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 */
64 #include <linux/atomic.h>
67 * cgroup_mutex is the master lock. Any modification to cgroup or its
68 * hierarchy must be performed while holding it.
70 * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
71 * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
72 * release_agent_path and so on. Modifying requires both cgroup_mutex and
73 * cgroup_root_mutex. Readers can acquire either of the two. This is to
74 * break the following locking order cycle.
76 * A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
77 * B. namespace_sem -> cgroup_mutex
79 * B happens only through cgroup_show_options() and using cgroup_root_mutex
82 static DEFINE_MUTEX(cgroup_mutex);
83 static DEFINE_MUTEX(cgroup_root_mutex);
86 * Generate an array of cgroup subsystem pointers. At boot time, this is
87 * populated up to CGROUP_BUILTIN_SUBSYS_COUNT, and modular subsystems are
88 * registered after that. The mutable section of this array is protected by
91 #define SUBSYS(_x) &_x ## _subsys,
92 static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
93 #include <linux/cgroup_subsys.h>
96 #define MAX_CGROUP_ROOT_NAMELEN 64
99 * A cgroupfs_root represents the root of a cgroup hierarchy,
100 * and may be associated with a superblock to form an active
103 struct cgroupfs_root {
104 struct super_block *sb;
107 * The bitmask of subsystems intended to be attached to this
110 unsigned long subsys_bits;
112 /* Unique id for this hierarchy. */
115 /* The bitmask of subsystems currently attached to this hierarchy */
116 unsigned long actual_subsys_bits;
118 /* A list running through the attached subsystems */
119 struct list_head subsys_list;
121 /* The root cgroup for this hierarchy */
122 struct cgroup top_cgroup;
124 /* Tracks how many cgroups are currently defined in hierarchy.*/
125 int number_of_cgroups;
127 /* A list running through the active hierarchies */
128 struct list_head root_list;
130 /* All cgroups on this root, cgroup_mutex protected */
131 struct list_head allcg_list;
133 /* Hierarchy-specific flags */
136 /* The path to use for release notifications. */
137 char release_agent_path[PATH_MAX];
139 /* The name for this hierarchy - may be empty */
140 char name[MAX_CGROUP_ROOT_NAMELEN];
144 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
145 * subsystems that are otherwise unattached - it never has more than a
146 * single cgroup, and all tasks are part of that cgroup.
148 static struct cgroupfs_root rootnode;
151 * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
152 * cgroup_subsys->use_id != 0.
154 #define CSS_ID_MAX (65535)
157 * The css to which this ID points. This pointer is set to valid value
158 * after cgroup is populated. If cgroup is removed, this will be NULL.
159 * This pointer is expected to be RCU-safe because destroy()
160 * is called after synchronize_rcu(). But for safe use, css_is_removed()
161 * css_tryget() should be used for avoiding race.
163 struct cgroup_subsys_state __rcu *css;
169 * Depth in hierarchy which this ID belongs to.
171 unsigned short depth;
173 * ID is freed by RCU. (and lookup routine is RCU safe.)
175 struct rcu_head rcu_head;
177 * Hierarchy of CSS ID belongs to.
179 unsigned short stack[0]; /* Array of Length (depth+1) */
183 * cgroup_event represents events which userspace want to receive.
185 struct cgroup_event {
187 * Cgroup which the event belongs to.
191 * Control file which the event associated.
195 * eventfd to signal userspace about the event.
197 struct eventfd_ctx *eventfd;
199 * Each of these stored in a list by the cgroup.
201 struct list_head list;
203 * All fields below needed to unregister event when
204 * userspace closes eventfd.
207 wait_queue_head_t *wqh;
209 struct work_struct remove;
212 /* The list of hierarchy roots */
214 static LIST_HEAD(roots);
215 static int root_count;
217 static DEFINE_IDA(hierarchy_ida);
218 static int next_hierarchy_id;
219 static DEFINE_SPINLOCK(hierarchy_id_lock);
221 /* dummytop is a shorthand for the dummy hierarchy's top cgroup */
222 #define dummytop (&rootnode.top_cgroup)
224 /* This flag indicates whether tasks in the fork and exit paths should
225 * check for fork/exit handlers to call. This avoids us having to do
226 * extra work in the fork/exit path if none of the subsystems need to
229 static int need_forkexit_callback __read_mostly;
231 #ifdef CONFIG_PROVE_LOCKING
232 int cgroup_lock_is_held(void)
234 return lockdep_is_held(&cgroup_mutex);
236 #else /* #ifdef CONFIG_PROVE_LOCKING */
237 int cgroup_lock_is_held(void)
239 return mutex_is_locked(&cgroup_mutex);
241 #endif /* #else #ifdef CONFIG_PROVE_LOCKING */
243 EXPORT_SYMBOL_GPL(cgroup_lock_is_held);
245 /* convenient tests for these bits */
246 inline int cgroup_is_removed(const struct cgroup *cgrp)
248 return test_bit(CGRP_REMOVED, &cgrp->flags);
251 /* bits in struct cgroupfs_root flags field */
253 ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
256 static int cgroup_is_releasable(const struct cgroup *cgrp)
259 (1 << CGRP_RELEASABLE) |
260 (1 << CGRP_NOTIFY_ON_RELEASE);
261 return (cgrp->flags & bits) == bits;
264 static int notify_on_release(const struct cgroup *cgrp)
266 return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
269 static int clone_children(const struct cgroup *cgrp)
271 return test_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
275 * for_each_subsys() allows you to iterate on each subsystem attached to
276 * an active hierarchy
278 #define for_each_subsys(_root, _ss) \
279 list_for_each_entry(_ss, &_root->subsys_list, sibling)
281 /* for_each_active_root() allows you to iterate across the active hierarchies */
282 #define for_each_active_root(_root) \
283 list_for_each_entry(_root, &roots, root_list)
285 /* the list of cgroups eligible for automatic release. Protected by
286 * release_list_lock */
287 static LIST_HEAD(release_list);
288 static DEFINE_RAW_SPINLOCK(release_list_lock);
289 static void cgroup_release_agent(struct work_struct *work);
290 static DECLARE_WORK(release_agent_work, cgroup_release_agent);
291 static void check_for_release(struct cgroup *cgrp);
293 /* Link structure for associating css_set objects with cgroups */
294 struct cg_cgroup_link {
296 * List running through cg_cgroup_links associated with a
297 * cgroup, anchored on cgroup->css_sets
299 struct list_head cgrp_link_list;
302 * List running through cg_cgroup_links pointing at a
303 * single css_set object, anchored on css_set->cg_links
305 struct list_head cg_link_list;
309 /* The default css_set - used by init and its children prior to any
310 * hierarchies being mounted. It contains a pointer to the root state
311 * for each subsystem. Also used to anchor the list of css_sets. Not
312 * reference-counted, to improve performance when child cgroups
313 * haven't been created.
316 static struct css_set init_css_set;
317 static struct cg_cgroup_link init_css_set_link;
319 static int cgroup_init_idr(struct cgroup_subsys *ss,
320 struct cgroup_subsys_state *css);
322 /* css_set_lock protects the list of css_set objects, and the
323 * chain of tasks off each css_set. Nests outside task->alloc_lock
324 * due to cgroup_iter_start() */
325 static DEFINE_RWLOCK(css_set_lock);
326 static int css_set_count;
329 * hash table for cgroup groups. This improves the performance to find
330 * an existing css_set. This hash doesn't (currently) take into
331 * account cgroups in empty hierarchies.
333 #define CSS_SET_HASH_BITS 7
334 #define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS)
335 static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
337 static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
341 unsigned long tmp = 0UL;
343 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
344 tmp += (unsigned long)css[i];
345 tmp = (tmp >> 16) ^ tmp;
347 index = hash_long(tmp, CSS_SET_HASH_BITS);
349 return &css_set_table[index];
352 /* We don't maintain the lists running through each css_set to its
353 * task until after the first call to cgroup_iter_start(). This
354 * reduces the fork()/exit() overhead for people who have cgroups
355 * compiled into their kernel but not actually in use */
356 static int use_task_css_set_links __read_mostly;
358 static void __put_css_set(struct css_set *cg, int taskexit)
360 struct cg_cgroup_link *link;
361 struct cg_cgroup_link *saved_link;
363 * Ensure that the refcount doesn't hit zero while any readers
364 * can see it. Similar to atomic_dec_and_lock(), but for an
367 if (atomic_add_unless(&cg->refcount, -1, 1))
369 write_lock(&css_set_lock);
370 if (!atomic_dec_and_test(&cg->refcount)) {
371 write_unlock(&css_set_lock);
375 /* This css_set is dead. unlink it and release cgroup refcounts */
376 hlist_del(&cg->hlist);
379 list_for_each_entry_safe(link, saved_link, &cg->cg_links,
381 struct cgroup *cgrp = link->cgrp;
382 list_del(&link->cg_link_list);
383 list_del(&link->cgrp_link_list);
384 if (atomic_dec_and_test(&cgrp->count) &&
385 notify_on_release(cgrp)) {
387 set_bit(CGRP_RELEASABLE, &cgrp->flags);
388 check_for_release(cgrp);
394 write_unlock(&css_set_lock);
395 kfree_rcu(cg, rcu_head);
399 * refcounted get/put for css_set objects
401 static inline void get_css_set(struct css_set *cg)
403 atomic_inc(&cg->refcount);
406 static inline void put_css_set(struct css_set *cg)
408 __put_css_set(cg, 0);
411 static inline void put_css_set_taskexit(struct css_set *cg)
413 __put_css_set(cg, 1);
417 * compare_css_sets - helper function for find_existing_css_set().
418 * @cg: candidate css_set being tested
419 * @old_cg: existing css_set for a task
420 * @new_cgrp: cgroup that's being entered by the task
421 * @template: desired set of css pointers in css_set (pre-calculated)
423 * Returns true if "cg" matches "old_cg" except for the hierarchy
424 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
426 static bool compare_css_sets(struct css_set *cg,
427 struct css_set *old_cg,
428 struct cgroup *new_cgrp,
429 struct cgroup_subsys_state *template[])
431 struct list_head *l1, *l2;
433 if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
434 /* Not all subsystems matched */
439 * Compare cgroup pointers in order to distinguish between
440 * different cgroups in heirarchies with no subsystems. We
441 * could get by with just this check alone (and skip the
442 * memcmp above) but on most setups the memcmp check will
443 * avoid the need for this more expensive check on almost all
448 l2 = &old_cg->cg_links;
450 struct cg_cgroup_link *cgl1, *cgl2;
451 struct cgroup *cg1, *cg2;
455 /* See if we reached the end - both lists are equal length. */
456 if (l1 == &cg->cg_links) {
457 BUG_ON(l2 != &old_cg->cg_links);
460 BUG_ON(l2 == &old_cg->cg_links);
462 /* Locate the cgroups associated with these links. */
463 cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
464 cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
467 /* Hierarchies should be linked in the same order. */
468 BUG_ON(cg1->root != cg2->root);
471 * If this hierarchy is the hierarchy of the cgroup
472 * that's changing, then we need to check that this
473 * css_set points to the new cgroup; if it's any other
474 * hierarchy, then this css_set should point to the
475 * same cgroup as the old css_set.
477 if (cg1->root == new_cgrp->root) {
489 * find_existing_css_set() is a helper for
490 * find_css_set(), and checks to see whether an existing
491 * css_set is suitable.
493 * oldcg: the cgroup group that we're using before the cgroup
496 * cgrp: the cgroup that we're moving into
498 * template: location in which to build the desired set of subsystem
499 * state objects for the new cgroup group
501 static struct css_set *find_existing_css_set(
502 struct css_set *oldcg,
504 struct cgroup_subsys_state *template[])
507 struct cgroupfs_root *root = cgrp->root;
508 struct hlist_head *hhead;
509 struct hlist_node *node;
513 * Build the set of subsystem state objects that we want to see in the
514 * new css_set. while subsystems can change globally, the entries here
515 * won't change, so no need for locking.
517 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
518 if (root->subsys_bits & (1UL << i)) {
519 /* Subsystem is in this hierarchy. So we want
520 * the subsystem state from the new
522 template[i] = cgrp->subsys[i];
524 /* Subsystem is not in this hierarchy, so we
525 * don't want to change the subsystem state */
526 template[i] = oldcg->subsys[i];
530 hhead = css_set_hash(template);
531 hlist_for_each_entry(cg, node, hhead, hlist) {
532 if (!compare_css_sets(cg, oldcg, cgrp, template))
535 /* This css_set matches what we need */
539 /* No existing cgroup group matched */
543 static void free_cg_links(struct list_head *tmp)
545 struct cg_cgroup_link *link;
546 struct cg_cgroup_link *saved_link;
548 list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
549 list_del(&link->cgrp_link_list);
555 * allocate_cg_links() allocates "count" cg_cgroup_link structures
556 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
557 * success or a negative error
559 static int allocate_cg_links(int count, struct list_head *tmp)
561 struct cg_cgroup_link *link;
564 for (i = 0; i < count; i++) {
565 link = kmalloc(sizeof(*link), GFP_KERNEL);
570 list_add(&link->cgrp_link_list, tmp);
576 * link_css_set - a helper function to link a css_set to a cgroup
577 * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
578 * @cg: the css_set to be linked
579 * @cgrp: the destination cgroup
581 static void link_css_set(struct list_head *tmp_cg_links,
582 struct css_set *cg, struct cgroup *cgrp)
584 struct cg_cgroup_link *link;
586 BUG_ON(list_empty(tmp_cg_links));
587 link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
591 atomic_inc(&cgrp->count);
592 list_move(&link->cgrp_link_list, &cgrp->css_sets);
594 * Always add links to the tail of the list so that the list
595 * is sorted by order of hierarchy creation
597 list_add_tail(&link->cg_link_list, &cg->cg_links);
601 * find_css_set() takes an existing cgroup group and a
602 * cgroup object, and returns a css_set object that's
603 * equivalent to the old group, but with the given cgroup
604 * substituted into the appropriate hierarchy. Must be called with
607 static struct css_set *find_css_set(
608 struct css_set *oldcg, struct cgroup *cgrp)
611 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
613 struct list_head tmp_cg_links;
615 struct hlist_head *hhead;
616 struct cg_cgroup_link *link;
618 /* First see if we already have a cgroup group that matches
620 read_lock(&css_set_lock);
621 res = find_existing_css_set(oldcg, cgrp, template);
624 read_unlock(&css_set_lock);
629 res = kmalloc(sizeof(*res), GFP_KERNEL);
633 /* Allocate all the cg_cgroup_link objects that we'll need */
634 if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
639 atomic_set(&res->refcount, 1);
640 INIT_LIST_HEAD(&res->cg_links);
641 INIT_LIST_HEAD(&res->tasks);
642 INIT_HLIST_NODE(&res->hlist);
644 /* Copy the set of subsystem state objects generated in
645 * find_existing_css_set() */
646 memcpy(res->subsys, template, sizeof(res->subsys));
648 write_lock(&css_set_lock);
649 /* Add reference counts and links from the new css_set. */
650 list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
651 struct cgroup *c = link->cgrp;
652 if (c->root == cgrp->root)
654 link_css_set(&tmp_cg_links, res, c);
657 BUG_ON(!list_empty(&tmp_cg_links));
661 /* Add this cgroup group to the hash table */
662 hhead = css_set_hash(res->subsys);
663 hlist_add_head(&res->hlist, hhead);
665 write_unlock(&css_set_lock);
671 * Return the cgroup for "task" from the given hierarchy. Must be
672 * called with cgroup_mutex held.
674 static struct cgroup *task_cgroup_from_root(struct task_struct *task,
675 struct cgroupfs_root *root)
678 struct cgroup *res = NULL;
680 BUG_ON(!mutex_is_locked(&cgroup_mutex));
681 read_lock(&css_set_lock);
683 * No need to lock the task - since we hold cgroup_mutex the
684 * task can't change groups, so the only thing that can happen
685 * is that it exits and its css is set back to init_css_set.
688 if (css == &init_css_set) {
689 res = &root->top_cgroup;
691 struct cg_cgroup_link *link;
692 list_for_each_entry(link, &css->cg_links, cg_link_list) {
693 struct cgroup *c = link->cgrp;
694 if (c->root == root) {
700 read_unlock(&css_set_lock);
706 * There is one global cgroup mutex. We also require taking
707 * task_lock() when dereferencing a task's cgroup subsys pointers.
708 * See "The task_lock() exception", at the end of this comment.
710 * A task must hold cgroup_mutex to modify cgroups.
712 * Any task can increment and decrement the count field without lock.
