4 * Generic process-grouping system.
6 * Based originally on the cpuset system, extracted by Paul Menage
7 * Copyright (C) 2006 Google, Inc
9 * Copyright notices from the original cpuset code:
10 * --------------------------------------------------
11 * Copyright (C) 2003 BULL SA.
12 * Copyright (C) 2004-2006 Silicon Graphics, Inc.
14 * Portions derived from Patrick Mochel's sysfs code.
15 * sysfs is Copyright (c) 2001-3 Patrick Mochel
17 * 2003-10-10 Written by Simon Derr.
18 * 2003-10-22 Updates by Stephen Hemminger.
19 * 2004 May-July Rework by Paul Jackson.
20 * ---------------------------------------------------
22 * This file is subject to the terms and conditions of the GNU General Public
23 * License. See the file COPYING in the main directory of the Linux
24 * distribution for more details.
27 #include <linux/cgroup.h>
28 #include <linux/errno.h>
30 #include <linux/kernel.h>
31 #include <linux/list.h>
33 #include <linux/mutex.h>
34 #include <linux/mount.h>
35 #include <linux/pagemap.h>
36 #include <linux/proc_fs.h>
37 #include <linux/rcupdate.h>
38 #include <linux/sched.h>
39 #include <linux/seq_file.h>
40 #include <linux/slab.h>
41 #include <linux/magic.h>
42 #include <linux/spinlock.h>
43 #include <linux/string.h>
44 #include <linux/sort.h>
45 #include <asm/atomic.h>
47 /* Generate an array of cgroup subsystem pointers */
48 #define SUBSYS(_x) &_x ## _subsys,
50 static struct cgroup_subsys
*subsys
[] = {
51 #include <linux/cgroup_subsys.h>
55 * A cgroupfs_root represents the root of a cgroup hierarchy,
56 * and may be associated with a superblock to form an active
59 struct cgroupfs_root
{
60 struct super_block
*sb
;
63 * The bitmask of subsystems intended to be attached to this
66 unsigned long subsys_bits
;
68 /* The bitmask of subsystems currently attached to this hierarchy */
69 unsigned long actual_subsys_bits
;
71 /* A list running through the attached subsystems */
72 struct list_head subsys_list
;
74 /* The root cgroup for this hierarchy */
75 struct cgroup top_cgroup
;
77 /* Tracks how many cgroups are currently defined in hierarchy.*/
78 int number_of_cgroups
;
80 /* A list running through the mounted hierarchies */
81 struct list_head root_list
;
83 /* Hierarchy-specific flags */
89 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
90 * subsystems that are otherwise unattached - it never has more than a
91 * single cgroup, and all tasks are part of that cgroup.
93 static struct cgroupfs_root rootnode
;
95 /* The list of hierarchy roots */
97 static LIST_HEAD(roots
);
99 /* dummytop is a shorthand for the dummy hierarchy's top cgroup */
100 #define dummytop (&rootnode.top_cgroup)
102 /* This flag indicates whether tasks in the fork and exit paths should
103 * take callback_mutex and check for fork/exit handlers to call. This
104 * avoids us having to do extra work in the fork/exit path if none of the
105 * subsystems need to be called.
107 static int need_forkexit_callback
;
109 /* bits in struct cgroup flags field */
114 /* convenient tests for these bits */
115 inline int cgroup_is_removed(const struct cgroup
*cont
)
117 return test_bit(CONT_REMOVED
, &cont
->flags
);
120 /* bits in struct cgroupfs_root flags field */
122 ROOT_NOPREFIX
, /* mounted subsystems have no named prefix */
126 * for_each_subsys() allows you to iterate on each subsystem attached to
127 * an active hierarchy
129 #define for_each_subsys(_root, _ss) \
130 list_for_each_entry(_ss, &_root->subsys_list, sibling)
132 /* for_each_root() allows you to iterate across the active hierarchies */
133 #define for_each_root(_root) \
134 list_for_each_entry(_root, &roots, root_list)
136 /* Each task_struct has an embedded css_set, so the get/put
137 * operation simply takes a reference count on all the cgroups
138 * referenced by subsystems in this css_set. This can end up
139 * multiple-counting some cgroups, but that's OK - the ref-count is
140 * just a busy/not-busy indicator; ensuring that we only count each
141 * cgroup once would require taking a global lock to ensure that no
142 * subsystems moved between hierarchies while we were doing so.
144 * Possible TODO: decide at boot time based on the number of
145 * registered subsystems and the number of CPUs or NUMA nodes whether
146 * it's better for performance to ref-count every subsystem, or to
147 * take a global lock and only add one ref count to each hierarchy.
149 static void get_css_set(struct css_set
*cg
)
152 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++)
153 atomic_inc(&cg
->subsys
[i
]->cgroup
->count
);
156 static void put_css_set(struct css_set
*cg
)
159 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++)
160 atomic_dec(&cg
->subsys
[i
]->cgroup
->count
);
164 * There is one global cgroup mutex. We also require taking
165 * task_lock() when dereferencing a task's cgroup subsys pointers.
166 * See "The task_lock() exception", at the end of this comment.
168 * A task must hold cgroup_mutex to modify cgroups.
170 * Any task can increment and decrement the count field without lock.
171 * So in general, code holding cgroup_mutex can't rely on the count
172 * field not changing. However, if the count goes to zero, then only
173 * attach_task() can increment it again. Because a count of zero
174 * means that no tasks are currently attached, therefore there is no
175 * way a task attached to that cgroup can fork (the other way to
176 * increment the count). So code holding cgroup_mutex can safely
177 * assume that if the count is zero, it will stay zero. Similarly, if
178 * a task holds cgroup_mutex on a cgroup with zero count, it
179 * knows that the cgroup won't be removed, as cgroup_rmdir()
182 * The cgroup_common_file_write handler for operations that modify
183 * the cgroup hierarchy holds cgroup_mutex across the entire operation,
184 * single threading all such cgroup modifications across the system.
186 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
187 * (usually) take cgroup_mutex. These are the two most performance
188 * critical pieces of code here. The exception occurs on cgroup_exit(),
189 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
190 * is taken, and if the cgroup count is zero, a usermode call made
191 * to /sbin/cgroup_release_agent with the name of the cgroup (path
192 * relative to the root of cgroup file system) as the argument.
194 * A cgroup can only be deleted if both its 'count' of using tasks
195 * is zero, and its list of 'children' cgroups is empty. Since all
196 * tasks in the system use _some_ cgroup, and since there is always at
197 * least one task in the system (init, pid == 1), therefore, top_cgroup
198 * always has either children cgroups and/or using tasks. So we don't
199 * need a special hack to ensure that top_cgroup cannot be deleted.
201 * The task_lock() exception
203 * The need for this exception arises from the action of
204 * attach_task(), which overwrites one tasks cgroup pointer with
205 * another. It does so using cgroup_mutexe, however there are
206 * several performance critical places that need to reference
207 * task->cgroup without the expense of grabbing a system global
208 * mutex. Therefore except as noted below, when dereferencing or, as
209 * in attach_task(), modifying a task'ss cgroup pointer we use
210 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
211 * the task_struct routinely used for such matters.
