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OpenCloudOS-Kernel/kernel/cgroup.c

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/*
* Generic process-grouping system.
*
* Based originally on the cpuset system, extracted by Paul Menage
* Copyright (C) 2006 Google, Inc
*
* Notifications support
* Copyright (C) 2009 Nokia Corporation
* Author: Kirill A. Shutemov
*
* Copyright notices from the original cpuset code:
* --------------------------------------------------
* Copyright (C) 2003 BULL SA.
* Copyright (C) 2004-2006 Silicon Graphics, Inc.
*
* Portions derived from Patrick Mochel's sysfs code.
* sysfs is Copyright (c) 2001-3 Patrick Mochel
*
* 2003-10-10 Written by Simon Derr.
* 2003-10-22 Updates by Stephen Hemminger.
* 2004 May-July Rework by Paul Jackson.
* ---------------------------------------------------
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of the Linux
* distribution for more details.
*/
#include <linux/cgroup.h>
#include <linux/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/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/flex_array.h> /* used in cgroup_attach_task */
#include <linux/kthread.h>
#include <linux/atomic.h>
/*
* pidlists linger the following amount before being destroyed. The goal
* is avoiding frequent destruction in the middle of consecutive read calls
* Expiring in the middle is a performance problem not a correctness one.
* 1 sec should be enough.
*/
#define CGROUP_PIDLIST_DESTROY_DELAY HZ
/*
* 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 lockdep */
#else
static DEFINE_MUTEX(cgroup_mutex);
#endif
static DEFINE_MUTEX(cgroup_root_mutex);
#define cgroup_assert_mutex_or_rcu_locked() \
rcu_lockdep_assert(rcu_read_lock_held() || \
lockdep_is_held(&cgroup_mutex), \
"cgroup_mutex or RCU read lock required");
#ifdef CONFIG_LOCKDEP
#define cgroup_assert_mutex_or_root_locked() \
WARN_ON_ONCE(debug_locks && (!lockdep_is_held(&cgroup_mutex) && \
!lockdep_is_held(&cgroup_root_mutex)))
#else
#define cgroup_assert_mutex_or_root_locked() do { } while (0)
#endif
/*
* cgroup destruction makes heavy use of work items and there can be a lot
* of concurrent destructions. Use a separate workqueue so that cgroup
* destruction work items don't end up filling up max_active of system_wq
* which may lead to deadlock.
*/
static struct workqueue_struct *cgroup_destroy_wq;
/*
* pidlist destructions need to be flushed on cgroup destruction. Use a
* separate workqueue as flush domain.
*/
static struct workqueue_struct *cgroup_pidlist_destroy_wq;
/*
* 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 *cgroup_subsys[CGROUP_SUBSYS_COUNT] = {
#include <linux/cgroup_subsys.h>
};
/*
* 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 cgroup_dummy_root;
/* dummy_top is a shorthand for the dummy hierarchy's top cgroup */
static struct cgroup * const cgroup_dummy_top = &cgroup_dummy_root.top_cgroup;
/* The list of hierarchy roots */
static LIST_HEAD(cgroup_roots);
static int cgroup_root_count;
/*
* Hierarchy ID allocation and mapping. It follows the same exclusion
* rules as other root ops - both cgroup_mutex and cgroup_root_mutex for
* writes, either for reads.
*/
static DEFINE_IDR(cgroup_hierarchy_idr);
static struct cgroup_name root_cgroup_name = { .name = "/" };
/*
* Assign a monotonically increasing serial number to cgroups. It
* guarantees cgroups with bigger numbers are newer than those with smaller
* numbers. Also, as cgroups are always appended to the parent's
* ->children list, it guarantees that sibling cgroups are always sorted in
* the ascending serial number order on the list. Protected by
* cgroup_mutex.
*/
static u64 cgroup_serial_nr_next = 1;
/* 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 struct cftype cgroup_base_files[];
static void cgroup_destroy_css_killed(struct cgroup *cgrp);
static int cgroup_destroy_locked(struct cgroup *cgrp);
static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
bool is_add);
static int cgroup_file_release(struct inode *inode, struct file *file);
static void cgroup_pidlist_destroy_all(struct cgroup *cgrp);
/**
* cgroup_css - obtain a cgroup's css for the specified subsystem
* @cgrp: the cgroup of interest
* @ss: the subsystem of interest (%NULL returns the dummy_css)
*
* Return @cgrp's css (cgroup_subsys_state) associated with @ss. This
* function must be called either under cgroup_mutex or rcu_read_lock() and
* the caller is responsible for pinning the returned css if it wants to
* keep accessing it outside the said locks. This function may return
* %NULL if @cgrp doesn't have @subsys_id enabled.
*/
static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
struct cgroup_subsys *ss)
{
if (ss)
return rcu_dereference_check(cgrp->subsys[ss->subsys_id],
lockdep_is_held(&cgroup_mutex));
else
return &cgrp->dummy_css;
}
/* convenient tests for these bits */
static inline bool cgroup_is_dead(const struct cgroup *cgrp)
{
return test_bit(CGRP_DEAD, &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_css - iterate all css's of a cgroup
* @css: the iteration cursor
* @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
* @cgrp: the target cgroup to iterate css's of
*
* Should be called under cgroup_mutex.
*/
#define for_each_css(css, ssid, cgrp) \
for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
if (!((css) = rcu_dereference_check( \
(cgrp)->subsys[(ssid)], \
lockdep_is_held(&cgroup_mutex)))) { } \
else
/**
* for_each_subsys - iterate all loaded cgroup subsystems
* @ss: the iteration cursor
* @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
*
* Iterates through all loaded subsystems. Should be called under
* cgroup_mutex or cgroup_root_mutex.
*/
#define for_each_subsys(ss, ssid) \
for (({ cgroup_assert_mutex_or_root_locked(); (ssid) = 0; }); \
(ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
if (!((ss) = cgroup_subsys[(ssid)])) { } \
else
/**
* for_each_builtin_subsys - iterate all built-in cgroup subsystems
* @ss: the iteration cursor
* @i: the index of @ss, CGROUP_BUILTIN_SUBSYS_COUNT after reaching the end
*
* Bulit-in subsystems are always present and iteration itself doesn't
* require any synchronization.
*/
#define for_each_builtin_subsys(ss, i) \
for ((i) = 0; (i) < CGROUP_BUILTIN_SUBSYS_COUNT && \
(((ss) = cgroup_subsys[i]) || true); (i)++)
/* iterate across the active hierarchies */
#define for_each_active_root(root) \
list_for_each_entry((root), &cgroup_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_dead(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);
/*
* A cgroup can be associated with multiple css_sets as different tasks may
* belong to different cgroups on different hierarchies. In the other
* direction, a css_set is naturally associated with multiple cgroups.
* This M:N relationship is represented by the following link structure
* which exists for each association and allows traversing the associations
* from both sides.
*/
struct cgrp_cset_link {
/* the cgroup and css_set this link associates */
struct cgroup *cgrp;
struct css_set *cset;
/* list of cgrp_cset_links anchored at cgrp->cset_links */
struct list_head cset_link;
/* list of cgrp_cset_links anchored at css_set->cgrp_links */
struct list_head cgrp_link;
};
/* 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 cgrp_cset_link init_cgrp_cset_link;
/*
* css_set_lock protects the list of css_set objects, and the chain of
* tasks off each css_set. Nests outside task->alloc_lock due to
* css_task_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[])
{
unsigned long key = 0UL;
struct cgroup_subsys *ss;
int i;
for_each_subsys(ss, 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 css_task_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 *cset, int taskexit)
{
struct cgrp_cset_link *link, *tmp_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(&cset->refcount, -1, 1))
return;
write_lock(&css_set_lock);
if (!atomic_dec_and_test(&cset->refcount)) {
write_unlock(&css_set_lock);
return;
}
/* This css_set is dead. unlink it and release cgroup refcounts */
hash_del(&cset->hlist);
css_set_count--;
list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
struct cgroup *cgrp = link->cgrp;
list_del(&link->cset_link);
list_del(&link->cgrp_link);
/* @cgrp can't go away while we're holding css_set_lock */
if (list_empty(&cgrp->cset_links) && notify_on_release(cgrp)) {
if (taskexit)
set_bit(CGRP_RELEASABLE, &cgrp->flags);
check_for_release(cgrp);
}
kfree(link);
}
write_unlock(&css_set_lock);
kfree_rcu(cset, rcu_head);
}
/*
* refcounted get/put for css_set objects
*/
static inline void get_css_set(struct css_set *cset)
{
atomic_inc(&cset->refcount);
}
static inline void put_css_set(struct css_set *cset)
{
__put_css_set(cset, 0);
}
static inline void put_css_set_taskexit(struct css_set *cset)
{
__put_css_set(cset, 1);
}
/**
* compare_css_sets - helper function for find_existing_css_set().
* @cset: candidate css_set being tested
* @old_cset: 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 "cset" matches "old_cset" except for the hierarchy
* which "new_cgrp" belongs to, for which it should match "new_cgrp".
