/*
* kernel/cgroup.c
*
* Generic process-grouping system.
*
* Based originally on the cpuset system, extracted by Paul Menage
* Copyright (C) 2006 Google, Inc
*
* Copyright notices from the original cpuset code:
* --------------------------------------------------
* Copyright (C) 2003 BULL SA.
* Copyright (C) 2004-2006 Silicon Graphics, Inc.
*
* Portions derived from Patrick Mochel's sysfs code.
* sysfs is Copyright (c) 2001-3 Patrick Mochel
*
* 2003-10-10 Written by Simon Derr.
* 2003-10-22 Updates by Stephen Hemminger.
* 2004 May-July Rework by Paul Jackson.
* ---------------------------------------------------
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of the Linux
* distribution for more details.
*/
#include <linux/cgroup.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/magic.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <asm/atomic.h>
/* Generate an array of cgroup subsystem pointers */
#define SUBSYS(_x) &_x ## _subsys,
static struct cgroup_subsys *subsys[] = {
#include <linux/cgroup_subsys.h>
};
/*
* A cgroupfs_root represents the root of a cgroup hierarchy,
* and may be associated with a superblock to form an active
* hierarchy
*/
struct cgroupfs_root {
struct super_block *sb;
/*
* The bitmask of subsystems intended to be attached to this
* hierarchy
*/
unsigned long subsys_bits;
/* The bitmask of subsystems currently attached to this hierarchy */
unsigned long actual_subsys_bits;
/* A list running through the attached subsystems */
struct list_head subsys_list;
/* The root cgroup for this hierarchy */
struct cgroup top_cgroup;
/* Tracks how many cgroups are currently defined in hierarchy.*/
int number_of_cgroups;
/* A list running through the mounted hierarchies */
struct list_head root_list;
/* Hierarchy-specific flags */
unsigned long flags;
};
/*
* The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
* subsystems that are otherwise unattached - it never has more than a
* single cgroup, and all tasks are part of that cgroup.
*/
static struct cgroupfs_root rootnode;
/* The list of hierarchy roots */
static LIST_HEAD(roots);
/* dummytop is a shorthand for the dummy hierarchy's top cgroup */
#define dummytop (&rootnode.top_cgroup)
/* This flag indicates whether tasks in the fork and exit paths should
* take callback_mutex and check for fork/exit handlers to call. This
* avoids us having to do extra work in the fork/exit path if none of the
* subsystems need to be called.
*/
static int need_forkexit_callback;
/* bits in struct cgroup flags field */
enum {
CONT_REMOVED,
};
/* convenient tests for these bits */
inline int cgroup_is_removed(const struct cgroup *cont)
{
return test_bit(CONT_REMOVED, &cont->flags);
}
/* bits in struct cgroupfs_root flags field */
enum {
ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
};
/*
* for_each_subsys() allows you to iterate on each subsystem attached to
* an active hierarchy
*/
#define for_each_subsys(_root, _ss) \
list_for_each_entry(_ss, &_root->subsys_list, sibling)
/* for_each_root() allows you to iterate across the active hierarchies */
#define for_each_root(_root) \
list_for_each_entry(_root, &roots, root_list)
/*
* There is one global cgroup mutex. We also require taking
* task_lock() when dereferencing a task's cgroup subsys pointers.
* See "The task_lock() exception", at the end of this comment.
*
* A task must hold cgroup_mutex to modify cgroups.
*
* Any task can increment and decrement the count field without lock.
* So in general, code holding cgroup_mutex can't rely on the count
* field not changing. However, if the count goes to zero, then only
* attach_task() can increment it again. Because a count of zero
* means that no tasks are currently attached, therefore there is no
* way a task attached to that cgroup can fork (the other way to
* increment the count). So code holding cgroup_mutex can safely
* assume that if the count is zero, it will stay zero. Similarly, if
* a task holds cgroup_mutex on a cgroup with zero count, it
* knows that the cgroup won't be removed, as cgroup_rmdir()
* needs that mutex.