213 * P.S. One more locking exception. RCU is used to guard the
214 * update of a tasks cgroup pointer by attach_task()
217 static DEFINE_MUTEX(cgroup_mutex
);
220 * cgroup_lock - lock out any changes to cgroup structures
224 void cgroup_lock(void)
226 mutex_lock(&cgroup_mutex
);
230 * cgroup_unlock - release lock on cgroup changes
232 * Undo the lock taken in a previous cgroup_lock() call.
235 void cgroup_unlock(void)
237 mutex_unlock(&cgroup_mutex
);
241 * A couple of forward declarations required, due to cyclic reference loop:
242 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
243 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
247 static int cgroup_mkdir(struct inode
*dir
, struct dentry
*dentry
, int mode
);
248 static int cgroup_rmdir(struct inode
*unused_dir
, struct dentry
*dentry
);
249 static int cgroup_populate_dir(struct cgroup
*cont
);
250 static struct inode_operations cgroup_dir_inode_operations
;
251 static struct file_operations proc_cgroupstats_operations
;
253 static struct backing_dev_info cgroup_backing_dev_info
= {
254 .capabilities
= BDI_CAP_NO_ACCT_DIRTY
| BDI_CAP_NO_WRITEBACK
,
257 static struct inode
*cgroup_new_inode(mode_t mode
, struct super_block
*sb
)
259 struct inode
*inode
= new_inode(sb
);
262 inode
->i_mode
= mode
;
263 inode
->i_uid
= current
->fsuid
;
264 inode
->i_gid
= current
->fsgid
;
266 inode
->i_atime
= inode
->i_mtime
= inode
->i_ctime
= CURRENT_TIME
;
267 inode
->i_mapping
->backing_dev_info
= &cgroup_backing_dev_info
;
272 static void cgroup_diput(struct dentry
*dentry
, struct inode
*inode
)
274 /* is dentry a directory ? if so, kfree() associated cgroup */
275 if (S_ISDIR(inode
->i_mode
)) {
276 struct cgroup
*cont
= dentry
->d_fsdata
;
277 BUG_ON(!(cgroup_is_removed(cont
)));
283 static void remove_dir(struct dentry
*d
)
285 struct dentry
*parent
= dget(d
->d_parent
);
288 simple_rmdir(parent
->d_inode
, d
);
292 static void cgroup_clear_directory(struct dentry
*dentry
)
294 struct list_head
*node
;
296 BUG_ON(!mutex_is_locked(&dentry
->d_inode
->i_mutex
));
297 spin_lock(&dcache_lock
);
298 node
= dentry
->d_subdirs
.next
;
299 while (node
!= &dentry
->d_subdirs
) {
300 struct dentry
*d
= list_entry(node
, struct dentry
, d_u
.d_child
);
303 /* This should never be called on a cgroup
304 * directory with child cgroups */
305 BUG_ON(d
->d_inode
->i_mode
& S_IFDIR
);
307 spin_unlock(&dcache_lock
);
309 simple_unlink(dentry
->d_inode
, d
);
311 spin_lock(&dcache_lock
);
313 node
= dentry
->d_subdirs
.next
;
315 spin_unlock(&dcache_lock
);
319 * NOTE : the dentry must have been dget()'ed
321 static void cgroup_d_remove_dir(struct dentry
*dentry
)
323 cgroup_clear_directory(dentry
);
325 spin_lock(&dcache_lock
);
326 list_del_init(&dentry
->d_u
.d_child
);
327 spin_unlock(&dcache_lock
);
331 static int rebind_subsystems(struct cgroupfs_root
*root
,
332 unsigned long final_bits
)
334 unsigned long added_bits
, removed_bits
;
335 struct cgroup
*cont
= &root
->top_cgroup
;
338 removed_bits
= root
->actual_subsys_bits
& ~final_bits
;
339 added_bits
= final_bits
& ~root
->actual_subsys_bits
;
340 /* Check that any added subsystems are currently free */
341 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
342 unsigned long long bit
= 1ull << i
;
343 struct cgroup_subsys
*ss
= subsys
[i
];
344 if (!(bit
& added_bits
))
346 if (ss
->root
!= &rootnode
) {
347 /* Subsystem isn't free */
352 /* Currently we don't handle adding/removing subsystems when
353 * any child cgroups exist. This is theoretically supportable
354 * but involves complex error handling, so it's being left until
356 if (!list_empty(&cont
->children
))
359 /* Process each subsystem */
360 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
361 struct cgroup_subsys
*ss
= subsys
[i
];
362 unsigned long bit
= 1UL << i
;
363 if (bit
& added_bits
) {
364 /* We're binding this subsystem to this hierarchy */
365 BUG_ON(cont
->subsys
[i
]);
366 BUG_ON(!dummytop
->subsys
[i
]);
367 BUG_ON(dummytop
->subsys
[i
]->cgroup
!= dummytop
);
368 cont
->subsys
[i
] = dummytop
->subsys
[i
];
369 cont
->subsys
[i
]->cgroup
= cont
;
370 list_add(&ss
->sibling
, &root
->subsys_list
);
371 rcu_assign_pointer(ss
->root
, root
);
375 } else if (bit
& removed_bits
) {
376 /* We're removing this subsystem */
377 BUG_ON(cont
->subsys
[i
] != dummytop
->subsys
[i
]);
378 BUG_ON(cont
->subsys
[i
]->cgroup
!= cont
);
380 ss
->bind(ss
, dummytop
);
381 dummytop
->subsys
[i
]->cgroup
= dummytop
;
382 cont
->subsys
[i
] = NULL
;
383 rcu_assign_pointer(subsys
[i
]->root
, &rootnode
);
384 list_del(&ss
->sibling
);
385 } else if (bit
& final_bits
) {
386 /* Subsystem state should already exist */
387 BUG_ON(!cont
->subsys
[i
]);
389 /* Subsystem state shouldn't exist */
390 BUG_ON(cont
->subsys
[i
]);
393 root
->subsys_bits
= root
->actual_subsys_bits
= final_bits
;
399 static int cgroup_show_options(struct seq_file
*seq
, struct vfsmount
*vfs
)
401 struct cgroupfs_root
*root
= vfs
->mnt_sb
->s_fs_info
;
402 struct cgroup_subsys
*ss
;
404 mutex_lock(&cgroup_mutex
);
405 for_each_subsys(root
, ss
)
406 seq_printf(seq
, ",%s", ss
->name
);
407 if (test_bit(ROOT_NOPREFIX
, &root
->flags
))
408 seq_puts(seq
, ",noprefix");
409 mutex_unlock(&cgroup_mutex
);
413 struct cgroup_sb_opts
{
414 unsigned long subsys_bits
;
418 /* Convert a hierarchy specifier into a bitmask of subsystems and
420 static int parse_cgroupfs_options(char *data
,
421 struct cgroup_sb_opts
*opts
)
423 char *token
, *o
= data
?: "all";
425 opts
->subsys_bits
= 0;
428 while ((token
= strsep(&o
