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;
166 /* file xattrs */
167 struct simple_xattrs xattrs;
168 };
170 /*
171 * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
172 * cgroup_subsys->use_id != 0.
173 */
174 #define CSS_ID_MAX (65535)
175 struct css_id {
176 /*
177 * The css to which this ID points. This pointer is set to valid value
178 * after cgroup is populated. If cgroup is removed, this will be NULL.
179 * This pointer is expected to be RCU-safe because destroy()
180 * is called after synchronize_rcu(). But for safe use, css_tryget()
181 * should be used for avoiding race.
182 */
183 struct cgroup_subsys_state __rcu *css;
184 /*
185 * ID of this css.
186 */
187 unsigned short id;
188 /*
189 * Depth in hierarchy which this ID belongs to.
190 */
191 unsigned short depth;
192 /*
193 * ID is freed by RCU. (and lookup routine is RCU safe.)
194 */
195 struct rcu_head rcu_head;
196 /*
197 * Hierarchy of CSS ID belongs to.
198 */
199 unsigned short stack[0]; /* Array of Length (depth+1) */
200 };
202 /*
203 * cgroup_event represents events which userspace want to receive.
204 */
205 struct cgroup_event {
206 /*
207 * Cgroup which the event belongs to.
208 */
209 struct cgroup *cgrp;
210 /*
211 * Control file which the event associated.
212 */
213 struct cftype *cft;
214 /*
215 * eventfd to signal userspace about the event.
216 */
217 struct eventfd_ctx *eventfd;
218 /*
219 * Each of these stored in a list by the cgroup.
220 */
221 struct list_head list;
222 /*
223 * All fields below needed to unregister event when
224 * userspace closes eventfd.
225 */
226 poll_table pt;
227 wait_queue_head_t *wqh;
228 wait_queue_t wait;
229 struct work_struct remove;
230 };
232 /* The list of hierarchy roots */
234 static LIST_HEAD(roots);
235 static int root_count;
237 static DEFINE_IDA(hierarchy_ida);
238 static int next_hierarchy_id;
239 static DEFINE_SPINLOCK(hierarchy_id_lock);
241 /* dummytop is a shorthand for the dummy hierarchy's top cgroup */
242 #define dummytop (&rootnode.top_cgroup)
244 /* This flag indicates whether tasks in the fork and exit paths should
245 * check for fork/exit handlers to call. This avoids us having to do
246 * extra work in the fork/exit path if none of the subsystems need to
247 * be called.
248 */
249 static int need_forkexit_callback __read_mostly;
251 static int cgroup_destroy_locked(struct cgroup *cgrp);
252 static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
253 struct cftype cfts[], bool is_add);
255 #ifdef CONFIG_PROVE_LOCKING
256 int cgroup_lock_is_held(void)
257 {
258 return lockdep_is_held(&cgroup_mutex);
259 }
260 #else /* #ifdef CONFIG_PROVE_LOCKING */
261 int cgroup_lock_is_held(void)
262 {
263 return mutex_is_locked(&cgroup_mutex);
264 }
265 #endif /* #else #ifdef CONFIG_PROVE_LOCKING */
267 EXPORT_SYMBOL_GPL(cgroup_lock_is_held);
269 static int css_unbias_refcnt(int refcnt)
270 {
271 return refcnt >= 0 ? refcnt : refcnt - CSS_DEACT_BIAS;
272 }
274 /* the current nr of refs, always >= 0 whether @css is deactivated or not */
275 static int css_refcnt(struct cgroup_subsys_state *css)
276 {
277 int v = atomic_read(&css->refcnt);
279 return css_unbias_refcnt(v);
280 }
282 /* convenient tests for these bits */
283 inline int cgroup_is_removed(const struct cgroup *cgrp)
284 {
285 return test_bit(CGRP_REMOVED, &cgrp->flags);
286 }
288 /* bits in struct cgroupfs_root flags field */
289 enum {
290 ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
291 ROOT_XATTR, /* supports extended attributes */
292 };
294 static int cgroup_is_releasable(const struct cgroup *cgrp)
295 {
296 const int bits =
297 (1 << CGRP_RELEASABLE) |
298 (1 << CGRP_NOTIFY_ON_RELEASE);
299 return (cgrp->flags & bits) == bits;
300 }
302 static int notify_on_release(const struct cgroup *cgrp)
303 {
304 return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
305 }
307 /*
308 * for_each_subsys() allows you to iterate on each subsystem attached to
309 * an active hierarchy
310 */
311 #define for_each_subsys(_root, _ss) \
312 list_for_each_entry(_ss, &_root->subsys_list, sibling)
314 /* for_each_active_root() allows you to iterate across the active hierarchies */
315 #define for_each_active_root(_root) \
316 list_for_each_entry(_root, &roots, root_list)
318 static inline struct cgroup *__d_cgrp(struct dentry *dentry)
319 {
320 return dentry->d_fsdata;
321 }
323 static inline struct cfent *__d_cfe(struct dentry *dentry)
324 {
325 return dentry->d_fsdata;
326 }
328 static inline struct cftype *__d_cft(struct dentry *dentry)
329 {
330 return __d_cfe(dentry)->type;
331 }
333 /* the list of cgroups eligible for automatic release. Protected by
334 * release_list_lock */
335 static LIST_HEAD(release_list);
336 static DEFINE_RAW_SPINLOCK(release_list_lock);
337 static void cgroup_release_agent(struct work_struct *work);
338 static DECLARE_WORK(release_agent_work, cgroup_release_agent);
339 static void check_for_release(struct cgroup *cgrp);
341 /* Link structure for associating css_set objects with cgroups */
342 struct cg_cgroup_link {
343 /*
344 * List running through cg_cgroup_links associated with a
345 * cgroup, anchored on cgroup->css_sets
346 */
347 struct list_head cgrp_link_list;
348 struct cgroup *cgrp;
349 /*
350 * List running through cg_cgroup_links pointing at a
351 * single css_set object, anchored on css_set->cg_links
352 */
353 struct list_head cg_link_list;
354 struct css_set *cg;
355 };
357 /* The default css_set - used by init and its children prior to any
358 * hierarchies being mounted. It contains a pointer to the root state
359 * for each subsystem. Also used to anchor the list of css_sets. Not
360 * reference-counted, to improve performance when child cgroups
361 * haven't been created.
362 */
364 static struct css_set init_css_set;
365 static struct cg_cgroup_link init_css_set_link;
367 static int cgroup_init_idr(struct cgroup_subsys *ss,
368 struct cgroup_subsys_state *css);
370 /* css_set_lock protects the list of css_set objects, and the
371 * chain of tasks off each css_set. Nests outside task->alloc_lock
372 * due to cgroup_iter_start() */
373 static DEFINE_RWLOCK(css_set_lock);
374 static int css_set_count;
376 /*
377 * hash table for cgroup groups. This improves the performance to find
378 * an existing css_set. This hash doesn't (currently) take into
379 * account cgroups in empty hierarchies.
380 */
381 #define CSS_SET_HASH_BITS 7
382 #define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS)
383 static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
385 static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
386 {
387 int i;
388 int index;
389 unsigned long tmp = 0UL;
391 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
392 tmp += (unsigned long)css[i];
393 tmp = (tmp >> 16) ^ tmp;
395 index = hash_long(tmp, CSS_SET_HASH_BITS);
397 return &css_set_table[index];
398 }
400 /* We don't maintain the lists running through each css_set to its
401 * task until after the first call to cgroup_iter_start(). This
402 * reduces the fork()/exit() overhead for people who have cgroups
403 * compiled into their kernel but not actually in use */
404 static int use_task_css_set_links __read_mostly;
406 static void __put_css_set(struct css_set *cg, int taskexit)
407 {
408 struct cg_cgroup_link *link;
409 struct cg_cgroup_link *saved_link;
410 /*
411 * Ensure that the refcount doesn't hit zero while any readers
412 * can see it. Similar to atomic_dec_and_lock(), but for an
413 * rwlock
414 */
415 if (atomic_add_unless(&cg->refcount, -1, 1))
416 return;
417 write_lock(&css_set_lock);
418 if (!atomic_dec_and_test(&cg->refcount)) {
419 write_unlock(&css_set_lock);
420 return;
421 }
423 /* This css_set is dead. unlink it and release cgroup refcounts */
424 hlist_del(&cg->hlist);
425 css_set_count--;
427 list_for_each_entry_safe(link, saved_link, &cg->cg_links,
428 cg_link_list) {
429 struct cgroup *cgrp = link->cgrp;
430 list_del(&link->cg_link_list);
431 list_del(&link->cgrp_link_list);
433 /*
434 * We may not be holding cgroup_mutex, and if cgrp->count is
435 * dropped to 0 the cgroup can be destroyed at any time, hence
436 * rcu_read_lock is used to keep it alive.
437 */
438 rcu_read_lock();
439 if (atomic_dec_and_test(&cgrp->count) &&
440 notify_on_release(cgrp)) {
441 if (taskexit)
442 set_bit(CGRP_RELEASABLE, &cgrp->flags);
443 check_for_release(cgrp);
444 }
445 rcu_read_unlock();
447 kfree(link);
448 }
450 write_unlock(&css_set_lock);
451 kfree_rcu(cg, rcu_head);
452 }
454 /*
455 * refcounted get/put for css_set objects
456 */
457 static inline void get_css_set(struct css_set *cg)
458 {
459 atomic_inc(&cg->refcount);
460 }
462 static inline void put_css_set(struct css_set *cg)
463 {
464 __put_css_set(cg, 0);
465 }
467 static inline void put_css_set_taskexit(struct css_set *cg)
468 {
469 __put_css_set(cg, 1);
470 }
472 /*
473 * compare_css_sets - helper function for find_existing_css_set().
474 * @cg: candidate css_set being tested
475 * @old_cg: existing css_set for a task
476 * @new_cgrp: cgroup that's being entered by the task
477 * @template: desired set of css pointers in css_set (pre-calculated)
478 *
479 * Returns true if "cg" matches "old_cg" except for the hierarchy
480 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
481 */
482 static bool compare_css_sets(struct css_set *cg,
483 struct css_set *old_cg,
484 struct cgroup *new_cgrp,
485 struct cgroup_subsys_state *template[])
486 {
487 struct list_head *l1, *l2;
489 if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
490 /* Not all subsystems matched */
491 return false;
492 }
494 /*
495 * Compare cgroup pointers in order to distinguish between
496 * different cgroups in heirarchies with no subsystems. We
497 * could get by with just this check alone (and skip the
498 * memcmp above) but on most setups the memcmp check will
499 * avoid the need for this more expensive check on almost all
500 * candidates.
501 */
503 l1 = &cg->cg_links;
504 l2 = &old_cg->cg_links;
505 while (1) {
506 struct cg_cgroup_link *cgl1, *cgl2;
507 struct cgroup *cg1, *cg2;
509 l1 = l1->next;
510 l2 = l2->next;
511 /* See if we reached the end - both lists are equal length. */
512 if (l1 == &cg->cg_links) {
513 BUG_ON(l2 != &old_cg->cg_links);
514 break;
515 } else {
516 BUG_ON(l2 == &old_cg->cg_links);
517 }
518 /* Locate the cgroups associated with these links. */
519 cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
520 cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
521 cg1 = cgl1->cgrp;
522 cg2 = cgl2->cgrp;
523 /* Hierarchies should be linked in the same order. */
524 BUG_ON(cg1->root != cg2->root);
526 /*
527 * If this hierarchy is the hierarchy of the cgroup
528 * that's changing, then we need to check that this
529 * css_set points to the new cgroup; if it's any other
530 * hierarchy, then this css_set should point to the
531 * same cgroup as the old css_set.
532 */
533 if (cg1->root == new_cgrp->root) {
534 if (cg1 != new_cgrp)
535 return false;
536 } else {
537 if (cg1 != cg2)
538 return false;
539 }
540 }
541 return true;
542 }
544 /*
545 * find_existing_css_set() is a helper for
546 * find_css_set(), and checks to see whether an existing
547 * css_set is suitable.
548 *
549 * oldcg: the cgroup group that we're using before the cgroup
550 * transition
551 *
552 * cgrp: the cgroup that we're moving into
553 *
554 * template: location in which to build the desired set of subsystem
555 * state objects for the new cgroup group
556 */
557 static struct css_set *find_existing_css_set(
558 struct css_set *oldcg,
559 struct cgroup *cgrp,
560 struct cgroup_subsys_state *template[])
561 {
562 int i;
563 struct cgroupfs_root *root = cgrp->root;
564 struct hlist_head *hhead;
565 struct hlist_node *node;
566 struct css_set *cg;
568 /*
569 * Build the set of subsystem state objects that we want to see in the
570 * new css_set. while subsystems can change globally, the entries here
571 * won't change, so no need for locking.
572 */
573 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
574 if (root->subsys_mask & (1UL << i)) {
575 /* Subsystem is in this hierarchy. So we want
576 * the subsystem state from the new
577 * cgroup */
578 template[i] = cgrp->subsys[i];
579 } else {
580 /* Subsystem is not in this hierarchy, so we
581 * don't want to change the subsystem state */
582 template[i] = oldcg->subsys[i];
583 }
584 }
586 hhead = css_set_hash(template);
587 hlist_for_each_entry(cg, node, hhead, hlist) {
588 if (!compare_css_sets(cg, oldcg, cgrp, template))
589 continue;
591 /* This css_set matches what we need */
592 return cg;
593 }
595 /* No existing cgroup group matched */
596 return NULL;
597 }
599 static void free_cg_links(struct list_head *tmp)
600 {
601 struct cg_cgroup_link *link;
602 struct cg_cgroup_link *saved_link;
604 list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
605 list_del(&link->cgrp_link_list);
606 kfree(link);
607 }
608 }
610 /*
611 * allocate_cg_links() allocates "count" cg_cgroup_link structures
612 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
613 * success or a negative error
614 */
615 static int allocate_cg_links(int count, struct list_head *tmp)
616 {
617 struct cg_cgroup_link *link;
618 int i;
619 INIT_LIST_HEAD(tmp);
620 for (i = 0; i < count; i++) {
621 link = kmalloc(sizeof(*link), GFP_KERNEL);
622 if (!link) {
623 free_cg_links(tmp);
624 return -ENOMEM;
625 }
626 list_add(&link->cgrp_link_list, tmp);
627 }
628 return 0;
629 }
631 /**
632 * link_css_set - a helper function to link a css_set to a cgroup
633 * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
634 * @cg: the css_set to be linked
635 * @cgrp: the destination cgroup
636 */
637 static void link_css_set(struct list_head *tmp_cg_links,
638 struct css_set *cg, struct cgroup *cgrp)
639 {
640 struct cg_cgroup_link *link;
642 BUG_ON(list_empty(tmp_cg_links));
643 link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
644 cgrp_link_list);
645 link->cg = cg;
646 link->cgrp = cgrp;
647 atomic_inc(&cgrp->count);
648 list_move(&link->cgrp_link_list, &cgrp->css_sets);
649 /*
650 * Always add links to the tail of the list so that the list
651 * is sorted by order of hierarchy creation
652 */
653 list_add_tail(&link->cg_link_list, &cg->cg_links);
654 }
656 /*
657 * find_css_set() takes an existing cgroup group and a
658 * cgroup object, and returns a css_set object that's
659 * equivalent to the old group, but with the given cgroup
660 * substituted into the appropriate hierarchy. Must be called with
661 * cgroup_mutex held
662 */
663 static struct css_set *find_css_set(
664 struct css_set *oldcg, struct cgroup *cgrp)
665 {
666 struct css_set *res;
667 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
669 struct list_head tmp_cg_links;
671 struct hlist_head *hhead;
672 struct cg_cgroup_link *link;
674 /* First see if we already have a cgroup group that matches
675 * the desired set */
676 read_lock(&css_set_lock);
677 res = find_existing_css_set(oldcg, cgrp, template);
678 if (res)
679 get_css_set(res);
680 read_unlock(&css_set_lock);
682 if (res)
683 return res;
685 res = kmalloc(sizeof(*res), GFP_KERNEL);
686 if (!res)
687 return NULL;
689 /* Allocate all the cg_cgroup_link objects that we'll need */
690 if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
691 kfree(res);
692 return NULL;
693 }
695 atomic_set(&res->refcount, 1);
696 INIT_LIST_HEAD(&res->cg_links);
697 INIT_LIST_HEAD(&res->tasks);
698 INIT_HLIST_NODE(&res->hlist);
700 /* Copy the set of subsystem state objects generated in
701 * find_existing_css_set() */
702 memcpy(res->subsys, template, sizeof(res->subsys));
704 write_lock(&css_set_lock);
705 /* Add reference counts and links from the new css_set. */
706 list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
707 struct cgroup *c = link->cgrp;
708 if (c->root == cgrp->root)
709 c = cgrp;
710 link_css_set(&tmp_cg_links, res, c);
711 }
713 BUG_ON(!list_empty(&tmp_cg_links));
715 css_set_count++;
717 /* Add this cgroup group to the hash table */
718 hhead = css_set_hash(res->subsys);
719 hlist_add_head(&res->hlist, hhead);
721 write_unlock(&css_set_lock);
723 return res;
724 }
726 /*
727 * Return the cgroup for "task" from the given hierarchy. Must be
728 * called with cgroup_mutex held.
729 */
730 static struct cgroup *task_cgroup_from_root(struct task_struct *task,
731 struct cgroupfs_root *root)
732 {
733 struct css_set *css;
734 struct cgroup *res = NULL;
736 BUG_ON(!mutex_is_locked(&cgroup_mutex));
737 read_lock(&css_set_lock);
738 /*
739 * No need to lock the task - since we hold cgroup_mutex the
740 * task can't change groups, so the only thing that can happen
741 * is that it exits and its css is set back to init_css_set.
742 */
743 css = task->cgroups;
744 if (css == &init_css_set) {
745 res = &root->top_cgroup;
746 } else {
747 struct cg_cgroup_link *link;
748 list_for_each_entry(link, &css->cg_links, cg_link_list) {
749 struct cgroup *c = link->cgrp;
750 if (c->root == root) {
751 res = c;
752 break;
753 }
754 }
755 }
756 read_unlock(&css_set_lock);
757 BUG_ON(!res);
758 return res;
759 }
761 /*
762 * There is one global cgroup mutex. We also require taking
763 * task_lock() when dereferencing a task's cgroup subsys pointers.
764 * See "The task_lock() exception", at the end of this comment.
765 *
766 * A task must hold cgroup_mutex to modify cgroups.
767 *
768 * Any task can increment and decrement the count field without lock.
769 * So in general, code holding cgroup_mutex can't rely on the count
770 * field not changing. However, if the count goes to zero, then only
771 * cgroup_attach_task() can increment it again. Because a count of zero
772 * means that no tasks are currently attached, therefore there is no
773 * way a task attached to that cgroup can fork (the other way to
774 * increment the count). So code holding cgroup_mutex can safely
775 * assume that if the count is zero, it will stay zero. Similarly, if
776 * a task holds cgroup_mutex on a cgroup with zero count, it
777 * knows that the cgroup won't be removed, as cgroup_rmdir()
778 * needs that mutex.
779 *
780 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
781 * (usually) take cgroup_mutex. These are the two most performance
782 * critical pieces of code here. The exception occurs on cgroup_exit(),
783 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
784 * is taken, and if the cgroup count is zero, a usermode call made
785 * to the release agent with the name of the cgroup (path relative to
786 * the root of cgroup file system) as the argument.
787 *
788 * A cgroup can only be deleted if both its 'count' of using tasks
789 * is zero, and its list of 'children' cgroups is empty. Since all
790 * tasks in the system use _some_ cgroup, and since there is always at
791 * least one task in the system (init, pid == 1), therefore, top_cgroup
792 * always has either children cgroups and/or using tasks. So we don't
793 * need a special hack to ensure that top_cgroup cannot be deleted.
794 *
795 * The task_lock() exception
796 *
797 * The need for this exception arises from the action of
798 * cgroup_attach_task(), which overwrites one task's cgroup pointer with
799 * another. It does so using cgroup_mutex, however there are
800 * several performance critical places that need to reference
801 * task->cgroup without the expense of grabbing a system global
802 * mutex. Therefore except as noted below, when dereferencing or, as
803 * in cgroup_attach_task(), modifying a task's cgroup pointer we use
804 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
805 * the task_struct routinely used for such matters.
806 *
807 * P.S. One more locking exception. RCU is used to guard the
808 * update of a tasks cgroup pointer by cgroup_attach_task()
809 */
811 /**
812 * cgroup_lock - lock out any changes to cgroup structures
813 *
814 */
815 void cgroup_lock(void)
816 {
817 mutex_lock(&cgroup_mutex);
818 }
819 EXPORT_SYMBOL_GPL(cgroup_lock);
821 /**
822 * cgroup_unlock - release lock on cgroup changes
823 *
824 * Undo the lock taken in a previous cgroup_lock() call.
825 */
826 void cgroup_unlock(void)
827 {
828 mutex_unlock(&cgroup_mutex);
829 }
830 EXPORT_SYMBOL_GPL(cgroup_unlock);
832 /*
833 * A couple of forward declarations required, due to cyclic reference loop:
834 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
835 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
836 * -> cgroup_mkdir.
