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/bpf-cgroup.h>
34 #include <linux/cred.h>
35 #include <linux/errno.h>
36 #include <linux/init_task.h>
37 #include <linux/kernel.h>
38 #include <linux/magic.h>
39 #include <linux/mutex.h>
40 #include <linux/mount.h>
41 #include <linux/pagemap.h>
42 #include <linux/proc_fs.h>
43 #include <linux/rcupdate.h>
44 #include <linux/sched.h>
45 #include <linux/sched/task.h>
46 #include <linux/slab.h>
47 #include <linux/spinlock.h>
48 #include <linux/percpu-rwsem.h>
49 #include <linux/string.h>
50 #include <linux/hashtable.h>
51 #include <linux/idr.h>
52 #include <linux/kthread.h>
53 #include <linux/atomic.h>
54 #include <linux/cpuset.h>
55 #include <linux/proc_ns.h>
56 #include <linux/nsproxy.h>
57 #include <linux/file.h>
58 #include <linux/fs_parser.h>
59 #include <linux/sched/cputime.h>
60 #include <linux/psi.h>
63 #define CREATE_TRACE_POINTS
64 #include <trace/events/cgroup.h>
66 #define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
68 /* let's not notify more than 100 times per second */
69 #define CGROUP_FILE_NOTIFY_MIN_INTV DIV_ROUND_UP(HZ, 100)
72 * To avoid confusing the compiler (and generating warnings) with code
73 * that attempts to access what would be a 0-element array (i.e. sized
74 * to a potentially empty array when CGROUP_SUBSYS_COUNT == 0), this
75 * constant expression can be added.
77 #define CGROUP_HAS_SUBSYS_CONFIG (CGROUP_SUBSYS_COUNT > 0)
80 * cgroup_mutex is the master lock. Any modification to cgroup or its
81 * hierarchy must be performed while holding it.
83 * css_set_lock protects task->cgroups pointer, the list of css_set
84 * objects, and the chain of tasks off each css_set.
86 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
87 * cgroup.h can use them for lockdep annotations.
89 DEFINE_MUTEX(cgroup_mutex);
90 DEFINE_SPINLOCK(css_set_lock);
92 #ifdef CONFIG_PROVE_RCU
93 EXPORT_SYMBOL_GPL(cgroup_mutex);
94 EXPORT_SYMBOL_GPL(css_set_lock);
97 DEFINE_SPINLOCK(trace_cgroup_path_lock);
98 char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
99 static bool cgroup_debug __read_mostly;
102 * Protects cgroup_idr and css_idr so that IDs can be released without
103 * grabbing cgroup_mutex.
105 static DEFINE_SPINLOCK(cgroup_idr_lock);
108 * Protects cgroup_file->kn for !self csses. It synchronizes notifications
109 * against file removal/re-creation across css hiding.
111 static DEFINE_SPINLOCK(cgroup_file_kn_lock);
113 DEFINE_PERCPU_RWSEM(cgroup_threadgroup_rwsem);
115 #define cgroup_assert_mutex_or_rcu_locked() \
116 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
117 !lockdep_is_held(&cgroup_mutex), \
118 "cgroup_mutex or RCU read lock required");
121 * cgroup destruction makes heavy use of work items and there can be a lot
122 * of concurrent destructions. Use a separate workqueue so that cgroup
123 * destruction work items don't end up filling up max_active of system_wq
124 * which may lead to deadlock.
126 static struct workqueue_struct *cgroup_destroy_wq;
128 /* generate an array of cgroup subsystem pointers */
129 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
130 struct cgroup_subsys *cgroup_subsys[] = {
131 #include <linux/cgroup_subsys.h>
135 /* array of cgroup subsystem names */
136 #define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
137 static const char *cgroup_subsys_name[] = {
138 #include <linux/cgroup_subsys.h>
142 /* array of static_keys for cgroup_subsys_enabled() and cgroup_subsys_on_dfl() */
144 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key); \
145 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key); \
146 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key); \
147 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key);
148 #include <linux/cgroup_subsys.h>
151 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_enabled_key,
152 static struct static_key_true *cgroup_subsys_enabled_key[] = {
153 #include <linux/cgroup_subsys.h>
157 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_on_dfl_key,
158 static struct static_key_true *cgroup_subsys_on_dfl_key[] = {
159 #include <linux/cgroup_subsys.h>
163 static DEFINE_PER_CPU(struct cgroup_rstat_cpu, cgrp_dfl_root_rstat_cpu);
165 /* the default hierarchy */
166 struct cgroup_root cgrp_dfl_root = { .cgrp.rstat_cpu = &cgrp_dfl_root_rstat_cpu };
167 EXPORT_SYMBOL_GPL(cgrp_dfl_root);
170 * The default hierarchy always exists but is hidden until mounted for the
171 * first time. This is for backward compatibility.
173 static bool cgrp_dfl_visible;
175 /* some controllers are not supported in the default hierarchy */
176 static u16 cgrp_dfl_inhibit_ss_mask;
178 /* some controllers are implicitly enabled on the default hierarchy */
179 static u16 cgrp_dfl_implicit_ss_mask;
181 /* some controllers can be threaded on the default hierarchy */
182 static u16 cgrp_dfl_threaded_ss_mask;
184 /* The list of hierarchy roots */
185 LIST_HEAD(cgroup_roots);
186 static int cgroup_root_count;
188 /* hierarchy ID allocation and mapping, protected by cgroup_mutex */
189 static DEFINE_IDR(cgroup_hierarchy_idr);
192 * Assign a monotonically increasing serial number to csses. It guarantees
193 * cgroups with bigger numbers are newer than those with smaller numbers.
194 * Also, as csses are always appended to the parent's ->children list, it
195 * guarantees that sibling csses are always sorted in the ascending serial
196 * number order on the list. Protected by cgroup_mutex.
198 static u64 css_serial_nr_next = 1;
201 * These bitmasks identify subsystems with specific features to avoid
202 * having to do iterative checks repeatedly.
204 static u16 have_fork_callback __read_mostly;
205 static u16 have_exit_callback __read_mostly;
206 static u16 have_release_callback __read_mostly;
207 static u16 have_canfork_callback __read_mostly;
209 /* cgroup namespace for init task */
210 struct cgroup_namespace init_cgroup_ns = {
211 .ns.count = REFCOUNT_INIT(2),
212 .user_ns = &init_user_ns,
213 .ns.ops = &cgroupns_operations,
214 .ns.inum = PROC_CGROUP_INIT_INO,
215 .root_cset = &init_css_set,
218 static struct file_system_type cgroup2_fs_type;
219 static struct cftype cgroup_base_files[];
221 /* cgroup optional features */
222 enum cgroup_opt_features {
224 OPT_FEATURE_PRESSURE,
229 static const char *cgroup_opt_feature_names[OPT_FEATURE_COUNT] = {
235 static u16 cgroup_feature_disable_mask __read_mostly;
237 static int cgroup_apply_control(struct cgroup *cgrp);
238 static void cgroup_finalize_control(struct cgroup *cgrp, int ret);
239 static void css_task_iter_skip(struct css_task_iter *it,
240 struct task_struct *task);
241 static int cgroup_destroy_locked(struct cgroup *cgrp);
242 static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
243 struct cgroup_subsys *ss);
244 static void css_release(struct percpu_ref *ref);
245 static void kill_css(struct cgroup_subsys_state *css);
246 static int cgroup_addrm_files(struct cgroup_subsys_state *css,
247 struct cgroup *cgrp, struct cftype cfts[],
251 * cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID
252 * @ssid: subsys ID of interest
254 * cgroup_subsys_enabled() can only be used with literal subsys names which
255 * is fine for individual subsystems but unsuitable for cgroup core. This
256 * is slower static_key_enabled() based test indexed by @ssid.
258 bool cgroup_ssid_enabled(int ssid)
260 if (!CGROUP_HAS_SUBSYS_CONFIG)
263 return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
267 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
268 * @cgrp: the cgroup of interest
270 * The default hierarchy is the v2 interface of cgroup and this function
271 * can be used to test whether a cgroup is on the default hierarchy for
272 * cases where a subsystem should behave differently depending on the
275 * List of changed behaviors:
277 * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
278 * and "name" are disallowed.
280 * - When mounting an existing superblock, mount options should match.
282 * - rename(2) is disallowed.
284 * - "tasks" is removed. Everything should be at process granularity. Use
285 * "cgroup.procs" instead.
287 * - "cgroup.procs" is not sorted. pids will be unique unless they got
288 * recycled in-between reads.
290 * - "release_agent" and "notify_on_release" are removed. Replacement
291 * notification mechanism will be implemented.
293 * - "cgroup.clone_children" is removed.
295 * - "cgroup.subtree_populated" is available. Its value is 0 if the cgroup
296 * and its descendants contain no task; otherwise, 1. The file also
297 * generates kernfs notification which can be monitored through poll and
298 * [di]notify when the value of the file changes.
300 * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
301 * take masks of ancestors with non-empty cpus/mems, instead of being
302 * moved to an ancestor.
304 * - cpuset: a task can be moved into an empty cpuset, and again it takes
305 * masks of ancestors.
307 * - blkcg: blk-throttle becomes properly hierarchical.
309 * - debug: disallowed on the default hierarchy.
311 bool cgroup_on_dfl(const struct cgroup *cgrp)
313 return cgrp->root == &cgrp_dfl_root;
316 /* IDR wrappers which synchronize using cgroup_idr_lock */
317 static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
322 idr_preload(gfp_mask);
323 spin_lock_bh(&cgroup_idr_lock);
324 ret = idr_alloc(idr, ptr, start, end, gfp_mask & ~__GFP_DIRECT_RECLAIM);
325 spin_unlock_bh(&cgroup_idr_lock);
330 static void *cgroup_idr_replace(struct idr *idr, void *ptr, int id)
334 spin_lock_bh(&cgroup_idr_lock);
335 ret = idr_replace(idr, ptr, id);
336 spin_unlock_bh(&cgroup_idr_lock);
340 static void cgroup_idr_remove(struct idr *idr, int id)
342 spin_lock_bh(&cgroup_idr_lock);
344 spin_unlock_bh(&cgroup_idr_lock);
347 static bool cgroup_has_tasks(struct cgroup *cgrp)
349 return cgrp->nr_populated_csets;
352 bool cgroup_is_threaded(struct cgroup *cgrp)
354 return cgrp->dom_cgrp != cgrp;
357 /* can @cgrp host both domain and threaded children? */
358 static bool cgroup_is_mixable(struct cgroup *cgrp)
361 * Root isn't under domain level resource control exempting it from
362 * the no-internal-process constraint, so it can serve as a thread
363 * root and a parent of resource domains at the same time.
365 return !cgroup_parent(cgrp);
368 /* can @cgrp become a thread root? Should always be true for a thread root */
369 static bool cgroup_can_be_thread_root(struct cgroup *cgrp)
371 /* mixables don't care */
372 if (cgroup_is_mixable(cgrp))
375 /* domain roots can't be nested under threaded */
376 if (cgroup_is_threaded(cgrp))
379 /* can only have either domain or threaded children */
380 if (cgrp->nr_populated_domain_children)
383 /* and no domain controllers can be enabled */
384 if (cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)
390 /* is @cgrp root of a threaded subtree? */
391 bool cgroup_is_thread_root(struct cgroup *cgrp)
393 /* thread root should be a domain */
394 if (cgroup_is_threaded(cgrp))
397 /* a domain w/ threaded children is a thread root */
398 if (cgrp->nr_threaded_children)
402 * A domain which has tasks and explicit threaded controllers
403 * enabled is a thread root.
405 if (cgroup_has_tasks(cgrp) &&
406 (cgrp->subtree_control & cgrp_dfl_threaded_ss_mask))
412 /* a domain which isn't connected to the root w/o brekage can't be used */
413 static bool cgroup_is_valid_domain(struct cgroup *cgrp)
415 /* the cgroup itself can be a thread root */
416 if (cgroup_is_threaded(cgrp))
419 /* but the ancestors can't be unless mixable */
420 while ((cgrp = cgroup_parent(cgrp))) {
421 if (!cgroup_is_mixable(cgrp) && cgroup_is_thread_root(cgrp))
423 if (cgroup_is_threaded(cgrp))
430 /* subsystems visibly enabled on a cgroup */
431 static u16 cgroup_control(struct cgroup *cgrp)
433 struct cgroup *parent = cgroup_parent(cgrp);
434 u16 root_ss_mask = cgrp->root->subsys_mask;
437 u16 ss_mask = parent->subtree_control;
439 /* threaded cgroups can only have threaded controllers */
440 if (cgroup_is_threaded(cgrp))
441 ss_mask &= cgrp_dfl_threaded_ss_mask;
445 if (cgroup_on_dfl(cgrp))
446 root_ss_mask &= ~(cgrp_dfl_inhibit_ss_mask |
447 cgrp_dfl_implicit_ss_mask);
451 /* subsystems enabled on a cgroup */
452 static u16 cgroup_ss_mask(struct cgroup *cgrp)
454 struct cgroup *parent = cgroup_parent(cgrp);
457 u16 ss_mask = parent->subtree_ss_mask;
459 /* threaded cgroups can only have threaded controllers */
460 if (cgroup_is_threaded(cgrp))
461 ss_mask &= cgrp_dfl_threaded_ss_mask;
465 return cgrp->root->subsys_mask;
469 * cgroup_css - obtain a cgroup's css for the specified subsystem
470 * @cgrp: the cgroup of interest
471 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
473 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
474 * function must be called either under cgroup_mutex or rcu_read_lock() and
475 * the caller is responsible for pinning the returned css if it wants to
476 * keep accessing it outside the said locks. This function may return
477 * %NULL if @cgrp doesn't have @subsys_id enabled.
479 static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
480 struct cgroup_subsys *ss)
482 if (CGROUP_HAS_SUBSYS_CONFIG && ss)
483 return rcu_dereference_check(cgrp->subsys[ss->id],
484 lockdep_is_held(&cgroup_mutex));
490 * cgroup_tryget_css - try to get a cgroup's css for the specified subsystem
491 * @cgrp: the cgroup of interest
492 * @ss: the subsystem of interest
494 * Find and get @cgrp's css associated with @ss. If the css doesn't exist
495 * or is offline, %NULL is returned.
497 static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp,
498 struct cgroup_subsys *ss)
500 struct cgroup_subsys_state *css;
503 css = cgroup_css(cgrp, ss);
504 if (css && !css_tryget_online(css))
512 * cgroup_e_css_by_mask - obtain a cgroup's effective css for the specified ss
513 * @cgrp: the cgroup of interest
514 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
516 * Similar to cgroup_css() but returns the effective css, which is defined
517 * as the matching css of the nearest ancestor including self which has @ss
518 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
519 * function is guaranteed to return non-NULL css.
521 static struct cgroup_subsys_state *cgroup_e_css_by_mask(struct cgroup *cgrp,
522 struct cgroup_subsys *ss)
524 lockdep_assert_held(&cgroup_mutex);
530 * This function is used while updating css associations and thus
531 * can't test the csses directly. Test ss_mask.
533 while (!(cgroup_ss_mask(cgrp) & (1 << ss->id))) {
534 cgrp = cgroup_parent(cgrp);
539 return cgroup_css(cgrp, ss);
543 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
544 * @cgrp: the cgroup of interest
545 * @ss: the subsystem of interest
547 * Find and get the effective css of @cgrp for @ss. The effective css is
548 * defined as the matching css of the nearest ancestor including self which
549 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
550 * the root css is returned, so this function always returns a valid css.
552 * The returned css is not guaranteed to be online, and therefore it is the
553 * callers responsibility to try get a reference for it.
555 struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
556 struct cgroup_subsys *ss)
558 struct cgroup_subsys_state *css;
560 if (!CGROUP_HAS_SUBSYS_CONFIG)
564 css = cgroup_css(cgrp, ss);
568 cgrp = cgroup_parent(cgrp);
571 return init_css_set.subsys[ss->id];
575 * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
576 * @cgrp: the cgroup of interest
577 * @ss: the subsystem of interest
579 * Find and get the effective css of @cgrp for @ss. The effective css is
580 * defined as the matching css of the nearest ancestor including self which
581 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
582 * the root css is returned, so this function always returns a valid css.
583 * The returned css must be put using css_put().
585 struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
586 struct cgroup_subsys *ss)
588 struct cgroup_subsys_state *css;
590 if (!CGROUP_HAS_SUBSYS_CONFIG)
596 css = cgroup_css(cgrp, ss);
598 if (css && css_tryget_online(css))
600 cgrp = cgroup_parent(cgrp);
603 css = init_css_set.subsys[ss->id];
609 EXPORT_SYMBOL_GPL(cgroup_get_e_css);
611 static void cgroup_get_live(struct cgroup *cgrp)
613 WARN_ON_ONCE(cgroup_is_dead(cgrp));
614 css_get(&cgrp->self);
618 * __cgroup_task_count - count the number of tasks in a cgroup. The caller
619 * is responsible for taking the css_set_lock.
620 * @cgrp: the cgroup in question
622 int __cgroup_task_count(const struct cgroup *cgrp)
625 struct cgrp_cset_link *link;
627 lockdep_assert_held(&css_set_lock);
629 list_for_each_entry(link, &cgrp->cset_links, cset_link)
630 count += link->cset->nr_tasks;
636 * cgroup_task_count - count the number of tasks in a cgroup.
637 * @cgrp: the cgroup in question
639 int cgroup_task_count(const struct cgroup *cgrp)
643 spin_lock_irq(&css_set_lock);
644 count = __cgroup_task_count(cgrp);
645 spin_unlock_irq(&css_set_lock);
650 struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
652 struct cgroup *cgrp = of->kn->parent->priv;
653 struct cftype *cft = of_cft(of);
656 * This is open and unprotected implementation of cgroup_css().
657 * seq_css() is only called from a kernfs file operation which has
658 * an active reference on the file. Because all the subsystem
659 * files are drained before a css is disassociated with a cgroup,
660 * the matching css from the cgroup's subsys table is guaranteed to
661 * be and stay valid until the enclosing operation is complete.
663 if (CGROUP_HAS_SUBSYS_CONFIG && cft->ss)
664 return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
668 EXPORT_SYMBOL_GPL(of_css);
671 * for_each_css - iterate all css's of a cgroup
672 * @css: the iteration cursor
673 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
674 * @cgrp: the target cgroup to iterate css's of
676 * Should be called under cgroup_[tree_]mutex.
678 #define for_each_css(css, ssid, cgrp) \
679 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
680 if (!((css) = rcu_dereference_check( \
681 (cgrp)->subsys[(ssid)], \
682 lockdep_is_held(&cgroup_mutex)))) { } \
686 * for_each_e_css - iterate all effective css's of a cgroup
687 * @css: the iteration cursor
688 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
689 * @cgrp: the target cgroup to iterate css's of
691 * Should be called under cgroup_[tree_]mutex.
693 #define for_each_e_css(css, ssid, cgrp) \
694 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
695 if (!((css) = cgroup_e_css_by_mask(cgrp, \
696 cgroup_subsys[(ssid)]))) \
701 * do_each_subsys_mask - filter for_each_subsys with a bitmask
702 * @ss: the iteration cursor
703 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
704 * @ss_mask: the bitmask
706 * The block will only run for cases where the ssid-th bit (1 << ssid) of
709 #define do_each_subsys_mask(ss, ssid, ss_mask) do { \
710 unsigned long __ss_mask = (ss_mask); \
711 if (!CGROUP_HAS_SUBSYS_CONFIG) { \
715 for_each_set_bit(ssid, &__ss_mask, CGROUP_SUBSYS_COUNT) { \
716 (ss) = cgroup_subsys[ssid]; \
719 #define while_each_subsys_mask() \
724 /* iterate over child cgrps, lock should be held throughout iteration */
725 #define cgroup_for_each_live_child(child, cgrp) \
726 list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
727 if (({ lockdep_assert_held(&cgroup_mutex); \
728 cgroup_is_dead(child); })) \
732 /* walk live descendants in pre order */
733 #define cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) \
734 css_for_each_descendant_pre((d_css), cgroup_css((cgrp), NULL)) \
735 if (({ lockdep_assert_held(&cgroup_mutex); \
736 (dsct) = (d_css)->cgroup; \
737 cgroup_is_dead(dsct); })) \
741 /* walk live descendants in postorder */
742 #define cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) \
743 css_for_each_descendant_post((d_css), cgroup_css((cgrp), NULL)) \
744 if (({ lockdep_assert_held(&cgroup_mutex); \
745 (dsct) = (d_css)->cgroup; \
746 cgroup_is_dead(dsct); })) \
751 * The default css_set - used by init and its children prior to any
752 * hierarchies being mounted. It contains a pointer to the root state
753 * for each subsystem. Also used to anchor the list of css_sets. Not
754 * reference-counted, to improve performance when child cgroups
755 * haven't been created.
757 struct css_set init_css_set = {
758 .refcount = REFCOUNT_INIT(1),
759 .dom_cset = &init_css_set,
760 .tasks = LIST_HEAD_INIT(init_css_set.tasks),
761 .mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
762 .dying_tasks = LIST_HEAD_INIT(init_css_set.dying_tasks),
763 .task_iters = LIST_HEAD_INIT(init_css_set.task_iters),
764 .threaded_csets = LIST_HEAD_INIT(init_css_set.threaded_csets),
765 .cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
766 .mg_src_preload_node = LIST_HEAD_INIT(init_css_set.mg_src_preload_node),
767 .mg_dst_preload_node = LIST_HEAD_INIT(init_css_set.mg_dst_preload_node),
768 .mg_node = LIST_HEAD_INIT(init_css_set.mg_node),
771 * The following field is re-initialized when this cset gets linked
772 * in cgroup_init(). However, let's initialize the field
773 * statically too so that the default cgroup can be accessed safely
776 .dfl_cgrp = &cgrp_dfl_root.cgrp,
779 static int css_set_count = 1; /* 1 for init_css_set */
781 static bool css_set_threaded(struct css_set *cset)
783 return cset->dom_cset != cset;
787 * css_set_populated - does a css_set contain any tasks?
788 * @cset: target css_set
790 * css_set_populated() should be the same as !!cset->nr_tasks at steady
791 * state. However, css_set_populated() can be called while a task is being
792 * added to or removed from the linked list before the nr_tasks is
793 * properly updated. Hence, we can't just look at ->nr_tasks here.
795 static bool css_set_populated(struct css_set *cset)
797 lockdep_assert_held(&css_set_lock);
799 return !list_empty(&cset->tasks) || !list_empty(&cset->mg_tasks);
803 * cgroup_update_populated - update the populated count of a cgroup
804 * @cgrp: the target cgroup
805 * @populated: inc or dec populated count
807 * One of the css_sets associated with @cgrp is either getting its first
808 * task or losing the last. Update @cgrp->nr_populated_* accordingly. The
809 * count is propagated towards root so that a given cgroup's
810 * nr_populated_children is zero iff none of its descendants contain any
813 * @cgrp's interface file "cgroup.populated" is zero if both
814 * @cgrp->nr_populated_csets and @cgrp->nr_populated_children are zero and
815 * 1 otherwise. When the sum changes from or to zero, userland is notified
816 * that the content of the interface file has changed. This can be used to
817 * detect when @cgrp and its descendants become populated or empty.
