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 #include <linux/cgroup.h>
30 #include <linux/cred.h>
31 #include <linux/ctype.h>
32 #include <linux/errno.h>
33 #include <linux/init_task.h>
34 #include <linux/kernel.h>
35 #include <linux/list.h>
37 #include <linux/mutex.h>
38 #include <linux/mount.h>
39 #include <linux/pagemap.h>
40 #include <linux/proc_fs.h>
41 #include <linux/rcupdate.h>
42 #include <linux/sched.h>
43 #include <linux/slab.h>
44 #include <linux/spinlock.h>
45 #include <linux/rwsem.h>
46 #include <linux/string.h>
47 #include <linux/sort.h>
48 #include <linux/kmod.h>
49 #include <linux/delayacct.h>
50 #include <linux/cgroupstats.h>
51 #include <linux/hashtable.h>
52 #include <linux/pid_namespace.h>
53 #include <linux/idr.h>
54 #include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
55 #include <linux/kthread.h>
56 #include <linux/delay.h>
58 #include <linux/atomic.h>
61 * pidlists linger the following amount before being destroyed. The goal
62 * is avoiding frequent destruction in the middle of consecutive read calls
63 * Expiring in the middle is a performance problem not a correctness one.
64 * 1 sec should be enough.
66 #define CGROUP_PIDLIST_DESTROY_DELAY HZ
68 #define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
72 * cgroup_tree_mutex nests above cgroup_mutex and protects cftypes, file
73 * creation/removal and hierarchy changing operations including cgroup
74 * creation, removal, css association and controller rebinding. This outer
75 * lock is needed mainly to resolve the circular dependency between kernfs
76 * active ref and cgroup_mutex. cgroup_tree_mutex nests above both.
78 static DEFINE_MUTEX(cgroup_tree_mutex
);
81 * cgroup_mutex is the master lock. Any modification to cgroup or its
82 * hierarchy must be performed while holding it.
84 * css_set_rwsem protects task->cgroups pointer, the list of css_set
85 * objects, and the chain of tasks off each css_set.
87 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
88 * cgroup.h can use them for lockdep annotations.
90 #ifdef CONFIG_PROVE_RCU
91 DEFINE_MUTEX(cgroup_mutex
);
92 DECLARE_RWSEM(css_set_rwsem
);
93 EXPORT_SYMBOL_GPL(cgroup_mutex
);
94 EXPORT_SYMBOL_GPL(css_set_rwsem
);
96 static DEFINE_MUTEX(cgroup_mutex
);
97 static DECLARE_RWSEM(css_set_rwsem
);
101 * Protects cgroup_subsys->release_agent_path. Modifying it also requires
102 * cgroup_mutex. Reading requires either cgroup_mutex or this spinlock.
104 static DEFINE_SPINLOCK(release_agent_path_lock
);
106 #define cgroup_assert_mutexes_or_rcu_locked() \
107 rcu_lockdep_assert(rcu_read_lock_held() || \
108 lockdep_is_held(&cgroup_tree_mutex) || \
109 lockdep_is_held(&cgroup_mutex), \
110 "cgroup_[tree_]mutex or RCU read lock required");
113 * cgroup destruction makes heavy use of work items and there can be a lot
114 * of concurrent destructions. Use a separate workqueue so that cgroup
115 * destruction work items don't end up filling up max_active of system_wq
116 * which may lead to deadlock.
118 static struct workqueue_struct
*cgroup_destroy_wq
;
121 * pidlist destructions need to be flushed on cgroup destruction. Use a
122 * separate workqueue as flush domain.
124 static struct workqueue_struct
*cgroup_pidlist_destroy_wq
;
126 /* generate an array of cgroup subsystem pointers */
127 #define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
128 static struct cgroup_subsys
*cgroup_subsys
[] = {
129 #include <linux/cgroup_subsys.h>
133 /* array of cgroup subsystem names */
134 #define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
135 static const char *cgroup_subsys_name
[] = {
136 #include <linux/cgroup_subsys.h>
141 * The default hierarchy, reserved for the subsystems that are otherwise
142 * unattached - it never has more than a single cgroup, and all tasks are
143 * part of that cgroup.
145 struct cgroup_root cgrp_dfl_root
;
148 * The default hierarchy always exists but is hidden until mounted for the
149 * first time. This is for backward compatibility.
151 static bool cgrp_dfl_root_visible
;
153 /* The list of hierarchy roots */
155 static LIST_HEAD(cgroup_roots
);
156 static int cgroup_root_count
;
158 /* hierarchy ID allocation and mapping, protected by cgroup_mutex */
159 static DEFINE_IDR(cgroup_hierarchy_idr
);
162 * Assign a monotonically increasing serial number to cgroups. It
163 * guarantees cgroups with bigger numbers are newer than those with smaller
164 * numbers. Also, as cgroups are always appended to the parent's
165 * ->children list, it guarantees that sibling cgroups are always sorted in
166 * the ascending serial number order on the list. Protected by
169 static u64 cgroup_serial_nr_next
= 1;
171 /* This flag indicates whether tasks in the fork and exit paths should
172 * check for fork/exit handlers to call. This avoids us having to do
173 * extra work in the fork/exit path if none of the subsystems need to
176 static int need_forkexit_callback __read_mostly
;
178 static struct cftype cgroup_base_files
[];
180 static void cgroup_put(struct cgroup
*cgrp
);
181 static int rebind_subsystems(struct cgroup_root
*dst_root
,
182 unsigned long ss_mask
);
183 static void cgroup_destroy_css_killed(struct cgroup
*cgrp
);
184 static int cgroup_destroy_locked(struct cgroup
*cgrp
);
185 static int cgroup_addrm_files(struct cgroup
*cgrp
, struct cftype cfts
[],
187 static void cgroup_pidlist_destroy_all(struct cgroup
*cgrp
);
190 * cgroup_css - obtain a cgroup's css for the specified subsystem
191 * @cgrp: the cgroup of interest
192 * @ss: the subsystem of interest (%NULL returns the dummy_css)
194 * Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
195 * function must be called either under cgroup_mutex or rcu_read_lock() and
196 * the caller is responsible for pinning the returned css if it wants to
197 * keep accessing it outside the said locks. This function may return
198 * %NULL if @cgrp doesn't have @subsys_id enabled.
200 static struct cgroup_subsys_state
*cgroup_css(struct cgroup
*cgrp
,
201 struct cgroup_subsys
*ss
)
204 return rcu_dereference_check(cgrp
->subsys
[ss
->id
],
205 lockdep_is_held(&cgroup_tree_mutex
) ||
206 lockdep_is_held(&cgroup_mutex
));
208 return &cgrp
->dummy_css
;
211 /* convenient tests for these bits */
212 static inline bool cgroup_is_dead(const struct cgroup
*cgrp
)
214 return test_bit(CGRP_DEAD
, &cgrp
->flags
);
217 struct cgroup_subsys_state
*seq_css(struct seq_file
*seq
)
219 struct kernfs_open_file
*of
= seq
->private;
220 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
221 struct cftype
*cft
= seq_cft(seq
);
224 * This is open and unprotected implementation of cgroup_css().
225 * seq_css() is only called from a kernfs file operation which has
226 * an active reference on the file. Because all the subsystem
227 * files are drained before a css is disassociated with a cgroup,
228 * the matching css from the cgroup's subsys table is guaranteed to
229 * be and stay valid until the enclosing operation is complete.
232 return rcu_dereference_raw(cgrp
->subsys
[cft
->ss
->id
]);
234 return &cgrp
->dummy_css
;
236 EXPORT_SYMBOL_GPL(seq_css
);
239 * cgroup_is_descendant - test ancestry
240 * @cgrp: the cgroup to be tested
241 * @ancestor: possible ancestor of @cgrp
243 * Test whether @cgrp is a descendant of @ancestor. It also returns %true
244 * if @cgrp == @ancestor. This function is safe to call as long as @cgrp
245 * and @ancestor are accessible.
247 bool cgroup_is_descendant(struct cgroup
*cgrp
, struct cgroup
*ancestor
)
250 if (cgrp
== ancestor
)
257 static int cgroup_is_releasable(const struct cgroup
*cgrp
)
260 (1 << CGRP_RELEASABLE
) |
261 (1 << CGRP_NOTIFY_ON_RELEASE
);
262 return (cgrp
->flags
& bits
) == bits
;
265 static int notify_on_release(const struct cgroup
*cgrp
)
267 return test_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
271 * for_each_css - iterate all css's of a cgroup
272 * @css: the iteration cursor
273 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
274 * @cgrp: the target cgroup to iterate css's of
276 * Should be called under cgroup_mutex.
278 #define for_each_css(css, ssid, cgrp) \
279 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
280 if (!((css) = rcu_dereference_check( \
281 (cgrp)->subsys[(ssid)], \
282 lockdep_is_held(&cgroup_tree_mutex) || \
283 lockdep_is_held(&cgroup_mutex)))) { } \
287 * for_each_subsys - iterate all enabled cgroup subsystems
288 * @ss: the iteration cursor
289 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
291 #define for_each_subsys(ss, ssid) \
292 for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
293 (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
295 /* iterate across the hierarchies */
296 #define for_each_root(root) \
297 list_for_each_entry((root), &cgroup_roots, root_list)
300 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
301 * @cgrp: the cgroup to be checked for liveness
303 * On success, returns true; the mutex should be later unlocked. On
304 * failure returns false with no lock held.
306 static bool cgroup_lock_live_group(struct cgroup
*cgrp
)
308 mutex_lock(&cgroup_mutex
);
309 if (cgroup_is_dead(cgrp
)) {
310 mutex_unlock(&cgroup_mutex
);
316 /* the list of cgroups eligible for automatic release. Protected by
317 * release_list_lock */
318 static LIST_HEAD(release_list
);
319 static DEFINE_RAW_SPINLOCK(release_list_lock
);
320 static void cgroup_release_agent(struct work_struct
*work
);
321 static DECLARE_WORK(release_agent_work
, cgroup_release_agent
);
322 static void check_for_release(struct cgroup
*cgrp
);
325 * A cgroup can be associated with multiple css_sets as different tasks may
326 * belong to different cgroups on different hierarchies. In the other
327 * direction, a css_set is naturally associated with multiple cgroups.
328 * This M:N relationship is represented by the following link structure
329 * which exists for each association and allows traversing the associations
332 struct cgrp_cset_link
{
333 /* the cgroup and css_set this link associates */
335 struct css_set
*cset
;
337 /* list of cgrp_cset_links anchored at cgrp->cset_links */
338 struct list_head cset_link
;
340 /* list of cgrp_cset_links anchored at css_set->cgrp_links */
341 struct list_head cgrp_link
;
345 * The default css_set - used by init and its children prior to any
346 * hierarchies being mounted. It contains a pointer to the root state
347 * for each subsystem. Also used to anchor the list of css_sets. Not
348 * reference-counted, to improve performance when child cgroups
349 * haven't been created.
351 static struct css_set init_css_set
= {
352 .refcount
= ATOMIC_INIT(1),
353 .cgrp_links
= LIST_HEAD_INIT(init_css_set
.cgrp_links
),
354 .tasks
= LIST_HEAD_INIT(init_css_set
.tasks
),
355 .mg_tasks
= LIST_HEAD_INIT(init_css_set
.mg_tasks
),
356 .mg_preload_node
= LIST_HEAD_INIT(init_css_set
.mg_preload_node
),
357 .mg_node
= LIST_HEAD_INIT(init_css_set
.mg_node
),
360 static int css_set_count
= 1; /* 1 for init_css_set */
363 * hash table for cgroup groups. This improves the performance to find
364 * an existing css_set. This hash doesn't (currently) take into
365 * account cgroups in empty hierarchies.
367 #define CSS_SET_HASH_BITS 7
368 static DEFINE_HASHTABLE(css_set_table
, CSS_SET_HASH_BITS
);
370 static unsigned long css_set_hash(struct cgroup_subsys_state
*css
[])
372 unsigned long key
= 0UL;
373 struct cgroup_subsys
*ss
;
376 for_each_subsys(ss
, i
)
377 key
+= (unsigned long)css
[i
];
378 key
= (key
>> 16) ^ key
;
383 static void put_css_set_locked(struct css_set
*cset
, bool taskexit
)
385 struct cgrp_cset_link
*link
, *tmp_link
;
387 lockdep_assert_held(&css_set_rwsem
);
389 if (!atomic_dec_and_test(&cset
->refcount
))
392 /* This css_set is dead. unlink it and release cgroup refcounts */
393 hash_del(&cset
->hlist
);
396 list_for_each_entry_safe(link
, tmp_link
, &cset
->cgrp_links
, cgrp_link
) {
397 struct cgroup
*cgrp
= link
->cgrp
;
399 list_del(&link
->cset_link
);
400 list_del(&link
->cgrp_link
);
402 /* @cgrp can't go away while we're holding css_set_rwsem */
403 if (list_empty(&cgrp
->cset_links
) && notify_on_release(cgrp
)) {
405 set_bit(CGRP_RELEASABLE
, &cgrp
->flags
);
406 check_for_release(cgrp
);
412 kfree_rcu(cset
, rcu_head
);
415 static void put_css_set(struct css_set
*cset
, bool taskexit
)
418 * Ensure that the refcount doesn't hit zero while any readers
419 * can see it. Similar to atomic_dec_and_lock(), but for an
422 if (atomic_add_unless(&cset
->refcount
, -1, 1))
425 down_write(&css_set_rwsem
);
426 put_css_set_locked(cset
, taskexit
);
427 up_write(&css_set_rwsem
);
431 * refcounted get/put for css_set objects
433 static inline void get_css_set(struct css_set
*cset
)
435 atomic_inc(&cset
->refcount
);
439 * compare_css_sets - helper function for find_existing_css_set().
440 * @cset: candidate css_set being tested
441 * @old_cset: existing css_set for a task
442 * @new_cgrp: cgroup that's being entered by the task
443 * @template: desired set of css pointers in css_set (pre-calculated)
445 * Returns true if "cset" matches "old_cset" except for the hierarchy
446 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
448 static bool compare_css_sets(struct css_set
*cset
,
449 struct css_set
*old_cset
,
450 struct cgroup
*new_cgrp
,
451 struct cgroup_subsys_state
*template[])
453 struct list_head
*l1
, *l2
;
455 if (memcmp(template, cset
->subsys
, sizeof(cset
->subsys
))) {
456 /* Not all subsystems matched */
461 * Compare cgroup pointers in order to distinguish between
462 * different cgroups in heirarchies with no subsystems. We
463 * could get by with just this check alone (and skip the
464 * memcmp above) but on most setups the memcmp check will
465 * avoid the need for this more expensive check on almost all
469 l1
= &cset
->cgrp_links
;
470 l2
= &old_cset
->cgrp_links
;
472 struct cgrp_cset_link
*link1
, *link2
;
473 struct cgroup
*cgrp1
, *cgrp2
;
477 /* See if we reached the end - both lists are equal length. */
478 if (l1
== &cset
->cgrp_links
) {
479 BUG_ON(l2
!= &old_cset
->cgrp_links
);
482 BUG_ON(l2
== &old_cset
->cgrp_links
);
484 /* Locate the cgroups associated with these links. */
485 link1
= list_entry(l1
, struct cgrp_cset_link
, cgrp_link
);
486 link2
= list_entry(l2
, struct cgrp_cset_link
, cgrp_link
);
489 /* Hierarchies should be linked in the same order. */
490 BUG_ON(cgrp1
->root
!= cgrp2
->root
);
493 * If this hierarchy is the hierarchy of the cgroup
494 * that's changing, then we need to check that this
495 * css_set points to the new cgroup; if it's any other
496 * hierarchy, then this css_set should point to the
497 * same cgroup as the old css_set.
499 if (cgrp1
->root
== new_cgrp
->root
) {
500 if (cgrp1
!= new_cgrp
)
511 * find_existing_css_set - init css array and find the matching css_set
512 * @old_cset: the css_set that we're using before the cgroup transition
513 * @cgrp: the cgroup that we're moving into
514 * @template: out param for the new set of csses, should be clear on entry
516 static struct css_set
*find_existing_css_set(struct css_set
*old_cset
,
518 struct cgroup_subsys_state
*template[])
520 struct cgroup_root
*root
= cgrp
->root
;
521 struct cgroup_subsys
*ss
;
522 struct css_set
*cset
;
527 * Build the set of subsystem state objects that we want to see in the
528 * new css_set. while subsystems can change globally, the entries here
529 * won't change, so no need for locking.
531 for_each_subsys(ss
, i
) {
532 if (root
->cgrp
.subsys_mask
& (1UL << i
)) {
533 /* Subsystem is in this hierarchy. So we want
534 * the subsystem state from the new
536 template[i
] = cgroup_css(cgrp
, ss
);
538 /* Subsystem is not in this hierarchy, so we
539 * don't want to change the subsystem state */
540 template[i
] = old_cset
->subsys
[i
];
544 key
= css_set_hash(template);
545 hash_for_each_possible(css_set_table
, cset
, hlist
, key
) {
546 if (!compare_css_sets(cset
, old_cset
, cgrp
, template))
549 /* This css_set matches what we need */
553 /* No existing cgroup group matched */
557 static void free_cgrp_cset_links(struct list_head
*links_to_free
)
559 struct cgrp_cset_link
*link
, *tmp_link
;
561 list_for_each_entry_safe(link
, tmp_link
, links_to_free
, cset_link
) {
562 list_del(&link
->cset_link
);
568 * allocate_cgrp_cset_links - allocate cgrp_cset_links
569 * @count: the number of links to allocate
570 * @tmp_links: list_head the allocated links are put on
572 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
573 * through ->cset_link. Returns 0 on success or -errno.
575 static int allocate_cgrp_cset_links(int count
, struct list_head
*tmp_links
)
577 struct cgrp_cset_link
*link
;
580 INIT_LIST_HEAD(tmp_links
);
582 for (i
= 0; i
< count
; i
++) {
583 link
= kzalloc(sizeof(*link
), GFP_KERNEL
);
585 free_cgrp_cset_links(tmp_links
);
588 list_add(&link
->cset_link
, tmp_links
);
594 * link_css_set - a helper function to link a css_set to a cgroup
595 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
596 * @cset: the css_set to be linked
597 * @cgrp: the destination cgroup
599 static void link_css_set(struct list_head
*tmp_links
, struct css_set
*cset
,
602 struct cgrp_cset_link
*link
;
604 BUG_ON(list_empty(tmp_links
));
605 link
= list_first_entry(tmp_links
, struct cgrp_cset_link
, cset_link
);
608 list_move(&link
->cset_link
, &cgrp
->cset_links
);
610 * Always add links to the tail of the list so that the list
611 * is sorted by order of hierarchy creation
613 list_add_tail(&link
->cgrp_link
, &cset
->cgrp_links
);
617 * find_css_set - return a new css_set with one cgroup updated
618 * @old_cset: the baseline css_set
619 * @cgrp: the cgroup to be updated
621 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
622 * substituted into the appropriate hierarchy.
