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linux/kernel/cgroup.c
Michael S. Tsirkin 31583bb0cf cgroups: fix API thinko 
Add cgroup_attach_task_all()

The existing cgroup_attach_task_current_cg() API is called by a thread to
attach another thread to all of its cgroups; this is unsuitable for cases
where a privileged task wants to attach itself to the cgroups of a less
privileged one, since the call must be made from the context of the target
task.

This patch adds a more generic cgroup_attach_task_all() API that allows
both the source task and to-be-moved task to be specified.
cgroup_attach_task_current_cg() becomes a specialization of the more
generic new function.

[menage@google.com: rewrote changelog]
[akpm@linux-foundation.org: address reviewer comments]
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Ben Blum <bblum@google.com>
Cc: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-09-09 18:57:23 -07:00

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/*
* Generic process-grouping system.
*
* Based originally on the cpuset system, extracted by Paul Menage
* Copyright (C) 2006 Google, Inc
*
* Notifications support
* Copyright (C) 2009 Nokia Corporation
* Author: Kirill A. Shutemov
*
* 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/ctype.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/module.h>
#include <linux/delayacct.h>
#include <linux/cgroupstats.h>
#include <linux/hash.h>
#include <linux/namei.h>
#include <linux/smp_lock.h>
#include <linux/pid_namespace.h>
#include <linux/idr.h>
#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
#include <linux/eventfd.h>
#include <linux/poll.h>
#include <asm/atomic.h>
static DEFINE_MUTEX(cgroup_mutex);
/*
* Generate an array of cgroup subsystem pointers. At boot time, this is
* populated up to CGROUP_BUILTIN_SUBSYS_COUNT, and modular subsystems are
* registered after that. The mutable section of this array is protected by
* cgroup_mutex.
*/
#define SUBSYS(_x) &_x ## _subsys,
static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
#include <linux/cgroup_subsys.h>
};
#define MAX_CGROUP_ROOT_NAMELEN 64
/*
* 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;
/* Unique id for this hierarchy. */
int hierarchy_id;
/* 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 name for this hierarchy - may be empty */
char name[MAX_CGROUP_ROOT_NAMELEN];
};
/*
* 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) */
};
/*
* cgroup_event represents events which userspace want to recieve.
*/
struct cgroup_event {
/*
* Cgroup which the event belongs to.
*/
struct cgroup *cgrp;
/*
* Control file which the event associated.
*/
struct cftype *cft;
/*
* eventfd to signal userspace about the event.
*/
struct eventfd_ctx *eventfd;
/*
* Each of these stored in a list by the cgroup.
*/
struct list_head list;
/*
* All fields below needed to unregister event when
* userspace closes eventfd.
*/
poll_table pt;
wait_queue_head_t *wqh;
wait_queue_t wait;
struct work_struct remove;
};
/* The list of hierarchy roots */
static LIST_HEAD(roots);
static int root_count;
static DEFINE_IDA(hierarchy_ida);
static int next_hierarchy_id;
static DEFINE_SPINLOCK(hierarchy_id_lock);
/* 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;
#ifdef CONFIG_PROVE_LOCKING
int cgroup_lock_is_held(void)
{
return lockdep_is_held(&cgroup_mutex);
}
#else /* #ifdef CONFIG_PROVE_LOCKING */
int cgroup_lock_is_held(void)
{
return mutex_is_locked(&cgroup_mutex);
}
#endif /* #else #ifdef CONFIG_PROVE_LOCKING */
EXPORT_SYMBOL_GPL(cgroup_lock_is_held);
/* 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;
struct cgroup *cgrp;
/*
* 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_init_idr(struct cgroup_subsys *ss,
struct cgroup_subsys_state *css);
/* 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. This hash doesn't (currently) take into
* account cgroups in empty hierarchies.
*/
#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];
}
static void free_css_set_rcu(struct rcu_head *obj)
{
struct css_set *cg = container_of(obj, struct css_set, rcu_head);
kfree(cg);
}
/* 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;
static void __put_css_set(struct css_set *cg, int taskexit)
{
struct cg_cgroup_link *link;
struct cg_cgroup_link *saved_link;
/*
* 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;
}
/* This css_set is dead. unlink it and release cgroup refcounts */
hlist_del(&cg->hlist);
css_set_count--;
list_for_each_entry_safe(link, saved_link, &cg->cg_links,
cg_link_list) {
struct cgroup *cgrp = link->cgrp;
list_del(&link->cg_link_list);
list_del(&link->cgrp_link_list);
if (atomic_dec_and_test(&cgrp->count) &&
notify_on_release(cgrp)) {
if (taskexit)
set_bit(CGRP_RELEASABLE, &cgrp->flags);
check_for_release(cgrp);
}
kfree(link);
}
write_unlock(&css_set_lock);
call_rcu(&cg->rcu_head, free_css_set_rcu);
}
/*
* 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);
}
/*
* compare_css_sets - helper function for find_existing_css_set().
* @cg: candidate css_set being tested
* @old_cg: existing css_set for a task
* @new_cgrp: cgroup that's being entered by the task
* @template: desired set of css pointers in css_set (pre-calculated)
*
* Returns true if "cg" matches "old_cg" except for the hierarchy
* which "new_cgrp" belongs to, for which it should match "new_cgrp".
*/
static bool compare_css_sets(struct css_set *cg,
struct css_set *old_cg,
struct cgroup *new_cgrp,
struct cgroup_subsys_state *template[])
{
struct list_head *l1, *l2;
if (memcmp(template, cg->subsys, sizeof(cg->subsys))) {
/* Not all subsystems matched */
return false;
}
/*
* Compare cgroup pointers in order to distinguish between
* different cgroups in heirarchies with no subsystems. We
* could get by with just this check alone (and skip the
* memcmp above) but on most setups the memcmp check will
* avoid the need for this more expensive check on almost all
* candidates.
*/
l1 = &cg->cg_links;
l2 = &old_cg->cg_links;
while (1) {
struct cg_cgroup_link *cgl1, *cgl2;
struct cgroup *cg1, *cg2;
l1 = l1->next;
l2 = l2->next;
/* See if we reached the end - both lists are equal length. */
if (l1 == &cg->cg_links) {
BUG_ON(l2 != &old_cg->cg_links);
break;
} else {
BUG_ON(l2 == &old_cg->cg_links);
}
/* Locate the cgroups associated with these links. */
cgl1 = list_entry(l1, struct cg_cgroup_link, cg_link_list);
cgl2 = list_entry(l2, struct cg_cgroup_link, cg_link_list);
cg1 = cgl1->cgrp;
cg2 = cgl2->cgrp;
/* Hierarchies should be linked in the same order. */
BUG_ON(cg1->root != cg2->root);
/*
* If this hierarchy is the hierarchy of the cgroup
* that's changing, then we need to check that this
* css_set points to the new cgroup; if it's any other
* hierarchy, then this css_set should point to the
* same cgroup as the old css_set.