713 * So in general, code holding cgroup_mutex can't rely on the count
714 * field not changing. However, if the count goes to zero, then only
715 * cgroup_attach_task() can increment it again. Because a count of zero
716 * means that no tasks are currently attached, therefore there is no
717 * way a task attached to that cgroup can fork (the other way to
718 * increment the count). So code holding cgroup_mutex can safely
719 * assume that if the count is zero, it will stay zero. Similarly, if
720 * a task holds cgroup_mutex on a cgroup with zero count, it
721 * knows that the cgroup won't be removed, as cgroup_rmdir()
724 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
725 * (usually) take cgroup_mutex. These are the two most performance
726 * critical pieces of code here. The exception occurs on cgroup_exit(),
727 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
728 * is taken, and if the cgroup count is zero, a usermode call made
729 * to the release agent with the name of the cgroup (path relative to
730 * the root of cgroup file system) as the argument.
732 * A cgroup can only be deleted if both its 'count' of using tasks
733 * is zero, and its list of 'children' cgroups is empty. Since all
734 * tasks in the system use _some_ cgroup, and since there is always at
735 * least one task in the system (init, pid == 1), therefore, top_cgroup
736 * always has either children cgroups and/or using tasks. So we don't
737 * need a special hack to ensure that top_cgroup cannot be deleted.
739 * The task_lock() exception
741 * The need for this exception arises from the action of
742 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
743 * another. It does so using cgroup_mutex, however there are
744 * several performance critical places that need to reference
745 * task->cgroup without the expense of grabbing a system global
746 * mutex. Therefore except as noted below, when dereferencing or, as
747 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
748 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
749 * the task_struct routinely used for such matters.
751 * P.S. One more locking exception. RCU is used to guard the
752 * update of a tasks cgroup pointer by cgroup_attach_task()
756 * cgroup_lock - lock out any changes to cgroup structures
759 void cgroup_lock(void)
761 mutex_lock(&cgroup_mutex);
763 EXPORT_SYMBOL_GPL(cgroup_lock);
766 * cgroup_unlock - release lock on cgroup changes
768 * Undo the lock taken in a previous cgroup_lock() call.
770 void cgroup_unlock(void)
772 mutex_unlock(&cgroup_mutex);
774 EXPORT_SYMBOL_GPL(cgroup_unlock);
777 * A couple of forward declarations required, due to cyclic reference loop:
778 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
779 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
783 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
784 static struct dentry *cgroup_lookup(struct inode *, struct dentry *, struct nameidata *);
785 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
786 static int cgroup_populate_dir(struct cgroup *cgrp);
787 static const struct inode_operations cgroup_dir_inode_operations;
788 static const struct file_operations proc_cgroupstats_operations;
790 static struct backing_dev_info cgroup_backing_dev_info = {
792 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
795 static int alloc_css_id(struct cgroup_subsys *ss,
796 struct cgroup *parent, struct cgroup *child);
798 static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
800 struct inode *inode = new_inode(sb);
803 inode->i_ino = get_next_ino();
804 inode->i_mode = mode;
805 inode->i_uid = current_fsuid();
806 inode->i_gid = current_fsgid();
807 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
808 inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
814 * Call subsys's pre_destroy handler.
815 * This is called before css refcnt check.
817 static int cgroup_call_pre_destroy(struct cgroup *cgrp)
819 struct cgroup_subsys *ss;
822 for_each_subsys(cgrp->root, ss)
823 if (ss->pre_destroy) {
824 ret = ss->pre_destroy(cgrp);
832 static void cgroup_diput(struct dentry *dentry, struct inode *inode)
834 /* is dentry a directory ? if so, kfree() associated cgroup */
835 if (S_ISDIR(inode->i_mode)) {
836 struct cgroup *cgrp = dentry->d_fsdata;
837 struct cgroup_subsys *ss;
838 BUG_ON(!(cgroup_is_removed(cgrp)));
839 /* It's possible for external users to be holding css
840 * reference counts on a cgroup; css_put() needs to
841 * be able to access the cgroup after decrementing
842 * the reference count in order to know if it needs to
843 * queue the cgroup to be handled by the release
847 mutex_lock(&cgroup_mutex);
849 * Release the subsystem state objects.
851 for_each_subsys(cgrp->root, ss)
854 cgrp->root->number_of_cgroups--;
855 mutex_unlock(&cgroup_mutex);
858 * Drop the active superblock reference that we took when we
861 deactivate_super(cgrp->root->sb);
864 * if we're getting rid of the cgroup, refcount should ensure
865 * that there are no pidlists left.
867 BUG_ON(!list_empty(&cgrp->pidlists));
869 kfree_rcu(cgrp, rcu_head);
874 static int cgroup_delete(const struct dentry *d)
879 static void remove_dir(struct dentry *d)
881 struct dentry *parent = dget(d->d_parent);
884 simple_rmdir(parent->d_inode, d);
888 static void cgroup_clear_directory(struct dentry *dentry)
890 struct list_head *node;
892 BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
893 spin_lock(&dentry->d_lock);
894 node = dentry->d_subdirs.next;
895 while (node != &dentry->d_subdirs) {
896 struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
898 spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
901 /* This should never be called on a cgroup
902 * directory with child cgroups */
903 BUG_ON(d->d_inode->i_mode & S_IFDIR);
905 spin_unlock(&d->d_lock);
906 spin_unlock(&dentry->d_lock);
908 simple_unlink(dentry->d_inode, d);
910 spin_lock(&dentry->d_lock);
912 spin_unlock(&d->d_lock);
913 node = dentry->d_subdirs.next;
915 spin_unlock(&dentry->d_lock);
919 * NOTE : the dentry must have been dget()'ed
921 static void cgroup_d_remove_dir(struct dentry *dentry)
923 struct dentry *parent;
925 cgroup_clear_directory(dentry);
927 parent = dentry->d_parent;
928 spin_lock(&parent->d_lock);
929 spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
930 list_del_init(&dentry->d_u.d_child);
931 spin_unlock(&dentry->d_lock);
932 spin_unlock(&parent->d_lock);
937 * A queue for waiters to do rmdir() cgroup. A tasks will sleep when
938 * cgroup->count == 0 && list_empty(&cgroup->children) && subsys has some
939 * reference to css->refcnt. In general, this refcnt is expected to goes down
942 * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
944 static DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
946 static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
948 if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
949 wake_up_all(&cgroup_rmdir_waitq);
952 void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
957 void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
959 cgroup_wakeup_rmdir_waiter(css->cgroup);
964 * Call with cgroup_mutex held. Drops reference counts on modules, including
965 * any duplicate ones that parse_cgroupfs_options took. If this function
966 * returns an error, no reference counts are touched.
968 static int rebind_subsystems(struct cgroupfs_root *root,
969 unsigned long final_bits)
971 unsigned long added_bits, removed_bits;
972 struct cgroup *cgrp = &root->top_cgroup;
975 BUG_ON(!mutex_is_locked(&cgroup_mutex));
976 BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
978 removed_bits = root->actual_subsys_bits & ~final_bits;
979 added_bits = final_bits & ~root->actual_subsys_bits;
980 /* Check that any added subsystems are currently free */
981 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
982 unsigned long bit = 1UL << i;
983 struct cgroup_subsys *ss = subsys[i];
984 if (!(bit & added_bits))
987 * Nobody should tell us to do a subsys that doesn't exist:
988 * parse_cgroupfs_options should catch that case and refcounts
989 * ensure that subsystems won't disappear once selected.
992 if (ss->root != &rootnode) {
993 /* Subsystem isn't free */
998 /* Currently we don't handle adding/removing subsystems when
999 * any child cgroups exist. This is theoretically supportable
1000 * but involves complex error handling, so it's being left until
1002 if (root->number_of_cgroups > 1)
1005 /* Process each subsystem */
1006 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1007 struct cgroup_subsys *ss = subsys[i];
1008 unsigned long bit = 1UL << i;
1009 if (bit & added_bits) {
1010 /* We're binding this subsystem to this hierarchy */
1012 BUG_ON(cgrp->subsys[i]);
1013 BUG_ON(!dummytop->subsys[i]);
1014 BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1015 mutex_lock(&ss->hierarchy_mutex);
1016 cgrp->subsys[i] = dummytop->subsys[i];
1017 cgrp->subsys[i]->cgroup = cgrp;
1018 list_move(&ss->sibling, &root->subsys_list);
1022 mutex_unlock(&ss->hierarchy_mutex);
1023 /* refcount was already taken, and we're keeping it */
1024 } else if (bit & removed_bits) {
1025 /* We're removing this subsystem */
1027 BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
1028 BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1029 mutex_lock(&ss->hierarchy_mutex);
1032 dummytop->subsys[i]->cgroup = dummytop;
1033 cgrp->subsys[i] = NULL;
1034 subsys[i]->root = &rootnode;
1035 list_move(&ss->sibling, &rootnode.subsys_list);
1036 mutex_unlock(&ss->hierarchy_mutex);
1037 /* subsystem is now free - drop reference on module */
1038 module_put(ss->module);
1039 } else if (bit & final_bits) {
1040 /* Subsystem state should already exist */
1042 BUG_ON(!cgrp->subsys[i]);
1044 * a refcount was taken, but we already had one, so
1045 * drop the extra reference.
1047 module_put(ss->module);
1048 #ifdef CONFIG_MODULE_UNLOAD
1049 BUG_ON(ss->module && !module_refcount(ss->module));
1052 /* Subsystem state shouldn't exist */
1053 BUG_ON(cgrp->subsys[i]);
1056 root->subsys_bits = root->actual_subsys_bits = final_bits;
1062 static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1064 struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1065 struct cgroup_subsys *ss;
1067 mutex_lock(&cgroup_root_mutex);
1068 for_each_subsys(root, ss)
1069 seq_printf(seq, ",%s", ss->name);
1070 if (test_bit(ROOT_NOPREFIX, &root->flags))
1071 seq_puts(seq, ",noprefix");
1072 if (strlen(root->release_agent_path))
1073 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1074 if (clone_children(&root->top_cgroup))
1075 seq_puts(seq, ",clone_children");
1076 if (strlen(root->name))
1077 seq_printf(seq, ",name=%s", root->name);
1078 mutex_unlock(&cgroup_root_mutex);
1082 struct cgroup_sb_opts {
1083 unsigned long subsys_bits;
1084 unsigned long flags;
1085 char *release_agent;
1086 bool clone_children;
1088 /* User explicitly requested empty subsystem */
1091 struct cgroupfs_root *new_root;
1096 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
1097 * with cgroup_mutex held to protect the subsys[] array. This function takes
1098 * refcounts on subsystems to be used, unless it returns error, in which case
1099 * no refcounts are taken.
1101 static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1103 char *token, *o = data;
1104 bool all_ss = false, one_ss = false;
1105 unsigned long mask = (unsigned long)-1;
1107 bool module_pin_failed = false;
1109 BUG_ON(!mutex_is_locked(&cgroup_mutex));
1111 #ifdef CONFIG_CPUSETS
1112 mask = ~(1UL << cpuset_subsys_id);
1115 memset(opts, 0, sizeof(*opts));
1117 while ((token = strsep(&o, ",")) != NULL) {
1120 if (!strcmp(token, "none")) {
1121 /* Explicitly have no subsystems */
1125 if (!strcmp(token, "all")) {
1126 /* Mutually exclusive option 'all' + subsystem name */
1132 if (!strcmp(token, "noprefix")) {
1133 set_bit(ROOT_NOPREFIX, &opts->flags);
1136 if (!strcmp(token, "clone_children")) {
1137 opts->clone_children = true;
1140 if (!strncmp(token, "release_agent=", 14)) {
1141 /* Specifying two release agents is forbidden */
1142 if (opts->release_agent)
1144 opts->release_agent =
1145 kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1146 if (!opts->release_agent)
1150 if (!strncmp(token, "name=", 5)) {
1151 const char *name = token + 5;
1152 /* Can't specify an empty name */
1155 /* Must match [\w.-]+ */
1156 for (i = 0; i < strlen(name); i++) {
1160 if ((c == '.') || (c == '-') || (c == '_'))
1164 /* Specifying two names is forbidden */
1167 opts->name = kstrndup(name,
1168 MAX_CGROUP_ROOT_NAMELEN - 1,
1176 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1177 struct cgroup_subsys *ss = subsys[i];
1180 if (strcmp(token, ss->name))
1185 /* Mutually exclusive option 'all' + subsystem name */
1188 set_bit(i, &opts->subsys_bits);
1193 if (i == CGROUP_SUBSYS_COUNT)
1198 * If the 'all' option was specified select all the subsystems,
1199 * otherwise if 'none', 'name=' and a subsystem name options
1200 * were not specified, let's default to 'all'
1202 if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1203 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1204 struct cgroup_subsys *ss = subsys[i];
1209 set_bit(i, &opts->subsys_bits);
1213 /* Consistency checks */
1216 * Option noprefix was introduced just for backward compatibility
1217 * with the old cpuset, so we allow noprefix only if mounting just
1218 * the cpuset subsystem.
1220 if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
1221 (opts->subsys_bits & mask))
1225 /* Can't specify "none" and some subsystems */
1226 if (opts->subsys_bits && opts->none)
1230 * We either have to specify by name or by subsystems. (So all
1231 * empty hierarchies must have a name).
1233 if (!opts->subsys_bits && !opts->name)
1237 * Grab references on all the modules we'll need, so the subsystems
1238 * don't dance around before rebind_subsystems attaches them. This may
1239 * take duplicate reference counts on a subsystem that's already used,
1240 * but rebind_subsystems handles this case.
1242 for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
1243 unsigned long bit = 1UL << i;
1245 if (!(bit & opts->subsys_bits))
1247 if (!try_module_get(subsys[i]->module)) {
1248 module_pin_failed = true;
1252 if (module_pin_failed) {
1254 * oops, one of the modules was going away. this means that we
1255 * raced with a module_delete call, and to the user this is
1256 * essentially a "subsystem doesn't exist" case.
