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/rcupdate.h>
37 #include <linux/sched.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>
44 #include <asm/atomic.h>
46 /* Generate an array of cgroup subsystem pointers */
47 #define SUBSYS(_x) &_x ## _subsys,
49 static struct cgroup_subsys *subsys[] = {
50 #include <linux/cgroup_subsys.h>
54 * A cgroupfs_root represents the root of a cgroup hierarchy,
55 * and may be associated with a superblock to form an active
58 struct cgroupfs_root {
59 struct super_block *sb;
62 * The bitmask of subsystems intended to be attached to this
65 unsigned long subsys_bits;
67 /* The bitmask of subsystems currently attached to this hierarchy */
68 unsigned long actual_subsys_bits;
70 /* A list running through the attached subsystems */
71 struct list_head subsys_list;
73 /* The root cgroup for this hierarchy */
74 struct cgroup top_cgroup;
76 /* Tracks how many cgroups are currently defined in hierarchy.*/
77 int number_of_cgroups;
79 /* A list running through the mounted hierarchies */
80 struct list_head root_list;
82 /* Hierarchy-specific flags */
88 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
89 * subsystems that are otherwise unattached - it never has more than a
90 * single cgroup, and all tasks are part of that cgroup.
92 static struct cgroupfs_root rootnode;
94 /* The list of hierarchy roots */
96 static LIST_HEAD(roots);
98 /* dummytop is a shorthand for the dummy hierarchy's top cgroup */
99 #define dummytop (&rootnode.top_cgroup)
101 /* This flag indicates whether tasks in the fork and exit paths should
102 * take callback_mutex and check for fork/exit handlers to call. This
103 * avoids us having to do extra work in the fork/exit path if none of the
104 * subsystems need to be called.
106 static int need_forkexit_callback;
108 /* bits in struct cgroup flags field */
113 /* convenient tests for these bits */
114 inline int cgroup_is_removed(const struct cgroup *cont)
116 return test_bit(CONT_REMOVED, &cont->flags);
119 /* bits in struct cgroupfs_root flags field */
121 ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
125 * for_each_subsys() allows you to iterate on each subsystem attached to
126 * an active hierarchy
128 #define for_each_subsys(_root, _ss) \
129 list_for_each_entry(_ss, &_root->subsys_list, sibling)
131 /* for_each_root() allows you to iterate across the active hierarchies */
132 #define for_each_root(_root) \
133 list_for_each_entry(_root, &roots, root_list)
136 * There is one global cgroup mutex. We also require taking
137 * task_lock() when dereferencing a task's cgroup subsys pointers.
138 * See "The task_lock() exception", at the end of this comment.
140 * A task must hold cgroup_mutex to modify cgroups.
142 * Any task can increment and decrement the count field without lock.
143 * So in general, code holding cgroup_mutex can't rely on the count
144 * field not changing. However, if the count goes to zero, then only
145 * attach_task() can increment it again. Because a count of zero
146 * means that no tasks are currently attached, therefore there is no
147 * way a task attached to that cgroup can fork (the other way to
148 * increment the count). So code holding cgroup_mutex can safely
149 * assume that if the count is zero, it will stay zero. Similarly, if
150 * a task holds cgroup_mutex on a cgroup with zero count, it
151 * knows that the cgroup won't be removed, as cgroup_rmdir()
154 * The cgroup_common_file_write handler for operations that modify
155 * the cgroup hierarchy holds cgroup_mutex across the entire operation,
156 * single threading all such cgroup modifications across the system.
158 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
159 * (usually) take cgroup_mutex. These are the two most performance
160 * critical pieces of code here. The exception occurs on cgroup_exit(),
161 * when a task in a notify_on_release cgroup exits. Then cgroup_mutex
162 * is taken, and if the cgroup count is zero, a usermode call made
163 * to /sbin/cgroup_release_agent with the name of the cgroup (path
164 * relative to the root of cgroup file system) as the argument.
166 * A cgroup can only be deleted if both its 'count' of using tasks
167 * is zero, and its list of 'children' cgroups is empty. Since all
168 * tasks in the system use _some_ cgroup, and since there is always at
169 * least one task in the system (init, pid == 1), therefore, top_cgroup
170 * always has either children cgroups and/or using tasks. So we don't
171 * need a special hack to ensure that top_cgroup cannot be deleted.
