/*
* 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/proc_fs.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
#include <linux/backing-dev.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/magic.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/sort.h>
#include <linux/kmod.h>
#include <linux/delayacct.h>
#include <linux/cgroupstats.h>
#include <asm/atomic.h>
static DEFINE_MUTEX(cgroup_mutex);
/* 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 path to use for release notifications. No locking
* between setting and use - so if userspace updates this
* while child cgroups exist, you could miss a
* notification. We ensure that it's always a valid
* NUL-terminated string */
char release_agent_path[PATH_MAX];
};
/*
* 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);
static int root_count;
/* 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 {
/* Control Group is dead */
CONT_REMOVED,
/* Control Group has previously had a child cgroup or a task,
* but no longer (only if CONT_NOTIFY_ON_RELEASE is set) */
CONT_RELEASABLE,
/* Control Group requires release notifications to userspace */
CONT_NOTIFY_ON_RELEASE,
};
/* 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 */
};
inline int cgroup_is_releasable(const struct cgroup *cont)
{
const int bits =
(1 << CONT_RELEASABLE) |
(1 << CONT_NOTIFY_ON_RELEASE);
return (cont->flags & bits) == bits;
}
inline int notify_on_release(const struct cgroup *cont)
{
return test_bit(CONT_NOTIFY_ON_RELEASE, &cont->flags);
}
/*
* 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)
/* the list of cgroups eligible for automatic release. Protected by
* release_list_lock */
static LIST_HEAD(release_list);
static DEFINE_SPINLOCK(release_list_lock);
static void cgroup_release_agent(struct work_struct *work);
static DECLARE_WORK(release_agent_work, cgroup_release_agent);
static void check_for_release(struct cgroup *cont);
/* Link structure for associating css_set objects with cgroups */
struct cg_cgroup_link {
/*
* List running through cg_cgroup_links associated with a
* cgroup, anchored on cgroup->css_sets
*/
struct list_head cont_link_list;
/*
* List running through cg_cgroup_links pointing at a
* single css_set object, anchored on css_set->cg_links
*/
struct list_head cg_link_list;
struct css_set *cg;
};
/* The default css_set - used by init and its children prior to any
* hierarchies being mounted. It contains a pointer to the root state
* for each subsystem. Also used to anchor the list of css_sets. Not
* reference-counted, to improve performance when child cgroups
* haven't been created.
*/
static struct css_set init_css_set;
static struct cg_cgroup_link init_css_set_link;
/* css_set_lock protects the list of css_set objects, and the
* chain of tasks off each css_set. Nests outside task->alloc_lock
* due to cgroup_iter_start() */
static DEFINE_RWLOCK(css_set_lock);
static int css_set_count;
/* We don't maintain the lists running through each css_set to its
* task until after the first call to cgroup_iter_start(). This
* reduces the fork()/exit() overhead for people who have cgroups
* compiled into their kernel but not actually in use */
static int use_task_css_set_links;
/* When we create or destroy a css_set, the operation simply
* takes/releases a reference count on all the cgroups referenced
* by subsystems in this css_set. This can end up multiple-counting
* some cgroups, but that's OK - the ref-count is just a
* busy/not-busy indicator; ensuring that we only count each cgroup
* once would require taking a global lock to ensure that no
* subsystems moved between hierarchies while we were doing so.
*
* Possible TODO: decide at boot time based on the number of
* registered subsystems and the number of CPUs or NUMA nodes whether
* it's better for performance to ref-count every subsystem, or to
* take a global lock and only add one ref count to each hierarchy.
*/
/*
* unlink a css_set from the list and free it
*/
static void unlink_css_set(struct css_set *cg)
{
write_lock(&css_set_lock);
list_del(&cg->list);
css_set_count--;
while (!list_empty(&cg->cg_links)) {
struct cg_cgroup_link *link;
link = list_entry(cg->cg_links.next,
struct cg_cgroup_link, cg_link_list);
list_del(&link->cg_link_list);
list_del(&link->cont_link_list);
kfree(link);
}
write_unlock(&css_set_lock);
}
static void __release_css_set(struct kref *k, int taskexit)
{
int i;
struct css_set *cg = container_of(k, struct css_set, ref);
unlink_css_set(cg);
rcu_read_lock();
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup *cont = cg->subsys[i]->cgroup;
if (atomic_dec_and_test(&cont->count) &&
notify_on_release(cont)) {
if (taskexit)
set_bit(CONT_RELEASABLE, &cont->flags);
check_for_release(cont);
}
}
rcu_read_unlock();
kfree(cg);
}
static void release_css_set(struct kref *k)
{
__release_css_set(k, 0);
}
static void release_css_set_taskexit(struct kref *k)
{
__release_css_set(k, 1);
}
/*
* refcounted get/put for css_set objects
*/
static inline void get_css_set(struct css_set *cg)
{
kref_get(&cg->ref);
}
static inline void put_css_set(struct css_set *cg)
{
kref_put(&cg->ref, release_css_set);
}
static inline void put_css_set_taskexit(struct css_set *cg)
{
kref_put(&cg->ref, release_css_set_taskexit);
}
/*
* find_existing_css_set() is a helper for
* find_css_set(), and checks to see whether an existing
* css_set is suitable. This currently walks a linked-list for
* simplicity; a later patch will use a hash table for better
* performance
*
