2 * Generic process-grouping system.
4 * Based originally on the cpuset system, extracted by Paul Menage
5 * Copyright (C) 2006 Google, Inc
7 * Notifications support
8 * Copyright (C) 2009 Nokia Corporation
9 * Author: Kirill A. Shutemov
11 * Copyright notices from the original cpuset code:
12 * --------------------------------------------------
13 * Copyright (C) 2003 BULL SA.
14 * Copyright (C) 2004-2006 Silicon Graphics, Inc.
16 * Portions derived from Patrick Mochel's sysfs code.
17 * sysfs is Copyright (c) 2001-3 Patrick Mochel
19 * 2003-10-10 Written by Simon Derr.
20 * 2003-10-22 Updates by Stephen Hemminger.
21 * 2004 May-July Rework by Paul Jackson.
22 * ---------------------------------------------------
24 * This file is subject to the terms and conditions of the GNU General Public
25 * License. See the file COPYING in the main directory of the Linux
26 * distribution for more details.
29 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
31 #include <linux/cgroup.h>
32 #include <linux/cred.h>
33 #include <linux/ctype.h>
34 #include <linux/errno.h>
35 #include <linux/init_task.h>
36 #include <linux/kernel.h>
37 #include <linux/list.h>
38 #include <linux/magic.h>
40 #include <linux/mutex.h>
41 #include <linux/mount.h>
42 #include <linux/pagemap.h>
43 #include <linux/proc_fs.h>
44 #include <linux/rcupdate.h>
45 #include <linux/sched.h>
46 #include <linux/slab.h>
47 #include <linux/spinlock.h>
48 #include <linux/rwsem.h>
49 #include <linux/percpu-rwsem.h>
50 #include <linux/string.h>
51 #include <linux/sort.h>
52 #include <linux/kmod.h>
53 #include <linux/delayacct.h>
54 #include <linux/cgroupstats.h>
55 #include <linux/hashtable.h>
56 #include <linux/pid_namespace.h>
57 #include <linux/idr.h>
58 #include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
59 #include <linux/kthread.h>
60 #include <linux/delay.h>
62 #include <linux/atomic.h>
65 * pidlists linger the following amount before being destroyed. The goal
66 * is avoiding frequent destruction in the middle of consecutive read calls
67 * Expiring in the middle is a performance problem not a correctness one.
68 * 1 sec should be enough.
70 #define CGROUP_PIDLIST_DESTROY_DELAY HZ
72 #define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
76 * cgroup_mutex is the master lock. Any modification to cgroup or its
77 * hierarchy must be performed while holding it.
79 * css_set_rwsem protects task->cgroups pointer, the list of css_set
80 * objects, and the chain of tasks off each css_set.
82 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
83 * cgroup.h can use them for lockdep annotations.
85 #ifdef CONFIG_PROVE_RCU
86 DEFINE_MUTEX(cgroup_mutex
);
87 DECLARE_RWSEM(css_set_rwsem
);
88 EXPORT_SYMBOL_GPL(cgroup_mutex
);
89 EXPORT_SYMBOL_GPL(css_set_rwsem
);
91 static DEFINE_MUTEX(cgroup_mutex
);
92 static DECLARE_RWSEM(css_set_rwsem
);
96 * Protects cgroup_idr and css_idr so that IDs can be released without
97 * grabbing cgroup_mutex.
99 static DEFINE_SPINLOCK(cgroup_idr_lock
);
102 * Protects cgroup_subsys->release_agent_path. Modifying it also requires
103 * cgroup_mutex. Reading requires either cgroup_mutex or this spinlock.
105 static DEFINE_SPINLOCK(release_agent_path_lock
);
107 struct percpu_rw_semaphore cgroup_threadgroup_rwsem
;
109 #define cgroup_assert_mutex_or_rcu_locked() \
110 rcu_lockdep_assert(rcu_read_lock_held() || \
111 lockdep_is_held(&cgroup_mutex), \
112 "cgroup_mutex or RCU read lock required");
115 * cgroup destruction makes heavy use of work items and there can be a lot
116 * of concurrent destructions. Use a separate workqueue so that cgroup
117 * destruction work items don't end up filling up max_active of system_wq
118 * which may lead to deadlock.
120 static struct workqueue_struct
*cgroup_destroy_wq
;
123 * pidlist destructions need to be flushed on cgroup destruction. Use a
124 * separate workqueue as flush domain.
126 static struct workqueue_struct
*cgroup_pidlist_destroy_wq
;
128 /* generate an array of cgroup subsystem pointers */
129 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
130 static struct cgroup_subsys
*cgroup_subsys
[] = {
131 #include <linux/cgroup_subsys.h>
135 /* array of cgroup subsystem names */
136 #define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
137 static const char *cgroup_subsys_name
[] = {
138 #include <linux/cgroup_subsys.h>
143 * The default hierarchy, reserved for the subsystems that are otherwise
144 * unattached - it never has more than a single cgroup, and all tasks are
145 * part of that cgroup.
147 struct cgroup_root cgrp_dfl_root
;
150 * The default hierarchy always exists but is hidden until mounted for the
151 * first time. This is for backward compatibility.
153 static bool cgrp_dfl_root_visible
;
156 * Set by the boot param of the same name and makes subsystems with NULL
157 * ->dfl_files to use ->legacy_files on the default hierarchy.
159 static bool cgroup_legacy_files_on_dfl
;
161 /* some controllers are not supported in the default hierarchy */
162 static unsigned long cgrp_dfl_root_inhibit_ss_mask
;
164 /* The list of hierarchy roots */
166 static LIST_HEAD(cgroup_roots
);
167 static int cgroup_root_count
;
169 /* hierarchy ID allocation and mapping, protected by cgroup_mutex */
170 static DEFINE_IDR(cgroup_hierarchy_idr
);
173 * Assign a monotonically increasing serial number to csses. It guarantees
174 * cgroups with bigger numbers are newer than those with smaller numbers.
175 * Also, as csses are always appended to the parent's ->children list, it
176 * guarantees that sibling csses are always sorted in the ascending serial
177 * number order on the list. Protected by cgroup_mutex.
179 static u64 css_serial_nr_next
= 1;
182 * These bitmask flags indicate whether tasks in the fork and exit paths have
183 * fork/exit handlers to call. This avoids us having to do extra work in the
184 * fork/exit path to check which subsystems have fork/exit callbacks.
186 static unsigned long have_fork_callback __read_mostly
;
187 static unsigned long have_exit_callback __read_mostly
;
189 static struct cftype cgroup_dfl_base_files
[];
190 static struct cftype cgroup_legacy_base_files
[];
192 static int rebind_subsystems(struct cgroup_root
*dst_root
,
193 unsigned long ss_mask
);
194 static int cgroup_destroy_locked(struct cgroup
*cgrp
);
195 static int create_css(struct cgroup
*cgrp
, struct cgroup_subsys
*ss
,
197 static void css_release(struct percpu_ref
*ref
);
198 static void kill_css(struct cgroup_subsys_state
*css
);
199 static int cgroup_addrm_files(struct cgroup
*cgrp
, struct cftype cfts
[],
202 /* IDR wrappers which synchronize using cgroup_idr_lock */
203 static int cgroup_idr_alloc(struct idr
*idr
, void *ptr
, int start
, int end
,
208 idr_preload(gfp_mask
);
209 spin_lock_bh(&cgroup_idr_lock
);
210 ret
= idr_alloc(idr
, ptr
, start
, end
, gfp_mask
);
211 spin_unlock_bh(&cgroup_idr_lock
);
216 static void *cgroup_idr_replace(struct idr
*idr
, void *ptr
, int id
)
220 spin_lock_bh(&cgroup_idr_lock
);
221 ret
= idr_replace(idr
, ptr
, id
);
222 spin_unlock_bh(&cgroup_idr_lock
);
226 static void cgroup_idr_remove(struct idr
*idr
, int id
)
228 spin_lock_bh(&cgroup_idr_lock
);
230 spin_unlock_bh(&cgroup_idr_lock
);
233 static struct cgroup
*cgroup_parent(struct cgroup
*cgrp
)
235 struct cgroup_subsys_state
*parent_css
= cgrp
->self
.parent
;
238 return container_of(parent_css
, struct cgroup
, self
);
243 * cgroup_css - obtain a cgroup's css for the specified subsystem
244 * @cgrp: the cgroup of interest
245 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
247 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
248 * function must be called either under cgroup_mutex or rcu_read_lock() and
249 * the caller is responsible for pinning the returned css if it wants to
250 * keep accessing it outside the said locks. This function may return
251 * %NULL if @cgrp doesn't have @subsys_id enabled.
253 static struct cgroup_subsys_state
*cgroup_css(struct cgroup
*cgrp
,
254 struct cgroup_subsys
*ss
)
257 return rcu_dereference_check(cgrp
->subsys
[ss
->id
],
258 lockdep_is_held(&cgroup_mutex
));
264 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
265 * @cgrp: the cgroup of interest
266 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
268 * Similar to cgroup_css() but returns the effective css, which is defined
269 * as the matching css of the nearest ancestor including self which has @ss
270 * enabled. If @ss is associated with the hierarchy @cgrp is on, this
271 * function is guaranteed to return non-NULL css.
273 static struct cgroup_subsys_state
*cgroup_e_css(struct cgroup
*cgrp
,
274 struct cgroup_subsys
*ss
)
276 lockdep_assert_held(&cgroup_mutex
);
281 if (!(cgrp
->root
->subsys_mask
& (1 << ss
->id
)))
285 * This function is used while updating css associations and thus
286 * can't test the csses directly. Use ->child_subsys_mask.
288 while (cgroup_parent(cgrp
) &&
289 !(cgroup_parent(cgrp
)->child_subsys_mask
& (1 << ss
->id
)))
290 cgrp
= cgroup_parent(cgrp
);
292 return cgroup_css(cgrp
, ss
);
296 * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
297 * @cgrp: the cgroup of interest
298 * @ss: the subsystem of interest
300 * Find and get the effective css of @cgrp for @ss. The effective css is
301 * defined as the matching css of the nearest ancestor including self which
302 * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on,
303 * the root css is returned, so this function always returns a valid css.
304 * The returned css must be put using css_put().
306 struct cgroup_subsys_state
*cgroup_get_e_css(struct cgroup
*cgrp
,
307 struct cgroup_subsys
*ss
)
309 struct cgroup_subsys_state
*css
;
314 css
= cgroup_css(cgrp
, ss
);
316 if (css
&& css_tryget_online(css
))
318 cgrp
= cgroup_parent(cgrp
);
321 css
= init_css_set
.subsys
[ss
->id
];
328 /* convenient tests for these bits */
329 static inline bool cgroup_is_dead(const struct cgroup
*cgrp
)
331 return !(cgrp
->self
.flags
& CSS_ONLINE
);
334 struct cgroup_subsys_state
*of_css(struct kernfs_open_file
*of
)
336 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
337 struct cftype
*cft
= of_cft(of
);
340 * This is open and unprotected implementation of cgroup_css().
341 * seq_css() is only called from a kernfs file operation which has
342 * an active reference on the file. Because all the subsystem
343 * files are drained before a css is disassociated with a cgroup,
344 * the matching css from the cgroup's subsys table is guaranteed to
345 * be and stay valid until the enclosing operation is complete.
348 return rcu_dereference_raw(cgrp
->subsys
[cft
->ss
->id
]);
352 EXPORT_SYMBOL_GPL(of_css
);
355 * cgroup_is_descendant - test ancestry
356 * @cgrp: the cgroup to be tested
357 * @ancestor: possible ancestor of @cgrp
359 * Test whether @cgrp is a descendant of @ancestor. It also returns %true
360 * if @cgrp == @ancestor. This function is safe to call as long as @cgrp
361 * and @ancestor are accessible.
363 bool cgroup_is_descendant(struct cgroup
*cgrp
, struct cgroup
*ancestor
)
366 if (cgrp
== ancestor
)
368 cgrp
= cgroup_parent(cgrp
);
373 static int notify_on_release(const struct cgroup
*cgrp
)
375 return test_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
379 * for_each_css - iterate all css's of a cgroup
380 * @css: the iteration cursor
381 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
382 * @cgrp: the target cgroup to iterate css's of
384 * Should be called under cgroup_[tree_]mutex.
386 #define for_each_css(css, ssid, cgrp) \
387 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
388 if (!((css) = rcu_dereference_check( \
389 (cgrp)->subsys[(ssid)], \
390 lockdep_is_held(&cgroup_mutex)))) { } \
394 * for_each_e_css - iterate all effective css's of a cgroup
395 * @css: the iteration cursor
396 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
397 * @cgrp: the target cgroup to iterate css's of
399 * Should be called under cgroup_[tree_]mutex.
401 #define for_each_e_css(css, ssid, cgrp) \
402 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
403 if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
408 * for_each_subsys - iterate all enabled cgroup subsystems
409 * @ss: the iteration cursor
410 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
412 #define for_each_subsys(ss, ssid) \
413 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
414 (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
417 * for_each_subsys_which - filter for_each_subsys with a bitmask
418 * @ss: the iteration cursor
419 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
420 * @ss_maskp: a pointer to the bitmask
422 * The block will only run for cases where the ssid-th bit (1 << ssid) of
425 #define for_each_subsys_which(ss, ssid, ss_maskp) \
426 if (!CGROUP_SUBSYS_COUNT) /* to avoid spurious gcc warning */ \
429 for_each_set_bit(ssid, ss_maskp, CGROUP_SUBSYS_COUNT) \
430 if (((ss) = cgroup_subsys[ssid]) && false) \
434 /* iterate across the hierarchies */
435 #define for_each_root(root) \
436 list_for_each_entry((root), &cgroup_roots, root_list)
438 /* iterate over child cgrps, lock should be held throughout iteration */
439 #define cgroup_for_each_live_child(child, cgrp) \
440 list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
441 if (({ lockdep_assert_held(&cgroup_mutex); \
442 cgroup_is_dead(child); })) \
446 static void cgroup_release_agent(struct work_struct
*work
);
447 static void check_for_release(struct cgroup
*cgrp
);
450 * A cgroup can be associated with multiple css_sets as different tasks may
451 * belong to different cgroups on different hierarchies. In the other
452 * direction, a css_set is naturally associated with multiple cgroups.
453 * This M:N relationship is represented by the following link structure
454 * which exists for each association and allows traversing the associations
457 struct cgrp_cset_link
{
458 /* the cgroup and css_set this link associates */
460 struct css_set
*cset
;
462 /* list of cgrp_cset_links anchored at cgrp->cset_links */
463 struct list_head cset_link
;
465 /* list of cgrp_cset_links anchored at css_set->cgrp_links */
466 struct list_head cgrp_link
;
470 * The default css_set - used by init and its children prior to any
471 * hierarchies being mounted. It contains a pointer to the root state
472 * for each subsystem. Also used to anchor the list of css_sets. Not
473 * reference-counted, to improve performance when child cgroups
474 * haven't been created.
476 struct css_set init_css_set
= {
477 .refcount
= ATOMIC_INIT(1),
478 .cgrp_links
= LIST_HEAD_INIT(init_css_set
.cgrp_links
),
479 .tasks
= LIST_HEAD_INIT(init_css_set
.tasks
),
480 .mg_tasks
= LIST_HEAD_INIT(init_css_set
.mg_tasks
),
481 .mg_preload_node
= LIST_HEAD_INIT(init_css_set
.mg_preload_node
),
482 .mg_node
= LIST_HEAD_INIT(init_css_set
.mg_node
),
485 static int css_set_count
= 1; /* 1 for init_css_set */
488 * cgroup_update_populated - updated populated count of a cgroup
489 * @cgrp: the target cgroup
490 * @populated: inc or dec populated count
492 * @cgrp is either getting the first task (css_set) or losing the last.
493 * Update @cgrp->populated_cnt accordingly. The count is propagated
494 * towards root so that a given cgroup's populated_cnt is zero iff the
495 * cgroup and all its descendants are empty.
497 * @cgrp's interface file "cgroup.populated" is zero if
498 * @cgrp->populated_cnt is zero and 1 otherwise. When @cgrp->populated_cnt
499 * changes from or to zero, userland is notified that the content of the
500 * interface file has changed. This can be used to detect when @cgrp and
501 * its descendants become populated or empty.
503 static void cgroup_update_populated(struct cgroup
*cgrp
, bool populated
)
505 lockdep_assert_held(&css_set_rwsem
);
511 trigger
= !cgrp
->populated_cnt
++;
513 trigger
= !--cgrp
->populated_cnt
;
518 if (cgrp
->populated_kn
)
519 kernfs_notify(cgrp
->populated_kn
);
520 cgrp
= cgroup_parent(cgrp
);
525 * hash table for cgroup groups. This improves the performance to find
526 * an existing css_set. This hash doesn't (currently) take into
527 * account cgroups in empty hierarchies.
529 #define CSS_SET_HASH_BITS 7
530 static DEFINE_HASHTABLE(css_set_table
, CSS_SET_HASH_BITS
);
532 static unsigned long css_set_hash(struct cgroup_subsys_state
*css
[])
534 unsigned long key
= 0UL;
535 struct cgroup_subsys
*ss
;
538 for_each_subsys(ss
, i
)
539 key
+= (unsigned long)css
[i
];
540 key
= (key
>> 16) ^ key
;
545 static void put_css_set_locked(struct css_set
*cset
)
547 struct cgrp_cset_link
*link
, *tmp_link
;
548 struct cgroup_subsys
*ss
;
551 lockdep_assert_held(&css_set_rwsem
);
553 if (!atomic_dec_and_test(&cset
->refcount
))
556 /* This css_set is dead. unlink it and release cgroup refcounts */
557 for_each_subsys(ss
, ssid
)
558 list_del(&cset
->e_cset_node
[ssid
]);
559 hash_del(&cset
->hlist
);
562 list_for_each_entry_safe(link
, tmp_link
, &cset
->cgrp_links
, cgrp_link
) {
563 struct cgroup
*cgrp
= link
->cgrp
;
565 list_del(&link
->cset_link
);
566 list_del(&link
->cgrp_link
);
568 /* @cgrp can't go away while we're holding css_set_rwsem */
569 if (list_empty(&cgrp
->cset_links
)) {
570 cgroup_update_populated(cgrp
, false);
571 check_for_release(cgrp
);
577 kfree_rcu(cset
, rcu_head
);
580 static void put_css_set(struct css_set
*cset
)
583 * Ensure that the refcount doesn't hit zero while any readers
584 * can see it. Similar to atomic_dec_and_lock(), but for an
587 if (atomic_add_unless(&cset
->refcount
, -1, 1))
590 down_write(&css_set_rwsem
);
591 put_css_set_locked(cset
);
592 up_write(&css_set_rwsem
);
596 * refcounted get/put for css_set objects
598 static inline void get_css_set(struct css_set
*cset
)
600 atomic_inc(&cset
->refcount
);
604 * compare_css_sets - helper function for find_existing_css_set().
605 * @cset: candidate css_set being tested
606 * @old_cset: existing css_set for a task
607 * @new_cgrp: cgroup that's being entered by the task
608 * @template: desired set of css pointers in css_set (pre-calculated)
610 * Returns true if "cset" matches "old_cset" except for the hierarchy
611 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
613 static bool compare_css_sets(struct css_set
*cset
,
614 struct css_set
*old_cset
,
615 struct cgroup
*new_cgrp
,
616 struct cgroup_subsys_state
*template[])
618 struct list_head
*l1
, *l2
;
621 * On the default hierarchy, there can be csets which are
622 * associated with the same set of cgroups but different csses.
623 * Let's first ensure that csses match.
625 if (memcmp(template, cset
->subsys
, sizeof(cset
->subsys
)))
629 * Compare cgroup pointers in order to distinguish between
630 * different cgroups in hierarchies. As different cgroups may
631 * share the same effective css, this comparison is always
634 l1
= &cset
->cgrp_links
;
635 l2
= &old_cset
->cgrp_links
;
637 struct cgrp_cset_link
*link1
, *link2
;
638 struct cgroup
*cgrp1
, *cgrp2
;
642 /* See if we reached the end - both lists are equal length. */
643 if (l1
== &cset
->cgrp_links
) {
644 BUG_ON(l2
!= &old_cset
->cgrp_links
);
647 BUG_ON(l2
== &old_cset
->cgrp_links
);
649 /* Locate the cgroups associated with these links. */
650 link1
= list_entry(l1
, struct cgrp_cset_link
, cgrp_link
);
651 link2
= list_entry(l2
, struct cgrp_cset_link
, cgrp_link
);
654 /* Hierarchies should be linked in the same order. */
655 BUG_ON(cgrp1
->root
!= cgrp2
->root
);
658 * If this hierarchy is the hierarchy of the cgroup
659 * that's changing, then we need to check that this
660 * css_set points to the new cgroup; if it's any other
661 * hierarchy, then this css_set should point to the
662 * same cgroup as the old css_set.
