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[];
220 static struct cftype cgroup_psi_files[];
222 /* cgroup optional features */
223 enum cgroup_opt_features {
225 OPT_FEATURE_PRESSURE,
230 static const char *cgroup_opt_feature_names[OPT_FEATURE_COUNT] = {
236 static u16 cgroup_feature_disable_mask __read_mostly;
238 static int cgroup_apply_control(struct cgroup *cgrp);
239 static void cgroup_finalize_control(struct cgroup *cgrp, int ret);
240 static void css_task_iter_skip(struct css_task_iter *it,
241 struct task_struct *task);
242 static int cgroup_destroy_locked(struct cgroup *cgrp);
243 static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
244 struct cgroup_subsys *ss);
245 static void css_release(struct percpu_ref *ref);
246 static void kill_css(struct cgroup_subsys_state *css);
247 static int cgroup_addrm_files(struct cgroup_subsys_state *css,
248 struct cgroup *cgrp, struct cftype cfts[],
252 * cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID
253 * @ssid: subsys ID of interest
255 * cgroup_subsys_enabled() can only be used with literal subsys names which
256 * is fine for individual subsystems but unsuitable for cgroup core. This
257 * is slower static_key_enabled() based test indexed by @ssid.
259 bool cgroup_ssid_enabled(int ssid)
261 if (!CGROUP_HAS_SUBSYS_CONFIG)
264 return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
268 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
269 * @cgrp: the cgroup of interest
271 * The default hierarchy is the v2 interface of cgroup and this function
272 * can be used to test whether a cgroup is on the default hierarchy for
273 * cases where a subsystem should behave differently depending on the
276 * List of changed behaviors:
278 * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
279 * and "name" are disallowed.
281 * - When mounting an existing superblock, mount options should match.
283 * - rename(2) is disallowed.
285 * - "tasks" is removed. Everything should be at process granularity. Use
286 * "cgroup.procs" instead.
288 * - "cgroup.procs" is not sorted. pids will be unique unless they got
289 * recycled in-between reads.
291 * - "release_agent" and "notify_on_release" are removed. Replacement
292 * notification mechanism will be implemented.
294 * - "cgroup.clone_children" is removed.
296 * - "cgroup.subtree_populated" is available. Its value is 0 if the cgroup
297 * and its descendants contain no task; otherwise, 1. The file also
298 * generates kernfs notification which can be monitored through poll and
299 * [di]notify when the value of the file changes.
301 * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
302 * take masks of ancestors with non-empty cpus/mems, instead of being
303 * moved to an ancestor.
305 * - cpuset: a task can be moved into an empty cpuset, and again it takes
306 * masks of ancestors.
308 * - blkcg: blk-throttle becomes properly hierarchical.
310 * - debug: disallowed on the default hierarchy.
312 bool cgroup_on_dfl(const struct cgroup *cgrp)
314 return cgrp->root == &cgrp_dfl_root;
317 /* IDR wrappers which synchronize using cgroup_idr_lock */
318 static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
323 idr_preload(gfp_mask);
324 spin_lock_bh(&cgroup_idr_lock);
325 ret = idr_alloc(idr, ptr, start, end, gfp_mask & ~__GFP_DIRECT_RECLAIM);
326 spin_unlock_bh(&cgroup_idr_lock);
331 static void *cgroup_idr_replace(struct idr *idr, void *ptr, int id)
335 spin_lock_bh(&cgroup_idr_lock);
336 ret = idr_replace(idr, ptr, id);
337 spin_unlock_bh(&cgroup_idr_lock);
341 static void cgroup_idr_remove(struct idr *idr, int id)
343 spin_lock_bh(&cgroup_idr_lock);
345 spin_unlock_bh(&cgroup_idr_lock);
348 static bool cgroup_has_tasks(struct cgroup *cgrp)
350 return cgrp->nr_populated_csets;
353 bool cgroup_is_threaded(struct cgroup *cgrp)
355 return cgrp->dom_cgrp != cgrp;
358 /* can @cgrp host both domain and threaded children? */
359 static bool cgroup_is_mixable(struct cgroup *cgrp)
362 * Root isn't under domain level resource control exempting it from
363 * the no-internal-process constraint, so it can serve as a thread
364 * root and a parent of resource domains at the same time.
366 return !cgroup_parent(cgrp);
369 /* can @cgrp become a thread root? Should always be true for a thread root */
370 static bool cgroup_can_be_thread_root(struct cgroup *cgrp)
372 /* mixables don't care */
373 if (cgroup_is_mixable(cgrp))
376 /* domain roots can't be nested under threaded */
377 if (cgroup_is_threaded(cgrp))
380 /* can only have either domain or threaded children */
381 if (cgrp->nr_populated_domain_children)
384 /* and no domain controllers can be enabled */
385 if (cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)
391 /* is @cgrp root of a threaded subtree? */
392 bool cgroup_is_thread_root(struct cgroup *cgrp)
394 /* thread root should be a domain */
395 if (cgroup_is_threaded(cgrp))
398 /* a domain w/ threaded children is a thread root */
399 if (cgrp->nr_threaded_children)
403 * A domain which has tasks and explicit threaded controllers
404 * enabled is a thread root.
406 if (cgroup_has_tasks(cgrp) &&
407 (cgrp->subtree_control & cgrp_dfl_threaded_ss_mask))
413 /* a domain which isn't connected to the root w/o brekage can't be used */
414 static bool cgroup_is_valid_domain(struct cgroup *cgrp)
416 /* the cgroup itself can be a thread root */
417 if (cgroup_is_threaded(cgrp))
420 /* but the ancestors can't be unless mixable */
421 while ((cgrp = cgroup_parent(cgrp))) {
422 if (!cgroup_is_mixable(cgrp) && cgroup_is_thread_root(cgrp))
424 if (cgroup_is_threaded(cgrp))
431 /* subsystems visibly enabled on a cgroup */
432 static u16 cgroup_control(struct cgroup *cgrp)
434 struct cgroup *parent = cgroup_parent(cgrp);
435 u16 root_ss_mask = cgrp->root->subsys_mask;
438 u16 ss_mask = parent->subtree_control;
440 /* threaded cgroups can only have threaded controllers */
441 if (cgroup_is_threaded(cgrp))
442 ss_mask &= cgrp_dfl_threaded_ss_mask;
446 if (cgroup_on_dfl(cgrp))
447 root_ss_mask &= ~(cgrp_dfl_inhibit_ss_mask |
448 cgrp_dfl_implicit_ss_mask);
452 /* subsystems enabled on a cgroup */
453 static u16 cgroup_ss_mask(struct cgroup *cgrp)
455 struct cgroup *parent = cgroup_parent(cgrp);
458 u16 ss_mask = parent->subtree_ss_mask;
460 /* threaded cgroups can only have threaded controllers */
461 if (cgroup_is_threaded(cgrp))
462 ss_mask &= cgrp_dfl_threaded_ss_mask;
466 return cgrp->root->subsys_mask;
470 * cgroup_css - obtain a cgroup's css for the specified subsystem
471 * @cgrp: the cgroup of interest
472 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
474 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
475 * function must be called either under cgroup_mutex or rcu_read_lock() and
476 * the caller is responsible for pinning the returned css if it wants to
477 * keep accessing it outside the said locks. This function may return
478 * %NULL if @cgrp doesn't have @subsys_id enabled.
480 static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
481 struct cgroup_subsys *ss)
483 if (CGROUP_HAS_SUBSYS_CONFIG && ss)
484 return rcu_dereference_check(cgrp->subsys[ss->id],
485 lockdep_is_held(&cgroup_mutex));
491 * cgroup_tryget_css - try to get a cgroup's css for the specified subsystem
492 * @cgrp: the cgroup of interest
493 * @ss: the subsystem of interest
495 * Find and get @cgrp's css associated with @ss. If the css doesn't exist
496 * or is offline, %NULL is returned.
498 static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp,
499 struct cgroup_subsys *ss)
501 struct cgroup_subsys_state *css;
504 css = cgroup_css(cgrp, ss);
505 if (css && !css_tryget_online(css))
513 * cgroup_e_css_by_mask - obtain a cgroup's effective css for the specified ss
514 * @cgrp: the cgroup of interest
515 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
517 * Similar to cgroup_css() but returns the effective css, which is defined
518 * as the matching css of the nearest ancestor including self which has @ss
519 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
520 * function is guaranteed to return non-NULL css.
522 static struct cgroup_subsys_state *cgroup_e_css_by_mask(struct cgroup *cgrp,
523 struct cgroup_subsys *ss)
525 lockdep_assert_held(&cgroup_mutex);
531 * This function is used while updating css associations and thus
532 * can't test the csses directly. Test ss_mask.
534 while (!(cgroup_ss_mask(cgrp) & (1 << ss->id))) {
535 cgrp = cgroup_parent(cgrp);
540 return cgroup_css(cgrp, ss);
544 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
545 * @cgrp: the cgroup of interest
546 * @ss: the subsystem of interest
548 * Find and get the effective css of @cgrp for @ss. The effective css is
549 * defined as the matching css of the nearest ancestor including self which
550 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
551 * the root css is returned, so this function always returns a valid css.
553 * The returned css is not guaranteed to be online, and therefore it is the
554 * callers responsibility to try get a reference for it.
556 struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
557 struct cgroup_subsys *ss)
559 struct cgroup_subsys_state *css;
561 if (!CGROUP_HAS_SUBSYS_CONFIG)
565 css = cgroup_css(cgrp, ss);
569 cgrp = cgroup_parent(cgrp);
572 return init_css_set.subsys[ss->id];
576 * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
577 * @cgrp: the cgroup of interest
578 * @ss: the subsystem of interest
580 * Find and get the effective css of @cgrp for @ss. The effective css is
581 * defined as the matching css of the nearest ancestor including self which
582 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
583 * the root css is returned, so this function always returns a valid css.
584 * The returned css must be put using css_put().
586 struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
587 struct cgroup_subsys *ss)
589 struct cgroup_subsys_state *css;
591 if (!CGROUP_HAS_SUBSYS_CONFIG)
597 css = cgroup_css(cgrp, ss);
599 if (css && css_tryget_online(css))
601 cgrp = cgroup_parent(cgrp);
604 css = init_css_set.subsys[ss->id];
610 EXPORT_SYMBOL_GPL(cgroup_get_e_css);
612 static void cgroup_get_live(struct cgroup *cgrp)
614 WARN_ON_ONCE(cgroup_is_dead(cgrp));
615 css_get(&cgrp->self);
619 * __cgroup_task_count - count the number of tasks in a cgroup. The caller
620 * is responsible for taking the css_set_lock.
621 * @cgrp: the cgroup in question
623 int __cgroup_task_count(const struct cgroup *cgrp)
626 struct cgrp_cset_link *link;
628 lockdep_assert_held(&css_set_lock);
630 list_for_each_entry(link, &cgrp->cset_links, cset_link)
631 count += link->cset->nr_tasks;
637 * cgroup_task_count - count the number of tasks in a cgroup.
638 * @cgrp: the cgroup in question
640 int cgroup_task_count(const struct cgroup *cgrp)
644 spin_lock_irq(&css_set_lock);
645 count = __cgroup_task_count(cgrp);
646 spin_unlock_irq(&css_set_lock);
651 struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
653 struct cgroup *cgrp = of->kn->parent->priv;
654 struct cftype *cft = of_cft(of);
657 * This is open and unprotected implementation of cgroup_css().
658 * seq_css() is only called from a kernfs file operation which has
659 * an active reference on the file. Because all the subsystem
660 * files are drained before a css is disassociated with a cgroup,
661 * the matching css from the cgroup's subsys table is guaranteed to
662 * be and stay valid until the enclosing operation is complete.
664 if (CGROUP_HAS_SUBSYS_CONFIG && cft->ss)
665 return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
669 EXPORT_SYMBOL_GPL(of_css);
672 * for_each_css - iterate all css's of a cgroup
673 * @css: the iteration cursor
674 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
675 * @cgrp: the target cgroup to iterate css's of
677 * Should be called under cgroup_[tree_]mutex.
679 #define for_each_css(css, ssid, cgrp) \
680 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
681 if (!((css) = rcu_dereference_check( \
682 (cgrp)->subsys[(ssid)], \
683 lockdep_is_held(&cgroup_mutex)))) { } \
687 * for_each_e_css - iterate all effective css's of a cgroup
688 * @css: the iteration cursor
689 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
690 * @cgrp: the target cgroup to iterate css's of
692 * Should be called under cgroup_[tree_]mutex.
694 #define for_each_e_css(css, ssid, cgrp) \
695 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
696 if (!((css) = cgroup_e_css_by_mask(cgrp, \
697 cgroup_subsys[(ssid)]))) \
702 * do_each_subsys_mask - filter for_each_subsys with a bitmask
703 * @ss: the iteration cursor
704 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
705 * @ss_mask: the bitmask
707 * The block will only run for cases where the ssid-th bit (1 << ssid) of
710 #define do_each_subsys_mask(ss, ssid, ss_mask) do { \
711 unsigned long __ss_mask = (ss_mask); \
712 if (!CGROUP_HAS_SUBSYS_CONFIG) { \
716 for_each_set_bit(ssid, &__ss_mask, CGROUP_SUBSYS_COUNT) { \
717 (ss) = cgroup_subsys[ssid]; \
720 #define while_each_subsys_mask() \
725 /* iterate over child cgrps, lock should be held throughout iteration */
726 #define cgroup_for_each_live_child(child, cgrp) \
727 list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
728 if (({ lockdep_assert_held(&cgroup_mutex); \
729 cgroup_is_dead(child); })) \
733 /* walk live descendants in pre order */
734 #define cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) \
735 css_for_each_descendant_pre((d_css), cgroup_css((cgrp), NULL)) \
736 if (({ lockdep_assert_held(&cgroup_mutex); \
737 (dsct) = (d_css)->cgroup; \
738 cgroup_is_dead(dsct); })) \
742 /* walk live descendants in postorder */
743 #define cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) \
744 css_for_each_descendant_post((d_css), cgroup_css((cgrp), NULL)) \
745 if (({ lockdep_assert_held(&cgroup_mutex); \
746 (dsct) = (d_css)->cgroup; \
747 cgroup_is_dead(dsct); })) \
752 * The default css_set - used by init and its children prior to any
753 * hierarchies being mounted. It contains a pointer to the root state
754 * for each subsystem. Also used to anchor the list of css_sets. Not
755 * reference-counted, to improve performance when child cgroups
756 * haven't been created.
758 struct css_set init_css_set = {
759 .refcount = REFCOUNT_INIT(1),
760 .dom_cset = &init_css_set,
761 .tasks = LIST_HEAD_INIT(init_css_set.tasks),
762 .mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
763 .dying_tasks = LIST_HEAD_INIT(init_css_set.dying_tasks),
764 .task_iters = LIST_HEAD_INIT(init_css_set.task_iters),
765 .threaded_csets = LIST_HEAD_INIT(init_css_set.threaded_csets),
766 .cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
767 .mg_src_preload_node = LIST_HEAD_INIT(init_css_set.mg_src_preload_node),
768 .mg_dst_preload_node = LIST_HEAD_INIT(init_css_set.mg_dst_preload_node),
769 .mg_node = LIST_HEAD_INIT(init_css_set.mg_node),
772 * The following field is re-initialized when this cset gets linked
773 * in cgroup_init(). However, let's initialize the field
774 * statically too so that the default cgroup can be accessed safely
777 .dfl_cgrp = &cgrp_dfl_root.cgrp,
780 static int css_set_count = 1; /* 1 for init_css_set */
782 static bool css_set_threaded(struct css_set *cset)
784 return cset->dom_cset != cset;
788 * css_set_populated - does a css_set contain any tasks?
789 * @cset: target css_set
791 * css_set_populated() should be the same as !!cset->nr_tasks at steady
792 * state. However, css_set_populated() can be called while a task is being
793 * added to or removed from the linked list before the nr_tasks is
794 * properly updated. Hence, we can't just look at ->nr_tasks here.
796 static bool css_set_populated(struct css_set *cset)
798 lockdep_assert_held(&css_set_lock);
800 return !list_empty(&cset->tasks) || !list_empty(&cset->mg_tasks);
804 * cgroup_update_populated - update the populated count of a cgroup
805 * @cgrp: the target cgroup
806 * @populated: inc or dec populated count
808 * One of the css_sets associated with @cgrp is either getting its first
809 * task or losing the last. Update @cgrp->nr_populated_* accordingly. The
810 * count is propagated towards root so that a given cgroup's
811 * nr_populated_children is zero iff none of its descendants contain any
814 * @cgrp's interface file "cgroup.populated" is zero if both
815 * @cgrp->nr_populated_csets and @cgrp->nr_populated_children are zero and
816 * 1 otherwise. When the sum changes from or to zero, userland is notified
817 * that the content of the interface file has changed. This can be used to
818 * detect when @cgrp and its descendants become populated or empty.
820 static void cgroup_update_populated(struct cgroup *cgrp, bool populated)
822 struct cgroup *child = NULL;
823 int adj = populated ? 1 : -1;
825 lockdep_assert_held(&css_set_lock);
828 bool was_populated = cgroup_is_populated(cgrp);
831 cgrp->nr_populated_csets += adj;
833 if (cgroup_is_threaded(child))
834 cgrp->nr_populated_threaded_children += adj;
836 cgrp->nr_populated_domain_children += adj;
839 if (was_populated == cgroup_is_populated(cgrp))
842 cgroup1_check_for_release(cgrp);
843 TRACE_CGROUP_PATH(notify_populated, cgrp,
844 cgroup_is_populated(cgrp));
845 cgroup_file_notify(&cgrp->events_file);
848 cgrp = cgroup_parent(cgrp);
853 * css_set_update_populated - update populated state of a css_set
854 * @cset: target css_set
855 * @populated: whether @cset is populated or depopulated
857 * @cset is either getting the first task or losing the last. Update the
858 * populated counters of all associated cgroups accordingly.
860 static void css_set_update_populated(struct css_set *cset, bool populated)
862 struct cgrp_cset_link *link;
864 lockdep_assert_held(&css_set_lock);
866 list_for_each_entry(link, &cset->cgrp_links, cgrp_link)
867 cgroup_update_populated(link->cgrp, populated);
871 * @task is leaving, advance task iterators which are pointing to it so
872 * that they can resume at the next position. Advancing an iterator might
873 * remove it from the list, use safe walk. See css_task_iter_skip() for
876 static void css_set_skip_task_iters(struct css_set *cset,
877 struct task_struct *task)
879 struct css_task_iter *it, *pos;
881 list_for_each_entry_safe(it, pos, &cset->task_iters, iters_node)
882 css_task_iter_skip(it, task);
886 * css_set_move_task - move a task from one css_set to another
887 * @task: task being moved
888 * @from_cset: css_set @task currently belongs to (may be NULL)
889 * @to_cset: new css_set @task is being moved to (may be NULL)
890 * @use_mg_tasks: move to @to_cset->mg_tasks instead of ->tasks
892 * Move @task from @from_cset to @to_cset. If @task didn't belong to any
893 * css_set, @from_cset can be NULL. If @task is being disassociated
894 * instead of moved, @to_cset can be NULL.
896 * This function automatically handles populated counter updates and
897 * css_task_iter adjustments but the caller is responsible for managing
898 * @from_cset and @to_cset's reference counts.
900 static void css_set_move_task(struct task_struct *task,
901 struct css_set *from_cset, struct css_set *to_cset,
904 lockdep_assert_held(&css_set_lock);
906 if (to_cset && !css_set_populated(to_cset))
907 css_set_update_populated(to_cset, true);
910 WARN_ON_ONCE(list_empty(&task->cg_list));
912 css_set_skip_task_iters(from_cset, task);
913 list_del_init(&task->cg_list);
914 if (!css_set_populated(from_cset))
915 css_set_update_populated(from_cset, false);
917 WARN_ON_ONCE(!list_empty(&task->cg_list));
922 * We are synchronized through cgroup_threadgroup_rwsem
923 * against PF_EXITING setting such that we can't race
924 * against cgroup_exit()/cgroup_free() dropping the css_set.
926 WARN_ON_ONCE(task->flags & PF_EXITING);
928 cgroup_move_task(task, to_cset);
929 list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks :
935 * hash table for cgroup groups. This improves the performance to find
936 * an existing css_set. This hash doesn't (currently) take into
937 * account cgroups in empty hierarchies.
939 #define CSS_SET_HASH_BITS 7
940 static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
942 static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
944 unsigned long key = 0UL;
945 struct cgroup_subsys *ss;
948 for_each_subsys(ss, i)
949 key += (unsigned long)css[i];
950 key = (key >> 16) ^ key;
955 void put_css_set_locked(struct css_set *cset)
957 struct cgrp_cset_link *link, *tmp_link;
958 struct cgroup_subsys *ss;
961 lockdep_assert_held(&css_set_lock);
963 if (!refcount_dec_and_test(&cset->refcount))
966 WARN_ON_ONCE(!list_empty(&cset->threaded_csets));
968 /* This css_set is dead. Unlink it and release cgroup and css refs */
969 for_each_subsys(ss, ssid) {
970 list_del(&cset->e_cset_node[ssid]);
971 css_put(cset->subsys[ssid]);
973 hash_del(&cset->hlist);
976 list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
977 list_del(&link->cset_link);
978 list_del(&link->cgrp_link);
979 if (cgroup_parent(link->cgrp))
980 cgroup_put(link->cgrp);
984 if (css_set_threaded(cset)) {
985 list_del(&cset->threaded_csets_node);
986 put_css_set_locked(cset->dom_cset);
989 kfree_rcu(cset, rcu_head);
993 * compare_css_sets - helper function for find_existing_css_set().
994 * @cset: candidate css_set being tested
995 * @old_cset: existing css_set for a task
996 * @new_cgrp: cgroup that's being entered by the task
997 * @template: desired set of css pointers in css_set (pre-calculated)
999 * Returns true if "cset" matches "old_cset" except for the hierarchy
1000 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
1002 static bool compare_css_sets(struct css_set *cset,
1003 struct css_set *old_cset,
1004 struct cgroup *new_cgrp,
1005 struct cgroup_subsys_state *template[])
1007 struct cgroup *new_dfl_cgrp;
1008 struct list_head *l1, *l2;
1011 * On the default hierarchy, there can be csets which are
1012 * associated with the same set of cgroups but different csses.
1013 * Let's first ensure that csses match.
1015 if (memcmp(template, cset->subsys, sizeof(cset->subsys)))
1019 /* @cset's domain should match the default cgroup's */
1020 if (cgroup_on_dfl(new_cgrp))
1021 new_dfl_cgrp = new_cgrp;
1023 new_dfl_cgrp = old_cset->dfl_cgrp;
1025 if (new_dfl_cgrp->dom_cgrp != cset->dom_cset->dfl_cgrp)
1029 * Compare cgroup pointers in order to distinguish between
1030 * different cgroups in hierarchies. As different cgroups may
1031 * share the same effective css, this comparison is always
1034 l1 = &cset->cgrp_links;
1035 l2 = &old_cset->cgrp_links;
1037 struct cgrp_cset_link *link1, *link2;
1038 struct cgroup *cgrp1, *cgrp2;
1042 /* See if we reached the end - both lists are equal length. */
1043 if (l1 == &cset->cgrp_links) {
1044 BUG_ON(l2 != &old_cset->cgrp_links);
1047 BUG_ON(l2 == &old_cset->cgrp_links);
1049 /* Locate the cgroups associated with these links. */
1050 link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
1051 link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
1052 cgrp1 = link1->cgrp;
1053 cgrp2 = link2->cgrp;
1054 /* Hierarchies should be linked in the same order. */
1055 BUG_ON(cgrp1->root != cgrp2->root);
1058 * If this hierarchy is the hierarchy of the cgroup
1059 * that's changing, then we need to check that this
1060 * css_set points to the new cgroup; if it's any other
1061 * hierarchy, then this css_set should point to the
1062 * same cgroup as the old css_set.
