2 * Generic process-grouping system.
4 * Based originally on the cpuset system, extracted by Paul Menage
5 * Copyright (C) 2006 Google, Inc
7 * Copyright notices from the original cpuset code:
8 * --------------------------------------------------
9 * Copyright (C) 2003 BULL SA.
10 * Copyright (C) 2004-2006 Silicon Graphics, Inc.
12 * Portions derived from Patrick Mochel's sysfs code.
13 * sysfs is Copyright (c) 2001-3 Patrick Mochel
15 * 2003-10-10 Written by Simon Derr.
16 * 2003-10-22 Updates by Stephen Hemminger.
17 * 2004 May-July Rework by Paul Jackson.
18 * ---------------------------------------------------
20 * This file is subject to the terms and conditions of the GNU General Public
21 * License. See the file COPYING in the main directory of the Linux
22 * distribution for more details.
25 #include <linux/cgroup.h>
26 #include <linux/ctype.h>
27 #include <linux/errno.h>
29 #include <linux/kernel.h>
30 #include <linux/list.h>
32 #include <linux/mutex.h>
33 #include <linux/mount.h>
34 #include <linux/pagemap.h>
35 #include <linux/proc_fs.h>
36 #include <linux/rcupdate.h>
37 #include <linux/sched.h>
38 #include <linux/backing-dev.h>
39 #include <linux/seq_file.h>
40 #include <linux/slab.h>
41 #include <linux/magic.h>
42 #include <linux/spinlock.h>
43 #include <linux/string.h>
44 #include <linux/sort.h>
45 #include <linux/kmod.h>
46 #include <linux/delayacct.h>
47 #include <linux/cgroupstats.h>
48 #include <linux/hash.h>
49 #include <linux/namei.h>
50 #include <linux/smp_lock.h>
51 #include <linux/pid_namespace.h>
52 #include <linux/idr.h>
54 #include <asm/atomic.h>
56 static DEFINE_MUTEX(cgroup_mutex);
58 /* Generate an array of cgroup subsystem pointers */
59 #define SUBSYS(_x) &_x ## _subsys,
61 static struct cgroup_subsys *subsys[] = {
62 #include <linux/cgroup_subsys.h>
65 #define MAX_CGROUP_ROOT_NAMELEN 64
68 * A cgroupfs_root represents the root of a cgroup hierarchy,
69 * and may be associated with a superblock to form an active
72 struct cgroupfs_root {
73 struct super_block *sb;
76 * The bitmask of subsystems intended to be attached to this
79 unsigned long subsys_bits;
81 /* Unique id for this hierarchy. */
84 /* The bitmask of subsystems currently attached to this hierarchy */
85 unsigned long actual_subsys_bits;
87 /* A list running through the attached subsystems */
88 struct list_head subsys_list;
90 /* The root cgroup for this hierarchy */
91 struct cgroup top_cgroup;
93 /* Tracks how many cgroups are currently defined in hierarchy.*/
94 int number_of_cgroups;
96 /* A list running through the active hierarchies */
97 struct list_head root_list;
99 /* Hierarchy-specific flags */
102 /* The path to use for release notifications. */
103 char release_agent_path[PATH_MAX];
105 /* The name for this hierarchy - may be empty */
106 char name[MAX_CGROUP_ROOT_NAMELEN];
110 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
111 * subsystems that are otherwise unattached - it never has more than a
112 * single cgroup, and all tasks are part of that cgroup.
114 static struct cgroupfs_root rootnode;
117 * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
118 * cgroup_subsys->use_id != 0.
120 #define CSS_ID_MAX (65535)
123 * The css to which this ID points. This pointer is set to valid value
124 * after cgroup is populated. If cgroup is removed, this will be NULL.
125 * This pointer is expected to be RCU-safe because destroy()
126 * is called after synchronize_rcu(). But for safe use, css_is_removed()
127 * css_tryget() should be used for avoiding race.
129 struct cgroup_subsys_state *css;
135 * Depth in hierarchy which this ID belongs to.
137 unsigned short depth;
139 * ID is freed by RCU. (and lookup routine is RCU safe.)
141 struct rcu_head rcu_head;
143 * Hierarchy of CSS ID belongs to.
145 unsigned short stack[0]; /* Array of Length (depth+1) */
149 /* The list of hierarchy roots */
151 static LIST_HEAD(roots);
152 static int root_count;
154 static DEFINE_IDA(hierarchy_ida);
155 static int next_hierarchy_id;
156 static DEFINE_SPINLOCK(hierarchy_id_lock);
158 /* dummytop is a shorthand for the dummy hierarchy's top cgroup */
159 #define dummytop (&rootnode.top_cgroup)
161 /* This flag indicates whether tasks in the fork and exit paths should
162 * check for fork/exit handlers to call. This avoids us having to do
163 * extra work in the fork/exit path if none of the subsystems need to
166 static int need_forkexit_callback __read_mostly;
168 /* convenient tests for these bits */
169 inline int cgroup_is_removed(const struct cgroup *cgrp)
171 return test_bit(CGRP_REMOVED, &cgrp->flags);
174 /* bits in struct cgroupfs_root flags field */
176 ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
179 static int cgroup_is_releasable(const struct cgroup *cgrp)
182 (1 << CGRP_RELEASABLE) |
183 (1 << CGRP_NOTIFY_ON_RELEASE);
184 return (cgrp->flags & bits) == bits;
187 static int notify_on_release(const struct cgroup *cgrp)
189 return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
193 * for_each_subsys() allows you to iterate on each subsystem attached to
194 * an active hierarchy
196 #define for_each_subsys(_root, _ss) \
197 list_for_each_entry(_ss, &_root->subsys_list, sibling)
199 /* for_each_active_root() allows you to iterate across the active hierarchies */
200 #define for_each_active_root(_root) \
201 list_for_each_entry(_root, &roots, root_list)
203 /* the list of cgroups eligible for automatic release. Protected by
204 * release_list_lock */
205 static LIST_HEAD(release_list);
206 static DEFINE_SPINLOCK(release_list_lock);
207 static void cgroup_release_agent(struct work_struct *work);
208 static DECLARE_WORK(release_agent_work, cgroup_release_agent);
209 static void check_for_release(struct cgroup *cgrp);
211 /* Link structure for associating css_set objects with cgroups */
212 struct cg_cgroup_link {
214 * List running through cg_cgroup_links associated with a
215 * cgroup, anchored on cgroup->css_sets
217 struct list_head cgrp_link_list;
220 * List running through cg_cgroup_links pointing at a
221 * single css_set object, anchored on css_set->cg_links
223 struct list_head cg_link_list;
227 /* The default css_set - used by init and its children prior to any
228 * hierarchies being mounted. It contains a pointer to the root state
229 * for each subsystem. Also used to anchor the list of css_sets. Not
230 * reference-counted, to improve performance when child cgroups
231 * haven't been created.
234 static struct css_set init_css_set;
235 static struct cg_cgroup_link init_css_set_link;
237 static int cgroup_subsys_init_idr(struct cgroup_subsys *ss);
239 /* css_set_lock protects the list of css_set objects, and the
240 * chain of tasks off each css_set. Nests outside task->alloc_lock
241 * due to cgroup_iter_start() */
242 static DEFINE_RWLOCK(css_set_lock);
243 static int css_set_count;
246 * hash table for cgroup groups. This improves the performance to find
247 * an existing css_set. This hash doesn't (currently) take into
248 * account cgroups in empty hierarchies.
250 #define CSS_SET_HASH_BITS 7
251 #define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS)
252 static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
254 static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
258 unsigned long tmp = 0UL;
260 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
261 tmp += (unsigned long)css[i];
262 tmp = (tmp >> 16) ^ tmp;
264 index = hash_long(tmp, CSS_SET_HASH_BITS);
266 return &css_set_table[index];
269 /* We don't maintain the lists running through each css_set to its
270 * task until after the first call to cgroup_iter_start(). This
271 * reduces the fork()/exit() overhead for people who have cgroups
272 * compiled into their kernel but not actually in use */
273 static int use_task_css_set_links __read_mostly;
275 static void __put_css_set(struct css_set *cg, int taskexit)
277 struct cg_cgroup_link *link;
278 struct cg_cgroup_link *saved_link;
280 * Ensure that the refcount doesn't hit zero while any readers
281 * can see it. Similar to atomic_dec_and_lock(), but for an
284 if (atomic_add_unless(&cg->refcount, -1, 1))
286 write_lock(&css_set_lock);
287 if (!atomic_dec_and_test(&cg->refcount)) {
288 write_unlock(&css_set_lock);
292 /* This css_set is dead. unlink it and release cgroup refcounts */
293 hlist_del(&cg->hlist);
296 list_for_each_entry_safe(link, saved_link, &cg->cg_links,
298 struct cgroup *cgrp = link->cgrp;
299 list_del(&link->cg_link_list);
300 list_del(&link->cgrp_link_list);
301 if (atomic_dec_and_test(&cgrp->count) &&
302 notify_on_release(cgrp)) {
304 set_bit(CGRP_RELEASABLE, &cgrp->flags);
305 check_for_release(cgrp);
311 write_unlock(&css_set_lock);
316 * refcounted get/put for css_set objects
318 static inline void get_css_set(struct css_set *cg)
320 atomic_inc(&cg->refcount);
323 static inline void put_css_set(struct css_set *cg)
325 __put_css_set(cg, 0);
328 static inline void put_css_set_taskexit(struct css_set *cg)
330 __put_css_set(cg, 1);
334 * compare_css_sets - helper function for find_existing_css_set().
335 * @cg: candidate css_set being tested
336 * @old_cg: existing css_set for a task
337 * @new_cgrp: cgroup that's being entered by the task
338 * @template: desired set of css pointers in css_set (pre-calculated)
340 * Returns true if "cg" matches "old_cg" except for the hierarchy
341 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
343 static bool compare_css_sets(struct css_set *cg,
344 struct css_set *old_cg,
345 struct cgroup *new_cgrp,
346 struct cgroup_subsys_state *template[])
348 struct list_head *l1, *l2;
350 if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
351 /* Not all subsystems matched */
356 * Compare cgroup pointers in order to distinguish between
357 * different cgroups in heirarchies with no subsystems. We
358 * could get by with just this check alone (and skip the
359 * memcmp above) but on most setups the memcmp check will
360 * avoid the need for this more expensive check on almost all
365 l2 = &old_cg->cg_links;
367 struct cg_cgroup_link *cgl1, *cgl2;
368 struct cgroup *cg1, *cg2;
372 /* See if we reached the end - both lists are equal length. */
373 if (l1 == &cg->cg_links) {
374 BUG_ON(l2 != &old_cg->cg_links);
377 BUG_ON(l2 == &old_cg->cg_links);
379 /* Locate the cgroups associated with these links. */
380 cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
381 cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
384 /* Hierarchies should be linked in the same order. */
385 BUG_ON(cg1->root != cg2->root);
388 * If this hierarchy is the hierarchy of the cgroup
389 * that's changing, then we need to check that this
390 * css_set points to the new cgroup; if it's any other
391 * hierarchy, then this css_set should point to the
392 * same cgroup as the old css_set.
394 if (cg1->root == new_cgrp->root) {
406 * find_existing_css_set() is a helper for
407 * find_css_set(), and checks to see whether an existing
408 * css_set is suitable.
