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 */
90 DEFINE_MUTEX(cgroup_mutex);
91 DEFINE_SPINLOCK(css_set_lock);
92
93 #ifdef CONFIG_PROVE_RCU
94 EXPORT_SYMBOL_GPL(cgroup_mutex);
95 EXPORT_SYMBOL_GPL(css_set_lock);
96 #endif
97
98 DEFINE_SPINLOCK(trace_cgroup_path_lock);
99 char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
100 static 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 */
106 static 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 */
112 static DEFINE_SPINLOCK(cgroup_file_kn_lock);
113
114 DEFINE_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 */
127 static 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,
131 struct 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,
138 static 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,
153 static 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,
159 static struct static_key_true *cgroup_subsys_on_dfl_key[] = {
160 #include <linux/cgroup_subsys.h>
161 };
162 #undef SUBSYS
163
164 static DEFINE_PER_CPU(struct cgroup_rstat_cpu, cgrp_dfl_root_rstat_cpu);
165
166 /* the default hierarchy */
167 struct cgroup_root cgrp_dfl_root = { .cgrp.rstat_cpu = &cgrp_dfl_root_rstat_cpu };
168 EXPORT_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 */
174 static bool cgrp_dfl_visible;
175
176 /* some controllers are not supported in the default hierarchy */
177 static u16 cgrp_dfl_inhibit_ss_mask;
178
179 /* some controllers are implicitly enabled on the default hierarchy */
180 static u16 cgrp_dfl_implicit_ss_mask;
181
182 /* some controllers can be threaded on the default hierarchy */
183 static u16 cgrp_dfl_threaded_ss_mask;
184
185 /* The list of hierarchy roots */
186 LIST_HEAD(cgroup_roots);
187 static int cgroup_root_count;
188
189 /* hierarchy ID allocation and mapping, protected by cgroup_mutex */
190 static 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 */
199 static 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 */
205 static u16 have_fork_callback __read_mostly;
206 static u16 have_exit_callback __read_mostly;
207 static u16 have_release_callback __read_mostly;
208 static u16 have_canfork_callback __read_mostly;
209
210 static bool have_favordynmods __ro_after_init = IS_ENABLED(CONFIG_CGROUP_FAVOR_DYNMODS);
211
212 /* cgroup namespace for init task */
213 struct 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
221 static struct file_system_type cgroup2_fs_type;
222 static struct cftype cgroup_base_files[];
223 static struct cftype cgroup_psi_files[];
224
225 /* cgroup optional features */
226 enum cgroup_opt_features {
227 #ifdef CONFIG_PSI
228 OPT_FEATURE_PRESSURE,
229 #endif
230 OPT_FEATURE_COUNT
231 };
232
233 static const char *cgroup_opt_feature_names[OPT_FEATURE_COUNT] = {
234 #ifdef CONFIG_PSI
235 "pressure",
236 #endif
237 };
238
239 static u16 cgroup_feature_disable_mask __read_mostly;
240
241 static int cgroup_apply_control(struct cgroup *cgrp);
242 static void cgroup_finalize_control(struct cgroup *cgrp, int ret);
243 static void css_task_iter_skip(struct css_task_iter *it,
244 struct task_struct *task);
245 static int cgroup_destroy_locked(struct cgroup *cgrp);
246 static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
247 struct cgroup_subsys *ss);
248 static void css_release(struct percpu_ref *ref);
249 static void kill_css(struct cgroup_subsys_state *css);
250 static 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 */
cgroup_ssid_enabled(int ssid)268 bool 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 */
cgroup_on_dfl(const struct cgroup * cgrp)319 bool 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 */
cgroup_idr_alloc(struct idr * idr,void * ptr,int start,int end,gfp_t gfp_mask)325 static 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
cgroup_idr_replace(struct idr * idr,void * ptr,int id)338 static 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
cgroup_idr_remove(struct idr * idr,int id)348 static 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
cgroup_has_tasks(struct cgroup * cgrp)355 static bool cgroup_has_tasks(struct cgroup *cgrp)
356 {
357 return cgrp->nr_populated_csets;
358 }
359
cgroup_is_threaded(struct cgroup * cgrp)360 static 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? */
cgroup_is_mixable(struct cgroup * cgrp)366 static 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 */
cgroup_can_be_thread_root(struct cgroup * cgrp)377 static 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? */
cgroup_is_thread_root(struct cgroup * cgrp)399 static 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 */
cgroup_is_valid_domain(struct cgroup * cgrp)421 static 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 */
cgroup_control(struct cgroup * cgrp)439 static 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 */
cgroup_ss_mask(struct cgroup * cgrp)460 static 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 */
cgroup_css(struct cgroup * cgrp,struct cgroup_subsys * ss)487 static 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 */
cgroup_e_css_by_mask(struct cgroup * cgrp,struct cgroup_subsys * ss)507 static 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 */
cgroup_e_css(struct cgroup * cgrp,struct cgroup_subsys * ss)541 struct 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 */
cgroup_get_e_css(struct cgroup * cgrp,struct cgroup_subsys * ss)571 struct 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);
591 out_unlock:
592 rcu_read_unlock();
593 return css;
594 }
595 EXPORT_SYMBOL_GPL(cgroup_get_e_css);
596
cgroup_get_live(struct cgroup * cgrp)597 static 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 */
__cgroup_task_count(const struct cgroup * cgrp)608 int __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 */
cgroup_task_count(const struct cgroup * cgrp)625 int 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
of_css(struct kernfs_open_file * of)636 struct 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 }
654 EXPORT_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 */
728 struct 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
750 static int css_set_count = 1; /* 1 for init_css_set */
751
css_set_threaded(struct css_set * cset)752 static 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 */
css_set_populated(struct css_set * cset)766 static 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 */
cgroup_update_populated(struct cgroup * cgrp,bool populated)790 static 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 */
css_set_update_populated(struct css_set * cset,bool populated)830 static 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 */
css_set_skip_task_iters(struct css_set * cset,struct task_struct * task)846 static 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 */
css_set_move_task(struct task_struct * task,struct css_set * from_cset,struct css_set * to_cset,bool use_mg_tasks)870 static 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
910 static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
911
css_set_hash(struct cgroup_subsys_state ** css)912 static 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
put_css_set_locked(struct css_set * cset)925 void 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 */
compare_css_sets(struct css_set * cset,struct css_set * old_cset,struct cgroup * new_cgrp,struct cgroup_subsys_state * template[])972 static 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 */
find_existing_css_set(struct css_set * old_cset,struct cgroup * cgrp,struct cgroup_subsys_state ** template)1051 static 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
free_cgrp_cset_links(struct list_head * links_to_free)1095 static 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 */
allocate_cgrp_cset_links(int count,struct list_head * tmp_links)1113 static 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 */
link_css_set(struct list_head * tmp_links,struct css_set * cset,struct cgroup * cgrp)1137 static 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 */
find_css_set(struct css_set * old_cset,struct cgroup * cgrp)1170 static 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
cgroup_root_from_kf(struct kernfs_root * kf_root)1274 struct 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
cgroup_favor_dynmods(struct cgroup_root * root,bool favor)1281 void 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
cgroup_init_root_id(struct cgroup_root * root)1295 static 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
cgroup_exit_root_id(struct cgroup_root * root)1309 static 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
cgroup_free_root(struct cgroup_root * root)1316 void cgroup_free_root(struct cgroup_root *root)
1317 {
1318 kfree_rcu(root, rcu);
1319 }
1320
cgroup_destroy_root(struct cgroup_root * root)1321 static 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 */
__cset_cgroup_from_root(struct css_set * cset,struct cgroup_root * root)1369 static 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 */
1408 static struct cgroup *
current_cgns_cgroup_from_root(struct cgroup_root * root)1409 current_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 */
current_cgns_cgroup_dfl(void)1442 static 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 */
cset_cgroup_from_root(struct css_set * cset,struct cgroup_root * root)1461 static 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 */
task_cgroup_from_root(struct task_struct * task,struct cgroup_root * root)1475 struct 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
1511 static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
1512
cgroup_file_name(struct cgroup * cgrp,const struct cftype * cft,char * buf)1513 static 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 */
cgroup_file_mode(const struct cftype * cft)1537 static 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 */
cgroup_calc_subtree_ss_mask(u16 subtree_control,u16 this_ss_mask)1566 static 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 */
cgroup_kn_unlock(struct kernfs_node * kn)1608 void 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 */
cgroup_kn_lock_live(struct kernfs_node * kn,bool drain_offline)1640 struct 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
cgroup_rm_file(struct cgroup * cgrp,const struct cftype * cft)1671 static 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 */
css_clear_dir(struct cgroup_subsys_state * css)1695 static 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 */
css_populate_dir(struct cgroup_subsys_state * css)1728 static 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;
1769 err:
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
rebind_subsystems(struct cgroup_root * dst_root,u16 ss_mask)1778 int 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
cgroup_show_path(struct seq_file * sf,struct kernfs_node * kf_node,struct kernfs_root * kf_root)1892 int 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
1919 enum 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
1928 static 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
cgroup2_parse_param(struct fs_context * fc,struct fs_parameter * param)1937 static 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
apply_cgroup_root_flags(unsigned int root_flags)1967 static 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
cgroup_show_options(struct seq_file * seq,struct kernfs_root * kf_root)1995 static 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
cgroup_reconfigure(struct fs_context * fc)2010 static 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
init_cgroup_housekeeping(struct cgroup * cgrp)2018 static 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
init_cgroup_root(struct cgroup_fs_context * ctx)2043 void 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
cgroup_setup_root(struct cgroup_root * root,u16 ss_mask)2063 int 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
2152 exit_stats:
2153 cgroup_rstat_exit(root_cgrp);
2154 destroy_root:
2155 kernfs_destroy_root(root->kf_root);
2156 root->kf_root = NULL;
2157 exit_root_id:
2158 cgroup_exit_root_id(root);
2159 cancel_ref:
2160 percpu_ref_exit(&root_cgrp->self.refcnt);
2161 out:
2162 free_cgrp_cset_links(&tmp_links);
2163 return ret;
2164 }
2165
cgroup_do_get_tree(struct fs_context * fc)2166 int 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 */
cgroup_fs_context_free(struct fs_context * fc)2214 static 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
cgroup_get_tree(struct fs_context * fc)2225 static 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
2240 static 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
2247 static 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 */
cgroup_init_fs_context(struct fs_context * fc)2258 static 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
cgroup_kill_sb(struct super_block * sb)2283 static 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
2303 struct 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
2311 static 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
2320 static 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 */
cpuset_init_fs_context(struct fs_context * fc)2330 static 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
2356 static 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
cgroup_path_ns_locked(struct cgroup * cgrp,char * buf,size_t buflen,struct cgroup_namespace * ns)2363 int 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
cgroup_path_ns(struct cgroup * cgrp,char * buf,size_t buflen,struct cgroup_namespace * ns)2371 int 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 }
2386 EXPORT_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 */
cgroup_attach_lock(bool lock_threadgroup)2411 void 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 */
cgroup_attach_unlock(bool lock_threadgroup)2422 void 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 */
cgroup_migrate_add_task(struct task_struct * task,struct cgroup_mgctx * mgctx)2439 static 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 */
cgroup_taskset_first(struct cgroup_taskset * tset,struct cgroup_subsys_state ** dst_cssp)2475 struct 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 */
cgroup_taskset_next(struct cgroup_taskset * tset,struct cgroup_subsys_state ** dst_cssp)2492 struct 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 */
cgroup_migrate_execute(struct cgroup_mgctx * mgctx)2539 static 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
2607 out_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 }
2618 out_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 */
cgroup_migrate_vet_dst(struct cgroup * dst_cgrp)2646 int 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 */
cgroup_migrate_finish(struct cgroup_mgctx * mgctx)2677 void 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 */