*
* The cgroup_common_file_write handler for operations that modify
* the cgroup hierarchy holds cgroup_mutex across the entire operation,
* single threading all such cgroup modifications across the system.
*
* The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
* (usually) take cgroup_mutex. These are the two most performance
* critical pieces of code here. The exception occurs on cgroup_exit(),
* when a task in a notify_on_release cgroup exits. Then cgroup_mutex
* is taken, and if the cgroup count is zero, a usermode call made
* to /sbin/cgroup_release_agent with the name of the cgroup (path
* relative to the root of cgroup file system) as the argument.
*
* A cgroup can only be deleted if both its 'count' of using tasks
* is zero, and its list of 'children' cgroups is empty. Since all
* tasks in the system use _some_ cgroup, and since there is always at
* least one task in the system (init, pid == 1), therefore, top_cgroup
* always has either children cgroups and/or using tasks. So we don't
* need a special hack to ensure that top_cgroup cannot be deleted.
*
* The task_lock() exception
*
* The need for this exception arises from the action of
* attach_task(), which overwrites one tasks cgroup pointer with
* another. It does so using cgroup_mutexe, however there are
* several performance critical places that need to reference
* task->cgroup without the expense of grabbing a system global
* mutex. Therefore except as noted below, when dereferencing or, as
* in attach_task(), modifying a task'ss cgroup pointer we use
* task_lock(), which acts on a spinlock (task->alloc_lock) already in
* the task_struct routinely used for such matters.
*
* P.S. One more locking exception. RCU is used to guard the
* update of a tasks cgroup pointer by attach_task()
*/
static DEFINE_MUTEX(cgroup_mutex);
/**
* cgroup_lock - lock out any changes to cgroup structures
*
*/
void cgroup_lock(void)
{
mutex_lock(&cgroup_mutex);
}
/**
* cgroup_unlock - release lock on cgroup changes
*
* Undo the lock taken in a previous cgroup_lock() call.
*/
void cgroup_unlock(void)
{
mutex_unlock(&cgroup_mutex);
}
/*
* A couple of forward declarations required, due to cyclic reference loop:
* cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
* cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
* -> cgroup_mkdir.
*/
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode);
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
static int cgroup_populate_dir(struct cgroup *cont);
static struct inode_operations cgroup_dir_inode_operations;
static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
{
struct inode *inode = new_inode(sb);
static struct backing_dev_info cgroup_backing_dev_info = {
.capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
};
if (inode) {
inode->i_mode = mode;
inode->i_uid = current->fsuid;
inode->i_gid = current->fsgid;
inode->i_blocks = 0;
inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
}
return inode;
}
static void cgroup_diput(struct dentry *dentry, struct inode *inode)
{
/* is dentry a directory ? if so, kfree() associated cgroup */
if (S_ISDIR(inode->i_mode)) {
struct cgroup *cont = dentry->d_fsdata;
BUG_ON(!(cgroup_is_removed(cont)));
kfree(cont);
}
iput(inode);
}
static void remove_dir(struct dentry *d)
{
struct dentry *parent = dget(d->d_parent);
