kernel-ark/kernel/cgroup.c
Jeff Liu 2a0ff3fbe3 cgroup: warn about mismatching options of a new mount of an existing hierarchy
With the new __DEVEL__sane_behavior mount option was introduced,
if the root cgroup is alive with no xattr function, to mount a
new cgroup with xattr will be rejected in terms of design which
just fine.  However, if the root cgroup does not mounted with
__DEVEL__sane_hehavior, to create a new cgroup with xattr option
will succeed although after that the EA function does not works
as expected but will get ENOTSUPP for setting up attributes under
either cgroup. e.g.

setfattr: /cgroup2/test: Operation not supported

Instead of keeping silence in this case, it's better to drop a log
entry in warning level.  That would be helpful to understand the
reason behind the scene from the user's perspective, and this is
essentially an improvement does not break the backward compatibilities.

With this fix, above mount attemption will keep up works as usual but
the following line cound be found at the system log:

[ ...] cgroup: new mount options do not match the existing superblock

tj: minor formatting / message updates.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Reported-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org
2013-05-29 07:59:39 +09:00

5447 lines
143 KiB
C

/*
* 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/cred.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/init_task.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/hashtable.h>
#include <linux/namei.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 <linux/flex_array.h> /* used in cgroup_attach_task */
#include <linux/kthread.h>
#include <linux/atomic.h>
/* css deactivation bias, makes css->refcnt negative to deny new trygets */
#define CSS_DEACT_BIAS INT_MIN
/*
* cgroup_mutex is the master lock. Any modification to cgroup or its
* hierarchy must be performed while holding it.
*
* cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
* cgroupfs_root of any cgroup hierarchy - subsys list, flags,
* release_agent_path and so on. Modifying requires both cgroup_mutex and
* cgroup_root_mutex. Readers can acquire either of the two. This is to
* break the following locking order cycle.
*
* A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
* B. namespace_sem -> cgroup_mutex
*
* B happens only through cgroup_show_options() and using cgroup_root_mutex
* breaks it.
*/
#ifdef CONFIG_PROVE_RCU
DEFINE_MUTEX(cgroup_mutex);
EXPORT_SYMBOL_GPL(cgroup_mutex); /* only for task_subsys_state_check() */
#else
static DEFINE_MUTEX(cgroup_mutex);
#endif
static DEFINE_MUTEX(cgroup_root_mutex);
/*
* Generate an array of cgroup subsystem pointers. At boot time, this is
* populated with the built in subsystems, and modular subsystems are
* registered after that. The mutable section of this array is protected by
* cgroup_mutex.
*/
#define SUBSYS(_x) [_x ## _subsys_id] = &_x ## _subsys,
#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
#include <linux/cgroup_subsys.h>
};
/*
* 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;
/*
* cgroupfs file entry, pointed to from leaf dentry->d_fsdata.
*/
struct cfent {
struct list_head node;
struct dentry *dentry;
struct cftype *type;
/* file xattrs */
struct simple_xattrs xattrs;
};
/*
* 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_tryget()
* should be used for avoiding race.
*/
struct cgroup_subsys_state __rcu *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 receive.
*/
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)
static struct cgroup_name root_cgroup_name = { .name = "/" };
/* 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;
static int cgroup_destroy_locked(struct cgroup *cgrp);
static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
struct cftype cfts[], bool is_add);
static int css_unbias_refcnt(int refcnt)
{
return refcnt >= 0 ? refcnt : refcnt - CSS_DEACT_BIAS;
}
/* the current nr of refs, always >= 0 whether @css is deactivated or not */
static int css_refcnt(struct cgroup_subsys_state *css)
{
int v = atomic_read(&css->refcnt);
return css_unbias_refcnt(v);
}
/* convenient tests for these bits */
inline int cgroup_is_removed(const struct cgroup *cgrp)
{
return test_bit(CGRP_REMOVED, &cgrp->flags);
}
/**
* cgroup_is_descendant - test ancestry
* @cgrp: the cgroup to be tested
* @ancestor: possible ancestor of @cgrp
*
* Test whether @cgrp is a descendant of @ancestor. It also returns %true
* if @cgrp == @ancestor. This function is safe to call as long as @cgrp
* and @ancestor are accessible.
*/
bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor)
{
while (cgrp) {
if (cgrp == ancestor)
return true;
cgrp = cgrp->parent;
}
return false;
}
EXPORT_SYMBOL_GPL(cgroup_is_descendant);
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)
static inline struct cgroup *__d_cgrp(struct dentry *dentry)
{
return dentry->d_fsdata;
}
static inline struct cfent *__d_cfe(struct dentry *dentry)
{
return dentry->d_fsdata;
}
static inline struct cftype *__d_cft(struct dentry *dentry)
{
return __d_cfe(dentry)->type;
}
/**
* 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 mutex should be later unlocked. On
* failure returns false with no lock held.
*/
static 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;
}
/* the list of cgroups eligible for automatic release. Protected by
* release_list_lock */
static LIST_HEAD(release_list);
static DEFINE_RAW_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
static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
{
int i;
unsigned long key = 0UL;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
key += (unsigned long)css[i];
key = (key >> 16) ^ key;
return key;
}
/* 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 */
hash_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);
/*
* We may not be holding cgroup_mutex, and if cgrp->count is
* dropped to 0 the cgroup can be destroyed at any time, hence
* rcu_read_lock is used to keep it alive.
*/
rcu_read_lock();
if (atomic_dec_and_test(&cgrp->count) &&
notify_on_release(cgrp)) {
if (taskexit)
set_bit(CGRP_RELEASABLE, &cgrp->flags);
check_for_release(cgrp);
}
rcu_read_unlock();
kfree(link);
}
write_unlock(&css_set_lock);
kfree_rcu(cg, rcu_head);
}
/*
* 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 css_set *cg;
unsigned long key;
/*
* 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_mask & (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];
}
}
key = css_set_hash(template);
hash_for_each_possible(css_set_table, cg, hlist, key) {
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 cg_cgroup_link *link;
unsigned long key;
/* 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 */
key = css_set_hash(res->subsys);
hash_add(css_set_table, &res->hlist, key);
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 task's 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's 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()
*/
/*
* 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, umode_t mode);
static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
unsigned long subsys_mask);
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(umode_t mode, struct super_block *sb)
{
struct inode *inode = new_inode(sb);
if (inode) {
inode->i_ino = get_next_ino();
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;
}
static struct cgroup_name *cgroup_alloc_name(struct dentry *dentry)
{
struct cgroup_name *name;
name = kmalloc(sizeof(*name) + dentry->d_name.len + 1, GFP_KERNEL);
if (!name)
return NULL;
strcpy(name->name, dentry->d_name.name);
return name;
}
static void cgroup_free_fn(struct work_struct *work)
{
struct cgroup *cgrp = container_of(work, struct cgroup, free_work);
struct cgroup_subsys *ss;
mutex_lock(&cgroup_mutex);
/*
* Release the subsystem state objects.
*/
for_each_subsys(cgrp->root, ss)
ss->css_free(cgrp);
cgrp->root->number_of_cgroups--;
mutex_unlock(&cgroup_mutex);
/*
* We get a ref to the parent's dentry, and put the ref when
* this cgroup is being freed, so it's guaranteed that the
* parent won't be destroyed before its children.
*/
dput(cgrp->parent->dentry);
ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id);
/*
* Drop the active superblock reference that we took when we
* created the cgroup. This will free cgrp->root, if we are
* holding the last reference to @sb.
*/
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));
simple_xattrs_free(&cgrp->xattrs);
kfree(rcu_dereference_raw(cgrp->name));
kfree(cgrp);
}
static void cgroup_free_rcu(struct rcu_head *head)
{
struct cgroup *cgrp = container_of(head, struct cgroup, rcu_head);
schedule_work(&cgrp->free_work);
}
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;
BUG_ON(!(cgroup_is_removed(cgrp)));
call_rcu(&cgrp->rcu_head, cgroup_free_rcu);
} else {
struct cfent *cfe = __d_cfe(dentry);
struct cgroup *cgrp = dentry->d_parent->d_fsdata;
WARN_ONCE(!list_empty(&cfe->node) &&
cgrp != &cgrp->root->top_cgroup,
"cfe still linked for %s\n", cfe->type->name);
simple_xattrs_free(&cfe->xattrs);
kfree(cfe);
}
iput(inode);
}
static int cgroup_delete(const struct dentry *d)
{
return 1;
}
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_rm_file(struct cgroup *cgrp, const struct cftype *cft)
{
struct cfent *cfe;
lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
lockdep_assert_held(&cgroup_mutex);
/*
* If we're doing cleanup due to failure of cgroup_create(),
* the corresponding @cfe may not exist.