1258 for (i--; i >= CGROUP_BUILTIN_SUBSYS_COUNT; i--) {
1259 /* drop refcounts only on the ones we took */
1260 unsigned long bit = 1UL << i;
1262 if (!(bit & opts->subsys_bits))
1264 module_put(subsys[i]->module);
1272 static void drop_parsed_module_refcounts(unsigned long subsys_bits)
1275 for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
1276 unsigned long bit = 1UL << i;
1278 if (!(bit & subsys_bits))
1280 module_put(subsys[i]->module);
1284 static int cgroup_remount(struct super_block *sb, int *flags, char *data)
1287 struct cgroupfs_root *root = sb->s_fs_info;
1288 struct cgroup *cgrp = &root->top_cgroup;
1289 struct cgroup_sb_opts opts;
1291 mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1292 mutex_lock(&cgroup_mutex);
1293 mutex_lock(&cgroup_root_mutex);
1295 /* See what subsystems are wanted */
1296 ret = parse_cgroupfs_options(data, &opts);
1300 /* See feature-removal-schedule.txt */
1301 if (opts.subsys_bits != root->actual_subsys_bits || opts.release_agent)
1302 pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
1303 task_tgid_nr(current), current->comm);
1305 /* Don't allow flags or name to change at remount */
1306 if (opts.flags != root->flags ||
1307 (opts.name && strcmp(opts.name, root->name))) {
1309 drop_parsed_module_refcounts(opts.subsys_bits);
1313 ret = rebind_subsystems(root, opts.subsys_bits);
1315 drop_parsed_module_refcounts(opts.subsys_bits);
1319 /* clear out any existing files and repopulate subsystem files */
1320 cgroup_clear_directory(cgrp->dentry);
1321 cgroup_populate_dir(cgrp);
1323 if (opts.release_agent)
1324 strcpy(root->release_agent_path, opts.release_agent);
1326 kfree(opts.release_agent);
1328 mutex_unlock(&cgroup_root_mutex);
1329 mutex_unlock(&cgroup_mutex);
1330 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1334 static const struct super_operations cgroup_ops = {
1335 .statfs = simple_statfs,
1336 .drop_inode = generic_delete_inode,
1337 .show_options = cgroup_show_options,
1338 .remount_fs = cgroup_remount,
1341 static void init_cgroup_housekeeping(struct cgroup *cgrp)
1343 INIT_LIST_HEAD(&cgrp->sibling);
1344 INIT_LIST_HEAD(&cgrp->children);
1345 INIT_LIST_HEAD(&cgrp->css_sets);
1346 INIT_LIST_HEAD(&cgrp->release_list);
1347 INIT_LIST_HEAD(&cgrp->pidlists);
1348 mutex_init(&cgrp->pidlist_mutex);
1349 INIT_LIST_HEAD(&cgrp->event_list);
1350 spin_lock_init(&cgrp->event_list_lock);
1353 static void init_cgroup_root(struct cgroupfs_root *root)
1355 struct cgroup *cgrp = &root->top_cgroup;
1357 INIT_LIST_HEAD(&root->subsys_list);
1358 INIT_LIST_HEAD(&root->root_list);
1359 INIT_LIST_HEAD(&root->allcg_list);
1360 root->number_of_cgroups = 1;
1362 cgrp->top_cgroup = cgrp;
1363 list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1364 init_cgroup_housekeeping(cgrp);
1367 static bool init_root_id(struct cgroupfs_root *root)
1372 if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
1374 spin_lock(&hierarchy_id_lock);
1375 /* Try to allocate the next unused ID */
1376 ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
1377 &root->hierarchy_id);
1379 /* Try again starting from 0 */
1380 ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
1382 next_hierarchy_id = root->hierarchy_id + 1;
1383 } else if (ret != -EAGAIN) {
1384 /* Can only get here if the 31-bit IDR is full ... */
1387 spin_unlock(&hierarchy_id_lock);
1392 static int cgroup_test_super(struct super_block *sb, void *data)
1394 struct cgroup_sb_opts *opts = data;
1395 struct cgroupfs_root *root = sb->s_fs_info;
1397 /* If we asked for a name then it must match */
1398 if (opts->name && strcmp(opts->name, root->name))
1402 * If we asked for subsystems (or explicitly for no
1403 * subsystems) then they must match
1405 if ((opts->subsys_bits || opts->none)
1406 && (opts->subsys_bits != root->subsys_bits))
1412 static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
1414 struct cgroupfs_root *root;
1416 if (!opts->subsys_bits && !opts->none)
1419 root = kzalloc(sizeof(*root), GFP_KERNEL);
1421 return ERR_PTR(-ENOMEM);
1423 if (!init_root_id(root)) {
1425 return ERR_PTR(-ENOMEM);
1427 init_cgroup_root(root);
1429 root->subsys_bits = opts->subsys_bits;
1430 root->flags = opts->flags;
1431 if (opts->release_agent)
1432 strcpy(root->release_agent_path, opts->release_agent);
1434 strcpy(root->name, opts->name);
1435 if (opts->clone_children)
1436 set_bit(CGRP_CLONE_CHILDREN, &root->top_cgroup.flags);
1440 static void cgroup_drop_root(struct cgroupfs_root *root)
1445 BUG_ON(!root->hierarchy_id);
1446 spin_lock(&hierarchy_id_lock);
1447 ida_remove(&hierarchy_ida, root->hierarchy_id);
1448 spin_unlock(&hierarchy_id_lock);
1452 static int cgroup_set_super(struct super_block *sb, void *data)
1455 struct cgroup_sb_opts *opts = data;
1457 /* If we don't have a new root, we can't set up a new sb */
1458 if (!opts->new_root)
1461 BUG_ON(!opts->subsys_bits && !opts->none);
1463 ret = set_anon_super(sb, NULL);
1467 sb->s_fs_info = opts->new_root;
1468 opts->new_root->sb = sb;
1470 sb->s_blocksize = PAGE_CACHE_SIZE;
1471 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
1472 sb->s_magic = CGROUP_SUPER_MAGIC;
1473 sb->s_op = &cgroup_ops;
1478 static int cgroup_get_rootdir(struct super_block *sb)
1480 static const struct dentry_operations cgroup_dops = {
1481 .d_iput = cgroup_diput,
1482 .d_delete = cgroup_delete,
1485 struct inode *inode =
1486 cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
1491 inode->i_fop = &simple_dir_operations;
1492 inode->i_op = &cgroup_dir_inode_operations;
1493 /* directories start off with i_nlink == 2 (for "." entry) */
1495 sb->s_root = d_make_root(inode);
1498 /* for everything else we want ->d_op set */
1499 sb->s_d_op = &cgroup_dops;
1503 static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1504 int flags, const char *unused_dev_name,
1507 struct cgroup_sb_opts opts;
1508 struct cgroupfs_root *root;
1510 struct super_block *sb;
1511 struct cgroupfs_root *new_root;
1512 struct inode *inode;
1514 /* First find the desired set of subsystems */
1515 mutex_lock(&cgroup_mutex);
1516 ret = parse_cgroupfs_options(data, &opts);
1517 mutex_unlock(&cgroup_mutex);
1522 * Allocate a new cgroup root. We may not need it if we're
1523 * reusing an existing hierarchy.
1525 new_root = cgroup_root_from_opts(&opts);
1526 if (IS_ERR(new_root)) {
1527 ret = PTR_ERR(new_root);
1530 opts.new_root = new_root;
1532 /* Locate an existing or new sb for this hierarchy */
1533 sb = sget(fs_type, cgroup_test_super, cgroup_set_super, &opts);
1536 cgroup_drop_root(opts.new_root);
1540 root = sb->s_fs_info;
1542 if (root == opts.new_root) {
1543 /* We used the new root structure, so this is a new hierarchy */
1544 struct list_head tmp_cg_links;
1545 struct cgroup *root_cgrp = &root->top_cgroup;
1546 struct cgroupfs_root *existing_root;
1547 const struct cred *cred;
1550 BUG_ON(sb->s_root != NULL);
1552 ret = cgroup_get_rootdir(sb);
1554 goto drop_new_super;
1555 inode = sb->s_root->d_inode;
1557 mutex_lock(&inode->i_mutex);
1558 mutex_lock(&cgroup_mutex);
1559 mutex_lock(&cgroup_root_mutex);
1561 /* Check for name clashes with existing mounts */
1563 if (strlen(root->name))
1564 for_each_active_root(existing_root)
1565 if (!strcmp(existing_root->name, root->name))
1569 * We're accessing css_set_count without locking
1570 * css_set_lock here, but that's OK - it can only be
1571 * increased by someone holding cgroup_lock, and
1572 * that's us. The worst that can happen is that we
1573 * have some link structures left over
1575 ret = allocate_cg_links(css_set_count, &tmp_cg_links);
1579 ret = rebind_subsystems(root, root->subsys_bits);
1580 if (ret == -EBUSY) {
1581 free_cg_links(&tmp_cg_links);
1585 * There must be no failure case after here, since rebinding
1586 * takes care of subsystems' refcounts, which are explicitly
1587 * dropped in the failure exit path.
1590 /* EBUSY should be the only error here */
1593 list_add(&root->root_list, &roots);
1596 sb->s_root->d_fsdata = root_cgrp;
1597 root->top_cgroup.dentry = sb->s_root;
1599 /* Link the top cgroup in this hierarchy into all
1600 * the css_set objects */
1601 write_lock(&css_set_lock);
1602 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
1603 struct hlist_head *hhead = &css_set_table[i];
1604 struct hlist_node *node;
1607 hlist_for_each_entry(cg, node, hhead, hlist)
1608 link_css_set(&tmp_cg_links, cg, root_cgrp);
1610 write_unlock(&css_set_lock);
1612 free_cg_links(&tmp_cg_links);
1614 BUG_ON(!list_empty(&root_cgrp->sibling));
1615 BUG_ON(!list_empty(&root_cgrp->children));
1616 BUG_ON(root->number_of_cgroups != 1);
1618 cred = override_creds(&init_cred);
1619 cgroup_populate_dir(root_cgrp);
1621 mutex_unlock(&cgroup_root_mutex);
1622 mutex_unlock(&cgroup_mutex);
1623 mutex_unlock(&inode->i_mutex);
1626 * We re-used an existing hierarchy - the new root (if
1627 * any) is not needed
1629 cgroup_drop_root(opts.new_root);
1630 /* no subsys rebinding, so refcounts don't change */
1631 drop_parsed_module_refcounts(opts.subsys_bits);
1634 kfree(opts.release_agent);
1636 return dget(sb->s_root);
1639 mutex_unlock(&cgroup_root_mutex);
1640 mutex_unlock(&cgroup_mutex);
1641 mutex_unlock(&inode->i_mutex);
1643 deactivate_locked_super(sb);
1645 drop_parsed_module_refcounts(opts.subsys_bits);
1647 kfree(opts.release_agent);
1649 return ERR_PTR(ret);
1652 static void cgroup_kill_sb(struct super_block *sb) {
1653 struct cgroupfs_root *root = sb->s_fs_info;
1654 struct cgroup *cgrp = &root->top_cgroup;
1656 struct cg_cgroup_link *link;
1657 struct cg_cgroup_link *saved_link;
1661 BUG_ON(root->number_of_cgroups != 1);
1662 BUG_ON(!list_empty(&cgrp->children));
1663 BUG_ON(!list_empty(&cgrp->sibling));
1665 mutex_lock(&cgroup_mutex);
1666 mutex_lock(&cgroup_root_mutex);
1668 /* Rebind all subsystems back to the default hierarchy */
1669 ret = rebind_subsystems(root, 0);
1670 /* Shouldn't be able to fail ... */
1674 * Release all the links from css_sets to this hierarchy's
1677 write_lock(&css_set_lock);
1679 list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
1681 list_del(&link->cg_link_list);
1682 list_del(&link->cgrp_link_list);
1685 write_unlock(&css_set_lock);
1687 if (!list_empty(&root->root_list)) {
1688 list_del(&root->root_list);
1692 mutex_unlock(&cgroup_root_mutex);
1693 mutex_unlock(&cgroup_mutex);
1695 kill_litter_super(sb);
1696 cgroup_drop_root(root);
1699 static struct file_system_type cgroup_fs_type = {
1701 .mount = cgroup_mount,
1702 .kill_sb = cgroup_kill_sb,
1705 static struct kobject *cgroup_kobj;
1707 static inline struct cgroup *__d_cgrp(struct dentry *dentry)
1709 return dentry->d_fsdata;
1712 static inline struct cftype *__d_cft(struct dentry *dentry)
1714 return dentry->d_fsdata;
1718 * cgroup_path - generate the path of a cgroup
1719 * @cgrp: the cgroup in question
1720 * @buf: the buffer to write the path into
1721 * @buflen: the length of the buffer
1723 * Called with cgroup_mutex held or else with an RCU-protected cgroup
1724 * reference. Writes path of cgroup into buf. Returns 0 on success,
1727 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1730 struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
1731 cgroup_lock_is_held());
1733 if (!dentry || cgrp == dummytop) {
1735 * Inactive subsystems have no dentry for their root
1742 start = buf + buflen;
1746 int len = dentry->d_name.len;
1748 if ((start -= len) < buf)
1749 return -ENAMETOOLONG;
1750 memcpy(start, dentry->d_name.name, len);
1751 cgrp = cgrp->parent;
1755 dentry = rcu_dereference_check(cgrp->dentry,
1756 cgroup_lock_is_held());
1760 return -ENAMETOOLONG;
1763 memmove(buf, start, buf + buflen - start);
1766 EXPORT_SYMBOL_GPL(cgroup_path);
1769 * Control Group taskset
1771 struct task_and_cgroup {
1772 struct task_struct *task;
1773 struct cgroup *cgrp;
1777 struct cgroup_taskset {
1778 struct task_and_cgroup single;
1779 struct flex_array *tc_array;
1782 struct cgroup *cur_cgrp;
1786 * cgroup_taskset_first - reset taskset and return the first task
1787 * @tset: taskset of interest
1789 * @tset iteration is initialized and the first task is returned.
1791 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
1793 if (tset->tc_array) {
1795 return cgroup_taskset_next(tset);
1797 tset->cur_cgrp = tset->single.cgrp;
1798 return tset->single.task;
1801 EXPORT_SYMBOL_GPL(cgroup_taskset_first);
1804 * cgroup_taskset_next - iterate to the next task in taskset
1805 * @tset: taskset of interest
1807 * Return the next task in @tset. Iteration must have been initialized
1808 * with cgroup_taskset_first().
1810 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
1812 struct task_and_cgroup *tc;
1814 if (!tset->tc_array || tset->idx >= tset->tc_array_len)
1817 tc = flex_array_get(tset->tc_array, tset->idx++);
1818 tset->cur_cgrp = tc->cgrp;
1821 EXPORT_SYMBOL_GPL(cgroup_taskset_next);
1824 * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
1825 * @tset: taskset of interest
1827 * Return the cgroup for the current (last returned) task of @tset. This
1828 * function must be preceded by either cgroup_taskset_first() or
1829 * cgroup_taskset_next().
1831 struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
1833 return tset->cur_cgrp;
1835 EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);
1838 * cgroup_taskset_size - return the number of tasks in taskset
1839 * @tset: taskset of interest
1841 int cgroup_taskset_size(struct cgroup_taskset *tset)
1843 return tset->tc_array ? tset->tc_array_len : 1;
1845 EXPORT_SYMBOL_GPL(cgroup_taskset_size);
1849 * cgroup_task_migrate - move a task from one cgroup to another.
1851 * 'guarantee' is set if the caller promises that a new css_set for the task
1852 * will already exist. If not set, this function might sleep, and can fail with
1853 * -ENOMEM. Must be called with cgroup_mutex and threadgroup locked.
1855 static void cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
1856 struct task_struct *tsk, struct css_set *newcg)
1858 struct css_set *oldcg;
1861 * We are synchronized through threadgroup_lock() against PF_EXITING
1862 * setting such that we can't race against cgroup_exit() changing the
1863 * css_set to init_css_set and dropping the old one.
1865 WARN_ON_ONCE(tsk->flags & PF_EXITING);
1866 oldcg = tsk->cgroups;
1869 rcu_assign_pointer(tsk->cgroups, newcg);
1872 /* Update the css_set linked lists if we're using them */
1873 write_lock(&css_set_lock);
1874 if (!list_empty(&tsk->cg_list))
1875 list_move(&tsk->cg_list, &newcg->tasks);
1876 write_unlock(&css_set_lock);
1879 * We just gained a reference on oldcg by taking it from the task. As
1880 * trading it for newcg is protected by cgroup_mutex, we're safe to drop
1881 * it here; it will be freed under RCU.
1885 set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1889 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
1890 * @cgrp: the cgroup the task is attaching to
1891 * @tsk: the task to be attached
1893 * Call with cgroup_mutex and threadgroup locked. May take task_lock of
1896 int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1899 struct cgroup_subsys *ss, *failed_ss = NULL;
1900 struct cgroup *oldcgrp;
1901 struct cgroupfs_root *root = cgrp->root;
1902 struct cgroup_taskset tset = { };
1903 struct css_set *newcg;
1905 /* @tsk either already exited or can't exit until the end */
1906 if (tsk->flags & PF_EXITING)
1909 /* Nothing to do if the task is already in that cgroup */
1910 oldcgrp = task_cgroup_from_root(tsk, root);
1911 if (cgrp == oldcgrp)
1914 tset.single.task = tsk;
1915 tset.single.cgrp = oldcgrp;
1917 for_each_subsys(root, ss) {
1918 if (ss->can_attach) {
1919 retval = ss->can_attach(cgrp, &tset);
1922 * Remember on which subsystem the can_attach()
1923 * failed, so that we only call cancel_attach()
1924 * against the subsystems whose can_attach()
1925 * succeeded. (See below)
1933 newcg = find_css_set(tsk->cgroups, cgrp);
1939 cgroup_task_migrate(cgrp, oldcgrp, tsk, newcg);
1941 for_each_subsys(root, ss) {
1943 ss->attach(cgrp, &tset);
1949 * wake up rmdir() waiter. the rmdir should fail since the cgroup
1950 * is no longer empty.
1952 cgroup_wakeup_rmdir_waiter(cgrp);
1955 for_each_subsys(root, ss) {
1956 if (ss == failed_ss)
1958 * This subsystem was the one that failed the
1959 * can_attach() check earlier, so we don't need
1960 * to call cancel_attach() against it or any
1961 * remaining subsystems.
1964 if (ss->cancel_attach)
1965 ss->cancel_attach(cgrp, &tset);
1972 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
1973 * @from: attach to all cgroups of a given task
1974 * @tsk: the task to be attached
1976 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
1978 struct cgroupfs_root *root;
1982 for_each_active_root(root) {
1983 struct cgroup *from_cg = task_cgroup_from_root(from, root);
1985 retval = cgroup_attach_task(from_cg, tsk);
1993 EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
1996 * cgroup_attach_proc - attach all threads in a threadgroup to a cgroup
1997 * @cgrp: the cgroup to attach to
1998 * @leader: the threadgroup leader task_struct of the group to be attached
2000 * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
2001 * task_lock of each thread in leader's threadgroup individually in turn.
2003 static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
2005 int retval, i, group_size;
2006 struct cgroup_subsys *ss, *failed_ss = NULL;
2007 /* guaranteed to be initialized later, but the compiler needs this */
2008 struct cgroupfs_root *root = cgrp->root;
2009 /* threadgroup list cursor and array */
2010 struct task_struct *tsk;
2011 struct task_and_cgroup *tc;
2012 struct flex_array *group;
2013 struct cgroup_taskset tset = { };
2016 * step 0: in order to do expensive, possibly blocking operations for
2017 * every thread, we cannot iterate the thread group list, since it needs
2018 * rcu or tasklist locked. instead, build an array of all threads in the
2019 * group - group_rwsem prevents new threads from appearing, and if
2020 * threads exit, this will just be an over-estimate.