d_delete(d);
simple_rmdir(parent->d_inode, d);
dput(parent);
}
static void cgroup_clear_directory(struct dentry *dentry)
{
struct list_head *node;
BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
spin_lock(&dcache_lock);
node = dentry->d_subdirs.next;
while (node != &dentry->d_subdirs) {
struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
list_del_init(node);
if (d->d_inode) {
/* This should never be called on a cgroup
* directory with child cgroups */
BUG_ON(d->d_inode->i_mode & S_IFDIR);
d = dget_locked(d);
spin_unlock(&dcache_lock);
d_delete(d);
simple_unlink(dentry->d_inode, d);
dput(d);
spin_lock(&dcache_lock);
}
node = dentry->d_subdirs.next;
}
spin_unlock(&dcache_lock);
}
/*
* NOTE : the dentry must have been dget()'ed
*/
static void cgroup_d_remove_dir(struct dentry *dentry)
{
cgroup_clear_directory(dentry);
spin_lock(&dcache_lock);
list_del_init(&dentry->d_u.d_child);
spin_unlock(&dcache_lock);
remove_dir(dentry);
}
static int rebind_subsystems(struct cgroupfs_root *root,
unsigned long final_bits)
{
unsigned long added_bits, removed_bits;
struct cgroup *cont = &root->top_cgroup;
int i;
removed_bits = root->actual_subsys_bits & ~final_bits;
added_bits = final_bits & ~root->actual_subsys_bits;
/* Check that any added subsystems are currently free */
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
unsigned long long bit = 1ull << i;
struct cgroup_subsys *ss = subsys[i];
if (!(bit & added_bits))
continue;
if (ss->root != &rootnode) {
/* Subsystem isn't free */
return -EBUSY;
}
}
/* Currently we don't handle adding/removing subsystems when
* any child cgroups exist. This is theoretically supportable
* but involves complex error handling, so it's being left until
* later */
if (!list_empty(&cont->children))
return -EBUSY;
/* Process each subsystem */
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
unsigned long bit = 1UL << i;
if (bit & added_bits) {
/* We're binding this subsystem to this hierarchy */
BUG_ON(cont->subsys[i]);
BUG_ON(!dummytop->subsys[i]);
BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
cont->subsys[i] = dummytop->subsys[i];
cont->subsys[i]->cgroup = cont;
list_add(&ss->sibling, &root->subsys_list);
rcu_assign_pointer(ss->root, root);
if (ss->bind)
ss->bind(ss, cont);
} else if (bit & removed_bits) {
/* We're removing this subsystem */
BUG_ON(cont->subsys[i] != dummytop->subsys[i]);
BUG_ON(cont->subsys[i]->cgroup != cont);
if (ss->bind)
ss->bind(ss, dummytop);
dummytop->subsys[i]->cgroup = dummytop;
cont->subsys[i] = NULL;
rcu_assign_pointer(subsys[i]->root, &rootnode);
list_del(&ss->sibling);
} else if (bit & final_bits) {
/* Subsystem state should already exist */
BUG_ON(!cont->subsys[i]);
} else {
/* Subsystem state shouldn't exist */
BUG_ON(cont->subsys[i]);
}
}
root->subsys_bits = root->actual_subsys_bits = final_bits;
synchronize_rcu();
return 0;
}
static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info;
struct cgroup_subsys *ss;
mutex_lock(&cgroup_mutex);
for_each_subsys(root, ss)
seq_printf(seq, ",%s", ss->name);
if (test_bit(ROOT_NOPREFIX, &root->flags))
seq_puts(seq, ",noprefix");
mutex_unlock(&cgroup_mutex);
return 0;
}
struct cgroup_sb_opts {
unsigned long subsys_bits;
unsigned long flags;
};
/* Convert a hierarchy specifier into a bitmask of subsystems and