*/
list_for_each_entry(cfe, &cgrp->files, node) {
struct dentry *d = cfe->dentry;
if (cft && cfe->type != cft)
continue;
dget(d);
d_delete(d);
simple_unlink(cgrp->dentry->d_inode, d);
list_del_init(&cfe->node);
dput(d);
break;
}
}
/**
* cgroup_clear_directory - selective removal of base and subsystem files
* @dir: directory containing the files
* @base_files: true if the base files should be removed
* @subsys_mask: mask of the subsystem ids whose files should be removed
*/
static void cgroup_clear_directory(struct dentry *dir, bool base_files,
unsigned long subsys_mask)
{
struct cgroup *cgrp = __d_cgrp(dir);
struct cgroup_subsys *ss;
for_each_subsys(cgrp->root, ss) {
struct cftype_set *set;
if (!test_bit(ss->subsys_id, &subsys_mask))
continue;
list_for_each_entry(set, &ss->cftsets, node)
cgroup_addrm_files(cgrp, NULL, set->cfts, false);
}
if (base_files) {
while (!list_empty(&cgrp->files))
cgroup_rm_file(cgrp, NULL);
}
}
/*
* NOTE : the dentry must have been dget()'ed
*/
static void cgroup_d_remove_dir(struct dentry *dentry)
{
struct dentry *parent;
struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
cgroup_clear_directory(dentry, true, root->subsys_mask);
parent = dentry->d_parent;
spin_lock(&parent->d_lock);
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
list_del_init(&dentry->d_u.d_child);
spin_unlock(&dentry->d_lock);
spin_unlock(&parent->d_lock);
remove_dir(dentry);
}
/*
* 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_subsys_mask)
{
unsigned long added_mask, removed_mask;
struct cgroup *cgrp = &root->top_cgroup;
int i;
BUG_ON(!mutex_is_locked(&cgroup_mutex));
BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
removed_mask = root->actual_subsys_mask & ~final_subsys_mask;
added_mask = final_subsys_mask & ~root->actual_subsys_mask;
/* 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_mask))
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_mask) {
/* 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);
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(cgrp);
/* refcount was already taken, and we're keeping it */
} else if (bit & removed_mask) {
/* We're removing this subsystem */
BUG_ON(ss == NULL);
BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
if (ss->bind)
ss->bind(dummytop);
dummytop->subsys[i]->cgroup = dummytop;
cgrp->subsys[i] = NULL;
subsys[i]->root = &rootnode;
list_move(&ss->sibling, &rootnode.subsys_list);
/* subsystem is now free - drop reference on module */
module_put(ss->module);
} else if (bit & final_subsys_mask) {
/* 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_mask = root->actual_subsys_mask = final_subsys_mask;
return 0;
}
static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
{
struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
struct cgroup_subsys *ss;
mutex_lock(&cgroup_root_mutex);
for_each_subsys(root, ss)
seq_printf(seq, ",%s", ss->name);
if (root->flags & CGRP_ROOT_SANE_BEHAVIOR)
seq_puts(seq, ",sane_behavior");
if (root->flags & CGRP_ROOT_NOPREFIX)
seq_puts(seq, ",noprefix");
if (root->flags & CGRP_ROOT_XATTR)
seq_puts(seq, ",xattr");
if (strlen(root->release_agent_path))
seq_printf(seq, ",release_agent=%s", root->release_agent_path);
if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags))
seq_puts(seq, ",clone_children");
if (strlen(root->name))
seq_printf(seq, ",name=%s", root->name);
mutex_unlock(&cgroup_root_mutex);
return 0;
}
struct cgroup_sb_opts {
unsigned long subsys_mask;
unsigned long flags;
char *release_agent;
bool cpuset_clone_children;
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;
bool all_ss = false, one_ss = false;
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, "none")) {
/* Explicitly have no subsystems */
opts->none = true;
continue;
}
if (!strcmp(token, "all")) {
/* Mutually exclusive option 'all' + subsystem name */
if (one_ss)
return -EINVAL;
all_ss = true;
continue;
}
if (!strcmp(token, "__DEVEL__sane_behavior")) {
opts->flags |= CGRP_ROOT_SANE_BEHAVIOR;
continue;
}
if (!strcmp(token, "noprefix")) {
opts->flags |= CGRP_ROOT_NOPREFIX;
continue;
}
if (!strcmp(token, "clone_children")) {
opts->cpuset_clone_children = true;
continue;
}
if (!strcmp(token, "xattr")) {
opts->flags |= CGRP_ROOT_XATTR;
continue;
}
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;
continue;
}
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;
continue;
}
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss == NULL)
continue;
if (strcmp(token, ss->name))
continue;
if (ss->disabled)
continue;
/* Mutually exclusive option 'all' + subsystem name */
if (all_ss)
return -EINVAL;
set_bit(i, &opts->subsys_mask);
one_ss = true;
break;
}
if (i == CGROUP_SUBSYS_COUNT)
return -ENOENT;
}
/*
* If the 'all' option was specified select all the subsystems,
* otherwise if 'none', 'name=' and a subsystem name options
* were not specified, let's default to 'all'
*/
if (all_ss || (!one_ss && !opts->none && !opts->name)) {
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss == NULL)
continue;
if (ss->disabled)
continue;
set_bit(i, &opts->subsys_mask);
}
}
/* Consistency checks */
if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
pr_warning("cgroup: sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
if (opts->flags & CGRP_ROOT_NOPREFIX) {
pr_err("cgroup: sane_behavior: noprefix is not allowed\n");
return -EINVAL;
}
if (opts->cpuset_clone_children) {
pr_err("cgroup: sane_behavior: clone_children is not allowed\n");
return -EINVAL;
}
}
/*
* Option noprefix was introduced just for backward compatibility
* with the old cpuset, so we allow noprefix only if mounting just
* the cpuset subsystem.
*/
if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
return -EINVAL;
/* Can't specify "none" and some subsystems */
if (opts->subsys_mask && 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_mask && !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 = 0; i < CGROUP_SUBSYS_COUNT; i++) {
unsigned long bit = 1UL << i;
if (!(bit & opts->subsys_mask))
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 >= 0; i--) {
/* drop refcounts only on the ones we took */
unsigned long bit = 1UL << i;
if (!(bit & opts->subsys_mask))
continue;
module_put(subsys[i]->module);
}
return -ENOENT;
}
return 0;
}
static void drop_parsed_module_refcounts(unsigned long subsys_mask)
{
int i;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
unsigned long bit = 1UL << i;
if (!(bit & subsys_mask))
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;
unsigned long added_mask, removed_mask;
if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) {
pr_err("cgroup: sane_behavior: remount is not allowed\n");
return -EINVAL;
}
mutex_lock(&cgrp->dentry->d_inode->i_mutex);
mutex_lock(&cgroup_mutex);
mutex_lock(&cgroup_root_mutex);
/* See what subsystems are wanted */
ret = parse_cgroupfs_options(data, &opts);
if (ret)
goto out_unlock;
if (opts.subsys_mask != root->actual_subsys_mask || opts.release_agent)
pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
task_tgid_nr(current), current->comm);
added_mask = opts.subsys_mask & ~root->subsys_mask;
removed_mask = root->subsys_mask & ~opts.subsys_mask;
/* 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_mask);
goto out_unlock;
}
/*
* Clear out the files of subsystems that should be removed, do
* this before rebind_subsystems, since rebind_subsystems may
* change this hierarchy's subsys_list.