410 * oldcg: the cgroup group that we're using before the cgroup
413 * cgrp: the cgroup that we're moving into
415 * template: location in which to build the desired set of subsystem
416 * state objects for the new cgroup group
418 static struct css_set *find_existing_css_set(
419 struct css_set *oldcg,
421 struct cgroup_subsys_state *template[])
424 struct cgroupfs_root *root = cgrp->root;
425 struct hlist_head *hhead;
426 struct hlist_node *node;
429 /* Built the set of subsystem state objects that we want to
430 * see in the new css_set */
431 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
432 if (root->subsys_bits & (1UL << i)) {
433 /* Subsystem is in this hierarchy. So we want
434 * the subsystem state from the new
436 template[i] = cgrp->subsys[i];
438 /* Subsystem is not in this hierarchy, so we
439 * don't want to change the subsystem state */
440 template[i] = oldcg->subsys[i];
444 hhead = css_set_hash(template);
445 hlist_for_each_entry(cg, node, hhead, hlist) {
446 if (!compare_css_sets(cg, oldcg, cgrp, template))
449 /* This css_set matches what we need */
453 /* No existing cgroup group matched */
457 static void free_cg_links(struct list_head *tmp)
459 struct cg_cgroup_link *link;
460 struct cg_cgroup_link *saved_link;
462 list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
463 list_del(&link->cgrp_link_list);
469 * allocate_cg_links() allocates "count" cg_cgroup_link structures
470 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
471 * success or a negative error
473 static int allocate_cg_links(int count, struct list_head *tmp)
475 struct cg_cgroup_link *link;
478 for (i = 0; i < count; i++) {
479 link = kmalloc(sizeof(*link), GFP_KERNEL);
484 list_add(&link->cgrp_link_list, tmp);
490 * link_css_set - a helper function to link a css_set to a cgroup
491 * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
492 * @cg: the css_set to be linked
493 * @cgrp: the destination cgroup
495 static void link_css_set(struct list_head *tmp_cg_links,
496 struct css_set *cg, struct cgroup *cgrp)
498 struct cg_cgroup_link *link;
500 BUG_ON(list_empty(tmp_cg_links));
501 link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
505 atomic_inc(&cgrp->count);
506 list_move(&link->cgrp_link_list, &cgrp->css_sets);
508 * Always add links to the tail of the list so that the list
509 * is sorted by order of hierarchy creation
511 list_add_tail(&link->cg_link_list, &cg->cg_links);
515 * find_css_set() takes an existing cgroup group and a
516 * cgroup object, and returns a css_set object that's
517 * equivalent to the old group, but with the given cgroup
518 * substituted into the appropriate hierarchy. Must be called with
521 static struct css_set *find_css_set(
522 struct css_set *oldcg, struct cgroup *cgrp)
525 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
527 struct list_head tmp_cg_links;
529 struct hlist_head *hhead;
530 struct cg_cgroup_link *link;
532 /* First see if we already have a cgroup group that matches
534 read_lock(&css_set_lock);
535 res = find_existing_css_set(oldcg, cgrp, template);
538 read_unlock(&css_set_lock);
543 res = kmalloc(sizeof(*res), GFP_KERNEL);
547 /* Allocate all the cg_cgroup_link objects that we'll need */
548 if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
553 atomic_set(&res->refcount, 1);
554 INIT_LIST_HEAD(&res->cg_links);
555 INIT_LIST_HEAD(&res->tasks);
556 INIT_HLIST_NODE(&res->hlist);
558 /* Copy the set of subsystem state objects generated in
559 * find_existing_css_set() */
560 memcpy(res->subsys, template, sizeof(res->subsys));
562 write_lock(&css_set_lock);
563 /* Add reference counts and links from the new css_set. */
564 list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
565 struct cgroup *c = link->cgrp;
566 if (c->root == cgrp->root)
568 link_css_set(&tmp_cg_links, res, c);
571 BUG_ON(!list_empty(&tmp_cg_links));
575 /* Add this cgroup group to the hash table */
576 hhead = css_set_hash(res->subsys);
577 hlist_add_head(&res->hlist, hhead);
579 write_unlock(&css_set_lock);
585 * Return the cgroup for "task" from the given hierarchy. Must be
586 * called with cgroup_mutex held.
588 static struct cgroup *task_cgroup_from_root(struct task_struct *task,
589 struct cgroupfs_root *root)
592 struct cgroup *res = NULL;
594 BUG_ON(!mutex_is_locked(&cgroup_mutex));
595 read_lock(&css_set_lock);
597 * No need to lock the task - since we hold cgroup_mutex the
598 * task can't change groups, so the only thing that can happen
599 * is that it exits and its css is set back to init_css_set.
602 if (css == &init_css_set) {
603 res = &root->top_cgroup;
605 struct cg_cgroup_link *link;
606 list_for_each_entry(link, &css->cg_links, cg_link_list) {
607 struct cgroup *c = link->cgrp;
608 if (c->root == root) {
614 read_unlock(&css_set_lock);
620 * There is one global cgroup mutex. We also require taking
621 * task_lock() when dereferencing a task's cgroup subsys pointers.
622 * See "The task_lock() exception", at the end of this comment.
624 * A task must hold cgroup_mutex to modify cgroups.
626 * Any task can increment and decrement the count field without lock.
627 * So in general, code holding cgroup_mutex can't rely on the count
628 * field not changing. However, if the count goes to zero, then only
629 * cgroup_attach_task() can increment it again. Because a count of zero
630 * means that no tasks are currently attached, therefore there is no
631 * way a task attached to that cgroup can fork (the other way to
632 * increment the count). So code holding cgroup_mutex can safely
633 * assume that if the count is zero, it will stay zero. Similarly, if
634 * a task holds cgroup_mutex on a cgroup with zero count, it
635 * knows that the cgroup won't be removed, as cgroup_rmdir()
638 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
639 * (usually) take cgroup_mutex. These are the two most performance
640 * critical pieces of code here. The exception occurs on cgroup_exit(),
641 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
642 * is taken, and if the cgroup count is zero, a usermode call made
643 * to the release agent with the name of the cgroup (path relative to
644 * the root of cgroup file system) as the argument.
646 * A cgroup can only be deleted if both its 'count' of using tasks
647 * is zero, and its list of 'children' cgroups is empty. Since all
648 * tasks in the system use _some_ cgroup, and since there is always at
649 * least one task in the system (init, pid == 1), therefore, top_cgroup
650 * always has either children cgroups and/or using tasks. So we don't
651 * need a special hack to ensure that top_cgroup cannot be deleted.
653 * The task_lock() exception
655 * The need for this exception arises from the action of
656 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
657 * another. It does so using cgroup_mutex, however there are
658 * several performance critical places that need to reference
659 * task->cgroup without the expense of grabbing a system global
660 * mutex. Therefore except as noted below, when dereferencing or, as
661 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
662 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
663 * the task_struct routinely used for such matters.
665 * P.S. One more locking exception. RCU is used to guard the
666 * update of a tasks cgroup pointer by cgroup_attach_task()
670 * cgroup_lock - lock out any changes to cgroup structures
673 void cgroup_lock(void)
675 mutex_lock(&cgroup_mutex);
679 * cgroup_unlock - release lock on cgroup changes
681 * Undo the lock taken in a previous cgroup_lock() call.
683 void cgroup_unlock(void)
685 mutex_unlock(&cgroup_mutex);
689 * A couple of forward declarations required, due to cyclic reference loop:
690 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
691 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
695 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode);
696 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
697 static int cgroup_populate_dir(struct cgroup *cgrp);
698 static const struct inode_operations cgroup_dir_inode_operations;
699 static struct file_operations proc_cgroupstats_operations;
701 static struct backing_dev_info cgroup_backing_dev_info = {
703 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
706 static int alloc_css_id(struct cgroup_subsys *ss,
707 struct cgroup *parent, struct cgroup *child);
709 static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
711 struct inode *inode = new_inode(sb);
714 inode->i_mode = mode;
715 inode->i_uid = current_fsuid();
716 inode->i_gid = current_fsgid();
717 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
718 inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
724 * Call subsys's pre_destroy handler.
725 * This is called before css refcnt check.
727 static int cgroup_call_pre_destroy(struct cgroup *cgrp)
729 struct cgroup_subsys *ss;
732 for_each_subsys(cgrp->root, ss)
733 if (ss->pre_destroy) {
734 ret = ss->pre_destroy(ss, cgrp);
741 static void free_cgroup_rcu(struct rcu_head *obj)
743 struct cgroup *cgrp = container_of(obj, struct cgroup, rcu_head);
748 static void cgroup_diput(struct dentry *dentry, struct inode *inode)
750 /* is dentry a directory ? if so, kfree() associated cgroup */
751 if (S_ISDIR(inode->i_mode)) {
752 struct cgroup *cgrp = dentry->d_fsdata;
753 struct cgroup_subsys *ss;
754 BUG_ON(!(cgroup_is_removed(cgrp)));
755 /* It's possible for external users to be holding css
756 * reference counts on a cgroup; css_put() needs to
757 * be able to access the cgroup after decrementing
758 * the reference count in order to know if it needs to
759 * queue the cgroup to be handled by the release
763 mutex_lock(&cgroup_mutex);
765 * Release the subsystem state objects.
767 for_each_subsys(cgrp->root, ss)
768 ss->destroy(ss, cgrp);
770 cgrp->root->number_of_cgroups--;
771 mutex_unlock(&cgroup_mutex);
774 * Drop the active superblock reference that we took when we
777 deactivate_super(cgrp->root->sb);
779 call_rcu(&cgrp->rcu_head, free_cgroup_rcu);
784 static void remove_dir(struct dentry *d)
786 struct dentry *parent = dget(d->d_parent);
789 simple_rmdir(parent->d_inode, d);
793 static void cgroup_clear_directory(struct dentry *dentry)
795 struct list_head *node;
797 BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
798 spin_lock(&dcache_lock);
799 node = dentry->d_subdirs.next;
800 while (node != &dentry->d_subdirs) {
801 struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
804 /* This should never be called on a cgroup
805 * directory with child cgroups */
806 BUG_ON(d->d_inode->i_mode & S_IFDIR);
808 spin_unlock(&dcache_lock);
810 simple_unlink(dentry->d_inode, d);
812 spin_lock(&dcache_lock);
814 node = dentry->d_subdirs.next;
816 spin_unlock(&dcache_lock);
820 * NOTE : the dentry must have been dget()'ed
822 static void cgroup_d_remove_dir(struct dentry *dentry)
824 cgroup_clear_directory(dentry);
826 spin_lock(&dcache_lock);
827 list_del_init(&dentry->d_u.d_child);
828 spin_unlock(&dcache_lock);
833 * A queue for waiters to do rmdir() cgroup. A tasks will sleep when
834 * cgroup->count == 0 && list_empty(&cgroup->children) && subsys has some
835 * reference to css->refcnt. In general, this refcnt is expected to goes down
838 * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
840 DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
842 static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
844 if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
845 wake_up_all(&cgroup_rmdir_waitq);
848 void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
853 void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
855 cgroup_wakeup_rmdir_waiter(css->cgroup);
860 static int rebind_subsystems(struct cgroupfs_root *root,
861 unsigned long final_bits)
863 unsigned long added_bits, removed_bits;
864 struct cgroup *cgrp = &root->top_cgroup;
867 removed_bits = root->actual_subsys_bits & ~final_bits;
868 added_bits = final_bits & ~root->actual_subsys_bits;
869 /* Check that any added subsystems are currently free */
870 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
871 unsigned long bit = 1UL << i;
872 struct cgroup_subsys *ss = subsys[i];
873 if (!(bit & added_bits))
875 if (ss->root != &rootnode) {
876 /* Subsystem isn't free */
881 /* Currently we don't handle adding/removing subsystems when
882 * any child cgroups exist. This is theoretically supportable
883 * but involves complex error handling, so it's being left until
885 if (root->number_of_cgroups > 1)
888 /* Process each subsystem */
889 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
890 struct cgroup_subsys *ss = subsys[i];
891 unsigned long bit = 1UL << i;
892 if (bit & added_bits) {
893 /* We're binding this subsystem to this hierarchy */
894 BUG_ON(cgrp->subsys[i]);
895 BUG_ON(!dummytop->subsys[i]);
896 BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
897 mutex_lock(&ss->hierarchy_mutex);
898 cgrp->subsys[i] = dummytop->subsys[i];
899 cgrp->subsys[i]->cgroup = cgrp;
900 list_move(&ss->sibling, &root->subsys_list);
904 mutex_unlock(&ss->hierarchy_mutex);
905 } else if (bit & removed_bits) {
906 /* We're removing this subsystem */
907 BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
908 BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
909 mutex_lock(&ss->hierarchy_mutex);
911 ss->bind(ss, dummytop);
912 dummytop->subsys[i]->cgroup = dummytop;
913 cgrp->subsys[i] = NULL;
914 subsys[i]->root = &rootnode;
915 list_move(&ss->sibling, &rootnode.subsys_list);
916 mutex_unlock(&ss->hierarchy_mutex);
917 } else if (bit & final_bits) {
918 /* Subsystem state should already exist */
919 BUG_ON(!cgrp->subsys[i]);
921 /* Subsystem state shouldn't exist */
922 BUG_ON(cgrp->subsys[i]);
925 root->subsys_bits = root->actual_subsys_bits = final_bits;
931 static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
933 struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info;
934 struct cgroup_subsys *ss;
936 mutex_lock(&cgroup_mutex);
937 for_each_subsys(root, ss)
938 seq_printf(seq, ",%s", ss->name);
939 if (test_bit(ROOT_NOPREFIX, &root->flags))
940 seq_puts(seq, ",noprefix");
941 if (strlen(root->release_agent_path))
942 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
943 if (strlen(root->name))
944 seq_printf(seq, ",name=%s", root->name);
945 mutex_unlock(&cgroup_mutex);
949 struct cgroup_sb_opts {
950 unsigned long subsys_bits;
954 /* User explicitly requested empty subsystem */
957 struct cgroupfs_root *new_root;
961 /* Convert a hierarchy specifier into a bitmask of subsystems and
963 static int parse_cgroupfs_options(char *data,
964 struct cgroup_sb_opts *opts)
966 char *token, *o = data ?: "all";
967 unsigned long mask = (unsigned long)-1;
969 #ifdef CONFIG_CPUSETS
970 mask = ~(1UL << cpuset_subsys_id);
973 memset(opts, 0, sizeof(*opts));
975 while ((token = strsep(&o, ",")) != NULL) {
978 if (!strcmp(token, "all")) {
979 /* Add all non-disabled subsystems */
981 opts->subsys_bits = 0;
982 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
983 struct cgroup_subsys *ss = subsys[i];
985 opts->subsys_bits |= 1ul << i;
987 } else if (!strcmp(token, "none")) {
988 /* Explicitly have no subsystems */
990 } else if (!strcmp(token, "noprefix")) {
991 set_bit(ROOT_NOPREFIX, &opts->flags);
992 } else if (!strncmp(token, "release_agent=", 14)) {
993 /* Specifying two release agents is forbidden */
994 if (opts->release_agent)
996 opts->release_agent =
997 kstrndup(token + 14, PATH_MAX, GFP_KERNEL);
998 if (!opts->release_agent)
1000 } else if (!strncmp(token, "name=", 5)) {
1002 const char *name = token + 5;
1003 /* Can't specify an empty name */
1006 /* Must match [\w.-]+ */
1007 for (i = 0; i < strlen(name); i++) {
1011 if ((c == '.') || (c == '-') || (c == '_'))
1015 /* Specifying two names is forbidden */
1018 opts->name = kstrndup(name,
1019 MAX_CGROUP_ROOT_NAMELEN,
1024 struct cgroup_subsys *ss;
1026 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1028 if (!strcmp(token, ss->name)) {
1030 set_bit(i, &opts->subsys_bits);
1034 if (i == CGROUP_SUBSYS_COUNT)
1039 /* Consistency checks */
1042 * Option noprefix was introduced just for backward compatibility
1043 * with the old cpuset, so we allow noprefix only if mounting just
1044 * the cpuset subsystem.