*/
if (cg1->root == new_cgrp->root) {
if (cg1 != new_cgrp)
return false;
} else {
if (cg1 != cg2)
return false;
}
}
return true;
}
/*
* 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;
/*
* Build the set of subsystem state objects that we want to see in the
* new css_set. while subsystems can change globally, the entries here
* won't change, so no need for locking.
*/
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 (!compare_css_sets(cg, oldcg, cgrp, template))
continue;
/* This css_set matches what we need */
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;
link->cgrp = cgrp;
atomic_inc(&cgrp->count);
list_move(&link->cgrp_link_list, &cgrp->css_sets);
/*
* Always add links to the tail of the list so that the list
* is sorted by order of hierarchy creation
*/
list_add_tail(&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];
struct list_head tmp_cg_links;
struct hlist_head *hhead;
struct cg_cgroup_link *link;
/* 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. */
list_for_each_entry(link, &oldcg->cg_links, cg_link_list) {
struct cgroup *c = link->cgrp;
if (c->root == cgrp->root)
c = cgrp;
link_css_set(&tmp_cg_links, res, c);
}
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;
}
/*
* Return the cgroup for "task" from the given hierarchy. Must be
* called with cgroup_mutex held.
*/
static struct cgroup *task_cgroup_from_root(struct task_struct *task,
struct cgroupfs_root *root)
{
struct css_set *css;
struct cgroup *res = NULL;
BUG_ON(!mutex_is_locked(&cgroup_mutex));
read_lock(&css_set_lock);
/*
* No need to lock the task - since we hold cgroup_mutex the
* task can't change groups, so the only thing that can happen
* is that it exits and its css is set back to init_css_set.
*/
css = task->cgroups;
if (css == &init_css_set) {
res = &root->top_cgroup;
} else {
struct cg_cgroup_link *link;
list_for_each_entry(link, &css->cg_links, cg_link_list) {
struct cgroup *c = link->cgrp;
if (c->root == root) {
res = c;
break;
}
}
}
read_unlock(&css_set_lock);
BUG_ON(!res);
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);
}
EXPORT_SYMBOL_GPL(cgroup_lock);
/**
* 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);
}
EXPORT_SYMBOL_GPL(cgroup_unlock);
/*
* 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 const struct inode_operations cgroup_dir_inode_operations;
static const struct file_operations proc_cgroupstats_operations;
static struct backing_dev_info cgroup_backing_dev_info = {
.name = "cgroup",
.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);
/*
* if we're getting rid of the cgroup, refcount should ensure
* that there are no pidlists left.
*/
BUG_ON(!list_empty(&cgrp->pidlists));
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 set under cgroup's inode->i_mutex;
*/
DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
{
if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
wake_up_all(&cgroup_rmdir_waitq);
}
void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
{
css_get(css);
}
void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
{
cgroup_wakeup_rmdir_waiter(css->cgroup);
css_put(css);
}
/*
* Call with cgroup_mutex held. Drops reference counts on modules, including
* any duplicate ones that parse_cgroupfs_options took. If this function
* returns an error, no reference counts are touched.
*/
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;
BUG_ON(!mutex_is_locked(&cgroup_mutex));
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;
/*
* Nobody should tell us to do a subsys that doesn't exist:
* parse_cgroupfs_options should catch that case and refcounts
* ensure that subsystems won't disappear once selected.
*/
BUG_ON(ss == NULL);
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(ss == NULL);
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);
/* refcount was already taken, and we're keeping it */
} else if (bit & removed_bits) {
/* We're removing this subsystem */
BUG_ON(ss == NULL);
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);
/* subsystem is now free - drop reference on module */
module_put(ss->module);
} else if (bit & final_bits) {
/* Subsystem state should already exist */
BUG_ON(ss == NULL);
BUG_ON(!cgrp->subsys[i]);
/*
* a refcount was taken, but we already had one, so
* drop the extra reference.
*/
module_put(ss->module);
#ifdef CONFIG_MODULE_UNLOAD
BUG_ON(ss->module && !module_refcount(ss->module));
#endif
} 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);
if (strlen(root->name))
seq_printf(seq, ",name=%s", root->name);
mutex_unlock(&cgroup_mutex);
return 0;
}
struct cgroup_sb_opts {
unsigned long subsys_bits;
unsigned long flags;
char *release_agent;
char *name;
/* User explicitly requested empty subsystem */
bool none;
struct cgroupfs_root *new_root;
};
/*
* Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
* with cgroup_mutex held to protect the subsys[] array. This function takes
* refcounts on subsystems to be used, unless it returns error, in which case
* no refcounts are taken.
*/
static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
{
char *token, *o = data ?: "all";
unsigned long mask = (unsigned long)-1;
int i;
bool module_pin_failed = false;
BUG_ON(!mutex_is_locked(&cgroup_mutex));
#ifdef CONFIG_CPUSETS
mask = ~(1UL << cpuset_subsys_id);
#endif
memset(opts, 0, sizeof(*opts));
while ((token = strsep(&o, ",")) != NULL) {
if (!*token)
return -EINVAL;
if (!strcmp(token, "all")) {
/* Add all non-disabled subsystems */
opts->subsys_bits = 0;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss == NULL)
continue;
if (!ss->disabled)
opts->subsys_bits |= 1ul << i;
}
} else if (!strcmp(token, "none")) {
/* Explicitly have no subsystems */
opts->none = true;
} 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 =
kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
if (!opts->release_agent)
return -ENOMEM;
} else if (!strncmp(token, "name=", 5)) {
const char *name = token + 5;
/* Can't specify an empty name */
if (!strlen(name))
return -EINVAL;
/* Must match [\w.-]+ */
for (i = 0; i < strlen(name); i++) {
char c = name[i];
if (isalnum(c))
continue;
if ((c == '.') || (c == '-') || (c == '_'))
continue;
return -EINVAL;
}
/* Specifying two names is forbidden */
if (opts->name)
return -EINVAL;
opts->name = kstrndup(name,
MAX_CGROUP_ROOT_NAMELEN - 1,
GFP_KERNEL);
if (!opts->name)
return -ENOMEM;
} else {
struct cgroup_subsys *ss;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
ss = subsys[i];
if (ss == NULL)
continue;
if (!strcmp(token, ss->name)) {
if (!ss->disabled)
set_bit(i, &opts->subsys_bits);
break;
}
}
if (i == CGROUP_SUBSYS_COUNT)
return -ENOENT;
}
}
/* Consistency checks */
/*
* 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;
/* Can't specify "none" and some subsystems */
if (opts->subsys_bits && opts->none)
return -EINVAL;
/*
* We either have to specify by name or by subsystems. (So all
* empty hierarchies must have a name).