cgroup_migrate_add_src(struct css_set * src_cset,struct cgroup * dst_cgrp,struct cgroup_mgctx * mgctx)2722 void 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 */
cgroup_migrate_prepare_dst(struct cgroup_mgctx * mgctx)2769 int 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 */
cgroup_migrate(struct task_struct * leader,bool threadgroup,struct cgroup_mgctx * mgctx)2836 int 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 */
cgroup_attach_task(struct cgroup * dst_cgrp,struct task_struct * leader,bool threadgroup)2866 int 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
cgroup_procs_write_start(char * buf,bool threadgroup,bool * threadgroup_locked)2898 struct 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
2947 out_unlock_threadgroup:
2948 cgroup_attach_unlock(*threadgroup_locked);
2949 *threadgroup_locked = false;
2950 out_unlock_rcu:
2951 rcu_read_unlock();
2952 return tsk;
2953 }
2954
cgroup_procs_write_finish(struct task_struct * task,bool threadgroup_locked)2955 void 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
cgroup_print_ss_mask(struct seq_file * seq,u16 ss_mask)2970 static 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 */
cgroup_controllers_show(struct seq_file * seq,void * v)2987 static 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 */
cgroup_subtree_control_show(struct seq_file * seq,void * v)2996 static 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 */
cgroup_update_dfl_csses(struct cgroup * cgrp)3013 static 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);
3069 out_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 */
cgroup_lock_and_drain_offline(struct cgroup * cgrp)3083 void 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
3091 restart:
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 */
cgroup_save_control(struct cgroup * cgrp)3124 static 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 */
cgroup_propagate_control(struct cgroup * cgrp)3144 static 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 */
cgroup_restore_control(struct cgroup * cgrp)3165 static 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
css_visible(struct cgroup_subsys_state * css)3177 static 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 */
cgroup_apply_control_enable(struct cgroup * cgrp)3202 static 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 */
cgroup_apply_control_disable(struct cgroup * cgrp)3248 static 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 */
cgroup_apply_control(struct cgroup * cgrp)3293 static 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 */
cgroup_finalize_control(struct cgroup * cgrp,int ret)3318 static 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
cgroup_vet_subtree_control_enable(struct cgroup * cgrp,u16 enable)3328 static 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 */
cgroup_subtree_control_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)3369 static 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);
3459 out_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 */
cgroup_enable_threaded(struct cgroup * cgrp)3473 static 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
cgroup_type_show(struct seq_file * seq,void * v)3520 static 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
cgroup_type_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)3536 static 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
cgroup_max_descendants_show(struct seq_file * seq,void * v)3558 static 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
cgroup_max_descendants_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)3571 static 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
cgroup_max_depth_show(struct seq_file * seq,void * v)3601 static 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
cgroup_max_depth_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)3614 static 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
cgroup_events_show(struct seq_file * seq,void * v)3644 static 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
cgroup_stat_show(struct seq_file * seq,void * v)3654 static 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 */
cgroup_tryget_css(struct cgroup * cgrp,struct cgroup_subsys * ss)3675 static 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
cgroup_extra_stat_show(struct seq_file * seq,int ssid)3689 static 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
cgroup_local_stat_show(struct seq_file * seq,struct cgroup * cgrp,int ssid)3708 static 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
cpu_stat_show(struct seq_file * seq,void * v)3728 static 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
cpu_local_stat_show(struct seq_file * seq,void * v)3739 static 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
cgroup_io_pressure_show(struct seq_file * seq,void * v)3751 static 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 }
cgroup_memory_pressure_show(struct seq_file * seq,void * v)3758 static 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 }
cgroup_cpu_pressure_show(struct seq_file * seq,void * v)3765 static 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
pressure_write(struct kernfs_open_file * of,char * buf,size_t nbytes,enum psi_res res)3773 static 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
cgroup_io_pressure_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)3807 static 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
cgroup_memory_pressure_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)3814 static 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
cgroup_cpu_pressure_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)3821 static 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
cgroup_irq_pressure_show(struct seq_file * seq,void * v)3829 static 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
cgroup_irq_pressure_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)3837 static 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
cgroup_pressure_show(struct seq_file * seq,void * v)3845 static 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
cgroup_pressure_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)3855 static 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
cgroup_pressure_poll(struct kernfs_open_file * of,poll_table * pt)3893 static __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
cgroup_pressure_release(struct kernfs_open_file * of)3901 static 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
cgroup_psi_enabled(void)3908 bool 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 */
cgroup_psi_enabled(void)3917 bool cgroup_psi_enabled(void)
3918 {
3919 return false;
3920 }
3921
3922 #endif /* CONFIG_PSI */
3923
cgroup_freeze_show(struct seq_file * seq,void * v)3924 static 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
cgroup_freeze_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)3933 static 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
__cgroup_kill(struct cgroup * cgrp)3958 static 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
cgroup_kill(struct cgroup * cgrp)3988 static 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
cgroup_kill_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)3999 static 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
cgroup_file_open(struct kernfs_open_file * of)4032 static 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
cgroup_file_release(struct kernfs_open_file * of)4057 static 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
cgroup_file_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)4068 static 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
cgroup_file_poll(struct kernfs_open_file * of,poll_table * pt)4121 static __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
cgroup_seqfile_start(struct seq_file * seq,loff_t * ppos)4131 static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
4132 {
4133 return seq_cft(seq)->seq_start(seq, ppos);
4134 }
4135
cgroup_seqfile_next(struct seq_file * seq,void * v,loff_t * ppos)4136 static 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
cgroup_seqfile_stop(struct seq_file * seq,void * v)4141 static 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
cgroup_seqfile_show(struct seq_file * m,void * arg)4147 static 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
4164 static 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
4173 static 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
cgroup_file_notify_timer(struct timer_list * timer)4185 static 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
cgroup_add_file(struct cgroup_subsys_state * css,struct cgroup * cgrp,struct cftype * cft)4191 static 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 */
cgroup_addrm_files(struct cgroup_subsys_state * css,struct cgroup * cgrp,struct cftype cfts[],bool is_add)4232 static 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
4241 restart:
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
cgroup_apply_cftypes(struct cftype * cfts,bool is_add)4270 static 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
cgroup_exit_cftypes(struct cftype * cfts)4296 static 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
cgroup_init_cftypes(struct cgroup_subsys * ss,struct cftype * cfts)4313 static 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
cgroup_rm_cftypes_locked(struct cftype * cfts)4356 static 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 */
cgroup_rm_cftypes(struct cftype * cfts)4376 int 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 */
cgroup_add_cftypes(struct cgroup_subsys * ss,struct cftype * cfts)4404 static 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 */
cgroup_add_dfl_cftypes(struct cgroup_subsys * ss,struct cftype * cfts)4437 int 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 */
cgroup_add_legacy_cftypes(struct cgroup_subsys * ss,struct cftype * cfts)4454 int 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 */
cgroup_file_notify(struct cgroup_file * cfile)4469 void 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 */
cgroup_file_show(struct cgroup_file * cfile,bool show)4493 void 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 */
css_next_child(struct cgroup_subsys_state * pos,struct cgroup_subsys_state * parent)4525 struct 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 */
4593 struct cgroup_subsys_state *
css_next_descendant_pre(struct cgroup_subsys_state * pos,struct cgroup_subsys_state * root)4594 css_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 }
4620 EXPORT_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 */
4635 struct cgroup_subsys_state *
css_rightmost_descendant(struct cgroup_subsys_state * pos)4636 css_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
4653 static struct cgroup_subsys_state *
css_leftmost_descendant(struct cgroup_subsys_state * pos)4654 css_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 */
4688 struct cgroup_subsys_state *
css_next_descendant_post(struct cgroup_subsys_state * pos,struct cgroup_subsys_state * root)4689 css_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 */
css_has_online_children(struct cgroup_subsys_state * css)4721 bool 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
css_task_iter_next_css_set(struct css_task_iter * it)4737 static 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 */
css_task_iter_advance_css_set(struct css_task_iter * it)4795 static 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
css_task_iter_skip(struct css_task_iter * it,struct task_struct * task)4844 static 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
css_task_iter_advance(struct css_task_iter * it)4855 static void css_task_iter_advance(struct css_task_iter *it)
4856 {
4857 struct task_struct *task;
4858
4859 lockdep_assert_held(&css_set_lock);
4860 repeat:
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 */
css_task_iter_start(struct cgroup_subsys_state * css,unsigned int flags,struct css_task_iter * it)4919 void 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 */
css_task_iter_next(struct css_task_iter * it)4951 struct 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 */
css_task_iter_end(struct css_task_iter * it)4984 void 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
cgroup_procs_release(struct kernfs_open_file * of)5002 static 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
cgroup_procs_next(struct seq_file * s,void * v,loff_t * pos)5010 static 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
__cgroup_procs_start(struct seq_file * s,loff_t * pos,unsigned int iter_flags)5021 static 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
cgroup_procs_start(struct seq_file * s,loff_t * pos)5047 static 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
cgroup_procs_show(struct seq_file * s,void * v)5064 static 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
cgroup_may_write(const struct cgroup * cgrp,struct super_block * sb)5070 static 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
cgroup_procs_write_permission(struct cgroup * src_cgrp,struct cgroup * dst_cgrp,struct super_block * sb,struct cgroup_namespace * ns)5086 static 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
cgroup_attach_permissions(struct cgroup * src_cgrp,struct cgroup * dst_cgrp,struct super_block * sb,bool threadgroup,struct cgroup_namespace * ns)5117 static 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
__cgroup_procs_write(struct kernfs_open_file * of,char * buf,bool threadgroup)5138 static 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
5177 out_finish:
5178 cgroup_procs_write_finish(task, threadgroup_locked);
5179 out_unlock:
5180 cgroup_kn_unlock(of->kn);
5181
5182 return ret;
5183 }
5184
cgroup_procs_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)5185 static 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
cgroup_threads_start(struct seq_file * s,loff_t * pos)5191 static void *cgroup_threads_start(struct seq_file *s, loff_t *pos)
5192 {
5193 return __cgroup_procs_start(s, pos, 0);
5194 }
5195
cgroup_threads_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)5196 static 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 */
5203 static 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
5281 static 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 */
css_free_rwork_fn(struct work_struct * work)5348 static 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 if (!cgroup_on_dfl(cgrp))
5372 cgroup1_pidlist_destroy_all(cgrp);
5373 cancel_work_sync(&cgrp->release_agent_work);
5374 bpf_cgrp_storage_free(cgrp);
5375
5376 if (cgroup_parent(cgrp)) {
5377 /*
5378 * We get a ref to the parent, and put the ref when
5379 * this cgroup is being freed, so it's guaranteed
5380 * that the parent won't be destroyed before its
5381 * children.