173 * The task_lock() exception
175 * The need for this exception arises from the action of
176 * attach_task(), which overwrites one tasks cgroup pointer with
177 * another. It does so using cgroup_mutexe, however there are
178 * several performance critical places that need to reference
179 * task->cgroup without the expense of grabbing a system global
180 * mutex. Therefore except as noted below, when dereferencing or, as
181 * in attach_task(), modifying a task'ss cgroup pointer we use
182 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
183 * the task_struct routinely used for such matters.
185 * P.S. One more locking exception. RCU is used to guard the
186 * update of a tasks cgroup pointer by attach_task()
189 static DEFINE_MUTEX(cgroup_mutex);
192 * cgroup_lock - lock out any changes to cgroup structures
196 void cgroup_lock(void)
198 mutex_lock(&cgroup_mutex);
202 * cgroup_unlock - release lock on cgroup changes
204 * Undo the lock taken in a previous cgroup_lock() call.
207 void cgroup_unlock(void)
209 mutex_unlock(&cgroup_mutex);
213 * A couple of forward declarations required, due to cyclic reference loop:
214 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
215 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
219 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode);
220 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
221 static int cgroup_populate_dir(struct cgroup *cont);
222 static struct inode_operations cgroup_dir_inode_operations;
224 static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
226 struct inode *inode = new_inode(sb);
227 static struct backing_dev_info cgroup_backing_dev_info = {
228 .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
232 inode->i_mode = mode;
233 inode->i_uid = current->fsuid;
234 inode->i_gid = current->fsgid;
236 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
237 inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
242 static void cgroup_diput(struct dentry *dentry, struct inode *inode)
244 /* is dentry a directory ? if so, kfree() associated cgroup */
245 if (S_ISDIR(inode->i_mode)) {
246 struct cgroup *cont = dentry->d_fsdata;
247 BUG_ON(!(cgroup_is_removed(cont)));
253 static void remove_dir(struct dentry *d)
255 struct dentry *parent = dget(d->d_parent);
258 simple_rmdir(parent->d_inode, d);
262 static void cgroup_clear_directory(struct dentry *dentry)
264 struct list_head *node;
266 BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
267 spin_lock(&dcache_lock);
268 node = dentry->d_subdirs.next;
269 while (node != &dentry->d_subdirs) {
270 struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
273 /* This should never be called on a cgroup
274 * directory with child cgroups */
275 BUG_ON(d->d_inode->i_mode & S_IFDIR);
277 spin_unlock(&dcache_lock);
279 simple_unlink(dentry->d_inode, d);
281 spin_lock(&dcache_lock);
283 node = dentry->d_subdirs.next;
285 spin_unlock(&dcache_lock);
289 * NOTE : the dentry must have been dget()'ed
291 static void cgroup_d_remove_dir(struct dentry *dentry)
293 cgroup_clear_directory(dentry);
295 spin_lock(&dcache_lock);
296 list_del_init(&dentry->d_u.d_child);
297 spin_unlock(&dcache_lock);
301 static int rebind_subsystems(struct cgroupfs_root *root,
302 unsigned long final_bits)
304 unsigned long added_bits, removed_bits;
305 struct cgroup *cont = &root->top_cgroup;
308 removed_bits = root->actual_subsys_bits & ~final_bits;
309 added_bits = final_bits & ~root->actual_subsys_bits;
310 /* Check that any added subsystems are currently free */
311 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
312 unsigned long long bit = 1ull << i;
313 struct cgroup_subsys *ss = subsys[i];
314 if (!(bit & added_bits))
