cgroup: move cgroup files under kernel/cgroup/

They're growing to be too many and planned to get split further.  Move
them under their own directory.

 kernel/cgroup.c		-> kernel/cgroup/cgroup.c
 kernel/cgroup_freezer.c	-> kernel/cgroup/freezer.c
 kernel/cgroup_pids.c		-> kernel/cgroup/pids.c
 kernel/cpuset.c		-> kernel/cgroup/cpuset.c

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Acked-by: Zefan Li <lizefan@huawei.com>

1 files changed, 0 insertions, 6705 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
deleted file mode 100644
index 1a815f275849..000000000000
--- a/kernel/cgroup.c
+++ /dev/null
@@ -1,6705 +0,0 @@
-/*
- *  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/percpu-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>
-#include <linux/cpuset.h>
-#include <linux/proc_ns.h>
-#include <linux/nsproxy.h>
-#include <linux/file.h>
-#include <net/sock.h>
-
-#define CREATE_TRACE_POINTS
-#include <trace/events/cgroup.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_lock 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);
-DEFINE_SPINLOCK(css_set_lock);
-EXPORT_SYMBOL_GPL(cgroup_mutex);
-EXPORT_SYMBOL_GPL(css_set_lock);
-#else
-static DEFINE_MUTEX(cgroup_mutex);
-static DEFINE_SPINLOCK(css_set_lock);
-#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_file->kn for !self csses.  It synchronizes notifications
- * against file removal/re-creation across css hiding.
- */
-static DEFINE_SPINLOCK(cgroup_file_kn_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);
-
-struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
-
-#define cgroup_assert_mutex_or_rcu_locked()				\
-	RCU_LOCKDEP_WARN(!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
-
-/* array of static_keys for cgroup_subsys_enabled() and cgroup_subsys_on_dfl() */
-#define SUBSYS(_x)								\
-	DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key);			\
-	DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key);			\
-	EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key);			\
-	EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key);
-#include <linux/cgroup_subsys.h>
-#undef SUBSYS
-
-#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_enabled_key,
-static struct static_key_true *cgroup_subsys_enabled_key[] = {
-#include <linux/cgroup_subsys.h>
-};
-#undef SUBSYS
-
-#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_on_dfl_key,
-static struct static_key_true *cgroup_subsys_on_dfl_key[] = {
-#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;
-EXPORT_SYMBOL_GPL(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_visible;
-
-/* Controllers blocked by the commandline in v1 */
-static u16 cgroup_no_v1_mask;
-
-/* some controllers are not supported in the default hierarchy */
-static u16 cgrp_dfl_inhibit_ss_mask;
-
-/* some controllers are implicitly enabled on the default hierarchy */
-static unsigned long cgrp_dfl_implicit_ss_mask;
-
-/* 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;
-
-/*
- * These bitmask flags indicate whether tasks in the fork and exit paths have
- * fork/exit handlers to call. This avoids us having to do extra work in the
- * fork/exit path to check which subsystems have fork/exit callbacks.
- */
-static u16 have_fork_callback __read_mostly;
-static u16 have_exit_callback __read_mostly;
-static u16 have_free_callback __read_mostly;
-
-/* cgroup namespace for init task */
-struct cgroup_namespace init_cgroup_ns = {
-	.count		= { .counter = 2, },
-	.user_ns	= &init_user_ns,
-	.ns.ops		= &cgroupns_operations,
-	.ns.inum	= PROC_CGROUP_INIT_INO,
-	.root_cset	= &init_css_set,
-};
-
-/* Ditto for the can_fork callback. */
-static u16 have_canfork_callback __read_mostly;
-
-static struct file_system_type cgroup2_fs_type;
-static struct cftype cgroup_dfl_base_files[];
-static struct cftype cgroup_legacy_base_files[];
-
-static int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask);
-static void cgroup_lock_and_drain_offline(struct cgroup *cgrp);
-static int cgroup_apply_control(struct cgroup *cgrp);
-static void cgroup_finalize_control(struct cgroup *cgrp, int ret);
-static void css_task_iter_advance(struct css_task_iter *it);
-static int cgroup_destroy_locked(struct cgroup *cgrp);
-static struct cgroup_subsys_state *css_create(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_subsys_state *css,
-			      struct cgroup *cgrp, struct cftype cfts[],
-			      bool is_add);
-
-/**
- * cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID
- * @ssid: subsys ID of interest
- *
- * cgroup_subsys_enabled() can only be used with literal subsys names which
- * is fine for individual subsystems but unsuitable for cgroup core.  This
- * is slower static_key_enabled() based test indexed by @ssid.
- */
-static bool cgroup_ssid_enabled(int ssid)
-{
-	if (CGROUP_SUBSYS_COUNT == 0)
-		return false;
-
-	return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
-}
-
-static bool cgroup_ssid_no_v1(int ssid)
-{
-	return cgroup_no_v1_mask & (1 << ssid);
-}
-
-/**
- * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
- * @cgrp: the cgroup of interest
- *
- * The default hierarchy is the v2 interface of cgroup and this function
- * can be used to test whether a cgroup is on the default hierarchy for
- * cases where a subsystem should behave differnetly depending on the
- * interface version.
- *
- * The set of behaviors which change on the default hierarchy are still
- * being determined and the mount option is prefixed with __DEVEL__.
- *
- * List of changed behaviors:
- *
- * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
- *   and "name" are disallowed.
- *
- * - When mounting an existing superblock, mount options should match.
- *
- * - Remount is disallowed.
- *
- * - rename(2) is disallowed.
- *
- * - "tasks" is removed.  Everything should be at process granularity.  Use
- *   "cgroup.procs" instead.
- *
- * - "cgroup.procs" is not sorted.  pids will be unique unless they got
- *   recycled inbetween reads.
- *
- * - "release_agent" and "notify_on_release" are removed.  Replacement
- *   notification mechanism will be implemented.
- *
- * - "cgroup.clone_children" is removed.
- *
- * - "cgroup.subtree_populated" is available.  Its value is 0 if the cgroup
- *   and its descendants contain no task; otherwise, 1.  The file also
- *   generates kernfs notification which can be monitored through poll and
- *   [di]notify when the value of the file changes.
- *
- * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
- *   take masks of ancestors with non-empty cpus/mems, instead of being
- *   moved to an ancestor.
- *
- * - cpuset: a task can be moved into an empty cpuset, and again it takes
- *   masks of ancestors.
- *
- * - memcg: use_hierarchy is on by default and the cgroup file for the flag
- *   is not created.
- *
- * - blkcg: blk-throttle becomes properly hierarchical.
- *
- * - debug: disallowed on the default hierarchy.
- */
-static bool cgroup_on_dfl(const struct cgroup *cgrp)
-{
-	return cgrp->root == &cgrp_dfl_root;
-}
-
-/* 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 & ~__GFP_DIRECT_RECLAIM);
-	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;
-}
-
-/* subsystems visibly enabled on a cgroup */
-static u16 cgroup_control(struct cgroup *cgrp)
-{
-	struct cgroup *parent = cgroup_parent(cgrp);
-	u16 root_ss_mask = cgrp->root->subsys_mask;
-
-	if (parent)
-		return parent->subtree_control;
-
-	if (cgroup_on_dfl(cgrp))
-		root_ss_mask &= ~(cgrp_dfl_inhibit_ss_mask |
-				  cgrp_dfl_implicit_ss_mask);
-	return root_ss_mask;
-}
-
-/* subsystems enabled on a cgroup */
-static u16 cgroup_ss_mask(struct cgroup *cgrp)
-{
-	struct cgroup *parent = cgroup_parent(cgrp);
-
-	if (parent)
-		return parent->subtree_ss_mask;
-
-	return cgrp->root->subsys_mask;
-}
-
-/**
- * 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 effective 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;
-
-	/*
-	 * This function is used while updating css associations and thus
-	 * can't test the csses directly.  Test ss_mask.
-	 */
-	while (!(cgroup_ss_mask(cgrp) & (1 << ss->id))) {
-		cgrp = cgroup_parent(cgrp);
-		if (!cgrp)
-			return NULL;
-	}
-
-	return cgroup_css(cgrp, ss);
-}
-
-/**
- * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
- * @cgrp: the cgroup of interest
- * @ss: the subsystem of interest
- *
- * Find and get the effective css of @cgrp for @ss.  The effective css is
- * defined as the matching css of the nearest ancestor including self which
- * has @ss enabled.  If @ss is not mounted on the hierarchy @cgrp is on,
- * the root css is returned, so this function always returns a valid css.
- * The returned css must be put using css_put().
- */
-struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
-					     struct cgroup_subsys *ss)
-{
-	struct cgroup_subsys_state *css;
-
-	rcu_read_lock();
-
-	do {
-		css = cgroup_css(cgrp, ss);
-
-		if (css && css_tryget_online(css))
-			goto out_unlock;
-		cgrp = cgroup_parent(cgrp);
-	} while (cgrp);
-
-	css = init_css_set.subsys[ss->id];
-	css_get(css);
-out_unlock:
-	rcu_read_unlock();
-	return css;
-}
-
-/* convenient tests for these bits */
-static inline bool cgroup_is_dead(const struct cgroup *cgrp)
-{
-	return !(cgrp->self.flags & CSS_ONLINE);
-}
-
-static void cgroup_get(struct cgroup *cgrp)
-{
-	WARN_ON_ONCE(cgroup_is_dead(cgrp));
-	css_get(&cgrp->self);
-}
-
-static bool cgroup_tryget(struct cgroup *cgrp)
-{
-	return css_tryget(&cgrp->self);
-}
-
-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);
-
-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)++)
-
-/**
- * do_each_subsys_mask - filter for_each_subsys with a bitmask
- * @ss: the iteration cursor
- * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
- * @ss_mask: the bitmask
- *
- * The block will only run for cases where the ssid-th bit (1 << ssid) of
- * @ss_mask is set.
- */
-#define do_each_subsys_mask(ss, ssid, ss_mask) do {			\
-	unsigned long __ss_mask = (ss_mask);				\
-	if (!CGROUP_SUBSYS_COUNT) { /* to avoid spurious gcc warning */	\
-		(ssid) = 0;						\
-		break;							\
-	}								\
-	for_each_set_bit(ssid, &__ss_mask, CGROUP_SUBSYS_COUNT) {	\
-		(ss) = cgroup_subsys[ssid];				\
-		{
-
-#define while_each_subsys_mask()					\
-		}							\
-	}								\
-} while (false)
-
-/* 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
-
-/* walk live descendants in preorder */
-#define cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp)		\
-	css_for_each_descendant_pre((d_css), cgroup_css((cgrp), NULL))	\
-		if (({ lockdep_assert_held(&cgroup_mutex);		\
-		       (dsct) = (d_css)->cgroup;			\
-		       cgroup_is_dead(dsct); }))			\
-			;						\
-		else
-
-/* walk live descendants in postorder */
-#define cgroup_for_each_live_descendant_post(dsct, d_css, cgrp)		\
-	css_for_each_descendant_post((d_css), cgroup_css((cgrp), NULL))	\
-		if (({ lockdep_assert_held(&cgroup_mutex);		\
-		       (dsct) = (d_css)->cgroup;			\
-		       cgroup_is_dead(dsct); }))			\
-			;						\
-		else
-
-static void cgroup_release_agent(struct work_struct *work);
-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),
-	.tasks			= LIST_HEAD_INIT(init_css_set.tasks),
-	.mg_tasks		= LIST_HEAD_INIT(init_css_set.mg_tasks),
-	.task_iters		= LIST_HEAD_INIT(init_css_set.task_iters),
-	.cgrp_links		= LIST_HEAD_INIT(init_css_set.cgrp_links),
-	.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 */
-
-/**
- * css_set_populated - does a css_set contain any tasks?
- * @cset: target css_set
- */
-static bool css_set_populated(struct css_set *cset)
-{
-	lockdep_assert_held(&css_set_lock);
-
-	return !list_empty(&cset->tasks) || !list_empty(&cset->mg_tasks);
-}
-
-/**
- * cgroup_update_populated - updated populated count of a cgroup
- * @cgrp: the target cgroup
- * @populated: inc or dec populated count
- *
- * One of the css_sets associated with @cgrp is either getting its first
- * task 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 don't contain any tasks.
