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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 */
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/sched/deadline.h>
61#include <linux/psi.h>
62#include <net/sock.h>
63
64#define CREATE_TRACE_POINTS
65#include <trace/events/cgroup.h>
66
67#define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
68 MAX_CFTYPE_NAME + 2)
69/* let's not notify more than 100 times per second */
70#define CGROUP_FILE_NOTIFY_MIN_INTV DIV_ROUND_UP(HZ, 100)
71
72/*
73 * To avoid confusing the compiler (and generating warnings) with code
74 * that attempts to access what would be a 0-element array (i.e. sized
75 * to a potentially empty array when CGROUP_SUBSYS_COUNT == 0), this
76 * constant expression can be added.
77 */
78#define CGROUP_HAS_SUBSYS_CONFIG (CGROUP_SUBSYS_COUNT > 0)
79
80/*
81 * cgroup_mutex is the master lock. Any modification to cgroup or its
82 * hierarchy must be performed while holding it.
83 *
84 * css_set_lock protects task->cgroups pointer, the list of css_set
85 * objects, and the chain of tasks off each css_set.
86 *
87 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
88 * cgroup.h can use them for lockdep annotations.
89 */
90DEFINE_MUTEX(cgroup_mutex);
91DEFINE_SPINLOCK(css_set_lock);
92
93#ifdef CONFIG_PROVE_RCU
94EXPORT_SYMBOL_GPL(cgroup_mutex);
95EXPORT_SYMBOL_GPL(css_set_lock);
96#endif
97
98DEFINE_SPINLOCK(trace_cgroup_path_lock);
99char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
100static bool cgroup_debug __read_mostly;
101
102/*
103 * Protects cgroup_idr and css_idr so that IDs can be released without
104 * grabbing cgroup_mutex.
105 */
106static DEFINE_SPINLOCK(cgroup_idr_lock);
107
108/*
109 * Protects cgroup_file->kn for !self csses. It synchronizes notifications
110 * against file removal/re-creation across css hiding.
111 */
112static DEFINE_SPINLOCK(cgroup_file_kn_lock);
113
114DEFINE_PERCPU_RWSEM(cgroup_threadgroup_rwsem);
115
116#define cgroup_assert_mutex_or_rcu_locked() \
117 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
118 !lockdep_is_held(&cgroup_mutex), \
119 "cgroup_mutex or RCU read lock required");
120
121/*
122 * cgroup destruction makes heavy use of work items and there can be a lot
123 * of concurrent destructions. Use a separate workqueue so that cgroup
124 * destruction work items don't end up filling up max_active of system_wq
125 * which may lead to deadlock.
126 */
127static struct workqueue_struct *cgroup_destroy_wq;
128
129/* generate an array of cgroup subsystem pointers */
130#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
131struct cgroup_subsys *cgroup_subsys[] = {
132#include <linux/cgroup_subsys.h>
133};
134#undef SUBSYS
135
136/* array of cgroup subsystem names */
137#define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
138static const char *cgroup_subsys_name[] = {
139#include <linux/cgroup_subsys.h>
140};
141#undef SUBSYS
142
143/* array of static_keys for cgroup_subsys_enabled() and cgroup_subsys_on_dfl() */
144#define SUBSYS(_x) \
145 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key); \
146 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key); \
147 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key); \
148 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key);
149#include <linux/cgroup_subsys.h>
150#undef SUBSYS
151
152#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_enabled_key,
153static struct static_key_true *cgroup_subsys_enabled_key[] = {
154#include <linux/cgroup_subsys.h>
155};
156#undef SUBSYS
157
158#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_on_dfl_key,
159static struct static_key_true *cgroup_subsys_on_dfl_key[] = {
160#include <linux/cgroup_subsys.h>
161};
162#undef SUBSYS
163
164static DEFINE_PER_CPU(struct cgroup_rstat_cpu, cgrp_dfl_root_rstat_cpu);
165
166/* the default hierarchy */
167struct cgroup_root cgrp_dfl_root = { .cgrp.rstat_cpu = &cgrp_dfl_root_rstat_cpu };
168EXPORT_SYMBOL_GPL(cgrp_dfl_root);
169
170/*
171 * The default hierarchy always exists but is hidden until mounted for the
172 * first time. This is for backward compatibility.
173 */
174static bool cgrp_dfl_visible;
175
176/* some controllers are not supported in the default hierarchy */
177static u16 cgrp_dfl_inhibit_ss_mask;
178
179/* some controllers are implicitly enabled on the default hierarchy */
180static u16 cgrp_dfl_implicit_ss_mask;
181
182/* some controllers can be threaded on the default hierarchy */
183static u16 cgrp_dfl_threaded_ss_mask;
184
185/* The list of hierarchy roots */
186LIST_HEAD(cgroup_roots);
187static int cgroup_root_count;
188
189/* hierarchy ID allocation and mapping, protected by cgroup_mutex */
190static DEFINE_IDR(cgroup_hierarchy_idr);
191
192/*
193 * Assign a monotonically increasing serial number to csses. It guarantees
194 * cgroups with bigger numbers are newer than those with smaller numbers.
195 * Also, as csses are always appended to the parent's ->children list, it
196 * guarantees that sibling csses are always sorted in the ascending serial
197 * number order on the list. Protected by cgroup_mutex.
198 */
199static u64 css_serial_nr_next = 1;
200
201/*
202 * These bitmasks identify subsystems with specific features to avoid
203 * having to do iterative checks repeatedly.
204 */
205static u16 have_fork_callback __read_mostly;
206static u16 have_exit_callback __read_mostly;
207static u16 have_release_callback __read_mostly;
208static u16 have_canfork_callback __read_mostly;
209
210static bool have_favordynmods __ro_after_init = IS_ENABLED(CONFIG_CGROUP_FAVOR_DYNMODS);
211
212/* cgroup namespace for init task */
213struct cgroup_namespace init_cgroup_ns = {
214 .ns.count = REFCOUNT_INIT(2),
215 .user_ns = &init_user_ns,
216 .ns.ops = &cgroupns_operations,
217 .ns.inum = PROC_CGROUP_INIT_INO,
218 .root_cset = &init_css_set,
219};
220
221static struct file_system_type cgroup2_fs_type;
222static struct cftype cgroup_base_files[];
223static struct cftype cgroup_psi_files[];
224
225/* cgroup optional features */
226enum cgroup_opt_features {
227#ifdef CONFIG_PSI
228 OPT_FEATURE_PRESSURE,
229#endif
230 OPT_FEATURE_COUNT
231};
232
233static const char *cgroup_opt_feature_names[OPT_FEATURE_COUNT] = {
234#ifdef CONFIG_PSI
235 "pressure",
236#endif
237};
238
239static u16 cgroup_feature_disable_mask __read_mostly;
240
241static int cgroup_apply_control(struct cgroup *cgrp);
242static void cgroup_finalize_control(struct cgroup *cgrp, int ret);
243static void css_task_iter_skip(struct css_task_iter *it,
244 struct task_struct *task);
245static int cgroup_destroy_locked(struct cgroup *cgrp);
246static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
247 struct cgroup_subsys *ss);
248static void css_release(struct percpu_ref *ref);
249static void kill_css(struct cgroup_subsys_state *css);
250static int cgroup_addrm_files(struct cgroup_subsys_state *css,
251 struct cgroup *cgrp, struct cftype cfts[],
252 bool is_add);
253
254#ifdef CONFIG_DEBUG_CGROUP_REF
255#define CGROUP_REF_FN_ATTRS noinline
256#define CGROUP_REF_EXPORT(fn) EXPORT_SYMBOL_GPL(fn);
257#include <linux/cgroup_refcnt.h>
258#endif
259
260/**
261 * cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID
262 * @ssid: subsys ID of interest
263 *
264 * cgroup_subsys_enabled() can only be used with literal subsys names which
265 * is fine for individual subsystems but unsuitable for cgroup core. This
266 * is slower static_key_enabled() based test indexed by @ssid.
267 */
268bool cgroup_ssid_enabled(int ssid)
269{
270 if (!CGROUP_HAS_SUBSYS_CONFIG)
271 return false;
272
273 return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
274}
275
276/**
277 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
278 * @cgrp: the cgroup of interest
279 *
280 * The default hierarchy is the v2 interface of cgroup and this function
281 * can be used to test whether a cgroup is on the default hierarchy for
282 * cases where a subsystem should behave differently depending on the
283 * interface version.
284 *
285 * List of changed behaviors:
286 *
287 * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
288 * and "name" are disallowed.
289 *
290 * - When mounting an existing superblock, mount options should match.
291 *
292 * - rename(2) is disallowed.
293 *
294 * - "tasks" is removed. Everything should be at process granularity. Use
295 * "cgroup.procs" instead.
296 *
297 * - "cgroup.procs" is not sorted. pids will be unique unless they got
298 * recycled in-between reads.
299 *
300 * - "release_agent" and "notify_on_release" are removed. Replacement
301 * notification mechanism will be implemented.
302 *
303 * - "cgroup.clone_children" is removed.
304 *
305 * - "cgroup.subtree_populated" is available. Its value is 0 if the cgroup
306 * and its descendants contain no task; otherwise, 1. The file also
307 * generates kernfs notification which can be monitored through poll and
308 * [di]notify when the value of the file changes.
309 *
310 * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
311 * take masks of ancestors with non-empty cpus/mems, instead of being
312 * moved to an ancestor.
313 *
314 * - cpuset: a task can be moved into an empty cpuset, and again it takes
315 * masks of ancestors.
316 *
317 * - blkcg: blk-throttle becomes properly hierarchical.
318 */
319bool cgroup_on_dfl(const struct cgroup *cgrp)
320{
321 return cgrp->root == &cgrp_dfl_root;
322}
323
324/* IDR wrappers which synchronize using cgroup_idr_lock */
325static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
326 gfp_t gfp_mask)
327{
328 int ret;
329
330 idr_preload(gfp_mask);
331 spin_lock_bh(&cgroup_idr_lock);
332 ret = idr_alloc(idr, ptr, start, end, gfp_mask & ~__GFP_DIRECT_RECLAIM);
333 spin_unlock_bh(&cgroup_idr_lock);
334 idr_preload_end();
335 return ret;
336}
337
338static void *cgroup_idr_replace(struct idr *idr, void *ptr, int id)
339{
340 void *ret;
341
342 spin_lock_bh(&cgroup_idr_lock);
343 ret = idr_replace(idr, ptr, id);
344 spin_unlock_bh(&cgroup_idr_lock);
345 return ret;
346}
347
348static void cgroup_idr_remove(struct idr *idr, int id)
349{
350 spin_lock_bh(&cgroup_idr_lock);
351 idr_remove(idr, id);
352 spin_unlock_bh(&cgroup_idr_lock);
353}
354
355static bool cgroup_has_tasks(struct cgroup *cgrp)
356{
357 return cgrp->nr_populated_csets;
358}
359
360static bool cgroup_is_threaded(struct cgroup *cgrp)
361{
362 return cgrp->dom_cgrp != cgrp;
363}
364
365/* can @cgrp host both domain and threaded children? */
366static bool cgroup_is_mixable(struct cgroup *cgrp)
367{
368 /*
369 * Root isn't under domain level resource control exempting it from
370 * the no-internal-process constraint, so it can serve as a thread
371 * root and a parent of resource domains at the same time.
372 */
373 return !cgroup_parent(cgrp);
374}
375
376/* can @cgrp become a thread root? Should always be true for a thread root */
377static bool cgroup_can_be_thread_root(struct cgroup *cgrp)
378{
379 /* mixables don't care */
380 if (cgroup_is_mixable(cgrp))
381 return true;
382
383 /* domain roots can't be nested under threaded */
384 if (cgroup_is_threaded(cgrp))
385 return false;
386
387 /* can only have either domain or threaded children */
388 if (cgrp->nr_populated_domain_children)
389 return false;
390
391 /* and no domain controllers can be enabled */
392 if (cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)
393 return false;
394
395 return true;
396}
397
398/* is @cgrp root of a threaded subtree? */
399static bool cgroup_is_thread_root(struct cgroup *cgrp)
400{
401 /* thread root should be a domain */
402 if (cgroup_is_threaded(cgrp))
403 return false;
404
405 /* a domain w/ threaded children is a thread root */
406 if (cgrp->nr_threaded_children)
407 return true;
408
409 /*
410 * A domain which has tasks and explicit threaded controllers
411 * enabled is a thread root.
412 */
413 if (cgroup_has_tasks(cgrp) &&
414 (cgrp->subtree_control & cgrp_dfl_threaded_ss_mask))
415 return true;
416
417 return false;
418}
419
420/* a domain which isn't connected to the root w/o brekage can't be used */
421static bool cgroup_is_valid_domain(struct cgroup *cgrp)
422{
423 /* the cgroup itself can be a thread root */
424 if (cgroup_is_threaded(cgrp))
425 return false;
426
427 /* but the ancestors can't be unless mixable */
428 while ((cgrp = cgroup_parent(cgrp))) {
429 if (!cgroup_is_mixable(cgrp) && cgroup_is_thread_root(cgrp))
430 return false;
431 if (cgroup_is_threaded(cgrp))
432 return false;
433 }
434
435 return true;
436}
437
438/* subsystems visibly enabled on a cgroup */
439static u16 cgroup_control(struct cgroup *cgrp)
440{
441 struct cgroup *parent = cgroup_parent(cgrp);
442 u16 root_ss_mask = cgrp->root->subsys_mask;
443
444 if (parent) {
445 u16 ss_mask = parent->subtree_control;
446
447 /* threaded cgroups can only have threaded controllers */
448 if (cgroup_is_threaded(cgrp))
449 ss_mask &= cgrp_dfl_threaded_ss_mask;
450 return ss_mask;
451 }
452
453 if (cgroup_on_dfl(cgrp))
454 root_ss_mask &= ~(cgrp_dfl_inhibit_ss_mask |
455 cgrp_dfl_implicit_ss_mask);
456 return root_ss_mask;
457}
458
459/* subsystems enabled on a cgroup */
460static u16 cgroup_ss_mask(struct cgroup *cgrp)
461{
462 struct cgroup *parent = cgroup_parent(cgrp);
463
464 if (parent) {
465 u16 ss_mask = parent->subtree_ss_mask;
466
467 /* threaded cgroups can only have threaded controllers */
468 if (cgroup_is_threaded(cgrp))
469 ss_mask &= cgrp_dfl_threaded_ss_mask;
470 return ss_mask;
471 }
472
473 return cgrp->root->subsys_mask;
474}
475
476/**
477 * cgroup_css - obtain a cgroup's css for the specified subsystem
478 * @cgrp: the cgroup of interest
479 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
480 *
481 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
482 * function must be called either under cgroup_mutex or rcu_read_lock() and
483 * the caller is responsible for pinning the returned css if it wants to
484 * keep accessing it outside the said locks. This function may return
485 * %NULL if @cgrp doesn't have @subsys_id enabled.
486 */
487static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
488 struct cgroup_subsys *ss)
489{
490 if (CGROUP_HAS_SUBSYS_CONFIG && ss)
491 return rcu_dereference_check(cgrp->subsys[ss->id],
492 lockdep_is_held(&cgroup_mutex));
493 else
494 return &cgrp->self;
495}
496
497/**
498 * cgroup_e_css_by_mask - obtain a cgroup's effective css for the specified ss
499 * @cgrp: the cgroup of interest
500 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
501 *
502 * Similar to cgroup_css() but returns the effective css, which is defined
503 * as the matching css of the nearest ancestor including self which has @ss
504 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
505 * function is guaranteed to return non-NULL css.
506 */
507static struct cgroup_subsys_state *cgroup_e_css_by_mask(struct cgroup *cgrp,
508 struct cgroup_subsys *ss)
509{
510 lockdep_assert_held(&cgroup_mutex);
511
512 if (!ss)
513 return &cgrp->self;
514
515 /*
516 * This function is used while updating css associations and thus
517 * can't test the csses directly. Test ss_mask.
518 */
519 while (!(cgroup_ss_mask(cgrp) & (1 << ss->id))) {
520 cgrp = cgroup_parent(cgrp);
521 if (!cgrp)
522 return NULL;
523 }
524
525 return cgroup_css(cgrp, ss);
526}
527
528/**
529 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
530 * @cgrp: the cgroup of interest
531 * @ss: the subsystem of interest
532 *
533 * Find and get the effective css of @cgrp for @ss. The effective css is
534 * defined as the matching css of the nearest ancestor including self which
535 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
536 * the root css is returned, so this function always returns a valid css.
537 *
538 * The returned css is not guaranteed to be online, and therefore it is the
539 * callers responsibility to try get a reference for it.
540 */
541struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
542 struct cgroup_subsys *ss)
543{
544 struct cgroup_subsys_state *css;
545
546 if (!CGROUP_HAS_SUBSYS_CONFIG)
547 return NULL;
548
549 do {
550 css = cgroup_css(cgrp, ss);
551
552 if (css)
553 return css;
554 cgrp = cgroup_parent(cgrp);
555 } while (cgrp);
556
557 return init_css_set.subsys[ss->id];
558}
559
560/**
561 * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
562 * @cgrp: the cgroup of interest
563 * @ss: the subsystem of interest
564 *
565 * Find and get the effective css of @cgrp for @ss. The effective css is
566 * defined as the matching css of the nearest ancestor including self which
567 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
568 * the root css is returned, so this function always returns a valid css.
569 * The returned css must be put using css_put().
570 */
571struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
572 struct cgroup_subsys *ss)
573{
574 struct cgroup_subsys_state *css;
575
576 if (!CGROUP_HAS_SUBSYS_CONFIG)
577 return NULL;
578
579 rcu_read_lock();
580
581 do {
582 css = cgroup_css(cgrp, ss);
583
584 if (css && css_tryget_online(css))
585 goto out_unlock;
586 cgrp = cgroup_parent(cgrp);
587 } while (cgrp);
588
589 css = init_css_set.subsys[ss->id];
590 css_get(css);
591out_unlock:
592 rcu_read_unlock();
593 return css;
594}
595EXPORT_SYMBOL_GPL(cgroup_get_e_css);
596
597static void cgroup_get_live(struct cgroup *cgrp)
598{
599 WARN_ON_ONCE(cgroup_is_dead(cgrp));
600 cgroup_get(cgrp);
601}
602
603/**
604 * __cgroup_task_count - count the number of tasks in a cgroup. The caller
605 * is responsible for taking the css_set_lock.
606 * @cgrp: the cgroup in question
607 */
608int __cgroup_task_count(const struct cgroup *cgrp)
609{
610 int count = 0;
611 struct cgrp_cset_link *link;
612
613 lockdep_assert_held(&css_set_lock);
614
615 list_for_each_entry(link, &cgrp->cset_links, cset_link)
616 count += link->cset->nr_tasks;
617
618 return count;
619}
620
621/**
622 * cgroup_task_count - count the number of tasks in a cgroup.
623 * @cgrp: the cgroup in question
624 */
625int cgroup_task_count(const struct cgroup *cgrp)
626{
627 int count;
628
629 spin_lock_irq(&css_set_lock);
630 count = __cgroup_task_count(cgrp);
631 spin_unlock_irq(&css_set_lock);
632
633 return count;
634}
635
636struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
637{
638 struct cgroup *cgrp = of->kn->parent->priv;
639 struct cftype *cft = of_cft(of);
640
641 /*
642 * This is open and unprotected implementation of cgroup_css().
643 * seq_css() is only called from a kernfs file operation which has
644 * an active reference on the file. Because all the subsystem
645 * files are drained before a css is disassociated with a cgroup,
646 * the matching css from the cgroup's subsys table is guaranteed to
647 * be and stay valid until the enclosing operation is complete.
648 */
649 if (CGROUP_HAS_SUBSYS_CONFIG && cft->ss)
650 return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
651 else
652 return &cgrp->self;
653}
654EXPORT_SYMBOL_GPL(of_css);
655
656/**
657 * for_each_css - iterate all css's of a cgroup
658 * @css: the iteration cursor
659 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
660 * @cgrp: the target cgroup to iterate css's of
661 *
662 * Should be called under cgroup_mutex.
663 */
664#define for_each_css(css, ssid, cgrp) \
665 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
666 if (!((css) = rcu_dereference_check( \
667 (cgrp)->subsys[(ssid)], \
668 lockdep_is_held(&cgroup_mutex)))) { } \
669 else
670
671/**
672 * do_each_subsys_mask - filter for_each_subsys with a bitmask
673 * @ss: the iteration cursor
674 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
675 * @ss_mask: the bitmask
676 *
677 * The block will only run for cases where the ssid-th bit (1 << ssid) of
678 * @ss_mask is set.
679 */
680#define do_each_subsys_mask(ss, ssid, ss_mask) do { \
681 unsigned long __ss_mask = (ss_mask); \
682 if (!CGROUP_HAS_SUBSYS_CONFIG) { \
683 (ssid) = 0; \
684 break; \
685 } \
686 for_each_set_bit(ssid, &__ss_mask, CGROUP_SUBSYS_COUNT) { \
687 (ss) = cgroup_subsys[ssid]; \
688 {
689
690#define while_each_subsys_mask() \
691 } \
692 } \
693} while (false)
694
695/* iterate over child cgrps, lock should be held throughout iteration */
696#define cgroup_for_each_live_child(child, cgrp) \
697 list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
698 if (({ lockdep_assert_held(&cgroup_mutex); \
699 cgroup_is_dead(child); })) \
700 ; \
701 else
702
703/* walk live descendants in pre order */
704#define cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) \
705 css_for_each_descendant_pre((d_css), cgroup_css((cgrp), NULL)) \
706 if (({ lockdep_assert_held(&cgroup_mutex); \
707 (dsct) = (d_css)->cgroup; \
708 cgroup_is_dead(dsct); })) \
709 ; \
710 else
711
712/* walk live descendants in postorder */
713#define cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) \
714 css_for_each_descendant_post((d_css), cgroup_css((cgrp), NULL)) \
715 if (({ lockdep_assert_held(&cgroup_mutex); \
716 (dsct) = (d_css)->cgroup; \
717 cgroup_is_dead(dsct); })) \
718 ; \
719 else
720
721/*
722 * The default css_set - used by init and its children prior to any
723 * hierarchies being mounted. It contains a pointer to the root state
724 * for each subsystem. Also used to anchor the list of css_sets. Not
725 * reference-counted, to improve performance when child cgroups
726 * haven't been created.
727 */
728struct css_set init_css_set = {
729 .refcount = REFCOUNT_INIT(1),
730 .dom_cset = &init_css_set,
731 .tasks = LIST_HEAD_INIT(init_css_set.tasks),
732 .mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
733 .dying_tasks = LIST_HEAD_INIT(init_css_set.dying_tasks),
734 .task_iters = LIST_HEAD_INIT(init_css_set.task_iters),
735 .threaded_csets = LIST_HEAD_INIT(init_css_set.threaded_csets),
736 .cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
737 .mg_src_preload_node = LIST_HEAD_INIT(init_css_set.mg_src_preload_node),
738 .mg_dst_preload_node = LIST_HEAD_INIT(init_css_set.mg_dst_preload_node),
739 .mg_node = LIST_HEAD_INIT(init_css_set.mg_node),
740
741 /*
742 * The following field is re-initialized when this cset gets linked
743 * in cgroup_init(). However, let's initialize the field
744 * statically too so that the default cgroup can be accessed safely
745 * early during boot.
746 */
747 .dfl_cgrp = &cgrp_dfl_root.cgrp,
748};
749
750static int css_set_count = 1; /* 1 for init_css_set */
751
752static bool css_set_threaded(struct css_set *cset)
753{
754 return cset->dom_cset != cset;
755}
756
757/**
758 * css_set_populated - does a css_set contain any tasks?
759 * @cset: target css_set
760 *
761 * css_set_populated() should be the same as !!cset->nr_tasks at steady
762 * state. However, css_set_populated() can be called while a task is being
763 * added to or removed from the linked list before the nr_tasks is
764 * properly updated. Hence, we can't just look at ->nr_tasks here.
765 */
766static bool css_set_populated(struct css_set *cset)
767{
768 lockdep_assert_held(&css_set_lock);
769
770 return !list_empty(&cset->tasks) || !list_empty(&cset->mg_tasks);
771}
772
773/**
774 * cgroup_update_populated - update the populated count of a cgroup
775 * @cgrp: the target cgroup
776 * @populated: inc or dec populated count
777 *
778 * One of the css_sets associated with @cgrp is either getting its first
779 * task or losing the last. Update @cgrp->nr_populated_* accordingly. The
780 * count is propagated towards root so that a given cgroup's
781 * nr_populated_children is zero iff none of its descendants contain any
782 * tasks.
783 *
784 * @cgrp's interface file "cgroup.populated" is zero if both
785 * @cgrp->nr_populated_csets and @cgrp->nr_populated_children are zero and
786 * 1 otherwise. When the sum changes from or to zero, userland is notified
787 * that the content of the interface file has changed. This can be used to
788 * detect when @cgrp and its descendants become populated or empty.
789 */
790static void cgroup_update_populated(struct cgroup *cgrp, bool populated)
791{
792 struct cgroup *child = NULL;
793 int adj = populated ? 1 : -1;
794
795 lockdep_assert_held(&css_set_lock);
796
797 do {
798 bool was_populated = cgroup_is_populated(cgrp);
799
800 if (!child) {
801 cgrp->nr_populated_csets += adj;
802 } else {
803 if (cgroup_is_threaded(child))
804 cgrp->nr_populated_threaded_children += adj;
805 else
806 cgrp->nr_populated_domain_children += adj;
807 }
808
809 if (was_populated == cgroup_is_populated(cgrp))
810 break;
811
812 cgroup1_check_for_release(cgrp);
813 TRACE_CGROUP_PATH(notify_populated, cgrp,
814 cgroup_is_populated(cgrp));
815 cgroup_file_notify(&cgrp->events_file);
816
817 child = cgrp;
818 cgrp = cgroup_parent(cgrp);
819 } while (cgrp);
820}
821
822/**
823 * css_set_update_populated - update populated state of a css_set
824 * @cset: target css_set
825 * @populated: whether @cset is populated or depopulated
826 *
827 * @cset is either getting the first task or losing the last. Update the
828 * populated counters of all associated cgroups accordingly.
829 */
830static void css_set_update_populated(struct css_set *cset, bool populated)
831{
832 struct cgrp_cset_link *link;
833
834 lockdep_assert_held(&css_set_lock);
835
836 list_for_each_entry(link, &cset->cgrp_links, cgrp_link)
837 cgroup_update_populated(link->cgrp, populated);
838}
839
840/*
841 * @task is leaving, advance task iterators which are pointing to it so
842 * that they can resume at the next position. Advancing an iterator might
843 * remove it from the list, use safe walk. See css_task_iter_skip() for
844 * details.
845 */
846static void css_set_skip_task_iters(struct css_set *cset,
847 struct task_struct *task)
848{
849 struct css_task_iter *it, *pos;
850
851 list_for_each_entry_safe(it, pos, &cset->task_iters, iters_node)
852 css_task_iter_skip(it, task);
853}
854
855/**
856 * css_set_move_task - move a task from one css_set to another
857 * @task: task being moved
858 * @from_cset: css_set @task currently belongs to (may be NULL)
859 * @to_cset: new css_set @task is being moved to (may be NULL)
860 * @use_mg_tasks: move to @to_cset->mg_tasks instead of ->tasks
861 *
862 * Move @task from @from_cset to @to_cset. If @task didn't belong to any
863 * css_set, @from_cset can be NULL. If @task is being disassociated
864 * instead of moved, @to_cset can be NULL.
865 *
866 * This function automatically handles populated counter updates and
867 * css_task_iter adjustments but the caller is responsible for managing
868 * @from_cset and @to_cset's reference counts.
869 */
870static void css_set_move_task(struct task_struct *task,
871 struct css_set *from_cset, struct css_set *to_cset,
872 bool use_mg_tasks)
873{
874 lockdep_assert_held(&css_set_lock);
875
876 if (to_cset && !css_set_populated(to_cset))
877 css_set_update_populated(to_cset, true);
878
879 if (from_cset) {
880 WARN_ON_ONCE(list_empty(&task->cg_list));
881
882 css_set_skip_task_iters(from_cset, task);
883 list_del_init(&task->cg_list);
884 if (!css_set_populated(from_cset))
885 css_set_update_populated(from_cset, false);
886 } else {
887 WARN_ON_ONCE(!list_empty(&task->cg_list));
888 }
889
890 if (to_cset) {
891 /*
892 * We are synchronized through cgroup_threadgroup_rwsem
893 * against PF_EXITING setting such that we can't race
894 * against cgroup_exit()/cgroup_free() dropping the css_set.
895 */
896 WARN_ON_ONCE(task->flags & PF_EXITING);
897
898 cgroup_move_task(task, to_cset);
899 list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks :
900 &to_cset->tasks);
901 }
902}
903
904/*
905 * hash table for cgroup groups. This improves the performance to find
906 * an existing css_set. This hash doesn't (currently) take into
907 * account cgroups in empty hierarchies.
908 */
909#define CSS_SET_HASH_BITS 7
910static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
911
912static unsigned long css_set_hash(struct cgroup_subsys_state **css)
913{
914 unsigned long key = 0UL;
915 struct cgroup_subsys *ss;
916 int i;
917
918 for_each_subsys(ss, i)
919 key += (unsigned long)css[i];
920 key = (key >> 16) ^ key;
921
922 return key;
923}
924
925void put_css_set_locked(struct css_set *cset)
926{
927 struct cgrp_cset_link *link, *tmp_link;
928 struct cgroup_subsys *ss;
929 int ssid;
930
931 lockdep_assert_held(&css_set_lock);
932
933 if (!refcount_dec_and_test(&cset->refcount))
934 return;
935
936 WARN_ON_ONCE(!list_empty(&cset->threaded_csets));
937
938 /* This css_set is dead. Unlink it and release cgroup and css refs */
939 for_each_subsys(ss, ssid) {
940 list_del(&cset->e_cset_node[ssid]);
941 css_put(cset->subsys[ssid]);
942 }
943 hash_del(&cset->hlist);
944 css_set_count--;
945
946 list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
947 list_del(&link->cset_link);
948 list_del(&link->cgrp_link);
949 if (cgroup_parent(link->cgrp))
950 cgroup_put(link->cgrp);
951 kfree(link);
952 }
953
954 if (css_set_threaded(cset)) {
955 list_del(&cset->threaded_csets_node);
956 put_css_set_locked(cset->dom_cset);
957 }
958
959 kfree_rcu(cset, rcu_head);
960}
961
962/**
963 * compare_css_sets - helper function for find_existing_css_set().