* oldcg: the cgroup group that we're using before the cgroup
* transition
*
* cont: the cgroup that we're moving into
*
* template: location in which to build the desired set of subsystem
* state objects for the new cgroup group
*/
static struct css_set *find_existing_css_set(
struct css_set *oldcg,
struct cgroup *cont,
struct cgroup_subsys_state *template[])
{
int i;
struct cgroupfs_root *root = cont->root;
struct list_head *l = &init_css_set.list;
/* Built the set of subsystem state objects that we want to
* see in the new css_set */
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
if (root->subsys_bits & (1ull << i)) {
/* Subsystem is in this hierarchy. So we want
* the subsystem state from the new
* cgroup */
template[i] = cont->subsys[i];
} else {
/* Subsystem is not in this hierarchy, so we
* don't want to change the subsystem state */
template[i] = oldcg->subsys[i];
}
}
/* Look through existing cgroup groups to find one to reuse */
do {
struct css_set *cg =
list_entry(l, struct css_set, list);
if (!memcmp(template, cg->subsys, sizeof(cg->subsys))) {
/* All subsystems matched */
return cg;
}
/* Try the next cgroup group */
l = l->next;
} while (l != &init_css_set.list);
/* No existing cgroup group matched */
return NULL;
}
/*
* allocate_cg_links() allocates "count" cg_cgroup_link structures
* and chains them on tmp through their cont_link_list fields. Returns 0 on
* success or a negative error
*/
static int allocate_cg_links(int count, struct list_head *tmp)
{
struct cg_cgroup_link *link;
int i;
INIT_LIST_HEAD(tmp);
for (i = 0; i < count; i++) {
link = kmalloc(sizeof(*link), GFP_KERNEL);
if (!link) {
while (!list_empty(tmp)) {
link = list_entry(tmp->next,
struct cg_cgroup_link,
cont_link_list);
list_del(&link->cont_link_list);
kfree(link);
}
return -ENOMEM;
}
list_add(&link->cont_link_list, tmp);
}
return 0;
}
static void free_cg_links(struct list_head *tmp)
{
while (!list_empty(tmp)) {
struct cg_cgroup_link *link;
link = list_entry(tmp->next,
struct cg_cgroup_link,
cont_link_list);
list_del(&link->cont_link_list);
kfree(link);
}
}
/*
* find_css_set() takes an existing cgroup group and a
* cgroup object, and returns a css_set object that's
* equivalent to the old group, but with the given cgroup
* substituted into the appropriate hierarchy. Must be called with
* cgroup_mutex held
*/
static struct css_set *find_css_set(
struct css_set *oldcg, struct cgroup *cont)
{
struct css_set *res;
struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
int i;
struct list_head tmp_cg_links;
struct cg_cgroup_link *link;
/* First see if we already have a cgroup group that matches
* the desired set */
write_lock(&css_set_lock);
res = find_existing_css_set(oldcg, cont, template);
if (res)
get_css_set(res);
write_unlock(&css_set_lock);
if (res)
return res;
res = kmalloc(sizeof(*res), GFP_KERNEL);
if (!res)
return NULL;
/* Allocate all the cg_cgroup_link objects that we'll need */
if (allocate_cg_links(root_count, &tmp_cg_links) < 0) {
kfree(res);
return NULL;
}
kref_init(&res->ref);
INIT_LIST_HEAD(&res->cg_links);
INIT_LIST_HEAD(&res->tasks);
/* Copy the set of subsystem state objects generated in
* find_existing_css_set() */
memcpy(res->subsys, template, sizeof(res->subsys));
write_lock(&css_set_lock);
/* Add reference counts and links from the new css_set. */
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup *cont = res->subsys[i]->cgroup;
struct cgroup_subsys *ss = subsys[i];
atomic_inc(&cont->count);
/*
* We want to add a link once per cgroup, so we
* only do it for the first subsystem in each
* hierarchy
*/
if (ss->root->subsys_list.next == &ss->sibling) {
BUG_ON(list_empty(&tmp_cg_links));
link = list_entry(tmp_cg_links.next,
struct cg_cgroup_link,
cont_link_list);
list_del(&link->cont_link_list);
list_add(&link->cont_link_list, &cont->css_sets);
link->cg = res;
list_add(&link->cg_link_list, &res->cg_links);
}
}
if (list_empty(&rootnode.subsys_list)) {
link = list_entry(tmp_cg_links.next,
struct cg_cgroup_link,
cont_link_list);
list_del(&link->cont_link_list);
list_add(&link->cont_link_list, &dummytop->css_sets);
link->cg = res;
list_add(&link->cg_link_list, &res->cg_links);
}
BUG_ON(!list_empty(&tmp_cg_links));
/* Link this cgroup group into the list */
list_add(&res->list, &init_css_set.list);
css_set_count++;
INIT_LIST_HEAD(&res->tasks);
write_unlock(&css_set_lock);
return res;
}
/*
* 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()
*/
/**
* 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 file_operations proc_cgroupstats_operations;
static struct backing_dev_info cgroup_backing_dev_info = {
.capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
};
static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
{
struct inode *inode = new_inode(sb);
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)));
/* It's possible for external users to be holding css
* reference counts on a cgroup; css_put() needs to
* be able to access the cgroup after decrementing
* the reference count in order to know if it needs to
* queue the cgroup to be handled by the release
* agent */
synchronize_rcu();
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");
if (strlen(root->release_agent_path))
seq_printf(seq, ",release_agent=%s", root->release_agent_path);
mutex_unlock(&cgroup_mutex);
return 0;
}
struct cgroup_sb_opts {
unsigned long subsys_bits;
unsigned long flags;
char *release_agent;
};
/* 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;
opts->release_agent = NULL;
