linux/kernel/cgroup.c
Linus Torvalds 14208b0ec5 Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:
 "A lot of activities on cgroup side.  Heavy restructuring including
  locking simplification took place to improve the code base and enable
  implementation of the unified hierarchy, which currently exists behind
  a __DEVEL__ mount option.  The core support is mostly complete but
  individual controllers need further work.  To explain the design and
  rationales of the the unified hierarchy

        Documentation/cgroups/unified-hierarchy.txt

  is added.

  Another notable change is css (cgroup_subsys_state - what each
  controller uses to identify and interact with a cgroup) iteration
  update.  This is part of continuing updates on css object lifetime and
  visibility.  cgroup started with reference count draining on removal
  way back and is now reaching a point where csses behave and are
  iterated like normal refcnted objects albeit with some complexities to
  allow distinguishing the state where they're being deleted.  The css
  iteration update isn't taken advantage of yet but is planned to be
  used to simplify memcg significantly"

* 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (77 commits)
  cgroup: disallow disabled controllers on the default hierarchy
  cgroup: don't destroy the default root
  cgroup: disallow debug controller on the default hierarchy
  cgroup: clean up MAINTAINERS entries
  cgroup: implement css_tryget()
  device_cgroup: use css_has_online_children() instead of has_children()
  cgroup: convert cgroup_has_live_children() into css_has_online_children()
  cgroup: use CSS_ONLINE instead of CGRP_DEAD
  cgroup: iterate cgroup_subsys_states directly
  cgroup: introduce CSS_RELEASED and reduce css iteration fallback window
  cgroup: move cgroup->serial_nr into cgroup_subsys_state
  cgroup: link all cgroup_subsys_states in their sibling lists
  cgroup: move cgroup->sibling and ->children into cgroup_subsys_state
  cgroup: remove cgroup->parent
  device_cgroup: remove direct access to cgroup->children
  memcg: update memcg_has_children() to use css_next_child()
  memcg: remove tasks/children test from mem_cgroup_force_empty()
  cgroup: remove css_parent()
  cgroup: skip refcnting on normal root csses and cgrp_dfl_root self css
  cgroup: use cgroup->self.refcnt for cgroup refcnting
  ...
2014-06-09 15:03:33 -07:00

5363 lines
144 KiB
C

/*
* Generic process-grouping system.
*
* Based originally on the cpuset system, extracted by Paul Menage
* Copyright (C) 2006 Google, Inc
*
* Notifications support
* Copyright (C) 2009 Nokia Corporation
* Author: Kirill A. Shutemov
*
* Copyright notices from the original cpuset code:
* --------------------------------------------------
* Copyright (C) 2003 BULL SA.
* Copyright (C) 2004-2006 Silicon Graphics, Inc.
*
* Portions derived from Patrick Mochel's sysfs code.
* sysfs is Copyright (c) 2001-3 Patrick Mochel
*
* 2003-10-10 Written by Simon Derr.
* 2003-10-22 Updates by Stephen Hemminger.
* 2004 May-July Rework by Paul Jackson.
* ---------------------------------------------------
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file COPYING in the main directory of the Linux
* distribution for more details.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#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/magic.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/slab.h>
#include <linux/spinlock.h>
#include <linux/rwsem.h>
#include <linux/string.h>
#include <linux/sort.h>
#include <linux/kmod.h>
#include <linux/delayacct.h>
#include <linux/cgroupstats.h>
#include <linux/hashtable.h>
#include <linux/pid_namespace.h>
#include <linux/idr.h>
#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
#include <linux/kthread.h>
#include <linux/delay.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
#define CGROUP_FILE_NAME_MAX (MAX_CGROUP_TYPE_NAMELEN + \
MAX_CFTYPE_NAME + 2)
/*
* cgroup_mutex is the master lock. Any modification to cgroup or its
* hierarchy must be performed while holding it.
*
* css_set_rwsem protects task->cgroups pointer, the list of css_set
* objects, and the chain of tasks off each css_set.
*
* These locks are exported if CONFIG_PROVE_RCU so that accessors in
* cgroup.h can use them for lockdep annotations.
*/
#ifdef CONFIG_PROVE_RCU
DEFINE_MUTEX(cgroup_mutex);
DECLARE_RWSEM(css_set_rwsem);
EXPORT_SYMBOL_GPL(cgroup_mutex);
EXPORT_SYMBOL_GPL(css_set_rwsem);
#else
static DEFINE_MUTEX(cgroup_mutex);
static DECLARE_RWSEM(css_set_rwsem);
#endif
/*
* Protects cgroup_idr and css_idr so that IDs can be released without
* grabbing cgroup_mutex.
*/
static DEFINE_SPINLOCK(cgroup_idr_lock);
/*
* Protects cgroup_subsys->release_agent_path. Modifying it also requires
* cgroup_mutex. Reading requires either cgroup_mutex or this spinlock.
*/
static DEFINE_SPINLOCK(release_agent_path_lock);
#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");
/*
* 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 */
#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
static struct cgroup_subsys *cgroup_subsys[] = {
#include <linux/cgroup_subsys.h>
};
#undef SUBSYS
/* array of cgroup subsystem names */
#define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
static const char *cgroup_subsys_name[] = {
#include <linux/cgroup_subsys.h>
};
#undef SUBSYS
/*
* The default 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.
*/
struct cgroup_root cgrp_dfl_root;
/*
* The default hierarchy always exists but is hidden until mounted for the
* first time. This is for backward compatibility.
*/
static bool cgrp_dfl_root_visible;
/* some controllers are not supported in the default hierarchy */
static const unsigned int cgrp_dfl_root_inhibit_ss_mask = 0
#ifdef CONFIG_CGROUP_DEBUG
| (1 << debug_cgrp_id)
#endif
;
/* The list of hierarchy roots */
static LIST_HEAD(cgroup_roots);
static int cgroup_root_count;
/* hierarchy ID allocation and mapping, protected by cgroup_mutex */
static DEFINE_IDR(cgroup_hierarchy_idr);
/*
* Assign a monotonically increasing serial number to csses. It guarantees
* cgroups with bigger numbers are newer than those with smaller numbers.
* Also, as csses are always appended to the parent's ->children list, it
* guarantees that sibling csses are always sorted in the ascending serial
* number order on the list. Protected by cgroup_mutex.
*/
static u64 css_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_put(struct cgroup *cgrp);
static int rebind_subsystems(struct cgroup_root *dst_root,
unsigned int ss_mask);
static int cgroup_destroy_locked(struct cgroup *cgrp);
static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss);
static void css_release(struct percpu_ref *ref);
static void kill_css(struct cgroup_subsys_state *css);
static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
bool is_add);
static void cgroup_pidlist_destroy_all(struct cgroup *cgrp);
/* IDR wrappers which synchronize using cgroup_idr_lock */
static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
gfp_t gfp_mask)
{
int ret;
idr_preload(gfp_mask);
spin_lock_bh(&cgroup_idr_lock);
ret = idr_alloc(idr, ptr, start, end, gfp_mask);
spin_unlock_bh(&cgroup_idr_lock);
idr_preload_end();
return ret;
}
static void *cgroup_idr_replace(struct idr *idr, void *ptr, int id)
{
void *ret;
spin_lock_bh(&cgroup_idr_lock);
ret = idr_replace(idr, ptr, id);
spin_unlock_bh(&cgroup_idr_lock);
return ret;
}
static void cgroup_idr_remove(struct idr *idr, int id)
{
spin_lock_bh(&cgroup_idr_lock);
idr_remove(idr, id);
spin_unlock_bh(&cgroup_idr_lock);
}
static struct cgroup *cgroup_parent(struct cgroup *cgrp)
{
struct cgroup_subsys_state *parent_css = cgrp->self.parent;
if (parent_css)
return container_of(parent_css, struct cgroup, self);
return NULL;
}
/**
* cgroup_css - obtain a cgroup's css for the specified subsystem
* @cgrp: the cgroup of interest
* @ss: the subsystem of interest (%NULL returns @cgrp->self)
*
* 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->id],
lockdep_is_held(&cgroup_mutex));
else
return &cgrp->self;
}
/**
* cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
* @cgrp: the cgroup of interest
* @ss: the subsystem of interest (%NULL returns @cgrp->self)
*
* Similar to cgroup_css() but returns the effctive css, which is defined
* as the matching css of the nearest ancestor including self which has @ss
* enabled. If @ss is associated with the hierarchy @cgrp is on, this
* function is guaranteed to return non-NULL css.
*/
static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
struct cgroup_subsys *ss)
{
lockdep_assert_held(&cgroup_mutex);
if (!ss)
return &cgrp->self;
if (!(cgrp->root->subsys_mask & (1 << ss->id)))
return NULL;
while (cgroup_parent(cgrp) &&
!(cgroup_parent(cgrp)->child_subsys_mask & (1 << ss->id)))
cgrp = cgroup_parent(cgrp);
return cgroup_css(cgrp, ss);
}
/* convenient tests for these bits */
static inline bool cgroup_is_dead(const struct cgroup *cgrp)
{
return !(cgrp->self.flags & CSS_ONLINE);
}
struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
{
struct cgroup *cgrp = of->kn->parent->priv;
struct cftype *cft = of_cft(of);
/*
* This is open and unprotected implementation of cgroup_css().
* seq_css() is only called from a kernfs file operation which has
* an active reference on the file. Because all the subsystem
* files are drained before a css is disassociated with a cgroup,
* the matching css from the cgroup's subsys table is guaranteed to
* be and stay valid until the enclosing operation is complete.
*/
if (cft->ss)
return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
else
return &cgrp->self;
}
EXPORT_SYMBOL_GPL(of_css);
/**
* 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 = cgroup_parent(cgrp);
}
return false;
}
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_[tree_]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_e_css - iterate all effective 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_[tree_]mutex.
*/
#define for_each_e_css(css, ssid, cgrp) \
for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
; \
else
/**
* for_each_subsys - iterate all enabled cgroup subsystems
* @ss: the iteration cursor
* @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
*/
#define for_each_subsys(ss, ssid) \
for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
(((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
/* iterate across the hierarchies */
#define for_each_root(root) \
list_for_each_entry((root), &cgroup_roots, root_list)
/* iterate over child cgrps, lock should be held throughout iteration */
#define cgroup_for_each_live_child(child, cgrp) \
list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
if (({ lockdep_assert_held(&cgroup_mutex); \
cgroup_is_dead(child); })) \
; \
else
/* 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.
*/
struct css_set init_css_set = {
.refcount = ATOMIC_INIT(1),
.cgrp_links = LIST_HEAD_INIT(init_css_set.cgrp_links),
.tasks = LIST_HEAD_INIT(init_css_set.tasks),
.mg_tasks = LIST_HEAD_INIT(init_css_set.mg_tasks),
.mg_preload_node = LIST_HEAD_INIT(init_css_set.mg_preload_node),
.mg_node = LIST_HEAD_INIT(init_css_set.mg_node),
};
static int css_set_count = 1; /* 1 for init_css_set */
/**
* cgroup_update_populated - updated populated count of a cgroup
* @cgrp: the target cgroup
* @populated: inc or dec populated count
*
* @cgrp is either getting the first task (css_set) or losing the last.
* Update @cgrp->populated_cnt accordingly. The count is propagated
* towards root so that a given cgroup's populated_cnt is zero iff the
* cgroup and all its descendants are empty.
