2 * Generic process-grouping system.
4 * Based originally on the cpuset system, extracted by Paul Menage
5 * Copyright (C) 2006 Google, Inc
7 * Notifications support
8 * Copyright (C) 2009 Nokia Corporation
9 * Author: Kirill A. Shutemov
11 * Copyright notices from the original cpuset code:
12 * --------------------------------------------------
13 * Copyright (C) 2003 BULL SA.
14 * Copyright (C) 2004-2006 Silicon Graphics, Inc.
16 * Portions derived from Patrick Mochel's sysfs code.
17 * sysfs is Copyright (c) 2001-3 Patrick Mochel
19 * 2003-10-10 Written by Simon Derr.
20 * 2003-10-22 Updates by Stephen Hemminger.
21 * 2004 May-July Rework by Paul Jackson.
22 * ---------------------------------------------------
24 * This file is subject to the terms and conditions of the GNU General Public
25 * License. See the file COPYING in the main directory of the Linux
26 * distribution for more details.
29 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
31 #include "cgroup-internal.h"
33 #include <linux/cred.h>
34 #include <linux/errno.h>
35 #include <linux/init_task.h>
36 #include <linux/kernel.h>
37 #include <linux/magic.h>
38 #include <linux/mutex.h>
39 #include <linux/mount.h>
40 #include <linux/pagemap.h>
41 #include <linux/proc_fs.h>
42 #include <linux/rcupdate.h>
43 #include <linux/sched.h>
44 #include <linux/sched/task.h>
45 #include <linux/slab.h>
46 #include <linux/spinlock.h>
47 #include <linux/percpu-rwsem.h>
48 #include <linux/string.h>
49 #include <linux/hashtable.h>
50 #include <linux/idr.h>
51 #include <linux/kthread.h>
52 #include <linux/atomic.h>
53 #include <linux/cpuset.h>
54 #include <linux/proc_ns.h>
55 #include <linux/nsproxy.h>
56 #include <linux/file.h>
59 #define CREATE_TRACE_POINTS
60 #include <trace/events/cgroup.h>
62 #define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
66 * cgroup_mutex is the master lock. Any modification to cgroup or its
67 * hierarchy must be performed while holding it.
69 * css_set_lock protects task->cgroups pointer, the list of css_set
70 * objects, and the chain of tasks off each css_set.
72 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
73 * cgroup.h can use them for lockdep annotations.
75 DEFINE_MUTEX(cgroup_mutex
);
76 DEFINE_SPINLOCK(css_set_lock
);
78 #ifdef CONFIG_PROVE_RCU
79 EXPORT_SYMBOL_GPL(cgroup_mutex
);
80 EXPORT_SYMBOL_GPL(css_set_lock
);
84 * Protects cgroup_idr and css_idr so that IDs can be released without
85 * grabbing cgroup_mutex.
87 static DEFINE_SPINLOCK(cgroup_idr_lock
);
90 * Protects cgroup_file->kn for !self csses. It synchronizes notifications
91 * against file removal/re-creation across css hiding.
93 static DEFINE_SPINLOCK(cgroup_file_kn_lock
);
95 struct percpu_rw_semaphore cgroup_threadgroup_rwsem
;
97 #define cgroup_assert_mutex_or_rcu_locked() \
98 RCU_LOCKDEP_WARN(!rcu_read_lock_held() && \
99 !lockdep_is_held(&cgroup_mutex), \
100 "cgroup_mutex or RCU read lock required");
103 * cgroup destruction makes heavy use of work items and there can be a lot
104 * of concurrent destructions. Use a separate workqueue so that cgroup
105 * destruction work items don't end up filling up max_active of system_wq
106 * which may lead to deadlock.
108 static struct workqueue_struct
*cgroup_destroy_wq
;
110 /* generate an array of cgroup subsystem pointers */
111 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
112 struct cgroup_subsys
*cgroup_subsys
[] = {
113 #include <linux/cgroup_subsys.h>
117 /* array of cgroup subsystem names */
118 #define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
119 static const char *cgroup_subsys_name
[] = {
120 #include <linux/cgroup_subsys.h>
124 /* array of static_keys for cgroup_subsys_enabled() and cgroup_subsys_on_dfl() */
126 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key); \
127 DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key); \
128 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key); \
129 EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key);
130 #include <linux/cgroup_subsys.h>
133 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_enabled_key,
134 static struct static_key_true
*cgroup_subsys_enabled_key
[] = {
135 #include <linux/cgroup_subsys.h>
139 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_on_dfl_key,
140 static struct static_key_true
*cgroup_subsys_on_dfl_key
[] = {
141 #include <linux/cgroup_subsys.h>
146 * The default hierarchy, reserved for the subsystems that are otherwise
147 * unattached - it never has more than a single cgroup, and all tasks are
148 * part of that cgroup.
150 struct cgroup_root cgrp_dfl_root
;
151 EXPORT_SYMBOL_GPL(cgrp_dfl_root
);
154 * The default hierarchy always exists but is hidden until mounted for the
155 * first time. This is for backward compatibility.
157 static bool cgrp_dfl_visible
;
159 /* some controllers are not supported in the default hierarchy */
160 static u16 cgrp_dfl_inhibit_ss_mask
;
162 /* some controllers are implicitly enabled on the default hierarchy */
163 static u16 cgrp_dfl_implicit_ss_mask
;
165 /* some controllers can be threaded on the default hierarchy */
166 static u16 cgrp_dfl_threaded_ss_mask
;
168 /* The list of hierarchy roots */
169 LIST_HEAD(cgroup_roots
);
170 static int cgroup_root_count
;
172 /* hierarchy ID allocation and mapping, protected by cgroup_mutex */
173 static DEFINE_IDR(cgroup_hierarchy_idr
);
176 * Assign a monotonically increasing serial number to csses. It guarantees
177 * cgroups with bigger numbers are newer than those with smaller numbers.
178 * Also, as csses are always appended to the parent's ->children list, it
179 * guarantees that sibling csses are always sorted in the ascending serial
180 * number order on the list. Protected by cgroup_mutex.
182 static u64 css_serial_nr_next
= 1;
185 * These bitmasks identify subsystems with specific features to avoid
186 * having to do iterative checks repeatedly.
188 static u16 have_fork_callback __read_mostly
;
189 static u16 have_exit_callback __read_mostly
;
190 static u16 have_free_callback __read_mostly
;
191 static u16 have_canfork_callback __read_mostly
;
193 /* cgroup namespace for init task */
194 struct cgroup_namespace init_cgroup_ns
= {
195 .count
= REFCOUNT_INIT(2),
196 .user_ns
= &init_user_ns
,
197 .ns
.ops
= &cgroupns_operations
,
198 .ns
.inum
= PROC_CGROUP_INIT_INO
,
199 .root_cset
= &init_css_set
,
202 static struct file_system_type cgroup2_fs_type
;
203 static struct cftype cgroup_base_files
[];
205 static int cgroup_apply_control(struct cgroup
*cgrp
);
206 static void cgroup_finalize_control(struct cgroup
*cgrp
, int ret
);
207 static void css_task_iter_advance(struct css_task_iter
*it
);
208 static int cgroup_destroy_locked(struct cgroup
*cgrp
);
209 static struct cgroup_subsys_state
*css_create(struct cgroup
*cgrp
,
210 struct cgroup_subsys
*ss
);
211 static void css_release(struct percpu_ref
*ref
);
212 static void kill_css(struct cgroup_subsys_state
*css
);
213 static int cgroup_addrm_files(struct cgroup_subsys_state
*css
,
214 struct cgroup
*cgrp
, struct cftype cfts
[],
218 * cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID
219 * @ssid: subsys ID of interest
221 * cgroup_subsys_enabled() can only be used with literal subsys names which
222 * is fine for individual subsystems but unsuitable for cgroup core. This
223 * is slower static_key_enabled() based test indexed by @ssid.
225 bool cgroup_ssid_enabled(int ssid
)
227 if (CGROUP_SUBSYS_COUNT
== 0)
230 return static_key_enabled(cgroup_subsys_enabled_key
[ssid
]);
234 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
235 * @cgrp: the cgroup of interest
237 * The default hierarchy is the v2 interface of cgroup and this function
238 * can be used to test whether a cgroup is on the default hierarchy for
239 * cases where a subsystem should behave differnetly depending on the
242 * The set of behaviors which change on the default hierarchy are still
243 * being determined and the mount option is prefixed with __DEVEL__.
245 * List of changed behaviors:
247 * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
248 * and "name" are disallowed.
250 * - When mounting an existing superblock, mount options should match.
252 * - Remount is disallowed.
254 * - rename(2) is disallowed.
256 * - "tasks" is removed. Everything should be at process granularity. Use
257 * "cgroup.procs" instead.
259 * - "cgroup.procs" is not sorted. pids will be unique unless they got
260 * recycled inbetween reads.
262 * - "release_agent" and "notify_on_release" are removed. Replacement
263 * notification mechanism will be implemented.
265 * - "cgroup.clone_children" is removed.
267 * - "cgroup.subtree_populated" is available. Its value is 0 if the cgroup
268 * and its descendants contain no task; otherwise, 1. The file also
269 * generates kernfs notification which can be monitored through poll and
270 * [di]notify when the value of the file changes.
272 * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
273 * take masks of ancestors with non-empty cpus/mems, instead of being
274 * moved to an ancestor.
276 * - cpuset: a task can be moved into an empty cpuset, and again it takes
277 * masks of ancestors.
279 * - memcg: use_hierarchy is on by default and the cgroup file for the flag
282 * - blkcg: blk-throttle becomes properly hierarchical.
284 * - debug: disallowed on the default hierarchy.
286 bool cgroup_on_dfl(const struct cgroup
*cgrp
)
288 return cgrp
->root
== &cgrp_dfl_root
;
291 /* IDR wrappers which synchronize using cgroup_idr_lock */
292 static int cgroup_idr_alloc(struct idr
*idr
, void *ptr
, int start
, int end
,
297 idr_preload(gfp_mask
);
298 spin_lock_bh(&cgroup_idr_lock
);
299 ret
= idr_alloc(idr
, ptr
, start
, end
, gfp_mask
& ~__GFP_DIRECT_RECLAIM
);
300 spin_unlock_bh(&cgroup_idr_lock
);
305 static void *cgroup_idr_replace(struct idr
*idr
, void *ptr
, int id
)
309 spin_lock_bh(&cgroup_idr_lock
);
310 ret
= idr_replace(idr
, ptr
, id
);
311 spin_unlock_bh(&cgroup_idr_lock
);
315 static void cgroup_idr_remove(struct idr
*idr
, int id
)
317 spin_lock_bh(&cgroup_idr_lock
);
319 spin_unlock_bh(&cgroup_idr_lock
);
322 static struct cgroup
*cgroup_parent(struct cgroup
*cgrp
)
324 struct cgroup_subsys_state
*parent_css
= cgrp
->self
.parent
;
327 return container_of(parent_css
, struct cgroup
, self
);
331 static bool cgroup_has_tasks(struct cgroup
*cgrp
)
333 return cgrp
->nr_populated_csets
;
336 bool cgroup_is_threaded(struct cgroup
*cgrp
)
338 return cgrp
->dom_cgrp
!= cgrp
;
341 /* can @cgrp host both domain and threaded children? */
342 static bool cgroup_is_mixable(struct cgroup
*cgrp
)
345 * Root isn't under domain level resource control exempting it from
346 * the no-internal-process constraint, so it can serve as a thread
347 * root and a parent of resource domains at the same time.
349 return !cgroup_parent(cgrp
);
352 /* can @cgrp become a thread root? should always be true for a thread root */
353 static bool cgroup_can_be_thread_root(struct cgroup
*cgrp
)
355 /* mixables don't care */
356 if (cgroup_is_mixable(cgrp
))
359 /* domain roots can't be nested under threaded */
360 if (cgroup_is_threaded(cgrp
))
363 /* can only have either domain or threaded children */
364 if (cgrp
->nr_populated_domain_children
)
367 /* and no domain controllers can be enabled */
368 if (cgrp
->subtree_control
& ~cgrp_dfl_threaded_ss_mask
)
374 /* is @cgrp root of a threaded subtree? */
375 bool cgroup_is_thread_root(struct cgroup
*cgrp
)
377 /* thread root should be a domain */
378 if (cgroup_is_threaded(cgrp
))
381 /* a domain w/ threaded children is a thread root */
382 if (cgrp
->nr_threaded_children
)
386 * A domain which has tasks and explicit threaded controllers
387 * enabled is a thread root.
389 if (cgroup_has_tasks(cgrp
) &&
390 (cgrp
->subtree_control
& cgrp_dfl_threaded_ss_mask
))
396 /* a domain which isn't connected to the root w/o brekage can't be used */
397 static bool cgroup_is_valid_domain(struct cgroup
*cgrp
)
399 /* the cgroup itself can be a thread root */
400 if (cgroup_is_threaded(cgrp
))
403 /* but the ancestors can't be unless mixable */
404 while ((cgrp
= cgroup_parent(cgrp
))) {
405 if (!cgroup_is_mixable(cgrp
) && cgroup_is_thread_root(cgrp
))
407 if (cgroup_is_threaded(cgrp
))
414 /* subsystems visibly enabled on a cgroup */
415 static u16
cgroup_control(struct cgroup
*cgrp
)
417 struct cgroup
*parent
= cgroup_parent(cgrp
);
418 u16 root_ss_mask
= cgrp
->root
->subsys_mask
;
421 u16 ss_mask
= parent
->subtree_control
;
423 /* threaded cgroups can only have threaded controllers */
424 if (cgroup_is_threaded(cgrp
))
425 ss_mask
&= cgrp_dfl_threaded_ss_mask
;
429 if (cgroup_on_dfl(cgrp
))
430 root_ss_mask
&= ~(cgrp_dfl_inhibit_ss_mask
|
431 cgrp_dfl_implicit_ss_mask
);
435 /* subsystems enabled on a cgroup */
436 static u16
cgroup_ss_mask(struct cgroup
*cgrp
)
438 struct cgroup
*parent
= cgroup_parent(cgrp
);
441 u16 ss_mask
= parent
->subtree_ss_mask
;
443 /* threaded cgroups can only have threaded controllers */
444 if (cgroup_is_threaded(cgrp
))
445 ss_mask
&= cgrp_dfl_threaded_ss_mask
;
449 return cgrp
->root
->subsys_mask
;
453 * cgroup_css - obtain a cgroup's css for the specified subsystem
454 * @cgrp: the cgroup of interest
455 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
457 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
458 * function must be called either under cgroup_mutex or rcu_read_lock() and
459 * the caller is responsible for pinning the returned css if it wants to
460 * keep accessing it outside the said locks. This function may return
461 * %NULL if @cgrp doesn't have @subsys_id enabled.
463 static struct cgroup_subsys_state
*cgroup_css(struct cgroup
*cgrp
,
464 struct cgroup_subsys
*ss
)
467 return rcu_dereference_check(cgrp
->subsys
[ss
->id
],
468 lockdep_is_held(&cgroup_mutex
));
474 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
475 * @cgrp: the cgroup of interest
476 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
478 * Similar to cgroup_css() but returns the effective css, which is defined
479 * as the matching css of the nearest ancestor including self which has @ss
480 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
481 * function is guaranteed to return non-NULL css.
483 static struct cgroup_subsys_state
*cgroup_e_css(struct cgroup
*cgrp
,
484 struct cgroup_subsys
*ss
)
486 lockdep_assert_held(&cgroup_mutex
);
492 * This function is used while updating css associations and thus
493 * can't test the csses directly. Test ss_mask.
495 while (!(cgroup_ss_mask(cgrp
) & (1 << ss
->id
))) {
496 cgrp
= cgroup_parent(cgrp
);
501 return cgroup_css(cgrp
, ss
);
505 * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
506 * @cgrp: the cgroup of interest
507 * @ss: the subsystem of interest
509 * Find and get the effective css of @cgrp for @ss. The effective css is
510 * defined as the matching css of the nearest ancestor including self which
511 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
512 * the root css is returned, so this function always returns a valid css.
513 * The returned css must be put using css_put().
515 struct cgroup_subsys_state
*cgroup_get_e_css(struct cgroup
*cgrp
,
516 struct cgroup_subsys
*ss
)
518 struct cgroup_subsys_state
*css
;
523 css
= cgroup_css(cgrp
, ss
);
525 if (css
&& css_tryget_online(css
))
527 cgrp
= cgroup_parent(cgrp
);
530 css
= init_css_set
.subsys
[ss
->id
];
537 static void __maybe_unused
cgroup_get(struct cgroup
*cgrp
)
539 css_get(&cgrp
->self
);
542 static void cgroup_get_live(struct cgroup
*cgrp
)
544 WARN_ON_ONCE(cgroup_is_dead(cgrp
));
545 css_get(&cgrp
->self
);
548 static bool cgroup_tryget(struct cgroup
*cgrp
)
550 return css_tryget(&cgrp
->self
);
553 struct cgroup_subsys_state
*of_css(struct kernfs_open_file
*of
)
555 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
556 struct cftype
*cft
= of_cft(of
);
559 * This is open and unprotected implementation of cgroup_css().
560 * seq_css() is only called from a kernfs file operation which has
561 * an active reference on the file. Because all the subsystem
562 * files are drained before a css is disassociated with a cgroup,
563 * the matching css from the cgroup's subsys table is guaranteed to
564 * be and stay valid until the enclosing operation is complete.
567 return rcu_dereference_raw(cgrp
->subsys
[cft
->ss
->id
]);
571 EXPORT_SYMBOL_GPL(of_css
);
574 * for_each_css - iterate all css's of a cgroup
575 * @css: the iteration cursor
576 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
577 * @cgrp: the target cgroup to iterate css's of
579 * Should be called under cgroup_[tree_]mutex.
581 #define for_each_css(css, ssid, cgrp) \
582 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
583 if (!((css) = rcu_dereference_check( \
584 (cgrp)->subsys[(ssid)], \
585 lockdep_is_held(&cgroup_mutex)))) { } \
589 * for_each_e_css - iterate all effective css's of a cgroup
590 * @css: the iteration cursor
591 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
592 * @cgrp: the target cgroup to iterate css's of
594 * Should be called under cgroup_[tree_]mutex.
596 #define for_each_e_css(css, ssid, cgrp) \
597 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
598 if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
603 * do_each_subsys_mask - filter for_each_subsys with a bitmask
604 * @ss: the iteration cursor
605 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
606 * @ss_mask: the bitmask
608 * The block will only run for cases where the ssid-th bit (1 << ssid) of
611 #define do_each_subsys_mask(ss, ssid, ss_mask) do { \
612 unsigned long __ss_mask = (ss_mask); \
613 if (!CGROUP_SUBSYS_COUNT) { /* to avoid spurious gcc warning */ \
617 for_each_set_bit(ssid, &__ss_mask, CGROUP_SUBSYS_COUNT) { \
618 (ss) = cgroup_subsys[ssid]; \
621 #define while_each_subsys_mask() \
626 /* iterate over child cgrps, lock should be held throughout iteration */
627 #define cgroup_for_each_live_child(child, cgrp) \
628 list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
629 if (({ lockdep_assert_held(&cgroup_mutex); \
630 cgroup_is_dead(child); })) \
634 /* walk live descendants in preorder */
635 #define cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) \
636 css_for_each_descendant_pre((d_css), cgroup_css((cgrp), NULL)) \
637 if (({ lockdep_assert_held(&cgroup_mutex); \
638 (dsct) = (d_css)->cgroup; \
639 cgroup_is_dead(dsct); })) \
643 /* walk live descendants in postorder */
644 #define cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) \
645 css_for_each_descendant_post((d_css), cgroup_css((cgrp), NULL)) \
646 if (({ lockdep_assert_held(&cgroup_mutex); \
647 (dsct) = (d_css)->cgroup; \
648 cgroup_is_dead(dsct); })) \
653 * The default css_set - used by init and its children prior to any
654 * hierarchies being mounted. It contains a pointer to the root state
655 * for each subsystem. Also used to anchor the list of css_sets. Not
656 * reference-counted, to improve performance when child cgroups
657 * haven't been created.
659 struct css_set init_css_set
= {
660 .refcount
= REFCOUNT_INIT(1),
661 .dom_cset
= &init_css_set
,
662 .tasks
= LIST_HEAD_INIT(init_css_set
.tasks
),
663 .mg_tasks
= LIST_HEAD_INIT(init_css_set
.mg_tasks
),
664 .task_iters
= LIST_HEAD_INIT(init_css_set
.task_iters
),
665 .threaded_csets
= LIST_HEAD_INIT(init_css_set
.threaded_csets
),
666 .cgrp_links
= LIST_HEAD_INIT(init_css_set
.cgrp_links
),
667 .mg_preload_node
= LIST_HEAD_INIT(init_css_set
.mg_preload_node
),
668 .mg_node
= LIST_HEAD_INIT(init_css_set
.mg_node
),
671 static int css_set_count
= 1; /* 1 for init_css_set */
673 static bool css_set_threaded(struct css_set
*cset
)
675 return cset
->dom_cset
!= cset
;
679 * css_set_populated - does a css_set contain any tasks?
680 * @cset: target css_set
682 * css_set_populated() should be the same as !!cset->nr_tasks at steady
683 * state. However, css_set_populated() can be called while a task is being
684 * added to or removed from the linked list before the nr_tasks is
685 * properly updated. Hence, we can't just look at ->nr_tasks here.
687 static bool css_set_populated(struct css_set
*cset
)
689 lockdep_assert_held(&css_set_lock
);
691 return !list_empty(&cset
->tasks
) || !list_empty(&cset
->mg_tasks
);
695 * cgroup_update_populated - update the populated count of a cgroup
696 * @cgrp: the target cgroup
697 * @populated: inc or dec populated count
699 * One of the css_sets associated with @cgrp is either getting its first
700 * task or losing the last. Update @cgrp->nr_populated_* accordingly. The
701 * count is propagated towards root so that a given cgroup's
702 * nr_populated_children is zero iff none of its descendants contain any
705 * @cgrp's interface file "cgroup.populated" is zero if both
706 * @cgrp->nr_populated_csets and @cgrp->nr_populated_children are zero and
707 * 1 otherwise. When the sum changes from or to zero, userland is notified
708 * that the content of the interface file has changed. This can be used to
709 * detect when @cgrp and its descendants become populated or empty.