837 */
839 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
840 static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);
841 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
842 static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
843 unsigned long subsys_mask);
844 static const struct inode_operations cgroup_dir_inode_operations;
845 static const struct file_operations proc_cgroupstats_operations;
847 static struct backing_dev_info cgroup_backing_dev_info = {
848 .name = "cgroup",
849 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
850 };
852 static int alloc_css_id(struct cgroup_subsys *ss,
853 struct cgroup *parent, struct cgroup *child);
855 static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
856 {
857 struct inode *inode = new_inode(sb);
859 if (inode) {
860 inode->i_ino = get_next_ino();
861 inode->i_mode = mode;
862 inode->i_uid = current_fsuid();
863 inode->i_gid = current_fsgid();
864 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
865 inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
866 }
867 return inode;
868 }
870 static void cgroup_diput(struct dentry *dentry, struct inode *inode)
871 {
872 /* is dentry a directory ? if so, kfree() associated cgroup */
873 if (S_ISDIR(inode->i_mode)) {
874 struct cgroup *cgrp = dentry->d_fsdata;
875 struct cgroup_subsys *ss;
876 BUG_ON(!(cgroup_is_removed(cgrp)));
877 /* It's possible for external users to be holding css
878 * reference counts on a cgroup; css_put() needs to
879 * be able to access the cgroup after decrementing
880 * the reference count in order to know if it needs to
881 * queue the cgroup to be handled by the release
882 * agent */
883 synchronize_rcu();
885 mutex_lock(&cgroup_mutex);
886 /*
887 * Release the subsystem state objects.
888 */
889 for_each_subsys(cgrp->root, ss)
890 ss->css_free(cgrp);
892 cgrp->root->number_of_cgroups--;
893 mutex_unlock(&cgroup_mutex);
895 /*
896 * Drop the active superblock reference that we took when we
897 * created the cgroup
898 */
899 deactivate_super(cgrp->root->sb);
901 /*
902 * if we're getting rid of the cgroup, refcount should ensure
903 * that there are no pidlists left.
904 */
905 BUG_ON(!list_empty(&cgrp->pidlists));
907 simple_xattrs_free(&cgrp->xattrs);
909 ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id);
910 kfree_rcu(cgrp, rcu_head);
911 } else {
912 struct cfent *cfe = __d_cfe(dentry);
913 struct cgroup *cgrp = dentry->d_parent->d_fsdata;
915 WARN_ONCE(!list_empty(&cfe->node) &&
916 cgrp != &cgrp->root->top_cgroup,
917 "cfe still linked for %s\n", cfe->type->name);
918 simple_xattrs_free(&cfe->xattrs);
919 kfree(cfe);
920 }
921 iput(inode);
922 }
924 static int cgroup_delete(const struct dentry *d)
925 {
926 return 1;
927 }
929 static void remove_dir(struct dentry *d)
930 {
931 struct dentry *parent = dget(d->d_parent);
933 d_delete(d);
934 simple_rmdir(parent->d_inode, d);
935 dput(parent);
936 }
938 static int cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
939 {
940 struct cfent *cfe;
942 lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
943 lockdep_assert_held(&cgroup_mutex);
945 list_for_each_entry(cfe, &cgrp->files, node) {
946 struct dentry *d = cfe->dentry;
948 if (cft && cfe->type != cft)
949 continue;
951 dget(d);
952 d_delete(d);
953 simple_unlink(cgrp->dentry->d_inode, d);
954 list_del_init(&cfe->node);
955 dput(d);
957 return 0;
958 }
959 return -ENOENT;
960 }
962 /**
963 * cgroup_clear_directory - selective removal of base and subsystem files
964 * @dir: directory containing the files
965 * @base_files: true if the base files should be removed
966 * @subsys_mask: mask of the subsystem ids whose files should be removed
967 */
968 static void cgroup_clear_directory(struct dentry *dir, bool base_files,
969 unsigned long subsys_mask)
970 {
971 struct cgroup *cgrp = __d_cgrp(dir);
972 struct cgroup_subsys *ss;
974 for_each_subsys(cgrp->root, ss) {
975 struct cftype_set *set;
976 if (!test_bit(ss->subsys_id, &subsys_mask))
977 continue;
978 list_for_each_entry(set, &ss->cftsets, node)
979 cgroup_addrm_files(cgrp, NULL, set->cfts, false);
980 }
981 if (base_files) {
982 while (!list_empty(&cgrp->files))
983 cgroup_rm_file(cgrp, NULL);
984 }
985 }
987 /*
988 * NOTE : the dentry must have been dget()'ed
989 */
990 static void cgroup_d_remove_dir(struct dentry *dentry)
991 {
992 struct dentry *parent;
993 struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
995 cgroup_clear_directory(dentry, true, root->subsys_mask);
997 parent = dentry->d_parent;
998 spin_lock(&parent->d_lock);
999 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
1000 list_del_init(&dentry->d_u.d_child);
1001 spin_unlock(&dentry->d_lock);
1002 spin_unlock(&parent->d_lock);
1003 remove_dir(dentry);
1004 }
1006 /*
1007 * Call with cgroup_mutex held. Drops reference counts on modules, including
1008 * any duplicate ones that parse_cgroupfs_options took. If this function
1009 * returns an error, no reference counts are touched.
1010 */
1011 static int rebind_subsystems(struct cgroupfs_root *root,
1012 unsigned long final_subsys_mask)
1013 {
1014 unsigned long added_mask, removed_mask;
1015 struct cgroup *cgrp = &root->top_cgroup;
1016 int i;
1018 BUG_ON(!mutex_is_locked(&cgroup_mutex));
1019 BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
1021 removed_mask = root->actual_subsys_mask & ~final_subsys_mask;
1022 added_mask = final_subsys_mask & ~root->actual_subsys_mask;
1023 /* Check that any added subsystems are currently free */
1024 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1025 unsigned long bit = 1UL << i;
1026 struct cgroup_subsys *ss = subsys[i];
1027 if (!(bit & added_mask))
1028 continue;
1029 /*
1030 * Nobody should tell us to do a subsys that doesn't exist:
1031 * parse_cgroupfs_options should catch that case and refcounts
1032 * ensure that subsystems won't disappear once selected.
1033 */
1034 BUG_ON(ss == NULL);
1035 if (ss->root != &rootnode) {
1036 /* Subsystem isn't free */
1037 return -EBUSY;
1038 }
1039 }
1041 /* Currently we don't handle adding/removing subsystems when
1042 * any child cgroups exist. This is theoretically supportable
1043 * but involves complex error handling, so it's being left until
1044 * later */
1045 if (root->number_of_cgroups > 1)
1046 return -EBUSY;
1048 /* Process each subsystem */
1049 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1050 struct cgroup_subsys *ss = subsys[i];
1051 unsigned long bit = 1UL << i;
1052 if (bit & added_mask) {
1053 /* We're binding this subsystem to this hierarchy */
1054 BUG_ON(ss == NULL);
1055 BUG_ON(cgrp->subsys[i]);
1056 BUG_ON(!dummytop->subsys[i]);
1057 BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1058 cgrp->subsys[i] = dummytop->subsys[i];
1059 cgrp->subsys[i]->cgroup = cgrp;
1060 list_move(&ss->sibling, &root->subsys_list);
1061 ss->root = root;
1062 if (ss->bind)
1063 ss->bind(cgrp);
1064 /* refcount was already taken, and we're keeping it */
1065 } else if (bit & removed_mask) {
1066 /* We're removing this subsystem */
1067 BUG_ON(ss == NULL);
1068 BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
1069 BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1070 if (ss->bind)
1071 ss->bind(dummytop);
1072 dummytop->subsys[i]->cgroup = dummytop;
1073 cgrp->subsys[i] = NULL;
1074 subsys[i]->root = &rootnode;
1075 list_move(&ss->sibling, &rootnode.subsys_list);
1076 /* subsystem is now free - drop reference on module */
1077 module_put(ss->module);
1078 } else if (bit & final_subsys_mask) {
1079 /* Subsystem state should already exist */
1080 BUG_ON(ss == NULL);
1081 BUG_ON(!cgrp->subsys[i]);
1082 /*
1083 * a refcount was taken, but we already had one, so
1084 * drop the extra reference.
1085 */
1086 module_put(ss->module);
1087 #ifdef CONFIG_MODULE_UNLOAD
1088 BUG_ON(ss->module && !module_refcount(ss->module));
1089 #endif
1090 } else {
1091 /* Subsystem state shouldn't exist */
1092 BUG_ON(cgrp->subsys[i]);
1093 }
1094 }
1095 root->subsys_mask = root->actual_subsys_mask = final_subsys_mask;
1096 synchronize_rcu();
1098 return 0;
1099 }
1101 static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1102 {
1103 struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1104 struct cgroup_subsys *ss;
1106 mutex_lock(&cgroup_root_mutex);
1107 for_each_subsys(root, ss)
1108 seq_printf(seq, ",%s", ss->name);
1109 if (test_bit(ROOT_NOPREFIX, &root->flags))
1110 seq_puts(seq, ",noprefix");
1111 if (test_bit(ROOT_XATTR, &root->flags))
1112 seq_puts(seq, ",xattr");
1113 if (strlen(root->release_agent_path))
1114 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1115 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags))
1116 seq_puts(seq, ",clone_children");
1117 if (strlen(root->name))
1118 seq_printf(seq, ",name=%s", root->name);
1119 mutex_unlock(&cgroup_root_mutex);
1120 return 0;
1121 }
1123 struct cgroup_sb_opts {
1124 unsigned long subsys_mask;
1125 unsigned long flags;
1126 char *release_agent;
1127 bool cpuset_clone_children;
1128 char *name;
1129 /* User explicitly requested empty subsystem */
1130 bool none;
1132 struct cgroupfs_root *new_root;
1134 };
1136 /*
1137 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
1138 * with cgroup_mutex held to protect the subsys[] array. This function takes
1139 * refcounts on subsystems to be used, unless it returns error, in which case
1140 * no refcounts are taken.
1141 */
1142 static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1143 {
1144 char *token, *o = data;
1145 bool all_ss = false, one_ss = false;
1146 unsigned long mask = (unsigned long)-1;
1147 int i;
1148 bool module_pin_failed = false;
1150 BUG_ON(!mutex_is_locked(&cgroup_mutex));
1152 #ifdef CONFIG_CPUSETS
1153 mask = ~(1UL << cpuset_subsys_id);
1154 #endif
1156 memset(opts, 0, sizeof(*opts));
1158 while ((token = strsep(&o, ",")) != NULL) {
1159 if (!*token)
1160 return -EINVAL;
1161 if (!strcmp(token, "none")) {
1162 /* Explicitly have no subsystems */
1163 opts->none = true;
1164 continue;
1165 }
1166 if (!strcmp(token, "all")) {
1167 /* Mutually exclusive option 'all' + subsystem name */
1168 if (one_ss)
1169 return -EINVAL;
1170 all_ss = true;
1171 continue;
1172 }
1173 if (!strcmp(token, "noprefix")) {
1174 set_bit(ROOT_NOPREFIX, &opts->flags);
1175 continue;
1176 }
1177 if (!strcmp(token, "clone_children")) {
1178 opts->cpuset_clone_children = true;
1179 continue;
1180 }
1181 if (!strcmp(token, "xattr")) {
1182 set_bit(ROOT_XATTR, &opts->flags);
1183 continue;
1184 }
1185 if (!strncmp(token, "release_agent=", 14)) {
1186 /* Specifying two release agents is forbidden */
1187 if (opts->release_agent)
1188 return -EINVAL;
1189 opts->release_agent =
1190 kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1191 if (!opts->release_agent)
1192 return -ENOMEM;
1193 continue;
1194 }
1195 if (!strncmp(token, "name=", 5)) {
1196 const char *name = token + 5;
1197 /* Can't specify an empty name */
1198 if (!strlen(name))
1199 return -EINVAL;
1200 /* Must match [\w.-]+ */
1201 for (i = 0; i < strlen(name); i++) {
1202 char c = name[i];
1203 if (isalnum(c))
1204 continue;
1205 if ((c == '.') || (c == '-') || (c == '_'))
1206 continue;
1207 return -EINVAL;
1208 }
1209 /* Specifying two names is forbidden */
1210 if (opts->name)
1211 return -EINVAL;
1212 opts->name = kstrndup(name,
1213 MAX_CGROUP_ROOT_NAMELEN - 1,
1214 GFP_KERNEL);
1215 if (!opts->name)
1216 return -ENOMEM;
1218 continue;
1219 }
1221 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1222 struct cgroup_subsys *ss = subsys[i];
1223 if (ss == NULL)
1224 continue;
1225 if (strcmp(token, ss->name))
1226 continue;
1227 if (ss->disabled)
1228 continue;
1230 /* Mutually exclusive option 'all' + subsystem name */
1231 if (all_ss)
1232 return -EINVAL;
1233 set_bit(i, &opts->subsys_mask);
1234 one_ss = true;
1236 break;
1237 }
1238 if (i == CGROUP_SUBSYS_COUNT)
1239 return -ENOENT;
1240 }
1242 /*
1243 * If the 'all' option was specified select all the subsystems,
1244 * otherwise if 'none', 'name=' and a subsystem name options
1245 * were not specified, let's default to 'all'
1246 */
1247 if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1248 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1249 struct cgroup_subsys *ss = subsys[i];
1250 if (ss == NULL)
1251 continue;
1252 if (ss->disabled)
1253 continue;
1254 set_bit(i, &opts->subsys_mask);
1255 }
1256 }
1258 /* Consistency checks */
1260 /*
1261 * Option noprefix was introduced just for backward compatibility
1262 * with the old cpuset, so we allow noprefix only if mounting just
1263 * the cpuset subsystem.
1264 */
1265 if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
1266 (opts->subsys_mask & mask))
1267 return -EINVAL;
1270 /* Can't specify "none" and some subsystems */
1271 if (opts->subsys_mask && opts->none)
1272 return -EINVAL;
1274 /*
1275 * We either have to specify by name or by subsystems. (So all
1276 * empty hierarchies must have a name).
1277 */
1278 if (!opts->subsys_mask && !opts->name)
1279 return -EINVAL;
1281 /*
1282 * Grab references on all the modules we'll need, so the subsystems
1283 * don't dance around before rebind_subsystems attaches them. This may
1284 * take duplicate reference counts on a subsystem that's already used,
1285 * but rebind_subsystems handles this case.
1286 */
1287 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1288 unsigned long bit = 1UL << i;
1290 if (!(bit & opts->subsys_mask))
1291 continue;
1292 if (!try_module_get(subsys[i]->module)) {
1293 module_pin_failed = true;
1294 break;
1295 }
1296 }
1297 if (module_pin_failed) {
1298 /*
1299 * oops, one of the modules was going away. this means that we
1300 * raced with a module_delete call, and to the user this is
1301 * essentially a "subsystem doesn't exist" case.
1302 */
1303 for (i--; i >= 0; i--) {
1304 /* drop refcounts only on the ones we took */
1305 unsigned long bit = 1UL << i;
1307 if (!(bit & opts->subsys_mask))
1308 continue;
1309 module_put(subsys[i]->module);
1310 }
1311 return -ENOENT;
1312 }
1314 return 0;
1315 }
1317 static void drop_parsed_module_refcounts(unsigned long subsys_mask)
1318 {
1319 int i;
1320 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1321 unsigned long bit = 1UL << i;
1323 if (!(bit & subsys_mask))
1324 continue;
1325 module_put(subsys[i]->module);
1326 }
1327 }
1329 static int cgroup_remount(struct super_block *sb, int *flags, char *data)
1330 {
1331 int ret = 0;
1332 struct cgroupfs_root *root = sb->s_fs_info;
1333 struct cgroup *cgrp = &root->top_cgroup;
1334 struct cgroup_sb_opts opts;
1335 unsigned long added_mask, removed_mask;
1337 mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1338 mutex_lock(&cgroup_mutex);
1339 mutex_lock(&cgroup_root_mutex);
1341 /* See what subsystems are wanted */
1342 ret = parse_cgroupfs_options(data, &opts);
1343 if (ret)
1344 goto out_unlock;
1346 if (opts.subsys_mask != root->actual_subsys_mask || opts.release_agent)
1347 pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
1348 task_tgid_nr(current), current->comm);
1350 added_mask = opts.subsys_mask & ~root->subsys_mask;
1351 removed_mask = root->subsys_mask & ~opts.subsys_mask;
1353 /* Don't allow flags or name to change at remount */
1354 if (opts.flags != root->flags ||
1355 (opts.name && strcmp(opts.name, root->name))) {
1356 ret = -EINVAL;
1357 drop_parsed_module_refcounts(opts.subsys_mask);
1358 goto out_unlock;
1359 }
1361 /*
1362 * Clear out the files of subsystems that should be removed, do
1363 * this before rebind_subsystems, since rebind_subsystems may
1364 * change this hierarchy's subsys_list.
1365 */
1366 cgroup_clear_directory(cgrp->dentry, false, removed_mask);
1368 ret = rebind_subsystems(root, opts.subsys_mask);
1369 if (ret) {
1370 /* rebind_subsystems failed, re-populate the removed files */
1371 cgroup_populate_dir(cgrp, false, removed_mask);
1372 drop_parsed_module_refcounts(opts.subsys_mask);
1373 goto out_unlock;
1374 }
1376 /* re-populate subsystem files */
1377 cgroup_populate_dir(cgrp, false, added_mask);
1379 if (opts.release_agent)
1380 strcpy(root->release_agent_path, opts.release_agent);
1381 out_unlock:
1382 kfree(opts.release_agent);
1383 kfree(opts.name);
1384 mutex_unlock(&cgroup_root_mutex);
1385 mutex_unlock(&cgroup_mutex);
1386 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1387 return ret;
1388 }
1390 static const struct super_operations cgroup_ops = {
1391 .statfs = simple_statfs,
1392 .drop_inode = generic_delete_inode,
1393 .show_options = cgroup_show_options,
1394 .remount_fs = cgroup_remount,
1395 };
1397 static void init_cgroup_housekeeping(struct cgroup *cgrp)
1398 {
1399 INIT_LIST_HEAD(&cgrp->sibling);
1400 INIT_LIST_HEAD(&cgrp->children);
1401 INIT_LIST_HEAD(&cgrp->files);
1402 INIT_LIST_HEAD(&cgrp->css_sets);
1403 INIT_LIST_HEAD(&cgrp->allcg_node);
1404 INIT_LIST_HEAD(&cgrp->release_list);
1405 INIT_LIST_HEAD(&cgrp->pidlists);
1406 mutex_init(&cgrp->pidlist_mutex);
1407 INIT_LIST_HEAD(&cgrp->event_list);
1408 spin_lock_init(&cgrp->event_list_lock);
1409 simple_xattrs_init(&cgrp->xattrs);
1410 }
1412 static void init_cgroup_root(struct cgroupfs_root *root)
1413 {
1414 struct cgroup *cgrp = &root->top_cgroup;
1416 INIT_LIST_HEAD(&root->subsys_list);
1417 INIT_LIST_HEAD(&root->root_list);
1418 INIT_LIST_HEAD(&root->allcg_list);
1419 root->number_of_cgroups = 1;
1420 cgrp->root = root;
1421 cgrp->top_cgroup = cgrp;
1422 init_cgroup_housekeeping(cgrp);
1423 list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1424 }
1426 static bool init_root_id(struct cgroupfs_root *root)
1427 {
1428 int ret = 0;
1430 do {
1431 if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
1432 return false;
1433 spin_lock(&hierarchy_id_lock);
1434 /* Try to allocate the next unused ID */
1435 ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
1436 &root->hierarchy_id);
1437 if (ret == -ENOSPC)
1438 /* Try again starting from 0 */
1439 ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
1440 if (!ret) {
1441 next_hierarchy_id = root->hierarchy_id + 1;
1442 } else if (ret != -EAGAIN) {
1443 /* Can only get here if the 31-bit IDR is full ... */
1444 BUG_ON(ret);
1445 }
1446 spin_unlock(&hierarchy_id_lock);
1447 } while (ret);
1448 return true;
1449 }
1451 static int cgroup_test_super(struct super_block *sb, void *data)
1452 {
1453 struct cgroup_sb_opts *opts = data;
1454 struct cgroupfs_root *root = sb->s_fs_info;
1456 /* If we asked for a name then it must match */
1457 if (opts->name && strcmp(opts->name, root->name))
1458 return 0;
1460 /*
1461 * If we asked for subsystems (or explicitly for no
1462 * subsystems) then they must match
1463 */
1464 if ((opts->subsys_mask || opts->none)
1465 && (opts->subsys_mask != root->subsys_mask))
1466 return 0;
1468 return 1;
1469 }
1471 static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
1472 {
1473 struct cgroupfs_root *root;
1475 if (!opts->subsys_mask && !opts->none)
1476 return NULL;
1478 root = kzalloc(sizeof(*root), GFP_KERNEL);
1479 if (!root)
1480 return ERR_PTR(-ENOMEM);
1482 if (!init_root_id(root)) {
1483 kfree(root);
1484 return ERR_PTR(-ENOMEM);
1485 }
1486 init_cgroup_root(root);
1488 root->subsys_mask = opts->subsys_mask;
1489 root->flags = opts->flags;
1490 ida_init(&root->cgroup_ida);
1491 if (opts->release_agent)
1492 strcpy(root->release_agent_path, opts->release_agent);
1493 if (opts->name)
1494 strcpy(root->name, opts->name);
1495 if (opts->cpuset_clone_children)
1496 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags);
1497 return root;
1498 }
1500 static void cgroup_drop_root(struct cgroupfs_root *root)
1501 {
1502 if (!root)
1503 return;
1505 BUG_ON(!root->hierarchy_id);
1506 spin_lock(&hierarchy_id_lock);
1507 ida_remove(&hierarchy_ida, root->hierarchy_id);
1508 spin_unlock(&hierarchy_id_lock);
1509 ida_destroy(&root->cgroup_ida);
1510 kfree(root);
1511 }
1513 static int cgroup_set_super(struct super_block *sb, void *data)
1514 {
1515 int ret;
1516 struct cgroup_sb_opts *opts = data;
1518 /* If we don't have a new root, we can't set up a new sb */
1519 if (!opts->new_root)
1520 return -EINVAL;
1522 BUG_ON(!opts->subsys_mask && !opts->none);
1524 ret = set_anon_super(sb, NULL);
1525 if (ret)
1526 return ret;
1528 sb->s_fs_info = opts->new_root;
1529 opts->new_root->sb = sb;
1531 sb->s_blocksize = PAGE_CACHE_SIZE;
1532 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
1533 sb->s_magic = CGROUP_SUPER_MAGIC;
1534 sb->s_op = &cgroup_ops;
1536 return 0;
1537 }
1539 static int cgroup_get_rootdir(struct super_block *sb)
1540 {
1541 static const struct dentry_operations cgroup_dops = {
1542 .d_iput = cgroup_diput,
1543 .d_delete = cgroup_delete,
1544 };
1546 struct inode *inode =
1547 cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
1549 if (!inode)
1550 return -ENOMEM;
1552 inode->i_fop = &simple_dir_operations;
1553 inode->i_op = &cgroup_dir_inode_operations;
1554 /* directories start off with i_nlink == 2 (for "." entry) */
1555 inc_nlink(inode);
1556 sb->s_root = d_make_root(inode);
1557 if (!sb->s_root)
1558 return -ENOMEM;
1559 /* for everything else we want ->d_op set */
1560 sb->s_d_op = &cgroup_dops;
1561 return 0;
1562 }
1564 static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1565 int flags, const char *unused_dev_name,
1566 void *data)
1567 {
1568 struct cgroup_sb_opts opts;
1569 struct cgroupfs_root *root;
1570 int ret = 0;
1571 struct super_block *sb;
1572 struct cgroupfs_root *new_root;
1573 struct inode *inode;
1575 /* First find the desired set of subsystems */
1576 mutex_lock(&cgroup_mutex);
1577 ret = parse_cgroupfs_options(data, &opts);
1578 mutex_unlock(&cgroup_mutex);
1579 if (ret)
1580 goto out_err;
1582 /*
1583 * Allocate a new cgroup root. We may not need it if we're
1584 * reusing an existing hierarchy.