*/
cgroup_clear_directory(cgrp->dentry, false, removed_mask);
ret = rebind_subsystems(root, opts.subsys_mask);
if (ret) {
/* rebind_subsystems failed, re-populate the removed files */
cgroup_populate_dir(cgrp, false, removed_mask);
drop_parsed_module_refcounts(opts.subsys_mask);
goto out_unlock;
}
/* re-populate subsystem files */
cgroup_populate_dir(cgrp, false, added_mask);
if (opts.release_agent)
strcpy(root->release_agent_path, opts.release_agent);
out_unlock:
kfree(opts.release_agent);
kfree(opts.name);
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
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->files);
INIT_LIST_HEAD(&cgrp->css_sets);
INIT_LIST_HEAD(&cgrp->allcg_node);
INIT_LIST_HEAD(&cgrp->release_list);
INIT_LIST_HEAD(&cgrp->pidlists);
INIT_WORK(&cgrp->free_work, cgroup_free_fn);
mutex_init(&cgrp->pidlist_mutex);
INIT_LIST_HEAD(&cgrp->event_list);
spin_lock_init(&cgrp->event_list_lock);
simple_xattrs_init(&cgrp->xattrs);
}
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);
INIT_LIST_HEAD(&root->allcg_list);
root->number_of_cgroups = 1;
cgrp->root = root;
cgrp->name = &root_cgroup_name;
init_cgroup_housekeeping(cgrp);
list_add_tail(&cgrp->allcg_node, &root->allcg_list);
}
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_mask || opts->none)
&& (opts->subsys_mask != root->subsys_mask))
return 0;
return 1;
}
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
struct cgroupfs_root *root;
if (!opts->subsys_mask && !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_mask = opts->subsys_mask;
root->flags = opts->flags;
ida_init(&root->cgroup_ida);
if (opts->release_agent)
strcpy(root->release_agent_path, opts->release_agent);
if (opts->name)
strcpy(root->name, opts->name);
if (opts->cpuset_clone_children)
set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags);
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);
ida_destroy(&root->cgroup_ida);
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_mask && !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)
{
static const struct dentry_operations cgroup_dops = {
.d_iput = cgroup_diput,
.d_delete = cgroup_delete,
};
struct inode *inode =
cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);
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);
sb->s_root = d_make_root(inode);
if (!sb->s_root)
return -ENOMEM;
/* for everything else we want ->d_op set */
sb->s_d_op = &cgroup_dops;
return 0;
}
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
int flags, const char *unused_dev_name,
void *data)
{
struct cgroup_sb_opts opts;
struct cgroupfs_root *root;
int ret = 0;
struct super_block *sb;
struct cgroupfs_root *new_root;
struct inode *inode;
/* 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, 0, &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 cgroupfs_root *existing_root;
const struct cred *cred;
int i;
struct css_set *cg;
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);
mutex_lock(&cgroup_root_mutex);
/* Check for name clashes with existing mounts */
ret = -EBUSY;
if (strlen(root->name))
for_each_active_root(existing_root)
if (!strcmp(existing_root->name, root->name))
goto unlock_drop;
/*
* 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)
goto unlock_drop;
ret = rebind_subsystems(root, root->subsys_mask);
if (ret == -EBUSY) {
free_cg_links(&tmp_cg_links);
goto unlock_drop;
}
/*
* 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);
hash_for_each(css_set_table, i, cg, 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->children));
BUG_ON(root->number_of_cgroups != 1);
cred = override_creds(&init_cred);
cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
revert_creds(cred);
mutex_unlock(&cgroup_root_mutex);
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);
if (root->flags != opts.flags) {
if ((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) {
pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n");
ret = -EINVAL;
goto drop_new_super;
} else {
pr_warning("cgroup: new mount options do not match the existing superblock, will be ignored\n");
}
}
/* no subsys rebinding, so refcounts don't change */
drop_parsed_module_refcounts(opts.subsys_mask);
}
kfree(opts.release_agent);
kfree(opts.name);
return dget(sb->s_root);
unlock_drop:
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);
drop_new_super:
deactivate_locked_super(sb);
drop_modules:
drop_parsed_module_refcounts(opts.subsys_mask);
out_err:
kfree(opts.release_agent);
kfree(opts.name);
return ERR_PTR(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));
mutex_lock(&cgroup_mutex);
mutex_lock(&cgroup_root_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_root_mutex);
mutex_unlock(&cgroup_mutex);
simple_xattrs_free(&cgrp->xattrs);
kill_litter_super(sb);
cgroup_drop_root(root);
}
static struct file_system_type cgroup_fs_type = {
.name = "cgroup",
.mount = cgroup_mount,
.kill_sb = cgroup_kill_sb,
};
static struct kobject *cgroup_kobj;
/**
* 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
*
* Writes path of cgroup into buf. Returns 0 on success, -errno on error.
*
* We can't generate cgroup path using dentry->d_name, as accessing
* dentry->name must be protected by irq-unsafe dentry->d_lock or parent
* inode's i_mutex, while on the other hand cgroup_path() can be called
* with some irq-safe spinlocks held.
*/
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
{
int ret = -ENAMETOOLONG;
char *start;
if (!cgrp->parent) {
if (strlcpy(buf, "/", buflen) >= buflen)
return -ENAMETOOLONG;
return 0;
}
start = buf + buflen - 1;
*start = '\0';
rcu_read_lock();
do {
const char *name = cgroup_name(cgrp);
int len;
len = strlen(name);
if ((start -= len) < buf)
goto out;
memcpy(start, name, len);
if (--start < buf)
goto out;
*start = '/';
cgrp = cgrp->parent;
} while (cgrp->parent);
ret = 0;
memmove(buf, start, buf + buflen - start);
out:
rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL_GPL(cgroup_path);
/*
* Control Group taskset
*/
struct task_and_cgroup {
struct task_struct *task;
struct cgroup *cgrp;
struct css_set *cg;
};
struct cgroup_taskset {
struct task_and_cgroup single;
struct flex_array *tc_array;
int tc_array_len;
int idx;
struct cgroup *cur_cgrp;
};
/**
* cgroup_taskset_first - reset taskset and return the first task
* @tset: taskset of interest
*
* @tset iteration is initialized and the first task is returned.
*/
struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
{
if (tset->tc_array) {
tset->idx = 0;
return cgroup_taskset_next(tset);
} else {
tset->cur_cgrp = tset->single.cgrp;
return tset->single.task;
}
}
EXPORT_SYMBOL_GPL(cgroup_taskset_first);
/**
* cgroup_taskset_next - iterate to the next task in taskset
* @tset: taskset of interest
*
* Return the next task in @tset. Iteration must have been initialized
* with cgroup_taskset_first().
*/
struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
{
struct task_and_cgroup *tc;
if (!tset->tc_array || tset->idx >= tset->tc_array_len)
return NULL;
tc = flex_array_get(tset->tc_array, tset->idx++);
tset->cur_cgrp = tc->cgrp;
return tc->task;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_next);
/**
* cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
* @tset: taskset of interest
*
* Return the cgroup for the current (last returned) task of @tset. This
* function must be preceded by either cgroup_taskset_first() or
* cgroup_taskset_next().
*/
struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
{
return tset->cur_cgrp;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);
/**
* cgroup_taskset_size - return the number of tasks in taskset
* @tset: taskset of interest
*/
int cgroup_taskset_size(struct cgroup_taskset *tset)
{
return tset->tc_array ? tset->tc_array_len : 1;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_size);
/*
* cgroup_task_migrate - move a task from one cgroup to another.
*
* Must be called with cgroup_mutex and threadgroup locked.
*/
static void cgroup_task_migrate(struct cgroup *oldcgrp,
struct task_struct *tsk, struct css_set *newcg)
{
struct css_set *oldcg;
/*
* We are synchronized through threadgroup_lock() against PF_EXITING
* setting such that we can't race against cgroup_exit() changing the
* css_set to init_css_set and dropping the old one.
*/
WARN_ON_ONCE(tsk->flags & PF_EXITING);
oldcg = tsk->cgroups;
task_lock(tsk);
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_move(&tsk->cg_list, &newcg->tasks);
write_unlock(&css_set_lock);
/*
* We just gained a reference on oldcg by taking it from the task. As
* trading it for newcg is protected by cgroup_mutex, we're safe to drop
* it here; it will be freed under RCU.
