linux/kernel/cgroup.c
Li Zefan f9ab5b5b0f cgroups: forbid noprefix if mounting more than just cpuset subsystem
The 'noprefix' option was introduced for backwards-compatibility of
cpuset, but actually it can be used when mounting other subsystems.

This results in possibility of name collision, and now the collision can
really happen, because we have 'stat' file in both memory and cpuacct
subsystem:

	# mount -t cgroup -o noprefix,memory,cpuacct xxx /mnt

Cgroup will happily mount the 2 subsystems, but only 'stat' file of memory
subsys can be seen.

We don't want users to use nopreifx, and also want to avoid name
collision, so we change to allow noprefix only if mounting just the cpuset
subsystem.

[akpm@linux-foundation.org: fix shift for cpuset_subsys_id >= 32]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-06-18 13:03:46 -07:00

3626 lines
94 KiB
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 <linux/hash.h>
#include <linux/namei.h>
#include <linux/smp_lock.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 active hierarchies */
struct list_head root_list;
/* Hierarchy-specific flags */
unsigned long flags;
/* The path to use for release notifications. */
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;
/*
* CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
* cgroup_subsys->use_id != 0.
*/
#define CSS_ID_MAX (65535)
struct css_id {
/*
* The css to which this ID points. This pointer is set to valid value
* after cgroup is populated. If cgroup is removed, this will be NULL.
* This pointer is expected to be RCU-safe because destroy()
* is called after synchronize_rcu(). But for safe use, css_is_removed()
* css_tryget() should be used for avoiding race.
*/
struct cgroup_subsys_state *css;
/*
* ID of this css.
*/
unsigned short id;
/*
* Depth in hierarchy which this ID belongs to.
*/
unsigned short depth;
/*
* ID is freed by RCU. (and lookup routine is RCU safe.)
*/
struct rcu_head rcu_head;
/*
* Hierarchy of CSS ID belongs to.
*/
unsigned short stack[0]; /* Array of Length (depth+1) */
};
/* 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
* 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 __read_mostly;
/* convenient tests for these bits */
inline int cgroup_is_removed(const struct cgroup *cgrp)
{
return test_bit(CGRP_REMOVED, &cgrp->flags);
}
/* bits in struct cgroupfs_root flags field */
enum {
ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
};
static int cgroup_is_releasable(const struct cgroup *cgrp)
{
const int bits =
(1 << CGRP_RELEASABLE) |
(1 << CGRP_NOTIFY_ON_RELEASE);
return (cgrp->flags & bits) == bits;
}
static int notify_on_release(const struct cgroup *cgrp)
{
return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->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_active_root() allows you to iterate across the active hierarchies */
#define for_each_active_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 *cgrp);
/* 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 cgrp_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;
static int cgroup_subsys_init_idr(struct cgroup_subsys *ss);
/* 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;
/* hash table for cgroup groups. This improves the performance to
* find an existing css_set */
#define CSS_SET_HASH_BITS 7
#define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS)
static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
{
int i;
int index;
unsigned long tmp = 0UL;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
tmp += (unsigned long)css[i];
tmp = (tmp >> 16) ^ tmp;
index = hash_long(tmp, CSS_SET_HASH_BITS);
return &css_set_table[index];
}
/* 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 __read_mostly;
/* 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)
{
struct cg_cgroup_link *link;
struct cg_cgroup_link *saved_link;
hlist_del(&cg->hlist);
css_set_count--;
list_for_each_entry_safe(link, saved_link, &cg->cg_links,
cg_link_list) {
list_del(&link->cg_link_list);
list_del(&link->cgrp_link_list);
kfree(link);
}
}
static void __put_css_set(struct css_set *cg, int taskexit)
{
int i;
/*
* Ensure that the refcount doesn't hit zero while any readers
* can see it. Similar to atomic_dec_and_lock(), but for an
* rwlock
*/
if (atomic_add_unless(&cg->refcount, -1, 1))
return;
write_lock(&css_set_lock);
if (!atomic_dec_and_test(&cg->refcount)) {
write_unlock(&css_set_lock);
return;
}
unlink_css_set(cg);
write_unlock(&css_set_lock);
rcu_read_lock();
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup *cgrp = rcu_dereference(cg->subsys[i]->cgroup);
if (atomic_dec_and_test(&cgrp->count) &&
notify_on_release(cgrp)) {
if (taskexit)
set_bit(CGRP_RELEASABLE, &cgrp->flags);
check_for_release(cgrp);
}
}
rcu_read_unlock();
kfree(cg);
}
/*
* refcounted get/put for css_set objects
*/
static inline void get_css_set(struct css_set *cg)
{
atomic_inc(&cg->refcount);
}
static inline void put_css_set(struct css_set *cg)
{
__put_css_set(cg, 0);
}
static inline void put_css_set_taskexit(struct css_set *cg)
{
__put_css_set(cg, 1);
}
/*
* find_existing_css_set() is a helper for
* find_css_set(), and checks to see whether an existing
* css_set is suitable.
*
* oldcg: the cgroup group that we're using before the cgroup
* transition
*
* cgrp: 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 *cgrp,
struct cgroup_subsys_state *template[])
{
int i;
struct cgroupfs_root *root = cgrp->root;
struct hlist_head *hhead;
struct hlist_node *node;
struct css_set *cg;
/* 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 & (1UL << i)) {
/* Subsystem is in this hierarchy. So we want
* the subsystem state from the new
* cgroup */
template[i] = cgrp->subsys[i];
} else {
/* Subsystem is not in this hierarchy, so we
* don't want to change the subsystem state */
template[i] = oldcg->subsys[i];
}
}
hhead = css_set_hash(template);
hlist_for_each_entry(cg, node, hhead, hlist) {
if (!memcmp(template, cg->subsys, sizeof(cg->subsys))) {
/* All subsystems matched */
return cg;
}
}
/* No existing cgroup group matched */
return NULL;
}
static void free_cg_links(struct list_head *tmp)
{
struct cg_cgroup_link *link;
struct cg_cgroup_link *saved_link;
list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) {
list_del(&link->cgrp_link_list);
kfree(link);
}
}
/*
* allocate_cg_links() allocates "count" cg_cgroup_link structures
* and chains them on tmp through their cgrp_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) {
free_cg_links(tmp);
return -ENOMEM;
}
list_add(&link->cgrp_link_list, tmp);
}
return 0;
}
/**
* link_css_set - a helper function to link a css_set to a cgroup
* @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
* @cg: the css_set to be linked
* @cgrp: the destination cgroup
*/
static void link_css_set(struct list_head *tmp_cg_links,
struct css_set *cg, struct cgroup *cgrp)
{
struct cg_cgroup_link *link;
BUG_ON(list_empty(tmp_cg_links));
link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
cgrp_link_list);
link->cg = cg;
list_move(&link->cgrp_link_list, &cgrp->css_sets);
list_add(&link->cg_link_list, &cg->cg_links);
}
/*
* 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 *cgrp)
{
struct css_set *res;
struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
int i;
struct list_head tmp_cg_links;
struct hlist_head *hhead;
/* First see if we already have a cgroup group that matches
* the desired set */
read_lock(&css_set_lock);
res = find_existing_css_set(oldcg, cgrp, template);
if (res)
get_css_set(res);
read_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;
}
atomic_set(&res->refcount, 1);
INIT_LIST_HEAD(&res->cg_links);
INIT_LIST_HEAD(&res->tasks);
INIT_HLIST_NODE(&res->hlist);
/* 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 *cgrp = res->subsys[i]->cgroup;
struct cgroup_subsys *ss = subsys[i];
atomic_inc(&cgrp->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)
link_css_set(&tmp_cg_links, res, cgrp);
}
if (list_empty(&rootnode.subsys_list))
link_css_set(&tmp_cg_links, res, dummytop);
BUG_ON(!list_empty(&tmp_cg_links));
css_set_count++;
/* Add this cgroup group to the hash table */
hhead = css_set_hash(res->subsys);
hlist_add_head(&res->hlist, hhead);
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
* cgroup_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 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 the 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
* cgroup_attach_task(), which overwrites one tasks cgroup pointer with
* another. It does so using cgroup_mutex, 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 cgroup_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 cgroup_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 *cgrp);
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_AND_WRITEBACK,
};
static int alloc_css_id(struct cgroup_subsys *ss,
struct cgroup *parent, struct cgroup *child);
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_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
}
return inode;
}
/*
* Call subsys's pre_destroy handler.
