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 <linux/cgroup.h>
32 #include <linux/cred.h>
33 #include <linux/ctype.h>
34 #include <linux/errno.h>
35 #include <linux/init_task.h>
36 #include <linux/kernel.h>
37 #include <linux/list.h>
38 #include <linux/magic.h>
40 #include <linux/mutex.h>
41 #include <linux/mount.h>
42 #include <linux/pagemap.h>
43 #include <linux/proc_fs.h>
44 #include <linux/rcupdate.h>
45 #include <linux/sched.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/sort.h>
51 #include <linux/kmod.h>
52 #include <linux/delayacct.h>
53 #include <linux/cgroupstats.h>
54 #include <linux/hashtable.h>
55 #include <linux/pid_namespace.h>
56 #include <linux/idr.h>
57 #include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
58 #include <linux/kthread.h>
59 #include <linux/delay.h>
60 #include <linux/atomic.h>
61 #include <linux/cpuset.h>
65 * pidlists linger the following amount before being destroyed. The goal
66 * is avoiding frequent destruction in the middle of consecutive read calls
67 * Expiring in the middle is a performance problem not a correctness one.
68 * 1 sec should be enough.
70 #define CGROUP_PIDLIST_DESTROY_DELAY HZ
72 #define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
76 * cgroup_mutex is the master lock. Any modification to cgroup or its
77 * hierarchy must be performed while holding it.
79 * css_set_lock protects task->cgroups pointer, the list of css_set
80 * objects, and the chain of tasks off each css_set.
82 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
83 * cgroup.h can use them for lockdep annotations.
85 #ifdef CONFIG_PROVE_RCU
86 DEFINE_MUTEX(cgroup_mutex
);
87 DEFINE_SPINLOCK(css_set_lock
);
88 EXPORT_SYMBOL_GPL(cgroup_mutex
);
89 EXPORT_SYMBOL_GPL(css_set_lock
);
91 static DEFINE_MUTEX(cgroup_mutex
);
92 static DEFINE_SPINLOCK(css_set_lock
);
96 * Protects cgroup_idr and css_idr so that IDs can be released without
97 * grabbing cgroup_mutex.
99 static DEFINE_SPINLOCK(cgroup_idr_lock
);
102 * Protects cgroup_file->kn for !self csses. It synchronizes notifications
103 * against file removal/re-creation across css hiding.
105 static DEFINE_SPINLOCK(cgroup_file_kn_lock
);
108 * Protects cgroup_subsys->release_agent_path. Modifying it also requires
109 * cgroup_mutex. Reading requires either cgroup_mutex or this spinlock.
111 static DEFINE_SPINLOCK(release_agent_path_lock
);
113 struct percpu_rw_semaphore 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
;
129 * pidlist destructions need to be flushed on cgroup destruction. Use a
130 * separate workqueue as flush domain.
132 static struct workqueue_struct
*cgroup_pidlist_destroy_wq
;
134 /* generate an array of cgroup subsystem pointers */
135 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
136 static struct cgroup_subsys
*cgroup_subsys
[] = {
137 #include <linux/cgroup_subsys.h>
141 /* array of cgroup subsystem names */
142 #define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
143 static const char *cgroup_subsys_name
[] = {
144 #include <linux/cgroup_subsys.h>
148 /* array of static_keys for cgroup_subsys_enabled() and cgroup_subsys_on_dfl() */
150 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key); \
151 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key); \
152 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key); \
153 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key);
154 #include <linux/cgroup_subsys.h>
157 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_enabled_key,
158 static struct static_key_true
*cgroup_subsys_enabled_key
[] = {
159 #include <linux/cgroup_subsys.h>
163 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_on_dfl_key,
164 static struct static_key_true
*cgroup_subsys_on_dfl_key
[] = {
165 #include <linux/cgroup_subsys.h>
170 * The default hierarchy, reserved for the subsystems that are otherwise
171 * unattached - it never has more than a single cgroup, and all tasks are
172 * part of that cgroup.
174 struct cgroup_root cgrp_dfl_root
;
175 EXPORT_SYMBOL_GPL(cgrp_dfl_root
);
178 * The default hierarchy always exists but is hidden until mounted for the
179 * first time. This is for backward compatibility.
181 static bool cgrp_dfl_root_visible
;
183 /* some controllers are not supported in the default hierarchy */
184 static unsigned long cgrp_dfl_root_inhibit_ss_mask
;
186 /* The list of hierarchy roots */
188 static LIST_HEAD(cgroup_roots
);
189 static int cgroup_root_count
;
191 /* hierarchy ID allocation and mapping, protected by cgroup_mutex */
192 static DEFINE_IDR(cgroup_hierarchy_idr
);
195 * Assign a monotonically increasing serial number to csses. It guarantees
196 * cgroups with bigger numbers are newer than those with smaller numbers.
197 * Also, as csses are always appended to the parent's ->children list, it
198 * guarantees that sibling csses are always sorted in the ascending serial
199 * number order on the list. Protected by cgroup_mutex.
201 static u64 css_serial_nr_next
= 1;
204 * These bitmask flags indicate whether tasks in the fork and exit paths have
205 * fork/exit handlers to call. This avoids us having to do extra work in the
206 * fork/exit path to check which subsystems have fork/exit callbacks.
208 static unsigned long have_fork_callback __read_mostly
;
209 static unsigned long have_exit_callback __read_mostly
;
210 static unsigned long have_free_callback __read_mostly
;
212 /* Ditto for the can_fork callback. */
213 static unsigned long have_canfork_callback __read_mostly
;
215 static struct file_system_type cgroup2_fs_type
;
216 static struct cftype cgroup_dfl_base_files
[];
217 static struct cftype cgroup_legacy_base_files
[];
219 static int rebind_subsystems(struct cgroup_root
*dst_root
,
220 unsigned long ss_mask
);
221 static void css_task_iter_advance(struct css_task_iter
*it
);
222 static int cgroup_destroy_locked(struct cgroup
*cgrp
);
223 static int create_css(struct cgroup
*cgrp
, struct cgroup_subsys
*ss
,
225 static void css_release(struct percpu_ref
*ref
);
226 static void kill_css(struct cgroup_subsys_state
*css
);
227 static int cgroup_addrm_files(struct cgroup_subsys_state
*css
,
228 struct cgroup
*cgrp
, struct cftype cfts
[],
232 * cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID
233 * @ssid: subsys ID of interest
235 * cgroup_subsys_enabled() can only be used with literal subsys names which
236 * is fine for individual subsystems but unsuitable for cgroup core. This
237 * is slower static_key_enabled() based test indexed by @ssid.
239 static bool cgroup_ssid_enabled(int ssid
)
241 return static_key_enabled(cgroup_subsys_enabled_key
[ssid
]);
245 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
246 * @cgrp: the cgroup of interest
248 * The default hierarchy is the v2 interface of cgroup and this function
249 * can be used to test whether a cgroup is on the default hierarchy for
250 * cases where a subsystem should behave differnetly depending on the
253 * The set of behaviors which change on the default hierarchy are still
254 * being determined and the mount option is prefixed with __DEVEL__.
256 * List of changed behaviors:
258 * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
259 * and "name" are disallowed.
261 * - When mounting an existing superblock, mount options should match.
263 * - Remount is disallowed.
265 * - rename(2) is disallowed.
267 * - "tasks" is removed. Everything should be at process granularity. Use
268 * "cgroup.procs" instead.
270 * - "cgroup.procs" is not sorted. pids will be unique unless they got
271 * recycled inbetween reads.
273 * - "release_agent" and "notify_on_release" are removed. Replacement
274 * notification mechanism will be implemented.
276 * - "cgroup.clone_children" is removed.
278 * - "cgroup.subtree_populated" is available. Its value is 0 if the cgroup
279 * and its descendants contain no task; otherwise, 1. The file also
280 * generates kernfs notification which can be monitored through poll and
281 * [di]notify when the value of the file changes.
283 * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
284 * take masks of ancestors with non-empty cpus/mems, instead of being
285 * moved to an ancestor.
287 * - cpuset: a task can be moved into an empty cpuset, and again it takes
288 * masks of ancestors.
290 * - memcg: use_hierarchy is on by default and the cgroup file for the flag
293 * - blkcg: blk-throttle becomes properly hierarchical.
295 * - debug: disallowed on the default hierarchy.
297 static bool cgroup_on_dfl(const struct cgroup
*cgrp
)
299 return cgrp
->root
== &cgrp_dfl_root
;
302 /* IDR wrappers which synchronize using cgroup_idr_lock */
303 static int cgroup_idr_alloc(struct idr
*idr
, void *ptr
, int start
, int end
,
308 idr_preload(gfp_mask
);
309 spin_lock_bh(&cgroup_idr_lock
);
310 ret
= idr_alloc(idr
, ptr
, start
, end
, gfp_mask
& ~__GFP_DIRECT_RECLAIM
);
311 spin_unlock_bh(&cgroup_idr_lock
);
316 static void *cgroup_idr_replace(struct idr
*idr
, void *ptr
, int id
)
320 spin_lock_bh(&cgroup_idr_lock
);
321 ret
= idr_replace(idr
, ptr
, id
);
322 spin_unlock_bh(&cgroup_idr_lock
);
326 static void cgroup_idr_remove(struct idr
*idr
, int id
)
328 spin_lock_bh(&cgroup_idr_lock
);
330 spin_unlock_bh(&cgroup_idr_lock
);
333 static struct cgroup
*cgroup_parent(struct cgroup
*cgrp
)
335 struct cgroup_subsys_state
*parent_css
= cgrp
->self
.parent
;
338 return container_of(parent_css
, struct cgroup
, self
);
343 * cgroup_css - obtain a cgroup's css for the specified subsystem
344 * @cgrp: the cgroup of interest
345 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
347 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
348 * function must be called either under cgroup_mutex or rcu_read_lock() and
349 * the caller is responsible for pinning the returned css if it wants to
350 * keep accessing it outside the said locks. This function may return
351 * %NULL if @cgrp doesn't have @subsys_id enabled.
353 static struct cgroup_subsys_state
*cgroup_css(struct cgroup
*cgrp
,
354 struct cgroup_subsys
*ss
)
357 return rcu_dereference_check(cgrp
->subsys
[ss
->id
],
358 lockdep_is_held(&cgroup_mutex
));
364 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
365 * @cgrp: the cgroup of interest
366 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
368 * Similar to cgroup_css() but returns the effective css, which is defined
369 * as the matching css of the nearest ancestor including self which has @ss
370 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
371 * function is guaranteed to return non-NULL css.
373 static struct cgroup_subsys_state
*cgroup_e_css(struct cgroup
*cgrp
,
374 struct cgroup_subsys
*ss
)
376 lockdep_assert_held(&cgroup_mutex
);
381 if (!(cgrp
->root
->subsys_mask
& (1 << ss
->id
)))
385 * This function is used while updating css associations and thus
386 * can't test the csses directly. Use ->child_subsys_mask.
388 while (cgroup_parent(cgrp
) &&
389 !(cgroup_parent(cgrp
)->child_subsys_mask
& (1 << ss
->id
)))
390 cgrp
= cgroup_parent(cgrp
);
392 return cgroup_css(cgrp
, ss
);
396 * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
397 * @cgrp: the cgroup of interest
398 * @ss: the subsystem of interest
400 * Find and get the effective css of @cgrp for @ss. The effective css is
401 * defined as the matching css of the nearest ancestor including self which
402 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
403 * the root css is returned, so this function always returns a valid css.
404 * The returned css must be put using css_put().
406 struct cgroup_subsys_state
*cgroup_get_e_css(struct cgroup
*cgrp
,
407 struct cgroup_subsys
*ss
)
409 struct cgroup_subsys_state
*css
;
414 css
= cgroup_css(cgrp
, ss
);
416 if (css
&& css_tryget_online(css
))
418 cgrp
= cgroup_parent(cgrp
);
421 css
= init_css_set
.subsys
[ss
->id
];
428 /* convenient tests for these bits */
429 static inline bool cgroup_is_dead(const struct cgroup
*cgrp
)
431 return !(cgrp
->self
.flags
& CSS_ONLINE
);
434 static void cgroup_get(struct cgroup
*cgrp
)
436 WARN_ON_ONCE(cgroup_is_dead(cgrp
));
437 css_get(&cgrp
->self
);
440 static bool cgroup_tryget(struct cgroup
*cgrp
)
442 return css_tryget(&cgrp
->self
);
445 struct cgroup_subsys_state
*of_css(struct kernfs_open_file
*of
)
447 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
448 struct cftype
*cft
= of_cft(of
);
451 * This is open and unprotected implementation of cgroup_css().
452 * seq_css() is only called from a kernfs file operation which has
453 * an active reference on the file. Because all the subsystem
454 * files are drained before a css is disassociated with a cgroup,
455 * the matching css from the cgroup's subsys table is guaranteed to
456 * be and stay valid until the enclosing operation is complete.
459 return rcu_dereference_raw(cgrp
->subsys
[cft
->ss
->id
]);
463 EXPORT_SYMBOL_GPL(of_css
);
465 static int notify_on_release(const struct cgroup
*cgrp
)
467 return test_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
471 * for_each_css - iterate all css's of a cgroup
472 * @css: the iteration cursor
473 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
474 * @cgrp: the target cgroup to iterate css's of
476 * Should be called under cgroup_[tree_]mutex.
478 #define for_each_css(css, ssid, cgrp) \
479 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
480 if (!((css) = rcu_dereference_check( \
481 (cgrp)->subsys[(ssid)], \
482 lockdep_is_held(&cgroup_mutex)))) { } \
486 * for_each_e_css - iterate all effective css's of a cgroup
487 * @css: the iteration cursor
488 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
489 * @cgrp: the target cgroup to iterate css's of
491 * Should be called under cgroup_[tree_]mutex.
493 #define for_each_e_css(css, ssid, cgrp) \
494 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
495 if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
500 * for_each_subsys - iterate all enabled cgroup subsystems
501 * @ss: the iteration cursor
502 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
504 #define for_each_subsys(ss, ssid) \
505 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
506 (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
509 * for_each_subsys_which - filter for_each_subsys with a bitmask
510 * @ss: the iteration cursor
511 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
512 * @ss_maskp: a pointer to the bitmask
514 * The block will only run for cases where the ssid-th bit (1 << ssid) of
517 #define for_each_subsys_which(ss, ssid, ss_maskp) \
518 if (!CGROUP_SUBSYS_COUNT) /* to avoid spurious gcc warning */ \
521 for_each_set_bit(ssid, ss_maskp, CGROUP_SUBSYS_COUNT) \
522 if (((ss) = cgroup_subsys[ssid]) && false) \
526 /* iterate across the hierarchies */
527 #define for_each_root(root) \
528 list_for_each_entry((root), &cgroup_roots, root_list)
530 /* iterate over child cgrps, lock should be held throughout iteration */
531 #define cgroup_for_each_live_child(child, cgrp) \
532 list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
533 if (({ lockdep_assert_held(&cgroup_mutex); \
534 cgroup_is_dead(child); })) \
538 static void cgroup_release_agent(struct work_struct
*work
);
539 static void check_for_release(struct cgroup
*cgrp
);
542 * A cgroup can be associated with multiple css_sets as different tasks may
543 * belong to different cgroups on different hierarchies. In the other
544 * direction, a css_set is naturally associated with multiple cgroups.
545 * This M:N relationship is represented by the following link structure
546 * which exists for each association and allows traversing the associations
549 struct cgrp_cset_link
{
550 /* the cgroup and css_set this link associates */
552 struct css_set
*cset
;
554 /* list of cgrp_cset_links anchored at cgrp->cset_links */
555 struct list_head cset_link
;
557 /* list of cgrp_cset_links anchored at css_set->cgrp_links */
558 struct list_head cgrp_link
;
562 * The default css_set - used by init and its children prior to any
563 * hierarchies being mounted. It contains a pointer to the root state
564 * for each subsystem. Also used to anchor the list of css_sets. Not
565 * reference-counted, to improve performance when child cgroups
566 * haven't been created.
568 struct css_set init_css_set
= {
569 .refcount
= ATOMIC_INIT(1),
570 .cgrp_links
= LIST_HEAD_INIT(init_css_set
.cgrp_links
),
571 .tasks
= LIST_HEAD_INIT(init_css_set
.tasks
),
572 .mg_tasks
= LIST_HEAD_INIT(init_css_set
.mg_tasks
),
573 .mg_preload_node
= LIST_HEAD_INIT(init_css_set
.mg_preload_node
),
574 .mg_node
= LIST_HEAD_INIT(init_css_set
.mg_node
),
575 .task_iters
= LIST_HEAD_INIT(init_css_set
.task_iters
),
578 static int css_set_count
= 1; /* 1 for init_css_set */
581 * css_set_populated - does a css_set contain any tasks?
582 * @cset: target css_set
584 static bool css_set_populated(struct css_set
*cset
)
586 lockdep_assert_held(&css_set_lock
);
588 return !list_empty(&cset
->tasks
) || !list_empty(&cset
->mg_tasks
);
592 * cgroup_update_populated - updated populated count of a cgroup
593 * @cgrp: the target cgroup
594 * @populated: inc or dec populated count
596 * One of the css_sets associated with @cgrp is either getting its first
597 * task or losing the last. Update @cgrp->populated_cnt accordingly. The
598 * count is propagated towards root so that a given cgroup's populated_cnt
599 * is zero iff the cgroup and all its descendants don't contain any tasks.
601 * @cgrp's interface file "cgroup.populated" is zero if
602 * @cgrp->populated_cnt is zero and 1 otherwise. When @cgrp->populated_cnt
603 * changes from or to zero, userland is notified that the content of the
604 * interface file has changed. This can be used to detect when @cgrp and
605 * its descendants become populated or empty.
607 static void cgroup_update_populated(struct cgroup
*cgrp
, bool populated
)
609 lockdep_assert_held(&css_set_lock
);
615 trigger
= !cgrp
->populated_cnt
++;
617 trigger
= !--cgrp
->populated_cnt
;
622 check_for_release(cgrp
);
623 cgroup_file_notify(&cgrp
->events_file
);
625 cgrp
= cgroup_parent(cgrp
);
630 * css_set_update_populated - update populated state of a css_set
631 * @cset: target css_set
632 * @populated: whether @cset is populated or depopulated
634 * @cset is either getting the first task or losing the last. Update the
635 * ->populated_cnt of all associated cgroups accordingly.
637 static void css_set_update_populated(struct css_set
*cset
, bool populated
)
639 struct cgrp_cset_link
*link
;
641 lockdep_assert_held(&css_set_lock
);
643 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
)
644 cgroup_update_populated(link
->cgrp
, populated
);
648 * css_set_move_task - move a task from one css_set to another
649 * @task: task being moved
650 * @from_cset: css_set @task currently belongs to (may be NULL)
651 * @to_cset: new css_set @task is being moved to (may be NULL)
652 * @use_mg_tasks: move to @to_cset->mg_tasks instead of ->tasks
654 * Move @task from @from_cset to @to_cset. If @task didn't belong to any
655 * css_set, @from_cset can be NULL. If @task is being disassociated
656 * instead of moved, @to_cset can be NULL.
658 * This function automatically handles populated_cnt updates and
659 * css_task_iter adjustments but the caller is responsible for managing
660 * @from_cset and @to_cset's reference counts.
662 static void css_set_move_task(struct task_struct
*task
,
663 struct css_set
*from_cset
, struct css_set
*to_cset
,
666 lockdep_assert_held(&css_set_lock
);
669 struct css_task_iter
*it
, *pos
;
671 WARN_ON_ONCE(list_empty(&task
->cg_list
));
674 * @task is leaving, advance task iterators which are
675 * pointing to it so that they can resume at the next
676 * position. Advancing an iterator might remove it from
677 * the list, use safe walk. See css_task_iter_advance*()
680 list_for_each_entry_safe(it
, pos
, &from_cset
->task_iters
,
682 if (it
->task_pos
== &task
->cg_list
)
683 css_task_iter_advance(it
);
685 list_del_init(&task
->cg_list
);
686 if (!css_set_populated(from_cset
))
687 css_set_update_populated(from_cset
, false);
689 WARN_ON_ONCE(!list_empty(&task
->cg_list
));
694 * We are synchronized through cgroup_threadgroup_rwsem
695 * against PF_EXITING setting such that we can't race
696 * against cgroup_exit() changing the css_set to
697 * init_css_set and dropping the old one.
699 WARN_ON_ONCE(task
->flags
& PF_EXITING
);
701 if (!css_set_populated(to_cset
))
702 css_set_update_populated(to_cset
, true);
703 rcu_assign_pointer(task
->cgroups
, to_cset
);
704 list_add_tail(&task
->cg_list
, use_mg_tasks
? &to_cset
->mg_tasks
:
710 * hash table for cgroup groups. This improves the performance to find
711 * an existing css_set. This hash doesn't (currently) take into
712 * account cgroups in empty hierarchies.
714 #define CSS_SET_HASH_BITS 7
715 static DEFINE_HASHTABLE(css_set_table
, CSS_SET_HASH_BITS
);
717 static unsigned long css_set_hash(struct cgroup_subsys_state
*css
[])
719 unsigned long key
= 0UL;
720 struct cgroup_subsys
*ss
;
723 for_each_subsys(ss
, i
)
724 key
+= (unsigned long)css
[i
];
725 key
= (key
>> 16) ^ key
;
730 static void put_css_set_locked(struct css_set
*cset
)
732 struct cgrp_cset_link
*link
, *tmp_link
;
733 struct cgroup_subsys
*ss
;
736 lockdep_assert_held(&css_set_lock
);
738 if (!atomic_dec_and_test(&cset
->refcount
))
741 /* This css_set is dead. unlink it and release cgroup and css refs */
742 for_each_subsys(ss
, ssid
) {
743 list_del(&cset
->e_cset_node
[ssid
]);
744 css_put(cset
->subsys
[ssid
]);
746 hash_del(&cset
->hlist
);
749 list_for_each_entry_safe(link
, tmp_link
, &cset
->cgrp_links
, cgrp_link
) {
750 list_del(&link
->cset_link
);
751 list_del(&link
->cgrp_link
);
752 if (cgroup_parent(link
->cgrp
))
753 cgroup_put(link
->cgrp
);
757 kfree_rcu(cset
, rcu_head
);
760 static void put_css_set(struct css_set
*cset
)
763 * Ensure that the refcount doesn't hit zero while any readers
764 * can see it. Similar to atomic_dec_and_lock(), but for an
767 if (atomic_add_unless(&cset
->refcount
, -1, 1))
770 spin_lock_bh(&css_set_lock
);
771 put_css_set_locked(cset
);
772 spin_unlock_bh(&css_set_lock
);
776 * refcounted get/put for css_set objects
778 static inline void get_css_set(struct css_set
*cset
)
780 atomic_inc(&cset
->refcount
);
784 * compare_css_sets - helper function for find_existing_css_set().
