thinkpad-acpi: improve Kconfig help text
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / cgroup.c
blobc882385bd8f0bbd22743f671f3bda5d594a7b35c
1 /*
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/errno.h>
27 #include <linux/fs.h>
28 #include <linux/kernel.h>
29 #include <linux/list.h>
30 #include <linux/mm.h>
31 #include <linux/mutex.h>
32 #include <linux/mount.h>
33 #include <linux/pagemap.h>
34 #include <linux/proc_fs.h>
35 #include <linux/rcupdate.h>
36 #include <linux/sched.h>
37 #include <linux/backing-dev.h>
38 #include <linux/seq_file.h>
39 #include <linux/slab.h>
40 #include <linux/magic.h>
41 #include <linux/spinlock.h>
42 #include <linux/string.h>
43 #include <linux/sort.h>
44 #include <linux/kmod.h>
45 #include <linux/delayacct.h>
46 #include <linux/cgroupstats.h>
47 #include <linux/hash.h>
48 #include <linux/namei.h>
50 #include <asm/atomic.h>
52 static DEFINE_MUTEX(cgroup_mutex);
54 /* Generate an array of cgroup subsystem pointers */
55 #define SUBSYS(_x) &_x ## _subsys,
57 static struct cgroup_subsys *subsys[] = {
58 #include <linux/cgroup_subsys.h>
62 * A cgroupfs_root represents the root of a cgroup hierarchy,
63 * and may be associated with a superblock to form an active
64 * hierarchy
66 struct cgroupfs_root {
67 struct super_block *sb;
70 * The bitmask of subsystems intended to be attached to this
71 * hierarchy
73 unsigned long subsys_bits;
75 /* The bitmask of subsystems currently attached to this hierarchy */
76 unsigned long actual_subsys_bits;
78 /* A list running through the attached subsystems */
79 struct list_head subsys_list;
81 /* The root cgroup for this hierarchy */
82 struct cgroup top_cgroup;
84 /* Tracks how many cgroups are currently defined in hierarchy.*/
85 int number_of_cgroups;
87 /* A list running through the mounted hierarchies */
88 struct list_head root_list;
90 /* Hierarchy-specific flags */
91 unsigned long flags;
93 /* The path to use for release notifications. */
94 char release_agent_path[PATH_MAX];
99 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
100 * subsystems that are otherwise unattached - it never has more than a
101 * single cgroup, and all tasks are part of that cgroup.
103 static struct cgroupfs_root rootnode;
105 /* The list of hierarchy roots */
107 static LIST_HEAD(roots);
108 static int root_count;
110 /* dummytop is a shorthand for the dummy hierarchy's top cgroup */
111 #define dummytop (&rootnode.top_cgroup)
113 /* This flag indicates whether tasks in the fork and exit paths should
114 * check for fork/exit handlers to call. This avoids us having to do
115 * extra work in the fork/exit path if none of the subsystems need to
116 * be called.
118 static int need_forkexit_callback __read_mostly;
119 static int need_mm_owner_callback __read_mostly;
121 /* convenient tests for these bits */
122 inline int cgroup_is_removed(const struct cgroup *cgrp)
124 return test_bit(CGRP_REMOVED, &cgrp->flags);
127 /* bits in struct cgroupfs_root flags field */
128 enum {
129 ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
132 static int cgroup_is_releasable(const struct cgroup *cgrp)
134 const int bits =
135 (1 << CGRP_RELEASABLE) |
136 (1 << CGRP_NOTIFY_ON_RELEASE);
137 return (cgrp->flags & bits) == bits;
140 static int notify_on_release(const struct cgroup *cgrp)
142 return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
146 * for_each_subsys() allows you to iterate on each subsystem attached to
147 * an active hierarchy
149 #define for_each_subsys(_root, _ss) \
150 list_for_each_entry(_ss, &_root->subsys_list, sibling)
152 /* for_each_root() allows you to iterate across the active hierarchies */
153 #define for_each_root(_root) \
154 list_for_each_entry(_root, &roots, root_list)
156 /* the list of cgroups eligible for automatic release. Protected by
157 * release_list_lock */
158 static LIST_HEAD(release_list);
159 static DEFINE_SPINLOCK(release_list_lock);
160 static void cgroup_release_agent(struct work_struct *work);
161 static DECLARE_WORK(release_agent_work, cgroup_release_agent);
162 static void check_for_release(struct cgroup *cgrp);
164 /* Link structure for associating css_set objects with cgroups */
165 struct cg_cgroup_link {
167 * List running through cg_cgroup_links associated with a
168 * cgroup, anchored on cgroup->css_sets
170 struct list_head cgrp_link_list;
172 * List running through cg_cgroup_links pointing at a
173 * single css_set object, anchored on css_set->cg_links
175 struct list_head cg_link_list;
176 struct css_set *cg;
179 /* The default css_set - used by init and its children prior to any
180 * hierarchies being mounted. It contains a pointer to the root state
181 * for each subsystem. Also used to anchor the list of css_sets. Not
182 * reference-counted, to improve performance when child cgroups
183 * haven't been created.
186 static struct css_set init_css_set;
187 static struct cg_cgroup_link init_css_set_link;
189 /* css_set_lock protects the list of css_set objects, and the
190 * chain of tasks off each css_set. Nests outside task->alloc_lock
191 * due to cgroup_iter_start() */
192 static DEFINE_RWLOCK(css_set_lock);
193 static int css_set_count;
195 /* hash table for cgroup groups. This improves the performance to
196 * find an existing css_set */
197 #define CSS_SET_HASH_BITS 7
198 #define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS)
199 static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
201 static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
203 int i;
204 int index;
205 unsigned long tmp = 0UL;
207 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
208 tmp += (unsigned long)css[i];
209 tmp = (tmp >> 16) ^ tmp;
211 index = hash_long(tmp, CSS_SET_HASH_BITS);
213 return &css_set_table[index];
216 /* We don't maintain the lists running through each css_set to its
217 * task until after the first call to cgroup_iter_start(). This
218 * reduces the fork()/exit() overhead for people who have cgroups
219 * compiled into their kernel but not actually in use */
220 static int use_task_css_set_links __read_mostly;
222 /* When we create or destroy a css_set, the operation simply
223 * takes/releases a reference count on all the cgroups referenced
224 * by subsystems in this css_set. This can end up multiple-counting
225 * some cgroups, but that's OK - the ref-count is just a
226 * busy/not-busy indicator; ensuring that we only count each cgroup
227 * once would require taking a global lock to ensure that no
228 * subsystems moved between hierarchies while we were doing so.
230 * Possible TODO: decide at boot time based on the number of
231 * registered subsystems and the number of CPUs or NUMA nodes whether
232 * it's better for performance to ref-count every subsystem, or to
233 * take a global lock and only add one ref count to each hierarchy.
237 * unlink a css_set from the list and free it
239 static void unlink_css_set(struct css_set *cg)
241 struct cg_cgroup_link *link;
242 struct cg_cgroup_link *saved_link;
244 hlist_del(&cg->hlist);
245 css_set_count--;
247 list_for_each_entry_safe(link, saved_link, &cg->cg_links,
248 cg_link_list) {
249 list_del(&link->cg_link_list);
250 list_del(&link->cgrp_link_list);
251 kfree(link);
255 static void __put_css_set(struct css_set *cg, int taskexit)
257 int i;
259 * Ensure that the refcount doesn't hit zero while any readers
260 * can see it. Similar to atomic_dec_and_lock(), but for an
261 * rwlock
263 if (atomic_add_unless(&cg->refcount, -1, 1))
264 return;
265 write_lock(&css_set_lock);
266 if (!atomic_dec_and_test(&cg->refcount)) {
267 write_unlock(&css_set_lock);
268 return;
270 unlink_css_set(cg);
271 write_unlock(&css_set_lock);
273 rcu_read_lock();
274 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
275 struct cgroup *cgrp = cg->subsys[i]->cgroup;
276 if (atomic_dec_and_test(&cgrp->count) &&
277 notify_on_release(cgrp)) {
278 if (taskexit)
279 set_bit(CGRP_RELEASABLE, &cgrp->flags);
280 check_for_release(cgrp);
283 rcu_read_unlock();
284 kfree(cg);
288 * refcounted get/put for css_set objects
290 static inline void get_css_set(struct css_set *cg)
292 atomic_inc(&cg->refcount);
295 static inline void put_css_set(struct css_set *cg)
297 __put_css_set(cg, 0);
300 static inline void put_css_set_taskexit(struct css_set *cg)
302 __put_css_set(cg, 1);
306 * find_existing_css_set() is a helper for
307 * find_css_set(), and checks to see whether an existing
308 * css_set is suitable.
310 * oldcg: the cgroup group that we're using before the cgroup
311 * transition
313 * cgrp: the cgroup that we're moving into
315 * template: location in which to build the desired set of subsystem
316 * state objects for the new cgroup group
318 static struct css_set *find_existing_css_set(
319 struct css_set *oldcg,
320 struct cgroup *cgrp,
321 struct cgroup_subsys_state *template[])
323 int i;
324 struct cgroupfs_root *root = cgrp->root;
325 struct hlist_head *hhead;
326 struct hlist_node *node;
327 struct css_set *cg;
329 /* Built the set of subsystem state objects that we want to
330 * see in the new css_set */
331 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
332 if (root->subsys_bits & (1UL << i)) {
333 /* Subsystem is in this hierarchy. So we want
334 * the subsystem state from the new
335 * cgroup */
336 template[i] = cgrp->subsys[i];
337 } else {
338 /* Subsystem is not in this hierarchy, so we
339 * don't want to change the subsystem state */
340 template[i] = oldcg->subsys[i];
344 hhead = css_set_hash(template);
345 hlist_for_each_entry(cg, node, hhead, hlist) {
346 if (!memcmp(template, cg->subsys, sizeof(cg->subsys))) {
347 /* All subsystems matched */
348 return cg;
352 /* No existing cgroup group matched */
353 return NULL;
356 static void free_cg_links(struct list_head *tmp)
358 struct cg_cgroup_link *link;
359 struct cg_cgroup_link *saved_link;
361 list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
362 list_del(&link->cgrp_link_list);
363 kfree(link);
368 * allocate_cg_links() allocates "count" cg_cgroup_link structures
369 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
370 * success or a negative error
372 static int allocate_cg_links(int count, struct list_head *tmp)
374 struct cg_cgroup_link *link;
375 int i;
376 INIT_LIST_HEAD(tmp);
377 for (i = 0; i < count; i++) {
378 link = kmalloc(sizeof(*link), GFP_KERNEL);
379 if (!link) {
380 free_cg_links(tmp);
381 return -ENOMEM;
383 list_add(&link->cgrp_link_list, tmp);
385 return 0;
389 * find_css_set() takes an existing cgroup group and a
390 * cgroup object, and returns a css_set object that's
391 * equivalent to the old group, but with the given cgroup
392 * substituted into the appropriate hierarchy. Must be called with
393 * cgroup_mutex held
395 static struct css_set *find_css_set(
396 struct css_set *oldcg, struct cgroup *cgrp)
398 struct css_set *res;
399 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
400 int i;
402 struct list_head tmp_cg_links;
403 struct cg_cgroup_link *link;
405 struct hlist_head *hhead;
407 /* First see if we already have a cgroup group that matches
408 * the desired set */
409 read_lock(&css_set_lock);
410 res = find_existing_css_set(oldcg, cgrp, template);
411 if (res)
412 get_css_set(res);
413 read_unlock(&css_set_lock);
415 if (res)
416 return res;
418 res = kmalloc(sizeof(*res), GFP_KERNEL);
419 if (!res)
420 return NULL;
422 /* Allocate all the cg_cgroup_link objects that we'll need */
423 if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
424 kfree(res);
425 return NULL;
428 atomic_set(&res->refcount, 1);
429 INIT_LIST_HEAD(&res->cg_links);
430 INIT_LIST_HEAD(&res->tasks);
431 INIT_HLIST_NODE(&res->hlist);
433 /* Copy the set of subsystem state objects generated in
434 * find_existing_css_set() */
435 memcpy(res->subsys, template, sizeof(res->subsys));
437 write_lock(&css_set_lock);
438 /* Add reference counts and links from the new css_set. */
439 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
440 struct cgroup *cgrp = res->subsys[i]->cgroup;
441 struct cgroup_subsys *ss = subsys[i];
442 atomic_inc(&cgrp->count);
444 * We want to add a link once per cgroup, so we
445 * only do it for the first subsystem in each
446 * hierarchy
448 if (ss->root->subsys_list.next == &ss->sibling) {
449 BUG_ON(list_empty(&tmp_cg_links));
450 link = list_entry(tmp_cg_links.next,
451 struct cg_cgroup_link,
452 cgrp_link_list);
453 list_del(&link->cgrp_link_list);
454 list_add(&link->cgrp_link_list, &cgrp->css_sets);
455 link->cg = res;
456 list_add(&link->cg_link_list, &res->cg_links);
459 if (list_empty(&rootnode.subsys_list)) {
460 link = list_entry(tmp_cg_links.next,
461 struct cg_cgroup_link,
462 cgrp_link_list);
463 list_del(&link->cgrp_link_list);
464 list_add(&link->cgrp_link_list, &dummytop->css_sets);
465 link->cg = res;
466 list_add(&link->cg_link_list, &res->cg_links);
469 BUG_ON(!list_empty(&tmp_cg_links));
471 css_set_count++;
473 /* Add this cgroup group to the hash table */
474 hhead = css_set_hash(res->subsys);
475 hlist_add_head(&res->hlist, hhead);
477 write_unlock(&css_set_lock);
479 return res;
483 * There is one global cgroup mutex. We also require taking
484 * task_lock() when dereferencing a task's cgroup subsys pointers.