* This is called before css refcnt check.
*/
static int cgroup_call_pre_destroy(struct cgroup *cgrp)
{
struct cgroup_subsys *ss;
int ret = 0;
for_each_subsys(cgrp->root, ss)
if (ss->pre_destroy) {
ret = ss->pre_destroy(ss, cgrp);
if (ret)
break;
}
return ret;
}
static void free_cgroup_rcu(struct rcu_head *obj)
{
struct cgroup *cgrp = container_of(obj, struct cgroup, rcu_head);
kfree(cgrp);
}
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 *cgrp = dentry->d_fsdata;
struct cgroup_subsys *ss;
BUG_ON(!(cgroup_is_removed(cgrp)));
/* 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();
mutex_lock(&cgroup_mutex);
/*
* Release the subsystem state objects.
*/
for_each_subsys(cgrp->root, ss)
ss->destroy(ss, cgrp);
cgrp->root->number_of_cgroups--;
mutex_unlock(&cgroup_mutex);
/*
* Drop the active superblock reference that we took when we
* created the cgroup
*/
deactivate_super(cgrp->root->sb);
call_rcu(&cgrp->rcu_head, free_cgroup_rcu);
}
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);
}
/*
* A queue for waiters to do rmdir() cgroup. A tasks will sleep when
* cgroup->count == 0 && list_empty(&cgroup->children) && subsys has some
* reference to css->refcnt. In general, this refcnt is expected to goes down
* to zero, soon.
*
* CGRP_WAIT_ON_RMDIR flag is modified under cgroup's inode->i_mutex;
*/
DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
static void cgroup_wakeup_rmdir_waiters(const struct cgroup *cgrp)
{
if (unlikely(test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
wake_up_all(&cgroup_rmdir_waitq);
}
static int rebind_subsystems(struct cgroupfs_root *root,
unsigned long final_bits)
{
unsigned long added_bits, removed_bits;
struct cgroup *cgrp = &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 bit = 1UL << 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 (root->number_of_cgroups > 1)
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(cgrp->subsys[i]);
BUG_ON(!dummytop->subsys[i]);
BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
mutex_lock(&ss->hierarchy_mutex);
cgrp->subsys[i] = dummytop->subsys[i];
cgrp->subsys[i]->cgroup = cgrp;
list_move(&ss->sibling, &root->subsys_list);
ss->root = root;
if (ss->bind)
ss->bind(ss, cgrp);
mutex_unlock(&ss->hierarchy_mutex);
} else if (bit & removed_bits) {
/* We're removing this subsystem */
BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
mutex_lock(&ss->hierarchy_mutex);
if (ss->bind)
ss->bind(ss, dummytop);
dummytop->subsys[i]->cgroup = dummytop;
cgrp->subsys[i] = NULL;
subsys[i]->root = &rootnode;
list_move(&ss->sibling, &rootnode.subsys_list);
mutex_unlock(&ss->hierarchy_mutex);
} else if (bit & final_bits) {
/* Subsystem state should already exist */
BUG_ON(!cgrp->subsys[i]);
} else {
/* Subsystem state shouldn't exist */
BUG_ON(cgrp->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";
unsigned long mask = (unsigned long)-1;
#ifdef CONFIG_CPUSETS
mask = ~(1UL << cpuset_subsys_id);
#endif
opts->subsys_bits = 0;
opts->flags = 0;
opts->release_agent = NULL;
while ((token = strsep(&o, ",")) != NULL) {
if (!*token)
return -EINVAL;
if (!strcmp(token, "all")) {
/* Add all non-disabled subsystems */
int i;
opts->subsys_bits = 0;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (!ss->disabled)
opts->subsys_bits |= 1ul << i;
}
} 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)) {
if (!ss->disabled)
set_bit(i, &opts->subsys_bits);
break;
}
}
if (i == CGROUP_SUBSYS_COUNT)
return -ENOENT;
}
}
/*
* Option noprefix was introduced just for backward compatibility
* with the old cpuset, so we allow noprefix only if mounting just
* the cpuset subsystem.
*/
if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
(opts->subsys_bits & mask))
return -EINVAL;
/* 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 *cgrp = &root->top_cgroup;
struct cgroup_sb_opts opts;
lock_kernel();
mutex_lock(&cgrp->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);
if (ret)
goto out_unlock;
/* (re)populate subsystem files */
cgroup_populate_dir(cgrp);
if (opts.release_agent)
strcpy(root->release_agent_path, opts.release_agent);
out_unlock:
kfree(opts.release_agent);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
unlock_kernel();
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_housekeeping(struct cgroup *cgrp)
{
INIT_LIST_HEAD(&cgrp->sibling);
INIT_LIST_HEAD(&cgrp->children);
INIT_LIST_HEAD(&cgrp->css_sets);
INIT_LIST_HEAD(&cgrp->release_list);
init_rwsem(&cgrp->pids_mutex);
}
static void init_cgroup_root(struct cgroupfs_root *root)
{
struct cgroup *cgrp = &root->top_cgroup;
INIT_LIST_HEAD(&root->subsys_list);
INIT_LIST_HEAD(&root->root_list);
root->number_of_cgroups = 1;
cgrp->root = root;
cgrp->top_cgroup = cgrp;
init_cgroup_housekeeping(cgrp);
}
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_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;
/* First find the desired set of subsystems */
ret = parse_cgroupfs_options(data, &opts);
if (ret) {
kfree(opts.release_agent);
return ret;
}
root = kzalloc(sizeof(*root), GFP_KERNEL);
if (!root) {
kfree(opts.release_agent);
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 *root_cgrp = &root->top_cgroup;
struct inode *inode;
int i;
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 free_cg_links;
}
/* EBUSY should be the only error here */
BUG_ON(ret);
list_add(&root->root_list, &roots);
root_count++;
sb->s_root->d_fsdata = root_cgrp;
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);
for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
struct hlist_head *hhead = &css_set_table[i];
struct hlist_node *node;
struct css_set *cg;
hlist_for_each_entry(cg, node, hhead, hlist)
link_css_set(&tmp_cg_links, cg, root_cgrp);
}
write_unlock(&css_set_lock);
free_cg_links(&tmp_cg_links);
BUG_ON(!list_empty(&root_cgrp->sibling));
BUG_ON(!list_empty(&root_cgrp->children));
BUG_ON(root->number_of_cgroups != 1);
cgroup_populate_dir(root_cgrp);
mutex_unlock(&inode->i_mutex);
mutex_unlock(&cgroup_mutex);
}
simple_set_mnt(mnt, sb);
return 0;
free_cg_links:
free_cg_links(&tmp_cg_links);
drop_new_super:
deactivate_locked_super(sb);
return ret;
}
static void cgroup_kill_sb(struct super_block *sb) {
struct cgroupfs_root *root = sb->s_fs_info;
struct cgroup *cgrp = &root->top_cgroup;
int ret;
struct cg_cgroup_link *link;
struct cg_cgroup_link *saved_link;
BUG_ON(!root);
BUG_ON(root->number_of_cgroups != 1);
BUG_ON(!list_empty(&cgrp->children));
BUG_ON(!list_empty(&cgrp->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);
list_for_each_entry_safe(link, saved_link, &cgrp->css_sets,
cgrp_link_list) {
list_del(&link->cg_link_list);
list_del(&link->cgrp_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);
kill_litter_super(sb);
kfree(root);
}
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_cgrp(struct dentry *dentry)
{
return dentry->d_fsdata;
}
static inline struct cftype *__d_cft(struct dentry *dentry)
{
return dentry->d_fsdata;
}
/**
* cgroup_path - generate the path of a cgroup
* @cgrp: the cgroup in question
* @buf: the buffer to write the path into
* @buflen: the length of the buffer
*
* Called with cgroup_mutex held or else with an RCU-protected cgroup
* reference. Writes path of cgroup into buf. Returns 0 on success,
* -errno on error.