664 if (cgrp1
->root
== new_cgrp
->root
) {
665 if (cgrp1
!= new_cgrp
)
676 * find_existing_css_set - init css array and find the matching css_set
677 * @old_cset: the css_set that we're using before the cgroup transition
678 * @cgrp: the cgroup that we're moving into
679 * @template: out param for the new set of csses, should be clear on entry
681 static struct css_set
*find_existing_css_set(struct css_set
*old_cset
,
683 struct cgroup_subsys_state
*template[])
685 struct cgroup_root
*root
= cgrp
->root
;
686 struct cgroup_subsys
*ss
;
687 struct css_set
*cset
;
692 * Build the set of subsystem state objects that we want to see in the
693 * new css_set. while subsystems can change globally, the entries here
694 * won't change, so no need for locking.
696 for_each_subsys(ss
, i
) {
697 if (root
->subsys_mask
& (1UL << i
)) {
699 * @ss is in this hierarchy, so we want the
700 * effective css from @cgrp.
702 template[i
] = cgroup_e_css(cgrp
, ss
);
705 * @ss is not in this hierarchy, so we don't want
708 template[i
] = old_cset
->subsys
[i
];
712 key
= css_set_hash(template);
713 hash_for_each_possible(css_set_table
, cset
, hlist
, key
) {
714 if (!compare_css_sets(cset
, old_cset
, cgrp
, template))
717 /* This css_set matches what we need */
721 /* No existing cgroup group matched */
725 static void free_cgrp_cset_links(struct list_head
*links_to_free
)
727 struct cgrp_cset_link
*link
, *tmp_link
;
729 list_for_each_entry_safe(link
, tmp_link
, links_to_free
, cset_link
) {
730 list_del(&link
->cset_link
);
736 * allocate_cgrp_cset_links - allocate cgrp_cset_links
737 * @count: the number of links to allocate
738 * @tmp_links: list_head the allocated links are put on
740 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
741 * through ->cset_link. Returns 0 on success or -errno.
743 static int allocate_cgrp_cset_links(int count
, struct list_head
*tmp_links
)
745 struct cgrp_cset_link
*link
;
748 INIT_LIST_HEAD(tmp_links
);
750 for (i
= 0; i
< count
; i
++) {
751 link
= kzalloc(sizeof(*link
), GFP_KERNEL
);
753 free_cgrp_cset_links(tmp_links
);
756 list_add(&link
->cset_link
, tmp_links
);
762 * link_css_set - a helper function to link a css_set to a cgroup
763 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
764 * @cset: the css_set to be linked
765 * @cgrp: the destination cgroup
767 static void link_css_set(struct list_head
*tmp_links
, struct css_set
*cset
,
770 struct cgrp_cset_link
*link
;
772 BUG_ON(list_empty(tmp_links
));
774 if (cgroup_on_dfl(cgrp
))
775 cset
->dfl_cgrp
= cgrp
;
777 link
= list_first_entry(tmp_links
, struct cgrp_cset_link
, cset_link
);
781 if (list_empty(&cgrp
->cset_links
))
782 cgroup_update_populated(cgrp
, true);
783 list_move(&link
->cset_link
, &cgrp
->cset_links
);
786 * Always add links to the tail of the list so that the list
787 * is sorted by order of hierarchy creation
789 list_add_tail(&link
->cgrp_link
, &cset
->cgrp_links
);
793 * find_css_set - return a new css_set with one cgroup updated
794 * @old_cset: the baseline css_set
795 * @cgrp: the cgroup to be updated
797 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
798 * substituted into the appropriate hierarchy.
800 static struct css_set
*find_css_set(struct css_set
*old_cset
,
803 struct cgroup_subsys_state
*template[CGROUP_SUBSYS_COUNT
] = { };
804 struct css_set
*cset
;
805 struct list_head tmp_links
;
806 struct cgrp_cset_link
*link
;
807 struct cgroup_subsys
*ss
;
811 lockdep_assert_held(&cgroup_mutex
);
813 /* First see if we already have a cgroup group that matches
815 down_read(&css_set_rwsem
);
816 cset
= find_existing_css_set(old_cset
, cgrp
, template);
819 up_read(&css_set_rwsem
);
824 cset
= kzalloc(sizeof(*cset
), GFP_KERNEL
);
828 /* Allocate all the cgrp_cset_link objects that we'll need */
829 if (allocate_cgrp_cset_links(cgroup_root_count
, &tmp_links
) < 0) {
834 atomic_set(&cset
->refcount
, 1);
835 INIT_LIST_HEAD(&cset
->cgrp_links
);
836 INIT_LIST_HEAD(&cset
->tasks
);
837 INIT_LIST_HEAD(&cset
->mg_tasks
);
838 INIT_LIST_HEAD(&cset
->mg_preload_node
);
839 INIT_LIST_HEAD(&cset
->mg_node
);
840 INIT_HLIST_NODE(&cset
->hlist
);
842 /* Copy the set of subsystem state objects generated in
843 * find_existing_css_set() */
844 memcpy(cset
->subsys
, template, sizeof(cset
->subsys
));
846 down_write(&css_set_rwsem
);
847 /* Add reference counts and links from the new css_set. */
848 list_for_each_entry(link
, &old_cset
->cgrp_links
, cgrp_link
) {
849 struct cgroup
*c
= link
->cgrp
;
851 if (c
->root
== cgrp
->root
)
853 link_css_set(&tmp_links
, cset
, c
);
856 BUG_ON(!list_empty(&tmp_links
));
860 /* Add @cset to the hash table */
861 key
= css_set_hash(cset
->subsys
);
862 hash_add(css_set_table
, &cset
->hlist
, key
);
864 for_each_subsys(ss
, ssid
)
865 list_add_tail(&cset
->e_cset_node
[ssid
],
866 &cset
->subsys
[ssid
]->cgroup
->e_csets
[ssid
]);
868 up_write(&css_set_rwsem
);
873 static struct cgroup_root
*cgroup_root_from_kf(struct kernfs_root
*kf_root
)
875 struct cgroup
*root_cgrp
= kf_root
->kn
->priv
;
877 return root_cgrp
->root
;
880 static int cgroup_init_root_id(struct cgroup_root
*root
)
884 lockdep_assert_held(&cgroup_mutex
);
886 id
= idr_alloc_cyclic(&cgroup_hierarchy_idr
, root
, 0, 0, GFP_KERNEL
);
890 root
->hierarchy_id
= id
;
894 static void cgroup_exit_root_id(struct cgroup_root
*root
)
896 lockdep_assert_held(&cgroup_mutex
);
898 if (root
->hierarchy_id
) {
899 idr_remove(&cgroup_hierarchy_idr
, root
->hierarchy_id
);
900 root
->hierarchy_id
= 0;
904 static void cgroup_free_root(struct cgroup_root
*root
)
907 /* hierarchy ID should already have been released */
908 WARN_ON_ONCE(root
->hierarchy_id
);
910 idr_destroy(&root
->cgroup_idr
);
915 static void cgroup_destroy_root(struct cgroup_root
*root
)
917 struct cgroup
*cgrp
= &root
->cgrp
;
918 struct cgrp_cset_link
*link
, *tmp_link
;
920 mutex_lock(&cgroup_mutex
);
922 BUG_ON(atomic_read(&root
->nr_cgrps
));
923 BUG_ON(!list_empty(&cgrp
->self
.children
));
925 /* Rebind all subsystems back to the default hierarchy */
926 rebind_subsystems(&cgrp_dfl_root
, root
->subsys_mask
);
929 * Release all the links from cset_links to this hierarchy's
932 down_write(&css_set_rwsem
);
934 list_for_each_entry_safe(link
, tmp_link
, &cgrp
->cset_links
, cset_link
) {
935 list_del(&link
->cset_link
);
936 list_del(&link
->cgrp_link
);
939 up_write(&css_set_rwsem
);
941 if (!list_empty(&root
->root_list
)) {
942 list_del(&root
->root_list
);
946 cgroup_exit_root_id(root
);
948 mutex_unlock(&cgroup_mutex
);
950 kernfs_destroy_root(root
->kf_root
);
951 cgroup_free_root(root
);
954 /* look up cgroup associated with given css_set on the specified hierarchy */
955 static struct cgroup
*cset_cgroup_from_root(struct css_set
*cset
,
956 struct cgroup_root
*root
)
958 struct cgroup
*res
= NULL
;
960 lockdep_assert_held(&cgroup_mutex
);
961 lockdep_assert_held(&css_set_rwsem
);
963 if (cset
== &init_css_set
) {
966 struct cgrp_cset_link
*link
;
968 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
969 struct cgroup
*c
= link
->cgrp
;
971 if (c
->root
== root
) {
983 * Return the cgroup for "task" from the given hierarchy. Must be
984 * called with cgroup_mutex and css_set_rwsem held.
986 static struct cgroup
*task_cgroup_from_root(struct task_struct
*task
,
987 struct cgroup_root
*root
)
990 * No need to lock the task - since we hold cgroup_mutex the
991 * task can't change groups, so the only thing that can happen
992 * is that it exits and its css is set back to init_css_set.
994 return cset_cgroup_from_root(task_css_set(task
), root
);
998 * A task must hold cgroup_mutex to modify cgroups.
1000 * Any task can increment and decrement the count field without lock.
1001 * So in general, code holding cgroup_mutex can't rely on the count
1002 * field not changing. However, if the count goes to zero, then only
1003 * cgroup_attach_task() can increment it again. Because a count of zero
1004 * means that no tasks are currently attached, therefore there is no
1005 * way a task attached to that cgroup can fork (the other way to
1006 * increment the count). So code holding cgroup_mutex can safely
1007 * assume that if the count is zero, it will stay zero. Similarly, if
1008 * a task holds cgroup_mutex on a cgroup with zero count, it
1009 * knows that the cgroup won't be removed, as cgroup_rmdir()
1012 * A cgroup can only be deleted if both its 'count' of using tasks
1013 * is zero, and its list of 'children' cgroups is empty. Since all
1014 * tasks in the system use _some_ cgroup, and since there is always at
1015 * least one task in the system (init, pid == 1), therefore, root cgroup
1016 * always has either children cgroups and/or using tasks. So we don't
1017 * need a special hack to ensure that root cgroup cannot be deleted.
1019 * P.S. One more locking exception. RCU is used to guard the
1020 * update of a tasks cgroup pointer by cgroup_attach_task()
1023 static int cgroup_populate_dir(struct cgroup
*cgrp
, unsigned long subsys_mask
);
1024 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
;
1025 static const struct file_operations proc_cgroupstats_operations
;
1027 static char *cgroup_file_name(struct cgroup
*cgrp
, const struct cftype
*cft
,
1030 if (cft
->ss
&& !(cft
->flags
& CFTYPE_NO_PREFIX
) &&
1031 !(cgrp
->root
->flags
& CGRP_ROOT_NOPREFIX
))
1032 snprintf(buf
, CGROUP_FILE_NAME_MAX
, "%s.%s",
1033 cft
->ss
->name
, cft
->name
);
1035 strncpy(buf
, cft
->name
, CGROUP_FILE_NAME_MAX
);
1040 * cgroup_file_mode - deduce file mode of a control file
1041 * @cft: the control file in question
1043 * returns cft->mode if ->mode is not 0
1044 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
1045 * returns S_IRUGO if it has only a read handler
1046 * returns S_IWUSR if it has only a write hander
1048 static umode_t
cgroup_file_mode(const struct cftype
*cft
)
1055 if (cft
->read_u64
|| cft
->read_s64
|| cft
->seq_show
)
1058 if (cft
->write_u64
|| cft
->write_s64
|| cft
->write
)
1064 static void cgroup_get(struct cgroup
*cgrp
)
1066 WARN_ON_ONCE(cgroup_is_dead(cgrp
));
1067 css_get(&cgrp
->self
);
1070 static bool cgroup_tryget(struct cgroup
*cgrp
)
1072 return css_tryget(&cgrp
->self
);
1075 static void cgroup_put(struct cgroup
*cgrp
)
1077 css_put(&cgrp
->self
);
1081 * cgroup_calc_child_subsys_mask - calculate child_subsys_mask
1082 * @cgrp: the target cgroup
1083 * @subtree_control: the new subtree_control mask to consider
1085 * On the default hierarchy, a subsystem may request other subsystems to be
1086 * enabled together through its ->depends_on mask. In such cases, more
1087 * subsystems than specified in "cgroup.subtree_control" may be enabled.
1089 * This function calculates which subsystems need to be enabled if
1090 * @subtree_control is to be applied to @cgrp. The returned mask is always
1091 * a superset of @subtree_control and follows the usual hierarchy rules.
1093 static unsigned long cgroup_calc_child_subsys_mask(struct cgroup
*cgrp
,
1094 unsigned long subtree_control
)
1096 struct cgroup
*parent
= cgroup_parent(cgrp
);
1097 unsigned long cur_ss_mask
= subtree_control
;
1098 struct cgroup_subsys
*ss
;
1101 lockdep_assert_held(&cgroup_mutex
);
1103 if (!cgroup_on_dfl(cgrp
))
1107 unsigned long new_ss_mask
= cur_ss_mask
;
1109 for_each_subsys_which(ss
, ssid
, &cur_ss_mask
)
1110 new_ss_mask
|= ss
->depends_on
;
1113 * Mask out subsystems which aren't available. This can
1114 * happen only if some depended-upon subsystems were bound
1115 * to non-default hierarchies.
1118 new_ss_mask
&= parent
->child_subsys_mask
;
1120 new_ss_mask
&= cgrp
->root
->subsys_mask
;
1122 if (new_ss_mask
== cur_ss_mask
)
1124 cur_ss_mask
= new_ss_mask
;
1131 * cgroup_refresh_child_subsys_mask - update child_subsys_mask
1132 * @cgrp: the target cgroup
1134 * Update @cgrp->child_subsys_mask according to the current
1135 * @cgrp->subtree_control using cgroup_calc_child_subsys_mask().
1137 static void cgroup_refresh_child_subsys_mask(struct cgroup
*cgrp
)
1139 cgrp
->child_subsys_mask
=
1140 cgroup_calc_child_subsys_mask(cgrp
, cgrp
->subtree_control
);
1144 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1145 * @kn: the kernfs_node being serviced
1147 * This helper undoes cgroup_kn_lock_live() and should be invoked before
1148 * the method finishes if locking succeeded. Note that once this function
1149 * returns the cgroup returned by cgroup_kn_lock_live() may become
1150 * inaccessible any time. If the caller intends to continue to access the
1151 * cgroup, it should pin it before invoking this function.
1153 static void cgroup_kn_unlock(struct kernfs_node
*kn
)
1155 struct cgroup
*cgrp
;
1157 if (kernfs_type(kn
) == KERNFS_DIR
)
1160 cgrp
= kn
->parent
->priv
;
1162 mutex_unlock(&cgroup_mutex
);
1164 kernfs_unbreak_active_protection(kn
);
1169 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1170 * @kn: the kernfs_node being serviced
1172 * This helper is to be used by a cgroup kernfs method currently servicing
1173 * @kn. It breaks the active protection, performs cgroup locking and
1174 * verifies that the associated cgroup is alive. Returns the cgroup if
1175 * alive; otherwise, %NULL. A successful return should be undone by a
1176 * matching cgroup_kn_unlock() invocation.
1178 * Any cgroup kernfs method implementation which requires locking the
1179 * associated cgroup should use this helper. It avoids nesting cgroup
1180 * locking under kernfs active protection and allows all kernfs operations
1181 * including self-removal.
1183 static struct cgroup
*cgroup_kn_lock_live(struct kernfs_node
*kn
)
1185 struct cgroup
*cgrp
;
1187 if (kernfs_type(kn
) == KERNFS_DIR
)
1190 cgrp
= kn
->parent
->priv
;
1193 * We're gonna grab cgroup_mutex which nests outside kernfs
1194 * active_ref. cgroup liveliness check alone provides enough
1195 * protection against removal. Ensure @cgrp stays accessible and
1196 * break the active_ref protection.
1198 if (!cgroup_tryget(cgrp
))
1200 kernfs_break_active_protection(kn
);
1202 mutex_lock(&cgroup_mutex
);
1204 if (!cgroup_is_dead(cgrp
))
1207 cgroup_kn_unlock(kn
);
1211 static void cgroup_rm_file(struct cgroup
*cgrp
, const struct cftype
*cft
)
1213 char name
[CGROUP_FILE_NAME_MAX
];
1215 lockdep_assert_held(&cgroup_mutex
);
1216 kernfs_remove_by_name(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
));
1220 * cgroup_clear_dir - remove subsys files in a cgroup directory
1221 * @cgrp: target cgroup
1222 * @subsys_mask: mask of the subsystem ids whose files should be removed
1224 static void cgroup_clear_dir(struct cgroup
*cgrp
, unsigned long subsys_mask
)
1226 struct cgroup_subsys
*ss
;
1229 for_each_subsys(ss
, i
) {
1230 struct cftype
*cfts
;
1232 if (!(subsys_mask
& (1 << i
)))
1234 list_for_each_entry(cfts
, &ss
->cfts
, node
)
1235 cgroup_addrm_files(cgrp
, cfts
, false);
1239 static int rebind_subsystems(struct cgroup_root
*dst_root
,
1240 unsigned long ss_mask
)
1242 struct cgroup_subsys
*ss
;
1243 unsigned long tmp_ss_mask
;
1246 lockdep_assert_held(&cgroup_mutex
);
1248 for_each_subsys_which(ss
, ssid
, &ss_mask
) {
1249 /* if @ss has non-root csses attached to it, can't move */
1250 if (css_next_child(NULL
, cgroup_css(&ss
->root
->cgrp
, ss
)))
1253 /* can't move between two non-dummy roots either */
1254 if (ss
->root
!= &cgrp_dfl_root
&& dst_root
!= &cgrp_dfl_root
)
1258 /* skip creating root files on dfl_root for inhibited subsystems */
1259 tmp_ss_mask
= ss_mask
;
1260 if (dst_root
== &cgrp_dfl_root
)
1261 tmp_ss_mask
&= ~cgrp_dfl_root_inhibit_ss_mask
;
1263 ret
= cgroup_populate_dir(&dst_root
->cgrp
, tmp_ss_mask
);
1265 if (dst_root
!= &cgrp_dfl_root
)
1269 * Rebinding back to the default root is not allowed to
1270 * fail. Using both default and non-default roots should
1271 * be rare. Moving subsystems back and forth even more so.
1272 * Just warn about it and continue.
1274 if (cgrp_dfl_root_visible
) {
1275 pr_warn("failed to create files (%d) while rebinding 0x%lx to default root\n",
1277 pr_warn("you may retry by moving them to a different hierarchy and unbinding\n");
1282 * Nothing can fail from this point on. Remove files for the
1283 * removed subsystems and rebind each subsystem.