785 * @cset: candidate css_set being tested
786 * @old_cset: existing css_set for a task
787 * @new_cgrp: cgroup that's being entered by the task
788 * @template: desired set of css pointers in css_set (pre-calculated)
790 * Returns true if "cset" matches "old_cset" except for the hierarchy
791 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
793 static bool compare_css_sets(struct css_set
*cset
,
794 struct css_set
*old_cset
,
795 struct cgroup
*new_cgrp
,
796 struct cgroup_subsys_state
*template[])
798 struct list_head
*l1
, *l2
;
801 * On the default hierarchy, there can be csets which are
802 * associated with the same set of cgroups but different csses.
803 * Let's first ensure that csses match.
805 if (memcmp(template, cset
->subsys
, sizeof(cset
->subsys
)))
809 * Compare cgroup pointers in order to distinguish between
810 * different cgroups in hierarchies. As different cgroups may
811 * share the same effective css, this comparison is always
814 l1
= &cset
->cgrp_links
;
815 l2
= &old_cset
->cgrp_links
;
817 struct cgrp_cset_link
*link1
, *link2
;
818 struct cgroup
*cgrp1
, *cgrp2
;
822 /* See if we reached the end - both lists are equal length. */
823 if (l1
== &cset
->cgrp_links
) {
824 BUG_ON(l2
!= &old_cset
->cgrp_links
);
827 BUG_ON(l2
== &old_cset
->cgrp_links
);
829 /* Locate the cgroups associated with these links. */
830 link1
= list_entry(l1
, struct cgrp_cset_link
, cgrp_link
);
831 link2
= list_entry(l2
, struct cgrp_cset_link
, cgrp_link
);
834 /* Hierarchies should be linked in the same order. */
835 BUG_ON(cgrp1
->root
!= cgrp2
->root
);
838 * If this hierarchy is the hierarchy of the cgroup
839 * that's changing, then we need to check that this
840 * css_set points to the new cgroup; if it's any other
841 * hierarchy, then this css_set should point to the
842 * same cgroup as the old css_set.
844 if (cgrp1
->root
== new_cgrp
->root
) {
845 if (cgrp1
!= new_cgrp
)
856 * find_existing_css_set - init css array and find the matching css_set
857 * @old_cset: the css_set that we're using before the cgroup transition
858 * @cgrp: the cgroup that we're moving into
859 * @template: out param for the new set of csses, should be clear on entry
861 static struct css_set
*find_existing_css_set(struct css_set
*old_cset
,
863 struct cgroup_subsys_state
*template[])
865 struct cgroup_root
*root
= cgrp
->root
;
866 struct cgroup_subsys
*ss
;
867 struct css_set
*cset
;
872 * Build the set of subsystem state objects that we want to see in the
873 * new css_set. while subsystems can change globally, the entries here
874 * won't change, so no need for locking.
876 for_each_subsys(ss
, i
) {
877 if (root
->subsys_mask
& (1UL << i
)) {
879 * @ss is in this hierarchy, so we want the
880 * effective css from @cgrp.
882 template[i
] = cgroup_e_css(cgrp
, ss
);
885 * @ss is not in this hierarchy, so we don't want
888 template[i
] = old_cset
->subsys
[i
];
892 key
= css_set_hash(template);
893 hash_for_each_possible(css_set_table
, cset
, hlist
, key
) {
894 if (!compare_css_sets(cset
, old_cset
, cgrp
, template))
897 /* This css_set matches what we need */
901 /* No existing cgroup group matched */
905 static void free_cgrp_cset_links(struct list_head
*links_to_free
)
907 struct cgrp_cset_link
*link
, *tmp_link
;
909 list_for_each_entry_safe(link
, tmp_link
, links_to_free
, cset_link
) {
910 list_del(&link
->cset_link
);
916 * allocate_cgrp_cset_links - allocate cgrp_cset_links
917 * @count: the number of links to allocate
918 * @tmp_links: list_head the allocated links are put on
920 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
921 * through ->cset_link. Returns 0 on success or -errno.
923 static int allocate_cgrp_cset_links(int count
, struct list_head
*tmp_links
)
925 struct cgrp_cset_link
*link
;
928 INIT_LIST_HEAD(tmp_links
);
930 for (i
= 0; i
< count
; i
++) {
931 link
= kzalloc(sizeof(*link
), GFP_KERNEL
);
933 free_cgrp_cset_links(tmp_links
);
936 list_add(&link
->cset_link
, tmp_links
);
942 * link_css_set - a helper function to link a css_set to a cgroup
943 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
944 * @cset: the css_set to be linked
945 * @cgrp: the destination cgroup
947 static void link_css_set(struct list_head
*tmp_links
, struct css_set
*cset
,
950 struct cgrp_cset_link
*link
;
952 BUG_ON(list_empty(tmp_links
));
954 if (cgroup_on_dfl(cgrp
))
955 cset
->dfl_cgrp
= cgrp
;
957 link
= list_first_entry(tmp_links
, struct cgrp_cset_link
, cset_link
);
962 * Always add links to the tail of the lists so that the lists are
963 * in choronological order.
965 list_move_tail(&link
->cset_link
, &cgrp
->cset_links
);
966 list_add_tail(&link
->cgrp_link
, &cset
->cgrp_links
);
968 if (cgroup_parent(cgrp
))
973 * find_css_set - return a new css_set with one cgroup updated
974 * @old_cset: the baseline css_set
975 * @cgrp: the cgroup to be updated
977 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
978 * substituted into the appropriate hierarchy.
980 static struct css_set
*find_css_set(struct css_set
*old_cset
,
983 struct cgroup_subsys_state
*template[CGROUP_SUBSYS_COUNT
] = { };
984 struct css_set
*cset
;
985 struct list_head tmp_links
;
986 struct cgrp_cset_link
*link
;
987 struct cgroup_subsys
*ss
;
991 lockdep_assert_held(&cgroup_mutex
);
993 /* First see if we already have a cgroup group that matches
995 spin_lock_bh(&css_set_lock
);
996 cset
= find_existing_css_set(old_cset
, cgrp
, template);
999 spin_unlock_bh(&css_set_lock
);
1004 cset
= kzalloc(sizeof(*cset
), GFP_KERNEL
);
1008 /* Allocate all the cgrp_cset_link objects that we'll need */
1009 if (allocate_cgrp_cset_links(cgroup_root_count
, &tmp_links
) < 0) {
1014 atomic_set(&cset
->refcount
, 1);
1015 INIT_LIST_HEAD(&cset
->cgrp_links
);
1016 INIT_LIST_HEAD(&cset
->tasks
);
1017 INIT_LIST_HEAD(&cset
->mg_tasks
);
1018 INIT_LIST_HEAD(&cset
->mg_preload_node
);
1019 INIT_LIST_HEAD(&cset
->mg_node
);
1020 INIT_LIST_HEAD(&cset
->task_iters
);
1021 INIT_HLIST_NODE(&cset
->hlist
);
1023 /* Copy the set of subsystem state objects generated in
1024 * find_existing_css_set() */
1025 memcpy(cset
->subsys
, template, sizeof(cset
->subsys
));
1027 spin_lock_bh(&css_set_lock
);
1028 /* Add reference counts and links from the new css_set. */
1029 list_for_each_entry(link
, &old_cset
->cgrp_links
, cgrp_link
) {
1030 struct cgroup
*c
= link
->cgrp
;
1032 if (c
->root
== cgrp
->root
)
1034 link_css_set(&tmp_links
, cset
, c
);
1037 BUG_ON(!list_empty(&tmp_links
));
1041 /* Add @cset to the hash table */
1042 key
= css_set_hash(cset
->subsys
);
1043 hash_add(css_set_table
, &cset
->hlist
, key
);
1045 for_each_subsys(ss
, ssid
) {
1046 struct cgroup_subsys_state
*css
= cset
->subsys
[ssid
];
1048 list_add_tail(&cset
->e_cset_node
[ssid
],
1049 &css
->cgroup
->e_csets
[ssid
]);
1053 spin_unlock_bh(&css_set_lock
);
1058 static struct cgroup_root
*cgroup_root_from_kf(struct kernfs_root
*kf_root
)
1060 struct cgroup
*root_cgrp
= kf_root
->kn
->priv
;
1062 return root_cgrp
->root
;
1065 static int cgroup_init_root_id(struct cgroup_root
*root
)
1069 lockdep_assert_held(&cgroup_mutex
);
1071 id
= idr_alloc_cyclic(&cgroup_hierarchy_idr
, root
, 0, 0, GFP_KERNEL
);
1075 root
->hierarchy_id
= id
;
1079 static void cgroup_exit_root_id(struct cgroup_root
*root
)
1081 lockdep_assert_held(&cgroup_mutex
);
1083 if (root
->hierarchy_id
) {
1084 idr_remove(&cgroup_hierarchy_idr
, root
->hierarchy_id
);
1085 root
->hierarchy_id
= 0;
1089 static void cgroup_free_root(struct cgroup_root
*root
)
1092 /* hierarchy ID should already have been released */
1093 WARN_ON_ONCE(root
->hierarchy_id
);
1095 idr_destroy(&root
->cgroup_idr
);
1100 static void cgroup_destroy_root(struct cgroup_root
*root
)
1102 struct cgroup
*cgrp
= &root
->cgrp
;
1103 struct cgrp_cset_link
*link
, *tmp_link
;
1105 mutex_lock(&cgroup_mutex
);
1107 BUG_ON(atomic_read(&root
->nr_cgrps
));
1108 BUG_ON(!list_empty(&cgrp
->self
.children
));
1110 /* Rebind all subsystems back to the default hierarchy */
1111 rebind_subsystems(&cgrp_dfl_root
, root
->subsys_mask
);
1114 * Release all the links from cset_links to this hierarchy's
1117 spin_lock_bh(&css_set_lock
);
1119 list_for_each_entry_safe(link
, tmp_link
, &cgrp
->cset_links
, cset_link
) {
1120 list_del(&link
->cset_link
);
1121 list_del(&link
->cgrp_link
);
1125 spin_unlock_bh(&css_set_lock
);
1127 if (!list_empty(&root
->root_list
)) {
1128 list_del(&root
->root_list
);
1129 cgroup_root_count
--;
1132 cgroup_exit_root_id(root
);
1134 mutex_unlock(&cgroup_mutex
);
1136 kernfs_destroy_root(root
->kf_root
);
1137 cgroup_free_root(root
);
1140 /* look up cgroup associated with given css_set on the specified hierarchy */
1141 static struct cgroup
*cset_cgroup_from_root(struct css_set
*cset
,
1142 struct cgroup_root
*root
)
1144 struct cgroup
*res
= NULL
;
1146 lockdep_assert_held(&cgroup_mutex
);
1147 lockdep_assert_held(&css_set_lock
);
1149 if (cset
== &init_css_set
) {
1152 struct cgrp_cset_link
*link
;
1154 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
1155 struct cgroup
*c
= link
->cgrp
;
1157 if (c
->root
== root
) {
1169 * Return the cgroup for "task" from the given hierarchy. Must be
1170 * called with cgroup_mutex and css_set_lock held.
1172 static struct cgroup
*task_cgroup_from_root(struct task_struct
*task
,
1173 struct cgroup_root
*root
)
1176 * No need to lock the task - since we hold cgroup_mutex the
1177 * task can't change groups, so the only thing that can happen
1178 * is that it exits and its css is set back to init_css_set.
1180 return cset_cgroup_from_root(task_css_set(task
), root
);
1184 * A task must hold cgroup_mutex to modify cgroups.
1186 * Any task can increment and decrement the count field without lock.
1187 * So in general, code holding cgroup_mutex can't rely on the count
1188 * field not changing. However, if the count goes to zero, then only
1189 * cgroup_attach_task() can increment it again. Because a count of zero
1190 * means that no tasks are currently attached, therefore there is no
1191 * way a task attached to that cgroup can fork (the other way to
1192 * increment the count). So code holding cgroup_mutex can safely
1193 * assume that if the count is zero, it will stay zero. Similarly, if
1194 * a task holds cgroup_mutex on a cgroup with zero count, it
1195 * knows that the cgroup won't be removed, as cgroup_rmdir()
1198 * A cgroup can only be deleted if both its 'count' of using tasks
1199 * is zero, and its list of 'children' cgroups is empty. Since all
1200 * tasks in the system use _some_ cgroup, and since there is always at
1201 * least one task in the system (init, pid == 1), therefore, root cgroup
1202 * always has either children cgroups and/or using tasks. So we don't
1203 * need a special hack to ensure that root cgroup cannot be deleted.
1205 * P.S. One more locking exception. RCU is used to guard the
1206 * update of a tasks cgroup pointer by cgroup_attach_task()
1209 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
;
1210 static const struct file_operations proc_cgroupstats_operations
;
1212 static char *cgroup_file_name(struct cgroup
*cgrp
, const struct cftype
*cft
,
1215 struct cgroup_subsys
*ss
= cft
->ss
;
1217 if (cft
->ss
&& !(cft
->flags
& CFTYPE_NO_PREFIX
) &&
1218 !(cgrp
->root
->flags
& CGRP_ROOT_NOPREFIX
))
1219 snprintf(buf
, CGROUP_FILE_NAME_MAX
, "%s.%s",
1220 cgroup_on_dfl(cgrp
) ? ss
->name
: ss
->legacy_name
,
1223 strncpy(buf
, cft
->name
, CGROUP_FILE_NAME_MAX
);
1228 * cgroup_file_mode - deduce file mode of a control file
1229 * @cft: the control file in question
1231 * S_IRUGO for read, S_IWUSR for write.
1233 static umode_t
cgroup_file_mode(const struct cftype
*cft
)
1237 if (cft
->read_u64
|| cft
->read_s64
|| cft
->seq_show
)
1240 if (cft
->write_u64
|| cft
->write_s64
|| cft
->write
) {
1241 if (cft
->flags
& CFTYPE_WORLD_WRITABLE
)
1251 * cgroup_calc_child_subsys_mask - calculate child_subsys_mask
1252 * @cgrp: the target cgroup
1253 * @subtree_control: the new subtree_control mask to consider
1255 * On the default hierarchy, a subsystem may request other subsystems to be
1256 * enabled together through its ->depends_on mask. In such cases, more
1257 * subsystems than specified in "cgroup.subtree_control" may be enabled.
1259 * This function calculates which subsystems need to be enabled if
1260 * @subtree_control is to be applied to @cgrp. The returned mask is always
1261 * a superset of @subtree_control and follows the usual hierarchy rules.
1263 static unsigned long cgroup_calc_child_subsys_mask(struct cgroup
*cgrp
,
1264 unsigned long subtree_control
)
1266 struct cgroup
*parent
= cgroup_parent(cgrp
);
1267 unsigned long cur_ss_mask
= subtree_control
;
1268 struct cgroup_subsys
*ss
;
1271 lockdep_assert_held(&cgroup_mutex
);
1273 if (!cgroup_on_dfl(cgrp
))
1277 unsigned long new_ss_mask
= cur_ss_mask
;
1279 for_each_subsys_which(ss
, ssid
, &cur_ss_mask
)
1280 new_ss_mask
|= ss
->depends_on
;
1283 * Mask out subsystems which aren't available. This can
1284 * happen only if some depended-upon subsystems were bound
1285 * to non-default hierarchies.
1288 new_ss_mask
&= parent
->child_subsys_mask
;
1290 new_ss_mask
&= cgrp
->root
->subsys_mask
;
1292 if (new_ss_mask
== cur_ss_mask
)
1294 cur_ss_mask
= new_ss_mask
;
1301 * cgroup_refresh_child_subsys_mask - update child_subsys_mask
1302 * @cgrp: the target cgroup
1304 * Update @cgrp->child_subsys_mask according to the current
1305 * @cgrp->subtree_control using cgroup_calc_child_subsys_mask().
1307 static void cgroup_refresh_child_subsys_mask(struct cgroup
*cgrp
)
1309 cgrp
->child_subsys_mask
=
1310 cgroup_calc_child_subsys_mask(cgrp
, cgrp
->subtree_control
);
1314 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1315 * @kn: the kernfs_node being serviced
1317 * This helper undoes cgroup_kn_lock_live() and should be invoked before
1318 * the method finishes if locking succeeded. Note that once this function
1319 * returns the cgroup returned by cgroup_kn_lock_live() may become
1320 * inaccessible any time. If the caller intends to continue to access the
1321 * cgroup, it should pin it before invoking this function.
1323 static void cgroup_kn_unlock(struct kernfs_node
*kn
)
1325 struct cgroup
*cgrp
;
1327 if (kernfs_type(kn
) == KERNFS_DIR
)
1330 cgrp
= kn
->parent
->priv
;
1332 mutex_unlock(&cgroup_mutex
);
1334 kernfs_unbreak_active_protection(kn
);
1339 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1340 * @kn: the kernfs_node being serviced
1342 * This helper is to be used by a cgroup kernfs method currently servicing
1343 * @kn. It breaks the active protection, performs cgroup locking and
1344 * verifies that the associated cgroup is alive. Returns the cgroup if
1345 * alive; otherwise, %NULL. A successful return should be undone by a
1346 * matching cgroup_kn_unlock() invocation.
1348 * Any cgroup kernfs method implementation which requires locking the
1349 * associated cgroup should use this helper. It avoids nesting cgroup
1350 * locking under kernfs active protection and allows all kernfs operations
1351 * including self-removal.
1353 static struct cgroup
*cgroup_kn_lock_live(struct kernfs_node
*kn
)
1355 struct cgroup
*cgrp
;
1357 if (kernfs_type(kn
) == KERNFS_DIR
)
1360 cgrp
= kn
->parent
->priv
;
1363 * We're gonna grab cgroup_mutex which nests outside kernfs
1364 * active_ref. cgroup liveliness check alone provides enough
1365 * protection against removal. Ensure @cgrp stays accessible and
1366 * break the active_ref protection.
1368 if (!cgroup_tryget(cgrp
))
1370 kernfs_break_active_protection(kn
);
1372 mutex_lock(&cgroup_mutex
);
1374 if (!cgroup_is_dead(cgrp
))
1377 cgroup_kn_unlock(kn
);
1381 static void cgroup_rm_file(struct cgroup
*cgrp
, const struct cftype
*cft
)
1383 char name
[CGROUP_FILE_NAME_MAX
];
1385 lockdep_assert_held(&cgroup_mutex
);
1387 if (cft
->file_offset
) {
1388 struct cgroup_subsys_state
*css
= cgroup_css(cgrp
, cft
->ss
);
1389 struct cgroup_file
*cfile
= (void *)css
+ cft
->file_offset
;
1391 spin_lock_irq(&cgroup_file_kn_lock
);
1393 spin_unlock_irq(&cgroup_file_kn_lock
);
1396 kernfs_remove_by_name(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
));
1400 * css_clear_dir - remove subsys files in a cgroup directory
1402 * @cgrp_override: specify if target cgroup is different from css->cgroup
1404 static void css_clear_dir(struct cgroup_subsys_state
*css
,
1405 struct cgroup
*cgrp_override
)
1407 struct cgroup
*cgrp
= cgrp_override
?: css
->cgroup
;
1408 struct cftype
*cfts
;
1410 list_for_each_entry(cfts
, &css
->ss
->cfts
, node
)
1411 cgroup_addrm_files(css
, cgrp
, cfts
, false);
1415 * css_populate_dir - create subsys files in a cgroup directory
1417 * @cgrp_overried: specify if target cgroup is different from css->cgroup
1419 * On failure, no file is added.
1421 static int css_populate_dir(struct cgroup_subsys_state
*css
,
1422 struct cgroup
*cgrp_override
)
1424 struct cgroup
*cgrp
= cgrp_override
?: css
->cgroup
;
1425 struct cftype
*cfts
, *failed_cfts
;
1429 if (cgroup_on_dfl(cgrp
))
1430 cfts
= cgroup_dfl_base_files
;
1432 cfts
= cgroup_legacy_base_files
;
1434 return cgroup_addrm_files(&cgrp
->self
, cgrp
, cfts
, true);
1437 list_for_each_entry(cfts
, &css
->ss
->cfts
, node
) {
1438 ret
= cgroup_addrm_files(css
, cgrp
, cfts
, true);
1446 list_for_each_entry(cfts
, &css
->ss
->cfts
, node
) {
1447 if (cfts
== failed_cfts
)
1449 cgroup_addrm_files(css
, cgrp
, cfts
, false);
1454 static int rebind_subsystems(struct cgroup_root
*dst_root
,
1455 unsigned long ss_mask
)
1457 struct cgroup
*dcgrp
= &dst_root
->cgrp
;
1458 struct cgroup_subsys
*ss
;
1459 unsigned long tmp_ss_mask
;
1462 lockdep_assert_held(&cgroup_mutex
);
1464 for_each_subsys_which(ss
, ssid
, &ss_mask
) {
1465 /* if @ss has non-root csses attached to it, can't move */
1466 if (css_next_child(NULL
, cgroup_css(&ss
->root
->cgrp
, ss
)))
1469 /* can't move between two non-dummy roots either */
1470 if (ss
->root
!= &cgrp_dfl_root
&& dst_root
!= &cgrp_dfl_root
)
1474 /* skip creating root files on dfl_root for inhibited subsystems */
1475 tmp_ss_mask
= ss_mask
;
1476 if (dst_root
== &cgrp_dfl_root
)
1477 tmp_ss_mask
&= ~cgrp_dfl_root_inhibit_ss_mask
;
1479 for_each_subsys_which(ss
, ssid
, &tmp_ss_mask
) {
1480 struct cgroup
*scgrp
= &ss
->root
->cgrp
;
1483 ret
= css_populate_dir(cgroup_css(scgrp
, ss
), dcgrp
);
1488 * Rebinding back to the default root is not allowed to
1489 * fail. Using both default and non-default roots should
1490 * be rare. Moving subsystems back and forth even more so.
1491 * Just warn about it and continue.
1493 if (dst_root
== &cgrp_dfl_root
) {
1494 if (cgrp_dfl_root_visible
) {
1495 pr_warn("failed to create files (%d) while rebinding 0x%lx to default root\n",
1497 pr_warn("you may retry by moving them to a different hierarchy and unbinding\n");
1502 for_each_subsys_which(ss
, tssid
, &tmp_ss_mask
) {
1505 css_clear_dir(cgroup_css(scgrp
, ss
), dcgrp
);
1511 * Nothing can fail from this point on. Remove files for the
1512 * removed subsystems and rebind each subsystem.