- *
- * @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_lock);
-
-	do {
-		bool trigger;
-
-		if (populated)
-			trigger = !cgrp->populated_cnt++;
-		else
-			trigger = !--cgrp->populated_cnt;
-
-		if (!trigger)
-			break;
-
-		check_for_release(cgrp);
-		cgroup_file_notify(&cgrp->events_file);
-
-		cgrp = cgroup_parent(cgrp);
-	} while (cgrp);
-}
-
-/**
- * css_set_update_populated - update populated state of a css_set
- * @cset: target css_set
- * @populated: whether @cset is populated or depopulated
- *
- * @cset is either getting the first task or losing the last.  Update the
- * ->populated_cnt of all associated cgroups accordingly.
- */
-static void css_set_update_populated(struct css_set *cset, bool populated)
-{
-	struct cgrp_cset_link *link;
-
-	lockdep_assert_held(&css_set_lock);
-
-	list_for_each_entry(link, &cset->cgrp_links, cgrp_link)
-		cgroup_update_populated(link->cgrp, populated);
-}
-
-/**
- * css_set_move_task - move a task from one css_set to another
- * @task: task being moved
- * @from_cset: css_set @task currently belongs to (may be NULL)
- * @to_cset: new css_set @task is being moved to (may be NULL)
- * @use_mg_tasks: move to @to_cset->mg_tasks instead of ->tasks
- *
- * Move @task from @from_cset to @to_cset.  If @task didn't belong to any
- * css_set, @from_cset can be NULL.  If @task is being disassociated
- * instead of moved, @to_cset can be NULL.
- *
- * This function automatically handles populated_cnt updates and
- * css_task_iter adjustments but the caller is responsible for managing
- * @from_cset and @to_cset's reference counts.
- */
-static void css_set_move_task(struct task_struct *task,
-			      struct css_set *from_cset, struct css_set *to_cset,
-			      bool use_mg_tasks)
-{
-	lockdep_assert_held(&css_set_lock);
-
-	if (to_cset && !css_set_populated(to_cset))
-		css_set_update_populated(to_cset, true);
-
-	if (from_cset) {
-		struct css_task_iter *it, *pos;
-
-		WARN_ON_ONCE(list_empty(&task->cg_list));
-
-		/*
-		 * @task is leaving, advance task iterators which are
-		 * pointing to it so that they can resume at the next
-		 * position.  Advancing an iterator might remove it from
-		 * the list, use safe walk.  See css_task_iter_advance*()
-		 * for details.
-		 */
-		list_for_each_entry_safe(it, pos, &from_cset->task_iters,
-					 iters_node)
-			if (it->task_pos == &task->cg_list)
-				css_task_iter_advance(it);
-
-		list_del_init(&task->cg_list);
-		if (!css_set_populated(from_cset))
-			css_set_update_populated(from_cset, false);
-	} else {
-		WARN_ON_ONCE(!list_empty(&task->cg_list));
-	}
-
-	if (to_cset) {
-		/*
-		 * We are synchronized through cgroup_threadgroup_rwsem
-		 * 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(task->flags & PF_EXITING);
-
-		rcu_assign_pointer(task->cgroups, to_cset);
-		list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks :
-							     &to_cset->tasks);
-	}
-}
-
-/*
- * 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)
-{
-	struct cgrp_cset_link *link, *tmp_link;
-	struct cgroup_subsys *ss;
-	int ssid;
-
-	lockdep_assert_held(&css_set_lock);
-
-	if (!atomic_dec_and_test(&cset->refcount))
-		return;
-
-	/* This css_set is dead. unlink it and release cgroup and css refs */
-	for_each_subsys(ss, ssid) {
-		list_del(&cset->e_cset_node[ssid]);
-		css_put(cset->subsys[ssid]);
-	}
-	hash_del(&cset->hlist);
-	css_set_count--;
-
-	list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
-		list_del(&link->cset_link);
-		list_del(&link->cgrp_link);
-		if (cgroup_parent(link->cgrp))
-			cgroup_put(link->cgrp);
-		kfree(link);
-	}
-
-	kfree_rcu(cset, rcu_head);
-}
-
-static void put_css_set(struct css_set *cset)
-{
-	unsigned long flags;
-
-	/*
-	 * 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;
-
-	spin_lock_irqsave(&css_set_lock, flags);
-	put_css_set_locked(cset);
-	spin_unlock_irqrestore(&css_set_lock, flags);
-}
-
-/*
- * 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;
-
-	/*
-	 * Always add links to the tail of the lists so that the lists are
-	 * in choronological order.
-	 */
-	list_move_tail(&link->cset_link, &cgrp->cset_links);
-	list_add_tail(&link->cgrp_link, &cset->cgrp_links);
-
-	if (cgroup_parent(cgrp))
-		cgroup_get(cgrp);
-}
-
-/**
- * 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 */
-	spin_lock_irq(&css_set_lock);
-	cset = find_existing_css_set(old_cset, cgrp, template);
-	if (cset)
-		get_css_set(cset);
-	spin_unlock_irq(&css_set_lock);
-
-	if (cset)
-		return cset;
-
-	cset = kzalloc(sizeof(*cset), GFP_KERNEL);
-	if (!cset)
-		return NULL;
-
-	/* Allocate all the cgrp_cset_link objects that we'll need */
-	if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
-		kfree(cset);
-		return NULL;
-	}
-
-	atomic_set(&cset->refcount, 1);
-	INIT_LIST_HEAD(&cset->tasks);
-	INIT_LIST_HEAD(&cset->mg_tasks);
-	INIT_LIST_HEAD(&cset->task_iters);
-	INIT_HLIST_NODE(&cset->hlist);
-	INIT_LIST_HEAD(&cset->cgrp_links);
-	INIT_LIST_HEAD(&cset->mg_preload_node);
-	INIT_LIST_HEAD(&cset->mg_node);
-
-	/* Copy the set of subsystem state objects generated in
-	 * find_existing_css_set() */
-	memcpy(cset->subsys, template, sizeof(cset->subsys));
-
-	spin_lock_irq(&css_set_lock);
-	/* Add reference counts and links from the new css_set. */
-	list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
-		struct cgroup *c = link->cgrp;
-
-		if (c->root == cgrp->root)
-			c = cgrp;
-		link_css_set(&tmp_links, cset, c);
-	}
-
-	BUG_ON(!list_empty(&tmp_links));
-
-	css_set_count++;
-
-	/* Add @cset to the hash table */
-	key = css_set_hash(cset->subsys);
-	hash_add(css_set_table, &cset->hlist, key);
-
-	for_each_subsys(ss, ssid) {
-		struct cgroup_subsys_state *css = cset->subsys[ssid];
-
-		list_add_tail(&cset->e_cset_node[ssid],
-			      &css->cgroup->e_csets[ssid]);
-		css_get(css);
-	}
-
-	spin_unlock_irq(&css_set_lock);
-
-	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);
-
-	idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
-}
-
-static void cgroup_free_root(struct cgroup_root *root)
-{
-	if (root) {
-		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;
-
-	trace_cgroup_destroy_root(root);
-
-	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
-
-	BUG_ON(atomic_read(&root->nr_cgrps));
-	BUG_ON(!list_empty(&cgrp->self.children));
-
-	/* Rebind all subsystems back to the default hierarchy */
-	WARN_ON(rebind_subsystems(&cgrp_dfl_root, root->subsys_mask));
-
-	/*
-	 * Release all the links from cset_links to this hierarchy's
-	 * root cgroup
-	 */
-	spin_lock_irq(&css_set_lock);
-
-	list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
-		list_del(&link->cset_link);
-		list_del(&link->cgrp_link);
-		kfree(link);
-	}
-
-	spin_unlock_irq(&css_set_lock);
-
-	if (!list_empty(&root->root_list)) {
-		list_del(&root->root_list);
-		cgroup_root_count--;
-	}
-
-	cgroup_exit_root_id(root);
-
-	mutex_unlock(&cgroup_mutex);
-
-	kernfs_destroy_root(root->kf_root);
-	cgroup_free_root(root);
-}
-
-/*
- * look up cgroup associated with current task's cgroup namespace on the
- * specified hierarchy
- */
-static struct cgroup *
-current_cgns_cgroup_from_root(struct cgroup_root *root)
-{
-	struct cgroup *res = NULL;
-	struct css_set *cset;
-
-	lockdep_assert_held(&css_set_lock);
-
-	rcu_read_lock();
-
-	cset = current->nsproxy->cgroup_ns->root_cset;
-	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;
-			}
-		}
-	}
-	rcu_read_unlock();
-
-	BUG_ON(!res);
-	return res;
-}
-
-/* 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_lock);
-
-	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_lock 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.
- *
- * 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 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)
-{
-	struct cgroup_subsys *ss = cft->ss;
-
-	if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
-	    !(cgrp->root->flags & CGRP_ROOT_NOPREFIX))
-		snprintf(buf, CGROUP_FILE_NAME_MAX, "%s.%s",
-			 cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_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
- *
- * S_IRUGO for read, S_IWUSR for write.
- */
-static umode_t cgroup_file_mode(const struct cftype *cft)
-{
-	umode_t mode = 0;
-
-	if (cft->read_u64 || cft->read_s64 || cft->seq_show)
-		mode |= S_IRUGO;
-
-	if (cft->write_u64 || cft->write_s64 || cft->write) {
-		if (cft->flags & CFTYPE_WORLD_WRITABLE)
-			mode |= S_IWUGO;
-		else
-			mode |= S_IWUSR;
-	}
-
-	return mode;
-}
-
-/**
- * cgroup_calc_subtree_ss_mask - calculate subtree_ss_mask
- * @subtree_control: the new subtree_control mask to consider
- * @this_ss_mask: available subsystems
- *
- * On the default hierarchy, a subsystem may request other subsystems to be
- * enabled together through its ->depends_on mask.  In such cases, more
- * subsystems than specified in "cgroup.subtree_control" may be enabled.
- *
- * This function calculates which subsystems need to be enabled if
- * @subtree_control is to be applied while restricted to @this_ss_mask.
- */
-static u16 cgroup_calc_subtree_ss_mask(u16 subtree_control, u16 this_ss_mask)
-{
-	u16 cur_ss_mask = subtree_control;
-	struct cgroup_subsys *ss;
-	int ssid;
-
-	lockdep_assert_held(&cgroup_mutex);
-
-	cur_ss_mask |= cgrp_dfl_implicit_ss_mask;
-
-	while (true) {
-		u16 new_ss_mask = cur_ss_mask;
-
-		do_each_subsys_mask(ss, ssid, cur_ss_mask) {
-			new_ss_mask |= ss->depends_on;
-		} while_each_subsys_mask();
-
-		/*
-		 * Mask out subsystems which aren't available.  This can
-		 * happen only if some depended-upon subsystems were bound
-		 * to non-default hierarchies.
-		 */
-		new_ss_mask &= this_ss_mask;
-
-		if (new_ss_mask == cur_ss_mask)
-			break;
-		cur_ss_mask = new_ss_mask;
-	}
-
-	return cur_ss_mask;
-}
-
-/**
- * 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
- * @drain_offline: perform offline draining on the cgroup
- *
- * 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.  If @drain_offline is %true, the
- * cgroup is drained of offlining csses before return.
- *
- * 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,
-					  bool drain_offline)
-{
-	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.
-	 */
-	if (!cgroup_tryget(cgrp))
-		return NULL;
-	kernfs_break_active_protection(kn);
-
-	if (drain_offline)
-		cgroup_lock_and_drain_offline(cgrp);
-	else
-		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);
-
-	if (cft->file_offset) {
-		struct cgroup_subsys_state *css = cgroup_css(cgrp, cft->ss);
-		struct cgroup_file *cfile = (void *)css + cft->file_offset;
-
-		spin_lock_irq(&cgroup_file_kn_lock);
-		cfile->kn = NULL;
-		spin_unlock_irq(&cgroup_file_kn_lock);
-	}
-
-	kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
-}
-
-/**
- * css_clear_dir - remove subsys files in a cgroup directory
- * @css: taget css
- */
-static void css_clear_dir(struct cgroup_subsys_state *css)
-{
-	struct cgroup *cgrp = css->cgroup;
-	struct cftype *cfts;
-
-	if (!(css->flags & CSS_VISIBLE))
-		return;
-
-	css->flags &= ~CSS_VISIBLE;
-
-	list_for_each_entry(cfts, &css->ss->cfts, node)
-		cgroup_addrm_files(css, cgrp, cfts, false);
-}
-
-/**
- * css_populate_dir - create subsys files in a cgroup directory
- * @css: target css
- *
- * On failure, no file is added.