316 if (ss->root != &rootnode) {
317 /* Subsystem isn't free */
322 /* Currently we don't handle adding/removing subsystems when
323 * any child cgroups exist. This is theoretically supportable
324 * but involves complex error handling, so it's being left until
326 if (!list_empty(&cont->children))
329 /* Process each subsystem */
330 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
331 struct cgroup_subsys *ss = subsys[i];
332 unsigned long bit = 1UL << i;
333 if (bit & added_bits) {
334 /* We're binding this subsystem to this hierarchy */
335 BUG_ON(cont->subsys[i]);
336 BUG_ON(!dummytop->subsys[i]);
337 BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
338 cont->subsys[i] = dummytop->subsys[i];
339 cont->subsys[i]->cgroup = cont;
340 list_add(&ss->sibling, &root->subsys_list);
341 rcu_assign_pointer(ss->root, root);
345 } else if (bit & removed_bits) {
346 /* We're removing this subsystem */
347 BUG_ON(cont->subsys[i] != dummytop->subsys[i]);
348 BUG_ON(cont->subsys[i]->cgroup != cont);
350 ss->bind(ss, dummytop);
351 dummytop->subsys[i]->cgroup = dummytop;
352 cont->subsys[i] = NULL;
353 rcu_assign_pointer(subsys[i]->root, &rootnode);
354 list_del(&ss->sibling);
355 } else if (bit & final_bits) {
356 /* Subsystem state should already exist */
357 BUG_ON(!cont->subsys[i]);
359 /* Subsystem state shouldn't exist */
360 BUG_ON(cont->subsys[i]);
363 root->subsys_bits = root->actual_subsys_bits = final_bits;
369 static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
371 struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info;
372 struct cgroup_subsys *ss;
374 mutex_lock(&cgroup_mutex);
375 for_each_subsys(root, ss)
376 seq_printf(seq, ",%s", ss->name);
377 if (test_bit(ROOT_NOPREFIX, &root->flags))
378 seq_puts(seq, ",noprefix");
379 mutex_unlock(&cgroup_mutex);
383 struct cgroup_sb_opts {
384 unsigned long subsys_bits;
388 /* Convert a hierarchy specifier into a bitmask of subsystems and
390 static int parse_cgroupfs_options(char *data,
391 struct cgroup_sb_opts *opts)
393 char *token, *o = data ?: "all";
395 opts->subsys_bits = 0;
398 while ((token = strsep(&o, ",")) != NULL) {
401 if (!strcmp(token, "all")) {
402 opts->subsys_bits = (1 << CGROUP_SUBSYS_COUNT) - 1;
403 } else if (!strcmp(token, "noprefix")) {
404 set_bit(ROOT_NOPREFIX, &opts->flags);
406 struct cgroup_subsys *ss;
408 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
410 if (!strcmp(token, ss->name)) {
411 set_bit(i, &opts->subsys_bits);
415 if (i == CGROUP_SUBSYS_COUNT)
420 /* We can't have an empty hierarchy */
421 if (!opts->subsys_bits)
427 static int cgroup_remount(struct super_block *sb, int *flags, char *data)
430 struct cgroupfs_root *root = sb->s_fs_info;
431 struct cgroup *cont = &root->top_cgroup;
432 struct cgroup_sb_opts opts;
434 mutex_lock(&cont->dentry->d_inode->i_mutex);
435 mutex_lock(&cgroup_mutex);
437 /* See what subsystems are wanted */
438 ret = parse_cgroupfs_options(data, &opts);
442 /* Don't allow flags to change at remount */
443 if (opts.flags != root->flags) {
448 ret = rebind_subsystems(root, opts.subsys_bits);
450 /* (re)populate subsystem files */
452 cgroup_populate_dir(cont);
455 mutex_unlock(&cgroup_mutex);
456 mutex_unlock(&cont->dentry->d_inode->i_mutex);
460 static struct super_operations cgroup_ops = {
461 .statfs = simple_statfs,
462 .drop_inode = generic_delete_inode,
463 .show_options = cgroup_show_options,
464 .remount_fs = cgroup_remount,
467 static void init_cgroup_root(struct cgroupfs_root *root)
469 struct cgroup *cont = &root->top_cgroup;
470 INIT_LIST_HEAD(&root->subsys_list);
471 INIT_LIST_HEAD(&root->root_list);
472 root->number_of_cgroups = 1;
474 cont->top_cgroup = cont;
475 INIT_LIST_HEAD(&cont->sibling);