5382 */
5383 cgroup_put(cgroup_parent(cgrp));
5384 kernfs_put(cgrp->kn);
5385 psi_cgroup_free(cgrp);
5386 cgroup_rstat_exit(cgrp);
5387 kfree(cgrp);
5388 } else {
5389 /*
5390 * This is root cgroup's refcnt reaching zero,
5391 * which indicates that the root should be
5392 * released.
5393 */
5394 cgroup_destroy_root(cgrp->root);
5395 }
5396 }
5397 }
5398
css_release_work_fn(struct work_struct * work)5399 static void css_release_work_fn(struct work_struct *work)
5400 {
5401 struct cgroup_subsys_state *css =
5402 container_of(work, struct cgroup_subsys_state, destroy_work);
5403 struct cgroup_subsys *ss = css->ss;
5404 struct cgroup *cgrp = css->cgroup;
5405
5406 cgroup_lock();
5407
5408 css->flags |= CSS_RELEASED;
5409 list_del_rcu(&css->sibling);
5410
5411 if (ss) {
5412 /* css release path */
5413 if (!list_empty(&css->rstat_css_node)) {
5414 cgroup_rstat_flush(cgrp);
5415 list_del_rcu(&css->rstat_css_node);
5416 }
5417
5418 cgroup_idr_replace(&ss->css_idr, NULL, css->id);
5419 if (ss->css_released)
5420 ss->css_released(css);
5421 } else {
5422 struct cgroup *tcgrp;
5423
5424 /* cgroup release path */
5425 TRACE_CGROUP_PATH(release, cgrp);
5426
5427 cgroup_rstat_flush(cgrp);
5428
5429 spin_lock_irq(&css_set_lock);
5430 for (tcgrp = cgroup_parent(cgrp); tcgrp;
5431 tcgrp = cgroup_parent(tcgrp))
5432 tcgrp->nr_dying_descendants--;
5433 spin_unlock_irq(&css_set_lock);
5434
5435 /*
5436 * There are two control paths which try to determine
5437 * cgroup from dentry without going through kernfs -
5438 * cgroupstats_build() and css_tryget_online_from_dir().
5439 * Those are supported by RCU protecting clearing of
5440 * cgrp->kn->priv backpointer.
5441 */
5442 if (cgrp->kn)
5443 RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv,
5444 NULL);
5445 }
5446
5447 cgroup_unlock();
5448
5449 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
5450 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
5451 }
5452
css_release(struct percpu_ref * ref)5453 static void css_release(struct percpu_ref *ref)
5454 {
5455 struct cgroup_subsys_state *css =
5456 container_of(ref, struct cgroup_subsys_state, refcnt);
5457
5458 INIT_WORK(&css->destroy_work, css_release_work_fn);
5459 queue_work(cgroup_destroy_wq, &css->destroy_work);
5460 }
5461
init_and_link_css(struct cgroup_subsys_state * css,struct cgroup_subsys * ss,struct cgroup * cgrp)5462 static void init_and_link_css(struct cgroup_subsys_state *css,
5463 struct cgroup_subsys *ss, struct cgroup *cgrp)
5464 {
5465 lockdep_assert_held(&cgroup_mutex);
5466
5467 cgroup_get_live(cgrp);
5468
5469 memset(css, 0, sizeof(*css));
5470 css->cgroup = cgrp;
5471 css->ss = ss;
5472 css->id = -1;
5473 INIT_LIST_HEAD(&css->sibling);
5474 INIT_LIST_HEAD(&css->children);
5475 INIT_LIST_HEAD(&css->rstat_css_node);
5476 css->serial_nr = css_serial_nr_next++;
5477 atomic_set(&css->online_cnt, 0);
5478
5479 if (cgroup_parent(cgrp)) {
5480 css->parent = cgroup_css(cgroup_parent(cgrp), ss);
5481 css_get(css->parent);
5482 }
5483
5484 if (ss->css_rstat_flush)
5485 list_add_rcu(&css->rstat_css_node, &cgrp->rstat_css_list);
5486
5487 BUG_ON(cgroup_css(cgrp, ss));
5488 }
5489
5490 /* invoke ->css_online() on a new CSS and mark it online if successful */
online_css(struct cgroup_subsys_state * css)5491 static int online_css(struct cgroup_subsys_state *css)
5492 {
5493 struct cgroup_subsys *ss = css->ss;
5494 int ret = 0;
5495
5496 lockdep_assert_held(&cgroup_mutex);
5497
5498 if (ss->css_online)
5499 ret = ss->css_online(css);
5500 if (!ret) {
5501 css->flags |= CSS_ONLINE;
5502 rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
5503
5504 atomic_inc(&css->online_cnt);
5505 if (css->parent)
5506 atomic_inc(&css->parent->online_cnt);
5507 }
5508 return ret;
5509 }
5510
5511 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
offline_css(struct cgroup_subsys_state * css)5512 static void offline_css(struct cgroup_subsys_state *css)
5513 {
5514 struct cgroup_subsys *ss = css->ss;
5515
5516 lockdep_assert_held(&cgroup_mutex);
5517
5518 if (!(css->flags & CSS_ONLINE))
5519 return;
5520
5521 if (ss->css_offline)
5522 ss->css_offline(css);
5523
5524 css->flags &= ~CSS_ONLINE;
5525 RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL);
5526
5527 wake_up_all(&css->cgroup->offline_waitq);
5528 }
5529
5530 /**
5531 * css_create - create a cgroup_subsys_state
5532 * @cgrp: the cgroup new css will be associated with
5533 * @ss: the subsys of new css
5534 *
5535 * Create a new css associated with @cgrp - @ss pair. On success, the new
5536 * css is online and installed in @cgrp. This function doesn't create the
5537 * interface files. Returns 0 on success, -errno on failure.
5538 */
css_create(struct cgroup * cgrp,struct cgroup_subsys * ss)5539 static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
5540 struct cgroup_subsys *ss)
5541 {
5542 struct cgroup *parent = cgroup_parent(cgrp);
5543 struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss);
5544 struct cgroup_subsys_state *css;
5545 int err;
5546
5547 lockdep_assert_held(&cgroup_mutex);
5548
5549 css = ss->css_alloc(parent_css);
5550 if (!css)
5551 css = ERR_PTR(-ENOMEM);
5552 if (IS_ERR(css))
5553 return css;
5554
5555 init_and_link_css(css, ss, cgrp);
5556
5557 err = percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL);
5558 if (err)
5559 goto err_free_css;
5560
5561 err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL);
5562 if (err < 0)
5563 goto err_free_css;
5564 css->id = err;
5565
5566 /* @css is ready to be brought online now, make it visible */
5567 list_add_tail_rcu(&css->sibling, &parent_css->children);
5568 cgroup_idr_replace(&ss->css_idr, css, css->id);
5569
5570 err = online_css(css);
5571 if (err)
5572 goto err_list_del;
5573
5574 return css;
5575
5576 err_list_del:
5577 list_del_rcu(&css->sibling);
5578 err_free_css:
5579 list_del_rcu(&css->rstat_css_node);
5580 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
5581 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
5582 return ERR_PTR(err);
5583 }
5584
5585 /*
5586 * The returned cgroup is fully initialized including its control mask, but
5587 * it doesn't have the control mask applied.
5588 */
cgroup_create(struct cgroup * parent,const char * name,umode_t mode)5589 static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
5590 umode_t mode)
5591 {
5592 struct cgroup_root *root = parent->root;
5593 struct cgroup *cgrp, *tcgrp;
5594 struct kernfs_node *kn;
5595 int level = parent->level + 1;
5596 int ret;
5597
5598 /* allocate the cgroup and its ID, 0 is reserved for the root */
5599 cgrp = kzalloc(struct_size(cgrp, ancestors, (level + 1)), GFP_KERNEL);
5600 if (!cgrp)
5601 return ERR_PTR(-ENOMEM);
5602
5603 ret = percpu_ref_init(&cgrp->self.refcnt, css_release, 0, GFP_KERNEL);
5604 if (ret)
5605 goto out_free_cgrp;
5606
5607 ret = cgroup_rstat_init(cgrp);
5608 if (ret)
5609 goto out_cancel_ref;
5610
5611 /* create the directory */
5612 kn = kernfs_create_dir_ns(parent->kn, name, mode,
5613 current_fsuid(), current_fsgid(),
5614 cgrp, NULL);
5615 if (IS_ERR(kn)) {
5616 ret = PTR_ERR(kn);
5617 goto out_stat_exit;
5618 }
5619 cgrp->kn = kn;
5620
5621 init_cgroup_housekeeping(cgrp);
5622
5623 cgrp->self.parent = &parent->self;
5624 cgrp->root = root;
5625 cgrp->level = level;
5626
5627 ret = psi_cgroup_alloc(cgrp);
5628 if (ret)
5629 goto out_kernfs_remove;
5630
5631 ret = cgroup_bpf_inherit(cgrp);
5632 if (ret)
5633 goto out_psi_free;
5634
5635 /*
5636 * New cgroup inherits effective freeze counter, and
5637 * if the parent has to be frozen, the child has too.
5638 */
5639 cgrp->freezer.e_freeze = parent->freezer.e_freeze;
5640 if (cgrp->freezer.e_freeze) {
5641 /*
5642 * Set the CGRP_FREEZE flag, so when a process will be
5643 * attached to the child cgroup, it will become frozen.