624 static struct css_set
*find_css_set(struct css_set
*old_cset
,
627 struct cgroup_subsys_state
*template[CGROUP_SUBSYS_COUNT
] = { };
628 struct css_set
*cset
;
629 struct list_head tmp_links
;
630 struct cgrp_cset_link
*link
;
633 lockdep_assert_held(&cgroup_mutex
);
635 /* First see if we already have a cgroup group that matches
637 down_read(&css_set_rwsem
);
638 cset
= find_existing_css_set(old_cset
, cgrp
, template);
641 up_read(&css_set_rwsem
);
646 cset
= kzalloc(sizeof(*cset
), GFP_KERNEL
);
650 /* Allocate all the cgrp_cset_link objects that we'll need */
651 if (allocate_cgrp_cset_links(cgroup_root_count
, &tmp_links
) < 0) {
656 atomic_set(&cset
->refcount
, 1);
657 INIT_LIST_HEAD(&cset
->cgrp_links
);
658 INIT_LIST_HEAD(&cset
->tasks
);
659 INIT_LIST_HEAD(&cset
->mg_tasks
);
660 INIT_LIST_HEAD(&cset
->mg_preload_node
);
661 INIT_LIST_HEAD(&cset
->mg_node
);
662 INIT_HLIST_NODE(&cset
->hlist
);
664 /* Copy the set of subsystem state objects generated in
665 * find_existing_css_set() */
666 memcpy(cset
->subsys
, template, sizeof(cset
->subsys
));
668 down_write(&css_set_rwsem
);
669 /* Add reference counts and links from the new css_set. */
670 list_for_each_entry(link
, &old_cset
->cgrp_links
, cgrp_link
) {
671 struct cgroup
*c
= link
->cgrp
;
673 if (c
->root
== cgrp
->root
)
675 link_css_set(&tmp_links
, cset
, c
);
678 BUG_ON(!list_empty(&tmp_links
));
682 /* Add this cgroup group to the hash table */
683 key
= css_set_hash(cset
->subsys
);
684 hash_add(css_set_table
, &cset
->hlist
, key
);
686 up_write(&css_set_rwsem
);
691 static struct cgroup_root
*cgroup_root_from_kf(struct kernfs_root
*kf_root
)
693 struct cgroup
*root_cgrp
= kf_root
->kn
->priv
;
695 return root_cgrp
->root
;
698 static int cgroup_init_root_id(struct cgroup_root
*root
)
702 lockdep_assert_held(&cgroup_mutex
);
704 id
= idr_alloc_cyclic(&cgroup_hierarchy_idr
, root
, 0, 0, GFP_KERNEL
);
708 root
->hierarchy_id
= id
;
712 static void cgroup_exit_root_id(struct cgroup_root
*root
)
714 lockdep_assert_held(&cgroup_mutex
);
716 if (root
->hierarchy_id
) {
717 idr_remove(&cgroup_hierarchy_idr
, root
->hierarchy_id
);
718 root
->hierarchy_id
= 0;
722 static void cgroup_free_root(struct cgroup_root
*root
)
725 /* hierarhcy ID shoulid already have been released */
726 WARN_ON_ONCE(root
->hierarchy_id
);
728 idr_destroy(&root
->cgroup_idr
);
733 static void cgroup_destroy_root(struct cgroup_root
*root
)
735 struct cgroup
*cgrp
= &root
->cgrp
;
736 struct cgrp_cset_link
*link
, *tmp_link
;
738 mutex_lock(&cgroup_tree_mutex
);
739 mutex_lock(&cgroup_mutex
);
741 BUG_ON(atomic_read(&root
->nr_cgrps
));
742 BUG_ON(!list_empty(&cgrp
->children
));
744 /* Rebind all subsystems back to the default hierarchy */
745 rebind_subsystems(&cgrp_dfl_root
, cgrp
->subsys_mask
);
748 * Release all the links from cset_links to this hierarchy's
751 down_write(&css_set_rwsem
);
753 list_for_each_entry_safe(link
, tmp_link
, &cgrp
->cset_links
, cset_link
) {
754 list_del(&link
->cset_link
);
755 list_del(&link
->cgrp_link
);
758 up_write(&css_set_rwsem
);
760 if (!list_empty(&root
->root_list
)) {
761 list_del(&root
->root_list
);
765 cgroup_exit_root_id(root
);
767 mutex_unlock(&cgroup_mutex
);
768 mutex_unlock(&cgroup_tree_mutex
);
770 kernfs_destroy_root(root
->kf_root
);
771 cgroup_free_root(root
);
774 /* look up cgroup associated with given css_set on the specified hierarchy */
775 static struct cgroup
*cset_cgroup_from_root(struct css_set
*cset
,
776 struct cgroup_root
*root
)
778 struct cgroup
*res
= NULL
;
780 lockdep_assert_held(&cgroup_mutex
);
781 lockdep_assert_held(&css_set_rwsem
);
783 if (cset
== &init_css_set
) {
786 struct cgrp_cset_link
*link
;
788 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
789 struct cgroup
*c
= link
->cgrp
;
791 if (c
->root
== root
) {
803 * Return the cgroup for "task" from the given hierarchy. Must be
804 * called with cgroup_mutex and css_set_rwsem held.
806 static struct cgroup
*task_cgroup_from_root(struct task_struct
*task
,
807 struct cgroup_root
*root
)
810 * No need to lock the task - since we hold cgroup_mutex the
811 * task can't change groups, so the only thing that can happen
812 * is that it exits and its css is set back to init_css_set.
814 return cset_cgroup_from_root(task_css_set(task
), root
);
818 * A task must hold cgroup_mutex to modify cgroups.
820 * Any task can increment and decrement the count field without lock.
821 * So in general, code holding cgroup_mutex can't rely on the count
822 * field not changing. However, if the count goes to zero, then only
823 * cgroup_attach_task() can increment it again. Because a count of zero
824 * means that no tasks are currently attached, therefore there is no
825 * way a task attached to that cgroup can fork (the other way to
826 * increment the count). So code holding cgroup_mutex can safely
827 * assume that if the count is zero, it will stay zero. Similarly, if
828 * a task holds cgroup_mutex on a cgroup with zero count, it
829 * knows that the cgroup won't be removed, as cgroup_rmdir()
832 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
833 * (usually) take cgroup_mutex. These are the two most performance
834 * critical pieces of code here. The exception occurs on cgroup_exit(),
835 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
836 * is taken, and if the cgroup count is zero, a usermode call made
837 * to the release agent with the name of the cgroup (path relative to
838 * the root of cgroup file system) as the argument.
840 * A cgroup can only be deleted if both its 'count' of using tasks
841 * is zero, and its list of 'children' cgroups is empty. Since all
842 * tasks in the system use _some_ cgroup, and since there is always at
843 * least one task in the system (init, pid == 1), therefore, root cgroup
844 * always has either children cgroups and/or using tasks. So we don't
845 * need a special hack to ensure that root cgroup cannot be deleted.
847 * P.S. One more locking exception. RCU is used to guard the
848 * update of a tasks cgroup pointer by cgroup_attach_task()
851 static int cgroup_populate_dir(struct cgroup
*cgrp
, unsigned long subsys_mask
);
852 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
;
853 static const struct file_operations proc_cgroupstats_operations
;
855 static char *cgroup_file_name(struct cgroup
*cgrp
, const struct cftype
*cft
,
858 if (cft
->ss
&& !(cft
->flags
& CFTYPE_NO_PREFIX
) &&
859 !(cgrp
->root
->flags
& CGRP_ROOT_NOPREFIX
))
860 snprintf(buf
, CGROUP_FILE_NAME_MAX
, "%s.%s",
861 cft
->ss
->name
, cft
->name
);
863 strncpy(buf
, cft
->name
, CGROUP_FILE_NAME_MAX
);
868 * cgroup_file_mode - deduce file mode of a control file
869 * @cft: the control file in question
871 * returns cft->mode if ->mode is not 0
872 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
873 * returns S_IRUGO if it has only a read handler
874 * returns S_IWUSR if it has only a write hander
876 static umode_t
cgroup_file_mode(const struct cftype
*cft
)
883 if (cft
->read_u64
|| cft
->read_s64
|| cft
->seq_show
)
886 if (cft
->write_u64
|| cft
->write_s64
|| cft
->write_string
||
893 static void cgroup_free_fn(struct work_struct
*work
)
895 struct cgroup
*cgrp
= container_of(work
, struct cgroup
, destroy_work
);
897 atomic_dec(&cgrp
->root
->nr_cgrps
);
898 cgroup_pidlist_destroy_all(cgrp
);
902 * We get a ref to the parent, and put the ref when this
903 * cgroup is being freed, so it's guaranteed that the
904 * parent won't be destroyed before its children.
906 cgroup_put(cgrp
->parent
);
907 kernfs_put(cgrp
->kn
);
911 * This is root cgroup's refcnt reaching zero, which
912 * indicates that the root should be released.
914 cgroup_destroy_root(cgrp
->root
);
918 static void cgroup_free_rcu(struct rcu_head
*head
)
920 struct cgroup
*cgrp
= container_of(head
, struct cgroup
, rcu_head
);
922 INIT_WORK(&cgrp
->destroy_work
, cgroup_free_fn
);
923 queue_work(cgroup_destroy_wq
, &cgrp
->destroy_work
);
926 static void cgroup_get(struct cgroup
*cgrp
)
928 WARN_ON_ONCE(cgroup_is_dead(cgrp
));
929 WARN_ON_ONCE(atomic_read(&cgrp
->refcnt
) <= 0);
930 atomic_inc(&cgrp
->refcnt
);
933 static void cgroup_put(struct cgroup
*cgrp
)
935 if (!atomic_dec_and_test(&cgrp
->refcnt
))
937 if (WARN_ON_ONCE(cgrp
->parent
&& !cgroup_is_dead(cgrp
)))
941 * XXX: cgrp->id is only used to look up css's. As cgroup and
942 * css's lifetimes will be decoupled, it should be made
943 * per-subsystem and moved to css->id so that lookups are
944 * successful until the target css is released.
946 mutex_lock(&cgroup_mutex
);
947 idr_remove(&cgrp
->root
->cgroup_idr
, cgrp
->id
);
948 mutex_unlock(&cgroup_mutex
);
951 call_rcu(&cgrp
->rcu_head
, cgroup_free_rcu
);
954 static void cgroup_rm_file(struct cgroup
*cgrp
, const struct cftype
*cft
)
956 char name
[CGROUP_FILE_NAME_MAX
];
958 lockdep_assert_held(&cgroup_tree_mutex
);
959 kernfs_remove_by_name(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
));
963 * cgroup_clear_dir - remove subsys files in a cgroup directory
964 * @cgrp: target cgroup
965 * @subsys_mask: mask of the subsystem ids whose files should be removed
967 static void cgroup_clear_dir(struct cgroup
*cgrp
, unsigned long subsys_mask
)
969 struct cgroup_subsys
*ss
;
972 for_each_subsys(ss
, i
) {
975 if (!test_bit(i
, &subsys_mask
))
977 list_for_each_entry(cfts
, &ss
->cfts
, node
)
978 cgroup_addrm_files(cgrp
, cfts
, false);
982 static int rebind_subsystems(struct cgroup_root
*dst_root
,
983 unsigned long ss_mask
)
985 struct cgroup_subsys
*ss
;
988 lockdep_assert_held(&cgroup_tree_mutex
);
989 lockdep_assert_held(&cgroup_mutex
);
991 for_each_subsys(ss
, ssid
) {
992 if (!(ss_mask
& (1 << ssid
)))
995 /* if @ss is on the dummy_root, we can always move it */
996 if (ss
->root
== &cgrp_dfl_root
)
999 /* if @ss has non-root cgroups attached to it, can't move */
1000 if (!list_empty(&ss
->root
->cgrp
.children
))
1003 /* can't move between two non-dummy roots either */
1004 if (dst_root
!= &cgrp_dfl_root
)
1008 ret
= cgroup_populate_dir(&dst_root
->cgrp
, ss_mask
);
1010 if (dst_root
!= &cgrp_dfl_root
)
1014 * Rebinding back to the default root is not allowed to
1015 * fail. Using both default and non-default roots should
1016 * be rare. Moving subsystems back and forth even more so.
1017 * Just warn about it and continue.
1019 if (cgrp_dfl_root_visible
) {
1020 pr_warning("cgroup: failed to create files (%d) while rebinding 0x%lx to default root\n",
1022 pr_warning("cgroup: you may retry by moving them to a different hierarchy and unbinding\n");
1027 * Nothing can fail from this point on. Remove files for the
1028 * removed subsystems and rebind each subsystem.
1030 mutex_unlock(&cgroup_mutex
);
1031 for_each_subsys(ss
, ssid
)
1032 if (ss_mask
& (1 << ssid
))
1033 cgroup_clear_dir(&ss
->root
->cgrp
, 1 << ssid
);
1034 mutex_lock(&cgroup_mutex
);
1036 for_each_subsys(ss
, ssid
) {
1037 struct cgroup_root
*src_root
;
1038 struct cgroup_subsys_state
*css
;
1040 if (!(ss_mask
& (1 << ssid
)))
1043 src_root
= ss
->root
;
1044 css
= cgroup_css(&src_root
->cgrp
, ss
);
1046 WARN_ON(!css
|| cgroup_css(&dst_root
->cgrp
, ss
));
1048 RCU_INIT_POINTER(src_root
->cgrp
.subsys
[ssid
], NULL
);
1049 rcu_assign_pointer(dst_root
->cgrp
.subsys
[ssid
], css
);
1050 ss
->root
= dst_root
;
1051 css
->cgroup
= &dst_root
->cgrp
;
1053 src_root
->cgrp
.subsys_mask
&= ~(1 << ssid
);
1054 dst_root
->cgrp
.subsys_mask
|= 1 << ssid
;
1060 kernfs_activate(dst_root
->cgrp
.kn
);
1064 static int cgroup_show_options(struct seq_file
*seq
,
1065 struct kernfs_root
*kf_root
)
1067 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1068 struct cgroup_subsys
*ss
;
1071 for_each_subsys(ss
, ssid
)
1072 if (root
->cgrp
.subsys_mask
& (1 << ssid
))
1073 seq_printf(seq
, ",%s", ss
->name
);
1074 if (root
->flags
& CGRP_ROOT_SANE_BEHAVIOR
)
1075 seq_puts(seq
, ",sane_behavior");
1076 if (root
->flags
& CGRP_ROOT_NOPREFIX
)
1077 seq_puts(seq
, ",noprefix");
1078 if (root
->flags
& CGRP_ROOT_XATTR
)
1079 seq_puts(seq
, ",xattr");
1081 spin_lock(&release_agent_path_lock
);
1082 if (strlen(root
->release_agent_path
))
1083 seq_printf(seq
, ",release_agent=%s", root
->release_agent_path
);
1084 spin_unlock(&release_agent_path_lock
);
1086 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
))
1087 seq_puts(seq
, ",clone_children");
1088 if (strlen(root
->name
))
1089 seq_printf(seq
, ",name=%s", root
->name
);
1093 struct cgroup_sb_opts
{
1094 unsigned long subsys_mask
;
1095 unsigned long flags
;
1096 char *release_agent
;
1097 bool cpuset_clone_children
;
1099 /* User explicitly requested empty subsystem */
1104 * Convert a hierarchy specifier into a bitmask of subsystems and
1105 * flags. Call with cgroup_mutex held to protect the cgroup_subsys[]
1106 * array. This function takes refcounts on subsystems to be used, unless it
1107 * returns error, in which case no refcounts are taken.
1109 static int parse_cgroupfs_options(char *data
, struct cgroup_sb_opts
*opts
)
1111 char *token
, *o
= data
;
1112 bool all_ss
= false, one_ss
= false;
1113 unsigned long mask
= (unsigned long)-1;
1114 struct cgroup_subsys
*ss
;
1117 BUG_ON(!mutex_is_locked(&cgroup_mutex
));
1119 #ifdef CONFIG_CPUSETS
1120 mask
= ~(1UL << cpuset_cgrp_id
);
1123 memset(opts
, 0, sizeof(*opts
));
1125 while ((token
= strsep(&o
, ",")) != NULL
) {
1128 if (!strcmp(token
, "none")) {
1129 /* Explicitly have no subsystems */
1133 if (!strcmp(token
, "all")) {
1134 /* Mutually exclusive option 'all' + subsystem name */
1140 if (!strcmp(token
, "__DEVEL__sane_behavior")) {
1141 opts
->flags
|= CGRP_ROOT_SANE_BEHAVIOR
;
1144 if (!strcmp(token
, "noprefix")) {
1145 opts
->flags
|= CGRP_ROOT_NOPREFIX
;
1148 if (!strcmp(token
, "clone_children")) {
1149 opts
->cpuset_clone_children
= true;
1152 if (!strcmp(token
, "xattr")) {
1153 opts
->flags
|= CGRP_ROOT_XATTR
;
1156 if (!strncmp(token
, "release_agent=", 14)) {
1157 /* Specifying two release agents is forbidden */
1158 if (opts
->release_agent
)
1160 opts
->release_agent
=
1161 kstrndup(token
+ 14, PATH_MAX
- 1, GFP_KERNEL
);
1162 if (!opts
->release_agent
)
1166 if (!strncmp(token
, "name=", 5)) {
1167 const char *name
= token
+ 5;
1168 /* Can't specify an empty name */
1171 /* Must match [\w.-]+ */
1172 for (i
= 0; i
< strlen(name
); i
++) {
1176 if ((c
== '.') || (c
== '-') || (c
== '_'))
1180 /* Specifying two names is forbidden */
1183 opts
->name
= kstrndup(name
,
1184 MAX_CGROUP_ROOT_NAMELEN
- 1,
1192 for_each_subsys(ss
, i
) {
1193 if (strcmp(token
, ss
->name
))
1198 /* Mutually exclusive option 'all' + subsystem name */
1201 set_bit(i
, &opts
->subsys_mask
);
1206 if (i
== CGROUP_SUBSYS_COUNT
)
1210 /* Consistency checks */
1212 if (opts
->flags
& CGRP_ROOT_SANE_BEHAVIOR
) {
1213 pr_warning("cgroup: sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
1215 if ((opts
->flags
& (CGRP_ROOT_NOPREFIX
| CGRP_ROOT_XATTR
)) ||
1216 opts
->cpuset_clone_children
|| opts
->release_agent
||
1218 pr_err("cgroup: sane_behavior: noprefix, xattr, clone_children, release_agent and name are not allowed\n");
1223 * If the 'all' option was specified select all the
1224 * subsystems, otherwise if 'none', 'name=' and a subsystem
1225 * name options were not specified, let's default to 'all'
1227 if (all_ss
|| (!one_ss
&& !opts
->none
&& !opts
->name
))
1228 for_each_subsys(ss
, i
)
1230 set_bit(i
, &opts
->subsys_mask
);
1233 * We either have to specify by name or by subsystems. (So
1234 * all empty hierarchies must have a name).