1285 for_each_subsys_which(ss
, ssid
, &ss_mask
)
1286 cgroup_clear_dir(&ss
->root
->cgrp
, 1 << ssid
);
1288 for_each_subsys_which(ss
, ssid
, &ss_mask
) {
1289 struct cgroup_root
*src_root
;
1290 struct cgroup_subsys_state
*css
;
1291 struct css_set
*cset
;
1293 src_root
= ss
->root
;
1294 css
= cgroup_css(&src_root
->cgrp
, ss
);
1296 WARN_ON(!css
|| cgroup_css(&dst_root
->cgrp
, ss
));
1298 RCU_INIT_POINTER(src_root
->cgrp
.subsys
[ssid
], NULL
);
1299 rcu_assign_pointer(dst_root
->cgrp
.subsys
[ssid
], css
);
1300 ss
->root
= dst_root
;
1301 css
->cgroup
= &dst_root
->cgrp
;
1303 down_write(&css_set_rwsem
);
1304 hash_for_each(css_set_table
, i
, cset
, hlist
)
1305 list_move_tail(&cset
->e_cset_node
[ss
->id
],
1306 &dst_root
->cgrp
.e_csets
[ss
->id
]);
1307 up_write(&css_set_rwsem
);
1309 src_root
->subsys_mask
&= ~(1 << ssid
);
1310 src_root
->cgrp
.subtree_control
&= ~(1 << ssid
);
1311 cgroup_refresh_child_subsys_mask(&src_root
->cgrp
);
1313 /* default hierarchy doesn't enable controllers by default */
1314 dst_root
->subsys_mask
|= 1 << ssid
;
1315 if (dst_root
!= &cgrp_dfl_root
) {
1316 dst_root
->cgrp
.subtree_control
|= 1 << ssid
;
1317 cgroup_refresh_child_subsys_mask(&dst_root
->cgrp
);
1324 kernfs_activate(dst_root
->cgrp
.kn
);
1328 static int cgroup_show_options(struct seq_file
*seq
,
1329 struct kernfs_root
*kf_root
)
1331 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1332 struct cgroup_subsys
*ss
;
1335 for_each_subsys(ss
, ssid
)
1336 if (root
->subsys_mask
& (1 << ssid
))
1337 seq_printf(seq
, ",%s", ss
->name
);
1338 if (root
->flags
& CGRP_ROOT_NOPREFIX
)
1339 seq_puts(seq
, ",noprefix");
1340 if (root
->flags
& CGRP_ROOT_XATTR
)
1341 seq_puts(seq
, ",xattr");
1343 spin_lock(&release_agent_path_lock
);
1344 if (strlen(root
->release_agent_path
))
1345 seq_printf(seq
, ",release_agent=%s", root
->release_agent_path
);
1346 spin_unlock(&release_agent_path_lock
);
1348 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
))
1349 seq_puts(seq
, ",clone_children");
1350 if (strlen(root
->name
))
1351 seq_printf(seq
, ",name=%s", root
->name
);
1355 struct cgroup_sb_opts
{
1356 unsigned long subsys_mask
;
1358 char *release_agent
;
1359 bool cpuset_clone_children
;
1361 /* User explicitly requested empty subsystem */
1365 static int parse_cgroupfs_options(char *data
, struct cgroup_sb_opts
*opts
)
1367 char *token
, *o
= data
;
1368 bool all_ss
= false, one_ss
= false;
1369 unsigned long mask
= -1UL;
1370 struct cgroup_subsys
*ss
;
1374 #ifdef CONFIG_CPUSETS
1375 mask
= ~(1U << cpuset_cgrp_id
);
1378 memset(opts
, 0, sizeof(*opts
));
1380 while ((token
= strsep(&o
, ",")) != NULL
) {
1385 if (!strcmp(token
, "none")) {
1386 /* Explicitly have no subsystems */
1390 if (!strcmp(token
, "all")) {
1391 /* Mutually exclusive option 'all' + subsystem name */
1397 if (!strcmp(token
, "__DEVEL__sane_behavior")) {
1398 opts
->flags
|= CGRP_ROOT_SANE_BEHAVIOR
;
1401 if (!strcmp(token
, "noprefix")) {
1402 opts
->flags
|= CGRP_ROOT_NOPREFIX
;
1405 if (!strcmp(token
, "clone_children")) {
1406 opts
->cpuset_clone_children
= true;
1409 if (!strcmp(token
, "xattr")) {
1410 opts
->flags
|= CGRP_ROOT_XATTR
;
1413 if (!strncmp(token
, "release_agent=", 14)) {
1414 /* Specifying two release agents is forbidden */
1415 if (opts
->release_agent
)
1417 opts
->release_agent
=
1418 kstrndup(token
+ 14, PATH_MAX
- 1, GFP_KERNEL
);
1419 if (!opts
->release_agent
)
1423 if (!strncmp(token
, "name=", 5)) {
1424 const char *name
= token
+ 5;
1425 /* Can't specify an empty name */
1428 /* Must match [\w.-]+ */
1429 for (i
= 0; i
< strlen(name
); i
++) {
1433 if ((c
== '.') || (c
== '-') || (c
== '_'))
1437 /* Specifying two names is forbidden */
1440 opts
->name
= kstrndup(name
,
1441 MAX_CGROUP_ROOT_NAMELEN
- 1,
1449 for_each_subsys(ss
, i
) {
1450 if (strcmp(token
, ss
->name
))
1455 /* Mutually exclusive option 'all' + subsystem name */
1458 opts
->subsys_mask
|= (1 << i
);
1463 if (i
== CGROUP_SUBSYS_COUNT
)
1467 if (opts
->flags
& CGRP_ROOT_SANE_BEHAVIOR
) {
1468 pr_warn("sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
1470 pr_err("sane_behavior: no other mount options allowed\n");
1477 * If the 'all' option was specified select all the subsystems,
1478 * otherwise if 'none', 'name=' and a subsystem name options were
1479 * not specified, let's default to 'all'
1481 if (all_ss
|| (!one_ss
&& !opts
->none
&& !opts
->name
))
1482 for_each_subsys(ss
, i
)
1484 opts
->subsys_mask
|= (1 << i
);
1487 * We either have to specify by name or by subsystems. (So all
1488 * empty hierarchies must have a name).
1490 if (!opts
->subsys_mask
&& !opts
->name
)
1494 * Option noprefix was introduced just for backward compatibility
1495 * with the old cpuset, so we allow noprefix only if mounting just
1496 * the cpuset subsystem.
1498 if ((opts
->flags
& CGRP_ROOT_NOPREFIX
) && (opts
->subsys_mask
& mask
))
1501 /* Can't specify "none" and some subsystems */
1502 if (opts
->subsys_mask
&& opts
->none
)
1508 static int cgroup_remount(struct kernfs_root
*kf_root
, int *flags
, char *data
)
1511 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1512 struct cgroup_sb_opts opts
;
1513 unsigned long added_mask
, removed_mask
;
1515 if (root
== &cgrp_dfl_root
) {
1516 pr_err("remount is not allowed\n");
1520 mutex_lock(&cgroup_mutex
);
1522 /* See what subsystems are wanted */
1523 ret
= parse_cgroupfs_options(data
, &opts
);
1527 if (opts
.subsys_mask
!= root
->subsys_mask
|| opts
.release_agent
)
1528 pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
1529 task_tgid_nr(current
), current
->comm
);
1531 added_mask
= opts
.subsys_mask
& ~root
->subsys_mask
;
1532 removed_mask
= root
->subsys_mask
& ~opts
.subsys_mask
;
1534 /* Don't allow flags or name to change at remount */
1535 if ((opts
.flags
^ root
->flags
) ||
1536 (opts
.name
&& strcmp(opts
.name
, root
->name
))) {
1537 pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n",
1538 opts
.flags
, opts
.name
?: "", root
->flags
, root
->name
);
1543 /* remounting is not allowed for populated hierarchies */
1544 if (!list_empty(&root
->cgrp
.self
.children
)) {
1549 ret
= rebind_subsystems(root
, added_mask
);
1553 rebind_subsystems(&cgrp_dfl_root
, removed_mask
);
1555 if (opts
.release_agent
) {
1556 spin_lock(&release_agent_path_lock
);
1557 strcpy(root
->release_agent_path
, opts
.release_agent
);
1558 spin_unlock(&release_agent_path_lock
);
1561 kfree(opts
.release_agent
);
1563 mutex_unlock(&cgroup_mutex
);
1568 * To reduce the fork() overhead for systems that are not actually using
1569 * their cgroups capability, we don't maintain the lists running through
1570 * each css_set to its tasks until we see the list actually used - in other
1571 * words after the first mount.
1573 static bool use_task_css_set_links __read_mostly
;
1575 static void cgroup_enable_task_cg_lists(void)
1577 struct task_struct
*p
, *g
;
1579 down_write(&css_set_rwsem
);
1581 if (use_task_css_set_links
)
1584 use_task_css_set_links
= true;
1587 * We need tasklist_lock because RCU is not safe against
1588 * while_each_thread(). Besides, a forking task that has passed
1589 * cgroup_post_fork() without seeing use_task_css_set_links = 1
1590 * is not guaranteed to have its child immediately visible in the
1591 * tasklist if we walk through it with RCU.
1593 read_lock(&tasklist_lock
);
1594 do_each_thread(g
, p
) {
1595 WARN_ON_ONCE(!list_empty(&p
->cg_list
) ||
1596 task_css_set(p
) != &init_css_set
);
1599 * We should check if the process is exiting, otherwise
1600 * it will race with cgroup_exit() in that the list
1601 * entry won't be deleted though the process has exited.
1602 * Do it while holding siglock so that we don't end up
1603 * racing against cgroup_exit().
1605 spin_lock_irq(&p
->sighand
->siglock
);
1606 if (!(p
->flags
& PF_EXITING
)) {
1607 struct css_set
*cset
= task_css_set(p
);
1609 list_add(&p
->cg_list
, &cset
->tasks
);
1612 spin_unlock_irq(&p
->sighand
->siglock
);
1613 } while_each_thread(g
, p
);
1614 read_unlock(&tasklist_lock
);
1616 up_write(&css_set_rwsem
);
1619 static void init_cgroup_housekeeping(struct cgroup
*cgrp
)
1621 struct cgroup_subsys
*ss
;
1624 INIT_LIST_HEAD(&cgrp
->self
.sibling
);
1625 INIT_LIST_HEAD(&cgrp
->self
.children
);
1626 INIT_LIST_HEAD(&cgrp
->cset_links
);
1627 INIT_LIST_HEAD(&cgrp
->pidlists
);
1628 mutex_init(&cgrp
->pidlist_mutex
);
1629 cgrp
->self
.cgroup
= cgrp
;
1630 cgrp
->self
.flags
|= CSS_ONLINE
;
1632 for_each_subsys(ss
, ssid
)
1633 INIT_LIST_HEAD(&cgrp
->e_csets
[ssid
]);
1635 init_waitqueue_head(&cgrp
->offline_waitq
);
1636 INIT_WORK(&cgrp
->release_agent_work
, cgroup_release_agent
);
1639 static void init_cgroup_root(struct cgroup_root
*root
,
1640 struct cgroup_sb_opts
*opts
)
1642 struct cgroup
*cgrp
= &root
->cgrp
;
1644 INIT_LIST_HEAD(&root
->root_list
);
1645 atomic_set(&root
->nr_cgrps
, 1);
1647 init_cgroup_housekeeping(cgrp
);
1648 idr_init(&root
->cgroup_idr
);
1650 root
->flags
= opts
->flags
;
1651 if (opts
->release_agent
)
1652 strcpy(root
->release_agent_path
, opts
->release_agent
);
1654 strcpy(root
->name
, opts
->name
);
1655 if (opts
->cpuset_clone_children
)
1656 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
);
1659 static int cgroup_setup_root(struct cgroup_root
*root
, unsigned long ss_mask
)
1661 LIST_HEAD(tmp_links
);
1662 struct cgroup
*root_cgrp
= &root
->cgrp
;
1663 struct cftype
*base_files
;
1664 struct css_set
*cset
;
1667 lockdep_assert_held(&cgroup_mutex
);
1669 ret
= cgroup_idr_alloc(&root
->cgroup_idr
, root_cgrp
, 1, 2, GFP_NOWAIT
);
1672 root_cgrp
->id
= ret
;
1674 ret
= percpu_ref_init(&root_cgrp
->self
.refcnt
, css_release
, 0,
1680 * We're accessing css_set_count without locking css_set_rwsem here,
1681 * but that's OK - it can only be increased by someone holding
1682 * cgroup_lock, and that's us. The worst that can happen is that we
1683 * have some link structures left over
1685 ret
= allocate_cgrp_cset_links(css_set_count
, &tmp_links
);
1689 ret
= cgroup_init_root_id(root
);
1693 root
->kf_root
= kernfs_create_root(&cgroup_kf_syscall_ops
,
1694 KERNFS_ROOT_CREATE_DEACTIVATED
,
1696 if (IS_ERR(root
->kf_root
)) {
1697 ret
= PTR_ERR(root
->kf_root
);
1700 root_cgrp
->kn
= root
->kf_root
->kn
;
1702 if (root
== &cgrp_dfl_root
)
1703 base_files
= cgroup_dfl_base_files
;
1705 base_files
= cgroup_legacy_base_files
;
1707 ret
= cgroup_addrm_files(root_cgrp
, base_files
, true);
1711 ret
= rebind_subsystems(root
, ss_mask
);
1716 * There must be no failure case after here, since rebinding takes
1717 * care of subsystems' refcounts, which are explicitly dropped in
1718 * the failure exit path.
1720 list_add(&root
->root_list
, &cgroup_roots
);
1721 cgroup_root_count
++;
1724 * Link the root cgroup in this hierarchy into all the css_set
1727 down_write(&css_set_rwsem
);
1728 hash_for_each(css_set_table
, i
, cset
, hlist
)
1729 link_css_set(&tmp_links
, cset
, root_cgrp
);
1730 up_write(&css_set_rwsem
);
1732 BUG_ON(!list_empty(&root_cgrp
->self
.children
));
1733 BUG_ON(atomic_read(&root
->nr_cgrps
) != 1);
1735 kernfs_activate(root_cgrp
->kn
);
1740 kernfs_destroy_root(root
->kf_root
);
1741 root
->kf_root
= NULL
;
1743 cgroup_exit_root_id(root
);
1745 percpu_ref_exit(&root_cgrp
->self
.refcnt
);
1747 free_cgrp_cset_links(&tmp_links
);
1751 static struct dentry
*cgroup_mount(struct file_system_type
*fs_type
,
1752 int flags
, const char *unused_dev_name
,
1755 struct super_block
*pinned_sb
= NULL
;
1756 struct cgroup_subsys
*ss
;
1757 struct cgroup_root
*root
;
1758 struct cgroup_sb_opts opts
;
1759 struct dentry
*dentry
;
1765 * The first time anyone tries to mount a cgroup, enable the list
1766 * linking each css_set to its tasks and fix up all existing tasks.
1768 if (!use_task_css_set_links
)
1769 cgroup_enable_task_cg_lists();
1771 mutex_lock(&cgroup_mutex
);
1773 /* First find the desired set of subsystems */
1774 ret
= parse_cgroupfs_options(data
, &opts
);
1778 /* look for a matching existing root */
1779 if (opts
.flags
& CGRP_ROOT_SANE_BEHAVIOR
) {
1780 cgrp_dfl_root_visible
= true;
1781 root
= &cgrp_dfl_root
;
1782 cgroup_get(&root
->cgrp
);
1788 * Destruction of cgroup root is asynchronous, so subsystems may
1789 * still be dying after the previous unmount. Let's drain the
1790 * dying subsystems. We just need to ensure that the ones
1791 * unmounted previously finish dying and don't care about new ones
1792 * starting. Testing ref liveliness is good enough.
1794 for_each_subsys(ss
, i
) {
1795 if (!(opts
.subsys_mask
& (1 << i
)) ||
1796 ss
->root
== &cgrp_dfl_root
)
1799 if (!percpu_ref_tryget_live(&ss
->root
->cgrp
.self
.refcnt
)) {
1800 mutex_unlock(&cgroup_mutex
);
1802 ret
= restart_syscall();
1805 cgroup_put(&ss
->root
->cgrp
);
1808 for_each_root(root
) {
1809 bool name_match
= false;
1811 if (root
== &cgrp_dfl_root
)
1815 * If we asked for a name then it must match. Also, if
1816 * name matches but sybsys_mask doesn't, we should fail.
1817 * Remember whether name matched.
1820 if (strcmp(opts
.name
, root
->name
))
1826 * If we asked for subsystems (or explicitly for no
1827 * subsystems) then they must match.
1829 if ((opts
.subsys_mask
|| opts
.none
) &&
1830 (opts
.subsys_mask
!= root
->subsys_mask
)) {
1837 if (root
->flags
^ opts
.flags
)
1838 pr_warn("new mount options do not match the existing superblock, will be ignored\n");
1841 * We want to reuse @root whose lifetime is governed by its
1842 * ->cgrp. Let's check whether @root is alive and keep it
1843 * that way. As cgroup_kill_sb() can happen anytime, we
1844 * want to block it by pinning the sb so that @root doesn't
1845 * get killed before mount is complete.
1847 * With the sb pinned, tryget_live can reliably indicate
1848 * whether @root can be reused. If it's being killed,
1849 * drain it. We can use wait_queue for the wait but this
1850 * path is super cold. Let's just sleep a bit and retry.
1852 pinned_sb
= kernfs_pin_sb(root
->kf_root
, NULL
);
1853 if (IS_ERR(pinned_sb
) ||
1854 !percpu_ref_tryget_live(&root
->cgrp
.self
.refcnt
)) {
1855 mutex_unlock(&cgroup_mutex
);
1856 if (!IS_ERR_OR_NULL(pinned_sb
))
1857 deactivate_super(pinned_sb
);
1859 ret
= restart_syscall();
1868 * No such thing, create a new one. name= matching without subsys
1869 * specification is allowed for already existing hierarchies but we
1870 * can't create new one without subsys specification.
1872 if (!opts
.subsys_mask
&& !opts
.none
) {
1877 root
= kzalloc(sizeof(*root
), GFP_KERNEL
);
1883 init_cgroup_root(root
, &opts
);
1885 ret
= cgroup_setup_root(root
, opts
.subsys_mask
);
1887 cgroup_free_root(root
);
1890 mutex_unlock(&cgroup_mutex
);
1892 kfree(opts
.release_agent
);
1896 return ERR_PTR(ret
);
1898 dentry
= kernfs_mount(fs_type
, flags
, root
->kf_root
,
1899 CGROUP_SUPER_MAGIC
, &new_sb
);
1900 if (IS_ERR(dentry
) || !new_sb
)
1901 cgroup_put(&root
->cgrp
);
1904 * If @pinned_sb, we're reusing an existing root and holding an
1905 * extra ref on its sb. Mount is complete. Put the extra ref.
1909 deactivate_super(pinned_sb
);
1915 static void cgroup_kill_sb(struct super_block
*sb
)
1917 struct kernfs_root
*kf_root
= kernfs_root_from_sb(sb
);
1918 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1921 * If @root doesn't have any mounts or children, start killing it.
1922 * This prevents new mounts by disabling percpu_ref_tryget_live().
1923 * cgroup_mount() may wait for @root's release.
1925 * And don't kill the default root.
1927 if (!list_empty(&root
->cgrp
.self
.children
) ||
1928 root
== &cgrp_dfl_root
)
1929 cgroup_put(&root
->cgrp
);
1931 percpu_ref_kill(&root
->cgrp
.self
.refcnt
);
1936 static struct file_system_type cgroup_fs_type
= {
1938 .mount
= cgroup_mount
,
1939 .kill_sb
= cgroup_kill_sb
,
1942 static struct kobject
*cgroup_kobj
;
1945 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
1946 * @task: target task
1947 * @buf: the buffer to write the path into
1948 * @buflen: the length of the buffer
1950 * Determine @task's cgroup on the first (the one with the lowest non-zero
1951 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
1952 * function grabs cgroup_mutex and shouldn't be used inside locks used by
1953 * cgroup controller callbacks.
1955 * Return value is the same as kernfs_path().
1957 char *task_cgroup_path(struct task_struct
*task
, char *buf
, size_t buflen
)
1959 struct cgroup_root
*root
;
1960 struct cgroup
*cgrp
;
1961 int hierarchy_id
= 1;
1964 mutex_lock(&cgroup_mutex
);
1965 down_read(&css_set_rwsem
);
1967 root
= idr_get_next(&cgroup_hierarchy_idr
, &hierarchy_id
);
1970 cgrp
= task_cgroup_from_root(task
, root
);
1971 path
= cgroup_path(cgrp
, buf
, buflen
);
1973 /* if no hierarchy exists, everyone is in "/" */
1974 if (strlcpy(buf
, "/", buflen
) < buflen
)
1978 up_read(&css_set_rwsem
);
1979 mutex_unlock(&cgroup_mutex
);
1982 EXPORT_SYMBOL_GPL(task_cgroup_path
);
1984 /* used to track tasks and other necessary states during migration */
1985 struct cgroup_taskset
{
1986 /* the src and dst cset list running through cset->mg_node */
1987 struct list_head src_csets
;
1988 struct list_head dst_csets
;
1991 * Fields for cgroup_taskset_*() iteration.
1993 * Before migration is committed, the target migration tasks are on
1994 * ->mg_tasks of the csets on ->src_csets. After, on ->mg_tasks of
1995 * the csets on ->dst_csets. ->csets point to either ->src_csets
1996 * or ->dst_csets depending on whether migration is committed.
1998 * ->cur_csets and ->cur_task point to the current task position
2001 struct list_head
*csets
;
2002 struct css_set
*cur_cset
;
2003 struct task_struct
*cur_task
;
2007 * cgroup_taskset_first - reset taskset and return the first task
2008 * @tset: taskset of interest
2010 * @tset iteration is initialized and the first task is returned.
2012 struct task_struct
*cgroup_taskset_first(struct cgroup_taskset
*tset
)
2014 tset
->cur_cset
= list_first_entry(tset
->csets
, struct css_set
, mg_node
);
2015 tset
->cur_task
= NULL
;
2017 return cgroup_taskset_next(tset
);
2021 * cgroup_taskset_next - iterate to the next task in taskset
2022 * @tset: taskset of interest
2024 * Return the next task in @tset. Iteration must have been initialized
2025 * with cgroup_taskset_first().
2027 struct task_struct
*cgroup_taskset_next(struct cgroup_taskset
*tset
)
2029 struct css_set
*cset
= tset
->cur_cset
;
2030 struct task_struct
*task
= tset
->cur_task
;
2032 while (&cset
->mg_node
!= tset
->csets
) {
2034 task
= list_first_entry(&cset
->mg_tasks
,
2035 struct task_struct
, cg_list
);
2037 task
= list_next_entry(task
, cg_list
);
2039 if (&task
->cg_list
!= &cset
->mg_tasks
) {
2040 tset
->cur_cset
= cset
;
2041 tset
->cur_task
= task
;
2045 cset
= list_next_entry(cset
, mg_node
);
2053 * cgroup_task_migrate - move a task from one cgroup to another.
2054 * @old_cgrp: the cgroup @tsk is being migrated from
2055 * @tsk: the task being migrated
2056 * @new_cset: the new css_set @tsk is being attached to
2058 * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
2060 static void cgroup_task_migrate(struct cgroup
*old_cgrp
,
2061 struct task_struct
*tsk
,
2062 struct css_set
*new_cset
)
2064 struct css_set
*old_cset
;
2066 lockdep_assert_held(&cgroup_mutex
);
2067 lockdep_assert_held(&css_set_rwsem
);
2070 * We are synchronized through cgroup_threadgroup_rwsem against
2071 * PF_EXITING setting such that we can't race against cgroup_exit()
2072 * changing the css_set to init_css_set and dropping the old one.