*/
static bool compare_css_sets(struct css_set *cset,
struct css_set *old_cset,
struct cgroup *new_cgrp,
struct cgroup_subsys_state *template[])
{
struct list_head *l1, *l2;
if (memcmp(template, cset->subsys, sizeof(cset->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 = &cset->cgrp_links;
l2 = &old_cset->cgrp_links;
while (1) {
struct cgrp_cset_link *link1, *link2;
struct cgroup *cgrp1, *cgrp2;
l1 = l1->next;
l2 = l2->next;
/* See if we reached the end - both lists are equal length. */
if (l1 == &cset->cgrp_links) {
BUG_ON(l2 != &old_cset->cgrp_links);
break;
} else {
BUG_ON(l2 == &old_cset->cgrp_links);
}
/* Locate the cgroups associated with these links. */
link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
cgrp1 = link1->cgrp;
cgrp2 = link2->cgrp;
/* Hierarchies should be linked in the same order. */
BUG_ON(cgrp1->root != cgrp2->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 (cgrp1->root == new_cgrp->root) {
if (cgrp1 != new_cgrp)
return false;
} else {
if (cgrp1 != cgrp2)
return false;
}
}
return true;
}
/**
* find_existing_css_set - init css array and find the matching css_set
* @old_cset: the css_set that we're using before the cgroup transition
* @cgrp: the cgroup that we're moving into
* @template: out param for the new set of csses, should be clear on entry
*/
static struct css_set *find_existing_css_set(struct css_set *old_cset,
struct cgroup *cgrp,
struct cgroup_subsys_state *template[])
{
struct cgroupfs_root *root = cgrp->root;
struct cgroup_subsys *ss;
struct css_set *cset;
unsigned long key;
int i;
/*
* 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_each_subsys(ss, i) {
if (root->subsys_mask & (1UL << i)) {
/* Subsystem is in this hierarchy. So we want
* the subsystem state from the new
* cgroup */
template[i] = cgroup_css(cgrp, ss);
} else {
/* Subsystem is not in this hierarchy, so we
* don't want to change the subsystem state */
template[i] = old_cset->subsys[i];
}
}
key = css_set_hash(template);
hash_for_each_possible(css_set_table, cset, hlist, key) {
if (!compare_css_sets(cset, old_cset, cgrp, template))
continue;
/* This css_set matches what we need */
return cset;
}
/* No existing cgroup group matched */
return NULL;
}
static void free_cgrp_cset_links(struct list_head *links_to_free)
{
struct cgrp_cset_link *link, *tmp_link;
list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
list_del(&link->cset_link);
kfree(link);
}
}
/**
* allocate_cgrp_cset_links - allocate cgrp_cset_links
* @count: the number of links to allocate
* @tmp_links: list_head the allocated links are put on
*
* Allocate @count cgrp_cset_link structures and chain them on @tmp_links
* through ->cset_link. Returns 0 on success or -errno.
*/
static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
{
struct cgrp_cset_link *link;
int i;
INIT_LIST_HEAD(tmp_links);
for (i = 0; i < count; i++) {
link = kzalloc(sizeof(*link), GFP_KERNEL);
if (!link) {
free_cgrp_cset_links(tmp_links);
return -ENOMEM;
}
list_add(&link->cset_link, tmp_links);
}
return 0;
}
/**
* link_css_set - a helper function to link a css_set to a cgroup
* @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
* @cset: the css_set to be linked
* @cgrp: the destination cgroup
*/
static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
struct cgroup *cgrp)
{
struct cgrp_cset_link *link;
BUG_ON(list_empty(tmp_links));
link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
link->cset = cset;
link->cgrp = cgrp;
list_move(&link->cset_link, &cgrp->cset_links);
/*
* Always add links to the tail of the list so that the list
* is sorted by order of hierarchy creation
*/
list_add_tail(&link->cgrp_link, &cset->cgrp_links);
}
/**
* find_css_set - return a new css_set with one cgroup updated
* @old_cset: the baseline css_set
* @cgrp: the cgroup to be updated
*
* Return a new css_set that's equivalent to @old_cset, but with @cgrp
* substituted into the appropriate hierarchy.
*/
static struct css_set *find_css_set(struct css_set *old_cset,
struct cgroup *cgrp)
{
struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
struct css_set *cset;
struct list_head tmp_links;
struct cgrp_cset_link *link;
unsigned long key;
lockdep_assert_held(&cgroup_mutex);
/* First see if we already have a cgroup group that matches
* the desired set */
read_lock(&css_set_lock);
cset = find_existing_css_set(old_cset, cgrp, template);
if (cset)
get_css_set(cset);
read_unlock(&css_set_lock);
if (cset)
return cset;
cset = kzalloc(sizeof(*cset), GFP_KERNEL);
if (!cset)
return NULL;
/* Allocate all the cgrp_cset_link objects that we'll need */
if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
kfree(cset);
return NULL;
}
atomic_set(&cset->refcount, 1);
INIT_LIST_HEAD(&cset->cgrp_links);
INIT_LIST_HEAD(&cset->tasks);
INIT_HLIST_NODE(&cset->hlist);
/* Copy the set of subsystem state objects generated in
* find_existing_css_set() */
memcpy(cset->subsys, template, sizeof(cset->subsys));
write_lock(&css_set_lock);
/* Add reference counts and links from the new css_set. */
list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
struct cgroup *c = link->cgrp;
if (c->root == cgrp->root)
c = cgrp;
link_css_set(&tmp_links, cset, c);
}
BUG_ON(!list_empty(&tmp_links));
css_set_count++;
/* Add this cgroup group to the hash table */
key = css_set_hash(cset->subsys);
hash_add(css_set_table, &cset->hlist, key);
write_unlock(&css_set_lock);
return cset;
}
/*
* 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 *cset;
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.
*/
cset = task_css_set(task);
if (cset == &init_css_set) {
res = &root->top_cgroup;
} else {
struct cgrp_cset_link *link;
list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
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 int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
static int cgroup_populate_dir(struct cgroup *cgrp, 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 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, destroy_work);
mutex_lock(&cgroup_mutex);
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);
/*
* 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);
cgroup_pidlist_destroy_all(cgrp);
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);
INIT_WORK(&cgrp->destroy_work, cgroup_free_fn);
queue_work(cgroup_destroy_wq, &cgrp->destroy_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_dead(cgrp)));
/*
* XXX: cgrp->id is only used to look up css's. As cgroup
* and css's lifetimes will be decoupled, it should be made
* per-subsystem and moved to css->id so that lookups are
* successful until the target css is released.
*/
mutex_lock(&cgroup_mutex);
idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
mutex_unlock(&cgroup_mutex);
cgrp->id = -1;
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 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_dir - remove subsys files in a cgroup directory
* @cgrp: target cgroup
* @subsys_mask: mask of the subsystem ids whose files should be removed
*/
static void cgroup_clear_dir(struct cgroup *cgrp, unsigned long subsys_mask)
{
struct cgroup_subsys *ss;
int i;
for_each_subsys(ss, i) {
struct cftype_set *set;
if (!test_bit(i, &subsys_mask))
continue;
list_for_each_entry(set, &ss->cftsets, node)
cgroup_addrm_files(cgrp, set->cfts, false);
}
}
/*
* NOTE : the dentry must have been dget()'ed
*/
static void cgroup_d_remove_dir(struct dentry *dentry)
{
struct dentry *parent;
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 added_mask, unsigned removed_mask)
{
struct cgroup *cgrp = &root->top_cgroup;
struct cgroup_subsys *ss;
unsigned long pinned = 0;
int i, ret;
BUG_ON(!mutex_is_locked(&cgroup_mutex));
BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
/* Check that any added subsystems are currently free */
for_each_subsys(ss, i) {
if (!(added_mask & (1 << i)))
continue;
/* is the subsystem mounted elsewhere? */
if (ss->root != &cgroup_dummy_root) {
ret = -EBUSY;
goto out_put;
}
/* pin the module */
if (!try_module_get(ss->module)) {
ret = -ENOENT;
goto out_put;
}
pinned |= 1 << i;
}
/* subsys could be missing if unloaded between parsing and here */
if (added_mask != pinned) {
ret = -ENOENT;
goto out_put;
}
ret = cgroup_populate_dir(cgrp, added_mask);
if (ret)
goto out_put;
/*
* Nothing can fail from this point on. Remove files for the
* removed subsystems and rebind each subsystem.
*/
cgroup_clear_dir(cgrp, removed_mask);
for_each_subsys(ss, i) {
unsigned long bit = 1UL << i;
if (bit & added_mask) {
/* We're binding this subsystem to this hierarchy */
BUG_ON(cgroup_css(cgrp, ss));
BUG_ON(!cgroup_css(cgroup_dummy_top, ss));
BUG_ON(cgroup_css(cgroup_dummy_top, ss)->cgroup != cgroup_dummy_top);
rcu_assign_pointer(cgrp->subsys[i],
cgroup_css(cgroup_dummy_top, ss));
cgroup_css(cgrp, ss)->cgroup = cgrp;
ss->root = root;
if (ss->bind)
ss->bind(cgroup_css(cgrp, ss));
/* refcount was already taken, and we're keeping it */
root->subsys_mask |= bit;
} else if (bit & removed_mask) {
/* We're removing this subsystem */
BUG_ON(cgroup_css(cgrp, ss) != cgroup_css(cgroup_dummy_top, ss));
BUG_ON(cgroup_css(cgrp, ss)->cgroup != cgrp);
if (ss->bind)
ss->bind(cgroup_css(cgroup_dummy_top, ss));
cgroup_css(cgroup_dummy_top, ss)->cgroup = cgroup_dummy_top;
RCU_INIT_POINTER(cgrp->subsys[i], NULL);
cgroup_subsys[i]->root = &cgroup_dummy_root;
/* subsystem is now free - drop reference on module */
module_put(ss->module);
root->subsys_mask &= ~bit;
}
}
/*
* Mark @root has finished binding subsystems. @root->subsys_mask
* now matches the bound subsystems.
*/
root->flags |= CGRP_ROOT_SUBSYS_BOUND;
return 0;
out_put:
for_each_subsys(ss, i)
if (pinned & (1 << i))
module_put(ss->module);
return ret;
}
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;
int ssid;
mutex_lock(&cgroup_root_mutex);
for_each_subsys(ss, ssid)
if (root->subsys_mask & (1 << ssid))
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 cgroup_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;
struct cgroup_subsys *ss;
int i;
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_each_subsys(ss, i) {
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_each_subsys(ss, i)
if (!ss->disabled)
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;
return 0;
}
static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
int ret = 0;
struct cgroupfs_root *root = sb->s_fs_info;
struct cgroup *cgrp = &root->top_cgroup;
struct cgroup_sb_opts opts;
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->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) & CGRP_ROOT_OPTION_MASK) ||
(opts.name && strcmp(opts.name, root->name))) {
pr_err("cgroup: option or name mismatch, new: 0x%lx \"%s\", old: 0x%lx \"%s\"\n",
opts.flags & CGRP_ROOT_OPTION_MASK, opts.name ?: "",
root->flags & CGRP_ROOT_OPTION_MASK, root->name);
ret = -EINVAL;
goto out_unlock;
}
/* remounting is not allowed for populated hierarchies */
if (root->number_of_cgroups > 1) {
ret = -EBUSY;
goto out_unlock;
}
ret = rebind_subsystems(root, added_mask, removed_mask);
if (ret)
goto out_unlock;
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->cset_links);
INIT_LIST_HEAD(&cgrp->release_list);
INIT_LIST_HEAD(&cgrp->pidlists);
mutex_init(&cgrp->pidlist_mutex);
cgrp->dummy_css.cgroup = cgrp;
simple_xattrs_init(&cgrp->xattrs);
}
static void init_cgroup_root(struct cgroupfs_root *root)
{
struct cgroup *cgrp = &root->top_cgroup;
INIT_LIST_HEAD(&root->root_list);
root->number_of_cgroups = 1;
cgrp->root = root;
RCU_INIT_POINTER(cgrp->name, &root_cgroup_name);
init_cgroup_housekeeping(cgrp);
idr_init(&root->cgroup_idr);
}
static int cgroup_init_root_id(struct cgroupfs_root *root, int start, int end)
{
int id;
lockdep_assert_held(&cgroup_mutex);
lockdep_assert_held(&cgroup_root_mutex);
id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, start, end,
GFP_KERNEL);
if (id < 0)
return id;
root->hierarchy_id = id;
return 0;
}
static void cgroup_exit_root_id(struct cgroupfs_root *root)
{
lockdep_assert_held(&cgroup_mutex);
lockdep_assert_held(&cgroup_root_mutex);
if (root->hierarchy_id) {
idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
root->hierarchy_id = 0;
}
}
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);
init_cgroup_root(root);
/*
* We need to set @root->subsys_mask now so that @root can be
* matched by cgroup_test_super() before it finishes
* initialization; otherwise, competing mounts with the same
* options may try to bind the same subsystems instead of waiting
* for the first one leading to unexpected mount errors.
