2 * Generic process-grouping system.
4 * Based originally on the cpuset system, extracted by Paul Menage
5 * Copyright (C) 2006 Google, Inc
7 * Notifications support
8 * Copyright (C) 2009 Nokia Corporation
9 * Author: Kirill A. Shutemov
11 * Copyright notices from the original cpuset code:
12 * --------------------------------------------------
13 * Copyright (C) 2003 BULL SA.
14 * Copyright (C) 2004-2006 Silicon Graphics, Inc.
16 * Portions derived from Patrick Mochel's sysfs code.
17 * sysfs is Copyright (c) 2001-3 Patrick Mochel
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 * ---------------------------------------------------
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.
29 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
31 #include "cgroup-internal.h"
33 #include <linux/cred.h>
34 #include <linux/errno.h>
35 #include <linux/init_task.h>
36 #include <linux/kernel.h>
37 #include <linux/magic.h>
38 #include <linux/mutex.h>
39 #include <linux/mount.h>
40 #include <linux/pagemap.h>
41 #include <linux/proc_fs.h>
42 #include <linux/rcupdate.h>
43 #include <linux/sched.h>
44 #include <linux/sched/task.h>
45 #include <linux/slab.h>
46 #include <linux/spinlock.h>
47 #include <linux/percpu-rwsem.h>
48 #include <linux/string.h>
49 #include <linux/hashtable.h>
50 #include <linux/idr.h>
51 #include <linux/kthread.h>
52 #include <linux/atomic.h>
53 #include <linux/cpuset.h>
54 #include <linux/proc_ns.h>
55 #include <linux/nsproxy.h>
56 #include <linux/file.h>
57 #include <linux/fs_parser.h>
58 #include <linux/sched/cputime.h>
59 #include <linux/psi.h>
62 #define CREATE_TRACE_POINTS
63 #include <trace/events/cgroup.h>
65 #define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
67 /* let's not notify more than 100 times per second */
68 #define CGROUP_FILE_NOTIFY_MIN_INTV DIV_ROUND_UP(HZ, 100)
71 * cgroup_mutex is the master lock. Any modification to cgroup or its
72 * hierarchy must be performed while holding it.
74 * css_set_lock protects task->cgroups pointer, the list of css_set
75 * objects, and the chain of tasks off each css_set.
77 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
78 * cgroup.h can use them for lockdep annotations.
80 DEFINE_MUTEX(cgroup_mutex);
81 DEFINE_SPINLOCK(css_set_lock);
83 #ifdef CONFIG_PROVE_RCU
84 EXPORT_SYMBOL_GPL(cgroup_mutex);
85 EXPORT_SYMBOL_GPL(css_set_lock);
88 DEFINE_SPINLOCK(trace_cgroup_path_lock);
89 char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
90 bool cgroup_debug __read_mostly;
93 * Protects cgroup_idr and css_idr so that IDs can be released without
94 * grabbing cgroup_mutex.
96 static DEFINE_SPINLOCK(cgroup_idr_lock);
99 * Protects cgroup_file->kn for !self csses. It synchronizes notifications
100 * against file removal/re-creation across css hiding.
102 static DEFINE_SPINLOCK(cgroup_file_kn_lock);
104 DEFINE_PERCPU_RWSEM(cgroup_threadgroup_rwsem);
106 #define cgroup_assert_mutex_or_rcu_locked() \
107 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
108 !lockdep_is_held(&cgroup_mutex), \
109 "cgroup_mutex or RCU read lock required");
112 * cgroup destruction makes heavy use of work items and there can be a lot
113 * of concurrent destructions. Use a separate workqueue so that cgroup
114 * destruction work items don't end up filling up max_active of system_wq
115 * which may lead to deadlock.
117 static struct workqueue_struct *cgroup_destroy_wq;
119 /* generate an array of cgroup subsystem pointers */
120 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
121 struct cgroup_subsys *cgroup_subsys[] = {
122 #include <linux/cgroup_subsys.h>
126 /* array of cgroup subsystem names */
127 #define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
128 static const char *cgroup_subsys_name[] = {
129 #include <linux/cgroup_subsys.h>
133 /* array of static_keys for cgroup_subsys_enabled() and cgroup_subsys_on_dfl() */
135 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key); \
136 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key); \
137 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key); \
138 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key);
139 #include <linux/cgroup_subsys.h>
142 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_enabled_key,
143 static struct static_key_true *cgroup_subsys_enabled_key[] = {
144 #include <linux/cgroup_subsys.h>
148 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_on_dfl_key,
149 static struct static_key_true *cgroup_subsys_on_dfl_key[] = {
150 #include <linux/cgroup_subsys.h>
154 static DEFINE_PER_CPU(struct cgroup_rstat_cpu, cgrp_dfl_root_rstat_cpu);
157 * The default hierarchy, reserved for the subsystems that are otherwise
158 * unattached - it never has more than a single cgroup, and all tasks are
159 * part of that cgroup.
161 struct cgroup_root cgrp_dfl_root = { .cgrp.rstat_cpu = &cgrp_dfl_root_rstat_cpu };
162 EXPORT_SYMBOL_GPL(cgrp_dfl_root);
165 * The default hierarchy always exists but is hidden until mounted for the
166 * first time. This is for backward compatibility.
168 static bool cgrp_dfl_visible;
170 /* some controllers are not supported in the default hierarchy */
171 static u16 cgrp_dfl_inhibit_ss_mask;
173 /* some controllers are implicitly enabled on the default hierarchy */
174 static u16 cgrp_dfl_implicit_ss_mask;
176 /* some controllers can be threaded on the default hierarchy */
177 static u16 cgrp_dfl_threaded_ss_mask;
179 /* The list of hierarchy roots */
180 LIST_HEAD(cgroup_roots);
181 static int cgroup_root_count;
183 /* hierarchy ID allocation and mapping, protected by cgroup_mutex */
184 static DEFINE_IDR(cgroup_hierarchy_idr);
187 * Assign a monotonically increasing serial number to csses. It guarantees
188 * cgroups with bigger numbers are newer than those with smaller numbers.
189 * Also, as csses are always appended to the parent's ->children list, it
190 * guarantees that sibling csses are always sorted in the ascending serial
191 * number order on the list. Protected by cgroup_mutex.
193 static u64 css_serial_nr_next = 1;
196 * These bitmasks identify subsystems with specific features to avoid
197 * having to do iterative checks repeatedly.
199 static u16 have_fork_callback __read_mostly;
200 static u16 have_exit_callback __read_mostly;
201 static u16 have_release_callback __read_mostly;
202 static u16 have_canfork_callback __read_mostly;
204 /* cgroup namespace for init task */
205 struct cgroup_namespace init_cgroup_ns = {
206 .count = REFCOUNT_INIT(2),
207 .user_ns = &init_user_ns,
208 .ns.ops = &cgroupns_operations,
209 .ns.inum = PROC_CGROUP_INIT_INO,
210 .root_cset = &init_css_set,
213 static struct file_system_type cgroup2_fs_type;
214 static struct cftype cgroup_base_files[];
216 static int cgroup_apply_control(struct cgroup *cgrp);
217 static void cgroup_finalize_control(struct cgroup *cgrp, int ret);
218 static void css_task_iter_skip(struct css_task_iter *it,
219 struct task_struct *task);
220 static int cgroup_destroy_locked(struct cgroup *cgrp);
221 static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
222 struct cgroup_subsys *ss);
223 static void css_release(struct percpu_ref *ref);
224 static void kill_css(struct cgroup_subsys_state *css);
225 static int cgroup_addrm_files(struct cgroup_subsys_state *css,
226 struct cgroup *cgrp, struct cftype cfts[],
230 * cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID
231 * @ssid: subsys ID of interest
233 * cgroup_subsys_enabled() can only be used with literal subsys names which
234 * is fine for individual subsystems but unsuitable for cgroup core. This
235 * is slower static_key_enabled() based test indexed by @ssid.
237 bool cgroup_ssid_enabled(int ssid)
239 if (CGROUP_SUBSYS_COUNT == 0)
242 return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
246 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
247 * @cgrp: the cgroup of interest
249 * The default hierarchy is the v2 interface of cgroup and this function
250 * can be used to test whether a cgroup is on the default hierarchy for
251 * cases where a subsystem should behave differnetly depending on the
254 * The set of behaviors which change on the default hierarchy are still
255 * being determined and the mount option is prefixed with __DEVEL__.
257 * List of changed behaviors:
259 * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
260 * and "name" are disallowed.
262 * - When mounting an existing superblock, mount options should match.
264 * - Remount is disallowed.
266 * - rename(2) is disallowed.
268 * - "tasks" is removed. Everything should be at process granularity. Use
269 * "cgroup.procs" instead.
271 * - "cgroup.procs" is not sorted. pids will be unique unless they got
272 * recycled inbetween reads.
274 * - "release_agent" and "notify_on_release" are removed. Replacement
275 * notification mechanism will be implemented.
277 * - "cgroup.clone_children" is removed.
279 * - "cgroup.subtree_populated" is available. Its value is 0 if the cgroup
280 * and its descendants contain no task; otherwise, 1. The file also
281 * generates kernfs notification which can be monitored through poll and
282 * [di]notify when the value of the file changes.
284 * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
285 * take masks of ancestors with non-empty cpus/mems, instead of being
286 * moved to an ancestor.
288 * - cpuset: a task can be moved into an empty cpuset, and again it takes
289 * masks of ancestors.
291 * - memcg: use_hierarchy is on by default and the cgroup file for the flag
294 * - blkcg: blk-throttle becomes properly hierarchical.
296 * - debug: disallowed on the default hierarchy.
298 bool cgroup_on_dfl(const struct cgroup *cgrp)
300 return cgrp->root == &cgrp_dfl_root;
303 /* IDR wrappers which synchronize using cgroup_idr_lock */
304 static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
309 idr_preload(gfp_mask);
310 spin_lock_bh(&cgroup_idr_lock);
311 ret = idr_alloc(idr, ptr, start, end, gfp_mask & ~__GFP_DIRECT_RECLAIM);
312 spin_unlock_bh(&cgroup_idr_lock);
317 static void *cgroup_idr_replace(struct idr *idr, void *ptr, int id)
321 spin_lock_bh(&cgroup_idr_lock);
322 ret = idr_replace(idr, ptr, id);
323 spin_unlock_bh(&cgroup_idr_lock);
327 static void cgroup_idr_remove(struct idr *idr, int id)
329 spin_lock_bh(&cgroup_idr_lock);
331 spin_unlock_bh(&cgroup_idr_lock);
334 static bool cgroup_has_tasks(struct cgroup *cgrp)
336 return cgrp->nr_populated_csets;
339 bool cgroup_is_threaded(struct cgroup *cgrp)
341 return cgrp->dom_cgrp != cgrp;
344 /* can @cgrp host both domain and threaded children? */
345 static bool cgroup_is_mixable(struct cgroup *cgrp)
348 * Root isn't under domain level resource control exempting it from
349 * the no-internal-process constraint, so it can serve as a thread
350 * root and a parent of resource domains at the same time.
352 return !cgroup_parent(cgrp);
355 /* can @cgrp become a thread root? should always be true for a thread root */
356 static bool cgroup_can_be_thread_root(struct cgroup *cgrp)
358 /* mixables don't care */
359 if (cgroup_is_mixable(cgrp))
362 /* domain roots can't be nested under threaded */
363 if (cgroup_is_threaded(cgrp))
366 /* can only have either domain or threaded children */
367 if (cgrp->nr_populated_domain_children)
370 /* and no domain controllers can be enabled */
371 if (cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)
377 /* is @cgrp root of a threaded subtree? */
378 bool cgroup_is_thread_root(struct cgroup *cgrp)
380 /* thread root should be a domain */
381 if (cgroup_is_threaded(cgrp))
384 /* a domain w/ threaded children is a thread root */
385 if (cgrp->nr_threaded_children)
389 * A domain which has tasks and explicit threaded controllers
390 * enabled is a thread root.
392 if (cgroup_has_tasks(cgrp) &&
393 (cgrp->subtree_control & cgrp_dfl_threaded_ss_mask))
399 /* a domain which isn't connected to the root w/o brekage can't be used */
400 static bool cgroup_is_valid_domain(struct cgroup *cgrp)
402 /* the cgroup itself can be a thread root */
403 if (cgroup_is_threaded(cgrp))
406 /* but the ancestors can't be unless mixable */
407 while ((cgrp = cgroup_parent(cgrp))) {
408 if (!cgroup_is_mixable(cgrp) && cgroup_is_thread_root(cgrp))
410 if (cgroup_is_threaded(cgrp))
417 /* subsystems visibly enabled on a cgroup */
418 static u16 cgroup_control(struct cgroup *cgrp)
420 struct cgroup *parent = cgroup_parent(cgrp);
421 u16 root_ss_mask = cgrp->root->subsys_mask;
424 u16 ss_mask = parent->subtree_control;
426 /* threaded cgroups can only have threaded controllers */
427 if (cgroup_is_threaded(cgrp))
428 ss_mask &= cgrp_dfl_threaded_ss_mask;
432 if (cgroup_on_dfl(cgrp))
433 root_ss_mask &= ~(cgrp_dfl_inhibit_ss_mask |
434 cgrp_dfl_implicit_ss_mask);
438 /* subsystems enabled on a cgroup */
439 static u16 cgroup_ss_mask(struct cgroup *cgrp)
441 struct cgroup *parent = cgroup_parent(cgrp);
444 u16 ss_mask = parent->subtree_ss_mask;
446 /* threaded cgroups can only have threaded controllers */
447 if (cgroup_is_threaded(cgrp))
448 ss_mask &= cgrp_dfl_threaded_ss_mask;
452 return cgrp->root->subsys_mask;
456 * cgroup_css - obtain a cgroup's css for the specified subsystem
457 * @cgrp: the cgroup of interest
458 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
460 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
461 * function must be called either under cgroup_mutex or rcu_read_lock() and
462 * the caller is responsible for pinning the returned css if it wants to
463 * keep accessing it outside the said locks. This function may return
464 * %NULL if @cgrp doesn't have @subsys_id enabled.
466 static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
467 struct cgroup_subsys *ss)
470 return rcu_dereference_check(cgrp->subsys[ss->id],
471 lockdep_is_held(&cgroup_mutex));
477 * cgroup_tryget_css - try to get a cgroup's css for the specified subsystem
478 * @cgrp: the cgroup of interest
479 * @ss: the subsystem of interest
481 * Find and get @cgrp's css assocaited with @ss. If the css doesn't exist
482 * or is offline, %NULL is returned.
484 static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp,
485 struct cgroup_subsys *ss)
487 struct cgroup_subsys_state *css;
490 css = cgroup_css(cgrp, ss);
491 if (css && !css_tryget_online(css))
499 * cgroup_e_css_by_mask - obtain a cgroup's effective css for the specified ss
500 * @cgrp: the cgroup of interest
501 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
503 * Similar to cgroup_css() but returns the effective css, which is defined
504 * as the matching css of the nearest ancestor including self which has @ss
505 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
506 * function is guaranteed to return non-NULL css.
508 static struct cgroup_subsys_state *cgroup_e_css_by_mask(struct cgroup *cgrp,
509 struct cgroup_subsys *ss)
511 lockdep_assert_held(&cgroup_mutex);
517 * This function is used while updating css associations and thus
518 * can't test the csses directly. Test ss_mask.
520 while (!(cgroup_ss_mask(cgrp) & (1 << ss->id))) {
521 cgrp = cgroup_parent(cgrp);
526 return cgroup_css(cgrp, ss);
530 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
531 * @cgrp: the cgroup of interest
532 * @ss: the subsystem of interest
534 * Find and get the effective css of @cgrp for @ss. The effective css is
535 * defined as the matching css of the nearest ancestor including self which
536 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
537 * the root css is returned, so this function always returns a valid css.
539 * The returned css is not guaranteed to be online, and therefore it is the
540 * callers responsiblity to tryget a reference for it.
542 struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
543 struct cgroup_subsys *ss)
545 struct cgroup_subsys_state *css;
548 css = cgroup_css(cgrp, ss);
552 cgrp = cgroup_parent(cgrp);
555 return init_css_set.subsys[ss->id];
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
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().
569 struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
570 struct cgroup_subsys *ss)
572 struct cgroup_subsys_state *css;
577 css = cgroup_css(cgrp, ss);
579 if (css && css_tryget_online(css))
581 cgrp = cgroup_parent(cgrp);
584 css = init_css_set.subsys[ss->id];
591 static void cgroup_get_live(struct cgroup *cgrp)
593 WARN_ON_ONCE(cgroup_is_dead(cgrp));
594 css_get(&cgrp->self);
598 * __cgroup_task_count - count the number of tasks in a cgroup. The caller
599 * is responsible for taking the css_set_lock.
600 * @cgrp: the cgroup in question
602 int __cgroup_task_count(const struct cgroup *cgrp)
605 struct cgrp_cset_link *link;
607 lockdep_assert_held(&css_set_lock);
609 list_for_each_entry(link, &cgrp->cset_links, cset_link)
610 count += link->cset->nr_tasks;
616 * cgroup_task_count - count the number of tasks in a cgroup.
617 * @cgrp: the cgroup in question
619 int cgroup_task_count(const struct cgroup *cgrp)
623 spin_lock_irq(&css_set_lock);
624 count = __cgroup_task_count(cgrp);
625 spin_unlock_irq(&css_set_lock);
630 struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
632 struct cgroup *cgrp = of->kn->parent->priv;
633 struct cftype *cft = of_cft(of);
636 * This is open and unprotected implementation of cgroup_css().
637 * seq_css() is only called from a kernfs file operation which has
638 * an active reference on the file. Because all the subsystem
639 * files are drained before a css is disassociated with a cgroup,
640 * the matching css from the cgroup's subsys table is guaranteed to
641 * be and stay valid until the enclosing operation is complete.
644 return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
648 EXPORT_SYMBOL_GPL(of_css);
651 * for_each_css - iterate all css's of a cgroup
652 * @css: the iteration cursor
653 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
654 * @cgrp: the target cgroup to iterate css's of
656 * Should be called under cgroup_[tree_]mutex.
658 #define for_each_css(css, ssid, cgrp) \
659 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
660 if (!((css) = rcu_dereference_check( \
661 (cgrp)->subsys[(ssid)], \
662 lockdep_is_held(&cgroup_mutex)))) { } \
666 * for_each_e_css - iterate all effective css's of a cgroup
667 * @css: the iteration cursor
668 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
669 * @cgrp: the target cgroup to iterate css's of
671 * Should be called under cgroup_[tree_]mutex.
673 #define for_each_e_css(css, ssid, cgrp) \
674 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
675 if (!((css) = cgroup_e_css_by_mask(cgrp, \
676 cgroup_subsys[(ssid)]))) \
681 * do_each_subsys_mask - filter for_each_subsys with a bitmask
682 * @ss: the iteration cursor
683 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
684 * @ss_mask: the bitmask
686 * The block will only run for cases where the ssid-th bit (1 << ssid) of
689 #define do_each_subsys_mask(ss, ssid, ss_mask) do { \
690 unsigned long __ss_mask = (ss_mask); \
691 if (!CGROUP_SUBSYS_COUNT) { /* to avoid spurious gcc warning */ \
695 for_each_set_bit(ssid, &__ss_mask, CGROUP_SUBSYS_COUNT) { \
696 (ss) = cgroup_subsys[ssid]; \
699 #define while_each_subsys_mask() \
704 /* iterate over child cgrps, lock should be held throughout iteration */
705 #define cgroup_for_each_live_child(child, cgrp) \
706 list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
707 if (({ lockdep_assert_held(&cgroup_mutex); \
708 cgroup_is_dead(child); })) \
712 /* walk live descendants in preorder */
713 #define cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) \
714 css_for_each_descendant_pre((d_css), cgroup_css((cgrp), NULL)) \
715 if (({ lockdep_assert_held(&cgroup_mutex); \
716 (dsct) = (d_css)->cgroup; \
717 cgroup_is_dead(dsct); })) \
721 /* walk live descendants in postorder */
722 #define cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) \
723 css_for_each_descendant_post((d_css), cgroup_css((cgrp), NULL)) \
724 if (({ lockdep_assert_held(&cgroup_mutex); \
725 (dsct) = (d_css)->cgroup; \
726 cgroup_is_dead(dsct); })) \
731 * The default css_set - used by init and its children prior to any
732 * hierarchies being mounted. It contains a pointer to the root state
733 * for each subsystem. Also used to anchor the list of css_sets. Not
734 * reference-counted, to improve performance when child cgroups
735 * haven't been created.
737 struct css_set init_css_set = {
738 .refcount = REFCOUNT_INIT(1),
739 .dom_cset = &init_css_set,
740 .tasks = LIST_HEAD_INIT(init_css_set.tasks),
741 .mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
742 .dying_tasks = LIST_HEAD_INIT(init_css_set.dying_tasks),
743 .task_iters = LIST_HEAD_INIT(init_css_set.task_iters),
744 .threaded_csets = LIST_HEAD_INIT(init_css_set.threaded_csets),
745 .cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
746 .mg_preload_node = LIST_HEAD_INIT(init_css_set.mg_preload_node),
747 .mg_node = LIST_HEAD_INIT(init_css_set.mg_node),
750 * The following field is re-initialized when this cset gets linked
751 * in cgroup_init(). However, let's initialize the field
752 * statically too so that the default cgroup can be accessed safely
755 .dfl_cgrp = &cgrp_dfl_root.cgrp,
758 static int css_set_count = 1; /* 1 for init_css_set */
760 static bool css_set_threaded(struct css_set *cset)
762 return cset->dom_cset != cset;
766 * css_set_populated - does a css_set contain any tasks?
767 * @cset: target css_set
769 * css_set_populated() should be the same as !!cset->nr_tasks at steady
770 * state. However, css_set_populated() can be called while a task is being
771 * added to or removed from the linked list before the nr_tasks is
772 * properly updated. Hence, we can't just look at ->nr_tasks here.
774 static bool css_set_populated(struct css_set *cset)
776 lockdep_assert_held(&css_set_lock);
778 return !list_empty(&cset->tasks) || !list_empty(&cset->mg_tasks);
782 * cgroup_update_populated - update the populated count of a cgroup
783 * @cgrp: the target cgroup
784 * @populated: inc or dec populated count
786 * One of the css_sets associated with @cgrp is either getting its first
787 * task or losing the last. Update @cgrp->nr_populated_* accordingly. The
788 * count is propagated towards root so that a given cgroup's
789 * nr_populated_children is zero iff none of its descendants contain any
792 * @cgrp's interface file "cgroup.populated" is zero if both
793 * @cgrp->nr_populated_csets and @cgrp->nr_populated_children are zero and
794 * 1 otherwise. When the sum changes from or to zero, userland is notified
795 * that the content of the interface file has changed. This can be used to
796 * detect when @cgrp and its descendants become populated or empty.
