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1/*
2 * Generic process-grouping system.
3 *
4 * Based originally on the cpuset system, extracted by Paul Menage
5 * Copyright (C) 2006 Google, Inc
6 *
7 * Notifications support
8 * Copyright (C) 2009 Nokia Corporation
9 * Author: Kirill A. Shutemov
10 *
11 * Copyright notices from the original cpuset code:
12 * --------------------------------------------------
13 * Copyright (C) 2003 BULL SA.
14 * Copyright (C) 2004-2006 Silicon Graphics, Inc.
15 *
16 * Portions derived from Patrick Mochel's sysfs code.
17 * sysfs is Copyright (c) 2001-3 Patrick Mochel
18 *
19 * 2003-10-10 Written by Simon Derr.
20 * 2003-10-22 Updates by Stephen Hemminger.
21 * 2004 May-July Rework by Paul Jackson.
22 * ---------------------------------------------------
23 *
24 * This file is subject to the terms and conditions of the GNU General Public
25 * License. See the file COPYING in the main directory of the Linux
26 * distribution for more details.
27 */
28
29#include <linux/cgroup.h>
30#include <linux/cred.h>
31#include <linux/ctype.h>
32#include <linux/errno.h>
33#include <linux/init_task.h>
34#include <linux/kernel.h>
35#include <linux/list.h>
36#include <linux/magic.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/slab.h>
45#include <linux/spinlock.h>
46#include <linux/rwsem.h>
47#include <linux/string.h>
48#include <linux/sort.h>
49#include <linux/kmod.h>
50#include <linux/delayacct.h>
51#include <linux/cgroupstats.h>
52#include <linux/hashtable.h>
53#include <linux/pid_namespace.h>
54#include <linux/idr.h>
55#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
56#include <linux/kthread.h>
57#include <linux/delay.h>
58
59#include <linux/atomic.h>
60
61/*
62 * pidlists linger the following amount before being destroyed. The goal
63 * is avoiding frequent destruction in the middle of consecutive read calls
64 * Expiring in the middle is a performance problem not a correctness one.
65 * 1 sec should be enough.
66 */
67#define CGROUP_PIDLIST_DESTROY_DELAY HZ
68
69#define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
70 MAX_CFTYPE_NAME + 2)
71
72/*
73 * cgroup_tree_mutex nests above cgroup_mutex and protects cftypes, file
74 * creation/removal and hierarchy changing operations including cgroup
75 * creation, removal, css association and controller rebinding. This outer
76 * lock is needed mainly to resolve the circular dependency between kernfs
77 * active ref and cgroup_mutex. cgroup_tree_mutex nests above both.
78 */
79static DEFINE_MUTEX(cgroup_tree_mutex);
80
81/*
82 * cgroup_mutex is the master lock. Any modification to cgroup or its
83 * hierarchy must be performed while holding it.
84 *
85 * css_set_rwsem protects task->cgroups pointer, the list of css_set
86 * objects, and the chain of tasks off each css_set.
87 *
88 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
89 * cgroup.h can use them for lockdep annotations.
90 */
91#ifdef CONFIG_PROVE_RCU
92DEFINE_MUTEX(cgroup_mutex);
93DECLARE_RWSEM(css_set_rwsem);
94EXPORT_SYMBOL_GPL(cgroup_mutex);
95EXPORT_SYMBOL_GPL(css_set_rwsem);
96#else
97static DEFINE_MUTEX(cgroup_mutex);
98static DECLARE_RWSEM(css_set_rwsem);
99#endif
100
101/*
102 * Protects cgroup_subsys->release_agent_path. Modifying it also requires
103 * cgroup_mutex. Reading requires either cgroup_mutex or this spinlock.
104 */
105static DEFINE_SPINLOCK(release_agent_path_lock);
106
107#define cgroup_assert_mutexes_or_rcu_locked() \
108 rcu_lockdep_assert(rcu_read_lock_held() || \
109 lockdep_is_held(&cgroup_tree_mutex) || \
110 lockdep_is_held(&cgroup_mutex), \
111 "cgroup_[tree_]mutex or RCU read lock required");
112
113/*
114 * cgroup destruction makes heavy use of work items and there can be a lot
115 * of concurrent destructions. Use a separate workqueue so that cgroup
116 * destruction work items don't end up filling up max_active of system_wq
117 * which may lead to deadlock.
118 */
119static struct workqueue_struct *cgroup_destroy_wq;
120
121/*
122 * pidlist destructions need to be flushed on cgroup destruction. Use a
123 * separate workqueue as flush domain.
124 */
125static struct workqueue_struct *cgroup_pidlist_destroy_wq;
126
127/* generate an array of cgroup subsystem pointers */
128#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
129static struct cgroup_subsys *cgroup_subsys[] = {
130#include <linux/cgroup_subsys.h>
131};
132#undef SUBSYS
133
134/* array of cgroup subsystem names */
135#define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
136static const char *cgroup_subsys_name[] = {
137#include <linux/cgroup_subsys.h>
138};
139#undef SUBSYS
140
141/*
142 * The default hierarchy, reserved for the subsystems that are otherwise
143 * unattached - it never has more than a single cgroup, and all tasks are
144 * part of that cgroup.
145 */
146struct cgroup_root cgrp_dfl_root;
147
148/*
149 * The default hierarchy always exists but is hidden until mounted for the
150 * first time. This is for backward compatibility.
151 */
152static bool cgrp_dfl_root_visible;
153
154/* The list of hierarchy roots */
155
156static LIST_HEAD(cgroup_roots);
157static int cgroup_root_count;
158
159/* hierarchy ID allocation and mapping, protected by cgroup_mutex */
160static DEFINE_IDR(cgroup_hierarchy_idr);
161
162/*
163 * Assign a monotonically increasing serial number to cgroups. It
164 * guarantees cgroups with bigger numbers are newer than those with smaller
165 * numbers. Also, as cgroups are always appended to the parent's
166 * ->children list, it guarantees that sibling cgroups are always sorted in
167 * the ascending serial number order on the list. Protected by
168 * cgroup_mutex.
169 */
170static u64 cgroup_serial_nr_next = 1;
171
172/* This flag indicates whether tasks in the fork and exit paths should
173 * check for fork/exit handlers to call. This avoids us having to do
174 * extra work in the fork/exit path if none of the subsystems need to
175 * be called.
176 */
177static int need_forkexit_callback __read_mostly;
178
179static struct cftype cgroup_base_files[];
180
181static void cgroup_put(struct cgroup *cgrp);
182static int rebind_subsystems(struct cgroup_root *dst_root,
183 unsigned long ss_mask);
184static void cgroup_destroy_css_killed(struct cgroup *cgrp);
185static int cgroup_destroy_locked(struct cgroup *cgrp);
186static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
187 bool is_add);
188static void cgroup_pidlist_destroy_all(struct cgroup *cgrp);
189
190/**
191 * cgroup_css - obtain a cgroup's css for the specified subsystem
192 * @cgrp: the cgroup of interest
193 * @ss: the subsystem of interest (%NULL returns the dummy_css)
194 *
195 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
196 * function must be called either under cgroup_mutex or rcu_read_lock() and
197 * the caller is responsible for pinning the returned css if it wants to
198 * keep accessing it outside the said locks. This function may return
199 * %NULL if @cgrp doesn't have @subsys_id enabled.
200 */
201static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
202 struct cgroup_subsys *ss)
203{
204 if (ss)
205 return rcu_dereference_check(cgrp->subsys[ss->id],
206 lockdep_is_held(&cgroup_tree_mutex) ||
207 lockdep_is_held(&cgroup_mutex));
208 else
209 return &cgrp->dummy_css;
210}
211
212/* convenient tests for these bits */
213static inline bool cgroup_is_dead(const struct cgroup *cgrp)
214{
215 return test_bit(CGRP_DEAD, &cgrp->flags);
216}
217
218struct cgroup_subsys_state *seq_css(struct seq_file *seq)
219{
220 struct kernfs_open_file *of = seq->private;
221 struct cgroup *cgrp = of->kn->parent->priv;
222 struct cftype *cft = seq_cft(seq);
223
224 /*
225 * This is open and unprotected implementation of cgroup_css().
226 * seq_css() is only called from a kernfs file operation which has
227 * an active reference on the file. Because all the subsystem
228 * files are drained before a css is disassociated with a cgroup,
229 * the matching css from the cgroup's subsys table is guaranteed to
230 * be and stay valid until the enclosing operation is complete.
231 */
232 if (cft->ss)
233 return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
234 else
235 return &cgrp->dummy_css;
236}
237EXPORT_SYMBOL_GPL(seq_css);
238
239/**
240 * cgroup_is_descendant - test ancestry
241 * @cgrp: the cgroup to be tested
242 * @ancestor: possible ancestor of @cgrp
243 *
244 * Test whether @cgrp is a descendant of @ancestor. It also returns %true
245 * if @cgrp == @ancestor. This function is safe to call as long as @cgrp
246 * and @ancestor are accessible.
247 */
248bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor)
249{
250 while (cgrp) {
251 if (cgrp == ancestor)
252 return true;
253 cgrp = cgrp->parent;
254 }
255 return false;
256}
257
258static int cgroup_is_releasable(const struct cgroup *cgrp)
259{
260 const int bits =
261 (1 << CGRP_RELEASABLE) |
262 (1 << CGRP_NOTIFY_ON_RELEASE);
263 return (cgrp->flags & bits) == bits;
264}
265
266static int notify_on_release(const struct cgroup *cgrp)
267{
268 return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
269}
270
271/**
272 * for_each_css - iterate all css's of a cgroup
273 * @css: the iteration cursor
274 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
275 * @cgrp: the target cgroup to iterate css's of
276 *
277 * Should be called under cgroup_mutex.
278 */
279#define for_each_css(css, ssid, cgrp) \
280 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
281 if (!((css) = rcu_dereference_check( \
282 (cgrp)->subsys[(ssid)], \
283 lockdep_is_held(&cgroup_tree_mutex) || \
284 lockdep_is_held(&cgroup_mutex)))) { } \
285 else
286
287/**
288 * for_each_subsys - iterate all enabled cgroup subsystems
289 * @ss: the iteration cursor
290 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
291 */
292#define for_each_subsys(ss, ssid) \
293 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
294 (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
295
296/* iterate across the hierarchies */
297#define for_each_root(root) \
298 list_for_each_entry((root), &cgroup_roots, root_list)
299
300/**
301 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
302 * @cgrp: the cgroup to be checked for liveness
303 *
304 * On success, returns true; the mutex should be later unlocked. On
305 * failure returns false with no lock held.
306 */
307static bool cgroup_lock_live_group(struct cgroup *cgrp)
308{
309 mutex_lock(&cgroup_mutex);
310 if (cgroup_is_dead(cgrp)) {
311 mutex_unlock(&cgroup_mutex);
312 return false;
313 }
314 return true;
315}
316
317/* the list of cgroups eligible for automatic release. Protected by
318 * release_list_lock */
319static LIST_HEAD(release_list);
320static DEFINE_RAW_SPINLOCK(release_list_lock);
321static void cgroup_release_agent(struct work_struct *work);
322static DECLARE_WORK(release_agent_work, cgroup_release_agent);
323static void check_for_release(struct cgroup *cgrp);
324
325/*
326 * A cgroup can be associated with multiple css_sets as different tasks may
327 * belong to different cgroups on different hierarchies. In the other
328 * direction, a css_set is naturally associated with multiple cgroups.
329 * This M:N relationship is represented by the following link structure
330 * which exists for each association and allows traversing the associations
331 * from both sides.
332 */
333struct cgrp_cset_link {
334 /* the cgroup and css_set this link associates */
335 struct cgroup *cgrp;
336 struct css_set *cset;
337
338 /* list of cgrp_cset_links anchored at cgrp->cset_links */
339 struct list_head cset_link;
340
341 /* list of cgrp_cset_links anchored at css_set->cgrp_links */
342 struct list_head cgrp_link;
343};
344
345/*
346 * The default css_set - used by init and its children prior to any
347 * hierarchies being mounted. It contains a pointer to the root state
348 * for each subsystem. Also used to anchor the list of css_sets. Not
349 * reference-counted, to improve performance when child cgroups
350 * haven't been created.
351 */
352struct css_set init_css_set = {
353 .refcount = ATOMIC_INIT(1),
354 .cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
355 .tasks = LIST_HEAD_INIT(init_css_set.tasks),
356 .mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
357 .mg_preload_node = LIST_HEAD_INIT(init_css_set.mg_preload_node),
358 .mg_node = LIST_HEAD_INIT(init_css_set.mg_node),
359};
360
361static int css_set_count = 1; /* 1 for init_css_set */
362
363/*
364 * hash table for cgroup groups. This improves the performance to find
365 * an existing css_set. This hash doesn't (currently) take into
366 * account cgroups in empty hierarchies.
367 */
368#define CSS_SET_HASH_BITS 7
369static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
370
371static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
372{
373 unsigned long key = 0UL;
374 struct cgroup_subsys *ss;
375 int i;
376
377 for_each_subsys(ss, i)
378 key += (unsigned long)css[i];
379 key = (key >> 16) ^ key;
380
381 return key;
382}
383
384static void put_css_set_locked(struct css_set *cset, bool taskexit)
385{
386 struct cgrp_cset_link *link, *tmp_link;
387
388 lockdep_assert_held(&css_set_rwsem);
389
390 if (!atomic_dec_and_test(&cset->refcount))
391 return;
392
393 /* This css_set is dead. unlink it and release cgroup refcounts */
394 hash_del(&cset->hlist);
395 css_set_count--;
396
397 list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
398 struct cgroup *cgrp = link->cgrp;
399
400 list_del(&link->cset_link);
401 list_del(&link->cgrp_link);
402
403 /* @cgrp can't go away while we're holding css_set_rwsem */
404 if (list_empty(&cgrp->cset_links) && notify_on_release(cgrp)) {
405 if (taskexit)
406 set_bit(CGRP_RELEASABLE, &cgrp->flags);
407 check_for_release(cgrp);
408 }
409
410 kfree(link);
411 }
412
413 kfree_rcu(cset, rcu_head);
414}
415
416static void put_css_set(struct css_set *cset, bool taskexit)
417{
418 /*
419 * Ensure that the refcount doesn't hit zero while any readers
420 * can see it. Similar to atomic_dec_and_lock(), but for an
421 * rwlock
422 */
423 if (atomic_add_unless(&cset->refcount, -1, 1))
424 return;
425
426 down_write(&css_set_rwsem);
427 put_css_set_locked(cset, taskexit);
428 up_write(&css_set_rwsem);
429}
430
431/*
432 * refcounted get/put for css_set objects
433 */
434static inline void get_css_set(struct css_set *cset)
435{
436 atomic_inc(&cset->refcount);
437}
438
439/**
440 * compare_css_sets - helper function for find_existing_css_set().
441 * @cset: candidate css_set being tested
442 * @old_cset: existing css_set for a task
443 * @new_cgrp: cgroup that's being entered by the task
444 * @template: desired set of css pointers in css_set (pre-calculated)
445 *
446 * Returns true if "cset" matches "old_cset" except for the hierarchy
447 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
448 */
449static bool compare_css_sets(struct css_set *cset,
450 struct css_set *old_cset,
451 struct cgroup *new_cgrp,
452 struct cgroup_subsys_state *template[])
453{
454 struct list_head *l1, *l2;
455
456 if (memcmp(template, cset->subsys, sizeof(cset->subsys))) {
457 /* Not all subsystems matched */
458 return false;
459 }
460
461 /*
462 * Compare cgroup pointers in order to distinguish between
463 * different cgroups in heirarchies with no subsystems. We
464 * could get by with just this check alone (and skip the
465 * memcmp above) but on most setups the memcmp check will
466 * avoid the need for this more expensive check on almost all
467 * candidates.
468 */
469
470 l1 = &cset->cgrp_links;
471 l2 = &old_cset->cgrp_links;
472 while (1) {
473 struct cgrp_cset_link *link1, *link2;
474 struct cgroup *cgrp1, *cgrp2;
475
476 l1 = l1->next;
477 l2 = l2->next;
478 /* See if we reached the end - both lists are equal length. */
479 if (l1 == &cset->cgrp_links) {
480 BUG_ON(l2 != &old_cset->cgrp_links);
481 break;
482 } else {
483 BUG_ON(l2 == &old_cset->cgrp_links);
484 }
485 /* Locate the cgroups associated with these links. */
486 link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
487 link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
488 cgrp1 = link1->cgrp;
489 cgrp2 = link2->cgrp;
490 /* Hierarchies should be linked in the same order. */
491 BUG_ON(cgrp1->root != cgrp2->root);
492
493 /*
494 * If this hierarchy is the hierarchy of the cgroup
495 * that's changing, then we need to check that this
496 * css_set points to the new cgroup; if it's any other
497 * hierarchy, then this css_set should point to the
498 * same cgroup as the old css_set.
499 */
500 if (cgrp1->root == new_cgrp->root) {
501 if (cgrp1 != new_cgrp)
502 return false;
503 } else {
504 if (cgrp1 != cgrp2)
505 return false;
506 }
507 }
508 return true;
509}
510
511/**
512 * find_existing_css_set - init css array and find the matching css_set
513 * @old_cset: the css_set that we're using before the cgroup transition
514 * @cgrp: the cgroup that we're moving into
515 * @template: out param for the new set of csses, should be clear on entry
516 */
517static struct css_set *find_existing_css_set(struct css_set *old_cset,
518 struct cgroup *cgrp,
519 struct cgroup_subsys_state *template[])
520{
521 struct cgroup_root *root = cgrp->root;
522 struct cgroup_subsys *ss;
523 struct css_set *cset;
524 unsigned long key;
525 int i;
526
527 /*
528 * Build the set of subsystem state objects that we want to see in the
529 * new css_set. while subsystems can change globally, the entries here
530 * won't change, so no need for locking.
531 */
532 for_each_subsys(ss, i) {
533 if (root->cgrp.subsys_mask & (1UL << i)) {
534 /* Subsystem is in this hierarchy. So we want
535 * the subsystem state from the new
536 * cgroup */
537 template[i] = cgroup_css(cgrp, ss);
538 } else {
539 /* Subsystem is not in this hierarchy, so we
540 * don't want to change the subsystem state */
541 template[i] = old_cset->subsys[i];
542 }
543 }
544
545 key = css_set_hash(template);
546 hash_for_each_possible(css_set_table, cset, hlist, key) {
547 if (!compare_css_sets(cset, old_cset, cgrp, template))
548 continue;
549
550 /* This css_set matches what we need */
551 return cset;
552 }
553
554 /* No existing cgroup group matched */
555 return NULL;
556}
557
558static void free_cgrp_cset_links(struct list_head *links_to_free)
559{
560 struct cgrp_cset_link *link, *tmp_link;
561
562 list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
563 list_del(&link->cset_link);
564 kfree(link);
565 }
566}
567
568/**
569 * allocate_cgrp_cset_links - allocate cgrp_cset_links
570 * @count: the number of links to allocate
571 * @tmp_links: list_head the allocated links are put on
572 *
573 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
574 * through ->cset_link. Returns 0 on success or -errno.
575 */
576static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
577{
578 struct cgrp_cset_link *link;
579 int i;
580
581 INIT_LIST_HEAD(tmp_links);
582
583 for (i = 0; i < count; i++) {
584 link = kzalloc(sizeof(*link), GFP_KERNEL);
585 if (!link) {
586 free_cgrp_cset_links(tmp_links);
587 return -ENOMEM;
588 }
589 list_add(&link->cset_link, tmp_links);
590 }
591 return 0;
592}
593
594/**
595 * link_css_set - a helper function to link a css_set to a cgroup
596 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
597 * @cset: the css_set to be linked
598 * @cgrp: the destination cgroup
599 */
600static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
601 struct cgroup *cgrp)
602{
603 struct cgrp_cset_link *link;
604
605 BUG_ON(list_empty(tmp_links));
606 link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
607 link->cset = cset;
608 link->cgrp = cgrp;
609 list_move(&link->cset_link, &cgrp->cset_links);
610 /*
611 * Always add links to the tail of the list so that the list
612 * is sorted by order of hierarchy creation
613 */
614 list_add_tail(&link->cgrp_link, &cset->cgrp_links);
615}
616
617/**
618 * find_css_set - return a new css_set with one cgroup updated
619 * @old_cset: the baseline css_set
620 * @cgrp: the cgroup to be updated
621 *
622 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
623 * substituted into the appropriate hierarchy.