711 static void cgroup_update_populated(struct cgroup
*cgrp
, bool populated
)
713 struct cgroup
*child
= NULL
;
714 int adj
= populated
? 1 : -1;
716 lockdep_assert_held(&css_set_lock
);
719 bool was_populated
= cgroup_is_populated(cgrp
);
722 cgrp
->nr_populated_csets
+= adj
;
724 if (cgroup_is_threaded(child
))
725 cgrp
->nr_populated_threaded_children
+= adj
;
727 cgrp
->nr_populated_domain_children
+= adj
;
730 if (was_populated
== cgroup_is_populated(cgrp
))
733 cgroup1_check_for_release(cgrp
);
734 cgroup_file_notify(&cgrp
->events_file
);
737 cgrp
= cgroup_parent(cgrp
);
742 * css_set_update_populated - update populated state of a css_set
743 * @cset: target css_set
744 * @populated: whether @cset is populated or depopulated
746 * @cset is either getting the first task or losing the last. Update the
747 * populated counters of all associated cgroups accordingly.
749 static void css_set_update_populated(struct css_set
*cset
, bool populated
)
751 struct cgrp_cset_link
*link
;
753 lockdep_assert_held(&css_set_lock
);
755 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
)
756 cgroup_update_populated(link
->cgrp
, populated
);
760 * css_set_move_task - move a task from one css_set to another
761 * @task: task being moved
762 * @from_cset: css_set @task currently belongs to (may be NULL)
763 * @to_cset: new css_set @task is being moved to (may be NULL)
764 * @use_mg_tasks: move to @to_cset->mg_tasks instead of ->tasks
766 * Move @task from @from_cset to @to_cset. If @task didn't belong to any
767 * css_set, @from_cset can be NULL. If @task is being disassociated
768 * instead of moved, @to_cset can be NULL.
770 * This function automatically handles populated counter updates and
771 * css_task_iter adjustments but the caller is responsible for managing
772 * @from_cset and @to_cset's reference counts.
774 static void css_set_move_task(struct task_struct
*task
,
775 struct css_set
*from_cset
, struct css_set
*to_cset
,
778 lockdep_assert_held(&css_set_lock
);
780 if (to_cset
&& !css_set_populated(to_cset
))
781 css_set_update_populated(to_cset
, true);
784 struct css_task_iter
*it
, *pos
;
786 WARN_ON_ONCE(list_empty(&task
->cg_list
));
789 * @task is leaving, advance task iterators which are
790 * pointing to it so that they can resume at the next
791 * position. Advancing an iterator might remove it from
792 * the list, use safe walk. See css_task_iter_advance*()
795 list_for_each_entry_safe(it
, pos
, &from_cset
->task_iters
,
797 if (it
->task_pos
== &task
->cg_list
)
798 css_task_iter_advance(it
);
800 list_del_init(&task
->cg_list
);
801 if (!css_set_populated(from_cset
))
802 css_set_update_populated(from_cset
, false);
804 WARN_ON_ONCE(!list_empty(&task
->cg_list
));
809 * We are synchronized through cgroup_threadgroup_rwsem
810 * against PF_EXITING setting such that we can't race
811 * against cgroup_exit() changing the css_set to
812 * init_css_set and dropping the old one.
814 WARN_ON_ONCE(task
->flags
& PF_EXITING
);
816 rcu_assign_pointer(task
->cgroups
, to_cset
);
817 list_add_tail(&task
->cg_list
, use_mg_tasks
? &to_cset
->mg_tasks
:
823 * hash table for cgroup groups. This improves the performance to find
824 * an existing css_set. This hash doesn't (currently) take into
825 * account cgroups in empty hierarchies.
827 #define CSS_SET_HASH_BITS 7
828 static DEFINE_HASHTABLE(css_set_table
, CSS_SET_HASH_BITS
);
830 static unsigned long css_set_hash(struct cgroup_subsys_state
*css
[])
832 unsigned long key
= 0UL;
833 struct cgroup_subsys
*ss
;
836 for_each_subsys(ss
, i
)
837 key
+= (unsigned long)css
[i
];
838 key
= (key
>> 16) ^ key
;
843 void put_css_set_locked(struct css_set
*cset
)
845 struct cgrp_cset_link
*link
, *tmp_link
;
846 struct cgroup_subsys
*ss
;
849 lockdep_assert_held(&css_set_lock
);
851 if (!refcount_dec_and_test(&cset
->refcount
))
854 WARN_ON_ONCE(!list_empty(&cset
->threaded_csets
));
856 /* This css_set is dead. unlink it and release cgroup and css refs */
857 for_each_subsys(ss
, ssid
) {
858 list_del(&cset
->e_cset_node
[ssid
]);
859 css_put(cset
->subsys
[ssid
]);
861 hash_del(&cset
->hlist
);
864 list_for_each_entry_safe(link
, tmp_link
, &cset
->cgrp_links
, cgrp_link
) {
865 list_del(&link
->cset_link
);
866 list_del(&link
->cgrp_link
);
867 if (cgroup_parent(link
->cgrp
))
868 cgroup_put(link
->cgrp
);
872 if (css_set_threaded(cset
)) {
873 list_del(&cset
->threaded_csets_node
);
874 put_css_set_locked(cset
->dom_cset
);
877 kfree_rcu(cset
, rcu_head
);
881 * compare_css_sets - helper function for find_existing_css_set().
882 * @cset: candidate css_set being tested
883 * @old_cset: existing css_set for a task
884 * @new_cgrp: cgroup that's being entered by the task
885 * @template: desired set of css pointers in css_set (pre-calculated)
887 * Returns true if "cset" matches "old_cset" except for the hierarchy
888 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
890 static bool compare_css_sets(struct css_set
*cset
,
891 struct css_set
*old_cset
,
892 struct cgroup
*new_cgrp
,
893 struct cgroup_subsys_state
*template[])
895 struct cgroup
*new_dfl_cgrp
;
896 struct list_head
*l1
, *l2
;
899 * On the default hierarchy, there can be csets which are
900 * associated with the same set of cgroups but different csses.
901 * Let's first ensure that csses match.
903 if (memcmp(template, cset
->subsys
, sizeof(cset
->subsys
)))
907 /* @cset's domain should match the default cgroup's */
908 if (cgroup_on_dfl(new_cgrp
))
909 new_dfl_cgrp
= new_cgrp
;
911 new_dfl_cgrp
= old_cset
->dfl_cgrp
;
913 if (new_dfl_cgrp
->dom_cgrp
!= cset
->dom_cset
->dfl_cgrp
)
917 * Compare cgroup pointers in order to distinguish between
918 * different cgroups in hierarchies. As different cgroups may
919 * share the same effective css, this comparison is always
922 l1
= &cset
->cgrp_links
;
923 l2
= &old_cset
->cgrp_links
;
925 struct cgrp_cset_link
*link1
, *link2
;
926 struct cgroup
*cgrp1
, *cgrp2
;
930 /* See if we reached the end - both lists are equal length. */
931 if (l1
== &cset
->cgrp_links
) {
932 BUG_ON(l2
!= &old_cset
->cgrp_links
);
935 BUG_ON(l2
== &old_cset
->cgrp_links
);
937 /* Locate the cgroups associated with these links. */
938 link1
= list_entry(l1
, struct cgrp_cset_link
, cgrp_link
);
939 link2
= list_entry(l2
, struct cgrp_cset_link
, cgrp_link
);
942 /* Hierarchies should be linked in the same order. */
943 BUG_ON(cgrp1
->root
!= cgrp2
->root
);
946 * If this hierarchy is the hierarchy of the cgroup
947 * that's changing, then we need to check that this
948 * css_set points to the new cgroup; if it's any other
949 * hierarchy, then this css_set should point to the
950 * same cgroup as the old css_set.
952 if (cgrp1
->root
== new_cgrp
->root
) {
953 if (cgrp1
!= new_cgrp
)
964 * find_existing_css_set - init css array and find the matching css_set
965 * @old_cset: the css_set that we're using before the cgroup transition
966 * @cgrp: the cgroup that we're moving into
967 * @template: out param for the new set of csses, should be clear on entry
969 static struct css_set
*find_existing_css_set(struct css_set
*old_cset
,
971 struct cgroup_subsys_state
*template[])
973 struct cgroup_root
*root
= cgrp
->root
;
974 struct cgroup_subsys
*ss
;
975 struct css_set
*cset
;
980 * Build the set of subsystem state objects that we want to see in the
981 * new css_set. while subsystems can change globally, the entries here
982 * won't change, so no need for locking.
984 for_each_subsys(ss
, i
) {
985 if (root
->subsys_mask
& (1UL << i
)) {
987 * @ss is in this hierarchy, so we want the
988 * effective css from @cgrp.
990 template[i
] = cgroup_e_css(cgrp
, ss
);
993 * @ss is not in this hierarchy, so we don't want
996 template[i
] = old_cset
->subsys
[i
];
1000 key
= css_set_hash(template);
1001 hash_for_each_possible(css_set_table
, cset
, hlist
, key
) {
1002 if (!compare_css_sets(cset
, old_cset
, cgrp
, template))
1005 /* This css_set matches what we need */
1009 /* No existing cgroup group matched */
1013 static void free_cgrp_cset_links(struct list_head
*links_to_free
)
1015 struct cgrp_cset_link
*link
, *tmp_link
;
1017 list_for_each_entry_safe(link
, tmp_link
, links_to_free
, cset_link
) {
1018 list_del(&link
->cset_link
);
1024 * allocate_cgrp_cset_links - allocate cgrp_cset_links
1025 * @count: the number of links to allocate
1026 * @tmp_links: list_head the allocated links are put on
1028 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
1029 * through ->cset_link. Returns 0 on success or -errno.
1031 static int allocate_cgrp_cset_links(int count
, struct list_head
*tmp_links
)
1033 struct cgrp_cset_link
*link
;
1036 INIT_LIST_HEAD(tmp_links
);
1038 for (i
= 0; i
< count
; i
++) {
1039 link
= kzalloc(sizeof(*link
), GFP_KERNEL
);
1041 free_cgrp_cset_links(tmp_links
);
1044 list_add(&link
->cset_link
, tmp_links
);
1050 * link_css_set - a helper function to link a css_set to a cgroup
1051 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
1052 * @cset: the css_set to be linked
1053 * @cgrp: the destination cgroup
1055 static void link_css_set(struct list_head
*tmp_links
, struct css_set
*cset
,
1056 struct cgroup
*cgrp
)
1058 struct cgrp_cset_link
*link
;
1060 BUG_ON(list_empty(tmp_links
));
1062 if (cgroup_on_dfl(cgrp
))
1063 cset
->dfl_cgrp
= cgrp
;
1065 link
= list_first_entry(tmp_links
, struct cgrp_cset_link
, cset_link
);
1070 * Always add links to the tail of the lists so that the lists are
1071 * in choronological order.
1073 list_move_tail(&link
->cset_link
, &cgrp
->cset_links
);
1074 list_add_tail(&link
->cgrp_link
, &cset
->cgrp_links
);
1076 if (cgroup_parent(cgrp
))
1077 cgroup_get_live(cgrp
);
1081 * find_css_set - return a new css_set with one cgroup updated
1082 * @old_cset: the baseline css_set
1083 * @cgrp: the cgroup to be updated
1085 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
1086 * substituted into the appropriate hierarchy.
1088 static struct css_set
*find_css_set(struct css_set
*old_cset
,
1089 struct cgroup
*cgrp
)
1091 struct cgroup_subsys_state
*template[CGROUP_SUBSYS_COUNT
] = { };
1092 struct css_set
*cset
;
1093 struct list_head tmp_links
;
1094 struct cgrp_cset_link
*link
;
1095 struct cgroup_subsys
*ss
;
1099 lockdep_assert_held(&cgroup_mutex
);
1101 /* First see if we already have a cgroup group that matches
1102 * the desired set */
1103 spin_lock_irq(&css_set_lock
);
1104 cset
= find_existing_css_set(old_cset
, cgrp
, template);
1107 spin_unlock_irq(&css_set_lock
);
1112 cset
= kzalloc(sizeof(*cset
), GFP_KERNEL
);
1116 /* Allocate all the cgrp_cset_link objects that we'll need */
1117 if (allocate_cgrp_cset_links(cgroup_root_count
, &tmp_links
) < 0) {
1122 refcount_set(&cset
->refcount
, 1);
1123 cset
->dom_cset
= cset
;
1124 INIT_LIST_HEAD(&cset
->tasks
);
1125 INIT_LIST_HEAD(&cset
->mg_tasks
);
1126 INIT_LIST_HEAD(&cset
->task_iters
);
1127 INIT_LIST_HEAD(&cset
->threaded_csets
);
1128 INIT_HLIST_NODE(&cset
->hlist
);
1129 INIT_LIST_HEAD(&cset
->cgrp_links
);
1130 INIT_LIST_HEAD(&cset
->mg_preload_node
);
1131 INIT_LIST_HEAD(&cset
->mg_node
);
1133 /* Copy the set of subsystem state objects generated in
1134 * find_existing_css_set() */
1135 memcpy(cset
->subsys
, template, sizeof(cset
->subsys
));
1137 spin_lock_irq(&css_set_lock
);
1138 /* Add reference counts and links from the new css_set. */
1139 list_for_each_entry(link
, &old_cset
->cgrp_links
, cgrp_link
) {
1140 struct cgroup
*c
= link
->cgrp
;
1142 if (c
->root
== cgrp
->root
)
1144 link_css_set(&tmp_links
, cset
, c
);
1147 BUG_ON(!list_empty(&tmp_links
));
1151 /* Add @cset to the hash table */
1152 key
= css_set_hash(cset
->subsys
);
1153 hash_add(css_set_table
, &cset
->hlist
, key
);
1155 for_each_subsys(ss
, ssid
) {
1156 struct cgroup_subsys_state
*css
= cset
->subsys
[ssid
];
1158 list_add_tail(&cset
->e_cset_node
[ssid
],
1159 &css
->cgroup
->e_csets
[ssid
]);
1163 spin_unlock_irq(&css_set_lock
);
1166 * If @cset should be threaded, look up the matching dom_cset and
1167 * link them up. We first fully initialize @cset then look for the
1168 * dom_cset. It's simpler this way and safe as @cset is guaranteed
1169 * to stay empty until we return.
1171 if (cgroup_is_threaded(cset
->dfl_cgrp
)) {
1172 struct css_set
*dcset
;
1174 dcset
= find_css_set(cset
, cset
->dfl_cgrp
->dom_cgrp
);
1180 spin_lock_irq(&css_set_lock
);
1181 cset
->dom_cset
= dcset
;
1182 list_add_tail(&cset
->threaded_csets_node
,
1183 &dcset
->threaded_csets
);
1184 spin_unlock_irq(&css_set_lock
);
1190 struct cgroup_root
*cgroup_root_from_kf(struct kernfs_root
*kf_root
)
1192 struct cgroup
*root_cgrp
= kf_root
->kn
->priv
;
1194 return root_cgrp
->root
;
1197 static int cgroup_init_root_id(struct cgroup_root
*root
)
1201 lockdep_assert_held(&cgroup_mutex
);
1203 id
= idr_alloc_cyclic(&cgroup_hierarchy_idr
, root
, 0, 0, GFP_KERNEL
);
1207 root
->hierarchy_id
= id
;
1211 static void cgroup_exit_root_id(struct cgroup_root
*root
)
1213 lockdep_assert_held(&cgroup_mutex
);
1215 idr_remove(&cgroup_hierarchy_idr
, root
->hierarchy_id
);
1218 void cgroup_free_root(struct cgroup_root
*root
)
1221 idr_destroy(&root
->cgroup_idr
);
1226 static void cgroup_destroy_root(struct cgroup_root
*root
)
1228 struct cgroup
*cgrp
= &root
->cgrp
;
1229 struct cgrp_cset_link
*link
, *tmp_link
;
1231 trace_cgroup_destroy_root(root
);
1233 cgroup_lock_and_drain_offline(&cgrp_dfl_root
.cgrp
);
1235 BUG_ON(atomic_read(&root
->nr_cgrps
));
1236 BUG_ON(!list_empty(&cgrp
->self
.children
));
1238 /* Rebind all subsystems back to the default hierarchy */
1239 WARN_ON(rebind_subsystems(&cgrp_dfl_root
, root
->subsys_mask
));
1242 * Release all the links from cset_links to this hierarchy's
1245 spin_lock_irq(&css_set_lock
);
1247 list_for_each_entry_safe(link
, tmp_link
, &cgrp
->cset_links
, cset_link
) {
1248 list_del(&link
->cset_link
);
1249 list_del(&link
->cgrp_link
);
1253 spin_unlock_irq(&css_set_lock
);
1255 if (!list_empty(&root
->root_list
)) {
1256 list_del(&root
->root_list
);
1257 cgroup_root_count
--;
1260 cgroup_exit_root_id(root
);
1262 mutex_unlock(&cgroup_mutex
);
1264 kernfs_destroy_root(root
->kf_root
);
1265 cgroup_free_root(root
);
1269 * look up cgroup associated with current task's cgroup namespace on the
1270 * specified hierarchy
1272 static struct cgroup
*
1273 current_cgns_cgroup_from_root(struct cgroup_root
*root
)
1275 struct cgroup
*res
= NULL
;
1276 struct css_set
*cset
;
1278 lockdep_assert_held(&css_set_lock
);
1282 cset
= current
->nsproxy
->cgroup_ns
->root_cset
;
1283 if (cset
== &init_css_set
) {
1286 struct cgrp_cset_link
*link
;
1288 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
1289 struct cgroup
*c
= link
->cgrp
;
1291 if (c
->root
== root
) {
1303 /* look up cgroup associated with given css_set on the specified hierarchy */
1304 static struct cgroup
*cset_cgroup_from_root(struct css_set
*cset
,
1305 struct cgroup_root
*root
)
1307 struct cgroup
*res
= NULL
;
1309 lockdep_assert_held(&cgroup_mutex
);
1310 lockdep_assert_held(&css_set_lock
);
1312 if (cset
== &init_css_set
) {
1315 struct cgrp_cset_link
*link
;
1317 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
1318 struct cgroup
*c
= link
->cgrp
;
1320 if (c
->root
== root
) {
1332 * Return the cgroup for "task" from the given hierarchy. Must be
1333 * called with cgroup_mutex and css_set_lock held.
1335 struct cgroup
*task_cgroup_from_root(struct task_struct
*task
,
1336 struct cgroup_root
*root
)
1339 * No need to lock the task - since we hold cgroup_mutex the
1340 * task can't change groups, so the only thing that can happen
1341 * is that it exits and its css is set back to init_css_set.
1343 return cset_cgroup_from_root(task_css_set(task
), root
);
1347 * A task must hold cgroup_mutex to modify cgroups.
1349 * Any task can increment and decrement the count field without lock.
1350 * So in general, code holding cgroup_mutex can't rely on the count
1351 * field not changing. However, if the count goes to zero, then only
1352 * cgroup_attach_task() can increment it again. Because a count of zero
1353 * means that no tasks are currently attached, therefore there is no
1354 * way a task attached to that cgroup can fork (the other way to
1355 * increment the count). So code holding cgroup_mutex can safely
1356 * assume that if the count is zero, it will stay zero. Similarly, if
1357 * a task holds cgroup_mutex on a cgroup with zero count, it
1358 * knows that the cgroup won't be removed, as cgroup_rmdir()
1361 * A cgroup can only be deleted if both its 'count' of using tasks
1362 * is zero, and its list of 'children' cgroups is empty. Since all
1363 * tasks in the system use _some_ cgroup, and since there is always at
1364 * least one task in the system (init, pid == 1), therefore, root cgroup
1365 * always has either children cgroups and/or using tasks. So we don't
1366 * need a special hack to ensure that root cgroup cannot be deleted.
1368 * P.S. One more locking exception. RCU is used to guard the
1369 * update of a tasks cgroup pointer by cgroup_attach_task()
1372 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
;
1374 static char *cgroup_file_name(struct cgroup
*cgrp
, const struct cftype
*cft
,
1377 struct cgroup_subsys
*ss
= cft
->ss
;
1379 if (cft
->ss
&& !(cft
->flags
& CFTYPE_NO_PREFIX
) &&
1380 !(cgrp
->root
->flags
& CGRP_ROOT_NOPREFIX
))
1381 snprintf(buf
, CGROUP_FILE_NAME_MAX
, "%s.%s",
1382 cgroup_on_dfl(cgrp
) ? ss
->name
: ss
->legacy_name
,
1385 strncpy(buf
, cft
->name
, CGROUP_FILE_NAME_MAX
);
1390 * cgroup_file_mode - deduce file mode of a control file
1391 * @cft: the control file in question
1393 * S_IRUGO for read, S_IWUSR for write.
1395 static umode_t
cgroup_file_mode(const struct cftype
*cft
)
1399 if (cft
->read_u64
|| cft
->read_s64
|| cft
->seq_show
)
1402 if (cft
->write_u64
|| cft
->write_s64
|| cft
->write
) {
1403 if (cft
->flags
& CFTYPE_WORLD_WRITABLE
)
1413 * cgroup_calc_subtree_ss_mask - calculate subtree_ss_mask
1414 * @subtree_control: the new subtree_control mask to consider
1415 * @this_ss_mask: available subsystems
1417 * On the default hierarchy, a subsystem may request other subsystems to be
1418 * enabled together through its ->depends_on mask. In such cases, more
1419 * subsystems than specified in "cgroup.subtree_control" may be enabled.
1421 * This function calculates which subsystems need to be enabled if
1422 * @subtree_control is to be applied while restricted to @this_ss_mask.
1424 static u16
cgroup_calc_subtree_ss_mask(u16 subtree_control
, u16 this_ss_mask
)
1426 u16 cur_ss_mask
= subtree_control
;
1427 struct cgroup_subsys
*ss
;
1430 lockdep_assert_held(&cgroup_mutex
);
1432 cur_ss_mask
|= cgrp_dfl_implicit_ss_mask
;
1435 u16 new_ss_mask
= cur_ss_mask
;
1437 do_each_subsys_mask(ss
, ssid
, cur_ss_mask
) {
1438 new_ss_mask
|= ss
->depends_on
;
1439 } while_each_subsys_mask();
1442 * Mask out subsystems which aren't available. This can
1443 * happen only if some depended-upon subsystems were bound
1444 * to non-default hierarchies.
