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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 */
1/*
2 * Generic process-grouping system.
3 *
4 * Based originally on the cpuset system, extracted by Paul Menage
5 * Copyright (C) 2006 Google, Inc
6 *
7 * Notifications support
8 * Copyright (C) 2009 Nokia Corporation
9 * Author: Kirill A. Shutemov
10 *
11 * Copyright notices from the original cpuset code:
12 * --------------------------------------------------
13 * Copyright (C) 2003 BULL SA.
14 * Copyright (C) 2004-2006 Silicon Graphics, Inc.
15 *
16 * Portions derived from Patrick Mochel's sysfs code.
17 * sysfs is Copyright (c) 2001-3 Patrick Mochel
18 *
19 * 2003-10-10 Written by Simon Derr.
20 * 2003-10-22 Updates by Stephen Hemminger.
21 * 2004 May-July Rework by Paul Jackson.
22 * ---------------------------------------------------
23 *
24 * This file is subject to the terms and conditions of the GNU General Public
25 * License. See the file COPYING in the main directory of the Linux
26 * distribution for more details.
27 */
28
29#include <linux/cgroup.h>
30#include <linux/cred.h>
31#include <linux/ctype.h>
32#include <linux/errno.h>
33#include <linux/fs.h>
34#include <linux/init_task.h>
35#include <linux/kernel.h>
36#include <linux/list.h>
37#include <linux/mm.h>
38#include <linux/mutex.h>
39#include <linux/mount.h>
40#include <linux/pagemap.h>
41#include <linux/proc_fs.h>
42#include <linux/rcupdate.h>
43#include <linux/sched.h>
44#include <linux/backing-dev.h>
45#include <linux/seq_file.h>
46#include <linux/slab.h>
47#include <linux/magic.h>
48#include <linux/spinlock.h>
49#include <linux/string.h>
50#include <linux/sort.h>
51#include <linux/kmod.h>
52#include <linux/module.h>
53#include <linux/delayacct.h>
54#include <linux/cgroupstats.h>
55#include <linux/hash.h>
56#include <linux/namei.h>
57#include <linux/pid_namespace.h>
58#include <linux/idr.h>
59#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
60#include <linux/eventfd.h>
61#include <linux/poll.h>
62#include <linux/flex_array.h> /* used in cgroup_attach_proc */
63
64#include <linux/atomic.h>
65
66static DEFINE_MUTEX(cgroup_mutex);
67
68/*
69 * Generate an array of cgroup subsystem pointers. At boot time, this is
70 * populated up to CGROUP_BUILTIN_SUBSYS_COUNT, and modular subsystems are
71 * registered after that. The mutable section of this array is protected by
72 * cgroup_mutex.
73 */
74#define SUBSYS(_x) &_x ## _subsys,
75static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
76#include <linux/cgroup_subsys.h>
77};
78
79#define MAX_CGROUP_ROOT_NAMELEN 64
80
81/*
82 * A cgroupfs_root represents the root of a cgroup hierarchy,
83 * and may be associated with a superblock to form an active
84 * hierarchy
85 */
86struct cgroupfs_root {
87 struct super_block *sb;
88
89 /*
90 * The bitmask of subsystems intended to be attached to this
91 * hierarchy
92 */
93 unsigned long subsys_bits;
94
95 /* Unique id for this hierarchy. */
96 int hierarchy_id;
97
98 /* The bitmask of subsystems currently attached to this hierarchy */
99 unsigned long actual_subsys_bits;
100
101 /* A list running through the attached subsystems */
102 struct list_head subsys_list;
103
104 /* The root cgroup for this hierarchy */
105 struct cgroup top_cgroup;
106
107 /* Tracks how many cgroups are currently defined in hierarchy.*/
108 int number_of_cgroups;
109
110 /* A list running through the active hierarchies */
111 struct list_head root_list;
112
113 /* Hierarchy-specific flags */
114 unsigned long flags;
115
116 /* The path to use for release notifications. */
117 char release_agent_path[PATH_MAX];
118
119 /* The name for this hierarchy - may be empty */
120 char name[MAX_CGROUP_ROOT_NAMELEN];
121};
122
123/*
124 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
125 * subsystems that are otherwise unattached - it never has more than a
126 * single cgroup, and all tasks are part of that cgroup.
127 */
128static struct cgroupfs_root rootnode;
129
130/*
131 * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
132 * cgroup_subsys->use_id != 0.
133 */
134#define CSS_ID_MAX (65535)
135struct css_id {
136 /*
137 * The css to which this ID points. This pointer is set to valid value
138 * after cgroup is populated. If cgroup is removed, this will be NULL.
139 * This pointer is expected to be RCU-safe because destroy()
140 * is called after synchronize_rcu(). But for safe use, css_is_removed()
141 * css_tryget() should be used for avoiding race.
142 */
143 struct cgroup_subsys_state __rcu *css;
144 /*
145 * ID of this css.
146 */
147 unsigned short id;
148 /*
149 * Depth in hierarchy which this ID belongs to.
150 */
151 unsigned short depth;
152 /*
153 * ID is freed by RCU. (and lookup routine is RCU safe.)
154 */
155 struct rcu_head rcu_head;
156 /*
157 * Hierarchy of CSS ID belongs to.
158 */
159 unsigned short stack[0]; /* Array of Length (depth+1) */
160};
161
162/*
163 * cgroup_event represents events which userspace want to receive.
164 */
165struct cgroup_event {
166 /*
167 * Cgroup which the event belongs to.
168 */
169 struct cgroup *cgrp;
170 /*
171 * Control file which the event associated.
172 */
173 struct cftype *cft;
174 /*
175 * eventfd to signal userspace about the event.
176 */
177 struct eventfd_ctx *eventfd;
178 /*
179 * Each of these stored in a list by the cgroup.
180 */
181 struct list_head list;
182 /*
183 * All fields below needed to unregister event when
184 * userspace closes eventfd.
185 */
186 poll_table pt;
187 wait_queue_head_t *wqh;
188 wait_queue_t wait;
189 struct work_struct remove;
190};
191
192/* The list of hierarchy roots */
193
194static LIST_HEAD(roots);
195static int root_count;
196
197static DEFINE_IDA(hierarchy_ida);
198static int next_hierarchy_id;
199static DEFINE_SPINLOCK(hierarchy_id_lock);
200
201/* dummytop is a shorthand for the dummy hierarchy's top cgroup */
202#define dummytop (&rootnode.top_cgroup)
203
204/* This flag indicates whether tasks in the fork and exit paths should
205 * check for fork/exit handlers to call. This avoids us having to do
206 * extra work in the fork/exit path if none of the subsystems need to
207 * be called.
208 */
209static int need_forkexit_callback __read_mostly;
210
211#ifdef CONFIG_PROVE_LOCKING
212int cgroup_lock_is_held(void)
213{
214 return lockdep_is_held(&cgroup_mutex);
215}
216#else /* #ifdef CONFIG_PROVE_LOCKING */
217int cgroup_lock_is_held(void)
218{
219 return mutex_is_locked(&cgroup_mutex);
220}
221#endif /* #else #ifdef CONFIG_PROVE_LOCKING */
222
223EXPORT_SYMBOL_GPL(cgroup_lock_is_held);
224
225/* convenient tests for these bits */
226inline int cgroup_is_removed(const struct cgroup *cgrp)
227{
228 return test_bit(CGRP_REMOVED, &cgrp->flags);
229}
230
231/* bits in struct cgroupfs_root flags field */
232enum {
233 ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
234};
235
236static int cgroup_is_releasable(const struct cgroup *cgrp)
237{
238 const int bits =
239 (1 << CGRP_RELEASABLE) |
240 (1 << CGRP_NOTIFY_ON_RELEASE);
241 return (cgrp->flags & bits) == bits;
242}
243
244static int notify_on_release(const struct cgroup *cgrp)
245{
246 return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
247}
248
249static int clone_children(const struct cgroup *cgrp)
250{
251 return test_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
252}
253
254/*
255 * for_each_subsys() allows you to iterate on each subsystem attached to
256 * an active hierarchy
257 */
258#define for_each_subsys(_root, _ss) \
259list_for_each_entry(_ss, &_root->subsys_list, sibling)
260
261/* for_each_active_root() allows you to iterate across the active hierarchies */
262#define for_each_active_root(_root) \
263list_for_each_entry(_root, &roots, root_list)
264
265/* the list of cgroups eligible for automatic release. Protected by
266 * release_list_lock */
267static LIST_HEAD(release_list);
268static DEFINE_SPINLOCK(release_list_lock);
269static void cgroup_release_agent(struct work_struct *work);
270static DECLARE_WORK(release_agent_work, cgroup_release_agent);
271static void check_for_release(struct cgroup *cgrp);
272
273/* Link structure for associating css_set objects with cgroups */
274struct cg_cgroup_link {
275 /*
276 * List running through cg_cgroup_links associated with a
277 * cgroup, anchored on cgroup->css_sets
278 */
279 struct list_head cgrp_link_list;
280 struct cgroup *cgrp;
281 /*
282 * List running through cg_cgroup_links pointing at a
283 * single css_set object, anchored on css_set->cg_links
284 */
285 struct list_head cg_link_list;
286 struct css_set *cg;
287};
288
289/* The default css_set - used by init and its children prior to any
290 * hierarchies being mounted. It contains a pointer to the root state
291 * for each subsystem. Also used to anchor the list of css_sets. Not
292 * reference-counted, to improve performance when child cgroups
293 * haven't been created.
294 */
295
296static struct css_set init_css_set;
297static struct cg_cgroup_link init_css_set_link;
298
299static int cgroup_init_idr(struct cgroup_subsys *ss,
300 struct cgroup_subsys_state *css);
301
302/* css_set_lock protects the list of css_set objects, and the
303 * chain of tasks off each css_set. Nests outside task->alloc_lock
304 * due to cgroup_iter_start() */
305static DEFINE_RWLOCK(css_set_lock);
306static int css_set_count;
307
308/*
309 * hash table for cgroup groups. This improves the performance to find
310 * an existing css_set. This hash doesn't (currently) take into
311 * account cgroups in empty hierarchies.
312 */
313#define CSS_SET_HASH_BITS 7
314#define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS)
315static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
316
317static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
318{
319 int i;
320 int index;
321 unsigned long tmp = 0UL;
322
323 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
324 tmp += (unsigned long)css[i];
325 tmp = (tmp >> 16) ^ tmp;
326
327 index = hash_long(tmp, CSS_SET_HASH_BITS);
328
329 return &css_set_table[index];
330}
331
332/* We don't maintain the lists running through each css_set to its
333 * task until after the first call to cgroup_iter_start(). This
334 * reduces the fork()/exit() overhead for people who have cgroups
335 * compiled into their kernel but not actually in use */
336static int use_task_css_set_links __read_mostly;
337
338static void __put_css_set(struct css_set *cg, int taskexit)
339{
340 struct cg_cgroup_link *link;
341 struct cg_cgroup_link *saved_link;
342 /*
343 * Ensure that the refcount doesn't hit zero while any readers
344 * can see it. Similar to atomic_dec_and_lock(), but for an
345 * rwlock
346 */
347 if (atomic_add_unless(&cg->refcount, -1, 1))
348 return;
349 write_lock(&css_set_lock);
350 if (!atomic_dec_and_test(&cg->refcount)) {
351 write_unlock(&css_set_lock);
352 return;
353 }
354
355 /* This css_set is dead. unlink it and release cgroup refcounts */
356 hlist_del(&cg->hlist);
357 css_set_count--;
358
359 list_for_each_entry_safe(link, saved_link, &cg->cg_links,
360 cg_link_list) {
361 struct cgroup *cgrp = link->cgrp;
362 list_del(&link->cg_link_list);
363 list_del(&link->cgrp_link_list);
364 if (atomic_dec_and_test(&cgrp->count) &&
365 notify_on_release(cgrp)) {
366 if (taskexit)
367 set_bit(CGRP_RELEASABLE, &cgrp->flags);
368 check_for_release(cgrp);
369 }
370
371 kfree(link);
372 }
373
374 write_unlock(&css_set_lock);
375 kfree_rcu(cg, rcu_head);
376}
377
378/*
379 * refcounted get/put for css_set objects
380 */
381static inline void get_css_set(struct css_set *cg)
382{
383 atomic_inc(&cg->refcount);
384}
385
386static inline void put_css_set(struct css_set *cg)
387{
388 __put_css_set(cg, 0);
389}
390
391static inline void put_css_set_taskexit(struct css_set *cg)
392{
393 __put_css_set(cg, 1);
394}
395
396/*
397 * compare_css_sets - helper function for find_existing_css_set().
398 * @cg: candidate css_set being tested
399 * @old_cg: existing css_set for a task
400 * @new_cgrp: cgroup that's being entered by the task
401 * @template: desired set of css pointers in css_set (pre-calculated)
402 *
403 * Returns true if "cg" matches "old_cg" except for the hierarchy
404 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
405 */
406static bool compare_css_sets(struct css_set *cg,
407 struct css_set *old_cg,
408 struct cgroup *new_cgrp,
409 struct cgroup_subsys_state *template[])
410{
411 struct list_head *l1, *l2;
412
413 if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
414 /* Not all subsystems matched */
415 return false;
416 }
417
418 /*
419 * Compare cgroup pointers in order to distinguish between
420 * different cgroups in heirarchies with no subsystems. We
421 * could get by with just this check alone (and skip the
422 * memcmp above) but on most setups the memcmp check will
423 * avoid the need for this more expensive check on almost all
424 * candidates.
425 */
426
427 l1 = &cg->cg_links;
428 l2 = &old_cg->cg_links;
429 while (1) {
430 struct cg_cgroup_link *cgl1, *cgl2;
431 struct cgroup *cg1, *cg2;
432
433 l1 = l1->next;
434 l2 = l2->next;
435 /* See if we reached the end - both lists are equal length. */
436 if (l1 == &cg->cg_links) {
437 BUG_ON(l2 != &old_cg->cg_links);
438 break;
439 } else {
440 BUG_ON(l2 == &old_cg->cg_links);
441 }
442 /* Locate the cgroups associated with these links. */
443 cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
444 cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
445 cg1 = cgl1->cgrp;
446 cg2 = cgl2->cgrp;
447 /* Hierarchies should be linked in the same order. */
448 BUG_ON(cg1->root != cg2->root);
449
450 /*
451 * If this hierarchy is the hierarchy of the cgroup
452 * that's changing, then we need to check that this
453 * css_set points to the new cgroup; if it's any other
454 * hierarchy, then this css_set should point to the
455 * same cgroup as the old css_set.
456 */
457 if (cg1->root == new_cgrp->root) {
458 if (cg1 != new_cgrp)
459 return false;
460 } else {
461 if (cg1 != cg2)
462 return false;
463 }
464 }
465 return true;
466}
467
468/*
469 * find_existing_css_set() is a helper for
470 * find_css_set(), and checks to see whether an existing
471 * css_set is suitable.
472 *
473 * oldcg: the cgroup group that we're using before the cgroup
474 * transition
475 *
476 * cgrp: the cgroup that we're moving into
477 *
478 * template: location in which to build the desired set of subsystem
479 * state objects for the new cgroup group
480 */
481static struct css_set *find_existing_css_set(
482 struct css_set *oldcg,
483 struct cgroup *cgrp,
484 struct cgroup_subsys_state *template[])
485{
486 int i;
487 struct cgroupfs_root *root = cgrp->root;
488 struct hlist_head *hhead;
489 struct hlist_node *node;
490 struct css_set *cg;
491
492 /*
493 * Build the set of subsystem state objects that we want to see in the
494 * new css_set. while subsystems can change globally, the entries here
495 * won't change, so no need for locking.
496 */
497 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
498 if (root->subsys_bits & (1UL << i)) {
499 /* Subsystem is in this hierarchy. So we want
500 * the subsystem state from the new
501 * cgroup */
502 template[i] = cgrp->subsys[i];
503 } else {
504 /* Subsystem is not in this hierarchy, so we
505 * don't want to change the subsystem state */
506 template[i] = oldcg->subsys[i];
507 }
508 }
509
510 hhead = css_set_hash(template);
511 hlist_for_each_entry(cg, node, hhead, hlist) {
512 if (!compare_css_sets(cg, oldcg, cgrp, template))
513 continue;
514
515 /* This css_set matches what we need */
516 return cg;
517 }
518
519 /* No existing cgroup group matched */
520 return NULL;
521}
522
523static void free_cg_links(struct list_head *tmp)
524{
525 struct cg_cgroup_link *link;
526 struct cg_cgroup_link *saved_link;
527
528 list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
529 list_del(&link->cgrp_link_list);
530 kfree(link);
531 }
532}
533
534/*
535 * allocate_cg_links() allocates "count" cg_cgroup_link structures
536 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
537 * success or a negative error
538 */
539static int allocate_cg_links(int count, struct list_head *tmp)
540{
541 struct cg_cgroup_link *link;
542 int i;
543 INIT_LIST_HEAD(tmp);
544 for (i = 0; i < count; i++) {
545 link = kmalloc(sizeof(*link), GFP_KERNEL);
546 if (!link) {
547 free_cg_links(tmp);
548 return -ENOMEM;
549 }
550 list_add(&link->cgrp_link_list, tmp);
551 }
552 return 0;
553}
554
555/**
556 * link_css_set - a helper function to link a css_set to a cgroup
557 * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
558 * @cg: the css_set to be linked
559 * @cgrp: the destination cgroup
560 */
561static void link_css_set(struct list_head *tmp_cg_links,
562 struct css_set *cg, struct cgroup *cgrp)
563{
564 struct cg_cgroup_link *link;
565
566 BUG_ON(list_empty(tmp_cg_links));
567 link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
568 cgrp_link_list);
569 link->cg = cg;
570 link->cgrp = cgrp;
571 atomic_inc(&cgrp->count);
572 list_move(&link->cgrp_link_list, &cgrp->css_sets);
573 /*
574 * Always add links to the tail of the list so that the list
575 * is sorted by order of hierarchy creation
576 */
577 list_add_tail(&link->cg_link_list, &cg->cg_links);
578}
579
580/*
581 * find_css_set() takes an existing cgroup group and a
582 * cgroup object, and returns a css_set object that's
583 * equivalent to the old group, but with the given cgroup
584 * substituted into the appropriate hierarchy. Must be called with
585 * cgroup_mutex held
586 */
587static struct css_set *find_css_set(
588 struct css_set *oldcg, struct cgroup *cgrp)
589{
590 struct css_set *res;
591 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
592
593 struct list_head tmp_cg_links;
594
595 struct hlist_head *hhead;
596 struct cg_cgroup_link *link;
597
598 /* First see if we already have a cgroup group that matches
599 * the desired set */
600 read_lock(&css_set_lock);
601 res = find_existing_css_set(oldcg, cgrp, template);
602 if (res)
603 get_css_set(res);
604 read_unlock(&css_set_lock);
605
606 if (res)
607 return res;
608
609 res = kmalloc(sizeof(*res), GFP_KERNEL);
610 if (!res)
611 return NULL;
612
613 /* Allocate all the cg_cgroup_link objects that we'll need */
614 if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
615 kfree(res);
616 return NULL;
617 }
618
619 atomic_set(&res->refcount, 1);
620 INIT_LIST_HEAD(&res->cg_links);
621 INIT_LIST_HEAD(&res->tasks);
622 INIT_HLIST_NODE(&res->hlist);
623
624 /* Copy the set of subsystem state objects generated in
625 * find_existing_css_set() */
626 memcpy(res->subsys, template, sizeof(res->subsys));
627
628 write_lock(&css_set_lock);
629 /* Add reference counts and links from the new css_set. */
630 list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
631 struct cgroup *c = link->cgrp;
632 if (c->root == cgrp->root)
633 c = cgrp;
634 link_css_set(&tmp_cg_links, res, c);
635 }
636
637 BUG_ON(!list_empty(&tmp_cg_links));
638
639 css_set_count++;
640
641 /* Add this cgroup group to the hash table */
642 hhead = css_set_hash(res->subsys);
643 hlist_add_head(&res->hlist, hhead);
644
645 write_unlock(&css_set_lock);
646
647 return res;
648}
649
650/*
651 * Return the cgroup for "task" from the given hierarchy. Must be
652 * called with cgroup_mutex held.
653 */
654static struct cgroup *task_cgroup_from_root(struct task_struct *task,
655 struct cgroupfs_root *root)
656{
657 struct css_set *css;
658 struct cgroup *res = NULL;
659
660 BUG_ON(!mutex_is_locked(&cgroup_mutex));
661 read_lock(&css_set_lock);
662 /*
663 * No need to lock the task - since we hold cgroup_mutex the
664 * task can't change groups, so the only thing that can happen
665 * is that it exits and its css is set back to init_css_set.
666 */
667 css = task->cgroups;
668 if (css == &init_css_set) {
669 res = &root->top_cgroup;
670 } else {
671 struct cg_cgroup_link *link;
672 list_for_each_entry(link, &css->cg_links, cg_link_list) {
673 struct cgroup *c = link->cgrp;
674 if (c->root == root) {
675 res = c;
676 break;
677 }
678 }
679 }
680 read_unlock(&css_set_lock);
681 BUG_ON(!res);
682 return res;
683}
684
685/*
686 * There is one global cgroup mutex. We also require taking
687 * task_lock() when dereferencing a task's cgroup subsys pointers.
