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 */
29 #include <linux/cgroup.h>
30 #include <linux/cred.h>
31 #include <linux/ctype.h>
32 #include <linux/errno.h>
33 #include <linux/fs.h>
34 #include <linux/init_task.h>
35 #include <linux/kernel.h>
36 #include <linux/list.h>
37 #include <linux/mm.h>
38 #include <linux/mutex.h>
39 #include <linux/mount.h>
40 #include <linux/pagemap.h>
41 #include <linux/proc_fs.h>
42 #include <linux/rcupdate.h>
43 #include <linux/sched.h>
44 #include <linux/backing-dev.h>
45 #include <linux/seq_file.h>
46 #include <linux/slab.h>
47 #include <linux/magic.h>
48 #include <linux/spinlock.h>
49 #include <linux/string.h>
50 #include <linux/sort.h>
51 #include <linux/kmod.h>
52 #include <linux/module.h>
53 #include <linux/delayacct.h>
54 #include <linux/cgroupstats.h>
55 #include <linux/hash.h>
56 #include <linux/namei.h>
57 #include <linux/pid_namespace.h>
58 #include <linux/idr.h>
59 #include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
60 #include <linux/eventfd.h>
61 #include <linux/poll.h>
62 #include <linux/flex_array.h> /* used in cgroup_attach_proc */
63 #include <linux/kthread.h>
65 #include <linux/atomic.h>
67 /* css deactivation bias, makes css->refcnt negative to deny new trygets */
68 #define CSS_DEACT_BIAS INT_MIN
70 /*
71 * cgroup_mutex is the master lock. Any modification to cgroup or its
72 * hierarchy must be performed while holding it.
73 *
74 * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
75 * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
76 * release_agent_path and so on. Modifying requires both cgroup_mutex and
77 * cgroup_root_mutex. Readers can acquire either of the two. This is to
78 * break the following locking order cycle.
79 *
80 * A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
81 * B. namespace_sem -> cgroup_mutex
82 *
83 * B happens only through cgroup_show_options() and using cgroup_root_mutex
84 * breaks it.
85 */
86 static DEFINE_MUTEX(cgroup_mutex);
87 static DEFINE_MUTEX(cgroup_root_mutex);
89 /*
90 * Generate an array of cgroup subsystem pointers. At boot time, this is
91 * populated with the built in subsystems, and modular subsystems are
92 * registered after that. The mutable section of this array is protected by
93 * cgroup_mutex.
94 */
95 #define SUBSYS(_x) [_x ## _subsys_id] = &_x ## _subsys,
96 #define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
97 static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
98 #include <linux/cgroup_subsys.h>
99 };
101 #define MAX_CGROUP_ROOT_NAMELEN 64
103 /*
104 * A cgroupfs_root represents the root of a cgroup hierarchy,
105 * and may be associated with a superblock to form an active
106 * hierarchy
107 */
108 struct cgroupfs_root {
109 struct super_block *sb;
111 /*
112 * The bitmask of subsystems intended to be attached to this
113 * hierarchy
114 */
115 unsigned long subsys_mask;
117 /* Unique id for this hierarchy. */
118 int hierarchy_id;
120 /* The bitmask of subsystems currently attached to this hierarchy */
121 unsigned long actual_subsys_mask;
123 /* A list running through the attached subsystems */
124 struct list_head subsys_list;
126 /* The root cgroup for this hierarchy */
127 struct cgroup top_cgroup;
129 /* Tracks how many cgroups are currently defined in hierarchy.*/
130 int number_of_cgroups;
132 /* A list running through the active hierarchies */
133 struct list_head root_list;
135 /* All cgroups on this root, cgroup_mutex protected */
136 struct list_head allcg_list;
138 /* Hierarchy-specific flags */
139 unsigned long flags;
141 /* IDs for cgroups in this hierarchy */
142 struct ida cgroup_ida;
144 /* The path to use for release notifications. */
145 char release_agent_path[PATH_MAX];
147 /* The name for this hierarchy - may be empty */
148 char name[MAX_CGROUP_ROOT_NAMELEN];
149 };
151 /*
152 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
153 * subsystems that are otherwise unattached - it never has more than a
154 * single cgroup, and all tasks are part of that cgroup.
155 */
156 static struct cgroupfs_root rootnode;
158 /*
159 * cgroupfs file entry, pointed to from leaf dentry->d_fsdata.
160 */
161 struct cfent {
162 struct list_head node;
163 struct dentry *dentry;
164 struct cftype *type;
165 };
167 /*
168 * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
169 * cgroup_subsys->use_id != 0.
170 */
171 #define CSS_ID_MAX (65535)
172 struct css_id {
173 /*
174 * The css to which this ID points. This pointer is set to valid value
175 * after cgroup is populated. If cgroup is removed, this will be NULL.
176 * This pointer is expected to be RCU-safe because destroy()
177 * is called after synchronize_rcu(). But for safe use, css_tryget()
178 * should be used for avoiding race.
179 */
180 struct cgroup_subsys_state __rcu *css;
181 /*
182 * ID of this css.
183 */
184 unsigned short id;
185 /*
186 * Depth in hierarchy which this ID belongs to.
187 */
188 unsigned short depth;
189 /*
190 * ID is freed by RCU. (and lookup routine is RCU safe.)
191 */
192 struct rcu_head rcu_head;
193 /*
194 * Hierarchy of CSS ID belongs to.
195 */
196 unsigned short stack[0]; /* Array of Length (depth+1) */
197 };
199 /*
200 * cgroup_event represents events which userspace want to receive.
201 */
202 struct cgroup_event {
203 /*
204 * Cgroup which the event belongs to.
205 */
206 struct cgroup *cgrp;
207 /*
208 * Control file which the event associated.
209 */
210 struct cftype *cft;
211 /*
212 * eventfd to signal userspace about the event.
213 */
214 struct eventfd_ctx *eventfd;
215 /*
216 * Each of these stored in a list by the cgroup.
217 */
218 struct list_head list;
219 /*
220 * All fields below needed to unregister event when
221 * userspace closes eventfd.
222 */
223 poll_table pt;
224 wait_queue_head_t *wqh;
225 wait_queue_t wait;
226 struct work_struct remove;
227 };
229 /* The list of hierarchy roots */
231 static LIST_HEAD(roots);
232 static int root_count;
234 static DEFINE_IDA(hierarchy_ida);
235 static int next_hierarchy_id;
236 static DEFINE_SPINLOCK(hierarchy_id_lock);
238 /* dummytop is a shorthand for the dummy hierarchy's top cgroup */
239 #define dummytop (&rootnode.top_cgroup)
241 /* This flag indicates whether tasks in the fork and exit paths should
242 * check for fork/exit handlers to call. This avoids us having to do
243 * extra work in the fork/exit path if none of the subsystems need to
244 * be called.
245 */
246 static int need_forkexit_callback __read_mostly;
248 static int cgroup_destroy_locked(struct cgroup *cgrp);
249 static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
250 struct cftype cfts[], bool is_add);
252 #ifdef CONFIG_PROVE_LOCKING
253 int cgroup_lock_is_held(void)
254 {
255 return lockdep_is_held(&cgroup_mutex);
256 }
257 #else /* #ifdef CONFIG_PROVE_LOCKING */
258 int cgroup_lock_is_held(void)
259 {
260 return mutex_is_locked(&cgroup_mutex);
261 }
262 #endif /* #else #ifdef CONFIG_PROVE_LOCKING */
264 EXPORT_SYMBOL_GPL(cgroup_lock_is_held);
266 static int css_unbias_refcnt(int refcnt)
267 {
268 return refcnt >= 0 ? refcnt : refcnt - CSS_DEACT_BIAS;
269 }
271 /* the current nr of refs, always >= 0 whether @css is deactivated or not */
272 static int css_refcnt(struct cgroup_subsys_state *css)
273 {
274 int v = atomic_read(&css->refcnt);
276 return css_unbias_refcnt(v);
277 }
279 /* convenient tests for these bits */
280 inline int cgroup_is_removed(const struct cgroup *cgrp)
281 {
282 return test_bit(CGRP_REMOVED, &cgrp->flags);
283 }
285 /* bits in struct cgroupfs_root flags field */
286 enum {
287 ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
288 ROOT_XATTR, /* supports extended attributes */
289 };
291 static int cgroup_is_releasable(const struct cgroup *cgrp)
292 {
293 const int bits =
294 (1 << CGRP_RELEASABLE) |
295 (1 << CGRP_NOTIFY_ON_RELEASE);
296 return (cgrp->flags & bits) == bits;
297 }
299 static int notify_on_release(const struct cgroup *cgrp)
300 {
301 return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
302 }
304 /*
305 * for_each_subsys() allows you to iterate on each subsystem attached to
306 * an active hierarchy
307 */
308 #define for_each_subsys(_root, _ss) \
309 list_for_each_entry(_ss, &_root->subsys_list, sibling)
311 /* for_each_active_root() allows you to iterate across the active hierarchies */
312 #define for_each_active_root(_root) \
313 list_for_each_entry(_root, &roots, root_list)
315 static inline struct cgroup *__d_cgrp(struct dentry *dentry)
316 {
317 return dentry->d_fsdata;
318 }
320 static inline struct cfent *__d_cfe(struct dentry *dentry)
321 {
322 return dentry->d_fsdata;
323 }
325 static inline struct cftype *__d_cft(struct dentry *dentry)
326 {
327 return __d_cfe(dentry)->type;
328 }
330 /* the list of cgroups eligible for automatic release. Protected by
331 * release_list_lock */
332 static LIST_HEAD(release_list);
333 static DEFINE_RAW_SPINLOCK(release_list_lock);
334 static void cgroup_release_agent(struct work_struct *work);
335 static DECLARE_WORK(release_agent_work, cgroup_release_agent);
336 static void check_for_release(struct cgroup *cgrp);
338 /* Link structure for associating css_set objects with cgroups */
339 struct cg_cgroup_link {
340 /*
341 * List running through cg_cgroup_links associated with a
342 * cgroup, anchored on cgroup->css_sets
343 */
344 struct list_head cgrp_link_list;
345 struct cgroup *cgrp;
346 /*
347 * List running through cg_cgroup_links pointing at a
348 * single css_set object, anchored on css_set->cg_links
349 */
350 struct list_head cg_link_list;
351 struct css_set *cg;
352 };
354 /* The default css_set - used by init and its children prior to any
355 * hierarchies being mounted. It contains a pointer to the root state
356 * for each subsystem. Also used to anchor the list of css_sets. Not
357 * reference-counted, to improve performance when child cgroups
358 * haven't been created.
359 */
361 static struct css_set init_css_set;
362 static struct cg_cgroup_link init_css_set_link;
364 static int cgroup_init_idr(struct cgroup_subsys *ss,
365 struct cgroup_subsys_state *css);
367 /* css_set_lock protects the list of css_set objects, and the
368 * chain of tasks off each css_set. Nests outside task->alloc_lock
369 * due to cgroup_iter_start() */
370 static DEFINE_RWLOCK(css_set_lock);
371 static int css_set_count;
373 /*
374 * hash table for cgroup groups. This improves the performance to find
375 * an existing css_set. This hash doesn't (currently) take into
376 * account cgroups in empty hierarchies.
377 */
378 #define CSS_SET_HASH_BITS 7
379 #define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS)
380 static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
382 static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
383 {
384 int i;
385 int index;
386 unsigned long tmp = 0UL;
388 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
389 tmp += (unsigned long)css[i];
390 tmp = (tmp >> 16) ^ tmp;
392 index = hash_long(tmp, CSS_SET_HASH_BITS);
394 return &css_set_table[index];
395 }
397 /* We don't maintain the lists running through each css_set to its
398 * task until after the first call to cgroup_iter_start(). This
399 * reduces the fork()/exit() overhead for people who have cgroups
400 * compiled into their kernel but not actually in use */
401 static int use_task_css_set_links __read_mostly;
403 static void __put_css_set(struct css_set *cg, int taskexit)
404 {
405 struct cg_cgroup_link *link;
406 struct cg_cgroup_link *saved_link;
407 /*
408 * Ensure that the refcount doesn't hit zero while any readers
409 * can see it. Similar to atomic_dec_and_lock(), but for an
410 * rwlock
411 */
412 if (atomic_add_unless(&cg->refcount, -1, 1))
413 return;
414 write_lock(&css_set_lock);
415 if (!atomic_dec_and_test(&cg->refcount)) {
416 write_unlock(&css_set_lock);
417 return;
418 }
420 /* This css_set is dead. unlink it and release cgroup refcounts */
421 hlist_del(&cg->hlist);
422 css_set_count--;
424 list_for_each_entry_safe(link, saved_link, &cg->cg_links,
425 cg_link_list) {
426 struct cgroup *cgrp = link->cgrp;
427 list_del(&link->cg_link_list);
428 list_del(&link->cgrp_link_list);
430 /*
431 * We may not be holding cgroup_mutex, and if cgrp->count is
432 * dropped to 0 the cgroup can be destroyed at any time, hence
433 * rcu_read_lock is used to keep it alive.
434 */
435 rcu_read_lock();
436 if (atomic_dec_and_test(&cgrp->count) &&
437 notify_on_release(cgrp)) {
438 if (taskexit)
439 set_bit(CGRP_RELEASABLE, &cgrp->flags);
440 check_for_release(cgrp);
441 }
442 rcu_read_unlock();
444 kfree(link);
445 }
447 write_unlock(&css_set_lock);
448 kfree_rcu(cg, rcu_head);
449 }
451 /*
452 * refcounted get/put for css_set objects
453 */
454 static inline void get_css_set(struct css_set *cg)
455 {
456 atomic_inc(&cg->refcount);
457 }
459 static inline void put_css_set(struct css_set *cg)
460 {
461 __put_css_set(cg, 0);
462 }
464 static inline void put_css_set_taskexit(struct css_set *cg)
465 {
466 __put_css_set(cg, 1);
467 }
469 /*
470 * compare_css_sets - helper function for find_existing_css_set().
471 * @cg: candidate css_set being tested
472 * @old_cg: existing css_set for a task
473 * @new_cgrp: cgroup that's being entered by the task
474 * @template: desired set of css pointers in css_set (pre-calculated)
475 *
476 * Returns true if "cg" matches "old_cg" except for the hierarchy
477 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
478 */
479 static bool compare_css_sets(struct css_set *cg,
480 struct css_set *old_cg,
481 struct cgroup *new_cgrp,
482 struct cgroup_subsys_state *template[])
483 {
484 struct list_head *l1, *l2;
486 if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
487 /* Not all subsystems matched */
488 return false;
489 }
491 /*
492 * Compare cgroup pointers in order to distinguish between
493 * different cgroups in heirarchies with no subsystems. We
494 * could get by with just this check alone (and skip the
495 * memcmp above) but on most setups the memcmp check will
496 * avoid the need for this more expensive check on almost all
497 * candidates.
498 */
500 l1 = &cg->cg_links;
501 l2 = &old_cg->cg_links;
502 while (1) {
503 struct cg_cgroup_link *cgl1, *cgl2;
504 struct cgroup *cg1, *cg2;
506 l1 = l1->next;
507 l2 = l2->next;
508 /* See if we reached the end - both lists are equal length. */
509 if (l1 == &cg->cg_links) {
510 BUG_ON(l2 != &old_cg->cg_links);
511 break;
512 } else {
513 BUG_ON(l2 == &old_cg->cg_links);
514 }
515 /* Locate the cgroups associated with these links. */
516 cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
517 cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
518 cg1 = cgl1->cgrp;
519 cg2 = cgl2->cgrp;
520 /* Hierarchies should be linked in the same order. */
521 BUG_ON(cg1->root != cg2->root);
523 /*
524 * If this hierarchy is the hierarchy of the cgroup
525 * that's changing, then we need to check that this
526 * css_set points to the new cgroup; if it's any other
527 * hierarchy, then this css_set should point to the
528 * same cgroup as the old css_set.
529 */
530 if (cg1->root == new_cgrp->root) {
531 if (cg1 != new_cgrp)
532 return false;
533 } else {
534 if (cg1 != cg2)
535 return false;
536 }
537 }
538 return true;
539 }
541 /*
542 * find_existing_css_set() is a helper for
543 * find_css_set(), and checks to see whether an existing
544 * css_set is suitable.
545 *
546 * oldcg: the cgroup group that we're using before the cgroup
547 * transition
548 *
549 * cgrp: the cgroup that we're moving into
550 *
551 * template: location in which to build the desired set of subsystem
552 * state objects for the new cgroup group
553 */
554 static struct css_set *find_existing_css_set(
555 struct css_set *oldcg,
556 struct cgroup *cgrp,
557 struct cgroup_subsys_state *template[])
558 {
559 int i;
560 struct cgroupfs_root *root = cgrp->root;
561 struct hlist_head *hhead;
562 struct hlist_node *node;
563 struct css_set *cg;
565 /*
566 * Build the set of subsystem state objects that we want to see in the
567 * new css_set. while subsystems can change globally, the entries here
568 * won't change, so no need for locking.
569 */
570 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
571 if (root->subsys_mask & (1UL << i)) {
572 /* Subsystem is in this hierarchy. So we want
573 * the subsystem state from the new
574 * cgroup */
575 template[i] = cgrp->subsys[i];
576 } else {
577 /* Subsystem is not in this hierarchy, so we
578 * don't want to change the subsystem state */
579 template[i] = oldcg->subsys[i];
580 }
581 }
583 hhead = css_set_hash(template);
584 hlist_for_each_entry(cg, node, hhead, hlist) {
585 if (!compare_css_sets(cg, oldcg, cgrp, template))
586 continue;
588 /* This css_set matches what we need */
589 return cg;
590 }
592 /* No existing cgroup group matched */
593 return NULL;
594 }
596 static void free_cg_links(struct list_head *tmp)
597 {
598 struct cg_cgroup_link *link;
599 struct cg_cgroup_link *saved_link;
601 list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
602 list_del(&link->cgrp_link_list);
603 kfree(link);
604 }
605 }
607 /*
608 * allocate_cg_links() allocates "count" cg_cgroup_link structures
609 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
610 * success or a negative error
611 */
612 static int allocate_cg_links(int count, struct list_head *tmp)
613 {
614 struct cg_cgroup_link *link;
615 int i;
616 INIT_LIST_HEAD(tmp);
617 for (i = 0; i < count; i++) {
618 link = kmalloc(sizeof(*link), GFP_KERNEL);
619 if (!link) {
620 free_cg_links(tmp);
621 return -ENOMEM;
622 }
623 list_add(&link->cgrp_link_list, tmp);
624 }
625 return 0;
626 }
628 /**
629 * link_css_set - a helper function to link a css_set to a cgroup
630 * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
631 * @cg: the css_set to be linked
632 * @cgrp: the destination cgroup
633 */
634 static void link_css_set(struct list_head *tmp_cg_links,
635 struct css_set *cg, struct cgroup *cgrp)
636 {
637 struct cg_cgroup_link *link;
639 BUG_ON(list_empty(tmp_cg_links));
640 link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
641 cgrp_link_list);
642 link->cg = cg;
643 link->cgrp = cgrp;
644 atomic_inc(&cgrp->count);
645 list_move(&link->cgrp_link_list, &cgrp->css_sets);
646 /*
647 * Always add links to the tail of the list so that the list
648 * is sorted by order of hierarchy creation
649 */
650 list_add_tail(&link->cg_link_list, &cg->cg_links);
651 }
653 /*
654 * find_css_set() takes an existing cgroup group and a
655 * cgroup object, and returns a css_set object that's
656 * equivalent to the old group, but with the given cgroup
657 * substituted into the appropriate hierarchy. Must be called with
658 * cgroup_mutex held
659 */
660 static struct css_set *find_css_set(
661 struct css_set *oldcg, struct cgroup *cgrp)
662 {
663 struct css_set *res;
664 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
666 struct list_head tmp_cg_links;
668 struct hlist_head *hhead;
669 struct cg_cgroup_link *link;
671 /* First see if we already have a cgroup group that matches
672 * the desired set */
673 read_lock(&css_set_lock);
674 res = find_existing_css_set(oldcg, cgrp, template);
675 if (res)
676 get_css_set(res);
677 read_unlock(&css_set_lock);
679 if (res)
680 return res;
682 res = kmalloc(sizeof(*res), GFP_KERNEL);
683 if (!res)
684 return NULL;
686 /* Allocate all the cg_cgroup_link objects that we'll need */
687 if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
688 kfree(res);
689 return NULL;
690 }
692 atomic_set(&res->refcount, 1);
693 INIT_LIST_HEAD(&res->cg_links);
694 INIT_LIST_HEAD(&res->tasks);
695 INIT_HLIST_NODE(&res->hlist);
697 /* Copy the set of subsystem state objects generated in
698 * find_existing_css_set() */
699 memcpy(res->subsys, template, sizeof(res->subsys));
701 write_lock(&css_set_lock);
702 /* Add reference counts and links from the new css_set. */
703 list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
704 struct cgroup *c = link->cgrp;
705 if (c->root == cgrp->root)
706 c = cgrp;
707 link_css_set(&tmp_cg_links, res, c);
708 }
710 BUG_ON(!list_empty(&tmp_cg_links));
712 css_set_count++;
714 /* Add this cgroup group to the hash table */
715 hhead = css_set_hash(res->subsys);
716 hlist_add_head(&res->hlist, hhead);
718 write_unlock(&css_set_lock);
720 return res;
721 }
723 /*
724 * Return the cgroup for "task" from the given hierarchy. Must be
725 * called with cgroup_mutex held.
726 */
727 static struct cgroup *task_cgroup_from_root(struct task_struct *task,
728 struct cgroupfs_root *root)
729 {
730 struct css_set *css;
731 struct cgroup *res = NULL;
733 BUG_ON(!mutex_is_locked(&cgroup_mutex));
734 read_lock(&css_set_lock);
735 /*
736 * No need to lock the task - since we hold cgroup_mutex the
737 * task can't change groups, so the only thing that can happen
738 * is that it exits and its css is set back to init_css_set.
739 */
740 css = task->cgroups;
741 if (css == &init_css_set) {
742 res = &root->top_cgroup;
743 } else {
744 struct cg_cgroup_link *link;
745 list_for_each_entry(link, &css->cg_links, cg_link_list) {
746 struct cgroup *c = link->cgrp;
747 if (c->root == root) {
748 res = c;
749 break;
750 }
751 }
752 }
753 read_unlock(&css_set_lock);
754 BUG_ON(!res);
755 return res;
756 }
758 /*
759 * There is one global cgroup mutex. We also require taking
760 * task_lock() when dereferencing a task's cgroup subsys pointers.