*/
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
{
char *start;
struct dentry *dentry = rcu_dereference(cgrp->dentry);
if (!dentry || cgrp == dummytop) {
/*
* Inactive subsystems have no dentry for their root
* cgroup
*/
strcpy(buf, "/");
return 0;
}
start = buf + buflen;
*--start = '\0';
for (;;) {
int len = dentry->d_name.len;
if ((start -= len) < buf)
return -ENAMETOOLONG;
memcpy(start, cgrp->dentry->d_name.name, len);
cgrp = cgrp->parent;
if (!cgrp)
break;
dentry = rcu_dereference(cgrp->dentry);
if (!cgrp->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 *cgrp,
struct cgroup_subsys_state **css, int *subsys_id)
{
const struct cgroupfs_root *root = cgrp->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 = cgrp->subsys[test_ss->subsys_id];
BUG_ON(!*css);
}
if (subsys_id)
*subsys_id = test_ss->subsys_id;
}
/**
* cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
* @cgrp: the cgroup the task is attaching to
* @tsk: the task to be attached
*
* Call holding cgroup_mutex. May take task_lock of
* the task 'tsk' during call.
*/
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
{
int retval = 0;
struct cgroup_subsys *ss;
struct cgroup *oldcgrp;
struct css_set *cg;
struct css_set *newcg;
struct cgroupfs_root *root = cgrp->root;
int subsys_id;
get_first_subsys(cgrp, NULL, &subsys_id);
/* Nothing to do if the task is already in that cgroup */
oldcgrp = task_cgroup(tsk, subsys_id);
if (cgrp == oldcgrp)
return 0;
for_each_subsys(root, ss) {
if (ss->can_attach) {
retval = ss->can_attach(ss, cgrp, tsk);
if (retval)
return retval;
}
}
task_lock(tsk);
cg = tsk->cgroups;
get_css_set(cg);
task_unlock(tsk);
/*
* Locate or allocate a new css_set for this task,
* based on its final set of cgroups
*/
newcg = find_css_set(cg, cgrp);
put_css_set(cg);
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, cgrp, oldcgrp, tsk);
}
set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
synchronize_rcu();
put_css_set(cg);
/*
* wake up rmdir() waiter. the rmdir should fail since the cgroup
* is no longer empty.
*/
cgroup_wakeup_rmdir_waiters(cgrp);
return 0;
}
/*
* Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex
* held. May take task_lock of task
*/
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid)
{
struct task_struct *tsk;
const struct cred *cred = current_cred(), *tcred;
int ret;
if (pid) {
rcu_read_lock();
tsk = find_task_by_vpid(pid);
if (!tsk || tsk->flags & PF_EXITING) {
rcu_read_unlock();
return -ESRCH;
}
tcred = __task_cred(tsk);
if (cred->euid &&
cred->euid != tcred->uid &&
cred->euid != tcred->suid) {
rcu_read_unlock();
return -EACCES;
}
get_task_struct(tsk);
rcu_read_unlock();
} else {
tsk = current;
get_task_struct(tsk);
}
ret = cgroup_attach_task(cgrp, tsk);
put_task_struct(tsk);
return ret;
}
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
{
int ret;
if (!cgroup_lock_live_group(cgrp))
return -ENODEV;
ret = attach_task_by_pid(cgrp, pid);
cgroup_unlock();
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_RELEASE_AGENT,
};
/**
* cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
* @cgrp: the cgroup to be checked for liveness
*
* On success, returns true; the lock should be later released with
* cgroup_unlock(). On failure returns false with no lock held.
*/
bool cgroup_lock_live_group(struct cgroup *cgrp)
{
mutex_lock(&cgroup_mutex);
if (cgroup_is_removed(cgrp)) {
mutex_unlock(&cgroup_mutex);
return false;
}
return true;
}
static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
const char *buffer)
{
BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
if (!cgroup_lock_live_group(cgrp))
return -ENODEV;
strcpy(cgrp->root->release_agent_path, buffer);
cgroup_unlock();
return 0;
}
static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
struct seq_file *seq)
{
if (!cgroup_lock_live_group(cgrp))
return -ENODEV;
seq_puts(seq, cgrp->root->release_agent_path);
seq_putc(seq, '\n');
cgroup_unlock();
return 0;
}
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
struct file *file,
const char __user *userbuf,
size_t nbytes, loff_t *unused_ppos)
{
char buffer[CGROUP_LOCAL_BUFFER_SIZE];
int retval = 0;
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 */
strstrip(buffer);
if (cft->write_u64) {
u64 val = simple_strtoull(buffer, &end, 0);
if (*end)
return -EINVAL;
retval = cft->write_u64(cgrp, cft, val);
} else {
s64 val = simple_strtoll(buffer, &end, 0);
if (*end)
return -EINVAL;
retval = cft->write_s64(cgrp, cft, val);
}
if (!retval)
retval = nbytes;
return retval;
}
static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
struct file *file,
const char __user *userbuf,
size_t nbytes, loff_t *unused_ppos)
{
char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
int retval = 0;
size_t max_bytes = cft->max_write_len;
char *buffer = local_buffer;
if (!max_bytes)
max_bytes = sizeof(local_buffer) - 1;
if (nbytes >= max_bytes)
return -E2BIG;
/* Allocate a dynamic buffer if we need one */
if (nbytes >= sizeof(local_buffer)) {
buffer = kmalloc(nbytes + 1, GFP_KERNEL);
if (buffer == NULL)
return -ENOMEM;
}
if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
retval = -EFAULT;
goto out;
}
buffer[nbytes] = 0; /* nul-terminate */
strstrip(buffer);
retval = cft->write_string(cgrp, cft, buffer);
if (!retval)
retval = nbytes;
out:
if (buffer != local_buffer)
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 *cgrp = __d_cgrp(file->f_dentry->d_parent);
if (cgroup_is_removed(cgrp))
return -ENODEV;
if (cft->write)
return cft->write(cgrp, cft, file, buf, nbytes, ppos);
if (cft->write_u64 || cft->write_s64)
return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
if (cft->write_string)
return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
if (cft->trigger) {
int ret = cft->trigger(cgrp, (unsigned int)cft->private);
return ret ? ret : nbytes;
}
return -EINVAL;
}
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
struct file *file,
char __user *buf, size_t nbytes,
loff_t *ppos)
{
char tmp[CGROUP_LOCAL_BUFFER_SIZE];
u64 val = cft->read_u64(cgrp, 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_read_s64(struct cgroup *cgrp, struct cftype *cft,
struct file *file,
char __user *buf, size_t nbytes,
loff_t *ppos)
{
char tmp[CGROUP_LOCAL_BUFFER_SIZE];
s64 val = cft->read_s64(cgrp, cft);
int len = sprintf(tmp, "%lld\n", (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 *cgrp = __d_cgrp(file->f_dentry->d_parent);
if (cgroup_is_removed(cgrp))
return -ENODEV;
if (cft->read)
return cft->read(cgrp, cft, file, buf, nbytes, ppos);
if (cft->read_u64)
return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
if (cft->read_s64)
return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
return -EINVAL;
}
/*
* seqfile ops/methods for returning structured data. Currently just
* supports string->u64 maps, but can be extended in future.