2022 group_size = get_nr_threads(leader);
2023 /* flex_array supports very large thread-groups better than kmalloc. */
2024 group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
2027 /* pre-allocate to guarantee space while iterating in rcu read-side. */
2028 retval = flex_array_prealloc(group, 0, group_size - 1, GFP_KERNEL);
2030 goto out_free_group_list;
2035 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2036 * already PF_EXITING could be freed from underneath us unless we
2037 * take an rcu_read_lock.
2041 struct task_and_cgroup ent;
2043 /* @tsk either already exited or can't exit until the end */
2044 if (tsk->flags & PF_EXITING)
2047 /* as per above, nr_threads may decrease, but not increase. */
2048 BUG_ON(i >= group_size);
2050 ent.cgrp = task_cgroup_from_root(tsk, root);
2051 /* nothing to do if this task is already in the cgroup */
2052 if (ent.cgrp == cgrp)
2055 * saying GFP_ATOMIC has no effect here because we did prealloc
2056 * earlier, but it's good form to communicate our expectations.
2058 retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2059 BUG_ON(retval != 0);
2061 } while_each_thread(leader, tsk);
2063 /* remember the number of threads in the array for later. */
2065 tset.tc_array = group;
2066 tset.tc_array_len = group_size;
2068 /* methods shouldn't be called if no task is actually migrating */
2071 goto out_free_group_list;
2074 * step 1: check that we can legitimately attach to the cgroup.
2076 for_each_subsys(root, ss) {
2077 if (ss->can_attach) {
2078 retval = ss->can_attach(cgrp, &tset);
2081 goto out_cancel_attach;
2087 * step 2: make sure css_sets exist for all threads to be migrated.
2088 * we use find_css_set, which allocates a new one if necessary.
2090 for (i = 0; i < group_size; i++) {
2091 tc = flex_array_get(group, i);
2092 tc->cg = find_css_set(tc->task->cgroups, cgrp);
2095 goto out_put_css_set_refs;
2100 * step 3: now that we're guaranteed success wrt the css_sets,
2101 * proceed to move all tasks to the new cgroup. There are no
2102 * failure cases after here, so this is the commit point.
2104 for (i = 0; i < group_size; i++) {
2105 tc = flex_array_get(group, i);
2106 cgroup_task_migrate(cgrp, tc->cgrp, tc->task, tc->cg);
2108 /* nothing is sensitive to fork() after this point. */
2111 * step 4: do subsystem attach callbacks.
2113 for_each_subsys(root, ss) {
2115 ss->attach(cgrp, &tset);
2119 * step 5: success! and cleanup
2122 cgroup_wakeup_rmdir_waiter(cgrp);
2124 out_put_css_set_refs:
2126 for (i = 0; i < group_size; i++) {
2127 tc = flex_array_get(group, i);
2130 put_css_set(tc->cg);
2135 for_each_subsys(root, ss) {
2136 if (ss == failed_ss)
2138 if (ss->cancel_attach)
2139 ss->cancel_attach(cgrp, &tset);
2142 out_free_group_list:
2143 flex_array_free(group);
2148 * Find the task_struct of the task to attach by vpid and pass it along to the
2149 * function to attach either it or all tasks in its threadgroup. Will lock
2150 * cgroup_mutex and threadgroup; may take task_lock of task.
2152 static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2154 struct task_struct *tsk;
2155 const struct cred *cred = current_cred(), *tcred;
2158 if (!cgroup_lock_live_group(cgrp))
2164 tsk = find_task_by_vpid(pid);
2168 goto out_unlock_cgroup;
2171 * even if we're attaching all tasks in the thread group, we
2172 * only need to check permissions on one of them.
2174 tcred = __task_cred(tsk);
2176 cred->euid != tcred->uid &&
2177 cred->euid != tcred->suid) {
2180 goto out_unlock_cgroup;
2186 tsk = tsk->group_leader;
2187 get_task_struct(tsk);
2190 threadgroup_lock(tsk);
2192 if (!thread_group_leader(tsk)) {
2194 * a race with de_thread from another thread's exec()
2195 * may strip us of our leadership, if this happens,
2196 * there is no choice but to throw this task away and
2197 * try again; this is
2198 * "double-double-toil-and-trouble-check locking".
2200 threadgroup_unlock(tsk);
2201 put_task_struct(tsk);
2202 goto retry_find_task;
2204 ret = cgroup_attach_proc(cgrp, tsk);
2206 ret = cgroup_attach_task(cgrp, tsk);
2207 threadgroup_unlock(tsk);
2209 put_task_struct(tsk);
2215 static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
2217 return attach_task_by_pid(cgrp, pid, false);
2220 static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2222 return attach_task_by_pid(cgrp, tgid, true);
2226 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
2227 * @cgrp: the cgroup to be checked for liveness
2229 * On success, returns true; the lock should be later released with
2230 * cgroup_unlock(). On failure returns false with no lock held.
2232 bool cgroup_lock_live_group(struct cgroup *cgrp)
2234 mutex_lock(&cgroup_mutex);
2235 if (cgroup_is_removed(cgrp)) {
2236 mutex_unlock(&cgroup_mutex);
2241 EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
2243 static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
2246 BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
2247 if (strlen(buffer) >= PATH_MAX)
2249 if (!cgroup_lock_live_group(cgrp))
2251 mutex_lock(&cgroup_root_mutex);
2252 strcpy(cgrp->root->release_agent_path, buffer);
2253 mutex_unlock(&cgroup_root_mutex);
2258 static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
2259 struct seq_file *seq)
2261 if (!cgroup_lock_live_group(cgrp))
2263 seq_puts(seq, cgrp->root->release_agent_path);
2264 seq_putc(seq, '\n');
2269 /* A buffer size big enough for numbers or short strings */
2270 #define CGROUP_LOCAL_BUFFER_SIZE 64
2272 static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2274 const char __user *userbuf,
2275 size_t nbytes, loff_t *unused_ppos)
2277 char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2283 if (nbytes >= sizeof(buffer))
2285 if (copy_from_user(buffer, userbuf, nbytes))
2288 buffer[nbytes] = 0; /* nul-terminate */
2289 if (cft->write_u64) {
2290 u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2293 retval = cft->write_u64(cgrp, cft, val);
2295 s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2298 retval = cft->write_s64(cgrp, cft, val);
2305 static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
2307 const char __user *userbuf,
2308 size_t nbytes, loff_t *unused_ppos)
2310 char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2312 size_t max_bytes = cft->max_write_len;
2313 char *buffer = local_buffer;
2316 max_bytes = sizeof(local_buffer) - 1;
2317 if (nbytes >= max_bytes)
2319 /* Allocate a dynamic buffer if we need one */
2320 if (nbytes >= sizeof(local_buffer)) {
2321 buffer = kmalloc(nbytes + 1, GFP_KERNEL);
2325 if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
2330 buffer[nbytes] = 0; /* nul-terminate */
2331 retval = cft->write_string(cgrp, cft, strstrip(buffer));
2335 if (buffer != local_buffer)
2340 static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
2341 size_t nbytes, loff_t *ppos)
2343 struct cftype *cft = __d_cft(file->f_dentry);
2344 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2346 if (cgroup_is_removed(cgrp))
2349 return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2350 if (cft->write_u64 || cft->write_s64)
2351 return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2352 if (cft->write_string)
2353 return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2355 int ret = cft->trigger(cgrp, (unsigned int)cft->private);
2356 return ret ? ret : nbytes;
2361 static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
2363 char __user *buf, size_t nbytes,
2366 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2367 u64 val = cft->read_u64(cgrp, cft);
2368 int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
2370 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2373 static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
2375 char __user *buf, size_t nbytes,
2378 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2379 s64 val = cft->read_s64(cgrp, cft);
2380 int len = sprintf(tmp, "%lld\n", (long long) val);
2382 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
2385 static ssize_t cgroup_file_read(struct file *file, char __user *buf,
2386 size_t nbytes, loff_t *ppos)
2388 struct cftype *cft = __d_cft(file->f_dentry);
2389 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2391 if (cgroup_is_removed(cgrp))
2395 return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2397 return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2399 return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2404 * seqfile ops/methods for returning structured data. Currently just
2405 * supports string->u64 maps, but can be extended in future.
2408 struct cgroup_seqfile_state {
2410 struct cgroup *cgroup;
2413 static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
2415 struct seq_file *sf = cb->state;
2416 return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
2419 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
2421 struct cgroup_seqfile_state *state = m->private;
2422 struct cftype *cft = state->cft;
2423 if (cft->read_map) {
2424 struct cgroup_map_cb cb = {
2425 .fill = cgroup_map_add,
2428 return cft->read_map(state->cgroup, cft, &cb);
2430 return cft->read_seq_string(state->cgroup, cft, m);
2433 static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2435 struct seq_file *seq = file->private_data;
2436 kfree(seq->private);
2437 return single_release(inode, file);
2440 static const struct file_operations cgroup_seqfile_operations = {
2442 .write = cgroup_file_write,
2443 .llseek = seq_lseek,
2444 .release = cgroup_seqfile_release,
2447 static int cgroup_file_open(struct inode *inode, struct file *file)
2452 err = generic_file_open(inode, file);
2455 cft = __d_cft(file->f_dentry);
2457 if (cft->read_map || cft->read_seq_string) {
2458 struct cgroup_seqfile_state *state =
2459 kzalloc(sizeof(*state), GFP_USER);
2463 state->cgroup = __d_cgrp(file->f_dentry->d_parent);
2464 file->f_op = &cgroup_seqfile_operations;
2465 err = single_open(file, cgroup_seqfile_show, state);
2468 } else if (cft->open)
2469 err = cft->open(inode, file);
2476 static int cgroup_file_release(struct inode *inode, struct file *file)
2478 struct cftype *cft = __d_cft(file->f_dentry);
2480 return cft->release(inode, file);
2485 * cgroup_rename - Only allow simple rename of directories in place.
2487 static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
2488 struct inode *new_dir, struct dentry *new_dentry)
2490 if (!S_ISDIR(old_dentry->d_inode->i_mode))
2492 if (new_dentry->d_inode)
2494 if (old_dir != new_dir)
2496 return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
2499 static const struct file_operations cgroup_file_operations = {
2500 .read = cgroup_file_read,
2501 .write = cgroup_file_write,
2502 .llseek = generic_file_llseek,
2503 .open = cgroup_file_open,
2504 .release = cgroup_file_release,
2507 static const struct inode_operations cgroup_dir_inode_operations = {
2508 .lookup = cgroup_lookup,
2509 .mkdir = cgroup_mkdir,
2510 .rmdir = cgroup_rmdir,
2511 .rename = cgroup_rename,
2514 static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
2516 if (dentry->d_name.len > NAME_MAX)
2517 return ERR_PTR(-ENAMETOOLONG);
2518 d_add(dentry, NULL);
2523 * Check if a file is a control file
2525 static inline struct cftype *__file_cft(struct file *file)
2527 if (file->f_dentry->d_inode->i_fop != &cgroup_file_operations)
2528 return ERR_PTR(-EINVAL);
2529 return __d_cft(file->f_dentry);
2532 static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2533 struct super_block *sb)
2535 struct inode *inode;
2539 if (dentry->d_inode)
2542 inode = cgroup_new_inode(mode, sb);
2546 if (S_ISDIR(mode)) {
2547 inode->i_op = &cgroup_dir_inode_operations;
2548 inode->i_fop = &simple_dir_operations;
2550 /* start off with i_nlink == 2 (for "." entry) */
2553 /* start with the directory inode held, so that we can
2554 * populate it without racing with another mkdir */
2555 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
2556 } else if (S_ISREG(mode)) {
2558 inode->i_fop = &cgroup_file_operations;
2560 d_instantiate(dentry, inode);
2561 dget(dentry); /* Extra count - pin the dentry in core */
2566 * cgroup_create_dir - create a directory for an object.
2567 * @cgrp: the cgroup we create the directory for. It must have a valid
2568 * ->parent field. And we are going to fill its ->dentry field.
2569 * @dentry: dentry of the new cgroup
2570 * @mode: mode to set on new directory.
2572 static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
2575 struct dentry *parent;
2578 parent = cgrp->parent->dentry;
2579 error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
2581 dentry->d_fsdata = cgrp;
2582 inc_nlink(parent->d_inode);
2583 rcu_assign_pointer(cgrp->dentry, dentry);
2592 * cgroup_file_mode - deduce file mode of a control file
2593 * @cft: the control file in question
2595 * returns cft->mode if ->mode is not 0
2596 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
2597 * returns S_IRUGO if it has only a read handler
2598 * returns S_IWUSR if it has only a write hander
2600 static umode_t cgroup_file_mode(const struct cftype *cft)
2607 if (cft->read || cft->read_u64 || cft->read_s64 ||
2608 cft->read_map || cft->read_seq_string)
2611 if (cft->write || cft->write_u64 || cft->write_s64 ||
2612 cft->write_string || cft->trigger)
2618 int cgroup_add_file(struct cgroup *cgrp,
2619 struct cgroup_subsys *subsys,
2620 const struct cftype *cft)
2622 struct dentry *dir = cgrp->dentry;
2623 struct dentry *dentry;
2626 char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2628 /* does @cft->flags tell us to skip creation on @cgrp? */
2629 if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
2631 if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
2634 if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2635 strcpy(name, subsys->name);
2638 strcat(name, cft->name);
2639 BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
2640 dentry = lookup_one_len(name, dir, strlen(name));
2641 if (!IS_ERR(dentry)) {
2642 mode = cgroup_file_mode(cft);
2643 error = cgroup_create_file(dentry, mode | S_IFREG,
2646 dentry->d_fsdata = (void *)cft;
2649 error = PTR_ERR(dentry);
2652 EXPORT_SYMBOL_GPL(cgroup_add_file);
2654 int cgroup_add_files(struct cgroup *cgrp,
2655 struct cgroup_subsys *subsys,
2656 const struct cftype cft[],
2660 for (i = 0; i < count; i++) {
2661 err = cgroup_add_file(cgrp, subsys, &cft[i]);
2667 EXPORT_SYMBOL_GPL(cgroup_add_files);
2669 static DEFINE_MUTEX(cgroup_cft_mutex);
2671 static void cgroup_cfts_prepare(void)
2672 __acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex)
2675 * Thanks to the entanglement with vfs inode locking, we can't walk
2676 * the existing cgroups under cgroup_mutex and create files.
2677 * Instead, we increment reference on all cgroups and build list of
2678 * them using @cgrp->cft_q_node. Grab cgroup_cft_mutex to ensure
2679 * exclusive access to the field.
2681 mutex_lock(&cgroup_cft_mutex);
2682 mutex_lock(&cgroup_mutex);
2685 static void cgroup_cfts_commit(struct cgroup_subsys *ss,
2686 const struct cftype *cfts)
2687 __releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
2690 struct cgroup *cgrp, *n;
2693 while (cfts[count].name[0] != '\0')
2696 /* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
2697 if (cfts && ss->root != &rootnode) {
2698 list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) {
2700 list_add_tail(&cgrp->cft_q_node, &pending);
2704 mutex_unlock(&cgroup_mutex);
2707 * All new cgroups will see @cfts update on @ss->cftsets. Add/rm
2708 * files for all cgroups which were created before.
2710 list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {
2711 struct inode *inode = cgrp->dentry->d_inode;
2713 mutex_lock(&inode->i_mutex);
2714 mutex_lock(&cgroup_mutex);
2715 if (!cgroup_is_removed(cgrp))
2716 cgroup_add_files(cgrp, ss, cfts, count);
2717 mutex_unlock(&cgroup_mutex);
2718 mutex_unlock(&inode->i_mutex);
2720 list_del_init(&cgrp->cft_q_node);
2724 mutex_unlock(&cgroup_cft_mutex);
2728 * cgroup_add_cftypes - add an array of cftypes to a subsystem
2729 * @ss: target cgroup subsystem
2730 * @cfts: zero-length name terminated array of cftypes
2732 * Register @cfts to @ss. Files described by @cfts are created for all
2733 * existing cgroups to which @ss is attached and all future cgroups will
2734 * have them too. This function can be called anytime whether @ss is
2737 * Returns 0 on successful registration, -errno on failure. Note that this
2738 * function currently returns 0 as long as @cfts registration is successful
2739 * even if some file creation attempts on existing cgroups fail.
2741 int cgroup_add_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
2743 struct cftype_set *set;
2745 set = kzalloc(sizeof(*set), GFP_KERNEL);
2749 cgroup_cfts_prepare();
2751 list_add_tail(&set->node, &ss->cftsets);
2752 cgroup_cfts_commit(ss, cfts);
2756 EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
2759 * cgroup_task_count - count the number of tasks in a cgroup.
2760 * @cgrp: the cgroup in question
2762 * Return the number of tasks in the cgroup.