, ",")) != NULL
) {
431 if (!strcmp(token
, "all")) {
432 opts
->subsys_bits
= (1 << CGROUP_SUBSYS_COUNT
) - 1;
433 } else if (!strcmp(token
, "noprefix")) {
434 set_bit(ROOT_NOPREFIX
, &opts
->flags
);
436 struct cgroup_subsys
*ss
;
438 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
440 if (!strcmp(token
, ss
->name
)) {
441 set_bit(i
, &opts
->subsys_bits
);
445 if (i
== CGROUP_SUBSYS_COUNT
)
450 /* We can't have an empty hierarchy */
451 if (!opts
->subsys_bits
)
457 static int cgroup_remount(struct super_block
*sb
, int *flags
, char *data
)
460 struct cgroupfs_root
*root
= sb
->s_fs_info
;
461 struct cgroup
*cont
= &root
->top_cgroup
;
462 struct cgroup_sb_opts opts
;
464 mutex_lock(&cont
->dentry
->d_inode
->i_mutex
);
465 mutex_lock(&cgroup_mutex
);
467 /* See what subsystems are wanted */
468 ret
= parse_cgroupfs_options(data
, &opts
);
472 /* Don't allow flags to change at remount */
473 if (opts
.flags
!= root
->flags
) {
478 ret
= rebind_subsystems(root
, opts
.subsys_bits
);
480 /* (re)populate subsystem files */
482 cgroup_populate_dir(cont
);
485 mutex_unlock(&cgroup_mutex
);
486 mutex_unlock(&cont
->dentry
->d_inode
->i_mutex
);
490 static struct super_operations cgroup_ops
= {
491 .statfs
= simple_statfs
,
492 .drop_inode
= generic_delete_inode
,
493 .show_options
= cgroup_show_options
,
494 .remount_fs
= cgroup_remount
,
497 static void init_cgroup_root(struct cgroupfs_root
*root
)
499 struct cgroup
*cont
= &root
->top_cgroup
;
500 INIT_LIST_HEAD(&root
->subsys_list
);
501 INIT_LIST_HEAD(&root
->root_list
);
502 root
->number_of_cgroups
= 1;
504 cont
->top_cgroup
= cont
;
505 INIT_LIST_HEAD(&cont
->sibling
);
506 INIT_LIST_HEAD(&cont
->children
);
509 static int cgroup_test_super(struct super_block
*sb
, void *data
)
511 struct cgroupfs_root
*new = data
;
512 struct cgroupfs_root
*root
= sb
->s_fs_info
;
514 /* First check subsystems */
515 if (new->subsys_bits
!= root
->subsys_bits
)
518 /* Next check flags */
519 if (new->flags
!= root
->flags
)
525 static int cgroup_set_super(struct super_block
*sb
, void *data
)
528 struct cgroupfs_root
*root
= data
;
530 ret
= set_anon_super(sb
, NULL
);
534 sb
->s_fs_info
= root
;
537 sb
->s_blocksize
= PAGE_CACHE_SIZE
;
538 sb
->s_blocksize_bits
= PAGE_CACHE_SHIFT
;
539 sb
->s_magic
= CGROUP_SUPER_MAGIC
;
540 sb
->s_op
= &cgroup_ops
;
545 static int cgroup_get_rootdir(struct super_block
*sb
)
547 struct inode
*inode
=
548 cgroup_new_inode(S_IFDIR
| S_IRUGO
| S_IXUGO
| S_IWUSR
, sb
);
549 struct dentry
*dentry
;
554 inode
->i_op
= &simple_dir_inode_operations
;
555 inode
->i_fop
= &simple_dir_operations
;
556 inode
->i_op
= &cgroup_dir_inode_operations
;
557 /* directories start off with i_nlink == 2 (for "." entry) */
559 dentry
= d_alloc_root(inode
);
568 static int cgroup_get_sb(struct file_system_type
*fs_type
,
569 int flags
, const char *unused_dev_name
,
570 void *data
, struct vfsmount
*mnt
)
572 struct cgroup_sb_opts opts
;
574 struct super_block
*sb
;
575 struct cgroupfs_root
*root
;
577 /* First find the desired set of subsystems */
578 ret
= parse_cgroupfs_options(data
, &opts
);
582 root
= kzalloc(sizeof(*root
), GFP_KERNEL
);
586 init_cgroup_root(root
);
587 root
->subsys_bits
= opts
.subsys_bits
;
588 root
->flags
= opts
.flags
;
590 sb
= sget(fs_type
, cgroup_test_super
, cgroup_set_super
, root
);
597 if (sb
->s_fs_info
!= root
) {
598 /* Reusing an existing superblock */
599 BUG_ON(sb
->s_root
== NULL
);
604 struct cgroup
*cont
= &root
->top_cgroup
;
606 BUG_ON(sb
->s_root
!= NULL
);
608 ret
= cgroup_get_rootdir(sb
);
612 mutex_lock(&cgroup_mutex
);
614 ret
= rebind_subsystems(root
, root
->subsys_bits
);
616 mutex_unlock(&cgroup_mutex
);
620 /* EBUSY should be the only error here */
623 list_add(&root
->root_list
, &roots
);
625 sb
->s_root
->d_fsdata
= &root
->top_cgroup
;
626 root
->top_cgroup
.dentry
= sb
->s_root
;
628 BUG_ON(!list_empty(&cont
->sibling
));
629 BUG_ON(!list_empty(&cont
->children
));
630 BUG_ON(root
->number_of_cgroups
!= 1);
633 * I believe that it's safe to nest i_mutex inside
634 * cgroup_mutex in this case, since no-one else can
635 * be accessing this directory yet. But we still need
636 * to teach lockdep that this is the case - currently
637 * a cgroupfs remount triggers a lockdep warning
639 mutex_lock(&cont
->dentry
->d_inode
->i_mutex
);
640 cgroup_populate_dir(cont
);
641 mutex_unlock(&cont
->dentry
->d_inode
->i_mutex
);
642 mutex_unlock(&cgroup_mutex
);
645 return simple_set_mnt(mnt
, sb
);
648 up_write(&sb
->s_umount
);
649 deactivate_super(sb
);
653 static void cgroup_kill_sb(struct super_block
*sb
) {
654 struct cgroupfs_root
*root
= sb
->s_fs_info
;
655 struct cgroup
*cont
= &root
->top_cgroup
;
660 BUG_ON(root
->number_of_cgroups
!= 1);
661 BUG_ON(!list_empty(&cont
->children
));
662 BUG_ON(!list_empty(&cont
->sibling
));
664 mutex_lock(&cgroup_mutex
);
666 /* Rebind all subsystems back to the default hierarchy */
667 ret
= rebind_subsystems(root
, 0);
668 /* Shouldn't be able to fail ... */
671 if (!list_empty(&root
->root_list
))
672 list_del(&root
->root_list
);
673 mutex_unlock(&cgroup_mutex
);
676 kill_litter_super(sb
);
679 static struct file_system_type cgroup_fs_type
= {
681 .get_sb
= cgroup_get_sb
,
682 .kill_sb
= cgroup_kill_sb
,
685 static inline struct cgroup
*__d_cont(struct dentry
*dentry
)
687 return dentry
->d_fsdata
;
690 static inline struct cftype
*__d_cft(struct dentry
*dentry
)
692 return dentry
->d_fsdata
;
696 * Called with cgroup_mutex held. Writes path of cgroup into buf.
697 * Returns 0 on success, -errno on error.