* flags. */
static int parse_cgroupfs_options(char *data,
struct cgroup_sb_opts *opts)
{
char *token, *o = data ?: "all";
opts->subsys_bits = 0;
opts->flags = 0;
while ((token = strsep(&o, ",")) != NULL) {
if (!*token)
return -EINVAL;
if (!strcmp(token, "all")) {
opts->subsys_bits = (1 << CGROUP_SUBSYS_COUNT) - 1;
} else if (!strcmp(token, "noprefix")) {
set_bit(ROOT_NOPREFIX, &opts->flags);
} else {
struct cgroup_subsys *ss;
int i;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
ss = subsys[i];
if (!strcmp(token, ss->name)) {
set_bit(i, &opts->subsys_bits);
break;
}
}
if (i == CGROUP_SUBSYS_COUNT)
return -ENOENT;
}
}
/* We can't have an empty hierarchy */
if (!opts->subsys_bits)
return -EINVAL;
return 0;
}
static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
int ret = 0;
struct cgroupfs_root *root = sb->s_fs_info;
struct cgroup *cont = &root->top_cgroup;
struct cgroup_sb_opts opts;
mutex_lock(&cont->dentry->d_inode->i_mutex);
mutex_lock(&cgroup_mutex);
/* See what subsystems are wanted */
ret = parse_cgroupfs_options(data, &opts);
if (ret)
goto out_unlock;
/* Don't allow flags to change at remount */
if (opts.flags != root->flags) {
ret = -EINVAL;
goto out_unlock;
}
ret = rebind_subsystems(root, opts.subsys_bits);
/* (re)populate subsystem files */
if (!ret)
cgroup_populate_dir(cont);
out_unlock:
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cont->dentry->d_inode->i_mutex);
return ret;
}
static struct super_operations cgroup_ops = {
.statfs = simple_statfs,
.drop_inode = generic_delete_inode,
.show_options = cgroup_show_options,
.remount_fs = cgroup_remount,
};
static void init_cgroup_root(struct cgroupfs_root *root)
{
struct cgroup *cont = &root->top_cgroup;
INIT_LIST_HEAD(&root->subsys_list);
INIT_LIST_HEAD(&root->root_list);
root->number_of_cgroups = 1;
cont->root = root;
cont->top_cgroup = cont;
INIT_LIST_HEAD(&cont->sibling);
INIT_LIST_HEAD(&cont->children);
}
static int cgroup_test_super(struct super_block *sb, void *data)
{
struct cgroupfs_root *new = data;
struct cgroupfs_root *root = sb->s_fs_info;
/* First check subsystems */
if (new->subsys_bits != root->subsys_bits)
return 0;
/* Next check flags */
if (new->flags != root->flags)
return 0;
return 1;
}
static int cgroup_set_super(struct super_block *sb, void *data)
{
int ret;
struct cgroupfs_root *root = data;
ret = set_anon_super(sb, NULL);
if (ret)
return ret;
sb->s_fs_info = root;
root->sb = sb;
sb->s_blocksize = PAGE_CACHE_SIZE;
sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
sb->s_magic = CGROUP_SUPER_MAGIC;
sb->s_op = &cgroup_ops;
return 0;
}
static int cgroup_get_rootdir(struct super_block *sb)
{
struct inode *inode =
cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
struct dentry *dentry;
if (!inode)
return -ENOMEM;
inode->i_op = &simple_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
inode->i_op = &cgroup_dir_inode_operations;
/* directories start off with i_nlink == 2 (for "." entry) */
inc_nlink(inode);
dentry = d_alloc_root(inode);
if (!dentry) {
iput(inode);
return -ENOMEM;
}
sb->s_root = dentry;
return 0;
}
static int cgroup_get_sb(struct file_system_type *fs_type,
int flags, const char *unused_dev_name,
void *data, struct vfsmount *mnt)
{
struct cgroup_sb_opts opts;
int ret = 0;
struct super_block *sb;
struct cgroupfs_root *root;