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 if (!strncmp(token, "release_agent=", 14)) {
/* Specifying two release agents is forbidden */
if (opts->release_agent)
return -EINVAL;
opts->release_agent = kzalloc(PATH_MAX, GFP_KERNEL);
if (!opts->release_agent)
return -ENOMEM;
strncpy(opts->release_agent, token + 14, PATH_MAX - 1);
opts->release_agent[PATH_MAX - 1] = 0;
} 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);
if (opts.release_agent)
strcpy(root->release_agent_path, opts.release_agent);
out_unlock:
if (opts.release_agent)
kfree(opts.release_agent);
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);
INIT_LIST_HEAD(&cont->css_sets);
INIT_LIST_HEAD(&cont->release_list);
}
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;
struct list_head tmp_cg_links, *l;
INIT_LIST_HEAD(&tmp_cg_links);
/* First find the desired set of subsystems */
ret = parse_cgroupfs_options(data, &opts);
if (ret) {
if (opts.release_agent)
kfree(opts.release_agent);
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;
if (opts.release_agent) {
strcpy(root->release_agent_path, opts.release_agent);
kfree(opts.release_agent);
}
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;
struct inode *inode;
BUG_ON(sb->s_root != NULL);
ret = cgroup_get_rootdir(sb);
if (ret)
goto drop_new_super;
inode = sb->s_root->d_inode;
mutex_lock(&inode->i_mutex);
mutex_lock(&cgroup_mutex);
/*
* We're accessing css_set_count without locking
* css_set_lock here, but that's OK - it can only be
* increased by someone holding cgroup_lock, and
* that's us. The worst that can happen is that we
* have some link structures left over
*/
ret = allocate_cg_links(css_set_count, &tmp_cg_links);
if (ret) {
mutex_unlock(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);
goto drop_new_super;
}
ret = rebind_subsystems(root, root->subsys_bits);
if (ret == -EBUSY) {
mutex_unlock(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);
goto drop_new_super;
}
/* EBUSY should be the only error here */
BUG_ON(ret);
list_add(&root->root_list, &roots);
root_count++;
sb->s_root->d_fsdata = &root->top_cgroup;
root->top_cgroup.dentry = sb->s_root;
/* Link the top cgroup in this hierarchy into all
* the css_set objects */
write_lock(&css_set_lock);
l = &init_css_set.list;
do {
struct css_set *cg;
struct cg_cgroup_link *link;
cg = list_entry(l, struct css_set, list);
BUG_ON(list_empty(&tmp_cg_links));
link = list_entry(tmp_cg_links.next,
struct cg_cgroup_link,
cont_link_list);
list_del(&link->cont_link_list);
link->cg = cg;
list_add(&link->cont_link_list,
&root->top_cgroup.css_sets);
list_add(&link->cg_link_list, &cg->cg_links);
l = l->next;
} while (l != &init_css_set.list);
write_unlock(&css_set_lock);
free_cg_links(&tmp_cg_links);
BUG_ON(!list_empty(&cont->sibling));
BUG_ON(!list_empty(&cont->children));
BUG_ON(root->number_of_cgroups != 1);
cgroup_populate_dir(cont);
mutex_unlock(&inode->i_mutex);
mutex_unlock(&cgroup_mutex);
}
return simple_set_mnt(mnt, sb);
drop_new_super:
up_write(&sb->s_umount);
deactivate_super(sb);
free_cg_links(&tmp_cg_links);
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);
/*
* Release all the links from css_sets to this hierarchy's
* root cgroup
*/
write_lock(&css_set_lock);
while (!list_empty(&cont->css_sets)) {
struct cg_cgroup_link *link;
link = list_entry(cont->css_sets.next,
struct cg_cgroup_link, cont_link_list);
list_del(&link->cg_link_list);
list_del(&link->cont_link_list);
kfree(link);
}
write_unlock(&css_set_lock);
if (!list_empty(&root->root_list)) {
list_del(&root->root_list);
root_count--;
}
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;
}
/*
* Return the first subsystem attached to a cgroup's hierarchy, and
* its subsystem id.
*/
static void get_first_subsys(const struct cgroup *cont,
struct cgroup_subsys_state **css, int *subsys_id)
{
const struct cgroupfs_root *root = cont->root;
const struct cgroup_subsys *test_ss;
BUG_ON(list_empty(&root->subsys_list));
test_ss = list_entry(root->subsys_list.next,
struct cgroup_subsys, sibling);
if (css) {
*css = cont->subsys[test_ss->subsys_id];
BUG_ON(!*css);
}
if (subsys_id)
*subsys_id = test_ss->subsys_id;
}
/*
* Attach task 'tsk' to cgroup 'cont'
*
* Call holding cgroup_mutex. May take task_lock of
* the task 'pid' during call.
*/
static int attach_task(struct cgroup *cont, struct task_struct *tsk)
{
int retval = 0;
struct cgroup_subsys *ss;
struct cgroup *oldcont;
struct css_set *cg = tsk->cgroups;
struct css_set *newcg;
struct cgroupfs_root *root = cont->root;
int subsys_id;
get_first_subsys(cont, NULL, &subsys_id);
/* Nothing to do if the task is already in that cgroup */
oldcont = task_cgroup(tsk, subsys_id);
if (cont == oldcont)
return 0;
for_each_subsys(root, ss) {
if (ss->can_attach) {
retval = ss->can_attach(ss, cont, tsk);
if (retval) {
return retval;
}
}
}
/*
* Locate or allocate a new css_set for this task,
* based on its final set of cgroups
*/
newcg = find_css_set(cg, cont);
if (!newcg) {
return -ENOMEM;
}
task_lock(tsk);
if (tsk->flags & PF_EXITING) {
task_unlock(tsk);
put_css_set(newcg);
return -ESRCH;
}
rcu_assign_pointer(tsk->cgroups, newcg);
task_unlock(tsk);
/* Update the css_set linked lists if we're using them */
write_lock(&css_set_lock);
if (!list_empty(&tsk->cg_list)) {
list_del(&tsk->cg_list);
list_add(&tsk->cg_list, &newcg->tasks);
}
write_unlock(&css_set_lock);
for_each_subsys(root, ss) {
if (ss->attach) {
ss->attach(ss, cont, oldcont, tsk);
}
}
set_bit(CONT_RELEASABLE, &oldcont->flags);