5644 * At this point the new cgroup is unpopulated, so we can
5645 * consider it frozen immediately.
5646 */
5647 set_bit(CGRP_FREEZE, &cgrp->flags);
5648 set_bit(CGRP_FROZEN, &cgrp->flags);
5649 }
5650
5651 spin_lock_irq(&css_set_lock);
5652 for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
5653 cgrp->ancestors[tcgrp->level] = tcgrp;
5654
5655 if (tcgrp != cgrp) {
5656 tcgrp->nr_descendants++;
5657
5658 /*
5659 * If the new cgroup is frozen, all ancestor cgroups
5660 * get a new frozen descendant, but their state can't
5661 * change because of this.
5662 */
5663 if (cgrp->freezer.e_freeze)
5664 tcgrp->freezer.nr_frozen_descendants++;
5665 }
5666 }
5667 spin_unlock_irq(&css_set_lock);
5668
5669 if (notify_on_release(parent))
5670 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
5671
5672 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
5673 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
5674
5675 cgrp->self.serial_nr = css_serial_nr_next++;
5676
5677 /* allocation complete, commit to creation */
5678 list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);
5679 atomic_inc(&root->nr_cgrps);
5680 cgroup_get_live(parent);
5681
5682 /*
5683 * On the default hierarchy, a child doesn't automatically inherit
5684 * subtree_control from the parent. Each is configured manually.
5685 */
5686 if (!cgroup_on_dfl(cgrp))
5687 cgrp->subtree_control = cgroup_control(cgrp);
5688
5689 cgroup_propagate_control(cgrp);
5690
5691 return cgrp;
5692
5693 out_psi_free:
5694 psi_cgroup_free(cgrp);
5695 out_kernfs_remove:
5696 kernfs_remove(cgrp->kn);
5697 out_stat_exit:
5698 cgroup_rstat_exit(cgrp);
5699 out_cancel_ref:
5700 percpu_ref_exit(&cgrp->self.refcnt);
5701 out_free_cgrp:
5702 kfree(cgrp);
5703 return ERR_PTR(ret);
5704 }
5705
cgroup_check_hierarchy_limits(struct cgroup * parent)5706 static bool cgroup_check_hierarchy_limits(struct cgroup *parent)
5707 {
5708 struct cgroup *cgroup;
5709 int ret = false;
5710 int level = 1;
5711
5712 lockdep_assert_held(&cgroup_mutex);
5713
5714 for (cgroup = parent; cgroup; cgroup = cgroup_parent(cgroup)) {
5715 if (cgroup->nr_descendants >= cgroup->max_descendants)
5716 goto fail;
5717
5718 if (level > cgroup->max_depth)
5719 goto fail;
5720
5721 level++;
5722 }
5723
5724 ret = true;
5725 fail:
5726 return ret;
5727 }
5728
cgroup_mkdir(struct kernfs_node * parent_kn,const char * name,umode_t mode)5729 int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
5730 {
5731 struct cgroup *parent, *cgrp;
5732 int ret;
5733
5734 /* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
5735 if (strchr(name, '\n'))
5736 return -EINVAL;
5737
5738 parent = cgroup_kn_lock_live(parent_kn, false);
5739 if (!parent)
5740 return -ENODEV;
5741
5742 if (!cgroup_check_hierarchy_limits(parent)) {
5743 ret = -EAGAIN;
5744 goto out_unlock;
5745 }
5746
5747 cgrp = cgroup_create(parent, name, mode);
5748 if (IS_ERR(cgrp)) {
5749 ret = PTR_ERR(cgrp);
5750 goto out_unlock;
5751 }
5752
5753 /*
5754 * This extra ref will be put in cgroup_free_fn() and guarantees
5755 * that @cgrp->kn is always accessible.
5756 */
5757 kernfs_get(cgrp->kn);
5758
5759 ret = css_populate_dir(&cgrp->self);
5760 if (ret)
5761 goto out_destroy;
5762
5763 ret = cgroup_apply_control_enable(cgrp);
5764 if (ret)
5765 goto out_destroy;
5766
5767 TRACE_CGROUP_PATH(mkdir, cgrp);
5768
5769 /* let's create and online css's */
5770 kernfs_activate(cgrp->kn);
5771
5772 ret = 0;
5773 goto out_unlock;
5774
5775 out_destroy:
5776 cgroup_destroy_locked(cgrp);
5777 out_unlock:
5778 cgroup_kn_unlock(parent_kn);
5779 return ret;
5780 }
5781
5782 /*
5783 * This is called when the refcnt of a css is confirmed to be killed.
5784 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
5785 * initiate destruction and put the css ref from kill_css().
5786 */
css_killed_work_fn(struct work_struct * work)5787 static void css_killed_work_fn(struct work_struct *work)
5788 {
5789 struct cgroup_subsys_state *css =
5790 container_of(work, struct cgroup_subsys_state, destroy_work);
5791
5792 cgroup_lock();
5793
5794 do {
5795 offline_css(css);
5796 css_put(css);
5797 /* @css can't go away while we're holding cgroup_mutex */
5798 css = css->parent;
5799 } while (css && atomic_dec_and_test(&css->online_cnt));
5800
5801 cgroup_unlock();
5802 }
5803
5804 /* css kill confirmation processing requires process context, bounce */
css_killed_ref_fn(struct percpu_ref * ref)5805 static void css_killed_ref_fn(struct percpu_ref *ref)
5806 {
5807 struct cgroup_subsys_state *css =
5808 container_of(ref, struct cgroup_subsys_state, refcnt);
5809
5810 if (atomic_dec_and_test(&css->online_cnt)) {
5811 INIT_WORK(&css->destroy_work, css_killed_work_fn);
5812 queue_work(cgroup_destroy_wq, &css->destroy_work);
5813 }
5814 }
5815
5816 /**
5817 * kill_css - destroy a css
5818 * @css: css to destroy
5819 *
5820 * This function initiates destruction of @css by removing cgroup interface
5821 * files and putting its base reference. ->css_offline() will be invoked
5822 * asynchronously once css_tryget_online() is guaranteed to fail and when
5823 * the reference count reaches zero, @css will be released.
5824 */
kill_css(struct cgroup_subsys_state * css)5825 static void kill_css(struct cgroup_subsys_state *css)
5826 {
5827 lockdep_assert_held(&cgroup_mutex);
5828
5829 if (css->flags & CSS_DYING)
5830 return;
5831
5832 css->flags |= CSS_DYING;
5833
5834 /*
5835 * This must happen before css is disassociated with its cgroup.
5836 * See seq_css() for details.
5837 */
5838 css_clear_dir(css);
5839
5840 /*
5841 * Killing would put the base ref, but we need to keep it alive
5842 * until after ->css_offline().
5843 */
5844 css_get(css);
5845
5846 /*
5847 * cgroup core guarantees that, by the time ->css_offline() is
5848 * invoked, no new css reference will be given out via
5849 * css_tryget_online(). We can't simply call percpu_ref_kill() and
5850 * proceed to offlining css's because percpu_ref_kill() doesn't
5851 * guarantee that the ref is seen as killed on all CPUs on return.
5852 *
5853 * Use percpu_ref_kill_and_confirm() to get notifications as each
5854 * css is confirmed to be seen as killed on all CPUs.
5855 */
5856 percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
5857 }
5858
5859 /**
5860 * cgroup_destroy_locked - the first stage of cgroup destruction
5861 * @cgrp: cgroup to be destroyed
5862 *
5863 * css's make use of percpu refcnts whose killing latency shouldn't be
5864 * exposed to userland and are RCU protected. Also, cgroup core needs to
5865 * guarantee that css_tryget_online() won't succeed by the time
5866 * ->css_offline() is invoked. To satisfy all the requirements,
5867 * destruction is implemented in the following two steps.
5868 *
5869 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
5870 * userland visible parts and start killing the percpu refcnts of
5871 * css's. Set up so that the next stage will be kicked off once all
5872 * the percpu refcnts are confirmed to be killed.
5873 *
5874 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
5875 * rest of destruction. Once all cgroup references are gone, the
5876 * cgroup is RCU-freed.
5877 *
5878 * This function implements s1. After this step, @cgrp is gone as far as
5879 * the userland is concerned and a new cgroup with the same name may be
5880 * created. As cgroup doesn't care about the names internally, this
5881 * doesn't cause any problem.
5882 */
cgroup_destroy_locked(struct cgroup * cgrp)5883 static int cgroup_destroy_locked(struct cgroup *cgrp)
5884 __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
5885 {
5886 struct cgroup *tcgrp, *parent = cgroup_parent(cgrp);
5887 struct cgroup_subsys_state *css;
5888 struct cgrp_cset_link *link;
5889 int ssid;
5890
5891 lockdep_assert_held(&cgroup_mutex);
5892
5893 /*
5894 * Only migration can raise populated from zero and we're already
5895 * holding cgroup_mutex.
5896 */
5897 if (cgroup_is_populated(cgrp))
5898 return -EBUSY;
5899
5900 /*
5901 * Make sure there's no live children. We can't test emptiness of
5902 * ->self.children as dead children linger on it while being
5903 * drained; otherwise, "rmdir parent/child parent" may fail.
5904 */
5905 if (css_has_online_children(&cgrp->self))
5906 return -EBUSY;
5907
5908 /*
5909 * Mark @cgrp and the associated csets dead. The former prevents
5910 * further task migration and child creation by disabling
5911 * cgroup_kn_lock_live(). The latter makes the csets ignored by
5912 * the migration path.
5913 */
5914 cgrp->self.flags &= ~CSS_ONLINE;
5915
5916 spin_lock_irq(&css_set_lock);
5917 list_for_each_entry(link, &cgrp->cset_links, cset_link)
5918 link->cset->dead = true;
5919 spin_unlock_irq(&css_set_lock);
5920
5921 /* initiate massacre of all css's */
5922 for_each_css(css, ssid, cgrp)
5923 kill_css(css);
5924
5925 /* clear and remove @cgrp dir, @cgrp has an extra ref on its kn */
5926 css_clear_dir(&cgrp->self);
5927 kernfs_remove(cgrp->kn);
5928
5929 if (cgroup_is_threaded(cgrp))
5930 parent->nr_threaded_children--;
5931
5932 spin_lock_irq(&css_set_lock);
5933 for (tcgrp = parent; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
5934 tcgrp->nr_descendants--;
5935 tcgrp->nr_dying_descendants++;
5936 /*
5937 * If the dying cgroup is frozen, decrease frozen descendants
5938 * counters of ancestor cgroups.