- */
-static int css_populate_dir(struct cgroup_subsys_state *css)
-{
-	struct cgroup *cgrp = css->cgroup;
-	struct cftype *cfts, *failed_cfts;
-	int ret;
-
-	if ((css->flags & CSS_VISIBLE) || !cgrp->kn)
-		return 0;
-
-	if (!css->ss) {
-		if (cgroup_on_dfl(cgrp))
-			cfts = cgroup_dfl_base_files;
-		else
-			cfts = cgroup_legacy_base_files;
-
-		return cgroup_addrm_files(&cgrp->self, cgrp, cfts, true);
-	}
-
-	list_for_each_entry(cfts, &css->ss->cfts, node) {
-		ret = cgroup_addrm_files(css, cgrp, cfts, true);
-		if (ret < 0) {
-			failed_cfts = cfts;
-			goto err;
-		}
-	}
-
-	css->flags |= CSS_VISIBLE;
-
-	return 0;
-err:
-	list_for_each_entry(cfts, &css->ss->cfts, node) {
-		if (cfts == failed_cfts)
-			break;
-		cgroup_addrm_files(css, cgrp, cfts, false);
-	}
-	return ret;
-}
-
-static int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
-{
-	struct cgroup *dcgrp = &dst_root->cgrp;
-	struct cgroup_subsys *ss;
-	int ssid, i, ret;
-
-	lockdep_assert_held(&cgroup_mutex);
-
-	do_each_subsys_mask(ss, ssid, ss_mask) {
-		/*
-		 * If @ss has non-root csses attached to it, can't move.
-		 * If @ss is an implicit controller, it is exempt from this
-		 * rule and can be stolen.
-		 */
-		if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)) &&
-		    !ss->implicit_on_dfl)
-			return -EBUSY;
-
-		/* can't move between two non-dummy roots either */
-		if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
-			return -EBUSY;
-	} while_each_subsys_mask();
-
-	do_each_subsys_mask(ss, ssid, ss_mask) {
-		struct cgroup_root *src_root = ss->root;
-		struct cgroup *scgrp = &src_root->cgrp;
-		struct cgroup_subsys_state *css = cgroup_css(scgrp, ss);
-		struct css_set *cset;
-
-		WARN_ON(!css || cgroup_css(dcgrp, ss));
-
-		/* disable from the source */
-		src_root->subsys_mask &= ~(1 << ssid);
-		WARN_ON(cgroup_apply_control(scgrp));
-		cgroup_finalize_control(scgrp, 0);
-
-		/* rebind */
-		RCU_INIT_POINTER(scgrp->subsys[ssid], NULL);
-		rcu_assign_pointer(dcgrp->subsys[ssid], css);
-		ss->root = dst_root;
-		css->cgroup = dcgrp;
-
-		spin_lock_irq(&css_set_lock);
-		hash_for_each(css_set_table, i, cset, hlist)
-			list_move_tail(&cset->e_cset_node[ss->id],
-				       &dcgrp->e_csets[ss->id]);
-		spin_unlock_irq(&css_set_lock);
-
-		/* default hierarchy doesn't enable controllers by default */
-		dst_root->subsys_mask |= 1 << ssid;
-		if (dst_root == &cgrp_dfl_root) {
-			static_branch_enable(cgroup_subsys_on_dfl_key[ssid]);
-		} else {
-			dcgrp->subtree_control |= 1 << ssid;
-			static_branch_disable(cgroup_subsys_on_dfl_key[ssid]);
-		}
-
-		ret = cgroup_apply_control(dcgrp);
-		if (ret)
-			pr_warn("partial failure to rebind %s controller (err=%d)\n",
-				ss->name, ret);
-
-		if (ss->bind)
-			ss->bind(css);
-	} while_each_subsys_mask();
-
-	kernfs_activate(dcgrp->kn);
-	return 0;
-}
-
-static int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
-			    struct kernfs_root *kf_root)
-{
-	int len = 0;
-	char *buf = NULL;
-	struct cgroup_root *kf_cgroot = cgroup_root_from_kf(kf_root);
-	struct cgroup *ns_cgroup;
-
-	buf = kmalloc(PATH_MAX, GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
-	spin_lock_irq(&css_set_lock);
-	ns_cgroup = current_cgns_cgroup_from_root(kf_cgroot);
-	len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX);
-	spin_unlock_irq(&css_set_lock);
-
-	if (len >= PATH_MAX)
-		len = -ERANGE;
-	else if (len > 0) {
-		seq_escape(sf, buf, " \t\n\\");
-		len = 0;
-	}
-	kfree(buf);
-	return len;
-}
-
-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;
-
-	if (root != &cgrp_dfl_root)
-		for_each_subsys(ss, ssid)
-			if (root->subsys_mask & (1 << ssid))
-				seq_show_option(seq, ss->legacy_name, NULL);
-	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_show_option(seq, "release_agent",
-				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_show_option(seq, "name", root->name);
-	return 0;
-}
-
-struct cgroup_sb_opts {
-	u16 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;
-	u16 mask = U16_MAX;
-	struct cgroup_subsys *ss;
-	int nr_opts = 0;
-	int i;
-
-#ifdef CONFIG_CPUSETS
-	mask = ~((u16)1 << cpuset_cgrp_id);
-#endif
-
-	memset(opts, 0, sizeof(*opts));
-
-	while ((token = strsep(&o, ",")) != NULL) {
-		nr_opts++;
-
-		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, "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->legacy_name))
-				continue;
-			if (!cgroup_ssid_enabled(i))
-				continue;
-			if (cgroup_ssid_no_v1(i))
-				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;
-	}
-
-	/*
-	 * 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 (cgroup_ssid_enabled(i) && !cgroup_ssid_no_v1(i))
-				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;
-	u16 added_mask, removed_mask;
-
-	if (root == &cgrp_dfl_root) {
-		pr_err("remount is not allowed\n");
-		return -EINVAL;
-	}
-
-	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
-
-	/* 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) ||
-	    (opts.name && strcmp(opts.name, root->name))) {
-		pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n",
-		       opts.flags, opts.name ?: "", root->flags, 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;
-
-	WARN_ON(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);
-	}
-
-	trace_cgroup_remount(root);
-
- 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;
-
-	spin_lock_irq(&css_set_lock);
-
-	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().
-		 *
-		 * Interrupts were already disabled while acquiring
-		 * the css_set_lock, so we do not need to disable it
-		 * again when acquiring the sighand->siglock here.
-		 */
-		spin_lock(&p->sighand->siglock);
-		if (!(p->flags & PF_EXITING)) {
-			struct css_set *cset = task_css_set(p);
-
-			if (!css_set_populated(cset))
-				css_set_update_populated(cset, true);
-			list_add_tail(&p->cg_list, &cset->tasks);
-			get_css_set(cset);
-		}
-		spin_unlock(&p->sighand->siglock);
-	} while_each_thread(g, p);
-	read_unlock(&tasklist_lock);
-out_unlock:
-	spin_unlock_irq(&css_set_lock);
-}
-
-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->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);
-	INIT_WORK(&cgrp->release_agent_work, cgroup_release_agent);
-}
-
-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, u16 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_KERNEL);
-	if (ret < 0)
-		goto out;
-	root_cgrp->id = ret;
-	root_cgrp->ancestor_ids[0] = ret;
-
-	ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release, 0,
-			      GFP_KERNEL);
-	if (ret)
-		goto out;
-
-	/*
-	 * We're accessing css_set_count without locking css_set_lock here,
-	 * but that's OK - it can only be increased by someone holding
-	 * cgroup_lock, and that's us.  Later rebinding may disable
-	 * controllers on the default hierarchy and thus create new csets,
-	 * which can't be more than the existing ones.  Allocate 2x.
-	 */
-	ret = allocate_cgrp_cset_links(2 * 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 = css_populate_dir(&root_cgrp->self);
-	if (ret)
-		goto destroy_root;
-
-	ret = rebind_subsystems(root, ss_mask);
-	if (ret)
-		goto destroy_root;
-
-	trace_cgroup_setup_root(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.
-	 */
-	spin_lock_irq(&css_set_lock);
-	hash_for_each(css_set_table, i, cset, hlist) {
-		link_css_set(&tmp_links, cset, root_cgrp);
-		if (css_set_populated(cset))
-			cgroup_update_populated(root_cgrp, true);
-	}
-	spin_unlock_irq(&css_set_lock);
-
-	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_exit(&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)
-{
-	bool is_v2 = fs_type == &cgroup2_fs_type;
-	struct super_block *pinned_sb = NULL;
-	struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
-	struct cgroup_subsys *ss;
-	struct cgroup_root *root;
-	struct cgroup_sb_opts opts;
-	struct dentry *dentry;
-	int ret;
-	int i;
-	bool new_sb;
-
-	get_cgroup_ns(ns);
-
-	/* Check if the caller has permission to mount. */
-	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) {
-		put_cgroup_ns(ns);
-		return ERR_PTR(-EPERM);
-	}
-
-	/*
-	 * 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();
-
-	if (is_v2) {
-		if (data) {
-			pr_err("cgroup2: unknown option \"%s\"\n", (char *)data);
-			put_cgroup_ns(ns);
-			return ERR_PTR(-EINVAL);
-		}
-		cgrp_dfl_visible = true;
-		root = &cgrp_dfl_root;
-		cgroup_get(&root->cgrp);
-		goto out_mount;
-	}
-
-	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
-
-	/* First find the desired set of subsystems */
-	ret = parse_cgroupfs_options(data, &opts);
-	if (ret)
-		goto out_unlock;
-
-	/*
-	 * Destruction of cgroup root is asynchronous, so subsystems may
-	 * still be dying after the previous unmount.  Let's drain the
-	 * dying subsystems.  We just need to ensure that the ones
-	 * unmounted previously finish dying and don't care about new ones
-	 * starting.  Testing ref liveliness is good enough.
-	 */
-	for_each_subsys(ss, i) {
-		if (!(opts.subsys_mask & (1 << i)) ||
-		    ss->root == &cgrp_dfl_root)
-			continue;
-
-		if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) {
-			mutex_unlock(&cgroup_mutex);
-			msleep(10);
-			ret = restart_syscall();
-			goto out_free;
-		}
-		cgroup_put(&ss->root->cgrp);
-	}
-
-	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)
-			pr_warn("new mount options do not match the existing superblock, will be ignored\n");
-
-		/*
-		 * We want to reuse @root whose lifetime is governed by its
-		 * ->cgrp.  Let's check whether @root is alive and keep it
-		 * that way.  As cgroup_kill_sb() can happen anytime, we
-		 * want to block it by pinning the sb so that @root doesn't
-		 * get killed before mount is complete.
-		 *
-		 * With the sb pinned, tryget_live can reliably indicate
-		 * whether @root can be reused.  If it's being killed,
-		 * drain it.  We can use wait_queue for the wait but this
-		 * path is super cold.  Let's just sleep a bit and retry.
-		 */
-		pinned_sb = kernfs_pin_sb(root->kf_root, NULL);
-		if (IS_ERR(pinned_sb) ||
-		    !percpu_ref_tryget_live(&root->cgrp.self.refcnt)) {
-			mutex_unlock(&cgroup_mutex);
-			if (!IS_ERR_OR_NULL(pinned_sb))
-				deactivate_super(pinned_sb);
-			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;
-	}
-
-	/* Hierarchies may only be created in the initial cgroup namespace. */
-	if (ns != &init_cgroup_ns) {
-		ret = -EPERM;
-		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) {
-		put_cgroup_ns(ns);
-		return ERR_PTR(ret);
-	}
-out_mount:
-	dentry = kernfs_mount(fs_type, flags, root->kf_root,
-			      is_v2 ? CGROUP2_SUPER_MAGIC : CGROUP_SUPER_MAGIC,
-			      &new_sb);
-
-	/*
-	 * In non-init cgroup namespace, instead of root cgroup's
-	 * dentry, we return the dentry corresponding to the
-	 * cgroupns->root_cgrp.
