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>
28 #include <linux/kernel.h>
29 #include <linux/list.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>
49 #include <asm/atomic.h>
51 static DEFINE_MUTEX(cgroup_mutex);
53 /* Generate an array of cgroup subsystem pointers */
54 #define SUBSYS(_x) &_x ## _subsys,
56 static struct cgroup_subsys *subsys[] = {
57 #include <linux/cgroup_subsys.h>
61 * A cgroupfs_root represents the root of a cgroup hierarchy,
62 * and may be associated with a superblock to form an active
65 struct cgroupfs_root {
66 struct super_block *sb;
69 * The bitmask of subsystems intended to be attached to this
72 unsigned long subsys_bits;
74 /* The bitmask of subsystems currently attached to this hierarchy */
75 unsigned long actual_subsys_bits;
77 /* A list running through the attached subsystems */
78 struct list_head subsys_list;
80 /* The root cgroup for this hierarchy */
81 struct cgroup top_cgroup;
83 /* Tracks how many cgroups are currently defined in hierarchy.*/
84 int number_of_cgroups;
86 /* A list running through the mounted hierarchies */
87 struct list_head root_list;
89 /* Hierarchy-specific flags */
92 /* The path to use for release notifications. No locking
93 * between setting and use - so if userspace updates this
94 * while child cgroups exist, you could miss a
95 * notification. We ensure that it's always a valid
96 * NUL-terminated string */
97 char release_agent_path[PATH_MAX];
102 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
103 * subsystems that are otherwise unattached - it never has more than a
104 * single cgroup, and all tasks are part of that cgroup.
106 static struct cgroupfs_root rootnode;
108 /* The list of hierarchy roots */
110 static LIST_HEAD(roots);
111 static int root_count;
113 /* dummytop is a shorthand for the dummy hierarchy's top cgroup */
114 #define dummytop (&rootnode.top_cgroup)
116 /* This flag indicates whether tasks in the fork and exit paths should
117 * check for fork/exit handlers to call. This avoids us having to do
118 * extra work in the fork/exit path if none of the subsystems need to
121 static int need_forkexit_callback;
123 /* convenient tests for these bits */
124 inline int cgroup_is_removed(const struct cgroup *cgrp)
126 return test_bit(CGRP_REMOVED, &cgrp->flags);
129 /* bits in struct cgroupfs_root flags field */
131 ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
134 static int cgroup_is_releasable(const struct cgroup *cgrp)
137 (1 << CGRP_RELEASABLE) |
138 (1 << CGRP_NOTIFY_ON_RELEASE);
139 return (cgrp->flags & bits) == bits;
142 static int notify_on_release(const struct cgroup *cgrp)
144 return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
148 * for_each_subsys() allows you to iterate on each subsystem attached to
149 * an active hierarchy
151 #define for_each_subsys(_root, _ss) \
152 list_for_each_entry(_ss, &_root->subsys_list, sibling)
154 /* for_each_root() allows you to iterate across the active hierarchies */
155 #define for_each_root(_root) \
156 list_for_each_entry(_root, &roots, root_list)
158 /* the list of cgroups eligible for automatic release. Protected by
159 * release_list_lock */
160 static LIST_HEAD(release_list);
161 static DEFINE_SPINLOCK(release_list_lock);
162 static void cgroup_release_agent(struct work_struct *work);
163 static DECLARE_WORK(release_agent_work, cgroup_release_agent);
164 static void check_for_release(struct cgroup *cgrp);
166 /* Link structure for associating css_set objects with cgroups */
167 struct cg_cgroup_link {
169 * List running through cg_cgroup_links associated with a
170 * cgroup, anchored on cgroup->css_sets
172 struct list_head cgrp_link_list;
174 * List running through cg_cgroup_links pointing at a
175 * single css_set object, anchored on css_set->cg_links
177 struct list_head cg_link_list;
181 /* The default css_set - used by init and its children prior to any
182 * hierarchies being mounted. It contains a pointer to the root state
183 * for each subsystem. Also used to anchor the list of css_sets. Not
184 * reference-counted, to improve performance when child cgroups
185 * haven't been created.
188 static struct css_set init_css_set;
189 static struct cg_cgroup_link init_css_set_link;
191 /* css_set_lock protects the list of css_set objects, and the
192 * chain of tasks off each css_set. Nests outside task->alloc_lock
193 * due to cgroup_iter_start() */
194 static DEFINE_RWLOCK(css_set_lock);
195 static int css_set_count;
197 /* hash table for cgroup groups. This improves the performance to
198 * find an existing css_set */
199 #define CSS_SET_HASH_BITS 7
200 #define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS)
201 static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
203 static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
207 unsigned long tmp = 0UL;
209 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
210 tmp += (unsigned long)css[i];
211 tmp = (tmp >> 16) ^ tmp;
213 index = hash_long(tmp, CSS_SET_HASH_BITS);
215 return &css_set_table[index];
218 /* We don't maintain the lists running through each css_set to its
219 * task until after the first call to cgroup_iter_start(). This
220 * reduces the fork()/exit() overhead for people who have cgroups
221 * compiled into their kernel but not actually in use */
222 static int use_task_css_set_links;
224 /* When we create or destroy a css_set, the operation simply
225 * takes/releases a reference count on all the cgroups referenced
226 * by subsystems in this css_set. This can end up multiple-counting
227 * some cgroups, but that's OK - the ref-count is just a
228 * busy/not-busy indicator; ensuring that we only count each cgroup
229 * once would require taking a global lock to ensure that no
230 * subsystems moved between hierarchies while we were doing so.
232 * Possible TODO: decide at boot time based on the number of
233 * registered subsystems and the number of CPUs or NUMA nodes whether
234 * it's better for performance to ref-count every subsystem, or to
235 * take a global lock and only add one ref count to each hierarchy.
239 * unlink a css_set from the list and free it
241 static void unlink_css_set(struct css_set *cg)
243 write_lock(&css_set_lock);
244 hlist_del(&cg->hlist);
247 while (!list_empty(&cg->cg_links)) {
248 struct cg_cgroup_link *link;
249 link = list_entry(cg->cg_links.next,
250 struct cg_cgroup_link, cg_link_list);
251 list_del(&link->cg_link_list);
252 list_del(&link->cgrp_link_list);
255 write_unlock(&css_set_lock);
258 static void __release_css_set(struct kref *k, int taskexit)
261 struct css_set *cg = container_of(k, struct css_set, ref);
266 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
267 struct cgroup *cgrp = cg->subsys[i]->cgroup;
268 if (atomic_dec_and_test(&cgrp->count) &&
269 notify_on_release(cgrp)) {
271 set_bit(CGRP_RELEASABLE, &cgrp->flags);
272 check_for_release(cgrp);
279 static void release_css_set(struct kref *k)
281 __release_css_set(k, 0);
284 static void release_css_set_taskexit(struct kref *k)
286 __release_css_set(k, 1);
290 * refcounted get/put for css_set objects
292 static inline void get_css_set(struct css_set *cg)
297 static inline void put_css_set(struct css_set *cg)
299 kref_put(&cg->ref, release_css_set);
302 static inline void put_css_set_taskexit(struct css_set *cg)
304 kref_put(&cg->ref, release_css_set_taskexit);
308 * find_existing_css_set() is a helper for
309 * find_css_set(), and checks to see whether an existing
310 * css_set is suitable.
312 * oldcg: the cgroup group that we're using before the cgroup
315 * cgrp: the cgroup that we're moving into
317 * template: location in which to build the desired set of subsystem
318 * state objects for the new cgroup group
320 static struct css_set *find_existing_css_set(
321 struct css_set *oldcg,
323 struct cgroup_subsys_state *template[])
326 struct cgroupfs_root *root = cgrp->root;
327 struct hlist_head *hhead;
328 struct hlist_node *node;
331 /* Built the set of subsystem state objects that we want to
332 * see in the new css_set */
333 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
334 if (root->subsys_bits & (1UL << i)) {
335 /* Subsystem is in this hierarchy. So we want
336 * the subsystem state from the new
338 template[i] = cgrp->subsys[i];
340 /* Subsystem is not in this hierarchy, so we
341 * don't want to change the subsystem state */
342 template[i] = oldcg->subsys[i];
346 hhead = css_set_hash(template);
347 hlist_for_each_entry(cg, node, hhead, hlist) {
348 if (!memcmp(template, cg->subsys, sizeof(cg->subsys))) {
349 /* All subsystems matched */
354 /* No existing cgroup group matched */
359 * allocate_cg_links() allocates "count" cg_cgroup_link structures
360 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
361 * success or a negative error
363 static int allocate_cg_links(int count, struct list_head *tmp)
365 struct cg_cgroup_link *link;
368 for (i = 0; i < count; i++) {
369 link = kmalloc(sizeof(*link), GFP_KERNEL);
371 while (!list_empty(tmp)) {
372 link = list_entry(tmp->next,
373 struct cg_cgroup_link,
375 list_del(&link->cgrp_link_list);
380 list_add(&link->cgrp_link_list, tmp);
385 static void free_cg_links(struct list_head *tmp)
387 while (!list_empty(tmp)) {
388 struct cg_cgroup_link *link;
389 link = list_entry(tmp->next,
390 struct cg_cgroup_link,
392 list_del(&link->cgrp_link_list);
398 * find_css_set() takes an existing cgroup group and a
399 * cgroup object, and returns a css_set object that's
400 * equivalent to the old group, but with the given cgroup
401 * substituted into the appropriate hierarchy. Must be called with
404 static struct css_set *find_css_set(
405 struct css_set *oldcg, struct cgroup *cgrp)
408 struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
411 struct list_head tmp_cg_links;
412 struct cg_cgroup_link *link;
414 struct hlist_head *hhead;
416 /* First see if we already have a cgroup group that matches
418 write_lock(&css_set_lock);
419 res = find_existing_css_set(oldcg, cgrp, template);
422 write_unlock(&css_set_lock);
427 res = kmalloc(sizeof(*res), GFP_KERNEL);
431 /* Allocate all the cg_cgroup_link objects that we'll need */
432 if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
437 kref_init(&res->ref);
438 INIT_LIST_HEAD(&res->cg_links);
439 INIT_LIST_HEAD(&res->tasks);
440 INIT_HLIST_NODE(&res->hlist);
442 /* Copy the set of subsystem state objects generated in
443 * find_existing_css_set() */
444 memcpy(res->subsys, template, sizeof(res->subsys));
446 write_lock(&css_set_lock);
447 /* Add reference counts and links from the new css_set. */
448 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
449 struct cgroup *cgrp = res->subsys[i]->cgroup;
450 struct cgroup_subsys *ss = subsys[i];
451 atomic_inc(&cgrp->count);
453 * We want to add a link once per cgroup, so we
454 * only do it for the first subsystem in each
457 if (ss->root->subsys_list.next == &ss->sibling) {
458 BUG_ON(list_empty(&tmp_cg_links));
459 link = list_entry(tmp_cg_links.next,
460 struct cg_cgroup_link,
462 list_del(&link->cgrp_link_list);
463 list_add(&link->cgrp_link_list, &cgrp->css_sets);
465 list_add(&link->cg_link_list, &res->cg_links);
468 if (list_empty(&rootnode.subsys_list)) {
469 link = list_entry(tmp_cg_links.next,
470 struct cg_cgroup_link,
472 list_del(&link->cgrp_link_list);
473 list_add(&link->cgrp_link_list, &dummytop->css_sets);
475 list_add(&link->cg_link_list, &res->cg_links);
478 BUG_ON(!list_empty(&tmp_cg_links));
480 /* Link this cgroup group into the list */
481 list_add(&res->list, &init_css_set.list);
484 /* Add this cgroup group to the hash table */
485 hhead = css_set_hash(res->subsys);
486 hlist_add_head(&res->hlist, hhead);
488 write_unlock(&css_set_lock);
494 * There is one global cgroup mutex. We also require taking
495 * task_lock() when dereferencing a task's cgroup subsys pointers.