2764 int cgroup_task_count(const struct cgroup *cgrp)
2767 struct cg_cgroup_link *link;
2769 read_lock(&css_set_lock);
2770 list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2771 count += atomic_read(&link->cg->refcount);
2773 read_unlock(&css_set_lock);
2778 * Advance a list_head iterator. The iterator should be positioned at
2779 * the start of a css_set
2781 static void cgroup_advance_iter(struct cgroup *cgrp,
2782 struct cgroup_iter *it)
2784 struct list_head *l = it->cg_link;
2785 struct cg_cgroup_link *link;
2788 /* Advance to the next non-empty css_set */
2791 if (l == &cgrp->css_sets) {
2795 link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2797 } while (list_empty(&cg->tasks));
2799 it->task = cg->tasks.next;
2803 * To reduce the fork() overhead for systems that are not actually
2804 * using their cgroups capability, we don't maintain the lists running
2805 * through each css_set to its tasks until we see the list actually
2806 * used - in other words after the first call to cgroup_iter_start().
2808 static void cgroup_enable_task_cg_lists(void)
2810 struct task_struct *p, *g;
2811 write_lock(&css_set_lock);
2812 use_task_css_set_links = 1;
2814 * We need tasklist_lock because RCU is not safe against
2815 * while_each_thread(). Besides, a forking task that has passed
2816 * cgroup_post_fork() without seeing use_task_css_set_links = 1
2817 * is not guaranteed to have its child immediately visible in the
2818 * tasklist if we walk through it with RCU.
2820 read_lock(&tasklist_lock);
2821 do_each_thread(g, p) {
2824 * We should check if the process is exiting, otherwise
2825 * it will race with cgroup_exit() in that the list
2826 * entry won't be deleted though the process has exited.
2828 if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
2829 list_add(&p->cg_list, &p->cgroups->tasks);
2831 } while_each_thread(g, p);
2832 read_unlock(&tasklist_lock);
2833 write_unlock(&css_set_lock);
2836 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
2837 __acquires(css_set_lock)
2840 * The first time anyone tries to iterate across a cgroup,
2841 * we need to enable the list linking each css_set to its
2842 * tasks, and fix up all existing tasks.
2844 if (!use_task_css_set_links)
2845 cgroup_enable_task_cg_lists();
2847 read_lock(&css_set_lock);
2848 it->cg_link = &cgrp->css_sets;
2849 cgroup_advance_iter(cgrp, it);
2852 struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
2853 struct cgroup_iter *it)
2855 struct task_struct *res;
2856 struct list_head *l = it->task;
2857 struct cg_cgroup_link *link;
2859 /* If the iterator cg is NULL, we have no tasks */
2862 res = list_entry(l, struct task_struct, cg_list);
2863 /* Advance iterator to find next entry */
2865 link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
2866 if (l == &link->cg->tasks) {
2867 /* We reached the end of this task list - move on to
2868 * the next cg_cgroup_link */
2869 cgroup_advance_iter(cgrp, it);
2876 void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
2877 __releases(css_set_lock)
2879 read_unlock(&css_set_lock);
2882 static inline int started_after_time(struct task_struct *t1,
2883 struct timespec *time,
2884 struct task_struct *t2)
2886 int start_diff = timespec_compare(&t1->start_time, time);
2887 if (start_diff > 0) {
2889 } else if (start_diff < 0) {
2893 * Arbitrarily, if two processes started at the same
2894 * time, we'll say that the lower pointer value
2895 * started first. Note that t2 may have exited by now
2896 * so this may not be a valid pointer any longer, but
2897 * that's fine - it still serves to distinguish
2898 * between two tasks started (effectively) simultaneously.
2905 * This function is a callback from heap_insert() and is used to order
2907 * In this case we order the heap in descending task start time.
2909 static inline int started_after(void *p1, void *p2)
2911 struct task_struct *t1 = p1;
2912 struct task_struct *t2 = p2;
2913 return started_after_time(t1, &t2->start_time, t2);
2917 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
2918 * @scan: struct cgroup_scanner containing arguments for the scan
2920 * Arguments include pointers to callback functions test_task() and
2922 * Iterate through all the tasks in a cgroup, calling test_task() for each,
2923 * and if it returns true, call process_task() for it also.
2924 * The test_task pointer may be NULL, meaning always true (select all tasks).
2925 * Effectively duplicates cgroup_iter_{start,next,end}()
2926 * but does not lock css_set_lock for the call to process_task().
2927 * The struct cgroup_scanner may be embedded in any structure of the caller's
2929 * It is guaranteed that process_task() will act on every task that
2930 * is a member of the cgroup for the duration of this call. This
2931 * function may or may not call process_task() for tasks that exit
2932 * or move to a different cgroup during the call, or are forked or
2933 * move into the cgroup during the call.
2935 * Note that test_task() may be called with locks held, and may in some
2936 * situations be called multiple times for the same task, so it should
2938 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
2939 * pre-allocated and will be used for heap operations (and its "gt" member will
2940 * be overwritten), else a temporary heap will be used (allocation of which
2941 * may cause this function to fail).
2943 int cgroup_scan_tasks(struct cgroup_scanner *scan)
2946 struct cgroup_iter it;
2947 struct task_struct *p, *dropped;
2948 /* Never dereference latest_task, since it's not refcounted */
2949 struct task_struct *latest_task = NULL;
2950 struct ptr_heap tmp_heap;
2951 struct ptr_heap *heap;
2952 struct timespec latest_time = { 0, 0 };
2955 /* The caller supplied our heap and pre-allocated its memory */
2957 heap->gt = &started_after;
2959 /* We need to allocate our own heap memory */
2961 retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
2963 /* cannot allocate the heap */
2969 * Scan tasks in the cgroup, using the scanner's "test_task" callback
2970 * to determine which are of interest, and using the scanner's
2971 * "process_task" callback to process any of them that need an update.
2972 * Since we don't want to hold any locks during the task updates,
2973 * gather tasks to be processed in a heap structure.
2974 * The heap is sorted by descending task start time.
2975 * If the statically-sized heap fills up, we overflow tasks that
2976 * started later, and in future iterations only consider tasks that
2977 * started after the latest task in the previous pass. This
2978 * guarantees forward progress and that we don't miss any tasks.
2981 cgroup_iter_start(scan->cg, &it);
2982 while ((p = cgroup_iter_next(scan->cg, &it))) {
2984 * Only affect tasks that qualify per the caller's callback,
2985 * if he provided one
2987 if (scan->test_task && !scan->test_task(p, scan))
2990 * Only process tasks that started after the last task
2993 if (!started_after_time(p, &latest_time, latest_task))
2995 dropped = heap_insert(heap, p);
2996 if (dropped == NULL) {
2998 * The new task was inserted; the heap wasn't
3002 } else if (dropped != p) {
3004 * The new task was inserted, and pushed out a
3008 put_task_struct(dropped);
3011 * Else the new task was newer than anything already in
3012 * the heap and wasn't inserted
3015 cgroup_iter_end(scan->cg, &it);
3018 for (i = 0; i < heap->size; i++) {
3019 struct task_struct *q = heap->ptrs[i];
3021 latest_time = q->start_time;
3024 /* Process the task per the caller's callback */
3025 scan->process_task(q, scan);
3029 * If we had to process any tasks at all, scan again
3030 * in case some of them were in the middle of forking
3031 * children that didn't get processed.
3032 * Not the most efficient way to do it, but it avoids
3033 * having to take callback_mutex in the fork path
3037 if (heap == &tmp_heap)
3038 heap_free(&tmp_heap);
3043 * Stuff for reading the 'tasks'/'procs' files.
3045 * Reading this file can return large amounts of data if a cgroup has
3046 * *lots* of attached tasks. So it may need several calls to read(),
3047 * but we cannot guarantee that the information we produce is correct
3048 * unless we produce it entirely atomically.
3052 /* which pidlist file are we talking about? */
3053 enum cgroup_filetype {
3059 * A pidlist is a list of pids that virtually represents the contents of one
3060 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
3061 * a pair (one each for procs, tasks) for each pid namespace that's relevant
3064 struct cgroup_pidlist {
3066 * used to find which pidlist is wanted. doesn't change as long as
3067 * this particular list stays in the list.
3069 struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
3072 /* how many elements the above list has */
3074 /* how many files are using the current array */
3076 /* each of these stored in a list by its cgroup */
3077 struct list_head links;
3078 /* pointer to the cgroup we belong to, for list removal purposes */
3079 struct cgroup *owner;
3080 /* protects the other fields */
3081 struct rw_semaphore mutex;
3085 * The following two functions "fix" the issue where there are more pids
3086 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
3087 * TODO: replace with a kernel-wide solution to this problem
3089 #define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
3090 static void *pidlist_allocate(int count)
3092 if (PIDLIST_TOO_LARGE(count))
3093 return vmalloc(count * sizeof(pid_t));
3095 return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
3097 static void pidlist_free(void *p)
3099 if (is_vmalloc_addr(p))
3104 static void *pidlist_resize(void *p, int newcount)
3107 /* note: if new alloc fails, old p will still be valid either way */
3108 if (is_vmalloc_addr(p)) {
3109 newlist = vmalloc(newcount * sizeof(pid_t));
3112 memcpy(newlist, p, newcount * sizeof(pid_t));
3115 newlist = krealloc(p, newcount * sizeof(pid_t), GFP_KERNEL);
3121 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3122 * If the new stripped list is sufficiently smaller and there's enough memory
3123 * to allocate a new buffer, will let go of the unneeded memory. Returns the
3124 * number of unique elements.
3126 /* is the size difference enough that we should re-allocate the array? */
3127 #define PIDLIST_REALLOC_DIFFERENCE(old, new) ((old) - PAGE_SIZE >= (new))
3128 static int pidlist_uniq(pid_t **p, int length)
3135 * we presume the 0th element is unique, so i starts at 1. trivial
3136 * edge cases first; no work needs to be done for either
3138 if (length == 0 || length == 1)
3140 /* src and dest walk down the list; dest counts unique elements */
3141 for (src = 1; src < length; src++) {
3142 /* find next unique element */
3143 while (list[src] == list[src-1]) {
3148 /* dest always points to where the next unique element goes */
3149 list[dest] = list[src];
3154 * if the length difference is large enough, we want to allocate a
3155 * smaller buffer to save memory. if this fails due to out of memory,
3156 * we'll just stay with what we've got.
3158 if (PIDLIST_REALLOC_DIFFERENCE(length, dest)) {
3159 newlist = pidlist_resize(list, dest);
3166 static int cmppid(const void *a, const void *b)
3168 return *(pid_t *)a - *(pid_t *)b;
3172 * find the appropriate pidlist for our purpose (given procs vs tasks)
3173 * returns with the lock on that pidlist already held, and takes care
3174 * of the use count, or returns NULL with no locks held if we're out of
3177 static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
3178 enum cgroup_filetype type)
3180 struct cgroup_pidlist *l;
3181 /* don't need task_nsproxy() if we're looking at ourself */
3182 struct pid_namespace *ns = current->nsproxy->pid_ns;
3185 * We can't drop the pidlist_mutex before taking the l->mutex in case
3186 * the last ref-holder is trying to remove l from the list at the same
3187 * time. Holding the pidlist_mutex precludes somebody taking whichever
3188 * list we find out from under us - compare release_pid_array().
3190 mutex_lock(&cgrp->pidlist_mutex);
3191 list_for_each_entry(l, &cgrp->pidlists, links) {
3192 if (l->key.type == type && l->key.ns == ns) {
3193 /* make sure l doesn't vanish out from under us */
3194 down_write(&l->mutex);
3195 mutex_unlock(&cgrp->pidlist_mutex);
3199 /* entry not found; create a new one */
3200 l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
3202 mutex_unlock(&cgrp->pidlist_mutex);
3205 init_rwsem(&l->mutex);
3206 down_write(&l->mutex);
3208 l->key.ns = get_pid_ns(ns);
3209 l->use_count = 0; /* don't increment here */
3212 list_add(&l->links, &cgrp->pidlists);
3213 mutex_unlock(&cgrp->pidlist_mutex);
3218 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
3220 static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
3221 struct cgroup_pidlist **lp)
3225 int pid, n = 0; /* used for populating the array */
3226 struct cgroup_iter it;
3227 struct task_struct *tsk;
3228 struct cgroup_pidlist *l;
3231 * If cgroup gets more users after we read count, we won't have
3232 * enough space - tough. This race is indistinguishable to the
3233 * caller from the case that the additional cgroup users didn't
3234 * show up until sometime later on.
3236 length = cgroup_task_count(cgrp);
3237 array = pidlist_allocate(length);
3240 /* now, populate the array */
3241 cgroup_iter_start(cgrp, &it);
3242 while ((tsk = cgroup_iter_next(cgrp, &it))) {
3243 if (unlikely(n == length))
3245 /* get tgid or pid for procs or tasks file respectively */
3246 if (type == CGROUP_FILE_PROCS)
3247 pid = task_tgid_vnr(tsk);
3249 pid = task_pid_vnr(tsk);
3250 if (pid > 0) /* make sure to only use valid results */
3253 cgroup_iter_end(cgrp, &it);
3255 /* now sort & (if procs) strip out duplicates */
3256 sort(array, length, sizeof(pid_t), cmppid, NULL);
3257 if (type == CGROUP_FILE_PROCS)
3258 length = pidlist_uniq(&array, length);
3259 l = cgroup_pidlist_find(cgrp, type);
3261 pidlist_free(array);
3264 /* store array, freeing old if necessary - lock already held */
3265 pidlist_free(l->list);
3269 up_write(&l->mutex);
3275 * cgroupstats_build - build and fill cgroupstats
3276 * @stats: cgroupstats to fill information into
3277 * @dentry: A dentry entry belonging to the cgroup for which stats have
3280 * Build and fill cgroupstats so that taskstats can export it to user
3283 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
3286 struct cgroup *cgrp;
3287 struct cgroup_iter it;
3288 struct task_struct *tsk;
3291 * Validate dentry by checking the superblock operations,
3292 * and make sure it's a directory.
3294 if (dentry->d_sb->s_op != &cgroup_ops ||
3295 !S_ISDIR(dentry->d_inode->i_mode))
3299 cgrp = dentry->d_fsdata;
3301 cgroup_iter_start(cgrp, &it);
3302 while ((tsk = cgroup_iter_next(cgrp, &it))) {
3303 switch (tsk->state) {
3305 stats->nr_running++;
3307 case TASK_INTERRUPTIBLE:
3308 stats->nr_sleeping++;
3310 case TASK_UNINTERRUPTIBLE:
3311 stats->nr_uninterruptible++;
3314 stats->nr_stopped++;
3317 if (delayacct_is_task_waiting_on_io(tsk))
3318 stats->nr_io_wait++;
3322 cgroup_iter_end(cgrp, &it);
3330 * seq_file methods for the tasks/procs files. The seq_file position is the
3331 * next pid to display; the seq_file iterator is a pointer to the pid
3332 * in the cgroup->l->list array.
3335 static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3338 * Initially we receive a position value that corresponds to
3339 * one more than the last pid shown (or 0 on the first call or
3340 * after a seek to the start). Use a binary-search to find the
3341 * next pid to display, if any
3343 struct cgroup_pidlist *l = s->private;
3344 int index = 0, pid = *pos;
3347 down_read(&l->mutex);
3349 int end = l->length;
3351 while (index < end) {
3352 int mid = (index + end) / 2;
3353 if (l->list[mid] == pid) {
3356 } else if (l->list[mid] <= pid)
3362 /* If we're off the end of the array, we're done */
3363 if (index >= l->length)
3365 /* Update the abstract position to be the actual pid that we found */
3366 iter = l->list + index;
3371 static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3373 struct cgroup_pidlist *l = s->private;
3377 static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3379 struct cgroup_pidlist *l = s->private;
3381 pid_t *end = l->list + l->length;
3383 * Advance to the next pid in the array. If this goes off the
3395 static int cgroup_pidlist_show(struct seq_file *s, void *v)
3397 return seq_printf(s, "%d\n", *(int *)v);
3401 * seq_operations functions for iterating on pidlists through seq_file -
3402 * independent of whether it's tasks or procs
3404 static const struct seq_operations cgroup_pidlist_seq_operations = {
3405 .start = cgroup_pidlist_start,
3406 .stop = cgroup_pidlist_stop,
3407 .next = cgroup_pidlist_next,
3408 .show = cgroup_pidlist_show,
3411 static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3414 * the case where we're the last user of this particular pidlist will
3415 * have us remove it from the cgroup's list, which entails taking the
3416 * mutex. since in pidlist_find the pidlist->lock depends on cgroup->
3417 * pidlist_mutex, we have to take pidlist_mutex first.
