
189 /*
190 * Hierarchy of CSS ID belongs to.
191 */
192 unsigned short stack[0]; /* Array of Length (depth+1) */
193};
194
195/*
196 * cgroup_event represents events which userspace want to receive.
197 */
198struct cgroup_event {
199 /*
200 * Cgroup which the event belongs to.
201 */
202 struct cgroup *cgrp;
203 /*
204 * Control file which the event associated.
205 */
206 struct cftype *cft;
207 /*
208 * eventfd to signal userspace about the event.
209 */
210 struct eventfd_ctx *eventfd;
211 /*
212 * Each of these stored in a list by the cgroup.
213 */
214 struct list_head list;
215 /*
216 * All fields below needed to unregister event when
217 * userspace closes eventfd.
218 */
219 poll_table pt;
220 wait_queue_head_t *wqh;
221 wait_queue_t wait;
222 struct work_struct remove;
223};
224
225/* The list of hierarchy roots */
226
227static LIST_HEAD(roots);
228static int root_count;
229
230static DEFINE_IDA(hierarchy_ida);
231static int next_hierarchy_id;
232static DEFINE_SPINLOCK(hierarchy_id_lock);
233
234/* dummytop is a shorthand for the dummy hierarchy's top cgroup */
235#define dummytop (&rootnode.top_cgroup)
236
237/* This flag indicates whether tasks in the fork and exit paths should
238 * check for fork/exit handlers to call. This avoids us having to do
239 * extra work in the fork/exit path if none of the subsystems need to
240 * be called.
241 */
242static int need_forkexit_callback __read_mostly;
243
244#ifdef CONFIG_PROVE_LOCKING
245int cgroup_lock_is_held(void)
246{
247 return lockdep_is_held(&cgroup_mutex);
248}
249#else /* #ifdef CONFIG_PROVE_LOCKING */
250int cgroup_lock_is_held(void)
251{
252 return mutex_is_locked(&cgroup_mutex);
253}
254#endif /* #else #ifdef CONFIG_PROVE_LOCKING */
255
256EXPORT_SYMBOL_GPL(cgroup_lock_is_held);
257
258static int css_unbias_refcnt(int refcnt)
259{
260 return refcnt >= 0 ? refcnt : refcnt - CSS_DEACT_BIAS;
261}
262
263/* the current nr of refs, always >= 0 whether @css is deactivated or not */
264static int css_refcnt(struct cgroup_subsys_state *css)
265{
266 int v = atomic_read(&css->refcnt);
267
268 return css_unbias_refcnt(v);
269}
270
271/* convenient tests for these bits */
272inline int cgroup_is_removed(const struct cgroup *cgrp)
273{
274 return test_bit(CGRP_REMOVED, &cgrp->flags);
275}
276
277/* bits in struct cgroupfs_root flags field */
278enum {
279 ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
280};
281
282static int cgroup_is_releasable(const struct cgroup *cgrp)
283{
284 const int bits =
285 (1 << CGRP_RELEASABLE) |
286 (1 << CGRP_NOTIFY_ON_RELEASE);
287 return (cgrp->flags & bits) == bits;
288}
289
290static int notify_on_release(const struct cgroup *cgrp)
291{
292 return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
293}
294
295static int clone_children(const struct cgroup *cgrp)
296{
297 return test_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
298}
299
300/*
301 * for_each_subsys() allows you to iterate on each subsystem attached to
302 * an active hierarchy
303 */
304#define for_each_subsys(_root, _ss) \
305list_for_each_entry(_ss, &_root->subsys_list, sibling)
306
307/* for_each_active_root() allows you to iterate across the active hierarchies */
308#define for_each_active_root(_root) \
309list_for_each_entry(_root, &roots, root_list)
310
311static inline struct cgroup *__d_cgrp(struct dentry *dentry)
312{
313 return dentry->d_fsdata;
314}
315
316static inline struct cfent *__d_cfe(struct dentry *dentry)
317{
318 return dentry->d_fsdata;
319}
320
321static inline struct cftype *__d_cft(struct dentry *dentry)
322{
323 return __d_cfe(dentry)->type;
324}
325
326/* the list of cgroups eligible for automatic release. Protected by
327 * release_list_lock */
328static LIST_HEAD(release_list);
329static DEFINE_RAW_SPINLOCK(release_list_lock);
330static void cgroup_release_agent(struct work_struct *work);
331static DECLARE_WORK(release_agent_work, cgroup_release_agent);
332static void check_for_release(struct cgroup *cgrp);
333
334/* Link structure for associating css_set objects with cgroups */
335struct cg_cgroup_link {
336 /*
337 * List running through cg_cgroup_links associated with a
338 * cgroup, anchored on cgroup->css_sets
339 */
340 struct list_head cgrp_link_list;
341 struct cgroup *cgrp;
342 /*
343 * List running through cg_cgroup_links pointing at a
344 * single css_set object, anchored on css_set->cg_links
345 */
346 struct list_head cg_link_list;
347 struct css_set *cg;
348};
349
350/* The default css_set - used by init and its children prior to any
351 * hierarchies being mounted. It contains a pointer to the root state
352 * for each subsystem. Also used to anchor the list of css_sets. Not
353 * reference-counted, to improve performance when child cgroups
354 * haven't been created.
355 */
356
357static struct css_set init_css_set;
358static struct cg_cgroup_link init_css_set_link;
359
360static int cgroup_init_idr(struct cgroup_subsys *ss,
361 struct cgroup_subsys_state *css);
362
363/* css_set_lock protects the list of css_set objects, and the
364 * chain of tasks off each css_set. Nests outside task->alloc_lock
365 * due to cgroup_iter_start() */
366static DEFINE_RWLOCK(css_set_lock);
367static int css_set_count;
368
369/*
370 * hash table for cgroup groups. This improves the performance to find
371 * an existing css_set. This hash doesn't (currently) take into
372 * account cgroups in empty hierarchies.
373 */
374#define CSS_SET_HASH_BITS 7
375#define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS)
376static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
377
378static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
379{
380 int i;
381 int index;
382 unsigned long tmp = 0UL;
383
384 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
385 tmp += (unsigned long)css[i];
386 tmp = (tmp >> 16) ^ tmp;
387
388 index = hash_long(tmp, CSS_SET_HASH_BITS);
389
390 return &css_set_table[index];
391}
392
393/* We don't maintain the lists running through each css_set to its
394 * task until after the first call to cgroup_iter_start(). This
395 * reduces the fork()/exit() overhead for people who have cgroups
396 * compiled into their kernel but not actually in use */
397static int use_task_css_set_links __read_mostly;
398
399static void __put_css_set(struct css_set *cg, int taskexit)
400{
401 struct cg_cgroup_link *link;
402 struct cg_cgroup_link *saved_link;
403 /*
404 * Ensure that the refcount doesn't hit zero while any readers
405 * can see it. Similar to atomic_dec_and_lock(), but for an
406 * rwlock
407 */
408 if (atomic_add_unless(&cg->refcount, -1, 1))
409 return;
410 write_lock(&css_set_lock);
411 if (!atomic_dec_and_test(&cg->refcount)) {
412 write_unlock(&css_set_lock);
413 return;
414 }
415
416 /* This css_set is dead. unlink it and release cgroup refcounts */
417 hlist_del(&cg->hlist);
418 css_set_count--;
419
420 list_for_each_entry_safe(link, saved_link, &cg->cg_links,
421 cg_link_list) {
422 struct cgroup *cgrp = link->cgrp;
423 list_del(&link->cg_link_list);
424 list_del(&link->cgrp_link_list);
425 if (atomic_dec_and_test(&cgrp->count) &&
426 notify_on_release(cgrp)) {
427 if (taskexit)
428 set_bit(CGRP_RELEASABLE, &cgrp->flags);
429 check_for_release(cgrp);
430 }
431
432 kfree(link);
433 }
434
435 write_unlock(&css_set_lock);
436 kfree_rcu(cg, rcu_head);
437}
438
439/*
440 * refcounted get/put for css_set objects
441 */
442static inline void get_css_set(struct css_set *cg)
443{
444 atomic_inc(&cg->refcount);
445}
446
447static inline void put_css_set(struct css_set *cg)
448{
449 __put_css_set(cg, 0);
450}
451
452static inline void put_css_set_taskexit(struct css_set *cg)
453{
454 __put_css_set(cg, 1);
455}
456
457/*
458 * compare_css_sets - helper function for find_existing_css_set().
459 * @cg: candidate css_set being tested
460 * @old_cg: existing css_set for a task
461 * @new_cgrp: cgroup that's being entered by the task
462 * @template: desired set of css pointers in css_set (pre-calculated)
463 *
464 * Returns true if "cg" matches "old_cg" except for the hierarchy
465 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
466 */
467static bool compare_css_sets(struct css_set *cg,
468 struct css_set *old_cg,
469 struct cgroup *new_cgrp,
470 struct cgroup_subsys_state *template[])
471{
472 struct list_head *l1, *l2;
473
474 if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
475 /* Not all subsystems matched */
476 return false;
477 }
478
479 /*
480 * Compare cgroup pointers in order to distinguish between
481 * different cgroups in heirarchies with no subsystems. We
482 * could get by with just this check alone (and skip the
483 * memcmp above) but on most setups the memcmp check will
484 * avoid the need for this more expensive check on almost all
485 * candidates.
486 */
487
488 l1 = &cg->cg_links;
489 l2 = &old_cg->cg_links;
490 while (1) {
491 struct cg_cgroup_link *cgl1, *cgl2;
492 struct cgroup *cg1, *cg2;
493
494 l1 = l1->next;
495 l2 = l2->next;
496 /* See if we reached the end - both lists are equal length. */
497 if (l1 == &cg->cg_links) {
498 BUG_ON(l2 != &old_cg->cg_links);
499 break;
500 } else {
501 BUG_ON(l2 == &old_cg->cg_links);
502 }
503 /* Locate the cgroups associated with these links. */
504 cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
505 cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
506 cg1 = cgl1->cgrp;
507 cg2 = cgl2->cgrp;
508 /* Hierarchies should be linked in the same order. */
509 BUG_ON(cg1->root != cg2->root);
510
511 /*
512 * If this hierarchy is the hierarchy of the cgroup
513 * that's changing, then we need to check that this
514 * css_set points to the new cgroup; if it's any other
515 * hierarchy, then this css_set should point to the
516 * same cgroup as the old css_set.
517 */
518 if (cg1->root == new_cgrp->root) {
519 if (cg1 != new_cgrp)
520 return false;
521 } else {
522 if (cg1 != cg2)
523 return false;
524 }
525 }
526 return true;
527}
528
529/*
530 * find_existing_css_set() is a helper for
531 * find_css_set(), and checks to see whether an existing
532 * css_set is suitable.
533 *
534 * oldcg: the cgroup group that we're using before the cgroup
535 * transition
536 *
537 * cgrp: the cgroup that we're moving into
538 *
539 * template: location in which to build the desired set of subsystem
540 * state objects for the new cgroup group
541 */
542static struct css_set *find_existing_css_set(
543 struct css_set *oldcg,
544 struct cgroup *cgrp,
545 struct cgroup_subsys_state *template[])
546{
547 int i;
548 struct cgroupfs_root *root = cgrp->root;
549 struct hlist_head *hhead;
550 struct hlist_node *node;
551 struct css_set *cg;
552
553 /*
554 * Build the set of subsystem state objects that we want to see in the
555 * new css_set. while subsystems can change globally, the entries here
556 * won't change, so no need for locking.
557 */
558 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
559 if (root->subsys_bits & (1UL << i)) {
560 /* Subsystem is in this hierarchy. So we want
561 * the subsystem state from the new
562 * cgroup */
563 template[i] = cgrp->subsys[i];
564 } else {
565 /* Subsystem is not in this hierarchy, so we
566 * don't want to change the subsystem state */
567 template[i] = oldcg->subsys[i];
568 }
569 }
570
571 hhead = css_set_hash(template);
572 hlist_for_each_entry(cg, node, hhead, hlist) {
573 if (!compare_css_sets(cg, oldcg, cgrp, template))
574 continue;
575
576 /* This css_set matches what we need */
577 return cg;
578 }
579
580 /* No existing cgroup group matched */
581 return NULL;
582}
583
584static void free_cg_links(struct list_head *tmp)
585{
586 struct cg_cgroup_link *link;
587 struct cg_cgroup_link *saved_link;
588
589 list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
590 list_del(&link->cgrp_link_list);
591 kfree(link);
592 }
593}
594
595/*
596 * allocate_cg_links() allocates "count" cg_cgroup_link structures
597 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
598 * success or a negative error
599 */
600static int allocate_cg_links(int count, struct list_head *tmp)
601{
602 struct cg_cgroup_link *link;
603 int i;
604 INIT_LIST_HEAD(tmp);
605 for (i = 0; i < count; i++) {
606 link = kmalloc(sizeof(*link), GFP_KERNEL);
607 if (!link) {
608 free_cg_links(tmp);
609 return -ENOMEM;
610 }
611 list_add(&link->cgrp_link_list, tmp);
612 }
613 return 0;
614}
615
616/**
617 * link_css_set - a helper function to link a css_set to a cgroup
618 * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
619 * @cg: the css_set to be linked
620 * @cgrp: the destination cgroup
621 */
622static void link_css_set(struct list_head *tmp_cg_links,
623 struct css_set *cg, struct cgroup *cgrp)
624{
625 struct cg_cgroup_link *link;
626
627 BUG_ON(list_empty(tmp_cg_links));
628 link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
629 cgrp_link_list);
630 link->cg = cg;
631 link->cgrp = cgrp;
632 atomic_inc(&cgrp->count);
633 list_move(&link->cgrp_link_list, &cgrp->css_sets);
634 /*
635 * Always add links to the tail of the list so that the list
636 * is sorted by order of hierarchy creation
637 */
638 list_add_tail(&link->cg_link_list, &cg->cg_links);
639}
640
641/*
642 * find_css_set() takes an existing cgroup group and a
643 * cgroup object, and returns a css_set object that's
644 * equivalent to the old group, but with the given cgroup
645 * substituted into the appropriate hierarchy. Must be called with
646 * cgroup_mutex held
647 */
648static struct css_set *find_css_set(
649 struct css_set *oldcg, struct cgroup *cgrp)
650{
651 struct css_set *res;
652 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
653
654 struct list_head tmp_cg_links;
655
656 struct hlist_head *hhead;
657 struct cg_cgroup_link *link;
658
659 /* First see if we already have a cgroup group that matches
660 * the desired set */
661 read_lock(&css_set_lock);
662 res = find_existing_css_set(oldcg, cgrp, template);
663 if (res)
664 get_css_set(res);
665 read_unlock(&css_set_lock);
666
667 if (res)
668 return res;
669
670 res = kmalloc(sizeof(*res), GFP_KERNEL);
671 if (!res)
672 return NULL;
673
674 /* Allocate all the cg_cgroup_link objects that we'll need */
675 if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
676 kfree(res);
677 return NULL;
678 }
679
680 atomic_set(&res->refcount, 1);
681 INIT_LIST_HEAD(&res->cg_links);
682 INIT_LIST_HEAD(&res->tasks);
683 INIT_HLIST_NODE(&res->hlist);
684
685 /* Copy the set of subsystem state objects generated in
686 * find_existing_css_set() */
687 memcpy(res->subsys, template, sizeof(res->subsys));
688
689 write_lock(&css_set_lock);
690 /* Add reference counts and links from the new css_set. */
691 list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
692 struct cgroup *c = link->cgrp;
693 if (c->root == cgrp->root)
694 c = cgrp;
695 link_css_set(&tmp_cg_links, res, c);
696 }
697
698 BUG_ON(!list_empty(&tmp_cg_links));
699
700 css_set_count++;
701
702 /* Add this cgroup group to the hash table */
703 hhead = css_set_hash(res->subsys);
704 hlist_add_head(&res->hlist, hhead);
705
706 write_unlock(&css_set_lock);
707
708 return res;
709}
710
711/*
712 * Return the cgroup for "task" from the given hierarchy. Must be
713 * called with cgroup_mutex held.
714 */
715static struct cgroup *task_cgroup_from_root(struct task_struct *task,
716 struct cgroupfs_root *root)
717{
718 struct css_set *css;
719 struct cgroup *res = NULL;
720
721 BUG_ON(!mutex_is_locked(&cgroup_mutex));
722 read_lock(&css_set_lock);
723 /*
724 * No need to lock the task - since we hold cgroup_mutex the
725 * task can't change groups, so the only thing that can happen
726 * is that it exits and its css is set back to init_css_set.
727 */
728 css = task->cgroups;
729 if (css == &init_css_set) {
730 res = &root->top_cgroup;
731 } else {
732 struct cg_cgroup_link *link;
733 list_for_each_entry(link, &css->cg_links, cg_link_list) {
734 struct cgroup *c = link->cgrp;
735 if (c->root == root) {
736 res = c;
737 break;
738 }
739 }
740 }
741 read_unlock(&css_set_lock);
742 BUG_ON(!res);
743 return res;
744}
745
746/*
747 * There is one global cgroup mutex. We also require taking
748 * task_lock() when dereferencing a task's cgroup subsys pointers.
749 * See "The task_lock() exception", at the end of this comment.
750 *
751 * A task must hold cgroup_mutex to modify cgroups.
752 *
753 * Any task can increment and decrement the count field without lock.
754 * So in general, code holding cgroup_mutex can't rely on the count
755 * field not changing. However, if the count goes to zero, then only
756 * cgroup_attach_task() can increment it again. Because a count of zero
757 * means that no tasks are currently attached, therefore there is no
758 * way a task attached to that cgroup can fork (the other way to
759 * increment the count). So code holding cgroup_mutex can safely
760 * assume that if the count is zero, it will stay zero. Similarly, if
761 * a task holds cgroup_mutex on a cgroup with zero count, it
762 * knows that the cgroup won't be removed, as cgroup_rmdir()
763 * needs that mutex.
764 *
765 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
766 * (usually) take cgroup_mutex. These are the two most performance
767 * critical pieces of code here. The exception occurs on cgroup_exit(),
768 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
769 * is taken, and if the cgroup count is zero, a usermode call made
770 * to the release agent with the name of the cgroup (path relative to
771 * the root of cgroup file system) as the argument.
772 *
773 * A cgroup can only be deleted if both its 'count' of using tasks
774 * is zero, and its list of 'children' cgroups is empty. Since all
775 * tasks in the system use _some_ cgroup, and since there is always at
776 * least one task in the system (init, pid == 1), therefore, top_cgroup
777 * always has either children cgroups and/or using tasks. So we don't
778 * need a special hack to ensure that top_cgroup cannot be deleted.
779 *
780 * The task_lock() exception
781 *
782 * The need for this exception arises from the action of
783 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
784 * another. It does so using cgroup_mutex, however there are
785 * several performance critical places that need to reference
786 * task->cgroup without the expense of grabbing a system global
787 * mutex. Therefore except as noted below, when dereferencing or, as
788 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
789 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
790 * the task_struct routinely used for such matters.
791 *
792 * P.S. One more locking exception. RCU is used to guard the
793 * update of a tasks cgroup pointer by cgroup_attach_task()
794 */
795
796/**
797 * cgroup_lock - lock out any changes to cgroup structures
798 *
799 */
800void cgroup_lock(void)
801{
802 mutex_lock(&cgroup_mutex);
803}
804EXPORT_SYMBOL_GPL(cgroup_lock);
805
806/**
807 * cgroup_unlock - release lock on cgroup changes
808 *
809 * Undo the lock taken in a previous cgroup_lock() call.
810 */
811void cgroup_unlock(void)
812{
813 mutex_unlock(&cgroup_mutex);
814}
815EXPORT_SYMBOL_GPL(cgroup_unlock);
816
817/*
818 * A couple of forward declarations required, due to cyclic reference loop:
819 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
820 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
821 * -> cgroup_mkdir.
822 */
823
824static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
825static struct dentry *cgroup_lookup(struct inode *, struct dentry *, struct nameidata *);
826static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
827static int cgroup_populate_dir(struct cgroup *cgrp);
828static const struct inode_operations cgroup_dir_inode_operations;
829static const struct file_operations proc_cgroupstats_operations;
830
831static struct backing_dev_info cgroup_backing_dev_info = {
832 .name = "cgroup",
833 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
834};
835
836static int alloc_css_id(struct cgroup_subsys *ss,
837 struct cgroup *parent, struct cgroup *child);
838
839static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
840{
841 struct inode *inode = new_inode(sb);
842
843 if (inode) {
844 inode->i_ino = get_next_ino();
845 inode->i_mode = mode;
846 inode->i_uid = current_fsuid();
847 inode->i_gid = current_fsgid();
848 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
849 inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
850 }
851 return inode;
852}
853
854/*
855 * Call subsys's pre_destroy handler.
856 * This is called before css refcnt check.
857 */
858static int cgroup_call_pre_destroy(struct cgroup *cgrp)
859{
860 struct cgroup_subsys *ss;
861 int ret = 0;
862
863 for_each_subsys(cgrp->root, ss) {
864 if (!ss->pre_destroy)
865 continue;
866
867 ret = ss->pre_destroy(cgrp);
868 if (ret) {
869 /* ->pre_destroy() failure is being deprecated */
870 WARN_ON_ONCE(!ss->__DEPRECATED_clear_css_refs);
871 break;
872 }
873 }
874
875 return ret;
876}
877
878static void cgroup_diput(struct dentry *dentry, struct inode *inode)
879{
880 /* is dentry a directory ? if so, kfree() associated cgroup */
881 if (S_ISDIR(inode->i_mode)) {
882 struct cgroup *cgrp = dentry->d_fsdata;
883 struct cgroup_subsys *ss;
884 BUG_ON(!(cgroup_is_removed(cgrp)));
885 /* It's possible for external users to be holding css
886 * reference counts on a cgroup; css_put() needs to
887 * be able to access the cgroup after decrementing
888 * the reference count in order to know if it needs to
889 * queue the cgroup to be handled by the release
890 * agent */
891 synchronize_rcu();
892
893 mutex_lock(&cgroup_mutex);
894 /*
895 * Release the subsystem state objects.