* SUBSYS_BOUND will be set once actual binding is complete.
*/
root->subsys_mask = opts->subsys_mask;
root->flags = opts->flags;
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_free_root(struct cgroupfs_root *root)
{
if (root) {
/* hierarhcy ID shoulid already have been released */
WARN_ON_ONCE(root->hierarchy_id);
idr_destroy(&root->cgroup_idr);
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 = always_delete_dentry,
};
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 list_head tmp_links;
struct inode *inode;
const struct cred *cred;
/* 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 out_err;
}
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_free_root(opts.new_root);
goto out_err;
}
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 cgroup *root_cgrp = &root->top_cgroup;
struct cgroupfs_root *existing_root;
int i;
struct css_set *cset;
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);
ret = idr_alloc(&root->cgroup_idr, root_cgrp, 0, 1, GFP_KERNEL);
if (ret < 0)
goto unlock_drop;
root_cgrp->id = ret;
/* 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_cgrp_cset_links(css_set_count, &tmp_links);
if (ret)
goto unlock_drop;
/* ID 0 is reserved for dummy root, 1 for unified hierarchy */
ret = cgroup_init_root_id(root, 2, 0);
if (ret)
goto unlock_drop;
sb->s_root->d_fsdata = root_cgrp;
root_cgrp->dentry = sb->s_root;
/*
* We're inside get_sb() and will call lookup_one_len() to
* create the root files, which doesn't work if SELinux is
* in use. The following cred dancing somehow works around
* it. See 2ce9738ba ("cgroupfs: use init_cred when
* populating new cgroupfs mount") for more details.
*/
cred = override_creds(&init_cred);
ret = cgroup_addrm_files(root_cgrp, cgroup_base_files, true);
if (ret)
goto rm_base_files;
ret = rebind_subsystems(root, root->subsys_mask, 0);
if (ret)
goto rm_base_files;
revert_creds(cred);
/*
* There must be no failure case after here, since rebinding
* takes care of subsystems' refcounts, which are explicitly
* dropped in the failure exit path.
*/
list_add(&root->root_list, &cgroup_roots);
cgroup_root_count++;
/* 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, cset, hlist)
link_css_set(&tmp_links, cset, root_cgrp);
write_unlock(&css_set_lock);
free_cgrp_cset_links(&tmp_links);
BUG_ON(!list_empty(&root_cgrp->children));
BUG_ON(root->number_of_cgroups != 1);
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_free_root(opts.new_root);
if ((root->flags ^ opts.flags) & CGRP_ROOT_OPTION_MASK) {
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");
}
}
}
kfree(opts.release_agent);
kfree(opts.name);
return dget(sb->s_root);
rm_base_files:
free_cgrp_cset_links(&tmp_links);
cgroup_addrm_files(&root->top_cgroup, cgroup_base_files, false);
revert_creds(cred);
unlock_drop:
cgroup_exit_root_id(root);
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);
drop_new_super:
deactivate_locked_super(sb);
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;
struct cgrp_cset_link *link, *tmp_link;
int ret;
BUG_ON(!root);
BUG_ON(root->number_of_cgroups != 1);
BUG_ON(!list_empty(&cgrp->children));
mutex_lock(&cgrp->dentry->d_inode->i_mutex);
mutex_lock(&cgroup_mutex);
mutex_lock(&cgroup_root_mutex);
/* Rebind all subsystems back to the default hierarchy */
if (root->flags & CGRP_ROOT_SUBSYS_BOUND) {
ret = rebind_subsystems(root, 0, root->subsys_mask);
/* Shouldn't be able to fail ... */
BUG_ON(ret);
}
/*
* Release all the links from cset_links to this hierarchy's
* root cgroup
*/
write_lock(&css_set_lock);
list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
list_del(&link->cset_link);
list_del(&link->cgrp_link);
kfree(link);
}
write_unlock(&css_set_lock);
if (!list_empty(&root->root_list)) {
list_del(&root->root_list);
cgroup_root_count--;
}
cgroup_exit_root_id(root);
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
simple_xattrs_free(&cgrp->xattrs);
kill_litter_super(sb);
cgroup_free_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);
/**
* task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
* @task: target task
* @buf: the buffer to write the path into
* @buflen: the length of the buffer
*
* Determine @task's cgroup on the first (the one with the lowest non-zero
* hierarchy_id) cgroup hierarchy and copy its path into @buf. This
* function grabs cgroup_mutex and shouldn't be used inside locks used by
* cgroup controller callbacks.
*
* Returns 0 on success, fails with -%ENAMETOOLONG if @buflen is too short.
*/
int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
{
struct cgroupfs_root *root;
struct cgroup *cgrp;
int hierarchy_id = 1, ret = 0;
if (buflen < 2)
return -ENAMETOOLONG;
mutex_lock(&cgroup_mutex);
root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
if (root) {
cgrp = task_cgroup_from_root(task, root);
ret = cgroup_path(cgrp, buf, buflen);
} else {
/* if no hierarchy exists, everyone is in "/" */
memcpy(buf, "/", 2);
}
mutex_unlock(&cgroup_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(task_cgroup_path);
/*
* Control Group taskset
*/
struct task_and_cgroup {
struct task_struct *task;
struct cgroup *cgrp;
struct css_set *cset;
};
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_css - return the matching css for the current task
* @tset: taskset of interest
* @subsys_id: the ID of the target subsystem
*
* Return the css for the current (last returned) task of @tset for
* subsystem specified by @subsys_id. This function must be preceded by
* either cgroup_taskset_first() or cgroup_taskset_next().
*/
struct cgroup_subsys_state *cgroup_taskset_cur_css(struct cgroup_taskset *tset,
int subsys_id)
{
return cgroup_css(tset->cur_cgrp, cgroup_subsys[subsys_id]);
}
EXPORT_SYMBOL_GPL(cgroup_taskset_cur_css);
/**
* 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 *old_cgrp,
struct task_struct *tsk,
struct css_set *new_cset)
{
struct css_set *old_cset;
/*
* 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);
old_cset = task_css_set(tsk);
task_lock(tsk);
rcu_assign_pointer(tsk->cgroups, new_cset);
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, &new_cset->tasks);
write_unlock(&css_set_lock);
/*
* We just gained a reference on old_cset by taking it from the
* task. As trading it for new_cset is protected by cgroup_mutex,
* we're safe to drop it here; it will be freed under RCU.
*/
set_bit(CGRP_RELEASABLE, &old_cgrp->flags);
put_css_set(old_cset);
}
/**
* 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 cgroupfs_root *root = cgrp->root;
struct cgroup_subsys_state *css, *failed_css = NULL;
/* 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)
goto next;
/* 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)
goto next;
/*
* 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++;
next:
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_css(css, i, cgrp) {
if (css->ss->can_attach) {
retval = css->ss->can_attach(css, &tset);
if (retval) {
failed_css = css;
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++) {
struct css_set *old_cset;
tc = flex_array_get(group, i);
old_cset = task_css_set(tc->task);
tc->cset = find_css_set(old_cset, cgrp);
if (!tc->cset) {
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->cset);
}
/* nothing is sensitive to fork() after this point. */
/*
* step 4: do subsystem attach callbacks.
*/
for_each_css(css, i, cgrp)
if (css->ss->attach)
css->ss->attach(css, &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->cset)
break;
put_css_set(tc->cset);
}
}
out_cancel_attach:
if (retval) {
for_each_css(css, i, cgrp) {
if (css == failed_css)
break;
if (css->ss->cancel_attach)
css->ss->cancel_attach(css, &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_cgrp = task_cgroup_from_root(from, root);
retval = cgroup_attach_task(from_cgrp, 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_subsys_state *css,
struct cftype *cft, u64 pid)
{
return attach_task_by_pid(css->cgroup, pid, false);
}
static int cgroup_procs_write(struct cgroup_subsys_state *css,
struct cftype *cft, u64 tgid)
{
return attach_task_by_pid(css->cgroup, tgid, true);
}
static int cgroup_release_agent_write(struct cgroup_subsys_state *css,
struct cftype *cft, const char *buffer)
{
BUILD_BUG_ON(sizeof(css->cgroup->root->release_agent_path) < PATH_MAX);
if (strlen(buffer) >= PATH_MAX)
return -EINVAL;
if (!cgroup_lock_live_group(css->cgroup))
return -ENODEV;
mutex_lock(&cgroup_root_mutex);
strcpy(css->cgroup->root->release_agent_path, buffer);
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
return 0;
}
static int cgroup_release_agent_show(struct seq_file *seq, void *v)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
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 seq_file *seq, void *v)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
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_file_write(struct file *file, const char __user *userbuf,
size_t nbytes, loff_t *ppos)
{
struct cfent *cfe = __d_cfe(file->f_dentry);
struct cftype *cft = __d_cft(file->f_dentry);
struct cgroup_subsys_state *css = cfe->css;
size_t max_bytes = cft->max_write_len ?: CGROUP_LOCAL_BUFFER_SIZE - 1;
char *buf;
int ret;
if (nbytes >= max_bytes)
return -E2BIG;
buf = kmalloc(nbytes + 1, GFP_KERNEL);
if (!buf)
return -ENOMEM;
if (copy_from_user(buf, userbuf, nbytes)) {
ret = -EFAULT;
goto out_free;
}
buf[nbytes] = '\0';
if (cft->write_string) {
ret = cft->write_string(css, cft, strstrip(buf));
} else if (cft->write_u64) {
unsigned long long v;
ret = kstrtoull(buf, 0, &v);
if (!ret)
ret = cft->write_u64(css, cft, v);
} else if (cft->write_s64) {
long long v;
ret = kstrtoll(buf, 0, &v);
if (!ret)
ret = cft->write_s64(css, cft, v);
} else if (cft->trigger) {
ret = cft->trigger(css, (unsigned int)cft->private);
} else {
ret = -EINVAL;
}
out_free:
kfree(buf);
return ret ?: nbytes;
}
/*
* seqfile ops/methods for returning structured data. Currently just
* supports string->u64 maps, but can be extended in future.