688 * See "The task_lock() exception", at the end of this comment.
689 *
690 * A task must hold cgroup_mutex to modify cgroups.
691 *
692 * Any task can increment and decrement the count field without lock.
693 * So in general, code holding cgroup_mutex can't rely on the count
694 * field not changing. However, if the count goes to zero, then only
695 * cgroup_attach_task() can increment it again. Because a count of zero
696 * means that no tasks are currently attached, therefore there is no
697 * way a task attached to that cgroup can fork (the other way to
698 * increment the count). So code holding cgroup_mutex can safely
699 * assume that if the count is zero, it will stay zero. Similarly, if
700 * a task holds cgroup_mutex on a cgroup with zero count, it
701 * knows that the cgroup won't be removed, as cgroup_rmdir()
702 * needs that mutex.
703 *
704 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
705 * (usually) take cgroup_mutex. These are the two most performance
706 * critical pieces of code here. The exception occurs on cgroup_exit(),
707 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
708 * is taken, and if the cgroup count is zero, a usermode call made
709 * to the release agent with the name of the cgroup (path relative to
710 * the root of cgroup file system) as the argument.
711 *
712 * A cgroup can only be deleted if both its 'count' of using tasks
713 * is zero, and its list of 'children' cgroups is empty. Since all
714 * tasks in the system use _some_ cgroup, and since there is always at
715 * least one task in the system (init, pid == 1), therefore, top_cgroup
716 * always has either children cgroups and/or using tasks. So we don't
717 * need a special hack to ensure that top_cgroup cannot be deleted.
718 *
719 * The task_lock() exception
720 *
721 * The need for this exception arises from the action of
722 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
723 * another. It does so using cgroup_mutex, however there are
724 * several performance critical places that need to reference
725 * task->cgroup without the expense of grabbing a system global
726 * mutex. Therefore except as noted below, when dereferencing or, as
727 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
728 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
729 * the task_struct routinely used for such matters.
730 *
731 * P.S. One more locking exception. RCU is used to guard the
732 * update of a tasks cgroup pointer by cgroup_attach_task()
733 */
734
735/**
736 * cgroup_lock - lock out any changes to cgroup structures
737 *
738 */
739void cgroup_lock(void)
740{
741 mutex_lock(&cgroup_mutex);
742}
743EXPORT_SYMBOL_GPL(cgroup_lock);
744
745/**
746 * cgroup_unlock - release lock on cgroup changes
747 *
748 * Undo the lock taken in a previous cgroup_lock() call.
749 */
750void cgroup_unlock(void)
751{
752 mutex_unlock(&cgroup_mutex);
753}
754EXPORT_SYMBOL_GPL(cgroup_unlock);
755
756/*
757 * A couple of forward declarations required, due to cyclic reference loop:
758 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
759 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
760 * -> cgroup_mkdir.
761 */
762
763static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode);
764static struct dentry *cgroup_lookup(struct inode *, struct dentry *, struct nameidata *);
765static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
766static int cgroup_populate_dir(struct cgroup *cgrp);
767static const struct inode_operations cgroup_dir_inode_operations;
768static const struct file_operations proc_cgroupstats_operations;
769
770static struct backing_dev_info cgroup_backing_dev_info = {
771 .name = "cgroup",
772 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
773};
774
775static int alloc_css_id(struct cgroup_subsys *ss,
776 struct cgroup *parent, struct cgroup *child);
777
778static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
779{
780 struct inode *inode = new_inode(sb);
781
782 if (inode) {
783 inode->i_ino = get_next_ino();
784 inode->i_mode = mode;
785 inode->i_uid = current_fsuid();
786 inode->i_gid = current_fsgid();
787 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
788 inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
789 }
790 return inode;
791}
792
793/*
794 * Call subsys's pre_destroy handler.
795 * This is called before css refcnt check.
796 */
797static int cgroup_call_pre_destroy(struct cgroup *cgrp)
798{
799 struct cgroup_subsys *ss;
800 int ret = 0;
801
802 for_each_subsys(cgrp->root, ss)
803 if (ss->pre_destroy) {
804 ret = ss->pre_destroy(ss, cgrp);
805 if (ret)
806 break;
807 }
808
809 return ret;
810}
811
812static void cgroup_diput(struct dentry *dentry, struct inode *inode)
813{
814 /* is dentry a directory ? if so, kfree() associated cgroup */
815 if (S_ISDIR(inode->i_mode)) {
816 struct cgroup *cgrp = dentry->d_fsdata;
817 struct cgroup_subsys *ss;
818 BUG_ON(!(cgroup_is_removed(cgrp)));
819 /* It's possible for external users to be holding css
820 * reference counts on a cgroup; css_put() needs to
821 * be able to access the cgroup after decrementing
822 * the reference count in order to know if it needs to
823 * queue the cgroup to be handled by the release
824 * agent */
825 synchronize_rcu();
826
827 mutex_lock(&cgroup_mutex);
828 /*
829 * Release the subsystem state objects.
830 */
831 for_each_subsys(cgrp->root, ss)
832 ss->destroy(ss, cgrp);
833
834 cgrp->root->number_of_cgroups--;
835 mutex_unlock(&cgroup_mutex);
836
837 /*
838 * Drop the active superblock reference that we took when we
839 * created the cgroup
840 */
841 deactivate_super(cgrp->root->sb);
842
843 /*
844 * if we're getting rid of the cgroup, refcount should ensure
845 * that there are no pidlists left.
846 */
847 BUG_ON(!list_empty(&cgrp->pidlists));
848
849 kfree_rcu(cgrp, rcu_head);
850 }
851 iput(inode);
852}
853
854static int cgroup_delete(const struct dentry *d)
855{
856 return 1;
857}
858
859static void remove_dir(struct dentry *d)
860{
861 struct dentry *parent = dget(d->d_parent);
862
863 d_delete(d);
864 simple_rmdir(parent->d_inode, d);
865 dput(parent);
866}
867
868static void cgroup_clear_directory(struct dentry *dentry)
869{
870 struct list_head *node;
871
872 BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
873 spin_lock(&dentry->d_lock);
874 node = dentry->d_subdirs.next;
875 while (node != &dentry->d_subdirs) {
876 struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
877
878 spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
879 list_del_init(node);
880 if (d->d_inode) {
881 /* This should never be called on a cgroup
882 * directory with child cgroups */
883 BUG_ON(d->d_inode->i_mode & S_IFDIR);
884 dget_dlock(d);
885 spin_unlock(&d->d_lock);
886 spin_unlock(&dentry->d_lock);
887 d_delete(d);
888 simple_unlink(dentry->d_inode, d);
889 dput(d);
890 spin_lock(&dentry->d_lock);
891 } else
892 spin_unlock(&d->d_lock);
893 node = dentry->d_subdirs.next;
894 }
895 spin_unlock(&dentry->d_lock);
896}
897
898/*
899 * NOTE : the dentry must have been dget()'ed
900 */
901static void cgroup_d_remove_dir(struct dentry *dentry)
902{
903 struct dentry *parent;
904
905 cgroup_clear_directory(dentry);
906
907 parent = dentry->d_parent;
908 spin_lock(&parent->d_lock);
909 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
910 list_del_init(&dentry->d_u.d_child);
911 spin_unlock(&dentry->d_lock);
912 spin_unlock(&parent->d_lock);
913 remove_dir(dentry);
914}
915
916/*
917 * A queue for waiters to do rmdir() cgroup. A tasks will sleep when
918 * cgroup->count == 0 && list_empty(&cgroup->children) && subsys has some
919 * reference to css->refcnt. In general, this refcnt is expected to goes down
920 * to zero, soon.
921 *
922 * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
923 */
924DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
925
926static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
927{
928 if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
929 wake_up_all(&cgroup_rmdir_waitq);
930}
931
932void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
933{
934 css_get(css);
935}
936
937void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
938{
939 cgroup_wakeup_rmdir_waiter(css->cgroup);
940 css_put(css);
941}
942
943/*
944 * Call with cgroup_mutex held. Drops reference counts on modules, including
945 * any duplicate ones that parse_cgroupfs_options took. If this function
946 * returns an error, no reference counts are touched.
947 */
948static int rebind_subsystems(struct cgroupfs_root *root,
949 unsigned long final_bits)
950{
951 unsigned long added_bits, removed_bits;
952 struct cgroup *cgrp = &root->top_cgroup;
953 int i;
954
955 BUG_ON(!mutex_is_locked(&cgroup_mutex));
956
957 removed_bits = root->actual_subsys_bits & ~final_bits;
958 added_bits = final_bits & ~root->actual_subsys_bits;
959 /* Check that any added subsystems are currently free */
960 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
961 unsigned long bit = 1UL << i;
962 struct cgroup_subsys *ss = subsys[i];
963 if (!(bit & added_bits))
964 continue;
965 /*
966 * Nobody should tell us to do a subsys that doesn't exist:
967 * parse_cgroupfs_options should catch that case and refcounts
968 * ensure that subsystems won't disappear once selected.
969 */
970 BUG_ON(ss == NULL);
971 if (ss->root != &rootnode) {
972 /* Subsystem isn't free */
973 return -EBUSY;
974 }
975 }
976
977 /* Currently we don't handle adding/removing subsystems when
978 * any child cgroups exist. This is theoretically supportable
979 * but involves complex error handling, so it's being left until
980 * later */
981 if (root->number_of_cgroups > 1)
982 return -EBUSY;
983
984 /* Process each subsystem */
985 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
986 struct cgroup_subsys *ss = subsys[i];
987 unsigned long bit = 1UL << i;
988 if (bit & added_bits) {
989 /* We're binding this subsystem to this hierarchy */
990 BUG_ON(ss == NULL);
991 BUG_ON(cgrp->subsys[i]);
992 BUG_ON(!dummytop->subsys[i]);
993 BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
994 mutex_lock(&ss->hierarchy_mutex);
995 cgrp->subsys[i] = dummytop->subsys[i];
996 cgrp->subsys[i]->cgroup = cgrp;
997 list_move(&ss->sibling, &root->subsys_list);
998 ss->root = root;
999 if (ss->bind)
1000 ss->bind(ss, cgrp);
1001 mutex_unlock(&ss->hierarchy_mutex);
1002 /* refcount was already taken, and we're keeping it */
1003 } else if (bit & removed_bits) {
1004 /* We're removing this subsystem */
1005 BUG_ON(ss == NULL);
1006 BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
1007 BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1008 mutex_lock(&ss->hierarchy_mutex);
1009 if (ss->bind)
1010 ss->bind(ss, dummytop);
1011 dummytop->subsys[i]->cgroup = dummytop;
1012 cgrp->subsys[i] = NULL;
1013 subsys[i]->root = &rootnode;
1014 list_move(&ss->sibling, &rootnode.subsys_list);
1015 mutex_unlock(&ss->hierarchy_mutex);
1016 /* subsystem is now free - drop reference on module */
1017 module_put(ss->module);
1018 } else if (bit & final_bits) {
1019 /* Subsystem state should already exist */
1020 BUG_ON(ss == NULL);
1021 BUG_ON(!cgrp->subsys[i]);
1022 /*
1023 * a refcount was taken, but we already had one, so
1024 * drop the extra reference.
1025 */
1026 module_put(ss->module);
1027#ifdef CONFIG_MODULE_UNLOAD
1028 BUG_ON(ss->module && !module_refcount(ss->module));
1029#endif
1030 } else {
1031 /* Subsystem state shouldn't exist */
1032 BUG_ON(cgrp->subsys[i]);
1033 }
1034 }
1035 root->subsys_bits = root->actual_subsys_bits = final_bits;
1036 synchronize_rcu();
1037
1038 return 0;
1039}
1040
1041static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
1042{
1043 struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info;
1044 struct cgroup_subsys *ss;
1045
1046 mutex_lock(&cgroup_mutex);
1047 for_each_subsys(root, ss)
1048 seq_printf(seq, ",%s", ss->name);
1049 if (test_bit(ROOT_NOPREFIX, &root->flags))
1050 seq_puts(seq, ",noprefix");
1051 if (strlen(root->release_agent_path))
1052 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1053 if (clone_children(&root->top_cgroup))
1054 seq_puts(seq, ",clone_children");
1055 if (strlen(root->name))
1056 seq_printf(seq, ",name=%s", root->name);
1057 mutex_unlock(&cgroup_mutex);
1058 return 0;
1059}
1060
1061struct cgroup_sb_opts {
1062 unsigned long subsys_bits;
1063 unsigned long flags;
1064 char *release_agent;
1065 bool clone_children;
1066 char *name;
1067 /* User explicitly requested empty subsystem */
1068 bool none;
1069
1070 struct cgroupfs_root *new_root;
1071
1072};
1073
1074/*
1075 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
1076 * with cgroup_mutex held to protect the subsys[] array. This function takes
1077 * refcounts on subsystems to be used, unless it returns error, in which case
1078 * no refcounts are taken.
1079 */
1080static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1081{
1082 char *token, *o = data;
1083 bool all_ss = false, one_ss = false;
1084 unsigned long mask = (unsigned long)-1;
1085 int i;
1086 bool module_pin_failed = false;
1087
1088 BUG_ON(!mutex_is_locked(&cgroup_mutex));
1089
1090#ifdef CONFIG_CPUSETS
1091 mask = ~(1UL << cpuset_subsys_id);
1092#endif
1093
1094 memset(opts, 0, sizeof(*opts));
1095
1096 while ((token = strsep(&o, ",")) != NULL) {
1097 if (!*token)
1098 return -EINVAL;
1099 if (!strcmp(token, "none")) {
1100 /* Explicitly have no subsystems */
1101 opts->none = true;
1102 continue;
1103 }
1104 if (!strcmp(token, "all")) {
1105 /* Mutually exclusive option 'all' + subsystem name */
1106 if (one_ss)
1107 return -EINVAL;
1108 all_ss = true;
1109 continue;
1110 }
1111 if (!strcmp(token, "noprefix")) {
1112 set_bit(ROOT_NOPREFIX, &opts->flags);
1113 continue;
1114 }
1115 if (!strcmp(token, "clone_children")) {
1116 opts->clone_children = true;
1117 continue;
1118 }
1119 if (!strncmp(token, "release_agent=", 14)) {
1120 /* Specifying two release agents is forbidden */
1121 if (opts->release_agent)
1122 return -EINVAL;
1123 opts->release_agent =
1124 kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1125 if (!opts->release_agent)
1126 return -ENOMEM;
1127 continue;
1128 }
1129 if (!strncmp(token, "name=", 5)) {
1130 const char *name = token + 5;
1131 /* Can't specify an empty name */
1132 if (!strlen(name))
1133 return -EINVAL;
1134 /* Must match [\w.-]+ */
1135 for (i = 0; i < strlen(name); i++) {
1136 char c = name[i];
1137 if (isalnum(c))
1138 continue;
1139 if ((c == '.') || (c == '-') || (c == '_'))
1140 continue;
1141 return -EINVAL;
1142 }
1143 /* Specifying two names is forbidden */
1144 if (opts->name)
1145 return -EINVAL;
1146 opts->name = kstrndup(name,
1147 MAX_CGROUP_ROOT_NAMELEN - 1,
1148 GFP_KERNEL);
1149 if (!opts->name)
1150 return -ENOMEM;
1151
1152 continue;
1153 }
1154
1155 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1156 struct cgroup_subsys *ss = subsys[i];
1157 if (ss == NULL)
1158 continue;
1159 if (strcmp(token, ss->name))
1160 continue;
1161 if (ss->disabled)
1162 continue;
1163
1164 /* Mutually exclusive option 'all' + subsystem name */
1165 if (all_ss)
1166 return -EINVAL;
1167 set_bit(i, &opts->subsys_bits);
1168 one_ss = true;
1169
1170 break;
1171 }
1172 if (i == CGROUP_SUBSYS_COUNT)
1173 return -ENOENT;
1174 }
1175
1176 /*
1177 * If the 'all' option was specified select all the subsystems,
1178 * otherwise 'all, 'none' and a subsystem name options were not
1179 * specified, let's default to 'all'
1180 */
1181 if (all_ss || (!all_ss && !one_ss && !opts->none)) {
1182 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1183 struct cgroup_subsys *ss = subsys[i];
1184 if (ss == NULL)
1185 continue;
1186 if (ss->disabled)
1187 continue;
1188 set_bit(i, &opts->subsys_bits);
1189 }
1190 }
1191
1192 /* Consistency checks */
1193
1194 /*
1195 * Option noprefix was introduced just for backward compatibility
1196 * with the old cpuset, so we allow noprefix only if mounting just
1197 * the cpuset subsystem.
1198 */
1199 if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
1200 (opts->subsys_bits & mask))
1201 return -EINVAL;
1202
1203
1204 /* Can't specify "none" and some subsystems */
1205 if (opts->subsys_bits && opts->none)
1206 return -EINVAL;
1207
1208 /*
1209 * We either have to specify by name or by subsystems. (So all
1210 * empty hierarchies must have a name).
1211 */
1212 if (!opts->subsys_bits && !opts->name)
1213 return -EINVAL;
1214
1215 /*
1216 * Grab references on all the modules we'll need, so the subsystems
1217 * don't dance around before rebind_subsystems attaches them. This may
1218 * take duplicate reference counts on a subsystem that's already used,
1219 * but rebind_subsystems handles this case.
1220 */
1221 for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
1222 unsigned long bit = 1UL << i;
1223
1224 if (!(bit & opts->subsys_bits))
1225 continue;
1226 if (!try_module_get(subsys[i]->module)) {
1227 module_pin_failed = true;
1228 break;
1229 }
1230 }
1231 if (module_pin_failed) {
1232 /*
1233 * oops, one of the modules was going away. this means that we
1234 * raced with a module_delete call, and to the user this is
1235 * essentially a "subsystem doesn't exist" case.