1046 if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
1047 (opts->subsys_bits & mask))
1051 /* Can't specify "none" and some subsystems */
1052 if (opts->subsys_bits && opts->none)
1056 * We either have to specify by name or by subsystems. (So all
1057 * empty hierarchies must have a name).
1059 if (!opts->subsys_bits && !opts->name)
1065 static int cgroup_remount(struct super_block *sb, int *flags, char *data)
1068 struct cgroupfs_root *root = sb->s_fs_info;
1069 struct cgroup *cgrp = &root->top_cgroup;
1070 struct cgroup_sb_opts opts;
1073 mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1074 mutex_lock(&cgroup_mutex);
1076 /* See what subsystems are wanted */
1077 ret = parse_cgroupfs_options(data, &opts);
1081 /* Don't allow flags to change at remount */
1082 if (opts.flags != root->flags) {
1087 /* Don't allow name to change at remount */
1088 if (opts.name && strcmp(opts.name, root->name)) {
1093 ret = rebind_subsystems(root, opts.subsys_bits);
1097 /* (re)populate subsystem files */
1098 cgroup_populate_dir(cgrp);
1100 if (opts.release_agent)
1101 strcpy(root->release_agent_path, opts.release_agent);
1103 kfree(opts.release_agent);
1105 mutex_unlock(&cgroup_mutex);
1106 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1111 static const struct super_operations cgroup_ops = {
1112 .statfs = simple_statfs,
1113 .drop_inode = generic_delete_inode,
1114 .show_options = cgroup_show_options,
1115 .remount_fs = cgroup_remount,
1118 static void init_cgroup_housekeeping(struct cgroup *cgrp)
1120 INIT_LIST_HEAD(&cgrp->sibling);
1121 INIT_LIST_HEAD(&cgrp->children);
1122 INIT_LIST_HEAD(&cgrp->css_sets);
1123 INIT_LIST_HEAD(&cgrp->release_list);
1124 init_rwsem(&cgrp->pids_mutex);
1127 static void init_cgroup_root(struct cgroupfs_root *root)
1129 struct cgroup *cgrp = &root->top_cgroup;
1130 INIT_LIST_HEAD(&root->subsys_list);
1131 INIT_LIST_HEAD(&root->root_list);
1132 root->number_of_cgroups = 1;
1134 cgrp->top_cgroup = cgrp;
1135 init_cgroup_housekeeping(cgrp);
1138 static bool init_root_id(struct cgroupfs_root *root)
1143 if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
1145 spin_lock(&hierarchy_id_lock);
1146 /* Try to allocate the next unused ID */
1147 ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
1148 &root->hierarchy_id);
1150 /* Try again starting from 0 */
1151 ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
1153 next_hierarchy_id = root->hierarchy_id + 1;
1154 } else if (ret != -EAGAIN) {
1155 /* Can only get here if the 31-bit IDR is full ... */
1158 spin_unlock(&hierarchy_id_lock);
1163 static int cgroup_test_super(struct super_block *sb, void *data)
1165 struct cgroup_sb_opts *opts = data;
1166 struct cgroupfs_root *root = sb->s_fs_info;
1168 /* If we asked for a name then it must match */
1169 if (opts->name && strcmp(opts->name, root->name))
1173 * If we asked for subsystems (or explicitly for no
1174 * subsystems) then they must match
1176 if ((opts->subsys_bits || opts->none)
1177 && (opts->subsys_bits != root->subsys_bits))
1183 static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
1185 struct cgroupfs_root *root;
1187 if (!opts->subsys_bits && !opts->none)
1190 root = kzalloc(sizeof(*root), GFP_KERNEL);
1192 return ERR_PTR(-ENOMEM);
1194 if (!init_root_id(root)) {
1196 return ERR_PTR(-ENOMEM);
1198 init_cgroup_root(root);
1200 root->subsys_bits = opts->subsys_bits;
1201 root->flags = opts->flags;
1202 if (opts->release_agent)
1203 strcpy(root->release_agent_path, opts->release_agent);
1205 strcpy(root->name, opts->name);
1209 static void cgroup_drop_root(struct cgroupfs_root *root)
1214 BUG_ON(!root->hierarchy_id);
1215 spin_lock(&hierarchy_id_lock);
1216 ida_remove(&hierarchy_ida, root->hierarchy_id);
1217 spin_unlock(&hierarchy_id_lock);
1221 static int cgroup_set_super(struct super_block *sb, void *data)
1224 struct cgroup_sb_opts *opts = data;
1226 /* If we don't have a new root, we can't set up a new sb */
1227 if (!opts->new_root)
1230 BUG_ON(!opts->subsys_bits && !opts->none);
1232 ret = set_anon_super(sb, NULL);
1236 sb->s_fs_info = opts->new_root;
1237 opts->new_root->sb = sb;
1239 sb->s_blocksize = PAGE_CACHE_SIZE;
1240 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
1241 sb->s_magic = CGROUP_SUPER_MAGIC;
1242 sb->s_op = &cgroup_ops;
1247 static int cgroup_get_rootdir(struct super_block *sb)
1249 struct inode *inode =
1250 cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
1251 struct dentry *dentry;
1256 inode->i_fop = &simple_dir_operations;
1257 inode->i_op = &cgroup_dir_inode_operations;
1258 /* directories start off with i_nlink == 2 (for "." entry) */
1260 dentry = d_alloc_root(inode);
1265 sb->s_root = dentry;
1269 static int cgroup_get_sb(struct file_system_type *fs_type,
1270 int flags, const char *unused_dev_name,
1271 void *data, struct vfsmount *mnt)
1273 struct cgroup_sb_opts opts;
1274 struct cgroupfs_root *root;
1276 struct super_block *sb;
1277 struct cgroupfs_root *new_root;
1279 /* First find the desired set of subsystems */
1280 ret = parse_cgroupfs_options(data, &opts);
1285 * Allocate a new cgroup root. We may not need it if we're
1286 * reusing an existing hierarchy.
1288 new_root = cgroup_root_from_opts(&opts);
1289 if (IS_ERR(new_root)) {
1290 ret = PTR_ERR(new_root);
1293 opts.new_root = new_root;
1295 /* Locate an existing or new sb for this hierarchy */
1296 sb = sget(fs_type, cgroup_test_super, cgroup_set_super, &opts);
1299 cgroup_drop_root(opts.new_root);
1303 root = sb->s_fs_info;
1305 if (root == opts.new_root) {
1306 /* We used the new root structure, so this is a new hierarchy */
1307 struct list_head tmp_cg_links;
1308 struct cgroup *root_cgrp = &root->top_cgroup;
1309 struct inode *inode;
1310 struct cgroupfs_root *existing_root;
1313 BUG_ON(sb->s_root != NULL);
1315 ret = cgroup_get_rootdir(sb);
1317 goto drop_new_super;
1318 inode = sb->s_root->d_inode;
1320 mutex_lock(&inode->i_mutex);
1321 mutex_lock(&cgroup_mutex);
1323 if (strlen(root->name)) {
1324 /* Check for name clashes with existing mounts */
1325 for_each_active_root(existing_root) {
1326 if (!strcmp(existing_root->name, root->name)) {
1328 mutex_unlock(&cgroup_mutex);
1329 mutex_unlock(&inode->i_mutex);
1330 goto drop_new_super;
1336 * We're accessing css_set_count without locking
1337 * css_set_lock here, but that's OK - it can only be
1338 * increased by someone holding cgroup_lock, and
1339 * that's us. The worst that can happen is that we
1340 * have some link structures left over
1342 ret = allocate_cg_links(css_set_count, &tmp_cg_links);
1344 mutex_unlock(&cgroup_mutex);
1345 mutex_unlock(&inode->i_mutex);
1346 goto drop_new_super;
1349 ret = rebind_subsystems(root, root->subsys_bits);
1350 if (ret == -EBUSY) {
1351 mutex_unlock(&cgroup_mutex);
1352 mutex_unlock(&inode->i_mutex);
1353 free_cg_links(&tmp_cg_links);
1354 goto drop_new_super;
1357 /* EBUSY should be the only error here */
1360 list_add(&root->root_list, &roots);
1363 sb->s_root->d_fsdata = root_cgrp;
1364 root->top_cgroup.dentry = sb->s_root;
1366 /* Link the top cgroup in this hierarchy into all
1367 * the css_set objects */
1368 write_lock(&css_set_lock);
1369 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
1370 struct hlist_head *hhead = &css_set_table[i];
1371 struct hlist_node *node;
1374 hlist_for_each_entry(cg, node, hhead, hlist)
1375 link_css_set(&tmp_cg_links, cg, root_cgrp);
1377 write_unlock(&css_set_lock);
1379 free_cg_links(&tmp_cg_links);
1381 BUG_ON(!list_empty(&root_cgrp->sibling));
1382 BUG_ON(!list_empty(&root_cgrp->children));
1383 BUG_ON(root->number_of_cgroups != 1);
1385 cgroup_populate_dir(root_cgrp);
1386 mutex_unlock(&cgroup_mutex);
1387 mutex_unlock(&inode->i_mutex);
1390 * We re-used an existing hierarchy - the new root (if
1391 * any) is not needed
1393 cgroup_drop_root(opts.new_root);
1396 simple_set_mnt(mnt, sb);
1397 kfree(opts.release_agent);
1402 deactivate_locked_super(sb);
1404 kfree(opts.release_agent);
1410 static void cgroup_kill_sb(struct super_block *sb) {
1411 struct cgroupfs_root *root = sb->s_fs_info;
1412 struct cgroup *cgrp = &root->top_cgroup;
1414 struct cg_cgroup_link *link;
1415 struct cg_cgroup_link *saved_link;
1419 BUG_ON(root->number_of_cgroups != 1);
1420 BUG_ON(!list_empty(&cgrp->children));
1421 BUG_ON(!list_empty(&cgrp->sibling));
1423 mutex_lock(&cgroup_mutex);
1425 /* Rebind all subsystems back to the default hierarchy */
1426 ret = rebind_subsystems(root, 0);
1427 /* Shouldn't be able to fail ... */
1431 * Release all the links from css_sets to this hierarchy's
1434 write_lock(&css_set_lock);
1436 list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
1438 list_del(&link->cg_link_list);
1439 list_del(&link->cgrp_link_list);
1442 write_unlock(&css_set_lock);
1444 if (!list_empty(&root->root_list)) {
1445 list_del(&root->root_list);
1449 mutex_unlock(&cgroup_mutex);
1451 kill_litter_super(sb);
1452 cgroup_drop_root(root);
1455 static struct file_system_type cgroup_fs_type = {
1457 .get_sb = cgroup_get_sb,
1458 .kill_sb = cgroup_kill_sb,
1461 static inline struct cgroup *__d_cgrp(struct dentry *dentry)
1463 return dentry->d_fsdata;
1466 static inline struct cftype *__d_cft(struct dentry *dentry)
1468 return dentry->d_fsdata;
1472 * cgroup_path - generate the path of a cgroup
1473 * @cgrp: the cgroup in question
1474 * @buf: the buffer to write the path into
1475 * @buflen: the length of the buffer
1477 * Called with cgroup_mutex held or else with an RCU-protected cgroup
1478 * reference. Writes path of cgroup into buf. Returns 0 on success,
1481 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1484 struct dentry *dentry = rcu_dereference(cgrp->dentry);
1486 if (!dentry || cgrp == dummytop) {
1488 * Inactive subsystems have no dentry for their root
1495 start = buf + buflen;
1499 int len = dentry->d_name.len;
1500 if ((start -= len) < buf)
1501 return -ENAMETOOLONG;
1502 memcpy(start, cgrp->dentry->d_name.name, len);
1503 cgrp = cgrp->parent;
1506 dentry = rcu_dereference(cgrp->dentry);
1510 return -ENAMETOOLONG;
1513 memmove(buf, start, buf + buflen - start);
1518 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
1519 * @cgrp: the cgroup the task is attaching to
1520 * @tsk: the task to be attached
1522 * Call holding cgroup_mutex. May take task_lock of
1523 * the task 'tsk' during call.