1585 */
1586 new_root = cgroup_root_from_opts(&opts);
1587 if (IS_ERR(new_root)) {
1588 ret = PTR_ERR(new_root);
1589 goto drop_modules;
1590 }
1591 opts.new_root = new_root;
1593 /* Locate an existing or new sb for this hierarchy */
1594 sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
1595 if (IS_ERR(sb)) {
1596 ret = PTR_ERR(sb);
1597 cgroup_drop_root(opts.new_root);
1598 goto drop_modules;
1599 }
1601 root = sb->s_fs_info;
1602 BUG_ON(!root);
1603 if (root == opts.new_root) {
1604 /* We used the new root structure, so this is a new hierarchy */
1605 struct list_head tmp_cg_links;
1606 struct cgroup *root_cgrp = &root->top_cgroup;
1607 struct cgroupfs_root *existing_root;
1608 const struct cred *cred;
1609 int i;
1611 BUG_ON(sb->s_root != NULL);
1613 ret = cgroup_get_rootdir(sb);
1614 if (ret)
1615 goto drop_new_super;
1616 inode = sb->s_root->d_inode;
1618 mutex_lock(&inode->i_mutex);
1619 mutex_lock(&cgroup_mutex);
1620 mutex_lock(&cgroup_root_mutex);
1622 /* Check for name clashes with existing mounts */
1623 ret = -EBUSY;
1624 if (strlen(root->name))
1625 for_each_active_root(existing_root)
1626 if (!strcmp(existing_root->name, root->name))
1627 goto unlock_drop;
1629 /*
1630 * We're accessing css_set_count without locking
1631 * css_set_lock here, but that's OK - it can only be
1632 * increased by someone holding cgroup_lock, and
1633 * that's us. The worst that can happen is that we
1634 * have some link structures left over
1635 */
1636 ret = allocate_cg_links(css_set_count, &tmp_cg_links);
1637 if (ret)
1638 goto unlock_drop;
1640 ret = rebind_subsystems(root, root->subsys_mask);
1641 if (ret == -EBUSY) {
1642 free_cg_links(&tmp_cg_links);
1643 goto unlock_drop;
1644 }
1645 /*
1646 * There must be no failure case after here, since rebinding
1647 * takes care of subsystems' refcounts, which are explicitly
1648 * dropped in the failure exit path.
1649 */
1651 /* EBUSY should be the only error here */
1652 BUG_ON(ret);
1654 list_add(&root->root_list, &roots);
1655 root_count++;
1657 sb->s_root->d_fsdata = root_cgrp;
1658 root->top_cgroup.dentry = sb->s_root;
1660 /* Link the top cgroup in this hierarchy into all
1661 * the css_set objects */
1662 write_lock(&css_set_lock);
1663 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
1664 struct hlist_head *hhead = &css_set_table[i];
1665 struct hlist_node *node;
1666 struct css_set *cg;
1668 hlist_for_each_entry(cg, node, hhead, hlist)
1669 link_css_set(&tmp_cg_links, cg, root_cgrp);
1670 }
1671 write_unlock(&css_set_lock);
1673 free_cg_links(&tmp_cg_links);
1675 BUG_ON(!list_empty(&root_cgrp->children));
1676 BUG_ON(root->number_of_cgroups != 1);
1678 cred = override_creds(&init_cred);
1679 cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
1680 revert_creds(cred);
1681 mutex_unlock(&cgroup_root_mutex);
1682 mutex_unlock(&cgroup_mutex);
1683 mutex_unlock(&inode->i_mutex);
1684 } else {
1685 /*
1686 * We re-used an existing hierarchy - the new root (if
1687 * any) is not needed
1688 */
1689 cgroup_drop_root(opts.new_root);
1690 /* no subsys rebinding, so refcounts don't change */
1691 drop_parsed_module_refcounts(opts.subsys_mask);
1692 }
1694 kfree(opts.release_agent);
1695 kfree(opts.name);
1696 return dget(sb->s_root);
1698 unlock_drop:
1699 mutex_unlock(&cgroup_root_mutex);
1700 mutex_unlock(&cgroup_mutex);
1701 mutex_unlock(&inode->i_mutex);
1702 drop_new_super:
1703 deactivate_locked_super(sb);
1704 drop_modules:
1705 drop_parsed_module_refcounts(opts.subsys_mask);
1706 out_err:
1707 kfree(opts.release_agent);
1708 kfree(opts.name);
1709 return ERR_PTR(ret);
1710 }
1712 static void cgroup_kill_sb(struct super_block *sb) {
1713 struct cgroupfs_root *root = sb->s_fs_info;
1714 struct cgroup *cgrp = &root->top_cgroup;
1715 int ret;
1716 struct cg_cgroup_link *link;
1717 struct cg_cgroup_link *saved_link;
1719 BUG_ON(!root);
1721 BUG_ON(root->number_of_cgroups != 1);
1722 BUG_ON(!list_empty(&cgrp->children));
1724 mutex_lock(&cgroup_mutex);
1725 mutex_lock(&cgroup_root_mutex);
1727 /* Rebind all subsystems back to the default hierarchy */
1728 ret = rebind_subsystems(root, 0);
1729 /* Shouldn't be able to fail ... */
1730 BUG_ON(ret);
1732 /*
1733 * Release all the links from css_sets to this hierarchy's
1734 * root cgroup
1735 */
1736 write_lock(&css_set_lock);
1738 list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
1739 cgrp_link_list) {
1740 list_del(&link->cg_link_list);
1741 list_del(&link->cgrp_link_list);
1742 kfree(link);
1743 }
1744 write_unlock(&css_set_lock);
1746 if (!list_empty(&root->root_list)) {
1747 list_del(&root->root_list);
1748 root_count--;
1749 }
1751 mutex_unlock(&cgroup_root_mutex);
1752 mutex_unlock(&cgroup_mutex);
1754 simple_xattrs_free(&cgrp->xattrs);
1756 kill_litter_super(sb);
1757 cgroup_drop_root(root);
1758 }
1760 static struct file_system_type cgroup_fs_type = {
1761 .name = "cgroup",
1762 .mount = cgroup_mount,
1763 .kill_sb = cgroup_kill_sb,
1764 };
1766 static struct kobject *cgroup_kobj;
1768 /**
1769 * cgroup_path - generate the path of a cgroup
1770 * @cgrp: the cgroup in question
1771 * @buf: the buffer to write the path into
1772 * @buflen: the length of the buffer
1773 *
1774 * Called with cgroup_mutex held or else with an RCU-protected cgroup
1775 * reference. Writes path of cgroup into buf. Returns 0 on success,
1776 * -errno on error.
1777 */
1778 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1779 {
1780 struct dentry *dentry = cgrp->dentry;
1781 char *start;
1783 rcu_lockdep_assert(rcu_read_lock_held() || cgroup_lock_is_held(),
1784 "cgroup_path() called without proper locking");
1786 if (!dentry || cgrp == dummytop) {
1787 /*
1788 * Inactive subsystems have no dentry for their root
1789 * cgroup
1790 */
1791 strcpy(buf, "/");
1792 return 0;
1793 }
1795 start = buf + buflen - 1;
1797 *start = '\0';
1798 for (;;) {
1799 int len = dentry->d_name.len;
1801 if ((start -= len) < buf)
1802 return -ENAMETOOLONG;
1803 memcpy(start, dentry->d_name.name, len);
1804 cgrp = cgrp->parent;
1805 if (!cgrp)
1806 break;
1808 dentry = cgrp->dentry;
1809 if (!cgrp->parent)
1810 continue;
1811 if (--start < buf)
1812 return -ENAMETOOLONG;
1813 *start = '/';
1814 }
1815 memmove(buf, start, buf + buflen - start);
1816 return 0;
1817 }
1818 EXPORT_SYMBOL_GPL(cgroup_path);
1820 /*
1821 * Control Group taskset
1822 */
1823 struct task_and_cgroup {
1824 struct task_struct *task;
1825 struct cgroup *cgrp;
1826 struct css_set *cg;
1827 };
1829 struct cgroup_taskset {
1830 struct task_and_cgroup single;
1831 struct flex_array *tc_array;
1832 int tc_array_len;
1833 int idx;
1834 struct cgroup *cur_cgrp;
1835 };
1837 /**
1838 * cgroup_taskset_first - reset taskset and return the first task
1839 * @tset: taskset of interest
1840 *
1841 * @tset iteration is initialized and the first task is returned.
1842 */
1843 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
1844 {
1845 if (tset->tc_array) {
1846 tset->idx = 0;
1847 return cgroup_taskset_next(tset);
1848 } else {
1849 tset->cur_cgrp = tset->single.cgrp;
1850 return tset->single.task;
1851 }
1852 }
1853 EXPORT_SYMBOL_GPL(cgroup_taskset_first);
1855 /**
1856 * cgroup_taskset_next - iterate to the next task in taskset
1857 * @tset: taskset of interest
1858 *
1859 * Return the next task in @tset. Iteration must have been initialized
1860 * with cgroup_taskset_first().
1861 */
1862 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
1863 {
1864 struct task_and_cgroup *tc;
1866 if (!tset->tc_array || tset->idx >= tset->tc_array_len)
1867 return NULL;
1869 tc = flex_array_get(tset->tc_array, tset->idx++);
1870 tset->cur_cgrp = tc->cgrp;
1871 return tc->task;
1872 }
1873 EXPORT_SYMBOL_GPL(cgroup_taskset_next);
1875 /**
1876 * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
1877 * @tset: taskset of interest
1878 *
1879 * Return the cgroup for the current (last returned) task of @tset. This
1880 * function must be preceded by either cgroup_taskset_first() or
1881 * cgroup_taskset_next().
1882 */
1883 struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
1884 {
1885 return tset->cur_cgrp;
1886 }
1887 EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);
1889 /**
1890 * cgroup_taskset_size - return the number of tasks in taskset
1891 * @tset: taskset of interest
1892 */
1893 int cgroup_taskset_size(struct cgroup_taskset *tset)
1894 {
1895 return tset->tc_array ? tset->tc_array_len : 1;
1896 }
1897 EXPORT_SYMBOL_GPL(cgroup_taskset_size);
1900 /*
1901 * cgroup_task_migrate - move a task from one cgroup to another.
1902 *
1903 * Must be called with cgroup_mutex and threadgroup locked.
1904 */
1905 static void cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
1906 struct task_struct *tsk, struct css_set *newcg)
1907 {
1908 struct css_set *oldcg;
1910 /*
1911 * We are synchronized through threadgroup_lock() against PF_EXITING
1912 * setting such that we can't race against cgroup_exit() changing the
1913 * css_set to init_css_set and dropping the old one.
1914 */
1915 WARN_ON_ONCE(tsk->flags & PF_EXITING);
1916 oldcg = tsk->cgroups;
1918 task_lock(tsk);
1919 rcu_assign_pointer(tsk->cgroups, newcg);
1920 task_unlock(tsk);
1922 /* Update the css_set linked lists if we're using them */
1923 write_lock(&css_set_lock);
1924 if (!list_empty(&tsk->cg_list))
1925 list_move(&tsk->cg_list, &newcg->tasks);
1926 write_unlock(&css_set_lock);
1928 /*
1929 * We just gained a reference on oldcg by taking it from the task. As
1930 * trading it for newcg is protected by cgroup_mutex, we're safe to drop
1931 * it here; it will be freed under RCU.
1932 */
1933 set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1934 put_css_set(oldcg);
1935 }
1937 /**
1938 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
1939 * @cgrp: the cgroup the task is attaching to
1940 * @tsk: the task to be attached
1941 *
1942 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
1943 * @tsk during call.
1944 */
1945 int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1946 {
1947 int retval = 0;
1948 struct cgroup_subsys *ss, *failed_ss = NULL;
1949 struct cgroup *oldcgrp;
1950 struct cgroupfs_root *root = cgrp->root;
1951 struct cgroup_taskset tset = { };
1952 struct css_set *newcg;
1954 /* @tsk either already exited or can't exit until the end */
1955 if (tsk->flags & PF_EXITING)
1956 return -ESRCH;
1958 /* Nothing to do if the task is already in that cgroup */
1959 oldcgrp = task_cgroup_from_root(tsk, root);
1960 if (cgrp == oldcgrp)
1961 return 0;
1963 tset.single.task = tsk;
1964 tset.single.cgrp = oldcgrp;
1966 for_each_subsys(root, ss) {
1967 if (ss->can_attach) {
1968 retval = ss->can_attach(cgrp, &tset);
1969 if (retval) {
1970 /*
1971 * Remember on which subsystem the can_attach()
1972 * failed, so that we only call cancel_attach()
1973 * against the subsystems whose can_attach()
1974 * succeeded. (See below)
1975 */
1976 failed_ss = ss;
1977 goto out;
1978 }
1979 }
1980 }
1982 newcg = find_css_set(tsk->cgroups, cgrp);
1983 if (!newcg) {
1984 retval = -ENOMEM;
1985 goto out;
1986 }
1988 cgroup_task_migrate(cgrp, oldcgrp, tsk, newcg);
1990 for_each_subsys(root, ss) {
1991 if (ss->attach)
1992 ss->attach(cgrp, &tset);
1993 }
1995 synchronize_rcu();
1996 out:
1997 if (retval) {
1998 for_each_subsys(root, ss) {
1999 if (ss == failed_ss)
2000 /*
2001 * This subsystem was the one that failed the
2002 * can_attach() check earlier, so we don't need
2003 * to call cancel_attach() against it or any
2004 * remaining subsystems.
2005 */
2006 break;
2007 if (ss->cancel_attach)
2008 ss->cancel_attach(cgrp, &tset);
2009 }
2010 }
2011 return retval;
2012 }
2014 /**
2015 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2016 * @from: attach to all cgroups of a given task
2017 * @tsk: the task to be attached
2018 */
2019 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2020 {
2021 struct cgroupfs_root *root;
2022 int retval = 0;
2024 cgroup_lock();
2025 for_each_active_root(root) {
2026 struct cgroup *from_cg = task_cgroup_from_root(from, root);
2028 retval = cgroup_attach_task(from_cg, tsk);
2029 if (retval)
2030 break;
2031 }
2032 cgroup_unlock();
2034 return retval;
2035 }
2036 EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2038 /**
2039 * cgroup_attach_proc - attach all threads in a threadgroup to a cgroup
2040 * @cgrp: the cgroup to attach to
2041 * @leader: the threadgroup leader task_struct of the group to be attached
2042 *
2043 * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
2044 * task_lock of each thread in leader's threadgroup individually in turn.
2045 */
2046 static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
2047 {
2048 int retval, i, group_size;
2049 struct cgroup_subsys *ss, *failed_ss = NULL;
2050 /* guaranteed to be initialized later, but the compiler needs this */
2051 struct cgroupfs_root *root = cgrp->root;
2052 /* threadgroup list cursor and array */
2053 struct task_struct *tsk;
2054 struct task_and_cgroup *tc;
2055 struct flex_array *group;
2056 struct cgroup_taskset tset = { };
2058 /*
2059 * step 0: in order to do expensive, possibly blocking operations for
2060 * every thread, we cannot iterate the thread group list, since it needs
2061 * rcu or tasklist locked. instead, build an array of all threads in the
2062 * group - group_rwsem prevents new threads from appearing, and if
2063 * threads exit, this will just be an over-estimate.
2064 */
2065 group_size = get_nr_threads(leader);
2066 /* flex_array supports very large thread-groups better than kmalloc. */
2067 group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
2068 if (!group)
2069 return -ENOMEM;
2070 /* pre-allocate to guarantee space while iterating in rcu read-side. */
2071 retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
2072 if (retval)
2073 goto out_free_group_list;
2075 tsk = leader;
2076 i = 0;
2077 /*
2078 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2079 * already PF_EXITING could be freed from underneath us unless we
2080 * take an rcu_read_lock.
2081 */
2082 rcu_read_lock();
2083 do {
2084 struct task_and_cgroup ent;
2086 /* @tsk either already exited or can't exit until the end */
2087 if (tsk->flags & PF_EXITING)
2088 continue;
2090 /* as per above, nr_threads may decrease, but not increase. */
2091 BUG_ON(i >= group_size);
2092 ent.task = tsk;
2093 ent.cgrp = task_cgroup_from_root(tsk, root);
2094 /* nothing to do if this task is already in the cgroup */
2095 if (ent.cgrp == cgrp)
2096 continue;
2097 /*
2098 * saying GFP_ATOMIC has no effect here because we did prealloc
2099 * earlier, but it's good form to communicate our expectations.
2100 */
2101 retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2102 BUG_ON(retval != 0);
2103 i++;
2104 } while_each_thread(leader, tsk);
2105 rcu_read_unlock();
2106 /* remember the number of threads in the array for later. */
2107 group_size = i;
2108 tset.tc_array = group;
2109 tset.tc_array_len = group_size;
2111 /* methods shouldn't be called if no task is actually migrating */
2112 retval = 0;
2113 if (!group_size)
2114 goto out_free_group_list;
2116 /*
2117 * step 1: check that we can legitimately attach to the cgroup.
2118 */
2119 for_each_subsys(root, ss) {
2120 if (ss->can_attach) {
2121 retval = ss->can_attach(cgrp, &tset);
2122 if (retval) {
2123 failed_ss = ss;
2124 goto out_cancel_attach;
2125 }
2126 }
2127 }
2129 /*
2130 * step 2: make sure css_sets exist for all threads to be migrated.
2131 * we use find_css_set, which allocates a new one if necessary.
2132 */
2133 for (i = 0; i < group_size; i++) {
2134 tc = flex_array_get(group, i);
2135 tc->cg = find_css_set(tc->task->cgroups, cgrp);
2136 if (!tc->cg) {
2137 retval = -ENOMEM;
2138 goto out_put_css_set_refs;
2139 }
2140 }
2142 /*
2143 * step 3: now that we're guaranteed success wrt the css_sets,
2144 * proceed to move all tasks to the new cgroup. There are no
2145 * failure cases after here, so this is the commit point.
2146 */
2147 for (i = 0; i < group_size; i++) {
2148 tc = flex_array_get(group, i);
2149 cgroup_task_migrate(cgrp, tc->cgrp, tc->task, tc->cg);
2150 }
2151 /* nothing is sensitive to fork() after this point. */
2153 /*
2154 * step 4: do subsystem attach callbacks.
2155 */
2156 for_each_subsys(root, ss) {
2157 if (ss->attach)
2158 ss->attach(cgrp, &tset);
2159 }
2161 /*
2162 * step 5: success! and cleanup
2163 */
2164 synchronize_rcu();
2165 retval = 0;
2166 out_put_css_set_refs:
2167 if (retval) {
2168 for (i = 0; i < group_size; i++) {
2169 tc = flex_array_get(group, i);
2170 if (!tc->cg)
2171 break;
2172 put_css_set(tc->cg);
2173 }
2174 }
2175 out_cancel_attach:
2176 if (retval) {
2177 for_each_subsys(root, ss) {
2178 if (ss == failed_ss)
2179 break;
2180 if (ss->cancel_attach)
2181 ss->cancel_attach(cgrp, &tset);
2182 }
2183 }
2184 out_free_group_list:
2185 flex_array_free(group);
2186 return retval;
2187 }
2189 static int cgroup_allow_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
2190 {
2191 struct cgroup_subsys *ss;
2192 int ret;
2194 for_each_subsys(cgrp->root, ss) {
2195 if (ss->allow_attach) {
2196 ret = ss->allow_attach(cgrp, tset);
2197 if (ret)
2198 return ret;
2199 } else {
2200 return -EACCES;
2201 }
2202 }
2204 return 0;
2205 }
2207 /*
2208 * Find the task_struct of the task to attach by vpid and pass it along to the
2209 * function to attach either it or all tasks in its threadgroup. Will lock
2210 * cgroup_mutex and threadgroup; may take task_lock of task.
2211 */
2212 static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2213 {
2214 struct task_struct *tsk;
2215 const struct cred *cred = current_cred(), *tcred;
2216 int ret;
2218 if (!cgroup_lock_live_group(cgrp))
2219 return -ENODEV;
2221 retry_find_task:
2222 rcu_read_lock();
2223 if (pid) {
2224 tsk = find_task_by_vpid(pid);
2225 if (!tsk) {
2226 rcu_read_unlock();
2227 ret= -ESRCH;
2228 goto out_unlock_cgroup;
2229 }
2230 /*
2231 * even if we're attaching all tasks in the thread group, we
2232 * only need to check permissions on one of them.