*/
if (!opts->subsys_bits && !opts->name)
return -EINVAL;
/*
* Grab references on all the modules we'll need, so the subsystems
* don't dance around before rebind_subsystems attaches them. This may
* take duplicate reference counts on a subsystem that's already used,
* but rebind_subsystems handles this case.
*/
for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
unsigned long bit = 1UL << i;
if (!(bit & opts->subsys_bits))
continue;
if (!try_module_get(subsys[i]->module)) {
module_pin_failed = true;
break;
}
}
if (module_pin_failed) {
/*
* oops, one of the modules was going away. this means that we
* raced with a module_delete call, and to the user this is
* essentially a "subsystem doesn't exist" case.
*/
for (i--; i >= CGROUP_BUILTIN_SUBSYS_COUNT; i--) {
/* drop refcounts only on the ones we took */
unsigned long bit = 1UL << i;
if (!(bit & opts->subsys_bits))
continue;
module_put(subsys[i]->module);
}
return -ENOENT;
}
return 0;
}
static void drop_parsed_module_refcounts(unsigned long subsys_bits)
{
int i;
for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
unsigned long bit = 1UL << i;
if (!(bit & subsys_bits))
continue;
module_put(subsys[i]->module);
}
}
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 or name to change at remount */
if (opts.flags != root->flags ||
(opts.name && strcmp(opts.name, root->name))) {
ret = -EINVAL;
drop_parsed_module_refcounts(opts.subsys_bits);
goto out_unlock;
}
ret = rebind_subsystems(root, opts.subsys_bits);
if (ret) {
drop_parsed_module_refcounts(opts.subsys_bits);
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);
kfree(opts.name);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
unlock_kernel();
return ret;
}
static const 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_LIST_HEAD(&cgrp->pidlists);
mutex_init(&cgrp->pidlist_mutex);
INIT_LIST_HEAD(&cgrp->event_list);
spin_lock_init(&cgrp->event_list_lock);
}
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 bool init_root_id(struct cgroupfs_root *root)
{
int ret = 0;
do {
if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
return false;
spin_lock(&hierarchy_id_lock);
/* Try to allocate the next unused ID */
ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
&root->hierarchy_id);
if (ret == -ENOSPC)
/* Try again starting from 0 */
ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
if (!ret) {
next_hierarchy_id = root->hierarchy_id + 1;
} else if (ret != -EAGAIN) {
/* Can only get here if the 31-bit IDR is full ... */
BUG_ON(ret);
}
spin_unlock(&hierarchy_id_lock);
} while (ret);
return true;
}
static int cgroup_test_super(struct super_block *sb, void *data)
{
struct cgroup_sb_opts *opts = data;
struct cgroupfs_root *root = sb->s_fs_info;
/* If we asked for a name then it must match */
if (opts->name && strcmp(opts->name, root->name))
return 0;
/*
* If we asked for subsystems (or explicitly for no
* subsystems) then they must match
*/
if ((opts->subsys_bits || opts->none)
&& (opts->subsys_bits != root->subsys_bits))
return 0;
return 1;
}
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
struct cgroupfs_root *root;
if (!opts->subsys_bits && !opts->none)
return NULL;
root = kzalloc(sizeof(*root), GFP_KERNEL);
if (!root)
return ERR_PTR(-ENOMEM);
if (!init_root_id(root)) {
kfree(root);
return ERR_PTR(-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);
if (opts->name)
strcpy(root->name, opts->name);
return root;
}
static void cgroup_drop_root(struct cgroupfs_root *root)
{
if (!root)
return;
BUG_ON(!root->hierarchy_id);
spin_lock(&hierarchy_id_lock);
ida_remove(&hierarchy_ida, root->hierarchy_id);
spin_unlock(&hierarchy_id_lock);
kfree(root);
}
static int cgroup_set_super(struct super_block *sb, void *data)
{
int ret;
struct cgroup_sb_opts *opts = data;
/* If we don't have a new root, we can't set up a new sb */
if (!opts->new_root)
return -EINVAL;
BUG_ON(!opts->subsys_bits && !opts->none);
ret = set_anon_super(sb, NULL);
if (ret)
return ret;
sb->s_fs_info = opts->new_root;
opts->new_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;
struct cgroupfs_root *root;
int ret = 0;
struct super_block *sb;
struct cgroupfs_root *new_root;
/* First find the desired set of subsystems */
mutex_lock(&cgroup_mutex);
ret = parse_cgroupfs_options(data, &opts);
mutex_unlock(&cgroup_mutex);
if (ret)
goto out_err;
/*
* Allocate a new cgroup root. We may not need it if we're
* reusing an existing hierarchy.
*/
new_root = cgroup_root_from_opts(&opts);
if (IS_ERR(new_root)) {
ret = PTR_ERR(new_root);
goto drop_modules;
}
opts.new_root = new_root;
/* Locate an existing or new sb for this hierarchy */
sb = sget(fs_type, cgroup_test_super, cgroup_set_super, &opts);
if (IS_ERR(sb)) {
ret = PTR_ERR(sb);
cgroup_drop_root(opts.new_root);
goto drop_modules;
}
root = sb->s_fs_info;
BUG_ON(!root);
if (root == opts.new_root) {
/* We used the new root structure, so this is a new hierarchy */
struct list_head tmp_cg_links;
struct cgroup *root_cgrp = &root->top_cgroup;
struct inode *inode;
struct cgroupfs_root *existing_root;
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);
if (strlen(root->name)) {
/* Check for name clashes with existing mounts */
for_each_active_root(existing_root) {
if (!strcmp(existing_root->name, root->name)) {
ret = -EBUSY;
mutex_unlock(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);
goto drop_new_super;
}
}
}
/*
* 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);
free_cg_links(&tmp_cg_links);
goto drop_new_super;
}
/*
* There must be no failure case after here, since rebinding
* takes care of subsystems' refcounts, which are explicitly
* dropped in the failure exit path.