624 */
625static struct css_set *find_css_set(struct css_set *old_cset,
626 struct cgroup *cgrp)
627{
628 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
629 struct css_set *cset;
630 struct list_head tmp_links;
631 struct cgrp_cset_link *link;
632 unsigned long key;
633
634 lockdep_assert_held(&cgroup_mutex);
635
636 /* First see if we already have a cgroup group that matches
637 * the desired set */
638 down_read(&css_set_rwsem);
639 cset = find_existing_css_set(old_cset, cgrp, template);
640 if (cset)
641 get_css_set(cset);
642 up_read(&css_set_rwsem);
643
644 if (cset)
645 return cset;
646
647 cset = kzalloc(sizeof(*cset), GFP_KERNEL);
648 if (!cset)
649 return NULL;
650
651 /* Allocate all the cgrp_cset_link objects that we'll need */
652 if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
653 kfree(cset);
654 return NULL;
655 }
656
657 atomic_set(&cset->refcount, 1);
658 INIT_LIST_HEAD(&cset->cgrp_links);
659 INIT_LIST_HEAD(&cset->tasks);
660 INIT_LIST_HEAD(&cset->mg_tasks);
661 INIT_LIST_HEAD(&cset->mg_preload_node);
662 INIT_LIST_HEAD(&cset->mg_node);
663 INIT_HLIST_NODE(&cset->hlist);
664
665 /* Copy the set of subsystem state objects generated in
666 * find_existing_css_set() */
667 memcpy(cset->subsys, template, sizeof(cset->subsys));
668
669 down_write(&css_set_rwsem);
670 /* Add reference counts and links from the new css_set. */
671 list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
672 struct cgroup *c = link->cgrp;
673
674 if (c->root == cgrp->root)
675 c = cgrp;
676 link_css_set(&tmp_links, cset, c);
677 }
678
679 BUG_ON(!list_empty(&tmp_links));
680
681 css_set_count++;
682
683 /* Add this cgroup group to the hash table */
684 key = css_set_hash(cset->subsys);
685 hash_add(css_set_table, &cset->hlist, key);
686
687 up_write(&css_set_rwsem);
688
689 return cset;
690}
691
692static struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
693{
694 struct cgroup *root_cgrp = kf_root->kn->priv;
695
696 return root_cgrp->root;
697}
698
699static int cgroup_init_root_id(struct cgroup_root *root)
700{
701 int id;
702
703 lockdep_assert_held(&cgroup_mutex);
704
705 id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
706 if (id < 0)
707 return id;
708
709 root->hierarchy_id = id;
710 return 0;
711}
712
713static void cgroup_exit_root_id(struct cgroup_root *root)
714{
715 lockdep_assert_held(&cgroup_mutex);
716
717 if (root->hierarchy_id) {
718 idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
719 root->hierarchy_id = 0;
720 }
721}
722
723static void cgroup_free_root(struct cgroup_root *root)
724{
725 if (root) {
726 /* hierarhcy ID shoulid already have been released */
727 WARN_ON_ONCE(root->hierarchy_id);
728
729 idr_destroy(&root->cgroup_idr);
730 kfree(root);
731 }
732}
733
734static void cgroup_destroy_root(struct cgroup_root *root)
735{
736 struct cgroup *cgrp = &root->cgrp;
737 struct cgrp_cset_link *link, *tmp_link;
738
739 mutex_lock(&cgroup_tree_mutex);
740 mutex_lock(&cgroup_mutex);
741
742 BUG_ON(atomic_read(&root->nr_cgrps));
743 BUG_ON(!list_empty(&cgrp->children));
744
745 /* Rebind all subsystems back to the default hierarchy */
746 rebind_subsystems(&cgrp_dfl_root, cgrp->subsys_mask);
747
748 /*
749 * Release all the links from cset_links to this hierarchy's
750 * root cgroup
751 */
752 down_write(&css_set_rwsem);
753
754 list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
755 list_del(&link->cset_link);
756 list_del(&link->cgrp_link);
757 kfree(link);
758 }
759 up_write(&css_set_rwsem);
760
761 if (!list_empty(&root->root_list)) {
762 list_del(&root->root_list);
763 cgroup_root_count--;
764 }
765
766 cgroup_exit_root_id(root);
767
768 mutex_unlock(&cgroup_mutex);
769 mutex_unlock(&cgroup_tree_mutex);
770
771 kernfs_destroy_root(root->kf_root);
772 cgroup_free_root(root);
773}
774
775/* look up cgroup associated with given css_set on the specified hierarchy */
776static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
777 struct cgroup_root *root)
778{
779 struct cgroup *res = NULL;
780
781 lockdep_assert_held(&cgroup_mutex);
782 lockdep_assert_held(&css_set_rwsem);
783
784 if (cset == &init_css_set) {
785 res = &root->cgrp;
786 } else {
787 struct cgrp_cset_link *link;
788
789 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
790 struct cgroup *c = link->cgrp;
791
792 if (c->root == root) {
793 res = c;
794 break;
795 }
796 }
797 }
798
799 BUG_ON(!res);
800 return res;
801}
802
803/*
804 * Return the cgroup for "task" from the given hierarchy. Must be
805 * called with cgroup_mutex and css_set_rwsem held.
806 */
807static struct cgroup *task_cgroup_from_root(struct task_struct *task,
808 struct cgroup_root *root)
809{
810 /*
811 * No need to lock the task - since we hold cgroup_mutex the
812 * task can't change groups, so the only thing that can happen
813 * is that it exits and its css is set back to init_css_set.
814 */
815 return cset_cgroup_from_root(task_css_set(task), root);
816}
817
818/*
819 * A task must hold cgroup_mutex to modify cgroups.
820 *
821 * Any task can increment and decrement the count field without lock.
822 * So in general, code holding cgroup_mutex can't rely on the count
823 * field not changing. However, if the count goes to zero, then only
824 * cgroup_attach_task() can increment it again. Because a count of zero
825 * means that no tasks are currently attached, therefore there is no
826 * way a task attached to that cgroup can fork (the other way to
827 * increment the count). So code holding cgroup_mutex can safely
828 * assume that if the count is zero, it will stay zero. Similarly, if
829 * a task holds cgroup_mutex on a cgroup with zero count, it
830 * knows that the cgroup won't be removed, as cgroup_rmdir()
831 * needs that mutex.
832 *
833 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
834 * (usually) take cgroup_mutex. These are the two most performance
835 * critical pieces of code here. The exception occurs on cgroup_exit(),
836 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
837 * is taken, and if the cgroup count is zero, a usermode call made
838 * to the release agent with the name of the cgroup (path relative to
839 * the root of cgroup file system) as the argument.
840 *
841 * A cgroup can only be deleted if both its 'count' of using tasks
842 * is zero, and its list of 'children' cgroups is empty. Since all
843 * tasks in the system use _some_ cgroup, and since there is always at
844 * least one task in the system (init, pid == 1), therefore, root cgroup
845 * always has either children cgroups and/or using tasks. So we don't
846 * need a special hack to ensure that root cgroup cannot be deleted.
847 *
848 * P.S. One more locking exception. RCU is used to guard the
849 * update of a tasks cgroup pointer by cgroup_attach_task()
850 */
851
852static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask);
853static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
854static const struct file_operations proc_cgroupstats_operations;
855
856static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
857 char *buf)
858{
859 if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
860 !(cgrp->root->flags & CGRP_ROOT_NOPREFIX))
861 snprintf(buf, CGROUP_FILE_NAME_MAX, "%s.%s",
862 cft->ss->name, cft->name);
863 else
864 strncpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
865 return buf;
866}
867
868/**
869 * cgroup_file_mode - deduce file mode of a control file
870 * @cft: the control file in question
871 *
872 * returns cft->mode if ->mode is not 0
873 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
874 * returns S_IRUGO if it has only a read handler
875 * returns S_IWUSR if it has only a write hander
876 */
877static umode_t cgroup_file_mode(const struct cftype *cft)
878{
879 umode_t mode = 0;
880
881 if (cft->mode)
882 return cft->mode;
883
884 if (cft->read_u64 || cft->read_s64 || cft->seq_show)
885 mode |= S_IRUGO;
886
887 if (cft->write_u64 || cft->write_s64 || cft->write_string ||
888 cft->trigger)
889 mode |= S_IWUSR;
890
891 return mode;
892}
893
894static void cgroup_free_fn(struct work_struct *work)
895{
896 struct cgroup *cgrp = container_of(work, struct cgroup, destroy_work);
897
898 atomic_dec(&cgrp->root->nr_cgrps);
899 cgroup_pidlist_destroy_all(cgrp);
900
901 if (cgrp->parent) {
902 /*
903 * We get a ref to the parent, and put the ref when this
904 * cgroup is being freed, so it's guaranteed that the
905 * parent won't be destroyed before its children.
906 */
907 cgroup_put(cgrp->parent);
908 kernfs_put(cgrp->kn);
909 kfree(cgrp);
910 } else {
911 /*
912 * This is root cgroup's refcnt reaching zero, which
913 * indicates that the root should be released.
914 */
915 cgroup_destroy_root(cgrp->root);
916 }
917}
918
919static void cgroup_free_rcu(struct rcu_head *head)
920{
921 struct cgroup *cgrp = container_of(head, struct cgroup, rcu_head);
922
923 INIT_WORK(&cgrp->destroy_work, cgroup_free_fn);
924 queue_work(cgroup_destroy_wq, &cgrp->destroy_work);
925}
926
927static void cgroup_get(struct cgroup *cgrp)
928{
929 WARN_ON_ONCE(cgroup_is_dead(cgrp));
930 WARN_ON_ONCE(atomic_read(&cgrp->refcnt) <= 0);
931 atomic_inc(&cgrp->refcnt);
932}
933
934static void cgroup_put(struct cgroup *cgrp)
935{
936 if (!atomic_dec_and_test(&cgrp->refcnt))
937 return;
938 if (WARN_ON_ONCE(cgrp->parent && !cgroup_is_dead(cgrp)))
939 return;
940
941 /*
942 * XXX: cgrp->id is only used to look up css's. As cgroup and
943 * css's lifetimes will be decoupled, it should be made
944 * per-subsystem and moved to css->id so that lookups are
945 * successful until the target css is released.
946 */
947 mutex_lock(&cgroup_mutex);
948 idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
949 mutex_unlock(&cgroup_mutex);
950 cgrp->id = -1;
951
952 call_rcu(&cgrp->rcu_head, cgroup_free_rcu);
953}
954
955static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
956{
957 char name[CGROUP_FILE_NAME_MAX];
958
959 lockdep_assert_held(&cgroup_tree_mutex);
960 kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
961}
962
963/**
964 * cgroup_clear_dir - remove subsys files in a cgroup directory
965 * @cgrp: target cgroup
966 * @subsys_mask: mask of the subsystem ids whose files should be removed
967 */
968static void cgroup_clear_dir(struct cgroup *cgrp, unsigned long subsys_mask)
969{
970 struct cgroup_subsys *ss;
971 int i;
972
973 for_each_subsys(ss, i) {
974 struct cftype *cfts;
975
976 if (!test_bit(i, &subsys_mask))
977 continue;
978 list_for_each_entry(cfts, &ss->cfts, node)
979 cgroup_addrm_files(cgrp, cfts, false);
980 }
981}
982
983static int rebind_subsystems(struct cgroup_root *dst_root,
984 unsigned long ss_mask)
985{
986 struct cgroup_subsys *ss;
987 int ssid, ret;
988
989 lockdep_assert_held(&cgroup_tree_mutex);
990 lockdep_assert_held(&cgroup_mutex);
991
992 for_each_subsys(ss, ssid) {
993 if (!(ss_mask & (1 << ssid)))
994 continue;
995
996 /* if @ss is on the dummy_root, we can always move it */
997 if (ss->root == &cgrp_dfl_root)
998 continue;
999
1000 /* if @ss has non-root cgroups attached to it, can't move */
1001 if (!list_empty(&ss->root->cgrp.children))
1002 return -EBUSY;
1003
1004 /* can't move between two non-dummy roots either */
1005 if (dst_root != &cgrp_dfl_root)
1006 return -EBUSY;
1007 }
1008
1009 ret = cgroup_populate_dir(&dst_root->cgrp, ss_mask);
1010 if (ret) {
1011 if (dst_root != &cgrp_dfl_root)
1012 return ret;
1013
1014 /*
1015 * Rebinding back to the default root is not allowed to
1016 * fail. Using both default and non-default roots should
1017 * be rare. Moving subsystems back and forth even more so.
1018 * Just warn about it and continue.
1019 */
1020 if (cgrp_dfl_root_visible) {
1021 pr_warning("cgroup: failed to create files (%d) while rebinding 0x%lx to default root\n",
1022 ret, ss_mask);
1023 pr_warning("cgroup: you may retry by moving them to a different hierarchy and unbinding\n");
1024 }
1025 }
1026
1027 /*
1028 * Nothing can fail from this point on. Remove files for the
1029 * removed subsystems and rebind each subsystem.
1030 */
1031 mutex_unlock(&cgroup_mutex);
1032 for_each_subsys(ss, ssid)
1033 if (ss_mask & (1 << ssid))
1034 cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
1035 mutex_lock(&cgroup_mutex);
1036
1037 for_each_subsys(ss, ssid) {
1038 struct cgroup_root *src_root;
1039 struct cgroup_subsys_state *css;
1040
1041 if (!(ss_mask & (1 << ssid)))
1042 continue;
1043
1044 src_root = ss->root;
1045 css = cgroup_css(&src_root->cgrp, ss);
1046
1047 WARN_ON(!css || cgroup_css(&dst_root->cgrp, ss));
1048
1049 RCU_INIT_POINTER(src_root->cgrp.subsys[ssid], NULL);
1050 rcu_assign_pointer(dst_root->cgrp.subsys[ssid], css);
1051 ss->root = dst_root;
1052 css->cgroup = &dst_root->cgrp;
1053
1054 src_root->cgrp.subsys_mask &= ~(1 << ssid);
1055 dst_root->cgrp.subsys_mask |= 1 << ssid;
1056
1057 if (ss->bind)
1058 ss->bind(css);
1059 }
1060
1061 kernfs_activate(dst_root->cgrp.kn);
1062 return 0;
1063}
1064
1065static int cgroup_show_options(struct seq_file *seq,
1066 struct kernfs_root *kf_root)
1067{
1068 struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1069 struct cgroup_subsys *ss;
1070 int ssid;
1071
1072 for_each_subsys(ss, ssid)
1073 if (root->cgrp.subsys_mask & (1 << ssid))
1074 seq_printf(seq, ",%s", ss->name);
1075 if (root->flags & CGRP_ROOT_SANE_BEHAVIOR)
1076 seq_puts(seq, ",sane_behavior");
1077 if (root->flags & CGRP_ROOT_NOPREFIX)
1078 seq_puts(seq, ",noprefix");
1079 if (root->flags & CGRP_ROOT_XATTR)
1080 seq_puts(seq, ",xattr");
1081
1082 spin_lock(&release_agent_path_lock);
1083 if (strlen(root->release_agent_path))
1084 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1085 spin_unlock(&release_agent_path_lock);
1086
1087 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags))
1088 seq_puts(seq, ",clone_children");
1089 if (strlen(root->name))
1090 seq_printf(seq, ",name=%s", root->name);
1091 return 0;
1092}
1093
1094struct cgroup_sb_opts {
1095 unsigned long subsys_mask;
1096 unsigned long flags;
1097 char *release_agent;
1098 bool cpuset_clone_children;
1099 char *name;
1100 /* User explicitly requested empty subsystem */
1101 bool none;
1102};
1103
1104/*
1105 * Convert a hierarchy specifier into a bitmask of subsystems and
1106 * flags. Call with cgroup_mutex held to protect the cgroup_subsys[]
1107 * array. This function takes refcounts on subsystems to be used, unless it
1108 * returns error, in which case no refcounts are taken.
1109 */
1110static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1111{
1112 char *token, *o = data;
1113 bool all_ss = false, one_ss = false;
1114 unsigned long mask = (unsigned long)-1;
1115 struct cgroup_subsys *ss;
1116 int i;
1117
1118 BUG_ON(!mutex_is_locked(&cgroup_mutex));
1119
1120#ifdef CONFIG_CPUSETS
1121 mask = ~(1UL << cpuset_cgrp_id);
1122#endif
1123
1124 memset(opts, 0, sizeof(*opts));
1125
1126 while ((token = strsep(&o, ",")) != NULL) {
1127 if (!*token)
1128 return -EINVAL;
1129 if (!strcmp(token, "none")) {
1130 /* Explicitly have no subsystems */
1131 opts->none = true;
1132 continue;
1133 }
1134 if (!strcmp(token, "all")) {
1135 /* Mutually exclusive option 'all' + subsystem name */
1136 if (one_ss)
1137 return -EINVAL;
1138 all_ss = true;
1139 continue;
1140 }
1141 if (!strcmp(token, "__DEVEL__sane_behavior")) {
1142 opts->flags |= CGRP_ROOT_SANE_BEHAVIOR;
1143 continue;
1144 }
1145 if (!strcmp(token, "noprefix")) {
1146 opts->flags |= CGRP_ROOT_NOPREFIX;
1147 continue;
1148 }
1149 if (!strcmp(token, "clone_children")) {
1150 opts->cpuset_clone_children = true;
1151 continue;
1152 }
1153 if (!strcmp(token, "xattr")) {
1154 opts->flags |= CGRP_ROOT_XATTR;
1155 continue;
1156 }
1157 if (!strncmp(token, "release_agent=", 14)) {
1158 /* Specifying two release agents is forbidden */
1159 if (opts->release_agent)
1160 return -EINVAL;
1161 opts->release_agent =
1162 kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1163 if (!opts->release_agent)
1164 return -ENOMEM;
1165 continue;
1166 }
1167 if (!strncmp(token, "name=", 5)) {
1168 const char *name = token + 5;
1169 /* Can't specify an empty name */
1170 if (!strlen(name))
1171 return -EINVAL;
1172 /* Must match [\w.-]+ */
1173 for (i = 0; i < strlen(name); i++) {
1174 char c = name[i];
1175 if (isalnum(c))
1176 continue;
1177 if ((c == '.') || (c == '-') || (c == '_'))
1178 continue;
1179 return -EINVAL;
1180 }
1181 /* Specifying two names is forbidden */
1182 if (opts->name)
1183 return -EINVAL;
1184 opts->name = kstrndup(name,
1185 MAX_CGROUP_ROOT_NAMELEN - 1,
1186 GFP_KERNEL);
1187 if (!opts->name)
1188 return -ENOMEM;
1189
1190 continue;
1191 }
1192
1193 for_each_subsys(ss, i) {
1194 if (strcmp(token, ss->name))
1195 continue;
1196 if (ss->disabled)
1197 continue;
1198
1199 /* Mutually exclusive option 'all' + subsystem name */
1200 if (all_ss)
1201 return -EINVAL;
1202 set_bit(i, &opts->subsys_mask);
1203 one_ss = true;
1204
1205 break;
1206 }
1207 if (i == CGROUP_SUBSYS_COUNT)
1208 return -ENOENT;
1209 }
1210
1211 /* Consistency checks */
1212
1213 if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
1214 pr_warning("cgroup: sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
1215
1216 if ((opts->flags & (CGRP_ROOT_NOPREFIX | CGRP_ROOT_XATTR)) ||
1217 opts->cpuset_clone_children || opts->release_agent ||
1218 opts->name) {
1219 pr_err("cgroup: sane_behavior: noprefix, xattr, clone_children, release_agent and name are not allowed\n");
1220 return -EINVAL;
1221 }
1222 } else {
1223 /*
1224 * If the 'all' option was specified select all the
1225 * subsystems, otherwise if 'none', 'name=' and a subsystem
1226 * name options were not specified, let's default to 'all'
1227 */
1228 if (all_ss || (!one_ss && !opts->none && !opts->name))
1229 for_each_subsys(ss, i)
1230 if (!ss->disabled)
1231 set_bit(i, &opts->subsys_mask);
1232
1233 /*
1234 * We either have to specify by name or by subsystems. (So
1235 * all empty hierarchies must have a name).