1236 */
1237 for (i--; i >= CGROUP_BUILTIN_SUBSYS_COUNT; i--) {
1238 /* drop refcounts only on the ones we took */
1239 unsigned long bit = 1UL << i;
1240
1241 if (!(bit & opts->subsys_bits))
1242 continue;
1243 module_put(subsys[i]->module);
1244 }
1245 return -ENOENT;
1246 }
1247
1248 return 0;
1249}
1250
1251static void drop_parsed_module_refcounts(unsigned long subsys_bits)
1252{
1253 int i;
1254 for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
1255 unsigned long bit = 1UL << i;
1256
1257 if (!(bit & subsys_bits))
1258 continue;
1259 module_put(subsys[i]->module);
1260 }
1261}
1262
1263static int cgroup_remount(struct super_block *sb, int *flags, char *data)
1264{
1265 int ret = 0;
1266 struct cgroupfs_root *root = sb->s_fs_info;
1267 struct cgroup *cgrp = &root->top_cgroup;
1268 struct cgroup_sb_opts opts;
1269
1270 mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1271 mutex_lock(&cgroup_mutex);
1272
1273 /* See what subsystems are wanted */
1274 ret = parse_cgroupfs_options(data, &opts);
1275 if (ret)
1276 goto out_unlock;
1277
1278 /* Don't allow flags or name to change at remount */
1279 if (opts.flags != root->flags ||
1280 (opts.name && strcmp(opts.name, root->name))) {
1281 ret = -EINVAL;
1282 drop_parsed_module_refcounts(opts.subsys_bits);
1283 goto out_unlock;
1284 }
1285
1286 ret = rebind_subsystems(root, opts.subsys_bits);
1287 if (ret) {
1288 drop_parsed_module_refcounts(opts.subsys_bits);
1289 goto out_unlock;
1290 }
1291
1292 /* (re)populate subsystem files */
1293 cgroup_populate_dir(cgrp);
1294
1295 if (opts.release_agent)
1296 strcpy(root->release_agent_path, opts.release_agent);
1297 out_unlock:
1298 kfree(opts.release_agent);
1299 kfree(opts.name);
1300 mutex_unlock(&cgroup_mutex);
1301 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1302 return ret;
1303}
1304
1305static const struct super_operations cgroup_ops = {
1306 .statfs = simple_statfs,
1307 .drop_inode = generic_delete_inode,
1308 .show_options = cgroup_show_options,
1309 .remount_fs = cgroup_remount,
1310};
1311
1312static void init_cgroup_housekeeping(struct cgroup *cgrp)
1313{
1314 INIT_LIST_HEAD(&cgrp->sibling);
1315 INIT_LIST_HEAD(&cgrp->children);
1316 INIT_LIST_HEAD(&cgrp->css_sets);
1317 INIT_LIST_HEAD(&cgrp->release_list);
1318 INIT_LIST_HEAD(&cgrp->pidlists);
1319 mutex_init(&cgrp->pidlist_mutex);
1320 INIT_LIST_HEAD(&cgrp->event_list);
1321 spin_lock_init(&cgrp->event_list_lock);
1322}
1323
1324static void init_cgroup_root(struct cgroupfs_root *root)
1325{
1326 struct cgroup *cgrp = &root->top_cgroup;
1327 INIT_LIST_HEAD(&root->subsys_list);
1328 INIT_LIST_HEAD(&root->root_list);
1329 root->number_of_cgroups = 1;
1330 cgrp->root = root;
1331 cgrp->top_cgroup = cgrp;
1332 init_cgroup_housekeeping(cgrp);
1333}
1334
1335static bool init_root_id(struct cgroupfs_root *root)
1336{
1337 int ret = 0;
1338
1339 do {
1340 if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
1341 return false;
1342 spin_lock(&hierarchy_id_lock);
1343 /* Try to allocate the next unused ID */
1344 ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
1345 &root->hierarchy_id);
1346 if (ret == -ENOSPC)
1347 /* Try again starting from 0 */
1348 ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
1349 if (!ret) {
1350 next_hierarchy_id = root->hierarchy_id + 1;
1351 } else if (ret != -EAGAIN) {
1352 /* Can only get here if the 31-bit IDR is full ... */
1353 BUG_ON(ret);
1354 }
1355 spin_unlock(&hierarchy_id_lock);
1356 } while (ret);
1357 return true;
1358}
1359
1360static int cgroup_test_super(struct super_block *sb, void *data)
1361{
1362 struct cgroup_sb_opts *opts = data;
1363 struct cgroupfs_root *root = sb->s_fs_info;
1364
1365 /* If we asked for a name then it must match */
1366 if (opts->name && strcmp(opts->name, root->name))
1367 return 0;
1368
1369 /*
1370 * If we asked for subsystems (or explicitly for no
1371 * subsystems) then they must match
1372 */
1373 if ((opts->subsys_bits || opts->none)
1374 && (opts->subsys_bits != root->subsys_bits))
1375 return 0;
1376
1377 return 1;
1378}
1379
1380static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
1381{
1382 struct cgroupfs_root *root;
1383
1384 if (!opts->subsys_bits && !opts->none)
1385 return NULL;
1386
1387 root = kzalloc(sizeof(*root), GFP_KERNEL);
1388 if (!root)
1389 return ERR_PTR(-ENOMEM);
1390
1391 if (!init_root_id(root)) {
1392 kfree(root);
1393 return ERR_PTR(-ENOMEM);
1394 }
1395 init_cgroup_root(root);
1396
1397 root->subsys_bits = opts->subsys_bits;
1398 root->flags = opts->flags;
1399 if (opts->release_agent)
1400 strcpy(root->release_agent_path, opts->release_agent);
1401 if (opts->name)
1402 strcpy(root->name, opts->name);
1403 if (opts->clone_children)
1404 set_bit(CGRP_CLONE_CHILDREN, &root->top_cgroup.flags);
1405 return root;
1406}
1407
1408static void cgroup_drop_root(struct cgroupfs_root *root)
1409{
1410 if (!root)
1411 return;
1412
1413 BUG_ON(!root->hierarchy_id);
1414 spin_lock(&hierarchy_id_lock);
1415 ida_remove(&hierarchy_ida, root->hierarchy_id);
1416 spin_unlock(&hierarchy_id_lock);
1417 kfree(root);
1418}
1419
1420static int cgroup_set_super(struct super_block *sb, void *data)
1421{
1422 int ret;
1423 struct cgroup_sb_opts *opts = data;
1424
1425 /* If we don't have a new root, we can't set up a new sb */
1426 if (!opts->new_root)
1427 return -EINVAL;
1428
1429 BUG_ON(!opts->subsys_bits && !opts->none);
1430
1431 ret = set_anon_super(sb, NULL);
1432 if (ret)
1433 return ret;
1434
1435 sb->s_fs_info = opts->new_root;
1436 opts->new_root->sb = sb;
1437
1438 sb->s_blocksize = PAGE_CACHE_SIZE;
1439 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
1440 sb->s_magic = CGROUP_SUPER_MAGIC;
1441 sb->s_op = &cgroup_ops;
1442
1443 return 0;
1444}
1445
1446static int cgroup_get_rootdir(struct super_block *sb)
1447{
1448 static const struct dentry_operations cgroup_dops = {
1449 .d_iput = cgroup_diput,
1450 .d_delete = cgroup_delete,
1451 };
1452
1453 struct inode *inode =
1454 cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
1455 struct dentry *dentry;
1456
1457 if (!inode)
1458 return -ENOMEM;
1459
1460 inode->i_fop = &simple_dir_operations;
1461 inode->i_op = &cgroup_dir_inode_operations;
1462 /* directories start off with i_nlink == 2 (for "." entry) */
1463 inc_nlink(inode);
1464 dentry = d_alloc_root(inode);
1465 if (!dentry) {
1466 iput(inode);
1467 return -ENOMEM;
1468 }
1469 sb->s_root = dentry;
1470 /* for everything else we want ->d_op set */
1471 sb->s_d_op = &cgroup_dops;
1472 return 0;
1473}
1474
1475static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1476 int flags, const char *unused_dev_name,
1477 void *data)
1478{
1479 struct cgroup_sb_opts opts;
1480 struct cgroupfs_root *root;
1481 int ret = 0;
1482 struct super_block *sb;
1483 struct cgroupfs_root *new_root;
1484
1485 /* First find the desired set of subsystems */
1486 mutex_lock(&cgroup_mutex);
1487 ret = parse_cgroupfs_options(data, &opts);
1488 mutex_unlock(&cgroup_mutex);
1489 if (ret)
1490 goto out_err;
1491
1492 /*
1493 * Allocate a new cgroup root. We may not need it if we're
1494 * reusing an existing hierarchy.
1495 */
1496 new_root = cgroup_root_from_opts(&opts);
1497 if (IS_ERR(new_root)) {
1498 ret = PTR_ERR(new_root);
1499 goto drop_modules;
1500 }
1501 opts.new_root = new_root;
1502
1503 /* Locate an existing or new sb for this hierarchy */
1504 sb = sget(fs_type, cgroup_test_super, cgroup_set_super, &opts);
1505 if (IS_ERR(sb)) {
1506 ret = PTR_ERR(sb);
1507 cgroup_drop_root(opts.new_root);
1508 goto drop_modules;
1509 }
1510
1511 root = sb->s_fs_info;
1512 BUG_ON(!root);
1513 if (root == opts.new_root) {
1514 /* We used the new root structure, so this is a new hierarchy */
1515 struct list_head tmp_cg_links;
1516 struct cgroup *root_cgrp = &root->top_cgroup;
1517 struct inode *inode;
1518 struct cgroupfs_root *existing_root;
1519 const struct cred *cred;
1520 int i;
1521
1522 BUG_ON(sb->s_root != NULL);
1523
1524 ret = cgroup_get_rootdir(sb);
1525 if (ret)
1526 goto drop_new_super;
1527 inode = sb->s_root->d_inode;
1528
1529 mutex_lock(&inode->i_mutex);
1530 mutex_lock(&cgroup_mutex);
1531
1532 if (strlen(root->name)) {
1533 /* Check for name clashes with existing mounts */
1534 for_each_active_root(existing_root) {
1535 if (!strcmp(existing_root->name, root->name)) {
1536 ret = -EBUSY;
1537 mutex_unlock(&cgroup_mutex);
1538 mutex_unlock(&inode->i_mutex);
1539 goto drop_new_super;
1540 }
1541 }
1542 }
1543
1544 /*
1545 * We're accessing css_set_count without locking
1546 * css_set_lock here, but that's OK - it can only be
1547 * increased by someone holding cgroup_lock, and
1548 * that's us. The worst that can happen is that we
1549 * have some link structures left over
1550 */
1551 ret = allocate_cg_links(css_set_count, &tmp_cg_links);
1552 if (ret) {
1553 mutex_unlock(&cgroup_mutex);
1554 mutex_unlock(&inode->i_mutex);
1555 goto drop_new_super;
1556 }
1557
1558 ret = rebind_subsystems(root, root->subsys_bits);
1559 if (ret == -EBUSY) {
1560 mutex_unlock(&cgroup_mutex);
1561 mutex_unlock(&inode->i_mutex);
1562 free_cg_links(&tmp_cg_links);
1563 goto drop_new_super;
1564 }
1565 /*
1566 * There must be no failure case after here, since rebinding
1567 * takes care of subsystems' refcounts, which are explicitly
1568 * dropped in the failure exit path.
1569 */
1570
1571 /* EBUSY should be the only error here */
1572 BUG_ON(ret);
1573
1574 list_add(&root->root_list, &roots);
1575 root_count++;
1576
1577 sb->s_root->d_fsdata = root_cgrp;
1578 root->top_cgroup.dentry = sb->s_root;
1579
1580 /* Link the top cgroup in this hierarchy into all
1581 * the css_set objects */
1582 write_lock(&css_set_lock);
1583 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
1584 struct hlist_head *hhead = &css_set_table[i];
1585 struct hlist_node *node;
1586 struct css_set *cg;
1587
1588 hlist_for_each_entry(cg, node, hhead, hlist)
1589 link_css_set(&tmp_cg_links, cg, root_cgrp);
1590 }
1591 write_unlock(&css_set_lock);
1592
1593 free_cg_links(&tmp_cg_links);
1594
1595 BUG_ON(!list_empty(&root_cgrp->sibling));
1596 BUG_ON(!list_empty(&root_cgrp->children));
1597 BUG_ON(root->number_of_cgroups != 1);
1598
1599 cred = override_creds(&init_cred);
1600 cgroup_populate_dir(root_cgrp);
1601 revert_creds(cred);
1602 mutex_unlock(&cgroup_mutex);
1603 mutex_unlock(&inode->i_mutex);
1604 } else {
1605 /*
1606 * We re-used an existing hierarchy - the new root (if
1607 * any) is not needed
1608 */
1609 cgroup_drop_root(opts.new_root);
1610 /* no subsys rebinding, so refcounts don't change */
1611 drop_parsed_module_refcounts(opts.subsys_bits);
1612 }
1613
1614 kfree(opts.release_agent);
1615 kfree(opts.name);
1616 return dget(sb->s_root);
1617
1618 drop_new_super:
1619 deactivate_locked_super(sb);
1620 drop_modules:
1621 drop_parsed_module_refcounts(opts.subsys_bits);
1622 out_err:
1623 kfree(opts.release_agent);
1624 kfree(opts.name);
1625 return ERR_PTR(ret);
1626}
1627
1628static void cgroup_kill_sb(struct super_block *sb) {
1629 struct cgroupfs_root *root = sb->s_fs_info;
1630 struct cgroup *cgrp = &root->top_cgroup;
1631 int ret;
1632 struct cg_cgroup_link *link;
1633 struct cg_cgroup_link *saved_link;
1634
1635 BUG_ON(!root);
1636
1637 BUG_ON(root->number_of_cgroups != 1);
1638 BUG_ON(!list_empty(&cgrp->children));
1639 BUG_ON(!list_empty(&cgrp->sibling));
1640
1641 mutex_lock(&cgroup_mutex);
1642
1643 /* Rebind all subsystems back to the default hierarchy */
1644 ret = rebind_subsystems(root, 0);
1645 /* Shouldn't be able to fail ... */
1646 BUG_ON(ret);
1647
1648 /*
1649 * Release all the links from css_sets to this hierarchy's
1650 * root cgroup
1651 */
1652 write_lock(&css_set_lock);
1653
1654 list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
1655 cgrp_link_list) {
1656 list_del(&link->cg_link_list);
1657 list_del(&link->cgrp_link_list);
1658 kfree(link);
1659 }
1660 write_unlock(&css_set_lock);
1661
1662 if (!list_empty(&root->root_list)) {
1663 list_del(&root->root_list);
1664 root_count--;
1665 }
1666
1667 mutex_unlock(&cgroup_mutex);
1668
1669 kill_litter_super(sb);
1670 cgroup_drop_root(root);
1671}
1672
1673static struct file_system_type cgroup_fs_type = {
1674 .name = "cgroup",
1675 .mount = cgroup_mount,
1676 .kill_sb = cgroup_kill_sb,
1677};
1678
1679static struct kobject *cgroup_kobj;
1680
1681static inline struct cgroup *__d_cgrp(struct dentry *dentry)
1682{
1683 return dentry->d_fsdata;
1684}
1685
1686static inline struct cftype *__d_cft(struct dentry *dentry)
1687{
1688 return dentry->d_fsdata;
1689}
1690
1691/**
1692 * cgroup_path - generate the path of a cgroup
1693 * @cgrp: the cgroup in question
1694 * @buf: the buffer to write the path into
1695 * @buflen: the length of the buffer
1696 *
1697 * Called with cgroup_mutex held or else with an RCU-protected cgroup
1698 * reference. Writes path of cgroup into buf. Returns 0 on success,
1699 * -errno on error.
1700 */
1701int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1702{
1703 char *start;
1704 struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
1705 cgroup_lock_is_held());
1706
1707 if (!dentry || cgrp == dummytop) {
1708 /*
1709 * Inactive subsystems have no dentry for their root
1710 * cgroup
1711 */
1712 strcpy(buf, "/");
1713 return 0;
1714 }
1715
1716 start = buf + buflen;
1717
1718 *--start = '\0';
1719 for (;;) {
1720 int len = dentry->d_name.len;
1721
1722 if ((start -= len) < buf)
1723 return -ENAMETOOLONG;
1724 memcpy(start, dentry->d_name.name, len);
1725 cgrp = cgrp->parent;
1726 if (!cgrp)
1727 break;
1728
1729 dentry = rcu_dereference_check(cgrp->dentry,
1730 cgroup_lock_is_held());
1731 if (!cgrp->parent)
1732 continue;
1733 if (--start < buf)
1734 return -ENAMETOOLONG;
1735 *start = '/';
1736 }
1737 memmove(buf, start, buf + buflen - start);
1738 return 0;
1739}
1740EXPORT_SYMBOL_GPL(cgroup_path);
1741
1742/*
1743 * cgroup_task_migrate - move a task from one cgroup to another.
1744 *
1745 * 'guarantee' is set if the caller promises that a new css_set for the task
1746 * will already exist. If not set, this function might sleep, and can fail with
1747 * -ENOMEM. Otherwise, it can only fail with -ESRCH.
1748 */
1749static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
1750 struct task_struct *tsk, bool guarantee)
1751{
1752 struct css_set *oldcg;
1753 struct css_set *newcg;
1754
1755 /*
1756 * get old css_set. we need to take task_lock and refcount it, because
1757 * an exiting task can change its css_set to init_css_set and drop its
1758 * old one without taking cgroup_mutex.
1759 */
1760 task_lock(tsk);
1761 oldcg = tsk->cgroups;
1762 get_css_set(oldcg);
1763 task_unlock(tsk);
1764
1765 /* locate or allocate a new css_set for this task. */
1766 if (guarantee) {
1767 /* we know the css_set we want already exists. */
1768 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
1769 read_lock(&css_set_lock);
1770 newcg = find_existing_css_set(oldcg, cgrp, template);
1771 BUG_ON(!newcg);
1772 get_css_set(newcg);
1773 read_unlock(&css_set_lock);
1774 } else {
1775 might_sleep();
1776 /* find_css_set will give us newcg already referenced. */
1777 newcg = find_css_set(oldcg, cgrp);
1778 if (!newcg) {
1779 put_css_set(oldcg);
1780 return -ENOMEM;
1781 }
1782 }
1783 put_css_set(oldcg);
1784
1785 /* if PF_EXITING is set, the tsk->cgroups pointer is no longer safe. */
1786 task_lock(tsk);
1787 if (tsk->flags & PF_EXITING) {
1788 task_unlock(tsk);
1789 put_css_set(newcg);
1790 return -ESRCH;
1791 }
1792 rcu_assign_pointer(tsk->cgroups, newcg);
1793 task_unlock(tsk);
1794
1795 /* Update the css_set linked lists if we're using them */
1796 write_lock(&css_set_lock);
1797 if (!list_empty(&tsk->cg_list))
1798 list_move(&tsk->cg_list, &newcg->tasks);
1799 write_unlock(&css_set_lock);
1800
1801 /*
1802 * We just gained a reference on oldcg by taking it from the task. As
1803 * trading it for newcg is protected by cgroup_mutex, we're safe to drop
1804 * it here; it will be freed under RCU.
1805 */
1806 put_css_set(oldcg);
1807
1808 set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1809 return 0;
1810}
1811
1812/**
1813 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
1814 * @cgrp: the cgroup the task is attaching to
1815 * @tsk: the task to be attached
1816 *
1817 * Call holding cgroup_mutex. May take task_lock of
1818 * the task 'tsk' during call.
1819 */
1820int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1821{
1822 int retval;
1823 struct cgroup_subsys *ss, *failed_ss = NULL;
1824 struct cgroup *oldcgrp;
1825 struct cgroupfs_root *root = cgrp->root;
1826
1827 /* Nothing to do if the task is already in that cgroup */
1828 oldcgrp = task_cgroup_from_root(tsk, root);
1829 if (cgrp == oldcgrp)
1830 return 0;
1831
1832 for_each_subsys(root, ss) {
1833 if (ss->can_attach) {
1834 retval = ss->can_attach(ss, cgrp, tsk);
1835 if (retval) {
1836 /*
1837 * Remember on which subsystem the can_attach()
1838 * failed, so that we only call cancel_attach()
1839 * against the subsystems whose can_attach()
1840 * succeeded. (See below)
1841 */
1842 failed_ss = ss;
1843 goto out;
1844 }
1845 }
1846 if (ss->can_attach_task) {
1847 retval = ss->can_attach_task(cgrp, tsk);
1848 if (retval) {
1849 failed_ss = ss;
1850 goto out;
1851 }
1852 }
1853 }
1854
1855 retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, false);
1856 if (retval)
1857 goto out;
1858
1859 for_each_subsys(root, ss) {
1860 if (ss->pre_attach)
1861 ss->pre_attach(cgrp);
1862 if (ss->attach_task)
1863 ss->attach_task(cgrp, tsk);
1864 if (ss->attach)
1865 ss->attach(ss, cgrp, oldcgrp, tsk);
1866 }
1867
1868 synchronize_rcu();
1869
1870 /*
1871 * wake up rmdir() waiter. the rmdir should fail since the cgroup
1872 * is no longer empty.
1873 */
1874 cgroup_wakeup_rmdir_waiter(cgrp);
1875out:
1876 if (retval) {
1877 for_each_subsys(root, ss) {
1878 if (ss == failed_ss)
1879 /*
1880 * This subsystem was the one that failed the
1881 * can_attach() check earlier, so we don't need
1882 * to call cancel_attach() against it or any
1883 * remaining subsystems.
1884 */
1885 break;
1886 if (ss->cancel_attach)
1887 ss->cancel_attach(ss, cgrp, tsk);
1888 }
1889 }
1890 return retval;
1891}
1892
1893/**
1894 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
1895 * @from: attach to all cgroups of a given task
1896 * @tsk: the task to be attached
1897 */
1898int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
1899{
1900 struct cgroupfs_root *root;
1901 int retval = 0;
1902
1903 cgroup_lock();
1904 for_each_active_root(root) {
1905 struct cgroup *from_cg = task_cgroup_from_root(from, root);
1906
1907 retval = cgroup_attach_task(from_cg, tsk);
1908 if (retval)
1909 break;
1910 }
1911 cgroup_unlock();
1912
1913 return retval;
1914}
1915EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
1916
1917/*
1918 * cgroup_attach_proc works in two stages, the first of which prefetches all
1919 * new css_sets needed (to make sure we have enough memory before committing
1920 * to the move) and stores them in a list of entries of the following type.
1921 * TODO: possible optimization: use css_set->rcu_head for chaining instead
1922 */
1923struct cg_list_entry {
1924 struct css_set *cg;
1925 struct list_head links;
1926};
1927
1928static bool css_set_check_fetched(struct cgroup *cgrp,
1929 struct task_struct *tsk, struct css_set *cg,
1930 struct list_head *newcg_list)
1931{
1932 struct css_set *newcg;
1933 struct cg_list_entry *cg_entry;
1934 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
1935
1936 read_lock(&css_set_lock);
1937 newcg = find_existing_css_set(cg, cgrp, template);
1938 if (newcg)
1939 get_css_set(newcg);
1940 read_unlock(&css_set_lock);
1941
1942 /* doesn't exist at all? */
1943 if (!newcg)
1944 return false;
1945 /* see if it's already in the list */
1946 list_for_each_entry(cg_entry, newcg_list, links) {
1947 if (cg_entry->cg == newcg) {
1948 put_css_set(newcg);
1949 return true;
1950 }
1951 }
1952
1953 /* not found */
1954 put_css_set(newcg);
1955 return false;
1956}
1957
1958/*
1959 * Find the new css_set and store it in the list in preparation for moving the
1960 * given task to the given cgroup. Returns 0 or -ENOMEM.
1961 */
1962static int css_set_prefetch(struct cgroup *cgrp, struct css_set *cg,
1963 struct list_head *newcg_list)
1964{
1965 struct css_set *newcg;
1966 struct cg_list_entry *cg_entry;
1967
1968 /* ensure a new css_set will exist for this thread */
1969 newcg = find_css_set(cg, cgrp);
1970 if (!newcg)
1971 return -ENOMEM;
1972 /* add it to the list */
1973 cg_entry = kmalloc(sizeof(struct cg_list_entry), GFP_KERNEL);
1974 if (!cg_entry) {
1975 put_css_set(newcg);
1976 return -ENOMEM;
1977 }
1978 cg_entry->cg = newcg;
1979 list_add(&cg_entry->links, newcg_list);
1980 return 0;
1981}
1982
1983/**
1984 * cgroup_attach_proc - attach all threads in a threadgroup to a cgroup
1985 * @cgrp: the cgroup to attach to
1986 * @leader: the threadgroup leader task_struct of the group to be attached
1987 *
1988 * Call holding cgroup_mutex and the threadgroup_fork_lock of the leader. Will
1989 * take task_lock of each thread in leader's threadgroup individually in turn.