1236 if (!opts
->subsys_mask
&& !opts
->name
)
1241 * Option noprefix was introduced just for backward compatibility
1242 * with the old cpuset, so we allow noprefix only if mounting just
1243 * the cpuset subsystem.
1245 if ((opts
->flags
& CGRP_ROOT_NOPREFIX
) && (opts
->subsys_mask
& mask
))
1249 /* Can't specify "none" and some subsystems */
1250 if (opts
->subsys_mask
&& opts
->none
)
1256 static int cgroup_remount(struct kernfs_root
*kf_root
, int *flags
, char *data
)
1259 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1260 struct cgroup_sb_opts opts
;
1261 unsigned long added_mask
, removed_mask
;
1263 if (root
->flags
& CGRP_ROOT_SANE_BEHAVIOR
) {
1264 pr_err("cgroup: sane_behavior: remount is not allowed\n");
1268 mutex_lock(&cgroup_tree_mutex
);
1269 mutex_lock(&cgroup_mutex
);
1271 /* See what subsystems are wanted */
1272 ret
= parse_cgroupfs_options(data
, &opts
);
1276 if (opts
.subsys_mask
!= root
->cgrp
.subsys_mask
|| opts
.release_agent
)
1277 pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
1278 task_tgid_nr(current
), current
->comm
);
1280 added_mask
= opts
.subsys_mask
& ~root
->cgrp
.subsys_mask
;
1281 removed_mask
= root
->cgrp
.subsys_mask
& ~opts
.subsys_mask
;
1283 /* Don't allow flags or name to change at remount */
1284 if (((opts
.flags
^ root
->flags
) & CGRP_ROOT_OPTION_MASK
) ||
1285 (opts
.name
&& strcmp(opts
.name
, root
->name
))) {
1286 pr_err("cgroup: option or name mismatch, new: 0x%lx \"%s\", old: 0x%lx \"%s\"\n",
1287 opts
.flags
& CGRP_ROOT_OPTION_MASK
, opts
.name
?: "",
1288 root
->flags
& CGRP_ROOT_OPTION_MASK
, root
->name
);
1293 /* remounting is not allowed for populated hierarchies */
1294 if (!list_empty(&root
->cgrp
.children
)) {
1299 ret
= rebind_subsystems(root
, added_mask
);
1303 rebind_subsystems(&cgrp_dfl_root
, removed_mask
);
1305 if (opts
.release_agent
) {
1306 spin_lock(&release_agent_path_lock
);
1307 strcpy(root
->release_agent_path
, opts
.release_agent
);
1308 spin_unlock(&release_agent_path_lock
);
1311 kfree(opts
.release_agent
);
1313 mutex_unlock(&cgroup_mutex
);
1314 mutex_unlock(&cgroup_tree_mutex
);
1319 * To reduce the fork() overhead for systems that are not actually using
1320 * their cgroups capability, we don't maintain the lists running through
1321 * each css_set to its tasks until we see the list actually used - in other
1322 * words after the first mount.
1324 static bool use_task_css_set_links __read_mostly
;
1326 static void cgroup_enable_task_cg_lists(void)
1328 struct task_struct
*p
, *g
;
1330 down_write(&css_set_rwsem
);
1332 if (use_task_css_set_links
)
1335 use_task_css_set_links
= true;
1338 * We need tasklist_lock because RCU is not safe against
1339 * while_each_thread(). Besides, a forking task that has passed
1340 * cgroup_post_fork() without seeing use_task_css_set_links = 1
1341 * is not guaranteed to have its child immediately visible in the
1342 * tasklist if we walk through it with RCU.
1344 read_lock(&tasklist_lock
);
1345 do_each_thread(g
, p
) {
1346 WARN_ON_ONCE(!list_empty(&p
->cg_list
) ||
1347 task_css_set(p
) != &init_css_set
);
1350 * We should check if the process is exiting, otherwise
1351 * it will race with cgroup_exit() in that the list
1352 * entry won't be deleted though the process has exited.
1353 * Do it while holding siglock so that we don't end up
1354 * racing against cgroup_exit().
1356 spin_lock_irq(&p
->sighand
->siglock
);
1357 if (!(p
->flags
& PF_EXITING
)) {
1358 struct css_set
*cset
= task_css_set(p
);
1360 list_add(&p
->cg_list
, &cset
->tasks
);
1363 spin_unlock_irq(&p
->sighand
->siglock
);
1364 } while_each_thread(g
, p
);
1365 read_unlock(&tasklist_lock
);
1367 up_write(&css_set_rwsem
);
1370 static void init_cgroup_housekeeping(struct cgroup
*cgrp
)
1372 atomic_set(&cgrp
->refcnt
, 1);
1373 INIT_LIST_HEAD(&cgrp
->sibling
);
1374 INIT_LIST_HEAD(&cgrp
->children
);
1375 INIT_LIST_HEAD(&cgrp
->cset_links
);
1376 INIT_LIST_HEAD(&cgrp
->release_list
);
1377 INIT_LIST_HEAD(&cgrp
->pidlists
);
1378 mutex_init(&cgrp
->pidlist_mutex
);
1379 cgrp
->dummy_css
.cgroup
= cgrp
;
1382 static void init_cgroup_root(struct cgroup_root
*root
,
1383 struct cgroup_sb_opts
*opts
)
1385 struct cgroup
*cgrp
= &root
->cgrp
;
1387 INIT_LIST_HEAD(&root
->root_list
);
1388 atomic_set(&root
->nr_cgrps
, 1);
1390 init_cgroup_housekeeping(cgrp
);
1391 idr_init(&root
->cgroup_idr
);
1393 root
->flags
= opts
->flags
;
1394 if (opts
->release_agent
)
1395 strcpy(root
->release_agent_path
, opts
->release_agent
);
1397 strcpy(root
->name
, opts
->name
);
1398 if (opts
->cpuset_clone_children
)
1399 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &root
->cgrp
.flags
);
1402 static int cgroup_setup_root(struct cgroup_root
*root
, unsigned long ss_mask
)
1404 LIST_HEAD(tmp_links
);
1405 struct cgroup
*root_cgrp
= &root
->cgrp
;
1406 struct css_set
*cset
;
1409 lockdep_assert_held(&cgroup_tree_mutex
);
1410 lockdep_assert_held(&cgroup_mutex
);
1412 ret
= idr_alloc(&root
->cgroup_idr
, root_cgrp
, 0, 1, GFP_KERNEL
);
1415 root_cgrp
->id
= ret
;
1418 * We're accessing css_set_count without locking css_set_rwsem here,
1419 * but that's OK - it can only be increased by someone holding
1420 * cgroup_lock, and that's us. The worst that can happen is that we
1421 * have some link structures left over
1423 ret
= allocate_cgrp_cset_links(css_set_count
, &tmp_links
);
1427 ret
= cgroup_init_root_id(root
);
1431 root
->kf_root
= kernfs_create_root(&cgroup_kf_syscall_ops
,
1432 KERNFS_ROOT_CREATE_DEACTIVATED
,
1434 if (IS_ERR(root
->kf_root
)) {
1435 ret
= PTR_ERR(root
->kf_root
);
1438 root_cgrp
->kn
= root
->kf_root
->kn
;
1440 ret
= cgroup_addrm_files(root_cgrp
, cgroup_base_files
, true);
1444 ret
= rebind_subsystems(root
, ss_mask
);
1449 * There must be no failure case after here, since rebinding takes
1450 * care of subsystems' refcounts, which are explicitly dropped in
1451 * the failure exit path.
1453 list_add(&root
->root_list
, &cgroup_roots
);
1454 cgroup_root_count
++;
1457 * Link the root cgroup in this hierarchy into all the css_set
1460 down_write(&css_set_rwsem
);
1461 hash_for_each(css_set_table
, i
, cset
, hlist
)
1462 link_css_set(&tmp_links
, cset
, root_cgrp
);
1463 up_write(&css_set_rwsem
);
1465 BUG_ON(!list_empty(&root_cgrp
->children
));
1466 BUG_ON(atomic_read(&root
->nr_cgrps
) != 1);
1468 kernfs_activate(root_cgrp
->kn
);
1473 kernfs_destroy_root(root
->kf_root
);
1474 root
->kf_root
= NULL
;
1476 cgroup_exit_root_id(root
);
1478 free_cgrp_cset_links(&tmp_links
);
1482 static struct dentry
*cgroup_mount(struct file_system_type
*fs_type
,
1483 int flags
, const char *unused_dev_name
,
1486 struct cgroup_root
*root
;
1487 struct cgroup_sb_opts opts
;
1488 struct dentry
*dentry
;
1493 * The first time anyone tries to mount a cgroup, enable the list
1494 * linking each css_set to its tasks and fix up all existing tasks.
1496 if (!use_task_css_set_links
)
1497 cgroup_enable_task_cg_lists();
1499 mutex_lock(&cgroup_tree_mutex
);
1500 mutex_lock(&cgroup_mutex
);
1502 /* First find the desired set of subsystems */
1503 ret
= parse_cgroupfs_options(data
, &opts
);
1507 /* look for a matching existing root */
1508 if (!opts
.subsys_mask
&& !opts
.none
&& !opts
.name
) {
1509 cgrp_dfl_root_visible
= true;
1510 root
= &cgrp_dfl_root
;
1511 cgroup_get(&root
->cgrp
);
1516 for_each_root(root
) {
1517 bool name_match
= false;
1519 if (root
== &cgrp_dfl_root
)
1523 * If we asked for a name then it must match. Also, if
1524 * name matches but sybsys_mask doesn't, we should fail.
1525 * Remember whether name matched.
1528 if (strcmp(opts
.name
, root
->name
))
1534 * If we asked for subsystems (or explicitly for no
1535 * subsystems) then they must match.
1537 if ((opts
.subsys_mask
|| opts
.none
) &&
1538 (opts
.subsys_mask
!= root
->cgrp
.subsys_mask
)) {
1545 if ((root
->flags
^ opts
.flags
) & CGRP_ROOT_OPTION_MASK
) {
1546 if ((root
->flags
| opts
.flags
) & CGRP_ROOT_SANE_BEHAVIOR
) {
1547 pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n");
1551 pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n");
1556 * A root's lifetime is governed by its root cgroup. Zero
1557 * ref indicate that the root is being destroyed. Wait for
1558 * destruction to complete so that the subsystems are free.
1559 * We can use wait_queue for the wait but this path is
1560 * super cold. Let's just sleep for a bit and retry.
1562 if (!atomic_inc_not_zero(&root
->cgrp
.refcnt
)) {
1563 mutex_unlock(&cgroup_mutex
);
1564 mutex_unlock(&cgroup_tree_mutex
);
1565 kfree(opts
.release_agent
);
1576 * No such thing, create a new one. name= matching without subsys
1577 * specification is allowed for already existing hierarchies but we
1578 * can't create new one without subsys specification.
1580 if (!opts
.subsys_mask
&& !opts
.none
) {
1585 root
= kzalloc(sizeof(*root
), GFP_KERNEL
);
1591 init_cgroup_root(root
, &opts
);
1593 ret
= cgroup_setup_root(root
, opts
.subsys_mask
);
1595 cgroup_free_root(root
);
1598 mutex_unlock(&cgroup_mutex
);
1599 mutex_unlock(&cgroup_tree_mutex
);
1601 kfree(opts
.release_agent
);
1605 return ERR_PTR(ret
);
1607 dentry
= kernfs_mount(fs_type
, flags
, root
->kf_root
, &new_sb
);
1608 if (IS_ERR(dentry
) || !new_sb
)
1609 cgroup_put(&root
->cgrp
);
1613 static void cgroup_kill_sb(struct super_block
*sb
)
1615 struct kernfs_root
*kf_root
= kernfs_root_from_sb(sb
);
1616 struct cgroup_root
*root
= cgroup_root_from_kf(kf_root
);
1618 cgroup_put(&root
->cgrp
);
1622 static struct file_system_type cgroup_fs_type
= {
1624 .mount
= cgroup_mount
,
1625 .kill_sb
= cgroup_kill_sb
,
1628 static struct kobject
*cgroup_kobj
;
1631 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
1632 * @task: target task
1633 * @buf: the buffer to write the path into
1634 * @buflen: the length of the buffer
1636 * Determine @task's cgroup on the first (the one with the lowest non-zero
1637 * hierarchy_id) cgroup hierarchy and copy its path into @buf. This
1638 * function grabs cgroup_mutex and shouldn't be used inside locks used by
1639 * cgroup controller callbacks.
1641 * Return value is the same as kernfs_path().
1643 char *task_cgroup_path(struct task_struct
*task
, char *buf
, size_t buflen
)
1645 struct cgroup_root
*root
;
1646 struct cgroup
*cgrp
;
1647 int hierarchy_id
= 1;
1650 mutex_lock(&cgroup_mutex
);
1651 down_read(&css_set_rwsem
);
1653 root
= idr_get_next(&cgroup_hierarchy_idr
, &hierarchy_id
);
1656 cgrp
= task_cgroup_from_root(task
, root
);
1657 path
= cgroup_path(cgrp
, buf
, buflen
);
1659 /* if no hierarchy exists, everyone is in "/" */
1660 if (strlcpy(buf
, "/", buflen
) < buflen
)
1664 up_read(&css_set_rwsem
);
1665 mutex_unlock(&cgroup_mutex
);
1668 EXPORT_SYMBOL_GPL(task_cgroup_path
);
1670 /* used to track tasks and other necessary states during migration */
1671 struct cgroup_taskset
{
1672 /* the src and dst cset list running through cset->mg_node */
1673 struct list_head src_csets
;
1674 struct list_head dst_csets
;
1677 * Fields for cgroup_taskset_*() iteration.
1679 * Before migration is committed, the target migration tasks are on
1680 * ->mg_tasks of the csets on ->src_csets. After, on ->mg_tasks of
1681 * the csets on ->dst_csets. ->csets point to either ->src_csets
1682 * or ->dst_csets depending on whether migration is committed.
1684 * ->cur_csets and ->cur_task point to the current task position
1687 struct list_head
*csets
;
1688 struct css_set
*cur_cset
;
1689 struct task_struct
*cur_task
;
1693 * cgroup_taskset_first - reset taskset and return the first task
1694 * @tset: taskset of interest
1696 * @tset iteration is initialized and the first task is returned.
1698 struct task_struct
*cgroup_taskset_first(struct cgroup_taskset
*tset
)
1700 tset
->cur_cset
= list_first_entry(tset
->csets
, struct css_set
, mg_node
);
1701 tset
->cur_task
= NULL
;
1703 return cgroup_taskset_next(tset
);
1707 * cgroup_taskset_next - iterate to the next task in taskset
1708 * @tset: taskset of interest
1710 * Return the next task in @tset. Iteration must have been initialized
1711 * with cgroup_taskset_first().
1713 struct task_struct
*cgroup_taskset_next(struct cgroup_taskset
*tset
)
1715 struct css_set
*cset
= tset
->cur_cset
;
1716 struct task_struct
*task
= tset
->cur_task
;
1718 while (&cset
->mg_node
!= tset
->csets
) {
1720 task
= list_first_entry(&cset
->mg_tasks
,
1721 struct task_struct
, cg_list
);
1723 task
= list_next_entry(task
, cg_list
);
1725 if (&task
->cg_list
!= &cset
->mg_tasks
) {
1726 tset
->cur_cset
= cset
;
1727 tset
->cur_task
= task
;
1731 cset
= list_next_entry(cset
, mg_node
);
1739 * cgroup_task_migrate - move a task from one cgroup to another.
1740 * @old_cgrp; the cgroup @tsk is being migrated from
1741 * @tsk: the task being migrated
1742 * @new_cset: the new css_set @tsk is being attached to
1744 * Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
1746 static void cgroup_task_migrate(struct cgroup
*old_cgrp
,
1747 struct task_struct
*tsk
,
1748 struct css_set
*new_cset
)
1750 struct css_set
*old_cset
;
1752 lockdep_assert_held(&cgroup_mutex
);
1753 lockdep_assert_held(&css_set_rwsem
);
1756 * We are synchronized through threadgroup_lock() against PF_EXITING
1757 * setting such that we can't race against cgroup_exit() changing the
1758 * css_set to init_css_set and dropping the old one.
1760 WARN_ON_ONCE(tsk
->flags
& PF_EXITING
);
1761 old_cset
= task_css_set(tsk
);
1763 get_css_set(new_cset
);
1764 rcu_assign_pointer(tsk
->cgroups
, new_cset
);
1767 * Use move_tail so that cgroup_taskset_first() still returns the
1768 * leader after migration. This works because cgroup_migrate()
1769 * ensures that the dst_cset of the leader is the first on the
1770 * tset's dst_csets list.
1772 list_move_tail(&tsk
->cg_list
, &new_cset
->mg_tasks
);
1775 * We just gained a reference on old_cset by taking it from the
1776 * task. As trading it for new_cset is protected by cgroup_mutex,
1777 * we're safe to drop it here; it will be freed under RCU.
1779 set_bit(CGRP_RELEASABLE
, &old_cgrp
->flags
);
1780 put_css_set_locked(old_cset
, false);
1784 * cgroup_migrate_finish - cleanup after attach
1785 * @preloaded_csets: list of preloaded css_sets
1787 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
1788 * those functions for details.
1790 static void cgroup_migrate_finish(struct list_head
*preloaded_csets
)
1792 struct css_set
*cset
, *tmp_cset
;
1794 lockdep_assert_held(&cgroup_mutex
);
1796 down_write(&css_set_rwsem
);
1797 list_for_each_entry_safe(cset
, tmp_cset
, preloaded_csets
, mg_preload_node
) {
1798 cset
->mg_src_cgrp
= NULL
;
1799 cset
->mg_dst_cset
= NULL
;
1800 list_del_init(&cset
->mg_preload_node
);
1801 put_css_set_locked(cset
, false);
1803 up_write(&css_set_rwsem
);
1807 * cgroup_migrate_add_src - add a migration source css_set
1808 * @src_cset: the source css_set to add
1809 * @dst_cgrp: the destination cgroup
1810 * @preloaded_csets: list of preloaded css_sets
1812 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
1813 * @src_cset and add it to @preloaded_csets, which should later be cleaned
1814 * up by cgroup_migrate_finish().