*/
struct cgroup_seqfile_state {
struct cftype *cft;
struct cgroup *cgroup;
};
static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
{
struct seq_file *sf = cb->state;
return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
}
static int cgroup_seqfile_show(struct seq_file *m, void *arg)
{
struct cgroup_seqfile_state *state = m->private;
struct cftype *cft = state->cft;
if (cft->read_map) {
struct cgroup_map_cb cb = {
.fill = cgroup_map_add,
.state = m,
};
return cft->read_map(state->cgroup, cft, &cb);
}
return cft->read_seq_string(state->cgroup, cft, m);
}
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
{
struct seq_file *seq = file->private_data;
kfree(seq->private);
return single_release(inode, file);
}
static struct file_operations cgroup_seqfile_operations = {
.read = seq_read,
.write = cgroup_file_write,
.llseek = seq_lseek,
.release = cgroup_seqfile_release,
};
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->read_map || cft->read_seq_string) {
struct cgroup_seqfile_state *state =
kzalloc(sizeof(*state), GFP_USER);
if (!state)
return -ENOMEM;
state->cft = cft;
state->cgroup = __d_cgrp(file->f_dentry->d_parent);
file->f_op = &cgroup_seqfile_operations;
err = single_open(file, cgroup_seqfile_show, state);
if (err < 0)
kfree(state);
} else 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, mode_t mode,
struct super_block *sb)
{
static const 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.
* @cgrp: 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 cgroup
* @mode: mode to set on new directory.
*/
static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry,
mode_t mode)
{
struct dentry *parent;
int error = 0;
parent = cgrp->parent->dentry;
error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb);
if (!error) {
dentry->d_fsdata = cgrp;
inc_nlink(parent->d_inode);
rcu_assign_pointer(cgrp->dentry, dentry);
dget(dentry);
}
dput(dentry);
return error;
}
/**
* cgroup_file_mode - deduce file mode of a control file
* @cft: the control file in question
*
* returns cft->mode if ->mode is not 0
* returns S_IRUGO|S_IWUSR if it has both a read and a write handler
* returns S_IRUGO if it has only a read handler
* returns S_IWUSR if it has only a write hander
*/
static mode_t cgroup_file_mode(const struct cftype *cft)
{
mode_t mode = 0;
if (cft->mode)
return cft->mode;
if (cft->read || cft->read_u64 || cft->read_s64 ||
cft->read_map || cft->read_seq_string)
mode |= S_IRUGO;
if (cft->write || cft->write_u64 || cft->write_s64 ||
cft->write_string || cft->trigger)
mode |= S_IWUSR;
return mode;
}
int cgroup_add_file(struct cgroup *cgrp,
struct cgroup_subsys *subsys,
const struct cftype *cft)
{
struct dentry *dir = cgrp->dentry;
struct dentry *dentry;
int error;
mode_t mode;
char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->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)) {
mode = cgroup_file_mode(cft);
error = cgroup_create_file(dentry, mode | S_IFREG,
cgrp->root->sb);
if (!error)
dentry->d_fsdata = (void *)cft;
dput(dentry);
} else
error = PTR_ERR(dentry);
return error;
}
int cgroup_add_files(struct cgroup *cgrp,
struct cgroup_subsys *subsys,
const struct cftype cft[],
int count)
{
int i, err;
for (i = 0; i < count; i++) {
err = cgroup_add_file(cgrp, subsys, &cft[i]);
if (err)
return err;
}
return 0;
}
/**
* cgroup_task_count - count the number of tasks in a cgroup.
* @cgrp: the cgroup in question
*
* Return the number of tasks in the cgroup.
*/
int cgroup_task_count(const struct cgroup *cgrp)
{
int count = 0;
struct cg_cgroup_link *link;
read_lock(&css_set_lock);
list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
count += atomic_read(&link->cg->refcount);
}
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 *cgrp,
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 == &cgrp->css_sets) {
it->cg_link = NULL;
return;
}
link = list_entry(l, struct cg_cgroup_link, cgrp_link_list);
cg = link->cg;
} while (list_empty(&cg->tasks));
it->cg_link = l;
it->task = cg->tasks.next;
}
/*
* To reduce the fork() overhead for systems that are not actually
* using their cgroups capability, we don't maintain the lists running
* through each css_set to its tasks until we see the list actually
* used - in other words after the first call to cgroup_iter_start().
*
* The tasklist_lock is not held here, as do_each_thread() and
* while_each_thread() are protected by RCU.
*/
static void cgroup_enable_task_cg_lists(void)
{
struct task_struct *p, *g;
write_lock(&css_set_lock);
use_task_css_set_links = 1;
do_each_thread(g, p) {
task_lock(p);
/*
* We should check if the process is exiting, otherwise
* it will race with cgroup_exit() in that the list
* entry won't be deleted though the process has exited.
*/
if (!(p->flags & PF_EXITING) && 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);
}
void cgroup_iter_start(struct cgroup *cgrp, 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)
cgroup_enable_task_cg_lists();
read_lock(&css_set_lock);
it->cg_link = &cgrp->css_sets;
cgroup_advance_iter(cgrp, it);
}
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
struct cgroup_iter *it)
{
struct task_struct *res;
struct list_head *l = it->task;
struct cg_cgroup_link *link;
/* 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;
link = list_entry(it->cg_link, struct cg_cgroup_link, cgrp_link_list);
if (l == &link->cg->tasks) {
/* We reached the end of this task list - move on to
* the next cg_cgroup_link */
cgroup_advance_iter(cgrp, it);
} else {
it->task = l;
}
return res;
}
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
{
read_unlock(&css_set_lock);
}
static inline int started_after_time(struct task_struct *t1,
struct timespec *time,
struct task_struct *t2)
{
int start_diff = timespec_compare(&t1->start_time, time);
if (start_diff > 0) {
return 1;
} else if (start_diff < 0) {
return 0;
} else {
/*
* Arbitrarily, if two processes started at the same
* time, we'll say that the lower pointer value
* started first. Note that t2 may have exited by now
* so this may not be a valid pointer any longer, but
* that's fine - it still serves to distinguish
* between two tasks started (effectively) simultaneously.
*/
return t1 > t2;
}
}
/*
* This function is a callback from heap_insert() and is used to order
* the heap.
* In this case we order the heap in descending task start time.
*/
static inline int started_after(void *p1, void *p2)
{
struct task_struct *t1 = p1;
struct task_struct *t2 = p2;
return started_after_time(t1, &t2->start_time, t2);
}
/**
* cgroup_scan_tasks - iterate though all the tasks in a cgroup
* @scan: struct cgroup_scanner containing arguments for the scan
*
* Arguments include pointers to callback functions test_task() and
* process_task().