496 * See "The task_lock() exception", at the end of this comment.
498 * A task must hold cgroup_mutex to modify cgroups.
500 * Any task can increment and decrement the count field without lock.
501 * So in general, code holding cgroup_mutex can't rely on the count
502 * field not changing. However, if the count goes to zero, then only
503 * cgroup_attach_task() can increment it again. Because a count of zero
504 * means that no tasks are currently attached, therefore there is no
505 * way a task attached to that cgroup can fork (the other way to
506 * increment the count). So code holding cgroup_mutex can safely
507 * assume that if the count is zero, it will stay zero. Similarly, if
508 * a task holds cgroup_mutex on a cgroup with zero count, it
509 * knows that the cgroup won't be removed, as cgroup_rmdir()
512 * The cgroup_common_file_write handler for operations that modify
513 * the cgroup hierarchy holds cgroup_mutex across the entire operation,
514 * single threading all such cgroup modifications across the system.
516 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
517 * (usually) take cgroup_mutex. These are the two most performance
518 * critical pieces of code here. The exception occurs on cgroup_exit(),
519 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
520 * is taken, and if the cgroup count is zero, a usermode call made
521 * to the release agent with the name of the cgroup (path relative to
522 * the root of cgroup file system) as the argument.
524 * A cgroup can only be deleted if both its 'count' of using tasks
525 * is zero, and its list of 'children' cgroups is empty. Since all
526 * tasks in the system use _some_ cgroup, and since there is always at
527 * least one task in the system (init, pid == 1), therefore, top_cgroup
528 * always has either children cgroups and/or using tasks. So we don't
529 * need a special hack to ensure that top_cgroup cannot be deleted.
531 * The task_lock() exception
533 * The need for this exception arises from the action of
534 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
535 * another. It does so using cgroup_mutex, however there are
536 * several performance critical places that need to reference
537 * task->cgroup without the expense of grabbing a system global
538 * mutex. Therefore except as noted below, when dereferencing or, as
539 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
540 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
541 * the task_struct routinely used for such matters.
543 * P.S. One more locking exception. RCU is used to guard the
544 * update of a tasks cgroup pointer by cgroup_attach_task()
548 * cgroup_lock - lock out any changes to cgroup structures
551 void cgroup_lock(void)
553 mutex_lock(&cgroup_mutex);
557 * cgroup_unlock - release lock on cgroup changes
559 * Undo the lock taken in a previous cgroup_lock() call.
561 void cgroup_unlock(void)
563 mutex_unlock(&cgroup_mutex);
567 * A couple of forward declarations required, due to cyclic reference loop:
568 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
569 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
573 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode);
574 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
575 static int cgroup_populate_dir(struct cgroup *cgrp);
576 static struct inode_operations cgroup_dir_inode_operations;
577 static struct file_operations proc_cgroupstats_operations;
579 static struct backing_dev_info cgroup_backing_dev_info = {
580 .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
583 static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
585 struct inode *inode = new_inode(sb);
588 inode->i_mode = mode;
589 inode->i_uid = current->fsuid;
590 inode->i_gid = current->fsgid;
592 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
593 inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
599 * Call subsys's pre_destroy handler.
600 * This is called before css refcnt check.
602 static void cgroup_call_pre_destroy(struct cgroup *cgrp)
604 struct cgroup_subsys *ss;
605 for_each_subsys(cgrp->root, ss)
606 if (ss->pre_destroy && cgrp->subsys[ss->subsys_id])
607 ss->pre_destroy(ss, cgrp);
611 static void cgroup_diput(struct dentry *dentry, struct inode *inode)
613 /* is dentry a directory ? if so, kfree() associated cgroup */
614 if (S_ISDIR(inode->i_mode)) {
615 struct cgroup *cgrp = dentry->d_fsdata;
616 struct cgroup_subsys *ss;
617 BUG_ON(!(cgroup_is_removed(cgrp)));
618 /* It's possible for external users to be holding css
619 * reference counts on a cgroup; css_put() needs to
620 * be able to access the cgroup after decrementing
621 * the reference count in order to know if it needs to
622 * queue the cgroup to be handled by the release
626 mutex_lock(&cgroup_mutex);
628 * Release the subsystem state objects.
630 for_each_subsys(cgrp->root, ss) {
631 if (cgrp->subsys[ss->subsys_id])
632 ss->destroy(ss, cgrp);
635 cgrp->root->number_of_cgroups--;
636 mutex_unlock(&cgroup_mutex);
638 /* Drop the active superblock reference that we took when we
639 * created the cgroup */
640 deactivate_super(cgrp->root->sb);
647 static void remove_dir(struct dentry *d)
649 struct dentry *parent = dget(d->d_parent);
652 simple_rmdir(parent->d_inode, d);
656 static void cgroup_clear_directory(struct dentry *dentry)
658 struct list_head *node;
660 BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
661 spin_lock(&dcache_lock);
662 node = dentry->d_subdirs.next;
663 while (node != &dentry->d_subdirs) {
664 struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
667 /* This should never be called on a cgroup
668 * directory with child cgroups */
669 BUG_ON(d->d_inode->i_mode & S_IFDIR);
671 spin_unlock(&dcache_lock);
673 simple_unlink(dentry->d_inode, d);
675 spin_lock(&dcache_lock);
677 node = dentry->d_subdirs.next;
679 spin_unlock(&dcache_lock);
683 * NOTE : the dentry must have been dget()'ed
685 static void cgroup_d_remove_dir(struct dentry *dentry)
687 cgroup_clear_directory(dentry);
689 spin_lock(&dcache_lock);
690 list_del_init(&dentry->d_u.d_child);
691 spin_unlock(&dcache_lock);
695 static int rebind_subsystems(struct cgroupfs_root *root,
696 unsigned long final_bits)
698 unsigned long added_bits, removed_bits;
699 struct cgroup *cgrp = &root->top_cgroup;
702 removed_bits = root->actual_subsys_bits & ~final_bits;
703 added_bits = final_bits & ~root->actual_subsys_bits;
704 /* Check that any added subsystems are currently free */
705 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
706 unsigned long bit = 1UL << i;
707 struct cgroup_subsys *ss = subsys[i];
708 if (!(bit & added_bits))
710 if (ss->root != &rootnode) {
711 /* Subsystem isn't free */
716 /* Currently we don't handle adding/removing subsystems when
717 * any child cgroups exist. This is theoretically supportable
718 * but involves complex error handling, so it's being left until
720 if (!list_empty(&cgrp->children))
723 /* Process each subsystem */
724 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
725 struct cgroup_subsys *ss = subsys[i];
726 unsigned long bit = 1UL << i;
727 if (bit & added_bits) {
728 /* We're binding this subsystem to this hierarchy */
729 BUG_ON(cgrp->subsys[i]);
730 BUG_ON(!dummytop->subsys[i]);
731 BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
732 cgrp->subsys[i] = dummytop->subsys[i];
733 cgrp->subsys[i]->cgroup = cgrp;
734 list_add(&ss->sibling, &root->subsys_list);
735 rcu_assign_pointer(ss->root, root);
739 } else if (bit & removed_bits) {
740 /* We're removing this subsystem */
741 BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
742 BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
744 ss->bind(ss, dummytop);
745 dummytop->subsys[i]->cgroup = dummytop;
746 cgrp->subsys[i] = NULL;
747 rcu_assign_pointer(subsys[i]->root, &rootnode);
748 list_del(&ss->sibling);
749 } else if (bit & final_bits) {
750 /* Subsystem state should already exist */
751 BUG_ON(!cgrp->subsys[i]);
753 /* Subsystem state shouldn't exist */
754 BUG_ON(cgrp->subsys[i]);
757 root->subsys_bits = root->actual_subsys_bits = final_bits;
763 static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
765 struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info;
766 struct cgroup_subsys *ss;
768 mutex_lock(&cgroup_mutex);
769 for_each_subsys(root, ss)
770 seq_printf(seq, ",%s", ss->name);
771 if (test_bit(ROOT_NOPREFIX, &root->flags))
