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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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
30
31#include "cgroup-internal.h"
32
33#include <linux/bpf-cgroup.h>
34#include <linux/cred.h>
35#include <linux/errno.h>
36#include <linux/init_task.h>
37#include <linux/kernel.h>
38#include <linux/magic.h>
39#include <linux/mutex.h>
40#include <linux/mount.h>
41#include <linux/pagemap.h>
42#include <linux/proc_fs.h>
43#include <linux/rcupdate.h>
44#include <linux/sched.h>
45#include <linux/sched/task.h>
46#include <linux/slab.h>
47#include <linux/spinlock.h>
48#include <linux/percpu-rwsem.h>
49#include <linux/string.h>
50#include <linux/hashtable.h>
51#include <linux/idr.h>
52#include <linux/kthread.h>
53#include <linux/atomic.h>
54#include <linux/cpuset.h>
55#include <linux/proc_ns.h>
56#include <linux/nsproxy.h>
57#include <linux/file.h>
58#include <linux/fs_parser.h>
59#include <linux/sched/cputime.h>
60#include <linux/psi.h>
61#include <net/sock.h>
62
63#define CREATE_TRACE_POINTS
64#include <trace/events/cgroup.h>
65
66#define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
67 MAX_CFTYPE_NAME + 2)
68/* let's not notify more than 100 times per second */
69#define CGROUP_FILE_NOTIFY_MIN_INTV DIV_ROUND_UP(HZ, 100)
70
71/*
72 * To avoid confusing the compiler (and generating warnings) with code
73 * that attempts to access what would be a 0-element array (i.e. sized
74 * to a potentially empty array when CGROUP_SUBSYS_COUNT == 0), this
75 * constant expression can be added.
76 */
77#define CGROUP_HAS_SUBSYS_CONFIG (CGROUP_SUBSYS_COUNT > 0)
78
79/*
80 * cgroup_mutex is the master lock. Any modification to cgroup or its
81 * hierarchy must be performed while holding it.
82 *
83 * css_set_lock protects task->cgroups pointer, the list of css_set
84 * objects, and the chain of tasks off each css_set.
85 *
86 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
87 * cgroup.h can use them for lockdep annotations.
88 */
89DEFINE_MUTEX(cgroup_mutex);
90DEFINE_SPINLOCK(css_set_lock);
91
92#ifdef CONFIG_PROVE_RCU
93EXPORT_SYMBOL_GPL(cgroup_mutex);
94EXPORT_SYMBOL_GPL(css_set_lock);
95#endif
96
97DEFINE_SPINLOCK(trace_cgroup_path_lock);
98char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
99static bool cgroup_debug __read_mostly;
100
101/*
102 * Protects cgroup_idr and css_idr so that IDs can be released without
103 * grabbing cgroup_mutex.
104 */
105static DEFINE_SPINLOCK(cgroup_idr_lock);
106
107/*
108 * Protects cgroup_file->kn for !self csses. It synchronizes notifications
109 * against file removal/re-creation across css hiding.
110 */
111static DEFINE_SPINLOCK(cgroup_file_kn_lock);
112
113DEFINE_PERCPU_RWSEM(cgroup_threadgroup_rwsem);
114
115#define cgroup_assert_mutex_or_rcu_locked() \
116 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
117 !lockdep_is_held(&cgroup_mutex), \
118 "cgroup_mutex or RCU read lock required");
119
120/*
121 * cgroup destruction makes heavy use of work items and there can be a lot
122 * of concurrent destructions. Use a separate workqueue so that cgroup
123 * destruction work items don't end up filling up max_active of system_wq
124 * which may lead to deadlock.
125 */
126static struct workqueue_struct *cgroup_destroy_wq;
127
128/* generate an array of cgroup subsystem pointers */
129#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
130struct cgroup_subsys *cgroup_subsys[] = {
131#include <linux/cgroup_subsys.h>
132};
133#undef SUBSYS
134
135/* array of cgroup subsystem names */
136#define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
137static const char *cgroup_subsys_name[] = {
138#include <linux/cgroup_subsys.h>
139};
140#undef SUBSYS
141
142/* array of static_keys for cgroup_subsys_enabled() and cgroup_subsys_on_dfl() */
143#define SUBSYS(_x) \
144 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key); \
145 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key); \
146 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key); \
147 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key);
148#include <linux/cgroup_subsys.h>
149#undef SUBSYS
150
151#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_enabled_key,
152static struct static_key_true *cgroup_subsys_enabled_key[] = {
153#include <linux/cgroup_subsys.h>
154};
155#undef SUBSYS
156
157#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_on_dfl_key,
158static struct static_key_true *cgroup_subsys_on_dfl_key[] = {
159#include <linux/cgroup_subsys.h>
160};
161#undef SUBSYS
162
163static DEFINE_PER_CPU(struct cgroup_rstat_cpu, cgrp_dfl_root_rstat_cpu);
164
165/* the default hierarchy */
166struct cgroup_root cgrp_dfl_root = { .cgrp.rstat_cpu = &cgrp_dfl_root_rstat_cpu };
167EXPORT_SYMBOL_GPL(cgrp_dfl_root);
168
169/*
170 * The default hierarchy always exists but is hidden until mounted for the
171 * first time. This is for backward compatibility.
172 */
173static bool cgrp_dfl_visible;
174
175/* some controllers are not supported in the default hierarchy */
176static u16 cgrp_dfl_inhibit_ss_mask;
177
178/* some controllers are implicitly enabled on the default hierarchy */
179static u16 cgrp_dfl_implicit_ss_mask;
180
181/* some controllers can be threaded on the default hierarchy */
182static u16 cgrp_dfl_threaded_ss_mask;
183
184/* The list of hierarchy roots */
185LIST_HEAD(cgroup_roots);
186static int cgroup_root_count;
187
188/* hierarchy ID allocation and mapping, protected by cgroup_mutex */
189static DEFINE_IDR(cgroup_hierarchy_idr);
190
191/*
192 * Assign a monotonically increasing serial number to csses. It guarantees
193 * cgroups with bigger numbers are newer than those with smaller numbers.
194 * Also, as csses are always appended to the parent's ->children list, it
195 * guarantees that sibling csses are always sorted in the ascending serial
196 * number order on the list. Protected by cgroup_mutex.
197 */
198static u64 css_serial_nr_next = 1;
199
200/*
201 * These bitmasks identify subsystems with specific features to avoid
202 * having to do iterative checks repeatedly.
203 */
204static u16 have_fork_callback __read_mostly;
205static u16 have_exit_callback __read_mostly;
206static u16 have_release_callback __read_mostly;
207static u16 have_canfork_callback __read_mostly;
208
209/* cgroup namespace for init task */
210struct cgroup_namespace init_cgroup_ns = {
211 .ns.count = REFCOUNT_INIT(2),
212 .user_ns = &init_user_ns,
213 .ns.ops = &cgroupns_operations,
214 .ns.inum = PROC_CGROUP_INIT_INO,
215 .root_cset = &init_css_set,
216};
217
218static struct file_system_type cgroup2_fs_type;
219static struct cftype cgroup_base_files[];
220static struct cftype cgroup_psi_files[];
221
222/* cgroup optional features */
223enum cgroup_opt_features {
224#ifdef CONFIG_PSI
225 OPT_FEATURE_PRESSURE,
226#endif
227 OPT_FEATURE_COUNT
228};
229
230static const char *cgroup_opt_feature_names[OPT_FEATURE_COUNT] = {
231#ifdef CONFIG_PSI
232 "pressure",
233#endif
234};
235
236static u16 cgroup_feature_disable_mask __read_mostly;
237
238static int cgroup_apply_control(struct cgroup *cgrp);
239static void cgroup_finalize_control(struct cgroup *cgrp, int ret);
240static void css_task_iter_skip(struct css_task_iter *it,
241 struct task_struct *task);
242static int cgroup_destroy_locked(struct cgroup *cgrp);
243static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
244 struct cgroup_subsys *ss);
245static void css_release(struct percpu_ref *ref);
246static void kill_css(struct cgroup_subsys_state *css);
247static int cgroup_addrm_files(struct cgroup_subsys_state *css,
248 struct cgroup *cgrp, struct cftype cfts[],
249 bool is_add);
250
251#ifdef CONFIG_DEBUG_CGROUP_REF
252#define CGROUP_REF_FN_ATTRS noinline
253#define CGROUP_REF_EXPORT(fn) EXPORT_SYMBOL_GPL(fn);
254#include <linux/cgroup_refcnt.h>
255#endif
256
257/**
258 * cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID
259 * @ssid: subsys ID of interest
260 *
261 * cgroup_subsys_enabled() can only be used with literal subsys names which
262 * is fine for individual subsystems but unsuitable for cgroup core. This
263 * is slower static_key_enabled() based test indexed by @ssid.
264 */
265bool cgroup_ssid_enabled(int ssid)
266{
267 if (!CGROUP_HAS_SUBSYS_CONFIG)
268 return false;
269
270 return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
271}
272
273/**
274 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
275 * @cgrp: the cgroup of interest
276 *
277 * The default hierarchy is the v2 interface of cgroup and this function
278 * can be used to test whether a cgroup is on the default hierarchy for
279 * cases where a subsystem should behave differently depending on the
280 * interface version.
281 *
282 * List of changed behaviors:
283 *
284 * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
285 * and "name" are disallowed.
286 *
287 * - When mounting an existing superblock, mount options should match.
288 *
289 * - rename(2) is disallowed.
290 *
291 * - "tasks" is removed. Everything should be at process granularity. Use
292 * "cgroup.procs" instead.
293 *
294 * - "cgroup.procs" is not sorted. pids will be unique unless they got
295 * recycled in-between reads.
296 *
297 * - "release_agent" and "notify_on_release" are removed. Replacement
298 * notification mechanism will be implemented.
299 *
300 * - "cgroup.clone_children" is removed.
301 *
302 * - "cgroup.subtree_populated" is available. Its value is 0 if the cgroup
303 * and its descendants contain no task; otherwise, 1. The file also
304 * generates kernfs notification which can be monitored through poll and
305 * [di]notify when the value of the file changes.
306 *
307 * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
308 * take masks of ancestors with non-empty cpus/mems, instead of being
309 * moved to an ancestor.
310 *
311 * - cpuset: a task can be moved into an empty cpuset, and again it takes
312 * masks of ancestors.
313 *
314 * - blkcg: blk-throttle becomes properly hierarchical.
315 *
316 * - debug: disallowed on the default hierarchy.
317 */
318bool cgroup_on_dfl(const struct cgroup *cgrp)
319{
320 return cgrp->root == &cgrp_dfl_root;
321}
322
323/* IDR wrappers which synchronize using cgroup_idr_lock */
324static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
325 gfp_t gfp_mask)
326{
327 int ret;
328
329 idr_preload(gfp_mask);
330 spin_lock_bh(&cgroup_idr_lock);
331 ret = idr_alloc(idr, ptr, start, end, gfp_mask & ~__GFP_DIRECT_RECLAIM);
332 spin_unlock_bh(&cgroup_idr_lock);
333 idr_preload_end();
334 return ret;
335}
336
337static void *cgroup_idr_replace(struct idr *idr, void *ptr, int id)
338{
339 void *ret;
340
341 spin_lock_bh(&cgroup_idr_lock);
342 ret = idr_replace(idr, ptr, id);
343 spin_unlock_bh(&cgroup_idr_lock);
344 return ret;
345}
346
347static void cgroup_idr_remove(struct idr *idr, int id)
348{
349 spin_lock_bh(&cgroup_idr_lock);
350 idr_remove(idr, id);
351 spin_unlock_bh(&cgroup_idr_lock);
352}
353
354static bool cgroup_has_tasks(struct cgroup *cgrp)
355{
356 return cgrp->nr_populated_csets;
357}
358
359bool cgroup_is_threaded(struct cgroup *cgrp)
360{
361 return cgrp->dom_cgrp != cgrp;
362}
363
364/* can @cgrp host both domain and threaded children? */
365static bool cgroup_is_mixable(struct cgroup *cgrp)
366{
367 /*
368 * Root isn't under domain level resource control exempting it from
369 * the no-internal-process constraint, so it can serve as a thread
370 * root and a parent of resource domains at the same time.
371 */
372 return !cgroup_parent(cgrp);
373}
374
375/* can @cgrp become a thread root? Should always be true for a thread root */
376static bool cgroup_can_be_thread_root(struct cgroup *cgrp)
377{
378 /* mixables don't care */
379 if (cgroup_is_mixable(cgrp))
380 return true;
381
382 /* domain roots can't be nested under threaded */
383 if (cgroup_is_threaded(cgrp))
384 return false;
385
386 /* can only have either domain or threaded children */
387 if (cgrp->nr_populated_domain_children)
388 return false;
389
390 /* and no domain controllers can be enabled */
391 if (cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)
392 return false;
393
394 return true;
395}
396
397/* is @cgrp root of a threaded subtree? */
398bool cgroup_is_thread_root(struct cgroup *cgrp)
399{
400 /* thread root should be a domain */
401 if (cgroup_is_threaded(cgrp))
402 return false;
403
404 /* a domain w/ threaded children is a thread root */
405 if (cgrp->nr_threaded_children)
406 return true;
407
408 /*
409 * A domain which has tasks and explicit threaded controllers
410 * enabled is a thread root.
411 */
412 if (cgroup_has_tasks(cgrp) &&
413 (cgrp->subtree_control & cgrp_dfl_threaded_ss_mask))
414 return true;
415
416 return false;
417}
418
419/* a domain which isn't connected to the root w/o brekage can't be used */
420static bool cgroup_is_valid_domain(struct cgroup *cgrp)
421{
422 /* the cgroup itself can be a thread root */
423 if (cgroup_is_threaded(cgrp))
424 return false;
425
426 /* but the ancestors can't be unless mixable */
427 while ((cgrp = cgroup_parent(cgrp))) {
428 if (!cgroup_is_mixable(cgrp) && cgroup_is_thread_root(cgrp))
429 return false;
430 if (cgroup_is_threaded(cgrp))
431 return false;
432 }
433
434 return true;
435}
436
437/* subsystems visibly enabled on a cgroup */
438static u16 cgroup_control(struct cgroup *cgrp)
439{
440 struct cgroup *parent = cgroup_parent(cgrp);
441 u16 root_ss_mask = cgrp->root->subsys_mask;
442
443 if (parent) {
444 u16 ss_mask = parent->subtree_control;
445
446 /* threaded cgroups can only have threaded controllers */
447 if (cgroup_is_threaded(cgrp))
448 ss_mask &= cgrp_dfl_threaded_ss_mask;
449 return ss_mask;
450 }
451
452 if (cgroup_on_dfl(cgrp))
453 root_ss_mask &= ~(cgrp_dfl_inhibit_ss_mask |
454 cgrp_dfl_implicit_ss_mask);
455 return root_ss_mask;
456}
457
458/* subsystems enabled on a cgroup */
459static u16 cgroup_ss_mask(struct cgroup *cgrp)
460{
461 struct cgroup *parent = cgroup_parent(cgrp);
462
463 if (parent) {
464 u16 ss_mask = parent->subtree_ss_mask;
465
466 /* threaded cgroups can only have threaded controllers */
467 if (cgroup_is_threaded(cgrp))
468 ss_mask &= cgrp_dfl_threaded_ss_mask;
469 return ss_mask;
470 }
471
472 return cgrp->root->subsys_mask;
473}
474
475/**
476 * cgroup_css - obtain a cgroup's css for the specified subsystem
477 * @cgrp: the cgroup of interest
478 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
479 *
480 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
481 * function must be called either under cgroup_mutex or rcu_read_lock() and
482 * the caller is responsible for pinning the returned css if it wants to
483 * keep accessing it outside the said locks. This function may return
484 * %NULL if @cgrp doesn't have @subsys_id enabled.
485 */
486static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
487 struct cgroup_subsys *ss)
488{
489 if (CGROUP_HAS_SUBSYS_CONFIG && ss)
490 return rcu_dereference_check(cgrp->subsys[ss->id],
491 lockdep_is_held(&cgroup_mutex));
492 else
493 return &cgrp->self;
494}
495
496/**
497 * cgroup_tryget_css - try to get a cgroup's css for the specified subsystem
498 * @cgrp: the cgroup of interest
499 * @ss: the subsystem of interest
500 *
501 * Find and get @cgrp's css associated with @ss. If the css doesn't exist
502 * or is offline, %NULL is returned.
503 */
504static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp,
505 struct cgroup_subsys *ss)
506{
507 struct cgroup_subsys_state *css;
508
509 rcu_read_lock();
510 css = cgroup_css(cgrp, ss);
511 if (css && !css_tryget_online(css))
512 css = NULL;
513 rcu_read_unlock();
514
515 return css;
516}
517
518/**
519 * cgroup_e_css_by_mask - obtain a cgroup's effective css for the specified ss
520 * @cgrp: the cgroup of interest
521 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
522 *
523 * Similar to cgroup_css() but returns the effective css, which is defined
524 * as the matching css of the nearest ancestor including self which has @ss
525 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
526 * function is guaranteed to return non-NULL css.
527 */
528static struct cgroup_subsys_state *cgroup_e_css_by_mask(struct cgroup *cgrp,
529 struct cgroup_subsys *ss)
530{
531 lockdep_assert_held(&cgroup_mutex);
532
533 if (!ss)
534 return &cgrp->self;
535
536 /*
537 * This function is used while updating css associations and thus
538 * can't test the csses directly. Test ss_mask.
539 */
540 while (!(cgroup_ss_mask(cgrp) & (1 << ss->id))) {
541 cgrp = cgroup_parent(cgrp);
542 if (!cgrp)
543 return NULL;
544 }
545
546 return cgroup_css(cgrp, ss);
547}
548
549/**
550 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
551 * @cgrp: the cgroup of interest
552 * @ss: the subsystem of interest
553 *
554 * Find and get the effective css of @cgrp for @ss. The effective css is
555 * defined as the matching css of the nearest ancestor including self which
556 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
557 * the root css is returned, so this function always returns a valid css.
558 *
559 * The returned css is not guaranteed to be online, and therefore it is the
560 * callers responsibility to try get a reference for it.
561 */
562struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
563 struct cgroup_subsys *ss)
564{
565 struct cgroup_subsys_state *css;
566
567 if (!CGROUP_HAS_SUBSYS_CONFIG)
568 return NULL;
569
570 do {
571 css = cgroup_css(cgrp, ss);
572
573 if (css)
574 return css;
575 cgrp = cgroup_parent(cgrp);
576 } while (cgrp);
577
578 return init_css_set.subsys[ss->id];
579}
580
581/**
582 * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
583 * @cgrp: the cgroup of interest
584 * @ss: the subsystem of interest
585 *
586 * Find and get the effective css of @cgrp for @ss. The effective css is
587 * defined as the matching css of the nearest ancestor including self which
588 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
589 * the root css is returned, so this function always returns a valid css.
590 * The returned css must be put using css_put().
591 */
592struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
593 struct cgroup_subsys *ss)
594{
595 struct cgroup_subsys_state *css;
596
597 if (!CGROUP_HAS_SUBSYS_CONFIG)
598 return NULL;
599
600 rcu_read_lock();
601
602 do {
603 css = cgroup_css(cgrp, ss);
604
605 if (css && css_tryget_online(css))
606 goto out_unlock;
607 cgrp = cgroup_parent(cgrp);
608 } while (cgrp);
609
610 css = init_css_set.subsys[ss->id];
611 css_get(css);
612out_unlock:
613 rcu_read_unlock();
614 return css;
615}
616EXPORT_SYMBOL_GPL(cgroup_get_e_css);
617
618static void cgroup_get_live(struct cgroup *cgrp)
619{
620 WARN_ON_ONCE(cgroup_is_dead(cgrp));
621 css_get(&cgrp->self);
622}
623
624/**
625 * __cgroup_task_count - count the number of tasks in a cgroup. The caller
626 * is responsible for taking the css_set_lock.
627 * @cgrp: the cgroup in question
628 */
629int __cgroup_task_count(const struct cgroup *cgrp)
630{
631 int count = 0;
632 struct cgrp_cset_link *link;
633
634 lockdep_assert_held(&css_set_lock);
635
636 list_for_each_entry(link, &cgrp->cset_links, cset_link)
637 count += link->cset->nr_tasks;
638
639 return count;
640}
641
642/**
643 * cgroup_task_count - count the number of tasks in a cgroup.
644 * @cgrp: the cgroup in question
645 */
646int cgroup_task_count(const struct cgroup *cgrp)
647{
648 int count;
649
650 spin_lock_irq(&css_set_lock);
651 count = __cgroup_task_count(cgrp);
652 spin_unlock_irq(&css_set_lock);
653
654 return count;
655}
656
657struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
658{
659 struct cgroup *cgrp = of->kn->parent->priv;
660 struct cftype *cft = of_cft(of);
661
662 /*
663 * This is open and unprotected implementation of cgroup_css().
664 * seq_css() is only called from a kernfs file operation which has
665 * an active reference on the file. Because all the subsystem
666 * files are drained before a css is disassociated with a cgroup,
667 * the matching css from the cgroup's subsys table is guaranteed to
668 * be and stay valid until the enclosing operation is complete.
669 */
670 if (CGROUP_HAS_SUBSYS_CONFIG && cft->ss)
671 return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
672 else
673 return &cgrp->self;
674}
675EXPORT_SYMBOL_GPL(of_css);
676
677/**
678 * for_each_css - iterate all css's of a cgroup
679 * @css: the iteration cursor
680 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
681 * @cgrp: the target cgroup to iterate css's of
682 *
683 * Should be called under cgroup_[tree_]mutex.
684 */
685#define for_each_css(css, ssid, cgrp) \
686 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
687 if (!((css) = rcu_dereference_check( \
688 (cgrp)->subsys[(ssid)], \
689 lockdep_is_held(&cgroup_mutex)))) { } \
690 else
691
692/**
693 * for_each_e_css - iterate all effective css's of a cgroup
694 * @css: the iteration cursor
695 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
696 * @cgrp: the target cgroup to iterate css's of
697 *
698 * Should be called under cgroup_[tree_]mutex.
699 */
700#define for_each_e_css(css, ssid, cgrp) \
701 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
702 if (!((css) = cgroup_e_css_by_mask(cgrp, \
703 cgroup_subsys[(ssid)]))) \
704 ; \
705 else
706
707/**
708 * do_each_subsys_mask - filter for_each_subsys with a bitmask
709 * @ss: the iteration cursor
710 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
711 * @ss_mask: the bitmask
712 *
713 * The block will only run for cases where the ssid-th bit (1 << ssid) of
714 * @ss_mask is set.
715 */
716#define do_each_subsys_mask(ss, ssid, ss_mask) do { \
717 unsigned long __ss_mask = (ss_mask); \
718 if (!CGROUP_HAS_SUBSYS_CONFIG) { \
719 (ssid) = 0; \
720 break; \
721 } \
722 for_each_set_bit(ssid, &__ss_mask, CGROUP_SUBSYS_COUNT) { \
723 (ss) = cgroup_subsys[ssid]; \
724 {
725
726#define while_each_subsys_mask() \
727 } \
728 } \
729} while (false)
730
731/* iterate over child cgrps, lock should be held throughout iteration */
732#define cgroup_for_each_live_child(child, cgrp) \
733 list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
734 if (({ lockdep_assert_held(&cgroup_mutex); \
735 cgroup_is_dead(child); })) \
736 ; \
737 else
738
739/* walk live descendants in pre order */
740#define cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) \
741 css_for_each_descendant_pre((d_css), cgroup_css((cgrp), NULL)) \
742 if (({ lockdep_assert_held(&cgroup_mutex); \
743 (dsct) = (d_css)->cgroup; \
744 cgroup_is_dead(dsct); })) \
745 ; \
746 else
747
748/* walk live descendants in postorder */
749#define cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) \
750 css_for_each_descendant_post((d_css), cgroup_css((cgrp), NULL)) \
751 if (({ lockdep_assert_held(&cgroup_mutex); \
752 (dsct) = (d_css)->cgroup; \
753 cgroup_is_dead(dsct); })) \
754 ; \
755 else
756
757/*
758 * The default css_set - used by init and its children prior to any
759 * hierarchies being mounted. It contains a pointer to the root state
760 * for each subsystem. Also used to anchor the list of css_sets. Not
761 * reference-counted, to improve performance when child cgroups
762 * haven't been created.
763 */
764struct css_set init_css_set = {
765 .refcount = REFCOUNT_INIT(1),
766 .dom_cset = &init_css_set,
767 .tasks = LIST_HEAD_INIT(init_css_set.tasks),
768 .mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
769 .dying_tasks = LIST_HEAD_INIT(init_css_set.dying_tasks),
770 .task_iters = LIST_HEAD_INIT(init_css_set.task_iters),
771 .threaded_csets = LIST_HEAD_INIT(init_css_set.threaded_csets),
772 .cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
773 .mg_src_preload_node = LIST_HEAD_INIT(init_css_set.mg_src_preload_node),
774 .mg_dst_preload_node = LIST_HEAD_INIT(init_css_set.mg_dst_preload_node),
775 .mg_node = LIST_HEAD_INIT(init_css_set.mg_node),
776
777 /*
778 * The following field is re-initialized when this cset gets linked
779 * in cgroup_init(). However, let's initialize the field
780 * statically too so that the default cgroup can be accessed safely
781 * early during boot.
782 */
783 .dfl_cgrp = &cgrp_dfl_root.cgrp,
784};
785
786static int css_set_count = 1; /* 1 for init_css_set */
787
788static bool css_set_threaded(struct css_set *cset)
789{
790 return cset->dom_cset != cset;
791}
792
793/**
794 * css_set_populated - does a css_set contain any tasks?
795 * @cset: target css_set
796 *
797 * css_set_populated() should be the same as !!cset->nr_tasks at steady
798 * state. However, css_set_populated() can be called while a task is being
799 * added to or removed from the linked list before the nr_tasks is
800 * properly updated. Hence, we can't just look at ->nr_tasks here.
801 */
802static bool css_set_populated(struct css_set *cset)
803{
804 lockdep_assert_held(&css_set_lock);
805
806 return !list_empty(&cset->tasks) || !list_empty(&cset->mg_tasks);
807}
808
809/**
810 * cgroup_update_populated - update the populated count of a cgroup
811 * @cgrp: the target cgroup
812 * @populated: inc or dec populated count
813 *
814 * One of the css_sets associated with @cgrp is either getting its first
815 * task or losing the last. Update @cgrp->nr_populated_* accordingly. The
816 * count is propagated towards root so that a given cgroup's
817 * nr_populated_children is zero iff none of its descendants contain any
818 * tasks.
819 *
820 * @cgrp's interface file "cgroup.populated" is zero if both
821 * @cgrp->nr_populated_csets and @cgrp->nr_populated_children are zero and
822 * 1 otherwise. When the sum changes from or to zero, userland is notified
823 * that the content of the interface file has changed. This can be used to
824 * detect when @cgrp and its descendants become populated or empty.
825 */
826static void cgroup_update_populated(struct cgroup *cgrp, bool populated)
827{
828 struct cgroup *child = NULL;
829 int adj = populated ? 1 : -1;
830
831 lockdep_assert_held(&css_set_lock);
832
833 do {
834 bool was_populated = cgroup_is_populated(cgrp);
835
836 if (!child) {
837 cgrp->nr_populated_csets += adj;
838 } else {
839 if (cgroup_is_threaded(child))
840 cgrp->nr_populated_threaded_children += adj;
841 else
842 cgrp->nr_populated_domain_children += adj;
843 }
844
845 if (was_populated == cgroup_is_populated(cgrp))
846 break;
847
848 cgroup1_check_for_release(cgrp);
849 TRACE_CGROUP_PATH(notify_populated, cgrp,
850 cgroup_is_populated(cgrp));
851 cgroup_file_notify(&cgrp->events_file);
852
853 child = cgrp;
854 cgrp = cgroup_parent(cgrp);
855 } while (cgrp);
856}
857
858/**
859 * css_set_update_populated - update populated state of a css_set
860 * @cset: target css_set
861 * @populated: whether @cset is populated or depopulated
862 *
863 * @cset is either getting the first task or losing the last. Update the
864 * populated counters of all associated cgroups accordingly.
865 */
866static void css_set_update_populated(struct css_set *cset, bool populated)
867{
868 struct cgrp_cset_link *link;
869
870 lockdep_assert_held(&css_set_lock);
871
872 list_for_each_entry(link, &cset->cgrp_links, cgrp_link)
873 cgroup_update_populated(link->cgrp, populated);
874}
875
876/*
877 * @task is leaving, advance task iterators which are pointing to it so
878 * that they can resume at the next position. Advancing an iterator might
879 * remove it from the list, use safe walk. See css_task_iter_skip() for
880 * details.
881 */
882static void css_set_skip_task_iters(struct css_set *cset,
883 struct task_struct *task)
884{
885 struct css_task_iter *it, *pos;
886
887 list_for_each_entry_safe(it, pos, &cset->task_iters, iters_node)
888 css_task_iter_skip(it, task);
889}
890
891/**
892 * css_set_move_task - move a task from one css_set to another
893 * @task: task being moved
894 * @from_cset: css_set @task currently belongs to (may be NULL)
895 * @to_cset: new css_set @task is being moved to (may be NULL)
896 * @use_mg_tasks: move to @to_cset->mg_tasks instead of ->tasks
897 *
898 * Move @task from @from_cset to @to_cset. If @task didn't belong to any
899 * css_set, @from_cset can be NULL. If @task is being disassociated
900 * instead of moved, @to_cset can be NULL.
901 *
902 * This function automatically handles populated counter updates and
903 * css_task_iter adjustments but the caller is responsible for managing
904 * @from_cset and @to_cset's reference counts.
905 */
906static void css_set_move_task(struct task_struct *task,
907 struct css_set *from_cset, struct css_set *to_cset,
908 bool use_mg_tasks)
909{
910 lockdep_assert_held(&css_set_lock);
911
912 if (to_cset && !css_set_populated(to_cset))
913 css_set_update_populated(to_cset, true);
914
915 if (from_cset) {
916 WARN_ON_ONCE(list_empty(&task->cg_list));
917
918 css_set_skip_task_iters(from_cset, task);
919 list_del_init(&task->cg_list);
920 if (!css_set_populated(from_cset))
921 css_set_update_populated(from_cset, false);
922 } else {
923 WARN_ON_ONCE(!list_empty(&task->cg_list));
924 }
925
926 if (to_cset) {
927 /*
928 * We are synchronized through cgroup_threadgroup_rwsem
929 * against PF_EXITING setting such that we can't race
930 * against cgroup_exit()/cgroup_free() dropping the css_set.