1236 */
1237 if (!opts->subsys_mask && !opts->name)
1238 return -EINVAL;
1239 }
1240
1241 /*
1242 * Option noprefix was introduced just for backward compatibility
1243 * with the old cpuset, so we allow noprefix only if mounting just
1244 * the cpuset subsystem.
1245 */
1246 if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
1247 return -EINVAL;
1248
1249
1250 /* Can't specify "none" and some subsystems */
1251 if (opts->subsys_mask && opts->none)
1252 return -EINVAL;
1253
1254 return 0;
1255}
1256
1257static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
1258{
1259 int ret = 0;
1260 struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1261 struct cgroup_sb_opts opts;
1262 unsigned long added_mask, removed_mask;
1263
1264 if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) {
1265 pr_err("cgroup: sane_behavior: remount is not allowed\n");
1266 return -EINVAL;
1267 }
1268
1269 mutex_lock(&cgroup_tree_mutex);
1270 mutex_lock(&cgroup_mutex);
1271
1272 /* See what subsystems are wanted */
1273 ret = parse_cgroupfs_options(data, &opts);
1274 if (ret)
1275 goto out_unlock;
1276
1277 if (opts.subsys_mask != root->cgrp.subsys_mask || opts.release_agent)
1278 pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
1279 task_tgid_nr(current), current->comm);
1280
1281 added_mask = opts.subsys_mask & ~root->cgrp.subsys_mask;
1282 removed_mask = root->cgrp.subsys_mask & ~opts.subsys_mask;
1283
1284 /* Don't allow flags or name to change at remount */
1285 if (((opts.flags ^ root->flags) & CGRP_ROOT_OPTION_MASK) ||
1286 (opts.name && strcmp(opts.name, root->name))) {
1287 pr_err("cgroup: option or name mismatch, new: 0x%lx \"%s\", old: 0x%lx \"%s\"\n",
1288 opts.flags & CGRP_ROOT_OPTION_MASK, opts.name ?: "",
1289 root->flags & CGRP_ROOT_OPTION_MASK, root->name);
1290 ret = -EINVAL;
1291 goto out_unlock;
1292 }
1293
1294 /* remounting is not allowed for populated hierarchies */
1295 if (!list_empty(&root->cgrp.children)) {
1296 ret = -EBUSY;
1297 goto out_unlock;
1298 }
1299
1300 ret = rebind_subsystems(root, added_mask);
1301 if (ret)
1302 goto out_unlock;
1303
1304 rebind_subsystems(&cgrp_dfl_root, removed_mask);
1305
1306 if (opts.release_agent) {
1307 spin_lock(&release_agent_path_lock);
1308 strcpy(root->release_agent_path, opts.release_agent);
1309 spin_unlock(&release_agent_path_lock);
1310 }
1311 out_unlock:
1312 kfree(opts.release_agent);
1313 kfree(opts.name);
1314 mutex_unlock(&cgroup_mutex);
1315 mutex_unlock(&cgroup_tree_mutex);
1316 return ret;
1317}
1318
1319/*
1320 * To reduce the fork() overhead for systems that are not actually using
1321 * their cgroups capability, we don't maintain the lists running through
1322 * each css_set to its tasks until we see the list actually used - in other
1323 * words after the first mount.
1324 */
1325static bool use_task_css_set_links __read_mostly;
1326
1327static void cgroup_enable_task_cg_lists(void)
1328{
1329 struct task_struct *p, *g;
1330
1331 down_write(&css_set_rwsem);
1332
1333 if (use_task_css_set_links)
1334 goto out_unlock;
1335
1336 use_task_css_set_links = true;
1337
1338 /*
1339 * We need tasklist_lock because RCU is not safe against
1340 * while_each_thread(). Besides, a forking task that has passed
1341 * cgroup_post_fork() without seeing use_task_css_set_links = 1
1342 * is not guaranteed to have its child immediately visible in the
1343 * tasklist if we walk through it with RCU.
1344 */
1345 read_lock(&tasklist_lock);
1346 do_each_thread(g, p) {
1347 WARN_ON_ONCE(!list_empty(&p->cg_list) ||
1348 task_css_set(p) != &init_css_set);
1349
1350 /*
1351 * We should check if the process is exiting, otherwise
1352 * it will race with cgroup_exit() in that the list
1353 * entry won't be deleted though the process has exited.
1354 * Do it while holding siglock so that we don't end up
1355 * racing against cgroup_exit().
1356 */
1357 spin_lock_irq(&p->sighand->siglock);
1358 if (!(p->flags & PF_EXITING)) {
1359 struct css_set *cset = task_css_set(p);
1360
1361 list_add(&p->cg_list, &cset->tasks);
1362 get_css_set(cset);
1363 }
1364 spin_unlock_irq(&p->sighand->siglock);
1365 } while_each_thread(g, p);
1366 read_unlock(&tasklist_lock);
1367out_unlock:
1368 up_write(&css_set_rwsem);
1369}
1370
1371static void init_cgroup_housekeeping(struct cgroup *cgrp)
1372{
1373 atomic_set(&cgrp->refcnt, 1);
1374 INIT_LIST_HEAD(&cgrp->sibling);
1375 INIT_LIST_HEAD(&cgrp->children);
1376 INIT_LIST_HEAD(&cgrp->cset_links);
1377 INIT_LIST_HEAD(&cgrp->release_list);
1378 INIT_LIST_HEAD(&cgrp->pidlists);
1379 mutex_init(&cgrp->pidlist_mutex);
1380 cgrp->dummy_css.cgroup = cgrp;
1381}
1382
1383static void init_cgroup_root(struct cgroup_root *root,
1384 struct cgroup_sb_opts *opts)
1385{
1386 struct cgroup *cgrp = &root->cgrp;
1387
1388 INIT_LIST_HEAD(&root->root_list);
1389 atomic_set(&root->nr_cgrps, 1);
1390 cgrp->root = root;
1391 init_cgroup_housekeeping(cgrp);
1392 idr_init(&root->cgroup_idr);
1393
1394 root->flags = opts->flags;
1395 if (opts->release_agent)
1396 strcpy(root->release_agent_path, opts->release_agent);
1397 if (opts->name)
1398 strcpy(root->name, opts->name);
1399 if (opts->cpuset_clone_children)
1400 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
1401}
1402
1403static int cgroup_setup_root(struct cgroup_root *root, unsigned long ss_mask)
1404{
1405 LIST_HEAD(tmp_links);
1406 struct cgroup *root_cgrp = &root->cgrp;
1407 struct css_set *cset;
1408 int i, ret;
1409
1410 lockdep_assert_held(&cgroup_tree_mutex);
1411 lockdep_assert_held(&cgroup_mutex);
1412
1413 ret = idr_alloc(&root->cgroup_idr, root_cgrp, 0, 1, GFP_KERNEL);
1414 if (ret < 0)
1415 goto out;
1416 root_cgrp->id = ret;
1417
1418 /*
1419 * We're accessing css_set_count without locking css_set_rwsem here,
1420 * but that's OK - it can only be increased by someone holding
1421 * cgroup_lock, and that's us. The worst that can happen is that we
1422 * have some link structures left over
1423 */
1424 ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
1425 if (ret)
1426 goto out;
1427
1428 ret = cgroup_init_root_id(root);
1429 if (ret)
1430 goto out;
1431
1432 root->kf_root = kernfs_create_root(&cgroup_kf_syscall_ops,
1433 KERNFS_ROOT_CREATE_DEACTIVATED,
1434 root_cgrp);
1435 if (IS_ERR(root->kf_root)) {
1436 ret = PTR_ERR(root->kf_root);
1437 goto exit_root_id;
1438 }
1439 root_cgrp->kn = root->kf_root->kn;
1440
1441 ret = cgroup_addrm_files(root_cgrp, cgroup_base_files, true);
1442 if (ret)
1443 goto destroy_root;
1444
1445 ret = rebind_subsystems(root, ss_mask);
1446 if (ret)
1447 goto destroy_root;
1448
1449 /*
1450 * There must be no failure case after here, since rebinding takes
1451 * care of subsystems' refcounts, which are explicitly dropped in
1452 * the failure exit path.
1453 */
1454 list_add(&root->root_list, &cgroup_roots);
1455 cgroup_root_count++;
1456
1457 /*
1458 * Link the root cgroup in this hierarchy into all the css_set
1459 * objects.
1460 */
1461 down_write(&css_set_rwsem);
1462 hash_for_each(css_set_table, i, cset, hlist)
1463 link_css_set(&tmp_links, cset, root_cgrp);
1464 up_write(&css_set_rwsem);
1465
1466 BUG_ON(!list_empty(&root_cgrp->children));
1467 BUG_ON(atomic_read(&root->nr_cgrps) != 1);
1468
1469 kernfs_activate(root_cgrp->kn);
1470 ret = 0;
1471 goto out;
1472
1473destroy_root:
1474 kernfs_destroy_root(root->kf_root);
1475 root->kf_root = NULL;
1476exit_root_id:
1477 cgroup_exit_root_id(root);
1478out:
1479 free_cgrp_cset_links(&tmp_links);
1480 return ret;
1481}
1482
1483static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1484 int flags, const char *unused_dev_name,
1485 void *data)
1486{
1487 struct cgroup_root *root;
1488 struct cgroup_sb_opts opts;
1489 struct dentry *dentry;
1490 int ret;
1491 bool new_sb;
1492
1493 /*
1494 * The first time anyone tries to mount a cgroup, enable the list
1495 * linking each css_set to its tasks and fix up all existing tasks.
1496 */
1497 if (!use_task_css_set_links)
1498 cgroup_enable_task_cg_lists();
1499
1500 mutex_lock(&cgroup_tree_mutex);
1501 mutex_lock(&cgroup_mutex);
1502
1503 /* First find the desired set of subsystems */
1504 ret = parse_cgroupfs_options(data, &opts);
1505 if (ret)
1506 goto out_unlock;
1507retry:
1508 /* look for a matching existing root */
1509 if (!opts.subsys_mask && !opts.none && !opts.name) {
1510 cgrp_dfl_root_visible = true;
1511 root = &cgrp_dfl_root;
1512 cgroup_get(&root->cgrp);
1513 ret = 0;
1514 goto out_unlock;
1515 }
1516
1517 for_each_root(root) {
1518 bool name_match = false;
1519
1520 if (root == &cgrp_dfl_root)
1521 continue;
1522
1523 /*
1524 * If we asked for a name then it must match. Also, if
1525 * name matches but sybsys_mask doesn't, we should fail.
1526 * Remember whether name matched.
1527 */
1528 if (opts.name) {
1529 if (strcmp(opts.name, root->name))
1530 continue;
1531 name_match = true;
1532 }
1533
1534 /*
1535 * If we asked for subsystems (or explicitly for no
1536 * subsystems) then they must match.
1537 */
1538 if ((opts.subsys_mask || opts.none) &&
1539 (opts.subsys_mask != root->cgrp.subsys_mask)) {
1540 if (!name_match)
1541 continue;
1542 ret = -EBUSY;
1543 goto out_unlock;
1544 }
1545
1546 if ((root->flags ^ opts.flags) & CGRP_ROOT_OPTION_MASK) {
1547 if ((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) {
1548 pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n");
1549 ret = -EINVAL;
1550 goto out_unlock;
1551 } else {
1552 pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n");
1553 }
1554 }
1555
1556 /*
1557 * A root's lifetime is governed by its root cgroup. Zero
1558 * ref indicate that the root is being destroyed. Wait for
1559 * destruction to complete so that the subsystems are free.
1560 * We can use wait_queue for the wait but this path is
1561 * super cold. Let's just sleep for a bit and retry.
1562 */
1563 if (!atomic_inc_not_zero(&root->cgrp.refcnt)) {
1564 mutex_unlock(&cgroup_mutex);
1565 mutex_unlock(&cgroup_tree_mutex);
1566 msleep(10);
1567 mutex_lock(&cgroup_tree_mutex);
1568 mutex_lock(&cgroup_mutex);
1569 goto retry;
1570 }
1571
1572 ret = 0;
1573 goto out_unlock;
1574 }
1575
1576 /*
1577 * No such thing, create a new one. name= matching without subsys
1578 * specification is allowed for already existing hierarchies but we
1579 * can't create new one without subsys specification.
1580 */
1581 if (!opts.subsys_mask && !opts.none) {
1582 ret = -EINVAL;
1583 goto out_unlock;
1584 }
1585
1586 root = kzalloc(sizeof(*root), GFP_KERNEL);
1587 if (!root) {
1588 ret = -ENOMEM;
1589 goto out_unlock;
1590 }
1591
1592 init_cgroup_root(root, &opts);
1593
1594 ret = cgroup_setup_root(root, opts.subsys_mask);
1595 if (ret)
1596 cgroup_free_root(root);
1597
1598out_unlock:
1599 mutex_unlock(&cgroup_mutex);
1600 mutex_unlock(&cgroup_tree_mutex);
1601
1602 kfree(opts.release_agent);
1603 kfree(opts.name);
1604
1605 if (ret)
1606 return ERR_PTR(ret);
1607
1608 dentry = kernfs_mount(fs_type, flags, root->kf_root,
1609 CGROUP_SUPER_MAGIC, &new_sb);
1610 if (IS_ERR(dentry) || !new_sb)
1611 cgroup_put(&root->cgrp);
1612 return dentry;
1613}
1614
1615static void cgroup_kill_sb(struct super_block *sb)
1616{
1617 struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
1618 struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1619
1620 cgroup_put(&root->cgrp);
1621 kernfs_kill_sb(sb);
1622}
1623
1624static struct file_system_type cgroup_fs_type = {
1625 .name = "cgroup",
1626 .mount = cgroup_mount,
1627 .kill_sb = cgroup_kill_sb,
1628};
1629
1630static struct kobject *cgroup_kobj;
1631
1632/**
1633 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
1634 * @task: target task
1635 * @buf: the buffer to write the path into
1636 * @buflen: the length of the buffer
1637 *
1638 * Determine @task's cgroup on the first (the one with the lowest non-zero
1639 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
1640 * function grabs cgroup_mutex and shouldn't be used inside locks used by
1641 * cgroup controller callbacks.
1642 *
1643 * Return value is the same as kernfs_path().
1644 */
1645char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
1646{
1647 struct cgroup_root *root;
1648 struct cgroup *cgrp;
1649 int hierarchy_id = 1;
1650 char *path = NULL;
1651
1652 mutex_lock(&cgroup_mutex);
1653 down_read(&css_set_rwsem);
1654
1655 root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
1656
1657 if (root) {
1658 cgrp = task_cgroup_from_root(task, root);
1659 path = cgroup_path(cgrp, buf, buflen);
1660 } else {
1661 /* if no hierarchy exists, everyone is in "/" */
1662 if (strlcpy(buf, "/", buflen) < buflen)
1663 path = buf;
1664 }
1665
1666 up_read(&css_set_rwsem);
1667 mutex_unlock(&cgroup_mutex);
1668 return path;
1669}
1670EXPORT_SYMBOL_GPL(task_cgroup_path);
1671
1672/* used to track tasks and other necessary states during migration */
1673struct cgroup_taskset {
1674 /* the src and dst cset list running through cset->mg_node */
1675 struct list_head src_csets;
1676 struct list_head dst_csets;
1677
1678 /*
1679 * Fields for cgroup_taskset_*() iteration.
1680 *
1681 * Before migration is committed, the target migration tasks are on
1682 * ->mg_tasks of the csets on ->src_csets. After, on ->mg_tasks of
1683 * the csets on ->dst_csets. ->csets point to either ->src_csets
1684 * or ->dst_csets depending on whether migration is committed.
1685 *
1686 * ->cur_csets and ->cur_task point to the current task position
1687 * during iteration.
1688 */
1689 struct list_head *csets;
1690 struct css_set *cur_cset;
1691 struct task_struct *cur_task;
1692};
1693
1694/**
1695 * cgroup_taskset_first - reset taskset and return the first task
1696 * @tset: taskset of interest
1697 *
1698 * @tset iteration is initialized and the first task is returned.
1699 */
1700struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
1701{
1702 tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
1703 tset->cur_task = NULL;
1704
1705 return cgroup_taskset_next(tset);
1706}
1707
1708/**
1709 * cgroup_taskset_next - iterate to the next task in taskset
1710 * @tset: taskset of interest
1711 *
1712 * Return the next task in @tset. Iteration must have been initialized
1713 * with cgroup_taskset_first().
1714 */
1715struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
1716{
1717 struct css_set *cset = tset->cur_cset;
1718 struct task_struct *task = tset->cur_task;
1719
1720 while (&cset->mg_node != tset->csets) {
1721 if (!task)
1722 task = list_first_entry(&cset->mg_tasks,
1723 struct task_struct, cg_list);
1724 else
1725 task = list_next_entry(task, cg_list);
1726
1727 if (&task->cg_list != &cset->mg_tasks) {
1728 tset->cur_cset = cset;
1729 tset->cur_task = task;
1730 return task;
1731 }
1732
1733 cset = list_next_entry(cset, mg_node);
1734 task = NULL;
1735 }
1736
1737 return NULL;
1738}
1739
1740/**
1741 * cgroup_task_migrate - move a task from one cgroup to another.
1742 * @old_cgrp; the cgroup @tsk is being migrated from
1743 * @tsk: the task being migrated
1744 * @new_cset: the new css_set @tsk is being attached to
1745 *
1746 * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
1747 */
1748static void cgroup_task_migrate(struct cgroup *old_cgrp,
1749 struct task_struct *tsk,
1750 struct css_set *new_cset)
1751{
1752 struct css_set *old_cset;
1753
1754 lockdep_assert_held(&cgroup_mutex);
1755 lockdep_assert_held(&css_set_rwsem);
1756
1757 /*
1758 * We are synchronized through threadgroup_lock() against PF_EXITING
1759 * setting such that we can't race against cgroup_exit() changing the
1760 * css_set to init_css_set and dropping the old one.
1761 */
1762 WARN_ON_ONCE(tsk->flags & PF_EXITING);
1763 old_cset = task_css_set(tsk);
1764
1765 get_css_set(new_cset);
1766 rcu_assign_pointer(tsk->cgroups, new_cset);
1767
1768 /*
1769 * Use move_tail so that cgroup_taskset_first() still returns the
1770 * leader after migration. This works because cgroup_migrate()
1771 * ensures that the dst_cset of the leader is the first on the
1772 * tset's dst_csets list.
1773 */
1774 list_move_tail(&tsk->cg_list, &new_cset->mg_tasks);
1775
1776 /*
1777 * We just gained a reference on old_cset by taking it from the
1778 * task. As trading it for new_cset is protected by cgroup_mutex,
1779 * we're safe to drop it here; it will be freed under RCU.
1780 */
1781 set_bit(CGRP_RELEASABLE, &old_cgrp->flags);
1782 put_css_set_locked(old_cset, false);
1783}
1784
1785/**
1786 * cgroup_migrate_finish - cleanup after attach
1787 * @preloaded_csets: list of preloaded css_sets
1788 *
1789 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
1790 * those functions for details.
1791 */
1792static void cgroup_migrate_finish(struct list_head *preloaded_csets)
1793{
1794 struct css_set *cset, *tmp_cset;
1795
1796 lockdep_assert_held(&cgroup_mutex);
1797
1798 down_write(&css_set_rwsem);
1799 list_for_each_entry_safe(cset, tmp_cset, preloaded_csets, mg_preload_node) {
1800 cset->mg_src_cgrp = NULL;
1801 cset->mg_dst_cset = NULL;
1802 list_del_init(&cset->mg_preload_node);
1803 put_css_set_locked(cset, false);
1804 }
1805 up_write(&css_set_rwsem);
1806}
1807
1808/**
1809 * cgroup_migrate_add_src - add a migration source css_set
1810 * @src_cset: the source css_set to add
1811 * @dst_cgrp: the destination cgroup
1812 * @preloaded_csets: list of preloaded css_sets
1813 *
1814 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
1815 * @src_cset and add it to @preloaded_csets, which should later be cleaned
1816 * up by cgroup_migrate_finish().
1817 *
1818 * This function may be called without holding threadgroup_lock even if the
1819 * target is a process. Threads may be created and destroyed but as long
1820 * as cgroup_mutex is not dropped, no new css_set can be put into play and
1821 * the preloaded css_sets are guaranteed to cover all migrations.
