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>
34 #include <linux/init_task.h>
35 #include <linux/kernel.h>
36 #include <linux/list.h>
38 #include <linux/mutex.h>
39 #include <linux/mount.h>
40 #include <linux/pagemap.h>
41 #include <linux/proc_fs.h>
42 #include <linux/rcupdate.h>
43 #include <linux/sched.h>
44 #include <linux/backing-dev.h>
45 #include <linux/seq_file.h>
46 #include <linux/slab.h>
47 #include <linux/magic.h>
48 #include <linux/spinlock.h>
49 #include <linux/string.h>
50 #include <linux/sort.h>
51 #include <linux/kmod.h>
52 #include <linux/module.h>
53 #include <linux/delayacct.h>
54 #include <linux/cgroupstats.h>
55 #include <linux/hash.h>
56 #include <linux/namei.h>
57 #include <linux/pid_namespace.h>
58 #include <linux/idr.h>
59 #include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
60 #include <linux/eventfd.h>
61 #include <linux/poll.h>
62 #include <linux/flex_array.h> /* used in cgroup_attach_proc */
63 #include <linux/kthread.h>
65 #include <linux/atomic.h>
67 /* css deactivation bias, makes css->refcnt negative to deny new trygets */
68 #define CSS_DEACT_BIAS INT_MIN
71 * cgroup_mutex is the master lock. Any modification to cgroup or its
72 * hierarchy must be performed while holding it.
74 * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
75 * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
76 * release_agent_path and so on. Modifying requires both cgroup_mutex and
77 * cgroup_root_mutex. Readers can acquire either of the two. This is to
78 * break the following locking order cycle.
80 * A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
81 * B. namespace_sem -> cgroup_mutex
83 * B happens only through cgroup_show_options() and using cgroup_root_mutex
86 static DEFINE_MUTEX(cgroup_mutex);
87 static DEFINE_MUTEX(cgroup_root_mutex);
90 * Generate an array of cgroup subsystem pointers. At boot time, this is
91 * populated up to CGROUP_BUILTIN_SUBSYS_COUNT, and modular subsystems are
92 * registered after that. The mutable section of this array is protected by
95 #define SUBSYS(_x) &_x ## _subsys,
96 static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
97 #include <linux/cgroup_subsys.h>
100 #define MAX_CGROUP_ROOT_NAMELEN 64
103 * A cgroupfs_root represents the root of a cgroup hierarchy,
104 * and may be associated with a superblock to form an active
107 struct cgroupfs_root {
108 struct super_block *sb;
111 * The bitmask of subsystems intended to be attached to this
114 unsigned long subsys_bits;
116 /* Unique id for this hierarchy. */
119 /* The bitmask of subsystems currently attached to this hierarchy */
120 unsigned long actual_subsys_bits;
122 /* A list running through the attached subsystems */
123 struct list_head subsys_list;
125 /* The root cgroup for this hierarchy */
126 struct cgroup top_cgroup;
128 /* Tracks how many cgroups are currently defined in hierarchy.*/
129 int number_of_cgroups;
131 /* A list running through the active hierarchies */
132 struct list_head root_list;
134 /* All cgroups on this root, cgroup_mutex protected */
135 struct list_head allcg_list;
137 /* Hierarchy-specific flags */
140 /* The path to use for release notifications. */
141 char release_agent_path[PATH_MAX];
143 /* The name for this hierarchy - may be empty */
144 char name[MAX_CGROUP_ROOT_NAMELEN];
148 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
149 * subsystems that are otherwise unattached - it never has more than a
150 * single cgroup, and all tasks are part of that cgroup.
152 static struct cgroupfs_root rootnode;
155 * cgroupfs file entry, pointed to from leaf dentry->d_fsdata.
158 struct list_head node;
159 struct dentry *dentry;
164 * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
165 * cgroup_subsys->use_id != 0.
167 #define CSS_ID_MAX (65535)
170 * The css to which this ID points. This pointer is set to valid value
171 * after cgroup is populated. If cgroup is removed, this will be NULL.
172 * This pointer is expected to be RCU-safe because destroy()
173 * is called after synchronize_rcu(). But for safe use, css_tryget()
174 * should be used for avoiding race.
176 struct cgroup_subsys_state __rcu *css;
182 * Depth in hierarchy which this ID belongs to.
184 unsigned short depth;
186 * ID is freed by RCU. (and lookup routine is RCU safe.)
188 struct rcu_head rcu_head;
190 * Hierarchy of CSS ID belongs to.
192 unsigned short stack[0]; /* Array of Length (depth+1) */
196 * cgroup_event represents events which userspace want to receive.
198 struct cgroup_event {
200 * Cgroup which the event belongs to.
204 * Control file which the event associated.
208 * eventfd to signal userspace about the event.
210 struct eventfd_ctx *eventfd;
212 * Each of these stored in a list by the cgroup.
214 struct list_head list;
216 * All fields below needed to unregister event when
217 * userspace closes eventfd.
220 wait_queue_head_t *wqh;
222 struct work_struct remove;
225 /* The list of hierarchy roots */
227 static LIST_HEAD(roots);
228 static int root_count;
230 static DEFINE_IDA(hierarchy_ida);
231 static int next_hierarchy_id;
232 static DEFINE_SPINLOCK(hierarchy_id_lock);
234 /* dummytop is a shorthand for the dummy hierarchy's top cgroup */
235 #define dummytop (&rootnode.top_cgroup)
237 /* This flag indicates whether tasks in the fork and exit paths should
238 * check for fork/exit handlers to call. This avoids us having to do
239 * extra work in the fork/exit path if none of the subsystems need to
242 static int need_forkexit_callback __read_mostly;
244 #ifdef CONFIG_PROVE_LOCKING
245 int cgroup_lock_is_held(void)
247 return lockdep_is_held(&cgroup_mutex);
249 #else /* #ifdef CONFIG_PROVE_LOCKING */
250 int cgroup_lock_is_held(void)
252 return mutex_is_locked(&cgroup_mutex);
254 #endif /* #else #ifdef CONFIG_PROVE_LOCKING */
256 EXPORT_SYMBOL_GPL(cgroup_lock_is_held);
258 static int css_unbias_refcnt(int refcnt)
260 return refcnt >= 0 ? refcnt : refcnt - CSS_DEACT_BIAS;
263 /* the current nr of refs, always >= 0 whether @css is deactivated or not */
264 static int css_refcnt(struct cgroup_subsys_state *css)
266 int v = atomic_read(&css->refcnt);
268 return css_unbias_refcnt(v);
271 /* convenient tests for these bits */
272 inline int cgroup_is_removed(const struct cgroup *cgrp)
274 return test_bit(CGRP_REMOVED, &cgrp->flags);
277 /* bits in struct cgroupfs_root flags field */
279 ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
282 static int cgroup_is_releasable(const struct cgroup *cgrp)
285 (1 << CGRP_RELEASABLE) |
286 (1 << CGRP_NOTIFY_ON_RELEASE);
287 return (cgrp->flags & bits) == bits;
290 static int notify_on_release(const struct cgroup *cgrp)
292 return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
295 static int clone_children(const struct cgroup *cgrp)
297 return test_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
301 * for_each_subsys() allows you to iterate on each subsystem attached to
302 * an active hierarchy
304 #define for_each_subsys(_root, _ss) \
305 list_for_each_entry(_ss, &_root->subsys_list, sibling)
307 /* for_each_active_root() allows you to iterate across the active hierarchies */
308 #define for_each_active_root(_root) \
309 list_for_each_entry(_root, &roots, root_list)
311 static inline struct cgroup *__d_cgrp(struct dentry *dentry)
313 return dentry->d_fsdata;
316 static inline struct cfent *__d_cfe(struct dentry *dentry)
318 return dentry->d_fsdata;
321 static inline struct cftype *__d_cft(struct dentry *dentry)
323 return __d_cfe(dentry)->type;
326 /* the list of cgroups eligible for automatic release. Protected by
327 * release_list_lock */
328 static LIST_HEAD(release_list);
329 static DEFINE_RAW_SPINLOCK(release_list_lock);
330 static void cgroup_release_agent(struct work_struct *work);
331 static DECLARE_WORK(release_agent_work, cgroup_release_agent);
332 static void check_for_release(struct cgroup *cgrp);
334 /* Link structure for associating css_set objects with cgroups */
335 struct cg_cgroup_link {
337 * List running through cg_cgroup_links associated with a
338 * cgroup, anchored on cgroup->css_sets
340 struct list_head cgrp_link_list;
343 * List running through cg_cgroup_links pointing at a
344 * single css_set object, anchored on css_set->cg_links
346 struct list_head cg_link_list;
350 /* The default css_set - used by init and its children prior to any
351 * hierarchies being mounted. It contains a pointer to the root state
352 * for each subsystem. Also used to anchor the list of css_sets. Not
353 * reference-counted, to improve performance when child cgroups
354 * haven't been created.
357 static struct css_set init_css_set;
358 static struct cg_cgroup_link init_css_set_link;
360 static int cgroup_init_idr(struct cgroup_subsys *ss,
361 struct cgroup_subsys_state *css);
363 /* css_set_lock protects the list of css_set objects, and the
364 * chain of tasks off each css_set. Nests outside task->alloc_lock
365 * due to cgroup_iter_start() */
366 static DEFINE_RWLOCK(css_set_lock);
367 static int css_set_count;
370 * hash table for cgroup groups. This improves the performance to find
371 * an existing css_set. This hash doesn't (currently) take into
372 * account cgroups in empty hierarchies.
374 #define CSS_SET_HASH_BITS 7
375 #define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS)
376 static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
378 static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
382 unsigned long tmp = 0UL;
384 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
385 tmp += (unsigned long)css[i];
386 tmp = (tmp >> 16) ^ tmp;
388 index = hash_long(tmp, CSS_SET_HASH_BITS);
390 return &css_set_table[index];
393 /* We don't maintain the lists running through each css_set to its
394 * task until after the first call to cgroup_iter_start(). This
395 * reduces the fork()/exit() overhead for people who have cgroups
396 * compiled into their kernel but not actually in use */
397 static int use_task_css_set_links __read_mostly;
399 static void __put_css_set(struct css_set *cg, int taskexit)
401 struct cg_cgroup_link *link;
402 struct cg_cgroup_link *saved_link;
404 * Ensure that the refcount doesn't hit zero while any readers
405 * can see it. Similar to atomic_dec_and_lock(), but for an
408 if (atomic_add_unless(&cg->refcount, -1, 1))
410 write_lock(&css_set_lock);
411 if (!atomic_dec_and_test(&cg->refcount)) {
412 write_unlock(&css_set_lock);
416 /* This css_set is dead. unlink it and release cgroup refcounts */
417 hlist_del(&cg->hlist);
420 list_for_each_entry_safe(link, saved_link, &cg->cg_links,
422 struct cgroup *cgrp = link->cgrp;
423 list_del(&link->cg_link_list);
424 list_del(&link->cgrp_link_list);
425 if (atomic_dec_and_test(&cgrp->count) &&
426 notify_on_release(cgrp)) {
428 set_bit(CGRP_RELEASABLE, &cgrp->flags);
429 check_for_release(cgrp);
435 write_unlock(&css_set_lock);
436 kfree_rcu(cg, rcu_head);
440 * refcounted get/put for css_set objects
442 static inline void get_css_set(struct css_set *cg)
444 atomic_inc(&cg->refcount);
447 static inline void put_css_set(struct css_set *cg)
449 __put_css_set(cg, 0);
452 static inline void put_css_set_taskexit(struct css_set *cg)
454 __put_css_set(cg, 1);
458 * compare_css_sets - helper function for find_existing_css_set().
459 * @cg: candidate css_set being tested
460 * @old_cg: existing css_set for a task
461 * @new_cgrp: cgroup that's being entered by the task
462 * @template: desired set of css pointers in css_set (pre-calculated)
464 * Returns true if "cg" matches "old_cg" except for the hierarchy
465 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
467 static bool compare_css_sets(struct css_set *cg,
468 struct css_set *old_cg,
469 struct cgroup *new_cgrp,
470 struct cgroup_subsys_state *template[])
472 struct list_head *l1, *l2;
474 if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
475 /* Not all subsystems matched */
480 * Compare cgroup pointers in order to distinguish between
481 * different cgroups in heirarchies with no subsystems. We
482 * could get by with just this check alone (and skip the
483 * memcmp above) but on most setups the memcmp check will
484 * avoid the need for this more expensive check on almost all
489 l2 = &old_cg->cg_links;
491 struct cg_cgroup_link *cgl1, *cgl2;
492 struct cgroup *cg1, *cg2;
496 /* See if we reached the end - both lists are equal length. */
497 if (l1 == &cg->cg_links) {
498 BUG_ON(l2 != &old_cg->cg_links);
501 BUG_ON(l2 == &old_cg->cg_links);
503 /* Locate the cgroups associated with these links. */
504 cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
505 cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
508 /* Hierarchies should be linked in the same order. */
509 BUG_ON(cg1->root != cg2->root);
512 * If this hierarchy is the hierarchy of the cgroup
513 * that's changing, then we need to check that this
514 * css_set points to the new cgroup; if it's any other
515 * hierarchy, then this css_set should point to the
516 * same cgroup as the old css_set.
518 if (cg1->root == new_cgrp->root) {
530 * find_existing_css_set() is a helper for
531 * find_css_set(), and checks to see whether an existing
532 * css_set is suitable.
534 * oldcg: the cgroup group that we're using before the cgroup
537 * cgrp: the cgroup that we're moving into
539 * template: location in which to build the desired set of subsystem
540 * state objects for the new cgroup group
542 static struct css_set *find_existing_css_set(
543 struct css_set *oldcg,
545 struct cgroup_subsys_state *template[])
548 struct cgroupfs_root *root = cgrp->root;
549 struct hlist_head *hhead;
550 struct hlist_node *node;
554 * Build the set of subsystem state objects that we want to see in the
555 * new css_set. while subsystems can change globally, the entries here
556 * won't change, so no need for locking.
558 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
559 if (root->subsys_bits & (1UL << i)) {
560 /* Subsystem is in this hierarchy. So we want
561 * the subsystem state from the new
563 template[i] = cgrp->subsys[i];
565 /* Subsystem is not in this hierarchy, so we
566 * don't want to change the subsystem state */
567 template[i] = oldcg->subsys[i];
571 hhead = css_set_hash(template);
572 hlist_for_each_entry(cg, node, hhead, hlist) {
573 if (!compare_css_sets(cg, oldcg, cgrp, template))
576 /* This css_set matches what we need */
580 /* No existing cgroup group matched */
584 static void free_cg_links(struct list_head *tmp)
586 struct cg_cgroup_link *link;
587 struct cg_cgroup_link *saved_link;
589 list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
590 list_del(&link->cgrp_link_list);
596 * allocate_cg_links() allocates "count" cg_cgroup_link structures
597 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
598 * success or a negative error
600 static int allocate_cg_links(int count, struct list_head *tmp)
602 struct cg_cgroup_link *link;
605 for (i = 0; i < count; i++) {
606 link = kmalloc(sizeof(*link), GFP_KERNEL);
611 list_add(&link->cgrp_link_list, tmp);
617 * link_css_set - a helper function to link a css_set to a cgroup
618 * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
619 * @cg: the css_set to be linked
620 * @cgrp: the destination cgroup
622 static void link_css_set(struct list_head *tmp_cg_links,
623 struct css_set *cg, struct cgroup *cgrp)
625 struct cg_cgroup_link *link;
627 BUG_ON(list_empty(tmp_cg_links));
628 link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
632 atomic_inc(&cgrp->count);
633 list_move(&link->cgrp_link_list, &cgrp->css_sets);
635 * Always add links to the tail of the list so that the list
636 * is sorted by order of hierarchy creation
638 list_add_tail(&link->cg_link_list, &cg->cg_links);
642 * find_css_set() takes an existing cgroup group and a
643 * cgroup object, and returns a css_set object that's
644 * equivalent to the old group, but with the given cgroup
645 * substituted into the appropriate hierarchy. Must be called with
648 static struct css_set *find_css_set(
649 struct css_set *oldcg, struct cgroup *cgrp)
652 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
654 struct list_head tmp_cg_links;
656 struct hlist_head *hhead;
657 struct cg_cgroup_link *link;
659 /* First see if we already have a cgroup group that matches
661 read_lock(&css_set_lock);
662 res = find_existing_css_set(oldcg, cgrp, template);
665 read_unlock(&css_set_lock);
670 res = kmalloc(sizeof(*res), GFP_KERNEL);
674 /* Allocate all the cg_cgroup_link objects that we'll need */
675 if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
680 atomic_set(&res->refcount, 1);
681 INIT_LIST_HEAD(&res->cg_links);
682 INIT_LIST_HEAD(&res->tasks);
683 INIT_HLIST_NODE(&res->hlist);
685 /* Copy the set of subsystem state objects generated in
686 * find_existing_css_set() */
687 memcpy(res->subsys, template, sizeof(res->subsys));
689 write_lock(&css_set_lock);
690 /* Add reference counts and links from the new css_set. */
691 list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
692 struct cgroup *c = link->cgrp;
693 if (c->root == cgrp->root)
695 link_css_set(&tmp_cg_links, res, c);
698 BUG_ON(!list_empty(&tmp_cg_links));
702 /* Add this cgroup group to the hash table */
703 hhead = css_set_hash(res->subsys);
704 hlist_add_head(&res->hlist, hhead);
706 write_unlock(&css_set_lock);
712 * Return the cgroup for "task" from the given hierarchy. Must be
713 * called with cgroup_mutex held.