896 */
897 for_each_subsys(cgrp->root, ss)
898 ss->destroy(cgrp);
899
900 cgrp->root->number_of_cgroups--;
901 mutex_unlock(&cgroup_mutex);
902
903 /*
904 * Drop the active superblock reference that we took when we
905 * created the cgroup
906 */
907 deactivate_super(cgrp->root->sb);
908
909 /*
910 * if we're getting rid of the cgroup, refcount should ensure
911 * that there are no pidlists left.
912 */
913 BUG_ON(!list_empty(&cgrp->pidlists));
914
915 kfree_rcu(cgrp, rcu_head);
916 } else {
917 struct cfent *cfe = __d_cfe(dentry);
918 struct cgroup *cgrp = dentry->d_parent->d_fsdata;
919
920 WARN_ONCE(!list_empty(&cfe->node) &&
921 cgrp != &cgrp->root->top_cgroup,
922 "cfe still linked for %s\n", cfe->type->name);
923 kfree(cfe);
924 }
925 iput(inode);
926}
927
928static int cgroup_delete(const struct dentry *d)
929{
930 return 1;
931}
932
933static void remove_dir(struct dentry *d)
934{
935 struct dentry *parent = dget(d->d_parent);
936
937 d_delete(d);
938 simple_rmdir(parent->d_inode, d);
939 dput(parent);
940}
941
942static int cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
943{
944 struct cfent *cfe;
945
946 lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
947 lockdep_assert_held(&cgroup_mutex);
948
949 list_for_each_entry(cfe, &cgrp->files, node) {
950 struct dentry *d = cfe->dentry;
951
952 if (cft && cfe->type != cft)
953 continue;
954
955 dget(d);
956 d_delete(d);
957 simple_unlink(cgrp->dentry->d_inode, d);
958 list_del_init(&cfe->node);
959 dput(d);
960
961 return 0;
962 }
963 return -ENOENT;
964}
965
966static void cgroup_clear_directory(struct dentry *dir)
967{
968 struct cgroup *cgrp = __d_cgrp(dir);
969
970 while (!list_empty(&cgrp->files))
971 cgroup_rm_file(cgrp, NULL);
972}
973
974/*
975 * NOTE : the dentry must have been dget()'ed
976 */
977static void cgroup_d_remove_dir(struct dentry *dentry)
978{
979 struct dentry *parent;
980
981 cgroup_clear_directory(dentry);
982
983 parent = dentry->d_parent;
984 spin_lock(&parent->d_lock);
985 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
986 list_del_init(&dentry->d_u.d_child);
987 spin_unlock(&dentry->d_lock);
988 spin_unlock(&parent->d_lock);
989 remove_dir(dentry);
990}
991
992/*
993 * A queue for waiters to do rmdir() cgroup. A tasks will sleep when
994 * cgroup->count == 0 && list_empty(&cgroup->children) && subsys has some
995 * reference to css->refcnt. In general, this refcnt is expected to goes down
996 * to zero, soon.
997 *
998 * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
999 */
1000static DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
1001
1002static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
1003{
1004 if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
1005 wake_up_all(&cgroup_rmdir_waitq);
1006}
1007
1008void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
1009{
1010 css_get(css);
1011}
1012
1013void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
1014{
1015 cgroup_wakeup_rmdir_waiter(css->cgroup);
1016 css_put(css);
1017}
1018
1019/*
1020 * Call with cgroup_mutex held. Drops reference counts on modules, including
1021 * any duplicate ones that parse_cgroupfs_options took. If this function
1022 * returns an error, no reference counts are touched.
1023 */
1024static int rebind_subsystems(struct cgroupfs_root *root,
1025 unsigned long final_bits)
1026{
1027 unsigned long added_bits, removed_bits;
1028 struct cgroup *cgrp = &root->top_cgroup;
1029 int i;
1030
1031 BUG_ON(!mutex_is_locked(&cgroup_mutex));
1032 BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
1033
1034 removed_bits = root->actual_subsys_bits & ~final_bits;
1035 added_bits = final_bits & ~root->actual_subsys_bits;
1036 /* Check that any added subsystems are currently free */
1037 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1038 unsigned long bit = 1UL << i;
1039 struct cgroup_subsys *ss = subsys[i];
1040 if (!(bit & added_bits))
1041 continue;
1042 /*
1043 * Nobody should tell us to do a subsys that doesn't exist:
1044 * parse_cgroupfs_options should catch that case and refcounts
1045 * ensure that subsystems won't disappear once selected.
1046 */
1047 BUG_ON(ss == NULL);
1048 if (ss->root != &rootnode) {
1049 /* Subsystem isn't free */
1050 return -EBUSY;
1051 }
1052 }
1053
1054 /* Currently we don't handle adding/removing subsystems when
1055 * any child cgroups exist. This is theoretically supportable
1056 * but involves complex error handling, so it's being left until
1057 * later */
1058 if (root->number_of_cgroups > 1)
1059 return -EBUSY;
1060
1061 /* Process each subsystem */
1062 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1063 struct cgroup_subsys *ss = subsys[i];
1064 unsigned long bit = 1UL << i;
1065 if (bit & added_bits) {
1066 /* We're binding this subsystem to this hierarchy */
1067 BUG_ON(ss == NULL);
1068 BUG_ON(cgrp->subsys[i]);
1069 BUG_ON(!dummytop->subsys[i]);
1070 BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1071 mutex_lock(&ss->hierarchy_mutex);
1072 cgrp->subsys[i] = dummytop->subsys[i];
1073 cgrp->subsys[i]->cgroup = cgrp;
1074 list_move(&ss->sibling, &root->subsys_list);
1075 ss->root = root;
1076 if (ss->bind)
1077 ss->bind(cgrp);
1078 mutex_unlock(&ss->hierarchy_mutex);
1079 /* refcount was already taken, and we're keeping it */
1080 } else if (bit & removed_bits) {
1081 /* We're removing this subsystem */
1082 BUG_ON(ss == NULL);
1083 BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
1084 BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1085 mutex_lock(&ss->hierarchy_mutex);
1086 if (ss->bind)
1087 ss->bind(dummytop);
1088 dummytop->subsys[i]->cgroup = dummytop;
1089 cgrp->subsys[i] = NULL;
1090 subsys[i]->root = &rootnode;
1091 list_move(&ss->sibling, &rootnode.subsys_list);
1092 mutex_unlock(&ss->hierarchy_mutex);
1093 /* subsystem is now free - drop reference on module */
1094 module_put(ss->module);
1095 } else if (bit & final_bits) {
1096 /* Subsystem state should already exist */
1097 BUG_ON(ss == NULL);
1098 BUG_ON(!cgrp->subsys[i]);
1099 /*
1100 * a refcount was taken, but we already had one, so
1101 * drop the extra reference.
1102 */
1103 module_put(ss->module);
1104#ifdef CONFIG_MODULE_UNLOAD
1105 BUG_ON(ss->module && !module_refcount(ss->module));
1106#endif
1107 } else {
1108 /* Subsystem state shouldn't exist */
1109 BUG_ON(cgrp->subsys[i]);
1110 }
1111 }
1112 root->subsys_bits = root->actual_subsys_bits = final_bits;
1113 synchronize_rcu();
1114
1115 return 0;
1116}
1117
1118static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1119{
1120 struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1121 struct cgroup_subsys *ss;
1122
1123 mutex_lock(&cgroup_root_mutex);
1124 for_each_subsys(root, ss)
1125 seq_printf(seq, ",%s", ss->name);
1126 if (test_bit(ROOT_NOPREFIX, &root->flags))
1127 seq_puts(seq, ",noprefix");
1128 if (strlen(root->release_agent_path))
1129 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1130 if (clone_children(&root->top_cgroup))
1131 seq_puts(seq, ",clone_children");
1132 if (strlen(root->name))
1133 seq_printf(seq, ",name=%s", root->name);
1134 mutex_unlock(&cgroup_root_mutex);
1135 return 0;
1136}
1137
1138struct cgroup_sb_opts {
1139 unsigned long subsys_bits;
1140 unsigned long flags;
1141 char *release_agent;
1142 bool clone_children;
1143 char *name;
1144 /* User explicitly requested empty subsystem */
1145 bool none;
1146
1147 struct cgroupfs_root *new_root;
1148
1149};
1150
1151/*
1152 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
1153 * with cgroup_mutex held to protect the subsys[] array. This function takes
1154 * refcounts on subsystems to be used, unless it returns error, in which case
1155 * no refcounts are taken.
1156 */
1157static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1158{
1159 char *token, *o = data;
1160 bool all_ss = false, one_ss = false;
1161 unsigned long mask = (unsigned long)-1;
1162 int i;
1163 bool module_pin_failed = false;
1164
1165 BUG_ON(!mutex_is_locked(&cgroup_mutex));
1166
1167#ifdef CONFIG_CPUSETS
1168 mask = ~(1UL << cpuset_subsys_id);
1169#endif
1170
1171 memset(opts, 0, sizeof(*opts));
1172
1173 while ((token = strsep(&o, ",")) != NULL) {
1174 if (!*token)
1175 return -EINVAL;
1176 if (!strcmp(token, "none")) {
1177 /* Explicitly have no subsystems */
1178 opts->none = true;
1179 continue;
1180 }
1181 if (!strcmp(token, "all")) {
1182 /* Mutually exclusive option 'all' + subsystem name */
1183 if (one_ss)
1184 return -EINVAL;
1185 all_ss = true;
1186 continue;
1187 }
1188 if (!strcmp(token, "noprefix")) {
1189 set_bit(ROOT_NOPREFIX, &opts->flags);
1190 continue;
1191 }
1192 if (!strcmp(token, "clone_children")) {
1193 opts->clone_children = true;
1194 continue;
1195 }
1196 if (!strncmp(token, "release_agent=", 14)) {
1197 /* Specifying two release agents is forbidden */
1198 if (opts->release_agent)
1199 return -EINVAL;
1200 opts->release_agent =
1201 kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1202 if (!opts->release_agent)
1203 return -ENOMEM;
1204 continue;
1205 }
1206 if (!strncmp(token, "name=", 5)) {
1207 const char *name = token + 5;
1208 /* Can't specify an empty name */
1209 if (!strlen(name))
1210 return -EINVAL;
1211 /* Must match [\w.-]+ */
1212 for (i = 0; i < strlen(name); i++) {
1213 char c = name[i];
1214 if (isalnum(c))
1215 continue;
1216 if ((c == '.') || (c == '-') || (c == '_'))
1217 continue;
1218 return -EINVAL;
1219 }
1220 /* Specifying two names is forbidden */
1221 if (opts->name)
1222 return -EINVAL;
1223 opts->name = kstrndup(name,
1224 MAX_CGROUP_ROOT_NAMELEN - 1,
1225 GFP_KERNEL);
1226 if (!opts->name)
1227 return -ENOMEM;
1228
1229 continue;
1230 }
1231
1232 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1233 struct cgroup_subsys *ss = subsys[i];
1234 if (ss == NULL)
1235 continue;
1236 if (strcmp(token, ss->name))
1237 continue;
1238 if (ss->disabled)
1239 continue;
1240
1241 /* Mutually exclusive option 'all' + subsystem name */
1242 if (all_ss)
1243 return -EINVAL;
1244 set_bit(i, &opts->subsys_bits);
1245 one_ss = true;
1246
1247 break;
1248 }
1249 if (i == CGROUP_SUBSYS_COUNT)
1250 return -ENOENT;
1251 }
1252
1253 /*
1254 * If the 'all' option was specified select all the subsystems,
1255 * otherwise if 'none', 'name=' and a subsystem name options
1256 * were not specified, let's default to 'all'
1257 */
1258 if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1259 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1260 struct cgroup_subsys *ss = subsys[i];
1261 if (ss == NULL)
1262 continue;
1263 if (ss->disabled)
1264 continue;
1265 set_bit(i, &opts->subsys_bits);
1266 }
1267 }
1268
1269 /* Consistency checks */
1270
1271 /*
1272 * Option noprefix was introduced just for backward compatibility
1273 * with the old cpuset, so we allow noprefix only if mounting just
1274 * the cpuset subsystem.
1275 */
1276 if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
1277 (opts->subsys_bits & mask))
1278 return -EINVAL;
1279
1280
1281 /* Can't specify "none" and some subsystems */
1282 if (opts->subsys_bits && opts->none)
1283 return -EINVAL;
1284
1285 /*
1286 * We either have to specify by name or by subsystems. (So all
1287 * empty hierarchies must have a name).
1288 */
1289 if (!opts->subsys_bits && !opts->name)
1290 return -EINVAL;
1291
1292 /*
1293 * Grab references on all the modules we'll need, so the subsystems
1294 * don't dance around before rebind_subsystems attaches them. This may
1295 * take duplicate reference counts on a subsystem that's already used,
1296 * but rebind_subsystems handles this case.
1297 */
1298 for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
1299 unsigned long bit = 1UL << i;
1300
1301 if (!(bit & opts->subsys_bits))
1302 continue;
1303 if (!try_module_get(subsys[i]->module)) {
1304 module_pin_failed = true;
1305 break;
1306 }
1307 }
1308 if (module_pin_failed) {
1309 /*
1310 * oops, one of the modules was going away. this means that we
1311 * raced with a module_delete call, and to the user this is
1312 * essentially a "subsystem doesn't exist" case.
1313 */
1314 for (i--; i >= CGROUP_BUILTIN_SUBSYS_COUNT; i--) {
1315 /* drop refcounts only on the ones we took */
1316 unsigned long bit = 1UL << i;
1317
1318 if (!(bit & opts->subsys_bits))
1319 continue;
1320 module_put(subsys[i]->module);
1321 }
1322 return -ENOENT;
1323 }
1324
1325 return 0;
1326}
1327
1328static void drop_parsed_module_refcounts(unsigned long subsys_bits)
1329{
1330 int i;
1331 for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
1332 unsigned long bit = 1UL << i;
1333
1334 if (!(bit & subsys_bits))
1335 continue;
1336 module_put(subsys[i]->module);
1337 }
1338}
1339
1340static int cgroup_remount(struct super_block *sb, int *flags, char *data)
1341{
1342 int ret = 0;
1343 struct cgroupfs_root *root = sb->s_fs_info;
1344 struct cgroup *cgrp = &root->top_cgroup;
1345 struct cgroup_sb_opts opts;
1346
1347 mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1348 mutex_lock(&cgroup_mutex);
1349 mutex_lock(&cgroup_root_mutex);
1350
1351 /* See what subsystems are wanted */
1352 ret = parse_cgroupfs_options(data, &opts);
1353 if (ret)
1354 goto out_unlock;
1355
1356 /* See feature-removal-schedule.txt */
1357 if (opts.subsys_bits != root->actual_subsys_bits || opts.release_agent)
1358 pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
1359 task_tgid_nr(current), current->comm);
1360
1361 /* Don't allow flags or name to change at remount */
1362 if (opts.flags != root->flags ||
1363 (opts.name && strcmp(opts.name, root->name))) {
1364 ret = -EINVAL;
1365 drop_parsed_module_refcounts(opts.subsys_bits);
1366 goto out_unlock;
1367 }
1368
1369 ret = rebind_subsystems(root, opts.subsys_bits);
1370 if (ret) {
1371 drop_parsed_module_refcounts(opts.subsys_bits);
1372 goto out_unlock;
1373 }
1374
1375 /* clear out any existing files and repopulate subsystem files */
1376 cgroup_clear_directory(cgrp->dentry);
1377 cgroup_populate_dir(cgrp);
1378
1379 if (opts.release_agent)
1380 strcpy(root->release_agent_path, opts.release_agent);
1381 out_unlock:
1382 kfree(opts.release_agent);
1383 kfree(opts.name);
1384 mutex_unlock(&cgroup_root_mutex);
1385 mutex_unlock(&cgroup_mutex);
1386 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1387 return ret;
1388}
1389
1390static const struct super_operations cgroup_ops = {
1391 .statfs = simple_statfs,
1392 .drop_inode = generic_delete_inode,
1393 .show_options = cgroup_show_options,
1394 .remount_fs = cgroup_remount,
1395};
1396
1397static void init_cgroup_housekeeping(struct cgroup *cgrp)
1398{
1399 INIT_LIST_HEAD(&cgrp->sibling);
1400 INIT_LIST_HEAD(&cgrp->children);
1401 INIT_LIST_HEAD(&cgrp->files);
1402 INIT_LIST_HEAD(&cgrp->css_sets);
1403 INIT_LIST_HEAD(&cgrp->release_list);
1404 INIT_LIST_HEAD(&cgrp->pidlists);
1405 mutex_init(&cgrp->pidlist_mutex);
1406 INIT_LIST_HEAD(&cgrp->event_list);
1407 spin_lock_init(&cgrp->event_list_lock);
1408}
1409
1410static void init_cgroup_root(struct cgroupfs_root *root)
1411{
1412 struct cgroup *cgrp = &root->top_cgroup;
1413
1414 INIT_LIST_HEAD(&root->subsys_list);
1415 INIT_LIST_HEAD(&root->root_list);
1416 INIT_LIST_HEAD(&root->allcg_list);
1417 root->number_of_cgroups = 1;
1418 cgrp->root = root;
1419 cgrp->top_cgroup = cgrp;
1420 list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1421 init_cgroup_housekeeping(cgrp);
1422}
1423
1424static bool init_root_id(struct cgroupfs_root *root)
1425{
1426 int ret = 0;
1427
1428 do {
1429 if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
1430 return false;
1431 spin_lock(&hierarchy_id_lock);
1432 /* Try to allocate the next unused ID */
1433 ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
1434 &root->hierarchy_id);
1435 if (ret == -ENOSPC)
1436 /* Try again starting from 0 */
1437 ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
1438 if (!ret) {
1439 next_hierarchy_id = root->hierarchy_id + 1;
1440 } else if (ret != -EAGAIN) {
1441 /* Can only get here if the 31-bit IDR is full ... */
1442 BUG_ON(ret);
1443 }
1444 spin_unlock(&hierarchy_id_lock);
1445 } while (ret);
1446 return true;
1447}
1448
1449static int cgroup_test_super(struct super_block *sb, void *data)
1450{
1451 struct cgroup_sb_opts *opts = data;
1452 struct cgroupfs_root *root = sb->s_fs_info;
1453
1454 /* If we asked for a name then it must match */
1455 if (opts->name && strcmp(opts->name, root->name))
1456 return 0;
1457
1458 /*
1459 * If we asked for subsystems (or explicitly for no
1460 * subsystems) then they must match
1461 */
1462 if ((opts->subsys_bits || opts->none)
1463 && (opts->subsys_bits != root->subsys_bits))
1464 return 0;
1465
1466 return 1;
1467}
1468
1469static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
1470{
1471 struct cgroupfs_root *root;
1472
1473 if (!opts->subsys_bits && !opts->none)
1474 return NULL;
1475
1476 root = kzalloc(sizeof(*root), GFP_KERNEL);
1477 if (!root)
1478 return ERR_PTR(-ENOMEM);
1479
1480 if (!init_root_id(root)) {
1481 kfree(root);
1482 return ERR_PTR(-ENOMEM);
1483 }
1484 init_cgroup_root(root);
1485
1486 root->subsys_bits = opts->subsys_bits;
1487 root->flags = opts->flags;
1488 if (opts->release_agent)
1489 strcpy(root->release_agent_path, opts->release_agent);
1490 if (opts->name)
1491 strcpy(root->name, opts->name);
1492 if (opts->clone_children)
1493 set_bit(CGRP_CLONE_CHILDREN, &root->top_cgroup.flags);
1494 return root;
1495}
1496
1497static void cgroup_drop_root(struct cgroupfs_root *root)
1498{
1499 if (!root)
1500 return;
1501
1502 BUG_ON(!root->hierarchy_id);
1503 spin_lock(&hierarchy_id_lock);
1504 ida_remove(&hierarchy_ida, root->hierarchy_id);
1505 spin_unlock(&hierarchy_id_lock);
1506 kfree(root);
1507}
1508
1509static int cgroup_set_super(struct super_block *sb, void *data)
1510{
1511 int ret;
1512 struct cgroup_sb_opts *opts = data;
1513
1514 /* If we don't have a new root, we can't set up a new sb */
1515 if (!opts->new_root)
1516 return -EINVAL;
1517
1518 BUG_ON(!opts->subsys_bits && !opts->none);
1519
1520 ret = set_anon_super(sb, NULL);
1521 if (ret)
1522 return ret;
1523
1524 sb->s_fs_info = opts->new_root;
1525 opts->new_root->sb = sb;
1526
1527 sb->s_blocksize = PAGE_CACHE_SIZE;
1528 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
1529 sb->s_magic = CGROUP_SUPER_MAGIC;
1530 sb->s_op = &cgroup_ops;
1531
1532 return 0;
1533}
1534
1535static int cgroup_get_rootdir(struct super_block *sb)
1536{
1537 static const struct dentry_operations cgroup_dops = {
1538 .d_iput = cgroup_diput,
1539 .d_delete = cgroup_delete,
1540 };
1541
1542 struct inode *inode =
1543 cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
1544
1545 if (!inode)
1546 return -ENOMEM;
1547
1548 inode->i_fop = &simple_dir_operations;
1549 inode->i_op = &cgroup_dir_inode_operations;
1550 /* directories start off with i_nlink == 2 (for "." entry) */
1551 inc_nlink(inode);
1552 sb->s_root = d_make_root(inode);
1553 if (!sb->s_root)
1554 return -ENOMEM;
1555 /* for everything else we want ->d_op set */
1556 sb->s_d_op = &cgroup_dops;
1557 return 0;
1558}
1559
1560static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1561 int flags, const char *unused_dev_name,
1562 void *data)
1563{
1564 struct cgroup_sb_opts opts;
1565 struct cgroupfs_root *root;
1566 int ret = 0;
1567 struct super_block *sb;
1568 struct cgroupfs_root *new_root;
1569 struct inode *inode;
1570
1571 /* First find the desired set of subsystems */
1572 mutex_lock(&cgroup_mutex);
1573 ret = parse_cgroupfs_options(data, &opts);
1574 mutex_unlock(&cgroup_mutex);
1575 if (ret)
1576 goto out_err;
1577
1578 /*
1579 * Allocate a new cgroup root. We may not need it if we're
1580 * reusing an existing hierarchy.
