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