761 * See "The task_lock() exception", at the end of this comment.
762 *
763 * A task must hold cgroup_mutex to modify cgroups.
764 *
765 * Any task can increment and decrement the count field without lock.
766 * So in general, code holding cgroup_mutex can't rely on the count
767 * field not changing. However, if the count goes to zero, then only
768 * cgroup_attach_task() can increment it again. Because a count of zero
769 * means that no tasks are currently attached, therefore there is no
770 * way a task attached to that cgroup can fork (the other way to
771 * increment the count). So code holding cgroup_mutex can safely
772 * assume that if the count is zero, it will stay zero. Similarly, if
773 * a task holds cgroup_mutex on a cgroup with zero count, it
774 * knows that the cgroup won't be removed, as cgroup_rmdir()
775 * needs that mutex.
776 *
777 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
778 * (usually) take cgroup_mutex. These are the two most performance
779 * critical pieces of code here. The exception occurs on cgroup_exit(),
780 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
781 * is taken, and if the cgroup count is zero, a usermode call made
782 * to the release agent with the name of the cgroup (path relative to
783 * the root of cgroup file system) as the argument.
784 *
785 * A cgroup can only be deleted if both its 'count' of using tasks
786 * is zero, and its list of 'children' cgroups is empty. Since all
787 * tasks in the system use _some_ cgroup, and since there is always at
788 * least one task in the system (init, pid == 1), therefore, top_cgroup
789 * always has either children cgroups and/or using tasks. So we don't
790 * need a special hack to ensure that top_cgroup cannot be deleted.
791 *
792 * The task_lock() exception
793 *
794 * The need for this exception arises from the action of
795 * cgroup_attach_task(), which overwrites one task's cgroup pointer with
796 * another. It does so using cgroup_mutex, however there are
797 * several performance critical places that need to reference
798 * task->cgroup without the expense of grabbing a system global
799 * mutex. Therefore except as noted below, when dereferencing or, as
800 * in cgroup_attach_task(), modifying a task's cgroup pointer we use
801 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
802 * the task_struct routinely used for such matters.
803 *
804 * P.S. One more locking exception. RCU is used to guard the
805 * update of a tasks cgroup pointer by cgroup_attach_task()
806 */
808 /**
809 * cgroup_lock - lock out any changes to cgroup structures
810 *
811 */
812 void cgroup_lock(void)
813 {
814 mutex_lock(&cgroup_mutex);
815 }
816 EXPORT_SYMBOL_GPL(cgroup_lock);
818 /**
819 * cgroup_unlock - release lock on cgroup changes
820 *
821 * Undo the lock taken in a previous cgroup_lock() call.
822 */
823 void cgroup_unlock(void)
824 {
825 mutex_unlock(&cgroup_mutex);
826 }
827 EXPORT_SYMBOL_GPL(cgroup_unlock);
829 /*
830 * A couple of forward declarations required, due to cyclic reference loop:
831 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
832 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
833 * -> cgroup_mkdir.
834 */
836 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
837 static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);
838 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
839 static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
840 unsigned long subsys_mask);
841 static const struct inode_operations cgroup_dir_inode_operations;
842 static const struct file_operations proc_cgroupstats_operations;
844 static struct backing_dev_info cgroup_backing_dev_info = {
845 .name = "cgroup",
846 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
847 };
849 static int alloc_css_id(struct cgroup_subsys *ss,
850 struct cgroup *parent, struct cgroup *child);
852 static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
853 {
854 struct inode *inode = new_inode(sb);
856 if (inode) {
857 inode->i_ino = get_next_ino();
858 inode->i_mode = mode;
859 inode->i_uid = current_fsuid();
860 inode->i_gid = current_fsgid();
861 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
862 inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
863 }
864 return inode;
865 }
867 static void cgroup_diput(struct dentry *dentry, struct inode *inode)
868 {
869 /* is dentry a directory ? if so, kfree() associated cgroup */
870 if (S_ISDIR(inode->i_mode)) {
871 struct cgroup *cgrp = dentry->d_fsdata;
872 struct cgroup_subsys *ss;
873 BUG_ON(!(cgroup_is_removed(cgrp)));
874 /* It's possible for external users to be holding css
875 * reference counts on a cgroup; css_put() needs to
876 * be able to access the cgroup after decrementing
877 * the reference count in order to know if it needs to
878 * queue the cgroup to be handled by the release
879 * agent */
880 synchronize_rcu();
882 mutex_lock(&cgroup_mutex);
883 /*
884 * Release the subsystem state objects.
885 */
886 for_each_subsys(cgrp->root, ss)
887 ss->css_free(cgrp);
889 cgrp->root->number_of_cgroups--;
890 mutex_unlock(&cgroup_mutex);
892 /*
893 * Drop the active superblock reference that we took when we
894 * created the cgroup
895 */
896 deactivate_super(cgrp->root->sb);
898 /*
899 * if we're getting rid of the cgroup, refcount should ensure
900 * that there are no pidlists left.
901 */
902 BUG_ON(!list_empty(&cgrp->pidlists));
904 simple_xattrs_free(&cgrp->xattrs);
906 ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id);
907 kfree_rcu(cgrp, rcu_head);
908 } else {
909 struct cfent *cfe = __d_cfe(dentry);
910 struct cgroup *cgrp = dentry->d_parent->d_fsdata;
911 struct cftype *cft = cfe->type;
913 WARN_ONCE(!list_empty(&cfe->node) &&
914 cgrp != &cgrp->root->top_cgroup,
915 "cfe still linked for %s\n", cfe->type->name);
916 kfree(cfe);
917 simple_xattrs_free(&cft->xattrs);
918 }
919 iput(inode);
920 }
922 static int cgroup_delete(const struct dentry *d)
923 {
924 return 1;
925 }
927 static void remove_dir(struct dentry *d)
928 {
929 struct dentry *parent = dget(d->d_parent);
931 d_delete(d);
932 simple_rmdir(parent->d_inode, d);
933 dput(parent);
934 }
936 static int cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
937 {
938 struct cfent *cfe;
940 lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
941 lockdep_assert_held(&cgroup_mutex);
943 list_for_each_entry(cfe, &cgrp->files, node) {
944 struct dentry *d = cfe->dentry;
946 if (cft && cfe->type != cft)
947 continue;
949 dget(d);
950 d_delete(d);
951 simple_unlink(cgrp->dentry->d_inode, d);
952 list_del_init(&cfe->node);
953 dput(d);
955 return 0;
956 }
957 return -ENOENT;
958 }
960 /**
961 * cgroup_clear_directory - selective removal of base and subsystem files
962 * @dir: directory containing the files
963 * @base_files: true if the base files should be removed
964 * @subsys_mask: mask of the subsystem ids whose files should be removed
965 */
966 static void cgroup_clear_directory(struct dentry *dir, bool base_files,
967 unsigned long subsys_mask)
968 {
969 struct cgroup *cgrp = __d_cgrp(dir);
970 struct cgroup_subsys *ss;
972 for_each_subsys(cgrp->root, ss) {
973 struct cftype_set *set;
974 if (!test_bit(ss->subsys_id, &subsys_mask))
975 continue;
976 list_for_each_entry(set, &ss->cftsets, node)
977 cgroup_addrm_files(cgrp, NULL, set->cfts, false);
978 }
979 if (base_files) {
980 while (!list_empty(&cgrp->files))
981 cgroup_rm_file(cgrp, NULL);
982 }
983 }
985 /*
986 * NOTE : the dentry must have been dget()'ed
987 */
988 static void cgroup_d_remove_dir(struct dentry *dentry)
989 {
990 struct dentry *parent;
991 struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
993 cgroup_clear_directory(dentry, true, root->subsys_mask);
995 parent = dentry->d_parent;
996 spin_lock(&parent->d_lock);
997 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
998 list_del_init(&dentry->d_u.d_child);
999 spin_unlock(&dentry->d_lock);
1000 spin_unlock(&parent->d_lock);
1001 remove_dir(dentry);
1002 }
1004 /*
1005 * Call with cgroup_mutex held. Drops reference counts on modules, including
1006 * any duplicate ones that parse_cgroupfs_options took. If this function
1007 * returns an error, no reference counts are touched.
1008 */
1009 static int rebind_subsystems(struct cgroupfs_root *root,
1010 unsigned long final_subsys_mask)
1011 {
1012 unsigned long added_mask, removed_mask;
1013 struct cgroup *cgrp = &root->top_cgroup;
1014 int i;
1016 BUG_ON(!mutex_is_locked(&cgroup_mutex));
1017 BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
1019 removed_mask = root->actual_subsys_mask & ~final_subsys_mask;
1020 added_mask = final_subsys_mask & ~root->actual_subsys_mask;
1021 /* Check that any added subsystems are currently free */
1022 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1023 unsigned long bit = 1UL << i;
1024 struct cgroup_subsys *ss = subsys[i];
1025 if (!(bit & added_mask))
1026 continue;
1027 /*
1028 * Nobody should tell us to do a subsys that doesn't exist:
1029 * parse_cgroupfs_options should catch that case and refcounts
1030 * ensure that subsystems won't disappear once selected.
1031 */
1032 BUG_ON(ss == NULL);
1033 if (ss->root != &rootnode) {
1034 /* Subsystem isn't free */
1035 return -EBUSY;
1036 }
1037 }
1039 /* Currently we don't handle adding/removing subsystems when
1040 * any child cgroups exist. This is theoretically supportable
1041 * but involves complex error handling, so it's being left until
1042 * later */
1043 if (root->number_of_cgroups > 1)
1044 return -EBUSY;
1046 /* Process each subsystem */
1047 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1048 struct cgroup_subsys *ss = subsys[i];
1049 unsigned long bit = 1UL << i;
1050 if (bit & added_mask) {
1051 /* We're binding this subsystem to this hierarchy */
1052 BUG_ON(ss == NULL);
1053 BUG_ON(cgrp->subsys[i]);
1054 BUG_ON(!dummytop->subsys[i]);
1055 BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1056 cgrp->subsys[i] = dummytop->subsys[i];
1057 cgrp->subsys[i]->cgroup = cgrp;
1058 list_move(&ss->sibling, &root->subsys_list);
1059 ss->root = root;
1060 if (ss->bind)
1061 ss->bind(cgrp);
1062 /* refcount was already taken, and we're keeping it */
1063 } else if (bit & removed_mask) {
1064 /* We're removing this subsystem */
1065 BUG_ON(ss == NULL);
1066 BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
1067 BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1068 if (ss->bind)
1069 ss->bind(dummytop);
1070 dummytop->subsys[i]->cgroup = dummytop;
1071 cgrp->subsys[i] = NULL;
1072 subsys[i]->root = &rootnode;
1073 list_move(&ss->sibling, &rootnode.subsys_list);
1074 /* subsystem is now free - drop reference on module */
1075 module_put(ss->module);
1076 } else if (bit & final_subsys_mask) {
1077 /* Subsystem state should already exist */
1078 BUG_ON(ss == NULL);
1079 BUG_ON(!cgrp->subsys[i]);
1080 /*
1081 * a refcount was taken, but we already had one, so
1082 * drop the extra reference.
1083 */
1084 module_put(ss->module);
1085 #ifdef CONFIG_MODULE_UNLOAD
1086 BUG_ON(ss->module && !module_refcount(ss->module));
1087 #endif
1088 } else {
1089 /* Subsystem state shouldn't exist */
1090 BUG_ON(cgrp->subsys[i]);
1091 }
1092 }
1093 root->subsys_mask = root->actual_subsys_mask = final_subsys_mask;
1094 synchronize_rcu();
1096 return 0;
1097 }
1099 static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1100 {
1101 struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1102 struct cgroup_subsys *ss;
1104 mutex_lock(&cgroup_root_mutex);
1105 for_each_subsys(root, ss)
1106 seq_printf(seq, ",%s", ss->name);
1107 if (test_bit(ROOT_NOPREFIX, &root->flags))
1108 seq_puts(seq, ",noprefix");
1109 if (test_bit(ROOT_XATTR, &root->flags))
1110 seq_puts(seq, ",xattr");
1111 if (strlen(root->release_agent_path))
1112 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1113 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags))
1114 seq_puts(seq, ",clone_children");
1115 if (strlen(root->name))
1116 seq_printf(seq, ",name=%s", root->name);
1117 mutex_unlock(&cgroup_root_mutex);
1118 return 0;
1119 }
1121 struct cgroup_sb_opts {
1122 unsigned long subsys_mask;
1123 unsigned long flags;
1124 char *release_agent;
1125 bool cpuset_clone_children;
1126 char *name;
1127 /* User explicitly requested empty subsystem */
1128 bool none;
1130 struct cgroupfs_root *new_root;
1132 };
1134 /*
1135 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
1136 * with cgroup_mutex held to protect the subsys[] array. This function takes
1137 * refcounts on subsystems to be used, unless it returns error, in which case
1138 * no refcounts are taken.
1139 */
1140 static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1141 {
1142 char *token, *o = data;
1143 bool all_ss = false, one_ss = false;
1144 unsigned long mask = (unsigned long)-1;
1145 int i;
1146 bool module_pin_failed = false;
1148 BUG_ON(!mutex_is_locked(&cgroup_mutex));
1150 #ifdef CONFIG_CPUSETS
1151 mask = ~(1UL << cpuset_subsys_id);
1152 #endif
1154 memset(opts, 0, sizeof(*opts));
1156 while ((token = strsep(&o, ",")) != NULL) {
1157 if (!*token)
1158 return -EINVAL;
1159 if (!strcmp(token, "none")) {
1160 /* Explicitly have no subsystems */
1161 opts->none = true;
1162 continue;
1163 }
1164 if (!strcmp(token, "all")) {
1165 /* Mutually exclusive option 'all' + subsystem name */
1166 if (one_ss)
1167 return -EINVAL;
1168 all_ss = true;
1169 continue;
1170 }
1171 if (!strcmp(token, "noprefix")) {
1172 set_bit(ROOT_NOPREFIX, &opts->flags);
1173 continue;
1174 }
1175 if (!strcmp(token, "clone_children")) {
1176 opts->cpuset_clone_children = true;
1177 continue;
1178 }
1179 if (!strcmp(token, "xattr")) {
1180 set_bit(ROOT_XATTR, &opts->flags);
1181 continue;
1182 }
1183 if (!strncmp(token, "release_agent=", 14)) {
1184 /* Specifying two release agents is forbidden */
1185 if (opts->release_agent)
1186 return -EINVAL;
1187 opts->release_agent =
1188 kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1189 if (!opts->release_agent)
1190 return -ENOMEM;
1191 continue;
1192 }
1193 if (!strncmp(token, "name=", 5)) {
1194 const char *name = token + 5;
1195 /* Can't specify an empty name */
1196 if (!strlen(name))
1197 return -EINVAL;
1198 /* Must match [\w.-]+ */
1199 for (i = 0; i < strlen(name); i++) {
1200 char c = name[i];
1201 if (isalnum(c))
1202 continue;
1203 if ((c == '.') || (c == '-') || (c == '_'))
1204 continue;
1205 return -EINVAL;
1206 }
1207 /* Specifying two names is forbidden */
1208 if (opts->name)
1209 return -EINVAL;
1210 opts->name = kstrndup(name,
1211 MAX_CGROUP_ROOT_NAMELEN - 1,
1212 GFP_KERNEL);
1213 if (!opts->name)
1214 return -ENOMEM;
1216 continue;
1217 }
1219 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1220 struct cgroup_subsys *ss = subsys[i];
1221 if (ss == NULL)
1222 continue;
1223 if (strcmp(token, ss->name))
1224 continue;
1225 if (ss->disabled)
1226 continue;
1228 /* Mutually exclusive option 'all' + subsystem name */
1229 if (all_ss)
1230 return -EINVAL;
1231 set_bit(i, &opts->subsys_mask);
1232 one_ss = true;
1234 break;
1235 }
1236 if (i == CGROUP_SUBSYS_COUNT)
1237 return -ENOENT;
1238 }
1240 /*
1241 * If the 'all' option was specified select all the subsystems,
1242 * otherwise if 'none', 'name=' and a subsystem name options
1243 * were not specified, let's default to 'all'
1244 */
1245 if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1246 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1247 struct cgroup_subsys *ss = subsys[i];
1248 if (ss == NULL)
1249 continue;
1250 if (ss->disabled)
1251 continue;
1252 set_bit(i, &opts->subsys_mask);
1253 }
1254 }
1256 /* Consistency checks */
1258 /*
1259 * Option noprefix was introduced just for backward compatibility
1260 * with the old cpuset, so we allow noprefix only if mounting just
1261 * the cpuset subsystem.
1262 */
1263 if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
1264 (opts->subsys_mask & mask))
1265 return -EINVAL;
1268 /* Can't specify "none" and some subsystems */
1269 if (opts->subsys_mask && opts->none)
1270 return -EINVAL;
1272 /*
1273 * We either have to specify by name or by subsystems. (So all
1274 * empty hierarchies must have a name).
1275 */
1276 if (!opts->subsys_mask && !opts->name)
1277 return -EINVAL;
1279 /*
1280 * Grab references on all the modules we'll need, so the subsystems
1281 * don't dance around before rebind_subsystems attaches them. This may
1282 * take duplicate reference counts on a subsystem that's already used,
1283 * but rebind_subsystems handles this case.
1284 */
1285 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1286 unsigned long bit = 1UL << i;
1288 if (!(bit & opts->subsys_mask))
1289 continue;
1290 if (!try_module_get(subsys[i]->module)) {
1291 module_pin_failed = true;
1292 break;
1293 }
1294 }
1295 if (module_pin_failed) {
1296 /*
1297 * oops, one of the modules was going away. this means that we
1298 * raced with a module_delete call, and to the user this is
1299 * essentially a "subsystem doesn't exist" case.
1300 */
1301 for (i--; i >= 0; i--) {
1302 /* drop refcounts only on the ones we took */
1303 unsigned long bit = 1UL << i;
1305 if (!(bit & opts->subsys_mask))
1306 continue;
1307 module_put(subsys[i]->module);
1308 }
1309 return -ENOENT;
1310 }
1312 return 0;
1313 }
1315 static void drop_parsed_module_refcounts(unsigned long subsys_mask)
1316 {
1317 int i;
1318 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1319 unsigned long bit = 1UL << i;
1321 if (!(bit & subsys_mask))
1322 continue;
1323 module_put(subsys[i]->module);
1324 }
1325 }
1327 static int cgroup_remount(struct super_block *sb, int *flags, char *data)
1328 {
1329 int ret = 0;
1330 struct cgroupfs_root *root = sb->s_fs_info;
1331 struct cgroup *cgrp = &root->top_cgroup;
1332 struct cgroup_sb_opts opts;
1333 unsigned long added_mask, removed_mask;
1335 mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1336 mutex_lock(&cgroup_mutex);
1337 mutex_lock(&cgroup_root_mutex);
1339 /* See what subsystems are wanted */
1340 ret = parse_cgroupfs_options(data, &opts);
1341 if (ret)
1342 goto out_unlock;
1344 if (opts.subsys_mask != root->actual_subsys_mask || opts.release_agent)
1345 pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
1346 task_tgid_nr(current), current->comm);
1348 added_mask = opts.subsys_mask & ~root->subsys_mask;
1349 removed_mask = root->subsys_mask & ~opts.subsys_mask;
1351 /* Don't allow flags or name to change at remount */
1352 if (opts.flags != root->flags ||
1353 (opts.name && strcmp(opts.name, root->name))) {
1354 ret = -EINVAL;
1355 drop_parsed_module_refcounts(opts.subsys_mask);
1356 goto out_unlock;
1357 }
1359 /*
1360 * Clear out the files of subsystems that should be removed, do
1361 * this before rebind_subsystems, since rebind_subsystems may
1362 * change this hierarchy's subsys_list.