*/
/* 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(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);
} else {
/*
* We re-used an existing hierarchy - the new root (if
* any) is not needed
*/
cgroup_drop_root(opts.new_root);
/* no subsys rebinding, so refcounts don't change */
drop_parsed_module_refcounts(opts.subsys_bits);
}
simple_set_mnt(mnt, sb);
kfree(opts.release_agent);
kfree(opts.name);
return 0;
drop_new_super:
deactivate_locked_super(sb);
drop_modules:
drop_parsed_module_refcounts(opts.subsys_bits);
out_err:
kfree(opts.release_agent);
kfree(opts.name);
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);
cgroup_drop_root(root);
}
static struct file_system_type cgroup_fs_type = {
.name = "cgroup",
.get_sb = cgroup_get_sb,
.kill_sb = cgroup_kill_sb,
};
static struct kobject *cgroup_kobj;
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_check(cgrp->dentry,
rcu_read_lock_held() ||
cgroup_lock_is_held());
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, dentry->d_name.name, len);
cgrp = cgrp->parent;
if (!cgrp)
break;
dentry = rcu_dereference_check(cgrp->dentry,
rcu_read_lock_held() ||
cgroup_lock_is_held());
if (!cgrp->parent)
continue;
if (--start < buf)
return -ENAMETOOLONG;
*start = '/';
}
memmove(buf, start, buf + buflen - start);
return 0;
}
EXPORT_SYMBOL_GPL(cgroup_path);
/**
* 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, *failed_ss = NULL;
struct cgroup *oldcgrp;
struct css_set *cg;
struct css_set *newcg;
struct cgroupfs_root *root = cgrp->root;
/* Nothing to do if the task is already in that cgroup */
oldcgrp = task_cgroup_from_root(tsk, root);
if (cgrp == oldcgrp)
return 0;
for_each_subsys(root, ss) {
if (ss->can_attach) {
retval = ss->can_attach(ss, cgrp, tsk, false);
if (retval) {
/*
* Remember on which subsystem the can_attach()
* failed, so that we only call cancel_attach()
* against the subsystems whose can_attach()
* succeeded. (See below)
*/
failed_ss = ss;
goto out;
}
}
}
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) {
retval = -ENOMEM;
goto out;
}
task_lock(tsk);
if (tsk->flags & PF_EXITING) {
task_unlock(tsk);
put_css_set(newcg);
retval = -ESRCH;
goto out;
}
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, false);
}
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_waiter(cgrp);
out:
if (retval) {
for_each_subsys(root, ss) {
if (ss == failed_ss)
/*
* This subsystem was the one that failed the
* can_attach() check earlier, so we don't need
* to call cancel_attach() against it or any
* remaining subsystems.
*/
break;
if (ss->cancel_attach)
ss->cancel_attach(ss, cgrp, tsk, false);
}
}
return retval;
}
/**
* cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
* @from: attach to all cgroups of a given task
* @tsk: the task to be attached
*/
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
{
struct cgroupfs_root *root;
int retval = 0;
cgroup_lock();
for_each_active_root(root) {
struct cgroup *from_cg = task_cgroup_from_root(from, root);
retval = cgroup_attach_task(from_cg, tsk);
if (retval)
break;
}
cgroup_unlock();
return retval;
}
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
/*
* 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;
}
/**
* 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;
}
EXPORT_SYMBOL_GPL(cgroup_lock_live_group);
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 */
if (cft->write_u64) {
u64 val = simple_strtoull(strstrip(buffer), &end, 0);
if (*end)
return -EINVAL;
retval = cft->write_u64(cgrp, cft, val);
} else {
s64 val = simple_strtoll(strstrip(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 */
retval = cft->write_string(cgrp, cft, strstrip(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 const 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 const 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 const struct inode_operations cgroup_dir_inode_operations = {
.lookup = simple_lookup,
.mkdir = cgroup_mkdir,
.rmdir = cgroup_rmdir,
.rename = cgroup_rename,
};
/*
* Check if a file is a control file
*/
static inline struct cftype *__file_cft(struct file *file)
{
if (file->f_dentry->d_inode->i_fop != &cgroup_file_operations)
return ERR_PTR(-EINVAL);
return __d_cft(file->f_dentry);
}
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;
}
EXPORT_SYMBOL_GPL(cgroup_add_file);
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;
}
EXPORT_SYMBOL_GPL(cgroup_add_files);
/**
* 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'/'procs' files.
*
* 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.
*
*/
/*
* The following two functions "fix" the issue where there are more pids
* than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
* TODO: replace with a kernel-wide solution to this problem
*/
#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
static void *pidlist_allocate(int count)
{
if (PIDLIST_TOO_LARGE(count))
return vmalloc(count * sizeof(pid_t));
else
return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
}
static void pidlist_free(void *p)
{
if (is_vmalloc_addr(p))
vfree(p);
else
kfree(p);
}
static void *pidlist_resize(void *p, int newcount)
{
void *newlist;
/* note: if new alloc fails, old p will still be valid either way */
if (is_vmalloc_addr(p)) {
newlist = vmalloc(newcount * sizeof(pid_t));
if (!newlist)
return NULL;
memcpy(newlist, p, newcount * sizeof(pid_t));
vfree(p);
} else {
newlist = krealloc(p, newcount * sizeof(pid_t), GFP_KERNEL);
}
return newlist;
}
/*
* pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
* If the new stripped list is sufficiently smaller and there's enough memory
* to allocate a new buffer, will let go of the unneeded memory. Returns the
* number of unique elements.
*/
/* is the size difference enough that we should re-allocate the array? */
#define PIDLIST_REALLOC_DIFFERENCE(old, new) ((old) - PAGE_SIZE >= (new))
static int pidlist_uniq(pid_t **p, int length)
{
int src, dest = 1;
pid_t *list = *p;
pid_t *newlist;
/*
* we presume the 0th element is unique, so i starts at 1. trivial
* edge cases first; no work needs to be done for either
*/
if (length == 0 || length == 1)
return length;
/* src and dest walk down the list; dest counts unique elements */
for (src = 1; src < length; src++) {
/* find next unique element */
while (list[src] == list[src-1]) {
src++;
if (src == length)
goto after;
}
/* dest always points to where the next unique element goes */
list[dest] = list[src];
dest++;
}
after:
/*
* if the length difference is large enough, we want to allocate a
* smaller buffer to save memory. if this fails due to out of memory,
* we'll just stay with what we've got.
*/
if (PIDLIST_REALLOC_DIFFERENCE(length, dest)) {
newlist = pidlist_resize(list, dest);
if (newlist)
*p = newlist;
}
return dest;
}
static int cmppid(const void *a, const void *b)
{
return *(pid_t *)a - *(pid_t *)b;
}
/*
* find the appropriate pidlist for our purpose (given procs vs tasks)
* returns with the lock on that pidlist already held, and takes care
* of the use count, or returns NULL with no locks held if we're out of
* memory.
*/
static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
enum cgroup_filetype type)
{
struct cgroup_pidlist *l;
/* don't need task_nsproxy() if we're looking at ourself */
struct pid_namespace *ns = current->nsproxy->pid_ns;
/*
* We can't drop the pidlist_mutex before taking the l->mutex in case
* the last ref-holder is trying to remove l from the list at the same
* time. Holding the pidlist_mutex precludes somebody taking whichever
* list we find out from under us - compare release_pid_array().