1525 int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1528 struct cgroup_subsys *ss;
1529 struct cgroup *oldcgrp;
1531 struct css_set *newcg;
1532 struct cgroupfs_root *root = cgrp->root;
1534 /* Nothing to do if the task is already in that cgroup */
1535 oldcgrp = task_cgroup_from_root(tsk, root);
1536 if (cgrp == oldcgrp)
1539 for_each_subsys(root, ss) {
1540 if (ss->can_attach) {
1541 retval = ss->can_attach(ss, cgrp, tsk);
1552 * Locate or allocate a new css_set for this task,
1553 * based on its final set of cgroups
1555 newcg = find_css_set(cg, cgrp);
1561 if (tsk->flags & PF_EXITING) {
1566 rcu_assign_pointer(tsk->cgroups, newcg);
1569 /* Update the css_set linked lists if we're using them */
1570 write_lock(&css_set_lock);
1571 if (!list_empty(&tsk->cg_list)) {
1572 list_del(&tsk->cg_list);
1573 list_add(&tsk->cg_list, &newcg->tasks);
1575 write_unlock(&css_set_lock);
1577 for_each_subsys(root, ss) {
1579 ss->attach(ss, cgrp, oldcgrp, tsk);
1581 set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1586 * wake up rmdir() waiter. the rmdir should fail since the cgroup
1587 * is no longer empty.
1589 cgroup_wakeup_rmdir_waiter(cgrp);
1594 * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex
1595 * held. May take task_lock of task
1597 static int attach_task_by_pid(struct cgroup *cgrp, u64 pid)
1599 struct task_struct *tsk;
1600 const struct cred *cred = current_cred(), *tcred;
1605 tsk = find_task_by_vpid(pid);
1606 if (!tsk || tsk->flags & PF_EXITING) {
1611 tcred = __task_cred(tsk);
1613 cred->euid != tcred->uid &&
1614 cred->euid != tcred->suid) {
1618 get_task_struct(tsk);
1622 get_task_struct(tsk);
1625 ret = cgroup_attach_task(cgrp, tsk);
1626 put_task_struct(tsk);
1630 static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
1633 if (!cgroup_lock_live_group(cgrp))
1635 ret = attach_task_by_pid(cgrp, pid);
1640 /* The various types of files and directories in a cgroup file system */
1641 enum cgroup_filetype {
1645 FILE_NOTIFY_ON_RELEASE,
1650 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
1651 * @cgrp: the cgroup to be checked for liveness
1653 * On success, returns true; the lock should be later released with
1654 * cgroup_unlock(). On failure returns false with no lock held.
1656 bool cgroup_lock_live_group(struct cgroup *cgrp)
1658 mutex_lock(&cgroup_mutex);
1659 if (cgroup_is_removed(cgrp)) {
1660 mutex_unlock(&cgroup_mutex);
1666 static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
1669 BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
1670 if (!cgroup_lock_live_group(cgrp))
1672 strcpy(cgrp->root->release_agent_path, buffer);
1677 static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
1678 struct seq_file *seq)
1680 if (!cgroup_lock_live_group(cgrp))
1682 seq_puts(seq, cgrp->root->release_agent_path);
1683 seq_putc(seq, '\n');
1688 /* A buffer size big enough for numbers or short strings */
1689 #define CGROUP_LOCAL_BUFFER_SIZE 64
1691 static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
1693 const char __user *userbuf,
1694 size_t nbytes, loff_t *unused_ppos)
1696 char buffer[CGROUP_LOCAL_BUFFER_SIZE];
1702 if (nbytes >= sizeof(buffer))
1704 if (copy_from_user(buffer, userbuf, nbytes))
1707 buffer[nbytes] = 0; /* nul-terminate */
1709 if (cft->write_u64) {
1710 u64 val = simple_strtoull(buffer, &end, 0);
1713 retval = cft->write_u64(cgrp, cft, val);
1715 s64 val = simple_strtoll(buffer, &end, 0);
1718 retval = cft->write_s64(cgrp, cft, val);
1725 static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
1727 const char __user *userbuf,
1728 size_t nbytes, loff_t *unused_ppos)
1730 char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
1732 size_t max_bytes = cft->max_write_len;
1733 char *buffer = local_buffer;
1736 max_bytes = sizeof(local_buffer) - 1;
1737 if (nbytes >= max_bytes)
1739 /* Allocate a dynamic buffer if we need one */
1740 if (nbytes >= sizeof(local_buffer)) {
1741 buffer = kmalloc(nbytes + 1, GFP_KERNEL);
1745 if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
1750 buffer[nbytes] = 0; /* nul-terminate */
1752 retval = cft->write_string(cgrp, cft, buffer);
1756 if (buffer != local_buffer)
1761 static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
1762 size_t nbytes, loff_t *ppos)
1764 struct cftype *cft = __d_cft(file->f_dentry);
1765 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
1767 if (cgroup_is_removed(cgrp))
1770 return cft->write(cgrp, cft, file, buf, nbytes, ppos);
1771 if (cft->write_u64 || cft->write_s64)
1772 return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
1773 if (cft->write_string)
1774 return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
1776 int ret = cft->trigger(cgrp, (unsigned int)cft->private);
1777 return ret ? ret : nbytes;
1782 static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
1784 char __user *buf, size_t nbytes,
1787 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
1788 u64 val = cft->read_u64(cgrp, cft);
1789 int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
1791 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
1794 static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
1796 char __user *buf, size_t nbytes,
1799 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
1800 s64 val = cft->read_s64(cgrp, cft);
1801 int len = sprintf(tmp, "%lld\n", (long long) val);
1803 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
1806 static ssize_t cgroup_file_read(struct file *file, char __user *buf,
1807 size_t nbytes, loff_t *ppos)
1809 struct cftype *cft = __d_cft(file->f_dentry);
1810 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
1812 if (cgroup_is_removed(cgrp))
1816 return cft->read(cgrp, cft, file, buf, nbytes, ppos);
1818 return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
1820 return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
1825 * seqfile ops/methods for returning structured data. Currently just
1826 * supports string->u64 maps, but can be extended in future.
1829 struct cgroup_seqfile_state {
1831 struct cgroup *cgroup;
1834 static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
1836 struct seq_file *sf = cb->state;
1837 return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
1840 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
1842 struct cgroup_seqfile_state *state = m->private;
1843 struct cftype *cft = state->cft;
1844 if (cft->read_map) {
1845 struct cgroup_map_cb cb = {
1846 .fill = cgroup_map_add,
1849 return cft->read_map(state->cgroup, cft, &cb);
1851 return cft->read_seq_string(state->cgroup, cft, m);
1854 static int cgroup_seqfile_release(struct inode *inode, struct file *file)
1856 struct seq_file *seq = file->private_data;
1857 kfree(seq->private);
1858 return single_release(inode, file);
1861 static struct file_operations cgroup_seqfile_operations = {
1863 .write = cgroup_file_write,
1864 .llseek = seq_lseek,
1865 .release = cgroup_seqfile_release,
1868 static int cgroup_file_open(struct inode *inode, struct file *file)
1873 err = generic_file_open(inode, file);
1876 cft = __d_cft(file->f_dentry);
1878 if (cft->read_map || cft->read_seq_string) {
1879 struct cgroup_seqfile_state *state =
1880 kzalloc(sizeof(*state), GFP_USER);
1884 state->cgroup = __d_cgrp(file->f_dentry->d_parent);
1885 file->f_op = &cgroup_seqfile_operations;
1886 err = single_open(file, cgroup_seqfile_show, state);
1889 } else if (cft->open)
1890 err = cft->open(inode, file);
1897 static int cgroup_file_release(struct inode *inode, struct file *file)
1899 struct cftype *cft = __d_cft(file->f_dentry);
1901 return cft->release(inode, file);
1906 * cgroup_rename - Only allow simple rename of directories in place.
1908 static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
1909 struct inode *new_dir, struct dentry *new_dentry)
1911 if (!S_ISDIR(old_dentry->d_inode->i_mode))
1913 if (new_dentry->d_inode)
1915 if (old_dir != new_dir)
1917 return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
1920 static struct file_operations cgroup_file_operations = {
1921 .read = cgroup_file_read,
1922 .write = cgroup_file_write,
1923 .llseek = generic_file_llseek,
1924 .open = cgroup_file_open,
1925 .release = cgroup_file_release,
1928 static const struct inode_operations cgroup_dir_inode_operations = {
1929 .lookup = simple_lookup,
1930 .mkdir = cgroup_mkdir,
1931 .rmdir = cgroup_rmdir,
1932 .rename = cgroup_rename,
1935 static int cgroup_create_file(struct dentry *dentry, mode_t mode,
1936 struct super_block *sb)
1938 static const struct dentry_operations cgroup_dops = {
1939 .d_iput = cgroup_diput,
1942 struct inode *inode;
1946 if (dentry->d_inode)
1949 inode = cgroup_new_inode(mode, sb);
1953 if (S_ISDIR(mode)) {
1954 inode->i_op = &cgroup_dir_inode_operations;
1955 inode->i_fop = &simple_dir_operations;
1957 /* start off with i_nlink == 2 (for "." entry) */
1960 /* start with the directory inode held, so that we can
1961 * populate it without racing with another mkdir */
1962 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1963 } else if (S_ISREG(mode)) {
1965 inode->i_fop = &cgroup_file_operations;
1967 dentry->d_op = &cgroup_dops;
1968 d_instantiate(dentry, inode);
1969 dget(dentry); /* Extra count - pin the dentry in core */
1974 * cgroup_create_dir - create a directory for an object.
1975 * @cgrp: the cgroup we create the directory for. It must have a valid
1976 * ->parent field. And we are going to fill its ->dentry field.
1977 * @dentry: dentry of the new cgroup
1978 * @mode: mode to set on new directory.
1980 static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
1983 struct dentry *parent;
1986 parent = cgrp->parent->dentry;
1987 error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
1989 dentry->d_fsdata = cgrp;
1990 inc_nlink(parent->d_inode);
1991 rcu_assign_pointer(cgrp->dentry, dentry);
2000 * cgroup_file_mode - deduce file mode of a control file
2001 * @cft: the control file in question
2003 * returns cft->mode if ->mode is not 0
2004 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
2005 * returns S_IRUGO if it has only a read handler
2006 * returns S_IWUSR if it has only a write hander
2008 static mode_t cgroup_file_mode(const struct cftype *cft)
2015 if (cft->read || cft->read_u64 || cft->read_s64 ||
2016 cft->read_map || cft->read_seq_string)
2019 if (cft->write || cft->write_u64 || cft->write_s64 ||
2020 cft->write_string || cft->trigger)
2026 int cgroup_add_file(struct cgroup *cgrp,
2027 struct cgroup_subsys *subsys,
2028 const struct cftype *cft)
2030 struct dentry *dir = cgrp->dentry;
2031 struct dentry *dentry;
2035 char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2036 if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
2037 strcpy(name, subsys->name);
2040 strcat(name, cft->name);
2041 BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
2042 dentry = lookup_one_len(name, dir, strlen(name));
2043 if (!IS_ERR(dentry)) {
2044 mode = cgroup_file_mode(cft);
2045 error = cgroup_create_file(dentry, mode | S_IFREG,
2048 dentry->d_fsdata = (void *)cft;
2051 error = PTR_ERR(dentry);
2055 int cgroup_add_files(struct cgroup *cgrp,
2056 struct cgroup_subsys *subsys,
2057 const struct cftype cft[],
2061 for (i = 0; i < count; i++) {
2062 err = cgroup_add_file(cgrp, subsys, &cft[i]);
2070 * cgroup_task_count - count the number of tasks in a cgroup.