1990 */
1991int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
1992{
1993 int retval, i, group_size;
1994 struct cgroup_subsys *ss, *failed_ss = NULL;
1995 bool cancel_failed_ss = false;
1996 /* guaranteed to be initialized later, but the compiler needs this */
1997 struct cgroup *oldcgrp = NULL;
1998 struct css_set *oldcg;
1999 struct cgroupfs_root *root = cgrp->root;
2000 /* threadgroup list cursor and array */
2001 struct task_struct *tsk;
2002 struct flex_array *group;
2003 /*
2004 * we need to make sure we have css_sets for all the tasks we're
2005 * going to move -before- we actually start moving them, so that in
2006 * case we get an ENOMEM we can bail out before making any changes.
2007 */
2008 struct list_head newcg_list;
2009 struct cg_list_entry *cg_entry, *temp_nobe;
2010
2011 /*
2012 * step 0: in order to do expensive, possibly blocking operations for
2013 * every thread, we cannot iterate the thread group list, since it needs
2014 * rcu or tasklist locked. instead, build an array of all threads in the
2015 * group - threadgroup_fork_lock prevents new threads from appearing,
2016 * and if threads exit, this will just be an over-estimate.
2017 */
2018 group_size = get_nr_threads(leader);
2019 /* flex_array supports very large thread-groups better than kmalloc. */
2020 group = flex_array_alloc(sizeof(struct task_struct *), group_size,
2021 GFP_KERNEL);
2022 if (!group)
2023 return -ENOMEM;
2024 /* pre-allocate to guarantee space while iterating in rcu read-side. */
2025 retval = flex_array_prealloc(group, 0, group_size - 1, GFP_KERNEL);
2026 if (retval)
2027 goto out_free_group_list;
2028
2029 /* prevent changes to the threadgroup list while we take a snapshot. */
2030 rcu_read_lock();
2031 if (!thread_group_leader(leader)) {
2032 /*
2033 * a race with de_thread from another thread's exec() may strip
2034 * us of our leadership, making while_each_thread unsafe to use
2035 * on this task. if this happens, there is no choice but to
2036 * throw this task away and try again (from cgroup_procs_write);
2037 * this is "double-double-toil-and-trouble-check locking".
2038 */
2039 rcu_read_unlock();
2040 retval = -EAGAIN;
2041 goto out_free_group_list;
2042 }
2043 /* take a reference on each task in the group to go in the array. */
2044 tsk = leader;
2045 i = 0;
2046 do {
2047 /* as per above, nr_threads may decrease, but not increase. */
2048 BUG_ON(i >= group_size);
2049 get_task_struct(tsk);
2050 /*
2051 * saying GFP_ATOMIC has no effect here because we did prealloc
2052 * earlier, but it's good form to communicate our expectations.
2053 */
2054 retval = flex_array_put_ptr(group, i, tsk, GFP_ATOMIC);
2055 BUG_ON(retval != 0);
2056 i++;
2057 } while_each_thread(leader, tsk);
2058 /* remember the number of threads in the array for later. */
2059 group_size = i;
2060 rcu_read_unlock();
2061
2062 /*
2063 * step 1: check that we can legitimately attach to the cgroup.
2064 */
2065 for_each_subsys(root, ss) {
2066 if (ss->can_attach) {
2067 retval = ss->can_attach(ss, cgrp, leader);
2068 if (retval) {
2069 failed_ss = ss;
2070 goto out_cancel_attach;
2071 }
2072 }
2073 /* a callback to be run on every thread in the threadgroup. */
2074 if (ss->can_attach_task) {
2075 /* run on each task in the threadgroup. */
2076 for (i = 0; i < group_size; i++) {
2077 tsk = flex_array_get_ptr(group, i);
2078 retval = ss->can_attach_task(cgrp, tsk);
2079 if (retval) {
2080 failed_ss = ss;
2081 cancel_failed_ss = true;
2082 goto out_cancel_attach;
2083 }
2084 }
2085 }
2086 }
2087
2088 /*
2089 * step 2: make sure css_sets exist for all threads to be migrated.
2090 * we use find_css_set, which allocates a new one if necessary.
2091 */
2092 INIT_LIST_HEAD(&newcg_list);
2093 for (i = 0; i < group_size; i++) {
2094 tsk = flex_array_get_ptr(group, i);
2095 /* nothing to do if this task is already in the cgroup */
2096 oldcgrp = task_cgroup_from_root(tsk, root);
2097 if (cgrp == oldcgrp)
2098 continue;
2099 /* get old css_set pointer */
2100 task_lock(tsk);
2101 if (tsk->flags & PF_EXITING) {
2102 /* ignore this task if it's going away */
2103 task_unlock(tsk);
2104 continue;
2105 }
2106 oldcg = tsk->cgroups;
2107 get_css_set(oldcg);
2108 task_unlock(tsk);
2109 /* see if the new one for us is already in the list? */
2110 if (css_set_check_fetched(cgrp, tsk, oldcg, &newcg_list)) {
2111 /* was already there, nothing to do. */
2112 put_css_set(oldcg);
2113 } else {
2114 /* we don't already have it. get new one. */
2115 retval = css_set_prefetch(cgrp, oldcg, &newcg_list);
2116 put_css_set(oldcg);
2117 if (retval)
2118 goto out_list_teardown;
2119 }
2120 }
2121
2122 /*
2123 * step 3: now that we're guaranteed success wrt the css_sets, proceed
2124 * to move all tasks to the new cgroup, calling ss->attach_task for each
2125 * one along the way. there are no failure cases after here, so this is
2126 * the commit point.
2127 */
2128 for_each_subsys(root, ss) {
2129 if (ss->pre_attach)
2130 ss->pre_attach(cgrp);
2131 }
2132 for (i = 0; i < group_size; i++) {
2133 tsk = flex_array_get_ptr(group, i);
2134 /* leave current thread as it is if it's already there */
2135 oldcgrp = task_cgroup_from_root(tsk, root);
2136 if (cgrp == oldcgrp)
2137 continue;
2138 /* attach each task to each subsystem */
2139 for_each_subsys(root, ss) {
2140 if (ss->attach_task)
2141 ss->attach_task(cgrp, tsk);
2142 }
2143 /* if the thread is PF_EXITING, it can just get skipped. */
2144 retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, true);
2145 BUG_ON(retval != 0 && retval != -ESRCH);
2146 }
2147 /* nothing is sensitive to fork() after this point. */
2148
2149 /*
2150 * step 4: do expensive, non-thread-specific subsystem callbacks.
2151 * TODO: if ever a subsystem needs to know the oldcgrp for each task
2152 * being moved, this call will need to be reworked to communicate that.
2153 */
2154 for_each_subsys(root, ss) {
2155 if (ss->attach)
2156 ss->attach(ss, cgrp, oldcgrp, leader);
2157 }
2158
2159 /*
2160 * step 5: success! and cleanup
2161 */
2162 synchronize_rcu();
2163 cgroup_wakeup_rmdir_waiter(cgrp);
2164 retval = 0;
2165out_list_teardown:
2166 /* clean up the list of prefetched css_sets. */
2167 list_for_each_entry_safe(cg_entry, temp_nobe, &newcg_list, links) {
2168 list_del(&cg_entry->links);
2169 put_css_set(cg_entry->cg);
2170 kfree(cg_entry);
2171 }
2172out_cancel_attach:
2173 /* same deal as in cgroup_attach_task */
2174 if (retval) {
2175 for_each_subsys(root, ss) {
2176 if (ss == failed_ss) {
2177 if (cancel_failed_ss && ss->cancel_attach)
2178 ss->cancel_attach(ss, cgrp, leader);
2179 break;
2180 }
2181 if (ss->cancel_attach)
2182 ss->cancel_attach(ss, cgrp, leader);
2183 }
2184 }
2185 /* clean up the array of referenced threads in the group. */
2186 for (i = 0; i < group_size; i++) {
2187 tsk = flex_array_get_ptr(group, i);
2188 put_task_struct(tsk);
2189 }
2190out_free_group_list:
2191 flex_array_free(group);
2192 return retval;
2193}
2194
2195/*
2196 * Find the task_struct of the task to attach by vpid and pass it along to the
2197 * function to attach either it or all tasks in its threadgroup. Will take
2198 * cgroup_mutex; may take task_lock of task.
2199 */
2200static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2201{
2202 struct task_struct *tsk;
2203 const struct cred *cred = current_cred(), *tcred;
2204 int ret;
2205
2206 if (!cgroup_lock_live_group(cgrp))
2207 return -ENODEV;
2208
2209 if (pid) {
2210 rcu_read_lock();
2211 tsk = find_task_by_vpid(pid);
2212 if (!tsk) {
2213 rcu_read_unlock();
2214 cgroup_unlock();
2215 return -ESRCH;
2216 }
2217 if (threadgroup) {
2218 /*
2219 * RCU protects this access, since tsk was found in the
2220 * tid map. a race with de_thread may cause group_leader
2221 * to stop being the leader, but cgroup_attach_proc will
2222 * detect it later.
2223 */
2224 tsk = tsk->group_leader;
2225 } else if (tsk->flags & PF_EXITING) {
2226 /* optimization for the single-task-only case */
2227 rcu_read_unlock();
2228 cgroup_unlock();
2229 return -ESRCH;
2230 }
2231
2232 /*
2233 * even if we're attaching all tasks in the thread group, we
2234 * only need to check permissions on one of them.
2235 */
2236 tcred = __task_cred(tsk);
2237 if (cred->euid &&
2238 cred->euid != tcred->uid &&
2239 cred->euid != tcred->suid) {
2240 rcu_read_unlock();
2241 cgroup_unlock();
2242 return -EACCES;
2243 }
2244 get_task_struct(tsk);
2245 rcu_read_unlock();
2246 } else {
2247 if (threadgroup)
2248 tsk = current->group_leader;
2249 else
2250 tsk = current;
2251 get_task_struct(tsk);
2252 }
2253
2254 if (threadgroup) {
2255 threadgroup_fork_write_lock(tsk);
2256 ret = cgroup_attach_proc(cgrp, tsk);
2257 threadgroup_fork_write_unlock(tsk);
2258 } else {
2259 ret = cgroup_attach_task(cgrp, tsk);
2260 }
2261 put_task_struct(tsk);
2262 cgroup_unlock();
2263 return ret;
2264}
2265
2266static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
2267{
2268 return attach_task_by_pid(cgrp, pid, false);
2269}
2270
2271static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2272{
2273 int ret;
2274 do {
2275 /*
2276 * attach_proc fails with -EAGAIN if threadgroup leadership
2277 * changes in the middle of the operation, in which case we need
2278 * to find the task_struct for the new leader and start over.
2279 */
2280 ret = attach_task_by_pid(cgrp, tgid, true);
2281 } while (ret == -EAGAIN);
2282 return ret;
2283}
2284
2285/**
2286 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
2287 * @cgrp: the cgroup to be checked for liveness
2288 *
2289 * On success, returns true; the lock should be later released with
2290 * cgroup_unlock(). On failure returns false with no lock held.
2291 */
2292bool cgroup_lock_live_group(struct cgroup *cgrp)
2293{
2294 mutex_lock(&cgroup_mutex);
2295 if (cgroup_is_removed(cgrp)) {
2296 mutex_unlock(&cgroup_mutex);
2297 return false;
2298 }
2299 return true;
2300}
2301EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2302
2303static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
2304 const char *buffer)
2305{
2306 BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
2307 if (strlen(buffer) >= PATH_MAX)
2308 return -EINVAL;
2309 if (!cgroup_lock_live_group(cgrp))
2310 return -ENODEV;
2311 strcpy(cgrp->root->release_agent_path, buffer);
2312 cgroup_unlock();
2313 return 0;
2314}
2315
2316static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
2317 struct seq_file *seq)
2318{
2319 if (!cgroup_lock_live_group(cgrp))
2320 return -ENODEV;
2321 seq_puts(seq, cgrp->root->release_agent_path);
2322 seq_putc(seq, '\n');
2323 cgroup_unlock();
2324 return 0;
2325}
2326
2327/* A buffer size big enough for numbers or short strings */
2328#define CGROUP_LOCAL_BUFFER_SIZE 64
2329
2330static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2331 struct file *file,
2332 const char __user *userbuf,
2333 size_t nbytes, loff_t *unused_ppos)
2334{
2335 char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2336 int retval = 0;
2337 char *end;
2338
2339 if (!nbytes)
2340 return -EINVAL;
2341 if (nbytes >= sizeof(buffer))
2342 return -E2BIG;
2343 if (copy_from_user(buffer, userbuf, nbytes))
2344 return -EFAULT;
2345
2346 buffer[nbytes] = 0; /* nul-terminate */
2347 if (cft->write_u64) {
2348 u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2349 if (*end)
2350 return -EINVAL;
2351 retval = cft->write_u64(cgrp, cft, val);
2352 } else {
2353 s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2354 if (*end)
2355 return -EINVAL;
2356 retval = cft->write_s64(cgrp, cft, val);
2357 }
2358 if (!retval)
2359 retval = nbytes;
2360 return retval;
2361}
2362
2363static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
2364 struct file *file,
2365 const char __user *userbuf,
2366 size_t nbytes, loff_t *unused_ppos)
2367{
2368 char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2369 int retval = 0;
2370 size_t max_bytes = cft->max_write_len;
2371 char *buffer = local_buffer;
2372
2373 if (!max_bytes)
2374 max_bytes = sizeof(local_buffer) - 1;
2375 if (nbytes >= max_bytes)
2376 return -E2BIG;
2377 /* Allocate a dynamic buffer if we need one */
2378 if (nbytes >= sizeof(local_buffer)) {
2379 buffer = kmalloc(nbytes + 1, GFP_KERNEL);
2380 if (buffer == NULL)
2381 return -ENOMEM;
2382 }
2383 if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
2384 retval = -EFAULT;
2385 goto out;
2386 }
2387
2388 buffer[nbytes] = 0; /* nul-terminate */
2389 retval = cft->write_string(cgrp, cft, strstrip(buffer));
2390 if (!retval)
2391 retval = nbytes;
2392out:
2393 if (buffer != local_buffer)
2394 kfree(buffer);
2395 return retval;
2396}
2397
2398static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
2399 size_t nbytes, loff_t *ppos)
2400{
2401 struct cftype *cft = __d_cft(file->f_dentry);
2402 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2403
2404 if (cgroup_is_removed(cgrp))
2405 return -ENODEV;
2406 if (cft->write)
2407 return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2408 if (cft->write_u64 || cft->write_s64)
2409 return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2410 if (cft->write_string)
2411 return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2412 if (cft->trigger) {
2413 int ret = cft->trigger(cgrp, (unsigned int)cft->private);
2414 return ret ? ret : nbytes;
2415 }
2416 return -EINVAL;
2417}
2418
2419static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
2420 struct file *file,
2421 char __user *buf, size_t nbytes,
2422 loff_t *ppos)
2423{
2424 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2425 u64 val = cft->read_u64(cgrp, cft);
2426 int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
2427
2428 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2429}
2430
2431static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
2432 struct file *file,
2433 char __user *buf, size_t nbytes,
2434 loff_t *ppos)
2435{
2436 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2437 s64 val = cft->read_s64(cgrp, cft);
2438 int len = sprintf(tmp, "%lld\n", (long long) val);
2439
2440 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2441}
2442
2443static ssize_t cgroup_file_read(struct file *file, char __user *buf,
2444 size_t nbytes, loff_t *ppos)
2445{
2446 struct cftype *cft = __d_cft(file->f_dentry);
2447 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2448
2449 if (cgroup_is_removed(cgrp))
2450 return -ENODEV;
2451
2452 if (cft->read)
2453 return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2454 if (cft->read_u64)
2455 return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2456 if (cft->read_s64)
2457 return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2458 return -EINVAL;
2459}
2460
2461/*
2462 * seqfile ops/methods for returning structured data. Currently just
2463 * supports string->u64 maps, but can be extended in future.
2464 */
2465
2466struct cgroup_seqfile_state {
2467 struct cftype *cft;
2468 struct cgroup *cgroup;
2469};
2470
2471static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
2472{
2473 struct seq_file *sf = cb->state;
2474 return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
2475}
2476
2477static int cgroup_seqfile_show(struct seq_file *m, void *arg)
2478{
2479 struct cgroup_seqfile_state *state = m->private;
2480 struct cftype *cft = state->cft;
2481 if (cft->read_map) {
2482 struct cgroup_map_cb cb = {
2483 .fill = cgroup_map_add,
2484 .state = m,
2485 };
2486 return cft->read_map(state->cgroup, cft, &cb);
2487 }
2488 return cft->read_seq_string(state->cgroup, cft, m);
2489}
2490
2491static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2492{
2493 struct seq_file *seq = file->private_data;
2494 kfree(seq->private);
2495 return single_release(inode, file);
2496}
2497
2498static const struct file_operations cgroup_seqfile_operations = {
2499 .read = seq_read,
2500 .write = cgroup_file_write,
2501 .llseek = seq_lseek,
2502 .release = cgroup_seqfile_release,
2503};
2504
2505static int cgroup_file_open(struct inode *inode, struct file *file)
2506{
2507 int err;
2508 struct cftype *cft;
2509
2510 err = generic_file_open(inode, file);
2511 if (err)
2512 return err;
2513 cft = __d_cft(file->f_dentry);
2514
2515 if (cft->read_map || cft->read_seq_string) {
2516 struct cgroup_seqfile_state *state =
2517 kzalloc(sizeof(*state), GFP_USER);
2518 if (!state)
2519 return -ENOMEM;
2520 state->cft = cft;
2521 state->cgroup = __d_cgrp(file->f_dentry->d_parent);
2522 file->f_op = &cgroup_seqfile_operations;
2523 err = single_open(file, cgroup_seqfile_show, state);
2524 if (err < 0)
2525 kfree(state);
2526 } else if (cft->open)
2527 err = cft->open(inode, file);
2528 else
2529 err = 0;
2530
2531 return err;
2532}
2533
2534static int cgroup_file_release(struct inode *inode, struct file *file)
2535{
2536 struct cftype *cft = __d_cft(file->f_dentry);
2537 if (cft->release)
2538 return cft->release(inode, file);
2539 return 0;
2540}
2541
2542/*
2543 * cgroup_rename - Only allow simple rename of directories in place.
2544 */
2545static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
2546 struct inode *new_dir, struct dentry *new_dentry)
2547{
2548 if (!S_ISDIR(old_dentry->d_inode->i_mode))
2549 return -ENOTDIR;
2550 if (new_dentry->d_inode)
2551 return -EEXIST;
2552 if (old_dir != new_dir)
2553 return -EIO;
2554 return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
2555}
2556
2557static const struct file_operations cgroup_file_operations = {
2558 .read = cgroup_file_read,
2559 .write = cgroup_file_write,
2560 .llseek = generic_file_llseek,
2561 .open = cgroup_file_open,
2562 .release = cgroup_file_release,
2563};
2564
2565static const struct inode_operations cgroup_dir_inode_operations = {
2566 .lookup = cgroup_lookup,
2567 .mkdir = cgroup_mkdir,
2568 .rmdir = cgroup_rmdir,
2569 .rename = cgroup_rename,
2570};
2571
2572static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
2573{
2574 if (dentry->d_name.len > NAME_MAX)
2575 return ERR_PTR(-ENAMETOOLONG);
2576 d_add(dentry, NULL);
2577 return NULL;
2578}
2579
2580/*
2581 * Check if a file is a control file
2582 */
2583static inline struct cftype *__file_cft(struct file *file)
2584{
2585 if (file->f_dentry->d_inode->i_fop != &cgroup_file_operations)
2586 return ERR_PTR(-EINVAL);
2587 return __d_cft(file->f_dentry);
2588}
2589
2590static int cgroup_create_file(struct dentry *dentry, mode_t mode,
2591 struct super_block *sb)
2592{
2593 struct inode *inode;
2594
2595 if (!dentry)
2596 return -ENOENT;
2597 if (dentry->d_inode)
2598 return -EEXIST;
2599
2600 inode = cgroup_new_inode(mode, sb);
2601 if (!inode)
2602 return -ENOMEM;
2603
2604 if (S_ISDIR(mode)) {
2605 inode->i_op = &cgroup_dir_inode_operations;
2606 inode->i_fop = &simple_dir_operations;
2607
2608 /* start off with i_nlink == 2 (for "." entry) */
2609 inc_nlink(inode);
2610
2611 /* start with the directory inode held, so that we can
2612 * populate it without racing with another mkdir */
2613 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
2614 } else if (S_ISREG(mode)) {
2615 inode->i_size = 0;
2616 inode->i_fop = &cgroup_file_operations;
2617 }
2618 d_instantiate(dentry, inode);
2619 dget(dentry); /* Extra count - pin the dentry in core */
2620 return 0;
2621}
2622
2623/*
2624 * cgroup_create_dir - create a directory for an object.
2625 * @cgrp: the cgroup we create the directory for. It must have a valid
2626 * ->parent field. And we are going to fill its ->dentry field.
2627 * @dentry: dentry of the new cgroup
2628 * @mode: mode to set on new directory.