1816 * This function may be called without holding threadgroup_lock even if the
1817 * target is a process. Threads may be created and destroyed but as long
1818 * as cgroup_mutex is not dropped, no new css_set can be put into play and
1819 * the preloaded css_sets are guaranteed to cover all migrations.
1821 static void cgroup_migrate_add_src(struct css_set
*src_cset
,
1822 struct cgroup
*dst_cgrp
,
1823 struct list_head
*preloaded_csets
)
1825 struct cgroup
*src_cgrp
;
1827 lockdep_assert_held(&cgroup_mutex
);
1828 lockdep_assert_held(&css_set_rwsem
);
1830 src_cgrp
= cset_cgroup_from_root(src_cset
, dst_cgrp
->root
);
1832 /* nothing to do if this cset already belongs to the cgroup */
1833 if (src_cgrp
== dst_cgrp
)
1836 if (!list_empty(&src_cset
->mg_preload_node
))
1839 WARN_ON(src_cset
->mg_src_cgrp
);
1840 WARN_ON(!list_empty(&src_cset
->mg_tasks
));
1841 WARN_ON(!list_empty(&src_cset
->mg_node
));
1843 src_cset
->mg_src_cgrp
= src_cgrp
;
1844 get_css_set(src_cset
);
1845 list_add(&src_cset
->mg_preload_node
, preloaded_csets
);
1849 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
1850 * @dst_cgrp: the destination cgroup
1851 * @preloaded_csets: list of preloaded source css_sets
1853 * Tasks are about to be moved to @dst_cgrp and all the source css_sets
1854 * have been preloaded to @preloaded_csets. This function looks up and
1855 * pins all destination css_sets, links each to its source, and put them on
1858 * This function must be called after cgroup_migrate_add_src() has been
1859 * called on each migration source css_set. After migration is performed
1860 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
1863 static int cgroup_migrate_prepare_dst(struct cgroup
*dst_cgrp
,
1864 struct list_head
*preloaded_csets
)
1867 struct css_set
*src_cset
;
1869 lockdep_assert_held(&cgroup_mutex
);
1871 /* look up the dst cset for each src cset and link it to src */
1872 list_for_each_entry(src_cset
, preloaded_csets
, mg_preload_node
) {
1873 struct css_set
*dst_cset
;
1875 dst_cset
= find_css_set(src_cset
, dst_cgrp
);
1879 WARN_ON_ONCE(src_cset
->mg_dst_cset
|| dst_cset
->mg_dst_cset
);
1880 src_cset
->mg_dst_cset
= dst_cset
;
1882 if (list_empty(&dst_cset
->mg_preload_node
))
1883 list_add(&dst_cset
->mg_preload_node
, &csets
);
1885 put_css_set(dst_cset
, false);
1888 list_splice(&csets
, preloaded_csets
);
1891 cgroup_migrate_finish(&csets
);
1896 * cgroup_migrate - migrate a process or task to a cgroup
1897 * @cgrp: the destination cgroup
1898 * @leader: the leader of the process or the task to migrate
1899 * @threadgroup: whether @leader points to the whole process or a single task
1901 * Migrate a process or task denoted by @leader to @cgrp. If migrating a
1902 * process, the caller must be holding threadgroup_lock of @leader. The
1903 * caller is also responsible for invoking cgroup_migrate_add_src() and
1904 * cgroup_migrate_prepare_dst() on the targets before invoking this
1905 * function and following up with cgroup_migrate_finish().
1907 * As long as a controller's ->can_attach() doesn't fail, this function is
1908 * guaranteed to succeed. This means that, excluding ->can_attach()
1909 * failure, when migrating multiple targets, the success or failure can be
1910 * decided for all targets by invoking group_migrate_prepare_dst() before
1911 * actually starting migrating.
1913 static int cgroup_migrate(struct cgroup
*cgrp
, struct task_struct
*leader
,
1916 struct cgroup_taskset tset
= {
1917 .src_csets
= LIST_HEAD_INIT(tset
.src_csets
),
1918 .dst_csets
= LIST_HEAD_INIT(tset
.dst_csets
),
1919 .csets
= &tset
.src_csets
,
1921 struct cgroup_subsys_state
*css
, *failed_css
= NULL
;
1922 struct css_set
*cset
, *tmp_cset
;
1923 struct task_struct
*task
, *tmp_task
;
1927 * Prevent freeing of tasks while we take a snapshot. Tasks that are
1928 * already PF_EXITING could be freed from underneath us unless we
1929 * take an rcu_read_lock.
1931 down_write(&css_set_rwsem
);
1935 /* @task either already exited or can't exit until the end */
1936 if (task
->flags
& PF_EXITING
)
1939 /* leave @task alone if post_fork() hasn't linked it yet */
1940 if (list_empty(&task
->cg_list
))
1943 cset
= task_css_set(task
);
1944 if (!cset
->mg_src_cgrp
)
1948 * cgroup_taskset_first() must always return the leader.
1949 * Take care to avoid disturbing the ordering.
1951 list_move_tail(&task
->cg_list
, &cset
->mg_tasks
);
1952 if (list_empty(&cset
->mg_node
))
1953 list_add_tail(&cset
->mg_node
, &tset
.src_csets
);
1954 if (list_empty(&cset
->mg_dst_cset
->mg_node
))
1955 list_move_tail(&cset
->mg_dst_cset
->mg_node
,
1960 } while_each_thread(leader
, task
);
1962 up_write(&css_set_rwsem
);
1964 /* methods shouldn't be called if no task is actually migrating */
1965 if (list_empty(&tset
.src_csets
))
1968 /* check that we can legitimately attach to the cgroup */
1969 for_each_css(css
, i
, cgrp
) {
1970 if (css
->ss
->can_attach
) {
1971 ret
= css
->ss
->can_attach(css
, &tset
);
1974 goto out_cancel_attach
;
1980 * Now that we're guaranteed success, proceed to move all tasks to
1981 * the new cgroup. There are no failure cases after here, so this
1982 * is the commit point.
1984 down_write(&css_set_rwsem
);
1985 list_for_each_entry(cset
, &tset
.src_csets
, mg_node
) {
1986 list_for_each_entry_safe(task
, tmp_task
, &cset
->mg_tasks
, cg_list
)
1987 cgroup_task_migrate(cset
->mg_src_cgrp
, task
,
1990 up_write(&css_set_rwsem
);
1993 * Migration is committed, all target tasks are now on dst_csets.
1994 * Nothing is sensitive to fork() after this point. Notify
1995 * controllers that migration is complete.
1997 tset
.csets
= &tset
.dst_csets
;
1999 for_each_css(css
, i
, cgrp
)
2000 if (css
->ss
->attach
)
2001 css
->ss
->attach(css
, &tset
);
2004 goto out_release_tset
;
2007 for_each_css(css
, i
, cgrp
) {
2008 if (css
== failed_css
)
2010 if (css
->ss
->cancel_attach
)
2011 css
->ss
->cancel_attach(css
, &tset
);
2014 down_write(&css_set_rwsem
);
2015 list_splice_init(&tset
.dst_csets
, &tset
.src_csets
);
2016 list_for_each_entry_safe(cset
, tmp_cset
, &tset
.src_csets
, mg_node
) {
2017 list_splice_tail_init(&cset
->mg_tasks
, &cset
->tasks
);
2018 list_del_init(&cset
->mg_node
);
2020 up_write(&css_set_rwsem
);
2025 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2026 * @dst_cgrp: the cgroup to attach to
2027 * @leader: the task or the leader of the threadgroup to be attached
2028 * @threadgroup: attach the whole threadgroup?
2030 * Call holding cgroup_mutex and threadgroup_lock of @leader.
2032 static int cgroup_attach_task(struct cgroup
*dst_cgrp
,
2033 struct task_struct
*leader
, bool threadgroup
)
2035 LIST_HEAD(preloaded_csets
);
2036 struct task_struct
*task
;
2039 /* look up all src csets */
2040 down_read(&css_set_rwsem
);
2044 cgroup_migrate_add_src(task_css_set(task
), dst_cgrp
,
2048 } while_each_thread(leader
, task
);
2050 up_read(&css_set_rwsem
);
2052 /* prepare dst csets and commit */
2053 ret
= cgroup_migrate_prepare_dst(dst_cgrp
, &preloaded_csets
);
2055 ret
= cgroup_migrate(dst_cgrp
, leader
, threadgroup
);
2057 cgroup_migrate_finish(&preloaded_csets
);
2062 * Find the task_struct of the task to attach by vpid and pass it along to the
2063 * function to attach either it or all tasks in its threadgroup. Will lock
2064 * cgroup_mutex and threadgroup.
2066 static int attach_task_by_pid(struct cgroup
*cgrp
, u64 pid
, bool threadgroup
)
2068 struct task_struct
*tsk
;
2069 const struct cred
*cred
= current_cred(), *tcred
;
2072 if (!cgroup_lock_live_group(cgrp
))
2078 tsk
= find_task_by_vpid(pid
);
2082 goto out_unlock_cgroup
;
2085 * even if we're attaching all tasks in the thread group, we
2086 * only need to check permissions on one of them.
2088 tcred
= __task_cred(tsk
);
2089 if (!uid_eq(cred
->euid
, GLOBAL_ROOT_UID
) &&
2090 !uid_eq(cred
->euid
, tcred
->uid
) &&
2091 !uid_eq(cred
->euid
, tcred
->suid
)) {
2094 goto out_unlock_cgroup
;
2100 tsk
= tsk
->group_leader
;
2103 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2104 * trapped in a cpuset, or RT worker may be born in a cgroup
2105 * with no rt_runtime allocated. Just say no.
2107 if (tsk
== kthreadd_task
|| (tsk
->flags
& PF_NO_SETAFFINITY
)) {
2110 goto out_unlock_cgroup
;
2113 get_task_struct(tsk
);
2116 threadgroup_lock(tsk
);
2118 if (!thread_group_leader(tsk
)) {
2120 * a race with de_thread from another thread's exec()
2121 * may strip us of our leadership, if this happens,
2122 * there is no choice but to throw this task away and
2123 * try again; this is
2124 * "double-double-toil-and-trouble-check locking".
2126 threadgroup_unlock(tsk
);
2127 put_task_struct(tsk
);
2128 goto retry_find_task
;
2132 ret
= cgroup_attach_task(cgrp
, tsk
, threadgroup
);
2134 threadgroup_unlock(tsk
);
2136 put_task_struct(tsk
);
2138 mutex_unlock(&cgroup_mutex
);
2143 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2144 * @from: attach to all cgroups of a given task
2145 * @tsk: the task to be attached
2147 int cgroup_attach_task_all(struct task_struct
*from
, struct task_struct
*tsk
)
2149 struct cgroup_root
*root
;
2152 mutex_lock(&cgroup_mutex
);
2153 for_each_root(root
) {
2154 struct cgroup
*from_cgrp
;
2156 if (root
== &cgrp_dfl_root
)
2159 down_read(&css_set_rwsem
);
2160 from_cgrp
= task_cgroup_from_root(from
, root
);
2161 up_read(&css_set_rwsem
);
2163 retval
= cgroup_attach_task(from_cgrp
, tsk
, false);
2167 mutex_unlock(&cgroup_mutex
);
2171 EXPORT_SYMBOL_GPL(cgroup_attach_task_all
);
2173 static int cgroup_tasks_write(struct cgroup_subsys_state
*css
,
2174 struct cftype
*cft
, u64 pid
)
2176 return attach_task_by_pid(css
->cgroup
, pid
, false);
2179 static int cgroup_procs_write(struct cgroup_subsys_state
*css
,
2180 struct cftype
*cft
, u64 tgid
)
2182 return attach_task_by_pid(css
->cgroup
, tgid
, true);
2185 static int cgroup_release_agent_write(struct cgroup_subsys_state
*css
,
2186 struct cftype
*cft
, char *buffer
)
2188 struct cgroup_root
*root
= css
->cgroup
->root
;
2190 BUILD_BUG_ON(sizeof(root
->release_agent_path
) < PATH_MAX
);
2191 if (!cgroup_lock_live_group(css
->cgroup
))
2193 spin_lock(&release_agent_path_lock
);
2194 strlcpy(root
->release_agent_path
, buffer
,
2195 sizeof(root
->release_agent_path
));
2196 spin_unlock(&release_agent_path_lock
);
2197 mutex_unlock(&cgroup_mutex
);
2201 static int cgroup_release_agent_show(struct seq_file
*seq
, void *v
)
2203 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2205 if (!cgroup_lock_live_group(cgrp
))
2207 seq_puts(seq
, cgrp
->root
->release_agent_path
);
2208 seq_putc(seq
, '\n');
2209 mutex_unlock(&cgroup_mutex
);
2213 static int cgroup_sane_behavior_show(struct seq_file
*seq
, void *v
)
2215 struct cgroup
*cgrp
= seq_css(seq
)->cgroup
;
2217 seq_printf(seq
, "%d\n", cgroup_sane_behavior(cgrp
));
2221 static ssize_t
cgroup_file_write(struct kernfs_open_file
*of
, char *buf
,
2222 size_t nbytes
, loff_t off
)
2224 struct cgroup
*cgrp
= of
->kn
->parent
->priv
;
2225 struct cftype
*cft
= of
->kn
->priv
;
2226 struct cgroup_subsys_state
*css
;
2230 * kernfs guarantees that a file isn't deleted with operations in
2231 * flight, which means that the matching css is and stays alive and
2232 * doesn't need to be pinned. The RCU locking is not necessary
2233 * either. It's just for the convenience of using cgroup_css().
2236 css
= cgroup_css(cgrp
, cft
->ss
);
2239 if (cft
->write_string
) {
2240 ret
= cft
->write_string(css
, cft
, strstrip(buf
));
2241 } else if (cft
->write_u64
) {
2242 unsigned long long v
;
2243 ret
= kstrtoull(buf
, 0, &v
);
2245 ret
= cft
->write_u64(css
, cft
, v
);
2246 } else if (cft
->write_s64
) {
2248 ret
= kstrtoll(buf
, 0, &v
);
2250 ret
= cft
->write_s64(css
, cft
, v
);
2251 } else if (cft
->trigger
) {
2252 ret
= cft
->trigger(css
, (unsigned int)cft
->private);
2257 return ret
?: nbytes
;
2260 static void *cgroup_seqfile_start(struct seq_file
*seq
, loff_t
*ppos
)
2262 return seq_cft(seq
)->seq_start(seq
, ppos
);
2265 static void *cgroup_seqfile_next(struct seq_file
*seq
, void *v
, loff_t
*ppos
)
2267 return seq_cft(seq
)->seq_next(seq
, v
, ppos
);
2270 static void cgroup_seqfile_stop(struct seq_file
*seq
, void *v
)
2272 seq_cft(seq
)->seq_stop(seq
, v
);
2275 static int cgroup_seqfile_show(struct seq_file
*m
, void *arg
)
2277 struct cftype
*cft
= seq_cft(m
);
2278 struct cgroup_subsys_state
*css
= seq_css(m
);
2281 return cft
->seq_show(m
, arg
);
2284 seq_printf(m
, "%llu\n", cft
->read_u64(css
, cft
));
2285 else if (cft
->read_s64
)
2286 seq_printf(m
, "%lld\n", cft
->read_s64(css
, cft
));
2292 static struct kernfs_ops cgroup_kf_single_ops
= {
2293 .atomic_write_len
= PAGE_SIZE
,
2294 .write
= cgroup_file_write
,
2295 .seq_show
= cgroup_seqfile_show
,
2298 static struct kernfs_ops cgroup_kf_ops
= {
2299 .atomic_write_len
= PAGE_SIZE
,
2300 .write
= cgroup_file_write
,
2301 .seq_start
= cgroup_seqfile_start
,
2302 .seq_next
= cgroup_seqfile_next
,
2303 .seq_stop
= cgroup_seqfile_stop
,
2304 .seq_show
= cgroup_seqfile_show
,
2308 * cgroup_rename - Only allow simple rename of directories in place.
2310 static int cgroup_rename(struct kernfs_node
*kn
, struct kernfs_node
*new_parent
,
2311 const char *new_name_str
)
2313 struct cgroup
*cgrp
= kn
->priv
;
2316 if (kernfs_type(kn
) != KERNFS_DIR
)
2318 if (kn
->parent
!= new_parent
)
2322 * This isn't a proper migration and its usefulness is very
2323 * limited. Disallow if sane_behavior.
2325 if (cgroup_sane_behavior(cgrp
))
2329 * We're gonna grab cgroup_tree_mutex which nests outside kernfs
2330 * active_ref. kernfs_rename() doesn't require active_ref
2331 * protection. Break them before grabbing cgroup_tree_mutex.