* Iterate through all the tasks in a cgroup, calling test_task() for each,
* and if it returns true, call process_task() for it also.
* The test_task pointer may be NULL, meaning always true (select all tasks).
* Effectively duplicates cgroup_iter_{start,next,end}()
* but does not lock css_set_lock for the call to process_task().
* The struct cgroup_scanner may be embedded in any structure of the caller's
* creation.
* It is guaranteed that process_task() will act on every task that
* is a member of the cgroup for the duration of this call. This
* function may or may not call process_task() for tasks that exit
* or move to a different cgroup during the call, or are forked or
* move into the cgroup during the call.
*
* Note that test_task() may be called with locks held, and may in some
* situations be called multiple times for the same task, so it should
* be cheap.
* If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
* pre-allocated and will be used for heap operations (and its "gt" member will
* be overwritten), else a temporary heap will be used (allocation of which
* may cause this function to fail).
*/
int cgroup_scan_tasks(struct cgroup_scanner *scan)
{
int retval, i;
struct cgroup_iter it;
struct task_struct *p, *dropped;
/* Never dereference latest_task, since it's not refcounted */
struct task_struct *latest_task = NULL;
struct ptr_heap tmp_heap;
struct ptr_heap *heap;
struct timespec latest_time = { 0, 0 };
if (scan->heap) {
/* The caller supplied our heap and pre-allocated its memory */
heap = scan->heap;
heap->gt = &started_after;
} else {
/* We need to allocate our own heap memory */
heap = &tmp_heap;
retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
if (retval)
/* cannot allocate the heap */
return retval;
}
again:
/*
* Scan tasks in the cgroup, using the scanner's "test_task" callback
* to determine which are of interest, and using the scanner's
* "process_task" callback to process any of them that need an update.
* Since we don't want to hold any locks during the task updates,
* gather tasks to be processed in a heap structure.
* The heap is sorted by descending task start time.
* If the statically-sized heap fills up, we overflow tasks that
* started later, and in future iterations only consider tasks that
* started after the latest task in the previous pass. This
* guarantees forward progress and that we don't miss any tasks.
*/
heap->size = 0;
cgroup_iter_start(scan->cg, &it);
while ((p = cgroup_iter_next(scan->cg, &it))) {
/*
* Only affect tasks that qualify per the caller's callback,
* if he provided one
*/
if (scan->test_task && !scan->test_task(p, scan))
continue;
/*
* Only process tasks that started after the last task
* we processed
*/
if (!started_after_time(p, &latest_time, latest_task))
continue;
dropped = heap_insert(heap, p);
if (dropped == NULL) {
/*
* The new task was inserted; the heap wasn't
* previously full
*/
get_task_struct(p);
} else if (dropped != p) {
/*
* The new task was inserted, and pushed out a
* different task
*/
get_task_struct(p);
put_task_struct(dropped);
}
/*
* Else the new task was newer than anything already in
* the heap and wasn't inserted
*/
}
cgroup_iter_end(scan->cg, &it);
if (heap->size) {
for (i = 0; i < heap->size; i++) {
struct task_struct *q = heap->ptrs[i];
if (i == 0) {
latest_time = q->start_time;
latest_task = q;
}
/* Process the task per the caller's callback */
scan->process_task(q, scan);
put_task_struct(q);
}
/*
* If we had to process any tasks at all, scan again
* in case some of them were in the middle of forking
* children that didn't get processed.
* Not the most efficient way to do it, but it avoids
* having to take callback_mutex in the fork path
*/
goto again;
}
if (heap == &tmp_heap)
heap_free(&tmp_heap);
return 0;
}
/*
* 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.
*
*/
/*
* Load into 'pidarray' up to 'npids' of the tasks using cgroup
* 'cgrp'. 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 *cgrp)
{
int n = 0, pid;
struct cgroup_iter it;
struct task_struct *tsk;
cgroup_iter_start(cgrp, &it);
while ((tsk = cgroup_iter_next(cgrp, &it))) {
if (unlikely(n == npids))
break;
pid = task_pid_vnr(tsk);
if (pid > 0)
pidarray[n++] = pid;
}
cgroup_iter_end(cgrp, &it);
return n;
}
/**
* cgroupstats_build - build and fill cgroupstats
* @stats: cgroupstats to fill information into
* @dentry: A dentry entry belonging to the cgroup for which stats have
* been requested.
*
* Build and fill cgroupstats so that taskstats can export it to user
* space.
*/
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
int ret = -EINVAL;
struct cgroup *cgrp;
struct cgroup_iter it;
struct task_struct *tsk;
/*
* Validate dentry by checking the superblock operations,
* and make sure it's a directory.
*/
if (dentry->d_sb->s_op != &cgroup_ops ||
!S_ISDIR(dentry->d_inode->i_mode))
goto err;
ret = 0;
cgrp = dentry->d_fsdata;
cgroup_iter_start(cgrp, &it);
while ((tsk = cgroup_iter_next(cgrp, &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(cgrp, &it);
err:
return ret;
}
static int cmppid(const void *a, const void *b)
{
return *(pid_t *)a - *(pid_t *)b;
}
/*
* seq_file methods for the "tasks" file. The seq_file position is the
* next pid to display; the seq_file iterator is a pointer to the pid
* in the cgroup->tasks_pids array.
*/
static void *cgroup_tasks_start(struct seq_file *s, loff_t *pos)
{
/*
* Initially we receive a position value that corresponds to
* one more than the last pid shown (or 0 on the first call or
* after a seek to the start). Use a binary-search to find the
* next pid to display, if any
*/
struct cgroup *cgrp = s->private;
int index = 0, pid = *pos;
int *iter;
down_read(&cgrp->pids_mutex);
if (pid) {
int end = cgrp->pids_length;
while (index < end) {
int mid = (index + end) / 2;
if (cgrp->tasks_pids[mid] == pid) {
index = mid;
break;
} else if (cgrp->tasks_pids[mid] <= pid)
index = mid + 1;
else
end = mid;
}
}
/* If we're off the end of the array, we're done */
if (index >= cgrp->pids_length)
return NULL;
/* Update the abstract position to be the actual pid that we found */
iter = cgrp->tasks_pids + index;
*pos = *iter;
return iter;
}
static void cgroup_tasks_stop(struct seq_file *s, void *v)
{
struct cgroup *cgrp = s->private;
up_read(&cgrp->pids_mutex);
}
static void *cgroup_tasks_next(struct seq_file *s, void *v, loff_t *pos)
{
struct cgroup *cgrp = s->private;
int *p = v;
int *end = cgrp->tasks_pids + cgrp->pids_length;
/*
* Advance to the next pid in the array. If this goes off the
* end, we're done
*/
p++;
if (p >= end) {
return NULL;
} else {
*pos = *p;
return p;
}
}
static int cgroup_tasks_show(struct seq_file *s, void *v)
{
return seq_printf(s, "%d\n", *(int *)v);
}
static struct seq_operations cgroup_tasks_seq_operations = {
.start = cgroup_tasks_start,
.stop = cgroup_tasks_stop,
.next = cgroup_tasks_next,
.show = cgroup_tasks_show,
};
static void release_cgroup_pid_array(struct cgroup *cgrp)
{
down_write(&cgrp->pids_mutex);
BUG_ON(!cgrp->pids_use_count);
if (!--cgrp->pids_use_count) {
kfree(cgrp->tasks_pids);
cgrp->tasks_pids = NULL;
cgrp->pids_length = 0;
}
up_write(&cgrp->pids_mutex);
}
static int cgroup_tasks_release(struct inode *inode, struct file *file)
{
struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
if (!(file->f_mode & FMODE_READ))
return 0;
release_cgroup_pid_array(cgrp);
return seq_release(inode, file);
}
static struct file_operations cgroup_tasks_operations = {
.read = seq_read,
.llseek = seq_lseek,
.write = cgroup_file_write,
.release = cgroup_tasks_release,
};
/*
* Handle an open on 'tasks' file. Prepare an array containing the
* process id's of tasks currently attached to the cgroup being opened.
