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>
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
66 struct cgroupfs_root
{
67 struct super_block
*sb
;
70 * The bitmask of subsystems intended to be attached to this
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 active hierarchies */
88 struct list_head root_list
;
90 /* Hierarchy-specific 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
118 static int need_forkexit_callback __read_mostly
;
120 /* convenient tests for these bits */
121 inline int cgroup_is_removed(const struct cgroup
*cgrp
)
123 return test_bit(CGRP_REMOVED
, &cgrp
->flags
);
126 /* bits in struct cgroupfs_root flags field */
128 ROOT_NOPREFIX
, /* mounted subsystems have no named prefix */
131 static int cgroup_is_releasable(const struct cgroup
*cgrp
)
134 (1 << CGRP_RELEASABLE
) |
135 (1 << CGRP_NOTIFY_ON_RELEASE
);
136 return (cgrp
->flags
& bits
) == bits
;
139 static int notify_on_release(const struct cgroup
*cgrp
)
141 return test_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
145 * for_each_subsys() allows you to iterate on each subsystem attached to
146 * an active hierarchy
148 #define for_each_subsys(_root, _ss) \
149 list_for_each_entry(_ss, &_root->subsys_list, sibling)
151 /* for_each_active_root() allows you to iterate across the active hierarchies */
152 #define for_each_active_root(_root) \
153 list_for_each_entry(_root, &roots, root_list)
155 /* the list of cgroups eligible for automatic release. Protected by
156 * release_list_lock */
157 static LIST_HEAD(release_list
);
158 static DEFINE_SPINLOCK(release_list_lock
);
159 static void cgroup_release_agent(struct work_struct
*work
);
160 static DECLARE_WORK(release_agent_work
, cgroup_release_agent
);
161 static void check_for_release(struct cgroup
*cgrp
);
163 /* Link structure for associating css_set objects with cgroups */
164 struct cg_cgroup_link
{
166 * List running through cg_cgroup_links associated with a
167 * cgroup, anchored on cgroup->css_sets
169 struct list_head cgrp_link_list
;
171 * List running through cg_cgroup_links pointing at a
172 * single css_set object, anchored on css_set->cg_links
174 struct list_head cg_link_list
;
178 /* The default css_set - used by init and its children prior to any
179 * hierarchies being mounted. It contains a pointer to the root state
180 * for each subsystem. Also used to anchor the list of css_sets. Not
181 * reference-counted, to improve performance when child cgroups
182 * haven't been created.
185 static struct css_set init_css_set
;
186 static struct cg_cgroup_link init_css_set_link
;
188 /* css_set_lock protects the list of css_set objects, and the
189 * chain of tasks off each css_set. Nests outside task->alloc_lock
190 * due to cgroup_iter_start() */
191 static DEFINE_RWLOCK(css_set_lock
);
192 static int css_set_count
;
194 /* hash table for cgroup groups. This improves the performance to
195 * find an existing css_set */
196 #define CSS_SET_HASH_BITS 7
197 #define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS)
198 static struct hlist_head css_set_table
[CSS_SET_TABLE_SIZE
];
200 static struct hlist_head
*css_set_hash(struct cgroup_subsys_state
*css
[])
204 unsigned long tmp
= 0UL;
206 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++)
207 tmp
+= (unsigned long)css
[i
];
208 tmp
= (tmp
>> 16) ^ tmp
;
210 index
= hash_long(tmp
, CSS_SET_HASH_BITS
);
212 return &css_set_table
[index
];
215 /* We don't maintain the lists running through each css_set to its
216 * task until after the first call to cgroup_iter_start(). This
217 * reduces the fork()/exit() overhead for people who have cgroups
218 * compiled into their kernel but not actually in use */
219 static int use_task_css_set_links __read_mostly
;
221 /* When we create or destroy a css_set, the operation simply
222 * takes/releases a reference count on all the cgroups referenced
223 * by subsystems in this css_set. This can end up multiple-counting
224 * some cgroups, but that's OK - the ref-count is just a
225 * busy/not-busy indicator; ensuring that we only count each cgroup
226 * once would require taking a global lock to ensure that no
227 * subsystems moved between hierarchies while we were doing so.
229 * Possible TODO: decide at boot time based on the number of
230 * registered subsystems and the number of CPUs or NUMA nodes whether
231 * it's better for performance to ref-count every subsystem, or to
232 * take a global lock and only add one ref count to each hierarchy.
236 * unlink a css_set from the list and free it
238 static void unlink_css_set(struct css_set
*cg
)
240 struct cg_cgroup_link
*link
;
241 struct cg_cgroup_link
*saved_link
;
243 hlist_del(&cg
->hlist
);
246 list_for_each_entry_safe(link
, saved_link
, &cg
->cg_links
,
248 list_del(&link
->cg_link_list
);
249 list_del(&link
->cgrp_link_list
);
254 static void __put_css_set(struct css_set
*cg
, int taskexit
)
258 * Ensure that the refcount doesn't hit zero while any readers
259 * can see it. Similar to atomic_dec_and_lock(), but for an
262 if (atomic_add_unless(&cg
->refcount
, -1, 1))
264 write_lock(&css_set_lock
);
265 if (!atomic_dec_and_test(&cg
->refcount
)) {
266 write_unlock(&css_set_lock
);
270 write_unlock(&css_set_lock
);
273 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
274 struct cgroup
*cgrp
= cg
->subsys
[i
]->cgroup
;
275 if (atomic_dec_and_test(&cgrp
->count
) &&
276 notify_on_release(cgrp
)) {
278 set_bit(CGRP_RELEASABLE
, &cgrp
->flags
);
279 check_for_release(cgrp
);
287 * refcounted get/put for css_set objects
289 static inline void get_css_set(struct css_set
*cg
)
291 atomic_inc(&cg
->refcount
);
294 static inline void put_css_set(struct css_set
*cg
)
296 __put_css_set(cg
, 0);
299 static inline void put_css_set_taskexit(struct css_set
*cg
)
301 __put_css_set(cg
, 1);
305 * find_existing_css_set() is a helper for
306 * find_css_set(), and checks to see whether an existing
307 * css_set is suitable.
309 * oldcg: the cgroup group that we're using before the cgroup
312 * cgrp: the cgroup that we're moving into
314 * template: location in which to build the desired set of subsystem
315 * state objects for the new cgroup group
317 static struct css_set
*find_existing_css_set(
318 struct css_set
*oldcg
,
320 struct cgroup_subsys_state
*template[])
323 struct cgroupfs_root
*root
= cgrp
->root
;
324 struct hlist_head
*hhead
;
325 struct hlist_node
*node
;
328 /* Built the set of subsystem state objects that we want to
329 * see in the new css_set */
330 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
331 if (root
->subsys_bits
& (1UL << i
)) {
332 /* Subsystem is in this hierarchy. So we want
333 * the subsystem state from the new
335 template[i
] = cgrp
->subsys
[i
];
337 /* Subsystem is not in this hierarchy, so we
338 * don't want to change the subsystem state */
339 template[i
] = oldcg
->subsys
[i
];
343 hhead
= css_set_hash(template);
344 hlist_for_each_entry(cg
, node
, hhead
, hlist
) {
345 if (!memcmp(template, cg
->subsys
, sizeof(cg
->subsys
))) {
346 /* All subsystems matched */
351 /* No existing cgroup group matched */
355 static void free_cg_links(struct list_head
*tmp
)
357 struct cg_cgroup_link
*link
;
358 struct cg_cgroup_link
*saved_link
;
360 list_for_each_entry_safe(link
, saved_link
, tmp
, cgrp_link_list
) {
361 list_del(&link
->cgrp_link_list
);
367 * allocate_cg_links() allocates "count" cg_cgroup_link structures
368 * and chains them on tmp through their cgrp_link_list fields. Returns 0 on
369 * success or a negative error
371 static int allocate_cg_links(int count
, struct list_head
*tmp
)
373 struct cg_cgroup_link
*link
;
376 for (i
= 0; i
< count
; i
++) {
377 link
= kmalloc(sizeof(*link
), GFP_KERNEL
);
382 list_add(&link
->cgrp_link_list
, tmp
);
388 * link_css_set - a helper function to link a css_set to a cgroup
389 * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
390 * @cg: the css_set to be linked
391 * @cgrp: the destination cgroup
393 static void link_css_set(struct list_head
*tmp_cg_links
,
394 struct css_set
*cg
, struct cgroup
*cgrp
)
396 struct cg_cgroup_link
*link
;
398 BUG_ON(list_empty(tmp_cg_links
));
399 link
= list_first_entry(tmp_cg_links
, struct cg_cgroup_link
,
402 list_move(&link
->cgrp_link_list
, &cgrp
->css_sets
);
403 list_add(&link
->cg_link_list
, &cg
->cg_links
);
407 * find_css_set() takes an existing cgroup group and a
408 * cgroup object, and returns a css_set object that's
409 * equivalent to the old group, but with the given cgroup
410 * substituted into the appropriate hierarchy. Must be called with
413 static struct css_set
*find_css_set(
414 struct css_set
*oldcg
, struct cgroup
*cgrp
)
417 struct cgroup_subsys_state
*template[CGROUP_SUBSYS_COUNT
];
420 struct list_head tmp_cg_links
;
422 struct hlist_head
*hhead
;
424 /* First see if we already have a cgroup group that matches
426 read_lock(&css_set_lock
);
427 res
= find_existing_css_set(oldcg
, cgrp
, template);
430 read_unlock(&css_set_lock
);
435 res
= kmalloc(sizeof(*res
), GFP_KERNEL
);
439 /* Allocate all the cg_cgroup_link objects that we'll need */
440 if (allocate_cg_links(root_count
, &tmp_cg_links
) < 0) {
445 atomic_set(&res
->refcount
, 1);
446 INIT_LIST_HEAD(&res
->cg_links
);
447 INIT_LIST_HEAD(&res
->tasks
);
448 INIT_HLIST_NODE(&res
->hlist
);
450 /* Copy the set of subsystem state objects generated in
451 * find_existing_css_set() */
452 memcpy(res
->subsys
, template, sizeof(res
->subsys
));
454 write_lock(&css_set_lock
);
455 /* Add reference counts and links from the new css_set. */
456 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
457 struct cgroup
*cgrp
= res
->subsys
[i
]->cgroup
;
458 struct cgroup_subsys
*ss
= subsys
[i
];
459 atomic_inc(&cgrp
->count
);
461 * We want to add a link once per cgroup, so we
462 * only do it for the first subsystem in each
465 if (ss
->root
->subsys_list
.next
== &ss
->sibling
)
466 link_css_set(&tmp_cg_links
, res
, cgrp
);
468 if (list_empty(&rootnode
.subsys_list
))
469 link_css_set(&tmp_cg_links
, res
, dummytop
);
471 BUG_ON(!list_empty(&tmp_cg_links
));
475 /* Add this cgroup group to the hash table */
476 hhead
= css_set_hash(res
->subsys
);
477 hlist_add_head(&res
->hlist
, hhead
);
479 write_unlock(&css_set_lock
);
485 * There is one global cgroup mutex. We also require taking
486 * task_lock() when dereferencing a task's cgroup subsys pointers.
487 * See "The task_lock() exception", at the end of this comment.
489 * A task must hold cgroup_mutex to modify cgroups.
491 * Any task can increment and decrement the count field without lock.