*/
set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
put_css_set(oldcg);
}
/**
* cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
* @cgrp: the cgroup to attach to
* @tsk: the task or the leader of the threadgroup to be attached
* @threadgroup: attach the whole threadgroup?
*
* Call holding cgroup_mutex and the group_rwsem of the leader. Will take
* task_lock of @tsk or each thread in the threadgroup individually in turn.
*/
static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
bool threadgroup)
{
int retval, i, group_size;
struct cgroup_subsys *ss, *failed_ss = NULL;
struct cgroupfs_root *root = cgrp->root;
/* threadgroup list cursor and array */
struct task_struct *leader = tsk;
struct task_and_cgroup *tc;
struct flex_array *group;
struct cgroup_taskset tset = { };
/*
* step 0: in order to do expensive, possibly blocking operations for
* every thread, we cannot iterate the thread group list, since it needs
* rcu or tasklist locked. instead, build an array of all threads in the
* group - group_rwsem prevents new threads from appearing, and if
* threads exit, this will just be an over-estimate.
*/
if (threadgroup)
group_size = get_nr_threads(tsk);
else
group_size = 1;
/* flex_array supports very large thread-groups better than kmalloc. */
group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
if (!group)
return -ENOMEM;
/* pre-allocate to guarantee space while iterating in rcu read-side. */
retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
if (retval)
goto out_free_group_list;
i = 0;
/*
* Prevent freeing of tasks while we take a snapshot. Tasks that are
* already PF_EXITING could be freed from underneath us unless we
* take an rcu_read_lock.
*/
rcu_read_lock();
do {
struct task_and_cgroup ent;
/* @tsk either already exited or can't exit until the end */
if (tsk->flags & PF_EXITING)
continue;
/* as per above, nr_threads may decrease, but not increase. */
BUG_ON(i >= group_size);
ent.task = tsk;
ent.cgrp = task_cgroup_from_root(tsk, root);
/* nothing to do if this task is already in the cgroup */
if (ent.cgrp == cgrp)
continue;
/*
* saying GFP_ATOMIC has no effect here because we did prealloc
* earlier, but it's good form to communicate our expectations.
*/
retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
BUG_ON(retval != 0);
i++;
if (!threadgroup)
break;
} while_each_thread(leader, tsk);
rcu_read_unlock();
/* remember the number of threads in the array for later. */
group_size = i;
tset.tc_array = group;
tset.tc_array_len = group_size;
/* methods shouldn't be called if no task is actually migrating */
retval = 0;
if (!group_size)
goto out_free_group_list;
/*
* step 1: check that we can legitimately attach to the cgroup.
*/
for_each_subsys(root, ss) {
if (ss->can_attach) {
retval = ss->can_attach(cgrp, &tset);
if (retval) {
failed_ss = ss;
goto out_cancel_attach;
}
}
}
/*
* step 2: make sure css_sets exist for all threads to be migrated.
* we use find_css_set, which allocates a new one if necessary.
*/
for (i = 0; i < group_size; i++) {
tc = flex_array_get(group, i);
tc->cg = find_css_set(tc->task->cgroups, cgrp);
if (!tc->cg) {
retval = -ENOMEM;
goto out_put_css_set_refs;
}
}
/*
* step 3: now that we're guaranteed success wrt the css_sets,
* proceed to move all tasks to the new cgroup. There are no
* failure cases after here, so this is the commit point.
*/
for (i = 0; i < group_size; i++) {
tc = flex_array_get(group, i);
cgroup_task_migrate(tc->cgrp, tc->task, tc->cg);
}
/* nothing is sensitive to fork() after this point. */
/*
* step 4: do subsystem attach callbacks.
*/
for_each_subsys(root, ss) {
if (ss->attach)
ss->attach(cgrp, &tset);
}
/*
* step 5: success! and cleanup
*/
retval = 0;
out_put_css_set_refs:
if (retval) {
for (i = 0; i < group_size; i++) {
tc = flex_array_get(group, i);
if (!tc->cg)
break;
put_css_set(tc->cg);
}
}
out_cancel_attach:
if (retval) {
for_each_subsys(root, ss) {
if (ss == failed_ss)
break;
if (ss->cancel_attach)
ss->cancel_attach(cgrp, &tset);
}
}
out_free_group_list:
flex_array_free(group);
return retval;
}
/*
* Find the task_struct of the task to attach by vpid and pass it along to the
* function to attach either it or all tasks in its threadgroup. Will lock
* cgroup_mutex and threadgroup; may take task_lock of task.
*/
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
{
struct task_struct *tsk;
const struct cred *cred = current_cred(), *tcred;
int ret;
if (!cgroup_lock_live_group(cgrp))
return -ENODEV;
retry_find_task:
rcu_read_lock();
if (pid) {
tsk = find_task_by_vpid(pid);
if (!tsk) {
rcu_read_unlock();
ret= -ESRCH;
goto out_unlock_cgroup;
}
/*
* even if we're attaching all tasks in the thread group, we
* only need to check permissions on one of them.
*/
tcred = __task_cred(tsk);
if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
!uid_eq(cred->euid, tcred->uid) &&
!uid_eq(cred->euid, tcred->suid)) {
rcu_read_unlock();
ret = -EACCES;
goto out_unlock_cgroup;
}
} else
tsk = current;
if (threadgroup)
tsk = tsk->group_leader;
/*
* Workqueue threads may acquire PF_NO_SETAFFINITY and become
* trapped in a cpuset, or RT worker may be born in a cgroup
* with no rt_runtime allocated. Just say no.
*/
if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) {
ret = -EINVAL;
rcu_read_unlock();
goto out_unlock_cgroup;
}
get_task_struct(tsk);
rcu_read_unlock();
threadgroup_lock(tsk);
if (threadgroup) {
if (!thread_group_leader(tsk)) {
/*
* a race with de_thread from another thread's exec()
* may strip us of our leadership, if this happens,
* there is no choice but to throw this task away and
* try again; this is
* "double-double-toil-and-trouble-check locking".
*/
threadgroup_unlock(tsk);
put_task_struct(tsk);
goto retry_find_task;
}
}
ret = cgroup_attach_task(cgrp, tsk, threadgroup);
threadgroup_unlock(tsk);
put_task_struct(tsk);
out_unlock_cgroup:
mutex_unlock(&cgroup_mutex);
return ret;
}
/**
* 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;
mutex_lock(&cgroup_mutex);
for_each_active_root(root) {
struct cgroup *from_cg = task_cgroup_from_root(from, root);
retval = cgroup_attach_task(from_cg, tsk, false);
if (retval)
break;
}
mutex_unlock(&cgroup_mutex);
return retval;
}
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
{
return attach_task_by_pid(cgrp, pid, false);
}
static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
{
return attach_task_by_pid(cgrp, tgid, true);
}
static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
const char *buffer)
{
BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
if (strlen(buffer) >= PATH_MAX)
return -EINVAL;
if (!cgroup_lock_live_group(cgrp))
return -ENODEV;
mutex_lock(&cgroup_root_mutex);
strcpy(cgrp->root->release_agent_path, buffer);
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
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');
mutex_unlock(&cgroup_mutex);
return 0;
}
static int cgroup_sane_behavior_show(struct cgroup *cgrp, struct cftype *cft,
struct seq_file *seq)
{
seq_printf(seq, "%d\n", cgroup_sane_behavior(cgrp));
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)
{
int ret;
struct cgroup_name *name, *old_name;
struct cgroup *cgrp;
/*
* It's convinient to use parent dir's i_mutex to protected
* cgrp->name.