*/
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
pid_t *pidarray;
int npids;
int retval;
/* Nothing to do for write-only files */
if (!(file->f_mode & FMODE_READ))
return 0;
/*
* 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(cgrp);
pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL);
if (!pidarray)
return -ENOMEM;
npids = pid_array_load(pidarray, npids, cgrp);
sort(pidarray, npids, sizeof(pid_t), cmppid, NULL);
/*
* Store the array in the cgroup, freeing the old
* array if necessary
*/
down_write(&cgrp->pids_mutex);
kfree(cgrp->tasks_pids);
cgrp->tasks_pids = pidarray;
cgrp->pids_length = npids;
cgrp->pids_use_count++;
up_write(&cgrp->pids_mutex);
file->f_op = &cgroup_tasks_operations;
retval = seq_open(file, &cgroup_tasks_seq_operations);
if (retval) {
release_cgroup_pid_array(cgrp);
return retval;
}
((struct seq_file *)file->private_data)->private = cgrp;
return 0;
}
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
struct cftype *cft)
{
return notify_on_release(cgrp);
}
static int cgroup_write_notify_on_release(struct cgroup *cgrp,
struct cftype *cft,
u64 val)
{
clear_bit(CGRP_RELEASABLE, &cgrp->flags);
if (val)
set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
else
clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
return 0;
}
/*
* for the common functions, 'private' gives the type of file
*/
static struct cftype files[] = {
{
.name = "tasks",
.open = cgroup_tasks_open,
.write_u64 = cgroup_tasks_write,
.release = cgroup_tasks_release,
.private = FILE_TASKLIST,
.mode = S_IRUGO | S_IWUSR,
},
{
.name = "notify_on_release",
.read_u64 = cgroup_read_notify_on_release,
.write_u64 = cgroup_write_notify_on_release,
.private = FILE_NOTIFY_ON_RELEASE,
},
};
static struct cftype cft_release_agent = {
.name = "release_agent",
.read_seq_string = cgroup_release_agent_show,
.write_string = cgroup_release_agent_write,
.max_write_len = PATH_MAX,
.private = FILE_RELEASE_AGENT,
};
static int cgroup_populate_dir(struct cgroup *cgrp)
{
int err;
struct cgroup_subsys *ss;
/* First clear out any existing files */
cgroup_clear_directory(cgrp->dentry);
err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));
if (err < 0)
return err;
if (cgrp == cgrp->top_cgroup) {
if ((err = cgroup_add_file(cgrp, NULL, &cft_release_agent)) < 0)
return err;
}
for_each_subsys(cgrp->root, ss) {
if (ss->populate && (err = ss->populate(ss, cgrp)) < 0)
return err;
}
/* This cgroup is ready now */
for_each_subsys(cgrp->root, ss) {
struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
/*
* Update id->css pointer and make this css visible from
* CSS ID functions. This pointer will be dereferened
* from RCU-read-side without locks.
*/
if (css->id)
rcu_assign_pointer(css->id->css, css);
}
return 0;
}
static void init_cgroup_css(struct cgroup_subsys_state *css,
struct cgroup_subsys *ss,
struct cgroup *cgrp)
{
css->cgroup = cgrp;
atomic_set(&css->refcnt, 1);
css->flags = 0;
css->id = NULL;
if (cgrp == dummytop)
set_bit(CSS_ROOT, &css->flags);
BUG_ON(cgrp->subsys[ss->subsys_id]);
cgrp->subsys[ss->subsys_id] = css;
}
static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
{
/* We need to take each hierarchy_mutex in a consistent order */
int i;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss->root == root)
mutex_lock(&ss->hierarchy_mutex);
}
}
static void cgroup_unlock_hierarchy(struct cgroupfs_root *root)
{
int i;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss->root == root)
mutex_unlock(&ss->hierarchy_mutex);
}
}
/*
* cgroup_create - create a cgroup
* @parent: cgroup that will be parent of the new cgroup
* @dentry: dentry of the new cgroup
* @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,
mode_t mode)
{
struct cgroup *cgrp;
struct cgroupfs_root *root = parent->root;
int err = 0;
struct cgroup_subsys *ss;
struct super_block *sb = root->sb;
cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
if (!cgrp)
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);
init_cgroup_housekeeping(cgrp);
cgrp->parent = parent;
cgrp->root = parent->root;
cgrp->top_cgroup = parent->top_cgroup;
if (notify_on_release(parent))
set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
for_each_subsys(root, ss) {
struct cgroup_subsys_state *css = ss->create(ss, cgrp);
if (IS_ERR(css)) {
err = PTR_ERR(css);
goto err_destroy;
}
init_cgroup_css(css, ss, cgrp);
if (ss->use_id)
if (alloc_css_id(ss, parent, cgrp))
goto err_destroy;
/* At error, ->destroy() callback has to free assigned ID. */
}
cgroup_lock_hierarchy(root);
list_add(&cgrp->sibling, &cgrp->parent->children);
cgroup_unlock_hierarchy(root);
root->number_of_cgroups++;
err = cgroup_create_dir(cgrp, dentry, mode);
if (err < 0)
goto err_remove;
/* The cgroup directory was pre-locked for us */
BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
err = cgroup_populate_dir(cgrp);
/* If err < 0, we have a half-filled directory - oh well ;) */
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
return 0;
err_remove:
cgroup_lock_hierarchy(root);
list_del(&cgrp->sibling);
cgroup_unlock_hierarchy(root);
root->number_of_cgroups--;
err_destroy:
for_each_subsys(root, ss) {
if (cgrp->subsys[ss->subsys_id])
ss->destroy(ss, cgrp);
}
mutex_unlock(&cgroup_mutex);
/* Release the reference count that we took on the superblock */
deactivate_super(sb);
kfree(cgrp);
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_has_css_refs(struct cgroup *cgrp)
{
/* 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 1, 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 != cgrp->root)
continue;
css = cgrp->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) > 1))
return 1;
}
return 0;
}
/*
* Atomically mark all (or else none) of the cgroup's CSS objects as
* CSS_REMOVED. Return true on success, or false if the cgroup has
* busy subsystems. Call with cgroup_mutex held
*/
static int cgroup_clear_css_refs(struct cgroup *cgrp)
{
struct cgroup_subsys *ss;
unsigned long flags;
bool failed = false;
local_irq_save(flags);
for_each_subsys(cgrp->root, ss) {
struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
int refcnt;
while (1) {
/* We can only remove a CSS with a refcnt==1 */
refcnt = atomic_read(&css->refcnt);
if (refcnt > 1) {
failed = true;
goto done;
}
BUG_ON(!refcnt);
/*
* Drop the refcnt to 0 while we check other
* subsystems. This will cause any racing
* css_tryget() to spin until we set the
* CSS_REMOVED bits or abort
*/
if (atomic_cmpxchg(&css->refcnt, refcnt, 0) == refcnt)
break;
cpu_relax();
}
}
done:
for_each_subsys(cgrp->root, ss) {
struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
if (failed) {
/*
* Restore old refcnt if we previously managed
* to clear it from 1 to 0
*/
if (!atomic_read(&css->refcnt))
atomic_set(&css->refcnt, 1);
} else {
/* Commit the fact that the CSS is removed */
set_bit(CSS_REMOVED, &css->flags);
}
}
local_irq_restore(flags);
return !failed;
}
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
struct cgroup *cgrp = dentry->d_fsdata;
struct dentry *d;
struct cgroup *parent;
DEFINE_WAIT(wait);
int ret;
/* the vfs holds both inode->i_mutex already */
again:
mutex_lock(&cgroup_mutex);
if (atomic_read(&cgrp->count) != 0) {
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
if (!list_empty(&cgrp->children)) {
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
mutex_unlock(&cgroup_mutex);
/*
* Call pre_destroy handlers of subsys. Notify subsystems
* that rmdir() request comes.