-	 */
-	if (!IS_ERR(dentry) && ns != &init_cgroup_ns) {
-		struct dentry *nsdentry;
-		struct cgroup *cgrp;
-
-		mutex_lock(&cgroup_mutex);
-		spin_lock_irq(&css_set_lock);
-
-		cgrp = cset_cgroup_from_root(ns->root_cset, root);
-
-		spin_unlock_irq(&css_set_lock);
-		mutex_unlock(&cgroup_mutex);
-
-		nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb);
-		dput(dentry);
-		dentry = nsdentry;
-	}
-
-	if (IS_ERR(dentry) || !new_sb)
-		cgroup_put(&root->cgrp);
-
-	/*
-	 * If @pinned_sb, we're reusing an existing root and holding an
-	 * extra ref on its sb.  Mount is complete.  Put the extra ref.
-	 */
-	if (pinned_sb) {
-		WARN_ON(new_sb);
-		deactivate_super(pinned_sb);
-	}
-
-	put_cgroup_ns(ns);
-	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 (!list_empty(&root->cgrp.self.children) ||
-	    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,
-	.fs_flags = FS_USERNS_MOUNT,
-};
-
-static struct file_system_type cgroup2_fs_type = {
-	.name = "cgroup2",
-	.mount = cgroup_mount,
-	.kill_sb = cgroup_kill_sb,
-	.fs_flags = FS_USERNS_MOUNT,
-};
-
-static int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
-				 struct cgroup_namespace *ns)
-{
-	struct cgroup *root = cset_cgroup_from_root(ns->root_cset, cgrp->root);
-
-	return kernfs_path_from_node(cgrp->kn, root->kn, buf, buflen);
-}
-
-int cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
-		   struct cgroup_namespace *ns)
-{
-	int ret;
-
-	mutex_lock(&cgroup_mutex);
-	spin_lock_irq(&css_set_lock);
-
-	ret = cgroup_path_ns_locked(cgrp, buf, buflen, ns);
-
-	spin_unlock_irq(&css_set_lock);
-	mutex_unlock(&cgroup_mutex);
-
-	return ret;
-}
-EXPORT_SYMBOL_GPL(cgroup_path_ns);
-
-/**
- * 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().
- */
-int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
-{
-	struct cgroup_root *root;
-	struct cgroup *cgrp;
-	int hierarchy_id = 1;
-	int ret;
-
-	mutex_lock(&cgroup_mutex);
-	spin_lock_irq(&css_set_lock);
-
-	root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
-
-	if (root) {
-		cgrp = task_cgroup_from_root(task, root);
-		ret = cgroup_path_ns_locked(cgrp, buf, buflen, &init_cgroup_ns);
-	} else {
-		/* if no hierarchy exists, everyone is in "/" */
-		ret = strlcpy(buf, "/", buflen);
-	}
-
-	spin_unlock_irq(&css_set_lock);
-	mutex_unlock(&cgroup_mutex);
-	return ret;
-}
-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;
-
-	/* the subsys currently being processed */
-	int			ssid;
-
-	/*
-	 * 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;
-};
-
-#define CGROUP_TASKSET_INIT(tset)	(struct cgroup_taskset){	\
-	.src_csets		= LIST_HEAD_INIT(tset.src_csets),	\
-	.dst_csets		= LIST_HEAD_INIT(tset.dst_csets),	\
-	.csets			= &tset.src_csets,			\
-}
-
-/**
- * cgroup_taskset_add - try to add a migration target task to a taskset
- * @task: target task
- * @tset: target taskset
- *
- * Add @task, which is a migration target, to @tset.  This function becomes
- * noop if @task doesn't need to be migrated.  @task's css_set should have
- * been added as a migration source and @task->cg_list will be moved from
- * the css_set's tasks list to mg_tasks one.
- */
-static void cgroup_taskset_add(struct task_struct *task,
-			       struct cgroup_taskset *tset)
-{
-	struct css_set *cset;
-
-	lockdep_assert_held(&css_set_lock);
-
-	/* @task either already exited or can't exit until the end */
-	if (task->flags & PF_EXITING)
-		return;
-
-	/* leave @task alone if post_fork() hasn't linked it yet */
-	if (list_empty(&task->cg_list))
-		return;
-
-	cset = task_css_set(task);
-	if (!cset->mg_src_cgrp)
-		return;
-
-	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);
-}
-
-/**
- * cgroup_taskset_first - reset taskset and return the first task
- * @tset: taskset of interest
- * @dst_cssp: output variable for the destination css
- *
- * @tset iteration is initialized and the first task is returned.
- */
-struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset,
-					 struct cgroup_subsys_state **dst_cssp)
-{
-	tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
-	tset->cur_task = NULL;
-
-	return cgroup_taskset_next(tset, dst_cssp);
-}
-
-/**
- * cgroup_taskset_next - iterate to the next task in taskset
- * @tset: taskset of interest
- * @dst_cssp: output variable for the destination css
- *
- * 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 cgroup_subsys_state **dst_cssp)
-{
-	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;
-
-			/*
-			 * This function may be called both before and
-			 * after cgroup_taskset_migrate().  The two cases
-			 * can be distinguished by looking at whether @cset
-			 * has its ->mg_dst_cset set.
-			 */
-			if (cset->mg_dst_cset)
-				*dst_cssp = cset->mg_dst_cset->subsys[tset->ssid];
-			else
-				*dst_cssp = cset->subsys[tset->ssid];
-
-			return task;
-		}
-
-		cset = list_next_entry(cset, mg_node);
-		task = NULL;
-	}
-
-	return NULL;
-}
-
-/**
- * cgroup_taskset_migrate - migrate a taskset
- * @tset: taget taskset
- * @root: cgroup root the migration is taking place on
- *
- * Migrate tasks in @tset as setup by migration preparation functions.
- * This function fails iff one of the ->can_attach callbacks fails and
- * guarantees that either all or none of the tasks in @tset are migrated.
- * @tset is consumed regardless of success.
- */
-static int cgroup_taskset_migrate(struct cgroup_taskset *tset,
-				  struct cgroup_root *root)
-{
-	struct cgroup_subsys *ss;
-	struct task_struct *task, *tmp_task;
-	struct css_set *cset, *tmp_cset;
-	int ssid, failed_ssid, ret;
-
-	/* 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 */
-	do_each_subsys_mask(ss, ssid, root->subsys_mask) {
-		if (ss->can_attach) {
-			tset->ssid = ssid;
-			ret = ss->can_attach(tset);
-			if (ret) {
-				failed_ssid = ssid;
-				goto out_cancel_attach;
-			}
-		}
-	} while_each_subsys_mask();
-
-	/*
-	 * 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.
-	 */
-	spin_lock_irq(&css_set_lock);
-	list_for_each_entry(cset, &tset->src_csets, mg_node) {
-		list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list) {
-			struct css_set *from_cset = task_css_set(task);
-			struct css_set *to_cset = cset->mg_dst_cset;
-
-			get_css_set(to_cset);
-			css_set_move_task(task, from_cset, to_cset, true);
-			put_css_set_locked(from_cset);
-		}
-	}
-	spin_unlock_irq(&css_set_lock);
-
-	/*
-	 * 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;
-
-	do_each_subsys_mask(ss, ssid, root->subsys_mask) {
-		if (ss->attach) {
-			tset->ssid = ssid;
-			ss->attach(tset);
-		}
-	} while_each_subsys_mask();
-
-	ret = 0;
-	goto out_release_tset;
-
-out_cancel_attach:
-	do_each_subsys_mask(ss, ssid, root->subsys_mask) {
-		if (ssid == failed_ssid)
-			break;
-		if (ss->cancel_attach) {
-			tset->ssid = ssid;
-			ss->cancel_attach(tset);
-		}
-	} while_each_subsys_mask();
-out_release_tset:
-	spin_lock_irq(&css_set_lock);
-	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);
-	}
-	spin_unlock_irq(&css_set_lock);
-	return ret;
-}
-
-/**
- * cgroup_may_migrate_to - verify whether a cgroup can be migration destination
- * @dst_cgrp: destination cgroup to test
- *
- * On the default hierarchy, except for the root, subtree_control must be
- * zero for migration destination cgroups with tasks so that child cgroups
- * don't compete against tasks.
- */
-static bool cgroup_may_migrate_to(struct cgroup *dst_cgrp)
-{
-	return !cgroup_on_dfl(dst_cgrp) || !cgroup_parent(dst_cgrp) ||
-		!dst_cgrp->subtree_control;
-}
-
-/**
- * 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);
-
-	spin_lock_irq(&css_set_lock);
-	list_for_each_entry_safe(cset, tmp_cset, preloaded_csets, mg_preload_node) {
-		cset->mg_src_cgrp = NULL;
-		cset->mg_dst_cgrp = NULL;
-		cset->mg_dst_cset = NULL;
-		list_del_init(&cset->mg_preload_node);
-		put_css_set_locked(cset);
-	}
-	spin_unlock_irq(&css_set_lock);
-}
-
-/**
- * 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 cgroup_threadgroup_rwsem
- * 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_lock);
-
-	/*
-	 * If ->dead, @src_set is associated with one or more dead cgroups
-	 * and doesn't contain any migratable tasks.  Ignore it early so
-	 * that the rest of migration path doesn't get confused by it.
-	 */
-	if (src_cset->dead)
-		return;
-
-	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(src_cset->mg_dst_cgrp);
-	WARN_ON(!list_empty(&src_cset->mg_tasks));
-	WARN_ON(!list_empty(&src_cset->mg_node));
-
-	src_cset->mg_src_cgrp = src_cgrp;
-	src_cset->mg_dst_cgrp = dst_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
- * @preloaded_csets: list of preloaded source css_sets
- *
- * Tasks are about to be moved 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.
- *
- * 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 list_head *preloaded_csets)
-{
-	LIST_HEAD(csets);
-	struct css_set *src_cset, *tmp_cset;
-
-	lockdep_assert_held(&cgroup_mutex);
-
-	/* 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, src_cset->mg_dst_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;
-			src_cset->mg_dst_cgrp = NULL;
-			list_del_init(&src_cset->mg_preload_node);
-			put_css_set(src_cset);
-			put_css_set(dst_cset);
-			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);
-	}
-
-	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
- * @leader: the leader of the process or the task to migrate
- * @threadgroup: whether @leader points to the whole process or a single task
- * @root: cgroup root migration is taking place on
- *
- * Migrate a process or task denoted by @leader.  If migrating a process,
- * the caller must be holding cgroup_threadgroup_rwsem.  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 task_struct *leader, bool threadgroup,
-			  struct cgroup_root *root)
-{
-	struct cgroup_taskset tset = CGROUP_TASKSET_INIT(tset);
-	struct task_struct *task;
-
-	/*
-	 * 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.
-	 */
-	spin_lock_irq(&css_set_lock);
-	rcu_read_lock();
-	task = leader;
-	do {
-		cgroup_taskset_add(task, &tset);
-		if (!threadgroup)
-			break;
-	} while_each_thread(leader, task);
-	rcu_read_unlock();
-	spin_unlock_irq(&css_set_lock);
-
-	return cgroup_taskset_migrate(&tset, root);
-}
-
-/**
- * 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 cgroup_threadgroup_rwsem.