964 * @cset: candidate css_set being tested
965 * @old_cset: existing css_set for a task
966 * @new_cgrp: cgroup that's being entered by the task
967 * @template: desired set of css pointers in css_set (pre-calculated)
968 *
969 * Returns true if "cset" matches "old_cset" except for the hierarchy
970 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
971 */
972static bool compare_css_sets(struct css_set *cset,
973 struct css_set *old_cset,
974 struct cgroup *new_cgrp,
975 struct cgroup_subsys_state *template[])
976{
977 struct cgroup *new_dfl_cgrp;
978 struct list_head *l1, *l2;
979
980 /*
981 * On the default hierarchy, there can be csets which are
982 * associated with the same set of cgroups but different csses.
983 * Let's first ensure that csses match.
984 */
985 if (memcmp(template, cset->subsys, sizeof(cset->subsys)))
986 return false;
987
988
989 /* @cset's domain should match the default cgroup's */
990 if (cgroup_on_dfl(new_cgrp))
991 new_dfl_cgrp = new_cgrp;
992 else
993 new_dfl_cgrp = old_cset->dfl_cgrp;
994
995 if (new_dfl_cgrp->dom_cgrp != cset->dom_cset->dfl_cgrp)
996 return false;
997
998 /*
999 * Compare cgroup pointers in order to distinguish between
1000 * different cgroups in hierarchies. As different cgroups may
1001 * share the same effective css, this comparison is always
1002 * necessary.
1003 */
1004 l1 = &cset->cgrp_links;
1005 l2 = &old_cset->cgrp_links;
1006 while (1) {
1007 struct cgrp_cset_link *link1, *link2;
1008 struct cgroup *cgrp1, *cgrp2;
1009
1010 l1 = l1->next;
1011 l2 = l2->next;
1012 /* See if we reached the end - both lists are equal length. */
1013 if (l1 == &cset->cgrp_links) {
1014 BUG_ON(l2 != &old_cset->cgrp_links);
1015 break;
1016 } else {
1017 BUG_ON(l2 == &old_cset->cgrp_links);
1018 }
1019 /* Locate the cgroups associated with these links. */
1020 link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
1021 link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
1022 cgrp1 = link1->cgrp;
1023 cgrp2 = link2->cgrp;
1024 /* Hierarchies should be linked in the same order. */
1025 BUG_ON(cgrp1->root != cgrp2->root);
1026
1027 /*
1028 * If this hierarchy is the hierarchy of the cgroup
1029 * that's changing, then we need to check that this
1030 * css_set points to the new cgroup; if it's any other
1031 * hierarchy, then this css_set should point to the
1032 * same cgroup as the old css_set.
1033 */
1034 if (cgrp1->root == new_cgrp->root) {
1035 if (cgrp1 != new_cgrp)
1036 return false;
1037 } else {
1038 if (cgrp1 != cgrp2)
1039 return false;
1040 }
1041 }
1042 return true;
1043}
1044
1045/**
1046 * find_existing_css_set - init css array and find the matching css_set
1047 * @old_cset: the css_set that we're using before the cgroup transition
1048 * @cgrp: the cgroup that we're moving into
1049 * @template: out param for the new set of csses, should be clear on entry
1050 */
1051static struct css_set *find_existing_css_set(struct css_set *old_cset,
1052 struct cgroup *cgrp,
1053 struct cgroup_subsys_state **template)
1054{
1055 struct cgroup_root *root = cgrp->root;
1056 struct cgroup_subsys *ss;
1057 struct css_set *cset;
1058 unsigned long key;
1059 int i;
1060
1061 /*
1062 * Build the set of subsystem state objects that we want to see in the
1063 * new css_set. While subsystems can change globally, the entries here
1064 * won't change, so no need for locking.
1065 */
1066 for_each_subsys(ss, i) {
1067 if (root->subsys_mask & (1UL << i)) {
1068 /*
1069 * @ss is in this hierarchy, so we want the
1070 * effective css from @cgrp.
1071 */
1072 template[i] = cgroup_e_css_by_mask(cgrp, ss);
1073 } else {
1074 /*
1075 * @ss is not in this hierarchy, so we don't want
1076 * to change the css.
1077 */
1078 template[i] = old_cset->subsys[i];
1079 }
1080 }
1081
1082 key = css_set_hash(template);
1083 hash_for_each_possible(css_set_table, cset, hlist, key) {
1084 if (!compare_css_sets(cset, old_cset, cgrp, template))
1085 continue;
1086
1087 /* This css_set matches what we need */
1088 return cset;
1089 }
1090
1091 /* No existing cgroup group matched */
1092 return NULL;
1093}
1094
1095static void free_cgrp_cset_links(struct list_head *links_to_free)
1096{
1097 struct cgrp_cset_link *link, *tmp_link;
1098
1099 list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
1100 list_del(&link->cset_link);
1101 kfree(link);
1102 }
1103}
1104
1105/**
1106 * allocate_cgrp_cset_links - allocate cgrp_cset_links
1107 * @count: the number of links to allocate
1108 * @tmp_links: list_head the allocated links are put on
1109 *
1110 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
1111 * through ->cset_link. Returns 0 on success or -errno.
1112 */
1113static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
1114{
1115 struct cgrp_cset_link *link;
1116 int i;
1117
1118 INIT_LIST_HEAD(tmp_links);
1119
1120 for (i = 0; i < count; i++) {
1121 link = kzalloc(sizeof(*link), GFP_KERNEL);
1122 if (!link) {
1123 free_cgrp_cset_links(tmp_links);
1124 return -ENOMEM;
1125 }
1126 list_add(&link->cset_link, tmp_links);
1127 }
1128 return 0;
1129}
1130
1131/**
1132 * link_css_set - a helper function to link a css_set to a cgroup
1133 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
1134 * @cset: the css_set to be linked
1135 * @cgrp: the destination cgroup
1136 */
1137static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
1138 struct cgroup *cgrp)
1139{
1140 struct cgrp_cset_link *link;
1141
1142 BUG_ON(list_empty(tmp_links));
1143
1144 if (cgroup_on_dfl(cgrp))
1145 cset->dfl_cgrp = cgrp;
1146
1147 link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
1148 link->cset = cset;
1149 link->cgrp = cgrp;
1150
1151 /*
1152 * Always add links to the tail of the lists so that the lists are
1153 * in chronological order.
1154 */
1155 list_move_tail(&link->cset_link, &cgrp->cset_links);
1156 list_add_tail(&link->cgrp_link, &cset->cgrp_links);
1157
1158 if (cgroup_parent(cgrp))
1159 cgroup_get_live(cgrp);
1160}
1161
1162/**
1163 * find_css_set - return a new css_set with one cgroup updated
1164 * @old_cset: the baseline css_set
1165 * @cgrp: the cgroup to be updated
1166 *
1167 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
1168 * substituted into the appropriate hierarchy.
1169 */
1170static struct css_set *find_css_set(struct css_set *old_cset,
1171 struct cgroup *cgrp)
1172{
1173 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
1174 struct css_set *cset;
1175 struct list_head tmp_links;
1176 struct cgrp_cset_link *link;
1177 struct cgroup_subsys *ss;
1178 unsigned long key;
1179 int ssid;
1180
1181 lockdep_assert_held(&cgroup_mutex);
1182
1183 /* First see if we already have a cgroup group that matches
1184 * the desired set */
1185 spin_lock_irq(&css_set_lock);
1186 cset = find_existing_css_set(old_cset, cgrp, template);
1187 if (cset)
1188 get_css_set(cset);
1189 spin_unlock_irq(&css_set_lock);
1190
1191 if (cset)
1192 return cset;
1193
1194 cset = kzalloc(sizeof(*cset), GFP_KERNEL);
1195 if (!cset)
1196 return NULL;
1197
1198 /* Allocate all the cgrp_cset_link objects that we'll need */
1199 if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
1200 kfree(cset);
1201 return NULL;
1202 }
1203
1204 refcount_set(&cset->refcount, 1);
1205 cset->dom_cset = cset;
1206 INIT_LIST_HEAD(&cset->tasks);
1207 INIT_LIST_HEAD(&cset->mg_tasks);
1208 INIT_LIST_HEAD(&cset->dying_tasks);
1209 INIT_LIST_HEAD(&cset->task_iters);
1210 INIT_LIST_HEAD(&cset->threaded_csets);
1211 INIT_HLIST_NODE(&cset->hlist);
1212 INIT_LIST_HEAD(&cset->cgrp_links);
1213 INIT_LIST_HEAD(&cset->mg_src_preload_node);
1214 INIT_LIST_HEAD(&cset->mg_dst_preload_node);
1215 INIT_LIST_HEAD(&cset->mg_node);
1216
1217 /* Copy the set of subsystem state objects generated in
1218 * find_existing_css_set() */
1219 memcpy(cset->subsys, template, sizeof(cset->subsys));
1220
1221 spin_lock_irq(&css_set_lock);
1222 /* Add reference counts and links from the new css_set. */
1223 list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
1224 struct cgroup *c = link->cgrp;
1225
1226 if (c->root == cgrp->root)
1227 c = cgrp;
1228 link_css_set(&tmp_links, cset, c);
1229 }
1230
1231 BUG_ON(!list_empty(&tmp_links));
1232
1233 css_set_count++;
1234
1235 /* Add @cset to the hash table */
1236 key = css_set_hash(cset->subsys);
1237 hash_add(css_set_table, &cset->hlist, key);
1238
1239 for_each_subsys(ss, ssid) {
1240 struct cgroup_subsys_state *css = cset->subsys[ssid];
1241
1242 list_add_tail(&cset->e_cset_node[ssid],
1243 &css->cgroup->e_csets[ssid]);
1244 css_get(css);
1245 }
1246
1247 spin_unlock_irq(&css_set_lock);
1248
1249 /*
1250 * If @cset should be threaded, look up the matching dom_cset and
1251 * link them up. We first fully initialize @cset then look for the
1252 * dom_cset. It's simpler this way and safe as @cset is guaranteed
1253 * to stay empty until we return.
1254 */
1255 if (cgroup_is_threaded(cset->dfl_cgrp)) {
1256 struct css_set *dcset;
1257
1258 dcset = find_css_set(cset, cset->dfl_cgrp->dom_cgrp);
1259 if (!dcset) {
1260 put_css_set(cset);
1261 return NULL;
1262 }
1263
1264 spin_lock_irq(&css_set_lock);
1265 cset->dom_cset = dcset;
1266 list_add_tail(&cset->threaded_csets_node,
1267 &dcset->threaded_csets);
1268 spin_unlock_irq(&css_set_lock);
1269 }
1270
1271 return cset;
1272}
1273
1274struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
1275{
1276 struct cgroup *root_cgrp = kernfs_root_to_node(kf_root)->priv;
1277
1278 return root_cgrp->root;
1279}
1280
1281void cgroup_favor_dynmods(struct cgroup_root *root, bool favor)
1282{
1283 bool favoring = root->flags & CGRP_ROOT_FAVOR_DYNMODS;
1284
1285 /* see the comment above CGRP_ROOT_FAVOR_DYNMODS definition */
1286 if (favor && !favoring) {
1287 rcu_sync_enter(&cgroup_threadgroup_rwsem.rss);
1288 root->flags |= CGRP_ROOT_FAVOR_DYNMODS;
1289 } else if (!favor && favoring) {
1290 rcu_sync_exit(&cgroup_threadgroup_rwsem.rss);
1291 root->flags &= ~CGRP_ROOT_FAVOR_DYNMODS;
1292 }
1293}
1294
1295static int cgroup_init_root_id(struct cgroup_root *root)
1296{
1297 int id;
1298
1299 lockdep_assert_held(&cgroup_mutex);
1300
1301 id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
1302 if (id < 0)
1303 return id;
1304
1305 root->hierarchy_id = id;
1306 return 0;
1307}
1308
1309static void cgroup_exit_root_id(struct cgroup_root *root)
1310{
1311 lockdep_assert_held(&cgroup_mutex);
1312
1313 idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
1314}
1315
1316void cgroup_free_root(struct cgroup_root *root)
1317{
1318 kfree_rcu(root, rcu);
1319}
1320
1321static void cgroup_destroy_root(struct cgroup_root *root)
1322{
1323 struct cgroup *cgrp = &root->cgrp;
1324 struct cgrp_cset_link *link, *tmp_link;
1325
1326 trace_cgroup_destroy_root(root);
1327
1328 cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1329
1330 BUG_ON(atomic_read(&root->nr_cgrps));
1331 BUG_ON(!list_empty(&cgrp->self.children));
1332
1333 /* Rebind all subsystems back to the default hierarchy */
1334 WARN_ON(rebind_subsystems(&cgrp_dfl_root, root->subsys_mask));
1335
1336 /*
1337 * Release all the links from cset_links to this hierarchy's
1338 * root cgroup
1339 */
1340 spin_lock_irq(&css_set_lock);
1341
1342 list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
1343 list_del(&link->cset_link);
1344 list_del(&link->cgrp_link);
1345 kfree(link);
1346 }
1347
1348 spin_unlock_irq(&css_set_lock);
1349
1350 WARN_ON_ONCE(list_empty(&root->root_list));
1351 list_del_rcu(&root->root_list);
1352 cgroup_root_count--;
1353
1354 if (!have_favordynmods)
1355 cgroup_favor_dynmods(root, false);
1356
1357 cgroup_exit_root_id(root);
1358
1359 cgroup_unlock();
1360
1361 cgroup_rstat_exit(cgrp);
1362 kernfs_destroy_root(root->kf_root);
1363 cgroup_free_root(root);
1364}
1365
1366/*
1367 * Returned cgroup is without refcount but it's valid as long as cset pins it.
1368 */
1369static inline struct cgroup *__cset_cgroup_from_root(struct css_set *cset,
1370 struct cgroup_root *root)
1371{
1372 struct cgroup *res_cgroup = NULL;
1373
1374 if (cset == &init_css_set) {
1375 res_cgroup = &root->cgrp;
1376 } else if (root == &cgrp_dfl_root) {
1377 res_cgroup = cset->dfl_cgrp;
1378 } else {
1379 struct cgrp_cset_link *link;
1380 lockdep_assert_held(&css_set_lock);
1381
1382 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
1383 struct cgroup *c = link->cgrp;
1384
1385 if (c->root == root) {
1386 res_cgroup = c;
1387 break;
1388 }
1389 }
1390 }
1391
1392 /*
1393 * If cgroup_mutex is not held, the cgrp_cset_link will be freed
1394 * before we remove the cgroup root from the root_list. Consequently,
1395 * when accessing a cgroup root, the cset_link may have already been
1396 * freed, resulting in a NULL res_cgroup. However, by holding the
1397 * cgroup_mutex, we ensure that res_cgroup can't be NULL.
1398 * If we don't hold cgroup_mutex in the caller, we must do the NULL
1399 * check.
1400 */
1401 return res_cgroup;
1402}
1403
1404/*
1405 * look up cgroup associated with current task's cgroup namespace on the
1406 * specified hierarchy
1407 */
1408static struct cgroup *
1409current_cgns_cgroup_from_root(struct cgroup_root *root)
1410{
1411 struct cgroup *res = NULL;
1412 struct css_set *cset;
1413
1414 lockdep_assert_held(&css_set_lock);
1415
1416 rcu_read_lock();
1417
1418 cset = current->nsproxy->cgroup_ns->root_cset;
1419 res = __cset_cgroup_from_root(cset, root);
1420
1421 rcu_read_unlock();
1422
1423 /*
1424 * The namespace_sem is held by current, so the root cgroup can't
1425 * be umounted. Therefore, we can ensure that the res is non-NULL.
1426 */
1427 WARN_ON_ONCE(!res);
1428 return res;
1429}
1430
1431/*
1432 * Look up cgroup associated with current task's cgroup namespace on the default
1433 * hierarchy.
1434 *
1435 * Unlike current_cgns_cgroup_from_root(), this doesn't need locks:
1436 * - Internal rcu_read_lock is unnecessary because we don't dereference any rcu
1437 * pointers.
1438 * - css_set_lock is not needed because we just read cset->dfl_cgrp.
1439 * - As a bonus returned cgrp is pinned with the current because it cannot
1440 * switch cgroup_ns asynchronously.
1441 */
1442static struct cgroup *current_cgns_cgroup_dfl(void)
1443{
1444 struct css_set *cset;
1445
1446 if (current->nsproxy) {
1447 cset = current->nsproxy->cgroup_ns->root_cset;
1448 return __cset_cgroup_from_root(cset, &cgrp_dfl_root);
1449 } else {
1450 /*
1451 * NOTE: This function may be called from bpf_cgroup_from_id()
1452 * on a task which has already passed exit_task_namespaces() and
1453 * nsproxy == NULL. Fall back to cgrp_dfl_root which will make all
1454 * cgroups visible for lookups.
1455 */
1456 return &cgrp_dfl_root.cgrp;
1457 }
1458}
1459
1460/* look up cgroup associated with given css_set on the specified hierarchy */
1461static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
1462 struct cgroup_root *root)
1463{
1464 lockdep_assert_held(&css_set_lock);
1465
1466 return __cset_cgroup_from_root(cset, root);
1467}
1468
1469/*
1470 * Return the cgroup for "task" from the given hierarchy. Must be
1471 * called with css_set_lock held to prevent task's groups from being modified.
1472 * Must be called with either cgroup_mutex or rcu read lock to prevent the
1473 * cgroup root from being destroyed.
1474 */
1475struct cgroup *task_cgroup_from_root(struct task_struct *task,
1476 struct cgroup_root *root)
1477{
1478 /*
1479 * No need to lock the task - since we hold css_set_lock the
1480 * task can't change groups.
1481 */
1482 return cset_cgroup_from_root(task_css_set(task), root);
1483}
1484
1485/*
1486 * A task must hold cgroup_mutex to modify cgroups.
1487 *
1488 * Any task can increment and decrement the count field without lock.
1489 * So in general, code holding cgroup_mutex can't rely on the count
1490 * field not changing. However, if the count goes to zero, then only
1491 * cgroup_attach_task() can increment it again. Because a count of zero
1492 * means that no tasks are currently attached, therefore there is no
1493 * way a task attached to that cgroup can fork (the other way to
1494 * increment the count). So code holding cgroup_mutex can safely
1495 * assume that if the count is zero, it will stay zero. Similarly, if
1496 * a task holds cgroup_mutex on a cgroup with zero count, it
1497 * knows that the cgroup won't be removed, as cgroup_rmdir()
1498 * needs that mutex.
1499 *
1500 * A cgroup can only be deleted if both its 'count' of using tasks
1501 * is zero, and its list of 'children' cgroups is empty. Since all
1502 * tasks in the system use _some_ cgroup, and since there is always at
1503 * least one task in the system (init, pid == 1), therefore, root cgroup
1504 * always has either children cgroups and/or using tasks. So we don't
1505 * need a special hack to ensure that root cgroup cannot be deleted.
1506 *
1507 * P.S. One more locking exception. RCU is used to guard the
1508 * update of a tasks cgroup pointer by cgroup_attach_task()
1509 */
1510
1511static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
1512
1513static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
1514 char *buf)
1515{
1516 struct cgroup_subsys *ss = cft->ss;
1517
1518 if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
1519 !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
1520 const char *dbg = (cft->flags & CFTYPE_DEBUG) ? ".__DEBUG__." : "";
1521
1522 snprintf(buf, CGROUP_FILE_NAME_MAX, "%s%s.%s",
1523 dbg, cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name,
1524 cft->name);
1525 } else {
1526 strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
1527 }
1528 return buf;
1529}
1530
1531/**
1532 * cgroup_file_mode - deduce file mode of a control file
1533 * @cft: the control file in question
1534 *
1535 * S_IRUGO for read, S_IWUSR for write.
1536 */
1537static umode_t cgroup_file_mode(const struct cftype *cft)
1538{
1539 umode_t mode = 0;
1540
1541 if (cft->read_u64 || cft->read_s64 || cft->seq_show)
1542 mode |= S_IRUGO;
1543
1544 if (cft->write_u64 || cft->write_s64 || cft->write) {
1545 if (cft->flags & CFTYPE_WORLD_WRITABLE)
1546 mode |= S_IWUGO;
1547 else
1548 mode |= S_IWUSR;
1549 }
1550
1551 return mode;
1552}
1553
1554/**
1555 * cgroup_calc_subtree_ss_mask - calculate subtree_ss_mask
1556 * @subtree_control: the new subtree_control mask to consider
1557 * @this_ss_mask: available subsystems
1558 *
1559 * On the default hierarchy, a subsystem may request other subsystems to be
1560 * enabled together through its ->depends_on mask. In such cases, more
1561 * subsystems than specified in "cgroup.subtree_control" may be enabled.
1562 *
1563 * This function calculates which subsystems need to be enabled if
1564 * @subtree_control is to be applied while restricted to @this_ss_mask.
1565 */
1566static u16 cgroup_calc_subtree_ss_mask(u16 subtree_control, u16 this_ss_mask)
1567{
1568 u16 cur_ss_mask = subtree_control;
1569 struct cgroup_subsys *ss;
1570 int ssid;
1571
1572 lockdep_assert_held(&cgroup_mutex);
1573
1574 cur_ss_mask |= cgrp_dfl_implicit_ss_mask;
1575
1576 while (true) {
1577 u16 new_ss_mask = cur_ss_mask;
1578
1579 do_each_subsys_mask(ss, ssid, cur_ss_mask) {
1580 new_ss_mask |= ss->depends_on;
1581 } while_each_subsys_mask();
1582
1583 /*
1584 * Mask out subsystems which aren't available. This can
1585 * happen only if some depended-upon subsystems were bound
1586 * to non-default hierarchies.
1587 */
1588 new_ss_mask &= this_ss_mask;
1589
1590 if (new_ss_mask == cur_ss_mask)
1591 break;
1592 cur_ss_mask = new_ss_mask;
1593 }
1594
1595 return cur_ss_mask;
1596}
1597
1598/**
1599 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1600 * @kn: the kernfs_node being serviced
1601 *
1602 * This helper undoes cgroup_kn_lock_live() and should be invoked before
1603 * the method finishes if locking succeeded. Note that once this function
1604 * returns the cgroup returned by cgroup_kn_lock_live() may become
1605 * inaccessible any time. If the caller intends to continue to access the
1606 * cgroup, it should pin it before invoking this function.
1607 */
1608void cgroup_kn_unlock(struct kernfs_node *kn)
1609{
1610 struct cgroup *cgrp;
1611
1612 if (kernfs_type(kn) == KERNFS_DIR)
1613 cgrp = kn->priv;
1614 else
1615 cgrp = kn->parent->priv;
1616
1617 cgroup_unlock();
1618
1619 kernfs_unbreak_active_protection(kn);
1620 cgroup_put(cgrp);
1621}
1622
1623/**
1624 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1625 * @kn: the kernfs_node being serviced
1626 * @drain_offline: perform offline draining on the cgroup
1627 *
1628 * This helper is to be used by a cgroup kernfs method currently servicing
1629 * @kn. It breaks the active protection, performs cgroup locking and
1630 * verifies that the associated cgroup is alive. Returns the cgroup if
1631 * alive; otherwise, %NULL. A successful return should be undone by a
1632 * matching cgroup_kn_unlock() invocation. If @drain_offline is %true, the
1633 * cgroup is drained of offlining csses before return.
1634 *
1635 * Any cgroup kernfs method implementation which requires locking the
1636 * associated cgroup should use this helper. It avoids nesting cgroup
1637 * locking under kernfs active protection and allows all kernfs operations
1638 * including self-removal.
1639 */
1640struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn, bool drain_offline)
1641{
1642 struct cgroup *cgrp;
1643
1644 if (kernfs_type(kn) == KERNFS_DIR)
1645 cgrp = kn->priv;
1646 else
1647 cgrp = kn->parent->priv;
1648
1649 /*
1650 * We're gonna grab cgroup_mutex which nests outside kernfs
1651 * active_ref. cgroup liveliness check alone provides enough
1652 * protection against removal. Ensure @cgrp stays accessible and
1653 * break the active_ref protection.
1654 */
1655 if (!cgroup_tryget(cgrp))
1656 return NULL;
1657 kernfs_break_active_protection(kn);
1658
1659 if (drain_offline)
1660 cgroup_lock_and_drain_offline(cgrp);
1661 else
1662 cgroup_lock();
1663
1664 if (!cgroup_is_dead(cgrp))
1665 return cgrp;
1666
1667 cgroup_kn_unlock(kn);
1668 return NULL;
1669}
1670
1671static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
1672{
1673 char name[CGROUP_FILE_NAME_MAX];
1674
1675 lockdep_assert_held(&cgroup_mutex);
1676
1677 if (cft->file_offset) {
1678 struct cgroup_subsys_state *css = cgroup_css(cgrp, cft->ss);
1679 struct cgroup_file *cfile = (void *)css + cft->file_offset;
1680
1681 spin_lock_irq(&cgroup_file_kn_lock);
1682 cfile->kn = NULL;
1683 spin_unlock_irq(&cgroup_file_kn_lock);
1684
1685 del_timer_sync(&cfile->notify_timer);
1686 }
1687
1688 kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
1689}
1690
1691/**
1692 * css_clear_dir - remove subsys files in a cgroup directory
1693 * @css: target css
1694 */
1695static void css_clear_dir(struct cgroup_subsys_state *css)
1696{
1697 struct cgroup *cgrp = css->cgroup;
1698 struct cftype *cfts;
1699
1700 if (!(css->flags & CSS_VISIBLE))
1701 return;
1702
1703 css->flags &= ~CSS_VISIBLE;
1704
1705 if (!css->ss) {
1706 if (cgroup_on_dfl(cgrp)) {
1707 cgroup_addrm_files(css, cgrp,
1708 cgroup_base_files, false);
1709 if (cgroup_psi_enabled())
1710 cgroup_addrm_files(css, cgrp,
1711 cgroup_psi_files, false);
1712 } else {
1713 cgroup_addrm_files(css, cgrp,
1714 cgroup1_base_files, false);
1715 }
1716 } else {
1717 list_for_each_entry(cfts, &css->ss->cfts, node)
1718 cgroup_addrm_files(css, cgrp, cfts, false);
1719 }
1720}
1721
1722/**
1723 * css_populate_dir - create subsys files in a cgroup directory
1724 * @css: target css
1725 *
1726 * On failure, no file is added.
1727 */
1728static int css_populate_dir(struct cgroup_subsys_state *css)
1729{
1730 struct cgroup *cgrp = css->cgroup;
1731 struct cftype *cfts, *failed_cfts;
1732 int ret;
1733
1734 if (css->flags & CSS_VISIBLE)
1735 return 0;
1736
1737 if (!css->ss) {
1738 if (cgroup_on_dfl(cgrp)) {
1739 ret = cgroup_addrm_files(css, cgrp,
1740 cgroup_base_files, true);
1741 if (ret < 0)
1742 return ret;
1743
1744 if (cgroup_psi_enabled()) {
1745 ret = cgroup_addrm_files(css, cgrp,
1746 cgroup_psi_files, true);
1747 if (ret < 0)
1748 return ret;
1749 }
1750 } else {
1751 ret = cgroup_addrm_files(css, cgrp,
1752 cgroup1_base_files, true);
1753 if (ret < 0)
1754 return ret;
1755 }
1756 } else {
1757 list_for_each_entry(cfts, &css->ss->cfts, node) {
1758 ret = cgroup_addrm_files(css, cgrp, cfts, true);
1759 if (ret < 0) {
1760 failed_cfts = cfts;
1761 goto err;
1762 }
1763 }
1764 }
1765
1766 css->flags |= CSS_VISIBLE;
1767
1768 return 0;
1769err:
1770 list_for_each_entry(cfts, &css->ss->cfts, node) {
1771 if (cfts == failed_cfts)
1772 break;
1773 cgroup_addrm_files(css, cgrp, cfts, false);
1774 }
1775 return ret;
1776}
1777
1778int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
1779{
1780 struct cgroup *dcgrp = &dst_root->cgrp;
1781 struct cgroup_subsys *ss;
1782 int ssid, ret;
1783 u16 dfl_disable_ss_mask = 0;
1784
1785 lockdep_assert_held(&cgroup_mutex);
1786
1787 do_each_subsys_mask(ss, ssid, ss_mask) {
1788 /*
1789 * If @ss has non-root csses attached to it, can't move.
1790 * If @ss is an implicit controller, it is exempt from this
1791 * rule and can be stolen.
1792 */
1793 if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)) &&
1794 !ss->implicit_on_dfl)
1795 return -EBUSY;
1796
1797 /* can't move between two non-dummy roots either */
1798 if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
1799 return -EBUSY;
1800
1801 /*
1802 * Collect ssid's that need to be disabled from default
1803 * hierarchy.
1804 */
1805 if (ss->root == &cgrp_dfl_root)
1806 dfl_disable_ss_mask |= 1 << ssid;
1807
1808 } while_each_subsys_mask();
1809
1810 if (dfl_disable_ss_mask) {
1811 struct cgroup *scgrp = &cgrp_dfl_root.cgrp;
1812
1813 /*
1814 * Controllers from default hierarchy that need to be rebound
1815 * are all disabled together in one go.
1816 */
1817 cgrp_dfl_root.subsys_mask &= ~dfl_disable_ss_mask;
1818 WARN_ON(cgroup_apply_control(scgrp));
1819 cgroup_finalize_control(scgrp, 0);
1820 }
1821
1822 do_each_subsys_mask(ss, ssid, ss_mask) {
1823 struct cgroup_root *src_root = ss->root;
1824 struct cgroup *scgrp = &src_root->cgrp;
1825 struct cgroup_subsys_state *css = cgroup_css(scgrp, ss);
1826 struct css_set *cset, *cset_pos;
1827 struct css_task_iter *it;
1828
1829 WARN_ON(!css || cgroup_css(dcgrp, ss));
1830
1831 if (src_root != &cgrp_dfl_root) {
1832 /* disable from the source */
1833 src_root->subsys_mask &= ~(1 << ssid);
1834 WARN_ON(cgroup_apply_control(scgrp));
1835 cgroup_finalize_control(scgrp, 0);
1836 }
1837
1838 /* rebind */
1839 RCU_INIT_POINTER(scgrp->subsys[ssid], NULL);
1840 rcu_assign_pointer(dcgrp->subsys[ssid], css);
1841 ss->root = dst_root;
1842 css->cgroup = dcgrp;
1843
1844 spin_lock_irq(&css_set_lock);
1845 WARN_ON(!list_empty(&dcgrp->e_csets[ss->id]));
1846 list_for_each_entry_safe(cset, cset_pos, &scgrp->e_csets[ss->id],
1847 e_cset_node[ss->id]) {
1848 list_move_tail(&cset->e_cset_node[ss->id],
1849 &dcgrp->e_csets[ss->id]);
1850 /*
1851 * all css_sets of scgrp together in same order to dcgrp,
1852 * patch in-flight iterators to preserve correct iteration.