*/
static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
{
struct cftype *cft = seq_cft(seq);
if (cft->seq_start) {
return cft->seq_start(seq, ppos);
} else {
/*
* The same behavior and code as single_open(). Returns
* !NULL if pos is at the beginning; otherwise, NULL.
*/
return NULL + !*ppos;
}
}
static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
{
struct cftype *cft = seq_cft(seq);
if (cft->seq_next) {
return cft->seq_next(seq, v, ppos);
} else {
/*
* The same behavior and code as single_open(), always
* terminate after the initial read.
*/
++*ppos;
return NULL;
}
}
static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
{
struct cftype *cft = seq_cft(seq);
if (cft->seq_stop)
cft->seq_stop(seq, v);
}
static int cgroup_seqfile_show(struct seq_file *m, void *arg)
{
struct cftype *cft = seq_cft(m);
struct cgroup_subsys_state *css = seq_css(m);
if (cft->seq_show)
return cft->seq_show(m, arg);
if (cft->read_u64)
seq_printf(m, "%llu\n", cft->read_u64(css, cft));
else if (cft->read_s64)
seq_printf(m, "%lld\n", cft->read_s64(css, cft));
else
return -EINVAL;
return 0;
}
static struct seq_operations cgroup_seq_operations = {
.start = cgroup_seqfile_start,
.next = cgroup_seqfile_next,
.stop = cgroup_seqfile_stop,
.show = cgroup_seqfile_show,
};
static int cgroup_file_open(struct inode *inode, struct file *file)
{
struct cfent *cfe = __d_cfe(file->f_dentry);
struct cftype *cft = __d_cft(file->f_dentry);
struct cgroup *cgrp = __d_cgrp(cfe->dentry->d_parent);
struct cgroup_subsys_state *css;
struct cgroup_open_file *of;
int err;
err = generic_file_open(inode, file);
if (err)
return err;
/*
* If the file belongs to a subsystem, pin the css. Will be
* unpinned either on open failure or release. This ensures that
* @css stays alive for all file operations.
*/
rcu_read_lock();
css = cgroup_css(cgrp, cft->ss);
if (cft->ss && !css_tryget(css))
css = NULL;
rcu_read_unlock();
if (!css)
return -ENODEV;
/*
* @cfe->css is used by read/write/close to determine the
* associated css. @file->private_data would be a better place but
* that's already used by seqfile. Multiple accessors may use it
* simultaneously which is okay as the association never changes.
*/
WARN_ON_ONCE(cfe->css && cfe->css != css);
cfe->css = css;
of = __seq_open_private(file, &cgroup_seq_operations,
sizeof(struct cgroup_open_file));
if (of) {
of->cfe = cfe;
return 0;
}
if (css->ss)
css_put(css);
return -ENOMEM;
}
static int cgroup_file_release(struct inode *inode, struct file *file)
{
struct cfent *cfe = __d_cfe(file->f_dentry);
struct cgroup_subsys_state *css = cfe->css;
if (css->ss)
css_put(css);
return seq_release_private(inode, file);
}
/*
* 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);
/*
* This isn't a proper migration and its usefulness is very
* limited. Disallow if sane_behavior.
*/
if (cgroup_sane_behavior(cgrp))
return -EPERM;
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 = rcu_dereference_protected(cgrp->name, true);
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 = seq_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 = simple_lookup,
.mkdir = cgroup_mkdir,
.rmdir = cgroup_rmdir,
.rename = cgroup_rename,
.setxattr = cgroup_setxattr,
.getxattr = cgroup_getxattr,
.listxattr = cgroup_listxattr,
.removexattr = cgroup_removexattr,
};
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_u64 || cft->read_s64 || cft->seq_show)
mode |= S_IRUGO;
if (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 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 (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
!(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
strcpy(name, cft->ss->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;
}
/**
* cgroup_addrm_files - add or remove files to a cgroup directory
* @cgrp: the target cgroup
* @cfts: array of cftypes to be added
* @is_add: whether to add or remove
*
* Depending on @is_add, add or remove files defined by @cfts on @cgrp.
* For removals, this function never fails. If addition fails, this
* function doesn't remove files already added. The caller is responsible
* for cleaning up.
*/
static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
bool is_add)
{
struct cftype *cft;
int ret;
lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
lockdep_assert_held(&cgroup_mutex);
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) {
ret = cgroup_add_file(cgrp, cft);
if (ret) {
pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
cft->name, ret);
return ret;
}
} else {
cgroup_rm_file(cgrp, cft);
}
}
return 0;
}
static void cgroup_cfts_prepare(void)
__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 use css_for_each_descendant_pre() and drop RCU read
* lock before calling cgroup_addrm_files().
*/
mutex_lock(&cgroup_mutex);
}
static int cgroup_cfts_commit(struct cftype *cfts, bool is_add)
__releases(&cgroup_mutex)
{
LIST_HEAD(pending);
struct cgroup_subsys *ss = cfts[0].ss;
struct cgroup *root = &ss->root->top_cgroup;
struct super_block *sb = ss->root->sb;
struct dentry *prev = NULL;
struct inode *inode;
struct cgroup_subsys_state *css;
u64 update_before;
int ret = 0;
/* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
if (!cfts || ss->root == &cgroup_dummy_root ||
!atomic_inc_not_zero(&sb->s_active)) {
mutex_unlock(&cgroup_mutex);
return 0;
}
/*
* All cgroups which are created after we drop cgroup_mutex will
* have the updated set of files, so we only need to update the
* cgroups created before the current @cgroup_serial_nr_next.
*/
update_before = cgroup_serial_nr_next;
/* add/rm files for all cgroups created before */
css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
struct cgroup *cgrp = css->cgroup;
if (cgroup_is_dead(cgrp))
continue;
inode = cgrp->dentry->d_inode;
dget(cgrp->dentry);
dput(prev);
prev = cgrp->dentry;
mutex_unlock(&cgroup_mutex);
mutex_lock(&inode->i_mutex);
mutex_lock(&cgroup_mutex);
if (cgrp->serial_nr < update_before && !cgroup_is_dead(cgrp))
ret = cgroup_addrm_files(cgrp, cfts, is_add);
mutex_unlock(&inode->i_mutex);
if (ret)
break;
}
mutex_unlock(&cgroup_mutex);
dput(prev);
deactivate_super(sb);
return ret;
}
/**
* 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;
struct cftype *cft;
int ret;
set = kzalloc(sizeof(*set), GFP_KERNEL);
if (!set)
return -ENOMEM;
for (cft = cfts; cft->name[0] != '\0'; cft++)
cft->ss = ss;
cgroup_cfts_prepare();
set->cfts = cfts;
list_add_tail(&set->node, &ss->cftsets);
ret = cgroup_cfts_commit(cfts, true);
if (ret)
cgroup_rm_cftypes(cfts);
return ret;
}
EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
/**
* cgroup_rm_cftypes - remove an array of cftypes from a subsystem
* @cfts: zero-length name terminated array of cftypes
*
* Unregister @cfts. Files described by @cfts are removed from all
* existing cgroups and all future cgroups won't have them either. This
* function can be called anytime whether @cfts' subsys is attached or not.
*
* Returns 0 on successful unregistration, -ENOENT if @cfts is not
* registered.
*/
int cgroup_rm_cftypes(struct cftype *cfts)
{
struct cftype_set *set;
if (!cfts || !cfts[0].ss)
return -ENOENT;
cgroup_cfts_prepare();
list_for_each_entry(set, &cfts[0].ss->cftsets, node) {
if (set->cfts == cfts) {
list_del(&set->node);
kfree(set);
cgroup_cfts_commit(cfts, false);
return 0;
}
}
cgroup_cfts_commit(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 cgrp_cset_link *link;
read_lock(&css_set_lock);
list_for_each_entry(link, &cgrp->cset_links, cset_link)
count += atomic_read(&link->cset->refcount);
read_unlock(&css_set_lock);
return count;
}
/*
* 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 css_task_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.
* Do it while holding siglock so that we don't end up
* racing against cgroup_exit().
*/
spin_lock_irq(&p->sighand->siglock);
if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
list_add(&p->cg_list, &task_css_set(p)->tasks);
spin_unlock_irq(&p->sighand->siglock);
task_unlock(p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
write_unlock(&css_set_lock);
}
/**
* css_next_child - find the next child of a given css
* @pos_css: the current position (%NULL to initiate traversal)
* @parent_css: css whose children to walk
*
* This function returns the next child of @parent_css and should be called
* under either cgroup_mutex or RCU read lock. The only requirement is
* that @parent_css and @pos_css are accessible. The next sibling is
* guaranteed to be returned regardless of their states.
*/
struct cgroup_subsys_state *
css_next_child(struct cgroup_subsys_state *pos_css,
struct cgroup_subsys_state *parent_css)
{
struct cgroup *pos = pos_css ? pos_css->cgroup : NULL;
struct cgroup *cgrp = parent_css->cgroup;
struct cgroup *next;
cgroup_assert_mutex_or_rcu_locked();
/*
* @pos could already have been removed. Once a cgroup is removed,
* its ->sibling.next is no longer updated when its next sibling
* changes. As CGRP_DEAD assertion is serialized and happens
* before the cgroup is taken off the ->sibling list, if we see it
* unasserted, it's guaranteed that the next sibling hasn't
* finished its grace period even if it's already removed, and thus
* safe to dereference from this RCU critical section. If
* ->sibling.next is inaccessible, cgroup_is_dead() is guaranteed
* to be visible as %true here.