2233 */
2234 tcred = __task_cred(tsk);
2235 if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
2236 !uid_eq(cred->euid, tcred->uid) &&
2237 !uid_eq(cred->euid, tcred->suid)) {
2238 /*
2239 * if the default permission check fails, give each
2240 * cgroup a chance to extend the permission check
2241 */
2242 struct cgroup_taskset tset = { };
2243 tset.single.task = tsk;
2244 tset.single.cgrp = cgrp;
2245 ret = cgroup_allow_attach(cgrp, &tset);
2246 if (ret) {
2247 rcu_read_unlock();
2248 goto out_unlock_cgroup;
2249 }
2250 }
2251 } else
2252 tsk = current;
2254 if (threadgroup)
2255 tsk = tsk->group_leader;
2257 /*
2258 * Workqueue threads may acquire PF_THREAD_BOUND and become
2259 * trapped in a cpuset, or RT worker may be born in a cgroup
2260 * with no rt_runtime allocated. Just say no.
2261 */
2262 if (tsk == kthreadd_task || (tsk->flags & PF_THREAD_BOUND)) {
2263 ret = -EINVAL;
2264 rcu_read_unlock();
2265 goto out_unlock_cgroup;
2266 }
2268 get_task_struct(tsk);
2269 rcu_read_unlock();
2271 threadgroup_lock(tsk);
2272 if (threadgroup) {
2273 if (!thread_group_leader(tsk)) {
2274 /*
2275 * a race with de_thread from another thread's exec()
2276 * may strip us of our leadership, if this happens,
2277 * there is no choice but to throw this task away and
2278 * try again; this is
2279 * "double-double-toil-and-trouble-check locking".
2280 */
2281 threadgroup_unlock(tsk);
2282 put_task_struct(tsk);
2283 goto retry_find_task;
2284 }
2285 ret = cgroup_attach_proc(cgrp, tsk);
2286 } else
2287 ret = cgroup_attach_task(cgrp, tsk);
2288 threadgroup_unlock(tsk);
2290 put_task_struct(tsk);
2291 out_unlock_cgroup:
2292 cgroup_unlock();
2293 return ret;
2294 }
2296 static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
2297 {
2298 return attach_task_by_pid(cgrp, pid, false);
2299 }
2301 static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2302 {
2303 return attach_task_by_pid(cgrp, tgid, true);
2304 }
2306 /**
2307 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
2308 * @cgrp: the cgroup to be checked for liveness
2309 *
2310 * On success, returns true; the lock should be later released with
2311 * cgroup_unlock(). On failure returns false with no lock held.
2312 */
2313 bool cgroup_lock_live_group(struct cgroup *cgrp)
2314 {
2315 mutex_lock(&cgroup_mutex);
2316 if (cgroup_is_removed(cgrp)) {
2317 mutex_unlock(&cgroup_mutex);
2318 return false;
2319 }
2320 return true;
2321 }
2322 EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2324 static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
2325 const char *buffer)
2326 {
2327 BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
2328 if (strlen(buffer) >= PATH_MAX)
2329 return -EINVAL;
2330 if (!cgroup_lock_live_group(cgrp))
2331 return -ENODEV;
2332 mutex_lock(&cgroup_root_mutex);
2333 strcpy(cgrp->root->release_agent_path, buffer);
2334 mutex_unlock(&cgroup_root_mutex);
2335 cgroup_unlock();
2336 return 0;
2337 }
2339 static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
2340 struct seq_file *seq)
2341 {
2342 if (!cgroup_lock_live_group(cgrp))
2343 return -ENODEV;
2344 seq_puts(seq, cgrp->root->release_agent_path);
2345 seq_putc(seq, '\n');
2346 cgroup_unlock();
2347 return 0;
2348 }
2350 /* A buffer size big enough for numbers or short strings */
2351 #define CGROUP_LOCAL_BUFFER_SIZE 64
2353 static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2354 struct file *file,
2355 const char __user *userbuf,
2356 size_t nbytes, loff_t *unused_ppos)
2357 {
2358 char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2359 int retval = 0;
2360 char *end;
2362 if (!nbytes)
2363 return -EINVAL;
2364 if (nbytes >= sizeof(buffer))
2365 return -E2BIG;
2366 if (copy_from_user(buffer, userbuf, nbytes))
2367 return -EFAULT;
2369 buffer[nbytes] = 0; /* nul-terminate */
2370 if (cft->write_u64) {
2371 u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2372 if (*end)
2373 return -EINVAL;
2374 retval = cft->write_u64(cgrp, cft, val);
2375 } else {
2376 s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2377 if (*end)
2378 return -EINVAL;
2379 retval = cft->write_s64(cgrp, cft, val);
2380 }
2381 if (!retval)
2382 retval = nbytes;
2383 return retval;
2384 }
2386 static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
2387 struct file *file,
2388 const char __user *userbuf,
2389 size_t nbytes, loff_t *unused_ppos)
2390 {
2391 char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2392 int retval = 0;
2393 size_t max_bytes = cft->max_write_len;
2394 char *buffer = local_buffer;
2396 if (!max_bytes)
2397 max_bytes = sizeof(local_buffer) - 1;
2398 if (nbytes >= max_bytes)
2399 return -E2BIG;
2400 /* Allocate a dynamic buffer if we need one */
2401 if (nbytes >= sizeof(local_buffer)) {
2402 buffer = kmalloc(nbytes + 1, GFP_KERNEL);
2403 if (buffer == NULL)
2404 return -ENOMEM;
2405 }
2406 if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
2407 retval = -EFAULT;
2408 goto out;
2409 }
2411 buffer[nbytes] = 0; /* nul-terminate */
2412 retval = cft->write_string(cgrp, cft, strstrip(buffer));
2413 if (!retval)
2414 retval = nbytes;
2415 out:
2416 if (buffer != local_buffer)
2417 kfree(buffer);
2418 return retval;
2419 }
2421 static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
2422 size_t nbytes, loff_t *ppos)
2423 {
2424 struct cftype *cft = __d_cft(file->f_dentry);
2425 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2427 if (cgroup_is_removed(cgrp))
2428 return -ENODEV;
2429 if (cft->write)
2430 return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2431 if (cft->write_u64 || cft->write_s64)
2432 return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2433 if (cft->write_string)
2434 return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2435 if (cft->trigger) {
2436 int ret = cft->trigger(cgrp, (unsigned int)cft->private);
2437 return ret ? ret : nbytes;
2438 }
2439 return -EINVAL;
2440 }
2442 static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
2443 struct file *file,
2444 char __user *buf, size_t nbytes,
2445 loff_t *ppos)
2446 {
2447 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2448 u64 val = cft->read_u64(cgrp, cft);
2449 int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
2451 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2452 }
2454 static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
2455 struct file *file,
2456 char __user *buf, size_t nbytes,
2457 loff_t *ppos)
2458 {
2459 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2460 s64 val = cft->read_s64(cgrp, cft);
2461 int len = sprintf(tmp, "%lld\n", (long long) val);
2463 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2464 }
2466 static ssize_t cgroup_file_read(struct file *file, char __user *buf,
2467 size_t nbytes, loff_t *ppos)
2468 {
2469 struct cftype *cft = __d_cft(file->f_dentry);
2470 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2472 if (cgroup_is_removed(cgrp))
2473 return -ENODEV;
2475 if (cft->read)
2476 return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2477 if (cft->read_u64)
2478 return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2479 if (cft->read_s64)
2480 return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2481 return -EINVAL;
2482 }
2484 /*
2485 * seqfile ops/methods for returning structured data. Currently just
2486 * supports string->u64 maps, but can be extended in future.
2487 */
2489 struct cgroup_seqfile_state {
2490 struct cftype *cft;
2491 struct cgroup *cgroup;
2492 };
2494 static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
2495 {
2496 struct seq_file *sf = cb->state;
2497 return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
2498 }
2500 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
2501 {
2502 struct cgroup_seqfile_state *state = m->private;
2503 struct cftype *cft = state->cft;
2504 if (cft->read_map) {
2505 struct cgroup_map_cb cb = {
2506 .fill = cgroup_map_add,
2507 .state = m,
2508 };
2509 return cft->read_map(state->cgroup, cft, &cb);
2510 }
2511 return cft->read_seq_string(state->cgroup, cft, m);
2512 }
2514 static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2515 {
2516 struct seq_file *seq = file->private_data;
2517 kfree(seq->private);
2518 return single_release(inode, file);
2519 }
2521 static const struct file_operations cgroup_seqfile_operations = {
2522 .read = seq_read,
2523 .write = cgroup_file_write,
2524 .llseek = seq_lseek,
2525 .release = cgroup_seqfile_release,
2526 };
2528 static int cgroup_file_open(struct inode *inode, struct file *file)
2529 {
2530 int err;
2531 struct cftype *cft;
2533 err = generic_file_open(inode, file);
2534 if (err)
2535 return err;
2536 cft = __d_cft(file->f_dentry);
2538 if (cft->read_map || cft->read_seq_string) {
2539 struct cgroup_seqfile_state *state =
2540 kzalloc(sizeof(*state), GFP_USER);
2541 if (!state)
2542 return -ENOMEM;
2543 state->cft = cft;
2544 state->cgroup = __d_cgrp(file->f_dentry->d_parent);
2545 file->f_op = &cgroup_seqfile_operations;
2546 err = single_open(file, cgroup_seqfile_show, state);
2547 if (err < 0)
2548 kfree(state);
2549 } else if (cft->open)
2550 err = cft->open(inode, file);
2551 else
2552 err = 0;
2554 return err;
2555 }
2557 static int cgroup_file_release(struct inode *inode, struct file *file)
2558 {
2559 struct cftype *cft = __d_cft(file->f_dentry);
2560 if (cft->release)
2561 return cft->release(inode, file);
2562 return 0;
2563 }
2565 /*
2566 * cgroup_rename - Only allow simple rename of directories in place.
2567 */
2568 static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
2569 struct inode *new_dir, struct dentry *new_dentry)
2570 {
2571 if (!S_ISDIR(old_dentry->d_inode->i_mode))
2572 return -ENOTDIR;
2573 if (new_dentry->d_inode)
2574 return -EEXIST;
2575 if (old_dir != new_dir)
2576 return -EIO;
2577 return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
2578 }
2580 static struct simple_xattrs *__d_xattrs(struct dentry *dentry)
2581 {
2582 if (S_ISDIR(dentry->d_inode->i_mode))
2583 return &__d_cgrp(dentry)->xattrs;
2584 else
2585 return &__d_cfe(dentry)->xattrs;
2586 }
2588 static inline int xattr_enabled(struct dentry *dentry)
2589 {
2590 struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
2591 return test_bit(ROOT_XATTR, &root->flags);
2592 }
2594 static bool is_valid_xattr(const char *name)
2595 {
2596 if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
2597 !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN))
2598 return true;
2599 return false;
2600 }
2602 static int cgroup_setxattr(struct dentry *dentry, const char *name,
2603 const void *val, size_t size, int flags)
2604 {
2605 if (!xattr_enabled(dentry))
2606 return -EOPNOTSUPP;
2607 if (!is_valid_xattr(name))
2608 return -EINVAL;
2609 return simple_xattr_set(__d_xattrs(dentry), name, val, size, flags);
2610 }
2612 static int cgroup_removexattr(struct dentry *dentry, const char *name)
2613 {
2614 if (!xattr_enabled(dentry))
2615 return -EOPNOTSUPP;
2616 if (!is_valid_xattr(name))
2617 return -EINVAL;
2618 return simple_xattr_remove(__d_xattrs(dentry), name);
2619 }
2621 static ssize_t cgroup_getxattr(struct dentry *dentry, const char *name,
2622 void *buf, size_t size)
2623 {
2624 if (!xattr_enabled(dentry))
2625 return -EOPNOTSUPP;
2626 if (!is_valid_xattr(name))
2627 return -EINVAL;
2628 return simple_xattr_get(__d_xattrs(dentry), name, buf, size);
2629 }
2631 static ssize_t cgroup_listxattr(struct dentry *dentry, char *buf, size_t size)
2632 {
2633 if (!xattr_enabled(dentry))
2634 return -EOPNOTSUPP;
2635 return simple_xattr_list(__d_xattrs(dentry), buf, size);
2636 }
2638 static const struct file_operations cgroup_file_operations = {
2639 .read = cgroup_file_read,
2640 .write = cgroup_file_write,
2641 .llseek = generic_file_llseek,
2642 .open = cgroup_file_open,
2643 .release = cgroup_file_release,
2644 };
2646 static const struct inode_operations cgroup_file_inode_operations = {
2647 .setxattr = cgroup_setxattr,
2648 .getxattr = cgroup_getxattr,
2649 .listxattr = cgroup_listxattr,
2650 .removexattr = cgroup_removexattr,
2651 };
2653 static const struct inode_operations cgroup_dir_inode_operations = {
2654 .lookup = cgroup_lookup,
2655 .mkdir = cgroup_mkdir,
2656 .rmdir = cgroup_rmdir,
2657 .rename = cgroup_rename,
2658 .setxattr = cgroup_setxattr,
2659 .getxattr = cgroup_getxattr,
2660 .listxattr = cgroup_listxattr,
2661 .removexattr = cgroup_removexattr,
2662 };
2664 static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
2665 {
2666 if (dentry->d_name.len > NAME_MAX)
2667 return ERR_PTR(-ENAMETOOLONG);
2668 d_add(dentry, NULL);
2669 return NULL;
2670 }
2672 /*
2673 * Check if a file is a control file
2674 */
2675 static inline struct cftype *__file_cft(struct file *file)
2676 {
2677 if (file->f_dentry->d_inode->i_fop != &cgroup_file_operations)
2678 return ERR_PTR(-EINVAL);
2679 return __d_cft(file->f_dentry);
2680 }
2682 static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2683 struct super_block *sb)
2684 {
2685 struct inode *inode;
2687 if (!dentry)
2688 return -ENOENT;
2689 if (dentry->d_inode)
2690 return -EEXIST;
2692 inode = cgroup_new_inode(mode, sb);
2693 if (!inode)
2694 return -ENOMEM;
2696 if (S_ISDIR(mode)) {
2697 inode->i_op = &cgroup_dir_inode_operations;
2698 inode->i_fop = &simple_dir_operations;
2700 /* start off with i_nlink == 2 (for "." entry) */
2701 inc_nlink(inode);
2702 inc_nlink(dentry->d_parent->d_inode);
2704 /*
2705 * Control reaches here with cgroup_mutex held.
2706 * @inode->i_mutex should nest outside cgroup_mutex but we
2707 * want to populate it immediately without releasing
2708 * cgroup_mutex. As @inode isn't visible to anyone else
2709 * yet, trylock will always succeed without affecting
2710 * lockdep checks.
2711 */
2712 WARN_ON_ONCE(!mutex_trylock(&inode->i_mutex));
2713 } else if (S_ISREG(mode)) {
2714 inode->i_size = 0;
2715 inode->i_fop = &cgroup_file_operations;
2716 inode->i_op = &cgroup_file_inode_operations;
2717 }
2718 d_instantiate(dentry, inode);
2719 dget(dentry); /* Extra count - pin the dentry in core */
2720 return 0;
2721 }
2723 /**
2724 * cgroup_file_mode - deduce file mode of a control file
2725 * @cft: the control file in question
2726 *
2727 * returns cft->mode if ->mode is not 0
2728 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
2729 * returns S_IRUGO if it has only a read handler
2730 * returns S_IWUSR if it has only a write hander
2731 */
2732 static umode_t cgroup_file_mode(const struct cftype *cft)
2733 {
2734 umode_t mode = 0;
2736 if (cft->mode)
2737 return cft->mode;
2739 if (cft->read || cft->read_u64 || cft->read_s64 ||
2740 cft->read_map || cft->read_seq_string)
2741 mode |= S_IRUGO;
2743 if (cft->write || cft->write_u64 || cft->write_s64 ||
2744 cft->write_string || cft->trigger)
2745 mode |= S_IWUSR;
2747 return mode;
2748 }
2750 static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
2751 struct cftype *cft)
2752 {
2753 struct dentry *dir = cgrp->dentry;
2754 struct cgroup *parent = __d_cgrp(dir);
2755 struct dentry *dentry;
2756 struct cfent *cfe;
2757 int error;
2758 umode_t mode;
2759 char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2761 if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2762 strcpy(name, subsys->name);
2763 strcat(name, ".");
2764 }
2765 strcat(name, cft->name);
2767 BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
2769 cfe = kzalloc(sizeof(*cfe), GFP_KERNEL);
2770 if (!cfe)
2771 return -ENOMEM;
2773 dentry = lookup_one_len(name, dir, strlen(name));
2774 if (IS_ERR(dentry)) {
2775 error = PTR_ERR(dentry);
2776 goto out;
2777 }
2779 mode = cgroup_file_mode(cft);
2780 error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
2781 if (!error) {
2782 cfe->type = (void *)cft;
2783 cfe->dentry = dentry;
2784 dentry->d_fsdata = cfe;
2785 simple_xattrs_init(&cfe->xattrs);
2786 list_add_tail(&cfe->node, &parent->files);
2787 cfe = NULL;
2788 }
2789 dput(dentry);
2790 out:
2791 kfree(cfe);
2792 return error;
2793 }
2795 static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
2796 struct cftype cfts[], bool is_add)
2797 {
2798 struct cftype *cft;
2799 int err, ret = 0;
2801 for (cft = cfts; cft->name[0] != '\0'; cft++) {
2802 /* does cft->flags tell us to skip this file on @cgrp? */
2803 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
2804 continue;
2805 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
2806 continue;
2808 if (is_add)
2809 err = cgroup_add_file(cgrp, subsys, cft);
2810 else
2811 err = cgroup_rm_file(cgrp, cft);
2812 if (err) {
2813 pr_warning("cgroup_addrm_files: failed to %s %s, err=%d\n",
2814 is_add ? "add" : "remove", cft->name, err);
2815 ret = err;
2816 }
2817 }
2818 return ret;
2819 }
2821 static DEFINE_MUTEX(cgroup_cft_mutex);
2823 static void cgroup_cfts_prepare(void)
2824 __acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex)
2825 {
2826 /*
2827 * Thanks to the entanglement with vfs inode locking, we can't walk
2828 * the existing cgroups under cgroup_mutex and create files.
2829 * Instead, we increment reference on all cgroups and build list of
2830 * them using @cgrp->cft_q_node. Grab cgroup_cft_mutex to ensure
2831 * exclusive access to the field.
2832 */
2833 mutex_lock(&cgroup_cft_mutex);
2834 mutex_lock(&cgroup_mutex);
2835 }
2837 static void cgroup_cfts_commit(struct cgroup_subsys *ss,
2838 struct cftype *cfts, bool is_add)
2839 __releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
2840 {
2841 LIST_HEAD(pending);
2842 struct cgroup *cgrp, *n;
2844 /* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
2845 if (cfts && ss->root != &rootnode) {
2846 list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) {
2847 dget(cgrp->dentry);
2848 list_add_tail(&cgrp->cft_q_node, &pending);
2849 }
2850 }
2852 mutex_unlock(&cgroup_mutex);
2854 /*
2855 * All new cgroups will see @cfts update on @ss->cftsets. Add/rm
2856 * files for all cgroups which were created before.
2857 */
2858 list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {
2859 struct inode *inode = cgrp->dentry->d_inode;
2861 mutex_lock(&inode->i_mutex);
2862 mutex_lock(&cgroup_mutex);
2863 if (!cgroup_is_removed(cgrp))
2864 cgroup_addrm_files(cgrp, ss, cfts, is_add);
2865 mutex_unlock(&cgroup_mutex);
2866 mutex_unlock(&inode->i_mutex);
2868 list_del_init(&cgrp->cft_q_node);
2869 dput(cgrp->dentry);
2870 }
2872 mutex_unlock(&cgroup_cft_mutex);
2873 }
2875 /**
2876 * cgroup_add_cftypes - add an array of cftypes to a subsystem
2877 * @ss: target cgroup subsystem
2878 * @cfts: zero-length name terminated array of cftypes
2879 *
2880 * Register @cfts to @ss. Files described by @cfts are created for all
2881 * existing cgroups to which @ss is attached and all future cgroups will
2882 * have them too. This function can be called anytime whether @ss is
2883 * attached or not.
2884 *
2885 * Returns 0 on successful registration, -errno on failure. Note that this
2886 * function currently returns 0 as long as @cfts registration is successful
2887 * even if some file creation attempts on existing cgroups fail.
2888 */
2889 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2890 {
2891 struct cftype_set *set;
2893 set = kzalloc(sizeof(*set), GFP_KERNEL);
2894 if (!set)
2895 return -ENOMEM;
2897 cgroup_cfts_prepare();
2898 set->cfts = cfts;
2899 list_add_tail(&set->node, &ss->cftsets);
2900 cgroup_cfts_commit(ss, cfts, true);
2902 return 0;
2903 }
2904 EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
2906 /**
2907 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
2908 * @ss: target cgroup subsystem
2909 * @cfts: zero-length name terminated array of cftypes
2910 *
2911 * Unregister @cfts from @ss. Files described by @cfts are removed from
2912 * all existing cgroups to which @ss is attached and all future cgroups
2913 * won't have them either. This function can be called anytime whether @ss
2914 * is attached or not.
2915 *
2916 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
2917 * registered with @ss.