1853 * since the iterator is always advanced right away and
1854 * finished when it->cset_pos meets it->cset_head, so only
1855 * update it->cset_head is enough here.
1856 */
1857 list_for_each_entry(it, &cset->task_iters, iters_node)
1858 if (it->cset_head == &scgrp->e_csets[ss->id])
1859 it->cset_head = &dcgrp->e_csets[ss->id];
1860 }
1861 spin_unlock_irq(&css_set_lock);
1862
1863 if (ss->css_rstat_flush) {
1864 list_del_rcu(&css->rstat_css_node);
1865 synchronize_rcu();
1866 list_add_rcu(&css->rstat_css_node,
1867 &dcgrp->rstat_css_list);
1868 }
1869
1870 /* default hierarchy doesn't enable controllers by default */
1871 dst_root->subsys_mask |= 1 << ssid;
1872 if (dst_root == &cgrp_dfl_root) {
1873 static_branch_enable(cgroup_subsys_on_dfl_key[ssid]);
1874 } else {
1875 dcgrp->subtree_control |= 1 << ssid;
1876 static_branch_disable(cgroup_subsys_on_dfl_key[ssid]);
1877 }
1878
1879 ret = cgroup_apply_control(dcgrp);
1880 if (ret)
1881 pr_warn("partial failure to rebind %s controller (err=%d)\n",
1882 ss->name, ret);
1883
1884 if (ss->bind)
1885 ss->bind(css);
1886 } while_each_subsys_mask();
1887
1888 kernfs_activate(dcgrp->kn);
1889 return 0;
1890}
1891
1892int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
1893 struct kernfs_root *kf_root)
1894{
1895 int len = 0;
1896 char *buf = NULL;
1897 struct cgroup_root *kf_cgroot = cgroup_root_from_kf(kf_root);
1898 struct cgroup *ns_cgroup;
1899
1900 buf = kmalloc(PATH_MAX, GFP_KERNEL);
1901 if (!buf)
1902 return -ENOMEM;
1903
1904 spin_lock_irq(&css_set_lock);
1905 ns_cgroup = current_cgns_cgroup_from_root(kf_cgroot);
1906 len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX);
1907 spin_unlock_irq(&css_set_lock);
1908
1909 if (len == -E2BIG)
1910 len = -ERANGE;
1911 else if (len > 0) {
1912 seq_escape(sf, buf, " \t\n\\");
1913 len = 0;
1914 }
1915 kfree(buf);
1916 return len;
1917}
1918
1919enum cgroup2_param {
1920 Opt_nsdelegate,
1921 Opt_favordynmods,
1922 Opt_memory_localevents,
1923 Opt_memory_recursiveprot,
1924 Opt_memory_hugetlb_accounting,
1925 nr__cgroup2_params
1926};
1927
1928static const struct fs_parameter_spec cgroup2_fs_parameters[] = {
1929 fsparam_flag("nsdelegate", Opt_nsdelegate),
1930 fsparam_flag("favordynmods", Opt_favordynmods),
1931 fsparam_flag("memory_localevents", Opt_memory_localevents),
1932 fsparam_flag("memory_recursiveprot", Opt_memory_recursiveprot),
1933 fsparam_flag("memory_hugetlb_accounting", Opt_memory_hugetlb_accounting),
1934 {}
1935};
1936
1937static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param)
1938{
1939 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1940 struct fs_parse_result result;
1941 int opt;
1942
1943 opt = fs_parse(fc, cgroup2_fs_parameters, param, &result);
1944 if (opt < 0)
1945 return opt;
1946
1947 switch (opt) {
1948 case Opt_nsdelegate:
1949 ctx->flags |= CGRP_ROOT_NS_DELEGATE;
1950 return 0;
1951 case Opt_favordynmods:
1952 ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
1953 return 0;
1954 case Opt_memory_localevents:
1955 ctx->flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1956 return 0;
1957 case Opt_memory_recursiveprot:
1958 ctx->flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;
1959 return 0;
1960 case Opt_memory_hugetlb_accounting:
1961 ctx->flags |= CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
1962 return 0;
1963 }
1964 return -EINVAL;
1965}
1966
1967static void apply_cgroup_root_flags(unsigned int root_flags)
1968{
1969 if (current->nsproxy->cgroup_ns == &init_cgroup_ns) {
1970 if (root_flags & CGRP_ROOT_NS_DELEGATE)
1971 cgrp_dfl_root.flags |= CGRP_ROOT_NS_DELEGATE;
1972 else
1973 cgrp_dfl_root.flags &= ~CGRP_ROOT_NS_DELEGATE;
1974
1975 cgroup_favor_dynmods(&cgrp_dfl_root,
1976 root_flags & CGRP_ROOT_FAVOR_DYNMODS);
1977
1978 if (root_flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
1979 cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1980 else
1981 cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1982
1983 if (root_flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)
1984 cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;
1985 else
1986 cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_RECURSIVE_PROT;
1987
1988 if (root_flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING)
1989 cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
1990 else
1991 cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING;
1992 }
1993}
1994
1995static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
1996{
1997 if (cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE)
1998 seq_puts(seq, ",nsdelegate");
1999 if (cgrp_dfl_root.flags & CGRP_ROOT_FAVOR_DYNMODS)
2000 seq_puts(seq, ",favordynmods");
2001 if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
2002 seq_puts(seq, ",memory_localevents");
2003 if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)
2004 seq_puts(seq, ",memory_recursiveprot");
2005 if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_HUGETLB_ACCOUNTING)
2006 seq_puts(seq, ",memory_hugetlb_accounting");
2007 return 0;
2008}
2009
2010static int cgroup_reconfigure(struct fs_context *fc)
2011{
2012 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2013
2014 apply_cgroup_root_flags(ctx->flags);
2015 return 0;
2016}
2017
2018static void init_cgroup_housekeeping(struct cgroup *cgrp)
2019{
2020 struct cgroup_subsys *ss;
2021 int ssid;
2022
2023 INIT_LIST_HEAD(&cgrp->self.sibling);
2024 INIT_LIST_HEAD(&cgrp->self.children);
2025 INIT_LIST_HEAD(&cgrp->cset_links);
2026 INIT_LIST_HEAD(&cgrp->pidlists);
2027 mutex_init(&cgrp->pidlist_mutex);
2028 cgrp->self.cgroup = cgrp;
2029 cgrp->self.flags |= CSS_ONLINE;
2030 cgrp->dom_cgrp = cgrp;
2031 cgrp->max_descendants = INT_MAX;
2032 cgrp->max_depth = INT_MAX;
2033 INIT_LIST_HEAD(&cgrp->rstat_css_list);
2034 prev_cputime_init(&cgrp->prev_cputime);
2035
2036 for_each_subsys(ss, ssid)
2037 INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
2038
2039 init_waitqueue_head(&cgrp->offline_waitq);
2040 INIT_WORK(&cgrp->release_agent_work, cgroup1_release_agent);
2041}
2042
2043void init_cgroup_root(struct cgroup_fs_context *ctx)
2044{
2045 struct cgroup_root *root = ctx->root;
2046 struct cgroup *cgrp = &root->cgrp;
2047
2048 INIT_LIST_HEAD_RCU(&root->root_list);
2049 atomic_set(&root->nr_cgrps, 1);
2050 cgrp->root = root;
2051 init_cgroup_housekeeping(cgrp);
2052
2053 /* DYNMODS must be modified through cgroup_favor_dynmods() */
2054 root->flags = ctx->flags & ~CGRP_ROOT_FAVOR_DYNMODS;
2055 if (ctx->release_agent)
2056 strscpy(root->release_agent_path, ctx->release_agent, PATH_MAX);
2057 if (ctx->name)
2058 strscpy(root->name, ctx->name, MAX_CGROUP_ROOT_NAMELEN);
2059 if (ctx->cpuset_clone_children)
2060 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
2061}
2062
2063int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
2064{
2065 LIST_HEAD(tmp_links);
2066 struct cgroup *root_cgrp = &root->cgrp;
2067 struct kernfs_syscall_ops *kf_sops;
2068 struct css_set *cset;
2069 int i, ret;
2070
2071 lockdep_assert_held(&cgroup_mutex);
2072
2073 ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release,
2074 0, GFP_KERNEL);
2075 if (ret)
2076 goto out;
2077
2078 /*
2079 * We're accessing css_set_count without locking css_set_lock here,
2080 * but that's OK - it can only be increased by someone holding
2081 * cgroup_lock, and that's us. Later rebinding may disable
2082 * controllers on the default hierarchy and thus create new csets,
2083 * which can't be more than the existing ones. Allocate 2x.
2084 */
2085 ret = allocate_cgrp_cset_links(2 * css_set_count, &tmp_links);
2086 if (ret)
2087 goto cancel_ref;
2088
2089 ret = cgroup_init_root_id(root);
2090 if (ret)
2091 goto cancel_ref;
2092
2093 kf_sops = root == &cgrp_dfl_root ?
2094 &cgroup_kf_syscall_ops : &cgroup1_kf_syscall_ops;
2095
2096 root->kf_root = kernfs_create_root(kf_sops,
2097 KERNFS_ROOT_CREATE_DEACTIVATED |
2098 KERNFS_ROOT_SUPPORT_EXPORTOP |
2099 KERNFS_ROOT_SUPPORT_USER_XATTR,
2100 root_cgrp);
2101 if (IS_ERR(root->kf_root)) {
2102 ret = PTR_ERR(root->kf_root);
2103 goto exit_root_id;
2104 }
2105 root_cgrp->kn = kernfs_root_to_node(root->kf_root);
2106 WARN_ON_ONCE(cgroup_ino(root_cgrp) != 1);
2107 root_cgrp->ancestors[0] = root_cgrp;
2108
2109 ret = css_populate_dir(&root_cgrp->self);
2110 if (ret)
2111 goto destroy_root;
2112
2113 ret = cgroup_rstat_init(root_cgrp);
2114 if (ret)
2115 goto destroy_root;
2116
2117 ret = rebind_subsystems(root, ss_mask);
2118 if (ret)
2119 goto exit_stats;
2120
2121 ret = cgroup_bpf_inherit(root_cgrp);
2122 WARN_ON_ONCE(ret);
2123
2124 trace_cgroup_setup_root(root);
2125
2126 /*
2127 * There must be no failure case after here, since rebinding takes
2128 * care of subsystems' refcounts, which are explicitly dropped in
2129 * the failure exit path.
2130 */
2131 list_add_rcu(&root->root_list, &cgroup_roots);
2132 cgroup_root_count++;
2133
2134 /*
2135 * Link the root cgroup in this hierarchy into all the css_set
2136 * objects.
2137 */
2138 spin_lock_irq(&css_set_lock);
2139 hash_for_each(css_set_table, i, cset, hlist) {
2140 link_css_set(&tmp_links, cset, root_cgrp);
2141 if (css_set_populated(cset))
2142 cgroup_update_populated(root_cgrp, true);
2143 }
2144 spin_unlock_irq(&css_set_lock);
2145
2146 BUG_ON(!list_empty(&root_cgrp->self.children));
2147 BUG_ON(atomic_read(&root->nr_cgrps) != 1);
2148
2149 ret = 0;
2150 goto out;
2151
2152exit_stats:
2153 cgroup_rstat_exit(root_cgrp);
2154destroy_root:
2155 kernfs_destroy_root(root->kf_root);
2156 root->kf_root = NULL;
2157exit_root_id:
2158 cgroup_exit_root_id(root);
2159cancel_ref:
2160 percpu_ref_exit(&root_cgrp->self.refcnt);
2161out:
2162 free_cgrp_cset_links(&tmp_links);
2163 return ret;
2164}
2165
2166int cgroup_do_get_tree(struct fs_context *fc)
2167{
2168 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2169 int ret;
2170
2171 ctx->kfc.root = ctx->root->kf_root;
2172 if (fc->fs_type == &cgroup2_fs_type)
2173 ctx->kfc.magic = CGROUP2_SUPER_MAGIC;
2174 else
2175 ctx->kfc.magic = CGROUP_SUPER_MAGIC;
2176 ret = kernfs_get_tree(fc);
2177
2178 /*
2179 * In non-init cgroup namespace, instead of root cgroup's dentry,
2180 * we return the dentry corresponding to the cgroupns->root_cgrp.
2181 */
2182 if (!ret && ctx->ns != &init_cgroup_ns) {
2183 struct dentry *nsdentry;
2184 struct super_block *sb = fc->root->d_sb;
2185 struct cgroup *cgrp;
2186
2187 cgroup_lock();
2188 spin_lock_irq(&css_set_lock);
2189
2190 cgrp = cset_cgroup_from_root(ctx->ns->root_cset, ctx->root);
2191
2192 spin_unlock_irq(&css_set_lock);
2193 cgroup_unlock();
2194
2195 nsdentry = kernfs_node_dentry(cgrp->kn, sb);
2196 dput(fc->root);
2197 if (IS_ERR(nsdentry)) {
2198 deactivate_locked_super(sb);
2199 ret = PTR_ERR(nsdentry);
2200 nsdentry = NULL;
2201 }
2202 fc->root = nsdentry;
2203 }
2204
2205 if (!ctx->kfc.new_sb_created)
2206 cgroup_put(&ctx->root->cgrp);
2207
2208 return ret;
2209}
2210
2211/*
2212 * Destroy a cgroup filesystem context.
2213 */
2214static void cgroup_fs_context_free(struct fs_context *fc)
2215{
2216 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2217
2218 kfree(ctx->name);
2219 kfree(ctx->release_agent);
2220 put_cgroup_ns(ctx->ns);
2221 kernfs_free_fs_context(fc);
2222 kfree(ctx);
2223}
2224
2225static int cgroup_get_tree(struct fs_context *fc)
2226{
2227 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2228 int ret;
2229
2230 WRITE_ONCE(cgrp_dfl_visible, true);
2231 cgroup_get_live(&cgrp_dfl_root.cgrp);
2232 ctx->root = &cgrp_dfl_root;
2233
2234 ret = cgroup_do_get_tree(fc);
2235 if (!ret)
2236 apply_cgroup_root_flags(ctx->flags);
2237 return ret;
2238}
2239
2240static const struct fs_context_operations cgroup_fs_context_ops = {
2241 .free = cgroup_fs_context_free,
2242 .parse_param = cgroup2_parse_param,
2243 .get_tree = cgroup_get_tree,
2244 .reconfigure = cgroup_reconfigure,
2245};
2246
2247static const struct fs_context_operations cgroup1_fs_context_ops = {
2248 .free = cgroup_fs_context_free,
2249 .parse_param = cgroup1_parse_param,
2250 .get_tree = cgroup1_get_tree,
2251 .reconfigure = cgroup1_reconfigure,
2252};
2253
2254/*
2255 * Initialise the cgroup filesystem creation/reconfiguration context. Notably,
2256 * we select the namespace we're going to use.
2257 */
2258static int cgroup_init_fs_context(struct fs_context *fc)
2259{
2260 struct cgroup_fs_context *ctx;
2261
2262 ctx = kzalloc(sizeof(struct cgroup_fs_context), GFP_KERNEL);
2263 if (!ctx)
2264 return -ENOMEM;
2265
2266 ctx->ns = current->nsproxy->cgroup_ns;
2267 get_cgroup_ns(ctx->ns);
2268 fc->fs_private = &ctx->kfc;
2269 if (fc->fs_type == &cgroup2_fs_type)
2270 fc->ops = &cgroup_fs_context_ops;
2271 else
2272 fc->ops = &cgroup1_fs_context_ops;
2273 put_user_ns(fc->user_ns);
2274 fc->user_ns = get_user_ns(ctx->ns->user_ns);
2275 fc->global = true;
2276
2277 if (have_favordynmods)
2278 ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
2279
2280 return 0;
2281}
2282
2283static void cgroup_kill_sb(struct super_block *sb)
2284{
2285 struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
2286 struct cgroup_root *root = cgroup_root_from_kf(kf_root);
2287
2288 /*
2289 * If @root doesn't have any children, start killing it.
2290 * This prevents new mounts by disabling percpu_ref_tryget_live().
2291 *
2292 * And don't kill the default root.
2293 */
2294 if (list_empty(&root->cgrp.self.children) && root != &cgrp_dfl_root &&
2295 !percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
2296 cgroup_bpf_offline(&root->cgrp);
2297 percpu_ref_kill(&root->cgrp.self.refcnt);
2298 }
2299 cgroup_put(&root->cgrp);
2300 kernfs_kill_sb(sb);
2301}
2302
2303struct file_system_type cgroup_fs_type = {
2304 .name = "cgroup",
2305 .init_fs_context = cgroup_init_fs_context,
2306 .parameters = cgroup1_fs_parameters,
2307 .kill_sb = cgroup_kill_sb,
2308 .fs_flags = FS_USERNS_MOUNT,
2309};
2310
2311static struct file_system_type cgroup2_fs_type = {
2312 .name = "cgroup2",
2313 .init_fs_context = cgroup_init_fs_context,
2314 .parameters = cgroup2_fs_parameters,
2315 .kill_sb = cgroup_kill_sb,
2316 .fs_flags = FS_USERNS_MOUNT,
2317};
2318
2319#ifdef CONFIG_CPUSETS
2320static const struct fs_context_operations cpuset_fs_context_ops = {
2321 .get_tree = cgroup1_get_tree,
2322 .free = cgroup_fs_context_free,
2323};
2324
2325/*
2326 * This is ugly, but preserves the userspace API for existing cpuset
2327 * users. If someone tries to mount the "cpuset" filesystem, we
2328 * silently switch it to mount "cgroup" instead
2329 */
2330static int cpuset_init_fs_context(struct fs_context *fc)
2331{
2332 char *agent = kstrdup("/sbin/cpuset_release_agent", GFP_USER);
2333 struct cgroup_fs_context *ctx;
2334 int err;
2335
2336 err = cgroup_init_fs_context(fc);
2337 if (err) {
2338 kfree(agent);
2339 return err;
2340 }
2341
2342 fc->ops = &cpuset_fs_context_ops;
2343
2344 ctx = cgroup_fc2context(fc);
2345 ctx->subsys_mask = 1 << cpuset_cgrp_id;
2346 ctx->flags |= CGRP_ROOT_NOPREFIX;
2347 ctx->release_agent = agent;
2348
2349 get_filesystem(&cgroup_fs_type);
2350 put_filesystem(fc->fs_type);
2351 fc->fs_type = &cgroup_fs_type;
2352
2353 return 0;
2354}
2355
2356static struct file_system_type cpuset_fs_type = {
2357 .name = "cpuset",
2358 .init_fs_context = cpuset_init_fs_context,
2359 .fs_flags = FS_USERNS_MOUNT,
2360};
2361#endif
2362
2363int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
2364 struct cgroup_namespace *ns)
2365{
2366 struct cgroup *root = cset_cgroup_from_root(ns->root_cset, cgrp->root);
2367
2368 return kernfs_path_from_node(cgrp->kn, root->kn, buf, buflen);
2369}
2370
2371int cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
2372 struct cgroup_namespace *ns)
2373{
2374 int ret;
2375
2376 cgroup_lock();
2377 spin_lock_irq(&css_set_lock);
2378
2379 ret = cgroup_path_ns_locked(cgrp, buf, buflen, ns);
2380
2381 spin_unlock_irq(&css_set_lock);
2382 cgroup_unlock();
2383
2384 return ret;
2385}
2386EXPORT_SYMBOL_GPL(cgroup_path_ns);
2387
2388/**
2389 * cgroup_attach_lock - Lock for ->attach()
2390 * @lock_threadgroup: whether to down_write cgroup_threadgroup_rwsem
2391 *
2392 * cgroup migration sometimes needs to stabilize threadgroups against forks and
2393 * exits by write-locking cgroup_threadgroup_rwsem. However, some ->attach()
2394 * implementations (e.g. cpuset), also need to disable CPU hotplug.
2395 * Unfortunately, letting ->attach() operations acquire cpus_read_lock() can
2396 * lead to deadlocks.
2397 *
2398 * Bringing up a CPU may involve creating and destroying tasks which requires
2399 * read-locking threadgroup_rwsem, so threadgroup_rwsem nests inside
2400 * cpus_read_lock(). If we call an ->attach() which acquires the cpus lock while
2401 * write-locking threadgroup_rwsem, the locking order is reversed and we end up
2402 * waiting for an on-going CPU hotplug operation which in turn is waiting for
2403 * the threadgroup_rwsem to be released to create new tasks. For more details:
2404 *
2405 * http://lkml.kernel.org/r/20220711174629.uehfmqegcwn2lqzu@wubuntu
2406 *
2407 * Resolve the situation by always acquiring cpus_read_lock() before optionally
2408 * write-locking cgroup_threadgroup_rwsem. This allows ->attach() to assume that
2409 * CPU hotplug is disabled on entry.
2410 */
2411void cgroup_attach_lock(bool lock_threadgroup)
2412{
2413 cpus_read_lock();
2414 if (lock_threadgroup)
2415 percpu_down_write(&cgroup_threadgroup_rwsem);
2416}
2417
2418/**
2419 * cgroup_attach_unlock - Undo cgroup_attach_lock()
2420 * @lock_threadgroup: whether to up_write cgroup_threadgroup_rwsem
2421 */
2422void cgroup_attach_unlock(bool lock_threadgroup)
2423{
2424 if (lock_threadgroup)
2425 percpu_up_write(&cgroup_threadgroup_rwsem);
2426 cpus_read_unlock();
2427}
2428
2429/**
2430 * cgroup_migrate_add_task - add a migration target task to a migration context
2431 * @task: target task
2432 * @mgctx: target migration context
2433 *
2434 * Add @task, which is a migration target, to @mgctx->tset. This function
2435 * becomes noop if @task doesn't need to be migrated. @task's css_set
2436 * should have been added as a migration source and @task->cg_list will be
2437 * moved from the css_set's tasks list to mg_tasks one.
2438 */
2439static void cgroup_migrate_add_task(struct task_struct *task,
2440 struct cgroup_mgctx *mgctx)
2441{
2442 struct css_set *cset;
2443
2444 lockdep_assert_held(&css_set_lock);
2445
2446 /* @task either already exited or can't exit until the end */
2447 if (task->flags & PF_EXITING)
2448 return;
2449
2450 /* cgroup_threadgroup_rwsem protects racing against forks */
2451 WARN_ON_ONCE(list_empty(&task->cg_list));
2452
2453 cset = task_css_set(task);
2454 if (!cset->mg_src_cgrp)
2455 return;
2456
2457 mgctx->tset.nr_tasks++;
2458
2459 list_move_tail(&task->cg_list, &cset->mg_tasks);
2460 if (list_empty(&cset->mg_node))
2461 list_add_tail(&cset->mg_node,
2462 &mgctx->tset.src_csets);
2463 if (list_empty(&cset->mg_dst_cset->mg_node))
2464 list_add_tail(&cset->mg_dst_cset->mg_node,
2465 &mgctx->tset.dst_csets);
2466}
2467
2468/**
2469 * cgroup_taskset_first - reset taskset and return the first task
2470 * @tset: taskset of interest
2471 * @dst_cssp: output variable for the destination css
2472 *
2473 * @tset iteration is initialized and the first task is returned.
2474 */
2475struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset,
2476 struct cgroup_subsys_state **dst_cssp)
2477{
2478 tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
2479 tset->cur_task = NULL;
2480
2481 return cgroup_taskset_next(tset, dst_cssp);
2482}
2483
2484/**
2485 * cgroup_taskset_next - iterate to the next task in taskset
2486 * @tset: taskset of interest
2487 * @dst_cssp: output variable for the destination css
2488 *
2489 * Return the next task in @tset. Iteration must have been initialized
2490 * with cgroup_taskset_first().
2491 */
2492struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
2493 struct cgroup_subsys_state **dst_cssp)
2494{
2495 struct css_set *cset = tset->cur_cset;
2496 struct task_struct *task = tset->cur_task;
2497
2498 while (CGROUP_HAS_SUBSYS_CONFIG && &cset->mg_node != tset->csets) {
2499 if (!task)
2500 task = list_first_entry(&cset->mg_tasks,
2501 struct task_struct, cg_list);
2502 else
2503 task = list_next_entry(task, cg_list);
2504
2505 if (&task->cg_list != &cset->mg_tasks) {
2506 tset->cur_cset = cset;
2507 tset->cur_task = task;
2508
2509 /*
2510 * This function may be called both before and
2511 * after cgroup_migrate_execute(). The two cases
2512 * can be distinguished by looking at whether @cset
2513 * has its ->mg_dst_cset set.
2514 */
2515 if (cset->mg_dst_cset)
2516 *dst_cssp = cset->mg_dst_cset->subsys[tset->ssid];
2517 else
2518 *dst_cssp = cset->subsys[tset->ssid];
2519
2520 return task;
2521 }
2522
2523 cset = list_next_entry(cset, mg_node);
2524 task = NULL;
2525 }
2526
2527 return NULL;
2528}
2529
2530/**
2531 * cgroup_migrate_execute - migrate a taskset
2532 * @mgctx: migration context
2533 *
2534 * Migrate tasks in @mgctx as setup by migration preparation functions.
2535 * This function fails iff one of the ->can_attach callbacks fails and
2536 * guarantees that either all or none of the tasks in @mgctx are migrated.
2537 * @mgctx is consumed regardless of success.
2538 */
2539static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx)
2540{
2541 struct cgroup_taskset *tset = &mgctx->tset;
2542 struct cgroup_subsys *ss;
2543 struct task_struct *task, *tmp_task;
2544 struct css_set *cset, *tmp_cset;
2545 int ssid, failed_ssid, ret;
2546
2547 /* check that we can legitimately attach to the cgroup */
2548 if (tset->nr_tasks) {
2549 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2550 if (ss->can_attach) {
2551 tset->ssid = ssid;
2552 ret = ss->can_attach(tset);
2553 if (ret) {
2554 failed_ssid = ssid;
2555 goto out_cancel_attach;
2556 }
2557 }
2558 } while_each_subsys_mask();
2559 }
2560
2561 /*
2562 * Now that we're guaranteed success, proceed to move all tasks to
2563 * the new cgroup. There are no failure cases after here, so this
2564 * is the commit point.
2565 */
2566 spin_lock_irq(&css_set_lock);
2567 list_for_each_entry(cset, &tset->src_csets, mg_node) {
2568 list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list) {
2569 struct css_set *from_cset = task_css_set(task);
2570 struct css_set *to_cset = cset->mg_dst_cset;
2571
2572 get_css_set(to_cset);
2573 to_cset->nr_tasks++;
2574 css_set_move_task(task, from_cset, to_cset, true);
2575 from_cset->nr_tasks--;
2576 /*
2577 * If the source or destination cgroup is frozen,
2578 * the task might require to change its state.
2579 */
2580 cgroup_freezer_migrate_task(task, from_cset->dfl_cgrp,
2581 to_cset->dfl_cgrp);
2582 put_css_set_locked(from_cset);
2583
2584 }
2585 }
2586 spin_unlock_irq(&css_set_lock);
2587
2588 /*
2589 * Migration is committed, all target tasks are now on dst_csets.
2590 * Nothing is sensitive to fork() after this point. Notify
2591 * controllers that migration is complete.
2592 */
2593 tset->csets = &tset->dst_csets;
2594
2595 if (tset->nr_tasks) {
2596 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2597 if (ss->attach) {
2598 tset->ssid = ssid;
2599 ss->attach(tset);
2600 }
2601 } while_each_subsys_mask();
2602 }
2603
2604 ret = 0;
2605 goto out_release_tset;
2606
2607out_cancel_attach:
2608 if (tset->nr_tasks) {
2609 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2610 if (ssid == failed_ssid)
2611 break;
2612 if (ss->cancel_attach) {
2613 tset->ssid = ssid;
2614 ss->cancel_attach(tset);
2615 }
2616 } while_each_subsys_mask();
2617 }
2618out_release_tset:
2619 spin_lock_irq(&css_set_lock);
2620 list_splice_init(&tset->dst_csets, &tset->src_csets);
2621 list_for_each_entry_safe(cset, tmp_cset, &tset->src_csets, mg_node) {
2622 list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
2623 list_del_init(&cset->mg_node);
2624 }
2625 spin_unlock_irq(&css_set_lock);
2626
2627 /*
2628 * Re-initialize the cgroup_taskset structure in case it is reused
2629 * again in another cgroup_migrate_add_task()/cgroup_migrate_execute()
2630 * iteration.
2631 */
2632 tset->nr_tasks = 0;
2633 tset->csets = &tset->src_csets;
2634 return ret;
2635}
2636
2637/**
2638 * cgroup_migrate_vet_dst - verify whether a cgroup can be migration destination
2639 * @dst_cgrp: destination cgroup to test
2640 *
2641 * On the default hierarchy, except for the mixable, (possible) thread root
2642 * and threaded cgroups, subtree_control must be zero for migration
2643 * destination cgroups with tasks so that child cgroups don't compete
2644 * against tasks.
2645 */
2646int cgroup_migrate_vet_dst(struct cgroup *dst_cgrp)
2647{
2648 /* v1 doesn't have any restriction */
2649 if (!cgroup_on_dfl(dst_cgrp))
2650 return 0;
2651
2652 /* verify @dst_cgrp can host resources */
2653 if (!cgroup_is_valid_domain(dst_cgrp->dom_cgrp))
2654 return -EOPNOTSUPP;
2655
2656 /*
2657 * If @dst_cgrp is already or can become a thread root or is
2658 * threaded, it doesn't matter.
2659 */
2660 if (cgroup_can_be_thread_root(dst_cgrp) || cgroup_is_threaded(dst_cgrp))
2661 return 0;
2662
2663 /* apply no-internal-process constraint */
2664 if (dst_cgrp->subtree_control)
2665 return -EBUSY;
2666
2667 return 0;
2668}
2669
2670/**
2671 * cgroup_migrate_finish - cleanup after attach
2672 * @mgctx: migration context
2673 *
2674 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
2675 * those functions for details.