819 static void cgroup_update_populated(struct cgroup *cgrp, bool populated)
821 struct cgroup *child = NULL;
822 int adj = populated ? 1 : -1;
824 lockdep_assert_held(&css_set_lock);
827 bool was_populated = cgroup_is_populated(cgrp);
830 cgrp->nr_populated_csets += adj;
832 if (cgroup_is_threaded(child))
833 cgrp->nr_populated_threaded_children += adj;
835 cgrp->nr_populated_domain_children += adj;
838 if (was_populated == cgroup_is_populated(cgrp))
841 cgroup1_check_for_release(cgrp);
842 TRACE_CGROUP_PATH(notify_populated, cgrp,
843 cgroup_is_populated(cgrp));
844 cgroup_file_notify(&cgrp->events_file);
847 cgrp = cgroup_parent(cgrp);
852 * css_set_update_populated - update populated state of a css_set
853 * @cset: target css_set
854 * @populated: whether @cset is populated or depopulated
856 * @cset is either getting the first task or losing the last. Update the
857 * populated counters of all associated cgroups accordingly.
859 static void css_set_update_populated(struct css_set *cset, bool populated)
861 struct cgrp_cset_link *link;
863 lockdep_assert_held(&css_set_lock);
865 list_for_each_entry(link, &cset->cgrp_links, cgrp_link)
866 cgroup_update_populated(link->cgrp, populated);
870 * @task is leaving, advance task iterators which are pointing to it so
871 * that they can resume at the next position. Advancing an iterator might
872 * remove it from the list, use safe walk. See css_task_iter_skip() for
875 static void css_set_skip_task_iters(struct css_set *cset,
876 struct task_struct *task)
878 struct css_task_iter *it, *pos;
880 list_for_each_entry_safe(it, pos, &cset->task_iters, iters_node)
881 css_task_iter_skip(it, task);
885 * css_set_move_task - move a task from one css_set to another
886 * @task: task being moved
887 * @from_cset: css_set @task currently belongs to (may be NULL)
888 * @to_cset: new css_set @task is being moved to (may be NULL)
889 * @use_mg_tasks: move to @to_cset->mg_tasks instead of ->tasks
891 * Move @task from @from_cset to @to_cset. If @task didn't belong to any
892 * css_set, @from_cset can be NULL. If @task is being disassociated
893 * instead of moved, @to_cset can be NULL.
895 * This function automatically handles populated counter updates and
896 * css_task_iter adjustments but the caller is responsible for managing
897 * @from_cset and @to_cset's reference counts.
899 static void css_set_move_task(struct task_struct *task,
900 struct css_set *from_cset, struct css_set *to_cset,
903 lockdep_assert_held(&css_set_lock);
905 if (to_cset && !css_set_populated(to_cset))
906 css_set_update_populated(to_cset, true);
909 WARN_ON_ONCE(list_empty(&task->cg_list));
911 css_set_skip_task_iters(from_cset, task);
912 list_del_init(&task->cg_list);
913 if (!css_set_populated(from_cset))
914 css_set_update_populated(from_cset, false);
916 WARN_ON_ONCE(!list_empty(&task->cg_list));
921 * We are synchronized through cgroup_threadgroup_rwsem
922 * against PF_EXITING setting such that we can't race
923 * against cgroup_exit()/cgroup_free() dropping the css_set.
925 WARN_ON_ONCE(task->flags & PF_EXITING);
927 cgroup_move_task(task, to_cset);
928 list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks :
934 * hash table for cgroup groups. This improves the performance to find
935 * an existing css_set. This hash doesn't (currently) take into
936 * account cgroups in empty hierarchies.
938 #define CSS_SET_HASH_BITS 7
939 static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
941 static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
943 unsigned long key = 0UL;
944 struct cgroup_subsys *ss;
947 for_each_subsys(ss, i)
948 key += (unsigned long)css[i];
949 key = (key >> 16) ^ key;
954 void put_css_set_locked(struct css_set *cset)
956 struct cgrp_cset_link *link, *tmp_link;
957 struct cgroup_subsys *ss;
960 lockdep_assert_held(&css_set_lock);
962 if (!refcount_dec_and_test(&cset->refcount))
965 WARN_ON_ONCE(!list_empty(&cset->threaded_csets));
967 /* This css_set is dead. Unlink it and release cgroup and css refs */
968 for_each_subsys(ss, ssid) {
969 list_del(&cset->e_cset_node[ssid]);
970 css_put(cset->subsys[ssid]);
972 hash_del(&cset->hlist);
975 list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
976 list_del(&link->cset_link);
977 list_del(&link->cgrp_link);
978 if (cgroup_parent(link->cgrp))
979 cgroup_put(link->cgrp);
983 if (css_set_threaded(cset)) {
984 list_del(&cset->threaded_csets_node);
985 put_css_set_locked(cset->dom_cset);
988 kfree_rcu(cset, rcu_head);
992 * compare_css_sets - helper function for find_existing_css_set().
993 * @cset: candidate css_set being tested
994 * @old_cset: existing css_set for a task
995 * @new_cgrp: cgroup that's being entered by the task
996 * @template: desired set of css pointers in css_set (pre-calculated)
998 * Returns true if "cset" matches "old_cset" except for the hierarchy
999 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
1001 static bool compare_css_sets(struct css_set *cset,
1002 struct css_set *old_cset,
1003 struct cgroup *new_cgrp,
1004 struct cgroup_subsys_state *template[])
1006 struct cgroup *new_dfl_cgrp;
1007 struct list_head *l1, *l2;
1010 * On the default hierarchy, there can be csets which are
1011 * associated with the same set of cgroups but different csses.
1012 * Let's first ensure that csses match.
1014 if (memcmp(template, cset->subsys, sizeof(cset->subsys)))
1018 /* @cset's domain should match the default cgroup's */
1019 if (cgroup_on_dfl(new_cgrp))
1020 new_dfl_cgrp = new_cgrp;
1022 new_dfl_cgrp = old_cset->dfl_cgrp;
1024 if (new_dfl_cgrp->dom_cgrp != cset->dom_cset->dfl_cgrp)
1028 * Compare cgroup pointers in order to distinguish between
1029 * different cgroups in hierarchies. As different cgroups may
1030 * share the same effective css, this comparison is always
1033 l1 = &cset->cgrp_links;
1034 l2 = &old_cset->cgrp_links;
1036 struct cgrp_cset_link *link1, *link2;
1037 struct cgroup *cgrp1, *cgrp2;
1041 /* See if we reached the end - both lists are equal length. */
1042 if (l1 == &cset->cgrp_links) {
1043 BUG_ON(l2 != &old_cset->cgrp_links);
1046 BUG_ON(l2 == &old_cset->cgrp_links);
1048 /* Locate the cgroups associated with these links. */
1049 link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
1050 link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
1051 cgrp1 = link1->cgrp;
1052 cgrp2 = link2->cgrp;
1053 /* Hierarchies should be linked in the same order. */
1054 BUG_ON(cgrp1->root != cgrp2->root);
1057 * If this hierarchy is the hierarchy of the cgroup
1058 * that's changing, then we need to check that this
1059 * css_set points to the new cgroup; if it's any other
1060 * hierarchy, then this css_set should point to the
1061 * same cgroup as the old css_set.
1063 if (cgrp1->root == new_cgrp->root) {
1064 if (cgrp1 != new_cgrp)
1075 * find_existing_css_set - init css array and find the matching css_set
1076 * @old_cset: the css_set that we're using before the cgroup transition
1077 * @cgrp: the cgroup that we're moving into
1078 * @template: out param for the new set of csses, should be clear on entry
1080 static struct css_set *find_existing_css_set(struct css_set *old_cset,
1081 struct cgroup *cgrp,
1082 struct cgroup_subsys_state *template[])
1084 struct cgroup_root *root = cgrp->root;
1085 struct cgroup_subsys *ss;
1086 struct css_set *cset;
1091 * Build the set of subsystem state objects that we want to see in the
1092 * new css_set. While subsystems can change globally, the entries here
1093 * won't change, so no need for locking.
1095 for_each_subsys(ss, i) {
1096 if (root->subsys_mask & (1UL << i)) {
1098 * @ss is in this hierarchy, so we want the
1099 * effective css from @cgrp.
1101 template[i] = cgroup_e_css_by_mask(cgrp, ss);
1104 * @ss is not in this hierarchy, so we don't want
1105 * to change the css.
1107 template[i] = old_cset->subsys[i];
1111 key = css_set_hash(template);
1112 hash_for_each_possible(css_set_table, cset, hlist, key) {
1113 if (!compare_css_sets(cset, old_cset, cgrp, template))
1116 /* This css_set matches what we need */
1120 /* No existing cgroup group matched */
1124 static void free_cgrp_cset_links(struct list_head *links_to_free)
1126 struct cgrp_cset_link *link, *tmp_link;
1128 list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
1129 list_del(&link->cset_link);
1135 * allocate_cgrp_cset_links - allocate cgrp_cset_links
1136 * @count: the number of links to allocate
1137 * @tmp_links: list_head the allocated links are put on
1139 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
1140 * through ->cset_link. Returns 0 on success or -errno.
1142 static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
1144 struct cgrp_cset_link *link;
1147 INIT_LIST_HEAD(tmp_links);
1149 for (i = 0; i < count; i++) {
1150 link = kzalloc(sizeof(*link), GFP_KERNEL);
1152 free_cgrp_cset_links(tmp_links);
1155 list_add(&link->cset_link, tmp_links);
1161 * link_css_set - a helper function to link a css_set to a cgroup
1162 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
1163 * @cset: the css_set to be linked
1164 * @cgrp: the destination cgroup
1166 static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
1167 struct cgroup *cgrp)
1169 struct cgrp_cset_link *link;
1171 BUG_ON(list_empty(tmp_links));
1173 if (cgroup_on_dfl(cgrp))
1174 cset->dfl_cgrp = cgrp;
1176 link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
1181 * Always add links to the tail of the lists so that the lists are
1182 * in chronological order.
1184 list_move_tail(&link->cset_link, &cgrp->cset_links);
1185 list_add_tail(&link->cgrp_link, &cset->cgrp_links);
1187 if (cgroup_parent(cgrp))
1188 cgroup_get_live(cgrp);
1192 * find_css_set - return a new css_set with one cgroup updated
1193 * @old_cset: the baseline css_set
1194 * @cgrp: the cgroup to be updated
1196 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
1197 * substituted into the appropriate hierarchy.
1199 static struct css_set *find_css_set(struct css_set *old_cset,
1200 struct cgroup *cgrp)
1202 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
1203 struct css_set *cset;
1204 struct list_head tmp_links;
1205 struct cgrp_cset_link *link;
1206 struct cgroup_subsys *ss;
1210 lockdep_assert_held(&cgroup_mutex);
1212 /* First see if we already have a cgroup group that matches
1213 * the desired set */
1214 spin_lock_irq(&css_set_lock);
1215 cset = find_existing_css_set(old_cset, cgrp, template);
1218 spin_unlock_irq(&css_set_lock);
1223 cset = kzalloc(sizeof(*cset), GFP_KERNEL);
1227 /* Allocate all the cgrp_cset_link objects that we'll need */
1228 if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
1233 refcount_set(&cset->refcount, 1);
1234 cset->dom_cset = cset;
1235 INIT_LIST_HEAD(&cset->tasks);
1236 INIT_LIST_HEAD(&cset->mg_tasks);
1237 INIT_LIST_HEAD(&cset->dying_tasks);
1238 INIT_LIST_HEAD(&cset->task_iters);
1239 INIT_LIST_HEAD(&cset->threaded_csets);
1240 INIT_HLIST_NODE(&cset->hlist);
1241 INIT_LIST_HEAD(&cset->cgrp_links);
1242 INIT_LIST_HEAD(&cset->mg_src_preload_node);
1243 INIT_LIST_HEAD(&cset->mg_dst_preload_node);
1244 INIT_LIST_HEAD(&cset->mg_node);
1246 /* Copy the set of subsystem state objects generated in
1247 * find_existing_css_set() */
1248 memcpy(cset->subsys, template, sizeof(cset->subsys));
1250 spin_lock_irq(&css_set_lock);
1251 /* Add reference counts and links from the new css_set. */
1252 list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
1253 struct cgroup *c = link->cgrp;
1255 if (c->root == cgrp->root)
1257 link_css_set(&tmp_links, cset, c);
1260 BUG_ON(!list_empty(&tmp_links));
1264 /* Add @cset to the hash table */
1265 key = css_set_hash(cset->subsys);
1266 hash_add(css_set_table, &cset->hlist, key);
1268 for_each_subsys(ss, ssid) {
1269 struct cgroup_subsys_state *css = cset->subsys[ssid];
1271 list_add_tail(&cset->e_cset_node[ssid],
1272 &css->cgroup->e_csets[ssid]);
1276 spin_unlock_irq(&css_set_lock);
1279 * If @cset should be threaded, look up the matching dom_cset and
1280 * link them up. We first fully initialize @cset then look for the
1281 * dom_cset. It's simpler this way and safe as @cset is guaranteed
1282 * to stay empty until we return.
1284 if (cgroup_is_threaded(cset->dfl_cgrp)) {
1285 struct css_set *dcset;
1287 dcset = find_css_set(cset, cset->dfl_cgrp->dom_cgrp);
1293 spin_lock_irq(&css_set_lock);
1294 cset->dom_cset = dcset;
1295 list_add_tail(&cset->threaded_csets_node,
1296 &dcset->threaded_csets);
1297 spin_unlock_irq(&css_set_lock);
1303 struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
1305 struct cgroup *root_cgrp = kernfs_root_to_node(kf_root)->priv;
1307 return root_cgrp->root;
1310 void cgroup_favor_dynmods(struct cgroup_root *root, bool favor)
1312 bool favoring = root->flags & CGRP_ROOT_FAVOR_DYNMODS;
1314 /* see the comment above CGRP_ROOT_FAVOR_DYNMODS definition */
1315 if (favor && !favoring) {
1316 rcu_sync_enter(&cgroup_threadgroup_rwsem.rss);
1317 root->flags |= CGRP_ROOT_FAVOR_DYNMODS;
1318 } else if (!favor && favoring) {
1319 rcu_sync_exit(&cgroup_threadgroup_rwsem.rss);
1320 root->flags &= ~CGRP_ROOT_FAVOR_DYNMODS;
1324 static int cgroup_init_root_id(struct cgroup_root *root)
1328 lockdep_assert_held(&cgroup_mutex);
1330 id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
1334 root->hierarchy_id = id;
1338 static void cgroup_exit_root_id(struct cgroup_root *root)
1340 lockdep_assert_held(&cgroup_mutex);
1342 idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
1345 void cgroup_free_root(struct cgroup_root *root)
1350 static void cgroup_destroy_root(struct cgroup_root *root)
1352 struct cgroup *cgrp = &root->cgrp;
1353 struct cgrp_cset_link *link, *tmp_link;
1355 trace_cgroup_destroy_root(root);
1357 cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1359 BUG_ON(atomic_read(&root->nr_cgrps));
1360 BUG_ON(!list_empty(&cgrp->self.children));
1362 /* Rebind all subsystems back to the default hierarchy */
1363 WARN_ON(rebind_subsystems(&cgrp_dfl_root, root->subsys_mask));
1366 * Release all the links from cset_links to this hierarchy's
1369 spin_lock_irq(&css_set_lock);
1371 list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
1372 list_del(&link->cset_link);
1373 list_del(&link->cgrp_link);
1377 spin_unlock_irq(&css_set_lock);
1379 if (!list_empty(&root->root_list)) {
1380 list_del(&root->root_list);
1381 cgroup_root_count--;
1384 cgroup_favor_dynmods(root, false);
1385 cgroup_exit_root_id(root);
1387 mutex_unlock(&cgroup_mutex);
1389 cgroup_rstat_exit(cgrp);
1390 kernfs_destroy_root(root->kf_root);
1391 cgroup_free_root(root);
1394 static inline struct cgroup *__cset_cgroup_from_root(struct css_set *cset,
1395 struct cgroup_root *root)
1397 struct cgroup *res_cgroup = NULL;
1399 if (cset == &init_css_set) {
1400 res_cgroup = &root->cgrp;
1401 } else if (root == &cgrp_dfl_root) {
1402 res_cgroup = cset->dfl_cgrp;
1404 struct cgrp_cset_link *link;
1406 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
1407 struct cgroup *c = link->cgrp;
1409 if (c->root == root) {
1420 * look up cgroup associated with current task's cgroup namespace on the
1421 * specified hierarchy
1423 static struct cgroup *
1424 current_cgns_cgroup_from_root(struct cgroup_root *root)
1426 struct cgroup *res = NULL;
1427 struct css_set *cset;
1429 lockdep_assert_held(&css_set_lock);
1433 cset = current->nsproxy->cgroup_ns->root_cset;
1434 res = __cset_cgroup_from_root(cset, root);
1442 /* look up cgroup associated with given css_set on the specified hierarchy */
1443 static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
1444 struct cgroup_root *root)
1446 struct cgroup *res = NULL;
1448 lockdep_assert_held(&cgroup_mutex);
1449 lockdep_assert_held(&css_set_lock);
1451 res = __cset_cgroup_from_root(cset, root);
1458 * Return the cgroup for "task" from the given hierarchy. Must be
1459 * called with cgroup_mutex and css_set_lock held.
1461 struct cgroup *task_cgroup_from_root(struct task_struct *task,
1462 struct cgroup_root *root)
1465 * No need to lock the task - since we hold css_set_lock the
1466 * task can't change groups.
1468 return cset_cgroup_from_root(task_css_set(task), root);
1472 * A task must hold cgroup_mutex to modify cgroups.
1474 * Any task can increment and decrement the count field without lock.
1475 * So in general, code holding cgroup_mutex can't rely on the count
1476 * field not changing. However, if the count goes to zero, then only
1477 * cgroup_attach_task() can increment it again. Because a count of zero
1478 * means that no tasks are currently attached, therefore there is no
1479 * way a task attached to that cgroup can fork (the other way to
1480 * increment the count). So code holding cgroup_mutex can safely
1481 * assume that if the count is zero, it will stay zero. Similarly, if
1482 * a task holds cgroup_mutex on a cgroup with zero count, it
1483 * knows that the cgroup won't be removed, as cgroup_rmdir()
1486 * A cgroup can only be deleted if both its 'count' of using tasks
1487 * is zero, and its list of 'children' cgroups is empty. Since all
1488 * tasks in the system use _some_ cgroup, and since there is always at
1489 * least one task in the system (init, pid == 1), therefore, root cgroup
1490 * always has either children cgroups and/or using tasks. So we don't
1491 * need a special hack to ensure that root cgroup cannot be deleted.
1493 * P.S. One more locking exception. RCU is used to guard the
1494 * update of a tasks cgroup pointer by cgroup_attach_task()
1497 static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
1499 static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
1502 struct cgroup_subsys *ss = cft->ss;
1504 if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
1505 !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
1506 const char *dbg = (cft->flags & CFTYPE_DEBUG) ? ".__DEBUG__." : "";
1508 snprintf(buf, CGROUP_FILE_NAME_MAX, "%s%s.%s",
1509 dbg, cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name,
1512 strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
1518 * cgroup_file_mode - deduce file mode of a control file
1519 * @cft: the control file in question
1521 * S_IRUGO for read, S_IWUSR for write.
1523 static umode_t cgroup_file_mode(const struct cftype *cft)
1527 if (cft->read_u64 || cft->read_s64 || cft->seq_show)
1530 if (cft->write_u64 || cft->write_s64 || cft->write) {
1531 if (cft->flags & CFTYPE_WORLD_WRITABLE)
1541 * cgroup_calc_subtree_ss_mask - calculate subtree_ss_mask
1542 * @subtree_control: the new subtree_control mask to consider
1543 * @this_ss_mask: available subsystems
1545 * On the default hierarchy, a subsystem may request other subsystems to be
1546 * enabled together through its ->depends_on mask. In such cases, more
1547 * subsystems than specified in "cgroup.subtree_control" may be enabled.
1549 * This function calculates which subsystems need to be enabled if
1550 * @subtree_control is to be applied while restricted to @this_ss_mask.
1552 static u16 cgroup_calc_subtree_ss_mask(u16 subtree_control, u16 this_ss_mask)
1554 u16 cur_ss_mask = subtree_control;
1555 struct cgroup_subsys *ss;
1558 lockdep_assert_held(&cgroup_mutex);
1560 cur_ss_mask |= cgrp_dfl_implicit_ss_mask;
1563 u16 new_ss_mask = cur_ss_mask;
1565 do_each_subsys_mask(ss, ssid, cur_ss_mask) {
1566 new_ss_mask |= ss->depends_on;
1567 } while_each_subsys_mask();
1570 * Mask out subsystems which aren't available. This can
1571 * happen only if some depended-upon subsystems were bound
1572 * to non-default hierarchies.
1574 new_ss_mask &= this_ss_mask;
1576 if (new_ss_mask == cur_ss_mask)
1578 cur_ss_mask = new_ss_mask;
1585 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1586 * @kn: the kernfs_node being serviced
1588 * This helper undoes cgroup_kn_lock_live() and should be invoked before
1589 * the method finishes if locking succeeded. Note that once this function
1590 * returns the cgroup returned by cgroup_kn_lock_live() may become
1591 * inaccessible any time. If the caller intends to continue to access the
1592 * cgroup, it should pin it before invoking this function.
1594 void cgroup_kn_unlock(struct kernfs_node *kn)
1596 struct cgroup *cgrp;
1598 if (kernfs_type(kn) == KERNFS_DIR)
1601 cgrp = kn->parent->priv;
1603 mutex_unlock(&cgroup_mutex);
1605 kernfs_unbreak_active_protection(kn);
1610 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1611 * @kn: the kernfs_node being serviced
1612 * @drain_offline: perform offline draining on the cgroup
1614 * This helper is to be used by a cgroup kernfs method currently servicing
1615 * @kn. It breaks the active protection, performs cgroup locking and
1616 * verifies that the associated cgroup is alive. Returns the cgroup if
1617 * alive; otherwise, %NULL. A successful return should be undone by a
1618 * matching cgroup_kn_unlock() invocation. If @drain_offline is %true, the
1619 * cgroup is drained of offlining csses before return.
1621 * Any cgroup kernfs method implementation which requires locking the
1622 * associated cgroup should use this helper. It avoids nesting cgroup
1623 * locking under kernfs active protection and allows all kernfs operations
1624 * including self-removal.
1626 struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn, bool drain_offline)
1628 struct cgroup *cgrp;
1630 if (kernfs_type(kn) == KERNFS_DIR)
1633 cgrp = kn->parent->priv;
1636 * We're gonna grab cgroup_mutex which nests outside kernfs
1637 * active_ref. cgroup liveliness check alone provides enough
1638 * protection against removal. Ensure @cgrp stays accessible and
1639 * break the active_ref protection.
1641 if (!cgroup_tryget(cgrp))
1643 kernfs_break_active_protection(kn);
1646 cgroup_lock_and_drain_offline(cgrp);
1648 mutex_lock(&cgroup_mutex);
1650 if (!cgroup_is_dead(cgrp))
1653 cgroup_kn_unlock(kn);
1657 static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
1659 char name[CGROUP_FILE_NAME_MAX];
1661 lockdep_assert_held(&cgroup_mutex);
1663 if (cft->file_offset) {
1664 struct cgroup_subsys_state *css = cgroup_css(cgrp, cft->ss);
1665 struct cgroup_file *cfile = (void *)css + cft->file_offset;
1667 spin_lock_irq(&cgroup_file_kn_lock);
1669 spin_unlock_irq(&cgroup_file_kn_lock);
1671 del_timer_sync(&cfile->notify_timer);
1674 kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
1678 * css_clear_dir - remove subsys files in a cgroup directory
1681 static void css_clear_dir(struct cgroup_subsys_state *css)
1683 struct cgroup *cgrp = css->cgroup;
1684 struct cftype *cfts;
1686 if (!(css->flags & CSS_VISIBLE))
1689 css->flags &= ~CSS_VISIBLE;
1692 if (cgroup_on_dfl(cgrp))
1693 cfts = cgroup_base_files;
1695 cfts = cgroup1_base_files;
1697 cgroup_addrm_files(css, cgrp, cfts, false);
1699 list_for_each_entry(cfts, &css->ss->cfts, node)
1700 cgroup_addrm_files(css, cgrp, cfts, false);
1705 * css_populate_dir - create subsys files in a cgroup directory
1708 * On failure, no file is added.