1446 new_ss_mask
&= this_ss_mask
;
1448 if (new_ss_mask
== cur_ss_mask
)
1450 cur_ss_mask
= new_ss_mask
;
1457 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1458 * @kn: the kernfs_node being serviced
1460 * This helper undoes cgroup_kn_lock_live() and should be invoked before
1461 * the method finishes if locking succeeded. Note that once this function
1462 * returns the cgroup returned by cgroup_kn_lock_live() may become
1463 * inaccessible any time. If the caller intends to continue to access the
1464 * cgroup, it should pin it before invoking this function.
1466 void cgroup_kn_unlock(struct kernfs_node
*kn
)
1468 struct cgroup
*cgrp
;
1470 if (kernfs_type(kn
) == KERNFS_DIR
)
1473 cgrp
= kn
->parent
->priv
;
1475 mutex_unlock(&cgroup_mutex
);
1477 kernfs_unbreak_active_protection(kn
);
1482 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1483 * @kn: the kernfs_node being serviced
1484 * @drain_offline: perform offline draining on the cgroup
1486 * This helper is to be used by a cgroup kernfs method currently servicing
1487 * @kn. It breaks the active protection, performs cgroup locking and
1488 * verifies that the associated cgroup is alive. Returns the cgroup if
1489 * alive; otherwise, %NULL. A successful return should be undone by a
1490 * matching cgroup_kn_unlock() invocation. If @drain_offline is %true, the
1491 * cgroup is drained of offlining csses before return.
1493 * Any cgroup kernfs method implementation which requires locking the
1494 * associated cgroup should use this helper. It avoids nesting cgroup
1495 * locking under kernfs active protection and allows all kernfs operations
1496 * including self-removal.
1498 struct cgroup
*cgroup_kn_lock_live(struct kernfs_node
*kn
, bool drain_offline
)
1500 struct cgroup
*cgrp
;
1502 if (kernfs_type(kn
) == KERNFS_DIR
)
1505 cgrp
= kn
->parent
->priv
;
1508 * We're gonna grab cgroup_mutex which nests outside kernfs
1509 * active_ref. cgroup liveliness check alone provides enough
1510 * protection against removal. Ensure @cgrp stays accessible and
1511 * break the active_ref protection.
1513 if (!cgroup_tryget(cgrp
))
1515 kernfs_break_active_protection(kn
);
1518 cgroup_lock_and_drain_offline(cgrp
);
1520 mutex_lock(&cgroup_mutex
);
1522 if (!cgroup_is_dead(cgrp
))
1525 cgroup_kn_unlock(kn
);
1529 static void cgroup_rm_file(struct cgroup
*cgrp
, const struct cftype
*cft
)
1531 char name
[CGROUP_FILE_NAME_MAX
];
1533 lockdep_assert_held(&cgroup_mutex
);
1535 if (cft
->file_offset
) {
1536 struct cgroup_subsys_state
*css
= cgroup_css(cgrp
, cft
->ss
);
1537 struct cgroup_file
*cfile
= (void *)css
+ cft
->file_offset
;
1539 spin_lock_irq(&cgroup_file_kn_lock
);
1541 spin_unlock_irq(&cgroup_file_kn_lock
);
1544 kernfs_remove_by_name(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
));
1548 * css_clear_dir - remove subsys files in a cgroup directory
1551 static void css_clear_dir(struct cgroup_subsys_state
*css
)
1553 struct cgroup
*cgrp
= css
->cgroup
;
1554 struct cftype
*cfts
;
1556 if (!(css
->flags
& CSS_VISIBLE
))
1559 css
->flags
&= ~CSS_VISIBLE
;
1561 list_for_each_entry(cfts
, &css
->ss
->cfts
, node
)
1562 cgroup_addrm_files(css
, cgrp
, cfts
, false);
1566 * css_populate_dir - create subsys files in a cgroup directory
1569 * On failure, no file is added.
1571 static int css_populate_dir(struct cgroup_subsys_state
*css
)
1573 struct cgroup
*cgrp
= css
->cgroup
;
1574 struct cftype
*cfts
, *failed_cfts
;
1577 if ((css
->flags
& CSS_VISIBLE
) || !cgrp
->kn
)
1581 if (cgroup_on_dfl(cgrp
))
1582 cfts
= cgroup_base_files
;
1584 cfts
= cgroup1_base_files
;
1586 return cgroup_addrm_files(&cgrp
->self
, cgrp
, cfts
, true);
1589 list_for_each_entry(cfts
, &css
->ss
->cfts
, node
) {
1590 ret
= cgroup_addrm_files(css
, cgrp
, cfts
, true);
1597 css
->flags
|= CSS_VISIBLE
;
1601 list_for_each_entry(cfts
, &css
->ss
->cfts
, node
) {
1602 if (cfts
== failed_cfts
)
1604 cgroup_addrm_files(css
, cgrp
, cfts
, false);
1609 int rebind_subsystems(struct cgroup_root
*dst_root
, u16 ss_mask
)
1611 struct cgroup
*dcgrp
= &dst_root
->cgrp
;
1612 struct cgroup_subsys
*ss
;
1615 lockdep_assert_held(&cgroup_mutex
);
1617 do_each_subsys_mask(ss
, ssid
, ss_mask
) {
1619 * If @ss has non-root csses attached to it, can't move.
1620 * If @ss is an implicit controller, it is exempt from this
1621 * rule and can be stolen.
1623 if (css_next_child(NULL
, cgroup_css(&ss
->root
->cgrp
, ss
)) &&
1624 !ss
->implicit_on_dfl
)
1627 /* can't move between two non-dummy roots either */
1628 if (ss
->root
!= &cgrp_dfl_root
&& dst_root
!= &cgrp_dfl_root
)
1630 } while_each_subsys_mask();
1632 do_each_subsys_mask(ss
, ssid
, ss_mask
) {
1633 struct cgroup_root
*src_root
= ss
->root
;
1634 struct cgroup
*scgrp
= &src_root
->cgrp
;
1635 struct cgroup_subsys_state
*css
= cgroup_css(scgrp
, ss
);
1636 struct css_set
*cset
;
1638 WARN_ON(!css
|| cgroup_css(dcgrp
, ss
));
1640 /* disable from the source */
1641 src_root
->subsys_mask
&= ~(1 << ssid
);
1642 WARN_ON(cgroup_apply_control(scgrp
));
1643 cgroup_finalize_control(scgrp
, 0);
1646 RCU_INIT_POINTER(scgrp
->subsys
[ssid
], NULL
);
1647 rcu_assign_pointer(dcgrp
->subsys
[ssid
], css
);
1648 ss
->root
= dst_root
;
1649 css
->cgroup
= dcgrp
;
1651 spin_lock_irq(&css_set_lock
);
1652 hash_for_each(css_set_table
, i
, cset
, hlist
)
1653 list_move_tail(&cset
->e_cset_node
[ss
->id
],
1654 &dcgrp
->e_csets
[ss
->id
]);
1655 spin_unlock_irq(&css_set_lock
);
1657 /* default hierarchy doesn't enable controllers by default */
1658 dst_root
->subsys_mask
|= 1 << ssid
;
1659 if (dst_root
== &cgrp_dfl_root
) {
1660 static_branch_enable(cgroup_subsys_on_dfl_key
[ssid
]);
1662 dcgrp
->subtree_control
|= 1 << ssid
;
1663 static_branch_disable(cgroup_subsys_on_dfl_key
[ssid
]);
1666 ret
= cgroup_apply_control(dcgrp
);
1668 pr_warn("partial failure to rebind %s controller (err=%d)\n",
1673 } while_each_subsys_mask();
1675 kernfs_activate(dcgrp
->kn
);
1679 int cgroup_show_path(struct seq_file
*sf
, struct kernfs_node
*kf_node
,
1680 struct kernfs_root
*kf_root
)
1684 struct cgroup_root
*kf_cgroot
= cgroup_root_from_kf(kf_root
);
1685 struct cgroup
*ns_cgroup
;
1687 buf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
1691 spin_lock_irq(&css_set_lock
);
1692 ns_cgroup
= current_cgns_cgroup_from_root(kf_cgroot
);
1693 len
= kernfs_path_from_node(kf_node
, ns_cgroup
->kn
, buf
, PATH_MAX
);
1694 spin_unlock_irq(&css_set_lock
);
1696 if (len
>= PATH_MAX
)
1699 seq_escape(sf
, buf
, " \t\n\\");
1706 static int parse_cgroup_root_flags(char *data
, unsigned int *root_flags
)
1715 while ((token
= strsep(&data
, ",")) != NULL
) {
1716 if (!strcmp(token
, "nsdelegate")) {
1717 *root_flags
|= CGRP_ROOT_NS_DELEGATE
;
1721 pr_err("cgroup2: unknown option \"%s\"\n", token
);
1728 static void apply_cgroup_root_flags(unsigned int root_flags
)
1730 if (current
->nsproxy
->cgroup_ns
== &init_cgroup_ns
) {
1731 if (root_flags
& CGRP_ROOT_NS_DELEGATE
)
1732 cgrp_dfl_root
.flags
|= CGRP_ROOT_NS_DELEGATE
;
1734 cgrp_dfl_root
.flags
&= ~CGRP_ROOT_NS_DELEGATE
;
1738 static int cgroup_show_options(struct seq_file
*seq
, struct kernfs_root
*kf_root
)
1740 if (cgrp_dfl_root
.flags
& CGRP_ROOT_NS_DELEGATE
)
1741 seq_puts(seq
, ",nsdelegate");
1745 static int cgroup_remount(struct kernfs_root
*kf_root
, int *flags
, char *data
)
1747 unsigned int root_flags
;
1750 ret
= parse_cgroup_root_flags(data
, &root_flags
);
1754 apply_cgroup_root_flags(root_flags
);
1759 * To reduce the fork() overhead for systems that are not actually using
1760 * their cgroups capability, we don't maintain the lists running through
1761 * each css_set to its tasks until we see the list actually used - in other
1762 * words after the first mount.
1764 static bool use_task_css_set_links __read_mostly
;
1766 static void cgroup_enable_task_cg_lists(void)
1768 struct task_struct
*p
, *g
;
1770 spin_lock_irq(&css_set_lock
);
1772 if (use_task_css_set_links
)
1775 use_task_css_set_links
= true;
1778 * We need tasklist_lock because RCU is not safe against
1779 * while_each_thread(). Besides, a forking task that has passed
1780 * cgroup_post_fork() without seeing use_task_css_set_links = 1
1781 * is not guaranteed to have its child immediately visible in the
1782 * tasklist if we walk through it with RCU.
1784 read_lock(&tasklist_lock
);
1785 do_each_thread(g
, p
) {
1786 WARN_ON_ONCE(!list_empty(&p
->cg_list
) ||
1787 task_css_set(p
) != &init_css_set
);
1790 * We should check if the process is exiting, otherwise
1791 * it will race with cgroup_exit() in that the list
1792 * entry won't be deleted though the process has exited.
1793 * Do it while holding siglock so that we don't end up
1794 * racing against cgroup_exit().
1796 * Interrupts were already disabled while acquiring
1797 * the css_set_lock, so we do not need to disable it
1798 * again when acquiring the sighand->siglock here.
1800 spin_lock(&p
->sighand
->siglock
);
1801 if (!(p
->flags
& PF_EXITING
)) {
1802 struct css_set
*cset
= task_css_set(p
);
1804 if (!css_set_populated(cset
))
1805 css_set_update_populated(cset
, true);
1806 list_add_tail(&p
->cg_list
, &cset
->tasks
);
1810 spin_unlock(&p
->sighand
->siglock
);
1811 } while_each_thread(g
, p
);
1812 read_unlock(&tasklist_lock
);
1814 spin_unlock_irq(&css_set_lock
);
1817 static void init_cgroup_housekeeping(struct cgroup
*cgrp
)
1819 struct cgroup_subsys
*ss
;
1822 INIT_LIST_HEAD(&cgrp
->self
.sibling
);
1823 INIT_LIST_HEAD(&cgrp
->self
.children
);
1824 INIT_LIST_HEAD(&cgrp
->cset_links
);
1825 INIT_LIST_HEAD(&cgrp
->pidlists
);
1826 mutex_init(&cgrp
->pidlist_mutex
);
1827 cgrp
->self
.cgroup
= cgrp
;
1828 cgrp
->self
.flags
|= CSS_ONLINE
;
1829 cgrp
->dom_cgrp
= cgrp
;
1830 cgrp
->max_descendants
= INT_MAX
;
1831 cgrp
->max_depth
= INT_MAX
;
1833 for_each_subsys(ss
, ssid
)
1834 INIT_LIST_HEAD(&cgrp
->e_csets
[ssid
]);
1836 init_waitqueue_head(&cgrp
->offline_waitq
);
1837 INIT_WORK(&cgrp
->release_agent_work
, cgroup1_release_agent
);
1840 void init_cgroup_root(struct cgroup_root
*root
, struct cgroup_sb_opts
*opts
)
1842 struct cgroup
*cgrp
= &root
->cgrp
;
1844 INIT_LIST_HEAD(&root
->root_list
);
1845 atomic_set(&root
->nr_cgrps
, 1);
1847 init_cgroup_housekeeping(cgrp
);
1848 idr_init(&root
->cgroup_idr
);
1850 root
->flags
= opts
->flags
;
1851 if (opts
->release_agent
)
1852 strcpy(root
->release_agent_path
, opts
->release_agent
);
1854 strcpy(root
->name
, opts
->name
);
1855 if (opts
->cpuset_clone_children
)
1856 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
);
1859 int cgroup_setup_root(struct cgroup_root
*root
, u16 ss_mask
, int ref_flags
)
1861 LIST_HEAD(tmp_links
);
1862 struct cgroup
*root_cgrp
= &root
->cgrp
;
1863 struct kernfs_syscall_ops
*kf_sops
;
1864 struct css_set
*cset
;
1867 lockdep_assert_held(&cgroup_mutex
);
1869 ret
= cgroup_idr_alloc(&root
->cgroup_idr
, root_cgrp
, 1, 2, GFP_KERNEL
);
1872 root_cgrp
->id
= ret
;
1873 root_cgrp
->ancestor_ids
[0] = ret
;
1875 ret
= percpu_ref_init(&root_cgrp
->self
.refcnt
, css_release
,
1876 ref_flags
, GFP_KERNEL
);
1881 * We're accessing css_set_count without locking css_set_lock here,
1882 * but that's OK - it can only be increased by someone holding
1883 * cgroup_lock, and that's us. Later rebinding may disable
1884 * controllers on the default hierarchy and thus create new csets,
1885 * which can't be more than the existing ones. Allocate 2x.
1887 ret
= allocate_cgrp_cset_links(2 * css_set_count
, &tmp_links
);
1891 ret
= cgroup_init_root_id(root
);
1895 kf_sops
= root
== &cgrp_dfl_root
?
1896 &cgroup_kf_syscall_ops
: &cgroup1_kf_syscall_ops
;
1898 root
->kf_root
= kernfs_create_root(kf_sops
,
1899 KERNFS_ROOT_CREATE_DEACTIVATED
,
1901 if (IS_ERR(root
->kf_root
)) {
1902 ret
= PTR_ERR(root
->kf_root
);
1905 root_cgrp
->kn
= root
->kf_root
->kn
;
1907 ret
= css_populate_dir(&root_cgrp
->self
);
1911 ret
= rebind_subsystems(root
, ss_mask
);
1915 trace_cgroup_setup_root(root
);
1918 * There must be no failure case after here, since rebinding takes
1919 * care of subsystems' refcounts, which are explicitly dropped in
1920 * the failure exit path.
1922 list_add(&root
->root_list
, &cgroup_roots
);
1923 cgroup_root_count
++;
1926 * Link the root cgroup in this hierarchy into all the css_set
1929 spin_lock_irq(&css_set_lock
);
1930 hash_for_each(css_set_table
, i
, cset
, hlist
) {
1931 link_css_set(&tmp_links
, cset
, root_cgrp
);
1932 if (css_set_populated(cset
))
1933 cgroup_update_populated(root_cgrp
, true);
1935 spin_unlock_irq(&css_set_lock
);
1937 BUG_ON(!list_empty(&root_cgrp
->self
.children
));
1938 BUG_ON(atomic_read(&root
->nr_cgrps
) != 1);
1940 kernfs_activate(root_cgrp
->kn
);
1945 kernfs_destroy_root(root
->kf_root
);
1946 root
->kf_root
= NULL
;
1948 cgroup_exit_root_id(root
);
1950 percpu_ref_exit(&root_cgrp
->self
.refcnt
);
1952 free_cgrp_cset_links(&tmp_links
);
1956 struct dentry
*cgroup_do_mount(struct file_system_type
*fs_type
, int flags
,
1957 struct cgroup_root
*root
, unsigned long magic
,
1958 struct cgroup_namespace
*ns
)
1960 struct dentry
*dentry
;
1963 dentry
= kernfs_mount(fs_type
, flags
, root
->kf_root
, magic
, &new_sb
);
1966 * In non-init cgroup namespace, instead of root cgroup's dentry,
1967 * we return the dentry corresponding to the cgroupns->root_cgrp.
1969 if (!IS_ERR(dentry
) && ns
!= &init_cgroup_ns
) {
1970 struct dentry
*nsdentry
;
1971 struct cgroup
*cgrp
;
1973 mutex_lock(&cgroup_mutex
);
1974 spin_lock_irq(&css_set_lock
);
1976 cgrp
= cset_cgroup_from_root(ns
->root_cset
, root
);
1978 spin_unlock_irq(&css_set_lock
);
1979 mutex_unlock(&cgroup_mutex
);
1981 nsdentry
= kernfs_node_dentry(cgrp
->kn
, dentry
->d_sb
);
1986 if (IS_ERR(dentry
) || !new_sb
)
1987 cgroup_put(&root
->cgrp
);
1992 static struct dentry
*cgroup_mount(struct file_system_type
*fs_type
,
1993 int flags
, const char *unused_dev_name
,
1996 struct cgroup_namespace
*ns
= current
->nsproxy
->cgroup_ns
;
1997 struct dentry
*dentry
;
2002 /* Check if the caller has permission to mount. */
2003 if (!ns_capable(ns
->user_ns
, CAP_SYS_ADMIN
)) {
2005 return ERR_PTR(-EPERM
);
2009 * The first time anyone tries to mount a cgroup, enable the list
2010 * linking each css_set to its tasks and fix up all existing tasks.
2012 if (!use_task_css_set_links
)
2013 cgroup_enable_task_cg_lists();
2015 if (fs_type
== &cgroup2_fs_type
) {
2016 unsigned int root_flags
;
2018 ret
= parse_cgroup_root_flags(data
, &root_flags
);
2021 return ERR_PTR(ret
);
2024 cgrp_dfl_visible
= true;
2025 cgroup_get_live(&cgrp_dfl_root
.cgrp
);
2027 dentry
= cgroup_do_mount(&cgroup2_fs_type
, flags
, &cgrp_dfl_root
,
2028 CGROUP2_SUPER_MAGIC
, ns
);
2029 if (!IS_ERR(dentry
))
2030 apply_cgroup_root_flags(root_flags
);
2032 dentry
= cgroup1_mount(&cgroup_fs_type
, flags
, data
,
2033 CGROUP_SUPER_MAGIC
, ns
);
2040 static void cgroup_kill_sb(struct super_block
*sb
)
2042 struct kernfs_root
*kf_root
= kernfs_root_from_sb(sb
);
2043 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
2046 * If @root doesn't have any mounts or children, start killing it.
2047 * This prevents new mounts by disabling percpu_ref_tryget_live().
2048 * cgroup_mount() may wait for @root's release.
2050 * And don't kill the default root.
2052 if (!list_empty(&root
->cgrp
.self
.children
) ||
2053 root
== &cgrp_dfl_root
)
2054 cgroup_put(&root
->cgrp
);
2056 percpu_ref_kill(&root
->cgrp
.self
.refcnt
);
2061 struct file_system_type cgroup_fs_type
= {
2063 .mount
= cgroup_mount
,
2064 .kill_sb
= cgroup_kill_sb
,
2065 .fs_flags
= FS_USERNS_MOUNT
,
2068 static struct file_system_type cgroup2_fs_type
= {
2070 .mount
= cgroup_mount
,
2071 .kill_sb
= cgroup_kill_sb
,
2072 .fs_flags
= FS_USERNS_MOUNT
,
2075 int cgroup_path_ns_locked(struct cgroup
*cgrp
, char *buf
, size_t buflen
,
2076 struct cgroup_namespace
*ns
)
2078 struct cgroup
*root
= cset_cgroup_from_root(ns
->root_cset
, cgrp
->root
);
2080 return kernfs_path_from_node(cgrp
->kn
, root
->kn
, buf
, buflen
);
2083 int cgroup_path_ns(struct cgroup
*cgrp
, char *buf
, size_t buflen
,
2084 struct cgroup_namespace
*ns
)
2088 mutex_lock(&cgroup_mutex
);
2089 spin_lock_irq(&css_set_lock
);
2091 ret
= cgroup_path_ns_locked(cgrp
, buf
, buflen
, ns
);
2093 spin_unlock_irq(&css_set_lock
);
2094 mutex_unlock(&cgroup_mutex
);
2098 EXPORT_SYMBOL_GPL(cgroup_path_ns
);
2101 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
2102 * @task: target task
2103 * @buf: the buffer to write the path into
2104 * @buflen: the length of the buffer
2106 * Determine @task's cgroup on the first (the one with the lowest non-zero
2107 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
2108 * function grabs cgroup_mutex and shouldn't be used inside locks used by
2109 * cgroup controller callbacks.
2111 * Return value is the same as kernfs_path().