931 */
932 WARN_ON_ONCE(task->flags & PF_EXITING);
933
934 cgroup_move_task(task, to_cset);
935 list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks :
936 &to_cset->tasks);
937 }
938}
939
940/*
941 * hash table for cgroup groups. This improves the performance to find
942 * an existing css_set. This hash doesn't (currently) take into
943 * account cgroups in empty hierarchies.
944 */
945#define CSS_SET_HASH_BITS 7
946static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
947
948static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
949{
950 unsigned long key = 0UL;
951 struct cgroup_subsys *ss;
952 int i;
953
954 for_each_subsys(ss, i)
955 key += (unsigned long)css[i];
956 key = (key >> 16) ^ key;
957
958 return key;
959}
960
961void put_css_set_locked(struct css_set *cset)
962{
963 struct cgrp_cset_link *link, *tmp_link;
964 struct cgroup_subsys *ss;
965 int ssid;
966
967 lockdep_assert_held(&css_set_lock);
968
969 if (!refcount_dec_and_test(&cset->refcount))
970 return;
971
972 WARN_ON_ONCE(!list_empty(&cset->threaded_csets));
973
974 /* This css_set is dead. Unlink it and release cgroup and css refs */
975 for_each_subsys(ss, ssid) {
976 list_del(&cset->e_cset_node[ssid]);
977 css_put(cset->subsys[ssid]);
978 }
979 hash_del(&cset->hlist);
980 css_set_count--;
981
982 list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
983 list_del(&link->cset_link);
984 list_del(&link->cgrp_link);
985 if (cgroup_parent(link->cgrp))
986 cgroup_put(link->cgrp);
987 kfree(link);
988 }
989
990 if (css_set_threaded(cset)) {
991 list_del(&cset->threaded_csets_node);
992 put_css_set_locked(cset->dom_cset);
993 }
994
995 kfree_rcu(cset, rcu_head);
996}
997
998/**
999 * compare_css_sets - helper function for find_existing_css_set().
1000 * @cset: candidate css_set being tested
1001 * @old_cset: existing css_set for a task
1002 * @new_cgrp: cgroup that's being entered by the task
1003 * @template: desired set of css pointers in css_set (pre-calculated)
1004 *
1005 * Returns true if "cset" matches "old_cset" except for the hierarchy
1006 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
1007 */
1008static bool compare_css_sets(struct css_set *cset,
1009 struct css_set *old_cset,
1010 struct cgroup *new_cgrp,
1011 struct cgroup_subsys_state *template[])
1012{
1013 struct cgroup *new_dfl_cgrp;
1014 struct list_head *l1, *l2;
1015
1016 /*
1017 * On the default hierarchy, there can be csets which are
1018 * associated with the same set of cgroups but different csses.
1019 * Let's first ensure that csses match.
1020 */
1021 if (memcmp(template, cset->subsys, sizeof(cset->subsys)))
1022 return false;
1023
1024
1025 /* @cset's domain should match the default cgroup's */
1026 if (cgroup_on_dfl(new_cgrp))
1027 new_dfl_cgrp = new_cgrp;
1028 else
1029 new_dfl_cgrp = old_cset->dfl_cgrp;
1030
1031 if (new_dfl_cgrp->dom_cgrp != cset->dom_cset->dfl_cgrp)
1032 return false;
1033
1034 /*
1035 * Compare cgroup pointers in order to distinguish between
1036 * different cgroups in hierarchies. As different cgroups may
1037 * share the same effective css, this comparison is always
1038 * necessary.
1039 */
1040 l1 = &cset->cgrp_links;
1041 l2 = &old_cset->cgrp_links;
1042 while (1) {
1043 struct cgrp_cset_link *link1, *link2;
1044 struct cgroup *cgrp1, *cgrp2;
1045
1046 l1 = l1->next;
1047 l2 = l2->next;
1048 /* See if we reached the end - both lists are equal length. */
1049 if (l1 == &cset->cgrp_links) {
1050 BUG_ON(l2 != &old_cset->cgrp_links);
1051 break;
1052 } else {
1053 BUG_ON(l2 == &old_cset->cgrp_links);
1054 }
1055 /* Locate the cgroups associated with these links. */
1056 link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
1057 link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
1058 cgrp1 = link1->cgrp;
1059 cgrp2 = link2->cgrp;
1060 /* Hierarchies should be linked in the same order. */
1061 BUG_ON(cgrp1->root != cgrp2->root);
1062
1063 /*
1064 * If this hierarchy is the hierarchy of the cgroup
1065 * that's changing, then we need to check that this
1066 * css_set points to the new cgroup; if it's any other
1067 * hierarchy, then this css_set should point to the
1068 * same cgroup as the old css_set.
1069 */
1070 if (cgrp1->root == new_cgrp->root) {
1071 if (cgrp1 != new_cgrp)
1072 return false;
1073 } else {
1074 if (cgrp1 != cgrp2)
1075 return false;
1076 }
1077 }
1078 return true;
1079}
1080
1081/**
1082 * find_existing_css_set - init css array and find the matching css_set
1083 * @old_cset: the css_set that we're using before the cgroup transition
1084 * @cgrp: the cgroup that we're moving into
1085 * @template: out param for the new set of csses, should be clear on entry
1086 */
1087static struct css_set *find_existing_css_set(struct css_set *old_cset,
1088 struct cgroup *cgrp,
1089 struct cgroup_subsys_state *template[])
1090{
1091 struct cgroup_root *root = cgrp->root;
1092 struct cgroup_subsys *ss;
1093 struct css_set *cset;
1094 unsigned long key;
1095 int i;
1096
1097 /*
1098 * Build the set of subsystem state objects that we want to see in the
1099 * new css_set. While subsystems can change globally, the entries here
1100 * won't change, so no need for locking.
1101 */
1102 for_each_subsys(ss, i) {
1103 if (root->subsys_mask & (1UL << i)) {
1104 /*
1105 * @ss is in this hierarchy, so we want the
1106 * effective css from @cgrp.
1107 */
1108 template[i] = cgroup_e_css_by_mask(cgrp, ss);
1109 } else {
1110 /*
1111 * @ss is not in this hierarchy, so we don't want
1112 * to change the css.
1113 */
1114 template[i] = old_cset->subsys[i];
1115 }
1116 }
1117
1118 key = css_set_hash(template);
1119 hash_for_each_possible(css_set_table, cset, hlist, key) {
1120 if (!compare_css_sets(cset, old_cset, cgrp, template))
1121 continue;
1122
1123 /* This css_set matches what we need */
1124 return cset;
1125 }
1126
1127 /* No existing cgroup group matched */
1128 return NULL;
1129}
1130
1131static void free_cgrp_cset_links(struct list_head *links_to_free)
1132{
1133 struct cgrp_cset_link *link, *tmp_link;
1134
1135 list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
1136 list_del(&link->cset_link);
1137 kfree(link);
1138 }
1139}
1140
1141/**
1142 * allocate_cgrp_cset_links - allocate cgrp_cset_links
1143 * @count: the number of links to allocate
1144 * @tmp_links: list_head the allocated links are put on
1145 *
1146 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
1147 * through ->cset_link. Returns 0 on success or -errno.
1148 */
1149static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
1150{
1151 struct cgrp_cset_link *link;
1152 int i;
1153
1154 INIT_LIST_HEAD(tmp_links);
1155
1156 for (i = 0; i < count; i++) {
1157 link = kzalloc(sizeof(*link), GFP_KERNEL);
1158 if (!link) {
1159 free_cgrp_cset_links(tmp_links);
1160 return -ENOMEM;
1161 }
1162 list_add(&link->cset_link, tmp_links);
1163 }
1164 return 0;
1165}
1166
1167/**
1168 * link_css_set - a helper function to link a css_set to a cgroup
1169 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
1170 * @cset: the css_set to be linked
1171 * @cgrp: the destination cgroup
1172 */
1173static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
1174 struct cgroup *cgrp)
1175{
1176 struct cgrp_cset_link *link;
1177
1178 BUG_ON(list_empty(tmp_links));
1179
1180 if (cgroup_on_dfl(cgrp))
1181 cset->dfl_cgrp = cgrp;
1182
1183 link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
1184 link->cset = cset;
1185 link->cgrp = cgrp;
1186
1187 /*
1188 * Always add links to the tail of the lists so that the lists are
1189 * in chronological order.
1190 */
1191 list_move_tail(&link->cset_link, &cgrp->cset_links);
1192 list_add_tail(&link->cgrp_link, &cset->cgrp_links);
1193
1194 if (cgroup_parent(cgrp))
1195 cgroup_get_live(cgrp);
1196}
1197
1198/**
1199 * find_css_set - return a new css_set with one cgroup updated
1200 * @old_cset: the baseline css_set
1201 * @cgrp: the cgroup to be updated
1202 *
1203 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
1204 * substituted into the appropriate hierarchy.
1205 */
1206static struct css_set *find_css_set(struct css_set *old_cset,
1207 struct cgroup *cgrp)
1208{
1209 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
1210 struct css_set *cset;
1211 struct list_head tmp_links;
1212 struct cgrp_cset_link *link;
1213 struct cgroup_subsys *ss;
1214 unsigned long key;
1215 int ssid;
1216
1217 lockdep_assert_held(&cgroup_mutex);
1218
1219 /* First see if we already have a cgroup group that matches
1220 * the desired set */
1221 spin_lock_irq(&css_set_lock);
1222 cset = find_existing_css_set(old_cset, cgrp, template);
1223 if (cset)
1224 get_css_set(cset);
1225 spin_unlock_irq(&css_set_lock);
1226
1227 if (cset)
1228 return cset;
1229
1230 cset = kzalloc(sizeof(*cset), GFP_KERNEL);
1231 if (!cset)
1232 return NULL;
1233
1234 /* Allocate all the cgrp_cset_link objects that we'll need */
1235 if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
1236 kfree(cset);
1237 return NULL;
1238 }
1239
1240 refcount_set(&cset->refcount, 1);
1241 cset->dom_cset = cset;
1242 INIT_LIST_HEAD(&cset->tasks);
1243 INIT_LIST_HEAD(&cset->mg_tasks);
1244 INIT_LIST_HEAD(&cset->dying_tasks);
1245 INIT_LIST_HEAD(&cset->task_iters);
1246 INIT_LIST_HEAD(&cset->threaded_csets);
1247 INIT_HLIST_NODE(&cset->hlist);
1248 INIT_LIST_HEAD(&cset->cgrp_links);
1249 INIT_LIST_HEAD(&cset->mg_src_preload_node);
1250 INIT_LIST_HEAD(&cset->mg_dst_preload_node);
1251 INIT_LIST_HEAD(&cset->mg_node);
1252
1253 /* Copy the set of subsystem state objects generated in
1254 * find_existing_css_set() */
1255 memcpy(cset->subsys, template, sizeof(cset->subsys));
1256
1257 spin_lock_irq(&css_set_lock);
1258 /* Add reference counts and links from the new css_set. */
1259 list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
1260 struct cgroup *c = link->cgrp;
1261
1262 if (c->root == cgrp->root)
1263 c = cgrp;
1264 link_css_set(&tmp_links, cset, c);
1265 }
1266
1267 BUG_ON(!list_empty(&tmp_links));
1268
1269 css_set_count++;
1270
1271 /* Add @cset to the hash table */
1272 key = css_set_hash(cset->subsys);
1273 hash_add(css_set_table, &cset->hlist, key);
1274
1275 for_each_subsys(ss, ssid) {
1276 struct cgroup_subsys_state *css = cset->subsys[ssid];
1277
1278 list_add_tail(&cset->e_cset_node[ssid],
1279 &css->cgroup->e_csets[ssid]);
1280 css_get(css);
1281 }
1282
1283 spin_unlock_irq(&css_set_lock);
1284
1285 /*
1286 * If @cset should be threaded, look up the matching dom_cset and
1287 * link them up. We first fully initialize @cset then look for the
1288 * dom_cset. It's simpler this way and safe as @cset is guaranteed
1289 * to stay empty until we return.
1290 */
1291 if (cgroup_is_threaded(cset->dfl_cgrp)) {
1292 struct css_set *dcset;
1293
1294 dcset = find_css_set(cset, cset->dfl_cgrp->dom_cgrp);
1295 if (!dcset) {
1296 put_css_set(cset);
1297 return NULL;
1298 }
1299
1300 spin_lock_irq(&css_set_lock);
1301 cset->dom_cset = dcset;
1302 list_add_tail(&cset->threaded_csets_node,
1303 &dcset->threaded_csets);
1304 spin_unlock_irq(&css_set_lock);
1305 }
1306
1307 return cset;
1308}
1309
1310struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
1311{
1312 struct cgroup *root_cgrp = kernfs_root_to_node(kf_root)->priv;
1313
1314 return root_cgrp->root;
1315}
1316
1317void cgroup_favor_dynmods(struct cgroup_root *root, bool favor)
1318{
1319 bool favoring = root->flags & CGRP_ROOT_FAVOR_DYNMODS;
1320
1321 /* see the comment above CGRP_ROOT_FAVOR_DYNMODS definition */
1322 if (favor && !favoring) {
1323 rcu_sync_enter(&cgroup_threadgroup_rwsem.rss);
1324 root->flags |= CGRP_ROOT_FAVOR_DYNMODS;
1325 } else if (!favor && favoring) {
1326 rcu_sync_exit(&cgroup_threadgroup_rwsem.rss);
1327 root->flags &= ~CGRP_ROOT_FAVOR_DYNMODS;
1328 }
1329}
1330
1331static int cgroup_init_root_id(struct cgroup_root *root)
1332{
1333 int id;
1334
1335 lockdep_assert_held(&cgroup_mutex);
1336
1337 id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
1338 if (id < 0)
1339 return id;
1340
1341 root->hierarchy_id = id;
1342 return 0;
1343}
1344
1345static void cgroup_exit_root_id(struct cgroup_root *root)
1346{
1347 lockdep_assert_held(&cgroup_mutex);
1348
1349 idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
1350}
1351
1352void cgroup_free_root(struct cgroup_root *root)
1353{
1354 kfree(root);
1355}
1356
1357static void cgroup_destroy_root(struct cgroup_root *root)
1358{
1359 struct cgroup *cgrp = &root->cgrp;
1360 struct cgrp_cset_link *link, *tmp_link;
1361
1362 trace_cgroup_destroy_root(root);
1363
1364 cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1365
1366 BUG_ON(atomic_read(&root->nr_cgrps));
1367 BUG_ON(!list_empty(&cgrp->self.children));
1368
1369 /* Rebind all subsystems back to the default hierarchy */
1370 WARN_ON(rebind_subsystems(&cgrp_dfl_root, root->subsys_mask));
1371
1372 /*
1373 * Release all the links from cset_links to this hierarchy's
1374 * root cgroup
1375 */
1376 spin_lock_irq(&css_set_lock);
1377
1378 list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
1379 list_del(&link->cset_link);
1380 list_del(&link->cgrp_link);
1381 kfree(link);
1382 }
1383
1384 spin_unlock_irq(&css_set_lock);
1385
1386 if (!list_empty(&root->root_list)) {
1387 list_del(&root->root_list);
1388 cgroup_root_count--;
1389 }
1390
1391 cgroup_favor_dynmods(root, false);
1392 cgroup_exit_root_id(root);
1393
1394 mutex_unlock(&cgroup_mutex);
1395
1396 cgroup_rstat_exit(cgrp);
1397 kernfs_destroy_root(root->kf_root);
1398 cgroup_free_root(root);
1399}
1400
1401/*
1402 * Returned cgroup is without refcount but it's valid as long as cset pins it.
1403 */
1404static inline struct cgroup *__cset_cgroup_from_root(struct css_set *cset,
1405 struct cgroup_root *root)
1406{
1407 struct cgroup *res_cgroup = NULL;
1408
1409 if (cset == &init_css_set) {
1410 res_cgroup = &root->cgrp;
1411 } else if (root == &cgrp_dfl_root) {
1412 res_cgroup = cset->dfl_cgrp;
1413 } else {
1414 struct cgrp_cset_link *link;
1415 lockdep_assert_held(&css_set_lock);
1416
1417 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
1418 struct cgroup *c = link->cgrp;
1419
1420 if (c->root == root) {
1421 res_cgroup = c;
1422 break;
1423 }
1424 }
1425 }
1426
1427 BUG_ON(!res_cgroup);
1428 return res_cgroup;
1429}
1430
1431/*
1432 * look up cgroup associated with current task's cgroup namespace on the
1433 * specified hierarchy
1434 */
1435static struct cgroup *
1436current_cgns_cgroup_from_root(struct cgroup_root *root)
1437{
1438 struct cgroup *res = NULL;
1439 struct css_set *cset;
1440
1441 lockdep_assert_held(&css_set_lock);
1442
1443 rcu_read_lock();
1444
1445 cset = current->nsproxy->cgroup_ns->root_cset;
1446 res = __cset_cgroup_from_root(cset, root);
1447
1448 rcu_read_unlock();
1449
1450 return res;
1451}
1452
1453/*
1454 * Look up cgroup associated with current task's cgroup namespace on the default
1455 * hierarchy.
1456 *
1457 * Unlike current_cgns_cgroup_from_root(), this doesn't need locks:
1458 * - Internal rcu_read_lock is unnecessary because we don't dereference any rcu
1459 * pointers.
1460 * - css_set_lock is not needed because we just read cset->dfl_cgrp.
1461 * - As a bonus returned cgrp is pinned with the current because it cannot
1462 * switch cgroup_ns asynchronously.
1463 */
1464static struct cgroup *current_cgns_cgroup_dfl(void)
1465{
1466 struct css_set *cset;
1467
1468 cset = current->nsproxy->cgroup_ns->root_cset;
1469 return __cset_cgroup_from_root(cset, &cgrp_dfl_root);
1470}
1471
1472/* look up cgroup associated with given css_set on the specified hierarchy */
1473static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
1474 struct cgroup_root *root)
1475{
1476 lockdep_assert_held(&cgroup_mutex);
1477 lockdep_assert_held(&css_set_lock);
1478
1479 return __cset_cgroup_from_root(cset, root);
1480}
1481
1482/*
1483 * Return the cgroup for "task" from the given hierarchy. Must be
1484 * called with cgroup_mutex and css_set_lock held.
1485 */
1486struct cgroup *task_cgroup_from_root(struct task_struct *task,
1487 struct cgroup_root *root)
1488{
1489 /*
1490 * No need to lock the task - since we hold css_set_lock the
1491 * task can't change groups.
1492 */
1493 return cset_cgroup_from_root(task_css_set(task), root);
1494}
1495
1496/*
1497 * A task must hold cgroup_mutex to modify cgroups.
1498 *
1499 * Any task can increment and decrement the count field without lock.
1500 * So in general, code holding cgroup_mutex can't rely on the count
1501 * field not changing. However, if the count goes to zero, then only
1502 * cgroup_attach_task() can increment it again. Because a count of zero
1503 * means that no tasks are currently attached, therefore there is no
1504 * way a task attached to that cgroup can fork (the other way to
1505 * increment the count). So code holding cgroup_mutex can safely
1506 * assume that if the count is zero, it will stay zero. Similarly, if
1507 * a task holds cgroup_mutex on a cgroup with zero count, it
1508 * knows that the cgroup won't be removed, as cgroup_rmdir()
1509 * needs that mutex.
1510 *
1511 * A cgroup can only be deleted if both its 'count' of using tasks
1512 * is zero, and its list of 'children' cgroups is empty. Since all
1513 * tasks in the system use _some_ cgroup, and since there is always at
1514 * least one task in the system (init, pid == 1), therefore, root cgroup
1515 * always has either children cgroups and/or using tasks. So we don't
1516 * need a special hack to ensure that root cgroup cannot be deleted.
1517 *
1518 * P.S. One more locking exception. RCU is used to guard the
1519 * update of a tasks cgroup pointer by cgroup_attach_task()
1520 */
1521
1522static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
1523
1524static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
1525 char *buf)
1526{
1527 struct cgroup_subsys *ss = cft->ss;
1528
1529 if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
1530 !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
1531 const char *dbg = (cft->flags & CFTYPE_DEBUG) ? ".__DEBUG__." : "";
1532
1533 snprintf(buf, CGROUP_FILE_NAME_MAX, "%s%s.%s",
1534 dbg, cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name,
1535 cft->name);
1536 } else {
1537 strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
1538 }
1539 return buf;
1540}
1541
1542/**
1543 * cgroup_file_mode - deduce file mode of a control file
1544 * @cft: the control file in question
1545 *
1546 * S_IRUGO for read, S_IWUSR for write.
1547 */
1548static umode_t cgroup_file_mode(const struct cftype *cft)
1549{
1550 umode_t mode = 0;
1551
1552 if (cft->read_u64 || cft->read_s64 || cft->seq_show)
1553 mode |= S_IRUGO;
1554
1555 if (cft->write_u64 || cft->write_s64 || cft->write) {
1556 if (cft->flags & CFTYPE_WORLD_WRITABLE)
1557 mode |= S_IWUGO;
1558 else
1559 mode |= S_IWUSR;
1560 }
1561
1562 return mode;
1563}
1564
1565/**
1566 * cgroup_calc_subtree_ss_mask - calculate subtree_ss_mask
1567 * @subtree_control: the new subtree_control mask to consider
1568 * @this_ss_mask: available subsystems
1569 *
1570 * On the default hierarchy, a subsystem may request other subsystems to be
1571 * enabled together through its ->depends_on mask. In such cases, more
1572 * subsystems than specified in "cgroup.subtree_control" may be enabled.
1573 *
1574 * This function calculates which subsystems need to be enabled if
1575 * @subtree_control is to be applied while restricted to @this_ss_mask.
1576 */
1577static u16 cgroup_calc_subtree_ss_mask(u16 subtree_control, u16 this_ss_mask)
1578{
1579 u16 cur_ss_mask = subtree_control;
1580 struct cgroup_subsys *ss;
1581 int ssid;
1582
1583 lockdep_assert_held(&cgroup_mutex);
1584
1585 cur_ss_mask |= cgrp_dfl_implicit_ss_mask;
1586
1587 while (true) {
1588 u16 new_ss_mask = cur_ss_mask;
1589
1590 do_each_subsys_mask(ss, ssid, cur_ss_mask) {
1591 new_ss_mask |= ss->depends_on;
1592 } while_each_subsys_mask();
1593
1594 /*
1595 * Mask out subsystems which aren't available. This can
1596 * happen only if some depended-upon subsystems were bound
1597 * to non-default hierarchies.
1598 */
1599 new_ss_mask &= this_ss_mask;
1600
1601 if (new_ss_mask == cur_ss_mask)
1602 break;
1603 cur_ss_mask = new_ss_mask;
1604 }
1605
1606 return cur_ss_mask;
1607}
1608
1609/**
1610 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1611 * @kn: the kernfs_node being serviced
1612 *
1613 * This helper undoes cgroup_kn_lock_live() and should be invoked before
1614 * the method finishes if locking succeeded. Note that once this function
1615 * returns the cgroup returned by cgroup_kn_lock_live() may become
1616 * inaccessible any time. If the caller intends to continue to access the
1617 * cgroup, it should pin it before invoking this function.
1618 */
1619void cgroup_kn_unlock(struct kernfs_node *kn)
1620{
1621 struct cgroup *cgrp;
1622
1623 if (kernfs_type(kn) == KERNFS_DIR)
1624 cgrp = kn->priv;
1625 else
1626 cgrp = kn->parent->priv;
1627
1628 mutex_unlock(&cgroup_mutex);
1629
1630 kernfs_unbreak_active_protection(kn);
1631 cgroup_put(cgrp);
1632}
1633
1634/**
1635 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1636 * @kn: the kernfs_node being serviced
1637 * @drain_offline: perform offline draining on the cgroup
1638 *
1639 * This helper is to be used by a cgroup kernfs method currently servicing
1640 * @kn. It breaks the active protection, performs cgroup locking and
1641 * verifies that the associated cgroup is alive. Returns the cgroup if
1642 * alive; otherwise, %NULL. A successful return should be undone by a
1643 * matching cgroup_kn_unlock() invocation. If @drain_offline is %true, the
1644 * cgroup is drained of offlining csses before return.
1645 *
1646 * Any cgroup kernfs method implementation which requires locking the
1647 * associated cgroup should use this helper. It avoids nesting cgroup
1648 * locking under kernfs active protection and allows all kernfs operations
1649 * including self-removal.
1650 */
1651struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn, bool drain_offline)
1652{
1653 struct cgroup *cgrp;
1654
1655 if (kernfs_type(kn) == KERNFS_DIR)
1656 cgrp = kn->priv;
1657 else
1658 cgrp = kn->parent->priv;
1659
1660 /*
1661 * We're gonna grab cgroup_mutex which nests outside kernfs
1662 * active_ref. cgroup liveliness check alone provides enough
1663 * protection against removal. Ensure @cgrp stays accessible and
1664 * break the active_ref protection.
1665 */
1666 if (!cgroup_tryget(cgrp))
1667 return NULL;
1668 kernfs_break_active_protection(kn);
1669
1670 if (drain_offline)
1671 cgroup_lock_and_drain_offline(cgrp);
1672 else
1673 mutex_lock(&cgroup_mutex);
1674
1675 if (!cgroup_is_dead(cgrp))
1676 return cgrp;
1677
1678 cgroup_kn_unlock(kn);
1679 return NULL;
1680}
1681
1682static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
1683{
1684 char name[CGROUP_FILE_NAME_MAX];
1685
1686 lockdep_assert_held(&cgroup_mutex);
1687
1688 if (cft->file_offset) {
1689 struct cgroup_subsys_state *css = cgroup_css(cgrp, cft->ss);
1690 struct cgroup_file *cfile = (void *)css + cft->file_offset;
1691
1692 spin_lock_irq(&cgroup_file_kn_lock);
1693 cfile->kn = NULL;
1694 spin_unlock_irq(&cgroup_file_kn_lock);
1695
1696 del_timer_sync(&cfile->notify_timer);
1697 }
1698
1699 kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
1700}
1701
1702/**
1703 * css_clear_dir - remove subsys files in a cgroup directory
1704 * @css: target css
1705 */
1706static void css_clear_dir(struct cgroup_subsys_state *css)
1707{
1708 struct cgroup *cgrp = css->cgroup;
1709 struct cftype *cfts;
1710
1711 if (!(css->flags & CSS_VISIBLE))
1712 return;
1713
1714 css->flags &= ~CSS_VISIBLE;
1715
1716 if (!css->ss) {
1717 if (cgroup_on_dfl(cgrp)) {
1718 cgroup_addrm_files(css, cgrp,
1719 cgroup_base_files, false);
1720 if (cgroup_psi_enabled())
1721 cgroup_addrm_files(css, cgrp,
1722 cgroup_psi_files, false);
1723 } else {
1724 cgroup_addrm_files(css, cgrp,
1725 cgroup1_base_files, false);
1726 }
1727 } else {
1728 list_for_each_entry(cfts, &css->ss->cfts, node)
1729 cgroup_addrm_files(css, cgrp, cfts, false);
1730 }
1731}
1732
1733/**
1734 * css_populate_dir - create subsys files in a cgroup directory
1735 * @css: target css
1736 *
1737 * On failure, no file is added.
1738 */
1739static int css_populate_dir(struct cgroup_subsys_state *css)
1740{
1741 struct cgroup *cgrp = css->cgroup;
1742 struct cftype *cfts, *failed_cfts;
1743 int ret;
1744
1745 if ((css->flags & CSS_VISIBLE) || !cgrp->kn)
1746 return 0;
1747
1748 if (!css->ss) {
1749 if (cgroup_on_dfl(cgrp)) {
1750 ret = cgroup_addrm_files(&cgrp->self, cgrp,
1751 cgroup_base_files, true);
1752 if (ret < 0)
1753 return ret;
1754
1755 if (cgroup_psi_enabled()) {
1756 ret = cgroup_addrm_files(&cgrp->self, cgrp,
1757 cgroup_psi_files, true);
1758 if (ret < 0)
1759 return ret;
1760 }
1761 } else {
1762 cgroup_addrm_files(css, cgrp,
1763 cgroup1_base_files, true);
1764 }
1765 } else {
1766 list_for_each_entry(cfts, &css->ss->cfts, node) {
1767 ret = cgroup_addrm_files(css, cgrp, cfts, true);
1768 if (ret < 0) {
1769 failed_cfts = cfts;
1770 goto err;
1771 }
1772 }
1773 }
1774
1775 css->flags |= CSS_VISIBLE;
1776
1777 return 0;
1778err:
1779 list_for_each_entry(cfts, &css->ss->cfts, node) {
1780 if (cfts == failed_cfts)
1781 break;
1782 cgroup_addrm_files(css, cgrp, cfts, false);
1783 }
1784 return ret;
1785}
1786
1787int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
1788{
1789 struct cgroup *dcgrp = &dst_root->cgrp;
1790 struct cgroup_subsys *ss;
1791 int ssid, i, ret;
1792 u16 dfl_disable_ss_mask = 0;
1793
1794 lockdep_assert_held(&cgroup_mutex);
1795
1796 do_each_subsys_mask(ss, ssid, ss_mask) {
1797 /*
1798 * If @ss has non-root csses attached to it, can't move.
1799 * If @ss is an implicit controller, it is exempt from this
1800 * rule and can be stolen.
1801 */
1802 if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)) &&
1803 !ss->implicit_on_dfl)
1804 return -EBUSY;
1805
1806 /* can't move between two non-dummy roots either */
1807 if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
1808 return -EBUSY;
1809
1810 /*
1811 * Collect ssid's that need to be disabled from default
1812 * hierarchy.
1813 */
1814 if (ss->root == &cgrp_dfl_root)
1815 dfl_disable_ss_mask |= 1 << ssid;
1816
1817 } while_each_subsys_mask();
1818
1819 if (dfl_disable_ss_mask) {
1820 struct cgroup *scgrp = &cgrp_dfl_root.cgrp;
1821
1822 /*
1823 * Controllers from default hierarchy that need to be rebound
1824 * are all disabled together in one go.