492 * So in general, code holding cgroup_mutex can't rely on the count
493 * field not changing. However, if the count goes to zero, then only
494 * cgroup_attach_task() can increment it again. Because a count of zero
495 * means that no tasks are currently attached, therefore there is no
496 * way a task attached to that cgroup can fork (the other way to
497 * increment the count). So code holding cgroup_mutex can safely
498 * assume that if the count is zero, it will stay zero. Similarly, if
499 * a task holds cgroup_mutex on a cgroup with zero count, it
500 * knows that the cgroup won't be removed, as cgroup_rmdir()
503 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
504 * (usually) take cgroup_mutex. These are the two most performance
505 * critical pieces of code here. The exception occurs on cgroup_exit(),
506 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
507 * is taken, and if the cgroup count is zero, a usermode call made
508 * to the release agent with the name of the cgroup (path relative to
509 * the root of cgroup file system) as the argument.
511 * A cgroup can only be deleted if both its 'count' of using tasks
512 * is zero, and its list of 'children' cgroups is empty. Since all
513 * tasks in the system use _some_ cgroup, and since there is always at
514 * least one task in the system (init, pid == 1), therefore, top_cgroup
515 * always has either children cgroups and/or using tasks. So we don't
516 * need a special hack to ensure that top_cgroup cannot be deleted.
518 * The task_lock() exception
520 * The need for this exception arises from the action of
521 * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
522 * another. It does so using cgroup_mutex, however there are
523 * several performance critical places that need to reference
524 * task->cgroup without the expense of grabbing a system global
525 * mutex. Therefore except as noted below, when dereferencing or, as
526 * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
527 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
528 * the task_struct routinely used for such matters.
530 * P.S. One more locking exception. RCU is used to guard the
531 * update of a tasks cgroup pointer by cgroup_attach_task()
535 * cgroup_lock - lock out any changes to cgroup structures
538 void cgroup_lock(void)
540 mutex_lock(&cgroup_mutex
);
544 * cgroup_unlock - release lock on cgroup changes
546 * Undo the lock taken in a previous cgroup_lock() call.
548 void cgroup_unlock(void)
550 mutex_unlock(&cgroup_mutex
);
554 * A couple of forward declarations required, due to cyclic reference loop:
555 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
556 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
560 static int cgroup_mkdir(struct inode
*dir
, struct dentry
*dentry
, int mode
);
561 static int cgroup_rmdir(struct inode
*unused_dir
, struct dentry
*dentry
);
562 static int cgroup_populate_dir(struct cgroup
*cgrp
);
563 static struct inode_operations cgroup_dir_inode_operations
;
564 static struct file_operations proc_cgroupstats_operations
;
566 static struct backing_dev_info cgroup_backing_dev_info
= {
567 .capabilities
= BDI_CAP_NO_ACCT_AND_WRITEBACK
,
570 static struct inode
*cgroup_new_inode(mode_t mode
, struct super_block
*sb
)
572 struct inode
*inode
= new_inode(sb
);
575 inode
->i_mode
= mode
;
576 inode
->i_uid
= current_fsuid();
577 inode
->i_gid
= current_fsgid();
578 inode
->i_atime
= inode
->i_mtime
= inode
->i_ctime
= CURRENT_TIME
;
579 inode
->i_mapping
->backing_dev_info
= &cgroup_backing_dev_info
;
585 * Call subsys's pre_destroy handler.
586 * This is called before css refcnt check.
588 static void cgroup_call_pre_destroy(struct cgroup
*cgrp
)
590 struct cgroup_subsys
*ss
;
591 for_each_subsys(cgrp
->root
, ss
)
593 ss
->pre_destroy(ss
, cgrp
);
597 static void cgroup_diput(struct dentry
*dentry
, struct inode
*inode
)
599 /* is dentry a directory ? if so, kfree() associated cgroup */
600 if (S_ISDIR(inode
->i_mode
)) {
601 struct cgroup
*cgrp
= dentry
->d_fsdata
;
602 struct cgroup_subsys
*ss
;
603 BUG_ON(!(cgroup_is_removed(cgrp
)));
604 /* It's possible for external users to be holding css
605 * reference counts on a cgroup; css_put() needs to
606 * be able to access the cgroup after decrementing
607 * the reference count in order to know if it needs to
608 * queue the cgroup to be handled by the release
612 mutex_lock(&cgroup_mutex
);
614 * Release the subsystem state objects.
616 for_each_subsys(cgrp
->root
, ss
)
617 ss
->destroy(ss
, cgrp
);
619 cgrp
->root
->number_of_cgroups
--;
620 mutex_unlock(&cgroup_mutex
);
622 /* Drop the active superblock reference that we took when we
623 * created the cgroup */
624 deactivate_super(cgrp
->root
->sb
);
631 static void remove_dir(struct dentry
*d
)
633 struct dentry
*parent
= dget(d
->d_parent
);
636 simple_rmdir(parent
->d_inode
, d
);
640 static void cgroup_clear_directory(struct dentry
*dentry
)
642 struct list_head
*node
;
644 BUG_ON(!mutex_is_locked(&dentry
->d_inode
->i_mutex
));
645 spin_lock(&dcache_lock
);
646 node
= dentry
->d_subdirs
.next
;
647 while (node
!= &dentry
->d_subdirs
) {
648 struct dentry
*d
= list_entry(node
, struct dentry
, d_u
.d_child
);
651 /* This should never be called on a cgroup
652 * directory with child cgroups */
653 BUG_ON(d
->d_inode
->i_mode
& S_IFDIR
);
655 spin_unlock(&dcache_lock
);
657 simple_unlink(dentry
->d_inode
, d
);
659 spin_lock(&dcache_lock
);
661 node
= dentry
->d_subdirs
.next
;
663 spin_unlock(&dcache_lock
);
667 * NOTE : the dentry must have been dget()'ed
669 static void cgroup_d_remove_dir(struct dentry
*dentry
)
671 cgroup_clear_directory(dentry
);
673 spin_lock(&dcache_lock
);
674 list_del_init(&dentry
->d_u
.d_child
);
675 spin_unlock(&dcache_lock
);
679 static int rebind_subsystems(struct cgroupfs_root
*root
,
680 unsigned long final_bits
)
682 unsigned long added_bits
, removed_bits
;
683 struct cgroup
*cgrp
= &root
->top_cgroup
;
686 removed_bits
= root
->actual_subsys_bits
& ~final_bits
;
687 added_bits
= final_bits
& ~root
->actual_subsys_bits
;
688 /* Check that any added subsystems are currently free */
689 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
690 unsigned long bit
= 1UL << i
;
691 struct cgroup_subsys
*ss
= subsys
[i
];
692 if (!(bit
& added_bits
))
694 if (ss
->root
!= &rootnode
) {
695 /* Subsystem isn't free */
700 /* Currently we don't handle adding/removing subsystems when
701 * any child cgroups exist. This is theoretically supportable
702 * but involves complex error handling, so it's being left until
704 if (root
->number_of_cgroups
> 1)
707 /* Process each subsystem */
708 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
709 struct cgroup_subsys
*ss
= subsys
[i
];
710 unsigned long bit
= 1UL << i
;
711 if (bit
& added_bits
) {
712 /* We're binding this subsystem to this hierarchy */
713 BUG_ON(cgrp
->subsys
[i
]);
714 BUG_ON(!dummytop
->subsys
[i
]);
715 BUG_ON(dummytop
->subsys
[i
]->cgroup
!= dummytop
);
716 cgrp
->subsys
[i
] = dummytop
->subsys
[i
];
717 cgrp
->subsys
[i
]->cgroup
= cgrp
;
718 list_move(&ss
->sibling
, &root
->subsys_list
);
723 } else if (bit
& removed_bits
) {
724 /* We're removing this subsystem */
725 BUG_ON(cgrp
->subsys
[i
] != dummytop
->subsys
[i
]);
726 BUG_ON(cgrp
->subsys
[i
]->cgroup
!= cgrp
);
728 ss
->bind(ss
, dummytop
);
729 dummytop
->subsys
[i
]->cgroup
= dummytop
;
730 cgrp
->subsys
[i
] = NULL
;
731 subsys
[i
]->root
= &rootnode
;
732 list_move(&ss
->sibling
, &rootnode
.subsys_list
);
733 } else if (bit
& final_bits
) {
734 /* Subsystem state should already exist */
735 BUG_ON(!cgrp
->subsys
[i
]);
737 /* Subsystem state shouldn't exist */
738 BUG_ON(cgrp
->subsys
[i
]);
741 root
->subsys_bits
= root
->actual_subsys_bits
= final_bits
;
747 static int cgroup_show_options(struct seq_file
*seq
, struct vfsmount
*vfs
)
749 struct cgroupfs_root
*root
= vfs
->mnt_sb
->s_fs_info
;
750 struct cgroup_subsys
*ss
;
752 mutex_lock(&cgroup_mutex
);
753 for_each_subsys(root
, ss
)
754 seq_printf(seq
, ",%s", ss
->name
);
755 if (test_bit(ROOT_NOPREFIX
, &root
->flags
))
756 seq_puts(seq
, ",noprefix");
757 if (strlen(root
->release_agent_path
))
758 seq_printf(seq
, ",release_agent=%s", root
->release_agent_path
);
759 mutex_unlock(&cgroup_mutex
);
763 struct cgroup_sb_opts
{
764 unsigned long subsys_bits
;
769 /* Convert a hierarchy specifier into a bitmask of subsystems and
771 static int parse_cgroupfs_options(char *data
,
772 struct cgroup_sb_opts
*opts
)
774 char *token
, *o
= data
?: "all";
776 opts
->subsys_bits
= 0;
778 opts
->release_agent
= NULL
;
780 while ((token
= strsep(&o
, ",")) != NULL
) {
783 if (!strcmp(token
, "all")) {
784 /* Add all non-disabled subsystems */
786 opts
->subsys_bits
= 0;
787 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
788 struct cgroup_subsys
*ss
= subsys
[i
];
790 opts
->subsys_bits