798 static void cgroup_update_populated(struct cgroup *cgrp, bool populated)
800 struct cgroup *child = NULL;
801 int adj = populated ? 1 : -1;
803 lockdep_assert_held(&css_set_lock);
806 bool was_populated = cgroup_is_populated(cgrp);
809 cgrp->nr_populated_csets += adj;
811 if (cgroup_is_threaded(child))
812 cgrp->nr_populated_threaded_children += adj;
814 cgrp->nr_populated_domain_children += adj;
817 if (was_populated == cgroup_is_populated(cgrp))
820 cgroup1_check_for_release(cgrp);
821 TRACE_CGROUP_PATH(notify_populated, cgrp,
822 cgroup_is_populated(cgrp));
823 cgroup_file_notify(&cgrp->events_file);
826 cgrp = cgroup_parent(cgrp);
831 * css_set_update_populated - update populated state of a css_set
832 * @cset: target css_set
833 * @populated: whether @cset is populated or depopulated
835 * @cset is either getting the first task or losing the last. Update the
836 * populated counters of all associated cgroups accordingly.
838 static void css_set_update_populated(struct css_set *cset, bool populated)
840 struct cgrp_cset_link *link;
842 lockdep_assert_held(&css_set_lock);
844 list_for_each_entry(link, &cset->cgrp_links, cgrp_link)
845 cgroup_update_populated(link->cgrp, populated);
849 * @task is leaving, advance task iterators which are pointing to it so
850 * that they can resume at the next position. Advancing an iterator might
851 * remove it from the list, use safe walk. See css_task_iter_skip() for
854 static void css_set_skip_task_iters(struct css_set *cset,
855 struct task_struct *task)
857 struct css_task_iter *it, *pos;
859 list_for_each_entry_safe(it, pos, &cset->task_iters, iters_node)
860 css_task_iter_skip(it, task);
864 * css_set_move_task - move a task from one css_set to another
865 * @task: task being moved
866 * @from_cset: css_set @task currently belongs to (may be NULL)
867 * @to_cset: new css_set @task is being moved to (may be NULL)
868 * @use_mg_tasks: move to @to_cset->mg_tasks instead of ->tasks
870 * Move @task from @from_cset to @to_cset. If @task didn't belong to any
871 * css_set, @from_cset can be NULL. If @task is being disassociated
872 * instead of moved, @to_cset can be NULL.
874 * This function automatically handles populated counter updates and
875 * css_task_iter adjustments but the caller is responsible for managing
876 * @from_cset and @to_cset's reference counts.
878 static void css_set_move_task(struct task_struct *task,
879 struct css_set *from_cset, struct css_set *to_cset,
882 lockdep_assert_held(&css_set_lock);
884 if (to_cset && !css_set_populated(to_cset))
885 css_set_update_populated(to_cset, true);
888 WARN_ON_ONCE(list_empty(&task->cg_list));
890 css_set_skip_task_iters(from_cset, task);
891 list_del_init(&task->cg_list);
892 if (!css_set_populated(from_cset))
893 css_set_update_populated(from_cset, false);
895 WARN_ON_ONCE(!list_empty(&task->cg_list));
900 * We are synchronized through cgroup_threadgroup_rwsem
901 * against PF_EXITING setting such that we can't race
902 * against cgroup_exit() changing the css_set to
903 * init_css_set and dropping the old one.
905 WARN_ON_ONCE(task->flags & PF_EXITING);
907 cgroup_move_task(task, to_cset);
908 list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks :
914 * hash table for cgroup groups. This improves the performance to find
915 * an existing css_set. This hash doesn't (currently) take into
916 * account cgroups in empty hierarchies.
918 #define CSS_SET_HASH_BITS 7
919 static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
921 static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
923 unsigned long key = 0UL;
924 struct cgroup_subsys *ss;
927 for_each_subsys(ss, i)
928 key += (unsigned long)css[i];
929 key = (key >> 16) ^ key;
934 void put_css_set_locked(struct css_set *cset)
936 struct cgrp_cset_link *link, *tmp_link;
937 struct cgroup_subsys *ss;
940 lockdep_assert_held(&css_set_lock);
942 if (!refcount_dec_and_test(&cset->refcount))
945 WARN_ON_ONCE(!list_empty(&cset->threaded_csets));
947 /* This css_set is dead. unlink it and release cgroup and css refs */
948 for_each_subsys(ss, ssid) {
949 list_del(&cset->e_cset_node[ssid]);
950 css_put(cset->subsys[ssid]);
952 hash_del(&cset->hlist);
955 list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
956 list_del(&link->cset_link);
957 list_del(&link->cgrp_link);
958 if (cgroup_parent(link->cgrp))
959 cgroup_put(link->cgrp);
963 if (css_set_threaded(cset)) {
964 list_del(&cset->threaded_csets_node);
965 put_css_set_locked(cset->dom_cset);
968 kfree_rcu(cset, rcu_head);
972 * compare_css_sets - helper function for find_existing_css_set().
973 * @cset: candidate css_set being tested
974 * @old_cset: existing css_set for a task
975 * @new_cgrp: cgroup that's being entered by the task
976 * @template: desired set of css pointers in css_set (pre-calculated)
978 * Returns true if "cset" matches "old_cset" except for the hierarchy
979 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
981 static bool compare_css_sets(struct css_set *cset,
982 struct css_set *old_cset,
983 struct cgroup *new_cgrp,
984 struct cgroup_subsys_state *template[])
986 struct cgroup *new_dfl_cgrp;
987 struct list_head *l1, *l2;
990 * On the default hierarchy, there can be csets which are
991 * associated with the same set of cgroups but different csses.
992 * Let's first ensure that csses match.
994 if (memcmp(template, cset->subsys, sizeof(cset->subsys)))
998 /* @cset's domain should match the default cgroup's */
999 if (cgroup_on_dfl(new_cgrp))
1000 new_dfl_cgrp = new_cgrp;
1002 new_dfl_cgrp = old_cset->dfl_cgrp;
1004 if (new_dfl_cgrp->dom_cgrp != cset->dom_cset->dfl_cgrp)
1008 * Compare cgroup pointers in order to distinguish between
1009 * different cgroups in hierarchies. As different cgroups may
1010 * share the same effective css, this comparison is always
1013 l1 = &cset->cgrp_links;
1014 l2 = &old_cset->cgrp_links;
1016 struct cgrp_cset_link *link1, *link2;
1017 struct cgroup *cgrp1, *cgrp2;
1021 /* See if we reached the end - both lists are equal length. */
1022 if (l1 == &cset->cgrp_links) {
1023 BUG_ON(l2 != &old_cset->cgrp_links);
1026 BUG_ON(l2 == &old_cset->cgrp_links);
1028 /* Locate the cgroups associated with these links. */
1029 link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
1030 link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
1031 cgrp1 = link1->cgrp;
1032 cgrp2 = link2->cgrp;
1033 /* Hierarchies should be linked in the same order. */
1034 BUG_ON(cgrp1->root != cgrp2->root);
1037 * If this hierarchy is the hierarchy of the cgroup
1038 * that's changing, then we need to check that this
1039 * css_set points to the new cgroup; if it's any other
1040 * hierarchy, then this css_set should point to the
1041 * same cgroup as the old css_set.
1043 if (cgrp1->root == new_cgrp->root) {
1044 if (cgrp1 != new_cgrp)
1055 * find_existing_css_set - init css array and find the matching css_set
1056 * @old_cset: the css_set that we're using before the cgroup transition
1057 * @cgrp: the cgroup that we're moving into
1058 * @template: out param for the new set of csses, should be clear on entry
1060 static struct css_set *find_existing_css_set(struct css_set *old_cset,
1061 struct cgroup *cgrp,
1062 struct cgroup_subsys_state *template[])
1064 struct cgroup_root *root = cgrp->root;
1065 struct cgroup_subsys *ss;
1066 struct css_set *cset;
1071 * Build the set of subsystem state objects that we want to see in the
1072 * new css_set. while subsystems can change globally, the entries here
1073 * won't change, so no need for locking.
1075 for_each_subsys(ss, i) {
1076 if (root->subsys_mask & (1UL << i)) {
1078 * @ss is in this hierarchy, so we want the
1079 * effective css from @cgrp.
1081 template[i] = cgroup_e_css_by_mask(cgrp, ss);
1084 * @ss is not in this hierarchy, so we don't want
1085 * to change the css.
1087 template[i] = old_cset->subsys[i];
1091 key = css_set_hash(template);
1092 hash_for_each_possible(css_set_table, cset, hlist, key) {
1093 if (!compare_css_sets(cset, old_cset, cgrp, template))
1096 /* This css_set matches what we need */
1100 /* No existing cgroup group matched */
1104 static void free_cgrp_cset_links(struct list_head *links_to_free)
1106 struct cgrp_cset_link *link, *tmp_link;
1108 list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
1109 list_del(&link->cset_link);
1115 * allocate_cgrp_cset_links - allocate cgrp_cset_links
1116 * @count: the number of links to allocate
1117 * @tmp_links: list_head the allocated links are put on
1119 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
1120 * through ->cset_link. Returns 0 on success or -errno.
1122 static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
1124 struct cgrp_cset_link *link;
1127 INIT_LIST_HEAD(tmp_links);
1129 for (i = 0; i < count; i++) {
1130 link = kzalloc(sizeof(*link), GFP_KERNEL);
1132 free_cgrp_cset_links(tmp_links);
1135 list_add(&link->cset_link, tmp_links);
1141 * link_css_set - a helper function to link a css_set to a cgroup
1142 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
1143 * @cset: the css_set to be linked
1144 * @cgrp: the destination cgroup
1146 static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
1147 struct cgroup *cgrp)
1149 struct cgrp_cset_link *link;
1151 BUG_ON(list_empty(tmp_links));
1153 if (cgroup_on_dfl(cgrp))
1154 cset->dfl_cgrp = cgrp;
1156 link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
1161 * Always add links to the tail of the lists so that the lists are
1162 * in choronological order.
1164 list_move_tail(&link->cset_link, &cgrp->cset_links);
1165 list_add_tail(&link->cgrp_link, &cset->cgrp_links);
1167 if (cgroup_parent(cgrp))
1168 cgroup_get_live(cgrp);
1172 * find_css_set - return a new css_set with one cgroup updated
1173 * @old_cset: the baseline css_set
1174 * @cgrp: the cgroup to be updated
1176 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
1177 * substituted into the appropriate hierarchy.
1179 static struct css_set *find_css_set(struct css_set *old_cset,
1180 struct cgroup *cgrp)
1182 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
1183 struct css_set *cset;
1184 struct list_head tmp_links;
1185 struct cgrp_cset_link *link;
1186 struct cgroup_subsys *ss;
1190 lockdep_assert_held(&cgroup_mutex);
1192 /* First see if we already have a cgroup group that matches
1193 * the desired set */
1194 spin_lock_irq(&css_set_lock);
1195 cset = find_existing_css_set(old_cset, cgrp, template);
1198 spin_unlock_irq(&css_set_lock);
1203 cset = kzalloc(sizeof(*cset), GFP_KERNEL);
1207 /* Allocate all the cgrp_cset_link objects that we'll need */
1208 if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
1213 refcount_set(&cset->refcount, 1);
1214 cset->dom_cset = cset;
1215 INIT_LIST_HEAD(&cset->tasks);
1216 INIT_LIST_HEAD(&cset->mg_tasks);
1217 INIT_LIST_HEAD(&cset->dying_tasks);
1218 INIT_LIST_HEAD(&cset->task_iters);
1219 INIT_LIST_HEAD(&cset->threaded_csets);
1220 INIT_HLIST_NODE(&cset->hlist);
1221 INIT_LIST_HEAD(&cset->cgrp_links);
1222 INIT_LIST_HEAD(&cset->mg_preload_node);
1223 INIT_LIST_HEAD(&cset->mg_node);
1225 /* Copy the set of subsystem state objects generated in
1226 * find_existing_css_set() */
1227 memcpy(cset->subsys, template, sizeof(cset->subsys));
1229 spin_lock_irq(&css_set_lock);
1230 /* Add reference counts and links from the new css_set. */
1231 list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
1232 struct cgroup *c = link->cgrp;
1234 if (c->root == cgrp->root)
1236 link_css_set(&tmp_links, cset, c);
1239 BUG_ON(!list_empty(&tmp_links));
1243 /* Add @cset to the hash table */
1244 key = css_set_hash(cset->subsys);
1245 hash_add(css_set_table, &cset->hlist, key);
1247 for_each_subsys(ss, ssid) {
1248 struct cgroup_subsys_state *css = cset->subsys[ssid];
1250 list_add_tail(&cset->e_cset_node[ssid],
1251 &css->cgroup->e_csets[ssid]);
1255 spin_unlock_irq(&css_set_lock);
1258 * If @cset should be threaded, look up the matching dom_cset and
1259 * link them up. We first fully initialize @cset then look for the
1260 * dom_cset. It's simpler this way and safe as @cset is guaranteed
1261 * to stay empty until we return.
1263 if (cgroup_is_threaded(cset->dfl_cgrp)) {
1264 struct css_set *dcset;
1266 dcset = find_css_set(cset, cset->dfl_cgrp->dom_cgrp);
1272 spin_lock_irq(&css_set_lock);
1273 cset->dom_cset = dcset;
1274 list_add_tail(&cset->threaded_csets_node,
1275 &dcset->threaded_csets);
1276 spin_unlock_irq(&css_set_lock);
1282 struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
1284 struct cgroup *root_cgrp = kf_root->kn->priv;
1286 return root_cgrp->root;
1289 static int cgroup_init_root_id(struct cgroup_root *root)
1293 lockdep_assert_held(&cgroup_mutex);
1295 id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
1299 root->hierarchy_id = id;
1303 static void cgroup_exit_root_id(struct cgroup_root *root)
1305 lockdep_assert_held(&cgroup_mutex);
1307 idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
1310 void cgroup_free_root(struct cgroup_root *root)
1313 idr_destroy(&root->cgroup_idr);
1318 static void cgroup_destroy_root(struct cgroup_root *root)
1320 struct cgroup *cgrp = &root->cgrp;
1321 struct cgrp_cset_link *link, *tmp_link;
1323 trace_cgroup_destroy_root(root);
1325 cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1327 BUG_ON(atomic_read(&root->nr_cgrps));
1328 BUG_ON(!list_empty(&cgrp->self.children));
1330 /* Rebind all subsystems back to the default hierarchy */
1331 WARN_ON(rebind_subsystems(&cgrp_dfl_root, root->subsys_mask));
1334 * Release all the links from cset_links to this hierarchy's
1337 spin_lock_irq(&css_set_lock);
1339 list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
1340 list_del(&link->cset_link);
1341 list_del(&link->cgrp_link);
1345 spin_unlock_irq(&css_set_lock);
1347 if (!list_empty(&root->root_list)) {
1348 list_del(&root->root_list);
1349 cgroup_root_count--;
1352 cgroup_exit_root_id(root);
1354 mutex_unlock(&cgroup_mutex);
1356 kernfs_destroy_root(root->kf_root);
1357 cgroup_free_root(root);
1361 * look up cgroup associated with current task's cgroup namespace on the
1362 * specified hierarchy
1364 static struct cgroup *
1365 current_cgns_cgroup_from_root(struct cgroup_root *root)
1367 struct cgroup *res = NULL;
1368 struct css_set *cset;
1370 lockdep_assert_held(&css_set_lock);
1374 cset = current->nsproxy->cgroup_ns->root_cset;
1375 if (cset == &init_css_set) {
1378 struct cgrp_cset_link *link;
1380 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
1381 struct cgroup *c = link->cgrp;
1383 if (c->root == root) {
1395 /* look up cgroup associated with given css_set on the specified hierarchy */
1396 static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
1397 struct cgroup_root *root)
1399 struct cgroup *res = NULL;
1401 lockdep_assert_held(&cgroup_mutex);
1402 lockdep_assert_held(&css_set_lock);
1404 if (cset == &init_css_set) {
1406 } else if (root == &cgrp_dfl_root) {
1407 res = cset->dfl_cgrp;
1409 struct cgrp_cset_link *link;
1411 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
1412 struct cgroup *c = link->cgrp;
1414 if (c->root == root) {
1426 * Return the cgroup for "task" from the given hierarchy. Must be
1427 * called with cgroup_mutex and css_set_lock held.
1429 struct cgroup *task_cgroup_from_root(struct task_struct *task,
1430 struct cgroup_root *root)
1433 * No need to lock the task - since we hold cgroup_mutex the
1434 * task can't change groups, so the only thing that can happen
1435 * is that it exits and its css is set back to init_css_set.
1437 return cset_cgroup_from_root(task_css_set(task), root);
1441 * A task must hold cgroup_mutex to modify cgroups.
1443 * Any task can increment and decrement the count field without lock.
1444 * So in general, code holding cgroup_mutex can't rely on the count
1445 * field not changing. However, if the count goes to zero, then only
1446 * cgroup_attach_task() can increment it again. Because a count of zero
1447 * means that no tasks are currently attached, therefore there is no
1448 * way a task attached to that cgroup can fork (the other way to
1449 * increment the count). So code holding cgroup_mutex can safely
1450 * assume that if the count is zero, it will stay zero. Similarly, if
1451 * a task holds cgroup_mutex on a cgroup with zero count, it
1452 * knows that the cgroup won't be removed, as cgroup_rmdir()
1455 * A cgroup can only be deleted if both its 'count' of using tasks
1456 * is zero, and its list of 'children' cgroups is empty. Since all
1457 * tasks in the system use _some_ cgroup, and since there is always at
1458 * least one task in the system (init, pid == 1), therefore, root cgroup
1459 * always has either children cgroups and/or using tasks. So we don't
1460 * need a special hack to ensure that root cgroup cannot be deleted.
1462 * P.S. One more locking exception. RCU is used to guard the
1463 * update of a tasks cgroup pointer by cgroup_attach_task()
1466 static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
1468 static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
1471 struct cgroup_subsys *ss = cft->ss;
1473 if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
1474 !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
1475 const char *dbg = (cft->flags & CFTYPE_DEBUG) ? ".__DEBUG__." : "";
1477 snprintf(buf, CGROUP_FILE_NAME_MAX, "%s%s.%s",
1478 dbg, cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name,
1481 strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
1487 * cgroup_file_mode - deduce file mode of a control file
1488 * @cft: the control file in question
1490 * S_IRUGO for read, S_IWUSR for write.
1492 static umode_t cgroup_file_mode(const struct cftype *cft)
1496 if (cft->read_u64 || cft->read_s64 || cft->seq_show)
1499 if (cft->write_u64 || cft->write_s64 || cft->write) {
1500 if (cft->flags & CFTYPE_WORLD_WRITABLE)
1510 * cgroup_calc_subtree_ss_mask - calculate subtree_ss_mask
1511 * @subtree_control: the new subtree_control mask to consider
1512 * @this_ss_mask: available subsystems
1514 * On the default hierarchy, a subsystem may request other subsystems to be
1515 * enabled together through its ->depends_on mask. In such cases, more
1516 * subsystems than specified in "cgroup.subtree_control" may be enabled.
1518 * This function calculates which subsystems need to be enabled if
1519 * @subtree_control is to be applied while restricted to @this_ss_mask.
1521 static u16 cgroup_calc_subtree_ss_mask(u16 subtree_control, u16 this_ss_mask)
1523 u16 cur_ss_mask = subtree_control;
1524 struct cgroup_subsys *ss;
1527 lockdep_assert_held(&cgroup_mutex);
1529 cur_ss_mask |= cgrp_dfl_implicit_ss_mask;
1532 u16 new_ss_mask = cur_ss_mask;
1534 do_each_subsys_mask(ss, ssid, cur_ss_mask) {
1535 new_ss_mask |= ss->depends_on;
1536 } while_each_subsys_mask();
1539 * Mask out subsystems which aren't available. This can
1540 * happen only if some depended-upon subsystems were bound
1541 * to non-default hierarchies.
1543 new_ss_mask &= this_ss_mask;
1545 if (new_ss_mask == cur_ss_mask)
1547 cur_ss_mask = new_ss_mask;
1554 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1555 * @kn: the kernfs_node being serviced
1557 * This helper undoes cgroup_kn_lock_live() and should be invoked before
1558 * the method finishes if locking succeeded. Note that once this function
1559 * returns the cgroup returned by cgroup_kn_lock_live() may become
1560 * inaccessible any time. If the caller intends to continue to access the
1561 * cgroup, it should pin it before invoking this function.
1563 void cgroup_kn_unlock(struct kernfs_node *kn)
1565 struct cgroup *cgrp;
1567 if (kernfs_type(kn) == KERNFS_DIR)
1570 cgrp = kn->parent->priv;
1572 mutex_unlock(&cgroup_mutex);
1574 kernfs_unbreak_active_protection(kn);
1579 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1580 * @kn: the kernfs_node being serviced
1581 * @drain_offline: perform offline draining on the cgroup
1583 * This helper is to be used by a cgroup kernfs method currently servicing
1584 * @kn. It breaks the active protection, performs cgroup locking and
1585 * verifies that the associated cgroup is alive. Returns the cgroup if
1586 * alive; otherwise, %NULL. A successful return should be undone by a
1587 * matching cgroup_kn_unlock() invocation. If @drain_offline is %true, the
1588 * cgroup is drained of offlining csses before return.
1590 * Any cgroup kernfs method implementation which requires locking the
1591 * associated cgroup should use this helper. It avoids nesting cgroup
1592 * locking under kernfs active protection and allows all kernfs operations
1593 * including self-removal.
1595 struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn, bool drain_offline)
1597 struct cgroup *cgrp;
1599 if (kernfs_type(kn) == KERNFS_DIR)
1602 cgrp = kn->parent->priv;
1605 * We're gonna grab cgroup_mutex which nests outside kernfs
1606 * active_ref. cgroup liveliness check alone provides enough
1607 * protection against removal. Ensure @cgrp stays accessible and
1608 * break the active_ref protection.