2333 kernfs_break_active_protection(new_parent
);
2334 kernfs_break_active_protection(kn
);
2336 mutex_lock(&cgroup_tree_mutex
);
2337 mutex_lock(&cgroup_mutex
);
2339 ret
= kernfs_rename(kn
, new_parent
, new_name_str
);
2341 mutex_unlock(&cgroup_mutex
);
2342 mutex_unlock(&cgroup_tree_mutex
);
2344 kernfs_unbreak_active_protection(kn
);
2345 kernfs_unbreak_active_protection(new_parent
);
2349 /* set uid and gid of cgroup dirs and files to that of the creator */
2350 static int cgroup_kn_set_ugid(struct kernfs_node
*kn
)
2352 struct iattr iattr
= { .ia_valid
= ATTR_UID
| ATTR_GID
,
2353 .ia_uid
= current_fsuid(),
2354 .ia_gid
= current_fsgid(), };
2356 if (uid_eq(iattr
.ia_uid
, GLOBAL_ROOT_UID
) &&
2357 gid_eq(iattr
.ia_gid
, GLOBAL_ROOT_GID
))
2360 return kernfs_setattr(kn
, &iattr
);
2363 static int cgroup_add_file(struct cgroup
*cgrp
, struct cftype
*cft
)
2365 char name
[CGROUP_FILE_NAME_MAX
];
2366 struct kernfs_node
*kn
;
2367 struct lock_class_key
*key
= NULL
;
2370 #ifdef CONFIG_DEBUG_LOCK_ALLOC
2371 key
= &cft
->lockdep_key
;
2373 kn
= __kernfs_create_file(cgrp
->kn
, cgroup_file_name(cgrp
, cft
, name
),
2374 cgroup_file_mode(cft
), 0, cft
->kf_ops
, cft
,
2379 ret
= cgroup_kn_set_ugid(kn
);
2386 * cgroup_addrm_files - add or remove files to a cgroup directory
2387 * @cgrp: the target cgroup
2388 * @cfts: array of cftypes to be added
2389 * @is_add: whether to add or remove
2391 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
2392 * For removals, this function never fails. If addition fails, this
2393 * function doesn't remove files already added. The caller is responsible
2396 static int cgroup_addrm_files(struct cgroup
*cgrp
, struct cftype cfts
[],
2402 lockdep_assert_held(&cgroup_tree_mutex
);
2404 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
2405 /* does cft->flags tell us to skip this file on @cgrp? */
2406 if ((cft
->flags
& CFTYPE_ONLY_ON_DFL
) && !cgroup_on_dfl(cgrp
))
2408 if ((cft
->flags
& CFTYPE_INSANE
) && cgroup_sane_behavior(cgrp
))
2410 if ((cft
->flags
& CFTYPE_NOT_ON_ROOT
) && !cgrp
->parent
)
2412 if ((cft
->flags
& CFTYPE_ONLY_ON_ROOT
) && cgrp
->parent
)
2416 ret
= cgroup_add_file(cgrp
, cft
);
2418 pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
2423 cgroup_rm_file(cgrp
, cft
);
2429 static int cgroup_apply_cftypes(struct cftype
*cfts
, bool is_add
)
2432 struct cgroup_subsys
*ss
= cfts
[0].ss
;
2433 struct cgroup
*root
= &ss
->root
->cgrp
;
2434 struct cgroup_subsys_state
*css
;
2437 lockdep_assert_held(&cgroup_tree_mutex
);
2439 /* don't bother if @ss isn't attached */
2440 if (ss
->root
== &cgrp_dfl_root
)
2443 /* add/rm files for all cgroups created before */
2444 css_for_each_descendant_pre(css
, cgroup_css(root
, ss
)) {
2445 struct cgroup
*cgrp
= css
->cgroup
;
2447 if (cgroup_is_dead(cgrp
))
2450 ret
= cgroup_addrm_files(cgrp
, cfts
, is_add
);
2456 kernfs_activate(root
->kn
);
2460 static void cgroup_exit_cftypes(struct cftype
*cfts
)
2464 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
2465 /* free copy for custom atomic_write_len, see init_cftypes() */
2466 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
)
2473 static int cgroup_init_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
2477 for (cft
= cfts
; cft
->name
[0] != '\0'; cft
++) {
2478 struct kernfs_ops
*kf_ops
;
2480 WARN_ON(cft
->ss
|| cft
->kf_ops
);
2483 kf_ops
= &cgroup_kf_ops
;
2485 kf_ops
= &cgroup_kf_single_ops
;
2488 * Ugh... if @cft wants a custom max_write_len, we need to
2489 * make a copy of kf_ops to set its atomic_write_len.
2491 if (cft
->max_write_len
&& cft
->max_write_len
!= PAGE_SIZE
) {
2492 kf_ops
= kmemdup(kf_ops
, sizeof(*kf_ops
), GFP_KERNEL
);
2494 cgroup_exit_cftypes(cfts
);
2497 kf_ops
->atomic_write_len
= cft
->max_write_len
;
2500 cft
->kf_ops
= kf_ops
;
2507 static int cgroup_rm_cftypes_locked(struct cftype
*cfts
)
2509 lockdep_assert_held(&cgroup_tree_mutex
);
2511 if (!cfts
|| !cfts
[0].ss
)
2514 list_del(&cfts
->node
);
2515 cgroup_apply_cftypes(cfts
, false);
2516 cgroup_exit_cftypes(cfts
);
2521 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
2522 * @cfts: zero-length name terminated array of cftypes
2524 * Unregister @cfts. Files described by @cfts are removed from all
2525 * existing cgroups and all future cgroups won't have them either. This
2526 * function can be called anytime whether @cfts' subsys is attached or not.
2528 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
2531 int cgroup_rm_cftypes(struct cftype
*cfts
)
2535 mutex_lock(&cgroup_tree_mutex
);
2536 ret
= cgroup_rm_cftypes_locked(cfts
);
2537 mutex_unlock(&cgroup_tree_mutex
);
2542 * cgroup_add_cftypes - add an array of cftypes to a subsystem
2543 * @ss: target cgroup subsystem
2544 * @cfts: zero-length name terminated array of cftypes
2546 * Register @cfts to @ss. Files described by @cfts are created for all
2547 * existing cgroups to which @ss is attached and all future cgroups will
2548 * have them too. This function can be called anytime whether @ss is
2551 * Returns 0 on successful registration, -errno on failure. Note that this
2552 * function currently returns 0 as long as @cfts registration is successful
2553 * even if some file creation attempts on existing cgroups fail.
2555 int cgroup_add_cftypes(struct cgroup_subsys
*ss
, struct cftype
*cfts
)
2559 if (!cfts
|| cfts
[0].name
[0] == '\0')
2562 ret
= cgroup_init_cftypes(ss
, cfts
);
2566 mutex_lock(&cgroup_tree_mutex
);
2568 list_add_tail(&cfts
->node
, &ss
->cfts
);
2569 ret
= cgroup_apply_cftypes(cfts
, true);
2571 cgroup_rm_cftypes_locked(cfts
);
2573 mutex_unlock(&cgroup_tree_mutex
);
2578 * cgroup_task_count - count the number of tasks in a cgroup.
2579 * @cgrp: the cgroup in question
2581 * Return the number of tasks in the cgroup.
2583 static int cgroup_task_count(const struct cgroup
*cgrp
)
2586 struct cgrp_cset_link
*link
;
2588 down_read(&css_set_rwsem
);
2589 list_for_each_entry(link
, &cgrp
->cset_links
, cset_link
)
2590 count
+= atomic_read(&link
->cset
->refcount
);
2591 up_read(&css_set_rwsem
);
2596 * css_next_child - find the next child of a given css
2597 * @pos_css: the current position (%NULL to initiate traversal)
2598 * @parent_css: css whose children to walk
2600 * This function returns the next child of @parent_css and should be called
2601 * under either cgroup_mutex or RCU read lock. The only requirement is
2602 * that @parent_css and @pos_css are accessible. The next sibling is
2603 * guaranteed to be returned regardless of their states.
2605 struct cgroup_subsys_state
*
2606 css_next_child(struct cgroup_subsys_state
*pos_css
,
2607 struct cgroup_subsys_state
*parent_css
)
2609 struct cgroup
*pos
= pos_css
? pos_css
->cgroup
: NULL
;
2610 struct cgroup
*cgrp
= parent_css
->cgroup
;
2611 struct cgroup
*next
;
2613 cgroup_assert_mutexes_or_rcu_locked();
2616 * @pos could already have been removed. Once a cgroup is removed,
2617 * its ->sibling.next is no longer updated when its next sibling
2618 * changes. As CGRP_DEAD assertion is serialized and happens
2619 * before the cgroup is taken off the ->sibling list, if we see it
2620 * unasserted, it's guaranteed that the next sibling hasn't
2621 * finished its grace period even if it's already removed, and thus
2622 * safe to dereference from this RCU critical section. If
2623 * ->sibling.next is inaccessible, cgroup_is_dead() is guaranteed
2624 * to be visible as %true here.
2626 * If @pos is dead, its next pointer can't be dereferenced;
2627 * however, as each cgroup is given a monotonically increasing
2628 * unique serial number and always appended to the sibling list,
2629 * the next one can be found by walking the parent's children until
2630 * we see a cgroup with higher serial number than @pos's. While
2631 * this path can be slower, it's taken only when either the current
2632 * cgroup is removed or iteration and removal race.
2635 next
= list_entry_rcu(cgrp
->children
.next
, struct cgroup
, sibling
);
2636 } else if (likely(!cgroup_is_dead(pos
))) {
2637 next
= list_entry_rcu(pos
->sibling
.next
, struct cgroup
, sibling
);
2639 list_for_each_entry_rcu(next
, &cgrp
->children
, sibling
)
2640 if (next
->serial_nr
> pos
->serial_nr
)
2644 if (&next
->sibling
== &cgrp
->children
)
2647 return cgroup_css(next
, parent_css
->ss
);
2651 * css_next_descendant_pre - find the next descendant for pre-order walk
2652 * @pos: the current position (%NULL to initiate traversal)
2653 * @root: css whose descendants to walk
2655 * To be used by css_for_each_descendant_pre(). Find the next descendant
2656 * to visit for pre-order traversal of @root's descendants. @root is
2657 * included in the iteration and the first node to be visited.
2659 * While this function requires cgroup_mutex or RCU read locking, it
2660 * doesn't require the whole traversal to be contained in a single critical
2661 * section. This function will return the correct next descendant as long
2662 * as both @pos and @root are accessible and @pos is a descendant of @root.
2664 struct cgroup_subsys_state
*
2665 css_next_descendant_pre(struct cgroup_subsys_state
*pos
,
2666 struct cgroup_subsys_state
*root
)
2668 struct cgroup_subsys_state
*next
;
2670 cgroup_assert_mutexes_or_rcu_locked();
2672 /* if first iteration, visit @root */
2676 /* visit the first child if exists */
2677 next
= css_next_child(NULL
, pos
);
2681 /* no child, visit my or the closest ancestor's next sibling */
2682 while (pos
!= root
) {
2683 next
= css_next_child(pos
, css_parent(pos
));
2686 pos
= css_parent(pos
);
2693 * css_rightmost_descendant - return the rightmost descendant of a css
2694 * @pos: css of interest
2696 * Return the rightmost descendant of @pos. If there's no descendant, @pos
2697 * is returned. This can be used during pre-order traversal to skip
2700 * While this function requires cgroup_mutex or RCU read locking, it
2701 * doesn't require the whole traversal to be contained in a single critical
2702 * section. This function will return the correct rightmost descendant as
2703 * long as @pos is accessible.
2705 struct cgroup_subsys_state
*
2706 css_rightmost_descendant(struct cgroup_subsys_state
*pos
)
2708 struct cgroup_subsys_state
*last
, *tmp
;
2710 cgroup_assert_mutexes_or_rcu_locked();
2714 /* ->prev isn't RCU safe, walk ->next till the end */
2716 css_for_each_child(tmp
, last
)
2723 static struct cgroup_subsys_state
*
2724 css_leftmost_descendant(struct cgroup_subsys_state
*pos
)
2726 struct cgroup_subsys_state
*last
;
2730 pos
= css_next_child(NULL
, pos
);
2737 * css_next_descendant_post - find the next descendant for post-order walk
2738 * @pos: the current position (%NULL to initiate traversal)
2739 * @root: css whose descendants to walk
2741 * To be used by css_for_each_descendant_post(). Find the next descendant
2742 * to visit for post-order traversal of @root's descendants. @root is
2743 * included in the iteration and the last node to be visited.
2745 * While this function requires cgroup_mutex or RCU read locking, it
2746 * doesn't require the whole traversal to be contained in a single critical
2747 * section. This function will return the correct next descendant as long
2748 * as both @pos and @cgroup are accessible and @pos is a descendant of
2751 struct cgroup_subsys_state
*
2752 css_next_descendant_post(struct cgroup_subsys_state
*pos
,
2753 struct cgroup_subsys_state
*root
)
2755 struct cgroup_subsys_state
*next
;
2757 cgroup_assert_mutexes_or_rcu_locked();
2759 /* if first iteration, visit leftmost descendant which may be @root */
2761 return css_leftmost_descendant(root
);
2763 /* if we visited @root, we're done */
2767 /* if there's an unvisited sibling, visit its leftmost descendant */
2768 next
= css_next_child(pos
, css_parent(pos
));
2770 return css_leftmost_descendant(next
);
2772 /* no sibling left, visit parent */
2773 return css_parent(pos
);
2777 * css_advance_task_iter - advance a task itererator to the next css_set
2778 * @it: the iterator to advance
2780 * Advance @it to the next css_set to walk.
2782 static void css_advance_task_iter(struct css_task_iter
*it
)
2784 struct list_head
*l
= it
->cset_link
;
2785 struct cgrp_cset_link
*link
;
2786 struct css_set
*cset
;
2788 /* Advance to the next non-empty css_set */
2791 if (l
== &it
->origin_css
->cgroup
->cset_links
) {
2792 it
->cset_link
= NULL
;
2795 link
= list_entry(l
, struct cgrp_cset_link
, cset_link
);
2797 } while (list_empty(&cset
->tasks
) && list_empty(&cset
->mg_tasks
));
2801 if (!list_empty(&cset
->tasks
))
2802 it
->task
= cset
->tasks
.next
;
2804 it
->task
= cset
->mg_tasks
.next
;
2808 * css_task_iter_start - initiate task iteration
2809 * @css: the css to walk tasks of
2810 * @it: the task iterator to use
2812 * Initiate iteration through the tasks of @css. The caller can call
2813 * css_task_iter_next() to walk through the tasks until the function
2814 * returns NULL. On completion of iteration, css_task_iter_end() must be
2817 * Note that this function acquires a lock which is released when the
2818 * iteration finishes. The caller can't sleep while iteration is in
2821 void css_task_iter_start(struct cgroup_subsys_state
*css
,
2822 struct css_task_iter
*it
)
2823 __acquires(css_set_rwsem
)
2825 /* no one should try to iterate before mounting cgroups */
2826 WARN_ON_ONCE(!use_task_css_set_links
);
2828 down_read(&css_set_rwsem
);
2830 it
->origin_css
= css
;
2831 it
->cset_link
= &css
->cgroup
->cset_links
;
2833 css_advance_task_iter(it
);
2837 * css_task_iter_next - return the next task for the iterator
2838 * @it: the task iterator being iterated
2840 * The "next" function for task iteration. @it should have been
2841 * initialized via css_task_iter_start(). Returns NULL when the iteration
2844 struct task_struct
*css_task_iter_next(struct css_task_iter
*it
)
2846 struct task_struct
*res
;
2847 struct list_head
*l
= it
->task
;
2848 struct cgrp_cset_link
*link
= list_entry(it
->cset_link
,
2849 struct cgrp_cset_link
, cset_link
);
2851 /* If the iterator cg is NULL, we have no tasks */
2854 res
= list_entry(l
, struct task_struct
, cg_list
);
2857 * Advance iterator to find next entry. cset->tasks is consumed
2858 * first and then ->mg_tasks. After ->mg_tasks, we move onto the
2863 if (l
== &link
->cset
->tasks
)
2864 l
= link
->cset
->mg_tasks
.next
;
2866 if (l
== &link
->cset
->mg_tasks
)
2867 css_advance_task_iter(it
);
2875 * css_task_iter_end - finish task iteration
2876 * @it: the task iterator to finish
2878 * Finish task iteration started by css_task_iter_start().
2880 void css_task_iter_end(struct css_task_iter
*it
)
2881 __releases(css_set_rwsem
)
2883 up_read(&css_set_rwsem
);
2887 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
2888 * @to: cgroup to which the tasks will be moved
2889 * @from: cgroup in which the tasks currently reside
2891 * Locking rules between cgroup_post_fork() and the migration path
2892 * guarantee that, if a task is forking while being migrated, the new child
2893 * is guaranteed to be either visible in the source cgroup after the
2894 * parent's migration is complete or put into the target cgroup. No task
2895 * can slip out of migration through forking.
2897 int cgroup_transfer_tasks(struct cgroup
*to
, struct cgroup
*from
)
2899 LIST_HEAD(preloaded_csets
);
2900 struct cgrp_cset_link
*link
;
2901 struct css_task_iter it
;
2902 struct task_struct
*task
;
2905 mutex_lock(&cgroup_mutex
);
2907 /* all tasks in @from are being moved, all csets are source */
2908 down_read(&css_set_rwsem
);
2909 list_for_each_entry(link
, &from
->cset_links
, cset_link
)
2910 cgroup_migrate_add_src(link
->cset
, to
, &preloaded_csets
);
2911 up_read(&css_set_rwsem
);
2913 ret
= cgroup_migrate_prepare_dst(to
, &preloaded_csets
);
2918 * Migrate tasks one-by-one until @form is empty. This fails iff
2919 * ->can_attach() fails.
2922 css_task_iter_start(&from
->dummy_css
, &it
);
2923 task
= css_task_iter_next(&it
);
2925 get_task_struct(task
);
2926 css_task_iter_end(&it
);
2929 ret
= cgroup_migrate(to
, task
, false);
2930 put_task_struct(task
);
2932 } while (task
&& !ret
);
2934 cgroup_migrate_finish(&preloaded_csets
);
2935 mutex_unlock(&cgroup_mutex
);
2940 * Stuff for reading the 'tasks'/'procs' files.
2942 * Reading this file can return large amounts of data if a cgroup has
2943 * *lots* of attached tasks. So it may need several calls to read(),
2944 * but we cannot guarantee that the information we produce is correct
2945 * unless we produce it entirely atomically.
2949 /* which pidlist file are we talking about? */
2950 enum cgroup_filetype
{
2956 * A pidlist is a list of pids that virtually represents the contents of one
2957 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
2958 * a pair (one each for procs, tasks) for each pid namespace that's relevant
2961 struct cgroup_pidlist
{
2963 * used to find which pidlist is wanted. doesn't change as long as
2964 * this particular list stays in the list.
2966 struct { enum cgroup_filetype type
; struct pid_namespace
*ns
; } key
;
2969 /* how many elements the above list has */
2971 /* each of these stored in a list by its cgroup */
2972 struct list_head links
;
2973 /* pointer to the cgroup we belong to, for list removal purposes */
2974 struct cgroup
*owner
;
2975 /* for delayed destruction */
2976 struct delayed_work destroy_dwork
;
2980 * The following two functions "fix" the issue where there are more pids
2981 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
2982 * TODO: replace with a kernel-wide solution to this problem
2984 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
2985 static void *pidlist_allocate(int count
)
2987 if (PIDLIST_TOO_LARGE(count
))
2988 return vmalloc(count
* sizeof(pid_t
));
2990 return kmalloc(count
* sizeof(pid_t
), GFP_KERNEL
);
2993 static void pidlist_free(void *p
)
2995 if (is_vmalloc_addr(p
))
3002 * Used to destroy all pidlists lingering waiting for destroy timer. None
3003 * should be left afterwards.