|= 1ul << i
;
792 } else if (!strcmp(token
, "noprefix")) {
793 set_bit(ROOT_NOPREFIX
, &opts
->flags
);
794 } else if (!strncmp(token
, "release_agent=", 14)) {
795 /* Specifying two release agents is forbidden */
796 if (opts
->release_agent
)
798 opts
->release_agent
= kzalloc(PATH_MAX
, GFP_KERNEL
);
799 if (!opts
->release_agent
)
801 strncpy(opts
->release_agent
, token
+ 14, PATH_MAX
- 1);
802 opts
->release_agent
[PATH_MAX
- 1] = 0;
804 struct cgroup_subsys
*ss
;
806 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
808 if (!strcmp(token
, ss
->name
)) {
810 set_bit(i
, &opts
->subsys_bits
);
814 if (i
== CGROUP_SUBSYS_COUNT
)
819 /* We can't have an empty hierarchy */
820 if (!opts
->subsys_bits
)
826 static int cgroup_remount(struct super_block
*sb
, int *flags
, char *data
)
829 struct cgroupfs_root
*root
= sb
->s_fs_info
;
830 struct cgroup
*cgrp
= &root
->top_cgroup
;
831 struct cgroup_sb_opts opts
;
833 mutex_lock(&cgrp
->dentry
->d_inode
->i_mutex
);
834 mutex_lock(&cgroup_mutex
);
836 /* See what subsystems are wanted */
837 ret
= parse_cgroupfs_options(data
, &opts
);
841 /* Don't allow flags to change at remount */
842 if (opts
.flags
!= root
->flags
) {
847 ret
= rebind_subsystems(root
, opts
.subsys_bits
);
849 /* (re)populate subsystem files */
851 cgroup_populate_dir(cgrp
);
853 if (opts
.release_agent
)
854 strcpy(root
->release_agent_path
, opts
.release_agent
);
856 if (opts
.release_agent
)
857 kfree(opts
.release_agent
);
858 mutex_unlock(&cgroup_mutex
);
859 mutex_unlock(&cgrp
->dentry
->d_inode
->i_mutex
);
863 static struct super_operations cgroup_ops
= {
864 .statfs
= simple_statfs
,
865 .drop_inode
= generic_delete_inode
,
866 .show_options
= cgroup_show_options
,
867 .remount_fs
= cgroup_remount
,
870 static void init_cgroup_housekeeping(struct cgroup
*cgrp
)
872 INIT_LIST_HEAD(&cgrp
->sibling
);
873 INIT_LIST_HEAD(&cgrp
->children
);
874 INIT_LIST_HEAD(&cgrp
->css_sets
);
875 INIT_LIST_HEAD(&cgrp
->release_list
);
876 init_rwsem(&cgrp
->pids_mutex
);
878 static void init_cgroup_root(struct cgroupfs_root
*root
)
880 struct cgroup
*cgrp
= &root
->top_cgroup
;
881 INIT_LIST_HEAD(&root
->subsys_list
);
882 INIT_LIST_HEAD(&root
->root_list
);
883 root
->number_of_cgroups
= 1;
885 cgrp
->top_cgroup
= cgrp
;
886 init_cgroup_housekeeping(cgrp
);
889 static int cgroup_test_super(struct super_block
*sb
, void *data
)
891 struct cgroupfs_root
*new = data
;
892 struct cgroupfs_root
*root
= sb
->s_fs_info
;
894 /* First check subsystems */
895 if (new->subsys_bits
!= root
->subsys_bits
)
898 /* Next check flags */
899 if (new->flags
!= root
->flags
)
905 static int cgroup_set_super(struct super_block
*sb
, void *data
)
908 struct cgroupfs_root
*root
= data
;
910 ret
= set_anon_super(sb
, NULL
);
914 sb
->s_fs_info
= root
;
917 sb
->s_blocksize
= PAGE_CACHE_SIZE
;
918 sb
->s_blocksize_bits
= PAGE_CACHE_SHIFT
;
919 sb
->s_magic
= CGROUP_SUPER_MAGIC
;
920 sb
->s_op
= &cgroup_ops
;
925 static int cgroup_get_rootdir(struct super_block
*sb
)
927 struct inode
*inode
=
928 cgroup_new_inode(S_IFDIR
| S_IRUGO
| S_IXUGO
| S_IWUSR
, sb
);
929 struct dentry
*dentry
;
934 inode
->i_fop
= &simple_dir_operations
;
935 inode
->i_op
= &cgroup_dir_inode_operations
;
936 /* directories start off with i_nlink == 2 (for "." entry) */
938 dentry
= d_alloc_root(inode
);
947 static int cgroup_get_sb(struct file_system_type
*fs_type
,
948 int flags
, const char *unused_dev_name
,
949 void *data
, struct vfsmount
*mnt
)
951 struct cgroup_sb_opts opts
;
953 struct super_block
*sb
;
954 struct cgroupfs_root
*root
;
955 struct list_head tmp_cg_links
;
957 /* First find the desired set of subsystems */
958 ret
= parse_cgroupfs_options(data
, &opts
);
960 if (opts
.release_agent
)
961 kfree(opts
.release_agent
);
965 root
= kzalloc(sizeof(*root
), GFP_KERNEL
);
967 if (opts
.release_agent
)
968 kfree(opts
.release_agent
);
972 init_cgroup_root(root
);
973 root
->subsys_bits
= opts
.subsys_bits
;
974 root
->flags
= opts
.flags
;
975 if (opts
.release_agent
) {
976 strcpy(root
->release_agent_path
, opts
.release_agent
);
977 kfree(opts
.release_agent
);
980 sb
= sget(fs_type
, cgroup_test_super
, cgroup_set_super
, root
);
987 if (sb
->s_fs_info
!= root
) {
988 /* Reusing an existing superblock */
989 BUG_ON(sb
->s_root
== NULL
);
994 struct cgroup
*root_cgrp
= &root
->top_cgroup
;
998 BUG_ON(sb
->s_root
!= NULL
);
1000 ret
= cgroup_get_rootdir(sb
);
1002 goto drop_new_super
;
1003 inode
= sb
->s_root
->d_inode
;
1005 mutex_lock(&inode
->i_mutex
);
1006 mutex_lock(&cgroup_mutex
);
1009 * We're accessing css_set_count without locking
1010 * css_set_lock here, but that's OK - it can only be
1011 * increased by someone holding cgroup_lock, and
1012 * that's us. The worst that can happen is that we
1013 * have some link structures left over
1015 ret
= allocate_cg_links(css_set_count
, &tmp_cg_links
);
1017 mutex_unlock(&cgroup_mutex
);
1018 mutex_unlock(&inode
->i_mutex
);
1019 goto drop_new_super
;
1022 ret
= rebind_subsystems(root
, root
->subsys_bits
);
1023 if (ret
== -EBUSY
) {
1024 mutex_unlock(&cgroup_mutex
);
1025 mutex_unlock(&inode
->i_mutex
);
1029 /* EBUSY should be the only error here */
1032 list_add(&root
->root_list
, &roots
);
1035 sb
->s_root
->d_fsdata
= root_cgrp
;
1036 root
->top_cgroup
.dentry
= sb
->s_root
;
1038 /* Link the top cgroup in this hierarchy into all
1039 * the css_set objects */
1040 write_lock(&css_set_lock
);
1041 for (i
= 0; i
< CSS_SET_TABLE_SIZE
; i
++) {
1042 struct hlist_head
*hhead
= &css_set_table
[i
];
1043 struct hlist_node
*node
;
1046 hlist_for_each_entry(cg
, node
, hhead
, hlist
)
1047 link_css_set(&tmp_cg_links
, cg
, root_cgrp
);
1049 write_unlock(&css_set_lock
);
1051 free_cg_links(&tmp_cg_links
);
1053 BUG_ON(!list_empty(&root_cgrp
->sibling
));
1054 BUG_ON(!list_empty(&root_cgrp
->children
));
1055 BUG_ON(root
->number_of_cgroups
!= 1);
1057 cgroup_populate_dir(root_cgrp
);
1058 mutex_unlock(&inode
->i_mutex
);
1059 mutex_unlock(&cgroup_mutex
);
1062 return simple_set_mnt(mnt
, sb
);
1065 free_cg_links(&tmp_cg_links
);
1067 up_write(&sb
->s_umount
);
1068 deactivate_super(sb
);
1072 static void cgroup_kill_sb(struct super_block
*sb
) {
1073 struct cgroupfs_root
*root
= sb
->s_fs_info
;
1074 struct cgroup
*cgrp
= &root
->top_cgroup
;
1076 struct cg_cgroup_link
*link
;
1077 struct cg_cgroup_link
*saved_link
;
1081 BUG_ON(root
->number_of_cgroups
!= 1);
1082 BUG_ON(!list_empty(&cgrp
->children
));
1083 BUG_ON(!list_empty(&cgrp
->sibling
));
1085 mutex_lock(&cgroup_mutex
);
1087 /* Rebind all subsystems back to the default hierarchy */
1088 ret
= rebind_subsystems(root
, 0);
1089 /* Shouldn't be able to fail ... */
1093 * Release all the links from css_sets to this hierarchy's
1096 write_lock(&css_set_lock
);
1098 list_for_each_entry_safe(link
, saved_link
, &cgrp
->css_sets
,
1100 list_del(&link
->cg_link_list
);
1101 list_del(&link
->cgrp_link_list
);
1104 write_unlock(&css_set_lock
);
1106 list_del(&root
->root_list
);
1109 mutex_unlock(&cgroup_mutex
);
1112 kill_litter_super(sb
);
1115 static struct file_system_type cgroup_fs_type
= {
1117 .get_sb
= cgroup_get_sb
,
1118 .kill_sb
= cgroup_kill_sb
,
1121 static inline struct cgroup
*__d_cgrp(struct dentry
*dentry
)
1123 return dentry
->d_fsdata
;
1126 static inline struct cftype
*__d_cft(struct dentry
*dentry
)
1128 return dentry
->d_fsdata
;
1132 * cgroup_path - generate the path of a cgroup
1133 * @cgrp: the cgroup in question
1134 * @buf: the buffer to write the path into
1135 * @buflen: the length of the buffer
1137 * Called with cgroup_mutex held. Writes path of cgroup into buf.
1138 * Returns 0 on success, -errno on error.
1140 int cgroup_path(const struct cgroup
*cgrp
, char *buf
, int buflen
)
1144 if (cgrp
== dummytop
) {
1146 * Inactive subsystems have no dentry for their root
1153 start
= buf
+ buflen
;
1157 int len
= cgrp
->dentry
->d_name
.len
;
1158 if ((start
-= len
) < buf
)
1159 return -ENAMETOOLONG
;
1160 memcpy(start
, cgrp
->dentry
->d_name
.name
, len
);
1161 cgrp
= cgrp
->parent
;
1167 return -ENAMETOOLONG
;
1170 memmove(buf
, start
, buf
+ buflen
- start
);
1175 * Return the first subsystem attached to a cgroup's hierarchy, and
1179 static void get_first_subsys(const struct cgroup
*cgrp
,
1180 struct cgroup_subsys_state
**css
, int *subsys_id
)
1182 const struct cgroupfs_root
*root
= cgrp
->root
;
1183 const struct cgroup_subsys
*test_ss
;
1184 BUG_ON(list_empty(&root
->subsys_list
));
1185 test_ss
= list_entry(root
->subsys_list
.next
,
1186 struct cgroup_subsys
, sibling
);
1188 *css
= cgrp
->subsys
[test_ss
->subsys_id
];
1192 *subsys_id
= test_ss
->subsys_id
;
1196 * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
1197 * @cgrp: the cgroup the task is attaching to
1198 * @tsk: the task to be attached
1200 * Call holding cgroup_mutex. May take task_lock of
1201 * the task 'tsk' during call.