*
* @cgrp's interface file "cgroup.populated" is zero if
* @cgrp->populated_cnt is zero and 1 otherwise. When @cgrp->populated_cnt
* changes from or to zero, userland is notified that the content of the
* interface file has changed. This can be used to detect when @cgrp and
* its descendants become populated or empty.
*/
static void cgroup_update_populated(struct cgroup *cgrp, bool populated)
{
lockdep_assert_held(&css_set_rwsem);
do {
bool trigger;
if (populated)
trigger = !cgrp->populated_cnt++;
else
trigger = !--cgrp->populated_cnt;
if (!trigger)
break;
if (cgrp->populated_kn)
kernfs_notify(cgrp->populated_kn);
cgrp = cgroup_parent(cgrp);
} while (cgrp);
}
/*
* 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;
}
static void put_css_set_locked(struct css_set *cset, bool taskexit)
{
struct cgrp_cset_link *link, *tmp_link;
struct cgroup_subsys *ss;
int ssid;
lockdep_assert_held(&css_set_rwsem);
if (!atomic_dec_and_test(&cset->refcount))
return;
/* This css_set is dead. unlink it and release cgroup refcounts */
for_each_subsys(ss, ssid)
list_del(&cset->e_cset_node[ssid]);
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_rwsem */
if (list_empty(&cgrp->cset_links)) {
cgroup_update_populated(cgrp, false);
if (notify_on_release(cgrp)) {
if (taskexit)
set_bit(CGRP_RELEASABLE, &cgrp->flags);
check_for_release(cgrp);
}
}
kfree(link);
}
kfree_rcu(cset, rcu_head);
}
static void put_css_set(struct css_set *cset, bool taskexit)
{
/*
* 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;
down_write(&css_set_rwsem);
put_css_set_locked(cset, taskexit);
up_write(&css_set_rwsem);
}
/*
* refcounted get/put for css_set objects
*/
static inline void get_css_set(struct css_set *cset)
{
atomic_inc(&cset->refcount);
}
/**
* 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;
/*
* On the default hierarchy, there can be csets which are
* associated with the same set of cgroups but different csses.
* Let's first ensure that csses match.
*/
if (memcmp(template, cset->subsys, sizeof(cset->subsys)))
return false;
/*
* Compare cgroup pointers in order to distinguish between
* different cgroups in hierarchies. As different cgroups may
* share the same effective css, this comparison is always
* necessary.
*/
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 cgroup_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)) {
/*
* @ss is in this hierarchy, so we want the
* effective css from @cgrp.
*/
template[i] = cgroup_e_css(cgrp, ss);
} else {
/*
* @ss is not in this hierarchy, so we don't want
* to change the css.
*/
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));
if (cgroup_on_dfl(cgrp))
cset->dfl_cgrp = cgrp;
link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
link->cset = cset;
link->cgrp = cgrp;
if (list_empty(&cgrp->cset_links))
cgroup_update_populated(cgrp, true);
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;
struct cgroup_subsys *ss;
unsigned long key;
int ssid;
lockdep_assert_held(&cgroup_mutex);
/* First see if we already have a cgroup group that matches
* the desired set */
down_read(&css_set_rwsem);
cset = find_existing_css_set(old_cset, cgrp, template);
if (cset)
get_css_set(cset);
up_read(&css_set_rwsem);
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_LIST_HEAD(&cset->mg_tasks);
INIT_LIST_HEAD(&cset->mg_preload_node);
INIT_LIST_HEAD(&cset->mg_node);
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));
down_write(&css_set_rwsem);
/* 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 @cset to the hash table */
key = css_set_hash(cset->subsys);
hash_add(css_set_table, &cset->hlist, key);
for_each_subsys(ss, ssid)
list_add_tail(&cset->e_cset_node[ssid],
&cset->subsys[ssid]->cgroup->e_csets[ssid]);
up_write(&css_set_rwsem);
return cset;
}
static struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
{
struct cgroup *root_cgrp = kf_root->kn->priv;
return root_cgrp->root;
}
static int cgroup_init_root_id(struct cgroup_root *root)
{
int id;
lockdep_assert_held(&cgroup_mutex);
id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
if (id < 0)
return id;
root->hierarchy_id = id;
return 0;
}
static void cgroup_exit_root_id(struct cgroup_root *root)
{
lockdep_assert_held(&cgroup_mutex);
if (root->hierarchy_id) {
idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
root->hierarchy_id = 0;
}
}
static void cgroup_free_root(struct cgroup_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 void cgroup_destroy_root(struct cgroup_root *root)
{
struct cgroup *cgrp = &root->cgrp;
struct cgrp_cset_link *link, *tmp_link;
mutex_lock(&cgroup_mutex);
BUG_ON(atomic_read(&root->nr_cgrps));
BUG_ON(!list_empty(&cgrp->self.children));
/* Rebind all subsystems back to the default hierarchy */
rebind_subsystems(&cgrp_dfl_root, root->subsys_mask);
/*
* Release all the links from cset_links to this hierarchy's
* root cgroup
*/
down_write(&css_set_rwsem);
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);
}
up_write(&css_set_rwsem);
if (!list_empty(&root->root_list)) {
list_del(&root->root_list);
cgroup_root_count--;
}
cgroup_exit_root_id(root);
mutex_unlock(&cgroup_mutex);
kernfs_destroy_root(root->kf_root);
cgroup_free_root(root);
}
/* look up cgroup associated with given css_set on the specified hierarchy */
static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
struct cgroup_root *root)
{
struct cgroup *res = NULL;
lockdep_assert_held(&cgroup_mutex);
lockdep_assert_held(&css_set_rwsem);
if (cset == &init_css_set) {
res = &root->cgrp;
} 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;
}
}
}
BUG_ON(!res);
return res;
}
/*
* Return the cgroup for "task" from the given hierarchy. Must be
* called with cgroup_mutex and css_set_rwsem held.
*/
static struct cgroup *task_cgroup_from_root(struct task_struct *task,
struct cgroup_root *root)
{
/*
* 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.
*/
return cset_cgroup_from_root(task_css_set(task), root);
}
/*
* 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, root cgroup
* always has either children cgroups and/or using tasks. So we don't
* need a special hack to ensure that root cgroup cannot be deleted.
*
* P.S. One more locking exception. RCU is used to guard the
* update of a tasks cgroup pointer by cgroup_attach_task()
*/
static int cgroup_populate_dir(struct cgroup *cgrp, unsigned int subsys_mask);
static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
static const struct file_operations proc_cgroupstats_operations;
static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
char *buf)
{
if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
!(cgrp->root->flags & CGRP_ROOT_NOPREFIX))
snprintf(buf, CGROUP_FILE_NAME_MAX, "%s.%s",
cft->ss->name, cft->name);
else
strncpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
return buf;
}
/**
* 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)
mode |= S_IWUSR;
return mode;
}
static void cgroup_get(struct cgroup *cgrp)
{
WARN_ON_ONCE(cgroup_is_dead(cgrp));
css_get(&cgrp->self);
}
static void cgroup_put(struct cgroup *cgrp)
{
css_put(&cgrp->self);
}
/**
* cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
* @kn: the kernfs_node being serviced
*
* This helper undoes cgroup_kn_lock_live() and should be invoked before
* the method finishes if locking succeeded. Note that once this function
* returns the cgroup returned by cgroup_kn_lock_live() may become
* inaccessible any time. If the caller intends to continue to access the
* cgroup, it should pin it before invoking this function.
*/
static void cgroup_kn_unlock(struct kernfs_node *kn)
{
struct cgroup *cgrp;
if (kernfs_type(kn) == KERNFS_DIR)
cgrp = kn->priv;
else
cgrp = kn->parent->priv;
mutex_unlock(&cgroup_mutex);
kernfs_unbreak_active_protection(kn);
cgroup_put(cgrp);
}
/**
* cgroup_kn_lock_live - locking helper for cgroup kernfs methods
* @kn: the kernfs_node being serviced
*
* This helper is to be used by a cgroup kernfs method currently servicing
* @kn. It breaks the active protection, performs cgroup locking and
* verifies that the associated cgroup is alive. Returns the cgroup if
* alive; otherwise, %NULL. A successful return should be undone by a
* matching cgroup_kn_unlock() invocation.
*
* Any cgroup kernfs method implementation which requires locking the
* associated cgroup should use this helper. It avoids nesting cgroup
* locking under kernfs active protection and allows all kernfs operations
* including self-removal.
*/
static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn)
{
struct cgroup *cgrp;
if (kernfs_type(kn) == KERNFS_DIR)
cgrp = kn->priv;
else
cgrp = kn->parent->priv;
/*
* We're gonna grab cgroup_mutex which nests outside kernfs
* active_ref. cgroup liveliness check alone provides enough
* protection against removal. Ensure @cgrp stays accessible and
* break the active_ref protection.
*/
cgroup_get(cgrp);
kernfs_break_active_protection(kn);
mutex_lock(&cgroup_mutex);
if (!cgroup_is_dead(cgrp))
return cgrp;
cgroup_kn_unlock(kn);
return NULL;
}
static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
{
char name[CGROUP_FILE_NAME_MAX];
lockdep_assert_held(&cgroup_mutex);
kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
}
/**
* 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 int subsys_mask)
{
struct cgroup_subsys *ss;
int i;
for_each_subsys(ss, i) {
struct cftype *cfts;
if (!(subsys_mask & (1 << i)))
continue;
list_for_each_entry(cfts, &ss->cfts, node)
cgroup_addrm_files(cgrp, cfts, false);
}
}
static int rebind_subsystems(struct cgroup_root *dst_root, unsigned int ss_mask)
{
struct cgroup_subsys *ss;
unsigned int tmp_ss_mask;
int ssid, i, ret;
lockdep_assert_held(&cgroup_mutex);
for_each_subsys(ss, ssid) {
if (!(ss_mask & (1 << ssid)))
continue;
/* if @ss has non-root csses attached to it, can't move */
if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)))
return -EBUSY;
/* can't move between two non-dummy roots either */
if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
return -EBUSY;
}
/* skip creating root files on dfl_root for inhibited subsystems */
tmp_ss_mask = ss_mask;
if (dst_root == &cgrp_dfl_root)
tmp_ss_mask &= ~cgrp_dfl_root_inhibit_ss_mask;
ret = cgroup_populate_dir(&dst_root->cgrp, tmp_ss_mask);
if (ret) {
if (dst_root != &cgrp_dfl_root)
return ret;
/*
* Rebinding back to the default root is not allowed to
* fail. Using both default and non-default roots should
* be rare. Moving subsystems back and forth even more so.
* Just warn about it and continue.
*/
if (cgrp_dfl_root_visible) {
pr_warn("failed to create files (%d) while rebinding 0x%x to default root\n",
ret, ss_mask);
pr_warn("you may retry by moving them to a different hierarchy and unbinding\n");
}
}
/*
* Nothing can fail from this point on. Remove files for the
* removed subsystems and rebind each subsystem.