1610 if (!cgroup_tryget(cgrp))
1612 kernfs_break_active_protection(kn);
1615 cgroup_lock_and_drain_offline(cgrp);
1617 mutex_lock(&cgroup_mutex);
1619 if (!cgroup_is_dead(cgrp))
1622 cgroup_kn_unlock(kn);
1626 static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
1628 char name[CGROUP_FILE_NAME_MAX];
1630 lockdep_assert_held(&cgroup_mutex);
1632 if (cft->file_offset) {
1633 struct cgroup_subsys_state *css = cgroup_css(cgrp, cft->ss);
1634 struct cgroup_file *cfile = (void *)css + cft->file_offset;
1636 spin_lock_irq(&cgroup_file_kn_lock);
1638 spin_unlock_irq(&cgroup_file_kn_lock);
1640 del_timer_sync(&cfile->notify_timer);
1643 kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
1647 * css_clear_dir - remove subsys files in a cgroup directory
1650 static void css_clear_dir(struct cgroup_subsys_state *css)
1652 struct cgroup *cgrp = css->cgroup;
1653 struct cftype *cfts;
1655 if (!(css->flags & CSS_VISIBLE))
1658 css->flags &= ~CSS_VISIBLE;
1661 if (cgroup_on_dfl(cgrp))
1662 cfts = cgroup_base_files;
1664 cfts = cgroup1_base_files;
1666 cgroup_addrm_files(css, cgrp, cfts, false);
1668 list_for_each_entry(cfts, &css->ss->cfts, node)
1669 cgroup_addrm_files(css, cgrp, cfts, false);
1674 * css_populate_dir - create subsys files in a cgroup directory
1677 * On failure, no file is added.
1679 static int css_populate_dir(struct cgroup_subsys_state *css)
1681 struct cgroup *cgrp = css->cgroup;
1682 struct cftype *cfts, *failed_cfts;
1685 if ((css->flags & CSS_VISIBLE) || !cgrp->kn)
1689 if (cgroup_on_dfl(cgrp))
1690 cfts = cgroup_base_files;
1692 cfts = cgroup1_base_files;
1694 ret = cgroup_addrm_files(&cgrp->self, cgrp, cfts, true);
1698 list_for_each_entry(cfts, &css->ss->cfts, node) {
1699 ret = cgroup_addrm_files(css, cgrp, cfts, true);
1707 css->flags |= CSS_VISIBLE;
1711 list_for_each_entry(cfts, &css->ss->cfts, node) {
1712 if (cfts == failed_cfts)
1714 cgroup_addrm_files(css, cgrp, cfts, false);
1719 int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
1721 struct cgroup *dcgrp = &dst_root->cgrp;
1722 struct cgroup_subsys *ss;
1725 lockdep_assert_held(&cgroup_mutex);
1727 do_each_subsys_mask(ss, ssid, ss_mask) {
1729 * If @ss has non-root csses attached to it, can't move.
1730 * If @ss is an implicit controller, it is exempt from this
1731 * rule and can be stolen.
1733 if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)) &&
1734 !ss->implicit_on_dfl)
1737 /* can't move between two non-dummy roots either */
1738 if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
1740 } while_each_subsys_mask();
1742 do_each_subsys_mask(ss, ssid, ss_mask) {
1743 struct cgroup_root *src_root = ss->root;
1744 struct cgroup *scgrp = &src_root->cgrp;
1745 struct cgroup_subsys_state *css = cgroup_css(scgrp, ss);
1746 struct css_set *cset;
1748 WARN_ON(!css || cgroup_css(dcgrp, ss));
1750 /* disable from the source */
1751 src_root->subsys_mask &= ~(1 << ssid);
1752 WARN_ON(cgroup_apply_control(scgrp));
1753 cgroup_finalize_control(scgrp, 0);
1756 RCU_INIT_POINTER(scgrp->subsys[ssid], NULL);
1757 rcu_assign_pointer(dcgrp->subsys[ssid], css);
1758 ss->root = dst_root;
1759 css->cgroup = dcgrp;
1761 spin_lock_irq(&css_set_lock);
1762 hash_for_each(css_set_table, i, cset, hlist)
1763 list_move_tail(&cset->e_cset_node[ss->id],
1764 &dcgrp->e_csets[ss->id]);
1765 spin_unlock_irq(&css_set_lock);
1767 /* default hierarchy doesn't enable controllers by default */
1768 dst_root->subsys_mask |= 1 << ssid;
1769 if (dst_root == &cgrp_dfl_root) {
1770 static_branch_enable(cgroup_subsys_on_dfl_key[ssid]);
1772 dcgrp->subtree_control |= 1 << ssid;
1773 static_branch_disable(cgroup_subsys_on_dfl_key[ssid]);
1776 ret = cgroup_apply_control(dcgrp);
1778 pr_warn("partial failure to rebind %s controller (err=%d)\n",
1783 } while_each_subsys_mask();
1785 kernfs_activate(dcgrp->kn);
1789 int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
1790 struct kernfs_root *kf_root)
1794 struct cgroup_root *kf_cgroot = cgroup_root_from_kf(kf_root);
1795 struct cgroup *ns_cgroup;
1797 buf = kmalloc(PATH_MAX, GFP_KERNEL);
1801 spin_lock_irq(&css_set_lock);
1802 ns_cgroup = current_cgns_cgroup_from_root(kf_cgroot);
1803 len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX);
1804 spin_unlock_irq(&css_set_lock);
1806 if (len >= PATH_MAX)
1809 seq_escape(sf, buf, " \t\n\\");
1816 enum cgroup2_param {
1818 Opt_memory_localevents,
1822 static const struct fs_parameter_spec cgroup2_param_specs[] = {
1823 fsparam_flag("nsdelegate", Opt_nsdelegate),
1824 fsparam_flag("memory_localevents", Opt_memory_localevents),
1828 static const struct fs_parameter_description cgroup2_fs_parameters = {
1830 .specs = cgroup2_param_specs,
1833 static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param)
1835 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1836 struct fs_parse_result result;
1839 opt = fs_parse(fc, &cgroup2_fs_parameters, param, &result);
1844 case Opt_nsdelegate:
1845 ctx->flags |= CGRP_ROOT_NS_DELEGATE;
1847 case Opt_memory_localevents:
1848 ctx->flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1854 static void apply_cgroup_root_flags(unsigned int root_flags)
1856 if (current->nsproxy->cgroup_ns == &init_cgroup_ns) {
1857 if (root_flags & CGRP_ROOT_NS_DELEGATE)
1858 cgrp_dfl_root.flags |= CGRP_ROOT_NS_DELEGATE;
1860 cgrp_dfl_root.flags &= ~CGRP_ROOT_NS_DELEGATE;
1862 if (root_flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
1863 cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1865 cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1869 static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
1871 if (cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE)
1872 seq_puts(seq, ",nsdelegate");
1873 if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
1874 seq_puts(seq, ",memory_localevents");
1878 static int cgroup_reconfigure(struct fs_context *fc)
1880 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1882 apply_cgroup_root_flags(ctx->flags);
1887 * To reduce the fork() overhead for systems that are not actually using
1888 * their cgroups capability, we don't maintain the lists running through
1889 * each css_set to its tasks until we see the list actually used - in other
1890 * words after the first mount.
1892 static bool use_task_css_set_links __read_mostly;
1894 void cgroup_enable_task_cg_lists(void)
1896 struct task_struct *p, *g;
1899 * We need tasklist_lock because RCU is not safe against
1900 * while_each_thread(). Besides, a forking task that has passed
1901 * cgroup_post_fork() without seeing use_task_css_set_links = 1
1902 * is not guaranteed to have its child immediately visible in the
1903 * tasklist if we walk through it with RCU.
1905 read_lock(&tasklist_lock);
1906 spin_lock_irq(&css_set_lock);
1908 if (use_task_css_set_links)
1911 use_task_css_set_links = true;
1913 do_each_thread(g, p) {
1914 WARN_ON_ONCE(!list_empty(&p->cg_list) ||
1915 task_css_set(p) != &init_css_set);
1918 * We should check if the process is exiting, otherwise
1919 * it will race with cgroup_exit() in that the list
1920 * entry won't be deleted though the process has exited.
1921 * Do it while holding siglock so that we don't end up
1922 * racing against cgroup_exit().
1924 * Interrupts were already disabled while acquiring
1925 * the css_set_lock, so we do not need to disable it
1926 * again when acquiring the sighand->siglock here.
1928 spin_lock(&p->sighand->siglock);
1929 if (!(p->flags & PF_EXITING)) {
1930 struct css_set *cset = task_css_set(p);
1932 if (!css_set_populated(cset))
1933 css_set_update_populated(cset, true);
1934 list_add_tail(&p->cg_list, &cset->tasks);
1938 spin_unlock(&p->sighand->siglock);
1939 } while_each_thread(g, p);
1941 spin_unlock_irq(&css_set_lock);
1942 read_unlock(&tasklist_lock);
1945 static void init_cgroup_housekeeping(struct cgroup *cgrp)
1947 struct cgroup_subsys *ss;
1950 INIT_LIST_HEAD(&cgrp->self.sibling);
1951 INIT_LIST_HEAD(&cgrp->self.children);
1952 INIT_LIST_HEAD(&cgrp->cset_links);
1953 INIT_LIST_HEAD(&cgrp->pidlists);
1954 mutex_init(&cgrp->pidlist_mutex);
1955 cgrp->self.cgroup = cgrp;
1956 cgrp->self.flags |= CSS_ONLINE;
1957 cgrp->dom_cgrp = cgrp;
1958 cgrp->max_descendants = INT_MAX;
1959 cgrp->max_depth = INT_MAX;
1960 INIT_LIST_HEAD(&cgrp->rstat_css_list);
1961 prev_cputime_init(&cgrp->prev_cputime);
1963 for_each_subsys(ss, ssid)
1964 INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
1966 init_waitqueue_head(&cgrp->offline_waitq);
1967 INIT_WORK(&cgrp->release_agent_work, cgroup1_release_agent);
1970 void init_cgroup_root(struct cgroup_fs_context *ctx)
1972 struct cgroup_root *root = ctx->root;
1973 struct cgroup *cgrp = &root->cgrp;
1975 INIT_LIST_HEAD(&root->root_list);
1976 atomic_set(&root->nr_cgrps, 1);
1978 init_cgroup_housekeeping(cgrp);
1979 idr_init(&root->cgroup_idr);
1981 root->flags = ctx->flags;
1982 if (ctx->release_agent)
1983 strscpy(root->release_agent_path, ctx->release_agent, PATH_MAX);
1985 strscpy(root->name, ctx->name, MAX_CGROUP_ROOT_NAMELEN);
1986 if (ctx->cpuset_clone_children)
1987 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
1990 int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
1992 LIST_HEAD(tmp_links);
1993 struct cgroup *root_cgrp = &root->cgrp;
1994 struct kernfs_syscall_ops *kf_sops;
1995 struct css_set *cset;
1998 lockdep_assert_held(&cgroup_mutex);
2000 ret = cgroup_idr_alloc(&root->cgroup_idr, root_cgrp, 1, 2, GFP_KERNEL);
2003 root_cgrp->id = ret;
2004 root_cgrp->ancestor_ids[0] = ret;
2006 ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release,
2012 * We're accessing css_set_count without locking css_set_lock here,
2013 * but that's OK - it can only be increased by someone holding
2014 * cgroup_lock, and that's us. Later rebinding may disable
2015 * controllers on the default hierarchy and thus create new csets,
2016 * which can't be more than the existing ones. Allocate 2x.
2018 ret = allocate_cgrp_cset_links(2 * css_set_count, &tmp_links);
2022 ret = cgroup_init_root_id(root);
2026 kf_sops = root == &cgrp_dfl_root ?
2027 &cgroup_kf_syscall_ops : &cgroup1_kf_syscall_ops;
2029 root->kf_root = kernfs_create_root(kf_sops,
2030 KERNFS_ROOT_CREATE_DEACTIVATED |
2031 KERNFS_ROOT_SUPPORT_EXPORTOP,
2033 if (IS_ERR(root->kf_root)) {
2034 ret = PTR_ERR(root->kf_root);
2037 root_cgrp->kn = root->kf_root->kn;
2039 ret = css_populate_dir(&root_cgrp->self);
2043 ret = rebind_subsystems(root, ss_mask);
2047 ret = cgroup_bpf_inherit(root_cgrp);
2050 trace_cgroup_setup_root(root);
2053 * There must be no failure case after here, since rebinding takes
2054 * care of subsystems' refcounts, which are explicitly dropped in
2055 * the failure exit path.
2057 list_add(&root->root_list, &cgroup_roots);
2058 cgroup_root_count++;
2061 * Link the root cgroup in this hierarchy into all the css_set
2064 spin_lock_irq(&css_set_lock);
2065 hash_for_each(css_set_table, i, cset, hlist) {
2066 link_css_set(&tmp_links, cset, root_cgrp);
2067 if (css_set_populated(cset))
2068 cgroup_update_populated(root_cgrp, true);
2070 spin_unlock_irq(&css_set_lock);
2072 BUG_ON(!list_empty(&root_cgrp->self.children));
2073 BUG_ON(atomic_read(&root->nr_cgrps) != 1);
2075 kernfs_activate(root_cgrp->kn);
2080 kernfs_destroy_root(root->kf_root);
2081 root->kf_root = NULL;
2083 cgroup_exit_root_id(root);
2085 percpu_ref_exit(&root_cgrp->self.refcnt);
2087 free_cgrp_cset_links(&tmp_links);
2091 int cgroup_do_get_tree(struct fs_context *fc)
2093 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2096 ctx->kfc.root = ctx->root->kf_root;
2097 if (fc->fs_type == &cgroup2_fs_type)
2098 ctx->kfc.magic = CGROUP2_SUPER_MAGIC;
2100 ctx->kfc.magic = CGROUP_SUPER_MAGIC;
2101 ret = kernfs_get_tree(fc);
2104 * In non-init cgroup namespace, instead of root cgroup's dentry,
2105 * we return the dentry corresponding to the cgroupns->root_cgrp.
2107 if (!ret && ctx->ns != &init_cgroup_ns) {
2108 struct dentry *nsdentry;
2109 struct super_block *sb = fc->root->d_sb;
2110 struct cgroup *cgrp;
2112 mutex_lock(&cgroup_mutex);
2113 spin_lock_irq(&css_set_lock);
2115 cgrp = cset_cgroup_from_root(ctx->ns->root_cset, ctx->root);
2117 spin_unlock_irq(&css_set_lock);
2118 mutex_unlock(&cgroup_mutex);
2120 nsdentry = kernfs_node_dentry(cgrp->kn, sb);
2122 fc->root = nsdentry;
2123 if (IS_ERR(nsdentry)) {
2124 ret = PTR_ERR(nsdentry);
2125 deactivate_locked_super(sb);
2129 if (!ctx->kfc.new_sb_created)
2130 cgroup_put(&ctx->root->cgrp);
2136 * Destroy a cgroup filesystem context.
2138 static void cgroup_fs_context_free(struct fs_context *fc)
2140 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2143 kfree(ctx->release_agent);
2144 put_cgroup_ns(ctx->ns);
2145 kernfs_free_fs_context(fc);
2149 static int cgroup_get_tree(struct fs_context *fc)
2151 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2154 cgrp_dfl_visible = true;
2155 cgroup_get_live(&cgrp_dfl_root.cgrp);
2156 ctx->root = &cgrp_dfl_root;
2158 ret = cgroup_do_get_tree(fc);
2160 apply_cgroup_root_flags(ctx->flags);
2164 static const struct fs_context_operations cgroup_fs_context_ops = {
2165 .free = cgroup_fs_context_free,
2166 .parse_param = cgroup2_parse_param,
2167 .get_tree = cgroup_get_tree,
2168 .reconfigure = cgroup_reconfigure,
2171 static const struct fs_context_operations cgroup1_fs_context_ops = {
2172 .free = cgroup_fs_context_free,
2173 .parse_param = cgroup1_parse_param,
2174 .get_tree = cgroup1_get_tree,
2175 .reconfigure = cgroup1_reconfigure,
2179 * Initialise the cgroup filesystem creation/reconfiguration context. Notably,
2180 * we select the namespace we're going to use.
2182 static int cgroup_init_fs_context(struct fs_context *fc)
2184 struct cgroup_fs_context *ctx;
2186 ctx = kzalloc(sizeof(struct cgroup_fs_context), GFP_KERNEL);
2191 * The first time anyone tries to mount a cgroup, enable the list
2192 * linking each css_set to its tasks and fix up all existing tasks.
2194 if (!use_task_css_set_links)
2195 cgroup_enable_task_cg_lists();
2197 ctx->ns = current->nsproxy->cgroup_ns;
2198 get_cgroup_ns(ctx->ns);
2199 fc->fs_private = &ctx->kfc;
2200 if (fc->fs_type == &cgroup2_fs_type)
2201 fc->ops = &cgroup_fs_context_ops;
2203 fc->ops = &cgroup1_fs_context_ops;
2204 put_user_ns(fc->user_ns);
2205 fc->user_ns = get_user_ns(ctx->ns->user_ns);
2210 static void cgroup_kill_sb(struct super_block *sb)
2212 struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
2213 struct cgroup_root *root = cgroup_root_from_kf(kf_root);
2216 * If @root doesn't have any children, start killing it.
2217 * This prevents new mounts by disabling percpu_ref_tryget_live().
2218 * cgroup_mount() may wait for @root's release.
2220 * And don't kill the default root.
2222 if (list_empty(&root->cgrp.self.children) && root != &cgrp_dfl_root &&
2223 !percpu_ref_is_dying(&root->cgrp.self.refcnt))
2224 percpu_ref_kill(&root->cgrp.self.refcnt);
2225 cgroup_put(&root->cgrp);
2229 struct file_system_type cgroup_fs_type = {
2231 .init_fs_context = cgroup_init_fs_context,
2232 .parameters = &cgroup1_fs_parameters,
2233 .kill_sb = cgroup_kill_sb,
2234 .fs_flags = FS_USERNS_MOUNT,
2237 static struct file_system_type cgroup2_fs_type = {
2239 .init_fs_context = cgroup_init_fs_context,
2240 .parameters = &cgroup2_fs_parameters,
2241 .kill_sb = cgroup_kill_sb,
2242 .fs_flags = FS_USERNS_MOUNT,
2245 #ifdef CONFIG_CPUSETS
2246 static const struct fs_context_operations cpuset_fs_context_ops = {
2247 .get_tree = cgroup1_get_tree,
2248 .free = cgroup_fs_context_free,
2252 * This is ugly, but preserves the userspace API for existing cpuset
2253 * users. If someone tries to mount the "cpuset" filesystem, we
2254 * silently switch it to mount "cgroup" instead
2256 static int cpuset_init_fs_context(struct fs_context *fc)
2258 char *agent = kstrdup("/sbin/cpuset_release_agent", GFP_USER);
2259 struct cgroup_fs_context *ctx;
2262 err = cgroup_init_fs_context(fc);
2268 fc->ops = &cpuset_fs_context_ops;
2270 ctx = cgroup_fc2context(fc);
2271 ctx->subsys_mask = 1 << cpuset_cgrp_id;
2272 ctx->flags |= CGRP_ROOT_NOPREFIX;
2273 ctx->release_agent = agent;
2275 get_filesystem(&cgroup_fs_type);
2276 put_filesystem(fc->fs_type);
2277 fc->fs_type = &cgroup_fs_type;
2282 static struct file_system_type cpuset_fs_type = {
2284 .init_fs_context = cpuset_init_fs_context,
2285 .fs_flags = FS_USERNS_MOUNT,
2289 int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
2290 struct cgroup_namespace *ns)
2292 struct cgroup *root = cset_cgroup_from_root(ns->root_cset, cgrp->root);
2294 return kernfs_path_from_node(cgrp->kn, root->kn, buf, buflen);
2297 int cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
2298 struct cgroup_namespace *ns)
2302 mutex_lock(&cgroup_mutex);
2303 spin_lock_irq(&css_set_lock);
2305 ret = cgroup_path_ns_locked(cgrp, buf, buflen, ns);
2307 spin_unlock_irq(&css_set_lock);
2308 mutex_unlock(&cgroup_mutex);
2312 EXPORT_SYMBOL_GPL(cgroup_path_ns);
2315 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
2316 * @task: target task
2317 * @buf: the buffer to write the path into
2318 * @buflen: the length of the buffer
2320 * Determine @task's cgroup on the first (the one with the lowest non-zero
2321 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
2322 * function grabs cgroup_mutex and shouldn't be used inside locks used by
2323 * cgroup controller callbacks.
2325 * Return value is the same as kernfs_path().
2327 int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
2329 struct cgroup_root *root;
2330 struct cgroup *cgrp;
2331 int hierarchy_id = 1;
2334 mutex_lock(&cgroup_mutex);
2335 spin_lock_irq(&css_set_lock);
2337 root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
2340 cgrp = task_cgroup_from_root(task, root);
2341 ret = cgroup_path_ns_locked(cgrp, buf, buflen, &init_cgroup_ns);
2343 /* if no hierarchy exists, everyone is in "/" */
2344 ret = strlcpy(buf, "/", buflen);
2347 spin_unlock_irq(&css_set_lock);
2348 mutex_unlock(&cgroup_mutex);
2351 EXPORT_SYMBOL_GPL(task_cgroup_path);
2354 * cgroup_migrate_add_task - add a migration target task to a migration context
2355 * @task: target task
2356 * @mgctx: target migration context
2358 * Add @task, which is a migration target, to @mgctx->tset. This function
2359 * becomes noop if @task doesn't need to be migrated. @task's css_set
2360 * should have been added as a migration source and @task->cg_list will be
2361 * moved from the css_set's tasks list to mg_tasks one.
2363 static void cgroup_migrate_add_task(struct task_struct *task,
2364 struct cgroup_mgctx *mgctx)
2366 struct css_set *cset;
2368 lockdep_assert_held(&css_set_lock);
2370 /* @task either already exited or can't exit until the end */
2371 if (task->flags & PF_EXITING)
2374 /* leave @task alone if post_fork() hasn't linked it yet */
2375 if (list_empty(&task->cg_list))
2378 cset = task_css_set(task);
2379 if (!cset->mg_src_cgrp)
2382 mgctx->tset.nr_tasks++;
2384 list_move_tail(&task->cg_list, &cset->mg_tasks);
2385 if (list_empty(&cset->mg_node))
2386 list_add_tail(&cset->mg_node,
2387 &mgctx->tset.src_csets);
2388 if (list_empty(&cset->mg_dst_cset->mg_node))
2389 list_add_tail(&cset->mg_dst_cset->mg_node,
2390 &mgctx->tset.dst_csets);
2394 * cgroup_taskset_first - reset taskset and return the first task
2395 * @tset: taskset of interest
2396 * @dst_cssp: output variable for the destination css
2398 * @tset iteration is initialized and the first task is returned.