1581 */
1582 new_root = cgroup_root_from_opts(&opts);
1583 if (IS_ERR(new_root)) {
1584 ret = PTR_ERR(new_root);
1585 goto drop_modules;
1586 }
1587 opts.new_root = new_root;
1588
1589 /* Locate an existing or new sb for this hierarchy */
1590 sb = sget(fs_type, cgroup_test_super, cgroup_set_super, &opts);
1591 if (IS_ERR(sb)) {
1592 ret = PTR_ERR(sb);
1593 cgroup_drop_root(opts.new_root);
1594 goto drop_modules;
1595 }
1596
1597 root = sb->s_fs_info;
1598 BUG_ON(!root);
1599 if (root == opts.new_root) {
1600 /* We used the new root structure, so this is a new hierarchy */
1601 struct list_head tmp_cg_links;
1602 struct cgroup *root_cgrp = &root->top_cgroup;
1603 struct cgroupfs_root *existing_root;
1604 const struct cred *cred;
1605 int i;
1606
1607 BUG_ON(sb->s_root != NULL);
1608
1609 ret = cgroup_get_rootdir(sb);
1610 if (ret)
1611 goto drop_new_super;
1612 inode = sb->s_root->d_inode;
1613
1614 mutex_lock(&inode->i_mutex);
1615 mutex_lock(&cgroup_mutex);
1616 mutex_lock(&cgroup_root_mutex);
1617
1618 /* Check for name clashes with existing mounts */
1619 ret = -EBUSY;
1620 if (strlen(root->name))
1621 for_each_active_root(existing_root)
1622 if (!strcmp(existing_root->name, root->name))
1623 goto unlock_drop;
1624
1625 /*
1626 * We're accessing css_set_count without locking
1627 * css_set_lock here, but that's OK - it can only be
1628 * increased by someone holding cgroup_lock, and
1629 * that's us. The worst that can happen is that we
1630 * have some link structures left over
1631 */
1632 ret = allocate_cg_links(css_set_count, &tmp_cg_links);
1633 if (ret)
1634 goto unlock_drop;
1635
1636 ret = rebind_subsystems(root, root->subsys_bits);
1637 if (ret == -EBUSY) {
1638 free_cg_links(&tmp_cg_links);
1639 goto unlock_drop;
1640 }
1641 /*
1642 * There must be no failure case after here, since rebinding
1643 * takes care of subsystems' refcounts, which are explicitly
1644 * dropped in the failure exit path.
1645 */
1646
1647 /* EBUSY should be the only error here */
1648 BUG_ON(ret);
1649
1650 list_add(&root->root_list, &roots);
1651 root_count++;
1652
1653 sb->s_root->d_fsdata = root_cgrp;
1654 root->top_cgroup.dentry = sb->s_root;
1655
1656 /* Link the top cgroup in this hierarchy into all
1657 * the css_set objects */
1658 write_lock(&css_set_lock);
1659 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
1660 struct hlist_head *hhead = &css_set_table[i];
1661 struct hlist_node *node;
1662 struct css_set *cg;
1663
1664 hlist_for_each_entry(cg, node, hhead, hlist)
1665 link_css_set(&tmp_cg_links, cg, root_cgrp);
1666 }
1667 write_unlock(&css_set_lock);
1668
1669 free_cg_links(&tmp_cg_links);
1670
1671 BUG_ON(!list_empty(&root_cgrp->sibling));
1672 BUG_ON(!list_empty(&root_cgrp->children));
1673 BUG_ON(root->number_of_cgroups != 1);
1674
1675 cred = override_creds(&init_cred);
1676 cgroup_populate_dir(root_cgrp);
1677 revert_creds(cred);
1678 mutex_unlock(&cgroup_root_mutex);
1679 mutex_unlock(&cgroup_mutex);
1680 mutex_unlock(&inode->i_mutex);
1681 } else {
1682 /*
1683 * We re-used an existing hierarchy - the new root (if
1684 * any) is not needed
1685 */
1686 cgroup_drop_root(opts.new_root);
1687 /* no subsys rebinding, so refcounts don't change */
1688 drop_parsed_module_refcounts(opts.subsys_bits);
1689 }
1690
1691 kfree(opts.release_agent);
1692 kfree(opts.name);
1693 return dget(sb->s_root);
1694
1695 unlock_drop:
1696 mutex_unlock(&cgroup_root_mutex);
1697 mutex_unlock(&cgroup_mutex);
1698 mutex_unlock(&inode->i_mutex);
1699 drop_new_super:
1700 deactivate_locked_super(sb);
1701 drop_modules:
1702 drop_parsed_module_refcounts(opts.subsys_bits);
1703 out_err:
1704 kfree(opts.release_agent);
1705 kfree(opts.name);
1706 return ERR_PTR(ret);
1707}
1708
1709static void cgroup_kill_sb(struct super_block *sb) {
1710 struct cgroupfs_root *root = sb->s_fs_info;
1711 struct cgroup *cgrp = &root->top_cgroup;
1712 int ret;
1713 struct cg_cgroup_link *link;
1714 struct cg_cgroup_link *saved_link;
1715
1716 BUG_ON(!root);
1717
1718 BUG_ON(root->number_of_cgroups != 1);
1719 BUG_ON(!list_empty(&cgrp->children));
1720 BUG_ON(!list_empty(&cgrp->sibling));
1721
1722 mutex_lock(&cgroup_mutex);
1723 mutex_lock(&cgroup_root_mutex);
1724
1725 /* Rebind all subsystems back to the default hierarchy */
1726 ret = rebind_subsystems(root, 0);
1727 /* Shouldn't be able to fail ... */
1728 BUG_ON(ret);
1729
1730 /*
1731 * Release all the links from css_sets to this hierarchy's
1732 * root cgroup
1733 */
1734 write_lock(&css_set_lock);
1735
1736 list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
1737 cgrp_link_list) {
1738 list_del(&link->cg_link_list);
1739 list_del(&link->cgrp_link_list);
1740 kfree(link);
1741 }
1742 write_unlock(&css_set_lock);
1743
1744 if (!list_empty(&root->root_list)) {
1745 list_del(&root->root_list);
1746 root_count--;
1747 }
1748
1749 mutex_unlock(&cgroup_root_mutex);
1750 mutex_unlock(&cgroup_mutex);
1751
1752 kill_litter_super(sb);
1753 cgroup_drop_root(root);
1754}
1755
1756static struct file_system_type cgroup_fs_type = {
1757 .name = "cgroup",
1758 .mount = cgroup_mount,
1759 .kill_sb = cgroup_kill_sb,
1760};
1761
1762static struct kobject *cgroup_kobj;
1763
1764/**
1765 * cgroup_path - generate the path of a cgroup
1766 * @cgrp: the cgroup in question
1767 * @buf: the buffer to write the path into
1768 * @buflen: the length of the buffer
1769 *
1770 * Called with cgroup_mutex held or else with an RCU-protected cgroup
1771 * reference. Writes path of cgroup into buf. Returns 0 on success,
1772 * -errno on error.
1773 */
1774int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1775{
1776 char *start;
1777 struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
1778 cgroup_lock_is_held());
1779
1780 if (!dentry || cgrp == dummytop) {
1781 /*
1782 * Inactive subsystems have no dentry for their root
1783 * cgroup
1784 */
1785 strcpy(buf, "/");
1786 return 0;
1787 }
1788
1789 start = buf + buflen;
1790
1791 *--start = '\0';
1792 for (;;) {
1793 int len = dentry->d_name.len;
1794
1795 if ((start -= len) < buf)
1796 return -ENAMETOOLONG;
1797 memcpy(start, dentry->d_name.name, len);
1798 cgrp = cgrp->parent;
1799 if (!cgrp)
1800 break;
1801
1802 dentry = rcu_dereference_check(cgrp->dentry,
1803 cgroup_lock_is_held());
1804 if (!cgrp->parent)
1805 continue;
1806 if (--start < buf)
1807 return -ENAMETOOLONG;
1808 *start = '/';
1809 }
1810 memmove(buf, start, buf + buflen - start);
1811 return 0;
1812}
1813EXPORT_SYMBOL_GPL(cgroup_path);
1814
1815/*
1816 * Control Group taskset
1817 */
1818struct task_and_cgroup {
1819 struct task_struct *task;
1820 struct cgroup *cgrp;
1821 struct css_set *cg;
1822};
1823
1824struct cgroup_taskset {
1825 struct task_and_cgroup single;
1826 struct flex_array *tc_array;
1827 int tc_array_len;
1828 int idx;
1829 struct cgroup *cur_cgrp;
1830};
1831
1832/**
1833 * cgroup_taskset_first - reset taskset and return the first task
1834 * @tset: taskset of interest
1835 *
1836 * @tset iteration is initialized and the first task is returned.
1837 */
1838struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
1839{
1840 if (tset->tc_array) {
1841 tset->idx = 0;
1842 return cgroup_taskset_next(tset);
1843 } else {
1844 tset->cur_cgrp = tset->single.cgrp;
1845 return tset->single.task;
1846 }
1847}
1848EXPORT_SYMBOL_GPL(cgroup_taskset_first);
1849
1850/**
1851 * cgroup_taskset_next - iterate to the next task in taskset
1852 * @tset: taskset of interest
1853 *
1854 * Return the next task in @tset. Iteration must have been initialized
1855 * with cgroup_taskset_first().
1856 */
1857struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
1858{
1859 struct task_and_cgroup *tc;
1860
1861 if (!tset->tc_array || tset->idx >= tset->tc_array_len)
1862 return NULL;
1863
1864 tc = flex_array_get(tset->tc_array, tset->idx++);
1865 tset->cur_cgrp = tc->cgrp;
1866 return tc->task;
1867}
1868EXPORT_SYMBOL_GPL(cgroup_taskset_next);
1869
1870/**
1871 * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
1872 * @tset: taskset of interest
1873 *
1874 * Return the cgroup for the current (last returned) task of @tset. This
1875 * function must be preceded by either cgroup_taskset_first() or
1876 * cgroup_taskset_next().
1877 */
1878struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
1879{
1880 return tset->cur_cgrp;
1881}
1882EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);
1883
1884/**
1885 * cgroup_taskset_size - return the number of tasks in taskset
1886 * @tset: taskset of interest
1887 */
1888int cgroup_taskset_size(struct cgroup_taskset *tset)
1889{
1890 return tset->tc_array ? tset->tc_array_len : 1;
1891}
1892EXPORT_SYMBOL_GPL(cgroup_taskset_size);
1893
1894
1895/*
1896 * cgroup_task_migrate - move a task from one cgroup to another.
1897 *
1898 * 'guarantee' is set if the caller promises that a new css_set for the task
1899 * will already exist. If not set, this function might sleep, and can fail with
1900 * -ENOMEM. Must be called with cgroup_mutex and threadgroup locked.
1901 */
1902static void cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
1903 struct task_struct *tsk, struct css_set *newcg)
1904{
1905 struct css_set *oldcg;
1906
1907 /*
1908 * We are synchronized through threadgroup_lock() against PF_EXITING
1909 * setting such that we can't race against cgroup_exit() changing the
1910 * css_set to init_css_set and dropping the old one.
1911 */
1912 WARN_ON_ONCE(tsk->flags & PF_EXITING);
1913 oldcg = tsk->cgroups;
1914
1915 task_lock(tsk);
1916 rcu_assign_pointer(tsk->cgroups, newcg);
1917 task_unlock(tsk);
1918
1919 /* Update the css_set linked lists if we're using them */
1920 write_lock(&css_set_lock);
1921 if (!list_empty(&tsk->cg_list))
1922 list_move(&tsk->cg_list, &newcg->tasks);
1923 write_unlock(&css_set_lock);
1924
1925 /*
1926 * We just gained a reference on oldcg by taking it from the task. As
1927 * trading it for newcg is protected by cgroup_mutex, we're safe to drop
1928 * it here; it will be freed under RCU.
1929 */
1930 put_css_set(oldcg);
1931
1932 set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1933}
1934
1935/**
1936 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
1937 * @cgrp: the cgroup the task is attaching to
1938 * @tsk: the task to be attached
1939 *
1940 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
1941 * @tsk during call.
1942 */
1943int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1944{
1945 int retval = 0;
1946 struct cgroup_subsys *ss, *failed_ss = NULL;
1947 struct cgroup *oldcgrp;
1948 struct cgroupfs_root *root = cgrp->root;
1949 struct cgroup_taskset tset = { };
1950 struct css_set *newcg;
1951
1952 /* @tsk either already exited or can't exit until the end */
1953 if (tsk->flags & PF_EXITING)
1954 return -ESRCH;
1955
1956 /* Nothing to do if the task is already in that cgroup */
1957 oldcgrp = task_cgroup_from_root(tsk, root);
1958 if (cgrp == oldcgrp)
1959 return 0;
1960
1961 tset.single.task = tsk;
1962 tset.single.cgrp = oldcgrp;
1963
1964 for_each_subsys(root, ss) {
1965 if (ss->can_attach) {
1966 retval = ss->can_attach(cgrp, &tset);
1967 if (retval) {
1968 /*
1969 * Remember on which subsystem the can_attach()
1970 * failed, so that we only call cancel_attach()
1971 * against the subsystems whose can_attach()
1972 * succeeded. (See below)
1973 */
1974 failed_ss = ss;
1975 goto out;
1976 }
1977 }
1978 }
1979
1980 newcg = find_css_set(tsk->cgroups, cgrp);
1981 if (!newcg) {
1982 retval = -ENOMEM;
1983 goto out;
1984 }
1985
1986 cgroup_task_migrate(cgrp, oldcgrp, tsk, newcg);
1987
1988 for_each_subsys(root, ss) {
1989 if (ss->attach)
1990 ss->attach(cgrp, &tset);
1991 }
1992
1993 synchronize_rcu();
1994
1995 /*
1996 * wake up rmdir() waiter. the rmdir should fail since the cgroup
1997 * is no longer empty.
1998 */
1999 cgroup_wakeup_rmdir_waiter(cgrp);
2000out:
2001 if (retval) {
2002 for_each_subsys(root, ss) {
2003 if (ss == failed_ss)
2004 /*
2005 * This subsystem was the one that failed the
2006 * can_attach() check earlier, so we don't need
2007 * to call cancel_attach() against it or any
2008 * remaining subsystems.
2009 */
2010 break;
2011 if (ss->cancel_attach)
2012 ss->cancel_attach(cgrp, &tset);
2013 }
2014 }
2015 return retval;
2016}
2017
2018/**
2019 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2020 * @from: attach to all cgroups of a given task
2021 * @tsk: the task to be attached
2022 */
2023int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2024{
2025 struct cgroupfs_root *root;
2026 int retval = 0;
2027
2028 cgroup_lock();
2029 for_each_active_root(root) {
2030 struct cgroup *from_cg = task_cgroup_from_root(from, root);
2031
2032 retval = cgroup_attach_task(from_cg, tsk);
2033 if (retval)
2034 break;
2035 }
2036 cgroup_unlock();
2037
2038 return retval;
2039}
2040EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2041
2042/**
2043 * cgroup_attach_proc - attach all threads in a threadgroup to a cgroup
2044 * @cgrp: the cgroup to attach to
2045 * @leader: the threadgroup leader task_struct of the group to be attached
2046 *
2047 * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
2048 * task_lock of each thread in leader's threadgroup individually in turn.
2049 */
2050static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
2051{
2052 int retval, i, group_size;
2053 struct cgroup_subsys *ss, *failed_ss = NULL;
2054 /* guaranteed to be initialized later, but the compiler needs this */
2055 struct cgroupfs_root *root = cgrp->root;
2056 /* threadgroup list cursor and array */
2057 struct task_struct *tsk;
2058 struct task_and_cgroup *tc;
2059 struct flex_array *group;
2060 struct cgroup_taskset tset = { };
2061
2062 /*
2063 * step 0: in order to do expensive, possibly blocking operations for
2064 * every thread, we cannot iterate the thread group list, since it needs
2065 * rcu or tasklist locked. instead, build an array of all threads in the
2066 * group - group_rwsem prevents new threads from appearing, and if
2067 * threads exit, this will just be an over-estimate.
2068 */
2069 group_size = get_nr_threads(leader);
2070 /* flex_array supports very large thread-groups better than kmalloc. */
2071 group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
2072 if (!group)
2073 return -ENOMEM;
2074 /* pre-allocate to guarantee space while iterating in rcu read-side. */
2075 retval = flex_array_prealloc(group, 0, group_size - 1, GFP_KERNEL);
2076 if (retval)
2077 goto out_free_group_list;
2078
2079 tsk = leader;
2080 i = 0;
2081 /*
2082 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2083 * already PF_EXITING could be freed from underneath us unless we
2084 * take an rcu_read_lock.
2085 */
2086 rcu_read_lock();
2087 do {
2088 struct task_and_cgroup ent;
2089
2090 /* @tsk either already exited or can't exit until the end */
2091 if (tsk->flags & PF_EXITING)
2092 continue;
2093
2094 /* as per above, nr_threads may decrease, but not increase. */
2095 BUG_ON(i >= group_size);
2096 ent.task = tsk;
2097 ent.cgrp = task_cgroup_from_root(tsk, root);
2098 /* nothing to do if this task is already in the cgroup */
2099 if (ent.cgrp == cgrp)
2100 continue;
2101 /*
2102 * saying GFP_ATOMIC has no effect here because we did prealloc
2103 * earlier, but it's good form to communicate our expectations.
2104 */
2105 retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2106 BUG_ON(retval != 0);
2107 i++;
2108 } while_each_thread(leader, tsk);
2109 rcu_read_unlock();
2110 /* remember the number of threads in the array for later. */
2111 group_size = i;
2112 tset.tc_array = group;
2113 tset.tc_array_len = group_size;
2114
2115 /* methods shouldn't be called if no task is actually migrating */
2116 retval = 0;
2117 if (!group_size)
2118 goto out_free_group_list;
2119
2120 /*
2121 * step 1: check that we can legitimately attach to the cgroup.
2122 */
2123 for_each_subsys(root, ss) {
2124 if (ss->can_attach) {
2125 retval = ss->can_attach(cgrp, &tset);
2126 if (retval) {
2127 failed_ss = ss;
2128 goto out_cancel_attach;
2129 }
2130 }
2131 }
2132
2133 /*
2134 * step 2: make sure css_sets exist for all threads to be migrated.
2135 * we use find_css_set, which allocates a new one if necessary.
2136 */
2137 for (i = 0; i < group_size; i++) {
2138 tc = flex_array_get(group, i);
2139 tc->cg = find_css_set(tc->task->cgroups, cgrp);
2140 if (!tc->cg) {
2141 retval = -ENOMEM;
2142 goto out_put_css_set_refs;
2143 }
2144 }
2145
2146 /*
2147 * step 3: now that we're guaranteed success wrt the css_sets,
2148 * proceed to move all tasks to the new cgroup. There are no
2149 * failure cases after here, so this is the commit point.
2150 */
2151 for (i = 0; i < group_size; i++) {
2152 tc = flex_array_get(group, i);
2153 cgroup_task_migrate(cgrp, tc->cgrp, tc->task, tc->cg);
2154 }
2155 /* nothing is sensitive to fork() after this point. */
2156
2157 /*
2158 * step 4: do subsystem attach callbacks.
2159 */
2160 for_each_subsys(root, ss) {
2161 if (ss->attach)
2162 ss->attach(cgrp, &tset);
2163 }
2164
2165 /*
2166 * step 5: success! and cleanup
2167 */
2168 synchronize_rcu();
2169 cgroup_wakeup_rmdir_waiter(cgrp);
2170 retval = 0;
2171out_put_css_set_refs:
2172 if (retval) {
2173 for (i = 0; i < group_size; i++) {
2174 tc = flex_array_get(group, i);
2175 if (!tc->cg)
2176 break;
2177 put_css_set(tc->cg);
2178 }
2179 }
2180out_cancel_attach:
2181 if (retval) {
2182 for_each_subsys(root, ss) {
2183 if (ss == failed_ss)
2184 break;
2185 if (ss->cancel_attach)
2186 ss->cancel_attach(cgrp, &tset);
2187 }
2188 }
2189out_free_group_list:
2190 flex_array_free(group);
2191 return retval;
2192}
2193
2194/*
2195 * Find the task_struct of the task to attach by vpid and pass it along to the
2196 * function to attach either it or all tasks in its threadgroup. Will lock
2197 * cgroup_mutex and threadgroup; may take task_lock of task.