1710 static int css_populate_dir(struct cgroup_subsys_state *css)
1712 struct cgroup *cgrp = css->cgroup;
1713 struct cftype *cfts, *failed_cfts;
1716 if ((css->flags & CSS_VISIBLE) || !cgrp->kn)
1720 if (cgroup_on_dfl(cgrp))
1721 cfts = cgroup_base_files;
1723 cfts = cgroup1_base_files;
1725 ret = cgroup_addrm_files(&cgrp->self, cgrp, cfts, true);
1729 list_for_each_entry(cfts, &css->ss->cfts, node) {
1730 ret = cgroup_addrm_files(css, cgrp, cfts, true);
1738 css->flags |= CSS_VISIBLE;
1742 list_for_each_entry(cfts, &css->ss->cfts, node) {
1743 if (cfts == failed_cfts)
1745 cgroup_addrm_files(css, cgrp, cfts, false);
1750 int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
1752 struct cgroup *dcgrp = &dst_root->cgrp;
1753 struct cgroup_subsys *ss;
1755 u16 dfl_disable_ss_mask = 0;
1757 lockdep_assert_held(&cgroup_mutex);
1759 do_each_subsys_mask(ss, ssid, ss_mask) {
1761 * If @ss has non-root csses attached to it, can't move.
1762 * If @ss is an implicit controller, it is exempt from this
1763 * rule and can be stolen.
1765 if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)) &&
1766 !ss->implicit_on_dfl)
1769 /* can't move between two non-dummy roots either */
1770 if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
1774 * Collect ssid's that need to be disabled from default
1777 if (ss->root == &cgrp_dfl_root)
1778 dfl_disable_ss_mask |= 1 << ssid;
1780 } while_each_subsys_mask();
1782 if (dfl_disable_ss_mask) {
1783 struct cgroup *scgrp = &cgrp_dfl_root.cgrp;
1786 * Controllers from default hierarchy that need to be rebound
1787 * are all disabled together in one go.
1789 cgrp_dfl_root.subsys_mask &= ~dfl_disable_ss_mask;
1790 WARN_ON(cgroup_apply_control(scgrp));
1791 cgroup_finalize_control(scgrp, 0);
1794 do_each_subsys_mask(ss, ssid, ss_mask) {
1795 struct cgroup_root *src_root = ss->root;
1796 struct cgroup *scgrp = &src_root->cgrp;
1797 struct cgroup_subsys_state *css = cgroup_css(scgrp, ss);
1798 struct css_set *cset;
1800 WARN_ON(!css || cgroup_css(dcgrp, ss));
1802 if (src_root != &cgrp_dfl_root) {
1803 /* disable from the source */
1804 src_root->subsys_mask &= ~(1 << ssid);
1805 WARN_ON(cgroup_apply_control(scgrp));
1806 cgroup_finalize_control(scgrp, 0);
1810 RCU_INIT_POINTER(scgrp->subsys[ssid], NULL);
1811 rcu_assign_pointer(dcgrp->subsys[ssid], css);
1812 ss->root = dst_root;
1813 css->cgroup = dcgrp;
1815 spin_lock_irq(&css_set_lock);
1816 hash_for_each(css_set_table, i, cset, hlist)
1817 list_move_tail(&cset->e_cset_node[ss->id],
1818 &dcgrp->e_csets[ss->id]);
1819 spin_unlock_irq(&css_set_lock);
1821 if (ss->css_rstat_flush) {
1822 list_del_rcu(&css->rstat_css_node);
1823 list_add_rcu(&css->rstat_css_node,
1824 &dcgrp->rstat_css_list);
1827 /* default hierarchy doesn't enable controllers by default */
1828 dst_root->subsys_mask |= 1 << ssid;
1829 if (dst_root == &cgrp_dfl_root) {
1830 static_branch_enable(cgroup_subsys_on_dfl_key[ssid]);
1832 dcgrp->subtree_control |= 1 << ssid;
1833 static_branch_disable(cgroup_subsys_on_dfl_key[ssid]);
1836 ret = cgroup_apply_control(dcgrp);
1838 pr_warn("partial failure to rebind %s controller (err=%d)\n",
1843 } while_each_subsys_mask();
1845 kernfs_activate(dcgrp->kn);
1849 int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
1850 struct kernfs_root *kf_root)
1854 struct cgroup_root *kf_cgroot = cgroup_root_from_kf(kf_root);
1855 struct cgroup *ns_cgroup;
1857 buf = kmalloc(PATH_MAX, GFP_KERNEL);
1861 spin_lock_irq(&css_set_lock);
1862 ns_cgroup = current_cgns_cgroup_from_root(kf_cgroot);
1863 len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX);
1864 spin_unlock_irq(&css_set_lock);
1866 if (len >= PATH_MAX)
1869 seq_escape(sf, buf, " \t\n\\");
1876 enum cgroup2_param {
1879 Opt_memory_localevents,
1880 Opt_memory_recursiveprot,
1884 static const struct fs_parameter_spec cgroup2_fs_parameters[] = {
1885 fsparam_flag("nsdelegate", Opt_nsdelegate),
1886 fsparam_flag("favordynmods", Opt_favordynmods),
1887 fsparam_flag("memory_localevents", Opt_memory_localevents),
1888 fsparam_flag("memory_recursiveprot", Opt_memory_recursiveprot),
1892 static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param)
1894 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1895 struct fs_parse_result result;
1898 opt = fs_parse(fc, cgroup2_fs_parameters, param, &result);
1903 case Opt_nsdelegate:
1904 ctx->flags |= CGRP_ROOT_NS_DELEGATE;
1906 case Opt_favordynmods:
1907 ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
1909 case Opt_memory_localevents:
1910 ctx->flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1912 case Opt_memory_recursiveprot:
1913 ctx->flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;
1919 static void apply_cgroup_root_flags(unsigned int root_flags)
1921 if (current->nsproxy->cgroup_ns == &init_cgroup_ns) {
1922 if (root_flags & CGRP_ROOT_NS_DELEGATE)
1923 cgrp_dfl_root.flags |= CGRP_ROOT_NS_DELEGATE;
1925 cgrp_dfl_root.flags &= ~CGRP_ROOT_NS_DELEGATE;
1927 cgroup_favor_dynmods(&cgrp_dfl_root,
1928 root_flags & CGRP_ROOT_FAVOR_DYNMODS);
1930 if (root_flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
1931 cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1933 cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1935 if (root_flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)
1936 cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;
1938 cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_RECURSIVE_PROT;
1942 static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
1944 if (cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE)
1945 seq_puts(seq, ",nsdelegate");
1946 if (cgrp_dfl_root.flags & CGRP_ROOT_FAVOR_DYNMODS)
1947 seq_puts(seq, ",favordynmods");
1948 if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
1949 seq_puts(seq, ",memory_localevents");
1950 if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)
1951 seq_puts(seq, ",memory_recursiveprot");
1955 static int cgroup_reconfigure(struct fs_context *fc)
1957 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1959 apply_cgroup_root_flags(ctx->flags);
1963 static void init_cgroup_housekeeping(struct cgroup *cgrp)
1965 struct cgroup_subsys *ss;
1968 INIT_LIST_HEAD(&cgrp->self.sibling);
1969 INIT_LIST_HEAD(&cgrp->self.children);
1970 INIT_LIST_HEAD(&cgrp->cset_links);
1971 INIT_LIST_HEAD(&cgrp->pidlists);
1972 mutex_init(&cgrp->pidlist_mutex);
1973 cgrp->self.cgroup = cgrp;
1974 cgrp->self.flags |= CSS_ONLINE;
1975 cgrp->dom_cgrp = cgrp;
1976 cgrp->max_descendants = INT_MAX;
1977 cgrp->max_depth = INT_MAX;
1978 INIT_LIST_HEAD(&cgrp->rstat_css_list);
1979 prev_cputime_init(&cgrp->prev_cputime);
1981 for_each_subsys(ss, ssid)
1982 INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
1984 init_waitqueue_head(&cgrp->offline_waitq);
1985 INIT_WORK(&cgrp->release_agent_work, cgroup1_release_agent);
1988 void init_cgroup_root(struct cgroup_fs_context *ctx)
1990 struct cgroup_root *root = ctx->root;
1991 struct cgroup *cgrp = &root->cgrp;
1993 INIT_LIST_HEAD(&root->root_list);
1994 atomic_set(&root->nr_cgrps, 1);
1996 init_cgroup_housekeeping(cgrp);
1998 /* DYNMODS must be modified through cgroup_favor_dynmods() */
1999 root->flags = ctx->flags & ~CGRP_ROOT_FAVOR_DYNMODS;
2000 if (ctx->release_agent)
2001 strscpy(root->release_agent_path, ctx->release_agent, PATH_MAX);
2003 strscpy(root->name, ctx->name, MAX_CGROUP_ROOT_NAMELEN);
2004 if (ctx->cpuset_clone_children)
2005 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
2008 int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
2010 LIST_HEAD(tmp_links);
2011 struct cgroup *root_cgrp = &root->cgrp;
2012 struct kernfs_syscall_ops *kf_sops;
2013 struct css_set *cset;
2016 lockdep_assert_held(&cgroup_mutex);
2018 ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release,
2024 * We're accessing css_set_count without locking css_set_lock here,
2025 * but that's OK - it can only be increased by someone holding
2026 * cgroup_lock, and that's us. Later rebinding may disable
2027 * controllers on the default hierarchy and thus create new csets,
2028 * which can't be more than the existing ones. Allocate 2x.
2030 ret = allocate_cgrp_cset_links(2 * css_set_count, &tmp_links);
2034 ret = cgroup_init_root_id(root);
2038 kf_sops = root == &cgrp_dfl_root ?
2039 &cgroup_kf_syscall_ops : &cgroup1_kf_syscall_ops;
2041 root->kf_root = kernfs_create_root(kf_sops,
2042 KERNFS_ROOT_CREATE_DEACTIVATED |
2043 KERNFS_ROOT_SUPPORT_EXPORTOP |
2044 KERNFS_ROOT_SUPPORT_USER_XATTR,
2046 if (IS_ERR(root->kf_root)) {
2047 ret = PTR_ERR(root->kf_root);
2050 root_cgrp->kn = kernfs_root_to_node(root->kf_root);
2051 WARN_ON_ONCE(cgroup_ino(root_cgrp) != 1);
2052 root_cgrp->ancestor_ids[0] = cgroup_id(root_cgrp);
2054 ret = css_populate_dir(&root_cgrp->self);
2058 ret = cgroup_rstat_init(root_cgrp);
2062 ret = rebind_subsystems(root, ss_mask);
2066 ret = cgroup_bpf_inherit(root_cgrp);
2069 trace_cgroup_setup_root(root);
2072 * There must be no failure case after here, since rebinding takes
2073 * care of subsystems' refcounts, which are explicitly dropped in
2074 * the failure exit path.
2076 list_add(&root->root_list, &cgroup_roots);
2077 cgroup_root_count++;
2080 * Link the root cgroup in this hierarchy into all the css_set
2083 spin_lock_irq(&css_set_lock);
2084 hash_for_each(css_set_table, i, cset, hlist) {
2085 link_css_set(&tmp_links, cset, root_cgrp);
2086 if (css_set_populated(cset))
2087 cgroup_update_populated(root_cgrp, true);
2089 spin_unlock_irq(&css_set_lock);
2091 BUG_ON(!list_empty(&root_cgrp->self.children));
2092 BUG_ON(atomic_read(&root->nr_cgrps) != 1);
2098 cgroup_rstat_exit(root_cgrp);
2100 kernfs_destroy_root(root->kf_root);
2101 root->kf_root = NULL;
2103 cgroup_exit_root_id(root);
2105 percpu_ref_exit(&root_cgrp->self.refcnt);
2107 free_cgrp_cset_links(&tmp_links);
2111 int cgroup_do_get_tree(struct fs_context *fc)
2113 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2116 ctx->kfc.root = ctx->root->kf_root;
2117 if (fc->fs_type == &cgroup2_fs_type)
2118 ctx->kfc.magic = CGROUP2_SUPER_MAGIC;
2120 ctx->kfc.magic = CGROUP_SUPER_MAGIC;
2121 ret = kernfs_get_tree(fc);
2124 * In non-init cgroup namespace, instead of root cgroup's dentry,
2125 * we return the dentry corresponding to the cgroupns->root_cgrp.
2127 if (!ret && ctx->ns != &init_cgroup_ns) {
2128 struct dentry *nsdentry;
2129 struct super_block *sb = fc->root->d_sb;
2130 struct cgroup *cgrp;
2132 mutex_lock(&cgroup_mutex);
2133 spin_lock_irq(&css_set_lock);
2135 cgrp = cset_cgroup_from_root(ctx->ns->root_cset, ctx->root);
2137 spin_unlock_irq(&css_set_lock);
2138 mutex_unlock(&cgroup_mutex);
2140 nsdentry = kernfs_node_dentry(cgrp->kn, sb);
2142 if (IS_ERR(nsdentry)) {
2143 deactivate_locked_super(sb);
2144 ret = PTR_ERR(nsdentry);
2147 fc->root = nsdentry;
2150 if (!ctx->kfc.new_sb_created)
2151 cgroup_put(&ctx->root->cgrp);
2157 * Destroy a cgroup filesystem context.
2159 static void cgroup_fs_context_free(struct fs_context *fc)
2161 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2164 kfree(ctx->release_agent);
2165 put_cgroup_ns(ctx->ns);
2166 kernfs_free_fs_context(fc);
2170 static int cgroup_get_tree(struct fs_context *fc)
2172 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2175 cgrp_dfl_visible = true;
2176 cgroup_get_live(&cgrp_dfl_root.cgrp);
2177 ctx->root = &cgrp_dfl_root;
2179 ret = cgroup_do_get_tree(fc);
2181 apply_cgroup_root_flags(ctx->flags);
2185 static const struct fs_context_operations cgroup_fs_context_ops = {
2186 .free = cgroup_fs_context_free,
2187 .parse_param = cgroup2_parse_param,
2188 .get_tree = cgroup_get_tree,
2189 .reconfigure = cgroup_reconfigure,
2192 static const struct fs_context_operations cgroup1_fs_context_ops = {
2193 .free = cgroup_fs_context_free,
2194 .parse_param = cgroup1_parse_param,
2195 .get_tree = cgroup1_get_tree,
2196 .reconfigure = cgroup1_reconfigure,
2200 * Initialise the cgroup filesystem creation/reconfiguration context. Notably,
2201 * we select the namespace we're going to use.
2203 static int cgroup_init_fs_context(struct fs_context *fc)
2205 struct cgroup_fs_context *ctx;
2207 ctx = kzalloc(sizeof(struct cgroup_fs_context), GFP_KERNEL);
2211 ctx->ns = current->nsproxy->cgroup_ns;
2212 get_cgroup_ns(ctx->ns);
2213 fc->fs_private = &ctx->kfc;
2214 if (fc->fs_type == &cgroup2_fs_type)
2215 fc->ops = &cgroup_fs_context_ops;
2217 fc->ops = &cgroup1_fs_context_ops;
2218 put_user_ns(fc->user_ns);
2219 fc->user_ns = get_user_ns(ctx->ns->user_ns);
2222 #ifdef CONFIG_CGROUP_FAVOR_DYNMODS
2223 ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
2228 static void cgroup_kill_sb(struct super_block *sb)
2230 struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
2231 struct cgroup_root *root = cgroup_root_from_kf(kf_root);
2234 * If @root doesn't have any children, start killing it.
2235 * This prevents new mounts by disabling percpu_ref_tryget_live().
2237 * And don't kill the default root.
2239 if (list_empty(&root->cgrp.self.children) && root != &cgrp_dfl_root &&
2240 !percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
2241 cgroup_bpf_offline(&root->cgrp);
2242 percpu_ref_kill(&root->cgrp.self.refcnt);
2244 cgroup_put(&root->cgrp);
2248 struct file_system_type cgroup_fs_type = {
2250 .init_fs_context = cgroup_init_fs_context,
2251 .parameters = cgroup1_fs_parameters,
2252 .kill_sb = cgroup_kill_sb,
2253 .fs_flags = FS_USERNS_MOUNT,
2256 static struct file_system_type cgroup2_fs_type = {
2258 .init_fs_context = cgroup_init_fs_context,
2259 .parameters = cgroup2_fs_parameters,
2260 .kill_sb = cgroup_kill_sb,
2261 .fs_flags = FS_USERNS_MOUNT,
2264 #ifdef CONFIG_CPUSETS
2265 static const struct fs_context_operations cpuset_fs_context_ops = {
2266 .get_tree = cgroup1_get_tree,
2267 .free = cgroup_fs_context_free,
2271 * This is ugly, but preserves the userspace API for existing cpuset
2272 * users. If someone tries to mount the "cpuset" filesystem, we
2273 * silently switch it to mount "cgroup" instead
2275 static int cpuset_init_fs_context(struct fs_context *fc)
2277 char *agent = kstrdup("/sbin/cpuset_release_agent", GFP_USER);
2278 struct cgroup_fs_context *ctx;
2281 err = cgroup_init_fs_context(fc);
2287 fc->ops = &cpuset_fs_context_ops;
2289 ctx = cgroup_fc2context(fc);
2290 ctx->subsys_mask = 1 << cpuset_cgrp_id;
2291 ctx->flags |= CGRP_ROOT_NOPREFIX;
2292 ctx->release_agent = agent;
2294 get_filesystem(&cgroup_fs_type);
2295 put_filesystem(fc->fs_type);
2296 fc->fs_type = &cgroup_fs_type;
2301 static struct file_system_type cpuset_fs_type = {
2303 .init_fs_context = cpuset_init_fs_context,
2304 .fs_flags = FS_USERNS_MOUNT,
2308 int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
2309 struct cgroup_namespace *ns)
2311 struct cgroup *root = cset_cgroup_from_root(ns->root_cset, cgrp->root);
2313 return kernfs_path_from_node(cgrp->kn, root->kn, buf, buflen);
2316 int cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
2317 struct cgroup_namespace *ns)
2321 mutex_lock(&cgroup_mutex);
2322 spin_lock_irq(&css_set_lock);
2324 ret = cgroup_path_ns_locked(cgrp, buf, buflen, ns);
2326 spin_unlock_irq(&css_set_lock);
2327 mutex_unlock(&cgroup_mutex);
2331 EXPORT_SYMBOL_GPL(cgroup_path_ns);
2334 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
2335 * @task: target task
2336 * @buf: the buffer to write the path into
2337 * @buflen: the length of the buffer
2339 * Determine @task's cgroup on the first (the one with the lowest non-zero
2340 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
2341 * function grabs cgroup_mutex and shouldn't be used inside locks used by
2342 * cgroup controller callbacks.
2344 * Return value is the same as kernfs_path().
2346 int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
2348 struct cgroup_root *root;
2349 struct cgroup *cgrp;
2350 int hierarchy_id = 1;
2353 mutex_lock(&cgroup_mutex);
2354 spin_lock_irq(&css_set_lock);
2356 root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
2359 cgrp = task_cgroup_from_root(task, root);
2360 ret = cgroup_path_ns_locked(cgrp, buf, buflen, &init_cgroup_ns);
2362 /* if no hierarchy exists, everyone is in "/" */
2363 ret = strlcpy(buf, "/", buflen);
2366 spin_unlock_irq(&css_set_lock);
2367 mutex_unlock(&cgroup_mutex);
2370 EXPORT_SYMBOL_GPL(task_cgroup_path);
2373 * cgroup_migrate_add_task - add a migration target task to a migration context
2374 * @task: target task
2375 * @mgctx: target migration context
2377 * Add @task, which is a migration target, to @mgctx->tset. This function
2378 * becomes noop if @task doesn't need to be migrated. @task's css_set
2379 * should have been added as a migration source and @task->cg_list will be
2380 * moved from the css_set's tasks list to mg_tasks one.
2382 static void cgroup_migrate_add_task(struct task_struct *task,
2383 struct cgroup_mgctx *mgctx)
2385 struct css_set *cset;
2387 lockdep_assert_held(&css_set_lock);
2389 /* @task either already exited or can't exit until the end */
2390 if (task->flags & PF_EXITING)
2393 /* cgroup_threadgroup_rwsem protects racing against forks */
2394 WARN_ON_ONCE(list_empty(&task->cg_list));
2396 cset = task_css_set(task);
2397 if (!cset->mg_src_cgrp)
2400 mgctx->tset.nr_tasks++;
2402 list_move_tail(&task->cg_list, &cset->mg_tasks);
2403 if (list_empty(&cset->mg_node))
2404 list_add_tail(&cset->mg_node,
2405 &mgctx->tset.src_csets);
2406 if (list_empty(&cset->mg_dst_cset->mg_node))
2407 list_add_tail(&cset->mg_dst_cset->mg_node,
2408 &mgctx->tset.dst_csets);
2412 * cgroup_taskset_first - reset taskset and return the first task
2413 * @tset: taskset of interest
2414 * @dst_cssp: output variable for the destination css
2416 * @tset iteration is initialized and the first task is returned.
2418 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset,
2419 struct cgroup_subsys_state **dst_cssp)
2421 tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
2422 tset->cur_task = NULL;
2424 return cgroup_taskset_next(tset, dst_cssp);
2428 * cgroup_taskset_next - iterate to the next task in taskset
2429 * @tset: taskset of interest
2430 * @dst_cssp: output variable for the destination css
2432 * Return the next task in @tset. Iteration must have been initialized
2433 * with cgroup_taskset_first().
2435 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
2436 struct cgroup_subsys_state **dst_cssp)
2438 struct css_set *cset = tset->cur_cset;
2439 struct task_struct *task = tset->cur_task;
2441 while (CGROUP_HAS_SUBSYS_CONFIG && &cset->mg_node != tset->csets) {
2443 task = list_first_entry(&cset->mg_tasks,
2444 struct task_struct, cg_list);
2446 task = list_next_entry(task, cg_list);
2448 if (&task->cg_list != &cset->mg_tasks) {
2449 tset->cur_cset = cset;
2450 tset->cur_task = task;
2453 * This function may be called both before and
2454 * after cgroup_taskset_migrate(). The two cases
2455 * can be distinguished by looking at whether @cset
2456 * has its ->mg_dst_cset set.
2458 if (cset->mg_dst_cset)
2459 *dst_cssp = cset->mg_dst_cset->subsys[tset->ssid];
2461 *dst_cssp = cset->subsys[tset->ssid];
2466 cset = list_next_entry(cset, mg_node);
2474 * cgroup_migrate_execute - migrate a taskset
2475 * @mgctx: migration context
2477 * Migrate tasks in @mgctx as setup by migration preparation functions.
2478 * This function fails iff one of the ->can_attach callbacks fails and
2479 * guarantees that either all or none of the tasks in @mgctx are migrated.
2480 * @mgctx is consumed regardless of success.