2074 WARN_ON_ONCE(tsk
->flags
& PF_EXITING
);
2075 old_cset
= task_css_set(tsk
);
2077 get_css_set(new_cset
);
2078 rcu_assign_pointer(tsk
->cgroups
, new_cset
);
2081 * Use move_tail so that cgroup_taskset_first() still returns the
2082 * leader after migration. This works because cgroup_migrate()
2083 * ensures that the dst_cset of the leader is the first on the
2084 * tset's dst_csets list.
2086 list_move_tail(&tsk
->cg_list
, &new_cset
->mg_tasks
);
2089 * We just gained a reference on old_cset by taking it from the
2090 * task. As trading it for new_cset is protected by cgroup_mutex,
2091 * we're safe to drop it here; it will be freed under RCU.
2093 put_css_set_locked(old_cset
);
2097 * cgroup_migrate_finish - cleanup after attach
2098 * @preloaded_csets: list of preloaded css_sets
2100 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
2101 * those functions for details.
2103 static void cgroup_migrate_finish(struct list_head
*preloaded_csets
)
2105 struct css_set
*cset
, *tmp_cset
;
2107 lockdep_assert_held(&cgroup_mutex
);
2109 down_write(&css_set_rwsem
);
2110 list_for_each_entry_safe(cset
, tmp_cset
, preloaded_csets
, mg_preload_node
) {
2111 cset
->mg_src_cgrp
= NULL
;
2112 cset
->mg_dst_cset
= NULL
;
2113 list_del_init(&cset
->mg_preload_node
);
2114 put_css_set_locked(cset
);
2116 up_write(&css_set_rwsem
);
2120 * cgroup_migrate_add_src - add a migration source css_set
2121 * @src_cset: the source css_set to add
2122 * @dst_cgrp: the destination cgroup
2123 * @preloaded_csets: list of preloaded css_sets
2125 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
2126 * @src_cset and add it to @preloaded_csets, which should later be cleaned
2127 * up by cgroup_migrate_finish().
2129 * This function may be called without holding cgroup_threadgroup_rwsem
2130 * even if the target is a process. Threads may be created and destroyed
2131 * but as long as cgroup_mutex is not dropped, no new css_set can be put
2132 * into play and the preloaded css_sets are guaranteed to cover all
2135 static void cgroup_migrate_add_src(struct css_set
*src_cset
,
2136 struct cgroup
*dst_cgrp
,
2137 struct list_head
*preloaded_csets
)
2139 struct cgroup
*src_cgrp
;
2141 lockdep_assert_held(&cgroup_mutex
);
2142 lockdep_assert_held(&css_set_rwsem
);
2144 src_cgrp
= cset_cgroup_from_root(src_cset
, dst_cgrp
->root
);
2146 if (!list_empty(&src_cset
->mg_preload_node
))
2149 WARN_ON(src_cset
->mg_src_cgrp
);
2150 WARN_ON(!list_empty(&src_cset
->mg_tasks
));
2151 WARN_ON(!list_empty(&src_cset
->mg_node
));
2153 src_cset
->mg_src_cgrp
= src_cgrp
;
2154 get_css_set(src_cset
);
2155 list_add(&src_cset
->mg_preload_node
, preloaded_csets
);
2159 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2160 * @dst_cgrp: the destination cgroup (may be %NULL)
2161 * @preloaded_csets: list of preloaded source css_sets
2163 * Tasks are about to be moved to @dst_cgrp and all the source css_sets
2164 * have been preloaded to @preloaded_csets. This function looks up and
2165 * pins all destination css_sets, links each to its source, and append them
2166 * to @preloaded_csets. If @dst_cgrp is %NULL, the destination of each
2167 * source css_set is assumed to be its cgroup on the default hierarchy.
2169 * This function must be called after cgroup_migrate_add_src() has been
2170 * called on each migration source css_set. After migration is performed
2171 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2174 static int cgroup_migrate_prepare_dst(struct cgroup
*dst_cgrp
,
2175 struct list_head
*preloaded_csets
)
2178 struct css_set
*src_cset
, *tmp_cset
;
2180 lockdep_assert_held(&cgroup_mutex
);
2183 * Except for the root, child_subsys_mask must be zero for a cgroup
2184 * with tasks so that child cgroups don't compete against tasks.
2186 if (dst_cgrp
&& cgroup_on_dfl(dst_cgrp
) && cgroup_parent(dst_cgrp
) &&
2187 dst_cgrp
->child_subsys_mask
)
2190 /* look up the dst cset for each src cset and link it to src */
2191 list_for_each_entry_safe(src_cset
, tmp_cset
, preloaded_csets
, mg_preload_node
) {
2192 struct css_set
*dst_cset
;
2194 dst_cset
= find_css_set(src_cset
,
2195 dst_cgrp
?: src_cset
->dfl_cgrp
);
2199 WARN_ON_ONCE(src_cset
->mg_dst_cset
|| dst_cset
->mg_dst_cset
);
2202 * If src cset equals dst, it's noop. Drop the src.
2203 * cgroup_migrate() will skip the cset too. Note that we
2204 * can't handle src == dst as some nodes are used by both.
2206 if (src_cset
== dst_cset
) {
2207 src_cset
->mg_src_cgrp
= NULL
;
2208 list_del_init(&src_cset
->mg_preload_node
);
2209 put_css_set(src_cset
);
2210 put_css_set(dst_cset
);
2214 src_cset
->mg_dst_cset
= dst_cset
;
2216 if (list_empty(&dst_cset
->mg_preload_node
))
2217 list_add(&dst_cset
->mg_preload_node
, &csets
);
2219 put_css_set(dst_cset
);
2222 list_splice_tail(&csets
, preloaded_csets
);
2225 cgroup_migrate_finish(&csets
);
2230 * cgroup_migrate - migrate a process or task to a cgroup
2231 * @cgrp: the destination cgroup
2232 * @leader: the leader of the process or the task to migrate
2233 * @threadgroup: whether @leader points to the whole process or a single task
2235 * Migrate a process or task denoted by @leader to @cgrp. If migrating a
2236 * process, the caller must be holding cgroup_threadgroup_rwsem. The
2237 * caller is also responsible for invoking cgroup_migrate_add_src() and
2238 * cgroup_migrate_prepare_dst() on the targets before invoking this
2239 * function and following up with cgroup_migrate_finish().
2241 * As long as a controller's ->can_attach() doesn't fail, this function is
2242 * guaranteed to succeed. This means that, excluding ->can_attach()
2243 * failure, when migrating multiple targets, the success or failure can be
2244 * decided for all targets by invoking group_migrate_prepare_dst() before
2245 * actually starting migrating.
2247 static int cgroup_migrate(struct cgroup
*cgrp
, struct task_struct
*leader
,
2250 struct cgroup_taskset tset
= {
2251 .src_csets
= LIST_HEAD_INIT(tset
.src_csets
),
2252 .dst_csets
= LIST_HEAD_INIT(tset
.dst_csets
),
2253 .csets
= &tset
.src_csets
,
2255 struct cgroup_subsys_state
*css
, *failed_css
= NULL
;
2256 struct css_set
*cset
, *tmp_cset
;
2257 struct task_struct
*task
, *tmp_task
;
2261 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2262 * already PF_EXITING could be freed from underneath us unless we
2263 * take an rcu_read_lock.
2265 down_write(&css_set_rwsem
);
2269 /* @task either already exited or can't exit until the end */
2270 if (task
->flags
& PF_EXITING
)
2273 /* leave @task alone if post_fork() hasn't linked it yet */
2274 if (list_empty(&task
->cg_list
))
2277 cset
= task_css_set(task
);
2278 if (!cset
->mg_src_cgrp
)
2282 * cgroup_taskset_first() must always return the leader.
2283 * Take care to avoid disturbing the ordering.
2285 list_move_tail(&task
->cg_list
, &cset
->mg_tasks
);
2286 if (list_empty(&cset
->mg_node
))
2287 list_add_tail(&cset
->mg_node
, &tset
.src_csets
);
2288 if (list_empty(&cset
->mg_dst_cset
->mg_node
))
2289 list_move_tail(&cset
->mg_dst_cset
->mg_node
,
2294 } while_each_thread(leader
, task
);
2296 up_write(&css_set_rwsem
);
2298 /* methods shouldn't be called if no task is actually migrating */
2299 if (list_empty(&tset
.src_csets
))
2302 /* check that we can legitimately attach to the cgroup */
2303 for_each_e_css(css
, i
, cgrp
) {
2304 if (css
->ss
->can_attach
) {
2305 ret
= css
->ss
->can_attach(css
, &tset
);
2308 goto out_cancel_attach
;
2314 * Now that we're guaranteed success, proceed to move all tasks to
2315 * the new cgroup. There are no failure cases after here, so this
2316 * is the commit point.
2318 down_write(&css_set_rwsem
);
2319 list_for_each_entry(cset
, &tset
.src_csets
, mg_node
) {
2320 list_for_each_entry_safe(task
, tmp_task
, &cset
->mg_tasks
, cg_list
)
2321 cgroup_task_migrate(cset
->mg_src_cgrp
, task
,
2324 up_write(&css_set_rwsem
);
2327 * Migration is committed, all target tasks are now on dst_csets.
2328 * Nothing is sensitive to fork() after this point. Notify
2329 * controllers that migration is complete.
2331 tset
.csets
= &tset
.dst_csets
;
2333 for_each_e_css(css
, i
, cgrp
)
2334 if (css
->ss
->attach
)
2335 css
->ss
->attach(css
, &tset
);
2338 goto out_release_tset
;
2341 for_each_e_css(css
, i
, cgrp
) {
2342 if (css
== failed_css
)
2344 if (css
->ss
->cancel_attach
)
2345 css
->ss
->cancel_attach(css
, &tset
);
2348 down_write(&css_set_rwsem
);
2349 list_splice_init(&tset
.dst_csets
, &tset
.src_csets
);
2350 list_for_each_entry_safe(cset
, tmp_cset
, &tset
.src_csets
, mg_node
) {
2351 list_splice_tail_init(&cset
->mg_tasks
, &cset
->tasks
);
2352 list_del_init(&cset
->mg_node
);
2354 up_write(&css_set_rwsem
);
2359 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2360 * @dst_cgrp: the cgroup to attach to
2361 * @leader: the task or the leader of the threadgroup to be attached
2362 * @threadgroup: attach the whole threadgroup?
2364 * Call holding cgroup_mutex and cgroup_threadgroup_rwsem.
2366 static int cgroup_attach_task(struct cgroup
*dst_cgrp
,
2367 struct task_struct
*leader
, bool threadgroup
)
2369 LIST_HEAD(preloaded_csets
);
2370 struct task_struct
*task
;
2373 /* look up all src csets */
2374 down_read(&css_set_rwsem
);
2378 cgroup_migrate_add_src(task_css_set(task
), dst_cgrp
,
2382 } while_each_thread(leader
, task
);
2384 up_read(&css_set_rwsem
);
2386 /* prepare dst csets and commit */
2387 ret
= cgroup_migrate_prepare_dst(dst_cgrp
, &preloaded_csets
);
2389 ret
= cgroup_migrate(dst_cgrp
, leader
, threadgroup
);
2391 cgroup_migrate_finish(&preloaded_csets
);
2396 * Find the task_struct of the task to attach by vpid and pass it along to the
2397 * function to attach either it or all tasks in its threadgroup. Will lock
2398 * cgroup_mutex and threadgroup.
2400 static ssize_t
__cgroup_procs_write(struct kernfs_open_file
*of
, char *buf
,
2401 size_t nbytes
, loff_t off
, bool threadgroup
)
2403 struct task_struct
*tsk
;
2404 const struct cred
*cred
= current_cred(), *tcred
;
2405 struct cgroup
*cgrp
;
2409 if (kstrtoint(strstrip(buf
), 0, &pid
) || pid
< 0)
2412 cgrp
= cgroup_kn_lock_live(of
->kn
);
2416 percpu_down_write(&cgroup_threadgroup_rwsem
);
2419 tsk
= find_task_by_vpid(pid
);
2422 goto out_unlock_rcu
;
2425 * even if we're attaching all tasks in the thread group, we
2426 * only need to check permissions on one of them.
2428 tcred
= __task_cred(tsk
);
2429 if (!uid_eq(cred
->euid
, GLOBAL_ROOT_UID
) &&
2430 !uid_eq(cred
->euid
, tcred
->uid
) &&
2431 !uid_eq(cred
->euid
, tcred
->suid
)) {
2433 goto out_unlock_rcu
;
2439 tsk
= tsk
->group_leader
;
2442 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2443 * trapped in a cpuset, or RT worker may be born in a cgroup
2444 * with no rt_runtime allocated. Just say no.
2446 if (tsk
== kthreadd_task
|| (tsk
->flags
& PF_NO_SETAFFINITY
)) {
2448 goto out_unlock_rcu
;
2451 get_task_struct(tsk
);
2454 ret
= cgroup_attach_task(cgrp
, tsk
, threadgroup
);
2456 put_task_struct(tsk
);
2457 goto out_unlock_threadgroup
;
2461 out_unlock_threadgroup
:
2462 percpu_up_write(&cgroup_threadgroup_rwsem
);
2463 cgroup_kn_unlock(of
->kn
);
2464 return ret
?: nbytes
;
2468 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2469 * @from: attach to all cgroups of a given task
2470 * @tsk: the task to be attached
2472 int cgroup_attach_task_all(struct task_struct
*from
, struct task_struct
*tsk
)
2474 struct cgroup_root
*root
;
2477 mutex_lock(&cgroup_mutex
);
2478 for_each_root(root
) {
2479 struct cgroup
*from_cgrp
;
2481 if (root
== &cgrp_dfl_root
)
2484 down_read(&css_set_rwsem
);
2485 from_cgrp
= task_cgroup_from_root(from
, root
);
2486 up_read(&css_set_rwsem
);
2488 retval
= cgroup_attach_task(from_cgrp
, tsk
, false);
2492 mutex_unlock(&cgroup_mutex
);
2496 EXPORT_SYMBOL_GPL(cgroup_attach_task_all
);
2498 static ssize_t
cgroup_tasks_write(struct kernfs_open_file
*of
,
2499 char *buf
, size_t nbytes
, loff_t off
)
2501 return __cgroup_procs_write(of
, buf
, nbytes
, off
, false);
2504 static ssize_t
cgroup_procs_write(struct kernfs_open_file
*of
,
2505 char *buf
, size_t nbytes
, loff_t off
)
2507 return __cgroup_procs_write(of
, buf
, nbytes
, off
, true);
2510 static ssize_t
cgroup_release_agent_write(struct kernfs_open_file
*of
,
2511 char *buf
, size_t nbytes
, loff_t off
)
2513 struct cgroup
*cgrp
;
2515 BUILD_BUG_ON(sizeof(cgrp
->root
->release_agent_path
) < PATH_MAX
);
2517 cgrp
= cgroup_kn_lock_live(of
->kn
);
2520 spin_lock(&release_agent_path_lock
);
2521 strlcpy(cgrp
->root
->release_agent_path
, strstrip(buf
),
2522 sizeof(cgrp
->root
->release_agent_path
));
2523 spin_unlock(&release_agent_path_lock
);
2524 cgroup_kn_unlock(of
->kn
);
2528 static int cgroup_release_agent_show(struct seq_file
*seq
, void *v
)
2530 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2532 spin_lock(&release_agent_path_lock
);
2533 seq_puts(seq
, cgrp
->root
->release_agent_path
);
2534 spin_unlock(&release_agent_path_lock
);
2535 seq_putc(seq
, '\n');
2539 static int cgroup_sane_behavior_show(struct seq_file
*seq
, void *v
)
2541 seq_puts(seq
, "0\n");
2545 static void cgroup_print_ss_mask(struct seq_file
*seq
, unsigned long ss_mask
)
2547 struct cgroup_subsys
*ss
;
2548 bool printed
= false;
2551 for_each_subsys_which(ss
, ssid
, &ss_mask
) {
2554 seq_printf(seq
, "%s", ss
->name
);
2558 seq_putc(seq
, '\n');
2561 /* show controllers which are currently attached to the default hierarchy */
2562 static int cgroup_root_controllers_show(struct seq_file
*seq
, void *v
)
2564 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2566 cgroup_print_ss_mask(seq
, cgrp
->root
->subsys_mask
&
2567 ~cgrp_dfl_root_inhibit_ss_mask
);
2571 /* show controllers which are enabled from the parent */
2572 static int cgroup_controllers_show(struct seq_file
*seq
, void *v
)
2574 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2576 cgroup_print_ss_mask(seq
, cgroup_parent(cgrp
)->subtree_control
);
2580 /* show controllers which are enabled for a given cgroup's children */
2581 static int cgroup_subtree_control_show(struct seq_file
*seq
, void *v
)
2583 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2585 cgroup_print_ss_mask(seq
, cgrp
->subtree_control
);
2590 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
2591 * @cgrp: root of the subtree to update csses for
2593 * @cgrp's child_subsys_mask has changed and its subtree's (self excluded)
2594 * css associations need to be updated accordingly. This function looks up
2595 * all css_sets which are attached to the subtree, creates the matching
2596 * updated css_sets and migrates the tasks to the new ones.
2598 static int cgroup_update_dfl_csses(struct cgroup
*cgrp
)
2600 LIST_HEAD(preloaded_csets
);
2601 struct cgroup_subsys_state
*css
;
2602 struct css_set
*src_cset
;
2605 lockdep_assert_held(&cgroup_mutex
);
2607 percpu_down_write(&cgroup_threadgroup_rwsem
);
2609 /* look up all csses currently attached to @cgrp's subtree */
2610 down_read(&css_set_rwsem
);
2611 css_for_each_descendant_pre(css
, cgroup_css(cgrp
, NULL
)) {
2612 struct cgrp_cset_link
*link
;
2614 /* self is not affected by child_subsys_mask change */
2615 if (css
->cgroup
== cgrp
)
2618 list_for_each_entry(link
, &css
->cgroup
->cset_links
, cset_link
)
2619 cgroup_migrate_add_src(link
->cset
, cgrp
,
2622 up_read(&css_set_rwsem
);
2624 /* NULL dst indicates self on default hierarchy */
2625 ret
= cgroup_migrate_prepare_dst(NULL
, &preloaded_csets
);
2629 list_for_each_entry(src_cset
, &preloaded_csets
, mg_preload_node
) {
2630 struct task_struct
*last_task
= NULL
, *task
;
2632 /* src_csets precede dst_csets, break on the first dst_cset */
2633 if (!src_cset
->mg_src_cgrp
)
2637 * All tasks in src_cset need to be migrated to the
2638 * matching dst_cset. Empty it process by process. We
2639 * walk tasks but migrate processes. The leader might even
2640 * belong to a different cset but such src_cset would also
2641 * be among the target src_csets because the default
2642 * hierarchy enforces per-process membership.
2645 down_read(&css_set_rwsem
);
2646 task
= list_first_entry_or_null(&src_cset
->tasks
,
2647 struct task_struct
, cg_list
);
2649 task
= task
->group_leader
;
2650 WARN_ON_ONCE(!task_css_set(task
)->mg_src_cgrp
);
2651 get_task_struct(task
);
2653 up_read(&css_set_rwsem
);
2658 /* guard against possible infinite loop */
2659 if (WARN(last_task
== task
,
2660 "cgroup: update_dfl_csses failed to make progress, aborting in inconsistent state\n"))
2664 ret
= cgroup_migrate(src_cset
->dfl_cgrp
, task
, true);
2666 put_task_struct(task
);
2668 if (WARN(ret
, "cgroup: failed to update controllers for the default hierarchy (%d), further operations may crash or hang\n", ret
))
2674 cgroup_migrate_finish(&preloaded_csets
);
2675 percpu_up_write(&cgroup_threadgroup_rwsem
);
2679 /* change the enabled child controllers for a cgroup in the default hierarchy */
2680 static ssize_t
cgroup_subtree_control_write(struct kernfs_open_file
*of
,
2681 char *buf
, size_t nbytes
,
2684 unsigned long enable
= 0, disable
= 0;
2685 unsigned long css_enable
, css_disable
, old_sc
, new_sc
, old_ss
, new_ss
;
2686 struct cgroup
*cgrp
, *child
;
2687 struct cgroup_subsys
*ss
;
2692 * Parse input - space separated list of subsystem names prefixed
2693 * with either + or -.