2113 int task_cgroup_path(struct task_struct
*task
, char *buf
, size_t buflen
)
2115 struct cgroup_root
*root
;
2116 struct cgroup
*cgrp
;
2117 int hierarchy_id
= 1;
2120 mutex_lock(&cgroup_mutex
);
2121 spin_lock_irq(&css_set_lock
);
2123 root
= idr_get_next(&cgroup_hierarchy_idr
, &hierarchy_id
);
2126 cgrp
= task_cgroup_from_root(task
, root
);
2127 ret
= cgroup_path_ns_locked(cgrp
, buf
, buflen
, &init_cgroup_ns
);
2129 /* if no hierarchy exists, everyone is in "/" */
2130 ret
= strlcpy(buf
, "/", buflen
);
2133 spin_unlock_irq(&css_set_lock
);
2134 mutex_unlock(&cgroup_mutex
);
2137 EXPORT_SYMBOL_GPL(task_cgroup_path
);
2140 * cgroup_migrate_add_task - add a migration target task to a migration context
2141 * @task: target task
2142 * @mgctx: target migration context
2144 * Add @task, which is a migration target, to @mgctx->tset. This function
2145 * becomes noop if @task doesn't need to be migrated. @task's css_set
2146 * should have been added as a migration source and @task->cg_list will be
2147 * moved from the css_set's tasks list to mg_tasks one.
2149 static void cgroup_migrate_add_task(struct task_struct
*task
,
2150 struct cgroup_mgctx
*mgctx
)
2152 struct css_set
*cset
;
2154 lockdep_assert_held(&css_set_lock
);
2156 /* @task either already exited or can't exit until the end */
2157 if (task
->flags
& PF_EXITING
)
2160 /* leave @task alone if post_fork() hasn't linked it yet */
2161 if (list_empty(&task
->cg_list
))
2164 cset
= task_css_set(task
);
2165 if (!cset
->mg_src_cgrp
)
2168 list_move_tail(&task
->cg_list
, &cset
->mg_tasks
);
2169 if (list_empty(&cset
->mg_node
))
2170 list_add_tail(&cset
->mg_node
,
2171 &mgctx
->tset
.src_csets
);
2172 if (list_empty(&cset
->mg_dst_cset
->mg_node
))
2173 list_add_tail(&cset
->mg_dst_cset
->mg_node
,
2174 &mgctx
->tset
.dst_csets
);
2178 * cgroup_taskset_first - reset taskset and return the first task
2179 * @tset: taskset of interest
2180 * @dst_cssp: output variable for the destination css
2182 * @tset iteration is initialized and the first task is returned.
2184 struct task_struct
*cgroup_taskset_first(struct cgroup_taskset
*tset
,
2185 struct cgroup_subsys_state
**dst_cssp
)
2187 tset
->cur_cset
= list_first_entry(tset
->csets
, struct css_set
, mg_node
);
2188 tset
->cur_task
= NULL
;
2190 return cgroup_taskset_next(tset
, dst_cssp
);
2194 * cgroup_taskset_next - iterate to the next task in taskset
2195 * @tset: taskset of interest
2196 * @dst_cssp: output variable for the destination css
2198 * Return the next task in @tset. Iteration must have been initialized
2199 * with cgroup_taskset_first().
2201 struct task_struct
*cgroup_taskset_next(struct cgroup_taskset
*tset
,
2202 struct cgroup_subsys_state
**dst_cssp
)
2204 struct css_set
*cset
= tset
->cur_cset
;
2205 struct task_struct
*task
= tset
->cur_task
;
2207 while (&cset
->mg_node
!= tset
->csets
) {
2209 task
= list_first_entry(&cset
->mg_tasks
,
2210 struct task_struct
, cg_list
);
2212 task
= list_next_entry(task
, cg_list
);
2214 if (&task
->cg_list
!= &cset
->mg_tasks
) {
2215 tset
->cur_cset
= cset
;
2216 tset
->cur_task
= task
;
2219 * This function may be called both before and
2220 * after cgroup_taskset_migrate(). The two cases
2221 * can be distinguished by looking at whether @cset
2222 * has its ->mg_dst_cset set.
2224 if (cset
->mg_dst_cset
)
2225 *dst_cssp
= cset
->mg_dst_cset
->subsys
[tset
->ssid
];
2227 *dst_cssp
= cset
->subsys
[tset
->ssid
];
2232 cset
= list_next_entry(cset
, mg_node
);
2240 * cgroup_taskset_migrate - migrate a taskset
2241 * @mgctx: migration context
2243 * Migrate tasks in @mgctx as setup by migration preparation functions.
2244 * This function fails iff one of the ->can_attach callbacks fails and
2245 * guarantees that either all or none of the tasks in @mgctx are migrated.
2246 * @mgctx is consumed regardless of success.
2248 static int cgroup_migrate_execute(struct cgroup_mgctx
*mgctx
)
2250 struct cgroup_taskset
*tset
= &mgctx
->tset
;
2251 struct cgroup_subsys
*ss
;
2252 struct task_struct
*task
, *tmp_task
;
2253 struct css_set
*cset
, *tmp_cset
;
2254 int ssid
, failed_ssid
, ret
;
2256 /* methods shouldn't be called if no task is actually migrating */
2257 if (list_empty(&tset
->src_csets
))
2260 /* check that we can legitimately attach to the cgroup */
2261 do_each_subsys_mask(ss
, ssid
, mgctx
->ss_mask
) {
2262 if (ss
->can_attach
) {
2264 ret
= ss
->can_attach(tset
);
2267 goto out_cancel_attach
;
2270 } while_each_subsys_mask();
2273 * Now that we're guaranteed success, proceed to move all tasks to
2274 * the new cgroup. There are no failure cases after here, so this
2275 * is the commit point.
2277 spin_lock_irq(&css_set_lock
);
2278 list_for_each_entry(cset
, &tset
->src_csets
, mg_node
) {
2279 list_for_each_entry_safe(task
, tmp_task
, &cset
->mg_tasks
, cg_list
) {
2280 struct css_set
*from_cset
= task_css_set(task
);
2281 struct css_set
*to_cset
= cset
->mg_dst_cset
;
2283 get_css_set(to_cset
);
2284 to_cset
->nr_tasks
++;
2285 css_set_move_task(task
, from_cset
, to_cset
, true);
2286 put_css_set_locked(from_cset
);
2287 from_cset
->nr_tasks
--;
2290 spin_unlock_irq(&css_set_lock
);
2293 * Migration is committed, all target tasks are now on dst_csets.
2294 * Nothing is sensitive to fork() after this point. Notify
2295 * controllers that migration is complete.
2297 tset
->csets
= &tset
->dst_csets
;
2299 do_each_subsys_mask(ss
, ssid
, mgctx
->ss_mask
) {
2304 } while_each_subsys_mask();
2307 goto out_release_tset
;
2310 do_each_subsys_mask(ss
, ssid
, mgctx
->ss_mask
) {
2311 if (ssid
== failed_ssid
)
2313 if (ss
->cancel_attach
) {
2315 ss
->cancel_attach(tset
);
2317 } while_each_subsys_mask();
2319 spin_lock_irq(&css_set_lock
);
2320 list_splice_init(&tset
->dst_csets
, &tset
->src_csets
);
2321 list_for_each_entry_safe(cset
, tmp_cset
, &tset
->src_csets
, mg_node
) {
2322 list_splice_tail_init(&cset
->mg_tasks
, &cset
->tasks
);
2323 list_del_init(&cset
->mg_node
);
2325 spin_unlock_irq(&css_set_lock
);
2330 * cgroup_migrate_vet_dst - verify whether a cgroup can be migration destination
2331 * @dst_cgrp: destination cgroup to test
2333 * On the default hierarchy, except for the mixable, (possible) thread root
2334 * and threaded cgroups, subtree_control must be zero for migration
2335 * destination cgroups with tasks so that child cgroups don't compete
2338 int cgroup_migrate_vet_dst(struct cgroup
*dst_cgrp
)
2340 /* v1 doesn't have any restriction */
2341 if (!cgroup_on_dfl(dst_cgrp
))
2344 /* verify @dst_cgrp can host resources */
2345 if (!cgroup_is_valid_domain(dst_cgrp
->dom_cgrp
))
2348 /* mixables don't care */
2349 if (cgroup_is_mixable(dst_cgrp
))
2353 * If @dst_cgrp is already or can become a thread root or is
2354 * threaded, it doesn't matter.
2356 if (cgroup_can_be_thread_root(dst_cgrp
) || cgroup_is_threaded(dst_cgrp
))
2359 /* apply no-internal-process constraint */
2360 if (dst_cgrp
->subtree_control
)
2367 * cgroup_migrate_finish - cleanup after attach
2368 * @mgctx: migration context
2370 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
2371 * those functions for details.
2373 void cgroup_migrate_finish(struct cgroup_mgctx
*mgctx
)
2375 LIST_HEAD(preloaded
);
2376 struct css_set
*cset
, *tmp_cset
;
2378 lockdep_assert_held(&cgroup_mutex
);
2380 spin_lock_irq(&css_set_lock
);
2382 list_splice_tail_init(&mgctx
->preloaded_src_csets
, &preloaded
);
2383 list_splice_tail_init(&mgctx
->preloaded_dst_csets
, &preloaded
);
2385 list_for_each_entry_safe(cset
, tmp_cset
, &preloaded
, mg_preload_node
) {
2386 cset
->mg_src_cgrp
= NULL
;
2387 cset
->mg_dst_cgrp
= NULL
;
2388 cset
->mg_dst_cset
= NULL
;
2389 list_del_init(&cset
->mg_preload_node
);
2390 put_css_set_locked(cset
);
2393 spin_unlock_irq(&css_set_lock
);
2397 * cgroup_migrate_add_src - add a migration source css_set
2398 * @src_cset: the source css_set to add
2399 * @dst_cgrp: the destination cgroup
2400 * @mgctx: migration context
2402 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
2403 * @src_cset and add it to @mgctx->src_csets, which should later be cleaned
2404 * up by cgroup_migrate_finish().
2406 * This function may be called without holding cgroup_threadgroup_rwsem
2407 * even if the target is a process. Threads may be created and destroyed
2408 * but as long as cgroup_mutex is not dropped, no new css_set can be put
2409 * into play and the preloaded css_sets are guaranteed to cover all
2412 void cgroup_migrate_add_src(struct css_set
*src_cset
,
2413 struct cgroup
*dst_cgrp
,
2414 struct cgroup_mgctx
*mgctx
)
2416 struct cgroup
*src_cgrp
;
2418 lockdep_assert_held(&cgroup_mutex
);
2419 lockdep_assert_held(&css_set_lock
);
2422 * If ->dead, @src_set is associated with one or more dead cgroups
2423 * and doesn't contain any migratable tasks. Ignore it early so
2424 * that the rest of migration path doesn't get confused by it.
2429 src_cgrp
= cset_cgroup_from_root(src_cset
, dst_cgrp
->root
);
2431 if (!list_empty(&src_cset
->mg_preload_node
))
2434 WARN_ON(src_cset
->mg_src_cgrp
);
2435 WARN_ON(src_cset
->mg_dst_cgrp
);
2436 WARN_ON(!list_empty(&src_cset
->mg_tasks
));
2437 WARN_ON(!list_empty(&src_cset
->mg_node
));
2439 src_cset
->mg_src_cgrp
= src_cgrp
;
2440 src_cset
->mg_dst_cgrp
= dst_cgrp
;
2441 get_css_set(src_cset
);
2442 list_add_tail(&src_cset
->mg_preload_node
, &mgctx
->preloaded_src_csets
);
2446 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2447 * @mgctx: migration context
2449 * Tasks are about to be moved and all the source css_sets have been
2450 * preloaded to @mgctx->preloaded_src_csets. This function looks up and
2451 * pins all destination css_sets, links each to its source, and append them
2452 * to @mgctx->preloaded_dst_csets.
2454 * This function must be called after cgroup_migrate_add_src() has been
2455 * called on each migration source css_set. After migration is performed
2456 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2459 int cgroup_migrate_prepare_dst(struct cgroup_mgctx
*mgctx
)
2461 struct css_set
*src_cset
, *tmp_cset
;
2463 lockdep_assert_held(&cgroup_mutex
);
2465 /* look up the dst cset for each src cset and link it to src */
2466 list_for_each_entry_safe(src_cset
, tmp_cset
, &mgctx
->preloaded_src_csets
,
2468 struct css_set
*dst_cset
;
2469 struct cgroup_subsys
*ss
;
2472 dst_cset
= find_css_set(src_cset
, src_cset
->mg_dst_cgrp
);
2476 WARN_ON_ONCE(src_cset
->mg_dst_cset
|| dst_cset
->mg_dst_cset
);
2479 * If src cset equals dst, it's noop. Drop the src.
2480 * cgroup_migrate() will skip the cset too. Note that we
2481 * can't handle src == dst as some nodes are used by both.
2483 if (src_cset
== dst_cset
) {
2484 src_cset
->mg_src_cgrp
= NULL
;
2485 src_cset
->mg_dst_cgrp
= NULL
;
2486 list_del_init(&src_cset
->mg_preload_node
);
2487 put_css_set(src_cset
);
2488 put_css_set(dst_cset
);
2492 src_cset
->mg_dst_cset
= dst_cset
;
2494 if (list_empty(&dst_cset
->mg_preload_node
))
2495 list_add_tail(&dst_cset
->mg_preload_node
,
2496 &mgctx
->preloaded_dst_csets
);
2498 put_css_set(dst_cset
);
2500 for_each_subsys(ss
, ssid
)
2501 if (src_cset
->subsys
[ssid
] != dst_cset
->subsys
[ssid
])
2502 mgctx
->ss_mask
|= 1 << ssid
;
2507 cgroup_migrate_finish(mgctx
);
2512 * cgroup_migrate - migrate a process or task to a cgroup
2513 * @leader: the leader of the process or the task to migrate
2514 * @threadgroup: whether @leader points to the whole process or a single task
2515 * @mgctx: migration context
2517 * Migrate a process or task denoted by @leader. If migrating a process,
2518 * the caller must be holding cgroup_threadgroup_rwsem. The caller is also
2519 * responsible for invoking cgroup_migrate_add_src() and
2520 * cgroup_migrate_prepare_dst() on the targets before invoking this
2521 * function and following up with cgroup_migrate_finish().
2523 * As long as a controller's ->can_attach() doesn't fail, this function is
2524 * guaranteed to succeed. This means that, excluding ->can_attach()
2525 * failure, when migrating multiple targets, the success or failure can be
2526 * decided for all targets by invoking group_migrate_prepare_dst() before
2527 * actually starting migrating.
2529 int cgroup_migrate(struct task_struct
*leader
, bool threadgroup
,
2530 struct cgroup_mgctx
*mgctx
)
2532 struct task_struct
*task
;
2535 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2536 * already PF_EXITING could be freed from underneath us unless we
2537 * take an rcu_read_lock.
2539 spin_lock_irq(&css_set_lock
);
2543 cgroup_migrate_add_task(task
, mgctx
);
2546 } while_each_thread(leader
, task
);
2548 spin_unlock_irq(&css_set_lock
);
2550 return cgroup_migrate_execute(mgctx
);
2554 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2555 * @dst_cgrp: the cgroup to attach to
2556 * @leader: the task or the leader of the threadgroup to be attached
2557 * @threadgroup: attach the whole threadgroup?
2559 * Call holding cgroup_mutex and cgroup_threadgroup_rwsem.
2561 int cgroup_attach_task(struct cgroup
*dst_cgrp
, struct task_struct
*leader
,
2564 DEFINE_CGROUP_MGCTX(mgctx
);
2565 struct task_struct
*task
;
2568 ret
= cgroup_migrate_vet_dst(dst_cgrp
);
2572 /* look up all src csets */
2573 spin_lock_irq(&css_set_lock
);
2577 cgroup_migrate_add_src(task_css_set(task
), dst_cgrp
, &mgctx
);
2580 } while_each_thread(leader
, task
);
2582 spin_unlock_irq(&css_set_lock
);
2584 /* prepare dst csets and commit */
2585 ret
= cgroup_migrate_prepare_dst(&mgctx
);
2587 ret
= cgroup_migrate(leader
, threadgroup
, &mgctx
);
2589 cgroup_migrate_finish(&mgctx
);
2592 trace_cgroup_attach_task(dst_cgrp
, leader
, threadgroup
);
2597 struct task_struct
*cgroup_procs_write_start(char *buf
, bool threadgroup
)
2598 __acquires(&cgroup_threadgroup_rwsem
)
2600 struct task_struct
*tsk
;
2603 if (kstrtoint(strstrip(buf
), 0, &pid
) || pid
< 0)
2604 return ERR_PTR(-EINVAL
);
2606 percpu_down_write(&cgroup_threadgroup_rwsem
);
2610 tsk
= find_task_by_vpid(pid
);
2612 tsk
= ERR_PTR(-ESRCH
);
2613 goto out_unlock_threadgroup
;
2620 tsk
= tsk
->group_leader
;
2623 * kthreads may acquire PF_NO_SETAFFINITY during initialization.
2624 * If userland migrates such a kthread to a non-root cgroup, it can
2625 * become trapped in a cpuset, or RT kthread may be born in a
2626 * cgroup with no rt_runtime allocated. Just say no.
2628 if (tsk
->no_cgroup_migration
|| (tsk
->flags
& PF_NO_SETAFFINITY
)) {
2629 tsk
= ERR_PTR(-EINVAL
);
2630 goto out_unlock_threadgroup
;
2633 get_task_struct(tsk
);
2634 goto out_unlock_rcu
;
2636 out_unlock_threadgroup
:
2637 percpu_up_write(&cgroup_threadgroup_rwsem
);
2643 void cgroup_procs_write_finish(struct task_struct
*task
)
2644 __releases(&cgroup_threadgroup_rwsem
)
2646 struct cgroup_subsys
*ss
;
2649 /* release reference from cgroup_procs_write_start() */
2650 put_task_struct(task
);
2652 percpu_up_write(&cgroup_threadgroup_rwsem
);
2653 for_each_subsys(ss
, ssid
)
2654 if (ss
->post_attach
)
2658 static void cgroup_print_ss_mask(struct seq_file
*seq
, u16 ss_mask
)
2660 struct cgroup_subsys
*ss
;
2661 bool printed
= false;
2664 do_each_subsys_mask(ss
, ssid
, ss_mask
) {
2667 seq_printf(seq
, "%s", ss
->name
);
2669 } while_each_subsys_mask();
2671 seq_putc(seq
, '\n');
2674 /* show controllers which are enabled from the parent */
2675 static int cgroup_controllers_show(struct seq_file
*seq
, void *v
)
2677 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2679 cgroup_print_ss_mask(seq
, cgroup_control(cgrp
));
2683 /* show controllers which are enabled for a given cgroup's children */
2684 static int cgroup_subtree_control_show(struct seq_file
*seq
, void *v
)
2686 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2688 cgroup_print_ss_mask(seq
, cgrp
->subtree_control
);
2693 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
2694 * @cgrp: root of the subtree to update csses for
2696 * @cgrp's control masks have changed and its subtree's css associations
2697 * need to be updated accordingly. This function looks up all css_sets
2698 * which are attached to the subtree, creates the matching updated css_sets
2699 * and migrates the tasks to the new ones.
2701 static int cgroup_update_dfl_csses(struct cgroup
*cgrp
)
2703 DEFINE_CGROUP_MGCTX(mgctx
);
2704 struct cgroup_subsys_state
*d_css
;
2705 struct cgroup
*dsct
;
2706 struct css_set
*src_cset
;
2709 lockdep_assert_held(&cgroup_mutex
);
2711 percpu_down_write(&cgroup_threadgroup_rwsem
);
2713 /* look up all csses currently attached to @cgrp's subtree */
2714 spin_lock_irq(&css_set_lock
);
2715 cgroup_for_each_live_descendant_pre(dsct
, d_css
, cgrp
) {
2716 struct cgrp_cset_link
*link
;
2718 list_for_each_entry(link
, &dsct
->cset_links
, cset_link
)
2719 cgroup_migrate_add_src(link
->cset
, dsct
, &mgctx
);
2721 spin_unlock_irq(&css_set_lock
);
2723 /* NULL dst indicates self on default hierarchy */
2724 ret
= cgroup_migrate_prepare_dst(&mgctx
);
2728 spin_lock_irq(&css_set_lock
);
2729 list_for_each_entry(src_cset
, &mgctx
.preloaded_src_csets
, mg_preload_node
) {
2730 struct task_struct
*task
, *ntask
;
2732 /* all tasks in src_csets need to be migrated */
2733 list_for_each_entry_safe(task
, ntask
, &src_cset
->tasks
, cg_list
)
2734 cgroup_migrate_add_task(task
, &mgctx
);
2736 spin_unlock_irq(&css_set_lock
);
2738 ret
= cgroup_migrate_execute(&mgctx
);
2740 cgroup_migrate_finish(&mgctx
);
2741 percpu_up_write(&cgroup_threadgroup_rwsem
);
2746 * cgroup_lock_and_drain_offline - lock cgroup_mutex and drain offlined csses
2747 * @cgrp: root of the target subtree
2749 * Because css offlining is asynchronous, userland may try to re-enable a
2750 * controller while the previous css is still around. This function grabs
2751 * cgroup_mutex and drains the previous css instances of @cgrp's subtree.
2753 void cgroup_lock_and_drain_offline(struct cgroup
*cgrp
)
2754 __acquires(&cgroup_mutex
)
2756 struct cgroup
*dsct
;
2757 struct cgroup_subsys_state
*d_css
;
2758 struct cgroup_subsys
*ss
;
2762 mutex_lock(&cgroup_mutex
);
2764 cgroup_for_each_live_descendant_post(dsct
, d_css
, cgrp
) {
2765 for_each_subsys(ss
, ssid
) {
2766 struct cgroup_subsys_state
*css
= cgroup_css(dsct
, ss
);
2769 if (!css
|| !percpu_ref_is_dying(&css
->refcnt
))
2772 cgroup_get_live(dsct
);
2773 prepare_to_wait(&dsct
->offline_waitq
, &wait
,
2774 TASK_UNINTERRUPTIBLE
);
2776 mutex_unlock(&cgroup_mutex
);
2778 finish_wait(&dsct
->offline_waitq
, &wait
);
2787 * cgroup_save_control - save control masks of a subtree
2788 * @cgrp: root of the target subtree
2790 * Save ->subtree_control and ->subtree_ss_mask to the respective old_
2791 * prefixed fields for @cgrp's subtree including @cgrp itself.