1822 */
1823static void cgroup_migrate_add_src(struct css_set *src_cset,
1824 struct cgroup *dst_cgrp,
1825 struct list_head *preloaded_csets)
1826{
1827 struct cgroup *src_cgrp;
1828
1829 lockdep_assert_held(&cgroup_mutex);
1830 lockdep_assert_held(&css_set_rwsem);
1831
1832 src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);
1833
1834 /* nothing to do if this cset already belongs to the cgroup */
1835 if (src_cgrp == dst_cgrp)
1836 return;
1837
1838 if (!list_empty(&src_cset->mg_preload_node))
1839 return;
1840
1841 WARN_ON(src_cset->mg_src_cgrp);
1842 WARN_ON(!list_empty(&src_cset->mg_tasks));
1843 WARN_ON(!list_empty(&src_cset->mg_node));
1844
1845 src_cset->mg_src_cgrp = src_cgrp;
1846 get_css_set(src_cset);
1847 list_add(&src_cset->mg_preload_node, preloaded_csets);
1848}
1849
1850/**
1851 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
1852 * @dst_cgrp: the destination cgroup
1853 * @preloaded_csets: list of preloaded source css_sets
1854 *
1855 * Tasks are about to be moved to @dst_cgrp and all the source css_sets
1856 * have been preloaded to @preloaded_csets. This function looks up and
1857 * pins all destination css_sets, links each to its source, and put them on
1858 * @preloaded_csets.
1859 *
1860 * This function must be called after cgroup_migrate_add_src() has been
1861 * called on each migration source css_set. After migration is performed
1862 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
1863 * @preloaded_csets.
1864 */
1865static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp,
1866 struct list_head *preloaded_csets)
1867{
1868 LIST_HEAD(csets);
1869 struct css_set *src_cset;
1870
1871 lockdep_assert_held(&cgroup_mutex);
1872
1873 /* look up the dst cset for each src cset and link it to src */
1874 list_for_each_entry(src_cset, preloaded_csets, mg_preload_node) {
1875 struct css_set *dst_cset;
1876
1877 dst_cset = find_css_set(src_cset, dst_cgrp);
1878 if (!dst_cset)
1879 goto err;
1880
1881 WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
1882 src_cset->mg_dst_cset = dst_cset;
1883
1884 if (list_empty(&dst_cset->mg_preload_node))
1885 list_add(&dst_cset->mg_preload_node, &csets);
1886 else
1887 put_css_set(dst_cset, false);
1888 }
1889
1890 list_splice(&csets, preloaded_csets);
1891 return 0;
1892err:
1893 cgroup_migrate_finish(&csets);
1894 return -ENOMEM;
1895}
1896
1897/**
1898 * cgroup_migrate - migrate a process or task to a cgroup
1899 * @cgrp: the destination cgroup
1900 * @leader: the leader of the process or the task to migrate
1901 * @threadgroup: whether @leader points to the whole process or a single task
1902 *
1903 * Migrate a process or task denoted by @leader to @cgrp. If migrating a
1904 * process, the caller must be holding threadgroup_lock of @leader. The
1905 * caller is also responsible for invoking cgroup_migrate_add_src() and
1906 * cgroup_migrate_prepare_dst() on the targets before invoking this
1907 * function and following up with cgroup_migrate_finish().
1908 *
1909 * As long as a controller's ->can_attach() doesn't fail, this function is
1910 * guaranteed to succeed. This means that, excluding ->can_attach()
1911 * failure, when migrating multiple targets, the success or failure can be
1912 * decided for all targets by invoking group_migrate_prepare_dst() before
1913 * actually starting migrating.
1914 */
1915static int cgroup_migrate(struct cgroup *cgrp, struct task_struct *leader,
1916 bool threadgroup)
1917{
1918 struct cgroup_taskset tset = {
1919 .src_csets = LIST_HEAD_INIT(tset.src_csets),
1920 .dst_csets = LIST_HEAD_INIT(tset.dst_csets),
1921 .csets = &tset.src_csets,
1922 };
1923 struct cgroup_subsys_state *css, *failed_css = NULL;
1924 struct css_set *cset, *tmp_cset;
1925 struct task_struct *task, *tmp_task;
1926 int i, ret;
1927
1928 /*
1929 * Prevent freeing of tasks while we take a snapshot. Tasks that are
1930 * already PF_EXITING could be freed from underneath us unless we
1931 * take an rcu_read_lock.
1932 */
1933 down_write(&css_set_rwsem);
1934 rcu_read_lock();
1935 task = leader;
1936 do {
1937 /* @task either already exited or can't exit until the end */
1938 if (task->flags & PF_EXITING)
1939 goto next;
1940
1941 /* leave @task alone if post_fork() hasn't linked it yet */
1942 if (list_empty(&task->cg_list))
1943 goto next;
1944
1945 cset = task_css_set(task);
1946 if (!cset->mg_src_cgrp)
1947 goto next;
1948
1949 /*
1950 * cgroup_taskset_first() must always return the leader.
1951 * Take care to avoid disturbing the ordering.
1952 */
1953 list_move_tail(&task->cg_list, &cset->mg_tasks);
1954 if (list_empty(&cset->mg_node))
1955 list_add_tail(&cset->mg_node, &tset.src_csets);
1956 if (list_empty(&cset->mg_dst_cset->mg_node))
1957 list_move_tail(&cset->mg_dst_cset->mg_node,
1958 &tset.dst_csets);
1959 next:
1960 if (!threadgroup)
1961 break;
1962 } while_each_thread(leader, task);
1963 rcu_read_unlock();
1964 up_write(&css_set_rwsem);
1965
1966 /* methods shouldn't be called if no task is actually migrating */
1967 if (list_empty(&tset.src_csets))
1968 return 0;
1969
1970 /* check that we can legitimately attach to the cgroup */
1971 for_each_css(css, i, cgrp) {
1972 if (css->ss->can_attach) {
1973 ret = css->ss->can_attach(css, &tset);
1974 if (ret) {
1975 failed_css = css;
1976 goto out_cancel_attach;
1977 }
1978 }
1979 }
1980
1981 /*
1982 * Now that we're guaranteed success, proceed to move all tasks to
1983 * the new cgroup. There are no failure cases after here, so this
1984 * is the commit point.
1985 */
1986 down_write(&css_set_rwsem);
1987 list_for_each_entry(cset, &tset.src_csets, mg_node) {
1988 list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list)
1989 cgroup_task_migrate(cset->mg_src_cgrp, task,
1990 cset->mg_dst_cset);
1991 }
1992 up_write(&css_set_rwsem);
1993
1994 /*
1995 * Migration is committed, all target tasks are now on dst_csets.
1996 * Nothing is sensitive to fork() after this point. Notify
1997 * controllers that migration is complete.
1998 */
1999 tset.csets = &tset.dst_csets;
2000
2001 for_each_css(css, i, cgrp)
2002 if (css->ss->attach)
2003 css->ss->attach(css, &tset);
2004
2005 ret = 0;
2006 goto out_release_tset;
2007
2008out_cancel_attach:
2009 for_each_css(css, i, cgrp) {
2010 if (css == failed_css)
2011 break;
2012 if (css->ss->cancel_attach)
2013 css->ss->cancel_attach(css, &tset);
2014 }
2015out_release_tset:
2016 down_write(&css_set_rwsem);
2017 list_splice_init(&tset.dst_csets, &tset.src_csets);
2018 list_for_each_entry_safe(cset, tmp_cset, &tset.src_csets, mg_node) {
2019 list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
2020 list_del_init(&cset->mg_node);
2021 }
2022 up_write(&css_set_rwsem);
2023 return ret;
2024}
2025
2026/**
2027 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2028 * @dst_cgrp: the cgroup to attach to
2029 * @leader: the task or the leader of the threadgroup to be attached
2030 * @threadgroup: attach the whole threadgroup?
2031 *
2032 * Call holding cgroup_mutex and threadgroup_lock of @leader.
2033 */
2034static int cgroup_attach_task(struct cgroup *dst_cgrp,
2035 struct task_struct *leader, bool threadgroup)
2036{
2037 LIST_HEAD(preloaded_csets);
2038 struct task_struct *task;
2039 int ret;
2040
2041 /* look up all src csets */
2042 down_read(&css_set_rwsem);
2043 rcu_read_lock();
2044 task = leader;
2045 do {
2046 cgroup_migrate_add_src(task_css_set(task), dst_cgrp,
2047 &preloaded_csets);
2048 if (!threadgroup)
2049 break;
2050 } while_each_thread(leader, task);
2051 rcu_read_unlock();
2052 up_read(&css_set_rwsem);
2053
2054 /* prepare dst csets and commit */
2055 ret = cgroup_migrate_prepare_dst(dst_cgrp, &preloaded_csets);
2056 if (!ret)
2057 ret = cgroup_migrate(dst_cgrp, leader, threadgroup);
2058
2059 cgroup_migrate_finish(&preloaded_csets);
2060 return ret;
2061}
2062
2063/*
2064 * Find the task_struct of the task to attach by vpid and pass it along to the
2065 * function to attach either it or all tasks in its threadgroup. Will lock
2066 * cgroup_mutex and threadgroup.
2067 */
2068static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2069{
2070 struct task_struct *tsk;
2071 const struct cred *cred = current_cred(), *tcred;
2072 int ret;
2073
2074 if (!cgroup_lock_live_group(cgrp))
2075 return -ENODEV;
2076
2077retry_find_task:
2078 rcu_read_lock();
2079 if (pid) {
2080 tsk = find_task_by_vpid(pid);
2081 if (!tsk) {
2082 rcu_read_unlock();
2083 ret = -ESRCH;
2084 goto out_unlock_cgroup;
2085 }
2086 /*
2087 * even if we're attaching all tasks in the thread group, we
2088 * only need to check permissions on one of them.
2089 */
2090 tcred = __task_cred(tsk);
2091 if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
2092 !uid_eq(cred->euid, tcred->uid) &&
2093 !uid_eq(cred->euid, tcred->suid)) {
2094 rcu_read_unlock();
2095 ret = -EACCES;
2096 goto out_unlock_cgroup;
2097 }
2098 } else
2099 tsk = current;
2100
2101 if (threadgroup)
2102 tsk = tsk->group_leader;
2103
2104 /*
2105 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2106 * trapped in a cpuset, or RT worker may be born in a cgroup
2107 * with no rt_runtime allocated. Just say no.
2108 */
2109 if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) {
2110 ret = -EINVAL;
2111 rcu_read_unlock();
2112 goto out_unlock_cgroup;
2113 }
2114
2115 get_task_struct(tsk);
2116 rcu_read_unlock();
2117
2118 threadgroup_lock(tsk);
2119 if (threadgroup) {
2120 if (!thread_group_leader(tsk)) {
2121 /*
2122 * a race with de_thread from another thread's exec()
2123 * may strip us of our leadership, if this happens,
2124 * there is no choice but to throw this task away and
2125 * try again; this is
2126 * "double-double-toil-and-trouble-check locking".
2127 */
2128 threadgroup_unlock(tsk);
2129 put_task_struct(tsk);
2130 goto retry_find_task;
2131 }
2132 }
2133
2134 ret = cgroup_attach_task(cgrp, tsk, threadgroup);
2135
2136 threadgroup_unlock(tsk);
2137
2138 put_task_struct(tsk);
2139out_unlock_cgroup:
2140 mutex_unlock(&cgroup_mutex);
2141 return ret;
2142}
2143
2144/**
2145 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2146 * @from: attach to all cgroups of a given task
2147 * @tsk: the task to be attached
2148 */
2149int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2150{
2151 struct cgroup_root *root;
2152 int retval = 0;
2153
2154 mutex_lock(&cgroup_mutex);
2155 for_each_root(root) {
2156 struct cgroup *from_cgrp;
2157
2158 if (root == &cgrp_dfl_root)
2159 continue;
2160
2161 down_read(&css_set_rwsem);
2162 from_cgrp = task_cgroup_from_root(from, root);
2163 up_read(&css_set_rwsem);
2164
2165 retval = cgroup_attach_task(from_cgrp, tsk, false);
2166 if (retval)
2167 break;
2168 }
2169 mutex_unlock(&cgroup_mutex);
2170
2171 return retval;
2172}
2173EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2174
2175static int cgroup_tasks_write(struct cgroup_subsys_state *css,
2176 struct cftype *cft, u64 pid)
2177{
2178 return attach_task_by_pid(css->cgroup, pid, false);
2179}
2180
2181static int cgroup_procs_write(struct cgroup_subsys_state *css,
2182 struct cftype *cft, u64 tgid)
2183{
2184 return attach_task_by_pid(css->cgroup, tgid, true);
2185}
2186
2187static int cgroup_release_agent_write(struct cgroup_subsys_state *css,
2188 struct cftype *cft, char *buffer)
2189{
2190 struct cgroup_root *root = css->cgroup->root;
2191
2192 BUILD_BUG_ON(sizeof(root->release_agent_path) < PATH_MAX);
2193 if (!cgroup_lock_live_group(css->cgroup))
2194 return -ENODEV;
2195 spin_lock(&release_agent_path_lock);
2196 strlcpy(root->release_agent_path, buffer,
2197 sizeof(root->release_agent_path));
2198 spin_unlock(&release_agent_path_lock);
2199 mutex_unlock(&cgroup_mutex);
2200 return 0;
2201}
2202
2203static int cgroup_release_agent_show(struct seq_file *seq, void *v)
2204{
2205 struct cgroup *cgrp = seq_css(seq)->cgroup;
2206
2207 if (!cgroup_lock_live_group(cgrp))
2208 return -ENODEV;
2209 seq_puts(seq, cgrp->root->release_agent_path);
2210 seq_putc(seq, '\n');
2211 mutex_unlock(&cgroup_mutex);
2212 return 0;
2213}
2214
2215static int cgroup_sane_behavior_show(struct seq_file *seq, void *v)
2216{
2217 struct cgroup *cgrp = seq_css(seq)->cgroup;
2218
2219 seq_printf(seq, "%d\n", cgroup_sane_behavior(cgrp));
2220 return 0;
2221}
2222
2223static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
2224 size_t nbytes, loff_t off)
2225{
2226 struct cgroup *cgrp = of->kn->parent->priv;
2227 struct cftype *cft = of->kn->priv;
2228 struct cgroup_subsys_state *css;
2229 int ret;
2230
2231 /*
2232 * kernfs guarantees that a file isn't deleted with operations in
2233 * flight, which means that the matching css is and stays alive and
2234 * doesn't need to be pinned. The RCU locking is not necessary
2235 * either. It's just for the convenience of using cgroup_css().
2236 */
2237 rcu_read_lock();
2238 css = cgroup_css(cgrp, cft->ss);
2239 rcu_read_unlock();
2240
2241 if (cft->write_string) {
2242 ret = cft->write_string(css, cft, strstrip(buf));
2243 } else if (cft->write_u64) {
2244 unsigned long long v;
2245 ret = kstrtoull(buf, 0, &v);
2246 if (!ret)
2247 ret = cft->write_u64(css, cft, v);
2248 } else if (cft->write_s64) {
2249 long long v;
2250 ret = kstrtoll(buf, 0, &v);
2251 if (!ret)
2252 ret = cft->write_s64(css, cft, v);
2253 } else if (cft->trigger) {
2254 ret = cft->trigger(css, (unsigned int)cft->private);
2255 } else {
2256 ret = -EINVAL;
2257 }
2258
2259 return ret ?: nbytes;
2260}
2261
2262static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
2263{
2264 return seq_cft(seq)->seq_start(seq, ppos);
2265}
2266
2267static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
2268{
2269 return seq_cft(seq)->seq_next(seq, v, ppos);
2270}
2271
2272static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
2273{
2274 seq_cft(seq)->seq_stop(seq, v);
2275}
2276
2277static int cgroup_seqfile_show(struct seq_file *m, void *arg)
2278{
2279 struct cftype *cft = seq_cft(m);
2280 struct cgroup_subsys_state *css = seq_css(m);
2281
2282 if (cft->seq_show)
2283 return cft->seq_show(m, arg);
2284
2285 if (cft->read_u64)
2286 seq_printf(m, "%llu\n", cft->read_u64(css, cft));
2287 else if (cft->read_s64)
2288 seq_printf(m, "%lld\n", cft->read_s64(css, cft));
2289 else
2290 return -EINVAL;
2291 return 0;
2292}
2293
2294static struct kernfs_ops cgroup_kf_single_ops = {
2295 .atomic_write_len = PAGE_SIZE,
2296 .write = cgroup_file_write,
2297 .seq_show = cgroup_seqfile_show,
2298};
2299
2300static struct kernfs_ops cgroup_kf_ops = {
2301 .atomic_write_len = PAGE_SIZE,
2302 .write = cgroup_file_write,
2303 .seq_start = cgroup_seqfile_start,
2304 .seq_next = cgroup_seqfile_next,
2305 .seq_stop = cgroup_seqfile_stop,
2306 .seq_show = cgroup_seqfile_show,
2307};
2308
2309/*
2310 * cgroup_rename - Only allow simple rename of directories in place.
2311 */
2312static int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
2313 const char *new_name_str)
2314{
2315 struct cgroup *cgrp = kn->priv;
2316 int ret;
2317
2318 if (kernfs_type(kn) != KERNFS_DIR)
2319 return -ENOTDIR;
2320 if (kn->parent != new_parent)
2321 return -EIO;
2322
2323 /*
2324 * This isn't a proper migration and its usefulness is very
2325 * limited. Disallow if sane_behavior.
2326 */
2327 if (cgroup_sane_behavior(cgrp))
2328 return -EPERM;
2329
2330 /*
2331 * We're gonna grab cgroup_tree_mutex which nests outside kernfs
2332 * active_ref. kernfs_rename() doesn't require active_ref
2333 * protection. Break them before grabbing cgroup_tree_mutex.
2334 */
2335 kernfs_break_active_protection(new_parent);
2336 kernfs_break_active_protection(kn);
2337
2338 mutex_lock(&cgroup_tree_mutex);
2339 mutex_lock(&cgroup_mutex);
2340
2341 ret = kernfs_rename(kn, new_parent, new_name_str);
2342
2343 mutex_unlock(&cgroup_mutex);
2344 mutex_unlock(&cgroup_tree_mutex);
2345
2346 kernfs_unbreak_active_protection(kn);
2347 kernfs_unbreak_active_protection(new_parent);
2348 return ret;
2349}
2350
2351/* set uid and gid of cgroup dirs and files to that of the creator */
2352static int cgroup_kn_set_ugid(struct kernfs_node *kn)
2353{
2354 struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
2355 .ia_uid = current_fsuid(),
2356 .ia_gid = current_fsgid(), };
2357
2358 if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
2359 gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
2360 return 0;
2361
2362 return kernfs_setattr(kn, &iattr);
2363}
2364
2365static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
2366{
2367 char name[CGROUP_FILE_NAME_MAX];
2368 struct kernfs_node *kn;
2369 struct lock_class_key *key = NULL;
2370 int ret;
2371
2372#ifdef CONFIG_DEBUG_LOCK_ALLOC
2373 key = &cft->lockdep_key;
2374#endif
2375 kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
2376 cgroup_file_mode(cft), 0, cft->kf_ops, cft,
2377 NULL, false, key);
2378 if (IS_ERR(kn))
2379 return PTR_ERR(kn);
2380
2381 ret = cgroup_kn_set_ugid(kn);
2382 if (ret)
2383 kernfs_remove(kn);
2384 return ret;
2385}
2386
2387/**
2388 * cgroup_addrm_files - add or remove files to a cgroup directory
2389 * @cgrp: the target cgroup
2390 * @cfts: array of cftypes to be added
2391 * @is_add: whether to add or remove
2392 *
2393 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
2394 * For removals, this function never fails. If addition fails, this
2395 * function doesn't remove files already added. The caller is responsible
2396 * for cleaning up.