2695 buf
= strstrip(buf
);
2696 while ((tok
= strsep(&buf
, " "))) {
2697 unsigned long tmp_ss_mask
= ~cgrp_dfl_root_inhibit_ss_mask
;
2701 for_each_subsys_which(ss
, ssid
, &tmp_ss_mask
) {
2702 if (ss
->disabled
|| strcmp(tok
+ 1, ss
->name
))
2706 enable
|= 1 << ssid
;
2707 disable
&= ~(1 << ssid
);
2708 } else if (*tok
== '-') {
2709 disable
|= 1 << ssid
;
2710 enable
&= ~(1 << ssid
);
2716 if (ssid
== CGROUP_SUBSYS_COUNT
)
2720 cgrp
= cgroup_kn_lock_live(of
->kn
);
2724 for_each_subsys(ss
, ssid
) {
2725 if (enable
& (1 << ssid
)) {
2726 if (cgrp
->subtree_control
& (1 << ssid
)) {
2727 enable
&= ~(1 << ssid
);
2731 /* unavailable or not enabled on the parent? */
2732 if (!(cgrp_dfl_root
.subsys_mask
& (1 << ssid
)) ||
2733 (cgroup_parent(cgrp
) &&
2734 !(cgroup_parent(cgrp
)->subtree_control
& (1 << ssid
)))) {
2738 } else if (disable
& (1 << ssid
)) {
2739 if (!(cgrp
->subtree_control
& (1 << ssid
))) {
2740 disable
&= ~(1 << ssid
);
2744 /* a child has it enabled? */
2745 cgroup_for_each_live_child(child
, cgrp
) {
2746 if (child
->subtree_control
& (1 << ssid
)) {
2754 if (!enable
&& !disable
) {
2760 * Except for the root, subtree_control must be zero for a cgroup
2761 * with tasks so that child cgroups don't compete against tasks.
2763 if (enable
&& cgroup_parent(cgrp
) && !list_empty(&cgrp
->cset_links
)) {
2769 * Update subsys masks and calculate what needs to be done. More
2770 * subsystems than specified may need to be enabled or disabled
2771 * depending on subsystem dependencies.
2773 old_sc
= cgrp
->subtree_control
;
2774 old_ss
= cgrp
->child_subsys_mask
;
2775 new_sc
= (old_sc
| enable
) & ~disable
;
2776 new_ss
= cgroup_calc_child_subsys_mask(cgrp
, new_sc
);
2778 css_enable
= ~old_ss
& new_ss
;
2779 css_disable
= old_ss
& ~new_ss
;
2780 enable
|= css_enable
;
2781 disable
|= css_disable
;
2784 * Because css offlining is asynchronous, userland might try to
2785 * re-enable the same controller while the previous instance is
2786 * still around. In such cases, wait till it's gone using
2789 for_each_subsys_which(ss
, ssid
, &css_enable
) {
2790 cgroup_for_each_live_child(child
, cgrp
) {
2793 if (!cgroup_css(child
, ss
))
2797 prepare_to_wait(&child
->offline_waitq
, &wait
,
2798 TASK_UNINTERRUPTIBLE
);
2799 cgroup_kn_unlock(of
->kn
);
2801 finish_wait(&child
->offline_waitq
, &wait
);
2804 return restart_syscall();
2808 cgrp
->subtree_control
= new_sc
;
2809 cgrp
->child_subsys_mask
= new_ss
;
2812 * Create new csses or make the existing ones visible. A css is
2813 * created invisible if it's being implicitly enabled through
2814 * dependency. An invisible css is made visible when the userland
2815 * explicitly enables it.
2817 for_each_subsys(ss
, ssid
) {
2818 if (!(enable
& (1 << ssid
)))
2821 cgroup_for_each_live_child(child
, cgrp
) {
2822 if (css_enable
& (1 << ssid
))
2823 ret
= create_css(child
, ss
,
2824 cgrp
->subtree_control
& (1 << ssid
));
2826 ret
= cgroup_populate_dir(child
, 1 << ssid
);
2833 * At this point, cgroup_e_css() results reflect the new csses
2834 * making the following cgroup_update_dfl_csses() properly update
2835 * css associations of all tasks in the subtree.
2837 ret
= cgroup_update_dfl_csses(cgrp
);
2842 * All tasks are migrated out of disabled csses. Kill or hide
2843 * them. A css is hidden when the userland requests it to be
2844 * disabled while other subsystems are still depending on it. The
2845 * css must not actively control resources and be in the vanilla
2846 * state if it's made visible again later. Controllers which may
2847 * be depended upon should provide ->css_reset() for this purpose.
2849 for_each_subsys(ss
, ssid
) {
2850 if (!(disable
& (1 << ssid
)))
2853 cgroup_for_each_live_child(child
, cgrp
) {
2854 struct cgroup_subsys_state
*css
= cgroup_css(child
, ss
);
2856 if (css_disable
& (1 << ssid
)) {
2859 cgroup_clear_dir(child
, 1 << ssid
);
2867 * The effective csses of all the descendants (excluding @cgrp) may
2868 * have changed. Subsystems can optionally subscribe to this event
2869 * by implementing ->css_e_css_changed() which is invoked if any of
2870 * the effective csses seen from the css's cgroup may have changed.
2872 for_each_subsys(ss
, ssid
) {
2873 struct cgroup_subsys_state
*this_css
= cgroup_css(cgrp
, ss
);
2874 struct cgroup_subsys_state
*css
;
2876 if (!ss
->css_e_css_changed
|| !this_css
)
2879 css_for_each_descendant_pre(css
, this_css
)
2880 if (css
!= this_css
)
2881 ss
->css_e_css_changed(css
);
2884 kernfs_activate(cgrp
->kn
);
2887 cgroup_kn_unlock(of
->kn
);
2888 return ret
?: nbytes
;
2891 cgrp
->subtree_control
= old_sc
;
2892 cgrp
->child_subsys_mask
= old_ss
;
2894 for_each_subsys(ss
, ssid
) {
2895 if (!(enable
& (1 << ssid
)))
2898 cgroup_for_each_live_child(child
, cgrp
) {
2899 struct cgroup_subsys_state
*css
= cgroup_css(child
, ss
);
2904 if (css_enable
& (1 << ssid
))
2907 cgroup_clear_dir(child
, 1 << ssid
);
2913 static int cgroup_populated_show(struct seq_file
*seq
, void *v
)
2915 seq_printf(seq
, "%d\n", (bool)seq_css(seq
)->cgroup
->populated_cnt
);
2919 static ssize_t
cgroup_file_write(struct kernfs_open_file
*of
, char *buf
,
2920 size_t nbytes
, loff_t off
)
2922 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
2923 struct cftype
*cft
= of
->kn
->priv
;
2924 struct cgroup_subsys_state
*css
;
2928 return cft
->write(of
, buf
, nbytes
, off
);
2931 * kernfs guarantees that a file isn't deleted with operations in
2932 * flight, which means that the matching css is and stays alive and
2933 * doesn't need to be pinned. The RCU locking is not necessary
2934 * either. It's just for the convenience of using cgroup_css().
2937 css
= cgroup_css(cgrp
, cft
->ss
);
2940 if (cft
->write_u64
) {
2941 unsigned long long v
;
2942 ret
= kstrtoull(buf
, 0, &v
);
2944 ret
= cft
->write_u64(css
, cft
, v
);
2945 } else if (cft
->write_s64
) {
2947 ret
= kstrtoll(buf
, 0, &v
);
2949 ret
= cft
->write_s64(css
, cft
, v
);
2954 return ret
?: nbytes
;
2957 static void *cgroup_seqfile_start(struct seq_file
*seq
, loff_t
*ppos
)
2959 return seq_cft(seq
)->seq_start(seq
, ppos
);
2962 static void *cgroup_seqfile_next(struct seq_file
*seq
, void *v
, loff_t
*ppos
)
2964 return seq_cft(seq
)->seq_next(seq
, v
, ppos
);
2967 static void cgroup_seqfile_stop(struct seq_file
*seq
, void *v
)
2969 seq_cft(seq
)->seq_stop(seq
, v
);
2972 static int cgroup_seqfile_show(struct seq_file
*m
, void *arg
)
2974 struct cftype
*cft
= seq_cft(m
);
2975 struct cgroup_subsys_state
*css
= seq_css(m
);
2978 return cft
->seq_show(m
, arg
);
2981 seq_printf(m
, "%llu\n", cft
->read_u64(css
, cft
));
2982 else if (cft
->read_s64
)
2983 seq_printf(m
, "%lld\n", cft
->read_s64(css
, cft
));
2989 static struct kernfs_ops cgroup_kf_single_ops
= {
2990 .atomic_write_len
= PAGE_SIZE
,
2991 .write
= cgroup_file_write
,
2992 .seq_show
= cgroup_seqfile_show
,
2995 static struct kernfs_ops cgroup_kf_ops
= {
2996 .atomic_write_len
= PAGE_SIZE
,
2997 .write
= cgroup_file_write
,
2998 .seq_start
= cgroup_seqfile_start
,
2999 .seq_next
= cgroup_seqfile_next
,
3000 .seq_stop
= cgroup_seqfile_stop
,
3001 .seq_show
= cgroup_seqfile_show
,
3005 * cgroup_rename - Only allow simple rename of directories in place.
3007 static int cgroup_rename(struct kernfs_node
*kn
, struct kernfs_node
*new_parent
,
3008 const char *new_name_str
)
3010 struct cgroup
*cgrp
= kn
->priv
;
3013 if (kernfs_type(kn
) != KERNFS_DIR
)
3015 if (kn
->parent
!= new_parent
)
3019 * This isn't a proper migration and its usefulness is very
3020 * limited. Disallow on the default hierarchy.
3022 if (cgroup_on_dfl(cgrp
))
3026 * We're gonna grab cgroup_mutex which nests outside kernfs
3027 * active_ref. kernfs_rename() doesn't require active_ref
3028 * protection. Break them before grabbing cgroup_mutex.
3030 kernfs_break_active_protection(new_parent
);
3031 kernfs_break_active_protection(kn
);
3033 mutex_lock(&cgroup_mutex
);
3035 ret
= kernfs_rename(kn
, new_parent
, new_name_str
);
3037 mutex_unlock(&cgroup_mutex
);
3039 kernfs_unbreak_active_protection(kn
);
3040 kernfs_unbreak_active_protection(new_parent
);
3044 /* set uid and gid of cgroup dirs and files to that of the creator */
3045 static int cgroup_kn_set_ugid(struct kernfs_node
*kn
)
3047 struct iattr iattr
= { .ia_valid
= ATTR_UID
| ATTR_GID
,
3048 .ia_uid
= current_fsuid(),
3049 .ia_gid
= current_fsgid(), };
3051 if (uid_eq(iattr
.ia_uid
, GLOBAL_ROOT_UID
) &&
3052 gid_eq(iattr
.ia_gid
, GLOBAL_ROOT_GID
))
3055 return kernfs_setattr(kn
, &iattr
);
3058 static int cgroup_add_file(struct cgroup
*cgrp
, struct cftype
*cft
)
3060 char name
[CGROUP_FILE_NAME_MAX
];
3061 struct kernfs_node
*kn
;
3062 struct lock_class_key
*key
= NULL
;
3065 #ifdef CONFIG_DEBUG_LOCK_ALLOC
3066 key
= &cft
->lockdep_key
;
3068 kn
= __kernfs_create_file(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
),
3069 cgroup_file_mode(cft
), 0, cft
->kf_ops
, cft
,
3074 ret
= cgroup_kn_set_ugid(kn
);
3080 if (cft
->seq_show
== cgroup_populated_show
)
3081 cgrp
->populated_kn
= kn
;
3086 * cgroup_addrm_files - add or remove files to a cgroup directory
3087 * @cgrp: the target cgroup
3088 * @cfts: array of cftypes to be added
3089 * @is_add: whether to add or remove
3091 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
3092 * For removals, this function never fails. If addition fails, this
3093 * function doesn't remove files already added. The caller is responsible
3096 static int cgroup_addrm_files(struct cgroup
*cgrp
, struct cftype cfts
[],
3102 lockdep_assert_held(&cgroup_mutex
);
3104 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3105 /* does cft->flags tell us to skip this file on @cgrp? */
3106 if ((cft
->flags
& __CFTYPE_ONLY_ON_DFL
) && !cgroup_on_dfl(cgrp
))
3108 if ((cft
->flags
& __CFTYPE_NOT_ON_DFL
) && cgroup_on_dfl(cgrp
))
3110 if ((cft
->flags
& CFTYPE_NOT_ON_ROOT
) && !cgroup_parent(cgrp
))
3112 if ((cft
->flags
& CFTYPE_ONLY_ON_ROOT
) && cgroup_parent(cgrp
))
3116 ret
= cgroup_add_file(cgrp
, cft
);
3118 pr_warn("%s: failed to add %s, err=%d\n",
3119 __func__
, cft
->name
, ret
);
3123 cgroup_rm_file(cgrp
, cft
);
3129 static int cgroup_apply_cftypes(struct cftype
*cfts
, bool is_add
)
3132 struct cgroup_subsys
*ss
= cfts
[0].ss
;
3133 struct cgroup
*root
= &ss
->root
->cgrp
;
3134 struct cgroup_subsys_state
*css
;
3137 lockdep_assert_held(&cgroup_mutex
);
3139 /* add/rm files for all cgroups created before */
3140 css_for_each_descendant_pre(css
, cgroup_css(root
, ss
)) {
3141 struct cgroup
*cgrp
= css
->cgroup
;
3143 if (cgroup_is_dead(cgrp
))
3146 ret
= cgroup_addrm_files(cgrp
, cfts
, is_add
);
3152 kernfs_activate(root
->kn
);
3156 static void cgroup_exit_cftypes(struct cftype
*cfts
)
3160 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3161 /* free copy for custom atomic_write_len, see init_cftypes() */
3162 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
)
3167 /* revert flags set by cgroup core while adding @cfts */
3168 cft
->flags
&= ~(__CFTYPE_ONLY_ON_DFL
| __CFTYPE_NOT_ON_DFL
);
3172 static int cgroup_init_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3176 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
3177 struct kernfs_ops
*kf_ops
;
3179 WARN_ON(cft
->ss
|| cft
->kf_ops
);
3182 kf_ops
= &cgroup_kf_ops
;
3184 kf_ops
= &cgroup_kf_single_ops
;
3187 * Ugh... if @cft wants a custom max_write_len, we need to
3188 * make a copy of kf_ops to set its atomic_write_len.
3190 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
) {
3191 kf_ops
= kmemdup(kf_ops
, sizeof(*kf_ops
), GFP_KERNEL
);
3193 cgroup_exit_cftypes(cfts
);
3196 kf_ops
->atomic_write_len
= cft
->max_write_len
;
3199 cft
->kf_ops
= kf_ops
;
3206 static int cgroup_rm_cftypes_locked(struct cftype
*cfts
)
3208 lockdep_assert_held(&cgroup_mutex
);
3210 if (!cfts
|| !cfts
[0].ss
)
3213 list_del(&cfts
->node
);
3214 cgroup_apply_cftypes(cfts
, false);
3215 cgroup_exit_cftypes(cfts
);
3220 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
3221 * @cfts: zero-length name terminated array of cftypes
3223 * Unregister @cfts. Files described by @cfts are removed from all
3224 * existing cgroups and all future cgroups won't have them either. This
3225 * function can be called anytime whether @cfts' subsys is attached or not.
3227 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
3230 int cgroup_rm_cftypes(struct cftype
*cfts
)
3234 mutex_lock(&cgroup_mutex
);
3235 ret
= cgroup_rm_cftypes_locked(cfts
);
3236 mutex_unlock(&cgroup_mutex
);
3241 * cgroup_add_cftypes - add an array of cftypes to a subsystem
3242 * @ss: target cgroup subsystem
3243 * @cfts: zero-length name terminated array of cftypes
3245 * Register @cfts to @ss. Files described by @cfts are created for all
3246 * existing cgroups to which @ss is attached and all future cgroups will
3247 * have them too. This function can be called anytime whether @ss is
3250 * Returns 0 on successful registration, -errno on failure. Note that this
3251 * function currently returns 0 as long as @cfts registration is successful
3252 * even if some file creation attempts on existing cgroups fail.
3254 static int cgroup_add_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3261 if (!cfts
|| cfts
[0].name
[0] == '\0')
3264 ret
= cgroup_init_cftypes(ss
, cfts
);
3268 mutex_lock(&cgroup_mutex
);
3270 list_add_tail(&cfts
->node
, &ss
->cfts
);
3271 ret
= cgroup_apply_cftypes(cfts
, true);
3273 cgroup_rm_cftypes_locked(cfts
);
3275 mutex_unlock(&cgroup_mutex
);
3280 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
3281 * @ss: target cgroup subsystem
3282 * @cfts: zero-length name terminated array of cftypes
3284 * Similar to cgroup_add_cftypes() but the added files are only used for
3285 * the default hierarchy.
3287 int cgroup_add_dfl_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3291 for (cft
= cfts
; cft
&& cft
->name
[0] != '\0'; cft
++)
3292 cft
->flags
|= __CFTYPE_ONLY_ON_DFL
;
3293 return cgroup_add_cftypes(ss
, cfts
);
3297 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
3298 * @ss: target cgroup subsystem
3299 * @cfts: zero-length name terminated array of cftypes
3301 * Similar to cgroup_add_cftypes() but the added files are only used for
3302 * the legacy hierarchies.
3304 int cgroup_add_legacy_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
3309 * If legacy_flies_on_dfl, we want to show the legacy files on the
3310 * dfl hierarchy but iff the target subsystem hasn't been updated
3311 * for the dfl hierarchy yet.
3313 if (!cgroup_legacy_files_on_dfl
||
3314 ss
->dfl_cftypes
!= ss
->legacy_cftypes
) {
3315 for (cft
= cfts
; cft
&& cft
->name
[0] != '\0'; cft
++)
3316 cft
->flags
|= __CFTYPE_NOT_ON_DFL
;
3319 return cgroup_add_cftypes(ss
, cfts
);
3323 * cgroup_task_count - count the number of tasks in a cgroup.
3324 * @cgrp: the cgroup in question
3326 * Return the number of tasks in the cgroup.
3328 static int cgroup_task_count(const struct cgroup
*cgrp
)
3331 struct cgrp_cset_link
*link
;
3333 down_read(&css_set_rwsem
);
3334 list_for_each_entry(link
, &cgrp
->cset_links
, cset_link
)
3335 count
+= atomic_read(&link
->cset
->refcount
);
3336 up_read(&css_set_rwsem
);
3341 * css_next_child - find the next child of a given css
3342 * @pos: the current position (%NULL to initiate traversal)
3343 * @parent: css whose children to walk
3345 * This function returns the next child of @parent and should be called
3346 * under either cgroup_mutex or RCU read lock. The only requirement is
3347 * that @parent and @pos are accessible. The next sibling is guaranteed to
3348 * be returned regardless of their states.
3350 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3351 * css which finished ->css_online() is guaranteed to be visible in the
3352 * future iterations and will stay visible until the last reference is put.
3353 * A css which hasn't finished ->css_online() or already finished
3354 * ->css_offline() may show up during traversal. It's each subsystem's
3355 * responsibility to synchronize against on/offlining.
3357 struct cgroup_subsys_state
*css_next_child(struct cgroup_subsys_state
*pos
,
3358 struct cgroup_subsys_state
*parent
)
3360 struct cgroup_subsys_state
*next
;
3362 cgroup_assert_mutex_or_rcu_locked();
3365 * @pos could already have been unlinked from the sibling list.
3366 * Once a cgroup is removed, its ->sibling.next is no longer
3367 * updated when its next sibling changes. CSS_RELEASED is set when
3368 * @pos is taken off list, at which time its next pointer is valid,
3369 * and, as releases are serialized, the one pointed to by the next
3370 * pointer is guaranteed to not have started release yet. This
3371 * implies that if we observe !CSS_RELEASED on @pos in this RCU
3372 * critical section, the one pointed to by its next pointer is
3373 * guaranteed to not have finished its RCU grace period even if we
3374 * have dropped rcu_read_lock() inbetween iterations.
3376 * If @pos has CSS_RELEASED set, its next pointer can't be
3377 * dereferenced; however, as each css is given a monotonically
3378 * increasing unique serial number and always appended to the
3379 * sibling list, the next one can be found by walking the parent's
3380 * children until the first css with higher serial number than
3381 * @pos's. While this path can be slower, it happens iff iteration
3382 * races against release and the race window is very small.
3385 next
= list_entry_rcu(parent
->children
.next
, struct cgroup_subsys_state
, sibling
);
3386 } else if (likely(!(pos
->flags
& CSS_RELEASED
))) {
3387 next
= list_entry_rcu(pos
->sibling
.next
, struct cgroup_subsys_state
, sibling
);
3389 list_for_each_entry_rcu(next
, &parent
->children
, sibling
)
3390 if (next
->serial_nr
> pos
->serial_nr
)
3395 * @next, if not pointing to the head, can be dereferenced and is
3398 if (&next
->sibling
!= &parent
->children
)
3404 * css_next_descendant_pre - find the next descendant for pre-order walk
3405 * @pos: the current position (%NULL to initiate traversal)
3406 * @root: css whose descendants to walk
3408 * To be used by css_for_each_descendant_pre(). Find the next descendant
3409 * to visit for pre-order traversal of @root's descendants. @root is
3410 * included in the iteration and the first node to be visited.
3412 * While this function requires cgroup_mutex or RCU read locking, it
3413 * doesn't require the whole traversal to be contained in a single critical
3414 * section. This function will return the correct next descendant as long
3415 * as both @pos and @root are accessible and @pos is a descendant of @root.
3417 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3418 * css which finished ->css_online() is guaranteed to be visible in the
3419 * future iterations and will stay visible until the last reference is put.
3420 * A css which hasn't finished ->css_online() or already finished
3421 * ->css_offline() may show up during traversal. It's each subsystem's
3422 * responsibility to synchronize against on/offlining.