1514 for_each_subsys_which(ss
, ssid
, &ss_mask
) {
1515 struct cgroup_root
*src_root
= ss
->root
;
1516 struct cgroup
*scgrp
= &src_root
->cgrp
;
1517 struct cgroup_subsys_state
*css
= cgroup_css(scgrp
, ss
);
1518 struct css_set
*cset
;
1520 WARN_ON(!css
|| cgroup_css(dcgrp
, ss
));
1522 css_clear_dir(css
, NULL
);
1524 RCU_INIT_POINTER(scgrp
->subsys
[ssid
], NULL
);
1525 rcu_assign_pointer(dcgrp
->subsys
[ssid
], css
);
1526 ss
->root
= dst_root
;
1527 css
->cgroup
= dcgrp
;
1529 spin_lock_bh(&css_set_lock
);
1530 hash_for_each(css_set_table
, i
, cset
, hlist
)
1531 list_move_tail(&cset
->e_cset_node
[ss
->id
],
1532 &dcgrp
->e_csets
[ss
->id
]);
1533 spin_unlock_bh(&css_set_lock
);
1535 src_root
->subsys_mask
&= ~(1 << ssid
);
1536 scgrp
->subtree_control
&= ~(1 << ssid
);
1537 cgroup_refresh_child_subsys_mask(scgrp
);
1539 /* default hierarchy doesn't enable controllers by default */
1540 dst_root
->subsys_mask
|= 1 << ssid
;
1541 if (dst_root
== &cgrp_dfl_root
) {
1542 static_branch_enable(cgroup_subsys_on_dfl_key
[ssid
]);
1544 dcgrp
->subtree_control
|= 1 << ssid
;
1545 cgroup_refresh_child_subsys_mask(dcgrp
);
1546 static_branch_disable(cgroup_subsys_on_dfl_key
[ssid
]);
1553 kernfs_activate(dcgrp
->kn
);
1557 static int cgroup_show_options(struct seq_file
*seq
,
1558 struct kernfs_root
*kf_root
)
1560 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1561 struct cgroup_subsys
*ss
;
1564 if (root
!= &cgrp_dfl_root
)
1565 for_each_subsys(ss
, ssid
)
1566 if (root
->subsys_mask
& (1 << ssid
))
1567 seq_show_option(seq
, ss
->legacy_name
, NULL
);
1568 if (root
->flags
& CGRP_ROOT_NOPREFIX
)
1569 seq_puts(seq
, ",noprefix");
1570 if (root
->flags
& CGRP_ROOT_XATTR
)
1571 seq_puts(seq
, ",xattr");
1573 spin_lock(&release_agent_path_lock
);
1574 if (strlen(root
->release_agent_path
))
1575 seq_show_option(seq
, "release_agent",
1576 root
->release_agent_path
);
1577 spin_unlock(&release_agent_path_lock
);
1579 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
))
1580 seq_puts(seq
, ",clone_children");
1581 if (strlen(root
->name
))
1582 seq_show_option(seq
, "name", root
->name
);
1586 struct cgroup_sb_opts
{
1587 unsigned long subsys_mask
;
1589 char *release_agent
;
1590 bool cpuset_clone_children
;
1592 /* User explicitly requested empty subsystem */
1596 static int parse_cgroupfs_options(char *data
, struct cgroup_sb_opts
*opts
)
1598 char *token
, *o
= data
;
1599 bool all_ss
= false, one_ss
= false;
1600 unsigned long mask
= -1UL;
1601 struct cgroup_subsys
*ss
;
1605 #ifdef CONFIG_CPUSETS
1606 mask
= ~(1U << cpuset_cgrp_id
);
1609 memset(opts
, 0, sizeof(*opts
));
1611 while ((token
= strsep(&o
, ",")) != NULL
) {
1616 if (!strcmp(token
, "none")) {
1617 /* Explicitly have no subsystems */
1621 if (!strcmp(token
, "all")) {
1622 /* Mutually exclusive option 'all' + subsystem name */
1628 if (!strcmp(token
, "noprefix")) {
1629 opts
->flags
|= CGRP_ROOT_NOPREFIX
;
1632 if (!strcmp(token
, "clone_children")) {
1633 opts
->cpuset_clone_children
= true;
1636 if (!strcmp(token
, "xattr")) {
1637 opts
->flags
|= CGRP_ROOT_XATTR
;
1640 if (!strncmp(token
, "release_agent=", 14)) {
1641 /* Specifying two release agents is forbidden */
1642 if (opts
->release_agent
)
1644 opts
->release_agent
=
1645 kstrndup(token
+ 14, PATH_MAX
- 1, GFP_KERNEL
);
1646 if (!opts
->release_agent
)
1650 if (!strncmp(token
, "name=", 5)) {
1651 const char *name
= token
+ 5;
1652 /* Can't specify an empty name */
1655 /* Must match [\w.-]+ */
1656 for (i
= 0; i
< strlen(name
); i
++) {
1660 if ((c
== '.') || (c
== '-') || (c
== '_'))
1664 /* Specifying two names is forbidden */
1667 opts
->name
= kstrndup(name
,
1668 MAX_CGROUP_ROOT_NAMELEN
- 1,
1676 for_each_subsys(ss
, i
) {
1677 if (strcmp(token
, ss
->legacy_name
))
1679 if (!cgroup_ssid_enabled(i
))
1682 /* Mutually exclusive option 'all' + subsystem name */
1685 opts
->subsys_mask
|= (1 << i
);
1690 if (i
== CGROUP_SUBSYS_COUNT
)
1695 * If the 'all' option was specified select all the subsystems,
1696 * otherwise if 'none', 'name=' and a subsystem name options were
1697 * not specified, let's default to 'all'
1699 if (all_ss
|| (!one_ss
&& !opts
->none
&& !opts
->name
))
1700 for_each_subsys(ss
, i
)
1701 if (cgroup_ssid_enabled(i
))
1702 opts
->subsys_mask
|= (1 << i
);
1705 * We either have to specify by name or by subsystems. (So all
1706 * empty hierarchies must have a name).
1708 if (!opts
->subsys_mask
&& !opts
->name
)
1712 * Option noprefix was introduced just for backward compatibility
1713 * with the old cpuset, so we allow noprefix only if mounting just
1714 * the cpuset subsystem.
1716 if ((opts
->flags
& CGRP_ROOT_NOPREFIX
) && (opts
->subsys_mask
& mask
))
1719 /* Can't specify "none" and some subsystems */
1720 if (opts
->subsys_mask
&& opts
->none
)
1726 static int cgroup_remount(struct kernfs_root
*kf_root
, int *flags
, char *data
)
1729 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1730 struct cgroup_sb_opts opts
;
1731 unsigned long added_mask
, removed_mask
;
1733 if (root
== &cgrp_dfl_root
) {
1734 pr_err("remount is not allowed\n");
1738 mutex_lock(&cgroup_mutex
);
1740 /* See what subsystems are wanted */
1741 ret
= parse_cgroupfs_options(data
, &opts
);
1745 if (opts
.subsys_mask
!= root
->subsys_mask
|| opts
.release_agent
)
1746 pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
1747 task_tgid_nr(current
), current
->comm
);
1749 added_mask
= opts
.subsys_mask
& ~root
->subsys_mask
;
1750 removed_mask
= root
->subsys_mask
& ~opts
.subsys_mask
;
1752 /* Don't allow flags or name to change at remount */
1753 if ((opts
.flags
^ root
->flags
) ||
1754 (opts
.name
&& strcmp(opts
.name
, root
->name
))) {
1755 pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n",
1756 opts
.flags
, opts
.name
?: "", root
->flags
, root
->name
);
1761 /* remounting is not allowed for populated hierarchies */
1762 if (!list_empty(&root
->cgrp
.self
.children
)) {
1767 ret
= rebind_subsystems(root
, added_mask
);
1771 rebind_subsystems(&cgrp_dfl_root
, removed_mask
);
1773 if (opts
.release_agent
) {
1774 spin_lock(&release_agent_path_lock
);
1775 strcpy(root
->release_agent_path
, opts
.release_agent
);
1776 spin_unlock(&release_agent_path_lock
);
1779 kfree(opts
.release_agent
);
1781 mutex_unlock(&cgroup_mutex
);
1786 * To reduce the fork() overhead for systems that are not actually using
1787 * their cgroups capability, we don't maintain the lists running through
1788 * each css_set to its tasks until we see the list actually used - in other
1789 * words after the first mount.
1791 static bool use_task_css_set_links __read_mostly
;
1793 static void cgroup_enable_task_cg_lists(void)
1795 struct task_struct
*p
, *g
;
1797 spin_lock_bh(&css_set_lock
);
1799 if (use_task_css_set_links
)
1802 use_task_css_set_links
= true;
1805 * We need tasklist_lock because RCU is not safe against
1806 * while_each_thread(). Besides, a forking task that has passed
1807 * cgroup_post_fork() without seeing use_task_css_set_links = 1
1808 * is not guaranteed to have its child immediately visible in the
1809 * tasklist if we walk through it with RCU.
1811 read_lock(&tasklist_lock
);
1812 do_each_thread(g
, p
) {
1813 WARN_ON_ONCE(!list_empty(&p
->cg_list
) ||
1814 task_css_set(p
) != &init_css_set
);
1817 * We should check if the process is exiting, otherwise
1818 * it will race with cgroup_exit() in that the list
1819 * entry won't be deleted though the process has exited.
1820 * Do it while holding siglock so that we don't end up
1821 * racing against cgroup_exit().
1823 spin_lock_irq(&p
->sighand
->siglock
);
1824 if (!(p
->flags
& PF_EXITING
)) {
1825 struct css_set
*cset
= task_css_set(p
);
1827 if (!css_set_populated(cset
))
1828 css_set_update_populated(cset
, true);
1829 list_add_tail(&p
->cg_list
, &cset
->tasks
);
1832 spin_unlock_irq(&p
->sighand
->siglock
);
1833 } while_each_thread(g
, p
);
1834 read_unlock(&tasklist_lock
);
1836 spin_unlock_bh(&css_set_lock
);
1839 static void init_cgroup_housekeeping(struct cgroup
*cgrp
)
1841 struct cgroup_subsys
*ss
;
1844 INIT_LIST_HEAD(&cgrp
->self
.sibling
);
1845 INIT_LIST_HEAD(&cgrp
->self
.children
);
1846 INIT_LIST_HEAD(&cgrp
->cset_links
);
1847 INIT_LIST_HEAD(&cgrp
->pidlists
);
1848 mutex_init(&cgrp
->pidlist_mutex
);
1849 cgrp
->self
.cgroup
= cgrp
;
1850 cgrp
->self
.flags
|= CSS_ONLINE
;
1852 for_each_subsys(ss
, ssid
)
1853 INIT_LIST_HEAD(&cgrp
->e_csets
[ssid
]);
1855 init_waitqueue_head(&cgrp
->offline_waitq
);
1856 INIT_WORK(&cgrp
->release_agent_work
, cgroup_release_agent
);
1859 static void init_cgroup_root(struct cgroup_root
*root
,
1860 struct cgroup_sb_opts
*opts
)
1862 struct cgroup
*cgrp
= &root
->cgrp
;
1864 INIT_LIST_HEAD(&root
->root_list
);
1865 atomic_set(&root
->nr_cgrps
, 1);
1867 init_cgroup_housekeeping(cgrp
);
1868 idr_init(&root
->cgroup_idr
);
1870 root
->flags
= opts
->flags
;
1871 if (opts
->release_agent
)
1872 strcpy(root
->release_agent_path
, opts
->release_agent
);
1874 strcpy(root
->name
, opts
->name
);
1875 if (opts
->cpuset_clone_children
)
1876 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
);
1879 static int cgroup_setup_root(struct cgroup_root
*root
, unsigned long ss_mask
)
1881 LIST_HEAD(tmp_links
);
1882 struct cgroup
*root_cgrp
= &root
->cgrp
;
1883 struct css_set
*cset
;
1886 lockdep_assert_held(&cgroup_mutex
);
1888 ret
= cgroup_idr_alloc(&root
->cgroup_idr
, root_cgrp
, 1, 2, GFP_KERNEL
);
1891 root_cgrp
->id
= ret
;
1892 root_cgrp
->ancestor_ids
[0] = ret
;
1894 ret
= percpu_ref_init(&root_cgrp
->self
.refcnt
, css_release
, 0,
1900 * We're accessing css_set_count without locking css_set_lock here,
1901 * but that's OK - it can only be increased by someone holding
1902 * cgroup_lock, and that's us. The worst that can happen is that we
1903 * have some link structures left over
1905 ret
= allocate_cgrp_cset_links(css_set_count
, &tmp_links
);
1909 ret
= cgroup_init_root_id(root
);
1913 root
->kf_root
= kernfs_create_root(&cgroup_kf_syscall_ops
,
1914 KERNFS_ROOT_CREATE_DEACTIVATED
,
1916 if (IS_ERR(root
->kf_root
)) {
1917 ret
= PTR_ERR(root
->kf_root
);
1920 root_cgrp
->kn
= root
->kf_root
->kn
;
1922 ret
= css_populate_dir(&root_cgrp
->self
, NULL
);
1926 ret
= rebind_subsystems(root
, ss_mask
);
1931 * There must be no failure case after here, since rebinding takes
1932 * care of subsystems' refcounts, which are explicitly dropped in
1933 * the failure exit path.
1935 list_add(&root
->root_list
, &cgroup_roots
);
1936 cgroup_root_count
++;
1939 * Link the root cgroup in this hierarchy into all the css_set
1942 spin_lock_bh(&css_set_lock
);
1943 hash_for_each(css_set_table
, i
, cset
, hlist
) {
1944 link_css_set(&tmp_links
, cset
, root_cgrp
);
1945 if (css_set_populated(cset
))
1946 cgroup_update_populated(root_cgrp
, true);
1948 spin_unlock_bh(&css_set_lock
);
1950 BUG_ON(!list_empty(&root_cgrp
->self
.children
));
1951 BUG_ON(atomic_read(&root
->nr_cgrps
) != 1);
1953 kernfs_activate(root_cgrp
->kn
);
1958 kernfs_destroy_root(root
->kf_root
);
1959 root
->kf_root
= NULL
;
1961 cgroup_exit_root_id(root
);
1963 percpu_ref_exit(&root_cgrp
->self
.refcnt
);
1965 free_cgrp_cset_links(&tmp_links
);
1969 static struct dentry
*cgroup_mount(struct file_system_type
*fs_type
,
1970 int flags
, const char *unused_dev_name
,
1973 bool is_v2
= fs_type
== &cgroup2_fs_type
;
1974 struct super_block
*pinned_sb
= NULL
;
1975 struct cgroup_subsys
*ss
;
1976 struct cgroup_root
*root
;
1977 struct cgroup_sb_opts opts
;
1978 struct dentry
*dentry
;
1984 * The first time anyone tries to mount a cgroup, enable the list
1985 * linking each css_set to its tasks and fix up all existing tasks.
1987 if (!use_task_css_set_links
)
1988 cgroup_enable_task_cg_lists();
1992 pr_err("cgroup2: unknown option \"%s\"\n", (char *)data
);
1993 return ERR_PTR(-EINVAL
);
1995 cgrp_dfl_root_visible
= true;
1996 root
= &cgrp_dfl_root
;
1997 cgroup_get(&root
->cgrp
);
2001 mutex_lock(&cgroup_mutex
);
2003 /* First find the desired set of subsystems */
2004 ret
= parse_cgroupfs_options(data
, &opts
);
2009 * Destruction of cgroup root is asynchronous, so subsystems may
2010 * still be dying after the previous unmount. Let's drain the
2011 * dying subsystems. We just need to ensure that the ones
2012 * unmounted previously finish dying and don't care about new ones
2013 * starting. Testing ref liveliness is good enough.
2015 for_each_subsys(ss
, i
) {
2016 if (!(opts
.subsys_mask
& (1 << i
)) ||
2017 ss
->root
== &cgrp_dfl_root
)
2020 if (!percpu_ref_tryget_live(&ss
->root
->cgrp
.self
.refcnt
)) {
2021 mutex_unlock(&cgroup_mutex
);
2023 ret
= restart_syscall();
2026 cgroup_put(&ss
->root
->cgrp
);
2029 for_each_root(root
) {
2030 bool name_match
= false;
2032 if (root
== &cgrp_dfl_root
)
2036 * If we asked for a name then it must match. Also, if
2037 * name matches but sybsys_mask doesn't, we should fail.
2038 * Remember whether name matched.
2041 if (strcmp(opts
.name
, root
->name
))
2047 * If we asked for subsystems (or explicitly for no
2048 * subsystems) then they must match.
2050 if ((opts
.subsys_mask
|| opts
.none
) &&
2051 (opts
.subsys_mask
!= root
->subsys_mask
)) {
2058 if (root
->flags
^ opts
.flags
)
2059 pr_warn("new mount options do not match the existing superblock, will be ignored\n");
2062 * We want to reuse @root whose lifetime is governed by its
2063 * ->cgrp. Let's check whether @root is alive and keep it
2064 * that way. As cgroup_kill_sb() can happen anytime, we
2065 * want to block it by pinning the sb so that @root doesn't
2066 * get killed before mount is complete.
2068 * With the sb pinned, tryget_live can reliably indicate
2069 * whether @root can be reused. If it's being killed,
2070 * drain it. We can use wait_queue for the wait but this
2071 * path is super cold. Let's just sleep a bit and retry.
2073 pinned_sb
= kernfs_pin_sb(root
->kf_root
, NULL
);
2074 if (IS_ERR(pinned_sb
) ||
2075 !percpu_ref_tryget_live(&root
->cgrp
.self
.refcnt
)) {
2076 mutex_unlock(&cgroup_mutex
);
2077 if (!IS_ERR_OR_NULL(pinned_sb
))
2078 deactivate_super(pinned_sb
);
2080 ret
= restart_syscall();
2089 * No such thing, create a new one. name= matching without subsys
2090 * specification is allowed for already existing hierarchies but we
2091 * can't create new one without subsys specification.
2093 if (!opts
.subsys_mask
&& !opts
.none
) {
2098 root
= kzalloc(sizeof(*root
), GFP_KERNEL
);
2104 init_cgroup_root(root
, &opts
);
2106 ret
= cgroup_setup_root(root
, opts
.subsys_mask
);
2108 cgroup_free_root(root
);
2111 mutex_unlock(&cgroup_mutex
);
2113 kfree(opts
.release_agent
);
2117 return ERR_PTR(ret
);
2119 dentry
= kernfs_mount(fs_type
, flags
, root
->kf_root
,
2120 is_v2
? CGROUP2_SUPER_MAGIC
: CGROUP_SUPER_MAGIC
,
2122 if (IS_ERR(dentry
) || !new_sb
)
2123 cgroup_put(&root
->cgrp
);
2126 * If @pinned_sb, we're reusing an existing root and holding an
2127 * extra ref on its sb. Mount is complete. Put the extra ref.
2131 deactivate_super(pinned_sb
);
2137 static void cgroup_kill_sb(struct super_block
*sb
)
2139 struct kernfs_root
*kf_root
= kernfs_root_from_sb(sb
);
2140 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
2143 * If @root doesn't have any mounts or children, start killing it.
2144 * This prevents new mounts by disabling percpu_ref_tryget_live().
2145 * cgroup_mount() may wait for @root's release.
2147 * And don't kill the default root.
2149 if (!list_empty(&root
->cgrp
.self
.children
) ||
2150 root
== &cgrp_dfl_root
)
2151 cgroup_put(&root
->cgrp
);
2153 percpu_ref_kill(&root
->cgrp
.self
.refcnt
);
2158 static struct file_system_type cgroup_fs_type
= {
2160 .mount
= cgroup_mount
,
2161 .kill_sb
= cgroup_kill_sb
,
2164 static struct file_system_type cgroup2_fs_type
= {
2166 .mount
= cgroup_mount
,
2167 .kill_sb
= cgroup_kill_sb
,
2171 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
2172 * @task: target task
2173 * @buf: the buffer to write the path into
2174 * @buflen: the length of the buffer
2176 * Determine @task's cgroup on the first (the one with the lowest non-zero
2177 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
2178 * function grabs cgroup_mutex and shouldn't be used inside locks used by
2179 * cgroup controller callbacks.
2181 * Return value is the same as kernfs_path().
2183 char *task_cgroup_path(struct task_struct
*task
, char *buf
, size_t buflen
)
2185 struct cgroup_root
*root
;
2186 struct cgroup
*cgrp
;
2187 int hierarchy_id
= 1;
2190 mutex_lock(&cgroup_mutex
);
2191 spin_lock_bh(&css_set_lock
);
2193 root
= idr_get_next(&cgroup_hierarchy_idr
, &hierarchy_id
);
2196 cgrp
= task_cgroup_from_root(task
, root
);
2197 path
= cgroup_path(cgrp
, buf
, buflen
);
2199 /* if no hierarchy exists, everyone is in "/" */
2200 if (strlcpy(buf
, "/", buflen
) < buflen
)
2204 spin_unlock_bh(&css_set_lock
);
2205 mutex_unlock(&cgroup_mutex
);
2208 EXPORT_SYMBOL_GPL(task_cgroup_path
);
2210 /* used to track tasks and other necessary states during migration */
2211 struct cgroup_taskset
{
2212 /* the src and dst cset list running through cset->mg_node */
2213 struct list_head src_csets
;
2214 struct list_head dst_csets
;
2216 /* the subsys currently being processed */
2220 * Fields for cgroup_taskset_*() iteration.
2222 * Before migration is committed, the target migration tasks are on
2223 * ->mg_tasks of the csets on ->src_csets. After, on ->mg_tasks of
2224 * the csets on ->dst_csets. ->csets point to either ->src_csets
2225 * or ->dst_csets depending on whether migration is committed.
2227 * ->cur_csets and ->cur_task point to the current task position
2230 struct list_head
*csets
;
2231 struct css_set
*cur_cset
;
2232 struct task_struct
*cur_task
;
2235 #define CGROUP_TASKSET_INIT(tset) (struct cgroup_taskset){ \
2236 .src_csets = LIST_HEAD_INIT(tset.src_csets), \
2237 .dst_csets = LIST_HEAD_INIT(tset.dst_csets), \
2238 .csets = &tset.src_csets, \
2242 * cgroup_taskset_add - try to add a migration target task to a taskset
2243 * @task: target task
2244 * @tset: target taskset
2246 * Add @task, which is a migration target, to @tset. This function becomes
2247 * noop if @task doesn't need to be migrated. @task's css_set should have
2248 * been added as a migration source and @task->cg_list will be moved from
2249 * the css_set's tasks list to mg_tasks one.