1363 */
1364 cgroup_clear_directory(cgrp->dentry, false, removed_mask);
1366 ret = rebind_subsystems(root, opts.subsys_mask);
1367 if (ret) {
1368 /* rebind_subsystems failed, re-populate the removed files */
1369 cgroup_populate_dir(cgrp, false, removed_mask);
1370 drop_parsed_module_refcounts(opts.subsys_mask);
1371 goto out_unlock;
1372 }
1374 /* re-populate subsystem files */
1375 cgroup_populate_dir(cgrp, false, added_mask);
1377 if (opts.release_agent)
1378 strcpy(root->release_agent_path, opts.release_agent);
1379 out_unlock:
1380 kfree(opts.release_agent);
1381 kfree(opts.name);
1382 mutex_unlock(&cgroup_root_mutex);
1383 mutex_unlock(&cgroup_mutex);
1384 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1385 return ret;
1386 }
1388 static const struct super_operations cgroup_ops = {
1389 .statfs = simple_statfs,
1390 .drop_inode = generic_delete_inode,
1391 .show_options = cgroup_show_options,
1392 .remount_fs = cgroup_remount,
1393 };
1395 static void init_cgroup_housekeeping(struct cgroup *cgrp)
1396 {
1397 INIT_LIST_HEAD(&cgrp->sibling);
1398 INIT_LIST_HEAD(&cgrp->children);
1399 INIT_LIST_HEAD(&cgrp->files);
1400 INIT_LIST_HEAD(&cgrp->css_sets);
1401 INIT_LIST_HEAD(&cgrp->allcg_node);
1402 INIT_LIST_HEAD(&cgrp->release_list);
1403 INIT_LIST_HEAD(&cgrp->pidlists);
1404 mutex_init(&cgrp->pidlist_mutex);
1405 INIT_LIST_HEAD(&cgrp->event_list);
1406 spin_lock_init(&cgrp->event_list_lock);
1407 simple_xattrs_init(&cgrp->xattrs);
1408 }
1410 static void init_cgroup_root(struct cgroupfs_root *root)
1411 {
1412 struct cgroup *cgrp = &root->top_cgroup;
1414 INIT_LIST_HEAD(&root->subsys_list);
1415 INIT_LIST_HEAD(&root->root_list);
1416 INIT_LIST_HEAD(&root->allcg_list);
1417 root->number_of_cgroups = 1;
1418 cgrp->root = root;
1419 cgrp->top_cgroup = cgrp;
1420 init_cgroup_housekeeping(cgrp);
1421 list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1422 }
1424 static bool init_root_id(struct cgroupfs_root *root)
1425 {
1426 int ret = 0;
1428 do {
1429 if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
1430 return false;
1431 spin_lock(&hierarchy_id_lock);
1432 /* Try to allocate the next unused ID */
1433 ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
1434 &root->hierarchy_id);
1435 if (ret == -ENOSPC)
1436 /* Try again starting from 0 */
1437 ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
1438 if (!ret) {
1439 next_hierarchy_id = root->hierarchy_id + 1;
1440 } else if (ret != -EAGAIN) {
1441 /* Can only get here if the 31-bit IDR is full ... */
1442 BUG_ON(ret);
1443 }
1444 spin_unlock(&hierarchy_id_lock);
1445 } while (ret);
1446 return true;
1447 }
1449 static int cgroup_test_super(struct super_block *sb, void *data)
1450 {
1451 struct cgroup_sb_opts *opts = data;
1452 struct cgroupfs_root *root = sb->s_fs_info;
1454 /* If we asked for a name then it must match */
1455 if (opts->name && strcmp(opts->name, root->name))
1456 return 0;
1458 /*
1459 * If we asked for subsystems (or explicitly for no
1460 * subsystems) then they must match
1461 */
1462 if ((opts->subsys_mask || opts->none)
1463 && (opts->subsys_mask != root->subsys_mask))
1464 return 0;
1466 return 1;
1467 }
1469 static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
1470 {
1471 struct cgroupfs_root *root;
1473 if (!opts->subsys_mask && !opts->none)
1474 return NULL;
1476 root = kzalloc(sizeof(*root), GFP_KERNEL);
1477 if (!root)
1478 return ERR_PTR(-ENOMEM);
1480 if (!init_root_id(root)) {
1481 kfree(root);
1482 return ERR_PTR(-ENOMEM);
1483 }
1484 init_cgroup_root(root);
1486 root->subsys_mask = opts->subsys_mask;
1487 root->flags = opts->flags;
1488 ida_init(&root->cgroup_ida);
1489 if (opts->release_agent)
1490 strcpy(root->release_agent_path, opts->release_agent);
1491 if (opts->name)
1492 strcpy(root->name, opts->name);
1493 if (opts->cpuset_clone_children)
1494 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags);
1495 return root;
1496 }
1498 static void cgroup_drop_root(struct cgroupfs_root *root)
1499 {
1500 if (!root)
1501 return;
1503 BUG_ON(!root->hierarchy_id);
1504 spin_lock(&hierarchy_id_lock);
1505 ida_remove(&hierarchy_ida, root->hierarchy_id);
1506 spin_unlock(&hierarchy_id_lock);
1507 ida_destroy(&root->cgroup_ida);
1508 kfree(root);
1509 }
1511 static int cgroup_set_super(struct super_block *sb, void *data)
1512 {
1513 int ret;
1514 struct cgroup_sb_opts *opts = data;
1516 /* If we don't have a new root, we can't set up a new sb */
1517 if (!opts->new_root)
1518 return -EINVAL;
1520 BUG_ON(!opts->subsys_mask && !opts->none);
1522 ret = set_anon_super(sb, NULL);
1523 if (ret)
1524 return ret;
1526 sb->s_fs_info = opts->new_root;
1527 opts->new_root->sb = sb;
1529 sb->s_blocksize = PAGE_CACHE_SIZE;
1530 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
1531 sb->s_magic = CGROUP_SUPER_MAGIC;
1532 sb->s_op = &cgroup_ops;
1534 return 0;
1535 }
1537 static int cgroup_get_rootdir(struct super_block *sb)
1538 {
1539 static const struct dentry_operations cgroup_dops = {
1540 .d_iput = cgroup_diput,
1541 .d_delete = cgroup_delete,
1542 };
1544 struct inode *inode =
1545 cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
1547 if (!inode)
1548 return -ENOMEM;
1550 inode->i_fop = &simple_dir_operations;
1551 inode->i_op = &cgroup_dir_inode_operations;
1552 /* directories start off with i_nlink == 2 (for "." entry) */
1553 inc_nlink(inode);
1554 sb->s_root = d_make_root(inode);
1555 if (!sb->s_root)
1556 return -ENOMEM;
1557 /* for everything else we want ->d_op set */
1558 sb->s_d_op = &cgroup_dops;
1559 return 0;
1560 }
1562 static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1563 int flags, const char *unused_dev_name,
1564 void *data)
1565 {
1566 struct cgroup_sb_opts opts;
1567 struct cgroupfs_root *root;
1568 int ret = 0;
1569 struct super_block *sb;
1570 struct cgroupfs_root *new_root;
1571 struct inode *inode;
1573 /* First find the desired set of subsystems */
1574 mutex_lock(&cgroup_mutex);
1575 ret = parse_cgroupfs_options(data, &opts);
1576 mutex_unlock(&cgroup_mutex);
1577 if (ret)
1578 goto out_err;
1580 /*
1581 * Allocate a new cgroup root. We may not need it if we're
1582 * reusing an existing hierarchy.
1583 */
1584 new_root = cgroup_root_from_opts(&opts);
1585 if (IS_ERR(new_root)) {
1586 ret = PTR_ERR(new_root);
1587 goto drop_modules;
1588 }
1589 opts.new_root = new_root;
1591 /* Locate an existing or new sb for this hierarchy */
1592 sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
1593 if (IS_ERR(sb)) {
1594 ret = PTR_ERR(sb);
1595 cgroup_drop_root(opts.new_root);
1596 goto drop_modules;
1597 }
1599 root = sb->s_fs_info;
1600 BUG_ON(!root);
1601 if (root == opts.new_root) {
1602 /* We used the new root structure, so this is a new hierarchy */
1603 struct list_head tmp_cg_links;
1604 struct cgroup *root_cgrp = &root->top_cgroup;
1605 struct cgroupfs_root *existing_root;
1606 const struct cred *cred;
1607 int i;
1609 BUG_ON(sb->s_root != NULL);
1611 ret = cgroup_get_rootdir(sb);
1612 if (ret)
1613 goto drop_new_super;
1614 inode = sb->s_root->d_inode;
1616 mutex_lock(&inode->i_mutex);
1617 mutex_lock(&cgroup_mutex);
1618 mutex_lock(&cgroup_root_mutex);
1620 /* Check for name clashes with existing mounts */
1621 ret = -EBUSY;
1622 if (strlen(root->name))
1623 for_each_active_root(existing_root)
1624 if (!strcmp(existing_root->name, root->name))
1625 goto unlock_drop;
1627 /*
1628 * We're accessing css_set_count without locking
1629 * css_set_lock here, but that's OK - it can only be
1630 * increased by someone holding cgroup_lock, and
1631 * that's us. The worst that can happen is that we
1632 * have some link structures left over
1633 */
1634 ret = allocate_cg_links(css_set_count, &tmp_cg_links);
1635 if (ret)
1636 goto unlock_drop;
1638 ret = rebind_subsystems(root, root->subsys_mask);
1639 if (ret == -EBUSY) {
1640 free_cg_links(&tmp_cg_links);
1641 goto unlock_drop;
1642 }
1643 /*
1644 * There must be no failure case after here, since rebinding
1645 * takes care of subsystems' refcounts, which are explicitly
1646 * dropped in the failure exit path.
1647 */
1649 /* EBUSY should be the only error here */
1650 BUG_ON(ret);
1652 list_add(&root->root_list, &roots);
1653 root_count++;
1655 sb->s_root->d_fsdata = root_cgrp;
1656 root->top_cgroup.dentry = sb->s_root;
1658 /* Link the top cgroup in this hierarchy into all
1659 * the css_set objects */
1660 write_lock(&css_set_lock);
1661 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
1662 struct hlist_head *hhead = &css_set_table[i];
1663 struct hlist_node *node;
1664 struct css_set *cg;
1666 hlist_for_each_entry(cg, node, hhead, hlist)
1667 link_css_set(&tmp_cg_links, cg, root_cgrp);
1668 }
1669 write_unlock(&css_set_lock);
1671 free_cg_links(&tmp_cg_links);
1673 BUG_ON(!list_empty(&root_cgrp->children));
1674 BUG_ON(root->number_of_cgroups != 1);
1676 cred = override_creds(&init_cred);
1677 cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
1678 revert_creds(cred);
1679 mutex_unlock(&cgroup_root_mutex);
1680 mutex_unlock(&cgroup_mutex);
1681 mutex_unlock(&inode->i_mutex);
1682 } else {
1683 /*
1684 * We re-used an existing hierarchy - the new root (if
1685 * any) is not needed
1686 */
1687 cgroup_drop_root(opts.new_root);
1688 /* no subsys rebinding, so refcounts don't change */
1689 drop_parsed_module_refcounts(opts.subsys_mask);
1690 }
1692 kfree(opts.release_agent);
1693 kfree(opts.name);
1694 return dget(sb->s_root);
1696 unlock_drop:
1697 mutex_unlock(&cgroup_root_mutex);
1698 mutex_unlock(&cgroup_mutex);
1699 mutex_unlock(&inode->i_mutex);
1700 drop_new_super:
1701 deactivate_locked_super(sb);
1702 drop_modules:
1703 drop_parsed_module_refcounts(opts.subsys_mask);
1704 out_err:
1705 kfree(opts.release_agent);
1706 kfree(opts.name);
1707 return ERR_PTR(ret);
1708 }
1710 static void cgroup_kill_sb(struct super_block *sb) {
1711 struct cgroupfs_root *root = sb->s_fs_info;
1712 struct cgroup *cgrp = &root->top_cgroup;
1713 int ret;
1714 struct cg_cgroup_link *link;
1715 struct cg_cgroup_link *saved_link;
1717 BUG_ON(!root);
1719 BUG_ON(root->number_of_cgroups != 1);
1720 BUG_ON(!list_empty(&cgrp->children));
1722 mutex_lock(&cgroup_mutex);
1723 mutex_lock(&cgroup_root_mutex);
1725 /* Rebind all subsystems back to the default hierarchy */
1726 ret = rebind_subsystems(root, 0);
1727 /* Shouldn't be able to fail ... */
1728 BUG_ON(ret);
1730 /*
1731 * Release all the links from css_sets to this hierarchy's
1732 * root cgroup
1733 */
1734 write_lock(&css_set_lock);
1736 list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
1737 cgrp_link_list) {
1738 list_del(&link->cg_link_list);
1739 list_del(&link->cgrp_link_list);
1740 kfree(link);
1741 }
1742 write_unlock(&css_set_lock);
1744 if (!list_empty(&root->root_list)) {
1745 list_del(&root->root_list);
1746 root_count--;
1747 }
1749 mutex_unlock(&cgroup_root_mutex);
1750 mutex_unlock(&cgroup_mutex);
1752 simple_xattrs_free(&cgrp->xattrs);
1754 kill_litter_super(sb);
1755 cgroup_drop_root(root);
1756 }
1758 static struct file_system_type cgroup_fs_type = {
1759 .name = "cgroup",
1760 .mount = cgroup_mount,
1761 .kill_sb = cgroup_kill_sb,
1762 };
1764 static struct kobject *cgroup_kobj;
1766 /**
1767 * cgroup_path - generate the path of a cgroup
1768 * @cgrp: the cgroup in question
1769 * @buf: the buffer to write the path into
1770 * @buflen: the length of the buffer
1771 *
1772 * Called with cgroup_mutex held or else with an RCU-protected cgroup
1773 * reference. Writes path of cgroup into buf. Returns 0 on success,
1774 * -errno on error.
1775 */
1776 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1777 {
1778 struct dentry *dentry = cgrp->dentry;
1779 char *start;
1781 rcu_lockdep_assert(rcu_read_lock_held() || cgroup_lock_is_held(),
1782 "cgroup_path() called without proper locking");
1784 if (!dentry || cgrp == dummytop) {
1785 /*
1786 * Inactive subsystems have no dentry for their root
1787 * cgroup
1788 */
1789 strcpy(buf, "/");
1790 return 0;
1791 }
1793 start = buf + buflen - 1;
1795 *start = '\0';
1796 for (;;) {
1797 int len = dentry->d_name.len;
1799 if ((start -= len) < buf)
1800 return -ENAMETOOLONG;
1801 memcpy(start, dentry->d_name.name, len);
1802 cgrp = cgrp->parent;
1803 if (!cgrp)
1804 break;
1806 dentry = cgrp->dentry;
1807 if (!cgrp->parent)
1808 continue;
1809 if (--start < buf)
1810 return -ENAMETOOLONG;
1811 *start = '/';
1812 }
1813 memmove(buf, start, buf + buflen - start);
1814 return 0;
1815 }
1816 EXPORT_SYMBOL_GPL(cgroup_path);
1818 /*
1819 * Control Group taskset
1820 */
1821 struct task_and_cgroup {
1822 struct task_struct *task;
1823 struct cgroup *cgrp;
1824 struct css_set *cg;
1825 };
1827 struct cgroup_taskset {
1828 struct task_and_cgroup single;
1829 struct flex_array *tc_array;
1830 int tc_array_len;
1831 int idx;
1832 struct cgroup *cur_cgrp;
1833 };
1835 /**
1836 * cgroup_taskset_first - reset taskset and return the first task
1837 * @tset: taskset of interest
1838 *
1839 * @tset iteration is initialized and the first task is returned.
1840 */
1841 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
1842 {
1843 if (tset->tc_array) {
1844 tset->idx = 0;
1845 return cgroup_taskset_next(tset);
1846 } else {
1847 tset->cur_cgrp = tset->single.cgrp;
1848 return tset->single.task;
1849 }
1850 }
1851 EXPORT_SYMBOL_GPL(cgroup_taskset_first);
1853 /**
1854 * cgroup_taskset_next - iterate to the next task in taskset
1855 * @tset: taskset of interest
1856 *
1857 * Return the next task in @tset. Iteration must have been initialized
1858 * with cgroup_taskset_first().
1859 */
1860 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
1861 {
1862 struct task_and_cgroup *tc;
1864 if (!tset->tc_array || tset->idx >= tset->tc_array_len)
1865 return NULL;
1867 tc = flex_array_get(tset->tc_array, tset->idx++);
1868 tset->cur_cgrp = tc->cgrp;
1869 return tc->task;
1870 }
1871 EXPORT_SYMBOL_GPL(cgroup_taskset_next);
1873 /**
1874 * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
1875 * @tset: taskset of interest
1876 *
1877 * Return the cgroup for the current (last returned) task of @tset. This
1878 * function must be preceded by either cgroup_taskset_first() or
1879 * cgroup_taskset_next().
1880 */
1881 struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
1882 {
1883 return tset->cur_cgrp;
1884 }
1885 EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);
1887 /**
1888 * cgroup_taskset_size - return the number of tasks in taskset
1889 * @tset: taskset of interest
1890 */
1891 int cgroup_taskset_size(struct cgroup_taskset *tset)
1892 {
1893 return tset->tc_array ? tset->tc_array_len : 1;
1894 }
1895 EXPORT_SYMBOL_GPL(cgroup_taskset_size);
1898 /*
1899 * cgroup_task_migrate - move a task from one cgroup to another.
1900 *
1901 * Must be called with cgroup_mutex and threadgroup locked.
1902 */
1903 static void cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
1904 struct task_struct *tsk, struct css_set *newcg)
1905 {
1906 struct css_set *oldcg;
1908 /*
1909 * We are synchronized through threadgroup_lock() against PF_EXITING
1910 * setting such that we can't race against cgroup_exit() changing the
1911 * css_set to init_css_set and dropping the old one.
1912 */
1913 WARN_ON_ONCE(tsk->flags & PF_EXITING);
1914 oldcg = tsk->cgroups;
1916 task_lock(tsk);
1917 rcu_assign_pointer(tsk->cgroups, newcg);
1918 task_unlock(tsk);
1920 /* Update the css_set linked lists if we're using them */
1921 write_lock(&css_set_lock);
1922 if (!list_empty(&tsk->cg_list))
1923 list_move(&tsk->cg_list, &newcg->tasks);
1924 write_unlock(&css_set_lock);
1926 /*
1927 * We just gained a reference on oldcg by taking it from the task. As
1928 * trading it for newcg is protected by cgroup_mutex, we're safe to drop
1929 * it here; it will be freed under RCU.
1930 */
1931 set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1932 put_css_set(oldcg);
1933 }
1935 /**
1936 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
1937 * @cgrp: the cgroup the task is attaching to
1938 * @tsk: the task to be attached
1939 *
1940 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
1941 * @tsk during call.
1942 */
1943 int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1944 {
1945 int retval = 0;
1946 struct cgroup_subsys *ss, *failed_ss = NULL;
1947 struct cgroup *oldcgrp;
1948 struct cgroupfs_root *root = cgrp->root;
1949 struct cgroup_taskset tset = { };
1950 struct css_set *newcg;
1952 /* @tsk either already exited or can't exit until the end */
1953 if (tsk->flags & PF_EXITING)
1954 return -ESRCH;
1956 /* Nothing to do if the task is already in that cgroup */
1957 oldcgrp = task_cgroup_from_root(tsk, root);
1958 if (cgrp == oldcgrp)
1959 return 0;
1961 tset.single.task = tsk;
1962 tset.single.cgrp = oldcgrp;
1964 for_each_subsys(root, ss) {
1965 if (ss->can_attach) {
1966 retval = ss->can_attach(cgrp, &tset);
1967 if (retval) {
1968 /*
1969 * Remember on which subsystem the can_attach()
1970 * failed, so that we only call cancel_attach()
1971 * against the subsystems whose can_attach()
1972 * succeeded. (See below)
1973 */
1974 failed_ss = ss;
1975 goto out;
1976 }
1977 }
1978 }
1980 newcg = find_css_set(tsk->cgroups, cgrp);
1981 if (!newcg) {
1982 retval = -ENOMEM;
1983 goto out;
1984 }
1986 cgroup_task_migrate(cgrp, oldcgrp, tsk, newcg);
1988 for_each_subsys(root, ss) {
1989 if (ss->attach)
1990 ss->attach(cgrp, &tset);
1991 }
1993 synchronize_rcu();
1994 out:
1995 if (retval) {
1996 for_each_subsys(root, ss) {
1997 if (ss == failed_ss)
1998 /*
1999 * This subsystem was the one that failed the
2000 * can_attach() check earlier, so we don't need
2001 * to call cancel_attach() against it or any
2002 * remaining subsystems.
2003 */
2004 break;
2005 if (ss->cancel_attach)
2006 ss->cancel_attach(cgrp, &tset);
2007 }
2008 }
2009 return retval;
2010 }
2012 /**
2013 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2014 * @from: attach to all cgroups of a given task
2015 * @tsk: the task to be attached
2016 */
2017 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2018 {
2019 struct cgroupfs_root *root;
2020 int retval = 0;
2022 cgroup_lock();
2023 for_each_active_root(root) {
2024 struct cgroup *from_cg = task_cgroup_from_root(from, root);
2026 retval = cgroup_attach_task(from_cg, tsk);
2027 if (retval)
2028 break;
2029 }
2030 cgroup_unlock();
2032 return retval;
2033 }
2034 EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2036 /**
2037 * cgroup_attach_proc - attach all threads in a threadgroup to a cgroup
2038 * @cgrp: the cgroup to attach to
2039 * @leader: the threadgroup leader task_struct of the group to be attached
2040 *
2041 * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
2042 * task_lock of each thread in leader's threadgroup individually in turn.
2043 */
2044 static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
2045 {
2046 int retval, i, group_size;
2047 struct cgroup_subsys *ss, *failed_ss = NULL;
2048 /* guaranteed to be initialized later, but the compiler needs this */
2049 struct cgroupfs_root *root = cgrp->root;
2050 /* threadgroup list cursor and array */
2051 struct task_struct *tsk;
2052 struct task_and_cgroup *tc;
2053 struct flex_array *group;
2054 struct cgroup_taskset tset = { };
2056 /*
2057 * step 0: in order to do expensive, possibly blocking operations for
2058 * every thread, we cannot iterate the thread group list, since it needs
2059 * rcu or tasklist locked. instead, build an array of all threads in the
2060 * group - group_rwsem prevents new threads from appearing, and if
2061 * threads exit, this will just be an over-estimate.
2062 */
2063 group_size = get_nr_threads(leader);
2064 /* flex_array supports very large thread-groups better than kmalloc. */
2065 group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
2066 if (!group)
2067 return -ENOMEM;
2068 /* pre-allocate to guarantee space while iterating in rcu read-side. */
2069 retval = flex_array_prealloc(group, 0, group_size - 1, GFP_KERNEL);
2070 if (retval)
2071 goto out_free_group_list;
2073 tsk = leader;
2074 i = 0;
2075 /*
2076 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2077 * already PF_EXITING could be freed from underneath us unless we
2078 * take an rcu_read_lock.
2079 */
2080 rcu_read_lock();
2081 do {
2082 struct task_and_cgroup ent;
2084 /* @tsk either already exited or can't exit until the end */
2085 if (tsk->flags & PF_EXITING)
2086 continue;
2088 /* as per above, nr_threads may decrease, but not increase. */
2089 BUG_ON(i >= group_size);
2090 ent.task = tsk;
2091 ent.cgrp = task_cgroup_from_root(tsk, root);
2092 /* nothing to do if this task is already in the cgroup */
2093 if (ent.cgrp == cgrp)
2094 continue;
2095 /*
2096 * saying GFP_ATOMIC has no effect here because we did prealloc
2097 * earlier, but it's good form to communicate our expectations.
2098 */
2099 retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2100 BUG_ON(retval != 0);
2101 i++;
2102 } while_each_thread(leader, tsk);
2103 rcu_read_unlock();
2104 /* remember the number of threads in the array for later. */
2105 group_size = i;
2106 tset.tc_array = group;
2107 tset.tc_array_len = group_size;
2109 /* methods shouldn't be called if no task is actually migrating */
2110 retval = 0;
2111 if (!group_size)
2112 goto out_free_group_list;
2114 /*
2115 * step 1: check that we can legitimately attach to the cgroup.