476 INIT_LIST_HEAD(&cont->children);
479 static int cgroup_test_super(struct super_block *sb, void *data)
481 struct cgroupfs_root *new = data;
482 struct cgroupfs_root *root = sb->s_fs_info;
484 /* First check subsystems */
485 if (new->subsys_bits != root->subsys_bits)
488 /* Next check flags */
489 if (new->flags != root->flags)
495 static int cgroup_set_super(struct super_block *sb, void *data)
498 struct cgroupfs_root *root = data;
500 ret = set_anon_super(sb, NULL);
504 sb->s_fs_info = root;
507 sb->s_blocksize = PAGE_CACHE_SIZE;
508 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
509 sb->s_magic = CGROUP_SUPER_MAGIC;
510 sb->s_op = &cgroup_ops;
515 static int cgroup_get_rootdir(struct super_block *sb)
517 struct inode *inode =
518 cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
519 struct dentry *dentry;
524 inode->i_op = &simple_dir_inode_operations;
525 inode->i_fop = &simple_dir_operations;
526 inode->i_op = &cgroup_dir_inode_operations;
527 /* directories start off with i_nlink == 2 (for "." entry) */
529 dentry = d_alloc_root(inode);
538 static int cgroup_get_sb(struct file_system_type *fs_type,
539 int flags, const char *unused_dev_name,
540 void *data, struct vfsmount *mnt)
542 struct cgroup_sb_opts opts;
544 struct super_block *sb;
545 struct cgroupfs_root *root;
547 /* First find the desired set of subsystems */
548 ret = parse_cgroupfs_options(data, &opts);
552 root = kzalloc(sizeof(*root), GFP_KERNEL);
556 init_cgroup_root(root);
557 root->subsys_bits = opts.subsys_bits;
558 root->flags = opts.flags;
560 sb = sget(fs_type, cgroup_test_super, cgroup_set_super, root);
567 if (sb->s_fs_info != root) {
568 /* Reusing an existing superblock */
569 BUG_ON(sb->s_root == NULL);
574 struct cgroup *cont = &root->top_cgroup;
576 BUG_ON(sb->s_root != NULL);
578 ret = cgroup_get_rootdir(sb);
582 mutex_lock(&cgroup_mutex);
584 ret = rebind_subsystems(root, root->subsys_bits);
586 mutex_unlock(&cgroup_mutex);
590 /* EBUSY should be the only error here */
593 list_add(&root->root_list, &roots);
595 sb->s_root->d_fsdata = &root->top_cgroup;
596 root->top_cgroup.dentry = sb->s_root;
598 BUG_ON(!list_empty(&cont->sibling));
599 BUG_ON(!list_empty(&cont->children));
600 BUG_ON(root->number_of_cgroups != 1);
603 * I believe that it's safe to nest i_mutex inside
604 * cgroup_mutex in this case, since no-one else can
605 * be accessing this directory yet. But we still need
606 * to teach lockdep that this is the case - currently
607 * a cgroupfs remount triggers a lockdep warning
609 mutex_lock(&cont->dentry->d_inode->i_mutex);
610 cgroup_populate_dir(cont);
611 mutex_unlock(&cont->dentry->d_inode->i_mutex);
612 mutex_unlock(&cgroup_mutex);
615 return simple_set_mnt(mnt, sb);
618 up_write(&sb->s_umount);
619 deactivate_super(sb);
623 static void cgroup_kill_sb(struct super_block *sb) {
624 struct cgroupfs_root *root = sb->s_fs_info;
625 struct cgroup *cont = &root->top_cgroup;
630 BUG_ON(root->number_of_cgroups != 1);
631 BUG_ON(!list_empty(&cont->children));
632 BUG_ON(!list_empty(&cont->sibling));
634 mutex_lock(&cgroup_mutex);
636 /* Rebind all subsystems back to the default hierarchy */
637 ret = rebind_subsystems(root, 0);
638 /* Shouldn't be able to fail ... */
641 if (!list_empty(&root->root_list))
642 list_del(&root->root_list);
643 mutex_unlock(&cgroup_mutex);
646 kill_litter_super(sb);
649 static struct file_system_type cgroup_fs_type = {
651 .get_sb = cgroup_get_sb,
652 .kill_sb = cgroup_kill_sb,
655 static inline struct cgroup *__d_cont(struct dentry *dentry)
657 return dentry->d_fsdata;
660 static inline struct cftype *__d_cft(struct dentry *dentry)
662 return dentry->d_fsdata;
666 * Called with cgroup_mutex held. Writes path of cgroup into buf.