2482 static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx)
2484 struct cgroup_taskset *tset = &mgctx->tset;
2485 struct cgroup_subsys *ss;
2486 struct task_struct *task, *tmp_task;
2487 struct css_set *cset, *tmp_cset;
2488 int ssid, failed_ssid, ret;
2490 /* check that we can legitimately attach to the cgroup */
2491 if (tset->nr_tasks) {
2492 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2493 if (ss->can_attach) {
2495 ret = ss->can_attach(tset);
2498 goto out_cancel_attach;
2501 } while_each_subsys_mask();
2505 * Now that we're guaranteed success, proceed to move all tasks to
2506 * the new cgroup. There are no failure cases after here, so this
2507 * is the commit point.
2509 spin_lock_irq(&css_set_lock);
2510 list_for_each_entry(cset, &tset->src_csets, mg_node) {
2511 list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list) {
2512 struct css_set *from_cset = task_css_set(task);
2513 struct css_set *to_cset = cset->mg_dst_cset;
2515 get_css_set(to_cset);
2516 to_cset->nr_tasks++;
2517 css_set_move_task(task, from_cset, to_cset, true);
2518 from_cset->nr_tasks--;
2520 * If the source or destination cgroup is frozen,
2521 * the task might require to change its state.
2523 cgroup_freezer_migrate_task(task, from_cset->dfl_cgrp,
2525 put_css_set_locked(from_cset);
2529 spin_unlock_irq(&css_set_lock);
2532 * Migration is committed, all target tasks are now on dst_csets.
2533 * Nothing is sensitive to fork() after this point. Notify
2534 * controllers that migration is complete.
2536 tset->csets = &tset->dst_csets;
2538 if (tset->nr_tasks) {
2539 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2544 } while_each_subsys_mask();
2548 goto out_release_tset;
2551 if (tset->nr_tasks) {
2552 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2553 if (ssid == failed_ssid)
2555 if (ss->cancel_attach) {
2557 ss->cancel_attach(tset);
2559 } while_each_subsys_mask();
2562 spin_lock_irq(&css_set_lock);
2563 list_splice_init(&tset->dst_csets, &tset->src_csets);
2564 list_for_each_entry_safe(cset, tmp_cset, &tset->src_csets, mg_node) {
2565 list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
2566 list_del_init(&cset->mg_node);
2568 spin_unlock_irq(&css_set_lock);
2571 * Re-initialize the cgroup_taskset structure in case it is reused
2572 * again in another cgroup_migrate_add_task()/cgroup_migrate_execute()
2576 tset->csets = &tset->src_csets;
2581 * cgroup_migrate_vet_dst - verify whether a cgroup can be migration destination
2582 * @dst_cgrp: destination cgroup to test
2584 * On the default hierarchy, except for the mixable, (possible) thread root
2585 * and threaded cgroups, subtree_control must be zero for migration
2586 * destination cgroups with tasks so that child cgroups don't compete
2589 int cgroup_migrate_vet_dst(struct cgroup *dst_cgrp)
2591 /* v1 doesn't have any restriction */
2592 if (!cgroup_on_dfl(dst_cgrp))
2595 /* verify @dst_cgrp can host resources */
2596 if (!cgroup_is_valid_domain(dst_cgrp->dom_cgrp))
2600 * If @dst_cgrp is already or can become a thread root or is
2601 * threaded, it doesn't matter.
2603 if (cgroup_can_be_thread_root(dst_cgrp) || cgroup_is_threaded(dst_cgrp))
2606 /* apply no-internal-process constraint */
2607 if (dst_cgrp->subtree_control)
2614 * cgroup_migrate_finish - cleanup after attach
2615 * @mgctx: migration context
2617 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
2618 * those functions for details.
2620 void cgroup_migrate_finish(struct cgroup_mgctx *mgctx)
2622 struct css_set *cset, *tmp_cset;
2624 lockdep_assert_held(&cgroup_mutex);
2626 spin_lock_irq(&css_set_lock);
2628 list_for_each_entry_safe(cset, tmp_cset, &mgctx->preloaded_src_csets,
2629 mg_src_preload_node) {
2630 cset->mg_src_cgrp = NULL;
2631 cset->mg_dst_cgrp = NULL;
2632 cset->mg_dst_cset = NULL;
2633 list_del_init(&cset->mg_src_preload_node);
2634 put_css_set_locked(cset);
2637 list_for_each_entry_safe(cset, tmp_cset, &mgctx->preloaded_dst_csets,
2638 mg_dst_preload_node) {
2639 cset->mg_src_cgrp = NULL;
2640 cset->mg_dst_cgrp = NULL;
2641 cset->mg_dst_cset = NULL;
2642 list_del_init(&cset->mg_dst_preload_node);
2643 put_css_set_locked(cset);
2646 spin_unlock_irq(&css_set_lock);
2650 * cgroup_migrate_add_src - add a migration source css_set
2651 * @src_cset: the source css_set to add
2652 * @dst_cgrp: the destination cgroup
2653 * @mgctx: migration context
2655 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
2656 * @src_cset and add it to @mgctx->src_csets, which should later be cleaned
2657 * up by cgroup_migrate_finish().
2659 * This function may be called without holding cgroup_threadgroup_rwsem
2660 * even if the target is a process. Threads may be created and destroyed
2661 * but as long as cgroup_mutex is not dropped, no new css_set can be put
2662 * into play and the preloaded css_sets are guaranteed to cover all
2665 void cgroup_migrate_add_src(struct css_set *src_cset,
2666 struct cgroup *dst_cgrp,
2667 struct cgroup_mgctx *mgctx)
2669 struct cgroup *src_cgrp;
2671 lockdep_assert_held(&cgroup_mutex);
2672 lockdep_assert_held(&css_set_lock);
2675 * If ->dead, @src_set is associated with one or more dead cgroups
2676 * and doesn't contain any migratable tasks. Ignore it early so
2677 * that the rest of migration path doesn't get confused by it.
2682 if (!list_empty(&src_cset->mg_src_preload_node))
2685 src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);
2687 WARN_ON(src_cset->mg_src_cgrp);
2688 WARN_ON(src_cset->mg_dst_cgrp);
2689 WARN_ON(!list_empty(&src_cset->mg_tasks));
2690 WARN_ON(!list_empty(&src_cset->mg_node));
2692 src_cset->mg_src_cgrp = src_cgrp;
2693 src_cset->mg_dst_cgrp = dst_cgrp;
2694 get_css_set(src_cset);
2695 list_add_tail(&src_cset->mg_src_preload_node, &mgctx->preloaded_src_csets);
2699 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2700 * @mgctx: migration context
2702 * Tasks are about to be moved and all the source css_sets have been
2703 * preloaded to @mgctx->preloaded_src_csets. This function looks up and
2704 * pins all destination css_sets, links each to its source, and append them
2705 * to @mgctx->preloaded_dst_csets.
2707 * This function must be called after cgroup_migrate_add_src() has been
2708 * called on each migration source css_set. After migration is performed
2709 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2712 int cgroup_migrate_prepare_dst(struct cgroup_mgctx *mgctx)
2714 struct css_set *src_cset, *tmp_cset;
2716 lockdep_assert_held(&cgroup_mutex);
2718 /* look up the dst cset for each src cset and link it to src */
2719 list_for_each_entry_safe(src_cset, tmp_cset, &mgctx->preloaded_src_csets,
2720 mg_src_preload_node) {
2721 struct css_set *dst_cset;
2722 struct cgroup_subsys *ss;
2725 dst_cset = find_css_set(src_cset, src_cset->mg_dst_cgrp);
2729 WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
2732 * If src cset equals dst, it's noop. Drop the src.
2733 * cgroup_migrate() will skip the cset too. Note that we
2734 * can't handle src == dst as some nodes are used by both.
2736 if (src_cset == dst_cset) {
2737 src_cset->mg_src_cgrp = NULL;
2738 src_cset->mg_dst_cgrp = NULL;
2739 list_del_init(&src_cset->mg_src_preload_node);
2740 put_css_set(src_cset);
2741 put_css_set(dst_cset);
2745 src_cset->mg_dst_cset = dst_cset;
2747 if (list_empty(&dst_cset->mg_dst_preload_node))
2748 list_add_tail(&dst_cset->mg_dst_preload_node,
2749 &mgctx->preloaded_dst_csets);
2751 put_css_set(dst_cset);
2753 for_each_subsys(ss, ssid)
2754 if (src_cset->subsys[ssid] != dst_cset->subsys[ssid])
2755 mgctx->ss_mask |= 1 << ssid;
2762 * cgroup_migrate - migrate a process or task to a cgroup
2763 * @leader: the leader of the process or the task to migrate
2764 * @threadgroup: whether @leader points to the whole process or a single task
2765 * @mgctx: migration context
2767 * Migrate a process or task denoted by @leader. If migrating a process,
2768 * the caller must be holding cgroup_threadgroup_rwsem. The caller is also
2769 * responsible for invoking cgroup_migrate_add_src() and
2770 * cgroup_migrate_prepare_dst() on the targets before invoking this
2771 * function and following up with cgroup_migrate_finish().
2773 * As long as a controller's ->can_attach() doesn't fail, this function is
2774 * guaranteed to succeed. This means that, excluding ->can_attach()
2775 * failure, when migrating multiple targets, the success or failure can be
2776 * decided for all targets by invoking group_migrate_prepare_dst() before
2777 * actually starting migrating.
2779 int cgroup_migrate(struct task_struct *leader, bool threadgroup,
2780 struct cgroup_mgctx *mgctx)
2782 struct task_struct *task;
2785 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2786 * already PF_EXITING could be freed from underneath us unless we
2787 * take an rcu_read_lock.
2789 spin_lock_irq(&css_set_lock);
2793 cgroup_migrate_add_task(task, mgctx);
2796 } while_each_thread(leader, task);
2798 spin_unlock_irq(&css_set_lock);
2800 return cgroup_migrate_execute(mgctx);
2804 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2805 * @dst_cgrp: the cgroup to attach to
2806 * @leader: the task or the leader of the threadgroup to be attached
2807 * @threadgroup: attach the whole threadgroup?
2809 * Call holding cgroup_mutex and cgroup_threadgroup_rwsem.
2811 int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
2814 DEFINE_CGROUP_MGCTX(mgctx);
2815 struct task_struct *task;
2818 /* look up all src csets */
2819 spin_lock_irq(&css_set_lock);
2823 cgroup_migrate_add_src(task_css_set(task), dst_cgrp, &mgctx);
2826 } while_each_thread(leader, task);
2828 spin_unlock_irq(&css_set_lock);
2830 /* prepare dst csets and commit */
2831 ret = cgroup_migrate_prepare_dst(&mgctx);
2833 ret = cgroup_migrate(leader, threadgroup, &mgctx);
2835 cgroup_migrate_finish(&mgctx);
2838 TRACE_CGROUP_PATH(attach_task, dst_cgrp, leader, threadgroup);
2843 struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup,
2845 __acquires(&cgroup_threadgroup_rwsem)
2847 struct task_struct *tsk;
2850 if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
2851 return ERR_PTR(-EINVAL);
2854 * If we migrate a single thread, we don't care about threadgroup
2855 * stability. If the thread is `current`, it won't exit(2) under our
2856 * hands or change PID through exec(2). We exclude
2857 * cgroup_update_dfl_csses and other cgroup_{proc,thread}s_write
2858 * callers by cgroup_mutex.
2859 * Therefore, we can skip the global lock.
2861 lockdep_assert_held(&cgroup_mutex);
2862 if (pid || threadgroup) {
2863 percpu_down_write(&cgroup_threadgroup_rwsem);
2871 tsk = find_task_by_vpid(pid);
2873 tsk = ERR_PTR(-ESRCH);
2874 goto out_unlock_threadgroup;
2881 tsk = tsk->group_leader;
2884 * kthreads may acquire PF_NO_SETAFFINITY during initialization.
2885 * If userland migrates such a kthread to a non-root cgroup, it can
2886 * become trapped in a cpuset, or RT kthread may be born in a
2887 * cgroup with no rt_runtime allocated. Just say no.
2889 if (tsk->no_cgroup_migration || (tsk->flags & PF_NO_SETAFFINITY)) {
2890 tsk = ERR_PTR(-EINVAL);
2891 goto out_unlock_threadgroup;
2894 get_task_struct(tsk);
2895 goto out_unlock_rcu;
2897 out_unlock_threadgroup:
2899 percpu_up_write(&cgroup_threadgroup_rwsem);
2907 void cgroup_procs_write_finish(struct task_struct *task, bool locked)
2908 __releases(&cgroup_threadgroup_rwsem)
2910 struct cgroup_subsys *ss;
2913 /* release reference from cgroup_procs_write_start() */
2914 put_task_struct(task);
2917 percpu_up_write(&cgroup_threadgroup_rwsem);
2918 for_each_subsys(ss, ssid)
2919 if (ss->post_attach)
2923 static void cgroup_print_ss_mask(struct seq_file *seq, u16 ss_mask)
2925 struct cgroup_subsys *ss;
2926 bool printed = false;
2929 do_each_subsys_mask(ss, ssid, ss_mask) {
2932 seq_puts(seq, ss->name);
2934 } while_each_subsys_mask();
2936 seq_putc(seq, '\n');
2939 /* show controllers which are enabled from the parent */
2940 static int cgroup_controllers_show(struct seq_file *seq, void *v)
2942 struct cgroup *cgrp = seq_css(seq)->cgroup;
2944 cgroup_print_ss_mask(seq, cgroup_control(cgrp));
2948 /* show controllers which are enabled for a given cgroup's children */
2949 static int cgroup_subtree_control_show(struct seq_file *seq, void *v)
2951 struct cgroup *cgrp = seq_css(seq)->cgroup;
2953 cgroup_print_ss_mask(seq, cgrp->subtree_control);
2958 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
2959 * @cgrp: root of the subtree to update csses for
2961 * @cgrp's control masks have changed and its subtree's css associations
2962 * need to be updated accordingly. This function looks up all css_sets
2963 * which are attached to the subtree, creates the matching updated css_sets
2964 * and migrates the tasks to the new ones.
2966 static int cgroup_update_dfl_csses(struct cgroup *cgrp)
2968 DEFINE_CGROUP_MGCTX(mgctx);
2969 struct cgroup_subsys_state *d_css;
2970 struct cgroup *dsct;
2971 struct css_set *src_cset;
2975 lockdep_assert_held(&cgroup_mutex);
2977 /* look up all csses currently attached to @cgrp's subtree */
2978 spin_lock_irq(&css_set_lock);
2979 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
2980 struct cgrp_cset_link *link;
2983 * As cgroup_update_dfl_csses() is only called by
2984 * cgroup_apply_control(). The csses associated with the
2985 * given cgrp will not be affected by changes made to
2986 * its subtree_control file. We can skip them.
2991 list_for_each_entry(link, &dsct->cset_links, cset_link)
2992 cgroup_migrate_add_src(link->cset, dsct, &mgctx);
2994 spin_unlock_irq(&css_set_lock);
2997 * We need to write-lock threadgroup_rwsem while migrating tasks.
2998 * However, if there are no source csets for @cgrp, changing its
2999 * controllers isn't gonna produce any task migrations and the
3000 * write-locking can be skipped safely.
3002 has_tasks = !list_empty(&mgctx.preloaded_src_csets);
3004 percpu_down_write(&cgroup_threadgroup_rwsem);
3006 /* NULL dst indicates self on default hierarchy */
3007 ret = cgroup_migrate_prepare_dst(&mgctx);
3011 spin_lock_irq(&css_set_lock);
3012 list_for_each_entry(src_cset, &mgctx.preloaded_src_csets,
3013 mg_src_preload_node) {
3014 struct task_struct *task, *ntask;
3016 /* all tasks in src_csets need to be migrated */
3017 list_for_each_entry_safe(task, ntask, &src_cset->tasks, cg_list)
3018 cgroup_migrate_add_task(task, &mgctx);
3020 spin_unlock_irq(&css_set_lock);
3022 ret = cgroup_migrate_execute(&mgctx);
3024 cgroup_migrate_finish(&mgctx);
3026 percpu_up_write(&cgroup_threadgroup_rwsem);
3031 * cgroup_lock_and_drain_offline - lock cgroup_mutex and drain offlined csses
3032 * @cgrp: root of the target subtree
3034 * Because css offlining is asynchronous, userland may try to re-enable a
3035 * controller while the previous css is still around. This function grabs
3036 * cgroup_mutex and drains the previous css instances of @cgrp's subtree.
3038 void cgroup_lock_and_drain_offline(struct cgroup *cgrp)
3039 __acquires(&cgroup_mutex)
3041 struct cgroup *dsct;
3042 struct cgroup_subsys_state *d_css;
3043 struct cgroup_subsys *ss;
3047 mutex_lock(&cgroup_mutex);
3049 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3050 for_each_subsys(ss, ssid) {
3051 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3054 if (!css || !percpu_ref_is_dying(&css->refcnt))
3057 cgroup_get_live(dsct);
3058 prepare_to_wait(&dsct->offline_waitq, &wait,
3059 TASK_UNINTERRUPTIBLE);
3061 mutex_unlock(&cgroup_mutex);
3063 finish_wait(&dsct->offline_waitq, &wait);
3072 * cgroup_save_control - save control masks and dom_cgrp of a subtree
3073 * @cgrp: root of the target subtree
3075 * Save ->subtree_control, ->subtree_ss_mask and ->dom_cgrp to the
3076 * respective old_ prefixed fields for @cgrp's subtree including @cgrp
3079 static void cgroup_save_control(struct cgroup *cgrp)
3081 struct cgroup *dsct;
3082 struct cgroup_subsys_state *d_css;
3084 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3085 dsct->old_subtree_control = dsct->subtree_control;
3086 dsct->old_subtree_ss_mask = dsct->subtree_ss_mask;
3087 dsct->old_dom_cgrp = dsct->dom_cgrp;
3092 * cgroup_propagate_control - refresh control masks of a subtree
3093 * @cgrp: root of the target subtree
3095 * For @cgrp and its subtree, ensure ->subtree_ss_mask matches
3096 * ->subtree_control and propagate controller availability through the
3097 * subtree so that descendants don't have unavailable controllers enabled.
3099 static void cgroup_propagate_control(struct cgroup *cgrp)
3101 struct cgroup *dsct;
3102 struct cgroup_subsys_state *d_css;
3104 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3105 dsct->subtree_control &= cgroup_control(dsct);
3106 dsct->subtree_ss_mask =
3107 cgroup_calc_subtree_ss_mask(dsct->subtree_control,
3108 cgroup_ss_mask(dsct));
3113 * cgroup_restore_control - restore control masks and dom_cgrp of a subtree
3114 * @cgrp: root of the target subtree
3116 * Restore ->subtree_control, ->subtree_ss_mask and ->dom_cgrp from the
3117 * respective old_ prefixed fields for @cgrp's subtree including @cgrp
3120 static void cgroup_restore_control(struct cgroup *cgrp)
3122 struct cgroup *dsct;
3123 struct cgroup_subsys_state *d_css;
3125 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3126 dsct->subtree_control = dsct->old_subtree_control;
3127 dsct->subtree_ss_mask = dsct->old_subtree_ss_mask;
3128 dsct->dom_cgrp = dsct->old_dom_cgrp;
3132 static bool css_visible(struct cgroup_subsys_state *css)
3134 struct cgroup_subsys *ss = css->ss;
3135 struct cgroup *cgrp = css->cgroup;
3137 if (cgroup_control(cgrp) & (1 << ss->id))
3139 if (!(cgroup_ss_mask(cgrp) & (1 << ss->id)))
3141 return cgroup_on_dfl(cgrp) && ss->implicit_on_dfl;
3145 * cgroup_apply_control_enable - enable or show csses according to control
3146 * @cgrp: root of the target subtree
3148 * Walk @cgrp's subtree and create new csses or make the existing ones
3149 * visible. A css is created invisible if it's being implicitly enabled
3150 * through dependency. An invisible css is made visible when the userland
3151 * explicitly enables it.
3153 * Returns 0 on success, -errno on failure. On failure, csses which have
3154 * been processed already aren't cleaned up. The caller is responsible for
3155 * cleaning up with cgroup_apply_control_disable().
3157 static int cgroup_apply_control_enable(struct cgroup *cgrp)
3159 struct cgroup *dsct;
3160 struct cgroup_subsys_state *d_css;
3161 struct cgroup_subsys *ss;
3164 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3165 for_each_subsys(ss, ssid) {
3166 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3168 if (!(cgroup_ss_mask(dsct) & (1 << ss->id)))
3172 css = css_create(dsct, ss);
3174 return PTR_ERR(css);
3177 WARN_ON_ONCE(percpu_ref_is_dying(&css->refcnt));
3179 if (css_visible(css)) {
3180 ret = css_populate_dir(css);
3191 * cgroup_apply_control_disable - kill or hide csses according to control
3192 * @cgrp: root of the target subtree
3194 * Walk @cgrp's subtree and kill and hide csses so that they match
3195 * cgroup_ss_mask() and cgroup_visible_mask().
3197 * A css is hidden when the userland requests it to be disabled while other
3198 * subsystems are still depending on it. The css must not actively control
3199 * resources and be in the vanilla state if it's made visible again later.
3200 * Controllers which may be depended upon should provide ->css_reset() for
3203 static void cgroup_apply_control_disable(struct cgroup *cgrp)
3205 struct cgroup *dsct;
3206 struct cgroup_subsys_state *d_css;
3207 struct cgroup_subsys *ss;
3210 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3211 for_each_subsys(ss, ssid) {
3212 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3217 WARN_ON_ONCE(percpu_ref_is_dying(&css->refcnt));
3220 !(cgroup_ss_mask(dsct) & (1 << ss->id))) {
3222 } else if (!css_visible(css)) {
3232 * cgroup_apply_control - apply control mask updates to the subtree
3233 * @cgrp: root of the target subtree
3235 * subsystems can be enabled and disabled in a subtree using the following
3238 * 1. Call cgroup_save_control() to stash the current state.
3239 * 2. Update ->subtree_control masks in the subtree as desired.
3240 * 3. Call cgroup_apply_control() to apply the changes.
3241 * 4. Optionally perform other related operations.
3242 * 5. Call cgroup_finalize_control() to finish up.
3244 * This function implements step 3 and propagates the mask changes
3245 * throughout @cgrp's subtree, updates csses accordingly and perform
3246 * process migrations.
3248 static int cgroup_apply_control(struct cgroup *cgrp)
3252 cgroup_propagate_control(cgrp);
3254 ret = cgroup_apply_control_enable(cgrp);
3259 * At this point, cgroup_e_css_by_mask() results reflect the new csses
3260 * making the following cgroup_update_dfl_csses() properly update
3261 * css associations of all tasks in the subtree.
3263 ret = cgroup_update_dfl_csses(cgrp);
3271 * cgroup_finalize_control - finalize control mask update
3272 * @cgrp: root of the target subtree
3273 * @ret: the result of the update
3275 * Finalize control mask update. See cgroup_apply_control() for more info.