1064 if (cgrp1->root == new_cgrp->root) {
1065 if (cgrp1 != new_cgrp)
1076 * find_existing_css_set - init css array and find the matching css_set
1077 * @old_cset: the css_set that we're using before the cgroup transition
1078 * @cgrp: the cgroup that we're moving into
1079 * @template: out param for the new set of csses, should be clear on entry
1081 static struct css_set *find_existing_css_set(struct css_set *old_cset,
1082 struct cgroup *cgrp,
1083 struct cgroup_subsys_state *template[])
1085 struct cgroup_root *root = cgrp->root;
1086 struct cgroup_subsys *ss;
1087 struct css_set *cset;
1092 * Build the set of subsystem state objects that we want to see in the
1093 * new css_set. While subsystems can change globally, the entries here
1094 * won't change, so no need for locking.
1096 for_each_subsys(ss, i) {
1097 if (root->subsys_mask & (1UL << i)) {
1099 * @ss is in this hierarchy, so we want the
1100 * effective css from @cgrp.
1102 template[i] = cgroup_e_css_by_mask(cgrp, ss);
1105 * @ss is not in this hierarchy, so we don't want
1106 * to change the css.
1108 template[i] = old_cset->subsys[i];
1112 key = css_set_hash(template);
1113 hash_for_each_possible(css_set_table, cset, hlist, key) {
1114 if (!compare_css_sets(cset, old_cset, cgrp, template))
1117 /* This css_set matches what we need */
1121 /* No existing cgroup group matched */
1125 static void free_cgrp_cset_links(struct list_head *links_to_free)
1127 struct cgrp_cset_link *link, *tmp_link;
1129 list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
1130 list_del(&link->cset_link);
1136 * allocate_cgrp_cset_links - allocate cgrp_cset_links
1137 * @count: the number of links to allocate
1138 * @tmp_links: list_head the allocated links are put on
1140 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
1141 * through ->cset_link. Returns 0 on success or -errno.
1143 static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
1145 struct cgrp_cset_link *link;
1148 INIT_LIST_HEAD(tmp_links);
1150 for (i = 0; i < count; i++) {
1151 link = kzalloc(sizeof(*link), GFP_KERNEL);
1153 free_cgrp_cset_links(tmp_links);
1156 list_add(&link->cset_link, tmp_links);
1162 * link_css_set - a helper function to link a css_set to a cgroup
1163 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
1164 * @cset: the css_set to be linked
1165 * @cgrp: the destination cgroup
1167 static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
1168 struct cgroup *cgrp)
1170 struct cgrp_cset_link *link;
1172 BUG_ON(list_empty(tmp_links));
1174 if (cgroup_on_dfl(cgrp))
1175 cset->dfl_cgrp = cgrp;
1177 link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
1182 * Always add links to the tail of the lists so that the lists are
1183 * in chronological order.
1185 list_move_tail(&link->cset_link, &cgrp->cset_links);
1186 list_add_tail(&link->cgrp_link, &cset->cgrp_links);
1188 if (cgroup_parent(cgrp))
1189 cgroup_get_live(cgrp);
1193 * find_css_set - return a new css_set with one cgroup updated
1194 * @old_cset: the baseline css_set
1195 * @cgrp: the cgroup to be updated
1197 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
1198 * substituted into the appropriate hierarchy.
1200 static struct css_set *find_css_set(struct css_set *old_cset,
1201 struct cgroup *cgrp)
1203 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
1204 struct css_set *cset;
1205 struct list_head tmp_links;
1206 struct cgrp_cset_link *link;
1207 struct cgroup_subsys *ss;
1211 lockdep_assert_held(&cgroup_mutex);
1213 /* First see if we already have a cgroup group that matches
1214 * the desired set */
1215 spin_lock_irq(&css_set_lock);
1216 cset = find_existing_css_set(old_cset, cgrp, template);
1219 spin_unlock_irq(&css_set_lock);
1224 cset = kzalloc(sizeof(*cset), GFP_KERNEL);
1228 /* Allocate all the cgrp_cset_link objects that we'll need */
1229 if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
1234 refcount_set(&cset->refcount, 1);
1235 cset->dom_cset = cset;
1236 INIT_LIST_HEAD(&cset->tasks);
1237 INIT_LIST_HEAD(&cset->mg_tasks);
1238 INIT_LIST_HEAD(&cset->dying_tasks);
1239 INIT_LIST_HEAD(&cset->task_iters);
1240 INIT_LIST_HEAD(&cset->threaded_csets);
1241 INIT_HLIST_NODE(&cset->hlist);
1242 INIT_LIST_HEAD(&cset->cgrp_links);
1243 INIT_LIST_HEAD(&cset->mg_src_preload_node);
1244 INIT_LIST_HEAD(&cset->mg_dst_preload_node);
1245 INIT_LIST_HEAD(&cset->mg_node);
1247 /* Copy the set of subsystem state objects generated in
1248 * find_existing_css_set() */
1249 memcpy(cset->subsys, template, sizeof(cset->subsys));
1251 spin_lock_irq(&css_set_lock);
1252 /* Add reference counts and links from the new css_set. */
1253 list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
1254 struct cgroup *c = link->cgrp;
1256 if (c->root == cgrp->root)
1258 link_css_set(&tmp_links, cset, c);
1261 BUG_ON(!list_empty(&tmp_links));
1265 /* Add @cset to the hash table */
1266 key = css_set_hash(cset->subsys);
1267 hash_add(css_set_table, &cset->hlist, key);
1269 for_each_subsys(ss, ssid) {
1270 struct cgroup_subsys_state *css = cset->subsys[ssid];
1272 list_add_tail(&cset->e_cset_node[ssid],
1273 &css->cgroup->e_csets[ssid]);
1277 spin_unlock_irq(&css_set_lock);
1280 * If @cset should be threaded, look up the matching dom_cset and
1281 * link them up. We first fully initialize @cset then look for the
1282 * dom_cset. It's simpler this way and safe as @cset is guaranteed
1283 * to stay empty until we return.
1285 if (cgroup_is_threaded(cset->dfl_cgrp)) {
1286 struct css_set *dcset;
1288 dcset = find_css_set(cset, cset->dfl_cgrp->dom_cgrp);
1294 spin_lock_irq(&css_set_lock);
1295 cset->dom_cset = dcset;
1296 list_add_tail(&cset->threaded_csets_node,
1297 &dcset->threaded_csets);
1298 spin_unlock_irq(&css_set_lock);
1304 struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
1306 struct cgroup *root_cgrp = kernfs_root_to_node(kf_root)->priv;
1308 return root_cgrp->root;
1311 void cgroup_favor_dynmods(struct cgroup_root *root, bool favor)
1313 bool favoring = root->flags & CGRP_ROOT_FAVOR_DYNMODS;
1315 /* see the comment above CGRP_ROOT_FAVOR_DYNMODS definition */
1316 if (favor && !favoring) {
1317 rcu_sync_enter(&cgroup_threadgroup_rwsem.rss);
1318 root->flags |= CGRP_ROOT_FAVOR_DYNMODS;
1319 } else if (!favor && favoring) {
1320 rcu_sync_exit(&cgroup_threadgroup_rwsem.rss);
1321 root->flags &= ~CGRP_ROOT_FAVOR_DYNMODS;
1325 static int cgroup_init_root_id(struct cgroup_root *root)
1329 lockdep_assert_held(&cgroup_mutex);
1331 id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
1335 root->hierarchy_id = id;
1339 static void cgroup_exit_root_id(struct cgroup_root *root)
1341 lockdep_assert_held(&cgroup_mutex);
1343 idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
1346 void cgroup_free_root(struct cgroup_root *root)
1351 static void cgroup_destroy_root(struct cgroup_root *root)
1353 struct cgroup *cgrp = &root->cgrp;
1354 struct cgrp_cset_link *link, *tmp_link;
1356 trace_cgroup_destroy_root(root);
1358 cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1360 BUG_ON(atomic_read(&root->nr_cgrps));
1361 BUG_ON(!list_empty(&cgrp->self.children));
1363 /* Rebind all subsystems back to the default hierarchy */
1364 WARN_ON(rebind_subsystems(&cgrp_dfl_root, root->subsys_mask));
1367 * Release all the links from cset_links to this hierarchy's
1370 spin_lock_irq(&css_set_lock);
1372 list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
1373 list_del(&link->cset_link);
1374 list_del(&link->cgrp_link);
1378 spin_unlock_irq(&css_set_lock);
1380 if (!list_empty(&root->root_list)) {
1381 list_del(&root->root_list);
1382 cgroup_root_count--;
1385 cgroup_favor_dynmods(root, false);
1386 cgroup_exit_root_id(root);
1388 mutex_unlock(&cgroup_mutex);
1390 cgroup_rstat_exit(cgrp);
1391 kernfs_destroy_root(root->kf_root);
1392 cgroup_free_root(root);
1396 * Returned cgroup is without refcount but it's valid as long as cset pins it.
1398 static inline struct cgroup *__cset_cgroup_from_root(struct css_set *cset,
1399 struct cgroup_root *root)
1401 struct cgroup *res_cgroup = NULL;
1403 if (cset == &init_css_set) {
1404 res_cgroup = &root->cgrp;
1405 } else if (root == &cgrp_dfl_root) {
1406 res_cgroup = cset->dfl_cgrp;
1408 struct cgrp_cset_link *link;
1409 lockdep_assert_held(&css_set_lock);
1411 list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
1412 struct cgroup *c = link->cgrp;
1414 if (c->root == root) {
1421 BUG_ON(!res_cgroup);
1426 * look up cgroup associated with current task's cgroup namespace on the
1427 * specified hierarchy
1429 static struct cgroup *
1430 current_cgns_cgroup_from_root(struct cgroup_root *root)
1432 struct cgroup *res = NULL;
1433 struct css_set *cset;
1435 lockdep_assert_held(&css_set_lock);
1439 cset = current->nsproxy->cgroup_ns->root_cset;
1440 res = __cset_cgroup_from_root(cset, root);
1448 * Look up cgroup associated with current task's cgroup namespace on the default
1451 * Unlike current_cgns_cgroup_from_root(), this doesn't need locks:
1452 * - Internal rcu_read_lock is unnecessary because we don't dereference any rcu
1454 * - css_set_lock is not needed because we just read cset->dfl_cgrp.
1455 * - As a bonus returned cgrp is pinned with the current because it cannot
1456 * switch cgroup_ns asynchronously.
1458 static struct cgroup *current_cgns_cgroup_dfl(void)
1460 struct css_set *cset;
1462 cset = current->nsproxy->cgroup_ns->root_cset;
1463 return __cset_cgroup_from_root(cset, &cgrp_dfl_root);
1466 /* look up cgroup associated with given css_set on the specified hierarchy */
1467 static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
1468 struct cgroup_root *root)
1470 lockdep_assert_held(&cgroup_mutex);
1471 lockdep_assert_held(&css_set_lock);
1473 return __cset_cgroup_from_root(cset, root);
1477 * Return the cgroup for "task" from the given hierarchy. Must be
1478 * called with cgroup_mutex and css_set_lock held.
1480 struct cgroup *task_cgroup_from_root(struct task_struct *task,
1481 struct cgroup_root *root)
1484 * No need to lock the task - since we hold css_set_lock the
1485 * task can't change groups.
1487 return cset_cgroup_from_root(task_css_set(task), root);
1491 * A task must hold cgroup_mutex to modify cgroups.
1493 * Any task can increment and decrement the count field without lock.
1494 * So in general, code holding cgroup_mutex can't rely on the count
1495 * field not changing. However, if the count goes to zero, then only
1496 * cgroup_attach_task() can increment it again. Because a count of zero
1497 * means that no tasks are currently attached, therefore there is no
1498 * way a task attached to that cgroup can fork (the other way to
1499 * increment the count). So code holding cgroup_mutex can safely
1500 * assume that if the count is zero, it will stay zero. Similarly, if
1501 * a task holds cgroup_mutex on a cgroup with zero count, it
1502 * knows that the cgroup won't be removed, as cgroup_rmdir()
1505 * A cgroup can only be deleted if both its 'count' of using tasks
1506 * is zero, and its list of 'children' cgroups is empty. Since all
1507 * tasks in the system use _some_ cgroup, and since there is always at
1508 * least one task in the system (init, pid == 1), therefore, root cgroup
1509 * always has either children cgroups and/or using tasks. So we don't
1510 * need a special hack to ensure that root cgroup cannot be deleted.
1512 * P.S. One more locking exception. RCU is used to guard the
1513 * update of a tasks cgroup pointer by cgroup_attach_task()
1516 static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
1518 static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
1521 struct cgroup_subsys *ss = cft->ss;
1523 if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
1524 !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
1525 const char *dbg = (cft->flags & CFTYPE_DEBUG) ? ".__DEBUG__." : "";
1527 snprintf(buf, CGROUP_FILE_NAME_MAX, "%s%s.%s",
1528 dbg, cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name,
1531 strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
1537 * cgroup_file_mode - deduce file mode of a control file
1538 * @cft: the control file in question
1540 * S_IRUGO for read, S_IWUSR for write.
1542 static umode_t cgroup_file_mode(const struct cftype *cft)
1546 if (cft->read_u64 || cft->read_s64 || cft->seq_show)
1549 if (cft->write_u64 || cft->write_s64 || cft->write) {
1550 if (cft->flags & CFTYPE_WORLD_WRITABLE)
1560 * cgroup_calc_subtree_ss_mask - calculate subtree_ss_mask
1561 * @subtree_control: the new subtree_control mask to consider
1562 * @this_ss_mask: available subsystems
1564 * On the default hierarchy, a subsystem may request other subsystems to be
1565 * enabled together through its ->depends_on mask. In such cases, more
1566 * subsystems than specified in "cgroup.subtree_control" may be enabled.
1568 * This function calculates which subsystems need to be enabled if
1569 * @subtree_control is to be applied while restricted to @this_ss_mask.
1571 static u16 cgroup_calc_subtree_ss_mask(u16 subtree_control, u16 this_ss_mask)
1573 u16 cur_ss_mask = subtree_control;
1574 struct cgroup_subsys *ss;
1577 lockdep_assert_held(&cgroup_mutex);
1579 cur_ss_mask |= cgrp_dfl_implicit_ss_mask;
1582 u16 new_ss_mask = cur_ss_mask;
1584 do_each_subsys_mask(ss, ssid, cur_ss_mask) {
1585 new_ss_mask |= ss->depends_on;
1586 } while_each_subsys_mask();
1589 * Mask out subsystems which aren't available. This can
1590 * happen only if some depended-upon subsystems were bound
1591 * to non-default hierarchies.
1593 new_ss_mask &= this_ss_mask;
1595 if (new_ss_mask == cur_ss_mask)
1597 cur_ss_mask = new_ss_mask;
1604 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1605 * @kn: the kernfs_node being serviced
1607 * This helper undoes cgroup_kn_lock_live() and should be invoked before
1608 * the method finishes if locking succeeded. Note that once this function
1609 * returns the cgroup returned by cgroup_kn_lock_live() may become
1610 * inaccessible any time. If the caller intends to continue to access the
1611 * cgroup, it should pin it before invoking this function.
1613 void cgroup_kn_unlock(struct kernfs_node *kn)
1615 struct cgroup *cgrp;
1617 if (kernfs_type(kn) == KERNFS_DIR)
1620 cgrp = kn->parent->priv;
1622 mutex_unlock(&cgroup_mutex);
1624 kernfs_unbreak_active_protection(kn);
1629 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1630 * @kn: the kernfs_node being serviced
1631 * @drain_offline: perform offline draining on the cgroup
1633 * This helper is to be used by a cgroup kernfs method currently servicing
1634 * @kn. It breaks the active protection, performs cgroup locking and
1635 * verifies that the associated cgroup is alive. Returns the cgroup if
1636 * alive; otherwise, %NULL. A successful return should be undone by a
1637 * matching cgroup_kn_unlock() invocation. If @drain_offline is %true, the
1638 * cgroup is drained of offlining csses before return.
1640 * Any cgroup kernfs method implementation which requires locking the
1641 * associated cgroup should use this helper. It avoids nesting cgroup
1642 * locking under kernfs active protection and allows all kernfs operations
1643 * including self-removal.
1645 struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn, bool drain_offline)
1647 struct cgroup *cgrp;
1649 if (kernfs_type(kn) == KERNFS_DIR)
1652 cgrp = kn->parent->priv;
1655 * We're gonna grab cgroup_mutex which nests outside kernfs
1656 * active_ref. cgroup liveliness check alone provides enough
1657 * protection against removal. Ensure @cgrp stays accessible and
1658 * break the active_ref protection.
1660 if (!cgroup_tryget(cgrp))
1662 kernfs_break_active_protection(kn);
1665 cgroup_lock_and_drain_offline(cgrp);
1667 mutex_lock(&cgroup_mutex);
1669 if (!cgroup_is_dead(cgrp))
1672 cgroup_kn_unlock(kn);
1676 static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
1678 char name[CGROUP_FILE_NAME_MAX];
1680 lockdep_assert_held(&cgroup_mutex);
1682 if (cft->file_offset) {
1683 struct cgroup_subsys_state *css = cgroup_css(cgrp, cft->ss);
1684 struct cgroup_file *cfile = (void *)css + cft->file_offset;
1686 spin_lock_irq(&cgroup_file_kn_lock);
1688 spin_unlock_irq(&cgroup_file_kn_lock);
1690 del_timer_sync(&cfile->notify_timer);
1693 kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
1697 * css_clear_dir - remove subsys files in a cgroup directory
1700 static void css_clear_dir(struct cgroup_subsys_state *css)
1702 struct cgroup *cgrp = css->cgroup;
1703 struct cftype *cfts;
1705 if (!(css->flags & CSS_VISIBLE))
1708 css->flags &= ~CSS_VISIBLE;
1711 if (cgroup_on_dfl(cgrp)) {
1712 cgroup_addrm_files(css, cgrp,
1713 cgroup_base_files, false);
1714 if (cgroup_psi_enabled())
1715 cgroup_addrm_files(css, cgrp,
1716 cgroup_psi_files, false);
1718 cgroup_addrm_files(css, cgrp,
1719 cgroup1_base_files, false);
1722 list_for_each_entry(cfts, &css->ss->cfts, node)
1723 cgroup_addrm_files(css, cgrp, cfts, false);
1728 * css_populate_dir - create subsys files in a cgroup directory
1731 * On failure, no file is added.
1733 static int css_populate_dir(struct cgroup_subsys_state *css)
1735 struct cgroup *cgrp = css->cgroup;
1736 struct cftype *cfts, *failed_cfts;
1739 if ((css->flags & CSS_VISIBLE) || !cgrp->kn)
1743 if (cgroup_on_dfl(cgrp)) {
1744 ret = cgroup_addrm_files(&cgrp->self, cgrp,
1745 cgroup_base_files, true);
1749 if (cgroup_psi_enabled()) {
1750 ret = cgroup_addrm_files(&cgrp->self, cgrp,
1751 cgroup_psi_files, true);
1756 cgroup_addrm_files(css, cgrp,
1757 cgroup1_base_files, true);
1760 list_for_each_entry(cfts, &css->ss->cfts, node) {
1761 ret = cgroup_addrm_files(css, cgrp, cfts, true);
1769 css->flags |= CSS_VISIBLE;
1773 list_for_each_entry(cfts, &css->ss->cfts, node) {
1774 if (cfts == failed_cfts)
1776 cgroup_addrm_files(css, cgrp, cfts, false);
1781 int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
1783 struct cgroup *dcgrp = &dst_root->cgrp;
1784 struct cgroup_subsys *ss;
1786 u16 dfl_disable_ss_mask = 0;
1788 lockdep_assert_held(&cgroup_mutex);
1790 do_each_subsys_mask(ss, ssid, ss_mask) {
1792 * If @ss has non-root csses attached to it, can't move.
1793 * If @ss is an implicit controller, it is exempt from this
1794 * rule and can be stolen.
1796 if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)) &&
1797 !ss->implicit_on_dfl)
1800 /* can't move between two non-dummy roots either */
1801 if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
1805 * Collect ssid's that need to be disabled from default
1808 if (ss->root == &cgrp_dfl_root)
1809 dfl_disable_ss_mask |= 1 << ssid;
1811 } while_each_subsys_mask();
1813 if (dfl_disable_ss_mask) {
1814 struct cgroup *scgrp = &cgrp_dfl_root.cgrp;
1817 * Controllers from default hierarchy that need to be rebound
1818 * are all disabled together in one go.