synchronize_rcu();
put_css_set(cg);
return 0;
}
/*
* Attach task with pid 'pid' to cgroup 'cont'. Call with
* cgroup_mutex, may take task_lock of task
*/
static int attach_task_by_pid(struct cgroup *cont, char *pidbuf)
{
pid_t pid;
struct task_struct *tsk;
int ret;
if (sscanf(pidbuf, "%d", &pid) != 1)
return -EIO;
if (pid) {
rcu_read_lock();
tsk = find_task_by_pid(pid);
if (!tsk || tsk->flags & PF_EXITING) {
rcu_read_unlock();
return -ESRCH;
}
get_task_struct(tsk);
rcu_read_unlock();
if ((current->euid) && (current->euid != tsk->uid)
&& (current->euid != tsk->suid)) {
put_task_struct(tsk);
return -EACCES;
}
} else {
tsk = current;
get_task_struct(tsk);
}
ret = attach_task(cont, tsk);
put_task_struct(tsk);
return ret;
}
/* The various types of files and directories in a cgroup file system */
enum cgroup_filetype {
FILE_ROOT,
FILE_DIR,
FILE_TASKLIST,
FILE_NOTIFY_ON_RELEASE,
FILE_RELEASABLE,
FILE_RELEASE_AGENT,
};
static ssize_t cgroup_write_uint(struct cgroup *cont, struct cftype *cft,
struct file *file,
const char __user *userbuf,
size_t nbytes, loff_t *unused_ppos)
{
char buffer[64];
int retval = 0;
u64 val;
char *end;
if (!nbytes)
return -EINVAL;
if (nbytes >= sizeof(buffer))
return -E2BIG;
if (copy_from_user(buffer, userbuf, nbytes))
return -EFAULT;
buffer[nbytes] = 0; /* nul-terminate */
/* strip newline if necessary */
if (nbytes && (buffer[nbytes-1] == '\n'))
buffer[nbytes-1] = 0;
val = simple_strtoull(buffer, &end, 0);
if (*end)
return -EINVAL;
/* Pass to subsystem */
retval = cft->write_uint(cont, cft, val);
if (!retval)
retval = nbytes;
return retval;
}
static ssize_t cgroup_common_file_write(struct cgroup *cont,
struct cftype *cft,
struct file *file,
const char __user *userbuf,
size_t nbytes, loff_t *unused_ppos)
{
enum cgroup_filetype type = cft->private;
char *buffer;
int retval = 0;
if (nbytes >= PATH_MAX)
return -E2BIG;
/* +1 for nul-terminator */
buffer = kmalloc(nbytes + 1, GFP_KERNEL);
if (buffer == NULL)
return -ENOMEM;
if (copy_from_user(buffer, userbuf, nbytes)) {
retval = -EFAULT;
goto out1;
}
buffer[nbytes] = 0; /* nul-terminate */
mutex_lock(&cgroup_mutex);
if (cgroup_is_removed(cont)) {
retval = -ENODEV;
goto out2;
}
switch (type) {
case FILE_TASKLIST:
retval = attach_task_by_pid(cont, buffer);
break;
case FILE_NOTIFY_ON_RELEASE:
clear_bit(CONT_RELEASABLE, &cont->flags);
if (simple_strtoul(buffer, NULL, 10) != 0)
set_bit(CONT_NOTIFY_ON_RELEASE, &cont->flags);
else
clear_bit(CONT_NOTIFY_ON_RELEASE, &cont->flags);
break;
case FILE_RELEASE_AGENT:
{
struct cgroupfs_root *root = cont->root;
/* Strip trailing newline */
if (nbytes && (buffer[nbytes-1] == '\n')) {
buffer[nbytes-1] = 0;
}
if (nbytes < sizeof(root->release_agent_path)) {
/* We never write anything other than '\0'
* into the last char of release_agent_path,
* so it always remains a NUL-terminated
* string */
strncpy(root->release_agent_path, buffer, nbytes);
root->release_agent_path[nbytes] = 0;
} else {
retval = -ENOSPC;
}
break;
}
default:
retval = -EINVAL;
goto out2;
}
if (retval == 0)
retval = nbytes;
out2:
mutex_unlock(&cgroup_mutex);
out1:
kfree(buffer);
return retval;
}
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 cft->write(cont, cft, file, buf, nbytes, ppos);
if (cft->write_uint)
return cgroup_write_uint(cont, cft, file, buf, nbytes, ppos);
return -EINVAL;
}
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_common_file_read(struct cgroup *cont,
struct cftype *cft,
struct file *file,
char __user *buf,
size_t nbytes, loff_t *ppos)
{
enum cgroup_filetype type = cft->private;
char *page;
ssize_t retval = 0;
char *s;
if (!(page = (char *)__get_free_page(GFP_KERNEL)))
return -ENOMEM;
s = page;
switch (type) {
case FILE_RELEASE_AGENT:
{
struct cgroupfs_root *root;
size_t n;
mutex_lock(&cgroup_mutex);
root = cont->root;
n = strnlen(root->release_agent_path,
sizeof(root->release_agent_path));
n = min(n, (size_t) PAGE_SIZE);
strncpy(s, root->release_agent_path, n);
mutex_unlock(&cgroup_mutex);
s += n;
break;
}
default:
retval = -EINVAL;
goto out;
}
*s++ = '\n';
retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page);
out:
free_page((unsigned long)page);
return retval;
}
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_nested(&inode->i_mutex, I_MUTEX_CHILD);
} 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;
}
/* Count the number of tasks in a cgroup. */
int cgroup_task_count(const struct cgroup *cont)
{
int count = 0;
struct list_head *l;
read_lock(&css_set_lock);
l = cont->css_sets.next;
while (l != &cont->css_sets) {
struct cg_cgroup_link *link =
list_entry(l, struct cg_cgroup_link, cont_link_list);
count += atomic_read(&link->cg->ref.refcount);
l = l->next;
}
read_unlock(&css_set_lock);
return count;
}
/*
* Advance a list_head iterator. The iterator should be positioned at
* the start of a css_set
*/
static void cgroup_advance_iter(struct cgroup *cont,
struct cgroup_iter *it)
{
struct list_head *l = it->cg_link;
struct cg_cgroup_link *link;
struct css_set *cg;
/* Advance to the next non-empty css_set */
do {
l = l->next;
if (l == &cont->css_sets) {
it->cg_link = NULL;
return;
}
link = list_entry(l, struct cg_cgroup_link, cont_link_list);
cg = link->cg;
} while (list_empty(&cg->tasks));
it->cg_link = l;
it->task = cg->tasks.next;
}
void cgroup_iter_start(struct cgroup *cont, struct cgroup_iter *it)
{
/*
* The first time anyone tries to iterate across a cgroup,
* we need to enable the list linking each css_set to its
* tasks, and fix up all existing tasks.