2251 static void cgroup_taskset_add(struct task_struct
*task
,
2252 struct cgroup_taskset
*tset
)
2254 struct css_set
*cset
;
2256 lockdep_assert_held(&css_set_lock
);
2258 /* @task either already exited or can't exit until the end */
2259 if (task
->flags
& PF_EXITING
)
2262 /* leave @task alone if post_fork() hasn't linked it yet */
2263 if (list_empty(&task
->cg_list
))
2266 cset
= task_css_set(task
);
2267 if (!cset
->mg_src_cgrp
)
2270 list_move_tail(&task
->cg_list
, &cset
->mg_tasks
);
2271 if (list_empty(&cset
->mg_node
))
2272 list_add_tail(&cset
->mg_node
, &tset
->src_csets
);
2273 if (list_empty(&cset
->mg_dst_cset
->mg_node
))
2274 list_move_tail(&cset
->mg_dst_cset
->mg_node
,
2279 * cgroup_taskset_first - reset taskset and return the first task
2280 * @tset: taskset of interest
2281 * @dst_cssp: output variable for the destination css
2283 * @tset iteration is initialized and the first task is returned.
2285 struct task_struct
*cgroup_taskset_first(struct cgroup_taskset
*tset
,
2286 struct cgroup_subsys_state
**dst_cssp
)
2288 tset
->cur_cset
= list_first_entry(tset
->csets
, struct css_set
, mg_node
);
2289 tset
->cur_task
= NULL
;
2291 return cgroup_taskset_next(tset
, dst_cssp
);
2295 * cgroup_taskset_next - iterate to the next task in taskset
2296 * @tset: taskset of interest
2297 * @dst_cssp: output variable for the destination css
2299 * Return the next task in @tset. Iteration must have been initialized
2300 * with cgroup_taskset_first().
2302 struct task_struct
*cgroup_taskset_next(struct cgroup_taskset
*tset
,
2303 struct cgroup_subsys_state
**dst_cssp
)
2305 struct css_set
*cset
= tset
->cur_cset
;
2306 struct task_struct
*task
= tset
->cur_task
;
2308 while (&cset
->mg_node
!= tset
->csets
) {
2310 task
= list_first_entry(&cset
->mg_tasks
,
2311 struct task_struct
, cg_list
);
2313 task
= list_next_entry(task
, cg_list
);
2315 if (&task
->cg_list
!= &cset
->mg_tasks
) {
2316 tset
->cur_cset
= cset
;
2317 tset
->cur_task
= task
;
2320 * This function may be called both before and
2321 * after cgroup_taskset_migrate(). The two cases
2322 * can be distinguished by looking at whether @cset
2323 * has its ->mg_dst_cset set.
2325 if (cset
->mg_dst_cset
)
2326 *dst_cssp
= cset
->mg_dst_cset
->subsys
[tset
->ssid
];
2328 *dst_cssp
= cset
->subsys
[tset
->ssid
];
2333 cset
= list_next_entry(cset
, mg_node
);
2341 * cgroup_taskset_migrate - migrate a taskset to a cgroup
2342 * @tset: taget taskset
2343 * @dst_cgrp: destination cgroup
2345 * Migrate tasks in @tset to @dst_cgrp. This function fails iff one of the
2346 * ->can_attach callbacks fails and guarantees that either all or none of
2347 * the tasks in @tset are migrated. @tset is consumed regardless of
2350 static int cgroup_taskset_migrate(struct cgroup_taskset
*tset
,
2351 struct cgroup
*dst_cgrp
)
2353 struct cgroup_subsys_state
*css
, *failed_css
= NULL
;
2354 struct task_struct
*task
, *tmp_task
;
2355 struct css_set
*cset
, *tmp_cset
;
2358 /* methods shouldn't be called if no task is actually migrating */
2359 if (list_empty(&tset
->src_csets
))
2362 /* check that we can legitimately attach to the cgroup */
2363 for_each_e_css(css
, i
, dst_cgrp
) {
2364 if (css
->ss
->can_attach
) {
2366 ret
= css
->ss
->can_attach(tset
);
2369 goto out_cancel_attach
;
2375 * Now that we're guaranteed success, proceed to move all tasks to
2376 * the new cgroup. There are no failure cases after here, so this
2377 * is the commit point.
2379 spin_lock_bh(&css_set_lock
);
2380 list_for_each_entry(cset
, &tset
->src_csets
, mg_node
) {
2381 list_for_each_entry_safe(task
, tmp_task
, &cset
->mg_tasks
, cg_list
) {
2382 struct css_set
*from_cset
= task_css_set(task
);
2383 struct css_set
*to_cset
= cset
->mg_dst_cset
;
2385 get_css_set(to_cset
);
2386 css_set_move_task(task
, from_cset
, to_cset
, true);
2387 put_css_set_locked(from_cset
);
2390 spin_unlock_bh(&css_set_lock
);
2393 * Migration is committed, all target tasks are now on dst_csets.
2394 * Nothing is sensitive to fork() after this point. Notify
2395 * controllers that migration is complete.
2397 tset
->csets
= &tset
->dst_csets
;
2399 for_each_e_css(css
, i
, dst_cgrp
) {
2400 if (css
->ss
->attach
) {
2402 css
->ss
->attach(tset
);
2407 goto out_release_tset
;
2410 for_each_e_css(css
, i
, dst_cgrp
) {
2411 if (css
== failed_css
)
2413 if (css
->ss
->cancel_attach
) {
2415 css
->ss
->cancel_attach(tset
);
2419 spin_lock_bh(&css_set_lock
);
2420 list_splice_init(&tset
->dst_csets
, &tset
->src_csets
);
2421 list_for_each_entry_safe(cset
, tmp_cset
, &tset
->src_csets
, mg_node
) {
2422 list_splice_tail_init(&cset
->mg_tasks
, &cset
->tasks
);
2423 list_del_init(&cset
->mg_node
);
2425 spin_unlock_bh(&css_set_lock
);
2430 * cgroup_migrate_finish - cleanup after attach
2431 * @preloaded_csets: list of preloaded css_sets
2433 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
2434 * those functions for details.
2436 static void cgroup_migrate_finish(struct list_head
*preloaded_csets
)
2438 struct css_set
*cset
, *tmp_cset
;
2440 lockdep_assert_held(&cgroup_mutex
);
2442 spin_lock_bh(&css_set_lock
);
2443 list_for_each_entry_safe(cset
, tmp_cset
, preloaded_csets
, mg_preload_node
) {
2444 cset
->mg_src_cgrp
= NULL
;
2445 cset
->mg_dst_cset
= NULL
;
2446 list_del_init(&cset
->mg_preload_node
);
2447 put_css_set_locked(cset
);
2449 spin_unlock_bh(&css_set_lock
);
2453 * cgroup_migrate_add_src - add a migration source css_set
2454 * @src_cset: the source css_set to add
2455 * @dst_cgrp: the destination cgroup
2456 * @preloaded_csets: list of preloaded css_sets
2458 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
2459 * @src_cset and add it to @preloaded_csets, which should later be cleaned
2460 * up by cgroup_migrate_finish().
2462 * This function may be called without holding cgroup_threadgroup_rwsem
2463 * even if the target is a process. Threads may be created and destroyed
2464 * but as long as cgroup_mutex is not dropped, no new css_set can be put
2465 * into play and the preloaded css_sets are guaranteed to cover all
2468 static void cgroup_migrate_add_src(struct css_set
*src_cset
,
2469 struct cgroup
*dst_cgrp
,
2470 struct list_head
*preloaded_csets
)
2472 struct cgroup
*src_cgrp
;
2474 lockdep_assert_held(&cgroup_mutex
);
2475 lockdep_assert_held(&css_set_lock
);
2477 src_cgrp
= cset_cgroup_from_root(src_cset
, dst_cgrp
->root
);
2479 if (!list_empty(&src_cset
->mg_preload_node
))
2482 WARN_ON(src_cset
->mg_src_cgrp
);
2483 WARN_ON(!list_empty(&src_cset
->mg_tasks
));
2484 WARN_ON(!list_empty(&src_cset
->mg_node
));
2486 src_cset
->mg_src_cgrp
= src_cgrp
;
2487 get_css_set(src_cset
);
2488 list_add(&src_cset
->mg_preload_node
, preloaded_csets
);
2492 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2493 * @dst_cgrp: the destination cgroup (may be %NULL)
2494 * @preloaded_csets: list of preloaded source css_sets
2496 * Tasks are about to be moved to @dst_cgrp and all the source css_sets
2497 * have been preloaded to @preloaded_csets. This function looks up and
2498 * pins all destination css_sets, links each to its source, and append them
2499 * to @preloaded_csets. If @dst_cgrp is %NULL, the destination of each
2500 * source css_set is assumed to be its cgroup on the default hierarchy.
2502 * This function must be called after cgroup_migrate_add_src() has been
2503 * called on each migration source css_set. After migration is performed
2504 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2507 static int cgroup_migrate_prepare_dst(struct cgroup
*dst_cgrp
,
2508 struct list_head
*preloaded_csets
)
2511 struct css_set
*src_cset
, *tmp_cset
;
2513 lockdep_assert_held(&cgroup_mutex
);
2516 * Except for the root, child_subsys_mask must be zero for a cgroup
2517 * with tasks so that child cgroups don't compete against tasks.
2519 if (dst_cgrp
&& cgroup_on_dfl(dst_cgrp
) && cgroup_parent(dst_cgrp
) &&
2520 dst_cgrp
->child_subsys_mask
)
2523 /* look up the dst cset for each src cset and link it to src */
2524 list_for_each_entry_safe(src_cset
, tmp_cset
, preloaded_csets
, mg_preload_node
) {
2525 struct css_set
*dst_cset
;
2527 dst_cset
= find_css_set(src_cset
,
2528 dst_cgrp
?: src_cset
->dfl_cgrp
);
2532 WARN_ON_ONCE(src_cset
->mg_dst_cset
|| dst_cset
->mg_dst_cset
);
2535 * If src cset equals dst, it's noop. Drop the src.
2536 * cgroup_migrate() will skip the cset too. Note that we
2537 * can't handle src == dst as some nodes are used by both.
2539 if (src_cset
== dst_cset
) {
2540 src_cset
->mg_src_cgrp
= NULL
;
2541 list_del_init(&src_cset
->mg_preload_node
);
2542 put_css_set(src_cset
);
2543 put_css_set(dst_cset
);
2547 src_cset
->mg_dst_cset
= dst_cset
;
2549 if (list_empty(&dst_cset
->mg_preload_node
))
2550 list_add(&dst_cset
->mg_preload_node
, &csets
);
2552 put_css_set(dst_cset
);
2555 list_splice_tail(&csets
, preloaded_csets
);
2558 cgroup_migrate_finish(&csets
);
2563 * cgroup_migrate - migrate a process or task to a cgroup
2564 * @leader: the leader of the process or the task to migrate
2565 * @threadgroup: whether @leader points to the whole process or a single task
2566 * @cgrp: the destination cgroup
2568 * Migrate a process or task denoted by @leader to @cgrp. If migrating a
2569 * process, the caller must be holding cgroup_threadgroup_rwsem. The
2570 * caller is also responsible for invoking cgroup_migrate_add_src() and
2571 * cgroup_migrate_prepare_dst() on the targets before invoking this
2572 * function and following up with cgroup_migrate_finish().
2574 * As long as a controller's ->can_attach() doesn't fail, this function is
2575 * guaranteed to succeed. This means that, excluding ->can_attach()
2576 * failure, when migrating multiple targets, the success or failure can be
2577 * decided for all targets by invoking group_migrate_prepare_dst() before
2578 * actually starting migrating.
2580 static int cgroup_migrate(struct task_struct
*leader
, bool threadgroup
,
2581 struct cgroup
*cgrp
)
2583 struct cgroup_taskset tset
= CGROUP_TASKSET_INIT(tset
);
2584 struct task_struct
*task
;
2587 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2588 * already PF_EXITING could be freed from underneath us unless we
2589 * take an rcu_read_lock.
2591 spin_lock_bh(&css_set_lock
);
2595 cgroup_taskset_add(task
, &tset
);
2598 } while_each_thread(leader
, task
);
2600 spin_unlock_bh(&css_set_lock
);
2602 return cgroup_taskset_migrate(&tset
, cgrp
);
2606 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2607 * @dst_cgrp: the cgroup to attach to
2608 * @leader: the task or the leader of the threadgroup to be attached
2609 * @threadgroup: attach the whole threadgroup?
2611 * Call holding cgroup_mutex and cgroup_threadgroup_rwsem.
2613 static int cgroup_attach_task(struct cgroup
*dst_cgrp
,
2614 struct task_struct
*leader
, bool threadgroup
)
2616 LIST_HEAD(preloaded_csets
);
2617 struct task_struct
*task
;
2620 /* look up all src csets */
2621 spin_lock_bh(&css_set_lock
);
2625 cgroup_migrate_add_src(task_css_set(task
), dst_cgrp
,
2629 } while_each_thread(leader
, task
);
2631 spin_unlock_bh(&css_set_lock
);
2633 /* prepare dst csets and commit */
2634 ret
= cgroup_migrate_prepare_dst(dst_cgrp
, &preloaded_csets
);
2636 ret
= cgroup_migrate(leader
, threadgroup
, dst_cgrp
);
2638 cgroup_migrate_finish(&preloaded_csets
);
2642 static int cgroup_procs_write_permission(struct task_struct
*task
,
2643 struct cgroup
*dst_cgrp
,
2644 struct kernfs_open_file
*of
)
2646 const struct cred
*cred
= current_cred();
2647 const struct cred
*tcred
= get_task_cred(task
);
2651 * even if we're attaching all tasks in the thread group, we only
2652 * need to check permissions on one of them.
2654 if (!uid_eq(cred
->euid
, GLOBAL_ROOT_UID
) &&
2655 !uid_eq(cred
->euid
, tcred
->uid
) &&
2656 !uid_eq(cred
->euid
, tcred
->suid
))
2659 if (!ret
&& cgroup_on_dfl(dst_cgrp
)) {
2660 struct super_block
*sb
= of
->file
->f_path
.dentry
->d_sb
;
2661 struct cgroup
*cgrp
;
2662 struct inode
*inode
;
2664 spin_lock_bh(&css_set_lock
);
2665 cgrp
= task_cgroup_from_root(task
, &cgrp_dfl_root
);
2666 spin_unlock_bh(&css_set_lock
);
2668 while (!cgroup_is_descendant(dst_cgrp
, cgrp
))
2669 cgrp
= cgroup_parent(cgrp
);
2672 inode
= kernfs_get_inode(sb
, cgrp
->procs_file
.kn
);
2674 ret
= inode_permission(inode
, MAY_WRITE
);
2684 * Find the task_struct of the task to attach by vpid and pass it along to the
2685 * function to attach either it or all tasks in its threadgroup. Will lock
2686 * cgroup_mutex and threadgroup.
2688 static ssize_t
__cgroup_procs_write(struct kernfs_open_file
*of
, char *buf
,
2689 size_t nbytes
, loff_t off
, bool threadgroup
)
2691 struct task_struct
*tsk
;
2692 struct cgroup
*cgrp
;
2696 if (kstrtoint(strstrip(buf
), 0, &pid
) || pid
< 0)
2699 cgrp
= cgroup_kn_lock_live(of
->kn
);
2703 percpu_down_write(&cgroup_threadgroup_rwsem
);
2706 tsk
= find_task_by_vpid(pid
);
2709 goto out_unlock_rcu
;
2716 tsk
= tsk
->group_leader
;
2719 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2720 * trapped in a cpuset, or RT worker may be born in a cgroup
2721 * with no rt_runtime allocated. Just say no.
2723 if (tsk
== kthreadd_task
|| (tsk
->flags
& PF_NO_SETAFFINITY
)) {
2725 goto out_unlock_rcu
;
2728 get_task_struct(tsk
);
2731 ret
= cgroup_procs_write_permission(tsk
, cgrp
, of
);
2733 ret
= cgroup_attach_task(cgrp
, tsk
, threadgroup
);
2735 put_task_struct(tsk
);
2736 goto out_unlock_threadgroup
;
2740 out_unlock_threadgroup
:
2741 percpu_up_write(&cgroup_threadgroup_rwsem
);
2742 cgroup_kn_unlock(of
->kn
);
2743 cpuset_post_attach_flush();
2744 return ret
?: nbytes
;
2748 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2749 * @from: attach to all cgroups of a given task
2750 * @tsk: the task to be attached
2752 int cgroup_attach_task_all(struct task_struct
*from
, struct task_struct
*tsk
)
2754 struct cgroup_root
*root
;
2757 mutex_lock(&cgroup_mutex
);
2758 for_each_root(root
) {
2759 struct cgroup
*from_cgrp
;
2761 if (root
== &cgrp_dfl_root
)
2764 spin_lock_bh(&css_set_lock
);
2765 from_cgrp
= task_cgroup_from_root(from
, root
);
2766 spin_unlock_bh(&css_set_lock
);
2768 retval
= cgroup_attach_task(from_cgrp
, tsk
, false);
2772 mutex_unlock(&cgroup_mutex
);
2776 EXPORT_SYMBOL_GPL(cgroup_attach_task_all
);
2778 static ssize_t
cgroup_tasks_write(struct kernfs_open_file
*of
,
2779 char *buf
, size_t nbytes
, loff_t off
)
2781 return __cgroup_procs_write(of
, buf
, nbytes
, off
, false);
2784 static ssize_t
cgroup_procs_write(struct kernfs_open_file
*of
,
2785 char *buf
, size_t nbytes
, loff_t off
)
2787 return __cgroup_procs_write(of
, buf
, nbytes
, off
, true);
2790 static ssize_t
cgroup_release_agent_write(struct kernfs_open_file
*of
,
2791 char *buf
, size_t nbytes
, loff_t off
)
2793 struct cgroup
*cgrp
;
2795 BUILD_BUG_ON(sizeof(cgrp
->root
->release_agent_path
) < PATH_MAX
);
2797 cgrp
= cgroup_kn_lock_live(of
->kn
);
2800 spin_lock(&release_agent_path_lock
);
2801 strlcpy(cgrp
->root
->release_agent_path
, strstrip(buf
),
2802 sizeof(cgrp
->root
->release_agent_path
));
2803 spin_unlock(&release_agent_path_lock
);
2804 cgroup_kn_unlock(of
->kn
);
2808 static int cgroup_release_agent_show(struct seq_file
*seq
, void *v
)
2810 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2812 spin_lock(&release_agent_path_lock
);
2813 seq_puts(seq
, cgrp
->root
->release_agent_path
);
2814 spin_unlock(&release_agent_path_lock
);
2815 seq_putc(seq
, '\n');
2819 static int cgroup_sane_behavior_show(struct seq_file
*seq
, void *v
)
2821 seq_puts(seq
, "0\n");
2825 static void cgroup_print_ss_mask(struct seq_file
*seq
, unsigned long ss_mask
)
2827 struct cgroup_subsys
*ss
;
2828 bool printed
= false;
2831 for_each_subsys_which(ss
, ssid
, &ss_mask
) {
2834 seq_printf(seq
, "%s", ss
->name
);
2838 seq_putc(seq
, '\n');
2841 /* show controllers which are currently attached to the default hierarchy */
2842 static int cgroup_root_controllers_show(struct seq_file
*seq
, void *v
)
2844 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2846 cgroup_print_ss_mask(seq
, cgrp
->root
->subsys_mask
&
2847 ~cgrp_dfl_root_inhibit_ss_mask
);
2851 /* show controllers which are enabled from the parent */
2852 static int cgroup_controllers_show(struct seq_file
*seq
, void *v
)
2854 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2856 cgroup_print_ss_mask(seq
, cgroup_parent(cgrp
)->subtree_control
);
2860 /* show controllers which are enabled for a given cgroup's children */
2861 static int cgroup_subtree_control_show(struct seq_file
*seq
, void *v
)
2863 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2865 cgroup_print_ss_mask(seq
, cgrp
->subtree_control
);
2870 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
2871 * @cgrp: root of the subtree to update csses for
2873 * @cgrp's child_subsys_mask has changed and its subtree's (self excluded)
2874 * css associations need to be updated accordingly. This function looks up
2875 * all css_sets which are attached to the subtree, creates the matching
2876 * updated css_sets and migrates the tasks to the new ones.
2878 static int cgroup_update_dfl_csses(struct cgroup
*cgrp
)
2880 LIST_HEAD(preloaded_csets
);
2881 struct cgroup_taskset tset
= CGROUP_TASKSET_INIT(tset
);
2882 struct cgroup_subsys_state
*css
;
2883 struct css_set
*src_cset
;
2886 lockdep_assert_held(&cgroup_mutex
);
2888 percpu_down_write(&cgroup_threadgroup_rwsem
);
2890 /* look up all csses currently attached to @cgrp's subtree */
2891 spin_lock_bh(&css_set_lock
);
2892 css_for_each_descendant_pre(css
, cgroup_css(cgrp
, NULL
)) {
2893 struct cgrp_cset_link
*link
;
2895 /* self is not affected by child_subsys_mask change */
2896 if (css
->cgroup
== cgrp
)
2899 list_for_each_entry(link
, &css
->cgroup
->cset_links
, cset_link
)
2900 cgroup_migrate_add_src(link
->cset
, cgrp
,
2903 spin_unlock_bh(&css_set_lock
);
2905 /* NULL dst indicates self on default hierarchy */
2906 ret
= cgroup_migrate_prepare_dst(NULL
, &preloaded_csets
);
2910 spin_lock_bh(&css_set_lock
);
2911 list_for_each_entry(src_cset
, &preloaded_csets
, mg_preload_node
) {
2912 struct task_struct
*task
, *ntask
;
2914 /* src_csets precede dst_csets, break on the first dst_cset */
2915 if (!src_cset
->mg_src_cgrp
)
2918 /* all tasks in src_csets need to be migrated */
2919 list_for_each_entry_safe(task
, ntask
, &src_cset
->tasks
, cg_list
)
2920 cgroup_taskset_add(task
, &tset
);
2922 spin_unlock_bh(&css_set_lock
);
2924 ret
= cgroup_taskset_migrate(&tset
, cgrp
);
2926 cgroup_migrate_finish(&preloaded_csets
);
2927 percpu_up_write(&cgroup_threadgroup_rwsem
);
2931 /* change the enabled child controllers for a cgroup in the default hierarchy */
2932 static ssize_t
cgroup_subtree_control_write(struct kernfs_open_file
*of
,
2933 char *buf
, size_t nbytes
,
2936 unsigned long enable
= 0, disable
= 0;
2937 unsigned long css_enable
, css_disable
, old_sc
, new_sc
, old_ss
, new_ss
;
2938 struct cgroup
*cgrp
, *child
;
2939 struct cgroup_subsys
*ss
;
2944 * Parse input - space separated list of subsystem names prefixed
2945 * with either + or -.