485 * See "The task_lock() exception", at the end of this comment.
487 * A task must hold cgroup_mutex to modify cgroups.
489 * Any task can increment and decrement the count field without lock.
490 * So in general, code holding cgroup_mutex can't rely on the count
491 * field not changing. However, if the count goes to zero, then only
492 * cgroup_attach_task() can increment it again. Because a count of zero
493 * means that no tasks are currently attached, therefore there is no
494 * way a task attached to that cgroup can fork (the other way to
495 * increment the count). So code holding cgroup_mutex can safely
496 * assume that if the count is zero, it will stay zero. Similarly, if
497 * a task holds cgroup_mutex on a cgroup with zero count, it
498 * knows that the cgroup won't be removed, as cgroup_rmdir()
499 * needs that mutex.
501 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
502 * (usually) take cgroup_mutex. These are the two most performance
503 * critical pieces of code here. The exception occurs on cgroup_exit(),
504 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
505 * is taken, and if the cgroup count is zero, a usermode call made
506 * to the release agent with the name of the cgroup (path relative to
507 * the root of cgroup file system) as the argument.
509 * A cgroup can only be deleted if both its 'count' of using tasks
510 * is zero, and its list of 'children' cgroups is empty. Since all
511 * tasks in the system use _some_ cgroup, and since there is always at
512 * least one task in the system (init, pid == 1), therefore, top_cgroup
513 * always has either children cgroups and/or using tasks. So we don't
514 * need a special hack to ensure that top_cgroup cannot be deleted.
516 * The task_lock() exception
518 * The need for this exception arises from the action of
519 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
520 * another. It does so using cgroup_mutex, however there are
521 * several performance critical places that need to reference
522 * task->cgroup without the expense of grabbing a system global
523 * mutex. Therefore except as noted below, when dereferencing or, as
524 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
525 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
526 * the task_struct routinely used for such matters.
528 * P.S. One more locking exception. RCU is used to guard the
529 * update of a tasks cgroup pointer by cgroup_attach_task()
533 * cgroup_lock - lock out any changes to cgroup structures
536 void cgroup_lock(void)
538 mutex_lock(&cgroup_mutex);
542 * cgroup_unlock - release lock on cgroup changes
544 * Undo the lock taken in a previous cgroup_lock() call.
546 void cgroup_unlock(void)
548 mutex_unlock(&cgroup_mutex);
552 * A couple of forward declarations required, due to cyclic reference loop:
553 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
554 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
555 * -> cgroup_mkdir.
558 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode);
559 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
560 static int cgroup_populate_dir(struct cgroup *cgrp);
561 static struct inode_operations cgroup_dir_inode_operations;
562 static struct file_operations proc_cgroupstats_operations;
564 static struct backing_dev_info cgroup_backing_dev_info = {
565 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
568 static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
570 struct inode *inode = new_inode(sb);
572 if (inode) {
573 inode->i_mode = mode;
574 inode->i_uid = current->fsuid;
575 inode->i_gid = current->fsgid;
576 inode->i_blocks = 0;
577 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
578 inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
580 return inode;
584 * Call subsys's pre_destroy handler.
585 * This is called before css refcnt check.
587 static void cgroup_call_pre_destroy(struct cgroup *cgrp)
589 struct cgroup_subsys *ss;
590 for_each_subsys(cgrp->root, ss)
591 if (ss->pre_destroy && cgrp->subsys[ss->subsys_id])
592 ss->pre_destroy(ss, cgrp);
593 return;
596 static void cgroup_diput(struct dentry *dentry, struct inode *inode)
598 /* is dentry a directory ? if so, kfree() associated cgroup */
599 if (S_ISDIR(inode->i_mode)) {
600 struct cgroup *cgrp = dentry->d_fsdata;
601 struct cgroup_subsys *ss;
602 BUG_ON(!(cgroup_is_removed(cgrp)));
603 /* It's possible for external users to be holding css
604 * reference counts on a cgroup; css_put() needs to
605 * be able to access the cgroup after decrementing
606 * the reference count in order to know if it needs to
607 * queue the cgroup to be handled by the release
608 * agent */
609 synchronize_rcu();
611 mutex_lock(&cgroup_mutex);
613 * Release the subsystem state objects.
615 for_each_subsys(cgrp->root, ss) {
616 if (cgrp->subsys[ss->subsys_id])
617 ss->destroy(ss, cgrp);
620 cgrp->root->number_of_cgroups--;
621 mutex_unlock(&cgroup_mutex);
623 /* Drop the active superblock reference that we took when we
624 * created the cgroup */
625 deactivate_super(cgrp->root->sb);
627 kfree(cgrp);
629 iput(inode);
632 static void remove_dir(struct dentry *d)
634 struct dentry *parent = dget(d->d_parent);
636 d_delete(d);
637 simple_rmdir(parent->d_inode, d);
638 dput(parent);
641 static void cgroup_clear_directory(struct dentry *dentry)
643 struct list_head *node;
645 BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
646 spin_lock(&dcache_lock);
647 node = dentry->d_subdirs.next;
648 while (node != &dentry->d_subdirs) {
649 struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
650 list_del_init(node);
651 if (d->d_inode) {
652 /* This should never be called on a cgroup
653 * directory with child cgroups */
654 BUG_ON(d->d_inode->i_mode & S_IFDIR);
655 d = dget_locked(d);
656 spin_unlock(&dcache_lock);
657 d_delete(d);
658 simple_unlink(dentry->d_inode, d);
659 dput(d);
660 spin_lock(&dcache_lock);
662 node = dentry->d_subdirs.next;
664 spin_unlock(&dcache_lock);
668 * NOTE : the dentry must have been dget()'ed
670 static void cgroup_d_remove_dir(struct dentry *dentry)
672 cgroup_clear_directory(dentry);
674 spin_lock(&dcache_lock);
675 list_del_init(&dentry->d_u.d_child);
676 spin_unlock(&dcache_lock);
677 remove_dir(dentry);
680 static int rebind_subsystems(struct cgroupfs_root *root,
681 unsigned long final_bits)
683 unsigned long added_bits, removed_bits;
684 struct cgroup *cgrp = &root->top_cgroup;
685 int i;
687 removed_bits = root->actual_subsys_bits & ~final_bits;
688 added_bits = final_bits & ~root->actual_subsys_bits;
689 /* Check that any added subsystems are currently free */
690 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
691 unsigned long bit = 1UL << i;
692 struct cgroup_subsys *ss = subsys[i];
693 if (!(bit & added_bits))
694 continue;
695 if (ss->root != &rootnode) {
696 /* Subsystem isn't free */
697 return -EBUSY;
701 /* Currently we don't handle adding/removing subsystems when
702 * any child cgroups exist. This is theoretically supportable
703 * but involves complex error handling, so it's being left until
704 * later */
705 if (root->number_of_cgroups > 1)
706 return -EBUSY;
708 /* Process each subsystem */
709 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
710 struct cgroup_subsys *ss = subsys[i];
711 unsigned long bit = 1UL << i;
712 if (bit & added_bits) {
713 /* We're binding this subsystem to this hierarchy */
714 BUG_ON(cgrp->subsys[i]);
715 BUG_ON(!dummytop->subsys[i]);
716 BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
717 cgrp->subsys[i] = dummytop->subsys[i];
718 cgrp->subsys[i]->cgroup = cgrp;
719 list_add(&ss->sibling, &root->subsys_list);
720 rcu_assign_pointer(ss->root, root);
721 if (ss->bind)
722 ss->bind(ss, cgrp);
724 } else if (bit & removed_bits) {
725 /* We're removing this subsystem */
726 BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
727 BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
728 if (ss->bind)
729 ss->bind(ss, dummytop);
730 dummytop->subsys[i]->cgroup = dummytop;
731 cgrp->subsys[i] = NULL;
732 rcu_assign_pointer(subsys[i]->root, &rootnode);
733 list_del(&ss->sibling);
734 } else if (bit & final_bits) {
735 /* Subsystem state should already exist */
736 BUG_ON(!cgrp->subsys[i]);
737 } else {
738 /* Subsystem state shouldn't exist */
739 BUG_ON(cgrp->subsys[i]);
742 root->subsys_bits = root->actual_subsys_bits = final_bits;
743 synchronize_rcu();
745 return 0;
748 static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
750 struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info;
751 struct cgroup_subsys *ss;
753 mutex_lock(&cgroup_mutex);
754 for_each_subsys(root, ss)
755 seq_printf(seq, ",%s", ss->name);
756 if (test_bit(ROOT_NOPREFIX, &root->flags))
757 seq_puts(seq, ",noprefix");
758 if (strlen(root->release_agent_path))
759 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
760 mutex_unlock(&cgroup_mutex);
761 return 0;
764 struct cgroup_sb_opts {
765 unsigned long subsys_bits;
766 unsigned long flags;
767 char *release_agent;
770 /* Convert a hierarchy specifier into a bitmask of subsystems and
771 * flags. */
772 static int parse_cgroupfs_options(char *data,
773 struct cgroup_sb_opts *opts)
775 char *token, *o = data ?: "all";
777 opts->subsys_bits = 0;
778 opts->flags = 0;
779 opts->release_agent = NULL;
781 while ((token = strsep(&o, ",")) != NULL) {
782 if (!*token)
783 return -EINVAL;
784 if (!strcmp(token, "all")) {
785 /* Add all non-disabled subsystems */
786 int i;
787 opts->subsys_bits = 0;
788 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
789 struct cgroup_subsys *ss = subsys[i];
790 if (!ss->disabled)
791 opts->subsys_bits |= 1ul << i;
793 } else if (!strcmp(token, "noprefix")) {
794 set_bit(ROOT_NOPREFIX, &opts->flags);
795 } else if (!strncmp(token, "release_agent=", 14)) {
796 /* Specifying two release agents is forbidden */
797 if (opts->release_agent)
798 return -EINVAL;
799 opts->release_agent = kzalloc(PATH_MAX, GFP_KERNEL);
800 if (!opts->release_agent)
801 return -ENOMEM;
802 strncpy(opts->release_agent, token + 14, PATH_MAX - 1);