*/
lockdep_assert_held(&old_dir->i_mutex);
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;
cgrp = __d_cgrp(old_dentry);
name = cgroup_alloc_name(new_dentry);
if (!name)
return -ENOMEM;
ret = simple_rename(old_dir, old_dentry, new_dir, new_dentry);
if (ret) {
kfree(name);
return ret;
}
old_name = cgrp->name;
rcu_assign_pointer(cgrp->name, name);
kfree_rcu(old_name, rcu_head);
return 0;
}
static struct simple_xattrs *__d_xattrs(struct dentry *dentry)
{
if (S_ISDIR(dentry->d_inode->i_mode))
return &__d_cgrp(dentry)->xattrs;
else
return &__d_cfe(dentry)->xattrs;
}
static inline int xattr_enabled(struct dentry *dentry)
{
struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
return root->flags & CGRP_ROOT_XATTR;
}
static bool is_valid_xattr(const char *name)
{
if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN))
return true;
return false;
}
static int cgroup_setxattr(struct dentry *dentry, const char *name,
const void *val, size_t size, int flags)
{
if (!xattr_enabled(dentry))
return -EOPNOTSUPP;
if (!is_valid_xattr(name))
return -EINVAL;
return simple_xattr_set(__d_xattrs(dentry), name, val, size, flags);
}
static int cgroup_removexattr(struct dentry *dentry, const char *name)
{
if (!xattr_enabled(dentry))
return -EOPNOTSUPP;
if (!is_valid_xattr(name))
return -EINVAL;
return simple_xattr_remove(__d_xattrs(dentry), name);
}
static ssize_t cgroup_getxattr(struct dentry *dentry, const char *name,
void *buf, size_t size)
{
if (!xattr_enabled(dentry))
return -EOPNOTSUPP;
if (!is_valid_xattr(name))
return -EINVAL;
return simple_xattr_get(__d_xattrs(dentry), name, buf, size);
}
static ssize_t cgroup_listxattr(struct dentry *dentry, char *buf, size_t size)
{
if (!xattr_enabled(dentry))
return -EOPNOTSUPP;
return simple_xattr_list(__d_xattrs(dentry), buf, size);
}
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_file_inode_operations = {
.setxattr = cgroup_setxattr,
.getxattr = cgroup_getxattr,
.listxattr = cgroup_listxattr,
.removexattr = cgroup_removexattr,
};
static const struct inode_operations cgroup_dir_inode_operations = {
.lookup = cgroup_lookup,
.mkdir = cgroup_mkdir,
.rmdir = cgroup_rmdir,
.rename = cgroup_rename,
.setxattr = cgroup_setxattr,
.getxattr = cgroup_getxattr,
.listxattr = cgroup_listxattr,
.removexattr = cgroup_removexattr,
};
static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
{
if (dentry->d_name.len > NAME_MAX)
return ERR_PTR(-ENAMETOOLONG);
d_add(dentry, NULL);
return NULL;
}
/*
* Check if a file is a control file
*/
static inline struct cftype *__file_cft(struct file *file)
{
if (file_inode(file)->i_fop != &cgroup_file_operations)
return ERR_PTR(-EINVAL);
return __d_cft(file->f_dentry);
}
static int cgroup_create_file(struct dentry *dentry, umode_t mode,
struct super_block *sb)
{
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);
inc_nlink(dentry->d_parent->d_inode);
/*
* Control reaches here with cgroup_mutex held.
* @inode->i_mutex should nest outside cgroup_mutex but we
* want to populate it immediately without releasing
* cgroup_mutex. As @inode isn't visible to anyone else
* yet, trylock will always succeed without affecting
* lockdep checks.
*/
WARN_ON_ONCE(!mutex_trylock(&inode->i_mutex));
} else if (S_ISREG(mode)) {
inode->i_size = 0;
inode->i_fop = &cgroup_file_operations;
inode->i_op = &cgroup_file_inode_operations;
}
d_instantiate(dentry, inode);
dget(dentry); /* Extra count - pin the dentry in core */
return 0;
}
/**
* 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 umode_t cgroup_file_mode(const struct cftype *cft)
{
umode_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;
}
static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
struct cftype *cft)
{
struct dentry *dir = cgrp->dentry;
struct cgroup *parent = __d_cgrp(dir);
struct dentry *dentry;
struct cfent *cfe;
int error;
umode_t mode;
char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
if (subsys && !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
strcpy(name, subsys->name);
strcat(name, ".");
}
strcat(name, cft->name);
BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
cfe = kzalloc(sizeof(*cfe), GFP_KERNEL);
if (!cfe)
return -ENOMEM;
dentry = lookup_one_len(name, dir, strlen(name));
if (IS_ERR(dentry)) {
error = PTR_ERR(dentry);
goto out;
}
cfe->type = (void *)cft;
cfe->dentry = dentry;
dentry->d_fsdata = cfe;
simple_xattrs_init(&cfe->xattrs);
mode = cgroup_file_mode(cft);
error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
if (!error) {
list_add_tail(&cfe->node, &parent->files);
cfe = NULL;
}
dput(dentry);
out:
kfree(cfe);
return error;
}
static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
struct cftype cfts[], bool is_add)
{
struct cftype *cft;
int err, ret = 0;
for (cft = cfts; cft->name[0] != '\0'; cft++) {
/* does cft->flags tell us to skip this file on @cgrp? */
if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp))
continue;
if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
continue;
if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
continue;
if (is_add) {
err = cgroup_add_file(cgrp, subsys, cft);
if (err)
pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
cft->name, err);
ret = err;
} else {
cgroup_rm_file(cgrp, cft);
}
}
return ret;
}
static DEFINE_MUTEX(cgroup_cft_mutex);
static void cgroup_cfts_prepare(void)
__acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex)
{
/*
* Thanks to the entanglement with vfs inode locking, we can't walk
* the existing cgroups under cgroup_mutex and create files.
* Instead, we increment reference on all cgroups and build list of
* them using @cgrp->cft_q_node. Grab cgroup_cft_mutex to ensure
* exclusive access to the field.
*/
mutex_lock(&cgroup_cft_mutex);
mutex_lock(&cgroup_mutex);
}
static void cgroup_cfts_commit(struct cgroup_subsys *ss,
struct cftype *cfts, bool is_add)
__releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
{
LIST_HEAD(pending);
struct cgroup *cgrp, *n;
/* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
if (cfts && ss->root != &rootnode) {
list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) {
dget(cgrp->dentry);
list_add_tail(&cgrp->cft_q_node, &pending);
}
}
mutex_unlock(&cgroup_mutex);
/*
* All new cgroups will see @cfts update on @ss->cftsets. Add/rm
* files for all cgroups which were created before.
*/
list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {
struct inode *inode = cgrp->dentry->d_inode;
mutex_lock(&inode->i_mutex);
mutex_lock(&cgroup_mutex);
if (!cgroup_is_removed(cgrp))
cgroup_addrm_files(cgrp, ss, cfts, is_add);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);
list_del_init(&cgrp->cft_q_node);
dput(cgrp->dentry);
}
mutex_unlock(&cgroup_cft_mutex);
}
/**
* cgroup_add_cftypes - add an array of cftypes to a subsystem
* @ss: target cgroup subsystem
* @cfts: zero-length name terminated array of cftypes
*
* Register @cfts to @ss. Files described by @cfts are created for all
* existing cgroups to which @ss is attached and all future cgroups will
* have them too. This function can be called anytime whether @ss is
* attached or not.
*
* Returns 0 on successful registration, -errno on failure. Note that this
* function currently returns 0 as long as @cfts registration is successful
* even if some file creation attempts on existing cgroups fail.
*/
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
{
struct cftype_set *set;
set = kzalloc(sizeof(*set), GFP_KERNEL);
if (!set)
return -ENOMEM;
cgroup_cfts_prepare();
set->cfts = cfts;
list_add_tail(&set->node, &ss->cftsets);
cgroup_cfts_commit(ss, cfts, true);
return 0;
}
EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
/**
* cgroup_rm_cftypes - remove an array of cftypes from a subsystem
* @ss: target cgroup subsystem
* @cfts: zero-length name terminated array of cftypes
*
* Unregister @cfts from @ss. Files described by @cfts are removed from
* all existing cgroups to which @ss is attached and all future cgroups
* won't have them either. This function can be called anytime whether @ss
* is attached or not.
*
* Returns 0 on successful unregistration, -ENOENT if @cfts is not
* registered with @ss.