2116 */
2117 for_each_subsys(root, ss) {
2118 if (ss->can_attach) {
2119 retval = ss->can_attach(cgrp, &tset);
2120 if (retval) {
2121 failed_ss = ss;
2122 goto out_cancel_attach;
2123 }
2124 }
2125 }
2127 /*
2128 * step 2: make sure css_sets exist for all threads to be migrated.
2129 * we use find_css_set, which allocates a new one if necessary.
2130 */
2131 for (i = 0; i < group_size; i++) {
2132 tc = flex_array_get(group, i);
2133 tc->cg = find_css_set(tc->task->cgroups, cgrp);
2134 if (!tc->cg) {
2135 retval = -ENOMEM;
2136 goto out_put_css_set_refs;
2137 }
2138 }
2140 /*
2141 * step 3: now that we're guaranteed success wrt the css_sets,
2142 * proceed to move all tasks to the new cgroup. There are no
2143 * failure cases after here, so this is the commit point.
2144 */
2145 for (i = 0; i < group_size; i++) {
2146 tc = flex_array_get(group, i);
2147 cgroup_task_migrate(cgrp, tc->cgrp, tc->task, tc->cg);
2148 }
2149 /* nothing is sensitive to fork() after this point. */
2151 /*
2152 * step 4: do subsystem attach callbacks.
2153 */
2154 for_each_subsys(root, ss) {
2155 if (ss->attach)
2156 ss->attach(cgrp, &tset);
2157 }
2159 /*
2160 * step 5: success! and cleanup
2161 */
2162 synchronize_rcu();
2163 retval = 0;
2164 out_put_css_set_refs:
2165 if (retval) {
2166 for (i = 0; i < group_size; i++) {
2167 tc = flex_array_get(group, i);
2168 if (!tc->cg)
2169 break;
2170 put_css_set(tc->cg);
2171 }
2172 }
2173 out_cancel_attach:
2174 if (retval) {
2175 for_each_subsys(root, ss) {
2176 if (ss == failed_ss)
2177 break;
2178 if (ss->cancel_attach)
2179 ss->cancel_attach(cgrp, &tset);
2180 }
2181 }
2182 out_free_group_list:
2183 flex_array_free(group);
2184 return retval;
2185 }
2187 /*
2188 * Find the task_struct of the task to attach by vpid and pass it along to the
2189 * function to attach either it or all tasks in its threadgroup. Will lock
2190 * cgroup_mutex and threadgroup; may take task_lock of task.
2191 */
2192 static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2193 {
2194 struct task_struct *tsk;
2195 const struct cred *cred = current_cred(), *tcred;
2196 int ret;
2198 if (!cgroup_lock_live_group(cgrp))
2199 return -ENODEV;
2201 retry_find_task:
2202 rcu_read_lock();
2203 if (pid) {
2204 tsk = find_task_by_vpid(pid);
2205 if (!tsk) {
2206 rcu_read_unlock();
2207 ret= -ESRCH;
2208 goto out_unlock_cgroup;
2209 }
2210 /*
2211 * even if we're attaching all tasks in the thread group, we
2212 * only need to check permissions on one of them.
2213 */
2214 tcred = __task_cred(tsk);
2215 if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
2216 !uid_eq(cred->euid, tcred->uid) &&
2217 !uid_eq(cred->euid, tcred->suid)) {
2218 rcu_read_unlock();
2219 ret = -EACCES;
2220 goto out_unlock_cgroup;
2221 }
2222 } else
2223 tsk = current;
2225 if (threadgroup)
2226 tsk = tsk->group_leader;
2228 /*
2229 * Workqueue threads may acquire PF_THREAD_BOUND and become
2230 * trapped in a cpuset, or RT worker may be born in a cgroup
2231 * with no rt_runtime allocated. Just say no.
2232 */
2233 if (tsk == kthreadd_task || (tsk->flags & PF_THREAD_BOUND)) {
2234 ret = -EINVAL;
2235 rcu_read_unlock();
2236 goto out_unlock_cgroup;
2237 }
2239 get_task_struct(tsk);
2240 rcu_read_unlock();
2242 threadgroup_lock(tsk);
2243 if (threadgroup) {
2244 if (!thread_group_leader(tsk)) {
2245 /*
2246 * a race with de_thread from another thread's exec()
2247 * may strip us of our leadership, if this happens,
2248 * there is no choice but to throw this task away and
2249 * try again; this is
2250 * "double-double-toil-and-trouble-check locking".
2251 */
2252 threadgroup_unlock(tsk);
2253 put_task_struct(tsk);
2254 goto retry_find_task;
2255 }
2256 ret = cgroup_attach_proc(cgrp, tsk);
2257 } else
2258 ret = cgroup_attach_task(cgrp, tsk);
2259 threadgroup_unlock(tsk);
2261 put_task_struct(tsk);
2262 out_unlock_cgroup:
2263 cgroup_unlock();
2264 return ret;
2265 }
2267 static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
2268 {
2269 return attach_task_by_pid(cgrp, pid, false);
2270 }
2272 static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2273 {
2274 return attach_task_by_pid(cgrp, tgid, true);
2275 }
2277 /**
2278 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
2279 * @cgrp: the cgroup to be checked for liveness
2280 *
2281 * On success, returns true; the lock should be later released with
2282 * cgroup_unlock(). On failure returns false with no lock held.
2283 */
2284 bool cgroup_lock_live_group(struct cgroup *cgrp)
2285 {
2286 mutex_lock(&cgroup_mutex);
2287 if (cgroup_is_removed(cgrp)) {
2288 mutex_unlock(&cgroup_mutex);
2289 return false;
2290 }
2291 return true;
2292 }
2293 EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2295 static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
2296 const char *buffer)
2297 {
2298 BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
2299 if (strlen(buffer) >= PATH_MAX)
2300 return -EINVAL;
2301 if (!cgroup_lock_live_group(cgrp))
2302 return -ENODEV;
2303 mutex_lock(&cgroup_root_mutex);
2304 strcpy(cgrp->root->release_agent_path, buffer);
2305 mutex_unlock(&cgroup_root_mutex);
2306 cgroup_unlock();
2307 return 0;
2308 }
2310 static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
2311 struct seq_file *seq)
2312 {
2313 if (!cgroup_lock_live_group(cgrp))
2314 return -ENODEV;
2315 seq_puts(seq, cgrp->root->release_agent_path);
2316 seq_putc(seq, '\n');
2317 cgroup_unlock();
2318 return 0;
2319 }
2321 /* A buffer size big enough for numbers or short strings */
2322 #define CGROUP_LOCAL_BUFFER_SIZE 64
2324 static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2325 struct file *file,
2326 const char __user *userbuf,
2327 size_t nbytes, loff_t *unused_ppos)
2328 {
2329 char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2330 int retval = 0;
2331 char *end;
2333 if (!nbytes)
2334 return -EINVAL;
2335 if (nbytes >= sizeof(buffer))
2336 return -E2BIG;
2337 if (copy_from_user(buffer, userbuf, nbytes))
2338 return -EFAULT;
2340 buffer[nbytes] = 0; /* nul-terminate */
2341 if (cft->write_u64) {
2342 u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2343 if (*end)
2344 return -EINVAL;
2345 retval = cft->write_u64(cgrp, cft, val);
2346 } else {
2347 s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2348 if (*end)
2349 return -EINVAL;
2350 retval = cft->write_s64(cgrp, cft, val);
2351 }
2352 if (!retval)
2353 retval = nbytes;
2354 return retval;
2355 }
2357 static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
2358 struct file *file,
2359 const char __user *userbuf,
2360 size_t nbytes, loff_t *unused_ppos)
2361 {
2362 char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2363 int retval = 0;
2364 size_t max_bytes = cft->max_write_len;
2365 char *buffer = local_buffer;
2367 if (!max_bytes)
2368 max_bytes = sizeof(local_buffer) - 1;
2369 if (nbytes >= max_bytes)
2370 return -E2BIG;
2371 /* Allocate a dynamic buffer if we need one */
2372 if (nbytes >= sizeof(local_buffer)) {
2373 buffer = kmalloc(nbytes + 1, GFP_KERNEL);
2374 if (buffer == NULL)
2375 return -ENOMEM;
2376 }
2377 if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
2378 retval = -EFAULT;
2379 goto out;
2380 }
2382 buffer[nbytes] = 0; /* nul-terminate */
2383 retval = cft->write_string(cgrp, cft, strstrip(buffer));
2384 if (!retval)
2385 retval = nbytes;
2386 out:
2387 if (buffer != local_buffer)
2388 kfree(buffer);
2389 return retval;
2390 }
2392 static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
2393 size_t nbytes, loff_t *ppos)
2394 {
2395 struct cftype *cft = __d_cft(file->f_dentry);
2396 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2398 if (cgroup_is_removed(cgrp))
2399 return -ENODEV;
2400 if (cft->write)
2401 return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2402 if (cft->write_u64 || cft->write_s64)
2403 return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2404 if (cft->write_string)
2405 return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2406 if (cft->trigger) {
2407 int ret = cft->trigger(cgrp, (unsigned int)cft->private);
2408 return ret ? ret : nbytes;
2409 }
2410 return -EINVAL;
2411 }
2413 static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
2414 struct file *file,
2415 char __user *buf, size_t nbytes,
2416 loff_t *ppos)
2417 {
2418 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2419 u64 val = cft->read_u64(cgrp, cft);
2420 int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
2422 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2423 }
2425 static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
2426 struct file *file,
2427 char __user *buf, size_t nbytes,
2428 loff_t *ppos)
2429 {
2430 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2431 s64 val = cft->read_s64(cgrp, cft);
2432 int len = sprintf(tmp, "%lld\n", (long long) val);
2434 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2435 }
2437 static ssize_t cgroup_file_read(struct file *file, char __user *buf,
2438 size_t nbytes, loff_t *ppos)
2439 {
2440 struct cftype *cft = __d_cft(file->f_dentry);
2441 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2443 if (cgroup_is_removed(cgrp))
2444 return -ENODEV;
2446 if (cft->read)
2447 return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2448 if (cft->read_u64)
2449 return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2450 if (cft->read_s64)
2451 return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2452 return -EINVAL;
2453 }
2455 /*
2456 * seqfile ops/methods for returning structured data. Currently just
2457 * supports string->u64 maps, but can be extended in future.
2458 */
2460 struct cgroup_seqfile_state {
2461 struct cftype *cft;
2462 struct cgroup *cgroup;
2463 };
2465 static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
2466 {
2467 struct seq_file *sf = cb->state;
2468 return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
2469 }
2471 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
2472 {
2473 struct cgroup_seqfile_state *state = m->private;
2474 struct cftype *cft = state->cft;
2475 if (cft->read_map) {
2476 struct cgroup_map_cb cb = {
2477 .fill = cgroup_map_add,
2478 .state = m,
2479 };
2480 return cft->read_map(state->cgroup, cft, &cb);
2481 }
2482 return cft->read_seq_string(state->cgroup, cft, m);
2483 }
2485 static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2486 {
2487 struct seq_file *seq = file->private_data;
2488 kfree(seq->private);
2489 return single_release(inode, file);
2490 }
2492 static const struct file_operations cgroup_seqfile_operations = {
2493 .read = seq_read,
2494 .write = cgroup_file_write,
2495 .llseek = seq_lseek,
2496 .release = cgroup_seqfile_release,
2497 };
2499 static int cgroup_file_open(struct inode *inode, struct file *file)
2500 {
2501 int err;
2502 struct cftype *cft;
2504 err = generic_file_open(inode, file);
2505 if (err)
2506 return err;
2507 cft = __d_cft(file->f_dentry);
2509 if (cft->read_map || cft->read_seq_string) {
2510 struct cgroup_seqfile_state *state =
2511 kzalloc(sizeof(*state), GFP_USER);
2512 if (!state)
2513 return -ENOMEM;
2514 state->cft = cft;
2515 state->cgroup = __d_cgrp(file->f_dentry->d_parent);
2516 file->f_op = &cgroup_seqfile_operations;
2517 err = single_open(file, cgroup_seqfile_show, state);
2518 if (err < 0)
2519 kfree(state);
2520 } else if (cft->open)
2521 err = cft->open(inode, file);
2522 else
2523 err = 0;
2525 return err;
2526 }
2528 static int cgroup_file_release(struct inode *inode, struct file *file)
2529 {
2530 struct cftype *cft = __d_cft(file->f_dentry);
2531 if (cft->release)
2532 return cft->release(inode, file);
2533 return 0;
2534 }
2536 /*
2537 * cgroup_rename - Only allow simple rename of directories in place.
2538 */
2539 static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
2540 struct inode *new_dir, struct dentry *new_dentry)
2541 {
2542 if (!S_ISDIR(old_dentry->d_inode->i_mode))
2543 return -ENOTDIR;
2544 if (new_dentry->d_inode)
2545 return -EEXIST;
2546 if (old_dir != new_dir)
2547 return -EIO;
2548 return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
2549 }
2551 static struct simple_xattrs *__d_xattrs(struct dentry *dentry)
2552 {
2553 if (S_ISDIR(dentry->d_inode->i_mode))
2554 return &__d_cgrp(dentry)->xattrs;
2555 else
2556 return &__d_cft(dentry)->xattrs;
2557 }
2559 static inline int xattr_enabled(struct dentry *dentry)
2560 {
2561 struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
2562 return test_bit(ROOT_XATTR, &root->flags);
2563 }
2565 static bool is_valid_xattr(const char *name)
2566 {
2567 if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
2568 !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN))
2569 return true;
2570 return false;
2571 }
2573 static int cgroup_setxattr(struct dentry *dentry, const char *name,
2574 const void *val, size_t size, int flags)
2575 {
2576 if (!xattr_enabled(dentry))
2577 return -EOPNOTSUPP;
2578 if (!is_valid_xattr(name))
2579 return -EINVAL;
2580 return simple_xattr_set(__d_xattrs(dentry), name, val, size, flags);
2581 }
2583 static int cgroup_removexattr(struct dentry *dentry, const char *name)
2584 {
2585 if (!xattr_enabled(dentry))
2586 return -EOPNOTSUPP;
2587 if (!is_valid_xattr(name))
2588 return -EINVAL;
2589 return simple_xattr_remove(__d_xattrs(dentry), name);
2590 }
2592 static ssize_t cgroup_getxattr(struct dentry *dentry, const char *name,
2593 void *buf, size_t size)
2594 {
2595 if (!xattr_enabled(dentry))
2596 return -EOPNOTSUPP;
2597 if (!is_valid_xattr(name))
2598 return -EINVAL;
2599 return simple_xattr_get(__d_xattrs(dentry), name, buf, size);
2600 }
2602 static ssize_t cgroup_listxattr(struct dentry *dentry, char *buf, size_t size)
2603 {
2604 if (!xattr_enabled(dentry))
2605 return -EOPNOTSUPP;
2606 return simple_xattr_list(__d_xattrs(dentry), buf, size);
2607 }
2609 static const struct file_operations cgroup_file_operations = {
2610 .read = cgroup_file_read,
2611 .write = cgroup_file_write,
2612 .llseek = generic_file_llseek,
2613 .open = cgroup_file_open,
2614 .release = cgroup_file_release,
2615 };
2617 static const struct inode_operations cgroup_file_inode_operations = {
2618 .setxattr = cgroup_setxattr,
2619 .getxattr = cgroup_getxattr,
2620 .listxattr = cgroup_listxattr,
2621 .removexattr = cgroup_removexattr,
2622 };
2624 static const struct inode_operations cgroup_dir_inode_operations = {
2625 .lookup = cgroup_lookup,
2626 .mkdir = cgroup_mkdir,
2627 .rmdir = cgroup_rmdir,
2628 .rename = cgroup_rename,
2629 .setxattr = cgroup_setxattr,
2630 .getxattr = cgroup_getxattr,
2631 .listxattr = cgroup_listxattr,
2632 .removexattr = cgroup_removexattr,
2633 };
2635 static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
2636 {
2637 if (dentry->d_name.len > NAME_MAX)
2638 return ERR_PTR(-ENAMETOOLONG);
2639 d_add(dentry, NULL);
2640 return NULL;
2641 }
2643 /*
2644 * Check if a file is a control file
2645 */
2646 static inline struct cftype *__file_cft(struct file *file)
2647 {
2648 if (file->f_dentry->d_inode->i_fop != &cgroup_file_operations)
2649 return ERR_PTR(-EINVAL);
2650 return __d_cft(file->f_dentry);
2651 }
2653 static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2654 struct super_block *sb)
2655 {
2656 struct inode *inode;
2658 if (!dentry)
2659 return -ENOENT;
2660 if (dentry->d_inode)
2661 return -EEXIST;
2663 inode = cgroup_new_inode(mode, sb);
2664 if (!inode)
2665 return -ENOMEM;
2667 if (S_ISDIR(mode)) {
2668 inode->i_op = &cgroup_dir_inode_operations;
2669 inode->i_fop = &simple_dir_operations;
2671 /* start off with i_nlink == 2 (for "." entry) */
2672 inc_nlink(inode);
2673 inc_nlink(dentry->d_parent->d_inode);
2675 /*
2676 * Control reaches here with cgroup_mutex held.
2677 * @inode->i_mutex should nest outside cgroup_mutex but we
2678 * want to populate it immediately without releasing
2679 * cgroup_mutex. As @inode isn't visible to anyone else
2680 * yet, trylock will always succeed without affecting
2681 * lockdep checks.
2682 */
2683 WARN_ON_ONCE(!mutex_trylock(&inode->i_mutex));
2684 } else if (S_ISREG(mode)) {
2685 inode->i_size = 0;
2686 inode->i_fop = &cgroup_file_operations;
2687 inode->i_op = &cgroup_file_inode_operations;
2688 }
2689 d_instantiate(dentry, inode);
2690 dget(dentry); /* Extra count - pin the dentry in core */
2691 return 0;
2692 }
2694 /**
2695 * cgroup_file_mode - deduce file mode of a control file
2696 * @cft: the control file in question
2697 *
2698 * returns cft->mode if ->mode is not 0
2699 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
2700 * returns S_IRUGO if it has only a read handler
2701 * returns S_IWUSR if it has only a write hander
2702 */
2703 static umode_t cgroup_file_mode(const struct cftype *cft)
2704 {
2705 umode_t mode = 0;
2707 if (cft->mode)
2708 return cft->mode;
2710 if (cft->read || cft->read_u64 || cft->read_s64 ||
2711 cft->read_map || cft->read_seq_string)
2712 mode |= S_IRUGO;
2714 if (cft->write || cft->write_u64 || cft->write_s64 ||
2715 cft->write_string || cft->trigger)
2716 mode |= S_IWUSR;
2718 return mode;
2719 }
2721 static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
2722 struct cftype *cft)
2723 {
2724 struct dentry *dir = cgrp->dentry;
2725 struct cgroup *parent = __d_cgrp(dir);
2726 struct dentry *dentry;
2727 struct cfent *cfe;
2728 int error;
2729 umode_t mode;
2730 char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2732 simple_xattrs_init(&cft->xattrs);
2734 if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2735 strcpy(name, subsys->name);
2736 strcat(name, ".");
2737 }
2738 strcat(name, cft->name);
2740 BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
2742 cfe = kzalloc(sizeof(*cfe), GFP_KERNEL);
2743 if (!cfe)
2744 return -ENOMEM;
2746 dentry = lookup_one_len(name, dir, strlen(name));
2747 if (IS_ERR(dentry)) {
2748 error = PTR_ERR(dentry);
2749 goto out;
2750 }
2752 mode = cgroup_file_mode(cft);
2753 error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
2754 if (!error) {
2755 cfe->type = (void *)cft;
2756 cfe->dentry = dentry;
2757 dentry->d_fsdata = cfe;
2758 list_add_tail(&cfe->node, &parent->files);
2759 cfe = NULL;
2760 }
2761 dput(dentry);
2762 out:
2763 kfree(cfe);
2764 return error;
2765 }
2767 static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
2768 struct cftype cfts[], bool is_add)
2769 {
2770 struct cftype *cft;
2771 int err, ret = 0;
2773 for (cft = cfts; cft->name[0] != '\0'; cft++) {
2774 /* does cft->flags tell us to skip this file on @cgrp? */
2775 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
2776 continue;
2777 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
2778 continue;
2780 if (is_add)
2781 err = cgroup_add_file(cgrp, subsys, cft);
2782 else
2783 err = cgroup_rm_file(cgrp, cft);
2784 if (err) {
2785 pr_warning("cgroup_addrm_files: failed to %s %s, err=%d\n",
2786 is_add ? "add" : "remove", cft->name, err);
2787 ret = err;
2788 }
2789 }
2790 return ret;
2791 }
2793 static DEFINE_MUTEX(cgroup_cft_mutex);
2795 static void cgroup_cfts_prepare(void)
2796 __acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex)
2797 {
2798 /*
2799 * Thanks to the entanglement with vfs inode locking, we can't walk
2800 * the existing cgroups under cgroup_mutex and create files.
2801 * Instead, we increment reference on all cgroups and build list of
2802 * them using @cgrp->cft_q_node. Grab cgroup_cft_mutex to ensure
2803 * exclusive access to the field.
2804 */
2805 mutex_lock(&cgroup_cft_mutex);
2806 mutex_lock(&cgroup_mutex);
2807 }
2809 static void cgroup_cfts_commit(struct cgroup_subsys *ss,
2810 struct cftype *cfts, bool is_add)
2811 __releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
2812 {
2813 LIST_HEAD(pending);
2814 struct cgroup *cgrp, *n;
2816 /* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
2817 if (cfts && ss->root != &rootnode) {
2818 list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) {
2819 dget(cgrp->dentry);
2820 list_add_tail(&cgrp->cft_q_node, &pending);
2821 }
2822 }
2824 mutex_unlock(&cgroup_mutex);
2826 /*
2827 * All new cgroups will see @cfts update on @ss->cftsets. Add/rm
2828 * files for all cgroups which were created before.