2400 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset,
2401 struct cgroup_subsys_state **dst_cssp)
2403 tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
2404 tset->cur_task = NULL;
2406 return cgroup_taskset_next(tset, dst_cssp);
2410 * cgroup_taskset_next - iterate to the next task in taskset
2411 * @tset: taskset of interest
2412 * @dst_cssp: output variable for the destination css
2414 * Return the next task in @tset. Iteration must have been initialized
2415 * with cgroup_taskset_first().
2417 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
2418 struct cgroup_subsys_state **dst_cssp)
2420 struct css_set *cset = tset->cur_cset;
2421 struct task_struct *task = tset->cur_task;
2423 while (&cset->mg_node != tset->csets) {
2425 task = list_first_entry(&cset->mg_tasks,
2426 struct task_struct, cg_list);
2428 task = list_next_entry(task, cg_list);
2430 if (&task->cg_list != &cset->mg_tasks) {
2431 tset->cur_cset = cset;
2432 tset->cur_task = task;
2435 * This function may be called both before and
2436 * after cgroup_taskset_migrate(). The two cases
2437 * can be distinguished by looking at whether @cset
2438 * has its ->mg_dst_cset set.
2440 if (cset->mg_dst_cset)
2441 *dst_cssp = cset->mg_dst_cset->subsys[tset->ssid];
2443 *dst_cssp = cset->subsys[tset->ssid];
2448 cset = list_next_entry(cset, mg_node);
2456 * cgroup_taskset_migrate - migrate a taskset
2457 * @mgctx: migration context
2459 * Migrate tasks in @mgctx as setup by migration preparation functions.
2460 * This function fails iff one of the ->can_attach callbacks fails and
2461 * guarantees that either all or none of the tasks in @mgctx are migrated.
2462 * @mgctx is consumed regardless of success.
2464 static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx)
2466 struct cgroup_taskset *tset = &mgctx->tset;
2467 struct cgroup_subsys *ss;
2468 struct task_struct *task, *tmp_task;
2469 struct css_set *cset, *tmp_cset;
2470 int ssid, failed_ssid, ret;
2472 /* check that we can legitimately attach to the cgroup */
2473 if (tset->nr_tasks) {
2474 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2475 if (ss->can_attach) {
2477 ret = ss->can_attach(tset);
2480 goto out_cancel_attach;
2483 } while_each_subsys_mask();
2487 * Now that we're guaranteed success, proceed to move all tasks to
2488 * the new cgroup. There are no failure cases after here, so this
2489 * is the commit point.
2491 spin_lock_irq(&css_set_lock);
2492 list_for_each_entry(cset, &tset->src_csets, mg_node) {
2493 list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list) {
2494 struct css_set *from_cset = task_css_set(task);
2495 struct css_set *to_cset = cset->mg_dst_cset;
2497 get_css_set(to_cset);
2498 to_cset->nr_tasks++;
2499 css_set_move_task(task, from_cset, to_cset, true);
2500 from_cset->nr_tasks--;
2502 * If the source or destination cgroup is frozen,
2503 * the task might require to change its state.
2505 cgroup_freezer_migrate_task(task, from_cset->dfl_cgrp,
2507 put_css_set_locked(from_cset);
2511 spin_unlock_irq(&css_set_lock);
2514 * Migration is committed, all target tasks are now on dst_csets.
2515 * Nothing is sensitive to fork() after this point. Notify
2516 * controllers that migration is complete.
2518 tset->csets = &tset->dst_csets;
2520 if (tset->nr_tasks) {
2521 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2526 } while_each_subsys_mask();
2530 goto out_release_tset;
2533 if (tset->nr_tasks) {
2534 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2535 if (ssid == failed_ssid)
2537 if (ss->cancel_attach) {
2539 ss->cancel_attach(tset);
2541 } while_each_subsys_mask();
2544 spin_lock_irq(&css_set_lock);
2545 list_splice_init(&tset->dst_csets, &tset->src_csets);
2546 list_for_each_entry_safe(cset, tmp_cset, &tset->src_csets, mg_node) {
2547 list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
2548 list_del_init(&cset->mg_node);
2550 spin_unlock_irq(&css_set_lock);
2553 * Re-initialize the cgroup_taskset structure in case it is reused
2554 * again in another cgroup_migrate_add_task()/cgroup_migrate_execute()
2558 tset->csets = &tset->src_csets;
2563 * cgroup_migrate_vet_dst - verify whether a cgroup can be migration destination
2564 * @dst_cgrp: destination cgroup to test
2566 * On the default hierarchy, except for the mixable, (possible) thread root
2567 * and threaded cgroups, subtree_control must be zero for migration
2568 * destination cgroups with tasks so that child cgroups don't compete
2571 int cgroup_migrate_vet_dst(struct cgroup *dst_cgrp)
2573 /* v1 doesn't have any restriction */
2574 if (!cgroup_on_dfl(dst_cgrp))
2577 /* verify @dst_cgrp can host resources */
2578 if (!cgroup_is_valid_domain(dst_cgrp->dom_cgrp))
2581 /* mixables don't care */
2582 if (cgroup_is_mixable(dst_cgrp))
2586 * If @dst_cgrp is already or can become a thread root or is
2587 * threaded, it doesn't matter.
2589 if (cgroup_can_be_thread_root(dst_cgrp) || cgroup_is_threaded(dst_cgrp))
2592 /* apply no-internal-process constraint */
2593 if (dst_cgrp->subtree_control)
2600 * cgroup_migrate_finish - cleanup after attach
2601 * @mgctx: migration context
2603 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
2604 * those functions for details.
2606 void cgroup_migrate_finish(struct cgroup_mgctx *mgctx)
2608 LIST_HEAD(preloaded);
2609 struct css_set *cset, *tmp_cset;
2611 lockdep_assert_held(&cgroup_mutex);
2613 spin_lock_irq(&css_set_lock);
2615 list_splice_tail_init(&mgctx->preloaded_src_csets, &preloaded);
2616 list_splice_tail_init(&mgctx->preloaded_dst_csets, &preloaded);
2618 list_for_each_entry_safe(cset, tmp_cset, &preloaded, mg_preload_node) {
2619 cset->mg_src_cgrp = NULL;
2620 cset->mg_dst_cgrp = NULL;
2621 cset->mg_dst_cset = NULL;
2622 list_del_init(&cset->mg_preload_node);
2623 put_css_set_locked(cset);
2626 spin_unlock_irq(&css_set_lock);
2630 * cgroup_migrate_add_src - add a migration source css_set
2631 * @src_cset: the source css_set to add
2632 * @dst_cgrp: the destination cgroup
2633 * @mgctx: migration context
2635 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
2636 * @src_cset and add it to @mgctx->src_csets, which should later be cleaned
2637 * up by cgroup_migrate_finish().
2639 * This function may be called without holding cgroup_threadgroup_rwsem
2640 * even if the target is a process. Threads may be created and destroyed
2641 * but as long as cgroup_mutex is not dropped, no new css_set can be put
2642 * into play and the preloaded css_sets are guaranteed to cover all
2645 void cgroup_migrate_add_src(struct css_set *src_cset,
2646 struct cgroup *dst_cgrp,
2647 struct cgroup_mgctx *mgctx)
2649 struct cgroup *src_cgrp;
2651 lockdep_assert_held(&cgroup_mutex);
2652 lockdep_assert_held(&css_set_lock);
2655 * If ->dead, @src_set is associated with one or more dead cgroups
2656 * and doesn't contain any migratable tasks. Ignore it early so
2657 * that the rest of migration path doesn't get confused by it.
2662 src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);
2664 if (!list_empty(&src_cset->mg_preload_node))
2667 WARN_ON(src_cset->mg_src_cgrp);
2668 WARN_ON(src_cset->mg_dst_cgrp);
2669 WARN_ON(!list_empty(&src_cset->mg_tasks));
2670 WARN_ON(!list_empty(&src_cset->mg_node));
2672 src_cset->mg_src_cgrp = src_cgrp;
2673 src_cset->mg_dst_cgrp = dst_cgrp;
2674 get_css_set(src_cset);
2675 list_add_tail(&src_cset->mg_preload_node, &mgctx->preloaded_src_csets);
2679 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2680 * @mgctx: migration context
2682 * Tasks are about to be moved and all the source css_sets have been
2683 * preloaded to @mgctx->preloaded_src_csets. This function looks up and
2684 * pins all destination css_sets, links each to its source, and append them
2685 * to @mgctx->preloaded_dst_csets.
2687 * This function must be called after cgroup_migrate_add_src() has been
2688 * called on each migration source css_set. After migration is performed
2689 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2692 int cgroup_migrate_prepare_dst(struct cgroup_mgctx *mgctx)
2694 struct css_set *src_cset, *tmp_cset;
2696 lockdep_assert_held(&cgroup_mutex);
2698 /* look up the dst cset for each src cset and link it to src */
2699 list_for_each_entry_safe(src_cset, tmp_cset, &mgctx->preloaded_src_csets,
2701 struct css_set *dst_cset;
2702 struct cgroup_subsys *ss;
2705 dst_cset = find_css_set(src_cset, src_cset->mg_dst_cgrp);
2709 WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
2712 * If src cset equals dst, it's noop. Drop the src.
2713 * cgroup_migrate() will skip the cset too. Note that we
2714 * can't handle src == dst as some nodes are used by both.
2716 if (src_cset == dst_cset) {
2717 src_cset->mg_src_cgrp = NULL;
2718 src_cset->mg_dst_cgrp = NULL;
2719 list_del_init(&src_cset->mg_preload_node);
2720 put_css_set(src_cset);
2721 put_css_set(dst_cset);
2725 src_cset->mg_dst_cset = dst_cset;
2727 if (list_empty(&dst_cset->mg_preload_node))
2728 list_add_tail(&dst_cset->mg_preload_node,
2729 &mgctx->preloaded_dst_csets);
2731 put_css_set(dst_cset);
2733 for_each_subsys(ss, ssid)
2734 if (src_cset->subsys[ssid] != dst_cset->subsys[ssid])
2735 mgctx->ss_mask |= 1 << ssid;
2742 * cgroup_migrate - migrate a process or task to a cgroup
2743 * @leader: the leader of the process or the task to migrate
2744 * @threadgroup: whether @leader points to the whole process or a single task
2745 * @mgctx: migration context
2747 * Migrate a process or task denoted by @leader. If migrating a process,
2748 * the caller must be holding cgroup_threadgroup_rwsem. The caller is also
2749 * responsible for invoking cgroup_migrate_add_src() and
2750 * cgroup_migrate_prepare_dst() on the targets before invoking this
2751 * function and following up with cgroup_migrate_finish().
2753 * As long as a controller's ->can_attach() doesn't fail, this function is
2754 * guaranteed to succeed. This means that, excluding ->can_attach()
2755 * failure, when migrating multiple targets, the success or failure can be
2756 * decided for all targets by invoking group_migrate_prepare_dst() before
2757 * actually starting migrating.
2759 int cgroup_migrate(struct task_struct *leader, bool threadgroup,
2760 struct cgroup_mgctx *mgctx)
2762 struct task_struct *task;
2765 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2766 * already PF_EXITING could be freed from underneath us unless we
2767 * take an rcu_read_lock.
2769 spin_lock_irq(&css_set_lock);
2773 cgroup_migrate_add_task(task, mgctx);
2776 } while_each_thread(leader, task);
2778 spin_unlock_irq(&css_set_lock);
2780 return cgroup_migrate_execute(mgctx);
2784 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2785 * @dst_cgrp: the cgroup to attach to
2786 * @leader: the task or the leader of the threadgroup to be attached
2787 * @threadgroup: attach the whole threadgroup?
2789 * Call holding cgroup_mutex and cgroup_threadgroup_rwsem.
2791 int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
2794 DEFINE_CGROUP_MGCTX(mgctx);
2795 struct task_struct *task;
2798 ret = cgroup_migrate_vet_dst(dst_cgrp);
2802 /* look up all src csets */
2803 spin_lock_irq(&css_set_lock);
2807 cgroup_migrate_add_src(task_css_set(task), dst_cgrp, &mgctx);
2810 } while_each_thread(leader, task);
2812 spin_unlock_irq(&css_set_lock);
2814 /* prepare dst csets and commit */
2815 ret = cgroup_migrate_prepare_dst(&mgctx);
2817 ret = cgroup_migrate(leader, threadgroup, &mgctx);
2819 cgroup_migrate_finish(&mgctx);
2822 TRACE_CGROUP_PATH(attach_task, dst_cgrp, leader, threadgroup);
2827 struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup)
2828 __acquires(&cgroup_threadgroup_rwsem)
2830 struct task_struct *tsk;
2833 if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
2834 return ERR_PTR(-EINVAL);
2836 percpu_down_write(&cgroup_threadgroup_rwsem);
2840 tsk = find_task_by_vpid(pid);
2842 tsk = ERR_PTR(-ESRCH);
2843 goto out_unlock_threadgroup;
2850 tsk = tsk->group_leader;
2853 * kthreads may acquire PF_NO_SETAFFINITY during initialization.
2854 * If userland migrates such a kthread to a non-root cgroup, it can
2855 * become trapped in a cpuset, or RT kthread may be born in a
2856 * cgroup with no rt_runtime allocated. Just say no.
2858 if (tsk->no_cgroup_migration || (tsk->flags & PF_NO_SETAFFINITY)) {
2859 tsk = ERR_PTR(-EINVAL);
2860 goto out_unlock_threadgroup;
2863 get_task_struct(tsk);
2864 goto out_unlock_rcu;
2866 out_unlock_threadgroup:
2867 percpu_up_write(&cgroup_threadgroup_rwsem);
2873 void cgroup_procs_write_finish(struct task_struct *task)
2874 __releases(&cgroup_threadgroup_rwsem)
2876 struct cgroup_subsys *ss;
2879 /* release reference from cgroup_procs_write_start() */
2880 put_task_struct(task);
2882 percpu_up_write(&cgroup_threadgroup_rwsem);
2883 for_each_subsys(ss, ssid)
2884 if (ss->post_attach)
2888 static void cgroup_print_ss_mask(struct seq_file *seq, u16 ss_mask)
2890 struct cgroup_subsys *ss;
2891 bool printed = false;
2894 do_each_subsys_mask(ss, ssid, ss_mask) {
2897 seq_puts(seq, ss->name);
2899 } while_each_subsys_mask();
2901 seq_putc(seq, '\n');
2904 /* show controllers which are enabled from the parent */
2905 static int cgroup_controllers_show(struct seq_file *seq, void *v)
2907 struct cgroup *cgrp = seq_css(seq)->cgroup;
2909 cgroup_print_ss_mask(seq, cgroup_control(cgrp));
2913 /* show controllers which are enabled for a given cgroup's children */
2914 static int cgroup_subtree_control_show(struct seq_file *seq, void *v)
2916 struct cgroup *cgrp = seq_css(seq)->cgroup;
2918 cgroup_print_ss_mask(seq, cgrp->subtree_control);
2923 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
2924 * @cgrp: root of the subtree to update csses for
2926 * @cgrp's control masks have changed and its subtree's css associations
2927 * need to be updated accordingly. This function looks up all css_sets
2928 * which are attached to the subtree, creates the matching updated css_sets
2929 * and migrates the tasks to the new ones.
2931 static int cgroup_update_dfl_csses(struct cgroup *cgrp)
2933 DEFINE_CGROUP_MGCTX(mgctx);
2934 struct cgroup_subsys_state *d_css;
2935 struct cgroup *dsct;
2936 struct css_set *src_cset;
2939 lockdep_assert_held(&cgroup_mutex);
2941 percpu_down_write(&cgroup_threadgroup_rwsem);
2943 /* look up all csses currently attached to @cgrp's subtree */
2944 spin_lock_irq(&css_set_lock);
2945 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
2946 struct cgrp_cset_link *link;
2948 list_for_each_entry(link, &dsct->cset_links, cset_link)
2949 cgroup_migrate_add_src(link->cset, dsct, &mgctx);
2951 spin_unlock_irq(&css_set_lock);
2953 /* NULL dst indicates self on default hierarchy */
2954 ret = cgroup_migrate_prepare_dst(&mgctx);
2958 spin_lock_irq(&css_set_lock);
2959 list_for_each_entry(src_cset, &mgctx.preloaded_src_csets, mg_preload_node) {
2960 struct task_struct *task, *ntask;
2962 /* all tasks in src_csets need to be migrated */
2963 list_for_each_entry_safe(task, ntask, &src_cset->tasks, cg_list)
2964 cgroup_migrate_add_task(task, &mgctx);
2966 spin_unlock_irq(&css_set_lock);
2968 ret = cgroup_migrate_execute(&mgctx);
2970 cgroup_migrate_finish(&mgctx);
2971 percpu_up_write(&cgroup_threadgroup_rwsem);
2976 * cgroup_lock_and_drain_offline - lock cgroup_mutex and drain offlined csses
2977 * @cgrp: root of the target subtree
2979 * Because css offlining is asynchronous, userland may try to re-enable a
2980 * controller while the previous css is still around. This function grabs
2981 * cgroup_mutex and drains the previous css instances of @cgrp's subtree.
2983 void cgroup_lock_and_drain_offline(struct cgroup *cgrp)
2984 __acquires(&cgroup_mutex)
2986 struct cgroup *dsct;
2987 struct cgroup_subsys_state *d_css;
2988 struct cgroup_subsys *ss;
2992 mutex_lock(&cgroup_mutex);
2994 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
2995 for_each_subsys(ss, ssid) {
2996 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
2999 if (!css || !percpu_ref_is_dying(&css->refcnt))
3002 cgroup_get_live(dsct);
3003 prepare_to_wait(&dsct->offline_waitq, &wait,
3004 TASK_UNINTERRUPTIBLE);
3006 mutex_unlock(&cgroup_mutex);
3008 finish_wait(&dsct->offline_waitq, &wait);
3017 * cgroup_save_control - save control masks and dom_cgrp of a subtree
3018 * @cgrp: root of the target subtree
3020 * Save ->subtree_control, ->subtree_ss_mask and ->dom_cgrp to the
3021 * respective old_ prefixed fields for @cgrp's subtree including @cgrp
3024 static void cgroup_save_control(struct cgroup *cgrp)
3026 struct cgroup *dsct;
3027 struct cgroup_subsys_state *d_css;
3029 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3030 dsct->old_subtree_control = dsct->subtree_control;
3031 dsct->old_subtree_ss_mask = dsct->subtree_ss_mask;
3032 dsct->old_dom_cgrp = dsct->dom_cgrp;
3037 * cgroup_propagate_control - refresh control masks of a subtree
3038 * @cgrp: root of the target subtree
3040 * For @cgrp and its subtree, ensure ->subtree_ss_mask matches
3041 * ->subtree_control and propagate controller availability through the
3042 * subtree so that descendants don't have unavailable controllers enabled.
3044 static void cgroup_propagate_control(struct cgroup *cgrp)
3046 struct cgroup *dsct;
3047 struct cgroup_subsys_state *d_css;
3049 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3050 dsct->subtree_control &= cgroup_control(dsct);
3051 dsct->subtree_ss_mask =
3052 cgroup_calc_subtree_ss_mask(dsct->subtree_control,
3053 cgroup_ss_mask(dsct));
3058 * cgroup_restore_control - restore control masks and dom_cgrp of a subtree
3059 * @cgrp: root of the target subtree
3061 * Restore ->subtree_control, ->subtree_ss_mask and ->dom_cgrp from the
3062 * respective old_ prefixed fields for @cgrp's subtree including @cgrp
3065 static void cgroup_restore_control(struct cgroup *cgrp)
3067 struct cgroup *dsct;
3068 struct cgroup_subsys_state *d_css;
3070 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3071 dsct->subtree_control = dsct->old_subtree_control;
3072 dsct->subtree_ss_mask = dsct->old_subtree_ss_mask;
3073 dsct->dom_cgrp = dsct->old_dom_cgrp;
3077 static bool css_visible(struct cgroup_subsys_state *css)
3079 struct cgroup_subsys *ss = css->ss;
3080 struct cgroup *cgrp = css->cgroup;
3082 if (cgroup_control(cgrp) & (1 << ss->id))
3084 if (!(cgroup_ss_mask(cgrp) & (1 << ss->id)))
3086 return cgroup_on_dfl(cgrp) && ss->implicit_on_dfl;
3090 * cgroup_apply_control_enable - enable or show csses according to control
3091 * @cgrp: root of the target subtree
3093 * Walk @cgrp's subtree and create new csses or make the existing ones
3094 * visible. A css is created invisible if it's being implicitly enabled
3095 * through dependency. An invisible css is made visible when the userland
3096 * explicitly enables it.
3098 * Returns 0 on success, -errno on failure. On failure, csses which have
3099 * been processed already aren't cleaned up. The caller is responsible for
3100 * cleaning up with cgroup_apply_control_disable().
3102 static int cgroup_apply_control_enable(struct cgroup *cgrp)
3104 struct cgroup *dsct;
3105 struct cgroup_subsys_state *d_css;
3106 struct cgroup_subsys *ss;
3109 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3110 for_each_subsys(ss, ssid) {
3111 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3113 WARN_ON_ONCE(css && percpu_ref_is_dying(&css->refcnt));
3115 if (!(cgroup_ss_mask(dsct) & (1 << ss->id)))
3119 css = css_create(dsct, ss);
3121 return PTR_ERR(css);
3124 if (css_visible(css)) {
3125 ret = css_populate_dir(css);
3136 * cgroup_apply_control_disable - kill or hide csses according to control
3137 * @cgrp: root of the target subtree
3139 * Walk @cgrp's subtree and kill and hide csses so that they match
3140 * cgroup_ss_mask() and cgroup_visible_mask().
3142 * A css is hidden when the userland requests it to be disabled while other
3143 * subsystems are still depending on it. The css must not actively control
3144 * resources and be in the vanilla state if it's made visible again later.
3145 * Controllers which may be depended upon should provide ->css_reset() for
3148 static void cgroup_apply_control_disable(struct cgroup *cgrp)
3150 struct cgroup *dsct;
3151 struct cgroup_subsys_state *d_css;
3152 struct cgroup_subsys *ss;
3155 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3156 for_each_subsys(ss, ssid) {
3157 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3159 WARN_ON_ONCE(css && percpu_ref_is_dying(&css->refcnt));
3165 !(cgroup_ss_mask(dsct) & (1 << ss->id))) {
3167 } else if (!css_visible(css)) {
3177 * cgroup_apply_control - apply control mask updates to the subtree
3178 * @cgrp: root of the target subtree
3180 * subsystems can be enabled and disabled in a subtree using the following
3183 * 1. Call cgroup_save_control() to stash the current state.