2918 */
2919 int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2920 {
2921 struct cftype_set *set;
2923 cgroup_cfts_prepare();
2925 list_for_each_entry(set, &ss->cftsets, node) {
2926 if (set->cfts == cfts) {
2927 list_del_init(&set->node);
2928 cgroup_cfts_commit(ss, cfts, false);
2929 return 0;
2930 }
2931 }
2933 cgroup_cfts_commit(ss, NULL, false);
2934 return -ENOENT;
2935 }
2937 /**
2938 * cgroup_task_count - count the number of tasks in a cgroup.
2939 * @cgrp: the cgroup in question
2940 *
2941 * Return the number of tasks in the cgroup.
2942 */
2943 int cgroup_task_count(const struct cgroup *cgrp)
2944 {
2945 int count = 0;
2946 struct cg_cgroup_link *link;
2948 read_lock(&css_set_lock);
2949 list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2950 count += atomic_read(&link->cg->refcount);
2951 }
2952 read_unlock(&css_set_lock);
2953 return count;
2954 }
2956 /*
2957 * Advance a list_head iterator. The iterator should be positioned at
2958 * the start of a css_set
2959 */
2960 static void cgroup_advance_iter(struct cgroup *cgrp,
2961 struct cgroup_iter *it)
2962 {
2963 struct list_head *l = it->cg_link;
2964 struct cg_cgroup_link *link;
2965 struct css_set *cg;
2967 /* Advance to the next non-empty css_set */
2968 do {
2969 l = l->next;
2970 if (l == &cgrp->css_sets) {
2971 it->cg_link = NULL;
2972 return;
2973 }
2974 link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2975 cg = link->cg;
2976 } while (list_empty(&cg->tasks));
2977 it->cg_link = l;
2978 it->task = cg->tasks.next;
2979 }
2981 /*
2982 * To reduce the fork() overhead for systems that are not actually
2983 * using their cgroups capability, we don't maintain the lists running
2984 * through each css_set to its tasks until we see the list actually
2985 * used - in other words after the first call to cgroup_iter_start().
2986 */
2987 static void cgroup_enable_task_cg_lists(void)
2988 {
2989 struct task_struct *p, *g;
2990 write_lock(&css_set_lock);
2991 use_task_css_set_links = 1;
2992 /*
2993 * We need tasklist_lock because RCU is not safe against
2994 * while_each_thread(). Besides, a forking task that has passed
2995 * cgroup_post_fork() without seeing use_task_css_set_links = 1
2996 * is not guaranteed to have its child immediately visible in the
2997 * tasklist if we walk through it with RCU.
2998 */
2999 read_lock(&tasklist_lock);
3000 do_each_thread(g, p) {
3001 task_lock(p);
3002 /*
3003 * We should check if the process is exiting, otherwise
3004 * it will race with cgroup_exit() in that the list
3005 * entry won't be deleted though the process has exited.
3006 */
3007 if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
3008 list_add(&p->cg_list, &p->cgroups->tasks);
3009 task_unlock(p);
3010 } while_each_thread(g, p);
3011 read_unlock(&tasklist_lock);
3012 write_unlock(&css_set_lock);
3013 }
3015 /**
3016 * cgroup_next_descendant_pre - find the next descendant for pre-order walk
3017 * @pos: the current position (%NULL to initiate traversal)
3018 * @cgroup: cgroup whose descendants to walk
3019 *
3020 * To be used by cgroup_for_each_descendant_pre(). Find the next
3021 * descendant to visit for pre-order traversal of @cgroup's descendants.
3022 */
3023 struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
3024 struct cgroup *cgroup)
3025 {
3026 struct cgroup *next;
3028 WARN_ON_ONCE(!rcu_read_lock_held());
3030 /* if first iteration, pretend we just visited @cgroup */
3031 if (!pos) {
3032 if (list_empty(&cgroup->children))
3033 return NULL;
3034 pos = cgroup;
3035 }
3037 /* visit the first child if exists */
3038 next = list_first_or_null_rcu(&pos->children, struct cgroup, sibling);
3039 if (next)
3040 return next;
3042 /* no child, visit my or the closest ancestor's next sibling */
3043 do {
3044 next = list_entry_rcu(pos->sibling.next, struct cgroup,
3045 sibling);
3046 if (&next->sibling != &pos->parent->children)
3047 return next;
3049 pos = pos->parent;
3050 } while (pos != cgroup);
3052 return NULL;
3053 }
3054 EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre);
3056 static struct cgroup *cgroup_leftmost_descendant(struct cgroup *pos)
3057 {
3058 struct cgroup *last;
3060 do {
3061 last = pos;
3062 pos = list_first_or_null_rcu(&pos->children, struct cgroup,
3063 sibling);
3064 } while (pos);
3066 return last;
3067 }
3069 /**
3070 * cgroup_next_descendant_post - find the next descendant for post-order walk
3071 * @pos: the current position (%NULL to initiate traversal)
3072 * @cgroup: cgroup whose descendants to walk
3073 *
3074 * To be used by cgroup_for_each_descendant_post(). Find the next
3075 * descendant to visit for post-order traversal of @cgroup's descendants.
3076 */
3077 struct cgroup *cgroup_next_descendant_post(struct cgroup *pos,
3078 struct cgroup *cgroup)
3079 {
3080 struct cgroup *next;
3082 WARN_ON_ONCE(!rcu_read_lock_held());
3084 /* if first iteration, visit the leftmost descendant */
3085 if (!pos) {
3086 next = cgroup_leftmost_descendant(cgroup);
3087 return next != cgroup ? next : NULL;
3088 }
3090 /* if there's an unvisited sibling, visit its leftmost descendant */
3091 next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
3092 if (&next->sibling != &pos->parent->children)
3093 return cgroup_leftmost_descendant(next);
3095 /* no sibling left, visit parent */
3096 next = pos->parent;
3097 return next != cgroup ? next : NULL;
3098 }
3099 EXPORT_SYMBOL_GPL(cgroup_next_descendant_post);
3101 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
3102 __acquires(css_set_lock)
3103 {
3104 /*
3105 * The first time anyone tries to iterate across a cgroup,
3106 * we need to enable the list linking each css_set to its
3107 * tasks, and fix up all existing tasks.
3108 */
3109 if (!use_task_css_set_links)
3110 cgroup_enable_task_cg_lists();
3112 read_lock(&css_set_lock);
3113 it->cg_link = &cgrp->css_sets;
3114 cgroup_advance_iter(cgrp, it);
3115 }
3117 struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
3118 struct cgroup_iter *it)
3119 {
3120 struct task_struct *res;
3121 struct list_head *l = it->task;
3122 struct cg_cgroup_link *link;
3124 /* If the iterator cg is NULL, we have no tasks */
3125 if (!it->cg_link)
3126 return NULL;
3127 res = list_entry(l, struct task_struct, cg_list);
3128 /* Advance iterator to find next entry */
3129 l = l->next;
3130 link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
3131 if (l == &link->cg->tasks) {
3132 /* We reached the end of this task list - move on to
3133 * the next cg_cgroup_link */
3134 cgroup_advance_iter(cgrp, it);
3135 } else {
3136 it->task = l;
3137 }
3138 return res;
3139 }
3141 void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
3142 __releases(css_set_lock)
3143 {
3144 read_unlock(&css_set_lock);
3145 }
3147 static inline int started_after_time(struct task_struct *t1,
3148 struct timespec *time,
3149 struct task_struct *t2)
3150 {
3151 int start_diff = timespec_compare(&t1->start_time, time);
3152 if (start_diff > 0) {
3153 return 1;
3154 } else if (start_diff < 0) {
3155 return 0;
3156 } else {
3157 /*
3158 * Arbitrarily, if two processes started at the same
3159 * time, we'll say that the lower pointer value
3160 * started first. Note that t2 may have exited by now
3161 * so this may not be a valid pointer any longer, but
3162 * that's fine - it still serves to distinguish
3163 * between two tasks started (effectively) simultaneously.
3164 */
3165 return t1 > t2;
3166 }
3167 }
3169 /*
3170 * This function is a callback from heap_insert() and is used to order
3171 * the heap.
3172 * In this case we order the heap in descending task start time.
3173 */
3174 static inline int started_after(void *p1, void *p2)
3175 {
3176 struct task_struct *t1 = p1;
3177 struct task_struct *t2 = p2;
3178 return started_after_time(t1, &t2->start_time, t2);
3179 }
3181 /**
3182 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
3183 * @scan: struct cgroup_scanner containing arguments for the scan
3184 *
3185 * Arguments include pointers to callback functions test_task() and
3186 * process_task().
3187 * Iterate through all the tasks in a cgroup, calling test_task() for each,
3188 * and if it returns true, call process_task() for it also.
3189 * The test_task pointer may be NULL, meaning always true (select all tasks).
3190 * Effectively duplicates cgroup_iter_{start,next,end}()
3191 * but does not lock css_set_lock for the call to process_task().
3192 * The struct cgroup_scanner may be embedded in any structure of the caller's
3193 * creation.
3194 * It is guaranteed that process_task() will act on every task that
3195 * is a member of the cgroup for the duration of this call. This
3196 * function may or may not call process_task() for tasks that exit
3197 * or move to a different cgroup during the call, or are forked or
3198 * move into the cgroup during the call.
3199 *
3200 * Note that test_task() may be called with locks held, and may in some
3201 * situations be called multiple times for the same task, so it should
3202 * be cheap.
3203 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
3204 * pre-allocated and will be used for heap operations (and its "gt" member will
3205 * be overwritten), else a temporary heap will be used (allocation of which
3206 * may cause this function to fail).
3207 */
3208 int cgroup_scan_tasks(struct cgroup_scanner *scan)
3209 {
3210 int retval, i;
3211 struct cgroup_iter it;
3212 struct task_struct *p, *dropped;
3213 /* Never dereference latest_task, since it's not refcounted */
3214 struct task_struct *latest_task = NULL;
3215 struct ptr_heap tmp_heap;
3216 struct ptr_heap *heap;
3217 struct timespec latest_time = { 0, 0 };
3219 if (scan->heap) {
3220 /* The caller supplied our heap and pre-allocated its memory */
3221 heap = scan->heap;
3222 heap->gt = &started_after;
3223 } else {
3224 /* We need to allocate our own heap memory */
3225 heap = &tmp_heap;
3226 retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
3227 if (retval)
3228 /* cannot allocate the heap */
3229 return retval;
3230 }
3232 again:
3233 /*
3234 * Scan tasks in the cgroup, using the scanner's "test_task" callback
3235 * to determine which are of interest, and using the scanner's
3236 * "process_task" callback to process any of them that need an update.
3237 * Since we don't want to hold any locks during the task updates,
3238 * gather tasks to be processed in a heap structure.
3239 * The heap is sorted by descending task start time.
3240 * If the statically-sized heap fills up, we overflow tasks that
3241 * started later, and in future iterations only consider tasks that
3242 * started after the latest task in the previous pass. This
3243 * guarantees forward progress and that we don't miss any tasks.
3244 */
3245 heap->size = 0;
3246 cgroup_iter_start(scan->cg, &it);
3247 while ((p = cgroup_iter_next(scan->cg, &it))) {
3248 /*
3249 * Only affect tasks that qualify per the caller's callback,
3250 * if he provided one
3251 */
3252 if (scan->test_task && !scan->test_task(p, scan))
3253 continue;
3254 /*
3255 * Only process tasks that started after the last task
3256 * we processed
3257 */
3258 if (!started_after_time(p, &latest_time, latest_task))
3259 continue;
3260 dropped = heap_insert(heap, p);
3261 if (dropped == NULL) {
3262 /*
3263 * The new task was inserted; the heap wasn't
3264 * previously full
3265 */
3266 get_task_struct(p);
3267 } else if (dropped != p) {
3268 /*
3269 * The new task was inserted, and pushed out a
3270 * different task
3271 */
3272 get_task_struct(p);
3273 put_task_struct(dropped);
3274 }
3275 /*
3276 * Else the new task was newer than anything already in
3277 * the heap and wasn't inserted
3278 */
3279 }
3280 cgroup_iter_end(scan->cg, &it);
3282 if (heap->size) {
3283 for (i = 0; i < heap->size; i++) {
3284 struct task_struct *q = heap->ptrs[i];
3285 if (i == 0) {
3286 latest_time = q->start_time;
3287 latest_task = q;
3288 }
3289 /* Process the task per the caller's callback */
3290 scan->process_task(q, scan);
3291 put_task_struct(q);
3292 }
3293 /*
3294 * If we had to process any tasks at all, scan again
3295 * in case some of them were in the middle of forking
3296 * children that didn't get processed.
3297 * Not the most efficient way to do it, but it avoids
3298 * having to take callback_mutex in the fork path
3299 */
3300 goto again;
3301 }
3302 if (heap == &tmp_heap)
3303 heap_free(&tmp_heap);
3304 return 0;
3305 }
3307 /*
3308 * Stuff for reading the 'tasks'/'procs' files.
3309 *
3310 * Reading this file can return large amounts of data if a cgroup has
3311 * *lots* of attached tasks. So it may need several calls to read(),
3312 * but we cannot guarantee that the information we produce is correct
3313 * unless we produce it entirely atomically.
3314 *
3315 */
3317 /* which pidlist file are we talking about? */
3318 enum cgroup_filetype {
3319 CGROUP_FILE_PROCS,
3320 CGROUP_FILE_TASKS,
3321 };
3323 /*
3324 * A pidlist is a list of pids that virtually represents the contents of one
3325 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3326 * a pair (one each for procs, tasks) for each pid namespace that's relevant
3327 * to the cgroup.
3328 */
3329 struct cgroup_pidlist {
3330 /*
3331 * used to find which pidlist is wanted. doesn't change as long as
3332 * this particular list stays in the list.
3333 */
3334 struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
3335 /* array of xids */
3336 pid_t *list;
3337 /* how many elements the above list has */
3338 int length;
3339 /* how many files are using the current array */
3340 int use_count;
3341 /* each of these stored in a list by its cgroup */
3342 struct list_head links;
3343 /* pointer to the cgroup we belong to, for list removal purposes */
3344 struct cgroup *owner;
3345 /* protects the other fields */
3346 struct rw_semaphore mutex;
3347 };
3349 /*
3350 * The following two functions "fix" the issue where there are more pids
3351 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3352 * TODO: replace with a kernel-wide solution to this problem
3353 */
3354 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3355 static void *pidlist_allocate(int count)
3356 {
3357 if (PIDLIST_TOO_LARGE(count))
3358 return vmalloc(count * sizeof(pid_t));
3359 else
3360 return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
3361 }
3362 static void pidlist_free(void *p)
3363 {
3364 if (is_vmalloc_addr(p))
3365 vfree(p);
3366 else
3367 kfree(p);
3368 }
3369 static void *pidlist_resize(void *p, int newcount)
3370 {
3371 void *newlist;
3372 /* note: if new alloc fails, old p will still be valid either way */
3373 if (is_vmalloc_addr(p)) {
3374 newlist = vmalloc(newcount * sizeof(pid_t));
3375 if (!newlist)
3376 return NULL;
3377 memcpy(newlist, p, newcount * sizeof(pid_t));
3378 vfree(p);
3379 } else {
3380 newlist = krealloc(p, newcount * sizeof(pid_t), GFP_KERNEL);
3381 }
3382 return newlist;
3383 }
3385 /*
3386 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3387 * If the new stripped list is sufficiently smaller and there's enough memory
3388 * to allocate a new buffer, will let go of the unneeded memory. Returns the
3389 * number of unique elements.
3390 */
3391 /* is the size difference enough that we should re-allocate the array? */
3392 #define PIDLIST_REALLOC_DIFFERENCE(old, new) ((old) - PAGE_SIZE >= (new))
3393 static int pidlist_uniq(pid_t **p, int length)
3394 {
3395 int src, dest = 1;
3396 pid_t *list = *p;
3397 pid_t *newlist;
3399 /*
3400 * we presume the 0th element is unique, so i starts at 1. trivial
3401 * edge cases first; no work needs to be done for either
3402 */
3403 if (length == 0 || length == 1)
3404 return length;
3405 /* src and dest walk down the list; dest counts unique elements */
3406 for (src = 1; src < length; src++) {
3407 /* find next unique element */
3408 while (list[src] == list[src-1]) {
3409 src++;
3410 if (src == length)
3411 goto after;
3412 }
3413 /* dest always points to where the next unique element goes */
3414 list[dest] = list[src];
3415 dest++;
3416 }
3417 after:
3418 /*
3419 * if the length difference is large enough, we want to allocate a
3420 * smaller buffer to save memory. if this fails due to out of memory,
3421 * we'll just stay with what we've got.
3422 */
3423 if (PIDLIST_REALLOC_DIFFERENCE(length, dest)) {
3424 newlist = pidlist_resize(list, dest);
3425 if (newlist)
3426 *p = newlist;
3427 }
3428 return dest;
3429 }
3431 static int cmppid(const void *a, const void *b)
3432 {
3433 return *(pid_t *)a - *(pid_t *)b;
3434 }
3436 /*
3437 * find the appropriate pidlist for our purpose (given procs vs tasks)
3438 * returns with the lock on that pidlist already held, and takes care
3439 * of the use count, or returns NULL with no locks held if we're out of
3440 * memory.
3441 */
3442 static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
3443 enum cgroup_filetype type)
3444 {
3445 struct cgroup_pidlist *l;
3446 /* don't need task_nsproxy() if we're looking at ourself */
3447 struct pid_namespace *ns = task_active_pid_ns(current);
3449 /*
3450 * We can't drop the pidlist_mutex before taking the l->mutex in case
3451 * the last ref-holder is trying to remove l from the list at the same
3452 * time. Holding the pidlist_mutex precludes somebody taking whichever
3453 * list we find out from under us - compare release_pid_array().
3454 */
3455 mutex_lock(&cgrp->pidlist_mutex);
3456 list_for_each_entry(l, &cgrp->pidlists, links) {
3457 if (l->key.type == type && l->key.ns == ns) {
3458 /* make sure l doesn't vanish out from under us */
3459 down_write(&l->mutex);
3460 mutex_unlock(&cgrp->pidlist_mutex);
3461 return l;
3462 }
3463 }
3464 /* entry not found; create a new one */
3465 l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3466 if (!l) {
3467 mutex_unlock(&cgrp->pidlist_mutex);
3468 return l;
3469 }
3470 init_rwsem(&l->mutex);
3471 down_write(&l->mutex);
3472 l->key.type = type;
3473 l->key.ns = get_pid_ns(ns);
3474 l->use_count = 0; /* don't increment here */
3475 l->list = NULL;
3476 l->owner = cgrp;
3477 list_add(&l->links, &cgrp->pidlists);
3478 mutex_unlock(&cgrp->pidlist_mutex);
3479 return l;
3480 }
3482 /*
3483 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3484 */
3485 static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
3486 struct cgroup_pidlist **lp)
3487 {
3488 pid_t *array;
3489 int length;
3490 int pid, n = 0; /* used for populating the array */
3491 struct cgroup_iter it;
3492 struct task_struct *tsk;
3493 struct cgroup_pidlist *l;
3495 /*
3496 * If cgroup gets more users after we read count, we won't have
3497 * enough space - tough. This race is indistinguishable to the
3498 * caller from the case that the additional cgroup users didn't
3499 * show up until sometime later on.
3500 */
3501 length = cgroup_task_count(cgrp);
3502 array = pidlist_allocate(length);
3503 if (!array)
3504 return -ENOMEM;
3505 /* now, populate the array */
3506 cgroup_iter_start(cgrp, &it);
3507 while ((tsk = cgroup_iter_next(cgrp, &it))) {
3508 if (unlikely(n == length))
3509 break;
3510 /* get tgid or pid for procs or tasks file respectively */
3511 if (type == CGROUP_FILE_PROCS)
3512 pid = task_tgid_vnr(tsk);
3513 else
3514 pid = task_pid_vnr(tsk);
3515 if (pid > 0) /* make sure to only use valid results */
3516 array[n++] = pid;
3517 }
3518 cgroup_iter_end(cgrp, &it);
3519 length = n;
3520 /* now sort & (if procs) strip out duplicates */
3521 sort(array, length, sizeof(pid_t), cmppid, NULL);
3522 if (type == CGROUP_FILE_PROCS)
3523 length = pidlist_uniq(&array, length);
3524 l = cgroup_pidlist_find(cgrp, type);
3525 if (!l) {
3526 pidlist_free(array);
3527 return -ENOMEM;
3528 }
3529 /* store array, freeing old if necessary - lock already held */
3530 pidlist_free(l->list);
3531 l->list = array;
3532 l->length = length;
3533 l->use_count++;
3534 up_write(&l->mutex);
3535 *lp = l;
3536 return 0;
3537 }
3539 /**
3540 * cgroupstats_build - build and fill cgroupstats
3541 * @stats: cgroupstats to fill information into
3542 * @dentry: A dentry entry belonging to the cgroup for which stats have
3543 * been requested.
3544 *
3545 * Build and fill cgroupstats so that taskstats can export it to user
3546 * space.
3547 */
3548 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
3549 {
3550 int ret = -EINVAL;
3551 struct cgroup *cgrp;
3552 struct cgroup_iter it;
3553 struct task_struct *tsk;
3555 /*
3556 * Validate dentry by checking the superblock operations,
3557 * and make sure it's a directory.
3558 */
3559 if (dentry->d_sb->s_op != &cgroup_ops ||
3560 !S_ISDIR(dentry->d_inode->i_mode))
3561 goto err;
3563 ret = 0;
3564 cgrp = dentry->d_fsdata;
3566 cgroup_iter_start(cgrp, &it);
3567 while ((tsk = cgroup_iter_next(cgrp, &it))) {
3568 switch (tsk->state) {
3569 case TASK_RUNNING:
3570 stats->nr_running++;
3571 break;
3572 case TASK_INTERRUPTIBLE:
3573 stats->nr_sleeping++;
3574 break;
3575 case TASK_UNINTERRUPTIBLE:
3576 stats->nr_uninterruptible++;
3577 break;
3578 case TASK_STOPPED:
3579 stats->nr_stopped++;
3580 break;
3581 default:
3582 if (delayacct_is_task_waiting_on_io(tsk))
3583 stats->nr_io_wait++;
3584 break;
3585 }
3586 }
3587 cgroup_iter_end(cgrp, &it);
3589 err:
3590 return ret;
3591 }
3594 /*
3595 * seq_file methods for the tasks/procs files. The seq_file position is the
3596 * next pid to display; the seq_file iterator is a pointer to the pid
3597 * in the cgroup->l->list array.