*/
if (!use_task_css_set_links) {
struct task_struct *p, *g;
write_lock(&css_set_lock);
use_task_css_set_links = 1;
do_each_thread(g, p) {
task_lock(p);
if (list_empty(&p->cg_list))
list_add(&p->cg_list, &p->cgroups->tasks);
task_unlock(p);
} while_each_thread(g, p);
write_unlock(&css_set_lock);
}
read_lock(&css_set_lock);
it->cg_link = &cont->css_sets;
cgroup_advance_iter(cont, it);
}
struct task_struct *cgroup_iter_next(struct cgroup *cont,
struct cgroup_iter *it)
{
struct task_struct *res;
struct list_head *l = it->task;
/* If the iterator cg is NULL, we have no tasks */
if (!it->cg_link)
return NULL;
res = list_entry(l, struct task_struct, cg_list);
/* Advance iterator to find next entry */
l = l->next;
if (l == &res->cgroups->tasks) {
/* We reached the end of this task list - move on to
* the next cg_cgroup_link */
cgroup_advance_iter(cont, it);
} else {
it->task = l;
}
return res;
}
void cgroup_iter_end(struct cgroup *cont, struct cgroup_iter *it)
{
read_unlock(&css_set_lock);
}
/*
* Stuff for reading the 'tasks' file.
*
* Reading this file can return large amounts of data if a cgroup has
* *lots* of attached tasks. So it may need several calls to read(),
* but we cannot guarantee that the information we produce is correct
* unless we produce it entirely atomically.
*
* Upon tasks file open(), a struct ctr_struct is allocated, that
* will have a pointer to an array (also allocated here). The struct
* ctr_struct * is stored in file->private_data. Its resources will
* be freed by release() when the file is closed. The array is used
* to sprintf the PIDs and then used by read().
*/
struct ctr_struct {
char *buf;
int bufsz;
};
/*
* Load into 'pidarray' up to 'npids' of the tasks using cgroup
* 'cont'. Return actual number of pids loaded. No need to
* task_lock(p) when reading out p->cgroup, since we're in an RCU
* read section, so the css_set can't go away, and is
* immutable after creation.
*/
static int pid_array_load(pid_t *pidarray, int npids, struct cgroup *cont)
{
int n = 0;
struct cgroup_iter it;
struct task_struct *tsk;
cgroup_iter_start(cont, &it);
while ((tsk = cgroup_iter_next(cont, &it))) {
if (unlikely(n == npids))
break;
pidarray[n++] = task_pid_nr(tsk);
}
cgroup_iter_end(cont, &it);
return n;
}
/**
* Build and fill cgroupstats so that taskstats can export it to user
* space.
*
* @stats: cgroupstats to fill information into
* @dentry: A dentry entry belonging to the cgroup for which stats have
* been requested.
*/
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
int ret = -EINVAL;
struct cgroup *cont;
struct cgroup_iter it;
struct task_struct *tsk;
/*
* Validate dentry by checking the superblock operations
*/
if (dentry->d_sb->s_op != &cgroup_ops)
goto err;
ret = 0;
cont = dentry->d_fsdata;
rcu_read_lock();
cgroup_iter_start(cont, &it);
while ((tsk = cgroup_iter_next(cont, &it))) {
switch (tsk->state) {
case TASK_RUNNING:
stats->nr_running++;
break;
case TASK_INTERRUPTIBLE:
stats->nr_sleeping++;
break;
case TASK_UNINTERRUPTIBLE:
stats->nr_uninterruptible++;
break;
case TASK_STOPPED:
stats->nr_stopped++;
break;
default:
if (delayacct_is_task_waiting_on_io(tsk))
stats->nr_io_wait++;
break;
}
}
cgroup_iter_end(cont, &it);
rcu_read_unlock();
err:
return ret;
}
static int cmppid(const void *a, const void *b)
{
return *(pid_t *)a - *(pid_t *)b;
}
/*
* Convert array 'a' of 'npids' pid_t's to a string of newline separated
* decimal pids in 'buf'. Don't write more than 'sz' chars, but return
* count 'cnt' of how many chars would be written if buf were large enough.
*/
static int pid_array_to_buf(char *buf, int sz, pid_t *a, int npids)
{
int cnt = 0;
int i;
for (i = 0; i < npids; i++)
cnt += snprintf(buf + cnt, max(sz - cnt, 0), "%d\n", a[i]);
return cnt;
}
/*
* Handle an open on 'tasks' file. Prepare a buffer listing the
* process id's of tasks currently attached to the cgroup being opened.
*
* Does not require any specific cgroup mutexes, and does not take any.
*/
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
struct cgroup *cont = __d_cont(file->f_dentry->d_parent);
struct ctr_struct *ctr;
pid_t *pidarray;
int npids;
char c;
if (!(file->f_mode & FMODE_READ))
return 0;
ctr = kmalloc(sizeof(*ctr), GFP_KERNEL);
if (!ctr)
goto err0;
/*
* If cgroup gets more users after we read count, we won't have
* enough space - tough. This race is indistinguishable to the
* caller from the case that the additional cgroup users didn't
* show up until sometime later on.