5939 */
5940 if (test_bit(CGRP_FROZEN, &cgrp->flags))
5941 tcgrp->freezer.nr_frozen_descendants--;
5942 }
5943 spin_unlock_irq(&css_set_lock);
5944
5945 cgroup1_check_for_release(parent);
5946
5947 cgroup_bpf_offline(cgrp);
5948
5949 /* put the base reference */
5950 percpu_ref_kill(&cgrp->self.refcnt);
5951
5952 return 0;
5953 };
5954
cgroup_rmdir(struct kernfs_node * kn)5955 int cgroup_rmdir(struct kernfs_node *kn)
5956 {
5957 struct cgroup *cgrp;
5958 int ret = 0;
5959
5960 cgrp = cgroup_kn_lock_live(kn, false);
5961 if (!cgrp)
5962 return 0;
5963
5964 ret = cgroup_destroy_locked(cgrp);
5965 if (!ret)
5966 TRACE_CGROUP_PATH(rmdir, cgrp);
5967
5968 cgroup_kn_unlock(kn);
5969 return ret;
5970 }
5971
5972 static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
5973 .show_options = cgroup_show_options,
5974 .mkdir = cgroup_mkdir,
5975 .rmdir = cgroup_rmdir,
5976 .show_path = cgroup_show_path,
5977 };
5978
cgroup_init_subsys(struct cgroup_subsys * ss,bool early)5979 static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
5980 {
5981 struct cgroup_subsys_state *css;
5982
5983 pr_debug("Initializing cgroup subsys %s\n", ss->name);
5984
5985 cgroup_lock();
5986
5987 idr_init(&ss->css_idr);
5988 INIT_LIST_HEAD(&ss->cfts);
5989
5990 /* Create the root cgroup state for this subsystem */
5991 ss->root = &cgrp_dfl_root;
5992 css = ss->css_alloc(NULL);
5993 /* We don't handle early failures gracefully */
5994 BUG_ON(IS_ERR(css));
5995 init_and_link_css(css, ss, &cgrp_dfl_root.cgrp);
5996
5997 /*
5998 * Root csses are never destroyed and we can't initialize
5999 * percpu_ref during early init. Disable refcnting.
6000 */
6001 css->flags |= CSS_NO_REF;
6002
6003 if (early) {
6004 /* allocation can't be done safely during early init */
6005 css->id = 1;
6006 } else {
6007 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL);
6008 BUG_ON(css->id < 0);
6009 }
6010
6011 /* Update the init_css_set to contain a subsys
6012 * pointer to this state - since the subsystem is
6013 * newly registered, all tasks and hence the
6014 * init_css_set is in the subsystem's root cgroup. */
6015 init_css_set.subsys[ss->id] = css;
6016
6017 have_fork_callback |= (bool)ss->fork << ss->id;
6018 have_exit_callback |= (bool)ss->exit << ss->id;
6019 have_release_callback |= (bool)ss->release << ss->id;
6020 have_canfork_callback |= (bool)ss->can_fork << ss->id;
6021
6022 /* At system boot, before all subsystems have been
6023 * registered, no tasks have been forked, so we don't
6024 * need to invoke fork callbacks here. */
6025 BUG_ON(!list_empty(&init_task.tasks));
6026
6027 BUG_ON(online_css(css));
6028
6029 cgroup_unlock();
6030 }
6031
6032 /**
6033 * cgroup_init_early - cgroup initialization at system boot
6034 *
6035 * Initialize cgroups at system boot, and initialize any
6036 * subsystems that request early init.
6037 */
cgroup_init_early(void)6038 int __init cgroup_init_early(void)
6039 {
6040 static struct cgroup_fs_context __initdata ctx;
6041 struct cgroup_subsys *ss;
6042 int i;
6043
6044 ctx.root = &cgrp_dfl_root;
6045 init_cgroup_root(&ctx);
6046 cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF;
6047
6048 RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
6049
6050 for_each_subsys(ss, i) {
6051 WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
6052 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p id:name=%d:%s\n",
6053 i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
6054 ss->id, ss->name);
6055 WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
6056 "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
6057
6058 ss->id = i;
6059 ss->name = cgroup_subsys_name[i];
6060 if (!ss->legacy_name)
6061 ss->legacy_name = cgroup_subsys_name[i];
6062
6063 if (ss->early_init)
6064 cgroup_init_subsys(ss, true);
6065 }
6066 return 0;
6067 }
6068
6069 /**
6070 * cgroup_init - cgroup initialization
6071 *
6072 * Register cgroup filesystem and /proc file, and initialize
6073 * any subsystems that didn't request early init.
6074 */
cgroup_init(void)6075 int __init cgroup_init(void)
6076 {
6077 struct cgroup_subsys *ss;
6078 int ssid;
6079
6080 BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
6081 BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
6082 BUG_ON(cgroup_init_cftypes(NULL, cgroup_psi_files));
6083 BUG_ON(cgroup_init_cftypes(NULL, cgroup1_base_files));
6084
6085 cgroup_rstat_boot();
6086
6087 get_user_ns(init_cgroup_ns.user_ns);
6088
6089 cgroup_lock();
6090
6091 /*
6092 * Add init_css_set to the hash table so that dfl_root can link to
6093 * it during init.
6094 */
6095 hash_add(css_set_table, &init_css_set.hlist,
6096 css_set_hash(init_css_set.subsys));
6097
6098 BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0));
6099
6100 cgroup_unlock();
6101
6102 for_each_subsys(ss, ssid) {
6103 if (ss->early_init) {
6104 struct cgroup_subsys_state *css =
6105 init_css_set.subsys[ss->id];
6106
6107 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2,
6108 GFP_KERNEL);
6109 BUG_ON(css->id < 0);
6110 } else {
6111 cgroup_init_subsys(ss, false);
6112 }
6113
6114 list_add_tail(&init_css_set.e_cset_node[ssid],
6115 &cgrp_dfl_root.cgrp.e_csets[ssid]);
6116
6117 /*
6118 * Setting dfl_root subsys_mask needs to consider the
6119 * disabled flag and cftype registration needs kmalloc,
6120 * both of which aren't available during early_init.
6121 */
6122 if (!cgroup_ssid_enabled(ssid))
6123 continue;
6124
6125 if (cgroup1_ssid_disabled(ssid))
6126 pr_info("Disabling %s control group subsystem in v1 mounts\n",
6127 ss->legacy_name);
6128
6129 cgrp_dfl_root.subsys_mask |= 1 << ss->id;
6130
6131 /* implicit controllers must be threaded too */
6132 WARN_ON(ss->implicit_on_dfl && !ss->threaded);
6133
6134 if (ss->implicit_on_dfl)
6135 cgrp_dfl_implicit_ss_mask |= 1 << ss->id;
6136 else if (!ss->dfl_cftypes)
6137 cgrp_dfl_inhibit_ss_mask |= 1 << ss->id;
6138
6139 if (ss->threaded)
6140 cgrp_dfl_threaded_ss_mask |= 1 << ss->id;
6141
6142 if (ss->dfl_cftypes == ss->legacy_cftypes) {
6143 WARN_ON(cgroup_add_cftypes(ss, ss->dfl_cftypes));
6144 } else {
6145 WARN_ON(cgroup_add_dfl_cftypes(ss, ss->dfl_cftypes));
6146 WARN_ON(cgroup_add_legacy_cftypes(ss, ss->legacy_cftypes));
6147 }
6148
6149 if (ss->bind)
6150 ss->bind(init_css_set.subsys[ssid]);
6151
6152 cgroup_lock();
6153 css_populate_dir(init_css_set.subsys[ssid]);
6154 cgroup_unlock();
6155 }
6156
6157 /* init_css_set.subsys[] has been updated, re-hash */
6158 hash_del(&init_css_set.hlist);
6159 hash_add(css_set_table, &init_css_set.hlist,
6160 css_set_hash(init_css_set.subsys));
6161
6162 WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup"));
6163 WARN_ON(register_filesystem(&cgroup_fs_type));
6164 WARN_ON(register_filesystem(&cgroup2_fs_type));
6165 WARN_ON(!proc_create_single("cgroups", 0, NULL, proc_cgroupstats_show));
6166 #ifdef CONFIG_CPUSETS
6167 WARN_ON(register_filesystem(&cpuset_fs_type));
6168 #endif
6169
6170 return 0;
6171 }
6172
cgroup_wq_init(void)6173 static int __init cgroup_wq_init(void)
6174 {
6175 /*
6176 * There isn't much point in executing destruction path in
6177 * parallel. Good chunk is serialized with cgroup_mutex anyway.
6178 * Use 1 for @max_active.
6179 *
6180 * We would prefer to do this in cgroup_init() above, but that
6181 * is called before init_workqueues(): so leave this until after.
6182 */
6183 cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
6184 BUG_ON(!cgroup_destroy_wq);
6185 return 0;
6186 }
6187 core_initcall(cgroup_wq_init);
6188
cgroup_path_from_kernfs_id(u64 id,char * buf,size_t buflen)6189 void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
6190 {
6191 struct kernfs_node *kn;
6192
6193 kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
6194 if (!kn)
6195 return;
6196 kernfs_path(kn, buf, buflen);
6197 kernfs_put(kn);
6198 }
6199
6200 /*
6201 * cgroup_get_from_id : get the cgroup associated with cgroup id
6202 * @id: cgroup id
6203 * On success return the cgrp or ERR_PTR on failure
6204 * Only cgroups within current task's cgroup NS are valid.
6205 */
cgroup_get_from_id(u64 id)6206 struct cgroup *cgroup_get_from_id(u64 id)
6207 {
6208 struct kernfs_node *kn;
6209 struct cgroup *cgrp, *root_cgrp;
6210
6211 kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
6212 if (!kn)
6213 return ERR_PTR(-ENOENT);
6214
6215 if (kernfs_type(kn) != KERNFS_DIR) {
6216 kernfs_put(kn);
6217 return ERR_PTR(-ENOENT);
6218 }
6219
6220 rcu_read_lock();
6221
6222 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6223 if (cgrp && !cgroup_tryget(cgrp))
6224 cgrp = NULL;
6225
6226 rcu_read_unlock();
6227 kernfs_put(kn);
6228
6229 if (!cgrp)
6230 return ERR_PTR(-ENOENT);
6231
6232 root_cgrp = current_cgns_cgroup_dfl();
6233 if (!cgroup_is_descendant(cgrp, root_cgrp)) {
6234 cgroup_put(cgrp);
6235 return ERR_PTR(-ENOENT);
6236 }
6237
6238 return cgrp;
6239 }
6240 EXPORT_SYMBOL_GPL(cgroup_get_from_id);
6241
6242 /*
6243 * proc_cgroup_show()
6244 * - Print task's cgroup paths into seq_file, one line for each hierarchy
6245 * - Used for /proc/<pid>/cgroup.