803 opts->release_agent[PATH_MAX - 1] = 0;
804 } else {
805 struct cgroup_subsys *ss;
806 int i;
807 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
808 ss = subsys[i];
809 if (!strcmp(token, ss->name)) {
810 if (!ss->disabled)
811 set_bit(i, &opts->subsys_bits);
812 break;
815 if (i == CGROUP_SUBSYS_COUNT)
816 return -ENOENT;
820 /* We can't have an empty hierarchy */
821 if (!opts->subsys_bits)
822 return -EINVAL;
824 return 0;
827 static int cgroup_remount(struct super_block *sb, int *flags, char *data)
829 int ret = 0;
830 struct cgroupfs_root *root = sb->s_fs_info;
831 struct cgroup *cgrp = &root->top_cgroup;
832 struct cgroup_sb_opts opts;
834 mutex_lock(&cgrp->dentry->d_inode->i_mutex);
835 mutex_lock(&cgroup_mutex);
837 /* See what subsystems are wanted */
838 ret = parse_cgroupfs_options(data, &opts);
839 if (ret)
840 goto out_unlock;
842 /* Don't allow flags to change at remount */
843 if (opts.flags != root->flags) {
844 ret = -EINVAL;
845 goto out_unlock;
848 ret = rebind_subsystems(root, opts.subsys_bits);
850 /* (re)populate subsystem files */
851 if (!ret)
852 cgroup_populate_dir(cgrp);
854 if (opts.release_agent)
855 strcpy(root->release_agent_path, opts.release_agent);
856 out_unlock:
857 if (opts.release_agent)
858 kfree(opts.release_agent);
859 mutex_unlock(&cgroup_mutex);
860 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
861 return ret;
864 static struct super_operations cgroup_ops = {
865 .statfs = simple_statfs,
866 .drop_inode = generic_delete_inode,
867 .show_options = cgroup_show_options,
868 .remount_fs = cgroup_remount,
871 static void init_cgroup_housekeeping(struct cgroup *cgrp)
873 INIT_LIST_HEAD(&cgrp->sibling);
874 INIT_LIST_HEAD(&cgrp->children);
875 INIT_LIST_HEAD(&cgrp->css_sets);
876 INIT_LIST_HEAD(&cgrp->release_list);
877 init_rwsem(&cgrp->pids_mutex);
879 static void init_cgroup_root(struct cgroupfs_root *root)
881 struct cgroup *cgrp = &root->top_cgroup;
882 INIT_LIST_HEAD(&root->subsys_list);
883 INIT_LIST_HEAD(&root->root_list);
884 root->number_of_cgroups = 1;
885 cgrp->root = root;
886 cgrp->top_cgroup = cgrp;
887 init_cgroup_housekeeping(cgrp);
890 static int cgroup_test_super(struct super_block *sb, void *data)
892 struct cgroupfs_root *new = data;
893 struct cgroupfs_root *root = sb->s_fs_info;
895 /* First check subsystems */
896 if (new->subsys_bits != root->subsys_bits)
897 return 0;
899 /* Next check flags */
900 if (new->flags != root->flags)
901 return 0;
903 return 1;
906 static int cgroup_set_super(struct super_block *sb, void *data)
908 int ret;
909 struct cgroupfs_root *root = data;
911 ret = set_anon_super(sb, NULL);
912 if (ret)
913 return ret;
915 sb->s_fs_info = root;
916 root->sb = sb;
918 sb->s_blocksize = PAGE_CACHE_SIZE;
919 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
920 sb->s_magic = CGROUP_SUPER_MAGIC;
921 sb->s_op = &cgroup_ops;
923 return 0;
926 static int cgroup_get_rootdir(struct super_block *sb)
928 struct inode *inode =
929 cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
930 struct dentry *dentry;
932 if (!inode)
933 return -ENOMEM;
935 inode->i_fop = &simple_dir_operations;
936 inode->i_op = &cgroup_dir_inode_operations;
937 /* directories start off with i_nlink == 2 (for "." entry) */
938 inc_nlink(inode);
939 dentry = d_alloc_root(inode);
940 if (!dentry) {
941 iput(inode);
942 return -ENOMEM;
944 sb->s_root = dentry;
945 return 0;
948 static int cgroup_get_sb(struct file_system_type *fs_type,
949 int flags, const char *unused_dev_name,
950 void *data, struct vfsmount *mnt)
952 struct cgroup_sb_opts opts;
953 int ret = 0;
954 struct super_block *sb;
955 struct cgroupfs_root *root;
956 struct list_head tmp_cg_links;
958 /* First find the desired set of subsystems */
959 ret = parse_cgroupfs_options(data, &opts);
960 if (ret) {
961 if (opts.release_agent)
962 kfree(opts.release_agent);
963 return ret;
966 root = kzalloc(sizeof(*root), GFP_KERNEL);
967 if (!root) {
968 if (opts.release_agent)
969 kfree(opts.release_agent);
970 return -ENOMEM;
973 init_cgroup_root(root);
974 root->subsys_bits = opts.subsys_bits;
975 root->flags = opts.flags;
976 if (opts.release_agent) {
977 strcpy(root->release_agent_path, opts.release_agent);
978 kfree(opts.release_agent);
981 sb = sget(fs_type, cgroup_test_super, cgroup_set_super, root);
983 if (IS_ERR(sb)) {
984 kfree(root);
985 return PTR_ERR(sb);
988 if (sb->s_fs_info != root) {
989 /* Reusing an existing superblock */
990 BUG_ON(sb->s_root == NULL);
991 kfree(root);
992 root = NULL;
993 } else {
994 /* New superblock */
995 struct cgroup *cgrp = &root->top_cgroup;
996 struct inode *inode;
997 int i;
999 BUG_ON(sb->s_root != NULL);
1001 ret = cgroup_get_rootdir(sb);
1002 if (ret)
1003 goto drop_new_super;
1004 inode = sb->s_root->d_inode;
1006 mutex_lock(&inode->i_mutex);
1007 mutex_lock(&cgroup_mutex);
1010 * We're accessing css_set_count without locking
1011 * css_set_lock here, but that's OK - it can only be
1012 * increased by someone holding cgroup_lock, and
1013 * that's us. The worst that can happen is that we
1014 * have some link structures left over
1016 ret = allocate_cg_links(css_set_count, &tmp_cg_links);
1017 if (ret) {
1018 mutex_unlock(&cgroup_mutex);
1019 mutex_unlock(&inode->i_mutex);
1020 goto drop_new_super;
1023 ret = rebind_subsystems(root, root->subsys_bits);
1024 if (ret == -EBUSY) {
1025 mutex_unlock(&cgroup_mutex);
1026 mutex_unlock(&inode->i_mutex);
1027 goto free_cg_links;
1030 /* EBUSY should be the only error here */
1031 BUG_ON(ret);
1033 list_add(&root->root_list, &roots);
1034 root_count++;
1036 sb->s_root->d_fsdata = &root->top_cgroup;
1037 root->top_cgroup.dentry = sb->s_root;
1039 /* Link the top cgroup in this hierarchy into all
1040 * the css_set objects */
1041 write_lock(&css_set_lock);
1042 for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
1043 struct hlist_head *hhead = &css_set_table[i];
1044 struct hlist_node *node;
1045 struct css_set *cg;
1047 hlist_for_each_entry(cg, node, hhead, hlist) {
1048 struct cg_cgroup_link *link;
1050 BUG_ON(list_empty(&tmp_cg_links));
1051 link = list_entry(tmp_cg_links.next,
1052 struct cg_cgroup_link,
1053 cgrp_link_list);
1054 list_del(&link->cgrp_link_list);
1055 link->cg = cg;
1056 list_add(&link->cgrp_link_list,
1057 &root->top_cgroup.css_sets);
1058 list_add(&link->cg_link_list, &cg->cg_links);
1061 write_unlock(&css_set_lock);
1063 free_cg_links(&tmp_cg_links);
1065 BUG_ON(!list_empty(&cgrp->sibling));
1066 BUG_ON(!list_empty(&cgrp->children));
1067 BUG_ON(root->number_of_cgroups != 1);
1069 cgroup_populate_dir(cgrp);
1070 mutex_unlock(&inode->i_mutex);
1071 mutex_unlock(&cgroup_mutex);
1074 return simple_set_mnt(mnt, sb);
1076 free_cg_links:
1077 free_cg_links(&tmp_cg_links);
1078 drop_new_super:
1079 up_write(&sb->s_umount);
1080 deactivate_super(sb);
1081 return ret;
1084 static void cgroup_kill_sb(struct super_block *sb) {
1085 struct cgroupfs_root *root = sb->s_fs_info;
1086 struct cgroup *cgrp = &root->top_cgroup;
1087 int ret;
1088 struct cg_cgroup_link *link;
1089 struct cg_cgroup_link *saved_link;
1091 BUG_ON(!root);
1093 BUG_ON(root->number_of_cgroups != 1);
1094 BUG_ON(!list_empty(&cgrp->children));
1095 BUG_ON(!list_empty(&cgrp->sibling));
1097 mutex_lock(&cgroup_mutex);
1099 /* Rebind all subsystems back to the default hierarchy */
1100 ret = rebind_subsystems(root, 0);
1101 /* Shouldn't be able to fail ... */
1102 BUG_ON(ret);
1105 * Release all the links from css_sets to this hierarchy's
1106 * root cgroup
1108 write_lock(&css_set_lock);
1110 list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
1111 cgrp_link_list) {
1112 list_del(&link->cg_link_list);
1113 list_del(&link->cgrp_link_list);
1114 kfree(link);
1116 write_unlock(&css_set_lock);
1118 if (!list_empty(&root->root_list)) {
1119 list_del(&root->root_list);
1120 root_count--;
1122 mutex_unlock(&cgroup_mutex);
1124 kfree(root);
1125 kill_litter_super(sb);
1128 static struct file_system_type cgroup_fs_type = {
1129 .name = "cgroup",
1130 .get_sb = cgroup_get_sb,
1131 .kill_sb = cgroup_kill_sb,
1134 static inline struct cgroup *__d_cgrp(struct dentry *dentry)
1136 return dentry->d_fsdata;
1139 static inline struct cftype *__d_cft(struct dentry *dentry)
1141 return dentry->d_fsdata;
1145 * cgroup_path - generate the path of a cgroup
1146 * @cgrp: the cgroup in question
1147 * @buf: the buffer to write the path into
1148 * @buflen: the length of the buffer
1150 * Called with cgroup_mutex held. Writes path of cgroup into buf.
1151 * Returns 0 on success, -errno on error.
1153 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1155 char *start;
1157 if (cgrp == dummytop) {
1159 * Inactive subsystems have no dentry for their root
1160 * cgroup
1162 strcpy(buf, "/");
1163 return 0;
1166 start = buf + buflen;
1168 *--start = '\0';
1169 for (;;) {
1170 int len = cgrp->dentry->d_name.len;
1171 if ((start -= len) < buf)
1172 return -ENAMETOOLONG;
1173 memcpy(start, cgrp->dentry->d_name.name, len);
1174 cgrp = cgrp->parent;
1175 if (!cgrp)
1176 break;
1177 if (!cgrp->parent)
1178 continue;
1179 if (--start < buf)
1180 return -ENAMETOOLONG;
1181 *start = '/';
1183 memmove(buf, start, buf + buflen - start);
1184 return 0;
1188 * Return the first subsystem attached to a cgroup's hierarchy, and
1189 * its subsystem id.
1192 static void get_first_subsys(const struct cgroup *cgrp,
1193 struct cgroup_subsys_state **css, int *subsys_id)
1195 const struct cgroupfs_root *root = cgrp->root;
1196 const struct cgroup_subsys *test_ss;
1197 BUG_ON(list_empty(&root->subsys_list));
1198 test_ss = list_entry(root->subsys_list.next,
1199 struct cgroup_subsys, sibling);
1200 if (css) {
1201 *css = cgrp->subsys[test_ss->subsys_id];
1202 BUG_ON(!*css);
1204 if (subsys_id)
1205 *subsys_id = test_ss->subsys_id;
1209 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
1210 * @cgrp: the cgroup the task is attaching to
1211 * @tsk: the task to be attached
1213 * Call holding cgroup_mutex. May take task_lock of
1214 * the task 'tsk' during call.