*/
npids = cgroup_task_count(cont);
if (npids) {
pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL);
if (!pidarray)
goto err1;
npids = pid_array_load(pidarray, npids, cont);
sort(pidarray, npids, sizeof(pid_t), cmppid, NULL);
/* Call pid_array_to_buf() twice, first just to get bufsz */
ctr->bufsz = pid_array_to_buf(&c, sizeof(c), pidarray, npids) + 1;
ctr->buf = kmalloc(ctr->bufsz, GFP_KERNEL);
if (!ctr->buf)
goto err2;
ctr->bufsz = pid_array_to_buf(ctr->buf, ctr->bufsz, pidarray, npids);
kfree(pidarray);
} else {
ctr->buf = 0;
ctr->bufsz = 0;
}
file->private_data = ctr;
return 0;
err2:
kfree(pidarray);
err1:
kfree(ctr);
err0:
return -ENOMEM;
}
static ssize_t cgroup_tasks_read(struct cgroup *cont,
struct cftype *cft,
struct file *file, char __user *buf,
size_t nbytes, loff_t *ppos)
{
struct ctr_struct *ctr = file->private_data;
return simple_read_from_buffer(buf, nbytes, ppos, ctr->buf, ctr->bufsz);
}
static int cgroup_tasks_release(struct inode *unused_inode,
struct file *file)
{
struct ctr_struct *ctr;
if (file->f_mode & FMODE_READ) {
ctr = file->private_data;
kfree(ctr->buf);
kfree(ctr);
}
return 0;
}
static u64 cgroup_read_notify_on_release(struct cgroup *cont,
struct cftype *cft)
{
return notify_on_release(cont);
}
static u64 cgroup_read_releasable(struct cgroup *cont, struct cftype *cft)
{
return test_bit(CONT_RELEASABLE, &cont->flags);
}
/*
* for the common functions, 'private' gives the type of file
*/
static struct cftype files[] = {
{
.name = "tasks",
.open = cgroup_tasks_open,
.read = cgroup_tasks_read,
.write = cgroup_common_file_write,
.release = cgroup_tasks_release,
.private = FILE_TASKLIST,
},
{
.name = "notify_on_release",
.read_uint = cgroup_read_notify_on_release,
.write = cgroup_common_file_write,
.private = FILE_NOTIFY_ON_RELEASE,
},
{
.name = "releasable",
.read_uint = cgroup_read_releasable,
.private = FILE_RELEASABLE,
}
};
static struct cftype cft_release_agent = {
.name = "release_agent",
.read = cgroup_common_file_read,
.write = cgroup_common_file_write,
.private = FILE_RELEASE_AGENT,
};
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);
err = cgroup_add_files(cont, NULL, files, ARRAY_SIZE(files));
if (err < 0)
return err;
if (cont == cont->top_cgroup) {
if ((err = cgroup_add_file(cont, NULL, &cft_release_agent)) < 0)
return err;
}
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);
INIT_LIST_HEAD(&cont->css_sets);
INIT_LIST_HEAD(&cont->release_list);
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 inline int cgroup_has_css_refs(struct cgroup *cont)
{
/* 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. We scan across all subsystems rather than using
* the per-hierarchy linked list of mounted subsystems since
* we can be called via check_for_release() with no
* synchronization other than RCU, and the subsystem linked
* list isn't RCU-safe */
int i;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
struct cgroup_subsys_state *css;
/* Skip subsystems not in this hierarchy */
if (ss->root != cont->root)
continue;
css = cont->subsys[ss->subsys_id];
/* When called from check_for_release() it's possible
* that by this point the cgroup has been removed
* and the css deleted. But a false-positive doesn't
* matter, since it can only happen if the cgroup
* has been deleted and hence no longer needs the
* release agent to be called anyway. */
if (css && atomic_read(&css->refcnt)) {
return 1;
}
}
return 0;
}
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;
/* 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;
if (cgroup_has_css_refs(cont)) {
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
for_each_subsys(root, ss) {
if (cont->subsys[ss->subsys_id])
ss->destroy(ss, cont);
}
spin_lock(&release_list_lock);
set_bit(CONT_REMOVED, &cont->flags);
if (!list_empty(&cont->release_list))
list_del(&cont->release_list);
spin_unlock(&release_list_lock);
/* 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--;
set_bit(CONT_RELEASABLE, &parent->flags);
check_for_release(parent);
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 cgroup_subsys_state *css;
struct list_head *l;
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 cgroup groups to contain a subsys
* pointer to this state - since the subsystem is
* newly registered, all tasks and hence all cgroup
* groups are in the subsystem's top cgroup. */
write_lock(&css_set_lock);
l = &init_css_set.list;
do {
struct css_set *cg =
list_entry(l, struct css_set, list);
cg->subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
l = l->next;
} while (l != &init_css_set.list);
write_unlock(&css_set_lock);
/* If this subsystem requested that it be notified with fork
* events, we should send it one now for every process in the
* system */
if (ss->fork) {
struct task_struct *g, *p;
read_lock(&tasklist_lock);
do_each_thread(g, p) {
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;
kref_init(&init_css_set.ref);
kref_get(&init_css_set.ref);
INIT_LIST_HEAD(&init_css_set.list);
INIT_LIST_HEAD(&init_css_set.cg_links);
INIT_LIST_HEAD(&init_css_set.tasks);
css_set_count = 1;
init_cgroup_root(&rootnode);
list_add(&rootnode.root_list, &roots);
root_count = 1;
init_task.cgroups = &init_css_set;
init_css_set_link.cg = &init_css_set;
list_add(&init_css_set_link.cont_link_list,
&rootnode.top_cgroup.css_sets);
list_add(&init_css_set_link.cg_link_list,
&init_css_set.cg_links);
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;
struct proc_dir_entry *entry;
err = bdi_init(&cgroup_backing_dev_info);
if (err)
return err;
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;
entry = create_proc_entry("cgroups", 0, NULL);
if (entry)
entry->proc_fops = &proc_cgroupstats_operations;
out:
if (err)
bdi_destroy(&cgroup_backing_dev_info);
return err;
}
/*
* proc_cgroup_show()
* - Print task's cgroup paths into seq_file, one line for each hierarchy
* - Used for /proc/<pid>/cgroup.
* - No need to task_lock(tsk) on this tsk->cgroup reference, as it
* doesn't really matter if tsk->cgroup changes after we read it,
* and we take cgroup_mutex, keeping attach_task() from changing it
* anyway. No need to check that tsk->cgroup != NULL, thanks to
* the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
* cgroup to top_cgroup.