1825 */
1826 cgrp_dfl_root.subsys_mask &= ~dfl_disable_ss_mask;
1827 WARN_ON(cgroup_apply_control(scgrp));
1828 cgroup_finalize_control(scgrp, 0);
1829 }
1830
1831 do_each_subsys_mask(ss, ssid, ss_mask) {
1832 struct cgroup_root *src_root = ss->root;
1833 struct cgroup *scgrp = &src_root->cgrp;
1834 struct cgroup_subsys_state *css = cgroup_css(scgrp, ss);
1835 struct css_set *cset;
1836
1837 WARN_ON(!css || cgroup_css(dcgrp, ss));
1838
1839 if (src_root != &cgrp_dfl_root) {
1840 /* disable from the source */
1841 src_root->subsys_mask &= ~(1 << ssid);
1842 WARN_ON(cgroup_apply_control(scgrp));
1843 cgroup_finalize_control(scgrp, 0);
1844 }
1845
1846 /* rebind */
1847 RCU_INIT_POINTER(scgrp->subsys[ssid], NULL);
1848 rcu_assign_pointer(dcgrp->subsys[ssid], css);
1849 ss->root = dst_root;
1850 css->cgroup = dcgrp;
1851
1852 spin_lock_irq(&css_set_lock);
1853 hash_for_each(css_set_table, i, cset, hlist)
1854 list_move_tail(&cset->e_cset_node[ss->id],
1855 &dcgrp->e_csets[ss->id]);
1856 spin_unlock_irq(&css_set_lock);
1857
1858 if (ss->css_rstat_flush) {
1859 list_del_rcu(&css->rstat_css_node);
1860 synchronize_rcu();
1861 list_add_rcu(&css->rstat_css_node,
1862 &dcgrp->rstat_css_list);
1863 }
1864
1865 /* default hierarchy doesn't enable controllers by default */
1866 dst_root->subsys_mask |= 1 << ssid;
1867 if (dst_root == &cgrp_dfl_root) {
1868 static_branch_enable(cgroup_subsys_on_dfl_key[ssid]);
1869 } else {
1870 dcgrp->subtree_control |= 1 << ssid;
1871 static_branch_disable(cgroup_subsys_on_dfl_key[ssid]);
1872 }
1873
1874 ret = cgroup_apply_control(dcgrp);
1875 if (ret)
1876 pr_warn("partial failure to rebind %s controller (err=%d)\n",
1877 ss->name, ret);
1878
1879 if (ss->bind)
1880 ss->bind(css);
1881 } while_each_subsys_mask();
1882
1883 kernfs_activate(dcgrp->kn);
1884 return 0;
1885}
1886
1887int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
1888 struct kernfs_root *kf_root)
1889{
1890 int len = 0;
1891 char *buf = NULL;
1892 struct cgroup_root *kf_cgroot = cgroup_root_from_kf(kf_root);
1893 struct cgroup *ns_cgroup;
1894
1895 buf = kmalloc(PATH_MAX, GFP_KERNEL);
1896 if (!buf)
1897 return -ENOMEM;
1898
1899 spin_lock_irq(&css_set_lock);
1900 ns_cgroup = current_cgns_cgroup_from_root(kf_cgroot);
1901 len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX);
1902 spin_unlock_irq(&css_set_lock);
1903
1904 if (len >= PATH_MAX)
1905 len = -ERANGE;
1906 else if (len > 0) {
1907 seq_escape(sf, buf, " \t\n\\");
1908 len = 0;
1909 }
1910 kfree(buf);
1911 return len;
1912}
1913
1914enum cgroup2_param {
1915 Opt_nsdelegate,
1916 Opt_favordynmods,
1917 Opt_memory_localevents,
1918 Opt_memory_recursiveprot,
1919 nr__cgroup2_params
1920};
1921
1922static const struct fs_parameter_spec cgroup2_fs_parameters[] = {
1923 fsparam_flag("nsdelegate", Opt_nsdelegate),
1924 fsparam_flag("favordynmods", Opt_favordynmods),
1925 fsparam_flag("memory_localevents", Opt_memory_localevents),
1926 fsparam_flag("memory_recursiveprot", Opt_memory_recursiveprot),
1927 {}
1928};
1929
1930static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param)
1931{
1932 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1933 struct fs_parse_result result;
1934 int opt;
1935
1936 opt = fs_parse(fc, cgroup2_fs_parameters, param, &result);
1937 if (opt < 0)
1938 return opt;
1939
1940 switch (opt) {
1941 case Opt_nsdelegate:
1942 ctx->flags |= CGRP_ROOT_NS_DELEGATE;
1943 return 0;
1944 case Opt_favordynmods:
1945 ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
1946 return 0;
1947 case Opt_memory_localevents:
1948 ctx->flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1949 return 0;
1950 case Opt_memory_recursiveprot:
1951 ctx->flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;
1952 return 0;
1953 }
1954 return -EINVAL;
1955}
1956
1957static void apply_cgroup_root_flags(unsigned int root_flags)
1958{
1959 if (current->nsproxy->cgroup_ns == &init_cgroup_ns) {
1960 if (root_flags & CGRP_ROOT_NS_DELEGATE)
1961 cgrp_dfl_root.flags |= CGRP_ROOT_NS_DELEGATE;
1962 else
1963 cgrp_dfl_root.flags &= ~CGRP_ROOT_NS_DELEGATE;
1964
1965 cgroup_favor_dynmods(&cgrp_dfl_root,
1966 root_flags & CGRP_ROOT_FAVOR_DYNMODS);
1967
1968 if (root_flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
1969 cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1970 else
1971 cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1972
1973 if (root_flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)
1974 cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;
1975 else
1976 cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_RECURSIVE_PROT;
1977 }
1978}
1979
1980static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
1981{
1982 if (cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE)
1983 seq_puts(seq, ",nsdelegate");
1984 if (cgrp_dfl_root.flags & CGRP_ROOT_FAVOR_DYNMODS)
1985 seq_puts(seq, ",favordynmods");
1986 if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
1987 seq_puts(seq, ",memory_localevents");
1988 if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)
1989 seq_puts(seq, ",memory_recursiveprot");
1990 return 0;
1991}
1992
1993static int cgroup_reconfigure(struct fs_context *fc)
1994{
1995 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1996
1997 apply_cgroup_root_flags(ctx->flags);
1998 return 0;
1999}
2000
2001static void init_cgroup_housekeeping(struct cgroup *cgrp)
2002{
2003 struct cgroup_subsys *ss;
2004 int ssid;
2005
2006 INIT_LIST_HEAD(&cgrp->self.sibling);
2007 INIT_LIST_HEAD(&cgrp->self.children);
2008 INIT_LIST_HEAD(&cgrp->cset_links);
2009 INIT_LIST_HEAD(&cgrp->pidlists);
2010 mutex_init(&cgrp->pidlist_mutex);
2011 cgrp->self.cgroup = cgrp;
2012 cgrp->self.flags |= CSS_ONLINE;
2013 cgrp->dom_cgrp = cgrp;
2014 cgrp->max_descendants = INT_MAX;
2015 cgrp->max_depth = INT_MAX;
2016 INIT_LIST_HEAD(&cgrp->rstat_css_list);
2017 prev_cputime_init(&cgrp->prev_cputime);
2018
2019 for_each_subsys(ss, ssid)
2020 INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
2021
2022 init_waitqueue_head(&cgrp->offline_waitq);
2023 INIT_WORK(&cgrp->release_agent_work, cgroup1_release_agent);
2024}
2025
2026void init_cgroup_root(struct cgroup_fs_context *ctx)
2027{
2028 struct cgroup_root *root = ctx->root;
2029 struct cgroup *cgrp = &root->cgrp;
2030
2031 INIT_LIST_HEAD(&root->root_list);
2032 atomic_set(&root->nr_cgrps, 1);
2033 cgrp->root = root;
2034 init_cgroup_housekeeping(cgrp);
2035
2036 /* DYNMODS must be modified through cgroup_favor_dynmods() */
2037 root->flags = ctx->flags & ~CGRP_ROOT_FAVOR_DYNMODS;
2038 if (ctx->release_agent)
2039 strscpy(root->release_agent_path, ctx->release_agent, PATH_MAX);
2040 if (ctx->name)
2041 strscpy(root->name, ctx->name, MAX_CGROUP_ROOT_NAMELEN);
2042 if (ctx->cpuset_clone_children)
2043 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
2044}
2045
2046int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
2047{
2048 LIST_HEAD(tmp_links);
2049 struct cgroup *root_cgrp = &root->cgrp;
2050 struct kernfs_syscall_ops *kf_sops;
2051 struct css_set *cset;
2052 int i, ret;
2053
2054 lockdep_assert_held(&cgroup_mutex);
2055
2056 ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release,
2057 0, GFP_KERNEL);
2058 if (ret)
2059 goto out;
2060
2061 /*
2062 * We're accessing css_set_count without locking css_set_lock here,
2063 * but that's OK - it can only be increased by someone holding
2064 * cgroup_lock, and that's us. Later rebinding may disable
2065 * controllers on the default hierarchy and thus create new csets,
2066 * which can't be more than the existing ones. Allocate 2x.
2067 */
2068 ret = allocate_cgrp_cset_links(2 * css_set_count, &tmp_links);
2069 if (ret)
2070 goto cancel_ref;
2071
2072 ret = cgroup_init_root_id(root);
2073 if (ret)
2074 goto cancel_ref;
2075
2076 kf_sops = root == &cgrp_dfl_root ?
2077 &cgroup_kf_syscall_ops : &cgroup1_kf_syscall_ops;
2078
2079 root->kf_root = kernfs_create_root(kf_sops,
2080 KERNFS_ROOT_CREATE_DEACTIVATED |
2081 KERNFS_ROOT_SUPPORT_EXPORTOP |
2082 KERNFS_ROOT_SUPPORT_USER_XATTR,
2083 root_cgrp);
2084 if (IS_ERR(root->kf_root)) {
2085 ret = PTR_ERR(root->kf_root);
2086 goto exit_root_id;
2087 }
2088 root_cgrp->kn = kernfs_root_to_node(root->kf_root);
2089 WARN_ON_ONCE(cgroup_ino(root_cgrp) != 1);
2090 root_cgrp->ancestors[0] = root_cgrp;
2091
2092 ret = css_populate_dir(&root_cgrp->self);
2093 if (ret)
2094 goto destroy_root;
2095
2096 ret = cgroup_rstat_init(root_cgrp);
2097 if (ret)
2098 goto destroy_root;
2099
2100 ret = rebind_subsystems(root, ss_mask);
2101 if (ret)
2102 goto exit_stats;
2103
2104 ret = cgroup_bpf_inherit(root_cgrp);
2105 WARN_ON_ONCE(ret);
2106
2107 trace_cgroup_setup_root(root);
2108
2109 /*
2110 * There must be no failure case after here, since rebinding takes
2111 * care of subsystems' refcounts, which are explicitly dropped in
2112 * the failure exit path.
2113 */
2114 list_add(&root->root_list, &cgroup_roots);
2115 cgroup_root_count++;
2116
2117 /*
2118 * Link the root cgroup in this hierarchy into all the css_set
2119 * objects.
2120 */
2121 spin_lock_irq(&css_set_lock);
2122 hash_for_each(css_set_table, i, cset, hlist) {
2123 link_css_set(&tmp_links, cset, root_cgrp);
2124 if (css_set_populated(cset))
2125 cgroup_update_populated(root_cgrp, true);
2126 }
2127 spin_unlock_irq(&css_set_lock);
2128
2129 BUG_ON(!list_empty(&root_cgrp->self.children));
2130 BUG_ON(atomic_read(&root->nr_cgrps) != 1);
2131
2132 ret = 0;
2133 goto out;
2134
2135exit_stats:
2136 cgroup_rstat_exit(root_cgrp);
2137destroy_root:
2138 kernfs_destroy_root(root->kf_root);
2139 root->kf_root = NULL;
2140exit_root_id:
2141 cgroup_exit_root_id(root);
2142cancel_ref:
2143 percpu_ref_exit(&root_cgrp->self.refcnt);
2144out:
2145 free_cgrp_cset_links(&tmp_links);
2146 return ret;
2147}
2148
2149int cgroup_do_get_tree(struct fs_context *fc)
2150{
2151 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2152 int ret;
2153
2154 ctx->kfc.root = ctx->root->kf_root;
2155 if (fc->fs_type == &cgroup2_fs_type)
2156 ctx->kfc.magic = CGROUP2_SUPER_MAGIC;
2157 else
2158 ctx->kfc.magic = CGROUP_SUPER_MAGIC;
2159 ret = kernfs_get_tree(fc);
2160
2161 /*
2162 * In non-init cgroup namespace, instead of root cgroup's dentry,
2163 * we return the dentry corresponding to the cgroupns->root_cgrp.
2164 */
2165 if (!ret && ctx->ns != &init_cgroup_ns) {
2166 struct dentry *nsdentry;
2167 struct super_block *sb = fc->root->d_sb;
2168 struct cgroup *cgrp;
2169
2170 mutex_lock(&cgroup_mutex);
2171 spin_lock_irq(&css_set_lock);
2172
2173 cgrp = cset_cgroup_from_root(ctx->ns->root_cset, ctx->root);
2174
2175 spin_unlock_irq(&css_set_lock);
2176 mutex_unlock(&cgroup_mutex);
2177
2178 nsdentry = kernfs_node_dentry(cgrp->kn, sb);
2179 dput(fc->root);
2180 if (IS_ERR(nsdentry)) {
2181 deactivate_locked_super(sb);
2182 ret = PTR_ERR(nsdentry);
2183 nsdentry = NULL;
2184 }
2185 fc->root = nsdentry;
2186 }
2187
2188 if (!ctx->kfc.new_sb_created)
2189 cgroup_put(&ctx->root->cgrp);
2190
2191 return ret;
2192}
2193
2194/*
2195 * Destroy a cgroup filesystem context.
2196 */
2197static void cgroup_fs_context_free(struct fs_context *fc)
2198{
2199 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2200
2201 kfree(ctx->name);
2202 kfree(ctx->release_agent);
2203 put_cgroup_ns(ctx->ns);
2204 kernfs_free_fs_context(fc);
2205 kfree(ctx);
2206}
2207
2208static int cgroup_get_tree(struct fs_context *fc)
2209{
2210 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2211 int ret;
2212
2213 WRITE_ONCE(cgrp_dfl_visible, true);
2214 cgroup_get_live(&cgrp_dfl_root.cgrp);
2215 ctx->root = &cgrp_dfl_root;
2216
2217 ret = cgroup_do_get_tree(fc);
2218 if (!ret)
2219 apply_cgroup_root_flags(ctx->flags);
2220 return ret;
2221}
2222
2223static const struct fs_context_operations cgroup_fs_context_ops = {
2224 .free = cgroup_fs_context_free,
2225 .parse_param = cgroup2_parse_param,
2226 .get_tree = cgroup_get_tree,
2227 .reconfigure = cgroup_reconfigure,
2228};
2229
2230static const struct fs_context_operations cgroup1_fs_context_ops = {
2231 .free = cgroup_fs_context_free,
2232 .parse_param = cgroup1_parse_param,
2233 .get_tree = cgroup1_get_tree,
2234 .reconfigure = cgroup1_reconfigure,
2235};
2236
2237/*
2238 * Initialise the cgroup filesystem creation/reconfiguration context. Notably,
2239 * we select the namespace we're going to use.
2240 */
2241static int cgroup_init_fs_context(struct fs_context *fc)
2242{
2243 struct cgroup_fs_context *ctx;
2244
2245 ctx = kzalloc(sizeof(struct cgroup_fs_context), GFP_KERNEL);
2246 if (!ctx)
2247 return -ENOMEM;
2248
2249 ctx->ns = current->nsproxy->cgroup_ns;
2250 get_cgroup_ns(ctx->ns);
2251 fc->fs_private = &ctx->kfc;
2252 if (fc->fs_type == &cgroup2_fs_type)
2253 fc->ops = &cgroup_fs_context_ops;
2254 else
2255 fc->ops = &cgroup1_fs_context_ops;
2256 put_user_ns(fc->user_ns);
2257 fc->user_ns = get_user_ns(ctx->ns->user_ns);
2258 fc->global = true;
2259
2260#ifdef CONFIG_CGROUP_FAVOR_DYNMODS
2261 ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
2262#endif
2263 return 0;
2264}
2265
2266static void cgroup_kill_sb(struct super_block *sb)
2267{
2268 struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
2269 struct cgroup_root *root = cgroup_root_from_kf(kf_root);
2270
2271 /*
2272 * If @root doesn't have any children, start killing it.
2273 * This prevents new mounts by disabling percpu_ref_tryget_live().
2274 *
2275 * And don't kill the default root.
2276 */
2277 if (list_empty(&root->cgrp.self.children) && root != &cgrp_dfl_root &&
2278 !percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
2279 cgroup_bpf_offline(&root->cgrp);
2280 percpu_ref_kill(&root->cgrp.self.refcnt);
2281 }
2282 cgroup_put(&root->cgrp);
2283 kernfs_kill_sb(sb);
2284}
2285
2286struct file_system_type cgroup_fs_type = {
2287 .name = "cgroup",
2288 .init_fs_context = cgroup_init_fs_context,
2289 .parameters = cgroup1_fs_parameters,
2290 .kill_sb = cgroup_kill_sb,
2291 .fs_flags = FS_USERNS_MOUNT,
2292};
2293
2294static struct file_system_type cgroup2_fs_type = {
2295 .name = "cgroup2",
2296 .init_fs_context = cgroup_init_fs_context,
2297 .parameters = cgroup2_fs_parameters,
2298 .kill_sb = cgroup_kill_sb,
2299 .fs_flags = FS_USERNS_MOUNT,
2300};
2301
2302#ifdef CONFIG_CPUSETS
2303static const struct fs_context_operations cpuset_fs_context_ops = {
2304 .get_tree = cgroup1_get_tree,
2305 .free = cgroup_fs_context_free,
2306};
2307
2308/*
2309 * This is ugly, but preserves the userspace API for existing cpuset
2310 * users. If someone tries to mount the "cpuset" filesystem, we
2311 * silently switch it to mount "cgroup" instead
2312 */
2313static int cpuset_init_fs_context(struct fs_context *fc)
2314{
2315 char *agent = kstrdup("/sbin/cpuset_release_agent", GFP_USER);
2316 struct cgroup_fs_context *ctx;
2317 int err;
2318
2319 err = cgroup_init_fs_context(fc);
2320 if (err) {
2321 kfree(agent);
2322 return err;
2323 }
2324
2325 fc->ops = &cpuset_fs_context_ops;
2326
2327 ctx = cgroup_fc2context(fc);
2328 ctx->subsys_mask = 1 << cpuset_cgrp_id;
2329 ctx->flags |= CGRP_ROOT_NOPREFIX;
2330 ctx->release_agent = agent;
2331
2332 get_filesystem(&cgroup_fs_type);
2333 put_filesystem(fc->fs_type);
2334 fc->fs_type = &cgroup_fs_type;
2335
2336 return 0;
2337}
2338
2339static struct file_system_type cpuset_fs_type = {
2340 .name = "cpuset",
2341 .init_fs_context = cpuset_init_fs_context,
2342 .fs_flags = FS_USERNS_MOUNT,
2343};
2344#endif
2345
2346int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
2347 struct cgroup_namespace *ns)
2348{
2349 struct cgroup *root = cset_cgroup_from_root(ns->root_cset, cgrp->root);
2350
2351 return kernfs_path_from_node(cgrp->kn, root->kn, buf, buflen);
2352}
2353
2354int cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
2355 struct cgroup_namespace *ns)
2356{
2357 int ret;
2358
2359 mutex_lock(&cgroup_mutex);
2360 spin_lock_irq(&css_set_lock);
2361
2362 ret = cgroup_path_ns_locked(cgrp, buf, buflen, ns);
2363
2364 spin_unlock_irq(&css_set_lock);
2365 mutex_unlock(&cgroup_mutex);
2366
2367 return ret;
2368}
2369EXPORT_SYMBOL_GPL(cgroup_path_ns);
2370
2371/**
2372 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
2373 * @task: target task
2374 * @buf: the buffer to write the path into
2375 * @buflen: the length of the buffer
2376 *
2377 * Determine @task's cgroup on the first (the one with the lowest non-zero
2378 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
2379 * function grabs cgroup_mutex and shouldn't be used inside locks used by
2380 * cgroup controller callbacks.
2381 *
2382 * Return value is the same as kernfs_path().
2383 */
2384int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
2385{
2386 struct cgroup_root *root;
2387 struct cgroup *cgrp;
2388 int hierarchy_id = 1;
2389 int ret;
2390
2391 mutex_lock(&cgroup_mutex);
2392 spin_lock_irq(&css_set_lock);
2393
2394 root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
2395
2396 if (root) {
2397 cgrp = task_cgroup_from_root(task, root);
2398 ret = cgroup_path_ns_locked(cgrp, buf, buflen, &init_cgroup_ns);
2399 } else {
2400 /* if no hierarchy exists, everyone is in "/" */
2401 ret = strscpy(buf, "/", buflen);
2402 }
2403
2404 spin_unlock_irq(&css_set_lock);
2405 mutex_unlock(&cgroup_mutex);
2406 return ret;
2407}
2408EXPORT_SYMBOL_GPL(task_cgroup_path);
2409
2410/**
2411 * cgroup_attach_lock - Lock for ->attach()
2412 * @lock_threadgroup: whether to down_write cgroup_threadgroup_rwsem
2413 *
2414 * cgroup migration sometimes needs to stabilize threadgroups against forks and
2415 * exits by write-locking cgroup_threadgroup_rwsem. However, some ->attach()
2416 * implementations (e.g. cpuset), also need to disable CPU hotplug.
2417 * Unfortunately, letting ->attach() operations acquire cpus_read_lock() can
2418 * lead to deadlocks.
2419 *
2420 * Bringing up a CPU may involve creating and destroying tasks which requires
2421 * read-locking threadgroup_rwsem, so threadgroup_rwsem nests inside
2422 * cpus_read_lock(). If we call an ->attach() which acquires the cpus lock while
2423 * write-locking threadgroup_rwsem, the locking order is reversed and we end up
2424 * waiting for an on-going CPU hotplug operation which in turn is waiting for
2425 * the threadgroup_rwsem to be released to create new tasks. For more details:
2426 *
2427 * http://lkml.kernel.org/r/20220711174629.uehfmqegcwn2lqzu@wubuntu
2428 *
2429 * Resolve the situation by always acquiring cpus_read_lock() before optionally
2430 * write-locking cgroup_threadgroup_rwsem. This allows ->attach() to assume that
2431 * CPU hotplug is disabled on entry.
2432 */
2433void cgroup_attach_lock(bool lock_threadgroup)
2434{
2435 cpus_read_lock();
2436 if (lock_threadgroup)
2437 percpu_down_write(&cgroup_threadgroup_rwsem);
2438}
2439
2440/**
2441 * cgroup_attach_unlock - Undo cgroup_attach_lock()
2442 * @lock_threadgroup: whether to up_write cgroup_threadgroup_rwsem
2443 */
2444void cgroup_attach_unlock(bool lock_threadgroup)
2445{
2446 if (lock_threadgroup)
2447 percpu_up_write(&cgroup_threadgroup_rwsem);
2448 cpus_read_unlock();
2449}
2450
2451/**
2452 * cgroup_migrate_add_task - add a migration target task to a migration context
2453 * @task: target task
2454 * @mgctx: target migration context
2455 *
2456 * Add @task, which is a migration target, to @mgctx->tset. This function
2457 * becomes noop if @task doesn't need to be migrated. @task's css_set
2458 * should have been added as a migration source and @task->cg_list will be
2459 * moved from the css_set's tasks list to mg_tasks one.
2460 */
2461static void cgroup_migrate_add_task(struct task_struct *task,
2462 struct cgroup_mgctx *mgctx)
2463{
2464 struct css_set *cset;
2465
2466 lockdep_assert_held(&css_set_lock);
2467
2468 /* @task either already exited or can't exit until the end */
2469 if (task->flags & PF_EXITING)
2470 return;
2471
2472 /* cgroup_threadgroup_rwsem protects racing against forks */
2473 WARN_ON_ONCE(list_empty(&task->cg_list));
2474
2475 cset = task_css_set(task);
2476 if (!cset->mg_src_cgrp)
2477 return;
2478
2479 mgctx->tset.nr_tasks++;
2480
2481 list_move_tail(&task->cg_list, &cset->mg_tasks);
2482 if (list_empty(&cset->mg_node))
2483 list_add_tail(&cset->mg_node,
2484 &mgctx->tset.src_csets);
2485 if (list_empty(&cset->mg_dst_cset->mg_node))
2486 list_add_tail(&cset->mg_dst_cset->mg_node,
2487 &mgctx->tset.dst_csets);
2488}
2489
2490/**
2491 * cgroup_taskset_first - reset taskset and return the first task
2492 * @tset: taskset of interest
2493 * @dst_cssp: output variable for the destination css
2494 *
2495 * @tset iteration is initialized and the first task is returned.
2496 */
2497struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset,
2498 struct cgroup_subsys_state **dst_cssp)
2499{
2500 tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
2501 tset->cur_task = NULL;
2502
2503 return cgroup_taskset_next(tset, dst_cssp);
2504}
2505
2506/**
2507 * cgroup_taskset_next - iterate to the next task in taskset
2508 * @tset: taskset of interest
2509 * @dst_cssp: output variable for the destination css
2510 *
2511 * Return the next task in @tset. Iteration must have been initialized
2512 * with cgroup_taskset_first().
2513 */
2514struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
2515 struct cgroup_subsys_state **dst_cssp)
2516{
2517 struct css_set *cset = tset->cur_cset;
2518 struct task_struct *task = tset->cur_task;
2519
2520 while (CGROUP_HAS_SUBSYS_CONFIG && &cset->mg_node != tset->csets) {
2521 if (!task)
2522 task = list_first_entry(&cset->mg_tasks,
2523 struct task_struct, cg_list);
2524 else
2525 task = list_next_entry(task, cg_list);
2526
2527 if (&task->cg_list != &cset->mg_tasks) {
2528 tset->cur_cset = cset;
2529 tset->cur_task = task;
2530
2531 /*
2532 * This function may be called both before and
2533 * after cgroup_taskset_migrate(). The two cases
2534 * can be distinguished by looking at whether @cset
2535 * has its ->mg_dst_cset set.
2536 */
2537 if (cset->mg_dst_cset)
2538 *dst_cssp = cset->mg_dst_cset->subsys[tset->ssid];
2539 else
2540 *dst_cssp = cset->subsys[tset->ssid];
2541
2542 return task;
2543 }
2544
2545 cset = list_next_entry(cset, mg_node);
2546 task = NULL;
2547 }
2548
2549 return NULL;
2550}
2551
2552/**
2553 * cgroup_migrate_execute - migrate a taskset
2554 * @mgctx: migration context
2555 *
2556 * Migrate tasks in @mgctx as setup by migration preparation functions.
2557 * This function fails iff one of the ->can_attach callbacks fails and
2558 * guarantees that either all or none of the tasks in @mgctx are migrated.
2559 * @mgctx is consumed regardless of success.
2560 */
2561static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx)
2562{
2563 struct cgroup_taskset *tset = &mgctx->tset;
2564 struct cgroup_subsys *ss;
2565 struct task_struct *task, *tmp_task;
2566 struct css_set *cset, *tmp_cset;
2567 int ssid, failed_ssid, ret;
2568
2569 /* check that we can legitimately attach to the cgroup */
2570 if (tset->nr_tasks) {
2571 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2572 if (ss->can_attach) {
2573 tset->ssid = ssid;
2574 ret = ss->can_attach(tset);
2575 if (ret) {
2576 failed_ssid = ssid;
2577 goto out_cancel_attach;
2578 }
2579 }
2580 } while_each_subsys_mask();
2581 }
2582
2583 /*
2584 * Now that we're guaranteed success, proceed to move all tasks to
2585 * the new cgroup. There are no failure cases after here, so this
2586 * is the commit point.
2587 */
2588 spin_lock_irq(&css_set_lock);
2589 list_for_each_entry(cset, &tset->src_csets, mg_node) {
2590 list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list) {
2591 struct css_set *from_cset = task_css_set(task);
2592 struct css_set *to_cset = cset->mg_dst_cset;
2593
2594 get_css_set(to_cset);
2595 to_cset->nr_tasks++;
2596 css_set_move_task(task, from_cset, to_cset, true);
2597 from_cset->nr_tasks--;
2598 /*
2599 * If the source or destination cgroup is frozen,
2600 * the task might require to change its state.
2601 */
2602 cgroup_freezer_migrate_task(task, from_cset->dfl_cgrp,
2603 to_cset->dfl_cgrp);
2604 put_css_set_locked(from_cset);
2605
2606 }
2607 }
2608 spin_unlock_irq(&css_set_lock);
2609
2610 /*
2611 * Migration is committed, all target tasks are now on dst_csets.
2612 * Nothing is sensitive to fork() after this point. Notify
2613 * controllers that migration is complete.
2614 */
2615 tset->csets = &tset->dst_csets;
2616
2617 if (tset->nr_tasks) {
2618 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2619 if (ss->attach) {
2620 tset->ssid = ssid;
2621 ss->attach(tset);
2622 }
2623 } while_each_subsys_mask();
2624 }
2625
2626 ret = 0;
2627 goto out_release_tset;
2628
2629out_cancel_attach:
2630 if (tset->nr_tasks) {
2631 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2632 if (ssid == failed_ssid)
2633 break;
2634 if (ss->cancel_attach) {
2635 tset->ssid = ssid;
2636 ss->cancel_attach(tset);
2637 }
2638 } while_each_subsys_mask();
2639 }
2640out_release_tset:
2641 spin_lock_irq(&css_set_lock);
2642 list_splice_init(&tset->dst_csets, &tset->src_csets);
2643 list_for_each_entry_safe(cset, tmp_cset, &tset->src_csets, mg_node) {
2644 list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
2645 list_del_init(&cset->mg_node);
2646 }
2647 spin_unlock_irq(&css_set_lock);
2648
2649 /*
2650 * Re-initialize the cgroup_taskset structure in case it is reused
2651 * again in another cgroup_migrate_add_task()/cgroup_migrate_execute()
2652 * iteration.