2829 */
2830 list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {
2831 struct inode *inode = cgrp->dentry->d_inode;
2833 mutex_lock(&inode->i_mutex);
2834 mutex_lock(&cgroup_mutex);
2835 if (!cgroup_is_removed(cgrp))
2836 cgroup_addrm_files(cgrp, ss, cfts, is_add);
2837 mutex_unlock(&cgroup_mutex);
2838 mutex_unlock(&inode->i_mutex);
2840 list_del_init(&cgrp->cft_q_node);
2841 dput(cgrp->dentry);
2842 }
2844 mutex_unlock(&cgroup_cft_mutex);
2845 }
2847 /**
2848 * cgroup_add_cftypes - add an array of cftypes to a subsystem
2849 * @ss: target cgroup subsystem
2850 * @cfts: zero-length name terminated array of cftypes
2851 *
2852 * Register @cfts to @ss. Files described by @cfts are created for all
2853 * existing cgroups to which @ss is attached and all future cgroups will
2854 * have them too. This function can be called anytime whether @ss is
2855 * attached or not.
2856 *
2857 * Returns 0 on successful registration, -errno on failure. Note that this
2858 * function currently returns 0 as long as @cfts registration is successful
2859 * even if some file creation attempts on existing cgroups fail.
2860 */
2861 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2862 {
2863 struct cftype_set *set;
2865 set = kzalloc(sizeof(*set), GFP_KERNEL);
2866 if (!set)
2867 return -ENOMEM;
2869 cgroup_cfts_prepare();
2870 set->cfts = cfts;
2871 list_add_tail(&set->node, &ss->cftsets);
2872 cgroup_cfts_commit(ss, cfts, true);
2874 return 0;
2875 }
2876 EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
2878 /**
2879 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
2880 * @ss: target cgroup subsystem
2881 * @cfts: zero-length name terminated array of cftypes
2882 *
2883 * Unregister @cfts from @ss. Files described by @cfts are removed from
2884 * all existing cgroups to which @ss is attached and all future cgroups
2885 * won't have them either. This function can be called anytime whether @ss
2886 * is attached or not.
2887 *
2888 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
2889 * registered with @ss.
2890 */
2891 int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2892 {
2893 struct cftype_set *set;
2895 cgroup_cfts_prepare();
2897 list_for_each_entry(set, &ss->cftsets, node) {
2898 if (set->cfts == cfts) {
2899 list_del_init(&set->node);
2900 cgroup_cfts_commit(ss, cfts, false);
2901 return 0;
2902 }
2903 }
2905 cgroup_cfts_commit(ss, NULL, false);
2906 return -ENOENT;
2907 }
2909 /**
2910 * cgroup_task_count - count the number of tasks in a cgroup.
2911 * @cgrp: the cgroup in question
2912 *
2913 * Return the number of tasks in the cgroup.
2914 */
2915 int cgroup_task_count(const struct cgroup *cgrp)
2916 {
2917 int count = 0;
2918 struct cg_cgroup_link *link;
2920 read_lock(&css_set_lock);
2921 list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2922 count += atomic_read(&link->cg->refcount);
2923 }
2924 read_unlock(&css_set_lock);
2925 return count;
2926 }
2928 /*
2929 * Advance a list_head iterator. The iterator should be positioned at
2930 * the start of a css_set
2931 */
2932 static void cgroup_advance_iter(struct cgroup *cgrp,
2933 struct cgroup_iter *it)
2934 {
2935 struct list_head *l = it->cg_link;
2936 struct cg_cgroup_link *link;
2937 struct css_set *cg;
2939 /* Advance to the next non-empty css_set */
2940 do {
2941 l = l->next;
2942 if (l == &cgrp->css_sets) {
2943 it->cg_link = NULL;
2944 return;
2945 }
2946 link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2947 cg = link->cg;
2948 } while (list_empty(&cg->tasks));
2949 it->cg_link = l;
2950 it->task = cg->tasks.next;
2951 }
2953 /*
2954 * To reduce the fork() overhead for systems that are not actually
2955 * using their cgroups capability, we don't maintain the lists running
2956 * through each css_set to its tasks until we see the list actually
2957 * used - in other words after the first call to cgroup_iter_start().
2958 */
2959 static void cgroup_enable_task_cg_lists(void)
2960 {
2961 struct task_struct *p, *g;
2962 write_lock(&css_set_lock);
2963 use_task_css_set_links = 1;
2964 /*
2965 * We need tasklist_lock because RCU is not safe against
2966 * while_each_thread(). Besides, a forking task that has passed
2967 * cgroup_post_fork() without seeing use_task_css_set_links = 1
2968 * is not guaranteed to have its child immediately visible in the
2969 * tasklist if we walk through it with RCU.
2970 */
2971 read_lock(&tasklist_lock);
2972 do_each_thread(g, p) {
2973 task_lock(p);
2974 /*
2975 * We should check if the process is exiting, otherwise
2976 * it will race with cgroup_exit() in that the list
2977 * entry won't be deleted though the process has exited.
2978 */
2979 if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
2980 list_add(&p->cg_list, &p->cgroups->tasks);
2981 task_unlock(p);
2982 } while_each_thread(g, p);
2983 read_unlock(&tasklist_lock);
2984 write_unlock(&css_set_lock);
2985 }
2987 /**
2988 * cgroup_next_descendant_pre - find the next descendant for pre-order walk
2989 * @pos: the current position (%NULL to initiate traversal)
2990 * @cgroup: cgroup whose descendants to walk
2991 *
2992 * To be used by cgroup_for_each_descendant_pre(). Find the next
2993 * descendant to visit for pre-order traversal of @cgroup's descendants.
2994 */
2995 struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
2996 struct cgroup *cgroup)
2997 {
2998 struct cgroup *next;
3000 WARN_ON_ONCE(!rcu_read_lock_held());
3002 /* if first iteration, pretend we just visited @cgroup */
3003 if (!pos) {
3004 if (list_empty(&cgroup->children))
3005 return NULL;
3006 pos = cgroup;
3007 }
3009 /* visit the first child if exists */
3010 next = list_first_or_null_rcu(&pos->children, struct cgroup, sibling);
3011 if (next)
3012 return next;
3014 /* no child, visit my or the closest ancestor's next sibling */
3015 do {
3016 next = list_entry_rcu(pos->sibling.next, struct cgroup,
3017 sibling);
3018 if (&next->sibling != &pos->parent->children)
3019 return next;
3021 pos = pos->parent;
3022 } while (pos != cgroup);
3024 return NULL;
3025 }
3026 EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre);
3028 static struct cgroup *cgroup_leftmost_descendant(struct cgroup *pos)
3029 {
3030 struct cgroup *last;
3032 do {
3033 last = pos;
3034 pos = list_first_or_null_rcu(&pos->children, struct cgroup,
3035 sibling);
3036 } while (pos);
3038 return last;
3039 }
3041 /**
3042 * cgroup_next_descendant_post - find the next descendant for post-order walk
3043 * @pos: the current position (%NULL to initiate traversal)
3044 * @cgroup: cgroup whose descendants to walk
3045 *
3046 * To be used by cgroup_for_each_descendant_post(). Find the next
3047 * descendant to visit for post-order traversal of @cgroup's descendants.
3048 */
3049 struct cgroup *cgroup_next_descendant_post(struct cgroup *pos,
3050 struct cgroup *cgroup)
3051 {
3052 struct cgroup *next;
3054 WARN_ON_ONCE(!rcu_read_lock_held());
3056 /* if first iteration, visit the leftmost descendant */
3057 if (!pos) {
3058 next = cgroup_leftmost_descendant(cgroup);
3059 return next != cgroup ? next : NULL;
3060 }
3062 /* if there's an unvisited sibling, visit its leftmost descendant */
3063 next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
3064 if (&next->sibling != &pos->parent->children)
3065 return cgroup_leftmost_descendant(next);
3067 /* no sibling left, visit parent */
3068 next = pos->parent;
3069 return next != cgroup ? next : NULL;
3070 }
3071 EXPORT_SYMBOL_GPL(cgroup_next_descendant_post);
3073 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
3074 __acquires(css_set_lock)
3075 {
3076 /*
3077 * The first time anyone tries to iterate across a cgroup,
3078 * we need to enable the list linking each css_set to its
3079 * tasks, and fix up all existing tasks.
3080 */
3081 if (!use_task_css_set_links)
3082 cgroup_enable_task_cg_lists();
3084 read_lock(&css_set_lock);
3085 it->cg_link = &cgrp->css_sets;
3086 cgroup_advance_iter(cgrp, it);
3087 }
3089 struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
3090 struct cgroup_iter *it)
3091 {
3092 struct task_struct *res;
3093 struct list_head *l = it->task;
3094 struct cg_cgroup_link *link;
3096 /* If the iterator cg is NULL, we have no tasks */
3097 if (!it->cg_link)
3098 return NULL;
3099 res = list_entry(l, struct task_struct, cg_list);
3100 /* Advance iterator to find next entry */
3101 l = l->next;
3102 link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
3103 if (l == &link->cg->tasks) {
3104 /* We reached the end of this task list - move on to
3105 * the next cg_cgroup_link */
3106 cgroup_advance_iter(cgrp, it);
3107 } else {
3108 it->task = l;
3109 }
3110 return res;
3111 }
3113 void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
3114 __releases(css_set_lock)
3115 {
3116 read_unlock(&css_set_lock);
3117 }
3119 static inline int started_after_time(struct task_struct *t1,
3120 struct timespec *time,
3121 struct task_struct *t2)
3122 {
3123 int start_diff = timespec_compare(&t1->start_time, time);
3124 if (start_diff > 0) {
3125 return 1;
3126 } else if (start_diff < 0) {
3127 return 0;
3128 } else {
3129 /*
3130 * Arbitrarily, if two processes started at the same
3131 * time, we'll say that the lower pointer value
3132 * started first. Note that t2 may have exited by now
3133 * so this may not be a valid pointer any longer, but
3134 * that's fine - it still serves to distinguish
3135 * between two tasks started (effectively) simultaneously.
3136 */
3137 return t1 > t2;
3138 }
3139 }
3141 /*
3142 * This function is a callback from heap_insert() and is used to order
3143 * the heap.
3144 * In this case we order the heap in descending task start time.
3145 */
3146 static inline int started_after(void *p1, void *p2)
3147 {
3148 struct task_struct *t1 = p1;
3149 struct task_struct *t2 = p2;
3150 return started_after_time(t1, &t2->start_time, t2);
3151 }
3153 /**
3154 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
3155 * @scan: struct cgroup_scanner containing arguments for the scan
3156 *
3157 * Arguments include pointers to callback functions test_task() and
3158 * process_task().
3159 * Iterate through all the tasks in a cgroup, calling test_task() for each,
3160 * and if it returns true, call process_task() for it also.
3161 * The test_task pointer may be NULL, meaning always true (select all tasks).
3162 * Effectively duplicates cgroup_iter_{start,next,end}()
3163 * but does not lock css_set_lock for the call to process_task().
3164 * The struct cgroup_scanner may be embedded in any structure of the caller's
3165 * creation.
3166 * It is guaranteed that process_task() will act on every task that
3167 * is a member of the cgroup for the duration of this call. This
3168 * function may or may not call process_task() for tasks that exit
3169 * or move to a different cgroup during the call, or are forked or
3170 * move into the cgroup during the call.
3171 *
3172 * Note that test_task() may be called with locks held, and may in some
3173 * situations be called multiple times for the same task, so it should
3174 * be cheap.
3175 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
3176 * pre-allocated and will be used for heap operations (and its "gt" member will
3177 * be overwritten), else a temporary heap will be used (allocation of which
3178 * may cause this function to fail).
3179 */
3180 int cgroup_scan_tasks(struct cgroup_scanner *scan)
3181 {
3182 int retval, i;
3183 struct cgroup_iter it;
3184 struct task_struct *p, *dropped;
3185 /* Never dereference latest_task, since it's not refcounted */
3186 struct task_struct *latest_task = NULL;
3187 struct ptr_heap tmp_heap;
3188 struct ptr_heap *heap;
3189 struct timespec latest_time = { 0, 0 };
3191 if (scan->heap) {
3192 /* The caller supplied our heap and pre-allocated its memory */
3193 heap = scan->heap;
3194 heap->gt = &started_after;
3195 } else {
3196 /* We need to allocate our own heap memory */
3197 heap = &tmp_heap;
3198 retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
3199 if (retval)
3200 /* cannot allocate the heap */
3201 return retval;
3202 }
3204 again:
3205 /*
3206 * Scan tasks in the cgroup, using the scanner's "test_task" callback
3207 * to determine which are of interest, and using the scanner's
3208 * "process_task" callback to process any of them that need an update.
3209 * Since we don't want to hold any locks during the task updates,
3210 * gather tasks to be processed in a heap structure.
3211 * The heap is sorted by descending task start time.
3212 * If the statically-sized heap fills up, we overflow tasks that
3213 * started later, and in future iterations only consider tasks that
3214 * started after the latest task in the previous pass. This
3215 * guarantees forward progress and that we don't miss any tasks.
3216 */
3217 heap->size = 0;
3218 cgroup_iter_start(scan->cg, &it);
3219 while ((p = cgroup_iter_next(scan->cg, &it))) {
3220 /*
3221 * Only affect tasks that qualify per the caller's callback,
3222 * if he provided one
3223 */
3224 if (scan->test_task && !scan->test_task(p, scan))
3225 continue;
3226 /*
3227 * Only process tasks that started after the last task
3228 * we processed
3229 */
3230 if (!started_after_time(p, &latest_time, latest_task))
3231 continue;
3232 dropped = heap_insert(heap, p);
3233 if (dropped == NULL) {
3234 /*
3235 * The new task was inserted; the heap wasn't
3236 * previously full
3237 */
3238 get_task_struct(p);
3239 } else if (dropped != p) {
3240 /*
3241 * The new task was inserted, and pushed out a
3242 * different task
3243 */
3244 get_task_struct(p);
3245 put_task_struct(dropped);
3246 }
3247 /*
3248 * Else the new task was newer than anything already in
3249 * the heap and wasn't inserted
3250 */
3251 }
3252 cgroup_iter_end(scan->cg, &it);
3254 if (heap->size) {
3255 for (i = 0; i < heap->size; i++) {
3256 struct task_struct *q = heap->ptrs[i];
3257 if (i == 0) {
3258 latest_time = q->start_time;
3259 latest_task = q;
3260 }
3261 /* Process the task per the caller's callback */
3262 scan->process_task(q, scan);
3263 put_task_struct(q);
3264 }
3265 /*
3266 * If we had to process any tasks at all, scan again
3267 * in case some of them were in the middle of forking
3268 * children that didn't get processed.
3269 * Not the most efficient way to do it, but it avoids
3270 * having to take callback_mutex in the fork path
3271 */
3272 goto again;
3273 }
3274 if (heap == &tmp_heap)
3275 heap_free(&tmp_heap);
3276 return 0;
3277 }
3279 /*
3280 * Stuff for reading the 'tasks'/'procs' files.
3281 *
3282 * Reading this file can return large amounts of data if a cgroup has
3283 * *lots* of attached tasks. So it may need several calls to read(),
3284 * but we cannot guarantee that the information we produce is correct
3285 * unless we produce it entirely atomically.
3286 *
3287 */
3289 /* which pidlist file are we talking about? */
3290 enum cgroup_filetype {
3291 CGROUP_FILE_PROCS,
3292 CGROUP_FILE_TASKS,
3293 };
3295 /*
3296 * A pidlist is a list of pids that virtually represents the contents of one
3297 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3298 * a pair (one each for procs, tasks) for each pid namespace that's relevant
3299 * to the cgroup.
3300 */
3301 struct cgroup_pidlist {
3302 /*
3303 * used to find which pidlist is wanted. doesn't change as long as
3304 * this particular list stays in the list.
3305 */
3306 struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
3307 /* array of xids */
3308 pid_t *list;
3309 /* how many elements the above list has */
3310 int length;
3311 /* how many files are using the current array */
3312 int use_count;
3313 /* each of these stored in a list by its cgroup */
3314 struct list_head links;
3315 /* pointer to the cgroup we belong to, for list removal purposes */
3316 struct cgroup *owner;
3317 /* protects the other fields */
3318 struct rw_semaphore mutex;
3319 };
3321 /*
3322 * The following two functions "fix" the issue where there are more pids
3323 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3324 * TODO: replace with a kernel-wide solution to this problem
3325 */
3326 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3327 static void *pidlist_allocate(int count)
3328 {
3329 if (PIDLIST_TOO_LARGE(count))
3330 return vmalloc(count * sizeof(pid_t));
3331 else
3332 return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
3333 }
3334 static void pidlist_free(void *p)
3335 {
3336 if (is_vmalloc_addr(p))
3337 vfree(p);
3338 else
3339 kfree(p);
3340 }
3341 static void *pidlist_resize(void *p, int newcount)
3342 {
3343 void *newlist;
3344 /* note: if new alloc fails, old p will still be valid either way */
3345 if (is_vmalloc_addr(p)) {
3346 newlist = vmalloc(newcount * sizeof(pid_t));
3347 if (!newlist)
3348 return NULL;
3349 memcpy(newlist, p, newcount * sizeof(pid_t));
3350 vfree(p);
3351 } else {
3352 newlist = krealloc(p, newcount * sizeof(pid_t), GFP_KERNEL);
3353 }
3354 return newlist;
3355 }
3357 /*
3358 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3359 * If the new stripped list is sufficiently smaller and there's enough memory
3360 * to allocate a new buffer, will let go of the unneeded memory. Returns the
3361 * number of unique elements.
3362 */
3363 /* is the size difference enough that we should re-allocate the array? */
3364 #define PIDLIST_REALLOC_DIFFERENCE(old, new) ((old) - PAGE_SIZE >= (new))
3365 static int pidlist_uniq(pid_t **p, int length)
3366 {
3367 int src, dest = 1;
3368 pid_t *list = *p;
3369 pid_t *newlist;
3371 /*
3372 * we presume the 0th element is unique, so i starts at 1. trivial
3373 * edge cases first; no work needs to be done for either
3374 */
3375 if (length == 0 || length == 1)
3376 return length;
3377 /* src and dest walk down the list; dest counts unique elements */
3378 for (src = 1; src < length; src++) {
3379 /* find next unique element */
3380 while (list[src] == list[src-1]) {
3381 src++;
3382 if (src == length)
3383 goto after;
3384 }
3385 /* dest always points to where the next unique element goes */
3386 list[dest] = list[src];
3387 dest++;
3388 }
3389 after:
3390 /*
3391 * if the length difference is large enough, we want to allocate a
3392 * smaller buffer to save memory. if this fails due to out of memory,
3393 * we'll just stay with what we've got.
3394 */
3395 if (PIDLIST_REALLOC_DIFFERENCE(length, dest)) {
3396 newlist = pidlist_resize(list, dest);
3397 if (newlist)
3398 *p = newlist;
3399 }
3400 return dest;
3401 }
3403 static int cmppid(const void *a, const void *b)
3404 {
3405 return *(pid_t *)a - *(pid_t *)b;
3406 }
3408 /*
3409 * find the appropriate pidlist for our purpose (given procs vs tasks)
3410 * returns with the lock on that pidlist already held, and takes care
3411 * of the use count, or returns NULL with no locks held if we're out of
3412 * memory.
3413 */
3414 static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
3415 enum cgroup_filetype type)
3416 {
3417 struct cgroup_pidlist *l;
3418 /* don't need task_nsproxy() if we're looking at ourself */
3419 struct pid_namespace *ns = task_active_pid_ns(current);
3421 /*
3422 * We can't drop the pidlist_mutex before taking the l->mutex in case
3423 * the last ref-holder is trying to remove l from the list at the same
3424 * time. Holding the pidlist_mutex precludes somebody taking whichever
3425 * list we find out from under us - compare release_pid_array().
3426 */
3427 mutex_lock(&cgrp->pidlist_mutex);
3428 list_for_each_entry(l, &cgrp->pidlists, links) {
3429 if (l->key.type == type && l->key.ns == ns) {
3430 /* make sure l doesn't vanish out from under us */
3431 down_write(&l->mutex);
3432 mutex_unlock(&cgrp->pidlist_mutex);
3433 return l;
3434 }
3435 }
3436 /* entry not found; create a new one */
3437 l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3438 if (!l) {
3439 mutex_unlock(&cgrp->pidlist_mutex);
3440 return l;
3441 }
3442 init_rwsem(&l->mutex);
3443 down_write(&l->mutex);
3444 l->key.type = type;
3445 l->key.ns = get_pid_ns(ns);
3446 l->use_count = 0; /* don't increment here */
3447 l->list = NULL;
3448 l->owner = cgrp;
3449 list_add(&l->links, &cgrp->pidlists);
3450 mutex_unlock(&cgrp->pidlist_mutex);
3451 return l;
3452 }
3454 /*
3455 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3456 */
3457 static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
3458 struct cgroup_pidlist **lp)
3459 {
3460 pid_t *array;
3461 int length;
3462 int pid, n = 0; /* used for populating the array */
3463 struct cgroup_iter it;
3464 struct task_struct *tsk;
3465 struct cgroup_pidlist *l;
3467 /*
3468 * If cgroup gets more users after we read count, we won't have
3469 * enough space - tough. This race is indistinguishable to the
3470 * caller from the case that the additional cgroup users didn't
3471 * show up until sometime later on.
3472 */
3473 length = cgroup_task_count(cgrp);
3474 array = pidlist_allocate(length);
3475 if (!array)
3476 return -ENOMEM;
3477 /* now, populate the array */
3478 cgroup_iter_start(cgrp, &it);
3479 while ((tsk = cgroup_iter_next(cgrp, &it))) {
3480 if (unlikely(n == length))
3481 break;
3482 /* get tgid or pid for procs or tasks file respectively */
3483 if (type == CGROUP_FILE_PROCS)
3484 pid = task_tgid_vnr(tsk);
3485 else
3486 pid = task_pid_vnr(tsk);
3487 if (pid > 0) /* make sure to only use valid results */
3488 array[n++] = pid;
3489 }
3490 cgroup_iter_end(cgrp, &it);
3491 length = n;
3492 /* now sort & (if procs) strip out duplicates */
3493 sort(array, length, sizeof(pid_t), cmppid, NULL);
3494 if (type == CGROUP_FILE_PROCS)
3495 length = pidlist_uniq(&array, length);
3496 l = cgroup_pidlist_find(cgrp, type);
3497 if (!l) {
3498 pidlist_free(array);
3499 return -ENOMEM;
3500 }
3501 /* store array, freeing old if necessary - lock already held */
3502 pidlist_free(l->list);
3503 l->list = array;
3504 l->length = length;
3505 l->use_count++;
3506 up_write(&l->mutex);
3507 *lp = l;
3508 return 0;
3509 }
3511 /**
3512 * cgroupstats_build - build and fill cgroupstats
3513 * @stats: cgroupstats to fill information into
3514 * @dentry: A dentry entry belonging to the cgroup for which stats have
3515 * been requested.