*/
int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
{
struct cftype_set *set;
cgroup_cfts_prepare();
list_for_each_entry(set, &ss->cftsets, node) {
if (set->cfts == cfts) {
list_del_init(&set->node);
cgroup_cfts_commit(ss, cfts, false);
return 0;
}
}
cgroup_cfts_commit(ss, NULL, false);
return -ENOENT;
}
/**
* 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().
*/
static void cgroup_enable_task_cg_lists(void)
{
struct task_struct *p, *g;
write_lock(&css_set_lock);
use_task_css_set_links = 1;
/*
* We need tasklist_lock because RCU is not safe against
* while_each_thread(). Besides, a forking task that has passed
* cgroup_post_fork() without seeing use_task_css_set_links = 1
* is not guaranteed to have its child immediately visible in the
* tasklist if we walk through it with RCU.
*/
read_lock(&tasklist_lock);
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);
read_unlock(&tasklist_lock);
write_unlock(&css_set_lock);
}
/**
* cgroup_next_descendant_pre - find the next descendant for pre-order walk
* @pos: the current position (%NULL to initiate traversal)
* @cgroup: cgroup whose descendants to walk
*
* To be used by cgroup_for_each_descendant_pre(). Find the next
* descendant to visit for pre-order traversal of @cgroup's descendants.
*/
struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
struct cgroup *cgroup)
{
struct cgroup *next;
WARN_ON_ONCE(!rcu_read_lock_held());
/* if first iteration, pretend we just visited @cgroup */
if (!pos)
pos = cgroup;
/* visit the first child if exists */
next = list_first_or_null_rcu(&pos->children, struct cgroup, sibling);
if (next)
return next;
/* no child, visit my or the closest ancestor's next sibling */
while (pos != cgroup) {
next = list_entry_rcu(pos->sibling.next, struct cgroup,
sibling);
if (&next->sibling != &pos->parent->children)
return next;
pos = pos->parent;
}
return NULL;
}
EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre);
/**
* cgroup_rightmost_descendant - return the rightmost descendant of a cgroup
* @pos: cgroup of interest
*
* Return the rightmost descendant of @pos. If there's no descendant,
* @pos is returned. This can be used during pre-order traversal to skip
* subtree of @pos.
*/
struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos)
{
struct cgroup *last, *tmp;
WARN_ON_ONCE(!rcu_read_lock_held());
do {
last = pos;
/* ->prev isn't RCU safe, walk ->next till the end */
pos = NULL;
list_for_each_entry_rcu(tmp, &last->children, sibling)
pos = tmp;
} while (pos);
return last;
}
EXPORT_SYMBOL_GPL(cgroup_rightmost_descendant);
static struct cgroup *cgroup_leftmost_descendant(struct cgroup *pos)
{
struct cgroup *last;
do {
last = pos;
pos = list_first_or_null_rcu(&pos->children, struct cgroup,
sibling);
} while (pos);
return last;
}
/**
* cgroup_next_descendant_post - find the next descendant for post-order walk
* @pos: the current position (%NULL to initiate traversal)
* @cgroup: cgroup whose descendants to walk
*
* To be used by cgroup_for_each_descendant_post(). Find the next
* descendant to visit for post-order traversal of @cgroup's descendants.
*/
struct cgroup *cgroup_next_descendant_post(struct cgroup *pos,
struct cgroup *cgroup)
{
struct cgroup *next;
WARN_ON_ONCE(!rcu_read_lock_held());
/* if first iteration, visit the leftmost descendant */
if (!pos) {
next = cgroup_leftmost_descendant(cgroup);
return next != cgroup ? next : NULL;
}
/* if there's an unvisited sibling, visit its leftmost descendant */
next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
if (&next->sibling != &pos->parent->children)
return cgroup_leftmost_descendant(next);
/* no sibling left, visit parent */
next = pos->parent;
return next != cgroup ? next : NULL;
}
EXPORT_SYMBOL_GPL(cgroup_next_descendant_post);
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
__acquires(css_set_lock)
{
/*
* 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)
__releases(css_set_lock)
{
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;
}
static void cgroup_transfer_one_task(struct task_struct *task,
struct cgroup_scanner *scan)
{
struct cgroup *new_cgroup = scan->data;
mutex_lock(&cgroup_mutex);
cgroup_attach_task(new_cgroup, task, false);
mutex_unlock(&cgroup_mutex);
}
/**
* cgroup_trasnsfer_tasks - move tasks from one cgroup to another
* @to: cgroup to which the tasks will be moved
* @from: cgroup in which the tasks currently reside
*/
int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
{
struct cgroup_scanner scan;
scan.cg = from;
scan.test_task = NULL; /* select all tasks in cgroup */
scan.process_task = cgroup_transfer_one_task;
scan.heap = NULL;
scan.data = to;
return cgroup_scan_tasks(&scan);
}
/*
* 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.
*
*/
/* which pidlist file are we talking about? */
enum cgroup_filetype {
CGROUP_FILE_PROCS,
CGROUP_FILE_TASKS,
};
/*
* A pidlist is a list of pids that virtually represents the contents of one
* of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
* a pair (one each for procs, tasks) for each pid namespace that's relevant
* to the cgroup.
*/
struct cgroup_pidlist {
/*
* used to find which pidlist is wanted. doesn't change as long as
* this particular list stays in the list.
*/
struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
/* array of xids */
pid_t *list;
/* how many elements the above list has */
int length;
/* how many files are using the current array */
int use_count;
/* each of these stored in a list by its cgroup */
struct list_head links;
/* pointer to the cgroup we belong to, for list removal purposes */
struct cgroup *owner;
/* protects the other fields */
struct rw_semaphore mutex;
};
/*
* 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);
}
/*
* pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
* Returns the number of unique elements.
*/
static int pidlist_uniq(pid_t *list, int length)
{
int src, dest = 1;
/*
* 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:
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 = task_active_pid_ns(current);
/*
* 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;
remove_wait_queue(event->wqh, &event->wait);
event->cft->unregister_event(cgrp, event->cft, event->eventfd);
/* Notify userspace the event is going away. */
eventfd_signal(event->eventfd, 1);
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) {
/*
* If the event has been detached at cgroup removal, we
* can simply return knowing the other side will cleanup
* for us.
*
* We can't race against event freeing since the other
* side will require wqh->lock via remove_wait_queue(),
* which we hold.
*/
spin_lock(&cgrp->event_list_lock);
if (!list_empty(&event->list)) {
list_del_init(&event->list);
/*
* We are in atomic context, but cgroup_event_remove()
* may sleep, so we have to call it in workqueue.
*/
schedule_work(&event->remove);
}
spin_unlock(&cgrp->event_list_lock);
}
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;
struct cgroup *cgrp_cfile;
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 */
/* AV: shouldn't we check that it's been opened for read instead? */
ret = inode_permission(file_inode(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;
}
/*
* The file to be monitored must be in the same cgroup as
* cgroup.event_control is.
*/
cgrp_cfile = __d_cgrp(cfile->f_dentry->d_parent);
if (cgrp_cfile != cgrp) {
ret = -EINVAL;
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;
efile->f_op->poll(efile, &event->pt);
/*
* 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;
}
static u64 cgroup_clone_children_read(struct cgroup *cgrp,
struct cftype *cft)
{
return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
}
static int cgroup_clone_children_write(struct cgroup *cgrp,
struct cftype *cft,
u64 val)
{
if (val)
set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
else
clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
return 0;
}
/*
* 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,
.release = cgroup_pidlist_release,
.mode = S_IRUGO | S_IWUSR,
},
{
.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,
},
{
.name = "cgroup.clone_children",
.flags = CFTYPE_INSANE,
.read_u64 = cgroup_clone_children_read,
.write_u64 = cgroup_clone_children_write,
},
{
.name = "cgroup.sane_behavior",
.flags = CFTYPE_ONLY_ON_ROOT,
.read_seq_string = cgroup_sane_behavior_show,
},
{
.name = "release_agent",
.flags = CFTYPE_ONLY_ON_ROOT,
.read_seq_string = cgroup_release_agent_show,
.write_string = cgroup_release_agent_write,
.max_write_len = PATH_MAX,
},
{ } /* terminate */
};
/**
* cgroup_populate_dir - selectively creation of files in a directory
* @cgrp: target cgroup
* @base_files: true if the base files should be added
* @subsys_mask: mask of the subsystem ids whose files should be added
*/
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
unsigned long subsys_mask)
{
int err;
struct cgroup_subsys *ss;
if (base_files) {
err = cgroup_addrm_files(cgrp, NULL, files, true);
if (err < 0)
return err;
}
/* process cftsets of each subsystem */
for_each_subsys(cgrp->root, ss) {
struct cftype_set *set;
if (!test_bit(ss->subsys_id, &subsys_mask))
continue;
list_for_each_entry(set, &ss->cftsets, node)
cgroup_addrm_files(cgrp, ss, set->cfts, true);
}
/* 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 css_dput_fn(struct work_struct *work)
{
struct cgroup_subsys_state *css =
container_of(work, struct cgroup_subsys_state, dput_work);
struct dentry *dentry = css->cgroup->dentry;
struct super_block *sb = dentry->d_sb;
atomic_inc(&sb->s_active);
dput(dentry);
deactivate_super(sb);
}
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)
css->flags |= CSS_ROOT;
BUG_ON(cgrp->subsys[ss->subsys_id]);
cgrp->subsys[ss->subsys_id] = css;
/*
* css holds an extra ref to @cgrp->dentry which is put on the last
* css_put(). dput() requires process context, which css_put() may
* be called without. @css->dput_work will be used to invoke
* dput() asynchronously from css_put().