1820 cgrp_dfl_root.subsys_mask &= ~dfl_disable_ss_mask;
1821 WARN_ON(cgroup_apply_control(scgrp));
1822 cgroup_finalize_control(scgrp, 0);
1825 do_each_subsys_mask(ss, ssid, ss_mask) {
1826 struct cgroup_root *src_root = ss->root;
1827 struct cgroup *scgrp = &src_root->cgrp;
1828 struct cgroup_subsys_state *css = cgroup_css(scgrp, ss);
1829 struct css_set *cset;
1831 WARN_ON(!css || cgroup_css(dcgrp, ss));
1833 if (src_root != &cgrp_dfl_root) {
1834 /* disable from the source */
1835 src_root->subsys_mask &= ~(1 << ssid);
1836 WARN_ON(cgroup_apply_control(scgrp));
1837 cgroup_finalize_control(scgrp, 0);
1841 RCU_INIT_POINTER(scgrp->subsys[ssid], NULL);
1842 rcu_assign_pointer(dcgrp->subsys[ssid], css);
1843 ss->root = dst_root;
1844 css->cgroup = dcgrp;
1846 spin_lock_irq(&css_set_lock);
1847 hash_for_each(css_set_table, i, cset, hlist)
1848 list_move_tail(&cset->e_cset_node[ss->id],
1849 &dcgrp->e_csets[ss->id]);
1850 spin_unlock_irq(&css_set_lock);
1852 if (ss->css_rstat_flush) {
1853 list_del_rcu(&css->rstat_css_node);
1855 list_add_rcu(&css->rstat_css_node,
1856 &dcgrp->rstat_css_list);
1859 /* default hierarchy doesn't enable controllers by default */
1860 dst_root->subsys_mask |= 1 << ssid;
1861 if (dst_root == &cgrp_dfl_root) {
1862 static_branch_enable(cgroup_subsys_on_dfl_key[ssid]);
1864 dcgrp->subtree_control |= 1 << ssid;
1865 static_branch_disable(cgroup_subsys_on_dfl_key[ssid]);
1868 ret = cgroup_apply_control(dcgrp);
1870 pr_warn("partial failure to rebind %s controller (err=%d)\n",
1875 } while_each_subsys_mask();
1877 kernfs_activate(dcgrp->kn);
1881 int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
1882 struct kernfs_root *kf_root)
1886 struct cgroup_root *kf_cgroot = cgroup_root_from_kf(kf_root);
1887 struct cgroup *ns_cgroup;
1889 buf = kmalloc(PATH_MAX, GFP_KERNEL);
1893 spin_lock_irq(&css_set_lock);
1894 ns_cgroup = current_cgns_cgroup_from_root(kf_cgroot);
1895 len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX);
1896 spin_unlock_irq(&css_set_lock);
1898 if (len >= PATH_MAX)
1901 seq_escape(sf, buf, " \t\n\\");
1908 enum cgroup2_param {
1911 Opt_memory_localevents,
1912 Opt_memory_recursiveprot,
1916 static const struct fs_parameter_spec cgroup2_fs_parameters[] = {
1917 fsparam_flag("nsdelegate", Opt_nsdelegate),
1918 fsparam_flag("favordynmods", Opt_favordynmods),
1919 fsparam_flag("memory_localevents", Opt_memory_localevents),
1920 fsparam_flag("memory_recursiveprot", Opt_memory_recursiveprot),
1924 static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param)
1926 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1927 struct fs_parse_result result;
1930 opt = fs_parse(fc, cgroup2_fs_parameters, param, &result);
1935 case Opt_nsdelegate:
1936 ctx->flags |= CGRP_ROOT_NS_DELEGATE;
1938 case Opt_favordynmods:
1939 ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
1941 case Opt_memory_localevents:
1942 ctx->flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1944 case Opt_memory_recursiveprot:
1945 ctx->flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;
1951 static void apply_cgroup_root_flags(unsigned int root_flags)
1953 if (current->nsproxy->cgroup_ns == &init_cgroup_ns) {
1954 if (root_flags & CGRP_ROOT_NS_DELEGATE)
1955 cgrp_dfl_root.flags |= CGRP_ROOT_NS_DELEGATE;
1957 cgrp_dfl_root.flags &= ~CGRP_ROOT_NS_DELEGATE;
1959 cgroup_favor_dynmods(&cgrp_dfl_root,
1960 root_flags & CGRP_ROOT_FAVOR_DYNMODS);
1962 if (root_flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
1963 cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1965 cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_LOCAL_EVENTS;
1967 if (root_flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)
1968 cgrp_dfl_root.flags |= CGRP_ROOT_MEMORY_RECURSIVE_PROT;
1970 cgrp_dfl_root.flags &= ~CGRP_ROOT_MEMORY_RECURSIVE_PROT;
1974 static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
1976 if (cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE)
1977 seq_puts(seq, ",nsdelegate");
1978 if (cgrp_dfl_root.flags & CGRP_ROOT_FAVOR_DYNMODS)
1979 seq_puts(seq, ",favordynmods");
1980 if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_LOCAL_EVENTS)
1981 seq_puts(seq, ",memory_localevents");
1982 if (cgrp_dfl_root.flags & CGRP_ROOT_MEMORY_RECURSIVE_PROT)
1983 seq_puts(seq, ",memory_recursiveprot");
1987 static int cgroup_reconfigure(struct fs_context *fc)
1989 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1991 apply_cgroup_root_flags(ctx->flags);
1995 static void init_cgroup_housekeeping(struct cgroup *cgrp)
1997 struct cgroup_subsys *ss;
2000 INIT_LIST_HEAD(&cgrp->self.sibling);
2001 INIT_LIST_HEAD(&cgrp->self.children);
2002 INIT_LIST_HEAD(&cgrp->cset_links);
2003 INIT_LIST_HEAD(&cgrp->pidlists);
2004 mutex_init(&cgrp->pidlist_mutex);
2005 cgrp->self.cgroup = cgrp;
2006 cgrp->self.flags |= CSS_ONLINE;
2007 cgrp->dom_cgrp = cgrp;
2008 cgrp->max_descendants = INT_MAX;
2009 cgrp->max_depth = INT_MAX;
2010 INIT_LIST_HEAD(&cgrp->rstat_css_list);
2011 prev_cputime_init(&cgrp->prev_cputime);
2013 for_each_subsys(ss, ssid)
2014 INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
2016 init_waitqueue_head(&cgrp->offline_waitq);
2017 INIT_WORK(&cgrp->release_agent_work, cgroup1_release_agent);
2020 void init_cgroup_root(struct cgroup_fs_context *ctx)
2022 struct cgroup_root *root = ctx->root;
2023 struct cgroup *cgrp = &root->cgrp;
2025 INIT_LIST_HEAD(&root->root_list);
2026 atomic_set(&root->nr_cgrps, 1);
2028 init_cgroup_housekeeping(cgrp);
2030 /* DYNMODS must be modified through cgroup_favor_dynmods() */
2031 root->flags = ctx->flags & ~CGRP_ROOT_FAVOR_DYNMODS;
2032 if (ctx->release_agent)
2033 strscpy(root->release_agent_path, ctx->release_agent, PATH_MAX);
2035 strscpy(root->name, ctx->name, MAX_CGROUP_ROOT_NAMELEN);
2036 if (ctx->cpuset_clone_children)
2037 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
2040 int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
2042 LIST_HEAD(tmp_links);
2043 struct cgroup *root_cgrp = &root->cgrp;
2044 struct kernfs_syscall_ops *kf_sops;
2045 struct css_set *cset;
2048 lockdep_assert_held(&cgroup_mutex);
2050 ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release,
2056 * We're accessing css_set_count without locking css_set_lock here,
2057 * but that's OK - it can only be increased by someone holding
2058 * cgroup_lock, and that's us. Later rebinding may disable
2059 * controllers on the default hierarchy and thus create new csets,
2060 * which can't be more than the existing ones. Allocate 2x.
2062 ret = allocate_cgrp_cset_links(2 * css_set_count, &tmp_links);
2066 ret = cgroup_init_root_id(root);
2070 kf_sops = root == &cgrp_dfl_root ?
2071 &cgroup_kf_syscall_ops : &cgroup1_kf_syscall_ops;
2073 root->kf_root = kernfs_create_root(kf_sops,
2074 KERNFS_ROOT_CREATE_DEACTIVATED |
2075 KERNFS_ROOT_SUPPORT_EXPORTOP |
2076 KERNFS_ROOT_SUPPORT_USER_XATTR,
2078 if (IS_ERR(root->kf_root)) {
2079 ret = PTR_ERR(root->kf_root);
2082 root_cgrp->kn = kernfs_root_to_node(root->kf_root);
2083 WARN_ON_ONCE(cgroup_ino(root_cgrp) != 1);
2084 root_cgrp->ancestors[0] = root_cgrp;
2086 ret = css_populate_dir(&root_cgrp->self);
2090 ret = cgroup_rstat_init(root_cgrp);
2094 ret = rebind_subsystems(root, ss_mask);
2098 ret = cgroup_bpf_inherit(root_cgrp);
2101 trace_cgroup_setup_root(root);
2104 * There must be no failure case after here, since rebinding takes
2105 * care of subsystems' refcounts, which are explicitly dropped in
2106 * the failure exit path.
2108 list_add(&root->root_list, &cgroup_roots);
2109 cgroup_root_count++;
2112 * Link the root cgroup in this hierarchy into all the css_set
2115 spin_lock_irq(&css_set_lock);
2116 hash_for_each(css_set_table, i, cset, hlist) {
2117 link_css_set(&tmp_links, cset, root_cgrp);
2118 if (css_set_populated(cset))
2119 cgroup_update_populated(root_cgrp, true);
2121 spin_unlock_irq(&css_set_lock);
2123 BUG_ON(!list_empty(&root_cgrp->self.children));
2124 BUG_ON(atomic_read(&root->nr_cgrps) != 1);
2130 cgroup_rstat_exit(root_cgrp);
2132 kernfs_destroy_root(root->kf_root);
2133 root->kf_root = NULL;
2135 cgroup_exit_root_id(root);
2137 percpu_ref_exit(&root_cgrp->self.refcnt);
2139 free_cgrp_cset_links(&tmp_links);
2143 int cgroup_do_get_tree(struct fs_context *fc)
2145 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2148 ctx->kfc.root = ctx->root->kf_root;
2149 if (fc->fs_type == &cgroup2_fs_type)
2150 ctx->kfc.magic = CGROUP2_SUPER_MAGIC;
2152 ctx->kfc.magic = CGROUP_SUPER_MAGIC;
2153 ret = kernfs_get_tree(fc);
2156 * In non-init cgroup namespace, instead of root cgroup's dentry,
2157 * we return the dentry corresponding to the cgroupns->root_cgrp.
2159 if (!ret && ctx->ns != &init_cgroup_ns) {
2160 struct dentry *nsdentry;
2161 struct super_block *sb = fc->root->d_sb;
2162 struct cgroup *cgrp;
2164 mutex_lock(&cgroup_mutex);
2165 spin_lock_irq(&css_set_lock);
2167 cgrp = cset_cgroup_from_root(ctx->ns->root_cset, ctx->root);
2169 spin_unlock_irq(&css_set_lock);
2170 mutex_unlock(&cgroup_mutex);
2172 nsdentry = kernfs_node_dentry(cgrp->kn, sb);
2174 if (IS_ERR(nsdentry)) {
2175 deactivate_locked_super(sb);
2176 ret = PTR_ERR(nsdentry);
2179 fc->root = nsdentry;
2182 if (!ctx->kfc.new_sb_created)
2183 cgroup_put(&ctx->root->cgrp);
2189 * Destroy a cgroup filesystem context.
2191 static void cgroup_fs_context_free(struct fs_context *fc)
2193 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2196 kfree(ctx->release_agent);
2197 put_cgroup_ns(ctx->ns);
2198 kernfs_free_fs_context(fc);
2202 static int cgroup_get_tree(struct fs_context *fc)
2204 struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
2207 WRITE_ONCE(cgrp_dfl_visible, true);
2208 cgroup_get_live(&cgrp_dfl_root.cgrp);
2209 ctx->root = &cgrp_dfl_root;
2211 ret = cgroup_do_get_tree(fc);
2213 apply_cgroup_root_flags(ctx->flags);
2217 static const struct fs_context_operations cgroup_fs_context_ops = {
2218 .free = cgroup_fs_context_free,
2219 .parse_param = cgroup2_parse_param,
2220 .get_tree = cgroup_get_tree,
2221 .reconfigure = cgroup_reconfigure,
2224 static const struct fs_context_operations cgroup1_fs_context_ops = {
2225 .free = cgroup_fs_context_free,
2226 .parse_param = cgroup1_parse_param,
2227 .get_tree = cgroup1_get_tree,
2228 .reconfigure = cgroup1_reconfigure,
2232 * Initialise the cgroup filesystem creation/reconfiguration context. Notably,
2233 * we select the namespace we're going to use.
2235 static int cgroup_init_fs_context(struct fs_context *fc)
2237 struct cgroup_fs_context *ctx;
2239 ctx = kzalloc(sizeof(struct cgroup_fs_context), GFP_KERNEL);
2243 ctx->ns = current->nsproxy->cgroup_ns;
2244 get_cgroup_ns(ctx->ns);
2245 fc->fs_private = &ctx->kfc;
2246 if (fc->fs_type == &cgroup2_fs_type)
2247 fc->ops = &cgroup_fs_context_ops;
2249 fc->ops = &cgroup1_fs_context_ops;
2250 put_user_ns(fc->user_ns);
2251 fc->user_ns = get_user_ns(ctx->ns->user_ns);
2254 #ifdef CONFIG_CGROUP_FAVOR_DYNMODS
2255 ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
2260 static void cgroup_kill_sb(struct super_block *sb)
2262 struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
2263 struct cgroup_root *root = cgroup_root_from_kf(kf_root);
2266 * If @root doesn't have any children, start killing it.
2267 * This prevents new mounts by disabling percpu_ref_tryget_live().
2269 * And don't kill the default root.
2271 if (list_empty(&root->cgrp.self.children) && root != &cgrp_dfl_root &&
2272 !percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
2273 cgroup_bpf_offline(&root->cgrp);
2274 percpu_ref_kill(&root->cgrp.self.refcnt);
2276 cgroup_put(&root->cgrp);
2280 struct file_system_type cgroup_fs_type = {
2282 .init_fs_context = cgroup_init_fs_context,
2283 .parameters = cgroup1_fs_parameters,
2284 .kill_sb = cgroup_kill_sb,
2285 .fs_flags = FS_USERNS_MOUNT,
2288 static struct file_system_type cgroup2_fs_type = {
2290 .init_fs_context = cgroup_init_fs_context,
2291 .parameters = cgroup2_fs_parameters,
2292 .kill_sb = cgroup_kill_sb,
2293 .fs_flags = FS_USERNS_MOUNT,
2296 #ifdef CONFIG_CPUSETS
2297 static const struct fs_context_operations cpuset_fs_context_ops = {
2298 .get_tree = cgroup1_get_tree,
2299 .free = cgroup_fs_context_free,
2303 * This is ugly, but preserves the userspace API for existing cpuset
2304 * users. If someone tries to mount the "cpuset" filesystem, we
2305 * silently switch it to mount "cgroup" instead
2307 static int cpuset_init_fs_context(struct fs_context *fc)
2309 char *agent = kstrdup("/sbin/cpuset_release_agent", GFP_USER);
2310 struct cgroup_fs_context *ctx;
2313 err = cgroup_init_fs_context(fc);
2319 fc->ops = &cpuset_fs_context_ops;
2321 ctx = cgroup_fc2context(fc);
2322 ctx->subsys_mask = 1 << cpuset_cgrp_id;
2323 ctx->flags |= CGRP_ROOT_NOPREFIX;
2324 ctx->release_agent = agent;
2326 get_filesystem(&cgroup_fs_type);
2327 put_filesystem(fc->fs_type);
2328 fc->fs_type = &cgroup_fs_type;
2333 static struct file_system_type cpuset_fs_type = {
2335 .init_fs_context = cpuset_init_fs_context,
2336 .fs_flags = FS_USERNS_MOUNT,
2340 int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
2341 struct cgroup_namespace *ns)
2343 struct cgroup *root = cset_cgroup_from_root(ns->root_cset, cgrp->root);
2345 return kernfs_path_from_node(cgrp->kn, root->kn, buf, buflen);
2348 int cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
2349 struct cgroup_namespace *ns)
2353 mutex_lock(&cgroup_mutex);
2354 spin_lock_irq(&css_set_lock);
2356 ret = cgroup_path_ns_locked(cgrp, buf, buflen, ns);
2358 spin_unlock_irq(&css_set_lock);
2359 mutex_unlock(&cgroup_mutex);
2363 EXPORT_SYMBOL_GPL(cgroup_path_ns);
2366 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
2367 * @task: target task
2368 * @buf: the buffer to write the path into
2369 * @buflen: the length of the buffer
2371 * Determine @task's cgroup on the first (the one with the lowest non-zero
2372 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
2373 * function grabs cgroup_mutex and shouldn't be used inside locks used by
2374 * cgroup controller callbacks.
2376 * Return value is the same as kernfs_path().
2378 int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
2380 struct cgroup_root *root;
2381 struct cgroup *cgrp;
2382 int hierarchy_id = 1;
2385 mutex_lock(&cgroup_mutex);
2386 spin_lock_irq(&css_set_lock);
2388 root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
2391 cgrp = task_cgroup_from_root(task, root);
2392 ret = cgroup_path_ns_locked(cgrp, buf, buflen, &init_cgroup_ns);
2394 /* if no hierarchy exists, everyone is in "/" */
2395 ret = strscpy(buf, "/", buflen);
2398 spin_unlock_irq(&css_set_lock);
2399 mutex_unlock(&cgroup_mutex);
2402 EXPORT_SYMBOL_GPL(task_cgroup_path);
2405 * cgroup_attach_lock - Lock for ->attach()
2406 * @lock_threadgroup: whether to down_write cgroup_threadgroup_rwsem
2408 * cgroup migration sometimes needs to stabilize threadgroups against forks and
2409 * exits by write-locking cgroup_threadgroup_rwsem. However, some ->attach()
2410 * implementations (e.g. cpuset), also need to disable CPU hotplug.
2411 * Unfortunately, letting ->attach() operations acquire cpus_read_lock() can
2412 * lead to deadlocks.
2414 * Bringing up a CPU may involve creating and destroying tasks which requires
2415 * read-locking threadgroup_rwsem, so threadgroup_rwsem nests inside
2416 * cpus_read_lock(). If we call an ->attach() which acquires the cpus lock while
2417 * write-locking threadgroup_rwsem, the locking order is reversed and we end up
2418 * waiting for an on-going CPU hotplug operation which in turn is waiting for
2419 * the threadgroup_rwsem to be released to create new tasks. For more details:
2421 * http://lkml.kernel.org/r/20220711174629.uehfmqegcwn2lqzu@wubuntu
2423 * Resolve the situation by always acquiring cpus_read_lock() before optionally
2424 * write-locking cgroup_threadgroup_rwsem. This allows ->attach() to assume that
2425 * CPU hotplug is disabled on entry.
2427 void cgroup_attach_lock(bool lock_threadgroup)
2430 if (lock_threadgroup)
2431 percpu_down_write(&cgroup_threadgroup_rwsem);
2435 * cgroup_attach_unlock - Undo cgroup_attach_lock()
2436 * @lock_threadgroup: whether to up_write cgroup_threadgroup_rwsem
2438 void cgroup_attach_unlock(bool lock_threadgroup)
2440 if (lock_threadgroup)
2441 percpu_up_write(&cgroup_threadgroup_rwsem);
2446 * cgroup_migrate_add_task - add a migration target task to a migration context
2447 * @task: target task
2448 * @mgctx: target migration context
2450 * Add @task, which is a migration target, to @mgctx->tset. This function
2451 * becomes noop if @task doesn't need to be migrated. @task's css_set
2452 * should have been added as a migration source and @task->cg_list will be
2453 * moved from the css_set's tasks list to mg_tasks one.
2455 static void cgroup_migrate_add_task(struct task_struct *task,
2456 struct cgroup_mgctx *mgctx)
2458 struct css_set *cset;
2460 lockdep_assert_held(&css_set_lock);
2462 /* @task either already exited or can't exit until the end */
2463 if (task->flags & PF_EXITING)
2466 /* cgroup_threadgroup_rwsem protects racing against forks */
2467 WARN_ON_ONCE(list_empty(&task->cg_list));
2469 cset = task_css_set(task);
2470 if (!cset->mg_src_cgrp)
2473 mgctx->tset.nr_tasks++;
2475 list_move_tail(&task->cg_list, &cset->mg_tasks);
2476 if (list_empty(&cset->mg_node))
2477 list_add_tail(&cset->mg_node,
2478 &mgctx->tset.src_csets);
2479 if (list_empty(&cset->mg_dst_cset->mg_node))
2480 list_add_tail(&cset->mg_dst_cset->mg_node,
2481 &mgctx->tset.dst_csets);
2485 * cgroup_taskset_first - reset taskset and return the first task
2486 * @tset: taskset of interest
2487 * @dst_cssp: output variable for the destination css
2489 * @tset iteration is initialized and the first task is returned.
2491 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset,
2492 struct cgroup_subsys_state **dst_cssp)
2494 tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
2495 tset->cur_task = NULL;
2497 return cgroup_taskset_next(tset, dst_cssp);
2501 * cgroup_taskset_next - iterate to the next task in taskset
2502 * @tset: taskset of interest
2503 * @dst_cssp: output variable for the destination css
2505 * Return the next task in @tset. Iteration must have been initialized
2506 * with cgroup_taskset_first().
2508 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
2509 struct cgroup_subsys_state **dst_cssp)
2511 struct css_set *cset = tset->cur_cset;
2512 struct task_struct *task = tset->cur_task;
2514 while (CGROUP_HAS_SUBSYS_CONFIG && &cset->mg_node != tset->csets) {
2516 task = list_first_entry(&cset->mg_tasks,
2517 struct task_struct, cg_list);
2519 task = list_next_entry(task, cg_list);
2521 if (&task->cg_list != &cset->mg_tasks) {
2522 tset->cur_cset = cset;
2523 tset->cur_task = task;
2526 * This function may be called both before and
2527 * after cgroup_taskset_migrate(). The two cases
2528 * can be distinguished by looking at whether @cset
2529 * has its ->mg_dst_cset set.
2531 if (cset->mg_dst_cset)
2532 *dst_cssp = cset->mg_dst_cset->subsys[tset->ssid];
2534 *dst_cssp = cset->subsys[tset->ssid];
2539 cset = list_next_entry(cset, mg_node);
2547 * cgroup_migrate_execute - migrate a taskset
2548 * @mgctx: migration context
2550 * Migrate tasks in @mgctx as setup by migration preparation functions.
2551 * This function fails iff one of the ->can_attach callbacks fails and
2552 * guarantees that either all or none of the tasks in @mgctx are migrated.
2553 * @mgctx is consumed regardless of success.
2555 static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx)
2557 struct cgroup_taskset *tset = &mgctx->tset;
2558 struct cgroup_subsys *ss;
2559 struct task_struct *task, *tmp_task;
2560 struct css_set *cset, *tmp_cset;
2561 int ssid, failed_ssid, ret;
2563 /* check that we can legitimately attach to the cgroup */
2564 if (tset->nr_tasks) {
2565 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2566 if (ss->can_attach) {
2568 ret = ss->can_attach(tset);
2571 goto out_cancel_attach;
2574 } while_each_subsys_mask();
2578 * Now that we're guaranteed success, proceed to move all tasks to
2579 * the new cgroup. There are no failure cases after here, so this
2580 * is the commit point.
2582 spin_lock_irq(&css_set_lock);
2583 list_for_each_entry(cset, &tset->src_csets, mg_node) {
2584 list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list) {
2585 struct css_set *from_cset = task_css_set(task);
2586 struct css_set *to_cset = cset->mg_dst_cset;
2588 get_css_set(to_cset);
2589 to_cset->nr_tasks++;
2590 css_set_move_task(task, from_cset, to_cset, true);
2591 from_cset->nr_tasks--;
2593 * If the source or destination cgroup is frozen,
2594 * the task might require to change its state.
2596 cgroup_freezer_migrate_task(task, from_cset->dfl_cgrp,
2598 put_css_set_locked(from_cset);
2602 spin_unlock_irq(&css_set_lock);
2605 * Migration is committed, all target tasks are now on dst_csets.
2606 * Nothing is sensitive to fork() after this point. Notify
2607 * controllers that migration is complete.
2609 tset->csets = &tset->dst_csets;
2611 if (tset->nr_tasks) {
2612 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2617 } while_each_subsys_mask();
2621 goto out_release_tset;
2624 if (tset->nr_tasks) {
2625 do_each_subsys_mask(ss, ssid, mgctx->ss_mask) {
2626 if (ssid == failed_ssid)
2628 if (ss->cancel_attach) {
2630 ss->cancel_attach(tset);
2632 } while_each_subsys_mask();
2635 spin_lock_irq(&css_set_lock);
2636 list_splice_init(&tset->dst_csets, &tset->src_csets);
2637 list_for_each_entry_safe(cset, tmp_cset, &tset->src_csets, mg_node) {
2638 list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
2639 list_del_init(&cset->mg_node);
2641 spin_unlock_irq(&css_set_lock);
2644 * Re-initialize the cgroup_taskset structure in case it is reused
2645 * again in another cgroup_migrate_add_task()/cgroup_migrate_execute()
2649 tset->csets = &tset->src_csets;
2654 * cgroup_migrate_vet_dst - verify whether a cgroup can be migration destination
2655 * @dst_cgrp: destination cgroup to test
2657 * On the default hierarchy, except for the mixable, (possible) thread root
2658 * and threaded cgroups, subtree_control must be zero for migration
2659 * destination cgroups with tasks so that child cgroups don't compete
2662 int cgroup_migrate_vet_dst(struct cgroup *dst_cgrp)
2664 /* v1 doesn't have any restriction */
2665 if (!cgroup_on_dfl(dst_cgrp))
2668 /* verify @dst_cgrp can host resources */
2669 if (!cgroup_is_valid_domain(dst_cgrp->dom_cgrp))
2673 * If @dst_cgrp is already or can become a thread root or is
2674 * threaded, it doesn't matter.
2676 if (cgroup_can_be_thread_root(dst_cgrp) || cgroup_is_threaded(dst_cgrp))
2679 /* apply no-internal-process constraint */
2680 if (dst_cgrp->subtree_control)
2687 * cgroup_migrate_finish - cleanup after attach
2688 * @mgctx: migration context
2690 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
2691 * those functions for details.