715 static struct cgroup *task_cgroup_from_root(struct task_struct *task,
716 struct cgroupfs_root *root)
719 struct cgroup *res = NULL;
721 BUG_ON(!mutex_is_locked(&cgroup_mutex));
722 read_lock(&css_set_lock);
724 * No need to lock the task - since we hold cgroup_mutex the
725 * task can't change groups, so the only thing that can happen
726 * is that it exits and its css is set back to init_css_set.
729 if (css == &init_css_set) {
730 res = &root->top_cgroup;
732 struct cg_cgroup_link *link;
733 list_for_each_entry(link, &css->cg_links, cg_link_list) {
734 struct cgroup *c = link->cgrp;
735 if (c->root == root) {
741 read_unlock(&css_set_lock);
747 * There is one global cgroup mutex. We also require taking
748 * task_lock() when dereferencing a task's cgroup subsys pointers.
749 * See "The task_lock() exception", at the end of this comment.
751 * A task must hold cgroup_mutex to modify cgroups.
753 * Any task can increment and decrement the count field without lock.
754 * So in general, code holding cgroup_mutex can't rely on the count
755 * field not changing. However, if the count goes to zero, then only
756 * cgroup_attach_task() can increment it again. Because a count of zero
757 * means that no tasks are currently attached, therefore there is no
758 * way a task attached to that cgroup can fork (the other way to
759 * increment the count). So code holding cgroup_mutex can safely
760 * assume that if the count is zero, it will stay zero. Similarly, if
761 * a task holds cgroup_mutex on a cgroup with zero count, it
762 * knows that the cgroup won't be removed, as cgroup_rmdir()
765 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
766 * (usually) take cgroup_mutex. These are the two most performance
767 * critical pieces of code here. The exception occurs on cgroup_exit(),
768 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
769 * is taken, and if the cgroup count is zero, a usermode call made
770 * to the release agent with the name of the cgroup (path relative to
771 * the root of cgroup file system) as the argument.
773 * A cgroup can only be deleted if both its 'count' of using tasks
774 * is zero, and its list of 'children' cgroups is empty. Since all
775 * tasks in the system use _some_ cgroup, and since there is always at
776 * least one task in the system (init, pid == 1), therefore, top_cgroup
777 * always has either children cgroups and/or using tasks. So we don't
778 * need a special hack to ensure that top_cgroup cannot be deleted.
780 * The task_lock() exception
782 * The need for this exception arises from the action of
783 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
784 * another. It does so using cgroup_mutex, however there are
785 * several performance critical places that need to reference
786 * task->cgroup without the expense of grabbing a system global
787 * mutex. Therefore except as noted below, when dereferencing or, as
788 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
789 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
790 * the task_struct routinely used for such matters.
792 * P.S. One more locking exception. RCU is used to guard the
793 * update of a tasks cgroup pointer by cgroup_attach_task()
797 * cgroup_lock - lock out any changes to cgroup structures
800 void cgroup_lock(void)
802 mutex_lock(&cgroup_mutex);
804 EXPORT_SYMBOL_GPL(cgroup_lock);
807 * cgroup_unlock - release lock on cgroup changes
809 * Undo the lock taken in a previous cgroup_lock() call.
811 void cgroup_unlock(void)
813 mutex_unlock(&cgroup_mutex);
815 EXPORT_SYMBOL_GPL(cgroup_unlock);
818 * A couple of forward declarations required, due to cyclic reference loop:
819 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
820 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
824 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
825 static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);
826 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
827 static int cgroup_populate_dir(struct cgroup *cgrp);
828 static const struct inode_operations cgroup_dir_inode_operations;
829 static const struct file_operations proc_cgroupstats_operations;
831 static struct backing_dev_info cgroup_backing_dev_info = {
833 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
836 static int alloc_css_id(struct cgroup_subsys *ss,
837 struct cgroup *parent, struct cgroup *child);
839 static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
841 struct inode *inode = new_inode(sb);
844 inode->i_ino = get_next_ino();
845 inode->i_mode = mode;
846 inode->i_uid = current_fsuid();
847 inode->i_gid = current_fsgid();
848 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
849 inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
854 static void cgroup_diput(struct dentry *dentry, struct inode *inode)
856 /* is dentry a directory ? if so, kfree() associated cgroup */
857 if (S_ISDIR(inode->i_mode)) {
858 struct cgroup *cgrp = dentry->d_fsdata;
859 struct cgroup_subsys *ss;
860 BUG_ON(!(cgroup_is_removed(cgrp)));
861 /* It's possible for external users to be holding css
862 * reference counts on a cgroup; css_put() needs to
863 * be able to access the cgroup after decrementing
864 * the reference count in order to know if it needs to
865 * queue the cgroup to be handled by the release
869 mutex_lock(&cgroup_mutex);
871 * Release the subsystem state objects.
873 for_each_subsys(cgrp->root, ss)
876 cgrp->root->number_of_cgroups--;
877 mutex_unlock(&cgroup_mutex);
880 * Drop the active superblock reference that we took when we
883 deactivate_super(cgrp->root->sb);
886 * if we're getting rid of the cgroup, refcount should ensure
887 * that there are no pidlists left.
889 BUG_ON(!list_empty(&cgrp->pidlists));
891 kfree_rcu(cgrp, rcu_head);
893 struct cfent *cfe = __d_cfe(dentry);
894 struct cgroup *cgrp = dentry->d_parent->d_fsdata;
896 WARN_ONCE(!list_empty(&cfe->node) &&
897 cgrp != &cgrp->root->top_cgroup,
898 "cfe still linked for %s\n", cfe->type->name);
904 static int cgroup_delete(const struct dentry *d)
909 static void remove_dir(struct dentry *d)
911 struct dentry *parent = dget(d->d_parent);
914 simple_rmdir(parent->d_inode, d);
918 static int cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
922 lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
923 lockdep_assert_held(&cgroup_mutex);
925 list_for_each_entry(cfe, &cgrp->files, node) {
926 struct dentry *d = cfe->dentry;
928 if (cft && cfe->type != cft)
933 simple_unlink(cgrp->dentry->d_inode, d);
934 list_del_init(&cfe->node);
942 static void cgroup_clear_directory(struct dentry *dir)
944 struct cgroup *cgrp = __d_cgrp(dir);
946 while (!list_empty(&cgrp->files))
947 cgroup_rm_file(cgrp, NULL);
951 * NOTE : the dentry must have been dget()'ed
953 static void cgroup_d_remove_dir(struct dentry *dentry)
955 struct dentry *parent;
957 cgroup_clear_directory(dentry);
959 parent = dentry->d_parent;
960 spin_lock(&parent->d_lock);
961 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
962 list_del_init(&dentry->d_u.d_child);
963 spin_unlock(&dentry->d_lock);
964 spin_unlock(&parent->d_lock);
969 * Call with cgroup_mutex held. Drops reference counts on modules, including
970 * any duplicate ones that parse_cgroupfs_options took. If this function
971 * returns an error, no reference counts are touched.
973 static int rebind_subsystems(struct cgroupfs_root *root,
974 unsigned long final_bits)
976 unsigned long added_bits, removed_bits;
977 struct cgroup *cgrp = &root->top_cgroup;
980 BUG_ON(!mutex_is_locked(&cgroup_mutex));
981 BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
983 removed_bits = root->actual_subsys_bits & ~final_bits;
984 added_bits = final_bits & ~root->actual_subsys_bits;
985 /* Check that any added subsystems are currently free */
986 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
987 unsigned long bit = 1UL << i;
988 struct cgroup_subsys *ss = subsys[i];
989 if (!(bit & added_bits))
992 * Nobody should tell us to do a subsys that doesn't exist:
993 * parse_cgroupfs_options should catch that case and refcounts
994 * ensure that subsystems won't disappear once selected.
997 if (ss->root != &rootnode) {
998 /* Subsystem isn't free */
1003 /* Currently we don't handle adding/removing subsystems when
1004 * any child cgroups exist. This is theoretically supportable
1005 * but involves complex error handling, so it's being left until
1007 if (root->number_of_cgroups > 1)
1010 /* Process each subsystem */
1011 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1012 struct cgroup_subsys *ss = subsys[i];
1013 unsigned long bit = 1UL << i;
1014 if (bit & added_bits) {
1015 /* We're binding this subsystem to this hierarchy */
1017 BUG_ON(cgrp->subsys[i]);
1018 BUG_ON(!dummytop->subsys[i]);
1019 BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1020 cgrp->subsys[i] = dummytop->subsys[i];
1021 cgrp->subsys[i]->cgroup = cgrp;
1022 list_move(&ss->sibling, &root->subsys_list);
1026 /* refcount was already taken, and we're keeping it */
1027 } else if (bit & removed_bits) {
1028 /* We're removing this subsystem */
1030 BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
1031 BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1034 dummytop->subsys[i]->cgroup = dummytop;
1035 cgrp->subsys[i] = NULL;
1036 subsys[i]->root = &rootnode;
1037 list_move(&ss->sibling, &rootnode.subsys_list);
1038 /* subsystem is now free - drop reference on module */
1039 module_put(ss->module);
1040 } else if (bit & final_bits) {
1041 /* Subsystem state should already exist */
1043 BUG_ON(!cgrp->subsys[i]);
1045 * a refcount was taken, but we already had one, so
1046 * drop the extra reference.
1048 module_put(ss->module);
1049 #ifdef CONFIG_MODULE_UNLOAD
1050 BUG_ON(ss->module && !module_refcount(ss->module));
1053 /* Subsystem state shouldn't exist */
1054 BUG_ON(cgrp->subsys[i]);
1057 root->subsys_bits = root->actual_subsys_bits = final_bits;
1063 static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1065 struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1066 struct cgroup_subsys *ss;
1068 mutex_lock(&cgroup_root_mutex);
1069 for_each_subsys(root, ss)
1070 seq_printf(seq, ",%s", ss->name);
1071 if (test_bit(ROOT_NOPREFIX, &root->flags))
1072 seq_puts(seq, ",noprefix");
1073 if (strlen(root->release_agent_path))
1074 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1075 if (clone_children(&root->top_cgroup))
1076 seq_puts(seq, ",clone_children");
1077 if (strlen(root->name))
1078 seq_printf(seq, ",name=%s", root->name);
1079 mutex_unlock(&cgroup_root_mutex);
1083 struct cgroup_sb_opts {
1084 unsigned long subsys_bits;
1085 unsigned long flags;
1086 char *release_agent;
1087 bool clone_children;
1089 /* User explicitly requested empty subsystem */
1092 struct cgroupfs_root *new_root;
1097 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
1098 * with cgroup_mutex held to protect the subsys[] array. This function takes
1099 * refcounts on subsystems to be used, unless it returns error, in which case
1100 * no refcounts are taken.
1102 static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1104 char *token, *o = data;
1105 bool all_ss = false, one_ss = false;
1106 unsigned long mask = (unsigned long)-1;
1108 bool module_pin_failed = false;
1110 BUG_ON(!mutex_is_locked(&cgroup_mutex));
1112 #ifdef CONFIG_CPUSETS
1113 mask = ~(1UL << cpuset_subsys_id);
1116 memset(opts, 0, sizeof(*opts));
1118 while ((token = strsep(&o, ",")) != NULL) {
1121 if (!strcmp(token, "none")) {
1122 /* Explicitly have no subsystems */
1126 if (!strcmp(token, "all")) {
1127 /* Mutually exclusive option 'all' + subsystem name */
1133 if (!strcmp(token, "noprefix")) {
1134 set_bit(ROOT_NOPREFIX, &opts->flags);
1137 if (!strcmp(token, "clone_children")) {
1138 opts->clone_children = true;
1141 if (!strncmp(token, "release_agent=", 14)) {
1142 /* Specifying two release agents is forbidden */
1143 if (opts->release_agent)
1145 opts->release_agent =
1146 kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1147 if (!opts->release_agent)
1151 if (!strncmp(token, "name=", 5)) {
1152 const char *name = token + 5;
1153 /* Can't specify an empty name */
1156 /* Must match [\w.-]+ */
1157 for (i = 0; i < strlen(name); i++) {
1161 if ((c == '.') || (c == '-') || (c == '_'))
1165 /* Specifying two names is forbidden */
1168 opts->name = kstrndup(name,
1169 MAX_CGROUP_ROOT_NAMELEN - 1,
1177 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1178 struct cgroup_subsys *ss = subsys[i];
1181 if (strcmp(token, ss->name))
1186 /* Mutually exclusive option 'all' + subsystem name */
1189 set_bit(i, &opts->subsys_bits);
1194 if (i == CGROUP_SUBSYS_COUNT)
1199 * If the 'all' option was specified select all the subsystems,
1200 * otherwise if 'none', 'name=' and a subsystem name options
1201 * were not specified, let's default to 'all'
1203 if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1204 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1205 struct cgroup_subsys *ss = subsys[i];
1210 set_bit(i, &opts->subsys_bits);
1214 /* Consistency checks */
1217 * Option noprefix was introduced just for backward compatibility
1218 * with the old cpuset, so we allow noprefix only if mounting just
1219 * the cpuset subsystem.
1221 if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
1222 (opts->subsys_bits & mask))
1226 /* Can't specify "none" and some subsystems */
1227 if (opts->subsys_bits && opts->none)
1231 * We either have to specify by name or by subsystems. (So all
1232 * empty hierarchies must have a name).
1234 if (!opts->subsys_bits && !opts->name)
1238 * Grab references on all the modules we'll need, so the subsystems
1239 * don't dance around before rebind_subsystems attaches them. This may
1240 * take duplicate reference counts on a subsystem that's already used,
1241 * but rebind_subsystems handles this case.
1243 for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
1244 unsigned long bit = 1UL << i;
1246 if (!(bit & opts->subsys_bits))
1248 if (!try_module_get(subsys[i]->module)) {
1249 module_pin_failed = true;
1253 if (module_pin_failed) {
1255 * oops, one of the modules was going away. this means that we
1256 * raced with a module_delete call, and to the user this is
1257 * essentially a "subsystem doesn't exist" case.