*/
INIT_WORK(&css->dput_work, css_dput_fn);
}
/* invoke ->post_create() on a new CSS and mark it online if successful */
static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
{
int ret = 0;
lockdep_assert_held(&cgroup_mutex);
if (ss->css_online)
ret = ss->css_online(cgrp);
if (!ret)
cgrp->subsys[ss->subsys_id]->flags |= CSS_ONLINE;
return ret;
}
/* if the CSS is online, invoke ->pre_destory() on it and mark it offline */
static void offline_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
{
struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
lockdep_assert_held(&cgroup_mutex);
if (!(css->flags & CSS_ONLINE))
return;
if (ss->css_offline)
ss->css_offline(cgrp);
cgrp->subsys[ss->subsys_id]->flags &= ~CSS_ONLINE;
}
/*
* 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,
umode_t mode)
{
struct cgroup *cgrp;
struct cgroup_name *name;
struct cgroupfs_root *root = parent->root;
int err = 0;
struct cgroup_subsys *ss;
struct super_block *sb = root->sb;
/* allocate the cgroup and its ID, 0 is reserved for the root */
cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
if (!cgrp)
return -ENOMEM;
name = cgroup_alloc_name(dentry);
if (!name)
goto err_free_cgrp;
rcu_assign_pointer(cgrp->name, name);
cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);
if (cgrp->id < 0)
goto err_free_name;
/*
* Only live parents can have children. Note that the liveliness
* check isn't strictly necessary because cgroup_mkdir() and
* cgroup_rmdir() are fully synchronized by i_mutex; however, do it
* anyway so that locking is contained inside cgroup proper and we
* don't get nasty surprises if we ever grow another caller.
*/
if (!cgroup_lock_live_group(parent)) {
err = -ENODEV;
goto err_free_id;
}
/* 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);
init_cgroup_housekeeping(cgrp);
dentry->d_fsdata = cgrp;
cgrp->dentry = dentry;
cgrp->parent = parent;
cgrp->root = parent->root;
if (notify_on_release(parent))
set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
for_each_subsys(root, ss) {
struct cgroup_subsys_state *css;
css = ss->css_alloc(cgrp);
if (IS_ERR(css)) {
err = PTR_ERR(css);
goto err_free_all;
}
init_cgroup_css(css, ss, cgrp);
if (ss->use_id) {
err = alloc_css_id(ss, parent, cgrp);
if (err)
goto err_free_all;
}
}
/*
* Create directory. cgroup_create_file() returns with the new
* directory locked on success so that it can be populated without
* dropping cgroup_mutex.
*/
err = cgroup_create_file(dentry, S_IFDIR | mode, sb);
if (err < 0)
goto err_free_all;
lockdep_assert_held(&dentry->d_inode->i_mutex);
/* allocation complete, commit to creation */
list_add_tail(&cgrp->allcg_node, &root->allcg_list);
list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
root->number_of_cgroups++;
/* each css holds a ref to the cgroup's dentry */
for_each_subsys(root, ss)
dget(dentry);
/* hold a ref to the parent's dentry */
dget(parent->dentry);
/* creation succeeded, notify subsystems */
for_each_subsys(root, ss) {
err = online_css(ss, cgrp);
if (err)
goto err_destroy;
if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
parent->parent) {
pr_warning("cgroup: %s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
current->comm, current->pid, ss->name);
if (!strcmp(ss->name, "memory"))
pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
ss->warned_broken_hierarchy = true;
}
}
err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
if (err)
goto err_destroy;
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
return 0;
err_free_all:
for_each_subsys(root, ss) {
if (cgrp->subsys[ss->subsys_id])
ss->css_free(cgrp);
}
mutex_unlock(&cgroup_mutex);
/* Release the reference count that we took on the superblock */
deactivate_super(sb);
err_free_id:
ida_simple_remove(&root->cgroup_ida, cgrp->id);
err_free_name:
kfree(rcu_dereference_raw(cgrp->name));
err_free_cgrp:
kfree(cgrp);
return err;
err_destroy:
cgroup_destroy_locked(cgrp);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&dentry->d_inode->i_mutex);
return err;
}
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t 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_destroy_locked(struct cgroup *cgrp)
__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
{
struct dentry *d = cgrp->dentry;
struct cgroup *parent = cgrp->parent;
struct cgroup_event *event, *tmp;
struct cgroup_subsys *ss;
lockdep_assert_held(&d->d_inode->i_mutex);
lockdep_assert_held(&cgroup_mutex);
if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children))
return -EBUSY;
/*
* Block new css_tryget() by deactivating refcnt and mark @cgrp
* removed. This makes future css_tryget() and child creation
* attempts fail thus maintaining the removal conditions verified
* above.
*/
for_each_subsys(cgrp->root, ss) {
struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
WARN_ON(atomic_read(&css->refcnt) < 0);
atomic_add(CSS_DEACT_BIAS, &css->refcnt);
}
set_bit(CGRP_REMOVED, &cgrp->flags);
/* tell subsystems to initate destruction */
for_each_subsys(cgrp->root, ss)
offline_css(ss, cgrp);
/*
* Put all the base refs. Each css holds an extra reference to the
* cgroup's dentry and cgroup removal proceeds regardless of css
* refs. On the last put of each css, whenever that may be, the
* extra dentry ref is put so that dentry destruction happens only
* after all css's are released.
*/
for_each_subsys(cgrp->root, ss)
css_put(cgrp->subsys[ss->subsys_id]);
raw_spin_lock(&release_list_lock);
if (!list_empty(&cgrp->release_list))
list_del_init(&cgrp->release_list);
raw_spin_unlock(&release_list_lock);
/* delete this cgroup from parent->children */
list_del_rcu(&cgrp->sibling);
list_del_init(&cgrp->allcg_node);
dget(d);
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_init(&event->list);
schedule_work(&event->remove);
}
spin_unlock(&cgrp->event_list_lock);
return 0;
}
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
int ret;
mutex_lock(&cgroup_mutex);
ret = cgroup_destroy_locked(dentry->d_fsdata);
mutex_unlock(&cgroup_mutex);
return ret;
}
static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
{
INIT_LIST_HEAD(&ss->cftsets);
/*
* base_cftset is embedded in subsys itself, no need to worry about
* deregistration.