2198 */
2199static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2200{
2201 struct task_struct *tsk;
2202 const struct cred *cred = current_cred(), *tcred;
2203 int ret;
2204
2205 if (!cgroup_lock_live_group(cgrp))
2206 return -ENODEV;
2207
2208retry_find_task:
2209 rcu_read_lock();
2210 if (pid) {
2211 tsk = find_task_by_vpid(pid);
2212 if (!tsk) {
2213 rcu_read_unlock();
2214 ret= -ESRCH;
2215 goto out_unlock_cgroup;
2216 }
2217 /*
2218 * even if we're attaching all tasks in the thread group, we
2219 * only need to check permissions on one of them.
2220 */
2221 tcred = __task_cred(tsk);
2222 if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
2223 !uid_eq(cred->euid, tcred->uid) &&
2224 !uid_eq(cred->euid, tcred->suid)) {
2225 rcu_read_unlock();
2226 ret = -EACCES;
2227 goto out_unlock_cgroup;
2228 }
2229 } else
2230 tsk = current;
2231
2232 if (threadgroup)
2233 tsk = tsk->group_leader;
2234
2235 /*
2236 * Workqueue threads may acquire PF_THREAD_BOUND and become
2237 * trapped in a cpuset, or RT worker may be born in a cgroup
2238 * with no rt_runtime allocated. Just say no.
2239 */
2240 if (tsk == kthreadd_task || (tsk->flags & PF_THREAD_BOUND)) {
2241 ret = -EINVAL;
2242 rcu_read_unlock();
2243 goto out_unlock_cgroup;
2244 }
2245
2246 get_task_struct(tsk);
2247 rcu_read_unlock();
2248
2249 threadgroup_lock(tsk);
2250 if (threadgroup) {
2251 if (!thread_group_leader(tsk)) {
2252 /*
2253 * a race with de_thread from another thread's exec()
2254 * may strip us of our leadership, if this happens,
2255 * there is no choice but to throw this task away and
2256 * try again; this is
2257 * "double-double-toil-and-trouble-check locking".
2258 */
2259 threadgroup_unlock(tsk);
2260 put_task_struct(tsk);
2261 goto retry_find_task;
2262 }
2263 ret = cgroup_attach_proc(cgrp, tsk);
2264 } else
2265 ret = cgroup_attach_task(cgrp, tsk);
2266 threadgroup_unlock(tsk);
2267
2268 put_task_struct(tsk);
2269out_unlock_cgroup:
2270 cgroup_unlock();
2271 return ret;
2272}
2273
2274static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
2275{
2276 return attach_task_by_pid(cgrp, pid, false);
2277}
2278
2279static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2280{
2281 return attach_task_by_pid(cgrp, tgid, true);
2282}
2283
2284/**
2285 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
2286 * @cgrp: the cgroup to be checked for liveness
2287 *
2288 * On success, returns true; the lock should be later released with
2289 * cgroup_unlock(). On failure returns false with no lock held.
2290 */
2291bool cgroup_lock_live_group(struct cgroup *cgrp)
2292{
2293 mutex_lock(&cgroup_mutex);
2294 if (cgroup_is_removed(cgrp)) {
2295 mutex_unlock(&cgroup_mutex);
2296 return false;
2297 }
2298 return true;
2299}
2300EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2301
2302static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
2303 const char *buffer)
2304{
2305 BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
2306 if (strlen(buffer) >= PATH_MAX)
2307 return -EINVAL;
2308 if (!cgroup_lock_live_group(cgrp))
2309 return -ENODEV;
2310 mutex_lock(&cgroup_root_mutex);
2311 strcpy(cgrp->root->release_agent_path, buffer);
2312 mutex_unlock(&cgroup_root_mutex);
2313 cgroup_unlock();
2314 return 0;
2315}
2316
2317static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
2318 struct seq_file *seq)
2319{
2320 if (!cgroup_lock_live_group(cgrp))
2321 return -ENODEV;
2322 seq_puts(seq, cgrp->root->release_agent_path);
2323 seq_putc(seq, '\n');
2324 cgroup_unlock();
2325 return 0;
2326}
2327
2328/* A buffer size big enough for numbers or short strings */
2329#define CGROUP_LOCAL_BUFFER_SIZE 64
2330
2331static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2332 struct file *file,
2333 const char __user *userbuf,
2334 size_t nbytes, loff_t *unused_ppos)
2335{
2336 char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2337 int retval = 0;
2338 char *end;
2339
2340 if (!nbytes)
2341 return -EINVAL;
2342 if (nbytes >= sizeof(buffer))
2343 return -E2BIG;
2344 if (copy_from_user(buffer, userbuf, nbytes))
2345 return -EFAULT;
2346
2347 buffer[nbytes] = 0; /* nul-terminate */
2348 if (cft->write_u64) {
2349 u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2350 if (*end)
2351 return -EINVAL;
2352 retval = cft->write_u64(cgrp, cft, val);
2353 } else {
2354 s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2355 if (*end)
2356 return -EINVAL;
2357 retval = cft->write_s64(cgrp, cft, val);
2358 }
2359 if (!retval)
2360 retval = nbytes;
2361 return retval;
2362}
2363
2364static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
2365 struct file *file,
2366 const char __user *userbuf,
2367 size_t nbytes, loff_t *unused_ppos)
2368{
2369 char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2370 int retval = 0;
2371 size_t max_bytes = cft->max_write_len;
2372 char *buffer = local_buffer;
2373
2374 if (!max_bytes)
2375 max_bytes = sizeof(local_buffer) - 1;
2376 if (nbytes >= max_bytes)
2377 return -E2BIG;
2378 /* Allocate a dynamic buffer if we need one */
2379 if (nbytes >= sizeof(local_buffer)) {
2380 buffer = kmalloc(nbytes + 1, GFP_KERNEL);
2381 if (buffer == NULL)
2382 return -ENOMEM;
2383 }
2384 if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
2385 retval = -EFAULT;
2386 goto out;
2387 }
2388
2389 buffer[nbytes] = 0; /* nul-terminate */
2390 retval = cft->write_string(cgrp, cft, strstrip(buffer));
2391 if (!retval)
2392 retval = nbytes;
2393out:
2394 if (buffer != local_buffer)
2395 kfree(buffer);
2396 return retval;
2397}
2398
2399static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
2400 size_t nbytes, loff_t *ppos)
2401{
2402 struct cftype *cft = __d_cft(file->f_dentry);
2403 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2404
2405 if (cgroup_is_removed(cgrp))
2406 return -ENODEV;
2407 if (cft->write)
2408 return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2409 if (cft->write_u64 || cft->write_s64)
2410 return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2411 if (cft->write_string)
2412 return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2413 if (cft->trigger) {
2414 int ret = cft->trigger(cgrp, (unsigned int)cft->private);
2415 return ret ? ret : nbytes;
2416 }
2417 return -EINVAL;
2418}
2419
2420static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
2421 struct file *file,
2422 char __user *buf, size_t nbytes,
2423 loff_t *ppos)
2424{
2425 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2426 u64 val = cft->read_u64(cgrp, cft);
2427 int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
2428
2429 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2430}
2431
2432static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
2433 struct file *file,
2434 char __user *buf, size_t nbytes,
2435 loff_t *ppos)
2436{
2437 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2438 s64 val = cft->read_s64(cgrp, cft);
2439 int len = sprintf(tmp, "%lld\n", (long long) val);
2440
2441 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2442}
2443
2444static ssize_t cgroup_file_read(struct file *file, char __user *buf,
2445 size_t nbytes, loff_t *ppos)
2446{
2447 struct cftype *cft = __d_cft(file->f_dentry);
2448 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2449
2450 if (cgroup_is_removed(cgrp))
2451 return -ENODEV;
2452
2453 if (cft->read)
2454 return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2455 if (cft->read_u64)
2456 return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2457 if (cft->read_s64)
2458 return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2459 return -EINVAL;
2460}
2461
2462/*
2463 * seqfile ops/methods for returning structured data. Currently just
2464 * supports string->u64 maps, but can be extended in future.
2465 */
2466
2467struct cgroup_seqfile_state {
2468 struct cftype *cft;
2469 struct cgroup *cgroup;
2470};
2471
2472static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
2473{
2474 struct seq_file *sf = cb->state;
2475 return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
2476}
2477
2478static int cgroup_seqfile_show(struct seq_file *m, void *arg)
2479{
2480 struct cgroup_seqfile_state *state = m->private;
2481 struct cftype *cft = state->cft;
2482 if (cft->read_map) {
2483 struct cgroup_map_cb cb = {
2484 .fill = cgroup_map_add,
2485 .state = m,
2486 };
2487 return cft->read_map(state->cgroup, cft, &cb);
2488 }
2489 return cft->read_seq_string(state->cgroup, cft, m);
2490}
2491
2492static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2493{
2494 struct seq_file *seq = file->private_data;
2495 kfree(seq->private);
2496 return single_release(inode, file);
2497}
2498
2499static const struct file_operations cgroup_seqfile_operations = {
2500 .read = seq_read,
2501 .write = cgroup_file_write,
2502 .llseek = seq_lseek,
2503 .release = cgroup_seqfile_release,
2504};
2505
2506static int cgroup_file_open(struct inode *inode, struct file *file)
2507{
2508 int err;
2509 struct cftype *cft;
2510
2511 err = generic_file_open(inode, file);
2512 if (err)
2513 return err;
2514 cft = __d_cft(file->f_dentry);
2515
2516 if (cft->read_map || cft->read_seq_string) {
2517 struct cgroup_seqfile_state *state =
2518 kzalloc(sizeof(*state), GFP_USER);
2519 if (!state)
2520 return -ENOMEM;
2521 state->cft = cft;
2522 state->cgroup = __d_cgrp(file->f_dentry->d_parent);
2523 file->f_op = &cgroup_seqfile_operations;
2524 err = single_open(file, cgroup_seqfile_show, state);
2525 if (err < 0)
2526 kfree(state);
2527 } else if (cft->open)
2528 err = cft->open(inode, file);
2529 else
2530 err = 0;
2531
2532 return err;
2533}
2534
2535static int cgroup_file_release(struct inode *inode, struct file *file)
2536{
2537 struct cftype *cft = __d_cft(file->f_dentry);
2538 if (cft->release)
2539 return cft->release(inode, file);
2540 return 0;
2541}
2542
2543/*
2544 * cgroup_rename - Only allow simple rename of directories in place.
2545 */
2546static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
2547 struct inode *new_dir, struct dentry *new_dentry)
2548{
2549 if (!S_ISDIR(old_dentry->d_inode->i_mode))
2550 return -ENOTDIR;
2551 if (new_dentry->d_inode)
2552 return -EEXIST;
2553 if (old_dir != new_dir)
2554 return -EIO;
2555 return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
2556}
2557
2558static const struct file_operations cgroup_file_operations = {
2559 .read = cgroup_file_read,
2560 .write = cgroup_file_write,
2561 .llseek = generic_file_llseek,
2562 .open = cgroup_file_open,
2563 .release = cgroup_file_release,
2564};
2565
2566static const struct inode_operations cgroup_dir_inode_operations = {
2567 .lookup = cgroup_lookup,
2568 .mkdir = cgroup_mkdir,
2569 .rmdir = cgroup_rmdir,
2570 .rename = cgroup_rename,
2571};
2572
2573static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
2574{
2575 if (dentry->d_name.len > NAME_MAX)
2576 return ERR_PTR(-ENAMETOOLONG);
2577 d_add(dentry, NULL);
2578 return NULL;
2579}
2580
2581/*
2582 * Check if a file is a control file
2583 */
2584static inline struct cftype *__file_cft(struct file *file)
2585{
2586 if (file->f_dentry->d_inode->i_fop != &cgroup_file_operations)
2587 return ERR_PTR(-EINVAL);
2588 return __d_cft(file->f_dentry);
2589}
2590
2591static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2592 struct super_block *sb)
2593{
2594 struct inode *inode;
2595
2596 if (!dentry)
2597 return -ENOENT;
2598 if (dentry->d_inode)
2599 return -EEXIST;
2600
2601 inode = cgroup_new_inode(mode, sb);
2602 if (!inode)
2603 return -ENOMEM;
2604
2605 if (S_ISDIR(mode)) {
2606 inode->i_op = &cgroup_dir_inode_operations;
2607 inode->i_fop = &simple_dir_operations;
2608
2609 /* start off with i_nlink == 2 (for "." entry) */
2610 inc_nlink(inode);
2611
2612 /* start with the directory inode held, so that we can
2613 * populate it without racing with another mkdir */
2614 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
2615 } else if (S_ISREG(mode)) {
2616 inode->i_size = 0;
2617 inode->i_fop = &cgroup_file_operations;
2618 }
2619 d_instantiate(dentry, inode);
2620 dget(dentry); /* Extra count - pin the dentry in core */
2621 return 0;
2622}
2623
2624/*
2625 * cgroup_create_dir - create a directory for an object.
2626 * @cgrp: the cgroup we create the directory for. It must have a valid
2627 * ->parent field. And we are going to fill its ->dentry field.
2628 * @dentry: dentry of the new cgroup
2629 * @mode: mode to set on new directory.
2630 */
2631static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
2632 umode_t mode)
2633{
2634 struct dentry *parent;
2635 int error = 0;
2636
2637 parent = cgrp->parent->dentry;
2638 error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
2639 if (!error) {
2640 dentry->d_fsdata = cgrp;
2641 inc_nlink(parent->d_inode);
2642 rcu_assign_pointer(cgrp->dentry, dentry);
2643 dget(dentry);
2644 }
2645 dput(dentry);
2646
2647 return error;
2648}
2649
2650/**
2651 * cgroup_file_mode - deduce file mode of a control file
2652 * @cft: the control file in question
2653 *
2654 * returns cft->mode if ->mode is not 0
2655 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
2656 * returns S_IRUGO if it has only a read handler
2657 * returns S_IWUSR if it has only a write hander
2658 */
2659static umode_t cgroup_file_mode(const struct cftype *cft)
2660{
2661 umode_t mode = 0;
2662
2663 if (cft->mode)
2664 return cft->mode;
2665
2666 if (cft->read || cft->read_u64 || cft->read_s64 ||
2667 cft->read_map || cft->read_seq_string)
2668 mode |= S_IRUGO;
2669
2670 if (cft->write || cft->write_u64 || cft->write_s64 ||
2671 cft->write_string || cft->trigger)
2672 mode |= S_IWUSR;
2673
2674 return mode;
2675}
2676
2677static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
2678 const struct cftype *cft)
2679{
2680 struct dentry *dir = cgrp->dentry;
2681 struct cgroup *parent = __d_cgrp(dir);
2682 struct dentry *dentry;
2683 struct cfent *cfe;
2684 int error;
2685 umode_t mode;
2686 char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2687
2688 /* does @cft->flags tell us to skip creation on @cgrp? */
2689 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
2690 return 0;
2691 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
2692 return 0;
2693
2694 if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2695 strcpy(name, subsys->name);
2696 strcat(name, ".");
2697 }
2698 strcat(name, cft->name);
2699
2700 BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
2701
2702 cfe = kzalloc(sizeof(*cfe), GFP_KERNEL);
2703 if (!cfe)
2704 return -ENOMEM;
2705
2706 dentry = lookup_one_len(name, dir, strlen(name));
2707 if (IS_ERR(dentry)) {
2708 error = PTR_ERR(dentry);
2709 goto out;
2710 }
2711
2712 mode = cgroup_file_mode(cft);
2713 error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
2714 if (!error) {
2715 cfe->type = (void *)cft;
2716 cfe->dentry = dentry;
2717 dentry->d_fsdata = cfe;
2718 list_add_tail(&cfe->node, &parent->files);
2719 cfe = NULL;
2720 }
2721 dput(dentry);
2722out:
2723 kfree(cfe);
2724 return error;
2725}
2726
2727static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
2728 const struct cftype cfts[], bool is_add)
2729{
2730 const struct cftype *cft;
2731 int err, ret = 0;
2732
2733 for (cft = cfts; cft->name[0] != '\0'; cft++) {
2734 if (is_add)
2735 err = cgroup_add_file(cgrp, subsys, cft);
2736 else
2737 err = cgroup_rm_file(cgrp, cft);
2738 if (err) {
2739 pr_warning("cgroup_addrm_files: failed to %s %s, err=%d\n",
2740 is_add ? "add" : "remove", cft->name, err);
2741 ret = err;
2742 }
2743 }
2744 return ret;
2745}
2746
2747static DEFINE_MUTEX(cgroup_cft_mutex);
2748
2749static void cgroup_cfts_prepare(void)
2750 __acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex)
2751{
2752 /*
2753 * Thanks to the entanglement with vfs inode locking, we can't walk
2754 * the existing cgroups under cgroup_mutex and create files.
2755 * Instead, we increment reference on all cgroups and build list of
2756 * them using @cgrp->cft_q_node. Grab cgroup_cft_mutex to ensure
2757 * exclusive access to the field.
2758 */
2759 mutex_lock(&cgroup_cft_mutex);
2760 mutex_lock(&cgroup_mutex);
2761}
2762
2763static void cgroup_cfts_commit(struct cgroup_subsys *ss,
2764 const struct cftype *cfts, bool is_add)
2765 __releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
2766{
2767 LIST_HEAD(pending);
2768 struct cgroup *cgrp, *n;
2769
2770 /* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
2771 if (cfts && ss->root != &rootnode) {
2772 list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) {
2773 dget(cgrp->dentry);
2774 list_add_tail(&cgrp->cft_q_node, &pending);
2775 }
2776 }
2777
2778 mutex_unlock(&cgroup_mutex);
2779
2780 /*
2781 * All new cgroups will see @cfts update on @ss->cftsets. Add/rm
2782 * files for all cgroups which were created before.
2783 */
2784 list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {
2785 struct inode *inode = cgrp->dentry->d_inode;
2786
2787 mutex_lock(&inode->i_mutex);
2788 mutex_lock(&cgroup_mutex);
2789 if (!cgroup_is_removed(cgrp))
2790 cgroup_addrm_files(cgrp, ss, cfts, is_add);
2791 mutex_unlock(&cgroup_mutex);
2792 mutex_unlock(&inode->i_mutex);
2793
2794 list_del_init(&cgrp->cft_q_node);
2795 dput(cgrp->dentry);
2796 }
2797
2798 mutex_unlock(&cgroup_cft_mutex);
2799}
2800
2801/**
2802 * cgroup_add_cftypes - add an array of cftypes to a subsystem
2803 * @ss: target cgroup subsystem
2804 * @cfts: zero-length name terminated array of cftypes
2805 *
2806 * Register @cfts to @ss. Files described by @cfts are created for all
2807 * existing cgroups to which @ss is attached and all future cgroups will
2808 * have them too. This function can be called anytime whether @ss is
2809 * attached or not.
2810 *
2811 * Returns 0 on successful registration, -errno on failure. Note that this
2812 * function currently returns 0 as long as @cfts registration is successful
2813 * even if some file creation attempts on existing cgroups fail.
2814 */
2815int cgroup_add_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
2816{
2817 struct cftype_set *set;
2818
2819 set = kzalloc(sizeof(*set), GFP_KERNEL);
2820 if (!set)
2821 return -ENOMEM;
2822
2823 cgroup_cfts_prepare();
2824 set->cfts = cfts;
2825 list_add_tail(&set->node, &ss->cftsets);
2826 cgroup_cfts_commit(ss, cfts, true);
2827
2828 return 0;
2829}
2830EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
2831
2832/**
2833 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
2834 * @ss: target cgroup subsystem
2835 * @cfts: zero-length name terminated array of cftypes
2836 *
2837 * Unregister @cfts from @ss. Files described by @cfts are removed from
2838 * all existing cgroups to which @ss is attached and all future cgroups
2839 * won't have them either. This function can be called anytime whether @ss
2840 * is attached or not.
2841 *
2842 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
2843 * registered with @ss.
2844 */
2845int cgroup_rm_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
2846{
2847 struct cftype_set *set;
2848
2849 cgroup_cfts_prepare();
2850
2851 list_for_each_entry(set, &ss->cftsets, node) {
2852 if (set->cfts == cfts) {
2853 list_del_init(&set->node);
2854 cgroup_cfts_commit(ss, cfts, false);
2855 return 0;
2856 }
2857 }
2858
2859 cgroup_cfts_commit(ss, NULL, false);
2860 return -ENOENT;
2861}
2862
2863/**
2864 * cgroup_task_count - count the number of tasks in a cgroup.
2865 * @cgrp: the cgroup in question
2866 *
2867 * Return the number of tasks in the cgroup.
2868 */
2869int cgroup_task_count(const struct cgroup *cgrp)
2870{
2871 int count = 0;
2872 struct cg_cgroup_link *link;
2873
2874 read_lock(&css_set_lock);
2875 list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2876 count += atomic_read(&link->cg->refcount);
2877 }
2878 read_unlock(&css_set_lock);
2879 return count;
2880}
2881
2882/*
2883 * Advance a list_head iterator. The iterator should be positioned at
2884 * the start of a css_set
2885 */
2886static void cgroup_advance_iter(struct cgroup *cgrp,
2887 struct cgroup_iter *it)
2888{
2889 struct list_head *l = it->cg_link;
2890 struct cg_cgroup_link *link;
2891 struct css_set *cg;
2892
2893 /* Advance to the next non-empty css_set */
2894 do {
2895 l = l->next;
2896 if (l == &cgrp->css_sets) {
2897 it->cg_link = NULL;
2898 return;
2899 }
2900 link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2901 cg = link->cg;
2902 } while (list_empty(&cg->tasks));
2903 it->cg_link = l;
2904 it->task = cg->tasks.next;
2905}
2906
2907/*
2908 * To reduce the fork() overhead for systems that are not actually
2909 * using their cgroups capability, we don't maintain the lists running
2910 * through each css_set to its tasks until we see the list actually
2911 * used - in other words after the first call to cgroup_iter_start().