3005 static void cgroup_pidlist_destroy_all(struct cgroup
*cgrp
)
3007 struct cgroup_pidlist
*l
, *tmp_l
;
3009 mutex_lock(&cgrp
->pidlist_mutex
);
3010 list_for_each_entry_safe(l
, tmp_l
, &cgrp
->pidlists
, links
)
3011 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
, 0);
3012 mutex_unlock(&cgrp
->pidlist_mutex
);
3014 flush_workqueue(cgroup_pidlist_destroy_wq
);
3015 BUG_ON(!list_empty(&cgrp
->pidlists
));
3018 static void cgroup_pidlist_destroy_work_fn(struct work_struct
*work
)
3020 struct delayed_work
*dwork
= to_delayed_work(work
);
3021 struct cgroup_pidlist
*l
= container_of(dwork
, struct cgroup_pidlist
,
3023 struct cgroup_pidlist
*tofree
= NULL
;
3025 mutex_lock(&l
->owner
->pidlist_mutex
);
3028 * Destroy iff we didn't get queued again. The state won't change
3029 * as destroy_dwork can only be queued while locked.
3031 if (!delayed_work_pending(dwork
)) {
3032 list_del(&l
->links
);
3033 pidlist_free(l
->list
);
3034 put_pid_ns(l
->key
.ns
);
3038 mutex_unlock(&l
->owner
->pidlist_mutex
);
3043 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3044 * Returns the number of unique elements.
3046 static int pidlist_uniq(pid_t
*list
, int length
)
3051 * we presume the 0th element is unique, so i starts at 1. trivial
3052 * edge cases first; no work needs to be done for either
3054 if (length
== 0 || length
== 1)
3056 /* src and dest walk down the list; dest counts unique elements */
3057 for (src
= 1; src
< length
; src
++) {
3058 /* find next unique element */
3059 while (list
[src
] == list
[src
-1]) {
3064 /* dest always points to where the next unique element goes */
3065 list
[dest
] = list
[src
];
3073 * The two pid files - task and cgroup.procs - guaranteed that the result
3074 * is sorted, which forced this whole pidlist fiasco. As pid order is
3075 * different per namespace, each namespace needs differently sorted list,
3076 * making it impossible to use, for example, single rbtree of member tasks
3077 * sorted by task pointer. As pidlists can be fairly large, allocating one
3078 * per open file is dangerous, so cgroup had to implement shared pool of
3079 * pidlists keyed by cgroup and namespace.
3081 * All this extra complexity was caused by the original implementation
3082 * committing to an entirely unnecessary property. In the long term, we
3083 * want to do away with it. Explicitly scramble sort order if
3084 * sane_behavior so that no such expectation exists in the new interface.
3086 * Scrambling is done by swapping every two consecutive bits, which is
3087 * non-identity one-to-one mapping which disturbs sort order sufficiently.
3089 static pid_t
pid_fry(pid_t pid
)
3091 unsigned a
= pid
& 0x55555555;
3092 unsigned b
= pid
& 0xAAAAAAAA;
3094 return (a
<< 1) | (b
>> 1);
3097 static pid_t
cgroup_pid_fry(struct cgroup
*cgrp
, pid_t pid
)
3099 if (cgroup_sane_behavior(cgrp
))
3100 return pid_fry(pid
);
3105 static int cmppid(const void *a
, const void *b
)
3107 return *(pid_t
*)a
- *(pid_t
*)b
;
3110 static int fried_cmppid(const void *a
, const void *b
)
3112 return pid_fry(*(pid_t
*)a
) - pid_fry(*(pid_t
*)b
);
3115 static struct cgroup_pidlist
*cgroup_pidlist_find(struct cgroup
*cgrp
,
3116 enum cgroup_filetype type
)
3118 struct cgroup_pidlist
*l
;
3119 /* don't need task_nsproxy() if we're looking at ourself */
3120 struct pid_namespace
*ns
= task_active_pid_ns(current
);
3122 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3124 list_for_each_entry(l
, &cgrp
->pidlists
, links
)
3125 if (l
->key
.type
== type
&& l
->key
.ns
== ns
)
3131 * find the appropriate pidlist for our purpose (given procs vs tasks)
3132 * returns with the lock on that pidlist already held, and takes care
3133 * of the use count, or returns NULL with no locks held if we're out of
3136 static struct cgroup_pidlist
*cgroup_pidlist_find_create(struct cgroup
*cgrp
,
3137 enum cgroup_filetype type
)
3139 struct cgroup_pidlist
*l
;
3141 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3143 l
= cgroup_pidlist_find(cgrp
, type
);
3147 /* entry not found; create a new one */
3148 l
= kzalloc(sizeof(struct cgroup_pidlist
), GFP_KERNEL
);
3152 INIT_DELAYED_WORK(&l
->destroy_dwork
, cgroup_pidlist_destroy_work_fn
);
3154 /* don't need task_nsproxy() if we're looking at ourself */
3155 l
->key
.ns
= get_pid_ns(task_active_pid_ns(current
));
3157 list_add(&l
->links
, &cgrp
->pidlists
);
3162 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3164 static int pidlist_array_load(struct cgroup
*cgrp
, enum cgroup_filetype type
,
3165 struct cgroup_pidlist
**lp
)
3169 int pid
, n
= 0; /* used for populating the array */
3170 struct css_task_iter it
;
3171 struct task_struct
*tsk
;
3172 struct cgroup_pidlist
*l
;
3174 lockdep_assert_held(&cgrp
->pidlist_mutex
);
3177 * If cgroup gets more users after we read count, we won't have
3178 * enough space - tough. This race is indistinguishable to the
3179 * caller from the case that the additional cgroup users didn't
3180 * show up until sometime later on.
3182 length
= cgroup_task_count(cgrp
);
3183 array
= pidlist_allocate(length
);
3186 /* now, populate the array */
3187 css_task_iter_start(&cgrp
->dummy_css
, &it
);
3188 while ((tsk
= css_task_iter_next(&it
))) {
3189 if (unlikely(n
== length
))
3191 /* get tgid or pid for procs or tasks file respectively */
3192 if (type
== CGROUP_FILE_PROCS
)
3193 pid
= task_tgid_vnr(tsk
);
3195 pid
= task_pid_vnr(tsk
);
3196 if (pid
> 0) /* make sure to only use valid results */
3199 css_task_iter_end(&it
);
3201 /* now sort & (if procs) strip out duplicates */
3202 if (cgroup_sane_behavior(cgrp
))
3203 sort(array
, length
, sizeof(pid_t
), fried_cmppid
, NULL
);
3205 sort(array
, length
, sizeof(pid_t
), cmppid
, NULL
);
3206 if (type
== CGROUP_FILE_PROCS
)
3207 length
= pidlist_uniq(array
, length
);
3209 l
= cgroup_pidlist_find_create(cgrp
, type
);
3211 mutex_unlock(&cgrp
->pidlist_mutex
);
3212 pidlist_free(array
);
3216 /* store array, freeing old if necessary */
3217 pidlist_free(l
->list
);
3225 * cgroupstats_build - build and fill cgroupstats
3226 * @stats: cgroupstats to fill information into
3227 * @dentry: A dentry entry belonging to the cgroup for which stats have
3230 * Build and fill cgroupstats so that taskstats can export it to user
3233 int cgroupstats_build(struct cgroupstats
*stats
, struct dentry
*dentry
)
3235 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
3236 struct cgroup
*cgrp
;
3237 struct css_task_iter it
;
3238 struct task_struct
*tsk
;
3240 /* it should be kernfs_node belonging to cgroupfs and is a directory */
3241 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
3242 kernfs_type(kn
) != KERNFS_DIR
)
3245 mutex_lock(&cgroup_mutex
);
3248 * We aren't being called from kernfs and there's no guarantee on
3249 * @kn->priv's validity. For this and css_tryget_from_dir(),
3250 * @kn->priv is RCU safe. Let's do the RCU dancing.
3253 cgrp
= rcu_dereference(kn
->priv
);
3254 if (!cgrp
|| cgroup_is_dead(cgrp
)) {
3256 mutex_unlock(&cgroup_mutex
);
3261 css_task_iter_start(&cgrp
->dummy_css
, &it
);
3262 while ((tsk
= css_task_iter_next(&it
))) {
3263 switch (tsk
->state
) {
3265 stats
->nr_running
++;
3267 case TASK_INTERRUPTIBLE
:
3268 stats
->nr_sleeping
++;
3270 case TASK_UNINTERRUPTIBLE
:
3271 stats
->nr_uninterruptible
++;
3274 stats
->nr_stopped
++;
3277 if (delayacct_is_task_waiting_on_io(tsk
))
3278 stats
->nr_io_wait
++;
3282 css_task_iter_end(&it
);
3284 mutex_unlock(&cgroup_mutex
);
3290 * seq_file methods for the tasks/procs files. The seq_file position is the
3291 * next pid to display; the seq_file iterator is a pointer to the pid
3292 * in the cgroup->l->list array.
3295 static void *cgroup_pidlist_start(struct seq_file
*s
, loff_t
*pos
)
3298 * Initially we receive a position value that corresponds to
3299 * one more than the last pid shown (or 0 on the first call or
3300 * after a seek to the start). Use a binary-search to find the
3301 * next pid to display, if any
3303 struct kernfs_open_file
*of
= s
->private;
3304 struct cgroup
*cgrp
= seq_css(s
)->cgroup
;
3305 struct cgroup_pidlist
*l
;
3306 enum cgroup_filetype type
= seq_cft(s
)->private;
3307 int index
= 0, pid
= *pos
;
3310 mutex_lock(&cgrp
->pidlist_mutex
);
3313 * !NULL @of->priv indicates that this isn't the first start()
3314 * after open. If the matching pidlist is around, we can use that.
3315 * Look for it. Note that @of->priv can't be used directly. It
3316 * could already have been destroyed.
3319 of
->priv
= cgroup_pidlist_find(cgrp
, type
);
3322 * Either this is the first start() after open or the matching
3323 * pidlist has been destroyed inbetween. Create a new one.
3326 ret
= pidlist_array_load(cgrp
, type
,
3327 (struct cgroup_pidlist
**)&of
->priv
);
3329 return ERR_PTR(ret
);
3334 int end
= l
->length
;
3336 while (index
< end
) {
3337 int mid
= (index
+ end
) / 2;
3338 if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) == pid
) {
3341 } else if (cgroup_pid_fry(cgrp
, l
->list
[mid
]) <= pid
)
3347 /* If we're off the end of the array, we're done */
3348 if (index
>= l
->length
)
3350 /* Update the abstract position to be the actual pid that we found */
3351 iter
= l
->list
+ index
;
3352 *pos
= cgroup_pid_fry(cgrp
, *iter
);
3356 static void cgroup_pidlist_stop(struct seq_file
*s
, void *v
)
3358 struct kernfs_open_file
*of
= s
->private;
3359 struct cgroup_pidlist
*l
= of
->priv
;
3362 mod_delayed_work(cgroup_pidlist_destroy_wq
, &l
->destroy_dwork
,
3363 CGROUP_PIDLIST_DESTROY_DELAY
);
3364 mutex_unlock(&seq_css(s
)->cgroup
->pidlist_mutex
);
3367 static void *cgroup_pidlist_next(struct seq_file
*s
, void *v
, loff_t
*pos
)
3369 struct kernfs_open_file
*of
= s
->private;
3370 struct cgroup_pidlist
*l
= of
->priv
;
3372 pid_t
*end
= l
->list
+ l
->length
;
3374 * Advance to the next pid in the array. If this goes off the
3381 *pos
= cgroup_pid_fry(seq_css(s
)->cgroup
, *p
);
3386 static int cgroup_pidlist_show(struct seq_file
*s
, void *v
)
3388 return seq_printf(s
, "%d\n", *(int *)v
);
3392 * seq_operations functions for iterating on pidlists through seq_file -
3393 * independent of whether it's tasks or procs
3395 static const struct seq_operations cgroup_pidlist_seq_operations
= {
3396 .start
= cgroup_pidlist_start
,
3397 .stop
= cgroup_pidlist_stop
,
3398 .next
= cgroup_pidlist_next
,
3399 .show
= cgroup_pidlist_show
,
3402 static u64
cgroup_read_notify_on_release(struct cgroup_subsys_state
*css
,
3405 return notify_on_release(css
->cgroup
);
3408 static int cgroup_write_notify_on_release(struct cgroup_subsys_state
*css
,
3409 struct cftype
*cft
, u64 val
)
3411 clear_bit(CGRP_RELEASABLE
, &css
->cgroup
->flags
);
3413 set_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
3415 clear_bit(CGRP_NOTIFY_ON_RELEASE
, &css
->cgroup
->flags
);
3419 static u64
cgroup_clone_children_read(struct cgroup_subsys_state
*css
,
3422 return test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
3425 static int cgroup_clone_children_write(struct cgroup_subsys_state
*css
,
3426 struct cftype
*cft
, u64 val
)
3429 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
3431 clear_bit(CGRP_CPUSET_CLONE_CHILDREN
, &css
->cgroup
->flags
);
3435 static struct cftype cgroup_base_files
[] = {
3437 .name
= "cgroup.procs",
3438 .seq_start
= cgroup_pidlist_start
,
3439 .seq_next
= cgroup_pidlist_next
,
3440 .seq_stop
= cgroup_pidlist_stop
,
3441 .seq_show
= cgroup_pidlist_show
,
3442 .private = CGROUP_FILE_PROCS
,
3443 .write_u64
= cgroup_procs_write
,
3444 .mode
= S_IRUGO
| S_IWUSR
,
3447 .name
= "cgroup.clone_children",
3448 .flags
= CFTYPE_INSANE
,
3449 .read_u64
= cgroup_clone_children_read
,
3450 .write_u64
= cgroup_clone_children_write
,
3453 .name
= "cgroup.sane_behavior",
3454 .flags
= CFTYPE_ONLY_ON_ROOT
,
3455 .seq_show
= cgroup_sane_behavior_show
,
3459 * Historical crazy stuff. These don't have "cgroup." prefix and
3460 * don't exist if sane_behavior. If you're depending on these, be
3461 * prepared to be burned.
3465 .flags
= CFTYPE_INSANE
, /* use "procs" instead */
3466 .seq_start
= cgroup_pidlist_start
,
3467 .seq_next
= cgroup_pidlist_next
,
3468 .seq_stop
= cgroup_pidlist_stop
,
3469 .seq_show
= cgroup_pidlist_show
,
3470 .private = CGROUP_FILE_TASKS
,
3471 .write_u64
= cgroup_tasks_write
,
3472 .mode
= S_IRUGO
| S_IWUSR
,
3475 .name
= "notify_on_release",
3476 .flags
= CFTYPE_INSANE
,
3477 .read_u64
= cgroup_read_notify_on_release
,
3478 .write_u64
= cgroup_write_notify_on_release
,
3481 .name
= "release_agent",
3482 .flags
= CFTYPE_INSANE
| CFTYPE_ONLY_ON_ROOT
,
3483 .seq_show
= cgroup_release_agent_show
,
3484 .write_string
= cgroup_release_agent_write
,
3485 .max_write_len
= PATH_MAX
- 1,
3491 * cgroup_populate_dir - create subsys files in a cgroup directory
3492 * @cgrp: target cgroup
3493 * @subsys_mask: mask of the subsystem ids whose files should be added
3495 * On failure, no file is added.
3497 static int cgroup_populate_dir(struct cgroup
*cgrp
, unsigned long subsys_mask
)
3499 struct cgroup_subsys
*ss
;
3502 /* process cftsets of each subsystem */
3503 for_each_subsys(ss
, i
) {
3504 struct cftype
*cfts
;
3506 if (!test_bit(i
, &subsys_mask
))
3509 list_for_each_entry(cfts
, &ss
->cfts
, node
) {
3510 ret
= cgroup_addrm_files(cgrp
, cfts
, true);
3517 cgroup_clear_dir(cgrp
, subsys_mask
);
3522 * css destruction is four-stage process.
3524 * 1. Destruction starts. Killing of the percpu_ref is initiated.
3525 * Implemented in kill_css().
3527 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
3528 * and thus css_tryget() is guaranteed to fail, the css can be offlined
3529 * by invoking offline_css(). After offlining, the base ref is put.
3530 * Implemented in css_killed_work_fn().
3532 * 3. When the percpu_ref reaches zero, the only possible remaining
3533 * accessors are inside RCU read sections. css_release() schedules the
3536 * 4. After the grace period, the css can be freed. Implemented in
3537 * css_free_work_fn().
3539 * It is actually hairier because both step 2 and 4 require process context
3540 * and thus involve punting to css->destroy_work adding two additional
3541 * steps to the already complex sequence.
3543 static void css_free_work_fn(struct work_struct
*work
)
3545 struct cgroup_subsys_state
*css
=
3546 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
3547 struct cgroup
*cgrp
= css
->cgroup
;
3550 css_put(css
->parent
);
3552 css
->ss
->css_free(css
);
3556 static void css_free_rcu_fn(struct rcu_head
*rcu_head
)
3558 struct cgroup_subsys_state
*css
=
3559 container_of(rcu_head
, struct cgroup_subsys_state
, rcu_head
);
3561 INIT_WORK(&css
->destroy_work
, css_free_work_fn
);
3562 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
3565 static void css_release(struct percpu_ref
*ref
)
3567 struct cgroup_subsys_state
*css
=
3568 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
3570 RCU_INIT_POINTER(css
->cgroup
->subsys
[css
->ss
->id
], NULL
);
3571 call_rcu(&css
->rcu_head
, css_free_rcu_fn
);
3574 static void init_css(struct cgroup_subsys_state
*css
, struct cgroup_subsys
*ss
,
3575 struct cgroup
*cgrp
)
3582 css
->parent
= cgroup_css(cgrp
->parent
, ss
);
3584 css
->flags
|= CSS_ROOT
;
3586 BUG_ON(cgroup_css(cgrp
, ss
));
3589 /* invoke ->css_online() on a new CSS and mark it online if successful */
3590 static int online_css(struct cgroup_subsys_state
*css
)
3592 struct cgroup_subsys
*ss
= css
->ss
;
3595 lockdep_assert_held(&cgroup_tree_mutex
);
3596 lockdep_assert_held(&cgroup_mutex
);
3599 ret
= ss
->css_online(css
);
3601 css
->flags
|= CSS_ONLINE
;
3602 css
->cgroup
->nr_css
++;
3603 rcu_assign_pointer(css
->cgroup
->subsys
[ss
->id
], css
);
3608 /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
3609 static void offline_css(struct cgroup_subsys_state
*css
)
3611 struct cgroup_subsys
*ss
= css
->ss
;
3613 lockdep_assert_held(&cgroup_tree_mutex
);
3614 lockdep_assert_held(&cgroup_mutex
);
3616 if (!(css
->flags
& CSS_ONLINE
))
3619 if (ss
->css_offline
)
3620 ss
->css_offline(css
);
3622 css
->flags
&= ~CSS_ONLINE
;
3623 css
->cgroup
->nr_css
--;
3624 RCU_INIT_POINTER(css
->cgroup
->subsys
[ss
->id
], css
);
3628 * create_css - create a cgroup_subsys_state
3629 * @cgrp: the cgroup new css will be associated with
3630 * @ss: the subsys of new css
3632 * Create a new css associated with @cgrp - @ss pair. On success, the new
3633 * css is online and installed in @cgrp with all interface files created.