2629 */
2630static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
2631 mode_t mode)
2632{
2633 struct dentry *parent;
2634 int error = 0;
2635
2636 parent = cgrp->parent->dentry;
2637 error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
2638 if (!error) {
2639 dentry->d_fsdata = cgrp;
2640 inc_nlink(parent->d_inode);
2641 rcu_assign_pointer(cgrp->dentry, dentry);
2642 dget(dentry);
2643 }
2644 dput(dentry);
2645
2646 return error;
2647}
2648
2649/**
2650 * cgroup_file_mode - deduce file mode of a control file
2651 * @cft: the control file in question
2652 *
2653 * returns cft->mode if ->mode is not 0
2654 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
2655 * returns S_IRUGO if it has only a read handler
2656 * returns S_IWUSR if it has only a write hander
2657 */
2658static mode_t cgroup_file_mode(const struct cftype *cft)
2659{
2660 mode_t mode = 0;
2661
2662 if (cft->mode)
2663 return cft->mode;
2664
2665 if (cft->read || cft->read_u64 || cft->read_s64 ||
2666 cft->read_map || cft->read_seq_string)
2667 mode |= S_IRUGO;
2668
2669 if (cft->write || cft->write_u64 || cft->write_s64 ||
2670 cft->write_string || cft->trigger)
2671 mode |= S_IWUSR;
2672
2673 return mode;
2674}
2675
2676int cgroup_add_file(struct cgroup *cgrp,
2677 struct cgroup_subsys *subsys,
2678 const struct cftype *cft)
2679{
2680 struct dentry *dir = cgrp->dentry;
2681 struct dentry *dentry;
2682 int error;
2683 mode_t mode;
2684
2685 char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2686 if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2687 strcpy(name, subsys->name);
2688 strcat(name, ".");
2689 }
2690 strcat(name, cft->name);
2691 BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
2692 dentry = lookup_one_len(name, dir, strlen(name));
2693 if (!IS_ERR(dentry)) {
2694 mode = cgroup_file_mode(cft);
2695 error = cgroup_create_file(dentry, mode | S_IFREG,
2696 cgrp->root->sb);
2697 if (!error)
2698 dentry->d_fsdata = (void *)cft;
2699 dput(dentry);
2700 } else
2701 error = PTR_ERR(dentry);
2702 return error;
2703}
2704EXPORT_SYMBOL_GPL(cgroup_add_file);
2705
2706int cgroup_add_files(struct cgroup *cgrp,
2707 struct cgroup_subsys *subsys,
2708 const struct cftype cft[],
2709 int count)
2710{
2711 int i, err;
2712 for (i = 0; i < count; i++) {
2713 err = cgroup_add_file(cgrp, subsys, &cft[i]);
2714 if (err)
2715 return err;
2716 }
2717 return 0;
2718}
2719EXPORT_SYMBOL_GPL(cgroup_add_files);
2720
2721/**
2722 * cgroup_task_count - count the number of tasks in a cgroup.
2723 * @cgrp: the cgroup in question
2724 *
2725 * Return the number of tasks in the cgroup.
2726 */
2727int cgroup_task_count(const struct cgroup *cgrp)
2728{
2729 int count = 0;
2730 struct cg_cgroup_link *link;
2731
2732 read_lock(&css_set_lock);
2733 list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2734 count += atomic_read(&link->cg->refcount);
2735 }
2736 read_unlock(&css_set_lock);
2737 return count;
2738}
2739
2740/*
2741 * Advance a list_head iterator. The iterator should be positioned at
2742 * the start of a css_set
2743 */
2744static void cgroup_advance_iter(struct cgroup *cgrp,
2745 struct cgroup_iter *it)
2746{
2747 struct list_head *l = it->cg_link;
2748 struct cg_cgroup_link *link;
2749 struct css_set *cg;
2750
2751 /* Advance to the next non-empty css_set */
2752 do {
2753 l = l->next;
2754 if (l == &cgrp->css_sets) {
2755 it->cg_link = NULL;
2756 return;
2757 }
2758 link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2759 cg = link->cg;
2760 } while (list_empty(&cg->tasks));
2761 it->cg_link = l;
2762 it->task = cg->tasks.next;
2763}
2764
2765/*
2766 * To reduce the fork() overhead for systems that are not actually
2767 * using their cgroups capability, we don't maintain the lists running
2768 * through each css_set to its tasks until we see the list actually
2769 * used - in other words after the first call to cgroup_iter_start().
2770 *
2771 * The tasklist_lock is not held here, as do_each_thread() and
2772 * while_each_thread() are protected by RCU.
2773 */
2774static void cgroup_enable_task_cg_lists(void)
2775{
2776 struct task_struct *p, *g;
2777 write_lock(&css_set_lock);
2778 use_task_css_set_links = 1;
2779 do_each_thread(g, p) {
2780 task_lock(p);
2781 /*
2782 * We should check if the process is exiting, otherwise
2783 * it will race with cgroup_exit() in that the list
2784 * entry won't be deleted though the process has exited.
2785 */
2786 if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
2787 list_add(&p->cg_list, &p->cgroups->tasks);
2788 task_unlock(p);
2789 } while_each_thread(g, p);
2790 write_unlock(&css_set_lock);
2791}
2792
2793void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
2794{
2795 /*
2796 * The first time anyone tries to iterate across a cgroup,
2797 * we need to enable the list linking each css_set to its
2798 * tasks, and fix up all existing tasks.
2799 */
2800 if (!use_task_css_set_links)
2801 cgroup_enable_task_cg_lists();
2802
2803 read_lock(&css_set_lock);
2804 it->cg_link = &cgrp->css_sets;
2805 cgroup_advance_iter(cgrp, it);
2806}
2807
2808struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
2809 struct cgroup_iter *it)
2810{
2811 struct task_struct *res;
2812 struct list_head *l = it->task;
2813 struct cg_cgroup_link *link;
2814
2815 /* If the iterator cg is NULL, we have no tasks */
2816 if (!it->cg_link)
2817 return NULL;
2818 res = list_entry(l, struct task_struct, cg_list);
2819 /* Advance iterator to find next entry */
2820 l = l->next;
2821 link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
2822 if (l == &link->cg->tasks) {
2823 /* We reached the end of this task list - move on to
2824 * the next cg_cgroup_link */
2825 cgroup_advance_iter(cgrp, it);
2826 } else {
2827 it->task = l;
2828 }
2829 return res;
2830}
2831
2832void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
2833{
2834 read_unlock(&css_set_lock);
2835}
2836
2837static inline int started_after_time(struct task_struct *t1,
2838 struct timespec *time,
2839 struct task_struct *t2)
2840{
2841 int start_diff = timespec_compare(&t1->start_time, time);
2842 if (start_diff > 0) {
2843 return 1;
2844 } else if (start_diff < 0) {
2845 return 0;
2846 } else {
2847 /*
2848 * Arbitrarily, if two processes started at the same
2849 * time, we'll say that the lower pointer value
2850 * started first. Note that t2 may have exited by now
2851 * so this may not be a valid pointer any longer, but
2852 * that's fine - it still serves to distinguish
2853 * between two tasks started (effectively) simultaneously.
2854 */
2855 return t1 > t2;
2856 }
2857}
2858
2859/*
2860 * This function is a callback from heap_insert() and is used to order
2861 * the heap.
2862 * In this case we order the heap in descending task start time.
2863 */
2864static inline int started_after(void *p1, void *p2)
2865{
2866 struct task_struct *t1 = p1;
2867 struct task_struct *t2 = p2;
2868 return started_after_time(t1, &t2->start_time, t2);
2869}
2870
2871/**
2872 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
2873 * @scan: struct cgroup_scanner containing arguments for the scan
2874 *
2875 * Arguments include pointers to callback functions test_task() and
2876 * process_task().
2877 * Iterate through all the tasks in a cgroup, calling test_task() for each,
2878 * and if it returns true, call process_task() for it also.
2879 * The test_task pointer may be NULL, meaning always true (select all tasks).
2880 * Effectively duplicates cgroup_iter_{start,next,end}()
2881 * but does not lock css_set_lock for the call to process_task().
2882 * The struct cgroup_scanner may be embedded in any structure of the caller's
2883 * creation.
2884 * It is guaranteed that process_task() will act on every task that
2885 * is a member of the cgroup for the duration of this call. This
2886 * function may or may not call process_task() for tasks that exit
2887 * or move to a different cgroup during the call, or are forked or
2888 * move into the cgroup during the call.
2889 *
2890 * Note that test_task() may be called with locks held, and may in some
2891 * situations be called multiple times for the same task, so it should
2892 * be cheap.
2893 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
2894 * pre-allocated and will be used for heap operations (and its "gt" member will
2895 * be overwritten), else a temporary heap will be used (allocation of which
2896 * may cause this function to fail).
2897 */
2898int cgroup_scan_tasks(struct cgroup_scanner *scan)
2899{
2900 int retval, i;
2901 struct cgroup_iter it;
2902 struct task_struct *p, *dropped;
2903 /* Never dereference latest_task, since it's not refcounted */
2904 struct task_struct *latest_task = NULL;
2905 struct ptr_heap tmp_heap;
2906 struct ptr_heap *heap;
2907 struct timespec latest_time = { 0, 0 };
2908
2909 if (scan->heap) {
2910 /* The caller supplied our heap and pre-allocated its memory */
2911 heap = scan->heap;
2912 heap->gt = &started_after;
2913 } else {
2914 /* We need to allocate our own heap memory */
2915 heap = &tmp_heap;
2916 retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
2917 if (retval)
2918 /* cannot allocate the heap */
2919 return retval;
2920 }
2921
2922 again:
2923 /*
2924 * Scan tasks in the cgroup, using the scanner's "test_task" callback
2925 * to determine which are of interest, and using the scanner's
2926 * "process_task" callback to process any of them that need an update.
2927 * Since we don't want to hold any locks during the task updates,
2928 * gather tasks to be processed in a heap structure.
2929 * The heap is sorted by descending task start time.
2930 * If the statically-sized heap fills up, we overflow tasks that
2931 * started later, and in future iterations only consider tasks that
2932 * started after the latest task in the previous pass. This
2933 * guarantees forward progress and that we don't miss any tasks.
2934 */
2935 heap->size = 0;
2936 cgroup_iter_start(scan->cg, &it);
2937 while ((p = cgroup_iter_next(scan->cg, &it))) {
2938 /*
2939 * Only affect tasks that qualify per the caller's callback,
2940 * if he provided one
2941 */
2942 if (scan->test_task && !scan->test_task(p, scan))
2943 continue;
2944 /*
2945 * Only process tasks that started after the last task
2946 * we processed
2947 */
2948 if (!started_after_time(p, &latest_time, latest_task))
2949 continue;
2950 dropped = heap_insert(heap, p);
2951 if (dropped == NULL) {
2952 /*
2953 * The new task was inserted; the heap wasn't
2954 * previously full
2955 */
2956 get_task_struct(p);
2957 } else if (dropped != p) {
2958 /*
2959 * The new task was inserted, and pushed out a
2960 * different task
2961 */
2962 get_task_struct(p);
2963 put_task_struct(dropped);
2964 }
2965 /*
2966 * Else the new task was newer than anything already in
2967 * the heap and wasn't inserted
2968 */
2969 }
2970 cgroup_iter_end(scan->cg, &it);
2971
2972 if (heap->size) {
2973 for (i = 0; i < heap->size; i++) {
2974 struct task_struct *q = heap->ptrs[i];
2975 if (i == 0) {
2976 latest_time = q->start_time;
2977 latest_task = q;
2978 }
2979 /* Process the task per the caller's callback */
2980 scan->process_task(q, scan);
2981 put_task_struct(q);
2982 }
2983 /*
2984 * If we had to process any tasks at all, scan again
2985 * in case some of them were in the middle of forking
2986 * children that didn't get processed.
2987 * Not the most efficient way to do it, but it avoids
2988 * having to take callback_mutex in the fork path
2989 */
2990 goto again;
2991 }
2992 if (heap == &tmp_heap)
2993 heap_free(&tmp_heap);
2994 return 0;
2995}
2996
2997/*
2998 * Stuff for reading the 'tasks'/'procs' files.
2999 *
3000 * Reading this file can return large amounts of data if a cgroup has
3001 * *lots* of attached tasks. So it may need several calls to read(),
3002 * but we cannot guarantee that the information we produce is correct
3003 * unless we produce it entirely atomically.
3004 *
3005 */
3006
3007/*
3008 * The following two functions "fix" the issue where there are more pids
3009 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3010 * TODO: replace with a kernel-wide solution to this problem
3011 */
3012#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3013static void *pidlist_allocate(int count)
3014{
3015 if (PIDLIST_TOO_LARGE(count))
3016 return vmalloc(count * sizeof(pid_t));
3017 else
3018 return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
3019}
3020static void pidlist_free(void *p)
3021{
3022 if (is_vmalloc_addr(p))
3023 vfree(p);
3024 else
3025 kfree(p);
3026}
3027static void *pidlist_resize(void *p, int newcount)
3028{
3029 void *newlist;
3030 /* note: if new alloc fails, old p will still be valid either way */
3031 if (is_vmalloc_addr(p)) {
3032 newlist = vmalloc(newcount * sizeof(pid_t));
3033 if (!newlist)
3034 return NULL;
3035 memcpy(newlist, p, newcount * sizeof(pid_t));
3036 vfree(p);
3037 } else {
3038 newlist = krealloc(p, newcount * sizeof(pid_t), GFP_KERNEL);
3039 }
3040 return newlist;
3041}
3042
3043/*
3044 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3045 * If the new stripped list is sufficiently smaller and there's enough memory
3046 * to allocate a new buffer, will let go of the unneeded memory. Returns the
3047 * number of unique elements.
3048 */
3049/* is the size difference enough that we should re-allocate the array? */
3050#define PIDLIST_REALLOC_DIFFERENCE(old, new) ((old) - PAGE_SIZE >= (new))
3051static int pidlist_uniq(pid_t **p, int length)
3052{
3053 int src, dest = 1;
3054 pid_t *list = *p;
3055 pid_t *newlist;
3056
3057 /*
3058 * we presume the 0th element is unique, so i starts at 1. trivial
3059 * edge cases first; no work needs to be done for either
3060 */
3061 if (length == 0 || length == 1)
3062 return length;
3063 /* src and dest walk down the list; dest counts unique elements */
3064 for (src = 1; src < length; src++) {
3065 /* find next unique element */
3066 while (list[src] == list[src-1]) {
3067 src++;
3068 if (src == length)
3069 goto after;
3070 }
3071 /* dest always points to where the next unique element goes */
3072 list[dest] = list[src];
3073 dest++;
3074 }
3075after:
3076 /*
3077 * if the length difference is large enough, we want to allocate a
3078 * smaller buffer to save memory. if this fails due to out of memory,
3079 * we'll just stay with what we've got.
3080 */
3081 if (PIDLIST_REALLOC_DIFFERENCE(length, dest)) {
3082 newlist = pidlist_resize(list, dest);
3083 if (newlist)
3084 *p = newlist;
3085 }
3086 return dest;
3087}
3088
3089static int cmppid(const void *a, const void *b)
3090{
3091 return *(pid_t *)a - *(pid_t *)b;
3092}
3093
3094/*
3095 * find the appropriate pidlist for our purpose (given procs vs tasks)
3096 * returns with the lock on that pidlist already held, and takes care
3097 * of the use count, or returns NULL with no locks held if we're out of
3098 * memory.
3099 */
3100static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
3101 enum cgroup_filetype type)
3102{
3103 struct cgroup_pidlist *l;
3104 /* don't need task_nsproxy() if we're looking at ourself */
3105 struct pid_namespace *ns = current->nsproxy->pid_ns;
3106
3107 /*
3108 * We can't drop the pidlist_mutex before taking the l->mutex in case
3109 * the last ref-holder is trying to remove l from the list at the same
3110 * time. Holding the pidlist_mutex precludes somebody taking whichever
3111 * list we find out from under us - compare release_pid_array().
3112 */
3113 mutex_lock(&cgrp->pidlist_mutex);
3114 list_for_each_entry(l, &cgrp->pidlists, links) {
3115 if (l->key.type == type && l->key.ns == ns) {
3116 /* make sure l doesn't vanish out from under us */
3117 down_write(&l->mutex);
3118 mutex_unlock(&cgrp->pidlist_mutex);
3119 return l;
3120 }
3121 }
3122 /* entry not found; create a new one */
3123 l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3124 if (!l) {
3125 mutex_unlock(&cgrp->pidlist_mutex);
3126 return l;
3127 }
3128 init_rwsem(&l->mutex);
3129 down_write(&l->mutex);
3130 l->key.type = type;
3131 l->key.ns = get_pid_ns(ns);
3132 l->use_count = 0; /* don't increment here */
3133 l->list = NULL;
3134 l->owner = cgrp;
3135 list_add(&l->links, &cgrp->pidlists);
3136 mutex_unlock(&cgrp->pidlist_mutex);
3137 return l;
3138}
3139
3140/*
3141 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3142 */
3143static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
3144 struct cgroup_pidlist **lp)
3145{
3146 pid_t *array;
3147 int length;
3148 int pid, n = 0; /* used for populating the array */
3149 struct cgroup_iter it;
3150 struct task_struct *tsk;
3151 struct cgroup_pidlist *l;
3152
3153 /*
3154 * If cgroup gets more users after we read count, we won't have
3155 * enough space - tough. This race is indistinguishable to the
3156 * caller from the case that the additional cgroup users didn't
3157 * show up until sometime later on.
3158 */
3159 length = cgroup_task_count(cgrp);
3160 array = pidlist_allocate(length);
3161 if (!array)
3162 return -ENOMEM;
3163 /* now, populate the array */
3164 cgroup_iter_start(cgrp, &it);
3165 while ((tsk = cgroup_iter_next(cgrp, &it))) {
3166 if (unlikely(n == length))
3167 break;
3168 /* get tgid or pid for procs or tasks file respectively */
3169 if (type == CGROUP_FILE_PROCS)
3170 pid = task_tgid_vnr(tsk);
3171 else
3172 pid = task_pid_vnr(tsk);
3173 if (pid > 0) /* make sure to only use valid results */
3174 array[n++] = pid;
3175 }
3176 cgroup_iter_end(cgrp, &it);
3177 length = n;
3178 /* now sort & (if procs) strip out duplicates */
3179 sort(array, length, sizeof(pid_t), cmppid, NULL);
3180 if (type == CGROUP_FILE_PROCS)
3181 length = pidlist_uniq(&array, length);
3182 l = cgroup_pidlist_find(cgrp, type);
3183 if (!l) {
3184 pidlist_free(array);
3185 return -ENOMEM;
3186 }
3187 /* store array, freeing old if necessary - lock already held */
3188 pidlist_free(l->list);
3189 l->list = array;
3190 l->length = length;
3191 l->use_count++;
3192 up_write(&l->mutex);
3193 *lp = l;
3194 return 0;
3195}
3196
3197/**
3198 * cgroupstats_build - build and fill cgroupstats
3199 * @stats: cgroupstats to fill information into
3200 * @dentry: A dentry entry belonging to the cgroup for which stats have
3201 * been requested.
3202 *
3203 * Build and fill cgroupstats so that taskstats can export it to user
3204 * space.
3205 */
3206int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
3207{
3208 int ret = -EINVAL;
3209 struct cgroup *cgrp;
3210 struct cgroup_iter it;
3211 struct task_struct *tsk;
3212
3213 /*
3214 * Validate dentry by checking the superblock operations,
3215 * and make sure it's a directory.
3216 */
3217 if (dentry->d_sb->s_op != &cgroup_ops ||
3218 !S_ISDIR(dentry->d_inode->i_mode))
3219 goto err;
3220
3221 ret = 0;
3222 cgrp = dentry->d_fsdata;
3223
3224 cgroup_iter_start(cgrp, &it);
3225 while ((tsk = cgroup_iter_next(cgrp, &it))) {
3226 switch (tsk->state) {
3227 case TASK_RUNNING:
3228 stats->nr_running++;
3229 break;
3230 case TASK_INTERRUPTIBLE:
3231 stats->nr_sleeping++;
3232 break;
3233 case TASK_UNINTERRUPTIBLE:
3234 stats->nr_uninterruptible++;
3235 break;
3236 case TASK_STOPPED:
3237 stats->nr_stopped++;
3238 break;
3239 default:
3240 if (delayacct_is_task_waiting_on_io(tsk))
3241 stats->nr_io_wait++;
3242 break;
3243 }
3244 }
3245 cgroup_iter_end(cgrp, &it);
3246
3247err:
3248 return ret;
3249}
3250
3251
3252/*
3253 * seq_file methods for the tasks/procs files. The seq_file position is the
3254 * next pid to display; the seq_file iterator is a pointer to the pid
3255 * in the cgroup->l->list array.
