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