6246 */
proc_cgroup_show(struct seq_file * m,struct pid_namespace * ns,struct pid * pid,struct task_struct * tsk)6247 int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
6248 struct pid *pid, struct task_struct *tsk)
6249 {
6250 char *buf;
6251 int retval;
6252 struct cgroup_root *root;
6253
6254 retval = -ENOMEM;
6255 buf = kmalloc(PATH_MAX, GFP_KERNEL);
6256 if (!buf)
6257 goto out;
6258
6259 rcu_read_lock();
6260 spin_lock_irq(&css_set_lock);
6261
6262 for_each_root(root) {
6263 struct cgroup_subsys *ss;
6264 struct cgroup *cgrp;
6265 int ssid, count = 0;
6266
6267 if (root == &cgrp_dfl_root && !READ_ONCE(cgrp_dfl_visible))
6268 continue;
6269
6270 cgrp = task_cgroup_from_root(tsk, root);
6271 /* The root has already been unmounted. */
6272 if (!cgrp)
6273 continue;
6274
6275 seq_printf(m, "%d:", root->hierarchy_id);
6276 if (root != &cgrp_dfl_root)
6277 for_each_subsys(ss, ssid)
6278 if (root->subsys_mask & (1 << ssid))
6279 seq_printf(m, "%s%s", count++ ? "," : "",
6280 ss->legacy_name);
6281 if (strlen(root->name))
6282 seq_printf(m, "%sname=%s", count ? "," : "",
6283 root->name);
6284 seq_putc(m, ':');
6285 /*
6286 * On traditional hierarchies, all zombie tasks show up as
6287 * belonging to the root cgroup. On the default hierarchy,
6288 * while a zombie doesn't show up in "cgroup.procs" and
6289 * thus can't be migrated, its /proc/PID/cgroup keeps
6290 * reporting the cgroup it belonged to before exiting. If
6291 * the cgroup is removed before the zombie is reaped,
6292 * " (deleted)" is appended to the cgroup path.
6293 */
6294 if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) {
6295 retval = cgroup_path_ns_locked(cgrp, buf, PATH_MAX,
6296 current->nsproxy->cgroup_ns);
6297 if (retval == -E2BIG)
6298 retval = -ENAMETOOLONG;
6299 if (retval < 0)
6300 goto out_unlock;
6301
6302 seq_puts(m, buf);
6303 } else {
6304 seq_puts(m, "/");
6305 }
6306
6307 if (cgroup_on_dfl(cgrp) && cgroup_is_dead(cgrp))
6308 seq_puts(m, " (deleted)\n");
6309 else
6310 seq_putc(m, '\n');
6311 }
6312
6313 retval = 0;
6314 out_unlock:
6315 spin_unlock_irq(&css_set_lock);
6316 rcu_read_unlock();
6317 kfree(buf);
6318 out:
6319 return retval;
6320 }
6321
6322 /**
6323 * cgroup_fork - initialize cgroup related fields during copy_process()
6324 * @child: pointer to task_struct of forking parent process.
6325 *
6326 * A task is associated with the init_css_set until cgroup_post_fork()
6327 * attaches it to the target css_set.
6328 */
cgroup_fork(struct task_struct * child)6329 void cgroup_fork(struct task_struct *child)
6330 {
6331 RCU_INIT_POINTER(child->cgroups, &init_css_set);
6332 INIT_LIST_HEAD(&child->cg_list);
6333 }
6334
6335 /**
6336 * cgroup_v1v2_get_from_file - get a cgroup pointer from a file pointer
6337 * @f: file corresponding to cgroup_dir
6338 *
6339 * Find the cgroup from a file pointer associated with a cgroup directory.
6340 * Returns a pointer to the cgroup on success. ERR_PTR is returned if the
6341 * cgroup cannot be found.
6342 */
cgroup_v1v2_get_from_file(struct file * f)6343 static struct cgroup *cgroup_v1v2_get_from_file(struct file *f)
6344 {
6345 struct cgroup_subsys_state *css;
6346
6347 css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
6348 if (IS_ERR(css))
6349 return ERR_CAST(css);
6350
6351 return css->cgroup;
6352 }
6353
6354 /**
6355 * cgroup_get_from_file - same as cgroup_v1v2_get_from_file, but only supports
6356 * cgroup2.
6357 * @f: file corresponding to cgroup2_dir
6358 */
cgroup_get_from_file(struct file * f)6359 static struct cgroup *cgroup_get_from_file(struct file *f)
6360 {
6361 struct cgroup *cgrp = cgroup_v1v2_get_from_file(f);
6362
6363 if (IS_ERR(cgrp))
6364 return ERR_CAST(cgrp);
6365
6366 if (!cgroup_on_dfl(cgrp)) {
6367 cgroup_put(cgrp);
6368 return ERR_PTR(-EBADF);
6369 }
6370
6371 return cgrp;
6372 }
6373
6374 /**
6375 * cgroup_css_set_fork - find or create a css_set for a child process
6376 * @kargs: the arguments passed to create the child process
6377 *
6378 * This functions finds or creates a new css_set which the child
6379 * process will be attached to in cgroup_post_fork(). By default,
6380 * the child process will be given the same css_set as its parent.
6381 *
6382 * If CLONE_INTO_CGROUP is specified this function will try to find an
6383 * existing css_set which includes the requested cgroup and if not create
6384 * a new css_set that the child will be attached to later. If this function
6385 * succeeds it will hold cgroup_threadgroup_rwsem on return. If
6386 * CLONE_INTO_CGROUP is requested this function will grab cgroup mutex
6387 * before grabbing cgroup_threadgroup_rwsem and will hold a reference
6388 * to the target cgroup.
6389 */
cgroup_css_set_fork(struct kernel_clone_args * kargs)6390 static int cgroup_css_set_fork(struct kernel_clone_args *kargs)
6391 __acquires(&cgroup_mutex) __acquires(&cgroup_threadgroup_rwsem)
6392 {
6393 int ret;
6394 struct cgroup *dst_cgrp = NULL;
6395 struct css_set *cset;
6396 struct super_block *sb;
6397 struct file *f;
6398
6399 if (kargs->flags & CLONE_INTO_CGROUP)
6400 cgroup_lock();
6401
6402 cgroup_threadgroup_change_begin(current);
6403
6404 spin_lock_irq(&css_set_lock);
6405 cset = task_css_set(current);
6406 get_css_set(cset);
6407 spin_unlock_irq(&css_set_lock);
6408
6409 if (!(kargs->flags & CLONE_INTO_CGROUP)) {
6410 kargs->cset = cset;
6411 return 0;
6412 }
6413
6414 f = fget_raw(kargs->cgroup);
6415 if (!f) {
6416 ret = -EBADF;
6417 goto err;
6418 }
6419 sb = f->f_path.dentry->d_sb;
6420
6421 dst_cgrp = cgroup_get_from_file(f);
6422 if (IS_ERR(dst_cgrp)) {
6423 ret = PTR_ERR(dst_cgrp);
6424 dst_cgrp = NULL;
6425 goto err;
6426 }
6427
6428 if (cgroup_is_dead(dst_cgrp)) {
6429 ret = -ENODEV;
6430 goto err;
6431 }
6432
6433 /*
6434 * Verify that we the target cgroup is writable for us. This is
6435 * usually done by the vfs layer but since we're not going through
6436 * the vfs layer here we need to do it "manually".
6437 */
6438 ret = cgroup_may_write(dst_cgrp, sb);
6439 if (ret)
6440 goto err;
6441
6442 /*
6443 * Spawning a task directly into a cgroup works by passing a file
6444 * descriptor to the target cgroup directory. This can even be an O_PATH
6445 * file descriptor. But it can never be a cgroup.procs file descriptor.
6446 * This was done on purpose so spawning into a cgroup could be
6447 * conceptualized as an atomic
6448 *
6449 * fd = openat(dfd_cgroup, "cgroup.procs", ...);
6450 * write(fd, <child-pid>, ...);
6451 *
6452 * sequence, i.e. it's a shorthand for the caller opening and writing
6453 * cgroup.procs of the cgroup indicated by @dfd_cgroup. This allows us
6454 * to always use the caller's credentials.
6455 */
6456 ret = cgroup_attach_permissions(cset->dfl_cgrp, dst_cgrp, sb,
6457 !(kargs->flags & CLONE_THREAD),
6458 current->nsproxy->cgroup_ns);
6459 if (ret)
6460 goto err;
6461
6462 kargs->cset = find_css_set(cset, dst_cgrp);
6463 if (!kargs->cset) {
6464 ret = -ENOMEM;
6465 goto err;
6466 }
6467
6468 put_css_set(cset);
6469 fput(f);
6470 kargs->cgrp = dst_cgrp;
6471 return ret;
6472
6473 err:
6474 cgroup_threadgroup_change_end(current);
6475 cgroup_unlock();
6476 if (f)
6477 fput(f);
6478 if (dst_cgrp)
6479 cgroup_put(dst_cgrp);
6480 put_css_set(cset);
6481 if (kargs->cset)
6482 put_css_set(kargs->cset);
6483 return ret;
6484 }
6485
6486 /**
6487 * cgroup_css_set_put_fork - drop references we took during fork
6488 * @kargs: the arguments passed to create the child process
6489 *
6490 * Drop references to the prepared css_set and target cgroup if
6491 * CLONE_INTO_CGROUP was requested.
6492 */
cgroup_css_set_put_fork(struct kernel_clone_args * kargs)6493 static void cgroup_css_set_put_fork(struct kernel_clone_args *kargs)
6494 __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
6495 {
6496 struct cgroup *cgrp = kargs->cgrp;
6497 struct css_set *cset = kargs->cset;
6498
6499 cgroup_threadgroup_change_end(current);
6500
6501 if (cset) {
6502 put_css_set(cset);
6503 kargs->cset = NULL;
6504 }
6505
6506 if (kargs->flags & CLONE_INTO_CGROUP) {
6507 cgroup_unlock();
6508 if (cgrp) {
6509 cgroup_put(cgrp);
6510 kargs->cgrp = NULL;
6511 }
6512 }
6513 }
6514
6515 /**
6516 * cgroup_can_fork - called on a new task before the process is exposed
6517 * @child: the child process
6518 * @kargs: the arguments passed to create the child process
6519 *
6520 * This prepares a new css_set for the child process which the child will
6521 * be attached to in cgroup_post_fork().
6522 * This calls the subsystem can_fork() callbacks. If the cgroup_can_fork()
6523 * callback returns an error, the fork aborts with that error code. This
6524 * allows for a cgroup subsystem to conditionally allow or deny new forks.