2071 * @cgrp: the cgroup in question
2073 * Return the number of tasks in the cgroup.
2075 int cgroup_task_count(const struct cgroup *cgrp)
2078 struct cg_cgroup_link *link;
2080 read_lock(&css_set_lock);
2081 list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
2082 count += atomic_read(&link->cg->refcount);
2084 read_unlock(&css_set_lock);
2089 * Advance a list_head iterator. The iterator should be positioned at
2090 * the start of a css_set
2092 static void cgroup_advance_iter(struct cgroup *cgrp,
2093 struct cgroup_iter *it)
2095 struct list_head *l = it->cg_link;
2096 struct cg_cgroup_link *link;
2099 /* Advance to the next non-empty css_set */
2102 if (l == &cgrp->css_sets) {
2106 link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
2108 } while (list_empty(&cg->tasks));
2110 it->task = cg->tasks.next;
2114 * To reduce the fork() overhead for systems that are not actually
2115 * using their cgroups capability, we don't maintain the lists running
2116 * through each css_set to its tasks until we see the list actually
2117 * used - in other words after the first call to cgroup_iter_start().
2119 * The tasklist_lock is not held here, as do_each_thread() and
2120 * while_each_thread() are protected by RCU.
2122 static void cgroup_enable_task_cg_lists(void)
2124 struct task_struct *p, *g;
2125 write_lock(&css_set_lock);
2126 use_task_css_set_links = 1;
2127 do_each_thread(g, p) {
2130 * We should check if the process is exiting, otherwise
2131 * it will race with cgroup_exit() in that the list
2132 * entry won't be deleted though the process has exited.
2134 if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
2135 list_add(&p->cg_list, &p->cgroups->tasks);
2137 } while_each_thread(g, p);
2138 write_unlock(&css_set_lock);
2141 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
2144 * The first time anyone tries to iterate across a cgroup,
2145 * we need to enable the list linking each css_set to its
2146 * tasks, and fix up all existing tasks.
2148 if (!use_task_css_set_links)
2149 cgroup_enable_task_cg_lists();
2151 read_lock(&css_set_lock);
2152 it->cg_link = &cgrp->css_sets;
2153 cgroup_advance_iter(cgrp, it);
2156 struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
2157 struct cgroup_iter *it)
2159 struct task_struct *res;
2160 struct list_head *l = it->task;
2161 struct cg_cgroup_link *link;
2163 /* If the iterator cg is NULL, we have no tasks */
2166 res = list_entry(l, struct task_struct, cg_list);
2167 /* Advance iterator to find next entry */
2169 link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
2170 if (l == &link->cg->tasks) {
2171 /* We reached the end of this task list - move on to
2172 * the next cg_cgroup_link */
2173 cgroup_advance_iter(cgrp, it);
2180 void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
2182 read_unlock(&css_set_lock);
2185 static inline int started_after_time(struct task_struct *t1,
2186 struct timespec *time,
2187 struct task_struct *t2)
2189 int start_diff = timespec_compare(&t1->start_time, time);
2190 if (start_diff > 0) {
2192 } else if (start_diff < 0) {
2196 * Arbitrarily, if two processes started at the same
2197 * time, we'll say that the lower pointer value
2198 * started first. Note that t2 may have exited by now
2199 * so this may not be a valid pointer any longer, but
2200 * that's fine - it still serves to distinguish
2201 * between two tasks started (effectively) simultaneously.
2208 * This function is a callback from heap_insert() and is used to order
2210 * In this case we order the heap in descending task start time.
2212 static inline int started_after(void *p1, void *p2)
2214 struct task_struct *t1 = p1;
2215 struct task_struct *t2 = p2;
2216 return started_after_time(t1, &t2->start_time, t2);
2220 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
2221 * @scan: struct cgroup_scanner containing arguments for the scan
2223 * Arguments include pointers to callback functions test_task() and
2225 * Iterate through all the tasks in a cgroup, calling test_task() for each,
2226 * and if it returns true, call process_task() for it also.
2227 * The test_task pointer may be NULL, meaning always true (select all tasks).
2228 * Effectively duplicates cgroup_iter_{start,next,end}()
2229 * but does not lock css_set_lock for the call to process_task().
2230 * The struct cgroup_scanner may be embedded in any structure of the caller's
2232 * It is guaranteed that process_task() will act on every task that
2233 * is a member of the cgroup for the duration of this call. This
2234 * function may or may not call process_task() for tasks that exit
2235 * or move to a different cgroup during the call, or are forked or
2236 * move into the cgroup during the call.
2238 * Note that test_task() may be called with locks held, and may in some
2239 * situations be called multiple times for the same task, so it should
2241 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
2242 * pre-allocated and will be used for heap operations (and its "gt" member will
2243 * be overwritten), else a temporary heap will be used (allocation of which
2244 * may cause this function to fail).
2246 int cgroup_scan_tasks(struct cgroup_scanner *scan)
2249 struct cgroup_iter it;
2250 struct task_struct *p, *dropped;
2251 /* Never dereference latest_task, since it's not refcounted */
2252 struct task_struct *latest_task = NULL;
2253 struct ptr_heap tmp_heap;
2254 struct ptr_heap *heap;
2255 struct timespec latest_time = { 0, 0 };
2258 /* The caller supplied our heap and pre-allocated its memory */
2260 heap->gt = &started_after;
2262 /* We need to allocate our own heap memory */
2264 retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
2266 /* cannot allocate the heap */
2272 * Scan tasks in the cgroup, using the scanner's "test_task" callback
2273 * to determine which are of interest, and using the scanner's
2274 * "process_task" callback to process any of them that need an update.
2275 * Since we don't want to hold any locks during the task updates,
2276 * gather tasks to be processed in a heap structure.
2277 * The heap is sorted by descending task start time.
2278 * If the statically-sized heap fills up, we overflow tasks that
2279 * started later, and in future iterations only consider tasks that
2280 * started after the latest task in the previous pass. This
2281 * guarantees forward progress and that we don't miss any tasks.
2284 cgroup_iter_start(scan->cg, &it);
2285 while ((p = cgroup_iter_next(scan->cg, &it))) {
2287 * Only affect tasks that qualify per the caller's callback,
2288 * if he provided one
2290 if (scan->test_task && !scan->test_task(p, scan))
2293 * Only process tasks that started after the last task
2296 if (!started_after_time(p, &latest_time, latest_task))
2298 dropped = heap_insert(heap, p);
2299 if (dropped == NULL) {
2301 * The new task was inserted; the heap wasn't
2305 } else if (dropped != p) {
2307 * The new task was inserted, and pushed out a
2311 put_task_struct(dropped);
2314 * Else the new task was newer than anything already in
2315 * the heap and wasn't inserted
2318 cgroup_iter_end(scan->cg, &it);
2321 for (i = 0; i < heap->size; i++) {
2322 struct task_struct *q = heap->ptrs[i];
2324 latest_time = q->start_time;
2327 /* Process the task per the caller's callback */
2328 scan->process_task(q, scan);
2332 * If we had to process any tasks at all, scan again
2333 * in case some of them were in the middle of forking
2334 * children that didn't get processed.
2335 * Not the most efficient way to do it, but it avoids
2336 * having to take callback_mutex in the fork path
2340 if (heap == &tmp_heap)
2341 heap_free(&tmp_heap);
2346 * Stuff for reading the 'tasks' file.
2348 * Reading this file can return large amounts of data if a cgroup has
2349 * *lots* of attached tasks. So it may need several calls to read(),
2350 * but we cannot guarantee that the information we produce is correct
2351 * unless we produce it entirely atomically.
2356 * Load into 'pidarray' up to 'npids' of the tasks using cgroup
2357 * 'cgrp'. Return actual number of pids loaded. No need to
2358 * task_lock(p) when reading out p->cgroup, since we're in an RCU
2359 * read section, so the css_set can't go away, and is
2360 * immutable after creation.
2362 static int pid_array_load(pid_t *pidarray, int npids, struct cgroup *cgrp)
2365 struct cgroup_iter it;
2366 struct task_struct *tsk;
2367 cgroup_iter_start(cgrp, &it);
2368 while ((tsk = cgroup_iter_next(cgrp, &it))) {
2369 if (unlikely(n == npids))
2371 pid = task_pid_vnr(tsk);
2373 pidarray[n++] = pid;
2375 cgroup_iter_end(cgrp, &it);
2380 * cgroupstats_build - build and fill cgroupstats
2381 * @stats: cgroupstats to fill information into
2382 * @dentry: A dentry entry belonging to the cgroup for which stats have
2385 * Build and fill cgroupstats so that taskstats can export it to user
2388 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
2391 struct cgroup *cgrp;
2392 struct cgroup_iter it;
2393 struct task_struct *tsk;
2396 * Validate dentry by checking the superblock operations,
2397 * and make sure it's a directory.
2399 if (dentry->d_sb->s_op != &cgroup_ops ||
2400 !S_ISDIR(dentry->d_inode->i_mode))
2404 cgrp = dentry->d_fsdata;
2406 cgroup_iter_start(cgrp, &it);
2407 while ((tsk = cgroup_iter_next(cgrp, &it))) {
2408 switch (tsk->state) {
2410 stats->nr_running++;
2412 case TASK_INTERRUPTIBLE:
2413 stats->nr_sleeping++;
2415 case TASK_UNINTERRUPTIBLE:
2416 stats->nr_uninterruptible++;
2419 stats->nr_stopped++;
2422 if (delayacct_is_task_waiting_on_io(tsk))
2423 stats->nr_io_wait++;
2427 cgroup_iter_end(cgrp, &it);
2433 static int cmppid(const void *a, const void *b)
2435 return *(pid_t *)a - *(pid_t *)b;
2440 * seq_file methods for the "tasks" file. The seq_file position is the
2441 * next pid to display; the seq_file iterator is a pointer to the pid
2442 * in the cgroup->tasks_pids array.
2445 static void *cgroup_tasks_start(struct seq_file *s, loff_t *pos)
2448 * Initially we receive a position value that corresponds to
2449 * one more than the last pid shown (or 0 on the first call or
2450 * after a seek to the start). Use a binary-search to find the
2451 * next pid to display, if any
2453 struct cgroup *cgrp = s->private;
2454 int index = 0, pid = *pos;
2457 down_read(&cgrp->pids_mutex);
2459 int end = cgrp->pids_length;
2461 while (index < end) {
2462 int mid = (index + end) / 2;
2463 if (cgrp->tasks_pids[mid] == pid) {
2466 } else if (cgrp->tasks_pids[mid] <= pid)
2472 /* If we're off the end of the array, we're done */
2473 if (index >= cgrp->pids_length)
2475 /* Update the abstract position to be the actual pid that we found */
2476 iter = cgrp->tasks_pids + index;
2481 static void cgroup_tasks_stop(struct seq_file *s, void *v)
2483 struct cgroup *cgrp = s->private;
2484 up_read(&cgrp->pids_mutex);
2487 static void *cgroup_tasks_next(struct seq_file *s, void *v, loff_t *pos)
2489 struct cgroup *cgrp = s->private;
2491 int *end = cgrp->tasks_pids + cgrp->pids_length;
2494 * Advance to the next pid in the array. If this goes off the
2506 static int cgroup_tasks_show(struct seq_file *s, void *v)
2508 return seq_printf(s, "%d\n", *(int *)v);
2511 static const struct seq_operations cgroup_tasks_seq_operations = {
2512 .start = cgroup_tasks_start,
2513 .stop = cgroup_tasks_stop,
2514 .next = cgroup_tasks_next,
2515 .show = cgroup_tasks_show,
2518 static void release_cgroup_pid_array(struct cgroup *cgrp)
2520 down_write(&cgrp->pids_mutex);
2521 BUG_ON(!cgrp->pids_use_count);
2522 if (!--cgrp->pids_use_count) {
2523 kfree(cgrp->tasks_pids);
2524 cgrp->tasks_pids = NULL;
2525 cgrp->pids_length = 0;
2527 up_write(&cgrp->pids_mutex);
2530 static int cgroup_tasks_release(struct inode *inode, struct file *file)
2532 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2534 if (!(file->f_mode & FMODE_READ))
2537 release_cgroup_pid_array(cgrp);
2538 return seq_release(inode, file);
2541 static struct file_operations cgroup_tasks_operations = {
2543 .llseek = seq_lseek,
2544 .write = cgroup_file_write,
2545 .release = cgroup_tasks_release,
2549 * Handle an open on 'tasks' file. Prepare an array containing the
2550 * process id's of tasks currently attached to the cgroup being opened.