*/
for_each_subsys(ss, ssid)
if (ss_mask & (1 << ssid))
cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
for_each_subsys(ss, ssid) {
struct cgroup_root *src_root;
struct cgroup_subsys_state *css;
struct css_set *cset;
if (!(ss_mask & (1 << ssid)))
continue;
src_root = ss->root;
css = cgroup_css(&src_root->cgrp, ss);
WARN_ON(!css || cgroup_css(&dst_root->cgrp, ss));
RCU_INIT_POINTER(src_root->cgrp.subsys[ssid], NULL);
rcu_assign_pointer(dst_root->cgrp.subsys[ssid], css);
ss->root = dst_root;
css->cgroup = &dst_root->cgrp;
down_write(&css_set_rwsem);
hash_for_each(css_set_table, i, cset, hlist)
list_move_tail(&cset->e_cset_node[ss->id],
&dst_root->cgrp.e_csets[ss->id]);
up_write(&css_set_rwsem);
src_root->subsys_mask &= ~(1 << ssid);
src_root->cgrp.child_subsys_mask &= ~(1 << ssid);
/* default hierarchy doesn't enable controllers by default */
dst_root->subsys_mask |= 1 << ssid;
if (dst_root != &cgrp_dfl_root)
dst_root->cgrp.child_subsys_mask |= 1 << ssid;
if (ss->bind)
ss->bind(css);
}
kernfs_activate(dst_root->cgrp.kn);
return 0;
}
static int cgroup_show_options(struct seq_file *seq,
struct kernfs_root *kf_root)
{
struct cgroup_root *root = cgroup_root_from_kf(kf_root);
struct cgroup_subsys *ss;
int ssid;
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");
spin_lock(&release_agent_path_lock);
if (strlen(root->release_agent_path))
seq_printf(seq, ",release_agent=%s", root->release_agent_path);
spin_unlock(&release_agent_path_lock);
if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags))
seq_puts(seq, ",clone_children");
if (strlen(root->name))
seq_printf(seq, ",name=%s", root->name);
return 0;
}
struct cgroup_sb_opts {
unsigned int subsys_mask;
unsigned int flags;
char *release_agent;
bool cpuset_clone_children;
char *name;
/* User explicitly requested empty subsystem */
bool none;
};
static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
{
char *token, *o = data;
bool all_ss = false, one_ss = false;
unsigned int mask = -1U;
struct cgroup_subsys *ss;
int i;
#ifdef CONFIG_CPUSETS
mask = ~(1U << cpuset_cgrp_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;
opts->subsys_mask |= (1 << i);
one_ss = true;
break;
}
if (i == CGROUP_SUBSYS_COUNT)
return -ENOENT;
}
/* Consistency checks */
if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
pr_warn("sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");
if ((opts->flags & (CGRP_ROOT_NOPREFIX | CGRP_ROOT_XATTR)) ||
opts->cpuset_clone_children || opts->release_agent ||
opts->name) {
pr_err("sane_behavior: noprefix, xattr, clone_children, release_agent and name are not allowed\n");
return -EINVAL;
}
} else {
/*
* 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)
opts->subsys_mask |= (1 << i);
/*
* 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;
}
/*
* 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;
return 0;
}
static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
{
int ret = 0;
struct cgroup_root *root = cgroup_root_from_kf(kf_root);
struct cgroup_sb_opts opts;
unsigned int added_mask, removed_mask;
if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) {
pr_err("sane_behavior: remount is not allowed\n");
return -EINVAL;
}
mutex_lock(&cgroup_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_warn("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("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%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 (!list_empty(&root->cgrp.self.children)) {
ret = -EBUSY;
goto out_unlock;
}
ret = rebind_subsystems(root, added_mask);
if (ret)
goto out_unlock;
rebind_subsystems(&cgrp_dfl_root, removed_mask);
if (opts.release_agent) {
spin_lock(&release_agent_path_lock);
strcpy(root->release_agent_path, opts.release_agent);
spin_unlock(&release_agent_path_lock);
}
out_unlock:
kfree(opts.release_agent);
kfree(opts.name);
mutex_unlock(&cgroup_mutex);
return ret;
}
/*
* 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 mount.
*/
static bool use_task_css_set_links __read_mostly;
static void cgroup_enable_task_cg_lists(void)
{
struct task_struct *p, *g;
down_write(&css_set_rwsem);
if (use_task_css_set_links)
goto out_unlock;
use_task_css_set_links = true;
/*
* 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) {
WARN_ON_ONCE(!list_empty(&p->cg_list) ||
task_css_set(p) != &init_css_set);
/*
* 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)) {
struct css_set *cset = task_css_set(p);
list_add(&p->cg_list, &cset->tasks);
get_css_set(cset);
}
spin_unlock_irq(&p->sighand->siglock);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
out_unlock:
up_write(&css_set_rwsem);
}
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
struct cgroup_subsys *ss;
int ssid;
INIT_LIST_HEAD(&cgrp->self.sibling);
INIT_LIST_HEAD(&cgrp->self.children);
INIT_LIST_HEAD(&cgrp->cset_links);
INIT_LIST_HEAD(&cgrp->release_list);
INIT_LIST_HEAD(&cgrp->pidlists);
mutex_init(&cgrp->pidlist_mutex);
cgrp->self.cgroup = cgrp;
cgrp->self.flags |= CSS_ONLINE;
for_each_subsys(ss, ssid)
INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
init_waitqueue_head(&cgrp->offline_waitq);
}
static void init_cgroup_root(struct cgroup_root *root,
struct cgroup_sb_opts *opts)
{
struct cgroup *cgrp = &root->cgrp;
INIT_LIST_HEAD(&root->root_list);
atomic_set(&root->nr_cgrps, 1);
cgrp->root = root;
init_cgroup_housekeeping(cgrp);
idr_init(&root->cgroup_idr);
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->cgrp.flags);
}
static int cgroup_setup_root(struct cgroup_root *root, unsigned int ss_mask)
{
LIST_HEAD(tmp_links);
struct cgroup *root_cgrp = &root->cgrp;
struct css_set *cset;
int i, ret;
lockdep_assert_held(&cgroup_mutex);
ret = cgroup_idr_alloc(&root->cgroup_idr, root_cgrp, 1, 2, GFP_NOWAIT);
if (ret < 0)
goto out;
root_cgrp->id = ret;
ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release);
if (ret)
goto out;
/*
* We're accessing css_set_count without locking css_set_rwsem 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 cancel_ref;
ret = cgroup_init_root_id(root);
if (ret)
goto cancel_ref;
root->kf_root = kernfs_create_root(&cgroup_kf_syscall_ops,
KERNFS_ROOT_CREATE_DEACTIVATED,
root_cgrp);
if (IS_ERR(root->kf_root)) {
ret = PTR_ERR(root->kf_root);
goto exit_root_id;
}
root_cgrp->kn = root->kf_root->kn;
ret = cgroup_addrm_files(root_cgrp, cgroup_base_files, true);
if (ret)
goto destroy_root;
ret = rebind_subsystems(root, ss_mask);
if (ret)
goto destroy_root;
/*
* 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 root cgroup in this hierarchy into all the css_set
* objects.
*/
down_write(&css_set_rwsem);
hash_for_each(css_set_table, i, cset, hlist)
link_css_set(&tmp_links, cset, root_cgrp);
up_write(&css_set_rwsem);
BUG_ON(!list_empty(&root_cgrp->self.children));
BUG_ON(atomic_read(&root->nr_cgrps) != 1);
kernfs_activate(root_cgrp->kn);
ret = 0;
goto out;
destroy_root:
kernfs_destroy_root(root->kf_root);
root->kf_root = NULL;
exit_root_id:
cgroup_exit_root_id(root);
cancel_ref:
percpu_ref_cancel_init(&root_cgrp->self.refcnt);
out:
free_cgrp_cset_links(&tmp_links);
return ret;
}
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
int flags, const char *unused_dev_name,
void *data)
{
struct cgroup_root *root;
struct cgroup_sb_opts opts;
struct dentry *dentry;
int ret;
bool new_sb;
/*
* The first time anyone tries to mount a cgroup, 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();
mutex_lock(&cgroup_mutex);
/* First find the desired set of subsystems */
ret = parse_cgroupfs_options(data, &opts);
if (ret)
goto out_unlock;
/* look for a matching existing root */
if (!opts.subsys_mask && !opts.none && !opts.name) {
cgrp_dfl_root_visible = true;
root = &cgrp_dfl_root;
cgroup_get(&root->cgrp);
ret = 0;
goto out_unlock;
}
for_each_root(root) {
bool name_match = false;
if (root == &cgrp_dfl_root)
continue;
/*
* If we asked for a name then it must match. Also, if
* name matches but sybsys_mask doesn't, we should fail.
* Remember whether name matched.
*/
if (opts.name) {
if (strcmp(opts.name, root->name))
continue;
name_match = true;
}
/*
* 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)) {
if (!name_match)
continue;
ret = -EBUSY;
goto out_unlock;
}
if ((root->flags ^ opts.flags) & CGRP_ROOT_OPTION_MASK) {
if ((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) {
pr_err("sane_behavior: new mount options should match the existing superblock\n");
ret = -EINVAL;
goto out_unlock;
} else {
pr_warn("new mount options do not match the existing superblock, will be ignored\n");
}
}
/*
* A root's lifetime is governed by its root cgroup.
* tryget_live failure indicate that the root is being
* destroyed. Wait for destruction to complete so that the
* subsystems are free. We can use wait_queue for the wait
* but this path is super cold. Let's just sleep for a bit
* and retry.
*/
if (!percpu_ref_tryget_live(&root->cgrp.self.refcnt)) {
mutex_unlock(&cgroup_mutex);
msleep(10);
ret = restart_syscall();
goto out_free;
}
ret = 0;
goto out_unlock;
}
/*
* No such thing, create a new one. name= matching without subsys
* specification is allowed for already existing hierarchies but we
* can't create new one without subsys specification.
*/
if (!opts.subsys_mask && !opts.none) {
ret = -EINVAL;
goto out_unlock;
}
root = kzalloc(sizeof(*root), GFP_KERNEL);
if (!root) {
ret = -ENOMEM;
goto out_unlock;
}
init_cgroup_root(root, &opts);
ret = cgroup_setup_root(root, opts.subsys_mask);
if (ret)
cgroup_free_root(root);
out_unlock:
mutex_unlock(&cgroup_mutex);
out_free:
kfree(opts.release_agent);
kfree(opts.name);
if (ret)
return ERR_PTR(ret);
dentry = kernfs_mount(fs_type, flags, root->kf_root,
CGROUP_SUPER_MAGIC, &new_sb);
if (IS_ERR(dentry) || !new_sb)
cgroup_put(&root->cgrp);
return dentry;
}
static void cgroup_kill_sb(struct super_block *sb)
{
struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
struct cgroup_root *root = cgroup_root_from_kf(kf_root);
/*
* If @root doesn't have any mounts or children, start killing it.
* This prevents new mounts by disabling percpu_ref_tryget_live().
* cgroup_mount() may wait for @root's release.
*
* And don't kill the default root.
*/
if (css_has_online_children(&root->cgrp.self) ||
root == &cgrp_dfl_root)
cgroup_put(&root->cgrp);
else
percpu_ref_kill(&root->cgrp.self.refcnt);
kernfs_kill_sb(sb);
}
static struct file_system_type cgroup_fs_type = {
.name = "cgroup",
.mount = cgroup_mount,
.kill_sb = cgroup_kill_sb,
};
static struct kobject *cgroup_kobj;
/**
* 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.
*
* Return value is the same as kernfs_path().
*/
char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
{
struct cgroup_root *root;
struct cgroup *cgrp;
int hierarchy_id = 1;
char *path = NULL;
mutex_lock(&cgroup_mutex);
down_read(&css_set_rwsem);
root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
if (root) {
cgrp = task_cgroup_from_root(task, root);
path = cgroup_path(cgrp, buf, buflen);
} else {
/* if no hierarchy exists, everyone is in "/" */
if (strlcpy(buf, "/", buflen) < buflen)
path = buf;
}
up_read(&css_set_rwsem);
mutex_unlock(&cgroup_mutex);
return path;
}
EXPORT_SYMBOL_GPL(task_cgroup_path);
/* used to track tasks and other necessary states during migration */
struct cgroup_taskset {
/* the src and dst cset list running through cset->mg_node */
struct list_head src_csets;
struct list_head dst_csets;
/*
* Fields for cgroup_taskset_*() iteration.