3634 * Returns 0 on success, -errno on failure.
3636 static int create_css(struct cgroup
*cgrp
, struct cgroup_subsys
*ss
)
3638 struct cgroup
*parent
= cgrp
->parent
;
3639 struct cgroup_subsys_state
*css
;
3642 lockdep_assert_held(&cgroup_mutex
);
3644 css
= ss
->css_alloc(cgroup_css(parent
, ss
));
3646 return PTR_ERR(css
);
3648 err
= percpu_ref_init(&css
->refcnt
, css_release
);
3652 init_css(css
, ss
, cgrp
);
3654 err
= cgroup_populate_dir(cgrp
, 1 << ss
->id
);
3656 goto err_free_percpu_ref
;
3658 err
= online_css(css
);
3663 css_get(css
->parent
);
3665 cgrp
->subsys_mask
|= 1 << ss
->id
;
3667 if (ss
->broken_hierarchy
&& !ss
->warned_broken_hierarchy
&&
3669 pr_warning("cgroup: %s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
3670 current
->comm
, current
->pid
, ss
->name
);
3671 if (!strcmp(ss
->name
, "memory"))
3672 pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
3673 ss
->warned_broken_hierarchy
= true;
3679 cgroup_clear_dir(css
->cgroup
, 1 << css
->ss
->id
);
3680 err_free_percpu_ref
:
3681 percpu_ref_cancel_init(&css
->refcnt
);
3688 * cgroup_create - create a cgroup
3689 * @parent: cgroup that will be parent of the new cgroup
3690 * @name: name of the new cgroup
3691 * @mode: mode to set on new cgroup
3693 static long cgroup_create(struct cgroup
*parent
, const char *name
,
3696 struct cgroup
*cgrp
;
3697 struct cgroup_root
*root
= parent
->root
;
3699 struct cgroup_subsys
*ss
;
3700 struct kernfs_node
*kn
;
3703 * XXX: The default hierarchy isn't fully implemented yet. Block
3704 * !root cgroup creation on it for now.
3706 if (root
== &cgrp_dfl_root
)
3709 /* allocate the cgroup and its ID, 0 is reserved for the root */
3710 cgrp
= kzalloc(sizeof(*cgrp
), GFP_KERNEL
);
3714 mutex_lock(&cgroup_tree_mutex
);
3717 * Only live parents can have children. Note that the liveliness
3718 * check isn't strictly necessary because cgroup_mkdir() and
3719 * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
3720 * anyway so that locking is contained inside cgroup proper and we
3721 * don't get nasty surprises if we ever grow another caller.
3723 if (!cgroup_lock_live_group(parent
)) {
3725 goto err_unlock_tree
;
3729 * Temporarily set the pointer to NULL, so idr_find() won't return
3730 * a half-baked cgroup.
3732 cgrp
->id
= idr_alloc(&root
->cgroup_idr
, NULL
, 1, 0, GFP_KERNEL
);
3738 init_cgroup_housekeeping(cgrp
);
3740 cgrp
->parent
= parent
;
3741 cgrp
->dummy_css
.parent
= &parent
->dummy_css
;
3742 cgrp
->root
= parent
->root
;
3744 if (notify_on_release(parent
))
3745 set_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
3747 if (test_bit(CGRP_CPUSET_CLONE_CHILDREN
, &parent
->flags
))
3748 set_bit(CGRP_CPUSET_CLONE_CHILDREN
, &cgrp
->flags
);
3750 /* create the directory */
3751 kn
= kernfs_create_dir(parent
->kn
, name
, mode
, cgrp
);
3759 * This extra ref will be put in cgroup_free_fn() and guarantees
3760 * that @cgrp->kn is always accessible.
3764 cgrp
->serial_nr
= cgroup_serial_nr_next
++;
3766 /* allocation complete, commit to creation */
3767 list_add_tail_rcu(&cgrp
->sibling
, &cgrp
->parent
->children
);
3768 atomic_inc(&root
->nr_cgrps
);
3772 * @cgrp is now fully operational. If something fails after this
3773 * point, it'll be released via the normal destruction path.
3775 idr_replace(&root
->cgroup_idr
, cgrp
, cgrp
->id
);
3777 err
= cgroup_kn_set_ugid(kn
);
3781 err
= cgroup_addrm_files(cgrp
, cgroup_base_files
, true);
3785 /* let's create and online css's */
3786 for_each_subsys(ss
, ssid
) {
3787 if (root
->cgrp
.subsys_mask
& (1 << ssid
)) {
3788 err
= create_css(cgrp
, ss
);
3794 kernfs_activate(kn
);
3796 mutex_unlock(&cgroup_mutex
);
3797 mutex_unlock(&cgroup_tree_mutex
);
3802 idr_remove(&root
->cgroup_idr
, cgrp
->id
);
3804 mutex_unlock(&cgroup_mutex
);
3806 mutex_unlock(&cgroup_tree_mutex
);
3811 cgroup_destroy_locked(cgrp
);
3812 mutex_unlock(&cgroup_mutex
);
3813 mutex_unlock(&cgroup_tree_mutex
);
3817 static int cgroup_mkdir(struct kernfs_node
*parent_kn
, const char *name
,
3820 struct cgroup
*parent
= parent_kn
->priv
;
3824 * cgroup_create() grabs cgroup_tree_mutex which nests outside
3825 * kernfs active_ref and cgroup_create() already synchronizes
3826 * properly against removal through cgroup_lock_live_group().
3827 * Break it before calling cgroup_create().
3830 kernfs_break_active_protection(parent_kn
);
3832 ret
= cgroup_create(parent
, name
, mode
);
3834 kernfs_unbreak_active_protection(parent_kn
);
3840 * This is called when the refcnt of a css is confirmed to be killed.
3841 * css_tryget() is now guaranteed to fail.
3843 static void css_killed_work_fn(struct work_struct
*work
)
3845 struct cgroup_subsys_state
*css
=
3846 container_of(work
, struct cgroup_subsys_state
, destroy_work
);
3847 struct cgroup
*cgrp
= css
->cgroup
;
3849 mutex_lock(&cgroup_tree_mutex
);
3850 mutex_lock(&cgroup_mutex
);
3853 * css_tryget() is guaranteed to fail now. Tell subsystems to
3854 * initate destruction.
3859 * If @cgrp is marked dead, it's waiting for refs of all css's to
3860 * be disabled before proceeding to the second phase of cgroup
3861 * destruction. If we are the last one, kick it off.
3863 if (!cgrp
->nr_css
&& cgroup_is_dead(cgrp
))
3864 cgroup_destroy_css_killed(cgrp
);
3866 mutex_unlock(&cgroup_mutex
);
3867 mutex_unlock(&cgroup_tree_mutex
);
3870 * Put the css refs from kill_css(). Each css holds an extra
3871 * reference to the cgroup's dentry and cgroup removal proceeds
3872 * regardless of css refs. On the last put of each css, whenever
3873 * that may be, the extra dentry ref is put so that dentry
3874 * destruction happens only after all css's are released.
3879 /* css kill confirmation processing requires process context, bounce */
3880 static void css_killed_ref_fn(struct percpu_ref
*ref
)
3882 struct cgroup_subsys_state
*css
=
3883 container_of(ref
, struct cgroup_subsys_state
, refcnt
);
3885 INIT_WORK(&css
->destroy_work
, css_killed_work_fn
);
3886 queue_work(cgroup_destroy_wq
, &css
->destroy_work
);
3889 static void __kill_css(struct cgroup_subsys_state
*css
)
3891 lockdep_assert_held(&cgroup_tree_mutex
);
3894 * This must happen before css is disassociated with its cgroup.
3895 * See seq_css() for details.
3897 cgroup_clear_dir(css
->cgroup
, 1 << css
->ss
->id
);
3900 * Killing would put the base ref, but we need to keep it alive
3901 * until after ->css_offline().
3906 * cgroup core guarantees that, by the time ->css_offline() is
3907 * invoked, no new css reference will be given out via
3908 * css_tryget(). We can't simply call percpu_ref_kill() and
3909 * proceed to offlining css's because percpu_ref_kill() doesn't
3910 * guarantee that the ref is seen as killed on all CPUs on return.
3912 * Use percpu_ref_kill_and_confirm() to get notifications as each
3913 * css is confirmed to be seen as killed on all CPUs.
3915 percpu_ref_kill_and_confirm(&css
->refcnt
, css_killed_ref_fn
);
3919 * kill_css - destroy a css
3920 * @css: css to destroy
3922 * This function initiates destruction of @css by removing cgroup interface
3923 * files and putting its base reference. ->css_offline() will be invoked
3924 * asynchronously once css_tryget() is guaranteed to fail and when the
3925 * reference count reaches zero, @css will be released.
3927 static void kill_css(struct cgroup_subsys_state
*css
)
3929 struct cgroup
*cgrp
= css
->cgroup
;
3931 lockdep_assert_held(&cgroup_tree_mutex
);
3933 /* if already killed, noop */
3934 if (cgrp
->subsys_mask
& (1 << css
->ss
->id
)) {
3935 cgrp
->subsys_mask
&= ~(1 << css
->ss
->id
);
3941 * cgroup_destroy_locked - the first stage of cgroup destruction
3942 * @cgrp: cgroup to be destroyed
3944 * css's make use of percpu refcnts whose killing latency shouldn't be
3945 * exposed to userland and are RCU protected. Also, cgroup core needs to
3946 * guarantee that css_tryget() won't succeed by the time ->css_offline() is
3947 * invoked. To satisfy all the requirements, destruction is implemented in
3948 * the following two steps.
3950 * s1. Verify @cgrp can be destroyed and mark it dying. Remove all
3951 * userland visible parts and start killing the percpu refcnts of
3952 * css's. Set up so that the next stage will be kicked off once all
3953 * the percpu refcnts are confirmed to be killed.
3955 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
3956 * rest of destruction. Once all cgroup references are gone, the
3957 * cgroup is RCU-freed.
3959 * This function implements s1. After this step, @cgrp is gone as far as
3960 * the userland is concerned and a new cgroup with the same name may be
3961 * created. As cgroup doesn't care about the names internally, this
3962 * doesn't cause any problem.
3964 static int cgroup_destroy_locked(struct cgroup
*cgrp
)
3965 __releases(&cgroup_mutex
) __acquires(&cgroup_mutex
)
3967 struct cgroup
*child
;
3968 struct cgroup_subsys_state
*css
;
3972 lockdep_assert_held(&cgroup_tree_mutex
);
3973 lockdep_assert_held(&cgroup_mutex
);
3976 * css_set_rwsem synchronizes access to ->cset_links and prevents
3977 * @cgrp from being removed while put_css_set() is in progress.
3979 down_read(&css_set_rwsem
);
3980 empty
= list_empty(&cgrp
->cset_links
);
3981 up_read(&css_set_rwsem
);
3986 * Make sure there's no live children. We can't test ->children
3987 * emptiness as dead children linger on it while being destroyed;
3988 * otherwise, "rmdir parent/child parent" may fail with -EBUSY.
3992 list_for_each_entry_rcu(child
, &cgrp
->children
, sibling
) {
3993 empty
= cgroup_is_dead(child
);
4002 * Mark @cgrp dead. This prevents further task migration and child
4003 * creation by disabling cgroup_lock_live_group(). Note that
4004 * CGRP_DEAD assertion is depended upon by css_next_child() to
4005 * resume iteration after dropping RCU read lock. See
4006 * css_next_child() for details.
4008 set_bit(CGRP_DEAD
, &cgrp
->flags
);
4011 * Initiate massacre of all css's. cgroup_destroy_css_killed()
4012 * will be invoked to perform the rest of destruction once the
4013 * percpu refs of all css's are confirmed to be killed. This
4014 * involves removing the subsystem's files, drop cgroup_mutex.
4016 mutex_unlock(&cgroup_mutex
);
4017 for_each_css(css
, ssid
, cgrp
)
4019 mutex_lock(&cgroup_mutex
);
4021 /* CGRP_DEAD is set, remove from ->release_list for the last time */
4022 raw_spin_lock(&release_list_lock
);
4023 if (!list_empty(&cgrp
->release_list
))
4024 list_del_init(&cgrp
->release_list
);
4025 raw_spin_unlock(&release_list_lock
);
4028 * If @cgrp has css's attached, the second stage of cgroup
4029 * destruction is kicked off from css_killed_work_fn() after the
4030 * refs of all attached css's are killed. If @cgrp doesn't have
4031 * any css, we kick it off here.
4034 cgroup_destroy_css_killed(cgrp
);
4036 /* remove @cgrp directory along with the base files */
4037 mutex_unlock(&cgroup_mutex
);
4040 * There are two control paths which try to determine cgroup from
4041 * dentry without going through kernfs - cgroupstats_build() and
4042 * css_tryget_from_dir(). Those are supported by RCU protecting
4043 * clearing of cgrp->kn->priv backpointer, which should happen
4044 * after all files under it have been removed.
4046 kernfs_remove(cgrp
->kn
); /* @cgrp has an extra ref on its kn */
4047 RCU_INIT_POINTER(*(void __rcu __force
**)&cgrp
->kn
->priv
, NULL
);
4049 mutex_lock(&cgroup_mutex
);
4055 * cgroup_destroy_css_killed - the second step of cgroup destruction
4056 * @work: cgroup->destroy_free_work
4058 * This function is invoked from a work item for a cgroup which is being
4059 * destroyed after all css's are offlined and performs the rest of
4060 * destruction. This is the second step of destruction described in the
4061 * comment above cgroup_destroy_locked().
4063 static void cgroup_destroy_css_killed(struct cgroup
*cgrp
)
4065 struct cgroup
*parent
= cgrp
->parent
;
4067 lockdep_assert_held(&cgroup_tree_mutex
);
4068 lockdep_assert_held(&cgroup_mutex
);
4070 /* delete this cgroup from parent->children */
4071 list_del_rcu(&cgrp
->sibling
);
4075 set_bit(CGRP_RELEASABLE
, &parent
->flags
);
4076 check_for_release(parent
);
4079 static int cgroup_rmdir(struct kernfs_node
*kn
)
4081 struct cgroup
*cgrp
= kn
->priv
;
4085 * This is self-destruction but @kn can't be removed while this
4086 * callback is in progress. Let's break active protection. Once
4087 * the protection is broken, @cgrp can be destroyed at any point.
4088 * Pin it so that it stays accessible.
4091 kernfs_break_active_protection(kn
);
4093 mutex_lock(&cgroup_tree_mutex
);
4094 mutex_lock(&cgroup_mutex
);
4097 * @cgrp might already have been destroyed while we're trying to
4100 if (!cgroup_is_dead(cgrp
))
4101 ret
= cgroup_destroy_locked(cgrp
);
4103 mutex_unlock(&cgroup_mutex
);
4104 mutex_unlock(&cgroup_tree_mutex
);
4106 kernfs_unbreak_active_protection(kn
);
4111 static struct kernfs_syscall_ops cgroup_kf_syscall_ops
= {
4112 .remount_fs
= cgroup_remount
,
4113 .show_options
= cgroup_show_options
,
4114 .mkdir
= cgroup_mkdir
,
4115 .rmdir
= cgroup_rmdir
,
4116 .rename
= cgroup_rename
,
4119 static void __init
cgroup_init_subsys(struct cgroup_subsys
*ss
)
4121 struct cgroup_subsys_state
*css
;
4123 printk(KERN_INFO
"Initializing cgroup subsys %s\n", ss
->name
);
4125 mutex_lock(&cgroup_tree_mutex
);
4126 mutex_lock(&cgroup_mutex
);
4128 INIT_LIST_HEAD(&ss
->cfts
);
4130 /* Create the root cgroup state for this subsystem */
4131 ss
->root
= &cgrp_dfl_root
;
4132 css
= ss
->css_alloc(cgroup_css(&cgrp_dfl_root
.cgrp
, ss
));
4133 /* We don't handle early failures gracefully */
4134 BUG_ON(IS_ERR(css
));
4135 init_css(css
, ss
, &cgrp_dfl_root
.cgrp
);
4137 /* Update the init_css_set to contain a subsys
4138 * pointer to this state - since the subsystem is
4139 * newly registered, all tasks and hence the
4140 * init_css_set is in the subsystem's root cgroup. */
4141 init_css_set
.subsys
[ss
->id
] = css
;
4143 need_forkexit_callback
|= ss
->fork
|| ss
->exit
;
4145 /* At system boot, before all subsystems have been
4146 * registered, no tasks have been forked, so we don't
4147 * need to invoke fork callbacks here. */
4148 BUG_ON(!list_empty(&init_task
.tasks
));
4150 BUG_ON(online_css(css
));
4152 cgrp_dfl_root
.cgrp
.subsys_mask
|= 1 << ss
->id
;
4154 mutex_unlock(&cgroup_mutex
);
4155 mutex_unlock(&cgroup_tree_mutex
);
4159 * cgroup_init_early - cgroup initialization at system boot
4161 * Initialize cgroups at system boot, and initialize any
4162 * subsystems that request early init.
4164 int __init
cgroup_init_early(void)
4166 static struct cgroup_sb_opts __initdata opts
=
4167 { .flags
= CGRP_ROOT_SANE_BEHAVIOR
};
4168 struct cgroup_subsys
*ss
;
4171 init_cgroup_root(&cgrp_dfl_root
, &opts
);
4172 RCU_INIT_POINTER(init_task
.cgroups
, &init_css_set
);
4174 for_each_subsys(ss
, i
) {
4175 WARN(!ss
->css_alloc
|| !ss
->css_free
|| ss
->name
|| ss
->id
,
4176 "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
4177 i
, cgroup_subsys_name
[i
], ss
->css_alloc
, ss
->css_free
,
4179 WARN(strlen(cgroup_subsys_name
[i
]) > MAX_CGROUP_TYPE_NAMELEN
,
4180 "cgroup_subsys_name %s too long\n", cgroup_subsys_name
[i
]);
4183 ss
->name
= cgroup_subsys_name
[i
];
4186 cgroup_init_subsys(ss
);
4192 * cgroup_init - cgroup initialization
4194 * Register cgroup filesystem and /proc file, and initialize
4195 * any subsystems that didn't request early init.