2912 */
2913static void cgroup_enable_task_cg_lists(void)
2914{
2915 struct task_struct *p, *g;
2916 write_lock(&css_set_lock);
2917 use_task_css_set_links = 1;
2918 /*
2919 * We need tasklist_lock because RCU is not safe against
2920 * while_each_thread(). Besides, a forking task that has passed
2921 * cgroup_post_fork() without seeing use_task_css_set_links = 1
2922 * is not guaranteed to have its child immediately visible in the
2923 * tasklist if we walk through it with RCU.
2924 */
2925 read_lock(&tasklist_lock);
2926 do_each_thread(g, p) {
2927 task_lock(p);
2928 /*
2929 * We should check if the process is exiting, otherwise
2930 * it will race with cgroup_exit() in that the list
2931 * entry won't be deleted though the process has exited.
2932 */
2933 if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
2934 list_add(&p->cg_list, &p->cgroups->tasks);
2935 task_unlock(p);
2936 } while_each_thread(g, p);
2937 read_unlock(&tasklist_lock);
2938 write_unlock(&css_set_lock);
2939}
2940
2941void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
2942 __acquires(css_set_lock)
2943{
2944 /*
2945 * The first time anyone tries to iterate across a cgroup,
2946 * we need to enable the list linking each css_set to its
2947 * tasks, and fix up all existing tasks.
2948 */
2949 if (!use_task_css_set_links)
2950 cgroup_enable_task_cg_lists();
2951
2952 read_lock(&css_set_lock);
2953 it->cg_link = &cgrp->css_sets;
2954 cgroup_advance_iter(cgrp, it);
2955}
2956
2957struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
2958 struct cgroup_iter *it)
2959{
2960 struct task_struct *res;
2961 struct list_head *l = it->task;
2962 struct cg_cgroup_link *link;
2963
2964 /* If the iterator cg is NULL, we have no tasks */
2965 if (!it->cg_link)
2966 return NULL;
2967 res = list_entry(l, struct task_struct, cg_list);
2968 /* Advance iterator to find next entry */
2969 l = l->next;
2970 link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
2971 if (l == &link->cg->tasks) {
2972 /* We reached the end of this task list - move on to
2973 * the next cg_cgroup_link */
2974 cgroup_advance_iter(cgrp, it);
2975 } else {
2976 it->task = l;
2977 }
2978 return res;
2979}
2980
2981void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
2982 __releases(css_set_lock)
2983{
2984 read_unlock(&css_set_lock);
2985}
2986
2987static inline int started_after_time(struct task_struct *t1,
2988 struct timespec *time,
2989 struct task_struct *t2)
2990{
2991 int start_diff = timespec_compare(&t1->start_time, time);
2992 if (start_diff > 0) {
2993 return 1;
2994 } else if (start_diff < 0) {
2995 return 0;
2996 } else {
2997 /*
2998 * Arbitrarily, if two processes started at the same
2999 * time, we'll say that the lower pointer value
3000 * started first. Note that t2 may have exited by now
3001 * so this may not be a valid pointer any longer, but
3002 * that's fine - it still serves to distinguish
3003 * between two tasks started (effectively) simultaneously.
3004 */
3005 return t1 > t2;
3006 }
3007}
3008
3009/*
3010 * This function is a callback from heap_insert() and is used to order
3011 * the heap.
3012 * In this case we order the heap in descending task start time.
3013 */
3014static inline int started_after(void *p1, void *p2)
3015{
3016 struct task_struct *t1 = p1;
3017 struct task_struct *t2 = p2;
3018 return started_after_time(t1, &t2->start_time, t2);
3019}
3020
3021/**
3022 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
3023 * @scan: struct cgroup_scanner containing arguments for the scan
3024 *
3025 * Arguments include pointers to callback functions test_task() and
3026 * process_task().
3027 * Iterate through all the tasks in a cgroup, calling test_task() for each,
3028 * and if it returns true, call process_task() for it also.
3029 * The test_task pointer may be NULL, meaning always true (select all tasks).
3030 * Effectively duplicates cgroup_iter_{start,next,end}()
3031 * but does not lock css_set_lock for the call to process_task().
3032 * The struct cgroup_scanner may be embedded in any structure of the caller's
3033 * creation.
3034 * It is guaranteed that process_task() will act on every task that
3035 * is a member of the cgroup for the duration of this call. This
3036 * function may or may not call process_task() for tasks that exit
3037 * or move to a different cgroup during the call, or are forked or
3038 * move into the cgroup during the call.
3039 *
3040 * Note that test_task() may be called with locks held, and may in some
3041 * situations be called multiple times for the same task, so it should
3042 * be cheap.
3043 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
3044 * pre-allocated and will be used for heap operations (and its "gt" member will
3045 * be overwritten), else a temporary heap will be used (allocation of which
3046 * may cause this function to fail).
3047 */
3048int cgroup_scan_tasks(struct cgroup_scanner *scan)
3049{
3050 int retval, i;
3051 struct cgroup_iter it;
3052 struct task_struct *p, *dropped;
3053 /* Never dereference latest_task, since it's not refcounted */
3054 struct task_struct *latest_task = NULL;
3055 struct ptr_heap tmp_heap;
3056 struct ptr_heap *heap;
3057 struct timespec latest_time = { 0, 0 };
3058
3059 if (scan->heap) {
3060 /* The caller supplied our heap and pre-allocated its memory */
3061 heap = scan->heap;
3062 heap->gt = &started_after;
3063 } else {
3064 /* We need to allocate our own heap memory */
3065 heap = &tmp_heap;
3066 retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
3067 if (retval)
3068 /* cannot allocate the heap */
3069 return retval;
3070 }
3071
3072 again:
3073 /*
3074 * Scan tasks in the cgroup, using the scanner's "test_task" callback
3075 * to determine which are of interest, and using the scanner's
3076 * "process_task" callback to process any of them that need an update.
3077 * Since we don't want to hold any locks during the task updates,
3078 * gather tasks to be processed in a heap structure.
3079 * The heap is sorted by descending task start time.
3080 * If the statically-sized heap fills up, we overflow tasks that
3081 * started later, and in future iterations only consider tasks that
3082 * started after the latest task in the previous pass. This
3083 * guarantees forward progress and that we don't miss any tasks.
3084 */
3085 heap->size = 0;
3086 cgroup_iter_start(scan->cg, &it);
3087 while ((p = cgroup_iter_next(scan->cg, &it))) {
3088 /*
3089 * Only affect tasks that qualify per the caller's callback,
3090 * if he provided one
3091 */
3092 if (scan->test_task && !scan->test_task(p, scan))
3093 continue;
3094 /*
3095 * Only process tasks that started after the last task
3096 * we processed
3097 */
3098 if (!started_after_time(p, &latest_time, latest_task))
3099 continue;
3100 dropped = heap_insert(heap, p);
3101 if (dropped == NULL) {
3102 /*
3103 * The new task was inserted; the heap wasn't
3104 * previously full
3105 */
3106 get_task_struct(p);
3107 } else if (dropped != p) {
3108 /*
3109 * The new task was inserted, and pushed out a
3110 * different task
3111 */
3112 get_task_struct(p);
3113 put_task_struct(dropped);
3114 }
3115 /*
3116 * Else the new task was newer than anything already in
3117 * the heap and wasn't inserted
3118 */
3119 }
3120 cgroup_iter_end(scan->cg, &it);
3121
3122 if (heap->size) {
3123 for (i = 0; i < heap->size; i++) {
3124 struct task_struct *q = heap->ptrs[i];
3125 if (i == 0) {
3126 latest_time = q->start_time;
3127 latest_task = q;
3128 }
3129 /* Process the task per the caller's callback */
3130 scan->process_task(q, scan);
3131 put_task_struct(q);
3132 }
3133 /*
3134 * If we had to process any tasks at all, scan again
3135 * in case some of them were in the middle of forking
3136 * children that didn't get processed.
3137 * Not the most efficient way to do it, but it avoids
3138 * having to take callback_mutex in the fork path
3139 */
3140 goto again;
3141 }
3142 if (heap == &tmp_heap)
3143 heap_free(&tmp_heap);
3144 return 0;
3145}
3146
3147/*
3148 * Stuff for reading the 'tasks'/'procs' files.
3149 *
3150 * Reading this file can return large amounts of data if a cgroup has
3151 * *lots* of attached tasks. So it may need several calls to read(),
3152 * but we cannot guarantee that the information we produce is correct
3153 * unless we produce it entirely atomically.
3154 *
3155 */
3156
3157/* which pidlist file are we talking about? */
3158enum cgroup_filetype {
3159 CGROUP_FILE_PROCS,
3160 CGROUP_FILE_TASKS,
3161};
3162
3163/*
3164 * A pidlist is a list of pids that virtually represents the contents of one
3165 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3166 * a pair (one each for procs, tasks) for each pid namespace that's relevant
3167 * to the cgroup.
3168 */
3169struct cgroup_pidlist {
3170 /*
3171 * used to find which pidlist is wanted. doesn't change as long as
3172 * this particular list stays in the list.
3173 */
3174 struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
3175 /* array of xids */
3176 pid_t *list;
3177 /* how many elements the above list has */
3178 int length;
3179 /* how many files are using the current array */
3180 int use_count;
3181 /* each of these stored in a list by its cgroup */
3182 struct list_head links;
3183 /* pointer to the cgroup we belong to, for list removal purposes */
3184 struct cgroup *owner;
3185 /* protects the other fields */
3186 struct rw_semaphore mutex;
3187};
3188
3189/*
3190 * The following two functions "fix" the issue where there are more pids
3191 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3192 * TODO: replace with a kernel-wide solution to this problem
3193 */
3194#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3195static void *pidlist_allocate(int count)
3196{
3197 if (PIDLIST_TOO_LARGE(count))
3198 return vmalloc(count * sizeof(pid_t));
3199 else
3200 return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
3201}
3202static void pidlist_free(void *p)
3203{
3204 if (is_vmalloc_addr(p))
3205 vfree(p);
3206 else
3207 kfree(p);
3208}
3209static void *pidlist_resize(void *p, int newcount)
3210{
3211 void *newlist;
3212 /* note: if new alloc fails, old p will still be valid either way */
3213 if (is_vmalloc_addr(p)) {
3214 newlist = vmalloc(newcount * sizeof(pid_t));
3215 if (!newlist)
3216 return NULL;
3217 memcpy(newlist, p, newcount * sizeof(pid_t));
3218 vfree(p);
3219 } else {
3220 newlist = krealloc(p, newcount * sizeof(pid_t), GFP_KERNEL);
3221 }
3222 return newlist;
3223}
3224
3225/*
3226 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3227 * If the new stripped list is sufficiently smaller and there's enough memory
3228 * to allocate a new buffer, will let go of the unneeded memory. Returns the
3229 * number of unique elements.
3230 */
3231/* is the size difference enough that we should re-allocate the array? */
3232#define PIDLIST_REALLOC_DIFFERENCE(old, new) ((old) - PAGE_SIZE >= (new))
3233static int pidlist_uniq(pid_t **p, int length)
3234{
3235 int src, dest = 1;
3236 pid_t *list = *p;
3237 pid_t *newlist;
3238
3239 /*
3240 * we presume the 0th element is unique, so i starts at 1. trivial
3241 * edge cases first; no work needs to be done for either
3242 */
3243 if (length == 0 || length == 1)
3244 return length;
3245 /* src and dest walk down the list; dest counts unique elements */
3246 for (src = 1; src < length; src++) {
3247 /* find next unique element */
3248 while (list[src] == list[src-1]) {
3249 src++;
3250 if (src == length)
3251 goto after;
3252 }
3253 /* dest always points to where the next unique element goes */
3254 list[dest] = list[src];
3255 dest++;
3256 }
3257after:
3258 /*
3259 * if the length difference is large enough, we want to allocate a
3260 * smaller buffer to save memory. if this fails due to out of memory,
3261 * we'll just stay with what we've got.
3262 */
3263 if (PIDLIST_REALLOC_DIFFERENCE(length, dest)) {
3264 newlist = pidlist_resize(list, dest);
3265 if (newlist)
3266 *p = newlist;
3267 }
3268 return dest;
3269}
3270
3271static int cmppid(const void *a, const void *b)
3272{
3273 return *(pid_t *)a - *(pid_t *)b;
3274}
3275
3276/*
3277 * find the appropriate pidlist for our purpose (given procs vs tasks)
3278 * returns with the lock on that pidlist already held, and takes care
3279 * of the use count, or returns NULL with no locks held if we're out of
3280 * memory.
3281 */
3282static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
3283 enum cgroup_filetype type)
3284{
3285 struct cgroup_pidlist *l;
3286 /* don't need task_nsproxy() if we're looking at ourself */
3287 struct pid_namespace *ns = current->nsproxy->pid_ns;
3288
3289 /*
3290 * We can't drop the pidlist_mutex before taking the l->mutex in case
3291 * the last ref-holder is trying to remove l from the list at the same
3292 * time. Holding the pidlist_mutex precludes somebody taking whichever
3293 * list we find out from under us - compare release_pid_array().
3294 */
3295 mutex_lock(&cgrp->pidlist_mutex);
3296 list_for_each_entry(l, &cgrp->pidlists, links) {
3297 if (l->key.type == type && l->key.ns == ns) {
3298 /* make sure l doesn't vanish out from under us */
3299 down_write(&l->mutex);
3300 mutex_unlock(&cgrp->pidlist_mutex);
3301 return l;
3302 }
3303 }
3304 /* entry not found; create a new one */
3305 l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3306 if (!l) {
3307 mutex_unlock(&cgrp->pidlist_mutex);
3308 return l;
3309 }
3310 init_rwsem(&l->mutex);
3311 down_write(&l->mutex);
3312 l->key.type = type;
3313 l->key.ns = get_pid_ns(ns);
3314 l->use_count = 0; /* don't increment here */
3315 l->list = NULL;
3316 l->owner = cgrp;
3317 list_add(&l->links, &cgrp->pidlists);
3318 mutex_unlock(&cgrp->pidlist_mutex);
3319 return l;
3320}
3321
3322/*
3323 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3324 */
3325static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
3326 struct cgroup_pidlist **lp)
3327{
3328 pid_t *array;
3329 int length;
3330 int pid, n = 0; /* used for populating the array */
3331 struct cgroup_iter it;
3332 struct task_struct *tsk;
3333 struct cgroup_pidlist *l;
3334
3335 /*
3336 * If cgroup gets more users after we read count, we won't have
3337 * enough space - tough. This race is indistinguishable to the
3338 * caller from the case that the additional cgroup users didn't
3339 * show up until sometime later on.
3340 */
3341 length = cgroup_task_count(cgrp);
3342 array = pidlist_allocate(length);
3343 if (!array)
3344 return -ENOMEM;
3345 /* now, populate the array */
3346 cgroup_iter_start(cgrp, &it);
3347 while ((tsk = cgroup_iter_next(cgrp, &it))) {
3348 if (unlikely(n == length))
3349 break;
3350 /* get tgid or pid for procs or tasks file respectively */
3351 if (type == CGROUP_FILE_PROCS)
3352 pid = task_tgid_vnr(tsk);
3353 else
3354 pid = task_pid_vnr(tsk);
3355 if (pid > 0) /* make sure to only use valid results */
3356 array[n++] = pid;
3357 }
3358 cgroup_iter_end(cgrp, &it);
3359 length = n;
3360 /* now sort & (if procs) strip out duplicates */
3361 sort(array, length, sizeof(pid_t), cmppid, NULL);
3362 if (type == CGROUP_FILE_PROCS)
3363 length = pidlist_uniq(&array, length);
3364 l = cgroup_pidlist_find(cgrp, type);
3365 if (!l) {
3366 pidlist_free(array);
3367 return -ENOMEM;
3368 }
3369 /* store array, freeing old if necessary - lock already held */
3370 pidlist_free(l->list);
3371 l->list = array;
3372 l->length = length;
3373 l->use_count++;
3374 up_write(&l->mutex);
3375 *lp = l;
3376 return 0;
3377}
3378
3379/**
3380 * cgroupstats_build - build and fill cgroupstats
3381 * @stats: cgroupstats to fill information into
3382 * @dentry: A dentry entry belonging to the cgroup for which stats have
3383 * been requested.
3384 *
3385 * Build and fill cgroupstats so that taskstats can export it to user
3386 * space.
3387 */
3388int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
3389{
3390 int ret = -EINVAL;
3391 struct cgroup *cgrp;
3392 struct cgroup_iter it;
3393 struct task_struct *tsk;
3394
3395 /*
3396 * Validate dentry by checking the superblock operations,
3397 * and make sure it's a directory.
3398 */
3399 if (dentry->d_sb->s_op != &cgroup_ops ||
3400 !S_ISDIR(dentry->d_inode->i_mode))
3401 goto err;
3402
3403 ret = 0;
3404 cgrp = dentry->d_fsdata;
3405
3406 cgroup_iter_start(cgrp, &it);
3407 while ((tsk = cgroup_iter_next(cgrp, &it))) {
3408 switch (tsk->state) {
3409 case TASK_RUNNING:
3410 stats->nr_running++;
3411 break;
3412 case TASK_INTERRUPTIBLE:
3413 stats->nr_sleeping++;
3414 break;
3415 case TASK_UNINTERRUPTIBLE:
3416 stats->nr_uninterruptible++;
3417 break;
3418 case TASK_STOPPED:
3419 stats->nr_stopped++;
3420 break;
3421 default:
3422 if (delayacct_is_task_waiting_on_io(tsk))
3423 stats->nr_io_wait++;
3424 break;
3425 }
3426 }
3427 cgroup_iter_end(cgrp, &it);
3428
3429err:
3430 return ret;
3431}
3432
3433
3434/*
3435 * seq_file methods for the tasks/procs files. The seq_file position is the
3436 * next pid to display; the seq_file iterator is a pointer to the pid
3437 * in the cgroup->l->list array.
3438 */
3439
3440static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3441{
3442 /*
3443 * Initially we receive a position value that corresponds to
3444 * one more than the last pid shown (or 0 on the first call or
3445 * after a seek to the start). Use a binary-search to find the
3446 * next pid to display, if any
3447 */
3448 struct cgroup_pidlist *l = s->private;
3449 int index = 0, pid = *pos;
3450 int *iter;
3451
3452 down_read(&l->mutex);
3453 if (pid) {
3454 int end = l->length;
3455
3456 while (index < end) {
3457 int mid = (index + end) / 2;
3458 if (l->list[mid] == pid) {
3459 index = mid;
3460 break;
3461 } else if (l->list[mid] <= pid)
3462 index = mid + 1;
3463 else
3464 end = mid;
3465 }
3466 }
3467 /* If we're off the end of the array, we're done */
3468 if (index >= l->length)
3469 return NULL;
3470 /* Update the abstract position to be the actual pid that we found */
3471 iter = l->list + index;
3472 *pos = *iter;
3473 return iter;
3474}
3475
3476static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3477{
3478 struct cgroup_pidlist *l = s->private;
3479 up_read(&l->mutex);
3480}
3481
3482static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3483{
3484 struct cgroup_pidlist *l = s->private;
3485 pid_t *p = v;
3486 pid_t *end = l->list + l->length;
3487 /*
3488 * Advance to the next pid in the array. If this goes off the
3489 * end, we're done
3490 */
3491 p++;
3492 if (p >= end) {
3493 return NULL;
3494 } else {
3495 *pos = *p;
3496 return p;
3497 }
3498}
3499
3500static int cgroup_pidlist_show(struct seq_file *s, void *v)
3501{
3502 return seq_printf(s, "%d\n", *(int *)v);
3503}
3504
3505/*
3506 * seq_operations functions for iterating on pidlists through seq_file -
3507 * independent of whether it's tasks or procs
3508 */
3509static const struct seq_operations cgroup_pidlist_seq_operations = {
3510 .start = cgroup_pidlist_start,
3511 .stop = cgroup_pidlist_stop,
3512 .next = cgroup_pidlist_next,
3513 .show = cgroup_pidlist_show,
3514};
3515
3516static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3517{
3518 /*
3519 * the case where we're the last user of this particular pidlist will
3520 * have us remove it from the cgroup's list, which entails taking the
3521 * mutex. since in pidlist_find the pidlist->lock depends on cgroup->
3522 * pidlist_mutex, we have to take pidlist_mutex first.
3523 */
3524 mutex_lock(&l->owner->pidlist_mutex);
3525 down_write(&l->mutex);
3526 BUG_ON(!l->use_count);
3527 if (!--l->use_count) {
3528 /* we're the last user if refcount is 0; remove and free */
3529 list_del(&l->links);
3530 mutex_unlock(&l->owner->pidlist_mutex);
3531 pidlist_free(l->list);
3532 put_pid_ns(l->key.ns);
3533 up_write(&l->mutex);
3534 kfree(l);
3535 return;
3536 }
3537 mutex_unlock(&l->owner->pidlist_mutex);
3538 up_write(&l->mutex);
3539}
3540
3541static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3542{
3543 struct cgroup_pidlist *l;
3544 if (!(file->f_mode & FMODE_READ))
3545 return 0;
3546 /*
3547 * the seq_file will only be initialized if the file was opened for
3548 * reading; hence we check if it's not null only in that case.
3549 */
3550 l = ((struct seq_file *)file->private_data)->private;
3551 cgroup_release_pid_array(l);
3552 return seq_release(inode, file);
3553}
3554
3555static const struct file_operations cgroup_pidlist_operations = {
3556 .read = seq_read,
3557 .llseek = seq_lseek,
3558 .write = cgroup_file_write,
3559 .release = cgroup_pidlist_release,
3560};
3561
3562/*
3563 * The following functions handle opens on a file that displays a pidlist
3564 * (tasks or procs). Prepare an array of the process/thread IDs of whoever's
3565 * in the cgroup.