3277 static void cgroup_finalize_control(struct cgroup *cgrp, int ret)
3280 cgroup_restore_control(cgrp);
3281 cgroup_propagate_control(cgrp);
3284 cgroup_apply_control_disable(cgrp);
3287 static int cgroup_vet_subtree_control_enable(struct cgroup *cgrp, u16 enable)
3289 u16 domain_enable = enable & ~cgrp_dfl_threaded_ss_mask;
3291 /* if nothing is getting enabled, nothing to worry about */
3295 /* can @cgrp host any resources? */
3296 if (!cgroup_is_valid_domain(cgrp->dom_cgrp))
3299 /* mixables don't care */
3300 if (cgroup_is_mixable(cgrp))
3303 if (domain_enable) {
3304 /* can't enable domain controllers inside a thread subtree */
3305 if (cgroup_is_thread_root(cgrp) || cgroup_is_threaded(cgrp))
3309 * Threaded controllers can handle internal competitions
3310 * and are always allowed inside a (prospective) thread
3313 if (cgroup_can_be_thread_root(cgrp) || cgroup_is_threaded(cgrp))
3318 * Controllers can't be enabled for a cgroup with tasks to avoid
3319 * child cgroups competing against tasks.
3321 if (cgroup_has_tasks(cgrp))
3327 /* change the enabled child controllers for a cgroup in the default hierarchy */
3328 static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
3329 char *buf, size_t nbytes,
3332 u16 enable = 0, disable = 0;
3333 struct cgroup *cgrp, *child;
3334 struct cgroup_subsys *ss;
3339 * Parse input - space separated list of subsystem names prefixed
3340 * with either + or -.
3342 buf = strstrip(buf);
3343 while ((tok = strsep(&buf, " "))) {
3346 do_each_subsys_mask(ss, ssid, ~cgrp_dfl_inhibit_ss_mask) {
3347 if (!cgroup_ssid_enabled(ssid) ||
3348 strcmp(tok + 1, ss->name))
3352 enable |= 1 << ssid;
3353 disable &= ~(1 << ssid);
3354 } else if (*tok == '-') {
3355 disable |= 1 << ssid;
3356 enable &= ~(1 << ssid);
3361 } while_each_subsys_mask();
3362 if (ssid == CGROUP_SUBSYS_COUNT)
3366 cgrp = cgroup_kn_lock_live(of->kn, true);
3370 for_each_subsys(ss, ssid) {
3371 if (enable & (1 << ssid)) {
3372 if (cgrp->subtree_control & (1 << ssid)) {
3373 enable &= ~(1 << ssid);
3377 if (!(cgroup_control(cgrp) & (1 << ssid))) {
3381 } else if (disable & (1 << ssid)) {
3382 if (!(cgrp->subtree_control & (1 << ssid))) {
3383 disable &= ~(1 << ssid);
3387 /* a child has it enabled? */
3388 cgroup_for_each_live_child(child, cgrp) {
3389 if (child->subtree_control & (1 << ssid)) {
3397 if (!enable && !disable) {
3402 ret = cgroup_vet_subtree_control_enable(cgrp, enable);
3406 /* save and update control masks and prepare csses */
3407 cgroup_save_control(cgrp);
3409 cgrp->subtree_control |= enable;
3410 cgrp->subtree_control &= ~disable;
3412 ret = cgroup_apply_control(cgrp);
3413 cgroup_finalize_control(cgrp, ret);
3417 kernfs_activate(cgrp->kn);
3419 cgroup_kn_unlock(of->kn);
3420 return ret ?: nbytes;
3424 * cgroup_enable_threaded - make @cgrp threaded
3425 * @cgrp: the target cgroup
3427 * Called when "threaded" is written to the cgroup.type interface file and
3428 * tries to make @cgrp threaded and join the parent's resource domain.
3429 * This function is never called on the root cgroup as cgroup.type doesn't
3432 static int cgroup_enable_threaded(struct cgroup *cgrp)
3434 struct cgroup *parent = cgroup_parent(cgrp);
3435 struct cgroup *dom_cgrp = parent->dom_cgrp;
3436 struct cgroup *dsct;
3437 struct cgroup_subsys_state *d_css;
3440 lockdep_assert_held(&cgroup_mutex);
3442 /* noop if already threaded */
3443 if (cgroup_is_threaded(cgrp))
3447 * If @cgroup is populated or has domain controllers enabled, it
3448 * can't be switched. While the below cgroup_can_be_thread_root()
3449 * test can catch the same conditions, that's only when @parent is
3450 * not mixable, so let's check it explicitly.
3452 if (cgroup_is_populated(cgrp) ||
3453 cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)
3456 /* we're joining the parent's domain, ensure its validity */
3457 if (!cgroup_is_valid_domain(dom_cgrp) ||
3458 !cgroup_can_be_thread_root(dom_cgrp))
3462 * The following shouldn't cause actual migrations and should
3465 cgroup_save_control(cgrp);
3467 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp)
3468 if (dsct == cgrp || cgroup_is_threaded(dsct))
3469 dsct->dom_cgrp = dom_cgrp;
3471 ret = cgroup_apply_control(cgrp);
3473 parent->nr_threaded_children++;
3475 cgroup_finalize_control(cgrp, ret);
3479 static int cgroup_type_show(struct seq_file *seq, void *v)
3481 struct cgroup *cgrp = seq_css(seq)->cgroup;
3483 if (cgroup_is_threaded(cgrp))
3484 seq_puts(seq, "threaded\n");
3485 else if (!cgroup_is_valid_domain(cgrp))
3486 seq_puts(seq, "domain invalid\n");
3487 else if (cgroup_is_thread_root(cgrp))
3488 seq_puts(seq, "domain threaded\n");
3490 seq_puts(seq, "domain\n");
3495 static ssize_t cgroup_type_write(struct kernfs_open_file *of, char *buf,
3496 size_t nbytes, loff_t off)
3498 struct cgroup *cgrp;
3501 /* only switching to threaded mode is supported */
3502 if (strcmp(strstrip(buf), "threaded"))
3505 /* drain dying csses before we re-apply (threaded) subtree control */
3506 cgrp = cgroup_kn_lock_live(of->kn, true);
3510 /* threaded can only be enabled */
3511 ret = cgroup_enable_threaded(cgrp);
3513 cgroup_kn_unlock(of->kn);
3514 return ret ?: nbytes;
3517 static int cgroup_max_descendants_show(struct seq_file *seq, void *v)
3519 struct cgroup *cgrp = seq_css(seq)->cgroup;
3520 int descendants = READ_ONCE(cgrp->max_descendants);
3522 if (descendants == INT_MAX)
3523 seq_puts(seq, "max\n");
3525 seq_printf(seq, "%d\n", descendants);
3530 static ssize_t cgroup_max_descendants_write(struct kernfs_open_file *of,
3531 char *buf, size_t nbytes, loff_t off)
3533 struct cgroup *cgrp;
3537 buf = strstrip(buf);
3538 if (!strcmp(buf, "max")) {
3539 descendants = INT_MAX;
3541 ret = kstrtoint(buf, 0, &descendants);
3546 if (descendants < 0)
3549 cgrp = cgroup_kn_lock_live(of->kn, false);
3553 cgrp->max_descendants = descendants;
3555 cgroup_kn_unlock(of->kn);
3560 static int cgroup_max_depth_show(struct seq_file *seq, void *v)
3562 struct cgroup *cgrp = seq_css(seq)->cgroup;
3563 int depth = READ_ONCE(cgrp->max_depth);
3565 if (depth == INT_MAX)
3566 seq_puts(seq, "max\n");
3568 seq_printf(seq, "%d\n", depth);
3573 static ssize_t cgroup_max_depth_write(struct kernfs_open_file *of,
3574 char *buf, size_t nbytes, loff_t off)
3576 struct cgroup *cgrp;
3580 buf = strstrip(buf);
3581 if (!strcmp(buf, "max")) {
3584 ret = kstrtoint(buf, 0, &depth);
3592 cgrp = cgroup_kn_lock_live(of->kn, false);
3596 cgrp->max_depth = depth;
3598 cgroup_kn_unlock(of->kn);
3603 static int cgroup_events_show(struct seq_file *seq, void *v)
3605 struct cgroup *cgrp = seq_css(seq)->cgroup;
3607 seq_printf(seq, "populated %d\n", cgroup_is_populated(cgrp));
3608 seq_printf(seq, "frozen %d\n", test_bit(CGRP_FROZEN, &cgrp->flags));
3613 static int cgroup_stat_show(struct seq_file *seq, void *v)
3615 struct cgroup *cgroup = seq_css(seq)->cgroup;
3617 seq_printf(seq, "nr_descendants %d\n",
3618 cgroup->nr_descendants);
3619 seq_printf(seq, "nr_dying_descendants %d\n",
3620 cgroup->nr_dying_descendants);
3625 static int __maybe_unused cgroup_extra_stat_show(struct seq_file *seq,
3626 struct cgroup *cgrp, int ssid)
3628 struct cgroup_subsys *ss = cgroup_subsys[ssid];
3629 struct cgroup_subsys_state *css;
3632 if (!ss->css_extra_stat_show)
3635 css = cgroup_tryget_css(cgrp, ss);
3639 ret = ss->css_extra_stat_show(seq, css);
3644 static int cpu_stat_show(struct seq_file *seq, void *v)
3646 struct cgroup __maybe_unused *cgrp = seq_css(seq)->cgroup;
3649 cgroup_base_stat_cputime_show(seq);
3650 #ifdef CONFIG_CGROUP_SCHED
3651 ret = cgroup_extra_stat_show(seq, cgrp, cpu_cgrp_id);
3657 static int cgroup_io_pressure_show(struct seq_file *seq, void *v)
3659 struct cgroup *cgrp = seq_css(seq)->cgroup;
3660 struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : cgrp->psi;
3662 return psi_show(seq, psi, PSI_IO);
3664 static int cgroup_memory_pressure_show(struct seq_file *seq, void *v)
3666 struct cgroup *cgrp = seq_css(seq)->cgroup;
3667 struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : cgrp->psi;
3669 return psi_show(seq, psi, PSI_MEM);
3671 static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v)
3673 struct cgroup *cgrp = seq_css(seq)->cgroup;
3674 struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : cgrp->psi;
3676 return psi_show(seq, psi, PSI_CPU);
3679 static ssize_t cgroup_pressure_write(struct kernfs_open_file *of, char *buf,
3680 size_t nbytes, enum psi_res res)
3682 struct cgroup_file_ctx *ctx = of->priv;
3683 struct psi_trigger *new;
3684 struct cgroup *cgrp;
3685 struct psi_group *psi;
3687 cgrp = cgroup_kn_lock_live(of->kn, false);
3692 cgroup_kn_unlock(of->kn);
3694 /* Allow only one trigger per file descriptor */
3695 if (ctx->psi.trigger) {
3700 psi = cgroup_ino(cgrp) == 1 ? &psi_system : cgrp->psi;
3701 new = psi_trigger_create(psi, buf, nbytes, res);
3704 return PTR_ERR(new);
3707 smp_store_release(&ctx->psi.trigger, new);
3713 static ssize_t cgroup_io_pressure_write(struct kernfs_open_file *of,
3714 char *buf, size_t nbytes,
3717 return cgroup_pressure_write(of, buf, nbytes, PSI_IO);
3720 static ssize_t cgroup_memory_pressure_write(struct kernfs_open_file *of,
3721 char *buf, size_t nbytes,
3724 return cgroup_pressure_write(of, buf, nbytes, PSI_MEM);
3727 static ssize_t cgroup_cpu_pressure_write(struct kernfs_open_file *of,
3728 char *buf, size_t nbytes,
3731 return cgroup_pressure_write(of, buf, nbytes, PSI_CPU);
3734 static __poll_t cgroup_pressure_poll(struct kernfs_open_file *of,
3737 struct cgroup_file_ctx *ctx = of->priv;
3739 return psi_trigger_poll(&ctx->psi.trigger, of->file, pt);
3742 static void cgroup_pressure_release(struct kernfs_open_file *of)
3744 struct cgroup_file_ctx *ctx = of->priv;
3746 psi_trigger_destroy(ctx->psi.trigger);
3749 bool cgroup_psi_enabled(void)
3751 return (cgroup_feature_disable_mask & (1 << OPT_FEATURE_PRESSURE)) == 0;
3754 #else /* CONFIG_PSI */
3755 bool cgroup_psi_enabled(void)
3760 #endif /* CONFIG_PSI */
3762 static int cgroup_freeze_show(struct seq_file *seq, void *v)
3764 struct cgroup *cgrp = seq_css(seq)->cgroup;
3766 seq_printf(seq, "%d\n", cgrp->freezer.freeze);
3771 static ssize_t cgroup_freeze_write(struct kernfs_open_file *of,
3772 char *buf, size_t nbytes, loff_t off)
3774 struct cgroup *cgrp;
3778 ret = kstrtoint(strstrip(buf), 0, &freeze);
3782 if (freeze < 0 || freeze > 1)
3785 cgrp = cgroup_kn_lock_live(of->kn, false);
3789 cgroup_freeze(cgrp, freeze);
3791 cgroup_kn_unlock(of->kn);
3796 static void __cgroup_kill(struct cgroup *cgrp)
3798 struct css_task_iter it;
3799 struct task_struct *task;
3801 lockdep_assert_held(&cgroup_mutex);
3803 spin_lock_irq(&css_set_lock);
3804 set_bit(CGRP_KILL, &cgrp->flags);
3805 spin_unlock_irq(&css_set_lock);
3807 css_task_iter_start(&cgrp->self, CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED, &it);
3808 while ((task = css_task_iter_next(&it))) {
3809 /* Ignore kernel threads here. */
3810 if (task->flags & PF_KTHREAD)
3813 /* Skip tasks that are already dying. */
3814 if (__fatal_signal_pending(task))
3817 send_sig(SIGKILL, task, 0);
3819 css_task_iter_end(&it);
3821 spin_lock_irq(&css_set_lock);
3822 clear_bit(CGRP_KILL, &cgrp->flags);
3823 spin_unlock_irq(&css_set_lock);
3826 static void cgroup_kill(struct cgroup *cgrp)
3828 struct cgroup_subsys_state *css;
3829 struct cgroup *dsct;
3831 lockdep_assert_held(&cgroup_mutex);
3833 cgroup_for_each_live_descendant_pre(dsct, css, cgrp)
3834 __cgroup_kill(dsct);
3837 static ssize_t cgroup_kill_write(struct kernfs_open_file *of, char *buf,
3838 size_t nbytes, loff_t off)
3842 struct cgroup *cgrp;
3844 ret = kstrtoint(strstrip(buf), 0, &kill);
3851 cgrp = cgroup_kn_lock_live(of->kn, false);
3856 * Killing is a process directed operation, i.e. the whole thread-group
3857 * is taken down so act like we do for cgroup.procs and only make this
3858 * writable in non-threaded cgroups.
3860 if (cgroup_is_threaded(cgrp))
3865 cgroup_kn_unlock(of->kn);
3867 return ret ?: nbytes;
3870 static int cgroup_file_open(struct kernfs_open_file *of)
3872 struct cftype *cft = of_cft(of);
3873 struct cgroup_file_ctx *ctx;
3876 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
3880 ctx->ns = current->nsproxy->cgroup_ns;
3881 get_cgroup_ns(ctx->ns);
3887 ret = cft->open(of);
3889 put_cgroup_ns(ctx->ns);
3895 static void cgroup_file_release(struct kernfs_open_file *of)
3897 struct cftype *cft = of_cft(of);
3898 struct cgroup_file_ctx *ctx = of->priv;
3902 put_cgroup_ns(ctx->ns);
3906 static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
3907 size_t nbytes, loff_t off)
3909 struct cgroup_file_ctx *ctx = of->priv;
3910 struct cgroup *cgrp = of->kn->parent->priv;
3911 struct cftype *cft = of_cft(of);
3912 struct cgroup_subsys_state *css;
3919 * If namespaces are delegation boundaries, disallow writes to
3920 * files in an non-init namespace root from inside the namespace
3921 * except for the files explicitly marked delegatable -
3922 * cgroup.procs and cgroup.subtree_control.
3924 if ((cgrp->root->flags & CGRP_ROOT_NS_DELEGATE) &&
3925 !(cft->flags & CFTYPE_NS_DELEGATABLE) &&
3926 ctx->ns != &init_cgroup_ns && ctx->ns->root_cset->dfl_cgrp == cgrp)
3930 return cft->write(of, buf, nbytes, off);
3933 * kernfs guarantees that a file isn't deleted with operations in
3934 * flight, which means that the matching css is and stays alive and
3935 * doesn't need to be pinned. The RCU locking is not necessary
3936 * either. It's just for the convenience of using cgroup_css().
3939 css = cgroup_css(cgrp, cft->ss);
3942 if (cft->write_u64) {
3943 unsigned long long v;
3944 ret = kstrtoull(buf, 0, &v);
3946 ret = cft->write_u64(css, cft, v);
3947 } else if (cft->write_s64) {
3949 ret = kstrtoll(buf, 0, &v);
3951 ret = cft->write_s64(css, cft, v);
3956 return ret ?: nbytes;
3959 static __poll_t cgroup_file_poll(struct kernfs_open_file *of, poll_table *pt)
3961 struct cftype *cft = of_cft(of);
3964 return cft->poll(of, pt);
3966 return kernfs_generic_poll(of, pt);
3969 static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
3971 return seq_cft(seq)->seq_start(seq, ppos);
3974 static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
3976 return seq_cft(seq)->seq_next(seq, v, ppos);
3979 static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
3981 if (seq_cft(seq)->seq_stop)
3982 seq_cft(seq)->seq_stop(seq, v);
3985 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
3987 struct cftype *cft = seq_cft(m);
3988 struct cgroup_subsys_state *css = seq_css(m);
3991 return cft->seq_show(m, arg);
3994 seq_printf(m, "%llu\n", cft->read_u64(css, cft));
3995 else if (cft->read_s64)
3996 seq_printf(m, "%lld\n", cft->read_s64(css, cft));
4002 static struct kernfs_ops cgroup_kf_single_ops = {
4003 .atomic_write_len = PAGE_SIZE,
4004 .open = cgroup_file_open,
4005 .release = cgroup_file_release,
4006 .write = cgroup_file_write,
4007 .poll = cgroup_file_poll,
4008 .seq_show = cgroup_seqfile_show,
4011 static struct kernfs_ops cgroup_kf_ops = {
4012 .atomic_write_len = PAGE_SIZE,
4013 .open = cgroup_file_open,
4014 .release = cgroup_file_release,
4015 .write = cgroup_file_write,
4016 .poll = cgroup_file_poll,
4017 .seq_start = cgroup_seqfile_start,
4018 .seq_next = cgroup_seqfile_next,
4019 .seq_stop = cgroup_seqfile_stop,
4020 .seq_show = cgroup_seqfile_show,
4023 /* set uid and gid of cgroup dirs and files to that of the creator */
4024 static int cgroup_kn_set_ugid(struct kernfs_node *kn)
4026 struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
4027 .ia_uid = current_fsuid(),
4028 .ia_gid = current_fsgid(), };
4030 if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
4031 gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
4034 return kernfs_setattr(kn, &iattr);
4037 static void cgroup_file_notify_timer(struct timer_list *timer)
4039 cgroup_file_notify(container_of(timer, struct cgroup_file,
4043 static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
4046 char name[CGROUP_FILE_NAME_MAX];
4047 struct kernfs_node *kn;
4048 struct lock_class_key *key = NULL;
4051 #ifdef CONFIG_DEBUG_LOCK_ALLOC
4052 key = &cft->lockdep_key;
4054 kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
4055 cgroup_file_mode(cft),
4056 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
4057 0, cft->kf_ops, cft,
4062 ret = cgroup_kn_set_ugid(kn);
4068 if (cft->file_offset) {
4069 struct cgroup_file *cfile = (void *)css + cft->file_offset;
4071 timer_setup(&cfile->notify_timer, cgroup_file_notify_timer, 0);
4073 spin_lock_irq(&cgroup_file_kn_lock);
4075 spin_unlock_irq(&cgroup_file_kn_lock);
4082 * cgroup_addrm_files - add or remove files to a cgroup directory
4083 * @css: the target css
4084 * @cgrp: the target cgroup (usually css->cgroup)
4085 * @cfts: array of cftypes to be added
4086 * @is_add: whether to add or remove
4088 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
4089 * For removals, this function never fails.
4091 static int cgroup_addrm_files(struct cgroup_subsys_state *css,
4092 struct cgroup *cgrp, struct cftype cfts[],
4095 struct cftype *cft, *cft_end = NULL;
4098 lockdep_assert_held(&cgroup_mutex);
4101 for (cft = cfts; cft != cft_end && cft->name[0] != '\0'; cft++) {
4102 /* does cft->flags tell us to skip this file on @cgrp? */
4103 if ((cft->flags & CFTYPE_PRESSURE) && !cgroup_psi_enabled())
4105 if ((cft->flags & __CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
4107 if ((cft->flags & __CFTYPE_NOT_ON_DFL) && cgroup_on_dfl(cgrp))
4109 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp))
4111 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp))
4113 if ((cft->flags & CFTYPE_DEBUG) && !cgroup_debug)
4116 ret = cgroup_add_file(css, cgrp, cft);
4118 pr_warn("%s: failed to add %s, err=%d\n",
4119 __func__, cft->name, ret);
4125 cgroup_rm_file(cgrp, cft);
4131 static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
4133 struct cgroup_subsys *ss = cfts[0].ss;
4134 struct cgroup *root = &ss->root->cgrp;
4135 struct cgroup_subsys_state *css;
4138 lockdep_assert_held(&cgroup_mutex);
4140 /* add/rm files for all cgroups created before */
4141 css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
4142 struct cgroup *cgrp = css->cgroup;
4144 if (!(css->flags & CSS_VISIBLE))
4147 ret = cgroup_addrm_files(css, cgrp, cfts, is_add);
4153 kernfs_activate(root->kn);
4157 static void cgroup_exit_cftypes(struct cftype *cfts)
4161 for (cft = cfts; cft->name[0] != '\0'; cft++) {
4162 /* free copy for custom atomic_write_len, see init_cftypes() */
4163 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
4168 /* revert flags set by cgroup core while adding @cfts */
4169 cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL);
4173 static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4177 for (cft = cfts; cft->name[0] != '\0'; cft++) {
4178 struct kernfs_ops *kf_ops;
4180 WARN_ON(cft->ss || cft->kf_ops);
4182 if ((cft->flags & CFTYPE_PRESSURE) && !cgroup_psi_enabled())
4186 kf_ops = &cgroup_kf_ops;
4188 kf_ops = &cgroup_kf_single_ops;
4191 * Ugh... if @cft wants a custom max_write_len, we need to
4192 * make a copy of kf_ops to set its atomic_write_len.
4194 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
4195 kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
4197 cgroup_exit_cftypes(cfts);
4200 kf_ops->atomic_write_len = cft->max_write_len;
4203 cft->kf_ops = kf_ops;
4210 static int cgroup_rm_cftypes_locked(struct cftype *cfts)
4212 lockdep_assert_held(&cgroup_mutex);
4214 if (!cfts || !cfts[0].ss)
4217 list_del(&cfts->node);
4218 cgroup_apply_cftypes(cfts, false);
4219 cgroup_exit_cftypes(cfts);
4224 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
4225 * @cfts: zero-length name terminated array of cftypes
4227 * Unregister @cfts. Files described by @cfts are removed from all
4228 * existing cgroups and all future cgroups won't have them either. This
4229 * function can be called anytime whether @cfts' subsys is attached or not.
4231 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
4234 int cgroup_rm_cftypes(struct cftype *cfts)
4238 mutex_lock(&cgroup_mutex);
4239 ret = cgroup_rm_cftypes_locked(cfts);
4240 mutex_unlock(&cgroup_mutex);
4245 * cgroup_add_cftypes - add an array of cftypes to a subsystem
4246 * @ss: target cgroup subsystem
4247 * @cfts: zero-length name terminated array of cftypes
4249 * Register @cfts to @ss. Files described by @cfts are created for all
4250 * existing cgroups to which @ss is attached and all future cgroups will
4251 * have them too. This function can be called anytime whether @ss is
4254 * Returns 0 on successful registration, -errno on failure. Note that this
4255 * function currently returns 0 as long as @cfts registration is successful
4256 * even if some file creation attempts on existing cgroups fail.