3184 * 2. Update ->subtree_control masks in the subtree as desired.
3185 * 3. Call cgroup_apply_control() to apply the changes.
3186 * 4. Optionally perform other related operations.
3187 * 5. Call cgroup_finalize_control() to finish up.
3189 * This function implements step 3 and propagates the mask changes
3190 * throughout @cgrp's subtree, updates csses accordingly and perform
3191 * process migrations.
3193 static int cgroup_apply_control(struct cgroup *cgrp)
3197 cgroup_propagate_control(cgrp);
3199 ret = cgroup_apply_control_enable(cgrp);
3204 * At this point, cgroup_e_css_by_mask() results reflect the new csses
3205 * making the following cgroup_update_dfl_csses() properly update
3206 * css associations of all tasks in the subtree.
3208 ret = cgroup_update_dfl_csses(cgrp);
3216 * cgroup_finalize_control - finalize control mask update
3217 * @cgrp: root of the target subtree
3218 * @ret: the result of the update
3220 * Finalize control mask update. See cgroup_apply_control() for more info.
3222 static void cgroup_finalize_control(struct cgroup *cgrp, int ret)
3225 cgroup_restore_control(cgrp);
3226 cgroup_propagate_control(cgrp);
3229 cgroup_apply_control_disable(cgrp);
3232 static int cgroup_vet_subtree_control_enable(struct cgroup *cgrp, u16 enable)
3234 u16 domain_enable = enable & ~cgrp_dfl_threaded_ss_mask;
3236 /* if nothing is getting enabled, nothing to worry about */
3240 /* can @cgrp host any resources? */
3241 if (!cgroup_is_valid_domain(cgrp->dom_cgrp))
3244 /* mixables don't care */
3245 if (cgroup_is_mixable(cgrp))
3248 if (domain_enable) {
3249 /* can't enable domain controllers inside a thread subtree */
3250 if (cgroup_is_thread_root(cgrp) || cgroup_is_threaded(cgrp))
3254 * Threaded controllers can handle internal competitions
3255 * and are always allowed inside a (prospective) thread
3258 if (cgroup_can_be_thread_root(cgrp) || cgroup_is_threaded(cgrp))
3263 * Controllers can't be enabled for a cgroup with tasks to avoid
3264 * child cgroups competing against tasks.
3266 if (cgroup_has_tasks(cgrp))
3272 /* change the enabled child controllers for a cgroup in the default hierarchy */
3273 static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
3274 char *buf, size_t nbytes,
3277 u16 enable = 0, disable = 0;
3278 struct cgroup *cgrp, *child;
3279 struct cgroup_subsys *ss;
3284 * Parse input - space separated list of subsystem names prefixed
3285 * with either + or -.
3287 buf = strstrip(buf);
3288 while ((tok = strsep(&buf, " "))) {
3291 do_each_subsys_mask(ss, ssid, ~cgrp_dfl_inhibit_ss_mask) {
3292 if (!cgroup_ssid_enabled(ssid) ||
3293 strcmp(tok + 1, ss->name))
3297 enable |= 1 << ssid;
3298 disable &= ~(1 << ssid);
3299 } else if (*tok == '-') {
3300 disable |= 1 << ssid;
3301 enable &= ~(1 << ssid);
3306 } while_each_subsys_mask();
3307 if (ssid == CGROUP_SUBSYS_COUNT)
3311 cgrp = cgroup_kn_lock_live(of->kn, true);
3315 for_each_subsys(ss, ssid) {
3316 if (enable & (1 << ssid)) {
3317 if (cgrp->subtree_control & (1 << ssid)) {
3318 enable &= ~(1 << ssid);
3322 if (!(cgroup_control(cgrp) & (1 << ssid))) {
3326 } else if (disable & (1 << ssid)) {
3327 if (!(cgrp->subtree_control & (1 << ssid))) {
3328 disable &= ~(1 << ssid);
3332 /* a child has it enabled? */
3333 cgroup_for_each_live_child(child, cgrp) {
3334 if (child->subtree_control & (1 << ssid)) {
3342 if (!enable && !disable) {
3347 ret = cgroup_vet_subtree_control_enable(cgrp, enable);
3351 /* save and update control masks and prepare csses */
3352 cgroup_save_control(cgrp);
3354 cgrp->subtree_control |= enable;
3355 cgrp->subtree_control &= ~disable;
3357 ret = cgroup_apply_control(cgrp);
3358 cgroup_finalize_control(cgrp, ret);
3362 kernfs_activate(cgrp->kn);
3364 cgroup_kn_unlock(of->kn);
3365 return ret ?: nbytes;
3369 * cgroup_enable_threaded - make @cgrp threaded
3370 * @cgrp: the target cgroup
3372 * Called when "threaded" is written to the cgroup.type interface file and
3373 * tries to make @cgrp threaded and join the parent's resource domain.
3374 * This function is never called on the root cgroup as cgroup.type doesn't
3377 static int cgroup_enable_threaded(struct cgroup *cgrp)
3379 struct cgroup *parent = cgroup_parent(cgrp);
3380 struct cgroup *dom_cgrp = parent->dom_cgrp;
3381 struct cgroup *dsct;
3382 struct cgroup_subsys_state *d_css;
3385 lockdep_assert_held(&cgroup_mutex);
3387 /* noop if already threaded */
3388 if (cgroup_is_threaded(cgrp))
3392 * If @cgroup is populated or has domain controllers enabled, it
3393 * can't be switched. While the below cgroup_can_be_thread_root()
3394 * test can catch the same conditions, that's only when @parent is
3395 * not mixable, so let's check it explicitly.
3397 if (cgroup_is_populated(cgrp) ||
3398 cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)
3401 /* we're joining the parent's domain, ensure its validity */
3402 if (!cgroup_is_valid_domain(dom_cgrp) ||
3403 !cgroup_can_be_thread_root(dom_cgrp))
3407 * The following shouldn't cause actual migrations and should
3410 cgroup_save_control(cgrp);
3412 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp)
3413 if (dsct == cgrp || cgroup_is_threaded(dsct))
3414 dsct->dom_cgrp = dom_cgrp;
3416 ret = cgroup_apply_control(cgrp);
3418 parent->nr_threaded_children++;
3420 cgroup_finalize_control(cgrp, ret);
3424 static int cgroup_type_show(struct seq_file *seq, void *v)
3426 struct cgroup *cgrp = seq_css(seq)->cgroup;
3428 if (cgroup_is_threaded(cgrp))
3429 seq_puts(seq, "threaded\n");
3430 else if (!cgroup_is_valid_domain(cgrp))
3431 seq_puts(seq, "domain invalid\n");
3432 else if (cgroup_is_thread_root(cgrp))
3433 seq_puts(seq, "domain threaded\n");
3435 seq_puts(seq, "domain\n");
3440 static ssize_t cgroup_type_write(struct kernfs_open_file *of, char *buf,
3441 size_t nbytes, loff_t off)
3443 struct cgroup *cgrp;
3446 /* only switching to threaded mode is supported */
3447 if (strcmp(strstrip(buf), "threaded"))
3450 cgrp = cgroup_kn_lock_live(of->kn, false);
3454 /* threaded can only be enabled */
3455 ret = cgroup_enable_threaded(cgrp);
3457 cgroup_kn_unlock(of->kn);
3458 return ret ?: nbytes;
3461 static int cgroup_max_descendants_show(struct seq_file *seq, void *v)
3463 struct cgroup *cgrp = seq_css(seq)->cgroup;
3464 int descendants = READ_ONCE(cgrp->max_descendants);
3466 if (descendants == INT_MAX)
3467 seq_puts(seq, "max\n");
3469 seq_printf(seq, "%d\n", descendants);
3474 static ssize_t cgroup_max_descendants_write(struct kernfs_open_file *of,
3475 char *buf, size_t nbytes, loff_t off)
3477 struct cgroup *cgrp;
3481 buf = strstrip(buf);
3482 if (!strcmp(buf, "max")) {
3483 descendants = INT_MAX;
3485 ret = kstrtoint(buf, 0, &descendants);
3490 if (descendants < 0)
3493 cgrp = cgroup_kn_lock_live(of->kn, false);
3497 cgrp->max_descendants = descendants;
3499 cgroup_kn_unlock(of->kn);
3504 static int cgroup_max_depth_show(struct seq_file *seq, void *v)
3506 struct cgroup *cgrp = seq_css(seq)->cgroup;
3507 int depth = READ_ONCE(cgrp->max_depth);
3509 if (depth == INT_MAX)
3510 seq_puts(seq, "max\n");
3512 seq_printf(seq, "%d\n", depth);
3517 static ssize_t cgroup_max_depth_write(struct kernfs_open_file *of,
3518 char *buf, size_t nbytes, loff_t off)
3520 struct cgroup *cgrp;
3524 buf = strstrip(buf);
3525 if (!strcmp(buf, "max")) {
3528 ret = kstrtoint(buf, 0, &depth);
3536 cgrp = cgroup_kn_lock_live(of->kn, false);
3540 cgrp->max_depth = depth;
3542 cgroup_kn_unlock(of->kn);
3547 static int cgroup_events_show(struct seq_file *seq, void *v)
3549 struct cgroup *cgrp = seq_css(seq)->cgroup;
3551 seq_printf(seq, "populated %d\n", cgroup_is_populated(cgrp));
3552 seq_printf(seq, "frozen %d\n", test_bit(CGRP_FROZEN, &cgrp->flags));
3557 static int cgroup_stat_show(struct seq_file *seq, void *v)
3559 struct cgroup *cgroup = seq_css(seq)->cgroup;
3561 seq_printf(seq, "nr_descendants %d\n",
3562 cgroup->nr_descendants);
3563 seq_printf(seq, "nr_dying_descendants %d\n",
3564 cgroup->nr_dying_descendants);
3569 static int __maybe_unused cgroup_extra_stat_show(struct seq_file *seq,
3570 struct cgroup *cgrp, int ssid)
3572 struct cgroup_subsys *ss = cgroup_subsys[ssid];
3573 struct cgroup_subsys_state *css;
3576 if (!ss->css_extra_stat_show)
3579 css = cgroup_tryget_css(cgrp, ss);
3583 ret = ss->css_extra_stat_show(seq, css);
3588 static int cpu_stat_show(struct seq_file *seq, void *v)
3590 struct cgroup __maybe_unused *cgrp = seq_css(seq)->cgroup;
3593 cgroup_base_stat_cputime_show(seq);
3594 #ifdef CONFIG_CGROUP_SCHED
3595 ret = cgroup_extra_stat_show(seq, cgrp, cpu_cgrp_id);
3601 static int cgroup_io_pressure_show(struct seq_file *seq, void *v)
3603 struct cgroup *cgroup = seq_css(seq)->cgroup;
3604 struct psi_group *psi = cgroup->id == 1 ? &psi_system : &cgroup->psi;
3606 return psi_show(seq, psi, PSI_IO);
3608 static int cgroup_memory_pressure_show(struct seq_file *seq, void *v)
3610 struct cgroup *cgroup = seq_css(seq)->cgroup;
3611 struct psi_group *psi = cgroup->id == 1 ? &psi_system : &cgroup->psi;
3613 return psi_show(seq, psi, PSI_MEM);
3615 static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v)
3617 struct cgroup *cgroup = seq_css(seq)->cgroup;
3618 struct psi_group *psi = cgroup->id == 1 ? &psi_system : &cgroup->psi;
3620 return psi_show(seq, psi, PSI_CPU);
3623 static ssize_t cgroup_pressure_write(struct kernfs_open_file *of, char *buf,
3624 size_t nbytes, enum psi_res res)
3626 struct psi_trigger *new;
3627 struct cgroup *cgrp;
3629 cgrp = cgroup_kn_lock_live(of->kn, false);
3634 cgroup_kn_unlock(of->kn);
3636 new = psi_trigger_create(&cgrp->psi, buf, nbytes, res);
3639 return PTR_ERR(new);
3642 psi_trigger_replace(&of->priv, new);
3649 static ssize_t cgroup_io_pressure_write(struct kernfs_open_file *of,
3650 char *buf, size_t nbytes,
3653 return cgroup_pressure_write(of, buf, nbytes, PSI_IO);
3656 static ssize_t cgroup_memory_pressure_write(struct kernfs_open_file *of,
3657 char *buf, size_t nbytes,
3660 return cgroup_pressure_write(of, buf, nbytes, PSI_MEM);
3663 static ssize_t cgroup_cpu_pressure_write(struct kernfs_open_file *of,
3664 char *buf, size_t nbytes,
3667 return cgroup_pressure_write(of, buf, nbytes, PSI_CPU);
3670 static __poll_t cgroup_pressure_poll(struct kernfs_open_file *of,
3673 return psi_trigger_poll(&of->priv, of->file, pt);
3676 static void cgroup_pressure_release(struct kernfs_open_file *of)
3678 psi_trigger_replace(&of->priv, NULL);
3680 #endif /* CONFIG_PSI */
3682 static int cgroup_freeze_show(struct seq_file *seq, void *v)
3684 struct cgroup *cgrp = seq_css(seq)->cgroup;
3686 seq_printf(seq, "%d\n", cgrp->freezer.freeze);
3691 static ssize_t cgroup_freeze_write(struct kernfs_open_file *of,
3692 char *buf, size_t nbytes, loff_t off)
3694 struct cgroup *cgrp;
3698 ret = kstrtoint(strstrip(buf), 0, &freeze);
3702 if (freeze < 0 || freeze > 1)
3705 cgrp = cgroup_kn_lock_live(of->kn, false);
3709 cgroup_freeze(cgrp, freeze);
3711 cgroup_kn_unlock(of->kn);
3716 static int cgroup_file_open(struct kernfs_open_file *of)
3718 struct cftype *cft = of->kn->priv;
3721 return cft->open(of);
3725 static void cgroup_file_release(struct kernfs_open_file *of)
3727 struct cftype *cft = of->kn->priv;
3733 static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
3734 size_t nbytes, loff_t off)
3736 struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
3737 struct cgroup *cgrp = of->kn->parent->priv;
3738 struct cftype *cft = of->kn->priv;
3739 struct cgroup_subsys_state *css;
3743 * If namespaces are delegation boundaries, disallow writes to
3744 * files in an non-init namespace root from inside the namespace
3745 * except for the files explicitly marked delegatable -
3746 * cgroup.procs and cgroup.subtree_control.
3748 if ((cgrp->root->flags & CGRP_ROOT_NS_DELEGATE) &&
3749 !(cft->flags & CFTYPE_NS_DELEGATABLE) &&
3750 ns != &init_cgroup_ns && ns->root_cset->dfl_cgrp == cgrp)
3754 return cft->write(of, buf, nbytes, off);
3757 * kernfs guarantees that a file isn't deleted with operations in
3758 * flight, which means that the matching css is and stays alive and
3759 * doesn't need to be pinned. The RCU locking is not necessary
3760 * either. It's just for the convenience of using cgroup_css().
3763 css = cgroup_css(cgrp, cft->ss);
3766 if (cft->write_u64) {
3767 unsigned long long v;
3768 ret = kstrtoull(buf, 0, &v);
3770 ret = cft->write_u64(css, cft, v);
3771 } else if (cft->write_s64) {
3773 ret = kstrtoll(buf, 0, &v);
3775 ret = cft->write_s64(css, cft, v);
3780 return ret ?: nbytes;
3783 static __poll_t cgroup_file_poll(struct kernfs_open_file *of, poll_table *pt)
3785 struct cftype *cft = of->kn->priv;
3788 return cft->poll(of, pt);
3790 return kernfs_generic_poll(of, pt);
3793 static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
3795 return seq_cft(seq)->seq_start(seq, ppos);
3798 static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
3800 return seq_cft(seq)->seq_next(seq, v, ppos);
3803 static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
3805 if (seq_cft(seq)->seq_stop)
3806 seq_cft(seq)->seq_stop(seq, v);
3809 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
3811 struct cftype *cft = seq_cft(m);
3812 struct cgroup_subsys_state *css = seq_css(m);
3815 return cft->seq_show(m, arg);
3818 seq_printf(m, "%llu\n", cft->read_u64(css, cft));
3819 else if (cft->read_s64)
3820 seq_printf(m, "%lld\n", cft->read_s64(css, cft));
3826 static struct kernfs_ops cgroup_kf_single_ops = {
3827 .atomic_write_len = PAGE_SIZE,
3828 .open = cgroup_file_open,
3829 .release = cgroup_file_release,
3830 .write = cgroup_file_write,
3831 .poll = cgroup_file_poll,
3832 .seq_show = cgroup_seqfile_show,
3835 static struct kernfs_ops cgroup_kf_ops = {
3836 .atomic_write_len = PAGE_SIZE,
3837 .open = cgroup_file_open,
3838 .release = cgroup_file_release,
3839 .write = cgroup_file_write,
3840 .poll = cgroup_file_poll,
3841 .seq_start = cgroup_seqfile_start,
3842 .seq_next = cgroup_seqfile_next,
3843 .seq_stop = cgroup_seqfile_stop,
3844 .seq_show = cgroup_seqfile_show,
3847 /* set uid and gid of cgroup dirs and files to that of the creator */
3848 static int cgroup_kn_set_ugid(struct kernfs_node *kn)
3850 struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
3851 .ia_uid = current_fsuid(),
3852 .ia_gid = current_fsgid(), };
3854 if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
3855 gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
3858 return kernfs_setattr(kn, &iattr);
3861 static void cgroup_file_notify_timer(struct timer_list *timer)
3863 cgroup_file_notify(container_of(timer, struct cgroup_file,
3867 static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
3870 char name[CGROUP_FILE_NAME_MAX];
3871 struct kernfs_node *kn;
3872 struct lock_class_key *key = NULL;
3875 #ifdef CONFIG_DEBUG_LOCK_ALLOC
3876 key = &cft->lockdep_key;
3878 kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
3879 cgroup_file_mode(cft),
3880 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
3881 0, cft->kf_ops, cft,
3886 ret = cgroup_kn_set_ugid(kn);
3892 if (cft->file_offset) {
3893 struct cgroup_file *cfile = (void *)css + cft->file_offset;
3895 timer_setup(&cfile->notify_timer, cgroup_file_notify_timer, 0);
3897 spin_lock_irq(&cgroup_file_kn_lock);
3899 spin_unlock_irq(&cgroup_file_kn_lock);
3906 * cgroup_addrm_files - add or remove files to a cgroup directory
3907 * @css: the target css
3908 * @cgrp: the target cgroup (usually css->cgroup)
3909 * @cfts: array of cftypes to be added
3910 * @is_add: whether to add or remove
3912 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
3913 * For removals, this function never fails.
3915 static int cgroup_addrm_files(struct cgroup_subsys_state *css,
3916 struct cgroup *cgrp, struct cftype cfts[],
3919 struct cftype *cft, *cft_end = NULL;
3922 lockdep_assert_held(&cgroup_mutex);
3925 for (cft = cfts; cft != cft_end && cft->name[0] != '\0'; cft++) {
3926 /* does cft->flags tell us to skip this file on @cgrp? */
3927 if ((cft->flags & __CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
3929 if ((cft->flags & __CFTYPE_NOT_ON_DFL) && cgroup_on_dfl(cgrp))
3931 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp))
3933 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp))
3935 if ((cft->flags & CFTYPE_DEBUG) && !cgroup_debug)
3938 ret = cgroup_add_file(css, cgrp, cft);
3940 pr_warn("%s: failed to add %s, err=%d\n",
3941 __func__, cft->name, ret);
3947 cgroup_rm_file(cgrp, cft);
3953 static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
3955 struct cgroup_subsys *ss = cfts[0].ss;
3956 struct cgroup *root = &ss->root->cgrp;
3957 struct cgroup_subsys_state *css;
3960 lockdep_assert_held(&cgroup_mutex);
3962 /* add/rm files for all cgroups created before */
3963 css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
3964 struct cgroup *cgrp = css->cgroup;
3966 if (!(css->flags & CSS_VISIBLE))
3969 ret = cgroup_addrm_files(css, cgrp, cfts, is_add);
3975 kernfs_activate(root->kn);
3979 static void cgroup_exit_cftypes(struct cftype *cfts)
3983 for (cft = cfts; cft->name[0] != '\0'; cft++) {
3984 /* free copy for custom atomic_write_len, see init_cftypes() */
3985 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
3990 /* revert flags set by cgroup core while adding @cfts */
3991 cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL);
3995 static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
3999 for (cft = cfts; cft->name[0] != '\0'; cft++) {
4000 struct kernfs_ops *kf_ops;
4002 WARN_ON(cft->ss || cft->kf_ops);
4005 kf_ops = &cgroup_kf_ops;
4007 kf_ops = &cgroup_kf_single_ops;
4010 * Ugh... if @cft wants a custom max_write_len, we need to
4011 * make a copy of kf_ops to set its atomic_write_len.
4013 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
4014 kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
4016 cgroup_exit_cftypes(cfts);
4019 kf_ops->atomic_write_len = cft->max_write_len;
4022 cft->kf_ops = kf_ops;
4029 static int cgroup_rm_cftypes_locked(struct cftype *cfts)
4031 lockdep_assert_held(&cgroup_mutex);
4033 if (!cfts || !cfts[0].ss)
4036 list_del(&cfts->node);
4037 cgroup_apply_cftypes(cfts, false);
4038 cgroup_exit_cftypes(cfts);
4043 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
4044 * @cfts: zero-length name terminated array of cftypes
4046 * Unregister @cfts. Files described by @cfts are removed from all
4047 * existing cgroups and all future cgroups won't have them either. This
4048 * function can be called anytime whether @cfts' subsys is attached or not.
4050 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
4053 int cgroup_rm_cftypes(struct cftype *cfts)
4057 mutex_lock(&cgroup_mutex);
4058 ret = cgroup_rm_cftypes_locked(cfts);
4059 mutex_unlock(&cgroup_mutex);
4064 * cgroup_add_cftypes - add an array of cftypes to a subsystem
4065 * @ss: target cgroup subsystem
4066 * @cfts: zero-length name terminated array of cftypes
4068 * Register @cfts to @ss. Files described by @cfts are created for all
4069 * existing cgroups to which @ss is attached and all future cgroups will
4070 * have them too. This function can be called anytime whether @ss is
4073 * Returns 0 on successful registration, -errno on failure. Note that this
4074 * function currently returns 0 as long as @cfts registration is successful
4075 * even if some file creation attempts on existing cgroups fail.