772 seq_puts(seq, ",noprefix");
773 if (strlen(root->release_agent_path))
774 seq_printf(seq, ",release_agent=%s", root->release_agent_path);
775 mutex_unlock(&cgroup_mutex);
779 struct cgroup_sb_opts {
780 unsigned long subsys_bits;
785 /* Convert a hierarchy specifier into a bitmask of subsystems and
787 static int parse_cgroupfs_options(char *data,
788 struct cgroup_sb_opts *opts)
790 char *token, *o = data ?: "all";
792 opts->subsys_bits = 0;
794 opts->release_agent = NULL;
796 while ((token = strsep(&o, ",")) != NULL) {
799 if (!strcmp(token, "all")) {
800 /* Add all non-disabled subsystems */
802 opts->subsys_bits = 0;
803 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
804 struct cgroup_subsys *ss = subsys[i];
806 opts->subsys_bits |= 1ul << i;
808 } else if (!strcmp(token, "noprefix")) {
809 set_bit(ROOT_NOPREFIX, &opts->flags);
810 } else if (!strncmp(token, "release_agent=", 14)) {
811 /* Specifying two release agents is forbidden */
812 if (opts->release_agent)
814 opts->release_agent = kzalloc(PATH_MAX, GFP_KERNEL);
815 if (!opts->release_agent)
817 strncpy(opts->release_agent, token + 14, PATH_MAX - 1);
818 opts->release_agent[PATH_MAX - 1] = 0;
820 struct cgroup_subsys *ss;
822 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
824 if (!strcmp(token, ss->name)) {
826 set_bit(i, &opts->subsys_bits);
830 if (i == CGROUP_SUBSYS_COUNT)
835 /* We can't have an empty hierarchy */
836 if (!opts->subsys_bits)
842 static int cgroup_remount(struct super_block *sb, int *flags, char *data)
845 struct cgroupfs_root *root = sb->s_fs_info;
846 struct cgroup *cgrp = &root->top_cgroup;
847 struct cgroup_sb_opts opts;
849 mutex_lock(&cgrp->dentry->d_inode->i_mutex);
850 mutex_lock(&cgroup_mutex);
852 /* See what subsystems are wanted */
853 ret = parse_cgroupfs_options(data, &opts);
857 /* Don't allow flags to change at remount */
858 if (opts.flags != root->flags) {
863 ret = rebind_subsystems(root, opts.subsys_bits);
865 /* (re)populate subsystem files */
867 cgroup_populate_dir(cgrp);
869 if (opts.release_agent)
870 strcpy(root->release_agent_path, opts.release_agent);
872 if (opts.release_agent)
873 kfree(opts.release_agent);
874 mutex_unlock(&cgroup_mutex);
875 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
879 static struct super_operations cgroup_ops = {
880 .statfs = simple_statfs,
881 .drop_inode = generic_delete_inode,
882 .show_options = cgroup_show_options,
883 .remount_fs = cgroup_remount,
886 static void init_cgroup_root(struct cgroupfs_root *root)
888 struct cgroup *cgrp = &root->top_cgroup;
889 INIT_LIST_HEAD(&root->subsys_list);
890 INIT_LIST_HEAD(&root->root_list);
891 root->number_of_cgroups = 1;
893 cgrp->top_cgroup = cgrp;
894 INIT_LIST_HEAD(&cgrp->sibling);
895 INIT_LIST_HEAD(&cgrp->children);
896 INIT_LIST_HEAD(&cgrp->css_sets);
897 INIT_LIST_HEAD(&cgrp->release_list);
900 static int cgroup_test_super(struct super_block *sb, void *data)
902 struct cgroupfs_root *new = data;
903 struct cgroupfs_root *root = sb->s_fs_info;
905 /* First check subsystems */
906 if (new->subsys_bits != root->subsys_bits)
909 /* Next check flags */
910 if (new->flags != root->flags)
916 static int cgroup_set_super(struct super_block *sb, void *data)
919 struct cgroupfs_root *root = data;
921 ret = set_anon_super(sb, NULL);
925 sb->s_fs_info = root;
928 sb->s_blocksize = PAGE_CACHE_SIZE;
929 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
930 sb->s_magic = CGROUP_SUPER_MAGIC;
931 sb->s_op = &cgroup_ops;
936 static int cgroup_get_rootdir(struct super_block *sb)
938 struct inode *inode =
939 cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
940 struct dentry *dentry;
945 inode->i_fop = &simple_dir_operations;
946 inode->i_op = &cgroup_dir_inode_operations;
947 /* directories start off with i_nlink == 2 (for "." entry) */
949 dentry = d_alloc_root(inode);
958 static int cgroup_get_sb(struct file_system_type *fs_type,
959 int flags, const char *unused_dev_name,
960 void *data, struct vfsmount *mnt)
962 struct cgroup_sb_opts opts;
964 struct super_block *sb;
965 struct cgroupfs_root *root;
966 struct list_head tmp_cg_links, *l;
967 INIT_LIST_HEAD(&tmp_cg_links);
969 /* First find the desired set of subsystems */
970 ret = parse_cgroupfs_options(data, &opts);
972 if (opts.release_agent)
973 kfree(opts.release_agent);
977 root = kzalloc(sizeof(*root), GFP_KERNEL);
979 if (opts.release_agent)
980 kfree(opts.release_agent);
984 init_cgroup_root(root);
985 root->subsys_bits = opts.subsys_bits;
986 root->flags = opts.flags;
987 if (opts.release_agent) {
988 strcpy(root->release_agent_path, opts.release_agent);
989 kfree(opts.release_agent);
992 sb = sget(fs_type, cgroup_test_super, cgroup_set_super, root);
999 if (sb->s_fs_info != root) {
1000 /* Reusing an existing superblock */
1001 BUG_ON(sb->s_root == NULL);
1005 /* New superblock */
1006 struct cgroup *cgrp = &root->top_cgroup;
1007 struct inode *inode;
1009 BUG_ON(sb->s_root != NULL);
1011 ret = cgroup_get_rootdir(sb);
1013 goto drop_new_super;
1014 inode = sb->s_root->d_inode;
1016 mutex_lock(&inode->i_mutex);
1017 mutex_lock(&cgroup_mutex);
1020 * We're accessing css_set_count without locking
1021 * css_set_lock here, but that's OK - it can only be
1022 * increased by someone holding cgroup_lock, and
1023 * that's us. The worst that can happen is that we
1024 * have some link structures left over
1026 ret = allocate_cg_links(css_set_count, &tmp_cg_links);
1028 mutex_unlock(&cgroup_mutex);
1029 mutex_unlock(&inode->i_mutex);
1030 goto drop_new_super;
1033 ret = rebind_subsystems(root, root->subsys_bits);
1034 if (ret == -EBUSY) {
1035 mutex_unlock(&cgroup_mutex);
1036 mutex_unlock(&inode->i_mutex);
1037 goto drop_new_super;
1040 /* EBUSY should be the only error here */
1043 list_add(&root->root_list, &roots);
1046 sb->s_root->d_fsdata = &root->top_cgroup;
1047 root->top_cgroup.dentry = sb->s_root;
1049 /* Link the top cgroup in this hierarchy into all
1050 * the css_set objects */
1051 write_lock(&css_set_lock);
1052 l = &init_css_set.list;
1055 struct cg_cgroup_link *link;
1056 cg = list_entry(l, struct css_set, list);
1057 BUG_ON(list_empty(&tmp_cg_links));
1058 link = list_entry(tmp_cg_links.next,
1059 struct cg_cgroup_link,
1061 list_del(&link->cgrp_link_list);
1063 list_add(&link->cgrp_link_list,
1064 &root->top_cgroup.css_sets);
1065 list_add(&link->cg_link_list, &cg->cg_links);
1067 } while (l != &init_css_set.list);
1068 write_unlock(&css_set_lock);
1070 free_cg_links(&tmp_cg_links);
1072 BUG_ON(!list_empty(&cgrp->sibling));
1073 BUG_ON(!list_empty(&cgrp->children));
1074 BUG_ON(root->number_of_cgroups != 1);
1076 cgroup_populate_dir(cgrp);
1077 mutex_unlock(&inode->i_mutex);
1078 mutex_unlock(&cgroup_mutex);
1081 return simple_set_mnt(mnt, sb);
1084 up_write(&sb->s_umount);
1085 deactivate_super(sb);
1086 free_cg_links(&tmp_cg_links);
1090 static void cgroup_kill_sb(struct super_block *sb) {
1091 struct cgroupfs_root *root = sb->s_fs_info;
1092 struct cgroup *cgrp = &root->top_cgroup;
1097 BUG_ON(root->number_of_cgroups != 1);
1098 BUG_ON(!list_empty(&cgrp->children));
1099 BUG_ON(!list_empty(&cgrp->sibling));
1101 mutex_lock(&cgroup_mutex);
1103 /* Rebind all subsystems back to the default hierarchy */
1104 ret = rebind_subsystems(root, 0);
1105 /* Shouldn't be able to fail ... */
1109 * Release all the links from css_sets to this hierarchy's
1112 write_lock(&css_set_lock);
1113 while (!list_empty(&cgrp->css_sets)) {
1114 struct cg_cgroup_link *link;
1115 link = list_entry(cgrp->css_sets.next,
1116 struct cg_cgroup_link, cgrp_link_list);
1117 list_del(&link->cg_link_list);
1118 list_del(&link->cgrp_link_list);
1121 write_unlock(&css_set_lock);
1123 if (!list_empty(&root->root_list)) {
1124 list_del(&root->root_list);
1127 mutex_unlock(&cgroup_mutex);
1130 kill_litter_super(sb);
1133 static struct file_system_type cgroup_fs_type = {
1135 .get_sb = cgroup_get_sb,
1136 .kill_sb = cgroup_kill_sb,
1139 static inline struct cgroup *__d_cgrp(struct dentry *dentry)
1141 return dentry->d_fsdata;
1144 static inline struct cftype *__d_cft(struct dentry *dentry)
1146 return dentry->d_fsdata;
1150 * cgroup_path - generate the path of a cgroup
1151 * @cgrp: the cgroup in question
1152 * @buf: the buffer to write the path into
1153 * @buflen: the length of the buffer
1155 * Called with cgroup_mutex held. Writes path of cgroup into buf.