2693 void cgroup_migrate_finish(struct cgroup_mgctx *mgctx)
2695 struct css_set *cset, *tmp_cset;
2697 lockdep_assert_held(&cgroup_mutex);
2699 spin_lock_irq(&css_set_lock);
2701 list_for_each_entry_safe(cset, tmp_cset, &mgctx->preloaded_src_csets,
2702 mg_src_preload_node) {
2703 cset->mg_src_cgrp = NULL;
2704 cset->mg_dst_cgrp = NULL;
2705 cset->mg_dst_cset = NULL;
2706 list_del_init(&cset->mg_src_preload_node);
2707 put_css_set_locked(cset);
2710 list_for_each_entry_safe(cset, tmp_cset, &mgctx->preloaded_dst_csets,
2711 mg_dst_preload_node) {
2712 cset->mg_src_cgrp = NULL;
2713 cset->mg_dst_cgrp = NULL;
2714 cset->mg_dst_cset = NULL;
2715 list_del_init(&cset->mg_dst_preload_node);
2716 put_css_set_locked(cset);
2719 spin_unlock_irq(&css_set_lock);
2723 * cgroup_migrate_add_src - add a migration source css_set
2724 * @src_cset: the source css_set to add
2725 * @dst_cgrp: the destination cgroup
2726 * @mgctx: migration context
2728 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
2729 * @src_cset and add it to @mgctx->src_csets, which should later be cleaned
2730 * up by cgroup_migrate_finish().
2732 * This function may be called without holding cgroup_threadgroup_rwsem
2733 * even if the target is a process. Threads may be created and destroyed
2734 * but as long as cgroup_mutex is not dropped, no new css_set can be put
2735 * into play and the preloaded css_sets are guaranteed to cover all
2738 void cgroup_migrate_add_src(struct css_set *src_cset,
2739 struct cgroup *dst_cgrp,
2740 struct cgroup_mgctx *mgctx)
2742 struct cgroup *src_cgrp;
2744 lockdep_assert_held(&cgroup_mutex);
2745 lockdep_assert_held(&css_set_lock);
2748 * If ->dead, @src_set is associated with one or more dead cgroups
2749 * and doesn't contain any migratable tasks. Ignore it early so
2750 * that the rest of migration path doesn't get confused by it.
2755 if (!list_empty(&src_cset->mg_src_preload_node))
2758 src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);
2760 WARN_ON(src_cset->mg_src_cgrp);
2761 WARN_ON(src_cset->mg_dst_cgrp);
2762 WARN_ON(!list_empty(&src_cset->mg_tasks));
2763 WARN_ON(!list_empty(&src_cset->mg_node));
2765 src_cset->mg_src_cgrp = src_cgrp;
2766 src_cset->mg_dst_cgrp = dst_cgrp;
2767 get_css_set(src_cset);
2768 list_add_tail(&src_cset->mg_src_preload_node, &mgctx->preloaded_src_csets);
2772 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2773 * @mgctx: migration context
2775 * Tasks are about to be moved and all the source css_sets have been
2776 * preloaded to @mgctx->preloaded_src_csets. This function looks up and
2777 * pins all destination css_sets, links each to its source, and append them
2778 * to @mgctx->preloaded_dst_csets.
2780 * This function must be called after cgroup_migrate_add_src() has been
2781 * called on each migration source css_set. After migration is performed
2782 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2785 int cgroup_migrate_prepare_dst(struct cgroup_mgctx *mgctx)
2787 struct css_set *src_cset, *tmp_cset;
2789 lockdep_assert_held(&cgroup_mutex);
2791 /* look up the dst cset for each src cset and link it to src */
2792 list_for_each_entry_safe(src_cset, tmp_cset, &mgctx->preloaded_src_csets,
2793 mg_src_preload_node) {
2794 struct css_set *dst_cset;
2795 struct cgroup_subsys *ss;
2798 dst_cset = find_css_set(src_cset, src_cset->mg_dst_cgrp);
2802 WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
2805 * If src cset equals dst, it's noop. Drop the src.
2806 * cgroup_migrate() will skip the cset too. Note that we
2807 * can't handle src == dst as some nodes are used by both.
2809 if (src_cset == dst_cset) {
2810 src_cset->mg_src_cgrp = NULL;
2811 src_cset->mg_dst_cgrp = NULL;
2812 list_del_init(&src_cset->mg_src_preload_node);
2813 put_css_set(src_cset);
2814 put_css_set(dst_cset);
2818 src_cset->mg_dst_cset = dst_cset;
2820 if (list_empty(&dst_cset->mg_dst_preload_node))
2821 list_add_tail(&dst_cset->mg_dst_preload_node,
2822 &mgctx->preloaded_dst_csets);
2824 put_css_set(dst_cset);
2826 for_each_subsys(ss, ssid)
2827 if (src_cset->subsys[ssid] != dst_cset->subsys[ssid])
2828 mgctx->ss_mask |= 1 << ssid;
2835 * cgroup_migrate - migrate a process or task to a cgroup
2836 * @leader: the leader of the process or the task to migrate
2837 * @threadgroup: whether @leader points to the whole process or a single task
2838 * @mgctx: migration context
2840 * Migrate a process or task denoted by @leader. If migrating a process,
2841 * the caller must be holding cgroup_threadgroup_rwsem. The caller is also
2842 * responsible for invoking cgroup_migrate_add_src() and
2843 * cgroup_migrate_prepare_dst() on the targets before invoking this
2844 * function and following up with cgroup_migrate_finish().
2846 * As long as a controller's ->can_attach() doesn't fail, this function is
2847 * guaranteed to succeed. This means that, excluding ->can_attach()
2848 * failure, when migrating multiple targets, the success or failure can be
2849 * decided for all targets by invoking group_migrate_prepare_dst() before
2850 * actually starting migrating.
2852 int cgroup_migrate(struct task_struct *leader, bool threadgroup,
2853 struct cgroup_mgctx *mgctx)
2855 struct task_struct *task;
2858 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2859 * already PF_EXITING could be freed from underneath us unless we
2860 * take an rcu_read_lock.
2862 spin_lock_irq(&css_set_lock);
2866 cgroup_migrate_add_task(task, mgctx);
2869 } while_each_thread(leader, task);
2871 spin_unlock_irq(&css_set_lock);
2873 return cgroup_migrate_execute(mgctx);
2877 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2878 * @dst_cgrp: the cgroup to attach to
2879 * @leader: the task or the leader of the threadgroup to be attached
2880 * @threadgroup: attach the whole threadgroup?
2882 * Call holding cgroup_mutex and cgroup_threadgroup_rwsem.
2884 int cgroup_attach_task(struct cgroup *dst_cgrp, struct task_struct *leader,
2887 DEFINE_CGROUP_MGCTX(mgctx);
2888 struct task_struct *task;
2891 /* look up all src csets */
2892 spin_lock_irq(&css_set_lock);
2896 cgroup_migrate_add_src(task_css_set(task), dst_cgrp, &mgctx);
2899 } while_each_thread(leader, task);
2901 spin_unlock_irq(&css_set_lock);
2903 /* prepare dst csets and commit */
2904 ret = cgroup_migrate_prepare_dst(&mgctx);
2906 ret = cgroup_migrate(leader, threadgroup, &mgctx);
2908 cgroup_migrate_finish(&mgctx);
2911 TRACE_CGROUP_PATH(attach_task, dst_cgrp, leader, threadgroup);
2916 struct task_struct *cgroup_procs_write_start(char *buf, bool threadgroup,
2917 bool *threadgroup_locked)
2919 struct task_struct *tsk;
2922 if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
2923 return ERR_PTR(-EINVAL);
2926 * If we migrate a single thread, we don't care about threadgroup
2927 * stability. If the thread is `current`, it won't exit(2) under our
2928 * hands or change PID through exec(2). We exclude
2929 * cgroup_update_dfl_csses and other cgroup_{proc,thread}s_write
2930 * callers by cgroup_mutex.
2931 * Therefore, we can skip the global lock.
2933 lockdep_assert_held(&cgroup_mutex);
2934 *threadgroup_locked = pid || threadgroup;
2935 cgroup_attach_lock(*threadgroup_locked);
2939 tsk = find_task_by_vpid(pid);
2941 tsk = ERR_PTR(-ESRCH);
2942 goto out_unlock_threadgroup;
2949 tsk = tsk->group_leader;
2952 * kthreads may acquire PF_NO_SETAFFINITY during initialization.
2953 * If userland migrates such a kthread to a non-root cgroup, it can
2954 * become trapped in a cpuset, or RT kthread may be born in a
2955 * cgroup with no rt_runtime allocated. Just say no.
2957 if (tsk->no_cgroup_migration || (tsk->flags & PF_NO_SETAFFINITY)) {
2958 tsk = ERR_PTR(-EINVAL);
2959 goto out_unlock_threadgroup;
2962 get_task_struct(tsk);
2963 goto out_unlock_rcu;
2965 out_unlock_threadgroup:
2966 cgroup_attach_unlock(*threadgroup_locked);
2967 *threadgroup_locked = false;
2973 void cgroup_procs_write_finish(struct task_struct *task, bool threadgroup_locked)
2975 struct cgroup_subsys *ss;
2978 /* release reference from cgroup_procs_write_start() */
2979 put_task_struct(task);
2981 cgroup_attach_unlock(threadgroup_locked);
2983 for_each_subsys(ss, ssid)
2984 if (ss->post_attach)
2988 static void cgroup_print_ss_mask(struct seq_file *seq, u16 ss_mask)
2990 struct cgroup_subsys *ss;
2991 bool printed = false;
2994 do_each_subsys_mask(ss, ssid, ss_mask) {
2997 seq_puts(seq, ss->name);
2999 } while_each_subsys_mask();
3001 seq_putc(seq, '\n');
3004 /* show controllers which are enabled from the parent */
3005 static int cgroup_controllers_show(struct seq_file *seq, void *v)
3007 struct cgroup *cgrp = seq_css(seq)->cgroup;
3009 cgroup_print_ss_mask(seq, cgroup_control(cgrp));
3013 /* show controllers which are enabled for a given cgroup's children */
3014 static int cgroup_subtree_control_show(struct seq_file *seq, void *v)
3016 struct cgroup *cgrp = seq_css(seq)->cgroup;
3018 cgroup_print_ss_mask(seq, cgrp->subtree_control);
3023 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
3024 * @cgrp: root of the subtree to update csses for
3026 * @cgrp's control masks have changed and its subtree's css associations
3027 * need to be updated accordingly. This function looks up all css_sets
3028 * which are attached to the subtree, creates the matching updated css_sets
3029 * and migrates the tasks to the new ones.
3031 static int cgroup_update_dfl_csses(struct cgroup *cgrp)
3033 DEFINE_CGROUP_MGCTX(mgctx);
3034 struct cgroup_subsys_state *d_css;
3035 struct cgroup *dsct;
3036 struct css_set *src_cset;
3040 lockdep_assert_held(&cgroup_mutex);
3042 /* look up all csses currently attached to @cgrp's subtree */
3043 spin_lock_irq(&css_set_lock);
3044 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3045 struct cgrp_cset_link *link;
3048 * As cgroup_update_dfl_csses() is only called by
3049 * cgroup_apply_control(). The csses associated with the
3050 * given cgrp will not be affected by changes made to
3051 * its subtree_control file. We can skip them.
3056 list_for_each_entry(link, &dsct->cset_links, cset_link)
3057 cgroup_migrate_add_src(link->cset, dsct, &mgctx);
3059 spin_unlock_irq(&css_set_lock);
3062 * We need to write-lock threadgroup_rwsem while migrating tasks.
3063 * However, if there are no source csets for @cgrp, changing its
3064 * controllers isn't gonna produce any task migrations and the
3065 * write-locking can be skipped safely.
3067 has_tasks = !list_empty(&mgctx.preloaded_src_csets);
3068 cgroup_attach_lock(has_tasks);
3070 /* NULL dst indicates self on default hierarchy */
3071 ret = cgroup_migrate_prepare_dst(&mgctx);
3075 spin_lock_irq(&css_set_lock);
3076 list_for_each_entry(src_cset, &mgctx.preloaded_src_csets,
3077 mg_src_preload_node) {
3078 struct task_struct *task, *ntask;
3080 /* all tasks in src_csets need to be migrated */
3081 list_for_each_entry_safe(task, ntask, &src_cset->tasks, cg_list)
3082 cgroup_migrate_add_task(task, &mgctx);
3084 spin_unlock_irq(&css_set_lock);
3086 ret = cgroup_migrate_execute(&mgctx);
3088 cgroup_migrate_finish(&mgctx);
3089 cgroup_attach_unlock(has_tasks);
3094 * cgroup_lock_and_drain_offline - lock cgroup_mutex and drain offlined csses
3095 * @cgrp: root of the target subtree
3097 * Because css offlining is asynchronous, userland may try to re-enable a
3098 * controller while the previous css is still around. This function grabs
3099 * cgroup_mutex and drains the previous css instances of @cgrp's subtree.
3101 void cgroup_lock_and_drain_offline(struct cgroup *cgrp)
3102 __acquires(&cgroup_mutex)
3104 struct cgroup *dsct;
3105 struct cgroup_subsys_state *d_css;
3106 struct cgroup_subsys *ss;
3110 mutex_lock(&cgroup_mutex);
3112 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3113 for_each_subsys(ss, ssid) {
3114 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3117 if (!css || !percpu_ref_is_dying(&css->refcnt))
3120 cgroup_get_live(dsct);
3121 prepare_to_wait(&dsct->offline_waitq, &wait,
3122 TASK_UNINTERRUPTIBLE);
3124 mutex_unlock(&cgroup_mutex);
3126 finish_wait(&dsct->offline_waitq, &wait);
3135 * cgroup_save_control - save control masks and dom_cgrp of a subtree
3136 * @cgrp: root of the target subtree
3138 * Save ->subtree_control, ->subtree_ss_mask and ->dom_cgrp to the
3139 * respective old_ prefixed fields for @cgrp's subtree including @cgrp
3142 static void cgroup_save_control(struct cgroup *cgrp)
3144 struct cgroup *dsct;
3145 struct cgroup_subsys_state *d_css;
3147 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3148 dsct->old_subtree_control = dsct->subtree_control;
3149 dsct->old_subtree_ss_mask = dsct->subtree_ss_mask;
3150 dsct->old_dom_cgrp = dsct->dom_cgrp;
3155 * cgroup_propagate_control - refresh control masks of a subtree
3156 * @cgrp: root of the target subtree
3158 * For @cgrp and its subtree, ensure ->subtree_ss_mask matches
3159 * ->subtree_control and propagate controller availability through the
3160 * subtree so that descendants don't have unavailable controllers enabled.
3162 static void cgroup_propagate_control(struct cgroup *cgrp)
3164 struct cgroup *dsct;
3165 struct cgroup_subsys_state *d_css;
3167 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3168 dsct->subtree_control &= cgroup_control(dsct);
3169 dsct->subtree_ss_mask =
3170 cgroup_calc_subtree_ss_mask(dsct->subtree_control,
3171 cgroup_ss_mask(dsct));
3176 * cgroup_restore_control - restore control masks and dom_cgrp of a subtree
3177 * @cgrp: root of the target subtree
3179 * Restore ->subtree_control, ->subtree_ss_mask and ->dom_cgrp from the
3180 * respective old_ prefixed fields for @cgrp's subtree including @cgrp
3183 static void cgroup_restore_control(struct cgroup *cgrp)
3185 struct cgroup *dsct;
3186 struct cgroup_subsys_state *d_css;
3188 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3189 dsct->subtree_control = dsct->old_subtree_control;
3190 dsct->subtree_ss_mask = dsct->old_subtree_ss_mask;
3191 dsct->dom_cgrp = dsct->old_dom_cgrp;
3195 static bool css_visible(struct cgroup_subsys_state *css)
3197 struct cgroup_subsys *ss = css->ss;
3198 struct cgroup *cgrp = css->cgroup;
3200 if (cgroup_control(cgrp) & (1 << ss->id))
3202 if (!(cgroup_ss_mask(cgrp) & (1 << ss->id)))
3204 return cgroup_on_dfl(cgrp) && ss->implicit_on_dfl;
3208 * cgroup_apply_control_enable - enable or show csses according to control
3209 * @cgrp: root of the target subtree
3211 * Walk @cgrp's subtree and create new csses or make the existing ones
3212 * visible. A css is created invisible if it's being implicitly enabled
3213 * through dependency. An invisible css is made visible when the userland
3214 * explicitly enables it.
3216 * Returns 0 on success, -errno on failure. On failure, csses which have
3217 * been processed already aren't cleaned up. The caller is responsible for
3218 * cleaning up with cgroup_apply_control_disable().
3220 static int cgroup_apply_control_enable(struct cgroup *cgrp)
3222 struct cgroup *dsct;
3223 struct cgroup_subsys_state *d_css;
3224 struct cgroup_subsys *ss;
3227 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3228 for_each_subsys(ss, ssid) {
3229 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3231 if (!(cgroup_ss_mask(dsct) & (1 << ss->id)))
3235 css = css_create(dsct, ss);
3237 return PTR_ERR(css);
3240 WARN_ON_ONCE(percpu_ref_is_dying(&css->refcnt));
3242 if (css_visible(css)) {
3243 ret = css_populate_dir(css);
3254 * cgroup_apply_control_disable - kill or hide csses according to control
3255 * @cgrp: root of the target subtree
3257 * Walk @cgrp's subtree and kill and hide csses so that they match
3258 * cgroup_ss_mask() and cgroup_visible_mask().
3260 * A css is hidden when the userland requests it to be disabled while other
3261 * subsystems are still depending on it. The css must not actively control
3262 * resources and be in the vanilla state if it's made visible again later.
3263 * Controllers which may be depended upon should provide ->css_reset() for
3266 static void cgroup_apply_control_disable(struct cgroup *cgrp)
3268 struct cgroup *dsct;
3269 struct cgroup_subsys_state *d_css;
3270 struct cgroup_subsys *ss;
3273 cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3274 for_each_subsys(ss, ssid) {
3275 struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3280 WARN_ON_ONCE(percpu_ref_is_dying(&css->refcnt));
3283 !(cgroup_ss_mask(dsct) & (1 << ss->id))) {
3285 } else if (!css_visible(css)) {
3295 * cgroup_apply_control - apply control mask updates to the subtree
3296 * @cgrp: root of the target subtree
3298 * subsystems can be enabled and disabled in a subtree using the following
3301 * 1. Call cgroup_save_control() to stash the current state.
3302 * 2. Update ->subtree_control masks in the subtree as desired.
3303 * 3. Call cgroup_apply_control() to apply the changes.
3304 * 4. Optionally perform other related operations.
3305 * 5. Call cgroup_finalize_control() to finish up.
3307 * This function implements step 3 and propagates the mask changes
3308 * throughout @cgrp's subtree, updates csses accordingly and perform
3309 * process migrations.
3311 static int cgroup_apply_control(struct cgroup *cgrp)
3315 cgroup_propagate_control(cgrp);
3317 ret = cgroup_apply_control_enable(cgrp);
3322 * At this point, cgroup_e_css_by_mask() results reflect the new csses
3323 * making the following cgroup_update_dfl_csses() properly update
3324 * css associations of all tasks in the subtree.
3326 return cgroup_update_dfl_csses(cgrp);
3330 * cgroup_finalize_control - finalize control mask update
3331 * @cgrp: root of the target subtree
3332 * @ret: the result of the update
3334 * Finalize control mask update. See cgroup_apply_control() for more info.
3336 static void cgroup_finalize_control(struct cgroup *cgrp, int ret)
3339 cgroup_restore_control(cgrp);
3340 cgroup_propagate_control(cgrp);
3343 cgroup_apply_control_disable(cgrp);
3346 static int cgroup_vet_subtree_control_enable(struct cgroup *cgrp, u16 enable)
3348 u16 domain_enable = enable & ~cgrp_dfl_threaded_ss_mask;
3350 /* if nothing is getting enabled, nothing to worry about */
3354 /* can @cgrp host any resources? */
3355 if (!cgroup_is_valid_domain(cgrp->dom_cgrp))
3358 /* mixables don't care */
3359 if (cgroup_is_mixable(cgrp))
3362 if (domain_enable) {
3363 /* can't enable domain controllers inside a thread subtree */
3364 if (cgroup_is_thread_root(cgrp) || cgroup_is_threaded(cgrp))
3368 * Threaded controllers can handle internal competitions
3369 * and are always allowed inside a (prospective) thread
3372 if (cgroup_can_be_thread_root(cgrp) || cgroup_is_threaded(cgrp))
3377 * Controllers can't be enabled for a cgroup with tasks to avoid
3378 * child cgroups competing against tasks.
3380 if (cgroup_has_tasks(cgrp))
3386 /* change the enabled child controllers for a cgroup in the default hierarchy */
3387 static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
3388 char *buf, size_t nbytes,
3391 u16 enable = 0, disable = 0;
3392 struct cgroup *cgrp, *child;
3393 struct cgroup_subsys *ss;
3398 * Parse input - space separated list of subsystem names prefixed
3399 * with either + or -.
3401 buf = strstrip(buf);
3402 while ((tok = strsep(&buf, " "))) {
3405 do_each_subsys_mask(ss, ssid, ~cgrp_dfl_inhibit_ss_mask) {
3406 if (!cgroup_ssid_enabled(ssid) ||
3407 strcmp(tok + 1, ss->name))
3411 enable |= 1 << ssid;
3412 disable &= ~(1 << ssid);
3413 } else if (*tok == '-') {
3414 disable |= 1 << ssid;
3415 enable &= ~(1 << ssid);
3420 } while_each_subsys_mask();
3421 if (ssid == CGROUP_SUBSYS_COUNT)
3425 cgrp = cgroup_kn_lock_live(of->kn, true);
3429 for_each_subsys(ss, ssid) {
3430 if (enable & (1 << ssid)) {
3431 if (cgrp->subtree_control & (1 << ssid)) {
3432 enable &= ~(1 << ssid);
3436 if (!(cgroup_control(cgrp) & (1 << ssid))) {
3440 } else if (disable & (1 << ssid)) {
3441 if (!(cgrp->subtree_control & (1 << ssid))) {
3442 disable &= ~(1 << ssid);
3446 /* a child has it enabled? */
3447 cgroup_for_each_live_child(child, cgrp) {
3448 if (child->subtree_control & (1 << ssid)) {
3456 if (!enable && !disable) {
3461 ret = cgroup_vet_subtree_control_enable(cgrp, enable);
3465 /* save and update control masks and prepare csses */
3466 cgroup_save_control(cgrp);
3468 cgrp->subtree_control |= enable;
3469 cgrp->subtree_control &= ~disable;
3471 ret = cgroup_apply_control(cgrp);
3472 cgroup_finalize_control(cgrp, ret);
3476 kernfs_activate(cgrp->kn);
3478 cgroup_kn_unlock(of->kn);
3479 return ret ?: nbytes;
3483 * cgroup_enable_threaded - make @cgrp threaded
3484 * @cgrp: the target cgroup
3486 * Called when "threaded" is written to the cgroup.type interface file and
3487 * tries to make @cgrp threaded and join the parent's resource domain.
3488 * This function is never called on the root cgroup as cgroup.type doesn't
3491 static int cgroup_enable_threaded(struct cgroup *cgrp)
3493 struct cgroup *parent = cgroup_parent(cgrp);
3494 struct cgroup *dom_cgrp = parent->dom_cgrp;
3495 struct cgroup *dsct;
3496 struct cgroup_subsys_state *d_css;
3499 lockdep_assert_held(&cgroup_mutex);
3501 /* noop if already threaded */
3502 if (cgroup_is_threaded(cgrp))
3506 * If @cgroup is populated or has domain controllers enabled, it
3507 * can't be switched. While the below cgroup_can_be_thread_root()
3508 * test can catch the same conditions, that's only when @parent is
3509 * not mixable, so let's check it explicitly.