*/
if (ss->base_cftypes) {
ss->base_cftset.cfts = ss->base_cftypes;
list_add_tail(&ss->base_cftset.node, &ss->cftsets);
}
}
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);
mutex_lock(&cgroup_mutex);
/* init base cftset */
cgroup_init_cftsets(ss);
/* Create the top cgroup state for this subsystem */
list_add(&ss->sibling, &rootnode.subsys_list);
ss->root = &rootnode;
css = ss->css_alloc(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] = css;
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));
BUG_ON(online_css(ss, dummytop));
mutex_unlock(&cgroup_mutex);
/* 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)
{
struct cgroup_subsys_state *css;
int i, ret;
struct hlist_node *tmp;
struct css_set *cg;
unsigned long key;
/* check name and function validity */
if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
ss->css_alloc == NULL || ss->css_free == 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 sanity check */
BUG_ON(subsys[ss->subsys_id] != ss);
return 0;
}
/* init base cftset */
cgroup_init_cftsets(ss);
mutex_lock(&cgroup_mutex);
subsys[ss->subsys_id] = ss;
/*
* no ss->css_alloc seems to need anything important in the ss
* struct, so this can happen first (i.e. before the rootnode
* attachment).
*/
css = ss->css_alloc(dummytop);
if (IS_ERR(css)) {
/* failure case - need to deassign the subsys[] slot. */
subsys[ss->subsys_id] = 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) {
ret = cgroup_init_idr(ss, css);
if (ret)
goto err_unload;
}
/*
* 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);
hash_for_each_safe(css_set_table, i, tmp, cg, hlist) {
/* skip entries that we already rehashed */
if (cg->subsys[ss->subsys_id])
continue;
/* remove existing entry */
hash_del(&cg->hlist);
/* set new value */
cg->subsys[ss->subsys_id] = css;
/* recompute hash and restore entry */
key = css_set_hash(cg->subsys);
hash_add(css_set_table, &cg->hlist, key);
}
write_unlock(&css_set_lock);
ret = online_css(ss, dummytop);
if (ret)
goto err_unload;
/* success! */
mutex_unlock(&cgroup_mutex);
return 0;
err_unload:
mutex_unlock(&cgroup_mutex);
/* @ss can't be mounted here as try_module_get() would fail */
cgroup_unload_subsys(ss);
return ret;
}
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;
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);
offline_css(ss, dummytop);
if (ss->use_id)
idr_destroy(&ss->idr);
/* deassign the subsys_id */
subsys[ss->subsys_id] = NULL;
/* remove subsystem from rootnode's list of subsystems */
list_del_init(&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;
unsigned long key;
hash_del(&cg->hlist);
cg->subsys[ss->subsys_id] = NULL;
key = css_set_hash(cg->subsys);
hash_add(css_set_table, &cg->hlist, key);
}
write_unlock(&css_set_lock);
/*
* remove subsystem's css from the dummytop and free it - need to
* free before marking as null because ss->css_free needs the
* cgrp->subsys pointer to find their state. note that this also
* takes care of freeing the css_id.
*/
ss->css_free(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 < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
/* at bootup time, we don't worry about modular subsystems */
if (!ss || ss->module)
continue;
BUG_ON(!ss->name);
BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
BUG_ON(!ss->css_alloc);
BUG_ON(!ss->css_free);
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;
unsigned long key;
err = bdi_init(&cgroup_backing_dev_info);
if (err)
return err;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
/* at bootup time, we don't worry about modular subsystems */
if (!ss || ss->module)
continue;
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 */
key = css_set_hash(init_css_set.subsys);
hash_add(css_set_table, &init_css_set.hlist, key);
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 */
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;
}
/* 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_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 and
* call the subsystem fork() callbacks. 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)
{
int i;
/*
* use_task_css_set_links is set to 1 before we walk the tasklist
* under the tasklist_lock and we read it here after we added the child
* to the tasklist under the tasklist_lock as well. If the child wasn't
* yet in the tasklist when we walked through it from
* cgroup_enable_task_cg_lists(), then use_task_css_set_links value
* should be visible now due to the paired locking and barriers implied
* by LOCK/UNLOCK: it is written before the tasklist_lock unlock
* in cgroup_enable_task_cg_lists() and read here after the tasklist_lock
* lock on fork.
*/
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);
}
/*
* Call ss->fork(). This must happen after @child is linked on
* css_set; otherwise, @child might change state between ->fork()
* and addition to css_set.
*/
if (need_forkexit_callback) {
/*
* fork/exit callbacks are supported only for builtin
* subsystems, and the builtin section of the subsys
* array is immutable, so we don't need to lock the
* subsys array here. On the other hand, modular section
* of the array can be freed at module unload, so we
* can't touch that.
*/
for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss->fork)
ss->fork(child);
}
}
}
/**
* 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)
{
struct css_set *cg;
int i;
/*
* 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_init(&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;
if (run_callbacks && need_forkexit_callback) {
/*
* fork/exit callbacks are supported only for builtin
* subsystems, see cgroup_post_fork() for details.
*/
for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss->exit) {
struct cgroup *old_cgrp =
rcu_dereference_raw(cg->subsys[i])->cgroup;
struct cgroup *cgrp = task_cgroup(tsk, i);
ss->exit(cgrp, old_cgrp, tsk);
}
}
}
task_unlock(tsk);
put_css_set_taskexit(cg);
}
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)) {
/*
* Control Group is currently removeable. If it's not
* already queued for a userspace notification, queue
* it now
*/
int need_schedule_work = 0;
raw_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;
}
raw_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 */
bool __css_tryget(struct cgroup_subsys_state *css)
{
while (true) {
int t, v;
v = css_refcnt(css);
t = atomic_cmpxchg(&css->refcnt, v, v + 1);
if (likely(t == v))
return true;
else if (t < 0)
return false;
cpu_relax();
}
}
EXPORT_SYMBOL_GPL(__css_tryget);
/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css)
{
int v;
v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));
if (v == 0)
schedule_work(&css->dput_work);
}
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);
raw_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);
raw_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);
raw_spin_lock(&release_list_lock);
}
raw_spin_unlock(&release_list_lock);
mutex_unlock(&cgroup_mutex);
}
static int __init cgroup_disable(char *str)
{
int i;
char *token;
while ((token = strsep(&str, ",")) != NULL) {
if (!*token)
continue;
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
/*
* cgroup_disable, being at boot time, can't
* know about module subsystems, so we don't
* worry about them.
*/
if (!ss || ss->module)
continue;
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, css_refcnt(css));
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, css_refcnt(css));
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, the caller must hold 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;
child_id = rcu_dereference(child->id);
if (!child_id)
return false;
root_id = rcu_dereference(root->id);
if (!root_id)
return false;
if (child_id->depth < root_id->depth)
return false;
if (child_id->stack[root_id->depth] != root_id->id)
return false;
return true;
}
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);
kfree_rcu(id, rcu_head);
}
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 ret, 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);
idr_preload(GFP_KERNEL);
spin_lock(&ss->id_lock);
/* Don't use 0. allocates an ID of 1-65535 */
ret = idr_alloc(&ss->idr, newid, 1, CSS_ID_MAX + 1, GFP_NOWAIT);
spin_unlock(&ss->id_lock);
idr_preload_end();
/* Returns error when there are no free spaces for new ID.*/
if (ret < 0)
goto err_out;
newid->id = ret;
newid->depth = depth;
return newid;
err_out:
kfree(newid);
return ERR_PTR(ret);
}
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);
/*
* get corresponding css from file open on cgroupfs directory
*/
struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
{
struct cgroup *cgrp;
struct inode *inode;
struct cgroup_subsys_state *css;
inode = file_inode(f);
/* check in cgroup filesystem dir */
if (inode->i_op != &cgroup_dir_inode_operations)
return ERR_PTR(-EBADF);
if (id < 0 || id >= CGROUP_SUBSYS_COUNT)
return ERR_PTR(-EINVAL);
/* get cgroup */
cgrp = __d_cgrp(f->f_dentry);
css = cgrp->subsys[id];
return css ? css : ERR_PTR(-ENOENT);
}
#ifdef CONFIG_CGROUP_DEBUG
static struct cgroup_subsys_state *debug_css_alloc(struct cgroup *cont)
{
struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
if (!css)
return ERR_PTR(-ENOMEM);
return css;
}
static void debug_css_free(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,
},
{ } /* terminate */
};
struct cgroup_subsys debug_subsys = {
.name = "debug",
.css_alloc = debug_css_alloc,
.css_free = debug_css_free,
.subsys_id = debug_subsys_id,
.base_cftypes = debug_files,
};
#endif /* CONFIG_CGROUP_DEBUG */