2397 */
2398static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
2399 bool is_add)
2400{
2401 struct cftype *cft;
2402 int ret;
2403
2404 lockdep_assert_held(&cgroup_tree_mutex);
2405
2406 for (cft = cfts; cft->name[0] != '\0'; cft++) {
2407 /* does cft->flags tell us to skip this file on @cgrp? */
2408 if ((cft->flags & CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
2409 continue;
2410 if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp))
2411 continue;
2412 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
2413 continue;
2414 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
2415 continue;
2416
2417 if (is_add) {
2418 ret = cgroup_add_file(cgrp, cft);
2419 if (ret) {
2420 pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
2421 cft->name, ret);
2422 return ret;
2423 }
2424 } else {
2425 cgroup_rm_file(cgrp, cft);
2426 }
2427 }
2428 return 0;
2429}
2430
2431static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
2432{
2433 LIST_HEAD(pending);
2434 struct cgroup_subsys *ss = cfts[0].ss;
2435 struct cgroup *root = &ss->root->cgrp;
2436 struct cgroup_subsys_state *css;
2437 int ret = 0;
2438
2439 lockdep_assert_held(&cgroup_tree_mutex);
2440
2441 /* don't bother if @ss isn't attached */
2442 if (ss->root == &cgrp_dfl_root)
2443 return 0;
2444
2445 /* add/rm files for all cgroups created before */
2446 css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
2447 struct cgroup *cgrp = css->cgroup;
2448
2449 if (cgroup_is_dead(cgrp))
2450 continue;
2451
2452 ret = cgroup_addrm_files(cgrp, cfts, is_add);
2453 if (ret)
2454 break;
2455 }
2456
2457 if (is_add && !ret)
2458 kernfs_activate(root->kn);
2459 return ret;
2460}
2461
2462static void cgroup_exit_cftypes(struct cftype *cfts)
2463{
2464 struct cftype *cft;
2465
2466 for (cft = cfts; cft->name[0] != '\0'; cft++) {
2467 /* free copy for custom atomic_write_len, see init_cftypes() */
2468 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
2469 kfree(cft->kf_ops);
2470 cft->kf_ops = NULL;
2471 cft->ss = NULL;
2472 }
2473}
2474
2475static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2476{
2477 struct cftype *cft;
2478
2479 for (cft = cfts; cft->name[0] != '\0'; cft++) {
2480 struct kernfs_ops *kf_ops;
2481
2482 WARN_ON(cft->ss || cft->kf_ops);
2483
2484 if (cft->seq_start)
2485 kf_ops = &cgroup_kf_ops;
2486 else
2487 kf_ops = &cgroup_kf_single_ops;
2488
2489 /*
2490 * Ugh... if @cft wants a custom max_write_len, we need to
2491 * make a copy of kf_ops to set its atomic_write_len.
2492 */
2493 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
2494 kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
2495 if (!kf_ops) {
2496 cgroup_exit_cftypes(cfts);
2497 return -ENOMEM;
2498 }
2499 kf_ops->atomic_write_len = cft->max_write_len;
2500 }
2501
2502 cft->kf_ops = kf_ops;
2503 cft->ss = ss;
2504 }
2505
2506 return 0;
2507}
2508
2509static int cgroup_rm_cftypes_locked(struct cftype *cfts)
2510{
2511 lockdep_assert_held(&cgroup_tree_mutex);
2512
2513 if (!cfts || !cfts[0].ss)
2514 return -ENOENT;
2515
2516 list_del(&cfts->node);
2517 cgroup_apply_cftypes(cfts, false);
2518 cgroup_exit_cftypes(cfts);
2519 return 0;
2520}
2521
2522/**
2523 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
2524 * @cfts: zero-length name terminated array of cftypes
2525 *
2526 * Unregister @cfts. Files described by @cfts are removed from all
2527 * existing cgroups and all future cgroups won't have them either. This
2528 * function can be called anytime whether @cfts' subsys is attached or not.
2529 *
2530 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
2531 * registered.
2532 */
2533int cgroup_rm_cftypes(struct cftype *cfts)
2534{
2535 int ret;
2536
2537 mutex_lock(&cgroup_tree_mutex);
2538 ret = cgroup_rm_cftypes_locked(cfts);
2539 mutex_unlock(&cgroup_tree_mutex);
2540 return ret;
2541}
2542
2543/**
2544 * cgroup_add_cftypes - add an array of cftypes to a subsystem
2545 * @ss: target cgroup subsystem
2546 * @cfts: zero-length name terminated array of cftypes
2547 *
2548 * Register @cfts to @ss. Files described by @cfts are created for all
2549 * existing cgroups to which @ss is attached and all future cgroups will
2550 * have them too. This function can be called anytime whether @ss is
2551 * attached or not.
2552 *
2553 * Returns 0 on successful registration, -errno on failure. Note that this
2554 * function currently returns 0 as long as @cfts registration is successful
2555 * even if some file creation attempts on existing cgroups fail.
2556 */
2557int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2558{
2559 int ret;
2560
2561 if (!cfts || cfts[0].name[0] == '\0')
2562 return 0;
2563
2564 ret = cgroup_init_cftypes(ss, cfts);
2565 if (ret)
2566 return ret;
2567
2568 mutex_lock(&cgroup_tree_mutex);
2569
2570 list_add_tail(&cfts->node, &ss->cfts);
2571 ret = cgroup_apply_cftypes(cfts, true);
2572 if (ret)
2573 cgroup_rm_cftypes_locked(cfts);
2574
2575 mutex_unlock(&cgroup_tree_mutex);
2576 return ret;
2577}
2578
2579/**
2580 * cgroup_task_count - count the number of tasks in a cgroup.
2581 * @cgrp: the cgroup in question
2582 *
2583 * Return the number of tasks in the cgroup.
2584 */
2585static int cgroup_task_count(const struct cgroup *cgrp)
2586{
2587 int count = 0;
2588 struct cgrp_cset_link *link;
2589
2590 down_read(&css_set_rwsem);
2591 list_for_each_entry(link, &cgrp->cset_links, cset_link)
2592 count += atomic_read(&link->cset->refcount);
2593 up_read(&css_set_rwsem);
2594 return count;
2595}
2596
2597/**
2598 * css_next_child - find the next child of a given css
2599 * @pos_css: the current position (%NULL to initiate traversal)
2600 * @parent_css: css whose children to walk
2601 *
2602 * This function returns the next child of @parent_css and should be called
2603 * under either cgroup_mutex or RCU read lock. The only requirement is
2604 * that @parent_css and @pos_css are accessible. The next sibling is
2605 * guaranteed to be returned regardless of their states.
2606 */
2607struct cgroup_subsys_state *
2608css_next_child(struct cgroup_subsys_state *pos_css,
2609 struct cgroup_subsys_state *parent_css)
2610{
2611 struct cgroup *pos = pos_css ? pos_css->cgroup : NULL;
2612 struct cgroup *cgrp = parent_css->cgroup;
2613 struct cgroup *next;
2614
2615 cgroup_assert_mutexes_or_rcu_locked();
2616
2617 /*
2618 * @pos could already have been removed. Once a cgroup is removed,
2619 * its ->sibling.next is no longer updated when its next sibling
2620 * changes. As CGRP_DEAD assertion is serialized and happens
2621 * before the cgroup is taken off the ->sibling list, if we see it
2622 * unasserted, it's guaranteed that the next sibling hasn't
2623 * finished its grace period even if it's already removed, and thus
2624 * safe to dereference from this RCU critical section. If
2625 * ->sibling.next is inaccessible, cgroup_is_dead() is guaranteed
2626 * to be visible as %true here.
2627 *
2628 * If @pos is dead, its next pointer can't be dereferenced;
2629 * however, as each cgroup is given a monotonically increasing
2630 * unique serial number and always appended to the sibling list,
2631 * the next one can be found by walking the parent's children until
2632 * we see a cgroup with higher serial number than @pos's. While
2633 * this path can be slower, it's taken only when either the current
2634 * cgroup is removed or iteration and removal race.
2635 */
2636 if (!pos) {
2637 next = list_entry_rcu(cgrp->children.next, struct cgroup, sibling);
2638 } else if (likely(!cgroup_is_dead(pos))) {
2639 next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
2640 } else {
2641 list_for_each_entry_rcu(next, &cgrp->children, sibling)
2642 if (next->serial_nr > pos->serial_nr)
2643 break;
2644 }
2645
2646 if (&next->sibling == &cgrp->children)
2647 return NULL;
2648
2649 return cgroup_css(next, parent_css->ss);
2650}
2651
2652/**
2653 * css_next_descendant_pre - find the next descendant for pre-order walk
2654 * @pos: the current position (%NULL to initiate traversal)
2655 * @root: css whose descendants to walk
2656 *
2657 * To be used by css_for_each_descendant_pre(). Find the next descendant
2658 * to visit for pre-order traversal of @root's descendants. @root is
2659 * included in the iteration and the first node to be visited.
2660 *
2661 * While this function requires cgroup_mutex or RCU read locking, it
2662 * doesn't require the whole traversal to be contained in a single critical
2663 * section. This function will return the correct next descendant as long
2664 * as both @pos and @root are accessible and @pos is a descendant of @root.
2665 */
2666struct cgroup_subsys_state *
2667css_next_descendant_pre(struct cgroup_subsys_state *pos,
2668 struct cgroup_subsys_state *root)
2669{
2670 struct cgroup_subsys_state *next;
2671
2672 cgroup_assert_mutexes_or_rcu_locked();
2673
2674 /* if first iteration, visit @root */
2675 if (!pos)
2676 return root;
2677
2678 /* visit the first child if exists */
2679 next = css_next_child(NULL, pos);
2680 if (next)
2681 return next;
2682
2683 /* no child, visit my or the closest ancestor's next sibling */
2684 while (pos != root) {
2685 next = css_next_child(pos, css_parent(pos));
2686 if (next)
2687 return next;
2688 pos = css_parent(pos);
2689 }
2690
2691 return NULL;
2692}
2693
2694/**
2695 * css_rightmost_descendant - return the rightmost descendant of a css
2696 * @pos: css of interest
2697 *
2698 * Return the rightmost descendant of @pos. If there's no descendant, @pos
2699 * is returned. This can be used during pre-order traversal to skip
2700 * subtree of @pos.
2701 *
2702 * While this function requires cgroup_mutex or RCU read locking, it
2703 * doesn't require the whole traversal to be contained in a single critical
2704 * section. This function will return the correct rightmost descendant as
2705 * long as @pos is accessible.
2706 */
2707struct cgroup_subsys_state *
2708css_rightmost_descendant(struct cgroup_subsys_state *pos)
2709{
2710 struct cgroup_subsys_state *last, *tmp;
2711
2712 cgroup_assert_mutexes_or_rcu_locked();
2713
2714 do {
2715 last = pos;
2716 /* ->prev isn't RCU safe, walk ->next till the end */
2717 pos = NULL;
2718 css_for_each_child(tmp, last)
2719 pos = tmp;
2720 } while (pos);
2721
2722 return last;
2723}
2724
2725static struct cgroup_subsys_state *
2726css_leftmost_descendant(struct cgroup_subsys_state *pos)
2727{
2728 struct cgroup_subsys_state *last;
2729
2730 do {
2731 last = pos;
2732 pos = css_next_child(NULL, pos);
2733 } while (pos);
2734
2735 return last;
2736}
2737
2738/**
2739 * css_next_descendant_post - find the next descendant for post-order walk
2740 * @pos: the current position (%NULL to initiate traversal)
2741 * @root: css whose descendants to walk
2742 *
2743 * To be used by css_for_each_descendant_post(). Find the next descendant
2744 * to visit for post-order traversal of @root's descendants. @root is
2745 * included in the iteration and the last node to be visited.
2746 *
2747 * While this function requires cgroup_mutex or RCU read locking, it
2748 * doesn't require the whole traversal to be contained in a single critical
2749 * section. This function will return the correct next descendant as long
2750 * as both @pos and @cgroup are accessible and @pos is a descendant of
2751 * @cgroup.
2752 */
2753struct cgroup_subsys_state *
2754css_next_descendant_post(struct cgroup_subsys_state *pos,
2755 struct cgroup_subsys_state *root)
2756{
2757 struct cgroup_subsys_state *next;
2758
2759 cgroup_assert_mutexes_or_rcu_locked();
2760
2761 /* if first iteration, visit leftmost descendant which may be @root */
2762 if (!pos)
2763 return css_leftmost_descendant(root);
2764
2765 /* if we visited @root, we're done */
2766 if (pos == root)
2767 return NULL;
2768
2769 /* if there's an unvisited sibling, visit its leftmost descendant */
2770 next = css_next_child(pos, css_parent(pos));
2771 if (next)
2772 return css_leftmost_descendant(next);
2773
2774 /* no sibling left, visit parent */
2775 return css_parent(pos);
2776}
2777
2778/**
2779 * css_advance_task_iter - advance a task itererator to the next css_set
2780 * @it: the iterator to advance
2781 *
2782 * Advance @it to the next css_set to walk.
2783 */
2784static void css_advance_task_iter(struct css_task_iter *it)
2785{
2786 struct list_head *l = it->cset_link;
2787 struct cgrp_cset_link *link;
2788 struct css_set *cset;
2789
2790 /* Advance to the next non-empty css_set */
2791 do {
2792 l = l->next;
2793 if (l == &it->origin_css->cgroup->cset_links) {
2794 it->cset_link = NULL;
2795 return;
2796 }
2797 link = list_entry(l, struct cgrp_cset_link, cset_link);
2798 cset = link->cset;
2799 } while (list_empty(&cset->tasks) && list_empty(&cset->mg_tasks));
2800
2801 it->cset_link = l;
2802
2803 if (!list_empty(&cset->tasks))
2804 it->task = cset->tasks.next;
2805 else
2806 it->task = cset->mg_tasks.next;
2807}
2808
2809/**
2810 * css_task_iter_start - initiate task iteration
2811 * @css: the css to walk tasks of
2812 * @it: the task iterator to use
2813 *
2814 * Initiate iteration through the tasks of @css. The caller can call
2815 * css_task_iter_next() to walk through the tasks until the function
2816 * returns NULL. On completion of iteration, css_task_iter_end() must be
2817 * called.
2818 *
2819 * Note that this function acquires a lock which is released when the
2820 * iteration finishes. The caller can't sleep while iteration is in
2821 * progress.
2822 */
2823void css_task_iter_start(struct cgroup_subsys_state *css,
2824 struct css_task_iter *it)
2825 __acquires(css_set_rwsem)
2826{
2827 /* no one should try to iterate before mounting cgroups */
2828 WARN_ON_ONCE(!use_task_css_set_links);
2829
2830 down_read(&css_set_rwsem);
2831
2832 it->origin_css = css;
2833 it->cset_link = &css->cgroup->cset_links;
2834
2835 css_advance_task_iter(it);
2836}
2837
2838/**
2839 * css_task_iter_next - return the next task for the iterator
2840 * @it: the task iterator being iterated
2841 *
2842 * The "next" function for task iteration. @it should have been
2843 * initialized via css_task_iter_start(). Returns NULL when the iteration
2844 * reaches the end.
2845 */
2846struct task_struct *css_task_iter_next(struct css_task_iter *it)
2847{
2848 struct task_struct *res;
2849 struct list_head *l = it->task;
2850 struct cgrp_cset_link *link = list_entry(it->cset_link,
2851 struct cgrp_cset_link, cset_link);
2852
2853 /* If the iterator cg is NULL, we have no tasks */
2854 if (!it->cset_link)
2855 return NULL;
2856 res = list_entry(l, struct task_struct, cg_list);
2857
2858 /*
2859 * Advance iterator to find next entry. cset->tasks is consumed
2860 * first and then ->mg_tasks. After ->mg_tasks, we move onto the
2861 * next cset.
2862 */
2863 l = l->next;
2864
2865 if (l == &link->cset->tasks)
2866 l = link->cset->mg_tasks.next;
2867
2868 if (l == &link->cset->mg_tasks)
2869 css_advance_task_iter(it);
2870 else
2871 it->task = l;
2872
2873 return res;
2874}
2875
2876/**
2877 * css_task_iter_end - finish task iteration
2878 * @it: the task iterator to finish
2879 *
2880 * Finish task iteration started by css_task_iter_start().
2881 */
2882void css_task_iter_end(struct css_task_iter *it)
2883 __releases(css_set_rwsem)
2884{
2885 up_read(&css_set_rwsem);
2886}
2887
2888/**
2889 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
2890 * @to: cgroup to which the tasks will be moved
2891 * @from: cgroup in which the tasks currently reside
2892 *
2893 * Locking rules between cgroup_post_fork() and the migration path
2894 * guarantee that, if a task is forking while being migrated, the new child
2895 * is guaranteed to be either visible in the source cgroup after the
2896 * parent's migration is complete or put into the target cgroup. No task
2897 * can slip out of migration through forking.
2898 */
2899int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
2900{
2901 LIST_HEAD(preloaded_csets);
2902 struct cgrp_cset_link *link;
2903 struct css_task_iter it;
2904 struct task_struct *task;
2905 int ret;
2906
2907 mutex_lock(&cgroup_mutex);
2908
2909 /* all tasks in @from are being moved, all csets are source */
2910 down_read(&css_set_rwsem);
2911 list_for_each_entry(link, &from->cset_links, cset_link)
2912 cgroup_migrate_add_src(link->cset, to, &preloaded_csets);
2913 up_read(&css_set_rwsem);
2914
2915 ret = cgroup_migrate_prepare_dst(to, &preloaded_csets);
2916 if (ret)
2917 goto out_err;
2918
2919 /*
2920 * Migrate tasks one-by-one until @form is empty. This fails iff
2921 * ->can_attach() fails.
2922 */
2923 do {
2924 css_task_iter_start(&from->dummy_css, &it);
2925 task = css_task_iter_next(&it);
2926 if (task)
2927 get_task_struct(task);
2928 css_task_iter_end(&it);
2929
2930 if (task) {
2931 ret = cgroup_migrate(to, task, false);
2932 put_task_struct(task);
2933 }
2934 } while (task && !ret);
2935out_err:
2936 cgroup_migrate_finish(&preloaded_csets);
2937 mutex_unlock(&cgroup_mutex);
2938 return ret;
2939}
2940
2941/*
2942 * Stuff for reading the 'tasks'/'procs' files.
2943 *
2944 * Reading this file can return large amounts of data if a cgroup has
2945 * *lots* of attached tasks. So it may need several calls to read(),
2946 * but we cannot guarantee that the information we produce is correct
2947 * unless we produce it entirely atomically.
2948 *
2949 */
2950
2951/* which pidlist file are we talking about? */
2952enum cgroup_filetype {
2953 CGROUP_FILE_PROCS,
2954 CGROUP_FILE_TASKS,
2955};
2956
2957/*
2958 * A pidlist is a list of pids that virtually represents the contents of one
2959 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
2960 * a pair (one each for procs, tasks) for each pid namespace that's relevant
2961 * to the cgroup.
2962 */
2963struct cgroup_pidlist {
2964 /*
2965 * used to find which pidlist is wanted. doesn't change as long as
2966 * this particular list stays in the list.
2967 */
2968 struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
2969 /* array of xids */
2970 pid_t *list;
2971 /* how many elements the above list has */
2972 int length;
2973 /* each of these stored in a list by its cgroup */
2974 struct list_head links;
2975 /* pointer to the cgroup we belong to, for list removal purposes */
2976 struct cgroup *owner;
2977 /* for delayed destruction */
2978 struct delayed_work destroy_dwork;
2979};
2980
2981/*
2982 * The following two functions "fix" the issue where there are more pids
2983 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
2984 * TODO: replace with a kernel-wide solution to this problem
2985 */
2986#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
2987static void *pidlist_allocate(int count)
2988{
2989 if (PIDLIST_TOO_LARGE(count))
2990 return vmalloc(count * sizeof(pid_t));
2991 else
2992 return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
2993}
2994
2995static void pidlist_free(void *p)
2996{
2997 if (is_vmalloc_addr(p))
2998 vfree(p);
2999 else
3000 kfree(p);
3001}
3002
3003/*
3004 * Used to destroy all pidlists lingering waiting for destroy timer. None
3005 * should be left afterwards.
3006 */
3007static void cgroup_pidlist_destroy_all(struct cgroup *cgrp)
3008{
3009 struct cgroup_pidlist *l, *tmp_l;
3010
3011 mutex_lock(&cgrp->pidlist_mutex);
3012 list_for_each_entry_safe(l, tmp_l, &cgrp->pidlists, links)
3013 mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, 0);
3014 mutex_unlock(&cgrp->pidlist_mutex);
3015
3016 flush_workqueue(cgroup_pidlist_destroy_wq);
3017 BUG_ON(!list_empty(&cgrp->pidlists));
3018}
3019
3020static void cgroup_pidlist_destroy_work_fn(struct work_struct *work)
3021{
3022 struct delayed_work *dwork = to_delayed_work(work);
3023 struct cgroup_pidlist *l = container_of(dwork, struct cgroup_pidlist,
3024 destroy_dwork);
3025 struct cgroup_pidlist *tofree = NULL;
3026
3027 mutex_lock(&l->owner->pidlist_mutex);
3028
3029 /*
3030 * Destroy iff we didn't get queued again. The state won't change
3031 * as destroy_dwork can only be queued while locked.