2553 static int cgroup_tasks_open(struct inode *unused, struct file *file)
2555 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2560 /* Nothing to do for write-only files */
2561 if (!(file->f_mode & FMODE_READ))
2565 * If cgroup gets more users after we read count, we won't have
2566 * enough space - tough. This race is indistinguishable to the
2567 * caller from the case that the additional cgroup users didn't
2568 * show up until sometime later on.
2570 npids = cgroup_task_count(cgrp);
2571 pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL);
2574 npids = pid_array_load(pidarray, npids, cgrp);
2575 sort(pidarray, npids, sizeof(pid_t), cmppid, NULL);
2578 * Store the array in the cgroup, freeing the old
2579 * array if necessary
2581 down_write(&cgrp->pids_mutex);
2582 kfree(cgrp->tasks_pids);
2583 cgrp->tasks_pids = pidarray;
2584 cgrp->pids_length = npids;
2585 cgrp->pids_use_count++;
2586 up_write(&cgrp->pids_mutex);
2588 file->f_op = &cgroup_tasks_operations;
2590 retval = seq_open(file, &cgroup_tasks_seq_operations);
2592 release_cgroup_pid_array(cgrp);
2595 ((struct seq_file *)file->private_data)->private = cgrp;
2599 static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
2602 return notify_on_release(cgrp);
2605 static int cgroup_write_notify_on_release(struct cgroup *cgrp,
2609 clear_bit(CGRP_RELEASABLE, &cgrp->flags);
2611 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
2613 clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
2618 * for the common functions, 'private' gives the type of file
2620 static struct cftype files[] = {
2623 .open = cgroup_tasks_open,
2624 .write_u64 = cgroup_tasks_write,
2625 .release = cgroup_tasks_release,
2626 .private = FILE_TASKLIST,
2627 .mode = S_IRUGO | S_IWUSR,
2631 .name = "notify_on_release",
2632 .read_u64 = cgroup_read_notify_on_release,
2633 .write_u64 = cgroup_write_notify_on_release,
2634 .private = FILE_NOTIFY_ON_RELEASE,
2638 static struct cftype cft_release_agent = {
2639 .name = "release_agent",
2640 .read_seq_string = cgroup_release_agent_show,
2641 .write_string = cgroup_release_agent_write,
2642 .max_write_len = PATH_MAX,
2643 .private = FILE_RELEASE_AGENT,
2646 static int cgroup_populate_dir(struct cgroup *cgrp)
2649 struct cgroup_subsys *ss;
2651 /* First clear out any existing files */
2652 cgroup_clear_directory(cgrp->dentry);
2654 err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));
2658 if (cgrp == cgrp->top_cgroup) {
2659 if ((err = cgroup_add_file(cgrp, NULL, &cft_release_agent)) < 0)
2663 for_each_subsys(cgrp->root, ss) {
2664 if (ss->populate && (err = ss->populate(ss, cgrp)) < 0)
2667 /* This cgroup is ready now */
2668 for_each_subsys(cgrp->root, ss) {
2669 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
2671 * Update id->css pointer and make this css visible from
2672 * CSS ID functions. This pointer will be dereferened
2673 * from RCU-read-side without locks.
2676 rcu_assign_pointer(css->id->css, css);
2682 static void init_cgroup_css(struct cgroup_subsys_state *css,
2683 struct cgroup_subsys *ss,
2684 struct cgroup *cgrp)
2687 atomic_set(&css->refcnt, 1);
2690 if (cgrp == dummytop)
2691 set_bit(CSS_ROOT, &css->flags);
2692 BUG_ON(cgrp->subsys[ss->subsys_id]);
2693 cgrp->subsys[ss->subsys_id] = css;
2696 static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
2698 /* We need to take each hierarchy_mutex in a consistent order */
2701 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2702 struct cgroup_subsys *ss = subsys[i];
2703 if (ss->root == root)
2704 mutex_lock(&ss->hierarchy_mutex);
2708 static void cgroup_unlock_hierarchy(struct cgroupfs_root *root)
2712 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2713 struct cgroup_subsys *ss = subsys[i];
2714 if (ss->root == root)
2715 mutex_unlock(&ss->hierarchy_mutex);
2720 * cgroup_create - create a cgroup
2721 * @parent: cgroup that will be parent of the new cgroup
2722 * @dentry: dentry of the new cgroup
2723 * @mode: mode to set on new inode
2725 * Must be called with the mutex on the parent inode held
2727 static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
2730 struct cgroup *cgrp;
2731 struct cgroupfs_root *root = parent->root;
2733 struct cgroup_subsys *ss;
2734 struct super_block *sb = root->sb;
2736 cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
2740 /* Grab a reference on the superblock so the hierarchy doesn't
2741 * get deleted on unmount if there are child cgroups. This
2742 * can be done outside cgroup_mutex, since the sb can't
2743 * disappear while someone has an open control file on the
2745 atomic_inc(&sb->s_active);
2747 mutex_lock(&cgroup_mutex);
2749 init_cgroup_housekeeping(cgrp);
2751 cgrp->parent = parent;
2752 cgrp->root = parent->root;
2753 cgrp->top_cgroup = parent->top_cgroup;
2755 if (notify_on_release(parent))
2756 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
2758 for_each_subsys(root, ss) {
2759 struct cgroup_subsys_state *css = ss->create(ss, cgrp);
2764 init_cgroup_css(css, ss, cgrp);
2766 if (alloc_css_id(ss, parent, cgrp))
2768 /* At error, ->destroy() callback has to free assigned ID. */
2771 cgroup_lock_hierarchy(root);
2772 list_add(&cgrp->sibling, &cgrp->parent->children);
2773 cgroup_unlock_hierarchy(root);
2774 root->number_of_cgroups++;
2776 err = cgroup_create_dir(cgrp, dentry, mode);
2780 /* The cgroup directory was pre-locked for us */
2781 BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
2783 err = cgroup_populate_dir(cgrp);
2784 /* If err < 0, we have a half-filled directory - oh well ;) */
2786 mutex_unlock(&cgroup_mutex);
2787 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
2793 cgroup_lock_hierarchy(root);
2794 list_del(&cgrp->sibling);
2795 cgroup_unlock_hierarchy(root);
2796 root->number_of_cgroups--;
2800 for_each_subsys(root, ss) {
2801 if (cgrp->subsys[ss->subsys_id])
2802 ss->destroy(ss, cgrp);
2805 mutex_unlock(&cgroup_mutex);
2807 /* Release the reference count that we took on the superblock */
2808 deactivate_super(sb);
2814 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode)
2816 struct cgroup *c_parent = dentry->d_parent->d_fsdata;
2818 /* the vfs holds inode->i_mutex already */
2819 return cgroup_create(c_parent, dentry, mode | S_IFDIR);
2822 static int cgroup_has_css_refs(struct cgroup *cgrp)
2824 /* Check the reference count on each subsystem. Since we
2825 * already established that there are no tasks in the
2826 * cgroup, if the css refcount is also 1, then there should
2827 * be no outstanding references, so the subsystem is safe to
2828 * destroy. We scan across all subsystems rather than using
2829 * the per-hierarchy linked list of mounted subsystems since
2830 * we can be called via check_for_release() with no
2831 * synchronization other than RCU, and the subsystem linked
2832 * list isn't RCU-safe */
2834 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2835 struct cgroup_subsys *ss = subsys[i];
2836 struct cgroup_subsys_state *css;
2837 /* Skip subsystems not in this hierarchy */
2838 if (ss->root != cgrp->root)
2840 css = cgrp->subsys[ss->subsys_id];
2841 /* When called from check_for_release() it's possible
2842 * that by this point the cgroup has been removed
2843 * and the css deleted. But a false-positive doesn't
2844 * matter, since it can only happen if the cgroup
2845 * has been deleted and hence no longer needs the
2846 * release agent to be called anyway. */
2847 if (css && (atomic_read(&css->refcnt) > 1))
2854 * Atomically mark all (or else none) of the cgroup's CSS objects as
2855 * CSS_REMOVED. Return true on success, or false if the cgroup has
2856 * busy subsystems. Call with cgroup_mutex held
2859 static int cgroup_clear_css_refs(struct cgroup *cgrp)
2861 struct cgroup_subsys *ss;
2862 unsigned long flags;
2863 bool failed = false;
2864 local_irq_save(flags);
2865 for_each_subsys(cgrp->root, ss) {
2866 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
2869 /* We can only remove a CSS with a refcnt==1 */
2870 refcnt = atomic_read(&css->refcnt);
2877 * Drop the refcnt to 0 while we check other
2878 * subsystems. This will cause any racing
2879 * css_tryget() to spin until we set the
2880 * CSS_REMOVED bits or abort
2882 if (atomic_cmpxchg(&css->refcnt, refcnt, 0) == refcnt)
2888 for_each_subsys(cgrp->root, ss) {
2889 struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
2892 * Restore old refcnt if we previously managed
2893 * to clear it from 1 to 0
2895 if (!atomic_read(&css->refcnt))
2896 atomic_set(&css->refcnt, 1);
2898 /* Commit the fact that the CSS is removed */
2899 set_bit(CSS_REMOVED, &css->flags);
2902 local_irq_restore(flags);
2906 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
2908 struct cgroup *cgrp = dentry->d_fsdata;
2910 struct cgroup *parent;
2914 /* the vfs holds both inode->i_mutex already */
2916 mutex_lock(&cgroup_mutex);
2917 if (atomic_read(&cgrp->count) != 0) {
2918 mutex_unlock(&cgroup_mutex);
2921 if (!list_empty(&cgrp->children)) {
2922 mutex_unlock(&cgroup_mutex);
2925 mutex_unlock(&cgroup_mutex);
2928 * In general, subsystem has no css->refcnt after pre_destroy(). But
2929 * in racy cases, subsystem may have to get css->refcnt after
2930 * pre_destroy() and it makes rmdir return with -EBUSY. This sometimes
2931 * make rmdir return -EBUSY too often. To avoid that, we use waitqueue
2932 * for cgroup's rmdir. CGRP_WAIT_ON_RMDIR is for synchronizing rmdir
2933 * and subsystem's reference count handling. Please see css_get/put
2934 * and css_tryget() and cgroup_wakeup_rmdir_waiter() implementation.
2936 set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
2939 * Call pre_destroy handlers of subsys. Notify subsystems
2940 * that rmdir() request comes.
2942 ret = cgroup_call_pre_destroy(cgrp);
2944 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
2948 mutex_lock(&cgroup_mutex);
2949 parent = cgrp->parent;
2950 if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
2951 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
2952 mutex_unlock(&cgroup_mutex);
2955 prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
2956 if (!cgroup_clear_css_refs(cgrp)) {
2957 mutex_unlock(&cgroup_mutex);
2959 * Because someone may call cgroup_wakeup_rmdir_waiter() before
2960 * prepare_to_wait(), we need to check this flag.
2962 if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))
2964 finish_wait(&cgroup_rmdir_waitq, &wait);
2965 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
2966 if (signal_pending(current))
2970 /* NO css_tryget() can success after here. */
2971 finish_wait(&cgroup_rmdir_waitq, &wait);
2972 clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
2974 spin_lock(&release_list_lock);
2975 set_bit(CGRP_REMOVED, &cgrp->flags);
2976 if (!list_empty(&cgrp->release_list))
2977 list_del(&cgrp->release_list);
2978 spin_unlock(&release_list_lock);
2980 cgroup_lock_hierarchy(cgrp->root);
2981 /* delete this cgroup from parent->children */
2982 list_del(&cgrp->sibling);
2983 cgroup_unlock_hierarchy(cgrp->root);
2985 spin_lock(&cgrp->dentry->d_lock);
2986 d = dget(cgrp->dentry);
2987 spin_unlock(&d->d_lock);
2989 cgroup_d_remove_dir(d);
2992 set_bit(CGRP_RELEASABLE, &parent->flags);
2993 check_for_release(parent);
2995 mutex_unlock(&cgroup_mutex);
2999 static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
3001 struct cgroup_subsys_state *css;
3003 printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
3005 /* Create the top cgroup state for this subsystem */
3006 list_add(&ss->sibling, &rootnode.subsys_list);
3007 ss->root = &rootnode;
3008 css = ss->create(ss, dummytop);
3009 /* We don't handle early failures gracefully */
3010 BUG_ON(IS_ERR(css));
3011 init_cgroup_css(css, ss, dummytop);
3013 /* Update the init_css_set to contain a subsys
3014 * pointer to this state - since the subsystem is
3015 * newly registered, all tasks and hence the
3016 * init_css_set is in the subsystem's top cgroup. */
3017 init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
3019 need_forkexit_callback |= ss->fork || ss->exit;
3021 /* At system boot, before all subsystems have been
3022 * registered, no tasks have been forked, so we don't
3023 * need to invoke fork callbacks here. */
3024 BUG_ON(!list_empty(&init_task.tasks));
3026 mutex_init(&ss->hierarchy_mutex);
3027 lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
3032 * cgroup_init_early - cgroup initialization at system boot
3034 * Initialize cgroups at system boot, and initialize any
3035 * subsystems that request early init.