3566 */
3567/* helper function for the two below it */
3568static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3569{
3570 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3571 struct cgroup_pidlist *l;
3572 int retval;
3573
3574 /* Nothing to do for write-only files */
3575 if (!(file->f_mode & FMODE_READ))
3576 return 0;
3577
3578 /* have the array populated */
3579 retval = pidlist_array_load(cgrp, type, &l);
3580 if (retval)
3581 return retval;
3582 /* configure file information */
3583 file->f_op = &cgroup_pidlist_operations;
3584
3585 retval = seq_open(file, &cgroup_pidlist_seq_operations);
3586 if (retval) {
3587 cgroup_release_pid_array(l);
3588 return retval;
3589 }
3590 ((struct seq_file *)file->private_data)->private = l;
3591 return 0;
3592}
3593static int cgroup_tasks_open(struct inode *unused, struct file *file)
3594{
3595 return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3596}
3597static int cgroup_procs_open(struct inode *unused, struct file *file)
3598{
3599 return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3600}
3601
3602static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3603 struct cftype *cft)
3604{
3605 return notify_on_release(cgrp);
3606}
3607
3608static int cgroup_write_notify_on_release(struct cgroup *cgrp,
3609 struct cftype *cft,
3610 u64 val)
3611{
3612 clear_bit(CGRP_RELEASABLE, &cgrp->flags);
3613 if (val)
3614 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3615 else
3616 clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3617 return 0;
3618}
3619
3620/*
3621 * Unregister event and free resources.
3622 *
3623 * Gets called from workqueue.
3624 */
3625static void cgroup_event_remove(struct work_struct *work)
3626{
3627 struct cgroup_event *event = container_of(work, struct cgroup_event,
3628 remove);
3629 struct cgroup *cgrp = event->cgrp;
3630
3631 event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3632
3633 eventfd_ctx_put(event->eventfd);
3634 kfree(event);
3635 dput(cgrp->dentry);
3636}
3637
3638/*
3639 * Gets called on POLLHUP on eventfd when user closes it.
3640 *
3641 * Called with wqh->lock held and interrupts disabled.
3642 */
3643static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
3644 int sync, void *key)
3645{
3646 struct cgroup_event *event = container_of(wait,
3647 struct cgroup_event, wait);
3648 struct cgroup *cgrp = event->cgrp;
3649 unsigned long flags = (unsigned long)key;
3650
3651 if (flags & POLLHUP) {
3652 __remove_wait_queue(event->wqh, &event->wait);
3653 spin_lock(&cgrp->event_list_lock);
3654 list_del(&event->list);
3655 spin_unlock(&cgrp->event_list_lock);
3656 /*
3657 * We are in atomic context, but cgroup_event_remove() may
3658 * sleep, so we have to call it in workqueue.
3659 */
3660 schedule_work(&event->remove);
3661 }
3662
3663 return 0;
3664}
3665
3666static void cgroup_event_ptable_queue_proc(struct file *file,
3667 wait_queue_head_t *wqh, poll_table *pt)
3668{
3669 struct cgroup_event *event = container_of(pt,
3670 struct cgroup_event, pt);
3671
3672 event->wqh = wqh;
3673 add_wait_queue(wqh, &event->wait);
3674}
3675
3676/*
3677 * Parse input and register new cgroup event handler.
3678 *
3679 * Input must be in format '<event_fd> <control_fd> <args>'.
3680 * Interpretation of args is defined by control file implementation.
3681 */
3682static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
3683 const char *buffer)
3684{
3685 struct cgroup_event *event = NULL;
3686 unsigned int efd, cfd;
3687 struct file *efile = NULL;
3688 struct file *cfile = NULL;
3689 char *endp;
3690 int ret;
3691
3692 efd = simple_strtoul(buffer, &endp, 10);
3693 if (*endp != ' ')
3694 return -EINVAL;
3695 buffer = endp + 1;
3696
3697 cfd = simple_strtoul(buffer, &endp, 10);
3698 if ((*endp != ' ') && (*endp != '\0'))
3699 return -EINVAL;
3700 buffer = endp + 1;
3701
3702 event = kzalloc(sizeof(*event), GFP_KERNEL);
3703 if (!event)
3704 return -ENOMEM;
3705 event->cgrp = cgrp;
3706 INIT_LIST_HEAD(&event->list);
3707 init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
3708 init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
3709 INIT_WORK(&event->remove, cgroup_event_remove);
3710
3711 efile = eventfd_fget(efd);
3712 if (IS_ERR(efile)) {
3713 ret = PTR_ERR(efile);
3714 goto fail;
3715 }
3716
3717 event->eventfd = eventfd_ctx_fileget(efile);
3718 if (IS_ERR(event->eventfd)) {
3719 ret = PTR_ERR(event->eventfd);
3720 goto fail;
3721 }
3722
3723 cfile = fget(cfd);
3724 if (!cfile) {
3725 ret = -EBADF;
3726 goto fail;
3727 }
3728
3729 /* the process need read permission on control file */
3730 /* AV: shouldn't we check that it's been opened for read instead? */
3731 ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3732 if (ret < 0)
3733 goto fail;
3734
3735 event->cft = __file_cft(cfile);
3736 if (IS_ERR(event->cft)) {
3737 ret = PTR_ERR(event->cft);
3738 goto fail;
3739 }
3740
3741 if (!event->cft->register_event || !event->cft->unregister_event) {
3742 ret = -EINVAL;
3743 goto fail;
3744 }
3745
3746 ret = event->cft->register_event(cgrp, event->cft,
3747 event->eventfd, buffer);
3748 if (ret)
3749 goto fail;
3750
3751 if (efile->f_op->poll(efile, &event->pt) & POLLHUP) {
3752 event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3753 ret = 0;
3754 goto fail;
3755 }
3756
3757 /*
3758 * Events should be removed after rmdir of cgroup directory, but before
3759 * destroying subsystem state objects. Let's take reference to cgroup
3760 * directory dentry to do that.
3761 */
3762 dget(cgrp->dentry);
3763
3764 spin_lock(&cgrp->event_list_lock);
3765 list_add(&event->list, &cgrp->event_list);
3766 spin_unlock(&cgrp->event_list_lock);
3767
3768 fput(cfile);
3769 fput(efile);
3770
3771 return 0;
3772
3773fail:
3774 if (cfile)
3775 fput(cfile);
3776
3777 if (event && event->eventfd && !IS_ERR(event->eventfd))
3778 eventfd_ctx_put(event->eventfd);
3779
3780 if (!IS_ERR_OR_NULL(efile))
3781 fput(efile);
3782
3783 kfree(event);
3784
3785 return ret;
3786}
3787
3788static u64 cgroup_clone_children_read(struct cgroup *cgrp,
3789 struct cftype *cft)
3790{
3791 return clone_children(cgrp);
3792}
3793
3794static int cgroup_clone_children_write(struct cgroup *cgrp,
3795 struct cftype *cft,
3796 u64 val)
3797{
3798 if (val)
3799 set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3800 else
3801 clear_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3802 return 0;
3803}
3804
3805/*
3806 * for the common functions, 'private' gives the type of file
3807 */
3808/* for hysterical raisins, we can't put this on the older files */
3809#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3810static struct cftype files[] = {
3811 {
3812 .name = "tasks",
3813 .open = cgroup_tasks_open,
3814 .write_u64 = cgroup_tasks_write,
3815 .release = cgroup_pidlist_release,
3816 .mode = S_IRUGO | S_IWUSR,
3817 },
3818 {
3819 .name = CGROUP_FILE_GENERIC_PREFIX "procs",
3820 .open = cgroup_procs_open,
3821 .write_u64 = cgroup_procs_write,
3822 .release = cgroup_pidlist_release,
3823 .mode = S_IRUGO | S_IWUSR,
3824 },
3825 {
3826 .name = "notify_on_release",
3827 .read_u64 = cgroup_read_notify_on_release,
3828 .write_u64 = cgroup_write_notify_on_release,
3829 },
3830 {
3831 .name = CGROUP_FILE_GENERIC_PREFIX "event_control",
3832 .write_string = cgroup_write_event_control,
3833 .mode = S_IWUGO,
3834 },
3835 {
3836 .name = "cgroup.clone_children",
3837 .read_u64 = cgroup_clone_children_read,
3838 .write_u64 = cgroup_clone_children_write,
3839 },
3840 {
3841 .name = "release_agent",
3842 .flags = CFTYPE_ONLY_ON_ROOT,
3843 .read_seq_string = cgroup_release_agent_show,
3844 .write_string = cgroup_release_agent_write,
3845 .max_write_len = PATH_MAX,
3846 },
3847 { } /* terminate */
3848};
3849
3850static int cgroup_populate_dir(struct cgroup *cgrp)
3851{
3852 int err;
3853 struct cgroup_subsys *ss;
3854
3855 err = cgroup_addrm_files(cgrp, NULL, files, true);
3856 if (err < 0)
3857 return err;
3858
3859 /* process cftsets of each subsystem */
3860 for_each_subsys(cgrp->root, ss) {
3861 struct cftype_set *set;
3862
3863 list_for_each_entry(set, &ss->cftsets, node)
3864 cgroup_addrm_files(cgrp, ss, set->cfts, true);
3865 }
3866
3867 /* This cgroup is ready now */
3868 for_each_subsys(cgrp->root, ss) {
3869 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
3870 /*
3871 * Update id->css pointer and make this css visible from
3872 * CSS ID functions. This pointer will be dereferened
3873 * from RCU-read-side without locks.
3874 */
3875 if (css->id)
3876 rcu_assign_pointer(css->id->css, css);
3877 }
3878
3879 return 0;
3880}
3881
3882static void css_dput_fn(struct work_struct *work)
3883{
3884 struct cgroup_subsys_state *css =
3885 container_of(work, struct cgroup_subsys_state, dput_work);
3886 struct dentry *dentry = css->cgroup->dentry;
3887 struct super_block *sb = dentry->d_sb;
3888
3889 atomic_inc(&sb->s_active);
3890 dput(dentry);
3891 deactivate_super(sb);
3892}
3893
3894static void init_cgroup_css(struct cgroup_subsys_state *css,
3895 struct cgroup_subsys *ss,
3896 struct cgroup *cgrp)
3897{
3898 css->cgroup = cgrp;
3899 atomic_set(&css->refcnt, 1);
3900 css->flags = 0;
3901 css->id = NULL;
3902 if (cgrp == dummytop)
3903 set_bit(CSS_ROOT, &css->flags);
3904 BUG_ON(cgrp->subsys[ss->subsys_id]);
3905 cgrp->subsys[ss->subsys_id] = css;
3906
3907 /*
3908 * If !clear_css_refs, css holds an extra ref to @cgrp->dentry
3909 * which is put on the last css_put(). dput() requires process
3910 * context, which css_put() may be called without. @css->dput_work
3911 * will be used to invoke dput() asynchronously from css_put().
3912 */
3913 INIT_WORK(&css->dput_work, css_dput_fn);
3914 if (ss->__DEPRECATED_clear_css_refs)
3915 set_bit(CSS_CLEAR_CSS_REFS, &css->flags);
3916}
3917
3918static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
3919{
3920 /* We need to take each hierarchy_mutex in a consistent order */
3921 int i;
3922
3923 /*
3924 * No worry about a race with rebind_subsystems that might mess up the
3925 * locking order, since both parties are under cgroup_mutex.
3926 */
3927 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3928 struct cgroup_subsys *ss = subsys[i];
3929 if (ss == NULL)
3930 continue;
3931 if (ss->root == root)
3932 mutex_lock(&ss->hierarchy_mutex);
3933 }
3934}
3935
3936static void cgroup_unlock_hierarchy(struct cgroupfs_root *root)
3937{
3938 int i;
3939
3940 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3941 struct cgroup_subsys *ss = subsys[i];
3942 if (ss == NULL)
3943 continue;
3944 if (ss->root == root)
3945 mutex_unlock(&ss->hierarchy_mutex);
3946 }
3947}
3948
3949/*
3950 * cgroup_create - create a cgroup
3951 * @parent: cgroup that will be parent of the new cgroup
3952 * @dentry: dentry of the new cgroup
3953 * @mode: mode to set on new inode
3954 *
3955 * Must be called with the mutex on the parent inode held
3956 */
3957static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
3958 umode_t mode)
3959{
3960 struct cgroup *cgrp;
3961 struct cgroupfs_root *root = parent->root;
3962 int err = 0;
3963 struct cgroup_subsys *ss;
3964 struct super_block *sb = root->sb;
3965
3966 cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
3967 if (!cgrp)
3968 return -ENOMEM;
3969
3970 /* Grab a reference on the superblock so the hierarchy doesn't
3971 * get deleted on unmount if there are child cgroups. This
3972 * can be done outside cgroup_mutex, since the sb can't
3973 * disappear while someone has an open control file on the
3974 * fs */
3975 atomic_inc(&sb->s_active);
3976
3977 mutex_lock(&cgroup_mutex);
3978
3979 init_cgroup_housekeeping(cgrp);
3980
3981 cgrp->parent = parent;
3982 cgrp->root = parent->root;
3983 cgrp->top_cgroup = parent->top_cgroup;
3984
3985 if (notify_on_release(parent))
3986 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3987
3988 if (clone_children(parent))
3989 set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3990
3991 for_each_subsys(root, ss) {
3992 struct cgroup_subsys_state *css = ss->create(cgrp);
3993
3994 if (IS_ERR(css)) {
3995 err = PTR_ERR(css);
3996 goto err_destroy;
3997 }
3998 init_cgroup_css(css, ss, cgrp);
3999 if (ss->use_id) {
4000 err = alloc_css_id(ss, parent, cgrp);
4001 if (err)
4002 goto err_destroy;
4003 }
4004 /* At error, ->destroy() callback has to free assigned ID. */
4005 if (clone_children(parent) && ss->post_clone)
4006 ss->post_clone(cgrp);
4007 }
4008
4009 cgroup_lock_hierarchy(root);
4010 list_add(&cgrp->sibling, &cgrp->parent->children);
4011 cgroup_unlock_hierarchy(root);
4012 root->number_of_cgroups++;
4013
4014 err = cgroup_create_dir(cgrp, dentry, mode);
4015 if (err < 0)
4016 goto err_remove;
4017
4018 /* If !clear_css_refs, each css holds a ref to the cgroup's dentry */
4019 for_each_subsys(root, ss)
4020 if (!ss->__DEPRECATED_clear_css_refs)
4021 dget(dentry);
4022
4023 /* The cgroup directory was pre-locked for us */
4024 BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
4025
4026 list_add_tail(&cgrp->allcg_node, &root->allcg_list);
4027
4028 err = cgroup_populate_dir(cgrp);
4029 /* If err < 0, we have a half-filled directory - oh well ;) */
4030
4031 mutex_unlock(&cgroup_mutex);
4032 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
4033
4034 return 0;
4035
4036 err_remove:
4037
4038 cgroup_lock_hierarchy(root);
4039 list_del(&cgrp->sibling);
4040 cgroup_unlock_hierarchy(root);
4041 root->number_of_cgroups--;
4042
4043 err_destroy:
4044
4045 for_each_subsys(root, ss) {
4046 if (cgrp->subsys[ss->subsys_id])
4047 ss->destroy(cgrp);
4048 }
4049
4050 mutex_unlock(&cgroup_mutex);
4051
4052 /* Release the reference count that we took on the superblock */
4053 deactivate_super(sb);
4054
4055 kfree(cgrp);
4056 return err;
4057}
4058
4059static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
4060{
4061 struct cgroup *c_parent = dentry->d_parent->d_fsdata;
4062
4063 /* the vfs holds inode->i_mutex already */
4064 return cgroup_create(c_parent, dentry, mode | S_IFDIR);
4065}
4066
4067/*
4068 * Check the reference count on each subsystem. Since we already
4069 * established that there are no tasks in the cgroup, if the css refcount
4070 * is also 1, then there should be no outstanding references, so the
4071 * subsystem is safe to destroy. We scan across all subsystems rather than
4072 * using the per-hierarchy linked list of mounted subsystems since we can
4073 * be called via check_for_release() with no synchronization other than
4074 * RCU, and the subsystem linked list isn't RCU-safe.
4075 */
4076static int cgroup_has_css_refs(struct cgroup *cgrp)
4077{
4078 int i;
4079
4080 /*
4081 * We won't need to lock the subsys array, because the subsystems
4082 * we're concerned about aren't going anywhere since our cgroup root
4083 * has a reference on them.
4084 */
4085 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4086 struct cgroup_subsys *ss = subsys[i];
4087 struct cgroup_subsys_state *css;
4088
4089 /* Skip subsystems not present or not in this hierarchy */
4090 if (ss == NULL || ss->root != cgrp->root)
4091 continue;
4092
4093 css = cgrp->subsys[ss->subsys_id];
4094 /*
4095 * When called from check_for_release() it's possible
4096 * that by this point the cgroup has been removed
4097 * and the css deleted. But a false-positive doesn't
4098 * matter, since it can only happen if the cgroup
4099 * has been deleted and hence no longer needs the
4100 * release agent to be called anyway.
4101 */
4102 if (css && css_refcnt(css) > 1)
4103 return 1;
4104 }
4105 return 0;
4106}
4107
4108/*
4109 * Atomically mark all (or else none) of the cgroup's CSS objects as
4110 * CSS_REMOVED. Return true on success, or false if the cgroup has
4111 * busy subsystems. Call with cgroup_mutex held
4112 *
4113 * Depending on whether a subsys has __DEPRECATED_clear_css_refs set or
4114 * not, cgroup removal behaves differently.
4115 *
4116 * If clear is set, css refcnt for the subsystem should be zero before
4117 * cgroup removal can be committed. This is implemented by
4118 * CGRP_WAIT_ON_RMDIR and retry logic around ->pre_destroy(), which may be
4119 * called multiple times until all css refcnts reach zero and is allowed to
4120 * veto removal on any invocation. This behavior is deprecated and will be
4121 * removed as soon as the existing user (memcg) is updated.
4122 *
4123 * If clear is not set, each css holds an extra reference to the cgroup's
4124 * dentry and cgroup removal proceeds regardless of css refs.
4125 * ->pre_destroy() will be called at least once and is not allowed to fail.
4126 * On the last put of each css, whenever that may be, the extra dentry ref
4127 * is put so that dentry destruction happens only after all css's are
4128 * released.
4129 */
4130static int cgroup_clear_css_refs(struct cgroup *cgrp)
4131{
4132 struct cgroup_subsys *ss;
4133 unsigned long flags;
4134 bool failed = false;
4135
4136 local_irq_save(flags);
4137
4138 /*
4139 * Block new css_tryget() by deactivating refcnt. If all refcnts
4140 * for subsystems w/ clear_css_refs set were 1 at the moment of
4141 * deactivation, we succeeded.
4142 */
4143 for_each_subsys(cgrp->root, ss) {
4144 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4145
4146 WARN_ON(atomic_read(&css->refcnt) < 0);
4147 atomic_add(CSS_DEACT_BIAS, &css->refcnt);
4148
4149 if (ss->__DEPRECATED_clear_css_refs)
4150 failed |= css_refcnt(css) != 1;
4151 }
4152
4153 /*
4154 * If succeeded, set REMOVED and put all the base refs; otherwise,
4155 * restore refcnts to positive values. Either way, all in-progress
4156 * css_tryget() will be released.
4157 */
4158 for_each_subsys(cgrp->root, ss) {
4159 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4160
4161 if (!failed) {
4162 set_bit(CSS_REMOVED, &css->flags);
4163 css_put(css);
4164 } else {
4165 atomic_sub(CSS_DEACT_BIAS, &css->refcnt);
4166 }
4167 }
4168
4169 local_irq_restore(flags);
4170 return !failed;
4171}
4172
4173static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
4174{
4175 struct cgroup *cgrp = dentry->d_fsdata;
4176 struct dentry *d;
4177 struct cgroup *parent;
4178 DEFINE_WAIT(wait);
4179 struct cgroup_event *event, *tmp;
4180 int ret;
4181
4182 /* the vfs holds both inode->i_mutex already */
4183again:
4184 mutex_lock(&cgroup_mutex);
4185 if (atomic_read(&cgrp->count) != 0) {
4186 mutex_unlock(&cgroup_mutex);
4187 return -EBUSY;
4188 }
4189 if (!list_empty(&cgrp->children)) {
4190 mutex_unlock(&cgroup_mutex);
4191 return -EBUSY;
4192 }
4193 mutex_unlock(&cgroup_mutex);
4194
4195 /*
4196 * In general, subsystem has no css->refcnt after pre_destroy(). But
4197 * in racy cases, subsystem may have to get css->refcnt after
4198 * pre_destroy() and it makes rmdir return with -EBUSY. This sometimes
4199 * make rmdir return -EBUSY too often. To avoid that, we use waitqueue
4200 * for cgroup's rmdir. CGRP_WAIT_ON_RMDIR is for synchronizing rmdir
4201 * and subsystem's reference count handling. Please see css_get/put
4202 * and css_tryget() and cgroup_wakeup_rmdir_waiter() implementation.
4203 */
4204 set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4205
4206 /*
4207 * Call pre_destroy handlers of subsys. Notify subsystems
4208 * that rmdir() request comes.
4209 */
4210 ret = cgroup_call_pre_destroy(cgrp);
4211 if (ret) {
4212 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4213 return ret;
4214 }
4215
4216 mutex_lock(&cgroup_mutex);
4217 parent = cgrp->parent;
4218 if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
4219 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4220 mutex_unlock(&cgroup_mutex);
4221 return -EBUSY;
4222 }
4223 prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
4224 if (!cgroup_clear_css_refs(cgrp)) {
4225 mutex_unlock(&cgroup_mutex);
4226 /*
4227 * Because someone may call cgroup_wakeup_rmdir_waiter() before
4228 * prepare_to_wait(), we need to check this flag.