2653 */
2654 tset->nr_tasks = 0;
2655 tset->csets = &tset->src_csets;
2656 return ret;
2657}
2658
2659/**
2660 * cgroup_migrate_vet_dst - verify whether a cgroup can be migration destination
2661 * @dst_cgrp: destination cgroup to test
2662 *
2663 * On the default hierarchy, except for the mixable, (possible) thread root
2664 * and threaded cgroups, subtree_control must be zero for migration
2665 * destination cgroups with tasks so that child cgroups don't compete
2666 * against tasks.
2667 */
2668int cgroup_migrate_vet_dst(struct cgroup *dst_cgrp)
2669{
2670 /* v1 doesn't have any restriction */
2671 if (!cgroup_on_dfl(dst_cgrp))
2672 return 0;
2673
2674 /* verify @dst_cgrp can host resources */
2675 if (!cgroup_is_valid_domain(dst_cgrp->dom_cgrp))
2676 return -EOPNOTSUPP;
2677
2678 /*
2679 * If @dst_cgrp is already or can become a thread root or is
2680 * threaded, it doesn't matter.
2681 */
2682 if (cgroup_can_be_thread_root(dst_cgrp) || cgroup_is_threaded(dst_cgrp))
2683 return 0;
2684
2685 /* apply no-internal-process constraint */
2686 if (dst_cgrp->subtree_control)
2687 return -EBUSY;
2688
2689 return 0;
2690}
2691
2692/**
2693 * cgroup_migrate_finish - cleanup after attach
2694 * @mgctx: migration context
2695 *
2696 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
2697 * those functions for details.
2698 */
2699void cgroup_migrate_finish(struct cgroup_mgctx *mgctx)
2700{
2701 struct css_set *cset, *tmp_cset;
2702
2703 lockdep_assert_held(&cgroup_mutex);
2704
2705 spin_lock_irq(&css_set_lock);
2706
2707 list_for_each_entry_safe(cset, tmp_cset, &mgctx->preloaded_src_csets,
2708 mg_src_preload_node) {
2709 cset->mg_src_cgrp = NULL;
2710 cset->mg_dst_cgrp = NULL;
2711 cset->mg_dst_cset = NULL;
2712 list_del_init(&cset->mg_src_preload_node);
2713 put_css_set_locked(cset);
2714 }
2715
2716 list_for_each_entry_safe(cset, tmp_cset, &mgctx->preloaded_dst_csets,
2717 mg_dst_preload_node) {
2718 cset->mg_src_cgrp = NULL;
2719 cset->mg_dst_cgrp = NULL;
2720 cset->mg_dst_cset = NULL;
2721 list_del_init(&cset->mg_dst_preload_node);
2722 put_css_set_locked(cset);
2723 }
2724
2725 spin_unlock_irq(&css_set_lock);
2726}
2727
2728/**
2729 * cgroup_migrate_add_src - add a migration source css_set
2730 * @src_cset: the source css_set to add
2731 * @dst_cgrp: the destination cgroup
2732 * @mgctx: migration context
2733 *
2734 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
2735 * @src_cset and add it to @mgctx->src_csets, which should later be cleaned
2736 * up by cgroup_migrate_finish().
2737 *
2738 * This function may be called without holding cgroup_threadgroup_rwsem
2739 * even if the target is a process. Threads may be created and destroyed
2740 * but as long as cgroup_mutex is not dropped, no new css_set can be put
2741 * into play and the preloaded css_sets are guaranteed to cover all
2742 * migrations.
2743 */
2744void cgroup_migrate_add_src(struct css_set *src_cset,
2745 struct cgroup *dst_cgrp,
2746 struct cgroup_mgctx *mgctx)
2747{
2748 struct cgroup *src_cgrp;
2749
2750 lockdep_assert_held(&cgroup_mutex);
2751 lockdep_assert_held(&css_set_lock);
2752
2753 /*
2754 * If ->dead, @src_set is associated with one or more dead cgroups
2755 * and doesn't contain any migratable tasks. Ignore it early so
2756 * that the rest of migration path doesn't get confused by it.
2757 */
2758 if (src_cset->dead)
2759 return;
2760
2761 if (!list_empty(&src_cset->mg_src_preload_node))
2762 return;
2763
2764 src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);
2765
2766 WARN_ON(src_cset->mg_src_cgrp);
2767 WARN_ON(src_cset->mg_dst_cgrp);
2768 WARN_ON(!list_empty(&src_cset->mg_tasks));
2769 WARN_ON(!list_empty(&src_cset->mg_node));
2770
2771 src_cset->mg_src_cgrp = src_cgrp;
2772 src_cset->mg_dst_cgrp = dst_cgrp;
2773 get_css_set(src_cset);
2774 list_add_tail(&src_cset->mg_src_preload_node, &mgctx->preloaded_src_csets);
2775}
2776
2777/**
2778 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2779 * @mgctx: migration context
2780 *
2781 * Tasks are about to be moved and all the source css_sets have been
2782 * preloaded to @mgctx->preloaded_src_csets. This function looks up and
2783 * pins all destination css_sets, links each to its source, and append them
2784 * to @mgctx->preloaded_dst_csets.
2785 *
2786 * This function must be called after cgroup_migrate_add_src() has been
2787 * called on each migration source css_set. After migration is performed
2788 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2789 * @mgctx.
2790 */
2791int cgroup_migrate_prepare_dst(struct cgroup_mgctx *mgctx)
2792{
2793 struct css_set *src_cset, *tmp_cset;
2794
2795 lockdep_assert_held(&cgroup_mutex);
2796
2797 /* look up the dst cset for each src cset and link it to src */
2798 list_for_each_entry_safe(src_cset, tmp_cset, &mgctx->preloaded_src_csets,
2799 mg_src_preload_node) {
2800 struct css_set *dst_cset;
2801 struct cgroup_subsys *ss;
2802 int ssid;
2803
2804 dst_cset = find_css_set(src_cset, src_cset->mg_dst_cgrp);
2805 if (!dst_cset)
2806 return -ENOMEM;
2807
2808 WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
2809
2810 /*
2811 * If src cset equals dst, it's noop. Drop the src.
2812 * cgroup_migrate() will skip the cset too. Note that we
2813 * can't handle src == dst as some nodes are used by both.
2814 */
2815 if (src_cset == dst_cset) {
2816 src_cset->mg_src_cgrp = NULL;
2817 src_cset->mg_dst_cgrp = NULL;
2818 list_del_init(&src_cset->mg_src_preload_node);
2819 put_css_set(src_cset);
2820 put_css_set(dst_cset);
2821 continue;
2822 }
2823
2824 src_cset->mg_dst_cset = dst_cset;
2825
2826 if (list_empty(&dst_cset->mg_dst_preload_node))
2827 list_add_tail(&dst_cset->mg_dst_preload_node,
2828 &mgctx->preloaded_dst_csets);
2829 else
2830 put_css_set(dst_cset);
2831
2832 for_each_subsys(ss, ssid)
2833 if (src_cset->subsys[ssid] != dst_cset->subsys[ssid])
2834 mgctx->ss_mask |= 1 << ssid;
2835 }
2836
2837 return 0;
2838}
2839
2840/**
2841 * cgroup_migrate - migrate a process or task to a cgroup
2842 * @leader: the leader of the process or the task to migrate
2843 * @threadgroup: whether @leader points to the whole process or a single task
2844 * @mgctx: migration context
2845 *
2846 * Migrate a process or task denoted by @leader. If migrating a process,
2847 * the caller must be holding cgroup_threadgroup_rwsem. The caller is also
2848 * responsible for invoking cgroup_migrate_add_src() and
2849 * cgroup_migrate_prepare_dst() on the targets before invoking this
2850 * function and following up with cgroup_migrate_finish().
2851 *
2852 * As long as a controller's ->can_attach() doesn't fail, this function is
2853 * guaranteed to succeed. This means that, excluding ->can_attach()
2854 * failure, when migrating multiple targets, the success or failure can be
2855 * decided for all targets by invoking group_migrate_prepare_dst() before
2856 * actually starting migrating.
2857 */
2858int cgroup_migrate(struct task_struct *leader, bool threadgroup,
2859 struct cgroup_mgctx *mgctx)
2860{
2861 struct task_struct *task;
2862
2863 /*
2864 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2865 * already PF_EXITING could be freed from underneath us unless we
2866 * take an rcu_read_lock.
2867 */
2868 spin_lock_irq(&css_set_lock);
2869 task = leader;
2870 do {
2871 cgroup_migrate_add_task(task, mgctx);
2872 if (!threadgroup)
2873 break;
2874 } while_each_thread(leader, task);
2875 spin_unlock_irq(&css_set_lock);
2876
2877 return cgroup_migrate_execute(mgctx);
2878}
2879
2880/**
2881 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2882 * @dst_cgrp: the cgroup to attach to
2883 * @leader: the task or the leader of the threadgroup to be attached
2884 * @threadgroup: attach the whole threadgroup?
2885 *
2886 * Call holding cgroup_mutex and cgroup_threadgroup_rwsem.
2887 */
2888int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
2889 bool threadgroup)
2890{
2891 DEFINE_CGROUP_MGCTX(mgctx);
2892 struct task_struct *task;
2893 int ret = 0;
2894
2895 /* look up all src csets */
2896 spin_lock_irq(&css_set_lock);
2897 rcu_read_lock();
2898 task = leader;
2899 do {
2900 cgroup_migrate_add_src(task_css_set(task), dst_cgrp, &mgctx);
2901 if (!threadgroup)
2902 break;
2903 } while_each_thread(leader, task);
2904 rcu_read_unlock();
2905 spin_unlock_irq(&css_set_lock);
2906
2907 /* prepare dst csets and commit */
2908 ret = cgroup_migrate_prepare_dst(&mgctx);
2909 if (!ret)
2910 ret = cgroup_migrate(leader, threadgroup, &mgctx);
2911
2912 cgroup_migrate_finish(&mgctx);
2913
2914 if (!ret)
2915 TRACE_CGROUP_PATH(attach_task, dst_cgrp, leader, threadgroup);
2916
2917 return ret;
2918}
2919
2920struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup,
2921 bool *threadgroup_locked)
2922{
2923 struct task_struct *tsk;
2924 pid_t pid;
2925
2926 if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
2927 return ERR_PTR(-EINVAL);
2928
2929 /*
2930 * If we migrate a single thread, we don't care about threadgroup
2931 * stability. If the thread is `current`, it won't exit(2) under our
2932 * hands or change PID through exec(2). We exclude
2933 * cgroup_update_dfl_csses and other cgroup_{proc,thread}s_write
2934 * callers by cgroup_mutex.
2935 * Therefore, we can skip the global lock.
2936 */
2937 lockdep_assert_held(&cgroup_mutex);
2938 *threadgroup_locked = pid || threadgroup;
2939 cgroup_attach_lock(*threadgroup_locked);
2940
2941 rcu_read_lock();
2942 if (pid) {
2943 tsk = find_task_by_vpid(pid);
2944 if (!tsk) {
2945 tsk = ERR_PTR(-ESRCH);
2946 goto out_unlock_threadgroup;
2947 }
2948 } else {
2949 tsk = current;
2950 }
2951
2952 if (threadgroup)
2953 tsk = tsk->group_leader;
2954
2955 /*
2956 * kthreads may acquire PF_NO_SETAFFINITY during initialization.
2957 * If userland migrates such a kthread to a non-root cgroup, it can
2958 * become trapped in a cpuset, or RT kthread may be born in a
2959 * cgroup with no rt_runtime allocated. Just say no.
2960 */
2961 if (tsk->no_cgroup_migration || (tsk->flags & PF_NO_SETAFFINITY)) {
2962 tsk = ERR_PTR(-EINVAL);
2963 goto out_unlock_threadgroup;
2964 }
2965
2966 get_task_struct(tsk);
2967 goto out_unlock_rcu;
2968
2969out_unlock_threadgroup:
2970 cgroup_attach_unlock(*threadgroup_locked);
2971 *threadgroup_locked = false;
2972out_unlock_rcu:
2973 rcu_read_unlock();
2974 return tsk;
2975}
2976
2977void cgroup_procs_write_finish(struct task_struct *task, bool threadgroup_locked)
2978{
2979 struct cgroup_subsys *ss;
2980 int ssid;
2981
2982 /* release reference from cgroup_procs_write_start() */
2983 put_task_struct(task);
2984
2985 cgroup_attach_unlock(threadgroup_locked);
2986
2987 for_each_subsys(ss, ssid)
2988 if (ss->post_attach)
2989 ss->post_attach();
2990}
2991
2992static void cgroup_print_ss_mask(struct seq_file *seq, u16 ss_mask)
2993{
2994 struct cgroup_subsys *ss;
2995 bool printed = false;
2996 int ssid;
2997
2998 do_each_subsys_mask(ss, ssid, ss_mask) {
2999 if (printed)
3000 seq_putc(seq, ' ');
3001 seq_puts(seq, ss->name);
3002 printed = true;
3003 } while_each_subsys_mask();
3004 if (printed)
3005 seq_putc(seq, '\n');
3006}
3007
3008/* show controllers which are enabled from the parent */
3009static int cgroup_controllers_show(struct seq_file *seq, void *v)
3010{
3011 struct cgroup *cgrp = seq_css(seq)->cgroup;
3012
3013 cgroup_print_ss_mask(seq, cgroup_control(cgrp));
3014 return 0;
3015}
3016
3017/* show controllers which are enabled for a given cgroup's children */
3018static int cgroup_subtree_control_show(struct seq_file *seq, void *v)
3019{
3020 struct cgroup *cgrp = seq_css(seq)->cgroup;
3021
3022 cgroup_print_ss_mask(seq, cgrp->subtree_control);
3023 return 0;
3024}
3025
3026/**
3027 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
3028 * @cgrp: root of the subtree to update csses for
3029 *
3030 * @cgrp's control masks have changed and its subtree's css associations
3031 * need to be updated accordingly. This function looks up all css_sets
3032 * which are attached to the subtree, creates the matching updated css_sets
3033 * and migrates the tasks to the new ones.
3034 */
3035static int cgroup_update_dfl_csses(struct cgroup *cgrp)
3036{
3037 DEFINE_CGROUP_MGCTX(mgctx);
3038 struct cgroup_subsys_state *d_css;
3039 struct cgroup *dsct;
3040 struct css_set *src_cset;
3041 bool has_tasks;
3042 int ret;
3043
3044 lockdep_assert_held(&cgroup_mutex);
3045
3046 /* look up all csses currently attached to @cgrp's subtree */
3047 spin_lock_irq(&css_set_lock);
3048 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3049 struct cgrp_cset_link *link;
3050
3051 /*
3052 * As cgroup_update_dfl_csses() is only called by
3053 * cgroup_apply_control(). The csses associated with the
3054 * given cgrp will not be affected by changes made to
3055 * its subtree_control file. We can skip them.
3056 */
3057 if (dsct == cgrp)
3058 continue;
3059
3060 list_for_each_entry(link, &dsct->cset_links, cset_link)
3061 cgroup_migrate_add_src(link->cset, dsct, &mgctx);
3062 }
3063 spin_unlock_irq(&css_set_lock);
3064
3065 /*
3066 * We need to write-lock threadgroup_rwsem while migrating tasks.
3067 * However, if there are no source csets for @cgrp, changing its
3068 * controllers isn't gonna produce any task migrations and the
3069 * write-locking can be skipped safely.
3070 */
3071 has_tasks = !list_empty(&mgctx.preloaded_src_csets);
3072 cgroup_attach_lock(has_tasks);
3073
3074 /* NULL dst indicates self on default hierarchy */
3075 ret = cgroup_migrate_prepare_dst(&mgctx);
3076 if (ret)
3077 goto out_finish;
3078
3079 spin_lock_irq(&css_set_lock);
3080 list_for_each_entry(src_cset, &mgctx.preloaded_src_csets,
3081 mg_src_preload_node) {
3082 struct task_struct *task, *ntask;
3083
3084 /* all tasks in src_csets need to be migrated */
3085 list_for_each_entry_safe(task, ntask, &src_cset->tasks, cg_list)
3086 cgroup_migrate_add_task(task, &mgctx);
3087 }
3088 spin_unlock_irq(&css_set_lock);
3089
3090 ret = cgroup_migrate_execute(&mgctx);
3091out_finish:
3092 cgroup_migrate_finish(&mgctx);
3093 cgroup_attach_unlock(has_tasks);
3094 return ret;
3095}
3096
3097/**
3098 * cgroup_lock_and_drain_offline - lock cgroup_mutex and drain offlined csses
3099 * @cgrp: root of the target subtree
3100 *
3101 * Because css offlining is asynchronous, userland may try to re-enable a
3102 * controller while the previous css is still around. This function grabs
3103 * cgroup_mutex and drains the previous css instances of @cgrp's subtree.
3104 */
3105void cgroup_lock_and_drain_offline(struct cgroup *cgrp)
3106 __acquires(&cgroup_mutex)
3107{
3108 struct cgroup *dsct;
3109 struct cgroup_subsys_state *d_css;
3110 struct cgroup_subsys *ss;
3111 int ssid;
3112
3113restart:
3114 mutex_lock(&cgroup_mutex);
3115
3116 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3117 for_each_subsys(ss, ssid) {
3118 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3119 DEFINE_WAIT(wait);
3120
3121 if (!css || !percpu_ref_is_dying(&css->refcnt))
3122 continue;
3123
3124 cgroup_get_live(dsct);
3125 prepare_to_wait(&dsct->offline_waitq, &wait,
3126 TASK_UNINTERRUPTIBLE);
3127
3128 mutex_unlock(&cgroup_mutex);
3129 schedule();
3130 finish_wait(&dsct->offline_waitq, &wait);
3131
3132 cgroup_put(dsct);
3133 goto restart;
3134 }
3135 }
3136}
3137
3138/**
3139 * cgroup_save_control - save control masks and dom_cgrp of a subtree
3140 * @cgrp: root of the target subtree
3141 *
3142 * Save ->subtree_control, ->subtree_ss_mask and ->dom_cgrp to the
3143 * respective old_ prefixed fields for @cgrp's subtree including @cgrp
3144 * itself.
3145 */
3146static void cgroup_save_control(struct cgroup *cgrp)
3147{
3148 struct cgroup *dsct;
3149 struct cgroup_subsys_state *d_css;
3150
3151 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3152 dsct->old_subtree_control = dsct->subtree_control;
3153 dsct->old_subtree_ss_mask = dsct->subtree_ss_mask;
3154 dsct->old_dom_cgrp = dsct->dom_cgrp;
3155 }
3156}
3157
3158/**
3159 * cgroup_propagate_control - refresh control masks of a subtree
3160 * @cgrp: root of the target subtree
3161 *
3162 * For @cgrp and its subtree, ensure ->subtree_ss_mask matches
3163 * ->subtree_control and propagate controller availability through the
3164 * subtree so that descendants don't have unavailable controllers enabled.
3165 */
3166static void cgroup_propagate_control(struct cgroup *cgrp)
3167{
3168 struct cgroup *dsct;
3169 struct cgroup_subsys_state *d_css;
3170
3171 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3172 dsct->subtree_control &= cgroup_control(dsct);
3173 dsct->subtree_ss_mask =
3174 cgroup_calc_subtree_ss_mask(dsct->subtree_control,
3175 cgroup_ss_mask(dsct));
3176 }
3177}
3178
3179/**
3180 * cgroup_restore_control - restore control masks and dom_cgrp of a subtree
3181 * @cgrp: root of the target subtree
3182 *
3183 * Restore ->subtree_control, ->subtree_ss_mask and ->dom_cgrp from the
3184 * respective old_ prefixed fields for @cgrp's subtree including @cgrp
3185 * itself.
3186 */
3187static void cgroup_restore_control(struct cgroup *cgrp)
3188{
3189 struct cgroup *dsct;
3190 struct cgroup_subsys_state *d_css;
3191
3192 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3193 dsct->subtree_control = dsct->old_subtree_control;
3194 dsct->subtree_ss_mask = dsct->old_subtree_ss_mask;
3195 dsct->dom_cgrp = dsct->old_dom_cgrp;
3196 }
3197}
3198
3199static bool css_visible(struct cgroup_subsys_state *css)
3200{
3201 struct cgroup_subsys *ss = css->ss;
3202 struct cgroup *cgrp = css->cgroup;
3203
3204 if (cgroup_control(cgrp) & (1 << ss->id))
3205 return true;
3206 if (!(cgroup_ss_mask(cgrp) & (1 << ss->id)))
3207 return false;
3208 return cgroup_on_dfl(cgrp) && ss->implicit_on_dfl;
3209}
3210
3211/**
3212 * cgroup_apply_control_enable - enable or show csses according to control
3213 * @cgrp: root of the target subtree
3214 *
3215 * Walk @cgrp's subtree and create new csses or make the existing ones
3216 * visible. A css is created invisible if it's being implicitly enabled
3217 * through dependency. An invisible css is made visible when the userland
3218 * explicitly enables it.
3219 *
3220 * Returns 0 on success, -errno on failure. On failure, csses which have
3221 * been processed already aren't cleaned up. The caller is responsible for
3222 * cleaning up with cgroup_apply_control_disable().
3223 */
3224static int cgroup_apply_control_enable(struct cgroup *cgrp)
3225{
3226 struct cgroup *dsct;
3227 struct cgroup_subsys_state *d_css;
3228 struct cgroup_subsys *ss;
3229 int ssid, ret;
3230
3231 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3232 for_each_subsys(ss, ssid) {
3233 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3234
3235 if (!(cgroup_ss_mask(dsct) & (1 << ss->id)))
3236 continue;
3237
3238 if (!css) {
3239 css = css_create(dsct, ss);
3240 if (IS_ERR(css))
3241 return PTR_ERR(css);
3242 }
3243
3244 WARN_ON_ONCE(percpu_ref_is_dying(&css->refcnt));
3245
3246 if (css_visible(css)) {
3247 ret = css_populate_dir(css);
3248 if (ret)
3249 return ret;
3250 }
3251 }
3252 }
3253
3254 return 0;
3255}
3256
3257/**
3258 * cgroup_apply_control_disable - kill or hide csses according to control
3259 * @cgrp: root of the target subtree
3260 *
3261 * Walk @cgrp's subtree and kill and hide csses so that they match
3262 * cgroup_ss_mask() and cgroup_visible_mask().
3263 *
3264 * A css is hidden when the userland requests it to be disabled while other
3265 * subsystems are still depending on it. The css must not actively control
3266 * resources and be in the vanilla state if it's made visible again later.
3267 * Controllers which may be depended upon should provide ->css_reset() for
3268 * this purpose.
3269 */
3270static void cgroup_apply_control_disable(struct cgroup *cgrp)
3271{
3272 struct cgroup *dsct;
3273 struct cgroup_subsys_state *d_css;
3274 struct cgroup_subsys *ss;
3275 int ssid;
3276
3277 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3278 for_each_subsys(ss, ssid) {
3279 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3280
3281 if (!css)
3282 continue;
3283
3284 WARN_ON_ONCE(percpu_ref_is_dying(&css->refcnt));
3285
3286 if (css->parent &&
3287 !(cgroup_ss_mask(dsct) & (1 << ss->id))) {
3288 kill_css(css);
3289 } else if (!css_visible(css)) {
3290 css_clear_dir(css);
3291 if (ss->css_reset)
3292 ss->css_reset(css);
3293 }
3294 }
3295 }
3296}
3297
3298/**
3299 * cgroup_apply_control - apply control mask updates to the subtree
3300 * @cgrp: root of the target subtree
3301 *
3302 * subsystems can be enabled and disabled in a subtree using the following
3303 * steps.
3304 *
3305 * 1. Call cgroup_save_control() to stash the current state.
3306 * 2. Update ->subtree_control masks in the subtree as desired.
3307 * 3. Call cgroup_apply_control() to apply the changes.
3308 * 4. Optionally perform other related operations.
3309 * 5. Call cgroup_finalize_control() to finish up.
3310 *
3311 * This function implements step 3 and propagates the mask changes
3312 * throughout @cgrp's subtree, updates csses accordingly and perform
3313 * process migrations.
3314 */
3315static int cgroup_apply_control(struct cgroup *cgrp)
3316{
3317 int ret;
3318
3319 cgroup_propagate_control(cgrp);
3320
3321 ret = cgroup_apply_control_enable(cgrp);
3322 if (ret)
3323 return ret;
3324
3325 /*
3326 * At this point, cgroup_e_css_by_mask() results reflect the new csses
3327 * making the following cgroup_update_dfl_csses() properly update
3328 * css associations of all tasks in the subtree.
3329 */
3330 return cgroup_update_dfl_csses(cgrp);
3331}
3332
3333/**
3334 * cgroup_finalize_control - finalize control mask update
3335 * @cgrp: root of the target subtree
3336 * @ret: the result of the update
3337 *
3338 * Finalize control mask update. See cgroup_apply_control() for more info.
3339 */
3340static void cgroup_finalize_control(struct cgroup *cgrp, int ret)
3341{
3342 if (ret) {
3343 cgroup_restore_control(cgrp);
3344 cgroup_propagate_control(cgrp);
3345 }
3346
3347 cgroup_apply_control_disable(cgrp);
3348}
3349
3350static int cgroup_vet_subtree_control_enable(struct cgroup *cgrp, u16 enable)
3351{
3352 u16 domain_enable = enable & ~cgrp_dfl_threaded_ss_mask;
3353
3354 /* if nothing is getting enabled, nothing to worry about */
3355 if (!enable)
3356 return 0;
3357
3358 /* can @cgrp host any resources? */
3359 if (!cgroup_is_valid_domain(cgrp->dom_cgrp))
3360 return -EOPNOTSUPP;
3361
3362 /* mixables don't care */
3363 if (cgroup_is_mixable(cgrp))
3364 return 0;
3365
3366 if (domain_enable) {
3367 /* can't enable domain controllers inside a thread subtree */
3368 if (cgroup_is_thread_root(cgrp) || cgroup_is_threaded(cgrp))
3369 return -EOPNOTSUPP;
3370 } else {
3371 /*
3372 * Threaded controllers can handle internal competitions
3373 * and are always allowed inside a (prospective) thread
3374 * subtree.
3375 */
3376 if (cgroup_can_be_thread_root(cgrp) || cgroup_is_threaded(cgrp))
3377 return 0;
3378 }
3379
3380 /*
3381 * Controllers can't be enabled for a cgroup with tasks to avoid
3382 * child cgroups competing against tasks.
3383 */
3384 if (cgroup_has_tasks(cgrp))
3385 return -EBUSY;
3386
3387 return 0;
3388}
3389
3390/* change the enabled child controllers for a cgroup in the default hierarchy */
3391static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
3392 char *buf, size_t nbytes,
3393 loff_t off)
3394{
3395 u16 enable = 0, disable = 0;
3396 struct cgroup *cgrp, *child;
3397 struct cgroup_subsys *ss;
3398 char *tok;
3399 int ssid, ret;
3400
3401 /*
3402 * Parse input - space separated list of subsystem names prefixed
3403 * with either + or -.
3404 */
3405 buf = strstrip(buf);
3406 while ((tok = strsep(&buf, " "))) {
3407 if (tok[0] == '\0')
3408 continue;
3409 do_each_subsys_mask(ss, ssid, ~cgrp_dfl_inhibit_ss_mask) {
3410 if (!cgroup_ssid_enabled(ssid) ||
3411 strcmp(tok + 1, ss->name))
3412 continue;
3413
3414 if (*tok == '+') {
3415 enable |= 1 << ssid;
3416 disable &= ~(1 << ssid);
3417 } else if (*tok == '-') {
3418 disable |= 1 << ssid;
3419 enable &= ~(1 << ssid);
3420 } else {
3421 return -EINVAL;
3422 }
3423 break;
3424 } while_each_subsys_mask();
3425 if (ssid == CGROUP_SUBSYS_COUNT)
3426 return -EINVAL;
3427 }
3428
3429 cgrp = cgroup_kn_lock_live(of->kn, true);
3430 if (!cgrp)
3431 return -ENODEV;
3432
3433 for_each_subsys(ss, ssid) {
3434 if (enable & (1 << ssid)) {
3435 if (cgrp->subtree_control & (1 << ssid)) {
3436 enable &= ~(1 << ssid);
3437 continue;
3438 }
3439
3440 if (!(cgroup_control(cgrp) & (1 << ssid))) {
3441 ret = -ENOENT;
3442 goto out_unlock;
3443 }
3444 } else if (disable & (1 << ssid)) {
3445 if (!(cgrp->subtree_control & (1 << ssid))) {
3446 disable &= ~(1 << ssid);
3447 continue;
3448 }
3449
3450 /* a child has it enabled? */
3451 cgroup_for_each_live_child(child, cgrp) {
3452 if (child->subtree_control & (1 << ssid)) {
3453 ret = -EBUSY;
3454 goto out_unlock;
3455 }
3456 }
3457 }
3458 }
3459
3460 if (!enable && !disable) {
3461 ret = 0;
3462 goto out_unlock;
3463 }
3464
3465 ret = cgroup_vet_subtree_control_enable(cgrp, enable);
3466 if (ret)
3467 goto out_unlock;
3468
3469 /* save and update control masks and prepare csses */
3470 cgroup_save_control(cgrp);
3471
3472 cgrp->subtree_control |= enable;
3473 cgrp->subtree_control &= ~disable;
3474
3475 ret = cgroup_apply_control(cgrp);
3476 cgroup_finalize_control(cgrp, ret);
3477 if (ret)
3478 goto out_unlock;
3479
3480 kernfs_activate(cgrp->kn);
3481out_unlock:
3482 cgroup_kn_unlock(of->kn);
3483 return ret ?: nbytes;
3484}
3485
3486/**
3487 * cgroup_enable_threaded - make @cgrp threaded
3488 * @cgrp: the target cgroup
3489 *
3490 * Called when "threaded" is written to the cgroup.type interface file and
3491 * tries to make @cgrp threaded and join the parent's resource domain.
3492 * This function is never called on the root cgroup as cgroup.type doesn't
3493 * exist on it.
3494 */
3495static int cgroup_enable_threaded(struct cgroup *cgrp)
3496{
3497 struct cgroup *parent = cgroup_parent(cgrp);
3498 struct cgroup *dom_cgrp = parent->dom_cgrp;
3499 struct cgroup *dsct;
3500 struct cgroup_subsys_state *d_css;
3501 int ret;
3502
3503 lockdep_assert_held(&cgroup_mutex);
3504
3505 /* noop if already threaded */
3506 if (cgroup_is_threaded(cgrp))
3507 return 0;
3508
3509 /*
3510 * If @cgroup is populated or has domain controllers enabled, it
3511 * can't be switched. While the below cgroup_can_be_thread_root()
3512 * test can catch the same conditions, that's only when @parent is
3513 * not mixable, so let's check it explicitly.