3424 struct cgroup_subsys_state
*
3425 css_next_descendant_pre(struct cgroup_subsys_state
*pos
,
3426 struct cgroup_subsys_state
*root
)
3428 struct cgroup_subsys_state
*next
;
3430 cgroup_assert_mutex_or_rcu_locked();
3432 /* if first iteration, visit @root */
3436 /* visit the first child if exists */
3437 next
= css_next_child(NULL
, pos
);
3441 /* no child, visit my or the closest ancestor's next sibling */
3442 while (pos
!= root
) {
3443 next
= css_next_child(pos
, pos
->parent
);
3453 * css_rightmost_descendant - return the rightmost descendant of a css
3454 * @pos: css of interest
3456 * Return the rightmost descendant of @pos. If there's no descendant, @pos
3457 * is returned. This can be used during pre-order traversal to skip
3460 * While this function requires cgroup_mutex or RCU read locking, it
3461 * doesn't require the whole traversal to be contained in a single critical
3462 * section. This function will return the correct rightmost descendant as
3463 * long as @pos is accessible.
3465 struct cgroup_subsys_state
*
3466 css_rightmost_descendant(struct cgroup_subsys_state
*pos
)
3468 struct cgroup_subsys_state
*last
, *tmp
;
3470 cgroup_assert_mutex_or_rcu_locked();
3474 /* ->prev isn't RCU safe, walk ->next till the end */
3476 css_for_each_child(tmp
, last
)
3483 static struct cgroup_subsys_state
*
3484 css_leftmost_descendant(struct cgroup_subsys_state
*pos
)
3486 struct cgroup_subsys_state
*last
;
3490 pos
= css_next_child(NULL
, pos
);
3497 * css_next_descendant_post - find the next descendant for post-order walk
3498 * @pos: the current position (%NULL to initiate traversal)
3499 * @root: css whose descendants to walk
3501 * To be used by css_for_each_descendant_post(). Find the next descendant
3502 * to visit for post-order traversal of @root's descendants. @root is
3503 * included in the iteration and the last node to be visited.
3505 * While this function requires cgroup_mutex or RCU read locking, it
3506 * doesn't require the whole traversal to be contained in a single critical
3507 * section. This function will return the correct next descendant as long
3508 * as both @pos and @cgroup are accessible and @pos is a descendant of
3511 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3512 * css which finished ->css_online() is guaranteed to be visible in the
3513 * future iterations and will stay visible until the last reference is put.
3514 * A css which hasn't finished ->css_online() or already finished
3515 * ->css_offline() may show up during traversal. It's each subsystem's
3516 * responsibility to synchronize against on/offlining.
3518 struct cgroup_subsys_state
*
3519 css_next_descendant_post(struct cgroup_subsys_state
*pos
,
3520 struct cgroup_subsys_state
*root
)
3522 struct cgroup_subsys_state
*next
;
3524 cgroup_assert_mutex_or_rcu_locked();
3526 /* if first iteration, visit leftmost descendant which may be @root */
3528 return css_leftmost_descendant(root
);
3530 /* if we visited @root, we're done */
3534 /* if there's an unvisited sibling, visit its leftmost descendant */
3535 next
= css_next_child(pos
, pos
->parent
);
3537 return css_leftmost_descendant(next
);
3539 /* no sibling left, visit parent */
3544 * css_has_online_children - does a css have online children
3545 * @css: the target css
3547 * Returns %true if @css has any online children; otherwise, %false. This
3548 * function can be called from any context but the caller is responsible
3549 * for synchronizing against on/offlining as necessary.
3551 bool css_has_online_children(struct cgroup_subsys_state
*css
)
3553 struct cgroup_subsys_state
*child
;
3557 css_for_each_child(child
, css
) {
3558 if (child
->flags
& CSS_ONLINE
) {
3568 * css_advance_task_iter - advance a task itererator to the next css_set
3569 * @it: the iterator to advance
3571 * Advance @it to the next css_set to walk.
3573 static void css_advance_task_iter(struct css_task_iter
*it
)
3575 struct list_head
*l
= it
->cset_pos
;
3576 struct cgrp_cset_link
*link
;
3577 struct css_set
*cset
;
3579 /* Advance to the next non-empty css_set */
3582 if (l
== it
->cset_head
) {
3583 it
->cset_pos
= NULL
;
3588 cset
= container_of(l
, struct css_set
,
3589 e_cset_node
[it
->ss
->id
]);
3591 link
= list_entry(l
, struct cgrp_cset_link
, cset_link
);
3594 } while (list_empty(&cset
->tasks
) && list_empty(&cset
->mg_tasks
));
3598 if (!list_empty(&cset
->tasks
))
3599 it
->task_pos
= cset
->tasks
.next
;
3601 it
->task_pos
= cset
->mg_tasks
.next
;
3603 it
->tasks_head
= &cset
->tasks
;
3604 it
->mg_tasks_head
= &cset
->mg_tasks
;
3608 * css_task_iter_start - initiate task iteration
3609 * @css: the css to walk tasks of
3610 * @it: the task iterator to use
3612 * Initiate iteration through the tasks of @css. The caller can call
3613 * css_task_iter_next() to walk through the tasks until the function
3614 * returns NULL. On completion of iteration, css_task_iter_end() must be
3617 * Note that this function acquires a lock which is released when the
3618 * iteration finishes. The caller can't sleep while iteration is in
3621 void css_task_iter_start(struct cgroup_subsys_state
*css
,
3622 struct css_task_iter
*it
)
3623 __acquires(css_set_rwsem
)
3625 /* no one should try to iterate before mounting cgroups */
3626 WARN_ON_ONCE(!use_task_css_set_links
);
3628 down_read(&css_set_rwsem
);
3633 it
->cset_pos
= &css
->cgroup
->e_csets
[css
->ss
->id
];
3635 it
->cset_pos
= &css
->cgroup
->cset_links
;
3637 it
->cset_head
= it
->cset_pos
;
3639 css_advance_task_iter(it
);
3643 * css_task_iter_next - return the next task for the iterator
3644 * @it: the task iterator being iterated
3646 * The "next" function for task iteration. @it should have been
3647 * initialized via css_task_iter_start(). Returns NULL when the iteration
3650 struct task_struct
*css_task_iter_next(struct css_task_iter
*it
)
3652 struct task_struct
*res
;
3653 struct list_head
*l
= it
->task_pos
;
3655 /* If the iterator cg is NULL, we have no tasks */
3658 res
= list_entry(l
, struct task_struct
, cg_list
);
3661 * Advance iterator to find next entry. cset->tasks is consumed
3662 * first and then ->mg_tasks. After ->mg_tasks, we move onto the
3667 if (l
== it
->tasks_head
)
3668 l
= it
->mg_tasks_head
->next
;
3670 if (l
== it
->mg_tasks_head
)
3671 css_advance_task_iter(it
);
3679 * css_task_iter_end - finish task iteration
3680 * @it: the task iterator to finish
3682 * Finish task iteration started by css_task_iter_start().
3684 void css_task_iter_end(struct css_task_iter
*it
)
3685 __releases(css_set_rwsem
)
3687 up_read(&css_set_rwsem
);
3691 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
3692 * @to: cgroup to which the tasks will be moved
3693 * @from: cgroup in which the tasks currently reside
3695 * Locking rules between cgroup_post_fork() and the migration path
3696 * guarantee that, if a task is forking while being migrated, the new child
3697 * is guaranteed to be either visible in the source cgroup after the
3698 * parent's migration is complete or put into the target cgroup. No task
3699 * can slip out of migration through forking.
3701 int cgroup_transfer_tasks(struct cgroup
*to
, struct cgroup
*from
)
3703 LIST_HEAD(preloaded_csets
);
3704 struct cgrp_cset_link
*link
;
3705 struct css_task_iter it
;
3706 struct task_struct
*task
;
3709 mutex_lock(&cgroup_mutex
);
3711 /* all tasks in @from are being moved, all csets are source */
3712 down_read(&css_set_rwsem
);
3713 list_for_each_entry(link
, &from
->cset_links
, cset_link
)
3714 cgroup_migrate_add_src(link
->cset
, to
, &preloaded_csets
);
3715 up_read(&css_set_rwsem
);
3717 ret
= cgroup_migrate_prepare_dst(to
, &preloaded_csets
);
3722 * Migrate tasks one-by-one until @form is empty. This fails iff
3723 * ->can_attach() fails.
3726 css_task_iter_start(&from
->self
, &it
);
3727 task
= css_task_iter_next(&it
);
3729 get_task_struct(task
);
3730 css_task_iter_end(&it
);
3733 ret
= cgroup_migrate(to
, task
, false);
3734 put_task_struct(task
);
3736 } while (task
&& !ret
);
3738 cgroup_migrate_finish(&preloaded_csets
);
3739 mutex_unlock(&cgroup_mutex
);
3744 * Stuff for reading the 'tasks'/'procs' files.
3746 * Reading this file can return large amounts of data if a cgroup has
3747 * *lots* of attached tasks. So it may need several calls to read(),
3748 * but we cannot guarantee that the information we produce is correct
3749 * unless we produce it entirely atomically.
3753 /* which pidlist file are we talking about? */
3754 enum cgroup_filetype
{
3760 * A pidlist is a list of pids that virtually represents the contents of one
3761 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3762 * a pair (one each for procs, tasks) for each pid namespace that's relevant
3765 struct cgroup_pidlist
{
3767 * used to find which pidlist is wanted. doesn't change as long as
3768 * this particular list stays in the list.
3770 struct { enum cgroup_filetype type
; struct pid_namespace
*ns
; } key
;
3773 /* how many elements the above list has */
3775 /* each of these stored in a list by its cgroup */
3776 struct list_head links
;
3777 /* pointer to the cgroup we belong to, for list removal purposes */
3778 struct cgroup
*owner
;
3779 /* for delayed destruction */
3780 struct delayed_work destroy_dwork
;
3784 * The following two functions "fix" the issue where there are more pids
3785 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3786 * TODO: replace with a kernel-wide solution to this problem
3788 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3789 static void *pidlist_allocate(int count
)
3791 if (PIDLIST_TOO_LARGE(count
))
3792 return vmalloc(count
* sizeof(pid_t
));
3794 return kmalloc(count
* sizeof(pid_t
), GFP_KERNEL
);
3797 static void pidlist_free(void *p
)
3803 * Used to destroy all pidlists lingering waiting for destroy timer. None
3804 * should be left afterwards.
3806 static void cgroup_pidlist_destroy_all(struct cgroup
*cgrp
)
3808 struct cgroup_pidlist
*l
, *tmp_l
;
3810 mutex_lock(&cgrp
->pidlist_mutex
);
3811 list_for_each_entry_safe(l
, tmp_l
, &cgrp
->pidlists
, links
)
3812 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
, 0);
3813 mutex_unlock(&cgrp
->pidlist_mutex
);
3815 flush_workqueue(cgroup_pidlist_destroy_wq
);
3816 BUG_ON(!list_empty(&cgrp
->pidlists
));
3819 static void cgroup_pidlist_destroy_work_fn(struct work_struct
*work
)
3821 struct delayed_work
*dwork
= to_delayed_work(work
);
3822 struct cgroup_pidlist
*l
= container_of(dwork
, struct cgroup_pidlist
,
3824 struct cgroup_pidlist
*tofree
= NULL
;
3826 mutex_lock(&l
->owner
->pidlist_mutex
);
3829 * Destroy iff we didn't get queued again. The state won't change
3830 * as destroy_dwork can only be queued while locked.
3832 if (!delayed_work_pending(dwork
)) {
3833 list_del(&l
->links
);
3834 pidlist_free(l
->list
);
3835 put_pid_ns(l
->key
.ns
);
3839 mutex_unlock(&l
->owner
->pidlist_mutex
);
3844 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3845 * Returns the number of unique elements.
3847 static int pidlist_uniq(pid_t
*list
, int length
)
3852 * we presume the 0th element is unique, so i starts at 1. trivial
3853 * edge cases first; no work needs to be done for either
3855 if (length
== 0 || length
== 1)
3857 /* src and dest walk down the list; dest counts unique elements */
3858 for (src
= 1; src
< length
; src
++) {
3859 /* find next unique element */
3860 while (list
[src
] == list
[src
-1]) {
3865 /* dest always points to where the next unique element goes */
3866 list
[dest
] = list
[src
];
3874 * The two pid files - task and cgroup.procs - guaranteed that the result
3875 * is sorted, which forced this whole pidlist fiasco. As pid order is
3876 * different per namespace, each namespace needs differently sorted list,
3877 * making it impossible to use, for example, single rbtree of member tasks
3878 * sorted by task pointer. As pidlists can be fairly large, allocating one
3879 * per open file is dangerous, so cgroup had to implement shared pool of
3880 * pidlists keyed by cgroup and namespace.
3882 * All this extra complexity was caused by the original implementation
3883 * committing to an entirely unnecessary property. In the long term, we
3884 * want to do away with it. Explicitly scramble sort order if on the
3885 * default hierarchy so that no such expectation exists in the new
3888 * Scrambling is done by swapping every two consecutive bits, which is
3889 * non-identity one-to-one mapping which disturbs sort order sufficiently.
3891 static pid_t
pid_fry(pid_t pid
)
3893 unsigned a
= pid
& 0x55555555;
3894 unsigned b
= pid
& 0xAAAAAAAA;
3896 return (a
<< 1) | (b
>> 1);
3899 static pid_t
cgroup_pid_fry(struct cgroup
*cgrp
, pid_t pid
)
3901 if (cgroup_on_dfl(cgrp
))
3902 return pid_fry(pid
);
3907 static int cmppid(const void *a
, const void *b
)
3909 return *(pid_t
*)a
- *(pid_t
*)b
;
3912 static int fried_cmppid(const void *a
, const void *b
)
3914 return pid_fry(*(pid_t
*)a
) - pid_fry(*(pid_t
*)b
);
3917 static struct cgroup_pidlist
*cgroup_pidlist_find(struct cgroup
*cgrp
,
3918 enum cgroup_filetype type
)
3920 struct cgroup_pidlist
*l
;
3921 /* don't need task_nsproxy() if we're looking at ourself */
3922 struct pid_namespace
*ns
= task_active_pid_ns(current
);
3924 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3926 list_for_each_entry(l
, &cgrp
->pidlists
, links
)
3927 if (l
->key
.type
== type
&& l
->key
.ns
== ns
)
3933 * find the appropriate pidlist for our purpose (given procs vs tasks)
3934 * returns with the lock on that pidlist already held, and takes care
3935 * of the use count, or returns NULL with no locks held if we're out of
3938 static struct cgroup_pidlist
*cgroup_pidlist_find_create(struct cgroup
*cgrp
,
3939 enum cgroup_filetype type
)
3941 struct cgroup_pidlist
*l
;
3943 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3945 l
= cgroup_pidlist_find(cgrp
, type
);
3949 /* entry not found; create a new one */
3950 l
= kzalloc(sizeof(struct cgroup_pidlist
), GFP_KERNEL
);
3954 INIT_DELAYED_WORK(&l
->destroy_dwork
, cgroup_pidlist_destroy_work_fn
);
3956 /* don't need task_nsproxy() if we're looking at ourself */
3957 l
->key
.ns
= get_pid_ns(task_active_pid_ns(current
));
3959 list_add(&l
->links
, &cgrp
->pidlists
);
3964 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3966 static int pidlist_array_load(struct cgroup
*cgrp
, enum cgroup_filetype type
,
3967 struct cgroup_pidlist
**lp
)
3971 int pid
, n
= 0; /* used for populating the array */
3972 struct css_task_iter it
;
3973 struct task_struct
*tsk
;
3974 struct cgroup_pidlist
*l
;
3976 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3979 * If cgroup gets more users after we read count, we won't have
3980 * enough space - tough. This race is indistinguishable to the
3981 * caller from the case that the additional cgroup users didn't
3982 * show up until sometime later on.
3984 length
= cgroup_task_count(cgrp
);
3985 array
= pidlist_allocate(length
);
3988 /* now, populate the array */
3989 css_task_iter_start(&cgrp
->self
, &it
);
3990 while ((tsk
= css_task_iter_next(&it
))) {
3991 if (unlikely(n
== length
))
3993 /* get tgid or pid for procs or tasks file respectively */
3994 if (type
== CGROUP_FILE_PROCS
)
3995 pid
= task_tgid_vnr(tsk
);
3997 pid
= task_pid_vnr(tsk
);
3998 if (pid
> 0) /* make sure to only use valid results */
4001 css_task_iter_end(&it
);
4003 /* now sort & (if procs) strip out duplicates */
4004 if (cgroup_on_dfl(cgrp
))
4005 sort(array
, length
, sizeof(pid_t
), fried_cmppid
, NULL
);
4007 sort(array
, length
, sizeof(pid_t
), cmppid
, NULL
);
4008 if (type
== CGROUP_FILE_PROCS
)
4009 length
= pidlist_uniq(array
, length
);
4011 l
= cgroup_pidlist_find_create(cgrp
, type
);
4013 pidlist_free(array
);
4017 /* store array, freeing old if necessary */
4018 pidlist_free(l
->list
);
4026 * cgroupstats_build - build and fill cgroupstats
4027 * @stats: cgroupstats to fill information into
4028 * @dentry: A dentry entry belonging to the cgroup for which stats have
4031 * Build and fill cgroupstats so that taskstats can export it to user
4034 int cgroupstats_build(struct cgroupstats
*stats
, struct dentry
*dentry
)
4036 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
4037 struct cgroup
*cgrp
;
4038 struct css_task_iter it
;
4039 struct task_struct
*tsk
;
4041 /* it should be kernfs_node belonging to cgroupfs and is a directory */
4042 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
4043 kernfs_type(kn
) != KERNFS_DIR
)
4046 mutex_lock(&cgroup_mutex
);
4049 * We aren't being called from kernfs and there's no guarantee on
4050 * @kn->priv's validity. For this and css_tryget_online_from_dir(),
4051 * @kn->priv is RCU safe. Let's do the RCU dancing.
4054 cgrp
= rcu_dereference(kn
->priv
);
4055 if (!cgrp
|| cgroup_is_dead(cgrp
)) {
4057 mutex_unlock(&cgroup_mutex
);
4062 css_task_iter_start(&cgrp
->self
, &it
);
4063 while ((tsk
= css_task_iter_next(&it
))) {
4064 switch (tsk
->state
) {
4066 stats
->nr_running
++;
4068 case TASK_INTERRUPTIBLE
:
4069 stats
->nr_sleeping
++;
4071 case TASK_UNINTERRUPTIBLE
:
4072 stats
->nr_uninterruptible
++;
4075 stats
->nr_stopped
++;
4078 if (delayacct_is_task_waiting_on_io(tsk
))
4079 stats
->nr_io_wait
++;
4083 css_task_iter_end(&it
);
4085 mutex_unlock(&cgroup_mutex
);
4091 * seq_file methods for the tasks/procs files. The seq_file position is the
4092 * next pid to display; the seq_file iterator is a pointer to the pid
4093 * in the cgroup->l->list array.
4096 static void *cgroup_pidlist_start(struct seq_file
*s
, loff_t
*pos
)
4099 * Initially we receive a position value that corresponds to
4100 * one more than the last pid shown (or 0 on the first call or
4101 * after a seek to the start). Use a binary-search to find the
4102 * next pid to display, if any
4104 struct kernfs_open_file
*of
= s
->private;
4105 struct cgroup
*cgrp
= seq_css(s
)->cgroup
;
4106 struct cgroup_pidlist
*l
;
4107 enum cgroup_filetype type
= seq_cft(s
)->private;
4108 int index
= 0, pid
= *pos
;
4111 mutex_lock(&cgrp
->pidlist_mutex
);
4114 * !NULL @of->priv indicates that this isn't the first start()
4115 * after open. If the matching pidlist is around, we can use that.
4116 * Look for it. Note that @of->priv can't be used directly. It
4117 * could already have been destroyed.
4120 of
->priv
= cgroup_pidlist_find(cgrp
, type
);
4123 * Either this is the first start() after open or the matching
4124 * pidlist has been destroyed inbetween. Create a new one.