- */
-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;
-
-	if (!cgroup_may_migrate_to(dst_cgrp))
-		return -EBUSY;
-
-	/* look up all src csets */
-	spin_lock_irq(&css_set_lock);
-	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();
-	spin_unlock_irq(&css_set_lock);
-
-	/* prepare dst csets and commit */
-	ret = cgroup_migrate_prepare_dst(&preloaded_csets);
-	if (!ret)
-		ret = cgroup_migrate(leader, threadgroup, dst_cgrp->root);
-
-	cgroup_migrate_finish(&preloaded_csets);
-
-	if (!ret)
-		trace_cgroup_attach_task(dst_cgrp, leader, threadgroup);
-
-	return ret;
-}
-
-static int cgroup_procs_write_permission(struct task_struct *task,
-					 struct cgroup *dst_cgrp,
-					 struct kernfs_open_file *of)
-{
-	const struct cred *cred = current_cred();
-	const struct cred *tcred = get_task_cred(task);
-	int ret = 0;
-
-	/*
-	 * even if we're attaching all tasks in the thread group, we only
-	 * need to check permissions on one of them.
-	 */
-	if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
-	    !uid_eq(cred->euid, tcred->uid) &&
-	    !uid_eq(cred->euid, tcred->suid))
-		ret = -EACCES;
-
-	if (!ret && cgroup_on_dfl(dst_cgrp)) {
-		struct super_block *sb = of->file->f_path.dentry->d_sb;
-		struct cgroup *cgrp;
-		struct inode *inode;
-
-		spin_lock_irq(&css_set_lock);
-		cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
-		spin_unlock_irq(&css_set_lock);
-
-		while (!cgroup_is_descendant(dst_cgrp, cgrp))
-			cgrp = cgroup_parent(cgrp);
-
-		ret = -ENOMEM;
-		inode = kernfs_get_inode(sb, cgrp->procs_file.kn);
-		if (inode) {
-			ret = inode_permission(inode, MAY_WRITE);
-			iput(inode);
-		}
-	}
-
-	put_cred(tcred);
-	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;
-	struct cgroup_subsys *ss;
-	struct cgroup *cgrp;
-	pid_t pid;
-	int ssid, ret;
-
-	if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
-		return -EINVAL;
-
-	cgrp = cgroup_kn_lock_live(of->kn, false);
-	if (!cgrp)
-		return -ENODEV;
-
-	percpu_down_write(&cgroup_threadgroup_rwsem);
-	rcu_read_lock();
-	if (pid) {
-		tsk = find_task_by_vpid(pid);
-		if (!tsk) {
-			ret = -ESRCH;
-			goto out_unlock_rcu;
-		}
-	} 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;
-		goto out_unlock_rcu;
-	}
-
-	get_task_struct(tsk);
-	rcu_read_unlock();
-
-	ret = cgroup_procs_write_permission(tsk, cgrp, of);
-	if (!ret)
-		ret = cgroup_attach_task(cgrp, tsk, threadgroup);
-
-	put_task_struct(tsk);
-	goto out_unlock_threadgroup;
-
-out_unlock_rcu:
-	rcu_read_unlock();
-out_unlock_threadgroup:
-	percpu_up_write(&cgroup_threadgroup_rwsem);
-	for_each_subsys(ss, ssid)
-		if (ss->post_attach)
-			ss->post_attach();
-	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);
-	percpu_down_write(&cgroup_threadgroup_rwsem);
-	for_each_root(root) {
-		struct cgroup *from_cgrp;
-
-		if (root == &cgrp_dfl_root)
-			continue;
-
-		spin_lock_irq(&css_set_lock);
-		from_cgrp = task_cgroup_from_root(from, root);
-		spin_unlock_irq(&css_set_lock);
-
-		retval = cgroup_attach_task(from_cgrp, tsk, false);
-		if (retval)
-			break;
-	}
-	percpu_up_write(&cgroup_threadgroup_rwsem);
-	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, false);
-	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)
-{
-	seq_puts(seq, "0\n");
-	return 0;
-}
-
-static void cgroup_print_ss_mask(struct seq_file *seq, u16 ss_mask)
-{
-	struct cgroup_subsys *ss;
-	bool printed = false;
-	int ssid;
-
-	do_each_subsys_mask(ss, ssid, ss_mask) {
-		if (printed)
-			seq_putc(seq, ' ');
-		seq_printf(seq, "%s", ss->name);
-		printed = true;
-	} while_each_subsys_mask();
-	if (printed)
-		seq_putc(seq, '\n');
-}
-
-/* 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_control(cgrp));
-	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->subtree_control);
-	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 control masks have changed and its subtree's 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_taskset tset = CGROUP_TASKSET_INIT(tset);
-	struct cgroup_subsys_state *d_css;
-	struct cgroup *dsct;
-	struct css_set *src_cset;
-	int ret;
-
-	lockdep_assert_held(&cgroup_mutex);
-
-	percpu_down_write(&cgroup_threadgroup_rwsem);
-
-	/* look up all csses currently attached to @cgrp's subtree */
-	spin_lock_irq(&css_set_lock);
-	cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
-		struct cgrp_cset_link *link;
-
-		list_for_each_entry(link, &dsct->cset_links, cset_link)
-			cgroup_migrate_add_src(link->cset, dsct,
-					       &preloaded_csets);
-	}
-	spin_unlock_irq(&css_set_lock);
-
-	/* NULL dst indicates self on default hierarchy */
-	ret = cgroup_migrate_prepare_dst(&preloaded_csets);
-	if (ret)
-		goto out_finish;
-
-	spin_lock_irq(&css_set_lock);
-	list_for_each_entry(src_cset, &preloaded_csets, mg_preload_node) {
-		struct task_struct *task, *ntask;
-
-		/* src_csets precede dst_csets, break on the first dst_cset */
-		if (!src_cset->mg_src_cgrp)
-			break;
-
-		/* all tasks in src_csets need to be migrated */
-		list_for_each_entry_safe(task, ntask, &src_cset->tasks, cg_list)
-			cgroup_taskset_add(task, &tset);
-	}
-	spin_unlock_irq(&css_set_lock);
-
-	ret = cgroup_taskset_migrate(&tset, cgrp->root);
-out_finish:
-	cgroup_migrate_finish(&preloaded_csets);
-	percpu_up_write(&cgroup_threadgroup_rwsem);
-	return ret;
-}
-
-/**
- * cgroup_lock_and_drain_offline - lock cgroup_mutex and drain offlined csses
- * @cgrp: root of the target subtree
- *
- * Because css offlining is asynchronous, userland may try to re-enable a
- * controller while the previous css is still around.  This function grabs
- * cgroup_mutex and drains the previous css instances of @cgrp's subtree.
- */
-static void cgroup_lock_and_drain_offline(struct cgroup *cgrp)
-	__acquires(&cgroup_mutex)
-{
-	struct cgroup *dsct;
-	struct cgroup_subsys_state *d_css;
-	struct cgroup_subsys *ss;
-	int ssid;
-
-restart:
-	mutex_lock(&cgroup_mutex);
-
-	cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
-		for_each_subsys(ss, ssid) {
-			struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
-			DEFINE_WAIT(wait);
-
-			if (!css || !percpu_ref_is_dying(&css->refcnt))
-				continue;
-
-			cgroup_get(dsct);
-			prepare_to_wait(&dsct->offline_waitq, &wait,
-					TASK_UNINTERRUPTIBLE);
-
-			mutex_unlock(&cgroup_mutex);
-			schedule();
-			finish_wait(&dsct->offline_waitq, &wait);
-
-			cgroup_put(dsct);
-			goto restart;
-		}
-	}
-}
-
-/**
- * cgroup_save_control - save control masks of a subtree
- * @cgrp: root of the target subtree
- *
- * Save ->subtree_control and ->subtree_ss_mask to the respective old_
- * prefixed fields for @cgrp's subtree including @cgrp itself.
- */
-static void cgroup_save_control(struct cgroup *cgrp)
-{
-	struct cgroup *dsct;
-	struct cgroup_subsys_state *d_css;
-
-	cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
-		dsct->old_subtree_control = dsct->subtree_control;
-		dsct->old_subtree_ss_mask = dsct->subtree_ss_mask;
-	}
-}
-
-/**
- * cgroup_propagate_control - refresh control masks of a subtree
- * @cgrp: root of the target subtree
- *
- * For @cgrp and its subtree, ensure ->subtree_ss_mask matches
- * ->subtree_control and propagate controller availability through the
- * subtree so that descendants don't have unavailable controllers enabled.
- */
-static void cgroup_propagate_control(struct cgroup *cgrp)
-{
-	struct cgroup *dsct;
-	struct cgroup_subsys_state *d_css;
-
-	cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
-		dsct->subtree_control &= cgroup_control(dsct);
-		dsct->subtree_ss_mask =
-			cgroup_calc_subtree_ss_mask(dsct->subtree_control,
-						    cgroup_ss_mask(dsct));
-	}
-}
-
-/**
- * cgroup_restore_control - restore control masks of a subtree
- * @cgrp: root of the target subtree
- *
- * Restore ->subtree_control and ->subtree_ss_mask from the respective old_
- * prefixed fields for @cgrp's subtree including @cgrp itself.
- */
-static void cgroup_restore_control(struct cgroup *cgrp)
-{
-	struct cgroup *dsct;
-	struct cgroup_subsys_state *d_css;
-
-	cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
-		dsct->subtree_control = dsct->old_subtree_control;
-		dsct->subtree_ss_mask = dsct->old_subtree_ss_mask;
-	}
-}
-
-static bool css_visible(struct cgroup_subsys_state *css)
-{
-	struct cgroup_subsys *ss = css->ss;
-	struct cgroup *cgrp = css->cgroup;
-
-	if (cgroup_control(cgrp) & (1 << ss->id))
-		return true;
-	if (!(cgroup_ss_mask(cgrp) & (1 << ss->id)))
-		return false;
-	return cgroup_on_dfl(cgrp) && ss->implicit_on_dfl;
-}
-
-/**
- * cgroup_apply_control_enable - enable or show csses according to control
- * @cgrp: root of the target subtree
- *
- * Walk @cgrp's subtree and create new csses or make the existing ones
- * visible.  A css is created invisible if it's being implicitly enabled
- * through dependency.  An invisible css is made visible when the userland
- * explicitly enables it.
- *
- * Returns 0 on success, -errno on failure.  On failure, csses which have
- * been processed already aren't cleaned up.  The caller is responsible for
- * cleaning up with cgroup_apply_control_disble().
- */
-static int cgroup_apply_control_enable(struct cgroup *cgrp)
-{
-	struct cgroup *dsct;
-	struct cgroup_subsys_state *d_css;
-	struct cgroup_subsys *ss;
-	int ssid, ret;
-
-	cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
-		for_each_subsys(ss, ssid) {
-			struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
-
-			WARN_ON_ONCE(css && percpu_ref_is_dying(&css->refcnt));
-
-			if (!(cgroup_ss_mask(dsct) & (1 << ss->id)))
-				continue;
-
-			if (!css) {
-				css = css_create(dsct, ss);
-				if (IS_ERR(css))
-					return PTR_ERR(css);
-			}
-
-			if (css_visible(css)) {
-				ret = css_populate_dir(css);
-				if (ret)
-					return ret;
-			}
-		}
-	}
-
-	return 0;
-}
-
-/**
- * cgroup_apply_control_disable - kill or hide csses according to control
- * @cgrp: root of the target subtree
- *
- * Walk @cgrp's subtree and kill and hide csses so that they match
- * cgroup_ss_mask() and cgroup_visible_mask().
- *
- * A css is hidden when the userland requests it to be disabled while other
- * subsystems are still depending on it.  The css must not actively control
- * resources and be in the vanilla state if it's made visible again later.
- * Controllers which may be depended upon should provide ->css_reset() for
- * this purpose.
- */
-static void cgroup_apply_control_disable(struct cgroup *cgrp)
-{
-	struct cgroup *dsct;
-	struct cgroup_subsys_state *d_css;
-	struct cgroup_subsys *ss;
-	int ssid;
-
-	cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
-		for_each_subsys(ss, ssid) {
-			struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
-
-			WARN_ON_ONCE(css && percpu_ref_is_dying(&css->refcnt));
-
-			if (!css)
-				continue;
-
-			if (css->parent &&
-			    !(cgroup_ss_mask(dsct) & (1 << ss->id))) {
-				kill_css(css);
-			} else if (!css_visible(css)) {
-				css_clear_dir(css);
-				if (ss->css_reset)
-					ss->css_reset(css);
-			}
-		}
-	}
-}
-
-/**
- * cgroup_apply_control - apply control mask updates to the subtree
- * @cgrp: root of the target subtree
- *
- * subsystems can be enabled and disabled in a subtree using the following
- * steps.