3032 */
3033 if (!delayed_work_pending(dwork)) {
3034 list_del(&l->links);
3035 pidlist_free(l->list);
3036 put_pid_ns(l->key.ns);
3037 tofree = l;
3038 }
3039
3040 mutex_unlock(&l->owner->pidlist_mutex);
3041 kfree(tofree);
3042}
3043
3044/*
3045 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3046 * Returns the number of unique elements.
3047 */
3048static int pidlist_uniq(pid_t *list, int length)
3049{
3050 int src, dest = 1;
3051
3052 /*
3053 * we presume the 0th element is unique, so i starts at 1. trivial
3054 * edge cases first; no work needs to be done for either
3055 */
3056 if (length == 0 || length == 1)
3057 return length;
3058 /* src and dest walk down the list; dest counts unique elements */
3059 for (src = 1; src < length; src++) {
3060 /* find next unique element */
3061 while (list[src] == list[src-1]) {
3062 src++;
3063 if (src == length)
3064 goto after;
3065 }
3066 /* dest always points to where the next unique element goes */
3067 list[dest] = list[src];
3068 dest++;
3069 }
3070after:
3071 return dest;
3072}
3073
3074/*
3075 * The two pid files - task and cgroup.procs - guaranteed that the result
3076 * is sorted, which forced this whole pidlist fiasco. As pid order is
3077 * different per namespace, each namespace needs differently sorted list,
3078 * making it impossible to use, for example, single rbtree of member tasks
3079 * sorted by task pointer. As pidlists can be fairly large, allocating one
3080 * per open file is dangerous, so cgroup had to implement shared pool of
3081 * pidlists keyed by cgroup and namespace.
3082 *
3083 * All this extra complexity was caused by the original implementation
3084 * committing to an entirely unnecessary property. In the long term, we
3085 * want to do away with it. Explicitly scramble sort order if
3086 * sane_behavior so that no such expectation exists in the new interface.
3087 *
3088 * Scrambling is done by swapping every two consecutive bits, which is
3089 * non-identity one-to-one mapping which disturbs sort order sufficiently.
3090 */
3091static pid_t pid_fry(pid_t pid)
3092{
3093 unsigned a = pid & 0x55555555;
3094 unsigned b = pid & 0xAAAAAAAA;
3095
3096 return (a << 1) | (b >> 1);
3097}
3098
3099static pid_t cgroup_pid_fry(struct cgroup *cgrp, pid_t pid)
3100{
3101 if (cgroup_sane_behavior(cgrp))
3102 return pid_fry(pid);
3103 else
3104 return pid;
3105}
3106
3107static int cmppid(const void *a, const void *b)
3108{
3109 return *(pid_t *)a - *(pid_t *)b;
3110}
3111
3112static int fried_cmppid(const void *a, const void *b)
3113{
3114 return pid_fry(*(pid_t *)a) - pid_fry(*(pid_t *)b);
3115}
3116
3117static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
3118 enum cgroup_filetype type)
3119{
3120 struct cgroup_pidlist *l;
3121 /* don't need task_nsproxy() if we're looking at ourself */
3122 struct pid_namespace *ns = task_active_pid_ns(current);
3123
3124 lockdep_assert_held(&cgrp->pidlist_mutex);
3125
3126 list_for_each_entry(l, &cgrp->pidlists, links)
3127 if (l->key.type == type && l->key.ns == ns)
3128 return l;
3129 return NULL;
3130}
3131
3132/*
3133 * find the appropriate pidlist for our purpose (given procs vs tasks)
3134 * returns with the lock on that pidlist already held, and takes care
3135 * of the use count, or returns NULL with no locks held if we're out of
3136 * memory.
3137 */
3138static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
3139 enum cgroup_filetype type)
3140{
3141 struct cgroup_pidlist *l;
3142
3143 lockdep_assert_held(&cgrp->pidlist_mutex);
3144
3145 l = cgroup_pidlist_find(cgrp, type);
3146 if (l)
3147 return l;
3148
3149 /* entry not found; create a new one */
3150 l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3151 if (!l)
3152 return l;
3153
3154 INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
3155 l->key.type = type;
3156 /* don't need task_nsproxy() if we're looking at ourself */
3157 l->key.ns = get_pid_ns(task_active_pid_ns(current));
3158 l->owner = cgrp;
3159 list_add(&l->links, &cgrp->pidlists);
3160 return l;
3161}
3162
3163/*
3164 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3165 */
3166static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
3167 struct cgroup_pidlist **lp)
3168{
3169 pid_t *array;
3170 int length;
3171 int pid, n = 0; /* used for populating the array */
3172 struct css_task_iter it;
3173 struct task_struct *tsk;
3174 struct cgroup_pidlist *l;
3175
3176 lockdep_assert_held(&cgrp->pidlist_mutex);
3177
3178 /*
3179 * If cgroup gets more users after we read count, we won't have
3180 * enough space - tough. This race is indistinguishable to the
3181 * caller from the case that the additional cgroup users didn't
3182 * show up until sometime later on.
3183 */
3184 length = cgroup_task_count(cgrp);
3185 array = pidlist_allocate(length);
3186 if (!array)
3187 return -ENOMEM;
3188 /* now, populate the array */
3189 css_task_iter_start(&cgrp->dummy_css, &it);
3190 while ((tsk = css_task_iter_next(&it))) {
3191 if (unlikely(n == length))
3192 break;
3193 /* get tgid or pid for procs or tasks file respectively */
3194 if (type == CGROUP_FILE_PROCS)
3195 pid = task_tgid_vnr(tsk);
3196 else
3197 pid = task_pid_vnr(tsk);
3198 if (pid > 0) /* make sure to only use valid results */
3199 array[n++] = pid;
3200 }
3201 css_task_iter_end(&it);
3202 length = n;
3203 /* now sort & (if procs) strip out duplicates */
3204 if (cgroup_sane_behavior(cgrp))
3205 sort(array, length, sizeof(pid_t), fried_cmppid, NULL);
3206 else
3207 sort(array, length, sizeof(pid_t), cmppid, NULL);
3208 if (type == CGROUP_FILE_PROCS)
3209 length = pidlist_uniq(array, length);
3210
3211 l = cgroup_pidlist_find_create(cgrp, type);
3212 if (!l) {
3213 mutex_unlock(&cgrp->pidlist_mutex);
3214 pidlist_free(array);
3215 return -ENOMEM;
3216 }
3217
3218 /* store array, freeing old if necessary */
3219 pidlist_free(l->list);
3220 l->list = array;
3221 l->length = length;
3222 *lp = l;
3223 return 0;
3224}
3225
3226/**
3227 * cgroupstats_build - build and fill cgroupstats
3228 * @stats: cgroupstats to fill information into
3229 * @dentry: A dentry entry belonging to the cgroup for which stats have
3230 * been requested.
3231 *
3232 * Build and fill cgroupstats so that taskstats can export it to user
3233 * space.
3234 */
3235int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
3236{
3237 struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
3238 struct cgroup *cgrp;
3239 struct css_task_iter it;
3240 struct task_struct *tsk;
3241
3242 /* it should be kernfs_node belonging to cgroupfs and is a directory */
3243 if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
3244 kernfs_type(kn) != KERNFS_DIR)
3245 return -EINVAL;
3246
3247 mutex_lock(&cgroup_mutex);
3248
3249 /*
3250 * We aren't being called from kernfs and there's no guarantee on
3251 * @kn->priv's validity. For this and css_tryget_from_dir(),
3252 * @kn->priv is RCU safe. Let's do the RCU dancing.
3253 */
3254 rcu_read_lock();
3255 cgrp = rcu_dereference(kn->priv);
3256 if (!cgrp || cgroup_is_dead(cgrp)) {
3257 rcu_read_unlock();
3258 mutex_unlock(&cgroup_mutex);
3259 return -ENOENT;
3260 }
3261 rcu_read_unlock();
3262
3263 css_task_iter_start(&cgrp->dummy_css, &it);
3264 while ((tsk = css_task_iter_next(&it))) {
3265 switch (tsk->state) {
3266 case TASK_RUNNING:
3267 stats->nr_running++;
3268 break;
3269 case TASK_INTERRUPTIBLE:
3270 stats->nr_sleeping++;
3271 break;
3272 case TASK_UNINTERRUPTIBLE:
3273 stats->nr_uninterruptible++;
3274 break;
3275 case TASK_STOPPED:
3276 stats->nr_stopped++;
3277 break;
3278 default:
3279 if (delayacct_is_task_waiting_on_io(tsk))
3280 stats->nr_io_wait++;
3281 break;
3282 }
3283 }
3284 css_task_iter_end(&it);
3285
3286 mutex_unlock(&cgroup_mutex);
3287 return 0;
3288}
3289
3290
3291/*
3292 * seq_file methods for the tasks/procs files. The seq_file position is the
3293 * next pid to display; the seq_file iterator is a pointer to the pid
3294 * in the cgroup->l->list array.
3295 */
3296
3297static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3298{
3299 /*
3300 * Initially we receive a position value that corresponds to
3301 * one more than the last pid shown (or 0 on the first call or
3302 * after a seek to the start). Use a binary-search to find the
3303 * next pid to display, if any
3304 */
3305 struct kernfs_open_file *of = s->private;
3306 struct cgroup *cgrp = seq_css(s)->cgroup;
3307 struct cgroup_pidlist *l;
3308 enum cgroup_filetype type = seq_cft(s)->private;
3309 int index = 0, pid = *pos;
3310 int *iter, ret;
3311
3312 mutex_lock(&cgrp->pidlist_mutex);
3313
3314 /*
3315 * !NULL @of->priv indicates that this isn't the first start()
3316 * after open. If the matching pidlist is around, we can use that.
3317 * Look for it. Note that @of->priv can't be used directly. It
3318 * could already have been destroyed.
3319 */
3320 if (of->priv)
3321 of->priv = cgroup_pidlist_find(cgrp, type);
3322
3323 /*
3324 * Either this is the first start() after open or the matching
3325 * pidlist has been destroyed inbetween. Create a new one.
3326 */
3327 if (!of->priv) {
3328 ret = pidlist_array_load(cgrp, type,
3329 (struct cgroup_pidlist **)&of->priv);
3330 if (ret)
3331 return ERR_PTR(ret);
3332 }
3333 l = of->priv;
3334
3335 if (pid) {
3336 int end = l->length;
3337
3338 while (index < end) {
3339 int mid = (index + end) / 2;
3340 if (cgroup_pid_fry(cgrp, l->list[mid]) == pid) {
3341 index = mid;
3342 break;
3343 } else if (cgroup_pid_fry(cgrp, l->list[mid]) <= pid)
3344 index = mid + 1;
3345 else
3346 end = mid;
3347 }
3348 }
3349 /* If we're off the end of the array, we're done */
3350 if (index >= l->length)
3351 return NULL;
3352 /* Update the abstract position to be the actual pid that we found */
3353 iter = l->list + index;
3354 *pos = cgroup_pid_fry(cgrp, *iter);
3355 return iter;
3356}
3357
3358static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3359{
3360 struct kernfs_open_file *of = s->private;
3361 struct cgroup_pidlist *l = of->priv;
3362
3363 if (l)
3364 mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
3365 CGROUP_PIDLIST_DESTROY_DELAY);
3366 mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
3367}
3368
3369static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3370{
3371 struct kernfs_open_file *of = s->private;
3372 struct cgroup_pidlist *l = of->priv;
3373 pid_t *p = v;
3374 pid_t *end = l->list + l->length;
3375 /*
3376 * Advance to the next pid in the array. If this goes off the
3377 * end, we're done
3378 */
3379 p++;
3380 if (p >= end) {
3381 return NULL;
3382 } else {
3383 *pos = cgroup_pid_fry(seq_css(s)->cgroup, *p);
3384 return p;
3385 }
3386}
3387
3388static int cgroup_pidlist_show(struct seq_file *s, void *v)
3389{
3390 return seq_printf(s, "%d\n", *(int *)v);
3391}
3392
3393/*
3394 * seq_operations functions for iterating on pidlists through seq_file -
3395 * independent of whether it's tasks or procs
3396 */
3397static const struct seq_operations cgroup_pidlist_seq_operations = {
3398 .start = cgroup_pidlist_start,
3399 .stop = cgroup_pidlist_stop,
3400 .next = cgroup_pidlist_next,
3401 .show = cgroup_pidlist_show,
3402};
3403
3404static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
3405 struct cftype *cft)
3406{
3407 return notify_on_release(css->cgroup);
3408}
3409
3410static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
3411 struct cftype *cft, u64 val)
3412{
3413 clear_bit(CGRP_RELEASABLE, &css->cgroup->flags);
3414 if (val)
3415 set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
3416 else
3417 clear_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
3418 return 0;
3419}
3420
3421static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
3422 struct cftype *cft)
3423{
3424 return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
3425}
3426
3427static int cgroup_clone_children_write(struct cgroup_subsys_state *css,
3428 struct cftype *cft, u64 val)
3429{
3430 if (val)
3431 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
3432 else
3433 clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
3434 return 0;
3435}
3436
3437static struct cftype cgroup_base_files[] = {
3438 {
3439 .name = "cgroup.procs",
3440 .seq_start = cgroup_pidlist_start,
3441 .seq_next = cgroup_pidlist_next,
3442 .seq_stop = cgroup_pidlist_stop,
3443 .seq_show = cgroup_pidlist_show,
3444 .private = CGROUP_FILE_PROCS,
3445 .write_u64 = cgroup_procs_write,
3446 .mode = S_IRUGO | S_IWUSR,
3447 },
3448 {
3449 .name = "cgroup.clone_children",
3450 .flags = CFTYPE_INSANE,
3451 .read_u64 = cgroup_clone_children_read,
3452 .write_u64 = cgroup_clone_children_write,
3453 },
3454 {
3455 .name = "cgroup.sane_behavior",
3456 .flags = CFTYPE_ONLY_ON_ROOT,
3457 .seq_show = cgroup_sane_behavior_show,
3458 },
3459
3460 /*
3461 * Historical crazy stuff. These don't have "cgroup." prefix and
3462 * don't exist if sane_behavior. If you're depending on these, be
3463 * prepared to be burned.
3464 */
3465 {
3466 .name = "tasks",
3467 .flags = CFTYPE_INSANE, /* use "procs" instead */
3468 .seq_start = cgroup_pidlist_start,
3469 .seq_next = cgroup_pidlist_next,
3470 .seq_stop = cgroup_pidlist_stop,
3471 .seq_show = cgroup_pidlist_show,
3472 .private = CGROUP_FILE_TASKS,
3473 .write_u64 = cgroup_tasks_write,
3474 .mode = S_IRUGO | S_IWUSR,
3475 },
3476 {
3477 .name = "notify_on_release",
3478 .flags = CFTYPE_INSANE,
3479 .read_u64 = cgroup_read_notify_on_release,
3480 .write_u64 = cgroup_write_notify_on_release,
3481 },
3482 {
3483 .name = "release_agent",
3484 .flags = CFTYPE_INSANE | CFTYPE_ONLY_ON_ROOT,
3485 .seq_show = cgroup_release_agent_show,
3486 .write_string = cgroup_release_agent_write,
3487 .max_write_len = PATH_MAX - 1,
3488 },
3489 { } /* terminate */
3490};
3491
3492/**
3493 * cgroup_populate_dir - create subsys files in a cgroup directory
3494 * @cgrp: target cgroup
3495 * @subsys_mask: mask of the subsystem ids whose files should be added
3496 *
3497 * On failure, no file is added.
3498 */
3499static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
3500{
3501 struct cgroup_subsys *ss;
3502 int i, ret = 0;
3503
3504 /* process cftsets of each subsystem */
3505 for_each_subsys(ss, i) {
3506 struct cftype *cfts;
3507
3508 if (!test_bit(i, &subsys_mask))
3509 continue;
3510
3511 list_for_each_entry(cfts, &ss->cfts, node) {
3512 ret = cgroup_addrm_files(cgrp, cfts, true);
3513 if (ret < 0)
3514 goto err;
3515 }
3516 }
3517 return 0;
3518err:
3519 cgroup_clear_dir(cgrp, subsys_mask);
3520 return ret;
3521}
3522
3523/*
3524 * css destruction is four-stage process.
3525 *
3526 * 1. Destruction starts. Killing of the percpu_ref is initiated.
3527 * Implemented in kill_css().
3528 *
3529 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
3530 * and thus css_tryget() is guaranteed to fail, the css can be offlined
3531 * by invoking offline_css(). After offlining, the base ref is put.
3532 * Implemented in css_killed_work_fn().
3533 *
3534 * 3. When the percpu_ref reaches zero, the only possible remaining
3535 * accessors are inside RCU read sections. css_release() schedules the
3536 * RCU callback.
3537 *
3538 * 4. After the grace period, the css can be freed. Implemented in
3539 * css_free_work_fn().
3540 *
3541 * It is actually hairier because both step 2 and 4 require process context
3542 * and thus involve punting to css->destroy_work adding two additional
3543 * steps to the already complex sequence.
3544 */
3545static void css_free_work_fn(struct work_struct *work)
3546{
3547 struct cgroup_subsys_state *css =
3548 container_of(work, struct cgroup_subsys_state, destroy_work);
3549 struct cgroup *cgrp = css->cgroup;
3550
3551 if (css->parent)
3552 css_put(css->parent);
3553
3554 css->ss->css_free(css);
3555 cgroup_put(cgrp);
3556}
3557
3558static void css_free_rcu_fn(struct rcu_head *rcu_head)
3559{
3560 struct cgroup_subsys_state *css =
3561 container_of(rcu_head, struct cgroup_subsys_state, rcu_head);
3562
3563 INIT_WORK(&css->destroy_work, css_free_work_fn);
3564 queue_work(cgroup_destroy_wq, &css->destroy_work);
3565}
3566
3567static void css_release(struct percpu_ref *ref)
3568{
3569 struct cgroup_subsys_state *css =
3570 container_of(ref, struct cgroup_subsys_state, refcnt);
3571
3572 RCU_INIT_POINTER(css->cgroup->subsys[css->ss->id], NULL);
3573 call_rcu(&css->rcu_head, css_free_rcu_fn);
3574}
3575
3576static void init_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss,
3577 struct cgroup *cgrp)
3578{
3579 css->cgroup = cgrp;
3580 css->ss = ss;
3581 css->flags = 0;
3582
3583 if (cgrp->parent)
3584 css->parent = cgroup_css(cgrp->parent, ss);
3585 else
3586 css->flags |= CSS_ROOT;
3587
3588 BUG_ON(cgroup_css(cgrp, ss));
3589}
3590
3591/* invoke ->css_online() on a new CSS and mark it online if successful */
3592static int online_css(struct cgroup_subsys_state *css)
3593{
3594 struct cgroup_subsys *ss = css->ss;
3595 int ret = 0;
3596
3597 lockdep_assert_held(&cgroup_tree_mutex);
3598 lockdep_assert_held(&cgroup_mutex);
3599
3600 if (ss->css_online)
3601 ret = ss->css_online(css);
3602 if (!ret) {
3603 css->flags |= CSS_ONLINE;
3604 css->cgroup->nr_css++;
3605 rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
3606 }
3607 return ret;
3608}
3609
3610/* if the CSS is online, invoke ->css_offline() on it and mark it offline */
3611static void offline_css(struct cgroup_subsys_state *css)
3612{
3613 struct cgroup_subsys *ss = css->ss;
3614
3615 lockdep_assert_held(&cgroup_tree_mutex);
3616 lockdep_assert_held(&cgroup_mutex);
3617
3618 if (!(css->flags & CSS_ONLINE))
3619 return;
3620
3621 if (ss->css_offline)
3622 ss->css_offline(css);
3623
3624 css->flags &= ~CSS_ONLINE;
3625 css->cgroup->nr_css--;
3626 RCU_INIT_POINTER(css->cgroup->subsys[ss->id], css);
3627}
3628
3629/**
3630 * create_css - create a cgroup_subsys_state
3631 * @cgrp: the cgroup new css will be associated with
3632 * @ss: the subsys of new css
3633 *
3634 * Create a new css associated with @cgrp - @ss pair. On success, the new
3635 * css is online and installed in @cgrp with all interface files created.