3514 */
3515 if (cgroup_is_populated(cgrp) ||
3516 cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)
3517 return -EOPNOTSUPP;
3518
3519 /* we're joining the parent's domain, ensure its validity */
3520 if (!cgroup_is_valid_domain(dom_cgrp) ||
3521 !cgroup_can_be_thread_root(dom_cgrp))
3522 return -EOPNOTSUPP;
3523
3524 /*
3525 * The following shouldn't cause actual migrations and should
3526 * always succeed.
3527 */
3528 cgroup_save_control(cgrp);
3529
3530 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp)
3531 if (dsct == cgrp || cgroup_is_threaded(dsct))
3532 dsct->dom_cgrp = dom_cgrp;
3533
3534 ret = cgroup_apply_control(cgrp);
3535 if (!ret)
3536 parent->nr_threaded_children++;
3537
3538 cgroup_finalize_control(cgrp, ret);
3539 return ret;
3540}
3541
3542static int cgroup_type_show(struct seq_file *seq, void *v)
3543{
3544 struct cgroup *cgrp = seq_css(seq)->cgroup;
3545
3546 if (cgroup_is_threaded(cgrp))
3547 seq_puts(seq, "threaded\n");
3548 else if (!cgroup_is_valid_domain(cgrp))
3549 seq_puts(seq, "domain invalid\n");
3550 else if (cgroup_is_thread_root(cgrp))
3551 seq_puts(seq, "domain threaded\n");
3552 else
3553 seq_puts(seq, "domain\n");
3554
3555 return 0;
3556}
3557
3558static ssize_t cgroup_type_write(struct kernfs_open_file *of, char *buf,
3559 size_t nbytes, loff_t off)
3560{
3561 struct cgroup *cgrp;
3562 int ret;
3563
3564 /* only switching to threaded mode is supported */
3565 if (strcmp(strstrip(buf), "threaded"))
3566 return -EINVAL;
3567
3568 /* drain dying csses before we re-apply (threaded) subtree control */
3569 cgrp = cgroup_kn_lock_live(of->kn, true);
3570 if (!cgrp)
3571 return -ENOENT;
3572
3573 /* threaded can only be enabled */
3574 ret = cgroup_enable_threaded(cgrp);
3575
3576 cgroup_kn_unlock(of->kn);
3577 return ret ?: nbytes;
3578}
3579
3580static int cgroup_max_descendants_show(struct seq_file *seq, void *v)
3581{
3582 struct cgroup *cgrp = seq_css(seq)->cgroup;
3583 int descendants = READ_ONCE(cgrp->max_descendants);
3584
3585 if (descendants == INT_MAX)
3586 seq_puts(seq, "max\n");
3587 else
3588 seq_printf(seq, "%d\n", descendants);
3589
3590 return 0;
3591}
3592
3593static ssize_t cgroup_max_descendants_write(struct kernfs_open_file *of,
3594 char *buf, size_t nbytes, loff_t off)
3595{
3596 struct cgroup *cgrp;
3597 int descendants;
3598 ssize_t ret;
3599
3600 buf = strstrip(buf);
3601 if (!strcmp(buf, "max")) {
3602 descendants = INT_MAX;
3603 } else {
3604 ret = kstrtoint(buf, 0, &descendants);
3605 if (ret)
3606 return ret;
3607 }
3608
3609 if (descendants < 0)
3610 return -ERANGE;
3611
3612 cgrp = cgroup_kn_lock_live(of->kn, false);
3613 if (!cgrp)
3614 return -ENOENT;
3615
3616 cgrp->max_descendants = descendants;
3617
3618 cgroup_kn_unlock(of->kn);
3619
3620 return nbytes;
3621}
3622
3623static int cgroup_max_depth_show(struct seq_file *seq, void *v)
3624{
3625 struct cgroup *cgrp = seq_css(seq)->cgroup;
3626 int depth = READ_ONCE(cgrp->max_depth);
3627
3628 if (depth == INT_MAX)
3629 seq_puts(seq, "max\n");
3630 else
3631 seq_printf(seq, "%d\n", depth);
3632
3633 return 0;
3634}
3635
3636static ssize_t cgroup_max_depth_write(struct kernfs_open_file *of,
3637 char *buf, size_t nbytes, loff_t off)
3638{
3639 struct cgroup *cgrp;
3640 ssize_t ret;
3641 int depth;
3642
3643 buf = strstrip(buf);
3644 if (!strcmp(buf, "max")) {
3645 depth = INT_MAX;
3646 } else {
3647 ret = kstrtoint(buf, 0, &depth);
3648 if (ret)
3649 return ret;
3650 }
3651
3652 if (depth < 0)
3653 return -ERANGE;
3654
3655 cgrp = cgroup_kn_lock_live(of->kn, false);
3656 if (!cgrp)
3657 return -ENOENT;
3658
3659 cgrp->max_depth = depth;
3660
3661 cgroup_kn_unlock(of->kn);
3662
3663 return nbytes;
3664}
3665
3666static int cgroup_events_show(struct seq_file *seq, void *v)
3667{
3668 struct cgroup *cgrp = seq_css(seq)->cgroup;
3669
3670 seq_printf(seq, "populated %d\n", cgroup_is_populated(cgrp));
3671 seq_printf(seq, "frozen %d\n", test_bit(CGRP_FROZEN, &cgrp->flags));
3672
3673 return 0;
3674}
3675
3676static int cgroup_stat_show(struct seq_file *seq, void *v)
3677{
3678 struct cgroup *cgroup = seq_css(seq)->cgroup;
3679
3680 seq_printf(seq, "nr_descendants %d\n",
3681 cgroup->nr_descendants);
3682 seq_printf(seq, "nr_dying_descendants %d\n",
3683 cgroup->nr_dying_descendants);
3684
3685 return 0;
3686}
3687
3688static int __maybe_unused cgroup_extra_stat_show(struct seq_file *seq,
3689 struct cgroup *cgrp, int ssid)
3690{
3691 struct cgroup_subsys *ss = cgroup_subsys[ssid];
3692 struct cgroup_subsys_state *css;
3693 int ret;
3694
3695 if (!ss->css_extra_stat_show)
3696 return 0;
3697
3698 css = cgroup_tryget_css(cgrp, ss);
3699 if (!css)
3700 return 0;
3701
3702 ret = ss->css_extra_stat_show(seq, css);
3703 css_put(css);
3704 return ret;
3705}
3706
3707static int cpu_stat_show(struct seq_file *seq, void *v)
3708{
3709 struct cgroup __maybe_unused *cgrp = seq_css(seq)->cgroup;
3710 int ret = 0;
3711
3712 cgroup_base_stat_cputime_show(seq);
3713#ifdef CONFIG_CGROUP_SCHED
3714 ret = cgroup_extra_stat_show(seq, cgrp, cpu_cgrp_id);
3715#endif
3716 return ret;
3717}
3718
3719#ifdef CONFIG_PSI
3720static int cgroup_io_pressure_show(struct seq_file *seq, void *v)
3721{
3722 struct cgroup *cgrp = seq_css(seq)->cgroup;
3723 struct psi_group *psi = cgroup_psi(cgrp);
3724
3725 return psi_show(seq, psi, PSI_IO);
3726}
3727static int cgroup_memory_pressure_show(struct seq_file *seq, void *v)
3728{
3729 struct cgroup *cgrp = seq_css(seq)->cgroup;
3730 struct psi_group *psi = cgroup_psi(cgrp);
3731
3732 return psi_show(seq, psi, PSI_MEM);
3733}
3734static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v)
3735{
3736 struct cgroup *cgrp = seq_css(seq)->cgroup;
3737 struct psi_group *psi = cgroup_psi(cgrp);
3738
3739 return psi_show(seq, psi, PSI_CPU);
3740}
3741
3742static ssize_t pressure_write(struct kernfs_open_file *of, char *buf,
3743 size_t nbytes, enum psi_res res)
3744{
3745 struct cgroup_file_ctx *ctx = of->priv;
3746 struct psi_trigger *new;
3747 struct cgroup *cgrp;
3748 struct psi_group *psi;
3749
3750 cgrp = cgroup_kn_lock_live(of->kn, false);
3751 if (!cgrp)
3752 return -ENODEV;
3753
3754 cgroup_get(cgrp);
3755 cgroup_kn_unlock(of->kn);
3756
3757 /* Allow only one trigger per file descriptor */
3758 if (ctx->psi.trigger) {
3759 cgroup_put(cgrp);
3760 return -EBUSY;
3761 }
3762
3763 psi = cgroup_psi(cgrp);
3764 new = psi_trigger_create(psi, buf, res);
3765 if (IS_ERR(new)) {
3766 cgroup_put(cgrp);
3767 return PTR_ERR(new);
3768 }
3769
3770 smp_store_release(&ctx->psi.trigger, new);
3771 cgroup_put(cgrp);
3772
3773 return nbytes;
3774}
3775
3776static ssize_t cgroup_io_pressure_write(struct kernfs_open_file *of,
3777 char *buf, size_t nbytes,
3778 loff_t off)
3779{
3780 return pressure_write(of, buf, nbytes, PSI_IO);
3781}
3782
3783static ssize_t cgroup_memory_pressure_write(struct kernfs_open_file *of,
3784 char *buf, size_t nbytes,
3785 loff_t off)
3786{
3787 return pressure_write(of, buf, nbytes, PSI_MEM);
3788}
3789
3790static ssize_t cgroup_cpu_pressure_write(struct kernfs_open_file *of,
3791 char *buf, size_t nbytes,
3792 loff_t off)
3793{
3794 return pressure_write(of, buf, nbytes, PSI_CPU);
3795}
3796
3797#ifdef CONFIG_IRQ_TIME_ACCOUNTING
3798static int cgroup_irq_pressure_show(struct seq_file *seq, void *v)
3799{
3800 struct cgroup *cgrp = seq_css(seq)->cgroup;
3801 struct psi_group *psi = cgroup_psi(cgrp);
3802
3803 return psi_show(seq, psi, PSI_IRQ);
3804}
3805
3806static ssize_t cgroup_irq_pressure_write(struct kernfs_open_file *of,
3807 char *buf, size_t nbytes,
3808 loff_t off)
3809{
3810 return pressure_write(of, buf, nbytes, PSI_IRQ);
3811}
3812#endif
3813
3814static int cgroup_pressure_show(struct seq_file *seq, void *v)
3815{
3816 struct cgroup *cgrp = seq_css(seq)->cgroup;
3817 struct psi_group *psi = cgroup_psi(cgrp);
3818
3819 seq_printf(seq, "%d\n", psi->enabled);
3820
3821 return 0;
3822}
3823
3824static ssize_t cgroup_pressure_write(struct kernfs_open_file *of,
3825 char *buf, size_t nbytes,
3826 loff_t off)
3827{
3828 ssize_t ret;
3829 int enable;
3830 struct cgroup *cgrp;
3831 struct psi_group *psi;
3832
3833 ret = kstrtoint(strstrip(buf), 0, &enable);
3834 if (ret)
3835 return ret;
3836
3837 if (enable < 0 || enable > 1)
3838 return -ERANGE;
3839
3840 cgrp = cgroup_kn_lock_live(of->kn, false);
3841 if (!cgrp)
3842 return -ENOENT;
3843
3844 psi = cgroup_psi(cgrp);
3845 if (psi->enabled != enable) {
3846 int i;
3847
3848 /* show or hide {cpu,memory,io,irq}.pressure files */
3849 for (i = 0; i < NR_PSI_RESOURCES; i++)
3850 cgroup_file_show(&cgrp->psi_files[i], enable);
3851
3852 psi->enabled = enable;
3853 if (enable)
3854 psi_cgroup_restart(psi);
3855 }
3856
3857 cgroup_kn_unlock(of->kn);
3858
3859 return nbytes;
3860}
3861
3862static __poll_t cgroup_pressure_poll(struct kernfs_open_file *of,
3863 poll_table *pt)
3864{
3865 struct cgroup_file_ctx *ctx = of->priv;
3866
3867 return psi_trigger_poll(&ctx->psi.trigger, of->file, pt);
3868}
3869
3870static void cgroup_pressure_release(struct kernfs_open_file *of)
3871{
3872 struct cgroup_file_ctx *ctx = of->priv;
3873
3874 psi_trigger_destroy(ctx->psi.trigger);
3875}
3876
3877bool cgroup_psi_enabled(void)
3878{
3879 if (static_branch_likely(&psi_disabled))
3880 return false;
3881
3882 return (cgroup_feature_disable_mask & (1 << OPT_FEATURE_PRESSURE)) == 0;
3883}
3884
3885#else /* CONFIG_PSI */
3886bool cgroup_psi_enabled(void)
3887{
3888 return false;
3889}
3890
3891#endif /* CONFIG_PSI */
3892
3893static int cgroup_freeze_show(struct seq_file *seq, void *v)
3894{
3895 struct cgroup *cgrp = seq_css(seq)->cgroup;
3896
3897 seq_printf(seq, "%d\n", cgrp->freezer.freeze);
3898
3899 return 0;
3900}
3901
3902static ssize_t cgroup_freeze_write(struct kernfs_open_file *of,
3903 char *buf, size_t nbytes, loff_t off)
3904{
3905 struct cgroup *cgrp;
3906 ssize_t ret;
3907 int freeze;
3908
3909 ret = kstrtoint(strstrip(buf), 0, &freeze);
3910 if (ret)
3911 return ret;
3912
3913 if (freeze < 0 || freeze > 1)
3914 return -ERANGE;
3915
3916 cgrp = cgroup_kn_lock_live(of->kn, false);
3917 if (!cgrp)
3918 return -ENOENT;
3919
3920 cgroup_freeze(cgrp, freeze);
3921
3922 cgroup_kn_unlock(of->kn);
3923
3924 return nbytes;
3925}
3926
3927static void __cgroup_kill(struct cgroup *cgrp)
3928{
3929 struct css_task_iter it;
3930 struct task_struct *task;
3931
3932 lockdep_assert_held(&cgroup_mutex);
3933
3934 spin_lock_irq(&css_set_lock);
3935 set_bit(CGRP_KILL, &cgrp->flags);
3936 spin_unlock_irq(&css_set_lock);
3937
3938 css_task_iter_start(&cgrp->self, CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED, &it);
3939 while ((task = css_task_iter_next(&it))) {
3940 /* Ignore kernel threads here. */
3941 if (task->flags & PF_KTHREAD)
3942 continue;
3943
3944 /* Skip tasks that are already dying. */
3945 if (__fatal_signal_pending(task))
3946 continue;
3947
3948 send_sig(SIGKILL, task, 0);
3949 }
3950 css_task_iter_end(&it);
3951
3952 spin_lock_irq(&css_set_lock);
3953 clear_bit(CGRP_KILL, &cgrp->flags);
3954 spin_unlock_irq(&css_set_lock);
3955}
3956
3957static void cgroup_kill(struct cgroup *cgrp)
3958{
3959 struct cgroup_subsys_state *css;
3960 struct cgroup *dsct;
3961
3962 lockdep_assert_held(&cgroup_mutex);
3963
3964 cgroup_for_each_live_descendant_pre(dsct, css, cgrp)
3965 __cgroup_kill(dsct);
3966}
3967
3968static ssize_t cgroup_kill_write(struct kernfs_open_file *of, char *buf,
3969 size_t nbytes, loff_t off)
3970{
3971 ssize_t ret = 0;
3972 int kill;
3973 struct cgroup *cgrp;
3974
3975 ret = kstrtoint(strstrip(buf), 0, &kill);
3976 if (ret)
3977 return ret;
3978
3979 if (kill != 1)
3980 return -ERANGE;
3981
3982 cgrp = cgroup_kn_lock_live(of->kn, false);
3983 if (!cgrp)
3984 return -ENOENT;
3985
3986 /*
3987 * Killing is a process directed operation, i.e. the whole thread-group
3988 * is taken down so act like we do for cgroup.procs and only make this
3989 * writable in non-threaded cgroups.
3990 */
3991 if (cgroup_is_threaded(cgrp))
3992 ret = -EOPNOTSUPP;
3993 else
3994 cgroup_kill(cgrp);
3995
3996 cgroup_kn_unlock(of->kn);
3997
3998 return ret ?: nbytes;
3999}
4000
4001static int cgroup_file_open(struct kernfs_open_file *of)
4002{
4003 struct cftype *cft = of_cft(of);
4004 struct cgroup_file_ctx *ctx;
4005 int ret;
4006
4007 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
4008 if (!ctx)
4009 return -ENOMEM;
4010
4011 ctx->ns = current->nsproxy->cgroup_ns;
4012 get_cgroup_ns(ctx->ns);
4013 of->priv = ctx;
4014
4015 if (!cft->open)
4016 return 0;
4017
4018 ret = cft->open(of);
4019 if (ret) {
4020 put_cgroup_ns(ctx->ns);
4021 kfree(ctx);
4022 }
4023 return ret;
4024}
4025
4026static void cgroup_file_release(struct kernfs_open_file *of)
4027{
4028 struct cftype *cft = of_cft(of);
4029 struct cgroup_file_ctx *ctx = of->priv;
4030
4031 if (cft->release)
4032 cft->release(of);
4033 put_cgroup_ns(ctx->ns);
4034 kfree(ctx);
4035}
4036
4037static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
4038 size_t nbytes, loff_t off)
4039{
4040 struct cgroup_file_ctx *ctx = of->priv;
4041 struct cgroup *cgrp = of->kn->parent->priv;
4042 struct cftype *cft = of_cft(of);
4043 struct cgroup_subsys_state *css;
4044 int ret;
4045
4046 if (!nbytes)
4047 return 0;
4048
4049 /*
4050 * If namespaces are delegation boundaries, disallow writes to
4051 * files in an non-init namespace root from inside the namespace
4052 * except for the files explicitly marked delegatable -
4053 * cgroup.procs and cgroup.subtree_control.
4054 */
4055 if ((cgrp->root->flags & CGRP_ROOT_NS_DELEGATE) &&
4056 !(cft->flags & CFTYPE_NS_DELEGATABLE) &&
4057 ctx->ns != &init_cgroup_ns && ctx->ns->root_cset->dfl_cgrp == cgrp)
4058 return -EPERM;
4059
4060 if (cft->write)
4061 return cft->write(of, buf, nbytes, off);
4062
4063 /*
4064 * kernfs guarantees that a file isn't deleted with operations in
4065 * flight, which means that the matching css is and stays alive and
4066 * doesn't need to be pinned. The RCU locking is not necessary
4067 * either. It's just for the convenience of using cgroup_css().
4068 */
4069 rcu_read_lock();
4070 css = cgroup_css(cgrp, cft->ss);
4071 rcu_read_unlock();
4072
4073 if (cft->write_u64) {
4074 unsigned long long v;
4075 ret = kstrtoull(buf, 0, &v);
4076 if (!ret)
4077 ret = cft->write_u64(css, cft, v);
4078 } else if (cft->write_s64) {
4079 long long v;
4080 ret = kstrtoll(buf, 0, &v);
4081 if (!ret)
4082 ret = cft->write_s64(css, cft, v);
4083 } else {
4084 ret = -EINVAL;
4085 }
4086
4087 return ret ?: nbytes;
4088}
4089
4090static __poll_t cgroup_file_poll(struct kernfs_open_file *of, poll_table *pt)
4091{
4092 struct cftype *cft = of_cft(of);
4093
4094 if (cft->poll)
4095 return cft->poll(of, pt);
4096
4097 return kernfs_generic_poll(of, pt);
4098}
4099
4100static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
4101{
4102 return seq_cft(seq)->seq_start(seq, ppos);
4103}
4104
4105static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
4106{
4107 return seq_cft(seq)->seq_next(seq, v, ppos);
4108}
4109
4110static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
4111{
4112 if (seq_cft(seq)->seq_stop)
4113 seq_cft(seq)->seq_stop(seq, v);
4114}
4115
4116static int cgroup_seqfile_show(struct seq_file *m, void *arg)
4117{
4118 struct cftype *cft = seq_cft(m);
4119 struct cgroup_subsys_state *css = seq_css(m);
4120
4121 if (cft->seq_show)
4122 return cft->seq_show(m, arg);
4123
4124 if (cft->read_u64)
4125 seq_printf(m, "%llu\n", cft->read_u64(css, cft));
4126 else if (cft->read_s64)
4127 seq_printf(m, "%lld\n", cft->read_s64(css, cft));
4128 else
4129 return -EINVAL;
4130 return 0;
4131}
4132
4133static struct kernfs_ops cgroup_kf_single_ops = {
4134 .atomic_write_len = PAGE_SIZE,
4135 .open = cgroup_file_open,
4136 .release = cgroup_file_release,
4137 .write = cgroup_file_write,
4138 .poll = cgroup_file_poll,
4139 .seq_show = cgroup_seqfile_show,
4140};
4141
4142static struct kernfs_ops cgroup_kf_ops = {
4143 .atomic_write_len = PAGE_SIZE,
4144 .open = cgroup_file_open,
4145 .release = cgroup_file_release,
4146 .write = cgroup_file_write,
4147 .poll = cgroup_file_poll,
4148 .seq_start = cgroup_seqfile_start,
4149 .seq_next = cgroup_seqfile_next,
4150 .seq_stop = cgroup_seqfile_stop,
4151 .seq_show = cgroup_seqfile_show,
4152};
4153
4154/* set uid and gid of cgroup dirs and files to that of the creator */
4155static int cgroup_kn_set_ugid(struct kernfs_node *kn)
4156{
4157 struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
4158 .ia_uid = current_fsuid(),
4159 .ia_gid = current_fsgid(), };
4160
4161 if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
4162 gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
4163 return 0;
4164
4165 return kernfs_setattr(kn, &iattr);
4166}
4167
4168static void cgroup_file_notify_timer(struct timer_list *timer)
4169{
4170 cgroup_file_notify(container_of(timer, struct cgroup_file,
4171 notify_timer));
4172}
4173
4174static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
4175 struct cftype *cft)
4176{
4177 char name[CGROUP_FILE_NAME_MAX];
4178 struct kernfs_node *kn;
4179 struct lock_class_key *key = NULL;
4180 int ret;
4181
4182#ifdef CONFIG_DEBUG_LOCK_ALLOC
4183 key = &cft->lockdep_key;
4184#endif
4185 kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
4186 cgroup_file_mode(cft),
4187 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
4188 0, cft->kf_ops, cft,
4189 NULL, key);
4190 if (IS_ERR(kn))
4191 return PTR_ERR(kn);
4192
4193 ret = cgroup_kn_set_ugid(kn);
4194 if (ret) {
4195 kernfs_remove(kn);
4196 return ret;
4197 }
4198
4199 if (cft->file_offset) {
4200 struct cgroup_file *cfile = (void *)css + cft->file_offset;
4201
4202 timer_setup(&cfile->notify_timer, cgroup_file_notify_timer, 0);
4203
4204 spin_lock_irq(&cgroup_file_kn_lock);
4205 cfile->kn = kn;
4206 spin_unlock_irq(&cgroup_file_kn_lock);
4207 }
4208
4209 return 0;
4210}
4211
4212/**
4213 * cgroup_addrm_files - add or remove files to a cgroup directory
4214 * @css: the target css
4215 * @cgrp: the target cgroup (usually css->cgroup)
4216 * @cfts: array of cftypes to be added
4217 * @is_add: whether to add or remove
4218 *
4219 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
4220 * For removals, this function never fails.
4221 */
4222static int cgroup_addrm_files(struct cgroup_subsys_state *css,
4223 struct cgroup *cgrp, struct cftype cfts[],
4224 bool is_add)
4225{
4226 struct cftype *cft, *cft_end = NULL;
4227 int ret = 0;
4228
4229 lockdep_assert_held(&cgroup_mutex);
4230
4231restart:
4232 for (cft = cfts; cft != cft_end && cft->name[0] != '\0'; cft++) {
4233 /* does cft->flags tell us to skip this file on @cgrp? */
4234 if ((cft->flags & __CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
4235 continue;
4236 if ((cft->flags & __CFTYPE_NOT_ON_DFL) && cgroup_on_dfl(cgrp))
4237 continue;
4238 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp))
4239 continue;
4240 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp))
4241 continue;
4242 if ((cft->flags & CFTYPE_DEBUG) && !cgroup_debug)
4243 continue;
4244 if (is_add) {
4245 ret = cgroup_add_file(css, cgrp, cft);
4246 if (ret) {
4247 pr_warn("%s: failed to add %s, err=%d\n",
4248 __func__, cft->name, ret);
4249 cft_end = cft;
4250 is_add = false;
4251 goto restart;
4252 }
4253 } else {
4254 cgroup_rm_file(cgrp, cft);
4255 }
4256 }
4257 return ret;
4258}
4259
4260static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
4261{
4262 struct cgroup_subsys *ss = cfts[0].ss;
4263 struct cgroup *root = &ss->root->cgrp;
4264 struct cgroup_subsys_state *css;
4265 int ret = 0;
4266
4267 lockdep_assert_held(&cgroup_mutex);
4268
4269 /* add/rm files for all cgroups created before */
4270 css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
4271 struct cgroup *cgrp = css->cgroup;
4272
4273 if (!(css->flags & CSS_VISIBLE))
4274 continue;
4275
4276 ret = cgroup_addrm_files(css, cgrp, cfts, is_add);
4277 if (ret)
4278 break;
4279 }
4280
4281 if (is_add && !ret)
4282 kernfs_activate(root->kn);
4283 return ret;
4284}
4285
4286static void cgroup_exit_cftypes(struct cftype *cfts)
4287{
4288 struct cftype *cft;
4289
4290 for (cft = cfts; cft->name[0] != '\0'; cft++) {
4291 /* free copy for custom atomic_write_len, see init_cftypes() */
4292 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
4293 kfree(cft->kf_ops);
4294 cft->kf_ops = NULL;
4295 cft->ss = NULL;
4296
4297 /* revert flags set by cgroup core while adding @cfts */
4298 cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL |
4299 __CFTYPE_ADDED);
4300 }
4301}
4302
4303static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4304{
4305 struct cftype *cft;
4306 int ret = 0;
4307
4308 for (cft = cfts; cft->name[0] != '\0'; cft++) {
4309 struct kernfs_ops *kf_ops;
4310
4311 WARN_ON(cft->ss || cft->kf_ops);
4312
4313 if (cft->flags & __CFTYPE_ADDED) {
4314 ret = -EBUSY;
4315 break;
4316 }
4317
4318 if (cft->seq_start)
4319 kf_ops = &cgroup_kf_ops;
4320 else
4321 kf_ops = &cgroup_kf_single_ops;
4322
4323 /*
4324 * Ugh... if @cft wants a custom max_write_len, we need to
4325 * make a copy of kf_ops to set its atomic_write_len.
4326 */
4327 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
4328 kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
4329 if (!kf_ops) {
4330 ret = -ENOMEM;
4331 break;
4332 }
4333 kf_ops->atomic_write_len = cft->max_write_len;
4334 }
4335
4336 cft->kf_ops = kf_ops;
4337 cft->ss = ss;
4338 cft->flags |= __CFTYPE_ADDED;
4339 }
4340
4341 if (ret)
4342 cgroup_exit_cftypes(cfts);
4343 return ret;
4344}
4345
4346static int cgroup_rm_cftypes_locked(struct cftype *cfts)
4347{
4348 lockdep_assert_held(&cgroup_mutex);
4349
4350 list_del(&cfts->node);
4351 cgroup_apply_cftypes(cfts, false);
4352 cgroup_exit_cftypes(cfts);
4353 return 0;
4354}
4355
4356/**
4357 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
4358 * @cfts: zero-length name terminated array of cftypes
4359 *
4360 * Unregister @cfts. Files described by @cfts are removed from all
4361 * existing cgroups and all future cgroups won't have them either. This
4362 * function can be called anytime whether @cfts' subsys is attached or not.
4363 *
4364 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
4365 * registered.
4366 */
4367int cgroup_rm_cftypes(struct cftype *cfts)
4368{
4369 int ret;
4370
4371 if (!cfts || cfts[0].name[0] == '\0')
4372 return 0;
4373
4374 if (!(cfts[0].flags & __CFTYPE_ADDED))
4375 return -ENOENT;
4376
4377 mutex_lock(&cgroup_mutex);
4378 ret = cgroup_rm_cftypes_locked(cfts);
4379 mutex_unlock(&cgroup_mutex);
4380 return ret;
4381}
4382
4383/**
4384 * cgroup_add_cftypes - add an array of cftypes to a subsystem
4385 * @ss: target cgroup subsystem
4386 * @cfts: zero-length name terminated array of cftypes
4387 *
4388 * Register @cfts to @ss. Files described by @cfts are created for all
4389 * existing cgroups to which @ss is attached and all future cgroups will
4390 * have them too. This function can be called anytime whether @ss is
4391 * attached or not.
4392 *
4393 * Returns 0 on successful registration, -errno on failure. Note that this
4394 * function currently returns 0 as long as @cfts registration is successful
4395 * even if some file creation attempts on existing cgroups fail.
4396 */
4397static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4398{
4399 int ret;
4400
4401 if (!cgroup_ssid_enabled(ss->id))
4402 return 0;
4403
4404 if (!cfts || cfts[0].name[0] == '\0')
4405 return 0;
4406
4407 ret = cgroup_init_cftypes(ss, cfts);
4408 if (ret)
4409 return ret;
4410
4411 mutex_lock(&cgroup_mutex);
4412
4413 list_add_tail(&cfts->node, &ss->cfts);
4414 ret = cgroup_apply_cftypes(cfts, true);
4415 if (ret)
4416 cgroup_rm_cftypes_locked(cfts);
4417
4418 mutex_unlock(&cgroup_mutex);
4419 return ret;
4420}
4421
4422/**
4423 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
4424 * @ss: target cgroup subsystem
4425 * @cfts: zero-length name terminated array of cftypes
4426 *
4427 * Similar to cgroup_add_cftypes() but the added files are only used for
4428 * the default hierarchy.
4429 */
4430int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4431{
4432 struct cftype *cft;
4433
4434 for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
4435 cft->flags |= __CFTYPE_ONLY_ON_DFL;
4436 return cgroup_add_cftypes(ss, cfts);
4437}
4438
4439/**
4440 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
4441 * @ss: target cgroup subsystem
4442 * @cfts: zero-length name terminated array of cftypes
4443 *
4444 * Similar to cgroup_add_cftypes() but the added files are only used for
4445 * the legacy hierarchies.