4258 static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4262 if (!cgroup_ssid_enabled(ss->id))
4265 if (!cfts || cfts[0].name[0] == '\0')
4268 ret = cgroup_init_cftypes(ss, cfts);
4272 mutex_lock(&cgroup_mutex);
4274 list_add_tail(&cfts->node, &ss->cfts);
4275 ret = cgroup_apply_cftypes(cfts, true);
4277 cgroup_rm_cftypes_locked(cfts);
4279 mutex_unlock(&cgroup_mutex);
4284 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
4285 * @ss: target cgroup subsystem
4286 * @cfts: zero-length name terminated array of cftypes
4288 * Similar to cgroup_add_cftypes() but the added files are only used for
4289 * the default hierarchy.
4291 int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4295 for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
4296 cft->flags |= __CFTYPE_ONLY_ON_DFL;
4297 return cgroup_add_cftypes(ss, cfts);
4301 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
4302 * @ss: target cgroup subsystem
4303 * @cfts: zero-length name terminated array of cftypes
4305 * Similar to cgroup_add_cftypes() but the added files are only used for
4306 * the legacy hierarchies.
4308 int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4312 for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
4313 cft->flags |= __CFTYPE_NOT_ON_DFL;
4314 return cgroup_add_cftypes(ss, cfts);
4318 * cgroup_file_notify - generate a file modified event for a cgroup_file
4319 * @cfile: target cgroup_file
4321 * @cfile must have been obtained by setting cftype->file_offset.
4323 void cgroup_file_notify(struct cgroup_file *cfile)
4325 unsigned long flags;
4327 spin_lock_irqsave(&cgroup_file_kn_lock, flags);
4329 unsigned long last = cfile->notified_at;
4330 unsigned long next = last + CGROUP_FILE_NOTIFY_MIN_INTV;
4332 if (time_in_range(jiffies, last, next)) {
4333 timer_reduce(&cfile->notify_timer, next);
4335 kernfs_notify(cfile->kn);
4336 cfile->notified_at = jiffies;
4339 spin_unlock_irqrestore(&cgroup_file_kn_lock, flags);
4343 * css_next_child - find the next child of a given css
4344 * @pos: the current position (%NULL to initiate traversal)
4345 * @parent: css whose children to walk
4347 * This function returns the next child of @parent and should be called
4348 * under either cgroup_mutex or RCU read lock. The only requirement is
4349 * that @parent and @pos are accessible. The next sibling is guaranteed to
4350 * be returned regardless of their states.
4352 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4353 * css which finished ->css_online() is guaranteed to be visible in the
4354 * future iterations and will stay visible until the last reference is put.
4355 * A css which hasn't finished ->css_online() or already finished
4356 * ->css_offline() may show up during traversal. It's each subsystem's
4357 * responsibility to synchronize against on/offlining.
4359 struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
4360 struct cgroup_subsys_state *parent)
4362 struct cgroup_subsys_state *next;
4364 cgroup_assert_mutex_or_rcu_locked();
4367 * @pos could already have been unlinked from the sibling list.
4368 * Once a cgroup is removed, its ->sibling.next is no longer
4369 * updated when its next sibling changes. CSS_RELEASED is set when
4370 * @pos is taken off list, at which time its next pointer is valid,
4371 * and, as releases are serialized, the one pointed to by the next
4372 * pointer is guaranteed to not have started release yet. This
4373 * implies that if we observe !CSS_RELEASED on @pos in this RCU
4374 * critical section, the one pointed to by its next pointer is
4375 * guaranteed to not have finished its RCU grace period even if we
4376 * have dropped rcu_read_lock() in-between iterations.
4378 * If @pos has CSS_RELEASED set, its next pointer can't be
4379 * dereferenced; however, as each css is given a monotonically
4380 * increasing unique serial number and always appended to the
4381 * sibling list, the next one can be found by walking the parent's
4382 * children until the first css with higher serial number than
4383 * @pos's. While this path can be slower, it happens iff iteration
4384 * races against release and the race window is very small.
4387 next = list_entry_rcu(parent->children.next, struct cgroup_subsys_state, sibling);
4388 } else if (likely(!(pos->flags & CSS_RELEASED))) {
4389 next = list_entry_rcu(pos->sibling.next, struct cgroup_subsys_state, sibling);
4391 list_for_each_entry_rcu(next, &parent->children, sibling,
4392 lockdep_is_held(&cgroup_mutex))
4393 if (next->serial_nr > pos->serial_nr)
4398 * @next, if not pointing to the head, can be dereferenced and is
4401 if (&next->sibling != &parent->children)
4407 * css_next_descendant_pre - find the next descendant for pre-order walk
4408 * @pos: the current position (%NULL to initiate traversal)
4409 * @root: css whose descendants to walk
4411 * To be used by css_for_each_descendant_pre(). Find the next descendant
4412 * to visit for pre-order traversal of @root's descendants. @root is
4413 * included in the iteration and the first node to be visited.
4415 * While this function requires cgroup_mutex or RCU read locking, it
4416 * doesn't require the whole traversal to be contained in a single critical
4417 * section. This function will return the correct next descendant as long
4418 * as both @pos and @root are accessible and @pos is a descendant of @root.
4420 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4421 * css which finished ->css_online() is guaranteed to be visible in the
4422 * future iterations and will stay visible until the last reference is put.
4423 * A css which hasn't finished ->css_online() or already finished
4424 * ->css_offline() may show up during traversal. It's each subsystem's
4425 * responsibility to synchronize against on/offlining.
4427 struct cgroup_subsys_state *
4428 css_next_descendant_pre(struct cgroup_subsys_state *pos,
4429 struct cgroup_subsys_state *root)
4431 struct cgroup_subsys_state *next;
4433 cgroup_assert_mutex_or_rcu_locked();
4435 /* if first iteration, visit @root */
4439 /* visit the first child if exists */
4440 next = css_next_child(NULL, pos);
4444 /* no child, visit my or the closest ancestor's next sibling */
4445 while (pos != root) {
4446 next = css_next_child(pos, pos->parent);
4454 EXPORT_SYMBOL_GPL(css_next_descendant_pre);
4457 * css_rightmost_descendant - return the rightmost descendant of a css
4458 * @pos: css of interest
4460 * Return the rightmost descendant of @pos. If there's no descendant, @pos
4461 * is returned. This can be used during pre-order traversal to skip
4464 * While this function requires cgroup_mutex or RCU read locking, it
4465 * doesn't require the whole traversal to be contained in a single critical
4466 * section. This function will return the correct rightmost descendant as
4467 * long as @pos is accessible.
4469 struct cgroup_subsys_state *
4470 css_rightmost_descendant(struct cgroup_subsys_state *pos)
4472 struct cgroup_subsys_state *last, *tmp;
4474 cgroup_assert_mutex_or_rcu_locked();
4478 /* ->prev isn't RCU safe, walk ->next till the end */
4480 css_for_each_child(tmp, last)
4487 static struct cgroup_subsys_state *
4488 css_leftmost_descendant(struct cgroup_subsys_state *pos)
4490 struct cgroup_subsys_state *last;
4494 pos = css_next_child(NULL, pos);
4501 * css_next_descendant_post - find the next descendant for post-order walk
4502 * @pos: the current position (%NULL to initiate traversal)
4503 * @root: css whose descendants to walk
4505 * To be used by css_for_each_descendant_post(). Find the next descendant
4506 * to visit for post-order traversal of @root's descendants. @root is
4507 * included in the iteration and the last node to be visited.
4509 * While this function requires cgroup_mutex or RCU read locking, it
4510 * doesn't require the whole traversal to be contained in a single critical
4511 * section. This function will return the correct next descendant as long
4512 * as both @pos and @cgroup are accessible and @pos is a descendant of
4515 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4516 * css which finished ->css_online() is guaranteed to be visible in the
4517 * future iterations and will stay visible until the last reference is put.
4518 * A css which hasn't finished ->css_online() or already finished
4519 * ->css_offline() may show up during traversal. It's each subsystem's
4520 * responsibility to synchronize against on/offlining.
4522 struct cgroup_subsys_state *
4523 css_next_descendant_post(struct cgroup_subsys_state *pos,
4524 struct cgroup_subsys_state *root)
4526 struct cgroup_subsys_state *next;
4528 cgroup_assert_mutex_or_rcu_locked();
4530 /* if first iteration, visit leftmost descendant which may be @root */
4532 return css_leftmost_descendant(root);
4534 /* if we visited @root, we're done */
4538 /* if there's an unvisited sibling, visit its leftmost descendant */
4539 next = css_next_child(pos, pos->parent);
4541 return css_leftmost_descendant(next);
4543 /* no sibling left, visit parent */
4548 * css_has_online_children - does a css have online children
4549 * @css: the target css
4551 * Returns %true if @css has any online children; otherwise, %false. This
4552 * function can be called from any context but the caller is responsible
4553 * for synchronizing against on/offlining as necessary.
4555 bool css_has_online_children(struct cgroup_subsys_state *css)
4557 struct cgroup_subsys_state *child;
4561 css_for_each_child(child, css) {
4562 if (child->flags & CSS_ONLINE) {
4571 static struct css_set *css_task_iter_next_css_set(struct css_task_iter *it)
4573 struct list_head *l;
4574 struct cgrp_cset_link *link;
4575 struct css_set *cset;
4577 lockdep_assert_held(&css_set_lock);
4579 /* find the next threaded cset */
4580 if (it->tcset_pos) {
4581 l = it->tcset_pos->next;
4583 if (l != it->tcset_head) {
4585 return container_of(l, struct css_set,
4586 threaded_csets_node);
4589 it->tcset_pos = NULL;
4592 /* find the next cset */
4595 if (l == it->cset_head) {
4596 it->cset_pos = NULL;
4601 cset = container_of(l, struct css_set, e_cset_node[it->ss->id]);
4603 link = list_entry(l, struct cgrp_cset_link, cset_link);
4609 /* initialize threaded css_set walking */
4610 if (it->flags & CSS_TASK_ITER_THREADED) {
4612 put_css_set_locked(it->cur_dcset);
4613 it->cur_dcset = cset;
4616 it->tcset_head = &cset->threaded_csets;
4617 it->tcset_pos = &cset->threaded_csets;
4624 * css_task_iter_advance_css_set - advance a task iterator to the next css_set
4625 * @it: the iterator to advance
4627 * Advance @it to the next css_set to walk.
4629 static void css_task_iter_advance_css_set(struct css_task_iter *it)
4631 struct css_set *cset;
4633 lockdep_assert_held(&css_set_lock);
4635 /* Advance to the next non-empty css_set and find first non-empty tasks list*/
4636 while ((cset = css_task_iter_next_css_set(it))) {
4637 if (!list_empty(&cset->tasks)) {
4638 it->cur_tasks_head = &cset->tasks;
4640 } else if (!list_empty(&cset->mg_tasks)) {
4641 it->cur_tasks_head = &cset->mg_tasks;
4643 } else if (!list_empty(&cset->dying_tasks)) {
4644 it->cur_tasks_head = &cset->dying_tasks;
4649 it->task_pos = NULL;
4652 it->task_pos = it->cur_tasks_head->next;
4655 * We don't keep css_sets locked across iteration steps and thus
4656 * need to take steps to ensure that iteration can be resumed after
4657 * the lock is re-acquired. Iteration is performed at two levels -
4658 * css_sets and tasks in them.
4660 * Once created, a css_set never leaves its cgroup lists, so a
4661 * pinned css_set is guaranteed to stay put and we can resume
4662 * iteration afterwards.
4664 * Tasks may leave @cset across iteration steps. This is resolved
4665 * by registering each iterator with the css_set currently being
4666 * walked and making css_set_move_task() advance iterators whose
4667 * next task is leaving.
4670 list_del(&it->iters_node);
4671 put_css_set_locked(it->cur_cset);
4674 it->cur_cset = cset;
4675 list_add(&it->iters_node, &cset->task_iters);
4678 static void css_task_iter_skip(struct css_task_iter *it,
4679 struct task_struct *task)
4681 lockdep_assert_held(&css_set_lock);
4683 if (it->task_pos == &task->cg_list) {
4684 it->task_pos = it->task_pos->next;
4685 it->flags |= CSS_TASK_ITER_SKIPPED;
4689 static void css_task_iter_advance(struct css_task_iter *it)
4691 struct task_struct *task;
4693 lockdep_assert_held(&css_set_lock);
4697 * Advance iterator to find next entry. We go through cset
4698 * tasks, mg_tasks and dying_tasks, when consumed we move onto
4701 if (it->flags & CSS_TASK_ITER_SKIPPED)
4702 it->flags &= ~CSS_TASK_ITER_SKIPPED;
4704 it->task_pos = it->task_pos->next;
4706 if (it->task_pos == &it->cur_cset->tasks) {
4707 it->cur_tasks_head = &it->cur_cset->mg_tasks;
4708 it->task_pos = it->cur_tasks_head->next;
4710 if (it->task_pos == &it->cur_cset->mg_tasks) {
4711 it->cur_tasks_head = &it->cur_cset->dying_tasks;
4712 it->task_pos = it->cur_tasks_head->next;
4714 if (it->task_pos == &it->cur_cset->dying_tasks)
4715 css_task_iter_advance_css_set(it);
4717 /* called from start, proceed to the first cset */
4718 css_task_iter_advance_css_set(it);
4724 task = list_entry(it->task_pos, struct task_struct, cg_list);
4726 if (it->flags & CSS_TASK_ITER_PROCS) {
4727 /* if PROCS, skip over tasks which aren't group leaders */
4728 if (!thread_group_leader(task))
4731 /* and dying leaders w/o live member threads */
4732 if (it->cur_tasks_head == &it->cur_cset->dying_tasks &&
4733 !atomic_read(&task->signal->live))
4736 /* skip all dying ones */
4737 if (it->cur_tasks_head == &it->cur_cset->dying_tasks)
4743 * css_task_iter_start - initiate task iteration
4744 * @css: the css to walk tasks of
4745 * @flags: CSS_TASK_ITER_* flags
4746 * @it: the task iterator to use
4748 * Initiate iteration through the tasks of @css. The caller can call
4749 * css_task_iter_next() to walk through the tasks until the function
4750 * returns NULL. On completion of iteration, css_task_iter_end() must be
4753 void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
4754 struct css_task_iter *it)
4756 memset(it, 0, sizeof(*it));
4758 spin_lock_irq(&css_set_lock);
4763 if (CGROUP_HAS_SUBSYS_CONFIG && it->ss)
4764 it->cset_pos = &css->cgroup->e_csets[css->ss->id];
4766 it->cset_pos = &css->cgroup->cset_links;
4768 it->cset_head = it->cset_pos;
4770 css_task_iter_advance(it);
4772 spin_unlock_irq(&css_set_lock);
4776 * css_task_iter_next - return the next task for the iterator
4777 * @it: the task iterator being iterated
4779 * The "next" function for task iteration. @it should have been
4780 * initialized via css_task_iter_start(). Returns NULL when the iteration
4783 struct task_struct *css_task_iter_next(struct css_task_iter *it)
4786 put_task_struct(it->cur_task);
4787 it->cur_task = NULL;
4790 spin_lock_irq(&css_set_lock);
4792 /* @it may be half-advanced by skips, finish advancing */
4793 if (it->flags & CSS_TASK_ITER_SKIPPED)
4794 css_task_iter_advance(it);
4797 it->cur_task = list_entry(it->task_pos, struct task_struct,
4799 get_task_struct(it->cur_task);
4800 css_task_iter_advance(it);
4803 spin_unlock_irq(&css_set_lock);
4805 return it->cur_task;
4809 * css_task_iter_end - finish task iteration
4810 * @it: the task iterator to finish
4812 * Finish task iteration started by css_task_iter_start().
4814 void css_task_iter_end(struct css_task_iter *it)
4817 spin_lock_irq(&css_set_lock);
4818 list_del(&it->iters_node);
4819 put_css_set_locked(it->cur_cset);
4820 spin_unlock_irq(&css_set_lock);
4824 put_css_set(it->cur_dcset);
4827 put_task_struct(it->cur_task);
4830 static void cgroup_procs_release(struct kernfs_open_file *of)
4832 struct cgroup_file_ctx *ctx = of->priv;
4834 if (ctx->procs.started)
4835 css_task_iter_end(&ctx->procs.iter);
4838 static void *cgroup_procs_next(struct seq_file *s, void *v, loff_t *pos)
4840 struct kernfs_open_file *of = s->private;
4841 struct cgroup_file_ctx *ctx = of->priv;
4846 return css_task_iter_next(&ctx->procs.iter);
4849 static void *__cgroup_procs_start(struct seq_file *s, loff_t *pos,
4850 unsigned int iter_flags)
4852 struct kernfs_open_file *of = s->private;
4853 struct cgroup *cgrp = seq_css(s)->cgroup;
4854 struct cgroup_file_ctx *ctx = of->priv;
4855 struct css_task_iter *it = &ctx->procs.iter;
4858 * When a seq_file is seeked, it's always traversed sequentially
4859 * from position 0, so we can simply keep iterating on !0 *pos.
4861 if (!ctx->procs.started) {
4862 if (WARN_ON_ONCE((*pos)))
4863 return ERR_PTR(-EINVAL);
4864 css_task_iter_start(&cgrp->self, iter_flags, it);
4865 ctx->procs.started = true;
4866 } else if (!(*pos)) {
4867 css_task_iter_end(it);
4868 css_task_iter_start(&cgrp->self, iter_flags, it);
4870 return it->cur_task;
4872 return cgroup_procs_next(s, NULL, NULL);
4875 static void *cgroup_procs_start(struct seq_file *s, loff_t *pos)
4877 struct cgroup *cgrp = seq_css(s)->cgroup;
4880 * All processes of a threaded subtree belong to the domain cgroup
4881 * of the subtree. Only threads can be distributed across the
4882 * subtree. Reject reads on cgroup.procs in the subtree proper.
4883 * They're always empty anyway.
4885 if (cgroup_is_threaded(cgrp))
4886 return ERR_PTR(-EOPNOTSUPP);
4888 return __cgroup_procs_start(s, pos, CSS_TASK_ITER_PROCS |
4889 CSS_TASK_ITER_THREADED);
4892 static int cgroup_procs_show(struct seq_file *s, void *v)
4894 seq_printf(s, "%d\n", task_pid_vnr(v));
4898 static int cgroup_may_write(const struct cgroup *cgrp, struct super_block *sb)
4901 struct inode *inode;
4903 lockdep_assert_held(&cgroup_mutex);
4905 inode = kernfs_get_inode(sb, cgrp->procs_file.kn);
4909 ret = inode_permission(&init_user_ns, inode, MAY_WRITE);
4914 static int cgroup_procs_write_permission(struct cgroup *src_cgrp,
4915 struct cgroup *dst_cgrp,
4916 struct super_block *sb,
4917 struct cgroup_namespace *ns)
4919 struct cgroup *com_cgrp = src_cgrp;
4922 lockdep_assert_held(&cgroup_mutex);
4924 /* find the common ancestor */
4925 while (!cgroup_is_descendant(dst_cgrp, com_cgrp))
4926 com_cgrp = cgroup_parent(com_cgrp);
4928 /* %current should be authorized to migrate to the common ancestor */
4929 ret = cgroup_may_write(com_cgrp, sb);
4934 * If namespaces are delegation boundaries, %current must be able
4935 * to see both source and destination cgroups from its namespace.
4937 if ((cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE) &&
4938 (!cgroup_is_descendant(src_cgrp, ns->root_cset->dfl_cgrp) ||
4939 !cgroup_is_descendant(dst_cgrp, ns->root_cset->dfl_cgrp)))
4945 static int cgroup_attach_permissions(struct cgroup *src_cgrp,
4946 struct cgroup *dst_cgrp,
4947 struct super_block *sb, bool threadgroup,
4948 struct cgroup_namespace *ns)
4952 ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp, sb, ns);
4956 ret = cgroup_migrate_vet_dst(dst_cgrp);
4960 if (!threadgroup && (src_cgrp->dom_cgrp != dst_cgrp->dom_cgrp))
4966 static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
4969 struct cgroup_file_ctx *ctx = of->priv;
4970 struct cgroup *src_cgrp, *dst_cgrp;
4971 struct task_struct *task;
4972 const struct cred *saved_cred;
4976 dst_cgrp = cgroup_kn_lock_live(of->kn, false);
4980 task = cgroup_procs_write_start(buf, threadgroup, &locked);
4981 ret = PTR_ERR_OR_ZERO(task);
4985 /* find the source cgroup */
4986 spin_lock_irq(&css_set_lock);
4987 src_cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
4988 spin_unlock_irq(&css_set_lock);
4991 * Process and thread migrations follow same delegation rule. Check
4992 * permissions using the credentials from file open to protect against
4993 * inherited fd attacks.
4995 saved_cred = override_creds(of->file->f_cred);
4996 ret = cgroup_attach_permissions(src_cgrp, dst_cgrp,
4997 of->file->f_path.dentry->d_sb,
4998 threadgroup, ctx->ns);
4999 revert_creds(saved_cred);
5003 ret = cgroup_attach_task(dst_cgrp, task, threadgroup);
5006 cgroup_procs_write_finish(task, locked);
5008 cgroup_kn_unlock(of->kn);
5013 static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
5014 char *buf, size_t nbytes, loff_t off)
5016 return __cgroup_procs_write(of, buf, true) ?: nbytes;
5019 static void *cgroup_threads_start(struct seq_file *s, loff_t *pos)
5021 return __cgroup_procs_start(s, pos, 0);
5024 static ssize_t cgroup_threads_write(struct kernfs_open_file *of,
5025 char *buf, size_t nbytes, loff_t off)
5027 return __cgroup_procs_write(of, buf, false) ?: nbytes;
5030 /* cgroup core interface files for the default hierarchy */
5031 static struct cftype cgroup_base_files[] = {
5033 .name = "cgroup.type",
5034 .flags = CFTYPE_NOT_ON_ROOT,
5035 .seq_show = cgroup_type_show,
5036 .write = cgroup_type_write,
5039 .name = "cgroup.procs",
5040 .flags = CFTYPE_NS_DELEGATABLE,
5041 .file_offset = offsetof(struct cgroup, procs_file),
5042 .release = cgroup_procs_release,
5043 .seq_start = cgroup_procs_start,
5044 .seq_next = cgroup_procs_next,
5045 .seq_show = cgroup_procs_show,
5046 .write = cgroup_procs_write,
5049 .name = "cgroup.threads",
5050 .flags = CFTYPE_NS_DELEGATABLE,
5051 .release = cgroup_procs_release,
5052 .seq_start = cgroup_threads_start,
5053 .seq_next = cgroup_procs_next,
5054 .seq_show = cgroup_procs_show,
5055 .write = cgroup_threads_write,
5058 .name = "cgroup.controllers",
5059 .seq_show = cgroup_controllers_show,
5062 .name = "cgroup.subtree_control",
5063 .flags = CFTYPE_NS_DELEGATABLE,
5064 .seq_show = cgroup_subtree_control_show,
5065 .write = cgroup_subtree_control_write,
5068 .name = "cgroup.events",
5069 .flags = CFTYPE_NOT_ON_ROOT,
5070 .file_offset = offsetof(struct cgroup, events_file),
5071 .seq_show = cgroup_events_show,
5074 .name = "cgroup.max.descendants",
5075 .seq_show = cgroup_max_descendants_show,
5076 .write = cgroup_max_descendants_write,
5079 .name = "cgroup.max.depth",
5080 .seq_show = cgroup_max_depth_show,
5081 .write = cgroup_max_depth_write,
5084 .name = "cgroup.stat",
5085 .seq_show = cgroup_stat_show,
5088 .name = "cgroup.freeze",
5089 .flags = CFTYPE_NOT_ON_ROOT,
5090 .seq_show = cgroup_freeze_show,
5091 .write = cgroup_freeze_write,
5094 .name = "cgroup.kill",
5095 .flags = CFTYPE_NOT_ON_ROOT,
5096 .write = cgroup_kill_write,
5100 .seq_show = cpu_stat_show,
5104 .name = "io.pressure",
5105 .flags = CFTYPE_PRESSURE,
5106 .seq_show = cgroup_io_pressure_show,
5107 .write = cgroup_io_pressure_write,
5108 .poll = cgroup_pressure_poll,
5109 .release = cgroup_pressure_release,
5112 .name = "memory.pressure",
5113 .flags = CFTYPE_PRESSURE,
5114 .seq_show = cgroup_memory_pressure_show,
5115 .write = cgroup_memory_pressure_write,
5116 .poll = cgroup_pressure_poll,
5117 .release = cgroup_pressure_release,
5120 .name = "cpu.pressure",
5121 .flags = CFTYPE_PRESSURE,
5122 .seq_show = cgroup_cpu_pressure_show,
5123 .write = cgroup_cpu_pressure_write,
5124 .poll = cgroup_pressure_poll,
5125 .release = cgroup_pressure_release,
5127 #endif /* CONFIG_PSI */
5132 * css destruction is four-stage process.