*
* Before migration is committed, the target migration tasks are on
* ->mg_tasks of the csets on ->src_csets. After, on ->mg_tasks of
* the csets on ->dst_csets. ->csets point to either ->src_csets
* or ->dst_csets depending on whether migration is committed.
*
* ->cur_csets and ->cur_task point to the current task position
* during iteration.
*/
struct list_head *csets;
struct css_set *cur_cset;
struct task_struct *cur_task;
};
/**
* 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)
{
tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
tset->cur_task = NULL;
return cgroup_taskset_next(tset);
}
/**
* 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 css_set *cset = tset->cur_cset;
struct task_struct *task = tset->cur_task;
while (&cset->mg_node != tset->csets) {
if (!task)
task = list_first_entry(&cset->mg_tasks,
struct task_struct, cg_list);
else
task = list_next_entry(task, cg_list);
if (&task->cg_list != &cset->mg_tasks) {
tset->cur_cset = cset;
tset->cur_task = task;
return task;
}
cset = list_next_entry(cset, mg_node);
task = NULL;
}
return NULL;
}
/**
* cgroup_task_migrate - move a task from one cgroup to another.
* @old_cgrp: the cgroup @tsk is being migrated from
* @tsk: the task being migrated
* @new_cset: the new css_set @tsk is being attached to
*
* Must be called with cgroup_mutex, threadgroup and css_set_rwsem locked.
*/
static void cgroup_task_migrate(struct cgroup *old_cgrp,
struct task_struct *tsk,
struct css_set *new_cset)
{
struct css_set *old_cset;
lockdep_assert_held(&cgroup_mutex);
lockdep_assert_held(&css_set_rwsem);
/*
* 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);
get_css_set(new_cset);
rcu_assign_pointer(tsk->cgroups, new_cset);
/*
* Use move_tail so that cgroup_taskset_first() still returns the
* leader after migration. This works because cgroup_migrate()
* ensures that the dst_cset of the leader is the first on the
* tset's dst_csets list.
*/
list_move_tail(&tsk->cg_list, &new_cset->mg_tasks);
/*
* 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_locked(old_cset, false);
}
/**
* cgroup_migrate_finish - cleanup after attach
* @preloaded_csets: list of preloaded css_sets
*
* Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst(). See
* those functions for details.
*/
static void cgroup_migrate_finish(struct list_head *preloaded_csets)
{
struct css_set *cset, *tmp_cset;
lockdep_assert_held(&cgroup_mutex);
down_write(&css_set_rwsem);
list_for_each_entry_safe(cset, tmp_cset, preloaded_csets, mg_preload_node) {
cset->mg_src_cgrp = NULL;
cset->mg_dst_cset = NULL;
list_del_init(&cset->mg_preload_node);
put_css_set_locked(cset, false);
}
up_write(&css_set_rwsem);
}
/**
* cgroup_migrate_add_src - add a migration source css_set
* @src_cset: the source css_set to add
* @dst_cgrp: the destination cgroup
* @preloaded_csets: list of preloaded css_sets
*
* Tasks belonging to @src_cset are about to be migrated to @dst_cgrp. Pin
* @src_cset and add it to @preloaded_csets, which should later be cleaned
* up by cgroup_migrate_finish().
*
* This function may be called without holding threadgroup_lock even if the
* target is a process. Threads may be created and destroyed but as long
* as cgroup_mutex is not dropped, no new css_set can be put into play and
* the preloaded css_sets are guaranteed to cover all migrations.
*/
static void cgroup_migrate_add_src(struct css_set *src_cset,
struct cgroup *dst_cgrp,
struct list_head *preloaded_csets)
{
struct cgroup *src_cgrp;
lockdep_assert_held(&cgroup_mutex);
lockdep_assert_held(&css_set_rwsem);
src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);
if (!list_empty(&src_cset->mg_preload_node))
return;
WARN_ON(src_cset->mg_src_cgrp);
WARN_ON(!list_empty(&src_cset->mg_tasks));
WARN_ON(!list_empty(&src_cset->mg_node));
src_cset->mg_src_cgrp = src_cgrp;
get_css_set(src_cset);
list_add(&src_cset->mg_preload_node, preloaded_csets);
}
/**
* cgroup_migrate_prepare_dst - prepare destination css_sets for migration
* @dst_cgrp: the destination cgroup (may be %NULL)
* @preloaded_csets: list of preloaded source css_sets
*
* Tasks are about to be moved to @dst_cgrp and all the source css_sets
* have been preloaded to @preloaded_csets. This function looks up and
* pins all destination css_sets, links each to its source, and append them
* to @preloaded_csets. If @dst_cgrp is %NULL, the destination of each
* source css_set is assumed to be its cgroup on the default hierarchy.
*
* This function must be called after cgroup_migrate_add_src() has been
* called on each migration source css_set. After migration is performed
* using cgroup_migrate(), cgroup_migrate_finish() must be called on
* @preloaded_csets.
*/
static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp,
struct list_head *preloaded_csets)
{
LIST_HEAD(csets);
struct css_set *src_cset, *tmp_cset;
lockdep_assert_held(&cgroup_mutex);
/*
* Except for the root, child_subsys_mask must be zero for a cgroup
* with tasks so that child cgroups don't compete against tasks.
*/
if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && cgroup_parent(dst_cgrp) &&
dst_cgrp->child_subsys_mask)
return -EBUSY;
/* look up the dst cset for each src cset and link it to src */
list_for_each_entry_safe(src_cset, tmp_cset, preloaded_csets, mg_preload_node) {
struct css_set *dst_cset;
dst_cset = find_css_set(src_cset,
dst_cgrp ?: src_cset->dfl_cgrp);
if (!dst_cset)
goto err;
WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
/*
* If src cset equals dst, it's noop. Drop the src.
* cgroup_migrate() will skip the cset too. Note that we
* can't handle src == dst as some nodes are used by both.
*/
if (src_cset == dst_cset) {
src_cset->mg_src_cgrp = NULL;
list_del_init(&src_cset->mg_preload_node);
put_css_set(src_cset, false);
put_css_set(dst_cset, false);
continue;
}
src_cset->mg_dst_cset = dst_cset;
if (list_empty(&dst_cset->mg_preload_node))
list_add(&dst_cset->mg_preload_node, &csets);
else
put_css_set(dst_cset, false);
}
list_splice_tail(&csets, preloaded_csets);
return 0;
err:
cgroup_migrate_finish(&csets);
return -ENOMEM;
}
/**
* cgroup_migrate - migrate a process or task to a cgroup
* @cgrp: the destination cgroup
* @leader: the leader of the process or the task to migrate
* @threadgroup: whether @leader points to the whole process or a single task
*
* Migrate a process or task denoted by @leader to @cgrp. If migrating a
* process, the caller must be holding threadgroup_lock of @leader. The
* caller is also responsible for invoking cgroup_migrate_add_src() and
* cgroup_migrate_prepare_dst() on the targets before invoking this
* function and following up with cgroup_migrate_finish().
*
* As long as a controller's ->can_attach() doesn't fail, this function is
* guaranteed to succeed. This means that, excluding ->can_attach()
* failure, when migrating multiple targets, the success or failure can be
* decided for all targets by invoking group_migrate_prepare_dst() before
* actually starting migrating.
*/
static int cgroup_migrate(struct cgroup *cgrp, struct task_struct *leader,
bool threadgroup)
{
struct cgroup_taskset tset = {
.src_csets = LIST_HEAD_INIT(tset.src_csets),
.dst_csets = LIST_HEAD_INIT(tset.dst_csets),
.csets = &tset.src_csets,
};
struct cgroup_subsys_state *css, *failed_css = NULL;
struct css_set *cset, *tmp_cset;
struct task_struct *task, *tmp_task;
int i, ret;
/*
* 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.
*/
down_write(&css_set_rwsem);
rcu_read_lock();
task = leader;
do {
/* @task either already exited or can't exit until the end */
if (task->flags & PF_EXITING)
goto next;
/* leave @task alone if post_fork() hasn't linked it yet */
if (list_empty(&task->cg_list))
goto next;
cset = task_css_set(task);
if (!cset->mg_src_cgrp)
goto next;
/*
* cgroup_taskset_first() must always return the leader.
* Take care to avoid disturbing the ordering.
*/
list_move_tail(&task->cg_list, &cset->mg_tasks);
if (list_empty(&cset->mg_node))
list_add_tail(&cset->mg_node, &tset.src_csets);
if (list_empty(&cset->mg_dst_cset->mg_node))
list_move_tail(&cset->mg_dst_cset->mg_node,
&tset.dst_csets);
next:
if (!threadgroup)
break;
} while_each_thread(leader, task);
rcu_read_unlock();
up_write(&css_set_rwsem);
/* methods shouldn't be called if no task is actually migrating */
if (list_empty(&tset.src_csets))
return 0;
/* check that we can legitimately attach to the cgroup */
for_each_e_css(css, i, cgrp) {
if (css->ss->can_attach) {
ret = css->ss->can_attach(css, &tset);
if (ret) {
failed_css = css;
goto out_cancel_attach;
}
}
}
/*
* Now that we're guaranteed success, proceed to move all tasks to
* the new cgroup. There are no failure cases after here, so this
* is the commit point.
*/
down_write(&css_set_rwsem);
list_for_each_entry(cset, &tset.src_csets, mg_node) {
list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list)
cgroup_task_migrate(cset->mg_src_cgrp, task,
cset->mg_dst_cset);
}
up_write(&css_set_rwsem);
/*
* Migration is committed, all target tasks are now on dst_csets.
* Nothing is sensitive to fork() after this point. Notify
* controllers that migration is complete.
*/
tset.csets = &tset.dst_csets;
for_each_e_css(css, i, cgrp)
if (css->ss->attach)
css->ss->attach(css, &tset);
ret = 0;
goto out_release_tset;
out_cancel_attach:
for_each_e_css(css, i, cgrp) {
if (css == failed_css)
break;
if (css->ss->cancel_attach)
css->ss->cancel_attach(css, &tset);
}
out_release_tset:
down_write(&css_set_rwsem);
list_splice_init(&tset.dst_csets, &tset.src_csets);
list_for_each_entry_safe(cset, tmp_cset, &tset.src_csets, mg_node) {
list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
list_del_init(&cset->mg_node);
}
up_write(&css_set_rwsem);
return ret;
}
/**
* cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
* @dst_cgrp: the cgroup to attach to
* @leader: the task or the leader of the threadgroup to be attached
* @threadgroup: attach the whole threadgroup?
*
* Call holding cgroup_mutex and threadgroup_lock of @leader.
*/
static int cgroup_attach_task(struct cgroup *dst_cgrp,
struct task_struct *leader, bool threadgroup)
{
LIST_HEAD(preloaded_csets);
struct task_struct *task;
int ret;
/* look up all src csets */
down_read(&css_set_rwsem);
rcu_read_lock();
task = leader;
do {
cgroup_migrate_add_src(task_css_set(task), dst_cgrp,
&preloaded_csets);
if (!threadgroup)
break;
} while_each_thread(leader, task);
rcu_read_unlock();
up_read(&css_set_rwsem);
/* prepare dst csets and commit */
ret = cgroup_migrate_prepare_dst(dst_cgrp, &preloaded_csets);
if (!ret)
ret = cgroup_migrate(dst_cgrp, leader, threadgroup);
cgroup_migrate_finish(&preloaded_csets);
return ret;
}
/*
* 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.