*/
/* TODO: Use a proper seq_file iterator */
static int proc_cgroup_show(struct seq_file *m, void *v)
{
struct pid *pid;
struct task_struct *tsk;
char *buf;
int retval;
struct cgroupfs_root *root;
retval = -ENOMEM;
buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!buf)
goto out;
retval = -ESRCH;
pid = m->private;
tsk = get_pid_task(pid, PIDTYPE_PID);
if (!tsk)
goto out_free;
retval = 0;
mutex_lock(&cgroup_mutex);
for_each_root(root) {
struct cgroup_subsys *ss;
struct cgroup *cont;
int subsys_id;
int count = 0;
/* Skip this hierarchy if it has no active subsystems */
if (!root->actual_subsys_bits)
continue;
for_each_subsys(root, ss)
seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
seq_putc(m, ':');
get_first_subsys(&root->top_cgroup, NULL, &subsys_id);
cont = task_cgroup(tsk, subsys_id);
retval = cgroup_path(cont, buf, PAGE_SIZE);
if (retval < 0)
goto out_unlock;
seq_puts(m, buf);
seq_putc(m, '\n');
}
out_unlock:
mutex_unlock(&cgroup_mutex);
put_task_struct(tsk);
out_free:
kfree(buf);
out:
return retval;
}
static int cgroup_open(struct inode *inode, struct file *file)
{
struct pid *pid = PROC_I(inode)->pid;
return single_open(file, proc_cgroup_show, pid);
}
struct file_operations proc_cgroup_operations = {
.open = cgroup_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
/* Display information about each subsystem and each hierarchy */
static int proc_cgroupstats_show(struct seq_file *m, void *v)
{
int i;
struct cgroupfs_root *root;
seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\n");
mutex_lock(&cgroup_mutex);
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
seq_printf(m, "%s\t%lu\t%d\n",
ss->name, ss->root->subsys_bits,
ss->root->number_of_cgroups);
}
mutex_unlock(&cgroup_mutex);
return 0;
}
static int cgroupstats_open(struct inode *inode, struct file *file)
{
return single_open(file, proc_cgroupstats_show, 0);
}
static struct file_operations proc_cgroupstats_operations = {
.open = cgroupstats_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
/**
* cgroup_fork - attach newly forked task to its parents cgroup.
* @tsk: pointer to task_struct of forking parent process.
*
* Description: A task inherits its parent's cgroup at fork().
*
* A pointer to the shared css_set was automatically copied in
* fork.c by dup_task_struct(). However, we ignore that copy, since
* it was not made under the protection of RCU or cgroup_mutex, so
* might no longer be a valid cgroup pointer. attach_task() might
* have already changed current->cgroups, allowing the previously
* referenced cgroup group to be removed and freed.
*
* At the point that cgroup_fork() is called, 'current' is the parent
* task, and the passed argument 'child' points to the child task.
*/
void cgroup_fork(struct task_struct *child)
{
task_lock(current);
child->cgroups = current->cgroups;
get_css_set(child->cgroups);
task_unlock(current);
INIT_LIST_HEAD(&child->cg_list);
}
/**
* cgroup_fork_callbacks - called on a new task very soon before
* adding it to the tasklist. No need to take any locks since no-one
* can be operating on this task
*/
void cgroup_fork_callbacks(struct task_struct *child)
{
if (need_forkexit_callback) {
int i;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss->fork)
ss->fork(ss, child);
}
}
}
/**
* cgroup_post_fork - called on a new task after adding it to the
* task list. Adds the task to the list running through its css_set
* if necessary. Has to be after the task is visible on the task list
* in case we race with the first call to cgroup_iter_start() - to
* guarantee that the new task ends up on its list. */
void cgroup_post_fork(struct task_struct *child)
{
if (use_task_css_set_links) {
write_lock(&css_set_lock);
if (list_empty(&child->cg_list))
list_add(&child->cg_list, &child->cgroups->tasks);
write_unlock(&css_set_lock);
}
}
/**
* cgroup_exit - detach cgroup from exiting task
* @tsk: pointer to task_struct of exiting process
*
* Description: Detach cgroup from @tsk and release it.
*
* Note that cgroups marked notify_on_release force every task in
* them to take the global cgroup_mutex mutex when exiting.
* This could impact scaling on very large systems. Be reluctant to
* use notify_on_release cgroups where very high task exit scaling
* is required on large systems.
*
* the_top_cgroup_hack:
*
* Set the exiting tasks cgroup to the root cgroup (top_cgroup).
*
* We call cgroup_exit() while the task is still competent to
* handle notify_on_release(), then leave the task attached to the
* root cgroup in each hierarchy for the remainder of its exit.
*
* To do this properly, we would increment the reference count on
* top_cgroup, and near the very end of the kernel/exit.c do_exit()
* code we would add a second cgroup function call, to drop that
* reference. This would just create an unnecessary hot spot on
* the top_cgroup reference count, to no avail.
*
* Normally, holding a reference to a cgroup without bumping its
* count is unsafe. The cgroup could go away, or someone could
* attach us to a different cgroup, decrementing the count on
* the first cgroup that we never incremented. But in this case,
* top_cgroup isn't going away, and either task has PF_EXITING set,
* which wards off any attach_task() attempts, or task is a failed
* fork, never visible to attach_task.
*
*/
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
int i;
struct css_set *cg;
if (run_callbacks && need_forkexit_callback) {
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss->exit)
ss->exit(ss, tsk);
}
}
/*
* Unlink from the css_set task list if necessary.