699 int cgroup_path(const struct cgroup
*cont
, char *buf
, int buflen
)
703 if (cont
== dummytop
) {
705 * Inactive subsystems have no dentry for their root
712 start
= buf
+ buflen
;
716 int len
= cont
->dentry
->d_name
.len
;
717 if ((start
-= len
) < buf
)
718 return -ENAMETOOLONG
;
719 memcpy(start
, cont
->dentry
->d_name
.name
, len
);
726 return -ENAMETOOLONG
;
729 memmove(buf
, start
, buf
+ buflen
- start
);
734 * Return the first subsystem attached to a cgroup's hierarchy, and
738 static void get_first_subsys(const struct cgroup
*cont
,
739 struct cgroup_subsys_state
**css
, int *subsys_id
)
741 const struct cgroupfs_root
*root
= cont
->root
;
742 const struct cgroup_subsys
*test_ss
;
743 BUG_ON(list_empty(&root
->subsys_list
));
744 test_ss
= list_entry(root
->subsys_list
.next
,
745 struct cgroup_subsys
, sibling
);
747 *css
= cont
->subsys
[test_ss
->subsys_id
];
751 *subsys_id
= test_ss
->subsys_id
;
755 * Attach task 'tsk' to cgroup 'cont'
757 * Call holding cgroup_mutex. May take task_lock of
758 * the task 'pid' during call.
760 static int attach_task(struct cgroup
*cont
, struct task_struct
*tsk
)
763 struct cgroup_subsys
*ss
;
764 struct cgroup
*oldcont
;
765 struct css_set
*cg
= &tsk
->cgroups
;
766 struct cgroupfs_root
*root
= cont
->root
;
770 get_first_subsys(cont
, NULL
, &subsys_id
);
772 /* Nothing to do if the task is already in that cgroup */
773 oldcont
= task_cgroup(tsk
, subsys_id
);
777 for_each_subsys(root
, ss
) {
778 if (ss
->can_attach
) {
779 retval
= ss
->can_attach(ss
, cont
, tsk
);
787 if (tsk
->flags
& PF_EXITING
) {
791 /* Update the css_set pointers for the subsystems in this
793 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
794 if (root
->subsys_bits
& (1ull << i
)) {
795 /* Subsystem is in this hierarchy. So we want
796 * the subsystem state from the new
797 * cgroup. Transfer the refcount from the
799 atomic_inc(&cont
->count
);
800 atomic_dec(&cg
->subsys
[i
]->cgroup
->count
);
801 rcu_assign_pointer(cg
->subsys
[i
], cont
->subsys
[i
]);
806 for_each_subsys(root
, ss
) {
808 ss
->attach(ss
, cont
, oldcont
, tsk
);
817 * Attach task with pid 'pid' to cgroup 'cont'. Call with
818 * cgroup_mutex, may take task_lock of task
820 static int attach_task_by_pid(struct cgroup
*cont
, char *pidbuf
)
823 struct task_struct
*tsk
;
826 if (sscanf(pidbuf
, "%d", &pid
) != 1)
831 tsk
= find_task_by_pid(pid
);
832 if (!tsk
|| tsk
->flags
& PF_EXITING
) {
836 get_task_struct(tsk
);
839 if ((current
->euid
) && (current
->euid
!= tsk
->uid
)
840 && (current
->euid
!= tsk
->suid
)) {
841 put_task_struct(tsk
);
846 get_task_struct(tsk
);
849 ret
= attach_task(cont
, tsk
);
850 put_task_struct(tsk
);
854 /* The various types of files and directories in a cgroup file system */
856 enum cgroup_filetype
{
862 static ssize_t
cgroup_write_uint(struct cgroup
*cont
, struct cftype
*cft
,
864 const char __user
*userbuf
,
865 size_t nbytes
, loff_t
*unused_ppos
)
874 if (nbytes
>= sizeof(buffer
))
876 if (copy_from_user(buffer
, userbuf
, nbytes
))
879 buffer
[nbytes
] = 0; /* nul-terminate */
881 /* strip newline if necessary */
882 if (nbytes
&& (buffer
[nbytes
-1] == '\n'))
883 buffer
[nbytes
-1] = 0;
884 val
= simple_strtoull(buffer
, &end
, 0);
888 /* Pass to subsystem */
889 retval
= cft
->write_uint(cont
, cft
, val
);
895 static ssize_t
cgroup_common_file_write(struct cgroup
*cont
,
898 const char __user
*userbuf
,
899 size_t nbytes
, loff_t
*unused_ppos
)
901 enum cgroup_filetype type
= cft
->private;
905 if (nbytes
>= PATH_MAX
)
908 /* +1 for nul-terminator */
909 buffer
= kmalloc(nbytes
+ 1, GFP_KERNEL
);
913 if (copy_from_user(buffer
, userbuf
, nbytes
)) {
917 buffer
[nbytes
] = 0; /* nul-terminate */
919 mutex_lock(&cgroup_mutex
);
921 if (cgroup_is_removed(cont
)) {
928 retval
= attach_task_by_pid(cont
, buffer
);
938 mutex_unlock(&cgroup_mutex
);
944 static ssize_t
cgroup_file_write(struct file
*file
, const char __user
*buf
,
945 size_t nbytes
, loff_t
*ppos
)
947 struct cftype
*cft
= __d_cft(file
->f_dentry
);
948 struct cgroup
*cont
= __d_cont(file
->f_dentry
->d_parent
);
953 return cft
->write(cont
, cft
, file
, buf
, nbytes
, ppos
);
955 return cgroup_write_uint(cont
, cft
, file
, buf
, nbytes
, ppos
);
959 static ssize_t
cgroup_read_uint(struct cgroup
*cont
, struct cftype
*cft
,
961 char __user
*buf
, size_t nbytes
,
965 u64 val
= cft
->read_uint(cont
, cft
);
966 int len
= sprintf(tmp
, "%llu\n", (unsigned long long) val
);
968 return simple_read_from_buffer(buf
, nbytes
, ppos
, tmp
, len
);
971 static ssize_t
cgroup_file_read(struct file
*file
, char __user
*buf
,
972 size_t nbytes
, loff_t
*ppos
)
974 struct cftype
*cft
= __d_cft(file
->f_dentry
);
975 struct cgroup
*cont
= __d_cont(file
->f_dentry
->d_parent
);
981 return cft
->read(cont
, cft
, file
, buf
, nbytes
, ppos
);
983 return cgroup_read_uint(cont
, cft
, file
, buf
, nbytes
, ppos
);
987 static int cgroup_file_open(struct inode
*inode
, struct file
*file
)
992 err
= generic_file_open(inode
, file
);
996 cft
= __d_cft(file
->f_dentry
);
1000 err
= cft
->open(inode
, file
);
1007 static int cgroup_file_release(struct inode
*inode
, struct file
*file
)
1009 struct cftype
*cft
= __d_cft(file
->f_dentry
);
1011 return cft
->release(inode
, file
);
1016 * cgroup_rename - Only allow simple rename of directories in place.