1216 int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1218 int retval = 0;
1219 struct cgroup_subsys *ss;
1220 struct cgroup *oldcgrp;
1221 struct css_set *cg = tsk->cgroups;
1222 struct css_set *newcg;
1223 struct cgroupfs_root *root = cgrp->root;
1224 int subsys_id;
1226 get_first_subsys(cgrp, NULL, &subsys_id);
1228 /* Nothing to do if the task is already in that cgroup */
1229 oldcgrp = task_cgroup(tsk, subsys_id);
1230 if (cgrp == oldcgrp)
1231 return 0;
1233 for_each_subsys(root, ss) {
1234 if (ss->can_attach) {
1235 retval = ss->can_attach(ss, cgrp, tsk);
1236 if (retval)
1237 return retval;
1242 * Locate or allocate a new css_set for this task,
1243 * based on its final set of cgroups
1245 newcg = find_css_set(cg, cgrp);
1246 if (!newcg)
1247 return -ENOMEM;
1249 task_lock(tsk);
1250 if (tsk->flags & PF_EXITING) {
1251 task_unlock(tsk);
1252 put_css_set(newcg);
1253 return -ESRCH;
1255 rcu_assign_pointer(tsk->cgroups, newcg);
1256 task_unlock(tsk);
1258 /* Update the css_set linked lists if we're using them */
1259 write_lock(&css_set_lock);
1260 if (!list_empty(&tsk->cg_list)) {
1261 list_del(&tsk->cg_list);
1262 list_add(&tsk->cg_list, &newcg->tasks);
1264 write_unlock(&css_set_lock);
1266 for_each_subsys(root, ss) {
1267 if (ss->attach)
1268 ss->attach(ss, cgrp, oldcgrp, tsk);
1270 set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1271 synchronize_rcu();
1272 put_css_set(cg);
1273 return 0;
1277 * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex
1278 * held. May take task_lock of task
1280 static int attach_task_by_pid(struct cgroup *cgrp, u64 pid)
1282 struct task_struct *tsk;
1283 int ret;
1285 if (pid) {
1286 rcu_read_lock();
1287 tsk = find_task_by_vpid(pid);
1288 if (!tsk || tsk->flags & PF_EXITING) {
1289 rcu_read_unlock();
1290 return -ESRCH;
1292 get_task_struct(tsk);
1293 rcu_read_unlock();
1295 if ((current->euid) && (current->euid != tsk->uid)
1296 && (current->euid != tsk->suid)) {
1297 put_task_struct(tsk);
1298 return -EACCES;
1300 } else {
1301 tsk = current;
1302 get_task_struct(tsk);
1305 ret = cgroup_attach_task(cgrp, tsk);
1306 put_task_struct(tsk);
1307 return ret;
1310 static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
1312 int ret;
1313 if (!cgroup_lock_live_group(cgrp))
1314 return -ENODEV;
1315 ret = attach_task_by_pid(cgrp, pid);
1316 cgroup_unlock();
1317 return ret;
1320 /* The various types of files and directories in a cgroup file system */
1321 enum cgroup_filetype {
1322 FILE_ROOT,
1323 FILE_DIR,
1324 FILE_TASKLIST,
1325 FILE_NOTIFY_ON_RELEASE,
1326 FILE_RELEASE_AGENT,
1330 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
1331 * @cgrp: the cgroup to be checked for liveness
1333 * On success, returns true; the lock should be later released with
1334 * cgroup_unlock(). On failure returns false with no lock held.
1336 bool cgroup_lock_live_group(struct cgroup *cgrp)
1338 mutex_lock(&cgroup_mutex);
1339 if (cgroup_is_removed(cgrp)) {
1340 mutex_unlock(&cgroup_mutex);
1341 return false;
1343 return true;
1346 static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
1347 const char *buffer)
1349 BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
1350 if (!cgroup_lock_live_group(cgrp))
1351 return -ENODEV;
1352 strcpy(cgrp->root->release_agent_path, buffer);
1353 cgroup_unlock();
1354 return 0;
1357 static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
1358 struct seq_file *seq)
1360 if (!cgroup_lock_live_group(cgrp))
1361 return -ENODEV;
1362 seq_puts(seq, cgrp->root->release_agent_path);
1363 seq_putc(seq, '\n');
1364 cgroup_unlock();
1365 return 0;
1368 /* A buffer size big enough for numbers or short strings */
1369 #define CGROUP_LOCAL_BUFFER_SIZE 64
1371 static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
1372 struct file *file,
1373 const char __user *userbuf,
1374 size_t nbytes, loff_t *unused_ppos)
1376 char buffer[CGROUP_LOCAL_BUFFER_SIZE];
1377 int retval = 0;
1378 char *end;
1380 if (!nbytes)
1381 return -EINVAL;
1382 if (nbytes >= sizeof(buffer))
1383 return -E2BIG;
1384 if (copy_from_user(buffer, userbuf, nbytes))
1385 return -EFAULT;
1387 buffer[nbytes] = 0; /* nul-terminate */
1388 strstrip(buffer);
1389 if (cft->write_u64) {
1390 u64 val = simple_strtoull(buffer, &end, 0);
1391 if (*end)
1392 return -EINVAL;
1393 retval = cft->write_u64(cgrp, cft, val);
1394 } else {
1395 s64 val = simple_strtoll(buffer, &end, 0);
1396 if (*end)
1397 return -EINVAL;
1398 retval = cft->write_s64(cgrp, cft, val);
1400 if (!retval)
1401 retval = nbytes;
1402 return retval;
1405 static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
1406 struct file *file,
1407 const char __user *userbuf,
1408 size_t nbytes, loff_t *unused_ppos)
1410 char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
1411 int retval = 0;
1412 size_t max_bytes = cft->max_write_len;
1413 char *buffer = local_buffer;
1415 if (!max_bytes)
1416 max_bytes = sizeof(local_buffer) - 1;
1417 if (nbytes >= max_bytes)
1418 return -E2BIG;
1419 /* Allocate a dynamic buffer if we need one */
1420 if (nbytes >= sizeof(local_buffer)) {
1421 buffer = kmalloc(nbytes + 1, GFP_KERNEL);
1422 if (buffer == NULL)
1423 return -ENOMEM;
1425 if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
1426 retval = -EFAULT;
1427 goto out;
1430 buffer[nbytes] = 0; /* nul-terminate */
1431 strstrip(buffer);
1432 retval = cft->write_string(cgrp, cft, buffer);
1433 if (!retval)
1434 retval = nbytes;
1435 out:
1436 if (buffer != local_buffer)
1437 kfree(buffer);
1438 return retval;
1441 static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
1442 size_t nbytes, loff_t *ppos)
1444 struct cftype *cft = __d_cft(file->f_dentry);
1445 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
1447 if (!cft || cgroup_is_removed(cgrp))
1448 return -ENODEV;
1449 if (cft->write)
1450 return cft->write(cgrp, cft, file, buf, nbytes, ppos);
1451 if (cft->write_u64 || cft->write_s64)
1452 return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
1453 if (cft->write_string)
1454 return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
1455 if (cft->trigger) {
1456 int ret = cft->trigger(cgrp, (unsigned int)cft->private);
1457 return ret ? ret : nbytes;
1459 return -EINVAL;
1462 static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
1463 struct file *file,
1464 char __user *buf, size_t nbytes,
1465 loff_t *ppos)
1467 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
1468 u64 val = cft->read_u64(cgrp, cft);
1469 int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
1471 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
1474 static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
1475 struct file *file,
1476 char __user *buf, size_t nbytes,
1477 loff_t *ppos)
1479 char tmp[CGROUP_LOCAL_BUFFER_SIZE];
1480 s64 val = cft->read_s64(cgrp, cft);
1481 int len = sprintf(tmp, "%lld\n", (long long) val);
1483 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
1486 static ssize_t cgroup_file_read(struct file *file, char __user *buf,
1487 size_t nbytes, loff_t *ppos)
1489 struct cftype *cft = __d_cft(file->f_dentry);
1490 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
1492 if (!cft || cgroup_is_removed(cgrp))
1493 return -ENODEV;
1495 if (cft->read)
1496 return cft->read(cgrp, cft, file, buf, nbytes, ppos);
1497 if (cft->read_u64)
1498 return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
1499 if (cft->read_s64)
1500 return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
1501 return -EINVAL;
1505 * seqfile ops/methods for returning structured data. Currently just
1506 * supports string->u64 maps, but can be extended in future.
1509 struct cgroup_seqfile_state {
1510 struct cftype *cft;
1511 struct cgroup *cgroup;
1514 static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
1516 struct seq_file *sf = cb->state;
1517 return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
1520 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
1522 struct cgroup_seqfile_state *state = m->private;
1523 struct cftype *cft = state->cft;
1524 if (cft->read_map) {
1525 struct cgroup_map_cb cb = {
1526 .fill = cgroup_map_add,
1527 .state = m,
1529 return cft->read_map(state->cgroup, cft, &cb);
1531 return cft->read_seq_string(state->cgroup, cft, m);
1534 static int cgroup_seqfile_release(struct inode *inode, struct file *file)
1536 struct seq_file *seq = file->private_data;
1537 kfree(seq->private);
1538 return single_release(inode, file);
1541 static struct file_operations cgroup_seqfile_operations = {
1542 .read = seq_read,
1543 .write = cgroup_file_write,
1544 .llseek = seq_lseek,
1545 .release = cgroup_seqfile_release,
1548 static int cgroup_file_open(struct inode *inode, struct file *file)
1550 int err;
1551 struct cftype *cft;
1553 err = generic_file_open(inode, file);
1554 if (err)
1555 return err;
1557 cft = __d_cft(file->f_dentry);
1558 if (!cft)
1559 return -ENODEV;
1560 if (cft->read_map || cft->read_seq_string) {
1561 struct cgroup_seqfile_state *state =
1562 kzalloc(sizeof(*state), GFP_USER);
1563 if (!state)
1564 return -ENOMEM;
1565 state->cft = cft;
1566 state->cgroup = __d_cgrp(file->f_dentry->d_parent);
1567 file->f_op = &cgroup_seqfile_operations;
1568 err = single_open(file, cgroup_seqfile_show, state);
1569 if (err < 0)
1570 kfree(state);
1571 } else if (cft->open)
1572 err = cft->open(inode, file);
1573 else
1574 err = 0;
1576 return err;
1579 static int cgroup_file_release(struct inode *inode, struct file *file)
1581 struct cftype *cft = __d_cft(file->f_dentry);
1582 if (cft->release)
1583 return cft->release(inode, file);
1584 return 0;
1588 * cgroup_rename - Only allow simple rename of directories in place.
1590 static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
1591 struct inode *new_dir, struct dentry *new_dentry)
1593 if (!S_ISDIR(old_dentry->d_inode->i_mode))
1594 return -ENOTDIR;
1595 if (new_dentry->d_inode)
1596 return -EEXIST;
1597 if (old_dir != new_dir)
1598 return -EIO;
1599 return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
1602 static struct file_operations cgroup_file_operations = {
1603 .read = cgroup_file_read,
1604 .write = cgroup_file_write,
1605 .llseek = generic_file_llseek,
1606 .open = cgroup_file_open,
1607 .release = cgroup_file_release,
1610 static struct inode_operations cgroup_dir_inode_operations = {
1611 .lookup = simple_lookup,
1612 .mkdir = cgroup_mkdir,
1613 .rmdir = cgroup_rmdir,
1614 .rename = cgroup_rename,
1617 static int cgroup_create_file(struct dentry *dentry, int mode,
1618 struct super_block *sb)
1620 static struct dentry_operations cgroup_dops = {
1621 .d_iput = cgroup_diput,
1624 struct inode *inode;
1626 if (!dentry)
1627 return -ENOENT;
1628 if (dentry->d_inode)
1629 return -EEXIST;
1631 inode = cgroup_new_inode(mode, sb);
1632 if (!inode)
1633 return -ENOMEM;
1635 if (S_ISDIR(mode)) {
1636 inode->i_op = &cgroup_dir_inode_operations;
1637 inode->i_fop = &simple_dir_operations;
1639 /* start off with i_nlink == 2 (for "." entry) */
1640 inc_nlink(inode);
1642 /* start with the directory inode held, so that we can
1643 * populate it without racing with another mkdir */
1644 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1645 } else if (S_ISREG(mode)) {
1646 inode->i_size = 0;
1647 inode->i_fop = &cgroup_file_operations;
1649 dentry->d_op = &cgroup_dops;
1650 d_instantiate(dentry, inode);
1651 dget(dentry); /* Extra count - pin the dentry in core */
1652 return 0;
1656 * cgroup_create_dir - create a directory for an object.