3511 if (cgroup_is_populated(cgrp) ||
3512 cgrp->subtree_control & ~cgrp_dfl_threaded_ss_mask)
3515 /* we're joining the parent's domain, ensure its validity */
3516 if (!cgroup_is_valid_domain(dom_cgrp) ||
3517 !cgroup_can_be_thread_root(dom_cgrp))
3521 * The following shouldn't cause actual migrations and should
3524 cgroup_save_control(cgrp);
3526 cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp)
3527 if (dsct == cgrp || cgroup_is_threaded(dsct))
3528 dsct->dom_cgrp = dom_cgrp;
3530 ret = cgroup_apply_control(cgrp);
3532 parent->nr_threaded_children++;
3534 cgroup_finalize_control(cgrp, ret);
3538 static int cgroup_type_show(struct seq_file *seq, void *v)
3540 struct cgroup *cgrp = seq_css(seq)->cgroup;
3542 if (cgroup_is_threaded(cgrp))
3543 seq_puts(seq, "threaded\n");
3544 else if (!cgroup_is_valid_domain(cgrp))
3545 seq_puts(seq, "domain invalid\n");
3546 else if (cgroup_is_thread_root(cgrp))
3547 seq_puts(seq, "domain threaded\n");
3549 seq_puts(seq, "domain\n");
3554 static ssize_t cgroup_type_write(struct kernfs_open_file *of, char *buf,
3555 size_t nbytes, loff_t off)
3557 struct cgroup *cgrp;
3560 /* only switching to threaded mode is supported */
3561 if (strcmp(strstrip(buf), "threaded"))
3564 /* drain dying csses before we re-apply (threaded) subtree control */
3565 cgrp = cgroup_kn_lock_live(of->kn, true);
3569 /* threaded can only be enabled */
3570 ret = cgroup_enable_threaded(cgrp);
3572 cgroup_kn_unlock(of->kn);
3573 return ret ?: nbytes;
3576 static int cgroup_max_descendants_show(struct seq_file *seq, void *v)
3578 struct cgroup *cgrp = seq_css(seq)->cgroup;
3579 int descendants = READ_ONCE(cgrp->max_descendants);
3581 if (descendants == INT_MAX)
3582 seq_puts(seq, "max\n");
3584 seq_printf(seq, "%d\n", descendants);
3589 static ssize_t cgroup_max_descendants_write(struct kernfs_open_file *of,
3590 char *buf, size_t nbytes, loff_t off)
3592 struct cgroup *cgrp;
3596 buf = strstrip(buf);
3597 if (!strcmp(buf, "max")) {
3598 descendants = INT_MAX;
3600 ret = kstrtoint(buf, 0, &descendants);
3605 if (descendants < 0)
3608 cgrp = cgroup_kn_lock_live(of->kn, false);
3612 cgrp->max_descendants = descendants;
3614 cgroup_kn_unlock(of->kn);
3619 static int cgroup_max_depth_show(struct seq_file *seq, void *v)
3621 struct cgroup *cgrp = seq_css(seq)->cgroup;
3622 int depth = READ_ONCE(cgrp->max_depth);
3624 if (depth == INT_MAX)
3625 seq_puts(seq, "max\n");
3627 seq_printf(seq, "%d\n", depth);
3632 static ssize_t cgroup_max_depth_write(struct kernfs_open_file *of,
3633 char *buf, size_t nbytes, loff_t off)
3635 struct cgroup *cgrp;
3639 buf = strstrip(buf);
3640 if (!strcmp(buf, "max")) {
3643 ret = kstrtoint(buf, 0, &depth);
3651 cgrp = cgroup_kn_lock_live(of->kn, false);
3655 cgrp->max_depth = depth;
3657 cgroup_kn_unlock(of->kn);
3662 static int cgroup_events_show(struct seq_file *seq, void *v)
3664 struct cgroup *cgrp = seq_css(seq)->cgroup;
3666 seq_printf(seq, "populated %d\n", cgroup_is_populated(cgrp));
3667 seq_printf(seq, "frozen %d\n", test_bit(CGRP_FROZEN, &cgrp->flags));
3672 static int cgroup_stat_show(struct seq_file *seq, void *v)
3674 struct cgroup *cgroup = seq_css(seq)->cgroup;
3676 seq_printf(seq, "nr_descendants %d\n",
3677 cgroup->nr_descendants);
3678 seq_printf(seq, "nr_dying_descendants %d\n",
3679 cgroup->nr_dying_descendants);
3684 static int __maybe_unused cgroup_extra_stat_show(struct seq_file *seq,
3685 struct cgroup *cgrp, int ssid)
3687 struct cgroup_subsys *ss = cgroup_subsys[ssid];
3688 struct cgroup_subsys_state *css;
3691 if (!ss->css_extra_stat_show)
3694 css = cgroup_tryget_css(cgrp, ss);
3698 ret = ss->css_extra_stat_show(seq, css);
3703 static int cpu_stat_show(struct seq_file *seq, void *v)
3705 struct cgroup __maybe_unused *cgrp = seq_css(seq)->cgroup;
3708 cgroup_base_stat_cputime_show(seq);
3709 #ifdef CONFIG_CGROUP_SCHED
3710 ret = cgroup_extra_stat_show(seq, cgrp, cpu_cgrp_id);
3716 static int cgroup_io_pressure_show(struct seq_file *seq, void *v)
3718 struct cgroup *cgrp = seq_css(seq)->cgroup;
3719 struct psi_group *psi = cgroup_psi(cgrp);
3721 return psi_show(seq, psi, PSI_IO);
3723 static int cgroup_memory_pressure_show(struct seq_file *seq, void *v)
3725 struct cgroup *cgrp = seq_css(seq)->cgroup;
3726 struct psi_group *psi = cgroup_psi(cgrp);
3728 return psi_show(seq, psi, PSI_MEM);
3730 static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v)
3732 struct cgroup *cgrp = seq_css(seq)->cgroup;
3733 struct psi_group *psi = cgroup_psi(cgrp);
3735 return psi_show(seq, psi, PSI_CPU);
3738 static ssize_t pressure_write(struct kernfs_open_file *of, char *buf,
3739 size_t nbytes, enum psi_res res)
3741 struct cgroup_file_ctx *ctx = of->priv;
3742 struct psi_trigger *new;
3743 struct cgroup *cgrp;
3744 struct psi_group *psi;
3746 cgrp = cgroup_kn_lock_live(of->kn, false);
3751 cgroup_kn_unlock(of->kn);
3753 /* Allow only one trigger per file descriptor */
3754 if (ctx->psi.trigger) {
3759 psi = cgroup_psi(cgrp);
3760 new = psi_trigger_create(psi, buf, res);
3763 return PTR_ERR(new);
3766 smp_store_release(&ctx->psi.trigger, new);
3772 static ssize_t cgroup_io_pressure_write(struct kernfs_open_file *of,
3773 char *buf, size_t nbytes,
3776 return pressure_write(of, buf, nbytes, PSI_IO);
3779 static ssize_t cgroup_memory_pressure_write(struct kernfs_open_file *of,
3780 char *buf, size_t nbytes,
3783 return pressure_write(of, buf, nbytes, PSI_MEM);
3786 static ssize_t cgroup_cpu_pressure_write(struct kernfs_open_file *of,
3787 char *buf, size_t nbytes,
3790 return pressure_write(of, buf, nbytes, PSI_CPU);
3793 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
3794 static int cgroup_irq_pressure_show(struct seq_file *seq, void *v)
3796 struct cgroup *cgrp = seq_css(seq)->cgroup;
3797 struct psi_group *psi = cgroup_psi(cgrp);
3799 return psi_show(seq, psi, PSI_IRQ);
3802 static ssize_t cgroup_irq_pressure_write(struct kernfs_open_file *of,
3803 char *buf, size_t nbytes,
3806 return pressure_write(of, buf, nbytes, PSI_IRQ);
3810 static int cgroup_pressure_show(struct seq_file *seq, void *v)
3812 struct cgroup *cgrp = seq_css(seq)->cgroup;
3813 struct psi_group *psi = cgroup_psi(cgrp);
3815 seq_printf(seq, "%d\n", psi->enabled);
3820 static ssize_t cgroup_pressure_write(struct kernfs_open_file *of,
3821 char *buf, size_t nbytes,
3826 struct cgroup *cgrp;
3827 struct psi_group *psi;
3829 ret = kstrtoint(strstrip(buf), 0, &enable);
3833 if (enable < 0 || enable > 1)
3836 cgrp = cgroup_kn_lock_live(of->kn, false);
3840 psi = cgroup_psi(cgrp);
3841 if (psi->enabled != enable) {
3844 /* show or hide {cpu,memory,io,irq}.pressure files */
3845 for (i = 0; i < NR_PSI_RESOURCES; i++)
3846 cgroup_file_show(&cgrp->psi_files[i], enable);
3848 psi->enabled = enable;
3850 psi_cgroup_restart(psi);
3853 cgroup_kn_unlock(of->kn);
3858 static __poll_t cgroup_pressure_poll(struct kernfs_open_file *of,
3861 struct cgroup_file_ctx *ctx = of->priv;
3863 return psi_trigger_poll(&ctx->psi.trigger, of->file, pt);
3866 static void cgroup_pressure_release(struct kernfs_open_file *of)
3868 struct cgroup_file_ctx *ctx = of->priv;
3870 psi_trigger_destroy(ctx->psi.trigger);
3873 bool cgroup_psi_enabled(void)
3875 if (static_branch_likely(&psi_disabled))
3878 return (cgroup_feature_disable_mask & (1 << OPT_FEATURE_PRESSURE)) == 0;
3881 #else /* CONFIG_PSI */
3882 bool cgroup_psi_enabled(void)
3887 #endif /* CONFIG_PSI */
3889 static int cgroup_freeze_show(struct seq_file *seq, void *v)
3891 struct cgroup *cgrp = seq_css(seq)->cgroup;
3893 seq_printf(seq, "%d\n", cgrp->freezer.freeze);
3898 static ssize_t cgroup_freeze_write(struct kernfs_open_file *of,
3899 char *buf, size_t nbytes, loff_t off)
3901 struct cgroup *cgrp;
3905 ret = kstrtoint(strstrip(buf), 0, &freeze);
3909 if (freeze < 0 || freeze > 1)
3912 cgrp = cgroup_kn_lock_live(of->kn, false);
3916 cgroup_freeze(cgrp, freeze);
3918 cgroup_kn_unlock(of->kn);
3923 static void __cgroup_kill(struct cgroup *cgrp)
3925 struct css_task_iter it;
3926 struct task_struct *task;
3928 lockdep_assert_held(&cgroup_mutex);
3930 spin_lock_irq(&css_set_lock);
3931 set_bit(CGRP_KILL, &cgrp->flags);
3932 spin_unlock_irq(&css_set_lock);
3934 css_task_iter_start(&cgrp->self, CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED, &it);
3935 while ((task = css_task_iter_next(&it))) {
3936 /* Ignore kernel threads here. */
3937 if (task->flags & PF_KTHREAD)
3940 /* Skip tasks that are already dying. */
3941 if (__fatal_signal_pending(task))
3944 send_sig(SIGKILL, task, 0);
3946 css_task_iter_end(&it);
3948 spin_lock_irq(&css_set_lock);
3949 clear_bit(CGRP_KILL, &cgrp->flags);
3950 spin_unlock_irq(&css_set_lock);
3953 static void cgroup_kill(struct cgroup *cgrp)
3955 struct cgroup_subsys_state *css;
3956 struct cgroup *dsct;
3958 lockdep_assert_held(&cgroup_mutex);
3960 cgroup_for_each_live_descendant_pre(dsct, css, cgrp)
3961 __cgroup_kill(dsct);
3964 static ssize_t cgroup_kill_write(struct kernfs_open_file *of, char *buf,
3965 size_t nbytes, loff_t off)
3969 struct cgroup *cgrp;
3971 ret = kstrtoint(strstrip(buf), 0, &kill);
3978 cgrp = cgroup_kn_lock_live(of->kn, false);
3983 * Killing is a process directed operation, i.e. the whole thread-group
3984 * is taken down so act like we do for cgroup.procs and only make this
3985 * writable in non-threaded cgroups.
3987 if (cgroup_is_threaded(cgrp))
3992 cgroup_kn_unlock(of->kn);
3994 return ret ?: nbytes;
3997 static int cgroup_file_open(struct kernfs_open_file *of)
3999 struct cftype *cft = of_cft(of);
4000 struct cgroup_file_ctx *ctx;
4003 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
4007 ctx->ns = current->nsproxy->cgroup_ns;
4008 get_cgroup_ns(ctx->ns);
4014 ret = cft->open(of);
4016 put_cgroup_ns(ctx->ns);
4022 static void cgroup_file_release(struct kernfs_open_file *of)
4024 struct cftype *cft = of_cft(of);
4025 struct cgroup_file_ctx *ctx = of->priv;
4029 put_cgroup_ns(ctx->ns);
4033 static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
4034 size_t nbytes, loff_t off)
4036 struct cgroup_file_ctx *ctx = of->priv;
4037 struct cgroup *cgrp = of->kn->parent->priv;
4038 struct cftype *cft = of_cft(of);
4039 struct cgroup_subsys_state *css;
4046 * If namespaces are delegation boundaries, disallow writes to
4047 * files in an non-init namespace root from inside the namespace
4048 * except for the files explicitly marked delegatable -
4049 * cgroup.procs and cgroup.subtree_control.
4051 if ((cgrp->root->flags & CGRP_ROOT_NS_DELEGATE) &&
4052 !(cft->flags & CFTYPE_NS_DELEGATABLE) &&
4053 ctx->ns != &init_cgroup_ns && ctx->ns->root_cset->dfl_cgrp == cgrp)
4057 return cft->write(of, buf, nbytes, off);
4060 * kernfs guarantees that a file isn't deleted with operations in
4061 * flight, which means that the matching css is and stays alive and
4062 * doesn't need to be pinned. The RCU locking is not necessary
4063 * either. It's just for the convenience of using cgroup_css().
4066 css = cgroup_css(cgrp, cft->ss);
4069 if (cft->write_u64) {
4070 unsigned long long v;
4071 ret = kstrtoull(buf, 0, &v);
4073 ret = cft->write_u64(css, cft, v);
4074 } else if (cft->write_s64) {
4076 ret = kstrtoll(buf, 0, &v);
4078 ret = cft->write_s64(css, cft, v);
4083 return ret ?: nbytes;
4086 static __poll_t cgroup_file_poll(struct kernfs_open_file *of, poll_table *pt)
4088 struct cftype *cft = of_cft(of);
4091 return cft->poll(of, pt);
4093 return kernfs_generic_poll(of, pt);
4096 static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
4098 return seq_cft(seq)->seq_start(seq, ppos);
4101 static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
4103 return seq_cft(seq)->seq_next(seq, v, ppos);
4106 static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
4108 if (seq_cft(seq)->seq_stop)
4109 seq_cft(seq)->seq_stop(seq, v);
4112 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
4114 struct cftype *cft = seq_cft(m);
4115 struct cgroup_subsys_state *css = seq_css(m);
4118 return cft->seq_show(m, arg);
4121 seq_printf(m, "%llu\n", cft->read_u64(css, cft));
4122 else if (cft->read_s64)
4123 seq_printf(m, "%lld\n", cft->read_s64(css, cft));
4129 static struct kernfs_ops cgroup_kf_single_ops = {
4130 .atomic_write_len = PAGE_SIZE,
4131 .open = cgroup_file_open,
4132 .release = cgroup_file_release,
4133 .write = cgroup_file_write,
4134 .poll = cgroup_file_poll,
4135 .seq_show = cgroup_seqfile_show,
4138 static struct kernfs_ops cgroup_kf_ops = {
4139 .atomic_write_len = PAGE_SIZE,
4140 .open = cgroup_file_open,
4141 .release = cgroup_file_release,
4142 .write = cgroup_file_write,
4143 .poll = cgroup_file_poll,
4144 .seq_start = cgroup_seqfile_start,
4145 .seq_next = cgroup_seqfile_next,
4146 .seq_stop = cgroup_seqfile_stop,
4147 .seq_show = cgroup_seqfile_show,
4150 /* set uid and gid of cgroup dirs and files to that of the creator */
4151 static int cgroup_kn_set_ugid(struct kernfs_node *kn)
4153 struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
4154 .ia_uid = current_fsuid(),
4155 .ia_gid = current_fsgid(), };
4157 if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
4158 gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
4161 return kernfs_setattr(kn, &iattr);
4164 static void cgroup_file_notify_timer(struct timer_list *timer)
4166 cgroup_file_notify(container_of(timer, struct cgroup_file,
4170 static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
4173 char name[CGROUP_FILE_NAME_MAX];
4174 struct kernfs_node *kn;
4175 struct lock_class_key *key = NULL;
4178 #ifdef CONFIG_DEBUG_LOCK_ALLOC
4179 key = &cft->lockdep_key;
4181 kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
4182 cgroup_file_mode(cft),
4183 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
4184 0, cft->kf_ops, cft,
4189 ret = cgroup_kn_set_ugid(kn);
4195 if (cft->file_offset) {
4196 struct cgroup_file *cfile = (void *)css + cft->file_offset;
4198 timer_setup(&cfile->notify_timer, cgroup_file_notify_timer, 0);
4200 spin_lock_irq(&cgroup_file_kn_lock);
4202 spin_unlock_irq(&cgroup_file_kn_lock);
4209 * cgroup_addrm_files - add or remove files to a cgroup directory
4210 * @css: the target css
4211 * @cgrp: the target cgroup (usually css->cgroup)
4212 * @cfts: array of cftypes to be added
4213 * @is_add: whether to add or remove
4215 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
4216 * For removals, this function never fails.
4218 static int cgroup_addrm_files(struct cgroup_subsys_state *css,
4219 struct cgroup *cgrp, struct cftype cfts[],
4222 struct cftype *cft, *cft_end = NULL;
4225 lockdep_assert_held(&cgroup_mutex);
4228 for (cft = cfts; cft != cft_end && cft->name[0] != '\0'; cft++) {
4229 /* does cft->flags tell us to skip this file on @cgrp? */
4230 if ((cft->flags & __CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
4232 if ((cft->flags & __CFTYPE_NOT_ON_DFL) && cgroup_on_dfl(cgrp))
4234 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp))
4236 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp))
4238 if ((cft->flags & CFTYPE_DEBUG) && !cgroup_debug)
4241 ret = cgroup_add_file(css, cgrp, cft);
4243 pr_warn("%s: failed to add %s, err=%d\n",
4244 __func__, cft->name, ret);
4250 cgroup_rm_file(cgrp, cft);
4256 static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
4258 struct cgroup_subsys *ss = cfts[0].ss;
4259 struct cgroup *root = &ss->root->cgrp;
4260 struct cgroup_subsys_state *css;
4263 lockdep_assert_held(&cgroup_mutex);
4265 /* add/rm files for all cgroups created before */
4266 css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
4267 struct cgroup *cgrp = css->cgroup;
4269 if (!(css->flags & CSS_VISIBLE))
4272 ret = cgroup_addrm_files(css, cgrp, cfts, is_add);
4278 kernfs_activate(root->kn);
4282 static void cgroup_exit_cftypes(struct cftype *cfts)
4286 for (cft = cfts; cft->name[0] != '\0'; cft++) {
4287 /* free copy for custom atomic_write_len, see init_cftypes() */
4288 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
4293 /* revert flags set by cgroup core while adding @cfts */
4294 cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL |
4299 static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4304 for (cft = cfts; cft->name[0] != '\0'; cft++) {
4305 struct kernfs_ops *kf_ops;
4307 WARN_ON(cft->ss || cft->kf_ops);
4309 if (cft->flags & __CFTYPE_ADDED) {
4315 kf_ops = &cgroup_kf_ops;
4317 kf_ops = &cgroup_kf_single_ops;
4320 * Ugh... if @cft wants a custom max_write_len, we need to
4321 * make a copy of kf_ops to set its atomic_write_len.
4323 if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
4324 kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
4329 kf_ops->atomic_write_len = cft->max_write_len;
4332 cft->kf_ops = kf_ops;
4334 cft->flags |= __CFTYPE_ADDED;
4338 cgroup_exit_cftypes(cfts);
4342 static int cgroup_rm_cftypes_locked(struct cftype *cfts)
4344 lockdep_assert_held(&cgroup_mutex);
4346 list_del(&cfts->node);
4347 cgroup_apply_cftypes(cfts, false);
4348 cgroup_exit_cftypes(cfts);
4353 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
4354 * @cfts: zero-length name terminated array of cftypes
4356 * Unregister @cfts. Files described by @cfts are removed from all
4357 * existing cgroups and all future cgroups won't have them either. This
4358 * function can be called anytime whether @cfts' subsys is attached or not.
4360 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
4363 int cgroup_rm_cftypes(struct cftype *cfts)
4367 if (!cfts || cfts[0].name[0] == '\0')
4370 if (!(cfts[0].flags & __CFTYPE_ADDED))
4373 mutex_lock(&cgroup_mutex);
4374 ret = cgroup_rm_cftypes_locked(cfts);
4375 mutex_unlock(&cgroup_mutex);
4380 * cgroup_add_cftypes - add an array of cftypes to a subsystem
4381 * @ss: target cgroup subsystem
4382 * @cfts: zero-length name terminated array of cftypes
4384 * Register @cfts to @ss. Files described by @cfts are created for all
4385 * existing cgroups to which @ss is attached and all future cgroups will
4386 * have them too. This function can be called anytime whether @ss is
4389 * Returns 0 on successful registration, -errno on failure. Note that this
4390 * function currently returns 0 as long as @cfts registration is successful
4391 * even if some file creation attempts on existing cgroups fail.
4393 static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4397 if (!cgroup_ssid_enabled(ss->id))
4400 if (!cfts || cfts[0].name[0] == '\0')
4403 ret = cgroup_init_cftypes(ss, cfts);
4407 mutex_lock(&cgroup_mutex);
4409 list_add_tail(&cfts->node, &ss->cfts);
4410 ret = cgroup_apply_cftypes(cfts, true);
4412 cgroup_rm_cftypes_locked(cfts);
4414 mutex_unlock(&cgroup_mutex);
4419 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
4420 * @ss: target cgroup subsystem
4421 * @cfts: zero-length name terminated array of cftypes
4423 * Similar to cgroup_add_cftypes() but the added files are only used for
4424 * the default hierarchy.
4426 int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4430 for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
4431 cft->flags |= __CFTYPE_ONLY_ON_DFL;
4432 return cgroup_add_cftypes(ss, cfts);
4436 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
4437 * @ss: target cgroup subsystem
4438 * @cfts: zero-length name terminated array of cftypes
4440 * Similar to cgroup_add_cftypes() but the added files are only used for
4441 * the legacy hierarchies.
4443 int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
4447 for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
4448 cft->flags |= __CFTYPE_NOT_ON_DFL;
4449 return cgroup_add_cftypes(ss, cfts);
4453 * cgroup_file_notify - generate a file modified event for a cgroup_file
4454 * @cfile: target cgroup_file
4456 * @cfile must have been obtained by setting cftype->file_offset.
4458 void cgroup_file_notify(struct cgroup_file *cfile)
4460 unsigned long flags;
4462 spin_lock_irqsave(&cgroup_file_kn_lock, flags);
4464 unsigned long last = cfile->notified_at;
4465 unsigned long next = last + CGROUP_FILE_NOTIFY_MIN_INTV;
4467 if (time_in_range(jiffies, last, next)) {
4468 timer_reduce(&cfile->notify_timer, next);
4470 kernfs_notify(cfile->kn);
4471 cfile->notified_at = jiffies;
4474 spin_unlock_irqrestore(&cgroup_file_kn_lock, flags);
4478 * cgroup_file_show - show or hide a hidden cgroup file
4479 * @cfile: target cgroup_file obtained by setting cftype->file_offset
4480 * @show: whether to show or hide
4482 void cgroup_file_show(struct cgroup_file *cfile, bool show)
4484 struct kernfs_node *kn;
4486 spin_lock_irq(&cgroup_file_kn_lock);
4489 spin_unlock_irq(&cgroup_file_kn_lock);
4492 kernfs_show(kn, show);
4498 * css_next_child - find the next child of a given css
4499 * @pos: the current position (%NULL to initiate traversal)
4500 * @parent: css whose children to walk
4502 * This function returns the next child of @parent and should be called
4503 * under either cgroup_mutex or RCU read lock. The only requirement is
4504 * that @parent and @pos are accessible. The next sibling is guaranteed to
4505 * be returned regardless of their states.