3636 * Returns 0 on success, -errno on failure.
3637 */
3638static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss)
3639{
3640 struct cgroup *parent = cgrp->parent;
3641 struct cgroup_subsys_state *css;
3642 int err;
3643
3644 lockdep_assert_held(&cgroup_mutex);
3645
3646 css = ss->css_alloc(cgroup_css(parent, ss));
3647 if (IS_ERR(css))
3648 return PTR_ERR(css);
3649
3650 err = percpu_ref_init(&css->refcnt, css_release);
3651 if (err)
3652 goto err_free_css;
3653
3654 init_css(css, ss, cgrp);
3655
3656 err = cgroup_populate_dir(cgrp, 1 << ss->id);
3657 if (err)
3658 goto err_free_percpu_ref;
3659
3660 err = online_css(css);
3661 if (err)
3662 goto err_clear_dir;
3663
3664 cgroup_get(cgrp);
3665 css_get(css->parent);
3666
3667 cgrp->subsys_mask |= 1 << ss->id;
3668
3669 if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
3670 parent->parent) {
3671 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",
3672 current->comm, current->pid, ss->name);
3673 if (!strcmp(ss->name, "memory"))
3674 pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
3675 ss->warned_broken_hierarchy = true;
3676 }
3677
3678 return 0;
3679
3680err_clear_dir:
3681 cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
3682err_free_percpu_ref:
3683 percpu_ref_cancel_init(&css->refcnt);
3684err_free_css:
3685 ss->css_free(css);
3686 return err;
3687}
3688
3689/**
3690 * cgroup_create - create a cgroup
3691 * @parent: cgroup that will be parent of the new cgroup
3692 * @name: name of the new cgroup
3693 * @mode: mode to set on new cgroup
3694 */
3695static long cgroup_create(struct cgroup *parent, const char *name,
3696 umode_t mode)
3697{
3698 struct cgroup *cgrp;
3699 struct cgroup_root *root = parent->root;
3700 int ssid, err;
3701 struct cgroup_subsys *ss;
3702 struct kernfs_node *kn;
3703
3704 /*
3705 * XXX: The default hierarchy isn't fully implemented yet. Block
3706 * !root cgroup creation on it for now.
3707 */
3708 if (root == &cgrp_dfl_root)
3709 return -EINVAL;
3710
3711 /* allocate the cgroup and its ID, 0 is reserved for the root */
3712 cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
3713 if (!cgrp)
3714 return -ENOMEM;
3715
3716 mutex_lock(&cgroup_tree_mutex);
3717
3718 /*
3719 * Only live parents can have children. Note that the liveliness
3720 * check isn't strictly necessary because cgroup_mkdir() and
3721 * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
3722 * anyway so that locking is contained inside cgroup proper and we
3723 * don't get nasty surprises if we ever grow another caller.
3724 */
3725 if (!cgroup_lock_live_group(parent)) {
3726 err = -ENODEV;
3727 goto err_unlock_tree;
3728 }
3729
3730 /*
3731 * Temporarily set the pointer to NULL, so idr_find() won't return
3732 * a half-baked cgroup.
3733 */
3734 cgrp->id = idr_alloc(&root->cgroup_idr, NULL, 1, 0, GFP_KERNEL);
3735 if (cgrp->id < 0) {
3736 err = -ENOMEM;
3737 goto err_unlock;
3738 }
3739
3740 init_cgroup_housekeeping(cgrp);
3741
3742 cgrp->parent = parent;
3743 cgrp->dummy_css.parent = &parent->dummy_css;
3744 cgrp->root = parent->root;
3745
3746 if (notify_on_release(parent))
3747 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3748
3749 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
3750 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
3751
3752 /* create the directory */
3753 kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
3754 if (IS_ERR(kn)) {
3755 err = PTR_ERR(kn);
3756 goto err_free_id;
3757 }
3758 cgrp->kn = kn;
3759
3760 /*
3761 * This extra ref will be put in cgroup_free_fn() and guarantees
3762 * that @cgrp->kn is always accessible.
3763 */
3764 kernfs_get(kn);
3765
3766 cgrp->serial_nr = cgroup_serial_nr_next++;
3767
3768 /* allocation complete, commit to creation */
3769 list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
3770 atomic_inc(&root->nr_cgrps);
3771 cgroup_get(parent);
3772
3773 /*
3774 * @cgrp is now fully operational. If something fails after this
3775 * point, it'll be released via the normal destruction path.
3776 */
3777 idr_replace(&root->cgroup_idr, cgrp, cgrp->id);
3778
3779 err = cgroup_kn_set_ugid(kn);
3780 if (err)
3781 goto err_destroy;
3782
3783 err = cgroup_addrm_files(cgrp, cgroup_base_files, true);
3784 if (err)
3785 goto err_destroy;
3786
3787 /* let's create and online css's */
3788 for_each_subsys(ss, ssid) {
3789 if (root->cgrp.subsys_mask & (1 << ssid)) {
3790 err = create_css(cgrp, ss);
3791 if (err)
3792 goto err_destroy;
3793 }
3794 }
3795
3796 kernfs_activate(kn);
3797
3798 mutex_unlock(&cgroup_mutex);
3799 mutex_unlock(&cgroup_tree_mutex);
3800
3801 return 0;
3802
3803err_free_id:
3804 idr_remove(&root->cgroup_idr, cgrp->id);
3805err_unlock:
3806 mutex_unlock(&cgroup_mutex);
3807err_unlock_tree:
3808 mutex_unlock(&cgroup_tree_mutex);
3809 kfree(cgrp);
3810 return err;
3811
3812err_destroy:
3813 cgroup_destroy_locked(cgrp);
3814 mutex_unlock(&cgroup_mutex);
3815 mutex_unlock(&cgroup_tree_mutex);
3816 return err;
3817}
3818
3819static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
3820 umode_t mode)
3821{
3822 struct cgroup *parent = parent_kn->priv;
3823 int ret;
3824
3825 /*
3826 * cgroup_create() grabs cgroup_tree_mutex which nests outside
3827 * kernfs active_ref and cgroup_create() already synchronizes
3828 * properly against removal through cgroup_lock_live_group().
3829 * Break it before calling cgroup_create().
3830 */
3831 cgroup_get(parent);
3832 kernfs_break_active_protection(parent_kn);
3833
3834 ret = cgroup_create(parent, name, mode);
3835
3836 kernfs_unbreak_active_protection(parent_kn);
3837 cgroup_put(parent);
3838 return ret;
3839}
3840
3841/*
3842 * This is called when the refcnt of a css is confirmed to be killed.
3843 * css_tryget() is now guaranteed to fail.
3844 */
3845static void css_killed_work_fn(struct work_struct *work)
3846{
3847 struct cgroup_subsys_state *css =
3848 container_of(work, struct cgroup_subsys_state, destroy_work);
3849 struct cgroup *cgrp = css->cgroup;
3850
3851 mutex_lock(&cgroup_tree_mutex);
3852 mutex_lock(&cgroup_mutex);
3853
3854 /*
3855 * css_tryget() is guaranteed to fail now. Tell subsystems to
3856 * initate destruction.
3857 */
3858 offline_css(css);
3859
3860 /*
3861 * If @cgrp is marked dead, it's waiting for refs of all css's to
3862 * be disabled before proceeding to the second phase of cgroup
3863 * destruction. If we are the last one, kick it off.
3864 */
3865 if (!cgrp->nr_css && cgroup_is_dead(cgrp))
3866 cgroup_destroy_css_killed(cgrp);
3867
3868 mutex_unlock(&cgroup_mutex);
3869 mutex_unlock(&cgroup_tree_mutex);
3870
3871 /*
3872 * Put the css refs from kill_css(). Each css holds an extra
3873 * reference to the cgroup's dentry and cgroup removal proceeds
3874 * regardless of css refs. On the last put of each css, whenever
3875 * that may be, the extra dentry ref is put so that dentry
3876 * destruction happens only after all css's are released.
3877 */
3878 css_put(css);
3879}
3880
3881/* css kill confirmation processing requires process context, bounce */
3882static void css_killed_ref_fn(struct percpu_ref *ref)
3883{
3884 struct cgroup_subsys_state *css =
3885 container_of(ref, struct cgroup_subsys_state, refcnt);
3886
3887 INIT_WORK(&css->destroy_work, css_killed_work_fn);
3888 queue_work(cgroup_destroy_wq, &css->destroy_work);
3889}
3890
3891static void __kill_css(struct cgroup_subsys_state *css)
3892{
3893 lockdep_assert_held(&cgroup_tree_mutex);
3894
3895 /*
3896 * This must happen before css is disassociated with its cgroup.
3897 * See seq_css() for details.
3898 */
3899 cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
3900
3901 /*
3902 * Killing would put the base ref, but we need to keep it alive
3903 * until after ->css_offline().
3904 */
3905 css_get(css);
3906
3907 /*
3908 * cgroup core guarantees that, by the time ->css_offline() is
3909 * invoked, no new css reference will be given out via
3910 * css_tryget(). We can't simply call percpu_ref_kill() and
3911 * proceed to offlining css's because percpu_ref_kill() doesn't
3912 * guarantee that the ref is seen as killed on all CPUs on return.
3913 *
3914 * Use percpu_ref_kill_and_confirm() to get notifications as each
3915 * css is confirmed to be seen as killed on all CPUs.
3916 */
3917 percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
3918}
3919
3920/**
3921 * kill_css - destroy a css
3922 * @css: css to destroy
3923 *
3924 * This function initiates destruction of @css by removing cgroup interface
3925 * files and putting its base reference. ->css_offline() will be invoked
3926 * asynchronously once css_tryget() is guaranteed to fail and when the
3927 * reference count reaches zero, @css will be released.
3928 */
3929static void kill_css(struct cgroup_subsys_state *css)
3930{
3931 struct cgroup *cgrp = css->cgroup;
3932
3933 lockdep_assert_held(&cgroup_tree_mutex);
3934
3935 /* if already killed, noop */
3936 if (cgrp->subsys_mask & (1 << css->ss->id)) {
3937 cgrp->subsys_mask &= ~(1 << css->ss->id);
3938 __kill_css(css);
3939 }
3940}
3941
3942/**
3943 * cgroup_destroy_locked - the first stage of cgroup destruction
3944 * @cgrp: cgroup to be destroyed
3945 *
3946 * css's make use of percpu refcnts whose killing latency shouldn't be
3947 * exposed to userland and are RCU protected. Also, cgroup core needs to
3948 * guarantee that css_tryget() won't succeed by the time ->css_offline() is
3949 * invoked. To satisfy all the requirements, destruction is implemented in
3950 * the following two steps.
3951 *
3952 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
3953 * userland visible parts and start killing the percpu refcnts of
3954 * css's. Set up so that the next stage will be kicked off once all
3955 * the percpu refcnts are confirmed to be killed.
3956 *
3957 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
3958 * rest of destruction. Once all cgroup references are gone, the
3959 * cgroup is RCU-freed.
3960 *
3961 * This function implements s1. After this step, @cgrp is gone as far as
3962 * the userland is concerned and a new cgroup with the same name may be
3963 * created. As cgroup doesn't care about the names internally, this
3964 * doesn't cause any problem.
3965 */
3966static int cgroup_destroy_locked(struct cgroup *cgrp)
3967 __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
3968{
3969 struct cgroup *child;
3970 struct cgroup_subsys_state *css;
3971 bool empty;
3972 int ssid;
3973
3974 lockdep_assert_held(&cgroup_tree_mutex);
3975 lockdep_assert_held(&cgroup_mutex);
3976
3977 /*
3978 * css_set_rwsem synchronizes access to ->cset_links and prevents
3979 * @cgrp from being removed while put_css_set() is in progress.
3980 */
3981 down_read(&css_set_rwsem);
3982 empty = list_empty(&cgrp->cset_links);
3983 up_read(&css_set_rwsem);
3984 if (!empty)
3985 return -EBUSY;
3986
3987 /*
3988 * Make sure there's no live children. We can't test ->children
3989 * emptiness as dead children linger on it while being destroyed;
3990 * otherwise, "rmdir parent/child parent" may fail with -EBUSY.
3991 */
3992 empty = true;
3993 rcu_read_lock();
3994 list_for_each_entry_rcu(child, &cgrp->children, sibling) {
3995 empty = cgroup_is_dead(child);
3996 if (!empty)
3997 break;
3998 }
3999 rcu_read_unlock();
4000 if (!empty)
4001 return -EBUSY;
4002
4003 /*
4004 * Mark @cgrp dead. This prevents further task migration and child
4005 * creation by disabling cgroup_lock_live_group(). Note that
4006 * CGRP_DEAD assertion is depended upon by css_next_child() to
4007 * resume iteration after dropping RCU read lock. See
4008 * css_next_child() for details.
4009 */
4010 set_bit(CGRP_DEAD, &cgrp->flags);
4011
4012 /*
4013 * Initiate massacre of all css's. cgroup_destroy_css_killed()
4014 * will be invoked to perform the rest of destruction once the
4015 * percpu refs of all css's are confirmed to be killed. This
4016 * involves removing the subsystem's files, drop cgroup_mutex.
4017 */
4018 mutex_unlock(&cgroup_mutex);
4019 for_each_css(css, ssid, cgrp)
4020 kill_css(css);
4021 mutex_lock(&cgroup_mutex);
4022
4023 /* CGRP_DEAD is set, remove from ->release_list for the last time */
4024 raw_spin_lock(&release_list_lock);
4025 if (!list_empty(&cgrp->release_list))
4026 list_del_init(&cgrp->release_list);
4027 raw_spin_unlock(&release_list_lock);
4028
4029 /*
4030 * If @cgrp has css's attached, the second stage of cgroup
4031 * destruction is kicked off from css_killed_work_fn() after the
4032 * refs of all attached css's are killed. If @cgrp doesn't have
4033 * any css, we kick it off here.
4034 */
4035 if (!cgrp->nr_css)
4036 cgroup_destroy_css_killed(cgrp);
4037
4038 /* remove @cgrp directory along with the base files */
4039 mutex_unlock(&cgroup_mutex);
4040
4041 /*
4042 * There are two control paths which try to determine cgroup from
4043 * dentry without going through kernfs - cgroupstats_build() and
4044 * css_tryget_from_dir(). Those are supported by RCU protecting
4045 * clearing of cgrp->kn->priv backpointer, which should happen
4046 * after all files under it have been removed.
4047 */
4048 kernfs_remove(cgrp->kn); /* @cgrp has an extra ref on its kn */
4049 RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL);
4050
4051 mutex_lock(&cgroup_mutex);
4052
4053 return 0;
4054};
4055
4056/**
4057 * cgroup_destroy_css_killed - the second step of cgroup destruction
4058 * @work: cgroup->destroy_free_work
4059 *
4060 * This function is invoked from a work item for a cgroup which is being
4061 * destroyed after all css's are offlined and performs the rest of
4062 * destruction. This is the second step of destruction described in the
4063 * comment above cgroup_destroy_locked().
4064 */
4065static void cgroup_destroy_css_killed(struct cgroup *cgrp)
4066{
4067 struct cgroup *parent = cgrp->parent;
4068
4069 lockdep_assert_held(&cgroup_tree_mutex);
4070 lockdep_assert_held(&cgroup_mutex);
4071
4072 /* delete this cgroup from parent->children */
4073 list_del_rcu(&cgrp->sibling);
4074
4075 cgroup_put(cgrp);
4076
4077 set_bit(CGRP_RELEASABLE, &parent->flags);
4078 check_for_release(parent);
4079}
4080
4081static int cgroup_rmdir(struct kernfs_node *kn)
4082{
4083 struct cgroup *cgrp = kn->priv;
4084 int ret = 0;
4085
4086 /*
4087 * This is self-destruction but @kn can't be removed while this
4088 * callback is in progress. Let's break active protection. Once
4089 * the protection is broken, @cgrp can be destroyed at any point.
4090 * Pin it so that it stays accessible.
4091 */
4092 cgroup_get(cgrp);
4093 kernfs_break_active_protection(kn);
4094
4095 mutex_lock(&cgroup_tree_mutex);
4096 mutex_lock(&cgroup_mutex);
4097
4098 /*
4099 * @cgrp might already have been destroyed while we're trying to
4100 * grab the mutexes.
4101 */
4102 if (!cgroup_is_dead(cgrp))
4103 ret = cgroup_destroy_locked(cgrp);
4104
4105 mutex_unlock(&cgroup_mutex);
4106 mutex_unlock(&cgroup_tree_mutex);
4107
4108 kernfs_unbreak_active_protection(kn);
4109 cgroup_put(cgrp);
4110 return ret;
4111}
4112
4113static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
4114 .remount_fs = cgroup_remount,
4115 .show_options = cgroup_show_options,
4116 .mkdir = cgroup_mkdir,
4117 .rmdir = cgroup_rmdir,
4118 .rename = cgroup_rename,
4119};
4120
4121static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4122{
4123 struct cgroup_subsys_state *css;
4124
4125 printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4126
4127 mutex_lock(&cgroup_tree_mutex);
4128 mutex_lock(&cgroup_mutex);
4129
4130 INIT_LIST_HEAD(&ss->cfts);
4131
4132 /* Create the root cgroup state for this subsystem */
4133 ss->root = &cgrp_dfl_root;
4134 css = ss->css_alloc(cgroup_css(&cgrp_dfl_root.cgrp, ss));
4135 /* We don't handle early failures gracefully */
4136 BUG_ON(IS_ERR(css));
4137 init_css(css, ss, &cgrp_dfl_root.cgrp);
4138
4139 /* Update the init_css_set to contain a subsys
4140 * pointer to this state - since the subsystem is
4141 * newly registered, all tasks and hence the
4142 * init_css_set is in the subsystem's root cgroup. */
4143 init_css_set.subsys[ss->id] = css;
4144
4145 need_forkexit_callback |= ss->fork || ss->exit;
4146
4147 /* At system boot, before all subsystems have been
4148 * registered, no tasks have been forked, so we don't
4149 * need to invoke fork callbacks here. */
4150 BUG_ON(!list_empty(&init_task.tasks));
4151
4152 BUG_ON(online_css(css));
4153
4154 cgrp_dfl_root.cgrp.subsys_mask |= 1 << ss->id;
4155
4156 mutex_unlock(&cgroup_mutex);
4157 mutex_unlock(&cgroup_tree_mutex);
4158}
4159
4160/**
4161 * cgroup_init_early - cgroup initialization at system boot
4162 *
4163 * Initialize cgroups at system boot, and initialize any
4164 * subsystems that request early init.
4165 */
4166int __init cgroup_init_early(void)
4167{
4168 static struct cgroup_sb_opts __initdata opts =
4169 { .flags = CGRP_ROOT_SANE_BEHAVIOR };
4170 struct cgroup_subsys *ss;
4171 int i;
4172
4173 init_cgroup_root(&cgrp_dfl_root, &opts);
4174 RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
4175
4176 for_each_subsys(ss, i) {
4177 WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
4178 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
4179 i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
4180 ss->id, ss->name);
4181 WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
4182 "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
4183
4184 ss->id = i;
4185 ss->name = cgroup_subsys_name[i];
4186
4187 if (ss->early_init)
4188 cgroup_init_subsys(ss);
4189 }
4190 return 0;
4191}
4192
4193/**
4194 * cgroup_init - cgroup initialization
4195 *
4196 * Register cgroup filesystem and /proc file, and initialize
4197 * any subsystems that didn't request early init.
4198 */
4199int __init cgroup_init(void)
4200{
4201 struct cgroup_subsys *ss;
4202 unsigned long key;
4203 int ssid, err;
4204
4205 BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
4206
4207 mutex_lock(&cgroup_tree_mutex);
4208 mutex_lock(&cgroup_mutex);
4209
4210 /* Add init_css_set to the hash table */
4211 key = css_set_hash(init_css_set.subsys);
4212 hash_add(css_set_table, &init_css_set.hlist, key);
4213
4214 BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0));
4215
4216 mutex_unlock(&cgroup_mutex);
4217 mutex_unlock(&cgroup_tree_mutex);
4218
4219 for_each_subsys(ss, ssid) {
4220 if (!ss->early_init)
4221 cgroup_init_subsys(ss);
4222
4223 /*
4224 * cftype registration needs kmalloc and can't be done
4225 * during early_init. Register base cftypes separately.