1657 * @cgrp: the cgroup we create the directory for. It must have a valid
1658 * ->parent field. And we are going to fill its ->dentry field.
1659 * @dentry: dentry of the new cgroup
1660 * @mode: mode to set on new directory.
1662 static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
1663 int mode)
1665 struct dentry *parent;
1666 int error = 0;
1668 parent = cgrp->parent->dentry;
1669 error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
1670 if (!error) {
1671 dentry->d_fsdata = cgrp;
1672 inc_nlink(parent->d_inode);
1673 cgrp->dentry = dentry;
1674 dget(dentry);
1676 dput(dentry);
1678 return error;
1681 int cgroup_add_file(struct cgroup *cgrp,
1682 struct cgroup_subsys *subsys,
1683 const struct cftype *cft)
1685 struct dentry *dir = cgrp->dentry;
1686 struct dentry *dentry;
1687 int error;
1689 char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
1690 if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
1691 strcpy(name, subsys->name);
1692 strcat(name, ".");
1694 strcat(name, cft->name);
1695 BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
1696 dentry = lookup_one_len(name, dir, strlen(name));
1697 if (!IS_ERR(dentry)) {
1698 error = cgroup_create_file(dentry, 0644 | S_IFREG,
1699 cgrp->root->sb);
1700 if (!error)
1701 dentry->d_fsdata = (void *)cft;
1702 dput(dentry);
1703 } else
1704 error = PTR_ERR(dentry);
1705 return error;
1708 int cgroup_add_files(struct cgroup *cgrp,
1709 struct cgroup_subsys *subsys,
1710 const struct cftype cft[],
1711 int count)
1713 int i, err;
1714 for (i = 0; i < count; i++) {
1715 err = cgroup_add_file(cgrp, subsys, &cft[i]);
1716 if (err)
1717 return err;
1719 return 0;
1723 * cgroup_task_count - count the number of tasks in a cgroup.
1724 * @cgrp: the cgroup in question
1726 * Return the number of tasks in the cgroup.
1728 int cgroup_task_count(const struct cgroup *cgrp)
1730 int count = 0;
1731 struct cg_cgroup_link *link;
1733 read_lock(&css_set_lock);
1734 list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
1735 count += atomic_read(&link->cg->refcount);
1737 read_unlock(&css_set_lock);
1738 return count;
1742 * Advance a list_head iterator. The iterator should be positioned at
1743 * the start of a css_set
1745 static void cgroup_advance_iter(struct cgroup *cgrp,
1746 struct cgroup_iter *it)
1748 struct list_head *l = it->cg_link;
1749 struct cg_cgroup_link *link;
1750 struct css_set *cg;
1752 /* Advance to the next non-empty css_set */
1753 do {
1754 l = l->next;
1755 if (l == &cgrp->css_sets) {
1756 it->cg_link = NULL;
1757 return;
1759 link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
1760 cg = link->cg;
1761 } while (list_empty(&cg->tasks));
1762 it->cg_link = l;
1763 it->task = cg->tasks.next;
1767 * To reduce the fork() overhead for systems that are not actually
1768 * using their cgroups capability, we don't maintain the lists running
1769 * through each css_set to its tasks until we see the list actually
1770 * used - in other words after the first call to cgroup_iter_start().
1772 * The tasklist_lock is not held here, as do_each_thread() and
1773 * while_each_thread() are protected by RCU.
1775 static void cgroup_enable_task_cg_lists(void)
1777 struct task_struct *p, *g;
1778 write_lock(&css_set_lock);
1779 use_task_css_set_links = 1;
1780 do_each_thread(g, p) {
1781 task_lock(p);
1783 * We should check if the process is exiting, otherwise
1784 * it will race with cgroup_exit() in that the list
1785 * entry won't be deleted though the process has exited.
1787 if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
1788 list_add(&p->cg_list, &p->cgroups->tasks);
1789 task_unlock(p);
1790 } while_each_thread(g, p);
1791 write_unlock(&css_set_lock);
1794 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
1797 * The first time anyone tries to iterate across a cgroup,
1798 * we need to enable the list linking each css_set to its
1799 * tasks, and fix up all existing tasks.
1801 if (!use_task_css_set_links)
1802 cgroup_enable_task_cg_lists();
1804 read_lock(&css_set_lock);
1805 it->cg_link = &cgrp->css_sets;
1806 cgroup_advance_iter(cgrp, it);
1809 struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
1810 struct cgroup_iter *it)
1812 struct task_struct *res;
1813 struct list_head *l = it->task;
1815 /* If the iterator cg is NULL, we have no tasks */
1816 if (!it->cg_link)
1817 return NULL;
1818 res = list_entry(l, struct task_struct, cg_list);
1819 /* Advance iterator to find next entry */
1820 l = l->next;
1821 if (l == &res->cgroups->tasks) {
1822 /* We reached the end of this task list - move on to
1823 * the next cg_cgroup_link */
1824 cgroup_advance_iter(cgrp, it);
1825 } else {
1826 it->task = l;
1828 return res;
1831 void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
1833 read_unlock(&css_set_lock);
1836 static inline int started_after_time(struct task_struct *t1,
1837 struct timespec *time,
1838 struct task_struct *t2)
1840 int start_diff = timespec_compare(&t1->start_time, time);
1841 if (start_diff > 0) {
1842 return 1;
1843 } else if (start_diff < 0) {
1844 return 0;
1845 } else {
1847 * Arbitrarily, if two processes started at the same
1848 * time, we'll say that the lower pointer value
1849 * started first. Note that t2 may have exited by now
1850 * so this may not be a valid pointer any longer, but
1851 * that's fine - it still serves to distinguish
1852 * between two tasks started (effectively) simultaneously.
1854 return t1 > t2;
1859 * This function is a callback from heap_insert() and is used to order
1860 * the heap.
1861 * In this case we order the heap in descending task start time.
1863 static inline int started_after(void *p1, void *p2)
1865 struct task_struct *t1 = p1;
1866 struct task_struct *t2 = p2;
1867 return started_after_time(t1, &t2->start_time, t2);
1871 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
1872 * @scan: struct cgroup_scanner containing arguments for the scan
1874 * Arguments include pointers to callback functions test_task() and
1875 * process_task().
1876 * Iterate through all the tasks in a cgroup, calling test_task() for each,
1877 * and if it returns true, call process_task() for it also.
1878 * The test_task pointer may be NULL, meaning always true (select all tasks).
1879 * Effectively duplicates cgroup_iter_{start,next,end}()
1880 * but does not lock css_set_lock for the call to process_task().
1881 * The struct cgroup_scanner may be embedded in any structure of the caller's
1882 * creation.
1883 * It is guaranteed that process_task() will act on every task that
1884 * is a member of the cgroup for the duration of this call. This
1885 * function may or may not call process_task() for tasks that exit
1886 * or move to a different cgroup during the call, or are forked or
1887 * move into the cgroup during the call.
1889 * Note that test_task() may be called with locks held, and may in some
1890 * situations be called multiple times for the same task, so it should
1891 * be cheap.
1892 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
1893 * pre-allocated and will be used for heap operations (and its "gt" member will
1894 * be overwritten), else a temporary heap will be used (allocation of which
1895 * may cause this function to fail).
1897 int cgroup_scan_tasks(struct cgroup_scanner *scan)
1899 int retval, i;
1900 struct cgroup_iter it;
1901 struct task_struct *p, *dropped;
1902 /* Never dereference latest_task, since it's not refcounted */
1903 struct task_struct *latest_task = NULL;
1904 struct ptr_heap tmp_heap;
1905 struct ptr_heap *heap;
1906 struct timespec latest_time = { 0, 0 };
1908 if (scan->heap) {
1909 /* The caller supplied our heap and pre-allocated its memory */
1910 heap = scan->heap;
1911 heap->gt = &started_after;
1912 } else {
1913 /* We need to allocate our own heap memory */
1914 heap = &tmp_heap;
1915 retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
1916 if (retval)
1917 /* cannot allocate the heap */
1918 return retval;
1921 again:
1923 * Scan tasks in the cgroup, using the scanner's "test_task" callback
1924 * to determine which are of interest, and using the scanner's
1925 * "process_task" callback to process any of them that need an update.
1926 * Since we don't want to hold any locks during the task updates,
1927 * gather tasks to be processed in a heap structure.
1928 * The heap is sorted by descending task start time.
1929 * If the statically-sized heap fills up, we overflow tasks that
1930 * started later, and in future iterations only consider tasks that
1931 * started after the latest task in the previous pass. This
1932 * guarantees forward progress and that we don't miss any tasks.
1934 heap->size = 0;
1935 cgroup_iter_start(scan->cg, &it);
1936 while ((p = cgroup_iter_next(scan->cg, &it))) {
1938 * Only affect tasks that qualify per the caller's callback,
1939 * if he provided one
1941 if (scan->test_task && !scan->test_task(p, scan))
1942 continue;
1944 * Only process tasks that started after the last task
1945 * we processed
1947 if (!started_after_time(p, &latest_time, latest_task))
1948 continue;
1949 dropped = heap_insert(heap, p);
1950 if (dropped == NULL) {
1952 * The new task was inserted; the heap wasn't
1953 * previously full
1955 get_task_struct(p);
1956 } else if (dropped != p) {
1958 * The new task was inserted, and pushed out a
1959 * different task
1961 get_task_struct(p);
1962 put_task_struct(dropped);
1965 * Else the new task was newer than anything already in
1966 * the heap and wasn't inserted
1969 cgroup_iter_end(scan->cg, &it);
1971 if (heap->size) {
1972 for (i = 0; i < heap->size; i++) {
1973 struct task_struct *q = heap->ptrs[i];
1974 if (i == 0) {
1975 latest_time = q->start_time;
1976 latest_task = q;
1978 /* Process the task per the caller's callback */
1979 scan->process_task(q, scan);
1980 put_task_struct(q);
1983 * If we had to process any tasks at all, scan again
1984 * in case some of them were in the middle of forking
1985 * children that didn't get processed.
1986 * Not the most efficient way to do it, but it avoids
1987 * having to take callback_mutex in the fork path
1989 goto again;
1991 if (heap == &tmp_heap)
1992 heap_free(&tmp_heap);
1993 return 0;
1997 * Stuff for reading the 'tasks' file.
1999 * Reading this file can return large amounts of data if a cgroup has
2000 * *lots* of attached tasks. So it may need several calls to read(),
2001 * but we cannot guarantee that the information we produce is correct
2002 * unless we produce it entirely atomically.
2007 * Load into 'pidarray' up to 'npids' of the tasks using cgroup
2008 * 'cgrp'. Return actual number of pids loaded. No need to
2009 * task_lock(p) when reading out p->cgroup, since we're in an RCU
2010 * read section, so the css_set can't go away, and is
2011 * immutable after creation.
2013 static int pid_array_load(pid_t *pidarray, int npids, struct cgroup *cgrp)
2015 int n = 0;
2016 struct cgroup_iter it;
2017 struct task_struct *tsk;
2018 cgroup_iter_start(cgrp, &it);
2019 while ((tsk = cgroup_iter_next(cgrp, &it))) {
2020 if (unlikely(n == npids))
2021 break;
2022 pidarray[n++] = task_pid_vnr(tsk);
2024 cgroup_iter_end(cgrp, &it);
2025 return n;
2029 * cgroupstats_build - build and fill cgroupstats
2030 * @stats: cgroupstats to fill information into
2031 * @dentry: A dentry entry belonging to the cgroup for which stats have
2032 * been requested.