3256 */
3257
3258static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3259{
3260 /*
3261 * Initially we receive a position value that corresponds to
3262 * one more than the last pid shown (or 0 on the first call or
3263 * after a seek to the start). Use a binary-search to find the
3264 * next pid to display, if any
3265 */
3266 struct cgroup_pidlist *l = s->private;
3267 int index = 0, pid = *pos;
3268 int *iter;
3269
3270 down_read(&l->mutex);
3271 if (pid) {
3272 int end = l->length;
3273
3274 while (index < end) {
3275 int mid = (index + end) / 2;
3276 if (l->list[mid] == pid) {
3277 index = mid;
3278 break;
3279 } else if (l->list[mid] <= pid)
3280 index = mid + 1;
3281 else
3282 end = mid;
3283 }
3284 }
3285 /* If we're off the end of the array, we're done */
3286 if (index >= l->length)
3287 return NULL;
3288 /* Update the abstract position to be the actual pid that we found */
3289 iter = l->list + index;
3290 *pos = *iter;
3291 return iter;
3292}
3293
3294static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3295{
3296 struct cgroup_pidlist *l = s->private;
3297 up_read(&l->mutex);
3298}
3299
3300static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3301{
3302 struct cgroup_pidlist *l = s->private;
3303 pid_t *p = v;
3304 pid_t *end = l->list + l->length;
3305 /*
3306 * Advance to the next pid in the array. If this goes off the
3307 * end, we're done
3308 */
3309 p++;
3310 if (p >= end) {
3311 return NULL;
3312 } else {
3313 *pos = *p;
3314 return p;
3315 }
3316}
3317
3318static int cgroup_pidlist_show(struct seq_file *s, void *v)
3319{
3320 return seq_printf(s, "%d\n", *(int *)v);
3321}
3322
3323/*
3324 * seq_operations functions for iterating on pidlists through seq_file -
3325 * independent of whether it's tasks or procs
3326 */
3327static const struct seq_operations cgroup_pidlist_seq_operations = {
3328 .start = cgroup_pidlist_start,
3329 .stop = cgroup_pidlist_stop,
3330 .next = cgroup_pidlist_next,
3331 .show = cgroup_pidlist_show,
3332};
3333
3334static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3335{
3336 /*
3337 * the case where we're the last user of this particular pidlist will
3338 * have us remove it from the cgroup's list, which entails taking the
3339 * mutex. since in pidlist_find the pidlist->lock depends on cgroup->
3340 * pidlist_mutex, we have to take pidlist_mutex first.
3341 */
3342 mutex_lock(&l->owner->pidlist_mutex);
3343 down_write(&l->mutex);
3344 BUG_ON(!l->use_count);
3345 if (!--l->use_count) {
3346 /* we're the last user if refcount is 0; remove and free */
3347 list_del(&l->links);
3348 mutex_unlock(&l->owner->pidlist_mutex);
3349 pidlist_free(l->list);
3350 put_pid_ns(l->key.ns);
3351 up_write(&l->mutex);
3352 kfree(l);
3353 return;
3354 }
3355 mutex_unlock(&l->owner->pidlist_mutex);
3356 up_write(&l->mutex);
3357}
3358
3359static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3360{
3361 struct cgroup_pidlist *l;
3362 if (!(file->f_mode & FMODE_READ))
3363 return 0;
3364 /*
3365 * the seq_file will only be initialized if the file was opened for
3366 * reading; hence we check if it's not null only in that case.
3367 */
3368 l = ((struct seq_file *)file->private_data)->private;
3369 cgroup_release_pid_array(l);
3370 return seq_release(inode, file);
3371}
3372
3373static const struct file_operations cgroup_pidlist_operations = {
3374 .read = seq_read,
3375 .llseek = seq_lseek,
3376 .write = cgroup_file_write,
3377 .release = cgroup_pidlist_release,
3378};
3379
3380/*
3381 * The following functions handle opens on a file that displays a pidlist
3382 * (tasks or procs). Prepare an array of the process/thread IDs of whoever's
3383 * in the cgroup.
3384 */
3385/* helper function for the two below it */
3386static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3387{
3388 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3389 struct cgroup_pidlist *l;
3390 int retval;
3391
3392 /* Nothing to do for write-only files */
3393 if (!(file->f_mode & FMODE_READ))
3394 return 0;
3395
3396 /* have the array populated */
3397 retval = pidlist_array_load(cgrp, type, &l);
3398 if (retval)
3399 return retval;
3400 /* configure file information */
3401 file->f_op = &cgroup_pidlist_operations;
3402
3403 retval = seq_open(file, &cgroup_pidlist_seq_operations);
3404 if (retval) {
3405 cgroup_release_pid_array(l);
3406 return retval;
3407 }
3408 ((struct seq_file *)file->private_data)->private = l;
3409 return 0;
3410}
3411static int cgroup_tasks_open(struct inode *unused, struct file *file)
3412{
3413 return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3414}
3415static int cgroup_procs_open(struct inode *unused, struct file *file)
3416{
3417 return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3418}
3419
3420static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3421 struct cftype *cft)
3422{
3423 return notify_on_release(cgrp);
3424}
3425
3426static int cgroup_write_notify_on_release(struct cgroup *cgrp,
3427 struct cftype *cft,
3428 u64 val)
3429{
3430 clear_bit(CGRP_RELEASABLE, &cgrp->flags);
3431 if (val)
3432 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3433 else
3434 clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3435 return 0;
3436}
3437
3438/*
3439 * Unregister event and free resources.
3440 *
3441 * Gets called from workqueue.
3442 */
3443static void cgroup_event_remove(struct work_struct *work)
3444{
3445 struct cgroup_event *event = container_of(work, struct cgroup_event,
3446 remove);
3447 struct cgroup *cgrp = event->cgrp;
3448
3449 event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3450
3451 eventfd_ctx_put(event->eventfd);
3452 kfree(event);
3453 dput(cgrp->dentry);
3454}
3455
3456/*
3457 * Gets called on POLLHUP on eventfd when user closes it.
3458 *
3459 * Called with wqh->lock held and interrupts disabled.
3460 */
3461static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
3462 int sync, void *key)
3463{
3464 struct cgroup_event *event = container_of(wait,
3465 struct cgroup_event, wait);
3466 struct cgroup *cgrp = event->cgrp;
3467 unsigned long flags = (unsigned long)key;
3468
3469 if (flags & POLLHUP) {
3470 __remove_wait_queue(event->wqh, &event->wait);
3471 spin_lock(&cgrp->event_list_lock);
3472 list_del(&event->list);
3473 spin_unlock(&cgrp->event_list_lock);
3474 /*
3475 * We are in atomic context, but cgroup_event_remove() may
3476 * sleep, so we have to call it in workqueue.
3477 */
3478 schedule_work(&event->remove);
3479 }
3480
3481 return 0;
3482}
3483
3484static void cgroup_event_ptable_queue_proc(struct file *file,
3485 wait_queue_head_t *wqh, poll_table *pt)
3486{
3487 struct cgroup_event *event = container_of(pt,
3488 struct cgroup_event, pt);
3489
3490 event->wqh = wqh;
3491 add_wait_queue(wqh, &event->wait);
3492}
3493
3494/*
3495 * Parse input and register new cgroup event handler.
3496 *
3497 * Input must be in format '<event_fd> <control_fd> <args>'.
3498 * Interpretation of args is defined by control file implementation.
3499 */
3500static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
3501 const char *buffer)
3502{
3503 struct cgroup_event *event = NULL;
3504 unsigned int efd, cfd;
3505 struct file *efile = NULL;
3506 struct file *cfile = NULL;
3507 char *endp;
3508 int ret;
3509
3510 efd = simple_strtoul(buffer, &endp, 10);
3511 if (*endp != ' ')
3512 return -EINVAL;
3513 buffer = endp + 1;
3514
3515 cfd = simple_strtoul(buffer, &endp, 10);
3516 if ((*endp != ' ') && (*endp != '\0'))
3517 return -EINVAL;
3518 buffer = endp + 1;
3519
3520 event = kzalloc(sizeof(*event), GFP_KERNEL);
3521 if (!event)
3522 return -ENOMEM;
3523 event->cgrp = cgrp;
3524 INIT_LIST_HEAD(&event->list);
3525 init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
3526 init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
3527 INIT_WORK(&event->remove, cgroup_event_remove);
3528
3529 efile = eventfd_fget(efd);
3530 if (IS_ERR(efile)) {
3531 ret = PTR_ERR(efile);
3532 goto fail;
3533 }
3534
3535 event->eventfd = eventfd_ctx_fileget(efile);
3536 if (IS_ERR(event->eventfd)) {
3537 ret = PTR_ERR(event->eventfd);
3538 goto fail;
3539 }
3540
3541 cfile = fget(cfd);
3542 if (!cfile) {
3543 ret = -EBADF;
3544 goto fail;
3545 }
3546
3547 /* the process need read permission on control file */
3548 /* AV: shouldn't we check that it's been opened for read instead? */
3549 ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3550 if (ret < 0)
3551 goto fail;
3552
3553 event->cft = __file_cft(cfile);
3554 if (IS_ERR(event->cft)) {
3555 ret = PTR_ERR(event->cft);
3556 goto fail;
3557 }
3558
3559 if (!event->cft->register_event || !event->cft->unregister_event) {
3560 ret = -EINVAL;
3561 goto fail;
3562 }
3563
3564 ret = event->cft->register_event(cgrp, event->cft,
3565 event->eventfd, buffer);
3566 if (ret)
3567 goto fail;
3568
3569 if (efile->f_op->poll(efile, &event->pt) & POLLHUP) {
3570 event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3571 ret = 0;
3572 goto fail;
3573 }
3574
3575 /*
3576 * Events should be removed after rmdir of cgroup directory, but before
3577 * destroying subsystem state objects. Let's take reference to cgroup
3578 * directory dentry to do that.
3579 */
3580 dget(cgrp->dentry);
3581
3582 spin_lock(&cgrp->event_list_lock);
3583 list_add(&event->list, &cgrp->event_list);
3584 spin_unlock(&cgrp->event_list_lock);
3585
3586 fput(cfile);
3587 fput(efile);
3588
3589 return 0;
3590
3591fail:
3592 if (cfile)
3593 fput(cfile);
3594
3595 if (event && event->eventfd && !IS_ERR(event->eventfd))
3596 eventfd_ctx_put(event->eventfd);
3597
3598 if (!IS_ERR_OR_NULL(efile))
3599 fput(efile);
3600
3601 kfree(event);
3602
3603 return ret;
3604}
3605
3606static u64 cgroup_clone_children_read(struct cgroup *cgrp,
3607 struct cftype *cft)
3608{
3609 return clone_children(cgrp);
3610}
3611
3612static int cgroup_clone_children_write(struct cgroup *cgrp,
3613 struct cftype *cft,
3614 u64 val)
3615{
3616 if (val)
3617 set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3618 else
3619 clear_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3620 return 0;
3621}
3622
3623/*
3624 * for the common functions, 'private' gives the type of file
3625 */
3626/* for hysterical raisins, we can't put this on the older files */
3627#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3628static struct cftype files[] = {
3629 {
3630 .name = "tasks",
3631 .open = cgroup_tasks_open,
3632 .write_u64 = cgroup_tasks_write,
3633 .release = cgroup_pidlist_release,
3634 .mode = S_IRUGO | S_IWUSR,
3635 },
3636 {
3637 .name = CGROUP_FILE_GENERIC_PREFIX "procs",
3638 .open = cgroup_procs_open,
3639 .write_u64 = cgroup_procs_write,
3640 .release = cgroup_pidlist_release,
3641 .mode = S_IRUGO | S_IWUSR,
3642 },
3643 {
3644 .name = "notify_on_release",
3645 .read_u64 = cgroup_read_notify_on_release,
3646 .write_u64 = cgroup_write_notify_on_release,
3647 },
3648 {
3649 .name = CGROUP_FILE_GENERIC_PREFIX "event_control",
3650 .write_string = cgroup_write_event_control,
3651 .mode = S_IWUGO,
3652 },
3653 {
3654 .name = "cgroup.clone_children",
3655 .read_u64 = cgroup_clone_children_read,
3656 .write_u64 = cgroup_clone_children_write,
3657 },
3658};
3659
3660static struct cftype cft_release_agent = {
3661 .name = "release_agent",
3662 .read_seq_string = cgroup_release_agent_show,
3663 .write_string = cgroup_release_agent_write,
3664 .max_write_len = PATH_MAX,
3665};
3666
3667static int cgroup_populate_dir(struct cgroup *cgrp)
3668{
3669 int err;
3670 struct cgroup_subsys *ss;
3671
3672 /* First clear out any existing files */
3673 cgroup_clear_directory(cgrp->dentry);
3674
3675 err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));
3676 if (err < 0)
3677 return err;
3678
3679 if (cgrp == cgrp->top_cgroup) {
3680 if ((err = cgroup_add_file(cgrp, NULL, &cft_release_agent)) < 0)
3681 return err;
3682 }
3683
3684 for_each_subsys(cgrp->root, ss) {
3685 if (ss->populate && (err = ss->populate(ss, cgrp)) < 0)
3686 return err;
3687 }
3688 /* This cgroup is ready now */
3689 for_each_subsys(cgrp->root, ss) {
3690 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
3691 /*
3692 * Update id->css pointer and make this css visible from
3693 * CSS ID functions. This pointer will be dereferened
3694 * from RCU-read-side without locks.
3695 */
3696 if (css->id)
3697 rcu_assign_pointer(css->id->css, css);
3698 }
3699
3700 return 0;
3701}
3702
3703static void init_cgroup_css(struct cgroup_subsys_state *css,
3704 struct cgroup_subsys *ss,
3705 struct cgroup *cgrp)
3706{
3707 css->cgroup = cgrp;
3708 atomic_set(&css->refcnt, 1);
3709 css->flags = 0;
3710 css->id = NULL;
3711 if (cgrp == dummytop)
3712 set_bit(CSS_ROOT, &css->flags);
3713 BUG_ON(cgrp->subsys[ss->subsys_id]);
3714 cgrp->subsys[ss->subsys_id] = css;
3715}
3716
3717static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
3718{
3719 /* We need to take each hierarchy_mutex in a consistent order */
3720 int i;
3721
3722 /*
3723 * No worry about a race with rebind_subsystems that might mess up the
3724 * locking order, since both parties are under cgroup_mutex.
3725 */
3726 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3727 struct cgroup_subsys *ss = subsys[i];
3728 if (ss == NULL)
3729 continue;
3730 if (ss->root == root)
3731 mutex_lock(&ss->hierarchy_mutex);
3732 }
3733}
3734
3735static void cgroup_unlock_hierarchy(struct cgroupfs_root *root)
3736{
3737 int i;
3738
3739 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3740 struct cgroup_subsys *ss = subsys[i];
3741 if (ss == NULL)
3742 continue;
3743 if (ss->root == root)
3744 mutex_unlock(&ss->hierarchy_mutex);
3745 }
3746}
3747
3748/*
3749 * cgroup_create - create a cgroup
3750 * @parent: cgroup that will be parent of the new cgroup
3751 * @dentry: dentry of the new cgroup
3752 * @mode: mode to set on new inode
3753 *
3754 * Must be called with the mutex on the parent inode held
3755 */
3756static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
3757 mode_t mode)
3758{
3759 struct cgroup *cgrp;
3760 struct cgroupfs_root *root = parent->root;
3761 int err = 0;
3762 struct cgroup_subsys *ss;
3763 struct super_block *sb = root->sb;
3764
3765 cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
3766 if (!cgrp)
3767 return -ENOMEM;
3768
3769 /* Grab a reference on the superblock so the hierarchy doesn't
3770 * get deleted on unmount if there are child cgroups. This
3771 * can be done outside cgroup_mutex, since the sb can't
3772 * disappear while someone has an open control file on the
3773 * fs */
3774 atomic_inc(&sb->s_active);
3775
3776 mutex_lock(&cgroup_mutex);
3777
3778 init_cgroup_housekeeping(cgrp);
3779
3780 cgrp->parent = parent;
3781 cgrp->root = parent->root;
3782 cgrp->top_cgroup = parent->top_cgroup;
3783
3784 if (notify_on_release(parent))
3785 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3786
3787 if (clone_children(parent))
3788 set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3789
3790 for_each_subsys(root, ss) {
3791 struct cgroup_subsys_state *css = ss->create(ss, cgrp);
3792
3793 if (IS_ERR(css)) {
3794 err = PTR_ERR(css);
3795 goto err_destroy;
3796 }
3797 init_cgroup_css(css, ss, cgrp);
3798 if (ss->use_id) {
3799 err = alloc_css_id(ss, parent, cgrp);
3800 if (err)
3801 goto err_destroy;
3802 }
3803 /* At error, ->destroy() callback has to free assigned ID. */
3804 if (clone_children(parent) && ss->post_clone)
3805 ss->post_clone(ss, cgrp);
3806 }
3807
3808 cgroup_lock_hierarchy(root);
3809 list_add(&cgrp->sibling, &cgrp->parent->children);
3810 cgroup_unlock_hierarchy(root);
3811 root->number_of_cgroups++;
3812
3813 err = cgroup_create_dir(cgrp, dentry, mode);
3814 if (err < 0)
3815 goto err_remove;
3816
3817 /* The cgroup directory was pre-locked for us */
3818 BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
3819
3820 err = cgroup_populate_dir(cgrp);
3821 /* If err < 0, we have a half-filled directory - oh well ;) */
3822
3823 mutex_unlock(&cgroup_mutex);
3824 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
3825
3826 return 0;
3827
3828 err_remove:
3829
3830 cgroup_lock_hierarchy(root);
3831 list_del(&cgrp->sibling);
3832 cgroup_unlock_hierarchy(root);
3833 root->number_of_cgroups--;
3834
3835 err_destroy:
3836
3837 for_each_subsys(root, ss) {
3838 if (cgrp->subsys[ss->subsys_id])
3839 ss->destroy(ss, cgrp);
3840 }
3841
3842 mutex_unlock(&cgroup_mutex);
3843
3844 /* Release the reference count that we took on the superblock */
3845 deactivate_super(sb);
3846
3847 kfree(cgrp);
3848 return err;
3849}
3850
3851static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode)
3852{
3853 struct cgroup *c_parent = dentry->d_parent->d_fsdata;
3854
3855 /* the vfs holds inode->i_mutex already */
3856 return cgroup_create(c_parent, dentry, mode | S_IFDIR);
3857}
3858
3859static int cgroup_has_css_refs(struct cgroup *cgrp)
3860{
3861 /* Check the reference count on each subsystem. Since we
3862 * already established that there are no tasks in the
3863 * cgroup, if the css refcount is also 1, then there should
3864 * be no outstanding references, so the subsystem is safe to
3865 * destroy. We scan across all subsystems rather than using
3866 * the per-hierarchy linked list of mounted subsystems since
3867 * we can be called via check_for_release() with no
3868 * synchronization other than RCU, and the subsystem linked
3869 * list isn't RCU-safe */
3870 int i;
3871 /*
3872 * We won't need to lock the subsys array, because the subsystems
3873 * we're concerned about aren't going anywhere since our cgroup root
3874 * has a reference on them.
3875 */
3876 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3877 struct cgroup_subsys *ss = subsys[i];
3878 struct cgroup_subsys_state *css;
3879 /* Skip subsystems not present or not in this hierarchy */
3880 if (ss == NULL || ss->root != cgrp->root)
3881 continue;
3882 css = cgrp->subsys[ss->subsys_id];
3883 /* When called from check_for_release() it's possible
3884 * that by this point the cgroup has been removed
3885 * and the css deleted. But a false-positive doesn't
3886 * matter, since it can only happen if the cgroup
3887 * has been deleted and hence no longer needs the
3888 * release agent to be called anyway. */
3889 if (css && (atomic_read(&css->refcnt) > 1))
3890 return 1;
3891 }
3892 return 0;
3893}
3894
3895/*
3896 * Atomically mark all (or else none) of the cgroup's CSS objects as
3897 * CSS_REMOVED. Return true on success, or false if the cgroup has
3898 * busy subsystems. Call with cgroup_mutex held
3899 */
3900
3901static int cgroup_clear_css_refs(struct cgroup *cgrp)
3902{
3903 struct cgroup_subsys *ss;
3904 unsigned long flags;
3905 bool failed = false;
3906 local_irq_save(flags);
3907 for_each_subsys(cgrp->root, ss) {
3908 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
3909 int refcnt;
3910 while (1) {
3911 /* We can only remove a CSS with a refcnt==1 */
3912 refcnt = atomic_read(&css->refcnt);
3913 if (refcnt > 1) {
3914 failed = true;
3915 goto done;
3916 }
3917 BUG_ON(!refcnt);
3918 /*
3919 * Drop the refcnt to 0 while we check other
3920 * subsystems. This will cause any racing
3921 * css_tryget() to spin until we set the
3922 * CSS_REMOVED bits or abort
3923 */
3924 if (atomic_cmpxchg(&css->refcnt, refcnt, 0) == refcnt)
3925 break;
3926 cpu_relax();
3927 }
3928 }
3929 done:
3930 for_each_subsys(cgrp->root, ss) {
3931 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
3932 if (failed) {
3933 /*
3934 * Restore old refcnt if we previously managed
3935 * to clear it from 1 to 0
3936 */
3937 if (!atomic_read(&css->refcnt))
3938 atomic_set(&css->refcnt, 1);
3939 } else {
3940 /* Commit the fact that the CSS is removed */
3941 set_bit(CSS_REMOVED, &css->flags);
3942 }
3943 }
3944 local_irq_restore(flags);
3945 return !failed;
3946}
3947
3948static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
3949{
3950 struct cgroup *cgrp = dentry->d_fsdata;
3951 struct dentry *d;
3952 struct cgroup *parent;
3953 DEFINE_WAIT(wait);
3954 struct cgroup_event *event, *tmp;
3955 int ret;
3956
3957 /* the vfs holds both inode->i_mutex already */
3958again:
3959 mutex_lock(&cgroup_mutex);
3960 if (atomic_read(&cgrp->count) != 0) {
3961 mutex_unlock(&cgroup_mutex);
3962 return -EBUSY;
3963 }
3964 if (!list_empty(&cgrp->children)) {
3965 mutex_unlock(&cgroup_mutex);
3966 return -EBUSY;
3967 }
3968 mutex_unlock(&cgroup_mutex);
3969
3970 /*
3971 * In general, subsystem has no css->refcnt after pre_destroy(). But
3972 * in racy cases, subsystem may have to get css->refcnt after
3973 * pre_destroy() and it makes rmdir return with -EBUSY. This sometimes
3974 * make rmdir return -EBUSY too often. To avoid that, we use waitqueue
3975 * for cgroup's rmdir. CGRP_WAIT_ON_RMDIR is for synchronizing rmdir
3976 * and subsystem's reference count handling. Please see css_get/put
3977 * and css_tryget() and cgroup_wakeup_rmdir_waiter() implementation.