1259 for (i--; i >= CGROUP_BUILTIN_SUBSYS_COUNT; i--) {
1260 /* drop refcounts only on the ones we took */
1261 unsigned long bit = 1UL << i;
1263 if (!(bit & opts->subsys_bits))
1265 module_put(subsys[i]->module);
1273 static void drop_parsed_module_refcounts(unsigned long subsys_bits)
1276 for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
1277 unsigned long bit = 1UL << i;
1279 if (!(bit & subsys_bits))
1281 module_put(subsys[i]->module);
1285 static int cgroup_remount(struct super_block *sb, int *flags, char *data)
1288 struct cgroupfs_root *root = sb->s_fs_info;
1289 struct cgroup *cgrp = &root->top_cgroup;
1290 struct cgroup_sb_opts opts;
1292 mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1293 mutex_lock(&cgroup_mutex);
1294 mutex_lock(&cgroup_root_mutex);
1296 /* See what subsystems are wanted */
1297 ret = parse_cgroupfs_options(data, &opts);
1301 /* See feature-removal-schedule.txt */
1302 if (opts.subsys_bits != root->actual_subsys_bits || opts.release_agent)
1303 pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
1304 task_tgid_nr(current), current->comm);
1306 /* Don't allow flags or name to change at remount */
1307 if (opts.flags != root->flags ||
1308 (opts.name && strcmp(opts.name, root->name))) {
1310 drop_parsed_module_refcounts(opts.subsys_bits);
1314 ret = rebind_subsystems(root, opts.subsys_bits);
1316 drop_parsed_module_refcounts(opts.subsys_bits);
1320 /* clear out any existing files and repopulate subsystem files */
1321 cgroup_clear_directory(cgrp->dentry);
1322 cgroup_populate_dir(cgrp);
1324 if (opts.release_agent)
1325 strcpy(root->release_agent_path, opts.release_agent);
1327 kfree(opts.release_agent);
1329 mutex_unlock(&cgroup_root_mutex);
1330 mutex_unlock(&cgroup_mutex);
1331 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1335 static const struct super_operations cgroup_ops = {
1336 .statfs = simple_statfs,
1337 .drop_inode = generic_delete_inode,
1338 .show_options = cgroup_show_options,
1339 .remount_fs = cgroup_remount,
1342 static void init_cgroup_housekeeping(struct cgroup *cgrp)
1344 INIT_LIST_HEAD(&cgrp->sibling);
1345 INIT_LIST_HEAD(&cgrp->children);
1346 INIT_LIST_HEAD(&cgrp->files);
1347 INIT_LIST_HEAD(&cgrp->css_sets);
1348 INIT_LIST_HEAD(&cgrp->release_list);
1349 INIT_LIST_HEAD(&cgrp->pidlists);
1350 mutex_init(&cgrp->pidlist_mutex);
1351 INIT_LIST_HEAD(&cgrp->event_list);
1352 spin_lock_init(&cgrp->event_list_lock);
1355 static void init_cgroup_root(struct cgroupfs_root *root)
1357 struct cgroup *cgrp = &root->top_cgroup;
1359 INIT_LIST_HEAD(&root->subsys_list);
1360 INIT_LIST_HEAD(&root->root_list);
1361 INIT_LIST_HEAD(&root->allcg_list);
1362 root->number_of_cgroups = 1;
1364 cgrp->top_cgroup = cgrp;
1365 list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1366 init_cgroup_housekeeping(cgrp);
1369 static bool init_root_id(struct cgroupfs_root *root)
1374 if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
1376 spin_lock(&hierarchy_id_lock);
1377 /* Try to allocate the next unused ID */
1378 ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
1379 &root->hierarchy_id);
1381 /* Try again starting from 0 */
1382 ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
1384 next_hierarchy_id = root->hierarchy_id + 1;
1385 } else if (ret != -EAGAIN) {
1386 /* Can only get here if the 31-bit IDR is full ... */
1389 spin_unlock(&hierarchy_id_lock);
1394 static int cgroup_test_super(struct super_block *sb, void *data)
1396 struct cgroup_sb_opts *opts = data;
1397 struct cgroupfs_root *root = sb->s_fs_info;
1399 /* If we asked for a name then it must match */
1400 if (opts->name && strcmp(opts->name, root->name))
1404 * If we asked for subsystems (or explicitly for no
1405 * subsystems) then they must match
1407 if ((opts->subsys_bits || opts->none)
1408 && (opts->subsys_bits != root->subsys_bits))
1414 static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
1416 struct cgroupfs_root *root;
1418 if (!opts->subsys_bits && !opts->none)
1421 root = kzalloc(sizeof(*root), GFP_KERNEL);
1423 return ERR_PTR(-ENOMEM);
1425 if (!init_root_id(root)) {
1427 return ERR_PTR(-ENOMEM);
1429 init_cgroup_root(root);
1431 root->subsys_bits = opts->subsys_bits;
1432 root->flags = opts->flags;
1433 if (opts->release_agent)
1434 strcpy(root->release_agent_path, opts->release_agent);
1436 strcpy(root->name, opts->name);
1437 if (opts->clone_children)
1438 set_bit(CGRP_CLONE_CHILDREN, &root->top_cgroup.flags);
1442 static void cgroup_drop_root(struct cgroupfs_root *root)
1447 BUG_ON(!root->hierarchy_id);
1448 spin_lock(&hierarchy_id_lock);
1449 ida_remove(&hierarchy_ida, root->hierarchy_id);
1450 spin_unlock(&hierarchy_id_lock);
1454 static int cgroup_set_super(struct super_block *sb, void *data)
1457 struct cgroup_sb_opts *opts = data;
1459 /* If we don't have a new root, we can't set up a new sb */
1460 if (!opts->new_root)
1463 BUG_ON(!opts->subsys_bits && !opts->none);
1465 ret = set_anon_super(sb, NULL);
1469 sb->s_fs_info = opts->new_root;
1470 opts->new_root->sb = sb;
1472 sb->s_blocksize = PAGE_CACHE_SIZE;
1473 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
1474 sb->s_magic = CGROUP_SUPER_MAGIC;
1475 sb->s_op = &cgroup_ops;
1480 static int cgroup_get_rootdir(struct super_block *sb)
1482 static const struct dentry_operations cgroup_dops = {
1483 .d_iput = cgroup_diput,
1484 .d_delete = cgroup_delete,
1487 struct inode *inode =
1488 cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
1493 inode->i_fop = &simple_dir_operations;
1494 inode->i_op = &cgroup_dir_inode_operations;
1495 /* directories start off with i_nlink == 2 (for "." entry) */
1497 sb->s_root = d_make_root(inode);
1500 /* for everything else we want ->d_op set */
1501 sb->s_d_op = &cgroup_dops;
1505 static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1506 int flags, const char *unused_dev_name,
1509 struct cgroup_sb_opts opts;
1510 struct cgroupfs_root *root;
1512 struct super_block *sb;
1513 struct cgroupfs_root *new_root;
1514 struct inode *inode;
1516 /* First find the desired set of subsystems */
1517 mutex_lock(&cgroup_mutex);
1518 ret = parse_cgroupfs_options(data, &opts);
1519 mutex_unlock(&cgroup_mutex);
1524 * Allocate a new cgroup root. We may not need it if we're
1525 * reusing an existing hierarchy.
1527 new_root = cgroup_root_from_opts(&opts);
1528 if (IS_ERR(new_root)) {
1529 ret = PTR_ERR(new_root);
1532 opts.new_root = new_root;
1534 /* Locate an existing or new sb for this hierarchy */
1535 sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
1538 cgroup_drop_root(opts.new_root);
1542 root = sb->s_fs_info;
1544 if (root == opts.new_root) {
1545 /* We used the new root structure, so this is a new hierarchy */
1546 struct list_head tmp_cg_links;
1547 struct cgroup *root_cgrp = &root->top_cgroup;
1548 struct cgroupfs_root *existing_root;
1549 const struct cred *cred;
1552 BUG_ON(sb->s_root != NULL);
1554 ret = cgroup_get_rootdir(sb);
1556 goto drop_new_super;
1557 inode = sb->s_root->d_inode;
1559 mutex_lock(&inode->i_mutex);
1560 mutex_lock(&cgroup_mutex);
1561 mutex_lock(&cgroup_root_mutex);
1563 /* Check for name clashes with existing mounts */
1565 if (strlen(root->name))
1566 for_each_active_root(existing_root)
1567 if (!strcmp(existing_root->name, root->name))
1571 * We're accessing css_set_count without locking
1572 * css_set_lock here, but that's OK - it can only be
1573 * increased by someone holding cgroup_lock, and
1574 * that's us. The worst that can happen is that we
1575 * have some link structures left over
1577 ret = allocate_cg_links(css_set_count, &tmp_cg_links);
1581 ret = rebind_subsystems(root, root->subsys_bits);
1582 if (ret == -EBUSY) {
1583 free_cg_links(&tmp_cg_links);
1587 * There must be no failure case after here, since rebinding
1588 * takes care of subsystems' refcounts, which are explicitly
1589 * dropped in the failure exit path.
1592 /* EBUSY should be the only error here */
1595 list_add(&root->root_list, &roots);
1598 sb->s_root->d_fsdata = root_cgrp;
1599 root->top_cgroup.dentry = sb->s_root;
1601 /* Link the top cgroup in this hierarchy into all
1602 * the css_set objects */
1603 write_lock(&css_set_lock);
1604 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
1605 struct hlist_head *hhead = &css_set_table[i];
1606 struct hlist_node *node;
1609 hlist_for_each_entry(cg, node, hhead, hlist)
1610 link_css_set(&tmp_cg_links, cg, root_cgrp);
1612 write_unlock(&css_set_lock);
1614 free_cg_links(&tmp_cg_links);
1616 BUG_ON(!list_empty(&root_cgrp->sibling));
1617 BUG_ON(!list_empty(&root_cgrp->children));
1618 BUG_ON(root->number_of_cgroups != 1);
1620 cred = override_creds(&init_cred);
1621 cgroup_populate_dir(root_cgrp);
1623 mutex_unlock(&cgroup_root_mutex);
1624 mutex_unlock(&cgroup_mutex);
1625 mutex_unlock(&inode->i_mutex);
1628 * We re-used an existing hierarchy - the new root (if
1629 * any) is not needed
1631 cgroup_drop_root(opts.new_root);
1632 /* no subsys rebinding, so refcounts don't change */
1633 drop_parsed_module_refcounts(opts.subsys_bits);
1636 kfree(opts.release_agent);
1638 return dget(sb->s_root);
1641 mutex_unlock(&cgroup_root_mutex);
1642 mutex_unlock(&cgroup_mutex);
1643 mutex_unlock(&inode->i_mutex);
1645 deactivate_locked_super(sb);
1647 drop_parsed_module_refcounts(opts.subsys_bits);
1649 kfree(opts.release_agent);
1651 return ERR_PTR(ret);
1654 static void cgroup_kill_sb(struct super_block *sb) {
1655 struct cgroupfs_root *root = sb->s_fs_info;
1656 struct cgroup *cgrp = &root->top_cgroup;
1658 struct cg_cgroup_link *link;
1659 struct cg_cgroup_link *saved_link;
1663 BUG_ON(root->number_of_cgroups != 1);
1664 BUG_ON(!list_empty(&cgrp->children));
1665 BUG_ON(!list_empty(&cgrp->sibling));
1667 mutex_lock(&cgroup_mutex);
1668 mutex_lock(&cgroup_root_mutex);
1670 /* Rebind all subsystems back to the default hierarchy */
1671 ret = rebind_subsystems(root, 0);
1672 /* Shouldn't be able to fail ... */
1676 * Release all the links from css_sets to this hierarchy's
1679 write_lock(&css_set_lock);
1681 list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
1683 list_del(&link->cg_link_list);
1684 list_del(&link->cgrp_link_list);
1687 write_unlock(&css_set_lock);
1689 if (!list_empty(&root->root_list)) {
1690 list_del(&root->root_list);
1694 mutex_unlock(&cgroup_root_mutex);
1695 mutex_unlock(&cgroup_mutex);
1697 kill_litter_super(sb);
1698 cgroup_drop_root(root);
1701 static struct file_system_type cgroup_fs_type = {
1703 .mount = cgroup_mount,
1704 .kill_sb = cgroup_kill_sb,
1707 static struct kobject *cgroup_kobj;
1710 * cgroup_path - generate the path of a cgroup
1711 * @cgrp: the cgroup in question
1712 * @buf: the buffer to write the path into
1713 * @buflen: the length of the buffer
1715 * Called with cgroup_mutex held or else with an RCU-protected cgroup
1716 * reference. Writes path of cgroup into buf. Returns 0 on success,
1719 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1722 struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
1723 cgroup_lock_is_held());
1725 if (!dentry || cgrp == dummytop) {
1727 * Inactive subsystems have no dentry for their root
1734 start = buf + buflen;
1738 int len = dentry->d_name.len;
1740 if ((start -= len) < buf)
1741 return -ENAMETOOLONG;
1742 memcpy(start, dentry->d_name.name, len);
1743 cgrp = cgrp->parent;
1747 dentry = rcu_dereference_check(cgrp->dentry,
1748 cgroup_lock_is_held());
1752 return -ENAMETOOLONG;
1755 memmove(buf, start, buf + buflen - start);
1758 EXPORT_SYMBOL_GPL(cgroup_path);
1761 * Control Group taskset
1763 struct task_and_cgroup {
1764 struct task_struct *task;
1765 struct cgroup *cgrp;
1769 struct cgroup_taskset {
1770 struct task_and_cgroup single;
1771 struct flex_array *tc_array;
1774 struct cgroup *cur_cgrp;
1778 * cgroup_taskset_first - reset taskset and return the first task
1779 * @tset: taskset of interest
1781 * @tset iteration is initialized and the first task is returned.
1783 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
1785 if (tset->tc_array) {
1787 return cgroup_taskset_next(tset);
1789 tset->cur_cgrp = tset->single.cgrp;
1790 return tset->single.task;
1793 EXPORT_SYMBOL_GPL(cgroup_taskset_first);
1796 * cgroup_taskset_next - iterate to the next task in taskset
1797 * @tset: taskset of interest
1799 * Return the next task in @tset. Iteration must have been initialized
1800 * with cgroup_taskset_first().
1802 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
1804 struct task_and_cgroup *tc;
1806 if (!tset->tc_array || tset->idx >= tset->tc_array_len)
1809 tc = flex_array_get(tset->tc_array, tset->idx++);
1810 tset->cur_cgrp = tc->cgrp;
1813 EXPORT_SYMBOL_GPL(cgroup_taskset_next);
1816 * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
1817 * @tset: taskset of interest
1819 * Return the cgroup for the current (last returned) task of @tset. This
1820 * function must be preceded by either cgroup_taskset_first() or
1821 * cgroup_taskset_next().
1823 struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
1825 return tset->cur_cgrp;
1827 EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);
1830 * cgroup_taskset_size - return the number of tasks in taskset
1831 * @tset: taskset of interest
1833 int cgroup_taskset_size(struct cgroup_taskset *tset)
1835 return tset->tc_array ? tset->tc_array_len : 1;
1837 EXPORT_SYMBOL_GPL(cgroup_taskset_size);
1841 * cgroup_task_migrate - move a task from one cgroup to another.
1843 * 'guarantee' is set if the caller promises that a new css_set for the task
1844 * will already exist. If not set, this function might sleep, and can fail with
1845 * -ENOMEM. Must be called with cgroup_mutex and threadgroup locked.
1847 static void cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
1848 struct task_struct *tsk, struct css_set *newcg)
1850 struct css_set *oldcg;
1853 * We are synchronized through threadgroup_lock() against PF_EXITING
1854 * setting such that we can't race against cgroup_exit() changing the
1855 * css_set to init_css_set and dropping the old one.
1857 WARN_ON_ONCE(tsk->flags & PF_EXITING);
1858 oldcg = tsk->cgroups;
1861 rcu_assign_pointer(tsk->cgroups, newcg);
1864 /* Update the css_set linked lists if we're using them */
1865 write_lock(&css_set_lock);
1866 if (!list_empty(&tsk->cg_list))
1867 list_move(&tsk->cg_list, &newcg->tasks);
1868 write_unlock(&css_set_lock);
1871 * We just gained a reference on oldcg by taking it from the task. As
1872 * trading it for newcg is protected by cgroup_mutex, we're safe to drop
1873 * it here; it will be freed under RCU.
1877 set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1881 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
1882 * @cgrp: the cgroup the task is attaching to
1883 * @tsk: the task to be attached
1885 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
1888 int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1891 struct cgroup_subsys *ss, *failed_ss = NULL;
1892 struct cgroup *oldcgrp;
1893 struct cgroupfs_root *root = cgrp->root;
1894 struct cgroup_taskset tset = { };
1895 struct css_set *newcg;
1897 /* @tsk either already exited or can't exit until the end */
1898 if (tsk->flags & PF_EXITING)
1901 /* Nothing to do if the task is already in that cgroup */
1902 oldcgrp = task_cgroup_from_root(tsk, root);
1903 if (cgrp == oldcgrp)
1906 tset.single.task = tsk;
1907 tset.single.cgrp = oldcgrp;
1909 for_each_subsys(root, ss) {
1910 if (ss->can_attach) {
1911 retval = ss->can_attach(cgrp, &tset);
1914 * Remember on which subsystem the can_attach()
1915 * failed, so that we only call cancel_attach()
1916 * against the subsystems whose can_attach()
1917 * succeeded. (See below)
1925 newcg = find_css_set(tsk->cgroups, cgrp);
1931 cgroup_task_migrate(cgrp, oldcgrp, tsk, newcg);
1933 for_each_subsys(root, ss) {
1935 ss->attach(cgrp, &tset);
1941 for_each_subsys(root, ss) {
1942 if (ss == failed_ss)
1944 * This subsystem was the one that failed the
1945 * can_attach() check earlier, so we don't need
1946 * to call cancel_attach() against it or any
1947 * remaining subsystems.
1950 if (ss->cancel_attach)
1951 ss->cancel_attach(cgrp, &tset);
1958 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
1959 * @from: attach to all cgroups of a given task
1960 * @tsk: the task to be attached
1962 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
1964 struct cgroupfs_root *root;
1968 for_each_active_root(root) {
1969 struct cgroup *from_cg = task_cgroup_from_root(from, root);
1971 retval = cgroup_attach_task(from_cg, tsk);
1979 EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
1982 * cgroup_attach_proc - attach all threads in a threadgroup to a cgroup
1983 * @cgrp: the cgroup to attach to
1984 * @leader: the threadgroup leader task_struct of the group to be attached
1986 * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
1987 * task_lock of each thread in leader's threadgroup individually in turn.