1018 static int cgroup_rename(struct inode
*old_dir
, struct dentry
*old_dentry
,
1019 struct inode
*new_dir
, struct dentry
*new_dentry
)
1021 if (!S_ISDIR(old_dentry
->d_inode
->i_mode
))
1023 if (new_dentry
->d_inode
)
1025 if (old_dir
!= new_dir
)
1027 return simple_rename(old_dir
, old_dentry
, new_dir
, new_dentry
);
1030 static struct file_operations cgroup_file_operations
= {
1031 .read
= cgroup_file_read
,
1032 .write
= cgroup_file_write
,
1033 .llseek
= generic_file_llseek
,
1034 .open
= cgroup_file_open
,
1035 .release
= cgroup_file_release
,
1038 static struct inode_operations cgroup_dir_inode_operations
= {
1039 .lookup
= simple_lookup
,
1040 .mkdir
= cgroup_mkdir
,
1041 .rmdir
= cgroup_rmdir
,
1042 .rename
= cgroup_rename
,
1045 static int cgroup_create_file(struct dentry
*dentry
, int mode
,
1046 struct super_block
*sb
)
1048 static struct dentry_operations cgroup_dops
= {
1049 .d_iput
= cgroup_diput
,
1052 struct inode
*inode
;
1056 if (dentry
->d_inode
)
1059 inode
= cgroup_new_inode(mode
, sb
);
1063 if (S_ISDIR(mode
)) {
1064 inode
->i_op
= &cgroup_dir_inode_operations
;
1065 inode
->i_fop
= &simple_dir_operations
;
1067 /* start off with i_nlink == 2 (for "." entry) */
1070 /* start with the directory inode held, so that we can
1071 * populate it without racing with another mkdir */
1072 mutex_lock(&inode
->i_mutex
);
1073 } else if (S_ISREG(mode
)) {
1075 inode
->i_fop
= &cgroup_file_operations
;
1077 dentry
->d_op
= &cgroup_dops
;
1078 d_instantiate(dentry
, inode
);
1079 dget(dentry
); /* Extra count - pin the dentry in core */
1084 * cgroup_create_dir - create a directory for an object.
1085 * cont: the cgroup we create the directory for.
1086 * It must have a valid ->parent field
1087 * And we are going to fill its ->dentry field.
1088 * dentry: dentry of the new container
1089 * mode: mode to set on new directory.
1091 static int cgroup_create_dir(struct cgroup
*cont
, struct dentry
*dentry
,
1094 struct dentry
*parent
;
1097 parent
= cont
->parent
->dentry
;
1098 error
= cgroup_create_file(dentry
, S_IFDIR
| mode
, cont
->root
->sb
);
1100 dentry
->d_fsdata
= cont
;
1101 inc_nlink(parent
->d_inode
);
1102 cont
->dentry
= dentry
;
1110 int cgroup_add_file(struct cgroup
*cont
,
1111 struct cgroup_subsys
*subsys
,
1112 const struct cftype
*cft
)
1114 struct dentry
*dir
= cont
->dentry
;
1115 struct dentry
*dentry
;
1118 char name
[MAX_CGROUP_TYPE_NAMELEN
+ MAX_CFTYPE_NAME
+ 2] = { 0 };
1119 if (subsys
&& !test_bit(ROOT_NOPREFIX
, &cont
->root
->flags
)) {
1120 strcpy(name
, subsys
->name
);
1123 strcat(name
, cft
->name
);
1124 BUG_ON(!mutex_is_locked(&dir
->d_inode
->i_mutex
));
1125 dentry
= lookup_one_len(name
, dir
, strlen(name
));
1126 if (!IS_ERR(dentry
)) {
1127 error
= cgroup_create_file(dentry
, 0644 | S_IFREG
,
1130 dentry
->d_fsdata
= (void *)cft
;
1133 error
= PTR_ERR(dentry
);
1137 int cgroup_add_files(struct cgroup
*cont
,
1138 struct cgroup_subsys
*subsys
,
1139 const struct cftype cft
[],
1143 for (i
= 0; i
< count
; i
++) {
1144 err
= cgroup_add_file(cont
, subsys
, &cft
[i
]);
1151 /* Count the number of tasks in a cgroup. Could be made more
1152 * time-efficient but less space-efficient with more linked lists
1153 * running through each cgroup and the css_set structures that
1154 * referenced it. Must be called with tasklist_lock held for read or
1155 * write or in an rcu critical section.
1157 int __cgroup_task_count(const struct cgroup
*cont
)
1160 struct task_struct
*g
, *p
;
1161 struct cgroup_subsys_state
*css
;
1164 get_first_subsys(cont
, &css
, &subsys_id
);
1165 do_each_thread(g
, p
) {
1166 if (task_subsys_state(p
, subsys_id
) == css
)
1168 } while_each_thread(g
, p
);
1173 * Stuff for reading the 'tasks' file.
1175 * Reading this file can return large amounts of data if a cgroup has
1176 * *lots* of attached tasks. So it may need several calls to read(),
1177 * but we cannot guarantee that the information we produce is correct
1178 * unless we produce it entirely atomically.
1180 * Upon tasks file open(), a struct ctr_struct is allocated, that
1181 * will have a pointer to an array (also allocated here). The struct
1182 * ctr_struct * is stored in file->private_data. Its resources will
1183 * be freed by release() when the file is closed. The array is used
1184 * to sprintf the PIDs and then used by read().
1192 * Load into 'pidarray' up to 'npids' of the tasks using cgroup
1193 * 'cont'. Return actual number of pids loaded. No need to
1194 * task_lock(p) when reading out p->cgroup, since we're in an RCU
1195 * read section, so the css_set can't go away, and is
1196 * immutable after creation.
1198 static int pid_array_load(pid_t
*pidarray
, int npids
, struct cgroup
*cont
)
1201 struct task_struct
*g
, *p
;
1202 struct cgroup_subsys_state
*css
;
1205 get_first_subsys(cont
, &css
, &subsys_id
);
1207 do_each_thread(g
, p
) {
1208 if (task_subsys_state(p
, subsys_id
) == css
) {
1209 pidarray
[n
++] = pid_nr(task_pid(p
));
1210 if (unlikely(n
== npids
))
1213 } while_each_thread(g
, p
);
1220 static int cmppid(const void *a
, const void *b
)
1222 return *(pid_t
*)a
- *(pid_t
*)b
;
1226 * Convert array 'a' of 'npids' pid_t's to a string of newline separated
1227 * decimal pids in 'buf'. Don't write more than 'sz' chars, but return
1228 * count 'cnt' of how many chars would be written if buf were large enough.
1230 static int pid_array_to_buf(char *buf
, int sz
, pid_t
*a
, int npids
)
1235 for (i
= 0; i
< npids
; i
++)
1236 cnt
+= snprintf(buf
+ cnt
, max(sz
- cnt
, 0), "%d\n", a
[i
]);
1241 * Handle an open on 'tasks' file. Prepare a buffer listing the
1242 * process id's of tasks currently attached to the cgroup being opened.
1244 * Does not require any specific cgroup mutexes, and does not take any.
1246 static int cgroup_tasks_open(struct inode
*unused
, struct file
*file
)
1248 struct cgroup
*cont
= __d_cont(file
->f_dentry
->d_parent
);
1249 struct ctr_struct
*ctr
;
1254 if (!(file
->f_mode
& FMODE_READ
))
1257 ctr
= kmalloc(sizeof(*ctr
), GFP_KERNEL
);
1262 * If cgroup gets more users after we read count, we won't have
1263 * enough space - tough. This race is indistinguishable to the
1264 * caller from the case that the additional cgroup users didn't
1265 * show up until sometime later on.