*/
ret = cgroup_call_pre_destroy(cgrp);
if (ret)
return ret;
mutex_lock(&cgroup_mutex);
parent = cgrp->parent;
if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
/*
* css_put/get is provided for subsys to grab refcnt to css. In typical
* case, subsystem has no reference after pre_destroy(). But, under
* hierarchy management, some *temporal* refcnt can be hold.
* To avoid returning -EBUSY to a user, waitqueue is used. If subsys
* is really busy, it should return -EBUSY at pre_destroy(). wake_up
* is called when css_put() is called and refcnt goes down to 0.
*/
set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
if (!cgroup_clear_css_refs(cgrp)) {
mutex_unlock(&cgroup_mutex);
schedule();
finish_wait(&cgroup_rmdir_waitq, &wait);
clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
if (signal_pending(current))
return -EINTR;
goto again;
}
/* NO css_tryget() can success after here. */
finish_wait(&cgroup_rmdir_waitq, &wait);
clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
spin_lock(&release_list_lock);
set_bit(CGRP_REMOVED, &cgrp->flags);
if (!list_empty(&cgrp->release_list))
list_del(&cgrp->release_list);
spin_unlock(&release_list_lock);
cgroup_lock_hierarchy(cgrp->root);
/* delete this cgroup from parent->children */
list_del(&cgrp->sibling);
cgroup_unlock_hierarchy(cgrp->root);
spin_lock(&cgrp->dentry->d_lock);
d = dget(cgrp->dentry);
spin_unlock(&d->d_lock);
cgroup_d_remove_dir(d);
dput(d);
set_bit(CGRP_RELEASABLE, &parent->flags);
check_for_release(parent);
mutex_unlock(&cgroup_mutex);
return 0;
}
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
{
struct cgroup_subsys_state *css;
printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
/* Create the top cgroup state for this subsystem */
list_add(&ss->sibling, &rootnode.subsys_list);
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 the init_css_set to contain a subsys
* pointer to this state - since the subsystem is
* newly registered, all tasks and hence the
* init_css_set is in the subsystem's top cgroup. */
init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id];
need_forkexit_callback |= ss->fork || ss->exit;
/* At system boot, before all subsystems have been
* registered, no tasks have been forked, so we don't
* need to invoke fork callbacks here. */
BUG_ON(!list_empty(&init_task.tasks));
mutex_init(&ss->hierarchy_mutex);
lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
ss->active = 1;
}
/**
* cgroup_init_early - cgroup initialization at system boot
*
* Initialize cgroups at system boot, and initialize any
* subsystems that request early init.
*/
int __init cgroup_init_early(void)
{
int i;
atomic_set(&init_css_set.refcount, 1);
INIT_LIST_HEAD(&init_css_set.cg_links);
INIT_LIST_HEAD(&init_css_set.tasks);
INIT_HLIST_NODE(&init_css_set.hlist);
css_set_count = 1;
init_cgroup_root(&rootnode);
root_count = 1;
init_task.cgroups = &init_css_set;
init_css_set_link.cg = &init_css_set;
list_add(&init_css_set_link.cgrp_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 < CSS_SET_TABLE_SIZE; i++)
INIT_HLIST_HEAD(&css_set_table[i]);
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 "cgroup: Subsys %s id == %d\n",
ss->name, ss->subsys_id);
BUG();
}
if (ss->early_init)
cgroup_init_subsys(ss);
}
return 0;
}
/**
* cgroup_init - cgroup initialization
*
* 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 hlist_head *hhead;
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);
if (ss->use_id)
cgroup_subsys_init_idr(ss);
}
/* Add init_css_set to the hash table */
hhead = css_set_hash(init_css_set.subsys);
hlist_add_head(&init_css_set.hlist, hhead);
err = register_filesystem(&cgroup_fs_type);
if (err < 0)
goto out;
proc_create("cgroups", 0, NULL, &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 cgroup_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_active_root(root) {
struct cgroup_subsys *ss;
struct cgroup *cgrp;
int subsys_id;
int count = 0;
seq_printf(m, "%lu:", root->subsys_bits);
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);
cgrp = task_cgroup(tsk, subsys_id);
retval = cgroup_path(cgrp, 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;
seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\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\t%d\n",
ss->name, ss->root->subsys_bits,
ss->root->number_of_cgroups, !ss->disabled);
}
mutex_unlock(&cgroup_mutex);
return 0;
}
static int cgroupstats_open(struct inode *inode, struct file *file)
{
return single_open(file, proc_cgroupstats_show, NULL);
}
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.
* @child: 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. cgroup_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 - run fork callbacks
* @child: the new task
*
* 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
* @child: the task in question
*
* 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);
task_lock(child);
if (list_empty(&child->cg_list))
list_add(&child->cg_list, &child->cgroups->tasks);
task_unlock(child);
write_unlock(&css_set_lock);
}
}
/**
* cgroup_exit - detach cgroup from exiting task
* @tsk: pointer to task_struct of exiting process
* @run_callback: run exit callbacks?