2793 static void cgroup_save_control(struct cgroup
*cgrp
)
2795 struct cgroup
*dsct
;
2796 struct cgroup_subsys_state
*d_css
;
2798 cgroup_for_each_live_descendant_pre(dsct
, d_css
, cgrp
) {
2799 dsct
->old_subtree_control
= dsct
->subtree_control
;
2800 dsct
->old_subtree_ss_mask
= dsct
->subtree_ss_mask
;
2805 * cgroup_propagate_control - refresh control masks of a subtree
2806 * @cgrp: root of the target subtree
2808 * For @cgrp and its subtree, ensure ->subtree_ss_mask matches
2809 * ->subtree_control and propagate controller availability through the
2810 * subtree so that descendants don't have unavailable controllers enabled.
2812 static void cgroup_propagate_control(struct cgroup
*cgrp
)
2814 struct cgroup
*dsct
;
2815 struct cgroup_subsys_state
*d_css
;
2817 cgroup_for_each_live_descendant_pre(dsct
, d_css
, cgrp
) {
2818 dsct
->subtree_control
&= cgroup_control(dsct
);
2819 dsct
->subtree_ss_mask
=
2820 cgroup_calc_subtree_ss_mask(dsct
->subtree_control
,
2821 cgroup_ss_mask(dsct
));
2826 * cgroup_restore_control - restore control masks of a subtree
2827 * @cgrp: root of the target subtree
2829 * Restore ->subtree_control and ->subtree_ss_mask from the respective old_
2830 * prefixed fields for @cgrp's subtree including @cgrp itself.
2832 static void cgroup_restore_control(struct cgroup
*cgrp
)
2834 struct cgroup
*dsct
;
2835 struct cgroup_subsys_state
*d_css
;
2837 cgroup_for_each_live_descendant_post(dsct
, d_css
, cgrp
) {
2838 dsct
->subtree_control
= dsct
->old_subtree_control
;
2839 dsct
->subtree_ss_mask
= dsct
->old_subtree_ss_mask
;
2843 static bool css_visible(struct cgroup_subsys_state
*css
)
2845 struct cgroup_subsys
*ss
= css
->ss
;
2846 struct cgroup
*cgrp
= css
->cgroup
;
2848 if (cgroup_control(cgrp
) & (1 << ss
->id
))
2850 if (!(cgroup_ss_mask(cgrp
) & (1 << ss
->id
)))
2852 return cgroup_on_dfl(cgrp
) && ss
->implicit_on_dfl
;
2856 * cgroup_apply_control_enable - enable or show csses according to control
2857 * @cgrp: root of the target subtree
2859 * Walk @cgrp's subtree and create new csses or make the existing ones
2860 * visible. A css is created invisible if it's being implicitly enabled
2861 * through dependency. An invisible css is made visible when the userland
2862 * explicitly enables it.
2864 * Returns 0 on success, -errno on failure. On failure, csses which have
2865 * been processed already aren't cleaned up. The caller is responsible for
2866 * cleaning up with cgroup_apply_control_disable().
2868 static int cgroup_apply_control_enable(struct cgroup
*cgrp
)
2870 struct cgroup
*dsct
;
2871 struct cgroup_subsys_state
*d_css
;
2872 struct cgroup_subsys
*ss
;
2875 cgroup_for_each_live_descendant_pre(dsct
, d_css
, cgrp
) {
2876 for_each_subsys(ss
, ssid
) {
2877 struct cgroup_subsys_state
*css
= cgroup_css(dsct
, ss
);
2879 WARN_ON_ONCE(css
&& percpu_ref_is_dying(&css
->refcnt
));
2881 if (!(cgroup_ss_mask(dsct
) & (1 << ss
->id
)))
2885 css
= css_create(dsct
, ss
);
2887 return PTR_ERR(css
);
2890 if (css_visible(css
)) {
2891 ret
= css_populate_dir(css
);
2902 * cgroup_apply_control_disable - kill or hide csses according to control
2903 * @cgrp: root of the target subtree
2905 * Walk @cgrp's subtree and kill and hide csses so that they match
2906 * cgroup_ss_mask() and cgroup_visible_mask().
2908 * A css is hidden when the userland requests it to be disabled while other
2909 * subsystems are still depending on it. The css must not actively control
2910 * resources and be in the vanilla state if it's made visible again later.
2911 * Controllers which may be depended upon should provide ->css_reset() for
2914 static void cgroup_apply_control_disable(struct cgroup
*cgrp
)
2916 struct cgroup
*dsct
;
2917 struct cgroup_subsys_state
*d_css
;
2918 struct cgroup_subsys
*ss
;
2921 cgroup_for_each_live_descendant_post(dsct
, d_css
, cgrp
) {
2922 for_each_subsys(ss
, ssid
) {
2923 struct cgroup_subsys_state
*css
= cgroup_css(dsct
, ss
);
2925 WARN_ON_ONCE(css
&& percpu_ref_is_dying(&css
->refcnt
));
2931 !(cgroup_ss_mask(dsct
) & (1 << ss
->id
))) {
2933 } else if (!css_visible(css
)) {
2943 * cgroup_apply_control - apply control mask updates to the subtree
2944 * @cgrp: root of the target subtree
2946 * subsystems can be enabled and disabled in a subtree using the following
2949 * 1. Call cgroup_save_control() to stash the current state.
2950 * 2. Update ->subtree_control masks in the subtree as desired.
2951 * 3. Call cgroup_apply_control() to apply the changes.
2952 * 4. Optionally perform other related operations.
2953 * 5. Call cgroup_finalize_control() to finish up.
2955 * This function implements step 3 and propagates the mask changes
2956 * throughout @cgrp's subtree, updates csses accordingly and perform
2957 * process migrations.
2959 static int cgroup_apply_control(struct cgroup
*cgrp
)
2963 cgroup_propagate_control(cgrp
);
2965 ret
= cgroup_apply_control_enable(cgrp
);
2970 * At this point, cgroup_e_css() results reflect the new csses
2971 * making the following cgroup_update_dfl_csses() properly update
2972 * css associations of all tasks in the subtree.
2974 ret
= cgroup_update_dfl_csses(cgrp
);
2982 * cgroup_finalize_control - finalize control mask update
2983 * @cgrp: root of the target subtree
2984 * @ret: the result of the update
2986 * Finalize control mask update. See cgroup_apply_control() for more info.
2988 static void cgroup_finalize_control(struct cgroup
*cgrp
, int ret
)
2991 cgroup_restore_control(cgrp
);
2992 cgroup_propagate_control(cgrp
);
2995 cgroup_apply_control_disable(cgrp
);
2998 static int cgroup_vet_subtree_control_enable(struct cgroup
*cgrp
, u16 enable
)
3000 u16 domain_enable
= enable
& ~cgrp_dfl_threaded_ss_mask
;
3002 /* if nothing is getting enabled, nothing to worry about */
3006 /* can @cgrp host any resources? */
3007 if (!cgroup_is_valid_domain(cgrp
->dom_cgrp
))
3010 /* mixables don't care */
3011 if (cgroup_is_mixable(cgrp
))
3014 if (domain_enable
) {
3015 /* can't enable domain controllers inside a thread subtree */
3016 if (cgroup_is_thread_root(cgrp
) || cgroup_is_threaded(cgrp
))
3020 * Threaded controllers can handle internal competitions
3021 * and are always allowed inside a (prospective) thread
3024 if (cgroup_can_be_thread_root(cgrp
) || cgroup_is_threaded(cgrp
))
3029 * Controllers can't be enabled for a cgroup with tasks to avoid
3030 * child cgroups competing against tasks.
3032 if (cgroup_has_tasks(cgrp
))
3038 /* change the enabled child controllers for a cgroup in the default hierarchy */
3039 static ssize_t
cgroup_subtree_control_write(struct kernfs_open_file
*of
,
3040 char *buf
, size_t nbytes
,
3043 u16 enable
= 0, disable
= 0;
3044 struct cgroup
*cgrp
, *child
;
3045 struct cgroup_subsys
*ss
;
3050 * Parse input - space separated list of subsystem names prefixed
3051 * with either + or -.
3053 buf
= strstrip(buf
);
3054 while ((tok
= strsep(&buf
, " "))) {
3057 do_each_subsys_mask(ss
, ssid
, ~cgrp_dfl_inhibit_ss_mask
) {
3058 if (!cgroup_ssid_enabled(ssid
) ||
3059 strcmp(tok
+ 1, ss
->name
))
3063 enable
|= 1 << ssid
;
3064 disable
&= ~(1 << ssid
);
3065 } else if (*tok
== '-') {
3066 disable
|= 1 << ssid
;
3067 enable
&= ~(1 << ssid
);
3072 } while_each_subsys_mask();
3073 if (ssid
== CGROUP_SUBSYS_COUNT
)
3077 cgrp
= cgroup_kn_lock_live(of
->kn
, true);
3081 for_each_subsys(ss
, ssid
) {
3082 if (enable
& (1 << ssid
)) {
3083 if (cgrp
->subtree_control
& (1 << ssid
)) {
3084 enable
&= ~(1 << ssid
);
3088 if (!(cgroup_control(cgrp
) & (1 << ssid
))) {
3092 } else if (disable
& (1 << ssid
)) {
3093 if (!(cgrp
->subtree_control
& (1 << ssid
))) {
3094 disable
&= ~(1 << ssid
);
3098 /* a child has it enabled? */
3099 cgroup_for_each_live_child(child
, cgrp
) {
3100 if (child
->subtree_control
& (1 << ssid
)) {
3108 if (!enable
&& !disable
) {
3113 ret
= cgroup_vet_subtree_control_enable(cgrp
, enable
);
3117 /* save and update control masks and prepare csses */
3118 cgroup_save_control(cgrp
);
3120 cgrp
->subtree_control
|= enable
;
3121 cgrp
->subtree_control
&= ~disable
;
3123 ret
= cgroup_apply_control(cgrp
);
3125 cgroup_finalize_control(cgrp
, ret
);
3127 kernfs_activate(cgrp
->kn
);
3130 cgroup_kn_unlock(of
->kn
);
3131 return ret
?: nbytes
;
3135 * cgroup_enable_threaded - make @cgrp threaded
3136 * @cgrp: the target cgroup
3138 * Called when "threaded" is written to the cgroup.type interface file and
3139 * tries to make @cgrp threaded and join the parent's resource domain.
3140 * This function is never called on the root cgroup as cgroup.type doesn't
3143 static int cgroup_enable_threaded(struct cgroup
*cgrp
)
3145 struct cgroup
*parent
= cgroup_parent(cgrp
);
3146 struct cgroup
*dom_cgrp
= parent
->dom_cgrp
;
3149 lockdep_assert_held(&cgroup_mutex
);
3151 /* noop if already threaded */
3152 if (cgroup_is_threaded(cgrp
))
3155 /* we're joining the parent's domain, ensure its validity */
3156 if (!cgroup_is_valid_domain(dom_cgrp
) ||
3157 !cgroup_can_be_thread_root(dom_cgrp
))
3161 * The following shouldn't cause actual migrations and should
3164 cgroup_save_control(cgrp
);
3166 cgrp
->dom_cgrp
= dom_cgrp
;
3167 ret
= cgroup_apply_control(cgrp
);
3169 parent
->nr_threaded_children
++;
3171 cgrp
->dom_cgrp
= cgrp
;
3173 cgroup_finalize_control(cgrp
, ret
);
3177 static int cgroup_type_show(struct seq_file
*seq
, void *v
)
3179 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
3181 if (cgroup_is_threaded(cgrp
))
3182 seq_puts(seq
, "threaded\n");
3183 else if (!cgroup_is_valid_domain(cgrp
))
3184 seq_puts(seq
, "domain invalid\n");
3185 else if (cgroup_is_thread_root(cgrp
))
3186 seq_puts(seq
, "domain threaded\n");
3188 seq_puts(seq
, "domain\n");
3193 static ssize_t
cgroup_type_write(struct kernfs_open_file
*of
, char *buf
,
3194 size_t nbytes
, loff_t off
)
3196 struct cgroup
*cgrp
;
3199 /* only switching to threaded mode is supported */
3200 if (strcmp(strstrip(buf
), "threaded"))
3203 cgrp
= cgroup_kn_lock_live(of
->kn
, false);
3207 /* threaded can only be enabled */
3208 ret
= cgroup_enable_threaded(cgrp
);
3210 cgroup_kn_unlock(of
->kn
);
3211 return ret
?: nbytes
;
3214 static int cgroup_max_descendants_show(struct seq_file
*seq
, void *v
)
3216 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
3217 int descendants
= READ_ONCE(cgrp
->max_descendants
);
3219 if (descendants
== INT_MAX
)
3220 seq_puts(seq
, "max\n");
3222 seq_printf(seq
, "%d\n", descendants
);
3227 static ssize_t
cgroup_max_descendants_write(struct kernfs_open_file
*of
,
3228 char *buf
, size_t nbytes
, loff_t off
)
3230 struct cgroup
*cgrp
;
3234 buf
= strstrip(buf
);
3235 if (!strcmp(buf
, "max")) {
3236 descendants
= INT_MAX
;
3238 ret
= kstrtoint(buf
, 0, &descendants
);
3243 if (descendants
< 0 || descendants
> INT_MAX
)
3246 cgrp
= cgroup_kn_lock_live(of
->kn
, false);
3250 cgrp
->max_descendants
= descendants
;
3252 cgroup_kn_unlock(of
->kn
);
3257 static int cgroup_max_depth_show(struct seq_file
*seq
, void *v
)
3259 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
3260 int depth
= READ_ONCE(cgrp
->max_depth
);
3262 if (depth
== INT_MAX
)
3263 seq_puts(seq
, "max\n");
3265 seq_printf(seq
, "%d\n", depth
);
3270 static ssize_t
cgroup_max_depth_write(struct kernfs_open_file
*of
,
3271 char *buf
, size_t nbytes
, loff_t off
)
3273 struct cgroup
*cgrp
;
3277 buf
= strstrip(buf
);
3278 if (!strcmp(buf
, "max")) {
3281 ret
= kstrtoint(buf
, 0, &depth
);
3286 if (depth
< 0 || depth
> INT_MAX
)
3289 cgrp
= cgroup_kn_lock_live(of
->kn
, false);
3293 cgrp
->max_depth
= depth
;
3295 cgroup_kn_unlock(of
->kn
);
3300 static int cgroup_events_show(struct seq_file
*seq
, void *v
)
3302 seq_printf(seq
, "populated %d\n",
3303 cgroup_is_populated(seq_css(seq
)->cgroup
));
3307 static int cgroup_stats_show(struct seq_file
*seq
, void *v
)
3309 struct cgroup
*cgroup
= seq_css(seq
)->cgroup
;
3311 seq_printf(seq
, "nr_descendants %d\n",
3312 cgroup
->nr_descendants
);
3313 seq_printf(seq
, "nr_dying_descendants %d\n",
3314 cgroup
->nr_dying_descendants
);
3319 static int cgroup_file_open(struct kernfs_open_file
*of
)
3321 struct cftype
*cft
= of
->kn
->priv
;
3324 return cft
->open(of
);
3328 static void cgroup_file_release(struct kernfs_open_file
*of
)
3330 struct cftype
*cft
= of
->kn
->priv
;
3336 static ssize_t
cgroup_file_write(struct kernfs_open_file
*of
, char *buf
,
3337 size_t nbytes
, loff_t off
)
3339 struct cgroup_namespace
*ns
= current
->nsproxy
->cgroup_ns
;
3340 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
3341 struct cftype
*cft
= of
->kn
->priv
;
3342 struct cgroup_subsys_state
*css
;
3346 * If namespaces are delegation boundaries, disallow writes to
3347 * files in an non-init namespace root from inside the namespace
3348 * except for the files explicitly marked delegatable -
3349 * cgroup.procs and cgroup.subtree_control.
3351 if ((cgrp
->root
->flags
& CGRP_ROOT_NS_DELEGATE
) &&
3352 !(cft
->flags
& CFTYPE_NS_DELEGATABLE
) &&
3353 ns
!= &init_cgroup_ns
&& ns
->root_cset
->dfl_cgrp
== cgrp
)
3357 return cft
->write(of
, buf
, nbytes
, off
);
3360 * kernfs guarantees that a file isn't deleted with operations in
3361 * flight, which means that the matching css is and stays alive and
3362 * doesn't need to be pinned. The RCU locking is not necessary
3363 * either. It's just for the convenience of using cgroup_css().
3366 css
= cgroup_css(cgrp
, cft
->ss
);
3369 if (cft
->write_u64
) {
3370 unsigned long long v
;
3371 ret
= kstrtoull(buf
, 0, &v
);
3373 ret
= cft
->write_u64(css
, cft
, v
);
3374 } else if (cft
->write_s64
) {
3376 ret
= kstrtoll(buf
, 0, &v
);
3378 ret
= cft
->write_s64(css
, cft
, v
);
3383 return ret
?: nbytes
;
3386 static void *cgroup_seqfile_start(struct seq_file
*seq
, loff_t
*ppos
)
3388 return seq_cft(seq
)->seq_start(seq
, ppos
);
3391 static void *cgroup_seqfile_next(struct seq_file
*seq
, void *v
, loff_t
*ppos
)
3393 return seq_cft(seq
)->seq_next(seq
, v
, ppos
);
3396 static void cgroup_seqfile_stop(struct seq_file
*seq
, void *v
)
3398 if (seq_cft(seq
)->seq_stop
)
3399 seq_cft(seq
)->seq_stop(seq
, v
);
3402 static int cgroup_seqfile_show(struct seq_file
*m
, void *arg
)
3404 struct cftype
*cft
= seq_cft(m
);
3405 struct cgroup_subsys_state
*css
= seq_css(m
);
3408 return cft
->seq_show(m
, arg
);
3411 seq_printf(m
, "%llu\n", cft
->read_u64(css
, cft
));
3412 else if (cft
->read_s64
)
3413 seq_printf(m
, "%lld\n", cft
->read_s64(css
, cft
));
3419 static struct kernfs_ops cgroup_kf_single_ops
= {
3420 .atomic_write_len
= PAGE_SIZE
,
3421 .open
= cgroup_file_open
,
3422 .release
= cgroup_file_release
,
3423 .write
= cgroup_file_write
,
3424 .seq_show
= cgroup_seqfile_show
,
3427 static struct kernfs_ops cgroup_kf_ops
= {
3428 .atomic_write_len
= PAGE_SIZE
,
3429 .open
= cgroup_file_open
,
3430 .release
= cgroup_file_release
,
3431 .write
= cgroup_file_write
,
3432 .seq_start
= cgroup_seqfile_start
,
3433 .seq_next
= cgroup_seqfile_next
,
3434 .seq_stop
= cgroup_seqfile_stop
,
3435 .seq_show
= cgroup_seqfile_show
,
3438 /* set uid and gid of cgroup dirs and files to that of the creator */
3439 static int cgroup_kn_set_ugid(struct kernfs_node
*kn
)
3441 struct iattr iattr
= { .ia_valid
= ATTR_UID
| ATTR_GID
,
3442 .ia_uid
= current_fsuid(),
3443 .ia_gid
= current_fsgid(), };
3445 if (uid_eq(iattr
.ia_uid
, GLOBAL_ROOT_UID
) &&
3446 gid_eq(iattr
.ia_gid
, GLOBAL_ROOT_GID
))
3449 return kernfs_setattr(kn
, &iattr
);
3452 static int cgroup_add_file(struct cgroup_subsys_state
*css
, struct cgroup
*cgrp
,
3455 char name
[CGROUP_FILE_NAME_MAX
];
3456 struct kernfs_node
*kn
;
3457 struct lock_class_key
*key
= NULL
;
3460 #ifdef CONFIG_DEBUG_LOCK_ALLOC
3461 key
= &cft
->lockdep_key
;
3463 kn
= __kernfs_create_file(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
),
3464 cgroup_file_mode(cft
), 0, cft
->kf_ops
, cft
,
3469 ret
= cgroup_kn_set_ugid(kn
);
3475 if (cft
->file_offset
) {
3476 struct cgroup_file
*cfile
= (void *)css
+ cft
->file_offset
;
3478 spin_lock_irq(&cgroup_file_kn_lock
);
3480 spin_unlock_irq(&cgroup_file_kn_lock
);
3487 * cgroup_addrm_files - add or remove files to a cgroup directory
3488 * @css: the target css
3489 * @cgrp: the target cgroup (usually css->cgroup)
3490 * @cfts: array of cftypes to be added
3491 * @is_add: whether to add or remove
3493 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
3494 * For removals, this function never fails.
3496 static int cgroup_addrm_files(struct cgroup_subsys_state
*css
,
3497 struct cgroup
*cgrp
, struct cftype cfts
[],
3500 struct cftype
*cft
, *cft_end
= NULL
;
3503 lockdep_assert_held(&cgroup_mutex
);
3506 for (cft
= cfts
; cft
!= cft_end
&& cft
->name
[0] != '\0'; cft
++) {
3507 /* does cft->flags tell us to skip this file on @cgrp? */
3508 if ((cft
->flags
& __CFTYPE_ONLY_ON_DFL
) && !cgroup_on_dfl(cgrp
))
3510 if ((cft
->flags
& __CFTYPE_NOT_ON_DFL
) && cgroup_on_dfl(cgrp
))
3512 if ((cft
->flags
& CFTYPE_NOT_ON_ROOT
) && !cgroup_parent(cgrp
))
3514 if ((cft
->flags
& CFTYPE_ONLY_ON_ROOT
) && cgroup_parent(cgrp
))
3518 ret
= cgroup_add_file(css
, cgrp
, cft
);
3520 pr_warn("%s: failed to add %s, err=%d\n",
3521 __func__
, cft
->name
, ret
);
3527 cgroup_rm_file(cgrp
, cft
);
3533 static int cgroup_apply_cftypes(struct cftype
*cfts
, bool is_add
)
3535 struct cgroup_subsys
*ss
= cfts
[0].ss
;
3536 struct cgroup
*root
= &ss
->root
->cgrp
;
3537 struct cgroup_subsys_state
*css
;
3540 lockdep_assert_held(&cgroup_mutex
);
3542 /* add/rm files for all cgroups created before */
3543 css_for_each_descendant_pre(css
, cgroup_css(root
, ss
)) {
3544 struct cgroup
*cgrp
= css
->cgroup
;
3546 if (!(css
->flags
& CSS_VISIBLE
))
3549 ret
= cgroup_addrm_files(css
, cgrp
, cfts
, is_add
);
3555 kernfs_activate(root
->kn
);
3559 static void cgroup_exit_cftypes(struct cftype
*cfts
)
3563 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3564 /* free copy for custom atomic_write_len, see init_cftypes() */
3565 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
)
3570 /* revert flags set by cgroup core while adding @cfts */
3571 cft
->flags
&= ~(__CFTYPE_ONLY_ON_DFL
| __CFTYPE_NOT_ON_DFL
);
3575 static int cgroup_init_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3579 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3580 struct kernfs_ops
*kf_ops
;
3582 WARN_ON(cft
->ss
|| cft
->kf_ops
);
3585 kf_ops
= &cgroup_kf_ops
;
3587 kf_ops
= &cgroup_kf_single_ops
;
3590 * Ugh... if @cft wants a custom max_write_len, we need to
3591 * make a copy of kf_ops to set its atomic_write_len.