3419 mutex_lock(&l->owner->pidlist_mutex);
3420 down_write(&l->mutex);
3421 BUG_ON(!l->use_count);
3422 if (!--l->use_count) {
3423 /* we're the last user if refcount is 0; remove and free */
3424 list_del(&l->links);
3425 mutex_unlock(&l->owner->pidlist_mutex);
3426 pidlist_free(l->list);
3427 put_pid_ns(l->key.ns);
3428 up_write(&l->mutex);
3432 mutex_unlock(&l->owner->pidlist_mutex);
3433 up_write(&l->mutex);
3436 static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3438 struct cgroup_pidlist *l;
3439 if (!(file->f_mode & FMODE_READ))
3442 * the seq_file will only be initialized if the file was opened for
3443 * reading; hence we check if it's not null only in that case.
3445 l = ((struct seq_file *)file->private_data)->private;
3446 cgroup_release_pid_array(l);
3447 return seq_release(inode, file);
3450 static const struct file_operations cgroup_pidlist_operations = {
3452 .llseek = seq_lseek,
3453 .write = cgroup_file_write,
3454 .release = cgroup_pidlist_release,
3458 * The following functions handle opens on a file that displays a pidlist
3459 * (tasks or procs). Prepare an array of the process/thread IDs of whoever's
3462 /* helper function for the two below it */
3463 static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3465 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3466 struct cgroup_pidlist *l;
3469 /* Nothing to do for write-only files */
3470 if (!(file->f_mode & FMODE_READ))
3473 /* have the array populated */
3474 retval = pidlist_array_load(cgrp, type, &l);
3477 /* configure file information */
3478 file->f_op = &cgroup_pidlist_operations;
3480 retval = seq_open(file, &cgroup_pidlist_seq_operations);
3482 cgroup_release_pid_array(l);
3485 ((struct seq_file *)file->private_data)->private = l;
3488 static int cgroup_tasks_open(struct inode *unused, struct file *file)
3490 return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3492 static int cgroup_procs_open(struct inode *unused, struct file *file)
3494 return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3497 static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3500 return notify_on_release(cgrp);
3503 static int cgroup_write_notify_on_release(struct cgroup *cgrp,
3507 clear_bit(CGRP_RELEASABLE, &cgrp->flags);
3509 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3511 clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3516 * Unregister event and free resources.
3518 * Gets called from workqueue.
3520 static void cgroup_event_remove(struct work_struct *work)
3522 struct cgroup_event *event = container_of(work, struct cgroup_event,
3524 struct cgroup *cgrp = event->cgrp;
3526 event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3528 eventfd_ctx_put(event->eventfd);
3534 * Gets called on POLLHUP on eventfd when user closes it.
3536 * Called with wqh->lock held and interrupts disabled.
3538 static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
3539 int sync, void *key)
3541 struct cgroup_event *event = container_of(wait,
3542 struct cgroup_event, wait);
3543 struct cgroup *cgrp = event->cgrp;
3544 unsigned long flags = (unsigned long)key;
3546 if (flags & POLLHUP) {
3547 __remove_wait_queue(event->wqh, &event->wait);
3548 spin_lock(&cgrp->event_list_lock);
3549 list_del(&event->list);
3550 spin_unlock(&cgrp->event_list_lock);
3552 * We are in atomic context, but cgroup_event_remove() may
3553 * sleep, so we have to call it in workqueue.
3555 schedule_work(&event->remove);
3561 static void cgroup_event_ptable_queue_proc(struct file *file,
3562 wait_queue_head_t *wqh, poll_table *pt)
3564 struct cgroup_event *event = container_of(pt,
3565 struct cgroup_event, pt);
3568 add_wait_queue(wqh, &event->wait);
3572 * Parse input and register new cgroup event handler.
3574 * Input must be in format '<event_fd> <control_fd> <args>'.
3575 * Interpretation of args is defined by control file implementation.
3577 static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
3580 struct cgroup_event *event = NULL;
3581 unsigned int efd, cfd;
3582 struct file *efile = NULL;
3583 struct file *cfile = NULL;
3587 efd = simple_strtoul(buffer, &endp, 10);
3592 cfd = simple_strtoul(buffer, &endp, 10);
3593 if ((*endp != ' ') && (*endp != '\0'))
3597 event = kzalloc(sizeof(*event), GFP_KERNEL);
3601 INIT_LIST_HEAD(&event->list);
3602 init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
3603 init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
3604 INIT_WORK(&event->remove, cgroup_event_remove);
3606 efile = eventfd_fget(efd);
3607 if (IS_ERR(efile)) {
3608 ret = PTR_ERR(efile);
3612 event->eventfd = eventfd_ctx_fileget(efile);
3613 if (IS_ERR(event->eventfd)) {
3614 ret = PTR_ERR(event->eventfd);
3624 /* the process need read permission on control file */
3625 /* AV: shouldn't we check that it's been opened for read instead? */
3626 ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
3630 event->cft = __file_cft(cfile);
3631 if (IS_ERR(event->cft)) {
3632 ret = PTR_ERR(event->cft);
3636 if (!event->cft->register_event || !event->cft->unregister_event) {
3641 ret = event->cft->register_event(cgrp, event->cft,
3642 event->eventfd, buffer);
3646 if (efile->f_op->poll(efile, &event->pt) & POLLHUP) {
3647 event->cft->unregister_event(cgrp, event->cft, event->eventfd);
3653 * Events should be removed after rmdir of cgroup directory, but before
3654 * destroying subsystem state objects. Let's take reference to cgroup
3655 * directory dentry to do that.
3659 spin_lock(&cgrp->event_list_lock);
3660 list_add(&event->list, &cgrp->event_list);
3661 spin_unlock(&cgrp->event_list_lock);
3672 if (event && event->eventfd && !IS_ERR(event->eventfd))
3673 eventfd_ctx_put(event->eventfd);
3675 if (!IS_ERR_OR_NULL(efile))
3683 static u64 cgroup_clone_children_read(struct cgroup *cgrp,
3686 return clone_children(cgrp);
3689 static int cgroup_clone_children_write(struct cgroup *cgrp,
3694 set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3696 clear_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3701 * for the common functions, 'private' gives the type of file
3703 /* for hysterical raisins, we can't put this on the older files */
3704 #define CGROUP_FILE_GENERIC_PREFIX "cgroup."
3705 static struct cftype files[] = {
3708 .open = cgroup_tasks_open,
3709 .write_u64 = cgroup_tasks_write,
3710 .release = cgroup_pidlist_release,
3711 .mode = S_IRUGO | S_IWUSR,
3714 .name = CGROUP_FILE_GENERIC_PREFIX "procs",
3715 .open = cgroup_procs_open,
3716 .write_u64 = cgroup_procs_write,
3717 .release = cgroup_pidlist_release,
3718 .mode = S_IRUGO | S_IWUSR,
3721 .name = "notify_on_release",
3722 .read_u64 = cgroup_read_notify_on_release,
3723 .write_u64 = cgroup_write_notify_on_release,
3726 .name = CGROUP_FILE_GENERIC_PREFIX "event_control",
3727 .write_string = cgroup_write_event_control,
3731 .name = "cgroup.clone_children",
3732 .read_u64 = cgroup_clone_children_read,
3733 .write_u64 = cgroup_clone_children_write,
3736 .name = "release_agent",
3737 .flags = CFTYPE_ONLY_ON_ROOT,
3738 .read_seq_string = cgroup_release_agent_show,
3739 .write_string = cgroup_release_agent_write,
3740 .max_write_len = PATH_MAX,
3744 static int cgroup_populate_dir(struct cgroup *cgrp)
3747 struct cgroup_subsys *ss;
3749 err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));
3753 /* process cftsets of each subsystem */
3754 for_each_subsys(cgrp->root, ss) {
3755 struct cftype_set *set;
3757 if (ss->populate && (err = ss->populate(ss, cgrp)) < 0)
3760 list_for_each_entry(set, &ss->cftsets, node) {
3761 const struct cftype *cft;
3763 for (cft = set->cfts; cft->name[0] != '\0'; cft++) {
3764 err = cgroup_add_file(cgrp, ss, cft);
3766 pr_warning("cgroup_populate_dir: failed to create %s, err=%d\n",
3772 /* This cgroup is ready now */
3773 for_each_subsys(cgrp->root, ss) {
3774 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
3776 * Update id->css pointer and make this css visible from
3777 * CSS ID functions. This pointer will be dereferened
3778 * from RCU-read-side without locks.
3781 rcu_assign_pointer(css->id->css, css);
3787 static void init_cgroup_css(struct cgroup_subsys_state *css,
3788 struct cgroup_subsys *ss,
3789 struct cgroup *cgrp)
3792 atomic_set(&css->refcnt, 1);
3795 if (cgrp == dummytop)
3796 set_bit(CSS_ROOT, &css->flags);
3797 BUG_ON(cgrp->subsys[ss->subsys_id]);
3798 cgrp->subsys[ss->subsys_id] = css;
3801 static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
3803 /* We need to take each hierarchy_mutex in a consistent order */
3807 * No worry about a race with rebind_subsystems that might mess up the
3808 * locking order, since both parties are under cgroup_mutex.
3810 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3811 struct cgroup_subsys *ss = subsys[i];
3814 if (ss->root == root)
3815 mutex_lock(&ss->hierarchy_mutex);
3819 static void cgroup_unlock_hierarchy(struct cgroupfs_root *root)
3823 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3824 struct cgroup_subsys *ss = subsys[i];
3827 if (ss->root == root)
3828 mutex_unlock(&ss->hierarchy_mutex);
3833 * cgroup_create - create a cgroup
3834 * @parent: cgroup that will be parent of the new cgroup
3835 * @dentry: dentry of the new cgroup
3836 * @mode: mode to set on new inode
3838 * Must be called with the mutex on the parent inode held
3840 static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
3843 struct cgroup *cgrp;
3844 struct cgroupfs_root *root = parent->root;
3846 struct cgroup_subsys *ss;
3847 struct super_block *sb = root->sb;
3849 cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
3853 /* Grab a reference on the superblock so the hierarchy doesn't
3854 * get deleted on unmount if there are child cgroups. This
3855 * can be done outside cgroup_mutex, since the sb can't
3856 * disappear while someone has an open control file on the
3858 atomic_inc(&sb->s_active);
3860 mutex_lock(&cgroup_mutex);
3862 init_cgroup_housekeeping(cgrp);
3864 cgrp->parent = parent;
3865 cgrp->root = parent->root;
3866 cgrp->top_cgroup = parent->top_cgroup;
3868 if (notify_on_release(parent))
3869 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
3871 if (clone_children(parent))
3872 set_bit(CGRP_CLONE_CHILDREN, &cgrp->flags);
3874 for_each_subsys(root, ss) {
3875 struct cgroup_subsys_state *css = ss->create(cgrp);
3881 init_cgroup_css(css, ss, cgrp);
3883 err = alloc_css_id(ss, parent, cgrp);
3887 /* At error, ->destroy() callback has to free assigned ID. */
3888 if (clone_children(parent) && ss->post_clone)
3889 ss->post_clone(cgrp);
3892 cgroup_lock_hierarchy(root);
3893 list_add(&cgrp->sibling, &cgrp->parent->children);
3894 cgroup_unlock_hierarchy(root);
3895 root->number_of_cgroups++;
3897 err = cgroup_create_dir(cgrp, dentry, mode);
3901 /* The cgroup directory was pre-locked for us */
3902 BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
3904 list_add_tail(&cgrp->allcg_node, &root->allcg_list);
3906 err = cgroup_populate_dir(cgrp);
3907 /* If err < 0, we have a half-filled directory - oh well ;) */
3909 mutex_unlock(&cgroup_mutex);
3910 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
3916 cgroup_lock_hierarchy(root);
3917 list_del(&cgrp->sibling);
3918 cgroup_unlock_hierarchy(root);
3919 root->number_of_cgroups--;
3923 for_each_subsys(root, ss) {
3924 if (cgrp->subsys[ss->subsys_id])
3928 mutex_unlock(&cgroup_mutex);
3930 /* Release the reference count that we took on the superblock */
3931 deactivate_super(sb);
3937 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3939 struct cgroup *c_parent = dentry->d_parent->d_fsdata;
3941 /* the vfs holds inode->i_mutex already */
3942 return cgroup_create(c_parent, dentry, mode | S_IFDIR);
3945 static int cgroup_has_css_refs(struct cgroup *cgrp)
3947 /* Check the reference count on each subsystem. Since we
3948 * already established that there are no tasks in the
3949 * cgroup, if the css refcount is also 1, then there should
3950 * be no outstanding references, so the subsystem is safe to
3951 * destroy. We scan across all subsystems rather than using
3952 * the per-hierarchy linked list of mounted subsystems since
3953 * we can be called via check_for_release() with no
3954 * synchronization other than RCU, and the subsystem linked
3955 * list isn't RCU-safe */
3958 * We won't need to lock the subsys array, because the subsystems
3959 * we're concerned about aren't going anywhere since our cgroup root
3960 * has a reference on them.
3962 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3963 struct cgroup_subsys *ss = subsys[i];
3964 struct cgroup_subsys_state *css;
3965 /* Skip subsystems not present or not in this hierarchy */
3966 if (ss == NULL || ss->root != cgrp->root)
3968 css = cgrp->subsys[ss->subsys_id];
3969 /* When called from check_for_release() it's possible
3970 * that by this point the cgroup has been removed
3971 * and the css deleted. But a false-positive doesn't
3972 * matter, since it can only happen if the cgroup
3973 * has been deleted and hence no longer needs the
3974 * release agent to be called anyway. */
3975 if (css && (atomic_read(&css->refcnt) > 1))
3982 * Atomically mark all (or else none) of the cgroup's CSS objects as
3983 * CSS_REMOVED. Return true on success, or false if the cgroup has
3984 * busy subsystems. Call with cgroup_mutex held
3987 static int cgroup_clear_css_refs(struct cgroup *cgrp)
3989 struct cgroup_subsys *ss;
3990 unsigned long flags;
3991 bool failed = false;
3992 local_irq_save(flags);
3993 for_each_subsys(cgrp->root, ss) {
3994 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
3997 /* We can only remove a CSS with a refcnt==1 */
3998 refcnt = atomic_read(&css->refcnt);
4005 * Drop the refcnt to 0 while we check other
4006 * subsystems. This will cause any racing
4007 * css_tryget() to spin until we set the
4008 * CSS_REMOVED bits or abort
4010 if (atomic_cmpxchg(&css->refcnt, refcnt, 0) == refcnt)
4016 for_each_subsys(cgrp->root, ss) {
4017 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4020 * Restore old refcnt if we previously managed
4021 * to clear it from 1 to 0
4023 if (!atomic_read(&css->refcnt))
4024 atomic_set(&css->refcnt, 1);
4026 /* Commit the fact that the CSS is removed */
4027 set_bit(CSS_REMOVED, &css->flags);
4030 local_irq_restore(flags);
4034 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
4036 struct cgroup *cgrp = dentry->d_fsdata;
4038 struct cgroup *parent;
4040 struct cgroup_event *event, *tmp;
4043 /* the vfs holds both inode->i_mutex already */
4045 mutex_lock(&cgroup_mutex);
4046 if (atomic_read(&cgrp->count) != 0) {
4047 mutex_unlock(&cgroup_mutex);
4050 if (!list_empty(&cgrp->children)) {
4051 mutex_unlock(&cgroup_mutex);
4054 mutex_unlock(&cgroup_mutex);
4057 * In general, subsystem has no css->refcnt after pre_destroy(). But
4058 * in racy cases, subsystem may have to get css->refcnt after
4059 * pre_destroy() and it makes rmdir return with -EBUSY. This sometimes
4060 * make rmdir return -EBUSY too often. To avoid that, we use waitqueue
4061 * for cgroup's rmdir. CGRP_WAIT_ON_RMDIR is for synchronizing rmdir
4062 * and subsystem's reference count handling. Please see css_get/put
4063 * and css_tryget() and cgroup_wakeup_rmdir_waiter() implementation.
4065 set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4068 * Call pre_destroy handlers of subsys. Notify subsystems
4069 * that rmdir() request comes.
4071 ret = cgroup_call_pre_destroy(cgrp);
4073 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4077 mutex_lock(&cgroup_mutex);
4078 parent = cgrp->parent;
4079 if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
4080 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4081 mutex_unlock(&cgroup_mutex);
4084 prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
4085 if (!cgroup_clear_css_refs(cgrp)) {
4086 mutex_unlock(&cgroup_mutex);
4088 * Because someone may call cgroup_wakeup_rmdir_waiter() before
4089 * prepare_to_wait(), we need to check this flag.