2676 */
2677void cgroup_migrate_finish(struct cgroup_mgctx *mgctx)
2678{
2679 struct css_set *cset, *tmp_cset;
2680
2681 lockdep_assert_held(&cgroup_mutex);
2682
2683 spin_lock_irq(&css_set_lock);
2684
2685 list_for_each_entry_safe(cset, tmp_cset, &mgctx->preloaded_src_csets,
2686 mg_src_preload_node) {
2687 cset->mg_src_cgrp = NULL;
2688 cset->mg_dst_cgrp = NULL;
2689 cset->mg_dst_cset = NULL;
2690 list_del_init(&cset->mg_src_preload_node);
2691 put_css_set_locked(cset);
2692 }
2693
2694 list_for_each_entry_safe(cset, tmp_cset, &mgctx->preloaded_dst_csets,
2695 mg_dst_preload_node) {
2696 cset->mg_src_cgrp = NULL;
2697 cset->mg_dst_cgrp = NULL;
2698 cset->mg_dst_cset = NULL;
2699 list_del_init(&cset->mg_dst_preload_node);
2700 put_css_set_locked(cset);
2701 }
2702
2703 spin_unlock_irq(&css_set_lock);
2704}
2705
2706/**
2707 * cgroup_migrate_add_src - add a migration source css_set
2708 * @src_cset: the source css_set to add
2709 * @dst_cgrp: the destination cgroup
2710 * @mgctx: migration context
2711 *
2712 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
2713 * @src_cset and add it to @mgctx->src_csets, which should later be cleaned
2714 * up by cgroup_migrate_finish().
2715 *
2716 * This function may be called without holding cgroup_threadgroup_rwsem
2717 * even if the target is a process. Threads may be created and destroyed
2718 * but as long as cgroup_mutex is not dropped, no new css_set can be put
2719 * into play and the preloaded css_sets are guaranteed to cover all
2720 * migrations.
2721 */
2722void cgroup_migrate_add_src(struct css_set *src_cset,
2723 struct cgroup *dst_cgrp,
2724 struct cgroup_mgctx *mgctx)
2725{
2726 struct cgroup *src_cgrp;
2727
2728 lockdep_assert_held(&cgroup_mutex);
2729 lockdep_assert_held(&css_set_lock);
2730
2731 /*
2732 * If ->dead, @src_set is associated with one or more dead cgroups
2733 * and doesn't contain any migratable tasks. Ignore it early so
2734 * that the rest of migration path doesn't get confused by it.
2735 */
2736 if (src_cset->dead)
2737 return;
2738
2739 if (!list_empty(&src_cset->mg_src_preload_node))
2740 return;
2741
2742 src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);
2743
2744 WARN_ON(src_cset->mg_src_cgrp);
2745 WARN_ON(src_cset->mg_dst_cgrp);
2746 WARN_ON(!list_empty(&src_cset->mg_tasks));
2747 WARN_ON(!list_empty(&src_cset->mg_node));
2748
2749 src_cset->mg_src_cgrp = src_cgrp;
2750 src_cset->mg_dst_cgrp = dst_cgrp;
2751 get_css_set(src_cset);
2752 list_add_tail(&src_cset->mg_src_preload_node, &mgctx->preloaded_src_csets);
2753}
2754
2755/**
2756 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2757 * @mgctx: migration context
2758 *
2759 * Tasks are about to be moved and all the source css_sets have been
2760 * preloaded to @mgctx->preloaded_src_csets. This function looks up and
2761 * pins all destination css_sets, links each to its source, and append them
2762 * to @mgctx->preloaded_dst_csets.
2763 *
2764 * This function must be called after cgroup_migrate_add_src() has been
2765 * called on each migration source css_set. After migration is performed
2766 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2767 * @mgctx.
2768 */
2769int cgroup_migrate_prepare_dst(struct cgroup_mgctx *mgctx)
2770{
2771 struct css_set *src_cset, *tmp_cset;
2772
2773 lockdep_assert_held(&cgroup_mutex);
2774
2775 /* look up the dst cset for each src cset and link it to src */
2776 list_for_each_entry_safe(src_cset, tmp_cset, &mgctx->preloaded_src_csets,
2777 mg_src_preload_node) {
2778 struct css_set *dst_cset;
2779 struct cgroup_subsys *ss;
2780 int ssid;
2781
2782 dst_cset = find_css_set(src_cset, src_cset->mg_dst_cgrp);
2783 if (!dst_cset)
2784 return -ENOMEM;
2785
2786 WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
2787
2788 /*
2789 * If src cset equals dst, it's noop. Drop the src.
2790 * cgroup_migrate() will skip the cset too. Note that we
2791 * can't handle src == dst as some nodes are used by both.
2792 */
2793 if (src_cset == dst_cset) {
2794 src_cset->mg_src_cgrp = NULL;
2795 src_cset->mg_dst_cgrp = NULL;
2796 list_del_init(&src_cset->mg_src_preload_node);
2797 put_css_set(src_cset);
2798 put_css_set(dst_cset);
2799 continue;
2800 }
2801
2802 src_cset->mg_dst_cset = dst_cset;
2803
2804 if (list_empty(&dst_cset->mg_dst_preload_node))
2805 list_add_tail(&dst_cset->mg_dst_preload_node,
2806 &mgctx->preloaded_dst_csets);
2807 else
2808 put_css_set(dst_cset);
2809
2810 for_each_subsys(ss, ssid)
2811 if (src_cset->subsys[ssid] != dst_cset->subsys[ssid])
2812 mgctx->ss_mask |= 1 << ssid;
2813 }
2814
2815 return 0;
2816}
2817
2818/**
2819 * cgroup_migrate - migrate a process or task to a cgroup
2820 * @leader: the leader of the process or the task to migrate
2821 * @threadgroup: whether @leader points to the whole process or a single task
2822 * @mgctx: migration context
2823 *
2824 * Migrate a process or task denoted by @leader. If migrating a process,
2825 * the caller must be holding cgroup_threadgroup_rwsem. The caller is also
2826 * responsible for invoking cgroup_migrate_add_src() and
2827 * cgroup_migrate_prepare_dst() on the targets before invoking this
2828 * function and following up with cgroup_migrate_finish().
2829 *
2830 * As long as a controller's ->can_attach() doesn't fail, this function is
2831 * guaranteed to succeed. This means that, excluding ->can_attach()
2832 * failure, when migrating multiple targets, the success or failure can be
2833 * decided for all targets by invoking group_migrate_prepare_dst() before
2834 * actually starting migrating.
2835 */
2836int cgroup_migrate(struct task_struct *leader, bool threadgroup,
2837 struct cgroup_mgctx *mgctx)
2838{
2839 struct task_struct *task;
2840
2841 /*
2842 * The following thread iteration should be inside an RCU critical
2843 * section to prevent tasks from being freed while taking the snapshot.
2844 * spin_lock_irq() implies RCU critical section here.
2845 */
2846 spin_lock_irq(&css_set_lock);
2847 task = leader;
2848 do {
2849 cgroup_migrate_add_task(task, mgctx);
2850 if (!threadgroup)
2851 break;
2852 } while_each_thread(leader, task);
2853 spin_unlock_irq(&css_set_lock);
2854
2855 return cgroup_migrate_execute(mgctx);
2856}
2857
2858/**
2859 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2860 * @dst_cgrp: the cgroup to attach to
2861 * @leader: the task or the leader of the threadgroup to be attached
2862 * @threadgroup: attach the whole threadgroup?
2863 *
2864 * Call holding cgroup_mutex and cgroup_threadgroup_rwsem.
2865 */
2866int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
2867 bool threadgroup)
2868{
2869 DEFINE_CGROUP_MGCTX(mgctx);
2870 struct task_struct *task;
2871 int ret = 0;
2872
2873 /* look up all src csets */
2874 spin_lock_irq(&css_set_lock);
2875 rcu_read_lock();
2876 task = leader;
2877 do {
2878 cgroup_migrate_add_src(task_css_set(task), dst_cgrp, &mgctx);
2879 if (!threadgroup)
2880 break;
2881 } while_each_thread(leader, task);
2882 rcu_read_unlock();
2883 spin_unlock_irq(&css_set_lock);
2884
2885 /* prepare dst csets and commit */
2886 ret = cgroup_migrate_prepare_dst(&mgctx);
2887 if (!ret)
2888 ret = cgroup_migrate(leader, threadgroup, &mgctx);
2889
2890 cgroup_migrate_finish(&mgctx);
2891
2892 if (!ret)
2893 TRACE_CGROUP_PATH(attach_task, dst_cgrp, leader, threadgroup);
2894
2895 return ret;
2896}
2897
2898struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup,
2899 bool *threadgroup_locked)
2900{
2901 struct task_struct *tsk;
2902 pid_t pid;
2903
2904 if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
2905 return ERR_PTR(-EINVAL);
2906
2907 /*
2908 * If we migrate a single thread, we don't care about threadgroup
2909 * stability. If the thread is `current`, it won't exit(2) under our
2910 * hands or change PID through exec(2). We exclude
2911 * cgroup_update_dfl_csses and other cgroup_{proc,thread}s_write
2912 * callers by cgroup_mutex.
2913 * Therefore, we can skip the global lock.
2914 */
2915 lockdep_assert_held(&cgroup_mutex);
2916 *threadgroup_locked = pid || threadgroup;
2917 cgroup_attach_lock(*threadgroup_locked);
2918
2919 rcu_read_lock();
2920 if (pid) {
2921 tsk = find_task_by_vpid(pid);
2922 if (!tsk) {
2923 tsk = ERR_PTR(-ESRCH);
2924 goto out_unlock_threadgroup;
2925 }
2926 } else {
2927 tsk = current;
2928 }
2929
2930 if (threadgroup)
2931 tsk = tsk->group_leader;
2932
2933 /*
2934 * kthreads may acquire PF_NO_SETAFFINITY during initialization.
2935 * If userland migrates such a kthread to a non-root cgroup, it can
2936 * become trapped in a cpuset, or RT kthread may be born in a
2937 * cgroup with no rt_runtime allocated. Just say no.
2938 */
2939 if (tsk->no_cgroup_migration || (tsk->flags & PF_NO_SETAFFINITY)) {
2940 tsk = ERR_PTR(-EINVAL);
2941 goto out_unlock_threadgroup;
2942 }
2943
2944 get_task_struct(tsk);
2945 goto out_unlock_rcu;
2946
2947out_unlock_threadgroup:
2948 cgroup_attach_unlock(*threadgroup_locked);
2949 *threadgroup_locked = false;
2950out_unlock_rcu:
2951 rcu_read_unlock();
2952 return tsk;
2953}
2954
2955void cgroup_procs_write_finish(struct task_struct *task, bool threadgroup_locked)
2956{
2957 struct cgroup_subsys *ss;
2958 int ssid;
2959
2960 /* release reference from cgroup_procs_write_start() */
2961 put_task_struct(task);
2962
2963 cgroup_attach_unlock(threadgroup_locked);
2964
2965 for_each_subsys(ss, ssid)
2966 if (ss->post_attach)
2967 ss->post_attach();
2968}
2969
2970static void cgroup_print_ss_mask(struct seq_file *seq, u16 ss_mask)
2971{
2972 struct cgroup_subsys *ss;
2973 bool printed = false;
2974 int ssid;
2975
2976 do_each_subsys_mask(ss, ssid, ss_mask) {
2977 if (printed)
2978 seq_putc(seq, ' ');
2979 seq_puts(seq, ss->name);
2980 printed = true;
2981 } while_each_subsys_mask();
2982 if (printed)
2983 seq_putc(seq, '\n');
2984}
2985
2986/* show controllers which are enabled from the parent */
2987static int cgroup_controllers_show(struct seq_file *seq, void *v)
2988{
2989 struct cgroup *cgrp = seq_css(seq)->cgroup;
2990
2991 cgroup_print_ss_mask(seq, cgroup_control(cgrp));
2992 return 0;
2993}
2994
2995/* show controllers which are enabled for a given cgroup's children */
2996static int cgroup_subtree_control_show(struct seq_file *seq, void *v)
2997{
2998 struct cgroup *cgrp = seq_css(seq)->cgroup;
2999
3000 cgroup_print_ss_mask(seq, cgrp->subtree_control);
3001 return 0;
3002}
3003
3004/**
3005 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
3006 * @cgrp: root of the subtree to update csses for
3007 *
3008 * @cgrp's control masks have changed and its subtree's css associations
3009 * need to be updated accordingly. This function looks up all css_sets
3010 * which are attached to the subtree, creates the matching updated css_sets
3011 * and migrates the tasks to the new ones.
3012 */
3013static int cgroup_update_dfl_csses(struct cgroup *cgrp)
3014{
3015 DEFINE_CGROUP_MGCTX(mgctx);
3016 struct cgroup_subsys_state *d_css;
3017 struct cgroup *dsct;
3018 struct css_set *src_cset;
3019 bool has_tasks;
3020 int ret;
3021
3022 lockdep_assert_held(&cgroup_mutex);
3023
3024 /* look up all csses currently attached to @cgrp's subtree */
3025 spin_lock_irq(&css_set_lock);
3026 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3027 struct cgrp_cset_link *link;
3028
3029 /*
3030 * As cgroup_update_dfl_csses() is only called by
3031 * cgroup_apply_control(). The csses associated with the
3032 * given cgrp will not be affected by changes made to
3033 * its subtree_control file. We can skip them.
3034 */
3035 if (dsct == cgrp)
3036 continue;
3037
3038 list_for_each_entry(link, &dsct->cset_links, cset_link)
3039 cgroup_migrate_add_src(link->cset, dsct, &mgctx);
3040 }
3041 spin_unlock_irq(&css_set_lock);
3042
3043 /*
3044 * We need to write-lock threadgroup_rwsem while migrating tasks.
3045 * However, if there are no source csets for @cgrp, changing its
3046 * controllers isn't gonna produce any task migrations and the
3047 * write-locking can be skipped safely.
3048 */
3049 has_tasks = !list_empty(&mgctx.preloaded_src_csets);
3050 cgroup_attach_lock(has_tasks);
3051
3052 /* NULL dst indicates self on default hierarchy */
3053 ret = cgroup_migrate_prepare_dst(&mgctx);
3054 if (ret)
3055 goto out_finish;
3056
3057 spin_lock_irq(&css_set_lock);
3058 list_for_each_entry(src_cset, &mgctx.preloaded_src_csets,
3059 mg_src_preload_node) {
3060 struct task_struct *task, *ntask;
3061
3062 /* all tasks in src_csets need to be migrated */
3063 list_for_each_entry_safe(task, ntask, &src_cset->tasks, cg_list)
3064 cgroup_migrate_add_task(task, &mgctx);
3065 }
3066 spin_unlock_irq(&css_set_lock);
3067
3068 ret = cgroup_migrate_execute(&mgctx);
3069out_finish:
3070 cgroup_migrate_finish(&mgctx);
3071 cgroup_attach_unlock(has_tasks);
3072 return ret;
3073}
3074
3075/**
3076 * cgroup_lock_and_drain_offline - lock cgroup_mutex and drain offlined csses
3077 * @cgrp: root of the target subtree
3078 *
3079 * Because css offlining is asynchronous, userland may try to re-enable a
3080 * controller while the previous css is still around. This function grabs
3081 * cgroup_mutex and drains the previous css instances of @cgrp's subtree.
3082 */
3083void cgroup_lock_and_drain_offline(struct cgroup *cgrp)
3084 __acquires(&cgroup_mutex)
3085{
3086 struct cgroup *dsct;
3087 struct cgroup_subsys_state *d_css;
3088 struct cgroup_subsys *ss;
3089 int ssid;
3090
3091restart:
3092 cgroup_lock();
3093
3094 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3095 for_each_subsys(ss, ssid) {
3096 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3097 DEFINE_WAIT(wait);
3098
3099 if (!css || !percpu_ref_is_dying(&css->refcnt))
3100 continue;
3101
3102 cgroup_get_live(dsct);
3103 prepare_to_wait(&dsct->offline_waitq, &wait,
3104 TASK_UNINTERRUPTIBLE);
3105
3106 cgroup_unlock();
3107 schedule();
3108 finish_wait(&dsct->offline_waitq, &wait);
3109
3110 cgroup_put(dsct);
3111 goto restart;
3112 }
3113 }
3114}
3115
3116/**
3117 * cgroup_save_control - save control masks and dom_cgrp of a subtree
3118 * @cgrp: root of the target subtree
3119 *
3120 * Save ->subtree_control, ->subtree_ss_mask and ->dom_cgrp to the
3121 * respective old_ prefixed fields for @cgrp's subtree including @cgrp
3122 * itself.
3123 */
3124static void cgroup_save_control(struct cgroup *cgrp)
3125{
3126 struct cgroup *dsct;
3127 struct cgroup_subsys_state *d_css;
3128
3129 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3130 dsct->old_subtree_control = dsct->subtree_control;
3131 dsct->old_subtree_ss_mask = dsct->subtree_ss_mask;
3132 dsct->old_dom_cgrp = dsct->dom_cgrp;
3133 }
3134}
3135
3136/**
3137 * cgroup_propagate_control - refresh control masks of a subtree
3138 * @cgrp: root of the target subtree
3139 *
3140 * For @cgrp and its subtree, ensure ->subtree_ss_mask matches
3141 * ->subtree_control and propagate controller availability through the
3142 * subtree so that descendants don't have unavailable controllers enabled.
3143 */
3144static void cgroup_propagate_control(struct cgroup *cgrp)
3145{
3146 struct cgroup *dsct;
3147 struct cgroup_subsys_state *d_css;
3148
3149 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3150 dsct->subtree_control &= cgroup_control(dsct);
3151 dsct->subtree_ss_mask =
3152 cgroup_calc_subtree_ss_mask(dsct->subtree_control,
3153 cgroup_ss_mask(dsct));
3154 }
3155}
3156
3157/**
3158 * cgroup_restore_control - restore control masks and dom_cgrp of a subtree
3159 * @cgrp: root of the target subtree
3160 *
3161 * Restore ->subtree_control, ->subtree_ss_mask and ->dom_cgrp from the
3162 * respective old_ prefixed fields for @cgrp's subtree including @cgrp
3163 * itself.
3164 */
3165static void cgroup_restore_control(struct cgroup *cgrp)
3166{
3167 struct cgroup *dsct;
3168 struct cgroup_subsys_state *d_css;
3169
3170 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3171 dsct->subtree_control = dsct->old_subtree_control;
3172 dsct->subtree_ss_mask = dsct->old_subtree_ss_mask;
3173 dsct->dom_cgrp = dsct->old_dom_cgrp;
3174 }
3175}
3176
3177static bool css_visible(struct cgroup_subsys_state *css)
3178{
3179 struct cgroup_subsys *ss = css->ss;
3180 struct cgroup *cgrp = css->cgroup;
3181
3182 if (cgroup_control(cgrp) & (1 << ss->id))
3183 return true;
3184 if (!(cgroup_ss_mask(cgrp) & (1 << ss->id)))
3185 return false;
3186 return cgroup_on_dfl(cgrp) && ss->implicit_on_dfl;
3187}
3188
3189/**
3190 * cgroup_apply_control_enable - enable or show csses according to control
3191 * @cgrp: root of the target subtree
3192 *
3193 * Walk @cgrp's subtree and create new csses or make the existing ones
3194 * visible. A css is created invisible if it's being implicitly enabled
3195 * through dependency. An invisible css is made visible when the userland
3196 * explicitly enables it.
3197 *
3198 * Returns 0 on success, -errno on failure. On failure, csses which have
3199 * been processed already aren't cleaned up. The caller is responsible for
3200 * cleaning up with cgroup_apply_control_disable().
3201 */
3202static int cgroup_apply_control_enable(struct cgroup *cgrp)
3203{
3204 struct cgroup *dsct;
3205 struct cgroup_subsys_state *d_css;
3206 struct cgroup_subsys *ss;
3207 int ssid, ret;
3208
3209 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3210 for_each_subsys(ss, ssid) {
3211 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3212
3213 if (!(cgroup_ss_mask(dsct) & (1 << ss->id)))
3214 continue;
3215
3216 if (!css) {
3217 css = css_create(dsct, ss);
3218 if (IS_ERR(css))
3219 return PTR_ERR(css);
3220 }
3221
3222 WARN_ON_ONCE(percpu_ref_is_dying(&css->refcnt));
3223
3224 if (css_visible(css)) {
3225 ret = css_populate_dir(css);
3226 if (ret)
3227 return ret;
3228 }
3229 }
3230 }
3231
3232 return 0;
3233}
3234
3235/**
3236 * cgroup_apply_control_disable - kill or hide csses according to control
3237 * @cgrp: root of the target subtree
3238 *
3239 * Walk @cgrp's subtree and kill and hide csses so that they match
3240 * cgroup_ss_mask() and cgroup_visible_mask().
3241 *
3242 * A css is hidden when the userland requests it to be disabled while other
3243 * subsystems are still depending on it. The css must not actively control
3244 * resources and be in the vanilla state if it's made visible again later.
3245 * Controllers which may be depended upon should provide ->css_reset() for
3246 * this purpose.
3247 */
3248static void cgroup_apply_control_disable(struct cgroup *cgrp)
3249{
3250 struct cgroup *dsct;
3251 struct cgroup_subsys_state *d_css;
3252 struct cgroup_subsys *ss;
3253 int ssid;
3254
3255 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3256 for_each_subsys(ss, ssid) {
3257 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3258
3259 if (!css)
3260 continue;
3261
3262 WARN_ON_ONCE(percpu_ref_is_dying(&css->refcnt));
3263
3264 if (css->parent &&
3265 !(cgroup_ss_mask(dsct) & (1 << ss->id))) {
3266 kill_css(css);
3267 } else if (!css_visible(css)) {
3268 css_clear_dir(css);
3269 if (ss->css_reset)
3270 ss->css_reset(css);
3271 }
3272 }
3273 }
3274}
3275
3276/**
3277 * cgroup_apply_control - apply control mask updates to the subtree
3278 * @cgrp: root of the target subtree
3279 *
3280 * subsystems can be enabled and disabled in a subtree using the following
3281 * steps.
3282 *
3283 * 1. Call cgroup_save_control() to stash the current state.
3284 * 2. Update ->subtree_control masks in the subtree as desired.
3285 * 3. Call cgroup_apply_control() to apply the changes.
3286 * 4. Optionally perform other related operations.
3287 * 5. Call cgroup_finalize_control() to finish up.
3288 *
3289 * This function implements step 3 and propagates the mask changes
3290 * throughout @cgrp's subtree, updates csses accordingly and perform
3291 * process migrations.
3292 */
3293static int cgroup_apply_control(struct cgroup *cgrp)
3294{
3295 int ret;
3296
3297 cgroup_propagate_control(cgrp);
3298
3299 ret = cgroup_apply_control_enable(cgrp);
3300 if (ret)
3301 return ret;
3302
3303 /*
3304 * At this point, cgroup_e_css_by_mask() results reflect the new csses
3305 * making the following cgroup_update_dfl_csses() properly update
3306 * css associations of all tasks in the subtree.
3307 */
3308 return cgroup_update_dfl_csses(cgrp);
3309}
3310
3311/**
3312 * cgroup_finalize_control - finalize control mask update
3313 * @cgrp: root of the target subtree
3314 * @ret: the result of the update
3315 *
3316 * Finalize control mask update. See cgroup_apply_control() for more info.
3317 */
3318static void cgroup_finalize_control(struct cgroup *cgrp, int ret)
3319{
3320 if (ret) {
3321 cgroup_restore_control(cgrp);
3322 cgroup_propagate_control(cgrp);
3323 }
3324
3325 cgroup_apply_control_disable(cgrp);
3326}
3327
3328static int cgroup_vet_subtree_control_enable(struct cgroup *cgrp, u16 enable)
3329{
3330 u16 domain_enable = enable & ~cgrp_dfl_threaded_ss_mask;
3331
3332 /* if nothing is getting enabled, nothing to worry about */
3333 if (!enable)
3334 return 0;
3335
3336 /* can @cgrp host any resources? */
3337 if (!cgroup_is_valid_domain(cgrp->dom_cgrp))
3338 return -EOPNOTSUPP;
3339
3340 /* mixables don't care */
3341 if (cgroup_is_mixable(cgrp))
3342 return 0;
3343
3344 if (domain_enable) {
3345 /* can't enable domain controllers inside a thread subtree */
3346 if (cgroup_is_thread_root(cgrp) || cgroup_is_threaded(cgrp))
3347 return -EOPNOTSUPP;
3348 } else {
3349 /*
3350 * Threaded controllers can handle internal competitions
3351 * and are always allowed inside a (prospective) thread
3352 * subtree.
3353 */
3354 if (cgroup_can_be_thread_root(cgrp) || cgroup_is_threaded(cgrp))
3355 return 0;
3356 }
3357
3358 /*
3359 * Controllers can't be enabled for a cgroup with tasks to avoid
3360 * child cgroups competing against tasks.
3361 */
3362 if (cgroup_has_tasks(cgrp))
3363 return -EBUSY;
3364
3365 return 0;
3366}
3367
3368/* change the enabled child controllers for a cgroup in the default hierarchy */
3369static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
3370 char *buf, size_t nbytes,
3371 loff_t off)
3372{
3373 u16 enable = 0, disable = 0;
3374 struct cgroup *cgrp, *child;
3375 struct cgroup_subsys *ss;
3376 char *tok;
3377 int ssid, ret;
3378
3379 /*
3380 * Parse input - space separated list of subsystem names prefixed
3381 * with either + or -.
3382 */
3383 buf = strstrip(buf);
3384 while ((tok = strsep(&buf, " "))) {
3385 if (tok[0] == '\0')
3386 continue;
3387 do_each_subsys_mask(ss, ssid, ~cgrp_dfl_inhibit_ss_mask) {
3388 if (!cgroup_ssid_enabled(ssid) ||
3389 strcmp(tok + 1, ss->name))
3390 continue;
3391
3392 if (*tok == '+') {
3393 enable |= 1 << ssid;
3394 disable &= ~(1 << ssid);
3395 } else if (*tok == '-') {
3396 disable |= 1 << ssid;
3397 enable &= ~(1 << ssid);
3398 } else {
3399 return -EINVAL;
3400 }
3401 break;
3402 } while_each_subsys_mask();
3403 if (ssid == CGROUP_SUBSYS_COUNT)
3404 return -EINVAL;
3405 }
3406
3407 cgrp = cgroup_kn_lock_live(of->kn, true);
3408 if (!cgrp)
3409 return -ENODEV;
3410
3411 for_each_subsys(ss, ssid) {
3412 if (enable & (1 << ssid)) {
3413 if (cgrp->subtree_control & (1 << ssid)) {
3414 enable &= ~(1 << ssid);
3415 continue;
3416 }
3417
3418 if (!(cgroup_control(cgrp) & (1 << ssid))) {
3419 ret = -ENOENT;
3420 goto out_unlock;
3421 }
3422 } else if (disable & (1 << ssid)) {
3423 if (!(cgrp->subtree_control & (1 << ssid))) {
3424 disable &= ~(1 << ssid);
3425 continue;
3426 }
3427
3428 /* a child has it enabled? */
3429 cgroup_for_each_live_child(child, cgrp) {
3430 if (child->subtree_control & (1 << ssid)) {
3431 ret = -EBUSY;
3432 goto out_unlock;
3433 }
3434 }
3435 }
3436 }
3437
3438 if (!enable && !disable) {
3439 ret = 0;
3440 goto out_unlock;
3441 }
3442
3443 ret = cgroup_vet_subtree_control_enable(cgrp, enable);
3444 if (ret)
3445 goto out_unlock;
3446
3447 /* save and update control masks and prepare csses */
3448 cgroup_save_control(cgrp);
3449
3450 cgrp->subtree_control |= enable;
3451 cgrp->subtree_control &= ~disable;
3452
3453 ret = cgroup_apply_control(cgrp);
3454 cgroup_finalize_control(cgrp, ret);
3455 if (ret)
3456 goto out_unlock;
3457
3458 kernfs_activate(cgrp->kn);
3459out_unlock:
3460 cgroup_kn_unlock(of->kn);
3461 return ret ?: nbytes;
3462}
3463
3464/**
3465 * cgroup_enable_threaded - make @cgrp threaded
3466 * @cgrp: the target cgroup
3467 *
3468 * Called when "threaded" is written to the cgroup.type interface file and
3469 * tries to make @cgrp threaded and join the parent's resource domain.
3470 * This function is never called on the root cgroup as cgroup.type doesn't
3471 * exist on it.
3472 */
3473static int cgroup_enable_threaded(struct cgroup *cgrp)
3474{
3475 struct cgroup *parent = cgroup_parent(cgrp);
3476 struct cgroup *dom_cgrp = parent->dom_cgrp;
3477 struct cgroup *dsct;
3478 struct cgroup_subsys_state *d_css;
3479 int ret;
3480
3481 lockdep_assert_held(&cgroup_mutex);
3482
3483 /* noop if already threaded */
3484 if (cgroup_is_threaded(cgrp))
3485 return 0;
3486
3487 /*
3488 * If @cgroup is populated or has domain controllers enabled, it
3489 * can't be switched. While the below cgroup_can_be_thread_root()
3490 * test can catch the same conditions, that's only when @parent is
3491 * not mixable, so let's check it explicitly.
3492 */
3493 if (cgroup_is_populated(cgrp) ||
3494 cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)
3495 return -EOPNOTSUPP;
3496
3497 /* we're joining the parent's domain, ensure its validity */
3498 if (!cgroup_is_valid_domain(dom_cgrp) ||
3499 !cgroup_can_be_thread_root(dom_cgrp))
3500 return -EOPNOTSUPP;
3501
3502 /*
3503 * The following shouldn't cause actual migrations and should
3504 * always succeed.