*
* If @pos is dead, its next pointer can't be dereferenced;
* however, as each cgroup is given a monotonically increasing
* unique serial number and always appended to the sibling list,
* the next one can be found by walking the parent's children until
* we see a cgroup with higher serial number than @pos's. While
* this path can be slower, it's taken only when either the current
* cgroup is removed or iteration and removal race.
*/
if (!pos) {
next = list_entry_rcu(cgrp->children.next, struct cgroup, sibling);
} else if (likely(!cgroup_is_dead(pos))) {
next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
} else {
list_for_each_entry_rcu(next, &cgrp->children, sibling)
if (next->serial_nr > pos->serial_nr)
break;
}
if (&next->sibling == &cgrp->children)
return NULL;
return cgroup_css(next, parent_css->ss);
}
EXPORT_SYMBOL_GPL(css_next_child);
/**
* css_next_descendant_pre - find the next descendant for pre-order walk
* @pos: the current position (%NULL to initiate traversal)
* @root: css whose descendants to walk
*
* To be used by css_for_each_descendant_pre(). Find the next descendant
* to visit for pre-order traversal of @root's descendants. @root is
* included in the iteration and the first node to be visited.
*
* While this function requires cgroup_mutex or RCU read locking, it
* doesn't require the whole traversal to be contained in a single critical
* section. This function will return the correct next descendant as long
* as both @pos and @root are accessible and @pos is a descendant of @root.
*/
struct cgroup_subsys_state *
css_next_descendant_pre(struct cgroup_subsys_state *pos,
struct cgroup_subsys_state *root)
{
struct cgroup_subsys_state *next;
cgroup_assert_mutex_or_rcu_locked();
/* if first iteration, visit @root */
if (!pos)
return root;
/* visit the first child if exists */
next = css_next_child(NULL, pos);
if (next)
return next;
/* no child, visit my or the closest ancestor's next sibling */
while (pos != root) {
next = css_next_child(pos, css_parent(pos));
if (next)
return next;
pos = css_parent(pos);
}
return NULL;
}
EXPORT_SYMBOL_GPL(css_next_descendant_pre);
/**
* css_rightmost_descendant - return the rightmost descendant of a css
* @pos: css 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.
*
* While this function requires cgroup_mutex or RCU read locking, it
* doesn't require the whole traversal to be contained in a single critical
* section. This function will return the correct rightmost descendant as
* long as @pos is accessible.
*/
struct cgroup_subsys_state *
css_rightmost_descendant(struct cgroup_subsys_state *pos)
{
struct cgroup_subsys_state *last, *tmp;
cgroup_assert_mutex_or_rcu_locked();
do {
last = pos;
/* ->prev isn't RCU safe, walk ->next till the end */
pos = NULL;
css_for_each_child(tmp, last)
pos = tmp;
} while (pos);
return last;
}
EXPORT_SYMBOL_GPL(css_rightmost_descendant);
static struct cgroup_subsys_state *
css_leftmost_descendant(struct cgroup_subsys_state *pos)
{
struct cgroup_subsys_state *last;
do {
last = pos;
pos = css_next_child(NULL, pos);
} while (pos);
return last;
}
/**
* css_next_descendant_post - find the next descendant for post-order walk
* @pos: the current position (%NULL to initiate traversal)
* @root: css whose descendants to walk
*
* To be used by css_for_each_descendant_post(). Find the next descendant
* to visit for post-order traversal of @root's descendants. @root is
* included in the iteration and the last node to be visited.
*
* While this function requires cgroup_mutex or RCU read locking, it
* doesn't require the whole traversal to be contained in a single critical
* section. This function will return the correct next descendant as long
* as both @pos and @cgroup are accessible and @pos is a descendant of
* @cgroup.
*/
struct cgroup_subsys_state *
css_next_descendant_post(struct cgroup_subsys_state *pos,
struct cgroup_subsys_state *root)
{
struct cgroup_subsys_state *next;
cgroup_assert_mutex_or_rcu_locked();
/* if first iteration, visit leftmost descendant which may be @root */
if (!pos)
return css_leftmost_descendant(root);
/* if we visited @root, we're done */
if (pos == root)
return NULL;
/* if there's an unvisited sibling, visit its leftmost descendant */
next = css_next_child(pos, css_parent(pos));
if (next)
return css_leftmost_descendant(next);
/* no sibling left, visit parent */
return css_parent(pos);
}
EXPORT_SYMBOL_GPL(css_next_descendant_post);
/**
* css_advance_task_iter - advance a task itererator to the next css_set
* @it: the iterator to advance
*
* Advance @it to the next css_set to walk.
*/
static void css_advance_task_iter(struct css_task_iter *it)
{
struct list_head *l = it->cset_link;
struct cgrp_cset_link *link;
struct css_set *cset;
/* Advance to the next non-empty css_set */
do {
l = l->next;
if (l == &it->origin_css->cgroup->cset_links) {
it->cset_link = NULL;
return;
}
link = list_entry(l, struct cgrp_cset_link, cset_link);
cset = link->cset;
} while (list_empty(&cset->tasks));
it->cset_link = l;
it->task = cset->tasks.next;
}
/**
* css_task_iter_start - initiate task iteration
* @css: the css to walk tasks of
* @it: the task iterator to use
*
* Initiate iteration through the tasks of @css. The caller can call
* css_task_iter_next() to walk through the tasks until the function
* returns NULL. On completion of iteration, css_task_iter_end() must be
* called.
*
* Note that this function acquires a lock which is released when the
* iteration finishes. The caller can't sleep while iteration is in
* progress.
*/
void css_task_iter_start(struct cgroup_subsys_state *css,
struct css_task_iter *it)
__acquires(css_set_lock)
{
/*
* The first time anyone tries to iterate across a css, 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->origin_css = css;
it->cset_link = &css->cgroup->cset_links;
css_advance_task_iter(it);
}
/**
* css_task_iter_next - return the next task for the iterator
* @it: the task iterator being iterated
*
* The "next" function for task iteration. @it should have been
* initialized via css_task_iter_start(). Returns NULL when the iteration
* reaches the end.
*/
struct task_struct *css_task_iter_next(struct css_task_iter *it)
{
struct task_struct *res;
struct list_head *l = it->task;
struct cgrp_cset_link *link;
/* If the iterator cg is NULL, we have no tasks */
if (!it->cset_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->cset_link, struct cgrp_cset_link, cset_link);
if (l == &link->cset->tasks) {
/*
* We reached the end of this task list - move on to the
* next cgrp_cset_link.
*/
css_advance_task_iter(it);
} else {
it->task = l;
}
return res;
}
/**
* css_task_iter_end - finish task iteration
* @it: the task iterator to finish
*
* Finish task iteration started by css_task_iter_start().
*/
void css_task_iter_end(struct css_task_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);
}
/**
* css_scan_tasks - iterate though all the tasks in a css
* @css: the css to iterate tasks of
* @test: optional test callback
* @process: process callback
* @data: data passed to @test and @process
* @heap: optional pre-allocated heap used for task iteration
*
* Iterate through all the tasks in @css, calling @test for each, and if it
* returns %true, call @process for it also.
*
* @test may be NULL, meaning always true (select all tasks), which
* effectively duplicates css_task_iter_{start,next,end}() but does not
* lock css_set_lock for the call to @process.
*
* It is guaranteed that @process will act on every task that is a member
* of @css for the duration of this call. This function may or may not
* call @process for tasks that exit or move to a different css during the
* call, or are forked or move into the css during the call.
*
* Note that @test 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 @heap 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 css_scan_tasks(struct cgroup_subsys_state *css,
bool (*test)(struct task_struct *, void *),
void (*process)(struct task_struct *, void *),
void *data, struct ptr_heap *heap)
{
int retval, i;
struct css_task_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 timespec latest_time = { 0, 0 };
if (heap) {
/* The caller supplied our heap and pre-allocated its memory */
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 css, using the @test callback to determine
* which are of interest, and invoking @process callback on the
* ones which 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;
css_task_iter_start(css, &it);
while ((p = css_task_iter_next(&it))) {
/*
* Only affect tasks that qualify per the caller's callback,
* if he provided one
*/
if (test && !test(p, data))
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
*/
}
css_task_iter_end(&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 */
process(q, data);
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, void *data)
{
struct cgroup *new_cgroup = 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)
{
return css_scan_tasks(&from->dummy_css, NULL, cgroup_transfer_one_task,
to, NULL);
}
/*
* 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;
/* 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;
/* for delayed destruction */
struct delayed_work destroy_dwork;
};
/*
* 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);
}
/*
* Used to destroy all pidlists lingering waiting for destroy timer. None
* should be left afterwards.
*/
static void cgroup_pidlist_destroy_all(struct cgroup *cgrp)
{
struct cgroup_pidlist *l, *tmp_l;
mutex_lock(&cgrp->pidlist_mutex);
list_for_each_entry_safe(l, tmp_l, &cgrp->pidlists, links)
mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, 0);
mutex_unlock(&cgrp->pidlist_mutex);
flush_workqueue(cgroup_pidlist_destroy_wq);
BUG_ON(!list_empty(&cgrp->pidlists));
}
static void cgroup_pidlist_destroy_work_fn(struct work_struct *work)
{
struct delayed_work *dwork = to_delayed_work(work);
struct cgroup_pidlist *l = container_of(dwork, struct cgroup_pidlist,
destroy_dwork);
struct cgroup_pidlist *tofree = NULL;
mutex_lock(&l->owner->pidlist_mutex);
/*
* Destroy iff we didn't get queued again. The state won't change
* as destroy_dwork can only be queued while locked.