* Optimistically check cg_list before taking
* css_set_lock
*/
if (!list_empty(&tsk->cg_list)) {
write_lock(&css_set_lock);
if (!list_empty(&tsk->cg_list))
list_del(&tsk->cg_list);
write_unlock(&css_set_lock);
}
/* Reassign the task to the init_css_set. */
task_lock(tsk);
cg = tsk->cgroups;
tsk->cgroups = &init_css_set;
task_unlock(tsk);
if (cg)
put_css_set_taskexit(cg);
}
/**
* cgroup_clone - duplicate the current cgroup in the hierarchy
* that the given subsystem is attached to, and move this task into
* the new child
*/
int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys)
{
struct dentry *dentry;
int ret = 0;
char nodename[MAX_CGROUP_TYPE_NAMELEN];
struct cgroup *parent, *child;
struct inode *inode;
struct css_set *cg;
struct cgroupfs_root *root;
struct cgroup_subsys *ss;
/* We shouldn't be called by an unregistered subsystem */
BUG_ON(!subsys->active);
/* First figure out what hierarchy and cgroup we're dealing
* with, and pin them so we can drop cgroup_mutex */
mutex_lock(&cgroup_mutex);
again:
root = subsys->root;
if (root == &rootnode) {
printk(KERN_INFO
"Not cloning cgroup for unused subsystem %s\n",
subsys->name);
mutex_unlock(&cgroup_mutex);
return 0;
}
cg = tsk->cgroups;
parent = task_cgroup(tsk, subsys->subsys_id);
snprintf(nodename, MAX_CGROUP_TYPE_NAMELEN, "node_%d", tsk->pid);
/* Pin the hierarchy */
atomic_inc(&parent->root->sb->s_active);
/* Keep the cgroup alive */
get_css_set(cg);
mutex_unlock(&cgroup_mutex);
/* Now do the VFS work to create a cgroup */
inode = parent->dentry->d_inode;
/* Hold the parent directory mutex across this operation to
* stop anyone else deleting the new cgroup */
mutex_lock(&inode->i_mutex);
dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));
if (IS_ERR(dentry)) {
printk(KERN_INFO
"Couldn't allocate dentry for %s: %ld\n", nodename,
PTR_ERR(dentry));
ret = PTR_ERR(dentry);
goto out_release;
}
/* Create the cgroup directory, which also creates the cgroup */
ret = vfs_mkdir(inode, dentry, S_IFDIR | 0755);
child = __d_cont(dentry);
dput(dentry);
if (ret) {
printk(KERN_INFO
"Failed to create cgroup %s: %d\n", nodename,
ret);
goto out_release;
}
if (!child) {
printk(KERN_INFO
"Couldn't find new cgroup %s\n", nodename);
ret = -ENOMEM;
goto out_release;
}
/* The cgroup now exists. Retake cgroup_mutex and check
* that we're still in the same state that we thought we
* were. */
mutex_lock(&cgroup_mutex);
if ((root != subsys->root) ||
(parent != task_cgroup(tsk, subsys->subsys_id))) {
/* Aargh, we raced ... */
mutex_unlock(&inode->i_mutex);
put_css_set(cg);
deactivate_super(parent->root->sb);
/* The cgroup is still accessible in the VFS, but
* we're not going to try to rmdir() it at this
* point. */
printk(KERN_INFO
"Race in cgroup_clone() - leaking cgroup %s\n",
nodename);
goto again;
}
/* do any required auto-setup */
for_each_subsys(root, ss) {
if (ss->post_clone)
ss->post_clone(ss, child);
}
/* All seems fine. Finish by moving the task into the new cgroup */
ret = attach_task(child, tsk);
mutex_unlock(&cgroup_mutex);
out_release:
mutex_unlock(&inode->i_mutex);
mutex_lock(&cgroup_mutex);
put_css_set(cg);
mutex_unlock(&cgroup_mutex);
deactivate_super(parent->root->sb);
return ret;
}
/*
* See if "cont" is a descendant of the current task's cgroup in
* the appropriate hierarchy
*
* If we are sending in dummytop, then presumably we are creating
* the top cgroup in the subsystem.
*
* Called only by the ns (nsproxy) cgroup.
*/
int cgroup_is_descendant(const struct cgroup *cont)
{
int ret;
struct cgroup *target;
int subsys_id;
if (cont == dummytop)
return 1;
get_first_subsys(cont, NULL, &subsys_id);
target = task_cgroup(current, subsys_id);
while (cont != target && cont!= cont->top_cgroup)
cont = cont->parent;
ret = (cont == target);
return ret;
}
static void check_for_release(struct cgroup *cont)
{
/* All of these checks rely on RCU to keep the cgroup
* structure alive */
if (cgroup_is_releasable(cont) && !atomic_read(&cont->count)
&& list_empty(&cont->children) && !cgroup_has_css_refs(cont)) {
/* Control Group is currently removeable. If it's not
* already queued for a userspace notification, queue
* it now */
int need_schedule_work = 0;
spin_lock(&release_list_lock);
if (!cgroup_is_removed(cont) &&
list_empty(&cont->release_list)) {
list_add(&cont->release_list, &release_list);
need_schedule_work = 1;
}
spin_unlock(&release_list_lock);
if (need_schedule_work)
schedule_work(&release_agent_work);
}
}
void __css_put(struct cgroup_subsys_state *css)
{
struct cgroup *cont = css->cgroup;
rcu_read_lock();
if (atomic_dec_and_test(&css->refcnt) && notify_on_release(cont)) {
set_bit(CONT_RELEASABLE, &cont->flags);
check_for_release(cont);
}
rcu_read_unlock();
}
/*
* Notify userspace when a cgroup is released, by running the
* configured release agent with the name of the cgroup (path
* relative to the root of cgroup file system) as the argument.
*
* Most likely, this user command will try to rmdir this cgroup.
*
* This races with the possibility that some other task will be
* attached to this cgroup before it is removed, or that some other
* user task will 'mkdir' a child cgroup of this cgroup. That's ok.
* The presumed 'rmdir' will fail quietly if this cgroup is no longer
* unused, and this cgroup will be reprieved from its death sentence,
* to continue to serve a useful existence. Next time it's released,
* we will get notified again, if it still has 'notify_on_release' set.
*
* The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
* means only wait until the task is successfully execve()'d. The
* separate release agent task is forked by call_usermodehelper(),
* then control in this thread returns here, without waiting for the
* release agent task. We don't bother to wait because the caller of
* this routine has no use for the exit status of the release agent
* task, so no sense holding our caller up for that.
*
*/
static void cgroup_release_agent(struct work_struct *work)
{
BUG_ON(work != &release_agent_work);
mutex_lock(&cgroup_mutex);
spin_lock(&release_list_lock);
while (!list_empty(&release_list)) {
char *argv[3], *envp[3];
int i;
char *pathbuf;
struct cgroup *cont = list_entry(release_list.next,
struct cgroup,
release_list);
list_del_init(&cont->release_list);
spin_unlock(&release_list_lock);
pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!pathbuf) {
spin_lock(&release_list_lock);
continue;
}
if (cgroup_path(cont, pathbuf, PAGE_SIZE) < 0) {
kfree(pathbuf);
spin_lock(&release_list_lock);
continue;
}
i = 0;
argv[i++] = cont->root->release_agent_path;
argv[i++] = (char *)pathbuf;
argv[i] = NULL;
i = 0;
/* minimal command environment */
envp[i++] = "HOME=/";
envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
envp[i] = NULL;
/* Drop the lock while we invoke the usermode helper,
* since the exec could involve hitting disk and hence
* be a slow process */
mutex_unlock(&cgroup_mutex);
call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
kfree(pathbuf);
mutex_lock(&cgroup_mutex);
spin_lock(&release_list_lock);
}
spin_unlock(&release_list_lock);
mutex_unlock(&cgroup_mutex);
}