*/
static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
size_t nbytes, loff_t off, bool threadgroup)
{
struct task_struct *tsk;
const struct cred *cred = current_cred(), *tcred;
struct cgroup *cgrp;
pid_t pid;
int ret;
if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
return -EINVAL;
cgrp = cgroup_kn_lock_live(of->kn);
if (!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:
cgroup_kn_unlock(of->kn);
return ret ?: nbytes;
}
/**
* 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 cgroup_root *root;
int retval = 0;
mutex_lock(&cgroup_mutex);
for_each_root(root) {
struct cgroup *from_cgrp;
if (root == &cgrp_dfl_root)
continue;
down_read(&css_set_rwsem);
from_cgrp = task_cgroup_from_root(from, root);
up_read(&css_set_rwsem);
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 ssize_t cgroup_tasks_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
return __cgroup_procs_write(of, buf, nbytes, off, false);
}
static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
return __cgroup_procs_write(of, buf, nbytes, off, true);
}
static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
struct cgroup *cgrp;
BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
cgrp = cgroup_kn_lock_live(of->kn);
if (!cgrp)
return -ENODEV;
spin_lock(&release_agent_path_lock);
strlcpy(cgrp->root->release_agent_path, strstrip(buf),
sizeof(cgrp->root->release_agent_path));
spin_unlock(&release_agent_path_lock);
cgroup_kn_unlock(of->kn);
return nbytes;
}
static int cgroup_release_agent_show(struct seq_file *seq, void *v)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
spin_lock(&release_agent_path_lock);
seq_puts(seq, cgrp->root->release_agent_path);
spin_unlock(&release_agent_path_lock);
seq_putc(seq, '\n');
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;
}
static void cgroup_print_ss_mask(struct seq_file *seq, unsigned int ss_mask)
{
struct cgroup_subsys *ss;
bool printed = false;
int ssid;
for_each_subsys(ss, ssid) {
if (ss_mask & (1 << ssid)) {
if (printed)
seq_putc(seq, ' ');
seq_printf(seq, "%s", ss->name);
printed = true;
}
}
if (printed)
seq_putc(seq, '\n');
}
/* show controllers which are currently attached to the default hierarchy */
static int cgroup_root_controllers_show(struct seq_file *seq, void *v)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
cgroup_print_ss_mask(seq, cgrp->root->subsys_mask &
~cgrp_dfl_root_inhibit_ss_mask);
return 0;
}
/* show controllers which are enabled from the parent */
static int cgroup_controllers_show(struct seq_file *seq, void *v)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
cgroup_print_ss_mask(seq, cgroup_parent(cgrp)->child_subsys_mask);
return 0;
}
/* show controllers which are enabled for a given cgroup's children */
static int cgroup_subtree_control_show(struct seq_file *seq, void *v)
{
struct cgroup *cgrp = seq_css(seq)->cgroup;
cgroup_print_ss_mask(seq, cgrp->child_subsys_mask);
return 0;
}
/**
* cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
* @cgrp: root of the subtree to update csses for
*
* @cgrp's child_subsys_mask has changed and its subtree's (self excluded)
* css associations need to be updated accordingly. This function looks up
* all css_sets which are attached to the subtree, creates the matching
* updated css_sets and migrates the tasks to the new ones.
*/
static int cgroup_update_dfl_csses(struct cgroup *cgrp)
{
LIST_HEAD(preloaded_csets);
struct cgroup_subsys_state *css;
struct css_set *src_cset;
int ret;
lockdep_assert_held(&cgroup_mutex);
/* look up all csses currently attached to @cgrp's subtree */
down_read(&css_set_rwsem);
css_for_each_descendant_pre(css, cgroup_css(cgrp, NULL)) {
struct cgrp_cset_link *link;
/* self is not affected by child_subsys_mask change */
if (css->cgroup == cgrp)
continue;
list_for_each_entry(link, &css->cgroup->cset_links, cset_link)
cgroup_migrate_add_src(link->cset, cgrp,
&preloaded_csets);
}
up_read(&css_set_rwsem);
/* NULL dst indicates self on default hierarchy */
ret = cgroup_migrate_prepare_dst(NULL, &preloaded_csets);
if (ret)
goto out_finish;
list_for_each_entry(src_cset, &preloaded_csets, mg_preload_node) {
struct task_struct *last_task = NULL, *task;
/* src_csets precede dst_csets, break on the first dst_cset */
if (!src_cset->mg_src_cgrp)
break;
/*
* All tasks in src_cset need to be migrated to the
* matching dst_cset. Empty it process by process. We
* walk tasks but migrate processes. The leader might even
* belong to a different cset but such src_cset would also
* be among the target src_csets because the default
* hierarchy enforces per-process membership.
*/
while (true) {
down_read(&css_set_rwsem);
task = list_first_entry_or_null(&src_cset->tasks,
struct task_struct, cg_list);
if (task) {
task = task->group_leader;
WARN_ON_ONCE(!task_css_set(task)->mg_src_cgrp);
get_task_struct(task);
}
up_read(&css_set_rwsem);
if (!task)
break;
/* guard against possible infinite loop */
if (WARN(last_task == task,
"cgroup: update_dfl_csses failed to make progress, aborting in inconsistent state\n"))
goto out_finish;
last_task = task;
threadgroup_lock(task);
/* raced against de_thread() from another thread? */
if (!thread_group_leader(task)) {
threadgroup_unlock(task);
put_task_struct(task);
continue;
}
ret = cgroup_migrate(src_cset->dfl_cgrp, task, true);
threadgroup_unlock(task);
put_task_struct(task);
if (WARN(ret, "cgroup: failed to update controllers for the default hierarchy (%d), further operations may crash or hang\n", ret))
goto out_finish;
}
}
out_finish:
cgroup_migrate_finish(&preloaded_csets);
return ret;
}
/* change the enabled child controllers for a cgroup in the default hierarchy */
static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
char *buf, size_t nbytes,
loff_t off)
{
unsigned int enable = 0, disable = 0;
struct cgroup *cgrp, *child;
struct cgroup_subsys *ss;
char *tok;
int ssid, ret;
/*
* Parse input - space separated list of subsystem names prefixed
* with either + or -.
*/
buf = strstrip(buf);
while ((tok = strsep(&buf, " "))) {
if (tok[0] == '\0')
continue;
for_each_subsys(ss, ssid) {
if (ss->disabled || strcmp(tok + 1, ss->name) ||
((1 << ss->id) & cgrp_dfl_root_inhibit_ss_mask))
continue;
if (*tok == '+') {
enable |= 1 << ssid;
disable &= ~(1 << ssid);
} else if (*tok == '-') {
disable |= 1 << ssid;
enable &= ~(1 << ssid);
} else {
return -EINVAL;
}
break;
}
if (ssid == CGROUP_SUBSYS_COUNT)
return -EINVAL;
}
cgrp = cgroup_kn_lock_live(of->kn);
if (!cgrp)
return -ENODEV;
for_each_subsys(ss, ssid) {
if (enable & (1 << ssid)) {
if (cgrp->child_subsys_mask & (1 << ssid)) {
enable &= ~(1 << ssid);
continue;
}
/*
* Because css offlining is asynchronous, userland
* might try to re-enable the same controller while
* the previous instance is still around. In such
* cases, wait till it's gone using offline_waitq.
*/
cgroup_for_each_live_child(child, cgrp) {
DEFINE_WAIT(wait);
if (!cgroup_css(child, ss))
continue;
cgroup_get(child);
prepare_to_wait(&child->offline_waitq, &wait,
TASK_UNINTERRUPTIBLE);
cgroup_kn_unlock(of->kn);
schedule();
finish_wait(&child->offline_waitq, &wait);
cgroup_put(child);
return restart_syscall();
}
/* unavailable or not enabled on the parent? */
if (!(cgrp_dfl_root.subsys_mask & (1 << ssid)) ||
(cgroup_parent(cgrp) &&
!(cgroup_parent(cgrp)->child_subsys_mask & (1 << ssid)))) {
ret = -ENOENT;
goto out_unlock;
}
} else if (disable & (1 << ssid)) {
if (!(cgrp->child_subsys_mask & (1 << ssid))) {
disable &= ~(1 << ssid);
continue;
}
/* a child has it enabled? */
cgroup_for_each_live_child(child, cgrp) {
if (child->child_subsys_mask & (1 << ssid)) {
ret = -EBUSY;
goto out_unlock;
}
}
}
}
if (!enable && !disable) {
ret = 0;
goto out_unlock;
}
/*
* Except for the root, child_subsys_mask must be zero for a cgroup
* with tasks so that child cgroups don't compete against tasks.
*/
if (enable && cgroup_parent(cgrp) && !list_empty(&cgrp->cset_links)) {
ret = -EBUSY;
goto out_unlock;
}
/*
* Create csses for enables and update child_subsys_mask. This
* changes cgroup_e_css() results which in turn makes the
* subsequent cgroup_update_dfl_csses() associate all tasks in the
* subtree to the updated csses.
*/
for_each_subsys(ss, ssid) {
if (!(enable & (1 << ssid)))
continue;
cgroup_for_each_live_child(child, cgrp) {
ret = create_css(child, ss);
if (ret)
goto err_undo_css;
}
}
cgrp->child_subsys_mask |= enable;
cgrp->child_subsys_mask &= ~disable;
ret = cgroup_update_dfl_csses(cgrp);
if (ret)
goto err_undo_css;
/* all tasks are now migrated away from the old csses, kill them */
for_each_subsys(ss, ssid) {
if (!(disable & (1 << ssid)))
continue;
cgroup_for_each_live_child(child, cgrp)
kill_css(cgroup_css(child, ss));
}
kernfs_activate(cgrp->kn);
ret = 0;
out_unlock:
cgroup_kn_unlock(of->kn);
return ret ?: nbytes;
err_undo_css:
cgrp->child_subsys_mask &= ~enable;
cgrp->child_subsys_mask |= disable;
for_each_subsys(ss, ssid) {
if (!(enable & (1 << ssid)))
continue;
cgroup_for_each_live_child(child, cgrp) {
struct cgroup_subsys_state *css = cgroup_css(child, ss);
if (css)
kill_css(css);
}
}
goto out_unlock;
}
static int cgroup_populated_show(struct seq_file *seq, void *v)
{
seq_printf(seq, "%d\n", (bool)seq_css(seq)->cgroup->populated_cnt);
return 0;
}
static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
size_t nbytes, loff_t off)
{
struct cgroup *cgrp = of->kn->parent->priv;
struct cftype *cft = of->kn->priv;
struct cgroup_subsys_state *css;
int ret;
if (cft->write)
return cft->write(of, buf, nbytes, off);
/*
* kernfs guarantees that a file isn't deleted with operations in
* flight, which means that the matching css is and stays alive and
* doesn't need to be pinned. The RCU locking is not necessary
* either. It's just for the convenience of using cgroup_css().