*/
mutex_lock(&cgrp->pidlist_mutex);
list_for_each_entry(l, &cgrp->pidlists, links) {
if (l->key.type == type && l->key.ns == ns) {
/* make sure l doesn't vanish out from under us */
down_write(&l->mutex);
mutex_unlock(&cgrp->pidlist_mutex);
return l;
}
}
/* entry not found; create a new one */
l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
if (!l) {
mutex_unlock(&cgrp->pidlist_mutex);
return l;
}
init_rwsem(&l->mutex);
down_write(&l->mutex);
l->key.type = type;
l->key.ns = get_pid_ns(ns);
l->use_count = 0; /* don't increment here */
l->list = NULL;
l->owner = cgrp;
list_add(&l->links, &cgrp->pidlists);
mutex_unlock(&cgrp->pidlist_mutex);
return l;
}
/*
* Load a cgroup's pidarray with either procs' tgids or tasks' pids
*/
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
struct cgroup_pidlist **lp)
{
pid_t *array;
int length;
int pid, n = 0; /* used for populating the array */
struct cgroup_iter it;
struct task_struct *tsk;
struct cgroup_pidlist *l;
/*
* 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.
*/
length = cgroup_task_count(cgrp);
array = pidlist_allocate(length);
if (!array)
return -ENOMEM;
/* now, populate the array */
cgroup_iter_start(cgrp, &it);
while ((tsk = cgroup_iter_next(cgrp, &it))) {
if (unlikely(n == length))
break;
/* get tgid or pid for procs or tasks file respectively */
if (type == CGROUP_FILE_PROCS)
pid = task_tgid_vnr(tsk);
else
pid = task_pid_vnr(tsk);
if (pid > 0) /* make sure to only use valid results */
array[n++] = pid;
}
cgroup_iter_end(cgrp, &it);
length = n;
/* now sort & (if procs) strip out duplicates */
sort(array, length, sizeof(pid_t), cmppid, NULL);
if (type == CGROUP_FILE_PROCS)
length = pidlist_uniq(&array, length);
l = cgroup_pidlist_find(cgrp, type);
if (!l) {
pidlist_free(array);
return -ENOMEM;
}
/* store array, freeing old if necessary - lock already held */
pidlist_free(l->list);
l->list = array;
l->length = length;
l->use_count++;
up_write(&l->mutex);
*lp = l;
return 0;
}
/**
* 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;
}
/*
* seq_file methods for the tasks/procs files. The seq_file position is the
* next pid to display; the seq_file iterator is a pointer to the pid
* in the cgroup->l->list array.
*/
static void *cgroup_pidlist_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_pidlist *l = s->private;
int index = 0, pid = *pos;
int *iter;
down_read(&l->mutex);
if (pid) {
int end = l->length;
while (index < end) {
int mid = (index + end) / 2;
if (l->list[mid] == pid) {
index = mid;
break;
} else if (l->list[mid] <= pid)
index = mid + 1;
else
end = mid;
}
}
/* If we're off the end of the array, we're done */
if (index >= l->length)
return NULL;
/* Update the abstract position to be the actual pid that we found */
iter = l->list + index;
*pos = *iter;
return iter;
}
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
{
struct cgroup_pidlist *l = s->private;
up_read(&l->mutex);
}
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
{
struct cgroup_pidlist *l = s->private;
pid_t *p = v;
pid_t *end = l->list + l->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_pidlist_show(struct seq_file *s, void *v)
{
return seq_printf(s, "%d\n", *(int *)v);
}
/*
* seq_operations functions for iterating on pidlists through seq_file -
* independent of whether it's tasks or procs
*/
static const struct seq_operations cgroup_pidlist_seq_operations = {
.start = cgroup_pidlist_start,
.stop = cgroup_pidlist_stop,
.next = cgroup_pidlist_next,
.show = cgroup_pidlist_show,
};
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
{
/*
* the case where we're the last user of this particular pidlist will
* have us remove it from the cgroup's list, which entails taking the
* mutex. since in pidlist_find the pidlist->lock depends on cgroup->
* pidlist_mutex, we have to take pidlist_mutex first.
*/
mutex_lock(&l->owner->pidlist_mutex);
down_write(&l->mutex);
BUG_ON(!l->use_count);
if (!--l->use_count) {
/* we're the last user if refcount is 0; remove and free */
list_del(&l->links);
mutex_unlock(&l->owner->pidlist_mutex);
pidlist_free(l->list);
put_pid_ns(l->key.ns);
up_write(&l->mutex);
kfree(l);
return;
}
mutex_unlock(&l->owner->pidlist_mutex);
up_write(&l->mutex);
}
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
{
struct cgroup_pidlist *l;
if (!(file->f_mode & FMODE_READ))
return 0;
/*
* the seq_file will only be initialized if the file was opened for
* reading; hence we check if it's not null only in that case.
*/
l = ((struct seq_file *)file->private_data)->private;
cgroup_release_pid_array(l);
return seq_release(inode, file);
}
static const struct file_operations cgroup_pidlist_operations = {
.read = seq_read,
.llseek = seq_lseek,
.write = cgroup_file_write,
.release = cgroup_pidlist_release,
};
/*
* The following functions handle opens on a file that displays a pidlist
* (tasks or procs). Prepare an array of the process/thread IDs of whoever's
* in the cgroup.
*/
/* helper function for the two below it */
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
{
struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
struct cgroup_pidlist *l;
int retval;
/* Nothing to do for write-only files */
if (!(file->f_mode & FMODE_READ))
return 0;
/* have the array populated */
retval = pidlist_array_load(cgrp, type, &l);
if (retval)
return retval;
/* configure file information */
file->f_op = &cgroup_pidlist_operations;
retval = seq_open(file, &cgroup_pidlist_seq_operations);
if (retval) {
cgroup_release_pid_array(l);
return retval;
}
((struct seq_file *)file->private_data)->private = l;
return 0;
}
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
}
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;
}
/*
* Unregister event and free resources.
*
* Gets called from workqueue.
*/
static void cgroup_event_remove(struct work_struct *work)
{
struct cgroup_event *event = container_of(work, struct cgroup_event,
remove);
struct cgroup *cgrp = event->cgrp;
event->cft->unregister_event(cgrp, event->cft, event->eventfd);
eventfd_ctx_put(event->eventfd);
kfree(event);
dput(cgrp->dentry);
}
/*
* Gets called on POLLHUP on eventfd when user closes it.
*
* Called with wqh->lock held and interrupts disabled.
*/
static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
int sync, void *key)
{
struct cgroup_event *event = container_of(wait,
struct cgroup_event, wait);
struct cgroup *cgrp = event->cgrp;
unsigned long flags = (unsigned long)key;
if (flags & POLLHUP) {
__remove_wait_queue(event->wqh, &event->wait);
spin_lock(&cgrp->event_list_lock);
list_del(&event->list);
spin_unlock(&cgrp->event_list_lock);
/*
* We are in atomic context, but cgroup_event_remove() may
* sleep, so we have to call it in workqueue.