2947 buf
= strstrip(buf
);
2948 while ((tok
= strsep(&buf
, " "))) {
2949 unsigned long tmp_ss_mask
= ~cgrp_dfl_root_inhibit_ss_mask
;
2953 for_each_subsys_which(ss
, ssid
, &tmp_ss_mask
) {
2954 if (!cgroup_ssid_enabled(ssid
) ||
2955 strcmp(tok
+ 1, ss
->name
))
2959 enable
|= 1 << ssid
;
2960 disable
&= ~(1 << ssid
);
2961 } else if (*tok
== '-') {
2962 disable
|= 1 << ssid
;
2963 enable
&= ~(1 << ssid
);
2969 if (ssid
== CGROUP_SUBSYS_COUNT
)
2973 cgrp
= cgroup_kn_lock_live(of
->kn
);
2977 for_each_subsys(ss
, ssid
) {
2978 if (enable
& (1 << ssid
)) {
2979 if (cgrp
->subtree_control
& (1 << ssid
)) {
2980 enable
&= ~(1 << ssid
);
2984 /* unavailable or not enabled on the parent? */
2985 if (!(cgrp_dfl_root
.subsys_mask
& (1 << ssid
)) ||
2986 (cgroup_parent(cgrp
) &&
2987 !(cgroup_parent(cgrp
)->subtree_control
& (1 << ssid
)))) {
2991 } else if (disable
& (1 << ssid
)) {
2992 if (!(cgrp
->subtree_control
& (1 << ssid
))) {
2993 disable
&= ~(1 << ssid
);
2997 /* a child has it enabled? */
2998 cgroup_for_each_live_child(child
, cgrp
) {
2999 if (child
->subtree_control
& (1 << ssid
)) {
3007 if (!enable
&& !disable
) {
3013 * Except for the root, subtree_control must be zero for a cgroup
3014 * with tasks so that child cgroups don't compete against tasks.
3016 if (enable
&& cgroup_parent(cgrp
) && !list_empty(&cgrp
->cset_links
)) {
3022 * Update subsys masks and calculate what needs to be done. More
3023 * subsystems than specified may need to be enabled or disabled
3024 * depending on subsystem dependencies.
3026 old_sc
= cgrp
->subtree_control
;
3027 old_ss
= cgrp
->child_subsys_mask
;
3028 new_sc
= (old_sc
| enable
) & ~disable
;
3029 new_ss
= cgroup_calc_child_subsys_mask(cgrp
, new_sc
);
3031 css_enable
= ~old_ss
& new_ss
;
3032 css_disable
= old_ss
& ~new_ss
;
3033 enable
|= css_enable
;
3034 disable
|= css_disable
;
3037 * Because css offlining is asynchronous, userland might try to
3038 * re-enable the same controller while the previous instance is
3039 * still around. In such cases, wait till it's gone using
3042 for_each_subsys_which(ss
, ssid
, &css_enable
) {
3043 cgroup_for_each_live_child(child
, cgrp
) {
3046 if (!cgroup_css(child
, ss
))
3050 prepare_to_wait(&child
->offline_waitq
, &wait
,
3051 TASK_UNINTERRUPTIBLE
);
3052 cgroup_kn_unlock(of
->kn
);
3054 finish_wait(&child
->offline_waitq
, &wait
);
3057 return restart_syscall();
3061 cgrp
->subtree_control
= new_sc
;
3062 cgrp
->child_subsys_mask
= new_ss
;
3065 * Create new csses or make the existing ones visible. A css is
3066 * created invisible if it's being implicitly enabled through
3067 * dependency. An invisible css is made visible when the userland
3068 * explicitly enables it.
3070 for_each_subsys(ss
, ssid
) {
3071 if (!(enable
& (1 << ssid
)))
3074 cgroup_for_each_live_child(child
, cgrp
) {
3075 if (css_enable
& (1 << ssid
))
3076 ret
= create_css(child
, ss
,
3077 cgrp
->subtree_control
& (1 << ssid
));
3079 ret
= css_populate_dir(cgroup_css(child
, ss
),
3087 * At this point, cgroup_e_css() results reflect the new csses
3088 * making the following cgroup_update_dfl_csses() properly update
3089 * css associations of all tasks in the subtree.
3091 ret
= cgroup_update_dfl_csses(cgrp
);
3096 * All tasks are migrated out of disabled csses. Kill or hide
3097 * them. A css is hidden when the userland requests it to be
3098 * disabled while other subsystems are still depending on it. The
3099 * css must not actively control resources and be in the vanilla
3100 * state if it's made visible again later. Controllers which may
3101 * be depended upon should provide ->css_reset() for this purpose.
3103 for_each_subsys(ss
, ssid
) {
3104 if (!(disable
& (1 << ssid
)))
3107 cgroup_for_each_live_child(child
, cgrp
) {
3108 struct cgroup_subsys_state
*css
= cgroup_css(child
, ss
);
3110 if (css_disable
& (1 << ssid
)) {
3113 css_clear_dir(css
, NULL
);
3121 * The effective csses of all the descendants (excluding @cgrp) may
3122 * have changed. Subsystems can optionally subscribe to this event
3123 * by implementing ->css_e_css_changed() which is invoked if any of
3124 * the effective csses seen from the css's cgroup may have changed.
3126 for_each_subsys(ss
, ssid
) {
3127 struct cgroup_subsys_state
*this_css
= cgroup_css(cgrp
, ss
);
3128 struct cgroup_subsys_state
*css
;
3130 if (!ss
->css_e_css_changed
|| !this_css
)
3133 css_for_each_descendant_pre(css
, this_css
)
3134 if (css
!= this_css
)
3135 ss
->css_e_css_changed(css
);
3138 kernfs_activate(cgrp
->kn
);
3141 cgroup_kn_unlock(of
->kn
);
3142 return ret
?: nbytes
;
3145 cgrp
->subtree_control
= old_sc
;
3146 cgrp
->child_subsys_mask
= old_ss
;
3148 for_each_subsys(ss
, ssid
) {
3149 if (!(enable
& (1 << ssid
)))
3152 cgroup_for_each_live_child(child
, cgrp
) {
3153 struct cgroup_subsys_state
*css
= cgroup_css(child
, ss
);
3158 if (css_enable
& (1 << ssid
))
3161 css_clear_dir(css
, NULL
);
3167 static int cgroup_events_show(struct seq_file
*seq
, void *v
)
3169 seq_printf(seq
, "populated %d\n",
3170 cgroup_is_populated(seq_css(seq
)->cgroup
));
3174 static ssize_t
cgroup_file_write(struct kernfs_open_file
*of
, char *buf
,
3175 size_t nbytes
, loff_t off
)
3177 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
3178 struct cftype
*cft
= of
->kn
->priv
;
3179 struct cgroup_subsys_state
*css
;
3183 return cft
->write(of
, buf
, nbytes
, off
);
3186 * kernfs guarantees that a file isn't deleted with operations in
3187 * flight, which means that the matching css is and stays alive and
3188 * doesn't need to be pinned. The RCU locking is not necessary
3189 * either. It's just for the convenience of using cgroup_css().
3192 css
= cgroup_css(cgrp
, cft
->ss
);
3195 if (cft
->write_u64
) {
3196 unsigned long long v
;
3197 ret
= kstrtoull(buf
, 0, &v
);
3199 ret
= cft
->write_u64(css
, cft
, v
);
3200 } else if (cft
->write_s64
) {
3202 ret
= kstrtoll(buf
, 0, &v
);
3204 ret
= cft
->write_s64(css
, cft
, v
);
3209 return ret
?: nbytes
;
3212 static void *cgroup_seqfile_start(struct seq_file
*seq
, loff_t
*ppos
)
3214 return seq_cft(seq
)->seq_start(seq
, ppos
);
3217 static void *cgroup_seqfile_next(struct seq_file
*seq
, void *v
, loff_t
*ppos
)
3219 return seq_cft(seq
)->seq_next(seq
, v
, ppos
);
3222 static void cgroup_seqfile_stop(struct seq_file
*seq
, void *v
)
3224 seq_cft(seq
)->seq_stop(seq
, v
);
3227 static int cgroup_seqfile_show(struct seq_file
*m
, void *arg
)
3229 struct cftype
*cft
= seq_cft(m
);
3230 struct cgroup_subsys_state
*css
= seq_css(m
);
3233 return cft
->seq_show(m
, arg
);
3236 seq_printf(m
, "%llu\n", cft
->read_u64(css
, cft
));
3237 else if (cft
->read_s64
)
3238 seq_printf(m
, "%lld\n", cft
->read_s64(css
, cft
));
3244 static struct kernfs_ops cgroup_kf_single_ops
= {
3245 .atomic_write_len
= PAGE_SIZE
,
3246 .write
= cgroup_file_write
,
3247 .seq_show
= cgroup_seqfile_show
,
3250 static struct kernfs_ops cgroup_kf_ops
= {
3251 .atomic_write_len
= PAGE_SIZE
,
3252 .write
= cgroup_file_write
,
3253 .seq_start
= cgroup_seqfile_start
,
3254 .seq_next
= cgroup_seqfile_next
,
3255 .seq_stop
= cgroup_seqfile_stop
,
3256 .seq_show
= cgroup_seqfile_show
,
3260 * cgroup_rename - Only allow simple rename of directories in place.
3262 static int cgroup_rename(struct kernfs_node
*kn
, struct kernfs_node
*new_parent
,
3263 const char *new_name_str
)
3265 struct cgroup
*cgrp
= kn
->priv
;
3268 if (kernfs_type(kn
) != KERNFS_DIR
)
3270 if (kn
->parent
!= new_parent
)
3274 * This isn't a proper migration and its usefulness is very
3275 * limited. Disallow on the default hierarchy.
3277 if (cgroup_on_dfl(cgrp
))
3281 * We're gonna grab cgroup_mutex which nests outside kernfs
3282 * active_ref. kernfs_rename() doesn't require active_ref
3283 * protection. Break them before grabbing cgroup_mutex.
3285 kernfs_break_active_protection(new_parent
);
3286 kernfs_break_active_protection(kn
);
3288 mutex_lock(&cgroup_mutex
);
3290 ret
= kernfs_rename(kn
, new_parent
, new_name_str
);
3292 mutex_unlock(&cgroup_mutex
);
3294 kernfs_unbreak_active_protection(kn
);
3295 kernfs_unbreak_active_protection(new_parent
);
3299 /* set uid and gid of cgroup dirs and files to that of the creator */
3300 static int cgroup_kn_set_ugid(struct kernfs_node
*kn
)
3302 struct iattr iattr
= { .ia_valid
= ATTR_UID
| ATTR_GID
,
3303 .ia_uid
= current_fsuid(),
3304 .ia_gid
= current_fsgid(), };
3306 if (uid_eq(iattr
.ia_uid
, GLOBAL_ROOT_UID
) &&
3307 gid_eq(iattr
.ia_gid
, GLOBAL_ROOT_GID
))
3310 return kernfs_setattr(kn
, &iattr
);
3313 static int cgroup_add_file(struct cgroup_subsys_state
*css
, struct cgroup
*cgrp
,
3316 char name
[CGROUP_FILE_NAME_MAX
];
3317 struct kernfs_node
*kn
;
3318 struct lock_class_key
*key
= NULL
;
3321 #ifdef CONFIG_DEBUG_LOCK_ALLOC
3322 key
= &cft
->lockdep_key
;
3324 kn
= __kernfs_create_file(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
),
3325 cgroup_file_mode(cft
), 0, cft
->kf_ops
, cft
,
3330 ret
= cgroup_kn_set_ugid(kn
);
3336 if (cft
->file_offset
) {
3337 struct cgroup_file
*cfile
= (void *)css
+ cft
->file_offset
;
3339 spin_lock_irq(&cgroup_file_kn_lock
);
3341 spin_unlock_irq(&cgroup_file_kn_lock
);
3348 * cgroup_addrm_files - add or remove files to a cgroup directory
3349 * @css: the target css
3350 * @cgrp: the target cgroup (usually css->cgroup)
3351 * @cfts: array of cftypes to be added
3352 * @is_add: whether to add or remove
3354 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
3355 * For removals, this function never fails.
3357 static int cgroup_addrm_files(struct cgroup_subsys_state
*css
,
3358 struct cgroup
*cgrp
, struct cftype cfts
[],
3361 struct cftype
*cft
, *cft_end
= NULL
;
3364 lockdep_assert_held(&cgroup_mutex
);
3367 for (cft
= cfts
; cft
!= cft_end
&& cft
->name
[0] != '\0'; cft
++) {
3368 /* does cft->flags tell us to skip this file on @cgrp? */
3369 if ((cft
->flags
& __CFTYPE_ONLY_ON_DFL
) && !cgroup_on_dfl(cgrp
))
3371 if ((cft
->flags
& __CFTYPE_NOT_ON_DFL
) && cgroup_on_dfl(cgrp
))
3373 if ((cft
->flags
& CFTYPE_NOT_ON_ROOT
) && !cgroup_parent(cgrp
))
3375 if ((cft
->flags
& CFTYPE_ONLY_ON_ROOT
) && cgroup_parent(cgrp
))
3379 ret
= cgroup_add_file(css
, cgrp
, cft
);
3381 pr_warn("%s: failed to add %s, err=%d\n",
3382 __func__
, cft
->name
, ret
);
3388 cgroup_rm_file(cgrp
, cft
);
3394 static int cgroup_apply_cftypes(struct cftype
*cfts
, bool is_add
)
3397 struct cgroup_subsys
*ss
= cfts
[0].ss
;
3398 struct cgroup
*root
= &ss
->root
->cgrp
;
3399 struct cgroup_subsys_state
*css
;
3402 lockdep_assert_held(&cgroup_mutex
);
3404 /* add/rm files for all cgroups created before */
3405 css_for_each_descendant_pre(css
, cgroup_css(root
, ss
)) {
3406 struct cgroup
*cgrp
= css
->cgroup
;
3408 if (cgroup_is_dead(cgrp
))
3411 ret
= cgroup_addrm_files(css
, cgrp
, cfts
, is_add
);
3417 kernfs_activate(root
->kn
);
3421 static void cgroup_exit_cftypes(struct cftype
*cfts
)
3425 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3426 /* free copy for custom atomic_write_len, see init_cftypes() */
3427 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
)
3432 /* revert flags set by cgroup core while adding @cfts */
3433 cft
->flags
&= ~(__CFTYPE_ONLY_ON_DFL
| __CFTYPE_NOT_ON_DFL
);
3437 static int cgroup_init_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3441 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3442 struct kernfs_ops
*kf_ops
;
3444 WARN_ON(cft
->ss
|| cft
->kf_ops
);
3447 kf_ops
= &cgroup_kf_ops
;
3449 kf_ops
= &cgroup_kf_single_ops
;
3452 * Ugh... if @cft wants a custom max_write_len, we need to
3453 * make a copy of kf_ops to set its atomic_write_len.
3455 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
) {
3456 kf_ops
= kmemdup(kf_ops
, sizeof(*kf_ops
), GFP_KERNEL
);
3458 cgroup_exit_cftypes(cfts
);
3461 kf_ops
->atomic_write_len
= cft
->max_write_len
;
3464 cft
->kf_ops
= kf_ops
;
3471 static int cgroup_rm_cftypes_locked(struct cftype
*cfts
)
3473 lockdep_assert_held(&cgroup_mutex
);
3475 if (!cfts
|| !cfts
[0].ss
)
3478 list_del(&cfts
->node
);
3479 cgroup_apply_cftypes(cfts
, false);
3480 cgroup_exit_cftypes(cfts
);
3485 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
3486 * @cfts: zero-length name terminated array of cftypes
3488 * Unregister @cfts. Files described by @cfts are removed from all
3489 * existing cgroups and all future cgroups won't have them either. This
3490 * function can be called anytime whether @cfts' subsys is attached or not.
3492 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
3495 int cgroup_rm_cftypes(struct cftype
*cfts
)
3499 mutex_lock(&cgroup_mutex
);
3500 ret
= cgroup_rm_cftypes_locked(cfts
);
3501 mutex_unlock(&cgroup_mutex
);
3506 * cgroup_add_cftypes - add an array of cftypes to a subsystem
3507 * @ss: target cgroup subsystem
3508 * @cfts: zero-length name terminated array of cftypes
3510 * Register @cfts to @ss. Files described by @cfts are created for all
3511 * existing cgroups to which @ss is attached and all future cgroups will
3512 * have them too. This function can be called anytime whether @ss is
3515 * Returns 0 on successful registration, -errno on failure. Note that this
3516 * function currently returns 0 as long as @cfts registration is successful
3517 * even if some file creation attempts on existing cgroups fail.
3519 static int cgroup_add_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3523 if (!cgroup_ssid_enabled(ss
->id
))
3526 if (!cfts
|| cfts
[0].name
[0] == '\0')
3529 ret
= cgroup_init_cftypes(ss
, cfts
);
3533 mutex_lock(&cgroup_mutex
);
3535 list_add_tail(&cfts
->node
, &ss
->cfts
);
3536 ret
= cgroup_apply_cftypes(cfts
, true);
3538 cgroup_rm_cftypes_locked(cfts
);
3540 mutex_unlock(&cgroup_mutex
);
3545 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
3546 * @ss: target cgroup subsystem
3547 * @cfts: zero-length name terminated array of cftypes
3549 * Similar to cgroup_add_cftypes() but the added files are only used for
3550 * the default hierarchy.
3552 int cgroup_add_dfl_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3556 for (cft
= cfts
; cft
&& cft
->name
[0] != '\0'; cft
++)
3557 cft
->flags
|= __CFTYPE_ONLY_ON_DFL
;
3558 return cgroup_add_cftypes(ss
, cfts
);
3562 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
3563 * @ss: target cgroup subsystem
3564 * @cfts: zero-length name terminated array of cftypes
3566 * Similar to cgroup_add_cftypes() but the added files are only used for
3567 * the legacy hierarchies.
3569 int cgroup_add_legacy_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3573 for (cft
= cfts
; cft
&& cft
->name
[0] != '\0'; cft
++)
3574 cft
->flags
|= __CFTYPE_NOT_ON_DFL
;
3575 return cgroup_add_cftypes(ss
, cfts
);
3579 * cgroup_file_notify - generate a file modified event for a cgroup_file
3580 * @cfile: target cgroup_file
3582 * @cfile must have been obtained by setting cftype->file_offset.
3584 void cgroup_file_notify(struct cgroup_file
*cfile
)
3586 unsigned long flags
;
3588 spin_lock_irqsave(&cgroup_file_kn_lock
, flags
);
3590 kernfs_notify(cfile
->kn
);
3591 spin_unlock_irqrestore(&cgroup_file_kn_lock
, flags
);
3595 * cgroup_task_count - count the number of tasks in a cgroup.
3596 * @cgrp: the cgroup in question
3598 * Return the number of tasks in the cgroup.
3600 static int cgroup_task_count(const struct cgroup
*cgrp
)
3603 struct cgrp_cset_link
*link
;
3605 spin_lock_bh(&css_set_lock
);
3606 list_for_each_entry(link
, &cgrp
->cset_links
, cset_link
)
3607 count
+= atomic_read(&link
->cset
->refcount
);
3608 spin_unlock_bh(&css_set_lock
);
3613 * css_next_child - find the next child of a given css
3614 * @pos: the current position (%NULL to initiate traversal)
3615 * @parent: css whose children to walk
3617 * This function returns the next child of @parent and should be called
3618 * under either cgroup_mutex or RCU read lock. The only requirement is
3619 * that @parent and @pos are accessible. The next sibling is guaranteed to
3620 * be returned regardless of their states.
3622 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3623 * css which finished ->css_online() is guaranteed to be visible in the
3624 * future iterations and will stay visible until the last reference is put.
3625 * A css which hasn't finished ->css_online() or already finished
3626 * ->css_offline() may show up during traversal. It's each subsystem's
3627 * responsibility to synchronize against on/offlining.
3629 struct cgroup_subsys_state
*css_next_child(struct cgroup_subsys_state
*pos
,
3630 struct cgroup_subsys_state
*parent
)
3632 struct cgroup_subsys_state
*next
;
3634 cgroup_assert_mutex_or_rcu_locked();
3637 * @pos could already have been unlinked from the sibling list.
3638 * Once a cgroup is removed, its ->sibling.next is no longer
3639 * updated when its next sibling changes. CSS_RELEASED is set when
3640 * @pos is taken off list, at which time its next pointer is valid,
3641 * and, as releases are serialized, the one pointed to by the next
3642 * pointer is guaranteed to not have started release yet. This
3643 * implies that if we observe !CSS_RELEASED on @pos in this RCU
3644 * critical section, the one pointed to by its next pointer is
3645 * guaranteed to not have finished its RCU grace period even if we
3646 * have dropped rcu_read_lock() inbetween iterations.
3648 * If @pos has CSS_RELEASED set, its next pointer can't be
3649 * dereferenced; however, as each css is given a monotonically
3650 * increasing unique serial number and always appended to the
3651 * sibling list, the next one can be found by walking the parent's
3652 * children until the first css with higher serial number than
3653 * @pos's. While this path can be slower, it happens iff iteration
3654 * races against release and the race window is very small.
3657 next
= list_entry_rcu(parent
->children
.next
, struct cgroup_subsys_state
, sibling
);
3658 } else if (likely(!(pos
->flags
& CSS_RELEASED
))) {
3659 next
= list_entry_rcu(pos
->sibling
.next
, struct cgroup_subsys_state
, sibling
);
3661 list_for_each_entry_rcu(next
, &parent
->children
, sibling
)
3662 if (next
->serial_nr
> pos
->serial_nr
)
3667 * @next, if not pointing to the head, can be dereferenced and is
3670 if (&next
->sibling
!= &parent
->children
)
3676 * css_next_descendant_pre - find the next descendant for pre-order walk
3677 * @pos: the current position (%NULL to initiate traversal)
3678 * @root: css whose descendants to walk
3680 * To be used by css_for_each_descendant_pre(). Find the next descendant
3681 * to visit for pre-order traversal of @root's descendants. @root is
3682 * included in the iteration and the first node to be visited.
3684 * While this function requires cgroup_mutex or RCU read locking, it
3685 * doesn't require the whole traversal to be contained in a single critical
3686 * section. This function will return the correct next descendant as long
3687 * as both @pos and @root are accessible and @pos is a descendant of @root.
3689 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3690 * css which finished ->css_online() is guaranteed to be visible in the
3691 * future iterations and will stay visible until the last reference is put.
3692 * A css which hasn't finished ->css_online() or already finished
3693 * ->css_offline() may show up during traversal. It's each subsystem's
3694 * responsibility to synchronize against on/offlining.