667 * Returns 0 on success, -errno on error.
669 int cgroup_path(const struct cgroup *cont, char *buf, int buflen)
673 if (cont == dummytop) {
675 * Inactive subsystems have no dentry for their root
682 start = buf + buflen;
686 int len = cont->dentry->d_name.len;
687 if ((start -= len) < buf)
688 return -ENAMETOOLONG;
689 memcpy(start, cont->dentry->d_name.name, len);
696 return -ENAMETOOLONG;
699 memmove(buf, start, buf + buflen - start);
703 /* The various types of files and directories in a cgroup file system */
705 enum cgroup_filetype {
711 static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
712 size_t nbytes, loff_t *ppos)
714 struct cftype *cft = __d_cft(file->f_dentry);
715 struct cgroup *cont = __d_cont(file->f_dentry->d_parent);
722 return cft->write(cont, cft, file, buf, nbytes, ppos);
725 static ssize_t cgroup_read_uint(struct cgroup *cont, struct cftype *cft,
727 char __user *buf, size_t nbytes,
731 u64 val = cft->read_uint(cont, cft);
732 int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
734 return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
737 static ssize_t cgroup_file_read(struct file *file, char __user *buf,
738 size_t nbytes, loff_t *ppos)
740 struct cftype *cft = __d_cft(file->f_dentry);
741 struct cgroup *cont = __d_cont(file->f_dentry->d_parent);
747 return cft->read(cont, cft, file, buf, nbytes, ppos);
749 return cgroup_read_uint(cont, cft, file, buf, nbytes, ppos);
753 static int cgroup_file_open(struct inode *inode, struct file *file)
758 err = generic_file_open(inode, file);
762 cft = __d_cft(file->f_dentry);
766 err = cft->open(inode, file);
773 static int cgroup_file_release(struct inode *inode, struct file *file)
775 struct cftype *cft = __d_cft(file->f_dentry);
777 return cft->release(inode, file);
782 * cgroup_rename - Only allow simple rename of directories in place.
784 static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
785 struct inode *new_dir, struct dentry *new_dentry)
787 if (!S_ISDIR(old_dentry->d_inode->i_mode))
789 if (new_dentry->d_inode)
791 if (old_dir != new_dir)
793 return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
796 static struct file_operations cgroup_file_operations = {
797 .read = cgroup_file_read,
798 .write = cgroup_file_write,
799 .llseek = generic_file_llseek,
800 .open = cgroup_file_open,
801 .release = cgroup_file_release,
804 static struct inode_operations cgroup_dir_inode_operations = {
805 .lookup = simple_lookup,
806 .mkdir = cgroup_mkdir,
807 .rmdir = cgroup_rmdir,
808 .rename = cgroup_rename,
811 static int cgroup_create_file(struct dentry *dentry, int mode,
812 struct super_block *sb)
814 static struct dentry_operations cgroup_dops = {
815 .d_iput = cgroup_diput,
825 inode = cgroup_new_inode(mode, sb);
830 inode->i_op = &cgroup_dir_inode_operations;
831 inode->i_fop = &simple_dir_operations;
833 /* start off with i_nlink == 2 (for "." entry) */
836 /* start with the directory inode held, so that we can
837 * populate it without racing with another mkdir */
838 mutex_lock(&inode->i_mutex);
839 } else if (S_ISREG(mode)) {
841 inode->i_fop = &cgroup_file_operations;
843 dentry->d_op = &cgroup_dops;
844 d_instantiate(dentry, inode);
845 dget(dentry); /* Extra count - pin the dentry in core */
850 * cgroup_create_dir - create a directory for an object.
851 * cont: the cgroup we create the directory for.
852 * It must have a valid ->parent field
853 * And we are going to fill its ->dentry field.
854 * dentry: dentry of the new container
855 * mode: mode to set on new directory.