*/
schedule_work(&event->remove);
}
return 0;
}
static void cgroup_event_ptable_queue_proc(struct file *file,
wait_queue_head_t *wqh, poll_table *pt)
{
struct cgroup_event *event = container_of(pt,
struct cgroup_event, pt);
event->wqh = wqh;
add_wait_queue(wqh, &event->wait);
}
/*
* Parse input and register new cgroup event handler.
*
* Input must be in format '<event_fd> <control_fd> <args>'.
* Interpretation of args is defined by control file implementation.
*/
static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
const char *buffer)
{
struct cgroup_event *event = NULL;
unsigned int efd, cfd;
struct file *efile = NULL;
struct file *cfile = NULL;
char *endp;
int ret;
efd = simple_strtoul(buffer, &endp, 10);
if (*endp != ' ')
return -EINVAL;
buffer = endp + 1;
cfd = simple_strtoul(buffer, &endp, 10);
if ((*endp != ' ') && (*endp != '\0'))
return -EINVAL;
buffer = endp + 1;
event = kzalloc(sizeof(*event), GFP_KERNEL);
if (!event)
return -ENOMEM;
event->cgrp = cgrp;
INIT_LIST_HEAD(&event->list);
init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
INIT_WORK(&event->remove, cgroup_event_remove);
efile = eventfd_fget(efd);
if (IS_ERR(efile)) {
ret = PTR_ERR(efile);
goto fail;
}
event->eventfd = eventfd_ctx_fileget(efile);
if (IS_ERR(event->eventfd)) {
ret = PTR_ERR(event->eventfd);
goto fail;
}
cfile = fget(cfd);
if (!cfile) {
ret = -EBADF;
goto fail;
}
/* the process need read permission on control file */
ret = file_permission(cfile, MAY_READ);
if (ret < 0)
goto fail;
event->cft = __file_cft(cfile);
if (IS_ERR(event->cft)) {
ret = PTR_ERR(event->cft);
goto fail;
}
if (!event->cft->register_event || !event->cft->unregister_event) {
ret = -EINVAL;
goto fail;
}
ret = event->cft->register_event(cgrp, event->cft,
event->eventfd, buffer);
if (ret)
goto fail;
if (efile->f_op->poll(efile, &event->pt) & POLLHUP) {
event->cft->unregister_event(cgrp, event->cft, event->eventfd);
ret = 0;
goto fail;
}
/*
* Events should be removed after rmdir of cgroup directory, but before
* destroying subsystem state objects. Let's take reference to cgroup
* directory dentry to do that.
*/
dget(cgrp->dentry);
spin_lock(&cgrp->event_list_lock);
list_add(&event->list, &cgrp->event_list);
spin_unlock(&cgrp->event_list_lock);
fput(cfile);
fput(efile);
return 0;
fail:
if (cfile)
fput(cfile);
if (event && event->eventfd && !IS_ERR(event->eventfd))
eventfd_ctx_put(event->eventfd);
if (!IS_ERR_OR_NULL(efile))
fput(efile);
kfree(event);
return ret;
}
/*
* for the common functions, 'private' gives the type of file
*/
/* for hysterical raisins, we can't put this on the older files */
#define CGROUP_FILE_GENERIC_PREFIX "cgroup."
static struct cftype files[] = {
{
.name = "tasks",
.open = cgroup_tasks_open,
.write_u64 = cgroup_tasks_write,
.release = cgroup_pidlist_release,
.mode = S_IRUGO | S_IWUSR,
},
{
.name = CGROUP_FILE_GENERIC_PREFIX "procs",
.open = cgroup_procs_open,
/* .write_u64 = cgroup_procs_write, TODO */
.release = cgroup_pidlist_release,
.mode = S_IRUGO,
},
{
.name = "notify_on_release",
.read_u64 = cgroup_read_notify_on_release,
.write_u64 = cgroup_write_notify_on_release,
},
{
.name = CGROUP_FILE_GENERIC_PREFIX "event_control",
.write_string = cgroup_write_event_control,
.mode = S_IWUGO,
},
};
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,
};
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;
/*
* No worry about a race with rebind_subsystems that might mess up the
* locking order, since both parties are under cgroup_mutex.
*/
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss == NULL)
continue;
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 == NULL)
continue;
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) {
err = alloc_css_id(ss, parent, cgrp);
if (err)
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;
/*
* We won't need to lock the subsys array, because the subsystems
* we're concerned about aren't going anywhere since our cgroup root
* has a reference on them.
*/
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
struct cgroup_subsys_state *css;
/* Skip subsystems not present or not in this hierarchy */
if (ss == NULL || 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);
struct cgroup_event *event, *tmp;
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);
/*
* In general, subsystem has no css->refcnt after pre_destroy(). But
* in racy cases, subsystem may have to get css->refcnt after
* pre_destroy() and it makes rmdir return with -EBUSY. This sometimes
* make rmdir return -EBUSY too often. To avoid that, we use waitqueue
* for cgroup's rmdir. CGRP_WAIT_ON_RMDIR is for synchronizing rmdir
* and subsystem's reference count handling. Please see css_get/put
* and css_tryget() and cgroup_wakeup_rmdir_waiter() implementation.
*/
set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
/*
* Call pre_destroy handlers of subsys. Notify subsystems
* that rmdir() request comes.
*/
ret = cgroup_call_pre_destroy(cgrp);
if (ret) {
clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
return ret;
}
mutex_lock(&cgroup_mutex);
parent = cgrp->parent;
if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
if (!cgroup_clear_css_refs(cgrp)) {
mutex_unlock(&cgroup_mutex);
/*
* Because someone may call cgroup_wakeup_rmdir_waiter() before
* prepare_to_wait(), we need to check this flag.
*/
if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))
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);
/*
* Unregister events and notify userspace.
* Notify userspace about cgroup removing only after rmdir of cgroup
* directory to avoid race between userspace and kernelspace
*/
spin_lock(&cgrp->event_list_lock);
list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
list_del(&event->list);
remove_wait_queue(event->wqh, &event->wait);
eventfd_signal(event->eventfd, 1);
schedule_work(&event->remove);
}
spin_unlock(&cgrp->event_list_lock);
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;
/* this function shouldn't be used with modular subsystems, since they
* need to register a subsys_id, among other things */
BUG_ON(ss->module);
}
/**
* cgroup_load_subsys: load and register a modular subsystem at runtime
* @ss: the subsystem to load
*
* This function should be called in a modular subsystem's initcall. If the
* subsystem is built as a module, it will be assigned a new subsys_id and set
* up for use. If the subsystem is built-in anyway, work is delegated to the
* simpler cgroup_init_subsys.
*/
int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
{
int i;
struct cgroup_subsys_state *css;
/* check name and function validity */
if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
ss->create == NULL || ss->destroy == NULL)
return -EINVAL;
/*
* we don't support callbacks in modular subsystems. this check is
* before the ss->module check for consistency; a subsystem that could
* be a module should still have no callbacks even if the user isn't
* compiling it as one.