3037 int __init cgroup_init_early(void)
3040 atomic_set(&init_css_set.refcount, 1);
3041 INIT_LIST_HEAD(&init_css_set.cg_links);
3042 INIT_LIST_HEAD(&init_css_set.tasks);
3043 INIT_HLIST_NODE(&init_css_set.hlist);
3045 init_cgroup_root(&rootnode);
3047 init_task.cgroups = &init_css_set;
3049 init_css_set_link.cg = &init_css_set;
3050 init_css_set_link.cgrp = dummytop;
3051 list_add(&init_css_set_link.cgrp_link_list,
3052 &rootnode.top_cgroup.css_sets);
3053 list_add(&init_css_set_link.cg_link_list,
3054 &init_css_set.cg_links);
3056 for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
3057 INIT_HLIST_HEAD(&css_set_table[i]);
3059 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3060 struct cgroup_subsys *ss = subsys[i];
3063 BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
3064 BUG_ON(!ss->create);
3065 BUG_ON(!ss->destroy);
3066 if (ss->subsys_id != i) {
3067 printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
3068 ss->name, ss->subsys_id);
3073 cgroup_init_subsys(ss);
3079 * cgroup_init - cgroup initialization
3081 * Register cgroup filesystem and /proc file, and initialize
3082 * any subsystems that didn't request early init.
3084 int __init cgroup_init(void)
3088 struct hlist_head *hhead;
3090 err = bdi_init(&cgroup_backing_dev_info);
3094 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3095 struct cgroup_subsys *ss = subsys[i];
3096 if (!ss->early_init)
3097 cgroup_init_subsys(ss);
3099 cgroup_subsys_init_idr(ss);
3102 /* Add init_css_set to the hash table */
3103 hhead = css_set_hash(init_css_set.subsys);
3104 hlist_add_head(&init_css_set.hlist, hhead);
3105 BUG_ON(!init_root_id(&rootnode));
3106 err = register_filesystem(&cgroup_fs_type);
3110 proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
3114 bdi_destroy(&cgroup_backing_dev_info);
3120 * proc_cgroup_show()
3121 * - Print task's cgroup paths into seq_file, one line for each hierarchy
3122 * - Used for /proc/<pid>/cgroup.
3123 * - No need to task_lock(tsk) on this tsk->cgroup reference, as it
3124 * doesn't really matter if tsk->cgroup changes after we read it,
3125 * and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
3126 * anyway. No need to check that tsk->cgroup != NULL, thanks to
3127 * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
3128 * cgroup to top_cgroup.
3131 /* TODO: Use a proper seq_file iterator */
3132 static int proc_cgroup_show(struct seq_file *m, void *v)
3135 struct task_struct *tsk;
3138 struct cgroupfs_root *root;
3141 buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
3147 tsk = get_pid_task(pid, PIDTYPE_PID);
3153 mutex_lock(&cgroup_mutex);
3155 for_each_active_root(root) {
3156 struct cgroup_subsys *ss;
3157 struct cgroup *cgrp;
3160 seq_printf(m, "%d:", root->hierarchy_id);
3161 for_each_subsys(root, ss)
3162 seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
3163 if (strlen(root->name))
3164 seq_printf(m, "%sname=%s", count ? "," : "",
3167 cgrp = task_cgroup_from_root(tsk, root);
3168 retval = cgroup_path(cgrp, buf, PAGE_SIZE);
3176 mutex_unlock(&cgroup_mutex);
3177 put_task_struct(tsk);
3184 static int cgroup_open(struct inode *inode, struct file *file)
3186 struct pid *pid = PROC_I(inode)->pid;
3187 return single_open(file, proc_cgroup_show, pid);
3190 struct file_operations proc_cgroup_operations = {
3191 .open = cgroup_open,
3193 .llseek = seq_lseek,
3194 .release = single_release,
3197 /* Display information about each subsystem and each hierarchy */
3198 static int proc_cgroupstats_show(struct seq_file *m, void *v)
3202 seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
3203 mutex_lock(&cgroup_mutex);
3204 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3205 struct cgroup_subsys *ss = subsys[i];
3206 seq_printf(m, "%s\t%d\t%d\t%d\n",
3207 ss->name, ss->root->hierarchy_id,
3208 ss->root->number_of_cgroups, !ss->disabled);
3210 mutex_unlock(&cgroup_mutex);
3214 static int cgroupstats_open(struct inode *inode, struct file *file)
3216 return single_open(file, proc_cgroupstats_show, NULL);
3219 static struct file_operations proc_cgroupstats_operations = {
3220 .open = cgroupstats_open,
3222 .llseek = seq_lseek,
3223 .release = single_release,
3227 * cgroup_fork - attach newly forked task to its parents cgroup.
3228 * @child: pointer to task_struct of forking parent process.
3230 * Description: A task inherits its parent's cgroup at fork().
3232 * A pointer to the shared css_set was automatically copied in
3233 * fork.c by dup_task_struct(). However, we ignore that copy, since
3234 * it was not made under the protection of RCU or cgroup_mutex, so
3235 * might no longer be a valid cgroup pointer. cgroup_attach_task() might
3236 * have already changed current->cgroups, allowing the previously
3237 * referenced cgroup group to be removed and freed.
3239 * At the point that cgroup_fork() is called, 'current' is the parent
3240 * task, and the passed argument 'child' points to the child task.
3242 void cgroup_fork(struct task_struct *child)
3245 child->cgroups = current->cgroups;
3246 get_css_set(child->cgroups);
3247 task_unlock(current);
3248 INIT_LIST_HEAD(&child->cg_list);
3252 * cgroup_fork_callbacks - run fork callbacks
3253 * @child: the new task
3255 * Called on a new task very soon before adding it to the
3256 * tasklist. No need to take any locks since no-one can
3257 * be operating on this task.
3259 void cgroup_fork_callbacks(struct task_struct *child)
3261 if (need_forkexit_callback) {
3263 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3264 struct cgroup_subsys *ss = subsys[i];
3266 ss->fork(ss, child);
3272 * cgroup_post_fork - called on a new task after adding it to the task list
3273 * @child: the task in question
3275 * Adds the task to the list running through its css_set if necessary.
3276 * Has to be after the task is visible on the task list in case we race
3277 * with the first call to cgroup_iter_start() - to guarantee that the
3278 * new task ends up on its list.
3280 void cgroup_post_fork(struct task_struct *child)
3282 if (use_task_css_set_links) {
3283 write_lock(&css_set_lock);
3285 if (list_empty(&child->cg_list))
3286 list_add(&child->cg_list, &child->cgroups->tasks);
3288 write_unlock(&css_set_lock);
3292 * cgroup_exit - detach cgroup from exiting task
3293 * @tsk: pointer to task_struct of exiting process
3294 * @run_callback: run exit callbacks?
3296 * Description: Detach cgroup from @tsk and release it.
3298 * Note that cgroups marked notify_on_release force every task in
3299 * them to take the global cgroup_mutex mutex when exiting.
3300 * This could impact scaling on very large systems. Be reluctant to
3301 * use notify_on_release cgroups where very high task exit scaling
3302 * is required on large systems.
3304 * the_top_cgroup_hack:
3306 * Set the exiting tasks cgroup to the root cgroup (top_cgroup).
3308 * We call cgroup_exit() while the task is still competent to
3309 * handle notify_on_release(), then leave the task attached to the
3310 * root cgroup in each hierarchy for the remainder of its exit.
3312 * To do this properly, we would increment the reference count on
3313 * top_cgroup, and near the very end of the kernel/exit.c do_exit()
3314 * code we would add a second cgroup function call, to drop that
3315 * reference. This would just create an unnecessary hot spot on
3316 * the top_cgroup reference count, to no avail.
3318 * Normally, holding a reference to a cgroup without bumping its
3319 * count is unsafe. The cgroup could go away, or someone could
3320 * attach us to a different cgroup, decrementing the count on
3321 * the first cgroup that we never incremented. But in this case,
3322 * top_cgroup isn't going away, and either task has PF_EXITING set,
3323 * which wards off any cgroup_attach_task() attempts, or task is a failed
3324 * fork, never visible to cgroup_attach_task.
3326 void cgroup_exit(struct task_struct *tsk, int run_callbacks)
3331 if (run_callbacks && need_forkexit_callback) {
3332 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3333 struct cgroup_subsys *ss = subsys[i];
3340 * Unlink from the css_set task list if necessary.
3341 * Optimistically check cg_list before taking
3344 if (!list_empty(&tsk->cg_list)) {
3345 write_lock(&css_set_lock);
3346 if (!list_empty(&tsk->cg_list))
3347 list_del(&tsk->cg_list);
3348 write_unlock(&css_set_lock);
3351 /* Reassign the task to the init_css_set. */
3354 tsk->cgroups = &init_css_set;
3357 put_css_set_taskexit(cg);
3361 * cgroup_clone - clone the cgroup the given subsystem is attached to
3362 * @tsk: the task to be moved
3363 * @subsys: the given subsystem
3364 * @nodename: the name for the new cgroup
3366 * Duplicate the current cgroup in the hierarchy that the given
3367 * subsystem is attached to, and move this task into the new
3370 int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
3373 struct dentry *dentry;
3375 struct cgroup *parent, *child;
3376 struct inode *inode;
3378 struct cgroupfs_root *root;
3379 struct cgroup_subsys *ss;
3381 /* We shouldn't be called by an unregistered subsystem */
3382 BUG_ON(!subsys->active);
3384 /* First figure out what hierarchy and cgroup we're dealing
3385 * with, and pin them so we can drop cgroup_mutex */
3386 mutex_lock(&cgroup_mutex);
3388 root = subsys->root;
3389 if (root == &rootnode) {
3390 mutex_unlock(&cgroup_mutex);
3394 /* Pin the hierarchy */
3395 if (!atomic_inc_not_zero(&root->sb->s_active)) {
3396 /* We race with the final deactivate_super() */
3397 mutex_unlock(&cgroup_mutex);
3401 /* Keep the cgroup alive */
3403 parent = task_cgroup(tsk, subsys->subsys_id);
3408 mutex_unlock(&cgroup_mutex);
3410 /* Now do the VFS work to create a cgroup */
3411 inode = parent->dentry->d_inode;
3413 /* Hold the parent directory mutex across this operation to
3414 * stop anyone else deleting the new cgroup */
3415 mutex_lock(&inode->i_mutex);
3416 dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));
3417 if (IS_ERR(dentry)) {
3419 "cgroup: Couldn't allocate dentry for %s: %ld\n", nodename,
3421 ret = PTR_ERR(dentry);
3425 /* Create the cgroup directory, which also creates the cgroup */
3426 ret = vfs_mkdir(inode, dentry, 0755);
3427 child = __d_cgrp(dentry);
3431 "Failed to create cgroup %s: %d\n", nodename,
3436 /* The cgroup now exists. Retake cgroup_mutex and check
3437 * that we're still in the same state that we thought we
3439 mutex_lock(&cgroup_mutex);
3440 if ((root != subsys->root) ||
3441 (parent != task_cgroup(tsk, subsys->subsys_id))) {
3442 /* Aargh, we raced ... */
3443 mutex_unlock(&inode->i_mutex);
3446 deactivate_super(root->sb);
3447 /* The cgroup is still accessible in the VFS, but
3448 * we're not going to try to rmdir() it at this
3451 "Race in cgroup_clone() - leaking cgroup %s\n",
3456 /* do any required auto-setup */
3457 for_each_subsys(root, ss) {
3459 ss->post_clone(ss, child);
3462 /* All seems fine. Finish by moving the task into the new cgroup */
3463 ret = cgroup_attach_task(child, tsk);
3464 mutex_unlock(&cgroup_mutex);
3467 mutex_unlock(&inode->i_mutex);
3469 mutex_lock(&cgroup_mutex);
3471 mutex_unlock(&cgroup_mutex);
3472 deactivate_super(root->sb);
3477 * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
3478 * @cgrp: the cgroup in question
3479 * @task: the task in question
3481 * See if @cgrp is a descendant of @task's cgroup in the appropriate
3484 * If we are sending in dummytop, then presumably we are creating
3485 * the top cgroup in the subsystem.