1156 * Returns 0 on success, -errno on error.
1158 int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1162 if (cgrp == dummytop) {
1164 * Inactive subsystems have no dentry for their root
1171 start = buf + buflen;
1175 int len = cgrp->dentry->d_name.len;
1176 if ((start -= len) < buf)
1177 return -ENAMETOOLONG;
1178 memcpy(start, cgrp->dentry->d_name.name, len);
1179 cgrp = cgrp->parent;
1185 return -ENAMETOOLONG;
1188 memmove(buf, start, buf + buflen - start);
1193 * Return the first subsystem attached to a cgroup's hierarchy, and
1197 static void get_first_subsys(const struct cgroup *cgrp,
1198 struct cgroup_subsys_state **css, int *subsys_id)
1200 const struct cgroupfs_root *root = cgrp->root;
1201 const struct cgroup_subsys *test_ss;
1202 BUG_ON(list_empty(&root->subsys_list));
1203 test_ss = list_entry(root->subsys_list.next,
1204 struct cgroup_subsys, sibling);
1206 *css = cgrp->subsys[test_ss->subsys_id];
1210 *subsys_id = test_ss->subsys_id;
1214 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
1215 * @cgrp: the cgroup the task is attaching to
1216 * @tsk: the task to be attached
1218 * Call holding cgroup_mutex. May take task_lock of
1219 * the task 'tsk' during call.
1221 int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
1224 struct cgroup_subsys *ss;
1225 struct cgroup *oldcgrp;
1226 struct css_set *cg = tsk->cgroups;
1227 struct css_set *newcg;
1228 struct cgroupfs_root *root = cgrp->root;
1231 get_first_subsys(cgrp, NULL, &subsys_id);
1233 /* Nothing to do if the task is already in that cgroup */
1234 oldcgrp = task_cgroup(tsk, subsys_id);
1235 if (cgrp == oldcgrp)
1238 for_each_subsys(root, ss) {
1239 if (ss->can_attach) {
1240 retval = ss->can_attach(ss, cgrp, tsk);
1247 * Locate or allocate a new css_set for this task,
1248 * based on its final set of cgroups
1250 newcg = find_css_set(cg, cgrp);
1255 if (tsk->flags & PF_EXITING) {
1260 rcu_assign_pointer(tsk->cgroups, newcg);
1263 /* Update the css_set linked lists if we're using them */
1264 write_lock(&css_set_lock);
1265 if (!list_empty(&tsk->cg_list)) {
1266 list_del(&tsk->cg_list);
1267 list_add(&tsk->cg_list, &newcg->tasks);
1269 write_unlock(&css_set_lock);
1271 for_each_subsys(root, ss) {
1273 ss->attach(ss, cgrp, oldcgrp, tsk);
1275 set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
1282 * Attach task with pid 'pid' to cgroup 'cgrp'. Call with
1283 * cgroup_mutex, may take task_lock of task
1285 static int attach_task_by_pid(struct cgroup *cgrp, char *pidbuf)
1288 struct task_struct *tsk;
1291 if (sscanf(pidbuf, "%d", &pid) != 1)
1296 tsk = find_task_by_vpid(pid);
1297 if (!tsk || tsk->flags & PF_EXITING) {
1301 get_task_struct(tsk);
1304 if ((current->euid) && (current->euid != tsk->uid)
1305 && (current->euid != tsk->suid)) {
1306 put_task_struct(tsk);
1311 get_task_struct(tsk);
1314 ret = cgroup_attach_task(cgrp, tsk);
1315 put_task_struct(tsk);
1319 /* The various types of files and directories in a cgroup file system */
1320 enum cgroup_filetype {
1324 FILE_NOTIFY_ON_RELEASE,
1328 static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
1330 const char __user *userbuf,
1331 size_t nbytes, loff_t *unused_ppos)
1339 if (nbytes >= sizeof(buffer))
1341 if (copy_from_user(buffer, userbuf, nbytes))
1344 buffer[nbytes] = 0; /* nul-terminate */
1346 if (cft->write_u64) {
1347 u64 val = simple_strtoull(buffer, &end, 0);
1350 retval = cft->write_u64(cgrp, cft, val);
1352 s64 val = simple_strtoll(buffer, &end, 0);
1355 retval = cft->write_s64(cgrp, cft, val);
1362 static ssize_t cgroup_common_file_write(struct cgroup *cgrp,
1365 const char __user *userbuf,
1366 size_t nbytes, loff_t *unused_ppos)
1368 enum cgroup_filetype type = cft->private;
1372 if (nbytes >= PATH_MAX)
1375 /* +1 for nul-terminator */
1376 buffer = kmalloc(nbytes + 1, GFP_KERNEL);
1380 if (copy_from_user(buffer, userbuf, nbytes)) {
1384 buffer[nbytes] = 0; /* nul-terminate */
1385 strstrip(buffer); /* strip -just- trailing whitespace */
1387 mutex_lock(&cgroup_mutex);
1390 * This was already checked for in cgroup_file_write(), but
1391 * check again now we're holding cgroup_mutex.
1393 if (cgroup_is_removed(cgrp)) {
1400 retval = attach_task_by_pid(cgrp, buffer);
1402 case FILE_NOTIFY_ON_RELEASE:
1403 clear_bit(CGRP_RELEASABLE, &cgrp->flags);
1404 if (simple_strtoul(buffer, NULL, 10) != 0)
1405 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
1407 clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
1409 case FILE_RELEASE_AGENT:
1410 BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
1411 strcpy(cgrp->root->release_agent_path, buffer);
1421 mutex_unlock(&cgroup_mutex);
1427 static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
1428 size_t nbytes, loff_t *ppos)
1430 struct cftype *cft = __d_cft(file->f_dentry);
1431 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
1433 if (!cft || cgroup_is_removed(cgrp))
1436 return cft->write(cgrp, cft, file, buf, nbytes, ppos);
1437 if (cft->write_u64 || cft->write_s64)
1438 return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
1440 int ret = cft->trigger(cgrp, (unsigned int)cft->private);
1441 return ret ? ret : nbytes;
1446 static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
1448 char __user *buf, size_t nbytes,
1452 u64 val = cft->read_u64(cgrp, cft);
1453 int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
1455 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
1458 static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
1460 char __user *buf, size_t nbytes,
1464 s64 val = cft->read_s64(cgrp, cft);
1465 int len = sprintf(tmp, "%lld\n", (long long) val);
1467 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
1470 static ssize_t cgroup_common_file_read(struct cgroup *cgrp,
1474 size_t nbytes, loff_t *ppos)
1476 enum cgroup_filetype type = cft->private;
1481 if (!(page = (char *)__get_free_page(GFP_KERNEL)))
1487 case FILE_RELEASE_AGENT:
1489 struct cgroupfs_root *root;
1491 mutex_lock(&cgroup_mutex);
1493 n = strnlen(root->release_agent_path,
1494 sizeof(root->release_agent_path));
1495 n = min(n, (size_t) PAGE_SIZE);
1496 strncpy(s, root->release_agent_path, n);
1497 mutex_unlock(&cgroup_mutex);
1507 retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page);
1509 free_page((unsigned long)page);
1513 static ssize_t cgroup_file_read(struct file *file, char __user *buf,
1514 size_t nbytes, loff_t *ppos)
1516 struct cftype *cft = __d_cft(file->f_dentry);
1517 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
1519 if (!cft || cgroup_is_removed(cgrp))
1523 return cft->read(cgrp, cft, file, buf, nbytes, ppos);
1525 return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
1527 return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
1532 * seqfile ops/methods for returning structured data. Currently just
1533 * supports string->u64 maps, but can be extended in future.
1536 struct cgroup_seqfile_state {
1538 struct cgroup *cgroup;
1541 static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
1543 struct seq_file *sf = cb->state;
1544 return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
1547 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
1549 struct cgroup_seqfile_state *state = m->private;
1550 struct cftype *cft = state->cft;
1551 struct cgroup_map_cb cb = {
1552 .fill = cgroup_map_add,
1555 return cft->read_map(state->cgroup, cft, &cb);
1558 int cgroup_seqfile_release(struct inode *inode, struct file *file)
1560 struct seq_file *seq = file->private_data;
1561 kfree(seq->private);
1562 return single_release(inode, file);
1565 static struct file_operations cgroup_seqfile_operations = {
1567 .llseek = seq_lseek,
1568 .release = cgroup_seqfile_release,
1571 static int cgroup_file_open(struct inode *inode, struct file *file)
1576 err = generic_file_open(inode, file);
1580 cft = __d_cft(file->f_dentry);
1583 if (cft->read_map) {
1584 struct cgroup_seqfile_state *state =
1585 kzalloc(sizeof(*state), GFP_USER);
1589 state->cgroup = __d_cgrp(file->f_dentry->d_parent);
1590 file->f_op = &cgroup_seqfile_operations;
1591 err = single_open(file, cgroup_seqfile_show, state);
1594 } else if (cft->open)
1595 err = cft->open(inode, file);
1602 static int cgroup_file_release(struct inode *inode, struct file *file)
1604 struct cftype *cft = __d_cft(file->f_dentry);
1606 return cft->release(inode, file);
1611 * cgroup_rename - Only allow simple rename of directories in place.