3978 */
3979 set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
3980
3981 /*
3982 * Call pre_destroy handlers of subsys. Notify subsystems
3983 * that rmdir() request comes.
3984 */
3985 ret = cgroup_call_pre_destroy(cgrp);
3986 if (ret) {
3987 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
3988 return ret;
3989 }
3990
3991 mutex_lock(&cgroup_mutex);
3992 parent = cgrp->parent;
3993 if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
3994 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
3995 mutex_unlock(&cgroup_mutex);
3996 return -EBUSY;
3997 }
3998 prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
3999 if (!cgroup_clear_css_refs(cgrp)) {
4000 mutex_unlock(&cgroup_mutex);
4001 /*
4002 * Because someone may call cgroup_wakeup_rmdir_waiter() before
4003 * prepare_to_wait(), we need to check this flag.
4004 */
4005 if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))
4006 schedule();
4007 finish_wait(&cgroup_rmdir_waitq, &wait);
4008 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4009 if (signal_pending(current))
4010 return -EINTR;
4011 goto again;
4012 }
4013 /* NO css_tryget() can success after here. */
4014 finish_wait(&cgroup_rmdir_waitq, &wait);
4015 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4016
4017 spin_lock(&release_list_lock);
4018 set_bit(CGRP_REMOVED, &cgrp->flags);
4019 if (!list_empty(&cgrp->release_list))
4020 list_del_init(&cgrp->release_list);
4021 spin_unlock(&release_list_lock);
4022
4023 cgroup_lock_hierarchy(cgrp->root);
4024 /* delete this cgroup from parent->children */
4025 list_del_init(&cgrp->sibling);
4026 cgroup_unlock_hierarchy(cgrp->root);
4027
4028 d = dget(cgrp->dentry);
4029
4030 cgroup_d_remove_dir(d);
4031 dput(d);
4032
4033 set_bit(CGRP_RELEASABLE, &parent->flags);
4034 check_for_release(parent);
4035
4036 /*
4037 * Unregister events and notify userspace.
4038 * Notify userspace about cgroup removing only after rmdir of cgroup
4039 * directory to avoid race between userspace and kernelspace
4040 */
4041 spin_lock(&cgrp->event_list_lock);
4042 list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
4043 list_del(&event->list);
4044 remove_wait_queue(event->wqh, &event->wait);
4045 eventfd_signal(event->eventfd, 1);
4046 schedule_work(&event->remove);
4047 }
4048 spin_unlock(&cgrp->event_list_lock);
4049
4050 mutex_unlock(&cgroup_mutex);
4051 return 0;
4052}
4053
4054static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4055{
4056 struct cgroup_subsys_state *css;
4057
4058 printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4059
4060 /* Create the top cgroup state for this subsystem */
4061 list_add(&ss->sibling, &rootnode.subsys_list);
4062 ss->root = &rootnode;
4063 css = ss->create(ss, dummytop);
4064 /* We don't handle early failures gracefully */
4065 BUG_ON(IS_ERR(css));
4066 init_cgroup_css(css, ss, dummytop);
4067
4068 /* Update the init_css_set to contain a subsys
4069 * pointer to this state - since the subsystem is
4070 * newly registered, all tasks and hence the
4071 * init_css_set is in the subsystem's top cgroup. */
4072 init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
4073
4074 need_forkexit_callback |= ss->fork || ss->exit;
4075
4076 /* At system boot, before all subsystems have been
4077 * registered, no tasks have been forked, so we don't
4078 * need to invoke fork callbacks here. */
4079 BUG_ON(!list_empty(&init_task.tasks));
4080
4081 mutex_init(&ss->hierarchy_mutex);
4082 lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
4083 ss->active = 1;
4084
4085 /* this function shouldn't be used with modular subsystems, since they
4086 * need to register a subsys_id, among other things */
4087 BUG_ON(ss->module);
4088}
4089
4090/**
4091 * cgroup_load_subsys: load and register a modular subsystem at runtime
4092 * @ss: the subsystem to load
4093 *
4094 * This function should be called in a modular subsystem's initcall. If the
4095 * subsystem is built as a module, it will be assigned a new subsys_id and set
4096 * up for use. If the subsystem is built-in anyway, work is delegated to the
4097 * simpler cgroup_init_subsys.
4098 */
4099int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
4100{
4101 int i;
4102 struct cgroup_subsys_state *css;
4103
4104 /* check name and function validity */
4105 if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
4106 ss->create == NULL || ss->destroy == NULL)
4107 return -EINVAL;
4108
4109 /*
4110 * we don't support callbacks in modular subsystems. this check is
4111 * before the ss->module check for consistency; a subsystem that could
4112 * be a module should still have no callbacks even if the user isn't
4113 * compiling it as one.
4114 */
4115 if (ss->fork || ss->exit)
4116 return -EINVAL;
4117
4118 /*
4119 * an optionally modular subsystem is built-in: we want to do nothing,
4120 * since cgroup_init_subsys will have already taken care of it.
4121 */
4122 if (ss->module == NULL) {
4123 /* a few sanity checks */
4124 BUG_ON(ss->subsys_id >= CGROUP_BUILTIN_SUBSYS_COUNT);
4125 BUG_ON(subsys[ss->subsys_id] != ss);
4126 return 0;
4127 }
4128
4129 /*
4130 * need to register a subsys id before anything else - for example,
4131 * init_cgroup_css needs it.
4132 */
4133 mutex_lock(&cgroup_mutex);
4134 /* find the first empty slot in the array */
4135 for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
4136 if (subsys[i] == NULL)
4137 break;
4138 }
4139 if (i == CGROUP_SUBSYS_COUNT) {
4140 /* maximum number of subsystems already registered! */
4141 mutex_unlock(&cgroup_mutex);
4142 return -EBUSY;
4143 }
4144 /* assign ourselves the subsys_id */
4145 ss->subsys_id = i;
4146 subsys[i] = ss;
4147
4148 /*
4149 * no ss->create seems to need anything important in the ss struct, so
4150 * this can happen first (i.e. before the rootnode attachment).
4151 */
4152 css = ss->create(ss, dummytop);
4153 if (IS_ERR(css)) {
4154 /* failure case - need to deassign the subsys[] slot. */
4155 subsys[i] = NULL;
4156 mutex_unlock(&cgroup_mutex);
4157 return PTR_ERR(css);
4158 }
4159
4160 list_add(&ss->sibling, &rootnode.subsys_list);
4161 ss->root = &rootnode;
4162
4163 /* our new subsystem will be attached to the dummy hierarchy. */
4164 init_cgroup_css(css, ss, dummytop);
4165 /* init_idr must be after init_cgroup_css because it sets css->id. */
4166 if (ss->use_id) {
4167 int ret = cgroup_init_idr(ss, css);
4168 if (ret) {
4169 dummytop->subsys[ss->subsys_id] = NULL;
4170 ss->destroy(ss, dummytop);
4171 subsys[i] = NULL;
4172 mutex_unlock(&cgroup_mutex);
4173 return ret;
4174 }
4175 }
4176
4177 /*
4178 * Now we need to entangle the css into the existing css_sets. unlike
4179 * in cgroup_init_subsys, there are now multiple css_sets, so each one
4180 * will need a new pointer to it; done by iterating the css_set_table.
4181 * furthermore, modifying the existing css_sets will corrupt the hash
4182 * table state, so each changed css_set will need its hash recomputed.
4183 * this is all done under the css_set_lock.
4184 */
4185 write_lock(&css_set_lock);
4186 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
4187 struct css_set *cg;
4188 struct hlist_node *node, *tmp;
4189 struct hlist_head *bucket = &css_set_table[i], *new_bucket;
4190
4191 hlist_for_each_entry_safe(cg, node, tmp, bucket, hlist) {
4192 /* skip entries that we already rehashed */
4193 if (cg->subsys[ss->subsys_id])
4194 continue;
4195 /* remove existing entry */
4196 hlist_del(&cg->hlist);
4197 /* set new value */
4198 cg->subsys[ss->subsys_id] = css;
4199 /* recompute hash and restore entry */
4200 new_bucket = css_set_hash(cg->subsys);
4201 hlist_add_head(&cg->hlist, new_bucket);
4202 }
4203 }
4204 write_unlock(&css_set_lock);
4205
4206 mutex_init(&ss->hierarchy_mutex);
4207 lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
4208 ss->active = 1;
4209
4210 /* success! */
4211 mutex_unlock(&cgroup_mutex);
4212 return 0;
4213}
4214EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4215
4216/**
4217 * cgroup_unload_subsys: unload a modular subsystem
4218 * @ss: the subsystem to unload
4219 *
4220 * This function should be called in a modular subsystem's exitcall. When this
4221 * function is invoked, the refcount on the subsystem's module will be 0, so
4222 * the subsystem will not be attached to any hierarchy.
4223 */
4224void cgroup_unload_subsys(struct cgroup_subsys *ss)
4225{
4226 struct cg_cgroup_link *link;
4227 struct hlist_head *hhead;
4228
4229 BUG_ON(ss->module == NULL);
4230
4231 /*
4232 * we shouldn't be called if the subsystem is in use, and the use of
4233 * try_module_get in parse_cgroupfs_options should ensure that it
4234 * doesn't start being used while we're killing it off.
4235 */
4236 BUG_ON(ss->root != &rootnode);
4237
4238 mutex_lock(&cgroup_mutex);
4239 /* deassign the subsys_id */
4240 BUG_ON(ss->subsys_id < CGROUP_BUILTIN_SUBSYS_COUNT);
4241 subsys[ss->subsys_id] = NULL;
4242
4243 /* remove subsystem from rootnode's list of subsystems */
4244 list_del_init(&ss->sibling);
4245
4246 /*
4247 * disentangle the css from all css_sets attached to the dummytop. as
4248 * in loading, we need to pay our respects to the hashtable gods.
4249 */
4250 write_lock(&css_set_lock);
4251 list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {
4252 struct css_set *cg = link->cg;
4253
4254 hlist_del(&cg->hlist);
4255 BUG_ON(!cg->subsys[ss->subsys_id]);
4256 cg->subsys[ss->subsys_id] = NULL;
4257 hhead = css_set_hash(cg->subsys);
4258 hlist_add_head(&cg->hlist, hhead);
4259 }
4260 write_unlock(&css_set_lock);
4261
4262 /*
4263 * remove subsystem's css from the dummytop and free it - need to free
4264 * before marking as null because ss->destroy needs the cgrp->subsys
4265 * pointer to find their state. note that this also takes care of
4266 * freeing the css_id.
4267 */
4268 ss->destroy(ss, dummytop);
4269 dummytop->subsys[ss->subsys_id] = NULL;
4270
4271 mutex_unlock(&cgroup_mutex);
4272}
4273EXPORT_SYMBOL_GPL(cgroup_unload_subsys);
4274
4275/**
4276 * cgroup_init_early - cgroup initialization at system boot
4277 *
4278 * Initialize cgroups at system boot, and initialize any
4279 * subsystems that request early init.
4280 */
4281int __init cgroup_init_early(void)
4282{
4283 int i;
4284 atomic_set(&init_css_set.refcount, 1);
4285 INIT_LIST_HEAD(&init_css_set.cg_links);
4286 INIT_LIST_HEAD(&init_css_set.tasks);
4287 INIT_HLIST_NODE(&init_css_set.hlist);
4288 css_set_count = 1;
4289 init_cgroup_root(&rootnode);
4290 root_count = 1;
4291 init_task.cgroups = &init_css_set;
4292
4293 init_css_set_link.cg = &init_css_set;
4294 init_css_set_link.cgrp = dummytop;
4295 list_add(&init_css_set_link.cgrp_link_list,
4296 &rootnode.top_cgroup.css_sets);
4297 list_add(&init_css_set_link.cg_link_list,
4298 &init_css_set.cg_links);
4299
4300 for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
4301 INIT_HLIST_HEAD(&css_set_table[i]);
4302
4303 /* at bootup time, we don't worry about modular subsystems */
4304 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4305 struct cgroup_subsys *ss = subsys[i];
4306
4307 BUG_ON(!ss->name);
4308 BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4309 BUG_ON(!ss->create);
4310 BUG_ON(!ss->destroy);
4311 if (ss->subsys_id != i) {
4312 printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4313 ss->name, ss->subsys_id);
4314 BUG();
4315 }
4316
4317 if (ss->early_init)
4318 cgroup_init_subsys(ss);
4319 }
4320 return 0;
4321}
4322
4323/**
4324 * cgroup_init - cgroup initialization
4325 *
4326 * Register cgroup filesystem and /proc file, and initialize
4327 * any subsystems that didn't request early init.
4328 */
4329int __init cgroup_init(void)
4330{
4331 int err;
4332 int i;
4333 struct hlist_head *hhead;
4334
4335 err = bdi_init(&cgroup_backing_dev_info);
4336 if (err)
4337 return err;
4338
4339 /* at bootup time, we don't worry about modular subsystems */
4340 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4341 struct cgroup_subsys *ss = subsys[i];
4342 if (!ss->early_init)
4343 cgroup_init_subsys(ss);
4344 if (ss->use_id)
4345 cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4346 }
4347
4348 /* Add init_css_set to the hash table */
4349 hhead = css_set_hash(init_css_set.subsys);
4350 hlist_add_head(&init_css_set.hlist, hhead);
4351 BUG_ON(!init_root_id(&rootnode));
4352
4353 cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
4354 if (!cgroup_kobj) {
4355 err = -ENOMEM;
4356 goto out;
4357 }
4358
4359 err = register_filesystem(&cgroup_fs_type);
4360 if (err < 0) {
4361 kobject_put(cgroup_kobj);
4362 goto out;
4363 }
4364
4365 proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4366
4367out:
4368 if (err)
4369 bdi_destroy(&cgroup_backing_dev_info);
4370
4371 return err;
4372}
4373
4374/*
4375 * proc_cgroup_show()
4376 * - Print task's cgroup paths into seq_file, one line for each hierarchy
4377 * - Used for /proc/<pid>/cgroup.
4378 * - No need to task_lock(tsk) on this tsk->cgroup reference, as it
4379 * doesn't really matter if tsk->cgroup changes after we read it,
4380 * and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4381 * anyway. No need to check that tsk->cgroup != NULL, thanks to
4382 * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
4383 * cgroup to top_cgroup.
4384 */
4385
4386/* TODO: Use a proper seq_file iterator */
4387static int proc_cgroup_show(struct seq_file *m, void *v)
4388{
4389 struct pid *pid;
4390 struct task_struct *tsk;
4391 char *buf;
4392 int retval;
4393 struct cgroupfs_root *root;
4394
4395 retval = -ENOMEM;
4396 buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4397 if (!buf)
4398 goto out;
4399
4400 retval = -ESRCH;
4401 pid = m->private;
4402 tsk = get_pid_task(pid, PIDTYPE_PID);
4403 if (!tsk)
4404 goto out_free;
4405
4406 retval = 0;
4407
4408 mutex_lock(&cgroup_mutex);
4409
4410 for_each_active_root(root) {
4411 struct cgroup_subsys *ss;
4412 struct cgroup *cgrp;
4413 int count = 0;
4414
4415 seq_printf(m, "%d:", root->hierarchy_id);
4416 for_each_subsys(root, ss)
4417 seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4418 if (strlen(root->name))
4419 seq_printf(m, "%sname=%s", count ? "," : "",
4420 root->name);
4421 seq_putc(m, ':');
4422 cgrp = task_cgroup_from_root(tsk, root);
4423 retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4424 if (retval < 0)
4425 goto out_unlock;
4426 seq_puts(m, buf);
4427 seq_putc(m, '\n');
4428 }
4429
4430out_unlock:
4431 mutex_unlock(&cgroup_mutex);
4432 put_task_struct(tsk);
4433out_free:
4434 kfree(buf);
4435out:
4436 return retval;
4437}
4438
4439static int cgroup_open(struct inode *inode, struct file *file)
4440{
4441 struct pid *pid = PROC_I(inode)->pid;
4442 return single_open(file, proc_cgroup_show, pid);
4443}
4444
4445const struct file_operations proc_cgroup_operations = {
4446 .open = cgroup_open,
4447 .read = seq_read,
4448 .llseek = seq_lseek,
4449 .release = single_release,
4450};
4451
4452/* Display information about each subsystem and each hierarchy */
4453static int proc_cgroupstats_show(struct seq_file *m, void *v)
4454{
4455 int i;
4456
4457 seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
4458 /*
4459 * ideally we don't want subsystems moving around while we do this.
4460 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
4461 * subsys/hierarchy state.
4462 */
4463 mutex_lock(&cgroup_mutex);
4464 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4465 struct cgroup_subsys *ss = subsys[i];
4466 if (ss == NULL)
4467 continue;
4468 seq_printf(m, "%s\t%d\t%d\t%d\n",
4469 ss->name, ss->root->hierarchy_id,
4470 ss->root->number_of_cgroups, !ss->disabled);
4471 }
4472 mutex_unlock(&cgroup_mutex);
4473 return 0;
4474}
4475
4476static int cgroupstats_open(struct inode *inode, struct file *file)
4477{
4478 return single_open(file, proc_cgroupstats_show, NULL);
4479}
4480
4481static const struct file_operations proc_cgroupstats_operations = {
4482 .open = cgroupstats_open,
4483 .read = seq_read,
4484 .llseek = seq_lseek,
4485 .release = single_release,
4486};
4487
4488/**
4489 * cgroup_fork - attach newly forked task to its parents cgroup.
4490 * @child: pointer to task_struct of forking parent process.
4491 *
4492 * Description: A task inherits its parent's cgroup at fork().
4493 *
4494 * A pointer to the shared css_set was automatically copied in
4495 * fork.c by dup_task_struct(). However, we ignore that copy, since
4496 * it was not made under the protection of RCU or cgroup_mutex, so
4497 * might no longer be a valid cgroup pointer. cgroup_attach_task() might
4498 * have already changed current->cgroups, allowing the previously
4499 * referenced cgroup group to be removed and freed.
4500 *
4501 * At the point that cgroup_fork() is called, 'current' is the parent
4502 * task, and the passed argument 'child' points to the child task.
4503 */
4504void cgroup_fork(struct task_struct *child)
4505{
4506 task_lock(current);
4507 child->cgroups = current->cgroups;
4508 get_css_set(child->cgroups);
4509 task_unlock(current);
4510 INIT_LIST_HEAD(&child->cg_list);
4511}
4512
4513/**
4514 * cgroup_fork_callbacks - run fork callbacks
4515 * @child: the new task
4516 *
4517 * Called on a new task very soon before adding it to the
4518 * tasklist. No need to take any locks since no-one can
4519 * be operating on this task.
4520 */
4521void cgroup_fork_callbacks(struct task_struct *child)
4522{
4523 if (need_forkexit_callback) {
4524 int i;
4525 /*
4526 * forkexit callbacks are only supported for builtin
4527 * subsystems, and the builtin section of the subsys array is
4528 * immutable, so we don't need to lock the subsys array here.
4529 */
4530 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4531 struct cgroup_subsys *ss = subsys[i];
4532 if (ss->fork)
4533 ss->fork(ss, child);
4534 }
4535 }
4536}
4537
4538/**
4539 * cgroup_post_fork - called on a new task after adding it to the task list
4540 * @child: the task in question
4541 *
4542 * Adds the task to the list running through its css_set if necessary.
4543 * Has to be after the task is visible on the task list in case we race
4544 * with the first call to cgroup_iter_start() - to guarantee that the
4545 * new task ends up on its list.
4546 */
4547void cgroup_post_fork(struct task_struct *child)
4548{
4549 if (use_task_css_set_links) {
4550 write_lock(&css_set_lock);
4551 task_lock(child);
4552 if (list_empty(&child->cg_list))
4553 list_add(&child->cg_list, &child->cgroups->tasks);
4554 task_unlock(child);
4555 write_unlock(&css_set_lock);
4556 }
4557}
4558/**
4559 * cgroup_exit - detach cgroup from exiting task
4560 * @tsk: pointer to task_struct of exiting process
4561 * @run_callback: run exit callbacks?
4562 *
4563 * Description: Detach cgroup from @tsk and release it.
4564 *
4565 * Note that cgroups marked notify_on_release force every task in
4566 * them to take the global cgroup_mutex mutex when exiting.
4567 * This could impact scaling on very large systems. Be reluctant to
4568 * use notify_on_release cgroups where very high task exit scaling
4569 * is required on large systems.