4127 ret
= pidlist_array_load(cgrp
, type
,
4128 (struct cgroup_pidlist
**)&of
->priv
);
4130 return ERR_PTR(ret
);
4135 int end
= l
->length
;
4137 while (index
< end
) {
4138 int mid
= (index
+ end
) / 2;
4139 if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) == pid
) {
4142 } else if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) <= pid
)
4148 /* If we're off the end of the array, we're done */
4149 if (index
>= l
->length
)
4151 /* Update the abstract position to be the actual pid that we found */
4152 iter
= l
->list
+ index
;
4153 *pos
= cgroup_pid_fry(cgrp
, *iter
);
4157 static void cgroup_pidlist_stop(struct seq_file
*s
, void *v
)
4159 struct kernfs_open_file
*of
= s
->private;
4160 struct cgroup_pidlist
*l
= of
->priv
;
4163 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
,
4164 CGROUP_PIDLIST_DESTROY_DELAY
);
4165 mutex_unlock(&seq_css(s
)->cgroup
->pidlist_mutex
);
4168 static void *cgroup_pidlist_next(struct seq_file
*s
, void *v
, loff_t
*pos
)
4170 struct kernfs_open_file
*of
= s
->private;
4171 struct cgroup_pidlist
*l
= of
->priv
;
4173 pid_t
*end
= l
->list
+ l
->length
;
4175 * Advance to the next pid in the array. If this goes off the
4182 *pos
= cgroup_pid_fry(seq_css(s
)->cgroup
, *p
);
4187 static int cgroup_pidlist_show(struct seq_file
*s
, void *v
)
4189 seq_printf(s
, "%d\n", *(int *)v
);
4194 static u64
cgroup_read_notify_on_release(struct cgroup_subsys_state
*css
,
4197 return notify_on_release(css
->cgroup
);
4200 static int cgroup_write_notify_on_release(struct cgroup_subsys_state
*css
,
4201 struct cftype
*cft
, u64 val
)
4204 set_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
4206 clear_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
4210 static u64
cgroup_clone_children_read(struct cgroup_subsys_state
*css
,
4213 return test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4216 static int cgroup_clone_children_write(struct cgroup_subsys_state
*css
,
4217 struct cftype
*cft
, u64 val
)
4220 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4222 clear_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
4226 /* cgroup core interface files for the default hierarchy */
4227 static struct cftype cgroup_dfl_base_files
[] = {
4229 .name
= "cgroup.procs",
4230 .seq_start
= cgroup_pidlist_start
,
4231 .seq_next
= cgroup_pidlist_next
,
4232 .seq_stop
= cgroup_pidlist_stop
,
4233 .seq_show
= cgroup_pidlist_show
,
4234 .private = CGROUP_FILE_PROCS
,
4235 .write
= cgroup_procs_write
,
4236 .mode
= S_IRUGO
| S_IWUSR
,
4239 .name
= "cgroup.controllers",
4240 .flags
= CFTYPE_ONLY_ON_ROOT
,
4241 .seq_show
= cgroup_root_controllers_show
,
4244 .name
= "cgroup.controllers",
4245 .flags
= CFTYPE_NOT_ON_ROOT
,
4246 .seq_show
= cgroup_controllers_show
,
4249 .name
= "cgroup.subtree_control",
4250 .seq_show
= cgroup_subtree_control_show
,
4251 .write
= cgroup_subtree_control_write
,
4254 .name
= "cgroup.populated",
4255 .flags
= CFTYPE_NOT_ON_ROOT
,
4256 .seq_show
= cgroup_populated_show
,
4261 /* cgroup core interface files for the legacy hierarchies */
4262 static struct cftype cgroup_legacy_base_files
[] = {
4264 .name
= "cgroup.procs",
4265 .seq_start
= cgroup_pidlist_start
,
4266 .seq_next
= cgroup_pidlist_next
,
4267 .seq_stop
= cgroup_pidlist_stop
,
4268 .seq_show
= cgroup_pidlist_show
,
4269 .private = CGROUP_FILE_PROCS
,
4270 .write
= cgroup_procs_write
,
4271 .mode
= S_IRUGO
| S_IWUSR
,
4274 .name
= "cgroup.clone_children",
4275 .read_u64
= cgroup_clone_children_read
,
4276 .write_u64
= cgroup_clone_children_write
,
4279 .name
= "cgroup.sane_behavior",
4280 .flags
= CFTYPE_ONLY_ON_ROOT
,
4281 .seq_show
= cgroup_sane_behavior_show
,
4285 .seq_start
= cgroup_pidlist_start
,
4286 .seq_next
= cgroup_pidlist_next
,
4287 .seq_stop
= cgroup_pidlist_stop
,
4288 .seq_show
= cgroup_pidlist_show
,
4289 .private = CGROUP_FILE_TASKS
,
4290 .write
= cgroup_tasks_write
,
4291 .mode
= S_IRUGO
| S_IWUSR
,
4294 .name
= "notify_on_release",
4295 .read_u64
= cgroup_read_notify_on_release
,
4296 .write_u64
= cgroup_write_notify_on_release
,
4299 .name
= "release_agent",
4300 .flags
= CFTYPE_ONLY_ON_ROOT
,
4301 .seq_show
= cgroup_release_agent_show
,
4302 .write
= cgroup_release_agent_write
,
4303 .max_write_len
= PATH_MAX
- 1,
4309 * cgroup_populate_dir - create subsys files in a cgroup directory
4310 * @cgrp: target cgroup
4311 * @subsys_mask: mask of the subsystem ids whose files should be added
4313 * On failure, no file is added.
4315 static int cgroup_populate_dir(struct cgroup
*cgrp
, unsigned long subsys_mask
)
4317 struct cgroup_subsys
*ss
;
4320 /* process cftsets of each subsystem */
4321 for_each_subsys(ss
, i
) {
4322 struct cftype
*cfts
;
4324 if (!(subsys_mask
& (1 << i
)))
4327 list_for_each_entry(cfts
, &ss
->cfts
, node
) {
4328 ret
= cgroup_addrm_files(cgrp
, cfts
, true);
4335 cgroup_clear_dir(cgrp
, subsys_mask
);
4340 * css destruction is four-stage process.
4342 * 1. Destruction starts. Killing of the percpu_ref is initiated.
4343 * Implemented in kill_css().
4345 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
4346 * and thus css_tryget_online() is guaranteed to fail, the css can be
4347 * offlined by invoking offline_css(). After offlining, the base ref is
4348 * put. Implemented in css_killed_work_fn().
4350 * 3. When the percpu_ref reaches zero, the only possible remaining
4351 * accessors are inside RCU read sections. css_release() schedules the
4354 * 4. After the grace period, the css can be freed. Implemented in
4355 * css_free_work_fn().
4357 * It is actually hairier because both step 2 and 4 require process context
4358 * and thus involve punting to css->destroy_work adding two additional
4359 * steps to the already complex sequence.
4361 static void css_free_work_fn(struct work_struct
*work
)
4363 struct cgroup_subsys_state
*css
=
4364 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4365 struct cgroup_subsys
*ss
= css
->ss
;
4366 struct cgroup
*cgrp
= css
->cgroup
;
4368 percpu_ref_exit(&css
->refcnt
);
4375 css_put(css
->parent
);
4378 cgroup_idr_remove(&ss
->css_idr
, id
);
4381 /* cgroup free path */
4382 atomic_dec(&cgrp
->root
->nr_cgrps
);
4383 cgroup_pidlist_destroy_all(cgrp
);
4384 cancel_work_sync(&cgrp
->release_agent_work
);
4386 if (cgroup_parent(cgrp
)) {
4388 * We get a ref to the parent, and put the ref when
4389 * this cgroup is being freed, so it's guaranteed
4390 * that the parent won't be destroyed before its
4393 cgroup_put(cgroup_parent(cgrp
));
4394 kernfs_put(cgrp
->kn
);
4398 * This is root cgroup's refcnt reaching zero,
4399 * which indicates that the root should be
4402 cgroup_destroy_root(cgrp
->root
);
4407 static void css_free_rcu_fn(struct rcu_head
*rcu_head
)
4409 struct cgroup_subsys_state
*css
=
4410 container_of(rcu_head
, struct cgroup_subsys_state
, rcu_head
);
4412 INIT_WORK(&css
->destroy_work
, css_free_work_fn
);
4413 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4416 static void css_release_work_fn(struct work_struct
*work
)
4418 struct cgroup_subsys_state
*css
=
4419 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4420 struct cgroup_subsys
*ss
= css
->ss
;
4421 struct cgroup
*cgrp
= css
->cgroup
;
4423 mutex_lock(&cgroup_mutex
);
4425 css
->flags
|= CSS_RELEASED
;
4426 list_del_rcu(&css
->sibling
);
4429 /* css release path */
4430 cgroup_idr_replace(&ss
->css_idr
, NULL
, css
->id
);
4431 if (ss
->css_released
)
4432 ss
->css_released(css
);
4434 /* cgroup release path */
4435 cgroup_idr_remove(&cgrp
->root
->cgroup_idr
, cgrp
->id
);
4439 * There are two control paths which try to determine
4440 * cgroup from dentry without going through kernfs -
4441 * cgroupstats_build() and css_tryget_online_from_dir().
4442 * Those are supported by RCU protecting clearing of
4443 * cgrp->kn->priv backpointer.
4445 RCU_INIT_POINTER(*(void __rcu __force
**)&cgrp
->kn
->priv
, NULL
);
4448 mutex_unlock(&cgroup_mutex
);
4450 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
4453 static void css_release(struct percpu_ref
*ref
)
4455 struct cgroup_subsys_state
*css
=
4456 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
4458 INIT_WORK(&css
->destroy_work
, css_release_work_fn
);
4459 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4462 static void init_and_link_css(struct cgroup_subsys_state
*css
,
4463 struct cgroup_subsys
*ss
, struct cgroup
*cgrp
)
4465 lockdep_assert_held(&cgroup_mutex
);
4469 memset(css
, 0, sizeof(*css
));
4472 INIT_LIST_HEAD(&css
->sibling
);
4473 INIT_LIST_HEAD(&css
->children
);
4474 css
->serial_nr
= css_serial_nr_next
++;
4476 if (cgroup_parent(cgrp
)) {
4477 css
->parent
= cgroup_css(cgroup_parent(cgrp
), ss
);
4478 css_get(css
->parent
);
4481 BUG_ON(cgroup_css(cgrp
, ss
));
4484 /* invoke ->css_online() on a new CSS and mark it online if successful */
4485 static int online_css(struct cgroup_subsys_state
*css
)
4487 struct cgroup_subsys
*ss
= css
->ss
;
4490 lockdep_assert_held(&cgroup_mutex
);
4493 ret
= ss
->css_online(css
);
4495 css
->flags
|= CSS_ONLINE
;
4496 rcu_assign_pointer(css
->cgroup
->subsys
[ss
->id
], css
);
4501 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
4502 static void offline_css(struct cgroup_subsys_state
*css
)
4504 struct cgroup_subsys
*ss
= css
->ss
;
4506 lockdep_assert_held(&cgroup_mutex
);
4508 if (!(css
->flags
& CSS_ONLINE
))
4511 if (ss
->css_offline
)
4512 ss
->css_offline(css
);
4514 css
->flags
&= ~CSS_ONLINE
;
4515 RCU_INIT_POINTER(css
->cgroup
->subsys
[ss
->id
], NULL
);
4517 wake_up_all(&css
->cgroup
->offline_waitq
);
4521 * create_css - create a cgroup_subsys_state
4522 * @cgrp: the cgroup new css will be associated with
4523 * @ss: the subsys of new css
4524 * @visible: whether to create control knobs for the new css or not
4526 * Create a new css associated with @cgrp - @ss pair. On success, the new
4527 * css is online and installed in @cgrp with all interface files created if
4528 * @visible. Returns 0 on success, -errno on failure.
4530 static int create_css(struct cgroup
*cgrp
, struct cgroup_subsys
*ss
,
4533 struct cgroup
*parent
= cgroup_parent(cgrp
);
4534 struct cgroup_subsys_state
*parent_css
= cgroup_css(parent
, ss
);
4535 struct cgroup_subsys_state
*css
;
4538 lockdep_assert_held(&cgroup_mutex
);
4540 css
= ss
->css_alloc(parent_css
);
4542 return PTR_ERR(css
);
4544 init_and_link_css(css
, ss
, cgrp
);
4546 err
= percpu_ref_init(&css
->refcnt
, css_release
, 0, GFP_KERNEL
);
4550 err
= cgroup_idr_alloc(&ss
->css_idr
, NULL
, 2, 0, GFP_NOWAIT
);
4552 goto err_free_percpu_ref
;
4556 err
= cgroup_populate_dir(cgrp
, 1 << ss
->id
);
4561 /* @css is ready to be brought online now, make it visible */
4562 list_add_tail_rcu(&css
->sibling
, &parent_css
->children
);
4563 cgroup_idr_replace(&ss
->css_idr
, css
, css
->id
);
4565 err
= online_css(css
);
4569 if (ss
->broken_hierarchy
&& !ss
->warned_broken_hierarchy
&&
4570 cgroup_parent(parent
)) {
4571 pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
4572 current
->comm
, current
->pid
, ss
->name
);
4573 if (!strcmp(ss
->name
, "memory"))
4574 pr_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n");
4575 ss
->warned_broken_hierarchy
= true;
4581 list_del_rcu(&css
->sibling
);
4582 cgroup_clear_dir(css
->cgroup
, 1 << css
->ss
->id
);
4584 cgroup_idr_remove(&ss
->css_idr
, css
->id
);
4585 err_free_percpu_ref
:
4586 percpu_ref_exit(&css
->refcnt
);
4588 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
4592 static int cgroup_mkdir(struct kernfs_node
*parent_kn
, const char *name
,
4595 struct cgroup
*parent
, *cgrp
;
4596 struct cgroup_root
*root
;
4597 struct cgroup_subsys
*ss
;
4598 struct kernfs_node
*kn
;
4599 struct cftype
*base_files
;
4602 /* Do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable.
4604 if (strchr(name
, '\n'))
4607 parent
= cgroup_kn_lock_live(parent_kn
);
4610 root
= parent
->root
;
4612 /* allocate the cgroup and its ID, 0 is reserved for the root */
4613 cgrp
= kzalloc(sizeof(*cgrp
), GFP_KERNEL
);
4619 ret
= percpu_ref_init(&cgrp
->self
.refcnt
, css_release
, 0, GFP_KERNEL
);
4624 * Temporarily set the pointer to NULL, so idr_find() won't return
4625 * a half-baked cgroup.
4627 cgrp
->id
= cgroup_idr_alloc(&root
->cgroup_idr
, NULL
, 2, 0, GFP_NOWAIT
);
4630 goto out_cancel_ref
;
4633 init_cgroup_housekeeping(cgrp
);
4635 cgrp
->self
.parent
= &parent
->self
;
4638 if (notify_on_release(parent
))
4639 set_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
4641 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &parent
->flags
))
4642 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &cgrp
->flags
);
4644 /* create the directory */
4645 kn
= kernfs_create_dir(parent
->kn
, name
, mode
, cgrp
);
4653 * This extra ref will be put in cgroup_free_fn() and guarantees
4654 * that @cgrp->kn is always accessible.
4658 cgrp
->self
.serial_nr
= css_serial_nr_next
++;
4660 /* allocation complete, commit to creation */
4661 list_add_tail_rcu(&cgrp
->self
.sibling
, &cgroup_parent(cgrp
)->self
.children
);
4662 atomic_inc(&root
->nr_cgrps
);
4666 * @cgrp is now fully operational. If something fails after this
4667 * point, it'll be released via the normal destruction path.
4669 cgroup_idr_replace(&root
->cgroup_idr
, cgrp
, cgrp
->id
);
4671 ret
= cgroup_kn_set_ugid(kn
);
4675 if (cgroup_on_dfl(cgrp
))
4676 base_files
= cgroup_dfl_base_files
;
4678 base_files
= cgroup_legacy_base_files
;
4680 ret
= cgroup_addrm_files(cgrp
, base_files
, true);
4684 /* let's create and online css's */
4685 for_each_subsys(ss
, ssid
) {
4686 if (parent
->child_subsys_mask
& (1 << ssid
)) {
4687 ret
= create_css(cgrp
, ss
,
4688 parent
->subtree_control
& (1 << ssid
));
4695 * On the default hierarchy, a child doesn't automatically inherit
4696 * subtree_control from the parent. Each is configured manually.
4698 if (!cgroup_on_dfl(cgrp
)) {
4699 cgrp
->subtree_control
= parent
->subtree_control
;
4700 cgroup_refresh_child_subsys_mask(cgrp
);
4703 kernfs_activate(kn
);
4709 cgroup_idr_remove(&root
->cgroup_idr
, cgrp
->id
);
4711 percpu_ref_exit(&cgrp
->self
.refcnt
);
4715 cgroup_kn_unlock(parent_kn
);
4719 cgroup_destroy_locked(cgrp
);
4724 * This is called when the refcnt of a css is confirmed to be killed.
4725 * css_tryget_online() is now guaranteed to fail. Tell the subsystem to
4726 * initate destruction and put the css ref from kill_css().
4728 static void css_killed_work_fn(struct work_struct
*work
)
4730 struct cgroup_subsys_state
*css
=
4731 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
4733 mutex_lock(&cgroup_mutex
);
4735 mutex_unlock(&cgroup_mutex
);
4740 /* css kill confirmation processing requires process context, bounce */
4741 static void css_killed_ref_fn(struct percpu_ref
*ref
)
4743 struct cgroup_subsys_state
*css
=
4744 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
4746 INIT_WORK(&css
->destroy_work
, css_killed_work_fn
);
4747 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
4751 * kill_css - destroy a css
4752 * @css: css to destroy
4754 * This function initiates destruction of @css by removing cgroup interface
4755 * files and putting its base reference. ->css_offline() will be invoked
4756 * asynchronously once css_tryget_online() is guaranteed to fail and when
4757 * the reference count reaches zero, @css will be released.
4759 static void kill_css(struct cgroup_subsys_state
*css
)
4761 lockdep_assert_held(&cgroup_mutex
);
4764 * This must happen before css is disassociated with its cgroup.
4765 * See seq_css() for details.
4767 cgroup_clear_dir(css
->cgroup
, 1 << css
->ss
->id
);
4770 * Killing would put the base ref, but we need to keep it alive
4771 * until after ->css_offline().
4776 * cgroup core guarantees that, by the time ->css_offline() is
4777 * invoked, no new css reference will be given out via
4778 * css_tryget_online(). We can't simply call percpu_ref_kill() and
4779 * proceed to offlining css's because percpu_ref_kill() doesn't
4780 * guarantee that the ref is seen as killed on all CPUs on return.
4782 * Use percpu_ref_kill_and_confirm() to get notifications as each
4783 * css is confirmed to be seen as killed on all CPUs.
4785 percpu_ref_kill_and_confirm(&css
->refcnt
, css_killed_ref_fn
);
4789 * cgroup_destroy_locked - the first stage of cgroup destruction
4790 * @cgrp: cgroup to be destroyed
4792 * css's make use of percpu refcnts whose killing latency shouldn't be
4793 * exposed to userland and are RCU protected. Also, cgroup core needs to
4794 * guarantee that css_tryget_online() won't succeed by the time
4795 * ->css_offline() is invoked. To satisfy all the requirements,
4796 * destruction is implemented in the following two steps.
4798 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
4799 * userland visible parts and start killing the percpu refcnts of
4800 * css's. Set up so that the next stage will be kicked off once all
4801 * the percpu refcnts are confirmed to be killed.
4803 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
4804 * rest of destruction. Once all cgroup references are gone, the
4805 * cgroup is RCU-freed.
4807 * This function implements s1. After this step, @cgrp is gone as far as
4808 * the userland is concerned and a new cgroup with the same name may be
4809 * created. As cgroup doesn't care about the names internally, this
4810 * doesn't cause any problem.
4812 static int cgroup_destroy_locked(struct cgroup
*cgrp
)
4813 __releases(&cgroup_mutex
) __acquires(&cgroup_mutex
)
4815 struct cgroup_subsys_state
*css
;
4819 lockdep_assert_held(&cgroup_mutex
);
4822 * css_set_rwsem synchronizes access to ->cset_links and prevents
4823 * @cgrp from being removed while put_css_set() is in progress.
4825 down_read(&css_set_rwsem
);
4826 empty
= list_empty(&cgrp
->cset_links
);
4827 up_read(&css_set_rwsem
);
4832 * Make sure there's no live children. We can't test emptiness of
4833 * ->self.children as dead children linger on it while being
4834 * drained; otherwise, "rmdir parent/child parent" may fail.
4836 if (css_has_online_children(&cgrp
->self
))
4840 * Mark @cgrp dead. This prevents further task migration and child
4841 * creation by disabling cgroup_lock_live_group().
4843 cgrp
->self
.flags
&= ~CSS_ONLINE
;
4845 /* initiate massacre of all css's */
4846 for_each_css(css
, ssid
, cgrp
)
4850 * Remove @cgrp directory along with the base files. @cgrp has an
4851 * extra ref on its kn.
4853 kernfs_remove(cgrp
->kn
);
4855 check_for_release(cgroup_parent(cgrp
));
4857 /* put the base reference */
4858 percpu_ref_kill(&cgrp
->self
.refcnt
);
4863 static int cgroup_rmdir(struct kernfs_node
*kn
)
4865 struct cgroup
*cgrp
;
4868 cgrp
= cgroup_kn_lock_live(kn
);
4872 ret
= cgroup_destroy_locked(cgrp
);
4874 cgroup_kn_unlock(kn
);
4878 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
= {
4879 .remount_fs
= cgroup_remount
,
4880 .show_options
= cgroup_show_options
,
4881 .mkdir
= cgroup_mkdir
,
4882 .rmdir
= cgroup_rmdir
,
4883 .rename
= cgroup_rename
,
4886 static void __init
cgroup_init_subsys(struct cgroup_subsys
*ss
, bool early
)
4888 struct cgroup_subsys_state
*css
;
4890 printk(KERN_INFO
"Initializing cgroup subsys %s\n", ss
->name
);
4892 mutex_lock(&cgroup_mutex
);
4894 idr_init(&ss
->css_idr
);
4895 INIT_LIST_HEAD(&ss
->cfts
);
4897 /* Create the root cgroup state for this subsystem */
4898 ss
->root
= &cgrp_dfl_root
;
4899 css
= ss
->css_alloc(cgroup_css(&cgrp_dfl_root
.cgrp
, ss
));
4900 /* We don't handle early failures gracefully */
4901 BUG_ON(IS_ERR(css
));
4902 init_and_link_css(css
, ss
, &cgrp_dfl_root
.cgrp
);
4905 * Root csses are never destroyed and we can't initialize
4906 * percpu_ref during early init. Disable refcnting.