4229 */
4230 if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))
4231 schedule();
4232 finish_wait(&cgroup_rmdir_waitq, &wait);
4233 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4234 if (signal_pending(current))
4235 return -EINTR;
4236 goto again;
4237 }
4238 /* NO css_tryget() can success after here. */
4239 finish_wait(&cgroup_rmdir_waitq, &wait);
4240 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4241
4242 raw_spin_lock(&release_list_lock);
4243 set_bit(CGRP_REMOVED, &cgrp->flags);
4244 if (!list_empty(&cgrp->release_list))
4245 list_del_init(&cgrp->release_list);
4246 raw_spin_unlock(&release_list_lock);
4247
4248 cgroup_lock_hierarchy(cgrp->root);
4249 /* delete this cgroup from parent->children */
4250 list_del_init(&cgrp->sibling);
4251 cgroup_unlock_hierarchy(cgrp->root);
4252
4253 list_del_init(&cgrp->allcg_node);
4254
4255 d = dget(cgrp->dentry);
4256
4257 cgroup_d_remove_dir(d);
4258 dput(d);
4259
4260 set_bit(CGRP_RELEASABLE, &parent->flags);
4261 check_for_release(parent);
4262
4263 /*
4264 * Unregister events and notify userspace.
4265 * Notify userspace about cgroup removing only after rmdir of cgroup
4266 * directory to avoid race between userspace and kernelspace
4267 */
4268 spin_lock(&cgrp->event_list_lock);
4269 list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
4270 list_del(&event->list);
4271 remove_wait_queue(event->wqh, &event->wait);
4272 eventfd_signal(event->eventfd, 1);
4273 schedule_work(&event->remove);
4274 }
4275 spin_unlock(&cgrp->event_list_lock);
4276
4277 mutex_unlock(&cgroup_mutex);
4278 return 0;
4279}
4280
4281static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
4282{
4283 INIT_LIST_HEAD(&ss->cftsets);
4284
4285 /*
4286 * base_cftset is embedded in subsys itself, no need to worry about
4287 * deregistration.
4288 */
4289 if (ss->base_cftypes) {
4290 ss->base_cftset.cfts = ss->base_cftypes;
4291 list_add_tail(&ss->base_cftset.node, &ss->cftsets);
4292 }
4293}
4294
4295static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4296{
4297 struct cgroup_subsys_state *css;
4298
4299 printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4300
4301 /* init base cftset */
4302 cgroup_init_cftsets(ss);
4303
4304 /* Create the top cgroup state for this subsystem */
4305 list_add(&ss->sibling, &rootnode.subsys_list);
4306 ss->root = &rootnode;
4307 css = ss->create(dummytop);
4308 /* We don't handle early failures gracefully */
4309 BUG_ON(IS_ERR(css));
4310 init_cgroup_css(css, ss, dummytop);
4311
4312 /* Update the init_css_set to contain a subsys
4313 * pointer to this state - since the subsystem is
4314 * newly registered, all tasks and hence the
4315 * init_css_set is in the subsystem's top cgroup. */
4316 init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
4317
4318 need_forkexit_callback |= ss->fork || ss->exit;
4319
4320 /* At system boot, before all subsystems have been
4321 * registered, no tasks have been forked, so we don't
4322 * need to invoke fork callbacks here. */
4323 BUG_ON(!list_empty(&init_task.tasks));
4324
4325 mutex_init(&ss->hierarchy_mutex);
4326 lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
4327 ss->active = 1;
4328
4329 /* this function shouldn't be used with modular subsystems, since they
4330 * need to register a subsys_id, among other things */
4331 BUG_ON(ss->module);
4332}
4333
4334/**
4335 * cgroup_load_subsys: load and register a modular subsystem at runtime
4336 * @ss: the subsystem to load
4337 *
4338 * This function should be called in a modular subsystem's initcall. If the
4339 * subsystem is built as a module, it will be assigned a new subsys_id and set
4340 * up for use. If the subsystem is built-in anyway, work is delegated to the
4341 * simpler cgroup_init_subsys.
4342 */
4343int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
4344{
4345 int i;
4346 struct cgroup_subsys_state *css;
4347
4348 /* check name and function validity */
4349 if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
4350 ss->create == NULL || ss->destroy == NULL)
4351 return -EINVAL;
4352
4353 /*
4354 * we don't support callbacks in modular subsystems. this check is
4355 * before the ss->module check for consistency; a subsystem that could
4356 * be a module should still have no callbacks even if the user isn't
4357 * compiling it as one.
4358 */
4359 if (ss->fork || ss->exit)
4360 return -EINVAL;
4361
4362 /*
4363 * an optionally modular subsystem is built-in: we want to do nothing,
4364 * since cgroup_init_subsys will have already taken care of it.
4365 */
4366 if (ss->module == NULL) {
4367 /* a few sanity checks */
4368 BUG_ON(ss->subsys_id >= CGROUP_BUILTIN_SUBSYS_COUNT);
4369 BUG_ON(subsys[ss->subsys_id] != ss);
4370 return 0;
4371 }
4372
4373 /* init base cftset */
4374 cgroup_init_cftsets(ss);
4375
4376 /*
4377 * need to register a subsys id before anything else - for example,
4378 * init_cgroup_css needs it.
4379 */
4380 mutex_lock(&cgroup_mutex);
4381 /* find the first empty slot in the array */
4382 for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
4383 if (subsys[i] == NULL)
4384 break;
4385 }
4386 if (i == CGROUP_SUBSYS_COUNT) {
4387 /* maximum number of subsystems already registered! */
4388 mutex_unlock(&cgroup_mutex);
4389 return -EBUSY;
4390 }
4391 /* assign ourselves the subsys_id */
4392 ss->subsys_id = i;
4393 subsys[i] = ss;
4394
4395 /*
4396 * no ss->create seems to need anything important in the ss struct, so
4397 * this can happen first (i.e. before the rootnode attachment).
4398 */
4399 css = ss->create(dummytop);
4400 if (IS_ERR(css)) {
4401 /* failure case - need to deassign the subsys[] slot. */
4402 subsys[i] = NULL;
4403 mutex_unlock(&cgroup_mutex);
4404 return PTR_ERR(css);
4405 }
4406
4407 list_add(&ss->sibling, &rootnode.subsys_list);
4408 ss->root = &rootnode;
4409
4410 /* our new subsystem will be attached to the dummy hierarchy. */
4411 init_cgroup_css(css, ss, dummytop);
4412 /* init_idr must be after init_cgroup_css because it sets css->id. */
4413 if (ss->use_id) {
4414 int ret = cgroup_init_idr(ss, css);
4415 if (ret) {
4416 dummytop->subsys[ss->subsys_id] = NULL;
4417 ss->destroy(dummytop);
4418 subsys[i] = NULL;
4419 mutex_unlock(&cgroup_mutex);
4420 return ret;
4421 }
4422 }
4423
4424 /*
4425 * Now we need to entangle the css into the existing css_sets. unlike
4426 * in cgroup_init_subsys, there are now multiple css_sets, so each one
4427 * will need a new pointer to it; done by iterating the css_set_table.
4428 * furthermore, modifying the existing css_sets will corrupt the hash
4429 * table state, so each changed css_set will need its hash recomputed.
4430 * this is all done under the css_set_lock.
4431 */
4432 write_lock(&css_set_lock);
4433 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
4434 struct css_set *cg;
4435 struct hlist_node *node, *tmp;
4436 struct hlist_head *bucket = &css_set_table[i], *new_bucket;
4437
4438 hlist_for_each_entry_safe(cg, node, tmp, bucket, hlist) {
4439 /* skip entries that we already rehashed */
4440 if (cg->subsys[ss->subsys_id])
4441 continue;
4442 /* remove existing entry */
4443 hlist_del(&cg->hlist);
4444 /* set new value */
4445 cg->subsys[ss->subsys_id] = css;
4446 /* recompute hash and restore entry */
4447 new_bucket = css_set_hash(cg->subsys);
4448 hlist_add_head(&cg->hlist, new_bucket);
4449 }
4450 }
4451 write_unlock(&css_set_lock);
4452
4453 mutex_init(&ss->hierarchy_mutex);
4454 lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
4455 ss->active = 1;
4456
4457 /* success! */
4458 mutex_unlock(&cgroup_mutex);
4459 return 0;
4460}
4461EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4462
4463/**
4464 * cgroup_unload_subsys: unload a modular subsystem
4465 * @ss: the subsystem to unload
4466 *
4467 * This function should be called in a modular subsystem's exitcall. When this
4468 * function is invoked, the refcount on the subsystem's module will be 0, so
4469 * the subsystem will not be attached to any hierarchy.
4470 */
4471void cgroup_unload_subsys(struct cgroup_subsys *ss)
4472{
4473 struct cg_cgroup_link *link;
4474 struct hlist_head *hhead;
4475
4476 BUG_ON(ss->module == NULL);
4477
4478 /*
4479 * we shouldn't be called if the subsystem is in use, and the use of
4480 * try_module_get in parse_cgroupfs_options should ensure that it
4481 * doesn't start being used while we're killing it off.
4482 */
4483 BUG_ON(ss->root != &rootnode);
4484
4485 mutex_lock(&cgroup_mutex);
4486 /* deassign the subsys_id */
4487 BUG_ON(ss->subsys_id < CGROUP_BUILTIN_SUBSYS_COUNT);
4488 subsys[ss->subsys_id] = NULL;
4489
4490 /* remove subsystem from rootnode's list of subsystems */
4491 list_del_init(&ss->sibling);
4492
4493 /*
4494 * disentangle the css from all css_sets attached to the dummytop. as
4495 * in loading, we need to pay our respects to the hashtable gods.
4496 */
4497 write_lock(&css_set_lock);
4498 list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {
4499 struct css_set *cg = link->cg;
4500
4501 hlist_del(&cg->hlist);
4502 BUG_ON(!cg->subsys[ss->subsys_id]);
4503 cg->subsys[ss->subsys_id] = NULL;
4504 hhead = css_set_hash(cg->subsys);
4505 hlist_add_head(&cg->hlist, hhead);
4506 }
4507 write_unlock(&css_set_lock);
4508
4509 /*
4510 * remove subsystem's css from the dummytop and free it - need to free
4511 * before marking as null because ss->destroy needs the cgrp->subsys
4512 * pointer to find their state. note that this also takes care of
4513 * freeing the css_id.
4514 */
4515 ss->destroy(dummytop);
4516 dummytop->subsys[ss->subsys_id] = NULL;
4517
4518 mutex_unlock(&cgroup_mutex);
4519}
4520EXPORT_SYMBOL_GPL(cgroup_unload_subsys);
4521
4522/**
4523 * cgroup_init_early - cgroup initialization at system boot
4524 *
4525 * Initialize cgroups at system boot, and initialize any
4526 * subsystems that request early init.
4527 */
4528int __init cgroup_init_early(void)
4529{
4530 int i;
4531 atomic_set(&init_css_set.refcount, 1);
4532 INIT_LIST_HEAD(&init_css_set.cg_links);
4533 INIT_LIST_HEAD(&init_css_set.tasks);
4534 INIT_HLIST_NODE(&init_css_set.hlist);
4535 css_set_count = 1;
4536 init_cgroup_root(&rootnode);
4537 root_count = 1;
4538 init_task.cgroups = &init_css_set;
4539
4540 init_css_set_link.cg = &init_css_set;
4541 init_css_set_link.cgrp = dummytop;
4542 list_add(&init_css_set_link.cgrp_link_list,
4543 &rootnode.top_cgroup.css_sets);
4544 list_add(&init_css_set_link.cg_link_list,
4545 &init_css_set.cg_links);
4546
4547 for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
4548 INIT_HLIST_HEAD(&css_set_table[i]);
4549
4550 /* at bootup time, we don't worry about modular subsystems */
4551 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4552 struct cgroup_subsys *ss = subsys[i];
4553
4554 BUG_ON(!ss->name);
4555 BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4556 BUG_ON(!ss->create);
4557 BUG_ON(!ss->destroy);
4558 if (ss->subsys_id != i) {
4559 printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4560 ss->name, ss->subsys_id);
4561 BUG();
4562 }
4563
4564 if (ss->early_init)
4565 cgroup_init_subsys(ss);
4566 }
4567 return 0;
4568}
4569
4570/**
4571 * cgroup_init - cgroup initialization
4572 *
4573 * Register cgroup filesystem and /proc file, and initialize
4574 * any subsystems that didn't request early init.
4575 */
4576int __init cgroup_init(void)
4577{
4578 int err;
4579 int i;
4580 struct hlist_head *hhead;
4581
4582 err = bdi_init(&cgroup_backing_dev_info);
4583 if (err)
4584 return err;
4585
4586 /* at bootup time, we don't worry about modular subsystems */
4587 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4588 struct cgroup_subsys *ss = subsys[i];
4589 if (!ss->early_init)
4590 cgroup_init_subsys(ss);
4591 if (ss->use_id)
4592 cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4593 }
4594
4595 /* Add init_css_set to the hash table */
4596 hhead = css_set_hash(init_css_set.subsys);
4597 hlist_add_head(&init_css_set.hlist, hhead);
4598 BUG_ON(!init_root_id(&rootnode));
4599
4600 cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
4601 if (!cgroup_kobj) {
4602 err = -ENOMEM;
4603 goto out;
4604 }
4605
4606 err = register_filesystem(&cgroup_fs_type);
4607 if (err < 0) {
4608 kobject_put(cgroup_kobj);
4609 goto out;
4610 }
4611
4612 proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4613
4614out:
4615 if (err)
4616 bdi_destroy(&cgroup_backing_dev_info);
4617
4618 return err;
4619}
4620
4621/*
4622 * proc_cgroup_show()
4623 * - Print task's cgroup paths into seq_file, one line for each hierarchy
4624 * - Used for /proc/<pid>/cgroup.
4625 * - No need to task_lock(tsk) on this tsk->cgroup reference, as it
4626 * doesn't really matter if tsk->cgroup changes after we read it,
4627 * and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4628 * anyway. No need to check that tsk->cgroup != NULL, thanks to
4629 * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
4630 * cgroup to top_cgroup.
4631 */
4632
4633/* TODO: Use a proper seq_file iterator */
4634static int proc_cgroup_show(struct seq_file *m, void *v)
4635{
4636 struct pid *pid;
4637 struct task_struct *tsk;
4638 char *buf;
4639 int retval;
4640 struct cgroupfs_root *root;
4641
4642 retval = -ENOMEM;
4643 buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4644 if (!buf)
4645 goto out;
4646
4647 retval = -ESRCH;
4648 pid = m->private;
4649 tsk = get_pid_task(pid, PIDTYPE_PID);
4650 if (!tsk)
4651 goto out_free;
4652
4653 retval = 0;
4654
4655 mutex_lock(&cgroup_mutex);
4656
4657 for_each_active_root(root) {
4658 struct cgroup_subsys *ss;
4659 struct cgroup *cgrp;
4660 int count = 0;
4661
4662 seq_printf(m, "%d:", root->hierarchy_id);
4663 for_each_subsys(root, ss)
4664 seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4665 if (strlen(root->name))
4666 seq_printf(m, "%sname=%s", count ? "," : "",
4667 root->name);
4668 seq_putc(m, ':');
4669 cgrp = task_cgroup_from_root(tsk, root);
4670 retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4671 if (retval < 0)
4672 goto out_unlock;
4673 seq_puts(m, buf);
4674 seq_putc(m, '\n');
4675 }
4676
4677out_unlock:
4678 mutex_unlock(&cgroup_mutex);
4679 put_task_struct(tsk);
4680out_free:
4681 kfree(buf);
4682out:
4683 return retval;
4684}
4685
4686static int cgroup_open(struct inode *inode, struct file *file)
4687{
4688 struct pid *pid = PROC_I(inode)->pid;
4689 return single_open(file, proc_cgroup_show, pid);
4690}
4691
4692const struct file_operations proc_cgroup_operations = {
4693 .open = cgroup_open,
4694 .read = seq_read,
4695 .llseek = seq_lseek,
4696 .release = single_release,
4697};
4698
4699/* Display information about each subsystem and each hierarchy */
4700static int proc_cgroupstats_show(struct seq_file *m, void *v)
4701{
4702 int i;
4703
4704 seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
4705 /*
4706 * ideally we don't want subsystems moving around while we do this.
4707 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
4708 * subsys/hierarchy state.
4709 */
4710 mutex_lock(&cgroup_mutex);
4711 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4712 struct cgroup_subsys *ss = subsys[i];
4713 if (ss == NULL)
4714 continue;
4715 seq_printf(m, "%s\t%d\t%d\t%d\n",
4716 ss->name, ss->root->hierarchy_id,
4717 ss->root->number_of_cgroups, !ss->disabled);
4718 }
4719 mutex_unlock(&cgroup_mutex);
4720 return 0;
4721}
4722
4723static int cgroupstats_open(struct inode *inode, struct file *file)
4724{
4725 return single_open(file, proc_cgroupstats_show, NULL);
4726}
4727
4728static const struct file_operations proc_cgroupstats_operations = {
4729 .open = cgroupstats_open,
4730 .read = seq_read,
4731 .llseek = seq_lseek,
4732 .release = single_release,
4733};
4734
4735/**
4736 * cgroup_fork - attach newly forked task to its parents cgroup.
4737 * @child: pointer to task_struct of forking parent process.
4738 *
4739 * Description: A task inherits its parent's cgroup at fork().
4740 *
4741 * A pointer to the shared css_set was automatically copied in
4742 * fork.c by dup_task_struct(). However, we ignore that copy, since
4743 * it was not made under the protection of RCU, cgroup_mutex or
4744 * threadgroup_change_begin(), so it might no longer be a valid
4745 * cgroup pointer. cgroup_attach_task() might have already changed
4746 * current->cgroups, allowing the previously referenced cgroup
4747 * group to be removed and freed.
4748 *
4749 * Outside the pointer validity we also need to process the css_set
4750 * inheritance between threadgoup_change_begin() and
4751 * threadgoup_change_end(), this way there is no leak in any process
4752 * wide migration performed by cgroup_attach_proc() that could otherwise
4753 * miss a thread because it is too early or too late in the fork stage.
4754 *
4755 * At the point that cgroup_fork() is called, 'current' is the parent
4756 * task, and the passed argument 'child' points to the child task.
4757 */
4758void cgroup_fork(struct task_struct *child)
4759{
4760 /*
4761 * We don't need to task_lock() current because current->cgroups
4762 * can't be changed concurrently here. The parent obviously hasn't
4763 * exited and called cgroup_exit(), and we are synchronized against
4764 * cgroup migration through threadgroup_change_begin().
4765 */
4766 child->cgroups = current->cgroups;
4767 get_css_set(child->cgroups);
4768 INIT_LIST_HEAD(&child->cg_list);
4769}
4770
4771/**
4772 * cgroup_fork_callbacks - run fork callbacks
4773 * @child: the new task
4774 *
4775 * Called on a new task very soon before adding it to the
4776 * tasklist. No need to take any locks since no-one can
4777 * be operating on this task.
4778 */
4779void cgroup_fork_callbacks(struct task_struct *child)
4780{
4781 if (need_forkexit_callback) {
4782 int i;
4783 /*
4784 * forkexit callbacks are only supported for builtin
4785 * subsystems, and the builtin section of the subsys array is
4786 * immutable, so we don't need to lock the subsys array here.
4787 */
4788 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4789 struct cgroup_subsys *ss = subsys[i];
4790 if (ss->fork)
4791 ss->fork(child);
4792 }
4793 }
4794}
4795
4796/**
4797 * cgroup_post_fork - called on a new task after adding it to the task list
4798 * @child: the task in question
4799 *
4800 * Adds the task to the list running through its css_set if necessary.
4801 * Has to be after the task is visible on the task list in case we race
4802 * with the first call to cgroup_iter_start() - to guarantee that the
4803 * new task ends up on its list.
4804 */
4805void cgroup_post_fork(struct task_struct *child)
4806{
4807 /*
4808 * use_task_css_set_links is set to 1 before we walk the tasklist
4809 * under the tasklist_lock and we read it here after we added the child
4810 * to the tasklist under the tasklist_lock as well. If the child wasn't
4811 * yet in the tasklist when we walked through it from
4812 * cgroup_enable_task_cg_lists(), then use_task_css_set_links value
4813 * should be visible now due to the paired locking and barriers implied
4814 * by LOCK/UNLOCK: it is written before the tasklist_lock unlock
4815 * in cgroup_enable_task_cg_lists() and read here after the tasklist_lock
4816 * lock on fork.
4817 */
4818 if (use_task_css_set_links) {
4819 write_lock(&css_set_lock);
4820 if (list_empty(&child->cg_list)) {
4821 /*
4822 * It's safe to use child->cgroups without task_lock()
4823 * here because we are protected through
4824 * threadgroup_change_begin() against concurrent
4825 * css_set change in cgroup_task_migrate(). Also
4826 * the task can't exit at that point until
4827 * wake_up_new_task() is called, so we are protected
4828 * against cgroup_exit() setting child->cgroup to
4829 * init_css_set.
4830 */
4831 list_add(&child->cg_list, &child->cgroups->tasks);
4832 }
4833 write_unlock(&css_set_lock);
4834 }
4835}
4836/**
4837 * cgroup_exit - detach cgroup from exiting task
4838 * @tsk: pointer to task_struct of exiting process
4839 * @run_callback: run exit callbacks?
4840 *
4841 * Description: Detach cgroup from @tsk and release it.
4842 *
4843 * Note that cgroups marked notify_on_release force every task in
4844 * them to take the global cgroup_mutex mutex when exiting.