*
* 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 cgroup_attach_task() attempts, or task is a failed
* fork, never visible to cgroup_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 - clone the cgroup the given subsystem is attached to
* @tsk: the task to be moved
* @subsys: the given subsystem
* @nodename: the name for the new cgroup
*
* 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,
char *nodename)
{
struct dentry *dentry;
int ret = 0;
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) {
mutex_unlock(&cgroup_mutex);
return 0;
}
/* Pin the hierarchy */
if (!atomic_inc_not_zero(&root->sb->s_active)) {
/* We race with the final deactivate_super() */
mutex_unlock(&cgroup_mutex);
return 0;
}
/* Keep the cgroup alive */
task_lock(tsk);
parent = task_cgroup(tsk, subsys->subsys_id);
cg = tsk->cgroups;
get_css_set(cg);
task_unlock(tsk);
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
"cgroup: 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, 0755);
child = __d_cgrp(dentry);
dput(dentry);
if (ret) {
printk(KERN_INFO
"Failed to create cgroup %s: %d\n", nodename,
ret);
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(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 = cgroup_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(root->sb);
return ret;
}
/**
* cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
* @cgrp: the cgroup in question
* @task: the task in question
*
* See if @cgrp is a descendant of @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 *cgrp, struct task_struct *task)
{
int ret;
struct cgroup *target;
int subsys_id;
if (cgrp == dummytop)
return 1;
get_first_subsys(cgrp, NULL, &subsys_id);
target = task_cgroup(task, subsys_id);
while (cgrp != target && cgrp!= cgrp->top_cgroup)
cgrp = cgrp->parent;
ret = (cgrp == target);
return ret;
}
static void check_for_release(struct cgroup *cgrp)
{
/* All of these checks rely on RCU to keep the cgroup
* structure alive */
if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count)
&& list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) {
/* 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(cgrp) &&
list_empty(&cgrp->release_list)) {
list_add(&cgrp->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 *cgrp = css->cgroup;
rcu_read_lock();
if (atomic_dec_return(&css->refcnt) == 1) {
if (notify_on_release(cgrp)) {
set_bit(CGRP_RELEASABLE, &cgrp->flags);
check_for_release(cgrp);
}
cgroup_wakeup_rmdir_waiters(cgrp);
}
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 = NULL, *agentbuf = NULL;
struct cgroup *cgrp = list_entry(release_list.next,
struct cgroup,
release_list);
list_del_init(&cgrp->release_list);
spin_unlock(&release_list_lock);
pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!pathbuf)
goto continue_free;
if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
goto continue_free;
agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
if (!agentbuf)
goto continue_free;
i = 0;
argv[i++] = agentbuf;
argv[i++] = 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);
mutex_lock(&cgroup_mutex);
continue_free:
kfree(pathbuf);
kfree(agentbuf);
spin_lock(&release_list_lock);
}
spin_unlock(&release_list_lock);
mutex_unlock(&cgroup_mutex);
}
static int __init cgroup_disable(char *str)
{
int i;
char *token;
while ((token = strsep(&str, ",")) != NULL) {
if (!*token)
continue;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (!strcmp(token, ss->name)) {
ss->disabled = 1;
printk(KERN_INFO "Disabling %s control group"
" subsystem\n", ss->name);
break;
}
}
}
return 1;
}
__setup("cgroup_disable=", cgroup_disable);
/*
* Functons for CSS ID.
*/
/*
*To get ID other than 0, this should be called when !cgroup_is_removed().
*/
unsigned short css_id(struct cgroup_subsys_state *css)
{
struct css_id *cssid = rcu_dereference(css->id);
if (cssid)
return cssid->id;
return 0;
}
unsigned short css_depth(struct cgroup_subsys_state *css)
{
struct css_id *cssid = rcu_dereference(css->id);
if (cssid)
return cssid->depth;
return 0;
}
bool css_is_ancestor(struct cgroup_subsys_state *child,
const struct cgroup_subsys_state *root)
{
struct css_id *child_id = rcu_dereference(child->id);
struct css_id *root_id = rcu_dereference(root->id);
if (!child_id || !root_id || (child_id->depth < root_id->depth))
return false;
return child_id->stack[root_id->depth] == root_id->id;
}
static void __free_css_id_cb(struct rcu_head *head)
{
struct css_id *id;
id = container_of(head, struct css_id, rcu_head);
kfree(id);
}
void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
{
struct css_id *id = css->id;
/* When this is called before css_id initialization, id can be NULL */
if (!id)
return;
BUG_ON(!ss->use_id);
rcu_assign_pointer(id->css, NULL);
rcu_assign_pointer(css->id, NULL);
spin_lock(&ss->id_lock);
idr_remove(&ss->idr, id->id);
spin_unlock(&ss->id_lock);
call_rcu(&id->rcu_head, __free_css_id_cb);
}
/*
* This is called by init or create(). Then, calls to this function are
* always serialized (By cgroup_mutex() at create()).
*/
static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
{
struct css_id *newid;
int myid, error, size;
BUG_ON(!ss->use_id);
size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
newid = kzalloc(size, GFP_KERNEL);
if (!newid)
return ERR_PTR(-ENOMEM);
/* get id */
if (unlikely(!idr_pre_get(&ss->idr, GFP_KERNEL))) {
error = -ENOMEM;
goto err_out;
}
spin_lock(&ss->id_lock);
/* Don't use 0. allocates an ID of 1-65535 */
error = idr_get_new_above(&ss->idr, newid, 1, &myid);
spin_unlock(&ss->id_lock);
/* Returns error when there are no free spaces for new ID.*/
if (error) {
error = -ENOSPC;
goto err_out;
}
if (myid > CSS_ID_MAX)
goto remove_idr;
newid->id = myid;
newid->depth = depth;
return newid;
remove_idr:
error = -ENOSPC;
spin_lock(&ss->id_lock);
idr_remove(&ss->idr, myid);
spin_unlock(&ss->id_lock);
err_out:
kfree(newid);
return ERR_PTR(error);
}
static int __init cgroup_subsys_init_idr(struct cgroup_subsys *ss)
{
struct css_id *newid;
struct cgroup_subsys_state *rootcss;
spin_lock_init(&ss->id_lock);
idr_init(&ss->idr);
rootcss = init_css_set.subsys[ss->subsys_id];
newid = get_new_cssid(ss, 0);
if (IS_ERR(newid))
return PTR_ERR(newid);
newid->stack[0] = newid->id;
newid->css = rootcss;
rootcss->id = newid;
return 0;
}
static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
struct cgroup *child)
{
int subsys_id, i, depth = 0;
struct cgroup_subsys_state *parent_css, *child_css;
struct css_id *child_id, *parent_id = NULL;
subsys_id = ss->subsys_id;
parent_css = parent->subsys[subsys_id];
child_css = child->subsys[subsys_id];
depth = css_depth(parent_css) + 1;
parent_id = parent_css->id;
child_id = get_new_cssid(ss, depth);
if (IS_ERR(child_id))
return PTR_ERR(child_id);
for (i = 0; i < depth; i++)
child_id->stack[i] = parent_id->stack[i];
child_id->stack[depth] = child_id->id;
/*
* child_id->css pointer will be set after this cgroup is available
* see cgroup_populate_dir()
*/
rcu_assign_pointer(child_css->id, child_id);
return 0;
}
/**
* css_lookup - lookup css by id
* @ss: cgroup subsys to be looked into.
* @id: the id
*
* Returns pointer to cgroup_subsys_state if there is valid one with id.
* NULL if not. Should be called under rcu_read_lock()
*/
struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
{
struct css_id *cssid = NULL;
BUG_ON(!ss->use_id);
cssid = idr_find(&ss->idr, id);
if (unlikely(!cssid))
return NULL;
return rcu_dereference(cssid->css);
}
/**
* css_get_next - lookup next cgroup under specified hierarchy.
* @ss: pointer to subsystem
* @id: current position of iteration.
* @root: pointer to css. search tree under this.
* @foundid: position of found object.
*
* Search next css under the specified hierarchy of rootid. Calling under
* rcu_read_lock() is necessary. Returns NULL if it reaches the end.
*/
struct cgroup_subsys_state *
css_get_next(struct cgroup_subsys *ss, int id,
struct cgroup_subsys_state *root, int *foundid)
{
struct cgroup_subsys_state *ret = NULL;
struct css_id *tmp;
int tmpid;
int rootid = css_id(root);
int depth = css_depth(root);
if (!rootid)
return NULL;
BUG_ON(!ss->use_id);
/* fill start point for scan */
tmpid = id;
while (1) {
/*
* scan next entry from bitmap(tree), tmpid is updated after
* idr_get_next().
*/
spin_lock(&ss->id_lock);
tmp = idr_get_next(&ss->idr, &tmpid);
spin_unlock(&ss->id_lock);
if (!tmp)
break;
if (tmp->depth >= depth && tmp->stack[depth] == rootid) {
ret = rcu_dereference(tmp->css);
if (ret) {
*foundid = tmpid;
break;
}
}
/* continue to scan from next id */
tmpid = tmpid + 1;
}
return ret;
}