1989 static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
1991 int retval, i, group_size;
1992 struct cgroup_subsys *ss, *failed_ss = NULL;
1993 /* guaranteed to be initialized later, but the compiler needs this */
1994 struct cgroupfs_root *root = cgrp->root;
1995 /* threadgroup list cursor and array */
1996 struct task_struct *tsk;
1997 struct task_and_cgroup *tc;
1998 struct flex_array *group;
1999 struct cgroup_taskset tset = { };
2002 * step 0: in order to do expensive, possibly blocking operations for
2003 * every thread, we cannot iterate the thread group list, since it needs
2004 * rcu or tasklist locked. instead, build an array of all threads in the
2005 * group - group_rwsem prevents new threads from appearing, and if
2006 * threads exit, this will just be an over-estimate.
2008 group_size = get_nr_threads(leader);
2009 /* flex_array supports very large thread-groups better than kmalloc. */
2010 group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
2013 /* pre-allocate to guarantee space while iterating in rcu read-side. */
2014 retval = flex_array_prealloc(group, 0, group_size - 1, GFP_KERNEL);
2016 goto out_free_group_list;
2021 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2022 * already PF_EXITING could be freed from underneath us unless we
2023 * take an rcu_read_lock.
2027 struct task_and_cgroup ent;
2029 /* @tsk either already exited or can't exit until the end */
2030 if (tsk->flags & PF_EXITING)
2033 /* as per above, nr_threads may decrease, but not increase. */
2034 BUG_ON(i >= group_size);
2036 ent.cgrp = task_cgroup_from_root(tsk, root);
2037 /* nothing to do if this task is already in the cgroup */
2038 if (ent.cgrp == cgrp)
2041 * saying GFP_ATOMIC has no effect here because we did prealloc
2042 * earlier, but it's good form to communicate our expectations.
2044 retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2045 BUG_ON(retval != 0);
2047 } while_each_thread(leader, tsk);
2049 /* remember the number of threads in the array for later. */
2051 tset.tc_array = group;
2052 tset.tc_array_len = group_size;
2054 /* methods shouldn't be called if no task is actually migrating */
2057 goto out_free_group_list;
2060 * step 1: check that we can legitimately attach to the cgroup.
2062 for_each_subsys(root, ss) {
2063 if (ss->can_attach) {
2064 retval = ss->can_attach(cgrp, &tset);
2067 goto out_cancel_attach;
2073 * step 2: make sure css_sets exist for all threads to be migrated.
2074 * we use find_css_set, which allocates a new one if necessary.
2076 for (i = 0; i < group_size; i++) {
2077 tc = flex_array_get(group, i);
2078 tc->cg = find_css_set(tc->task->cgroups, cgrp);
2081 goto out_put_css_set_refs;
2086 * step 3: now that we're guaranteed success wrt the css_sets,
2087 * proceed to move all tasks to the new cgroup. There are no
2088 * failure cases after here, so this is the commit point.
2090 for (i = 0; i < group_size; i++) {
2091 tc = flex_array_get(group, i);
2092 cgroup_task_migrate(cgrp, tc->cgrp, tc->task, tc->cg);
2094 /* nothing is sensitive to fork() after this point. */
2097 * step 4: do subsystem attach callbacks.
2099 for_each_subsys(root, ss) {
2101 ss->attach(cgrp, &tset);
2105 * step 5: success! and cleanup
2109 out_put_css_set_refs:
2111 for (i = 0; i < group_size; i++) {
2112 tc = flex_array_get(group, i);
2115 put_css_set(tc->cg);
2120 for_each_subsys(root, ss) {
2121 if (ss == failed_ss)
2123 if (ss->cancel_attach)
2124 ss->cancel_attach(cgrp, &tset);
2127 out_free_group_list:
2128 flex_array_free(group);
2133 * Find the task_struct of the task to attach by vpid and pass it along to the
2134 * function to attach either it or all tasks in its threadgroup. Will lock
2135 * cgroup_mutex and threadgroup; may take task_lock of task.
2137 static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2139 struct task_struct *tsk;
2140 const struct cred *cred = current_cred(), *tcred;
2143 if (!cgroup_lock_live_group(cgrp))
2149 tsk = find_task_by_vpid(pid);
2153 goto out_unlock_cgroup;
2156 * even if we're attaching all tasks in the thread group, we
2157 * only need to check permissions on one of them.
2159 tcred = __task_cred(tsk);
2160 if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
2161 !uid_eq(cred->euid, tcred->uid) &&
2162 !uid_eq(cred->euid, tcred->suid)) {
2165 goto out_unlock_cgroup;
2171 tsk = tsk->group_leader;
2174 * Workqueue threads may acquire PF_THREAD_BOUND and become
2175 * trapped in a cpuset, or RT worker may be born in a cgroup
2176 * with no rt_runtime allocated. Just say no.
2178 if (tsk == kthreadd_task || (tsk->flags & PF_THREAD_BOUND)) {
2181 goto out_unlock_cgroup;
2184 get_task_struct(tsk);
2187 threadgroup_lock(tsk);
2189 if (!thread_group_leader(tsk)) {
2191 * a race with de_thread from another thread's exec()
2192 * may strip us of our leadership, if this happens,
2193 * there is no choice but to throw this task away and
2194 * try again; this is
2195 * "double-double-toil-and-trouble-check locking".
2197 threadgroup_unlock(tsk);
2198 put_task_struct(tsk);
2199 goto retry_find_task;
2201 ret = cgroup_attach_proc(cgrp, tsk);
2203 ret = cgroup_attach_task(cgrp, tsk);
2204 threadgroup_unlock(tsk);
2206 put_task_struct(tsk);
2212 static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
2214 return attach_task_by_pid(cgrp, pid, false);
2217 static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2219 return attach_task_by_pid(cgrp, tgid, true);
2223 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
2224 * @cgrp: the cgroup to be checked for liveness
2226 * On success, returns true; the lock should be later released with
2227 * cgroup_unlock(). On failure returns false with no lock held.
2229 bool cgroup_lock_live_group(struct cgroup *cgrp)
2231 mutex_lock(&cgroup_mutex);
2232 if (cgroup_is_removed(cgrp)) {
2233 mutex_unlock(&cgroup_mutex);
2238 EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2240 static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
2243 BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
2244 if (strlen(buffer) >= PATH_MAX)
2246 if (!cgroup_lock_live_group(cgrp))
2248 mutex_lock(&cgroup_root_mutex);
2249 strcpy(cgrp->root->release_agent_path, buffer);
2250 mutex_unlock(&cgroup_root_mutex);
2255 static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
2256 struct seq_file *seq)
2258 if (!cgroup_lock_live_group(cgrp))
2260 seq_puts(seq, cgrp->root->release_agent_path);
2261 seq_putc(seq, '\n');
2266 /* A buffer size big enough for numbers or short strings */
2267 #define CGROUP_LOCAL_BUFFER_SIZE 64
2269 static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2271 const char __user *userbuf,
2272 size_t nbytes, loff_t *unused_ppos)
2274 char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2280 if (nbytes >= sizeof(buffer))
2282 if (copy_from_user(buffer, userbuf, nbytes))
2285 buffer[nbytes] = 0; /* nul-terminate */
2286 if (cft->write_u64) {
2287 u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2290 retval = cft->write_u64(cgrp, cft, val);
2292 s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2295 retval = cft->write_s64(cgrp, cft, val);
2302 static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
2304 const char __user *userbuf,
2305 size_t nbytes, loff_t *unused_ppos)
2307 char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2309 size_t max_bytes = cft->max_write_len;
2310 char *buffer = local_buffer;
2313 max_bytes = sizeof(local_buffer) - 1;
2314 if (nbytes >= max_bytes)
2316 /* Allocate a dynamic buffer if we need one */
2317 if (nbytes >= sizeof(local_buffer)) {
2318 buffer = kmalloc(nbytes + 1, GFP_KERNEL);
2322 if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
2327 buffer[nbytes] = 0; /* nul-terminate */
2328 retval = cft->write_string(cgrp, cft, strstrip(buffer));
2332 if (buffer != local_buffer)
2337 static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
2338 size_t nbytes, loff_t *ppos)
2340 struct cftype *cft = __d_cft(file->f_dentry);
2341 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2343 if (cgroup_is_removed(cgrp))
2346 return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2347 if (cft->write_u64 || cft->write_s64)
2348 return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2349 if (cft->write_string)
2350 return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2352 int ret = cft->trigger(cgrp, (unsigned int)cft->private);
2353 return ret ? ret : nbytes;
2358 static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
2360 char __user *buf, size_t nbytes,
2363 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2364 u64 val = cft->read_u64(cgrp, cft);
2365 int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
2367 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2370 static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
2372 char __user *buf, size_t nbytes,
2375 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2376 s64 val = cft->read_s64(cgrp, cft);
2377 int len = sprintf(tmp, "%lld\n", (long long) val);
2379 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2382 static ssize_t cgroup_file_read(struct file *file, char __user *buf,
2383 size_t nbytes, loff_t *ppos)
2385 struct cftype *cft = __d_cft(file->f_dentry);
2386 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2388 if (cgroup_is_removed(cgrp))
2392 return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2394 return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2396 return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2401 * seqfile ops/methods for returning structured data. Currently just
2402 * supports string->u64 maps, but can be extended in future.
2405 struct cgroup_seqfile_state {
2407 struct cgroup *cgroup;
2410 static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
2412 struct seq_file *sf = cb->state;
2413 return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
2416 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
2418 struct cgroup_seqfile_state *state = m->private;
2419 struct cftype *cft = state->cft;
2420 if (cft->read_map) {
2421 struct cgroup_map_cb cb = {
2422 .fill = cgroup_map_add,
2425 return cft->read_map(state->cgroup, cft, &cb);
2427 return cft->read_seq_string(state->cgroup, cft, m);
2430 static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2432 struct seq_file *seq = file->private_data;
2433 kfree(seq->private);
2434 return single_release(inode, file);
2437 static const struct file_operations cgroup_seqfile_operations = {
2439 .write = cgroup_file_write,
2440 .llseek = seq_lseek,
2441 .release = cgroup_seqfile_release,
2444 static int cgroup_file_open(struct inode *inode, struct file *file)
2449 err = generic_file_open(inode, file);
2452 cft = __d_cft(file->f_dentry);
2454 if (cft->read_map || cft->read_seq_string) {
2455 struct cgroup_seqfile_state *state =
2456 kzalloc(sizeof(*state), GFP_USER);
2460 state->cgroup = __d_cgrp(file->f_dentry->d_parent);
2461 file->f_op = &cgroup_seqfile_operations;
2462 err = single_open(file, cgroup_seqfile_show, state);
2465 } else if (cft->open)
2466 err = cft->open(inode, file);
2473 static int cgroup_file_release(struct inode *inode, struct file *file)
2475 struct cftype *cft = __d_cft(file->f_dentry);
2477 return cft->release(inode, file);
2482 * cgroup_rename - Only allow simple rename of directories in place.
2484 static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
2485 struct inode *new_dir, struct dentry *new_dentry)
2487 if (!S_ISDIR(old_dentry->d_inode->i_mode))
2489 if (new_dentry->d_inode)
2491 if (old_dir != new_dir)
2493 return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
2496 static const struct file_operations cgroup_file_operations = {
2497 .read = cgroup_file_read,
2498 .write = cgroup_file_write,
2499 .llseek = generic_file_llseek,
2500 .open = cgroup_file_open,
2501 .release = cgroup_file_release,
2504 static const struct inode_operations cgroup_dir_inode_operations = {
2505 .lookup = cgroup_lookup,
2506 .mkdir = cgroup_mkdir,
2507 .rmdir = cgroup_rmdir,
2508 .rename = cgroup_rename,
2511 static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
2513 if (dentry->d_name.len > NAME_MAX)
2514 return ERR_PTR(-ENAMETOOLONG);
2515 d_add(dentry, NULL);
2520 * Check if a file is a control file
2522 static inline struct cftype *__file_cft(struct file *file)
2524 if (file->f_dentry->d_inode->i_fop != &cgroup_file_operations)
2525 return ERR_PTR(-EINVAL);
2526 return __d_cft(file->f_dentry);
2529 static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2530 struct super_block *sb)
2532 struct inode *inode;
2536 if (dentry->d_inode)
2539 inode = cgroup_new_inode(mode, sb);
2543 if (S_ISDIR(mode)) {
2544 inode->i_op = &cgroup_dir_inode_operations;
2545 inode->i_fop = &simple_dir_operations;
2547 /* start off with i_nlink == 2 (for "." entry) */
2550 /* start with the directory inode held, so that we can
2551 * populate it without racing with another mkdir */
2552 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
2553 } else if (S_ISREG(mode)) {
2555 inode->i_fop = &cgroup_file_operations;
2557 d_instantiate(dentry, inode);
2558 dget(dentry); /* Extra count - pin the dentry in core */
2563 * cgroup_create_dir - create a directory for an object.
2564 * @cgrp: the cgroup we create the directory for. It must have a valid
2565 * ->parent field. And we are going to fill its ->dentry field.
2566 * @dentry: dentry of the new cgroup
2567 * @mode: mode to set on new directory.
2569 static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
2572 struct dentry *parent;
2575 parent = cgrp->parent->dentry;
2576 error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
2578 dentry->d_fsdata = cgrp;
2579 inc_nlink(parent->d_inode);
2580 rcu_assign_pointer(cgrp->dentry, dentry);
2589 * cgroup_file_mode - deduce file mode of a control file
2590 * @cft: the control file in question
2592 * returns cft->mode if ->mode is not 0
2593 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
2594 * returns S_IRUGO if it has only a read handler
2595 * returns S_IWUSR if it has only a write hander
2597 static umode_t cgroup_file_mode(const struct cftype *cft)
2604 if (cft->read || cft->read_u64 || cft->read_s64 ||
2605 cft->read_map || cft->read_seq_string)
2608 if (cft->write || cft->write_u64 || cft->write_s64 ||
2609 cft->write_string || cft->trigger)
2615 static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
2616 const struct cftype *cft)
2618 struct dentry *dir = cgrp->dentry;
2619 struct cgroup *parent = __d_cgrp(dir);
2620 struct dentry *dentry;
2624 char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2626 /* does @cft->flags tell us to skip creation on @cgrp? */
2627 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
2629 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
2632 if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2633 strcpy(name, subsys->name);
2636 strcat(name, cft->name);
2638 BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
2640 cfe = kzalloc(sizeof(*cfe), GFP_KERNEL);
2644 dentry = lookup_one_len(name, dir, strlen(name));
2645 if (IS_ERR(dentry)) {
2646 error = PTR_ERR(dentry);
2650 mode = cgroup_file_mode(cft);
2651 error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
2653 cfe->type = (void *)cft;
2654 cfe->dentry = dentry;
2655 dentry->d_fsdata = cfe;
2656 list_add_tail(&cfe->node, &parent->files);
2665 static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
2666 const struct cftype cfts[], bool is_add)
2668 const struct cftype *cft;
2671 for (cft = cfts; cft->name[0] != '\0'; cft++) {
2673 err = cgroup_add_file(cgrp, subsys, cft);
2675 err = cgroup_rm_file(cgrp, cft);
2677 pr_warning("cgroup_addrm_files: failed to %s %s, err=%d\n",
2678 is_add ? "add" : "remove", cft->name, err);
2685 static DEFINE_MUTEX(cgroup_cft_mutex);
2687 static void cgroup_cfts_prepare(void)
2688 __acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex)
2691 * Thanks to the entanglement with vfs inode locking, we can't walk
2692 * the existing cgroups under cgroup_mutex and create files.
2693 * Instead, we increment reference on all cgroups and build list of
2694 * them using @cgrp->cft_q_node. Grab cgroup_cft_mutex to ensure
2695 * exclusive access to the field.
2697 mutex_lock(&cgroup_cft_mutex);
2698 mutex_lock(&cgroup_mutex);
2701 static void cgroup_cfts_commit(struct cgroup_subsys *ss,
2702 const struct cftype *cfts, bool is_add)
2703 __releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
2706 struct cgroup *cgrp, *n;
2708 /* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
2709 if (cfts && ss->root != &rootnode) {
2710 list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) {
2712 list_add_tail(&cgrp->cft_q_node, &pending);
2716 mutex_unlock(&cgroup_mutex);
2719 * All new cgroups will see @cfts update on @ss->cftsets. Add/rm
2720 * files for all cgroups which were created before.