2034 * Build and fill cgroupstats so that taskstats can export it to user
2035 * space.
2037 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
2039 int ret = -EINVAL;
2040 struct cgroup *cgrp;
2041 struct cgroup_iter it;
2042 struct task_struct *tsk;
2045 * Validate dentry by checking the superblock operations,
2046 * and make sure it's a directory.
2048 if (dentry->d_sb->s_op != &cgroup_ops ||
2049 !S_ISDIR(dentry->d_inode->i_mode))
2050 goto err;
2052 ret = 0;
2053 cgrp = dentry->d_fsdata;
2054 rcu_read_lock();
2056 cgroup_iter_start(cgrp, &it);
2057 while ((tsk = cgroup_iter_next(cgrp, &it))) {
2058 switch (tsk->state) {
2059 case TASK_RUNNING:
2060 stats->nr_running++;
2061 break;
2062 case TASK_INTERRUPTIBLE:
2063 stats->nr_sleeping++;
2064 break;
2065 case TASK_UNINTERRUPTIBLE:
2066 stats->nr_uninterruptible++;
2067 break;
2068 case TASK_STOPPED:
2069 stats->nr_stopped++;
2070 break;
2071 default:
2072 if (delayacct_is_task_waiting_on_io(tsk))
2073 stats->nr_io_wait++;
2074 break;
2077 cgroup_iter_end(cgrp, &it);
2079 rcu_read_unlock();
2080 err:
2081 return ret;
2084 static int cmppid(const void *a, const void *b)
2086 return *(pid_t *)a - *(pid_t *)b;
2091 * seq_file methods for the "tasks" file. The seq_file position is the
2092 * next pid to display; the seq_file iterator is a pointer to the pid
2093 * in the cgroup->tasks_pids array.
2096 static void *cgroup_tasks_start(struct seq_file *s, loff_t *pos)
2099 * Initially we receive a position value that corresponds to
2100 * one more than the last pid shown (or 0 on the first call or
2101 * after a seek to the start). Use a binary-search to find the
2102 * next pid to display, if any
2104 struct cgroup *cgrp = s->private;
2105 int index = 0, pid = *pos;
2106 int *iter;
2108 down_read(&cgrp->pids_mutex);
2109 if (pid) {
2110 int end = cgrp->pids_length;
2112 while (index < end) {
2113 int mid = (index + end) / 2;
2114 if (cgrp->tasks_pids[mid] == pid) {
2115 index = mid;
2116 break;
2117 } else if (cgrp->tasks_pids[mid] <= pid)
2118 index = mid + 1;
2119 else
2120 end = mid;
2123 /* If we're off the end of the array, we're done */
2124 if (index >= cgrp->pids_length)
2125 return NULL;
2126 /* Update the abstract position to be the actual pid that we found */
2127 iter = cgrp->tasks_pids + index;
2128 *pos = *iter;
2129 return iter;
2132 static void cgroup_tasks_stop(struct seq_file *s, void *v)
2134 struct cgroup *cgrp = s->private;
2135 up_read(&cgrp->pids_mutex);
2138 static void *cgroup_tasks_next(struct seq_file *s, void *v, loff_t *pos)
2140 struct cgroup *cgrp = s->private;
2141 int *p = v;
2142 int *end = cgrp->tasks_pids + cgrp->pids_length;
2145 * Advance to the next pid in the array. If this goes off the
2146 * end, we're done
2148 p++;
2149 if (p >= end) {
2150 return NULL;
2151 } else {
2152 *pos = *p;
2153 return p;
2157 static int cgroup_tasks_show(struct seq_file *s, void *v)
2159 return seq_printf(s, "%d\n", *(int *)v);
2162 static struct seq_operations cgroup_tasks_seq_operations = {
2163 .start = cgroup_tasks_start,
2164 .stop = cgroup_tasks_stop,
2165 .next = cgroup_tasks_next,
2166 .show = cgroup_tasks_show,
2169 static void release_cgroup_pid_array(struct cgroup *cgrp)
2171 down_write(&cgrp->pids_mutex);
2172 BUG_ON(!cgrp->pids_use_count);
2173 if (!--cgrp->pids_use_count) {
2174 kfree(cgrp->tasks_pids);
2175 cgrp->tasks_pids = NULL;
2176 cgrp->pids_length = 0;
2178 up_write(&cgrp->pids_mutex);
2181 static int cgroup_tasks_release(struct inode *inode, struct file *file)
2183 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2185 if (!(file->f_mode & FMODE_READ))
2186 return 0;
2188 release_cgroup_pid_array(cgrp);
2189 return seq_release(inode, file);
2192 static struct file_operations cgroup_tasks_operations = {
2193 .read = seq_read,
2194 .llseek = seq_lseek,
2195 .write = cgroup_file_write,
2196 .release = cgroup_tasks_release,
2200 * Handle an open on 'tasks' file. Prepare an array containing the
2201 * process id's of tasks currently attached to the cgroup being opened.
2204 static int cgroup_tasks_open(struct inode *unused, struct file *file)
2206 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2207 pid_t *pidarray;
2208 int npids;
2209 int retval;
2211 /* Nothing to do for write-only files */
2212 if (!(file->f_mode & FMODE_READ))
2213 return 0;
2216 * If cgroup gets more users after we read count, we won't have
2217 * enough space - tough. This race is indistinguishable to the
2218 * caller from the case that the additional cgroup users didn't
2219 * show up until sometime later on.
2221 npids = cgroup_task_count(cgrp);
2222 pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL);
2223 if (!pidarray)
2224 return -ENOMEM;
2225 npids = pid_array_load(pidarray, npids, cgrp);
2226 sort(pidarray, npids, sizeof(pid_t), cmppid, NULL);
2229 * Store the array in the cgroup, freeing the old
2230 * array if necessary
2232 down_write(&cgrp->pids_mutex);
2233 kfree(cgrp->tasks_pids);
2234 cgrp->tasks_pids = pidarray;
2235 cgrp->pids_length = npids;
2236 cgrp->pids_use_count++;
2237 up_write(&cgrp->pids_mutex);
2239 file->f_op = &cgroup_tasks_operations;
2241 retval = seq_open(file, &cgroup_tasks_seq_operations);
2242 if (retval) {
2243 release_cgroup_pid_array(cgrp);
2244 return retval;
2246 ((struct seq_file *)file->private_data)->private = cgrp;
2247 return 0;
2250 static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
2251 struct cftype *cft)
2253 return notify_on_release(cgrp);
2256 static int cgroup_write_notify_on_release(struct cgroup *cgrp,
2257 struct cftype *cft,
2258 u64 val)
2260 clear_bit(CGRP_RELEASABLE, &cgrp->flags);
2261 if (val)
2262 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
2263 else
2264 clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
2265 return 0;
2269 * for the common functions, 'private' gives the type of file
2271 static struct cftype files[] = {
2273 .name = "tasks",
2274 .open = cgroup_tasks_open,
2275 .write_u64 = cgroup_tasks_write,
2276 .release = cgroup_tasks_release,
2277 .private = FILE_TASKLIST,
2281 .name = "notify_on_release",
2282 .read_u64 = cgroup_read_notify_on_release,
2283 .write_u64 = cgroup_write_notify_on_release,
2284 .private = FILE_NOTIFY_ON_RELEASE,
2288 static struct cftype cft_release_agent = {
2289 .name = "release_agent",
2290 .read_seq_string = cgroup_release_agent_show,
2291 .write_string = cgroup_release_agent_write,
2292 .max_write_len = PATH_MAX,
2293 .private = FILE_RELEASE_AGENT,
2296 static int cgroup_populate_dir(struct cgroup *cgrp)
2298 int err;
2299 struct cgroup_subsys *ss;
2301 /* First clear out any existing files */
2302 cgroup_clear_directory(cgrp->dentry);
2304 err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));
2305 if (err < 0)
2306 return err;
2308 if (cgrp == cgrp->top_cgroup) {
2309 if ((err = cgroup_add_file(cgrp, NULL, &cft_release_agent)) < 0)
2310 return err;
2313 for_each_subsys(cgrp->root, ss) {
2314 if (ss->populate && (err = ss->populate(ss, cgrp)) < 0)
2315 return err;
2318 return 0;
2321 static void init_cgroup_css(struct cgroup_subsys_state *css,
2322 struct cgroup_subsys *ss,
2323 struct cgroup *cgrp)
2325 css->cgroup = cgrp;
2326 atomic_set(&css->refcnt, 0);
2327 css->flags = 0;
2328 if (cgrp == dummytop)
2329 set_bit(CSS_ROOT, &css->flags);
2330 BUG_ON(cgrp->subsys[ss->subsys_id]);
2331 cgrp->subsys[ss->subsys_id] = css;
2335 * cgroup_create - create a cgroup
2336 * @parent: cgroup that will be parent of the new cgroup
2337 * @dentry: dentry of the new cgroup
2338 * @mode: mode to set on new inode
2340 * Must be called with the mutex on the parent inode held
2342 static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
2343 int mode)
2345 struct cgroup *cgrp;
2346 struct cgroupfs_root *root = parent->root;
2347 int err = 0;
2348 struct cgroup_subsys *ss;
2349 struct super_block *sb = root->sb;
2351 cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
2352 if (!cgrp)
2353 return -ENOMEM;
2355 /* Grab a reference on the superblock so the hierarchy doesn't
2356 * get deleted on unmount if there are child cgroups. This
2357 * can be done outside cgroup_mutex, since the sb can't
2358 * disappear while someone has an open control file on the
2359 * fs */
2360 atomic_inc(&sb->s_active);
2362 mutex_lock(&cgroup_mutex);
2364 init_cgroup_housekeeping(cgrp);
2366 cgrp->parent = parent;
2367 cgrp->root = parent->root;
2368 cgrp->top_cgroup = parent->top_cgroup;
2370 if (notify_on_release(parent))
2371 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
2373 for_each_subsys(root, ss) {
2374 struct cgroup_subsys_state *css = ss->create(ss, cgrp);
2375 if (IS_ERR(css)) {
2376 err = PTR_ERR(css);
2377 goto err_destroy;
2379 init_cgroup_css(css, ss, cgrp);
2382 list_add(&cgrp->sibling, &cgrp->parent->children);
2383 root->number_of_cgroups++;
2385 err = cgroup_create_dir(cgrp, dentry, mode);
2386 if (err < 0)
2387 goto err_remove;
2389 /* The cgroup directory was pre-locked for us */
2390 BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
2392 err = cgroup_populate_dir(cgrp);
2393 /* If err < 0, we have a half-filled directory - oh well ;) */
2395 mutex_unlock(&cgroup_mutex);
2396 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
2398 return 0;
2400 err_remove:
2402 list_del(&cgrp->sibling);
2403 root->number_of_cgroups--;
2405 err_destroy:
2407 for_each_subsys(root, ss) {
2408 if (cgrp->subsys[ss->subsys_id])
2409 ss->destroy(ss, cgrp);
2412 mutex_unlock(&cgroup_mutex);
2414 /* Release the reference count that we took on the superblock */
2415 deactivate_super(sb);
2417 kfree(cgrp);
2418 return err;
2421 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode)
2423 struct cgroup *c_parent = dentry->d_parent->d_fsdata;
2425 /* the vfs holds inode->i_mutex already */
2426 return cgroup_create(c_parent, dentry, mode | S_IFDIR);
2429 static int cgroup_has_css_refs(struct cgroup *cgrp)
2431 /* Check the reference count on each subsystem. Since we
2432 * already established that there are no tasks in the
2433 * cgroup, if the css refcount is also 0, then there should
2434 * be no outstanding references, so the subsystem is safe to
2435 * destroy. We scan across all subsystems rather than using
2436 * the per-hierarchy linked list of mounted subsystems since
2437 * we can be called via check_for_release() with no
2438 * synchronization other than RCU, and the subsystem linked
2439 * list isn't RCU-safe */
2440 int i;
2441 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2442 struct cgroup_subsys *ss = subsys[i];
2443 struct cgroup_subsys_state *css;
2444 /* Skip subsystems not in this hierarchy */
2445 if (ss->root != cgrp->root)
2446 continue;
2447 css = cgrp->subsys[ss->subsys_id];
2448 /* When called from check_for_release() it's possible
2449 * that by this point the cgroup has been removed
2450 * and the css deleted. But a false-positive doesn't
2451 * matter, since it can only happen if the cgroup
2452 * has been deleted and hence no longer needs the
2453 * release agent to be called anyway. */
2454 if (css && atomic_read(&css->refcnt))
2455 return 1;
2457 return 0;
2460 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
2462 struct cgroup *cgrp = dentry->d_fsdata;
2463 struct dentry *d;
2464 struct cgroup *parent;
2465 struct super_block *sb;
2466 struct cgroupfs_root *root;
2468 /* the vfs holds both inode->i_mutex already */
2470 mutex_lock(&cgroup_mutex);
2471 if (atomic_read(&cgrp->count) != 0) {
2472 mutex_unlock(&cgroup_mutex);
2473 return -EBUSY;
2475 if (!list_empty(&cgrp->children)) {
2476 mutex_unlock(&cgroup_mutex);
2477 return -EBUSY;
2479 mutex_unlock(&cgroup_mutex);
2482 * Call pre_destroy handlers of subsys. Notify subsystems
2483 * that rmdir() request comes.