1203 int cgroup_attach_task(struct cgroup
*cgrp
, struct task_struct
*tsk
)
1206 struct cgroup_subsys
*ss
;
1207 struct cgroup
*oldcgrp
;
1209 struct css_set
*newcg
;
1210 struct cgroupfs_root
*root
= cgrp
->root
;
1213 get_first_subsys(cgrp
, NULL
, &subsys_id
);
1215 /* Nothing to do if the task is already in that cgroup */
1216 oldcgrp
= task_cgroup(tsk
, subsys_id
);
1217 if (cgrp
== oldcgrp
)
1220 for_each_subsys(root
, ss
) {
1221 if (ss
->can_attach
) {
1222 retval
= ss
->can_attach(ss
, cgrp
, tsk
);
1233 * Locate or allocate a new css_set for this task,
1234 * based on its final set of cgroups
1236 newcg
= find_css_set(cg
, cgrp
);
1242 if (tsk
->flags
& PF_EXITING
) {
1247 rcu_assign_pointer(tsk
->cgroups
, newcg
);
1250 /* Update the css_set linked lists if we're using them */
1251 write_lock(&css_set_lock
);
1252 if (!list_empty(&tsk
->cg_list
)) {
1253 list_del(&tsk
->cg_list
);
1254 list_add(&tsk
->cg_list
, &newcg
->tasks
);
1256 write_unlock(&css_set_lock
);
1258 for_each_subsys(root
, ss
) {
1260 ss
->attach(ss
, cgrp
, oldcgrp
, tsk
);
1262 set_bit(CGRP_RELEASABLE
, &oldcgrp
->flags
);
1269 * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex
1270 * held. May take task_lock of task
1272 static int attach_task_by_pid(struct cgroup
*cgrp
, u64 pid
)
1274 struct task_struct
*tsk
;
1275 const struct cred
*cred
= current_cred(), *tcred
;
1280 tsk
= find_task_by_vpid(pid
);
1281 if (!tsk
|| tsk
->flags
& PF_EXITING
) {
1286 tcred
= __task_cred(tsk
);
1288 cred
->euid
!= tcred
->uid
&&
1289 cred
->euid
!= tcred
->suid
) {
1293 get_task_struct(tsk
);
1297 get_task_struct(tsk
);
1300 ret
= cgroup_attach_task(cgrp
, tsk
);
1301 put_task_struct(tsk
);
1305 static int cgroup_tasks_write(struct cgroup
*cgrp
, struct cftype
*cft
, u64 pid
)
1308 if (!cgroup_lock_live_group(cgrp
))
1310 ret
= attach_task_by_pid(cgrp
, pid
);
1315 /* The various types of files and directories in a cgroup file system */
1316 enum cgroup_filetype
{
1320 FILE_NOTIFY_ON_RELEASE
,
1325 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
1326 * @cgrp: the cgroup to be checked for liveness
1328 * On success, returns true; the lock should be later released with
1329 * cgroup_unlock(). On failure returns false with no lock held.
1331 bool cgroup_lock_live_group(struct cgroup
*cgrp
)
1333 mutex_lock(&cgroup_mutex
);
1334 if (cgroup_is_removed(cgrp
)) {
1335 mutex_unlock(&cgroup_mutex
);
1341 static int cgroup_release_agent_write(struct cgroup
*cgrp
, struct cftype
*cft
,
1344 BUILD_BUG_ON(sizeof(cgrp
->root
->release_agent_path
) < PATH_MAX
);
1345 if (!cgroup_lock_live_group(cgrp
))
1347 strcpy(cgrp
->root
->release_agent_path
, buffer
);
1352 static int cgroup_release_agent_show(struct cgroup
*cgrp
, struct cftype
*cft
,
1353 struct seq_file
*seq
)
1355 if (!cgroup_lock_live_group(cgrp
))
1357 seq_puts(seq
, cgrp
->root
->release_agent_path
);
1358 seq_putc(seq
, '\n');
1363 /* A buffer size big enough for numbers or short strings */
1364 #define CGROUP_LOCAL_BUFFER_SIZE 64
1366 static ssize_t
cgroup_write_X64(struct cgroup
*cgrp
, struct cftype
*cft
,
1368 const char __user
*userbuf
,
1369 size_t nbytes
, loff_t
*unused_ppos
)
1371 char buffer
[CGROUP_LOCAL_BUFFER_SIZE
];
1377 if (nbytes
>= sizeof(buffer
))
1379 if (copy_from_user(buffer
, userbuf
, nbytes
))
1382 buffer
[nbytes
] = 0; /* nul-terminate */
1384 if (cft
->write_u64
) {
1385 u64 val
= simple_strtoull(buffer
, &end
, 0);
1388 retval
= cft
->write_u64(cgrp
, cft
, val
);
1390 s64 val
= simple_strtoll(buffer
, &end
, 0);
1393 retval
= cft
->write_s64(cgrp
, cft
, val
);
1400 static ssize_t
cgroup_write_string(struct cgroup
*cgrp
, struct cftype
*cft
,
1402 const char __user
*userbuf
,
1403 size_t nbytes
, loff_t
*unused_ppos
)
1405 char local_buffer
[CGROUP_LOCAL_BUFFER_SIZE
];
1407 size_t max_bytes
= cft
->max_write_len
;
1408 char *buffer
= local_buffer
;
1411 max_bytes
= sizeof(local_buffer
) - 1;
1412 if (nbytes
>= max_bytes
)
1414 /* Allocate a dynamic buffer if we need one */
1415 if (nbytes
>= sizeof(local_buffer
)) {
1416 buffer
= kmalloc(nbytes
+ 1, GFP_KERNEL
);
1420 if (nbytes
&& copy_from_user(buffer
, userbuf
, nbytes
)) {
1425 buffer
[nbytes
] = 0; /* nul-terminate */
1427 retval
= cft
->write_string(cgrp
, cft
, buffer
);
1431 if (buffer
!= local_buffer
)
1436 static ssize_t
cgroup_file_write(struct file
*file
, const char __user
*buf
,
1437 size_t nbytes
, loff_t
*ppos
)
1439 struct cftype
*cft
= __d_cft(file
->f_dentry
);
1440 struct cgroup
*cgrp
= __d_cgrp(file
->f_dentry
->d_parent
);
1442 if (cgroup_is_removed(cgrp
))
1445 return cft
->write(cgrp
, cft
, file
, buf
, nbytes
, ppos
);
1446 if (cft
->write_u64
|| cft
->write_s64
)
1447 return cgroup_write_X64(cgrp
, cft
, file
, buf
, nbytes
, ppos
);
1448 if (cft
->write_string
)
1449 return cgroup_write_string(cgrp
, cft
, file
, buf
, nbytes
, ppos
);
1451 int ret
= cft
->trigger(cgrp
, (unsigned int)cft
->private);
1452 return ret
? ret
: nbytes
;
1457 static ssize_t
cgroup_read_u64(struct cgroup
*cgrp
, struct cftype
*cft
,
1459 char __user
*buf
, size_t nbytes
,
1462 char tmp
[CGROUP_LOCAL_BUFFER_SIZE
];
1463 u64 val
= cft
->read_u64(cgrp
, cft
);
1464 int len
= sprintf(tmp
, "%llu\n", (unsigned long long) val
);
1466 return simple_read_from_buffer(buf
, nbytes
, ppos
, tmp
, len
);
1469 static ssize_t
cgroup_read_s64(struct cgroup
*cgrp
, struct cftype
*cft
,
1471 char __user
*buf
, size_t nbytes
,
1474 char tmp
[CGROUP_LOCAL_BUFFER_SIZE
];
1475 s64 val
= cft
->read_s64(cgrp
, cft
);
1476 int len
= sprintf(tmp
, "%lld\n", (long long) val
);
1478 return simple_read_from_buffer(buf
, nbytes
, ppos
, tmp
, len
);
1481 static ssize_t
cgroup_file_read(struct file
*file
, char __user
*buf
,
1482 size_t nbytes
, loff_t
*ppos
)
1484 struct cftype
*cft
= __d_cft(file
->f_dentry
);
1485 struct cgroup
*cgrp
= __d_cgrp(file
->f_dentry
->d_parent
);
1487 if (cgroup_is_removed(cgrp
))
1491 return cft
->read(cgrp
, cft
, file
, buf
, nbytes
, ppos
);
1493 return cgroup_read_u64(cgrp
, cft
, file
, buf
, nbytes
, ppos
);
1495 return cgroup_read_s64(cgrp
, cft
, file
, buf
, nbytes
, ppos
);
1500 * seqfile ops/methods for returning structured data. Currently just
1501 * supports string->u64 maps, but can be extended in future.
1504 struct cgroup_seqfile_state
{
1506 struct cgroup
*cgroup
;
1509 static int cgroup_map_add(struct cgroup_map_cb
*cb
, const char *key
, u64 value
)
1511 struct seq_file
*sf
= cb
->state
;
1512 return seq_printf(sf
, "%s %llu\n", key
, (unsigned long long)value
);
1515 static int cgroup_seqfile_show(struct seq_file
*m
, void *arg
)
1517 struct cgroup_seqfile_state
*state
= m
->private;
1518 struct cftype
*cft
= state
->cft
;
1519 if (cft
->read_map
) {
1520 struct cgroup_map_cb cb
= {
1521 .fill
= cgroup_map_add
,
1524 return cft
->read_map(state
->cgroup
, cft
, &cb
);
1526 return cft
->read_seq_string(state
->cgroup
, cft
, m
);
1529 static int cgroup_seqfile_release(struct inode
*inode
, struct file
*file
)
1531 struct seq_file
*seq
= file
->private_data
;
1532 kfree(seq
->private);
1533 return single_release(inode
, file
);
1536 static struct file_operations cgroup_seqfile_operations
= {
1538 .write
= cgroup_file_write
,
1539 .llseek
= seq_lseek
,
1540 .release
= cgroup_seqfile_release
,
1543 static int cgroup_file_open(struct inode
*inode
, struct file
*file
)
1548 err
= generic_file_open(inode
, file
);
1551 cft
= __d_cft(file
->f_dentry
);
1553 if (cft
->read_map
|| cft
->read_seq_string
) {
1554 struct cgroup_seqfile_state
*state
=
1555 kzalloc(sizeof(*state
), GFP_USER
);
1559 state
->cgroup
= __d_cgrp(file
->f_dentry
->d_parent
);
1560 file
->f_op
= &cgroup_seqfile_operations
;
1561 err
= single_open(file
, cgroup_seqfile_show
, state
);
1564 } else if (cft
->open
)
1565 err
= cft
->open(inode
, file
);
1572 static int cgroup_file_release(struct inode
*inode
, struct file
*file
)
1574 struct cftype
*cft
= __d_cft(file
->f_dentry
);
1576 return cft
->release(inode
, file
);
1581 * cgroup_rename - Only allow simple rename of directories in place.
1583 static int cgroup_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
1584 struct inode
*new_dir
, struct dentry
*new_dentry
)
1586 if (!S_ISDIR(old_dentry
->d_inode
->i_mode
))
1588 if (new_dentry
->d_inode
)
1590 if (old_dir
!= new_dir
)
1592 return simple_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
1595 static struct file_operations cgroup_file_operations
= {
1596 .read
= cgroup_file_read
,
1597 .write
= cgroup_file_write
,
1598 .llseek
= generic_file_llseek
,
1599 .open
= cgroup_file_open
,
1600 .release
= cgroup_file_release
,
1603 static struct inode_operations cgroup_dir_inode_operations
= {
1604 .lookup
= simple_lookup
,
1605 .mkdir
= cgroup_mkdir
,
1606 .rmdir
= cgroup_rmdir
,
1607 .rename
= cgroup_rename
,
1610 static int cgroup_create_file(struct dentry
*dentry
, int mode
,
1611 struct super_block
*sb
)
1613 static struct dentry_operations cgroup_dops
= {
1614 .d_iput
= cgroup_diput
,
1617 struct inode
*inode
;
1621 if (dentry
->d_inode
)
1624 inode
= cgroup_new_inode(mode
, sb
);
1628 if (S_ISDIR(mode
)) {
1629 inode
->i_op
= &cgroup_dir_inode_operations
;
1630 inode
->i_fop
= &simple_dir_operations
;
1632 /* start off with i_nlink == 2 (for "." entry) */
1635 /* start with the directory inode held, so that we can
1636 * populate it without racing with another mkdir */
1637 mutex_lock_nested(&inode
->i_mutex
, I_MUTEX_CHILD
);
1638 } else if (S_ISREG(mode
)) {
1640 inode
->i_fop
= &cgroup_file_operations
;
1642 dentry
->d_op
= &cgroup_dops
;
1643 d_instantiate(dentry
, inode
);
1644 dget(dentry
); /* Extra count - pin the dentry in core */
1649 * cgroup_create_dir - create a directory for an object.