1613 static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
1614 struct inode *new_dir, struct dentry *new_dentry)
1616 if (!S_ISDIR(old_dentry->d_inode->i_mode))
1618 if (new_dentry->d_inode)
1620 if (old_dir != new_dir)
1622 return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
1625 static struct file_operations cgroup_file_operations = {
1626 .read = cgroup_file_read,
1627 .write = cgroup_file_write,
1628 .llseek = generic_file_llseek,
1629 .open = cgroup_file_open,
1630 .release = cgroup_file_release,
1633 static struct inode_operations cgroup_dir_inode_operations = {
1634 .lookup = simple_lookup,
1635 .mkdir = cgroup_mkdir,
1636 .rmdir = cgroup_rmdir,
1637 .rename = cgroup_rename,
1640 static int cgroup_create_file(struct dentry *dentry, int mode,
1641 struct super_block *sb)
1643 static struct dentry_operations cgroup_dops = {
1644 .d_iput = cgroup_diput,
1647 struct inode *inode;
1651 if (dentry->d_inode)
1654 inode = cgroup_new_inode(mode, sb);
1658 if (S_ISDIR(mode)) {
1659 inode->i_op = &cgroup_dir_inode_operations;
1660 inode->i_fop = &simple_dir_operations;
1662 /* start off with i_nlink == 2 (for "." entry) */
1665 /* start with the directory inode held, so that we can
1666 * populate it without racing with another mkdir */
1667 mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1668 } else if (S_ISREG(mode)) {
1670 inode->i_fop = &cgroup_file_operations;
1672 dentry->d_op = &cgroup_dops;
1673 d_instantiate(dentry, inode);
1674 dget(dentry); /* Extra count - pin the dentry in core */
1679 * cgroup_create_dir - create a directory for an object.
1680 * @cgrp: the cgroup we create the directory for. It must have a valid
1681 * ->parent field. And we are going to fill its ->dentry field.
1682 * @dentry: dentry of the new cgroup
1683 * @mode: mode to set on new directory.
1685 static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
1688 struct dentry *parent;
1691 parent = cgrp->parent->dentry;
1692 error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
1694 dentry->d_fsdata = cgrp;
1695 inc_nlink(parent->d_inode);
1696 cgrp->dentry = dentry;
1704 int cgroup_add_file(struct cgroup *cgrp,
1705 struct cgroup_subsys *subsys,
1706 const struct cftype *cft)
1708 struct dentry *dir = cgrp->dentry;
1709 struct dentry *dentry;
1712 char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
1713 if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
1714 strcpy(name, subsys->name);
1717 strcat(name, cft->name);
1718 BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
1719 dentry = lookup_one_len(name, dir, strlen(name));
1720 if (!IS_ERR(dentry)) {
1721 error = cgroup_create_file(dentry, 0644 | S_IFREG,
1724 dentry->d_fsdata = (void *)cft;
1727 error = PTR_ERR(dentry);
1731 int cgroup_add_files(struct cgroup *cgrp,
1732 struct cgroup_subsys *subsys,
1733 const struct cftype cft[],
1737 for (i = 0; i < count; i++) {
1738 err = cgroup_add_file(cgrp, subsys, &cft[i]);
1746 * cgroup_task_count - count the number of tasks in a cgroup.
1747 * @cgrp: the cgroup in question
1749 * Return the number of tasks in the cgroup.
1751 int cgroup_task_count(const struct cgroup *cgrp)
1754 struct list_head *l;
1756 read_lock(&css_set_lock);
1757 l = cgrp->css_sets.next;
1758 while (l != &cgrp->css_sets) {
1759 struct cg_cgroup_link *link =
1760 list_entry(l, struct cg_cgroup_link, cgrp_link_list);
1761 count += atomic_read(&link->cg->ref.refcount);
1764 read_unlock(&css_set_lock);
1769 * Advance a list_head iterator. The iterator should be positioned at
1770 * the start of a css_set
1772 static void cgroup_advance_iter(struct cgroup *cgrp,
1773 struct cgroup_iter *it)
1775 struct list_head *l = it->cg_link;
1776 struct cg_cgroup_link *link;
1779 /* Advance to the next non-empty css_set */
1782 if (l == &cgrp->css_sets) {
1786 link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
1788 } while (list_empty(&cg->tasks));
1790 it->task = cg->tasks.next;
1794 * To reduce the fork() overhead for systems that are not actually
1795 * using their cgroups capability, we don't maintain the lists running
1796 * through each css_set to its tasks until we see the list actually
1797 * used - in other words after the first call to cgroup_iter_start().
1799 * The tasklist_lock is not held here, as do_each_thread() and
1800 * while_each_thread() are protected by RCU.
1802 static void cgroup_enable_task_cg_lists(void)
1804 struct task_struct *p, *g;
1805 write_lock(&css_set_lock);
1806 use_task_css_set_links = 1;
1807 do_each_thread(g, p) {
1810 * We should check if the process is exiting, otherwise
1811 * it will race with cgroup_exit() in that the list
1812 * entry won't be deleted though the process has exited.
1814 if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
1815 list_add(&p->cg_list, &p->cgroups->tasks);
1817 } while_each_thread(g, p);
1818 write_unlock(&css_set_lock);
1821 void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
1824 * The first time anyone tries to iterate across a cgroup,
1825 * we need to enable the list linking each css_set to its
1826 * tasks, and fix up all existing tasks.
1828 if (!use_task_css_set_links)
1829 cgroup_enable_task_cg_lists();
1831 read_lock(&css_set_lock);
1832 it->cg_link = &cgrp->css_sets;
1833 cgroup_advance_iter(cgrp, it);
1836 struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
1837 struct cgroup_iter *it)
1839 struct task_struct *res;
1840 struct list_head *l = it->task;
1842 /* If the iterator cg is NULL, we have no tasks */
1845 res = list_entry(l, struct task_struct, cg_list);
1846 /* Advance iterator to find next entry */
1848 if (l == &res->cgroups->tasks) {
1849 /* We reached the end of this task list - move on to
1850 * the next cg_cgroup_link */
1851 cgroup_advance_iter(cgrp, it);
1858 void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
1860 read_unlock(&css_set_lock);
1863 static inline int started_after_time(struct task_struct *t1,
1864 struct timespec *time,
1865 struct task_struct *t2)
1867 int start_diff = timespec_compare(&t1->start_time, time);
1868 if (start_diff > 0) {
1870 } else if (start_diff < 0) {
1874 * Arbitrarily, if two processes started at the same
1875 * time, we'll say that the lower pointer value
1876 * started first. Note that t2 may have exited by now
1877 * so this may not be a valid pointer any longer, but
1878 * that's fine - it still serves to distinguish
1879 * between two tasks started (effectively) simultaneously.
1886 * This function is a callback from heap_insert() and is used to order
1888 * In this case we order the heap in descending task start time.
1890 static inline int started_after(void *p1, void *p2)
1892 struct task_struct *t1 = p1;
1893 struct task_struct *t2 = p2;
1894 return started_after_time(t1, &t2->start_time, t2);
1898 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
1899 * @scan: struct cgroup_scanner containing arguments for the scan
1901 * Arguments include pointers to callback functions test_task() and
1903 * Iterate through all the tasks in a cgroup, calling test_task() for each,
1904 * and if it returns true, call process_task() for it also.
1905 * The test_task pointer may be NULL, meaning always true (select all tasks).
1906 * Effectively duplicates cgroup_iter_{start,next,end}()
1907 * but does not lock css_set_lock for the call to process_task().
1908 * The struct cgroup_scanner may be embedded in any structure of the caller's
1910 * It is guaranteed that process_task() will act on every task that
1911 * is a member of the cgroup for the duration of this call. This
1912 * function may or may not call process_task() for tasks that exit
1913 * or move to a different cgroup during the call, or are forked or
1914 * move into the cgroup during the call.
1916 * Note that test_task() may be called with locks held, and may in some
1917 * situations be called multiple times for the same task, so it should
1919 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
1920 * pre-allocated and will be used for heap operations (and its "gt" member will
1921 * be overwritten), else a temporary heap will be used (allocation of which
1922 * may cause this function to fail).
1924 int cgroup_scan_tasks(struct cgroup_scanner *scan)
1927 struct cgroup_iter it;
1928 struct task_struct *p, *dropped;
1929 /* Never dereference latest_task, since it's not refcounted */
1930 struct task_struct *latest_task = NULL;
1931 struct ptr_heap tmp_heap;
1932 struct ptr_heap *heap;
1933 struct timespec latest_time = { 0, 0 };
1936 /* The caller supplied our heap and pre-allocated its memory */
1938 heap->gt = &started_after;
1940 /* We need to allocate our own heap memory */
1942 retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
1944 /* cannot allocate the heap */
1950 * Scan tasks in the cgroup, using the scanner's "test_task" callback
1951 * to determine which are of interest, and using the scanner's
1952 * "process_task" callback to process any of them that need an update.
1953 * Since we don't want to hold any locks during the task updates,
1954 * gather tasks to be processed in a heap structure.
1955 * The heap is sorted by descending task start time.
1956 * If the statically-sized heap fills up, we overflow tasks that
1957 * started later, and in future iterations only consider tasks that
1958 * started after the latest task in the previous pass. This
1959 * guarantees forward progress and that we don't miss any tasks.
1962 cgroup_iter_start(scan->cg, &it);
1963 while ((p = cgroup_iter_next(scan->cg, &it))) {
1965 * Only affect tasks that qualify per the caller's callback,
1966 * if he provided one
1968 if (scan->test_task && !scan->test_task(p, scan))
1971 * Only process tasks that started after the last task
1974 if (!started_after_time(p, &latest_time, latest_task))
1976 dropped = heap_insert(heap, p);
1977 if (dropped == NULL) {
1979 * The new task was inserted; the heap wasn't
1983 } else if (dropped != p) {
1985 * The new task was inserted, and pushed out a
1989 put_task_struct(dropped);
1992 * Else the new task was newer than anything already in
1993 * the heap and wasn't inserted
1996 cgroup_iter_end(scan->cg, &it);
1999 for (i = 0; i < heap->size; i++) {
2000 struct task_struct *q = heap->ptrs[i];
2002 latest_time = q->start_time;
2005 /* Process the task per the caller's callback */
2006 scan->process_task(q, scan);
2010 * If we had to process any tasks at all, scan again
2011 * in case some of them were in the middle of forking
2012 * children that didn't get processed.