4091 if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))
4093 finish_wait(&cgroup_rmdir_waitq, &wait);
4094 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4095 if (signal_pending(current))
4099 /* NO css_tryget() can success after here. */
4100 finish_wait(&cgroup_rmdir_waitq, &wait);
4101 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
4103 raw_spin_lock(&release_list_lock);
4104 set_bit(CGRP_REMOVED, &cgrp->flags);
4105 if (!list_empty(&cgrp->release_list))
4106 list_del_init(&cgrp->release_list);
4107 raw_spin_unlock(&release_list_lock);
4109 cgroup_lock_hierarchy(cgrp->root);
4110 /* delete this cgroup from parent->children */
4111 list_del_init(&cgrp->sibling);
4112 cgroup_unlock_hierarchy(cgrp->root);
4114 list_del_init(&cgrp->allcg_node);
4116 d = dget(cgrp->dentry);
4118 cgroup_d_remove_dir(d);
4121 set_bit(CGRP_RELEASABLE, &parent->flags);
4122 check_for_release(parent);
4125 * Unregister events and notify userspace.
4126 * Notify userspace about cgroup removing only after rmdir of cgroup
4127 * directory to avoid race between userspace and kernelspace
4129 spin_lock(&cgrp->event_list_lock);
4130 list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
4131 list_del(&event->list);
4132 remove_wait_queue(event->wqh, &event->wait);
4133 eventfd_signal(event->eventfd, 1);
4134 schedule_work(&event->remove);
4136 spin_unlock(&cgrp->event_list_lock);
4138 mutex_unlock(&cgroup_mutex);
4142 static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
4144 INIT_LIST_HEAD(&ss->cftsets);
4147 * base_cftset is embedded in subsys itself, no need to worry about
4150 if (ss->base_cftypes) {
4151 ss->base_cftset.cfts = ss->base_cftypes;
4152 list_add_tail(&ss->base_cftset.node, &ss->cftsets);
4156 static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4158 struct cgroup_subsys_state *css;
4160 printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4162 /* init base cftset */
4163 cgroup_init_cftsets(ss);
4165 /* Create the top cgroup state for this subsystem */
4166 list_add(&ss->sibling, &rootnode.subsys_list);
4167 ss->root = &rootnode;
4168 css = ss->create(dummytop);
4169 /* We don't handle early failures gracefully */
4170 BUG_ON(IS_ERR(css));
4171 init_cgroup_css(css, ss, dummytop);
4173 /* Update the init_css_set to contain a subsys
4174 * pointer to this state - since the subsystem is
4175 * newly registered, all tasks and hence the
4176 * init_css_set is in the subsystem's top cgroup. */
4177 init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
4179 need_forkexit_callback |= ss->fork || ss->exit;
4181 /* At system boot, before all subsystems have been
4182 * registered, no tasks have been forked, so we don't
4183 * need to invoke fork callbacks here. */
4184 BUG_ON(!list_empty(&init_task.tasks));
4186 mutex_init(&ss->hierarchy_mutex);
4187 lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
4190 /* this function shouldn't be used with modular subsystems, since they
4191 * need to register a subsys_id, among other things */
4196 * cgroup_load_subsys: load and register a modular subsystem at runtime
4197 * @ss: the subsystem to load
4199 * This function should be called in a modular subsystem's initcall. If the
4200 * subsystem is built as a module, it will be assigned a new subsys_id and set
4201 * up for use. If the subsystem is built-in anyway, work is delegated to the
4202 * simpler cgroup_init_subsys.
4204 int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
4207 struct cgroup_subsys_state *css;
4209 /* check name and function validity */
4210 if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
4211 ss->create == NULL || ss->destroy == NULL)
4215 * we don't support callbacks in modular subsystems. this check is
4216 * before the ss->module check for consistency; a subsystem that could
4217 * be a module should still have no callbacks even if the user isn't
4218 * compiling it as one.
4220 if (ss->fork || ss->exit)
4224 * an optionally modular subsystem is built-in: we want to do nothing,
4225 * since cgroup_init_subsys will have already taken care of it.
4227 if (ss->module == NULL) {
4228 /* a few sanity checks */
4229 BUG_ON(ss->subsys_id >= CGROUP_BUILTIN_SUBSYS_COUNT);
4230 BUG_ON(subsys[ss->subsys_id] != ss);
4234 /* init base cftset */
4235 cgroup_init_cftsets(ss);
4238 * need to register a subsys id before anything else - for example,
4239 * init_cgroup_css needs it.
4241 mutex_lock(&cgroup_mutex);
4242 /* find the first empty slot in the array */
4243 for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
4244 if (subsys[i] == NULL)
4247 if (i == CGROUP_SUBSYS_COUNT) {
4248 /* maximum number of subsystems already registered! */
4249 mutex_unlock(&cgroup_mutex);
4252 /* assign ourselves the subsys_id */
4257 * no ss->create seems to need anything important in the ss struct, so
4258 * this can happen first (i.e. before the rootnode attachment).
4260 css = ss->create(dummytop);
4262 /* failure case - need to deassign the subsys[] slot. */
4264 mutex_unlock(&cgroup_mutex);
4265 return PTR_ERR(css);
4268 list_add(&ss->sibling, &rootnode.subsys_list);
4269 ss->root = &rootnode;
4271 /* our new subsystem will be attached to the dummy hierarchy. */
4272 init_cgroup_css(css, ss, dummytop);
4273 /* init_idr must be after init_cgroup_css because it sets css->id. */
4275 int ret = cgroup_init_idr(ss, css);
4277 dummytop->subsys[ss->subsys_id] = NULL;
4278 ss->destroy(dummytop);
4280 mutex_unlock(&cgroup_mutex);
4286 * Now we need to entangle the css into the existing css_sets. unlike
4287 * in cgroup_init_subsys, there are now multiple css_sets, so each one
4288 * will need a new pointer to it; done by iterating the css_set_table.
4289 * furthermore, modifying the existing css_sets will corrupt the hash
4290 * table state, so each changed css_set will need its hash recomputed.
4291 * this is all done under the css_set_lock.
4293 write_lock(&css_set_lock);
4294 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
4296 struct hlist_node *node, *tmp;
4297 struct hlist_head *bucket = &css_set_table[i], *new_bucket;
4299 hlist_for_each_entry_safe(cg, node, tmp, bucket, hlist) {
4300 /* skip entries that we already rehashed */
4301 if (cg->subsys[ss->subsys_id])
4303 /* remove existing entry */
4304 hlist_del(&cg->hlist);
4306 cg->subsys[ss->subsys_id] = css;
4307 /* recompute hash and restore entry */
4308 new_bucket = css_set_hash(cg->subsys);
4309 hlist_add_head(&cg->hlist, new_bucket);
4312 write_unlock(&css_set_lock);
4314 mutex_init(&ss->hierarchy_mutex);
4315 lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
4319 mutex_unlock(&cgroup_mutex);
4322 EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4325 * cgroup_unload_subsys: unload a modular subsystem
4326 * @ss: the subsystem to unload
4328 * This function should be called in a modular subsystem's exitcall. When this
4329 * function is invoked, the refcount on the subsystem's module will be 0, so
4330 * the subsystem will not be attached to any hierarchy.
4332 void cgroup_unload_subsys(struct cgroup_subsys *ss)
4334 struct cg_cgroup_link *link;
4335 struct hlist_head *hhead;
4337 BUG_ON(ss->module == NULL);
4340 * we shouldn't be called if the subsystem is in use, and the use of
4341 * try_module_get in parse_cgroupfs_options should ensure that it
4342 * doesn't start being used while we're killing it off.
4344 BUG_ON(ss->root != &rootnode);
4346 mutex_lock(&cgroup_mutex);
4347 /* deassign the subsys_id */
4348 BUG_ON(ss->subsys_id < CGROUP_BUILTIN_SUBSYS_COUNT);
4349 subsys[ss->subsys_id] = NULL;
4351 /* remove subsystem from rootnode's list of subsystems */
4352 list_del_init(&ss->sibling);
4355 * disentangle the css from all css_sets attached to the dummytop. as
4356 * in loading, we need to pay our respects to the hashtable gods.
4358 write_lock(&css_set_lock);
4359 list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {
4360 struct css_set *cg = link->cg;
4362 hlist_del(&cg->hlist);
4363 BUG_ON(!cg->subsys[ss->subsys_id]);
4364 cg->subsys[ss->subsys_id] = NULL;
4365 hhead = css_set_hash(cg->subsys);
4366 hlist_add_head(&cg->hlist, hhead);
4368 write_unlock(&css_set_lock);
4371 * remove subsystem's css from the dummytop and free it - need to free
4372 * before marking as null because ss->destroy needs the cgrp->subsys
4373 * pointer to find their state. note that this also takes care of
4374 * freeing the css_id.
4376 ss->destroy(dummytop);
4377 dummytop->subsys[ss->subsys_id] = NULL;
4379 mutex_unlock(&cgroup_mutex);
4381 EXPORT_SYMBOL_GPL(cgroup_unload_subsys);
4384 * cgroup_init_early - cgroup initialization at system boot
4386 * Initialize cgroups at system boot, and initialize any
4387 * subsystems that request early init.
4389 int __init cgroup_init_early(void)
4392 atomic_set(&init_css_set.refcount, 1);
4393 INIT_LIST_HEAD(&init_css_set.cg_links);
4394 INIT_LIST_HEAD(&init_css_set.tasks);
4395 INIT_HLIST_NODE(&init_css_set.hlist);
4397 init_cgroup_root(&rootnode);
4399 init_task.cgroups = &init_css_set;
4401 init_css_set_link.cg = &init_css_set;
4402 init_css_set_link.cgrp = dummytop;
4403 list_add(&init_css_set_link.cgrp_link_list,
4404 &rootnode.top_cgroup.css_sets);
4405 list_add(&init_css_set_link.cg_link_list,
4406 &init_css_set.cg_links);
4408 for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
4409 INIT_HLIST_HEAD(&css_set_table[i]);
4411 /* at bootup time, we don't worry about modular subsystems */
4412 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4413 struct cgroup_subsys *ss = subsys[i];
4416 BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4417 BUG_ON(!ss->create);
4418 BUG_ON(!ss->destroy);
4419 if (ss->subsys_id != i) {
4420 printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4421 ss->name, ss->subsys_id);
4426 cgroup_init_subsys(ss);
4432 * cgroup_init - cgroup initialization
4434 * Register cgroup filesystem and /proc file, and initialize
4435 * any subsystems that didn't request early init.
4437 int __init cgroup_init(void)
4441 struct hlist_head *hhead;
4443 err = bdi_init(&cgroup_backing_dev_info);
4447 /* at bootup time, we don't worry about modular subsystems */
4448 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4449 struct cgroup_subsys *ss = subsys[i];
4450 if (!ss->early_init)
4451 cgroup_init_subsys(ss);
4453 cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4456 /* Add init_css_set to the hash table */
4457 hhead = css_set_hash(init_css_set.subsys);
4458 hlist_add_head(&init_css_set.hlist, hhead);
4459 BUG_ON(!init_root_id(&rootnode));
4461 cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
4467 err = register_filesystem(&cgroup_fs_type);
4469 kobject_put(cgroup_kobj);
4473 proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4477 bdi_destroy(&cgroup_backing_dev_info);
4483 * proc_cgroup_show()
4484 * - Print task's cgroup paths into seq_file, one line for each hierarchy
4485 * - Used for /proc/<pid>/cgroup.
4486 * - No need to task_lock(tsk) on this tsk->cgroup reference, as it
4487 * doesn't really matter if tsk->cgroup changes after we read it,
4488 * and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4489 * anyway. No need to check that tsk->cgroup != NULL, thanks to
4490 * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
4491 * cgroup to top_cgroup.
4494 /* TODO: Use a proper seq_file iterator */
4495 static int proc_cgroup_show(struct seq_file *m, void *v)
4498 struct task_struct *tsk;
4501 struct cgroupfs_root *root;
4504 buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4510 tsk = get_pid_task(pid, PIDTYPE_PID);
4516 mutex_lock(&cgroup_mutex);
4518 for_each_active_root(root) {
4519 struct cgroup_subsys *ss;
4520 struct cgroup *cgrp;
4523 seq_printf(m, "%d:", root->hierarchy_id);
4524 for_each_subsys(root, ss)
4525 seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4526 if (strlen(root->name))
4527 seq_printf(m, "%sname=%s", count ? "," : "",
4530 cgrp = task_cgroup_from_root(tsk, root);
4531 retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4539 mutex_unlock(&cgroup_mutex);
4540 put_task_struct(tsk);
4547 static int cgroup_open(struct inode *inode, struct file *file)
4549 struct pid *pid = PROC_I(inode)->pid;
4550 return single_open(file, proc_cgroup_show, pid);
4553 const struct file_operations proc_cgroup_operations = {
4554 .open = cgroup_open,
4556 .llseek = seq_lseek,
4557 .release = single_release,
4560 /* Display information about each subsystem and each hierarchy */
4561 static int proc_cgroupstats_show(struct seq_file *m, void *v)
4565 seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
4567 * ideally we don't want subsystems moving around while we do this.
4568 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
4569 * subsys/hierarchy state.
4571 mutex_lock(&cgroup_mutex);
4572 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4573 struct cgroup_subsys *ss = subsys[i];
4576 seq_printf(m, "%s\t%d\t%d\t%d\n",
4577 ss->name, ss->root->hierarchy_id,
4578 ss->root->number_of_cgroups, !ss->disabled);
4580 mutex_unlock(&cgroup_mutex);
4584 static int cgroupstats_open(struct inode *inode, struct file *file)
4586 return single_open(file, proc_cgroupstats_show, NULL);
4589 static const struct file_operations proc_cgroupstats_operations = {
4590 .open = cgroupstats_open,
4592 .llseek = seq_lseek,
4593 .release = single_release,
4597 * cgroup_fork - attach newly forked task to its parents cgroup.
4598 * @child: pointer to task_struct of forking parent process.
4600 * Description: A task inherits its parent's cgroup at fork().
4602 * A pointer to the shared css_set was automatically copied in
4603 * fork.c by dup_task_struct(). However, we ignore that copy, since
4604 * it was not made under the protection of RCU, cgroup_mutex or
4605 * threadgroup_change_begin(), so it might no longer be a valid
4606 * cgroup pointer. cgroup_attach_task() might have already changed
4607 * current->cgroups, allowing the previously referenced cgroup
4608 * group to be removed and freed.
4610 * Outside the pointer validity we also need to process the css_set
4611 * inheritance between threadgoup_change_begin() and
4612 * threadgoup_change_end(), this way there is no leak in any process
4613 * wide migration performed by cgroup_attach_proc() that could otherwise
4614 * miss a thread because it is too early or too late in the fork stage.
4616 * At the point that cgroup_fork() is called, 'current' is the parent
4617 * task, and the passed argument 'child' points to the child task.
4619 void cgroup_fork(struct task_struct *child)
4622 * We don't need to task_lock() current because current->cgroups
4623 * can't be changed concurrently here. The parent obviously hasn't
4624 * exited and called cgroup_exit(), and we are synchronized against
4625 * cgroup migration through threadgroup_change_begin().
4627 child->cgroups = current->cgroups;
4628 get_css_set(child->cgroups);
4629 INIT_LIST_HEAD(&child->cg_list);
4633 * cgroup_fork_callbacks - run fork callbacks
4634 * @child: the new task
4636 * Called on a new task very soon before adding it to the
4637 * tasklist. No need to take any locks since no-one can
4638 * be operating on this task.
4640 void cgroup_fork_callbacks(struct task_struct *child)
4642 if (need_forkexit_callback) {
4645 * forkexit callbacks are only supported for builtin
4646 * subsystems, and the builtin section of the subsys array is
4647 * immutable, so we don't need to lock the subsys array here.
4649 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4650 struct cgroup_subsys *ss = subsys[i];
4658 * cgroup_post_fork - called on a new task after adding it to the task list
4659 * @child: the task in question
4661 * Adds the task to the list running through its css_set if necessary.
4662 * Has to be after the task is visible on the task list in case we race
4663 * with the first call to cgroup_iter_start() - to guarantee that the
4664 * new task ends up on its list.
4666 void cgroup_post_fork(struct task_struct *child)
4669 * use_task_css_set_links is set to 1 before we walk the tasklist
4670 * under the tasklist_lock and we read it here after we added the child
4671 * to the tasklist under the tasklist_lock as well. If the child wasn't
4672 * yet in the tasklist when we walked through it from
4673 * cgroup_enable_task_cg_lists(), then use_task_css_set_links value
4674 * should be visible now due to the paired locking and barriers implied
4675 * by LOCK/UNLOCK: it is written before the tasklist_lock unlock
4676 * in cgroup_enable_task_cg_lists() and read here after the tasklist_lock
4679 if (use_task_css_set_links) {
4680 write_lock(&css_set_lock);
4681 if (list_empty(&child->cg_list)) {
4683 * It's safe to use child->cgroups without task_lock()
4684 * here because we are protected through
4685 * threadgroup_change_begin() against concurrent
4686 * css_set change in cgroup_task_migrate(). Also
4687 * the task can't exit at that point until
4688 * wake_up_new_task() is called, so we are protected
4689 * against cgroup_exit() setting child->cgroup to
4692 list_add(&child->cg_list, &child->cgroups->tasks);
4694 write_unlock(&css_set_lock);
4698 * cgroup_exit - detach cgroup from exiting task
4699 * @tsk: pointer to task_struct of exiting process
4700 * @run_callback: run exit callbacks?