5134 * 1. Destruction starts. Killing of the percpu_ref is initiated.
5135 * Implemented in kill_css().
5137 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
5138 * and thus css_tryget_online() is guaranteed to fail, the css can be
5139 * offlined by invoking offline_css(). After offlining, the base ref is
5140 * put. Implemented in css_killed_work_fn().
5142 * 3. When the percpu_ref reaches zero, the only possible remaining
5143 * accessors are inside RCU read sections. css_release() schedules the
5146 * 4. After the grace period, the css can be freed. Implemented in
5147 * css_free_work_fn().
5149 * It is actually hairier because both step 2 and 4 require process context
5150 * and thus involve punting to css->destroy_work adding two additional
5151 * steps to the already complex sequence.
5153 static void css_free_rwork_fn(struct work_struct *work)
5155 struct cgroup_subsys_state *css = container_of(to_rcu_work(work),
5156 struct cgroup_subsys_state, destroy_rwork);
5157 struct cgroup_subsys *ss = css->ss;
5158 struct cgroup *cgrp = css->cgroup;
5160 percpu_ref_exit(&css->refcnt);
5164 struct cgroup_subsys_state *parent = css->parent;
5168 cgroup_idr_remove(&ss->css_idr, id);
5174 /* cgroup free path */
5175 atomic_dec(&cgrp->root->nr_cgrps);
5176 cgroup1_pidlist_destroy_all(cgrp);
5177 cancel_work_sync(&cgrp->release_agent_work);
5179 if (cgroup_parent(cgrp)) {
5181 * We get a ref to the parent, and put the ref when
5182 * this cgroup is being freed, so it's guaranteed
5183 * that the parent won't be destroyed before its
5186 cgroup_put(cgroup_parent(cgrp));
5187 kernfs_put(cgrp->kn);
5188 psi_cgroup_free(cgrp);
5189 cgroup_rstat_exit(cgrp);
5193 * This is root cgroup's refcnt reaching zero,
5194 * which indicates that the root should be
5197 cgroup_destroy_root(cgrp->root);
5202 static void css_release_work_fn(struct work_struct *work)
5204 struct cgroup_subsys_state *css =
5205 container_of(work, struct cgroup_subsys_state, destroy_work);
5206 struct cgroup_subsys *ss = css->ss;
5207 struct cgroup *cgrp = css->cgroup;
5209 mutex_lock(&cgroup_mutex);
5211 css->flags |= CSS_RELEASED;
5212 list_del_rcu(&css->sibling);
5215 /* css release path */
5216 if (!list_empty(&css->rstat_css_node)) {
5217 cgroup_rstat_flush(cgrp);
5218 list_del_rcu(&css->rstat_css_node);
5221 cgroup_idr_replace(&ss->css_idr, NULL, css->id);
5222 if (ss->css_released)
5223 ss->css_released(css);
5225 struct cgroup *tcgrp;
5227 /* cgroup release path */
5228 TRACE_CGROUP_PATH(release, cgrp);
5230 cgroup_rstat_flush(cgrp);
5232 spin_lock_irq(&css_set_lock);
5233 for (tcgrp = cgroup_parent(cgrp); tcgrp;
5234 tcgrp = cgroup_parent(tcgrp))
5235 tcgrp->nr_dying_descendants--;
5236 spin_unlock_irq(&css_set_lock);
5239 * There are two control paths which try to determine
5240 * cgroup from dentry without going through kernfs -
5241 * cgroupstats_build() and css_tryget_online_from_dir().
5242 * Those are supported by RCU protecting clearing of
5243 * cgrp->kn->priv backpointer.
5246 RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv,
5250 mutex_unlock(&cgroup_mutex);
5252 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
5253 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
5256 static void css_release(struct percpu_ref *ref)
5258 struct cgroup_subsys_state *css =
5259 container_of(ref, struct cgroup_subsys_state, refcnt);
5261 INIT_WORK(&css->destroy_work, css_release_work_fn);
5262 queue_work(cgroup_destroy_wq, &css->destroy_work);
5265 static void init_and_link_css(struct cgroup_subsys_state *css,
5266 struct cgroup_subsys *ss, struct cgroup *cgrp)
5268 lockdep_assert_held(&cgroup_mutex);
5270 cgroup_get_live(cgrp);
5272 memset(css, 0, sizeof(*css));
5276 INIT_LIST_HEAD(&css->sibling);
5277 INIT_LIST_HEAD(&css->children);
5278 INIT_LIST_HEAD(&css->rstat_css_node);
5279 css->serial_nr = css_serial_nr_next++;
5280 atomic_set(&css->online_cnt, 0);
5282 if (cgroup_parent(cgrp)) {
5283 css->parent = cgroup_css(cgroup_parent(cgrp), ss);
5284 css_get(css->parent);
5287 if (ss->css_rstat_flush)
5288 list_add_rcu(&css->rstat_css_node, &cgrp->rstat_css_list);
5290 BUG_ON(cgroup_css(cgrp, ss));
5293 /* invoke ->css_online() on a new CSS and mark it online if successful */
5294 static int online_css(struct cgroup_subsys_state *css)
5296 struct cgroup_subsys *ss = css->ss;
5299 lockdep_assert_held(&cgroup_mutex);
5302 ret = ss->css_online(css);
5304 css->flags |= CSS_ONLINE;
5305 rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
5307 atomic_inc(&css->online_cnt);
5309 atomic_inc(&css->parent->online_cnt);
5314 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
5315 static void offline_css(struct cgroup_subsys_state *css)
5317 struct cgroup_subsys *ss = css->ss;
5319 lockdep_assert_held(&cgroup_mutex);
5321 if (!(css->flags & CSS_ONLINE))
5324 if (ss->css_offline)
5325 ss->css_offline(css);
5327 css->flags &= ~CSS_ONLINE;
5328 RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL);
5330 wake_up_all(&css->cgroup->offline_waitq);
5334 * css_create - create a cgroup_subsys_state
5335 * @cgrp: the cgroup new css will be associated with
5336 * @ss: the subsys of new css
5338 * Create a new css associated with @cgrp - @ss pair. On success, the new
5339 * css is online and installed in @cgrp. This function doesn't create the
5340 * interface files. Returns 0 on success, -errno on failure.
5342 static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
5343 struct cgroup_subsys *ss)
5345 struct cgroup *parent = cgroup_parent(cgrp);
5346 struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss);
5347 struct cgroup_subsys_state *css;
5350 lockdep_assert_held(&cgroup_mutex);
5352 css = ss->css_alloc(parent_css);
5354 css = ERR_PTR(-ENOMEM);
5358 init_and_link_css(css, ss, cgrp);
5360 err = percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL);
5364 err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL);
5369 /* @css is ready to be brought online now, make it visible */
5370 list_add_tail_rcu(&css->sibling, &parent_css->children);
5371 cgroup_idr_replace(&ss->css_idr, css, css->id);
5373 err = online_css(css);
5380 list_del_rcu(&css->sibling);
5382 list_del_rcu(&css->rstat_css_node);
5383 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
5384 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
5385 return ERR_PTR(err);
5389 * The returned cgroup is fully initialized including its control mask, but
5390 * it isn't associated with its kernfs_node and doesn't have the control
5393 static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
5396 struct cgroup_root *root = parent->root;
5397 struct cgroup *cgrp, *tcgrp;
5398 struct kernfs_node *kn;
5399 int level = parent->level + 1;
5402 /* allocate the cgroup and its ID, 0 is reserved for the root */
5403 cgrp = kzalloc(struct_size(cgrp, ancestor_ids, (level + 1)),
5406 return ERR_PTR(-ENOMEM);
5408 ret = percpu_ref_init(&cgrp->self.refcnt, css_release, 0, GFP_KERNEL);
5412 ret = cgroup_rstat_init(cgrp);
5414 goto out_cancel_ref;
5416 /* create the directory */
5417 kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
5424 init_cgroup_housekeeping(cgrp);
5426 cgrp->self.parent = &parent->self;
5428 cgrp->level = level;
5430 ret = psi_cgroup_alloc(cgrp);
5432 goto out_kernfs_remove;
5434 ret = cgroup_bpf_inherit(cgrp);
5439 * New cgroup inherits effective freeze counter, and
5440 * if the parent has to be frozen, the child has too.
5442 cgrp->freezer.e_freeze = parent->freezer.e_freeze;
5443 if (cgrp->freezer.e_freeze) {
5445 * Set the CGRP_FREEZE flag, so when a process will be
5446 * attached to the child cgroup, it will become frozen.
5447 * At this point the new cgroup is unpopulated, so we can
5448 * consider it frozen immediately.
5450 set_bit(CGRP_FREEZE, &cgrp->flags);
5451 set_bit(CGRP_FROZEN, &cgrp->flags);
5454 spin_lock_irq(&css_set_lock);
5455 for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
5456 cgrp->ancestor_ids[tcgrp->level] = cgroup_id(tcgrp);
5458 if (tcgrp != cgrp) {
5459 tcgrp->nr_descendants++;
5462 * If the new cgroup is frozen, all ancestor cgroups
5463 * get a new frozen descendant, but their state can't
5464 * change because of this.
5466 if (cgrp->freezer.e_freeze)
5467 tcgrp->freezer.nr_frozen_descendants++;
5470 spin_unlock_irq(&css_set_lock);
5472 if (notify_on_release(parent))
5473 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
5475 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
5476 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
5478 cgrp->self.serial_nr = css_serial_nr_next++;
5480 /* allocation complete, commit to creation */
5481 list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);
5482 atomic_inc(&root->nr_cgrps);
5483 cgroup_get_live(parent);
5486 * On the default hierarchy, a child doesn't automatically inherit
5487 * subtree_control from the parent. Each is configured manually.
5489 if (!cgroup_on_dfl(cgrp))
5490 cgrp->subtree_control = cgroup_control(cgrp);
5492 cgroup_propagate_control(cgrp);
5497 psi_cgroup_free(cgrp);
5499 kernfs_remove(cgrp->kn);
5501 cgroup_rstat_exit(cgrp);
5503 percpu_ref_exit(&cgrp->self.refcnt);
5506 return ERR_PTR(ret);
5509 static bool cgroup_check_hierarchy_limits(struct cgroup *parent)
5511 struct cgroup *cgroup;
5515 lockdep_assert_held(&cgroup_mutex);
5517 for (cgroup = parent; cgroup; cgroup = cgroup_parent(cgroup)) {
5518 if (cgroup->nr_descendants >= cgroup->max_descendants)
5521 if (level > cgroup->max_depth)
5532 int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
5534 struct cgroup *parent, *cgrp;
5537 /* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
5538 if (strchr(name, '\n'))
5541 parent = cgroup_kn_lock_live(parent_kn, false);
5545 if (!cgroup_check_hierarchy_limits(parent)) {
5550 cgrp = cgroup_create(parent, name, mode);
5552 ret = PTR_ERR(cgrp);
5557 * This extra ref will be put in cgroup_free_fn() and guarantees
5558 * that @cgrp->kn is always accessible.
5560 kernfs_get(cgrp->kn);
5562 ret = cgroup_kn_set_ugid(cgrp->kn);
5566 ret = css_populate_dir(&cgrp->self);
5570 ret = cgroup_apply_control_enable(cgrp);
5574 TRACE_CGROUP_PATH(mkdir, cgrp);
5576 /* let's create and online css's */
5577 kernfs_activate(cgrp->kn);
5583 cgroup_destroy_locked(cgrp);
5585 cgroup_kn_unlock(parent_kn);
5590 * This is called when the refcnt of a css is confirmed to be killed.
5591 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
5592 * initiate destruction and put the css ref from kill_css().
5594 static void css_killed_work_fn(struct work_struct *work)
5596 struct cgroup_subsys_state *css =
5597 container_of(work, struct cgroup_subsys_state, destroy_work);
5599 mutex_lock(&cgroup_mutex);
5604 /* @css can't go away while we're holding cgroup_mutex */
5606 } while (css && atomic_dec_and_test(&css->online_cnt));
5608 mutex_unlock(&cgroup_mutex);
5611 /* css kill confirmation processing requires process context, bounce */
5612 static void css_killed_ref_fn(struct percpu_ref *ref)
5614 struct cgroup_subsys_state *css =
5615 container_of(ref, struct cgroup_subsys_state, refcnt);
5617 if (atomic_dec_and_test(&css->online_cnt)) {
5618 INIT_WORK(&css->destroy_work, css_killed_work_fn);
5619 queue_work(cgroup_destroy_wq, &css->destroy_work);
5624 * kill_css - destroy a css
5625 * @css: css to destroy
5627 * This function initiates destruction of @css by removing cgroup interface
5628 * files and putting its base reference. ->css_offline() will be invoked
5629 * asynchronously once css_tryget_online() is guaranteed to fail and when
5630 * the reference count reaches zero, @css will be released.
5632 static void kill_css(struct cgroup_subsys_state *css)
5634 lockdep_assert_held(&cgroup_mutex);
5636 if (css->flags & CSS_DYING)
5639 css->flags |= CSS_DYING;
5642 * This must happen before css is disassociated with its cgroup.
5643 * See seq_css() for details.
5648 * Killing would put the base ref, but we need to keep it alive
5649 * until after ->css_offline().
5654 * cgroup core guarantees that, by the time ->css_offline() is
5655 * invoked, no new css reference will be given out via
5656 * css_tryget_online(). We can't simply call percpu_ref_kill() and
5657 * proceed to offlining css's because percpu_ref_kill() doesn't
5658 * guarantee that the ref is seen as killed on all CPUs on return.
5660 * Use percpu_ref_kill_and_confirm() to get notifications as each
5661 * css is confirmed to be seen as killed on all CPUs.
5663 percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
5667 * cgroup_destroy_locked - the first stage of cgroup destruction
5668 * @cgrp: cgroup to be destroyed
5670 * css's make use of percpu refcnts whose killing latency shouldn't be
5671 * exposed to userland and are RCU protected. Also, cgroup core needs to
5672 * guarantee that css_tryget_online() won't succeed by the time
5673 * ->css_offline() is invoked. To satisfy all the requirements,
5674 * destruction is implemented in the following two steps.
5676 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
5677 * userland visible parts and start killing the percpu refcnts of
5678 * css's. Set up so that the next stage will be kicked off once all
5679 * the percpu refcnts are confirmed to be killed.
5681 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
5682 * rest of destruction. Once all cgroup references are gone, the
5683 * cgroup is RCU-freed.
5685 * This function implements s1. After this step, @cgrp is gone as far as
5686 * the userland is concerned and a new cgroup with the same name may be
5687 * created. As cgroup doesn't care about the names internally, this
5688 * doesn't cause any problem.
5690 static int cgroup_destroy_locked(struct cgroup *cgrp)
5691 __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
5693 struct cgroup *tcgrp, *parent = cgroup_parent(cgrp);
5694 struct cgroup_subsys_state *css;
5695 struct cgrp_cset_link *link;
5698 lockdep_assert_held(&cgroup_mutex);
5701 * Only migration can raise populated from zero and we're already
5702 * holding cgroup_mutex.
5704 if (cgroup_is_populated(cgrp))
5708 * Make sure there's no live children. We can't test emptiness of
5709 * ->self.children as dead children linger on it while being
5710 * drained; otherwise, "rmdir parent/child parent" may fail.
5712 if (css_has_online_children(&cgrp->self))
5716 * Mark @cgrp and the associated csets dead. The former prevents
5717 * further task migration and child creation by disabling
5718 * cgroup_lock_live_group(). The latter makes the csets ignored by
5719 * the migration path.
5721 cgrp->self.flags &= ~CSS_ONLINE;
5723 spin_lock_irq(&css_set_lock);
5724 list_for_each_entry(link, &cgrp->cset_links, cset_link)
5725 link->cset->dead = true;
5726 spin_unlock_irq(&css_set_lock);
5728 /* initiate massacre of all css's */
5729 for_each_css(css, ssid, cgrp)
5732 /* clear and remove @cgrp dir, @cgrp has an extra ref on its kn */
5733 css_clear_dir(&cgrp->self);
5734 kernfs_remove(cgrp->kn);
5736 if (cgroup_is_threaded(cgrp))
5737 parent->nr_threaded_children--;
5739 spin_lock_irq(&css_set_lock);
5740 for (tcgrp = cgroup_parent(cgrp); tcgrp; tcgrp = cgroup_parent(tcgrp)) {
5741 tcgrp->nr_descendants--;
5742 tcgrp->nr_dying_descendants++;
5744 * If the dying cgroup is frozen, decrease frozen descendants
5745 * counters of ancestor cgroups.
5747 if (test_bit(CGRP_FROZEN, &cgrp->flags))
5748 tcgrp->freezer.nr_frozen_descendants--;
5750 spin_unlock_irq(&css_set_lock);
5752 cgroup1_check_for_release(parent);
5754 cgroup_bpf_offline(cgrp);
5756 /* put the base reference */
5757 percpu_ref_kill(&cgrp->self.refcnt);
5762 int cgroup_rmdir(struct kernfs_node *kn)
5764 struct cgroup *cgrp;
5767 cgrp = cgroup_kn_lock_live(kn, false);
5771 ret = cgroup_destroy_locked(cgrp);
5773 TRACE_CGROUP_PATH(rmdir, cgrp);
5775 cgroup_kn_unlock(kn);
5779 static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
5780 .show_options = cgroup_show_options,
5781 .mkdir = cgroup_mkdir,
5782 .rmdir = cgroup_rmdir,
5783 .show_path = cgroup_show_path,
5786 static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
5788 struct cgroup_subsys_state *css;
5790 pr_debug("Initializing cgroup subsys %s\n", ss->name);
5792 mutex_lock(&cgroup_mutex);
5794 idr_init(&ss->css_idr);
5795 INIT_LIST_HEAD(&ss->cfts);
5797 /* Create the root cgroup state for this subsystem */
5798 ss->root = &cgrp_dfl_root;
5799 css = ss->css_alloc(NULL);
5800 /* We don't handle early failures gracefully */
5801 BUG_ON(IS_ERR(css));
5802 init_and_link_css(css, ss, &cgrp_dfl_root.cgrp);
5805 * Root csses are never destroyed and we can't initialize
5806 * percpu_ref during early init. Disable refcnting.
5808 css->flags |= CSS_NO_REF;
5811 /* allocation can't be done safely during early init */
5814 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL);
5815 BUG_ON(css->id < 0);
5818 /* Update the init_css_set to contain a subsys
5819 * pointer to this state - since the subsystem is
5820 * newly registered, all tasks and hence the
5821 * init_css_set is in the subsystem's root cgroup. */
5822 init_css_set.subsys[ss->id] = css;
5824 have_fork_callback |= (bool)ss->fork << ss->id;
5825 have_exit_callback |= (bool)ss->exit << ss->id;
5826 have_release_callback |= (bool)ss->release << ss->id;
5827 have_canfork_callback |= (bool)ss->can_fork << ss->id;
5829 /* At system boot, before all subsystems have been
5830 * registered, no tasks have been forked, so we don't
5831 * need to invoke fork callbacks here. */
5832 BUG_ON(!list_empty(&init_task.tasks));
5834 BUG_ON(online_css(css));
5836 mutex_unlock(&cgroup_mutex);
5840 * cgroup_init_early - cgroup initialization at system boot
5842 * Initialize cgroups at system boot, and initialize any
5843 * subsystems that request early init.
5845 int __init cgroup_init_early(void)
5847 static struct cgroup_fs_context __initdata ctx;
5848 struct cgroup_subsys *ss;
5851 ctx.root = &cgrp_dfl_root;
5852 init_cgroup_root(&ctx);
5853 cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF;
5855 RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
5857 for_each_subsys(ss, i) {
5858 WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
5859 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p id:name=%d:%s\n",
5860 i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
5862 WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
5863 "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
5866 ss->name = cgroup_subsys_name[i];
5867 if (!ss->legacy_name)
5868 ss->legacy_name = cgroup_subsys_name[i];
5871 cgroup_init_subsys(ss, true);
5877 * cgroup_init - cgroup initialization
5879 * Register cgroup filesystem and /proc file, and initialize
5880 * any subsystems that didn't request early init.
5882 int __init cgroup_init(void)
5884 struct cgroup_subsys *ss;
5887 BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
5888 BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
5889 BUG_ON(cgroup_init_cftypes(NULL, cgroup1_base_files));
5891 cgroup_rstat_boot();
5893 get_user_ns(init_cgroup_ns.user_ns);
5895 mutex_lock(&cgroup_mutex);
5898 * Add init_css_set to the hash table so that dfl_root can link to
5901 hash_add(css_set_table, &init_css_set.hlist,
5902 css_set_hash(init_css_set.subsys));
5904 BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0));
5906 mutex_unlock(&cgroup_mutex);
5908 for_each_subsys(ss, ssid) {
5909 if (ss->early_init) {
5910 struct cgroup_subsys_state *css =
5911 init_css_set.subsys[ss->id];
5913 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2,
5915 BUG_ON(css->id < 0);
5917 cgroup_init_subsys(ss, false);
5920 list_add_tail(&init_css_set.e_cset_node[ssid],
5921 &cgrp_dfl_root.cgrp.e_csets[ssid]);
5924 * Setting dfl_root subsys_mask needs to consider the
5925 * disabled flag and cftype registration needs kmalloc,
5926 * both of which aren't available during early_init.