2722 list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {
2723 struct inode *inode = cgrp->dentry->d_inode;
2725 mutex_lock(&inode->i_mutex);
2726 mutex_lock(&cgroup_mutex);
2727 if (!cgroup_is_removed(cgrp))
2728 cgroup_addrm_files(cgrp, ss, cfts, is_add);
2729 mutex_unlock(&cgroup_mutex);
2730 mutex_unlock(&inode->i_mutex);
2732 list_del_init(&cgrp->cft_q_node);
2736 mutex_unlock(&cgroup_cft_mutex);
2740 * cgroup_add_cftypes - add an array of cftypes to a subsystem
2741 * @ss: target cgroup subsystem
2742 * @cfts: zero-length name terminated array of cftypes
2744 * Register @cfts to @ss. Files described by @cfts are created for all
2745 * existing cgroups to which @ss is attached and all future cgroups will
2746 * have them too. This function can be called anytime whether @ss is
2749 * Returns 0 on successful registration, -errno on failure. Note that this
2750 * function currently returns 0 as long as @cfts registration is successful
2751 * even if some file creation attempts on existing cgroups fail.
2753 int cgroup_add_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
2755 struct cftype_set *set;
2757 set = kzalloc(sizeof(*set), GFP_KERNEL);
2761 cgroup_cfts_prepare();
2763 list_add_tail(&set->node, &ss->cftsets);
2764 cgroup_cfts_commit(ss, cfts, true);
2768 EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
2771 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
2772 * @ss: target cgroup subsystem
2773 * @cfts: zero-length name terminated array of cftypes
2775 * Unregister @cfts from @ss. Files described by @cfts are removed from
2776 * all existing cgroups to which @ss is attached and all future cgroups
2777 * won't have them either. This function can be called anytime whether @ss
2778 * is attached or not.
2780 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
2781 * registered with @ss.
2783 int cgroup_rm_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
2785 struct cftype_set *set;
2787 cgroup_cfts_prepare();
2789 list_for_each_entry(set, &ss->cftsets, node) {
2790 if (set->cfts == cfts) {
2791 list_del_init(&set->node);
2792 cgroup_cfts_commit(ss, cfts, false);
2797 cgroup_cfts_commit(ss, NULL, false);
2802 * cgroup_task_count - count the number of tasks in a cgroup.
2803 * @cgrp: the cgroup in question
2805 * Return the number of tasks in the cgroup.
2807 int cgroup_task_count(const struct cgroup *cgrp)
2810 struct cg_cgroup_link *link;
2812 read_lock(&css_set_lock);
2813 list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2814 count += atomic_read(&link->cg->refcount);
2816 read_unlock(&css_set_lock);
2821 * Advance a list_head iterator. The iterator should be positioned at
2822 * the start of a css_set
2824 static void cgroup_advance_iter(struct cgroup *cgrp,
2825 struct cgroup_iter *it)
2827 struct list_head *l = it->cg_link;
2828 struct cg_cgroup_link *link;
2831 /* Advance to the next non-empty css_set */
2834 if (l == &cgrp->css_sets) {
2838 link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2840 } while (list_empty(&cg->tasks));
2842 it->task = cg->tasks.next;
2846 * To reduce the fork() overhead for systems that are not actually
2847 * using their cgroups capability, we don't maintain the lists running
2848 * through each css_set to its tasks until we see the list actually
2849 * used - in other words after the first call to cgroup_iter_start().
2851 static void cgroup_enable_task_cg_lists(void)
2853 struct task_struct *p, *g;
2854 write_lock(&css_set_lock);
2855 use_task_css_set_links = 1;
2857 * We need tasklist_lock because RCU is not safe against
2858 * while_each_thread(). Besides, a forking task that has passed
2859 * cgroup_post_fork() without seeing use_task_css_set_links = 1
2860 * is not guaranteed to have its child immediately visible in the
2861 * tasklist if we walk through it with RCU.
2863 read_lock(&tasklist_lock);
2864 do_each_thread(g, p) {
2867 * We should check if the process is exiting, otherwise
2868 * it will race with cgroup_exit() in that the list
2869 * entry won't be deleted though the process has exited.
2871 if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
2872 list_add(&p->cg_list, &p->cgroups->tasks);
2874 } while_each_thread(g, p);
2875 read_unlock(&tasklist_lock);
2876 write_unlock(&css_set_lock);
2879 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
2880 __acquires(css_set_lock)
2883 * The first time anyone tries to iterate across a cgroup,
2884 * we need to enable the list linking each css_set to its
2885 * tasks, and fix up all existing tasks.
2887 if (!use_task_css_set_links)
2888 cgroup_enable_task_cg_lists();
2890 read_lock(&css_set_lock);
2891 it->cg_link = &cgrp->css_sets;
2892 cgroup_advance_iter(cgrp, it);
2895 struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
2896 struct cgroup_iter *it)
2898 struct task_struct *res;
2899 struct list_head *l = it->task;
2900 struct cg_cgroup_link *link;
2902 /* If the iterator cg is NULL, we have no tasks */
2905 res = list_entry(l, struct task_struct, cg_list);
2906 /* Advance iterator to find next entry */
2908 link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
2909 if (l == &link->cg->tasks) {
2910 /* We reached the end of this task list - move on to
2911 * the next cg_cgroup_link */
2912 cgroup_advance_iter(cgrp, it);
2919 void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
2920 __releases(css_set_lock)
2922 read_unlock(&css_set_lock);
2925 static inline int started_after_time(struct task_struct *t1,
2926 struct timespec *time,
2927 struct task_struct *t2)
2929 int start_diff = timespec_compare(&t1->start_time, time);
2930 if (start_diff > 0) {
2932 } else if (start_diff < 0) {
2936 * Arbitrarily, if two processes started at the same
2937 * time, we'll say that the lower pointer value
2938 * started first. Note that t2 may have exited by now
2939 * so this may not be a valid pointer any longer, but
2940 * that's fine - it still serves to distinguish
2941 * between two tasks started (effectively) simultaneously.
2948 * This function is a callback from heap_insert() and is used to order
2950 * In this case we order the heap in descending task start time.
2952 static inline int started_after(void *p1, void *p2)
2954 struct task_struct *t1 = p1;
2955 struct task_struct *t2 = p2;
2956 return started_after_time(t1, &t2->start_time, t2);
2960 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
2961 * @scan: struct cgroup_scanner containing arguments for the scan
2963 * Arguments include pointers to callback functions test_task() and
2965 * Iterate through all the tasks in a cgroup, calling test_task() for each,
2966 * and if it returns true, call process_task() for it also.
2967 * The test_task pointer may be NULL, meaning always true (select all tasks).
2968 * Effectively duplicates cgroup_iter_{start,next,end}()
2969 * but does not lock css_set_lock for the call to process_task().
2970 * The struct cgroup_scanner may be embedded in any structure of the caller's
2972 * It is guaranteed that process_task() will act on every task that
2973 * is a member of the cgroup for the duration of this call. This
2974 * function may or may not call process_task() for tasks that exit
2975 * or move to a different cgroup during the call, or are forked or
2976 * move into the cgroup during the call.
2978 * Note that test_task() may be called with locks held, and may in some
2979 * situations be called multiple times for the same task, so it should
2981 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
2982 * pre-allocated and will be used for heap operations (and its "gt" member will
2983 * be overwritten), else a temporary heap will be used (allocation of which
2984 * may cause this function to fail).
2986 int cgroup_scan_tasks(struct cgroup_scanner *scan)
2989 struct cgroup_iter it;
2990 struct task_struct *p, *dropped;
2991 /* Never dereference latest_task, since it's not refcounted */
2992 struct task_struct *latest_task = NULL;
2993 struct ptr_heap tmp_heap;
2994 struct ptr_heap *heap;
2995 struct timespec latest_time = { 0, 0 };
2998 /* The caller supplied our heap and pre-allocated its memory */
3000 heap->gt = &started_after;
3002 /* We need to allocate our own heap memory */
3004 retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
3006 /* cannot allocate the heap */
3012 * Scan tasks in the cgroup, using the scanner's "test_task" callback
3013 * to determine which are of interest, and using the scanner's
3014 * "process_task" callback to process any of them that need an update.
3015 * Since we don't want to hold any locks during the task updates,
3016 * gather tasks to be processed in a heap structure.
3017 * The heap is sorted by descending task start time.
3018 * If the statically-sized heap fills up, we overflow tasks that
3019 * started later, and in future iterations only consider tasks that
3020 * started after the latest task in the previous pass. This
3021 * guarantees forward progress and that we don't miss any tasks.
3024 cgroup_iter_start(scan->cg, &it);
3025 while ((p = cgroup_iter_next(scan->cg, &it))) {
3027 * Only affect tasks that qualify per the caller's callback,
3028 * if he provided one
3030 if (scan->test_task && !scan->test_task(p, scan))
3033 * Only process tasks that started after the last task
3036 if (!started_after_time(p, &latest_time, latest_task))
3038 dropped = heap_insert(heap, p);
3039 if (dropped == NULL) {
3041 * The new task was inserted; the heap wasn't
3045 } else if (dropped != p) {
3047 * The new task was inserted, and pushed out a
3051 put_task_struct(dropped);
3054 * Else the new task was newer than anything already in
3055 * the heap and wasn't inserted
3058 cgroup_iter_end(scan->cg, &it);
3061 for (i = 0; i < heap->size; i++) {
3062 struct task_struct *q = heap->ptrs[i];
3064 latest_time = q->start_time;
3067 /* Process the task per the caller's callback */
3068 scan->process_task(q, scan);
3072 * If we had to process any tasks at all, scan again
3073 * in case some of them were in the middle of forking
3074 * children that didn't get processed.
3075 * Not the most efficient way to do it, but it avoids
3076 * having to take callback_mutex in the fork path
3080 if (heap == &tmp_heap)
3081 heap_free(&tmp_heap);
3086 * Stuff for reading the 'tasks'/'procs' files.
3088 * Reading this file can return large amounts of data if a cgroup has
3089 * *lots* of attached tasks. So it may need several calls to read(),
3090 * but we cannot guarantee that the information we produce is correct
3091 * unless we produce it entirely atomically.
3095 /* which pidlist file are we talking about? */
3096 enum cgroup_filetype {
3102 * A pidlist is a list of pids that virtually represents the contents of one
3103 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3104 * a pair (one each for procs, tasks) for each pid namespace that's relevant
3107 struct cgroup_pidlist {
3109 * used to find which pidlist is wanted. doesn't change as long as
3110 * this particular list stays in the list.
3112 struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
3115 /* how many elements the above list has */
3117 /* how many files are using the current array */
3119 /* each of these stored in a list by its cgroup */
3120 struct list_head links;
3121 /* pointer to the cgroup we belong to, for list removal purposes */
3122 struct cgroup *owner;
3123 /* protects the other fields */
3124 struct rw_semaphore mutex;
3128 * The following two functions "fix" the issue where there are more pids
3129 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3130 * TODO: replace with a kernel-wide solution to this problem
3132 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3133 static void *pidlist_allocate(int count)
3135 if (PIDLIST_TOO_LARGE(count))
3136 return vmalloc(count * sizeof(pid_t));
3138 return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
3140 static void pidlist_free(void *p)
3142 if (is_vmalloc_addr(p))
3147 static void *pidlist_resize(void *p, int newcount)
3150 /* note: if new alloc fails, old p will still be valid either way */
3151 if (is_vmalloc_addr(p)) {
3152 newlist = vmalloc(newcount * sizeof(pid_t));
3155 memcpy(newlist, p, newcount * sizeof(pid_t));
3158 newlist = krealloc(p, newcount * sizeof(pid_t), GFP_KERNEL);
3164 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3165 * If the new stripped list is sufficiently smaller and there's enough memory
3166 * to allocate a new buffer, will let go of the unneeded memory. Returns the
3167 * number of unique elements.
3169 /* is the size difference enough that we should re-allocate the array? */
3170 #define PIDLIST_REALLOC_DIFFERENCE(old, new) ((old) - PAGE_SIZE >= (new))
3171 static int pidlist_uniq(pid_t **p, int length)
3178 * we presume the 0th element is unique, so i starts at 1. trivial
3179 * edge cases first; no work needs to be done for either
3181 if (length == 0 || length == 1)
3183 /* src and dest walk down the list; dest counts unique elements */
3184 for (src = 1; src < length; src++) {
3185 /* find next unique element */
3186 while (list[src] == list[src-1]) {
3191 /* dest always points to where the next unique element goes */
3192 list[dest] = list[src];
3197 * if the length difference is large enough, we want to allocate a
3198 * smaller buffer to save memory. if this fails due to out of memory,
3199 * we'll just stay with what we've got.
3201 if (PIDLIST_REALLOC_DIFFERENCE(length, dest)) {
3202 newlist = pidlist_resize(list, dest);
3209 static int cmppid(const void *a, const void *b)
3211 return *(pid_t *)a - *(pid_t *)b;
3215 * find the appropriate pidlist for our purpose (given procs vs tasks)
3216 * returns with the lock on that pidlist already held, and takes care
3217 * of the use count, or returns NULL with no locks held if we're out of
3220 static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
3221 enum cgroup_filetype type)
3223 struct cgroup_pidlist *l;
3224 /* don't need task_nsproxy() if we're looking at ourself */
3225 struct pid_namespace *ns = current->nsproxy->pid_ns;
3228 * We can't drop the pidlist_mutex before taking the l->mutex in case
3229 * the last ref-holder is trying to remove l from the list at the same
3230 * time. Holding the pidlist_mutex precludes somebody taking whichever
3231 * list we find out from under us - compare release_pid_array().
3233 mutex_lock(&cgrp->pidlist_mutex);
3234 list_for_each_entry(l, &cgrp->pidlists, links) {
3235 if (l->key.type == type && l->key.ns == ns) {
3236 /* make sure l doesn't vanish out from under us */
3237 down_write(&l->mutex);
3238 mutex_unlock(&cgrp->pidlist_mutex);
3242 /* entry not found; create a new one */
3243 l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3245 mutex_unlock(&cgrp->pidlist_mutex);
3248 init_rwsem(&l->mutex);
3249 down_write(&l->mutex);
3251 l->key.ns = get_pid_ns(ns);
3252 l->use_count = 0; /* don't increment here */
3255 list_add(&l->links, &cgrp->pidlists);
3256 mutex_unlock(&cgrp->pidlist_mutex);
3261 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3263 static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
3264 struct cgroup_pidlist **lp)
3268 int pid, n = 0; /* used for populating the array */
3269 struct cgroup_iter it;
3270 struct task_struct *tsk;
3271 struct cgroup_pidlist *l;
3274 * If cgroup gets more users after we read count, we won't have
3275 * enough space - tough. This race is indistinguishable to the
3276 * caller from the case that the additional cgroup users didn't
3277 * show up until sometime later on.
3279 length = cgroup_task_count(cgrp);
3280 array = pidlist_allocate(length);
3283 /* now, populate the array */
3284 cgroup_iter_start(cgrp, &it);
3285 while ((tsk = cgroup_iter_next(cgrp, &it))) {
3286 if (unlikely(n == length))
3288 /* get tgid or pid for procs or tasks file respectively */
3289 if (type == CGROUP_FILE_PROCS)
3290 pid = task_tgid_vnr(tsk);
3292 pid = task_pid_vnr(tsk);
3293 if (pid > 0) /* make sure to only use valid results */
3296 cgroup_iter_end(cgrp, &it);
3298 /* now sort & (if procs) strip out duplicates */
3299 sort(array, length, sizeof(pid_t), cmppid, NULL);
3300 if (type == CGROUP_FILE_PROCS)
3301 length = pidlist_uniq(&array, length);
3302 l = cgroup_pidlist_find(cgrp, type);
3304 pidlist_free(array);
3307 /* store array, freeing old if necessary - lock already held */
3308 pidlist_free(l->list);
3312 up_write(&l->mutex);
3318 * cgroupstats_build - build and fill cgroupstats
3319 * @stats: cgroupstats to fill information into
3320 * @dentry: A dentry entry belonging to the cgroup for which stats have
3323 * Build and fill cgroupstats so that taskstats can export it to user
3326 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
3329 struct cgroup *cgrp;
3330 struct cgroup_iter it;
3331 struct task_struct *tsk;
3334 * Validate dentry by checking the superblock operations,
3335 * and make sure it's a directory.
3337 if (dentry->d_sb->s_op != &cgroup_ops ||
3338 !S_ISDIR(dentry->d_inode->i_mode))
3342 cgrp = dentry->d_fsdata;
3344 cgroup_iter_start(cgrp, &it);
3345 while ((tsk = cgroup_iter_next(cgrp, &it))) {
3346 switch (tsk->state) {
3348 stats->nr_running++;
3350 case TASK_INTERRUPTIBLE:
3351 stats->nr_sleeping++;
3353 case TASK_UNINTERRUPTIBLE:
3354 stats->nr_uninterruptible++;
3357 stats->nr_stopped++;
3360 if (delayacct_is_task_waiting_on_io(tsk))
3361 stats->nr_io_wait++;
3365 cgroup_iter_end(cgrp, &it);
3373 * seq_file methods for the tasks/procs files. The seq_file position is the
3374 * next pid to display; the seq_file iterator is a pointer to the pid
3375 * in the cgroup->l->list array.