*/
if (ss->fork || ss->exit)
return -EINVAL;
/*
* an optionally modular subsystem is built-in: we want to do nothing,
* since cgroup_init_subsys will have already taken care of it.
*/
if (ss->module == NULL) {
/* a few sanity checks */
BUG_ON(ss->subsys_id >= CGROUP_BUILTIN_SUBSYS_COUNT);
BUG_ON(subsys[ss->subsys_id] != ss);
return 0;
}
/*
* need to register a subsys id before anything else - for example,
* init_cgroup_css needs it.
*/
mutex_lock(&cgroup_mutex);
/* find the first empty slot in the array */
for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
if (subsys[i] == NULL)
break;
}
if (i == CGROUP_SUBSYS_COUNT) {
/* maximum number of subsystems already registered! */
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
/* assign ourselves the subsys_id */
ss->subsys_id = i;
subsys[i] = ss;
/*
* no ss->create seems to need anything important in the ss struct, so
* this can happen first (i.e. before the rootnode attachment).
*/
css = ss->create(ss, dummytop);
if (IS_ERR(css)) {
/* failure case - need to deassign the subsys[] slot. */
subsys[i] = NULL;
mutex_unlock(&cgroup_mutex);
return PTR_ERR(css);
}
list_add(&ss->sibling, &rootnode.subsys_list);
ss->root = &rootnode;
/* our new subsystem will be attached to the dummy hierarchy. */
init_cgroup_css(css, ss, dummytop);
/* init_idr must be after init_cgroup_css because it sets css->id. */
if (ss->use_id) {
int ret = cgroup_init_idr(ss, css);
if (ret) {
dummytop->subsys[ss->subsys_id] = NULL;
ss->destroy(ss, dummytop);
subsys[i] = NULL;
mutex_unlock(&cgroup_mutex);
return ret;
}
}
/*
* Now we need to entangle the css into the existing css_sets. unlike
* in cgroup_init_subsys, there are now multiple css_sets, so each one
* will need a new pointer to it; done by iterating the css_set_table.
* furthermore, modifying the existing css_sets will corrupt the hash
* table state, so each changed css_set will need its hash recomputed.
* this is all done under the css_set_lock.
*/
write_lock(&css_set_lock);
for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
struct css_set *cg;
struct hlist_node *node, *tmp;
struct hlist_head *bucket = &css_set_table[i], *new_bucket;
hlist_for_each_entry_safe(cg, node, tmp, bucket, hlist) {
/* skip entries that we already rehashed */
if (cg->subsys[ss->subsys_id])
continue;
/* remove existing entry */
hlist_del(&cg->hlist);
/* set new value */
cg->subsys[ss->subsys_id] = css;
/* recompute hash and restore entry */
new_bucket = css_set_hash(cg->subsys);
hlist_add_head(&cg->hlist, new_bucket);
}
}
write_unlock(&css_set_lock);
mutex_init(&ss->hierarchy_mutex);
lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
ss->active = 1;
/* success! */
mutex_unlock(&cgroup_mutex);
return 0;
}
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
/**
* cgroup_unload_subsys: unload a modular subsystem
* @ss: the subsystem to unload
*
* This function should be called in a modular subsystem's exitcall. When this
* function is invoked, the refcount on the subsystem's module will be 0, so
* the subsystem will not be attached to any hierarchy.
*/
void cgroup_unload_subsys(struct cgroup_subsys *ss)
{
struct cg_cgroup_link *link;
struct hlist_head *hhead;
BUG_ON(ss->module == NULL);
/*
* we shouldn't be called if the subsystem is in use, and the use of
* try_module_get in parse_cgroupfs_options should ensure that it
* doesn't start being used while we're killing it off.
*/
BUG_ON(ss->root != &rootnode);
mutex_lock(&cgroup_mutex);
/* deassign the subsys_id */
BUG_ON(ss->subsys_id < CGROUP_BUILTIN_SUBSYS_COUNT);
subsys[ss->subsys_id] = NULL;
/* remove subsystem from rootnode's list of subsystems */
list_del(&ss->sibling);
/*
* disentangle the css from all css_sets attached to the dummytop. as
* in loading, we need to pay our respects to the hashtable gods.
*/
write_lock(&css_set_lock);
list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {
struct css_set *cg = link->cg;
hlist_del(&cg->hlist);
BUG_ON(!cg->subsys[ss->subsys_id]);
cg->subsys[ss->subsys_id] = NULL;
hhead = css_set_hash(cg->subsys);
hlist_add_head(&cg->hlist, hhead);
}
write_unlock(&css_set_lock);
/*
* remove subsystem's css from the dummytop and free it - need to free
* before marking as null because ss->destroy needs the cgrp->subsys
* pointer to find their state. note that this also takes care of
* freeing the css_id.
*/
ss->destroy(ss, dummytop);
dummytop->subsys[ss->subsys_id] = NULL;
mutex_unlock(&cgroup_mutex);
}
EXPORT_SYMBOL_GPL(cgroup_unload_subsys);
/**
* 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;
init_css_set_link.cgrp = dummytop;
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]);
/* at bootup time, we don't worry about modular subsystems */
for (i = 0; i < CGROUP_BUILTIN_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;
/* at bootup time, we don't worry about modular subsystems */
for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (!ss->early_init)
cgroup_init_subsys(ss);
if (ss->use_id)
cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
}
/* Add init_css_set to the hash table */
hhead = css_set_hash(init_css_set.subsys);
hlist_add_head(&init_css_set.hlist, hhead);
BUG_ON(!init_root_id(&rootnode));
cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
if (!cgroup_kobj) {
err = -ENOMEM;
goto out;
}
err = register_filesystem(&cgroup_fs_type);
if (err < 0) {
kobject_put(cgroup_kobj);
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 count = 0;
seq_printf(m, "%d:", root->hierarchy_id);
for_each_subsys(root, ss)
seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
if (strlen(root->name))
seq_printf(m, "%sname=%s", count ? "," : "",
root->name);
seq_putc(m, ':');
cgrp = task_cgroup_from_root(tsk, root);
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);
}
const 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");
/*
* ideally we don't want subsystems moving around while we do this.
* cgroup_mutex is also necessary to guarantee an atomic snapshot of
* subsys/hierarchy state.
*/
mutex_lock(&cgroup_mutex);
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss == NULL)
continue;
seq_printf(m, "%s\t%d\t%d\t%d\n",
ss->name, ss->root->hierarchy_id,
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 const 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;
/*
* forkexit callbacks are only supported for builtin
* subsystems, and the builtin section of the subsys array is
* immutable, so we don't need to lock the subsys array here.