2013 * Not the most efficient way to do it, but it avoids
2014 * having to take callback_mutex in the fork path
2018 if (heap == &tmp_heap)
2019 heap_free(&tmp_heap);
2024 * Stuff for reading the 'tasks' file.
2026 * Reading this file can return large amounts of data if a cgroup has
2027 * *lots* of attached tasks. So it may need several calls to read(),
2028 * but we cannot guarantee that the information we produce is correct
2029 * unless we produce it entirely atomically.
2031 * Upon tasks file open(), a struct ctr_struct is allocated, that
2032 * will have a pointer to an array (also allocated here). The struct
2033 * ctr_struct * is stored in file->private_data. Its resources will
2034 * be freed by release() when the file is closed. The array is used
2035 * to sprintf the PIDs and then used by read().
2043 * Load into 'pidarray' up to 'npids' of the tasks using cgroup
2044 * 'cgrp'. Return actual number of pids loaded. No need to
2045 * task_lock(p) when reading out p->cgroup, since we're in an RCU
2046 * read section, so the css_set can't go away, and is
2047 * immutable after creation.
2049 static int pid_array_load(pid_t *pidarray, int npids, struct cgroup *cgrp)
2052 struct cgroup_iter it;
2053 struct task_struct *tsk;
2054 cgroup_iter_start(cgrp, &it);
2055 while ((tsk = cgroup_iter_next(cgrp, &it))) {
2056 if (unlikely(n == npids))
2058 pidarray[n++] = task_pid_vnr(tsk);
2060 cgroup_iter_end(cgrp, &it);
2065 * cgroupstats_build - build and fill cgroupstats
2066 * @stats: cgroupstats to fill information into
2067 * @dentry: A dentry entry belonging to the cgroup for which stats have
2070 * Build and fill cgroupstats so that taskstats can export it to user
2073 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
2076 struct cgroup *cgrp;
2077 struct cgroup_iter it;
2078 struct task_struct *tsk;
2080 * Validate dentry by checking the superblock operations
2082 if (dentry->d_sb->s_op != &cgroup_ops)
2086 cgrp = dentry->d_fsdata;
2089 cgroup_iter_start(cgrp, &it);
2090 while ((tsk = cgroup_iter_next(cgrp, &it))) {
2091 switch (tsk->state) {
2093 stats->nr_running++;
2095 case TASK_INTERRUPTIBLE:
2096 stats->nr_sleeping++;
2098 case TASK_UNINTERRUPTIBLE:
2099 stats->nr_uninterruptible++;
2102 stats->nr_stopped++;
2105 if (delayacct_is_task_waiting_on_io(tsk))
2106 stats->nr_io_wait++;
2110 cgroup_iter_end(cgrp, &it);
2117 static int cmppid(const void *a, const void *b)
2119 return *(pid_t *)a - *(pid_t *)b;
2123 * Convert array 'a' of 'npids' pid_t's to a string of newline separated
2124 * decimal pids in 'buf'. Don't write more than 'sz' chars, but return
2125 * count 'cnt' of how many chars would be written if buf were large enough.
2127 static int pid_array_to_buf(char *buf, int sz, pid_t *a, int npids)
2132 for (i = 0; i < npids; i++)
2133 cnt += snprintf(buf + cnt, max(sz - cnt, 0), "%d\n", a[i]);
2138 * Handle an open on 'tasks' file. Prepare a buffer listing the
2139 * process id's of tasks currently attached to the cgroup being opened.
2141 * Does not require any specific cgroup mutexes, and does not take any.
2143 static int cgroup_tasks_open(struct inode *unused, struct file *file)
2145 struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2146 struct ctr_struct *ctr;
2151 if (!(file->f_mode & FMODE_READ))
2154 ctr = kmalloc(sizeof(*ctr), GFP_KERNEL);
2159 * If cgroup gets more users after we read count, we won't have
2160 * enough space - tough. This race is indistinguishable to the
2161 * caller from the case that the additional cgroup users didn't
2162 * show up until sometime later on.
2164 npids = cgroup_task_count(cgrp);
2166 pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL);
2170 npids = pid_array_load(pidarray, npids, cgrp);
2171 sort(pidarray, npids, sizeof(pid_t), cmppid, NULL);
2173 /* Call pid_array_to_buf() twice, first just to get bufsz */
2174 ctr->bufsz = pid_array_to_buf(&c, sizeof(c), pidarray, npids) + 1;
2175 ctr->buf = kmalloc(ctr->bufsz, GFP_KERNEL);
2178 ctr->bufsz = pid_array_to_buf(ctr->buf, ctr->bufsz, pidarray, npids);
2185 file->private_data = ctr;
2196 static ssize_t cgroup_tasks_read(struct cgroup *cgrp,
2198 struct file *file, char __user *buf,
2199 size_t nbytes, loff_t *ppos)
2201 struct ctr_struct *ctr = file->private_data;
2203 return simple_read_from_buffer(buf, nbytes, ppos, ctr->buf, ctr->bufsz);
2206 static int cgroup_tasks_release(struct inode *unused_inode,
2209 struct ctr_struct *ctr;
2211 if (file->f_mode & FMODE_READ) {
2212 ctr = file->private_data;
2219 static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
2222 return notify_on_release(cgrp);
2226 * for the common functions, 'private' gives the type of file
2228 static struct cftype files[] = {
2231 .open = cgroup_tasks_open,
2232 .read = cgroup_tasks_read,
2233 .write = cgroup_common_file_write,
2234 .release = cgroup_tasks_release,
2235 .private = FILE_TASKLIST,
2239 .name = "notify_on_release",
2240 .read_u64 = cgroup_read_notify_on_release,
2241 .write = cgroup_common_file_write,
2242 .private = FILE_NOTIFY_ON_RELEASE,
2246 static struct cftype cft_release_agent = {
2247 .name = "release_agent",
2248 .read = cgroup_common_file_read,
2249 .write = cgroup_common_file_write,
2250 .private = FILE_RELEASE_AGENT,
2253 static int cgroup_populate_dir(struct cgroup *cgrp)
2256 struct cgroup_subsys *ss;
2258 /* First clear out any existing files */
2259 cgroup_clear_directory(cgrp->dentry);
2261 err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));
2265 if (cgrp == cgrp->top_cgroup) {
2266 if ((err = cgroup_add_file(cgrp, NULL, &cft_release_agent)) < 0)
2270 for_each_subsys(cgrp->root, ss) {
2271 if (ss->populate && (err = ss->populate(ss, cgrp)) < 0)
2278 static void init_cgroup_css(struct cgroup_subsys_state *css,
2279 struct cgroup_subsys *ss,
2280 struct cgroup *cgrp)
2283 atomic_set(&css->refcnt, 0);
2285 if (cgrp == dummytop)
2286 set_bit(CSS_ROOT, &css->flags);
2287 BUG_ON(cgrp->subsys[ss->subsys_id]);
2288 cgrp->subsys[ss->subsys_id] = css;
2292 * cgroup_create - create a cgroup
2293 * @parent: cgroup that will be parent of the new cgroup
2294 * @dentry: dentry of the new cgroup
2295 * @mode: mode to set on new inode
2297 * Must be called with the mutex on the parent inode held
2299 static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
2302 struct cgroup *cgrp;
2303 struct cgroupfs_root *root = parent->root;
2305 struct cgroup_subsys *ss;
2306 struct super_block *sb = root->sb;
2308 cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
2312 /* Grab a reference on the superblock so the hierarchy doesn't
2313 * get deleted on unmount if there are child cgroups. This
2314 * can be done outside cgroup_mutex, since the sb can't
2315 * disappear while someone has an open control file on the
2317 atomic_inc(&sb->s_active);
2319 mutex_lock(&cgroup_mutex);
2321 INIT_LIST_HEAD(&cgrp->sibling);
2322 INIT_LIST_HEAD(&cgrp->children);
2323 INIT_LIST_HEAD(&cgrp->css_sets);
2324 INIT_LIST_HEAD(&cgrp->release_list);
2326 cgrp->parent = parent;
2327 cgrp->root = parent->root;
2328 cgrp->top_cgroup = parent->top_cgroup;
2330 if (notify_on_release(parent))
2331 set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
2333 for_each_subsys(root, ss) {
2334 struct cgroup_subsys_state *css = ss->create(ss, cgrp);
2339 init_cgroup_css(css, ss, cgrp);
2342 list_add(&cgrp->sibling, &cgrp->parent->children);
2343 root->number_of_cgroups++;
2345 err = cgroup_create_dir(cgrp, dentry, mode);
2349 /* The cgroup directory was pre-locked for us */
2350 BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
2352 err = cgroup_populate_dir(cgrp);
2353 /* If err < 0, we have a half-filled directory - oh well ;) */
2355 mutex_unlock(&cgroup_mutex);
2356 mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
2362 list_del(&cgrp->sibling);
2363 root->number_of_cgroups--;
2367 for_each_subsys(root, ss) {
2368 if (cgrp->subsys[ss->subsys_id])
2369 ss->destroy(ss, cgrp);
2372 mutex_unlock(&cgroup_mutex);
2374 /* Release the reference count that we took on the superblock */
2375 deactivate_super(sb);
2381 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode)
2383 struct cgroup *c_parent = dentry->d_parent->d_fsdata;
2385 /* the vfs holds inode->i_mutex already */
2386 return cgroup_create(c_parent, dentry, mode | S_IFDIR);
2389 static inline int cgroup_has_css_refs(struct cgroup *cgrp)
2391 /* Check the reference count on each subsystem. Since we
2392 * already established that there are no tasks in the
2393 * cgroup, if the css refcount is also 0, then there should
2394 * be no outstanding references, so the subsystem is safe to
2395 * destroy. We scan across all subsystems rather than using
2396 * the per-hierarchy linked list of mounted subsystems since
2397 * we can be called via check_for_release() with no
2398 * synchronization other than RCU, and the subsystem linked
2399 * list isn't RCU-safe */
2401 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2402 struct cgroup_subsys *ss = subsys[i];
2403 struct cgroup_subsys_state *css;
2404 /* Skip subsystems not in this hierarchy */
2405 if (ss->root != cgrp->root)
2407 css = cgrp->subsys[ss->subsys_id];
2408 /* When called from check_for_release() it's possible
2409 * that by this point the cgroup has been removed
2410 * and the css deleted. But a false-positive doesn't
2411 * matter, since it can only happen if the cgroup
2412 * has been deleted and hence no longer needs the
2413 * release agent to be called anyway. */
2414 if (css && atomic_read(&css->refcnt))
2420 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
2422 struct cgroup *cgrp = dentry->d_fsdata;
2424 struct cgroup *parent;
2425 struct super_block *sb;
2426 struct cgroupfs_root *root;
2428 /* the vfs holds both inode->i_mutex already */
2430 mutex_lock(&cgroup_mutex);
2431 if (atomic_read(&cgrp->count) != 0) {
2432 mutex_unlock(&cgroup_mutex);
2435 if (!list_empty(&cgrp->children)) {
2436 mutex_unlock(&cgroup_mutex);
2440 parent = cgrp->parent;
2445 * Call pre_destroy handlers of subsys. Notify subsystems
2446 * that rmdir() request comes.