3516 *
3517 * Build and fill cgroupstats so that taskstats can export it to user
3518 * space.
3519 */
3520 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
3521 {
3522 int ret = -EINVAL;
3523 struct cgroup *cgrp;
3524 struct cgroup_iter it;
3525 struct task_struct *tsk;
3527 /*
3528 * Validate dentry by checking the superblock operations,
3529 * and make sure it's a directory.
3530 */
3531 if (dentry->d_sb->s_op != &cgroup_ops ||
3532 !S_ISDIR(dentry->d_inode->i_mode))
3533 goto err;
3535 ret = 0;
3536 cgrp = dentry->d_fsdata;
3538 cgroup_iter_start(cgrp, &it);
3539 while ((tsk = cgroup_iter_next(cgrp, &it))) {
3540 switch (tsk->state) {
3541 case TASK_RUNNING:
3542 stats->nr_running++;
3543 break;
3544 case TASK_INTERRUPTIBLE:
3545 stats->nr_sleeping++;
3546 break;
3547 case TASK_UNINTERRUPTIBLE:
3548 stats->nr_uninterruptible++;
3549 break;
3550 case TASK_STOPPED:
3551 stats->nr_stopped++;
3552 break;
3553 default:
3554 if (delayacct_is_task_waiting_on_io(tsk))
3555 stats->nr_io_wait++;
3556 break;
3557 }
3558 }
3559 cgroup_iter_end(cgrp, &it);
3561 err:
3562 return ret;
3563 }
3566 /*
3567 * seq_file methods for the tasks/procs files. The seq_file position is the
3568 * next pid to display; the seq_file iterator is a pointer to the pid
3569 * in the cgroup->l->list array.
3570 */
3572 static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3573 {
3574 /*
3575 * Initially we receive a position value that corresponds to
3576 * one more than the last pid shown (or 0 on the first call or
3577 * after a seek to the start). Use a binary-search to find the
3578 * next pid to display, if any
3579 */
3580 struct cgroup_pidlist *l = s->private;
3581 int index = 0, pid = *pos;
3582 int *iter;
3584 down_read(&l->mutex);
3585 if (pid) {
3586 int end = l->length;
3588 while (index < end) {
3589 int mid = (index + end) / 2;
3590 if (l->list[mid] == pid) {
3591 index = mid;
3592 break;
3593 } else if (l->list[mid] <= pid)
3594 index = mid + 1;
3595 else
3596 end = mid;
3597 }
3598 }
3599 /* If we're off the end of the array, we're done */
3600 if (index >= l->length)
3601 return NULL;
3602 /* Update the abstract position to be the actual pid that we found */
3603 iter = l->list + index;
3604 *pos = *iter;
3605 return iter;
3606 }
3608 static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3609 {
3610 struct cgroup_pidlist *l = s->private;
3611 up_read(&l->mutex);
3612 }
3614 static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3615 {
3616 struct cgroup_pidlist *l = s->private;
3617 pid_t *p = v;
3618 pid_t *end = l->list + l->length;
3619 /*
3620 * Advance to the next pid in the array. If this goes off the
3621 * end, we're done
3622 */
3623 p++;
3624 if (p >= end) {
3625 return NULL;
3626 } else {
3627 *pos = *p;
3628 return p;
3629 }
3630 }
3632 static int cgroup_pidlist_show(struct seq_file *s, void *v)
3633 {
3634 return seq_printf(s, "%d\n", *(int *)v);
3635 }
3637 /*
3638 * seq_operations functions for iterating on pidlists through seq_file -
3639 * independent of whether it's tasks or procs
3640 */
3641 static const struct seq_operations cgroup_pidlist_seq_operations = {
3642 .start = cgroup_pidlist_start,
3643 .stop = cgroup_pidlist_stop,
3644 .next = cgroup_pidlist_next,
3645 .show = cgroup_pidlist_show,
3646 };
3648 static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3649 {
3650 /*
3651 * the case where we're the last user of this particular pidlist will
3652 * have us remove it from the cgroup's list, which entails taking the
3653 * mutex. since in pidlist_find the pidlist->lock depends on cgroup->
3654 * pidlist_mutex, we have to take pidlist_mutex first.
3655 */
3656 mutex_lock(&l->owner->pidlist_mutex);
3657 down_write(&l->mutex);
3658 BUG_ON(!l->use_count);
3659 if (!--l->use_count) {
3660 /* we're the last user if refcount is 0; remove and free */
3661 list_del(&l->links);
3662 mutex_unlock(&l->owner->pidlist_mutex);
3663 pidlist_free(l->list);
3664 put_pid_ns(l->key.ns);
3665 up_write(&l->mutex);
3666 kfree(l);
3667 return;
3668 }
3669 mutex_unlock(&l->owner->pidlist_mutex);
3670 up_write(&l->mutex);
3671 }
3673 static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3674 {
3675 struct cgroup_pidlist *l;
3676 if (!(file->f_mode & FMODE_READ))
3677 return 0;
3678 /*
3679 * the seq_file will only be initialized if the file was opened for
3680 * reading; hence we check if it's not null only in that case.
3681 */
3682 l = ((struct seq_file *)file->private_data)->private;
3683 cgroup_release_pid_array(l);
3684 return seq_release(inode, file);
3685 }
3687 static const struct file_operations cgroup_pidlist_operations = {
3688 .read = seq_read,
3689 .llseek = seq_lseek,
3690 .write = cgroup_file_write,
3691 .release = cgroup_pidlist_release,
3692 };
3694 /*
3695 * The following functions handle opens on a file that displays a pidlist
3696 * (tasks or procs). Prepare an array of the process/thread IDs of whoever's
3697 * in the cgroup.
3698 */
3699 /* helper function for the two below it */
3700 static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3701 {
3702 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3703 struct cgroup_pidlist *l;
3704 int retval;
3706 /* Nothing to do for write-only files */
3707 if (!(file->f_mode & FMODE_READ))
3708 return 0;
3710 /* have the array populated */
3711 retval = pidlist_array_load(cgrp, type, &l);
3712 if (retval)
3713 return retval;
3714 /* configure file information */
3715 file->f_op = &cgroup_pidlist_operations;
3717 retval = seq_open(file, &cgroup_pidlist_seq_operations);
3718 if (retval) {
3719 cgroup_release_pid_array(l);
3720 return retval;
3721 }
3722 ((struct seq_file *)file->private_data)->private = l;
3723 return 0;
3724 }
3725 static int cgroup_tasks_open(struct inode *unused, struct file *file)
3726 {
3727 return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3728 }
3729 static int cgroup_procs_open(struct inode *unused, struct file *file)
3730 {
3731 return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3732 }
3734 static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3735 struct cftype *cft)
3736 {
3737 return notify_on_release(cgrp);
3738 }
3740 static int cgroup_write_notify_on_release(struct cgroup *cgrp,
3741 struct cftype *cft,
3742 u64 val)
3743 {
3744 clear_bit(CGRP_RELEASABLE, &cgrp->flags);
3745 if (val)
3746 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3747 else
3748 clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3749 return 0;
3750 }
3752 /*
3753 * Unregister event and free resources.
3754 *
3755 * Gets called from workqueue.
3756 */
3757 static void cgroup_event_remove(struct work_struct *work)
3758 {
3759 struct cgroup_event *event = container_of(work, struct cgroup_event,
3760 remove);
3761 struct cgroup *cgrp = event->cgrp;
3763 event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3765 eventfd_ctx_put(event->eventfd);
3766 kfree(event);
3767 dput(cgrp->dentry);
3768 }
3770 /*
3771 * Gets called on POLLHUP on eventfd when user closes it.
3772 *
3773 * Called with wqh->lock held and interrupts disabled.
3774 */
3775 static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
3776 int sync, void *key)
3777 {
3778 struct cgroup_event *event = container_of(wait,
3779 struct cgroup_event, wait);
3780 struct cgroup *cgrp = event->cgrp;
3781 unsigned long flags = (unsigned long)key;
3783 if (flags & POLLHUP) {
3784 __remove_wait_queue(event->wqh, &event->wait);
3785 spin_lock(&cgrp->event_list_lock);
3786 list_del_init(&event->list);
3787 spin_unlock(&cgrp->event_list_lock);
3788 /*
3789 * We are in atomic context, but cgroup_event_remove() may
3790 * sleep, so we have to call it in workqueue.
3791 */
3792 schedule_work(&event->remove);
3793 }
3795 return 0;
3796 }
3798 static void cgroup_event_ptable_queue_proc(struct file *file,
3799 wait_queue_head_t *wqh, poll_table *pt)
3800 {
3801 struct cgroup_event *event = container_of(pt,
3802 struct cgroup_event, pt);
3804 event->wqh = wqh;
3805 add_wait_queue(wqh, &event->wait);
3806 }
3808 /*
3809 * Parse input and register new cgroup event handler.
3810 *
3811 * Input must be in format '<event_fd> <control_fd> <args>'.
3812 * Interpretation of args is defined by control file implementation.
3813 */
3814 static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
3815 const char *buffer)
3816 {
3817 struct cgroup_event *event = NULL;
3818 unsigned int efd, cfd;
3819 struct file *efile = NULL;
3820 struct file *cfile = NULL;
3821 char *endp;
3822 int ret;
3824 efd = simple_strtoul(buffer, &endp, 10);
3825 if (*endp != ' ')
3826 return -EINVAL;
3827 buffer = endp + 1;
3829 cfd = simple_strtoul(buffer, &endp, 10);
3830 if ((*endp != ' ') && (*endp != '\0'))
3831 return -EINVAL;
3832 buffer = endp + 1;
3834 event = kzalloc(sizeof(*event), GFP_KERNEL);
3835 if (!event)
3836 return -ENOMEM;
3837 event->cgrp = cgrp;
3838 INIT_LIST_HEAD(&event->list);
3839 init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
3840 init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
3841 INIT_WORK(&event->remove, cgroup_event_remove);
3843 efile = eventfd_fget(efd);
3844 if (IS_ERR(efile)) {
3845 ret = PTR_ERR(efile);
3846 goto fail;
3847 }
3849 event->eventfd = eventfd_ctx_fileget(efile);
3850 if (IS_ERR(event->eventfd)) {
3851 ret = PTR_ERR(event->eventfd);
3852 goto fail;
3853 }
3855 cfile = fget(cfd);
3856 if (!cfile) {
3857 ret = -EBADF;
3858 goto fail;
3859 }
3861 /* the process need read permission on control file */
3862 /* AV: shouldn't we check that it's been opened for read instead? */
3863 ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3864 if (ret < 0)
3865 goto fail;
3867 event->cft = __file_cft(cfile);
3868 if (IS_ERR(event->cft)) {
3869 ret = PTR_ERR(event->cft);
3870 goto fail;
3871 }
3873 if (!event->cft->register_event || !event->cft->unregister_event) {
3874 ret = -EINVAL;
3875 goto fail;
3876 }
3878 ret = event->cft->register_event(cgrp, event->cft,
3879 event->eventfd, buffer);
3880 if (ret)
3881 goto fail;
3883 if (efile->f_op->poll(efile, &event->pt) & POLLHUP) {
3884 event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3885 ret = 0;
3886 goto fail;
3887 }
3889 /*
3890 * Events should be removed after rmdir of cgroup directory, but before
3891 * destroying subsystem state objects. Let's take reference to cgroup
3892 * directory dentry to do that.
3893 */
3894 dget(cgrp->dentry);
3896 spin_lock(&cgrp->event_list_lock);
3897 list_add(&event->list, &cgrp->event_list);
3898 spin_unlock(&cgrp->event_list_lock);
3900 fput(cfile);
3901 fput(efile);
3903 return 0;
3905 fail:
3906 if (cfile)
3907 fput(cfile);
3909 if (event && event->eventfd && !IS_ERR(event->eventfd))
3910 eventfd_ctx_put(event->eventfd);
3912 if (!IS_ERR_OR_NULL(efile))
3913 fput(efile);
3915 kfree(event);
3917 return ret;
3918 }
3920 static u64 cgroup_clone_children_read(struct cgroup *cgrp,
3921 struct cftype *cft)
3922 {
3923 return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3924 }
3926 static int cgroup_clone_children_write(struct cgroup *cgrp,
3927 struct cftype *cft,
3928 u64 val)
3929 {
3930 if (val)
3931 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3932 else
3933 clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3934 return 0;
3935 }
3937 /*
3938 * for the common functions, 'private' gives the type of file
3939 */
3940 /* for hysterical raisins, we can't put this on the older files */
3941 #define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3942 static struct cftype files[] = {
3943 {
3944 .name = "tasks",
3945 .open = cgroup_tasks_open,
3946 .write_u64 = cgroup_tasks_write,
3947 .release = cgroup_pidlist_release,
3948 .mode = S_IRUGO | S_IWUSR,
3949 },
3950 {
3951 .name = CGROUP_FILE_GENERIC_PREFIX "procs",
3952 .open = cgroup_procs_open,
3953 .write_u64 = cgroup_procs_write,
3954 .release = cgroup_pidlist_release,
3955 .mode = S_IRUGO | S_IWUSR,
3956 },
3957 {
3958 .name = "notify_on_release",
3959 .read_u64 = cgroup_read_notify_on_release,
3960 .write_u64 = cgroup_write_notify_on_release,
3961 },
3962 {
3963 .name = CGROUP_FILE_GENERIC_PREFIX "event_control",
3964 .write_string = cgroup_write_event_control,
3965 .mode = S_IWUGO,
3966 },
3967 {
3968 .name = "cgroup.clone_children",
3969 .read_u64 = cgroup_clone_children_read,
3970 .write_u64 = cgroup_clone_children_write,
3971 },
3972 {
3973 .name = "release_agent",
3974 .flags = CFTYPE_ONLY_ON_ROOT,
3975 .read_seq_string = cgroup_release_agent_show,
3976 .write_string = cgroup_release_agent_write,
3977 .max_write_len = PATH_MAX,
3978 },
3979 { } /* terminate */
3980 };
3982 /**
3983 * cgroup_populate_dir - selectively creation of files in a directory
3984 * @cgrp: target cgroup
3985 * @base_files: true if the base files should be added
3986 * @subsys_mask: mask of the subsystem ids whose files should be added
3987 */
3988 static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
3989 unsigned long subsys_mask)
3990 {
3991 int err;
3992 struct cgroup_subsys *ss;
3994 if (base_files) {
3995 err = cgroup_addrm_files(cgrp, NULL, files, true);
3996 if (err < 0)
3997 return err;
3998 }
4000 /* process cftsets of each subsystem */
4001 for_each_subsys(cgrp->root, ss) {
4002 struct cftype_set *set;
4003 if (!test_bit(ss->subsys_id, &subsys_mask))
4004 continue;
4006 list_for_each_entry(set, &ss->cftsets, node)
4007 cgroup_addrm_files(cgrp, ss, set->cfts, true);
4008 }
4010 /* This cgroup is ready now */
4011 for_each_subsys(cgrp->root, ss) {
4012 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4013 /*
4014 * Update id->css pointer and make this css visible from
4015 * CSS ID functions. This pointer will be dereferened
4016 * from RCU-read-side without locks.
4017 */
4018 if (css->id)
4019 rcu_assign_pointer(css->id->css, css);
4020 }
4022 return 0;
4023 }
4025 static void css_dput_fn(struct work_struct *work)
4026 {
4027 struct cgroup_subsys_state *css =
4028 container_of(work, struct cgroup_subsys_state, dput_work);
4029 struct dentry *dentry = css->cgroup->dentry;
4030 struct super_block *sb = dentry->d_sb;
4032 atomic_inc(&sb->s_active);
4033 dput(dentry);
4034 deactivate_super(sb);
4035 }
4037 static void init_cgroup_css(struct cgroup_subsys_state *css,
4038 struct cgroup_subsys *ss,
4039 struct cgroup *cgrp)
4040 {
4041 css->cgroup = cgrp;
4042 atomic_set(&css->refcnt, 1);
4043 css->flags = 0;
4044 css->id = NULL;
4045 if (cgrp == dummytop)
4046 css->flags |= CSS_ROOT;
4047 BUG_ON(cgrp->subsys[ss->subsys_id]);
4048 cgrp->subsys[ss->subsys_id] = css;
4050 /*
4051 * css holds an extra ref to @cgrp->dentry which is put on the last
4052 * css_put(). dput() requires process context, which css_put() may
4053 * be called without. @css->dput_work will be used to invoke
4054 * dput() asynchronously from css_put().
4055 */
4056 INIT_WORK(&css->dput_work, css_dput_fn);
4057 }
4059 /* invoke ->post_create() on a new CSS and mark it online if successful */
4060 static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
4061 {
4062 int ret = 0;
4064 lockdep_assert_held(&cgroup_mutex);
4066 if (ss->css_online)
4067 ret = ss->css_online(cgrp);
4068 if (!ret)
4069 cgrp->subsys[ss->subsys_id]->flags |= CSS_ONLINE;
4070 return ret;
4071 }
4073 /* if the CSS is online, invoke ->pre_destory() on it and mark it offline */
4074 static void offline_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
4075 __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4076 {
4077 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4079 lockdep_assert_held(&cgroup_mutex);
4081 if (!(css->flags & CSS_ONLINE))
4082 return;
4084 /*
4085 * css_offline() should be called with cgroup_mutex unlocked. See
4086 * 3fa59dfbc3 ("cgroup: fix potential deadlock in pre_destroy") for
4087 * details. This temporary unlocking should go away once
4088 * cgroup_mutex is unexported from controllers.
4089 */
4090 if (ss->css_offline) {
4091 mutex_unlock(&cgroup_mutex);
4092 ss->css_offline(cgrp);
4093 mutex_lock(&cgroup_mutex);
4094 }
4096 cgrp->subsys[ss->subsys_id]->flags &= ~CSS_ONLINE;
4097 }
4099 /*
4100 * cgroup_create - create a cgroup
4101 * @parent: cgroup that will be parent of the new cgroup
4102 * @dentry: dentry of the new cgroup
4103 * @mode: mode to set on new inode
4104 *
4105 * Must be called with the mutex on the parent inode held
4106 */
4107 static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
4108 umode_t mode)
4109 {
4110 struct cgroup *cgrp;
4111 struct cgroupfs_root *root = parent->root;
4112 int err = 0;
4113 struct cgroup_subsys *ss;
4114 struct super_block *sb = root->sb;
4116 /* allocate the cgroup and its ID, 0 is reserved for the root */
4117 cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
4118 if (!cgrp)
4119 return -ENOMEM;
4121 cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);
4122 if (cgrp->id < 0)
4123 goto err_free_cgrp;
4125 /*
4126 * Only live parents can have children. Note that the liveliness
4127 * check isn't strictly necessary because cgroup_mkdir() and
4128 * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
4129 * anyway so that locking is contained inside cgroup proper and we
4130 * don't get nasty surprises if we ever grow another caller.
4131 */
4132 if (!cgroup_lock_live_group(parent)) {
4133 err = -ENODEV;
4134 goto err_free_id;
4135 }
4137 /* Grab a reference on the superblock so the hierarchy doesn't
4138 * get deleted on unmount if there are child cgroups. This
4139 * can be done outside cgroup_mutex, since the sb can't
4140 * disappear while someone has an open control file on the
4141 * fs */
4142 atomic_inc(&sb->s_active);
4144 init_cgroup_housekeeping(cgrp);
4146 cgrp->parent = parent;
4147 cgrp->root = parent->root;
4148 cgrp->top_cgroup = parent->top_cgroup;
4150 if (notify_on_release(parent))
4151 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
4153 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
4154 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4156 for_each_subsys(root, ss) {
4157 struct cgroup_subsys_state *css;
4159 css = ss->css_alloc(cgrp);
4160 if (IS_ERR(css)) {
4161 err = PTR_ERR(css);
4162 goto err_free_all;
4163 }
4164 init_cgroup_css(css, ss, cgrp);
4165 if (ss->use_id) {
4166 err = alloc_css_id(ss, parent, cgrp);
4167 if (err)
4168 goto err_free_all;
4169 }
4170 }
4172 /*
4173 * Create directory. cgroup_create_file() returns with the new
4174 * directory locked on success so that it can be populated without
4175 * dropping cgroup_mutex.
4176 */
4177 err = cgroup_create_file(dentry, S_IFDIR | mode, sb);
4178 if (err < 0)
4179 goto err_free_all;
4180 lockdep_assert_held(&dentry->d_inode->i_mutex);
4182 /* allocation complete, commit to creation */
4183 dentry->d_fsdata = cgrp;
4184 cgrp->dentry = dentry;
4185 list_add_tail(&cgrp->allcg_node, &root->allcg_list);
4186 list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
4187 root->number_of_cgroups++;
4189 /* each css holds a ref to the cgroup's dentry */
4190 for_each_subsys(root, ss)
4191 dget(dentry);
4193 /* creation succeeded, notify subsystems */
4194 for_each_subsys(root, ss) {
4195 err = online_css(ss, cgrp);
4196 if (err)
4197 goto err_destroy;
4199 if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
4200 parent->parent) {
4201 pr_warning("cgroup: %s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
4202 current->comm, current->pid, ss->name);
4203 if (!strcmp(ss->name, "memory"))
4204 pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
4205 ss->warned_broken_hierarchy = true;
4206 }
4207 }
4209 err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
4210 if (err)
4211 goto err_destroy;
4213 mutex_unlock(&cgroup_mutex);
4214 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
4216 return 0;
4218 err_free_all:
4219 for_each_subsys(root, ss) {
4220 if (cgrp->subsys[ss->subsys_id])
4221 ss->css_free(cgrp);
4222 }
4223 mutex_unlock(&cgroup_mutex);
4224 /* Release the reference count that we took on the superblock */
4225 deactivate_super(sb);
4226 err_free_id:
4227 ida_simple_remove(&root->cgroup_ida, cgrp->id);
4228 err_free_cgrp:
4229 kfree(cgrp);
4230 return err;
4232 err_destroy:
4233 cgroup_destroy_locked(cgrp);
4234 mutex_unlock(&cgroup_mutex);
4235 mutex_unlock(&dentry->d_inode->i_mutex);
4236 return err;
4237 }
4239 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
4240 {
4241 struct cgroup *c_parent = dentry->d_parent->d_fsdata;
4243 /* the vfs holds inode->i_mutex already */
4244 return cgroup_create(c_parent, dentry, mode | S_IFDIR);
4245 }
4247 /*
4248 * Check the reference count on each subsystem. Since we already
4249 * established that there are no tasks in the cgroup, if the css refcount
4250 * is also 1, then there should be no outstanding references, so the
4251 * subsystem is safe to destroy. We scan across all subsystems rather than
4252 * using the per-hierarchy linked list of mounted subsystems since we can
4253 * be called via check_for_release() with no synchronization other than
4254 * RCU, and the subsystem linked list isn't RCU-safe.