4507 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4508 * css which finished ->css_online() is guaranteed to be visible in the
4509 * future iterations and will stay visible until the last reference is put.
4510 * A css which hasn't finished ->css_online() or already finished
4511 * ->css_offline() may show up during traversal. It's each subsystem's
4512 * responsibility to synchronize against on/offlining.
4514 struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
4515 struct cgroup_subsys_state *parent)
4517 struct cgroup_subsys_state *next;
4519 cgroup_assert_mutex_or_rcu_locked();
4522 * @pos could already have been unlinked from the sibling list.
4523 * Once a cgroup is removed, its ->sibling.next is no longer
4524 * updated when its next sibling changes. CSS_RELEASED is set when
4525 * @pos is taken off list, at which time its next pointer is valid,
4526 * and, as releases are serialized, the one pointed to by the next
4527 * pointer is guaranteed to not have started release yet. This
4528 * implies that if we observe !CSS_RELEASED on @pos in this RCU
4529 * critical section, the one pointed to by its next pointer is
4530 * guaranteed to not have finished its RCU grace period even if we
4531 * have dropped rcu_read_lock() in-between iterations.
4533 * If @pos has CSS_RELEASED set, its next pointer can't be
4534 * dereferenced; however, as each css is given a monotonically
4535 * increasing unique serial number and always appended to the
4536 * sibling list, the next one can be found by walking the parent's
4537 * children until the first css with higher serial number than
4538 * @pos's. While this path can be slower, it happens iff iteration
4539 * races against release and the race window is very small.
4542 next = list_entry_rcu(parent->children.next, struct cgroup_subsys_state, sibling);
4543 } else if (likely(!(pos->flags & CSS_RELEASED))) {
4544 next = list_entry_rcu(pos->sibling.next, struct cgroup_subsys_state, sibling);
4546 list_for_each_entry_rcu(next, &parent->children, sibling,
4547 lockdep_is_held(&cgroup_mutex))
4548 if (next->serial_nr > pos->serial_nr)
4553 * @next, if not pointing to the head, can be dereferenced and is
4556 if (&next->sibling != &parent->children)
4562 * css_next_descendant_pre - find the next descendant for pre-order walk
4563 * @pos: the current position (%NULL to initiate traversal)
4564 * @root: css whose descendants to walk
4566 * To be used by css_for_each_descendant_pre(). Find the next descendant
4567 * to visit for pre-order traversal of @root's descendants. @root is
4568 * included in the iteration and the first node to be visited.
4570 * While this function requires cgroup_mutex or RCU read locking, it
4571 * doesn't require the whole traversal to be contained in a single critical
4572 * section. This function will return the correct next descendant as long
4573 * as both @pos and @root are accessible and @pos is a descendant of @root.
4575 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4576 * css which finished ->css_online() is guaranteed to be visible in the
4577 * future iterations and will stay visible until the last reference is put.
4578 * A css which hasn't finished ->css_online() or already finished
4579 * ->css_offline() may show up during traversal. It's each subsystem's
4580 * responsibility to synchronize against on/offlining.
4582 struct cgroup_subsys_state *
4583 css_next_descendant_pre(struct cgroup_subsys_state *pos,
4584 struct cgroup_subsys_state *root)
4586 struct cgroup_subsys_state *next;
4588 cgroup_assert_mutex_or_rcu_locked();
4590 /* if first iteration, visit @root */
4594 /* visit the first child if exists */
4595 next = css_next_child(NULL, pos);
4599 /* no child, visit my or the closest ancestor's next sibling */
4600 while (pos != root) {
4601 next = css_next_child(pos, pos->parent);
4609 EXPORT_SYMBOL_GPL(css_next_descendant_pre);
4612 * css_rightmost_descendant - return the rightmost descendant of a css
4613 * @pos: css of interest
4615 * Return the rightmost descendant of @pos. If there's no descendant, @pos
4616 * is returned. This can be used during pre-order traversal to skip
4619 * While this function requires cgroup_mutex or RCU read locking, it
4620 * doesn't require the whole traversal to be contained in a single critical
4621 * section. This function will return the correct rightmost descendant as
4622 * long as @pos is accessible.
4624 struct cgroup_subsys_state *
4625 css_rightmost_descendant(struct cgroup_subsys_state *pos)
4627 struct cgroup_subsys_state *last, *tmp;
4629 cgroup_assert_mutex_or_rcu_locked();
4633 /* ->prev isn't RCU safe, walk ->next till the end */
4635 css_for_each_child(tmp, last)
4642 static struct cgroup_subsys_state *
4643 css_leftmost_descendant(struct cgroup_subsys_state *pos)
4645 struct cgroup_subsys_state *last;
4649 pos = css_next_child(NULL, pos);
4656 * css_next_descendant_post - find the next descendant for post-order walk
4657 * @pos: the current position (%NULL to initiate traversal)
4658 * @root: css whose descendants to walk
4660 * To be used by css_for_each_descendant_post(). Find the next descendant
4661 * to visit for post-order traversal of @root's descendants. @root is
4662 * included in the iteration and the last node to be visited.
4664 * While this function requires cgroup_mutex or RCU read locking, it
4665 * doesn't require the whole traversal to be contained in a single critical
4666 * section. This function will return the correct next descendant as long
4667 * as both @pos and @cgroup are accessible and @pos is a descendant of
4670 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4671 * css which finished ->css_online() is guaranteed to be visible in the
4672 * future iterations and will stay visible until the last reference is put.
4673 * A css which hasn't finished ->css_online() or already finished
4674 * ->css_offline() may show up during traversal. It's each subsystem's
4675 * responsibility to synchronize against on/offlining.
4677 struct cgroup_subsys_state *
4678 css_next_descendant_post(struct cgroup_subsys_state *pos,
4679 struct cgroup_subsys_state *root)
4681 struct cgroup_subsys_state *next;
4683 cgroup_assert_mutex_or_rcu_locked();
4685 /* if first iteration, visit leftmost descendant which may be @root */
4687 return css_leftmost_descendant(root);
4689 /* if we visited @root, we're done */
4693 /* if there's an unvisited sibling, visit its leftmost descendant */
4694 next = css_next_child(pos, pos->parent);
4696 return css_leftmost_descendant(next);
4698 /* no sibling left, visit parent */
4703 * css_has_online_children - does a css have online children
4704 * @css: the target css
4706 * Returns %true if @css has any online children; otherwise, %false. This
4707 * function can be called from any context but the caller is responsible
4708 * for synchronizing against on/offlining as necessary.
4710 bool css_has_online_children(struct cgroup_subsys_state *css)
4712 struct cgroup_subsys_state *child;
4716 css_for_each_child(child, css) {
4717 if (child->flags & CSS_ONLINE) {
4726 static struct css_set *css_task_iter_next_css_set(struct css_task_iter *it)
4728 struct list_head *l;
4729 struct cgrp_cset_link *link;
4730 struct css_set *cset;
4732 lockdep_assert_held(&css_set_lock);
4734 /* find the next threaded cset */
4735 if (it->tcset_pos) {
4736 l = it->tcset_pos->next;
4738 if (l != it->tcset_head) {
4740 return container_of(l, struct css_set,
4741 threaded_csets_node);
4744 it->tcset_pos = NULL;
4747 /* find the next cset */
4750 if (l == it->cset_head) {
4751 it->cset_pos = NULL;
4756 cset = container_of(l, struct css_set, e_cset_node[it->ss->id]);
4758 link = list_entry(l, struct cgrp_cset_link, cset_link);
4764 /* initialize threaded css_set walking */
4765 if (it->flags & CSS_TASK_ITER_THREADED) {
4767 put_css_set_locked(it->cur_dcset);
4768 it->cur_dcset = cset;
4771 it->tcset_head = &cset->threaded_csets;
4772 it->tcset_pos = &cset->threaded_csets;
4779 * css_task_iter_advance_css_set - advance a task iterator to the next css_set
4780 * @it: the iterator to advance
4782 * Advance @it to the next css_set to walk.
4784 static void css_task_iter_advance_css_set(struct css_task_iter *it)
4786 struct css_set *cset;
4788 lockdep_assert_held(&css_set_lock);
4790 /* Advance to the next non-empty css_set and find first non-empty tasks list*/
4791 while ((cset = css_task_iter_next_css_set(it))) {
4792 if (!list_empty(&cset->tasks)) {
4793 it->cur_tasks_head = &cset->tasks;
4795 } else if (!list_empty(&cset->mg_tasks)) {
4796 it->cur_tasks_head = &cset->mg_tasks;
4798 } else if (!list_empty(&cset->dying_tasks)) {
4799 it->cur_tasks_head = &cset->dying_tasks;
4804 it->task_pos = NULL;
4807 it->task_pos = it->cur_tasks_head->next;
4810 * We don't keep css_sets locked across iteration steps and thus
4811 * need to take steps to ensure that iteration can be resumed after
4812 * the lock is re-acquired. Iteration is performed at two levels -
4813 * css_sets and tasks in them.
4815 * Once created, a css_set never leaves its cgroup lists, so a
4816 * pinned css_set is guaranteed to stay put and we can resume
4817 * iteration afterwards.
4819 * Tasks may leave @cset across iteration steps. This is resolved
4820 * by registering each iterator with the css_set currently being
4821 * walked and making css_set_move_task() advance iterators whose
4822 * next task is leaving.
4825 list_del(&it->iters_node);
4826 put_css_set_locked(it->cur_cset);
4829 it->cur_cset = cset;
4830 list_add(&it->iters_node, &cset->task_iters);
4833 static void css_task_iter_skip(struct css_task_iter *it,
4834 struct task_struct *task)
4836 lockdep_assert_held(&css_set_lock);
4838 if (it->task_pos == &task->cg_list) {
4839 it->task_pos = it->task_pos->next;
4840 it->flags |= CSS_TASK_ITER_SKIPPED;
4844 static void css_task_iter_advance(struct css_task_iter *it)
4846 struct task_struct *task;
4848 lockdep_assert_held(&css_set_lock);
4852 * Advance iterator to find next entry. We go through cset
4853 * tasks, mg_tasks and dying_tasks, when consumed we move onto
4856 if (it->flags & CSS_TASK_ITER_SKIPPED)
4857 it->flags &= ~CSS_TASK_ITER_SKIPPED;
4859 it->task_pos = it->task_pos->next;
4861 if (it->task_pos == &it->cur_cset->tasks) {
4862 it->cur_tasks_head = &it->cur_cset->mg_tasks;
4863 it->task_pos = it->cur_tasks_head->next;
4865 if (it->task_pos == &it->cur_cset->mg_tasks) {
4866 it->cur_tasks_head = &it->cur_cset->dying_tasks;
4867 it->task_pos = it->cur_tasks_head->next;
4869 if (it->task_pos == &it->cur_cset->dying_tasks)
4870 css_task_iter_advance_css_set(it);
4872 /* called from start, proceed to the first cset */
4873 css_task_iter_advance_css_set(it);
4879 task = list_entry(it->task_pos, struct task_struct, cg_list);
4881 if (it->flags & CSS_TASK_ITER_PROCS) {
4882 /* if PROCS, skip over tasks which aren't group leaders */
4883 if (!thread_group_leader(task))
4886 /* and dying leaders w/o live member threads */
4887 if (it->cur_tasks_head == &it->cur_cset->dying_tasks &&
4888 !atomic_read(&task->signal->live))
4891 /* skip all dying ones */
4892 if (it->cur_tasks_head == &it->cur_cset->dying_tasks)
4898 * css_task_iter_start - initiate task iteration
4899 * @css: the css to walk tasks of
4900 * @flags: CSS_TASK_ITER_* flags
4901 * @it: the task iterator to use
4903 * Initiate iteration through the tasks of @css. The caller can call
4904 * css_task_iter_next() to walk through the tasks until the function
4905 * returns NULL. On completion of iteration, css_task_iter_end() must be
4908 void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
4909 struct css_task_iter *it)
4911 memset(it, 0, sizeof(*it));
4913 spin_lock_irq(&css_set_lock);
4918 if (CGROUP_HAS_SUBSYS_CONFIG && it->ss)
4919 it->cset_pos = &css->cgroup->e_csets[css->ss->id];
4921 it->cset_pos = &css->cgroup->cset_links;
4923 it->cset_head = it->cset_pos;
4925 css_task_iter_advance(it);
4927 spin_unlock_irq(&css_set_lock);
4931 * css_task_iter_next - return the next task for the iterator
4932 * @it: the task iterator being iterated
4934 * The "next" function for task iteration. @it should have been
4935 * initialized via css_task_iter_start(). Returns NULL when the iteration
4938 struct task_struct *css_task_iter_next(struct css_task_iter *it)
4941 put_task_struct(it->cur_task);
4942 it->cur_task = NULL;
4945 spin_lock_irq(&css_set_lock);
4947 /* @it may be half-advanced by skips, finish advancing */
4948 if (it->flags & CSS_TASK_ITER_SKIPPED)
4949 css_task_iter_advance(it);
4952 it->cur_task = list_entry(it->task_pos, struct task_struct,
4954 get_task_struct(it->cur_task);
4955 css_task_iter_advance(it);
4958 spin_unlock_irq(&css_set_lock);
4960 return it->cur_task;
4964 * css_task_iter_end - finish task iteration
4965 * @it: the task iterator to finish
4967 * Finish task iteration started by css_task_iter_start().
4969 void css_task_iter_end(struct css_task_iter *it)
4972 spin_lock_irq(&css_set_lock);
4973 list_del(&it->iters_node);
4974 put_css_set_locked(it->cur_cset);
4975 spin_unlock_irq(&css_set_lock);
4979 put_css_set(it->cur_dcset);
4982 put_task_struct(it->cur_task);
4985 static void cgroup_procs_release(struct kernfs_open_file *of)
4987 struct cgroup_file_ctx *ctx = of->priv;
4989 if (ctx->procs.started)
4990 css_task_iter_end(&ctx->procs.iter);
4993 static void *cgroup_procs_next(struct seq_file *s, void *v, loff_t *pos)
4995 struct kernfs_open_file *of = s->private;
4996 struct cgroup_file_ctx *ctx = of->priv;
5001 return css_task_iter_next(&ctx->procs.iter);
5004 static void *__cgroup_procs_start(struct seq_file *s, loff_t *pos,
5005 unsigned int iter_flags)
5007 struct kernfs_open_file *of = s->private;
5008 struct cgroup *cgrp = seq_css(s)->cgroup;
5009 struct cgroup_file_ctx *ctx = of->priv;
5010 struct css_task_iter *it = &ctx->procs.iter;
5013 * When a seq_file is seeked, it's always traversed sequentially
5014 * from position 0, so we can simply keep iterating on !0 *pos.
5016 if (!ctx->procs.started) {
5017 if (WARN_ON_ONCE((*pos)))
5018 return ERR_PTR(-EINVAL);
5019 css_task_iter_start(&cgrp->self, iter_flags, it);
5020 ctx->procs.started = true;
5021 } else if (!(*pos)) {
5022 css_task_iter_end(it);
5023 css_task_iter_start(&cgrp->self, iter_flags, it);
5025 return it->cur_task;
5027 return cgroup_procs_next(s, NULL, NULL);
5030 static void *cgroup_procs_start(struct seq_file *s, loff_t *pos)
5032 struct cgroup *cgrp = seq_css(s)->cgroup;
5035 * All processes of a threaded subtree belong to the domain cgroup
5036 * of the subtree. Only threads can be distributed across the
5037 * subtree. Reject reads on cgroup.procs in the subtree proper.
5038 * They're always empty anyway.
5040 if (cgroup_is_threaded(cgrp))
5041 return ERR_PTR(-EOPNOTSUPP);
5043 return __cgroup_procs_start(s, pos, CSS_TASK_ITER_PROCS |
5044 CSS_TASK_ITER_THREADED);
5047 static int cgroup_procs_show(struct seq_file *s, void *v)
5049 seq_printf(s, "%d\n", task_pid_vnr(v));
5053 static int cgroup_may_write(const struct cgroup *cgrp, struct super_block *sb)
5056 struct inode *inode;
5058 lockdep_assert_held(&cgroup_mutex);
5060 inode = kernfs_get_inode(sb, cgrp->procs_file.kn);
5064 ret = inode_permission(&init_user_ns, inode, MAY_WRITE);
5069 static int cgroup_procs_write_permission(struct cgroup *src_cgrp,
5070 struct cgroup *dst_cgrp,
5071 struct super_block *sb,
5072 struct cgroup_namespace *ns)
5074 struct cgroup *com_cgrp = src_cgrp;
5077 lockdep_assert_held(&cgroup_mutex);
5079 /* find the common ancestor */
5080 while (!cgroup_is_descendant(dst_cgrp, com_cgrp))
5081 com_cgrp = cgroup_parent(com_cgrp);
5083 /* %current should be authorized to migrate to the common ancestor */
5084 ret = cgroup_may_write(com_cgrp, sb);
5089 * If namespaces are delegation boundaries, %current must be able
5090 * to see both source and destination cgroups from its namespace.
5092 if ((cgrp_dfl_root.flags & CGRP_ROOT_NS_DELEGATE) &&
5093 (!cgroup_is_descendant(src_cgrp, ns->root_cset->dfl_cgrp) ||
5094 !cgroup_is_descendant(dst_cgrp, ns->root_cset->dfl_cgrp)))
5100 static int cgroup_attach_permissions(struct cgroup *src_cgrp,
5101 struct cgroup *dst_cgrp,
5102 struct super_block *sb, bool threadgroup,
5103 struct cgroup_namespace *ns)
5107 ret = cgroup_procs_write_permission(src_cgrp, dst_cgrp, sb, ns);
5111 ret = cgroup_migrate_vet_dst(dst_cgrp);
5115 if (!threadgroup && (src_cgrp->dom_cgrp != dst_cgrp->dom_cgrp))
5121 static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
5124 struct cgroup_file_ctx *ctx = of->priv;
5125 struct cgroup *src_cgrp, *dst_cgrp;
5126 struct task_struct *task;
5127 const struct cred *saved_cred;
5129 bool threadgroup_locked;
5131 dst_cgrp = cgroup_kn_lock_live(of->kn, false);
5135 task = cgroup_procs_write_start(buf, threadgroup, &threadgroup_locked);
5136 ret = PTR_ERR_OR_ZERO(task);
5140 /* find the source cgroup */
5141 spin_lock_irq(&css_set_lock);
5142 src_cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
5143 spin_unlock_irq(&css_set_lock);
5146 * Process and thread migrations follow same delegation rule. Check
5147 * permissions using the credentials from file open to protect against
5148 * inherited fd attacks.
5150 saved_cred = override_creds(of->file->f_cred);
5151 ret = cgroup_attach_permissions(src_cgrp, dst_cgrp,
5152 of->file->f_path.dentry->d_sb,
5153 threadgroup, ctx->ns);
5154 revert_creds(saved_cred);
5158 ret = cgroup_attach_task(dst_cgrp, task, threadgroup);
5161 cgroup_procs_write_finish(task, threadgroup_locked);
5163 cgroup_kn_unlock(of->kn);
5168 static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
5169 char *buf, size_t nbytes, loff_t off)
5171 return __cgroup_procs_write(of, buf, true) ?: nbytes;
5174 static void *cgroup_threads_start(struct seq_file *s, loff_t *pos)
5176 return __cgroup_procs_start(s, pos, 0);
5179 static ssize_t cgroup_threads_write(struct kernfs_open_file *of,
5180 char *buf, size_t nbytes, loff_t off)
5182 return __cgroup_procs_write(of, buf, false) ?: nbytes;
5185 /* cgroup core interface files for the default hierarchy */
5186 static struct cftype cgroup_base_files[] = {
5188 .name = "cgroup.type",
5189 .flags = CFTYPE_NOT_ON_ROOT,
5190 .seq_show = cgroup_type_show,
5191 .write = cgroup_type_write,
5194 .name = "cgroup.procs",
5195 .flags = CFTYPE_NS_DELEGATABLE,
5196 .file_offset = offsetof(struct cgroup, procs_file),
5197 .release = cgroup_procs_release,
5198 .seq_start = cgroup_procs_start,
5199 .seq_next = cgroup_procs_next,
5200 .seq_show = cgroup_procs_show,
5201 .write = cgroup_procs_write,
5204 .name = "cgroup.threads",
5205 .flags = CFTYPE_NS_DELEGATABLE,
5206 .release = cgroup_procs_release,
5207 .seq_start = cgroup_threads_start,
5208 .seq_next = cgroup_procs_next,
5209 .seq_show = cgroup_procs_show,
5210 .write = cgroup_threads_write,
5213 .name = "cgroup.controllers",
5214 .seq_show = cgroup_controllers_show,
5217 .name = "cgroup.subtree_control",
5218 .flags = CFTYPE_NS_DELEGATABLE,
5219 .seq_show = cgroup_subtree_control_show,
5220 .write = cgroup_subtree_control_write,
5223 .name = "cgroup.events",
5224 .flags = CFTYPE_NOT_ON_ROOT,
5225 .file_offset = offsetof(struct cgroup, events_file),
5226 .seq_show = cgroup_events_show,
5229 .name = "cgroup.max.descendants",
5230 .seq_show = cgroup_max_descendants_show,
5231 .write = cgroup_max_descendants_write,
5234 .name = "cgroup.max.depth",
5235 .seq_show = cgroup_max_depth_show,
5236 .write = cgroup_max_depth_write,
5239 .name = "cgroup.stat",
5240 .seq_show = cgroup_stat_show,
5243 .name = "cgroup.freeze",
5244 .flags = CFTYPE_NOT_ON_ROOT,
5245 .seq_show = cgroup_freeze_show,
5246 .write = cgroup_freeze_write,
5249 .name = "cgroup.kill",
5250 .flags = CFTYPE_NOT_ON_ROOT,
5251 .write = cgroup_kill_write,
5255 .seq_show = cpu_stat_show,
5260 static struct cftype cgroup_psi_files[] = {
5263 .name = "io.pressure",
5264 .file_offset = offsetof(struct cgroup, psi_files[PSI_IO]),
5265 .seq_show = cgroup_io_pressure_show,
5266 .write = cgroup_io_pressure_write,
5267 .poll = cgroup_pressure_poll,
5268 .release = cgroup_pressure_release,
5271 .name = "memory.pressure",
5272 .file_offset = offsetof(struct cgroup, psi_files[PSI_MEM]),
5273 .seq_show = cgroup_memory_pressure_show,
5274 .write = cgroup_memory_pressure_write,
5275 .poll = cgroup_pressure_poll,
5276 .release = cgroup_pressure_release,
5279 .name = "cpu.pressure",
5280 .file_offset = offsetof(struct cgroup, psi_files[PSI_CPU]),
5281 .seq_show = cgroup_cpu_pressure_show,
5282 .write = cgroup_cpu_pressure_write,
5283 .poll = cgroup_pressure_poll,
5284 .release = cgroup_pressure_release,
5286 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
5288 .name = "irq.pressure",
5289 .file_offset = offsetof(struct cgroup, psi_files[PSI_IRQ]),
5290 .seq_show = cgroup_irq_pressure_show,
5291 .write = cgroup_irq_pressure_write,
5292 .poll = cgroup_pressure_poll,
5293 .release = cgroup_pressure_release,
5297 .name = "cgroup.pressure",
5298 .seq_show = cgroup_pressure_show,
5299 .write = cgroup_pressure_write,
5301 #endif /* CONFIG_PSI */
5306 * css destruction is four-stage process.