3505 */
3506 cgroup_save_control(cgrp);
3507
3508 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp)
3509 if (dsct == cgrp || cgroup_is_threaded(dsct))
3510 dsct->dom_cgrp = dom_cgrp;
3511
3512 ret = cgroup_apply_control(cgrp);
3513 if (!ret)
3514 parent->nr_threaded_children++;
3515
3516 cgroup_finalize_control(cgrp, ret);
3517 return ret;
3518}
3519
3520static int cgroup_type_show(struct seq_file *seq, void *v)
3521{
3522 struct cgroup *cgrp = seq_css(seq)->cgroup;
3523
3524 if (cgroup_is_threaded(cgrp))
3525 seq_puts(seq, "threaded\n");
3526 else if (!cgroup_is_valid_domain(cgrp))
3527 seq_puts(seq, "domain invalid\n");
3528 else if (cgroup_is_thread_root(cgrp))
3529 seq_puts(seq, "domain threaded\n");
3530 else
3531 seq_puts(seq, "domain\n");
3532
3533 return 0;
3534}
3535
3536static ssize_t cgroup_type_write(struct kernfs_open_file *of, char *buf,
3537 size_t nbytes, loff_t off)
3538{
3539 struct cgroup *cgrp;
3540 int ret;
3541
3542 /* only switching to threaded mode is supported */
3543 if (strcmp(strstrip(buf), "threaded"))
3544 return -EINVAL;
3545
3546 /* drain dying csses before we re-apply (threaded) subtree control */
3547 cgrp = cgroup_kn_lock_live(of->kn, true);
3548 if (!cgrp)
3549 return -ENOENT;
3550
3551 /* threaded can only be enabled */
3552 ret = cgroup_enable_threaded(cgrp);
3553
3554 cgroup_kn_unlock(of->kn);
3555 return ret ?: nbytes;
3556}
3557
3558static int cgroup_max_descendants_show(struct seq_file *seq, void *v)
3559{
3560 struct cgroup *cgrp = seq_css(seq)->cgroup;
3561 int descendants = READ_ONCE(cgrp->max_descendants);
3562
3563 if (descendants == INT_MAX)
3564 seq_puts(seq, "max\n");
3565 else
3566 seq_printf(seq, "%d\n", descendants);
3567
3568 return 0;
3569}
3570
3571static ssize_t cgroup_max_descendants_write(struct kernfs_open_file *of,
3572 char *buf, size_t nbytes, loff_t off)
3573{
3574 struct cgroup *cgrp;
3575 int descendants;
3576 ssize_t ret;
3577
3578 buf = strstrip(buf);
3579 if (!strcmp(buf, "max")) {
3580 descendants = INT_MAX;
3581 } else {
3582 ret = kstrtoint(buf, 0, &descendants);
3583 if (ret)
3584 return ret;
3585 }
3586
3587 if (descendants < 0)
3588 return -ERANGE;
3589
3590 cgrp = cgroup_kn_lock_live(of->kn, false);
3591 if (!cgrp)
3592 return -ENOENT;
3593
3594 cgrp->max_descendants = descendants;
3595
3596 cgroup_kn_unlock(of->kn);
3597
3598 return nbytes;
3599}
3600
3601static int cgroup_max_depth_show(struct seq_file *seq, void *v)
3602{
3603 struct cgroup *cgrp = seq_css(seq)->cgroup;
3604 int depth = READ_ONCE(cgrp->max_depth);
3605
3606 if (depth == INT_MAX)
3607 seq_puts(seq, "max\n");
3608 else
3609 seq_printf(seq, "%d\n", depth);
3610
3611 return 0;
3612}
3613
3614static ssize_t cgroup_max_depth_write(struct kernfs_open_file *of,
3615 char *buf, size_t nbytes, loff_t off)
3616{
3617 struct cgroup *cgrp;
3618 ssize_t ret;
3619 int depth;
3620
3621 buf = strstrip(buf);
3622 if (!strcmp(buf, "max")) {
3623 depth = INT_MAX;
3624 } else {
3625 ret = kstrtoint(buf, 0, &depth);
3626 if (ret)
3627 return ret;
3628 }
3629
3630 if (depth < 0)
3631 return -ERANGE;
3632
3633 cgrp = cgroup_kn_lock_live(of->kn, false);
3634 if (!cgrp)
3635 return -ENOENT;
3636
3637 cgrp->max_depth = depth;
3638
3639 cgroup_kn_unlock(of->kn);
3640
3641 return nbytes;
3642}
3643
3644static int cgroup_events_show(struct seq_file *seq, void *v)
3645{
3646 struct cgroup *cgrp = seq_css(seq)->cgroup;
3647
3648 seq_printf(seq, "populated %d\n", cgroup_is_populated(cgrp));
3649 seq_printf(seq, "frozen %d\n", test_bit(CGRP_FROZEN, &cgrp->flags));
3650
3651 return 0;
3652}
3653
3654static int cgroup_stat_show(struct seq_file *seq, void *v)
3655{
3656 struct cgroup *cgroup = seq_css(seq)->cgroup;
3657
3658 seq_printf(seq, "nr_descendants %d\n",
3659 cgroup->nr_descendants);
3660 seq_printf(seq, "nr_dying_descendants %d\n",
3661 cgroup->nr_dying_descendants);
3662
3663 return 0;
3664}
3665
3666#ifdef CONFIG_CGROUP_SCHED
3667/**
3668 * cgroup_tryget_css - try to get a cgroup's css for the specified subsystem
3669 * @cgrp: the cgroup of interest
3670 * @ss: the subsystem of interest
3671 *
3672 * Find and get @cgrp's css associated with @ss. If the css doesn't exist
3673 * or is offline, %NULL is returned.
3674 */
3675static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp,
3676 struct cgroup_subsys *ss)
3677{
3678 struct cgroup_subsys_state *css;
3679
3680 rcu_read_lock();
3681 css = cgroup_css(cgrp, ss);
3682 if (css && !css_tryget_online(css))
3683 css = NULL;
3684 rcu_read_unlock();
3685
3686 return css;
3687}
3688
3689static int cgroup_extra_stat_show(struct seq_file *seq, int ssid)
3690{
3691 struct cgroup *cgrp = seq_css(seq)->cgroup;
3692 struct cgroup_subsys *ss = cgroup_subsys[ssid];
3693 struct cgroup_subsys_state *css;
3694 int ret;
3695
3696 if (!ss->css_extra_stat_show)
3697 return 0;
3698
3699 css = cgroup_tryget_css(cgrp, ss);
3700 if (!css)
3701 return 0;
3702
3703 ret = ss->css_extra_stat_show(seq, css);
3704 css_put(css);
3705 return ret;
3706}
3707
3708static int cgroup_local_stat_show(struct seq_file *seq,
3709 struct cgroup *cgrp, int ssid)
3710{
3711 struct cgroup_subsys *ss = cgroup_subsys[ssid];
3712 struct cgroup_subsys_state *css;
3713 int ret;
3714
3715 if (!ss->css_local_stat_show)
3716 return 0;
3717
3718 css = cgroup_tryget_css(cgrp, ss);
3719 if (!css)
3720 return 0;
3721
3722 ret = ss->css_local_stat_show(seq, css);
3723 css_put(css);
3724 return ret;
3725}
3726#endif
3727
3728static int cpu_stat_show(struct seq_file *seq, void *v)
3729{
3730 int ret = 0;
3731
3732 cgroup_base_stat_cputime_show(seq);
3733#ifdef CONFIG_CGROUP_SCHED
3734 ret = cgroup_extra_stat_show(seq, cpu_cgrp_id);
3735#endif
3736 return ret;
3737}
3738
3739static int cpu_local_stat_show(struct seq_file *seq, void *v)
3740{
3741 struct cgroup __maybe_unused *cgrp = seq_css(seq)->cgroup;
3742 int ret = 0;
3743
3744#ifdef CONFIG_CGROUP_SCHED
3745 ret = cgroup_local_stat_show(seq, cgrp, cpu_cgrp_id);
3746#endif
3747 return ret;
3748}
3749
3750#ifdef CONFIG_PSI
3751static int cgroup_io_pressure_show(struct seq_file *seq, void *v)
3752{
3753 struct cgroup *cgrp = seq_css(seq)->cgroup;
3754 struct psi_group *psi = cgroup_psi(cgrp);
3755
3756 return psi_show(seq, psi, PSI_IO);
3757}
3758static int cgroup_memory_pressure_show(struct seq_file *seq, void *v)
3759{
3760 struct cgroup *cgrp = seq_css(seq)->cgroup;
3761 struct psi_group *psi = cgroup_psi(cgrp);
3762
3763 return psi_show(seq, psi, PSI_MEM);
3764}
3765static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v)
3766{
3767 struct cgroup *cgrp = seq_css(seq)->cgroup;
3768 struct psi_group *psi = cgroup_psi(cgrp);
3769
3770 return psi_show(seq, psi, PSI_CPU);
3771}
3772
3773static ssize_t pressure_write(struct kernfs_open_file *of, char *buf,
3774 size_t nbytes, enum psi_res res)
3775{
3776 struct cgroup_file_ctx *ctx = of->priv;
3777 struct psi_trigger *new;
3778 struct cgroup *cgrp;
3779 struct psi_group *psi;
3780
3781 cgrp = cgroup_kn_lock_live(of->kn, false);
3782 if (!cgrp)
3783 return -ENODEV;
3784
3785 cgroup_get(cgrp);
3786 cgroup_kn_unlock(of->kn);
3787
3788 /* Allow only one trigger per file descriptor */
3789 if (ctx->psi.trigger) {
3790 cgroup_put(cgrp);
3791 return -EBUSY;
3792 }
3793
3794 psi = cgroup_psi(cgrp);
3795 new = psi_trigger_create(psi, buf, res, of->file, of);
3796 if (IS_ERR(new)) {
3797 cgroup_put(cgrp);
3798 return PTR_ERR(new);
3799 }
3800
3801 smp_store_release(&ctx->psi.trigger, new);
3802 cgroup_put(cgrp);
3803
3804 return nbytes;
3805}
3806
3807static ssize_t cgroup_io_pressure_write(struct kernfs_open_file *of,
3808 char *buf, size_t nbytes,
3809 loff_t off)
3810{
3811 return pressure_write(of, buf, nbytes, PSI_IO);
3812}
3813
3814static ssize_t cgroup_memory_pressure_write(struct kernfs_open_file *of,
3815 char *buf, size_t nbytes,
3816 loff_t off)
3817{
3818 return pressure_write(of, buf, nbytes, PSI_MEM);
3819}
3820
3821static ssize_t cgroup_cpu_pressure_write(struct kernfs_open_file *of,
3822 char *buf, size_t nbytes,
3823 loff_t off)
3824{
3825 return pressure_write(of, buf, nbytes, PSI_CPU);
3826}
3827
3828#ifdef CONFIG_IRQ_TIME_ACCOUNTING
3829static int cgroup_irq_pressure_show(struct seq_file *seq, void *v)
3830{
3831 struct cgroup *cgrp = seq_css(seq)->cgroup;
3832 struct psi_group *psi = cgroup_psi(cgrp);
3833
3834 return psi_show(seq, psi, PSI_IRQ);
3835}
3836
3837static ssize_t cgroup_irq_pressure_write(struct kernfs_open_file *of,
3838 char *buf, size_t nbytes,
3839 loff_t off)
3840{
3841 return pressure_write(of, buf, nbytes, PSI_IRQ);
3842}
3843#endif
3844
3845static int cgroup_pressure_show(struct seq_file *seq, void *v)
3846{
3847 struct cgroup *cgrp = seq_css(seq)->cgroup;
3848 struct psi_group *psi = cgroup_psi(cgrp);
3849
3850 seq_printf(seq, "%d\n", psi->enabled);
3851
3852 return 0;
3853}
3854
3855static ssize_t cgroup_pressure_write(struct kernfs_open_file *of,
3856 char *buf, size_t nbytes,
3857 loff_t off)
3858{
3859 ssize_t ret;
3860 int enable;
3861 struct cgroup *cgrp;
3862 struct psi_group *psi;
3863
3864 ret = kstrtoint(strstrip(buf), 0, &enable);
3865 if (ret)
3866 return ret;
3867
3868 if (enable < 0 || enable > 1)
3869 return -ERANGE;
3870
3871 cgrp = cgroup_kn_lock_live(of->kn, false);
3872 if (!cgrp)
3873 return -ENOENT;
3874
3875 psi = cgroup_psi(cgrp);
3876 if (psi->enabled != enable) {
3877 int i;
3878
3879 /* show or hide {cpu,memory,io,irq}.pressure files */
3880 for (i = 0; i < NR_PSI_RESOURCES; i++)
3881 cgroup_file_show(&cgrp->psi_files[i], enable);
3882
3883 psi->enabled = enable;
3884 if (enable)
3885 psi_cgroup_restart(psi);
3886 }
3887
3888 cgroup_kn_unlock(of->kn);
3889
3890 return nbytes;
3891}
3892
3893static __poll_t cgroup_pressure_poll(struct kernfs_open_file *of,
3894 poll_table *pt)
3895{
3896 struct cgroup_file_ctx *ctx = of->priv;
3897
3898 return psi_trigger_poll(&ctx->psi.trigger, of->file, pt);
3899}
3900
3901static void cgroup_pressure_release(struct kernfs_open_file *of)
3902{
3903 struct cgroup_file_ctx *ctx = of->priv;
3904
3905 psi_trigger_destroy(ctx->psi.trigger);
3906}
3907
3908bool cgroup_psi_enabled(void)
3909{
3910 if (static_branch_likely(&psi_disabled))
3911 return false;
3912
3913 return (cgroup_feature_disable_mask & (1 << OPT_FEATURE_PRESSURE)) == 0;
3914}
3915
3916#else /* CONFIG_PSI */
3917bool cgroup_psi_enabled(void)
3918{
3919 return false;
3920}
3921
3922#endif /* CONFIG_PSI */
3923
3924static int cgroup_freeze_show(struct seq_file *seq, void *v)
3925{
3926 struct cgroup *cgrp = seq_css(seq)->cgroup;
3927
3928 seq_printf(seq, "%d\n", cgrp->freezer.freeze);
3929
3930 return 0;
3931}
3932
3933static ssize_t cgroup_freeze_write(struct kernfs_open_file *of,
3934 char *buf, size_t nbytes, loff_t off)
3935{
3936 struct cgroup *cgrp;
3937 ssize_t ret;
3938 int freeze;
3939
3940 ret = kstrtoint(strstrip(buf), 0, &freeze);
3941 if (ret)
3942 return ret;
3943
3944 if (freeze < 0 || freeze > 1)
3945 return -ERANGE;
3946
3947 cgrp = cgroup_kn_lock_live(of->kn, false);
3948 if (!cgrp)
3949 return -ENOENT;
3950
3951 cgroup_freeze(cgrp, freeze);
3952
3953 cgroup_kn_unlock(of->kn);
3954
3955 return nbytes;
3956}
3957
3958static void __cgroup_kill(struct cgroup *cgrp)
3959{
3960 struct css_task_iter it;
3961 struct task_struct *task;
3962
3963 lockdep_assert_held(&cgroup_mutex);
3964
3965 spin_lock_irq(&css_set_lock);
3966 set_bit(CGRP_KILL, &cgrp->flags);
3967 spin_unlock_irq(&css_set_lock);
3968
3969 css_task_iter_start(&cgrp->self, CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED, &it);
3970 while ((task = css_task_iter_next(&it))) {
3971 /* Ignore kernel threads here. */
3972 if (task->flags & PF_KTHREAD)
3973 continue;
3974
3975 /* Skip tasks that are already dying. */
3976 if (__fatal_signal_pending(task))
3977 continue;
3978
3979 send_sig(SIGKILL, task, 0);
3980 }
3981 css_task_iter_end(&it);
3982
3983 spin_lock_irq(&css_set_lock);
3984 clear_bit(CGRP_KILL, &cgrp->flags);
3985 spin_unlock_irq(&css_set_lock);
3986}
3987
3988static void cgroup_kill(struct cgroup *cgrp)
3989{
3990 struct cgroup_subsys_state *css;
3991 struct cgroup *dsct;
3992
3993 lockdep_assert_held(&cgroup_mutex);
3994
3995 cgroup_for_each_live_descendant_pre(dsct, css, cgrp)
3996 __cgroup_kill(dsct);
3997}
3998
3999static ssize_t cgroup_kill_write(struct kernfs_open_file *of, char *buf,
4000 size_t nbytes, loff_t off)
4001{
4002 ssize_t ret = 0;
4003 int kill;
4004 struct cgroup *cgrp;
4005
4006 ret = kstrtoint(strstrip(buf), 0, &kill);
4007 if (ret)
4008 return ret;
4009
4010 if (kill != 1)
4011 return -ERANGE;
4012
4013 cgrp = cgroup_kn_lock_live(of->kn, false);
4014 if (!cgrp)
4015 return -ENOENT;
4016
4017 /*
4018 * Killing is a process directed operation, i.e. the whole thread-group
4019 * is taken down so act like we do for cgroup.procs and only make this
4020 * writable in non-threaded cgroups.
4021 */
4022 if (cgroup_is_threaded(cgrp))
4023 ret = -EOPNOTSUPP;
4024 else
4025 cgroup_kill(cgrp);
4026
4027 cgroup_kn_unlock(of->kn);
4028
4029 return ret ?: nbytes;
4030}
4031
4032static int cgroup_file_open(struct kernfs_open_file *of)
4033{
4034 struct cftype *cft = of_cft(of);
4035 struct cgroup_file_ctx *ctx;
4036 int ret;
4037
4038 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
4039 if (!ctx)
4040 return -ENOMEM;
4041
4042 ctx->ns = current->nsproxy->cgroup_ns;
4043 get_cgroup_ns(ctx->ns);
4044 of->priv = ctx;
4045
4046 if (!cft->open)
4047 return 0;
4048
4049 ret = cft->open(of);
4050 if (ret) {
4051 put_cgroup_ns(ctx->ns);
4052 kfree(ctx);
4053 }
4054 return ret;
4055}
4056
4057static void cgroup_file_release(struct kernfs_open_file *of)
4058{
4059 struct cftype *cft = of_cft(of);
4060 struct cgroup_file_ctx *ctx = of->priv;
4061
4062 if (cft->release)
4063 cft->release(of);
4064 put_cgroup_ns(ctx->ns);
4065 kfree(ctx);
4066}
4067
4068static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
4069 size_t nbytes, loff_t off)
4070{
4071 struct cgroup_file_ctx *ctx = of->priv;
4072 struct cgroup *cgrp = of->kn->parent->priv;
4073 struct cftype *cft = of_cft(of);
4074 struct cgroup_subsys_state *css;
4075 int ret;
4076
4077 if (!nbytes)
4078 return 0;
4079
4080 /*
4081 * If namespaces are delegation boundaries, disallow writes to
4082 * files in an non-init namespace root from inside the namespace
4083 * except for the files explicitly marked delegatable -
4084 * cgroup.procs and cgroup.subtree_control.
4085 */
4086 if ((cgrp->root->flags & CGRP_ROOT_NS_DELEGATE) &&
4087 !(cft->flags & CFTYPE_NS_DELEGATABLE) &&
4088 ctx->ns != &init_cgroup_ns && ctx->ns->root_cset->dfl_cgrp == cgrp)
4089 return -EPERM;
4090
4091 if (cft->write)
4092 return cft->write(of, buf, nbytes, off);
4093
4094 /*
4095 * kernfs guarantees that a file isn't deleted with operations in
4096 * flight, which means that the matching css is and stays alive and
4097 * doesn't need to be pinned. The RCU locking is not necessary
4098 * either. It's just for the convenience of using cgroup_css().
4099 */
4100 rcu_read_lock();
4101 css = cgroup_css(cgrp, cft->ss);
4102 rcu_read_unlock();
4103
4104 if (cft->write_u64) {
4105 unsigned long long v;
4106 ret = kstrtoull(buf, 0, &v);
4107 if (!ret)
4108 ret = cft->write_u64(css, cft, v);
4109 } else if (cft->write_s64) {
4110 long long v;
4111 ret = kstrtoll(buf, 0, &v);
4112 if (!ret)
4113 ret = cft->write_s64(css, cft, v);
4114 } else {
4115 ret = -EINVAL;
4116 }
4117
4118 return ret ?: nbytes;
4119}
4120
4121static __poll_t cgroup_file_poll(struct kernfs_open_file *of, poll_table *pt)
4122{
4123 struct cftype *cft = of_cft(of);
4124
4125 if (cft->poll)
4126 return cft->poll(of, pt);
4127
4128 return kernfs_generic_poll(of, pt);
4129}
4130
4131static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
4132{
4133 return seq_cft(seq)->seq_start(seq, ppos);
4134}
4135
4136static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
4137{
4138 return seq_cft(seq)->seq_next(seq, v, ppos);
4139}
4140
4141static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
4142{
4143 if (seq_cft(seq)->seq_stop)
4144 seq_cft(seq)->seq_stop(seq, v);
4145}
4146
4147static int cgroup_seqfile_show(struct seq_file *m, void *arg)
4148{
4149 struct cftype *cft = seq_cft(m);
4150 struct cgroup_subsys_state *css = seq_css(m);
4151
4152 if (cft->seq_show)
4153 return cft->seq_show(m, arg);
4154
4155 if (cft->read_u64)
4156 seq_printf(m, "%llu\n", cft->read_u64(css, cft));
4157 else if (cft->read_s64)
4158 seq_printf(m, "%lld\n", cft->read_s64(css, cft));
4159 else
4160 return -EINVAL;
4161 return 0;
4162}
4163
4164static struct kernfs_ops cgroup_kf_single_ops = {
4165 .atomic_write_len = PAGE_SIZE,
4166 .open = cgroup_file_open,
4167 .release = cgroup_file_release,
4168 .write = cgroup_file_write,
4169 .poll = cgroup_file_poll,
4170 .seq_show = cgroup_seqfile_show,
4171};
4172
4173static struct kernfs_ops cgroup_kf_ops = {
4174 .atomic_write_len = PAGE_SIZE,
4175 .open = cgroup_file_open,
4176 .release = cgroup_file_release,
4177 .write = cgroup_file_write,
4178 .poll = cgroup_file_poll,
4179 .seq_start = cgroup_seqfile_start,
4180 .seq_next = cgroup_seqfile_next,
4181 .seq_stop = cgroup_seqfile_stop,
4182 .seq_show = cgroup_seqfile_show,
4183};
4184
4185static void cgroup_file_notify_timer(struct timer_list *timer)
4186{
4187 cgroup_file_notify(container_of(timer, struct cgroup_file,
4188 notify_timer));
4189}
4190
4191static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
4192 struct cftype *cft)
4193{
4194 char name[CGROUP_FILE_NAME_MAX];
4195 struct kernfs_node *kn;
4196 struct lock_class_key *key = NULL;
4197
4198#ifdef CONFIG_DEBUG_LOCK_ALLOC
4199 key = &cft->lockdep_key;
4200#endif
4201 kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
4202 cgroup_file_mode(cft),
4203 current_fsuid(), current_fsgid(),
4204 0, cft->kf_ops, cft,
4205 NULL, key);
4206 if (IS_ERR(kn))
4207 return PTR_ERR(kn);
4208
4209 if (cft->file_offset) {
4210 struct cgroup_file *cfile = (void *)css + cft->file_offset;
4211
4212 timer_setup(&cfile->notify_timer, cgroup_file_notify_timer, 0);
4213
4214 spin_lock_irq(&cgroup_file_kn_lock);
4215 cfile->kn = kn;
4216 spin_unlock_irq(&cgroup_file_kn_lock);
4217 }
4218
4219 return 0;
4220}
4221
4222/**
4223 * cgroup_addrm_files - add or remove files to a cgroup directory
4224 * @css: the target css
4225 * @cgrp: the target cgroup (usually css->cgroup)
4226 * @cfts: array of cftypes to be added
4227 * @is_add: whether to add or remove
4228 *
4229 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
4230 * For removals, this function never fails.
4231 */
4232static int cgroup_addrm_files(struct cgroup_subsys_state *css,
4233 struct cgroup *cgrp, struct cftype cfts[],
4234 bool is_add)
4235{
4236 struct cftype *cft, *cft_end = NULL;
4237 int ret = 0;
4238
4239 lockdep_assert_held(&cgroup_mutex);
4240
4241restart:
4242 for (cft = cfts; cft != cft_end && cft->name[0] != '\0'; cft++) {
4243 /* does cft->flags tell us to skip this file on @cgrp? */
4244 if ((cft->flags & __CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
4245 continue;
4246 if ((cft->flags & __CFTYPE_NOT_ON_DFL) && cgroup_on_dfl(cgrp))
4247 continue;
4248 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp))
4249 continue;
4250 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp))
4251 continue;
4252 if ((cft->flags & CFTYPE_DEBUG) && !cgroup_debug)
4253 continue;
4254 if (is_add) {
4255 ret = cgroup_add_file(css, cgrp, cft);
4256 if (ret) {
4257 pr_warn("%s: failed to add %s, err=%d\n",
4258 __func__, cft->name, ret);
4259 cft_end = cft;
4260 is_add = false;
4261 goto restart;
4262 }
4263 } else {
4264 cgroup_rm_file(cgrp, cft);
4265 }
4266 }
4267 return ret;
4268}
4269
4270static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
4271{
4272 struct cgroup_subsys *ss = cfts[0].ss;
4273 struct cgroup *root = &ss->root->cgrp;
4274 struct cgroup_subsys_state *css;
4275 int ret = 0;
4276
4277 lockdep_assert_held(&cgroup_mutex);
4278
4279 /* add/rm files for all cgroups created before */
4280 css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
4281 struct cgroup *cgrp = css->cgroup;
4282
4283 if (!(css->flags & CSS_VISIBLE))
4284 continue;
4285
4286 ret = cgroup_addrm_files(css, cgrp, cfts, is_add);
4287 if (ret)
4288 break;
4289 }
4290
4291 if (is_add && !ret)
4292 kernfs_activate(root->kn);
4293 return ret;
4294}
4295
4296static void cgroup_exit_cftypes(struct cftype *cfts)
4297{
4298 struct cftype *cft;
4299
4300 for (cft = cfts; cft->name[0] != '\0'; cft++) {
4301 /* free copy for custom atomic_write_len, see init_cftypes() */
4302 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
4303 kfree(cft->kf_ops);
4304 cft->kf_ops = NULL;
4305 cft->ss = NULL;
4306
4307 /* revert flags set by cgroup core while adding @cfts */
4308 cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL |
4309 __CFTYPE_ADDED);
4310 }
4311}
4312
4313static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4314{
4315 struct cftype *cft;
4316 int ret = 0;
4317
4318 for (cft = cfts; cft->name[0] != '\0'; cft++) {
4319 struct kernfs_ops *kf_ops;
4320
4321 WARN_ON(cft->ss || cft->kf_ops);
4322
4323 if (cft->flags & __CFTYPE_ADDED) {
4324 ret = -EBUSY;
4325 break;
4326 }
4327
4328 if (cft->seq_start)
4329 kf_ops = &cgroup_kf_ops;
4330 else
4331 kf_ops = &cgroup_kf_single_ops;
4332
4333 /*
4334 * Ugh... if @cft wants a custom max_write_len, we need to
4335 * make a copy of kf_ops to set its atomic_write_len.
4336 */
4337 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
4338 kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
4339 if (!kf_ops) {
4340 ret = -ENOMEM;
4341 break;
4342 }
4343 kf_ops->atomic_write_len = cft->max_write_len;
4344 }
4345
4346 cft->kf_ops = kf_ops;
4347 cft->ss = ss;
4348 cft->flags |= __CFTYPE_ADDED;
4349 }
4350
4351 if (ret)
4352 cgroup_exit_cftypes(cfts);
4353 return ret;
4354}
4355
4356static void cgroup_rm_cftypes_locked(struct cftype *cfts)
4357{
4358 lockdep_assert_held(&cgroup_mutex);
4359
4360 list_del(&cfts->node);
4361 cgroup_apply_cftypes(cfts, false);
4362 cgroup_exit_cftypes(cfts);
4363}
4364
4365/**
4366 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
4367 * @cfts: zero-length name terminated array of cftypes
4368 *
4369 * Unregister @cfts. Files described by @cfts are removed from all
4370 * existing cgroups and all future cgroups won't have them either. This
4371 * function can be called anytime whether @cfts' subsys is attached or not.
4372 *
4373 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
4374 * registered.
4375 */
4376int cgroup_rm_cftypes(struct cftype *cfts)
4377{
4378 if (!cfts || cfts[0].name[0] == '\0')
4379 return 0;
4380
4381 if (!(cfts[0].flags & __CFTYPE_ADDED))
4382 return -ENOENT;
4383
4384 cgroup_lock();
4385 cgroup_rm_cftypes_locked(cfts);
4386 cgroup_unlock();
4387 return 0;
4388}
4389
4390/**
4391 * cgroup_add_cftypes - add an array of cftypes to a subsystem
4392 * @ss: target cgroup subsystem
4393 * @cfts: zero-length name terminated array of cftypes
4394 *
4395 * Register @cfts to @ss. Files described by @cfts are created for all
4396 * existing cgroups to which @ss is attached and all future cgroups will
4397 * have them too. This function can be called anytime whether @ss is
4398 * attached or not.
4399 *
4400 * Returns 0 on successful registration, -errno on failure. Note that this
4401 * function currently returns 0 as long as @cfts registration is successful
4402 * even if some file creation attempts on existing cgroups fail.
4403 */
4404static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4405{
4406 int ret;
4407
4408 if (!cgroup_ssid_enabled(ss->id))
4409 return 0;
4410
4411 if (!cfts || cfts[0].name[0] == '\0')
4412 return 0;
4413
4414 ret = cgroup_init_cftypes(ss, cfts);
4415 if (ret)
4416 return ret;
4417
4418 cgroup_lock();
4419
4420 list_add_tail(&cfts->node, &ss->cfts);
4421 ret = cgroup_apply_cftypes(cfts, true);
4422 if (ret)
4423 cgroup_rm_cftypes_locked(cfts);
4424
4425 cgroup_unlock();
4426 return ret;
4427}
4428
4429/**
4430 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
4431 * @ss: target cgroup subsystem
4432 * @cfts: zero-length name terminated array of cftypes
4433 *
4434 * Similar to cgroup_add_cftypes() but the added files are only used for
4435 * the default hierarchy.
4436 */
4437int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4438{
4439 struct cftype *cft;
4440
4441 for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
4442 cft->flags |= __CFTYPE_ONLY_ON_DFL;
4443 return cgroup_add_cftypes(ss, cfts);
4444}
4445
4446/**
4447 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
4448 * @ss: target cgroup subsystem
4449 * @cfts: zero-length name terminated array of cftypes
4450 *
4451 * Similar to cgroup_add_cftypes() but the added files are only used for
4452 * the legacy hierarchies.