3696 struct cgroup_subsys_state
*
3697 css_next_descendant_pre(struct cgroup_subsys_state
*pos
,
3698 struct cgroup_subsys_state
*root
)
3700 struct cgroup_subsys_state
*next
;
3702 cgroup_assert_mutex_or_rcu_locked();
3704 /* if first iteration, visit @root */
3708 /* visit the first child if exists */
3709 next
= css_next_child(NULL
, pos
);
3713 /* no child, visit my or the closest ancestor's next sibling */
3714 while (pos
!= root
) {
3715 next
= css_next_child(pos
, pos
->parent
);
3725 * css_rightmost_descendant - return the rightmost descendant of a css
3726 * @pos: css of interest
3728 * Return the rightmost descendant of @pos. If there's no descendant, @pos
3729 * is returned. This can be used during pre-order traversal to skip
3732 * While this function requires cgroup_mutex or RCU read locking, it
3733 * doesn't require the whole traversal to be contained in a single critical
3734 * section. This function will return the correct rightmost descendant as
3735 * long as @pos is accessible.
3737 struct cgroup_subsys_state
*
3738 css_rightmost_descendant(struct cgroup_subsys_state
*pos
)
3740 struct cgroup_subsys_state
*last
, *tmp
;
3742 cgroup_assert_mutex_or_rcu_locked();
3746 /* ->prev isn't RCU safe, walk ->next till the end */
3748 css_for_each_child(tmp
, last
)
3755 static struct cgroup_subsys_state
*
3756 css_leftmost_descendant(struct cgroup_subsys_state
*pos
)
3758 struct cgroup_subsys_state
*last
;
3762 pos
= css_next_child(NULL
, pos
);
3769 * css_next_descendant_post - find the next descendant for post-order walk
3770 * @pos: the current position (%NULL to initiate traversal)
3771 * @root: css whose descendants to walk
3773 * To be used by css_for_each_descendant_post(). Find the next descendant
3774 * to visit for post-order traversal of @root's descendants. @root is
3775 * included in the iteration and the last node to be visited.
3777 * While this function requires cgroup_mutex or RCU read locking, it
3778 * doesn't require the whole traversal to be contained in a single critical
3779 * section. This function will return the correct next descendant as long
3780 * as both @pos and @cgroup are accessible and @pos is a descendant of
3783 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3784 * css which finished ->css_online() is guaranteed to be visible in the
3785 * future iterations and will stay visible until the last reference is put.
3786 * A css which hasn't finished ->css_online() or already finished
3787 * ->css_offline() may show up during traversal. It's each subsystem's
3788 * responsibility to synchronize against on/offlining.
3790 struct cgroup_subsys_state
*
3791 css_next_descendant_post(struct cgroup_subsys_state
*pos
,
3792 struct cgroup_subsys_state
*root
)
3794 struct cgroup_subsys_state
*next
;
3796 cgroup_assert_mutex_or_rcu_locked();
3798 /* if first iteration, visit leftmost descendant which may be @root */
3800 return css_leftmost_descendant(root
);
3802 /* if we visited @root, we're done */
3806 /* if there's an unvisited sibling, visit its leftmost descendant */
3807 next
= css_next_child(pos
, pos
->parent
);
3809 return css_leftmost_descendant(next
);
3811 /* no sibling left, visit parent */
3816 * css_has_online_children - does a css have online children
3817 * @css: the target css
3819 * Returns %true if @css has any online children; otherwise, %false. This
3820 * function can be called from any context but the caller is responsible
3821 * for synchronizing against on/offlining as necessary.
3823 bool css_has_online_children(struct cgroup_subsys_state
*css
)
3825 struct cgroup_subsys_state
*child
;
3829 css_for_each_child(child
, css
) {
3830 if (child
->flags
& CSS_ONLINE
) {
3840 * css_task_iter_advance_css_set - advance a task itererator to the next css_set
3841 * @it: the iterator to advance
3843 * Advance @it to the next css_set to walk.
3845 static void css_task_iter_advance_css_set(struct css_task_iter
*it
)
3847 struct list_head
*l
= it
->cset_pos
;
3848 struct cgrp_cset_link
*link
;
3849 struct css_set
*cset
;
3851 lockdep_assert_held(&css_set_lock
);
3853 /* Advance to the next non-empty css_set */
3856 if (l
== it
->cset_head
) {
3857 it
->cset_pos
= NULL
;
3858 it
->task_pos
= NULL
;
3863 cset
= container_of(l
, struct css_set
,
3864 e_cset_node
[it
->ss
->id
]);
3866 link
= list_entry(l
, struct cgrp_cset_link
, cset_link
);
3869 } while (!css_set_populated(cset
));
3873 if (!list_empty(&cset
->tasks
))
3874 it
->task_pos
= cset
->tasks
.next
;
3876 it
->task_pos
= cset
->mg_tasks
.next
;
3878 it
->tasks_head
= &cset
->tasks
;
3879 it
->mg_tasks_head
= &cset
->mg_tasks
;
3882 * We don't keep css_sets locked across iteration steps and thus
3883 * need to take steps to ensure that iteration can be resumed after
3884 * the lock is re-acquired. Iteration is performed at two levels -
3885 * css_sets and tasks in them.
3887 * Once created, a css_set never leaves its cgroup lists, so a
3888 * pinned css_set is guaranteed to stay put and we can resume
3889 * iteration afterwards.
3891 * Tasks may leave @cset across iteration steps. This is resolved
3892 * by registering each iterator with the css_set currently being
3893 * walked and making css_set_move_task() advance iterators whose
3894 * next task is leaving.
3897 list_del(&it
->iters_node
);
3898 put_css_set_locked(it
->cur_cset
);
3901 it
->cur_cset
= cset
;
3902 list_add(&it
->iters_node
, &cset
->task_iters
);
3905 static void css_task_iter_advance(struct css_task_iter
*it
)
3907 struct list_head
*l
= it
->task_pos
;
3909 lockdep_assert_held(&css_set_lock
);
3913 * Advance iterator to find next entry. cset->tasks is consumed
3914 * first and then ->mg_tasks. After ->mg_tasks, we move onto the
3919 if (l
== it
->tasks_head
)
3920 l
= it
->mg_tasks_head
->next
;
3922 if (l
== it
->mg_tasks_head
)
3923 css_task_iter_advance_css_set(it
);
3929 * css_task_iter_start - initiate task iteration
3930 * @css: the css to walk tasks of
3931 * @it: the task iterator to use
3933 * Initiate iteration through the tasks of @css. The caller can call
3934 * css_task_iter_next() to walk through the tasks until the function
3935 * returns NULL. On completion of iteration, css_task_iter_end() must be
3938 void css_task_iter_start(struct cgroup_subsys_state
*css
,
3939 struct css_task_iter
*it
)
3941 /* no one should try to iterate before mounting cgroups */
3942 WARN_ON_ONCE(!use_task_css_set_links
);
3944 memset(it
, 0, sizeof(*it
));
3946 spin_lock_bh(&css_set_lock
);
3951 it
->cset_pos
= &css
->cgroup
->e_csets
[css
->ss
->id
];
3953 it
->cset_pos
= &css
->cgroup
->cset_links
;
3955 it
->cset_head
= it
->cset_pos
;
3957 css_task_iter_advance_css_set(it
);
3959 spin_unlock_bh(&css_set_lock
);
3963 * css_task_iter_next - return the next task for the iterator
3964 * @it: the task iterator being iterated
3966 * The "next" function for task iteration. @it should have been
3967 * initialized via css_task_iter_start(). Returns NULL when the iteration
3970 struct task_struct
*css_task_iter_next(struct css_task_iter
*it
)
3973 put_task_struct(it
->cur_task
);
3974 it
->cur_task
= NULL
;
3977 spin_lock_bh(&css_set_lock
);
3980 it
->cur_task
= list_entry(it
->task_pos
, struct task_struct
,
3982 get_task_struct(it
->cur_task
);
3983 css_task_iter_advance(it
);
3986 spin_unlock_bh(&css_set_lock
);
3988 return it
->cur_task
;
3992 * css_task_iter_end - finish task iteration
3993 * @it: the task iterator to finish
3995 * Finish task iteration started by css_task_iter_start().
3997 void css_task_iter_end(struct css_task_iter
*it
)
4000 spin_lock_bh(&css_set_lock
);
4001 list_del(&it
->iters_node
);
4002 put_css_set_locked(it
->cur_cset
);
4003 spin_unlock_bh(&css_set_lock
);
4007 put_task_struct(it
->cur_task
);
4011 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
4012 * @to: cgroup to which the tasks will be moved
4013 * @from: cgroup in which the tasks currently reside
4015 * Locking rules between cgroup_post_fork() and the migration path
4016 * guarantee that, if a task is forking while being migrated, the new child
4017 * is guaranteed to be either visible in the source cgroup after the
4018 * parent's migration is complete or put into the target cgroup. No task
4019 * can slip out of migration through forking.
4021 int cgroup_transfer_tasks(struct cgroup
*to
, struct cgroup
*from
)
4023 LIST_HEAD(preloaded_csets
);
4024 struct cgrp_cset_link
*link
;
4025 struct css_task_iter it
;
4026 struct task_struct
*task
;
4029 mutex_lock(&cgroup_mutex
);
4031 /* all tasks in @from are being moved, all csets are source */
4032 spin_lock_bh(&css_set_lock
);
4033 list_for_each_entry(link
, &from
->cset_links
, cset_link
)
4034 cgroup_migrate_add_src(link
->cset
, to
, &preloaded_csets
);
4035 spin_unlock_bh(&css_set_lock
);
4037 ret
= cgroup_migrate_prepare_dst(to
, &preloaded_csets
);
4042 * Migrate tasks one-by-one until @from is empty. This fails iff
4043 * ->can_attach() fails.
4046 css_task_iter_start(&from
->self
, &it
);
4047 task
= css_task_iter_next(&it
);
4049 get_task_struct(task
);
4050 css_task_iter_end(&it
);
4053 ret
= cgroup_migrate(task
, false, to
);
4054 put_task_struct(task
);
4056 } while (task
&& !ret
);
4058 cgroup_migrate_finish(&preloaded_csets
);
4059 mutex_unlock(&cgroup_mutex
);
4064 * Stuff for reading the 'tasks'/'procs' files.
4066 * Reading this file can return large amounts of data if a cgroup has
4067 * *lots* of attached tasks. So it may need several calls to read(),
4068 * but we cannot guarantee that the information we produce is correct
4069 * unless we produce it entirely atomically.
4073 /* which pidlist file are we talking about? */
4074 enum cgroup_filetype
{
4080 * A pidlist is a list of pids that virtually represents the contents of one
4081 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
4082 * a pair (one each for procs, tasks) for each pid namespace that's relevant
4085 struct cgroup_pidlist
{
4087 * used to find which pidlist is wanted. doesn't change as long as
4088 * this particular list stays in the list.
4090 struct { enum cgroup_filetype type
; struct pid_namespace
*ns
; } key
;
4093 /* how many elements the above list has */
4095 /* each of these stored in a list by its cgroup */
4096 struct list_head links
;
4097 /* pointer to the cgroup we belong to, for list removal purposes */
4098 struct cgroup
*owner
;
4099 /* for delayed destruction */
4100 struct delayed_work destroy_dwork
;
4104 * The following two functions "fix" the issue where there are more pids
4105 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
4106 * TODO: replace with a kernel-wide solution to this problem
4108 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
4109 static void *pidlist_allocate(int count
)
4111 if (PIDLIST_TOO_LARGE(count
))
4112 return vmalloc(count
* sizeof(pid_t
));
4114 return kmalloc(count
* sizeof(pid_t
), GFP_KERNEL
);
4117 static void pidlist_free(void *p
)
4123 * Used to destroy all pidlists lingering waiting for destroy timer. None
4124 * should be left afterwards.
4126 static void cgroup_pidlist_destroy_all(struct cgroup
*cgrp
)
4128 struct cgroup_pidlist
*l
, *tmp_l
;
4130 mutex_lock(&cgrp
->pidlist_mutex
);
4131 list_for_each_entry_safe(l
, tmp_l
, &cgrp
->pidlists
, links
)
4132 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
, 0);
4133 mutex_unlock(&cgrp
->pidlist_mutex
);
4135 flush_workqueue(cgroup_pidlist_destroy_wq
);
4136 BUG_ON(!list_empty(&cgrp
->pidlists
));
4139 static void cgroup_pidlist_destroy_work_fn(struct work_struct
*work
)
4141 struct delayed_work
*dwork
= to_delayed_work(work
);
4142 struct cgroup_pidlist
*l
= container_of(dwork
, struct cgroup_pidlist
,
4144 struct cgroup_pidlist
*tofree
= NULL
;
4146 mutex_lock(&l
->owner
->pidlist_mutex
);
4149 * Destroy iff we didn't get queued again. The state won't change
4150 * as destroy_dwork can only be queued while locked.
4152 if (!delayed_work_pending(dwork
)) {
4153 list_del(&l
->links
);
4154 pidlist_free(l
->list
);
4155 put_pid_ns(l
->key
.ns
);
4159 mutex_unlock(&l
->owner
->pidlist_mutex
);
4164 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
4165 * Returns the number of unique elements.
4167 static int pidlist_uniq(pid_t
*list
, int length
)
4172 * we presume the 0th element is unique, so i starts at 1. trivial
4173 * edge cases first; no work needs to be done for either
4175 if (length
== 0 || length
== 1)
4177 /* src and dest walk down the list; dest counts unique elements */
4178 for (src
= 1; src
< length
; src
++) {
4179 /* find next unique element */
4180 while (list
[src
] == list
[src
-1]) {
4185 /* dest always points to where the next unique element goes */
4186 list
[dest
] = list
[src
];
4194 * The two pid files - task and cgroup.procs - guaranteed that the result
4195 * is sorted, which forced this whole pidlist fiasco. As pid order is
4196 * different per namespace, each namespace needs differently sorted list,
4197 * making it impossible to use, for example, single rbtree of member tasks
4198 * sorted by task pointer. As pidlists can be fairly large, allocating one
4199 * per open file is dangerous, so cgroup had to implement shared pool of
4200 * pidlists keyed by cgroup and namespace.
4202 * All this extra complexity was caused by the original implementation
4203 * committing to an entirely unnecessary property. In the long term, we
4204 * want to do away with it. Explicitly scramble sort order if on the
4205 * default hierarchy so that no such expectation exists in the new
4208 * Scrambling is done by swapping every two consecutive bits, which is
4209 * non-identity one-to-one mapping which disturbs sort order sufficiently.
4211 static pid_t
pid_fry(pid_t pid
)
4213 unsigned a
= pid
& 0x55555555;
4214 unsigned b
= pid
& 0xAAAAAAAA;
4216 return (a
<< 1) | (b
>> 1);
4219 static pid_t
cgroup_pid_fry(struct cgroup
*cgrp
, pid_t pid
)
4221 if (cgroup_on_dfl(cgrp
))
4222 return pid_fry(pid
);
4227 static int cmppid(const void *a
, const void *b
)
4229 return *(pid_t
*)a
- *(pid_t
*)b
;
4232 static int fried_cmppid(const void *a
, const void *b
)
4234 return pid_fry(*(pid_t
*)a
) - pid_fry(*(pid_t
*)b
);
4237 static struct cgroup_pidlist
*cgroup_pidlist_find(struct cgroup
*cgrp
,
4238 enum cgroup_filetype type
)
4240 struct cgroup_pidlist
*l
;
4241 /* don't need task_nsproxy() if we're looking at ourself */
4242 struct pid_namespace
*ns
= task_active_pid_ns(current
);
4244 lockdep_assert_held(&cgrp
->pidlist_mutex
);
4246 list_for_each_entry(l
, &cgrp
->pidlists
, links
)
4247 if (l
->key
.type
== type
&& l
->key
.ns
== ns
)
4253 * find the appropriate pidlist for our purpose (given procs vs tasks)
4254 * returns with the lock on that pidlist already held, and takes care
4255 * of the use count, or returns NULL with no locks held if we're out of
4258 static struct cgroup_pidlist
*cgroup_pidlist_find_create(struct cgroup
*cgrp
,
4259 enum cgroup_filetype type
)
4261 struct cgroup_pidlist
*l
;
4263 lockdep_assert_held(&cgrp
->pidlist_mutex
);
4265 l
= cgroup_pidlist_find(cgrp
, type
);
4269 /* entry not found; create a new one */
4270 l
= kzalloc(sizeof(struct cgroup_pidlist
), GFP_KERNEL
);
4274 INIT_DELAYED_WORK(&l
->destroy_dwork
, cgroup_pidlist_destroy_work_fn
);
4276 /* don't need task_nsproxy() if we're looking at ourself */
4277 l
->key
.ns
= get_pid_ns(task_active_pid_ns(current
));
4279 list_add(&l
->links
, &cgrp
->pidlists
);
4284 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
4286 static int pidlist_array_load(struct cgroup
*cgrp
, enum cgroup_filetype type
,
4287 struct cgroup_pidlist
**lp
)
4291 int pid
, n
= 0; /* used for populating the array */
4292 struct css_task_iter it
;
4293 struct task_struct
*tsk
;
4294 struct cgroup_pidlist
*l
;
4296 lockdep_assert_held(&cgrp
->pidlist_mutex
);
4299 * If cgroup gets more users after we read count, we won't have
4300 * enough space - tough. This race is indistinguishable to the
4301 * caller from the case that the additional cgroup users didn't
4302 * show up until sometime later on.
4304 length
= cgroup_task_count(cgrp
);
4305 array
= pidlist_allocate(length
);
4308 /* now, populate the array */
4309 css_task_iter_start(&cgrp
->self
, &it
);
4310 while ((tsk
= css_task_iter_next(&it
))) {
4311 if (unlikely(n
== length
))
4313 /* get tgid or pid for procs or tasks file respectively */
4314 if (type
== CGROUP_FILE_PROCS
)
4315 pid
= task_tgid_vnr(tsk
);
4317 pid
= task_pid_vnr(tsk
);
4318 if (pid
> 0) /* make sure to only use valid results */
4321 css_task_iter_end(&it
);
4323 /* now sort & (if procs) strip out duplicates */
4324 if (cgroup_on_dfl(cgrp
))
4325 sort(array
, length
, sizeof(pid_t
), fried_cmppid
, NULL
);
4327 sort(array
, length
, sizeof(pid_t
), cmppid
, NULL
);
4328 if (type
== CGROUP_FILE_PROCS
)
4329 length
= pidlist_uniq(array
, length
);
4331 l
= cgroup_pidlist_find_create(cgrp
, type
);
4333 pidlist_free(array
);
4337 /* store array, freeing old if necessary */
4338 pidlist_free(l
->list
);
4346 * cgroupstats_build - build and fill cgroupstats
4347 * @stats: cgroupstats to fill information into
4348 * @dentry: A dentry entry belonging to the cgroup for which stats have
4351 * Build and fill cgroupstats so that taskstats can export it to user
4354 int cgroupstats_build(struct cgroupstats
*stats
, struct dentry
*dentry
)
4356 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
4357 struct cgroup
*cgrp
;
4358 struct css_task_iter it
;
4359 struct task_struct
*tsk
;
4361 /* it should be kernfs_node belonging to cgroupfs and is a directory */
4362 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
4363 kernfs_type(kn
) != KERNFS_DIR
)
4366 mutex_lock(&cgroup_mutex
);
4369 * We aren't being called from kernfs and there's no guarantee on
4370 * @kn->priv's validity. For this and css_tryget_online_from_dir(),
4371 * @kn->priv is RCU safe. Let's do the RCU dancing.
4374 cgrp
= rcu_dereference(kn
->priv
);
4375 if (!cgrp
|| cgroup_is_dead(cgrp
)) {
4377 mutex_unlock(&cgroup_mutex
);
4382 css_task_iter_start(&cgrp
->self
, &it
);
4383 while ((tsk
= css_task_iter_next(&it
))) {
4384 switch (tsk
->state
) {
4386 stats
->nr_running
++;
4388 case TASK_INTERRUPTIBLE
:
4389 stats
->nr_sleeping
++;
4391 case TASK_UNINTERRUPTIBLE
:
4392 stats
->nr_uninterruptible
++;
4395 stats
->nr_stopped
++;
4398 if (delayacct_is_task_waiting_on_io(tsk
))
4399 stats
->nr_io_wait
++;
4403 css_task_iter_end(&it
);
4405 mutex_unlock(&cgroup_mutex
);
4411 * seq_file methods for the tasks/procs files. The seq_file position is the
4412 * next pid to display; the seq_file iterator is a pointer to the pid
4413 * in the cgroup->l->list array.
4416 static void *cgroup_pidlist_start(struct seq_file
*s
, loff_t
*pos
)
4419 * Initially we receive a position value that corresponds to
4420 * one more than the last pid shown (or 0 on the first call or
4421 * after a seek to the start). Use a binary-search to find the
4422 * next pid to display, if any
4424 struct kernfs_open_file
*of
= s
->private;
4425 struct cgroup
*cgrp
= seq_css(s
)->cgroup
;
4426 struct cgroup_pidlist
*l
;
4427 enum cgroup_filetype type
= seq_cft(s
)->private;
4428 int index
= 0, pid
= *pos
;
4431 mutex_lock(&cgrp
->pidlist_mutex
);
4434 * !NULL @of->priv indicates that this isn't the first start()
4435 * after open. If the matching pidlist is around, we can use that.
4436 * Look for it. Note that @of->priv can't be used directly. It
4437 * could already have been destroyed.
4440 of
->priv
= cgroup_pidlist_find(cgrp
, type
);
4443 * Either this is the first start() after open or the matching
4444 * pidlist has been destroyed inbetween. Create a new one.