5308 * 1. Destruction starts. Killing of the percpu_ref is initiated.
5309 * Implemented in kill_css().
5311 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
5312 * and thus css_tryget_online() is guaranteed to fail, the css can be
5313 * offlined by invoking offline_css(). After offlining, the base ref is
5314 * put. Implemented in css_killed_work_fn().
5316 * 3. When the percpu_ref reaches zero, the only possible remaining
5317 * accessors are inside RCU read sections. css_release() schedules the
5320 * 4. After the grace period, the css can be freed. Implemented in
5321 * css_free_work_fn().
5323 * It is actually hairier because both step 2 and 4 require process context
5324 * and thus involve punting to css->destroy_work adding two additional
5325 * steps to the already complex sequence.
5327 static void css_free_rwork_fn(struct work_struct *work)
5329 struct cgroup_subsys_state *css = container_of(to_rcu_work(work),
5330 struct cgroup_subsys_state, destroy_rwork);
5331 struct cgroup_subsys *ss = css->ss;
5332 struct cgroup *cgrp = css->cgroup;
5334 percpu_ref_exit(&css->refcnt);
5338 struct cgroup_subsys_state *parent = css->parent;
5342 cgroup_idr_remove(&ss->css_idr, id);
5348 /* cgroup free path */
5349 atomic_dec(&cgrp->root->nr_cgrps);
5350 cgroup1_pidlist_destroy_all(cgrp);
5351 cancel_work_sync(&cgrp->release_agent_work);
5353 if (cgroup_parent(cgrp)) {
5355 * We get a ref to the parent, and put the ref when
5356 * this cgroup is being freed, so it's guaranteed
5357 * that the parent won't be destroyed before its
5360 cgroup_put(cgroup_parent(cgrp));
5361 kernfs_put(cgrp->kn);
5362 psi_cgroup_free(cgrp);
5363 cgroup_rstat_exit(cgrp);
5367 * This is root cgroup's refcnt reaching zero,
5368 * which indicates that the root should be
5371 cgroup_destroy_root(cgrp->root);
5376 static void css_release_work_fn(struct work_struct *work)
5378 struct cgroup_subsys_state *css =
5379 container_of(work, struct cgroup_subsys_state, destroy_work);
5380 struct cgroup_subsys *ss = css->ss;
5381 struct cgroup *cgrp = css->cgroup;
5383 mutex_lock(&cgroup_mutex);
5385 css->flags |= CSS_RELEASED;
5386 list_del_rcu(&css->sibling);
5389 /* css release path */
5390 if (!list_empty(&css->rstat_css_node)) {
5391 cgroup_rstat_flush(cgrp);
5392 list_del_rcu(&css->rstat_css_node);
5395 cgroup_idr_replace(&ss->css_idr, NULL, css->id);
5396 if (ss->css_released)
5397 ss->css_released(css);
5399 struct cgroup *tcgrp;
5401 /* cgroup release path */
5402 TRACE_CGROUP_PATH(release, cgrp);
5404 cgroup_rstat_flush(cgrp);
5406 spin_lock_irq(&css_set_lock);
5407 for (tcgrp = cgroup_parent(cgrp); tcgrp;
5408 tcgrp = cgroup_parent(tcgrp))
5409 tcgrp->nr_dying_descendants--;
5410 spin_unlock_irq(&css_set_lock);
5413 * There are two control paths which try to determine
5414 * cgroup from dentry without going through kernfs -
5415 * cgroupstats_build() and css_tryget_online_from_dir().
5416 * Those are supported by RCU protecting clearing of
5417 * cgrp->kn->priv backpointer.
5420 RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv,
5424 mutex_unlock(&cgroup_mutex);
5426 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
5427 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
5430 static void css_release(struct percpu_ref *ref)
5432 struct cgroup_subsys_state *css =
5433 container_of(ref, struct cgroup_subsys_state, refcnt);
5435 INIT_WORK(&css->destroy_work, css_release_work_fn);
5436 queue_work(cgroup_destroy_wq, &css->destroy_work);
5439 static void init_and_link_css(struct cgroup_subsys_state *css,
5440 struct cgroup_subsys *ss, struct cgroup *cgrp)
5442 lockdep_assert_held(&cgroup_mutex);
5444 cgroup_get_live(cgrp);
5446 memset(css, 0, sizeof(*css));
5450 INIT_LIST_HEAD(&css->sibling);
5451 INIT_LIST_HEAD(&css->children);
5452 INIT_LIST_HEAD(&css->rstat_css_node);
5453 css->serial_nr = css_serial_nr_next++;
5454 atomic_set(&css->online_cnt, 0);
5456 if (cgroup_parent(cgrp)) {
5457 css->parent = cgroup_css(cgroup_parent(cgrp), ss);
5458 css_get(css->parent);
5461 if (ss->css_rstat_flush)
5462 list_add_rcu(&css->rstat_css_node, &cgrp->rstat_css_list);
5464 BUG_ON(cgroup_css(cgrp, ss));
5467 /* invoke ->css_online() on a new CSS and mark it online if successful */
5468 static int online_css(struct cgroup_subsys_state *css)
5470 struct cgroup_subsys *ss = css->ss;
5473 lockdep_assert_held(&cgroup_mutex);
5476 ret = ss->css_online(css);
5478 css->flags |= CSS_ONLINE;
5479 rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
5481 atomic_inc(&css->online_cnt);
5483 atomic_inc(&css->parent->online_cnt);
5488 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
5489 static void offline_css(struct cgroup_subsys_state *css)
5491 struct cgroup_subsys *ss = css->ss;
5493 lockdep_assert_held(&cgroup_mutex);
5495 if (!(css->flags & CSS_ONLINE))
5498 if (ss->css_offline)
5499 ss->css_offline(css);
5501 css->flags &= ~CSS_ONLINE;
5502 RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL);
5504 wake_up_all(&css->cgroup->offline_waitq);
5508 * css_create - create a cgroup_subsys_state
5509 * @cgrp: the cgroup new css will be associated with
5510 * @ss: the subsys of new css
5512 * Create a new css associated with @cgrp - @ss pair. On success, the new
5513 * css is online and installed in @cgrp. This function doesn't create the
5514 * interface files. Returns 0 on success, -errno on failure.
5516 static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
5517 struct cgroup_subsys *ss)
5519 struct cgroup *parent = cgroup_parent(cgrp);
5520 struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss);
5521 struct cgroup_subsys_state *css;
5524 lockdep_assert_held(&cgroup_mutex);
5526 css = ss->css_alloc(parent_css);
5528 css = ERR_PTR(-ENOMEM);
5532 init_and_link_css(css, ss, cgrp);
5534 err = percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL);
5538 err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL);
5543 /* @css is ready to be brought online now, make it visible */
5544 list_add_tail_rcu(&css->sibling, &parent_css->children);
5545 cgroup_idr_replace(&ss->css_idr, css, css->id);
5547 err = online_css(css);
5554 list_del_rcu(&css->sibling);
5556 list_del_rcu(&css->rstat_css_node);
5557 INIT_RCU_WORK(&css->destroy_rwork, css_free_rwork_fn);
5558 queue_rcu_work(cgroup_destroy_wq, &css->destroy_rwork);
5559 return ERR_PTR(err);
5563 * The returned cgroup is fully initialized including its control mask, but
5564 * it isn't associated with its kernfs_node and doesn't have the control
5567 static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
5570 struct cgroup_root *root = parent->root;
5571 struct cgroup *cgrp, *tcgrp;
5572 struct kernfs_node *kn;
5573 int level = parent->level + 1;
5576 /* allocate the cgroup and its ID, 0 is reserved for the root */
5577 cgrp = kzalloc(struct_size(cgrp, ancestors, (level + 1)), GFP_KERNEL);
5579 return ERR_PTR(-ENOMEM);
5581 ret = percpu_ref_init(&cgrp->self.refcnt, css_release, 0, GFP_KERNEL);
5585 ret = cgroup_rstat_init(cgrp);
5587 goto out_cancel_ref;
5589 /* create the directory */
5590 kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
5597 init_cgroup_housekeeping(cgrp);
5599 cgrp->self.parent = &parent->self;
5601 cgrp->level = level;
5603 ret = psi_cgroup_alloc(cgrp);
5605 goto out_kernfs_remove;
5607 ret = cgroup_bpf_inherit(cgrp);
5612 * New cgroup inherits effective freeze counter, and
5613 * if the parent has to be frozen, the child has too.
5615 cgrp->freezer.e_freeze = parent->freezer.e_freeze;
5616 if (cgrp->freezer.e_freeze) {
5618 * Set the CGRP_FREEZE flag, so when a process will be
5619 * attached to the child cgroup, it will become frozen.
5620 * At this point the new cgroup is unpopulated, so we can
5621 * consider it frozen immediately.
5623 set_bit(CGRP_FREEZE, &cgrp->flags);
5624 set_bit(CGRP_FROZEN, &cgrp->flags);
5627 spin_lock_irq(&css_set_lock);
5628 for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
5629 cgrp->ancestors[tcgrp->level] = tcgrp;
5631 if (tcgrp != cgrp) {
5632 tcgrp->nr_descendants++;
5635 * If the new cgroup is frozen, all ancestor cgroups
5636 * get a new frozen descendant, but their state can't
5637 * change because of this.
5639 if (cgrp->freezer.e_freeze)
5640 tcgrp->freezer.nr_frozen_descendants++;
5643 spin_unlock_irq(&css_set_lock);
5645 if (notify_on_release(parent))
5646 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
5648 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
5649 set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
5651 cgrp->self.serial_nr = css_serial_nr_next++;
5653 /* allocation complete, commit to creation */
5654 list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);
5655 atomic_inc(&root->nr_cgrps);
5656 cgroup_get_live(parent);
5659 * On the default hierarchy, a child doesn't automatically inherit
5660 * subtree_control from the parent. Each is configured manually.
5662 if (!cgroup_on_dfl(cgrp))
5663 cgrp->subtree_control = cgroup_control(cgrp);
5665 cgroup_propagate_control(cgrp);
5670 psi_cgroup_free(cgrp);
5672 kernfs_remove(cgrp->kn);
5674 cgroup_rstat_exit(cgrp);
5676 percpu_ref_exit(&cgrp->self.refcnt);
5679 return ERR_PTR(ret);
5682 static bool cgroup_check_hierarchy_limits(struct cgroup *parent)
5684 struct cgroup *cgroup;
5688 lockdep_assert_held(&cgroup_mutex);
5690 for (cgroup = parent; cgroup; cgroup = cgroup_parent(cgroup)) {
5691 if (cgroup->nr_descendants >= cgroup->max_descendants)
5694 if (level > cgroup->max_depth)
5705 int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
5707 struct cgroup *parent, *cgrp;
5710 /* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
5711 if (strchr(name, '\n'))
5714 parent = cgroup_kn_lock_live(parent_kn, false);
5718 if (!cgroup_check_hierarchy_limits(parent)) {
5723 cgrp = cgroup_create(parent, name, mode);
5725 ret = PTR_ERR(cgrp);
5730 * This extra ref will be put in cgroup_free_fn() and guarantees
5731 * that @cgrp->kn is always accessible.
5733 kernfs_get(cgrp->kn);
5735 ret = cgroup_kn_set_ugid(cgrp->kn);
5739 ret = css_populate_dir(&cgrp->self);
5743 ret = cgroup_apply_control_enable(cgrp);
5747 TRACE_CGROUP_PATH(mkdir, cgrp);
5749 /* let's create and online css's */
5750 kernfs_activate(cgrp->kn);
5756 cgroup_destroy_locked(cgrp);
5758 cgroup_kn_unlock(parent_kn);
5763 * This is called when the refcnt of a css is confirmed to be killed.
5764 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
5765 * initiate destruction and put the css ref from kill_css().
5767 static void css_killed_work_fn(struct work_struct *work)
5769 struct cgroup_subsys_state *css =
5770 container_of(work, struct cgroup_subsys_state, destroy_work);
5772 mutex_lock(&cgroup_mutex);
5777 /* @css can't go away while we're holding cgroup_mutex */
5779 } while (css && atomic_dec_and_test(&css->online_cnt));
5781 mutex_unlock(&cgroup_mutex);
5784 /* css kill confirmation processing requires process context, bounce */
5785 static void css_killed_ref_fn(struct percpu_ref *ref)
5787 struct cgroup_subsys_state *css =
5788 container_of(ref, struct cgroup_subsys_state, refcnt);
5790 if (atomic_dec_and_test(&css->online_cnt)) {
5791 INIT_WORK(&css->destroy_work, css_killed_work_fn);
5792 queue_work(cgroup_destroy_wq, &css->destroy_work);
5797 * kill_css - destroy a css
5798 * @css: css to destroy
5800 * This function initiates destruction of @css by removing cgroup interface
5801 * files and putting its base reference. ->css_offline() will be invoked
5802 * asynchronously once css_tryget_online() is guaranteed to fail and when
5803 * the reference count reaches zero, @css will be released.
5805 static void kill_css(struct cgroup_subsys_state *css)
5807 lockdep_assert_held(&cgroup_mutex);
5809 if (css->flags & CSS_DYING)
5812 css->flags |= CSS_DYING;
5815 * This must happen before css is disassociated with its cgroup.
5816 * See seq_css() for details.
5821 * Killing would put the base ref, but we need to keep it alive
5822 * until after ->css_offline().
5827 * cgroup core guarantees that, by the time ->css_offline() is
5828 * invoked, no new css reference will be given out via
5829 * css_tryget_online(). We can't simply call percpu_ref_kill() and
5830 * proceed to offlining css's because percpu_ref_kill() doesn't
5831 * guarantee that the ref is seen as killed on all CPUs on return.
5833 * Use percpu_ref_kill_and_confirm() to get notifications as each
5834 * css is confirmed to be seen as killed on all CPUs.
5836 percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
5840 * cgroup_destroy_locked - the first stage of cgroup destruction
5841 * @cgrp: cgroup to be destroyed
5843 * css's make use of percpu refcnts whose killing latency shouldn't be
5844 * exposed to userland and are RCU protected. Also, cgroup core needs to
5845 * guarantee that css_tryget_online() won't succeed by the time
5846 * ->css_offline() is invoked. To satisfy all the requirements,
5847 * destruction is implemented in the following two steps.
5849 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
5850 * userland visible parts and start killing the percpu refcnts of
5851 * css's. Set up so that the next stage will be kicked off once all
5852 * the percpu refcnts are confirmed to be killed.
5854 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
5855 * rest of destruction. Once all cgroup references are gone, the
5856 * cgroup is RCU-freed.
5858 * This function implements s1. After this step, @cgrp is gone as far as
5859 * the userland is concerned and a new cgroup with the same name may be
5860 * created. As cgroup doesn't care about the names internally, this
5861 * doesn't cause any problem.
5863 static int cgroup_destroy_locked(struct cgroup *cgrp)
5864 __releases(&cgroup_mutex) __acquires(&cgroup_mutex)
5866 struct cgroup *tcgrp, *parent = cgroup_parent(cgrp);
5867 struct cgroup_subsys_state *css;
5868 struct cgrp_cset_link *link;
5871 lockdep_assert_held(&cgroup_mutex);
5874 * Only migration can raise populated from zero and we're already
5875 * holding cgroup_mutex.
5877 if (cgroup_is_populated(cgrp))
5881 * Make sure there's no live children. We can't test emptiness of
5882 * ->self.children as dead children linger on it while being
5883 * drained; otherwise, "rmdir parent/child parent" may fail.
5885 if (css_has_online_children(&cgrp->self))
5889 * Mark @cgrp and the associated csets dead. The former prevents
5890 * further task migration and child creation by disabling
5891 * cgroup_lock_live_group(). The latter makes the csets ignored by
5892 * the migration path.
5894 cgrp->self.flags &= ~CSS_ONLINE;
5896 spin_lock_irq(&css_set_lock);
5897 list_for_each_entry(link, &cgrp->cset_links, cset_link)
5898 link->cset->dead = true;
5899 spin_unlock_irq(&css_set_lock);
5901 /* initiate massacre of all css's */
5902 for_each_css(css, ssid, cgrp)
5905 /* clear and remove @cgrp dir, @cgrp has an extra ref on its kn */
5906 css_clear_dir(&cgrp->self);
5907 kernfs_remove(cgrp->kn);
5909 if (cgroup_is_threaded(cgrp))
5910 parent->nr_threaded_children--;
5912 spin_lock_irq(&css_set_lock);
5913 for (tcgrp = cgroup_parent(cgrp); tcgrp; tcgrp = cgroup_parent(tcgrp)) {
5914 tcgrp->nr_descendants--;
5915 tcgrp->nr_dying_descendants++;
5917 * If the dying cgroup is frozen, decrease frozen descendants
5918 * counters of ancestor cgroups.
5920 if (test_bit(CGRP_FROZEN, &cgrp->flags))
5921 tcgrp->freezer.nr_frozen_descendants--;
5923 spin_unlock_irq(&css_set_lock);
5925 cgroup1_check_for_release(parent);
5927 cgroup_bpf_offline(cgrp);
5929 /* put the base reference */
5930 percpu_ref_kill(&cgrp->self.refcnt);
5935 int cgroup_rmdir(struct kernfs_node *kn)
5937 struct cgroup *cgrp;
5940 cgrp = cgroup_kn_lock_live(kn, false);
5944 ret = cgroup_destroy_locked(cgrp);
5946 TRACE_CGROUP_PATH(rmdir, cgrp);
5948 cgroup_kn_unlock(kn);
5952 static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
5953 .show_options = cgroup_show_options,
5954 .mkdir = cgroup_mkdir,
5955 .rmdir = cgroup_rmdir,
5956 .show_path = cgroup_show_path,
5959 static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
5961 struct cgroup_subsys_state *css;
5963 pr_debug("Initializing cgroup subsys %s\n", ss->name);
5965 mutex_lock(&cgroup_mutex);
5967 idr_init(&ss->css_idr);
5968 INIT_LIST_HEAD(&ss->cfts);
5970 /* Create the root cgroup state for this subsystem */
5971 ss->root = &cgrp_dfl_root;
5972 css = ss->css_alloc(NULL);
5973 /* We don't handle early failures gracefully */
5974 BUG_ON(IS_ERR(css));
5975 init_and_link_css(css, ss, &cgrp_dfl_root.cgrp);
5978 * Root csses are never destroyed and we can't initialize
5979 * percpu_ref during early init. Disable refcnting.
5981 css->flags |= CSS_NO_REF;
5984 /* allocation can't be done safely during early init */
5987 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL);
5988 BUG_ON(css->id < 0);
5991 /* Update the init_css_set to contain a subsys
5992 * pointer to this state - since the subsystem is
5993 * newly registered, all tasks and hence the
5994 * init_css_set is in the subsystem's root cgroup. */
5995 init_css_set.subsys[ss->id] = css;
5997 have_fork_callback |= (bool)ss->fork << ss->id;
5998 have_exit_callback |= (bool)ss->exit << ss->id;
5999 have_release_callback |= (bool)ss->release << ss->id;
6000 have_canfork_callback |= (bool)ss->can_fork << ss->id;
6002 /* At system boot, before all subsystems have been
6003 * registered, no tasks have been forked, so we don't
6004 * need to invoke fork callbacks here. */
6005 BUG_ON(!list_empty(&init_task.tasks));
6007 BUG_ON(online_css(css));
6009 mutex_unlock(&cgroup_mutex);
6013 * cgroup_init_early - cgroup initialization at system boot
6015 * Initialize cgroups at system boot, and initialize any
6016 * subsystems that request early init.
6018 int __init cgroup_init_early(void)
6020 static struct cgroup_fs_context __initdata ctx;
6021 struct cgroup_subsys *ss;
6024 ctx.root = &cgrp_dfl_root;
6025 init_cgroup_root(&ctx);
6026 cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF;
6028 RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
6030 for_each_subsys(ss, i) {
6031 WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
6032 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p id:name=%d:%s\n",
6033 i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
6035 WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
6036 "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
6039 ss->name = cgroup_subsys_name[i];
6040 if (!ss->legacy_name)
6041 ss->legacy_name = cgroup_subsys_name[i];
6044 cgroup_init_subsys(ss, true);
6050 * cgroup_init - cgroup initialization
6052 * Register cgroup filesystem and /proc file, and initialize
6053 * any subsystems that didn't request early init.
6055 int __init cgroup_init(void)
6057 struct cgroup_subsys *ss;
6060 BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
6061 BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
6062 BUG_ON(cgroup_init_cftypes(NULL, cgroup_psi_files));
6063 BUG_ON(cgroup_init_cftypes(NULL, cgroup1_base_files));
6065 cgroup_rstat_boot();
6067 get_user_ns(init_cgroup_ns.user_ns);
6069 mutex_lock(&cgroup_mutex);
6072 * Add init_css_set to the hash table so that dfl_root can link to
6075 hash_add(css_set_table, &init_css_set.hlist,
6076 css_set_hash(init_css_set.subsys));
6078 BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0));
6080 mutex_unlock(&cgroup_mutex);
6082 for_each_subsys(ss, ssid) {
6083 if (ss->early_init) {
6084 struct cgroup_subsys_state *css =
6085 init_css_set.subsys[ss->id];
6087 css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2,
6089 BUG_ON(css->id < 0);
6091 cgroup_init_subsys(ss, false);
6094 list_add_tail(&init_css_set.e_cset_node[ssid],
6095 &cgrp_dfl_root.cgrp.e_csets[ssid]);
6098 * Setting dfl_root subsys_mask needs to consider the
6099 * disabled flag and cftype registration needs kmalloc,
6100 * both of which aren't available during early_init.
6102 if (!cgroup_ssid_enabled(ssid))
6105 if (cgroup1_ssid_disabled(ssid))
6106 printk(KERN_INFO "Disabling %s control group subsystem in v1 mounts\n",
6109 cgrp_dfl_root.subsys_mask |= 1 << ss->id;
6111 /* implicit controllers must be threaded too */
6112 WARN_ON(ss->implicit_on_dfl && !ss->threaded);
6114 if (ss->implicit_on_dfl)
6115 cgrp_dfl_implicit_ss_mask |= 1 << ss->id;
6116 else if (!ss->dfl_cftypes)
6117 cgrp_dfl_inhibit_ss_mask |= 1 << ss->id;
6120 cgrp_dfl_threaded_ss_mask |= 1 << ss->id;
6122 if (ss->dfl_cftypes == ss->legacy_cftypes) {
6123 WARN_ON(cgroup_add_cftypes(ss, ss->dfl_cftypes));
6125 WARN_ON(cgroup_add_dfl_cftypes(ss, ss->dfl_cftypes));
6126 WARN_ON(cgroup_add_legacy_cftypes(ss, ss->legacy_cftypes));
6130 ss->bind(init_css_set.subsys[ssid]);
6132 mutex_lock(&cgroup_mutex);
6133 css_populate_dir(init_css_set.subsys[ssid]);
6134 mutex_unlock(&cgroup_mutex);
6137 /* init_css_set.subsys[] has been updated, re-hash */
6138 hash_del(&init_css_set.hlist);
6139 hash_add(css_set_table, &init_css_set.hlist,
6140 css_set_hash(init_css_set.subsys));
6142 WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup"));
6143 WARN_ON(register_filesystem(&cgroup_fs_type));
6144 WARN_ON(register_filesystem(&cgroup2_fs_type));
6145 WARN_ON(!proc_create_single("cgroups", 0, NULL, proc_cgroupstats_show));
6146 #ifdef CONFIG_CPUSETS
6147 WARN_ON(register_filesystem(&cpuset_fs_type));
6153 static int __init cgroup_wq_init(void)
6156 * There isn't much point in executing destruction path in
6157 * parallel. Good chunk is serialized with cgroup_mutex anyway.