857 static int cgroup_create_dir(struct cgroup *cont, struct dentry *dentry,
860 struct dentry *parent;
863 parent = cont->parent->dentry;
864 error = cgroup_create_file(dentry, S_IFDIR | mode, cont->root->sb);
866 dentry->d_fsdata = cont;
867 inc_nlink(parent->d_inode);
868 cont->dentry = dentry;
876 int cgroup_add_file(struct cgroup *cont,
877 struct cgroup_subsys *subsys,
878 const struct cftype *cft)
880 struct dentry *dir = cont->dentry;
881 struct dentry *dentry;
884 char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
885 if (subsys && !test_bit(ROOT_NOPREFIX, &cont->root->flags)) {
886 strcpy(name, subsys->name);
889 strcat(name, cft->name);
890 BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
891 dentry = lookup_one_len(name, dir, strlen(name));
892 if (!IS_ERR(dentry)) {
893 error = cgroup_create_file(dentry, 0644 | S_IFREG,
896 dentry->d_fsdata = (void *)cft;
899 error = PTR_ERR(dentry);
903 int cgroup_add_files(struct cgroup *cont,
904 struct cgroup_subsys *subsys,
905 const struct cftype cft[],
909 for (i = 0; i < count; i++) {
910 err = cgroup_add_file(cont, subsys, &cft[i]);
917 static int cgroup_populate_dir(struct cgroup *cont)
920 struct cgroup_subsys *ss;
922 /* First clear out any existing files */
923 cgroup_clear_directory(cont->dentry);
925 for_each_subsys(cont->root, ss) {
926 if (ss->populate && (err = ss->populate(ss, cont)) < 0)
933 static void init_cgroup_css(struct cgroup_subsys_state *css,
934 struct cgroup_subsys *ss,
938 atomic_set(&css->refcnt, 0);
940 if (cont == dummytop)
941 set_bit(CSS_ROOT, &css->flags);
942 BUG_ON(cont->subsys[ss->subsys_id]);
943 cont->subsys[ss->subsys_id] = css;
947 * cgroup_create - create a cgroup
948 * parent: cgroup that will be parent of the new cgroup.
949 * name: name of the new cgroup. Will be strcpy'ed.
950 * mode: mode to set on new inode
952 * Must be called with the mutex on the parent inode held
955 static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
959 struct cgroupfs_root *root = parent->root;
961 struct cgroup_subsys *ss;
962 struct super_block *sb = root->sb;
964 cont = kzalloc(sizeof(*cont), GFP_KERNEL);
968 /* Grab a reference on the superblock so the hierarchy doesn't
969 * get deleted on unmount if there are child cgroups. This
970 * can be done outside cgroup_mutex, since the sb can't
971 * disappear while someone has an open control file on the
973 atomic_inc(&sb->s_active);
975 mutex_lock(&cgroup_mutex);
978 INIT_LIST_HEAD(&cont->sibling);
979 INIT_LIST_HEAD(&cont->children);
981 cont->parent = parent;
982 cont->root = parent->root;
983 cont->top_cgroup = parent->top_cgroup;
985 for_each_subsys(root, ss) {
986 struct cgroup_subsys_state *css = ss->create(ss, cont);
991 init_cgroup_css(css, ss, cont);
994 list_add(&cont->sibling, &cont->parent->children);
995 root->number_of_cgroups++;
997 err = cgroup_create_dir(cont, dentry, mode);
1001 /* The cgroup directory was pre-locked for us */
1002 BUG_ON(!mutex_is_locked(&cont->dentry->d_inode->i_mutex));
1004 err = cgroup_populate_dir(cont);
1005 /* If err < 0, we have a half-filled directory - oh well ;) */
1007 mutex_unlock(&cgroup_mutex);
1008 mutex_unlock(&cont->dentry->d_inode->i_mutex);
1014 list_del(&cont->sibling);
1015 root->number_of_cgroups--;
1019 for_each_subsys(root, ss) {
1020 if (cont->subsys[ss->subsys_id])
1021 ss->destroy(ss, cont);
1024 mutex_unlock(&cgroup_mutex);
1026 /* Release the reference count that we took on the superblock */
1027 deactivate_super(sb);
1033 static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode)
1035 struct cgroup *c_parent = dentry->d_parent->d_fsdata;
1037 /* the vfs holds inode->i_mutex already */