4570 *
4571 * the_top_cgroup_hack:
4572 *
4573 * Set the exiting tasks cgroup to the root cgroup (top_cgroup).
4574 *
4575 * We call cgroup_exit() while the task is still competent to
4576 * handle notify_on_release(), then leave the task attached to the
4577 * root cgroup in each hierarchy for the remainder of its exit.
4578 *
4579 * To do this properly, we would increment the reference count on
4580 * top_cgroup, and near the very end of the kernel/exit.c do_exit()
4581 * code we would add a second cgroup function call, to drop that
4582 * reference. This would just create an unnecessary hot spot on
4583 * the top_cgroup reference count, to no avail.
4584 *
4585 * Normally, holding a reference to a cgroup without bumping its
4586 * count is unsafe. The cgroup could go away, or someone could
4587 * attach us to a different cgroup, decrementing the count on
4588 * the first cgroup that we never incremented. But in this case,
4589 * top_cgroup isn't going away, and either task has PF_EXITING set,
4590 * which wards off any cgroup_attach_task() attempts, or task is a failed
4591 * fork, never visible to cgroup_attach_task.
4592 */
4593void cgroup_exit(struct task_struct *tsk, int run_callbacks)
4594{
4595 struct css_set *cg;
4596 int i;
4597
4598 /*
4599 * Unlink from the css_set task list if necessary.
4600 * Optimistically check cg_list before taking
4601 * css_set_lock
4602 */
4603 if (!list_empty(&tsk->cg_list)) {
4604 write_lock(&css_set_lock);
4605 if (!list_empty(&tsk->cg_list))
4606 list_del_init(&tsk->cg_list);
4607 write_unlock(&css_set_lock);
4608 }
4609
4610 /* Reassign the task to the init_css_set. */
4611 task_lock(tsk);
4612 cg = tsk->cgroups;
4613 tsk->cgroups = &init_css_set;
4614
4615 if (run_callbacks && need_forkexit_callback) {
4616 /*
4617 * modular subsystems can't use callbacks, so no need to lock
4618 * the subsys array
4619 */
4620 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4621 struct cgroup_subsys *ss = subsys[i];
4622 if (ss->exit) {
4623 struct cgroup *old_cgrp =
4624 rcu_dereference_raw(cg->subsys[i])->cgroup;
4625 struct cgroup *cgrp = task_cgroup(tsk, i);
4626 ss->exit(ss, cgrp, old_cgrp, tsk);
4627 }
4628 }
4629 }
4630 task_unlock(tsk);
4631
4632 if (cg)
4633 put_css_set_taskexit(cg);
4634}
4635
4636/**
4637 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
4638 * @cgrp: the cgroup in question
4639 * @task: the task in question
4640 *
4641 * See if @cgrp is a descendant of @task's cgroup in the appropriate
4642 * hierarchy.
4643 *
4644 * If we are sending in dummytop, then presumably we are creating
4645 * the top cgroup in the subsystem.
4646 *
4647 * Called only by the ns (nsproxy) cgroup.
4648 */
4649int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
4650{
4651 int ret;
4652 struct cgroup *target;
4653
4654 if (cgrp == dummytop)
4655 return 1;
4656
4657 target = task_cgroup_from_root(task, cgrp->root);
4658 while (cgrp != target && cgrp!= cgrp->top_cgroup)
4659 cgrp = cgrp->parent;
4660 ret = (cgrp == target);
4661 return ret;
4662}
4663
4664static void check_for_release(struct cgroup *cgrp)
4665{
4666 /* All of these checks rely on RCU to keep the cgroup
4667 * structure alive */
4668 if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
4669 && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
4670 /* Control Group is currently removeable. If it's not
4671 * already queued for a userspace notification, queue
4672 * it now */
4673 int need_schedule_work = 0;
4674 spin_lock(&release_list_lock);
4675 if (!cgroup_is_removed(cgrp) &&
4676 list_empty(&cgrp->release_list)) {
4677 list_add(&cgrp->release_list, &release_list);
4678 need_schedule_work = 1;
4679 }
4680 spin_unlock(&release_list_lock);
4681 if (need_schedule_work)
4682 schedule_work(&release_agent_work);
4683 }
4684}
4685
4686/* Caller must verify that the css is not for root cgroup */
4687void __css_put(struct cgroup_subsys_state *css, int count)
4688{
4689 struct cgroup *cgrp = css->cgroup;
4690 int val;
4691 rcu_read_lock();
4692 val = atomic_sub_return(count, &css->refcnt);
4693 if (val == 1) {
4694 if (notify_on_release(cgrp)) {
4695 set_bit(CGRP_RELEASABLE, &cgrp->flags);
4696 check_for_release(cgrp);
4697 }
4698 cgroup_wakeup_rmdir_waiter(cgrp);
4699 }
4700 rcu_read_unlock();
4701 WARN_ON_ONCE(val < 1);
4702}
4703EXPORT_SYMBOL_GPL(__css_put);
4704
4705/*
4706 * Notify userspace when a cgroup is released, by running the
4707 * configured release agent with the name of the cgroup (path
4708 * relative to the root of cgroup file system) as the argument.
4709 *
4710 * Most likely, this user command will try to rmdir this cgroup.
4711 *
4712 * This races with the possibility that some other task will be
4713 * attached to this cgroup before it is removed, or that some other
4714 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
4715 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
4716 * unused, and this cgroup will be reprieved from its death sentence,
4717 * to continue to serve a useful existence. Next time it's released,
4718 * we will get notified again, if it still has 'notify_on_release' set.
4719 *
4720 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
4721 * means only wait until the task is successfully execve()'d. The
4722 * separate release agent task is forked by call_usermodehelper(),
4723 * then control in this thread returns here, without waiting for the
4724 * release agent task. We don't bother to wait because the caller of
4725 * this routine has no use for the exit status of the release agent
4726 * task, so no sense holding our caller up for that.
4727 */
4728static void cgroup_release_agent(struct work_struct *work)
4729{
4730 BUG_ON(work != &release_agent_work);
4731 mutex_lock(&cgroup_mutex);
4732 spin_lock(&release_list_lock);
4733 while (!list_empty(&release_list)) {
4734 char *argv[3], *envp[3];
4735 int i;
4736 char *pathbuf = NULL, *agentbuf = NULL;
4737 struct cgroup *cgrp = list_entry(release_list.next,
4738 struct cgroup,
4739 release_list);
4740 list_del_init(&cgrp->release_list);
4741 spin_unlock(&release_list_lock);
4742 pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4743 if (!pathbuf)
4744 goto continue_free;
4745 if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
4746 goto continue_free;
4747 agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
4748 if (!agentbuf)
4749 goto continue_free;
4750
4751 i = 0;
4752 argv[i++] = agentbuf;
4753 argv[i++] = pathbuf;
4754 argv[i] = NULL;
4755
4756 i = 0;
4757 /* minimal command environment */
4758 envp[i++] = "HOME=/";
4759 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
4760 envp[i] = NULL;
4761
4762 /* Drop the lock while we invoke the usermode helper,
4763 * since the exec could involve hitting disk and hence
4764 * be a slow process */
4765 mutex_unlock(&cgroup_mutex);
4766 call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
4767 mutex_lock(&cgroup_mutex);
4768 continue_free:
4769 kfree(pathbuf);
4770 kfree(agentbuf);
4771 spin_lock(&release_list_lock);
4772 }
4773 spin_unlock(&release_list_lock);
4774 mutex_unlock(&cgroup_mutex);
4775}
4776
4777static int __init cgroup_disable(char *str)
4778{
4779 int i;
4780 char *token;
4781
4782 while ((token = strsep(&str, ",")) != NULL) {
4783 if (!*token)
4784 continue;
4785 /*
4786 * cgroup_disable, being at boot time, can't know about module
4787 * subsystems, so we don't worry about them.
4788 */
4789 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4790 struct cgroup_subsys *ss = subsys[i];
4791
4792 if (!strcmp(token, ss->name)) {
4793 ss->disabled = 1;
4794 printk(KERN_INFO "Disabling %s control group"
4795 " subsystem\n", ss->name);
4796 break;
4797 }
4798 }
4799 }
4800 return 1;
4801}
4802__setup("cgroup_disable=", cgroup_disable);
4803
4804/*
4805 * Functons for CSS ID.
4806 */
4807
4808/*
4809 *To get ID other than 0, this should be called when !cgroup_is_removed().
4810 */
4811unsigned short css_id(struct cgroup_subsys_state *css)
4812{
4813 struct css_id *cssid;
4814
4815 /*
4816 * This css_id() can return correct value when somone has refcnt
4817 * on this or this is under rcu_read_lock(). Once css->id is allocated,
4818 * it's unchanged until freed.
4819 */
4820 cssid = rcu_dereference_check(css->id, atomic_read(&css->refcnt));
4821
4822 if (cssid)
4823 return cssid->id;
4824 return 0;
4825}
4826EXPORT_SYMBOL_GPL(css_id);
4827
4828unsigned short css_depth(struct cgroup_subsys_state *css)
4829{
4830 struct css_id *cssid;
4831
4832 cssid = rcu_dereference_check(css->id, atomic_read(&css->refcnt));
4833
4834 if (cssid)
4835 return cssid->depth;
4836 return 0;
4837}
4838EXPORT_SYMBOL_GPL(css_depth);
4839
4840/**
4841 * css_is_ancestor - test "root" css is an ancestor of "child"
4842 * @child: the css to be tested.
4843 * @root: the css supporsed to be an ancestor of the child.
4844 *
4845 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
4846 * this function reads css->id, this use rcu_dereference() and rcu_read_lock().
4847 * But, considering usual usage, the csses should be valid objects after test.
4848 * Assuming that the caller will do some action to the child if this returns
4849 * returns true, the caller must take "child";s reference count.
4850 * If "child" is valid object and this returns true, "root" is valid, too.
4851 */
4852
4853bool css_is_ancestor(struct cgroup_subsys_state *child,
4854 const struct cgroup_subsys_state *root)
4855{
4856 struct css_id *child_id;
4857 struct css_id *root_id;
4858 bool ret = true;
4859
4860 rcu_read_lock();
4861 child_id = rcu_dereference(child->id);
4862 root_id = rcu_dereference(root->id);
4863 if (!child_id
4864 || !root_id
4865 || (child_id->depth < root_id->depth)
4866 || (child_id->stack[root_id->depth] != root_id->id))
4867 ret = false;
4868 rcu_read_unlock();
4869 return ret;
4870}
4871
4872void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
4873{
4874 struct css_id *id = css->id;
4875 /* When this is called before css_id initialization, id can be NULL */
4876 if (!id)
4877 return;
4878
4879 BUG_ON(!ss->use_id);
4880
4881 rcu_assign_pointer(id->css, NULL);
4882 rcu_assign_pointer(css->id, NULL);
4883 spin_lock(&ss->id_lock);
4884 idr_remove(&ss->idr, id->id);
4885 spin_unlock(&ss->id_lock);
4886 kfree_rcu(id, rcu_head);
4887}
4888EXPORT_SYMBOL_GPL(free_css_id);
4889
4890/*
4891 * This is called by init or create(). Then, calls to this function are
4892 * always serialized (By cgroup_mutex() at create()).
4893 */
4894
4895static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
4896{
4897 struct css_id *newid;
4898 int myid, error, size;
4899
4900 BUG_ON(!ss->use_id);
4901
4902 size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
4903 newid = kzalloc(size, GFP_KERNEL);
4904 if (!newid)
4905 return ERR_PTR(-ENOMEM);
4906 /* get id */
4907 if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
4908 error = -ENOMEM;
4909 goto err_out;
4910 }
4911 spin_lock(&ss->id_lock);
4912 /* Don't use 0. allocates an ID of 1-65535 */
4913 error = idr_get_new_above(&ss->idr, newid, 1, &myid);
4914 spin_unlock(&ss->id_lock);
4915
4916 /* Returns error when there are no free spaces for new ID.*/
4917 if (error) {
4918 error = -ENOSPC;
4919 goto err_out;
4920 }
4921 if (myid > CSS_ID_MAX)
4922 goto remove_idr;
4923
4924 newid->id = myid;
4925 newid->depth = depth;
4926 return newid;
4927remove_idr:
4928 error = -ENOSPC;
4929 spin_lock(&ss->id_lock);
4930 idr_remove(&ss->idr, myid);
4931 spin_unlock(&ss->id_lock);
4932err_out:
4933 kfree(newid);
4934 return ERR_PTR(error);
4935
4936}
4937
4938static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
4939 struct cgroup_subsys_state *rootcss)
4940{
4941 struct css_id *newid;
4942
4943 spin_lock_init(&ss->id_lock);
4944 idr_init(&ss->idr);
4945
4946 newid = get_new_cssid(ss, 0);
4947 if (IS_ERR(newid))
4948 return PTR_ERR(newid);
4949
4950 newid->stack[0] = newid->id;
4951 newid->css = rootcss;
4952 rootcss->id = newid;
4953 return 0;
4954}
4955
4956static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
4957 struct cgroup *child)
4958{
4959 int subsys_id, i, depth = 0;
4960 struct cgroup_subsys_state *parent_css, *child_css;
4961 struct css_id *child_id, *parent_id;
4962
4963 subsys_id = ss->subsys_id;
4964 parent_css = parent->subsys[subsys_id];
4965 child_css = child->subsys[subsys_id];
4966 parent_id = parent_css->id;
4967 depth = parent_id->depth + 1;
4968
4969 child_id = get_new_cssid(ss, depth);
4970 if (IS_ERR(child_id))
4971 return PTR_ERR(child_id);
4972
4973 for (i = 0; i < depth; i++)
4974 child_id->stack[i] = parent_id->stack[i];
4975 child_id->stack[depth] = child_id->id;
4976 /*
4977 * child_id->css pointer will be set after this cgroup is available
4978 * see cgroup_populate_dir()
4979 */
4980 rcu_assign_pointer(child_css->id, child_id);
4981
4982 return 0;
4983}
4984
4985/**
4986 * css_lookup - lookup css by id
4987 * @ss: cgroup subsys to be looked into.
4988 * @id: the id
4989 *
4990 * Returns pointer to cgroup_subsys_state if there is valid one with id.
4991 * NULL if not. Should be called under rcu_read_lock()
4992 */
4993struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
4994{
4995 struct css_id *cssid = NULL;
4996
4997 BUG_ON(!ss->use_id);
4998 cssid = idr_find(&ss->idr, id);
4999
5000 if (unlikely(!cssid))
5001 return NULL;
5002
5003 return rcu_dereference(cssid->css);
5004}
5005EXPORT_SYMBOL_GPL(css_lookup);
5006
5007/**
5008 * css_get_next - lookup next cgroup under specified hierarchy.
5009 * @ss: pointer to subsystem
5010 * @id: current position of iteration.
5011 * @root: pointer to css. search tree under this.
5012 * @foundid: position of found object.
5013 *
5014 * Search next css under the specified hierarchy of rootid. Calling under
5015 * rcu_read_lock() is necessary. Returns NULL if it reaches the end.
5016 */
5017struct cgroup_subsys_state *
5018css_get_next(struct cgroup_subsys *ss, int id,
5019 struct cgroup_subsys_state *root, int *foundid)
5020{
5021 struct cgroup_subsys_state *ret = NULL;
5022 struct css_id *tmp;
5023 int tmpid;
5024 int rootid = css_id(root);
5025 int depth = css_depth(root);
5026
5027 if (!rootid)
5028 return NULL;
5029
5030 BUG_ON(!ss->use_id);
5031 /* fill start point for scan */
5032 tmpid = id;
5033 while (1) {
5034 /*
5035 * scan next entry from bitmap(tree), tmpid is updated after
5036 * idr_get_next().
5037 */
5038 spin_lock(&ss->id_lock);
5039 tmp = idr_get_next(&ss->idr, &tmpid);
5040 spin_unlock(&ss->id_lock);
5041
5042 if (!tmp)
5043 break;
5044 if (tmp->depth >= depth && tmp->stack[depth] == rootid) {
5045 ret = rcu_dereference(tmp->css);
5046 if (ret) {
5047 *foundid = tmpid;
5048 break;
5049 }
5050 }
5051 /* continue to scan from next id */
5052 tmpid = tmpid + 1;
5053 }
5054 return ret;
5055}
5056
5057/*
5058 * get corresponding css from file open on cgroupfs directory
5059 */
5060struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
5061{
5062 struct cgroup *cgrp;
5063 struct inode *inode;
5064 struct cgroup_subsys_state *css;
5065
5066 inode = f->f_dentry->d_inode;
5067 /* check in cgroup filesystem dir */
5068 if (inode->i_op != &cgroup_dir_inode_operations)
5069 return ERR_PTR(-EBADF);
5070
5071 if (id < 0 || id >= CGROUP_SUBSYS_COUNT)
5072 return ERR_PTR(-EINVAL);
5073
5074 /* get cgroup */
5075 cgrp = __d_cgrp(f->f_dentry);
5076 css = cgrp->subsys[id];
5077 return css ? css : ERR_PTR(-ENOENT);
5078}
5079
5080#ifdef CONFIG_CGROUP_DEBUG
5081static struct cgroup_subsys_state *debug_create(struct cgroup_subsys *ss,
5082 struct cgroup *cont)
5083{
5084 struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
5085
5086 if (!css)
5087 return ERR_PTR(-ENOMEM);
5088
5089 return css;
5090}
5091
5092static void debug_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
5093{
5094 kfree(cont->subsys[debug_subsys_id]);
5095}
5096
5097static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
5098{
5099 return atomic_read(&cont->count);
5100}
5101
5102static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft)
5103{
5104 return cgroup_task_count(cont);
5105}
5106
5107static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
5108{
5109 return (u64)(unsigned long)current->cgroups;
5110}
5111
5112static u64 current_css_set_refcount_read(struct cgroup *cont,
5113 struct cftype *cft)
5114{
5115 u64 count;
5116
5117 rcu_read_lock();
5118 count = atomic_read(¤t->cgroups->refcount);
5119 rcu_read_unlock();
5120 return count;
5121}
5122
5123static int current_css_set_cg_links_read(struct cgroup *cont,
5124 struct cftype *cft,
5125 struct seq_file *seq)
5126{
5127 struct cg_cgroup_link *link;
5128 struct css_set *cg;
5129
5130 read_lock(&css_set_lock);
5131 rcu_read_lock();
5132 cg = rcu_dereference(current->cgroups);
5133 list_for_each_entry(link, &cg->cg_links, cg_link_list) {
5134 struct cgroup *c = link->cgrp;
5135 const char *name;
5136
5137 if (c->dentry)
5138 name = c->dentry->d_name.name;
5139 else
5140 name = "?";
5141 seq_printf(seq, "Root %d group %s\n",
5142 c->root->hierarchy_id, name);
5143 }
5144 rcu_read_unlock();
5145 read_unlock(&css_set_lock);
5146 return 0;
5147}
5148
5149#define MAX_TASKS_SHOWN_PER_CSS 25
5150static int cgroup_css_links_read(struct cgroup *cont,
5151 struct cftype *cft,
5152 struct seq_file *seq)
5153{
5154 struct cg_cgroup_link *link;
5155
5156 read_lock(&css_set_lock);
5157 list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
5158 struct css_set *cg = link->cg;
5159 struct task_struct *task;
5160 int count = 0;
5161 seq_printf(seq, "css_set %p\n", cg);
5162 list_for_each_entry(task, &cg->tasks, cg_list) {
5163 if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
5164 seq_puts(seq, " ...\n");
5165 break;
5166 } else {
5167 seq_printf(seq, " task %d\n",
5168 task_pid_vnr(task));
5169 }
5170 }
5171 }
5172 read_unlock(&css_set_lock);
5173 return 0;
5174}
5175
5176static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
5177{
5178 return test_bit(CGRP_RELEASABLE, &cgrp->flags);
5179}
5180
5181static struct cftype debug_files[] = {
5182 {
5183 .name = "cgroup_refcount",
5184 .read_u64 = cgroup_refcount_read,
5185 },
5186 {
5187 .name = "taskcount",
5188 .read_u64 = debug_taskcount_read,
5189 },
5190
5191 {
5192 .name = "current_css_set",
5193 .read_u64 = current_css_set_read,
5194 },
5195
5196 {
5197 .name = "current_css_set_refcount",
5198 .read_u64 = current_css_set_refcount_read,
5199 },
5200
5201 {
5202 .name = "current_css_set_cg_links",
5203 .read_seq_string = current_css_set_cg_links_read,
5204 },
5205
5206 {
5207 .name = "cgroup_css_links",
5208 .read_seq_string = cgroup_css_links_read,
5209 },
5210
5211 {
5212 .name = "releasable",
5213 .read_u64 = releasable_read,
5214 },
5215};
5216
5217static int debug_populate(struct cgroup_subsys *ss, struct cgroup *cont)
5218{
5219 return cgroup_add_files(cont, ss, debug_files,
5220 ARRAY_SIZE(debug_files));
5221}
5222
5223struct cgroup_subsys debug_subsys = {
5224 .name = "debug",
5225 .create = debug_create,
5226 .destroy = debug_destroy,
5227 .populate = debug_populate,
5228 .subsys_id = debug_subsys_id,
5229};
5230#endif /* CONFIG_CGROUP_DEBUG */