4845 * This could impact scaling on very large systems. Be reluctant to
4846 * use notify_on_release cgroups where very high task exit scaling
4847 * is required on large systems.
4848 *
4849 * the_top_cgroup_hack:
4850 *
4851 * Set the exiting tasks cgroup to the root cgroup (top_cgroup).
4852 *
4853 * We call cgroup_exit() while the task is still competent to
4854 * handle notify_on_release(), then leave the task attached to the
4855 * root cgroup in each hierarchy for the remainder of its exit.
4856 *
4857 * To do this properly, we would increment the reference count on
4858 * top_cgroup, and near the very end of the kernel/exit.c do_exit()
4859 * code we would add a second cgroup function call, to drop that
4860 * reference. This would just create an unnecessary hot spot on
4861 * the top_cgroup reference count, to no avail.
4862 *
4863 * Normally, holding a reference to a cgroup without bumping its
4864 * count is unsafe. The cgroup could go away, or someone could
4865 * attach us to a different cgroup, decrementing the count on
4866 * the first cgroup that we never incremented. But in this case,
4867 * top_cgroup isn't going away, and either task has PF_EXITING set,
4868 * which wards off any cgroup_attach_task() attempts, or task is a failed
4869 * fork, never visible to cgroup_attach_task.
4870 */
4871void cgroup_exit(struct task_struct *tsk, int run_callbacks)
4872{
4873 struct css_set *cg;
4874 int i;
4875
4876 /*
4877 * Unlink from the css_set task list if necessary.
4878 * Optimistically check cg_list before taking
4879 * css_set_lock
4880 */
4881 if (!list_empty(&tsk->cg_list)) {
4882 write_lock(&css_set_lock);
4883 if (!list_empty(&tsk->cg_list))
4884 list_del_init(&tsk->cg_list);
4885 write_unlock(&css_set_lock);
4886 }
4887
4888 /* Reassign the task to the init_css_set. */
4889 task_lock(tsk);
4890 cg = tsk->cgroups;
4891 tsk->cgroups = &init_css_set;
4892
4893 if (run_callbacks && need_forkexit_callback) {
4894 /*
4895 * modular subsystems can't use callbacks, so no need to lock
4896 * the subsys array
4897 */
4898 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4899 struct cgroup_subsys *ss = subsys[i];
4900 if (ss->exit) {
4901 struct cgroup *old_cgrp =
4902 rcu_dereference_raw(cg->subsys[i])->cgroup;
4903 struct cgroup *cgrp = task_cgroup(tsk, i);
4904 ss->exit(cgrp, old_cgrp, tsk);
4905 }
4906 }
4907 }
4908 task_unlock(tsk);
4909
4910 if (cg)
4911 put_css_set_taskexit(cg);
4912}
4913
4914/**
4915 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
4916 * @cgrp: the cgroup in question
4917 * @task: the task in question
4918 *
4919 * See if @cgrp is a descendant of @task's cgroup in the appropriate
4920 * hierarchy.
4921 *
4922 * If we are sending in dummytop, then presumably we are creating
4923 * the top cgroup in the subsystem.
4924 *
4925 * Called only by the ns (nsproxy) cgroup.
4926 */
4927int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
4928{
4929 int ret;
4930 struct cgroup *target;
4931
4932 if (cgrp == dummytop)
4933 return 1;
4934
4935 target = task_cgroup_from_root(task, cgrp->root);
4936 while (cgrp != target && cgrp!= cgrp->top_cgroup)
4937 cgrp = cgrp->parent;
4938 ret = (cgrp == target);
4939 return ret;
4940}
4941
4942static void check_for_release(struct cgroup *cgrp)
4943{
4944 /* All of these checks rely on RCU to keep the cgroup
4945 * structure alive */
4946 if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
4947 && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
4948 /* Control Group is currently removeable. If it's not
4949 * already queued for a userspace notification, queue
4950 * it now */
4951 int need_schedule_work = 0;
4952 raw_spin_lock(&release_list_lock);
4953 if (!cgroup_is_removed(cgrp) &&
4954 list_empty(&cgrp->release_list)) {
4955 list_add(&cgrp->release_list, &release_list);
4956 need_schedule_work = 1;
4957 }
4958 raw_spin_unlock(&release_list_lock);
4959 if (need_schedule_work)
4960 schedule_work(&release_agent_work);
4961 }
4962}
4963
4964/* Caller must verify that the css is not for root cgroup */
4965bool __css_tryget(struct cgroup_subsys_state *css)
4966{
4967 do {
4968 int v = css_refcnt(css);
4969
4970 if (atomic_cmpxchg(&css->refcnt, v, v + 1) == v)
4971 return true;
4972 cpu_relax();
4973 } while (!test_bit(CSS_REMOVED, &css->flags));
4974
4975 return false;
4976}
4977EXPORT_SYMBOL_GPL(__css_tryget);
4978
4979/* Caller must verify that the css is not for root cgroup */
4980void __css_put(struct cgroup_subsys_state *css)
4981{
4982 struct cgroup *cgrp = css->cgroup;
4983 int v;
4984
4985 rcu_read_lock();
4986 v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));
4987
4988 switch (v) {
4989 case 1:
4990 if (notify_on_release(cgrp)) {
4991 set_bit(CGRP_RELEASABLE, &cgrp->flags);
4992 check_for_release(cgrp);
4993 }
4994 cgroup_wakeup_rmdir_waiter(cgrp);
4995 break;
4996 case 0:
4997 if (!test_bit(CSS_CLEAR_CSS_REFS, &css->flags))
4998 schedule_work(&css->dput_work);
4999 break;
5000 }
5001 rcu_read_unlock();
5002}
5003EXPORT_SYMBOL_GPL(__css_put);
5004
5005/*
5006 * Notify userspace when a cgroup is released, by running the
5007 * configured release agent with the name of the cgroup (path
5008 * relative to the root of cgroup file system) as the argument.
5009 *
5010 * Most likely, this user command will try to rmdir this cgroup.
5011 *
5012 * This races with the possibility that some other task will be
5013 * attached to this cgroup before it is removed, or that some other
5014 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
5015 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
5016 * unused, and this cgroup will be reprieved from its death sentence,
5017 * to continue to serve a useful existence. Next time it's released,
5018 * we will get notified again, if it still has 'notify_on_release' set.
5019 *
5020 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
5021 * means only wait until the task is successfully execve()'d. The
5022 * separate release agent task is forked by call_usermodehelper(),
5023 * then control in this thread returns here, without waiting for the
5024 * release agent task. We don't bother to wait because the caller of
5025 * this routine has no use for the exit status of the release agent
5026 * task, so no sense holding our caller up for that.
5027 */
5028static void cgroup_release_agent(struct work_struct *work)
5029{
5030 BUG_ON(work != &release_agent_work);
5031 mutex_lock(&cgroup_mutex);
5032 raw_spin_lock(&release_list_lock);
5033 while (!list_empty(&release_list)) {
5034 char *argv[3], *envp[3];
5035 int i;
5036 char *pathbuf = NULL, *agentbuf = NULL;
5037 struct cgroup *cgrp = list_entry(release_list.next,
5038 struct cgroup,
5039 release_list);
5040 list_del_init(&cgrp->release_list);
5041 raw_spin_unlock(&release_list_lock);
5042 pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
5043 if (!pathbuf)
5044 goto continue_free;
5045 if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
5046 goto continue_free;
5047 agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
5048 if (!agentbuf)
5049 goto continue_free;
5050
5051 i = 0;
5052 argv[i++] = agentbuf;
5053 argv[i++] = pathbuf;
5054 argv[i] = NULL;
5055
5056 i = 0;
5057 /* minimal command environment */
5058 envp[i++] = "HOME=/";
5059 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
5060 envp[i] = NULL;
5061
5062 /* Drop the lock while we invoke the usermode helper,
5063 * since the exec could involve hitting disk and hence
5064 * be a slow process */
5065 mutex_unlock(&cgroup_mutex);
5066 call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
5067 mutex_lock(&cgroup_mutex);
5068 continue_free:
5069 kfree(pathbuf);
5070 kfree(agentbuf);
5071 raw_spin_lock(&release_list_lock);
5072 }
5073 raw_spin_unlock(&release_list_lock);
5074 mutex_unlock(&cgroup_mutex);
5075}
5076
5077static int __init cgroup_disable(char *str)
5078{
5079 int i;
5080 char *token;
5081
5082 while ((token = strsep(&str, ",")) != NULL) {
5083 if (!*token)
5084 continue;
5085 /*
5086 * cgroup_disable, being at boot time, can't know about module
5087 * subsystems, so we don't worry about them.
5088 */
5089 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
5090 struct cgroup_subsys *ss = subsys[i];
5091
5092 if (!strcmp(token, ss->name)) {
5093 ss->disabled = 1;
5094 printk(KERN_INFO "Disabling %s control group"
5095 " subsystem\n", ss->name);
5096 break;
5097 }
5098 }
5099 }
5100 return 1;
5101}
5102__setup("cgroup_disable=", cgroup_disable);
5103
5104/*
5105 * Functons for CSS ID.
5106 */
5107
5108/*
5109 *To get ID other than 0, this should be called when !cgroup_is_removed().
5110 */
5111unsigned short css_id(struct cgroup_subsys_state *css)
5112{
5113 struct css_id *cssid;
5114
5115 /*
5116 * This css_id() can return correct value when somone has refcnt
5117 * on this or this is under rcu_read_lock(). Once css->id is allocated,
5118 * it's unchanged until freed.
5119 */
5120 cssid = rcu_dereference_check(css->id, css_refcnt(css));
5121
5122 if (cssid)
5123 return cssid->id;
5124 return 0;
5125}
5126EXPORT_SYMBOL_GPL(css_id);
5127
5128unsigned short css_depth(struct cgroup_subsys_state *css)
5129{
5130 struct css_id *cssid;
5131
5132 cssid = rcu_dereference_check(css->id, css_refcnt(css));
5133
5134 if (cssid)
5135 return cssid->depth;
5136 return 0;
5137}
5138EXPORT_SYMBOL_GPL(css_depth);
5139
5140/**
5141 * css_is_ancestor - test "root" css is an ancestor of "child"
5142 * @child: the css to be tested.
5143 * @root: the css supporsed to be an ancestor of the child.
5144 *
5145 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
5146 * this function reads css->id, the caller must hold rcu_read_lock().
5147 * But, considering usual usage, the csses should be valid objects after test.
5148 * Assuming that the caller will do some action to the child if this returns
5149 * returns true, the caller must take "child";s reference count.
5150 * If "child" is valid object and this returns true, "root" is valid, too.
5151 */
5152
5153bool css_is_ancestor(struct cgroup_subsys_state *child,
5154 const struct cgroup_subsys_state *root)
5155{
5156 struct css_id *child_id;
5157 struct css_id *root_id;
5158
5159 child_id = rcu_dereference(child->id);
5160 if (!child_id)
5161 return false;
5162 root_id = rcu_dereference(root->id);
5163 if (!root_id)
5164 return false;
5165 if (child_id->depth < root_id->depth)
5166 return false;
5167 if (child_id->stack[root_id->depth] != root_id->id)
5168 return false;
5169 return true;
5170}
5171
5172void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
5173{
5174 struct css_id *id = css->id;
5175 /* When this is called before css_id initialization, id can be NULL */
5176 if (!id)
5177 return;
5178
5179 BUG_ON(!ss->use_id);
5180
5181 rcu_assign_pointer(id->css, NULL);
5182 rcu_assign_pointer(css->id, NULL);
5183 spin_lock(&ss->id_lock);
5184 idr_remove(&ss->idr, id->id);
5185 spin_unlock(&ss->id_lock);
5186 kfree_rcu(id, rcu_head);
5187}
5188EXPORT_SYMBOL_GPL(free_css_id);
5189
5190/*
5191 * This is called by init or create(). Then, calls to this function are
5192 * always serialized (By cgroup_mutex() at create()).
5193 */
5194
5195static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
5196{
5197 struct css_id *newid;
5198 int myid, error, size;
5199
5200 BUG_ON(!ss->use_id);
5201
5202 size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
5203 newid = kzalloc(size, GFP_KERNEL);
5204 if (!newid)
5205 return ERR_PTR(-ENOMEM);
5206 /* get id */
5207 if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
5208 error = -ENOMEM;
5209 goto err_out;
5210 }
5211 spin_lock(&ss->id_lock);
5212 /* Don't use 0. allocates an ID of 1-65535 */
5213 error = idr_get_new_above(&ss->idr, newid, 1, &myid);
5214 spin_unlock(&ss->id_lock);
5215
5216 /* Returns error when there are no free spaces for new ID.*/
5217 if (error) {
5218 error = -ENOSPC;
5219 goto err_out;
5220 }
5221 if (myid > CSS_ID_MAX)
5222 goto remove_idr;
5223
5224 newid->id = myid;
5225 newid->depth = depth;
5226 return newid;
5227remove_idr:
5228 error = -ENOSPC;
5229 spin_lock(&ss->id_lock);
5230 idr_remove(&ss->idr, myid);
5231 spin_unlock(&ss->id_lock);
5232err_out:
5233 kfree(newid);
5234 return ERR_PTR(error);
5235
5236}
5237
5238static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
5239 struct cgroup_subsys_state *rootcss)
5240{
5241 struct css_id *newid;
5242
5243 spin_lock_init(&ss->id_lock);
5244 idr_init(&ss->idr);
5245
5246 newid = get_new_cssid(ss, 0);
5247 if (IS_ERR(newid))
5248 return PTR_ERR(newid);
5249
5250 newid->stack[0] = newid->id;
5251 newid->css = rootcss;
5252 rootcss->id = newid;
5253 return 0;
5254}
5255
5256static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
5257 struct cgroup *child)
5258{
5259 int subsys_id, i, depth = 0;
5260 struct cgroup_subsys_state *parent_css, *child_css;
5261 struct css_id *child_id, *parent_id;
5262
5263 subsys_id = ss->subsys_id;
5264 parent_css = parent->subsys[subsys_id];
5265 child_css = child->subsys[subsys_id];
5266 parent_id = parent_css->id;
5267 depth = parent_id->depth + 1;
5268
5269 child_id = get_new_cssid(ss, depth);
5270 if (IS_ERR(child_id))
5271 return PTR_ERR(child_id);
5272
5273 for (i = 0; i < depth; i++)
5274 child_id->stack[i] = parent_id->stack[i];
5275 child_id->stack[depth] = child_id->id;
5276 /*
5277 * child_id->css pointer will be set after this cgroup is available
5278 * see cgroup_populate_dir()
5279 */
5280 rcu_assign_pointer(child_css->id, child_id);
5281
5282 return 0;
5283}
5284
5285/**
5286 * css_lookup - lookup css by id
5287 * @ss: cgroup subsys to be looked into.
5288 * @id: the id
5289 *
5290 * Returns pointer to cgroup_subsys_state if there is valid one with id.
5291 * NULL if not. Should be called under rcu_read_lock()
5292 */
5293struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
5294{
5295 struct css_id *cssid = NULL;
5296
5297 BUG_ON(!ss->use_id);
5298 cssid = idr_find(&ss->idr, id);
5299
5300 if (unlikely(!cssid))
5301 return NULL;
5302
5303 return rcu_dereference(cssid->css);
5304}
5305EXPORT_SYMBOL_GPL(css_lookup);
5306
5307/**
5308 * css_get_next - lookup next cgroup under specified hierarchy.
5309 * @ss: pointer to subsystem
5310 * @id: current position of iteration.
5311 * @root: pointer to css. search tree under this.
5312 * @foundid: position of found object.
5313 *
5314 * Search next css under the specified hierarchy of rootid. Calling under
5315 * rcu_read_lock() is necessary. Returns NULL if it reaches the end.
5316 */
5317struct cgroup_subsys_state *
5318css_get_next(struct cgroup_subsys *ss, int id,
5319 struct cgroup_subsys_state *root, int *foundid)
5320{
5321 struct cgroup_subsys_state *ret = NULL;
5322 struct css_id *tmp;
5323 int tmpid;
5324 int rootid = css_id(root);
5325 int depth = css_depth(root);
5326
5327 if (!rootid)
5328 return NULL;
5329
5330 BUG_ON(!ss->use_id);
5331 WARN_ON_ONCE(!rcu_read_lock_held());
5332
5333 /* fill start point for scan */
5334 tmpid = id;
5335 while (1) {
5336 /*
5337 * scan next entry from bitmap(tree), tmpid is updated after
5338 * idr_get_next().
5339 */
5340 tmp = idr_get_next(&ss->idr, &tmpid);
5341 if (!tmp)
5342 break;
5343 if (tmp->depth >= depth && tmp->stack[depth] == rootid) {
5344 ret = rcu_dereference(tmp->css);
5345 if (ret) {
5346 *foundid = tmpid;
5347 break;
5348 }
5349 }
5350 /* continue to scan from next id */
5351 tmpid = tmpid + 1;
5352 }
5353 return ret;
5354}
5355
5356/*
5357 * get corresponding css from file open on cgroupfs directory
5358 */
5359struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
5360{
5361 struct cgroup *cgrp;
5362 struct inode *inode;
5363 struct cgroup_subsys_state *css;
5364
5365 inode = f->f_dentry->d_inode;
5366 /* check in cgroup filesystem dir */
5367 if (inode->i_op != &cgroup_dir_inode_operations)
5368 return ERR_PTR(-EBADF);
5369
5370 if (id < 0 || id >= CGROUP_SUBSYS_COUNT)
5371 return ERR_PTR(-EINVAL);
5372
5373 /* get cgroup */
5374 cgrp = __d_cgrp(f->f_dentry);
5375 css = cgrp->subsys[id];
5376 return css ? css : ERR_PTR(-ENOENT);
5377}
5378
5379#ifdef CONFIG_CGROUP_DEBUG
5380static struct cgroup_subsys_state *debug_create(struct cgroup *cont)
5381{
5382 struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
5383
5384 if (!css)
5385 return ERR_PTR(-ENOMEM);
5386
5387 return css;
5388}
5389
5390static void debug_destroy(struct cgroup *cont)
5391{
5392 kfree(cont->subsys[debug_subsys_id]);
5393}
5394
5395static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
5396{
5397 return atomic_read(&cont->count);
5398}
5399
5400static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft)
5401{
5402 return cgroup_task_count(cont);
5403}
5404
5405static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
5406{
5407 return (u64)(unsigned long)current->cgroups;
5408}
5409
5410static u64 current_css_set_refcount_read(struct cgroup *cont,
5411 struct cftype *cft)
5412{
5413 u64 count;
5414
5415 rcu_read_lock();
5416 count = atomic_read(¤t->cgroups->refcount);
5417 rcu_read_unlock();
5418 return count;
5419}
5420
5421static int current_css_set_cg_links_read(struct cgroup *cont,
5422 struct cftype *cft,
5423 struct seq_file *seq)
5424{
5425 struct cg_cgroup_link *link;
5426 struct css_set *cg;
5427
5428 read_lock(&css_set_lock);
5429 rcu_read_lock();
5430 cg = rcu_dereference(current->cgroups);
5431 list_for_each_entry(link, &cg->cg_links, cg_link_list) {
5432 struct cgroup *c = link->cgrp;
5433 const char *name;
5434
5435 if (c->dentry)
5436 name = c->dentry->d_name.name;
5437 else
5438 name = "?";
5439 seq_printf(seq, "Root %d group %s\n",
5440 c->root->hierarchy_id, name);
5441 }
5442 rcu_read_unlock();
5443 read_unlock(&css_set_lock);
5444 return 0;
5445}
5446
5447#define MAX_TASKS_SHOWN_PER_CSS 25
5448static int cgroup_css_links_read(struct cgroup *cont,
5449 struct cftype *cft,
5450 struct seq_file *seq)
5451{
5452 struct cg_cgroup_link *link;
5453
5454 read_lock(&css_set_lock);
5455 list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
5456 struct css_set *cg = link->cg;
5457 struct task_struct *task;
5458 int count = 0;
5459 seq_printf(seq, "css_set %p\n", cg);
5460 list_for_each_entry(task, &cg->tasks, cg_list) {
5461 if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
5462 seq_puts(seq, " ...\n");
5463 break;
5464 } else {
5465 seq_printf(seq, " task %d\n",
5466 task_pid_vnr(task));
5467 }
5468 }
5469 }
5470 read_unlock(&css_set_lock);
5471 return 0;
5472}
5473
5474static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
5475{
5476 return test_bit(CGRP_RELEASABLE, &cgrp->flags);
5477}
5478
5479static struct cftype debug_files[] = {
5480 {
5481 .name = "cgroup_refcount",
5482 .read_u64 = cgroup_refcount_read,
5483 },
5484 {
5485 .name = "taskcount",
5486 .read_u64 = debug_taskcount_read,
5487 },
5488
5489 {
5490 .name = "current_css_set",
5491 .read_u64 = current_css_set_read,
5492 },
5493
5494 {
5495 .name = "current_css_set_refcount",
5496 .read_u64 = current_css_set_refcount_read,
5497 },
5498
5499 {
5500 .name = "current_css_set_cg_links",
5501 .read_seq_string = current_css_set_cg_links_read,
5502 },
5503
5504 {
5505 .name = "cgroup_css_links",
5506 .read_seq_string = cgroup_css_links_read,
5507 },
5508
5509 {
5510 .name = "releasable",
5511 .read_u64 = releasable_read,
5512 },
5513
5514 { } /* terminate */
5515};
5516
5517struct cgroup_subsys debug_subsys = {
5518 .name = "debug",
5519 .create = debug_create,
5520 .destroy = debug_destroy,
5521 .subsys_id = debug_subsys_id,
5522 .base_cftypes = debug_files,
5523};
5524#endif /* CONFIG_CGROUP_DEBUG */