/* First find the desired set of subsystems */
ret = parse_cgroupfs_options(data, &opts);
if (ret)
return ret;
root = kzalloc(sizeof(*root), GFP_KERNEL);
if (!root)
return -ENOMEM;
init_cgroup_root(root);
root->subsys_bits = opts.subsys_bits;
root->flags = opts.flags;
sb = sget(fs_type, cgroup_test_super, cgroup_set_super, root);
if (IS_ERR(sb)) {
kfree(root);
return PTR_ERR(sb);
}
if (sb->s_fs_info != root) {
/* Reusing an existing superblock */
BUG_ON(sb->s_root == NULL);
kfree(root);
root = NULL;
} else {
/* New superblock */
struct cgroup *cont = &root->top_cgroup;
BUG_ON(sb->s_root != NULL);
ret = cgroup_get_rootdir(sb);
if (ret)
goto drop_new_super;
mutex_lock(&cgroup_mutex);
ret = rebind_subsystems(root, root->subsys_bits);
if (ret == -EBUSY) {
mutex_unlock(&cgroup_mutex);
goto drop_new_super;
}
/* EBUSY should be the only error here */
BUG_ON(ret);
list_add(&root->root_list, &roots);
sb->s_root->d_fsdata = &root->top_cgroup;
root->top_cgroup.dentry = sb->s_root;
BUG_ON(!list_empty(&cont->sibling));
BUG_ON(!list_empty(&cont->children));
BUG_ON(root->number_of_cgroups != 1);
/*
* I believe that it's safe to nest i_mutex inside
* cgroup_mutex in this case, since no-one else can
* be accessing this directory yet. But we still need
* to teach lockdep that this is the case - currently
* a cgroupfs remount triggers a lockdep warning
*/
mutex_lock(&cont->dentry->d_inode->i_mutex);
cgroup_populate_dir(cont);
mutex_unlock(&cont->dentry->d_inode->i_mutex);
mutex_unlock(&cgroup_mutex);
}
return simple_set_mnt(mnt, sb);
drop_new_super:
up_write(&sb->s_umount);
deactivate_super(sb);
return ret;
}
static void cgroup_kill_sb(struct super_block *sb) {
struct cgroupfs_root *root = sb->s_fs_info;
struct cgroup *cont = &root->top_cgroup;
int ret;
BUG_ON(!root);
BUG_ON(root->number_of_cgroups != 1);
BUG_ON(!list_empty(&cont->children));
BUG_ON(!list_empty(&cont->sibling));
mutex_lock(&cgroup_mutex);
/* Rebind all subsystems back to the default hierarchy */
ret = rebind_subsystems(root, 0);
/* Shouldn't be able to fail ... */
BUG_ON(ret);
if (!list_empty(&root->root_list))
list_del(&root->root_list);
mutex_unlock(&cgroup_mutex);
kfree(root);
kill_litter_super(sb);
}
static struct file_system_type cgroup_fs_type = {
.name = "cgroup",
.get_sb = cgroup_get_sb,
.kill_sb = cgroup_kill_sb,
};
static inline struct cgroup *__d_cont(struct dentry *dentry)
{
return dentry->d_fsdata;
}
static inline struct cftype *__d_cft(struct dentry *dentry)
{
return dentry->d_fsdata;
}
/*
* Called with cgroup_mutex held. Writes path of cgroup into buf.
* Returns 0 on success, -errno on error.
*/
int cgroup_path(const struct cgroup *cont, char *buf, int buflen)
{
char *start;
if (cont == dummytop) {
/*
* Inactive subsystems have no dentry for their root
* cgroup
*/
strcpy(buf, "/");
return 0;
}
start = buf + buflen;
*--start = '\0';
for (;;) {
int len = cont->dentry->d_name.len;
if ((start -= len) < buf)
return -ENAMETOOLONG;
memcpy(start, cont->dentry->d_name.name, len);
cont = cont->parent;
if (!cont)
break;
if (!cont->parent)
continue;
if (--start < buf)
return -ENAMETOOLONG;
*start = '/';
}
memmove(buf, start, buf + buflen - start);
return 0;
}
/* The various types of files and directories in a cgroup file system */
enum cgroup_filetype {
FILE_ROOT,
FILE_DIR,
FILE_TASKLIST,
};