2448 cgroup_call_pre_destroy(cgrp);
2450 if (cgroup_has_css_refs(cgrp)) {
2451 mutex_unlock(&cgroup_mutex);
2455 spin_lock(&release_list_lock);
2456 set_bit(CGRP_REMOVED, &cgrp->flags);
2457 if (!list_empty(&cgrp->release_list))
2458 list_del(&cgrp->release_list);
2459 spin_unlock(&release_list_lock);
2460 /* delete my sibling from parent->children */
2461 list_del(&cgrp->sibling);
2462 spin_lock(&cgrp->dentry->d_lock);
2463 d = dget(cgrp->dentry);
2464 cgrp->dentry = NULL;
2465 spin_unlock(&d->d_lock);
2467 cgroup_d_remove_dir(d);
2470 set_bit(CGRP_RELEASABLE, &parent->flags);
2471 check_for_release(parent);
2473 mutex_unlock(&cgroup_mutex);
2477 static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
2479 struct cgroup_subsys_state *css;
2481 printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
2483 /* Create the top cgroup state for this subsystem */
2484 ss->root = &rootnode;
2485 css = ss->create(ss, dummytop);
2486 /* We don't handle early failures gracefully */
2487 BUG_ON(IS_ERR(css));
2488 init_cgroup_css(css, ss, dummytop);
2490 /* Update the init_css_set to contain a subsys
2491 * pointer to this state - since the subsystem is
2492 * newly registered, all tasks and hence the
2493 * init_css_set is in the subsystem's top cgroup. */
2494 init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
2496 need_forkexit_callback |= ss->fork || ss->exit;
2498 /* At system boot, before all subsystems have been
2499 * registered, no tasks have been forked, so we don't
2500 * need to invoke fork callbacks here. */
2501 BUG_ON(!list_empty(&init_task.tasks));
2507 * cgroup_init_early - cgroup initialization at system boot
2509 * Initialize cgroups at system boot, and initialize any
2510 * subsystems that request early init.
2512 int __init cgroup_init_early(void)
2515 kref_init(&init_css_set.ref);
2516 kref_get(&init_css_set.ref);
2517 INIT_LIST_HEAD(&init_css_set.list);
2518 INIT_LIST_HEAD(&init_css_set.cg_links);
2519 INIT_LIST_HEAD(&init_css_set.tasks);
2520 INIT_HLIST_NODE(&init_css_set.hlist);
2522 init_cgroup_root(&rootnode);
2523 list_add(&rootnode.root_list, &roots);
2525 init_task.cgroups = &init_css_set;
2527 init_css_set_link.cg = &init_css_set;
2528 list_add(&init_css_set_link.cgrp_link_list,
2529 &rootnode.top_cgroup.css_sets);
2530 list_add(&init_css_set_link.cg_link_list,
2531 &init_css_set.cg_links);
2533 for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
2534 INIT_HLIST_HEAD(&css_set_table[i]);
2536 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2537 struct cgroup_subsys *ss = subsys[i];
2540 BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
2541 BUG_ON(!ss->create);
2542 BUG_ON(!ss->destroy);
2543 if (ss->subsys_id != i) {
2544 printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
2545 ss->name, ss->subsys_id);
2550 cgroup_init_subsys(ss);
2556 * cgroup_init - cgroup initialization
2558 * Register cgroup filesystem and /proc file, and initialize
2559 * any subsystems that didn't request early init.
2561 int __init cgroup_init(void)
2565 struct hlist_head *hhead;
2567 err = bdi_init(&cgroup_backing_dev_info);
2571 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2572 struct cgroup_subsys *ss = subsys[i];
2573 if (!ss->early_init)
2574 cgroup_init_subsys(ss);
2577 /* Add init_css_set to the hash table */
2578 hhead = css_set_hash(init_css_set.subsys);
2579 hlist_add_head(&init_css_set.hlist, hhead);
2581 err = register_filesystem(&cgroup_fs_type);
2585 proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
2589 bdi_destroy(&cgroup_backing_dev_info);
2595 * proc_cgroup_show()
2596 * - Print task's cgroup paths into seq_file, one line for each hierarchy
2597 * - Used for /proc/<pid>/cgroup.
2598 * - No need to task_lock(tsk) on this tsk->cgroup reference, as it
2599 * doesn't really matter if tsk->cgroup changes after we read it,
2600 * and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
2601 * anyway. No need to check that tsk->cgroup != NULL, thanks to
2602 * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
2603 * cgroup to top_cgroup.
2606 /* TODO: Use a proper seq_file iterator */
2607 static int proc_cgroup_show(struct seq_file *m, void *v)
2610 struct task_struct *tsk;
2613 struct cgroupfs_root *root;
2616 buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
2622 tsk = get_pid_task(pid, PIDTYPE_PID);
2628 mutex_lock(&cgroup_mutex);
2630 for_each_root(root) {
2631 struct cgroup_subsys *ss;
2632 struct cgroup *cgrp;
2636 /* Skip this hierarchy if it has no active subsystems */
2637 if (!root->actual_subsys_bits)
2639 seq_printf(m, "%lu:", root->subsys_bits);
2640 for_each_subsys(root, ss)
2641 seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
2643 get_first_subsys(&root->top_cgroup, NULL, &subsys_id);
2644 cgrp = task_cgroup(tsk, subsys_id);
2645 retval = cgroup_path(cgrp, buf, PAGE_SIZE);
2653 mutex_unlock(&cgroup_mutex);
2654 put_task_struct(tsk);
2661 static int cgroup_open(struct inode *inode, struct file *file)
2663 struct pid *pid = PROC_I(inode)->pid;
2664 return single_open(file, proc_cgroup_show, pid);
2667 struct file_operations proc_cgroup_operations = {
2668 .open = cgroup_open,
2670 .llseek = seq_lseek,
2671 .release = single_release,
2674 /* Display information about each subsystem and each hierarchy */
2675 static int proc_cgroupstats_show(struct seq_file *m, void *v)
2679 seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
2680 mutex_lock(&cgroup_mutex);
2681 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2682 struct cgroup_subsys *ss = subsys[i];
2683 seq_printf(m, "%s\t%lu\t%d\t%d\n",
2684 ss->name, ss->root->subsys_bits,
2685 ss->root->number_of_cgroups, !ss->disabled);
2687 mutex_unlock(&cgroup_mutex);
2691 static int cgroupstats_open(struct inode *inode, struct file *file)
2693 return single_open(file, proc_cgroupstats_show, NULL);
2696 static struct file_operations proc_cgroupstats_operations = {
2697 .open = cgroupstats_open,
2699 .llseek = seq_lseek,
2700 .release = single_release,
2704 * cgroup_fork - attach newly forked task to its parents cgroup.
2705 * @child: pointer to task_struct of forking parent process.
2707 * Description: A task inherits its parent's cgroup at fork().
2709 * A pointer to the shared css_set was automatically copied in
2710 * fork.c by dup_task_struct(). However, we ignore that copy, since
2711 * it was not made under the protection of RCU or cgroup_mutex, so
2712 * might no longer be a valid cgroup pointer. cgroup_attach_task() might
2713 * have already changed current->cgroups, allowing the previously
2714 * referenced cgroup group to be removed and freed.
2716 * At the point that cgroup_fork() is called, 'current' is the parent
2717 * task, and the passed argument 'child' points to the child task.
2719 void cgroup_fork(struct task_struct *child)
2722 child->cgroups = current->cgroups;
2723 get_css_set(child->cgroups);
2724 task_unlock(current);
2725 INIT_LIST_HEAD(&child->cg_list);
2729 * cgroup_fork_callbacks - run fork callbacks
2730 * @child: the new task
2732 * Called on a new task very soon before adding it to the
2733 * tasklist. No need to take any locks since no-one can
2734 * be operating on this task.
2736 void cgroup_fork_callbacks(struct task_struct *child)
2738 if (need_forkexit_callback) {
2740 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2741 struct cgroup_subsys *ss = subsys[i];
2743 ss->fork(ss, child);
2749 * cgroup_post_fork - called on a new task after adding it to the task list
2750 * @child: the task in question
2752 * Adds the task to the list running through its css_set if necessary.
2753 * Has to be after the task is visible on the task list in case we race
2754 * with the first call to cgroup_iter_start() - to guarantee that the
2755 * new task ends up on its list.