1650 * @cgrp: the cgroup we create the directory for. It must have a valid
1651 * ->parent field. And we are going to fill its ->dentry field.
1652 * @dentry: dentry of the new cgroup
1653 * @mode: mode to set on new directory.
1655 static int cgroup_create_dir(struct cgroup
*cgrp
, struct dentry
*dentry
,
1658 struct dentry
*parent
;
1661 parent
= cgrp
->parent
->dentry
;
1662 error
= cgroup_create_file(dentry
, S_IFDIR
| mode
, cgrp
->root
->sb
);
1664 dentry
->d_fsdata
= cgrp
;
1665 inc_nlink(parent
->d_inode
);
1666 cgrp
->dentry
= dentry
;
1674 int cgroup_add_file(struct cgroup
*cgrp
,
1675 struct cgroup_subsys
*subsys
,
1676 const struct cftype
*cft
)
1678 struct dentry
*dir
= cgrp
->dentry
;
1679 struct dentry
*dentry
;
1682 char name
[MAX_CGROUP_TYPE_NAMELEN
+ MAX_CFTYPE_NAME
+ 2] = { 0 };
1683 if (subsys
&& !test_bit(ROOT_NOPREFIX
, &cgrp
->root
->flags
)) {
1684 strcpy(name
, subsys
->name
);
1687 strcat(name
, cft
->name
);
1688 BUG_ON(!mutex_is_locked(&dir
->d_inode
->i_mutex
));
1689 dentry
= lookup_one_len(name
, dir
, strlen(name
));
1690 if (!IS_ERR(dentry
)) {
1691 error
= cgroup_create_file(dentry
, 0644 | S_IFREG
,
1694 dentry
->d_fsdata
= (void *)cft
;
1697 error
= PTR_ERR(dentry
);
1701 int cgroup_add_files(struct cgroup
*cgrp
,
1702 struct cgroup_subsys
*subsys
,
1703 const struct cftype cft
[],
1707 for (i
= 0; i
< count
; i
++) {
1708 err
= cgroup_add_file(cgrp
, subsys
, &cft
[i
]);
1716 * cgroup_task_count - count the number of tasks in a cgroup.
1717 * @cgrp: the cgroup in question
1719 * Return the number of tasks in the cgroup.
1721 int cgroup_task_count(const struct cgroup
*cgrp
)
1724 struct cg_cgroup_link
*link
;
1726 read_lock(&css_set_lock
);
1727 list_for_each_entry(link
, &cgrp
->css_sets
, cgrp_link_list
) {
1728 count
+= atomic_read(&link
->cg
->refcount
);
1730 read_unlock(&css_set_lock
);
1735 * Advance a list_head iterator. The iterator should be positioned at
1736 * the start of a css_set
1738 static void cgroup_advance_iter(struct cgroup
*cgrp
,
1739 struct cgroup_iter
*it
)
1741 struct list_head
*l
= it
->cg_link
;
1742 struct cg_cgroup_link
*link
;
1745 /* Advance to the next non-empty css_set */
1748 if (l
== &cgrp
->css_sets
) {
1752 link
= list_entry(l
, struct cg_cgroup_link
, cgrp_link_list
);
1754 } while (list_empty(&cg
->tasks
));
1756 it
->task
= cg
->tasks
.next
;
1760 * To reduce the fork() overhead for systems that are not actually
1761 * using their cgroups capability, we don't maintain the lists running
1762 * through each css_set to its tasks until we see the list actually
1763 * used - in other words after the first call to cgroup_iter_start().
1765 * The tasklist_lock is not held here, as do_each_thread() and
1766 * while_each_thread() are protected by RCU.
1768 static void cgroup_enable_task_cg_lists(void)
1770 struct task_struct
*p
, *g
;
1771 write_lock(&css_set_lock
);
1772 use_task_css_set_links
= 1;
1773 do_each_thread(g
, p
) {
1776 * We should check if the process is exiting, otherwise
1777 * it will race with cgroup_exit() in that the list
1778 * entry won't be deleted though the process has exited.
1780 if (!(p
->flags
& PF_EXITING
) && list_empty(&p
->cg_list
))
1781 list_add(&p
->cg_list
, &p
->cgroups
->tasks
);
1783 } while_each_thread(g
, p
);
1784 write_unlock(&css_set_lock
);
1787 void cgroup_iter_start(struct cgroup
*cgrp
, struct cgroup_iter
*it
)
1790 * The first time anyone tries to iterate across a cgroup,
1791 * we need to enable the list linking each css_set to its
1792 * tasks, and fix up all existing tasks.
1794 if (!use_task_css_set_links
)
1795 cgroup_enable_task_cg_lists();
1797 read_lock(&css_set_lock
);
1798 it
->cg_link
= &cgrp
->css_sets
;
1799 cgroup_advance_iter(cgrp
, it
);
1802 struct task_struct
*cgroup_iter_next(struct cgroup
*cgrp
,
1803 struct cgroup_iter
*it
)
1805 struct task_struct
*res
;
1806 struct list_head
*l
= it
->task
;
1807 struct cg_cgroup_link
*link
;
1809 /* If the iterator cg is NULL, we have no tasks */
1812 res
= list_entry(l
, struct task_struct
, cg_list
);
1813 /* Advance iterator to find next entry */
1815 link
= list_entry(it
->cg_link
, struct cg_cgroup_link
, cgrp_link_list
);
1816 if (l
== &link
->cg
->tasks
) {
1817 /* We reached the end of this task list - move on to
1818 * the next cg_cgroup_link */
1819 cgroup_advance_iter(cgrp
, it
);
1826 void cgroup_iter_end(struct cgroup
*cgrp
, struct cgroup_iter
*it
)
1828 read_unlock(&css_set_lock
);
1831 static inline int started_after_time(struct task_struct
*t1
,
1832 struct timespec
*time
,
1833 struct task_struct
*t2
)
1835 int start_diff
= timespec_compare(&t1
->start_time
, time
);
1836 if (start_diff
> 0) {
1838 } else if (start_diff
< 0) {
1842 * Arbitrarily, if two processes started at the same
1843 * time, we'll say that the lower pointer value
1844 * started first. Note that t2 may have exited by now
1845 * so this may not be a valid pointer any longer, but
1846 * that's fine - it still serves to distinguish
1847 * between two tasks started (effectively) simultaneously.
1854 * This function is a callback from heap_insert() and is used to order
1856 * In this case we order the heap in descending task start time.
1858 static inline int started_after(void *p1
, void *p2
)
1860 struct task_struct
*t1
= p1
;
1861 struct task_struct
*t2
= p2
;
1862 return started_after_time(t1
, &t2
->start_time
, t2
);
1866 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
1867 * @scan: struct cgroup_scanner containing arguments for the scan
1869 * Arguments include pointers to callback functions test_task() and
1871 * Iterate through all the tasks in a cgroup, calling test_task() for each,
1872 * and if it returns true, call process_task() for it also.
1873 * The test_task pointer may be NULL, meaning always true (select all tasks).
1874 * Effectively duplicates cgroup_iter_{start,next,end}()
1875 * but does not lock css_set_lock for the call to process_task().
1876 * The struct cgroup_scanner may be embedded in any structure of the caller's
1878 * It is guaranteed that process_task() will act on every task that
1879 * is a member of the cgroup for the duration of this call. This
1880 * function may or may not call process_task() for tasks that exit
1881 * or move to a different cgroup during the call, or are forked or
1882 * move into the cgroup during the call.
1884 * Note that test_task() may be called with locks held, and may in some
1885 * situations be called multiple times for the same task, so it should
1887 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
1888 * pre-allocated and will be used for heap operations (and its "gt" member will
1889 * be overwritten), else a temporary heap will be used (allocation of which
1890 * may cause this function to fail).
1892 int cgroup_scan_tasks(struct cgroup_scanner
*scan
)
1895 struct cgroup_iter it
;
1896 struct task_struct
*p
, *dropped
;
1897 /* Never dereference latest_task, since it's not refcounted */
1898 struct task_struct
*latest_task
= NULL
;
1899 struct ptr_heap tmp_heap
;
1900 struct ptr_heap
*heap
;
1901 struct timespec latest_time
= { 0, 0 };
1904 /* The caller supplied our heap and pre-allocated its memory */
1906 heap
->gt
= &started_after
;
1908 /* We need to allocate our own heap memory */
1910 retval
= heap_init(heap
, PAGE_SIZE
, GFP_KERNEL
, &started_after
);
1912 /* cannot allocate the heap */
1918 * Scan tasks in the cgroup, using the scanner's "test_task" callback
1919 * to determine which are of interest, and using the scanner's
1920 * "process_task" callback to process any of them that need an update.
1921 * Since we don't want to hold any locks during the task updates,
1922 * gather tasks to be processed in a heap structure.
1923 * The heap is sorted by descending task start time.
1924 * If the statically-sized heap fills up, we overflow tasks that
1925 * started later, and in future iterations only consider tasks that
1926 * started after the latest task in the previous pass. This
1927 * guarantees forward progress and that we don't miss any tasks.
1930 cgroup_iter_start(scan
->cg
, &it
);
1931 while ((p
= cgroup_iter_next(scan
->cg
, &it
))) {
1933 * Only affect tasks that qualify per the caller's callback,
1934 * if he provided one
1936 if (scan
->test_task
&& !scan
->test_task(p
, scan
))
1939 * Only process tasks that started after the last task
1942 if (!started_after_time(p
, &latest_time
, latest_task
))
1944 dropped
= heap_insert(heap
, p
);
1945 if (dropped
== NULL
) {
1947 * The new task was inserted; the heap wasn't
1951 } else if (dropped
!= p
) {
1953 * The new task was inserted, and pushed out a
1957 put_task_struct(dropped
);
1960 * Else the new task was newer than anything already in
1961 * the heap and wasn't inserted
1964 cgroup_iter_end(scan
->cg
, &it
);
1967 for (i
= 0; i
< heap
->size
; i
++) {
1968 struct task_struct
*q
= heap
->ptrs
[i
];
1970 latest_time
= q
->start_time
;
1973 /* Process the task per the caller's callback */
1974 scan
->process_task(q
, scan
);
1978 * If we had to process any tasks at all, scan again
1979 * in case some of them were in the middle of forking
1980 * children that didn't get processed.
1981 * Not the most efficient way to do it, but it avoids
1982 * having to take callback_mutex in the fork path
1986 if (heap
== &tmp_heap
)
1987 heap_free(&tmp_heap
);
1992 * Stuff for reading the 'tasks' file.
1994 * Reading this file can return large amounts of data if a cgroup has
1995 * *lots* of attached tasks. So it may need several calls to read(),
1996 * but we cannot guarantee that the information we produce is correct
1997 * unless we produce it entirely atomically.
2002 * Load into 'pidarray' up to 'npids' of the tasks using cgroup
2003 * 'cgrp'. Return actual number of pids loaded. No need to
2004 * task_lock(p) when reading out p->cgroup, since we're in an RCU
2005 * read section, so the css_set can't go away, and is
2006 * immutable after creation.