4447 ret
= pidlist_array_load(cgrp
, type
,
4448 (struct cgroup_pidlist
**)&of
->priv
);
4450 return ERR_PTR(ret
);
4455 int end
= l
->length
;
4457 while (index
< end
) {
4458 int mid
= (index
+ end
) / 2;
4459 if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) == pid
) {
4462 } else if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) <= pid
)
4468 /* If we're off the end of the array, we're done */
4469 if (index
>= l
->length
)
4471 /* Update the abstract position to be the actual pid that we found */
4472 iter
= l
->list
+ index
;
4473 *pos
= cgroup_pid_fry(cgrp
, *iter
);
4477 static void cgroup_pidlist_stop(struct seq_file
*s
, void *v
)
4479 struct kernfs_open_file
*of
= s
->private;
4480 struct cgroup_pidlist
*l
= of
->priv
;
4483 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
,
4484 CGROUP_PIDLIST_DESTROY_DELAY
);
4485 mutex_unlock(&seq_css(s
)->cgroup
->pidlist_mutex
);
4488 static void *cgroup_pidlist_next(struct seq_file
*s
, void *v
, loff_t
*pos
)
4490 struct kernfs_open_file
*of
= s
->private;
4491 struct cgroup_pidlist
*l
= of
->priv
;
4493 pid_t
*end
= l
->list
+ l
->length
;
4495 * Advance to the next pid in the array. If this goes off the
4502 *pos
= cgroup_pid_fry(seq_css(s
)->cgroup
, *p
);
4507 static int cgroup_pidlist_show(struct seq_file
*s
, void *v
)
4509 seq_printf(s
, "%d\n", *(int *)v
);
4514 static u64
cgroup_read_notify_on_release(struct cgroup_subsys_state
*css
,
4517 return notify_on_release(css
->cgroup
);
4520 static int cgroup_write_notify_on_release(struct cgroup_subsys_state
*css
,
4521 struct cftype
*cft
, u64 val
)
4524 set_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
4526 clear_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
4530 static u64
cgroup_clone_children_read(struct cgroup_subsys_state
*css
,
4533 return test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4536 static int cgroup_clone_children_write(struct cgroup_subsys_state
*css
,
4537 struct cftype
*cft
, u64 val
)
4540 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4542 clear_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4546 /* cgroup core interface files for the default hierarchy */
4547 static struct cftype cgroup_dfl_base_files
[] = {
4549 .name
= "cgroup.procs",
4550 .file_offset
= offsetof(struct cgroup
, procs_file
),
4551 .seq_start
= cgroup_pidlist_start
,
4552 .seq_next
= cgroup_pidlist_next
,
4553 .seq_stop
= cgroup_pidlist_stop
,
4554 .seq_show
= cgroup_pidlist_show
,
4555 .private = CGROUP_FILE_PROCS
,
4556 .write
= cgroup_procs_write
,
4559 .name
= "cgroup.controllers",
4560 .flags
= CFTYPE_ONLY_ON_ROOT
,
4561 .seq_show
= cgroup_root_controllers_show
,
4564 .name
= "cgroup.controllers",
4565 .flags
= CFTYPE_NOT_ON_ROOT
,
4566 .seq_show
= cgroup_controllers_show
,
4569 .name
= "cgroup.subtree_control",
4570 .seq_show
= cgroup_subtree_control_show
,
4571 .write
= cgroup_subtree_control_write
,
4574 .name
= "cgroup.events",
4575 .flags
= CFTYPE_NOT_ON_ROOT
,
4576 .file_offset
= offsetof(struct cgroup
, events_file
),
4577 .seq_show
= cgroup_events_show
,
4582 /* cgroup core interface files for the legacy hierarchies */
4583 static struct cftype cgroup_legacy_base_files
[] = {
4585 .name
= "cgroup.procs",
4586 .seq_start
= cgroup_pidlist_start
,
4587 .seq_next
= cgroup_pidlist_next
,
4588 .seq_stop
= cgroup_pidlist_stop
,
4589 .seq_show
= cgroup_pidlist_show
,
4590 .private = CGROUP_FILE_PROCS
,
4591 .write
= cgroup_procs_write
,
4594 .name
= "cgroup.clone_children",
4595 .read_u64
= cgroup_clone_children_read
,
4596 .write_u64
= cgroup_clone_children_write
,
4599 .name
= "cgroup.sane_behavior",
4600 .flags
= CFTYPE_ONLY_ON_ROOT
,
4601 .seq_show
= cgroup_sane_behavior_show
,
4605 .seq_start
= cgroup_pidlist_start
,
4606 .seq_next
= cgroup_pidlist_next
,
4607 .seq_stop
= cgroup_pidlist_stop
,
4608 .seq_show
= cgroup_pidlist_show
,
4609 .private = CGROUP_FILE_TASKS
,
4610 .write
= cgroup_tasks_write
,
4613 .name
= "notify_on_release",
4614 .read_u64
= cgroup_read_notify_on_release
,
4615 .write_u64
= cgroup_write_notify_on_release
,
4618 .name
= "release_agent",
4619 .flags
= CFTYPE_ONLY_ON_ROOT
,
4620 .seq_show
= cgroup_release_agent_show
,
4621 .write
= cgroup_release_agent_write
,
4622 .max_write_len
= PATH_MAX
- 1,
4628 * css destruction is four-stage process.
4630 * 1. Destruction starts. Killing of the percpu_ref is initiated.
4631 * Implemented in kill_css().
4633 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
4634 * and thus css_tryget_online() is guaranteed to fail, the css can be
4635 * offlined by invoking offline_css(). After offlining, the base ref is
4636 * put. Implemented in css_killed_work_fn().
4638 * 3. When the percpu_ref reaches zero, the only possible remaining
4639 * accessors are inside RCU read sections. css_release() schedules the
4642 * 4. After the grace period, the css can be freed. Implemented in
4643 * css_free_work_fn().
4645 * It is actually hairier because both step 2 and 4 require process context
4646 * and thus involve punting to css->destroy_work adding two additional
4647 * steps to the already complex sequence.
4649 static void css_free_work_fn(struct work_struct
*work
)
4651 struct cgroup_subsys_state
*css
=
4652 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4653 struct cgroup_subsys
*ss
= css
->ss
;
4654 struct cgroup
*cgrp
= css
->cgroup
;
4656 percpu_ref_exit(&css
->refcnt
);
4660 struct cgroup_subsys_state
*parent
= css
->parent
;
4664 cgroup_idr_remove(&ss
->css_idr
, id
);
4670 /* cgroup free path */
4671 atomic_dec(&cgrp
->root
->nr_cgrps
);
4672 cgroup_pidlist_destroy_all(cgrp
);
4673 cancel_work_sync(&cgrp
->release_agent_work
);
4675 if (cgroup_parent(cgrp
)) {
4677 * We get a ref to the parent, and put the ref when
4678 * this cgroup is being freed, so it's guaranteed
4679 * that the parent won't be destroyed before its
4682 cgroup_put(cgroup_parent(cgrp
));
4683 kernfs_put(cgrp
->kn
);
4687 * This is root cgroup's refcnt reaching zero,
4688 * which indicates that the root should be
4691 cgroup_destroy_root(cgrp
->root
);
4696 static void css_free_rcu_fn(struct rcu_head
*rcu_head
)
4698 struct cgroup_subsys_state
*css
=
4699 container_of(rcu_head
, struct cgroup_subsys_state
, rcu_head
);
4701 INIT_WORK(&css
->destroy_work
, css_free_work_fn
);
4702 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4705 static void css_release_work_fn(struct work_struct
*work
)
4707 struct cgroup_subsys_state
*css
=
4708 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4709 struct cgroup_subsys
*ss
= css
->ss
;
4710 struct cgroup
*cgrp
= css
->cgroup
;
4712 mutex_lock(&cgroup_mutex
);
4714 css
->flags
|= CSS_RELEASED
;
4715 list_del_rcu(&css
->sibling
);
4718 /* css release path */
4719 cgroup_idr_replace(&ss
->css_idr
, NULL
, css
->id
);
4720 if (ss
->css_released
)
4721 ss
->css_released(css
);
4723 /* cgroup release path */
4724 cgroup_idr_remove(&cgrp
->root
->cgroup_idr
, cgrp
->id
);
4728 * There are two control paths which try to determine
4729 * cgroup from dentry without going through kernfs -
4730 * cgroupstats_build() and css_tryget_online_from_dir().
4731 * Those are supported by RCU protecting clearing of
4732 * cgrp->kn->priv backpointer.
4734 RCU_INIT_POINTER(*(void __rcu __force
**)&cgrp
->kn
->priv
, NULL
);
4737 mutex_unlock(&cgroup_mutex
);
4739 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
4742 static void css_release(struct percpu_ref
*ref
)
4744 struct cgroup_subsys_state
*css
=
4745 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
4747 INIT_WORK(&css
->destroy_work
, css_release_work_fn
);
4748 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4751 static void init_and_link_css(struct cgroup_subsys_state
*css
,
4752 struct cgroup_subsys
*ss
, struct cgroup
*cgrp
)
4754 lockdep_assert_held(&cgroup_mutex
);
4758 memset(css
, 0, sizeof(*css
));
4761 INIT_LIST_HEAD(&css
->sibling
);
4762 INIT_LIST_HEAD(&css
->children
);
4763 css
->serial_nr
= css_serial_nr_next
++;
4764 atomic_set(&css
->online_cnt
, 0);
4766 if (cgroup_parent(cgrp
)) {
4767 css
->parent
= cgroup_css(cgroup_parent(cgrp
), ss
);
4768 css_get(css
->parent
);
4771 BUG_ON(cgroup_css(cgrp
, ss
));
4774 /* invoke ->css_online() on a new CSS and mark it online if successful */
4775 static int online_css(struct cgroup_subsys_state
*css
)
4777 struct cgroup_subsys
*ss
= css
->ss
;
4780 lockdep_assert_held(&cgroup_mutex
);
4783 ret
= ss
->css_online(css
);
4785 css
->flags
|= CSS_ONLINE
;
4786 rcu_assign_pointer(css
->cgroup
->subsys
[ss
->id
], css
);
4788 atomic_inc(&css
->online_cnt
);
4790 atomic_inc(&css
->parent
->online_cnt
);
4795 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
4796 static void offline_css(struct cgroup_subsys_state
*css
)
4798 struct cgroup_subsys
*ss
= css
->ss
;
4800 lockdep_assert_held(&cgroup_mutex
);
4802 if (!(css
->flags
& CSS_ONLINE
))
4805 if (ss
->css_offline
)
4806 ss
->css_offline(css
);
4808 css
->flags
&= ~CSS_ONLINE
;
4809 RCU_INIT_POINTER(css
->cgroup
->subsys
[ss
->id
], NULL
);
4811 wake_up_all(&css
->cgroup
->offline_waitq
);
4815 * create_css - create a cgroup_subsys_state
4816 * @cgrp: the cgroup new css will be associated with
4817 * @ss: the subsys of new css
4818 * @visible: whether to create control knobs for the new css or not
4820 * Create a new css associated with @cgrp - @ss pair. On success, the new
4821 * css is online and installed in @cgrp with all interface files created if
4822 * @visible. Returns 0 on success, -errno on failure.
4824 static int create_css(struct cgroup
*cgrp
, struct cgroup_subsys
*ss
,
4827 struct cgroup
*parent
= cgroup_parent(cgrp
);
4828 struct cgroup_subsys_state
*parent_css
= cgroup_css(parent
, ss
);
4829 struct cgroup_subsys_state
*css
;
4832 lockdep_assert_held(&cgroup_mutex
);
4834 css
= ss
->css_alloc(parent_css
);
4836 return PTR_ERR(css
);
4838 init_and_link_css(css
, ss
, cgrp
);
4840 err
= percpu_ref_init(&css
->refcnt
, css_release
, 0, GFP_KERNEL
);
4844 err
= cgroup_idr_alloc(&ss
->css_idr
, NULL
, 2, 0, GFP_KERNEL
);
4846 goto err_free_percpu_ref
;
4850 err
= css_populate_dir(css
, NULL
);
4855 /* @css is ready to be brought online now, make it visible */
4856 list_add_tail_rcu(&css
->sibling
, &parent_css
->children
);
4857 cgroup_idr_replace(&ss
->css_idr
, css
, css
->id
);
4859 err
= online_css(css
);
4863 if (ss
->broken_hierarchy
&& !ss
->warned_broken_hierarchy
&&
4864 cgroup_parent(parent
)) {
4865 pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
4866 current
->comm
, current
->pid
, ss
->name
);
4867 if (!strcmp(ss
->name
, "memory"))
4868 pr_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n");
4869 ss
->warned_broken_hierarchy
= true;
4875 list_del_rcu(&css
->sibling
);
4876 css_clear_dir(css
, NULL
);
4878 cgroup_idr_remove(&ss
->css_idr
, css
->id
);
4879 err_free_percpu_ref
:
4880 percpu_ref_exit(&css
->refcnt
);
4882 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
4886 static int cgroup_mkdir(struct kernfs_node
*parent_kn
, const char *name
,
4889 struct cgroup
*parent
, *cgrp
, *tcgrp
;
4890 struct cgroup_root
*root
;
4891 struct cgroup_subsys
*ss
;
4892 struct kernfs_node
*kn
;
4893 int level
, ssid
, ret
;
4895 /* Do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable.
4897 if (strchr(name
, '\n'))
4900 parent
= cgroup_kn_lock_live(parent_kn
);
4903 root
= parent
->root
;
4904 level
= parent
->level
+ 1;
4906 /* allocate the cgroup and its ID, 0 is reserved for the root */
4907 cgrp
= kzalloc(sizeof(*cgrp
) +
4908 sizeof(cgrp
->ancestor_ids
[0]) * (level
+ 1), GFP_KERNEL
);
4914 ret
= percpu_ref_init(&cgrp
->self
.refcnt
, css_release
, 0, GFP_KERNEL
);
4919 * Temporarily set the pointer to NULL, so idr_find() won't return
4920 * a half-baked cgroup.
4922 cgrp
->id
= cgroup_idr_alloc(&root
->cgroup_idr
, NULL
, 2, 0, GFP_KERNEL
);
4925 goto out_cancel_ref
;
4928 init_cgroup_housekeeping(cgrp
);
4930 cgrp
->self
.parent
= &parent
->self
;
4932 cgrp
->level
= level
;
4934 for (tcgrp
= cgrp
; tcgrp
; tcgrp
= cgroup_parent(tcgrp
))
4935 cgrp
->ancestor_ids
[tcgrp
->level
] = tcgrp
->id
;
4937 if (notify_on_release(parent
))
4938 set_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
4940 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &parent
->flags
))
4941 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &cgrp
->flags
);
4943 /* create the directory */
4944 kn
= kernfs_create_dir(parent
->kn
, name
, mode
, cgrp
);
4952 * This extra ref will be put in cgroup_free_fn() and guarantees
4953 * that @cgrp->kn is always accessible.
4957 cgrp
->self
.serial_nr
= css_serial_nr_next
++;
4959 /* allocation complete, commit to creation */
4960 list_add_tail_rcu(&cgrp
->self
.sibling
, &cgroup_parent(cgrp
)->self
.children
);
4961 atomic_inc(&root
->nr_cgrps
);
4965 * @cgrp is now fully operational. If something fails after this
4966 * point, it'll be released via the normal destruction path.
4968 cgroup_idr_replace(&root
->cgroup_idr
, cgrp
, cgrp
->id
);
4970 ret
= cgroup_kn_set_ugid(kn
);
4974 ret
= css_populate_dir(&cgrp
->self
, NULL
);
4978 /* let's create and online css's */
4979 for_each_subsys(ss
, ssid
) {
4980 if (parent
->child_subsys_mask
& (1 << ssid
)) {
4981 ret
= create_css(cgrp
, ss
,
4982 parent
->subtree_control
& (1 << ssid
));
4989 * On the default hierarchy, a child doesn't automatically inherit
4990 * subtree_control from the parent. Each is configured manually.
4992 if (!cgroup_on_dfl(cgrp
)) {
4993 cgrp
->subtree_control
= parent
->subtree_control
;
4994 cgroup_refresh_child_subsys_mask(cgrp
);
4997 kernfs_activate(kn
);
5003 cgroup_idr_remove(&root
->cgroup_idr
, cgrp
->id
);
5005 percpu_ref_exit(&cgrp
->self
.refcnt
);
5009 cgroup_kn_unlock(parent_kn
);
5013 cgroup_destroy_locked(cgrp
);
5018 * This is called when the refcnt of a css is confirmed to be killed.
5019 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
5020 * initate destruction and put the css ref from kill_css().
5022 static void css_killed_work_fn(struct work_struct
*work
)
5024 struct cgroup_subsys_state
*css
=
5025 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
5027 mutex_lock(&cgroup_mutex
);
5032 /* @css can't go away while we're holding cgroup_mutex */
5034 } while (css
&& atomic_dec_and_test(&css
->online_cnt
));
5036 mutex_unlock(&cgroup_mutex
);
5039 /* css kill confirmation processing requires process context, bounce */
5040 static void css_killed_ref_fn(struct percpu_ref
*ref
)
5042 struct cgroup_subsys_state
*css
=
5043 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
5045 if (atomic_dec_and_test(&css
->online_cnt
)) {
5046 INIT_WORK(&css
->destroy_work
, css_killed_work_fn
);
5047 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
5052 * kill_css - destroy a css
5053 * @css: css to destroy
5055 * This function initiates destruction of @css by removing cgroup interface
5056 * files and putting its base reference. ->css_offline() will be invoked
5057 * asynchronously once css_tryget_online() is guaranteed to fail and when
5058 * the reference count reaches zero, @css will be released.
5060 static void kill_css(struct cgroup_subsys_state
*css
)
5062 lockdep_assert_held(&cgroup_mutex
);
5065 * This must happen before css is disassociated with its cgroup.
5066 * See seq_css() for details.
5068 css_clear_dir(css
, NULL
);
5071 * Killing would put the base ref, but we need to keep it alive
5072 * until after ->css_offline().
5077 * cgroup core guarantees that, by the time ->css_offline() is
5078 * invoked, no new css reference will be given out via
5079 * css_tryget_online(). We can't simply call percpu_ref_kill() and
5080 * proceed to offlining css's because percpu_ref_kill() doesn't
5081 * guarantee that the ref is seen as killed on all CPUs on return.
5083 * Use percpu_ref_kill_and_confirm() to get notifications as each
5084 * css is confirmed to be seen as killed on all CPUs.
5086 percpu_ref_kill_and_confirm(&css
->refcnt
, css_killed_ref_fn
);
5090 * cgroup_destroy_locked - the first stage of cgroup destruction
5091 * @cgrp: cgroup to be destroyed
5093 * css's make use of percpu refcnts whose killing latency shouldn't be
5094 * exposed to userland and are RCU protected. Also, cgroup core needs to
5095 * guarantee that css_tryget_online() won't succeed by the time
5096 * ->css_offline() is invoked. To satisfy all the requirements,
5097 * destruction is implemented in the following two steps.
5099 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
5100 * userland visible parts and start killing the percpu refcnts of
5101 * css's. Set up so that the next stage will be kicked off once all
5102 * the percpu refcnts are confirmed to be killed.
5104 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
5105 * rest of destruction. Once all cgroup references are gone, the
5106 * cgroup is RCU-freed.
5108 * This function implements s1. After this step, @cgrp is gone as far as
5109 * the userland is concerned and a new cgroup with the same name may be
5110 * created. As cgroup doesn't care about the names internally, this
5111 * doesn't cause any problem.
5113 static int cgroup_destroy_locked(struct cgroup
*cgrp
)
5114 __releases(&cgroup_mutex
) __acquires(&cgroup_mutex
)
5116 struct cgroup_subsys_state
*css
;
5119 lockdep_assert_held(&cgroup_mutex
);
5122 * Only migration can raise populated from zero and we're already
5123 * holding cgroup_mutex.
5125 if (cgroup_is_populated(cgrp
))
5129 * Make sure there's no live children. We can't test emptiness of
5130 * ->self.children as dead children linger on it while being
5131 * drained; otherwise, "rmdir parent/child parent" may fail.
5133 if (css_has_online_children(&cgrp
->self
))
5137 * Mark @cgrp dead. This prevents further task migration and child
5138 * creation by disabling cgroup_lock_live_group().
5140 cgrp
->self
.flags
&= ~CSS_ONLINE
;
5142 /* initiate massacre of all css's */
5143 for_each_css(css
, ssid
, cgrp
)
5147 * Remove @cgrp directory along with the base files. @cgrp has an
5148 * extra ref on its kn.
5150 kernfs_remove(cgrp
->kn
);
5152 check_for_release(cgroup_parent(cgrp
));
5154 /* put the base reference */
5155 percpu_ref_kill(&cgrp
->self
.refcnt
);
5160 static int cgroup_rmdir(struct kernfs_node
*kn
)
5162 struct cgroup
*cgrp
;
5165 cgrp
= cgroup_kn_lock_live(kn
);
5169 ret
= cgroup_destroy_locked(cgrp
);
5171 cgroup_kn_unlock(kn
);
5175 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
= {
5176 .remount_fs
= cgroup_remount
,
5177 .show_options
= cgroup_show_options
,
5178 .mkdir
= cgroup_mkdir
,
5179 .rmdir
= cgroup_rmdir
,
5180 .rename
= cgroup_rename
,
5183 static void __init
cgroup_init_subsys(struct cgroup_subsys
*ss
, bool early
)
5185 struct cgroup_subsys_state
*css
;
5187 pr_debug("Initializing cgroup subsys %s\n", ss
->name
);
5189 mutex_lock(&cgroup_mutex
);
5191 idr_init(&ss
->css_idr
);
5192 INIT_LIST_HEAD(&ss
->cfts
);
5194 /* Create the root cgroup state for this subsystem */
5195 ss
->root
= &cgrp_dfl_root
;
5196 css
= ss
->css_alloc(cgroup_css(&cgrp_dfl_root
.cgrp
, ss
));
5197 /* We don't handle early failures gracefully */
5198 BUG_ON(IS_ERR(css
));
5199 init_and_link_css(css
, ss
, &cgrp_dfl_root
.cgrp
);
5202 * Root csses are never destroyed and we can't initialize
5203 * percpu_ref during early init. Disable refcnting.
5205 css
->flags
|= CSS_NO_REF
;
5208 /* allocation can't be done safely during early init */
5211 css
->id
= cgroup_idr_alloc(&ss
->css_idr
, css
, 1, 2, GFP_KERNEL
);
5212 BUG_ON(css
->id
< 0);
5215 /* Update the init_css_set to contain a subsys
5216 * pointer to this state - since the subsystem is
5217 * newly registered, all tasks and hence the
5218 * init_css_set is in the subsystem's root cgroup. */
5219 init_css_set
.subsys
[ss
->id
] = css
;
5221 have_fork_callback
|= (bool)ss
->fork
<< ss
->id
;
5222 have_exit_callback
|= (bool)ss
->exit
<< ss
->id
;
5223 have_free_callback
|= (bool)ss
->free
<< ss
->id
;
5224 have_canfork_callback
|= (bool)ss
->can_fork
<< ss
->id
;
5226 /* At system boot, before all subsystems have been
5227 * registered, no tasks have been forked, so we don't
5228 * need to invoke fork callbacks here. */
5229 BUG_ON(!list_empty(&init_task
.tasks
));
5231 BUG_ON(online_css(css
));
5233 mutex_unlock(&cgroup_mutex
);
5237 * cgroup_init_early - cgroup initialization at system boot
5239 * Initialize cgroups at system boot, and initialize any
5240 * subsystems that request early init.
5242 int __init
cgroup_init_early(void)
5244 static struct cgroup_sb_opts __initdata opts
;
5245 struct cgroup_subsys
*ss
;
5248 init_cgroup_root(&cgrp_dfl_root
, &opts
);
5249 cgrp_dfl_root
.cgrp
.self
.flags
|= CSS_NO_REF
;
5251 RCU_INIT_POINTER(init_task
.cgroups
, &init_css_set
);
5253 for_each_subsys(ss
, i
) {
5254 WARN(!ss
->css_alloc
|| !ss
->css_free
|| ss
->name
|| ss
->id
,
5255 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
5256 i
, cgroup_subsys_name
[i
], ss
->css_alloc
, ss
->css_free
,
5258 WARN(strlen(cgroup_subsys_name
[i
]) > MAX_CGROUP_TYPE_NAMELEN
,
5259 "cgroup_subsys_name %s too long\n", cgroup_subsys_name
[i
]);
5262 ss
->name
= cgroup_subsys_name
[i
];
5263 if (!ss
->legacy_name
)
5264 ss
->legacy_name
= cgroup_subsys_name
[i
];
5267 cgroup_init_subsys(ss
, true);
5272 static unsigned long cgroup_disable_mask __initdata
;
5275 * cgroup_init - cgroup initialization
5277 * Register cgroup filesystem and /proc file, and initialize
5278 * any subsystems that didn't request early init.