6525 */
cgroup_can_fork(struct task_struct * child,struct kernel_clone_args * kargs)6526 int cgroup_can_fork(struct task_struct *child, struct kernel_clone_args *kargs)
6527 {
6528 struct cgroup_subsys *ss;
6529 int i, j, ret;
6530
6531 ret = cgroup_css_set_fork(kargs);
6532 if (ret)
6533 return ret;
6534
6535 do_each_subsys_mask(ss, i, have_canfork_callback) {
6536 ret = ss->can_fork(child, kargs->cset);
6537 if (ret)
6538 goto out_revert;
6539 } while_each_subsys_mask();
6540
6541 return 0;
6542
6543 out_revert:
6544 for_each_subsys(ss, j) {
6545 if (j >= i)
6546 break;
6547 if (ss->cancel_fork)
6548 ss->cancel_fork(child, kargs->cset);
6549 }
6550
6551 cgroup_css_set_put_fork(kargs);
6552
6553 return ret;
6554 }
6555
6556 /**
6557 * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
6558 * @child: the child process
6559 * @kargs: the arguments passed to create the child process
6560 *
6561 * This calls the cancel_fork() callbacks if a fork failed *after*
6562 * cgroup_can_fork() succeeded and cleans up references we took to
6563 * prepare a new css_set for the child process in cgroup_can_fork().
6564 */
cgroup_cancel_fork(struct task_struct * child,struct kernel_clone_args * kargs)6565 void cgroup_cancel_fork(struct task_struct *child,
6566 struct kernel_clone_args *kargs)
6567 {
6568 struct cgroup_subsys *ss;
6569 int i;
6570
6571 for_each_subsys(ss, i)
6572 if (ss->cancel_fork)
6573 ss->cancel_fork(child, kargs->cset);
6574
6575 cgroup_css_set_put_fork(kargs);
6576 }
6577
6578 /**
6579 * cgroup_post_fork - finalize cgroup setup for the child process
6580 * @child: the child process
6581 * @kargs: the arguments passed to create the child process
6582 *
6583 * Attach the child process to its css_set calling the subsystem fork()
6584 * callbacks.
6585 */
cgroup_post_fork(struct task_struct * child,struct kernel_clone_args * kargs)6586 void cgroup_post_fork(struct task_struct *child,
6587 struct kernel_clone_args *kargs)
6588 __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
6589 {
6590 unsigned long cgrp_flags = 0;
6591 bool kill = false;
6592 struct cgroup_subsys *ss;
6593 struct css_set *cset;
6594 int i;
6595
6596 cset = kargs->cset;
6597 kargs->cset = NULL;
6598
6599 spin_lock_irq(&css_set_lock);
6600
6601 /* init tasks are special, only link regular threads */
6602 if (likely(child->pid)) {
6603 if (kargs->cgrp)
6604 cgrp_flags = kargs->cgrp->flags;
6605 else
6606 cgrp_flags = cset->dfl_cgrp->flags;
6607
6608 WARN_ON_ONCE(!list_empty(&child->cg_list));
6609 cset->nr_tasks++;
6610 css_set_move_task(child, NULL, cset, false);
6611 } else {
6612 put_css_set(cset);
6613 cset = NULL;
6614 }
6615
6616 if (!(child->flags & PF_KTHREAD)) {
6617 if (unlikely(test_bit(CGRP_FREEZE, &cgrp_flags))) {
6618 /*
6619 * If the cgroup has to be frozen, the new task has
6620 * too. Let's set the JOBCTL_TRAP_FREEZE jobctl bit to
6621 * get the task into the frozen state.
6622 */
6623 spin_lock(&child->sighand->siglock);
6624 WARN_ON_ONCE(child->frozen);
6625 child->jobctl |= JOBCTL_TRAP_FREEZE;
6626 spin_unlock(&child->sighand->siglock);
6627
6628 /*
6629 * Calling cgroup_update_frozen() isn't required here,
6630 * because it will be called anyway a bit later from
6631 * do_freezer_trap(). So we avoid cgroup's transient
6632 * switch from the frozen state and back.
6633 */
6634 }
6635
6636 /*
6637 * If the cgroup is to be killed notice it now and take the
6638 * child down right after we finished preparing it for
6639 * userspace.
6640 */
6641 kill = test_bit(CGRP_KILL, &cgrp_flags);
6642 }
6643
6644 spin_unlock_irq(&css_set_lock);
6645
6646 /*
6647 * Call ss->fork(). This must happen after @child is linked on
6648 * css_set; otherwise, @child might change state between ->fork()
6649 * and addition to css_set.
6650 */
6651 do_each_subsys_mask(ss, i, have_fork_callback) {
6652 ss->fork(child);
6653 } while_each_subsys_mask();
6654
6655 /* Make the new cset the root_cset of the new cgroup namespace. */
6656 if (kargs->flags & CLONE_NEWCGROUP) {
6657 struct css_set *rcset = child->nsproxy->cgroup_ns->root_cset;
6658
6659 get_css_set(cset);
6660 child->nsproxy->cgroup_ns->root_cset = cset;
6661 put_css_set(rcset);
6662 }
6663
6664 /* Cgroup has to be killed so take down child immediately. */
6665 if (unlikely(kill))
6666 do_send_sig_info(SIGKILL, SEND_SIG_NOINFO, child, PIDTYPE_TGID);
6667
6668 cgroup_css_set_put_fork(kargs);
6669 }
6670
6671 /**
6672 * cgroup_exit - detach cgroup from exiting task
6673 * @tsk: pointer to task_struct of exiting process
6674 *
6675 * Description: Detach cgroup from @tsk.
6676 *
6677 */
cgroup_exit(struct task_struct * tsk)6678 void cgroup_exit(struct task_struct *tsk)
6679 {
6680 struct cgroup_subsys *ss;
6681 struct css_set *cset;
6682 int i;
6683
6684 spin_lock_irq(&css_set_lock);
6685
6686 WARN_ON_ONCE(list_empty(&tsk->cg_list));
6687 cset = task_css_set(tsk);
6688 css_set_move_task(tsk, cset, NULL, false);
6689 list_add_tail(&tsk->cg_list, &cset->dying_tasks);
6690 cset->nr_tasks--;
6691
6692 if (dl_task(tsk))
6693 dec_dl_tasks_cs(tsk);
6694
6695 WARN_ON_ONCE(cgroup_task_frozen(tsk));
6696 if (unlikely(!(tsk->flags & PF_KTHREAD) &&
6697 test_bit(CGRP_FREEZE, &task_dfl_cgroup(tsk)->flags)))
6698 cgroup_update_frozen(task_dfl_cgroup(tsk));
6699
6700 spin_unlock_irq(&css_set_lock);
6701
6702 /* see cgroup_post_fork() for details */
6703 do_each_subsys_mask(ss, i, have_exit_callback) {
6704 ss->exit(tsk);
6705 } while_each_subsys_mask();
6706 }
6707
cgroup_release(struct task_struct * task)6708 void cgroup_release(struct task_struct *task)
6709 {
6710 struct cgroup_subsys *ss;
6711 int ssid;
6712
6713 do_each_subsys_mask(ss, ssid, have_release_callback) {
6714 ss->release(task);
6715 } while_each_subsys_mask();
6716
6717 spin_lock_irq(&css_set_lock);
6718 css_set_skip_task_iters(task_css_set(task), task);
6719 list_del_init(&task->cg_list);
6720 spin_unlock_irq(&css_set_lock);
6721 }
6722
cgroup_free(struct task_struct * task)6723 void cgroup_free(struct task_struct *task)
6724 {
6725 struct css_set *cset = task_css_set(task);
6726 put_css_set(cset);
6727 }
6728
cgroup_disable(char * str)6729 static int __init cgroup_disable(char *str)
6730 {
6731 struct cgroup_subsys *ss;
6732 char *token;
6733 int i;
6734
6735 while ((token = strsep(&str, ",")) != NULL) {
6736 if (!*token)
6737 continue;
6738
6739 for_each_subsys(ss, i) {
6740 if (strcmp(token, ss->name) &&
6741 strcmp(token, ss->legacy_name))
6742 continue;
6743
6744 static_branch_disable(cgroup_subsys_enabled_key[i]);
6745 pr_info("Disabling %s control group subsystem\n",
6746 ss->name);
6747 }
6748
6749 for (i = 0; i < OPT_FEATURE_COUNT; i++) {
6750 if (strcmp(token, cgroup_opt_feature_names[i]))
6751 continue;
6752 cgroup_feature_disable_mask |= 1 << i;
6753 pr_info("Disabling %s control group feature\n",
6754 cgroup_opt_feature_names[i]);
6755 break;
6756 }
6757 }
6758 return 1;
6759 }
6760 __setup("cgroup_disable=", cgroup_disable);
6761
enable_debug_cgroup(void)6762 void __init __weak enable_debug_cgroup(void) { }
6763
enable_cgroup_debug(char * str)6764 static int __init enable_cgroup_debug(char *str)
6765 {
6766 cgroup_debug = true;
6767 enable_debug_cgroup();
6768 return 1;
6769 }
6770 __setup("cgroup_debug", enable_cgroup_debug);
6771
cgroup_favordynmods_setup(char * str)6772 static int __init cgroup_favordynmods_setup(char *str)
6773 {
6774 return (kstrtobool(str, &have_favordynmods) == 0);
6775 }
6776 __setup("cgroup_favordynmods=", cgroup_favordynmods_setup);
6777
6778 /**
6779 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
6780 * @dentry: directory dentry of interest
6781 * @ss: subsystem of interest
6782 *
6783 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
6784 * to get the corresponding css and return it. If such css doesn't exist
6785 * or can't be pinned, an ERR_PTR value is returned.
6786 */
css_tryget_online_from_dir(struct dentry * dentry,struct cgroup_subsys * ss)6787 struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
6788 struct cgroup_subsys *ss)
6789 {
6790 struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
6791 struct file_system_type *s_type = dentry->d_sb->s_type;
6792 struct cgroup_subsys_state *css = NULL;
6793 struct cgroup *cgrp;
6794
6795 /* is @dentry a cgroup dir? */
6796 if ((s_type != &cgroup_fs_type && s_type != &cgroup2_fs_type) ||
6797 !kn || kernfs_type(kn) != KERNFS_DIR)
6798 return ERR_PTR(-EBADF);
6799
6800 rcu_read_lock();
6801
6802 /*
6803 * This path doesn't originate from kernfs and @kn could already
6804 * have been or be removed at any point. @kn->priv is RCU
6805 * protected for this access. See css_release_work_fn() for details.