4077 static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4081 if (!cgroup_ssid_enabled(ss->id))
4084 if (!cfts || cfts[0].name[0] == '\0')
4087 ret = cgroup_init_cftypes(ss, cfts);
4091 mutex_lock(&cgroup_mutex);
4093 list_add_tail(&cfts->node, &ss->cfts);
4094 ret = cgroup_apply_cftypes(cfts, true);
4096 cgroup_rm_cftypes_locked(cfts);
4098 mutex_unlock(&cgroup_mutex);
4103 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
4104 * @ss: target cgroup subsystem
4105 * @cfts: zero-length name terminated array of cftypes
4107 * Similar to cgroup_add_cftypes() but the added files are only used for
4108 * the default hierarchy.
4110 int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4114 for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
4115 cft->flags |= __CFTYPE_ONLY_ON_DFL;
4116 return cgroup_add_cftypes(ss, cfts);
4120 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
4121 * @ss: target cgroup subsystem
4122 * @cfts: zero-length name terminated array of cftypes
4124 * Similar to cgroup_add_cftypes() but the added files are only used for
4125 * the legacy hierarchies.
4127 int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4131 for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
4132 cft->flags |= __CFTYPE_NOT_ON_DFL;
4133 return cgroup_add_cftypes(ss, cfts);
4137 * cgroup_file_notify - generate a file modified event for a cgroup_file
4138 * @cfile: target cgroup_file
4140 * @cfile must have been obtained by setting cftype->file_offset.
4142 void cgroup_file_notify(struct cgroup_file *cfile)
4144 unsigned long flags;
4146 spin_lock_irqsave(&cgroup_file_kn_lock, flags);
4148 unsigned long last = cfile->notified_at;
4149 unsigned long next = last + CGROUP_FILE_NOTIFY_MIN_INTV;
4151 if (time_in_range(jiffies, last, next)) {
4152 timer_reduce(&cfile->notify_timer, next);
4154 kernfs_notify(cfile->kn);
4155 cfile->notified_at = jiffies;
4158 spin_unlock_irqrestore(&cgroup_file_kn_lock, flags);
4162 * css_next_child - find the next child of a given css
4163 * @pos: the current position (%NULL to initiate traversal)
4164 * @parent: css whose children to walk
4166 * This function returns the next child of @parent and should be called
4167 * under either cgroup_mutex or RCU read lock. The only requirement is
4168 * that @parent and @pos are accessible. The next sibling is guaranteed to
4169 * be returned regardless of their states.
4171 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4172 * css which finished ->css_online() is guaranteed to be visible in the
4173 * future iterations and will stay visible until the last reference is put.
4174 * A css which hasn't finished ->css_online() or already finished
4175 * ->css_offline() may show up during traversal. It's each subsystem's
4176 * responsibility to synchronize against on/offlining.
4178 struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
4179 struct cgroup_subsys_state *parent)
4181 struct cgroup_subsys_state *next;
4183 cgroup_assert_mutex_or_rcu_locked();
4186 * @pos could already have been unlinked from the sibling list.
4187 * Once a cgroup is removed, its ->sibling.next is no longer
4188 * updated when its next sibling changes. CSS_RELEASED is set when
4189 * @pos is taken off list, at which time its next pointer is valid,
4190 * and, as releases are serialized, the one pointed to by the next
4191 * pointer is guaranteed to not have started release yet. This
4192 * implies that if we observe !CSS_RELEASED on @pos in this RCU
4193 * critical section, the one pointed to by its next pointer is
4194 * guaranteed to not have finished its RCU grace period even if we
4195 * have dropped rcu_read_lock() inbetween iterations.
4197 * If @pos has CSS_RELEASED set, its next pointer can't be
4198 * dereferenced; however, as each css is given a monotonically
4199 * increasing unique serial number and always appended to the
4200 * sibling list, the next one can be found by walking the parent's
4201 * children until the first css with higher serial number than
4202 * @pos's. While this path can be slower, it happens iff iteration
4203 * races against release and the race window is very small.
4206 next = list_entry_rcu(parent->children.next, struct cgroup_subsys_state, sibling);
4207 } else if (likely(!(pos->flags & CSS_RELEASED))) {
4208 next = list_entry_rcu(pos->sibling.next, struct cgroup_subsys_state, sibling);
4210 list_for_each_entry_rcu(next, &parent->children, sibling)
4211 if (next->serial_nr > pos->serial_nr)
4216 * @next, if not pointing to the head, can be dereferenced and is
4219 if (&next->sibling != &parent->children)
4225 * css_next_descendant_pre - find the next descendant for pre-order walk
4226 * @pos: the current position (%NULL to initiate traversal)
4227 * @root: css whose descendants to walk
4229 * To be used by css_for_each_descendant_pre(). Find the next descendant
4230 * to visit for pre-order traversal of @root's descendants. @root is
4231 * included in the iteration and the first node to be visited.
4233 * While this function requires cgroup_mutex or RCU read locking, it
4234 * doesn't require the whole traversal to be contained in a single critical
4235 * section. This function will return the correct next descendant as long
4236 * as both @pos and @root are accessible and @pos is a descendant of @root.
4238 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4239 * css which finished ->css_online() is guaranteed to be visible in the
4240 * future iterations and will stay visible until the last reference is put.
4241 * A css which hasn't finished ->css_online() or already finished
4242 * ->css_offline() may show up during traversal. It's each subsystem's
4243 * responsibility to synchronize against on/offlining.
4245 struct cgroup_subsys_state *
4246 css_next_descendant_pre(struct cgroup_subsys_state *pos,
4247 struct cgroup_subsys_state *root)
4249 struct cgroup_subsys_state *next;
4251 cgroup_assert_mutex_or_rcu_locked();
4253 /* if first iteration, visit @root */
4257 /* visit the first child if exists */
4258 next = css_next_child(NULL, pos);
4262 /* no child, visit my or the closest ancestor's next sibling */
4263 while (pos != root) {
4264 next = css_next_child(pos, pos->parent);
4272 EXPORT_SYMBOL_GPL(css_next_descendant_pre);
4275 * css_rightmost_descendant - return the rightmost descendant of a css
4276 * @pos: css of interest
4278 * Return the rightmost descendant of @pos. If there's no descendant, @pos
4279 * is returned. This can be used during pre-order traversal to skip
4282 * While this function requires cgroup_mutex or RCU read locking, it
4283 * doesn't require the whole traversal to be contained in a single critical
4284 * section. This function will return the correct rightmost descendant as
4285 * long as @pos is accessible.
4287 struct cgroup_subsys_state *
4288 css_rightmost_descendant(struct cgroup_subsys_state *pos)
4290 struct cgroup_subsys_state *last, *tmp;
4292 cgroup_assert_mutex_or_rcu_locked();
4296 /* ->prev isn't RCU safe, walk ->next till the end */
4298 css_for_each_child(tmp, last)
4305 static struct cgroup_subsys_state *
4306 css_leftmost_descendant(struct cgroup_subsys_state *pos)
4308 struct cgroup_subsys_state *last;
4312 pos = css_next_child(NULL, pos);
4319 * css_next_descendant_post - find the next descendant for post-order walk
4320 * @pos: the current position (%NULL to initiate traversal)
4321 * @root: css whose descendants to walk
4323 * To be used by css_for_each_descendant_post(). Find the next descendant
4324 * to visit for post-order traversal of @root's descendants. @root is
4325 * included in the iteration and the last node to be visited.
4327 * While this function requires cgroup_mutex or RCU read locking, it
4328 * doesn't require the whole traversal to be contained in a single critical
4329 * section. This function will return the correct next descendant as long
4330 * as both @pos and @cgroup are accessible and @pos is a descendant of
4333 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4334 * css which finished ->css_online() is guaranteed to be visible in the
4335 * future iterations and will stay visible until the last reference is put.
4336 * A css which hasn't finished ->css_online() or already finished
4337 * ->css_offline() may show up during traversal. It's each subsystem's
4338 * responsibility to synchronize against on/offlining.
4340 struct cgroup_subsys_state *
4341 css_next_descendant_post(struct cgroup_subsys_state *pos,
4342 struct cgroup_subsys_state *root)
4344 struct cgroup_subsys_state *next;
4346 cgroup_assert_mutex_or_rcu_locked();
4348 /* if first iteration, visit leftmost descendant which may be @root */
4350 return css_leftmost_descendant(root);
4352 /* if we visited @root, we're done */
4356 /* if there's an unvisited sibling, visit its leftmost descendant */
4357 next = css_next_child(pos, pos->parent);
4359 return css_leftmost_descendant(next);
4361 /* no sibling left, visit parent */
4366 * css_has_online_children - does a css have online children
4367 * @css: the target css
4369 * Returns %true if @css has any online children; otherwise, %false. This
4370 * function can be called from any context but the caller is responsible
4371 * for synchronizing against on/offlining as necessary.
4373 bool css_has_online_children(struct cgroup_subsys_state *css)
4375 struct cgroup_subsys_state *child;
4379 css_for_each_child(child, css) {
4380 if (child->flags & CSS_ONLINE) {
4389 static struct css_set *css_task_iter_next_css_set(struct css_task_iter *it)
4391 struct list_head *l;
4392 struct cgrp_cset_link *link;
4393 struct css_set *cset;
4395 lockdep_assert_held(&css_set_lock);
4397 /* find the next threaded cset */
4398 if (it->tcset_pos) {
4399 l = it->tcset_pos->next;
4401 if (l != it->tcset_head) {
4403 return container_of(l, struct css_set,
4404 threaded_csets_node);
4407 it->tcset_pos = NULL;
4410 /* find the next cset */
4413 if (l == it->cset_head) {
4414 it->cset_pos = NULL;
4419 cset = container_of(l, struct css_set, e_cset_node[it->ss->id]);
4421 link = list_entry(l, struct cgrp_cset_link, cset_link);
4427 /* initialize threaded css_set walking */
4428 if (it->flags & CSS_TASK_ITER_THREADED) {
4430 put_css_set_locked(it->cur_dcset);
4431 it->cur_dcset = cset;
4434 it->tcset_head = &cset->threaded_csets;
4435 it->tcset_pos = &cset->threaded_csets;
4442 * css_task_iter_advance_css_set - advance a task itererator to the next css_set
4443 * @it: the iterator to advance
4445 * Advance @it to the next css_set to walk.
4447 static void css_task_iter_advance_css_set(struct css_task_iter *it)
4449 struct css_set *cset;
4451 lockdep_assert_held(&css_set_lock);
4453 /* Advance to the next non-empty css_set */
4455 cset = css_task_iter_next_css_set(it);
4457 it->task_pos = NULL;
4460 } while (!css_set_populated(cset) && list_empty(&cset->dying_tasks));
4462 if (!list_empty(&cset->tasks))
4463 it->task_pos = cset->tasks.next;
4464 else if (!list_empty(&cset->mg_tasks))
4465 it->task_pos = cset->mg_tasks.next;
4467 it->task_pos = cset->dying_tasks.next;
4469 it->tasks_head = &cset->tasks;
4470 it->mg_tasks_head = &cset->mg_tasks;
4471 it->dying_tasks_head = &cset->dying_tasks;
4474 * We don't keep css_sets locked across iteration steps and thus
4475 * need to take steps to ensure that iteration can be resumed after
4476 * the lock is re-acquired. Iteration is performed at two levels -
4477 * css_sets and tasks in them.
4479 * Once created, a css_set never leaves its cgroup lists, so a
4480 * pinned css_set is guaranteed to stay put and we can resume
4481 * iteration afterwards.
4483 * Tasks may leave @cset across iteration steps. This is resolved
4484 * by registering each iterator with the css_set currently being
4485 * walked and making css_set_move_task() advance iterators whose
4486 * next task is leaving.
4489 list_del(&it->iters_node);
4490 put_css_set_locked(it->cur_cset);
4493 it->cur_cset = cset;
4494 list_add(&it->iters_node, &cset->task_iters);
4497 static void css_task_iter_skip(struct css_task_iter *it,
4498 struct task_struct *task)
4500 lockdep_assert_held(&css_set_lock);
4502 if (it->task_pos == &task->cg_list) {
4503 it->task_pos = it->task_pos->next;
4504 it->flags |= CSS_TASK_ITER_SKIPPED;
4508 static void css_task_iter_advance(struct css_task_iter *it)
4510 struct task_struct *task;
4512 lockdep_assert_held(&css_set_lock);
4516 * Advance iterator to find next entry. cset->tasks is
4517 * consumed first and then ->mg_tasks. After ->mg_tasks,
4518 * we move onto the next cset.
4520 if (it->flags & CSS_TASK_ITER_SKIPPED)
4521 it->flags &= ~CSS_TASK_ITER_SKIPPED;
4523 it->task_pos = it->task_pos->next;
4525 if (it->task_pos == it->tasks_head)
4526 it->task_pos = it->mg_tasks_head->next;
4527 if (it->task_pos == it->mg_tasks_head)
4528 it->task_pos = it->dying_tasks_head->next;
4529 if (it->task_pos == it->dying_tasks_head)
4530 css_task_iter_advance_css_set(it);
4532 /* called from start, proceed to the first cset */
4533 css_task_iter_advance_css_set(it);
4539 task = list_entry(it->task_pos, struct task_struct, cg_list);
4541 if (it->flags & CSS_TASK_ITER_PROCS) {
4542 /* if PROCS, skip over tasks which aren't group leaders */
4543 if (!thread_group_leader(task))
4546 /* and dying leaders w/o live member threads */
4547 if (!atomic_read(&task->signal->live))
4550 /* skip all dying ones */
4551 if (task->flags & PF_EXITING)
4557 * css_task_iter_start - initiate task iteration
4558 * @css: the css to walk tasks of
4559 * @flags: CSS_TASK_ITER_* flags
4560 * @it: the task iterator to use
4562 * Initiate iteration through the tasks of @css. The caller can call
4563 * css_task_iter_next() to walk through the tasks until the function
4564 * returns NULL. On completion of iteration, css_task_iter_end() must be
4567 void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
4568 struct css_task_iter *it)
4570 /* no one should try to iterate before mounting cgroups */
4571 WARN_ON_ONCE(!use_task_css_set_links);
4573 memset(it, 0, sizeof(*it));
4575 spin_lock_irq(&css_set_lock);
4581 it->cset_pos = &css->cgroup->e_csets[css->ss->id];
4583 it->cset_pos = &css->cgroup->cset_links;
4585 it->cset_head = it->cset_pos;
4587 css_task_iter_advance(it);
4589 spin_unlock_irq(&css_set_lock);
4593 * css_task_iter_next - return the next task for the iterator
4594 * @it: the task iterator being iterated
4596 * The "next" function for task iteration. @it should have been
4597 * initialized via css_task_iter_start(). Returns NULL when the iteration
4600 struct task_struct *css_task_iter_next(struct css_task_iter *it)
4603 put_task_struct(it->cur_task);
4604 it->cur_task = NULL;
4607 spin_lock_irq(&css_set_lock);
4609 /* @it may be half-advanced by skips, finish advancing */
4610 if (it->flags & CSS_TASK_ITER_SKIPPED)
4611 css_task_iter_advance(it);
4614 it->cur_task = list_entry(it->task_pos, struct task_struct,
4616 get_task_struct(it->cur_task);
4617 css_task_iter_advance(it);
4620 spin_unlock_irq(&css_set_lock);
4622 return it->cur_task;
4626 * css_task_iter_end - finish task iteration
4627 * @it: the task iterator to finish
4629 * Finish task iteration started by css_task_iter_start().
4631 void css_task_iter_end(struct css_task_iter *it)
4634 spin_lock_irq(&css_set_lock);
4635 list_del(&it->iters_node);
4636 put_css_set_locked(it->cur_cset);
4637 spin_unlock_irq(&css_set_lock);
4641 put_css_set(it->cur_dcset);
4644 put_task_struct(it->cur_task);
4647 static void cgroup_procs_release(struct kernfs_open_file *of)
4650 css_task_iter_end(of->priv);
4655 static void *cgroup_procs_next(struct seq_file *s, void *v, loff_t *pos)
4657 struct kernfs_open_file *of = s->private;
4658 struct css_task_iter *it = of->priv;
4660 return css_task_iter_next(it);
4663 static void *__cgroup_procs_start(struct seq_file *s, loff_t *pos,
4664 unsigned int iter_flags)
4666 struct kernfs_open_file *of = s->private;
4667 struct cgroup *cgrp = seq_css(s)->cgroup;
4668 struct css_task_iter *it = of->priv;
4671 * When a seq_file is seeked, it's always traversed sequentially
4672 * from position 0, so we can simply keep iterating on !0 *pos.
4675 if (WARN_ON_ONCE((*pos)++))
4676 return ERR_PTR(-EINVAL);
4678 it = kzalloc(sizeof(*it), GFP_KERNEL);
4680 return ERR_PTR(-ENOMEM);
4682 css_task_iter_start(&cgrp->self, iter_flags, it);
4683 } else if (!(*pos)++) {
4684 css_task_iter_end(it);
4685 css_task_iter_start(&cgrp->self, iter_flags, it);
4688 return cgroup_procs_next(s, NULL, NULL);
4691 static void *cgroup_procs_start(struct seq_file *s, loff_t *pos)
4693 struct cgroup *cgrp = seq_css(s)->cgroup;
4696 * All processes of a threaded subtree belong to the domain cgroup
4697 * of the subtree. Only threads can be distributed across the
4698 * subtree. Reject reads on cgroup.procs in the subtree proper.
4699 * They're always empty anyway.
4701 if (cgroup_is_threaded(cgrp))
4702 return ERR_PTR(-EOPNOTSUPP);
4704 return __cgroup_procs_start(s, pos, CSS_TASK_ITER_PROCS |
4705 CSS_TASK_ITER_THREADED);
4708 static int cgroup_procs_show(struct seq_file *s, void *v)
4710 seq_printf(s, "%d\n", task_pid_vnr(v));
4714 static int cgroup_procs_write_permission(struct cgroup *src_cgrp,
4715 struct cgroup *dst_cgrp,
4716 struct super_block *sb)
4718 struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
4719 struct cgroup *com_cgrp = src_cgrp;
4720 struct inode *inode;
4723 lockdep_assert_held(&cgroup_mutex);
4725 /* find the common ancestor */
4726 while (!cgroup_is_descendant(dst_cgrp, com_cgrp))
4727 com_cgrp = cgroup_parent(com_cgrp);
4729 /* %current should be authorized to migrate to the common ancestor */
4730 inode = kernfs_get_inode(sb, com_cgrp->procs_file.kn);
4734 ret = inode_permission(inode, MAY_WRITE);
4740 * If namespaces are delegation boundaries, %current must be able
4741 * to see both source and destination cgroups from its namespace.
4743 if ((cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE) &&
4744 (!cgroup_is_descendant(src_cgrp, ns->root_cset->dfl_cgrp) ||
4745 !cgroup_is_descendant(dst_cgrp, ns->root_cset->dfl_cgrp)))
4751 static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
4752 char *buf, size_t nbytes, loff_t off)
4754 struct cgroup *src_cgrp, *dst_cgrp;
4755 struct task_struct *task;
4758 dst_cgrp = cgroup_kn_lock_live(of->kn, false);
4762 task = cgroup_procs_write_start(buf, true);
4763 ret = PTR_ERR_OR_ZERO(task);
4767 /* find the source cgroup */
4768 spin_lock_irq(&css_set_lock);
4769 src_cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
4770 spin_unlock_irq(&css_set_lock);
4772 ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp,
4773 of->file->f_path.dentry->d_sb);
4777 ret = cgroup_attach_task(dst_cgrp, task, true);
4780 cgroup_procs_write_finish(task);
4782 cgroup_kn_unlock(of->kn);
4784 return ret ?: nbytes;
4787 static void *cgroup_threads_start(struct seq_file *s, loff_t *pos)
4789 return __cgroup_procs_start(s, pos, 0);
4792 static ssize_t cgroup_threads_write(struct kernfs_open_file *of,
4793 char *buf, size_t nbytes, loff_t off)
4795 struct cgroup *src_cgrp, *dst_cgrp;
4796 struct task_struct *task;
4799 buf = strstrip(buf);
4801 dst_cgrp = cgroup_kn_lock_live(of->kn, false);
4805 task = cgroup_procs_write_start(buf, false);
4806 ret = PTR_ERR_OR_ZERO(task);
4810 /* find the source cgroup */
4811 spin_lock_irq(&css_set_lock);
4812 src_cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
4813 spin_unlock_irq(&css_set_lock);
4815 /* thread migrations follow the cgroup.procs delegation rule */
4816 ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp,
4817 of->file->f_path.dentry->d_sb);
4821 /* and must be contained in the same domain */
4823 if (src_cgrp->dom_cgrp != dst_cgrp->dom_cgrp)
4826 ret = cgroup_attach_task(dst_cgrp, task, false);
4829 cgroup_procs_write_finish(task);
4831 cgroup_kn_unlock(of->kn);
4833 return ret ?: nbytes;
4836 /* cgroup core interface files for the default hierarchy */
4837 static struct cftype cgroup_base_files[] = {
4839 .name = "cgroup.type",
4840 .flags = CFTYPE_NOT_ON_ROOT,
4841 .seq_show = cgroup_type_show,
4842 .write = cgroup_type_write,
4845 .name = "cgroup.procs",
4846 .flags = CFTYPE_NS_DELEGATABLE,
4847 .file_offset = offsetof(struct cgroup, procs_file),
4848 .release = cgroup_procs_release,
4849 .seq_start = cgroup_procs_start,
4850 .seq_next = cgroup_procs_next,
4851 .seq_show = cgroup_procs_show,
4852 .write = cgroup_procs_write,
4855 .name = "cgroup.threads",
4856 .flags = CFTYPE_NS_DELEGATABLE,
4857 .release = cgroup_procs_release,
4858 .seq_start = cgroup_threads_start,
4859 .seq_next = cgroup_procs_next,
4860 .seq_show = cgroup_procs_show,
4861 .write = cgroup_threads_write,
4864 .name = "cgroup.controllers",
4865 .seq_show = cgroup_controllers_show,
4868 .name = "cgroup.subtree_control",
4869 .flags = CFTYPE_NS_DELEGATABLE,
4870 .seq_show = cgroup_subtree_control_show,
4871 .write = cgroup_subtree_control_write,
4874 .name = "cgroup.events",
4875 .flags = CFTYPE_NOT_ON_ROOT,
4876 .file_offset = offsetof(struct cgroup, events_file),
4877 .seq_show = cgroup_events_show,
4880 .name = "cgroup.max.descendants",
4881 .seq_show = cgroup_max_descendants_show,
4882 .write = cgroup_max_descendants_write,
4885 .name = "cgroup.max.depth",
4886 .seq_show = cgroup_max_depth_show,
4887 .write = cgroup_max_depth_write,
4890 .name = "cgroup.stat",
4891 .seq_show = cgroup_stat_show,
4894 .name = "cgroup.freeze",
4895 .flags = CFTYPE_NOT_ON_ROOT,
4896 .seq_show = cgroup_freeze_show,
4897 .write = cgroup_freeze_write,
4901 .flags = CFTYPE_NOT_ON_ROOT,
4902 .seq_show = cpu_stat_show,
4906 .name = "io.pressure",
4907 .seq_show = cgroup_io_pressure_show,
4908 .write = cgroup_io_pressure_write,
4909 .poll = cgroup_pressure_poll,
4910 .release = cgroup_pressure_release,
4913 .name = "memory.pressure",
4914 .seq_show = cgroup_memory_pressure_show,
4915 .write = cgroup_memory_pressure_write,
4916 .poll = cgroup_pressure_poll,
4917 .release = cgroup_pressure_release,
4920 .name = "cpu.pressure",
4921 .seq_show = cgroup_cpu_pressure_show,
4922 .write = cgroup_cpu_pressure_write,
4923 .poll = cgroup_pressure_poll,
4924 .release = cgroup_pressure_release,
4926 #endif /* CONFIG_PSI */
4931 * css destruction is four-stage process.