5928 if (!cgroup_ssid_enabled(ssid))
5931 if (cgroup1_ssid_disabled(ssid))
5932 printk(KERN_INFO "Disabling %s control group subsystem in v1 mounts\n",
5935 cgrp_dfl_root.subsys_mask |= 1 << ss->id;
5937 /* implicit controllers must be threaded too */
5938 WARN_ON(ss->implicit_on_dfl && !ss->threaded);
5940 if (ss->implicit_on_dfl)
5941 cgrp_dfl_implicit_ss_mask |= 1 << ss->id;
5942 else if (!ss->dfl_cftypes)
5943 cgrp_dfl_inhibit_ss_mask |= 1 << ss->id;
5946 cgrp_dfl_threaded_ss_mask |= 1 << ss->id;
5948 if (ss->dfl_cftypes == ss->legacy_cftypes) {
5949 WARN_ON(cgroup_add_cftypes(ss, ss->dfl_cftypes));
5951 WARN_ON(cgroup_add_dfl_cftypes(ss, ss->dfl_cftypes));
5952 WARN_ON(cgroup_add_legacy_cftypes(ss, ss->legacy_cftypes));
5956 ss->bind(init_css_set.subsys[ssid]);
5958 mutex_lock(&cgroup_mutex);
5959 css_populate_dir(init_css_set.subsys[ssid]);
5960 mutex_unlock(&cgroup_mutex);
5963 /* init_css_set.subsys[] has been updated, re-hash */
5964 hash_del(&init_css_set.hlist);
5965 hash_add(css_set_table, &init_css_set.hlist,
5966 css_set_hash(init_css_set.subsys));
5968 WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup"));
5969 WARN_ON(register_filesystem(&cgroup_fs_type));
5970 WARN_ON(register_filesystem(&cgroup2_fs_type));
5971 WARN_ON(!proc_create_single("cgroups", 0, NULL, proc_cgroupstats_show));
5972 #ifdef CONFIG_CPUSETS
5973 WARN_ON(register_filesystem(&cpuset_fs_type));
5979 static int __init cgroup_wq_init(void)
5982 * There isn't much point in executing destruction path in
5983 * parallel. Good chunk is serialized with cgroup_mutex anyway.
5984 * Use 1 for @max_active.
5986 * We would prefer to do this in cgroup_init() above, but that
5987 * is called before init_workqueues(): so leave this until after.
5989 cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
5990 BUG_ON(!cgroup_destroy_wq);
5993 core_initcall(cgroup_wq_init);
5995 void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
5997 struct kernfs_node *kn;
5999 kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
6002 kernfs_path(kn, buf, buflen);
6007 * cgroup_get_from_id : get the cgroup associated with cgroup id
6009 * On success return the cgrp, on failure return NULL
6011 struct cgroup *cgroup_get_from_id(u64 id)
6013 struct kernfs_node *kn;
6014 struct cgroup *cgrp = NULL;
6016 kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
6022 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6023 if (cgrp && !cgroup_tryget(cgrp))
6032 EXPORT_SYMBOL_GPL(cgroup_get_from_id);
6035 * proc_cgroup_show()
6036 * - Print task's cgroup paths into seq_file, one line for each hierarchy
6037 * - Used for /proc/<pid>/cgroup.
6039 int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
6040 struct pid *pid, struct task_struct *tsk)
6044 struct cgroup_root *root;
6047 buf = kmalloc(PATH_MAX, GFP_KERNEL);
6051 mutex_lock(&cgroup_mutex);
6052 spin_lock_irq(&css_set_lock);
6054 for_each_root(root) {
6055 struct cgroup_subsys *ss;
6056 struct cgroup *cgrp;
6057 int ssid, count = 0;
6059 if (root == &cgrp_dfl_root && !cgrp_dfl_visible)
6062 seq_printf(m, "%d:", root->hierarchy_id);
6063 if (root != &cgrp_dfl_root)
6064 for_each_subsys(ss, ssid)
6065 if (root->subsys_mask & (1 << ssid))
6066 seq_printf(m, "%s%s", count++ ? "," : "",
6068 if (strlen(root->name))
6069 seq_printf(m, "%sname=%s", count ? "," : "",
6073 cgrp = task_cgroup_from_root(tsk, root);
6076 * On traditional hierarchies, all zombie tasks show up as
6077 * belonging to the root cgroup. On the default hierarchy,
6078 * while a zombie doesn't show up in "cgroup.procs" and
6079 * thus can't be migrated, its /proc/PID/cgroup keeps
6080 * reporting the cgroup it belonged to before exiting. If
6081 * the cgroup is removed before the zombie is reaped,
6082 * " (deleted)" is appended to the cgroup path.
6084 if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) {
6085 retval = cgroup_path_ns_locked(cgrp, buf, PATH_MAX,
6086 current->nsproxy->cgroup_ns);
6087 if (retval >= PATH_MAX)
6088 retval = -ENAMETOOLONG;
6097 if (cgroup_on_dfl(cgrp) && cgroup_is_dead(cgrp))
6098 seq_puts(m, " (deleted)\n");
6105 spin_unlock_irq(&css_set_lock);
6106 mutex_unlock(&cgroup_mutex);
6113 * cgroup_fork - initialize cgroup related fields during copy_process()
6114 * @child: pointer to task_struct of forking parent process.
6116 * A task is associated with the init_css_set until cgroup_post_fork()
6117 * attaches it to the target css_set.
6119 void cgroup_fork(struct task_struct *child)
6121 RCU_INIT_POINTER(child->cgroups, &init_css_set);
6122 INIT_LIST_HEAD(&child->cg_list);
6125 static struct cgroup *cgroup_get_from_file(struct file *f)
6127 struct cgroup_subsys_state *css;
6128 struct cgroup *cgrp;
6130 css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
6132 return ERR_CAST(css);
6135 if (!cgroup_on_dfl(cgrp)) {
6137 return ERR_PTR(-EBADF);
6144 * cgroup_css_set_fork - find or create a css_set for a child process
6145 * @kargs: the arguments passed to create the child process
6147 * This functions finds or creates a new css_set which the child
6148 * process will be attached to in cgroup_post_fork(). By default,
6149 * the child process will be given the same css_set as its parent.
6151 * If CLONE_INTO_CGROUP is specified this function will try to find an
6152 * existing css_set which includes the requested cgroup and if not create
6153 * a new css_set that the child will be attached to later. If this function
6154 * succeeds it will hold cgroup_threadgroup_rwsem on return. If
6155 * CLONE_INTO_CGROUP is requested this function will grab cgroup mutex
6156 * before grabbing cgroup_threadgroup_rwsem and will hold a reference
6157 * to the target cgroup.
6159 static int cgroup_css_set_fork(struct kernel_clone_args *kargs)
6160 __acquires(&cgroup_mutex) __acquires(&cgroup_threadgroup_rwsem)
6163 struct cgroup *dst_cgrp = NULL;
6164 struct css_set *cset;
6165 struct super_block *sb;
6168 if (kargs->flags & CLONE_INTO_CGROUP)
6169 mutex_lock(&cgroup_mutex);
6171 cgroup_threadgroup_change_begin(current);
6173 spin_lock_irq(&css_set_lock);
6174 cset = task_css_set(current);
6176 spin_unlock_irq(&css_set_lock);
6178 if (!(kargs->flags & CLONE_INTO_CGROUP)) {
6183 f = fget_raw(kargs->cgroup);
6188 sb = f->f_path.dentry->d_sb;
6190 dst_cgrp = cgroup_get_from_file(f);
6191 if (IS_ERR(dst_cgrp)) {
6192 ret = PTR_ERR(dst_cgrp);
6197 if (cgroup_is_dead(dst_cgrp)) {
6203 * Verify that we the target cgroup is writable for us. This is
6204 * usually done by the vfs layer but since we're not going through
6205 * the vfs layer here we need to do it "manually".
6207 ret = cgroup_may_write(dst_cgrp, sb);
6212 * Spawning a task directly into a cgroup works by passing a file
6213 * descriptor to the target cgroup directory. This can even be an O_PATH
6214 * file descriptor. But it can never be a cgroup.procs file descriptor.
6215 * This was done on purpose so spawning into a cgroup could be
6216 * conceptualized as an atomic
6218 * fd = openat(dfd_cgroup, "cgroup.procs", ...);
6219 * write(fd, <child-pid>, ...);
6221 * sequence, i.e. it's a shorthand for the caller opening and writing
6222 * cgroup.procs of the cgroup indicated by @dfd_cgroup. This allows us
6223 * to always use the caller's credentials.
6225 ret = cgroup_attach_permissions(cset->dfl_cgrp, dst_cgrp, sb,
6226 !(kargs->flags & CLONE_THREAD),
6227 current->nsproxy->cgroup_ns);
6231 kargs->cset = find_css_set(cset, dst_cgrp);
6239 kargs->cgrp = dst_cgrp;
6243 cgroup_threadgroup_change_end(current);
6244 mutex_unlock(&cgroup_mutex);
6248 cgroup_put(dst_cgrp);
6251 put_css_set(kargs->cset);
6256 * cgroup_css_set_put_fork - drop references we took during fork
6257 * @kargs: the arguments passed to create the child process
6259 * Drop references to the prepared css_set and target cgroup if
6260 * CLONE_INTO_CGROUP was requested.
6262 static void cgroup_css_set_put_fork(struct kernel_clone_args *kargs)
6263 __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
6265 cgroup_threadgroup_change_end(current);
6267 if (kargs->flags & CLONE_INTO_CGROUP) {
6268 struct cgroup *cgrp = kargs->cgrp;
6269 struct css_set *cset = kargs->cset;
6271 mutex_unlock(&cgroup_mutex);
6286 * cgroup_can_fork - called on a new task before the process is exposed
6287 * @child: the child process
6288 * @kargs: the arguments passed to create the child process
6290 * This prepares a new css_set for the child process which the child will
6291 * be attached to in cgroup_post_fork().
6292 * This calls the subsystem can_fork() callbacks. If the cgroup_can_fork()
6293 * callback returns an error, the fork aborts with that error code. This
6294 * allows for a cgroup subsystem to conditionally allow or deny new forks.
6296 int cgroup_can_fork(struct task_struct *child, struct kernel_clone_args *kargs)
6298 struct cgroup_subsys *ss;
6301 ret = cgroup_css_set_fork(kargs);
6305 do_each_subsys_mask(ss, i, have_canfork_callback) {
6306 ret = ss->can_fork(child, kargs->cset);
6309 } while_each_subsys_mask();
6314 for_each_subsys(ss, j) {
6317 if (ss->cancel_fork)
6318 ss->cancel_fork(child, kargs->cset);
6321 cgroup_css_set_put_fork(kargs);
6327 * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
6328 * @child: the child process
6329 * @kargs: the arguments passed to create the child process
6331 * This calls the cancel_fork() callbacks if a fork failed *after*
6332 * cgroup_can_fork() succeeded and cleans up references we took to
6333 * prepare a new css_set for the child process in cgroup_can_fork().
6335 void cgroup_cancel_fork(struct task_struct *child,
6336 struct kernel_clone_args *kargs)
6338 struct cgroup_subsys *ss;
6341 for_each_subsys(ss, i)
6342 if (ss->cancel_fork)
6343 ss->cancel_fork(child, kargs->cset);
6345 cgroup_css_set_put_fork(kargs);
6349 * cgroup_post_fork - finalize cgroup setup for the child process
6350 * @child: the child process
6351 * @kargs: the arguments passed to create the child process
6353 * Attach the child process to its css_set calling the subsystem fork()
6356 void cgroup_post_fork(struct task_struct *child,
6357 struct kernel_clone_args *kargs)
6358 __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
6360 unsigned long cgrp_flags = 0;
6362 struct cgroup_subsys *ss;
6363 struct css_set *cset;
6369 spin_lock_irq(&css_set_lock);
6371 /* init tasks are special, only link regular threads */
6372 if (likely(child->pid)) {
6374 cgrp_flags = kargs->cgrp->flags;
6376 cgrp_flags = cset->dfl_cgrp->flags;
6378 WARN_ON_ONCE(!list_empty(&child->cg_list));
6380 css_set_move_task(child, NULL, cset, false);
6386 if (!(child->flags & PF_KTHREAD)) {
6387 if (unlikely(test_bit(CGRP_FREEZE, &cgrp_flags))) {
6389 * If the cgroup has to be frozen, the new task has
6390 * too. Let's set the JOBCTL_TRAP_FREEZE jobctl bit to
6391 * get the task into the frozen state.
6393 spin_lock(&child->sighand->siglock);
6394 WARN_ON_ONCE(child->frozen);
6395 child->jobctl |= JOBCTL_TRAP_FREEZE;
6396 spin_unlock(&child->sighand->siglock);
6399 * Calling cgroup_update_frozen() isn't required here,
6400 * because it will be called anyway a bit later from
6401 * do_freezer_trap(). So we avoid cgroup's transient
6402 * switch from the frozen state and back.
6407 * If the cgroup is to be killed notice it now and take the
6408 * child down right after we finished preparing it for
6411 kill = test_bit(CGRP_KILL, &cgrp_flags);
6414 spin_unlock_irq(&css_set_lock);
6417 * Call ss->fork(). This must happen after @child is linked on
6418 * css_set; otherwise, @child might change state between ->fork()
6419 * and addition to css_set.
6421 do_each_subsys_mask(ss, i, have_fork_callback) {
6423 } while_each_subsys_mask();
6425 /* Make the new cset the root_cset of the new cgroup namespace. */
6426 if (kargs->flags & CLONE_NEWCGROUP) {
6427 struct css_set *rcset = child->nsproxy->cgroup_ns->root_cset;
6430 child->nsproxy->cgroup_ns->root_cset = cset;
6434 /* Cgroup has to be killed so take down child immediately. */
6436 do_send_sig_info(SIGKILL, SEND_SIG_NOINFO, child, PIDTYPE_TGID);
6438 cgroup_css_set_put_fork(kargs);
6442 * cgroup_exit - detach cgroup from exiting task
6443 * @tsk: pointer to task_struct of exiting process
6445 * Description: Detach cgroup from @tsk.
6448 void cgroup_exit(struct task_struct *tsk)
6450 struct cgroup_subsys *ss;
6451 struct css_set *cset;
6454 spin_lock_irq(&css_set_lock);
6456 WARN_ON_ONCE(list_empty(&tsk->cg_list));
6457 cset = task_css_set(tsk);
6458 css_set_move_task(tsk, cset, NULL, false);
6459 list_add_tail(&tsk->cg_list, &cset->dying_tasks);
6462 WARN_ON_ONCE(cgroup_task_frozen(tsk));
6463 if (unlikely(!(tsk->flags & PF_KTHREAD) &&
6464 test_bit(CGRP_FREEZE, &task_dfl_cgroup(tsk)->flags)))
6465 cgroup_update_frozen(task_dfl_cgroup(tsk));
6467 spin_unlock_irq(&css_set_lock);
6469 /* see cgroup_post_fork() for details */
6470 do_each_subsys_mask(ss, i, have_exit_callback) {
6472 } while_each_subsys_mask();
6475 void cgroup_release(struct task_struct *task)
6477 struct cgroup_subsys *ss;
6480 do_each_subsys_mask(ss, ssid, have_release_callback) {
6482 } while_each_subsys_mask();
6484 spin_lock_irq(&css_set_lock);
6485 css_set_skip_task_iters(task_css_set(task), task);
6486 list_del_init(&task->cg_list);
6487 spin_unlock_irq(&css_set_lock);
6490 void cgroup_free(struct task_struct *task)
6492 struct css_set *cset = task_css_set(task);
6496 static int __init cgroup_disable(char *str)
6498 struct cgroup_subsys *ss;
6502 while ((token = strsep(&str, ",")) != NULL) {
6506 for_each_subsys(ss, i) {
6507 if (strcmp(token, ss->name) &&
6508 strcmp(token, ss->legacy_name))
6511 static_branch_disable(cgroup_subsys_enabled_key[i]);
6512 pr_info("Disabling %s control group subsystem\n",
6516 for (i = 0; i < OPT_FEATURE_COUNT; i++) {
6517 if (strcmp(token, cgroup_opt_feature_names[i]))
6519 cgroup_feature_disable_mask |= 1 << i;
6520 pr_info("Disabling %s control group feature\n",
6521 cgroup_opt_feature_names[i]);
6527 __setup("cgroup_disable=", cgroup_disable);
6529 void __init __weak enable_debug_cgroup(void) { }
6531 static int __init enable_cgroup_debug(char *str)
6533 cgroup_debug = true;
6534 enable_debug_cgroup();
6537 __setup("cgroup_debug", enable_cgroup_debug);
6540 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
6541 * @dentry: directory dentry of interest
6542 * @ss: subsystem of interest
6544 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
6545 * to get the corresponding css and return it. If such css doesn't exist
6546 * or can't be pinned, an ERR_PTR value is returned.
6548 struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
6549 struct cgroup_subsys *ss)
6551 struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
6552 struct file_system_type *s_type = dentry->d_sb->s_type;
6553 struct cgroup_subsys_state *css = NULL;
6554 struct cgroup *cgrp;
6556 /* is @dentry a cgroup dir? */
6557 if ((s_type != &cgroup_fs_type && s_type != &cgroup2_fs_type) ||
6558 !kn || kernfs_type(kn) != KERNFS_DIR)
6559 return ERR_PTR(-EBADF);
6564 * This path doesn't originate from kernfs and @kn could already
6565 * have been or be removed at any point. @kn->priv is RCU
6566 * protected for this access. See css_release_work_fn() for details.
6568 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6570 css = cgroup_css(cgrp, ss);
6572 if (!css || !css_tryget_online(css))
6573 css = ERR_PTR(-ENOENT);
6580 * css_from_id - lookup css by id
6581 * @id: the cgroup id
6582 * @ss: cgroup subsys to be looked into
6584 * Returns the css if there's valid one with @id, otherwise returns NULL.
6585 * Should be called under rcu_read_lock().
6587 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
6589 WARN_ON_ONCE(!rcu_read_lock_held());
6590 return idr_find(&ss->css_idr, id);
6594 * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path
6595 * @path: path on the default hierarchy
6597 * Find the cgroup at @path on the default hierarchy, increment its
6598 * reference count and return it. Returns pointer to the found cgroup on
6599 * success, ERR_PTR(-ENOENT) if @path doesn't exist or if the cgroup has already
6600 * been released and ERR_PTR(-ENOTDIR) if @path points to a non-directory.
6602 struct cgroup *cgroup_get_from_path(const char *path)
6604 struct kernfs_node *kn;
6605 struct cgroup *cgrp = ERR_PTR(-ENOENT);
6607 kn = kernfs_walk_and_get(cgrp_dfl_root.cgrp.kn, path);
6611 if (kernfs_type(kn) != KERNFS_DIR) {
6612 cgrp = ERR_PTR(-ENOTDIR);
6618 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6619 if (!cgrp || !cgroup_tryget(cgrp))
6620 cgrp = ERR_PTR(-ENOENT);
6629 EXPORT_SYMBOL_GPL(cgroup_get_from_path);
6632 * cgroup_get_from_fd - get a cgroup pointer from a fd
6633 * @fd: fd obtained by open(cgroup2_dir)
6635 * Find the cgroup from a fd which should be obtained
6636 * by opening a cgroup directory. Returns a pointer to the
6637 * cgroup on success. ERR_PTR is returned if the cgroup
6640 struct cgroup *cgroup_get_from_fd(int fd)
6642 struct cgroup *cgrp;
6647 return ERR_PTR(-EBADF);
6649 cgrp = cgroup_get_from_file(f);
6653 EXPORT_SYMBOL_GPL(cgroup_get_from_fd);
6655 static u64 power_of_ten(int power)
6664 * cgroup_parse_float - parse a floating number
6665 * @input: input string
6666 * @dec_shift: number of decimal digits to shift
6669 * Parse a decimal floating point number in @input and store the result in
6670 * @v with decimal point right shifted @dec_shift times. For example, if
6671 * @input is "12.3456" and @dec_shift is 3, *@v will be set to 12345.
6672 * Returns 0 on success, -errno otherwise.
6674 * There's nothing cgroup specific about this function except that it's
6675 * currently the only user.
6677 int cgroup_parse_float(const char *input, unsigned dec_shift, s64 *v)
6679 s64 whole, frac = 0;
6680 int fstart = 0, fend = 0, flen;
6682 if (!sscanf(input, "%lld.%n%lld%n", &whole, &fstart, &frac, &fend))
6687 flen = fend > fstart ? fend - fstart : 0;
6688 if (flen < dec_shift)
6689 frac *= power_of_ten(dec_shift - flen);
6691 frac = DIV_ROUND_CLOSEST_ULL(frac, power_of_ten(flen - dec_shift));
6693 *v = whole * power_of_ten(dec_shift) + frac;
6698 * sock->sk_cgrp_data handling. For more info, see sock_cgroup_data
6699 * definition in cgroup-defs.h.
6701 #ifdef CONFIG_SOCK_CGROUP_DATA
6703 void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
6705 struct cgroup *cgroup;
6708 /* Don't associate the sock with unrelated interrupted task's cgroup. */
6709 if (in_interrupt()) {
6710 cgroup = &cgrp_dfl_root.cgrp;
6716 struct css_set *cset;
6718 cset = task_css_set(current);
6719 if (likely(cgroup_tryget(cset->dfl_cgrp))) {
6720 cgroup = cset->dfl_cgrp;
6726 skcd->cgroup = cgroup;
6727 cgroup_bpf_get(cgroup);
6731 void cgroup_sk_clone(struct sock_cgroup_data *skcd)
6733 struct cgroup *cgrp = sock_cgroup_ptr(skcd);
6736 * We might be cloning a socket which is left in an empty
6737 * cgroup and the cgroup might have already been rmdir'd.
6738 * Don't use cgroup_get_live().
6741 cgroup_bpf_get(cgrp);
6744 void cgroup_sk_free(struct sock_cgroup_data *skcd)
6746 struct cgroup *cgrp = sock_cgroup_ptr(skcd);
6748 cgroup_bpf_put(cgrp);
6752 #endif /* CONFIG_SOCK_CGROUP_DATA */
6755 static ssize_t show_delegatable_files(struct cftype *files, char *buf,
6756 ssize_t size, const char *prefix)
6761 for (cft = files; cft && cft->name[0] != '\0'; cft++) {
6762 if (!(cft->flags & CFTYPE_NS_DELEGATABLE))
6765 if ((cft->flags & CFTYPE_PRESSURE) && !cgroup_psi_enabled())
6769 ret += snprintf(buf + ret, size - ret, "%s.", prefix);
6771 ret += snprintf(buf + ret, size - ret, "%s\n", cft->name);
6773 if (WARN_ON(ret >= size))
6780 static ssize_t delegate_show(struct kobject *kobj, struct kobj_attribute *attr,
6783 struct cgroup_subsys *ss;
6787 ret = show_delegatable_files(cgroup_base_files, buf, PAGE_SIZE - ret,
6790 for_each_subsys(ss, ssid)
6791 ret += show_delegatable_files(ss->dfl_cftypes, buf + ret,
6793 cgroup_subsys_name[ssid]);
6797 static struct kobj_attribute cgroup_delegate_attr = __ATTR_RO(delegate);
6799 static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr,
6802 return snprintf(buf, PAGE_SIZE,
6805 "memory_localevents\n"
6806 "memory_recursiveprot\n");
6808 static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features);
6810 static struct attribute *cgroup_sysfs_attrs[] = {
6811 &cgroup_delegate_attr.attr,
6812 &cgroup_features_attr.attr,
6816 static const struct attribute_group cgroup_sysfs_attr_group = {
6817 .attrs = cgroup_sysfs_attrs,
6821 static int __init cgroup_sysfs_init(void)
6823 return sysfs_create_group(kernel_kobj, &cgroup_sysfs_attr_group);
6825 subsys_initcall(cgroup_sysfs_init);
6827 #endif /* CONFIG_SYSFS */