- *
- * 1. Call cgroup_save_control() to stash the current state.
- * 2. Update ->subtree_control masks in the subtree as desired.
- * 3. Call cgroup_apply_control() to apply the changes.
- * 4. Optionally perform other related operations.
- * 5. Call cgroup_finalize_control() to finish up.
- *
- * This function implements step 3 and propagates the mask changes
- * throughout @cgrp's subtree, updates csses accordingly and perform
- * process migrations.
- */
-static int cgroup_apply_control(struct cgroup *cgrp)
-{
-	int ret;
-
-	cgroup_propagate_control(cgrp);
-
-	ret = cgroup_apply_control_enable(cgrp);
-	if (ret)
-		return ret;
-
-	/*
-	 * At this point, cgroup_e_css() results reflect the new csses
-	 * making the following cgroup_update_dfl_csses() properly update
-	 * css associations of all tasks in the subtree.
-	 */
-	ret = cgroup_update_dfl_csses(cgrp);
-	if (ret)
-		return ret;
-
-	return 0;
-}
-
-/**
- * cgroup_finalize_control - finalize control mask update
- * @cgrp: root of the target subtree
- * @ret: the result of the update
- *
- * Finalize control mask update.  See cgroup_apply_control() for more info.
- */
-static void cgroup_finalize_control(struct cgroup *cgrp, int ret)
-{
-	if (ret) {
-		cgroup_restore_control(cgrp);
-		cgroup_propagate_control(cgrp);
-	}
-
-	cgroup_apply_control_disable(cgrp);
-}
-
-/* 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)
-{
-	u16 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;
-		do_each_subsys_mask(ss, ssid, ~cgrp_dfl_inhibit_ss_mask) {
-			if (!cgroup_ssid_enabled(ssid) ||
-			    strcmp(tok + 1, ss->name))
-				continue;
-
-			if (*tok == '+') {
-				enable |= 1 << ssid;
-				disable &= ~(1 << ssid);
-			} else if (*tok == '-') {
-				disable |= 1 << ssid;
-				enable &= ~(1 << ssid);
-			} else {
-				return -EINVAL;
-			}
-			break;
-		} while_each_subsys_mask();
-		if (ssid == CGROUP_SUBSYS_COUNT)
-			return -EINVAL;
-	}
-
-	cgrp = cgroup_kn_lock_live(of->kn, true);
-	if (!cgrp)
-		return -ENODEV;
-
-	for_each_subsys(ss, ssid) {
-		if (enable & (1 << ssid)) {
-			if (cgrp->subtree_control & (1 << ssid)) {
-				enable &= ~(1 << ssid);
-				continue;
-			}
-
-			if (!(cgroup_control(cgrp) & (1 << ssid))) {
-				ret = -ENOENT;
-				goto out_unlock;
-			}
-		} else if (disable & (1 << ssid)) {
-			if (!(cgrp->subtree_control & (1 << ssid))) {
-				disable &= ~(1 << ssid);
-				continue;
-			}
-
-			/* a child has it enabled? */
-			cgroup_for_each_live_child(child, cgrp) {
-				if (child->subtree_control & (1 << ssid)) {
-					ret = -EBUSY;
-					goto out_unlock;
-				}
-			}
-		}
-	}
-
-	if (!enable && !disable) {
-		ret = 0;
-		goto out_unlock;
-	}
-
-	/*
-	 * Except for the root, subtree_control must be zero for a cgroup
-	 * with tasks so that child cgroups don't compete against tasks.
-	 */
-	if (enable && cgroup_parent(cgrp)) {
-		struct cgrp_cset_link *link;
-
-		/*
-		 * Because namespaces pin csets too, @cgrp->cset_links
-		 * might not be empty even when @cgrp is empty.  Walk and
-		 * verify each cset.
-		 */
-		spin_lock_irq(&css_set_lock);
-
-		ret = 0;
-		list_for_each_entry(link, &cgrp->cset_links, cset_link) {
-			if (css_set_populated(link->cset)) {
-				ret = -EBUSY;
-				break;
-			}
-		}
-
-		spin_unlock_irq(&css_set_lock);
-
-		if (ret)
-			goto out_unlock;
-	}
-
-	/* save and update control masks and prepare csses */
-	cgroup_save_control(cgrp);
-
-	cgrp->subtree_control |= enable;
-	cgrp->subtree_control &= ~disable;
-
-	ret = cgroup_apply_control(cgrp);
-
-	cgroup_finalize_control(cgrp, ret);
-
-	kernfs_activate(cgrp->kn);
-	ret = 0;
-out_unlock:
-	cgroup_kn_unlock(of->kn);
-	return ret ?: nbytes;
-}
-
-static int cgroup_events_show(struct seq_file *seq, void *v)
-{
-	seq_printf(seq, "populated %d\n",
-		   cgroup_is_populated(seq_css(seq)->cgroup));
-	return 0;
-}
-
-static int cgroup_file_open(struct kernfs_open_file *of)
-{
-	struct cftype *cft = of->kn->priv;
-
-	if (cft->open)
-		return cft->open(of);
-	return 0;
-}
-
-static void cgroup_file_release(struct kernfs_open_file *of)
-{
-	struct cftype *cft = of->kn->priv;
-
-	if (cft->release)
-		cft->release(of);
-}
-
-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)
-{
-	if (seq_cft(seq)->seq_stop)
-		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,
-	.open			= cgroup_file_open,
-	.release		= cgroup_file_release,
-	.write			= cgroup_file_write,
-	.seq_show		= cgroup_seqfile_show,
-};
-
-static struct kernfs_ops cgroup_kf_ops = {
-	.atomic_write_len	= PAGE_SIZE,
-	.open			= cgroup_file_open,
-	.release		= cgroup_file_release,
-	.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 on the default hierarchy.
-	 */
-	if (cgroup_on_dfl(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);
-	if (!ret)
-		trace_cgroup_rename(cgrp);
-
-	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_subsys_state *css, 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, key);
-	if (IS_ERR(kn))
-		return PTR_ERR(kn);
-
-	ret = cgroup_kn_set_ugid(kn);
-	if (ret) {
-		kernfs_remove(kn);
-		return ret;
-	}
-
-	if (cft->file_offset) {
-		struct cgroup_file *cfile = (void *)css + cft->file_offset;
-
-		spin_lock_irq(&cgroup_file_kn_lock);
-		cfile->kn = kn;
-		spin_unlock_irq(&cgroup_file_kn_lock);
-	}
-
-	return 0;
-}
-
-/**
- * cgroup_addrm_files - add or remove files to a cgroup directory
- * @css: the target css
- * @cgrp: the target cgroup (usually css->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.
- */
-static int cgroup_addrm_files(struct cgroup_subsys_state *css,
-			      struct cgroup *cgrp, struct cftype cfts[],
-			      bool is_add)
-{
-	struct cftype *cft, *cft_end = NULL;
-	int ret = 0;
-
-	lockdep_assert_held(&cgroup_mutex);
-
-restart:
-	for (cft = cfts; cft != cft_end && 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_NOT_ON_DFL) && cgroup_on_dfl(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(css, cgrp, cft);
-			if (ret) {
-				pr_warn("%s: failed to add %s, err=%d\n",
-					__func__, cft->name, ret);
-				cft_end = cft;
-				is_add = false;
-				goto restart;
-			}
-		} else {
-			cgroup_rm_file(cgrp, cft);
-		}
-	}
-	return ret;
-}
-
-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 (!(css->flags & CSS_VISIBLE))
-			continue;
-
-		ret = cgroup_addrm_files(css, 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;
-
-		/* revert flags set by cgroup core while adding @cfts */
-		cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL);
-	}
-}
-
-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.
- */
-static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
-{
-	int ret;
-
-	if (!cgroup_ssid_enabled(ss->id))
-		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_add_dfl_cftypes - add an array of cftypes for default hierarchy
- * @ss: target cgroup subsystem
- * @cfts: zero-length name terminated array of cftypes
- *
- * Similar to cgroup_add_cftypes() but the added files are only used for
- * the default hierarchy.
- */
-int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
-{
-	struct cftype *cft;
-
-	for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
-		cft->flags |= __CFTYPE_ONLY_ON_DFL;
-	return cgroup_add_cftypes(ss, cfts);
-}
-
-/**
- * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
- * @ss: target cgroup subsystem
- * @cfts: zero-length name terminated array of cftypes
- *
- * Similar to cgroup_add_cftypes() but the added files are only used for
- * the legacy hierarchies.
- */
-int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
-{
-	struct cftype *cft;
-
-	for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
-		cft->flags |= __CFTYPE_NOT_ON_DFL;
-	return cgroup_add_cftypes(ss, cfts);
-}
-
-/**
- * cgroup_file_notify - generate a file modified event for a cgroup_file
- * @cfile: target cgroup_file
- *
- * @cfile must have been obtained by setting cftype->file_offset.
- */
-void cgroup_file_notify(struct cgroup_file *cfile)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&cgroup_file_kn_lock, flags);
-	if (cfile->kn)
-		kernfs_notify(cfile->kn);
-	spin_unlock_irqrestore(&cgroup_file_kn_lock, flags);
-}
-
-/**
- * cgroup_task_count - count the number of tasks in a cgroup.
- * @cgrp: the cgroup in question
- *
- * Return the number of tasks in the cgroup.  The returned number can be
- * higher than the actual number of tasks due to css_set references from
- * namespace roots and temporary usages.
- */
-static int cgroup_task_count(const struct cgroup *cgrp)
-{
-	int count = 0;
-	struct cgrp_cset_link *link;
-
-	spin_lock_irq(&css_set_lock);
-	list_for_each_entry(link, &cgrp->cset_links, cset_link)
-		count += atomic_read(&link->cset->refcount);
-	spin_unlock_irq(&css_set_lock);
-	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 (child->flags & CSS_ONLINE) {
-			ret = true;
-			break;
-		}
-	}
-	rcu_read_unlock();
-	return ret;
-}
-
-/**
- * css_task_iter_advance_css_set - 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_task_iter_advance_css_set(struct css_task_iter *it)
-{
-	struct list_head *l = it->cset_pos;
-	struct cgrp_cset_link *link;
-	struct css_set *cset;
-
-	lockdep_assert_held(&css_set_lock);
-
-	/* Advance to the next non-empty css_set */
-	do {
-		l = l->next;
-		if (l == it->cset_head) {
-			it->cset_pos = NULL;
-			it->task_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 (!css_set_populated(cset));
-
-	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;
-
-	/*
-	 * We don't keep css_sets locked across iteration steps and thus
-	 * need to take steps to ensure that iteration can be resumed after
-	 * the lock is re-acquired.  Iteration is performed at two levels -
-	 * css_sets and tasks in them.
-	 *
-	 * Once created, a css_set never leaves its cgroup lists, so a
-	 * pinned css_set is guaranteed to stay put and we can resume
-	 * iteration afterwards.
-	 *
-	 * Tasks may leave @cset across iteration steps.  This is resolved
-	 * by registering each iterator with the css_set currently being
-	 * walked and making css_set_move_task() advance iterators whose
-	 * next task is leaving.
-	 */
-	if (it->cur_cset) {
-		list_del(&it->iters_node);
-		put_css_set_locked(it->cur_cset);
-	}
-	get_css_set(cset);
-	it->cur_cset = cset;
-	list_add(&it->iters_node, &cset->task_iters);
-}
-
-static void css_task_iter_advance(struct css_task_iter *it)
-{
-	struct list_head *l = it->task_pos;
-
-	lockdep_assert_held(&css_set_lock);
-	WARN_ON_ONCE(!l);
-
-	/*
-	 * 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_task_iter_advance_css_set(it);
-	else
-		it->task_pos = l;
-}
-
-/**
- * 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.