5280 int __init
cgroup_init(void)
5282 struct cgroup_subsys
*ss
;
5286 BUG_ON(percpu_init_rwsem(&cgroup_threadgroup_rwsem
));
5287 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_dfl_base_files
));
5288 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_legacy_base_files
));
5290 mutex_lock(&cgroup_mutex
);
5292 /* Add init_css_set to the hash table */
5293 key
= css_set_hash(init_css_set
.subsys
);
5294 hash_add(css_set_table
, &init_css_set
.hlist
, key
);
5296 BUG_ON(cgroup_setup_root(&cgrp_dfl_root
, 0));
5298 mutex_unlock(&cgroup_mutex
);
5300 for_each_subsys(ss
, ssid
) {
5301 if (ss
->early_init
) {
5302 struct cgroup_subsys_state
*css
=
5303 init_css_set
.subsys
[ss
->id
];
5305 css
->id
= cgroup_idr_alloc(&ss
->css_idr
, css
, 1, 2,
5307 BUG_ON(css
->id
< 0);
5309 cgroup_init_subsys(ss
, false);
5312 list_add_tail(&init_css_set
.e_cset_node
[ssid
],
5313 &cgrp_dfl_root
.cgrp
.e_csets
[ssid
]);
5316 * Setting dfl_root subsys_mask needs to consider the
5317 * disabled flag and cftype registration needs kmalloc,
5318 * both of which aren't available during early_init.
5320 if (cgroup_disable_mask
& (1 << ssid
)) {
5321 static_branch_disable(cgroup_subsys_enabled_key
[ssid
]);
5322 printk(KERN_INFO
"Disabling %s control group subsystem\n",
5327 cgrp_dfl_root
.subsys_mask
|= 1 << ss
->id
;
5329 if (!ss
->dfl_cftypes
)
5330 cgrp_dfl_root_inhibit_ss_mask
|= 1 << ss
->id
;
5332 if (ss
->dfl_cftypes
== ss
->legacy_cftypes
) {
5333 WARN_ON(cgroup_add_cftypes(ss
, ss
->dfl_cftypes
));
5335 WARN_ON(cgroup_add_dfl_cftypes(ss
, ss
->dfl_cftypes
));
5336 WARN_ON(cgroup_add_legacy_cftypes(ss
, ss
->legacy_cftypes
));
5340 ss
->bind(init_css_set
.subsys
[ssid
]);
5343 WARN_ON(sysfs_create_mount_point(fs_kobj
, "cgroup"));
5344 WARN_ON(register_filesystem(&cgroup_fs_type
));
5345 WARN_ON(register_filesystem(&cgroup2_fs_type
));
5346 WARN_ON(!proc_create("cgroups", 0, NULL
, &proc_cgroupstats_operations
));
5351 static int __init
cgroup_wq_init(void)
5354 * There isn't much point in executing destruction path in
5355 * parallel. Good chunk is serialized with cgroup_mutex anyway.
5356 * Use 1 for @max_active.
5358 * We would prefer to do this in cgroup_init() above, but that
5359 * is called before init_workqueues(): so leave this until after.
5361 cgroup_destroy_wq
= alloc_workqueue("cgroup_destroy", 0, 1);
5362 BUG_ON(!cgroup_destroy_wq
);
5365 * Used to destroy pidlists and separate to serve as flush domain.
5366 * Cap @max_active to 1 too.
5368 cgroup_pidlist_destroy_wq
= alloc_workqueue("cgroup_pidlist_destroy",
5370 BUG_ON(!cgroup_pidlist_destroy_wq
);
5374 core_initcall(cgroup_wq_init
);
5377 * proc_cgroup_show()
5378 * - Print task's cgroup paths into seq_file, one line for each hierarchy
5379 * - Used for /proc/<pid>/cgroup.
5381 int proc_cgroup_show(struct seq_file
*m
, struct pid_namespace
*ns
,
5382 struct pid
*pid
, struct task_struct
*tsk
)
5386 struct cgroup_root
*root
;
5389 buf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
5393 mutex_lock(&cgroup_mutex
);
5394 spin_lock_bh(&css_set_lock
);
5396 for_each_root(root
) {
5397 struct cgroup_subsys
*ss
;
5398 struct cgroup
*cgrp
;
5399 int ssid
, count
= 0;
5401 if (root
== &cgrp_dfl_root
&& !cgrp_dfl_root_visible
)
5404 seq_printf(m
, "%d:", root
->hierarchy_id
);
5405 if (root
!= &cgrp_dfl_root
)
5406 for_each_subsys(ss
, ssid
)
5407 if (root
->subsys_mask
& (1 << ssid
))
5408 seq_printf(m
, "%s%s", count
++ ? "," : "",
5410 if (strlen(root
->name
))
5411 seq_printf(m
, "%sname=%s", count
? "," : "",
5415 cgrp
= task_cgroup_from_root(tsk
, root
);
5418 * On traditional hierarchies, all zombie tasks show up as
5419 * belonging to the root cgroup. On the default hierarchy,
5420 * while a zombie doesn't show up in "cgroup.procs" and
5421 * thus can't be migrated, its /proc/PID/cgroup keeps
5422 * reporting the cgroup it belonged to before exiting. If
5423 * the cgroup is removed before the zombie is reaped,
5424 * " (deleted)" is appended to the cgroup path.
5426 if (cgroup_on_dfl(cgrp
) || !(tsk
->flags
& PF_EXITING
)) {
5427 path
= cgroup_path(cgrp
, buf
, PATH_MAX
);
5429 retval
= -ENAMETOOLONG
;
5438 if (cgroup_on_dfl(cgrp
) && cgroup_is_dead(cgrp
))
5439 seq_puts(m
, " (deleted)\n");
5446 spin_unlock_bh(&css_set_lock
);
5447 mutex_unlock(&cgroup_mutex
);
5453 /* Display information about each subsystem and each hierarchy */
5454 static int proc_cgroupstats_show(struct seq_file
*m
, void *v
)
5456 struct cgroup_subsys
*ss
;
5459 seq_puts(m
, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
5461 * ideally we don't want subsystems moving around while we do this.
5462 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
5463 * subsys/hierarchy state.
5465 mutex_lock(&cgroup_mutex
);
5467 for_each_subsys(ss
, i
)
5468 seq_printf(m
, "%s\t%d\t%d\t%d\n",
5469 ss
->legacy_name
, ss
->root
->hierarchy_id
,
5470 atomic_read(&ss
->root
->nr_cgrps
),
5471 cgroup_ssid_enabled(i
));
5473 mutex_unlock(&cgroup_mutex
);
5477 static int cgroupstats_open(struct inode
*inode
, struct file
*file
)
5479 return single_open(file
, proc_cgroupstats_show
, NULL
);
5482 static const struct file_operations proc_cgroupstats_operations
= {
5483 .open
= cgroupstats_open
,
5485 .llseek
= seq_lseek
,
5486 .release
= single_release
,
5490 * cgroup_fork - initialize cgroup related fields during copy_process()
5491 * @child: pointer to task_struct of forking parent process.
5493 * A task is associated with the init_css_set until cgroup_post_fork()
5494 * attaches it to the parent's css_set. Empty cg_list indicates that
5495 * @child isn't holding reference to its css_set.
5497 void cgroup_fork(struct task_struct
*child
)
5499 RCU_INIT_POINTER(child
->cgroups
, &init_css_set
);
5500 INIT_LIST_HEAD(&child
->cg_list
);
5504 * cgroup_can_fork - called on a new task before the process is exposed
5505 * @child: the task in question.
5507 * This calls the subsystem can_fork() callbacks. If the can_fork() callback
5508 * returns an error, the fork aborts with that error code. This allows for
5509 * a cgroup subsystem to conditionally allow or deny new forks.
5511 int cgroup_can_fork(struct task_struct
*child
)
5513 struct cgroup_subsys
*ss
;
5516 for_each_subsys_which(ss
, i
, &have_canfork_callback
) {
5517 ret
= ss
->can_fork(child
);
5525 for_each_subsys(ss
, j
) {
5528 if (ss
->cancel_fork
)
5529 ss
->cancel_fork(child
);
5536 * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
5537 * @child: the task in question
5539 * This calls the cancel_fork() callbacks if a fork failed *after*
5540 * cgroup_can_fork() succeded.
5542 void cgroup_cancel_fork(struct task_struct
*child
)
5544 struct cgroup_subsys
*ss
;
5547 for_each_subsys(ss
, i
)
5548 if (ss
->cancel_fork
)
5549 ss
->cancel_fork(child
);
5553 * cgroup_post_fork - called on a new task after adding it to the task list
5554 * @child: the task in question
5556 * Adds the task to the list running through its css_set if necessary and
5557 * call the subsystem fork() callbacks. Has to be after the task is
5558 * visible on the task list in case we race with the first call to
5559 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
5562 void cgroup_post_fork(struct task_struct
*child
)
5564 struct cgroup_subsys
*ss
;
5568 * This may race against cgroup_enable_task_cg_lists(). As that
5569 * function sets use_task_css_set_links before grabbing
5570 * tasklist_lock and we just went through tasklist_lock to add
5571 * @child, it's guaranteed that either we see the set
5572 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
5573 * @child during its iteration.
5575 * If we won the race, @child is associated with %current's
5576 * css_set. Grabbing css_set_lock guarantees both that the
5577 * association is stable, and, on completion of the parent's
5578 * migration, @child is visible in the source of migration or
5579 * already in the destination cgroup. This guarantee is necessary
5580 * when implementing operations which need to migrate all tasks of
5581 * a cgroup to another.
5583 * Note that if we lose to cgroup_enable_task_cg_lists(), @child
5584 * will remain in init_css_set. This is safe because all tasks are
5585 * in the init_css_set before cg_links is enabled and there's no
5586 * operation which transfers all tasks out of init_css_set.
5588 if (use_task_css_set_links
) {
5589 struct css_set
*cset
;
5591 spin_lock_bh(&css_set_lock
);
5592 cset
= task_css_set(current
);
5593 if (list_empty(&child
->cg_list
)) {
5595 css_set_move_task(child
, NULL
, cset
, false);
5597 spin_unlock_bh(&css_set_lock
);
5601 * Call ss->fork(). This must happen after @child is linked on
5602 * css_set; otherwise, @child might change state between ->fork()
5603 * and addition to css_set.
5605 for_each_subsys_which(ss
, i
, &have_fork_callback
)
5610 * cgroup_exit - detach cgroup from exiting task
5611 * @tsk: pointer to task_struct of exiting process
5613 * Description: Detach cgroup from @tsk and release it.
5615 * Note that cgroups marked notify_on_release force every task in
5616 * them to take the global cgroup_mutex mutex when exiting.
5617 * This could impact scaling on very large systems. Be reluctant to
5618 * use notify_on_release cgroups where very high task exit scaling
5619 * is required on large systems.
5621 * We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
5622 * call cgroup_exit() while the task is still competent to handle
5623 * notify_on_release(), then leave the task attached to the root cgroup in
5624 * each hierarchy for the remainder of its exit. No need to bother with
5625 * init_css_set refcnting. init_css_set never goes away and we can't race
5626 * with migration path - PF_EXITING is visible to migration path.
5628 void cgroup_exit(struct task_struct
*tsk
)
5630 struct cgroup_subsys
*ss
;
5631 struct css_set
*cset
;
5635 * Unlink from @tsk from its css_set. As migration path can't race
5636 * with us, we can check css_set and cg_list without synchronization.
5638 cset
= task_css_set(tsk
);
5640 if (!list_empty(&tsk
->cg_list
)) {
5641 spin_lock_bh(&css_set_lock
);
5642 css_set_move_task(tsk
, cset
, NULL
, false);
5643 spin_unlock_bh(&css_set_lock
);
5648 /* see cgroup_post_fork() for details */
5649 for_each_subsys_which(ss
, i
, &have_exit_callback
)
5653 void cgroup_free(struct task_struct
*task
)
5655 struct css_set
*cset
= task_css_set(task
);
5656 struct cgroup_subsys
*ss
;
5659 for_each_subsys_which(ss
, ssid
, &have_free_callback
)
5665 static void check_for_release(struct cgroup
*cgrp
)
5667 if (notify_on_release(cgrp
) && !cgroup_is_populated(cgrp
) &&
5668 !css_has_online_children(&cgrp
->self
) && !cgroup_is_dead(cgrp
))
5669 schedule_work(&cgrp
->release_agent_work
);
5673 * Notify userspace when a cgroup is released, by running the
5674 * configured release agent with the name of the cgroup (path
5675 * relative to the root of cgroup file system) as the argument.
5677 * Most likely, this user command will try to rmdir this cgroup.
5679 * This races with the possibility that some other task will be
5680 * attached to this cgroup before it is removed, or that some other
5681 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
5682 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
5683 * unused, and this cgroup will be reprieved from its death sentence,
5684 * to continue to serve a useful existence. Next time it's released,
5685 * we will get notified again, if it still has 'notify_on_release' set.
5687 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
5688 * means only wait until the task is successfully execve()'d. The
5689 * separate release agent task is forked by call_usermodehelper(),
5690 * then control in this thread returns here, without waiting for the
5691 * release agent task. We don't bother to wait because the caller of
5692 * this routine has no use for the exit status of the release agent
5693 * task, so no sense holding our caller up for that.
5695 static void cgroup_release_agent(struct work_struct
*work
)
5697 struct cgroup
*cgrp
=
5698 container_of(work
, struct cgroup
, release_agent_work
);
5699 char *pathbuf
= NULL
, *agentbuf
= NULL
, *path
;
5700 char *argv
[3], *envp
[3];
5702 mutex_lock(&cgroup_mutex
);
5704 pathbuf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
5705 agentbuf
= kstrdup(cgrp
->root
->release_agent_path
, GFP_KERNEL
);
5706 if (!pathbuf
|| !agentbuf
)
5709 path
= cgroup_path(cgrp
, pathbuf
, PATH_MAX
);
5717 /* minimal command environment */
5719 envp
[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
5722 mutex_unlock(&cgroup_mutex
);
5723 call_usermodehelper(argv
[0], argv
, envp
, UMH_WAIT_EXEC
);
5726 mutex_unlock(&cgroup_mutex
);
5732 static int __init
cgroup_disable(char *str
)
5734 struct cgroup_subsys
*ss
;
5738 while ((token
= strsep(&str
, ",")) != NULL
) {
5742 for_each_subsys(ss
, i
) {
5743 if (strcmp(token
, ss
->name
) &&
5744 strcmp(token
, ss
->legacy_name
))
5746 cgroup_disable_mask
|= 1 << i
;
5751 __setup("cgroup_disable=", cgroup_disable
);
5754 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
5755 * @dentry: directory dentry of interest
5756 * @ss: subsystem of interest
5758 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
5759 * to get the corresponding css and return it. If such css doesn't exist
5760 * or can't be pinned, an ERR_PTR value is returned.
5762 struct cgroup_subsys_state
*css_tryget_online_from_dir(struct dentry
*dentry
,
5763 struct cgroup_subsys
*ss
)
5765 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
5766 struct cgroup_subsys_state
*css
= NULL
;
5767 struct cgroup
*cgrp
;
5769 /* is @dentry a cgroup dir? */
5770 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
5771 kernfs_type(kn
) != KERNFS_DIR
)
5772 return ERR_PTR(-EBADF
);
5777 * This path doesn't originate from kernfs and @kn could already
5778 * have been or be removed at any point. @kn->priv is RCU
5779 * protected for this access. See css_release_work_fn() for details.
5781 cgrp
= rcu_dereference(kn
->priv
);
5783 css
= cgroup_css(cgrp
, ss
);
5785 if (!css
|| !css_tryget_online(css
))
5786 css
= ERR_PTR(-ENOENT
);
5793 * css_from_id - lookup css by id
5794 * @id: the cgroup id
5795 * @ss: cgroup subsys to be looked into
5797 * Returns the css if there's valid one with @id, otherwise returns NULL.
5798 * Should be called under rcu_read_lock().
5800 struct cgroup_subsys_state
*css_from_id(int id
, struct cgroup_subsys
*ss
)
5802 WARN_ON_ONCE(!rcu_read_lock_held());
5803 return id
> 0 ? idr_find(&ss
->css_idr
, id
) : NULL
;
5807 * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path
5808 * @path: path on the default hierarchy
5810 * Find the cgroup at @path on the default hierarchy, increment its
5811 * reference count and return it. Returns pointer to the found cgroup on
5812 * success, ERR_PTR(-ENOENT) if @path doens't exist and ERR_PTR(-ENOTDIR)
5813 * if @path points to a non-directory.
5815 struct cgroup
*cgroup_get_from_path(const char *path
)
5817 struct kernfs_node
*kn
;
5818 struct cgroup
*cgrp
;
5820 mutex_lock(&cgroup_mutex
);
5822 kn
= kernfs_walk_and_get(cgrp_dfl_root
.cgrp
.kn
, path
);
5824 if (kernfs_type(kn
) == KERNFS_DIR
) {
5828 cgrp
= ERR_PTR(-ENOTDIR
);
5832 cgrp
= ERR_PTR(-ENOENT
);
5835 mutex_unlock(&cgroup_mutex
);
5838 EXPORT_SYMBOL_GPL(cgroup_get_from_path
);
5841 * sock->sk_cgrp_data handling. For more info, see sock_cgroup_data
5842 * definition in cgroup-defs.h.
5844 #ifdef CONFIG_SOCK_CGROUP_DATA
5846 #if defined(CONFIG_CGROUP_NET_PRIO) || defined(CONFIG_CGROUP_NET_CLASSID)
5848 DEFINE_SPINLOCK(cgroup_sk_update_lock
);
5849 static bool cgroup_sk_alloc_disabled __read_mostly
;
5851 void cgroup_sk_alloc_disable(void)
5853 if (cgroup_sk_alloc_disabled
)
5855 pr_info("cgroup: disabling cgroup2 socket matching due to net_prio or net_cls activation\n");
5856 cgroup_sk_alloc_disabled
= true;
5861 #define cgroup_sk_alloc_disabled false
5865 void cgroup_sk_alloc(struct sock_cgroup_data
*skcd
)
5867 if (cgroup_sk_alloc_disabled
)
5873 struct css_set
*cset
;
5875 cset
= task_css_set(current
);
5876 if (likely(cgroup_tryget(cset
->dfl_cgrp
))) {
5877 skcd
->val
= (unsigned long)cset
->dfl_cgrp
;
5886 void cgroup_sk_free(struct sock_cgroup_data
*skcd
)
5888 cgroup_put(sock_cgroup_ptr(skcd
));
5891 #endif /* CONFIG_SOCK_CGROUP_DATA */
5893 #ifdef CONFIG_CGROUP_DEBUG
5894 static struct cgroup_subsys_state
*
5895 debug_css_alloc(struct cgroup_subsys_state
*parent_css
)
5897 struct cgroup_subsys_state
*css
= kzalloc(sizeof(*css
), GFP_KERNEL
);
5900 return ERR_PTR(-ENOMEM
);
5905 static void debug_css_free(struct cgroup_subsys_state
*css
)
5910 static u64
debug_taskcount_read(struct cgroup_subsys_state
*css
,
5913 return cgroup_task_count(css
->cgroup
);
5916 static u64
current_css_set_read(struct cgroup_subsys_state
*css
,
5919 return (u64
)(unsigned long)current
->cgroups
;
5922 static u64
current_css_set_refcount_read(struct cgroup_subsys_state
*css
,
5928 count
= atomic_read(&task_css_set(current
)->refcount
);
5933 static int current_css_set_cg_links_read(struct seq_file
*seq
, void *v
)
5935 struct cgrp_cset_link
*link
;
5936 struct css_set
*cset
;
5939 name_buf
= kmalloc(NAME_MAX
+ 1, GFP_KERNEL
);
5943 spin_lock_bh(&css_set_lock
);
5945 cset
= rcu_dereference(current
->cgroups
);
5946 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
5947 struct cgroup
*c
= link
->cgrp
;
5949 cgroup_name(c
, name_buf
, NAME_MAX
+ 1);
5950 seq_printf(seq
, "Root %d group %s\n",
5951 c
->root
->hierarchy_id
, name_buf
);
5954 spin_unlock_bh(&css_set_lock
);
5959 #define MAX_TASKS_SHOWN_PER_CSS 25
5960 static int cgroup_css_links_read(struct seq_file
*seq
, void *v
)
5962 struct cgroup_subsys_state
*css
= seq_css(seq
);
5963 struct cgrp_cset_link
*link
;
5965 spin_lock_bh(&css_set_lock
);
5966 list_for_each_entry(link
, &css
->cgroup
->cset_links
, cset_link
) {
5967 struct css_set
*cset
= link
->cset
;
5968 struct task_struct
*task
;
5971 seq_printf(seq
, "css_set %p\n", cset
);
5973 list_for_each_entry(task
, &cset
->tasks
, cg_list
) {
5974 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
5976 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
5979 list_for_each_entry(task
, &cset
->mg_tasks
, cg_list
) {
5980 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
5982 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
5986 seq_puts(seq
, " ...\n");
5988 spin_unlock_bh(&css_set_lock
);
5992 static u64
releasable_read(struct cgroup_subsys_state
*css
, struct cftype
*cft
)
5994 return (!cgroup_is_populated(css
->cgroup
) &&
5995 !css_has_online_children(&css
->cgroup
->self
));
5998 static struct cftype debug_files
[] = {
6000 .name
= "taskcount",
6001 .read_u64
= debug_taskcount_read
,
6005 .name
= "current_css_set",
6006 .read_u64
= current_css_set_read
,
6010 .name
= "current_css_set_refcount",
6011 .read_u64
= current_css_set_refcount_read
,
6015 .name
= "current_css_set_cg_links",
6016 .seq_show
= current_css_set_cg_links_read
,
6020 .name
= "cgroup_css_links",
6021 .seq_show
= cgroup_css_links_read
,
6025 .name
= "releasable",
6026 .read_u64
= releasable_read
,
6032 struct cgroup_subsys debug_cgrp_subsys
= {
6033 .css_alloc
= debug_css_alloc
,
6034 .css_free
= debug_css_free
,
6035 .legacy_cftypes
= debug_files
,
6037 #endif /* CONFIG_CGROUP_DEBUG */