*/
rcu_read_lock();
css = cgroup_css(cgrp, cft->ss);
rcu_read_unlock();
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 {
ret = -EINVAL;
}
return ret ?: nbytes;
}
static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
{
return seq_cft(seq)->seq_start(seq, ppos);
}
static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
{
return seq_cft(seq)->seq_next(seq, v, ppos);
}
static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
{
seq_cft(seq)->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 kernfs_ops cgroup_kf_single_ops = {
.atomic_write_len = PAGE_SIZE,
.write = cgroup_file_write,
.seq_show = cgroup_seqfile_show,
};
static struct kernfs_ops cgroup_kf_ops = {
.atomic_write_len = PAGE_SIZE,
.write = cgroup_file_write,
.seq_start = cgroup_seqfile_start,
.seq_next = cgroup_seqfile_next,
.seq_stop = cgroup_seqfile_stop,
.seq_show = cgroup_seqfile_show,
};
/*
* cgroup_rename - Only allow simple rename of directories in place.
*/
static int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
const char *new_name_str)
{
struct cgroup *cgrp = kn->priv;
int ret;
if (kernfs_type(kn) != KERNFS_DIR)
return -ENOTDIR;
if (kn->parent != new_parent)
return -EIO;
/*
* This isn't a proper migration and its usefulness is very
* limited. Disallow if sane_behavior.
*/
if (cgroup_sane_behavior(cgrp))
return -EPERM;
/*
* We're gonna grab cgroup_mutex which nests outside kernfs
* active_ref. kernfs_rename() doesn't require active_ref
* protection. Break them before grabbing cgroup_mutex.
*/
kernfs_break_active_protection(new_parent);
kernfs_break_active_protection(kn);
mutex_lock(&cgroup_mutex);
ret = kernfs_rename(kn, new_parent, new_name_str);
mutex_unlock(&cgroup_mutex);
kernfs_unbreak_active_protection(kn);
kernfs_unbreak_active_protection(new_parent);
return ret;
}
/* set uid and gid of cgroup dirs and files to that of the creator */
static int cgroup_kn_set_ugid(struct kernfs_node *kn)
{
struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
.ia_uid = current_fsuid(),
.ia_gid = current_fsgid(), };
if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
return 0;
return kernfs_setattr(kn, &iattr);
}
static int cgroup_add_file(struct cgroup *cgrp, struct cftype *cft)
{
char name[CGROUP_FILE_NAME_MAX];
struct kernfs_node *kn;
struct lock_class_key *key = NULL;
int ret;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
key = &cft->lockdep_key;
#endif
kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
cgroup_file_mode(cft), 0, cft->kf_ops, cft,
NULL, false, key);
if (IS_ERR(kn))
return PTR_ERR(kn);
ret = cgroup_kn_set_ugid(kn);
if (ret) {
kernfs_remove(kn);
return ret;
}
if (cft->seq_show == cgroup_populated_show)
cgrp->populated_kn = kn;
return 0;
}
/**
* 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(&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_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
continue;
if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp))
continue;
if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp))
continue;
if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp))
continue;
if (is_add) {
ret = cgroup_add_file(cgrp, cft);
if (ret) {
pr_warn("%s: failed to add %s, err=%d\n",
__func__, cft->name, ret);
return ret;
}
} else {
cgroup_rm_file(cgrp, cft);
}
}
return 0;
}
static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
{
LIST_HEAD(pending);
struct cgroup_subsys *ss = cfts[0].ss;
struct cgroup *root = &ss->root->cgrp;
struct cgroup_subsys_state *css;
int ret = 0;
lockdep_assert_held(&cgroup_mutex);
/* 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;
ret = cgroup_addrm_files(cgrp, cfts, is_add);
if (ret)
break;
}
if (is_add && !ret)
kernfs_activate(root->kn);
return ret;
}
static void cgroup_exit_cftypes(struct cftype *cfts)
{
struct cftype *cft;
for (cft = cfts; cft->name[0] != '\0'; cft++) {
/* free copy for custom atomic_write_len, see init_cftypes() */
if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
kfree(cft->kf_ops);
cft->kf_ops = NULL;
cft->ss = NULL;
}
}
static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
{
struct cftype *cft;
for (cft = cfts; cft->name[0] != '\0'; cft++) {
struct kernfs_ops *kf_ops;
WARN_ON(cft->ss || cft->kf_ops);
if (cft->seq_start)
kf_ops = &cgroup_kf_ops;
else
kf_ops = &cgroup_kf_single_ops;
/*
* Ugh... if @cft wants a custom max_write_len, we need to
* make a copy of kf_ops to set its atomic_write_len.
*/
if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
if (!kf_ops) {
cgroup_exit_cftypes(cfts);
return -ENOMEM;
}
kf_ops->atomic_write_len = cft->max_write_len;
}
cft->kf_ops = kf_ops;
cft->ss = ss;
}
return 0;
}
static int cgroup_rm_cftypes_locked(struct cftype *cfts)
{
lockdep_assert_held(&cgroup_mutex);
if (!cfts || !cfts[0].ss)
return -ENOENT;
list_del(&cfts->node);
cgroup_apply_cftypes(cfts, false);
cgroup_exit_cftypes(cfts);
return 0;
}
/**
* 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)
{
int ret;
mutex_lock(&cgroup_mutex);
ret = cgroup_rm_cftypes_locked(cfts);
mutex_unlock(&cgroup_mutex);
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)
{
int ret;
if (ss->disabled)
return 0;
if (!cfts || cfts[0].name[0] == '\0')
return 0;
ret = cgroup_init_cftypes(ss, cfts);
if (ret)
return ret;
mutex_lock(&cgroup_mutex);
list_add_tail(&cfts->node, &ss->cfts);
ret = cgroup_apply_cftypes(cfts, true);
if (ret)
cgroup_rm_cftypes_locked(cfts);
mutex_unlock(&cgroup_mutex);
return ret;
}
/**
* cgroup_task_count - count the number of tasks in a cgroup.
* @cgrp: the cgroup in question
*
* Return the number of tasks in the cgroup.
*/
static int cgroup_task_count(const struct cgroup *cgrp)
{
int count = 0;
struct cgrp_cset_link *link;
down_read(&css_set_rwsem);
list_for_each_entry(link, &cgrp->cset_links, cset_link)
count += atomic_read(&link->cset->refcount);
up_read(&css_set_rwsem);
return count;
}
/**
* css_next_child - find the next child of a given css
* @pos: the current position (%NULL to initiate traversal)
* @parent: css whose children to walk
*
* This function returns the next child of @parent and should be called
* under either cgroup_mutex or RCU read lock. The only requirement is
* that @parent and @pos are accessible. The next sibling is guaranteed to
* be returned regardless of their states.
*
* If a subsystem synchronizes ->css_online() and the start of iteration, a
* css which finished ->css_online() is guaranteed to be visible in the
* future iterations and will stay visible until the last reference is put.
* A css which hasn't finished ->css_online() or already finished
* ->css_offline() may show up during traversal. It's each subsystem's
* responsibility to synchronize against on/offlining.
*/
struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
struct cgroup_subsys_state *parent)
{
struct cgroup_subsys_state *next;
cgroup_assert_mutex_or_rcu_locked();
/*
* @pos could already have been unlinked from the sibling list.
* Once a cgroup is removed, its ->sibling.next is no longer
* updated when its next sibling changes. CSS_RELEASED is set when
* @pos is taken off list, at which time its next pointer is valid,
* and, as releases are serialized, the one pointed to by the next
* pointer is guaranteed to not have started release yet. This
* implies that if we observe !CSS_RELEASED on @pos in this RCU
* critical section, the one pointed to by its next pointer is
* guaranteed to not have finished its RCU grace period even if we
* have dropped rcu_read_lock() inbetween iterations.
*
* If @pos has CSS_RELEASED set, its next pointer can't be
* dereferenced; however, as each css 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 the first css with higher serial number than
* @pos's. While this path can be slower, it happens iff iteration
* races against release and the race window is very small.
*/
if (!pos) {
next = list_entry_rcu(parent->children.next, struct cgroup_subsys_state, sibling);
} else if (likely(!(pos->flags & CSS_RELEASED))) {
next = list_entry_rcu(pos->sibling.next, struct cgroup_subsys_state, sibling);
} else {
list_for_each_entry_rcu(next, &parent->children, sibling)
if (next->serial_nr > pos->serial_nr)
break;
}
/*
* @next, if not pointing to the head, can be dereferenced and is
* the next sibling.
*/
if (&next->sibling != &parent->children)
return next;
return NULL;
}
/**
* 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.
*
* If a subsystem synchronizes ->css_online() and the start of iteration, a
* css which finished ->css_online() is guaranteed to be visible in the
* future iterations and will stay visible until the last reference is put.
* A css which hasn't finished ->css_online() or already finished
* ->css_offline() may show up during traversal. It's each subsystem's
* responsibility to synchronize against on/offlining.
*/
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, pos->parent);
if (next)
return next;
pos = pos->parent;
}
return NULL;
}
/**
* 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;
}
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.
*
* If a subsystem synchronizes ->css_online() and the start of iteration, a
* css which finished ->css_online() is guaranteed to be visible in the
* future iterations and will stay visible until the last reference is put.
* A css which hasn't finished ->css_online() or already finished
* ->css_offline() may show up during traversal. It's each subsystem's
* responsibility to synchronize against on/offlining.
*/
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, pos->parent);
if (next)
return css_leftmost_descendant(next);
/* no sibling left, visit parent */
return pos->parent;
}
/**
* css_has_online_children - does a css have online children
* @css: the target css
*
* Returns %true if @css has any online children; otherwise, %false. This
* function can be called from any context but the caller is responsible
* for synchronizing against on/offlining as necessary.
*/
bool css_has_online_children(struct cgroup_subsys_state *css)
{
struct cgroup_subsys_state *child;
bool ret = false;
rcu_read_lock();
css_for_each_child(child, css) {
if (css->flags & CSS_ONLINE) {
ret = true;
break;
}
}
rcu_read_unlock();
return ret;
}
/**
* 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_pos;
struct cgrp_cset_link *link;
struct css_set *cset;
/* Advance to the next non-empty css_set */
do {
l = l->next;
if (l == it->cset_head) {
it->cset_pos = NULL;
return;
}
if (it->ss) {
cset = container_of(l, struct css_set,
e_cset_node[it->ss->id]);
} else {
link = list_entry(l, struct cgrp_cset_link, cset_link);
cset = link->cset;
}
} while (list_empty(&cset->tasks) && list_empty(&cset->mg_tasks));
it->cset_pos = l;
if (!list_empty(&cset->tasks))
it->task_pos = cset->tasks.next;
else
it->task_pos = cset->mg_tasks.next;
it->tasks_head = &cset->tasks;
it->mg_tasks_head = &cset->mg_tasks;
}
/**
* 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_rwsem)
{
/* no one should try to iterate before mounting cgroups */
WARN_ON_ONCE(!use_task_css_set_links);
down_read(&css_set_rwsem);
it->ss = css->ss;
if (it->ss)
it->cset_pos = &css->cgroup->e_csets[css->ss->id];
else
it->cset_pos = &css->cgroup->cset_links;
it->cset_head = it->cset_pos;
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_pos;
/* If the iterator cg is NULL, we have no tasks */
if (!it->cset_pos)
return NULL;
res = list_entry(l, struct task_struct, cg_list);
/*
* Advance iterator to find next entry. cset->tasks is consumed
* first and then ->mg_tasks. After ->mg_tasks, we move onto the
* next cset.
*/
l = l->next;
if (l == it->tasks_head)
l = it->mg_tasks_head->next;
if (l == it->mg_tasks_head)
css_advance_task_iter(it);
else
it->task_pos = 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_rwsem)
{
up_read(&css_set_rwsem);
}
/**
* 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
*
* Locking rules between cgroup_post_fork() and the migration path
* guarantee that, if a task is forking while being migrated, the new child
* is guaranteed to be either visible in the source cgroup after the
* parent's migration is complete or put into the target cgroup. No task
* can slip out of migration through forking.