3598 */
3600 static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3601 {
3602 /*
3603 * Initially we receive a position value that corresponds to
3604 * one more than the last pid shown (or 0 on the first call or
3605 * after a seek to the start). Use a binary-search to find the
3606 * next pid to display, if any
3607 */
3608 struct cgroup_pidlist *l = s->private;
3609 int index = 0, pid = *pos;
3610 int *iter;
3612 down_read(&l->mutex);
3613 if (pid) {
3614 int end = l->length;
3616 while (index < end) {
3617 int mid = (index + end) / 2;
3618 if (l->list[mid] == pid) {
3619 index = mid;
3620 break;
3621 } else if (l->list[mid] <= pid)
3622 index = mid + 1;
3623 else
3624 end = mid;
3625 }
3626 }
3627 /* If we're off the end of the array, we're done */
3628 if (index >= l->length)
3629 return NULL;
3630 /* Update the abstract position to be the actual pid that we found */
3631 iter = l->list + index;
3632 *pos = *iter;
3633 return iter;
3634 }
3636 static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3637 {
3638 struct cgroup_pidlist *l = s->private;
3639 up_read(&l->mutex);
3640 }
3642 static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3643 {
3644 struct cgroup_pidlist *l = s->private;
3645 pid_t *p = v;
3646 pid_t *end = l->list + l->length;
3647 /*
3648 * Advance to the next pid in the array. If this goes off the
3649 * end, we're done
3650 */
3651 p++;
3652 if (p >= end) {
3653 return NULL;
3654 } else {
3655 *pos = *p;
3656 return p;
3657 }
3658 }
3660 static int cgroup_pidlist_show(struct seq_file *s, void *v)
3661 {
3662 return seq_printf(s, "%d\n", *(int *)v);
3663 }
3665 /*
3666 * seq_operations functions for iterating on pidlists through seq_file -
3667 * independent of whether it's tasks or procs
3668 */
3669 static const struct seq_operations cgroup_pidlist_seq_operations = {
3670 .start = cgroup_pidlist_start,
3671 .stop = cgroup_pidlist_stop,
3672 .next = cgroup_pidlist_next,
3673 .show = cgroup_pidlist_show,
3674 };
3676 static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3677 {
3678 /*
3679 * the case where we're the last user of this particular pidlist will
3680 * have us remove it from the cgroup's list, which entails taking the
3681 * mutex. since in pidlist_find the pidlist->lock depends on cgroup->
3682 * pidlist_mutex, we have to take pidlist_mutex first.
3683 */
3684 mutex_lock(&l->owner->pidlist_mutex);
3685 down_write(&l->mutex);
3686 BUG_ON(!l->use_count);
3687 if (!--l->use_count) {
3688 /* we're the last user if refcount is 0; remove and free */
3689 list_del(&l->links);
3690 mutex_unlock(&l->owner->pidlist_mutex);
3691 pidlist_free(l->list);
3692 put_pid_ns(l->key.ns);
3693 up_write(&l->mutex);
3694 kfree(l);
3695 return;
3696 }
3697 mutex_unlock(&l->owner->pidlist_mutex);
3698 up_write(&l->mutex);
3699 }
3701 static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3702 {
3703 struct cgroup_pidlist *l;
3704 if (!(file->f_mode & FMODE_READ))
3705 return 0;
3706 /*
3707 * the seq_file will only be initialized if the file was opened for
3708 * reading; hence we check if it's not null only in that case.
3709 */
3710 l = ((struct seq_file *)file->private_data)->private;
3711 cgroup_release_pid_array(l);
3712 return seq_release(inode, file);
3713 }
3715 static const struct file_operations cgroup_pidlist_operations = {
3716 .read = seq_read,
3717 .llseek = seq_lseek,
3718 .write = cgroup_file_write,
3719 .release = cgroup_pidlist_release,
3720 };
3722 /*
3723 * The following functions handle opens on a file that displays a pidlist
3724 * (tasks or procs). Prepare an array of the process/thread IDs of whoever's
3725 * in the cgroup.
3726 */
3727 /* helper function for the two below it */
3728 static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3729 {
3730 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3731 struct cgroup_pidlist *l;
3732 int retval;
3734 /* Nothing to do for write-only files */
3735 if (!(file->f_mode & FMODE_READ))
3736 return 0;
3738 /* have the array populated */
3739 retval = pidlist_array_load(cgrp, type, &l);
3740 if (retval)
3741 return retval;
3742 /* configure file information */
3743 file->f_op = &cgroup_pidlist_operations;
3745 retval = seq_open(file, &cgroup_pidlist_seq_operations);
3746 if (retval) {
3747 cgroup_release_pid_array(l);
3748 return retval;
3749 }
3750 ((struct seq_file *)file->private_data)->private = l;
3751 return 0;
3752 }
3753 static int cgroup_tasks_open(struct inode *unused, struct file *file)
3754 {
3755 return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3756 }
3757 static int cgroup_procs_open(struct inode *unused, struct file *file)
3758 {
3759 return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3760 }
3762 static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3763 struct cftype *cft)
3764 {
3765 return notify_on_release(cgrp);
3766 }
3768 static int cgroup_write_notify_on_release(struct cgroup *cgrp,
3769 struct cftype *cft,
3770 u64 val)
3771 {
3772 clear_bit(CGRP_RELEASABLE, &cgrp->flags);
3773 if (val)
3774 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3775 else
3776 clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3777 return 0;
3778 }
3780 /*
3781 * Unregister event and free resources.
3782 *
3783 * Gets called from workqueue.
3784 */
3785 static void cgroup_event_remove(struct work_struct *work)
3786 {
3787 struct cgroup_event *event = container_of(work, struct cgroup_event,
3788 remove);
3789 struct cgroup *cgrp = event->cgrp;
3791 event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3793 eventfd_ctx_put(event->eventfd);
3794 kfree(event);
3795 dput(cgrp->dentry);
3796 }
3798 /*
3799 * Gets called on POLLHUP on eventfd when user closes it.
3800 *
3801 * Called with wqh->lock held and interrupts disabled.
3802 */
3803 static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
3804 int sync, void *key)
3805 {
3806 struct cgroup_event *event = container_of(wait,
3807 struct cgroup_event, wait);
3808 struct cgroup *cgrp = event->cgrp;
3809 unsigned long flags = (unsigned long)key;
3811 if (flags & POLLHUP) {
3812 __remove_wait_queue(event->wqh, &event->wait);
3813 spin_lock(&cgrp->event_list_lock);
3814 list_del_init(&event->list);
3815 spin_unlock(&cgrp->event_list_lock);
3816 /*
3817 * We are in atomic context, but cgroup_event_remove() may
3818 * sleep, so we have to call it in workqueue.
3819 */
3820 schedule_work(&event->remove);
3821 }
3823 return 0;
3824 }
3826 static void cgroup_event_ptable_queue_proc(struct file *file,
3827 wait_queue_head_t *wqh, poll_table *pt)
3828 {
3829 struct cgroup_event *event = container_of(pt,
3830 struct cgroup_event, pt);
3832 event->wqh = wqh;
3833 add_wait_queue(wqh, &event->wait);
3834 }
3836 /*
3837 * Parse input and register new cgroup event handler.
3838 *
3839 * Input must be in format '<event_fd> <control_fd> <args>'.
3840 * Interpretation of args is defined by control file implementation.
3841 */
3842 static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
3843 const char *buffer)
3844 {
3845 struct cgroup_event *event = NULL;
3846 unsigned int efd, cfd;
3847 struct file *efile = NULL;
3848 struct file *cfile = NULL;
3849 char *endp;
3850 int ret;
3852 efd = simple_strtoul(buffer, &endp, 10);
3853 if (*endp != ' ')
3854 return -EINVAL;
3855 buffer = endp + 1;
3857 cfd = simple_strtoul(buffer, &endp, 10);
3858 if ((*endp != ' ') && (*endp != '\0'))
3859 return -EINVAL;
3860 buffer = endp + 1;
3862 event = kzalloc(sizeof(*event), GFP_KERNEL);
3863 if (!event)
3864 return -ENOMEM;
3865 event->cgrp = cgrp;
3866 INIT_LIST_HEAD(&event->list);
3867 init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
3868 init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
3869 INIT_WORK(&event->remove, cgroup_event_remove);
3871 efile = eventfd_fget(efd);
3872 if (IS_ERR(efile)) {
3873 ret = PTR_ERR(efile);
3874 goto fail;
3875 }
3877 event->eventfd = eventfd_ctx_fileget(efile);
3878 if (IS_ERR(event->eventfd)) {
3879 ret = PTR_ERR(event->eventfd);
3880 goto fail;
3881 }
3883 cfile = fget(cfd);
3884 if (!cfile) {
3885 ret = -EBADF;
3886 goto fail;
3887 }
3889 /* the process need read permission on control file */
3890 /* AV: shouldn't we check that it's been opened for read instead? */
3891 ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3892 if (ret < 0)
3893 goto fail;
3895 event->cft = __file_cft(cfile);
3896 if (IS_ERR(event->cft)) {
3897 ret = PTR_ERR(event->cft);
3898 goto fail;
3899 }
3901 if (!event->cft->register_event || !event->cft->unregister_event) {
3902 ret = -EINVAL;
3903 goto fail;
3904 }
3906 ret = event->cft->register_event(cgrp, event->cft,
3907 event->eventfd, buffer);
3908 if (ret)
3909 goto fail;
3911 if (efile->f_op->poll(efile, &event->pt) & POLLHUP) {
3912 event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3913 ret = 0;
3914 goto fail;
3915 }
3917 /*
3918 * Events should be removed after rmdir of cgroup directory, but before
3919 * destroying subsystem state objects. Let's take reference to cgroup
3920 * directory dentry to do that.
3921 */
3922 dget(cgrp->dentry);
3924 spin_lock(&cgrp->event_list_lock);
3925 list_add(&event->list, &cgrp->event_list);
3926 spin_unlock(&cgrp->event_list_lock);
3928 fput(cfile);
3929 fput(efile);
3931 return 0;
3933 fail:
3934 if (cfile)
3935 fput(cfile);
3937 if (event && event->eventfd && !IS_ERR(event->eventfd))
3938 eventfd_ctx_put(event->eventfd);
3940 if (!IS_ERR_OR_NULL(efile))
3941 fput(efile);
3943 kfree(event);
3945 return ret;
3946 }
3948 static u64 cgroup_clone_children_read(struct cgroup *cgrp,
3949 struct cftype *cft)
3950 {
3951 return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3952 }
3954 static int cgroup_clone_children_write(struct cgroup *cgrp,
3955 struct cftype *cft,
3956 u64 val)
3957 {
3958 if (val)
3959 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3960 else
3961 clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3962 return 0;
3963 }
3965 /*
3966 * for the common functions, 'private' gives the type of file
3967 */
3968 /* for hysterical raisins, we can't put this on the older files */
3969 #define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3970 static struct cftype files[] = {
3971 {
3972 .name = "tasks",
3973 .open = cgroup_tasks_open,
3974 .write_u64 = cgroup_tasks_write,
3975 .release = cgroup_pidlist_release,
3976 .mode = S_IRUGO | S_IWUSR,
3977 },
3978 {
3979 .name = CGROUP_FILE_GENERIC_PREFIX "procs",
3980 .open = cgroup_procs_open,
3981 .write_u64 = cgroup_procs_write,
3982 .release = cgroup_pidlist_release,
3983 .mode = S_IRUGO | S_IWUSR,
3984 },
3985 {
3986 .name = "notify_on_release",
3987 .read_u64 = cgroup_read_notify_on_release,
3988 .write_u64 = cgroup_write_notify_on_release,
3989 },
3990 {
3991 .name = CGROUP_FILE_GENERIC_PREFIX "event_control",
3992 .write_string = cgroup_write_event_control,
3993 .mode = S_IWUGO,
3994 },
3995 {
3996 .name = "cgroup.clone_children",
3997 .read_u64 = cgroup_clone_children_read,
3998 .write_u64 = cgroup_clone_children_write,
3999 },
4000 {
4001 .name = "release_agent",
4002 .flags = CFTYPE_ONLY_ON_ROOT,
4003 .read_seq_string = cgroup_release_agent_show,
4004 .write_string = cgroup_release_agent_write,
4005 .max_write_len = PATH_MAX,
4006 },
4007 { } /* terminate */
4008 };
4010 /**
4011 * cgroup_populate_dir - selectively creation of files in a directory
4012 * @cgrp: target cgroup
4013 * @base_files: true if the base files should be added
4014 * @subsys_mask: mask of the subsystem ids whose files should be added
4015 */
4016 static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
4017 unsigned long subsys_mask)
4018 {
4019 int err;
4020 struct cgroup_subsys *ss;
4022 if (base_files) {
4023 err = cgroup_addrm_files(cgrp, NULL, files, true);
4024 if (err < 0)
4025 return err;
4026 }
4028 /* process cftsets of each subsystem */
4029 for_each_subsys(cgrp->root, ss) {
4030 struct cftype_set *set;
4031 if (!test_bit(ss->subsys_id, &subsys_mask))
4032 continue;
4034 list_for_each_entry(set, &ss->cftsets, node)
4035 cgroup_addrm_files(cgrp, ss, set->cfts, true);
4036 }
4038 /* This cgroup is ready now */
4039 for_each_subsys(cgrp->root, ss) {
4040 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4041 /*
4042 * Update id->css pointer and make this css visible from
4043 * CSS ID functions. This pointer will be dereferened
4044 * from RCU-read-side without locks.
4045 */
4046 if (css->id)
4047 rcu_assign_pointer(css->id->css, css);
4048 }
4050 return 0;
4051 }
4053 static void css_dput_fn(struct work_struct *work)
4054 {
4055 struct cgroup_subsys_state *css =
4056 container_of(work, struct cgroup_subsys_state, dput_work);
4057 struct dentry *dentry = css->cgroup->dentry;
4058 struct super_block *sb = dentry->d_sb;
4060 atomic_inc(&sb->s_active);
4061 dput(dentry);
4062 deactivate_super(sb);
4063 }
4065 static void init_cgroup_css(struct cgroup_subsys_state *css,
4066 struct cgroup_subsys *ss,
4067 struct cgroup *cgrp)
4068 {
4069 css->cgroup = cgrp;
4070 atomic_set(&css->refcnt, 1);
4071 css->flags = 0;
4072 css->id = NULL;
4073 if (cgrp == dummytop)
4074 css->flags |= CSS_ROOT;
4075 BUG_ON(cgrp->subsys[ss->subsys_id]);
4076 cgrp->subsys[ss->subsys_id] = css;
4078 /*
4079 * css holds an extra ref to @cgrp->dentry which is put on the last
4080 * css_put(). dput() requires process context, which css_put() may
4081 * be called without. @css->dput_work will be used to invoke
4082 * dput() asynchronously from css_put().
4083 */
4084 INIT_WORK(&css->dput_work, css_dput_fn);
4085 }
4087 /* invoke ->post_create() on a new CSS and mark it online if successful */
4088 static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
4089 {
4090 int ret = 0;
4092 lockdep_assert_held(&cgroup_mutex);
4094 if (ss->css_online)
4095 ret = ss->css_online(cgrp);
4096 if (!ret)
4097 cgrp->subsys[ss->subsys_id]->flags |= CSS_ONLINE;
4098 return ret;
4099 }
4101 /* if the CSS is online, invoke ->pre_destory() on it and mark it offline */
4102 static void offline_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
4103 __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4104 {
4105 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4107 lockdep_assert_held(&cgroup_mutex);
4109 if (!(css->flags & CSS_ONLINE))
4110 return;
4112 /*
4113 * css_offline() should be called with cgroup_mutex unlocked. See
4114 * 3fa59dfbc3 ("cgroup: fix potential deadlock in pre_destroy") for
4115 * details. This temporary unlocking should go away once
4116 * cgroup_mutex is unexported from controllers.
4117 */
4118 if (ss->css_offline) {
4119 mutex_unlock(&cgroup_mutex);
4120 ss->css_offline(cgrp);
4121 mutex_lock(&cgroup_mutex);
4122 }
4124 cgrp->subsys[ss->subsys_id]->flags &= ~CSS_ONLINE;
4125 }
4127 /*
4128 * cgroup_create - create a cgroup
4129 * @parent: cgroup that will be parent of the new cgroup
4130 * @dentry: dentry of the new cgroup
4131 * @mode: mode to set on new inode
4132 *
4133 * Must be called with the mutex on the parent inode held
4134 */
4135 static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
4136 umode_t mode)
4137 {
4138 struct cgroup *cgrp;
4139 struct cgroupfs_root *root = parent->root;
4140 int err = 0;
4141 struct cgroup_subsys *ss;
4142 struct super_block *sb = root->sb;
4144 /* allocate the cgroup and its ID, 0 is reserved for the root */
4145 cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
4146 if (!cgrp)
4147 return -ENOMEM;
4149 cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);
4150 if (cgrp->id < 0)
4151 goto err_free_cgrp;
4153 /*
4154 * Only live parents can have children. Note that the liveliness
4155 * check isn't strictly necessary because cgroup_mkdir() and
4156 * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
4157 * anyway so that locking is contained inside cgroup proper and we
4158 * don't get nasty surprises if we ever grow another caller.
4159 */
4160 if (!cgroup_lock_live_group(parent)) {
4161 err = -ENODEV;
4162 goto err_free_id;
4163 }
4165 /* Grab a reference on the superblock so the hierarchy doesn't
4166 * get deleted on unmount if there are child cgroups. This
4167 * can be done outside cgroup_mutex, since the sb can't
4168 * disappear while someone has an open control file on the
4169 * fs */
4170 atomic_inc(&sb->s_active);
4172 init_cgroup_housekeeping(cgrp);
4174 cgrp->parent = parent;
4175 cgrp->root = parent->root;
4176 cgrp->top_cgroup = parent->top_cgroup;
4178 if (notify_on_release(parent))
4179 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
4181 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
4182 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4184 for_each_subsys(root, ss) {
4185 struct cgroup_subsys_state *css;
4187 css = ss->css_alloc(cgrp);
4188 if (IS_ERR(css)) {
4189 err = PTR_ERR(css);
4190 goto err_free_all;
4191 }
4192 init_cgroup_css(css, ss, cgrp);
4193 if (ss->use_id) {
4194 err = alloc_css_id(ss, parent, cgrp);
4195 if (err)
4196 goto err_free_all;
4197 }
4198 }
4200 /*
4201 * Create directory. cgroup_create_file() returns with the new
4202 * directory locked on success so that it can be populated without
4203 * dropping cgroup_mutex.
4204 */
4205 err = cgroup_create_file(dentry, S_IFDIR | mode, sb);
4206 if (err < 0)
4207 goto err_free_all;
4208 lockdep_assert_held(&dentry->d_inode->i_mutex);
4210 /* allocation complete, commit to creation */
4211 dentry->d_fsdata = cgrp;
4212 cgrp->dentry = dentry;
4213 list_add_tail(&cgrp->allcg_node, &root->allcg_list);
4214 list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
4215 root->number_of_cgroups++;
4217 /* each css holds a ref to the cgroup's dentry */
4218 for_each_subsys(root, ss)
4219 dget(dentry);
4221 /* creation succeeded, notify subsystems */
4222 for_each_subsys(root, ss) {
4223 err = online_css(ss, cgrp);
4224 if (err)
4225 goto err_destroy;
4227 if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
4228 parent->parent) {
4229 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",
4230 current->comm, current->pid, ss->name);
4231 if (!strcmp(ss->name, "memory"))
4232 pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
4233 ss->warned_broken_hierarchy = true;
4234 }
4235 }
4237 err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
4238 if (err)
4239 goto err_destroy;
4241 mutex_unlock(&cgroup_mutex);
4242 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
4244 return 0;
4246 err_free_all:
4247 for_each_subsys(root, ss) {
4248 if (cgrp->subsys[ss->subsys_id])
4249 ss->css_free(cgrp);
4250 }
4251 mutex_unlock(&cgroup_mutex);
4252 /* Release the reference count that we took on the superblock */
4253 deactivate_super(sb);
4254 err_free_id:
4255 ida_simple_remove(&root->cgroup_ida, cgrp->id);
4256 err_free_cgrp:
4257 kfree(cgrp);
4258 return err;
4260 err_destroy:
4261 cgroup_destroy_locked(cgrp);
4262 mutex_unlock(&cgroup_mutex);
4263 mutex_unlock(&dentry->d_inode->i_mutex);
4264 return err;
4265 }
4267 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
4268 {
4269 struct cgroup *c_parent = dentry->d_parent->d_fsdata;
4271 /* the vfs holds inode->i_mutex already */
4272 return cgroup_create(c_parent, dentry, mode | S_IFDIR);
4273 }
4275 /*
4276 * Check the reference count on each subsystem. Since we already
4277 * established that there are no tasks in the cgroup, if the css refcount
4278 * is also 1, then there should be no outstanding references, so the
4279 * subsystem is safe to destroy. We scan across all subsystems rather than
4280 * using the per-hierarchy linked list of mounted subsystems since we can
4281 * be called via check_for_release() with no synchronization other than
4282 * RCU, and the subsystem linked list isn't RCU-safe.
4283 */
4284 static int cgroup_has_css_refs(struct cgroup *cgrp)
4285 {
4286 int i;
4288 /*
4289 * We won't need to lock the subsys array, because the subsystems
4290 * we're concerned about aren't going anywhere since our cgroup root
4291 * has a reference on them.