*/
if (!delayed_work_pending(dwork)) {
list_del(&l->links);
pidlist_free(l->list);
put_pid_ns(l->key.ns);
tofree = l;
}
mutex_unlock(&l->owner->pidlist_mutex);
kfree(tofree);
}
/*
* 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;
}
/*
* The two pid files - task and cgroup.procs - guaranteed that the result
* is sorted, which forced this whole pidlist fiasco. As pid order is
* different per namespace, each namespace needs differently sorted list,
* making it impossible to use, for example, single rbtree of member tasks
* sorted by task pointer. As pidlists can be fairly large, allocating one
* per open file is dangerous, so cgroup had to implement shared pool of
* pidlists keyed by cgroup and namespace.
*
* All this extra complexity was caused by the original implementation
* committing to an entirely unnecessary property. In the long term, we
* want to do away with it. Explicitly scramble sort order if
* sane_behavior so that no such expectation exists in the new interface.
*
* Scrambling is done by swapping every two consecutive bits, which is
* non-identity one-to-one mapping which disturbs sort order sufficiently.
*/
static pid_t pid_fry(pid_t pid)
{
unsigned a = pid & 0x55555555;
unsigned b = pid & 0xAAAAAAAA;
return (a << 1) | (b >> 1);
}
static pid_t cgroup_pid_fry(struct cgroup *cgrp, pid_t pid)
{
if (cgroup_sane_behavior(cgrp))
return pid_fry(pid);
else
return pid;
}
static int cmppid(const void *a, const void *b)
{
return *(pid_t *)a - *(pid_t *)b;
}
static int fried_cmppid(const void *a, const void *b)
{
return pid_fry(*(pid_t *)a) - pid_fry(*(pid_t *)b);
}
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);
lockdep_assert_held(&cgrp->pidlist_mutex);
list_for_each_entry(l, &cgrp->pidlists, links)
if (l->key.type == type && l->key.ns == ns)
return l;
return NULL;
}
/*
* 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_create(struct cgroup *cgrp,
enum cgroup_filetype type)
{
struct cgroup_pidlist *l;
lockdep_assert_held(&cgrp->pidlist_mutex);
l = cgroup_pidlist_find(cgrp, type);
if (l)
return l;
/* entry not found; create a new one */
l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
if (!l)
return l;
INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
l->key.type = type;
/* don't need task_nsproxy() if we're looking at ourself */
l->key.ns = get_pid_ns(task_active_pid_ns(current));
l->owner = cgrp;
list_add(&l->links, &cgrp->pidlists);
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 css_task_iter it;
struct task_struct *tsk;
struct cgroup_pidlist *l;
lockdep_assert_held(&cgrp->pidlist_mutex);
/*
* 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 */
css_task_iter_start(&cgrp->dummy_css, &it);
while ((tsk = css_task_iter_next(&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;
}
css_task_iter_end(&it);
length = n;
/* now sort & (if procs) strip out duplicates */
if (cgroup_sane_behavior(cgrp))
sort(array, length, sizeof(pid_t), fried_cmppid, NULL);
else
sort(array, length, sizeof(pid_t), cmppid, NULL);
if (type == CGROUP_FILE_PROCS)
length = pidlist_uniq(array, length);
l = cgroup_pidlist_find_create(cgrp, type);
if (!l) {
mutex_unlock(&cgrp->pidlist_mutex);
pidlist_free(array);
return -ENOMEM;
}
/* store array, freeing old if necessary */
pidlist_free(l->list);
l->list = array;
l->length = length;
*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 css_task_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;
css_task_iter_start(&cgrp->dummy_css, &it);
while ((tsk = css_task_iter_next(&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;
}
}
css_task_iter_end(&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_open_file *of = s->private;
struct cgroup *cgrp = seq_css(s)->cgroup;
struct cgroup_pidlist *l;
enum cgroup_filetype type = seq_cft(s)->private;
int index = 0, pid = *pos;
int *iter, ret;
mutex_lock(&cgrp->pidlist_mutex);
/*
* !NULL @of->priv indicates that this isn't the first start()
* after open. If the matching pidlist is around, we can use that.
* Look for it. Note that @of->priv can't be used directly. It
* could already have been destroyed.
*/
if (of->priv)
of->priv = cgroup_pidlist_find(cgrp, type);
/*
* Either this is the first start() after open or the matching
* pidlist has been destroyed inbetween. Create a new one.
*/
if (!of->priv) {
ret = pidlist_array_load(cgrp, type,
(struct cgroup_pidlist **)&of->priv);
if (ret)
return ERR_PTR(ret);
}
l = of->priv;
if (pid) {
int end = l->length;
while (index < end) {
int mid = (index + end) / 2;
if (cgroup_pid_fry(cgrp, l->list[mid]) == pid) {
index = mid;
break;
} else if (cgroup_pid_fry(cgrp, 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 = cgroup_pid_fry(cgrp, *iter);
return iter;
}
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
{
struct cgroup_open_file *of = s->private;
struct cgroup_pidlist *l = of->priv;
if (l)
mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
CGROUP_PIDLIST_DESTROY_DELAY);
mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
}
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
{
struct cgroup_open_file *of = s->private;
struct cgroup_pidlist *l = of->priv;
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 = cgroup_pid_fry(seq_css(s)->cgroup, *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 u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
struct cftype *cft)
{
return notify_on_release(css->cgroup);
}
static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
struct cftype *cft, u64 val)
{
clear_bit(CGRP_RELEASABLE, &css->cgroup->flags);
if (val)
set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
else
clear_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
return 0;
}
/*
* When dput() is called asynchronously, if umount has been done and
* then deactivate_super() in cgroup_free_fn() kills the superblock,
* there's a small window that vfs will see the root dentry with non-zero
* refcnt and trigger BUG().
*
* That's why we hold a reference before dput() and drop it right after.
*/
static void cgroup_dput(struct cgroup *cgrp)
{
struct super_block *sb = cgrp->root->sb;
atomic_inc(&sb->s_active);
dput(cgrp->dentry);
deactivate_super(sb);
}
static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
struct cftype *cft)
{
return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
}
static int cgroup_clone_children_write(struct cgroup_subsys_state *css,
struct cftype *cft, u64 val)
{
if (val)
set_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
else
clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
return 0;
}
static struct cftype cgroup_base_files[] = {
{
.name = "cgroup.procs",
.seq_start = cgroup_pidlist_start,
.seq_next = cgroup_pidlist_next,
.seq_stop = cgroup_pidlist_stop,
.seq_show = cgroup_pidlist_show,
.private = CGROUP_FILE_PROCS,
.write_u64 = cgroup_procs_write,
.mode = S_IRUGO | S_IWUSR,
},
{
.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,
.seq_show = cgroup_sane_behavior_show,
},
/*
* Historical crazy stuff. These don't have "cgroup." prefix and
* don't exist if sane_behavior. If you're depending on these, be
* prepared to be burned.
*/
{
.name = "tasks",
.flags = CFTYPE_INSANE, /* use "procs" instead */
.seq_start = cgroup_pidlist_start,
.seq_next = cgroup_pidlist_next,
.seq_stop = cgroup_pidlist_stop,
.seq_show = cgroup_pidlist_show,
.private = CGROUP_FILE_TASKS,
.write_u64 = cgroup_tasks_write,
.mode = S_IRUGO | S_IWUSR,
},
{
.name = "notify_on_release",
.flags = CFTYPE_INSANE,
.read_u64 = cgroup_read_notify_on_release,
.write_u64 = cgroup_write_notify_on_release,
},
{
.name = "release_agent",
.flags = CFTYPE_INSANE | CFTYPE_ONLY_ON_ROOT,
.seq_show = cgroup_release_agent_show,
.write_string = cgroup_release_agent_write,
.max_write_len = PATH_MAX,
},
{ } /* terminate */
};
/**
* cgroup_populate_dir - create subsys files in a cgroup directory
* @cgrp: target cgroup
* @subsys_mask: mask of the subsystem ids whose files should be added
*
* On failure, no file is added.
*/
static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
{
struct cgroup_subsys *ss;
int i, ret = 0;
/* process cftsets of each subsystem */
for_each_subsys(ss, i) {
struct cftype_set *set;
if (!test_bit(i, &subsys_mask))
continue;
list_for_each_entry(set, &ss->cftsets, node) {
ret = cgroup_addrm_files(cgrp, set->cfts, true);
if (ret < 0)
goto err;
}
}
return 0;
err:
cgroup_clear_dir(cgrp, subsys_mask);
return ret;
}
/*
* css destruction is four-stage process.
*
* 1. Destruction starts. Killing of the percpu_ref is initiated.
* Implemented in kill_css().
*
* 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
* and thus css_tryget() is guaranteed to fail, the css can be offlined
* by invoking offline_css(). After offlining, the base ref is put.
* Implemented in css_killed_work_fn().
*
* 3. When the percpu_ref reaches zero, the only possible remaining
* accessors are inside RCU read sections. css_release() schedules the
* RCU callback.
*
* 4. After the grace period, the css can be freed. Implemented in
* css_free_work_fn().
*
* It is actually hairier because both step 2 and 4 require process context
* and thus involve punting to css->destroy_work adding two additional
* steps to the already complex sequence.
*/
static void css_free_work_fn(struct work_struct *work)
{
struct cgroup_subsys_state *css =
container_of(work, struct cgroup_subsys_state, destroy_work);
struct cgroup *cgrp = css->cgroup;
if (css->parent)
css_put(css->parent);
css->ss->css_free(css);
cgroup_dput(cgrp);
}
static void css_free_rcu_fn(struct rcu_head *rcu_head)
{
struct cgroup_subsys_state *css =
container_of(rcu_head, struct cgroup_subsys_state, rcu_head);
/*
* css holds an extra ref to @cgrp->dentry which is put on the last
* css_put(). dput() requires process context which we don't have.