4908 css
->flags
|= CSS_NO_REF
;
4911 /* allocation can't be done safely during early init */
4914 css
->id
= cgroup_idr_alloc(&ss
->css_idr
, css
, 1, 2, GFP_KERNEL
);
4915 BUG_ON(css
->id
< 0);
4918 /* Update the init_css_set to contain a subsys
4919 * pointer to this state - since the subsystem is
4920 * newly registered, all tasks and hence the
4921 * init_css_set is in the subsystem's root cgroup. */
4922 init_css_set
.subsys
[ss
->id
] = css
;
4924 have_fork_callback
|= (bool)ss
->fork
<< ss
->id
;
4925 have_exit_callback
|= (bool)ss
->exit
<< ss
->id
;
4927 /* At system boot, before all subsystems have been
4928 * registered, no tasks have been forked, so we don't
4929 * need to invoke fork callbacks here. */
4930 BUG_ON(!list_empty(&init_task
.tasks
));
4932 BUG_ON(online_css(css
));
4934 mutex_unlock(&cgroup_mutex
);
4938 * cgroup_init_early - cgroup initialization at system boot
4940 * Initialize cgroups at system boot, and initialize any
4941 * subsystems that request early init.
4943 int __init
cgroup_init_early(void)
4945 static struct cgroup_sb_opts __initdata opts
;
4946 struct cgroup_subsys
*ss
;
4949 init_cgroup_root(&cgrp_dfl_root
, &opts
);
4950 cgrp_dfl_root
.cgrp
.self
.flags
|= CSS_NO_REF
;
4952 RCU_INIT_POINTER(init_task
.cgroups
, &init_css_set
);
4954 for_each_subsys(ss
, i
) {
4955 WARN(!ss
->css_alloc
|| !ss
->css_free
|| ss
->name
|| ss
->id
,
4956 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
4957 i
, cgroup_subsys_name
[i
], ss
->css_alloc
, ss
->css_free
,
4959 WARN(strlen(cgroup_subsys_name
[i
]) > MAX_CGROUP_TYPE_NAMELEN
,
4960 "cgroup_subsys_name %s too long\n", cgroup_subsys_name
[i
]);
4963 ss
->name
= cgroup_subsys_name
[i
];
4966 cgroup_init_subsys(ss
, true);
4972 * cgroup_init - cgroup initialization
4974 * Register cgroup filesystem and /proc file, and initialize
4975 * any subsystems that didn't request early init.
4977 int __init
cgroup_init(void)
4979 struct cgroup_subsys
*ss
;
4983 BUG_ON(percpu_init_rwsem(&cgroup_threadgroup_rwsem
));
4984 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_dfl_base_files
));
4985 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_legacy_base_files
));
4987 mutex_lock(&cgroup_mutex
);
4989 /* Add init_css_set to the hash table */
4990 key
= css_set_hash(init_css_set
.subsys
);
4991 hash_add(css_set_table
, &init_css_set
.hlist
, key
);
4993 BUG_ON(cgroup_setup_root(&cgrp_dfl_root
, 0));
4995 mutex_unlock(&cgroup_mutex
);
4997 for_each_subsys(ss
, ssid
) {
4998 if (ss
->early_init
) {
4999 struct cgroup_subsys_state
*css
=
5000 init_css_set
.subsys
[ss
->id
];
5002 css
->id
= cgroup_idr_alloc(&ss
->css_idr
, css
, 1, 2,
5004 BUG_ON(css
->id
< 0);
5006 cgroup_init_subsys(ss
, false);
5009 list_add_tail(&init_css_set
.e_cset_node
[ssid
],
5010 &cgrp_dfl_root
.cgrp
.e_csets
[ssid
]);
5013 * Setting dfl_root subsys_mask needs to consider the
5014 * disabled flag and cftype registration needs kmalloc,
5015 * both of which aren't available during early_init.
5020 cgrp_dfl_root
.subsys_mask
|= 1 << ss
->id
;
5022 if (cgroup_legacy_files_on_dfl
&& !ss
->dfl_cftypes
)
5023 ss
->dfl_cftypes
= ss
->legacy_cftypes
;
5025 if (!ss
->dfl_cftypes
)
5026 cgrp_dfl_root_inhibit_ss_mask
|= 1 << ss
->id
;
5028 if (ss
->dfl_cftypes
== ss
->legacy_cftypes
) {
5029 WARN_ON(cgroup_add_cftypes(ss
, ss
->dfl_cftypes
));
5031 WARN_ON(cgroup_add_dfl_cftypes(ss
, ss
->dfl_cftypes
));
5032 WARN_ON(cgroup_add_legacy_cftypes(ss
, ss
->legacy_cftypes
));
5036 ss
->bind(init_css_set
.subsys
[ssid
]);
5039 cgroup_kobj
= kobject_create_and_add("cgroup", fs_kobj
);
5043 err
= register_filesystem(&cgroup_fs_type
);
5045 kobject_put(cgroup_kobj
);
5049 proc_create("cgroups", 0, NULL
, &proc_cgroupstats_operations
);
5053 static int __init
cgroup_wq_init(void)
5056 * There isn't much point in executing destruction path in
5057 * parallel. Good chunk is serialized with cgroup_mutex anyway.
5058 * Use 1 for @max_active.
5060 * We would prefer to do this in cgroup_init() above, but that
5061 * is called before init_workqueues(): so leave this until after.
5063 cgroup_destroy_wq
= alloc_workqueue("cgroup_destroy", 0, 1);
5064 BUG_ON(!cgroup_destroy_wq
);
5067 * Used to destroy pidlists and separate to serve as flush domain.
5068 * Cap @max_active to 1 too.
5070 cgroup_pidlist_destroy_wq
= alloc_workqueue("cgroup_pidlist_destroy",
5072 BUG_ON(!cgroup_pidlist_destroy_wq
);
5076 core_initcall(cgroup_wq_init
);
5079 * proc_cgroup_show()
5080 * - Print task's cgroup paths into seq_file, one line for each hierarchy
5081 * - Used for /proc/<pid>/cgroup.
5083 int proc_cgroup_show(struct seq_file
*m
, struct pid_namespace
*ns
,
5084 struct pid
*pid
, struct task_struct
*tsk
)
5088 struct cgroup_root
*root
;
5091 buf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
5095 mutex_lock(&cgroup_mutex
);
5096 down_read(&css_set_rwsem
);
5098 for_each_root(root
) {
5099 struct cgroup_subsys
*ss
;
5100 struct cgroup
*cgrp
;
5101 int ssid
, count
= 0;
5103 if (root
== &cgrp_dfl_root
&& !cgrp_dfl_root_visible
)
5106 seq_printf(m
, "%d:", root
->hierarchy_id
);
5107 for_each_subsys(ss
, ssid
)
5108 if (root
->subsys_mask
& (1 << ssid
))
5109 seq_printf(m
, "%s%s", count
++ ? "," : "", ss
->name
);
5110 if (strlen(root
->name
))
5111 seq_printf(m
, "%sname=%s", count
? "," : "",
5114 cgrp
= task_cgroup_from_root(tsk
, root
);
5115 path
= cgroup_path(cgrp
, buf
, PATH_MAX
);
5117 retval
= -ENAMETOOLONG
;
5126 up_read(&css_set_rwsem
);
5127 mutex_unlock(&cgroup_mutex
);
5133 /* Display information about each subsystem and each hierarchy */
5134 static int proc_cgroupstats_show(struct seq_file
*m
, void *v
)
5136 struct cgroup_subsys
*ss
;
5139 seq_puts(m
, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
5141 * ideally we don't want subsystems moving around while we do this.
5142 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
5143 * subsys/hierarchy state.
5145 mutex_lock(&cgroup_mutex
);
5147 for_each_subsys(ss
, i
)
5148 seq_printf(m
, "%s\t%d\t%d\t%d\n",
5149 ss
->name
, ss
->root
->hierarchy_id
,
5150 atomic_read(&ss
->root
->nr_cgrps
), !ss
->disabled
);
5152 mutex_unlock(&cgroup_mutex
);
5156 static int cgroupstats_open(struct inode
*inode
, struct file
*file
)
5158 return single_open(file
, proc_cgroupstats_show
, NULL
);
5161 static const struct file_operations proc_cgroupstats_operations
= {
5162 .open
= cgroupstats_open
,
5164 .llseek
= seq_lseek
,
5165 .release
= single_release
,
5169 * cgroup_fork - initialize cgroup related fields during copy_process()
5170 * @child: pointer to task_struct of forking parent process.
5172 * A task is associated with the init_css_set until cgroup_post_fork()
5173 * attaches it to the parent's css_set. Empty cg_list indicates that
5174 * @child isn't holding reference to its css_set.
5176 void cgroup_fork(struct task_struct
*child
)
5178 RCU_INIT_POINTER(child
->cgroups
, &init_css_set
);
5179 INIT_LIST_HEAD(&child
->cg_list
);
5183 * cgroup_post_fork - called on a new task after adding it to the task list
5184 * @child: the task in question
5186 * Adds the task to the list running through its css_set if necessary and
5187 * call the subsystem fork() callbacks. Has to be after the task is
5188 * visible on the task list in case we race with the first call to
5189 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
5192 void cgroup_post_fork(struct task_struct
*child
)
5194 struct cgroup_subsys
*ss
;
5198 * This may race against cgroup_enable_task_cg_lists(). As that
5199 * function sets use_task_css_set_links before grabbing
5200 * tasklist_lock and we just went through tasklist_lock to add
5201 * @child, it's guaranteed that either we see the set
5202 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
5203 * @child during its iteration.
5205 * If we won the race, @child is associated with %current's
5206 * css_set. Grabbing css_set_rwsem guarantees both that the
5207 * association is stable, and, on completion of the parent's
5208 * migration, @child is visible in the source of migration or
5209 * already in the destination cgroup. This guarantee is necessary
5210 * when implementing operations which need to migrate all tasks of
5211 * a cgroup to another.
5213 * Note that if we lose to cgroup_enable_task_cg_lists(), @child
5214 * will remain in init_css_set. This is safe because all tasks are
5215 * in the init_css_set before cg_links is enabled and there's no
5216 * operation which transfers all tasks out of init_css_set.
5218 if (use_task_css_set_links
) {
5219 struct css_set
*cset
;
5221 down_write(&css_set_rwsem
);
5222 cset
= task_css_set(current
);
5223 if (list_empty(&child
->cg_list
)) {
5224 rcu_assign_pointer(child
->cgroups
, cset
);
5225 list_add(&child
->cg_list
, &cset
->tasks
);
5228 up_write(&css_set_rwsem
);
5232 * Call ss->fork(). This must happen after @child is linked on
5233 * css_set; otherwise, @child might change state between ->fork()
5234 * and addition to css_set.
5236 for_each_subsys_which(ss
, i
, &have_fork_callback
)
5241 * cgroup_exit - detach cgroup from exiting task
5242 * @tsk: pointer to task_struct of exiting process
5244 * Description: Detach cgroup from @tsk and release it.
5246 * Note that cgroups marked notify_on_release force every task in
5247 * them to take the global cgroup_mutex mutex when exiting.
5248 * This could impact scaling on very large systems. Be reluctant to
5249 * use notify_on_release cgroups where very high task exit scaling
5250 * is required on large systems.
5252 * We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
5253 * call cgroup_exit() while the task is still competent to handle
5254 * notify_on_release(), then leave the task attached to the root cgroup in
5255 * each hierarchy for the remainder of its exit. No need to bother with
5256 * init_css_set refcnting. init_css_set never goes away and we can't race
5257 * with migration path - PF_EXITING is visible to migration path.
5259 void cgroup_exit(struct task_struct
*tsk
)
5261 struct cgroup_subsys
*ss
;
5262 struct css_set
*cset
;
5263 bool put_cset
= false;
5267 * Unlink from @tsk from its css_set. As migration path can't race
5268 * with us, we can check cg_list without grabbing css_set_rwsem.
5270 if (!list_empty(&tsk
->cg_list
)) {
5271 down_write(&css_set_rwsem
);
5272 list_del_init(&tsk
->cg_list
);
5273 up_write(&css_set_rwsem
);
5277 /* Reassign the task to the init_css_set. */
5278 cset
= task_css_set(tsk
);
5279 RCU_INIT_POINTER(tsk
->cgroups
, &init_css_set
);
5281 /* see cgroup_post_fork() for details */
5282 for_each_subsys_which(ss
, i
, &have_exit_callback
) {
5283 struct cgroup_subsys_state
*old_css
= cset
->subsys
[i
];
5284 struct cgroup_subsys_state
*css
= task_css(tsk
, i
);
5286 ss
->exit(css
, old_css
, tsk
);
5293 static void check_for_release(struct cgroup
*cgrp
)
5295 if (notify_on_release(cgrp
) && !cgroup_has_tasks(cgrp
) &&
5296 !css_has_online_children(&cgrp
->self
) && !cgroup_is_dead(cgrp
))
5297 schedule_work(&cgrp
->release_agent_work
);
5301 * Notify userspace when a cgroup is released, by running the
5302 * configured release agent with the name of the cgroup (path
5303 * relative to the root of cgroup file system) as the argument.
5305 * Most likely, this user command will try to rmdir this cgroup.
5307 * This races with the possibility that some other task will be
5308 * attached to this cgroup before it is removed, or that some other
5309 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
5310 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
5311 * unused, and this cgroup will be reprieved from its death sentence,
5312 * to continue to serve a useful existence. Next time it's released,
5313 * we will get notified again, if it still has 'notify_on_release' set.
5315 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
5316 * means only wait until the task is successfully execve()'d. The
5317 * separate release agent task is forked by call_usermodehelper(),
5318 * then control in this thread returns here, without waiting for the
5319 * release agent task. We don't bother to wait because the caller of
5320 * this routine has no use for the exit status of the release agent
5321 * task, so no sense holding our caller up for that.
5323 static void cgroup_release_agent(struct work_struct
*work
)
5325 struct cgroup
*cgrp
=
5326 container_of(work
, struct cgroup
, release_agent_work
);
5327 char *pathbuf
= NULL
, *agentbuf
= NULL
, *path
;
5328 char *argv
[3], *envp
[3];
5330 mutex_lock(&cgroup_mutex
);
5332 pathbuf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
5333 agentbuf
= kstrdup(cgrp
->root
->release_agent_path
, GFP_KERNEL
);
5334 if (!pathbuf
|| !agentbuf
)
5337 path
= cgroup_path(cgrp
, pathbuf
, PATH_MAX
);
5345 /* minimal command environment */
5347 envp
[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
5350 mutex_unlock(&cgroup_mutex
);
5351 call_usermodehelper(argv
[0], argv
, envp
, UMH_WAIT_EXEC
);
5354 mutex_unlock(&cgroup_mutex
);
5360 static int __init
cgroup_disable(char *str
)
5362 struct cgroup_subsys
*ss
;
5366 while ((token
= strsep(&str
, ",")) != NULL
) {
5370 for_each_subsys(ss
, i
) {
5371 if (!strcmp(token
, ss
->name
)) {
5373 printk(KERN_INFO
"Disabling %s control group"
5374 " subsystem\n", ss
->name
);
5381 __setup("cgroup_disable=", cgroup_disable
);
5383 static int __init
cgroup_set_legacy_files_on_dfl(char *str
)
5385 printk("cgroup: using legacy files on the default hierarchy\n");
5386 cgroup_legacy_files_on_dfl
= true;
5389 __setup("cgroup__DEVEL__legacy_files_on_dfl", cgroup_set_legacy_files_on_dfl
);
5392 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
5393 * @dentry: directory dentry of interest
5394 * @ss: subsystem of interest
5396 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
5397 * to get the corresponding css and return it. If such css doesn't exist
5398 * or can't be pinned, an ERR_PTR value is returned.
5400 struct cgroup_subsys_state
*css_tryget_online_from_dir(struct dentry
*dentry
,
5401 struct cgroup_subsys
*ss
)
5403 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
5404 struct cgroup_subsys_state
*css
= NULL
;
5405 struct cgroup
*cgrp
;
5407 /* is @dentry a cgroup dir? */
5408 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
5409 kernfs_type(kn
) != KERNFS_DIR
)
5410 return ERR_PTR(-EBADF
);
5415 * This path doesn't originate from kernfs and @kn could already
5416 * have been or be removed at any point. @kn->priv is RCU
5417 * protected for this access. See css_release_work_fn() for details.
5419 cgrp
= rcu_dereference(kn
->priv
);
5421 css
= cgroup_css(cgrp
, ss
);
5423 if (!css
|| !css_tryget_online(css
))
5424 css
= ERR_PTR(-ENOENT
);
5431 * css_from_id - lookup css by id
5432 * @id: the cgroup id
5433 * @ss: cgroup subsys to be looked into
5435 * Returns the css if there's valid one with @id, otherwise returns NULL.
5436 * Should be called under rcu_read_lock().
5438 struct cgroup_subsys_state
*css_from_id(int id
, struct cgroup_subsys
*ss
)
5440 WARN_ON_ONCE(!rcu_read_lock_held());
5441 return id
> 0 ? idr_find(&ss
->css_idr
, id
) : NULL
;
5444 #ifdef CONFIG_CGROUP_DEBUG
5445 static struct cgroup_subsys_state
*
5446 debug_css_alloc(struct cgroup_subsys_state
*parent_css
)
5448 struct cgroup_subsys_state
*css
= kzalloc(sizeof(*css
), GFP_KERNEL
);
5451 return ERR_PTR(-ENOMEM
);
5456 static void debug_css_free(struct cgroup_subsys_state
*css
)
5461 static u64
debug_taskcount_read(struct cgroup_subsys_state
*css
,
5464 return cgroup_task_count(css
->cgroup
);
5467 static u64
current_css_set_read(struct cgroup_subsys_state
*css
,
5470 return (u64
)(unsigned long)current
->cgroups
;
5473 static u64
current_css_set_refcount_read(struct cgroup_subsys_state
*css
,
5479 count
= atomic_read(&task_css_set(current
)->refcount
);
5484 static int current_css_set_cg_links_read(struct seq_file
*seq
, void *v
)
5486 struct cgrp_cset_link
*link
;
5487 struct css_set
*cset
;
5490 name_buf
= kmalloc(NAME_MAX
+ 1, GFP_KERNEL
);
5494 down_read(&css_set_rwsem
);
5496 cset
= rcu_dereference(current
->cgroups
);
5497 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
5498 struct cgroup
*c
= link
->cgrp
;
5500 cgroup_name(c
, name_buf
, NAME_MAX
+ 1);
5501 seq_printf(seq
, "Root %d group %s\n",
5502 c
->root
->hierarchy_id
, name_buf
);
5505 up_read(&css_set_rwsem
);
5510 #define MAX_TASKS_SHOWN_PER_CSS 25
5511 static int cgroup_css_links_read(struct seq_file
*seq
, void *v
)
5513 struct cgroup_subsys_state
*css
= seq_css(seq
);
5514 struct cgrp_cset_link
*link
;
5516 down_read(&css_set_rwsem
);
5517 list_for_each_entry(link
, &css
->cgroup
->cset_links
, cset_link
) {
5518 struct css_set
*cset
= link
->cset
;
5519 struct task_struct
*task
;
5522 seq_printf(seq
, "css_set %p\n", cset
);
5524 list_for_each_entry(task
, &cset
->tasks
, cg_list
) {
5525 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
5527 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
5530 list_for_each_entry(task
, &cset
->mg_tasks
, cg_list
) {
5531 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
5533 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
5537 seq_puts(seq
, " ...\n");
5539 up_read(&css_set_rwsem
);
5543 static u64
releasable_read(struct cgroup_subsys_state
*css
, struct cftype
*cft
)
5545 return (!cgroup_has_tasks(css
->cgroup
) &&
5546 !css_has_online_children(&css
->cgroup
->self
));
5549 static struct cftype debug_files
[] = {
5551 .name
= "taskcount",
5552 .read_u64
= debug_taskcount_read
,
5556 .name
= "current_css_set",
5557 .read_u64
= current_css_set_read
,
5561 .name
= "current_css_set_refcount",
5562 .read_u64
= current_css_set_refcount_read
,
5566 .name
= "current_css_set_cg_links",
5567 .seq_show
= current_css_set_cg_links_read
,
5571 .name
= "cgroup_css_links",
5572 .seq_show
= cgroup_css_links_read
,
5576 .name
= "releasable",
5577 .read_u64
= releasable_read
,
5583 struct cgroup_subsys debug_cgrp_subsys
= {
5584 .css_alloc
= debug_css_alloc
,
5585 .css_free
= debug_css_free
,
5586 .legacy_cftypes
= debug_files
,
5588 #endif /* CONFIG_CGROUP_DEBUG */