4292 */
4293 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4294 struct cgroup_subsys *ss = subsys[i];
4295 struct cgroup_subsys_state *css;
4297 /* Skip subsystems not present or not in this hierarchy */
4298 if (ss == NULL || ss->root != cgrp->root)
4299 continue;
4301 css = cgrp->subsys[ss->subsys_id];
4302 /*
4303 * When called from check_for_release() it's possible
4304 * that by this point the cgroup has been removed
4305 * and the css deleted. But a false-positive doesn't
4306 * matter, since it can only happen if the cgroup
4307 * has been deleted and hence no longer needs the
4308 * release agent to be called anyway.
4309 */
4310 if (css && css_refcnt(css) > 1)
4311 return 1;
4312 }
4313 return 0;
4314 }
4316 static int cgroup_destroy_locked(struct cgroup *cgrp)
4317 __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4318 {
4319 struct dentry *d = cgrp->dentry;
4320 struct cgroup *parent = cgrp->parent;
4321 DEFINE_WAIT(wait);
4322 struct cgroup_event *event, *tmp;
4323 struct cgroup_subsys *ss;
4324 LIST_HEAD(tmp_list);
4326 lockdep_assert_held(&d->d_inode->i_mutex);
4327 lockdep_assert_held(&cgroup_mutex);
4329 if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children))
4330 return -EBUSY;
4332 /*
4333 * Block new css_tryget() by deactivating refcnt and mark @cgrp
4334 * removed. This makes future css_tryget() and child creation
4335 * attempts fail thus maintaining the removal conditions verified
4336 * above.
4337 */
4338 for_each_subsys(cgrp->root, ss) {
4339 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4341 WARN_ON(atomic_read(&css->refcnt) < 0);
4342 atomic_add(CSS_DEACT_BIAS, &css->refcnt);
4343 }
4344 set_bit(CGRP_REMOVED, &cgrp->flags);
4346 /* tell subsystems to initate destruction */
4347 for_each_subsys(cgrp->root, ss)
4348 offline_css(ss, cgrp);
4350 /*
4351 * Put all the base refs. Each css holds an extra reference to the
4352 * cgroup's dentry and cgroup removal proceeds regardless of css
4353 * refs. On the last put of each css, whenever that may be, the
4354 * extra dentry ref is put so that dentry destruction happens only
4355 * after all css's are released.
4356 */
4357 for_each_subsys(cgrp->root, ss)
4358 css_put(cgrp->subsys[ss->subsys_id]);
4360 raw_spin_lock(&release_list_lock);
4361 if (!list_empty(&cgrp->release_list))
4362 list_del_init(&cgrp->release_list);
4363 raw_spin_unlock(&release_list_lock);
4365 /* delete this cgroup from parent->children */
4366 list_del_rcu(&cgrp->sibling);
4367 list_del_init(&cgrp->allcg_node);
4369 dget(d);
4370 cgroup_d_remove_dir(d);
4371 dput(d);
4373 set_bit(CGRP_RELEASABLE, &parent->flags);
4374 check_for_release(parent);
4376 /*
4377 * Unregister events and notify userspace.
4378 * Notify userspace about cgroup removing only after rmdir of cgroup
4379 * directory to avoid race between userspace and kernelspace. Use
4380 * a temporary list to avoid a deadlock with cgroup_event_wake(). Since
4381 * cgroup_event_wake() is called with the wait queue head locked,
4382 * remove_wait_queue() cannot be called while holding event_list_lock.
4383 */
4384 spin_lock(&cgrp->event_list_lock);
4385 list_splice_init(&cgrp->event_list, &tmp_list);
4386 spin_unlock(&cgrp->event_list_lock);
4387 list_for_each_entry_safe(event, tmp, &tmp_list, list) {
4388 list_del_init(&event->list);
4389 remove_wait_queue(event->wqh, &event->wait);
4390 eventfd_signal(event->eventfd, 1);
4391 schedule_work(&event->remove);
4392 }
4394 return 0;
4395 }
4397 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
4398 {
4399 int ret;
4401 mutex_lock(&cgroup_mutex);
4402 ret = cgroup_destroy_locked(dentry->d_fsdata);
4403 mutex_unlock(&cgroup_mutex);
4405 return ret;
4406 }
4408 static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
4409 {
4410 INIT_LIST_HEAD(&ss->cftsets);
4412 /*
4413 * base_cftset is embedded in subsys itself, no need to worry about
4414 * deregistration.
4415 */
4416 if (ss->base_cftypes) {
4417 ss->base_cftset.cfts = ss->base_cftypes;
4418 list_add_tail(&ss->base_cftset.node, &ss->cftsets);
4419 }
4420 }
4422 static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4423 {
4424 struct cgroup_subsys_state *css;
4426 printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4428 mutex_lock(&cgroup_mutex);
4430 /* init base cftset */
4431 cgroup_init_cftsets(ss);
4433 /* Create the top cgroup state for this subsystem */
4434 list_add(&ss->sibling, &rootnode.subsys_list);
4435 ss->root = &rootnode;
4436 css = ss->css_alloc(dummytop);
4437 /* We don't handle early failures gracefully */
4438 BUG_ON(IS_ERR(css));
4439 init_cgroup_css(css, ss, dummytop);
4441 /* Update the init_css_set to contain a subsys
4442 * pointer to this state - since the subsystem is
4443 * newly registered, all tasks and hence the
4444 * init_css_set is in the subsystem's top cgroup. */
4445 init_css_set.subsys[ss->subsys_id] = css;
4447 need_forkexit_callback |= ss->fork || ss->exit;
4449 /* At system boot, before all subsystems have been
4450 * registered, no tasks have been forked, so we don't
4451 * need to invoke fork callbacks here. */
4452 BUG_ON(!list_empty(&init_task.tasks));
4454 ss->active = 1;
4455 BUG_ON(online_css(ss, dummytop));
4457 mutex_unlock(&cgroup_mutex);
4459 /* this function shouldn't be used with modular subsystems, since they
4460 * need to register a subsys_id, among other things */
4461 BUG_ON(ss->module);
4462 }
4464 /**
4465 * cgroup_load_subsys: load and register a modular subsystem at runtime
4466 * @ss: the subsystem to load
4467 *
4468 * This function should be called in a modular subsystem's initcall. If the
4469 * subsystem is built as a module, it will be assigned a new subsys_id and set
4470 * up for use. If the subsystem is built-in anyway, work is delegated to the
4471 * simpler cgroup_init_subsys.
4472 */
4473 int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
4474 {
4475 struct cgroup_subsys_state *css;
4476 int i, ret;
4478 /* check name and function validity */
4479 if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
4480 ss->css_alloc == NULL || ss->css_free == NULL)
4481 return -EINVAL;
4483 /*
4484 * we don't support callbacks in modular subsystems. this check is
4485 * before the ss->module check for consistency; a subsystem that could
4486 * be a module should still have no callbacks even if the user isn't
4487 * compiling it as one.
4488 */
4489 if (ss->fork || ss->exit)
4490 return -EINVAL;
4492 /*
4493 * an optionally modular subsystem is built-in: we want to do nothing,
4494 * since cgroup_init_subsys will have already taken care of it.
4495 */
4496 if (ss->module == NULL) {
4497 /* a sanity check */
4498 BUG_ON(subsys[ss->subsys_id] != ss);
4499 return 0;
4500 }
4502 /* init base cftset */
4503 cgroup_init_cftsets(ss);
4505 mutex_lock(&cgroup_mutex);
4506 subsys[ss->subsys_id] = ss;
4508 /*
4509 * no ss->css_alloc seems to need anything important in the ss
4510 * struct, so this can happen first (i.e. before the rootnode
4511 * attachment).
4512 */
4513 css = ss->css_alloc(dummytop);
4514 if (IS_ERR(css)) {
4515 /* failure case - need to deassign the subsys[] slot. */
4516 subsys[ss->subsys_id] = NULL;
4517 mutex_unlock(&cgroup_mutex);
4518 return PTR_ERR(css);
4519 }
4521 list_add(&ss->sibling, &rootnode.subsys_list);
4522 ss->root = &rootnode;
4524 /* our new subsystem will be attached to the dummy hierarchy. */
4525 init_cgroup_css(css, ss, dummytop);
4526 /* init_idr must be after init_cgroup_css because it sets css->id. */
4527 if (ss->use_id) {
4528 ret = cgroup_init_idr(ss, css);
4529 if (ret)
4530 goto err_unload;
4531 }
4533 /*
4534 * Now we need to entangle the css into the existing css_sets. unlike
4535 * in cgroup_init_subsys, there are now multiple css_sets, so each one
4536 * will need a new pointer to it; done by iterating the css_set_table.
4537 * furthermore, modifying the existing css_sets will corrupt the hash
4538 * table state, so each changed css_set will need its hash recomputed.
4539 * this is all done under the css_set_lock.
4540 */
4541 write_lock(&css_set_lock);
4542 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
4543 struct css_set *cg;
4544 struct hlist_node *node, *tmp;
4545 struct hlist_head *bucket = &css_set_table[i], *new_bucket;
4547 hlist_for_each_entry_safe(cg, node, tmp, bucket, hlist) {
4548 /* skip entries that we already rehashed */
4549 if (cg->subsys[ss->subsys_id])
4550 continue;
4551 /* remove existing entry */
4552 hlist_del(&cg->hlist);
4553 /* set new value */
4554 cg->subsys[ss->subsys_id] = css;
4555 /* recompute hash and restore entry */
4556 new_bucket = css_set_hash(cg->subsys);
4557 hlist_add_head(&cg->hlist, new_bucket);
4558 }
4559 }
4560 write_unlock(&css_set_lock);
4562 ss->active = 1;
4563 ret = online_css(ss, dummytop);
4564 if (ret)
4565 goto err_unload;
4567 /* success! */
4568 mutex_unlock(&cgroup_mutex);
4569 return 0;
4571 err_unload:
4572 mutex_unlock(&cgroup_mutex);
4573 /* @ss can't be mounted here as try_module_get() would fail */
4574 cgroup_unload_subsys(ss);
4575 return ret;
4576 }
4577 EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4579 /**
4580 * cgroup_unload_subsys: unload a modular subsystem
4581 * @ss: the subsystem to unload
4582 *
4583 * This function should be called in a modular subsystem's exitcall. When this
4584 * function is invoked, the refcount on the subsystem's module will be 0, so
4585 * the subsystem will not be attached to any hierarchy.
4586 */
4587 void cgroup_unload_subsys(struct cgroup_subsys *ss)
4588 {
4589 struct cg_cgroup_link *link;
4590 struct hlist_head *hhead;
4592 BUG_ON(ss->module == NULL);
4594 /*
4595 * we shouldn't be called if the subsystem is in use, and the use of
4596 * try_module_get in parse_cgroupfs_options should ensure that it
4597 * doesn't start being used while we're killing it off.
4598 */
4599 BUG_ON(ss->root != &rootnode);
4601 mutex_lock(&cgroup_mutex);
4603 offline_css(ss, dummytop);
4604 ss->active = 0;
4606 if (ss->use_id) {
4607 idr_remove_all(&ss->idr);
4608 idr_destroy(&ss->idr);
4609 }
4611 /* deassign the subsys_id */
4612 subsys[ss->subsys_id] = NULL;
4614 /* remove subsystem from rootnode's list of subsystems */
4615 list_del_init(&ss->sibling);
4617 /*
4618 * disentangle the css from all css_sets attached to the dummytop. as
4619 * in loading, we need to pay our respects to the hashtable gods.
4620 */
4621 write_lock(&css_set_lock);
4622 list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {
4623 struct css_set *cg = link->cg;
4625 hlist_del(&cg->hlist);
4626 cg->subsys[ss->subsys_id] = NULL;
4627 hhead = css_set_hash(cg->subsys);
4628 hlist_add_head(&cg->hlist, hhead);
4629 }
4630 write_unlock(&css_set_lock);
4632 /*
4633 * remove subsystem's css from the dummytop and free it - need to
4634 * free before marking as null because ss->css_free needs the
4635 * cgrp->subsys pointer to find their state. note that this also
4636 * takes care of freeing the css_id.
4637 */
4638 ss->css_free(dummytop);
4639 dummytop->subsys[ss->subsys_id] = NULL;
4641 mutex_unlock(&cgroup_mutex);
4642 }
4643 EXPORT_SYMBOL_GPL(cgroup_unload_subsys);
4645 /**
4646 * cgroup_init_early - cgroup initialization at system boot
4647 *
4648 * Initialize cgroups at system boot, and initialize any
4649 * subsystems that request early init.
4650 */
4651 int __init cgroup_init_early(void)
4652 {
4653 int i;
4654 atomic_set(&init_css_set.refcount, 1);
4655 INIT_LIST_HEAD(&init_css_set.cg_links);
4656 INIT_LIST_HEAD(&init_css_set.tasks);
4657 INIT_HLIST_NODE(&init_css_set.hlist);
4658 css_set_count = 1;
4659 init_cgroup_root(&rootnode);
4660 root_count = 1;
4661 init_task.cgroups = &init_css_set;
4663 init_css_set_link.cg = &init_css_set;
4664 init_css_set_link.cgrp = dummytop;
4665 list_add(&init_css_set_link.cgrp_link_list,
4666 &rootnode.top_cgroup.css_sets);
4667 list_add(&init_css_set_link.cg_link_list,
4668 &init_css_set.cg_links);
4670 for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
4671 INIT_HLIST_HEAD(&css_set_table[i]);
4673 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4674 struct cgroup_subsys *ss = subsys[i];
4676 /* at bootup time, we don't worry about modular subsystems */
4677 if (!ss || ss->module)
4678 continue;
4680 BUG_ON(!ss->name);
4681 BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4682 BUG_ON(!ss->css_alloc);
4683 BUG_ON(!ss->css_free);
4684 if (ss->subsys_id != i) {
4685 printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4686 ss->name, ss->subsys_id);
4687 BUG();
4688 }
4690 if (ss->early_init)
4691 cgroup_init_subsys(ss);
4692 }
4693 return 0;
4694 }
4696 /**
4697 * cgroup_init - cgroup initialization
4698 *
4699 * Register cgroup filesystem and /proc file, and initialize
4700 * any subsystems that didn't request early init.
4701 */
4702 int __init cgroup_init(void)
4703 {
4704 int err;
4705 int i;
4706 struct hlist_head *hhead;
4708 err = bdi_init(&cgroup_backing_dev_info);
4709 if (err)
4710 return err;
4712 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4713 struct cgroup_subsys *ss = subsys[i];
4715 /* at bootup time, we don't worry about modular subsystems */
4716 if (!ss || ss->module)
4717 continue;
4718 if (!ss->early_init)
4719 cgroup_init_subsys(ss);
4720 if (ss->use_id)
4721 cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4722 }
4724 /* Add init_css_set to the hash table */
4725 hhead = css_set_hash(init_css_set.subsys);
4726 hlist_add_head(&init_css_set.hlist, hhead);
4727 BUG_ON(!init_root_id(&rootnode));
4729 cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
4730 if (!cgroup_kobj) {
4731 err = -ENOMEM;
4732 goto out;
4733 }
4735 err = register_filesystem(&cgroup_fs_type);
4736 if (err < 0) {
4737 kobject_put(cgroup_kobj);
4738 goto out;
4739 }
4741 proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4743 out:
4744 if (err)
4745 bdi_destroy(&cgroup_backing_dev_info);
4747 return err;
4748 }
4750 /*
4751 * proc_cgroup_show()
4752 * - Print task's cgroup paths into seq_file, one line for each hierarchy
4753 * - Used for /proc/<pid>/cgroup.
4754 * - No need to task_lock(tsk) on this tsk->cgroup reference, as it
4755 * doesn't really matter if tsk->cgroup changes after we read it,
4756 * and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4757 * anyway. No need to check that tsk->cgroup != NULL, thanks to
4758 * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
4759 * cgroup to top_cgroup.
4760 */
4762 /* TODO: Use a proper seq_file iterator */
4763 static int proc_cgroup_show(struct seq_file *m, void *v)
4764 {
4765 struct pid *pid;
4766 struct task_struct *tsk;
4767 char *buf;
4768 int retval;
4769 struct cgroupfs_root *root;
4771 retval = -ENOMEM;
4772 buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4773 if (!buf)
4774 goto out;
4776 retval = -ESRCH;
4777 pid = m->private;
4778 tsk = get_pid_task(pid, PIDTYPE_PID);
4779 if (!tsk)
4780 goto out_free;
4782 retval = 0;
4784 mutex_lock(&cgroup_mutex);
4786 for_each_active_root(root) {
4787 struct cgroup_subsys *ss;
4788 struct cgroup *cgrp;
4789 int count = 0;
4791 seq_printf(m, "%d:", root->hierarchy_id);
4792 for_each_subsys(root, ss)
4793 seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4794 if (strlen(root->name))
4795 seq_printf(m, "%sname=%s", count ? "," : "",
4796 root->name);
4797 seq_putc(m, ':');
4798 cgrp = task_cgroup_from_root(tsk, root);
4799 retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4800 if (retval < 0)
4801 goto out_unlock;
4802 seq_puts(m, buf);
4803 seq_putc(m, '\n');
4804 }
4806 out_unlock:
4807 mutex_unlock(&cgroup_mutex);
4808 put_task_struct(tsk);
4809 out_free:
4810 kfree(buf);
4811 out:
4812 return retval;
4813 }
4815 static int cgroup_open(struct inode *inode, struct file *file)
4816 {
4817 struct pid *pid = PROC_I(inode)->pid;
4818 return single_open(file, proc_cgroup_show, pid);
4819 }
4821 const struct file_operations proc_cgroup_operations = {
4822 .open = cgroup_open,
4823 .read = seq_read,
4824 .llseek = seq_lseek,
4825 .release = single_release,
4826 };
4828 /* Display information about each subsystem and each hierarchy */
4829 static int proc_cgroupstats_show(struct seq_file *m, void *v)
4830 {
4831 int i;
4833 seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
4834 /*
4835 * ideally we don't want subsystems moving around while we do this.
4836 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
4837 * subsys/hierarchy state.
4838 */
4839 mutex_lock(&cgroup_mutex);
4840 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4841 struct cgroup_subsys *ss = subsys[i];
4842 if (ss == NULL)
4843 continue;
4844 seq_printf(m, "%s\t%d\t%d\t%d\n",
4845 ss->name, ss->root->hierarchy_id,
4846 ss->root->number_of_cgroups, !ss->disabled);
4847 }
4848 mutex_unlock(&cgroup_mutex);
4849 return 0;
4850 }
4852 static int cgroupstats_open(struct inode *inode, struct file *file)
4853 {
4854 return single_open(file, proc_cgroupstats_show, NULL);
4855 }
4857 static const struct file_operations proc_cgroupstats_operations = {
4858 .open = cgroupstats_open,
4859 .read = seq_read,
4860 .llseek = seq_lseek,
4861 .release = single_release,
4862 };
4864 /**
4865 * cgroup_fork - attach newly forked task to its parents cgroup.
4866 * @child: pointer to task_struct of forking parent process.
4867 *
4868 * Description: A task inherits its parent's cgroup at fork().
4869 *
4870 * A pointer to the shared css_set was automatically copied in
4871 * fork.c by dup_task_struct(). However, we ignore that copy, since
4872 * it was not made under the protection of RCU or cgroup_mutex, so
4873 * might no longer be a valid cgroup pointer. cgroup_attach_task() might
4874 * have already changed current->cgroups, allowing the previously
4875 * referenced cgroup group to be removed and freed.
4876 *
4877 * At the point that cgroup_fork() is called, 'current' is the parent
4878 * task, and the passed argument 'child' points to the child task.
4879 */
4880 void cgroup_fork(struct task_struct *child)
4881 {
4882 task_lock(current);
4883 child->cgroups = current->cgroups;
4884 get_css_set(child->cgroups);
4885 task_unlock(current);
4886 INIT_LIST_HEAD(&child->cg_list);
4887 }
4889 /**
4890 * cgroup_post_fork - called on a new task after adding it to the task list
4891 * @child: the task in question
4892 *
4893 * Adds the task to the list running through its css_set if necessary and
4894 * call the subsystem fork() callbacks. Has to be after the task is
4895 * visible on the task list in case we race with the first call to
4896 * cgroup_iter_start() - to guarantee that the new task ends up on its
4897 * list.
4898 */
4899 void cgroup_post_fork(struct task_struct *child)
4900 {
4901 int i;
4903 /*
4904 * use_task_css_set_links is set to 1 before we walk the tasklist
4905 * under the tasklist_lock and we read it here after we added the child
4906 * to the tasklist under the tasklist_lock as well. If the child wasn't
4907 * yet in the tasklist when we walked through it from
4908 * cgroup_enable_task_cg_lists(), then use_task_css_set_links value
4909 * should be visible now due to the paired locking and barriers implied
4910 * by LOCK/UNLOCK: it is written before the tasklist_lock unlock
4911 * in cgroup_enable_task_cg_lists() and read here after the tasklist_lock
4912 * lock on fork.
4913 */
4914 if (use_task_css_set_links) {
4915 write_lock(&css_set_lock);
4916 task_lock(child);
4917 if (list_empty(&child->cg_list))
4918 list_add(&child->cg_list, &child->cgroups->tasks);
4919 task_unlock(child);
4920 write_unlock(&css_set_lock);
4921 }
4923 /*
4924 * Call ss->fork(). This must happen after @child is linked on
4925 * css_set; otherwise, @child might change state between ->fork()
4926 * and addition to css_set.
4927 */
4928 if (need_forkexit_callback) {
4929 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4930 struct cgroup_subsys *ss = subsys[i];
4932 /*
4933 * fork/exit callbacks are supported only for
4934 * builtin subsystems and we don't need further
4935 * synchronization as they never go away.