4255 */
4256 static int cgroup_has_css_refs(struct cgroup *cgrp)
4257 {
4258 int i;
4260 /*
4261 * We won't need to lock the subsys array, because the subsystems
4262 * we're concerned about aren't going anywhere since our cgroup root
4263 * has a reference on them.
4264 */
4265 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4266 struct cgroup_subsys *ss = subsys[i];
4267 struct cgroup_subsys_state *css;
4269 /* Skip subsystems not present or not in this hierarchy */
4270 if (ss == NULL || ss->root != cgrp->root)
4271 continue;
4273 css = cgrp->subsys[ss->subsys_id];
4274 /*
4275 * When called from check_for_release() it's possible
4276 * that by this point the cgroup has been removed
4277 * and the css deleted. But a false-positive doesn't
4278 * matter, since it can only happen if the cgroup
4279 * has been deleted and hence no longer needs the
4280 * release agent to be called anyway.
4281 */
4282 if (css && css_refcnt(css) > 1)
4283 return 1;
4284 }
4285 return 0;
4286 }
4288 static int cgroup_destroy_locked(struct cgroup *cgrp)
4289 __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4290 {
4291 struct dentry *d = cgrp->dentry;
4292 struct cgroup *parent = cgrp->parent;
4293 DEFINE_WAIT(wait);
4294 struct cgroup_event *event, *tmp;
4295 struct cgroup_subsys *ss;
4296 LIST_HEAD(tmp_list);
4298 lockdep_assert_held(&d->d_inode->i_mutex);
4299 lockdep_assert_held(&cgroup_mutex);
4301 if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children))
4302 return -EBUSY;
4304 /*
4305 * Block new css_tryget() by deactivating refcnt and mark @cgrp
4306 * removed. This makes future css_tryget() and child creation
4307 * attempts fail thus maintaining the removal conditions verified
4308 * above.
4309 */
4310 for_each_subsys(cgrp->root, ss) {
4311 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4313 WARN_ON(atomic_read(&css->refcnt) < 0);
4314 atomic_add(CSS_DEACT_BIAS, &css->refcnt);
4315 }
4316 set_bit(CGRP_REMOVED, &cgrp->flags);
4318 /* tell subsystems to initate destruction */
4319 for_each_subsys(cgrp->root, ss)
4320 offline_css(ss, cgrp);
4322 /*
4323 * Put all the base refs. Each css holds an extra reference to the
4324 * cgroup's dentry and cgroup removal proceeds regardless of css
4325 * refs. On the last put of each css, whenever that may be, the
4326 * extra dentry ref is put so that dentry destruction happens only
4327 * after all css's are released.
4328 */
4329 for_each_subsys(cgrp->root, ss)
4330 css_put(cgrp->subsys[ss->subsys_id]);
4332 raw_spin_lock(&release_list_lock);
4333 if (!list_empty(&cgrp->release_list))
4334 list_del_init(&cgrp->release_list);
4335 raw_spin_unlock(&release_list_lock);
4337 /* delete this cgroup from parent->children */
4338 list_del_rcu(&cgrp->sibling);
4339 list_del_init(&cgrp->allcg_node);
4341 dget(d);
4342 cgroup_d_remove_dir(d);
4343 dput(d);
4345 set_bit(CGRP_RELEASABLE, &parent->flags);
4346 check_for_release(parent);
4348 /*
4349 * Unregister events and notify userspace.
4350 * Notify userspace about cgroup removing only after rmdir of cgroup
4351 * directory to avoid race between userspace and kernelspace. Use
4352 * a temporary list to avoid a deadlock with cgroup_event_wake(). Since
4353 * cgroup_event_wake() is called with the wait queue head locked,
4354 * remove_wait_queue() cannot be called while holding event_list_lock.
4355 */
4356 spin_lock(&cgrp->event_list_lock);
4357 list_splice_init(&cgrp->event_list, &tmp_list);
4358 spin_unlock(&cgrp->event_list_lock);
4359 list_for_each_entry_safe(event, tmp, &tmp_list, list) {
4360 list_del_init(&event->list);
4361 remove_wait_queue(event->wqh, &event->wait);
4362 eventfd_signal(event->eventfd, 1);
4363 schedule_work(&event->remove);
4364 }
4366 return 0;
4367 }
4369 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
4370 {
4371 int ret;
4373 mutex_lock(&cgroup_mutex);
4374 ret = cgroup_destroy_locked(dentry->d_fsdata);
4375 mutex_unlock(&cgroup_mutex);
4377 return ret;
4378 }
4380 static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
4381 {
4382 INIT_LIST_HEAD(&ss->cftsets);
4384 /*
4385 * base_cftset is embedded in subsys itself, no need to worry about
4386 * deregistration.
4387 */
4388 if (ss->base_cftypes) {
4389 ss->base_cftset.cfts = ss->base_cftypes;
4390 list_add_tail(&ss->base_cftset.node, &ss->cftsets);
4391 }
4392 }
4394 static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4395 {
4396 struct cgroup_subsys_state *css;
4398 printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4400 mutex_lock(&cgroup_mutex);
4402 /* init base cftset */
4403 cgroup_init_cftsets(ss);
4405 /* Create the top cgroup state for this subsystem */
4406 list_add(&ss->sibling, &rootnode.subsys_list);
4407 ss->root = &rootnode;
4408 css = ss->css_alloc(dummytop);
4409 /* We don't handle early failures gracefully */
4410 BUG_ON(IS_ERR(css));
4411 init_cgroup_css(css, ss, dummytop);
4413 /* Update the init_css_set to contain a subsys
4414 * pointer to this state - since the subsystem is
4415 * newly registered, all tasks and hence the
4416 * init_css_set is in the subsystem's top cgroup. */
4417 init_css_set.subsys[ss->subsys_id] = css;
4419 need_forkexit_callback |= ss->fork || ss->exit;
4421 /* At system boot, before all subsystems have been
4422 * registered, no tasks have been forked, so we don't
4423 * need to invoke fork callbacks here. */
4424 BUG_ON(!list_empty(&init_task.tasks));
4426 ss->active = 1;
4427 BUG_ON(online_css(ss, dummytop));
4429 mutex_unlock(&cgroup_mutex);
4431 /* this function shouldn't be used with modular subsystems, since they
4432 * need to register a subsys_id, among other things */
4433 BUG_ON(ss->module);
4434 }
4436 /**
4437 * cgroup_load_subsys: load and register a modular subsystem at runtime
4438 * @ss: the subsystem to load
4439 *
4440 * This function should be called in a modular subsystem's initcall. If the
4441 * subsystem is built as a module, it will be assigned a new subsys_id and set
4442 * up for use. If the subsystem is built-in anyway, work is delegated to the
4443 * simpler cgroup_init_subsys.
4444 */
4445 int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
4446 {
4447 struct cgroup_subsys_state *css;
4448 int i, ret;
4450 /* check name and function validity */
4451 if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
4452 ss->css_alloc == NULL || ss->css_free == NULL)
4453 return -EINVAL;
4455 /*
4456 * we don't support callbacks in modular subsystems. this check is
4457 * before the ss->module check for consistency; a subsystem that could
4458 * be a module should still have no callbacks even if the user isn't
4459 * compiling it as one.
4460 */
4461 if (ss->fork || ss->exit)
4462 return -EINVAL;
4464 /*
4465 * an optionally modular subsystem is built-in: we want to do nothing,
4466 * since cgroup_init_subsys will have already taken care of it.
4467 */
4468 if (ss->module == NULL) {
4469 /* a sanity check */
4470 BUG_ON(subsys[ss->subsys_id] != ss);
4471 return 0;
4472 }
4474 /* init base cftset */
4475 cgroup_init_cftsets(ss);
4477 mutex_lock(&cgroup_mutex);
4478 subsys[ss->subsys_id] = ss;
4480 /*
4481 * no ss->css_alloc seems to need anything important in the ss
4482 * struct, so this can happen first (i.e. before the rootnode
4483 * attachment).
4484 */
4485 css = ss->css_alloc(dummytop);
4486 if (IS_ERR(css)) {
4487 /* failure case - need to deassign the subsys[] slot. */
4488 subsys[ss->subsys_id] = NULL;
4489 mutex_unlock(&cgroup_mutex);
4490 return PTR_ERR(css);
4491 }
4493 list_add(&ss->sibling, &rootnode.subsys_list);
4494 ss->root = &rootnode;
4496 /* our new subsystem will be attached to the dummy hierarchy. */
4497 init_cgroup_css(css, ss, dummytop);
4498 /* init_idr must be after init_cgroup_css because it sets css->id. */
4499 if (ss->use_id) {
4500 ret = cgroup_init_idr(ss, css);
4501 if (ret)
4502 goto err_unload;
4503 }
4505 /*
4506 * Now we need to entangle the css into the existing css_sets. unlike
4507 * in cgroup_init_subsys, there are now multiple css_sets, so each one
4508 * will need a new pointer to it; done by iterating the css_set_table.
4509 * furthermore, modifying the existing css_sets will corrupt the hash
4510 * table state, so each changed css_set will need its hash recomputed.
4511 * this is all done under the css_set_lock.
4512 */
4513 write_lock(&css_set_lock);
4514 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
4515 struct css_set *cg;
4516 struct hlist_node *node, *tmp;
4517 struct hlist_head *bucket = &css_set_table[i], *new_bucket;
4519 hlist_for_each_entry_safe(cg, node, tmp, bucket, hlist) {
4520 /* skip entries that we already rehashed */
4521 if (cg->subsys[ss->subsys_id])
4522 continue;
4523 /* remove existing entry */
4524 hlist_del(&cg->hlist);
4525 /* set new value */
4526 cg->subsys[ss->subsys_id] = css;
4527 /* recompute hash and restore entry */
4528 new_bucket = css_set_hash(cg->subsys);
4529 hlist_add_head(&cg->hlist, new_bucket);
4530 }
4531 }
4532 write_unlock(&css_set_lock);
4534 ss->active = 1;
4535 ret = online_css(ss, dummytop);
4536 if (ret)
4537 goto err_unload;
4539 /* success! */
4540 mutex_unlock(&cgroup_mutex);
4541 return 0;
4543 err_unload:
4544 mutex_unlock(&cgroup_mutex);
4545 /* @ss can't be mounted here as try_module_get() would fail */
4546 cgroup_unload_subsys(ss);
4547 return ret;
4548 }
4549 EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4551 /**
4552 * cgroup_unload_subsys: unload a modular subsystem
4553 * @ss: the subsystem to unload
4554 *
4555 * This function should be called in a modular subsystem's exitcall. When this
4556 * function is invoked, the refcount on the subsystem's module will be 0, so
4557 * the subsystem will not be attached to any hierarchy.
4558 */
4559 void cgroup_unload_subsys(struct cgroup_subsys *ss)
4560 {
4561 struct cg_cgroup_link *link;
4562 struct hlist_head *hhead;
4564 BUG_ON(ss->module == NULL);
4566 /*
4567 * we shouldn't be called if the subsystem is in use, and the use of
4568 * try_module_get in parse_cgroupfs_options should ensure that it
4569 * doesn't start being used while we're killing it off.
4570 */
4571 BUG_ON(ss->root != &rootnode);
4573 mutex_lock(&cgroup_mutex);
4575 offline_css(ss, dummytop);
4576 ss->active = 0;
4578 if (ss->use_id) {
4579 idr_remove_all(&ss->idr);
4580 idr_destroy(&ss->idr);
4581 }
4583 /* deassign the subsys_id */
4584 subsys[ss->subsys_id] = NULL;
4586 /* remove subsystem from rootnode's list of subsystems */
4587 list_del_init(&ss->sibling);
4589 /*
4590 * disentangle the css from all css_sets attached to the dummytop. as
4591 * in loading, we need to pay our respects to the hashtable gods.
4592 */
4593 write_lock(&css_set_lock);
4594 list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {
4595 struct css_set *cg = link->cg;
4597 hlist_del(&cg->hlist);
4598 cg->subsys[ss->subsys_id] = NULL;
4599 hhead = css_set_hash(cg->subsys);
4600 hlist_add_head(&cg->hlist, hhead);
4601 }
4602 write_unlock(&css_set_lock);
4604 /*
4605 * remove subsystem's css from the dummytop and free it - need to
4606 * free before marking as null because ss->css_free needs the
4607 * cgrp->subsys pointer to find their state. note that this also
4608 * takes care of freeing the css_id.
4609 */
4610 ss->css_free(dummytop);
4611 dummytop->subsys[ss->subsys_id] = NULL;
4613 mutex_unlock(&cgroup_mutex);
4614 }
4615 EXPORT_SYMBOL_GPL(cgroup_unload_subsys);
4617 /**
4618 * cgroup_init_early - cgroup initialization at system boot
4619 *
4620 * Initialize cgroups at system boot, and initialize any
4621 * subsystems that request early init.
4622 */
4623 int __init cgroup_init_early(void)
4624 {
4625 int i;
4626 atomic_set(&init_css_set.refcount, 1);
4627 INIT_LIST_HEAD(&init_css_set.cg_links);
4628 INIT_LIST_HEAD(&init_css_set.tasks);
4629 INIT_HLIST_NODE(&init_css_set.hlist);
4630 css_set_count = 1;
4631 init_cgroup_root(&rootnode);
4632 root_count = 1;
4633 init_task.cgroups = &init_css_set;
4635 init_css_set_link.cg = &init_css_set;
4636 init_css_set_link.cgrp = dummytop;
4637 list_add(&init_css_set_link.cgrp_link_list,
4638 &rootnode.top_cgroup.css_sets);
4639 list_add(&init_css_set_link.cg_link_list,
4640 &init_css_set.cg_links);
4642 for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
4643 INIT_HLIST_HEAD(&css_set_table[i]);
4645 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4646 struct cgroup_subsys *ss = subsys[i];
4648 /* at bootup time, we don't worry about modular subsystems */
4649 if (!ss || ss->module)
4650 continue;
4652 BUG_ON(!ss->name);
4653 BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4654 BUG_ON(!ss->css_alloc);
4655 BUG_ON(!ss->css_free);
4656 if (ss->subsys_id != i) {
4657 printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4658 ss->name, ss->subsys_id);
4659 BUG();
4660 }
4662 if (ss->early_init)
4663 cgroup_init_subsys(ss);
4664 }
4665 return 0;
4666 }
4668 /**
4669 * cgroup_init - cgroup initialization
4670 *
4671 * Register cgroup filesystem and /proc file, and initialize
4672 * any subsystems that didn't request early init.
4673 */
4674 int __init cgroup_init(void)
4675 {
4676 int err;
4677 int i;
4678 struct hlist_head *hhead;
4680 err = bdi_init(&cgroup_backing_dev_info);
4681 if (err)
4682 return err;
4684 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4685 struct cgroup_subsys *ss = subsys[i];
4687 /* at bootup time, we don't worry about modular subsystems */
4688 if (!ss || ss->module)
4689 continue;
4690 if (!ss->early_init)
4691 cgroup_init_subsys(ss);
4692 if (ss->use_id)
4693 cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4694 }
4696 /* Add init_css_set to the hash table */
4697 hhead = css_set_hash(init_css_set.subsys);
4698 hlist_add_head(&init_css_set.hlist, hhead);
4699 BUG_ON(!init_root_id(&rootnode));
4701 cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
4702 if (!cgroup_kobj) {
4703 err = -ENOMEM;
4704 goto out;
4705 }
4707 err = register_filesystem(&cgroup_fs_type);
4708 if (err < 0) {
4709 kobject_put(cgroup_kobj);
4710 goto out;
4711 }
4713 proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4715 out:
4716 if (err)
4717 bdi_destroy(&cgroup_backing_dev_info);
4719 return err;
4720 }
4722 /*
4723 * proc_cgroup_show()
4724 * - Print task's cgroup paths into seq_file, one line for each hierarchy
4725 * - Used for /proc/<pid>/cgroup.
4726 * - No need to task_lock(tsk) on this tsk->cgroup reference, as it
4727 * doesn't really matter if tsk->cgroup changes after we read it,
4728 * and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4729 * anyway. No need to check that tsk->cgroup != NULL, thanks to
4730 * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
4731 * cgroup to top_cgroup.
4732 */
4734 /* TODO: Use a proper seq_file iterator */
4735 static int proc_cgroup_show(struct seq_file *m, void *v)
4736 {
4737 struct pid *pid;
4738 struct task_struct *tsk;
4739 char *buf;
4740 int retval;
4741 struct cgroupfs_root *root;
4743 retval = -ENOMEM;
4744 buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4745 if (!buf)
4746 goto out;
4748 retval = -ESRCH;
4749 pid = m->private;
4750 tsk = get_pid_task(pid, PIDTYPE_PID);
4751 if (!tsk)
4752 goto out_free;
4754 retval = 0;
4756 mutex_lock(&cgroup_mutex);
4758 for_each_active_root(root) {
4759 struct cgroup_subsys *ss;
4760 struct cgroup *cgrp;
4761 int count = 0;
4763 seq_printf(m, "%d:", root->hierarchy_id);
4764 for_each_subsys(root, ss)
4765 seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4766 if (strlen(root->name))
4767 seq_printf(m, "%sname=%s", count ? "," : "",
4768 root->name);
4769 seq_putc(m, ':');
4770 cgrp = task_cgroup_from_root(tsk, root);
4771 retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4772 if (retval < 0)
4773 goto out_unlock;
4774 seq_puts(m, buf);
4775 seq_putc(m, '\n');
4776 }
4778 out_unlock:
4779 mutex_unlock(&cgroup_mutex);
4780 put_task_struct(tsk);
4781 out_free:
4782 kfree(buf);
4783 out:
4784 return retval;
4785 }
4787 static int cgroup_open(struct inode *inode, struct file *file)
4788 {
4789 struct pid *pid = PROC_I(inode)->pid;
4790 return single_open(file, proc_cgroup_show, pid);
4791 }
4793 const struct file_operations proc_cgroup_operations = {
4794 .open = cgroup_open,
4795 .read = seq_read,
4796 .llseek = seq_lseek,
4797 .release = single_release,
4798 };
4800 /* Display information about each subsystem and each hierarchy */
4801 static int proc_cgroupstats_show(struct seq_file *m, void *v)
4802 {
4803 int i;
4805 seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
4806 /*
4807 * ideally we don't want subsystems moving around while we do this.
4808 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
4809 * subsys/hierarchy state.
4810 */
4811 mutex_lock(&cgroup_mutex);
4812 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4813 struct cgroup_subsys *ss = subsys[i];
4814 if (ss == NULL)
4815 continue;
4816 seq_printf(m, "%s\t%d\t%d\t%d\n",
4817 ss->name, ss->root->hierarchy_id,
4818 ss->root->number_of_cgroups, !ss->disabled);
4819 }
4820 mutex_unlock(&cgroup_mutex);
4821 return 0;
4822 }
4824 static int cgroupstats_open(struct inode *inode, struct file *file)
4825 {
4826 return single_open(file, proc_cgroupstats_show, NULL);
4827 }
4829 static const struct file_operations proc_cgroupstats_operations = {
4830 .open = cgroupstats_open,
4831 .read = seq_read,
4832 .llseek = seq_lseek,
4833 .release = single_release,
4834 };
4836 /**
4837 * cgroup_fork - attach newly forked task to its parents cgroup.
4838 * @child: pointer to task_struct of forking parent process.
4839 *
4840 * Description: A task inherits its parent's cgroup at fork().
4841 *
4842 * A pointer to the shared css_set was automatically copied in
4843 * fork.c by dup_task_struct(). However, we ignore that copy, since
4844 * it was not made under the protection of RCU or cgroup_mutex, so
4845 * might no longer be a valid cgroup pointer. cgroup_attach_task() might
4846 * have already changed current->cgroups, allowing the previously
4847 * referenced cgroup group to be removed and freed.
4848 *
4849 * At the point that cgroup_fork() is called, 'current' is the parent
4850 * task, and the passed argument 'child' points to the child task.
4851 */
4852 void cgroup_fork(struct task_struct *child)
4853 {
4854 task_lock(current);
4855 child->cgroups = current->cgroups;
4856 get_css_set(child->cgroups);
4857 task_unlock(current);
4858 INIT_LIST_HEAD(&child->cg_list);
4859 }
4861 /**
4862 * cgroup_post_fork - called on a new task after adding it to the task list
4863 * @child: the task in question
4864 *
4865 * Adds the task to the list running through its css_set if necessary and
4866 * call the subsystem fork() callbacks. Has to be after the task is
4867 * visible on the task list in case we race with the first call to
4868 * cgroup_iter_start() - to guarantee that the new task ends up on its
4869 * list.
4870 */
4871 void cgroup_post_fork(struct task_struct *child)
4872 {
4873 int i;
4875 /*
4876 * use_task_css_set_links is set to 1 before we walk the tasklist
4877 * under the tasklist_lock and we read it here after we added the child
4878 * to the tasklist under the tasklist_lock as well. If the child wasn't
4879 * yet in the tasklist when we walked through it from
4880 * cgroup_enable_task_cg_lists(), then use_task_css_set_links value
4881 * should be visible now due to the paired locking and barriers implied
4882 * by LOCK/UNLOCK: it is written before the tasklist_lock unlock
4883 * in cgroup_enable_task_cg_lists() and read here after the tasklist_lock
4884 * lock on fork.
4885 */
4886 if (use_task_css_set_links) {
4887 write_lock(&css_set_lock);
4888 task_lock(child);
4889 if (list_empty(&child->cg_list))
4890 list_add(&child->cg_list, &child->cgroups->tasks);
4891 task_unlock(child);
4892 write_unlock(&css_set_lock);
4893 }
4895 /*
4896 * Call ss->fork(). This must happen after @child is linked on
4897 * css_set; otherwise, @child might change state between ->fork()
4898 * and addition to css_set.