*/
INIT_WORK(&css->destroy_work, css_free_work_fn);
queue_work(cgroup_destroy_wq, &css->destroy_work);
}
static void css_release(struct percpu_ref *ref)
{
struct cgroup_subsys_state *css =
container_of(ref, struct cgroup_subsys_state, refcnt);
rcu_assign_pointer(css->cgroup->subsys[css->ss->subsys_id], NULL);
call_rcu(&css->rcu_head, css_free_rcu_fn);
}
static void init_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss,
struct cgroup *cgrp)
{
css->cgroup = cgrp;
css->ss = ss;
css->flags = 0;
if (cgrp->parent)
css->parent = cgroup_css(cgrp->parent, ss);
else
css->flags |= CSS_ROOT;
BUG_ON(cgroup_css(cgrp, ss));
}
/* invoke ->css_online() on a new CSS and mark it online if successful */
static int online_css(struct cgroup_subsys_state *css)
{
struct cgroup_subsys *ss = css->ss;
int ret = 0;
lockdep_assert_held(&cgroup_mutex);
if (ss->css_online)
ret = ss->css_online(css);
if (!ret) {
css->flags |= CSS_ONLINE;
css->cgroup->nr_css++;
rcu_assign_pointer(css->cgroup->subsys[ss->subsys_id], css);
}
return ret;
}
/* if the CSS is online, invoke ->css_offline() on it and mark it offline */
static void offline_css(struct cgroup_subsys_state *css)
{
struct cgroup_subsys *ss = css->ss;
lockdep_assert_held(&cgroup_mutex);
if (!(css->flags & CSS_ONLINE))
return;
if (ss->css_offline)
ss->css_offline(css);
css->flags &= ~CSS_ONLINE;
css->cgroup->nr_css--;
RCU_INIT_POINTER(css->cgroup->subsys[ss->subsys_id], css);
}
/**
* create_css - create a cgroup_subsys_state
* @cgrp: the cgroup new css will be associated with
* @ss: the subsys of new css
*
* Create a new css associated with @cgrp - @ss pair. On success, the new
* css is online and installed in @cgrp with all interface files created.
* Returns 0 on success, -errno on failure.
*/
static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss)
{
struct cgroup *parent = cgrp->parent;
struct cgroup_subsys_state *css;
int err;
lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
lockdep_assert_held(&cgroup_mutex);
css = ss->css_alloc(cgroup_css(parent, ss));
if (IS_ERR(css))
return PTR_ERR(css);
err = percpu_ref_init(&css->refcnt, css_release);
if (err)
goto err_free;
init_css(css, ss, cgrp);
err = cgroup_populate_dir(cgrp, 1 << ss->subsys_id);
if (err)
goto err_free;
err = online_css(css);
if (err)
goto err_free;
dget(cgrp->dentry);
css_get(css->parent);
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;
}
return 0;
err_free:
percpu_ref_cancel_init(&css->refcnt);
ss->css_free(css);
return err;
}
/*
* 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 ssid, err;
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) {
err = -ENOMEM;
goto err_free_cgrp;
}
rcu_assign_pointer(cgrp->name, 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_name;
}
/*
* Temporarily set the pointer to NULL, so idr_find() won't return
* a half-baked cgroup.
*/
cgrp->id = idr_alloc(&root->cgroup_idr, NULL, 1, 0, GFP_KERNEL);
if (cgrp->id < 0) {
err = -ENOMEM;
goto err_unlock;
}
/* 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->dummy_css.parent = &parent->dummy_css;
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);
/*
* 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_id;
lockdep_assert_held(&dentry->d_inode->i_mutex);
cgrp->serial_nr = cgroup_serial_nr_next++;
/* allocation complete, commit to creation */
list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
root->number_of_cgroups++;
/* hold a ref to the parent's dentry */
dget(parent->dentry);
/*
* @cgrp is now fully operational. If something fails after this
* point, it'll be released via the normal destruction path.
*/
idr_replace(&root->cgroup_idr, cgrp, cgrp->id);
err = cgroup_addrm_files(cgrp, cgroup_base_files, true);
if (err)
goto err_destroy;
/* let's create and online css's */
for_each_subsys(ss, ssid) {
if (root->subsys_mask & (1 << ssid)) {
err = create_css(cgrp, ss);
if (err)
goto err_destroy;
}
}
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
return 0;
err_free_id:
idr_remove(&root->cgroup_idr, cgrp->id);
/* Release the reference count that we took on the superblock */
deactivate_super(sb);
err_unlock:
mutex_unlock(&cgroup_mutex);
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);
}
/*
* This is called when the refcnt of a css is confirmed to be killed.
* css_tryget() is now guaranteed to fail.
*/
static void css_killed_work_fn(struct work_struct *work)
{
struct cgroup_subsys_state *css =
container_of(work, struct cgroup_subsys_state, destroy_work);
struct cgroup *cgrp = css->cgroup;
mutex_lock(&cgroup_mutex);
/*
* css_tryget() is guaranteed to fail now. Tell subsystems to
* initate destruction.
*/
offline_css(css);
/*
* If @cgrp is marked dead, it's waiting for refs of all css's to
* be disabled before proceeding to the second phase of cgroup
* destruction. If we are the last one, kick it off.
*/
if (!cgrp->nr_css && cgroup_is_dead(cgrp))
cgroup_destroy_css_killed(cgrp);
mutex_unlock(&cgroup_mutex);
/*
* Put the css refs from kill_css(). 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.
*/
css_put(css);
}
/* css kill confirmation processing requires process context, bounce */
static void css_killed_ref_fn(struct percpu_ref *ref)
{
struct cgroup_subsys_state *css =
container_of(ref, struct cgroup_subsys_state, refcnt);
INIT_WORK(&css->destroy_work, css_killed_work_fn);
queue_work(cgroup_destroy_wq, &css->destroy_work);
}
/**
* kill_css - destroy a css
* @css: css to destroy
*
* This function initiates destruction of @css by removing cgroup interface
* files and putting its base reference. ->css_offline() will be invoked
* asynchronously once css_tryget() is guaranteed to fail and when the
* reference count reaches zero, @css will be released.
*/
static void kill_css(struct cgroup_subsys_state *css)
{
cgroup_clear_dir(css->cgroup, 1 << css->ss->subsys_id);
/*
* Killing would put the base ref, but we need to keep it alive
* until after ->css_offline().
*/
css_get(css);
/*
* cgroup core guarantees that, by the time ->css_offline() is
* invoked, no new css reference will be given out via
* css_tryget(). We can't simply call percpu_ref_kill() and
* proceed to offlining css's because percpu_ref_kill() doesn't
* guarantee that the ref is seen as killed on all CPUs on return.
*
* Use percpu_ref_kill_and_confirm() to get notifications as each
* css is confirmed to be seen as killed on all CPUs.
*/
percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
}
/**
* cgroup_destroy_locked - the first stage of cgroup destruction
* @cgrp: cgroup to be destroyed
*
* css's make use of percpu refcnts whose killing latency shouldn't be
* exposed to userland and are RCU protected. Also, cgroup core needs to
* guarantee that css_tryget() won't succeed by the time ->css_offline() is
* invoked. To satisfy all the requirements, destruction is implemented in
* the following two steps.
*
* s1. Verify @cgrp can be destroyed and mark it dying. Remove all
* userland visible parts and start killing the percpu refcnts of
* css's. Set up so that the next stage will be kicked off once all
* the percpu refcnts are confirmed to be killed.
*
* s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
* rest of destruction. Once all cgroup references are gone, the
* cgroup is RCU-freed.
*
* This function implements s1. After this step, @cgrp is gone as far as
* the userland is concerned and a new cgroup with the same name may be
* created. As cgroup doesn't care about the names internally, this
* doesn't cause any problem.
*/
static int cgroup_destroy_locked(struct cgroup *cgrp)
__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
{
struct dentry *d = cgrp->dentry;
struct cgroup_subsys_state *css;
struct cgroup *child;
bool empty;
int ssid;
lockdep_assert_held(&d->d_inode->i_mutex);
lockdep_assert_held(&cgroup_mutex);
/*
* css_set_lock synchronizes access to ->cset_links and prevents
* @cgrp from being removed while __put_css_set() is in progress.
*/
read_lock(&css_set_lock);
empty = list_empty(&cgrp->cset_links);
read_unlock(&css_set_lock);
if (!empty)
return -EBUSY;
/*
* Make sure there's no live children. We can't test ->children
* emptiness as dead children linger on it while being destroyed;
* otherwise, "rmdir parent/child parent" may fail with -EBUSY.
*/
empty = true;
rcu_read_lock();
list_for_each_entry_rcu(child, &cgrp->children, sibling) {
empty = cgroup_is_dead(child);
if (!empty)
break;
}
rcu_read_unlock();
if (!empty)
return -EBUSY;
/*
* Initiate massacre of all css's. cgroup_destroy_css_killed()
* will be invoked to perform the rest of destruction once the
* percpu refs of all css's are confirmed to be killed.
*/
for_each_css(css, ssid, cgrp)
kill_css(css);
/*
* Mark @cgrp dead. This prevents further task migration and child
* creation by disabling cgroup_lock_live_group(). Note that
* CGRP_DEAD assertion is depended upon by css_next_child() to
* resume iteration after dropping RCU read lock. See
* css_next_child() for details.
*/
set_bit(CGRP_DEAD, &cgrp->flags);
/* CGRP_DEAD is set, remove from ->release_list for the last time */
raw_spin_lock(&release_list_lock);
if (!list_empty(&cgrp->release_list))
list_del_init(&cgrp->release_list);
raw_spin_unlock(&release_list_lock);
/*
* If @cgrp has css's attached, the second stage of cgroup
* destruction is kicked off from css_killed_work_fn() after the
* refs of all attached css's are killed. If @cgrp doesn't have
* any css, we kick it off here.
*/
if (!cgrp->nr_css)
cgroup_destroy_css_killed(cgrp);
/*
* Clear the base files and remove @cgrp directory. The removal
* puts the base ref but we aren't quite done with @cgrp yet, so
* hold onto it.
*/
cgroup_addrm_files(cgrp, cgroup_base_files, false);
dget(d);
cgroup_d_remove_dir(d);
return 0;
};
/**
* cgroup_destroy_css_killed - the second step of cgroup destruction
* @work: cgroup->destroy_free_work
*
* This function is invoked from a work item for a cgroup which is being
* destroyed after all css's are offlined and performs the rest of
* destruction. This is the second step of destruction described in the
* comment above cgroup_destroy_locked().