- */
-void css_task_iter_start(struct cgroup_subsys_state *css,
-			 struct css_task_iter *it)
-{
-	/* no one should try to iterate before mounting cgroups */
-	WARN_ON_ONCE(!use_task_css_set_links);
-
-	memset(it, 0, sizeof(*it));
-
-	spin_lock_irq(&css_set_lock);
-
-	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_task_iter_advance_css_set(it);
-
-	spin_unlock_irq(&css_set_lock);
-}
-
-/**
- * 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)
-{
-	if (it->cur_task) {
-		put_task_struct(it->cur_task);
-		it->cur_task = NULL;
-	}
-
-	spin_lock_irq(&css_set_lock);
-
-	if (it->task_pos) {
-		it->cur_task = list_entry(it->task_pos, struct task_struct,
-					  cg_list);
-		get_task_struct(it->cur_task);
-		css_task_iter_advance(it);
-	}
-
-	spin_unlock_irq(&css_set_lock);
-
-	return it->cur_task;
-}
-
-/**
- * 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)
-{
-	if (it->cur_cset) {
-		spin_lock_irq(&css_set_lock);
-		list_del(&it->iters_node);
-		put_css_set_locked(it->cur_cset);
-		spin_unlock_irq(&css_set_lock);
-	}
-
-	if (it->cur_task)
-		put_task_struct(it->cur_task);
-}
-
-/**
- * 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;
-
-	if (cgroup_on_dfl(to))
-		return -EINVAL;
-
-	if (!cgroup_may_migrate_to(to))
-		return -EBUSY;
-
-	mutex_lock(&cgroup_mutex);
-
-	percpu_down_write(&cgroup_threadgroup_rwsem);
-
-	/* all tasks in @from are being moved, all csets are source */
-	spin_lock_irq(&css_set_lock);
-	list_for_each_entry(link, &from->cset_links, cset_link)
-		cgroup_migrate_add_src(link->cset, to, &preloaded_csets);
-	spin_unlock_irq(&css_set_lock);
-
-	ret = cgroup_migrate_prepare_dst(&preloaded_csets);
-	if (ret)
-		goto out_err;
-
-	/*
-	 * Migrate tasks one-by-one until @from 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(task, false, to->root);
-			if (!ret)
-				trace_cgroup_transfer_tasks(to, task, false);
-			put_task_struct(task);
-		}
-	} while (task && !ret);
-out_err:
-	cgroup_migrate_finish(&preloaded_csets);
-	percpu_up_write(&cgroup_threadgroup_rwsem);
-	mutex_unlock(&cgroup_mutex);
-	return ret;
-}
-
-static void cgroup_procs_release(struct kernfs_open_file *of)
-{
-	if (of->priv) {
-		css_task_iter_end(of->priv);
-		kfree(of->priv);
-	}
-}
-
-static void *cgroup_procs_next(struct seq_file *s, void *v, loff_t *pos)
-{
-	struct kernfs_open_file *of = s->private;
-	struct css_task_iter *it = of->priv;
-	struct task_struct *task;
-
-	do {
-		task = css_task_iter_next(it);
-	} while (task && !thread_group_leader(task));
-
-	return task;
-}
-
-static void *cgroup_procs_start(struct seq_file *s, loff_t *pos)
-{
-	struct kernfs_open_file *of = s->private;
-	struct cgroup *cgrp = seq_css(s)->cgroup;
-	struct css_task_iter *it = of->priv;
-
-	/*
-	 * When a seq_file is seeked, it's always traversed sequentially
-	 * from position 0, so we can simply keep iterating on !0 *pos.
-	 */
-	if (!it) {
-		if (WARN_ON_ONCE((*pos)++))
-			return ERR_PTR(-EINVAL);
-
-		it = kzalloc(sizeof(*it), GFP_KERNEL);
-		if (!it)
-			return ERR_PTR(-ENOMEM);
-		of->priv = it;
-		css_task_iter_start(&cgrp->self, it);
-	} else if (!(*pos)++) {
-		css_task_iter_end(it);
-		css_task_iter_start(&cgrp->self, it);
-	}
-
-	return cgroup_procs_next(s, NULL, NULL);
-}
-
-static int cgroup_procs_show(struct seq_file *s, void *v)
-{
-	seq_printf(s, "%d\n", task_tgid_vnr(v));
-	return 0;
-}
-
-/*
- * Stuff for reading the 'tasks'/'procs' files.
- *
- * Reading this file can return large amounts of data if a cgroup has
- * *lots* of attached tasks. So it may need several calls to read(),
- * but we cannot guarantee that the information we produce is correct
- * unless we produce it entirely atomically.
- *
- */
-
-/* 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)
-{
-	kvfree(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.
- */
-static int cmppid(const void *a, const void *b)
-{
-	return *(pid_t *)a - *(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 */
-	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) {
-		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 (l->list[mid] == pid) {
-				index = mid;
-				break;
-			} else if (l->list[mid] <= pid)
-				index = mid + 1;
-			else
-				end = mid;
-		}
-	}
-	/* If we're off the end of the array, we're done */
-	if (index >= l->length)
-		return NULL;
-	/* Update the abstract position to be the actual pid that we found */
-	iter = l->list + index;
-	*pos = *iter;
-	return iter;
-}
-
-static void cgroup_pidlist_stop(struct seq_file *s, void *v)
-{
-	struct 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 = *p;
-		return p;
-	}
-}
-
-static int cgroup_pidlist_show(struct seq_file *s, void *v)
-{
-	seq_printf(s, "%d\n", *(int *)v);
-
-	return 0;
-}
-
-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)
-{
-	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;
-}
-
-/* cgroup core interface files for the default hierarchy */
-static struct cftype cgroup_dfl_base_files[] = {
-	{
-		.name = "cgroup.procs",
-		.file_offset = offsetof(struct cgroup, procs_file),
-		.release = cgroup_procs_release,
-		.seq_start = cgroup_procs_start,
-		.seq_next = cgroup_procs_next,
-		.seq_show = cgroup_procs_show,
-		.write = cgroup_procs_write,
-	},
-	{
-		.name = "cgroup.controllers",
-		.seq_show = cgroup_controllers_show,
-	},
-	{
-		.name = "cgroup.subtree_control",
-		.seq_show = cgroup_subtree_control_show,
-		.write = cgroup_subtree_control_write,
-	},
-	{
-		.name = "cgroup.events",
-		.flags = CFTYPE_NOT_ON_ROOT,
-		.file_offset = offsetof(struct cgroup, events_file),
-		.seq_show = cgroup_events_show,
-	},
-	{ }	/* terminate */
-};
-
-/* cgroup core interface files for the legacy hierarchies */
-static struct cftype cgroup_legacy_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,
-	},
-	{
-		.name = "cgroup.clone_children",
-		.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 = "tasks",
-		.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,
-	},
-	{
-		.name = "notify_on_release",
-		.read_u64 = cgroup_read_notify_on_release,
-		.write_u64 = cgroup_write_notify_on_release,
-	},
-	{
-		.name = "release_agent",
-		.flags = CFTYPE_ONLY_ON_ROOT,
-		.seq_show = cgroup_release_agent_show,
-		.write = cgroup_release_agent_write,
-		.max_write_len = PATH_MAX - 1,
-	},
-	{ }	/* terminate */
-};
-
-/*
- * 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_subsys *ss = css->ss;
-	struct cgroup *cgrp = css->cgroup;
-
-	percpu_ref_exit(&css->refcnt);
-
-	if (ss) {
-		/* css free path */
-		struct cgroup_subsys_state *parent = css->parent;
-		int id = css->id;
-
-		ss->css_free(css);
-		cgroup_idr_remove(&ss->css_idr, id);
-		cgroup_put(cgrp);
-
-		if (parent)
-			css_put(parent);
-	} else {
-		/* cgroup free path */
-		atomic_dec(&cgrp->root->nr_cgrps);
-		cgroup_pidlist_destroy_all(cgrp);
-		cancel_work_sync(&cgrp->release_agent_work);
-
-		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_replace(&ss->css_idr, NULL, css->id);
-		if (ss->css_released)
-			ss->css_released(css);
-	} else {
-		/* cgroup release path */
-		trace_cgroup_release(cgrp);
-
-		cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
-		cgrp->id = -1;
-
-		/*
-		 * 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.
-		 */
-		if (cgrp->kn)
-			RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv,
-					 NULL);
-
-		cgroup_bpf_put(cgrp);
-	}
-
-	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;
-	css->id = -1;
-	INIT_LIST_HEAD(&css->sibling);
-	INIT_LIST_HEAD(&css->children);
-	css->serial_nr = css_serial_nr_next++;
-	atomic_set(&css->online_cnt, 0);
-
-	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);
-
-		atomic_inc(&css->online_cnt);
-		if (css->parent)
-			atomic_inc(&css->parent->online_cnt);
-	}
-	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_reset)
-		ss->css_reset(css);
-
-	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);
-}
-
-/**
- * css_create - 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.  This function doesn't create the
- * interface files.  Returns 0 on success, -errno on failure.
- */
-static struct cgroup_subsys_state *css_create(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 (!css)
-		css = ERR_PTR(-ENOMEM);
-	if (IS_ERR(css))
-		return css;
-
-	init_and_link_css(css, ss, cgrp);
-
-	err = percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL);
-	if (err)
-		goto err_free_css;
-
-	err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL);
-	if (err < 0)
-		goto err_free_css;
-	css->id = err;
-
-	/* @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 css;
-
-err_list_del:
-	list_del_rcu(&css->sibling);
-err_free_css:
-	call_rcu(&css->rcu_head, css_free_rcu_fn);
-	return ERR_PTR(err);
-}
-
-static struct cgroup *cgroup_create(struct cgroup *parent)
-{
-	struct cgroup_root *root = parent->root;
-	struct cgroup *cgrp, *tcgrp;
-	int level = parent->level + 1;
-	int ret;
-
-	/* allocate the cgroup and its ID, 0 is reserved for the root */
-	cgrp = kzalloc(sizeof(*cgrp) +
-		       sizeof(cgrp->ancestor_ids[0]) * (level + 1), GFP_KERNEL);
-	if (!cgrp)
-		return ERR_PTR(-ENOMEM);
-
-	ret = percpu_ref_init(&cgrp->self.refcnt, css_release, 0, GFP_KERNEL);
-	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_KERNEL);
-	if (cgrp->id < 0) {
-		ret = -ENOMEM;
-		goto out_cancel_ref;
-	}
-
-	init_cgroup_housekeeping(cgrp);
-
-	cgrp->self.parent = &parent->self;
-	cgrp->root = root;
-	cgrp->level = level;
-
-	for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp))
-		cgrp->ancestor_ids[tcgrp->level] = tcgrp->id;
-
-	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);
-
-	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);
-
-	/*
-	 * On the default hierarchy, a child doesn't automatically inherit
-	 * subtree_control from the parent.  Each is configured manually.
-	 */
-	if (!cgroup_on_dfl(cgrp))
-		cgrp->subtree_control = cgroup_control(cgrp);
-
-	if (parent)
-		cgroup_bpf_inherit(cgrp, parent);
-
-	cgroup_propagate_control(cgrp);
-
-	/* @cgrp doesn't have dir yet so the following will only create csses */
-	ret = cgroup_apply_control_enable(cgrp);
-	if (ret)
-		goto out_destroy;
-
-	return cgrp;
-
-out_cancel_ref:
-	percpu_ref_exit(&cgrp->self.refcnt);
-out_free_cgrp:
-	kfree(cgrp);
-	return ERR_PTR(ret);
-out_destroy:
-	cgroup_destroy_locked(cgrp);
-	return ERR_PTR(ret);
-}
-
-static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
-			umode_t mode)
-{
-	struct cgroup *parent, *cgrp;
-	struct kernfs_node *kn;
-	int ret;
-
-	/* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
-	if (strchr(name, '\n'))
-		return -EINVAL;
-
-	parent = cgroup_kn_lock_live(parent_kn, false);
-	if (!parent)
-		return -ENODEV;
-
-	cgrp = cgroup_create(parent);
-	if (IS_ERR(cgrp)) {
-		ret = PTR_ERR(cgrp);
-		goto out_unlock;
-	}
-
-	/* create the directory */
-	kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
-	if (IS_ERR(kn)) {
-		ret = PTR_ERR(kn);
-		goto out_destroy;
-	}
-	cgrp->kn = kn;
-
-	/*
-	 * This extra ref will be put in cgroup_free_fn() and guarantees
-	 * that @cgrp->kn is always accessible.