4453 */
4454int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4455{
4456 struct cftype *cft;
4457
4458 for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
4459 cft->flags |= __CFTYPE_NOT_ON_DFL;
4460 return cgroup_add_cftypes(ss, cfts);
4461}
4462
4463/**
4464 * cgroup_file_notify - generate a file modified event for a cgroup_file
4465 * @cfile: target cgroup_file
4466 *
4467 * @cfile must have been obtained by setting cftype->file_offset.
4468 */
4469void cgroup_file_notify(struct cgroup_file *cfile)
4470{
4471 unsigned long flags;
4472
4473 spin_lock_irqsave(&cgroup_file_kn_lock, flags);
4474 if (cfile->kn) {
4475 unsigned long last = cfile->notified_at;
4476 unsigned long next = last + CGROUP_FILE_NOTIFY_MIN_INTV;
4477
4478 if (time_in_range(jiffies, last, next)) {
4479 timer_reduce(&cfile->notify_timer, next);
4480 } else {
4481 kernfs_notify(cfile->kn);
4482 cfile->notified_at = jiffies;
4483 }
4484 }
4485 spin_unlock_irqrestore(&cgroup_file_kn_lock, flags);
4486}
4487
4488/**
4489 * cgroup_file_show - show or hide a hidden cgroup file
4490 * @cfile: target cgroup_file obtained by setting cftype->file_offset
4491 * @show: whether to show or hide
4492 */
4493void cgroup_file_show(struct cgroup_file *cfile, bool show)
4494{
4495 struct kernfs_node *kn;
4496
4497 spin_lock_irq(&cgroup_file_kn_lock);
4498 kn = cfile->kn;
4499 kernfs_get(kn);
4500 spin_unlock_irq(&cgroup_file_kn_lock);
4501
4502 if (kn)
4503 kernfs_show(kn, show);
4504
4505 kernfs_put(kn);
4506}
4507
4508/**
4509 * css_next_child - find the next child of a given css
4510 * @pos: the current position (%NULL to initiate traversal)
4511 * @parent: css whose children to walk
4512 *
4513 * This function returns the next child of @parent and should be called
4514 * under either cgroup_mutex or RCU read lock. The only requirement is
4515 * that @parent and @pos are accessible. The next sibling is guaranteed to
4516 * be returned regardless of their states.
4517 *
4518 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4519 * css which finished ->css_online() is guaranteed to be visible in the
4520 * future iterations and will stay visible until the last reference is put.
4521 * A css which hasn't finished ->css_online() or already finished
4522 * ->css_offline() may show up during traversal. It's each subsystem's
4523 * responsibility to synchronize against on/offlining.
4524 */
4525struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
4526 struct cgroup_subsys_state *parent)
4527{
4528 struct cgroup_subsys_state *next;
4529
4530 cgroup_assert_mutex_or_rcu_locked();
4531
4532 /*
4533 * @pos could already have been unlinked from the sibling list.
4534 * Once a cgroup is removed, its ->sibling.next is no longer
4535 * updated when its next sibling changes. CSS_RELEASED is set when
4536 * @pos is taken off list, at which time its next pointer is valid,
4537 * and, as releases are serialized, the one pointed to by the next
4538 * pointer is guaranteed to not have started release yet. This
4539 * implies that if we observe !CSS_RELEASED on @pos in this RCU
4540 * critical section, the one pointed to by its next pointer is
4541 * guaranteed to not have finished its RCU grace period even if we
4542 * have dropped rcu_read_lock() in-between iterations.
4543 *
4544 * If @pos has CSS_RELEASED set, its next pointer can't be
4545 * dereferenced; however, as each css is given a monotonically
4546 * increasing unique serial number and always appended to the
4547 * sibling list, the next one can be found by walking the parent's
4548 * children until the first css with higher serial number than
4549 * @pos's. While this path can be slower, it happens iff iteration
4550 * races against release and the race window is very small.
4551 */
4552 if (!pos) {
4553 next = list_entry_rcu(parent->children.next, struct cgroup_subsys_state, sibling);
4554 } else if (likely(!(pos->flags & CSS_RELEASED))) {
4555 next = list_entry_rcu(pos->sibling.next, struct cgroup_subsys_state, sibling);
4556 } else {
4557 list_for_each_entry_rcu(next, &parent->children, sibling,
4558 lockdep_is_held(&cgroup_mutex))
4559 if (next->serial_nr > pos->serial_nr)
4560 break;
4561 }
4562
4563 /*
4564 * @next, if not pointing to the head, can be dereferenced and is
4565 * the next sibling.
4566 */
4567 if (&next->sibling != &parent->children)
4568 return next;
4569 return NULL;
4570}
4571
4572/**
4573 * css_next_descendant_pre - find the next descendant for pre-order walk
4574 * @pos: the current position (%NULL to initiate traversal)
4575 * @root: css whose descendants to walk
4576 *
4577 * To be used by css_for_each_descendant_pre(). Find the next descendant
4578 * to visit for pre-order traversal of @root's descendants. @root is
4579 * included in the iteration and the first node to be visited.
4580 *
4581 * While this function requires cgroup_mutex or RCU read locking, it
4582 * doesn't require the whole traversal to be contained in a single critical
4583 * section. This function will return the correct next descendant as long
4584 * as both @pos and @root are accessible and @pos is a descendant of @root.
4585 *
4586 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4587 * css which finished ->css_online() is guaranteed to be visible in the
4588 * future iterations and will stay visible until the last reference is put.
4589 * A css which hasn't finished ->css_online() or already finished
4590 * ->css_offline() may show up during traversal. It's each subsystem's
4591 * responsibility to synchronize against on/offlining.
4592 */
4593struct cgroup_subsys_state *
4594css_next_descendant_pre(struct cgroup_subsys_state *pos,
4595 struct cgroup_subsys_state *root)
4596{
4597 struct cgroup_subsys_state *next;
4598
4599 cgroup_assert_mutex_or_rcu_locked();
4600
4601 /* if first iteration, visit @root */
4602 if (!pos)
4603 return root;
4604
4605 /* visit the first child if exists */
4606 next = css_next_child(NULL, pos);
4607 if (next)
4608 return next;
4609
4610 /* no child, visit my or the closest ancestor's next sibling */
4611 while (pos != root) {
4612 next = css_next_child(pos, pos->parent);
4613 if (next)
4614 return next;
4615 pos = pos->parent;
4616 }
4617
4618 return NULL;
4619}
4620EXPORT_SYMBOL_GPL(css_next_descendant_pre);
4621
4622/**
4623 * css_rightmost_descendant - return the rightmost descendant of a css
4624 * @pos: css of interest
4625 *
4626 * Return the rightmost descendant of @pos. If there's no descendant, @pos
4627 * is returned. This can be used during pre-order traversal to skip
4628 * subtree of @pos.
4629 *
4630 * While this function requires cgroup_mutex or RCU read locking, it
4631 * doesn't require the whole traversal to be contained in a single critical
4632 * section. This function will return the correct rightmost descendant as
4633 * long as @pos is accessible.
4634 */
4635struct cgroup_subsys_state *
4636css_rightmost_descendant(struct cgroup_subsys_state *pos)
4637{
4638 struct cgroup_subsys_state *last, *tmp;
4639
4640 cgroup_assert_mutex_or_rcu_locked();
4641
4642 do {
4643 last = pos;
4644 /* ->prev isn't RCU safe, walk ->next till the end */
4645 pos = NULL;
4646 css_for_each_child(tmp, last)
4647 pos = tmp;
4648 } while (pos);
4649
4650 return last;
4651}
4652
4653static struct cgroup_subsys_state *
4654css_leftmost_descendant(struct cgroup_subsys_state *pos)
4655{
4656 struct cgroup_subsys_state *last;
4657
4658 do {
4659 last = pos;
4660 pos = css_next_child(NULL, pos);
4661 } while (pos);
4662
4663 return last;
4664}
4665
4666/**
4667 * css_next_descendant_post - find the next descendant for post-order walk
4668 * @pos: the current position (%NULL to initiate traversal)
4669 * @root: css whose descendants to walk
4670 *
4671 * To be used by css_for_each_descendant_post(). Find the next descendant
4672 * to visit for post-order traversal of @root's descendants. @root is
4673 * included in the iteration and the last node to be visited.
4674 *
4675 * While this function requires cgroup_mutex or RCU read locking, it
4676 * doesn't require the whole traversal to be contained in a single critical
4677 * section. This function will return the correct next descendant as long
4678 * as both @pos and @cgroup are accessible and @pos is a descendant of
4679 * @cgroup.
4680 *
4681 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4682 * css which finished ->css_online() is guaranteed to be visible in the
4683 * future iterations and will stay visible until the last reference is put.
4684 * A css which hasn't finished ->css_online() or already finished
4685 * ->css_offline() may show up during traversal. It's each subsystem's
4686 * responsibility to synchronize against on/offlining.
4687 */
4688struct cgroup_subsys_state *
4689css_next_descendant_post(struct cgroup_subsys_state *pos,
4690 struct cgroup_subsys_state *root)
4691{
4692 struct cgroup_subsys_state *next;
4693
4694 cgroup_assert_mutex_or_rcu_locked();
4695
4696 /* if first iteration, visit leftmost descendant which may be @root */
4697 if (!pos)
4698 return css_leftmost_descendant(root);
4699
4700 /* if we visited @root, we're done */
4701 if (pos == root)
4702 return NULL;
4703
4704 /* if there's an unvisited sibling, visit its leftmost descendant */
4705 next = css_next_child(pos, pos->parent);
4706 if (next)
4707 return css_leftmost_descendant(next);
4708
4709 /* no sibling left, visit parent */
4710 return pos->parent;
4711}
4712
4713/**
4714 * css_has_online_children - does a css have online children
4715 * @css: the target css
4716 *
4717 * Returns %true if @css has any online children; otherwise, %false. This
4718 * function can be called from any context but the caller is responsible
4719 * for synchronizing against on/offlining as necessary.
4720 */
4721bool css_has_online_children(struct cgroup_subsys_state *css)
4722{
4723 struct cgroup_subsys_state *child;
4724 bool ret = false;
4725
4726 rcu_read_lock();
4727 css_for_each_child(child, css) {
4728 if (child->flags & CSS_ONLINE) {
4729 ret = true;
4730 break;
4731 }
4732 }
4733 rcu_read_unlock();
4734 return ret;
4735}
4736
4737static struct css_set *css_task_iter_next_css_set(struct css_task_iter *it)
4738{
4739 struct list_head *l;
4740 struct cgrp_cset_link *link;
4741 struct css_set *cset;
4742
4743 lockdep_assert_held(&css_set_lock);
4744
4745 /* find the next threaded cset */
4746 if (it->tcset_pos) {
4747 l = it->tcset_pos->next;
4748
4749 if (l != it->tcset_head) {
4750 it->tcset_pos = l;
4751 return container_of(l, struct css_set,
4752 threaded_csets_node);
4753 }
4754
4755 it->tcset_pos = NULL;
4756 }
4757
4758 /* find the next cset */
4759 l = it->cset_pos;
4760 l = l->next;
4761 if (l == it->cset_head) {
4762 it->cset_pos = NULL;
4763 return NULL;
4764 }
4765
4766 if (it->ss) {
4767 cset = container_of(l, struct css_set, e_cset_node[it->ss->id]);
4768 } else {
4769 link = list_entry(l, struct cgrp_cset_link, cset_link);
4770 cset = link->cset;
4771 }
4772
4773 it->cset_pos = l;
4774
4775 /* initialize threaded css_set walking */
4776 if (it->flags & CSS_TASK_ITER_THREADED) {
4777 if (it->cur_dcset)
4778 put_css_set_locked(it->cur_dcset);
4779 it->cur_dcset = cset;
4780 get_css_set(cset);
4781
4782 it->tcset_head = &cset->threaded_csets;
4783 it->tcset_pos = &cset->threaded_csets;
4784 }
4785
4786 return cset;
4787}
4788
4789/**
4790 * css_task_iter_advance_css_set - advance a task iterator to the next css_set
4791 * @it: the iterator to advance
4792 *
4793 * Advance @it to the next css_set to walk.
4794 */
4795static void css_task_iter_advance_css_set(struct css_task_iter *it)
4796{
4797 struct css_set *cset;
4798
4799 lockdep_assert_held(&css_set_lock);
4800
4801 /* Advance to the next non-empty css_set and find first non-empty tasks list*/
4802 while ((cset = css_task_iter_next_css_set(it))) {
4803 if (!list_empty(&cset->tasks)) {
4804 it->cur_tasks_head = &cset->tasks;
4805 break;
4806 } else if (!list_empty(&cset->mg_tasks)) {
4807 it->cur_tasks_head = &cset->mg_tasks;
4808 break;
4809 } else if (!list_empty(&cset->dying_tasks)) {
4810 it->cur_tasks_head = &cset->dying_tasks;
4811 break;
4812 }
4813 }
4814 if (!cset) {
4815 it->task_pos = NULL;
4816 return;
4817 }
4818 it->task_pos = it->cur_tasks_head->next;
4819
4820 /*
4821 * We don't keep css_sets locked across iteration steps and thus
4822 * need to take steps to ensure that iteration can be resumed after
4823 * the lock is re-acquired. Iteration is performed at two levels -
4824 * css_sets and tasks in them.
4825 *
4826 * Once created, a css_set never leaves its cgroup lists, so a
4827 * pinned css_set is guaranteed to stay put and we can resume
4828 * iteration afterwards.
4829 *
4830 * Tasks may leave @cset across iteration steps. This is resolved
4831 * by registering each iterator with the css_set currently being
4832 * walked and making css_set_move_task() advance iterators whose
4833 * next task is leaving.
4834 */
4835 if (it->cur_cset) {
4836 list_del(&it->iters_node);
4837 put_css_set_locked(it->cur_cset);
4838 }
4839 get_css_set(cset);
4840 it->cur_cset = cset;
4841 list_add(&it->iters_node, &cset->task_iters);
4842}
4843
4844static void css_task_iter_skip(struct css_task_iter *it,
4845 struct task_struct *task)
4846{
4847 lockdep_assert_held(&css_set_lock);
4848
4849 if (it->task_pos == &task->cg_list) {
4850 it->task_pos = it->task_pos->next;
4851 it->flags |= CSS_TASK_ITER_SKIPPED;
4852 }
4853}
4854
4855static void css_task_iter_advance(struct css_task_iter *it)
4856{
4857 struct task_struct *task;
4858
4859 lockdep_assert_held(&css_set_lock);
4860repeat:
4861 if (it->task_pos) {
4862 /*
4863 * Advance iterator to find next entry. We go through cset
4864 * tasks, mg_tasks and dying_tasks, when consumed we move onto
4865 * the next cset.
4866 */
4867 if (it->flags & CSS_TASK_ITER_SKIPPED)
4868 it->flags &= ~CSS_TASK_ITER_SKIPPED;
4869 else
4870 it->task_pos = it->task_pos->next;
4871
4872 if (it->task_pos == &it->cur_cset->tasks) {
4873 it->cur_tasks_head = &it->cur_cset->mg_tasks;
4874 it->task_pos = it->cur_tasks_head->next;
4875 }
4876 if (it->task_pos == &it->cur_cset->mg_tasks) {
4877 it->cur_tasks_head = &it->cur_cset->dying_tasks;
4878 it->task_pos = it->cur_tasks_head->next;
4879 }
4880 if (it->task_pos == &it->cur_cset->dying_tasks)
4881 css_task_iter_advance_css_set(it);
4882 } else {
4883 /* called from start, proceed to the first cset */
4884 css_task_iter_advance_css_set(it);
4885 }
4886
4887 if (!it->task_pos)
4888 return;
4889
4890 task = list_entry(it->task_pos, struct task_struct, cg_list);
4891
4892 if (it->flags & CSS_TASK_ITER_PROCS) {
4893 /* if PROCS, skip over tasks which aren't group leaders */
4894 if (!thread_group_leader(task))
4895 goto repeat;
4896
4897 /* and dying leaders w/o live member threads */
4898 if (it->cur_tasks_head == &it->cur_cset->dying_tasks &&
4899 !atomic_read(&task->signal->live))
4900 goto repeat;
4901 } else {
4902 /* skip all dying ones */
4903 if (it->cur_tasks_head == &it->cur_cset->dying_tasks)
4904 goto repeat;
4905 }
4906}
4907
4908/**
4909 * css_task_iter_start - initiate task iteration
4910 * @css: the css to walk tasks of
4911 * @flags: CSS_TASK_ITER_* flags
4912 * @it: the task iterator to use
4913 *
4914 * Initiate iteration through the tasks of @css. The caller can call
4915 * css_task_iter_next() to walk through the tasks until the function
4916 * returns NULL. On completion of iteration, css_task_iter_end() must be
4917 * called.
4918 */
4919void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
4920 struct css_task_iter *it)
4921{
4922 unsigned long irqflags;
4923
4924 memset(it, 0, sizeof(*it));
4925
4926 spin_lock_irqsave(&css_set_lock, irqflags);
4927
4928 it->ss = css->ss;
4929 it->flags = flags;
4930
4931 if (CGROUP_HAS_SUBSYS_CONFIG && it->ss)
4932 it->cset_pos = &css->cgroup->e_csets[css->ss->id];
4933 else
4934 it->cset_pos = &css->cgroup->cset_links;
4935
4936 it->cset_head = it->cset_pos;
4937
4938 css_task_iter_advance(it);
4939
4940 spin_unlock_irqrestore(&css_set_lock, irqflags);
4941}
4942
4943/**
4944 * css_task_iter_next - return the next task for the iterator
4945 * @it: the task iterator being iterated
4946 *
4947 * The "next" function for task iteration. @it should have been
4948 * initialized via css_task_iter_start(). Returns NULL when the iteration
4949 * reaches the end.
4950 */
4951struct task_struct *css_task_iter_next(struct css_task_iter *it)
4952{
4953 unsigned long irqflags;
4954
4955 if (it->cur_task) {
4956 put_task_struct(it->cur_task);
4957 it->cur_task = NULL;
4958 }
4959
4960 spin_lock_irqsave(&css_set_lock, irqflags);
4961
4962 /* @it may be half-advanced by skips, finish advancing */
4963 if (it->flags & CSS_TASK_ITER_SKIPPED)
4964 css_task_iter_advance(it);
4965
4966 if (it->task_pos) {
4967 it->cur_task = list_entry(it->task_pos, struct task_struct,
4968 cg_list);
4969 get_task_struct(it->cur_task);
4970 css_task_iter_advance(it);
4971 }
4972
4973 spin_unlock_irqrestore(&css_set_lock, irqflags);
4974
4975 return it->cur_task;
4976}
4977
4978/**
4979 * css_task_iter_end - finish task iteration
4980 * @it: the task iterator to finish
4981 *
4982 * Finish task iteration started by css_task_iter_start().
4983 */
4984void css_task_iter_end(struct css_task_iter *it)
4985{
4986 unsigned long irqflags;
4987
4988 if (it->cur_cset) {
4989 spin_lock_irqsave(&css_set_lock, irqflags);
4990 list_del(&it->iters_node);
4991 put_css_set_locked(it->cur_cset);
4992 spin_unlock_irqrestore(&css_set_lock, irqflags);
4993 }
4994
4995 if (it->cur_dcset)
4996 put_css_set(it->cur_dcset);
4997
4998 if (it->cur_task)
4999 put_task_struct(it->cur_task);
5000}
5001
5002static void cgroup_procs_release(struct kernfs_open_file *of)
5003{
5004 struct cgroup_file_ctx *ctx = of->priv;
5005
5006 if (ctx->procs.started)
5007 css_task_iter_end(&ctx->procs.iter);
5008}
5009
5010static void *cgroup_procs_next(struct seq_file *s, void *v, loff_t *pos)
5011{
5012 struct kernfs_open_file *of = s->private;
5013 struct cgroup_file_ctx *ctx = of->priv;
5014
5015 if (pos)
5016 (*pos)++;
5017
5018 return css_task_iter_next(&ctx->procs.iter);
5019}
5020
5021static void *__cgroup_procs_start(struct seq_file *s, loff_t *pos,
5022 unsigned int iter_flags)
5023{
5024 struct kernfs_open_file *of = s->private;
5025 struct cgroup *cgrp = seq_css(s)->cgroup;
5026 struct cgroup_file_ctx *ctx = of->priv;
5027 struct css_task_iter *it = &ctx->procs.iter;
5028
5029 /*
5030 * When a seq_file is seeked, it's always traversed sequentially
5031 * from position 0, so we can simply keep iterating on !0 *pos.
5032 */
5033 if (!ctx->procs.started) {
5034 if (WARN_ON_ONCE((*pos)))
5035 return ERR_PTR(-EINVAL);
5036 css_task_iter_start(&cgrp->self, iter_flags, it);
5037 ctx->procs.started = true;
5038 } else if (!(*pos)) {
5039 css_task_iter_end(it);
5040 css_task_iter_start(&cgrp->self, iter_flags, it);
5041 } else
5042 return it->cur_task;
5043
5044 return cgroup_procs_next(s, NULL, NULL);
5045}
5046
5047static void *cgroup_procs_start(struct seq_file *s, loff_t *pos)
5048{
5049 struct cgroup *cgrp = seq_css(s)->cgroup;
5050
5051 /*
5052 * All processes of a threaded subtree belong to the domain cgroup
5053 * of the subtree. Only threads can be distributed across the
5054 * subtree. Reject reads on cgroup.procs in the subtree proper.
5055 * They're always empty anyway.
5056 */
5057 if (cgroup_is_threaded(cgrp))
5058 return ERR_PTR(-EOPNOTSUPP);
5059
5060 return __cgroup_procs_start(s, pos, CSS_TASK_ITER_PROCS |
5061 CSS_TASK_ITER_THREADED);
5062}
5063
5064static int cgroup_procs_show(struct seq_file *s, void *v)
5065{
5066 seq_printf(s, "%d\n", task_pid_vnr(v));
5067 return 0;
5068}
5069
5070static int cgroup_may_write(const struct cgroup *cgrp, struct super_block *sb)
5071{
5072 int ret;
5073 struct inode *inode;
5074
5075 lockdep_assert_held(&cgroup_mutex);
5076
5077 inode = kernfs_get_inode(sb, cgrp->procs_file.kn);
5078 if (!inode)
5079 return -ENOMEM;
5080
5081 ret = inode_permission(&nop_mnt_idmap, inode, MAY_WRITE);
5082 iput(inode);
5083 return ret;
5084}
5085
5086static int cgroup_procs_write_permission(struct cgroup *src_cgrp,
5087 struct cgroup *dst_cgrp,
5088 struct super_block *sb,
5089 struct cgroup_namespace *ns)
5090{
5091 struct cgroup *com_cgrp = src_cgrp;
5092 int ret;
5093
5094 lockdep_assert_held(&cgroup_mutex);
5095
5096 /* find the common ancestor */
5097 while (!cgroup_is_descendant(dst_cgrp, com_cgrp))
5098 com_cgrp = cgroup_parent(com_cgrp);
5099
5100 /* %current should be authorized to migrate to the common ancestor */
5101 ret = cgroup_may_write(com_cgrp, sb);
5102 if (ret)
5103 return ret;
5104
5105 /*
5106 * If namespaces are delegation boundaries, %current must be able
5107 * to see both source and destination cgroups from its namespace.
5108 */
5109 if ((cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE) &&
5110 (!cgroup_is_descendant(src_cgrp, ns->root_cset->dfl_cgrp) ||
5111 !cgroup_is_descendant(dst_cgrp, ns->root_cset->dfl_cgrp)))
5112 return -ENOENT;
5113
5114 return 0;
5115}
5116
5117static int cgroup_attach_permissions(struct cgroup *src_cgrp,
5118 struct cgroup *dst_cgrp,
5119 struct super_block *sb, bool threadgroup,
5120 struct cgroup_namespace *ns)
5121{
5122 int ret = 0;
5123
5124 ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp, sb, ns);
5125 if (ret)
5126 return ret;
5127
5128 ret = cgroup_migrate_vet_dst(dst_cgrp);
5129 if (ret)
5130 return ret;
5131
5132 if (!threadgroup && (src_cgrp->dom_cgrp != dst_cgrp->dom_cgrp))
5133 ret = -EOPNOTSUPP;
5134
5135 return ret;
5136}
5137
5138static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
5139 bool threadgroup)
5140{
5141 struct cgroup_file_ctx *ctx = of->priv;
5142 struct cgroup *src_cgrp, *dst_cgrp;
5143 struct task_struct *task;
5144 const struct cred *saved_cred;
5145 ssize_t ret;
5146 bool threadgroup_locked;
5147
5148 dst_cgrp = cgroup_kn_lock_live(of->kn, false);
5149 if (!dst_cgrp)
5150 return -ENODEV;
5151
5152 task = cgroup_procs_write_start(buf, threadgroup, &threadgroup_locked);
5153 ret = PTR_ERR_OR_ZERO(task);
5154 if (ret)
5155 goto out_unlock;
5156
5157 /* find the source cgroup */
5158 spin_lock_irq(&css_set_lock);
5159 src_cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
5160 spin_unlock_irq(&css_set_lock);
5161
5162 /*
5163 * Process and thread migrations follow same delegation rule. Check
5164 * permissions using the credentials from file open to protect against
5165 * inherited fd attacks.
5166 */
5167 saved_cred = override_creds(of->file->f_cred);
5168 ret = cgroup_attach_permissions(src_cgrp, dst_cgrp,
5169 of->file->f_path.dentry->d_sb,
5170 threadgroup, ctx->ns);
5171 revert_creds(saved_cred);
5172 if (ret)
5173 goto out_finish;
5174
5175 ret = cgroup_attach_task(dst_cgrp, task, threadgroup);
5176
5177out_finish:
5178 cgroup_procs_write_finish(task, threadgroup_locked);
5179out_unlock:
5180 cgroup_kn_unlock(of->kn);
5181
5182 return ret;
5183}
5184
5185static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
5186 char *buf, size_t nbytes, loff_t off)
5187{
5188 return __cgroup_procs_write(of, buf, true) ?: nbytes;
5189}
5190
5191static void *cgroup_threads_start(struct seq_file *s, loff_t *pos)
5192{
5193 return __cgroup_procs_start(s, pos, 0);
5194}
5195
5196static ssize_t cgroup_threads_write(struct kernfs_open_file *of,
5197 char *buf, size_t nbytes, loff_t off)
5198{
5199 return __cgroup_procs_write(of, buf, false) ?: nbytes;
5200}
5201
5202/* cgroup core interface files for the default hierarchy */
5203static struct cftype cgroup_base_files[] = {
5204 {
5205 .name = "cgroup.type",
5206 .flags = CFTYPE_NOT_ON_ROOT,
5207 .seq_show = cgroup_type_show,
5208 .write = cgroup_type_write,
5209 },
5210 {
5211 .name = "cgroup.procs",
5212 .flags = CFTYPE_NS_DELEGATABLE,
5213 .file_offset = offsetof(struct cgroup, procs_file),
5214 .release = cgroup_procs_release,
5215 .seq_start = cgroup_procs_start,
5216 .seq_next = cgroup_procs_next,
5217 .seq_show = cgroup_procs_show,
5218 .write = cgroup_procs_write,
5219 },
5220 {
5221 .name = "cgroup.threads",
5222 .flags = CFTYPE_NS_DELEGATABLE,
5223 .release = cgroup_procs_release,
5224 .seq_start = cgroup_threads_start,
5225 .seq_next = cgroup_procs_next,
5226 .seq_show = cgroup_procs_show,
5227 .write = cgroup_threads_write,
5228 },
5229 {
5230 .name = "cgroup.controllers",
5231 .seq_show = cgroup_controllers_show,
5232 },
5233 {
5234 .name = "cgroup.subtree_control",
5235 .flags = CFTYPE_NS_DELEGATABLE,
5236 .seq_show = cgroup_subtree_control_show,
5237 .write = cgroup_subtree_control_write,
5238 },
5239 {
5240 .name = "cgroup.events",
5241 .flags = CFTYPE_NOT_ON_ROOT,
5242 .file_offset = offsetof(struct cgroup, events_file),
5243 .seq_show = cgroup_events_show,
5244 },
5245 {
5246 .name = "cgroup.max.descendants",
5247 .seq_show = cgroup_max_descendants_show,
5248 .write = cgroup_max_descendants_write,
5249 },
5250 {
5251 .name = "cgroup.max.depth",
5252 .seq_show = cgroup_max_depth_show,
5253 .write = cgroup_max_depth_write,
5254 },
5255 {
5256 .name = "cgroup.stat",
5257 .seq_show = cgroup_stat_show,
5258 },
5259 {
5260 .name = "cgroup.freeze",
5261 .flags = CFTYPE_NOT_ON_ROOT,
5262 .seq_show = cgroup_freeze_show,
5263 .write = cgroup_freeze_write,
5264 },
5265 {
5266 .name = "cgroup.kill",
5267 .flags = CFTYPE_NOT_ON_ROOT,
5268 .write = cgroup_kill_write,
5269 },
5270 {
5271 .name = "cpu.stat",
5272 .seq_show = cpu_stat_show,
5273 },
5274 {
5275 .name = "cpu.stat.local",
5276 .seq_show = cpu_local_stat_show,
5277 },
5278 { } /* terminate */
5279};
5280
5281static struct cftype cgroup_psi_files[] = {
5282#ifdef CONFIG_PSI
5283 {
5284 .name = "io.pressure",
5285 .file_offset = offsetof(struct cgroup, psi_files[PSI_IO]),
5286 .seq_show = cgroup_io_pressure_show,
5287 .write = cgroup_io_pressure_write,
5288 .poll = cgroup_pressure_poll,
5289 .release = cgroup_pressure_release,
5290 },
5291 {
5292 .name = "memory.pressure",
5293 .file_offset = offsetof(struct cgroup, psi_files[PSI_MEM]),
5294 .seq_show = cgroup_memory_pressure_show,
5295 .write = cgroup_memory_pressure_write,
5296 .poll = cgroup_pressure_poll,
5297 .release = cgroup_pressure_release,
5298 },
5299 {
5300 .name = "cpu.pressure",
5301 .file_offset = offsetof(struct cgroup, psi_files[PSI_CPU]),
5302 .seq_show = cgroup_cpu_pressure_show,
5303 .write = cgroup_cpu_pressure_write,
5304 .poll = cgroup_pressure_poll,
5305 .release = cgroup_pressure_release,
5306 },
5307#ifdef CONFIG_IRQ_TIME_ACCOUNTING
5308 {
5309 .name = "irq.pressure",
5310 .file_offset = offsetof(struct cgroup, psi_files[PSI_IRQ]),
5311 .seq_show = cgroup_irq_pressure_show,
5312 .write = cgroup_irq_pressure_write,
5313 .poll = cgroup_pressure_poll,
5314 .release = cgroup_pressure_release,
5315 },
5316#endif
5317 {
5318 .name = "cgroup.pressure",
5319 .seq_show = cgroup_pressure_show,
5320 .write = cgroup_pressure_write,
5321 },
5322#endif /* CONFIG_PSI */
5323 { } /* terminate */
5324};
5325
5326/*
5327 * css destruction is four-stage process.