1267 npids
= cgroup_task_count(cont
);
1269 pidarray
= kmalloc(npids
* sizeof(pid_t
), GFP_KERNEL
);
1273 npids
= pid_array_load(pidarray
, npids
, cont
);
1274 sort(pidarray
, npids
, sizeof(pid_t
), cmppid
, NULL
);
1276 /* Call pid_array_to_buf() twice, first just to get bufsz */
1277 ctr
->bufsz
= pid_array_to_buf(&c
, sizeof(c
), pidarray
, npids
) + 1;
1278 ctr
->buf
= kmalloc(ctr
->bufsz
, GFP_KERNEL
);
1281 ctr
->bufsz
= pid_array_to_buf(ctr
->buf
, ctr
->bufsz
, pidarray
, npids
);
1288 file
->private_data
= ctr
;
1299 static ssize_t
cgroup_tasks_read(struct cgroup
*cont
,
1301 struct file
*file
, char __user
*buf
,
1302 size_t nbytes
, loff_t
*ppos
)
1304 struct ctr_struct
*ctr
= file
->private_data
;
1306 return simple_read_from_buffer(buf
, nbytes
, ppos
, ctr
->buf
, ctr
->bufsz
);
1309 static int cgroup_tasks_release(struct inode
*unused_inode
,
1312 struct ctr_struct
*ctr
;
1314 if (file
->f_mode
& FMODE_READ
) {
1315 ctr
= file
->private_data
;
1323 * for the common functions, 'private' gives the type of file
1325 static struct cftype cft_tasks
= {
1327 .open
= cgroup_tasks_open
,
1328 .read
= cgroup_tasks_read
,
1329 .write
= cgroup_common_file_write
,
1330 .release
= cgroup_tasks_release
,
1331 .private = FILE_TASKLIST
,
1334 static int cgroup_populate_dir(struct cgroup
*cont
)
1337 struct cgroup_subsys
*ss
;
1339 /* First clear out any existing files */
1340 cgroup_clear_directory(cont
->dentry
);
1342 err
= cgroup_add_file(cont
, NULL
, &cft_tasks
);
1346 for_each_subsys(cont
->root
, ss
) {
1347 if (ss
->populate
&& (err
= ss
->populate(ss
, cont
)) < 0)
1354 static void init_cgroup_css(struct cgroup_subsys_state
*css
,
1355 struct cgroup_subsys
*ss
,
1356 struct cgroup
*cont
)
1359 atomic_set(&css
->refcnt
, 0);
1361 if (cont
== dummytop
)
1362 set_bit(CSS_ROOT
, &css
->flags
);
1363 BUG_ON(cont
->subsys
[ss
->subsys_id
]);
1364 cont
->subsys
[ss
->subsys_id
] = css
;
1368 * cgroup_create - create a cgroup
1369 * parent: cgroup that will be parent of the new cgroup.
1370 * name: name of the new cgroup. Will be strcpy'ed.
1371 * mode: mode to set on new inode
1373 * Must be called with the mutex on the parent inode held
1376 static long cgroup_create(struct cgroup
*parent
, struct dentry
*dentry
,
1379 struct cgroup
*cont
;
1380 struct cgroupfs_root
*root
= parent
->root
;
1382 struct cgroup_subsys
*ss
;
1383 struct super_block
*sb
= root
->sb
;
1385 cont
= kzalloc(sizeof(*cont
), GFP_KERNEL
);
1389 /* Grab a reference on the superblock so the hierarchy doesn't
1390 * get deleted on unmount if there are child cgroups. This
1391 * can be done outside cgroup_mutex, since the sb can't
1392 * disappear while someone has an open control file on the
1394 atomic_inc(&sb
->s_active
);
1396 mutex_lock(&cgroup_mutex
);
1399 INIT_LIST_HEAD(&cont
->sibling
);
1400 INIT_LIST_HEAD(&cont
->children
);
1402 cont
->parent
= parent
;
1403 cont
->root
= parent
->root
;
1404 cont
->top_cgroup
= parent
->top_cgroup
;
1406 for_each_subsys(root
, ss
) {
1407 struct cgroup_subsys_state
*css
= ss
->create(ss
, cont
);
1412 init_cgroup_css(css
, ss
, cont
);
1415 list_add(&cont
->sibling
, &cont
->parent
->children
);
1416 root
->number_of_cgroups
++;
1418 err
= cgroup_create_dir(cont
, dentry
, mode
);
1422 /* The cgroup directory was pre-locked for us */
1423 BUG_ON(!mutex_is_locked(&cont
->dentry
->d_inode
->i_mutex
));
1425 err
= cgroup_populate_dir(cont
);
1426 /* If err < 0, we have a half-filled directory - oh well ;) */
1428 mutex_unlock(&cgroup_mutex
);
1429 mutex_unlock(&cont
->dentry
->d_inode
->i_mutex
);
1435 list_del(&cont
->sibling
);
1436 root
->number_of_cgroups
--;
1440 for_each_subsys(root
, ss
) {
1441 if (cont
->subsys
[ss
->subsys_id
])
1442 ss
->destroy(ss
, cont
);
1445 mutex_unlock(&cgroup_mutex
);
1447 /* Release the reference count that we took on the superblock */
1448 deactivate_super(sb
);
1454 static int cgroup_mkdir(struct inode
*dir
, struct dentry
*dentry
, int mode
)
1456 struct cgroup
*c_parent
= dentry
->d_parent
->d_fsdata
;
1458 /* the vfs holds inode->i_mutex already */
1459 return cgroup_create(c_parent
, dentry
, mode
| S_IFDIR
);
1462 static int cgroup_rmdir(struct inode
*unused_dir
, struct dentry
*dentry
)
1464 struct cgroup
*cont
= dentry
->d_fsdata
;
1466 struct cgroup
*parent
;
1467 struct cgroup_subsys
*ss
;
1468 struct super_block
*sb
;
1469 struct cgroupfs_root
*root
;
1472 /* the vfs holds both inode->i_mutex already */
1474 mutex_lock(&cgroup_mutex
);
1475 if (atomic_read(&cont
->count
) != 0) {
1476 mutex_unlock(&cgroup_mutex
);
1479 if (!list_empty(&cont
->children
)) {
1480 mutex_unlock(&cgroup_mutex
);
1484 parent
= cont
->parent
;
1488 /* Check the reference count on each subsystem. Since we
1489 * already established that there are no tasks in the
1490 * cgroup, if the css refcount is also 0, then there should
1491 * be no outstanding references, so the subsystem is safe to
1493 for_each_subsys(root
, ss
) {
1494 struct cgroup_subsys_state
*css
;
1495 css
= cont
->subsys
[ss
->subsys_id
];
1496 if (atomic_read(&css
->refcnt
)) {
1502 mutex_unlock(&cgroup_mutex
);
1506 for_each_subsys(root
, ss
) {
1507 if (cont
->subsys
[ss
->subsys_id
])
1508 ss
->destroy(ss
, cont
);
1511 set_bit(CONT_REMOVED
, &cont
->flags
);
1512 /* delete my sibling from parent->children */
1513 list_del(&cont
->sibling
);
1514 spin_lock(&cont
->dentry
->d_lock
);
1515 d
= dget(cont
->dentry
);
1516 cont
->dentry
= NULL
;
1517 spin_unlock(&d
->d_lock
);
1519 cgroup_d_remove_dir(d
);
1521 root
->number_of_cgroups
--;
1523 mutex_unlock(&cgroup_mutex
);
1524 /* Drop the active superblock reference that we took when we
1525 * created the cgroup */
1526 deactivate_super(sb
);
1530 static void cgroup_init_subsys(struct cgroup_subsys
*ss
)
1532 struct task_struct
*g
, *p
;
1533 struct cgroup_subsys_state
*css
;
1534 printk(KERN_ERR
"Initializing cgroup subsys %s\n", ss
->name
);
1536 /* Create the top cgroup state for this subsystem */
1537 ss
->root
= &rootnode
;
1538 css
= ss
->create(ss
, dummytop
);
1539 /* We don't handle early failures gracefully */
1540 BUG_ON(IS_ERR(css
));
1541 init_cgroup_css(css
, ss
, dummytop
);
1543 /* Update all tasks to contain a subsys pointer to this state
1544 * - since the subsystem is newly registered, all tasks are in
1545 * the subsystem's top cgroup. */
1547 /* If this subsystem requested that it be notified with fork
1548 * events, we should send it one now for every process in the
1551 read_lock(&tasklist_lock
);
1552 init_task
.cgroups
.subsys
[ss
->subsys_id
] = css
;
1554 ss
->fork(ss
, &init_task
);
1556 do_each_thread(g
, p
) {
1557 printk(KERN_INFO
"Setting task %p css to %p (%d)\n", css
, p
, p
->pid
);
1558 p
->cgroups
.subsys
[ss
->subsys_id
] = css
;
1561 } while_each_thread(g
, p
);
1562 read_unlock(&tasklist_lock
);
1564 need_forkexit_callback
|= ss
->fork
|| ss
->exit
;
1570 * cgroup_init_early - initialize cgroups at system boot, and
1571 * initialize any subsystems that request early init.