2757 void cgroup_post_fork(struct task_struct *child)
2759 if (use_task_css_set_links) {
2760 write_lock(&css_set_lock);
2761 if (list_empty(&child->cg_list))
2762 list_add(&child->cg_list, &child->cgroups->tasks);
2763 write_unlock(&css_set_lock);
2767 * cgroup_exit - detach cgroup from exiting task
2768 * @tsk: pointer to task_struct of exiting process
2769 * @run_callback: run exit callbacks?
2771 * Description: Detach cgroup from @tsk and release it.
2773 * Note that cgroups marked notify_on_release force every task in
2774 * them to take the global cgroup_mutex mutex when exiting.
2775 * This could impact scaling on very large systems. Be reluctant to
2776 * use notify_on_release cgroups where very high task exit scaling
2777 * is required on large systems.
2779 * the_top_cgroup_hack:
2781 * Set the exiting tasks cgroup to the root cgroup (top_cgroup).
2783 * We call cgroup_exit() while the task is still competent to
2784 * handle notify_on_release(), then leave the task attached to the
2785 * root cgroup in each hierarchy for the remainder of its exit.
2787 * To do this properly, we would increment the reference count on
2788 * top_cgroup, and near the very end of the kernel/exit.c do_exit()
2789 * code we would add a second cgroup function call, to drop that
2790 * reference. This would just create an unnecessary hot spot on
2791 * the top_cgroup reference count, to no avail.
2793 * Normally, holding a reference to a cgroup without bumping its
2794 * count is unsafe. The cgroup could go away, or someone could
2795 * attach us to a different cgroup, decrementing the count on
2796 * the first cgroup that we never incremented. But in this case,
2797 * top_cgroup isn't going away, and either task has PF_EXITING set,
2798 * which wards off any cgroup_attach_task() attempts, or task is a failed
2799 * fork, never visible to cgroup_attach_task.
2801 void cgroup_exit(struct task_struct *tsk, int run_callbacks)
2806 if (run_callbacks && need_forkexit_callback) {
2807 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
2808 struct cgroup_subsys *ss = subsys[i];
2815 * Unlink from the css_set task list if necessary.
2816 * Optimistically check cg_list before taking
2819 if (!list_empty(&tsk->cg_list)) {
2820 write_lock(&css_set_lock);
2821 if (!list_empty(&tsk->cg_list))
2822 list_del(&tsk->cg_list);
2823 write_unlock(&css_set_lock);
2826 /* Reassign the task to the init_css_set. */
2829 tsk->cgroups = &init_css_set;
2832 put_css_set_taskexit(cg);
2836 * cgroup_clone - clone the cgroup the given subsystem is attached to
2837 * @tsk: the task to be moved
2838 * @subsys: the given subsystem
2840 * Duplicate the current cgroup in the hierarchy that the given
2841 * subsystem is attached to, and move this task into the new
2844 int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys)
2846 struct dentry *dentry;
2848 char nodename[MAX_CGROUP_TYPE_NAMELEN];
2849 struct cgroup *parent, *child;
2850 struct inode *inode;
2852 struct cgroupfs_root *root;
2853 struct cgroup_subsys *ss;
2855 /* We shouldn't be called by an unregistered subsystem */
2856 BUG_ON(!subsys->active);
2858 /* First figure out what hierarchy and cgroup we're dealing
2859 * with, and pin them so we can drop cgroup_mutex */
2860 mutex_lock(&cgroup_mutex);
2862 root = subsys->root;
2863 if (root == &rootnode) {
2865 "Not cloning cgroup for unused subsystem %s\n",
2867 mutex_unlock(&cgroup_mutex);
2871 parent = task_cgroup(tsk, subsys->subsys_id);
2873 snprintf(nodename, MAX_CGROUP_TYPE_NAMELEN, "node_%d", tsk->pid);
2875 /* Pin the hierarchy */
2876 atomic_inc(&parent->root->sb->s_active);
2878 /* Keep the cgroup alive */
2880 mutex_unlock(&cgroup_mutex);
2882 /* Now do the VFS work to create a cgroup */
2883 inode = parent->dentry->d_inode;
2885 /* Hold the parent directory mutex across this operation to
2886 * stop anyone else deleting the new cgroup */
2887 mutex_lock(&inode->i_mutex);
2888 dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));
2889 if (IS_ERR(dentry)) {
2891 "cgroup: Couldn't allocate dentry for %s: %ld\n", nodename,
2893 ret = PTR_ERR(dentry);
2897 /* Create the cgroup directory, which also creates the cgroup */
2898 ret = vfs_mkdir(inode, dentry, S_IFDIR | 0755);
2899 child = __d_cgrp(dentry);
2903 "Failed to create cgroup %s: %d\n", nodename,
2910 "Couldn't find new cgroup %s\n", nodename);
2915 /* The cgroup now exists. Retake cgroup_mutex and check
2916 * that we're still in the same state that we thought we
2918 mutex_lock(&cgroup_mutex);
2919 if ((root != subsys->root) ||
2920 (parent != task_cgroup(tsk, subsys->subsys_id))) {
2921 /* Aargh, we raced ... */
2922 mutex_unlock(&inode->i_mutex);
2925 deactivate_super(parent->root->sb);
2926 /* The cgroup is still accessible in the VFS, but
2927 * we're not going to try to rmdir() it at this
2930 "Race in cgroup_clone() - leaking cgroup %s\n",
2935 /* do any required auto-setup */
2936 for_each_subsys(root, ss) {
2938 ss->post_clone(ss, child);
2941 /* All seems fine. Finish by moving the task into the new cgroup */
2942 ret = cgroup_attach_task(child, tsk);
2943 mutex_unlock(&cgroup_mutex);
2946 mutex_unlock(&inode->i_mutex);
2948 mutex_lock(&cgroup_mutex);
2950 mutex_unlock(&cgroup_mutex);
2951 deactivate_super(parent->root->sb);
2956 * cgroup_is_descendant - see if @cgrp is a descendant of current task's cgrp
2957 * @cgrp: the cgroup in question
2959 * See if @cgrp is a descendant of the current task's cgroup in
2960 * the appropriate hierarchy.
2962 * If we are sending in dummytop, then presumably we are creating
2963 * the top cgroup in the subsystem.
2965 * Called only by the ns (nsproxy) cgroup.
2967 int cgroup_is_descendant(const struct cgroup *cgrp)
2970 struct cgroup *target;
2973 if (cgrp == dummytop)
2976 get_first_subsys(cgrp, NULL, &subsys_id);
2977 target = task_cgroup(current, subsys_id);
2978 while (cgrp != target && cgrp!= cgrp->top_cgroup)
2979 cgrp = cgrp->parent;
2980 ret = (cgrp == target);
2984 static void check_for_release(struct cgroup *cgrp)
2986 /* All of these checks rely on RCU to keep the cgroup
2987 * structure alive */
2988 if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
2989 && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
2990 /* Control Group is currently removeable. If it's not
2991 * already queued for a userspace notification, queue
2993 int need_schedule_work = 0;
2994 spin_lock(&release_list_lock);
2995 if (!cgroup_is_removed(cgrp) &&
2996 list_empty(&cgrp->release_list)) {
2997 list_add(&cgrp->release_list, &release_list);
2998 need_schedule_work = 1;
3000 spin_unlock(&release_list_lock);
3001 if (need_schedule_work)
3002 schedule_work(&release_agent_work);
3006 void __css_put(struct cgroup_subsys_state *css)
3008 struct cgroup *cgrp = css->cgroup;
3010 if (atomic_dec_and_test(&css->refcnt) && notify_on_release(cgrp)) {
3011 set_bit(CGRP_RELEASABLE, &cgrp->flags);
3012 check_for_release(cgrp);
3018 * Notify userspace when a cgroup is released, by running the
3019 * configured release agent with the name of the cgroup (path
3020 * relative to the root of cgroup file system) as the argument.
3022 * Most likely, this user command will try to rmdir this cgroup.
3024 * This races with the possibility that some other task will be
3025 * attached to this cgroup before it is removed, or that some other
3026 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
3027 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
3028 * unused, and this cgroup will be reprieved from its death sentence,
3029 * to continue to serve a useful existence. Next time it's released,
3030 * we will get notified again, if it still has 'notify_on_release' set.
3032 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
3033 * means only wait until the task is successfully execve()'d. The
3034 * separate release agent task is forked by call_usermodehelper(),
3035 * then control in this thread returns here, without waiting for the
3036 * release agent task. We don't bother to wait because the caller of
3037 * this routine has no use for the exit status of the release agent
3038 * task, so no sense holding our caller up for that.
3040 static void cgroup_release_agent(struct work_struct *work)
3042 BUG_ON(work != &release_agent_work);
3043 mutex_lock(&cgroup_mutex);
3044 spin_lock(&release_list_lock);
3045 while (!list_empty(&release_list)) {
3046 char *argv[3], *envp[3];
3049 struct cgroup *cgrp = list_entry(release_list.next,
3052 list_del_init(&cgrp->release_list);
3053 spin_unlock(&release_list_lock);
3054 pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
3056 spin_lock(&release_list_lock);
3060 if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0) {
3062 spin_lock(&release_list_lock);
3067 argv[i++] = cgrp->root->release_agent_path;
3068 argv[i++] = (char *)pathbuf;
3072 /* minimal command environment */
3073 envp[i++] = "HOME=/";
3074 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
3077 /* Drop the lock while we invoke the usermode helper,
3078 * since the exec could involve hitting disk and hence
3079 * be a slow process */
3080 mutex_unlock(&cgroup_mutex);
3081 call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
3083 mutex_lock(&cgroup_mutex);
3084 spin_lock(&release_list_lock);
3086 spin_unlock(&release_list_lock);
3087 mutex_unlock(&cgroup_mutex);
3090 static int __init cgroup_disable(char *str)
3095 while ((token = strsep(&str, ",")) != NULL) {
3099 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3100 struct cgroup_subsys *ss = subsys[i];
3102 if (!strcmp(token, ss->name)) {
3104 printk(KERN_INFO "Disabling %s control group"
3105 " subsystem\n", ss->name);
3112 __setup("cgroup_disable=", cgroup_disable);