4446 */
4447int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4448{
4449 struct cftype *cft;
4450
4451 for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
4452 cft->flags |= __CFTYPE_NOT_ON_DFL;
4453 return cgroup_add_cftypes(ss, cfts);
4454}
4455
4456/**
4457 * cgroup_file_notify - generate a file modified event for a cgroup_file
4458 * @cfile: target cgroup_file
4459 *
4460 * @cfile must have been obtained by setting cftype->file_offset.
4461 */
4462void cgroup_file_notify(struct cgroup_file *cfile)
4463{
4464 unsigned long flags;
4465
4466 spin_lock_irqsave(&cgroup_file_kn_lock, flags);
4467 if (cfile->kn) {
4468 unsigned long last = cfile->notified_at;
4469 unsigned long next = last + CGROUP_FILE_NOTIFY_MIN_INTV;
4470
4471 if (time_in_range(jiffies, last, next)) {
4472 timer_reduce(&cfile->notify_timer, next);
4473 } else {
4474 kernfs_notify(cfile->kn);
4475 cfile->notified_at = jiffies;
4476 }
4477 }
4478 spin_unlock_irqrestore(&cgroup_file_kn_lock, flags);
4479}
4480
4481/**
4482 * cgroup_file_show - show or hide a hidden cgroup file
4483 * @cfile: target cgroup_file obtained by setting cftype->file_offset
4484 * @show: whether to show or hide
4485 */
4486void cgroup_file_show(struct cgroup_file *cfile, bool show)
4487{
4488 struct kernfs_node *kn;
4489
4490 spin_lock_irq(&cgroup_file_kn_lock);
4491 kn = cfile->kn;
4492 kernfs_get(kn);
4493 spin_unlock_irq(&cgroup_file_kn_lock);
4494
4495 if (kn)
4496 kernfs_show(kn, show);
4497
4498 kernfs_put(kn);
4499}
4500
4501/**
4502 * css_next_child - find the next child of a given css
4503 * @pos: the current position (%NULL to initiate traversal)
4504 * @parent: css whose children to walk
4505 *
4506 * This function returns the next child of @parent and should be called
4507 * under either cgroup_mutex or RCU read lock. The only requirement is
4508 * that @parent and @pos are accessible. The next sibling is guaranteed to
4509 * be returned regardless of their states.
4510 *
4511 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4512 * css which finished ->css_online() is guaranteed to be visible in the
4513 * future iterations and will stay visible until the last reference is put.
4514 * A css which hasn't finished ->css_online() or already finished
4515 * ->css_offline() may show up during traversal. It's each subsystem's
4516 * responsibility to synchronize against on/offlining.
4517 */
4518struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
4519 struct cgroup_subsys_state *parent)
4520{
4521 struct cgroup_subsys_state *next;
4522
4523 cgroup_assert_mutex_or_rcu_locked();
4524
4525 /*
4526 * @pos could already have been unlinked from the sibling list.
4527 * Once a cgroup is removed, its ->sibling.next is no longer
4528 * updated when its next sibling changes. CSS_RELEASED is set when
4529 * @pos is taken off list, at which time its next pointer is valid,
4530 * and, as releases are serialized, the one pointed to by the next
4531 * pointer is guaranteed to not have started release yet. This
4532 * implies that if we observe !CSS_RELEASED on @pos in this RCU
4533 * critical section, the one pointed to by its next pointer is
4534 * guaranteed to not have finished its RCU grace period even if we
4535 * have dropped rcu_read_lock() in-between iterations.
4536 *
4537 * If @pos has CSS_RELEASED set, its next pointer can't be
4538 * dereferenced; however, as each css is given a monotonically
4539 * increasing unique serial number and always appended to the
4540 * sibling list, the next one can be found by walking the parent's
4541 * children until the first css with higher serial number than
4542 * @pos's. While this path can be slower, it happens iff iteration
4543 * races against release and the race window is very small.
4544 */
4545 if (!pos) {
4546 next = list_entry_rcu(parent->children.next, struct cgroup_subsys_state, sibling);
4547 } else if (likely(!(pos->flags & CSS_RELEASED))) {
4548 next = list_entry_rcu(pos->sibling.next, struct cgroup_subsys_state, sibling);
4549 } else {
4550 list_for_each_entry_rcu(next, &parent->children, sibling,
4551 lockdep_is_held(&cgroup_mutex))
4552 if (next->serial_nr > pos->serial_nr)
4553 break;
4554 }
4555
4556 /*
4557 * @next, if not pointing to the head, can be dereferenced and is
4558 * the next sibling.
4559 */
4560 if (&next->sibling != &parent->children)
4561 return next;
4562 return NULL;
4563}
4564
4565/**
4566 * css_next_descendant_pre - find the next descendant for pre-order walk
4567 * @pos: the current position (%NULL to initiate traversal)
4568 * @root: css whose descendants to walk
4569 *
4570 * To be used by css_for_each_descendant_pre(). Find the next descendant
4571 * to visit for pre-order traversal of @root's descendants. @root is
4572 * included in the iteration and the first node to be visited.
4573 *
4574 * While this function requires cgroup_mutex or RCU read locking, it
4575 * doesn't require the whole traversal to be contained in a single critical
4576 * section. This function will return the correct next descendant as long
4577 * as both @pos and @root are accessible and @pos is a descendant of @root.
4578 *
4579 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4580 * css which finished ->css_online() is guaranteed to be visible in the
4581 * future iterations and will stay visible until the last reference is put.
4582 * A css which hasn't finished ->css_online() or already finished
4583 * ->css_offline() may show up during traversal. It's each subsystem's
4584 * responsibility to synchronize against on/offlining.
4585 */
4586struct cgroup_subsys_state *
4587css_next_descendant_pre(struct cgroup_subsys_state *pos,
4588 struct cgroup_subsys_state *root)
4589{
4590 struct cgroup_subsys_state *next;
4591
4592 cgroup_assert_mutex_or_rcu_locked();
4593
4594 /* if first iteration, visit @root */
4595 if (!pos)
4596 return root;
4597
4598 /* visit the first child if exists */
4599 next = css_next_child(NULL, pos);
4600 if (next)
4601 return next;
4602
4603 /* no child, visit my or the closest ancestor's next sibling */
4604 while (pos != root) {
4605 next = css_next_child(pos, pos->parent);
4606 if (next)
4607 return next;
4608 pos = pos->parent;
4609 }
4610
4611 return NULL;
4612}
4613EXPORT_SYMBOL_GPL(css_next_descendant_pre);
4614
4615/**
4616 * css_rightmost_descendant - return the rightmost descendant of a css
4617 * @pos: css of interest
4618 *
4619 * Return the rightmost descendant of @pos. If there's no descendant, @pos
4620 * is returned. This can be used during pre-order traversal to skip
4621 * subtree of @pos.
4622 *
4623 * While this function requires cgroup_mutex or RCU read locking, it
4624 * doesn't require the whole traversal to be contained in a single critical
4625 * section. This function will return the correct rightmost descendant as
4626 * long as @pos is accessible.
4627 */
4628struct cgroup_subsys_state *
4629css_rightmost_descendant(struct cgroup_subsys_state *pos)
4630{
4631 struct cgroup_subsys_state *last, *tmp;
4632
4633 cgroup_assert_mutex_or_rcu_locked();
4634
4635 do {
4636 last = pos;
4637 /* ->prev isn't RCU safe, walk ->next till the end */
4638 pos = NULL;
4639 css_for_each_child(tmp, last)
4640 pos = tmp;
4641 } while (pos);
4642
4643 return last;
4644}
4645
4646static struct cgroup_subsys_state *
4647css_leftmost_descendant(struct cgroup_subsys_state *pos)
4648{
4649 struct cgroup_subsys_state *last;
4650
4651 do {
4652 last = pos;
4653 pos = css_next_child(NULL, pos);
4654 } while (pos);
4655
4656 return last;
4657}
4658
4659/**
4660 * css_next_descendant_post - find the next descendant for post-order walk
4661 * @pos: the current position (%NULL to initiate traversal)
4662 * @root: css whose descendants to walk
4663 *
4664 * To be used by css_for_each_descendant_post(). Find the next descendant
4665 * to visit for post-order traversal of @root's descendants. @root is
4666 * included in the iteration and the last node to be visited.
4667 *
4668 * While this function requires cgroup_mutex or RCU read locking, it
4669 * doesn't require the whole traversal to be contained in a single critical
4670 * section. This function will return the correct next descendant as long
4671 * as both @pos and @cgroup are accessible and @pos is a descendant of
4672 * @cgroup.
4673 *
4674 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4675 * css which finished ->css_online() is guaranteed to be visible in the
4676 * future iterations and will stay visible until the last reference is put.
4677 * A css which hasn't finished ->css_online() or already finished
4678 * ->css_offline() may show up during traversal. It's each subsystem's
4679 * responsibility to synchronize against on/offlining.
4680 */
4681struct cgroup_subsys_state *
4682css_next_descendant_post(struct cgroup_subsys_state *pos,
4683 struct cgroup_subsys_state *root)
4684{
4685 struct cgroup_subsys_state *next;
4686
4687 cgroup_assert_mutex_or_rcu_locked();
4688
4689 /* if first iteration, visit leftmost descendant which may be @root */
4690 if (!pos)
4691 return css_leftmost_descendant(root);
4692
4693 /* if we visited @root, we're done */
4694 if (pos == root)
4695 return NULL;
4696
4697 /* if there's an unvisited sibling, visit its leftmost descendant */
4698 next = css_next_child(pos, pos->parent);
4699 if (next)
4700 return css_leftmost_descendant(next);
4701
4702 /* no sibling left, visit parent */
4703 return pos->parent;
4704}
4705
4706/**
4707 * css_has_online_children - does a css have online children
4708 * @css: the target css
4709 *
4710 * Returns %true if @css has any online children; otherwise, %false. This
4711 * function can be called from any context but the caller is responsible
4712 * for synchronizing against on/offlining as necessary.
4713 */
4714bool css_has_online_children(struct cgroup_subsys_state *css)
4715{
4716 struct cgroup_subsys_state *child;
4717 bool ret = false;
4718
4719 rcu_read_lock();
4720 css_for_each_child(child, css) {
4721 if (child->flags & CSS_ONLINE) {
4722 ret = true;
4723 break;
4724 }
4725 }
4726 rcu_read_unlock();
4727 return ret;
4728}
4729
4730static struct css_set *css_task_iter_next_css_set(struct css_task_iter *it)
4731{
4732 struct list_head *l;
4733 struct cgrp_cset_link *link;
4734 struct css_set *cset;
4735
4736 lockdep_assert_held(&css_set_lock);
4737
4738 /* find the next threaded cset */
4739 if (it->tcset_pos) {
4740 l = it->tcset_pos->next;
4741
4742 if (l != it->tcset_head) {
4743 it->tcset_pos = l;
4744 return container_of(l, struct css_set,
4745 threaded_csets_node);
4746 }
4747
4748 it->tcset_pos = NULL;
4749 }
4750
4751 /* find the next cset */
4752 l = it->cset_pos;
4753 l = l->next;
4754 if (l == it->cset_head) {
4755 it->cset_pos = NULL;
4756 return NULL;
4757 }
4758
4759 if (it->ss) {
4760 cset = container_of(l, struct css_set, e_cset_node[it->ss->id]);
4761 } else {
4762 link = list_entry(l, struct cgrp_cset_link, cset_link);
4763 cset = link->cset;
4764 }
4765
4766 it->cset_pos = l;
4767
4768 /* initialize threaded css_set walking */
4769 if (it->flags & CSS_TASK_ITER_THREADED) {
4770 if (it->cur_dcset)
4771 put_css_set_locked(it->cur_dcset);
4772 it->cur_dcset = cset;
4773 get_css_set(cset);
4774
4775 it->tcset_head = &cset->threaded_csets;
4776 it->tcset_pos = &cset->threaded_csets;
4777 }
4778
4779 return cset;
4780}
4781
4782/**
4783 * css_task_iter_advance_css_set - advance a task iterator to the next css_set
4784 * @it: the iterator to advance
4785 *
4786 * Advance @it to the next css_set to walk.
4787 */
4788static void css_task_iter_advance_css_set(struct css_task_iter *it)
4789{
4790 struct css_set *cset;
4791
4792 lockdep_assert_held(&css_set_lock);
4793
4794 /* Advance to the next non-empty css_set and find first non-empty tasks list*/
4795 while ((cset = css_task_iter_next_css_set(it))) {
4796 if (!list_empty(&cset->tasks)) {
4797 it->cur_tasks_head = &cset->tasks;
4798 break;
4799 } else if (!list_empty(&cset->mg_tasks)) {
4800 it->cur_tasks_head = &cset->mg_tasks;
4801 break;
4802 } else if (!list_empty(&cset->dying_tasks)) {
4803 it->cur_tasks_head = &cset->dying_tasks;
4804 break;
4805 }
4806 }
4807 if (!cset) {
4808 it->task_pos = NULL;
4809 return;
4810 }
4811 it->task_pos = it->cur_tasks_head->next;
4812
4813 /*
4814 * We don't keep css_sets locked across iteration steps and thus
4815 * need to take steps to ensure that iteration can be resumed after
4816 * the lock is re-acquired. Iteration is performed at two levels -
4817 * css_sets and tasks in them.
4818 *
4819 * Once created, a css_set never leaves its cgroup lists, so a
4820 * pinned css_set is guaranteed to stay put and we can resume
4821 * iteration afterwards.
4822 *
4823 * Tasks may leave @cset across iteration steps. This is resolved
4824 * by registering each iterator with the css_set currently being
4825 * walked and making css_set_move_task() advance iterators whose
4826 * next task is leaving.
4827 */
4828 if (it->cur_cset) {
4829 list_del(&it->iters_node);
4830 put_css_set_locked(it->cur_cset);
4831 }
4832 get_css_set(cset);
4833 it->cur_cset = cset;
4834 list_add(&it->iters_node, &cset->task_iters);
4835}
4836
4837static void css_task_iter_skip(struct css_task_iter *it,
4838 struct task_struct *task)
4839{
4840 lockdep_assert_held(&css_set_lock);
4841
4842 if (it->task_pos == &task->cg_list) {
4843 it->task_pos = it->task_pos->next;
4844 it->flags |= CSS_TASK_ITER_SKIPPED;
4845 }
4846}
4847
4848static void css_task_iter_advance(struct css_task_iter *it)
4849{
4850 struct task_struct *task;
4851
4852 lockdep_assert_held(&css_set_lock);
4853repeat:
4854 if (it->task_pos) {
4855 /*
4856 * Advance iterator to find next entry. We go through cset
4857 * tasks, mg_tasks and dying_tasks, when consumed we move onto
4858 * the next cset.
4859 */
4860 if (it->flags & CSS_TASK_ITER_SKIPPED)
4861 it->flags &= ~CSS_TASK_ITER_SKIPPED;
4862 else
4863 it->task_pos = it->task_pos->next;
4864
4865 if (it->task_pos == &it->cur_cset->tasks) {
4866 it->cur_tasks_head = &it->cur_cset->mg_tasks;
4867 it->task_pos = it->cur_tasks_head->next;
4868 }
4869 if (it->task_pos == &it->cur_cset->mg_tasks) {
4870 it->cur_tasks_head = &it->cur_cset->dying_tasks;
4871 it->task_pos = it->cur_tasks_head->next;
4872 }
4873 if (it->task_pos == &it->cur_cset->dying_tasks)
4874 css_task_iter_advance_css_set(it);
4875 } else {
4876 /* called from start, proceed to the first cset */
4877 css_task_iter_advance_css_set(it);
4878 }
4879
4880 if (!it->task_pos)
4881 return;
4882
4883 task = list_entry(it->task_pos, struct task_struct, cg_list);
4884
4885 if (it->flags & CSS_TASK_ITER_PROCS) {
4886 /* if PROCS, skip over tasks which aren't group leaders */
4887 if (!thread_group_leader(task))
4888 goto repeat;
4889
4890 /* and dying leaders w/o live member threads */
4891 if (it->cur_tasks_head == &it->cur_cset->dying_tasks &&
4892 !atomic_read(&task->signal->live))
4893 goto repeat;
4894 } else {
4895 /* skip all dying ones */
4896 if (it->cur_tasks_head == &it->cur_cset->dying_tasks)
4897 goto repeat;
4898 }
4899}
4900
4901/**
4902 * css_task_iter_start - initiate task iteration
4903 * @css: the css to walk tasks of
4904 * @flags: CSS_TASK_ITER_* flags
4905 * @it: the task iterator to use
4906 *
4907 * Initiate iteration through the tasks of @css. The caller can call
4908 * css_task_iter_next() to walk through the tasks until the function
4909 * returns NULL. On completion of iteration, css_task_iter_end() must be
4910 * called.
4911 */
4912void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
4913 struct css_task_iter *it)
4914{
4915 memset(it, 0, sizeof(*it));
4916
4917 spin_lock_irq(&css_set_lock);
4918
4919 it->ss = css->ss;
4920 it->flags = flags;
4921
4922 if (CGROUP_HAS_SUBSYS_CONFIG && it->ss)
4923 it->cset_pos = &css->cgroup->e_csets[css->ss->id];
4924 else
4925 it->cset_pos = &css->cgroup->cset_links;
4926
4927 it->cset_head = it->cset_pos;
4928
4929 css_task_iter_advance(it);
4930
4931 spin_unlock_irq(&css_set_lock);
4932}
4933
4934/**
4935 * css_task_iter_next - return the next task for the iterator
4936 * @it: the task iterator being iterated
4937 *
4938 * The "next" function for task iteration. @it should have been
4939 * initialized via css_task_iter_start(). Returns NULL when the iteration
4940 * reaches the end.
4941 */
4942struct task_struct *css_task_iter_next(struct css_task_iter *it)
4943{
4944 if (it->cur_task) {
4945 put_task_struct(it->cur_task);
4946 it->cur_task = NULL;
4947 }
4948
4949 spin_lock_irq(&css_set_lock);
4950
4951 /* @it may be half-advanced by skips, finish advancing */
4952 if (it->flags & CSS_TASK_ITER_SKIPPED)
4953 css_task_iter_advance(it);
4954
4955 if (it->task_pos) {
4956 it->cur_task = list_entry(it->task_pos, struct task_struct,
4957 cg_list);
4958 get_task_struct(it->cur_task);
4959 css_task_iter_advance(it);
4960 }
4961
4962 spin_unlock_irq(&css_set_lock);
4963
4964 return it->cur_task;
4965}
4966
4967/**
4968 * css_task_iter_end - finish task iteration
4969 * @it: the task iterator to finish
4970 *
4971 * Finish task iteration started by css_task_iter_start().
4972 */
4973void css_task_iter_end(struct css_task_iter *it)
4974{
4975 if (it->cur_cset) {
4976 spin_lock_irq(&css_set_lock);
4977 list_del(&it->iters_node);
4978 put_css_set_locked(it->cur_cset);
4979 spin_unlock_irq(&css_set_lock);
4980 }
4981
4982 if (it->cur_dcset)
4983 put_css_set(it->cur_dcset);
4984
4985 if (it->cur_task)
4986 put_task_struct(it->cur_task);
4987}
4988
4989static void cgroup_procs_release(struct kernfs_open_file *of)
4990{
4991 struct cgroup_file_ctx *ctx = of->priv;
4992
4993 if (ctx->procs.started)
4994 css_task_iter_end(&ctx->procs.iter);
4995}
4996
4997static void *cgroup_procs_next(struct seq_file *s, void *v, loff_t *pos)
4998{
4999 struct kernfs_open_file *of = s->private;
5000 struct cgroup_file_ctx *ctx = of->priv;
5001
5002 if (pos)
5003 (*pos)++;
5004
5005 return css_task_iter_next(&ctx->procs.iter);
5006}
5007
5008static void *__cgroup_procs_start(struct seq_file *s, loff_t *pos,
5009 unsigned int iter_flags)
5010{
5011 struct kernfs_open_file *of = s->private;
5012 struct cgroup *cgrp = seq_css(s)->cgroup;
5013 struct cgroup_file_ctx *ctx = of->priv;
5014 struct css_task_iter *it = &ctx->procs.iter;
5015
5016 /*
5017 * When a seq_file is seeked, it's always traversed sequentially
5018 * from position 0, so we can simply keep iterating on !0 *pos.
5019 */
5020 if (!ctx->procs.started) {
5021 if (WARN_ON_ONCE((*pos)))
5022 return ERR_PTR(-EINVAL);
5023 css_task_iter_start(&cgrp->self, iter_flags, it);
5024 ctx->procs.started = true;
5025 } else if (!(*pos)) {
5026 css_task_iter_end(it);
5027 css_task_iter_start(&cgrp->self, iter_flags, it);
5028 } else
5029 return it->cur_task;
5030
5031 return cgroup_procs_next(s, NULL, NULL);
5032}
5033
5034static void *cgroup_procs_start(struct seq_file *s, loff_t *pos)
5035{
5036 struct cgroup *cgrp = seq_css(s)->cgroup;
5037
5038 /*
5039 * All processes of a threaded subtree belong to the domain cgroup
5040 * of the subtree. Only threads can be distributed across the
5041 * subtree. Reject reads on cgroup.procs in the subtree proper.
5042 * They're always empty anyway.
5043 */
5044 if (cgroup_is_threaded(cgrp))
5045 return ERR_PTR(-EOPNOTSUPP);
5046
5047 return __cgroup_procs_start(s, pos, CSS_TASK_ITER_PROCS |
5048 CSS_TASK_ITER_THREADED);
5049}
5050
5051static int cgroup_procs_show(struct seq_file *s, void *v)
5052{
5053 seq_printf(s, "%d\n", task_pid_vnr(v));
5054 return 0;
5055}
5056
5057static int cgroup_may_write(const struct cgroup *cgrp, struct super_block *sb)
5058{
5059 int ret;
5060 struct inode *inode;
5061
5062 lockdep_assert_held(&cgroup_mutex);
5063
5064 inode = kernfs_get_inode(sb, cgrp->procs_file.kn);
5065 if (!inode)
5066 return -ENOMEM;
5067
5068 ret = inode_permission(&init_user_ns, inode, MAY_WRITE);
5069 iput(inode);
5070 return ret;
5071}
5072
5073static int cgroup_procs_write_permission(struct cgroup *src_cgrp,
5074 struct cgroup *dst_cgrp,
5075 struct super_block *sb,
5076 struct cgroup_namespace *ns)
5077{
5078 struct cgroup *com_cgrp = src_cgrp;
5079 int ret;
5080
5081 lockdep_assert_held(&cgroup_mutex);
5082
5083 /* find the common ancestor */
5084 while (!cgroup_is_descendant(dst_cgrp, com_cgrp))
5085 com_cgrp = cgroup_parent(com_cgrp);
5086
5087 /* %current should be authorized to migrate to the common ancestor */
5088 ret = cgroup_may_write(com_cgrp, sb);
5089 if (ret)
5090 return ret;
5091
5092 /*
5093 * If namespaces are delegation boundaries, %current must be able
5094 * to see both source and destination cgroups from its namespace.
5095 */
5096 if ((cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE) &&
5097 (!cgroup_is_descendant(src_cgrp, ns->root_cset->dfl_cgrp) ||
5098 !cgroup_is_descendant(dst_cgrp, ns->root_cset->dfl_cgrp)))
5099 return -ENOENT;
5100
5101 return 0;
5102}
5103
5104static int cgroup_attach_permissions(struct cgroup *src_cgrp,
5105 struct cgroup *dst_cgrp,
5106 struct super_block *sb, bool threadgroup,
5107 struct cgroup_namespace *ns)
5108{
5109 int ret = 0;
5110
5111 ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp, sb, ns);
5112 if (ret)
5113 return ret;
5114
5115 ret = cgroup_migrate_vet_dst(dst_cgrp);
5116 if (ret)
5117 return ret;
5118
5119 if (!threadgroup && (src_cgrp->dom_cgrp != dst_cgrp->dom_cgrp))
5120 ret = -EOPNOTSUPP;
5121
5122 return ret;
5123}
5124
5125static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
5126 bool threadgroup)
5127{
5128 struct cgroup_file_ctx *ctx = of->priv;
5129 struct cgroup *src_cgrp, *dst_cgrp;
5130 struct task_struct *task;
5131 const struct cred *saved_cred;
5132 ssize_t ret;
5133 bool threadgroup_locked;
5134
5135 dst_cgrp = cgroup_kn_lock_live(of->kn, false);
5136 if (!dst_cgrp)
5137 return -ENODEV;
5138
5139 task = cgroup_procs_write_start(buf, threadgroup, &threadgroup_locked);
5140 ret = PTR_ERR_OR_ZERO(task);
5141 if (ret)
5142 goto out_unlock;
5143
5144 /* find the source cgroup */
5145 spin_lock_irq(&css_set_lock);
5146 src_cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
5147 spin_unlock_irq(&css_set_lock);
5148
5149 /*
5150 * Process and thread migrations follow same delegation rule. Check
5151 * permissions using the credentials from file open to protect against
5152 * inherited fd attacks.
5153 */
5154 saved_cred = override_creds(of->file->f_cred);
5155 ret = cgroup_attach_permissions(src_cgrp, dst_cgrp,
5156 of->file->f_path.dentry->d_sb,
5157 threadgroup, ctx->ns);
5158 revert_creds(saved_cred);
5159 if (ret)
5160 goto out_finish;
5161
5162 ret = cgroup_attach_task(dst_cgrp, task, threadgroup);
5163
5164out_finish:
5165 cgroup_procs_write_finish(task, threadgroup_locked);
5166out_unlock:
5167 cgroup_kn_unlock(of->kn);
5168
5169 return ret;
5170}
5171
5172static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
5173 char *buf, size_t nbytes, loff_t off)
5174{
5175 return __cgroup_procs_write(of, buf, true) ?: nbytes;
5176}
5177
5178static void *cgroup_threads_start(struct seq_file *s, loff_t *pos)
5179{
5180 return __cgroup_procs_start(s, pos, 0);
5181}
5182
5183static ssize_t cgroup_threads_write(struct kernfs_open_file *of,
5184 char *buf, size_t nbytes, loff_t off)
5185{
5186 return __cgroup_procs_write(of, buf, false) ?: nbytes;
5187}
5188
5189/* cgroup core interface files for the default hierarchy */
5190static struct cftype cgroup_base_files[] = {
5191 {
5192 .name = "cgroup.type",
5193 .flags = CFTYPE_NOT_ON_ROOT,
5194 .seq_show = cgroup_type_show,
5195 .write = cgroup_type_write,
5196 },
5197 {
5198 .name = "cgroup.procs",
5199 .flags = CFTYPE_NS_DELEGATABLE,
5200 .file_offset = offsetof(struct cgroup, procs_file),
5201 .release = cgroup_procs_release,
5202 .seq_start = cgroup_procs_start,
5203 .seq_next = cgroup_procs_next,
5204 .seq_show = cgroup_procs_show,
5205 .write = cgroup_procs_write,
5206 },
5207 {
5208 .name = "cgroup.threads",
5209 .flags = CFTYPE_NS_DELEGATABLE,
5210 .release = cgroup_procs_release,
5211 .seq_start = cgroup_threads_start,
5212 .seq_next = cgroup_procs_next,
5213 .seq_show = cgroup_procs_show,
5214 .write = cgroup_threads_write,
5215 },
5216 {
5217 .name = "cgroup.controllers",
5218 .seq_show = cgroup_controllers_show,
5219 },
5220 {
5221 .name = "cgroup.subtree_control",
5222 .flags = CFTYPE_NS_DELEGATABLE,
5223 .seq_show = cgroup_subtree_control_show,
5224 .write = cgroup_subtree_control_write,
5225 },
5226 {
5227 .name = "cgroup.events",
5228 .flags = CFTYPE_NOT_ON_ROOT,
5229 .file_offset = offsetof(struct cgroup, events_file),
5230 .seq_show = cgroup_events_show,
5231 },
5232 {
5233 .name = "cgroup.max.descendants",
5234 .seq_show = cgroup_max_descendants_show,
5235 .write = cgroup_max_descendants_write,
5236 },
5237 {
5238 .name = "cgroup.max.depth",
5239 .seq_show = cgroup_max_depth_show,
5240 .write = cgroup_max_depth_write,
5241 },
5242 {
5243 .name = "cgroup.stat",
5244 .seq_show = cgroup_stat_show,
5245 },
5246 {
5247 .name = "cgroup.freeze",
5248 .flags = CFTYPE_NOT_ON_ROOT,
5249 .seq_show = cgroup_freeze_show,
5250 .write = cgroup_freeze_write,
5251 },
5252 {
5253 .name = "cgroup.kill",
5254 .flags = CFTYPE_NOT_ON_ROOT,
5255 .write = cgroup_kill_write,
5256 },
5257 {
5258 .name = "cpu.stat",
5259 .seq_show = cpu_stat_show,
5260 },
5261 { } /* terminate */
5262};
5263
5264static struct cftype cgroup_psi_files[] = {
5265#ifdef CONFIG_PSI
5266 {
5267 .name = "io.pressure",
5268 .file_offset = offsetof(struct cgroup, psi_files[PSI_IO]),
5269 .seq_show = cgroup_io_pressure_show,
5270 .write = cgroup_io_pressure_write,
5271 .poll = cgroup_pressure_poll,
5272 .release = cgroup_pressure_release,
5273 },
5274 {
5275 .name = "memory.pressure",
5276 .file_offset = offsetof(struct cgroup, psi_files[PSI_MEM]),
5277 .seq_show = cgroup_memory_pressure_show,
5278 .write = cgroup_memory_pressure_write,
5279 .poll = cgroup_pressure_poll,
5280 .release = cgroup_pressure_release,
5281 },
5282 {
5283 .name = "cpu.pressure",
5284 .file_offset = offsetof(struct cgroup, psi_files[PSI_CPU]),
5285 .seq_show = cgroup_cpu_pressure_show,
5286 .write = cgroup_cpu_pressure_write,
5287 .poll = cgroup_pressure_poll,
5288 .release = cgroup_pressure_release,
5289 },
5290#ifdef CONFIG_IRQ_TIME_ACCOUNTING
5291 {
5292 .name = "irq.pressure",
5293 .file_offset = offsetof(struct cgroup, psi_files[PSI_IRQ]),
5294 .seq_show = cgroup_irq_pressure_show,
5295 .write = cgroup_irq_pressure_write,
5296 .poll = cgroup_pressure_poll,
5297 .release = cgroup_pressure_release,
5298 },
5299#endif
5300 {
5301 .name = "cgroup.pressure",
5302 .seq_show = cgroup_pressure_show,
5303 .write = cgroup_pressure_write,
5304 },
5305#endif /* CONFIG_PSI */
5306 { } /* terminate */
5307};
5308
5309/*
5310 * css destruction is four-stage process.