static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
size_t nbytes, loff_t *ppos)
{
struct cftype *cft = __d_cft(file->f_dentry);
struct cgroup *cont = __d_cont(file->f_dentry->d_parent);
if (!cft)
return -ENODEV;
if (!cft->write)
return -EINVAL;
return cft->write(cont, cft, file, buf, nbytes, ppos);
}
static ssize_t cgroup_read_uint(struct cgroup *cont, struct cftype *cft,
struct file *file,
char __user *buf, size_t nbytes,
loff_t *ppos)
{
char tmp[64];
u64 val = cft->read_uint(cont, cft);
int len = sprintf(tmp, "%llu\n", (unsigned long long) val);
return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
}
static ssize_t cgroup_file_read(struct file *file, char __user *buf,
size_t nbytes, loff_t *ppos)
{
struct cftype *cft = __d_cft(file->f_dentry);
struct cgroup *cont = __d_cont(file->f_dentry->d_parent);
if (!cft)
return -ENODEV;
if (cft->read)
return cft->read(cont, cft, file, buf, nbytes, ppos);
if (cft->read_uint)
return cgroup_read_uint(cont, cft, file, buf, nbytes, ppos);
return -EINVAL;
}
static int cgroup_file_open(struct inode *inode, struct file *file)
{
int err;
struct cftype *cft;
err = generic_file_open(inode, file);
if (err)
return err;
cft = __d_cft(file->f_dentry);
if (!cft)
return -ENODEV;
if (cft->open)
err = cft->open(inode, file);
else
err = 0;
return err;
}
static int cgroup_file_release(struct inode *inode, struct file *file)
{
struct cftype *cft = __d_cft(file->f_dentry);
if (cft->release)
return cft->release(inode, file);
return 0;
}
/*
* cgroup_rename - Only allow simple rename of directories in place.
*/
static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry)
{
if (!S_ISDIR(old_dentry->d_inode->i_mode))
return -ENOTDIR;
if (new_dentry->d_inode)
return -EEXIST;
if (old_dir != new_dir)
return -EIO;
return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
}
static struct file_operations cgroup_file_operations = {
.read = cgroup_file_read,
.write = cgroup_file_write,
.llseek = generic_file_llseek,
.open = cgroup_file_open,
.release = cgroup_file_release,
};
static struct inode_operations cgroup_dir_inode_operations = {
.lookup = simple_lookup,
.mkdir = cgroup_mkdir,
.rmdir = cgroup_rmdir,
.rename = cgroup_rename,
};
static int cgroup_create_file(struct dentry *dentry, int mode,
struct super_block *sb)
{
static struct dentry_operations cgroup_dops = {
.d_iput = cgroup_diput,
};
struct inode *inode;
if (!dentry)
return -ENOENT;
if (dentry->d_inode)
return -EEXIST;
inode = cgroup_new_inode(mode, sb);
if (!inode)
return -ENOMEM;
if (S_ISDIR(mode)) {
inode->i_op = &cgroup_dir_inode_operations;
inode->i_fop = &simple_dir_operations;
/* start off with i_nlink == 2 (for "." entry) */
inc_nlink(inode);
/* start with the directory inode held, so that we can
* populate it without racing with another mkdir */
mutex_lock(&inode->i_mutex);
} else if (S_ISREG(mode)) {
inode->i_size = 0;
inode->i_fop = &cgroup_file_operations;
}
dentry->d_op = &cgroup_dops;
d_instantiate(dentry, inode);
dget(dentry); /* Extra count - pin the dentry in core */
return 0;
}
/*
* cgroup_create_dir - create a directory for an object.
* cont: the cgroup we create the directory for.
* It must have a valid ->parent field
* And we are going to fill its ->dentry field.
* dentry: dentry of the new container
* mode: mode to set on new directory.