*/
int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
{
LIST_HEAD(preloaded_csets);
struct cgrp_cset_link *link;
struct css_task_iter it;
struct task_struct *task;
int ret;
mutex_lock(&cgroup_mutex);
/* all tasks in @from are being moved, all csets are source */
down_read(&css_set_rwsem);
list_for_each_entry(link, &from->cset_links, cset_link)
cgroup_migrate_add_src(link->cset, to, &preloaded_csets);
up_read(&css_set_rwsem);
ret = cgroup_migrate_prepare_dst(to, &preloaded_csets);
if (ret)
goto out_err;
/*
* Migrate tasks one-by-one until @form is empty. This fails iff
* ->can_attach() fails.
*/
do {
css_task_iter_start(&from->self, &it);
task = css_task_iter_next(&it);
if (task)
get_task_struct(task);
css_task_iter_end(&it);
if (task) {
ret = cgroup_migrate(to, task, false);
put_task_struct(task);
}
} while (task && !ret);
out_err:
cgroup_migrate_finish(&preloaded_csets);
mutex_unlock(&cgroup_mutex);
return ret;
}
/*
* 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->self, &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)
{
struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
struct cgroup *cgrp;
struct css_task_iter it;
struct task_struct *tsk;
/* it should be kernfs_node belonging to cgroupfs and is a directory */
if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
kernfs_type(kn) != KERNFS_DIR)
return -EINVAL;
mutex_lock(&cgroup_mutex);
/*
* We aren't being called from kernfs and there's no guarantee on
* @kn->priv's validity. For this and css_tryget_online_from_dir(),
* @kn->priv is RCU safe. Let's do the RCU dancing.
*/
rcu_read_lock();
cgrp = rcu_dereference(kn->priv);
if (!cgrp || cgroup_is_dead(cgrp)) {
rcu_read_unlock();
mutex_unlock(&cgroup_mutex);
return -ENOENT;
}
rcu_read_unlock();
css_task_iter_start(&cgrp->self, &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);
mutex_unlock(&cgroup_mutex);
return 0;
}
/*
* 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 kernfs_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 kernfs_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 kernfs_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);
}
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;
}
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 = 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,
},
{
.name = "cgroup.controllers",
.flags = CFTYPE_ONLY_ON_DFL | CFTYPE_ONLY_ON_ROOT,
.seq_show = cgroup_root_controllers_show,
},
{
.name = "cgroup.controllers",
.flags = CFTYPE_ONLY_ON_DFL | CFTYPE_NOT_ON_ROOT,
.seq_show = cgroup_controllers_show,
},
{
.name = "cgroup.subtree_control",
.flags = CFTYPE_ONLY_ON_DFL,
.seq_show = cgroup_subtree_control_show,
.write = cgroup_subtree_control_write,
},
{
.name = "cgroup.populated",
.flags = CFTYPE_ONLY_ON_DFL | CFTYPE_NOT_ON_ROOT,
.seq_show = cgroup_populated_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 = 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 = cgroup_release_agent_write,
.max_write_len = PATH_MAX - 1,
},
{ } /* 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 int subsys_mask)
{
struct cgroup_subsys *ss;
int i, ret = 0;
/* process cftsets of each subsystem */
for_each_subsys(ss, i) {
struct cftype *cfts;
if (!(subsys_mask & (1 << i)))
continue;
list_for_each_entry(cfts, &ss->cfts, node) {
ret = cgroup_addrm_files(cgrp, 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_online() 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->ss) {
/* css free path */
if (css->parent)
css_put(css->parent);
css->ss->css_free(css);
cgroup_put(cgrp);
} else {
/* cgroup free path */
atomic_dec(&cgrp->root->nr_cgrps);
cgroup_pidlist_destroy_all(cgrp);
if (cgroup_parent(cgrp)) {
/*
* We get a ref to the parent, and put the ref when
* this cgroup is being freed, so it's guaranteed
* that the parent won't be destroyed before its
* children.
*/
cgroup_put(cgroup_parent(cgrp));
kernfs_put(cgrp->kn);
kfree(cgrp);
} else {
/*
* This is root cgroup's refcnt reaching zero,
* which indicates that the root should be
* released.
*/
cgroup_destroy_root(cgrp->root);
}
}
}
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);
INIT_WORK(&css->destroy_work, css_free_work_fn);
queue_work(cgroup_destroy_wq, &css->destroy_work);
}
static void css_release_work_fn(struct work_struct *work)
{
struct cgroup_subsys_state *css =
container_of(work, struct cgroup_subsys_state, destroy_work);
struct cgroup_subsys *ss = css->ss;
struct cgroup *cgrp = css->cgroup;
mutex_lock(&cgroup_mutex);
css->flags |= CSS_RELEASED;
list_del_rcu(&css->sibling);
if (ss) {
/* css release path */
cgroup_idr_remove(&ss->css_idr, css->id);
} else {
/* cgroup release path */
cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
cgrp->id = -1;
}
mutex_unlock(&cgroup_mutex);
call_rcu(&css->rcu_head, css_free_rcu_fn);
}
static void css_release(struct percpu_ref *ref)
{
struct cgroup_subsys_state *css =
container_of(ref, struct cgroup_subsys_state, refcnt);
INIT_WORK(&css->destroy_work, css_release_work_fn);
queue_work(cgroup_destroy_wq, &css->destroy_work);
}
static void init_and_link_css(struct cgroup_subsys_state *css,
struct cgroup_subsys *ss, struct cgroup *cgrp)
{
lockdep_assert_held(&cgroup_mutex);
cgroup_get(cgrp);
memset(css, 0, sizeof(*css));
css->cgroup = cgrp;
css->ss = ss;
INIT_LIST_HEAD(&css->sibling);
INIT_LIST_HEAD(&css->children);
css->serial_nr = css_serial_nr_next++;
if (cgroup_parent(cgrp)) {
css->parent = cgroup_css(cgroup_parent(cgrp), ss);
css_get(css->parent);
}
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;
rcu_assign_pointer(css->cgroup->subsys[ss->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;
RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL);
wake_up_all(&css->cgroup->offline_waitq);
}
/**
* 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 = cgroup_parent(cgrp);
struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss);
struct cgroup_subsys_state *css;
int err;
lockdep_assert_held(&cgroup_mutex);
css = ss->css_alloc(parent_css);
if (IS_ERR(css))
return PTR_ERR(css);
init_and_link_css(css, ss, cgrp);
err = percpu_ref_init(&css->refcnt, css_release);
if (err)
goto err_free_css;
err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_NOWAIT);
if (err < 0)
goto err_free_percpu_ref;
css->id = err;
err = cgroup_populate_dir(cgrp, 1 << ss->id);
if (err)
goto err_free_id;
/* @css is ready to be brought online now, make it visible */
list_add_tail_rcu(&css->sibling, &parent_css->children);
cgroup_idr_replace(&ss->css_idr, css, css->id);
err = online_css(css);
if (err)
goto err_list_del;
if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
cgroup_parent(parent)) {
pr_warn("%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_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n");
ss->warned_broken_hierarchy = true;
}
return 0;
err_list_del:
list_del_rcu(&css->sibling);
cgroup_clear_dir(css->cgroup, 1 << css->ss->id);
err_free_id:
cgroup_idr_remove(&ss->css_idr, css->id);
err_free_percpu_ref:
percpu_ref_cancel_init(&css->refcnt);
err_free_css:
call_rcu(&css->rcu_head, css_free_rcu_fn);
return err;
}
static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
umode_t mode)
{
struct cgroup *parent, *cgrp;
struct cgroup_root *root;
struct cgroup_subsys *ss;
struct kernfs_node *kn;
int ssid, ret;
parent = cgroup_kn_lock_live(parent_kn);
if (!parent)
return -ENODEV;
root = parent->root;
/* allocate the cgroup and its ID, 0 is reserved for the root */
cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
if (!cgrp) {
ret = -ENOMEM;
goto out_unlock;
}
ret = percpu_ref_init(&cgrp->self.refcnt, css_release);
if (ret)
goto out_free_cgrp;
/*
* Temporarily set the pointer to NULL, so idr_find() won't return
* a half-baked cgroup.
*/
cgrp->id = cgroup_idr_alloc(&root->cgroup_idr, NULL, 2, 0, GFP_NOWAIT);
if (cgrp->id < 0) {
ret = -ENOMEM;
goto out_cancel_ref;
}
init_cgroup_housekeeping(cgrp);
cgrp->self.parent = &parent->self;
cgrp->root = 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 the directory */
kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
if (IS_ERR(kn)) {
ret = PTR_ERR(kn);
goto out_free_id;
}
cgrp->kn = kn;
/*
* This extra ref will be put in cgroup_free_fn() and guarantees
* that @cgrp->kn is always accessible.
*/
kernfs_get(kn);
cgrp->self.serial_nr = css_serial_nr_next++;
/* allocation complete, commit to creation */
list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);
atomic_inc(&root->nr_cgrps);
cgroup_get(parent);
/*
* @cgrp is now fully operational. If something fails after this
* point, it'll be released via the normal destruction path.
*/
cgroup_idr_replace(&root->cgroup_idr, cgrp, cgrp->id);
ret = cgroup_kn_set_ugid(kn);
if (ret)
goto out_destroy;
ret = cgroup_addrm_files(cgrp, cgroup_base_files, true);
if (ret)
goto out_destroy;
/* let's create and online css's */
for_each_subsys(ss, ssid) {
if (parent->child_subsys_mask & (1 << ssid)) {
ret = create_css(cgrp, ss);
if (ret)
goto out_destroy;
}
}
/*
* On the default hierarchy, a child doesn't automatically inherit
* child_subsys_mask from the parent. Each is configured manually.
*/
if (!cgroup_on_dfl(cgrp))
cgrp->child_subsys_mask = parent->child_subsys_mask;
kernfs_activate(kn);
ret = 0;
goto out_unlock;
out_free_id:
cgroup_idr_remove(&root->cgroup_idr, cgrp->id);
out_cancel_ref:
percpu_ref_cancel_init(&cgrp->self.refcnt);
out_free_cgrp:
kfree(cgrp);
out_unlock:
cgroup_kn_unlock(parent_kn);
return ret;
out_destroy:
cgroup_destroy_locked(cgrp);
goto out_unlock;
}
/*
* This is called when the refcnt of a css is confirmed to be killed.
* css_tryget_online() is now guaranteed to fail. Tell the subsystem to
* initate destruction and put the css ref from kill_css().
*/
static void css_killed_work_fn(struct work_struct *work)
{
struct cgroup_subsys_state *css =
container_of(work, struct cgroup_subsys_state, destroy_work);
mutex_lock(&cgroup_mutex);
offline_css(css);
mutex_unlock(&cgroup_mutex);
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_online() is guaranteed to fail and when
* the reference count reaches zero, @css will be released.
*/
static void kill_css(struct cgroup_subsys_state *css)
{
lockdep_assert_held(&cgroup_mutex);
/*
* This must happen before css is disassociated with its cgroup.
* See seq_css() for details.
*/
cgroup_clear_dir(css->cgroup, 1 << css->ss->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_online(). 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_online() 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 cgroup_subsys_state *css;
bool empty;
int ssid;
lockdep_assert_held(&cgroup_mutex);
/*
* css_set_rwsem synchronizes access to ->cset_links and prevents
* @cgrp from being removed while put_css_set() is in progress.