5311 *
5312 * 1. Destruction starts. Killing of the percpu_ref is initiated.
5313 * Implemented in kill_css().
5314 *
5315 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
5316 * and thus css_tryget_online() is guaranteed to fail, the css can be
5317 * offlined by invoking offline_css(). After offlining, the base ref is
5318 * put. Implemented in css_killed_work_fn().
5319 *
5320 * 3. When the percpu_ref reaches zero, the only possible remaining
5321 * accessors are inside RCU read sections. css_release() schedules the
5322 * RCU callback.
5323 *
5324 * 4. After the grace period, the css can be freed. Implemented in
5325 * css_free_work_fn().
5326 *
5327 * It is actually hairier because both step 2 and 4 require process context
5328 * and thus involve punting to css->destroy_work adding two additional
5329 * steps to the already complex sequence.
5330 */
5331static void css_free_rwork_fn(struct work_struct *work)
5332{
5333 struct cgroup_subsys_state *css = container_of(to_rcu_work(work),
5334 struct cgroup_subsys_state, destroy_rwork);
5335 struct cgroup_subsys *ss = css->ss;
5336 struct cgroup *cgrp = css->cgroup;
5337
5338 percpu_ref_exit(&css->refcnt);
5339
5340 if (ss) {
5341 /* css free path */
5342 struct cgroup_subsys_state *parent = css->parent;
5343 int id = css->id;
5344
5345 ss->css_free(css);
5346 cgroup_idr_remove(&ss->css_idr, id);
5347 cgroup_put(cgrp);
5348
5349 if (parent)
5350 css_put(parent);
5351 } else {
5352 /* cgroup free path */
5353 atomic_dec(&cgrp->root->nr_cgrps);
5354 cgroup1_pidlist_destroy_all(cgrp);
5355 cancel_work_sync(&cgrp->release_agent_work);
5356 bpf_cgrp_storage_free(cgrp);
5357
5358 if (cgroup_parent(cgrp)) {
5359 /*
5360 * We get a ref to the parent, and put the ref when
5361 * this cgroup is being freed, so it's guaranteed
5362 * that the parent won't be destroyed before its
5363 * children.
5364 */
5365 cgroup_put(cgroup_parent(cgrp));
5366 kernfs_put(cgrp->kn);
5367 psi_cgroup_free(cgrp);
5368 cgroup_rstat_exit(cgrp);
5369 kfree(cgrp);
5370 } else {
5371 /*
5372 * This is root cgroup's refcnt reaching zero,
5373 * which indicates that the root should be
5374 * released.
5375 */
5376 cgroup_destroy_root(cgrp->root);
5377 }
5378 }
5379}
5380
5381static void css_release_work_fn(struct work_struct *work)
5382{
5383 struct cgroup_subsys_state *css =
5384 container_of(work, struct cgroup_subsys_state, destroy_work);
5385 struct cgroup_subsys *ss = css->ss;
5386 struct cgroup *cgrp = css->cgroup;
5387
5388 mutex_lock(&cgroup_mutex);
5389
5390 css->flags |= CSS_RELEASED;
5391 list_del_rcu(&css->sibling);
5392
5393 if (ss) {
5394 /* css release path */
5395 if (!list_empty(&css->rstat_css_node)) {
5396 cgroup_rstat_flush(cgrp);
5397 list_del_rcu(&css->rstat_css_node);
5398 }
5399
5400 cgroup_idr_replace(&ss->css_idr, NULL, css->id);
5401 if (ss->css_released)
5402 ss->css_released(css);
5403 } else {
5404 struct cgroup *tcgrp;
5405
5406 /* cgroup release path */
5407 TRACE_CGROUP_PATH(release, cgrp);
5408
5409 cgroup_rstat_flush(cgrp);
5410
5411 spin_lock_irq(&css_set_lock);
5412 for (tcgrp = cgroup_parent(cgrp); tcgrp;
5413 tcgrp = cgroup_parent(tcgrp))
5414 tcgrp->nr_dying_descendants--;
5415 spin_unlock_irq(&css_set_lock);
5416
5417 /*
5418 * There are two control paths which try to determine
5419 * cgroup from dentry without going through kernfs -
5420 * cgroupstats_build() and css_tryget_online_from_dir().
5421 * Those are supported by RCU protecting clearing of
5422 * cgrp->kn->priv backpointer.
5423 */
5424 if (cgrp->kn)
5425 RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv,
5426 NULL);
5427 }
5428
5429 mutex_unlock(&cgroup_mutex);
5430
5431 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
5432 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
5433}
5434
5435static void css_release(struct percpu_ref *ref)
5436{
5437 struct cgroup_subsys_state *css =
5438 container_of(ref, struct cgroup_subsys_state, refcnt);
5439
5440 INIT_WORK(&css->destroy_work, css_release_work_fn);
5441 queue_work(cgroup_destroy_wq, &css->destroy_work);
5442}
5443
5444static void init_and_link_css(struct cgroup_subsys_state *css,
5445 struct cgroup_subsys *ss, struct cgroup *cgrp)
5446{
5447 lockdep_assert_held(&cgroup_mutex);
5448
5449 cgroup_get_live(cgrp);
5450
5451 memset(css, 0, sizeof(*css));
5452 css->cgroup = cgrp;
5453 css->ss = ss;
5454 css->id = -1;
5455 INIT_LIST_HEAD(&css->sibling);
5456 INIT_LIST_HEAD(&css->children);
5457 INIT_LIST_HEAD(&css->rstat_css_node);
5458 css->serial_nr = css_serial_nr_next++;
5459 atomic_set(&css->online_cnt, 0);
5460
5461 if (cgroup_parent(cgrp)) {
5462 css->parent = cgroup_css(cgroup_parent(cgrp), ss);
5463 css_get(css->parent);
5464 }
5465
5466 if (ss->css_rstat_flush)
5467 list_add_rcu(&css->rstat_css_node, &cgrp->rstat_css_list);
5468
5469 BUG_ON(cgroup_css(cgrp, ss));
5470}
5471
5472/* invoke ->css_online() on a new CSS and mark it online if successful */
5473static int online_css(struct cgroup_subsys_state *css)
5474{
5475 struct cgroup_subsys *ss = css->ss;
5476 int ret = 0;
5477
5478 lockdep_assert_held(&cgroup_mutex);
5479
5480 if (ss->css_online)
5481 ret = ss->css_online(css);
5482 if (!ret) {
5483 css->flags |= CSS_ONLINE;
5484 rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
5485
5486 atomic_inc(&css->online_cnt);
5487 if (css->parent)
5488 atomic_inc(&css->parent->online_cnt);
5489 }
5490 return ret;
5491}
5492
5493/* if the CSS is online, invoke ->css_offline() on it and mark it offline */
5494static void offline_css(struct cgroup_subsys_state *css)
5495{
5496 struct cgroup_subsys *ss = css->ss;
5497
5498 lockdep_assert_held(&cgroup_mutex);
5499
5500 if (!(css->flags & CSS_ONLINE))
5501 return;
5502
5503 if (ss->css_offline)
5504 ss->css_offline(css);
5505
5506 css->flags &= ~CSS_ONLINE;
5507 RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL);
5508
5509 wake_up_all(&css->cgroup->offline_waitq);
5510}
5511
5512/**
5513 * css_create - create a cgroup_subsys_state
5514 * @cgrp: the cgroup new css will be associated with
5515 * @ss: the subsys of new css
5516 *
5517 * Create a new css associated with @cgrp - @ss pair. On success, the new
5518 * css is online and installed in @cgrp. This function doesn't create the
5519 * interface files. Returns 0 on success, -errno on failure.
5520 */
5521static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
5522 struct cgroup_subsys *ss)
5523{
5524 struct cgroup *parent = cgroup_parent(cgrp);
5525 struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss);
5526 struct cgroup_subsys_state *css;
5527 int err;
5528
5529 lockdep_assert_held(&cgroup_mutex);
5530
5531 css = ss->css_alloc(parent_css);
5532 if (!css)
5533 css = ERR_PTR(-ENOMEM);
5534 if (IS_ERR(css))
5535 return css;
5536
5537 init_and_link_css(css, ss, cgrp);
5538
5539 err = percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL);
5540 if (err)
5541 goto err_free_css;
5542
5543 err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL);
5544 if (err < 0)
5545 goto err_free_css;
5546 css->id = err;
5547
5548 /* @css is ready to be brought online now, make it visible */
5549 list_add_tail_rcu(&css->sibling, &parent_css->children);
5550 cgroup_idr_replace(&ss->css_idr, css, css->id);
5551
5552 err = online_css(css);
5553 if (err)
5554 goto err_list_del;
5555
5556 return css;
5557
5558err_list_del:
5559 list_del_rcu(&css->sibling);
5560err_free_css:
5561 list_del_rcu(&css->rstat_css_node);
5562 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
5563 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
5564 return ERR_PTR(err);
5565}
5566
5567/*
5568 * The returned cgroup is fully initialized including its control mask, but
5569 * it isn't associated with its kernfs_node and doesn't have the control
5570 * mask applied.
5571 */
5572static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
5573 umode_t mode)
5574{
5575 struct cgroup_root *root = parent->root;
5576 struct cgroup *cgrp, *tcgrp;
5577 struct kernfs_node *kn;
5578 int level = parent->level + 1;
5579 int ret;
5580
5581 /* allocate the cgroup and its ID, 0 is reserved for the root */
5582 cgrp = kzalloc(struct_size(cgrp, ancestors, (level + 1)), GFP_KERNEL);
5583 if (!cgrp)
5584 return ERR_PTR(-ENOMEM);
5585
5586 ret = percpu_ref_init(&cgrp->self.refcnt, css_release, 0, GFP_KERNEL);
5587 if (ret)
5588 goto out_free_cgrp;
5589
5590 ret = cgroup_rstat_init(cgrp);
5591 if (ret)
5592 goto out_cancel_ref;
5593
5594 /* create the directory */
5595 kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
5596 if (IS_ERR(kn)) {
5597 ret = PTR_ERR(kn);
5598 goto out_stat_exit;
5599 }
5600 cgrp->kn = kn;
5601
5602 init_cgroup_housekeeping(cgrp);
5603
5604 cgrp->self.parent = &parent->self;
5605 cgrp->root = root;
5606 cgrp->level = level;
5607
5608 ret = psi_cgroup_alloc(cgrp);
5609 if (ret)
5610 goto out_kernfs_remove;
5611
5612 ret = cgroup_bpf_inherit(cgrp);
5613 if (ret)
5614 goto out_psi_free;
5615
5616 /*
5617 * New cgroup inherits effective freeze counter, and
5618 * if the parent has to be frozen, the child has too.
5619 */
5620 cgrp->freezer.e_freeze = parent->freezer.e_freeze;
5621 if (cgrp->freezer.e_freeze) {
5622 /*
5623 * Set the CGRP_FREEZE flag, so when a process will be
5624 * attached to the child cgroup, it will become frozen.
5625 * At this point the new cgroup is unpopulated, so we can
5626 * consider it frozen immediately.
5627 */
5628 set_bit(CGRP_FREEZE, &cgrp->flags);
5629 set_bit(CGRP_FROZEN, &cgrp->flags);
5630 }
5631
5632 spin_lock_irq(&css_set_lock);
5633 for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
5634 cgrp->ancestors[tcgrp->level] = tcgrp;
5635
5636 if (tcgrp != cgrp) {
5637 tcgrp->nr_descendants++;
5638
5639 /*
5640 * If the new cgroup is frozen, all ancestor cgroups
5641 * get a new frozen descendant, but their state can't
5642 * change because of this.
5643 */
5644 if (cgrp->freezer.e_freeze)
5645 tcgrp->freezer.nr_frozen_descendants++;
5646 }
5647 }
5648 spin_unlock_irq(&css_set_lock);
5649
5650 if (notify_on_release(parent))
5651 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
5652
5653 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
5654 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
5655
5656 cgrp->self.serial_nr = css_serial_nr_next++;
5657
5658 /* allocation complete, commit to creation */
5659 list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);
5660 atomic_inc(&root->nr_cgrps);
5661 cgroup_get_live(parent);
5662
5663 /*
5664 * On the default hierarchy, a child doesn't automatically inherit
5665 * subtree_control from the parent. Each is configured manually.
5666 */
5667 if (!cgroup_on_dfl(cgrp))
5668 cgrp->subtree_control = cgroup_control(cgrp);
5669
5670 cgroup_propagate_control(cgrp);
5671
5672 return cgrp;
5673
5674out_psi_free:
5675 psi_cgroup_free(cgrp);
5676out_kernfs_remove:
5677 kernfs_remove(cgrp->kn);
5678out_stat_exit:
5679 cgroup_rstat_exit(cgrp);
5680out_cancel_ref:
5681 percpu_ref_exit(&cgrp->self.refcnt);
5682out_free_cgrp:
5683 kfree(cgrp);
5684 return ERR_PTR(ret);
5685}
5686
5687static bool cgroup_check_hierarchy_limits(struct cgroup *parent)
5688{
5689 struct cgroup *cgroup;
5690 int ret = false;
5691 int level = 1;
5692
5693 lockdep_assert_held(&cgroup_mutex);
5694
5695 for (cgroup = parent; cgroup; cgroup = cgroup_parent(cgroup)) {
5696 if (cgroup->nr_descendants >= cgroup->max_descendants)
5697 goto fail;
5698
5699 if (level > cgroup->max_depth)
5700 goto fail;
5701
5702 level++;
5703 }
5704
5705 ret = true;
5706fail:
5707 return ret;
5708}
5709
5710int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
5711{
5712 struct cgroup *parent, *cgrp;
5713 int ret;
5714
5715 /* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
5716 if (strchr(name, '\n'))
5717 return -EINVAL;
5718
5719 parent = cgroup_kn_lock_live(parent_kn, false);
5720 if (!parent)
5721 return -ENODEV;
5722
5723 if (!cgroup_check_hierarchy_limits(parent)) {
5724 ret = -EAGAIN;
5725 goto out_unlock;
5726 }
5727
5728 cgrp = cgroup_create(parent, name, mode);
5729 if (IS_ERR(cgrp)) {
5730 ret = PTR_ERR(cgrp);
5731 goto out_unlock;
5732 }
5733
5734 /*
5735 * This extra ref will be put in cgroup_free_fn() and guarantees
5736 * that @cgrp->kn is always accessible.
5737 */
5738 kernfs_get(cgrp->kn);
5739
5740 ret = cgroup_kn_set_ugid(cgrp->kn);
5741 if (ret)
5742 goto out_destroy;
5743
5744 ret = css_populate_dir(&cgrp->self);
5745 if (ret)
5746 goto out_destroy;
5747
5748 ret = cgroup_apply_control_enable(cgrp);
5749 if (ret)
5750 goto out_destroy;
5751
5752 TRACE_CGROUP_PATH(mkdir, cgrp);
5753
5754 /* let's create and online css's */
5755 kernfs_activate(cgrp->kn);
5756
5757 ret = 0;
5758 goto out_unlock;
5759
5760out_destroy:
5761 cgroup_destroy_locked(cgrp);
5762out_unlock:
5763 cgroup_kn_unlock(parent_kn);
5764 return ret;
5765}
5766
5767/*
5768 * This is called when the refcnt of a css is confirmed to be killed.
5769 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
5770 * initiate destruction and put the css ref from kill_css().
5771 */
5772static void css_killed_work_fn(struct work_struct *work)
5773{
5774 struct cgroup_subsys_state *css =
5775 container_of(work, struct cgroup_subsys_state, destroy_work);
5776
5777 mutex_lock(&cgroup_mutex);
5778
5779 do {
5780 offline_css(css);
5781 css_put(css);
5782 /* @css can't go away while we're holding cgroup_mutex */
5783 css = css->parent;
5784 } while (css && atomic_dec_and_test(&css->online_cnt));
5785
5786 mutex_unlock(&cgroup_mutex);
5787}
5788
5789/* css kill confirmation processing requires process context, bounce */
5790static void css_killed_ref_fn(struct percpu_ref *ref)
5791{
5792 struct cgroup_subsys_state *css =
5793 container_of(ref, struct cgroup_subsys_state, refcnt);
5794
5795 if (atomic_dec_and_test(&css->online_cnt)) {
5796 INIT_WORK(&css->destroy_work, css_killed_work_fn);
5797 queue_work(cgroup_destroy_wq, &css->destroy_work);
5798 }
5799}
5800
5801/**
5802 * kill_css - destroy a css
5803 * @css: css to destroy
5804 *
5805 * This function initiates destruction of @css by removing cgroup interface
5806 * files and putting its base reference. ->css_offline() will be invoked
5807 * asynchronously once css_tryget_online() is guaranteed to fail and when
5808 * the reference count reaches zero, @css will be released.
5809 */
5810static void kill_css(struct cgroup_subsys_state *css)
5811{
5812 lockdep_assert_held(&cgroup_mutex);
5813
5814 if (css->flags & CSS_DYING)
5815 return;
5816
5817 css->flags |= CSS_DYING;
5818
5819 /*
5820 * This must happen before css is disassociated with its cgroup.
5821 * See seq_css() for details.
5822 */
5823 css_clear_dir(css);
5824
5825 /*
5826 * Killing would put the base ref, but we need to keep it alive
5827 * until after ->css_offline().
5828 */
5829 css_get(css);
5830
5831 /*
5832 * cgroup core guarantees that, by the time ->css_offline() is
5833 * invoked, no new css reference will be given out via
5834 * css_tryget_online(). We can't simply call percpu_ref_kill() and
5835 * proceed to offlining css's because percpu_ref_kill() doesn't
5836 * guarantee that the ref is seen as killed on all CPUs on return.
5837 *
5838 * Use percpu_ref_kill_and_confirm() to get notifications as each
5839 * css is confirmed to be seen as killed on all CPUs.
5840 */
5841 percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
5842}
5843
5844/**
5845 * cgroup_destroy_locked - the first stage of cgroup destruction
5846 * @cgrp: cgroup to be destroyed
5847 *
5848 * css's make use of percpu refcnts whose killing latency shouldn't be
5849 * exposed to userland and are RCU protected. Also, cgroup core needs to
5850 * guarantee that css_tryget_online() won't succeed by the time
5851 * ->css_offline() is invoked. To satisfy all the requirements,
5852 * destruction is implemented in the following two steps.
5853 *
5854 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
5855 * userland visible parts and start killing the percpu refcnts of
5856 * css's. Set up so that the next stage will be kicked off once all
5857 * the percpu refcnts are confirmed to be killed.
5858 *
5859 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
5860 * rest of destruction. Once all cgroup references are gone, the
5861 * cgroup is RCU-freed.
5862 *
5863 * This function implements s1. After this step, @cgrp is gone as far as
5864 * the userland is concerned and a new cgroup with the same name may be
5865 * created. As cgroup doesn't care about the names internally, this
5866 * doesn't cause any problem.
5867 */
5868static int cgroup_destroy_locked(struct cgroup *cgrp)
5869 __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
5870{
5871 struct cgroup *tcgrp, *parent = cgroup_parent(cgrp);
5872 struct cgroup_subsys_state *css;
5873 struct cgrp_cset_link *link;
5874 int ssid;
5875
5876 lockdep_assert_held(&cgroup_mutex);
5877
5878 /*
5879 * Only migration can raise populated from zero and we're already
5880 * holding cgroup_mutex.
5881 */
5882 if (cgroup_is_populated(cgrp))
5883 return -EBUSY;
5884
5885 /*
5886 * Make sure there's no live children. We can't test emptiness of
5887 * ->self.children as dead children linger on it while being
5888 * drained; otherwise, "rmdir parent/child parent" may fail.
5889 */
5890 if (css_has_online_children(&cgrp->self))
5891 return -EBUSY;
5892
5893 /*
5894 * Mark @cgrp and the associated csets dead. The former prevents
5895 * further task migration and child creation by disabling
5896 * cgroup_lock_live_group(). The latter makes the csets ignored by
5897 * the migration path.
5898 */
5899 cgrp->self.flags &= ~CSS_ONLINE;
5900
5901 spin_lock_irq(&css_set_lock);
5902 list_for_each_entry(link, &cgrp->cset_links, cset_link)
5903 link->cset->dead = true;
5904 spin_unlock_irq(&css_set_lock);
5905
5906 /* initiate massacre of all css's */
5907 for_each_css(css, ssid, cgrp)
5908 kill_css(css);
5909
5910 /* clear and remove @cgrp dir, @cgrp has an extra ref on its kn */
5911 css_clear_dir(&cgrp->self);
5912 kernfs_remove(cgrp->kn);
5913
5914 if (cgroup_is_threaded(cgrp))
5915 parent->nr_threaded_children--;
5916
5917 spin_lock_irq(&css_set_lock);
5918 for (tcgrp = cgroup_parent(cgrp); tcgrp; tcgrp = cgroup_parent(tcgrp)) {
5919 tcgrp->nr_descendants--;
5920 tcgrp->nr_dying_descendants++;
5921 /*
5922 * If the dying cgroup is frozen, decrease frozen descendants
5923 * counters of ancestor cgroups.
5924 */
5925 if (test_bit(CGRP_FROZEN, &cgrp->flags))
5926 tcgrp->freezer.nr_frozen_descendants--;
5927 }
5928 spin_unlock_irq(&css_set_lock);
5929
5930 cgroup1_check_for_release(parent);
5931
5932 cgroup_bpf_offline(cgrp);
5933
5934 /* put the base reference */
5935 percpu_ref_kill(&cgrp->self.refcnt);
5936
5937 return 0;
5938};
5939
5940int cgroup_rmdir(struct kernfs_node *kn)
5941{
5942 struct cgroup *cgrp;
5943 int ret = 0;
5944
5945 cgrp = cgroup_kn_lock_live(kn, false);
5946 if (!cgrp)
5947 return 0;
5948
5949 ret = cgroup_destroy_locked(cgrp);
5950 if (!ret)
5951 TRACE_CGROUP_PATH(rmdir, cgrp);
5952
5953 cgroup_kn_unlock(kn);
5954 return ret;
5955}
5956
5957static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
5958 .show_options = cgroup_show_options,
5959 .mkdir = cgroup_mkdir,
5960 .rmdir = cgroup_rmdir,
5961 .show_path = cgroup_show_path,
5962};
5963
5964static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
5965{
5966 struct cgroup_subsys_state *css;
5967
5968 pr_debug("Initializing cgroup subsys %s\n", ss->name);
5969
5970 mutex_lock(&cgroup_mutex);
5971
5972 idr_init(&ss->css_idr);
5973 INIT_LIST_HEAD(&ss->cfts);
5974
5975 /* Create the root cgroup state for this subsystem */
5976 ss->root = &cgrp_dfl_root;
5977 css = ss->css_alloc(NULL);
5978 /* We don't handle early failures gracefully */
5979 BUG_ON(IS_ERR(css));
5980 init_and_link_css(css, ss, &cgrp_dfl_root.cgrp);
5981
5982 /*
5983 * Root csses are never destroyed and we can't initialize
5984 * percpu_ref during early init. Disable refcnting.
5985 */
5986 css->flags |= CSS_NO_REF;
5987
5988 if (early) {
5989 /* allocation can't be done safely during early init */
5990 css->id = 1;
5991 } else {
5992 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL);
5993 BUG_ON(css->id < 0);
5994 }
5995
5996 /* Update the init_css_set to contain a subsys
5997 * pointer to this state - since the subsystem is
5998 * newly registered, all tasks and hence the
5999 * init_css_set is in the subsystem's root cgroup. */
6000 init_css_set.subsys[ss->id] = css;
6001
6002 have_fork_callback |= (bool)ss->fork << ss->id;
6003 have_exit_callback |= (bool)ss->exit << ss->id;
6004 have_release_callback |= (bool)ss->release << ss->id;
6005 have_canfork_callback |= (bool)ss->can_fork << ss->id;
6006
6007 /* At system boot, before all subsystems have been
6008 * registered, no tasks have been forked, so we don't
6009 * need to invoke fork callbacks here. */
6010 BUG_ON(!list_empty(&init_task.tasks));
6011
6012 BUG_ON(online_css(css));
6013
6014 mutex_unlock(&cgroup_mutex);
6015}
6016
6017/**
6018 * cgroup_init_early - cgroup initialization at system boot
6019 *
6020 * Initialize cgroups at system boot, and initialize any
6021 * subsystems that request early init.
6022 */
6023int __init cgroup_init_early(void)
6024{
6025 static struct cgroup_fs_context __initdata ctx;
6026 struct cgroup_subsys *ss;
6027 int i;
6028
6029 ctx.root = &cgrp_dfl_root;
6030 init_cgroup_root(&ctx);
6031 cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF;
6032
6033 RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
6034
6035 for_each_subsys(ss, i) {
6036 WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
6037 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p id:name=%d:%s\n",
6038 i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
6039 ss->id, ss->name);
6040 WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
6041 "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
6042
6043 ss->id = i;
6044 ss->name = cgroup_subsys_name[i];
6045 if (!ss->legacy_name)
6046 ss->legacy_name = cgroup_subsys_name[i];
6047
6048 if (ss->early_init)
6049 cgroup_init_subsys(ss, true);
6050 }
6051 return 0;
6052}
6053
6054/**
6055 * cgroup_init - cgroup initialization
6056 *
6057 * Register cgroup filesystem and /proc file, and initialize
6058 * any subsystems that didn't request early init.
6059 */
6060int __init cgroup_init(void)
6061{
6062 struct cgroup_subsys *ss;
6063 int ssid;
6064
6065 BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
6066 BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
6067 BUG_ON(cgroup_init_cftypes(NULL, cgroup_psi_files));
6068 BUG_ON(cgroup_init_cftypes(NULL, cgroup1_base_files));
6069
6070 cgroup_rstat_boot();
6071
6072 get_user_ns(init_cgroup_ns.user_ns);
6073
6074 mutex_lock(&cgroup_mutex);
6075
6076 /*
6077 * Add init_css_set to the hash table so that dfl_root can link to
6078 * it during init.
6079 */
6080 hash_add(css_set_table, &init_css_set.hlist,
6081 css_set_hash(init_css_set.subsys));
6082
6083 BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0));
6084
6085 mutex_unlock(&cgroup_mutex);
6086
6087 for_each_subsys(ss, ssid) {
6088 if (ss->early_init) {
6089 struct cgroup_subsys_state *css =
6090 init_css_set.subsys[ss->id];
6091
6092 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2,
6093 GFP_KERNEL);
6094 BUG_ON(css->id < 0);
6095 } else {
6096 cgroup_init_subsys(ss, false);
6097 }
6098
6099 list_add_tail(&init_css_set.e_cset_node[ssid],
6100 &cgrp_dfl_root.cgrp.e_csets[ssid]);
6101
6102 /*
6103 * Setting dfl_root subsys_mask needs to consider the
6104 * disabled flag and cftype registration needs kmalloc,
6105 * both of which aren't available during early_init.
6106 */
6107 if (!cgroup_ssid_enabled(ssid))
6108 continue;
6109
6110 if (cgroup1_ssid_disabled(ssid))
6111 printk(KERN_INFO "Disabling %s control group subsystem in v1 mounts\n",
6112 ss->name);
6113
6114 cgrp_dfl_root.subsys_mask |= 1 << ss->id;
6115
6116 /* implicit controllers must be threaded too */
6117 WARN_ON(ss->implicit_on_dfl && !ss->threaded);
6118
6119 if (ss->implicit_on_dfl)
6120 cgrp_dfl_implicit_ss_mask |= 1 << ss->id;
6121 else if (!ss->dfl_cftypes)
6122 cgrp_dfl_inhibit_ss_mask |= 1 << ss->id;
6123
6124 if (ss->threaded)
6125 cgrp_dfl_threaded_ss_mask |= 1 << ss->id;
6126
6127 if (ss->dfl_cftypes == ss->legacy_cftypes) {
6128 WARN_ON(cgroup_add_cftypes(ss, ss->dfl_cftypes));
6129 } else {
6130 WARN_ON(cgroup_add_dfl_cftypes(ss, ss->dfl_cftypes));
6131 WARN_ON(cgroup_add_legacy_cftypes(ss, ss->legacy_cftypes));
6132 }
6133
6134 if (ss->bind)
6135 ss->bind(init_css_set.subsys[ssid]);
6136
6137 mutex_lock(&cgroup_mutex);
6138 css_populate_dir(init_css_set.subsys[ssid]);
6139 mutex_unlock(&cgroup_mutex);
6140 }
6141
6142 /* init_css_set.subsys[] has been updated, re-hash */
6143 hash_del(&init_css_set.hlist);
6144 hash_add(css_set_table, &init_css_set.hlist,
6145 css_set_hash(init_css_set.subsys));
6146
6147 WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup"));
6148 WARN_ON(register_filesystem(&cgroup_fs_type));
6149 WARN_ON(register_filesystem(&cgroup2_fs_type));
6150 WARN_ON(!proc_create_single("cgroups", 0, NULL, proc_cgroupstats_show));
6151#ifdef CONFIG_CPUSETS
6152 WARN_ON(register_filesystem(&cpuset_fs_type));
6153#endif
6154
6155 return 0;
6156}
6157
6158static int __init cgroup_wq_init(void)
6159{
6160 /*
6161 * There isn't much point in executing destruction path in
6162 * parallel. Good chunk is serialized with cgroup_mutex anyway.
6163 * Use 1 for @max_active.
6164 *
6165 * We would prefer to do this in cgroup_init() above, but that
6166 * is called before init_workqueues(): so leave this until after.
6167 */
6168 cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
6169 BUG_ON(!cgroup_destroy_wq);
6170 return 0;
6171}
6172core_initcall(cgroup_wq_init);
6173
6174void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
6175{
6176 struct kernfs_node *kn;
6177
6178 kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
6179 if (!kn)
6180 return;
6181 kernfs_path(kn, buf, buflen);
6182 kernfs_put(kn);
6183}
6184
6185/*
6186 * cgroup_get_from_id : get the cgroup associated with cgroup id
6187 * @id: cgroup id
6188 * On success return the cgrp or ERR_PTR on failure
6189 * Only cgroups within current task's cgroup NS are valid.