4702 * Description: Detach cgroup from @tsk and release it.
4704 * Note that cgroups marked notify_on_release force every task in
4705 * them to take the global cgroup_mutex mutex when exiting.
4706 * This could impact scaling on very large systems. Be reluctant to
4707 * use notify_on_release cgroups where very high task exit scaling
4708 * is required on large systems.
4710 * the_top_cgroup_hack:
4712 * Set the exiting tasks cgroup to the root cgroup (top_cgroup).
4714 * We call cgroup_exit() while the task is still competent to
4715 * handle notify_on_release(), then leave the task attached to the
4716 * root cgroup in each hierarchy for the remainder of its exit.
4718 * To do this properly, we would increment the reference count on
4719 * top_cgroup, and near the very end of the kernel/exit.c do_exit()
4720 * code we would add a second cgroup function call, to drop that
4721 * reference. This would just create an unnecessary hot spot on
4722 * the top_cgroup reference count, to no avail.
4724 * Normally, holding a reference to a cgroup without bumping its
4725 * count is unsafe. The cgroup could go away, or someone could
4726 * attach us to a different cgroup, decrementing the count on
4727 * the first cgroup that we never incremented. But in this case,
4728 * top_cgroup isn't going away, and either task has PF_EXITING set,
4729 * which wards off any cgroup_attach_task() attempts, or task is a failed
4730 * fork, never visible to cgroup_attach_task.
4732 void cgroup_exit(struct task_struct *tsk, int run_callbacks)
4738 * Unlink from the css_set task list if necessary.
4739 * Optimistically check cg_list before taking
4742 if (!list_empty(&tsk->cg_list)) {
4743 write_lock(&css_set_lock);
4744 if (!list_empty(&tsk->cg_list))
4745 list_del_init(&tsk->cg_list);
4746 write_unlock(&css_set_lock);
4749 /* Reassign the task to the init_css_set. */
4752 tsk->cgroups = &init_css_set;
4754 if (run_callbacks && need_forkexit_callback) {
4756 * modular subsystems can't use callbacks, so no need to lock
4759 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4760 struct cgroup_subsys *ss = subsys[i];
4762 struct cgroup *old_cgrp =
4763 rcu_dereference_raw(cg->subsys[i])->cgroup;
4764 struct cgroup *cgrp = task_cgroup(tsk, i);
4765 ss->exit(cgrp, old_cgrp, tsk);
4772 put_css_set_taskexit(cg);
4776 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
4777 * @cgrp: the cgroup in question
4778 * @task: the task in question
4780 * See if @cgrp is a descendant of @task's cgroup in the appropriate
4783 * If we are sending in dummytop, then presumably we are creating
4784 * the top cgroup in the subsystem.
4786 * Called only by the ns (nsproxy) cgroup.
4788 int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
4791 struct cgroup *target;
4793 if (cgrp == dummytop)
4796 target = task_cgroup_from_root(task, cgrp->root);
4797 while (cgrp != target && cgrp!= cgrp->top_cgroup)
4798 cgrp = cgrp->parent;
4799 ret = (cgrp == target);
4803 static void check_for_release(struct cgroup *cgrp)
4805 /* All of these checks rely on RCU to keep the cgroup
4806 * structure alive */
4807 if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
4808 && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
4809 /* Control Group is currently removeable. If it's not
4810 * already queued for a userspace notification, queue
4812 int need_schedule_work = 0;
4813 raw_spin_lock(&release_list_lock);
4814 if (!cgroup_is_removed(cgrp) &&
4815 list_empty(&cgrp->release_list)) {
4816 list_add(&cgrp->release_list, &release_list);
4817 need_schedule_work = 1;
4819 raw_spin_unlock(&release_list_lock);
4820 if (need_schedule_work)
4821 schedule_work(&release_agent_work);
4825 /* Caller must verify that the css is not for root cgroup */
4826 void __css_put(struct cgroup_subsys_state *css, int count)
4828 struct cgroup *cgrp = css->cgroup;
4831 val = atomic_sub_return(count, &css->refcnt);
4833 if (notify_on_release(cgrp)) {
4834 set_bit(CGRP_RELEASABLE, &cgrp->flags);
4835 check_for_release(cgrp);
4837 cgroup_wakeup_rmdir_waiter(cgrp);
4840 WARN_ON_ONCE(val < 1);
4842 EXPORT_SYMBOL_GPL(__css_put);
4845 * Notify userspace when a cgroup is released, by running the
4846 * configured release agent with the name of the cgroup (path
4847 * relative to the root of cgroup file system) as the argument.
4849 * Most likely, this user command will try to rmdir this cgroup.
4851 * This races with the possibility that some other task will be
4852 * attached to this cgroup before it is removed, or that some other
4853 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
4854 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
4855 * unused, and this cgroup will be reprieved from its death sentence,
4856 * to continue to serve a useful existence. Next time it's released,
4857 * we will get notified again, if it still has 'notify_on_release' set.
4859 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
4860 * means only wait until the task is successfully execve()'d. The
4861 * separate release agent task is forked by call_usermodehelper(),
4862 * then control in this thread returns here, without waiting for the
4863 * release agent task. We don't bother to wait because the caller of
4864 * this routine has no use for the exit status of the release agent
4865 * task, so no sense holding our caller up for that.
4867 static void cgroup_release_agent(struct work_struct *work)
4869 BUG_ON(work != &release_agent_work);
4870 mutex_lock(&cgroup_mutex);
4871 raw_spin_lock(&release_list_lock);
4872 while (!list_empty(&release_list)) {
4873 char *argv[3], *envp[3];
4875 char *pathbuf = NULL, *agentbuf = NULL;
4876 struct cgroup *cgrp = list_entry(release_list.next,
4879 list_del_init(&cgrp->release_list);
4880 raw_spin_unlock(&release_list_lock);
4881 pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
4884 if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
4886 agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
4891 argv[i++] = agentbuf;
4892 argv[i++] = pathbuf;
4896 /* minimal command environment */
4897 envp[i++] = "HOME=/";
4898 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
4901 /* Drop the lock while we invoke the usermode helper,
4902 * since the exec could involve hitting disk and hence
4903 * be a slow process */
4904 mutex_unlock(&cgroup_mutex);
4905 call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
4906 mutex_lock(&cgroup_mutex);
4910 raw_spin_lock(&release_list_lock);
4912 raw_spin_unlock(&release_list_lock);
4913 mutex_unlock(&cgroup_mutex);
4916 static int __init cgroup_disable(char *str)
4921 while ((token = strsep(&str, ",")) != NULL) {
4925 * cgroup_disable, being at boot time, can't know about module
4926 * subsystems, so we don't worry about them.
4928 for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4929 struct cgroup_subsys *ss = subsys[i];
4931 if (!strcmp(token, ss->name)) {
4933 printk(KERN_INFO "Disabling %s control group"
4934 " subsystem\n", ss->name);
4941 __setup("cgroup_disable=", cgroup_disable);
4944 * Functons for CSS ID.
4948 *To get ID other than 0, this should be called when !cgroup_is_removed().
4950 unsigned short css_id(struct cgroup_subsys_state *css)
4952 struct css_id *cssid;
4955 * This css_id() can return correct value when somone has refcnt
4956 * on this or this is under rcu_read_lock(). Once css->id is allocated,
4957 * it's unchanged until freed.
4959 cssid = rcu_dereference_check(css->id, atomic_read(&css->refcnt));
4965 EXPORT_SYMBOL_GPL(css_id);
4967 unsigned short css_depth(struct cgroup_subsys_state *css)
4969 struct css_id *cssid;
4971 cssid = rcu_dereference_check(css->id, atomic_read(&css->refcnt));
4974 return cssid->depth;
4977 EXPORT_SYMBOL_GPL(css_depth);
4980 * css_is_ancestor - test "root" css is an ancestor of "child"
4981 * @child: the css to be tested.
4982 * @root: the css supporsed to be an ancestor of the child.
4984 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
4985 * this function reads css->id, this use rcu_dereference() and rcu_read_lock().
4986 * But, considering usual usage, the csses should be valid objects after test.
4987 * Assuming that the caller will do some action to the child if this returns
4988 * returns true, the caller must take "child";s reference count.
4989 * If "child" is valid object and this returns true, "root" is valid, too.
4992 bool css_is_ancestor(struct cgroup_subsys_state *child,
4993 const struct cgroup_subsys_state *root)
4995 struct css_id *child_id;
4996 struct css_id *root_id;
5000 child_id = rcu_dereference(child->id);
5001 root_id = rcu_dereference(root->id);
5004 || (child_id->depth < root_id->depth)
5005 || (child_id->stack[root_id->depth] != root_id->id))
5011 void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
5013 struct css_id *id = css->id;
5014 /* When this is called before css_id initialization, id can be NULL */
5018 BUG_ON(!ss->use_id);
5020 rcu_assign_pointer(id->css, NULL);
5021 rcu_assign_pointer(css->id, NULL);
5022 spin_lock(&ss->id_lock);
5023 idr_remove(&ss->idr, id->id);
5024 spin_unlock(&ss->id_lock);
5025 kfree_rcu(id, rcu_head);
5027 EXPORT_SYMBOL_GPL(free_css_id);
5030 * This is called by init or create(). Then, calls to this function are
5031 * always serialized (By cgroup_mutex() at create()).
5034 static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
5036 struct css_id *newid;
5037 int myid, error, size;
5039 BUG_ON(!ss->use_id);
5041 size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
5042 newid = kzalloc(size, GFP_KERNEL);
5044 return ERR_PTR(-ENOMEM);
5046 if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
5050 spin_lock(&ss->id_lock);
5051 /* Don't use 0. allocates an ID of 1-65535 */
5052 error = idr_get_new_above(&ss->idr, newid, 1, &myid);
5053 spin_unlock(&ss->id_lock);
5055 /* Returns error when there are no free spaces for new ID.*/
5060 if (myid > CSS_ID_MAX)
5064 newid->depth = depth;
5068 spin_lock(&ss->id_lock);
5069 idr_remove(&ss->idr, myid);
5070 spin_unlock(&ss->id_lock);
5073 return ERR_PTR(error);
5077 static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
5078 struct cgroup_subsys_state *rootcss)
5080 struct css_id *newid;
5082 spin_lock_init(&ss->id_lock);
5085 newid = get_new_cssid(ss, 0);
5087 return PTR_ERR(newid);
5089 newid->stack[0] = newid->id;
5090 newid->css = rootcss;
5091 rootcss->id = newid;
5095 static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
5096 struct cgroup *child)
5098 int subsys_id, i, depth = 0;
5099 struct cgroup_subsys_state *parent_css, *child_css;
5100 struct css_id *child_id, *parent_id;
5102 subsys_id = ss->subsys_id;
5103 parent_css = parent->subsys[subsys_id];
5104 child_css = child->subsys[subsys_id];
5105 parent_id = parent_css->id;
5106 depth = parent_id->depth + 1;
5108 child_id = get_new_cssid(ss, depth);
5109 if (IS_ERR(child_id))
5110 return PTR_ERR(child_id);
5112 for (i = 0; i < depth; i++)
5113 child_id->stack[i] = parent_id->stack[i];
5114 child_id->stack[depth] = child_id->id;
5116 * child_id->css pointer will be set after this cgroup is available
5117 * see cgroup_populate_dir()
5119 rcu_assign_pointer(child_css->id, child_id);
5125 * css_lookup - lookup css by id
5126 * @ss: cgroup subsys to be looked into.
5129 * Returns pointer to cgroup_subsys_state if there is valid one with id.
5130 * NULL if not. Should be called under rcu_read_lock()
5132 struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
5134 struct css_id *cssid = NULL;
5136 BUG_ON(!ss->use_id);
5137 cssid = idr_find(&ss->idr, id);
5139 if (unlikely(!cssid))
5142 return rcu_dereference(cssid->css);
5144 EXPORT_SYMBOL_GPL(css_lookup);
5147 * css_get_next - lookup next cgroup under specified hierarchy.
5148 * @ss: pointer to subsystem
5149 * @id: current position of iteration.
5150 * @root: pointer to css. search tree under this.
5151 * @foundid: position of found object.
5153 * Search next css under the specified hierarchy of rootid. Calling under
5154 * rcu_read_lock() is necessary. Returns NULL if it reaches the end.
5156 struct cgroup_subsys_state *
5157 css_get_next(struct cgroup_subsys *ss, int id,
5158 struct cgroup_subsys_state *root, int *foundid)
5160 struct cgroup_subsys_state *ret = NULL;
5163 int rootid = css_id(root);
5164 int depth = css_depth(root);
5169 BUG_ON(!ss->use_id);
5170 WARN_ON_ONCE(!rcu_read_lock_held());
5172 /* fill start point for scan */
5176 * scan next entry from bitmap(tree), tmpid is updated after
5179 tmp = idr_get_next(&ss->idr, &tmpid);
5182 if (tmp->depth >= depth && tmp->stack[depth] == rootid) {
5183 ret = rcu_dereference(tmp->css);
5189 /* continue to scan from next id */
5196 * get corresponding css from file open on cgroupfs directory
5198 struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
5200 struct cgroup *cgrp;
5201 struct inode *inode;
5202 struct cgroup_subsys_state *css;
5204 inode = f->f_dentry->d_inode;
5205 /* check in cgroup filesystem dir */
5206 if (inode->i_op != &cgroup_dir_inode_operations)
5207 return ERR_PTR(-EBADF);
5209 if (id < 0 || id >= CGROUP_SUBSYS_COUNT)
5210 return ERR_PTR(-EINVAL);
5213 cgrp = __d_cgrp(f->f_dentry);
5214 css = cgrp->subsys[id];
5215 return css ? css : ERR_PTR(-ENOENT);
5218 #ifdef CONFIG_CGROUP_DEBUG
5219 static struct cgroup_subsys_state *debug_create(struct cgroup *cont)
5221 struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
5224 return ERR_PTR(-ENOMEM);
5229 static void debug_destroy(struct cgroup *cont)
5231 kfree(cont->subsys[debug_subsys_id]);
5234 static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
5236 return atomic_read(&cont->count);
5239 static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft)
5241 return cgroup_task_count(cont);
5244 static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
5246 return (u64)(unsigned long)current->cgroups;
5249 static u64 current_css_set_refcount_read(struct cgroup *cont,
5255 count = atomic_read(¤t->cgroups->refcount);
5260 static int current_css_set_cg_links_read(struct cgroup *cont,
5262 struct seq_file *seq)
5264 struct cg_cgroup_link *link;
5267 read_lock(&css_set_lock);
5269 cg = rcu_dereference(current->cgroups);
5270 list_for_each_entry(link, &cg->cg_links, cg_link_list) {
5271 struct cgroup *c = link->cgrp;
5275 name = c->dentry->d_name.name;
5278 seq_printf(seq, "Root %d group %s\n",
5279 c->root->hierarchy_id, name);
5282 read_unlock(&css_set_lock);
5286 #define MAX_TASKS_SHOWN_PER_CSS 25
5287 static int cgroup_css_links_read(struct cgroup *cont,
5289 struct seq_file *seq)
5291 struct cg_cgroup_link *link;
5293 read_lock(&css_set_lock);
5294 list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
5295 struct css_set *cg = link->cg;
5296 struct task_struct *task;
5298 seq_printf(seq, "css_set %p\n", cg);
5299 list_for_each_entry(task, &cg->tasks, cg_list) {
5300 if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
5301 seq_puts(seq, " ...\n");
5304 seq_printf(seq, " task %d\n",
5305 task_pid_vnr(task));
5309 read_unlock(&css_set_lock);
5313 static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
5315 return test_bit(CGRP_RELEASABLE, &cgrp->flags);
5318 static struct cftype debug_files[] = {
5320 .name = "cgroup_refcount",
5321 .read_u64 = cgroup_refcount_read,
5324 .name = "taskcount",
5325 .read_u64 = debug_taskcount_read,
5329 .name = "current_css_set",
5330 .read_u64 = current_css_set_read,
5334 .name = "current_css_set_refcount",
5335 .read_u64 = current_css_set_refcount_read,
5339 .name = "current_css_set_cg_links",
5340 .read_seq_string = current_css_set_cg_links_read,
5344 .name = "cgroup_css_links",
5345 .read_seq_string = cgroup_css_links_read,
5349 .name = "releasable",
5350 .read_u64 = releasable_read,
5356 struct cgroup_subsys debug_subsys = {
5358 .create = debug_create,
5359 .destroy = debug_destroy,
5360 .subsys_id = debug_subsys_id,
5361 .base_cftypes = debug_files,
5363 #endif /* CONFIG_CGROUP_DEBUG */