*/
static int cgroup_create_dir(struct cgroup *cont, struct dentry *dentry,
int mode)
{
struct dentry *parent;
int error = 0;
parent = cont->parent->dentry;
error = cgroup_create_file(dentry, S_IFDIR | mode, cont->root->sb);
if (!error) {
dentry->d_fsdata = cont;
inc_nlink(parent->d_inode);
cont->dentry = dentry;
dget(dentry);
}
dput(dentry);
return error;
}
int cgroup_add_file(struct cgroup *cont,
struct cgroup_subsys *subsys,
const struct cftype *cft)
{
struct dentry *dir = cont->dentry;
struct dentry *dentry;
int error;
char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
if (subsys && !test_bit(ROOT_NOPREFIX, &cont->root->flags)) {
strcpy(name, subsys->name);
strcat(name, ".");
}
strcat(name, cft->name);
BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
dentry = lookup_one_len(name, dir, strlen(name));
if (!IS_ERR(dentry)) {
error = cgroup_create_file(dentry, 0644 | S_IFREG,
cont->root->sb);
if (!error)
dentry->d_fsdata = (void *)cft;
dput(dentry);
} else
error = PTR_ERR(dentry);
return error;
}
int cgroup_add_files(struct cgroup *cont,
struct cgroup_subsys *subsys,
const struct cftype cft[],
int count)
{
int i, err;
for (i = 0; i < count; i++) {
err = cgroup_add_file(cont, subsys, &cft[i]);
if (err)
return err;
}
return 0;
}
static int cgroup_populate_dir(struct cgroup *cont)
{
int err;
struct cgroup_subsys *ss;
/* First clear out any existing files */
cgroup_clear_directory(cont->dentry);
for_each_subsys(cont->root, ss) {
if (ss->populate && (err = ss->populate(ss, cont)) < 0)
return err;
}
return 0;
}
static void init_cgroup_css(struct cgroup_subsys_state *css,
struct cgroup_subsys *ss,
struct cgroup *cont)
{
css->cgroup = cont;
atomic_set(&css->refcnt, 0);
css->flags = 0;
if (cont == dummytop)
set_bit(CSS_ROOT, &css->flags);
BUG_ON(cont->subsys[ss->subsys_id]);
cont->subsys[ss->subsys_id] = css;
}
/*
* cgroup_create - create a cgroup
* parent: cgroup that will be parent of the new cgroup.
* name: name of the new cgroup. Will be strcpy'ed.
* mode: mode to set on new inode
*
* Must be called with the mutex on the parent inode held
*/
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
int mode)
{
struct cgroup *cont;
struct cgroupfs_root *root = parent->root;
int err = 0;
struct cgroup_subsys *ss;
struct super_block *sb = root->sb;
cont = kzalloc(sizeof(*cont), GFP_KERNEL);
if (!cont)
return -ENOMEM;
/* Grab a reference on the superblock so the hierarchy doesn't
* get deleted on unmount if there are child cgroups. This
* can be done outside cgroup_mutex, since the sb can't
* disappear while someone has an open control file on the
* fs */
atomic_inc(&sb->s_active);
mutex_lock(&cgroup_mutex);
cont->flags = 0;
INIT_LIST_HEAD(&cont->sibling);
INIT_LIST_HEAD(&cont->children);
cont->parent = parent;
cont->root = parent->root;
cont->top_cgroup = parent->top_cgroup;
for_each_subsys(root, ss) {
struct cgroup_subsys_state *css = ss->create(ss, cont);
if (IS_ERR(css)) {
err = PTR_ERR(css);
goto err_destroy;
}
init_cgroup_css(css, ss, cont);
}
list_add(&cont->sibling, &cont->parent->children);
root->number_of_cgroups++;
err = cgroup_create_dir(cont, dentry, mode);
if (err < 0)
goto err_remove;
/* The cgroup directory was pre-locked for us */
BUG_ON(!mutex_is_locked(&cont->dentry->d_inode->i_mutex));
err = cgroup_populate_dir(cont);
/* If err < 0, we have a half-filled directory - oh well ;) */
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cont->dentry->d_inode->i_mutex);
return 0;
err_remove:
list_del(&cont->sibling);
root->number_of_cgroups--;
err_destroy:
for_each_subsys(root, ss) {
if (cont->subsys[ss->subsys_id])
ss->destroy(ss, cont);
}
mutex_unlock(&cgroup_mutex);
/* Release the reference count that we took on the superblock */
deactivate_super(sb);
kfree(cont);