2008 static int pid_array_load(pid_t
*pidarray
, int npids
, struct cgroup
*cgrp
)
2011 struct cgroup_iter it
;
2012 struct task_struct
*tsk
;
2013 cgroup_iter_start(cgrp
, &it
);
2014 while ((tsk
= cgroup_iter_next(cgrp
, &it
))) {
2015 if (unlikely(n
== npids
))
2017 pidarray
[n
++] = task_pid_vnr(tsk
);
2019 cgroup_iter_end(cgrp
, &it
);
2024 * cgroupstats_build - build and fill cgroupstats
2025 * @stats: cgroupstats to fill information into
2026 * @dentry: A dentry entry belonging to the cgroup for which stats have
2029 * Build and fill cgroupstats so that taskstats can export it to user
2032 int cgroupstats_build(struct cgroupstats
*stats
, struct dentry
*dentry
)
2035 struct cgroup
*cgrp
;
2036 struct cgroup_iter it
;
2037 struct task_struct
*tsk
;
2040 * Validate dentry by checking the superblock operations,
2041 * and make sure it's a directory.
2043 if (dentry
->d_sb
->s_op
!= &cgroup_ops
||
2044 !S_ISDIR(dentry
->d_inode
->i_mode
))
2048 cgrp
= dentry
->d_fsdata
;
2050 cgroup_iter_start(cgrp
, &it
);
2051 while ((tsk
= cgroup_iter_next(cgrp
, &it
))) {
2052 switch (tsk
->state
) {
2054 stats
->nr_running
++;
2056 case TASK_INTERRUPTIBLE
:
2057 stats
->nr_sleeping
++;
2059 case TASK_UNINTERRUPTIBLE
:
2060 stats
->nr_uninterruptible
++;
2063 stats
->nr_stopped
++;
2066 if (delayacct_is_task_waiting_on_io(tsk
))
2067 stats
->nr_io_wait
++;
2071 cgroup_iter_end(cgrp
, &it
);
2077 static int cmppid(const void *a
, const void *b
)
2079 return *(pid_t
*)a
- *(pid_t
*)b
;
2084 * seq_file methods for the "tasks" file. The seq_file position is the
2085 * next pid to display; the seq_file iterator is a pointer to the pid
2086 * in the cgroup->tasks_pids array.
2089 static void *cgroup_tasks_start(struct seq_file
*s
, loff_t
*pos
)
2092 * Initially we receive a position value that corresponds to
2093 * one more than the last pid shown (or 0 on the first call or
2094 * after a seek to the start). Use a binary-search to find the
2095 * next pid to display, if any
2097 struct cgroup
*cgrp
= s
->private;
2098 int index
= 0, pid
= *pos
;
2101 down_read(&cgrp
->pids_mutex
);
2103 int end
= cgrp
->pids_length
;
2105 while (index
< end
) {
2106 int mid
= (index
+ end
) / 2;
2107 if (cgrp
->tasks_pids
[mid
] == pid
) {
2110 } else if (cgrp
->tasks_pids
[mid
] <= pid
)
2116 /* If we're off the end of the array, we're done */
2117 if (index
>= cgrp
->pids_length
)
2119 /* Update the abstract position to be the actual pid that we found */
2120 iter
= cgrp
->tasks_pids
+ index
;
2125 static void cgroup_tasks_stop(struct seq_file
*s
, void *v
)
2127 struct cgroup
*cgrp
= s
->private;
2128 up_read(&cgrp
->pids_mutex
);
2131 static void *cgroup_tasks_next(struct seq_file
*s
, void *v
, loff_t
*pos
)
2133 struct cgroup
*cgrp
= s
->private;
2135 int *end
= cgrp
->tasks_pids
+ cgrp
->pids_length
;
2138 * Advance to the next pid in the array. If this goes off the
2150 static int cgroup_tasks_show(struct seq_file
*s
, void *v
)
2152 return seq_printf(s
, "%d\n", *(int *)v
);
2155 static struct seq_operations cgroup_tasks_seq_operations
= {
2156 .start
= cgroup_tasks_start
,
2157 .stop
= cgroup_tasks_stop
,
2158 .next
= cgroup_tasks_next
,
2159 .show
= cgroup_tasks_show
,
2162 static void release_cgroup_pid_array(struct cgroup
*cgrp
)
2164 down_write(&cgrp
->pids_mutex
);
2165 BUG_ON(!cgrp
->pids_use_count
);
2166 if (!--cgrp
->pids_use_count
) {
2167 kfree(cgrp
->tasks_pids
);
2168 cgrp
->tasks_pids
= NULL
;
2169 cgrp
->pids_length
= 0;
2171 up_write(&cgrp
->pids_mutex
);
2174 static int cgroup_tasks_release(struct inode
*inode
, struct file
*file
)
2176 struct cgroup
*cgrp
= __d_cgrp(file
->f_dentry
->d_parent
);
2178 if (!(file
->f_mode
& FMODE_READ
))
2181 release_cgroup_pid_array(cgrp
);
2182 return seq_release(inode
, file
);
2185 static struct file_operations cgroup_tasks_operations
= {
2187 .llseek
= seq_lseek
,
2188 .write
= cgroup_file_write
,
2189 .release
= cgroup_tasks_release
,
2193 * Handle an open on 'tasks' file. Prepare an array containing the
2194 * process id's of tasks currently attached to the cgroup being opened.
2197 static int cgroup_tasks_open(struct inode
*unused
, struct file
*file
)
2199 struct cgroup
*cgrp
= __d_cgrp(file
->f_dentry
->d_parent
);
2204 /* Nothing to do for write-only files */
2205 if (!(file
->f_mode
& FMODE_READ
))
2209 * If cgroup gets more users after we read count, we won't have
2210 * enough space - tough. This race is indistinguishable to the
2211 * caller from the case that the additional cgroup users didn't
2212 * show up until sometime later on.
2214 npids
= cgroup_task_count(cgrp
);
2215 pidarray
= kmalloc(npids
* sizeof(pid_t
), GFP_KERNEL
);
2218 npids
= pid_array_load(pidarray
, npids
, cgrp
);
2219 sort(pidarray
, npids
, sizeof(pid_t
), cmppid
, NULL
);
2222 * Store the array in the cgroup, freeing the old
2223 * array if necessary
2225 down_write(&cgrp
->pids_mutex
);
2226 kfree(cgrp
->tasks_pids
);
2227 cgrp
->tasks_pids
= pidarray
;
2228 cgrp
->pids_length
= npids
;
2229 cgrp
->pids_use_count
++;
2230 up_write(&cgrp
->pids_mutex
);
2232 file
->f_op
= &cgroup_tasks_operations
;
2234 retval
= seq_open(file
, &cgroup_tasks_seq_operations
);
2236 release_cgroup_pid_array(cgrp
);
2239 ((struct seq_file
*)file
->private_data
)->private = cgrp
;
2243 static u64
cgroup_read_notify_on_release(struct cgroup
*cgrp
,
2246 return notify_on_release(cgrp
);
2249 static int cgroup_write_notify_on_release(struct cgroup
*cgrp
,
2253 clear_bit(CGRP_RELEASABLE
, &cgrp
->flags
);
2255 set_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
2257 clear_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
2262 * for the common functions, 'private' gives the type of file
2264 static struct cftype files
[] = {
2267 .open
= cgroup_tasks_open
,
2268 .write_u64
= cgroup_tasks_write
,
2269 .release
= cgroup_tasks_release
,
2270 .private = FILE_TASKLIST
,
2274 .name
= "notify_on_release",
2275 .read_u64
= cgroup_read_notify_on_release
,
2276 .write_u64
= cgroup_write_notify_on_release
,
2277 .private = FILE_NOTIFY_ON_RELEASE
,
2281 static struct cftype cft_release_agent
= {
2282 .name
= "release_agent",
2283 .read_seq_string
= cgroup_release_agent_show
,
2284 .write_string
= cgroup_release_agent_write
,
2285 .max_write_len
= PATH_MAX
,
2286 .private = FILE_RELEASE_AGENT
,
2289 static int cgroup_populate_dir(struct cgroup
*cgrp
)
2292 struct cgroup_subsys
*ss
;
2294 /* First clear out any existing files */
2295 cgroup_clear_directory(cgrp
->dentry
);
2297 err
= cgroup_add_files(cgrp
, NULL
, files
, ARRAY_SIZE(files
));
2301 if (cgrp
== cgrp
->top_cgroup
) {
2302 if ((err
= cgroup_add_file(cgrp
, NULL
, &cft_release_agent
)) < 0)
2306 for_each_subsys(cgrp
->root
, ss
) {
2307 if (ss
->populate
&& (err
= ss
->populate(ss
, cgrp
)) < 0)
2314 static void init_cgroup_css(struct cgroup_subsys_state
*css
,
2315 struct cgroup_subsys
*ss
,
2316 struct cgroup
*cgrp
)
2319 atomic_set(&css
->refcnt
, 0);
2321 if (cgrp
== dummytop
)
2322 set_bit(CSS_ROOT
, &css
->flags
);
2323 BUG_ON(cgrp
->subsys
[ss
->subsys_id
]);
2324 cgrp
->subsys
[ss
->subsys_id
] = css
;
2328 * cgroup_create - create a cgroup
2329 * @parent: cgroup that will be parent of the new cgroup
2330 * @dentry: dentry of the new cgroup
2331 * @mode: mode to set on new inode
2333 * Must be called with the mutex on the parent inode held
2335 static long cgroup_create(struct cgroup
*parent
, struct dentry
*dentry
,
2338 struct cgroup
*cgrp
;
2339 struct cgroupfs_root
*root
= parent
->root
;
2341 struct cgroup_subsys
*ss
;
2342 struct super_block
*sb
= root
->sb
;
2344 cgrp
= kzalloc(sizeof(*cgrp
), GFP_KERNEL
);
2348 /* Grab a reference on the superblock so the hierarchy doesn't
2349 * get deleted on unmount if there are child cgroups. This
2350 * can be done outside cgroup_mutex, since the sb can't
2351 * disappear while someone has an open control file on the
2353 atomic_inc(&sb
->s_active
);
2355 mutex_lock(&cgroup_mutex
);
2357 init_cgroup_housekeeping(cgrp
);
2359 cgrp
->parent
= parent
;
2360 cgrp
->root
= parent
->root
;
2361 cgrp
->top_cgroup
= parent
->top_cgroup
;
2363 if (notify_on_release(parent
))
2364 set_bit(CGRP_NOTIFY_ON_RELEASE
, &cgrp
->flags
);
2366 for_each_subsys(root
, ss
) {
2367 struct cgroup_subsys_state
*css
= ss
->create(ss
, cgrp
);
2372 init_cgroup_css(css
, ss
, cgrp
);
2375 list_add(&cgrp
->sibling
, &cgrp
->parent
->children
);
2376 root
->number_of_cgroups
++;
2378 err
= cgroup_create_dir(cgrp
, dentry
, mode
);
2382 /* The cgroup directory was pre-locked for us */
2383 BUG_ON(!mutex_is_locked(&cgrp
->dentry
->d_inode
->i_mutex
));
2385 err
= cgroup_populate_dir(cgrp
);
2386 /* If err < 0, we have a half-filled directory - oh well ;) */
2388 mutex_unlock(&cgroup_mutex
);
2389 mutex_unlock(&cgrp
->dentry
->d_inode
->i_mutex
);
2395 list_del(&cgrp
->sibling
);
2396 root
->number_of_cgroups
--;
2400 for_each_subsys(root
, ss
) {
2401 if (cgrp
->subsys
[ss
->subsys_id
])
2402 ss
->destroy(ss
, cgrp
);
2405 mutex_unlock(&cgroup_mutex
);
2407 /* Release the reference count that we took on the superblock */
2408 deactivate_super(sb
);
2414 static int cgroup_mkdir(struct inode
*dir
, struct dentry
*dentry
, int mode
)
2416 struct cgroup
*c_parent
= dentry
->d_parent
->d_fsdata
;
2418 /* the vfs holds inode->i_mutex already */
2419 return cgroup_create(c_parent
, dentry
, mode
| S_IFDIR
);
2422 static int cgroup_has_css_refs(struct cgroup
*cgrp
)
2424 /* Check the reference count on each subsystem. Since we
2425 * already established that there are no tasks in the
2426 * cgroup, if the css refcount is also 0, then there should
2427 * be no outstanding references, so the subsystem is safe to
2428 * destroy. We scan across all subsystems rather than using
2429 * the per-hierarchy linked list of mounted subsystems since
2430 * we can be called via check_for_release() with no
2431 * synchronization other than RCU, and the subsystem linked
2432 * list isn't RCU-safe */
2434 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
2435 struct cgroup_subsys
*ss
= subsys
[i
];
2436 struct cgroup_subsys_state
*css
;
2437 /* Skip subsystems not in this hierarchy */
2438 if (ss
->root
!= cgrp
->root
)
2440 css
= cgrp
->subsys
[ss
->subsys_id
];
2441 /* When called from check_for_release() it's possible
2442 * that by this point the cgroup has been removed
2443 * and the css deleted. But a false-positive doesn't
2444 * matter, since it can only happen if the cgroup
2445 * has been deleted and hence no longer needs the
2446 * release agent to be called anyway. */
2447 if (css
&& atomic_read(&css
->refcnt
))
2453 static int cgroup_rmdir(struct inode
*unused_dir
, struct dentry
*dentry
)
2455 struct cgroup
*cgrp
= dentry
->d_fsdata
;
2457 struct cgroup
*parent
;
2459 /* the vfs holds both inode->i_mutex already */
2461 mutex_lock(&cgroup_mutex
);
2462 if (atomic_read(&cgrp
->count
) != 0) {
2463 mutex_unlock(&cgroup_mutex
);
2466 if (!list_empty(&cgrp
->children
)) {
2467 mutex_unlock(&cgroup_mutex
);
2470 mutex_unlock(&cgroup_mutex
);
2473 * Call pre_destroy handlers of subsys. Notify subsystems
2474 * that rmdir() request comes.