4933 * 1. Destruction starts. Killing of the percpu_ref is initiated.
4934 * Implemented in kill_css().
4936 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
4937 * and thus css_tryget_online() is guaranteed to fail, the css can be
4938 * offlined by invoking offline_css(). After offlining, the base ref is
4939 * put. Implemented in css_killed_work_fn().
4941 * 3. When the percpu_ref reaches zero, the only possible remaining
4942 * accessors are inside RCU read sections. css_release() schedules the
4945 * 4. After the grace period, the css can be freed. Implemented in
4946 * css_free_work_fn().
4948 * It is actually hairier because both step 2 and 4 require process context
4949 * and thus involve punting to css->destroy_work adding two additional
4950 * steps to the already complex sequence.
4952 static void css_free_rwork_fn(struct work_struct *work)
4954 struct cgroup_subsys_state *css = container_of(to_rcu_work(work),
4955 struct cgroup_subsys_state, destroy_rwork);
4956 struct cgroup_subsys *ss = css->ss;
4957 struct cgroup *cgrp = css->cgroup;
4959 percpu_ref_exit(&css->refcnt);
4963 struct cgroup_subsys_state *parent = css->parent;
4967 cgroup_idr_remove(&ss->css_idr, id);
4973 /* cgroup free path */
4974 atomic_dec(&cgrp->root->nr_cgrps);
4975 cgroup1_pidlist_destroy_all(cgrp);
4976 cancel_work_sync(&cgrp->release_agent_work);
4978 if (cgroup_parent(cgrp)) {
4980 * We get a ref to the parent, and put the ref when
4981 * this cgroup is being freed, so it's guaranteed
4982 * that the parent won't be destroyed before its
4985 cgroup_put(cgroup_parent(cgrp));
4986 kernfs_put(cgrp->kn);
4987 psi_cgroup_free(cgrp);
4988 if (cgroup_on_dfl(cgrp))
4989 cgroup_rstat_exit(cgrp);
4993 * This is root cgroup's refcnt reaching zero,
4994 * which indicates that the root should be
4997 cgroup_destroy_root(cgrp->root);
5002 static void css_release_work_fn(struct work_struct *work)
5004 struct cgroup_subsys_state *css =
5005 container_of(work, struct cgroup_subsys_state, destroy_work);
5006 struct cgroup_subsys *ss = css->ss;
5007 struct cgroup *cgrp = css->cgroup;
5009 mutex_lock(&cgroup_mutex);
5011 css->flags |= CSS_RELEASED;
5012 list_del_rcu(&css->sibling);
5015 /* css release path */
5016 if (!list_empty(&css->rstat_css_node)) {
5017 cgroup_rstat_flush(cgrp);
5018 list_del_rcu(&css->rstat_css_node);
5021 cgroup_idr_replace(&ss->css_idr, NULL, css->id);
5022 if (ss->css_released)
5023 ss->css_released(css);
5025 struct cgroup *tcgrp;
5027 /* cgroup release path */
5028 TRACE_CGROUP_PATH(release, cgrp);
5030 if (cgroup_on_dfl(cgrp))
5031 cgroup_rstat_flush(cgrp);
5033 spin_lock_irq(&css_set_lock);
5034 for (tcgrp = cgroup_parent(cgrp); tcgrp;
5035 tcgrp = cgroup_parent(tcgrp))
5036 tcgrp->nr_dying_descendants--;
5037 spin_unlock_irq(&css_set_lock);
5039 cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
5043 * There are two control paths which try to determine
5044 * cgroup from dentry without going through kernfs -
5045 * cgroupstats_build() and css_tryget_online_from_dir().
5046 * Those are supported by RCU protecting clearing of
5047 * cgrp->kn->priv backpointer.
5050 RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv,
5054 mutex_unlock(&cgroup_mutex);
5056 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
5057 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
5060 static void css_release(struct percpu_ref *ref)
5062 struct cgroup_subsys_state *css =
5063 container_of(ref, struct cgroup_subsys_state, refcnt);
5065 INIT_WORK(&css->destroy_work, css_release_work_fn);
5066 queue_work(cgroup_destroy_wq, &css->destroy_work);
5069 static void init_and_link_css(struct cgroup_subsys_state *css,
5070 struct cgroup_subsys *ss, struct cgroup *cgrp)
5072 lockdep_assert_held(&cgroup_mutex);
5074 cgroup_get_live(cgrp);
5076 memset(css, 0, sizeof(*css));
5080 INIT_LIST_HEAD(&css->sibling);
5081 INIT_LIST_HEAD(&css->children);
5082 INIT_LIST_HEAD(&css->rstat_css_node);
5083 css->serial_nr = css_serial_nr_next++;
5084 atomic_set(&css->online_cnt, 0);
5086 if (cgroup_parent(cgrp)) {
5087 css->parent = cgroup_css(cgroup_parent(cgrp), ss);
5088 css_get(css->parent);
5091 if (cgroup_on_dfl(cgrp) && ss->css_rstat_flush)
5092 list_add_rcu(&css->rstat_css_node, &cgrp->rstat_css_list);
5094 BUG_ON(cgroup_css(cgrp, ss));
5097 /* invoke ->css_online() on a new CSS and mark it online if successful */
5098 static int online_css(struct cgroup_subsys_state *css)
5100 struct cgroup_subsys *ss = css->ss;
5103 lockdep_assert_held(&cgroup_mutex);
5106 ret = ss->css_online(css);
5108 css->flags |= CSS_ONLINE;
5109 rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
5111 atomic_inc(&css->online_cnt);
5113 atomic_inc(&css->parent->online_cnt);
5118 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
5119 static void offline_css(struct cgroup_subsys_state *css)
5121 struct cgroup_subsys *ss = css->ss;
5123 lockdep_assert_held(&cgroup_mutex);
5125 if (!(css->flags & CSS_ONLINE))
5128 if (ss->css_offline)
5129 ss->css_offline(css);
5131 css->flags &= ~CSS_ONLINE;
5132 RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL);
5134 wake_up_all(&css->cgroup->offline_waitq);
5138 * css_create - create a cgroup_subsys_state
5139 * @cgrp: the cgroup new css will be associated with
5140 * @ss: the subsys of new css
5142 * Create a new css associated with @cgrp - @ss pair. On success, the new
5143 * css is online and installed in @cgrp. This function doesn't create the
5144 * interface files. Returns 0 on success, -errno on failure.
5146 static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
5147 struct cgroup_subsys *ss)
5149 struct cgroup *parent = cgroup_parent(cgrp);
5150 struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss);
5151 struct cgroup_subsys_state *css;
5154 lockdep_assert_held(&cgroup_mutex);
5156 css = ss->css_alloc(parent_css);
5158 css = ERR_PTR(-ENOMEM);
5162 init_and_link_css(css, ss, cgrp);
5164 err = percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL);
5168 err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL);
5173 /* @css is ready to be brought online now, make it visible */
5174 list_add_tail_rcu(&css->sibling, &parent_css->children);
5175 cgroup_idr_replace(&ss->css_idr, css, css->id);
5177 err = online_css(css);
5181 if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
5182 cgroup_parent(parent)) {
5183 pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
5184 current->comm, current->pid, ss->name);
5185 if (!strcmp(ss->name, "memory"))
5186 pr_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n");
5187 ss->warned_broken_hierarchy = true;
5193 list_del_rcu(&css->sibling);
5195 list_del_rcu(&css->rstat_css_node);
5196 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
5197 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
5198 return ERR_PTR(err);
5202 * The returned cgroup is fully initialized including its control mask, but
5203 * it isn't associated with its kernfs_node and doesn't have the control
5206 static struct cgroup *cgroup_create(struct cgroup *parent)
5208 struct cgroup_root *root = parent->root;
5209 struct cgroup *cgrp, *tcgrp;
5210 int level = parent->level + 1;
5213 /* allocate the cgroup and its ID, 0 is reserved for the root */
5214 cgrp = kzalloc(struct_size(cgrp, ancestor_ids, (level + 1)),
5217 return ERR_PTR(-ENOMEM);
5219 ret = percpu_ref_init(&cgrp->self.refcnt, css_release, 0, GFP_KERNEL);
5223 if (cgroup_on_dfl(parent)) {
5224 ret = cgroup_rstat_init(cgrp);
5226 goto out_cancel_ref;
5230 * Temporarily set the pointer to NULL, so idr_find() won't return
5231 * a half-baked cgroup.
5233 cgrp->id = cgroup_idr_alloc(&root->cgroup_idr, NULL, 2, 0, GFP_KERNEL);
5239 init_cgroup_housekeeping(cgrp);
5241 cgrp->self.parent = &parent->self;
5243 cgrp->level = level;
5245 ret = psi_cgroup_alloc(cgrp);
5249 ret = cgroup_bpf_inherit(cgrp);
5254 * New cgroup inherits effective freeze counter, and
5255 * if the parent has to be frozen, the child has too.
5257 cgrp->freezer.e_freeze = parent->freezer.e_freeze;
5258 if (cgrp->freezer.e_freeze) {
5260 * Set the CGRP_FREEZE flag, so when a process will be
5261 * attached to the child cgroup, it will become frozen.
5262 * At this point the new cgroup is unpopulated, so we can
5263 * consider it frozen immediately.
5265 set_bit(CGRP_FREEZE, &cgrp->flags);
5266 set_bit(CGRP_FROZEN, &cgrp->flags);
5269 spin_lock_irq(&css_set_lock);
5270 for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
5271 cgrp->ancestor_ids[tcgrp->level] = tcgrp->id;
5273 if (tcgrp != cgrp) {
5274 tcgrp->nr_descendants++;
5277 * If the new cgroup is frozen, all ancestor cgroups
5278 * get a new frozen descendant, but their state can't
5279 * change because of this.
5281 if (cgrp->freezer.e_freeze)
5282 tcgrp->freezer.nr_frozen_descendants++;
5285 spin_unlock_irq(&css_set_lock);
5287 if (notify_on_release(parent))
5288 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
5290 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
5291 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
5293 cgrp->self.serial_nr = css_serial_nr_next++;
5295 /* allocation complete, commit to creation */
5296 list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);
5297 atomic_inc(&root->nr_cgrps);
5298 cgroup_get_live(parent);
5301 * @cgrp is now fully operational. If something fails after this
5302 * point, it'll be released via the normal destruction path.
5304 cgroup_idr_replace(&root->cgroup_idr, cgrp, cgrp->id);
5307 * On the default hierarchy, a child doesn't automatically inherit
5308 * subtree_control from the parent. Each is configured manually.
5310 if (!cgroup_on_dfl(cgrp))
5311 cgrp->subtree_control = cgroup_control(cgrp);
5313 cgroup_propagate_control(cgrp);
5318 psi_cgroup_free(cgrp);
5320 cgroup_idr_remove(&root->cgroup_idr, cgrp->id);
5322 if (cgroup_on_dfl(parent))
5323 cgroup_rstat_exit(cgrp);
5325 percpu_ref_exit(&cgrp->self.refcnt);
5328 return ERR_PTR(ret);
5331 static bool cgroup_check_hierarchy_limits(struct cgroup *parent)
5333 struct cgroup *cgroup;
5337 lockdep_assert_held(&cgroup_mutex);
5339 for (cgroup = parent; cgroup; cgroup = cgroup_parent(cgroup)) {
5340 if (cgroup->nr_descendants >= cgroup->max_descendants)
5343 if (level > cgroup->max_depth)
5354 int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
5356 struct cgroup *parent, *cgrp;
5357 struct kernfs_node *kn;
5360 /* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
5361 if (strchr(name, '\n'))
5364 parent = cgroup_kn_lock_live(parent_kn, false);
5368 if (!cgroup_check_hierarchy_limits(parent)) {
5373 cgrp = cgroup_create(parent);
5375 ret = PTR_ERR(cgrp);
5379 /* create the directory */
5380 kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
5388 * This extra ref will be put in cgroup_free_fn() and guarantees
5389 * that @cgrp->kn is always accessible.
5393 ret = cgroup_kn_set_ugid(kn);
5397 ret = css_populate_dir(&cgrp->self);
5401 ret = cgroup_apply_control_enable(cgrp);
5405 TRACE_CGROUP_PATH(mkdir, cgrp);
5407 /* let's create and online css's */
5408 kernfs_activate(kn);
5414 cgroup_destroy_locked(cgrp);
5416 cgroup_kn_unlock(parent_kn);
5421 * This is called when the refcnt of a css is confirmed to be killed.
5422 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
5423 * initate destruction and put the css ref from kill_css().
5425 static void css_killed_work_fn(struct work_struct *work)
5427 struct cgroup_subsys_state *css =
5428 container_of(work, struct cgroup_subsys_state, destroy_work);
5430 mutex_lock(&cgroup_mutex);
5435 /* @css can't go away while we're holding cgroup_mutex */
5437 } while (css && atomic_dec_and_test(&css->online_cnt));
5439 mutex_unlock(&cgroup_mutex);
5442 /* css kill confirmation processing requires process context, bounce */
5443 static void css_killed_ref_fn(struct percpu_ref *ref)
5445 struct cgroup_subsys_state *css =
5446 container_of(ref, struct cgroup_subsys_state, refcnt);
5448 if (atomic_dec_and_test(&css->online_cnt)) {
5449 INIT_WORK(&css->destroy_work, css_killed_work_fn);
5450 queue_work(cgroup_destroy_wq, &css->destroy_work);
5455 * kill_css - destroy a css
5456 * @css: css to destroy
5458 * This function initiates destruction of @css by removing cgroup interface
5459 * files and putting its base reference. ->css_offline() will be invoked
5460 * asynchronously once css_tryget_online() is guaranteed to fail and when
5461 * the reference count reaches zero, @css will be released.
5463 static void kill_css(struct cgroup_subsys_state *css)
5465 lockdep_assert_held(&cgroup_mutex);
5467 if (css->flags & CSS_DYING)
5470 css->flags |= CSS_DYING;
5473 * This must happen before css is disassociated with its cgroup.
5474 * See seq_css() for details.
5479 * Killing would put the base ref, but we need to keep it alive
5480 * until after ->css_offline().
5485 * cgroup core guarantees that, by the time ->css_offline() is
5486 * invoked, no new css reference will be given out via
5487 * css_tryget_online(). We can't simply call percpu_ref_kill() and
5488 * proceed to offlining css's because percpu_ref_kill() doesn't
5489 * guarantee that the ref is seen as killed on all CPUs on return.
5491 * Use percpu_ref_kill_and_confirm() to get notifications as each
5492 * css is confirmed to be seen as killed on all CPUs.
5494 percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
5498 * cgroup_destroy_locked - the first stage of cgroup destruction
5499 * @cgrp: cgroup to be destroyed
5501 * css's make use of percpu refcnts whose killing latency shouldn't be
5502 * exposed to userland and are RCU protected. Also, cgroup core needs to
5503 * guarantee that css_tryget_online() won't succeed by the time
5504 * ->css_offline() is invoked. To satisfy all the requirements,
5505 * destruction is implemented in the following two steps.
5507 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
5508 * userland visible parts and start killing the percpu refcnts of
5509 * css's. Set up so that the next stage will be kicked off once all
5510 * the percpu refcnts are confirmed to be killed.
5512 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
5513 * rest of destruction. Once all cgroup references are gone, the
5514 * cgroup is RCU-freed.
5516 * This function implements s1. After this step, @cgrp is gone as far as
5517 * the userland is concerned and a new cgroup with the same name may be
5518 * created. As cgroup doesn't care about the names internally, this
5519 * doesn't cause any problem.
5521 static int cgroup_destroy_locked(struct cgroup *cgrp)
5522 __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
5524 struct cgroup *tcgrp, *parent = cgroup_parent(cgrp);
5525 struct cgroup_subsys_state *css;
5526 struct cgrp_cset_link *link;
5529 lockdep_assert_held(&cgroup_mutex);
5532 * Only migration can raise populated from zero and we're already
5533 * holding cgroup_mutex.
5535 if (cgroup_is_populated(cgrp))
5539 * Make sure there's no live children. We can't test emptiness of
5540 * ->self.children as dead children linger on it while being
5541 * drained; otherwise, "rmdir parent/child parent" may fail.
5543 if (css_has_online_children(&cgrp->self))
5547 * Mark @cgrp and the associated csets dead. The former prevents
5548 * further task migration and child creation by disabling
5549 * cgroup_lock_live_group(). The latter makes the csets ignored by
5550 * the migration path.
5552 cgrp->self.flags &= ~CSS_ONLINE;
5554 spin_lock_irq(&css_set_lock);
5555 list_for_each_entry(link, &cgrp->cset_links, cset_link)
5556 link->cset->dead = true;
5557 spin_unlock_irq(&css_set_lock);
5559 /* initiate massacre of all css's */
5560 for_each_css(css, ssid, cgrp)
5563 /* clear and remove @cgrp dir, @cgrp has an extra ref on its kn */
5564 css_clear_dir(&cgrp->self);
5565 kernfs_remove(cgrp->kn);
5567 if (parent && cgroup_is_threaded(cgrp))
5568 parent->nr_threaded_children--;
5570 spin_lock_irq(&css_set_lock);
5571 for (tcgrp = cgroup_parent(cgrp); tcgrp; tcgrp = cgroup_parent(tcgrp)) {
5572 tcgrp->nr_descendants--;
5573 tcgrp->nr_dying_descendants++;
5575 * If the dying cgroup is frozen, decrease frozen descendants
5576 * counters of ancestor cgroups.
5578 if (test_bit(CGRP_FROZEN, &cgrp->flags))
5579 tcgrp->freezer.nr_frozen_descendants--;
5581 spin_unlock_irq(&css_set_lock);
5583 cgroup1_check_for_release(parent);
5585 cgroup_bpf_offline(cgrp);
5587 /* put the base reference */
5588 percpu_ref_kill(&cgrp->self.refcnt);
5593 int cgroup_rmdir(struct kernfs_node *kn)
5595 struct cgroup *cgrp;
5598 cgrp = cgroup_kn_lock_live(kn, false);
5602 ret = cgroup_destroy_locked(cgrp);
5604 TRACE_CGROUP_PATH(rmdir, cgrp);
5606 cgroup_kn_unlock(kn);
5610 static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
5611 .show_options = cgroup_show_options,
5612 .mkdir = cgroup_mkdir,
5613 .rmdir = cgroup_rmdir,
5614 .show_path = cgroup_show_path,
5617 static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
5619 struct cgroup_subsys_state *css;
5621 pr_debug("Initializing cgroup subsys %s\n", ss->name);
5623 mutex_lock(&cgroup_mutex);
5625 idr_init(&ss->css_idr);
5626 INIT_LIST_HEAD(&ss->cfts);
5628 /* Create the root cgroup state for this subsystem */
5629 ss->root = &cgrp_dfl_root;
5630 css = ss->css_alloc(cgroup_css(&cgrp_dfl_root.cgrp, ss));
5631 /* We don't handle early failures gracefully */
5632 BUG_ON(IS_ERR(css));
5633 init_and_link_css(css, ss, &cgrp_dfl_root.cgrp);
5636 * Root csses are never destroyed and we can't initialize
5637 * percpu_ref during early init. Disable refcnting.
5639 css->flags |= CSS_NO_REF;
5642 /* allocation can't be done safely during early init */
5645 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL);
5646 BUG_ON(css->id < 0);
5649 /* Update the init_css_set to contain a subsys
5650 * pointer to this state - since the subsystem is
5651 * newly registered, all tasks and hence the
5652 * init_css_set is in the subsystem's root cgroup. */
5653 init_css_set.subsys[ss->id] = css;
5655 have_fork_callback |= (bool)ss->fork << ss->id;
5656 have_exit_callback |= (bool)ss->exit << ss->id;
5657 have_release_callback |= (bool)ss->release << ss->id;
5658 have_canfork_callback |= (bool)ss->can_fork << ss->id;
5660 /* At system boot, before all subsystems have been
5661 * registered, no tasks have been forked, so we don't
5662 * need to invoke fork callbacks here. */
5663 BUG_ON(!list_empty(&init_task.tasks));
5665 BUG_ON(online_css(css));
5667 mutex_unlock(&cgroup_mutex);
5671 * cgroup_init_early - cgroup initialization at system boot
5673 * Initialize cgroups at system boot, and initialize any
5674 * subsystems that request early init.
5676 int __init cgroup_init_early(void)
5678 static struct cgroup_fs_context __initdata ctx;
5679 struct cgroup_subsys *ss;
5682 ctx.root = &cgrp_dfl_root;
5683 init_cgroup_root(&ctx);
5684 cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF;
5686 RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
5688 for_each_subsys(ss, i) {
5689 WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
5690 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p id:name=%d:%s\n",
5691 i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
5693 WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
5694 "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
5697 ss->name = cgroup_subsys_name[i];
5698 if (!ss->legacy_name)
5699 ss->legacy_name = cgroup_subsys_name[i];
5702 cgroup_init_subsys(ss, true);
5707 static u16 cgroup_disable_mask __initdata;
5710 * cgroup_init - cgroup initialization
5712 * Register cgroup filesystem and /proc file, and initialize
5713 * any subsystems that didn't request early init.