6806 */
6807 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6808 if (cgrp)
6809 css = cgroup_css(cgrp, ss);
6810
6811 if (!css || !css_tryget_online(css))
6812 css = ERR_PTR(-ENOENT);
6813
6814 rcu_read_unlock();
6815 return css;
6816 }
6817
6818 /**
6819 * css_from_id - lookup css by id
6820 * @id: the cgroup id
6821 * @ss: cgroup subsys to be looked into
6822 *
6823 * Returns the css if there's valid one with @id, otherwise returns NULL.
6824 * Should be called under rcu_read_lock().
6825 */
css_from_id(int id,struct cgroup_subsys * ss)6826 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
6827 {
6828 WARN_ON_ONCE(!rcu_read_lock_held());
6829 return idr_find(&ss->css_idr, id);
6830 }
6831
6832 /**
6833 * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path
6834 * @path: path on the default hierarchy
6835 *
6836 * Find the cgroup at @path on the default hierarchy, increment its
6837 * reference count and return it. Returns pointer to the found cgroup on
6838 * success, ERR_PTR(-ENOENT) if @path doesn't exist or if the cgroup has already
6839 * been released and ERR_PTR(-ENOTDIR) if @path points to a non-directory.
6840 */
cgroup_get_from_path(const char * path)6841 struct cgroup *cgroup_get_from_path(const char *path)
6842 {
6843 struct kernfs_node *kn;
6844 struct cgroup *cgrp = ERR_PTR(-ENOENT);
6845 struct cgroup *root_cgrp;
6846
6847 root_cgrp = current_cgns_cgroup_dfl();
6848 kn = kernfs_walk_and_get(root_cgrp->kn, path);
6849 if (!kn)
6850 goto out;
6851
6852 if (kernfs_type(kn) != KERNFS_DIR) {
6853 cgrp = ERR_PTR(-ENOTDIR);
6854 goto out_kernfs;
6855 }
6856
6857 rcu_read_lock();
6858
6859 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6860 if (!cgrp || !cgroup_tryget(cgrp))
6861 cgrp = ERR_PTR(-ENOENT);
6862
6863 rcu_read_unlock();
6864
6865 out_kernfs:
6866 kernfs_put(kn);
6867 out:
6868 return cgrp;
6869 }
6870 EXPORT_SYMBOL_GPL(cgroup_get_from_path);
6871
6872 /**
6873 * cgroup_v1v2_get_from_fd - get a cgroup pointer from a fd
6874 * @fd: fd obtained by open(cgroup_dir)
6875 *
6876 * Find the cgroup from a fd which should be obtained
6877 * by opening a cgroup directory. Returns a pointer to the
6878 * cgroup on success. ERR_PTR is returned if the cgroup
6879 * cannot be found.
6880 */
cgroup_v1v2_get_from_fd(int fd)6881 struct cgroup *cgroup_v1v2_get_from_fd(int fd)
6882 {
6883 struct cgroup *cgrp;
6884 struct fd f = fdget_raw(fd);
6885 if (!f.file)
6886 return ERR_PTR(-EBADF);
6887
6888 cgrp = cgroup_v1v2_get_from_file(f.file);
6889 fdput(f);
6890 return cgrp;
6891 }
6892
6893 /**
6894 * cgroup_get_from_fd - same as cgroup_v1v2_get_from_fd, but only supports
6895 * cgroup2.
6896 * @fd: fd obtained by open(cgroup2_dir)
6897 */
cgroup_get_from_fd(int fd)6898 struct cgroup *cgroup_get_from_fd(int fd)
6899 {
6900 struct cgroup *cgrp = cgroup_v1v2_get_from_fd(fd);
6901
6902 if (IS_ERR(cgrp))
6903 return ERR_CAST(cgrp);
6904
6905 if (!cgroup_on_dfl(cgrp)) {
6906 cgroup_put(cgrp);
6907 return ERR_PTR(-EBADF);
6908 }
6909 return cgrp;
6910 }
6911 EXPORT_SYMBOL_GPL(cgroup_get_from_fd);
6912
power_of_ten(int power)6913 static u64 power_of_ten(int power)
6914 {
6915 u64 v = 1;
6916 while (power--)
6917 v *= 10;
6918 return v;
6919 }
6920
6921 /**
6922 * cgroup_parse_float - parse a floating number
6923 * @input: input string
6924 * @dec_shift: number of decimal digits to shift
6925 * @v: output
6926 *
6927 * Parse a decimal floating point number in @input and store the result in
6928 * @v with decimal point right shifted @dec_shift times. For example, if
6929 * @input is "12.3456" and @dec_shift is 3, *@v will be set to 12345.
6930 * Returns 0 on success, -errno otherwise.
6931 *
6932 * There's nothing cgroup specific about this function except that it's
6933 * currently the only user.
6934 */
cgroup_parse_float(const char * input,unsigned dec_shift,s64 * v)6935 int cgroup_parse_float(const char *input, unsigned dec_shift, s64 *v)
6936 {
6937 s64 whole, frac = 0;
6938 int fstart = 0, fend = 0, flen;
6939
6940 if (!sscanf(input, "%lld.%n%lld%n", &whole, &fstart, &frac, &fend))
6941 return -EINVAL;
6942 if (frac < 0)
6943 return -EINVAL;
6944
6945 flen = fend > fstart ? fend - fstart : 0;
6946 if (flen < dec_shift)
6947 frac *= power_of_ten(dec_shift - flen);
6948 else
6949 frac = DIV_ROUND_CLOSEST_ULL(frac, power_of_ten(flen - dec_shift));
6950
6951 *v = whole * power_of_ten(dec_shift) + frac;
6952 return 0;
6953 }
6954
6955 /*
6956 * sock->sk_cgrp_data handling. For more info, see sock_cgroup_data
6957 * definition in cgroup-defs.h.
6958 */
6959 #ifdef CONFIG_SOCK_CGROUP_DATA
6960
cgroup_sk_alloc(struct sock_cgroup_data * skcd)6961 void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
6962 {
6963 struct cgroup *cgroup;
6964
6965 rcu_read_lock();
6966 /* Don't associate the sock with unrelated interrupted task's cgroup. */
6967 if (in_interrupt()) {
6968 cgroup = &cgrp_dfl_root.cgrp;
6969 cgroup_get(cgroup);
6970 goto out;
6971 }
6972
6973 while (true) {
6974 struct css_set *cset;
6975
6976 cset = task_css_set(current);
6977 if (likely(cgroup_tryget(cset->dfl_cgrp))) {
6978 cgroup = cset->dfl_cgrp;
6979 break;
6980 }
6981 cpu_relax();
6982 }
6983 out:
6984 skcd->cgroup = cgroup;
6985 cgroup_bpf_get(cgroup);
6986 rcu_read_unlock();
6987 }
6988
cgroup_sk_clone(struct sock_cgroup_data * skcd)6989 void cgroup_sk_clone(struct sock_cgroup_data *skcd)
6990 {
6991 struct cgroup *cgrp = sock_cgroup_ptr(skcd);
6992
6993 /*
6994 * We might be cloning a socket which is left in an empty
6995 * cgroup and the cgroup might have already been rmdir'd.
6996 * Don't use cgroup_get_live().
6997 */
6998 cgroup_get(cgrp);
6999 cgroup_bpf_get(cgrp);
7000 }
7001
cgroup_sk_free(struct sock_cgroup_data * skcd)7002 void cgroup_sk_free(struct sock_cgroup_data *skcd)
7003 {
7004 struct cgroup *cgrp = sock_cgroup_ptr(skcd);
7005
7006 cgroup_bpf_put(cgrp);
7007 cgroup_put(cgrp);
7008 }
7009
7010 #endif /* CONFIG_SOCK_CGROUP_DATA */
7011
7012 #ifdef CONFIG_SYSFS
show_delegatable_files(struct cftype * files,char * buf,ssize_t size,const char * prefix)7013 static ssize_t show_delegatable_files(struct cftype *files, char *buf,
7014 ssize_t size, const char *prefix)
7015 {
7016 struct cftype *cft;
7017 ssize_t ret = 0;
7018
7019 for (cft = files; cft && cft->name[0] != '\0'; cft++) {
7020 if (!(cft->flags & CFTYPE_NS_DELEGATABLE))
7021 continue;
7022
7023 if (prefix)
7024 ret += snprintf(buf + ret, size - ret, "%s.", prefix);
7025
7026 ret += snprintf(buf + ret, size - ret, "%s\n", cft->name);
7027
7028 if (WARN_ON(ret >= size))
7029 break;
7030 }
7031
7032 return ret;
7033 }
7034
delegate_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)7035 static ssize_t delegate_show(struct kobject *kobj, struct kobj_attribute *attr,
7036 char *buf)
7037 {
7038 struct cgroup_subsys *ss;
7039 int ssid;
7040 ssize_t ret = 0;
7041
7042 ret = show_delegatable_files(cgroup_base_files, buf + ret,
7043 PAGE_SIZE - ret, NULL);
7044 if (cgroup_psi_enabled())
7045 ret += show_delegatable_files(cgroup_psi_files, buf + ret,
7046 PAGE_SIZE - ret, NULL);
7047
7048 for_each_subsys(ss, ssid)
7049 ret += show_delegatable_files(ss->dfl_cftypes, buf + ret,
7050 PAGE_SIZE - ret,
7051 cgroup_subsys_name[ssid]);
7052
7053 return ret;
7054 }
7055 static struct kobj_attribute cgroup_delegate_attr = __ATTR_RO(delegate);
7056
features_show(struct kobject * kobj,struct kobj_attribute * attr,char * buf)7057 static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr,
7058 char *buf)
7059 {
7060 return snprintf(buf, PAGE_SIZE,
7061 "nsdelegate\n"
7062 "favordynmods\n"
7063 "memory_localevents\n"
7064 "memory_recursiveprot\n"
7065 "memory_hugetlb_accounting\n");
7066 }
7067 static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features);
7068
7069 static struct attribute *cgroup_sysfs_attrs[] = {
7070 &cgroup_delegate_attr.attr,
7071 &cgroup_features_attr.attr,
7072 NULL,
7073 };
7074
7075 static const struct attribute_group cgroup_sysfs_attr_group = {
7076 .attrs = cgroup_sysfs_attrs,
7077 .name = "cgroup",
7078 };
7079
cgroup_sysfs_init(void)7080 static int __init cgroup_sysfs_init(void)
7081 {
7082 return sysfs_create_group(kernel_kobj, &cgroup_sysfs_attr_group);
7083 }
7084 subsys_initcall(cgroup_sysfs_init);
7085
7086 #endif /* CONFIG_SYSFS */
7087