4226 */
4227 if (ss->base_cftypes)
4228 WARN_ON(cgroup_add_cftypes(ss, ss->base_cftypes));
4229 }
4230
4231 cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
4232 if (!cgroup_kobj)
4233 return -ENOMEM;
4234
4235 err = register_filesystem(&cgroup_fs_type);
4236 if (err < 0) {
4237 kobject_put(cgroup_kobj);
4238 return err;
4239 }
4240
4241 proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4242 return 0;
4243}
4244
4245static int __init cgroup_wq_init(void)
4246{
4247 /*
4248 * There isn't much point in executing destruction path in
4249 * parallel. Good chunk is serialized with cgroup_mutex anyway.
4250 * Use 1 for @max_active.
4251 *
4252 * We would prefer to do this in cgroup_init() above, but that
4253 * is called before init_workqueues(): so leave this until after.
4254 */
4255 cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
4256 BUG_ON(!cgroup_destroy_wq);
4257
4258 /*
4259 * Used to destroy pidlists and separate to serve as flush domain.
4260 * Cap @max_active to 1 too.
4261 */
4262 cgroup_pidlist_destroy_wq = alloc_workqueue("cgroup_pidlist_destroy",
4263 0, 1);
4264 BUG_ON(!cgroup_pidlist_destroy_wq);
4265
4266 return 0;
4267}
4268core_initcall(cgroup_wq_init);
4269
4270/*
4271 * proc_cgroup_show()
4272 * - Print task's cgroup paths into seq_file, one line for each hierarchy
4273 * - Used for /proc/<pid>/cgroup.
4274 */
4275
4276/* TODO: Use a proper seq_file iterator */
4277int proc_cgroup_show(struct seq_file *m, void *v)
4278{
4279 struct pid *pid;
4280 struct task_struct *tsk;
4281 char *buf, *path;
4282 int retval;
4283 struct cgroup_root *root;
4284
4285 retval = -ENOMEM;
4286 buf = kmalloc(PATH_MAX, GFP_KERNEL);
4287 if (!buf)
4288 goto out;
4289
4290 retval = -ESRCH;
4291 pid = m->private;
4292 tsk = get_pid_task(pid, PIDTYPE_PID);
4293 if (!tsk)
4294 goto out_free;
4295
4296 retval = 0;
4297
4298 mutex_lock(&cgroup_mutex);
4299 down_read(&css_set_rwsem);
4300
4301 for_each_root(root) {
4302 struct cgroup_subsys *ss;
4303 struct cgroup *cgrp;
4304 int ssid, count = 0;
4305
4306 if (root == &cgrp_dfl_root && !cgrp_dfl_root_visible)
4307 continue;
4308
4309 seq_printf(m, "%d:", root->hierarchy_id);
4310 for_each_subsys(ss, ssid)
4311 if (root->cgrp.subsys_mask & (1 << ssid))
4312 seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4313 if (strlen(root->name))
4314 seq_printf(m, "%sname=%s", count ? "," : "",
4315 root->name);
4316 seq_putc(m, ':');
4317 cgrp = task_cgroup_from_root(tsk, root);
4318 path = cgroup_path(cgrp, buf, PATH_MAX);
4319 if (!path) {
4320 retval = -ENAMETOOLONG;
4321 goto out_unlock;
4322 }
4323 seq_puts(m, path);
4324 seq_putc(m, '\n');
4325 }
4326
4327out_unlock:
4328 up_read(&css_set_rwsem);
4329 mutex_unlock(&cgroup_mutex);
4330 put_task_struct(tsk);
4331out_free:
4332 kfree(buf);
4333out:
4334 return retval;
4335}
4336
4337/* Display information about each subsystem and each hierarchy */
4338static int proc_cgroupstats_show(struct seq_file *m, void *v)
4339{
4340 struct cgroup_subsys *ss;
4341 int i;
4342
4343 seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
4344 /*
4345 * ideally we don't want subsystems moving around while we do this.
4346 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
4347 * subsys/hierarchy state.
4348 */
4349 mutex_lock(&cgroup_mutex);
4350
4351 for_each_subsys(ss, i)
4352 seq_printf(m, "%s\t%d\t%d\t%d\n",
4353 ss->name, ss->root->hierarchy_id,
4354 atomic_read(&ss->root->nr_cgrps), !ss->disabled);
4355
4356 mutex_unlock(&cgroup_mutex);
4357 return 0;
4358}
4359
4360static int cgroupstats_open(struct inode *inode, struct file *file)
4361{
4362 return single_open(file, proc_cgroupstats_show, NULL);
4363}
4364
4365static const struct file_operations proc_cgroupstats_operations = {
4366 .open = cgroupstats_open,
4367 .read = seq_read,
4368 .llseek = seq_lseek,
4369 .release = single_release,
4370};
4371
4372/**
4373 * cgroup_fork - initialize cgroup related fields during copy_process()
4374 * @child: pointer to task_struct of forking parent process.
4375 *
4376 * A task is associated with the init_css_set until cgroup_post_fork()
4377 * attaches it to the parent's css_set. Empty cg_list indicates that
4378 * @child isn't holding reference to its css_set.
4379 */
4380void cgroup_fork(struct task_struct *child)
4381{
4382 RCU_INIT_POINTER(child->cgroups, &init_css_set);
4383 INIT_LIST_HEAD(&child->cg_list);
4384}
4385
4386/**
4387 * cgroup_post_fork - called on a new task after adding it to the task list
4388 * @child: the task in question
4389 *
4390 * Adds the task to the list running through its css_set if necessary and
4391 * call the subsystem fork() callbacks. Has to be after the task is
4392 * visible on the task list in case we race with the first call to
4393 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
4394 * list.
4395 */
4396void cgroup_post_fork(struct task_struct *child)
4397{
4398 struct cgroup_subsys *ss;
4399 int i;
4400
4401 /*
4402 * This may race against cgroup_enable_task_cg_links(). As that
4403 * function sets use_task_css_set_links before grabbing
4404 * tasklist_lock and we just went through tasklist_lock to add
4405 * @child, it's guaranteed that either we see the set
4406 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
4407 * @child during its iteration.
4408 *
4409 * If we won the race, @child is associated with %current's
4410 * css_set. Grabbing css_set_rwsem guarantees both that the
4411 * association is stable, and, on completion of the parent's
4412 * migration, @child is visible in the source of migration or
4413 * already in the destination cgroup. This guarantee is necessary
4414 * when implementing operations which need to migrate all tasks of
4415 * a cgroup to another.
4416 *
4417 * Note that if we lose to cgroup_enable_task_cg_links(), @child
4418 * will remain in init_css_set. This is safe because all tasks are
4419 * in the init_css_set before cg_links is enabled and there's no
4420 * operation which transfers all tasks out of init_css_set.
4421 */
4422 if (use_task_css_set_links) {
4423 struct css_set *cset;
4424
4425 down_write(&css_set_rwsem);
4426 cset = task_css_set(current);
4427 if (list_empty(&child->cg_list)) {
4428 rcu_assign_pointer(child->cgroups, cset);
4429 list_add(&child->cg_list, &cset->tasks);
4430 get_css_set(cset);
4431 }
4432 up_write(&css_set_rwsem);
4433 }
4434
4435 /*
4436 * Call ss->fork(). This must happen after @child is linked on
4437 * css_set; otherwise, @child might change state between ->fork()
4438 * and addition to css_set.
4439 */
4440 if (need_forkexit_callback) {
4441 for_each_subsys(ss, i)
4442 if (ss->fork)
4443 ss->fork(child);
4444 }
4445}
4446
4447/**
4448 * cgroup_exit - detach cgroup from exiting task
4449 * @tsk: pointer to task_struct of exiting process
4450 *
4451 * Description: Detach cgroup from @tsk and release it.
4452 *
4453 * Note that cgroups marked notify_on_release force every task in
4454 * them to take the global cgroup_mutex mutex when exiting.
4455 * This could impact scaling on very large systems. Be reluctant to
4456 * use notify_on_release cgroups where very high task exit scaling
4457 * is required on large systems.
4458 *
4459 * We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
4460 * call cgroup_exit() while the task is still competent to handle
4461 * notify_on_release(), then leave the task attached to the root cgroup in
4462 * each hierarchy for the remainder of its exit. No need to bother with
4463 * init_css_set refcnting. init_css_set never goes away and we can't race
4464 * with migration path - PF_EXITING is visible to migration path.
4465 */
4466void cgroup_exit(struct task_struct *tsk)
4467{
4468 struct cgroup_subsys *ss;
4469 struct css_set *cset;
4470 bool put_cset = false;
4471 int i;
4472
4473 /*
4474 * Unlink from @tsk from its css_set. As migration path can't race
4475 * with us, we can check cg_list without grabbing css_set_rwsem.
4476 */
4477 if (!list_empty(&tsk->cg_list)) {
4478 down_write(&css_set_rwsem);
4479 list_del_init(&tsk->cg_list);
4480 up_write(&css_set_rwsem);
4481 put_cset = true;
4482 }
4483
4484 /* Reassign the task to the init_css_set. */
4485 cset = task_css_set(tsk);
4486 RCU_INIT_POINTER(tsk->cgroups, &init_css_set);
4487
4488 if (need_forkexit_callback) {
4489 /* see cgroup_post_fork() for details */
4490 for_each_subsys(ss, i) {
4491 if (ss->exit) {
4492 struct cgroup_subsys_state *old_css = cset->subsys[i];
4493 struct cgroup_subsys_state *css = task_css(tsk, i);
4494
4495 ss->exit(css, old_css, tsk);
4496 }
4497 }
4498 }
4499
4500 if (put_cset)
4501 put_css_set(cset, true);
4502}
4503
4504static void check_for_release(struct cgroup *cgrp)
4505{
4506 if (cgroup_is_releasable(cgrp) &&
4507 list_empty(&cgrp->cset_links) && list_empty(&cgrp->children)) {
4508 /*
4509 * Control Group is currently removeable. If it's not
4510 * already queued for a userspace notification, queue
4511 * it now
4512 */
4513 int need_schedule_work = 0;
4514
4515 raw_spin_lock(&release_list_lock);
4516 if (!cgroup_is_dead(cgrp) &&
4517 list_empty(&cgrp->release_list)) {
4518 list_add(&cgrp->release_list, &release_list);
4519 need_schedule_work = 1;
4520 }
4521 raw_spin_unlock(&release_list_lock);
4522 if (need_schedule_work)
4523 schedule_work(&release_agent_work);
4524 }
4525}
4526
4527/*
4528 * Notify userspace when a cgroup is released, by running the
4529 * configured release agent with the name of the cgroup (path
4530 * relative to the root of cgroup file system) as the argument.
4531 *
4532 * Most likely, this user command will try to rmdir this cgroup.
4533 *
4534 * This races with the possibility that some other task will be
4535 * attached to this cgroup before it is removed, or that some other
4536 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
4537 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
4538 * unused, and this cgroup will be reprieved from its death sentence,
4539 * to continue to serve a useful existence. Next time it's released,
4540 * we will get notified again, if it still has 'notify_on_release' set.
4541 *
4542 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
4543 * means only wait until the task is successfully execve()'d. The
4544 * separate release agent task is forked by call_usermodehelper(),
4545 * then control in this thread returns here, without waiting for the
4546 * release agent task. We don't bother to wait because the caller of
4547 * this routine has no use for the exit status of the release agent
4548 * task, so no sense holding our caller up for that.
4549 */
4550static void cgroup_release_agent(struct work_struct *work)
4551{
4552 BUG_ON(work != &release_agent_work);
4553 mutex_lock(&cgroup_mutex);
4554 raw_spin_lock(&release_list_lock);
4555 while (!list_empty(&release_list)) {
4556 char *argv[3], *envp[3];
4557 int i;
4558 char *pathbuf = NULL, *agentbuf = NULL, *path;
4559 struct cgroup *cgrp = list_entry(release_list.next,
4560 struct cgroup,
4561 release_list);
4562 list_del_init(&cgrp->release_list);
4563 raw_spin_unlock(&release_list_lock);
4564 pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
4565 if (!pathbuf)
4566 goto continue_free;
4567 path = cgroup_path(cgrp, pathbuf, PATH_MAX);
4568 if (!path)
4569 goto continue_free;
4570 agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
4571 if (!agentbuf)
4572 goto continue_free;
4573
4574 i = 0;
4575 argv[i++] = agentbuf;
4576 argv[i++] = path;
4577 argv[i] = NULL;
4578
4579 i = 0;
4580 /* minimal command environment */
4581 envp[i++] = "HOME=/";
4582 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
4583 envp[i] = NULL;
4584
4585 /* Drop the lock while we invoke the usermode helper,
4586 * since the exec could involve hitting disk and hence
4587 * be a slow process */
4588 mutex_unlock(&cgroup_mutex);
4589 call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
4590 mutex_lock(&cgroup_mutex);
4591 continue_free:
4592 kfree(pathbuf);
4593 kfree(agentbuf);
4594 raw_spin_lock(&release_list_lock);
4595 }
4596 raw_spin_unlock(&release_list_lock);
4597 mutex_unlock(&cgroup_mutex);
4598}
4599
4600static int __init cgroup_disable(char *str)
4601{
4602 struct cgroup_subsys *ss;
4603 char *token;
4604 int i;
4605
4606 while ((token = strsep(&str, ",")) != NULL) {
4607 if (!*token)
4608 continue;
4609
4610 for_each_subsys(ss, i) {
4611 if (!strcmp(token, ss->name)) {
4612 ss->disabled = 1;
4613 printk(KERN_INFO "Disabling %s control group"
4614 " subsystem\n", ss->name);
4615 break;
4616 }
4617 }
4618 }
4619 return 1;
4620}
4621__setup("cgroup_disable=", cgroup_disable);
4622
4623/**
4624 * css_tryget_from_dir - get corresponding css from the dentry of a cgroup dir
4625 * @dentry: directory dentry of interest
4626 * @ss: subsystem of interest
4627 *
4628 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
4629 * to get the corresponding css and return it. If such css doesn't exist
4630 * or can't be pinned, an ERR_PTR value is returned.
4631 */
4632struct cgroup_subsys_state *css_tryget_from_dir(struct dentry *dentry,
4633 struct cgroup_subsys *ss)
4634{
4635 struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
4636 struct cgroup_subsys_state *css = NULL;
4637 struct cgroup *cgrp;
4638
4639 /* is @dentry a cgroup dir? */
4640 if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
4641 kernfs_type(kn) != KERNFS_DIR)
4642 return ERR_PTR(-EBADF);
4643
4644 rcu_read_lock();
4645
4646 /*
4647 * This path doesn't originate from kernfs and @kn could already
4648 * have been or be removed at any point. @kn->priv is RCU
4649 * protected for this access. See destroy_locked() for details.
4650 */
4651 cgrp = rcu_dereference(kn->priv);
4652 if (cgrp)
4653 css = cgroup_css(cgrp, ss);
4654
4655 if (!css || !css_tryget(css))
4656 css = ERR_PTR(-ENOENT);
4657
4658 rcu_read_unlock();
4659 return css;
4660}
4661
4662/**
4663 * css_from_id - lookup css by id
4664 * @id: the cgroup id
4665 * @ss: cgroup subsys to be looked into
4666 *
4667 * Returns the css if there's valid one with @id, otherwise returns NULL.
4668 * Should be called under rcu_read_lock().
4669 */
4670struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
4671{
4672 struct cgroup *cgrp;
4673
4674 cgroup_assert_mutexes_or_rcu_locked();
4675
4676 cgrp = idr_find(&ss->root->cgroup_idr, id);
4677 if (cgrp)
4678 return cgroup_css(cgrp, ss);
4679 return NULL;
4680}
4681
4682#ifdef CONFIG_CGROUP_DEBUG
4683static struct cgroup_subsys_state *
4684debug_css_alloc(struct cgroup_subsys_state *parent_css)
4685{
4686 struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
4687
4688 if (!css)
4689 return ERR_PTR(-ENOMEM);
4690
4691 return css;
4692}
4693
4694static void debug_css_free(struct cgroup_subsys_state *css)
4695{
4696 kfree(css);
4697}
4698
4699static u64 debug_taskcount_read(struct cgroup_subsys_state *css,
4700 struct cftype *cft)
4701{
4702 return cgroup_task_count(css->cgroup);
4703}
4704
4705static u64 current_css_set_read(struct cgroup_subsys_state *css,
4706 struct cftype *cft)
4707{
4708 return (u64)(unsigned long)current->cgroups;
4709}
4710
4711static u64 current_css_set_refcount_read(struct cgroup_subsys_state *css,
4712 struct cftype *cft)
4713{
4714 u64 count;
4715
4716 rcu_read_lock();
4717 count = atomic_read(&task_css_set(current)->refcount);
4718 rcu_read_unlock();
4719 return count;
4720}
4721
4722static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
4723{
4724 struct cgrp_cset_link *link;
4725 struct css_set *cset;
4726 char *name_buf;
4727
4728 name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
4729 if (!name_buf)
4730 return -ENOMEM;
4731
4732 down_read(&css_set_rwsem);
4733 rcu_read_lock();
4734 cset = rcu_dereference(current->cgroups);
4735 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
4736 struct cgroup *c = link->cgrp;
4737
4738 cgroup_name(c, name_buf, NAME_MAX + 1);
4739 seq_printf(seq, "Root %d group %s\n",
4740 c->root->hierarchy_id, name_buf);
4741 }
4742 rcu_read_unlock();
4743 up_read(&css_set_rwsem);
4744 kfree(name_buf);
4745 return 0;
4746}
4747
4748#define MAX_TASKS_SHOWN_PER_CSS 25
4749static int cgroup_css_links_read(struct seq_file *seq, void *v)
4750{
4751 struct cgroup_subsys_state *css = seq_css(seq);
4752 struct cgrp_cset_link *link;
4753
4754 down_read(&css_set_rwsem);
4755 list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
4756 struct css_set *cset = link->cset;
4757 struct task_struct *task;
4758 int count = 0;
4759
4760 seq_printf(seq, "css_set %p\n", cset);
4761
4762 list_for_each_entry(task, &cset->tasks, cg_list) {
4763 if (count++ > MAX_TASKS_SHOWN_PER_CSS)
4764 goto overflow;
4765 seq_printf(seq, " task %d\n", task_pid_vnr(task));
4766 }
4767
4768 list_for_each_entry(task, &cset->mg_tasks, cg_list) {
4769 if (count++ > MAX_TASKS_SHOWN_PER_CSS)
4770 goto overflow;
4771 seq_printf(seq, " task %d\n", task_pid_vnr(task));
4772 }
4773 continue;
4774 overflow:
4775 seq_puts(seq, " ...\n");
4776 }
4777 up_read(&css_set_rwsem);
4778 return 0;
4779}
4780
4781static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
4782{
4783 return test_bit(CGRP_RELEASABLE, &css->cgroup->flags);
4784}
4785
4786static struct cftype debug_files[] = {
4787 {
4788 .name = "taskcount",
4789 .read_u64 = debug_taskcount_read,
4790 },
4791
4792 {
4793 .name = "current_css_set",
4794 .read_u64 = current_css_set_read,
4795 },
4796
4797 {
4798 .name = "current_css_set_refcount",
4799 .read_u64 = current_css_set_refcount_read,
4800 },
4801
4802 {
4803 .name = "current_css_set_cg_links",
4804 .seq_show = current_css_set_cg_links_read,
4805 },
4806
4807 {
4808 .name = "cgroup_css_links",
4809 .seq_show = cgroup_css_links_read,
4810 },
4811
4812 {
4813 .name = "releasable",
4814 .read_u64 = releasable_read,
4815 },
4816
4817 { } /* terminate */
4818};
4819
4820struct cgroup_subsys debug_cgrp_subsys = {
4821 .css_alloc = debug_css_alloc,
4822 .css_free = debug_css_free,
4823 .base_cftypes = debug_files,
4824};
4825#endif /* CONFIG_CGROUP_DEBUG */