6158 * Use 1 for @max_active.
6160 * We would prefer to do this in cgroup_init() above, but that
6161 * is called before init_workqueues(): so leave this until after.
6163 cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
6164 BUG_ON(!cgroup_destroy_wq);
6167 core_initcall(cgroup_wq_init);
6169 void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
6171 struct kernfs_node *kn;
6173 kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
6176 kernfs_path(kn, buf, buflen);
6181 * cgroup_get_from_id : get the cgroup associated with cgroup id
6183 * On success return the cgrp or ERR_PTR on failure
6184 * Only cgroups within current task's cgroup NS are valid.
6186 struct cgroup *cgroup_get_from_id(u64 id)
6188 struct kernfs_node *kn;
6189 struct cgroup *cgrp, *root_cgrp;
6191 kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
6193 return ERR_PTR(-ENOENT);
6195 if (kernfs_type(kn) != KERNFS_DIR) {
6197 return ERR_PTR(-ENOENT);
6202 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6203 if (cgrp && !cgroup_tryget(cgrp))
6210 return ERR_PTR(-ENOENT);
6212 root_cgrp = current_cgns_cgroup_dfl();
6213 if (!cgroup_is_descendant(cgrp, root_cgrp)) {
6215 return ERR_PTR(-ENOENT);
6220 EXPORT_SYMBOL_GPL(cgroup_get_from_id);
6223 * proc_cgroup_show()
6224 * - Print task's cgroup paths into seq_file, one line for each hierarchy
6225 * - Used for /proc/<pid>/cgroup.
6227 int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
6228 struct pid *pid, struct task_struct *tsk)
6232 struct cgroup_root *root;
6235 buf = kmalloc(PATH_MAX, GFP_KERNEL);
6239 mutex_lock(&cgroup_mutex);
6240 spin_lock_irq(&css_set_lock);
6242 for_each_root(root) {
6243 struct cgroup_subsys *ss;
6244 struct cgroup *cgrp;
6245 int ssid, count = 0;
6247 if (root == &cgrp_dfl_root && !READ_ONCE(cgrp_dfl_visible))
6250 seq_printf(m, "%d:", root->hierarchy_id);
6251 if (root != &cgrp_dfl_root)
6252 for_each_subsys(ss, ssid)
6253 if (root->subsys_mask & (1 << ssid))
6254 seq_printf(m, "%s%s", count++ ? "," : "",
6256 if (strlen(root->name))
6257 seq_printf(m, "%sname=%s", count ? "," : "",
6261 cgrp = task_cgroup_from_root(tsk, root);
6264 * On traditional hierarchies, all zombie tasks show up as
6265 * belonging to the root cgroup. On the default hierarchy,
6266 * while a zombie doesn't show up in "cgroup.procs" and
6267 * thus can't be migrated, its /proc/PID/cgroup keeps
6268 * reporting the cgroup it belonged to before exiting. If
6269 * the cgroup is removed before the zombie is reaped,
6270 * " (deleted)" is appended to the cgroup path.
6272 if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) {
6273 retval = cgroup_path_ns_locked(cgrp, buf, PATH_MAX,
6274 current->nsproxy->cgroup_ns);
6275 if (retval >= PATH_MAX)
6276 retval = -ENAMETOOLONG;
6285 if (cgroup_on_dfl(cgrp) && cgroup_is_dead(cgrp))
6286 seq_puts(m, " (deleted)\n");
6293 spin_unlock_irq(&css_set_lock);
6294 mutex_unlock(&cgroup_mutex);
6301 * cgroup_fork - initialize cgroup related fields during copy_process()
6302 * @child: pointer to task_struct of forking parent process.
6304 * A task is associated with the init_css_set until cgroup_post_fork()
6305 * attaches it to the target css_set.
6307 void cgroup_fork(struct task_struct *child)
6309 RCU_INIT_POINTER(child->cgroups, &init_css_set);
6310 INIT_LIST_HEAD(&child->cg_list);
6314 * cgroup_v1v2_get_from_file - get a cgroup pointer from a file pointer
6315 * @f: file corresponding to cgroup_dir
6317 * Find the cgroup from a file pointer associated with a cgroup directory.
6318 * Returns a pointer to the cgroup on success. ERR_PTR is returned if the
6319 * cgroup cannot be found.
6321 static struct cgroup *cgroup_v1v2_get_from_file(struct file *f)
6323 struct cgroup_subsys_state *css;
6325 css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
6327 return ERR_CAST(css);
6333 * cgroup_get_from_file - same as cgroup_v1v2_get_from_file, but only supports
6335 * @f: file corresponding to cgroup2_dir
6337 static struct cgroup *cgroup_get_from_file(struct file *f)
6339 struct cgroup *cgrp = cgroup_v1v2_get_from_file(f);
6342 return ERR_CAST(cgrp);
6344 if (!cgroup_on_dfl(cgrp)) {
6346 return ERR_PTR(-EBADF);
6353 * cgroup_css_set_fork - find or create a css_set for a child process
6354 * @kargs: the arguments passed to create the child process
6356 * This functions finds or creates a new css_set which the child
6357 * process will be attached to in cgroup_post_fork(). By default,
6358 * the child process will be given the same css_set as its parent.
6360 * If CLONE_INTO_CGROUP is specified this function will try to find an
6361 * existing css_set which includes the requested cgroup and if not create
6362 * a new css_set that the child will be attached to later. If this function
6363 * succeeds it will hold cgroup_threadgroup_rwsem on return. If
6364 * CLONE_INTO_CGROUP is requested this function will grab cgroup mutex
6365 * before grabbing cgroup_threadgroup_rwsem and will hold a reference
6366 * to the target cgroup.
6368 static int cgroup_css_set_fork(struct kernel_clone_args *kargs)
6369 __acquires(&cgroup_mutex) __acquires(&cgroup_threadgroup_rwsem)
6372 struct cgroup *dst_cgrp = NULL;
6373 struct css_set *cset;
6374 struct super_block *sb;
6377 if (kargs->flags & CLONE_INTO_CGROUP)
6378 mutex_lock(&cgroup_mutex);
6380 cgroup_threadgroup_change_begin(current);
6382 spin_lock_irq(&css_set_lock);
6383 cset = task_css_set(current);
6385 spin_unlock_irq(&css_set_lock);
6387 if (!(kargs->flags & CLONE_INTO_CGROUP)) {
6392 f = fget_raw(kargs->cgroup);
6397 sb = f->f_path.dentry->d_sb;
6399 dst_cgrp = cgroup_get_from_file(f);
6400 if (IS_ERR(dst_cgrp)) {
6401 ret = PTR_ERR(dst_cgrp);
6406 if (cgroup_is_dead(dst_cgrp)) {
6412 * Verify that we the target cgroup is writable for us. This is
6413 * usually done by the vfs layer but since we're not going through
6414 * the vfs layer here we need to do it "manually".
6416 ret = cgroup_may_write(dst_cgrp, sb);
6421 * Spawning a task directly into a cgroup works by passing a file
6422 * descriptor to the target cgroup directory. This can even be an O_PATH
6423 * file descriptor. But it can never be a cgroup.procs file descriptor.
6424 * This was done on purpose so spawning into a cgroup could be
6425 * conceptualized as an atomic
6427 * fd = openat(dfd_cgroup, "cgroup.procs", ...);
6428 * write(fd, <child-pid>, ...);
6430 * sequence, i.e. it's a shorthand for the caller opening and writing
6431 * cgroup.procs of the cgroup indicated by @dfd_cgroup. This allows us
6432 * to always use the caller's credentials.
6434 ret = cgroup_attach_permissions(cset->dfl_cgrp, dst_cgrp, sb,
6435 !(kargs->flags & CLONE_THREAD),
6436 current->nsproxy->cgroup_ns);
6440 kargs->cset = find_css_set(cset, dst_cgrp);
6448 kargs->cgrp = dst_cgrp;
6452 cgroup_threadgroup_change_end(current);
6453 mutex_unlock(&cgroup_mutex);
6457 cgroup_put(dst_cgrp);
6460 put_css_set(kargs->cset);
6465 * cgroup_css_set_put_fork - drop references we took during fork
6466 * @kargs: the arguments passed to create the child process
6468 * Drop references to the prepared css_set and target cgroup if
6469 * CLONE_INTO_CGROUP was requested.
6471 static void cgroup_css_set_put_fork(struct kernel_clone_args *kargs)
6472 __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
6474 cgroup_threadgroup_change_end(current);
6476 if (kargs->flags & CLONE_INTO_CGROUP) {
6477 struct cgroup *cgrp = kargs->cgrp;
6478 struct css_set *cset = kargs->cset;
6480 mutex_unlock(&cgroup_mutex);
6495 * cgroup_can_fork - called on a new task before the process is exposed
6496 * @child: the child process
6497 * @kargs: the arguments passed to create the child process
6499 * This prepares a new css_set for the child process which the child will
6500 * be attached to in cgroup_post_fork().
6501 * This calls the subsystem can_fork() callbacks. If the cgroup_can_fork()
6502 * callback returns an error, the fork aborts with that error code. This
6503 * allows for a cgroup subsystem to conditionally allow or deny new forks.
6505 int cgroup_can_fork(struct task_struct *child, struct kernel_clone_args *kargs)
6507 struct cgroup_subsys *ss;
6510 ret = cgroup_css_set_fork(kargs);
6514 do_each_subsys_mask(ss, i, have_canfork_callback) {
6515 ret = ss->can_fork(child, kargs->cset);
6518 } while_each_subsys_mask();
6523 for_each_subsys(ss, j) {
6526 if (ss->cancel_fork)
6527 ss->cancel_fork(child, kargs->cset);
6530 cgroup_css_set_put_fork(kargs);
6536 * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
6537 * @child: the child process
6538 * @kargs: the arguments passed to create the child process
6540 * This calls the cancel_fork() callbacks if a fork failed *after*
6541 * cgroup_can_fork() succeeded and cleans up references we took to
6542 * prepare a new css_set for the child process in cgroup_can_fork().
6544 void cgroup_cancel_fork(struct task_struct *child,
6545 struct kernel_clone_args *kargs)
6547 struct cgroup_subsys *ss;
6550 for_each_subsys(ss, i)
6551 if (ss->cancel_fork)
6552 ss->cancel_fork(child, kargs->cset);
6554 cgroup_css_set_put_fork(kargs);
6558 * cgroup_post_fork - finalize cgroup setup for the child process
6559 * @child: the child process
6560 * @kargs: the arguments passed to create the child process
6562 * Attach the child process to its css_set calling the subsystem fork()
6565 void cgroup_post_fork(struct task_struct *child,
6566 struct kernel_clone_args *kargs)
6567 __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
6569 unsigned long cgrp_flags = 0;
6571 struct cgroup_subsys *ss;
6572 struct css_set *cset;
6578 spin_lock_irq(&css_set_lock);
6580 /* init tasks are special, only link regular threads */
6581 if (likely(child->pid)) {
6583 cgrp_flags = kargs->cgrp->flags;
6585 cgrp_flags = cset->dfl_cgrp->flags;
6587 WARN_ON_ONCE(!list_empty(&child->cg_list));
6589 css_set_move_task(child, NULL, cset, false);
6595 if (!(child->flags & PF_KTHREAD)) {
6596 if (unlikely(test_bit(CGRP_FREEZE, &cgrp_flags))) {
6598 * If the cgroup has to be frozen, the new task has
6599 * too. Let's set the JOBCTL_TRAP_FREEZE jobctl bit to
6600 * get the task into the frozen state.
6602 spin_lock(&child->sighand->siglock);
6603 WARN_ON_ONCE(child->frozen);
6604 child->jobctl |= JOBCTL_TRAP_FREEZE;
6605 spin_unlock(&child->sighand->siglock);
6608 * Calling cgroup_update_frozen() isn't required here,
6609 * because it will be called anyway a bit later from
6610 * do_freezer_trap(). So we avoid cgroup's transient
6611 * switch from the frozen state and back.
6616 * If the cgroup is to be killed notice it now and take the
6617 * child down right after we finished preparing it for
6620 kill = test_bit(CGRP_KILL, &cgrp_flags);
6623 spin_unlock_irq(&css_set_lock);
6626 * Call ss->fork(). This must happen after @child is linked on
6627 * css_set; otherwise, @child might change state between ->fork()
6628 * and addition to css_set.
6630 do_each_subsys_mask(ss, i, have_fork_callback) {
6632 } while_each_subsys_mask();
6634 /* Make the new cset the root_cset of the new cgroup namespace. */
6635 if (kargs->flags & CLONE_NEWCGROUP) {
6636 struct css_set *rcset = child->nsproxy->cgroup_ns->root_cset;
6639 child->nsproxy->cgroup_ns->root_cset = cset;
6643 /* Cgroup has to be killed so take down child immediately. */
6645 do_send_sig_info(SIGKILL, SEND_SIG_NOINFO, child, PIDTYPE_TGID);
6647 cgroup_css_set_put_fork(kargs);
6651 * cgroup_exit - detach cgroup from exiting task
6652 * @tsk: pointer to task_struct of exiting process
6654 * Description: Detach cgroup from @tsk.
6657 void cgroup_exit(struct task_struct *tsk)
6659 struct cgroup_subsys *ss;
6660 struct css_set *cset;
6663 spin_lock_irq(&css_set_lock);
6665 WARN_ON_ONCE(list_empty(&tsk->cg_list));
6666 cset = task_css_set(tsk);
6667 css_set_move_task(tsk, cset, NULL, false);
6668 list_add_tail(&tsk->cg_list, &cset->dying_tasks);
6671 WARN_ON_ONCE(cgroup_task_frozen(tsk));
6672 if (unlikely(!(tsk->flags & PF_KTHREAD) &&
6673 test_bit(CGRP_FREEZE, &task_dfl_cgroup(tsk)->flags)))
6674 cgroup_update_frozen(task_dfl_cgroup(tsk));
6676 spin_unlock_irq(&css_set_lock);
6678 /* see cgroup_post_fork() for details */
6679 do_each_subsys_mask(ss, i, have_exit_callback) {
6681 } while_each_subsys_mask();
6684 void cgroup_release(struct task_struct *task)
6686 struct cgroup_subsys *ss;
6689 do_each_subsys_mask(ss, ssid, have_release_callback) {
6691 } while_each_subsys_mask();
6693 spin_lock_irq(&css_set_lock);
6694 css_set_skip_task_iters(task_css_set(task), task);
6695 list_del_init(&task->cg_list);
6696 spin_unlock_irq(&css_set_lock);
6699 void cgroup_free(struct task_struct *task)
6701 struct css_set *cset = task_css_set(task);
6705 static int __init cgroup_disable(char *str)
6707 struct cgroup_subsys *ss;
6711 while ((token = strsep(&str, ",")) != NULL) {
6715 for_each_subsys(ss, i) {
6716 if (strcmp(token, ss->name) &&
6717 strcmp(token, ss->legacy_name))
6720 static_branch_disable(cgroup_subsys_enabled_key[i]);
6721 pr_info("Disabling %s control group subsystem\n",
6725 for (i = 0; i < OPT_FEATURE_COUNT; i++) {
6726 if (strcmp(token, cgroup_opt_feature_names[i]))
6728 cgroup_feature_disable_mask |= 1 << i;
6729 pr_info("Disabling %s control group feature\n",
6730 cgroup_opt_feature_names[i]);
6736 __setup("cgroup_disable=", cgroup_disable);
6738 void __init __weak enable_debug_cgroup(void) { }
6740 static int __init enable_cgroup_debug(char *str)
6742 cgroup_debug = true;
6743 enable_debug_cgroup();
6746 __setup("cgroup_debug", enable_cgroup_debug);
6749 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
6750 * @dentry: directory dentry of interest
6751 * @ss: subsystem of interest
6753 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
6754 * to get the corresponding css and return it. If such css doesn't exist
6755 * or can't be pinned, an ERR_PTR value is returned.
6757 struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
6758 struct cgroup_subsys *ss)
6760 struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
6761 struct file_system_type *s_type = dentry->d_sb->s_type;
6762 struct cgroup_subsys_state *css = NULL;
6763 struct cgroup *cgrp;
6765 /* is @dentry a cgroup dir? */
6766 if ((s_type != &cgroup_fs_type && s_type != &cgroup2_fs_type) ||
6767 !kn || kernfs_type(kn) != KERNFS_DIR)
6768 return ERR_PTR(-EBADF);
6773 * This path doesn't originate from kernfs and @kn could already
6774 * have been or be removed at any point. @kn->priv is RCU
6775 * protected for this access. See css_release_work_fn() for details.
6777 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6779 css = cgroup_css(cgrp, ss);
6781 if (!css || !css_tryget_online(css))
6782 css = ERR_PTR(-ENOENT);
6789 * css_from_id - lookup css by id
6790 * @id: the cgroup id
6791 * @ss: cgroup subsys to be looked into
6793 * Returns the css if there's valid one with @id, otherwise returns NULL.
6794 * Should be called under rcu_read_lock().
6796 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
6798 WARN_ON_ONCE(!rcu_read_lock_held());
6799 return idr_find(&ss->css_idr, id);
6803 * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path
6804 * @path: path on the default hierarchy
6806 * Find the cgroup at @path on the default hierarchy, increment its
6807 * reference count and return it. Returns pointer to the found cgroup on
6808 * success, ERR_PTR(-ENOENT) if @path doesn't exist or if the cgroup has already
6809 * been released and ERR_PTR(-ENOTDIR) if @path points to a non-directory.
6811 struct cgroup *cgroup_get_from_path(const char *path)
6813 struct kernfs_node *kn;
6814 struct cgroup *cgrp = ERR_PTR(-ENOENT);
6815 struct cgroup *root_cgrp;
6817 root_cgrp = current_cgns_cgroup_dfl();
6818 kn = kernfs_walk_and_get(root_cgrp->kn, path);
6822 if (kernfs_type(kn) != KERNFS_DIR) {
6823 cgrp = ERR_PTR(-ENOTDIR);
6829 cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
6830 if (!cgrp || !cgroup_tryget(cgrp))
6831 cgrp = ERR_PTR(-ENOENT);
6840 EXPORT_SYMBOL_GPL(cgroup_get_from_path);
6843 * cgroup_v1v2_get_from_fd - get a cgroup pointer from a fd
6844 * @fd: fd obtained by open(cgroup_dir)
6846 * Find the cgroup from a fd which should be obtained
6847 * by opening a cgroup directory. Returns a pointer to the
6848 * cgroup on success. ERR_PTR is returned if the cgroup
6851 struct cgroup *cgroup_v1v2_get_from_fd(int fd)
6853 struct cgroup *cgrp;
6858 return ERR_PTR(-EBADF);
6860 cgrp = cgroup_v1v2_get_from_file(f);
6866 * cgroup_get_from_fd - same as cgroup_v1v2_get_from_fd, but only supports
6868 * @fd: fd obtained by open(cgroup2_dir)
6870 struct cgroup *cgroup_get_from_fd(int fd)
6872 struct cgroup *cgrp = cgroup_v1v2_get_from_fd(fd);
6875 return ERR_CAST(cgrp);
6877 if (!cgroup_on_dfl(cgrp)) {
6879 return ERR_PTR(-EBADF);
6883 EXPORT_SYMBOL_GPL(cgroup_get_from_fd);
6885 static u64 power_of_ten(int power)
6894 * cgroup_parse_float - parse a floating number
6895 * @input: input string
6896 * @dec_shift: number of decimal digits to shift
6899 * Parse a decimal floating point number in @input and store the result in
6900 * @v with decimal point right shifted @dec_shift times. For example, if
6901 * @input is "12.3456" and @dec_shift is 3, *@v will be set to 12345.
6902 * Returns 0 on success, -errno otherwise.
6904 * There's nothing cgroup specific about this function except that it's
6905 * currently the only user.
6907 int cgroup_parse_float(const char *input, unsigned dec_shift, s64 *v)
6909 s64 whole, frac = 0;
6910 int fstart = 0, fend = 0, flen;
6912 if (!sscanf(input, "%lld.%n%lld%n", &whole, &fstart, &frac, &fend))
6917 flen = fend > fstart ? fend - fstart : 0;
6918 if (flen < dec_shift)
6919 frac *= power_of_ten(dec_shift - flen);
6921 frac = DIV_ROUND_CLOSEST_ULL(frac, power_of_ten(flen - dec_shift));
6923 *v = whole * power_of_ten(dec_shift) + frac;
6928 * sock->sk_cgrp_data handling. For more info, see sock_cgroup_data
6929 * definition in cgroup-defs.h.
6931 #ifdef CONFIG_SOCK_CGROUP_DATA
6933 void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
6935 struct cgroup *cgroup;
6938 /* Don't associate the sock with unrelated interrupted task's cgroup. */
6939 if (in_interrupt()) {
6940 cgroup = &cgrp_dfl_root.cgrp;
6946 struct css_set *cset;
6948 cset = task_css_set(current);
6949 if (likely(cgroup_tryget(cset->dfl_cgrp))) {
6950 cgroup = cset->dfl_cgrp;
6956 skcd->cgroup = cgroup;
6957 cgroup_bpf_get(cgroup);
6961 void cgroup_sk_clone(struct sock_cgroup_data *skcd)
6963 struct cgroup *cgrp = sock_cgroup_ptr(skcd);
6966 * We might be cloning a socket which is left in an empty
6967 * cgroup and the cgroup might have already been rmdir'd.
6968 * Don't use cgroup_get_live().
6971 cgroup_bpf_get(cgrp);
6974 void cgroup_sk_free(struct sock_cgroup_data *skcd)
6976 struct cgroup *cgrp = sock_cgroup_ptr(skcd);
6978 cgroup_bpf_put(cgrp);
6982 #endif /* CONFIG_SOCK_CGROUP_DATA */
6985 static ssize_t show_delegatable_files(struct cftype *files, char *buf,
6986 ssize_t size, const char *prefix)
6991 for (cft = files; cft && cft->name[0] != '\0'; cft++) {
6992 if (!(cft->flags & CFTYPE_NS_DELEGATABLE))
6996 ret += snprintf(buf + ret, size - ret, "%s.", prefix);
6998 ret += snprintf(buf + ret, size - ret, "%s\n", cft->name);
7000 if (WARN_ON(ret >= size))
7007 static ssize_t delegate_show(struct kobject *kobj, struct kobj_attribute *attr,
7010 struct cgroup_subsys *ss;
7014 ret = show_delegatable_files(cgroup_base_files, buf + ret,
7015 PAGE_SIZE - ret, NULL);
7016 if (cgroup_psi_enabled())
7017 ret += show_delegatable_files(cgroup_psi_files, buf + ret,
7018 PAGE_SIZE - ret, NULL);
7020 for_each_subsys(ss, ssid)
7021 ret += show_delegatable_files(ss->dfl_cftypes, buf + ret,
7023 cgroup_subsys_name[ssid]);
7027 static struct kobj_attribute cgroup_delegate_attr = __ATTR_RO(delegate);
7029 static ssize_t features_show(struct kobject *kobj, struct kobj_attribute *attr,
7032 return snprintf(buf, PAGE_SIZE,
7035 "memory_localevents\n"
7036 "memory_recursiveprot\n");
7038 static struct kobj_attribute cgroup_features_attr = __ATTR_RO(features);
7040 static struct attribute *cgroup_sysfs_attrs[] = {
7041 &cgroup_delegate_attr.attr,
7042 &cgroup_features_attr.attr,
7046 static const struct attribute_group cgroup_sysfs_attr_group = {
7047 .attrs = cgroup_sysfs_attrs,
7051 static int __init cgroup_sysfs_init(void)
7053 return sysfs_create_group(kernel_kobj, &cgroup_sysfs_attr_group);
7055 subsys_initcall(cgroup_sysfs_init);
7057 #endif /* CONFIG_SYSFS */