*/
for (i = 0; i < CGROUP_BUILTIN_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) {
/*
* modular subsystems can't use callbacks, so no need to lock
* the subsys array
*/
for (i = 0; i < CGROUP_BUILTIN_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;
if (cgrp == dummytop)
return 1;
target = task_cgroup_from_root(task, cgrp->root);
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);
}
}
/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css, int count)
{
struct cgroup *cgrp = css->cgroup;
int val;
rcu_read_lock();
val = atomic_sub_return(count, &css->refcnt);
if (val == 1) {
if (notify_on_release(cgrp)) {
set_bit(CGRP_RELEASABLE, &cgrp->flags);
check_for_release(cgrp);
}
cgroup_wakeup_rmdir_waiter(cgrp);
}
rcu_read_unlock();
WARN_ON_ONCE(val < 1);
}
EXPORT_SYMBOL_GPL(__css_put);
/*
* 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;
/*
* cgroup_disable, being at boot time, can't know about module
* subsystems, so we don't worry about them.
*/
for (i = 0; i < CGROUP_BUILTIN_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;
/*
* This css_id() can return correct value when somone has refcnt
* on this or this is under rcu_read_lock(). Once css->id is allocated,
* it's unchanged until freed.
*/
cssid = rcu_dereference_check(css->id,
rcu_read_lock_held() || atomic_read(&css->refcnt));
if (cssid)
return cssid->id;
return 0;
}
EXPORT_SYMBOL_GPL(css_id);
unsigned short css_depth(struct cgroup_subsys_state *css)
{
struct css_id *cssid;
cssid = rcu_dereference_check(css->id,
rcu_read_lock_held() || atomic_read(&css->refcnt));
if (cssid)
return cssid->depth;
return 0;
}
EXPORT_SYMBOL_GPL(css_depth);
/**
* css_is_ancestor - test "root" css is an ancestor of "child"
* @child: the css to be tested.
* @root: the css supporsed to be an ancestor of the child.
*
* Returns true if "root" is an ancestor of "child" in its hierarchy. Because
* this function reads css->id, this use rcu_dereference() and rcu_read_lock().
* But, considering usual usage, the csses should be valid objects after test.
* Assuming that the caller will do some action to the child if this returns
* returns true, the caller must take "child";s reference count.
* If "child" is valid object and this returns true, "root" is valid, too.
*/
bool css_is_ancestor(struct cgroup_subsys_state *child,
const struct cgroup_subsys_state *root)
{
struct css_id *child_id;
struct css_id *root_id;
bool ret = true;
rcu_read_lock();
child_id = rcu_dereference(child->id);
root_id = rcu_dereference(root->id);
if (!child_id
|| !root_id
|| (child_id->depth < root_id->depth)
|| (child_id->stack[root_id->depth] != root_id->id))
ret = false;
rcu_read_unlock();
return ret;
}
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);
}
EXPORT_SYMBOL_GPL(free_css_id);
/*
* 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_or_module cgroup_init_idr(struct cgroup_subsys *ss,
struct cgroup_subsys_state *rootcss)
{
struct css_id *newid;
spin_lock_init(&ss->id_lock);
idr_init(&ss->idr);
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;
subsys_id = ss->subsys_id;
parent_css = parent->subsys[subsys_id];
child_css = child->subsys[subsys_id];
parent_id = parent_css->id;
depth = parent_id->depth + 1;
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);
}
EXPORT_SYMBOL_GPL(css_lookup);
/**
* 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;
}
#ifdef CONFIG_CGROUP_DEBUG
static struct cgroup_subsys_state *debug_create(struct cgroup_subsys *ss,
struct cgroup *cont)
{
struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
if (!css)
return ERR_PTR(-ENOMEM);
return css;
}
static void debug_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
{
kfree(cont->subsys[debug_subsys_id]);
}
static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
{
return atomic_read(&cont->count);
}
static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft)
{
return cgroup_task_count(cont);
}
static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
{
return (u64)(unsigned long)current->cgroups;
}
static u64 current_css_set_refcount_read(struct cgroup *cont,
struct cftype *cft)
{
u64 count;
rcu_read_lock();
count = atomic_read(&current->cgroups->refcount);
rcu_read_unlock();
return count;
}
static int current_css_set_cg_links_read(struct cgroup *cont,
struct cftype *cft,
struct seq_file *seq)
{
struct cg_cgroup_link *link;
struct css_set *cg;
read_lock(&css_set_lock);
rcu_read_lock();
cg = rcu_dereference(current->cgroups);
list_for_each_entry(link, &cg->cg_links, cg_link_list) {
struct cgroup *c = link->cgrp;
const char *name;
if (c->dentry)
name = c->dentry->d_name.name;
else
name = "?";
seq_printf(seq, "Root %d group %s\n",
c->root->hierarchy_id, name);
}
rcu_read_unlock();
read_unlock(&css_set_lock);
return 0;
}
#define MAX_TASKS_SHOWN_PER_CSS 25
static int cgroup_css_links_read(struct cgroup *cont,
struct cftype *cft,
struct seq_file *seq)
{
struct cg_cgroup_link *link;
read_lock(&css_set_lock);
list_for_each_entry(link, &cont->css_sets, cgrp_link_list) {
struct css_set *cg = link->cg;
struct task_struct *task;
int count = 0;
seq_printf(seq, "css_set %p\n", cg);
list_for_each_entry(task, &cg->tasks, cg_list) {
if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
seq_puts(seq, " ...\n");
break;
} else {
seq_printf(seq, " task %d\n",
task_pid_vnr(task));
}
}
}
read_unlock(&css_set_lock);
return 0;
}
static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
{
return test_bit(CGRP_RELEASABLE, &cgrp->flags);
}
static struct cftype debug_files[] = {
{
.name = "cgroup_refcount",
.read_u64 = cgroup_refcount_read,
},
{
.name = "taskcount",
.read_u64 = debug_taskcount_read,
},
{
.name = "current_css_set",
.read_u64 = current_css_set_read,
},
{
.name = "current_css_set_refcount",
.read_u64 = current_css_set_refcount_read,
},
{
.name = "current_css_set_cg_links",
.read_seq_string = current_css_set_cg_links_read,
},
{
.name = "cgroup_css_links",
.read_seq_string = cgroup_css_links_read,
},
{
.name = "releasable",
.read_u64 = releasable_read,
},
};
static int debug_populate(struct cgroup_subsys *ss, struct cgroup *cont)
{
return cgroup_add_files(cont, ss, debug_files,
ARRAY_SIZE(debug_files));
}
struct cgroup_subsys debug_subsys = {
.name = "debug",
.create = debug_create,
.destroy = debug_destroy,
.populate = debug_populate,
.subsys_id = debug_subsys_id,
};
#endif /* CONFIG_CGROUP_DEBUG */
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