3378 static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3381 * Initially we receive a position value that corresponds to
3382 * one more than the last pid shown (or 0 on the first call or
3383 * after a seek to the start). Use a binary-search to find the
3384 * next pid to display, if any
3386 struct cgroup_pidlist *l = s->private;
3387 int index = 0, pid = *pos;
3390 down_read(&l->mutex);
3392 int end = l->length;
3394 while (index < end) {
3395 int mid = (index + end) / 2;
3396 if (l->list[mid] == pid) {
3399 } else if (l->list[mid] <= pid)
3405 /* If we're off the end of the array, we're done */
3406 if (index >= l->length)
3408 /* Update the abstract position to be the actual pid that we found */
3409 iter = l->list + index;
3414 static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3416 struct cgroup_pidlist *l = s->private;
3420 static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3422 struct cgroup_pidlist *l = s->private;
3424 pid_t *end = l->list + l->length;
3426 * Advance to the next pid in the array. If this goes off the
3438 static int cgroup_pidlist_show(struct seq_file *s, void *v)
3440 return seq_printf(s, "%d\n", *(int *)v);
3444 * seq_operations functions for iterating on pidlists through seq_file -
3445 * independent of whether it's tasks or procs
3447 static const struct seq_operations cgroup_pidlist_seq_operations = {
3448 .start = cgroup_pidlist_start,
3449 .stop = cgroup_pidlist_stop,
3450 .next = cgroup_pidlist_next,
3451 .show = cgroup_pidlist_show,
3454 static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3457 * the case where we're the last user of this particular pidlist will
3458 * have us remove it from the cgroup's list, which entails taking the
3459 * mutex. since in pidlist_find the pidlist->lock depends on cgroup->
3460 * pidlist_mutex, we have to take pidlist_mutex first.
3462 mutex_lock(&l->owner->pidlist_mutex);
3463 down_write(&l->mutex);
3464 BUG_ON(!l->use_count);
3465 if (!--l->use_count) {
3466 /* we're the last user if refcount is 0; remove and free */
3467 list_del(&l->links);
3468 mutex_unlock(&l->owner->pidlist_mutex);
3469 pidlist_free(l->list);
3470 put_pid_ns(l->key.ns);
3471 up_write(&l->mutex);
3475 mutex_unlock(&l->owner->pidlist_mutex);
3476 up_write(&l->mutex);
3479 static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3481 struct cgroup_pidlist *l;
3482 if (!(file->f_mode & FMODE_READ))
3485 * the seq_file will only be initialized if the file was opened for
3486 * reading; hence we check if it's not null only in that case.
3488 l = ((struct seq_file *)file->private_data)->private;
3489 cgroup_release_pid_array(l);
3490 return seq_release(inode, file);
3493 static const struct file_operations cgroup_pidlist_operations = {
3495 .llseek = seq_lseek,
3496 .write = cgroup_file_write,
3497 .release = cgroup_pidlist_release,
3501 * The following functions handle opens on a file that displays a pidlist
3502 * (tasks or procs). Prepare an array of the process/thread IDs of whoever's
3505 /* helper function for the two below it */
3506 static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3508 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3509 struct cgroup_pidlist *l;
3512 /* Nothing to do for write-only files */
3513 if (!(file->f_mode & FMODE_READ))
3516 /* have the array populated */
3517 retval = pidlist_array_load(cgrp, type, &l);
3520 /* configure file information */
3521 file->f_op = &cgroup_pidlist_operations;
3523 retval = seq_open(file, &cgroup_pidlist_seq_operations);
3525 cgroup_release_pid_array(l);
3528 ((struct seq_file *)file->private_data)->private = l;
3531 static int cgroup_tasks_open(struct inode *unused, struct file *file)
3533 return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3535 static int cgroup_procs_open(struct inode *unused, struct file *file)
3537 return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3540 static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3543 return notify_on_release(cgrp);
3546 static int cgroup_write_notify_on_release(struct cgroup *cgrp,
3550 clear_bit(CGRP_RELEASABLE, &cgrp->flags);
3552 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3554 clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3559 * Unregister event and free resources.
3561 * Gets called from workqueue.
3563 static void cgroup_event_remove(struct work_struct *work)
3565 struct cgroup_event *event = container_of(work, struct cgroup_event,
3567 struct cgroup *cgrp = event->cgrp;
3569 event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3571 eventfd_ctx_put(event->eventfd);
3577 * Gets called on POLLHUP on eventfd when user closes it.
3579 * Called with wqh->lock held and interrupts disabled.
3581 static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
3582 int sync, void *key)
3584 struct cgroup_event *event = container_of(wait,
3585 struct cgroup_event, wait);
3586 struct cgroup *cgrp = event->cgrp;
3587 unsigned long flags = (unsigned long)key;
3589 if (flags & POLLHUP) {
3590 __remove_wait_queue(event->wqh, &event->wait);
3591 spin_lock(&cgrp->event_list_lock);
3592 list_del(&event->list);
3593 spin_unlock(&cgrp->event_list_lock);
3595 * We are in atomic context, but cgroup_event_remove() may
3596 * sleep, so we have to call it in workqueue.
3598 schedule_work(&event->remove);
3604 static void cgroup_event_ptable_queue_proc(struct file *file,
3605 wait_queue_head_t *wqh, poll_table *pt)
3607 struct cgroup_event *event = container_of(pt,
3608 struct cgroup_event, pt);
3611 add_wait_queue(wqh, &event->wait);
3615 * Parse input and register new cgroup event handler.
3617 * Input must be in format '<event_fd> <control_fd> <args>'.
3618 * Interpretation of args is defined by control file implementation.
3620 static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
3623 struct cgroup_event *event = NULL;
3624 unsigned int efd, cfd;
3625 struct file *efile = NULL;
3626 struct file *cfile = NULL;
3630 efd = simple_strtoul(buffer, &endp, 10);
3635 cfd = simple_strtoul(buffer, &endp, 10);
3636 if ((*endp != ' ') && (*endp != '\0'))
3640 event = kzalloc(sizeof(*event), GFP_KERNEL);
3644 INIT_LIST_HEAD(&event->list);
3645 init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
3646 init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
3647 INIT_WORK(&event->remove, cgroup_event_remove);
3649 efile = eventfd_fget(efd);
3650 if (IS_ERR(efile)) {
3651 ret = PTR_ERR(efile);
3655 event->eventfd = eventfd_ctx_fileget(efile);
3656 if (IS_ERR(event->eventfd)) {
3657 ret = PTR_ERR(event->eventfd);
3667 /* the process need read permission on control file */
3668 /* AV: shouldn't we check that it's been opened for read instead? */
3669 ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3673 event->cft = __file_cft(cfile);
3674 if (IS_ERR(event->cft)) {
3675 ret = PTR_ERR(event->cft);
3679 if (!event->cft->register_event || !event->cft->unregister_event) {
3684 ret = event->cft->register_event(cgrp, event->cft,
3685 event->eventfd, buffer);
3689 if (efile->f_op->poll(efile, &event->pt) & POLLHUP) {
3690 event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3696 * Events should be removed after rmdir of cgroup directory, but before
3697 * destroying subsystem state objects. Let's take reference to cgroup
3698 * directory dentry to do that.
3702 spin_lock(&cgrp->event_list_lock);
3703 list_add(&event->list, &cgrp->event_list);
3704 spin_unlock(&cgrp->event_list_lock);
3715 if (event && event->eventfd && !IS_ERR(event->eventfd))
3716 eventfd_ctx_put(event->eventfd);
3718 if (!IS_ERR_OR_NULL(efile))
3726 static u64 cgroup_clone_children_read(struct cgroup *cgrp,
3729 return clone_children(cgrp);
3732 static int cgroup_clone_children_write(struct cgroup *cgrp,
3737 set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3739 clear_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3744 * for the common functions, 'private' gives the type of file
3746 /* for hysterical raisins, we can't put this on the older files */
3747 #define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3748 static struct cftype files[] = {
3751 .open = cgroup_tasks_open,
3752 .write_u64 = cgroup_tasks_write,
3753 .release = cgroup_pidlist_release,
3754 .mode = S_IRUGO | S_IWUSR,
3757 .name = CGROUP_FILE_GENERIC_PREFIX "procs",
3758 .open = cgroup_procs_open,
3759 .write_u64 = cgroup_procs_write,
3760 .release = cgroup_pidlist_release,
3761 .mode = S_IRUGO | S_IWUSR,
3764 .name = "notify_on_release",
3765 .read_u64 = cgroup_read_notify_on_release,
3766 .write_u64 = cgroup_write_notify_on_release,
3769 .name = CGROUP_FILE_GENERIC_PREFIX "event_control",
3770 .write_string = cgroup_write_event_control,
3774 .name = "cgroup.clone_children",
3775 .read_u64 = cgroup_clone_children_read,
3776 .write_u64 = cgroup_clone_children_write,
3779 .name = "release_agent",
3780 .flags = CFTYPE_ONLY_ON_ROOT,
3781 .read_seq_string = cgroup_release_agent_show,
3782 .write_string = cgroup_release_agent_write,
3783 .max_write_len = PATH_MAX,
3788 static int cgroup_populate_dir(struct cgroup *cgrp)
3791 struct cgroup_subsys *ss;
3793 err = cgroup_addrm_files(cgrp, NULL, files, true);
3797 /* process cftsets of each subsystem */
3798 for_each_subsys(cgrp->root, ss) {
3799 struct cftype_set *set;
3801 list_for_each_entry(set, &ss->cftsets, node)
3802 cgroup_addrm_files(cgrp, ss, set->cfts, true);
3805 /* This cgroup is ready now */
3806 for_each_subsys(cgrp->root, ss) {
3807 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
3809 * Update id->css pointer and make this css visible from
3810 * CSS ID functions. This pointer will be dereferened
3811 * from RCU-read-side without locks.
3814 rcu_assign_pointer(css->id->css, css);
3820 static void css_dput_fn(struct work_struct *work)
3822 struct cgroup_subsys_state *css =
3823 container_of(work, struct cgroup_subsys_state, dput_work);
3824 struct dentry *dentry = css->cgroup->dentry;
3825 struct super_block *sb = dentry->d_sb;
3827 atomic_inc(&sb->s_active);
3829 deactivate_super(sb);
3832 static void init_cgroup_css(struct cgroup_subsys_state *css,
3833 struct cgroup_subsys *ss,
3834 struct cgroup *cgrp)
3837 atomic_set(&css->refcnt, 1);
3840 if (cgrp == dummytop)
3841 set_bit(CSS_ROOT, &css->flags);
3842 BUG_ON(cgrp->subsys[ss->subsys_id]);
3843 cgrp->subsys[ss->subsys_id] = css;
3846 * css holds an extra ref to @cgrp->dentry which is put on the last
3847 * css_put(). dput() requires process context, which css_put() may
3848 * be called without. @css->dput_work will be used to invoke
3849 * dput() asynchronously from css_put().
3851 INIT_WORK(&css->dput_work, css_dput_fn);
3855 * cgroup_create - create a cgroup
3856 * @parent: cgroup that will be parent of the new cgroup
3857 * @dentry: dentry of the new cgroup
3858 * @mode: mode to set on new inode
3860 * Must be called with the mutex on the parent inode held
3862 static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
3865 struct cgroup *cgrp;
3866 struct cgroupfs_root *root = parent->root;
3868 struct cgroup_subsys *ss;
3869 struct super_block *sb = root->sb;
3871 cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
3876 * Only live parents can have children. Note that the liveliness
3877 * check isn't strictly necessary because cgroup_mkdir() and
3878 * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
3879 * anyway so that locking is contained inside cgroup proper and we
3880 * don't get nasty surprises if we ever grow another caller.
3882 if (!cgroup_lock_live_group(parent)) {
3887 /* Grab a reference on the superblock so the hierarchy doesn't
3888 * get deleted on unmount if there are child cgroups. This
3889 * can be done outside cgroup_mutex, since the sb can't
3890 * disappear while someone has an open control file on the
3892 atomic_inc(&sb->s_active);
3894 init_cgroup_housekeeping(cgrp);
3896 cgrp->parent = parent;
3897 cgrp->root = parent->root;
3898 cgrp->top_cgroup = parent->top_cgroup;
3900 if (notify_on_release(parent))
3901 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3903 if (clone_children(parent))
3904 set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3906 for_each_subsys(root, ss) {
3907 struct cgroup_subsys_state *css = ss->create(cgrp);
3913 init_cgroup_css(css, ss, cgrp);
3915 err = alloc_css_id(ss, parent, cgrp);
3919 /* At error, ->destroy() callback has to free assigned ID. */
3920 if (clone_children(parent) && ss->post_clone)
3921 ss->post_clone(cgrp);
3924 list_add(&cgrp->sibling, &cgrp->parent->children);
3925 root->number_of_cgroups++;
3927 err = cgroup_create_dir(cgrp, dentry, mode);
3931 /* each css holds a ref to the cgroup's dentry */
3932 for_each_subsys(root, ss)
3935 /* The cgroup directory was pre-locked for us */
3936 BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
3938 list_add_tail(&cgrp->allcg_node, &root->allcg_list);
3940 err = cgroup_populate_dir(cgrp);
3941 /* If err < 0, we have a half-filled directory - oh well ;) */
3943 mutex_unlock(&cgroup_mutex);
3944 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
3950 list_del(&cgrp->sibling);
3951 root->number_of_cgroups--;
3955 for_each_subsys(root, ss) {
3956 if (cgrp->subsys[ss->subsys_id])
3960 mutex_unlock(&cgroup_mutex);
3962 /* Release the reference count that we took on the superblock */
3963 deactivate_super(sb);
3969 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3971 struct cgroup *c_parent = dentry->d_parent->d_fsdata;
3973 /* the vfs holds inode->i_mutex already */
3974 return cgroup_create(c_parent, dentry, mode | S_IFDIR);
3978 * Check the reference count on each subsystem. Since we already
3979 * established that there are no tasks in the cgroup, if the css refcount
3980 * is also 1, then there should be no outstanding references, so the
3981 * subsystem is safe to destroy. We scan across all subsystems rather than
3982 * using the per-hierarchy linked list of mounted subsystems since we can
3983 * be called via check_for_release() with no synchronization other than
3984 * RCU, and the subsystem linked list isn't RCU-safe.
3986 static int cgroup_has_css_refs(struct cgroup *cgrp)
3991 * We won't need to lock the subsys array, because the subsystems
3992 * we're concerned about aren't going anywhere since our cgroup root
3993 * has a reference on them.
3995 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3996 struct cgroup_subsys *ss = subsys[i];
3997 struct cgroup_subsys_state *css;
3999 /* Skip subsystems not present or not in this hierarchy */
4000 if (ss == NULL || ss->root != cgrp->root)
4003 css = cgrp->subsys[ss->subsys_id];
4005 * When called from check_for_release() it's possible
4006 * that by this point the cgroup has been removed
4007 * and the css deleted. But a false-positive doesn't
4008 * matter, since it can only happen if the cgroup
4009 * has been deleted and hence no longer needs the
4010 * release agent to be called anyway.
4012 if (css && css_refcnt(css) > 1)
4018 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
4020 struct cgroup *cgrp = dentry->d_fsdata;
4022 struct cgroup *parent;
4024 struct cgroup_event *event, *tmp;
4025 struct cgroup_subsys *ss;
4027 /* the vfs holds both inode->i_mutex already */
4028 mutex_lock(&cgroup_mutex);
4029 parent = cgrp->parent;
4030 if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
4031 mutex_unlock(&cgroup_mutex);
4036 * Block new css_tryget() by deactivating refcnt and mark @cgrp
4037 * removed. This makes future css_tryget() and child creation
4038 * attempts fail thus maintaining the removal conditions verified
4041 for_each_subsys(cgrp->root, ss) {
4042 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4044 WARN_ON(atomic_read(&css->refcnt) < 0);
4045 atomic_add(CSS_DEACT_BIAS, &css->refcnt);
4047 set_bit(CGRP_REMOVED, &cgrp->flags);
4050 * Tell subsystems to initate destruction. pre_destroy() should be
4051 * called with cgroup_mutex unlocked. See 3fa59dfbc3 ("cgroup: fix
4052 * potential deadlock in pre_destroy") for details.
4054 mutex_unlock(&cgroup_mutex);
4055 for_each_subsys(cgrp->root, ss)
4056 if (ss->pre_destroy)
4057 WARN_ON_ONCE(ss->pre_destroy(cgrp));
4058 mutex_lock(&cgroup_mutex);
4061 * Put all the base refs. Each css holds an extra reference to the
4062 * cgroup's dentry and cgroup removal proceeds regardless of css
4063 * refs. On the last put of each css, whenever that may be, the
4064 * extra dentry ref is put so that dentry destruction happens only
4065 * after all css's are released.