2485 cgroup_call_pre_destroy(cgrp);
2487 mutex_lock(&cgroup_mutex);
2488 parent = cgrp->parent;
2489 root = cgrp->root;
2490 sb = root->sb;
2492 if (atomic_read(&cgrp->count)
2493 || !list_empty(&cgrp->children)
2494 || cgroup_has_css_refs(cgrp)) {
2495 mutex_unlock(&cgroup_mutex);
2496 return -EBUSY;
2499 spin_lock(&release_list_lock);
2500 set_bit(CGRP_REMOVED, &cgrp->flags);
2501 if (!list_empty(&cgrp->release_list))
2502 list_del(&cgrp->release_list);
2503 spin_unlock(&release_list_lock);
2504 /* delete my sibling from parent->children */
2505 list_del(&cgrp->sibling);
2506 spin_lock(&cgrp->dentry->d_lock);
2507 d = dget(cgrp->dentry);
2508 spin_unlock(&d->d_lock);
2510 cgroup_d_remove_dir(d);
2511 dput(d);
2513 set_bit(CGRP_RELEASABLE, &parent->flags);
2514 check_for_release(parent);
2516 mutex_unlock(&cgroup_mutex);
2517 return 0;
2520 static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
2522 struct cgroup_subsys_state *css;
2524 printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
2526 /* Create the top cgroup state for this subsystem */
2527 ss->root = &rootnode;
2528 css = ss->create(ss, dummytop);
2529 /* We don't handle early failures gracefully */
2530 BUG_ON(IS_ERR(css));
2531 init_cgroup_css(css, ss, dummytop);
2533 /* Update the init_css_set to contain a subsys
2534 * pointer to this state - since the subsystem is
2535 * newly registered, all tasks and hence the
2536 * init_css_set is in the subsystem's top cgroup. */
2537 init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
2539 need_forkexit_callback |= ss->fork || ss->exit;
2540 need_mm_owner_callback |= !!ss->mm_owner_changed;
2542 /* At system boot, before all subsystems have been
2543 * registered, no tasks have been forked, so we don't
2544 * need to invoke fork callbacks here. */
2545 BUG_ON(!list_empty(&init_task.tasks));
2547 ss->active = 1;
2551 * cgroup_init_early - cgroup initialization at system boot
2553 * Initialize cgroups at system boot, and initialize any
2554 * subsystems that request early init.
2556 int __init cgroup_init_early(void)
2558 int i;
2559 atomic_set(&init_css_set.refcount, 1);
2560 INIT_LIST_HEAD(&init_css_set.cg_links);
2561 INIT_LIST_HEAD(&init_css_set.tasks);
2562 INIT_HLIST_NODE(&init_css_set.hlist);
2563 css_set_count = 1;
2564 init_cgroup_root(&rootnode);
2565 list_add(&rootnode.root_list, &roots);
2566 root_count = 1;
2567 init_task.cgroups = &init_css_set;
2569 init_css_set_link.cg = &init_css_set;
2570 list_add(&init_css_set_link.cgrp_link_list,
2571 &rootnode.top_cgroup.css_sets);
2572 list_add(&init_css_set_link.cg_link_list,
2573 &init_css_set.cg_links);
2575 for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
2576 INIT_HLIST_HEAD(&css_set_table[i]);
2578 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2579 struct cgroup_subsys *ss = subsys[i];
2581 BUG_ON(!ss->name);
2582 BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
2583 BUG_ON(!ss->create);
2584 BUG_ON(!ss->destroy);
2585 if (ss->subsys_id != i) {
2586 printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
2587 ss->name, ss->subsys_id);
2588 BUG();
2591 if (ss->early_init)
2592 cgroup_init_subsys(ss);
2594 return 0;
2598 * cgroup_init - cgroup initialization
2600 * Register cgroup filesystem and /proc file, and initialize
2601 * any subsystems that didn't request early init.
2603 int __init cgroup_init(void)
2605 int err;
2606 int i;
2607 struct hlist_head *hhead;
2609 err = bdi_init(&cgroup_backing_dev_info);
2610 if (err)
2611 return err;
2613 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2614 struct cgroup_subsys *ss = subsys[i];
2615 if (!ss->early_init)
2616 cgroup_init_subsys(ss);
2619 /* Add init_css_set to the hash table */
2620 hhead = css_set_hash(init_css_set.subsys);
2621 hlist_add_head(&init_css_set.hlist, hhead);
2623 err = register_filesystem(&cgroup_fs_type);
2624 if (err < 0)
2625 goto out;
2627 proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
2629 out:
2630 if (err)
2631 bdi_destroy(&cgroup_backing_dev_info);
2633 return err;
2637 * proc_cgroup_show()
2638 * - Print task's cgroup paths into seq_file, one line for each hierarchy
2639 * - Used for /proc/<pid>/cgroup.
2640 * - No need to task_lock(tsk) on this tsk->cgroup reference, as it
2641 * doesn't really matter if tsk->cgroup changes after we read it,
2642 * and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
2643 * anyway. No need to check that tsk->cgroup != NULL, thanks to
2644 * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
2645 * cgroup to top_cgroup.
2648 /* TODO: Use a proper seq_file iterator */
2649 static int proc_cgroup_show(struct seq_file *m, void *v)
2651 struct pid *pid;
2652 struct task_struct *tsk;
2653 char *buf;
2654 int retval;
2655 struct cgroupfs_root *root;
2657 retval = -ENOMEM;
2658 buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
2659 if (!buf)
2660 goto out;
2662 retval = -ESRCH;
2663 pid = m->private;
2664 tsk = get_pid_task(pid, PIDTYPE_PID);
2665 if (!tsk)
2666 goto out_free;
2668 retval = 0;
2670 mutex_lock(&cgroup_mutex);
2672 for_each_root(root) {
2673 struct cgroup_subsys *ss;
2674 struct cgroup *cgrp;
2675 int subsys_id;
2676 int count = 0;
2678 /* Skip this hierarchy if it has no active subsystems */
2679 if (!root->actual_subsys_bits)
2680 continue;
2681 seq_printf(m, "%lu:", root->subsys_bits);
2682 for_each_subsys(root, ss)
2683 seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
2684 seq_putc(m, ':');
2685 get_first_subsys(&root->top_cgroup, NULL, &subsys_id);
2686 cgrp = task_cgroup(tsk, subsys_id);
2687 retval = cgroup_path(cgrp, buf, PAGE_SIZE);
2688 if (retval < 0)
2689 goto out_unlock;
2690 seq_puts(m, buf);
2691 seq_putc(m, '\n');
2694 out_unlock:
2695 mutex_unlock(&cgroup_mutex);
2696 put_task_struct(tsk);
2697 out_free:
2698 kfree(buf);
2699 out:
2700 return retval;
2703 static int cgroup_open(struct inode *inode, struct file *file)
2705 struct pid *pid = PROC_I(inode)->pid;
2706 return single_open(file, proc_cgroup_show, pid);
2709 struct file_operations proc_cgroup_operations = {
2710 .open = cgroup_open,
2711 .read = seq_read,
2712 .llseek = seq_lseek,
2713 .release = single_release,
2716 /* Display information about each subsystem and each hierarchy */
2717 static int proc_cgroupstats_show(struct seq_file *m, void *v)
2719 int i;
2721 seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
2722 mutex_lock(&cgroup_mutex);
2723 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2724 struct cgroup_subsys *ss = subsys[i];
2725 seq_printf(m, "%s\t%lu\t%d\t%d\n",
2726 ss->name, ss->root->subsys_bits,
2727 ss->root->number_of_cgroups, !ss->disabled);
2729 mutex_unlock(&cgroup_mutex);
2730 return 0;
2733 static int cgroupstats_open(struct inode *inode, struct file *file)
2735 return single_open(file, proc_cgroupstats_show, NULL);
2738 static struct file_operations proc_cgroupstats_operations = {
2739 .open = cgroupstats_open,
2740 .read = seq_read,
2741 .llseek = seq_lseek,
2742 .release = single_release,
2746 * cgroup_fork - attach newly forked task to its parents cgroup.
2747 * @child: pointer to task_struct of forking parent process.
2749 * Description: A task inherits its parent's cgroup at fork().
2751 * A pointer to the shared css_set was automatically copied in
2752 * fork.c by dup_task_struct(). However, we ignore that copy, since
2753 * it was not made under the protection of RCU or cgroup_mutex, so
2754 * might no longer be a valid cgroup pointer. cgroup_attach_task() might
2755 * have already changed current->cgroups, allowing the previously
2756 * referenced cgroup group to be removed and freed.
2758 * At the point that cgroup_fork() is called, 'current' is the parent
2759 * task, and the passed argument 'child' points to the child task.
2761 void cgroup_fork(struct task_struct *child)
2763 task_lock(current);
2764 child->cgroups = current->cgroups;
2765 get_css_set(child->cgroups);
2766 task_unlock(current);
2767 INIT_LIST_HEAD(&child->cg_list);
2771 * cgroup_fork_callbacks - run fork callbacks
2772 * @child: the new task
2774 * Called on a new task very soon before adding it to the
2775 * tasklist. No need to take any locks since no-one can
2776 * be operating on this task.
2778 void cgroup_fork_callbacks(struct task_struct *child)
2780 if (need_forkexit_callback) {
2781 int i;
2782 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2783 struct cgroup_subsys *ss = subsys[i];
2784 if (ss->fork)
2785 ss->fork(ss, child);
2790 #ifdef CONFIG_MM_OWNER
2792 * cgroup_mm_owner_callbacks - run callbacks when the mm->owner changes
2793 * @p: the new owner
2795 * Called on every change to mm->owner. mm_init_owner() does not
2796 * invoke this routine, since it assigns the mm->owner the first time
2797 * and does not change it.
2799 * The callbacks are invoked with mmap_sem held in read mode.
2801 void cgroup_mm_owner_callbacks(struct task_struct *old, struct task_struct *new)
2803 struct cgroup *oldcgrp, *newcgrp = NULL;
2805 if (need_mm_owner_callback) {
2806 int i;
2807 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2808 struct cgroup_subsys *ss = subsys[i];
2809 oldcgrp = task_cgroup(old, ss->subsys_id);
2810 if (new)
2811 newcgrp = task_cgroup(new, ss->subsys_id);
2812 if (oldcgrp == newcgrp)
2813 continue;
2814 if (ss->mm_owner_changed)
2815 ss->mm_owner_changed(ss, oldcgrp, newcgrp, new);
2819 #endif /* CONFIG_MM_OWNER */
2822 * cgroup_post_fork - called on a new task after adding it to the task list
2823 * @child: the task in question
2825 * Adds the task to the list running through its css_set if necessary.