3593 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
) {
3594 kf_ops
= kmemdup(kf_ops
, sizeof(*kf_ops
), GFP_KERNEL
);
3596 cgroup_exit_cftypes(cfts
);
3599 kf_ops
->atomic_write_len
= cft
->max_write_len
;
3602 cft
->kf_ops
= kf_ops
;
3609 static int cgroup_rm_cftypes_locked(struct cftype
*cfts
)
3611 lockdep_assert_held(&cgroup_mutex
);
3613 if (!cfts
|| !cfts
[0].ss
)
3616 list_del(&cfts
->node
);
3617 cgroup_apply_cftypes(cfts
, false);
3618 cgroup_exit_cftypes(cfts
);
3623 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
3624 * @cfts: zero-length name terminated array of cftypes
3626 * Unregister @cfts. Files described by @cfts are removed from all
3627 * existing cgroups and all future cgroups won't have them either. This
3628 * function can be called anytime whether @cfts' subsys is attached or not.
3630 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
3633 int cgroup_rm_cftypes(struct cftype
*cfts
)
3637 mutex_lock(&cgroup_mutex
);
3638 ret
= cgroup_rm_cftypes_locked(cfts
);
3639 mutex_unlock(&cgroup_mutex
);
3644 * cgroup_add_cftypes - add an array of cftypes to a subsystem
3645 * @ss: target cgroup subsystem
3646 * @cfts: zero-length name terminated array of cftypes
3648 * Register @cfts to @ss. Files described by @cfts are created for all
3649 * existing cgroups to which @ss is attached and all future cgroups will
3650 * have them too. This function can be called anytime whether @ss is
3653 * Returns 0 on successful registration, -errno on failure. Note that this
3654 * function currently returns 0 as long as @cfts registration is successful
3655 * even if some file creation attempts on existing cgroups fail.
3657 static int cgroup_add_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3661 if (!cgroup_ssid_enabled(ss
->id
))
3664 if (!cfts
|| cfts
[0].name
[0] == '\0')
3667 ret
= cgroup_init_cftypes(ss
, cfts
);
3671 mutex_lock(&cgroup_mutex
);
3673 list_add_tail(&cfts
->node
, &ss
->cfts
);
3674 ret
= cgroup_apply_cftypes(cfts
, true);
3676 cgroup_rm_cftypes_locked(cfts
);
3678 mutex_unlock(&cgroup_mutex
);
3683 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
3684 * @ss: target cgroup subsystem
3685 * @cfts: zero-length name terminated array of cftypes
3687 * Similar to cgroup_add_cftypes() but the added files are only used for
3688 * the default hierarchy.
3690 int cgroup_add_dfl_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3694 for (cft
= cfts
; cft
&& cft
->name
[0] != '\0'; cft
++)
3695 cft
->flags
|= __CFTYPE_ONLY_ON_DFL
;
3696 return cgroup_add_cftypes(ss
, cfts
);
3700 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
3701 * @ss: target cgroup subsystem
3702 * @cfts: zero-length name terminated array of cftypes
3704 * Similar to cgroup_add_cftypes() but the added files are only used for
3705 * the legacy hierarchies.
3707 int cgroup_add_legacy_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3711 for (cft
= cfts
; cft
&& cft
->name
[0] != '\0'; cft
++)
3712 cft
->flags
|= __CFTYPE_NOT_ON_DFL
;
3713 return cgroup_add_cftypes(ss
, cfts
);
3717 * cgroup_file_notify - generate a file modified event for a cgroup_file
3718 * @cfile: target cgroup_file
3720 * @cfile must have been obtained by setting cftype->file_offset.
3722 void cgroup_file_notify(struct cgroup_file
*cfile
)
3724 unsigned long flags
;
3726 spin_lock_irqsave(&cgroup_file_kn_lock
, flags
);
3728 kernfs_notify(cfile
->kn
);
3729 spin_unlock_irqrestore(&cgroup_file_kn_lock
, flags
);
3733 * css_next_child - find the next child of a given css
3734 * @pos: the current position (%NULL to initiate traversal)
3735 * @parent: css whose children to walk
3737 * This function returns the next child of @parent and should be called
3738 * under either cgroup_mutex or RCU read lock. The only requirement is
3739 * that @parent and @pos are accessible. The next sibling is guaranteed to
3740 * be returned regardless of their states.
3742 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3743 * css which finished ->css_online() is guaranteed to be visible in the
3744 * future iterations and will stay visible until the last reference is put.
3745 * A css which hasn't finished ->css_online() or already finished
3746 * ->css_offline() may show up during traversal. It's each subsystem's
3747 * responsibility to synchronize against on/offlining.
3749 struct cgroup_subsys_state
*css_next_child(struct cgroup_subsys_state
*pos
,
3750 struct cgroup_subsys_state
*parent
)
3752 struct cgroup_subsys_state
*next
;
3754 cgroup_assert_mutex_or_rcu_locked();
3757 * @pos could already have been unlinked from the sibling list.
3758 * Once a cgroup is removed, its ->sibling.next is no longer
3759 * updated when its next sibling changes. CSS_RELEASED is set when
3760 * @pos is taken off list, at which time its next pointer is valid,
3761 * and, as releases are serialized, the one pointed to by the next
3762 * pointer is guaranteed to not have started release yet. This
3763 * implies that if we observe !CSS_RELEASED on @pos in this RCU
3764 * critical section, the one pointed to by its next pointer is
3765 * guaranteed to not have finished its RCU grace period even if we
3766 * have dropped rcu_read_lock() inbetween iterations.
3768 * If @pos has CSS_RELEASED set, its next pointer can't be
3769 * dereferenced; however, as each css is given a monotonically
3770 * increasing unique serial number and always appended to the
3771 * sibling list, the next one can be found by walking the parent's
3772 * children until the first css with higher serial number than
3773 * @pos's. While this path can be slower, it happens iff iteration
3774 * races against release and the race window is very small.
3777 next
= list_entry_rcu(parent
->children
.next
, struct cgroup_subsys_state
, sibling
);
3778 } else if (likely(!(pos
->flags
& CSS_RELEASED
))) {
3779 next
= list_entry_rcu(pos
->sibling
.next
, struct cgroup_subsys_state
, sibling
);
3781 list_for_each_entry_rcu(next
, &parent
->children
, sibling
)
3782 if (next
->serial_nr
> pos
->serial_nr
)
3787 * @next, if not pointing to the head, can be dereferenced and is
3790 if (&next
->sibling
!= &parent
->children
)
3796 * css_next_descendant_pre - find the next descendant for pre-order walk
3797 * @pos: the current position (%NULL to initiate traversal)
3798 * @root: css whose descendants to walk
3800 * To be used by css_for_each_descendant_pre(). Find the next descendant
3801 * to visit for pre-order traversal of @root's descendants. @root is
3802 * included in the iteration and the first node to be visited.
3804 * While this function requires cgroup_mutex or RCU read locking, it
3805 * doesn't require the whole traversal to be contained in a single critical
3806 * section. This function will return the correct next descendant as long
3807 * as both @pos and @root are accessible and @pos is a descendant of @root.
3809 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3810 * css which finished ->css_online() is guaranteed to be visible in the
3811 * future iterations and will stay visible until the last reference is put.
3812 * A css which hasn't finished ->css_online() or already finished
3813 * ->css_offline() may show up during traversal. It's each subsystem's
3814 * responsibility to synchronize against on/offlining.
3816 struct cgroup_subsys_state
*
3817 css_next_descendant_pre(struct cgroup_subsys_state
*pos
,
3818 struct cgroup_subsys_state
*root
)
3820 struct cgroup_subsys_state
*next
;
3822 cgroup_assert_mutex_or_rcu_locked();
3824 /* if first iteration, visit @root */
3828 /* visit the first child if exists */
3829 next
= css_next_child(NULL
, pos
);
3833 /* no child, visit my or the closest ancestor's next sibling */
3834 while (pos
!= root
) {
3835 next
= css_next_child(pos
, pos
->parent
);
3845 * css_rightmost_descendant - return the rightmost descendant of a css
3846 * @pos: css of interest
3848 * Return the rightmost descendant of @pos. If there's no descendant, @pos
3849 * is returned. This can be used during pre-order traversal to skip
3852 * While this function requires cgroup_mutex or RCU read locking, it
3853 * doesn't require the whole traversal to be contained in a single critical
3854 * section. This function will return the correct rightmost descendant as
3855 * long as @pos is accessible.
3857 struct cgroup_subsys_state
*
3858 css_rightmost_descendant(struct cgroup_subsys_state
*pos
)
3860 struct cgroup_subsys_state
*last
, *tmp
;
3862 cgroup_assert_mutex_or_rcu_locked();
3866 /* ->prev isn't RCU safe, walk ->next till the end */
3868 css_for_each_child(tmp
, last
)
3875 static struct cgroup_subsys_state
*
3876 css_leftmost_descendant(struct cgroup_subsys_state
*pos
)
3878 struct cgroup_subsys_state
*last
;
3882 pos
= css_next_child(NULL
, pos
);
3889 * css_next_descendant_post - find the next descendant for post-order walk
3890 * @pos: the current position (%NULL to initiate traversal)
3891 * @root: css whose descendants to walk
3893 * To be used by css_for_each_descendant_post(). Find the next descendant
3894 * to visit for post-order traversal of @root's descendants. @root is
3895 * included in the iteration and the last node to be visited.
3897 * While this function requires cgroup_mutex or RCU read locking, it
3898 * doesn't require the whole traversal to be contained in a single critical
3899 * section. This function will return the correct next descendant as long
3900 * as both @pos and @cgroup are accessible and @pos is a descendant of
3903 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3904 * css which finished ->css_online() is guaranteed to be visible in the
3905 * future iterations and will stay visible until the last reference is put.
3906 * A css which hasn't finished ->css_online() or already finished
3907 * ->css_offline() may show up during traversal. It's each subsystem's
3908 * responsibility to synchronize against on/offlining.
3910 struct cgroup_subsys_state
*
3911 css_next_descendant_post(struct cgroup_subsys_state
*pos
,
3912 struct cgroup_subsys_state
*root
)
3914 struct cgroup_subsys_state
*next
;
3916 cgroup_assert_mutex_or_rcu_locked();
3918 /* if first iteration, visit leftmost descendant which may be @root */
3920 return css_leftmost_descendant(root
);
3922 /* if we visited @root, we're done */
3926 /* if there's an unvisited sibling, visit its leftmost descendant */
3927 next
= css_next_child(pos
, pos
->parent
);
3929 return css_leftmost_descendant(next
);
3931 /* no sibling left, visit parent */
3936 * css_has_online_children - does a css have online children
3937 * @css: the target css
3939 * Returns %true if @css has any online children; otherwise, %false. This
3940 * function can be called from any context but the caller is responsible
3941 * for synchronizing against on/offlining as necessary.
3943 bool css_has_online_children(struct cgroup_subsys_state
*css
)
3945 struct cgroup_subsys_state
*child
;
3949 css_for_each_child(child
, css
) {
3950 if (child
->flags
& CSS_ONLINE
) {
3959 static struct css_set
*css_task_iter_next_css_set(struct css_task_iter
*it
)
3961 struct list_head
*l
;
3962 struct cgrp_cset_link
*link
;
3963 struct css_set
*cset
;
3965 lockdep_assert_held(&css_set_lock
);
3967 /* find the next threaded cset */
3968 if (it
->tcset_pos
) {
3969 l
= it
->tcset_pos
->next
;
3971 if (l
!= it
->tcset_head
) {
3973 return container_of(l
, struct css_set
,
3974 threaded_csets_node
);
3977 it
->tcset_pos
= NULL
;
3980 /* find the next cset */
3983 if (l
== it
->cset_head
) {
3984 it
->cset_pos
= NULL
;
3989 cset
= container_of(l
, struct css_set
, e_cset_node
[it
->ss
->id
]);
3991 link
= list_entry(l
, struct cgrp_cset_link
, cset_link
);
3997 /* initialize threaded css_set walking */
3998 if (it
->flags
& CSS_TASK_ITER_THREADED
) {
4000 put_css_set_locked(it
->cur_dcset
);
4001 it
->cur_dcset
= cset
;
4004 it
->tcset_head
= &cset
->threaded_csets
;
4005 it
->tcset_pos
= &cset
->threaded_csets
;
4012 * css_task_iter_advance_css_set - advance a task itererator to the next css_set
4013 * @it: the iterator to advance
4015 * Advance @it to the next css_set to walk.
4017 static void css_task_iter_advance_css_set(struct css_task_iter
*it
)
4019 struct css_set
*cset
;
4021 lockdep_assert_held(&css_set_lock
);
4023 /* Advance to the next non-empty css_set */
4025 cset
= css_task_iter_next_css_set(it
);
4027 it
->task_pos
= NULL
;
4030 } while (!css_set_populated(cset
));
4032 if (!list_empty(&cset
->tasks
))
4033 it
->task_pos
= cset
->tasks
.next
;
4035 it
->task_pos
= cset
->mg_tasks
.next
;
4037 it
->tasks_head
= &cset
->tasks
;
4038 it
->mg_tasks_head
= &cset
->mg_tasks
;
4041 * We don't keep css_sets locked across iteration steps and thus
4042 * need to take steps to ensure that iteration can be resumed after
4043 * the lock is re-acquired. Iteration is performed at two levels -
4044 * css_sets and tasks in them.
4046 * Once created, a css_set never leaves its cgroup lists, so a
4047 * pinned css_set is guaranteed to stay put and we can resume
4048 * iteration afterwards.
4050 * Tasks may leave @cset across iteration steps. This is resolved
4051 * by registering each iterator with the css_set currently being
4052 * walked and making css_set_move_task() advance iterators whose
4053 * next task is leaving.
4056 list_del(&it
->iters_node
);
4057 put_css_set_locked(it
->cur_cset
);
4060 it
->cur_cset
= cset
;
4061 list_add(&it
->iters_node
, &cset
->task_iters
);
4064 static void css_task_iter_advance(struct css_task_iter
*it
)
4066 struct list_head
*l
= it
->task_pos
;
4068 lockdep_assert_held(&css_set_lock
);
4073 * Advance iterator to find next entry. cset->tasks is consumed
4074 * first and then ->mg_tasks. After ->mg_tasks, we move onto the
4079 if (l
== it
->tasks_head
)
4080 l
= it
->mg_tasks_head
->next
;
4082 if (l
== it
->mg_tasks_head
)
4083 css_task_iter_advance_css_set(it
);
4087 /* if PROCS, skip over tasks which aren't group leaders */
4088 if ((it
->flags
& CSS_TASK_ITER_PROCS
) && it
->task_pos
&&
4089 !thread_group_leader(list_entry(it
->task_pos
, struct task_struct
,
4095 * css_task_iter_start - initiate task iteration
4096 * @css: the css to walk tasks of
4097 * @flags: CSS_TASK_ITER_* flags
4098 * @it: the task iterator to use
4100 * Initiate iteration through the tasks of @css. The caller can call
4101 * css_task_iter_next() to walk through the tasks until the function
4102 * returns NULL. On completion of iteration, css_task_iter_end() must be
4105 void css_task_iter_start(struct cgroup_subsys_state
*css
, unsigned int flags
,
4106 struct css_task_iter
*it
)
4108 /* no one should try to iterate before mounting cgroups */
4109 WARN_ON_ONCE(!use_task_css_set_links
);
4111 memset(it
, 0, sizeof(*it
));
4113 spin_lock_irq(&css_set_lock
);
4119 it
->cset_pos
= &css
->cgroup
->e_csets
[css
->ss
->id
];
4121 it
->cset_pos
= &css
->cgroup
->cset_links
;
4123 it
->cset_head
= it
->cset_pos
;
4125 css_task_iter_advance_css_set(it
);
4127 spin_unlock_irq(&css_set_lock
);
4131 * css_task_iter_next - return the next task for the iterator
4132 * @it: the task iterator being iterated
4134 * The "next" function for task iteration. @it should have been
4135 * initialized via css_task_iter_start(). Returns NULL when the iteration
4138 struct task_struct
*css_task_iter_next(struct css_task_iter
*it
)
4141 put_task_struct(it
->cur_task
);
4142 it
->cur_task
= NULL
;
4145 spin_lock_irq(&css_set_lock
);
4148 it
->cur_task
= list_entry(it
->task_pos
, struct task_struct
,
4150 get_task_struct(it
->cur_task
);
4151 css_task_iter_advance(it
);
4154 spin_unlock_irq(&css_set_lock
);
4156 return it
->cur_task
;
4160 * css_task_iter_end - finish task iteration
4161 * @it: the task iterator to finish
4163 * Finish task iteration started by css_task_iter_start().
4165 void css_task_iter_end(struct css_task_iter
*it
)
4168 spin_lock_irq(&css_set_lock
);
4169 list_del(&it
->iters_node
);
4170 put_css_set_locked(it
->cur_cset
);
4171 spin_unlock_irq(&css_set_lock
);
4175 put_css_set(it
->cur_dcset
);
4178 put_task_struct(it
->cur_task
);
4181 static void cgroup_procs_release(struct kernfs_open_file
*of
)
4184 css_task_iter_end(of
->priv
);
4189 static void *cgroup_procs_next(struct seq_file
*s
, void *v
, loff_t
*pos
)
4191 struct kernfs_open_file
*of
= s
->private;
4192 struct css_task_iter
*it
= of
->priv
;
4194 return css_task_iter_next(it
);
4197 static void *__cgroup_procs_start(struct seq_file
*s
, loff_t
*pos
,
4198 unsigned int iter_flags
)
4200 struct kernfs_open_file
*of
= s
->private;
4201 struct cgroup
*cgrp
= seq_css(s
)->cgroup
;
4202 struct css_task_iter
*it
= of
->priv
;
4205 * When a seq_file is seeked, it's always traversed sequentially
4206 * from position 0, so we can simply keep iterating on !0 *pos.
4209 if (WARN_ON_ONCE((*pos
)++))
4210 return ERR_PTR(-EINVAL
);
4212 it
= kzalloc(sizeof(*it
), GFP_KERNEL
);
4214 return ERR_PTR(-ENOMEM
);
4216 css_task_iter_start(&cgrp
->self
, iter_flags
, it
);
4217 } else if (!(*pos
)++) {
4218 css_task_iter_end(it
);
4219 css_task_iter_start(&cgrp
->self
, iter_flags
, it
);
4222 return cgroup_procs_next(s
, NULL
, NULL
);
4225 static void *cgroup_procs_start(struct seq_file
*s
, loff_t
*pos
)
4227 struct cgroup
*cgrp
= seq_css(s
)->cgroup
;
4230 * All processes of a threaded subtree belong to the domain cgroup
4231 * of the subtree. Only threads can be distributed across the
4232 * subtree. Reject reads on cgroup.procs in the subtree proper.
4233 * They're always empty anyway.
4235 if (cgroup_is_threaded(cgrp
))
4236 return ERR_PTR(-EOPNOTSUPP
);
4238 return __cgroup_procs_start(s
, pos
, CSS_TASK_ITER_PROCS
|
4239 CSS_TASK_ITER_THREADED
);
4242 static int cgroup_procs_show(struct seq_file
*s
, void *v
)
4244 seq_printf(s
, "%d\n", task_pid_vnr(v
));
4248 static int cgroup_procs_write_permission(struct cgroup
*src_cgrp
,
4249 struct cgroup
*dst_cgrp
,
4250 struct super_block
*sb
)
4252 struct cgroup_namespace
*ns
= current
->nsproxy
->cgroup_ns
;
4253 struct cgroup
*com_cgrp
= src_cgrp
;
4254 struct inode
*inode
;
4257 lockdep_assert_held(&cgroup_mutex
);
4259 /* find the common ancestor */
4260 while (!cgroup_is_descendant(dst_cgrp
, com_cgrp
))
4261 com_cgrp
= cgroup_parent(com_cgrp
);
4263 /* %current should be authorized to migrate to the common ancestor */
4264 inode
= kernfs_get_inode(sb
, com_cgrp
->procs_file
.kn
);
4268 ret
= inode_permission(inode
, MAY_WRITE
);
4274 * If namespaces are delegation boundaries, %current must be able
4275 * to see both source and destination cgroups from its namespace.