5328 *
5329 * 1. Destruction starts. Killing of the percpu_ref is initiated.
5330 * Implemented in kill_css().
5331 *
5332 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
5333 * and thus css_tryget_online() is guaranteed to fail, the css can be
5334 * offlined by invoking offline_css(). After offlining, the base ref is
5335 * put. Implemented in css_killed_work_fn().
5336 *
5337 * 3. When the percpu_ref reaches zero, the only possible remaining
5338 * accessors are inside RCU read sections. css_release() schedules the
5339 * RCU callback.
5340 *
5341 * 4. After the grace period, the css can be freed. Implemented in
5342 * css_free_rwork_fn().
5343 *
5344 * It is actually hairier because both step 2 and 4 require process context
5345 * and thus involve punting to css->destroy_work adding two additional
5346 * steps to the already complex sequence.
5347 */
5348static void css_free_rwork_fn(struct work_struct *work)
5349{
5350 struct cgroup_subsys_state *css = container_of(to_rcu_work(work),
5351 struct cgroup_subsys_state, destroy_rwork);
5352 struct cgroup_subsys *ss = css->ss;
5353 struct cgroup *cgrp = css->cgroup;
5354
5355 percpu_ref_exit(&css->refcnt);
5356
5357 if (ss) {
5358 /* css free path */
5359 struct cgroup_subsys_state *parent = css->parent;
5360 int id = css->id;
5361
5362 ss->css_free(css);
5363 cgroup_idr_remove(&ss->css_idr, id);
5364 cgroup_put(cgrp);
5365
5366 if (parent)
5367 css_put(parent);
5368 } else {
5369 /* cgroup free path */
5370 atomic_dec(&cgrp->root->nr_cgrps);
5371 cgroup1_pidlist_destroy_all(cgrp);
5372 cancel_work_sync(&cgrp->release_agent_work);
5373 bpf_cgrp_storage_free(cgrp);
5374
5375 if (cgroup_parent(cgrp)) {
5376 /*
5377 * We get a ref to the parent, and put the ref when
5378 * this cgroup is being freed, so it's guaranteed
5379 * that the parent won't be destroyed before its
5380 * children.
5381 */
5382 cgroup_put(cgroup_parent(cgrp));
5383 kernfs_put(cgrp->kn);
5384 psi_cgroup_free(cgrp);
5385 cgroup_rstat_exit(cgrp);
5386 kfree(cgrp);
5387 } else {
5388 /*
5389 * This is root cgroup's refcnt reaching zero,
5390 * which indicates that the root should be
5391 * released.
5392 */
5393 cgroup_destroy_root(cgrp->root);
5394 }
5395 }
5396}
5397
5398static void css_release_work_fn(struct work_struct *work)
5399{
5400 struct cgroup_subsys_state *css =
5401 container_of(work, struct cgroup_subsys_state, destroy_work);
5402 struct cgroup_subsys *ss = css->ss;
5403 struct cgroup *cgrp = css->cgroup;
5404
5405 cgroup_lock();
5406
5407 css->flags |= CSS_RELEASED;
5408 list_del_rcu(&css->sibling);
5409
5410 if (ss) {
5411 /* css release path */
5412 if (!list_empty(&css->rstat_css_node)) {
5413 cgroup_rstat_flush(cgrp);
5414 list_del_rcu(&css->rstat_css_node);
5415 }
5416
5417 cgroup_idr_replace(&ss->css_idr, NULL, css->id);
5418 if (ss->css_released)
5419 ss->css_released(css);
5420 } else {
5421 struct cgroup *tcgrp;
5422
5423 /* cgroup release path */
5424 TRACE_CGROUP_PATH(release, cgrp);
5425
5426 cgroup_rstat_flush(cgrp);
5427
5428 spin_lock_irq(&css_set_lock);
5429 for (tcgrp = cgroup_parent(cgrp); tcgrp;
5430 tcgrp = cgroup_parent(tcgrp))
5431 tcgrp->nr_dying_descendants--;
5432 spin_unlock_irq(&css_set_lock);
5433
5434 /*
5435 * There are two control paths which try to determine
5436 * cgroup from dentry without going through kernfs -
5437 * cgroupstats_build() and css_tryget_online_from_dir().
5438 * Those are supported by RCU protecting clearing of
5439 * cgrp->kn->priv backpointer.
5440 */
5441 if (cgrp->kn)
5442 RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv,
5443 NULL);
5444 }
5445
5446 cgroup_unlock();
5447
5448 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
5449 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
5450}
5451
5452static void css_release(struct percpu_ref *ref)
5453{
5454 struct cgroup_subsys_state *css =
5455 container_of(ref, struct cgroup_subsys_state, refcnt);
5456
5457 INIT_WORK(&css->destroy_work, css_release_work_fn);
5458 queue_work(cgroup_destroy_wq, &css->destroy_work);
5459}
5460
5461static void init_and_link_css(struct cgroup_subsys_state *css,
5462 struct cgroup_subsys *ss, struct cgroup *cgrp)
5463{
5464 lockdep_assert_held(&cgroup_mutex);
5465
5466 cgroup_get_live(cgrp);
5467
5468 memset(css, 0, sizeof(*css));
5469 css->cgroup = cgrp;
5470 css->ss = ss;
5471 css->id = -1;
5472 INIT_LIST_HEAD(&css->sibling);
5473 INIT_LIST_HEAD(&css->children);
5474 INIT_LIST_HEAD(&css->rstat_css_node);
5475 css->serial_nr = css_serial_nr_next++;
5476 atomic_set(&css->online_cnt, 0);
5477
5478 if (cgroup_parent(cgrp)) {
5479 css->parent = cgroup_css(cgroup_parent(cgrp), ss);
5480 css_get(css->parent);
5481 }
5482
5483 if (ss->css_rstat_flush)
5484 list_add_rcu(&css->rstat_css_node, &cgrp->rstat_css_list);
5485
5486 BUG_ON(cgroup_css(cgrp, ss));
5487}
5488
5489/* invoke ->css_online() on a new CSS and mark it online if successful */
5490static int online_css(struct cgroup_subsys_state *css)
5491{
5492 struct cgroup_subsys *ss = css->ss;
5493 int ret = 0;
5494
5495 lockdep_assert_held(&cgroup_mutex);
5496
5497 if (ss->css_online)
5498 ret = ss->css_online(css);
5499 if (!ret) {
5500 css->flags |= CSS_ONLINE;
5501 rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
5502
5503 atomic_inc(&css->online_cnt);
5504 if (css->parent)
5505 atomic_inc(&css->parent->online_cnt);
5506 }
5507 return ret;
5508}
5509
5510/* if the CSS is online, invoke ->css_offline() on it and mark it offline */
5511static void offline_css(struct cgroup_subsys_state *css)
5512{
5513 struct cgroup_subsys *ss = css->ss;
5514
5515 lockdep_assert_held(&cgroup_mutex);
5516
5517 if (!(css->flags & CSS_ONLINE))
5518 return;
5519
5520 if (ss->css_offline)
5521 ss->css_offline(css);
5522
5523 css->flags &= ~CSS_ONLINE;
5524 RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL);
5525
5526 wake_up_all(&css->cgroup->offline_waitq);
5527}
5528
5529/**
5530 * css_create - create a cgroup_subsys_state
5531 * @cgrp: the cgroup new css will be associated with
5532 * @ss: the subsys of new css
5533 *
5534 * Create a new css associated with @cgrp - @ss pair. On success, the new
5535 * css is online and installed in @cgrp. This function doesn't create the
5536 * interface files. Returns 0 on success, -errno on failure.
5537 */
5538static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
5539 struct cgroup_subsys *ss)
5540{
5541 struct cgroup *parent = cgroup_parent(cgrp);
5542 struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss);
5543 struct cgroup_subsys_state *css;
5544 int err;
5545
5546 lockdep_assert_held(&cgroup_mutex);
5547
5548 css = ss->css_alloc(parent_css);
5549 if (!css)
5550 css = ERR_PTR(-ENOMEM);
5551 if (IS_ERR(css))
5552 return css;
5553
5554 init_and_link_css(css, ss, cgrp);
5555
5556 err = percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL);
5557 if (err)
5558 goto err_free_css;
5559
5560 err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL);
5561 if (err < 0)
5562 goto err_free_css;
5563 css->id = err;
5564
5565 /* @css is ready to be brought online now, make it visible */
5566 list_add_tail_rcu(&css->sibling, &parent_css->children);
5567 cgroup_idr_replace(&ss->css_idr, css, css->id);
5568
5569 err = online_css(css);
5570 if (err)
5571 goto err_list_del;
5572
5573 return css;
5574
5575err_list_del:
5576 list_del_rcu(&css->sibling);
5577err_free_css:
5578 list_del_rcu(&css->rstat_css_node);
5579 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
5580 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
5581 return ERR_PTR(err);
5582}
5583
5584/*
5585 * The returned cgroup is fully initialized including its control mask, but
5586 * it doesn't have the control mask applied.
5587 */
5588static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
5589 umode_t mode)
5590{
5591 struct cgroup_root *root = parent->root;
5592 struct cgroup *cgrp, *tcgrp;
5593 struct kernfs_node *kn;
5594 int level = parent->level + 1;
5595 int ret;
5596
5597 /* allocate the cgroup and its ID, 0 is reserved for the root */
5598 cgrp = kzalloc(struct_size(cgrp, ancestors, (level + 1)), GFP_KERNEL);
5599 if (!cgrp)
5600 return ERR_PTR(-ENOMEM);
5601
5602 ret = percpu_ref_init(&cgrp->self.refcnt, css_release, 0, GFP_KERNEL);
5603 if (ret)
5604 goto out_free_cgrp;
5605
5606 ret = cgroup_rstat_init(cgrp);
5607 if (ret)
5608 goto out_cancel_ref;
5609
5610 /* create the directory */
5611 kn = kernfs_create_dir_ns(parent->kn, name, mode,
5612 current_fsuid(), current_fsgid(),
5613 cgrp, NULL);
5614 if (IS_ERR(kn)) {
5615 ret = PTR_ERR(kn);
5616 goto out_stat_exit;
5617 }
5618 cgrp->kn = kn;
5619
5620 init_cgroup_housekeeping(cgrp);
5621
5622 cgrp->self.parent = &parent->self;
5623 cgrp->root = root;
5624 cgrp->level = level;
5625
5626 ret = psi_cgroup_alloc(cgrp);
5627 if (ret)
5628 goto out_kernfs_remove;
5629
5630 ret = cgroup_bpf_inherit(cgrp);
5631 if (ret)
5632 goto out_psi_free;
5633
5634 /*
5635 * New cgroup inherits effective freeze counter, and
5636 * if the parent has to be frozen, the child has too.
5637 */
5638 cgrp->freezer.e_freeze = parent->freezer.e_freeze;
5639 if (cgrp->freezer.e_freeze) {
5640 /*
5641 * Set the CGRP_FREEZE flag, so when a process will be
5642 * attached to the child cgroup, it will become frozen.
5643 * At this point the new cgroup is unpopulated, so we can
5644 * consider it frozen immediately.
5645 */
5646 set_bit(CGRP_FREEZE, &cgrp->flags);
5647 set_bit(CGRP_FROZEN, &cgrp->flags);
5648 }
5649
5650 spin_lock_irq(&css_set_lock);
5651 for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
5652 cgrp->ancestors[tcgrp->level] = tcgrp;
5653
5654 if (tcgrp != cgrp) {
5655 tcgrp->nr_descendants++;
5656
5657 /*
5658 * If the new cgroup is frozen, all ancestor cgroups
5659 * get a new frozen descendant, but their state can't
5660 * change because of this.
5661 */
5662 if (cgrp->freezer.e_freeze)
5663 tcgrp->freezer.nr_frozen_descendants++;
5664 }
5665 }
5666 spin_unlock_irq(&css_set_lock);
5667
5668 if (notify_on_release(parent))
5669 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
5670
5671 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
5672 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
5673
5674 cgrp->self.serial_nr = css_serial_nr_next++;
5675
5676 /* allocation complete, commit to creation */
5677 list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);
5678 atomic_inc(&root->nr_cgrps);
5679 cgroup_get_live(parent);
5680
5681 /*
5682 * On the default hierarchy, a child doesn't automatically inherit
5683 * subtree_control from the parent. Each is configured manually.
5684 */
5685 if (!cgroup_on_dfl(cgrp))
5686 cgrp->subtree_control = cgroup_control(cgrp);
5687
5688 cgroup_propagate_control(cgrp);
5689
5690 return cgrp;
5691
5692out_psi_free:
5693 psi_cgroup_free(cgrp);
5694out_kernfs_remove:
5695 kernfs_remove(cgrp->kn);
5696out_stat_exit:
5697 cgroup_rstat_exit(cgrp);
5698out_cancel_ref:
5699 percpu_ref_exit(&cgrp->self.refcnt);
5700out_free_cgrp:
5701 kfree(cgrp);
5702 return ERR_PTR(ret);
5703}
5704
5705static bool cgroup_check_hierarchy_limits(struct cgroup *parent)
5706{
5707 struct cgroup *cgroup;
5708 int ret = false;
5709 int level = 1;
5710
5711 lockdep_assert_held(&cgroup_mutex);
5712
5713 for (cgroup = parent; cgroup; cgroup = cgroup_parent(cgroup)) {
5714 if (cgroup->nr_descendants >= cgroup->max_descendants)
5715 goto fail;
5716
5717 if (level > cgroup->max_depth)
5718 goto fail;
5719
5720 level++;
5721 }
5722
5723 ret = true;
5724fail:
5725 return ret;
5726}
5727
5728int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
5729{
5730 struct cgroup *parent, *cgrp;
5731 int ret;
5732
5733 /* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
5734 if (strchr(name, '\n'))
5735 return -EINVAL;
5736
5737 parent = cgroup_kn_lock_live(parent_kn, false);
5738 if (!parent)
5739 return -ENODEV;
5740
5741 if (!cgroup_check_hierarchy_limits(parent)) {
5742 ret = -EAGAIN;
5743 goto out_unlock;
5744 }
5745
5746 cgrp = cgroup_create(parent, name, mode);
5747 if (IS_ERR(cgrp)) {
5748 ret = PTR_ERR(cgrp);
5749 goto out_unlock;
5750 }
5751
5752 /*
5753 * This extra ref will be put in cgroup_free_fn() and guarantees
5754 * that @cgrp->kn is always accessible.
5755 */
5756 kernfs_get(cgrp->kn);
5757
5758 ret = css_populate_dir(&cgrp->self);
5759 if (ret)
5760 goto out_destroy;
5761
5762 ret = cgroup_apply_control_enable(cgrp);
5763 if (ret)
5764 goto out_destroy;
5765
5766 TRACE_CGROUP_PATH(mkdir, cgrp);
5767
5768 /* let's create and online css's */
5769 kernfs_activate(cgrp->kn);
5770
5771 ret = 0;
5772 goto out_unlock;
5773
5774out_destroy:
5775 cgroup_destroy_locked(cgrp);
5776out_unlock:
5777 cgroup_kn_unlock(parent_kn);
5778 return ret;
5779}
5780
5781/*
5782 * This is called when the refcnt of a css is confirmed to be killed.
5783 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
5784 * initiate destruction and put the css ref from kill_css().
5785 */
5786static void css_killed_work_fn(struct work_struct *work)
5787{
5788 struct cgroup_subsys_state *css =
5789 container_of(work, struct cgroup_subsys_state, destroy_work);
5790
5791 cgroup_lock();
5792
5793 do {
5794 offline_css(css);
5795 css_put(css);
5796 /* @css can't go away while we're holding cgroup_mutex */
5797 css = css->parent;
5798 } while (css && atomic_dec_and_test(&css->online_cnt));
5799
5800 cgroup_unlock();
5801}
5802
5803/* css kill confirmation processing requires process context, bounce */
5804static void css_killed_ref_fn(struct percpu_ref *ref)
5805{
5806 struct cgroup_subsys_state *css =
5807 container_of(ref, struct cgroup_subsys_state, refcnt);
5808
5809 if (atomic_dec_and_test(&css->online_cnt)) {
5810 INIT_WORK(&css->destroy_work, css_killed_work_fn);
5811 queue_work(cgroup_destroy_wq, &css->destroy_work);
5812 }
5813}
5814
5815/**
5816 * kill_css - destroy a css
5817 * @css: css to destroy
5818 *
5819 * This function initiates destruction of @css by removing cgroup interface
5820 * files and putting its base reference. ->css_offline() will be invoked
5821 * asynchronously once css_tryget_online() is guaranteed to fail and when
5822 * the reference count reaches zero, @css will be released.
5823 */
5824static void kill_css(struct cgroup_subsys_state *css)
5825{
5826 lockdep_assert_held(&cgroup_mutex);
5827
5828 if (css->flags & CSS_DYING)
5829 return;
5830
5831 css->flags |= CSS_DYING;
5832
5833 /*
5834 * This must happen before css is disassociated with its cgroup.
5835 * See seq_css() for details.
5836 */
5837 css_clear_dir(css);
5838
5839 /*
5840 * Killing would put the base ref, but we need to keep it alive
5841 * until after ->css_offline().
5842 */
5843 css_get(css);
5844
5845 /*
5846 * cgroup core guarantees that, by the time ->css_offline() is
5847 * invoked, no new css reference will be given out via
5848 * css_tryget_online(). We can't simply call percpu_ref_kill() and
5849 * proceed to offlining css's because percpu_ref_kill() doesn't
5850 * guarantee that the ref is seen as killed on all CPUs on return.
5851 *
5852 * Use percpu_ref_kill_and_confirm() to get notifications as each
5853 * css is confirmed to be seen as killed on all CPUs.
5854 */
5855 percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
5856}
5857
5858/**
5859 * cgroup_destroy_locked - the first stage of cgroup destruction
5860 * @cgrp: cgroup to be destroyed
5861 *
5862 * css's make use of percpu refcnts whose killing latency shouldn't be
5863 * exposed to userland and are RCU protected. Also, cgroup core needs to
5864 * guarantee that css_tryget_online() won't succeed by the time
5865 * ->css_offline() is invoked. To satisfy all the requirements,
5866 * destruction is implemented in the following two steps.
5867 *
5868 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
5869 * userland visible parts and start killing the percpu refcnts of
5870 * css's. Set up so that the next stage will be kicked off once all
5871 * the percpu refcnts are confirmed to be killed.
5872 *
5873 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
5874 * rest of destruction. Once all cgroup references are gone, the
5875 * cgroup is RCU-freed.
5876 *
5877 * This function implements s1. After this step, @cgrp is gone as far as
5878 * the userland is concerned and a new cgroup with the same name may be
5879 * created. As cgroup doesn't care about the names internally, this
5880 * doesn't cause any problem.
5881 */
5882static int cgroup_destroy_locked(struct cgroup *cgrp)
5883 __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
5884{
5885 struct cgroup *tcgrp, *parent = cgroup_parent(cgrp);
5886 struct cgroup_subsys_state *css;
5887 struct cgrp_cset_link *link;
5888 int ssid;
5889
5890 lockdep_assert_held(&cgroup_mutex);
5891
5892 /*
5893 * Only migration can raise populated from zero and we're already
5894 * holding cgroup_mutex.
5895 */
5896 if (cgroup_is_populated(cgrp))
5897 return -EBUSY;
5898
5899 /*
5900 * Make sure there's no live children. We can't test emptiness of
5901 * ->self.children as dead children linger on it while being
5902 * drained; otherwise, "rmdir parent/child parent" may fail.
5903 */
5904 if (css_has_online_children(&cgrp->self))
5905 return -EBUSY;
5906
5907 /*
5908 * Mark @cgrp and the associated csets dead. The former prevents
5909 * further task migration and child creation by disabling
5910 * cgroup_kn_lock_live(). The latter makes the csets ignored by
5911 * the migration path.
5912 */
5913 cgrp->self.flags &= ~CSS_ONLINE;
5914
5915 spin_lock_irq(&css_set_lock);
5916 list_for_each_entry(link, &cgrp->cset_links, cset_link)
5917 link->cset->dead = true;
5918 spin_unlock_irq(&css_set_lock);
5919
5920 /* initiate massacre of all css's */
5921 for_each_css(css, ssid, cgrp)
5922 kill_css(css);
5923
5924 /* clear and remove @cgrp dir, @cgrp has an extra ref on its kn */
5925 css_clear_dir(&cgrp->self);
5926 kernfs_remove(cgrp->kn);
5927
5928 if (cgroup_is_threaded(cgrp))
5929 parent->nr_threaded_children--;
5930
5931 spin_lock_irq(&css_set_lock);
5932 for (tcgrp = parent; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
5933 tcgrp->nr_descendants--;
5934 tcgrp->nr_dying_descendants++;
5935 /*
5936 * If the dying cgroup is frozen, decrease frozen descendants
5937 * counters of ancestor cgroups.
5938 */
5939 if (test_bit(CGRP_FROZEN, &cgrp->flags))
5940 tcgrp->freezer.nr_frozen_descendants--;
5941 }
5942 spin_unlock_irq(&css_set_lock);
5943
5944 cgroup1_check_for_release(parent);
5945
5946 cgroup_bpf_offline(cgrp);
5947
5948 /* put the base reference */
5949 percpu_ref_kill(&cgrp->self.refcnt);
5950
5951 return 0;
5952};
5953
5954int cgroup_rmdir(struct kernfs_node *kn)
5955{
5956 struct cgroup *cgrp;
5957 int ret = 0;
5958
5959 cgrp = cgroup_kn_lock_live(kn, false);
5960 if (!cgrp)
5961 return 0;
5962
5963 ret = cgroup_destroy_locked(cgrp);
5964 if (!ret)
5965 TRACE_CGROUP_PATH(rmdir, cgrp);
5966
5967 cgroup_kn_unlock(kn);
5968 return ret;
5969}
5970
5971static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
5972 .show_options = cgroup_show_options,
5973 .mkdir = cgroup_mkdir,
5974 .rmdir = cgroup_rmdir,
5975 .show_path = cgroup_show_path,
5976};
5977
5978static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
5979{
5980 struct cgroup_subsys_state *css;
5981
5982 pr_debug("Initializing cgroup subsys %s\n", ss->name);
5983
5984 cgroup_lock();
5985
5986 idr_init(&ss->css_idr);
5987 INIT_LIST_HEAD(&ss->cfts);
5988
5989 /* Create the root cgroup state for this subsystem */
5990 ss->root = &cgrp_dfl_root;
5991 css = ss->css_alloc(NULL);
5992 /* We don't handle early failures gracefully */
5993 BUG_ON(IS_ERR(css));
5994 init_and_link_css(css, ss, &cgrp_dfl_root.cgrp);
5995
5996 /*
5997 * Root csses are never destroyed and we can't initialize
5998 * percpu_ref during early init. Disable refcnting.
5999 */
6000 css->flags |= CSS_NO_REF;
6001
6002 if (early) {
6003 /* allocation can't be done safely during early init */
6004 css->id = 1;
6005 } else {
6006 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL);
6007 BUG_ON(css->id < 0);
6008 }
6009
6010 /* Update the init_css_set to contain a subsys
6011 * pointer to this state - since the subsystem is
6012 * newly registered, all tasks and hence the
6013 * init_css_set is in the subsystem's root cgroup. */
6014 init_css_set.subsys[ss->id] = css;
6015
6016 have_fork_callback |= (bool)ss->fork << ss->id;
6017 have_exit_callback |= (bool)ss->exit << ss->id;
6018 have_release_callback |= (bool)ss->release << ss->id;
6019 have_canfork_callback |= (bool)ss->can_fork << ss->id;
6020
6021 /* At system boot, before all subsystems have been
6022 * registered, no tasks have been forked, so we don't
6023 * need to invoke fork callbacks here. */
6024 BUG_ON(!list_empty(&init_task.tasks));
6025
6026 BUG_ON(online_css(css));
6027
6028 cgroup_unlock();
6029}
6030
6031/**
6032 * cgroup_init_early - cgroup initialization at system boot
6033 *
6034 * Initialize cgroups at system boot, and initialize any
6035 * subsystems that request early init.
6036 */
6037int __init cgroup_init_early(void)
6038{
6039 static struct cgroup_fs_context __initdata ctx;
6040 struct cgroup_subsys *ss;
6041 int i;
6042
6043 ctx.root = &cgrp_dfl_root;
6044 init_cgroup_root(&ctx);
6045 cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF;
6046
6047 RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
6048
6049 for_each_subsys(ss, i) {
6050 WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
6051 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p id:name=%d:%s\n",
6052 i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
6053 ss->id, ss->name);
6054 WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
6055 "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
6056
6057 ss->id = i;
6058 ss->name = cgroup_subsys_name[i];
6059 if (!ss->legacy_name)
6060 ss->legacy_name = cgroup_subsys_name[i];
6061
6062 if (ss->early_init)
6063 cgroup_init_subsys(ss, true);
6064 }
6065 return 0;
6066}
6067
6068/**
6069 * cgroup_init - cgroup initialization
6070 *
6071 * Register cgroup filesystem and /proc file, and initialize
6072 * any subsystems that didn't request early init.
6073 */
6074int __init cgroup_init(void)
6075{
6076 struct cgroup_subsys *ss;
6077 int ssid;
6078
6079 BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
6080 BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
6081 BUG_ON(cgroup_init_cftypes(NULL, cgroup_psi_files));
6082 BUG_ON(cgroup_init_cftypes(NULL, cgroup1_base_files));
6083
6084 cgroup_rstat_boot();
6085
6086 get_user_ns(init_cgroup_ns.user_ns);
6087
6088 cgroup_lock();
6089
6090 /*
6091 * Add init_css_set to the hash table so that dfl_root can link to
6092 * it during init.
6093 */
6094 hash_add(css_set_table, &init_css_set.hlist,
6095 css_set_hash(init_css_set.subsys));
6096
6097 BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0));
6098
6099 cgroup_unlock();
6100
6101 for_each_subsys(ss, ssid) {
6102 if (ss->early_init) {
6103 struct cgroup_subsys_state *css =
6104 init_css_set.subsys[ss->id];
6105
6106 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2,
6107 GFP_KERNEL);
6108 BUG_ON(css->id < 0);
6109 } else {
6110 cgroup_init_subsys(ss, false);
6111 }
6112
6113 list_add_tail(&init_css_set.e_cset_node[ssid],
6114 &cgrp_dfl_root.cgrp.e_csets[ssid]);
6115
6116 /*
6117 * Setting dfl_root subsys_mask needs to consider the
6118 * disabled flag and cftype registration needs kmalloc,
6119 * both of which aren't available during early_init.
6120 */
6121 if (!cgroup_ssid_enabled(ssid))
6122 continue;
6123
6124 if (cgroup1_ssid_disabled(ssid))
6125 pr_info("Disabling %s control group subsystem in v1 mounts\n",
6126 ss->legacy_name);
6127
6128 cgrp_dfl_root.subsys_mask |= 1 << ss->id;
6129
6130 /* implicit controllers must be threaded too */
6131 WARN_ON(ss->implicit_on_dfl && !ss->threaded);
6132
6133 if (ss->implicit_on_dfl)
6134 cgrp_dfl_implicit_ss_mask |= 1 << ss->id;
6135 else if (!ss->dfl_cftypes)
6136 cgrp_dfl_inhibit_ss_mask |= 1 << ss->id;
6137
6138 if (ss->threaded)
6139 cgrp_dfl_threaded_ss_mask |= 1 << ss->id;
6140
6141 if (ss->dfl_cftypes == ss->legacy_cftypes) {
6142 WARN_ON(cgroup_add_cftypes(ss, ss->dfl_cftypes));
6143 } else {
6144 WARN_ON(cgroup_add_dfl_cftypes(ss, ss->dfl_cftypes));
6145 WARN_ON(cgroup_add_legacy_cftypes(ss, ss->legacy_cftypes));
6146 }
6147
6148 if (ss->bind)
6149 ss->bind(init_css_set.subsys[ssid]);
6150
6151 cgroup_lock();
6152 css_populate_dir(init_css_set.subsys[ssid]);
6153 cgroup_unlock();
6154 }
6155
6156 /* init_css_set.subsys[] has been updated, re-hash */
6157 hash_del(&init_css_set.hlist);
6158 hash_add(css_set_table, &init_css_set.hlist,
6159 css_set_hash(init_css_set.subsys));
6160
6161 WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup"));
6162 WARN_ON(register_filesystem(&cgroup_fs_type));
6163 WARN_ON(register_filesystem(&cgroup2_fs_type));
6164 WARN_ON(!proc_create_single("cgroups", 0, NULL, proc_cgroupstats_show));
6165#ifdef CONFIG_CPUSETS
6166 WARN_ON(register_filesystem(&cpuset_fs_type));
6167#endif
6168
6169 return 0;
6170}
6171
6172static int __init cgroup_wq_init(void)
6173{
6174 /*
6175 * There isn't much point in executing destruction path in
6176 * parallel. Good chunk is serialized with cgroup_mutex anyway.
6177 * Use 1 for @max_active.
6178 *
6179 * We would prefer to do this in cgroup_init() above, but that
6180 * is called before init_workqueues(): so leave this until after.
6181 */
6182 cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
6183 BUG_ON(!cgroup_destroy_wq);
6184 return 0;
6185}
6186core_initcall(cgroup_wq_init);
6187
6188void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
6189{
6190 struct kernfs_node *kn;
6191
6192 kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
6193 if (!kn)
6194 return;
6195 kernfs_path(kn, buf, buflen);
6196 kernfs_put(kn);
6197}
6198
6199/*
6200 * cgroup_get_from_id : get the cgroup associated with cgroup id
6201 * @id: cgroup id
6202 * On success return the cgrp or ERR_PTR on failure
6203 * Only cgroups within current task's cgroup NS are valid.