4067 for_each_subsys(cgrp->root, ss)
4068 css_put(cgrp->subsys[ss->subsys_id]);
4070 raw_spin_lock(&release_list_lock);
4071 if (!list_empty(&cgrp->release_list))
4072 list_del_init(&cgrp->release_list);
4073 raw_spin_unlock(&release_list_lock);
4075 /* delete this cgroup from parent->children */
4076 list_del_init(&cgrp->sibling);
4078 list_del_init(&cgrp->allcg_node);
4080 d = dget(cgrp->dentry);
4082 cgroup_d_remove_dir(d);
4085 set_bit(CGRP_RELEASABLE, &parent->flags);
4086 check_for_release(parent);
4089 * Unregister events and notify userspace.
4090 * Notify userspace about cgroup removing only after rmdir of cgroup
4091 * directory to avoid race between userspace and kernelspace
4093 spin_lock(&cgrp->event_list_lock);
4094 list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
4095 list_del(&event->list);
4096 remove_wait_queue(event->wqh, &event->wait);
4097 eventfd_signal(event->eventfd, 1);
4098 schedule_work(&event->remove);
4100 spin_unlock(&cgrp->event_list_lock);
4102 mutex_unlock(&cgroup_mutex);
4106 static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
4108 INIT_LIST_HEAD(&ss->cftsets);
4111 * base_cftset is embedded in subsys itself, no need to worry about
4114 if (ss->base_cftypes) {
4115 ss->base_cftset.cfts = ss->base_cftypes;
4116 list_add_tail(&ss->base_cftset.node, &ss->cftsets);
4120 static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4122 struct cgroup_subsys_state *css;
4124 printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4126 /* init base cftset */
4127 cgroup_init_cftsets(ss);
4129 /* Create the top cgroup state for this subsystem */
4130 list_add(&ss->sibling, &rootnode.subsys_list);
4131 ss->root = &rootnode;
4132 css = ss->create(dummytop);
4133 /* We don't handle early failures gracefully */
4134 BUG_ON(IS_ERR(css));
4135 init_cgroup_css(css, ss, dummytop);
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 top cgroup. */
4141 init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
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));
4152 /* this function shouldn't be used with modular subsystems, since they
4153 * need to register a subsys_id, among other things */
4158 * cgroup_load_subsys: load and register a modular subsystem at runtime
4159 * @ss: the subsystem to load
4161 * This function should be called in a modular subsystem's initcall. If the
4162 * subsystem is built as a module, it will be assigned a new subsys_id and set
4163 * up for use. If the subsystem is built-in anyway, work is delegated to the
4164 * simpler cgroup_init_subsys.
4166 int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
4169 struct cgroup_subsys_state *css;
4171 /* check name and function validity */
4172 if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
4173 ss->create == NULL || ss->destroy == NULL)
4177 * we don't support callbacks in modular subsystems. this check is
4178 * before the ss->module check for consistency; a subsystem that could
4179 * be a module should still have no callbacks even if the user isn't
4180 * compiling it as one.
4182 if (ss->fork || ss->exit)
4186 * an optionally modular subsystem is built-in: we want to do nothing,
4187 * since cgroup_init_subsys will have already taken care of it.
4189 if (ss->module == NULL) {
4190 /* a few sanity checks */
4191 BUG_ON(ss->subsys_id >= CGROUP_BUILTIN_SUBSYS_COUNT);
4192 BUG_ON(subsys[ss->subsys_id] != ss);
4196 /* init base cftset */
4197 cgroup_init_cftsets(ss);
4200 * need to register a subsys id before anything else - for example,
4201 * init_cgroup_css needs it.
4203 mutex_lock(&cgroup_mutex);
4204 /* find the first empty slot in the array */
4205 for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
4206 if (subsys[i] == NULL)
4209 if (i == CGROUP_SUBSYS_COUNT) {
4210 /* maximum number of subsystems already registered! */
4211 mutex_unlock(&cgroup_mutex);
4214 /* assign ourselves the subsys_id */
4219 * no ss->create seems to need anything important in the ss struct, so
4220 * this can happen first (i.e. before the rootnode attachment).
4222 css = ss->create(dummytop);
4224 /* failure case - need to deassign the subsys[] slot. */
4226 mutex_unlock(&cgroup_mutex);
4227 return PTR_ERR(css);
4230 list_add(&ss->sibling, &rootnode.subsys_list);
4231 ss->root = &rootnode;
4233 /* our new subsystem will be attached to the dummy hierarchy. */
4234 init_cgroup_css(css, ss, dummytop);
4235 /* init_idr must be after init_cgroup_css because it sets css->id. */
4237 int ret = cgroup_init_idr(ss, css);
4239 dummytop->subsys[ss->subsys_id] = NULL;
4240 ss->destroy(dummytop);
4242 mutex_unlock(&cgroup_mutex);
4248 * Now we need to entangle the css into the existing css_sets. unlike
4249 * in cgroup_init_subsys, there are now multiple css_sets, so each one
4250 * will need a new pointer to it; done by iterating the css_set_table.
4251 * furthermore, modifying the existing css_sets will corrupt the hash
4252 * table state, so each changed css_set will need its hash recomputed.
4253 * this is all done under the css_set_lock.
4255 write_lock(&css_set_lock);
4256 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
4258 struct hlist_node *node, *tmp;
4259 struct hlist_head *bucket = &css_set_table[i], *new_bucket;
4261 hlist_for_each_entry_safe(cg, node, tmp, bucket, hlist) {
4262 /* skip entries that we already rehashed */
4263 if (cg->subsys[ss->subsys_id])
4265 /* remove existing entry */
4266 hlist_del(&cg->hlist);
4268 cg->subsys[ss->subsys_id] = css;
4269 /* recompute hash and restore entry */
4270 new_bucket = css_set_hash(cg->subsys);
4271 hlist_add_head(&cg->hlist, new_bucket);
4274 write_unlock(&css_set_lock);
4279 mutex_unlock(&cgroup_mutex);
4282 EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4285 * cgroup_unload_subsys: unload a modular subsystem
4286 * @ss: the subsystem to unload
4288 * This function should be called in a modular subsystem's exitcall. When this
4289 * function is invoked, the refcount on the subsystem's module will be 0, so
4290 * the subsystem will not be attached to any hierarchy.
4292 void cgroup_unload_subsys(struct cgroup_subsys *ss)
4294 struct cg_cgroup_link *link;
4295 struct hlist_head *hhead;
4297 BUG_ON(ss->module == NULL);
4300 * we shouldn't be called if the subsystem is in use, and the use of
4301 * try_module_get in parse_cgroupfs_options should ensure that it
4302 * doesn't start being used while we're killing it off.
4304 BUG_ON(ss->root != &rootnode);
4306 mutex_lock(&cgroup_mutex);
4307 /* deassign the subsys_id */
4308 BUG_ON(ss->subsys_id < CGROUP_BUILTIN_SUBSYS_COUNT);
4309 subsys[ss->subsys_id] = NULL;
4311 /* remove subsystem from rootnode's list of subsystems */
4312 list_del_init(&ss->sibling);
4315 * disentangle the css from all css_sets attached to the dummytop. as
4316 * in loading, we need to pay our respects to the hashtable gods.
4318 write_lock(&css_set_lock);
4319 list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {
4320 struct css_set *cg = link->cg;
4322 hlist_del(&cg->hlist);
4323 BUG_ON(!cg->subsys[ss->subsys_id]);
4324 cg->subsys[ss->subsys_id] = NULL;
4325 hhead = css_set_hash(cg->subsys);
4326 hlist_add_head(&cg->hlist, hhead);
4328 write_unlock(&css_set_lock);
4331 * remove subsystem's css from the dummytop and free it - need to free
4332 * before marking as null because ss->destroy needs the cgrp->subsys
4333 * pointer to find their state. note that this also takes care of
4334 * freeing the css_id.
4336 ss->destroy(dummytop);
4337 dummytop->subsys[ss->subsys_id] = NULL;
4339 mutex_unlock(&cgroup_mutex);
4341 EXPORT_SYMBOL_GPL(cgroup_unload_subsys);
4344 * cgroup_init_early - cgroup initialization at system boot
4346 * Initialize cgroups at system boot, and initialize any
4347 * subsystems that request early init.
4349 int __init cgroup_init_early(void)
4352 atomic_set(&init_css_set.refcount, 1);
4353 INIT_LIST_HEAD(&init_css_set.cg_links);
4354 INIT_LIST_HEAD(&init_css_set.tasks);
4355 INIT_HLIST_NODE(&init_css_set.hlist);
4357 init_cgroup_root(&rootnode);
4359 init_task.cgroups = &init_css_set;
4361 init_css_set_link.cg = &init_css_set;
4362 init_css_set_link.cgrp = dummytop;
4363 list_add(&init_css_set_link.cgrp_link_list,
4364 &rootnode.top_cgroup.css_sets);
4365 list_add(&init_css_set_link.cg_link_list,
4366 &init_css_set.cg_links);
4368 for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
4369 INIT_HLIST_HEAD(&css_set_table[i]);
4371 /* at bootup time, we don't worry about modular subsystems */
4372 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4373 struct cgroup_subsys *ss = subsys[i];
4376 BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4377 BUG_ON(!ss->create);
4378 BUG_ON(!ss->destroy);
4379 if (ss->subsys_id != i) {
4380 printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4381 ss->name, ss->subsys_id);
4386 cgroup_init_subsys(ss);
4392 * cgroup_init - cgroup initialization
4394 * Register cgroup filesystem and /proc file, and initialize
4395 * any subsystems that didn't request early init.
4397 int __init cgroup_init(void)
4401 struct hlist_head *hhead;
4403 err = bdi_init(&cgroup_backing_dev_info);
4407 /* at bootup time, we don't worry about modular subsystems */
4408 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4409 struct cgroup_subsys *ss = subsys[i];
4410 if (!ss->early_init)
4411 cgroup_init_subsys(ss);
4413 cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4416 /* Add init_css_set to the hash table */
4417 hhead = css_set_hash(init_css_set.subsys);
4418 hlist_add_head(&init_css_set.hlist, hhead);
4419 BUG_ON(!init_root_id(&rootnode));
4421 cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
4427 err = register_filesystem(&cgroup_fs_type);
4429 kobject_put(cgroup_kobj);
4433 proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4437 bdi_destroy(&cgroup_backing_dev_info);
4443 * proc_cgroup_show()
4444 * - Print task's cgroup paths into seq_file, one line for each hierarchy
4445 * - Used for /proc/<pid>/cgroup.
4446 * - No need to task_lock(tsk) on this tsk->cgroup reference, as it
4447 * doesn't really matter if tsk->cgroup changes after we read it,
4448 * and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4449 * anyway. No need to check that tsk->cgroup != NULL, thanks to
4450 * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
4451 * cgroup to top_cgroup.
4454 /* TODO: Use a proper seq_file iterator */
4455 static int proc_cgroup_show(struct seq_file *m, void *v)
4458 struct task_struct *tsk;
4461 struct cgroupfs_root *root;
4464 buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4470 tsk = get_pid_task(pid, PIDTYPE_PID);
4476 mutex_lock(&cgroup_mutex);
4478 for_each_active_root(root) {
4479 struct cgroup_subsys *ss;
4480 struct cgroup *cgrp;
4483 seq_printf(m, "%d:", root->hierarchy_id);
4484 for_each_subsys(root, ss)
4485 seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4486 if (strlen(root->name))
4487 seq_printf(m, "%sname=%s", count ? "," : "",
4490 cgrp = task_cgroup_from_root(tsk, root);
4491 retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4499 mutex_unlock(&cgroup_mutex);
4500 put_task_struct(tsk);
4507 static int cgroup_open(struct inode *inode, struct file *file)
4509 struct pid *pid = PROC_I(inode)->pid;
4510 return single_open(file, proc_cgroup_show, pid);
4513 const struct file_operations proc_cgroup_operations = {
4514 .open = cgroup_open,
4516 .llseek = seq_lseek,
4517 .release = single_release,
4520 /* Display information about each subsystem and each hierarchy */
4521 static int proc_cgroupstats_show(struct seq_file *m, void *v)
4525 seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
4527 * ideally we don't want subsystems moving around while we do this.
4528 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
4529 * subsys/hierarchy state.
4531 mutex_lock(&cgroup_mutex);
4532 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4533 struct cgroup_subsys *ss = subsys[i];
4536 seq_printf(m, "%s\t%d\t%d\t%d\n",
4537 ss->name, ss->root->hierarchy_id,
4538 ss->root->number_of_cgroups, !ss->disabled);
4540 mutex_unlock(&cgroup_mutex);
4544 static int cgroupstats_open(struct inode *inode, struct file *file)
4546 return single_open(file, proc_cgroupstats_show, NULL);
4549 static const struct file_operations proc_cgroupstats_operations = {
4550 .open = cgroupstats_open,
4552 .llseek = seq_lseek,
4553 .release = single_release,
4557 * cgroup_fork - attach newly forked task to its parents cgroup.
4558 * @child: pointer to task_struct of forking parent process.
4560 * Description: A task inherits its parent's cgroup at fork().
4562 * A pointer to the shared css_set was automatically copied in
4563 * fork.c by dup_task_struct(). However, we ignore that copy, since
4564 * it was not made under the protection of RCU, cgroup_mutex or
4565 * threadgroup_change_begin(), so it might no longer be a valid
4566 * cgroup pointer. cgroup_attach_task() might have already changed
4567 * current->cgroups, allowing the previously referenced cgroup
4568 * group to be removed and freed.
4570 * Outside the pointer validity we also need to process the css_set
4571 * inheritance between threadgoup_change_begin() and
4572 * threadgoup_change_end(), this way there is no leak in any process
4573 * wide migration performed by cgroup_attach_proc() that could otherwise
4574 * miss a thread because it is too early or too late in the fork stage.
4576 * At the point that cgroup_fork() is called, 'current' is the parent
4577 * task, and the passed argument 'child' points to the child task.
4579 void cgroup_fork(struct task_struct *child)
4582 * We don't need to task_lock() current because current->cgroups
4583 * can't be changed concurrently here. The parent obviously hasn't
4584 * exited and called cgroup_exit(), and we are synchronized against
4585 * cgroup migration through threadgroup_change_begin().
4587 child->cgroups = current->cgroups;
4588 get_css_set(child->cgroups);
4589 INIT_LIST_HEAD(&child->cg_list);
4593 * cgroup_fork_callbacks - run fork callbacks
4594 * @child: the new task
4596 * Called on a new task very soon before adding it to the
4597 * tasklist. No need to take any locks since no-one can
4598 * be operating on this task.
4600 void cgroup_fork_callbacks(struct task_struct *child)
4602 if (need_forkexit_callback) {
4605 * forkexit callbacks are only supported for builtin
4606 * subsystems, and the builtin section of the subsys array is
4607 * immutable, so we don't need to lock the subsys array here.
4609 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4610 struct cgroup_subsys *ss = subsys[i];
4618 * cgroup_post_fork - called on a new task after adding it to the task list
4619 * @child: the task in question
4621 * Adds the task to the list running through its css_set if necessary.
4622 * Has to be after the task is visible on the task list in case we race
4623 * with the first call to cgroup_iter_start() - to guarantee that the
4624 * new task ends up on its list.
4626 void cgroup_post_fork(struct task_struct *child)
4629 * use_task_css_set_links is set to 1 before we walk the tasklist
4630 * under the tasklist_lock and we read it here after we added the child
4631 * to the tasklist under the tasklist_lock as well. If the child wasn't
4632 * yet in the tasklist when we walked through it from
4633 * cgroup_enable_task_cg_lists(), then use_task_css_set_links value
4634 * should be visible now due to the paired locking and barriers implied
4635 * by LOCK/UNLOCK: it is written before the tasklist_lock unlock
4636 * in cgroup_enable_task_cg_lists() and read here after the tasklist_lock
4639 if (use_task_css_set_links) {
4640 write_lock(&css_set_lock);
4641 if (list_empty(&child->cg_list)) {
4643 * It's safe to use child->cgroups without task_lock()
4644 * here because we are protected through
4645 * threadgroup_change_begin() against concurrent
4646 * css_set change in cgroup_task_migrate(). Also
4647 * the task can't exit at that point until
4648 * wake_up_new_task() is called, so we are protected
4649 * against cgroup_exit() setting child->cgroup to
4652 list_add(&child->cg_list, &child->cgroups->tasks);
4654 write_unlock(&css_set_lock);
4658 * cgroup_exit - detach cgroup from exiting task
4659 * @tsk: pointer to task_struct of exiting process
4660 * @run_callback: run exit callbacks?