4197 int __init
cgroup_init(void)
4199 struct cgroup_subsys
*ss
;
4203 BUG_ON(cgroup_init_cftypes(NULL
, cgroup_base_files
));
4205 mutex_lock(&cgroup_tree_mutex
);
4206 mutex_lock(&cgroup_mutex
);
4208 /* Add init_css_set to the hash table */
4209 key
= css_set_hash(init_css_set
.subsys
);
4210 hash_add(css_set_table
, &init_css_set
.hlist
, key
);
4212 BUG_ON(cgroup_setup_root(&cgrp_dfl_root
, 0));
4214 mutex_unlock(&cgroup_mutex
);
4215 mutex_unlock(&cgroup_tree_mutex
);
4217 for_each_subsys(ss
, ssid
) {
4218 if (!ss
->early_init
)
4219 cgroup_init_subsys(ss
);
4222 * cftype registration needs kmalloc and can't be done
4223 * during early_init. Register base cftypes separately.
4225 if (ss
->base_cftypes
)
4226 WARN_ON(cgroup_add_cftypes(ss
, ss
->base_cftypes
));
4229 cgroup_kobj
= kobject_create_and_add("cgroup", fs_kobj
);
4233 err
= register_filesystem(&cgroup_fs_type
);
4235 kobject_put(cgroup_kobj
);
4239 proc_create("cgroups", 0, NULL
, &proc_cgroupstats_operations
);
4243 static int __init
cgroup_wq_init(void)
4246 * There isn't much point in executing destruction path in
4247 * parallel. Good chunk is serialized with cgroup_mutex anyway.
4248 * Use 1 for @max_active.
4250 * We would prefer to do this in cgroup_init() above, but that
4251 * is called before init_workqueues(): so leave this until after.
4253 cgroup_destroy_wq
= alloc_workqueue("cgroup_destroy", 0, 1);
4254 BUG_ON(!cgroup_destroy_wq
);
4257 * Used to destroy pidlists and separate to serve as flush domain.
4258 * Cap @max_active to 1 too.
4260 cgroup_pidlist_destroy_wq
= alloc_workqueue("cgroup_pidlist_destroy",
4262 BUG_ON(!cgroup_pidlist_destroy_wq
);
4266 core_initcall(cgroup_wq_init
);
4269 * proc_cgroup_show()
4270 * - Print task's cgroup paths into seq_file, one line for each hierarchy
4271 * - Used for /proc/<pid>/cgroup.
4274 /* TODO: Use a proper seq_file iterator */
4275 int proc_cgroup_show(struct seq_file
*m
, void *v
)
4278 struct task_struct
*tsk
;
4281 struct cgroup_root
*root
;
4284 buf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
4290 tsk
= get_pid_task(pid
, PIDTYPE_PID
);
4296 mutex_lock(&cgroup_mutex
);
4297 down_read(&css_set_rwsem
);
4299 for_each_root(root
) {
4300 struct cgroup_subsys
*ss
;
4301 struct cgroup
*cgrp
;
4302 int ssid
, count
= 0;
4304 if (root
== &cgrp_dfl_root
&& !cgrp_dfl_root_visible
)
4307 seq_printf(m
, "%d:", root
->hierarchy_id
);
4308 for_each_subsys(ss
, ssid
)
4309 if (root
->cgrp
.subsys_mask
& (1 << ssid
))
4310 seq_printf(m
, "%s%s", count
++ ? "," : "", ss
->name
);
4311 if (strlen(root
->name
))
4312 seq_printf(m
, "%sname=%s", count
? "," : "",
4315 cgrp
= task_cgroup_from_root(tsk
, root
);
4316 path
= cgroup_path(cgrp
, buf
, PATH_MAX
);
4318 retval
= -ENAMETOOLONG
;
4326 up_read(&css_set_rwsem
);
4327 mutex_unlock(&cgroup_mutex
);
4328 put_task_struct(tsk
);
4335 /* Display information about each subsystem and each hierarchy */
4336 static int proc_cgroupstats_show(struct seq_file
*m
, void *v
)
4338 struct cgroup_subsys
*ss
;
4341 seq_puts(m
, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
4343 * ideally we don't want subsystems moving around while we do this.
4344 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
4345 * subsys/hierarchy state.
4347 mutex_lock(&cgroup_mutex
);
4349 for_each_subsys(ss
, i
)
4350 seq_printf(m
, "%s\t%d\t%d\t%d\n",
4351 ss
->name
, ss
->root
->hierarchy_id
,
4352 atomic_read(&ss
->root
->nr_cgrps
), !ss
->disabled
);
4354 mutex_unlock(&cgroup_mutex
);
4358 static int cgroupstats_open(struct inode
*inode
, struct file
*file
)
4360 return single_open(file
, proc_cgroupstats_show
, NULL
);
4363 static const struct file_operations proc_cgroupstats_operations
= {
4364 .open
= cgroupstats_open
,
4366 .llseek
= seq_lseek
,
4367 .release
= single_release
,
4371 * cgroup_fork - initialize cgroup related fields during copy_process()
4372 * @child: pointer to task_struct of forking parent process.
4374 * A task is associated with the init_css_set until cgroup_post_fork()
4375 * attaches it to the parent's css_set. Empty cg_list indicates that
4376 * @child isn't holding reference to its css_set.
4378 void cgroup_fork(struct task_struct
*child
)
4380 RCU_INIT_POINTER(child
->cgroups
, &init_css_set
);
4381 INIT_LIST_HEAD(&child
->cg_list
);
4385 * cgroup_post_fork - called on a new task after adding it to the task list
4386 * @child: the task in question
4388 * Adds the task to the list running through its css_set if necessary and
4389 * call the subsystem fork() callbacks. Has to be after the task is
4390 * visible on the task list in case we race with the first call to
4391 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
4394 void cgroup_post_fork(struct task_struct
*child
)
4396 struct cgroup_subsys
*ss
;
4400 * This may race against cgroup_enable_task_cg_links(). As that
4401 * function sets use_task_css_set_links before grabbing
4402 * tasklist_lock and we just went through tasklist_lock to add
4403 * @child, it's guaranteed that either we see the set
4404 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
4405 * @child during its iteration.
4407 * If we won the race, @child is associated with %current's
4408 * css_set. Grabbing css_set_rwsem guarantees both that the
4409 * association is stable, and, on completion of the parent's
4410 * migration, @child is visible in the source of migration or
4411 * already in the destination cgroup. This guarantee is necessary
4412 * when implementing operations which need to migrate all tasks of
4413 * a cgroup to another.
4415 * Note that if we lose to cgroup_enable_task_cg_links(), @child
4416 * will remain in init_css_set. This is safe because all tasks are
4417 * in the init_css_set before cg_links is enabled and there's no
4418 * operation which transfers all tasks out of init_css_set.
4420 if (use_task_css_set_links
) {
4421 struct css_set
*cset
;
4423 down_write(&css_set_rwsem
);
4424 cset
= task_css_set(current
);
4425 if (list_empty(&child
->cg_list
)) {
4426 rcu_assign_pointer(child
->cgroups
, cset
);
4427 list_add(&child
->cg_list
, &cset
->tasks
);
4430 up_write(&css_set_rwsem
);
4434 * Call ss->fork(). This must happen after @child is linked on
4435 * css_set; otherwise, @child might change state between ->fork()
4436 * and addition to css_set.
4438 if (need_forkexit_callback
) {
4439 for_each_subsys(ss
, i
)
4446 * cgroup_exit - detach cgroup from exiting task
4447 * @tsk: pointer to task_struct of exiting process
4449 * Description: Detach cgroup from @tsk and release it.
4451 * Note that cgroups marked notify_on_release force every task in
4452 * them to take the global cgroup_mutex mutex when exiting.
4453 * This could impact scaling on very large systems. Be reluctant to
4454 * use notify_on_release cgroups where very high task exit scaling
4455 * is required on large systems.
4457 * We set the exiting tasks cgroup to the root cgroup (top_cgroup). We
4458 * call cgroup_exit() while the task is still competent to handle
4459 * notify_on_release(), then leave the task attached to the root cgroup in
4460 * each hierarchy for the remainder of its exit. No need to bother with
4461 * init_css_set refcnting. init_css_set never goes away and we can't race
4462 * with migration path - PF_EXITING is visible to migration path.
4464 void cgroup_exit(struct task_struct
*tsk
)
4466 struct cgroup_subsys
*ss
;
4467 struct css_set
*cset
;
4468 bool put_cset
= false;
4472 * Unlink from @tsk from its css_set. As migration path can't race
4473 * with us, we can check cg_list without grabbing css_set_rwsem.
4475 if (!list_empty(&tsk
->cg_list
)) {
4476 down_write(&css_set_rwsem
);
4477 list_del_init(&tsk
->cg_list
);
4478 up_write(&css_set_rwsem
);
4482 /* Reassign the task to the init_css_set. */
4483 cset
= task_css_set(tsk
);
4484 RCU_INIT_POINTER(tsk
->cgroups
, &init_css_set
);
4486 if (need_forkexit_callback
) {
4487 /* see cgroup_post_fork() for details */
4488 for_each_subsys(ss
, i
) {
4490 struct cgroup_subsys_state
*old_css
= cset
->subsys
[i
];
4491 struct cgroup_subsys_state
*css
= task_css(tsk
, i
);
4493 ss
->exit(css
, old_css
, tsk
);
4499 put_css_set(cset
, true);
4502 static void check_for_release(struct cgroup
*cgrp
)
4504 if (cgroup_is_releasable(cgrp
) &&
4505 list_empty(&cgrp
->cset_links
) && list_empty(&cgrp
->children
)) {
4507 * Control Group is currently removeable. If it's not
4508 * already queued for a userspace notification, queue
4511 int need_schedule_work
= 0;
4513 raw_spin_lock(&release_list_lock
);
4514 if (!cgroup_is_dead(cgrp
) &&
4515 list_empty(&cgrp
->release_list
)) {
4516 list_add(&cgrp
->release_list
, &release_list
);
4517 need_schedule_work
= 1;
4519 raw_spin_unlock(&release_list_lock
);
4520 if (need_schedule_work
)
4521 schedule_work(&release_agent_work
);
4526 * Notify userspace when a cgroup is released, by running the
4527 * configured release agent with the name of the cgroup (path
4528 * relative to the root of cgroup file system) as the argument.
4530 * Most likely, this user command will try to rmdir this cgroup.
4532 * This races with the possibility that some other task will be
4533 * attached to this cgroup before it is removed, or that some other
4534 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
4535 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
4536 * unused, and this cgroup will be reprieved from its death sentence,
4537 * to continue to serve a useful existence. Next time it's released,
4538 * we will get notified again, if it still has 'notify_on_release' set.
4540 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
4541 * means only wait until the task is successfully execve()'d. The
4542 * separate release agent task is forked by call_usermodehelper(),
4543 * then control in this thread returns here, without waiting for the
4544 * release agent task. We don't bother to wait because the caller of
4545 * this routine has no use for the exit status of the release agent
4546 * task, so no sense holding our caller up for that.
4548 static void cgroup_release_agent(struct work_struct
*work
)
4550 BUG_ON(work
!= &release_agent_work
);
4551 mutex_lock(&cgroup_mutex
);
4552 raw_spin_lock(&release_list_lock
);
4553 while (!list_empty(&release_list
)) {
4554 char *argv
[3], *envp
[3];
4556 char *pathbuf
= NULL
, *agentbuf
= NULL
, *path
;
4557 struct cgroup
*cgrp
= list_entry(release_list
.next
,
4560 list_del_init(&cgrp
->release_list
);
4561 raw_spin_unlock(&release_list_lock
);
4562 pathbuf
= kmalloc(PATH_MAX
, GFP_KERNEL
);
4565 path
= cgroup_path(cgrp
, pathbuf
, PATH_MAX
);
4568 agentbuf
= kstrdup(cgrp
->root
->release_agent_path
, GFP_KERNEL
);
4573 argv
[i
++] = agentbuf
;
4578 /* minimal command environment */
4579 envp
[i
++] = "HOME=/";
4580 envp
[i
++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
4583 /* Drop the lock while we invoke the usermode helper,
4584 * since the exec could involve hitting disk and hence
4585 * be a slow process */
4586 mutex_unlock(&cgroup_mutex
);
4587 call_usermodehelper(argv
[0], argv
, envp
, UMH_WAIT_EXEC
);
4588 mutex_lock(&cgroup_mutex
);
4592 raw_spin_lock(&release_list_lock
);
4594 raw_spin_unlock(&release_list_lock
);
4595 mutex_unlock(&cgroup_mutex
);
4598 static int __init
cgroup_disable(char *str
)
4600 struct cgroup_subsys
*ss
;
4604 while ((token
= strsep(&str
, ",")) != NULL
) {
4608 for_each_subsys(ss
, i
) {
4609 if (!strcmp(token
, ss
->name
)) {
4611 printk(KERN_INFO
"Disabling %s control group"
4612 " subsystem\n", ss
->name
);
4619 __setup("cgroup_disable=", cgroup_disable
);
4622 * css_tryget_from_dir - get corresponding css from the dentry of a cgroup dir
4623 * @dentry: directory dentry of interest
4624 * @ss: subsystem of interest
4626 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
4627 * to get the corresponding css and return it. If such css doesn't exist
4628 * or can't be pinned, an ERR_PTR value is returned.
4630 struct cgroup_subsys_state
*css_tryget_from_dir(struct dentry
*dentry
,
4631 struct cgroup_subsys
*ss
)
4633 struct kernfs_node
*kn
= kernfs_node_from_dentry(dentry
);
4634 struct cgroup_subsys_state
*css
= NULL
;
4635 struct cgroup
*cgrp
;
4637 /* is @dentry a cgroup dir? */
4638 if (dentry
->d_sb
->s_type
!= &cgroup_fs_type
|| !kn
||
4639 kernfs_type(kn
) != KERNFS_DIR
)
4640 return ERR_PTR(-EBADF
);
4645 * This path doesn't originate from kernfs and @kn could already
4646 * have been or be removed at any point. @kn->priv is RCU
4647 * protected for this access. See destroy_locked() for details.
4649 cgrp
= rcu_dereference(kn
->priv
);
4651 css
= cgroup_css(cgrp
, ss
);
4653 if (!css
|| !css_tryget(css
))
4654 css
= ERR_PTR(-ENOENT
);
4661 * css_from_id - lookup css by id
4662 * @id: the cgroup id
4663 * @ss: cgroup subsys to be looked into
4665 * Returns the css if there's valid one with @id, otherwise returns NULL.
4666 * Should be called under rcu_read_lock().
4668 struct cgroup_subsys_state
*css_from_id(int id
, struct cgroup_subsys
*ss
)
4670 struct cgroup
*cgrp
;
4672 cgroup_assert_mutexes_or_rcu_locked();
4674 cgrp
= idr_find(&ss
->root
->cgroup_idr
, id
);
4676 return cgroup_css(cgrp
, ss
);
4680 #ifdef CONFIG_CGROUP_DEBUG
4681 static struct cgroup_subsys_state
*
4682 debug_css_alloc(struct cgroup_subsys_state
*parent_css
)
4684 struct cgroup_subsys_state
*css
= kzalloc(sizeof(*css
), GFP_KERNEL
);
4687 return ERR_PTR(-ENOMEM
);
4692 static void debug_css_free(struct cgroup_subsys_state
*css
)
4697 static u64
debug_taskcount_read(struct cgroup_subsys_state
*css
,
4700 return cgroup_task_count(css
->cgroup
);
4703 static u64
current_css_set_read(struct cgroup_subsys_state
*css
,
4706 return (u64
)(unsigned long)current
->cgroups
;
4709 static u64
current_css_set_refcount_read(struct cgroup_subsys_state
*css
,
4715 count
= atomic_read(&task_css_set(current
)->refcount
);
4720 static int current_css_set_cg_links_read(struct seq_file
*seq
, void *v
)
4722 struct cgrp_cset_link
*link
;
4723 struct css_set
*cset
;
4726 name_buf
= kmalloc(NAME_MAX
+ 1, GFP_KERNEL
);
4730 down_read(&css_set_rwsem
);
4732 cset
= rcu_dereference(current
->cgroups
);
4733 list_for_each_entry(link
, &cset
->cgrp_links
, cgrp_link
) {
4734 struct cgroup
*c
= link
->cgrp
;
4736 cgroup_name(c
, name_buf
, NAME_MAX
+ 1);
4737 seq_printf(seq
, "Root %d group %s\n",
4738 c
->root
->hierarchy_id
, name_buf
);
4741 up_read(&css_set_rwsem
);
4746 #define MAX_TASKS_SHOWN_PER_CSS 25
4747 static int cgroup_css_links_read(struct seq_file
*seq
, void *v
)
4749 struct cgroup_subsys_state
*css
= seq_css(seq
);
4750 struct cgrp_cset_link
*link
;
4752 down_read(&css_set_rwsem
);
4753 list_for_each_entry(link
, &css
->cgroup
->cset_links
, cset_link
) {
4754 struct css_set
*cset
= link
->cset
;
4755 struct task_struct
*task
;
4758 seq_printf(seq
, "css_set %p\n", cset
);
4760 list_for_each_entry(task
, &cset
->tasks
, cg_list
) {
4761 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
4763 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
4766 list_for_each_entry(task
, &cset
->mg_tasks
, cg_list
) {
4767 if (count
++ > MAX_TASKS_SHOWN_PER_CSS
)
4769 seq_printf(seq
, " task %d\n", task_pid_vnr(task
));
4773 seq_puts(seq
, " ...\n");
4775 up_read(&css_set_rwsem
);
4779 static u64
releasable_read(struct cgroup_subsys_state
*css
, struct cftype
*cft
)
4781 return test_bit(CGRP_RELEASABLE
, &css
->cgroup
->flags
);
4784 static struct cftype debug_files
[] = {
4786 .name
= "taskcount",
4787 .read_u64
= debug_taskcount_read
,
4791 .name
= "current_css_set",
4792 .read_u64
= current_css_set_read
,
4796 .name
= "current_css_set_refcount",
4797 .read_u64
= current_css_set_refcount_read
,
4801 .name
= "current_css_set_cg_links",
4802 .seq_show
= current_css_set_cg_links_read
,
4806 .name
= "cgroup_css_links",
4807 .seq_show
= cgroup_css_links_read
,
4811 .name
= "releasable",
4812 .read_u64
= releasable_read
,
4818 struct cgroup_subsys debug_cgrp_subsys
= {
4819 .css_alloc
= debug_css_alloc
,
4820 .css_free
= debug_css_free
,
4821 .base_cftypes
= debug_files
,
4823 #endif /* CONFIG_CGROUP_DEBUG */