1038 return cgroup_create(c_parent, dentry, mode | S_IFDIR);
1041 static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
1043 struct cgroup *cont = dentry->d_fsdata;
1045 struct cgroup *parent;
1046 struct cgroup_subsys *ss;
1047 struct super_block *sb;
1048 struct cgroupfs_root *root;
1051 /* the vfs holds both inode->i_mutex already */
1053 mutex_lock(&cgroup_mutex);
1054 if (atomic_read(&cont->count) != 0) {
1055 mutex_unlock(&cgroup_mutex);
1058 if (!list_empty(&cont->children)) {
1059 mutex_unlock(&cgroup_mutex);
1063 parent = cont->parent;
1067 /* Check the reference count on each subsystem. Since we
1068 * already established that there are no tasks in the
1069 * cgroup, if the css refcount is also 0, then there should
1070 * be no outstanding references, so the subsystem is safe to
1072 for_each_subsys(root, ss) {
1073 struct cgroup_subsys_state *css;
1074 css = cont->subsys[ss->subsys_id];
1075 if (atomic_read(&css->refcnt)) {
1081 mutex_unlock(&cgroup_mutex);
1085 for_each_subsys(root, ss) {
1086 if (cont->subsys[ss->subsys_id])
1087 ss->destroy(ss, cont);
1090 set_bit(CONT_REMOVED, &cont->flags);
1091 /* delete my sibling from parent->children */
1092 list_del(&cont->sibling);
1093 spin_lock(&cont->dentry->d_lock);
1094 d = dget(cont->dentry);
1095 cont->dentry = NULL;
1096 spin_unlock(&d->d_lock);
1098 cgroup_d_remove_dir(d);
1100 root->number_of_cgroups--;
1102 mutex_unlock(&cgroup_mutex);
1103 /* Drop the active superblock reference that we took when we
1104 * created the cgroup */
1105 deactivate_super(sb);
1109 static void cgroup_init_subsys(struct cgroup_subsys *ss)
1111 struct task_struct *g, *p;
1112 struct cgroup_subsys_state *css;
1113 printk(KERN_ERR "Initializing cgroup subsys %s\n", ss->name);
1115 /* Create the top cgroup state for this subsystem */
1116 ss->root = &rootnode;
1117 css = ss->create(ss, dummytop);
1118 /* We don't handle early failures gracefully */
1119 BUG_ON(IS_ERR(css));
1120 init_cgroup_css(css, ss, dummytop);
1122 /* Update all tasks to contain a subsys pointer to this state
1123 * - since the subsystem is newly registered, all tasks are in
1124 * the subsystem's top cgroup. */
1126 /* If this subsystem requested that it be notified with fork
1127 * events, we should send it one now for every process in the
1130 read_lock(&tasklist_lock);
1131 init_task.cgroups.subsys[ss->subsys_id] = css;
1133 ss->fork(ss, &init_task);
1135 do_each_thread(g, p) {
1136 printk(KERN_INFO "Setting task %p css to %p (%d)\n", css, p, p->pid);
1137 p->cgroups.subsys[ss->subsys_id] = css;
1140 } while_each_thread(g, p);
1141 read_unlock(&tasklist_lock);
1143 need_forkexit_callback |= ss->fork || ss->exit;
1149 * cgroup_init_early - initialize cgroups at system boot, and
1150 * initialize any subsystems that request early init.
1152 int __init cgroup_init_early(void)
1155 init_cgroup_root(&rootnode);
1156 list_add(&rootnode.root_list, &roots);
1158 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1159 struct cgroup_subsys *ss = subsys[i];
1162 BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
1163 BUG_ON(!ss->create);
1164 BUG_ON(!ss->destroy);
1165 if (ss->subsys_id != i) {
1166 printk(KERN_ERR "Subsys %s id == %d\n",
1167 ss->name, ss->subsys_id);
1172 cgroup_init_subsys(ss);
1178 * cgroup_init - register cgroup filesystem and /proc file, and
1179 * initialize any subsystems that didn't request early init.
1181 int __init cgroup_init(void)
1186 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
1187 struct cgroup_subsys *ss = subsys[i];
1188 if (!ss->early_init)
1189 cgroup_init_subsys(ss);
1192 err = register_filesystem(&cgroup_fs_type);