4277 if ((cgrp_dfl_root
.flags
& CGRP_ROOT_NS_DELEGATE
) &&
4278 (!cgroup_is_descendant(src_cgrp
, ns
->root_cset
->dfl_cgrp
) ||
4279 !cgroup_is_descendant(dst_cgrp
, ns
->root_cset
->dfl_cgrp
)))
4285 static ssize_t
cgroup_procs_write(struct kernfs_open_file
*of
,
4286 char *buf
, size_t nbytes
, loff_t off
)
4288 struct cgroup
*src_cgrp
, *dst_cgrp
;
4289 struct task_struct
*task
;
4292 dst_cgrp
= cgroup_kn_lock_live(of
->kn
, false);
4296 task
= cgroup_procs_write_start(buf
, true);
4297 ret
= PTR_ERR_OR_ZERO(task
);
4301 /* find the source cgroup */
4302 spin_lock_irq(&css_set_lock
);
4303 src_cgrp
= task_cgroup_from_root(task
, &cgrp_dfl_root
);
4304 spin_unlock_irq(&css_set_lock
);
4306 ret
= cgroup_procs_write_permission(src_cgrp
, dst_cgrp
,
4307 of
->file
->f_path
.dentry
->d_sb
);
4311 ret
= cgroup_attach_task(dst_cgrp
, task
, true);
4314 cgroup_procs_write_finish(task
);
4316 cgroup_kn_unlock(of
->kn
);
4318 return ret
?: nbytes
;
4321 static void *cgroup_threads_start(struct seq_file
*s
, loff_t
*pos
)
4323 return __cgroup_procs_start(s
, pos
, 0);
4326 static ssize_t
cgroup_threads_write(struct kernfs_open_file
*of
,
4327 char *buf
, size_t nbytes
, loff_t off
)
4329 struct cgroup
*src_cgrp
, *dst_cgrp
;
4330 struct task_struct
*task
;
4333 buf
= strstrip(buf
);
4335 dst_cgrp
= cgroup_kn_lock_live(of
->kn
, false);
4339 task
= cgroup_procs_write_start(buf
, false);
4340 ret
= PTR_ERR_OR_ZERO(task
);
4344 /* find the source cgroup */
4345 spin_lock_irq(&css_set_lock
);
4346 src_cgrp
= task_cgroup_from_root(task
, &cgrp_dfl_root
);
4347 spin_unlock_irq(&css_set_lock
);
4349 /* thread migrations follow the cgroup.procs delegation rule */
4350 ret
= cgroup_procs_write_permission(src_cgrp
, dst_cgrp
,
4351 of
->file
->f_path
.dentry
->d_sb
);
4355 /* and must be contained in the same domain */
4357 if (src_cgrp
->dom_cgrp
!= dst_cgrp
->dom_cgrp
)
4360 ret
= cgroup_attach_task(dst_cgrp
, task
, false);
4363 cgroup_procs_write_finish(task
);
4365 cgroup_kn_unlock(of
->kn
);
4367 return ret
?: nbytes
;
4370 /* cgroup core interface files for the default hierarchy */
4371 static struct cftype cgroup_base_files
[] = {
4373 .name
= "cgroup.type",
4374 .flags
= CFTYPE_NOT_ON_ROOT
,
4375 .seq_show
= cgroup_type_show
,
4376 .write
= cgroup_type_write
,
4379 .name
= "cgroup.procs",
4380 .flags
= CFTYPE_NS_DELEGATABLE
,
4381 .file_offset
= offsetof(struct cgroup
, procs_file
),
4382 .release
= cgroup_procs_release
,
4383 .seq_start
= cgroup_procs_start
,
4384 .seq_next
= cgroup_procs_next
,
4385 .seq_show
= cgroup_procs_show
,
4386 .write
= cgroup_procs_write
,
4389 .name
= "cgroup.threads",
4390 .release
= cgroup_procs_release
,
4391 .seq_start
= cgroup_threads_start
,
4392 .seq_next
= cgroup_procs_next
,
4393 .seq_show
= cgroup_procs_show
,
4394 .write
= cgroup_threads_write
,
4397 .name
= "cgroup.controllers",
4398 .seq_show
= cgroup_controllers_show
,
4401 .name
= "cgroup.subtree_control",
4402 .flags
= CFTYPE_NS_DELEGATABLE
,
4403 .seq_show
= cgroup_subtree_control_show
,
4404 .write
= cgroup_subtree_control_write
,
4407 .name
= "cgroup.events",
4408 .flags
= CFTYPE_NOT_ON_ROOT
,
4409 .file_offset
= offsetof(struct cgroup
, events_file
),
4410 .seq_show
= cgroup_events_show
,
4413 .name
= "cgroup.max.descendants",
4414 .seq_show
= cgroup_max_descendants_show
,
4415 .write
= cgroup_max_descendants_write
,
4418 .name
= "cgroup.max.depth",
4419 .seq_show
= cgroup_max_depth_show
,
4420 .write
= cgroup_max_depth_write
,
4423 .name
= "cgroup.stat",
4424 .seq_show
= cgroup_stats_show
,
4430 * css destruction is four-stage process.
4432 * 1. Destruction starts. Killing of the percpu_ref is initiated.
4433 * Implemented in kill_css().
4435 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
4436 * and thus css_tryget_online() is guaranteed to fail, the css can be
4437 * offlined by invoking offline_css(). After offlining, the base ref is
4438 * put. Implemented in css_killed_work_fn().
4440 * 3. When the percpu_ref reaches zero, the only possible remaining
4441 * accessors are inside RCU read sections. css_release() schedules the
4444 * 4. After the grace period, the css can be freed. Implemented in
4445 * css_free_work_fn().
4447 * It is actually hairier because both step 2 and 4 require process context
4448 * and thus involve punting to css->destroy_work adding two additional
4449 * steps to the already complex sequence.
4451 static void css_free_work_fn(struct work_struct
*work
)
4453 struct cgroup_subsys_state
*css
=
4454 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4455 struct cgroup_subsys
*ss
= css
->ss
;
4456 struct cgroup
*cgrp
= css
->cgroup
;
4458 percpu_ref_exit(&css
->refcnt
);
4462 struct cgroup_subsys_state
*parent
= css
->parent
;
4466 cgroup_idr_remove(&ss
->css_idr
, id
);
4472 /* cgroup free path */
4473 atomic_dec(&cgrp
->root
->nr_cgrps
);
4474 cgroup1_pidlist_destroy_all(cgrp
);
4475 cancel_work_sync(&cgrp
->release_agent_work
);
4477 if (cgroup_parent(cgrp
)) {
4479 * We get a ref to the parent, and put the ref when
4480 * this cgroup is being freed, so it's guaranteed
4481 * that the parent won't be destroyed before its
4484 cgroup_put(cgroup_parent(cgrp
));
4485 kernfs_put(cgrp
->kn
);
4489 * This is root cgroup's refcnt reaching zero,
4490 * which indicates that the root should be
4493 cgroup_destroy_root(cgrp
->root
);
4498 static void css_free_rcu_fn(struct rcu_head
*rcu_head
)
4500 struct cgroup_subsys_state
*css
=
4501 container_of(rcu_head
, struct cgroup_subsys_state
, rcu_head
);
4503 INIT_WORK(&css
->destroy_work
, css_free_work_fn
);
4504 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4507 static void css_release_work_fn(struct work_struct
*work
)
4509 struct cgroup_subsys_state
*css
=
4510 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4511 struct cgroup_subsys
*ss
= css
->ss
;
4512 struct cgroup
*cgrp
= css
->cgroup
;
4514 mutex_lock(&cgroup_mutex
);
4516 css
->flags
|= CSS_RELEASED
;
4517 list_del_rcu(&css
->sibling
);
4520 /* css release path */
4521 cgroup_idr_replace(&ss
->css_idr
, NULL
, css
->id
);
4522 if (ss
->css_released
)
4523 ss
->css_released(css
);
4525 struct cgroup
*tcgrp
;
4527 /* cgroup release path */
4528 trace_cgroup_release(cgrp
);
4530 for (tcgrp
= cgroup_parent(cgrp
); tcgrp
;
4531 tcgrp
= cgroup_parent(tcgrp
))
4532 tcgrp
->nr_dying_descendants
--;
4534 cgroup_idr_remove(&cgrp
->root
->cgroup_idr
, cgrp
->id
);
4538 * There are two control paths which try to determine
4539 * cgroup from dentry without going through kernfs -
4540 * cgroupstats_build() and css_tryget_online_from_dir().
4541 * Those are supported by RCU protecting clearing of
4542 * cgrp->kn->priv backpointer.
4545 RCU_INIT_POINTER(*(void __rcu __force
**)&cgrp
->kn
->priv
,
4548 cgroup_bpf_put(cgrp
);
4551 mutex_unlock(&cgroup_mutex
);
4553 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
4556 static void css_release(struct percpu_ref
*ref
)
4558 struct cgroup_subsys_state
*css
=
4559 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
4561 INIT_WORK(&css
->destroy_work
, css_release_work_fn
);
4562 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4565 static void init_and_link_css(struct cgroup_subsys_state
*css
,
4566 struct cgroup_subsys
*ss
, struct cgroup
*cgrp
)
4568 lockdep_assert_held(&cgroup_mutex
);
4570 cgroup_get_live(cgrp
);
4572 memset(css
, 0, sizeof(*css
));
4576 INIT_LIST_HEAD(&css
->sibling
);
4577 INIT_LIST_HEAD(&css
->children
);
4578 css
->serial_nr
= css_serial_nr_next
++;
4579 atomic_set(&css
->online_cnt
, 0);
4581 if (cgroup_parent(cgrp
)) {
4582 css
->parent
= cgroup_css(cgroup_parent(cgrp
), ss
);
4583 css_get(css
->parent
);
4586 BUG_ON(cgroup_css(cgrp
, ss
));
4589 /* invoke ->css_online() on a new CSS and mark it online if successful */
4590 static int online_css(struct cgroup_subsys_state
*css
)
4592 struct cgroup_subsys
*ss
= css
->ss
;
4595 lockdep_assert_held(&cgroup_mutex
);
4598 ret
= ss
->css_online(css
);
4600 css
->flags
|= CSS_ONLINE
;
4601 rcu_assign_pointer(css
->cgroup
->subsys
[ss
->id
], css
);
4603 atomic_inc(&css
->online_cnt
);
4605 atomic_inc(&css
->parent
->online_cnt
);
4610 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
4611 static void offline_css(struct cgroup_subsys_state
*css
)
4613 struct cgroup_subsys
*ss
= css
->ss
;
4615 lockdep_assert_held(&cgroup_mutex
);
4617 if (!(css
->flags
& CSS_ONLINE
))
4623 if (ss
->css_offline
)
4624 ss
->css_offline(css
);
4626 css
->flags
&= ~CSS_ONLINE
;
4627 RCU_INIT_POINTER(css
->cgroup
->subsys
[ss
->id
], NULL
);
4629 wake_up_all(&css
->cgroup
->offline_waitq
);
4633 * css_create - create a cgroup_subsys_state
4634 * @cgrp: the cgroup new css will be associated with
4635 * @ss: the subsys of new css
4637 * Create a new css associated with @cgrp - @ss pair. On success, the new
4638 * css is online and installed in @cgrp. This function doesn't create the
4639 * interface files. Returns 0 on success, -errno on failure.
4641 static struct cgroup_subsys_state
*css_create(struct cgroup
*cgrp
,
4642 struct cgroup_subsys
*ss
)
4644 struct cgroup
*parent
= cgroup_parent(cgrp
);
4645 struct cgroup_subsys_state
*parent_css
= cgroup_css(parent
, ss
);
4646 struct cgroup_subsys_state
*css
;
4649 lockdep_assert_held(&cgroup_mutex
);
4651 css
= ss
->css_alloc(parent_css
);
4653 css
= ERR_PTR(-ENOMEM
);
4657 init_and_link_css(css
, ss
, cgrp
);
4659 err
= percpu_ref_init(&css
->refcnt
, css_release
, 0, GFP_KERNEL
);
4663 err
= cgroup_idr_alloc(&ss
->css_idr
, NULL
, 2, 0, GFP_KERNEL
);
4668 /* @css is ready to be brought online now, make it visible */
4669 list_add_tail_rcu(&css
->sibling
, &parent_css
->children
);
4670 cgroup_idr_replace(&ss
->css_idr
, css
, css
->id
);
4672 err
= online_css(css
);
4676 if (ss
->broken_hierarchy
&& !ss
->warned_broken_hierarchy
&&
4677 cgroup_parent(parent
)) {
4678 pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
4679 current
->comm
, current
->pid
, ss
->name
);
4680 if (!strcmp(ss
->name
, "memory"))
4681 pr_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n");
4682 ss
->warned_broken_hierarchy
= true;
4688 list_del_rcu(&css
->sibling
);
4690 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
4691 return ERR_PTR(err
);
4695 * The returned cgroup is fully initialized including its control mask, but
4696 * it isn't associated with its kernfs_node and doesn't have the control
4699 static struct cgroup
*cgroup_create(struct cgroup
*parent
)
4701 struct cgroup_root
*root
= parent
->root
;
4702 struct cgroup
*cgrp
, *tcgrp
;
4703 int level
= parent
->level
+ 1;
4706 /* allocate the cgroup and its ID, 0 is reserved for the root */
4707 cgrp
= kzalloc(sizeof(*cgrp
) +
4708 sizeof(cgrp
->ancestor_ids
[0]) * (level
+ 1), GFP_KERNEL
);
4710 return ERR_PTR(-ENOMEM
);
4712 ret
= percpu_ref_init(&cgrp
->self
.refcnt
, css_release
, 0, GFP_KERNEL
);
4717 * Temporarily set the pointer to NULL, so idr_find() won't return
4718 * a half-baked cgroup.
4720 cgrp
->id
= cgroup_idr_alloc(&root
->cgroup_idr
, NULL
, 2, 0, GFP_KERNEL
);
4723 goto out_cancel_ref
;
4726 init_cgroup_housekeeping(cgrp
);
4728 cgrp
->self
.parent
= &parent
->self
;
4730 cgrp
->level
= level
;
4732 for (tcgrp
= cgrp
; tcgrp
; tcgrp
= cgroup_parent(tcgrp
)) {
4733 cgrp
->ancestor_ids
[tcgrp
->level
] = tcgrp
->id
;
4736 tcgrp
->nr_descendants
++;
4739 if (notify_on_release(parent
))
4740 set_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
4742 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &parent
->flags
))
4743 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &cgrp
->flags
);
4745 cgrp
->self
.serial_nr
= css_serial_nr_next
++;
4747 /* allocation complete, commit to creation */
4748 list_add_tail_rcu(&cgrp
->self
.sibling
, &cgroup_parent(cgrp
)->self
.children
);
4749 atomic_inc(&root
->nr_cgrps
);
4750 cgroup_get_live(parent
);
4753 * @cgrp is now fully operational. If something fails after this
4754 * point, it'll be released via the normal destruction path.
4756 cgroup_idr_replace(&root
->cgroup_idr
, cgrp
, cgrp
->id
);
4759 * On the default hierarchy, a child doesn't automatically inherit
4760 * subtree_control from the parent. Each is configured manually.
4762 if (!cgroup_on_dfl(cgrp
))
4763 cgrp
->subtree_control
= cgroup_control(cgrp
);
4766 cgroup_bpf_inherit(cgrp
, parent
);
4768 cgroup_propagate_control(cgrp
);
4773 percpu_ref_exit(&cgrp
->self
.refcnt
);
4776 return ERR_PTR(ret
);
4779 static bool cgroup_check_hierarchy_limits(struct cgroup
*parent
)
4781 struct cgroup
*cgroup
;
4785 lockdep_assert_held(&cgroup_mutex
);
4787 for (cgroup
= parent
; cgroup
; cgroup
= cgroup_parent(cgroup
)) {
4788 if (cgroup
->nr_descendants
>= cgroup
->max_descendants
)
4791 if (level
> cgroup
->max_depth
)
4802 int cgroup_mkdir(struct kernfs_node
*parent_kn
, const char *name
, umode_t mode
)
4804 struct cgroup
*parent
, *cgrp
;
4805 struct kernfs_node
*kn
;
4808 /* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
4809 if (strchr(name
, '\n'))
4812 parent
= cgroup_kn_lock_live(parent_kn
, false);
4816 if (!cgroup_check_hierarchy_limits(parent
)) {
4821 cgrp
= cgroup_create(parent
);
4823 ret
= PTR_ERR(cgrp
);
4827 /* create the directory */
4828 kn
= kernfs_create_dir(parent
->kn
, name
, mode
, cgrp
);
4836 * This extra ref will be put in cgroup_free_fn() and guarantees
4837 * that @cgrp->kn is always accessible.
4841 ret
= cgroup_kn_set_ugid(kn
);
4845 ret
= css_populate_dir(&cgrp
->self
);
4849 ret
= cgroup_apply_control_enable(cgrp
);
4853 trace_cgroup_mkdir(cgrp
);
4855 /* let's create and online css's */
4856 kernfs_activate(kn
);
4862 cgroup_destroy_locked(cgrp
);
4864 cgroup_kn_unlock(parent_kn
);
4869 * This is called when the refcnt of a css is confirmed to be killed.
4870 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
4871 * initate destruction and put the css ref from kill_css().
4873 static void css_killed_work_fn(struct work_struct
*work
)
4875 struct cgroup_subsys_state
*css
=
4876 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4878 mutex_lock(&cgroup_mutex
);
4883 /* @css can't go away while we're holding cgroup_mutex */
4885 } while (css
&& atomic_dec_and_test(&css
->online_cnt
));
4887 mutex_unlock(&cgroup_mutex
);
4890 /* css kill confirmation processing requires process context, bounce */
4891 static void css_killed_ref_fn(struct percpu_ref
*ref
)
4893 struct cgroup_subsys_state
*css
=
4894 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
4896 if (atomic_dec_and_test(&css
->online_cnt
)) {
4897 INIT_WORK(&css
->destroy_work
, css_killed_work_fn
);
4898 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4903 * kill_css - destroy a css
4904 * @css: css to destroy
4906 * This function initiates destruction of @css by removing cgroup interface
4907 * files and putting its base reference. ->css_offline() will be invoked
4908 * asynchronously once css_tryget_online() is guaranteed to fail and when
4909 * the reference count reaches zero, @css will be released.
4911 static void kill_css(struct cgroup_subsys_state
*css
)
4913 lockdep_assert_held(&cgroup_mutex
);
4915 if (css
->flags
& CSS_DYING
)
4918 css
->flags
|= CSS_DYING
;
4921 * This must happen before css is disassociated with its cgroup.
4922 * See seq_css() for details.
4927 * Killing would put the base ref, but we need to keep it alive
4928 * until after ->css_offline().
4933 * cgroup core guarantees that, by the time ->css_offline() is
4934 * invoked, no new css reference will be given out via
4935 * css_tryget_online(). We can't simply call percpu_ref_kill() and
4936 * proceed to offlining css's because percpu_ref_kill() doesn't
4937 * guarantee that the ref is seen as killed on all CPUs on return.
4939 * Use percpu_ref_kill_and_confirm() to get notifications as each
4940 * css is confirmed to be seen as killed on all CPUs.
4942 percpu_ref_kill_and_confirm(&css
->refcnt
, css_killed_ref_fn
);
4946 * cgroup_destroy_locked - the first stage of cgroup destruction
4947 * @cgrp: cgroup to be destroyed
4949 * css's make use of percpu refcnts whose killing latency shouldn't be
4950 * exposed to userland and are RCU protected. Also, cgroup core needs to
4951 * guarantee that css_tryget_online() won't succeed by the time
4952 * ->css_offline() is invoked. To satisfy all the requirements,
4953 * destruction is implemented in the following two steps.
4955 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
4956 * userland visible parts and start killing the percpu refcnts of
4957 * css's. Set up so that the next stage will be kicked off once all
4958 * the percpu refcnts are confirmed to be killed.
4960 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
4961 * rest of destruction. Once all cgroup references are gone, the
4962 * cgroup is RCU-freed.
4964 * This function implements s1. After this step, @cgrp is gone as far as
4965 * the userland is concerned and a new cgroup with the same name may be
4966 * created. As cgroup doesn't care about the names internally, this
4967 * doesn't cause any problem.
4969 static int cgroup_destroy_locked(struct cgroup
*cgrp
)
4970 __releases(&cgroup_mutex
) __acquires(&cgroup_mutex
)
4972 struct cgroup
*tcgrp
, *parent
= cgroup_parent(cgrp
);
4973 struct cgroup_subsys_state
*css
;
4974 struct cgrp_cset_link
*link
;
4977 lockdep_assert_held(&cgroup_mutex
);
4980 * Only migration can raise populated from zero and we're already
4981 * holding cgroup_mutex.
4983 if (cgroup_is_populated(cgrp
))
4987 * Make sure there's no live children. We can't test emptiness of
4988 * ->self.children as dead children linger on it while being
4989 * drained; otherwise, "rmdir parent/child parent" may fail.
4991 if (css_has_online_children(&cgrp
->self
))
4995 * Mark @cgrp and the associated csets dead. The former prevents
4996 * further task migration and child creation by disabling
4997 * cgroup_lock_live_group(). The latter makes the csets ignored by
4998 * the migration path.
5000 cgrp
->self
.flags
&= ~CSS_ONLINE
;
5002 spin_lock_irq(&css_set_lock
);
5003 list_for_each_entry(link
, &cgrp
->cset_links
, cset_link
)
5004 link
->cset
->dead
= true;
5005 spin_unlock_irq(&css_set_lock
);
5007 /* initiate massacre of all css's */
5008 for_each_css(css
, ssid
, cgrp
)
5012 * Remove @cgrp directory along with the base files. @cgrp has an
5013 * extra ref on its kn.
5015 kernfs_remove(cgrp
->kn
);
5017 if (parent
&& cgroup_is_threaded(cgrp
))
5018 parent
->nr_threaded_children
--;
5020 for (tcgrp
= cgroup_parent(cgrp
); tcgrp
; tcgrp
= cgroup_parent(tcgrp
)) {
5021 tcgrp
->nr_descendants
--;
5022 tcgrp
->nr_dying_descendants
++;
5025 cgroup1_check_for_release(parent
);
5027 /* put the base reference */
5028 percpu_ref_kill(&cgrp
->self
.refcnt
);
5033 int cgroup_rmdir(struct kernfs_node
*kn
)
5035 struct cgroup
*cgrp
;
5038 cgrp
= cgroup_kn_lock_live(kn
, false);
5042 ret
= cgroup_destroy_locked(cgrp
);
5045 trace_cgroup_rmdir(cgrp
);
5047 cgroup_kn_unlock(kn
);
5051 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
= {
5052 .show_options
= cgroup_show_options
,
5053 .remount_fs
= cgroup_remount
,
5054 .mkdir
= cgroup_mkdir
,
5055 .rmdir
= cgroup_rmdir
,
5056 .show_path
= cgroup_show_path
,
5059 static void __init
cgroup_init_subsys(struct cgroup_subsys
*ss
, bool early
)
5061 struct cgroup_subsys_state
*css
;
5063 pr_debug("Initializing cgroup subsys %s\n", ss
->name
);
5065 mutex_lock(&cgroup_mutex
);
5067 idr_init(&ss
->css_idr
);
5068 INIT_LIST_HEAD(&ss
->cfts
);
5070 /* Create the root cgroup state for this subsystem */
5071 ss
->root
= &cgrp_dfl_root
;
5072 css
= ss
->css_alloc(cgroup_css(&cgrp_dfl_root
.cgrp
, ss
));
5073 /* We don't handle early failures gracefully */
5074 BUG_ON(IS_ERR(css
));
5075 init_and_link_css(css
, ss
, &cgrp_dfl_root
.cgrp
);
5078 * Root csses are never destroyed and we can't initialize
5079 * percpu_ref during early init. Disable refcnting.