4936 */
4937 if (!ss || ss->module)
4938 continue;
4940 if (ss->fork)
4941 ss->fork(child);
4942 }
4943 }
4944 }
4946 /**
4947 * cgroup_exit - detach cgroup from exiting task
4948 * @tsk: pointer to task_struct of exiting process
4949 * @run_callback: run exit callbacks?
4950 *
4951 * Description: Detach cgroup from @tsk and release it.
4952 *
4953 * Note that cgroups marked notify_on_release force every task in
4954 * them to take the global cgroup_mutex mutex when exiting.
4955 * This could impact scaling on very large systems. Be reluctant to
4956 * use notify_on_release cgroups where very high task exit scaling
4957 * is required on large systems.
4958 *
4959 * the_top_cgroup_hack:
4960 *
4961 * Set the exiting tasks cgroup to the root cgroup (top_cgroup).
4962 *
4963 * We call cgroup_exit() while the task is still competent to
4964 * handle notify_on_release(), then leave the task attached to the
4965 * root cgroup in each hierarchy for the remainder of its exit.
4966 *
4967 * To do this properly, we would increment the reference count on
4968 * top_cgroup, and near the very end of the kernel/exit.c do_exit()
4969 * code we would add a second cgroup function call, to drop that
4970 * reference. This would just create an unnecessary hot spot on
4971 * the top_cgroup reference count, to no avail.
4972 *
4973 * Normally, holding a reference to a cgroup without bumping its
4974 * count is unsafe. The cgroup could go away, or someone could
4975 * attach us to a different cgroup, decrementing the count on
4976 * the first cgroup that we never incremented. But in this case,
4977 * top_cgroup isn't going away, and either task has PF_EXITING set,
4978 * which wards off any cgroup_attach_task() attempts, or task is a failed
4979 * fork, never visible to cgroup_attach_task.
4980 */
4981 void cgroup_exit(struct task_struct *tsk, int run_callbacks)
4982 {
4983 struct css_set *cg;
4984 int i;
4986 /*
4987 * Unlink from the css_set task list if necessary.
4988 * Optimistically check cg_list before taking
4989 * css_set_lock
4990 */
4991 if (!list_empty(&tsk->cg_list)) {
4992 write_lock(&css_set_lock);
4993 if (!list_empty(&tsk->cg_list))
4994 list_del_init(&tsk->cg_list);
4995 write_unlock(&css_set_lock);
4996 }
4998 /* Reassign the task to the init_css_set. */
4999 task_lock(tsk);
5000 cg = tsk->cgroups;
5001 tsk->cgroups = &init_css_set;
5003 if (run_callbacks && need_forkexit_callback) {
5004 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
5005 struct cgroup_subsys *ss = subsys[i];
5007 /* modular subsystems can't use callbacks */
5008 if (!ss || ss->module)
5009 continue;
5011 if (ss->exit) {
5012 struct cgroup *old_cgrp =
5013 rcu_dereference_raw(cg->subsys[i])->cgroup;
5014 struct cgroup *cgrp = task_cgroup(tsk, i);
5015 ss->exit(cgrp, old_cgrp, tsk);
5016 }
5017 }
5018 }
5019 task_unlock(tsk);
5021 if (cg)
5022 put_css_set_taskexit(cg);
5023 }
5025 /**
5026 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
5027 * @cgrp: the cgroup in question
5028 * @task: the task in question
5029 *
5030 * See if @cgrp is a descendant of @task's cgroup in the appropriate
5031 * hierarchy.
5032 *
5033 * If we are sending in dummytop, then presumably we are creating
5034 * the top cgroup in the subsystem.
5035 *
5036 * Called only by the ns (nsproxy) cgroup.
5037 */
5038 int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
5039 {
5040 int ret;
5041 struct cgroup *target;
5043 if (cgrp == dummytop)
5044 return 1;
5046 target = task_cgroup_from_root(task, cgrp->root);
5047 while (cgrp != target && cgrp!= cgrp->top_cgroup)
5048 cgrp = cgrp->parent;
5049 ret = (cgrp == target);
5050 return ret;
5051 }
5053 static void check_for_release(struct cgroup *cgrp)
5054 {
5055 /* All of these checks rely on RCU to keep the cgroup
5056 * structure alive */
5057 if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
5058 && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
5059 /* Control Group is currently removeable. If it's not
5060 * already queued for a userspace notification, queue
5061 * it now */
5062 int need_schedule_work = 0;
5063 raw_spin_lock(&release_list_lock);
5064 if (!cgroup_is_removed(cgrp) &&
5065 list_empty(&cgrp->release_list)) {
5066 list_add(&cgrp->release_list, &release_list);
5067 need_schedule_work = 1;
5068 }
5069 raw_spin_unlock(&release_list_lock);
5070 if (need_schedule_work)
5071 schedule_work(&release_agent_work);
5072 }
5073 }
5075 /* Caller must verify that the css is not for root cgroup */
5076 bool __css_tryget(struct cgroup_subsys_state *css)
5077 {
5078 while (true) {
5079 int t, v;
5081 v = css_refcnt(css);
5082 t = atomic_cmpxchg(&css->refcnt, v, v + 1);
5083 if (likely(t == v))
5084 return true;
5085 else if (t < 0)
5086 return false;
5087 cpu_relax();
5088 }
5089 }
5090 EXPORT_SYMBOL_GPL(__css_tryget);
5092 /* Caller must verify that the css is not for root cgroup */
5093 void __css_put(struct cgroup_subsys_state *css)
5094 {
5095 struct cgroup *cgrp = css->cgroup;
5096 int v;
5098 rcu_read_lock();
5099 v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));
5101 switch (v) {
5102 case 1:
5103 if (notify_on_release(cgrp)) {
5104 set_bit(CGRP_RELEASABLE, &cgrp->flags);
5105 check_for_release(cgrp);
5106 }
5107 break;
5108 case 0:
5109 schedule_work(&css->dput_work);
5110 break;
5111 }
5112 rcu_read_unlock();
5113 }
5114 EXPORT_SYMBOL_GPL(__css_put);
5116 /*
5117 * Notify userspace when a cgroup is released, by running the
5118 * configured release agent with the name of the cgroup (path
5119 * relative to the root of cgroup file system) as the argument.
5120 *
5121 * Most likely, this user command will try to rmdir this cgroup.
5122 *
5123 * This races with the possibility that some other task will be
5124 * attached to this cgroup before it is removed, or that some other
5125 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
5126 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
5127 * unused, and this cgroup will be reprieved from its death sentence,
5128 * to continue to serve a useful existence. Next time it's released,
5129 * we will get notified again, if it still has 'notify_on_release' set.
5130 *
5131 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
5132 * means only wait until the task is successfully execve()'d. The
5133 * separate release agent task is forked by call_usermodehelper(),
5134 * then control in this thread returns here, without waiting for the
5135 * release agent task. We don't bother to wait because the caller of
5136 * this routine has no use for the exit status of the release agent
5137 * task, so no sense holding our caller up for that.
5138 */
5139 static void cgroup_release_agent(struct work_struct *work)
5140 {
5141 BUG_ON(work != &release_agent_work);
5142 mutex_lock(&cgroup_mutex);
5143 raw_spin_lock(&release_list_lock);
5144 while (!list_empty(&release_list)) {
5145 char *argv[3], *envp[3];
5146 int i;
5147 char *pathbuf = NULL, *agentbuf = NULL;
5148 struct cgroup *cgrp = list_entry(release_list.next,
5149 struct cgroup,
5150 release_list);
5151 list_del_init(&cgrp->release_list);
5152 raw_spin_unlock(&release_list_lock);
5153 pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
5154 if (!pathbuf)
5155 goto continue_free;
5156 if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
5157 goto continue_free;
5158 agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
5159 if (!agentbuf)
5160 goto continue_free;
5162 i = 0;
5163 argv[i++] = agentbuf;
5164 argv[i++] = pathbuf;
5165 argv[i] = NULL;
5167 i = 0;
5168 /* minimal command environment */
5169 envp[i++] = "HOME=/";
5170 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
5171 envp[i] = NULL;
5173 /* Drop the lock while we invoke the usermode helper,
5174 * since the exec could involve hitting disk and hence
5175 * be a slow process */
5176 mutex_unlock(&cgroup_mutex);
5177 call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
5178 mutex_lock(&cgroup_mutex);
5179 continue_free:
5180 kfree(pathbuf);
5181 kfree(agentbuf);
5182 raw_spin_lock(&release_list_lock);
5183 }
5184 raw_spin_unlock(&release_list_lock);
5185 mutex_unlock(&cgroup_mutex);
5186 }
5188 static int __init cgroup_disable(char *str)
5189 {
5190 int i;
5191 char *token;
5193 while ((token = strsep(&str, ",")) != NULL) {
5194 if (!*token)
5195 continue;
5196 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
5197 struct cgroup_subsys *ss = subsys[i];
5199 /*
5200 * cgroup_disable, being at boot time, can't
5201 * know about module subsystems, so we don't
5202 * worry about them.
5203 */
5204 if (!ss || ss->module)
5205 continue;
5207 if (!strcmp(token, ss->name)) {
5208 ss->disabled = 1;
5209 printk(KERN_INFO "Disabling %s control group"
5210 " subsystem\n", ss->name);
5211 break;
5212 }
5213 }
5214 }
5215 return 1;
5216 }
5217 __setup("cgroup_disable=", cgroup_disable);
5219 /*
5220 * Functons for CSS ID.
5221 */
5223 /*
5224 *To get ID other than 0, this should be called when !cgroup_is_removed().
5225 */
5226 unsigned short css_id(struct cgroup_subsys_state *css)
5227 {
5228 struct css_id *cssid;
5230 /*
5231 * This css_id() can return correct value when somone has refcnt
5232 * on this or this is under rcu_read_lock(). Once css->id is allocated,
5233 * it's unchanged until freed.
5234 */
5235 cssid = rcu_dereference_check(css->id, css_refcnt(css));
5237 if (cssid)
5238 return cssid->id;
5239 return 0;
5240 }
5241 EXPORT_SYMBOL_GPL(css_id);
5243 unsigned short css_depth(struct cgroup_subsys_state *css)
5244 {
5245 struct css_id *cssid;
5247 cssid = rcu_dereference_check(css->id, css_refcnt(css));
5249 if (cssid)
5250 return cssid->depth;
5251 return 0;
5252 }
5253 EXPORT_SYMBOL_GPL(css_depth);
5255 /**
5256 * css_is_ancestor - test "root" css is an ancestor of "child"
5257 * @child: the css to be tested.
5258 * @root: the css supporsed to be an ancestor of the child.
5259 *
5260 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
5261 * this function reads css->id, the caller must hold rcu_read_lock().
5262 * But, considering usual usage, the csses should be valid objects after test.
5263 * Assuming that the caller will do some action to the child if this returns
5264 * returns true, the caller must take "child";s reference count.
5265 * If "child" is valid object and this returns true, "root" is valid, too.
5266 */
5268 bool css_is_ancestor(struct cgroup_subsys_state *child,
5269 const struct cgroup_subsys_state *root)
5270 {
5271 struct css_id *child_id;
5272 struct css_id *root_id;
5274 child_id = rcu_dereference(child->id);
5275 if (!child_id)
5276 return false;
5277 root_id = rcu_dereference(root->id);
5278 if (!root_id)
5279 return false;
5280 if (child_id->depth < root_id->depth)
5281 return false;
5282 if (child_id->stack[root_id->depth] != root_id->id)
5283 return false;
5284 return true;
5285 }
5287 void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
5288 {
5289 struct css_id *id = css->id;
5290 /* When this is called before css_id initialization, id can be NULL */
5291 if (!id)
5292 return;
5294 BUG_ON(!ss->use_id);
5296 rcu_assign_pointer(id->css, NULL);
5297 rcu_assign_pointer(css->id, NULL);
5298 spin_lock(&ss->id_lock);
5299 idr_remove(&ss->idr, id->id);
5300 spin_unlock(&ss->id_lock);
5301 kfree_rcu(id, rcu_head);
5302 }
5303 EXPORT_SYMBOL_GPL(free_css_id);
5305 /*
5306 * This is called by init or create(). Then, calls to this function are
5307 * always serialized (By cgroup_mutex() at create()).
5308 */
5310 static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
5311 {
5312 struct css_id *newid;
5313 int myid, error, size;
5315 BUG_ON(!ss->use_id);
5317 size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
5318 newid = kzalloc(size, GFP_KERNEL);
5319 if (!newid)
5320 return ERR_PTR(-ENOMEM);
5321 /* get id */
5322 if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
5323 error = -ENOMEM;
5324 goto err_out;
5325 }
5326 spin_lock(&ss->id_lock);
5327 /* Don't use 0. allocates an ID of 1-65535 */
5328 error = idr_get_new_above(&ss->idr, newid, 1, &myid);
5329 spin_unlock(&ss->id_lock);
5331 /* Returns error when there are no free spaces for new ID.*/
5332 if (error) {
5333 error = -ENOSPC;
5334 goto err_out;
5335 }
5336 if (myid > CSS_ID_MAX)
5337 goto remove_idr;
5339 newid->id = myid;
5340 newid->depth = depth;
5341 return newid;
5342 remove_idr:
5343 error = -ENOSPC;
5344 spin_lock(&ss->id_lock);
5345 idr_remove(&ss->idr, myid);
5346 spin_unlock(&ss->id_lock);
5347 err_out:
5348 kfree(newid);
5349 return ERR_PTR(error);
5351 }
5353 static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
5354 struct cgroup_subsys_state *rootcss)
5355 {
5356 struct css_id *newid;
5358 spin_lock_init(&ss->id_lock);
5359 idr_init(&ss->idr);
5361 newid = get_new_cssid(ss, 0);
5362 if (IS_ERR(newid))
5363 return PTR_ERR(newid);
5365 newid->stack[0] = newid->id;
5366 newid->css = rootcss;
5367 rootcss->id = newid;
5368 return 0;
5369 }
5371 static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
5372 struct cgroup *child)
5373 {
5374 int subsys_id, i, depth = 0;
5375 struct cgroup_subsys_state *parent_css, *child_css;
5376 struct css_id *child_id, *parent_id;
5378 subsys_id = ss->subsys_id;
5379 parent_css = parent->subsys[subsys_id];
5380 child_css = child->subsys[subsys_id];
5381 parent_id = parent_css->id;
5382 depth = parent_id->depth + 1;
5384 child_id = get_new_cssid(ss, depth);
5385 if (IS_ERR(child_id))
5386 return PTR_ERR(child_id);
5388 for (i = 0; i < depth; i++)
5389 child_id->stack[i] = parent_id->stack[i];
5390 child_id->stack[depth] = child_id->id;
5391 /*
5392 * child_id->css pointer will be set after this cgroup is available
5393 * see cgroup_populate_dir()
5394 */
5395 rcu_assign_pointer(child_css->id, child_id);
5397 return 0;
5398 }
5400 /**
5401 * css_lookup - lookup css by id
5402 * @ss: cgroup subsys to be looked into.
5403 * @id: the id
5404 *
5405 * Returns pointer to cgroup_subsys_state if there is valid one with id.
5406 * NULL if not. Should be called under rcu_read_lock()
5407 */
5408 struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
5409 {
5410 struct css_id *cssid = NULL;
5412 BUG_ON(!ss->use_id);
5413 cssid = idr_find(&ss->idr, id);
5415 if (unlikely(!cssid))
5416 return NULL;
5418 return rcu_dereference(cssid->css);
5419 }
5420 EXPORT_SYMBOL_GPL(css_lookup);
5422 /**
5423 * css_get_next - lookup next cgroup under specified hierarchy.
5424 * @ss: pointer to subsystem
5425 * @id: current position of iteration.
5426 * @root: pointer to css. search tree under this.
5427 * @foundid: position of found object.
5428 *
5429 * Search next css under the specified hierarchy of rootid. Calling under
5430 * rcu_read_lock() is necessary. Returns NULL if it reaches the end.
5431 */
5432 struct cgroup_subsys_state *
5433 css_get_next(struct cgroup_subsys *ss, int id,
5434 struct cgroup_subsys_state *root, int *foundid)
5435 {
5436 struct cgroup_subsys_state *ret = NULL;
5437 struct css_id *tmp;
5438 int tmpid;
5439 int rootid = css_id(root);
5440 int depth = css_depth(root);
5442 if (!rootid)
5443 return NULL;
5445 BUG_ON(!ss->use_id);
5446 WARN_ON_ONCE(!rcu_read_lock_held());
5448 /* fill start point for scan */
5449 tmpid = id;
5450 while (1) {
5451 /*
5452 * scan next entry from bitmap(tree), tmpid is updated after
5453 * idr_get_next().
5454 */
5455 tmp = idr_get_next(&ss->idr, &tmpid);
5456 if (!tmp)
5457 break;
5458 if (tmp->depth >= depth && tmp->stack[depth] == rootid) {
5459 ret = rcu_dereference(tmp->css);
5460 if (ret) {
5461 *foundid = tmpid;
5462 break;
5463 }
5464 }
5465 /* continue to scan from next id */
5466 tmpid = tmpid + 1;
5467 }
5468 return ret;
5469 }
5471 /*
5472 * get corresponding css from file open on cgroupfs directory
5473 */
5474 struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
5475 {
5476 struct cgroup *cgrp;
5477 struct inode *inode;
5478 struct cgroup_subsys_state *css;
5480 inode = f->f_dentry->d_inode;
5481 /* check in cgroup filesystem dir */
5482 if (inode->i_op != &cgroup_dir_inode_operations)
5483 return ERR_PTR(-EBADF);
5485 if (id < 0 || id >= CGROUP_SUBSYS_COUNT)
5486 return ERR_PTR(-EINVAL);
5488 /* get cgroup */
5489 cgrp = __d_cgrp(f->f_dentry);
5490 css = cgrp->subsys[id];
5491 return css ? css : ERR_PTR(-ENOENT);
5492 }
5494 #ifdef CONFIG_CGROUP_DEBUG
5495 static struct cgroup_subsys_state *debug_css_alloc(struct cgroup *cont)
5496 {
5497 struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
5499 if (!css)
5500 return ERR_PTR(-ENOMEM);
5502 return css;
5503 }
5505 static void debug_css_free(struct cgroup *cont)
5506 {
5507 kfree(cont->subsys[debug_subsys_id]);
5508 }
5510 static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
5511 {
5512 return atomic_read(&cont->count);
5513 }
5515 static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft)
5516 {
5517 return cgroup_task_count(cont);
5518 }
5520 static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
5521 {
5522 return (u64)(unsigned long)current->cgroups;
5523 }
5525 static u64 current_css_set_refcount_read(struct cgroup *cont,
5526 struct cftype *cft)
5527 {
5528 u64 count;
5530 rcu_read_lock();
5531 count = atomic_read(¤t->cgroups->refcount);
5532 rcu_read_unlock();
5533 return count;
5534 }
5536 static int current_css_set_cg_links_read(struct cgroup *cont,
5537 struct cftype *cft,
5538 struct seq_file *seq)
5539 {
5540 struct cg_cgroup_link *link;
5541 struct css_set *cg;
5543 read_lock(&css_set_lock);
5544 rcu_read_lock();
5545 cg = rcu_dereference(current->cgroups);
5546 list_for_each_entry(link, &cg->cg_links, cg_link_list) {
5547 struct cgroup *c = link->cgrp;
5548 const char *name;
5550 if (c->dentry)
5551 name = c->dentry->d_name.name;
5552 else
5553 name = "?";
5554 seq_printf(seq, "Root %d group %s\n",
5555 c->root->hierarchy_id, name);
5556 }
5557 rcu_read_unlock();
5558 read_unlock(&css_set_lock);
5559 return 0;
5560 }
5562 #define MAX_TASKS_SHOWN_PER_CSS 25
5563 static int cgroup_css_links_read(struct cgroup *cont,
5564 struct cftype *cft,
5565 struct seq_file *seq)
5566 {
5567 struct cg_cgroup_link *link;
5569 read_lock(&css_set_lock);
5570 list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
5571 struct css_set *cg = link->cg;
5572 struct task_struct *task;
5573 int count = 0;
5574 seq_printf(seq, "css_set %p\n", cg);
5575 list_for_each_entry(task, &cg->tasks, cg_list) {
5576 if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
5577 seq_puts(seq, " ...\n");
5578 break;
5579 } else {
5580 seq_printf(seq, " task %d\n",
5581 task_pid_vnr(task));
5582 }
5583 }
5584 }
5585 read_unlock(&css_set_lock);
5586 return 0;
5587 }
5589 static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
5590 {
5591 return test_bit(CGRP_RELEASABLE, &cgrp->flags);
5592 }
5594 static struct cftype debug_files[] = {
5595 {
5596 .name = "cgroup_refcount",
5597 .read_u64 = cgroup_refcount_read,
5598 },
5599 {
5600 .name = "taskcount",
5601 .read_u64 = debug_taskcount_read,
5602 },
5604 {
5605 .name = "current_css_set",
5606 .read_u64 = current_css_set_read,
5607 },
5609 {
5610 .name = "current_css_set_refcount",
5611 .read_u64 = current_css_set_refcount_read,
5612 },
5614 {
5615 .name = "current_css_set_cg_links",
5616 .read_seq_string = current_css_set_cg_links_read,
5617 },
5619 {
5620 .name = "cgroup_css_links",
5621 .read_seq_string = cgroup_css_links_read,
5622 },
5624 {
5625 .name = "releasable",
5626 .read_u64 = releasable_read,
5627 },
5629 { } /* terminate */
5630 };
5632 struct cgroup_subsys debug_subsys = {
5633 .name = "debug",
5634 .css_alloc = debug_css_alloc,
5635 .css_free = debug_css_free,
5636 .subsys_id = debug_subsys_id,
5637 .base_cftypes = debug_files,
5638 };
5639 #endif /* CONFIG_CGROUP_DEBUG */