return err;
}
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
struct cgroup *c_parent = dentry->d_parent->d_fsdata;
/* the vfs holds inode->i_mutex already */
return cgroup_create(c_parent, dentry, mode | S_IFDIR);
}
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
struct cgroup *cont = dentry->d_fsdata;
struct dentry *d;
struct cgroup *parent;
struct cgroup_subsys *ss;
struct super_block *sb;
struct cgroupfs_root *root;
int css_busy = 0;
/* the vfs holds both inode->i_mutex already */
mutex_lock(&cgroup_mutex);
if (atomic_read(&cont->count) != 0) {
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
if (!list_empty(&cont->children)) {
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
parent = cont->parent;
root = cont->root;
sb = root->sb;
/* Check the reference count on each subsystem. Since we
* already established that there are no tasks in the
* cgroup, if the css refcount is also 0, then there should
* be no outstanding references, so the subsystem is safe to
* destroy */
for_each_subsys(root, ss) {
struct cgroup_subsys_state *css;
css = cont->subsys[ss->subsys_id];
if (atomic_read(&css->refcnt)) {
css_busy = 1;
break;
}
}
if (css_busy) {
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
for_each_subsys(root, ss) {
if (cont->subsys[ss->subsys_id])
ss->destroy(ss, cont);
}
set_bit(CONT_REMOVED, &cont->flags);
/* delete my sibling from parent->children */
list_del(&cont->sibling);
spin_lock(&cont->dentry->d_lock);
d = dget(cont->dentry);
cont->dentry = NULL;
spin_unlock(&d->d_lock);
cgroup_d_remove_dir(d);
dput(d);
root->number_of_cgroups--;
mutex_unlock(&cgroup_mutex);
/* Drop the active superblock reference that we took when we
* created the cgroup */
deactivate_super(sb);
return 0;
}
static void cgroup_init_subsys(struct cgroup_subsys *ss)
{
struct task_struct *g, *p;
struct cgroup_subsys_state *css;
printk(KERN_ERR "Initializing cgroup subsys %s\n", ss->name);
/* Create the top cgroup state for this subsystem */
ss->root = &rootnode;
css = ss->create(ss, dummytop);
/* We don't handle early failures gracefully */
BUG_ON(IS_ERR(css));
init_cgroup_css(css, ss, dummytop);
/* Update all tasks to contain a subsys pointer to this state
* - since the subsystem is newly registered, all tasks are in
* the subsystem's top cgroup. */
/* If this subsystem requested that it be notified with fork
* events, we should send it one now for every process in the
* system */
read_lock(&tasklist_lock);
init_task.cgroups.subsys[ss->subsys_id] = css;
if (ss->fork)
ss->fork(ss, &init_task);
do_each_thread(g, p) {
printk(KERN_INFO "Setting task %p css to %p (%d)\n", css, p, p->pid);
p->cgroups.subsys[ss->subsys_id] = css;
if (ss->fork)
ss->fork(ss, p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
need_forkexit_callback |= ss->fork || ss->exit;
ss->active = 1;
}
/**
* cgroup_init_early - initialize cgroups at system boot, and
* initialize any subsystems that request early init.
*/
int __init cgroup_init_early(void)
{
int i;
init_cgroup_root(&rootnode);
list_add(&rootnode.root_list, &roots);
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
BUG_ON(!ss->name);
BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
BUG_ON(!ss->create);
BUG_ON(!ss->destroy);
if (ss->subsys_id != i) {
printk(KERN_ERR "Subsys %s id == %d\n",
ss->name, ss->subsys_id);
BUG();
}
if (ss->early_init)
cgroup_init_subsys(ss);
}
return 0;
}
/**
* cgroup_init - register cgroup filesystem and /proc file, and
* initialize any subsystems that didn't request early init.
*/
int __init cgroup_init(void)
{
int err;
int i;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (!ss->early_init)
cgroup_init_subsys(ss);
}
err = register_filesystem(&cgroup_fs_type);
if (err < 0)
goto out;
out:
return err;
}