6190 */
6191struct cgroup *cgroup_get_from_id(u64 id)
6192{
6193 struct kernfs_node *kn;
6194 struct cgroup *cgrp, *root_cgrp;
6195
6196 kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
6197 if (!kn)
6198 return ERR_PTR(-ENOENT);
6199
6200 if (kernfs_type(kn) != KERNFS_DIR) {
6201 kernfs_put(kn);
6202 return ERR_PTR(-ENOENT);
6203 }
6204
6205 rcu_read_lock();
6206
6207 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6208 if (cgrp && !cgroup_tryget(cgrp))
6209 cgrp = NULL;
6210
6211 rcu_read_unlock();
6212 kernfs_put(kn);
6213
6214 if (!cgrp)
6215 return ERR_PTR(-ENOENT);
6216
6217 root_cgrp = current_cgns_cgroup_dfl();
6218 if (!cgroup_is_descendant(cgrp, root_cgrp)) {
6219 cgroup_put(cgrp);
6220 return ERR_PTR(-ENOENT);
6221 }
6222
6223 return cgrp;
6224}
6225EXPORT_SYMBOL_GPL(cgroup_get_from_id);
6226
6227/*
6228 * proc_cgroup_show()
6229 * - Print task's cgroup paths into seq_file, one line for each hierarchy
6230 * - Used for /proc/<pid>/cgroup.
6231 */
6232int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
6233 struct pid *pid, struct task_struct *tsk)
6234{
6235 char *buf;
6236 int retval;
6237 struct cgroup_root *root;
6238
6239 retval = -ENOMEM;
6240 buf = kmalloc(PATH_MAX, GFP_KERNEL);
6241 if (!buf)
6242 goto out;
6243
6244 mutex_lock(&cgroup_mutex);
6245 spin_lock_irq(&css_set_lock);
6246
6247 for_each_root(root) {
6248 struct cgroup_subsys *ss;
6249 struct cgroup *cgrp;
6250 int ssid, count = 0;
6251
6252 if (root == &cgrp_dfl_root && !READ_ONCE(cgrp_dfl_visible))
6253 continue;
6254
6255 seq_printf(m, "%d:", root->hierarchy_id);
6256 if (root != &cgrp_dfl_root)
6257 for_each_subsys(ss, ssid)
6258 if (root->subsys_mask & (1 << ssid))
6259 seq_printf(m, "%s%s", count++ ? "," : "",
6260 ss->legacy_name);
6261 if (strlen(root->name))
6262 seq_printf(m, "%sname=%s", count ? "," : "",
6263 root->name);
6264 seq_putc(m, ':');
6265
6266 cgrp = task_cgroup_from_root(tsk, root);
6267
6268 /*
6269 * On traditional hierarchies, all zombie tasks show up as
6270 * belonging to the root cgroup. On the default hierarchy,
6271 * while a zombie doesn't show up in "cgroup.procs" and
6272 * thus can't be migrated, its /proc/PID/cgroup keeps
6273 * reporting the cgroup it belonged to before exiting. If
6274 * the cgroup is removed before the zombie is reaped,
6275 * " (deleted)" is appended to the cgroup path.
6276 */
6277 if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) {
6278 retval = cgroup_path_ns_locked(cgrp, buf, PATH_MAX,
6279 current->nsproxy->cgroup_ns);
6280 if (retval >= PATH_MAX)
6281 retval = -ENAMETOOLONG;
6282 if (retval < 0)
6283 goto out_unlock;
6284
6285 seq_puts(m, buf);
6286 } else {
6287 seq_puts(m, "/");
6288 }
6289
6290 if (cgroup_on_dfl(cgrp) && cgroup_is_dead(cgrp))
6291 seq_puts(m, " (deleted)\n");
6292 else
6293 seq_putc(m, '\n');
6294 }
6295
6296 retval = 0;
6297out_unlock:
6298 spin_unlock_irq(&css_set_lock);
6299 mutex_unlock(&cgroup_mutex);
6300 kfree(buf);
6301out:
6302 return retval;
6303}
6304
6305/**
6306 * cgroup_fork - initialize cgroup related fields during copy_process()
6307 * @child: pointer to task_struct of forking parent process.
6308 *
6309 * A task is associated with the init_css_set until cgroup_post_fork()
6310 * attaches it to the target css_set.
6311 */
6312void cgroup_fork(struct task_struct *child)
6313{
6314 RCU_INIT_POINTER(child->cgroups, &init_css_set);
6315 INIT_LIST_HEAD(&child->cg_list);
6316}
6317
6318/**
6319 * cgroup_v1v2_get_from_file - get a cgroup pointer from a file pointer
6320 * @f: file corresponding to cgroup_dir
6321 *
6322 * Find the cgroup from a file pointer associated with a cgroup directory.
6323 * Returns a pointer to the cgroup on success. ERR_PTR is returned if the
6324 * cgroup cannot be found.
6325 */
6326static struct cgroup *cgroup_v1v2_get_from_file(struct file *f)
6327{
6328 struct cgroup_subsys_state *css;
6329
6330 css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
6331 if (IS_ERR(css))
6332 return ERR_CAST(css);
6333
6334 return css->cgroup;
6335}
6336
6337/**
6338 * cgroup_get_from_file - same as cgroup_v1v2_get_from_file, but only supports
6339 * cgroup2.
6340 * @f: file corresponding to cgroup2_dir
6341 */
6342static struct cgroup *cgroup_get_from_file(struct file *f)
6343{
6344 struct cgroup *cgrp = cgroup_v1v2_get_from_file(f);
6345
6346 if (IS_ERR(cgrp))
6347 return ERR_CAST(cgrp);
6348
6349 if (!cgroup_on_dfl(cgrp)) {
6350 cgroup_put(cgrp);
6351 return ERR_PTR(-EBADF);
6352 }
6353
6354 return cgrp;
6355}
6356
6357/**
6358 * cgroup_css_set_fork - find or create a css_set for a child process
6359 * @kargs: the arguments passed to create the child process
6360 *
6361 * This functions finds or creates a new css_set which the child
6362 * process will be attached to in cgroup_post_fork(). By default,
6363 * the child process will be given the same css_set as its parent.
6364 *
6365 * If CLONE_INTO_CGROUP is specified this function will try to find an
6366 * existing css_set which includes the requested cgroup and if not create
6367 * a new css_set that the child will be attached to later. If this function
6368 * succeeds it will hold cgroup_threadgroup_rwsem on return. If
6369 * CLONE_INTO_CGROUP is requested this function will grab cgroup mutex
6370 * before grabbing cgroup_threadgroup_rwsem and will hold a reference
6371 * to the target cgroup.
6372 */
6373static int cgroup_css_set_fork(struct kernel_clone_args *kargs)
6374 __acquires(&cgroup_mutex) __acquires(&cgroup_threadgroup_rwsem)
6375{
6376 int ret;
6377 struct cgroup *dst_cgrp = NULL;
6378 struct css_set *cset;
6379 struct super_block *sb;
6380 struct file *f;
6381
6382 if (kargs->flags & CLONE_INTO_CGROUP)
6383 mutex_lock(&cgroup_mutex);
6384
6385 cgroup_threadgroup_change_begin(current);
6386
6387 spin_lock_irq(&css_set_lock);
6388 cset = task_css_set(current);
6389 get_css_set(cset);
6390 spin_unlock_irq(&css_set_lock);
6391
6392 if (!(kargs->flags & CLONE_INTO_CGROUP)) {
6393 kargs->cset = cset;
6394 return 0;
6395 }
6396
6397 f = fget_raw(kargs->cgroup);
6398 if (!f) {
6399 ret = -EBADF;
6400 goto err;
6401 }
6402 sb = f->f_path.dentry->d_sb;
6403
6404 dst_cgrp = cgroup_get_from_file(f);
6405 if (IS_ERR(dst_cgrp)) {
6406 ret = PTR_ERR(dst_cgrp);
6407 dst_cgrp = NULL;
6408 goto err;
6409 }
6410
6411 if (cgroup_is_dead(dst_cgrp)) {
6412 ret = -ENODEV;
6413 goto err;
6414 }
6415
6416 /*
6417 * Verify that we the target cgroup is writable for us. This is
6418 * usually done by the vfs layer but since we're not going through
6419 * the vfs layer here we need to do it "manually".
6420 */
6421 ret = cgroup_may_write(dst_cgrp, sb);
6422 if (ret)
6423 goto err;
6424
6425 /*
6426 * Spawning a task directly into a cgroup works by passing a file
6427 * descriptor to the target cgroup directory. This can even be an O_PATH
6428 * file descriptor. But it can never be a cgroup.procs file descriptor.
6429 * This was done on purpose so spawning into a cgroup could be
6430 * conceptualized as an atomic
6431 *
6432 * fd = openat(dfd_cgroup, "cgroup.procs", ...);
6433 * write(fd, <child-pid>, ...);
6434 *
6435 * sequence, i.e. it's a shorthand for the caller opening and writing
6436 * cgroup.procs of the cgroup indicated by @dfd_cgroup. This allows us
6437 * to always use the caller's credentials.
6438 */
6439 ret = cgroup_attach_permissions(cset->dfl_cgrp, dst_cgrp, sb,
6440 !(kargs->flags & CLONE_THREAD),
6441 current->nsproxy->cgroup_ns);
6442 if (ret)
6443 goto err;
6444
6445 kargs->cset = find_css_set(cset, dst_cgrp);
6446 if (!kargs->cset) {
6447 ret = -ENOMEM;
6448 goto err;
6449 }
6450
6451 put_css_set(cset);
6452 fput(f);
6453 kargs->cgrp = dst_cgrp;
6454 return ret;
6455
6456err:
6457 cgroup_threadgroup_change_end(current);
6458 mutex_unlock(&cgroup_mutex);
6459 if (f)
6460 fput(f);
6461 if (dst_cgrp)
6462 cgroup_put(dst_cgrp);
6463 put_css_set(cset);
6464 if (kargs->cset)
6465 put_css_set(kargs->cset);
6466 return ret;
6467}
6468
6469/**
6470 * cgroup_css_set_put_fork - drop references we took during fork
6471 * @kargs: the arguments passed to create the child process
6472 *
6473 * Drop references to the prepared css_set and target cgroup if
6474 * CLONE_INTO_CGROUP was requested.
6475 */
6476static void cgroup_css_set_put_fork(struct kernel_clone_args *kargs)
6477 __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
6478{
6479 cgroup_threadgroup_change_end(current);
6480
6481 if (kargs->flags & CLONE_INTO_CGROUP) {
6482 struct cgroup *cgrp = kargs->cgrp;
6483 struct css_set *cset = kargs->cset;
6484
6485 mutex_unlock(&cgroup_mutex);
6486
6487 if (cset) {
6488 put_css_set(cset);
6489 kargs->cset = NULL;
6490 }
6491
6492 if (cgrp) {
6493 cgroup_put(cgrp);
6494 kargs->cgrp = NULL;
6495 }
6496 }
6497}
6498
6499/**
6500 * cgroup_can_fork - called on a new task before the process is exposed
6501 * @child: the child process
6502 * @kargs: the arguments passed to create the child process
6503 *
6504 * This prepares a new css_set for the child process which the child will
6505 * be attached to in cgroup_post_fork().
6506 * This calls the subsystem can_fork() callbacks. If the cgroup_can_fork()
6507 * callback returns an error, the fork aborts with that error code. This
6508 * allows for a cgroup subsystem to conditionally allow or deny new forks.
6509 */
6510int cgroup_can_fork(struct task_struct *child, struct kernel_clone_args *kargs)
6511{
6512 struct cgroup_subsys *ss;
6513 int i, j, ret;
6514
6515 ret = cgroup_css_set_fork(kargs);
6516 if (ret)
6517 return ret;
6518
6519 do_each_subsys_mask(ss, i, have_canfork_callback) {
6520 ret = ss->can_fork(child, kargs->cset);
6521 if (ret)
6522 goto out_revert;
6523 } while_each_subsys_mask();
6524
6525 return 0;
6526
6527out_revert:
6528 for_each_subsys(ss, j) {
6529 if (j >= i)
6530 break;
6531 if (ss->cancel_fork)
6532 ss->cancel_fork(child, kargs->cset);
6533 }
6534
6535 cgroup_css_set_put_fork(kargs);
6536
6537 return ret;
6538}
6539
6540/**
6541 * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
6542 * @child: the child process
6543 * @kargs: the arguments passed to create the child process
6544 *
6545 * This calls the cancel_fork() callbacks if a fork failed *after*
6546 * cgroup_can_fork() succeeded and cleans up references we took to
6547 * prepare a new css_set for the child process in cgroup_can_fork().
6548 */
6549void cgroup_cancel_fork(struct task_struct *child,
6550 struct kernel_clone_args *kargs)
6551{
6552 struct cgroup_subsys *ss;
6553 int i;
6554
6555 for_each_subsys(ss, i)
6556 if (ss->cancel_fork)
6557 ss->cancel_fork(child, kargs->cset);
6558
6559 cgroup_css_set_put_fork(kargs);
6560}
6561
6562/**
6563 * cgroup_post_fork - finalize cgroup setup for the child process
6564 * @child: the child process
6565 * @kargs: the arguments passed to create the child process
6566 *
6567 * Attach the child process to its css_set calling the subsystem fork()
6568 * callbacks.
6569 */
6570void cgroup_post_fork(struct task_struct *child,
6571 struct kernel_clone_args *kargs)
6572 __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
6573{
6574 unsigned long cgrp_flags = 0;
6575 bool kill = false;
6576 struct cgroup_subsys *ss;
6577 struct css_set *cset;
6578 int i;
6579
6580 cset = kargs->cset;
6581 kargs->cset = NULL;
6582
6583 spin_lock_irq(&css_set_lock);
6584
6585 /* init tasks are special, only link regular threads */
6586 if (likely(child->pid)) {
6587 if (kargs->cgrp)
6588 cgrp_flags = kargs->cgrp->flags;
6589 else
6590 cgrp_flags = cset->dfl_cgrp->flags;
6591
6592 WARN_ON_ONCE(!list_empty(&child->cg_list));
6593 cset->nr_tasks++;
6594 css_set_move_task(child, NULL, cset, false);
6595 } else {
6596 put_css_set(cset);
6597 cset = NULL;
6598 }
6599
6600 if (!(child->flags & PF_KTHREAD)) {
6601 if (unlikely(test_bit(CGRP_FREEZE, &cgrp_flags))) {
6602 /*
6603 * If the cgroup has to be frozen, the new task has
6604 * too. Let's set the JOBCTL_TRAP_FREEZE jobctl bit to
6605 * get the task into the frozen state.
6606 */
6607 spin_lock(&child->sighand->siglock);
6608 WARN_ON_ONCE(child->frozen);
6609 child->jobctl |= JOBCTL_TRAP_FREEZE;
6610 spin_unlock(&child->sighand->siglock);
6611
6612 /*
6613 * Calling cgroup_update_frozen() isn't required here,
6614 * because it will be called anyway a bit later from
6615 * do_freezer_trap(). So we avoid cgroup's transient
6616 * switch from the frozen state and back.
6617 */
6618 }
6619
6620 /*
6621 * If the cgroup is to be killed notice it now and take the
6622 * child down right after we finished preparing it for
6623 * userspace.
6624 */
6625 kill = test_bit(CGRP_KILL, &cgrp_flags);
6626 }
6627
6628 spin_unlock_irq(&css_set_lock);
6629
6630 /*
6631 * Call ss->fork(). This must happen after @child is linked on
6632 * css_set; otherwise, @child might change state between ->fork()
6633 * and addition to css_set.
6634 */
6635 do_each_subsys_mask(ss, i, have_fork_callback) {
6636 ss->fork(child);
6637 } while_each_subsys_mask();
6638
6639 /* Make the new cset the root_cset of the new cgroup namespace. */
6640 if (kargs->flags & CLONE_NEWCGROUP) {
6641 struct css_set *rcset = child->nsproxy->cgroup_ns->root_cset;
6642
6643 get_css_set(cset);
6644 child->nsproxy->cgroup_ns->root_cset = cset;
6645 put_css_set(rcset);
6646 }
6647
6648 /* Cgroup has to be killed so take down child immediately. */
6649 if (unlikely(kill))
6650 do_send_sig_info(SIGKILL, SEND_SIG_NOINFO, child, PIDTYPE_TGID);
6651
6652 cgroup_css_set_put_fork(kargs);
6653}
6654
6655/**
6656 * cgroup_exit - detach cgroup from exiting task
6657 * @tsk: pointer to task_struct of exiting process
6658 *
6659 * Description: Detach cgroup from @tsk.
6660 *
6661 */
6662void cgroup_exit(struct task_struct *tsk)
6663{
6664 struct cgroup_subsys *ss;
6665 struct css_set *cset;
6666 int i;
6667
6668 spin_lock_irq(&css_set_lock);
6669
6670 WARN_ON_ONCE(list_empty(&tsk->cg_list));
6671 cset = task_css_set(tsk);
6672 css_set_move_task(tsk, cset, NULL, false);
6673 list_add_tail(&tsk->cg_list, &cset->dying_tasks);
6674 cset->nr_tasks--;
6675
6676 WARN_ON_ONCE(cgroup_task_frozen(tsk));
6677 if (unlikely(!(tsk->flags & PF_KTHREAD) &&
6678 test_bit(CGRP_FREEZE, &task_dfl_cgroup(tsk)->flags)))
6679 cgroup_update_frozen(task_dfl_cgroup(tsk));
6680
6681 spin_unlock_irq(&css_set_lock);
6682
6683 /* see cgroup_post_fork() for details */
6684 do_each_subsys_mask(ss, i, have_exit_callback) {
6685 ss->exit(tsk);
6686 } while_each_subsys_mask();
6687}
6688
6689void cgroup_release(struct task_struct *task)
6690{
6691 struct cgroup_subsys *ss;
6692 int ssid;
6693
6694 do_each_subsys_mask(ss, ssid, have_release_callback) {
6695 ss->release(task);
6696 } while_each_subsys_mask();
6697
6698 spin_lock_irq(&css_set_lock);
6699 css_set_skip_task_iters(task_css_set(task), task);
6700 list_del_init(&task->cg_list);
6701 spin_unlock_irq(&css_set_lock);
6702}
6703
6704void cgroup_free(struct task_struct *task)
6705{
6706 struct css_set *cset = task_css_set(task);
6707 put_css_set(cset);
6708}
6709
6710static int __init cgroup_disable(char *str)
6711{
6712 struct cgroup_subsys *ss;
6713 char *token;
6714 int i;
6715
6716 while ((token = strsep(&str, ",")) != NULL) {
6717 if (!*token)
6718 continue;
6719
6720 for_each_subsys(ss, i) {
6721 if (strcmp(token, ss->name) &&
6722 strcmp(token, ss->legacy_name))
6723 continue;
6724
6725 static_branch_disable(cgroup_subsys_enabled_key[i]);
6726 pr_info("Disabling %s control group subsystem\n",
6727 ss->name);
6728 }
6729
6730 for (i = 0; i < OPT_FEATURE_COUNT; i++) {
6731 if (strcmp(token, cgroup_opt_feature_names[i]))
6732 continue;
6733 cgroup_feature_disable_mask |= 1 << i;
6734 pr_info("Disabling %s control group feature\n",
6735 cgroup_opt_feature_names[i]);
6736 break;
6737 }
6738 }
6739 return 1;
6740}
6741__setup("cgroup_disable=", cgroup_disable);
6742
6743void __init __weak enable_debug_cgroup(void) { }
6744
6745static int __init enable_cgroup_debug(char *str)
6746{
6747 cgroup_debug = true;
6748 enable_debug_cgroup();
6749 return 1;
6750}
6751__setup("cgroup_debug", enable_cgroup_debug);
6752
6753/**
6754 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
6755 * @dentry: directory dentry of interest
6756 * @ss: subsystem of interest
6757 *
6758 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
6759 * to get the corresponding css and return it. If such css doesn't exist
6760 * or can't be pinned, an ERR_PTR value is returned.
6761 */
6762struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
6763 struct cgroup_subsys *ss)
6764{
6765 struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
6766 struct file_system_type *s_type = dentry->d_sb->s_type;
6767 struct cgroup_subsys_state *css = NULL;
6768 struct cgroup *cgrp;
6769
6770 /* is @dentry a cgroup dir? */
6771 if ((s_type != &cgroup_fs_type && s_type != &cgroup2_fs_type) ||
6772 !kn || kernfs_type(kn) != KERNFS_DIR)
6773 return ERR_PTR(-EBADF);
6774
6775 rcu_read_lock();
6776
6777 /*
6778 * This path doesn't originate from kernfs and @kn could already
6779 * have been or be removed at any point. @kn->priv is RCU
6780 * protected for this access. See css_release_work_fn() for details.
6781 */
6782 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6783 if (cgrp)
6784 css = cgroup_css(cgrp, ss);
6785
6786 if (!css || !css_tryget_online(css))
6787 css = ERR_PTR(-ENOENT);
6788
6789 rcu_read_unlock();
6790 return css;
6791}
6792
6793/**
6794 * css_from_id - lookup css by id
6795 * @id: the cgroup id
6796 * @ss: cgroup subsys to be looked into
6797 *
6798 * Returns the css if there's valid one with @id, otherwise returns NULL.
6799 * Should be called under rcu_read_lock().
6800 */
6801struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
6802{
6803 WARN_ON_ONCE(!rcu_read_lock_held());
6804 return idr_find(&ss->css_idr, id);
6805}
6806
6807/**
6808 * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path
6809 * @path: path on the default hierarchy
6810 *
6811 * Find the cgroup at @path on the default hierarchy, increment its
6812 * reference count and return it. Returns pointer to the found cgroup on
6813 * success, ERR_PTR(-ENOENT) if @path doesn't exist or if the cgroup has already
6814 * been released and ERR_PTR(-ENOTDIR) if @path points to a non-directory.
6815 */
6816struct cgroup *cgroup_get_from_path(const char *path)
6817{
6818 struct kernfs_node *kn;
6819 struct cgroup *cgrp = ERR_PTR(-ENOENT);
6820 struct cgroup *root_cgrp;
6821
6822 root_cgrp = current_cgns_cgroup_dfl();
6823 kn = kernfs_walk_and_get(root_cgrp->kn, path);
6824 if (!kn)
6825 goto out;
6826
6827 if (kernfs_type(kn) != KERNFS_DIR) {
6828 cgrp = ERR_PTR(-ENOTDIR);
6829 goto out_kernfs;
6830 }
6831
6832 rcu_read_lock();
6833
6834 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6835 if (!cgrp || !cgroup_tryget(cgrp))
6836 cgrp = ERR_PTR(-ENOENT);
6837
6838 rcu_read_unlock();
6839
6840out_kernfs:
6841 kernfs_put(kn);
6842out:
6843 return cgrp;
6844}
6845EXPORT_SYMBOL_GPL(cgroup_get_from_path);
6846
6847/**
6848 * cgroup_v1v2_get_from_fd - get a cgroup pointer from a fd
6849 * @fd: fd obtained by open(cgroup_dir)
6850 *
6851 * Find the cgroup from a fd which should be obtained
6852 * by opening a cgroup directory. Returns a pointer to the
6853 * cgroup on success. ERR_PTR is returned if the cgroup
6854 * cannot be found.
6855 */
6856struct cgroup *cgroup_v1v2_get_from_fd(int fd)
6857{
6858 struct cgroup *cgrp;
6859 struct file *f;
6860
6861 f = fget_raw(fd);
6862 if (!f)
6863 return ERR_PTR(-EBADF);
6864
6865 cgrp = cgroup_v1v2_get_from_file(f);
6866 fput(f);
6867 return cgrp;
6868}
6869
6870/**
6871 * cgroup_get_from_fd - same as cgroup_v1v2_get_from_fd, but only supports
6872 * cgroup2.
6873 * @fd: fd obtained by open(cgroup2_dir)
6874 */
6875struct cgroup *cgroup_get_from_fd(int fd)
6876{
6877 struct cgroup *cgrp = cgroup_v1v2_get_from_fd(fd);
6878
6879 if (IS_ERR(cgrp))
6880 return ERR_CAST(cgrp);
6881
6882 if (!cgroup_on_dfl(cgrp)) {
6883 cgroup_put(cgrp);
6884 return ERR_PTR(-EBADF);
6885 }
6886 return cgrp;
6887}
6888EXPORT_SYMBOL_GPL(cgroup_get_from_fd);
6889
6890static u64 power_of_ten(int power)
6891{
6892 u64 v = 1;
6893 while (power--)
6894 v *= 10;
6895 return v;
6896}
6897
6898/**
6899 * cgroup_parse_float - parse a floating number
6900 * @input: input string
6901 * @dec_shift: number of decimal digits to shift
6902 * @v: output
6903 *
6904 * Parse a decimal floating point number in @input and store the result in
6905 * @v with decimal point right shifted @dec_shift times. For example, if
6906 * @input is "12.3456" and @dec_shift is 3, *@v will be set to 12345.
6907 * Returns 0 on success, -errno otherwise.
6908 *
6909 * There's nothing cgroup specific about this function except that it's
6910 * currently the only user.
6911 */
6912int cgroup_parse_float(const char *input, unsigned dec_shift, s64 *v)
6913{
6914 s64 whole, frac = 0;
6915 int fstart = 0, fend = 0, flen;
6916
6917 if (!sscanf(input, "%lld.%n%lld%n", &whole, &fstart, &frac, &fend))
6918 return -EINVAL;
6919 if (frac < 0)
6920 return -EINVAL;
6921
6922 flen = fend > fstart ? fend - fstart : 0;
6923 if (flen < dec_shift)
6924 frac *= power_of_ten(dec_shift - flen);
6925 else
6926 frac = DIV_ROUND_CLOSEST_ULL(frac, power_of_ten(flen - dec_shift));
6927
6928 *v = whole * power_of_ten(dec_shift) + frac;
6929 return 0;
6930}
6931
6932/*
6933 * sock->sk_cgrp_data handling. For more info, see sock_cgroup_data
6934 * definition in cgroup-defs.h.
6935 */
6936#ifdef CONFIG_SOCK_CGROUP_DATA
6937
6938void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
6939{
6940 struct cgroup *cgroup;
6941
6942 rcu_read_lock();
6943 /* Don't associate the sock with unrelated interrupted task's cgroup. */
6944 if (in_interrupt()) {
6945 cgroup = &cgrp_dfl_root.cgrp;
6946 cgroup_get(cgroup);
6947 goto out;
6948 }
6949
6950 while (true) {
6951 struct css_set *cset;
6952
6953 cset = task_css_set(current);
6954 if (likely(cgroup_tryget(cset->dfl_cgrp))) {
6955 cgroup = cset->dfl_cgrp;
6956 break;
6957 }
6958 cpu_relax();
6959 }
6960out:
6961 skcd->cgroup = cgroup;
6962 cgroup_bpf_get(cgroup);
6963 rcu_read_unlock();
6964}
6965
6966void cgroup_sk_clone(struct sock_cgroup_data *skcd)
6967{
6968 struct cgroup *cgrp = sock_cgroup_ptr(skcd);
6969
6970 /*
6971 * We might be cloning a socket which is left in an empty
6972 * cgroup and the cgroup might have already been rmdir'd.
6973 * Don't use cgroup_get_live().
6974 */
6975 cgroup_get(cgrp);
6976 cgroup_bpf_get(cgrp);
6977}
6978
6979void cgroup_sk_free(struct sock_cgroup_data *skcd)
6980{
6981 struct cgroup *cgrp = sock_cgroup_ptr(skcd);
6982
6983 cgroup_bpf_put(cgrp);
6984 cgroup_put(cgrp);
6985}
6986
6987#endif /* CONFIG_SOCK_CGROUP_DATA */
6988
6989#ifdef CONFIG_SYSFS
6990static ssize_t show_delegatable_files(struct cftype *files, char *buf,
6991 ssize_t size, const char *prefix)
6992{
6993 struct cftype *cft;
6994 ssize_t ret = 0;
6995
6996 for (cft = files; cft && cft->name[0] != '\0'; cft++) {
6997 if (!(cft->flags & CFTYPE_NS_DELEGATABLE))
6998 continue;
6999
7000 if (prefix)
7001 ret += snprintf(buf + ret, size - ret, "%s.", prefix);
7002
7003 ret += snprintf(buf + ret, size - ret, "%s\n", cft->name);
7004
7005 if (WARN_ON(ret >= size))
7006 break;
7007 }
7008
7009 return ret;
7010}
7011
7012static ssize_t delegate_show(struct kobject *kobj, struct kobj_attribute *attr,
7013 char *buf)
7014{
7015 struct cgroup_subsys *ss;
7016 int ssid;
7017 ssize_t ret = 0;
7018
7019 ret = show_delegatable_files(cgroup_base_files, buf + ret,
7020 PAGE_SIZE - ret, NULL);
7021 if (cgroup_psi_enabled())
7022 ret += show_delegatable_files(cgroup_psi_files, buf + ret,
7023 PAGE_SIZE - ret, NULL);
7024
7025 for_each_subsys(ss, ssid)
7026 ret += show_delegatable_files(ss->dfl_cftypes, buf + ret,
7027 PAGE_SIZE - ret,
7028 cgroup_subsys_name[ssid]);
7029
7030 return ret;
7031}
7032static struct kobj_attribute cgroup_delegate_attr = __ATTR_RO(delegate);
7033
7034static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr,
7035 char *buf)
7036{
7037 return snprintf(buf, PAGE_SIZE,
7038 "nsdelegate\n"
7039 "favordynmods\n"
7040 "memory_localevents\n"
7041 "memory_recursiveprot\n");
7042}
7043static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features);
7044
7045static struct attribute *cgroup_sysfs_attrs[] = {
7046 &cgroup_delegate_attr.attr,
7047 &cgroup_features_attr.attr,
7048 NULL,
7049};
7050
7051static const struct attribute_group cgroup_sysfs_attr_group = {
7052 .attrs = cgroup_sysfs_attrs,
7053 .name = "cgroup",
7054};
7055
7056static int __init cgroup_sysfs_init(void)
7057{
7058 return sysfs_create_group(kernel_kobj, &cgroup_sysfs_attr_group);
7059}
7060subsys_initcall(cgroup_sysfs_init);
7061
7062#endif /* CONFIG_SYSFS */