*/
down_read(&css_set_rwsem);
empty = list_empty(&cgrp->cset_links);
up_read(&css_set_rwsem);
if (!empty)
return -EBUSY;
/*
* Make sure there's no live children. We can't test emptiness of
* ->self.children as dead children linger on it while being
* drained; otherwise, "rmdir parent/child parent" may fail.
*/
if (css_has_online_children(&cgrp->self))
return -EBUSY;
/*
* Mark @cgrp dead. This prevents further task migration and child
* creation by disabling cgroup_lock_live_group().
*/
cgrp->self.flags &= ~CSS_ONLINE;
/* initiate massacre of all css's */
for_each_css(css, ssid, cgrp)
kill_css(css);
/* CSS_ONLINE is clear, 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);
/*
* Remove @cgrp directory along with the base files. @cgrp has an
* extra ref on its kn.
*/
kernfs_remove(cgrp->kn);
set_bit(CGRP_RELEASABLE, &cgroup_parent(cgrp)->flags);
check_for_release(cgroup_parent(cgrp));
/* put the base reference */
percpu_ref_kill(&cgrp->self.refcnt);
return 0;
};
static int cgroup_rmdir(struct kernfs_node *kn)
{
struct cgroup *cgrp;
int ret = 0;
cgrp = cgroup_kn_lock_live(kn);
if (!cgrp)
return 0;
cgroup_get(cgrp); /* for @kn->priv clearing */
ret = cgroup_destroy_locked(cgrp);
cgroup_kn_unlock(kn);
/*
* There are two control paths which try to determine cgroup from
* dentry without going through kernfs - cgroupstats_build() and
* css_tryget_online_from_dir(). Those are supported by RCU
* protecting clearing of cgrp->kn->priv backpointer, which should
* happen after all files under it have been removed.
*/
if (!ret)
RCU_INIT_POINTER(*(void __rcu __force **)&kn->priv, NULL);
cgroup_put(cgrp);
return ret;
}
static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
.remount_fs = cgroup_remount,
.show_options = cgroup_show_options,
.mkdir = cgroup_mkdir,
.rmdir = cgroup_rmdir,
.rename = cgroup_rename,
};
static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
{
struct cgroup_subsys_state *css;
printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
mutex_lock(&cgroup_mutex);
idr_init(&ss->css_idr);
INIT_LIST_HEAD(&ss->cfts);
/* Create the root cgroup state for this subsystem */
ss->root = &cgrp_dfl_root;
css = ss->css_alloc(cgroup_css(&cgrp_dfl_root.cgrp, ss));
/* We don't handle early failures gracefully */
BUG_ON(IS_ERR(css));
init_and_link_css(css, ss, &cgrp_dfl_root.cgrp);
/*
* Root csses are never destroyed and we can't initialize
* percpu_ref during early init. Disable refcnting.
*/
css->flags |= CSS_NO_REF;
if (early) {
/* allocation can't be done safely during early init */
css->id = 1;
} else {
css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL);
BUG_ON(css->id < 0);
}
/* 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 root cgroup. */
init_css_set.subsys[ss->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);
}
/**
* 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)
{
static struct cgroup_sb_opts __initdata opts =
{ .flags = CGRP_ROOT_SANE_BEHAVIOR };
struct cgroup_subsys *ss;
int i;
init_cgroup_root(&cgrp_dfl_root, &opts);
cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF;
RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
for_each_subsys(ss, i) {
WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
"invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p name:id=%d:%s\n",
i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
ss->id, ss->name);
WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
"cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
ss->id = i;
ss->name = cgroup_subsys_name[i];
if (ss->early_init)
cgroup_init_subsys(ss, true);
}
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 ssid, err;
BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
mutex_lock(&cgroup_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_setup_root(&cgrp_dfl_root, 0));
mutex_unlock(&cgroup_mutex);
for_each_subsys(ss, ssid) {
if (ss->early_init) {
struct cgroup_subsys_state *css =
init_css_set.subsys[ss->id];
css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2,
GFP_KERNEL);
BUG_ON(css->id < 0);
} else {
cgroup_init_subsys(ss, false);
}
list_add_tail(&init_css_set.e_cset_node[ssid],
&cgrp_dfl_root.cgrp.e_csets[ssid]);
/*
* Setting dfl_root subsys_mask needs to consider the
* disabled flag and cftype registration needs kmalloc,
* both of which aren't available during early_init.
*/
if (!ss->disabled) {
cgrp_dfl_root.subsys_mask |= 1 << ss->id;
WARN_ON(cgroup_add_cftypes(ss, ss->base_cftypes));
}
}
cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
if (!cgroup_kobj)
return -ENOMEM;
err = register_filesystem(&cgroup_fs_type);
if (err < 0) {
kobject_put(cgroup_kobj);
return err;
}
proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
return 0;
}
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.
*/
/* 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, *path;
int retval;
struct cgroup_root *root;
retval = -ENOMEM;
buf = kmalloc(PATH_MAX, 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);
down_read(&css_set_rwsem);
for_each_root(root) {
struct cgroup_subsys *ss;
struct cgroup *cgrp;
int ssid, count = 0;
if (root == &cgrp_dfl_root && !cgrp_dfl_root_visible)
continue;
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);
path = cgroup_path(cgrp, buf, PATH_MAX);
if (!path) {
retval = -ENAMETOOLONG;
goto out_unlock;
}
seq_puts(m, path);
seq_putc(m, '\n');
}
out_unlock:
up_read(&css_set_rwsem);
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,
atomic_read(&ss->root->nr_cgrps), !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 - initialize cgroup related fields during copy_process()
* @child: pointer to task_struct of forking parent process.
*
* A task is associated with the init_css_set until cgroup_post_fork()
* attaches it to the parent's css_set. Empty cg_list indicates that
* @child isn't holding reference to its css_set.
*/
void cgroup_fork(struct task_struct *child)
{
RCU_INIT_POINTER(child->cgroups, &init_css_set);
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;
/*
* This may race against cgroup_enable_task_cg_links(). As that
* function sets use_task_css_set_links before grabbing
* tasklist_lock and we just went through tasklist_lock to add
* @child, it's guaranteed that either we see the set
* use_task_css_set_links or cgroup_enable_task_cg_lists() sees
* @child during its iteration.
*
* If we won the race, @child is associated with %current's
* css_set. Grabbing css_set_rwsem guarantees both that the
* association is stable, and, on completion of the parent's
* migration, @child is visible in the source of migration or
* already in the destination cgroup. This guarantee is necessary
* when implementing operations which need to migrate all tasks of
* a cgroup to another.
*
* Note that if we lose to cgroup_enable_task_cg_links(), @child
* will remain in init_css_set. This is safe because all tasks are
* in the init_css_set before cg_links is enabled and there's no
* operation which transfers all tasks out of init_css_set.
*/
if (use_task_css_set_links) {
struct css_set *cset;
down_write(&css_set_rwsem);
cset = task_css_set(current);
if (list_empty(&child->cg_list)) {
rcu_assign_pointer(child->cgroups, cset);
list_add(&child->cg_list, &cset->tasks);
get_css_set(cset);
}
up_write(&css_set_rwsem);
}
/*
* 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) {
for_each_subsys(ss, i)
if (ss->fork)
ss->fork(child);
}
}
/**
* cgroup_exit - detach cgroup from exiting task
* @tsk: pointer to task_struct of exiting process
*
* Description: Detach cgroup from @tsk and release it.
*
* Note that cgroups marked notify_on_release force every task in
* them to take the global cgroup_mutex mutex when exiting.
* This could impact scaling on very large systems. Be reluctant to
* use notify_on_release cgroups where very high task exit scaling
* is required on large systems.
*
* We 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. No need to bother with
* init_css_set refcnting. init_css_set never goes away and we can't race
* with migration path - PF_EXITING is visible to migration path.
*/
void cgroup_exit(struct task_struct *tsk)
{
struct cgroup_subsys *ss;
struct css_set *cset;
bool put_cset = false;
int i;
/*
* Unlink from @tsk from its css_set. As migration path can't race
* with us, we can check cg_list without grabbing css_set_rwsem.
*/
if (!list_empty(&tsk->cg_list)) {
down_write(&css_set_rwsem);
list_del_init(&tsk->cg_list);
up_write(&css_set_rwsem);
put_cset = true;
}
/* Reassign the task to the init_css_set. */
cset = task_css_set(tsk);
RCU_INIT_POINTER(tsk->cgroups, &init_css_set);
if (need_forkexit_callback) {
/* see cgroup_post_fork() for details */
for_each_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);
}
}
}
if (put_cset)
put_css_set(cset, true);
}
static void check_for_release(struct cgroup *cgrp)
{
if (cgroup_is_releasable(cgrp) && list_empty(&cgrp->cset_links) &&
!css_has_online_children(&cgrp->self)) {
/*
* 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, *path;
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(PATH_MAX, GFP_KERNEL);
if (!pathbuf)
goto continue_free;
path = cgroup_path(cgrp, pathbuf, PATH_MAX);
if (!path)
goto continue_free;
agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
if (!agentbuf)
goto continue_free;
i = 0;
argv[i++] = agentbuf;
argv[i++] = path;
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;
for_each_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_tryget_online_from_dir - get corresponding css from a cgroup dentry
* @dentry: directory dentry of interest
* @ss: subsystem of interest
*
* If @dentry is a directory for a cgroup which has @ss enabled on it, try
* to get the corresponding css and return it. If such css doesn't exist
* or can't be pinned, an ERR_PTR value is returned.
*/
struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
struct cgroup_subsys *ss)
{
struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
struct cgroup_subsys_state *css = NULL;
struct cgroup *cgrp;
/* is @dentry a cgroup dir? */
if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
kernfs_type(kn) != KERNFS_DIR)
return ERR_PTR(-EBADF);
rcu_read_lock();
/*
* This path doesn't originate from kernfs and @kn could already
* have been or be removed at any point. @kn->priv is RCU
* protected for this access. See cgroup_rmdir() for details.
*/
cgrp = rcu_dereference(kn->priv);
if (cgrp)
css = cgroup_css(cgrp, ss);
if (!css || !css_tryget_online(css))
css = ERR_PTR(-ENOENT);
rcu_read_unlock();
return css;
}
/**
* 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)
{
WARN_ON_ONCE(!rcu_read_lock_held());
return idr_find(&ss->css_idr, id);
}
#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;
char *name_buf;
name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
if (!name_buf)
return -ENOMEM;
down_read(&css_set_rwsem);
rcu_read_lock();
cset = rcu_dereference(current->cgroups);
list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
struct cgroup *c = link->cgrp;
cgroup_name(c, name_buf, NAME_MAX + 1);
seq_printf(seq, "Root %d group %s\n",
c->root->hierarchy_id, name_buf);
}
rcu_read_unlock();
up_read(&css_set_rwsem);
kfree(name_buf);
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;
down_read(&css_set_rwsem);
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)
goto overflow;
seq_printf(seq, " task %d\n", task_pid_vnr(task));
}
list_for_each_entry(task, &cset->mg_tasks, cg_list) {
if (count++ > MAX_TASKS_SHOWN_PER_CSS)
goto overflow;
seq_printf(seq, " task %d\n", task_pid_vnr(task));
}
continue;
overflow:
seq_puts(seq, " ...\n");
}
up_read(&css_set_rwsem);
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_cgrp_subsys = {
.css_alloc = debug_css_alloc,
.css_free = debug_css_free,
.base_cftypes = debug_files,
};
#endif /* CONFIG_CGROUP_DEBUG */