1573 int __init
cgroup_init_early(void)
1576 init_cgroup_root(&rootnode
);
1577 list_add(&rootnode
.root_list
, &roots
);
1579 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
1580 struct cgroup_subsys
*ss
= subsys
[i
];
1583 BUG_ON(strlen(ss
->name
) > MAX_CGROUP_TYPE_NAMELEN
);
1584 BUG_ON(!ss
->create
);
1585 BUG_ON(!ss
->destroy
);
1586 if (ss
->subsys_id
!= i
) {
1587 printk(KERN_ERR
"Subsys %s id == %d\n",
1588 ss
->name
, ss
->subsys_id
);
1593 cgroup_init_subsys(ss
);
1599 * cgroup_init - register cgroup filesystem and /proc file, and
1600 * initialize any subsystems that didn't request early init.
1602 int __init
cgroup_init(void)
1606 struct proc_dir_entry
*entry
;
1608 err
= bdi_init(&cgroup_backing_dev_info
);
1612 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
1613 struct cgroup_subsys
*ss
= subsys
[i
];
1614 if (!ss
->early_init
)
1615 cgroup_init_subsys(ss
);
1618 err
= register_filesystem(&cgroup_fs_type
);
1622 entry
= create_proc_entry("cgroups", 0, NULL
);
1624 entry
->proc_fops
= &proc_cgroupstats_operations
;
1628 bdi_destroy(&cgroup_backing_dev_info
);
1634 * proc_cgroup_show()
1635 * - Print task's cgroup paths into seq_file, one line for each hierarchy
1636 * - Used for /proc/<pid>/cgroup.
1637 * - No need to task_lock(tsk) on this tsk->cgroup reference, as it
1638 * doesn't really matter if tsk->cgroup changes after we read it,
1639 * and we take cgroup_mutex, keeping attach_task() from changing it
1640 * anyway. No need to check that tsk->cgroup != NULL, thanks to
1641 * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
1642 * cgroup to top_cgroup.
1645 /* TODO: Use a proper seq_file iterator */
1646 static int proc_cgroup_show(struct seq_file
*m
, void *v
)
1649 struct task_struct
*tsk
;
1652 struct cgroupfs_root
*root
;
1655 buf
= kmalloc(PAGE_SIZE
, GFP_KERNEL
);
1661 tsk
= get_pid_task(pid
, PIDTYPE_PID
);
1667 mutex_lock(&cgroup_mutex
);
1669 for_each_root(root
) {
1670 struct cgroup_subsys
*ss
;
1671 struct cgroup
*cont
;
1675 /* Skip this hierarchy if it has no active subsystems */
1676 if (!root
->actual_subsys_bits
)
1678 for_each_subsys(root
, ss
)
1679 seq_printf(m
, "%s%s", count
++ ? "," : "", ss
->name
);
1681 get_first_subsys(&root
->top_cgroup
, NULL
, &subsys_id
);
1682 cont
= task_cgroup(tsk
, subsys_id
);
1683 retval
= cgroup_path(cont
, buf
, PAGE_SIZE
);
1691 mutex_unlock(&cgroup_mutex
);
1692 put_task_struct(tsk
);
1699 static int cgroup_open(struct inode
*inode
, struct file
*file
)
1701 struct pid
*pid
= PROC_I(inode
)->pid
;
1702 return single_open(file
, proc_cgroup_show
, pid
);
1705 struct file_operations proc_cgroup_operations
= {
1706 .open
= cgroup_open
,
1708 .llseek
= seq_lseek
,
1709 .release
= single_release
,
1712 /* Display information about each subsystem and each hierarchy */
1713 static int proc_cgroupstats_show(struct seq_file
*m
, void *v
)
1716 struct cgroupfs_root
*root
;
1718 mutex_lock(&cgroup_mutex
);
1719 seq_puts(m
, "Hierarchies:\n");
1720 for_each_root(root
) {
1721 struct cgroup_subsys
*ss
;
1723 seq_printf(m
, "%p: bits=%lx cgroups=%d (", root
,
1724 root
->subsys_bits
, root
->number_of_cgroups
);
1725 for_each_subsys(root
, ss
) {
1726 seq_printf(m
, "%s%s", first
? "" : ", ", ss
->name
);
1731 seq_printf(m
, " s_active=%d",
1732 atomic_read(&root
->sb
->s_active
));
1736 seq_puts(m
, "Subsystems:\n");
1737 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
1738 struct cgroup_subsys
*ss
= subsys
[i
];
1739 seq_printf(m
, "%d: name=%s hierarchy=%p\n",
1740 i
, ss
->name
, ss
->root
);
1742 mutex_unlock(&cgroup_mutex
);
1746 static int cgroupstats_open(struct inode
*inode
, struct file
*file
)
1748 return single_open(file
, proc_cgroupstats_show
, 0);
1751 static struct file_operations proc_cgroupstats_operations
= {
1752 .open
= cgroupstats_open
,
1754 .llseek
= seq_lseek
,
1755 .release
= single_release
,
1759 * cgroup_fork - attach newly forked task to its parents cgroup.
1760 * @tsk: pointer to task_struct of forking parent process.