2476 cgroup_call_pre_destroy(cgrp
);
2478 mutex_lock(&cgroup_mutex
);
2479 parent
= cgrp
->parent
;
2481 if (atomic_read(&cgrp
->count
)
2482 || !list_empty(&cgrp
->children
)
2483 || cgroup_has_css_refs(cgrp
)) {
2484 mutex_unlock(&cgroup_mutex
);
2488 spin_lock(&release_list_lock
);
2489 set_bit(CGRP_REMOVED
, &cgrp
->flags
);
2490 if (!list_empty(&cgrp
->release_list
))
2491 list_del(&cgrp
->release_list
);
2492 spin_unlock(&release_list_lock
);
2493 /* delete my sibling from parent->children */
2494 list_del(&cgrp
->sibling
);
2495 spin_lock(&cgrp
->dentry
->d_lock
);
2496 d
= dget(cgrp
->dentry
);
2497 spin_unlock(&d
->d_lock
);
2499 cgroup_d_remove_dir(d
);
2502 set_bit(CGRP_RELEASABLE
, &parent
->flags
);
2503 check_for_release(parent
);
2505 mutex_unlock(&cgroup_mutex
);
2509 static void __init
cgroup_init_subsys(struct cgroup_subsys
*ss
)
2511 struct cgroup_subsys_state
*css
;
2513 printk(KERN_INFO
"Initializing cgroup subsys %s\n", ss
->name
);
2515 /* Create the top cgroup state for this subsystem */
2516 list_add(&ss
->sibling
, &rootnode
.subsys_list
);
2517 ss
->root
= &rootnode
;
2518 css
= ss
->create(ss
, dummytop
);
2519 /* We don't handle early failures gracefully */
2520 BUG_ON(IS_ERR(css
));
2521 init_cgroup_css(css
, ss
, dummytop
);
2523 /* Update the init_css_set to contain a subsys
2524 * pointer to this state - since the subsystem is
2525 * newly registered, all tasks and hence the
2526 * init_css_set is in the subsystem's top cgroup. */
2527 init_css_set
.subsys
[ss
->subsys_id
] = dummytop
->subsys
[ss
->subsys_id
];
2529 need_forkexit_callback
|= ss
->fork
|| ss
->exit
;
2531 /* At system boot, before all subsystems have been
2532 * registered, no tasks have been forked, so we don't
2533 * need to invoke fork callbacks here. */
2534 BUG_ON(!list_empty(&init_task
.tasks
));
2540 * cgroup_init_early - cgroup initialization at system boot
2542 * Initialize cgroups at system boot, and initialize any
2543 * subsystems that request early init.
2545 int __init
cgroup_init_early(void)
2548 atomic_set(&init_css_set
.refcount
, 1);
2549 INIT_LIST_HEAD(&init_css_set
.cg_links
);
2550 INIT_LIST_HEAD(&init_css_set
.tasks
);
2551 INIT_HLIST_NODE(&init_css_set
.hlist
);
2553 init_cgroup_root(&rootnode
);
2555 init_task
.cgroups
= &init_css_set
;
2557 init_css_set_link
.cg
= &init_css_set
;
2558 list_add(&init_css_set_link
.cgrp_link_list
,
2559 &rootnode
.top_cgroup
.css_sets
);
2560 list_add(&init_css_set_link
.cg_link_list
,
2561 &init_css_set
.cg_links
);
2563 for (i
= 0; i
< CSS_SET_TABLE_SIZE
; i
++)
2564 INIT_HLIST_HEAD(&css_set_table
[i
]);
2566 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
2567 struct cgroup_subsys
*ss
= subsys
[i
];
2570 BUG_ON(strlen(ss
->name
) > MAX_CGROUP_TYPE_NAMELEN
);
2571 BUG_ON(!ss
->create
);
2572 BUG_ON(!ss
->destroy
);
2573 if (ss
->subsys_id
!= i
) {
2574 printk(KERN_ERR
"cgroup: Subsys %s id == %d\n",
2575 ss
->name
, ss
->subsys_id
);
2580 cgroup_init_subsys(ss
);
2586 * cgroup_init - cgroup initialization
2588 * Register cgroup filesystem and /proc file, and initialize
2589 * any subsystems that didn't request early init.
2591 int __init
cgroup_init(void)
2595 struct hlist_head
*hhead
;
2597 err
= bdi_init(&cgroup_backing_dev_info
);
2601 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
2602 struct cgroup_subsys
*ss
= subsys
[i
];
2603 if (!ss
->early_init
)
2604 cgroup_init_subsys(ss
);
2607 /* Add init_css_set to the hash table */
2608 hhead
= css_set_hash(init_css_set
.subsys
);
2609 hlist_add_head(&init_css_set
.hlist
, hhead
);
2611 err
= register_filesystem(&cgroup_fs_type
);
2615 proc_create("cgroups", 0, NULL
, &proc_cgroupstats_operations
);
2619 bdi_destroy(&cgroup_backing_dev_info
);
2625 * proc_cgroup_show()
2626 * - Print task's cgroup paths into seq_file, one line for each hierarchy
2627 * - Used for /proc/<pid>/cgroup.
2628 * - No need to task_lock(tsk) on this tsk->cgroup reference, as it
2629 * doesn't really matter if tsk->cgroup changes after we read it,
2630 * and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
2631 * anyway. No need to check that tsk->cgroup != NULL, thanks to
2632 * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
2633 * cgroup to top_cgroup.
2636 /* TODO: Use a proper seq_file iterator */
2637 static int proc_cgroup_show(struct seq_file
*m
, void *v
)
2640 struct task_struct
*tsk
;
2643 struct cgroupfs_root
*root
;
2646 buf
= kmalloc(PAGE_SIZE
, GFP_KERNEL
);
2652 tsk
= get_pid_task(pid
, PIDTYPE_PID
);
2658 mutex_lock(&cgroup_mutex
);
2660 for_each_active_root(root
) {
2661 struct cgroup_subsys
*ss
;
2662 struct cgroup
*cgrp
;
2666 seq_printf(m
, "%lu:", root
->subsys_bits
);
2667 for_each_subsys(root
, ss
)
2668 seq_printf(m
, "%s%s", count
++ ? "," : "", ss
->name
);
2670 get_first_subsys(&root
->top_cgroup
, NULL
, &subsys_id
);
2671 cgrp
= task_cgroup(tsk
, subsys_id
);
2672 retval
= cgroup_path(cgrp
, buf
, PAGE_SIZE
);
2680 mutex_unlock(&cgroup_mutex
);
2681 put_task_struct(tsk
);
2688 static int cgroup_open(struct inode
*inode
, struct file
*file
)
2690 struct pid
*pid
= PROC_I(inode
)->pid
;
2691 return single_open(file
, proc_cgroup_show
, pid
);
2694 struct file_operations proc_cgroup_operations
= {
2695 .open
= cgroup_open
,
2697 .llseek
= seq_lseek
,
2698 .release
= single_release
,
2701 /* Display information about each subsystem and each hierarchy */
2702 static int proc_cgroupstats_show(struct seq_file
*m
, void *v
)
2706 seq_puts(m
, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
2707 mutex_lock(&cgroup_mutex
);
2708 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
2709 struct cgroup_subsys
*ss
= subsys
[i
];
2710 seq_printf(m
, "%s\t%lu\t%d\t%d\n",
2711 ss
->name
, ss
->root
->subsys_bits
,
2712 ss
->root
->number_of_cgroups
, !ss
->disabled
);
2714 mutex_unlock(&cgroup_mutex
);
2718 static int cgroupstats_open(struct inode
*inode
, struct file
*file
)
2720 return single_open(file
, proc_cgroupstats_show
, NULL
);
2723 static struct file_operations proc_cgroupstats_operations
= {
2724 .open
= cgroupstats_open
,
2726 .llseek
= seq_lseek
,
2727 .release
= single_release
,
2731 * cgroup_fork - attach newly forked task to its parents cgroup.
2732 * @child: pointer to task_struct of forking parent process.
2734 * Description: A task inherits its parent's cgroup at fork().
2736 * A pointer to the shared css_set was automatically copied in
2737 * fork.c by dup_task_struct(). However, we ignore that copy, since
2738 * it was not made under the protection of RCU or cgroup_mutex, so
2739 * might no longer be a valid cgroup pointer. cgroup_attach_task() might
2740 * have already changed current->cgroups, allowing the previously
2741 * referenced cgroup group to be removed and freed.
2743 * At the point that cgroup_fork() is called, 'current' is the parent
2744 * task, and the passed argument 'child' points to the child task.
2746 void cgroup_fork(struct task_struct
*child
)
2749 child
->cgroups
= current
->cgroups
;
2750 get_css_set(child
->cgroups
);
2751 task_unlock(current
);
2752 INIT_LIST_HEAD(&child
->cg_list
);
2756 * cgroup_fork_callbacks - run fork callbacks
2757 * @child: the new task
2759 * Called on a new task very soon before adding it to the
2760 * tasklist. No need to take any locks since no-one can
2761 * be operating on this task.
2763 void cgroup_fork_callbacks(struct task_struct
*child
)
2765 if (need_forkexit_callback
) {
2767 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
2768 struct cgroup_subsys
*ss
= subsys
[i
];
2770 ss
->fork(ss
, child
);
2776 * cgroup_post_fork - called on a new task after adding it to the task list
2777 * @child: the task in question
2779 * Adds the task to the list running through its css_set if necessary.