4662 * Description: Detach cgroup from @tsk and release it.
4664 * Note that cgroups marked notify_on_release force every task in
4665 * them to take the global cgroup_mutex mutex when exiting.
4666 * This could impact scaling on very large systems. Be reluctant to
4667 * use notify_on_release cgroups where very high task exit scaling
4668 * is required on large systems.
4670 * the_top_cgroup_hack:
4672 * Set the exiting tasks cgroup to the root cgroup (top_cgroup).
4674 * We call cgroup_exit() while the task is still competent to
4675 * handle notify_on_release(), then leave the task attached to the
4676 * root cgroup in each hierarchy for the remainder of its exit.
4678 * To do this properly, we would increment the reference count on
4679 * top_cgroup, and near the very end of the kernel/exit.c do_exit()
4680 * code we would add a second cgroup function call, to drop that
4681 * reference. This would just create an unnecessary hot spot on
4682 * the top_cgroup reference count, to no avail.
4684 * Normally, holding a reference to a cgroup without bumping its
4685 * count is unsafe. The cgroup could go away, or someone could
4686 * attach us to a different cgroup, decrementing the count on
4687 * the first cgroup that we never incremented. But in this case,
4688 * top_cgroup isn't going away, and either task has PF_EXITING set,
4689 * which wards off any cgroup_attach_task() attempts, or task is a failed
4690 * fork, never visible to cgroup_attach_task.
4692 void cgroup_exit(struct task_struct *tsk, int run_callbacks)
4698 * Unlink from the css_set task list if necessary.
4699 * Optimistically check cg_list before taking
4702 if (!list_empty(&tsk->cg_list)) {
4703 write_lock(&css_set_lock);
4704 if (!list_empty(&tsk->cg_list))
4705 list_del_init(&tsk->cg_list);
4706 write_unlock(&css_set_lock);
4709 /* Reassign the task to the init_css_set. */
4712 tsk->cgroups = &init_css_set;
4714 if (run_callbacks && need_forkexit_callback) {
4716 * modular subsystems can't use callbacks, so no need to lock
4719 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4720 struct cgroup_subsys *ss = subsys[i];
4722 struct cgroup *old_cgrp =
4723 rcu_dereference_raw(cg->subsys[i])->cgroup;
4724 struct cgroup *cgrp = task_cgroup(tsk, i);
4725 ss->exit(cgrp, old_cgrp, tsk);
4732 put_css_set_taskexit(cg);
4736 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
4737 * @cgrp: the cgroup in question
4738 * @task: the task in question
4740 * See if @cgrp is a descendant of @task's cgroup in the appropriate
4743 * If we are sending in dummytop, then presumably we are creating
4744 * the top cgroup in the subsystem.
4746 * Called only by the ns (nsproxy) cgroup.
4748 int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
4751 struct cgroup *target;
4753 if (cgrp == dummytop)
4756 target = task_cgroup_from_root(task, cgrp->root);
4757 while (cgrp != target && cgrp!= cgrp->top_cgroup)
4758 cgrp = cgrp->parent;
4759 ret = (cgrp == target);
4763 static void check_for_release(struct cgroup *cgrp)
4765 /* All of these checks rely on RCU to keep the cgroup
4766 * structure alive */
4767 if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
4768 && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
4769 /* Control Group is currently removeable. If it's not
4770 * already queued for a userspace notification, queue
4772 int need_schedule_work = 0;
4773 raw_spin_lock(&release_list_lock);
4774 if (!cgroup_is_removed(cgrp) &&
4775 list_empty(&cgrp->release_list)) {
4776 list_add(&cgrp->release_list, &release_list);
4777 need_schedule_work = 1;
4779 raw_spin_unlock(&release_list_lock);
4780 if (need_schedule_work)
4781 schedule_work(&release_agent_work);
4785 /* Caller must verify that the css is not for root cgroup */
4786 bool __css_tryget(struct cgroup_subsys_state *css)
4791 v = css_refcnt(css);
4792 t = atomic_cmpxchg(&css->refcnt, v, v + 1);
4800 EXPORT_SYMBOL_GPL(__css_tryget);
4802 /* Caller must verify that the css is not for root cgroup */
4803 void __css_put(struct cgroup_subsys_state *css)
4805 struct cgroup *cgrp = css->cgroup;
4809 v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));
4813 if (notify_on_release(cgrp)) {
4814 set_bit(CGRP_RELEASABLE, &cgrp->flags);
4815 check_for_release(cgrp);
4819 schedule_work(&css->dput_work);
4824 EXPORT_SYMBOL_GPL(__css_put);
4827 * Notify userspace when a cgroup is released, by running the
4828 * configured release agent with the name of the cgroup (path
4829 * relative to the root of cgroup file system) as the argument.
4831 * Most likely, this user command will try to rmdir this cgroup.
4833 * This races with the possibility that some other task will be
4834 * attached to this cgroup before it is removed, or that some other
4835 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
4836 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
4837 * unused, and this cgroup will be reprieved from its death sentence,
4838 * to continue to serve a useful existence. Next time it's released,
4839 * we will get notified again, if it still has 'notify_on_release' set.
4841 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
4842 * means only wait until the task is successfully execve()'d. The
4843 * separate release agent task is forked by call_usermodehelper(),
4844 * then control in this thread returns here, without waiting for the
4845 * release agent task. We don't bother to wait because the caller of
4846 * this routine has no use for the exit status of the release agent
4847 * task, so no sense holding our caller up for that.
4849 static void cgroup_release_agent(struct work_struct *work)
4851 BUG_ON(work != &release_agent_work);
4852 mutex_lock(&cgroup_mutex);
4853 raw_spin_lock(&release_list_lock);
4854 while (!list_empty(&release_list)) {
4855 char *argv[3], *envp[3];
4857 char *pathbuf = NULL, *agentbuf = NULL;
4858 struct cgroup *cgrp = list_entry(release_list.next,
4861 list_del_init(&cgrp->release_list);
4862 raw_spin_unlock(&release_list_lock);
4863 pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4866 if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
4868 agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
4873 argv[i++] = agentbuf;
4874 argv[i++] = pathbuf;
4878 /* minimal command environment */
4879 envp[i++] = "HOME=/";
4880 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
4883 /* Drop the lock while we invoke the usermode helper,
4884 * since the exec could involve hitting disk and hence
4885 * be a slow process */
4886 mutex_unlock(&cgroup_mutex);
4887 call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
4888 mutex_lock(&cgroup_mutex);
4892 raw_spin_lock(&release_list_lock);
4894 raw_spin_unlock(&release_list_lock);
4895 mutex_unlock(&cgroup_mutex);
4898 static int __init cgroup_disable(char *str)
4903 while ((token = strsep(&str, ",")) != NULL) {
4907 * cgroup_disable, being at boot time, can't know about module
4908 * subsystems, so we don't worry about them.
4910 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4911 struct cgroup_subsys *ss = subsys[i];
4913 if (!strcmp(token, ss->name)) {
4915 printk(KERN_INFO "Disabling %s control group"
4916 " subsystem\n", ss->name);
4923 __setup("cgroup_disable=", cgroup_disable);
4926 * Functons for CSS ID.
4930 *To get ID other than 0, this should be called when !cgroup_is_removed().
4932 unsigned short css_id(struct cgroup_subsys_state *css)
4934 struct css_id *cssid;
4937 * This css_id() can return correct value when somone has refcnt
4938 * on this or this is under rcu_read_lock(). Once css->id is allocated,
4939 * it's unchanged until freed.
4941 cssid = rcu_dereference_check(css->id, css_refcnt(css));
4947 EXPORT_SYMBOL_GPL(css_id);
4949 unsigned short css_depth(struct cgroup_subsys_state *css)
4951 struct css_id *cssid;
4953 cssid = rcu_dereference_check(css->id, css_refcnt(css));
4956 return cssid->depth;
4959 EXPORT_SYMBOL_GPL(css_depth);
4962 * css_is_ancestor - test "root" css is an ancestor of "child"
4963 * @child: the css to be tested.
4964 * @root: the css supporsed to be an ancestor of the child.
4966 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
4967 * this function reads css->id, the caller must hold rcu_read_lock().
4968 * But, considering usual usage, the csses should be valid objects after test.
4969 * Assuming that the caller will do some action to the child if this returns
4970 * returns true, the caller must take "child";s reference count.
4971 * If "child" is valid object and this returns true, "root" is valid, too.
4974 bool css_is_ancestor(struct cgroup_subsys_state *child,
4975 const struct cgroup_subsys_state *root)
4977 struct css_id *child_id;
4978 struct css_id *root_id;
4980 child_id = rcu_dereference(child->id);
4983 root_id = rcu_dereference(root->id);
4986 if (child_id->depth < root_id->depth)
4988 if (child_id->stack[root_id->depth] != root_id->id)
4993 void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
4995 struct css_id *id = css->id;
4996 /* When this is called before css_id initialization, id can be NULL */
5000 BUG_ON(!ss->use_id);
5002 rcu_assign_pointer(id->css, NULL);
5003 rcu_assign_pointer(css->id, NULL);
5004 spin_lock(&ss->id_lock);
5005 idr_remove(&ss->idr, id->id);
5006 spin_unlock(&ss->id_lock);
5007 kfree_rcu(id, rcu_head);
5009 EXPORT_SYMBOL_GPL(free_css_id);
5012 * This is called by init or create(). Then, calls to this function are
5013 * always serialized (By cgroup_mutex() at create()).
5016 static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
5018 struct css_id *newid;
5019 int myid, error, size;
5021 BUG_ON(!ss->use_id);
5023 size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
5024 newid = kzalloc(size, GFP_KERNEL);
5026 return ERR_PTR(-ENOMEM);
5028 if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
5032 spin_lock(&ss->id_lock);
5033 /* Don't use 0. allocates an ID of 1-65535 */
5034 error = idr_get_new_above(&ss->idr, newid, 1, &myid);
5035 spin_unlock(&ss->id_lock);
5037 /* Returns error when there are no free spaces for new ID.*/
5042 if (myid > CSS_ID_MAX)
5046 newid->depth = depth;
5050 spin_lock(&ss->id_lock);
5051 idr_remove(&ss->idr, myid);
5052 spin_unlock(&ss->id_lock);
5055 return ERR_PTR(error);
5059 static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
5060 struct cgroup_subsys_state *rootcss)
5062 struct css_id *newid;
5064 spin_lock_init(&ss->id_lock);
5067 newid = get_new_cssid(ss, 0);
5069 return PTR_ERR(newid);
5071 newid->stack[0] = newid->id;
5072 newid->css = rootcss;
5073 rootcss->id = newid;
5077 static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
5078 struct cgroup *child)
5080 int subsys_id, i, depth = 0;
5081 struct cgroup_subsys_state *parent_css, *child_css;
5082 struct css_id *child_id, *parent_id;
5084 subsys_id = ss->subsys_id;
5085 parent_css = parent->subsys[subsys_id];
5086 child_css = child->subsys[subsys_id];
5087 parent_id = parent_css->id;
5088 depth = parent_id->depth + 1;
5090 child_id = get_new_cssid(ss, depth);
5091 if (IS_ERR(child_id))
5092 return PTR_ERR(child_id);
5094 for (i = 0; i < depth; i++)
5095 child_id->stack[i] = parent_id->stack[i];
5096 child_id->stack[depth] = child_id->id;
5098 * child_id->css pointer will be set after this cgroup is available
5099 * see cgroup_populate_dir()
5101 rcu_assign_pointer(child_css->id, child_id);
5107 * css_lookup - lookup css by id
5108 * @ss: cgroup subsys to be looked into.
5111 * Returns pointer to cgroup_subsys_state if there is valid one with id.
5112 * NULL if not. Should be called under rcu_read_lock()
5114 struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
5116 struct css_id *cssid = NULL;
5118 BUG_ON(!ss->use_id);
5119 cssid = idr_find(&ss->idr, id);
5121 if (unlikely(!cssid))
5124 return rcu_dereference(cssid->css);
5126 EXPORT_SYMBOL_GPL(css_lookup);
5129 * css_get_next - lookup next cgroup under specified hierarchy.
5130 * @ss: pointer to subsystem
5131 * @id: current position of iteration.
5132 * @root: pointer to css. search tree under this.
5133 * @foundid: position of found object.
5135 * Search next css under the specified hierarchy of rootid. Calling under
5136 * rcu_read_lock() is necessary. Returns NULL if it reaches the end.
5138 struct cgroup_subsys_state *
5139 css_get_next(struct cgroup_subsys *ss, int id,
5140 struct cgroup_subsys_state *root, int *foundid)
5142 struct cgroup_subsys_state *ret = NULL;
5145 int rootid = css_id(root);
5146 int depth = css_depth(root);
5151 BUG_ON(!ss->use_id);
5152 WARN_ON_ONCE(!rcu_read_lock_held());
5154 /* fill start point for scan */
5158 * scan next entry from bitmap(tree), tmpid is updated after
5161 tmp = idr_get_next(&ss->idr, &tmpid);
5164 if (tmp->depth >= depth && tmp->stack[depth] == rootid) {
5165 ret = rcu_dereference(tmp->css);
5171 /* continue to scan from next id */
5178 * get corresponding css from file open on cgroupfs directory
5180 struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
5182 struct cgroup *cgrp;
5183 struct inode *inode;
5184 struct cgroup_subsys_state *css;
5186 inode = f->f_dentry->d_inode;
5187 /* check in cgroup filesystem dir */
5188 if (inode->i_op != &cgroup_dir_inode_operations)
5189 return ERR_PTR(-EBADF);
5191 if (id < 0 || id >= CGROUP_SUBSYS_COUNT)
5192 return ERR_PTR(-EINVAL);
5195 cgrp = __d_cgrp(f->f_dentry);
5196 css = cgrp->subsys[id];
5197 return css ? css : ERR_PTR(-ENOENT);
5200 #ifdef CONFIG_CGROUP_DEBUG
5201 static struct cgroup_subsys_state *debug_create(struct cgroup *cont)
5203 struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
5206 return ERR_PTR(-ENOMEM);
5211 static void debug_destroy(struct cgroup *cont)
5213 kfree(cont->subsys[debug_subsys_id]);
5216 static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
5218 return atomic_read(&cont->count);
5221 static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft)
5223 return cgroup_task_count(cont);
5226 static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
5228 return (u64)(unsigned long)current->cgroups;
5231 static u64 current_css_set_refcount_read(struct cgroup *cont,
5237 count = atomic_read(¤t->cgroups->refcount);
5242 static int current_css_set_cg_links_read(struct cgroup *cont,
5244 struct seq_file *seq)
5246 struct cg_cgroup_link *link;
5249 read_lock(&css_set_lock);
5251 cg = rcu_dereference(current->cgroups);
5252 list_for_each_entry(link, &cg->cg_links, cg_link_list) {
5253 struct cgroup *c = link->cgrp;
5257 name = c->dentry->d_name.name;
5260 seq_printf(seq, "Root %d group %s\n",
5261 c->root->hierarchy_id, name);
5264 read_unlock(&css_set_lock);
5268 #define MAX_TASKS_SHOWN_PER_CSS 25
5269 static int cgroup_css_links_read(struct cgroup *cont,
5271 struct seq_file *seq)
5273 struct cg_cgroup_link *link;
5275 read_lock(&css_set_lock);
5276 list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
5277 struct css_set *cg = link->cg;
5278 struct task_struct *task;
5280 seq_printf(seq, "css_set %p\n", cg);
5281 list_for_each_entry(task, &cg->tasks, cg_list) {
5282 if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
5283 seq_puts(seq, " ...\n");
5286 seq_printf(seq, " task %d\n",
5287 task_pid_vnr(task));
5291 read_unlock(&css_set_lock);
5295 static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
5297 return test_bit(CGRP_RELEASABLE, &cgrp->flags);
5300 static struct cftype debug_files[] = {
5302 .name = "cgroup_refcount",
5303 .read_u64 = cgroup_refcount_read,
5306 .name = "taskcount",
5307 .read_u64 = debug_taskcount_read,
5311 .name = "current_css_set",
5312 .read_u64 = current_css_set_read,
5316 .name = "current_css_set_refcount",
5317 .read_u64 = current_css_set_refcount_read,
5321 .name = "current_css_set_cg_links",
5322 .read_seq_string = current_css_set_cg_links_read,
5326 .name = "cgroup_css_links",
5327 .read_seq_string = cgroup_css_links_read,
5331 .name = "releasable",
5332 .read_u64 = releasable_read,
5338 struct cgroup_subsys debug_subsys = {
5340 .create = debug_create,
5341 .destroy = debug_destroy,
5342 .subsys_id = debug_subsys_id,
5343 .base_cftypes = debug_files,
5345 #endif /* CONFIG_CGROUP_DEBUG */