5715 int __init cgroup_init(void)
5717 struct cgroup_subsys *ss;
5720 BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
5721 BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
5722 BUG_ON(cgroup_init_cftypes(NULL, cgroup1_base_files));
5724 cgroup_rstat_boot();
5727 * The latency of the synchronize_rcu() is too high for cgroups,
5728 * avoid it at the cost of forcing all readers into the slow path.
5730 rcu_sync_enter_start(&cgroup_threadgroup_rwsem.rss);
5732 get_user_ns(init_cgroup_ns.user_ns);
5734 mutex_lock(&cgroup_mutex);
5737 * Add init_css_set to the hash table so that dfl_root can link to
5740 hash_add(css_set_table, &init_css_set.hlist,
5741 css_set_hash(init_css_set.subsys));
5743 BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0));
5745 mutex_unlock(&cgroup_mutex);
5747 for_each_subsys(ss, ssid) {
5748 if (ss->early_init) {
5749 struct cgroup_subsys_state *css =
5750 init_css_set.subsys[ss->id];
5752 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2,
5754 BUG_ON(css->id < 0);
5756 cgroup_init_subsys(ss, false);
5759 list_add_tail(&init_css_set.e_cset_node[ssid],
5760 &cgrp_dfl_root.cgrp.e_csets[ssid]);
5763 * Setting dfl_root subsys_mask needs to consider the
5764 * disabled flag and cftype registration needs kmalloc,
5765 * both of which aren't available during early_init.
5767 if (cgroup_disable_mask & (1 << ssid)) {
5768 static_branch_disable(cgroup_subsys_enabled_key[ssid]);
5769 printk(KERN_INFO "Disabling %s control group subsystem\n",
5774 if (cgroup1_ssid_disabled(ssid))
5775 printk(KERN_INFO "Disabling %s control group subsystem in v1 mounts\n",
5778 cgrp_dfl_root.subsys_mask |= 1 << ss->id;
5780 /* implicit controllers must be threaded too */
5781 WARN_ON(ss->implicit_on_dfl && !ss->threaded);
5783 if (ss->implicit_on_dfl)
5784 cgrp_dfl_implicit_ss_mask |= 1 << ss->id;
5785 else if (!ss->dfl_cftypes)
5786 cgrp_dfl_inhibit_ss_mask |= 1 << ss->id;
5789 cgrp_dfl_threaded_ss_mask |= 1 << ss->id;
5791 if (ss->dfl_cftypes == ss->legacy_cftypes) {
5792 WARN_ON(cgroup_add_cftypes(ss, ss->dfl_cftypes));
5794 WARN_ON(cgroup_add_dfl_cftypes(ss, ss->dfl_cftypes));
5795 WARN_ON(cgroup_add_legacy_cftypes(ss, ss->legacy_cftypes));
5799 ss->bind(init_css_set.subsys[ssid]);
5801 mutex_lock(&cgroup_mutex);
5802 css_populate_dir(init_css_set.subsys[ssid]);
5803 mutex_unlock(&cgroup_mutex);
5806 /* init_css_set.subsys[] has been updated, re-hash */
5807 hash_del(&init_css_set.hlist);
5808 hash_add(css_set_table, &init_css_set.hlist,
5809 css_set_hash(init_css_set.subsys));
5811 WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup"));
5812 WARN_ON(register_filesystem(&cgroup_fs_type));
5813 WARN_ON(register_filesystem(&cgroup2_fs_type));
5814 WARN_ON(!proc_create_single("cgroups", 0, NULL, proc_cgroupstats_show));
5815 #ifdef CONFIG_CPUSETS
5816 WARN_ON(register_filesystem(&cpuset_fs_type));
5822 static int __init cgroup_wq_init(void)
5825 * There isn't much point in executing destruction path in
5826 * parallel. Good chunk is serialized with cgroup_mutex anyway.
5827 * Use 1 for @max_active.
5829 * We would prefer to do this in cgroup_init() above, but that
5830 * is called before init_workqueues(): so leave this until after.
5832 cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
5833 BUG_ON(!cgroup_destroy_wq);
5836 core_initcall(cgroup_wq_init);
5838 void cgroup_path_from_kernfs_id(const union kernfs_node_id *id,
5839 char *buf, size_t buflen)
5841 struct kernfs_node *kn;
5843 kn = kernfs_get_node_by_id(cgrp_dfl_root.kf_root, id);
5846 kernfs_path(kn, buf, buflen);
5851 * proc_cgroup_show()
5852 * - Print task's cgroup paths into seq_file, one line for each hierarchy
5853 * - Used for /proc/<pid>/cgroup.
5855 int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
5856 struct pid *pid, struct task_struct *tsk)
5860 struct cgroup_root *root;
5863 buf = kmalloc(PATH_MAX, GFP_KERNEL);
5867 mutex_lock(&cgroup_mutex);
5868 spin_lock_irq(&css_set_lock);
5870 for_each_root(root) {
5871 struct cgroup_subsys *ss;
5872 struct cgroup *cgrp;
5873 int ssid, count = 0;
5875 if (root == &cgrp_dfl_root && !cgrp_dfl_visible)
5878 seq_printf(m, "%d:", root->hierarchy_id);
5879 if (root != &cgrp_dfl_root)
5880 for_each_subsys(ss, ssid)
5881 if (root->subsys_mask & (1 << ssid))
5882 seq_printf(m, "%s%s", count++ ? "," : "",
5884 if (strlen(root->name))
5885 seq_printf(m, "%sname=%s", count ? "," : "",
5889 cgrp = task_cgroup_from_root(tsk, root);
5892 * On traditional hierarchies, all zombie tasks show up as
5893 * belonging to the root cgroup. On the default hierarchy,
5894 * while a zombie doesn't show up in "cgroup.procs" and
5895 * thus can't be migrated, its /proc/PID/cgroup keeps
5896 * reporting the cgroup it belonged to before exiting. If
5897 * the cgroup is removed before the zombie is reaped,
5898 * " (deleted)" is appended to the cgroup path.
5900 if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) {
5901 retval = cgroup_path_ns_locked(cgrp, buf, PATH_MAX,
5902 current->nsproxy->cgroup_ns);
5903 if (retval >= PATH_MAX)
5904 retval = -ENAMETOOLONG;
5913 if (cgroup_on_dfl(cgrp) && cgroup_is_dead(cgrp))
5914 seq_puts(m, " (deleted)\n");
5921 spin_unlock_irq(&css_set_lock);
5922 mutex_unlock(&cgroup_mutex);
5929 * cgroup_fork - initialize cgroup related fields during copy_process()
5930 * @child: pointer to task_struct of forking parent process.
5932 * A task is associated with the init_css_set until cgroup_post_fork()
5933 * attaches it to the parent's css_set. Empty cg_list indicates that
5934 * @child isn't holding reference to its css_set.
5936 void cgroup_fork(struct task_struct *child)
5938 RCU_INIT_POINTER(child->cgroups, &init_css_set);
5939 INIT_LIST_HEAD(&child->cg_list);
5943 * cgroup_can_fork - called on a new task before the process is exposed
5944 * @child: the task in question.
5946 * This calls the subsystem can_fork() callbacks. If the can_fork() callback
5947 * returns an error, the fork aborts with that error code. This allows for
5948 * a cgroup subsystem to conditionally allow or deny new forks.
5950 int cgroup_can_fork(struct task_struct *child)
5952 struct cgroup_subsys *ss;
5955 do_each_subsys_mask(ss, i, have_canfork_callback) {
5956 ret = ss->can_fork(child);
5959 } while_each_subsys_mask();
5964 for_each_subsys(ss, j) {
5967 if (ss->cancel_fork)
5968 ss->cancel_fork(child);
5975 * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
5976 * @child: the task in question
5978 * This calls the cancel_fork() callbacks if a fork failed *after*
5979 * cgroup_can_fork() succeded.
5981 void cgroup_cancel_fork(struct task_struct *child)
5983 struct cgroup_subsys *ss;
5986 for_each_subsys(ss, i)
5987 if (ss->cancel_fork)
5988 ss->cancel_fork(child);
5992 * cgroup_post_fork - called on a new task after adding it to the task list
5993 * @child: the task in question
5995 * Adds the task to the list running through its css_set if necessary and
5996 * call the subsystem fork() callbacks. Has to be after the task is
5997 * visible on the task list in case we race with the first call to
5998 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
6001 void cgroup_post_fork(struct task_struct *child)
6003 struct cgroup_subsys *ss;
6007 * This may race against cgroup_enable_task_cg_lists(). As that
6008 * function sets use_task_css_set_links before grabbing
6009 * tasklist_lock and we just went through tasklist_lock to add
6010 * @child, it's guaranteed that either we see the set
6011 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
6012 * @child during its iteration.
6014 * If we won the race, @child is associated with %current's
6015 * css_set. Grabbing css_set_lock guarantees both that the
6016 * association is stable, and, on completion of the parent's
6017 * migration, @child is visible in the source of migration or
6018 * already in the destination cgroup. This guarantee is necessary
6019 * when implementing operations which need to migrate all tasks of
6020 * a cgroup to another.
6022 * Note that if we lose to cgroup_enable_task_cg_lists(), @child
6023 * will remain in init_css_set. This is safe because all tasks are
6024 * in the init_css_set before cg_links is enabled and there's no
6025 * operation which transfers all tasks out of init_css_set.
6027 if (use_task_css_set_links) {
6028 struct css_set *cset;
6030 spin_lock_irq(&css_set_lock);
6031 cset = task_css_set(current);
6032 if (list_empty(&child->cg_list)) {
6035 css_set_move_task(child, NULL, cset, false);
6039 * If the cgroup has to be frozen, the new task has too.
6040 * Let's set the JOBCTL_TRAP_FREEZE jobctl bit to get
6041 * the task into the frozen state.
6043 if (unlikely(cgroup_task_freeze(child))) {
6044 spin_lock(&child->sighand->siglock);
6045 WARN_ON_ONCE(child->frozen);
6046 child->jobctl |= JOBCTL_TRAP_FREEZE;
6047 spin_unlock(&child->sighand->siglock);
6050 * Calling cgroup_update_frozen() isn't required here,
6051 * because it will be called anyway a bit later
6052 * from do_freezer_trap(). So we avoid cgroup's
6053 * transient switch from the frozen state and back.
6057 spin_unlock_irq(&css_set_lock);
6061 * Call ss->fork(). This must happen after @child is linked on
6062 * css_set; otherwise, @child might change state between ->fork()
6063 * and addition to css_set.
6065 do_each_subsys_mask(ss, i, have_fork_callback) {
6067 } while_each_subsys_mask();
6071 * cgroup_exit - detach cgroup from exiting task
6072 * @tsk: pointer to task_struct of exiting process
6074 * Description: Detach cgroup from @tsk and release it.
6076 * Note that cgroups marked notify_on_release force every task in
6077 * them to take the global cgroup_mutex mutex when exiting.
6078 * This could impact scaling on very large systems. Be reluctant to
6079 * use notify_on_release cgroups where very high task exit scaling
6080 * is required on large systems.
6082 * We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
6083 * call cgroup_exit() while the task is still competent to handle
6084 * notify_on_release(), then leave the task attached to the root cgroup in
6085 * each hierarchy for the remainder of its exit. No need to bother with
6086 * init_css_set refcnting. init_css_set never goes away and we can't race
6087 * with migration path - PF_EXITING is visible to migration path.
6089 void cgroup_exit(struct task_struct *tsk)
6091 struct cgroup_subsys *ss;
6092 struct css_set *cset;
6096 * Unlink from @tsk from its css_set. As migration path can't race
6097 * with us, we can check css_set and cg_list without synchronization.
6099 cset = task_css_set(tsk);
6101 if (!list_empty(&tsk->cg_list)) {
6102 spin_lock_irq(&css_set_lock);
6103 css_set_move_task(tsk, cset, NULL, false);
6104 list_add_tail(&tsk->cg_list, &cset->dying_tasks);
6107 WARN_ON_ONCE(cgroup_task_frozen(tsk));
6108 if (unlikely(cgroup_task_freeze(tsk)))
6109 cgroup_update_frozen(task_dfl_cgroup(tsk));
6111 spin_unlock_irq(&css_set_lock);
6116 /* see cgroup_post_fork() for details */
6117 do_each_subsys_mask(ss, i, have_exit_callback) {
6119 } while_each_subsys_mask();
6122 void cgroup_release(struct task_struct *task)
6124 struct cgroup_subsys *ss;
6127 do_each_subsys_mask(ss, ssid, have_release_callback) {
6129 } while_each_subsys_mask();
6131 if (use_task_css_set_links) {
6132 spin_lock_irq(&css_set_lock);
6133 css_set_skip_task_iters(task_css_set(task), task);
6134 list_del_init(&task->cg_list);
6135 spin_unlock_irq(&css_set_lock);
6139 void cgroup_free(struct task_struct *task)
6141 struct css_set *cset = task_css_set(task);
6145 static int __init cgroup_disable(char *str)
6147 struct cgroup_subsys *ss;
6151 while ((token = strsep(&str, ",")) != NULL) {
6155 for_each_subsys(ss, i) {
6156 if (strcmp(token, ss->name) &&
6157 strcmp(token, ss->legacy_name))
6159 cgroup_disable_mask |= 1 << i;
6164 __setup("cgroup_disable=", cgroup_disable);
6166 void __init __weak enable_debug_cgroup(void) { }
6168 static int __init enable_cgroup_debug(char *str)
6170 cgroup_debug = true;
6171 enable_debug_cgroup();
6174 __setup("cgroup_debug", enable_cgroup_debug);
6177 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
6178 * @dentry: directory dentry of interest
6179 * @ss: subsystem of interest
6181 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
6182 * to get the corresponding css and return it. If such css doesn't exist
6183 * or can't be pinned, an ERR_PTR value is returned.
6185 struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
6186 struct cgroup_subsys *ss)
6188 struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
6189 struct file_system_type *s_type = dentry->d_sb->s_type;
6190 struct cgroup_subsys_state *css = NULL;
6191 struct cgroup *cgrp;
6193 /* is @dentry a cgroup dir? */
6194 if ((s_type != &cgroup_fs_type && s_type != &cgroup2_fs_type) ||
6195 !kn || kernfs_type(kn) != KERNFS_DIR)
6196 return ERR_PTR(-EBADF);
6201 * This path doesn't originate from kernfs and @kn could already
6202 * have been or be removed at any point. @kn->priv is RCU
6203 * protected for this access. See css_release_work_fn() for details.
6205 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6207 css = cgroup_css(cgrp, ss);
6209 if (!css || !css_tryget_online(css))
6210 css = ERR_PTR(-ENOENT);
6217 * css_from_id - lookup css by id
6218 * @id: the cgroup id
6219 * @ss: cgroup subsys to be looked into
6221 * Returns the css if there's valid one with @id, otherwise returns NULL.
6222 * Should be called under rcu_read_lock().
6224 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
6226 WARN_ON_ONCE(!rcu_read_lock_held());
6227 return idr_find(&ss->css_idr, id);
6231 * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path
6232 * @path: path on the default hierarchy
6234 * Find the cgroup at @path on the default hierarchy, increment its
6235 * reference count and return it. Returns pointer to the found cgroup on
6236 * success, ERR_PTR(-ENOENT) if @path doens't exist and ERR_PTR(-ENOTDIR)
6237 * if @path points to a non-directory.
6239 struct cgroup *cgroup_get_from_path(const char *path)
6241 struct kernfs_node *kn;
6242 struct cgroup *cgrp;
6244 mutex_lock(&cgroup_mutex);
6246 kn = kernfs_walk_and_get(cgrp_dfl_root.cgrp.kn, path);
6248 if (kernfs_type(kn) == KERNFS_DIR) {
6250 cgroup_get_live(cgrp);
6252 cgrp = ERR_PTR(-ENOTDIR);
6256 cgrp = ERR_PTR(-ENOENT);
6259 mutex_unlock(&cgroup_mutex);
6262 EXPORT_SYMBOL_GPL(cgroup_get_from_path);
6265 * cgroup_get_from_fd - get a cgroup pointer from a fd
6266 * @fd: fd obtained by open(cgroup2_dir)
6268 * Find the cgroup from a fd which should be obtained
6269 * by opening a cgroup directory. Returns a pointer to the
6270 * cgroup on success. ERR_PTR is returned if the cgroup
6273 struct cgroup *cgroup_get_from_fd(int fd)
6275 struct cgroup_subsys_state *css;
6276 struct cgroup *cgrp;
6281 return ERR_PTR(-EBADF);
6283 css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
6286 return ERR_CAST(css);
6289 if (!cgroup_on_dfl(cgrp)) {
6291 return ERR_PTR(-EBADF);
6296 EXPORT_SYMBOL_GPL(cgroup_get_from_fd);
6298 static u64 power_of_ten(int power)
6307 * cgroup_parse_float - parse a floating number
6308 * @input: input string
6309 * @dec_shift: number of decimal digits to shift
6312 * Parse a decimal floating point number in @input and store the result in
6313 * @v with decimal point right shifted @dec_shift times. For example, if
6314 * @input is "12.3456" and @dec_shift is 3, *@v will be set to 12345.
6315 * Returns 0 on success, -errno otherwise.
6317 * There's nothing cgroup specific about this function except that it's
6318 * currently the only user.
6320 int cgroup_parse_float(const char *input, unsigned dec_shift, s64 *v)
6322 s64 whole, frac = 0;
6323 int fstart = 0, fend = 0, flen;
6325 if (!sscanf(input, "%lld.%n%lld%n", &whole, &fstart, &frac, &fend))
6330 flen = fend > fstart ? fend - fstart : 0;
6331 if (flen < dec_shift)
6332 frac *= power_of_ten(dec_shift - flen);
6334 frac = DIV_ROUND_CLOSEST_ULL(frac, power_of_ten(flen - dec_shift));
6336 *v = whole * power_of_ten(dec_shift) + frac;
6341 * sock->sk_cgrp_data handling. For more info, see sock_cgroup_data
6342 * definition in cgroup-defs.h.
6344 #ifdef CONFIG_SOCK_CGROUP_DATA
6346 #if defined(CONFIG_CGROUP_NET_PRIO) || defined(CONFIG_CGROUP_NET_CLASSID)
6348 DEFINE_SPINLOCK(cgroup_sk_update_lock);
6349 static bool cgroup_sk_alloc_disabled __read_mostly;
6351 void cgroup_sk_alloc_disable(void)
6353 if (cgroup_sk_alloc_disabled)
6355 pr_info("cgroup: disabling cgroup2 socket matching due to net_prio or net_cls activation\n");
6356 cgroup_sk_alloc_disabled = true;
6361 #define cgroup_sk_alloc_disabled false
6365 void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
6367 if (cgroup_sk_alloc_disabled)
6370 /* Socket clone path */
6373 * We might be cloning a socket which is left in an empty
6374 * cgroup and the cgroup might have already been rmdir'd.
6375 * Don't use cgroup_get_live().
6377 cgroup_get(sock_cgroup_ptr(skcd));
6378 cgroup_bpf_get(sock_cgroup_ptr(skcd));
6385 struct css_set *cset;
6387 cset = task_css_set(current);
6388 if (likely(cgroup_tryget(cset->dfl_cgrp))) {
6389 skcd->val = (unsigned long)cset->dfl_cgrp;
6390 cgroup_bpf_get(cset->dfl_cgrp);
6399 void cgroup_sk_free(struct sock_cgroup_data *skcd)
6401 struct cgroup *cgrp = sock_cgroup_ptr(skcd);
6403 cgroup_bpf_put(cgrp);
6407 #endif /* CONFIG_SOCK_CGROUP_DATA */
6409 #ifdef CONFIG_CGROUP_BPF
6410 int cgroup_bpf_attach(struct cgroup *cgrp, struct bpf_prog *prog,
6411 enum bpf_attach_type type, u32 flags)
6415 mutex_lock(&cgroup_mutex);
6416 ret = __cgroup_bpf_attach(cgrp, prog, type, flags);
6417 mutex_unlock(&cgroup_mutex);
6420 int cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
6421 enum bpf_attach_type type, u32 flags)
6425 mutex_lock(&cgroup_mutex);
6426 ret = __cgroup_bpf_detach(cgrp, prog, type);
6427 mutex_unlock(&cgroup_mutex);
6430 int cgroup_bpf_query(struct cgroup *cgrp, const union bpf_attr *attr,
6431 union bpf_attr __user *uattr)
6435 mutex_lock(&cgroup_mutex);
6436 ret = __cgroup_bpf_query(cgrp, attr, uattr);
6437 mutex_unlock(&cgroup_mutex);
6440 #endif /* CONFIG_CGROUP_BPF */
6443 static ssize_t show_delegatable_files(struct cftype *files, char *buf,
6444 ssize_t size, const char *prefix)
6449 for (cft = files; cft && cft->name[0] != '\0'; cft++) {
6450 if (!(cft->flags & CFTYPE_NS_DELEGATABLE))
6454 ret += snprintf(buf + ret, size - ret, "%s.", prefix);
6456 ret += snprintf(buf + ret, size - ret, "%s\n", cft->name);
6458 if (WARN_ON(ret >= size))
6465 static ssize_t delegate_show(struct kobject *kobj, struct kobj_attribute *attr,
6468 struct cgroup_subsys *ss;
6472 ret = show_delegatable_files(cgroup_base_files, buf, PAGE_SIZE - ret,
6475 for_each_subsys(ss, ssid)
6476 ret += show_delegatable_files(ss->dfl_cftypes, buf + ret,
6478 cgroup_subsys_name[ssid]);
6482 static struct kobj_attribute cgroup_delegate_attr = __ATTR_RO(delegate);
6484 static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr,
6487 return snprintf(buf, PAGE_SIZE, "nsdelegate\nmemory_localevents\n");
6489 static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features);
6491 static struct attribute *cgroup_sysfs_attrs[] = {
6492 &cgroup_delegate_attr.attr,
6493 &cgroup_features_attr.attr,
6497 static const struct attribute_group cgroup_sysfs_attr_group = {
6498 .attrs = cgroup_sysfs_attrs,
6502 static int __init cgroup_sysfs_init(void)
6504 return sysfs_create_group(kernel_kobj, &cgroup_sysfs_attr_group);
6506 subsys_initcall(cgroup_sysfs_init);
6508 #endif /* CONFIG_SYSFS */