6204 */
6205struct cgroup *cgroup_get_from_id(u64 id)
6206{
6207 struct kernfs_node *kn;
6208 struct cgroup *cgrp, *root_cgrp;
6209
6210 kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
6211 if (!kn)
6212 return ERR_PTR(-ENOENT);
6213
6214 if (kernfs_type(kn) != KERNFS_DIR) {
6215 kernfs_put(kn);
6216 return ERR_PTR(-ENOENT);
6217 }
6218
6219 rcu_read_lock();
6220
6221 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6222 if (cgrp && !cgroup_tryget(cgrp))
6223 cgrp = NULL;
6224
6225 rcu_read_unlock();
6226 kernfs_put(kn);
6227
6228 if (!cgrp)
6229 return ERR_PTR(-ENOENT);
6230
6231 root_cgrp = current_cgns_cgroup_dfl();
6232 if (!cgroup_is_descendant(cgrp, root_cgrp)) {
6233 cgroup_put(cgrp);
6234 return ERR_PTR(-ENOENT);
6235 }
6236
6237 return cgrp;
6238}
6239EXPORT_SYMBOL_GPL(cgroup_get_from_id);
6240
6241/*
6242 * proc_cgroup_show()
6243 * - Print task's cgroup paths into seq_file, one line for each hierarchy
6244 * - Used for /proc/<pid>/cgroup.
6245 */
6246int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
6247 struct pid *pid, struct task_struct *tsk)
6248{
6249 char *buf;
6250 int retval;
6251 struct cgroup_root *root;
6252
6253 retval = -ENOMEM;
6254 buf = kmalloc(PATH_MAX, GFP_KERNEL);
6255 if (!buf)
6256 goto out;
6257
6258 rcu_read_lock();
6259 spin_lock_irq(&css_set_lock);
6260
6261 for_each_root(root) {
6262 struct cgroup_subsys *ss;
6263 struct cgroup *cgrp;
6264 int ssid, count = 0;
6265
6266 if (root == &cgrp_dfl_root && !READ_ONCE(cgrp_dfl_visible))
6267 continue;
6268
6269 cgrp = task_cgroup_from_root(tsk, root);
6270 /* The root has already been unmounted. */
6271 if (!cgrp)
6272 continue;
6273
6274 seq_printf(m, "%d:", root->hierarchy_id);
6275 if (root != &cgrp_dfl_root)
6276 for_each_subsys(ss, ssid)
6277 if (root->subsys_mask & (1 << ssid))
6278 seq_printf(m, "%s%s", count++ ? "," : "",
6279 ss->legacy_name);
6280 if (strlen(root->name))
6281 seq_printf(m, "%sname=%s", count ? "," : "",
6282 root->name);
6283 seq_putc(m, ':');
6284 /*
6285 * On traditional hierarchies, all zombie tasks show up as
6286 * belonging to the root cgroup. On the default hierarchy,
6287 * while a zombie doesn't show up in "cgroup.procs" and
6288 * thus can't be migrated, its /proc/PID/cgroup keeps
6289 * reporting the cgroup it belonged to before exiting. If
6290 * the cgroup is removed before the zombie is reaped,
6291 * " (deleted)" is appended to the cgroup path.
6292 */
6293 if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) {
6294 retval = cgroup_path_ns_locked(cgrp, buf, PATH_MAX,
6295 current->nsproxy->cgroup_ns);
6296 if (retval == -E2BIG)
6297 retval = -ENAMETOOLONG;
6298 if (retval < 0)
6299 goto out_unlock;
6300
6301 seq_puts(m, buf);
6302 } else {
6303 seq_puts(m, "/");
6304 }
6305
6306 if (cgroup_on_dfl(cgrp) && cgroup_is_dead(cgrp))
6307 seq_puts(m, " (deleted)\n");
6308 else
6309 seq_putc(m, '\n');
6310 }
6311
6312 retval = 0;
6313out_unlock:
6314 spin_unlock_irq(&css_set_lock);
6315 rcu_read_unlock();
6316 kfree(buf);
6317out:
6318 return retval;
6319}
6320
6321/**
6322 * cgroup_fork - initialize cgroup related fields during copy_process()
6323 * @child: pointer to task_struct of forking parent process.
6324 *
6325 * A task is associated with the init_css_set until cgroup_post_fork()
6326 * attaches it to the target css_set.
6327 */
6328void cgroup_fork(struct task_struct *child)
6329{
6330 RCU_INIT_POINTER(child->cgroups, &init_css_set);
6331 INIT_LIST_HEAD(&child->cg_list);
6332}
6333
6334/**
6335 * cgroup_v1v2_get_from_file - get a cgroup pointer from a file pointer
6336 * @f: file corresponding to cgroup_dir
6337 *
6338 * Find the cgroup from a file pointer associated with a cgroup directory.
6339 * Returns a pointer to the cgroup on success. ERR_PTR is returned if the
6340 * cgroup cannot be found.
6341 */
6342static struct cgroup *cgroup_v1v2_get_from_file(struct file *f)
6343{
6344 struct cgroup_subsys_state *css;
6345
6346 css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
6347 if (IS_ERR(css))
6348 return ERR_CAST(css);
6349
6350 return css->cgroup;
6351}
6352
6353/**
6354 * cgroup_get_from_file - same as cgroup_v1v2_get_from_file, but only supports
6355 * cgroup2.
6356 * @f: file corresponding to cgroup2_dir
6357 */
6358static struct cgroup *cgroup_get_from_file(struct file *f)
6359{
6360 struct cgroup *cgrp = cgroup_v1v2_get_from_file(f);
6361
6362 if (IS_ERR(cgrp))
6363 return ERR_CAST(cgrp);
6364
6365 if (!cgroup_on_dfl(cgrp)) {
6366 cgroup_put(cgrp);
6367 return ERR_PTR(-EBADF);
6368 }
6369
6370 return cgrp;
6371}
6372
6373/**
6374 * cgroup_css_set_fork - find or create a css_set for a child process
6375 * @kargs: the arguments passed to create the child process
6376 *
6377 * This functions finds or creates a new css_set which the child
6378 * process will be attached to in cgroup_post_fork(). By default,
6379 * the child process will be given the same css_set as its parent.
6380 *
6381 * If CLONE_INTO_CGROUP is specified this function will try to find an
6382 * existing css_set which includes the requested cgroup and if not create
6383 * a new css_set that the child will be attached to later. If this function
6384 * succeeds it will hold cgroup_threadgroup_rwsem on return. If
6385 * CLONE_INTO_CGROUP is requested this function will grab cgroup mutex
6386 * before grabbing cgroup_threadgroup_rwsem and will hold a reference
6387 * to the target cgroup.
6388 */
6389static int cgroup_css_set_fork(struct kernel_clone_args *kargs)
6390 __acquires(&cgroup_mutex) __acquires(&cgroup_threadgroup_rwsem)
6391{
6392 int ret;
6393 struct cgroup *dst_cgrp = NULL;
6394 struct css_set *cset;
6395 struct super_block *sb;
6396 struct file *f;
6397
6398 if (kargs->flags & CLONE_INTO_CGROUP)
6399 cgroup_lock();
6400
6401 cgroup_threadgroup_change_begin(current);
6402
6403 spin_lock_irq(&css_set_lock);
6404 cset = task_css_set(current);
6405 get_css_set(cset);
6406 spin_unlock_irq(&css_set_lock);
6407
6408 if (!(kargs->flags & CLONE_INTO_CGROUP)) {
6409 kargs->cset = cset;
6410 return 0;
6411 }
6412
6413 f = fget_raw(kargs->cgroup);
6414 if (!f) {
6415 ret = -EBADF;
6416 goto err;
6417 }
6418 sb = f->f_path.dentry->d_sb;
6419
6420 dst_cgrp = cgroup_get_from_file(f);
6421 if (IS_ERR(dst_cgrp)) {
6422 ret = PTR_ERR(dst_cgrp);
6423 dst_cgrp = NULL;
6424 goto err;
6425 }
6426
6427 if (cgroup_is_dead(dst_cgrp)) {
6428 ret = -ENODEV;
6429 goto err;
6430 }
6431
6432 /*
6433 * Verify that we the target cgroup is writable for us. This is
6434 * usually done by the vfs layer but since we're not going through
6435 * the vfs layer here we need to do it "manually".
6436 */
6437 ret = cgroup_may_write(dst_cgrp, sb);
6438 if (ret)
6439 goto err;
6440
6441 /*
6442 * Spawning a task directly into a cgroup works by passing a file
6443 * descriptor to the target cgroup directory. This can even be an O_PATH
6444 * file descriptor. But it can never be a cgroup.procs file descriptor.
6445 * This was done on purpose so spawning into a cgroup could be
6446 * conceptualized as an atomic
6447 *
6448 * fd = openat(dfd_cgroup, "cgroup.procs", ...);
6449 * write(fd, <child-pid>, ...);
6450 *
6451 * sequence, i.e. it's a shorthand for the caller opening and writing
6452 * cgroup.procs of the cgroup indicated by @dfd_cgroup. This allows us
6453 * to always use the caller's credentials.
6454 */
6455 ret = cgroup_attach_permissions(cset->dfl_cgrp, dst_cgrp, sb,
6456 !(kargs->flags & CLONE_THREAD),
6457 current->nsproxy->cgroup_ns);
6458 if (ret)
6459 goto err;
6460
6461 kargs->cset = find_css_set(cset, dst_cgrp);
6462 if (!kargs->cset) {
6463 ret = -ENOMEM;
6464 goto err;
6465 }
6466
6467 put_css_set(cset);
6468 fput(f);
6469 kargs->cgrp = dst_cgrp;
6470 return ret;
6471
6472err:
6473 cgroup_threadgroup_change_end(current);
6474 cgroup_unlock();
6475 if (f)
6476 fput(f);
6477 if (dst_cgrp)
6478 cgroup_put(dst_cgrp);
6479 put_css_set(cset);
6480 if (kargs->cset)
6481 put_css_set(kargs->cset);
6482 return ret;
6483}
6484
6485/**
6486 * cgroup_css_set_put_fork - drop references we took during fork
6487 * @kargs: the arguments passed to create the child process
6488 *
6489 * Drop references to the prepared css_set and target cgroup if
6490 * CLONE_INTO_CGROUP was requested.
6491 */
6492static void cgroup_css_set_put_fork(struct kernel_clone_args *kargs)
6493 __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
6494{
6495 struct cgroup *cgrp = kargs->cgrp;
6496 struct css_set *cset = kargs->cset;
6497
6498 cgroup_threadgroup_change_end(current);
6499
6500 if (cset) {
6501 put_css_set(cset);
6502 kargs->cset = NULL;
6503 }
6504
6505 if (kargs->flags & CLONE_INTO_CGROUP) {
6506 cgroup_unlock();
6507 if (cgrp) {
6508 cgroup_put(cgrp);
6509 kargs->cgrp = NULL;
6510 }
6511 }
6512}
6513
6514/**
6515 * cgroup_can_fork - called on a new task before the process is exposed
6516 * @child: the child process
6517 * @kargs: the arguments passed to create the child process
6518 *
6519 * This prepares a new css_set for the child process which the child will
6520 * be attached to in cgroup_post_fork().
6521 * This calls the subsystem can_fork() callbacks. If the cgroup_can_fork()
6522 * callback returns an error, the fork aborts with that error code. This
6523 * allows for a cgroup subsystem to conditionally allow or deny new forks.
6524 */
6525int cgroup_can_fork(struct task_struct *child, struct kernel_clone_args *kargs)
6526{
6527 struct cgroup_subsys *ss;
6528 int i, j, ret;
6529
6530 ret = cgroup_css_set_fork(kargs);
6531 if (ret)
6532 return ret;
6533
6534 do_each_subsys_mask(ss, i, have_canfork_callback) {
6535 ret = ss->can_fork(child, kargs->cset);
6536 if (ret)
6537 goto out_revert;
6538 } while_each_subsys_mask();
6539
6540 return 0;
6541
6542out_revert:
6543 for_each_subsys(ss, j) {
6544 if (j >= i)
6545 break;
6546 if (ss->cancel_fork)
6547 ss->cancel_fork(child, kargs->cset);
6548 }
6549
6550 cgroup_css_set_put_fork(kargs);
6551
6552 return ret;
6553}
6554
6555/**
6556 * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
6557 * @child: the child process
6558 * @kargs: the arguments passed to create the child process
6559 *
6560 * This calls the cancel_fork() callbacks if a fork failed *after*
6561 * cgroup_can_fork() succeeded and cleans up references we took to
6562 * prepare a new css_set for the child process in cgroup_can_fork().
6563 */
6564void cgroup_cancel_fork(struct task_struct *child,
6565 struct kernel_clone_args *kargs)
6566{
6567 struct cgroup_subsys *ss;
6568 int i;
6569
6570 for_each_subsys(ss, i)
6571 if (ss->cancel_fork)
6572 ss->cancel_fork(child, kargs->cset);
6573
6574 cgroup_css_set_put_fork(kargs);
6575}
6576
6577/**
6578 * cgroup_post_fork - finalize cgroup setup for the child process
6579 * @child: the child process
6580 * @kargs: the arguments passed to create the child process
6581 *
6582 * Attach the child process to its css_set calling the subsystem fork()
6583 * callbacks.
6584 */
6585void cgroup_post_fork(struct task_struct *child,
6586 struct kernel_clone_args *kargs)
6587 __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
6588{
6589 unsigned long cgrp_flags = 0;
6590 bool kill = false;
6591 struct cgroup_subsys *ss;
6592 struct css_set *cset;
6593 int i;
6594
6595 cset = kargs->cset;
6596 kargs->cset = NULL;
6597
6598 spin_lock_irq(&css_set_lock);
6599
6600 /* init tasks are special, only link regular threads */
6601 if (likely(child->pid)) {
6602 if (kargs->cgrp)
6603 cgrp_flags = kargs->cgrp->flags;
6604 else
6605 cgrp_flags = cset->dfl_cgrp->flags;
6606
6607 WARN_ON_ONCE(!list_empty(&child->cg_list));
6608 cset->nr_tasks++;
6609 css_set_move_task(child, NULL, cset, false);
6610 } else {
6611 put_css_set(cset);
6612 cset = NULL;
6613 }
6614
6615 if (!(child->flags & PF_KTHREAD)) {
6616 if (unlikely(test_bit(CGRP_FREEZE, &cgrp_flags))) {
6617 /*
6618 * If the cgroup has to be frozen, the new task has
6619 * too. Let's set the JOBCTL_TRAP_FREEZE jobctl bit to
6620 * get the task into the frozen state.
6621 */
6622 spin_lock(&child->sighand->siglock);
6623 WARN_ON_ONCE(child->frozen);
6624 child->jobctl |= JOBCTL_TRAP_FREEZE;
6625 spin_unlock(&child->sighand->siglock);
6626
6627 /*
6628 * Calling cgroup_update_frozen() isn't required here,
6629 * because it will be called anyway a bit later from
6630 * do_freezer_trap(). So we avoid cgroup's transient
6631 * switch from the frozen state and back.
6632 */
6633 }
6634
6635 /*
6636 * If the cgroup is to be killed notice it now and take the
6637 * child down right after we finished preparing it for
6638 * userspace.
6639 */
6640 kill = test_bit(CGRP_KILL, &cgrp_flags);
6641 }
6642
6643 spin_unlock_irq(&css_set_lock);
6644
6645 /*
6646 * Call ss->fork(). This must happen after @child is linked on
6647 * css_set; otherwise, @child might change state between ->fork()
6648 * and addition to css_set.
6649 */
6650 do_each_subsys_mask(ss, i, have_fork_callback) {
6651 ss->fork(child);
6652 } while_each_subsys_mask();
6653
6654 /* Make the new cset the root_cset of the new cgroup namespace. */
6655 if (kargs->flags & CLONE_NEWCGROUP) {
6656 struct css_set *rcset = child->nsproxy->cgroup_ns->root_cset;
6657
6658 get_css_set(cset);
6659 child->nsproxy->cgroup_ns->root_cset = cset;
6660 put_css_set(rcset);
6661 }
6662
6663 /* Cgroup has to be killed so take down child immediately. */
6664 if (unlikely(kill))
6665 do_send_sig_info(SIGKILL, SEND_SIG_NOINFO, child, PIDTYPE_TGID);
6666
6667 cgroup_css_set_put_fork(kargs);
6668}
6669
6670/**
6671 * cgroup_exit - detach cgroup from exiting task
6672 * @tsk: pointer to task_struct of exiting process
6673 *
6674 * Description: Detach cgroup from @tsk.
6675 *
6676 */
6677void cgroup_exit(struct task_struct *tsk)
6678{
6679 struct cgroup_subsys *ss;
6680 struct css_set *cset;
6681 int i;
6682
6683 spin_lock_irq(&css_set_lock);
6684
6685 WARN_ON_ONCE(list_empty(&tsk->cg_list));
6686 cset = task_css_set(tsk);
6687 css_set_move_task(tsk, cset, NULL, false);
6688 list_add_tail(&tsk->cg_list, &cset->dying_tasks);
6689 cset->nr_tasks--;
6690
6691 if (dl_task(tsk))
6692 dec_dl_tasks_cs(tsk);
6693
6694 WARN_ON_ONCE(cgroup_task_frozen(tsk));
6695 if (unlikely(!(tsk->flags & PF_KTHREAD) &&
6696 test_bit(CGRP_FREEZE, &task_dfl_cgroup(tsk)->flags)))
6697 cgroup_update_frozen(task_dfl_cgroup(tsk));
6698
6699 spin_unlock_irq(&css_set_lock);
6700
6701 /* see cgroup_post_fork() for details */
6702 do_each_subsys_mask(ss, i, have_exit_callback) {
6703 ss->exit(tsk);
6704 } while_each_subsys_mask();
6705}
6706
6707void cgroup_release(struct task_struct *task)
6708{
6709 struct cgroup_subsys *ss;
6710 int ssid;
6711
6712 do_each_subsys_mask(ss, ssid, have_release_callback) {
6713 ss->release(task);
6714 } while_each_subsys_mask();
6715
6716 spin_lock_irq(&css_set_lock);
6717 css_set_skip_task_iters(task_css_set(task), task);
6718 list_del_init(&task->cg_list);
6719 spin_unlock_irq(&css_set_lock);
6720}
6721
6722void cgroup_free(struct task_struct *task)
6723{
6724 struct css_set *cset = task_css_set(task);
6725 put_css_set(cset);
6726}
6727
6728static int __init cgroup_disable(char *str)
6729{
6730 struct cgroup_subsys *ss;
6731 char *token;
6732 int i;
6733
6734 while ((token = strsep(&str, ",")) != NULL) {
6735 if (!*token)
6736 continue;
6737
6738 for_each_subsys(ss, i) {
6739 if (strcmp(token, ss->name) &&
6740 strcmp(token, ss->legacy_name))
6741 continue;
6742
6743 static_branch_disable(cgroup_subsys_enabled_key[i]);
6744 pr_info("Disabling %s control group subsystem\n",
6745 ss->name);
6746 }
6747
6748 for (i = 0; i < OPT_FEATURE_COUNT; i++) {
6749 if (strcmp(token, cgroup_opt_feature_names[i]))
6750 continue;
6751 cgroup_feature_disable_mask |= 1 << i;
6752 pr_info("Disabling %s control group feature\n",
6753 cgroup_opt_feature_names[i]);
6754 break;
6755 }
6756 }
6757 return 1;
6758}
6759__setup("cgroup_disable=", cgroup_disable);
6760
6761void __init __weak enable_debug_cgroup(void) { }
6762
6763static int __init enable_cgroup_debug(char *str)
6764{
6765 cgroup_debug = true;
6766 enable_debug_cgroup();
6767 return 1;
6768}
6769__setup("cgroup_debug", enable_cgroup_debug);
6770
6771static int __init cgroup_favordynmods_setup(char *str)
6772{
6773 return (kstrtobool(str, &have_favordynmods) == 0);
6774}
6775__setup("cgroup_favordynmods=", cgroup_favordynmods_setup);
6776
6777/**
6778 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
6779 * @dentry: directory dentry of interest
6780 * @ss: subsystem of interest
6781 *
6782 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
6783 * to get the corresponding css and return it. If such css doesn't exist
6784 * or can't be pinned, an ERR_PTR value is returned.
6785 */
6786struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
6787 struct cgroup_subsys *ss)
6788{
6789 struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
6790 struct file_system_type *s_type = dentry->d_sb->s_type;
6791 struct cgroup_subsys_state *css = NULL;
6792 struct cgroup *cgrp;
6793
6794 /* is @dentry a cgroup dir? */
6795 if ((s_type != &cgroup_fs_type && s_type != &cgroup2_fs_type) ||
6796 !kn || kernfs_type(kn) != KERNFS_DIR)
6797 return ERR_PTR(-EBADF);
6798
6799 rcu_read_lock();
6800
6801 /*
6802 * This path doesn't originate from kernfs and @kn could already
6803 * have been or be removed at any point. @kn->priv is RCU
6804 * protected for this access. See css_release_work_fn() for details.
6805 */
6806 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6807 if (cgrp)
6808 css = cgroup_css(cgrp, ss);
6809
6810 if (!css || !css_tryget_online(css))
6811 css = ERR_PTR(-ENOENT);
6812
6813 rcu_read_unlock();
6814 return css;
6815}
6816
6817/**
6818 * css_from_id - lookup css by id
6819 * @id: the cgroup id
6820 * @ss: cgroup subsys to be looked into
6821 *
6822 * Returns the css if there's valid one with @id, otherwise returns NULL.
6823 * Should be called under rcu_read_lock().
6824 */
6825struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
6826{
6827 WARN_ON_ONCE(!rcu_read_lock_held());
6828 return idr_find(&ss->css_idr, id);
6829}
6830
6831/**
6832 * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path
6833 * @path: path on the default hierarchy
6834 *
6835 * Find the cgroup at @path on the default hierarchy, increment its
6836 * reference count and return it. Returns pointer to the found cgroup on
6837 * success, ERR_PTR(-ENOENT) if @path doesn't exist or if the cgroup has already
6838 * been released and ERR_PTR(-ENOTDIR) if @path points to a non-directory.
6839 */
6840struct cgroup *cgroup_get_from_path(const char *path)
6841{
6842 struct kernfs_node *kn;
6843 struct cgroup *cgrp = ERR_PTR(-ENOENT);
6844 struct cgroup *root_cgrp;
6845
6846 root_cgrp = current_cgns_cgroup_dfl();
6847 kn = kernfs_walk_and_get(root_cgrp->kn, path);
6848 if (!kn)
6849 goto out;
6850
6851 if (kernfs_type(kn) != KERNFS_DIR) {
6852 cgrp = ERR_PTR(-ENOTDIR);
6853 goto out_kernfs;
6854 }
6855
6856 rcu_read_lock();
6857
6858 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6859 if (!cgrp || !cgroup_tryget(cgrp))
6860 cgrp = ERR_PTR(-ENOENT);
6861
6862 rcu_read_unlock();
6863
6864out_kernfs:
6865 kernfs_put(kn);
6866out:
6867 return cgrp;
6868}
6869EXPORT_SYMBOL_GPL(cgroup_get_from_path);
6870
6871/**
6872 * cgroup_v1v2_get_from_fd - get a cgroup pointer from a fd
6873 * @fd: fd obtained by open(cgroup_dir)
6874 *
6875 * Find the cgroup from a fd which should be obtained
6876 * by opening a cgroup directory. Returns a pointer to the
6877 * cgroup on success. ERR_PTR is returned if the cgroup
6878 * cannot be found.
6879 */
6880struct cgroup *cgroup_v1v2_get_from_fd(int fd)
6881{
6882 struct cgroup *cgrp;
6883 struct fd f = fdget_raw(fd);
6884 if (!f.file)
6885 return ERR_PTR(-EBADF);
6886
6887 cgrp = cgroup_v1v2_get_from_file(f.file);
6888 fdput(f);
6889 return cgrp;
6890}
6891
6892/**
6893 * cgroup_get_from_fd - same as cgroup_v1v2_get_from_fd, but only supports
6894 * cgroup2.
6895 * @fd: fd obtained by open(cgroup2_dir)
6896 */
6897struct cgroup *cgroup_get_from_fd(int fd)
6898{
6899 struct cgroup *cgrp = cgroup_v1v2_get_from_fd(fd);
6900
6901 if (IS_ERR(cgrp))
6902 return ERR_CAST(cgrp);
6903
6904 if (!cgroup_on_dfl(cgrp)) {
6905 cgroup_put(cgrp);
6906 return ERR_PTR(-EBADF);
6907 }
6908 return cgrp;
6909}
6910EXPORT_SYMBOL_GPL(cgroup_get_from_fd);
6911
6912static u64 power_of_ten(int power)
6913{
6914 u64 v = 1;
6915 while (power--)
6916 v *= 10;
6917 return v;
6918}
6919
6920/**
6921 * cgroup_parse_float - parse a floating number
6922 * @input: input string
6923 * @dec_shift: number of decimal digits to shift
6924 * @v: output
6925 *
6926 * Parse a decimal floating point number in @input and store the result in
6927 * @v with decimal point right shifted @dec_shift times. For example, if
6928 * @input is "12.3456" and @dec_shift is 3, *@v will be set to 12345.
6929 * Returns 0 on success, -errno otherwise.
6930 *
6931 * There's nothing cgroup specific about this function except that it's
6932 * currently the only user.
6933 */
6934int cgroup_parse_float(const char *input, unsigned dec_shift, s64 *v)
6935{
6936 s64 whole, frac = 0;
6937 int fstart = 0, fend = 0, flen;
6938
6939 if (!sscanf(input, "%lld.%n%lld%n", &whole, &fstart, &frac, &fend))
6940 return -EINVAL;
6941 if (frac < 0)
6942 return -EINVAL;
6943
6944 flen = fend > fstart ? fend - fstart : 0;
6945 if (flen < dec_shift)
6946 frac *= power_of_ten(dec_shift - flen);
6947 else
6948 frac = DIV_ROUND_CLOSEST_ULL(frac, power_of_ten(flen - dec_shift));
6949
6950 *v = whole * power_of_ten(dec_shift) + frac;
6951 return 0;
6952}
6953
6954/*
6955 * sock->sk_cgrp_data handling. For more info, see sock_cgroup_data
6956 * definition in cgroup-defs.h.
6957 */
6958#ifdef CONFIG_SOCK_CGROUP_DATA
6959
6960void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
6961{
6962 struct cgroup *cgroup;
6963
6964 rcu_read_lock();
6965 /* Don't associate the sock with unrelated interrupted task's cgroup. */
6966 if (in_interrupt()) {
6967 cgroup = &cgrp_dfl_root.cgrp;
6968 cgroup_get(cgroup);
6969 goto out;
6970 }
6971
6972 while (true) {
6973 struct css_set *cset;
6974
6975 cset = task_css_set(current);
6976 if (likely(cgroup_tryget(cset->dfl_cgrp))) {
6977 cgroup = cset->dfl_cgrp;
6978 break;
6979 }
6980 cpu_relax();
6981 }
6982out:
6983 skcd->cgroup = cgroup;
6984 cgroup_bpf_get(cgroup);
6985 rcu_read_unlock();
6986}
6987
6988void cgroup_sk_clone(struct sock_cgroup_data *skcd)
6989{
6990 struct cgroup *cgrp = sock_cgroup_ptr(skcd);
6991
6992 /*
6993 * We might be cloning a socket which is left in an empty
6994 * cgroup and the cgroup might have already been rmdir'd.
6995 * Don't use cgroup_get_live().
6996 */
6997 cgroup_get(cgrp);
6998 cgroup_bpf_get(cgrp);
6999}
7000
7001void cgroup_sk_free(struct sock_cgroup_data *skcd)
7002{
7003 struct cgroup *cgrp = sock_cgroup_ptr(skcd);
7004
7005 cgroup_bpf_put(cgrp);
7006 cgroup_put(cgrp);
7007}
7008
7009#endif /* CONFIG_SOCK_CGROUP_DATA */
7010
7011#ifdef CONFIG_SYSFS
7012static ssize_t show_delegatable_files(struct cftype *files, char *buf,
7013 ssize_t size, const char *prefix)
7014{
7015 struct cftype *cft;
7016 ssize_t ret = 0;
7017
7018 for (cft = files; cft && cft->name[0] != '\0'; cft++) {
7019 if (!(cft->flags & CFTYPE_NS_DELEGATABLE))
7020 continue;
7021
7022 if (prefix)
7023 ret += snprintf(buf + ret, size - ret, "%s.", prefix);
7024
7025 ret += snprintf(buf + ret, size - ret, "%s\n", cft->name);
7026
7027 if (WARN_ON(ret >= size))
7028 break;
7029 }
7030
7031 return ret;
7032}
7033
7034static ssize_t delegate_show(struct kobject *kobj, struct kobj_attribute *attr,
7035 char *buf)
7036{
7037 struct cgroup_subsys *ss;
7038 int ssid;
7039 ssize_t ret = 0;
7040
7041 ret = show_delegatable_files(cgroup_base_files, buf + ret,
7042 PAGE_SIZE - ret, NULL);
7043 if (cgroup_psi_enabled())
7044 ret += show_delegatable_files(cgroup_psi_files, buf + ret,
7045 PAGE_SIZE - ret, NULL);
7046
7047 for_each_subsys(ss, ssid)
7048 ret += show_delegatable_files(ss->dfl_cftypes, buf + ret,
7049 PAGE_SIZE - ret,
7050 cgroup_subsys_name[ssid]);
7051
7052 return ret;
7053}
7054static struct kobj_attribute cgroup_delegate_attr = __ATTR_RO(delegate);
7055
7056static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr,
7057 char *buf)
7058{
7059 return snprintf(buf, PAGE_SIZE,
7060 "nsdelegate\n"
7061 "favordynmods\n"
7062 "memory_localevents\n"
7063 "memory_recursiveprot\n"
7064 "memory_hugetlb_accounting\n");
7065}
7066static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features);
7067
7068static struct attribute *cgroup_sysfs_attrs[] = {
7069 &cgroup_delegate_attr.attr,
7070 &cgroup_features_attr.attr,
7071 NULL,
7072};
7073
7074static const struct attribute_group cgroup_sysfs_attr_group = {
7075 .attrs = cgroup_sysfs_attrs,
7076 .name = "cgroup",
7077};
7078
7079static int __init cgroup_sysfs_init(void)
7080{
7081 return sysfs_create_group(kernel_kobj, &cgroup_sysfs_attr_group);
7082}
7083subsys_initcall(cgroup_sysfs_init);
7084
7085#endif /* CONFIG_SYSFS */