*/
static void cgroup_destroy_css_killed(struct cgroup *cgrp)
{
struct cgroup *parent = cgrp->parent;
struct dentry *d = cgrp->dentry;
lockdep_assert_held(&cgroup_mutex);
/* delete this cgroup from parent->children */
list_del_rcu(&cgrp->sibling);
dput(d);
set_bit(CGRP_RELEASABLE, &parent->flags);
check_for_release(parent);
}
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) {
struct cftype *cft;
for (cft = ss->base_cftypes; cft->name[0] != '\0'; cft++)
cft->ss = ss;
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 */
ss->root = &cgroup_dummy_root;
css = ss->css_alloc(cgroup_css(cgroup_dummy_top, ss));
/* We don't handle early failures gracefully */
BUG_ON(IS_ERR(css));
init_css(css, ss, cgroup_dummy_top);
/* 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(css));
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 *cset;
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(cgroup_subsys[ss->subsys_id] != ss);
return 0;
}
/* init base cftset */
cgroup_init_cftsets(ss);
mutex_lock(&cgroup_mutex);
mutex_lock(&cgroup_root_mutex);
cgroup_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 dummy root
* attachment).
*/
css = ss->css_alloc(cgroup_css(cgroup_dummy_top, ss));
if (IS_ERR(css)) {
/* failure case - need to deassign the cgroup_subsys[] slot. */
cgroup_subsys[ss->subsys_id] = NULL;
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
return PTR_ERR(css);
}
ss->root = &cgroup_dummy_root;
/* our new subsystem will be attached to the dummy hierarchy. */
init_css(css, ss, cgroup_dummy_top);
/*
* 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, cset, hlist) {
/* skip entries that we already rehashed */
if (cset->subsys[ss->subsys_id])
continue;
/* remove existing entry */
hash_del(&cset->hlist);
/* set new value */
cset->subsys[ss->subsys_id] = css;
/* recompute hash and restore entry */
key = css_set_hash(cset->subsys);
hash_add(css_set_table, &cset->hlist, key);
}
write_unlock(&css_set_lock);
ret = online_css(css);
if (ret) {
ss->css_free(css);
goto err_unload;
}
/* success! */
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
return 0;
err_unload:
mutex_unlock(&cgroup_root_mutex);
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 cgrp_cset_link *link;
struct cgroup_subsys_state *css;
BUG_ON(ss->module == NULL);
/*
* we shouldn't be called if the subsystem is in use, and the use of
* try_module_get() in rebind_subsystems() should ensure that it
* doesn't start being used while we're killing it off.
*/
BUG_ON(ss->root != &cgroup_dummy_root);
mutex_lock(&cgroup_mutex);
mutex_lock(&cgroup_root_mutex);
css = cgroup_css(cgroup_dummy_top, ss);
if (css)
offline_css(css);
/* deassign the subsys_id */
cgroup_subsys[ss->subsys_id] = NULL;
/*
* disentangle the css from all css_sets attached to the dummy
* top. as in loading, we need to pay our respects to the hashtable
* gods.
*/
write_lock(&css_set_lock);
list_for_each_entry(link, &cgroup_dummy_top->cset_links, cset_link) {
struct css_set *cset = link->cset;
unsigned long key;
hash_del(&cset->hlist);
cset->subsys[ss->subsys_id] = NULL;
key = css_set_hash(cset->subsys);
hash_add(css_set_table, &cset->hlist, key);
}
write_unlock(&css_set_lock);
/*
* remove subsystem's css from the cgroup_dummy_top and free it -
* need to free before marking as null because ss->css_free needs
* the cgrp->subsys pointer to find their state.
*/
if (css)
ss->css_free(css);
RCU_INIT_POINTER(cgroup_dummy_top->subsys[ss->subsys_id], NULL);
mutex_unlock(&cgroup_root_mutex);
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)
{
struct cgroup_subsys *ss;
int i;
atomic_set(&init_css_set.refcount, 1);
INIT_LIST_HEAD(&init_css_set.cgrp_links);
INIT_LIST_HEAD(&init_css_set.tasks);
INIT_HLIST_NODE(&init_css_set.hlist);
css_set_count = 1;
init_cgroup_root(&cgroup_dummy_root);
cgroup_root_count = 1;
RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
init_cgrp_cset_link.cset = &init_css_set;
init_cgrp_cset_link.cgrp = cgroup_dummy_top;
list_add(&init_cgrp_cset_link.cset_link, &cgroup_dummy_top->cset_links);
list_add(&init_cgrp_cset_link.cgrp_link, &init_css_set.cgrp_links);
/* at bootup time, we don't worry about modular subsystems */
for_each_builtin_subsys(ss, i) {
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)
{
struct cgroup_subsys *ss;
unsigned long key;
int i, err;
err = bdi_init(&cgroup_backing_dev_info);
if (err)
return err;
for_each_builtin_subsys(ss, i) {
if (!ss->early_init)
cgroup_init_subsys(ss);
}
/* allocate id for the dummy hierarchy */
mutex_lock(&cgroup_mutex);
mutex_lock(&cgroup_root_mutex);
/* 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(cgroup_init_root_id(&cgroup_dummy_root, 0, 1));
err = idr_alloc(&cgroup_dummy_root.cgroup_idr, cgroup_dummy_top,
0, 1, GFP_KERNEL);
BUG_ON(err < 0);
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
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;
}
static int __init cgroup_wq_init(void)
{
/*
* There isn't much point in executing destruction path in
* parallel. Good chunk is serialized with cgroup_mutex anyway.
* Use 1 for @max_active.
*
* We would prefer to do this in cgroup_init() above, but that
* is called before init_workqueues(): so leave this until after.
*/
cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
BUG_ON(!cgroup_destroy_wq);
/*
* Used to destroy pidlists and separate to serve as flush domain.
* Cap @max_active to 1 too.
*/
cgroup_pidlist_destroy_wq = alloc_workqueue("cgroup_pidlist_destroy",
0, 1);
BUG_ON(!cgroup_pidlist_destroy_wq);
return 0;
}
core_initcall(cgroup_wq_init);
/*
* 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 ssid, count = 0;
seq_printf(m, "%d:", root->hierarchy_id);
for_each_subsys(ss, ssid)
if (root->subsys_mask & (1 << ssid))
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)
{
struct cgroup_subsys *ss;
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_each_subsys(ss, i)
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);
get_css_set(task_css_set(current));
child->cgroups = current->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_task_iter_start() - to guarantee that the new task ends up on its
* list.
*/
void cgroup_post_fork(struct task_struct *child)
{
struct cgroup_subsys *ss;
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, &task_css_set(child)->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_each_builtin_subsys(ss, 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 cgroup_subsys *ss;
struct css_set *cset;
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);
cset = task_css_set(tsk);
RCU_INIT_POINTER(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_each_builtin_subsys(ss, i) {
if (ss->exit) {
struct cgroup_subsys_state *old_css = cset->subsys[i];
struct cgroup_subsys_state *css = task_css(tsk, i);
ss->exit(css, old_css, tsk);
}
}
}
task_unlock(tsk);
put_css_set_taskexit(cset);
}
static void check_for_release(struct cgroup *cgrp)
{
if (cgroup_is_releasable(cgrp) &&
list_empty(&cgrp->cset_links) && 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_dead(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);
}
}
/*
* 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)
{
struct cgroup_subsys *ss;
char *token;
int i;
while ((token = strsep(&str, ",")) != NULL) {
if (!*token)
continue;
/*
* cgroup_disable, being at boot time, can't know about
* module subsystems, so we don't worry about them.
*/
for_each_builtin_subsys(ss, i) {
if (!strcmp(token, ss->name)) {
ss->disabled = 1;
printk(KERN_INFO "Disabling %s control group"
" subsystem\n", ss->name);
break;
}
}
}
return 1;
}
__setup("cgroup_disable=", cgroup_disable);
/**
* css_from_dir - get corresponding css from the dentry of a cgroup dir
* @dentry: directory dentry of interest
* @ss: subsystem of interest
*
* Must be called under cgroup_mutex or RCU read lock. The caller is
* responsible for pinning the returned css if it needs to be accessed
* outside the critical section.
*/
struct cgroup_subsys_state *css_from_dir(struct dentry *dentry,
struct cgroup_subsys *ss)
{
struct cgroup *cgrp;
cgroup_assert_mutex_or_rcu_locked();
/* is @dentry a cgroup dir? */
if (!dentry->d_inode ||
dentry->d_inode->i_op != &cgroup_dir_inode_operations)
return ERR_PTR(-EBADF);
cgrp = __d_cgrp(dentry);
return cgroup_css(cgrp, ss) ?: ERR_PTR(-ENOENT);
}
/**
* css_from_id - lookup css by id
* @id: the cgroup id
* @ss: cgroup subsys to be looked into
*
* Returns the css if there's valid one with @id, otherwise returns NULL.
* Should be called under rcu_read_lock().
*/
struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
{
struct cgroup *cgrp;
cgroup_assert_mutex_or_rcu_locked();
cgrp = idr_find(&ss->root->cgroup_idr, id);
if (cgrp)
return cgroup_css(cgrp, ss);
return NULL;
}
#ifdef CONFIG_CGROUP_DEBUG
static struct cgroup_subsys_state *
debug_css_alloc(struct cgroup_subsys_state *parent_css)
{
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_subsys_state *css)
{
kfree(css);
}
static u64 debug_taskcount_read(struct cgroup_subsys_state *css,
struct cftype *cft)
{
return cgroup_task_count(css->cgroup);
}
static u64 current_css_set_read(struct cgroup_subsys_state *css,
struct cftype *cft)
{
return (u64)(unsigned long)current->cgroups;
}
static u64 current_css_set_refcount_read(struct cgroup_subsys_state *css,
struct cftype *cft)
{
u64 count;
rcu_read_lock();
count = atomic_read(&task_css_set(current)->refcount);
rcu_read_unlock();
return count;
}
static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
{
struct cgrp_cset_link *link;
struct css_set *cset;
read_lock(&css_set_lock);
rcu_read_lock();
cset = rcu_dereference(current->cgroups);
list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
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 seq_file *seq, void *v)
{
struct cgroup_subsys_state *css = seq_css(seq);
struct cgrp_cset_link *link;
read_lock(&css_set_lock);
list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
struct css_set *cset = link->cset;
struct task_struct *task;
int count = 0;
seq_printf(seq, "css_set %p\n", cset);
list_for_each_entry(task, &cset->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_subsys_state *css, struct cftype *cft)
{
return test_bit(CGRP_RELEASABLE, &css->cgroup->flags);
}
static struct cftype debug_files[] = {
{
.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",
.seq_show = current_css_set_cg_links_read,
},
{
.name = "cgroup_css_links",
.seq_show = 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 */
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