4899 */
4900 if (need_forkexit_callback) {
4901 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4902 struct cgroup_subsys *ss = subsys[i];
4904 /*
4905 * fork/exit callbacks are supported only for
4906 * builtin subsystems and we don't need further
4907 * synchronization as they never go away.
4908 */
4909 if (!ss || ss->module)
4910 continue;
4912 if (ss->fork)
4913 ss->fork(child);
4914 }
4915 }
4916 }
4918 /**
4919 * cgroup_exit - detach cgroup from exiting task
4920 * @tsk: pointer to task_struct of exiting process
4921 * @run_callback: run exit callbacks?
4922 *
4923 * Description: Detach cgroup from @tsk and release it.
4924 *
4925 * Note that cgroups marked notify_on_release force every task in
4926 * them to take the global cgroup_mutex mutex when exiting.
4927 * This could impact scaling on very large systems. Be reluctant to
4928 * use notify_on_release cgroups where very high task exit scaling
4929 * is required on large systems.
4930 *
4931 * the_top_cgroup_hack:
4932 *
4933 * Set the exiting tasks cgroup to the root cgroup (top_cgroup).
4934 *
4935 * We call cgroup_exit() while the task is still competent to
4936 * handle notify_on_release(), then leave the task attached to the
4937 * root cgroup in each hierarchy for the remainder of its exit.
4938 *
4939 * To do this properly, we would increment the reference count on
4940 * top_cgroup, and near the very end of the kernel/exit.c do_exit()
4941 * code we would add a second cgroup function call, to drop that
4942 * reference. This would just create an unnecessary hot spot on
4943 * the top_cgroup reference count, to no avail.
4944 *
4945 * Normally, holding a reference to a cgroup without bumping its
4946 * count is unsafe. The cgroup could go away, or someone could
4947 * attach us to a different cgroup, decrementing the count on
4948 * the first cgroup that we never incremented. But in this case,
4949 * top_cgroup isn't going away, and either task has PF_EXITING set,
4950 * which wards off any cgroup_attach_task() attempts, or task is a failed
4951 * fork, never visible to cgroup_attach_task.
4952 */
4953 void cgroup_exit(struct task_struct *tsk, int run_callbacks)
4954 {
4955 struct css_set *cg;
4956 int i;
4958 /*
4959 * Unlink from the css_set task list if necessary.
4960 * Optimistically check cg_list before taking
4961 * css_set_lock
4962 */
4963 if (!list_empty(&tsk->cg_list)) {
4964 write_lock(&css_set_lock);
4965 if (!list_empty(&tsk->cg_list))
4966 list_del_init(&tsk->cg_list);
4967 write_unlock(&css_set_lock);
4968 }
4970 /* Reassign the task to the init_css_set. */
4971 task_lock(tsk);
4972 cg = tsk->cgroups;
4973 tsk->cgroups = &init_css_set;
4975 if (run_callbacks && need_forkexit_callback) {
4976 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4977 struct cgroup_subsys *ss = subsys[i];
4979 /* modular subsystems can't use callbacks */
4980 if (!ss || ss->module)
4981 continue;
4983 if (ss->exit) {
4984 struct cgroup *old_cgrp =
4985 rcu_dereference_raw(cg->subsys[i])->cgroup;
4986 struct cgroup *cgrp = task_cgroup(tsk, i);
4987 ss->exit(cgrp, old_cgrp, tsk);
4988 }
4989 }
4990 }
4991 task_unlock(tsk);
4993 if (cg)
4994 put_css_set_taskexit(cg);
4995 }
4997 /**
4998 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
4999 * @cgrp: the cgroup in question
5000 * @task: the task in question
5001 *
5002 * See if @cgrp is a descendant of @task's cgroup in the appropriate
5003 * hierarchy.
5004 *
5005 * If we are sending in dummytop, then presumably we are creating
5006 * the top cgroup in the subsystem.
5007 *
5008 * Called only by the ns (nsproxy) cgroup.
5009 */
5010 int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
5011 {
5012 int ret;
5013 struct cgroup *target;
5015 if (cgrp == dummytop)
5016 return 1;
5018 target = task_cgroup_from_root(task, cgrp->root);
5019 while (cgrp != target && cgrp!= cgrp->top_cgroup)
5020 cgrp = cgrp->parent;
5021 ret = (cgrp == target);
5022 return ret;
5023 }
5025 static void check_for_release(struct cgroup *cgrp)
5026 {
5027 /* All of these checks rely on RCU to keep the cgroup
5028 * structure alive */
5029 if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
5030 && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
5031 /* Control Group is currently removeable. If it's not
5032 * already queued for a userspace notification, queue
5033 * it now */
5034 int need_schedule_work = 0;
5035 raw_spin_lock(&release_list_lock);
5036 if (!cgroup_is_removed(cgrp) &&
5037 list_empty(&cgrp->release_list)) {
5038 list_add(&cgrp->release_list, &release_list);
5039 need_schedule_work = 1;
5040 }
5041 raw_spin_unlock(&release_list_lock);
5042 if (need_schedule_work)
5043 schedule_work(&release_agent_work);
5044 }
5045 }
5047 /* Caller must verify that the css is not for root cgroup */
5048 bool __css_tryget(struct cgroup_subsys_state *css)
5049 {
5050 while (true) {
5051 int t, v;
5053 v = css_refcnt(css);
5054 t = atomic_cmpxchg(&css->refcnt, v, v + 1);
5055 if (likely(t == v))
5056 return true;
5057 else if (t < 0)
5058 return false;
5059 cpu_relax();
5060 }
5061 }
5062 EXPORT_SYMBOL_GPL(__css_tryget);
5064 /* Caller must verify that the css is not for root cgroup */
5065 void __css_put(struct cgroup_subsys_state *css)
5066 {
5067 struct cgroup *cgrp = css->cgroup;
5068 int v;
5070 rcu_read_lock();
5071 v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));
5073 switch (v) {
5074 case 1:
5075 if (notify_on_release(cgrp)) {
5076 set_bit(CGRP_RELEASABLE, &cgrp->flags);
5077 check_for_release(cgrp);
5078 }
5079 break;
5080 case 0:
5081 schedule_work(&css->dput_work);
5082 break;
5083 }
5084 rcu_read_unlock();
5085 }
5086 EXPORT_SYMBOL_GPL(__css_put);
5088 /*
5089 * Notify userspace when a cgroup is released, by running the
5090 * configured release agent with the name of the cgroup (path
5091 * relative to the root of cgroup file system) as the argument.
5092 *
5093 * Most likely, this user command will try to rmdir this cgroup.
5094 *
5095 * This races with the possibility that some other task will be
5096 * attached to this cgroup before it is removed, or that some other
5097 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
5098 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
5099 * unused, and this cgroup will be reprieved from its death sentence,
5100 * to continue to serve a useful existence. Next time it's released,
5101 * we will get notified again, if it still has 'notify_on_release' set.
5102 *
5103 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
5104 * means only wait until the task is successfully execve()'d. The
5105 * separate release agent task is forked by call_usermodehelper(),
5106 * then control in this thread returns here, without waiting for the
5107 * release agent task. We don't bother to wait because the caller of
5108 * this routine has no use for the exit status of the release agent
5109 * task, so no sense holding our caller up for that.
5110 */
5111 static void cgroup_release_agent(struct work_struct *work)
5112 {
5113 BUG_ON(work != &release_agent_work);
5114 mutex_lock(&cgroup_mutex);
5115 raw_spin_lock(&release_list_lock);
5116 while (!list_empty(&release_list)) {
5117 char *argv[3], *envp[3];
5118 int i;
5119 char *pathbuf = NULL, *agentbuf = NULL;
5120 struct cgroup *cgrp = list_entry(release_list.next,
5121 struct cgroup,
5122 release_list);
5123 list_del_init(&cgrp->release_list);
5124 raw_spin_unlock(&release_list_lock);
5125 pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
5126 if (!pathbuf)
5127 goto continue_free;
5128 if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
5129 goto continue_free;
5130 agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
5131 if (!agentbuf)
5132 goto continue_free;
5134 i = 0;
5135 argv[i++] = agentbuf;
5136 argv[i++] = pathbuf;
5137 argv[i] = NULL;
5139 i = 0;
5140 /* minimal command environment */
5141 envp[i++] = "HOME=/";
5142 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
5143 envp[i] = NULL;
5145 /* Drop the lock while we invoke the usermode helper,
5146 * since the exec could involve hitting disk and hence
5147 * be a slow process */
5148 mutex_unlock(&cgroup_mutex);
5149 call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
5150 mutex_lock(&cgroup_mutex);
5151 continue_free:
5152 kfree(pathbuf);
5153 kfree(agentbuf);
5154 raw_spin_lock(&release_list_lock);
5155 }
5156 raw_spin_unlock(&release_list_lock);
5157 mutex_unlock(&cgroup_mutex);
5158 }
5160 static int __init cgroup_disable(char *str)
5161 {
5162 int i;
5163 char *token;
5165 while ((token = strsep(&str, ",")) != NULL) {
5166 if (!*token)
5167 continue;
5168 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
5169 struct cgroup_subsys *ss = subsys[i];
5171 /*
5172 * cgroup_disable, being at boot time, can't
5173 * know about module subsystems, so we don't
5174 * worry about them.
5175 */
5176 if (!ss || ss->module)
5177 continue;
5179 if (!strcmp(token, ss->name)) {
5180 ss->disabled = 1;
5181 printk(KERN_INFO "Disabling %s control group"
5182 " subsystem\n", ss->name);
5183 break;
5184 }
5185 }
5186 }
5187 return 1;
5188 }
5189 __setup("cgroup_disable=", cgroup_disable);
5191 /*
5192 * Functons for CSS ID.
5193 */
5195 /*
5196 *To get ID other than 0, this should be called when !cgroup_is_removed().
5197 */
5198 unsigned short css_id(struct cgroup_subsys_state *css)
5199 {
5200 struct css_id *cssid;
5202 /*
5203 * This css_id() can return correct value when somone has refcnt
5204 * on this or this is under rcu_read_lock(). Once css->id is allocated,
5205 * it's unchanged until freed.
5206 */
5207 cssid = rcu_dereference_check(css->id, css_refcnt(css));
5209 if (cssid)
5210 return cssid->id;
5211 return 0;
5212 }
5213 EXPORT_SYMBOL_GPL(css_id);
5215 unsigned short css_depth(struct cgroup_subsys_state *css)
5216 {
5217 struct css_id *cssid;
5219 cssid = rcu_dereference_check(css->id, css_refcnt(css));
5221 if (cssid)
5222 return cssid->depth;
5223 return 0;
5224 }
5225 EXPORT_SYMBOL_GPL(css_depth);
5227 /**
5228 * css_is_ancestor - test "root" css is an ancestor of "child"
5229 * @child: the css to be tested.
5230 * @root: the css supporsed to be an ancestor of the child.
5231 *
5232 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
5233 * this function reads css->id, the caller must hold rcu_read_lock().
5234 * But, considering usual usage, the csses should be valid objects after test.
5235 * Assuming that the caller will do some action to the child if this returns
5236 * returns true, the caller must take "child";s reference count.
5237 * If "child" is valid object and this returns true, "root" is valid, too.
5238 */
5240 bool css_is_ancestor(struct cgroup_subsys_state *child,
5241 const struct cgroup_subsys_state *root)
5242 {
5243 struct css_id *child_id;
5244 struct css_id *root_id;
5246 child_id = rcu_dereference(child->id);
5247 if (!child_id)
5248 return false;
5249 root_id = rcu_dereference(root->id);
5250 if (!root_id)
5251 return false;
5252 if (child_id->depth < root_id->depth)
5253 return false;
5254 if (child_id->stack[root_id->depth] != root_id->id)
5255 return false;
5256 return true;
5257 }
5259 void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
5260 {
5261 struct css_id *id = css->id;
5262 /* When this is called before css_id initialization, id can be NULL */
5263 if (!id)
5264 return;
5266 BUG_ON(!ss->use_id);
5268 rcu_assign_pointer(id->css, NULL);
5269 rcu_assign_pointer(css->id, NULL);
5270 spin_lock(&ss->id_lock);
5271 idr_remove(&ss->idr, id->id);
5272 spin_unlock(&ss->id_lock);
5273 kfree_rcu(id, rcu_head);
5274 }
5275 EXPORT_SYMBOL_GPL(free_css_id);
5277 /*
5278 * This is called by init or create(). Then, calls to this function are
5279 * always serialized (By cgroup_mutex() at create()).
5280 */
5282 static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
5283 {
5284 struct css_id *newid;
5285 int myid, error, size;
5287 BUG_ON(!ss->use_id);
5289 size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
5290 newid = kzalloc(size, GFP_KERNEL);
5291 if (!newid)
5292 return ERR_PTR(-ENOMEM);
5293 /* get id */
5294 if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
5295 error = -ENOMEM;
5296 goto err_out;
5297 }
5298 spin_lock(&ss->id_lock);
5299 /* Don't use 0. allocates an ID of 1-65535 */
5300 error = idr_get_new_above(&ss->idr, newid, 1, &myid);
5301 spin_unlock(&ss->id_lock);
5303 /* Returns error when there are no free spaces for new ID.*/
5304 if (error) {
5305 error = -ENOSPC;
5306 goto err_out;
5307 }
5308 if (myid > CSS_ID_MAX)
5309 goto remove_idr;
5311 newid->id = myid;
5312 newid->depth = depth;
5313 return newid;
5314 remove_idr:
5315 error = -ENOSPC;
5316 spin_lock(&ss->id_lock);
5317 idr_remove(&ss->idr, myid);
5318 spin_unlock(&ss->id_lock);
5319 err_out:
5320 kfree(newid);
5321 return ERR_PTR(error);
5323 }
5325 static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
5326 struct cgroup_subsys_state *rootcss)
5327 {
5328 struct css_id *newid;
5330 spin_lock_init(&ss->id_lock);
5331 idr_init(&ss->idr);
5333 newid = get_new_cssid(ss, 0);
5334 if (IS_ERR(newid))
5335 return PTR_ERR(newid);
5337 newid->stack[0] = newid->id;
5338 newid->css = rootcss;
5339 rootcss->id = newid;
5340 return 0;
5341 }
5343 static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
5344 struct cgroup *child)
5345 {
5346 int subsys_id, i, depth = 0;
5347 struct cgroup_subsys_state *parent_css, *child_css;
5348 struct css_id *child_id, *parent_id;
5350 subsys_id = ss->subsys_id;
5351 parent_css = parent->subsys[subsys_id];
5352 child_css = child->subsys[subsys_id];
5353 parent_id = parent_css->id;
5354 depth = parent_id->depth + 1;
5356 child_id = get_new_cssid(ss, depth);
5357 if (IS_ERR(child_id))
5358 return PTR_ERR(child_id);
5360 for (i = 0; i < depth; i++)
5361 child_id->stack[i] = parent_id->stack[i];
5362 child_id->stack[depth] = child_id->id;
5363 /*
5364 * child_id->css pointer will be set after this cgroup is available
5365 * see cgroup_populate_dir()
5366 */
5367 rcu_assign_pointer(child_css->id, child_id);
5369 return 0;
5370 }
5372 /**
5373 * css_lookup - lookup css by id
5374 * @ss: cgroup subsys to be looked into.
5375 * @id: the id
5376 *
5377 * Returns pointer to cgroup_subsys_state if there is valid one with id.
5378 * NULL if not. Should be called under rcu_read_lock()
5379 */
5380 struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
5381 {
5382 struct css_id *cssid = NULL;
5384 BUG_ON(!ss->use_id);
5385 cssid = idr_find(&ss->idr, id);
5387 if (unlikely(!cssid))
5388 return NULL;
5390 return rcu_dereference(cssid->css);
5391 }
5392 EXPORT_SYMBOL_GPL(css_lookup);
5394 /**
5395 * css_get_next - lookup next cgroup under specified hierarchy.
5396 * @ss: pointer to subsystem
5397 * @id: current position of iteration.
5398 * @root: pointer to css. search tree under this.
5399 * @foundid: position of found object.
5400 *
5401 * Search next css under the specified hierarchy of rootid. Calling under
5402 * rcu_read_lock() is necessary. Returns NULL if it reaches the end.
5403 */
5404 struct cgroup_subsys_state *
5405 css_get_next(struct cgroup_subsys *ss, int id,
5406 struct cgroup_subsys_state *root, int *foundid)
5407 {
5408 struct cgroup_subsys_state *ret = NULL;
5409 struct css_id *tmp;
5410 int tmpid;
5411 int rootid = css_id(root);
5412 int depth = css_depth(root);
5414 if (!rootid)
5415 return NULL;
5417 BUG_ON(!ss->use_id);
5418 WARN_ON_ONCE(!rcu_read_lock_held());
5420 /* fill start point for scan */
5421 tmpid = id;
5422 while (1) {
5423 /*
5424 * scan next entry from bitmap(tree), tmpid is updated after
5425 * idr_get_next().
5426 */
5427 tmp = idr_get_next(&ss->idr, &tmpid);
5428 if (!tmp)
5429 break;
5430 if (tmp->depth >= depth && tmp->stack[depth] == rootid) {
5431 ret = rcu_dereference(tmp->css);
5432 if (ret) {
5433 *foundid = tmpid;
5434 break;
5435 }
5436 }
5437 /* continue to scan from next id */
5438 tmpid = tmpid + 1;
5439 }
5440 return ret;
5441 }
5443 /*
5444 * get corresponding css from file open on cgroupfs directory
5445 */
5446 struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
5447 {
5448 struct cgroup *cgrp;
5449 struct inode *inode;
5450 struct cgroup_subsys_state *css;
5452 inode = f->f_dentry->d_inode;
5453 /* check in cgroup filesystem dir */
5454 if (inode->i_op != &cgroup_dir_inode_operations)
5455 return ERR_PTR(-EBADF);
5457 if (id < 0 || id >= CGROUP_SUBSYS_COUNT)
5458 return ERR_PTR(-EINVAL);
5460 /* get cgroup */
5461 cgrp = __d_cgrp(f->f_dentry);
5462 css = cgrp->subsys[id];
5463 return css ? css : ERR_PTR(-ENOENT);
5464 }
5466 #ifdef CONFIG_CGROUP_DEBUG
5467 static struct cgroup_subsys_state *debug_css_alloc(struct cgroup *cont)
5468 {
5469 struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
5471 if (!css)
5472 return ERR_PTR(-ENOMEM);
5474 return css;
5475 }
5477 static void debug_css_free(struct cgroup *cont)
5478 {
5479 kfree(cont->subsys[debug_subsys_id]);
5480 }
5482 static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
5483 {
5484 return atomic_read(&cont->count);
5485 }
5487 static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft)
5488 {
5489 return cgroup_task_count(cont);
5490 }
5492 static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
5493 {
5494 return (u64)(unsigned long)current->cgroups;
5495 }
5497 static u64 current_css_set_refcount_read(struct cgroup *cont,
5498 struct cftype *cft)
5499 {
5500 u64 count;
5502 rcu_read_lock();
5503 count = atomic_read(¤t->cgroups->refcount);
5504 rcu_read_unlock();
5505 return count;
5506 }
5508 static int current_css_set_cg_links_read(struct cgroup *cont,
5509 struct cftype *cft,
5510 struct seq_file *seq)
5511 {
5512 struct cg_cgroup_link *link;
5513 struct css_set *cg;
5515 read_lock(&css_set_lock);
5516 rcu_read_lock();
5517 cg = rcu_dereference(current->cgroups);
5518 list_for_each_entry(link, &cg->cg_links, cg_link_list) {
5519 struct cgroup *c = link->cgrp;
5520 const char *name;
5522 if (c->dentry)
5523 name = c->dentry->d_name.name;
5524 else
5525 name = "?";
5526 seq_printf(seq, "Root %d group %s\n",
5527 c->root->hierarchy_id, name);
5528 }
5529 rcu_read_unlock();
5530 read_unlock(&css_set_lock);
5531 return 0;
5532 }
5534 #define MAX_TASKS_SHOWN_PER_CSS 25
5535 static int cgroup_css_links_read(struct cgroup *cont,
5536 struct cftype *cft,
5537 struct seq_file *seq)
5538 {
5539 struct cg_cgroup_link *link;
5541 read_lock(&css_set_lock);
5542 list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
5543 struct css_set *cg = link->cg;
5544 struct task_struct *task;
5545 int count = 0;
5546 seq_printf(seq, "css_set %p\n", cg);
5547 list_for_each_entry(task, &cg->tasks, cg_list) {
5548 if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
5549 seq_puts(seq, " ...\n");
5550 break;
5551 } else {
5552 seq_printf(seq, " task %d\n",
5553 task_pid_vnr(task));
5554 }
5555 }
5556 }
5557 read_unlock(&css_set_lock);
5558 return 0;
5559 }
5561 static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
5562 {
5563 return test_bit(CGRP_RELEASABLE, &cgrp->flags);
5564 }
5566 static struct cftype debug_files[] = {
5567 {
5568 .name = "cgroup_refcount",
5569 .read_u64 = cgroup_refcount_read,
5570 },
5571 {
5572 .name = "taskcount",
5573 .read_u64 = debug_taskcount_read,
5574 },
5576 {
5577 .name = "current_css_set",
5578 .read_u64 = current_css_set_read,
5579 },
5581 {
5582 .name = "current_css_set_refcount",
5583 .read_u64 = current_css_set_refcount_read,
5584 },
5586 {
5587 .name = "current_css_set_cg_links",
5588 .read_seq_string = current_css_set_cg_links_read,
5589 },
5591 {
5592 .name = "cgroup_css_links",
5593 .read_seq_string = cgroup_css_links_read,
5594 },
5596 {
5597 .name = "releasable",
5598 .read_u64 = releasable_read,
5599 },
5601 { } /* terminate */
5602 };
5604 struct cgroup_subsys debug_subsys = {
5605 .name = "debug",
5606 .css_alloc = debug_css_alloc,
5607 .css_free = debug_css_free,
5608 .subsys_id = debug_subsys_id,
5609 .base_cftypes = debug_files,
5610 };
5611 #endif /* CONFIG_CGROUP_DEBUG */