2826 * Has to be after the task is visible on the task list in case we race
2827 * with the first call to cgroup_iter_start() - to guarantee that the
2828 * new task ends up on its list.
2830 void cgroup_post_fork(struct task_struct *child)
2832 if (use_task_css_set_links) {
2833 write_lock(&css_set_lock);
2834 if (list_empty(&child->cg_list))
2835 list_add(&child->cg_list, &child->cgroups->tasks);
2836 write_unlock(&css_set_lock);
2840 * cgroup_exit - detach cgroup from exiting task
2841 * @tsk: pointer to task_struct of exiting process
2842 * @run_callback: run exit callbacks?
2844 * Description: Detach cgroup from @tsk and release it.
2846 * Note that cgroups marked notify_on_release force every task in
2847 * them to take the global cgroup_mutex mutex when exiting.
2848 * This could impact scaling on very large systems. Be reluctant to
2849 * use notify_on_release cgroups where very high task exit scaling
2850 * is required on large systems.
2852 * the_top_cgroup_hack:
2854 * Set the exiting tasks cgroup to the root cgroup (top_cgroup).
2856 * We call cgroup_exit() while the task is still competent to
2857 * handle notify_on_release(), then leave the task attached to the
2858 * root cgroup in each hierarchy for the remainder of its exit.
2860 * To do this properly, we would increment the reference count on
2861 * top_cgroup, and near the very end of the kernel/exit.c do_exit()
2862 * code we would add a second cgroup function call, to drop that
2863 * reference. This would just create an unnecessary hot spot on
2864 * the top_cgroup reference count, to no avail.
2866 * Normally, holding a reference to a cgroup without bumping its
2867 * count is unsafe. The cgroup could go away, or someone could
2868 * attach us to a different cgroup, decrementing the count on
2869 * the first cgroup that we never incremented. But in this case,
2870 * top_cgroup isn't going away, and either task has PF_EXITING set,
2871 * which wards off any cgroup_attach_task() attempts, or task is a failed
2872 * fork, never visible to cgroup_attach_task.
2874 void cgroup_exit(struct task_struct *tsk, int run_callbacks)
2876 int i;
2877 struct css_set *cg;
2879 if (run_callbacks && need_forkexit_callback) {
2880 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2881 struct cgroup_subsys *ss = subsys[i];
2882 if (ss->exit)
2883 ss->exit(ss, tsk);
2888 * Unlink from the css_set task list if necessary.
2889 * Optimistically check cg_list before taking
2890 * css_set_lock
2892 if (!list_empty(&tsk->cg_list)) {
2893 write_lock(&css_set_lock);
2894 if (!list_empty(&tsk->cg_list))
2895 list_del(&tsk->cg_list);
2896 write_unlock(&css_set_lock);
2899 /* Reassign the task to the init_css_set. */
2900 task_lock(tsk);
2901 cg = tsk->cgroups;
2902 tsk->cgroups = &init_css_set;
2903 task_unlock(tsk);
2904 if (cg)
2905 put_css_set_taskexit(cg);
2909 * cgroup_clone - clone the cgroup the given subsystem is attached to
2910 * @tsk: the task to be moved
2911 * @subsys: the given subsystem
2912 * @nodename: the name for the new cgroup
2914 * Duplicate the current cgroup in the hierarchy that the given
2915 * subsystem is attached to, and move this task into the new
2916 * child.
2918 int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
2919 char *nodename)
2921 struct dentry *dentry;
2922 int ret = 0;
2923 struct cgroup *parent, *child;
2924 struct inode *inode;
2925 struct css_set *cg;
2926 struct cgroupfs_root *root;
2927 struct cgroup_subsys *ss;
2929 /* We shouldn't be called by an unregistered subsystem */
2930 BUG_ON(!subsys->active);
2932 /* First figure out what hierarchy and cgroup we're dealing
2933 * with, and pin them so we can drop cgroup_mutex */
2934 mutex_lock(&cgroup_mutex);
2935 again:
2936 root = subsys->root;
2937 if (root == &rootnode) {
2938 mutex_unlock(&cgroup_mutex);
2939 return 0;
2941 cg = tsk->cgroups;
2942 parent = task_cgroup(tsk, subsys->subsys_id);
2944 /* Pin the hierarchy */
2945 if (!atomic_inc_not_zero(&parent->root->sb->s_active)) {
2946 /* We race with the final deactivate_super() */
2947 mutex_unlock(&cgroup_mutex);
2948 return 0;
2951 /* Keep the cgroup alive */
2952 get_css_set(cg);
2953 mutex_unlock(&cgroup_mutex);
2955 /* Now do the VFS work to create a cgroup */
2956 inode = parent->dentry->d_inode;
2958 /* Hold the parent directory mutex across this operation to
2959 * stop anyone else deleting the new cgroup */
2960 mutex_lock(&inode->i_mutex);
2961 dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));
2962 if (IS_ERR(dentry)) {
2963 printk(KERN_INFO
2964 "cgroup: Couldn't allocate dentry for %s: %ld\n", nodename,
2965 PTR_ERR(dentry));
2966 ret = PTR_ERR(dentry);
2967 goto out_release;
2970 /* Create the cgroup directory, which also creates the cgroup */
2971 ret = vfs_mkdir(inode, dentry, S_IFDIR | 0755);
2972 child = __d_cgrp(dentry);
2973 dput(dentry);
2974 if (ret) {
2975 printk(KERN_INFO
2976 "Failed to create cgroup %s: %d\n", nodename,
2977 ret);
2978 goto out_release;
2981 if (!child) {
2982 printk(KERN_INFO
2983 "Couldn't find new cgroup %s\n", nodename);
2984 ret = -ENOMEM;
2985 goto out_release;
2988 /* The cgroup now exists. Retake cgroup_mutex and check
2989 * that we're still in the same state that we thought we
2990 * were. */
2991 mutex_lock(&cgroup_mutex);
2992 if ((root != subsys->root) ||
2993 (parent != task_cgroup(tsk, subsys->subsys_id))) {
2994 /* Aargh, we raced ... */
2995 mutex_unlock(&inode->i_mutex);
2996 put_css_set(cg);
2998 deactivate_super(parent->root->sb);
2999 /* The cgroup is still accessible in the VFS, but
3000 * we're not going to try to rmdir() it at this
3001 * point. */
3002 printk(KERN_INFO
3003 "Race in cgroup_clone() - leaking cgroup %s\n",
3004 nodename);
3005 goto again;
3008 /* do any required auto-setup */
3009 for_each_subsys(root, ss) {
3010 if (ss->post_clone)
3011 ss->post_clone(ss, child);
3014 /* All seems fine. Finish by moving the task into the new cgroup */
3015 ret = cgroup_attach_task(child, tsk);
3016 mutex_unlock(&cgroup_mutex);
3018 out_release:
3019 mutex_unlock(&inode->i_mutex);
3021 mutex_lock(&cgroup_mutex);
3022 put_css_set(cg);
3023 mutex_unlock(&cgroup_mutex);
3024 deactivate_super(parent->root->sb);
3025 return ret;
3029 * cgroup_is_descendant - see if @cgrp is a descendant of current task's cgrp
3030 * @cgrp: the cgroup in question
3032 * See if @cgrp is a descendant of the current task's cgroup in
3033 * the appropriate hierarchy.
3035 * If we are sending in dummytop, then presumably we are creating
3036 * the top cgroup in the subsystem.
3038 * Called only by the ns (nsproxy) cgroup.
3040 int cgroup_is_descendant(const struct cgroup *cgrp)
3042 int ret;
3043 struct cgroup *target;
3044 int subsys_id;
3046 if (cgrp == dummytop)
3047 return 1;
3049 get_first_subsys(cgrp, NULL, &subsys_id);
3050 target = task_cgroup(current, subsys_id);
3051 while (cgrp != target && cgrp!= cgrp->top_cgroup)
3052 cgrp = cgrp->parent;
3053 ret = (cgrp == target);
3054 return ret;
3057 static void check_for_release(struct cgroup *cgrp)
3059 /* All of these checks rely on RCU to keep the cgroup
3060 * structure alive */
3061 if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
3062 && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
3063 /* Control Group is currently removeable. If it's not
3064 * already queued for a userspace notification, queue
3065 * it now */
3066 int need_schedule_work = 0;
3067 spin_lock(&release_list_lock);
3068 if (!cgroup_is_removed(cgrp) &&
3069 list_empty(&cgrp->release_list)) {
3070 list_add(&cgrp->release_list, &release_list);
3071 need_schedule_work = 1;
3073 spin_unlock(&release_list_lock);
3074 if (need_schedule_work)
3075 schedule_work(&release_agent_work);
3079 void __css_put(struct cgroup_subsys_state *css)
3081 struct cgroup *cgrp = css->cgroup;
3082 rcu_read_lock();
3083 if (atomic_dec_and_test(&css->refcnt) && notify_on_release(cgrp)) {
3084 set_bit(CGRP_RELEASABLE, &cgrp->flags);
3085 check_for_release(cgrp);
3087 rcu_read_unlock();
3091 * Notify userspace when a cgroup is released, by running the
3092 * configured release agent with the name of the cgroup (path
3093 * relative to the root of cgroup file system) as the argument.
3095 * Most likely, this user command will try to rmdir this cgroup.
3097 * This races with the possibility that some other task will be
3098 * attached to this cgroup before it is removed, or that some other
3099 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
3100 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
3101 * unused, and this cgroup will be reprieved from its death sentence,
3102 * to continue to serve a useful existence. Next time it's released,
3103 * we will get notified again, if it still has 'notify_on_release' set.
3105 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
3106 * means only wait until the task is successfully execve()'d. The
3107 * separate release agent task is forked by call_usermodehelper(),
3108 * then control in this thread returns here, without waiting for the
3109 * release agent task. We don't bother to wait because the caller of
3110 * this routine has no use for the exit status of the release agent
3111 * task, so no sense holding our caller up for that.
3113 static void cgroup_release_agent(struct work_struct *work)
3115 BUG_ON(work != &release_agent_work);
3116 mutex_lock(&cgroup_mutex);
3117 spin_lock(&release_list_lock);
3118 while (!list_empty(&release_list)) {
3119 char *argv[3], *envp[3];
3120 int i;
3121 char *pathbuf = NULL, *agentbuf = NULL;
3122 struct cgroup *cgrp = list_entry(release_list.next,
3123 struct cgroup,
3124 release_list);
3125 list_del_init(&cgrp->release_list);
3126 spin_unlock(&release_list_lock);
3127 pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
3128 if (!pathbuf)
3129 goto continue_free;
3130 if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
3131 goto continue_free;
3132 agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
3133 if (!agentbuf)
3134 goto continue_free;
3136 i = 0;
3137 argv[i++] = agentbuf;
3138 argv[i++] = pathbuf;
3139 argv[i] = NULL;
3141 i = 0;
3142 /* minimal command environment */
3143 envp[i++] = "HOME=/";
3144 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
3145 envp[i] = NULL;
3147 /* Drop the lock while we invoke the usermode helper,
3148 * since the exec could involve hitting disk and hence
3149 * be a slow process */
3150 mutex_unlock(&cgroup_mutex);
3151 call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
3152 mutex_lock(&cgroup_mutex);
3153 continue_free:
3154 kfree(pathbuf);
3155 kfree(agentbuf);
3156 spin_lock(&release_list_lock);
3158 spin_unlock(&release_list_lock);
3159 mutex_unlock(&cgroup_mutex);
3162 static int __init cgroup_disable(char *str)
3164 int i;
3165 char *token;
3167 while ((token = strsep(&str, ",")) != NULL) {
3168 if (!*token)
3169 continue;
3171 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3172 struct cgroup_subsys *ss = subsys[i];
3174 if (!strcmp(token, ss->name)) {
3175 ss->disabled = 1;
3176 printk(KERN_INFO "Disabling %s control group"
3177 " subsystem\n", ss->name);
3178 break;
3182 return 1;
3184 __setup("cgroup_disable=", cgroup_disable);