2780 * Has to be after the task is visible on the task list in case we race
2781 * with the first call to cgroup_iter_start() - to guarantee that the
2782 * new task ends up on its list.
2784 void cgroup_post_fork(struct task_struct
*child
)
2786 if (use_task_css_set_links
) {
2787 write_lock(&css_set_lock
);
2789 if (list_empty(&child
->cg_list
))
2790 list_add(&child
->cg_list
, &child
->cgroups
->tasks
);
2792 write_unlock(&css_set_lock
);
2796 * cgroup_exit - detach cgroup from exiting task
2797 * @tsk: pointer to task_struct of exiting process
2798 * @run_callback: run exit callbacks?
2800 * Description: Detach cgroup from @tsk and release it.
2802 * Note that cgroups marked notify_on_release force every task in
2803 * them to take the global cgroup_mutex mutex when exiting.
2804 * This could impact scaling on very large systems. Be reluctant to
2805 * use notify_on_release cgroups where very high task exit scaling
2806 * is required on large systems.
2808 * the_top_cgroup_hack:
2810 * Set the exiting tasks cgroup to the root cgroup (top_cgroup).
2812 * We call cgroup_exit() while the task is still competent to
2813 * handle notify_on_release(), then leave the task attached to the
2814 * root cgroup in each hierarchy for the remainder of its exit.
2816 * To do this properly, we would increment the reference count on
2817 * top_cgroup, and near the very end of the kernel/exit.c do_exit()
2818 * code we would add a second cgroup function call, to drop that
2819 * reference. This would just create an unnecessary hot spot on
2820 * the top_cgroup reference count, to no avail.
2822 * Normally, holding a reference to a cgroup without bumping its
2823 * count is unsafe. The cgroup could go away, or someone could
2824 * attach us to a different cgroup, decrementing the count on
2825 * the first cgroup that we never incremented. But in this case,
2826 * top_cgroup isn't going away, and either task has PF_EXITING set,
2827 * which wards off any cgroup_attach_task() attempts, or task is a failed
2828 * fork, never visible to cgroup_attach_task.
2830 void cgroup_exit(struct task_struct
*tsk
, int run_callbacks
)
2835 if (run_callbacks
&& need_forkexit_callback
) {
2836 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
2837 struct cgroup_subsys
*ss
= subsys
[i
];
2844 * Unlink from the css_set task list if necessary.
2845 * Optimistically check cg_list before taking
2848 if (!list_empty(&tsk
->cg_list
)) {
2849 write_lock(&css_set_lock
);
2850 if (!list_empty(&tsk
->cg_list
))
2851 list_del(&tsk
->cg_list
);
2852 write_unlock(&css_set_lock
);
2855 /* Reassign the task to the init_css_set. */
2858 tsk
->cgroups
= &init_css_set
;
2861 put_css_set_taskexit(cg
);
2865 * cgroup_clone - clone the cgroup the given subsystem is attached to
2866 * @tsk: the task to be moved
2867 * @subsys: the given subsystem
2868 * @nodename: the name for the new cgroup
2870 * Duplicate the current cgroup in the hierarchy that the given
2871 * subsystem is attached to, and move this task into the new
2874 int cgroup_clone(struct task_struct
*tsk
, struct cgroup_subsys
*subsys
,
2877 struct dentry
*dentry
;
2879 struct cgroup
*parent
, *child
;
2880 struct inode
*inode
;
2882 struct cgroupfs_root
*root
;
2883 struct cgroup_subsys
*ss
;
2885 /* We shouldn't be called by an unregistered subsystem */
2886 BUG_ON(!subsys
->active
);
2888 /* First figure out what hierarchy and cgroup we're dealing
2889 * with, and pin them so we can drop cgroup_mutex */
2890 mutex_lock(&cgroup_mutex
);
2892 root
= subsys
->root
;
2893 if (root
== &rootnode
) {
2894 mutex_unlock(&cgroup_mutex
);
2899 parent
= task_cgroup(tsk
, subsys
->subsys_id
);
2901 /* Pin the hierarchy */
2902 if (!atomic_inc_not_zero(&parent
->root
->sb
->s_active
)) {
2903 /* We race with the final deactivate_super() */
2904 mutex_unlock(&cgroup_mutex
);
2908 /* Keep the cgroup alive */
2911 mutex_unlock(&cgroup_mutex
);
2913 /* Now do the VFS work to create a cgroup */
2914 inode
= parent
->dentry
->d_inode
;
2916 /* Hold the parent directory mutex across this operation to
2917 * stop anyone else deleting the new cgroup */
2918 mutex_lock(&inode
->i_mutex
);
2919 dentry
= lookup_one_len(nodename
, parent
->dentry
, strlen(nodename
));
2920 if (IS_ERR(dentry
)) {
2922 "cgroup: Couldn't allocate dentry for %s: %ld\n", nodename
,
2924 ret
= PTR_ERR(dentry
);
2928 /* Create the cgroup directory, which also creates the cgroup */
2929 ret
= vfs_mkdir(inode
, dentry
, 0755);
2930 child
= __d_cgrp(dentry
);
2934 "Failed to create cgroup %s: %d\n", nodename
,
2939 /* The cgroup now exists. Retake cgroup_mutex and check
2940 * that we're still in the same state that we thought we
2942 mutex_lock(&cgroup_mutex
);
2943 if ((root
!= subsys
->root
) ||
2944 (parent
!= task_cgroup(tsk
, subsys
->subsys_id
))) {
2945 /* Aargh, we raced ... */
2946 mutex_unlock(&inode
->i_mutex
);
2949 deactivate_super(parent
->root
->sb
);
2950 /* The cgroup is still accessible in the VFS, but
2951 * we're not going to try to rmdir() it at this
2954 "Race in cgroup_clone() - leaking cgroup %s\n",
2959 /* do any required auto-setup */
2960 for_each_subsys(root
, ss
) {
2962 ss
->post_clone(ss
, child
);
2965 /* All seems fine. Finish by moving the task into the new cgroup */
2966 ret
= cgroup_attach_task(child
, tsk
);
2967 mutex_unlock(&cgroup_mutex
);
2970 mutex_unlock(&inode
->i_mutex
);
2972 mutex_lock(&cgroup_mutex
);
2974 mutex_unlock(&cgroup_mutex
);
2975 deactivate_super(parent
->root
->sb
);
2980 * cgroup_is_descendant - see if @cgrp is a descendant of current task's cgrp
2981 * @cgrp: the cgroup in question
2983 * See if @cgrp is a descendant of the current task's cgroup in
2984 * the appropriate hierarchy.
2986 * If we are sending in dummytop, then presumably we are creating
2987 * the top cgroup in the subsystem.
2989 * Called only by the ns (nsproxy) cgroup.
2991 int cgroup_is_descendant(const struct cgroup
*cgrp
)
2994 struct cgroup
*target
;
2997 if (cgrp
== dummytop
)
3000 get_first_subsys(cgrp
, NULL
, &subsys_id
);
3001 target
= task_cgroup(current
, subsys_id
);
3002 while (cgrp
!= target
&& cgrp
!= cgrp
->top_cgroup
)
3003 cgrp
= cgrp
->parent
;
3004 ret
= (cgrp
== target
);
3008 static void check_for_release(struct cgroup
*cgrp
)
3010 /* All of these checks rely on RCU to keep the cgroup
3011 * structure alive */
3012 if (cgroup_is_releasable(cgrp
) && !atomic_read(&cgrp
->count
)
3013 && list_empty(&cgrp
->children
) && !cgroup_has_css_refs(cgrp
)) {
3014 /* Control Group is currently removeable. If it's not
3015 * already queued for a userspace notification, queue
3017 int need_schedule_work
= 0;
3018 spin_lock(&release_list_lock
);
3019 if (!cgroup_is_removed(cgrp
) &&
3020 list_empty(&cgrp
->release_list
)) {
3021 list_add(&cgrp
->release_list
, &release_list
);
3022 need_schedule_work
= 1;
3024 spin_unlock(&release_list_lock
);
3025 if (need_schedule_work
)
3026 schedule_work(&release_agent_work
);
3030 void __css_put(struct cgroup_subsys_state
*css
)
3032 struct cgroup
*cgrp
= css
->cgroup
;
3034 if (atomic_dec_and_test(&css
->refcnt
) && notify_on_release(cgrp
)) {
3035 set_bit(CGRP_RELEASABLE
, &cgrp
->flags
);
3036 check_for_release(cgrp
);
3042 * Notify userspace when a cgroup is released, by running the
3043 * configured release agent with the name of the cgroup (path
3044 * relative to the root of cgroup file system) as the argument.
3046 * Most likely, this user command will try to rmdir this cgroup.
3048 * This races with the possibility that some other task will be
3049 * attached to this cgroup before it is removed, or that some other
3050 * user task will 'mkdir' a child cgroup of this cgroup. That's ok.
3051 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
3052 * unused, and this cgroup will be reprieved from its death sentence,
3053 * to continue to serve a useful existence. Next time it's released,
3054 * we will get notified again, if it still has 'notify_on_release' set.
3056 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
3057 * means only wait until the task is successfully execve()'d. The
3058 * separate release agent task is forked by call_usermodehelper(),
3059 * then control in this thread returns here, without waiting for the
3060 * release agent task. We don't bother to wait because the caller of
3061 * this routine has no use for the exit status of the release agent
3062 * task, so no sense holding our caller up for that.
3064 static void cgroup_release_agent(struct work_struct
*work
)
3066 BUG_ON(work
!= &release_agent_work
);
3067 mutex_lock(&cgroup_mutex
);
3068 spin_lock(&release_list_lock
);
3069 while (!list_empty(&release_list
)) {
3070 char *argv
[3], *envp
[3];
3072 char *pathbuf
= NULL
, *agentbuf
= NULL
;
3073 struct cgroup
*cgrp
= list_entry(release_list
.next
,
3076 list_del_init(&cgrp
->release_list
);
3077 spin_unlock(&release_list_lock
);
3078 pathbuf
= kmalloc(PAGE_SIZE
, GFP_KERNEL
);
3081 if (cgroup_path(cgrp
, pathbuf
, PAGE_SIZE
) < 0)
3083 agentbuf
= kstrdup(cgrp
->root
->release_agent_path
, GFP_KERNEL
);
3088 argv
[i
++] = agentbuf
;
3089 argv
[i
++] = pathbuf
;
3093 /* minimal command environment */
3094 envp
[i
++] = "HOME=/";
3095 envp
[i
++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
3098 /* Drop the lock while we invoke the usermode helper,
3099 * since the exec could involve hitting disk and hence
3100 * be a slow process */
3101 mutex_unlock(&cgroup_mutex
);
3102 call_usermodehelper(argv
[0], argv
, envp
, UMH_WAIT_EXEC
);
3103 mutex_lock(&cgroup_mutex
);
3107 spin_lock(&release_list_lock
);
3109 spin_unlock(&release_list_lock
);
3110 mutex_unlock(&cgroup_mutex
);
3113 static int __init
cgroup_disable(char *str
)
3118 while ((token
= strsep(&str
, ",")) != NULL
) {
3122 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
3123 struct cgroup_subsys
*ss
= subsys
[i
];
3125 if (!strcmp(token
, ss
->name
)) {
3127 printk(KERN_INFO
"Disabling %s control group"
3128 " subsystem\n", ss
->name
);
3135 __setup("cgroup_disable=", cgroup_disable
);