5081 css
->flags
|= CSS_NO_REF
;
5084 /* allocation can't be done safely during early init */
5087 css
->id
= cgroup_idr_alloc(&ss
->css_idr
, css
, 1, 2, GFP_KERNEL
);
5088 BUG_ON(css
->id
< 0);
5091 /* Update the init_css_set to contain a subsys
5092 * pointer to this state - since the subsystem is
5093 * newly registered, all tasks and hence the
5094 * init_css_set is in the subsystem's root cgroup. */
5095 init_css_set
.subsys
[ss
->id
] = css
;
5097 have_fork_callback
|= (bool)ss
->fork
<< ss
->id
;
5098 have_exit_callback
|= (bool)ss
->exit
<< ss
->id
;
5099 have_free_callback
|= (bool)ss
->free
<< ss
->id
;
5100 have_canfork_callback
|= (bool)ss
->can_fork
<< ss
->id
;
5102 /* At system boot, before all subsystems have been
5103 * registered, no tasks have been forked, so we don't
5104 * need to invoke fork callbacks here. */
5105 BUG_ON(!list_empty(&init_task
.tasks
));
5107 BUG_ON(online_css(css
));
5109 mutex_unlock(&cgroup_mutex
);
5113 * cgroup_init_early - cgroup initialization at system boot
5115 * Initialize cgroups at system boot, and initialize any
5116 * subsystems that request early init.
5118 int __init
cgroup_init_early(void)
5120 static struct cgroup_sb_opts __initdata opts
;
5121 struct cgroup_subsys
*ss
;
5124 init_cgroup_root(&cgrp_dfl_root
, &opts
);
5125 cgrp_dfl_root
.cgrp
.self
.flags
|= CSS_NO_REF
;
5127 RCU_INIT_POINTER(init_task
.cgroups
, &init_css_set
);
5129 for_each_subsys(ss
, i
) {
5130 WARN(!ss
->css_alloc
|| !ss
->css_free
|| ss
->name
|| ss
->id
,
5131 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p id:name=%d:%s\n",
5132 i
, cgroup_subsys_name
[i
], ss
->css_alloc
, ss
->css_free
,
5134 WARN(strlen(cgroup_subsys_name
[i
]) > MAX_CGROUP_TYPE_NAMELEN
,
5135 "cgroup_subsys_name %s too long\n", cgroup_subsys_name
[i
]);
5138 ss
->name
= cgroup_subsys_name
[i
];
5139 if (!ss
->legacy_name
)
5140 ss
->legacy_name
= cgroup_subsys_name
[i
];
5143 cgroup_init_subsys(ss
, true);
5148 static u16 cgroup_disable_mask __initdata
;
5151 * cgroup_init - cgroup initialization
5153 * Register cgroup filesystem and /proc file, and initialize
5154 * any subsystems that didn't request early init.
5156 int __init
cgroup_init(void)
5158 struct cgroup_subsys
*ss
;
5161 BUILD_BUG_ON(CGROUP_SUBSYS_COUNT
> 16);
5162 BUG_ON(percpu_init_rwsem(&cgroup_threadgroup_rwsem
));
5163 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_base_files
));
5164 BUG_ON(cgroup_init_cftypes(NULL
, cgroup1_base_files
));
5167 * The latency of the synchronize_sched() is too high for cgroups,
5168 * avoid it at the cost of forcing all readers into the slow path.
5170 rcu_sync_enter_start(&cgroup_threadgroup_rwsem
.rss
);
5172 get_user_ns(init_cgroup_ns
.user_ns
);
5174 mutex_lock(&cgroup_mutex
);
5177 * Add init_css_set to the hash table so that dfl_root can link to
5180 hash_add(css_set_table
, &init_css_set
.hlist
,
5181 css_set_hash(init_css_set
.subsys
));
5183 BUG_ON(cgroup_setup_root(&cgrp_dfl_root
, 0, 0));
5185 mutex_unlock(&cgroup_mutex
);
5187 for_each_subsys(ss
, ssid
) {
5188 if (ss
->early_init
) {
5189 struct cgroup_subsys_state
*css
=
5190 init_css_set
.subsys
[ss
->id
];
5192 css
->id
= cgroup_idr_alloc(&ss
->css_idr
, css
, 1, 2,
5194 BUG_ON(css
->id
< 0);
5196 cgroup_init_subsys(ss
, false);
5199 list_add_tail(&init_css_set
.e_cset_node
[ssid
],
5200 &cgrp_dfl_root
.cgrp
.e_csets
[ssid
]);
5203 * Setting dfl_root subsys_mask needs to consider the
5204 * disabled flag and cftype registration needs kmalloc,
5205 * both of which aren't available during early_init.
5207 if (cgroup_disable_mask
& (1 << ssid
)) {
5208 static_branch_disable(cgroup_subsys_enabled_key
[ssid
]);
5209 printk(KERN_INFO
"Disabling %s control group subsystem\n",
5214 if (cgroup1_ssid_disabled(ssid
))
5215 printk(KERN_INFO
"Disabling %s control group subsystem in v1 mounts\n",
5218 cgrp_dfl_root
.subsys_mask
|= 1 << ss
->id
;
5220 /* implicit controllers must be threaded too */
5221 WARN_ON(ss
->implicit_on_dfl
&& !ss
->threaded
);
5223 if (ss
->implicit_on_dfl
)
5224 cgrp_dfl_implicit_ss_mask
|= 1 << ss
->id
;
5225 else if (!ss
->dfl_cftypes
)
5226 cgrp_dfl_inhibit_ss_mask
|= 1 << ss
->id
;
5229 cgrp_dfl_threaded_ss_mask
|= 1 << ss
->id
;
5231 if (ss
->dfl_cftypes
== ss
->legacy_cftypes
) {
5232 WARN_ON(cgroup_add_cftypes(ss
, ss
->dfl_cftypes
));
5234 WARN_ON(cgroup_add_dfl_cftypes(ss
, ss
->dfl_cftypes
));
5235 WARN_ON(cgroup_add_legacy_cftypes(ss
, ss
->legacy_cftypes
));
5239 ss
->bind(init_css_set
.subsys
[ssid
]);
5242 /* init_css_set.subsys[] has been updated, re-hash */
5243 hash_del(&init_css_set
.hlist
);
5244 hash_add(css_set_table
, &init_css_set
.hlist
,
5245 css_set_hash(init_css_set
.subsys
));
5247 WARN_ON(sysfs_create_mount_point(fs_kobj
, "cgroup"));
5248 WARN_ON(register_filesystem(&cgroup_fs_type
));
5249 WARN_ON(register_filesystem(&cgroup2_fs_type
));
5250 WARN_ON(!proc_create("cgroups", 0, NULL
, &proc_cgroupstats_operations
));
5255 static int __init
cgroup_wq_init(void)
5258 * There isn't much point in executing destruction path in
5259 * parallel. Good chunk is serialized with cgroup_mutex anyway.
5260 * Use 1 for @max_active.
5262 * We would prefer to do this in cgroup_init() above, but that
5263 * is called before init_workqueues(): so leave this until after.
5265 cgroup_destroy_wq
= alloc_workqueue("cgroup_destroy", 0, 1);
5266 BUG_ON(!cgroup_destroy_wq
);
5269 core_initcall(cgroup_wq_init
);
5272 * proc_cgroup_show()
5273 * - Print task's cgroup paths into seq_file, one line for each hierarchy
5274 * - Used for /proc/<pid>/cgroup.
5276 int proc_cgroup_show(struct seq_file
*m
, struct pid_namespace
*ns
,
5277 struct pid
*pid
, struct task_struct
*tsk
)
5281 struct cgroup_root
*root
;
5284 buf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
5288 mutex_lock(&cgroup_mutex
);
5289 spin_lock_irq(&css_set_lock
);
5291 for_each_root(root
) {
5292 struct cgroup_subsys
*ss
;
5293 struct cgroup
*cgrp
;
5294 int ssid
, count
= 0;
5296 if (root
== &cgrp_dfl_root
&& !cgrp_dfl_visible
)
5299 seq_printf(m
, "%d:", root
->hierarchy_id
);
5300 if (root
!= &cgrp_dfl_root
)
5301 for_each_subsys(ss
, ssid
)
5302 if (root
->subsys_mask
& (1 << ssid
))
5303 seq_printf(m
, "%s%s", count
++ ? "," : "",
5305 if (strlen(root
->name
))
5306 seq_printf(m
, "%sname=%s", count
? "," : "",
5310 cgrp
= task_cgroup_from_root(tsk
, root
);
5313 * On traditional hierarchies, all zombie tasks show up as
5314 * belonging to the root cgroup. On the default hierarchy,
5315 * while a zombie doesn't show up in "cgroup.procs" and
5316 * thus can't be migrated, its /proc/PID/cgroup keeps
5317 * reporting the cgroup it belonged to before exiting. If
5318 * the cgroup is removed before the zombie is reaped,
5319 * " (deleted)" is appended to the cgroup path.
5321 if (cgroup_on_dfl(cgrp
) || !(tsk
->flags
& PF_EXITING
)) {
5322 retval
= cgroup_path_ns_locked(cgrp
, buf
, PATH_MAX
,
5323 current
->nsproxy
->cgroup_ns
);
5324 if (retval
>= PATH_MAX
)
5325 retval
= -ENAMETOOLONG
;
5334 if (cgroup_on_dfl(cgrp
) && cgroup_is_dead(cgrp
))
5335 seq_puts(m
, " (deleted)\n");
5342 spin_unlock_irq(&css_set_lock
);
5343 mutex_unlock(&cgroup_mutex
);
5350 * cgroup_fork - initialize cgroup related fields during copy_process()
5351 * @child: pointer to task_struct of forking parent process.
5353 * A task is associated with the init_css_set until cgroup_post_fork()
5354 * attaches it to the parent's css_set. Empty cg_list indicates that
5355 * @child isn't holding reference to its css_set.
5357 void cgroup_fork(struct task_struct
*child
)
5359 RCU_INIT_POINTER(child
->cgroups
, &init_css_set
);
5360 INIT_LIST_HEAD(&child
->cg_list
);
5364 * cgroup_can_fork - called on a new task before the process is exposed
5365 * @child: the task in question.
5367 * This calls the subsystem can_fork() callbacks. If the can_fork() callback
5368 * returns an error, the fork aborts with that error code. This allows for
5369 * a cgroup subsystem to conditionally allow or deny new forks.
5371 int cgroup_can_fork(struct task_struct
*child
)
5373 struct cgroup_subsys
*ss
;
5376 do_each_subsys_mask(ss
, i
, have_canfork_callback
) {
5377 ret
= ss
->can_fork(child
);
5380 } while_each_subsys_mask();
5385 for_each_subsys(ss
, j
) {
5388 if (ss
->cancel_fork
)
5389 ss
->cancel_fork(child
);
5396 * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
5397 * @child: the task in question
5399 * This calls the cancel_fork() callbacks if a fork failed *after*
5400 * cgroup_can_fork() succeded.
5402 void cgroup_cancel_fork(struct task_struct
*child
)
5404 struct cgroup_subsys
*ss
;
5407 for_each_subsys(ss
, i
)
5408 if (ss
->cancel_fork
)
5409 ss
->cancel_fork(child
);
5413 * cgroup_post_fork - called on a new task after adding it to the task list
5414 * @child: the task in question
5416 * Adds the task to the list running through its css_set if necessary and
5417 * call the subsystem fork() callbacks. Has to be after the task is
5418 * visible on the task list in case we race with the first call to
5419 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
5422 void cgroup_post_fork(struct task_struct
*child
)
5424 struct cgroup_subsys
*ss
;
5428 * This may race against cgroup_enable_task_cg_lists(). As that
5429 * function sets use_task_css_set_links before grabbing
5430 * tasklist_lock and we just went through tasklist_lock to add
5431 * @child, it's guaranteed that either we see the set
5432 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
5433 * @child during its iteration.
5435 * If we won the race, @child is associated with %current's
5436 * css_set. Grabbing css_set_lock guarantees both that the
5437 * association is stable, and, on completion of the parent's
5438 * migration, @child is visible in the source of migration or
5439 * already in the destination cgroup. This guarantee is necessary
5440 * when implementing operations which need to migrate all tasks of
5441 * a cgroup to another.
5443 * Note that if we lose to cgroup_enable_task_cg_lists(), @child
5444 * will remain in init_css_set. This is safe because all tasks are
5445 * in the init_css_set before cg_links is enabled and there's no
5446 * operation which transfers all tasks out of init_css_set.
5448 if (use_task_css_set_links
) {
5449 struct css_set
*cset
;
5451 spin_lock_irq(&css_set_lock
);
5452 cset
= task_css_set(current
);
5453 if (list_empty(&child
->cg_list
)) {
5456 css_set_move_task(child
, NULL
, cset
, false);
5458 spin_unlock_irq(&css_set_lock
);
5462 * Call ss->fork(). This must happen after @child is linked on
5463 * css_set; otherwise, @child might change state between ->fork()
5464 * and addition to css_set.
5466 do_each_subsys_mask(ss
, i
, have_fork_callback
) {
5468 } while_each_subsys_mask();
5472 * cgroup_exit - detach cgroup from exiting task
5473 * @tsk: pointer to task_struct of exiting process
5475 * Description: Detach cgroup from @tsk and release it.
5477 * Note that cgroups marked notify_on_release force every task in
5478 * them to take the global cgroup_mutex mutex when exiting.
5479 * This could impact scaling on very large systems. Be reluctant to
5480 * use notify_on_release cgroups where very high task exit scaling
5481 * is required on large systems.
5483 * We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
5484 * call cgroup_exit() while the task is still competent to handle
5485 * notify_on_release(), then leave the task attached to the root cgroup in
5486 * each hierarchy for the remainder of its exit. No need to bother with
5487 * init_css_set refcnting. init_css_set never goes away and we can't race
5488 * with migration path - PF_EXITING is visible to migration path.
5490 void cgroup_exit(struct task_struct
*tsk
)
5492 struct cgroup_subsys
*ss
;
5493 struct css_set
*cset
;
5497 * Unlink from @tsk from its css_set. As migration path can't race
5498 * with us, we can check css_set and cg_list without synchronization.
5500 cset
= task_css_set(tsk
);
5502 if (!list_empty(&tsk
->cg_list
)) {
5503 spin_lock_irq(&css_set_lock
);
5504 css_set_move_task(tsk
, cset
, NULL
, false);
5506 spin_unlock_irq(&css_set_lock
);
5511 /* see cgroup_post_fork() for details */
5512 do_each_subsys_mask(ss
, i
, have_exit_callback
) {
5514 } while_each_subsys_mask();
5517 void cgroup_free(struct task_struct
*task
)
5519 struct css_set
*cset
= task_css_set(task
);
5520 struct cgroup_subsys
*ss
;
5523 do_each_subsys_mask(ss
, ssid
, have_free_callback
) {
5525 } while_each_subsys_mask();
5530 static int __init
cgroup_disable(char *str
)
5532 struct cgroup_subsys
*ss
;
5536 while ((token
= strsep(&str
, ",")) != NULL
) {
5540 for_each_subsys(ss
, i
) {
5541 if (strcmp(token
, ss
->name
) &&
5542 strcmp(token
, ss
->legacy_name
))
5544 cgroup_disable_mask
|= 1 << i
;
5549 __setup("cgroup_disable=", cgroup_disable
);
5552 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
5553 * @dentry: directory dentry of interest
5554 * @ss: subsystem of interest
5556 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
5557 * to get the corresponding css and return it. If such css doesn't exist
5558 * or can't be pinned, an ERR_PTR value is returned.
5560 struct cgroup_subsys_state
*css_tryget_online_from_dir(struct dentry
*dentry
,
5561 struct cgroup_subsys
*ss
)
5563 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
5564 struct file_system_type
*s_type
= dentry
->d_sb
->s_type
;
5565 struct cgroup_subsys_state
*css
= NULL
;
5566 struct cgroup
*cgrp
;
5568 /* is @dentry a cgroup dir? */
5569 if ((s_type
!= &cgroup_fs_type
&& s_type
!= &cgroup2_fs_type
) ||
5570 !kn
|| kernfs_type(kn
) != KERNFS_DIR
)
5571 return ERR_PTR(-EBADF
);
5576 * This path doesn't originate from kernfs and @kn could already
5577 * have been or be removed at any point. @kn->priv is RCU
5578 * protected for this access. See css_release_work_fn() for details.
5580 cgrp
= rcu_dereference(*(void __rcu __force
**)&kn
->priv
);
5582 css
= cgroup_css(cgrp
, ss
);
5584 if (!css
|| !css_tryget_online(css
))
5585 css
= ERR_PTR(-ENOENT
);
5592 * css_from_id - lookup css by id
5593 * @id: the cgroup id
5594 * @ss: cgroup subsys to be looked into
5596 * Returns the css if there's valid one with @id, otherwise returns NULL.
5597 * Should be called under rcu_read_lock().
5599 struct cgroup_subsys_state
*css_from_id(int id
, struct cgroup_subsys
*ss
)
5601 WARN_ON_ONCE(!rcu_read_lock_held());
5602 return idr_find(&ss
->css_idr
, id
);
5606 * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path
5607 * @path: path on the default hierarchy
5609 * Find the cgroup at @path on the default hierarchy, increment its
5610 * reference count and return it. Returns pointer to the found cgroup on
5611 * success, ERR_PTR(-ENOENT) if @path doens't exist and ERR_PTR(-ENOTDIR)
5612 * if @path points to a non-directory.
5614 struct cgroup
*cgroup_get_from_path(const char *path
)
5616 struct kernfs_node
*kn
;
5617 struct cgroup
*cgrp
;
5619 mutex_lock(&cgroup_mutex
);
5621 kn
= kernfs_walk_and_get(cgrp_dfl_root
.cgrp
.kn
, path
);
5623 if (kernfs_type(kn
) == KERNFS_DIR
) {
5625 cgroup_get_live(cgrp
);
5627 cgrp
= ERR_PTR(-ENOTDIR
);
5631 cgrp
= ERR_PTR(-ENOENT
);
5634 mutex_unlock(&cgroup_mutex
);
5637 EXPORT_SYMBOL_GPL(cgroup_get_from_path
);
5640 * cgroup_get_from_fd - get a cgroup pointer from a fd
5641 * @fd: fd obtained by open(cgroup2_dir)
5643 * Find the cgroup from a fd which should be obtained
5644 * by opening a cgroup directory. Returns a pointer to the
5645 * cgroup on success. ERR_PTR is returned if the cgroup
5648 struct cgroup
*cgroup_get_from_fd(int fd
)
5650 struct cgroup_subsys_state
*css
;
5651 struct cgroup
*cgrp
;
5656 return ERR_PTR(-EBADF
);
5658 css
= css_tryget_online_from_dir(f
->f_path
.dentry
, NULL
);
5661 return ERR_CAST(css
);
5664 if (!cgroup_on_dfl(cgrp
)) {
5666 return ERR_PTR(-EBADF
);
5671 EXPORT_SYMBOL_GPL(cgroup_get_from_fd
);
5674 * sock->sk_cgrp_data handling. For more info, see sock_cgroup_data
5675 * definition in cgroup-defs.h.
5677 #ifdef CONFIG_SOCK_CGROUP_DATA
5679 #if defined(CONFIG_CGROUP_NET_PRIO) || defined(CONFIG_CGROUP_NET_CLASSID)
5681 DEFINE_SPINLOCK(cgroup_sk_update_lock
);
5682 static bool cgroup_sk_alloc_disabled __read_mostly
;
5684 void cgroup_sk_alloc_disable(void)
5686 if (cgroup_sk_alloc_disabled
)
5688 pr_info("cgroup: disabling cgroup2 socket matching due to net_prio or net_cls activation\n");
5689 cgroup_sk_alloc_disabled
= true;
5694 #define cgroup_sk_alloc_disabled false
5698 void cgroup_sk_alloc(struct sock_cgroup_data
*skcd
)
5700 if (cgroup_sk_alloc_disabled
)
5703 /* Socket clone path */
5706 * We might be cloning a socket which is left in an empty
5707 * cgroup and the cgroup might have already been rmdir'd.
5708 * Don't use cgroup_get_live().
5710 cgroup_get(sock_cgroup_ptr(skcd
));
5717 struct css_set
*cset
;
5719 cset
= task_css_set(current
);
5720 if (likely(cgroup_tryget(cset
->dfl_cgrp
))) {
5721 skcd
->val
= (unsigned long)cset
->dfl_cgrp
;
5730 void cgroup_sk_free(struct sock_cgroup_data
*skcd
)
5732 cgroup_put(sock_cgroup_ptr(skcd
));
5735 #endif /* CONFIG_SOCK_CGROUP_DATA */
5737 #ifdef CONFIG_CGROUP_BPF
5738 int cgroup_bpf_update(struct cgroup
*cgrp
, struct bpf_prog
*prog
,
5739 enum bpf_attach_type type
, bool overridable
)
5741 struct cgroup
*parent
= cgroup_parent(cgrp
);
5744 mutex_lock(&cgroup_mutex
);
5745 ret
= __cgroup_bpf_update(cgrp
, parent
, prog
, type
, overridable
);
5746 mutex_unlock(&cgroup_mutex
);
5749 #endif /* CONFIG_CGROUP_BPF */