3487 * Called only by the ns (nsproxy) cgroup.
3489 int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
3492 struct cgroup *target;
3494 if (cgrp == dummytop)
3497 target = task_cgroup_from_root(task, cgrp->root);
3498 while (cgrp != target && cgrp!= cgrp->top_cgroup)
3499 cgrp = cgrp->parent;
3500 ret = (cgrp == target);
3504 static void check_for_release(struct cgroup *cgrp)
3506 /* All of these checks rely on RCU to keep the cgroup
3507 * structure alive */
3508 if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
3509 && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
3510 /* Control Group is currently removeable. If it's not
3511 * already queued for a userspace notification, queue
3513 int need_schedule_work = 0;
3514 spin_lock(&release_list_lock);
3515 if (!cgroup_is_removed(cgrp) &&
3516 list_empty(&cgrp->release_list)) {
3517 list_add(&cgrp->release_list, &release_list);
3518 need_schedule_work = 1;
3520 spin_unlock(&release_list_lock);
3521 if (need_schedule_work)
3522 schedule_work(&release_agent_work);
3526 void __css_put(struct cgroup_subsys_state *css)
3528 struct cgroup *cgrp = css->cgroup;
3530 if (atomic_dec_return(&css->refcnt) == 1) {
3531 if (notify_on_release(cgrp)) {
3532 set_bit(CGRP_RELEASABLE, &cgrp->flags);
3533 check_for_release(cgrp);
3535 cgroup_wakeup_rmdir_waiter(cgrp);
3541 * Notify userspace when a cgroup is released, by running the
3542 * configured release agent with the name of the cgroup (path
3543 * relative to the root of cgroup file system) as the argument.
3545 * Most likely, this user command will try to rmdir this cgroup.
3547 * This races with the possibility that some other task will be
3548 * attached to this cgroup before it is removed, or that some other
3549 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
3550 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
3551 * unused, and this cgroup will be reprieved from its death sentence,
3552 * to continue to serve a useful existence. Next time it's released,
3553 * we will get notified again, if it still has 'notify_on_release' set.
3555 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
3556 * means only wait until the task is successfully execve()'d. The
3557 * separate release agent task is forked by call_usermodehelper(),
3558 * then control in this thread returns here, without waiting for the
3559 * release agent task. We don't bother to wait because the caller of
3560 * this routine has no use for the exit status of the release agent
3561 * task, so no sense holding our caller up for that.
3563 static void cgroup_release_agent(struct work_struct *work)
3565 BUG_ON(work != &release_agent_work);
3566 mutex_lock(&cgroup_mutex);
3567 spin_lock(&release_list_lock);
3568 while (!list_empty(&release_list)) {
3569 char *argv[3], *envp[3];
3571 char *pathbuf = NULL, *agentbuf = NULL;
3572 struct cgroup *cgrp = list_entry(release_list.next,
3575 list_del_init(&cgrp->release_list);
3576 spin_unlock(&release_list_lock);
3577 pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
3580 if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
3582 agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
3587 argv[i++] = agentbuf;
3588 argv[i++] = pathbuf;
3592 /* minimal command environment */
3593 envp[i++] = "HOME=/";
3594 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
3597 /* Drop the lock while we invoke the usermode helper,
3598 * since the exec could involve hitting disk and hence
3599 * be a slow process */
3600 mutex_unlock(&cgroup_mutex);
3601 call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
3602 mutex_lock(&cgroup_mutex);
3606 spin_lock(&release_list_lock);
3608 spin_unlock(&release_list_lock);
3609 mutex_unlock(&cgroup_mutex);
3612 static int __init cgroup_disable(char *str)
3617 while ((token = strsep(&str, ",")) != NULL) {
3621 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3622 struct cgroup_subsys *ss = subsys[i];
3624 if (!strcmp(token, ss->name)) {
3626 printk(KERN_INFO "Disabling %s control group"
3627 " subsystem\n", ss->name);
3634 __setup("cgroup_disable=", cgroup_disable);
3637 * Functons for CSS ID.
3641 *To get ID other than 0, this should be called when !cgroup_is_removed().
3643 unsigned short css_id(struct cgroup_subsys_state *css)
3645 struct css_id *cssid = rcu_dereference(css->id);
3652 unsigned short css_depth(struct cgroup_subsys_state *css)
3654 struct css_id *cssid = rcu_dereference(css->id);
3657 return cssid->depth;
3661 bool css_is_ancestor(struct cgroup_subsys_state *child,
3662 const struct cgroup_subsys_state *root)
3664 struct css_id *child_id = rcu_dereference(child->id);
3665 struct css_id *root_id = rcu_dereference(root->id);
3667 if (!child_id || !root_id || (child_id->depth < root_id->depth))
3669 return child_id->stack[root_id->depth] == root_id->id;
3672 static void __free_css_id_cb(struct rcu_head *head)
3676 id = container_of(head, struct css_id, rcu_head);
3680 void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
3682 struct css_id *id = css->id;
3683 /* When this is called before css_id initialization, id can be NULL */
3687 BUG_ON(!ss->use_id);
3689 rcu_assign_pointer(id->css, NULL);
3690 rcu_assign_pointer(css->id, NULL);
3691 spin_lock(&ss->id_lock);
3692 idr_remove(&ss->idr, id->id);
3693 spin_unlock(&ss->id_lock);
3694 call_rcu(&id->rcu_head, __free_css_id_cb);
3698 * This is called by init or create(). Then, calls to this function are
3699 * always serialized (By cgroup_mutex() at create()).
3702 static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
3704 struct css_id *newid;
3705 int myid, error, size;
3707 BUG_ON(!ss->use_id);
3709 size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
3710 newid = kzalloc(size, GFP_KERNEL);
3712 return ERR_PTR(-ENOMEM);
3714 if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
3718 spin_lock(&ss->id_lock);
3719 /* Don't use 0. allocates an ID of 1-65535 */
3720 error = idr_get_new_above(&ss->idr, newid, 1, &myid);
3721 spin_unlock(&ss->id_lock);
3723 /* Returns error when there are no free spaces for new ID.*/
3728 if (myid > CSS_ID_MAX)
3732 newid->depth = depth;
3736 spin_lock(&ss->id_lock);
3737 idr_remove(&ss->idr, myid);
3738 spin_unlock(&ss->id_lock);
3741 return ERR_PTR(error);
3745 static int __init cgroup_subsys_init_idr(struct cgroup_subsys *ss)
3747 struct css_id *newid;
3748 struct cgroup_subsys_state *rootcss;
3750 spin_lock_init(&ss->id_lock);
3753 rootcss = init_css_set.subsys[ss->subsys_id];
3754 newid = get_new_cssid(ss, 0);
3756 return PTR_ERR(newid);
3758 newid->stack[0] = newid->id;
3759 newid->css = rootcss;
3760 rootcss->id = newid;
3764 static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
3765 struct cgroup *child)
3767 int subsys_id, i, depth = 0;
3768 struct cgroup_subsys_state *parent_css, *child_css;
3769 struct css_id *child_id, *parent_id = NULL;
3771 subsys_id = ss->subsys_id;
3772 parent_css = parent->subsys[subsys_id];
3773 child_css = child->subsys[subsys_id];
3774 depth = css_depth(parent_css) + 1;
3775 parent_id = parent_css->id;
3777 child_id = get_new_cssid(ss, depth);
3778 if (IS_ERR(child_id))
3779 return PTR_ERR(child_id);
3781 for (i = 0; i < depth; i++)
3782 child_id->stack[i] = parent_id->stack[i];
3783 child_id->stack[depth] = child_id->id;
3785 * child_id->css pointer will be set after this cgroup is available
3786 * see cgroup_populate_dir()
3788 rcu_assign_pointer(child_css->id, child_id);
3794 * css_lookup - lookup css by id
3795 * @ss: cgroup subsys to be looked into.
3798 * Returns pointer to cgroup_subsys_state if there is valid one with id.
3799 * NULL if not. Should be called under rcu_read_lock()
3801 struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
3803 struct css_id *cssid = NULL;
3805 BUG_ON(!ss->use_id);
3806 cssid = idr_find(&ss->idr, id);
3808 if (unlikely(!cssid))
3811 return rcu_dereference(cssid->css);
3815 * css_get_next - lookup next cgroup under specified hierarchy.
3816 * @ss: pointer to subsystem
3817 * @id: current position of iteration.
3818 * @root: pointer to css. search tree under this.
3819 * @foundid: position of found object.
3821 * Search next css under the specified hierarchy of rootid. Calling under
3822 * rcu_read_lock() is necessary. Returns NULL if it reaches the end.
3824 struct cgroup_subsys_state *
3825 css_get_next(struct cgroup_subsys *ss, int id,
3826 struct cgroup_subsys_state *root, int *foundid)
3828 struct cgroup_subsys_state *ret = NULL;
3831 int rootid = css_id(root);
3832 int depth = css_depth(root);
3837 BUG_ON(!ss->use_id);
3838 /* fill start point for scan */
3842 * scan next entry from bitmap(tree), tmpid is updated after
3845 spin_lock(&ss->id_lock);
3846 tmp = idr_get_next(&ss->idr, &tmpid);
3847 spin_unlock(&ss->id_lock);
3851 if (tmp->depth >= depth && tmp->stack[depth] == rootid) {
3852 ret = rcu_dereference(tmp->css);
3858 /* continue to scan from next id */
3864 #ifdef CONFIG_CGROUP_DEBUG
3865 static struct cgroup_subsys_state *debug_create(struct cgroup_subsys *ss,
3866 struct cgroup *cont)
3868 struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
3871 return ERR_PTR(-ENOMEM);
3876 static void debug_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
3878 kfree(cont->subsys[debug_subsys_id]);
3881 static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
3883 return atomic_read(&cont->count);
3886 static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft)
3888 return cgroup_task_count(cont);
3891 static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
3893 return (u64)(unsigned long)current->cgroups;
3896 static u64 current_css_set_refcount_read(struct cgroup *cont,
3902 count = atomic_read(¤t->cgroups->refcount);
3907 static int current_css_set_cg_links_read(struct cgroup *cont,
3909 struct seq_file *seq)
3911 struct cg_cgroup_link *link;
3914 read_lock(&css_set_lock);
3916 cg = rcu_dereference(current->cgroups);
3917 list_for_each_entry(link, &cg->cg_links, cg_link_list) {
3918 struct cgroup *c = link->cgrp;
3922 name = c->dentry->d_name.name;
3925 seq_printf(seq, "Root %d group %s\n",
3926 c->root->hierarchy_id, name);
3929 read_unlock(&css_set_lock);
3933 #define MAX_TASKS_SHOWN_PER_CSS 25
3934 static int cgroup_css_links_read(struct cgroup *cont,
3936 struct seq_file *seq)
3938 struct cg_cgroup_link *link;
3940 read_lock(&css_set_lock);
3941 list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
3942 struct css_set *cg = link->cg;
3943 struct task_struct *task;
3945 seq_printf(seq, "css_set %p\n", cg);
3946 list_for_each_entry(task, &cg->tasks, cg_list) {
3947 if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
3948 seq_puts(seq, " ...\n");
3951 seq_printf(seq, " task %d\n",
3952 task_pid_vnr(task));
3956 read_unlock(&css_set_lock);
3960 static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
3962 return test_bit(CGRP_RELEASABLE, &cgrp->flags);
3965 static struct cftype debug_files[] = {
3967 .name = "cgroup_refcount",
3968 .read_u64 = cgroup_refcount_read,
3971 .name = "taskcount",
3972 .read_u64 = debug_taskcount_read,
3976 .name = "current_css_set",
3977 .read_u64 = current_css_set_read,
3981 .name = "current_css_set_refcount",
3982 .read_u64 = current_css_set_refcount_read,
3986 .name = "current_css_set_cg_links",
3987 .read_seq_string = current_css_set_cg_links_read,
3991 .name = "cgroup_css_links",
3992 .read_seq_string = cgroup_css_links_read,
3996 .name = "releasable",
3997 .read_u64 = releasable_read,
4001 static int debug_populate(struct cgroup_subsys *ss, struct cgroup *cont)
4003 return cgroup_add_files(cont, ss, debug_files,
4004 ARRAY_SIZE(debug_files));
4007 struct cgroup_subsys debug_subsys = {
4009 .create = debug_create,
4010 .destroy = debug_destroy,
4011 .populate = debug_populate,
4012 .subsys_id = debug_subsys_id,
4014 #endif /* CONFIG_CGROUP_DEBUG */