1762 * Description: A task inherits its parent's cgroup at fork().
1764 * A pointer to the shared css_set was automatically copied in
1765 * fork.c by dup_task_struct(). However, we ignore that copy, since
1766 * it was not made under the protection of RCU or cgroup_mutex, so
1767 * might no longer be a valid cgroup pointer. attach_task() might
1768 * have already changed current->cgroup, allowing the previously
1769 * referenced cgroup to be removed and freed.
1771 * At the point that cgroup_fork() is called, 'current' is the parent
1772 * task, and the passed argument 'child' points to the child task.
1774 void cgroup_fork(struct task_struct
*child
)
1777 child
->cgroups
= rcu_dereference(current
->cgroups
);
1778 get_css_set(&child
->cgroups
);
1783 * cgroup_fork_callbacks - called on a new task very soon before
1784 * adding it to the tasklist. No need to take any locks since no-one
1785 * can be operating on this task
1787 void cgroup_fork_callbacks(struct task_struct
*child
)
1789 if (need_forkexit_callback
) {
1791 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
1792 struct cgroup_subsys
*ss
= subsys
[i
];
1794 ss
->fork(ss
, child
);
1800 * cgroup_exit - detach cgroup from exiting task
1801 * @tsk: pointer to task_struct of exiting process
1803 * Description: Detach cgroup from @tsk and release it.
1805 * Note that cgroups marked notify_on_release force every task in
1806 * them to take the global cgroup_mutex mutex when exiting.
1807 * This could impact scaling on very large systems. Be reluctant to
1808 * use notify_on_release cgroups where very high task exit scaling
1809 * is required on large systems.
1811 * the_top_cgroup_hack:
1813 * Set the exiting tasks cgroup to the root cgroup (top_cgroup).
1815 * We call cgroup_exit() while the task is still competent to
1816 * handle notify_on_release(), then leave the task attached to the
1817 * root cgroup in each hierarchy for the remainder of its exit.
1819 * To do this properly, we would increment the reference count on
1820 * top_cgroup, and near the very end of the kernel/exit.c do_exit()
1821 * code we would add a second cgroup function call, to drop that
1822 * reference. This would just create an unnecessary hot spot on
1823 * the top_cgroup reference count, to no avail.
1825 * Normally, holding a reference to a cgroup without bumping its
1826 * count is unsafe. The cgroup could go away, or someone could
1827 * attach us to a different cgroup, decrementing the count on
1828 * the first cgroup that we never incremented. But in this case,
1829 * top_cgroup isn't going away, and either task has PF_EXITING set,
1830 * which wards off any attach_task() attempts, or task is a failed
1831 * fork, never visible to attach_task.
1834 void cgroup_exit(struct task_struct
*tsk
, int run_callbacks
)
1838 if (run_callbacks
&& need_forkexit_callback
) {
1839 for (i
= 0; i
< CGROUP_SUBSYS_COUNT
; i
++) {
1840 struct cgroup_subsys
*ss
= subsys
[i
];
1845 /* Reassign the task to the init_css_set. */
1847 put_css_set(&tsk
->cgroups
);
1848 tsk
->cgroups
= init_task
.cgroups
;
1853 * cgroup_clone - duplicate the current cgroup in the hierarchy
1854 * that the given subsystem is attached to, and move this task into
1857 int cgroup_clone(struct task_struct
*tsk
, struct cgroup_subsys
*subsys
)
1859 struct dentry
*dentry
;
1861 char nodename
[MAX_CGROUP_TYPE_NAMELEN
];
1862 struct cgroup
*parent
, *child
;
1863 struct inode
*inode
;
1865 struct cgroupfs_root
*root
;
1866 struct cgroup_subsys
*ss
;
1868 /* We shouldn't be called by an unregistered subsystem */
1869 BUG_ON(!subsys
->active
);
1871 /* First figure out what hierarchy and cgroup we're dealing
1872 * with, and pin them so we can drop cgroup_mutex */
1873 mutex_lock(&cgroup_mutex
);
1875 root
= subsys
->root
;
1876 if (root
== &rootnode
) {
1878 "Not cloning cgroup for unused subsystem %s\n",
1880 mutex_unlock(&cgroup_mutex
);
1884 parent
= task_cgroup(tsk
, subsys
->subsys_id
);
1886 snprintf(nodename
, MAX_CGROUP_TYPE_NAMELEN
, "node_%d", tsk
->pid
);
1888 /* Pin the hierarchy */
1889 atomic_inc(&parent
->root
->sb
->s_active
);
1891 mutex_unlock(&cgroup_mutex
);
1893 /* Now do the VFS work to create a cgroup */
1894 inode
= parent
->dentry
->d_inode
;
1896 /* Hold the parent directory mutex across this operation to
1897 * stop anyone else deleting the new cgroup */
1898 mutex_lock(&inode
->i_mutex
);
1899 dentry
= lookup_one_len(nodename
, parent
->dentry
, strlen(nodename
));
1900 if (IS_ERR(dentry
)) {
1902 "Couldn't allocate dentry for %s: %ld\n", nodename
,
1904 ret
= PTR_ERR(dentry
);
1908 /* Create the cgroup directory, which also creates the cgroup */
1909 ret
= vfs_mkdir(inode
, dentry
, S_IFDIR
| 0755);
1910 child
= __d_cont(dentry
);
1914 "Failed to create cgroup %s: %d\n", nodename
,
1921 "Couldn't find new cgroup %s\n", nodename
);
1926 /* The cgroup now exists. Retake cgroup_mutex and check
1927 * that we're still in the same state that we thought we
1929 mutex_lock(&cgroup_mutex
);
1930 if ((root
!= subsys
->root
) ||
1931 (parent
!= task_cgroup(tsk
, subsys
->subsys_id
))) {
1932 /* Aargh, we raced ... */
1933 mutex_unlock(&inode
->i_mutex
);
1935 deactivate_super(parent
->root
->sb
);
1936 /* The cgroup is still accessible in the VFS, but
1937 * we're not going to try to rmdir() it at this
1940 "Race in cgroup_clone() - leaking cgroup %s\n",
1945 /* do any required auto-setup */
1946 for_each_subsys(root
, ss
) {
1948 ss
->post_clone(ss
, child
);
1951 /* All seems fine. Finish by moving the task into the new cgroup */
1952 ret
= attach_task(child
, tsk
);
1953 mutex_unlock(&cgroup_mutex
);
1956 mutex_unlock(&inode
->i_mutex
);
1957 deactivate_super(parent
->root
->sb
);
1962 * See if "cont" is a descendant of the current task's cgroup in
1963 * the appropriate hierarchy
1965 * If we are sending in dummytop, then presumably we are creating
1966 * the top cgroup in the subsystem.
1968 * Called only by the ns (nsproxy) cgroup.
1970 int cgroup_is_descendant(const struct cgroup
*cont
)
1973 struct cgroup
*target
;
1976 if (cont
== dummytop
)
1979 get_first_subsys(cont
, NULL
, &subsys_id
);
1980 target
= task_cgroup(current
, subsys_id
);
1981 while (cont
!= target
&& cont
!= cont
->top_cgroup
)
1982 cont
= cont
->parent
;
1983 ret
= (cont
== target
);