-	 */
-	kernfs_get(kn);
-
-	ret = cgroup_kn_set_ugid(kn);
-	if (ret)
-		goto out_destroy;
-
-	ret = css_populate_dir(&cgrp->self);
-	if (ret)
-		goto out_destroy;
-
-	ret = cgroup_apply_control_enable(cgrp);
-	if (ret)
-		goto out_destroy;
-
-	trace_cgroup_mkdir(cgrp);
-
-	/* let's create and online css's */
-	kernfs_activate(kn);
-
-	ret = 0;
-	goto out_unlock;
-
-out_destroy:
-	cgroup_destroy_locked(cgrp);
-out_unlock:
-	cgroup_kn_unlock(parent_kn);
-	return ret;
-}
-
-/*
- * 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);
-
-	do {
-		offline_css(css);
-		css_put(css);
-		/* @css can't go away while we're holding cgroup_mutex */
-		css = css->parent;
-	} while (css && atomic_dec_and_test(&css->online_cnt));
-
-	mutex_unlock(&cgroup_mutex);
-}
-
-/* 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);
-
-	if (atomic_dec_and_test(&css->online_cnt)) {
-		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.
-	 */
-	css_clear_dir(css);
-
-	/*
-	 * 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;
-	struct cgrp_cset_link *link;
-	int ssid;
-
-	lockdep_assert_held(&cgroup_mutex);
-
-	/*
-	 * Only migration can raise populated from zero and we're already
-	 * holding cgroup_mutex.
-	 */
-	if (cgroup_is_populated(cgrp))
-		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 and the associated csets dead.  The former prevents
-	 * further task migration and child creation by disabling
-	 * cgroup_lock_live_group().  The latter makes the csets ignored by
-	 * the migration path.
-	 */
-	cgrp->self.flags &= ~CSS_ONLINE;
-
-	spin_lock_irq(&css_set_lock);
-	list_for_each_entry(link, &cgrp->cset_links, cset_link)
-		link->cset->dead = true;
-	spin_unlock_irq(&css_set_lock);
-
-	/* initiate massacre of all css's */
-	for_each_css(css, ssid, cgrp)
-		kill_css(css);
-
-	/*
-	 * Remove @cgrp directory along with the base files.  @cgrp has an
-	 * extra ref on its kn.
-	 */
-	kernfs_remove(cgrp->kn);
-
-	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, false);
-	if (!cgrp)
-		return 0;
-
-	ret = cgroup_destroy_locked(cgrp);
-
-	if (!ret)
-		trace_cgroup_rmdir(cgrp);
-
-	cgroup_kn_unlock(kn);
-	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,
-	.show_path		= cgroup_show_path,
-};
-
-static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
-{
-	struct cgroup_subsys_state *css;
-
-	pr_debug("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;
-
-	have_fork_callback |= (bool)ss->fork << ss->id;
-	have_exit_callback |= (bool)ss->exit << ss->id;
-	have_free_callback |= (bool)ss->free << ss->id;
-	have_canfork_callback |= (bool)ss->can_fork << ss->id;
-
-	/* 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;
-	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 id:name=%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->legacy_name)
-			ss->legacy_name = cgroup_subsys_name[i];
-
-		if (ss->early_init)
-			cgroup_init_subsys(ss, true);
-	}
-	return 0;
-}
-
-static u16 cgroup_disable_mask __initdata;
-
-/**
- * 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;
-	int ssid;
-
-	BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
-	BUG_ON(percpu_init_rwsem(&cgroup_threadgroup_rwsem));
-	BUG_ON(cgroup_init_cftypes(NULL, cgroup_dfl_base_files));
-	BUG_ON(cgroup_init_cftypes(NULL, cgroup_legacy_base_files));
-
-	/*
-	 * The latency of the synchronize_sched() is too high for cgroups,
-	 * avoid it at the cost of forcing all readers into the slow path.
-	 */
-	rcu_sync_enter_start(&cgroup_threadgroup_rwsem.rss);
-
-	get_user_ns(init_cgroup_ns.user_ns);
-
-	mutex_lock(&cgroup_mutex);
-
-	/*
-	 * Add init_css_set to the hash table so that dfl_root can link to
-	 * it during init.
-	 */
-	hash_add(css_set_table, &init_css_set.hlist,
-		 css_set_hash(init_css_set.subsys));
-
-	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 (cgroup_disable_mask & (1 << ssid)) {
-			static_branch_disable(cgroup_subsys_enabled_key[ssid]);
-			printk(KERN_INFO "Disabling %s control group subsystem\n",
-			       ss->name);
-			continue;
-		}
-
-		if (cgroup_ssid_no_v1(ssid))
-			printk(KERN_INFO "Disabling %s control group subsystem in v1 mounts\n",
-			       ss->name);
-
-		cgrp_dfl_root.subsys_mask |= 1 << ss->id;
-
-		if (ss->implicit_on_dfl)
-			cgrp_dfl_implicit_ss_mask |= 1 << ss->id;
-		else if (!ss->dfl_cftypes)
-			cgrp_dfl_inhibit_ss_mask |= 1 << ss->id;
-
-		if (ss->dfl_cftypes == ss->legacy_cftypes) {
-			WARN_ON(cgroup_add_cftypes(ss, ss->dfl_cftypes));
-		} else {
-			WARN_ON(cgroup_add_dfl_cftypes(ss, ss->dfl_cftypes));
-			WARN_ON(cgroup_add_legacy_cftypes(ss, ss->legacy_cftypes));
-		}
-
-		if (ss->bind)
-			ss->bind(init_css_set.subsys[ssid]);
-	}
-
-	/* init_css_set.subsys[] has been updated, re-hash */
-	hash_del(&init_css_set.hlist);
-	hash_add(css_set_table, &init_css_set.hlist,
-		 css_set_hash(init_css_set.subsys));
-
-	WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup"));
-	WARN_ON(register_filesystem(&cgroup_fs_type));
-	WARN_ON(register_filesystem(&cgroup2_fs_type));
-	WARN_ON(!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.
- */
-int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
-		     struct pid *pid, struct task_struct *tsk)
-{
-	char *buf;
-	int retval;
-	struct cgroup_root *root;
-
-	retval = -ENOMEM;
-	buf = kmalloc(PATH_MAX, GFP_KERNEL);
-	if (!buf)
-		goto out;
-
-	mutex_lock(&cgroup_mutex);
-	spin_lock_irq(&css_set_lock);
-
-	for_each_root(root) {
-		struct cgroup_subsys *ss;
-		struct cgroup *cgrp;
-		int ssid, count = 0;
-
-		if (root == &cgrp_dfl_root && !cgrp_dfl_visible)
-			continue;
-
-		seq_printf(m, "%d:", root->hierarchy_id);
-		if (root != &cgrp_dfl_root)
-			for_each_subsys(ss, ssid)
-				if (root->subsys_mask & (1 << ssid))
-					seq_printf(m, "%s%s", count++ ? "," : "",
-						   ss->legacy_name);
-		if (strlen(root->name))
-			seq_printf(m, "%sname=%s", count ? "," : "",
-				   root->name);
-		seq_putc(m, ':');
-
-		cgrp = task_cgroup_from_root(tsk, root);
-
-		/*
-		 * On traditional hierarchies, all zombie tasks show up as
-		 * belonging to the root cgroup.  On the default hierarchy,
-		 * while a zombie doesn't show up in "cgroup.procs" and
-		 * thus can't be migrated, its /proc/PID/cgroup keeps
-		 * reporting the cgroup it belonged to before exiting.  If
-		 * the cgroup is removed before the zombie is reaped,
-		 * " (deleted)" is appended to the cgroup path.
-		 */
-		if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) {
-			retval = cgroup_path_ns_locked(cgrp, buf, PATH_MAX,
-						current->nsproxy->cgroup_ns);
-			if (retval >= PATH_MAX)
-				retval = -ENAMETOOLONG;
-			if (retval < 0)
-				goto out_unlock;
-
-			seq_puts(m, buf);
-		} else {
-			seq_puts(m, "/");
-		}
-
-		if (cgroup_on_dfl(cgrp) && cgroup_is_dead(cgrp))
-			seq_puts(m, " (deleted)\n");
-		else
-			seq_putc(m, '\n');
-	}
-
-	retval = 0;
-out_unlock:
-	spin_unlock_irq(&css_set_lock);
-	mutex_unlock(&cgroup_mutex);
-	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->legacy_name, ss->root->hierarchy_id,
-			   atomic_read(&ss->root->nr_cgrps),
-			   cgroup_ssid_enabled(i));
-
-	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_can_fork - called on a new task before the process is exposed
- * @child: the task in question.
- *
- * This calls the subsystem can_fork() callbacks. If the can_fork() callback
- * returns an error, the fork aborts with that error code. This allows for
- * a cgroup subsystem to conditionally allow or deny new forks.
- */
-int cgroup_can_fork(struct task_struct *child)
-{
-	struct cgroup_subsys *ss;
-	int i, j, ret;
-
-	do_each_subsys_mask(ss, i, have_canfork_callback) {
-		ret = ss->can_fork(child);
-		if (ret)
-			goto out_revert;
-	} while_each_subsys_mask();
-
-	return 0;
-
-out_revert:
-	for_each_subsys(ss, j) {
-		if (j >= i)
-			break;
-		if (ss->cancel_fork)
-			ss->cancel_fork(child);
-	}
-
-	return ret;
-}
-
-/**
- * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
- * @child: the task in question
- *
- * This calls the cancel_fork() callbacks if a fork failed *after*
- * cgroup_can_fork() succeded.
- */
-void cgroup_cancel_fork(struct task_struct *child)
-{
-	struct cgroup_subsys *ss;
-	int i;
-
-	for_each_subsys(ss, i)
-		if (ss->cancel_fork)
-			ss->cancel_fork(child);
-}
-
-/**
- * cgroup_post_fork - called on a new task after adding it to the task list
- * @child: the task in question
- *
- * Adds the task to the list running through its css_set if necessary 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_lists().  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_lock 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_lists(), @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;
-
-		spin_lock_irq(&css_set_lock);
-		cset = task_css_set(current);
-		if (list_empty(&child->cg_list)) {
-			get_css_set(cset);
-			css_set_move_task(child, NULL, cset, false);
-		}
-		spin_unlock_irq(&css_set_lock);
-	}
-
-	/*
-	 * Call ss->fork().  This must happen after @child is linked on
-	 * css_set; otherwise, @child might change state between ->fork()
-	 * and addition to css_set.
-	 */
-	do_each_subsys_mask(ss, i, have_fork_callback) {
-		ss->fork(child);
-	} while_each_subsys_mask();
-}
-
-/**
- * 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;
-	int i;
-
-	/*
-	 * Unlink from @tsk from its css_set.  As migration path can't race
-	 * with us, we can check css_set and cg_list without synchronization.
-	 */
-	cset = task_css_set(tsk);
-
-	if (!list_empty(&tsk->cg_list)) {
-		spin_lock_irq(&css_set_lock);
-		css_set_move_task(tsk, cset, NULL, false);
-		spin_unlock_irq(&css_set_lock);
-	} else {
-		get_css_set(cset);
-	}
-
-	/* see cgroup_post_fork() for details */
-	do_each_subsys_mask(ss, i, have_exit_callback) {
-		ss->exit(tsk);
-	} while_each_subsys_mask();
-}
-
-void cgroup_free(struct task_struct *task)
-{
-	struct css_set *cset = task_css_set(task);
-	struct cgroup_subsys *ss;
-	int ssid;
-
-	do_each_subsys_mask(ss, ssid, have_free_callback) {
-		ss->free(task);
-	} while_each_subsys_mask();
-
-	put_css_set(cset);
-}
-
-static void check_for_release(struct cgroup *cgrp)
-{
-	if (notify_on_release(cgrp) && !cgroup_is_populated(cgrp) &&
-	    !css_has_online_children(&cgrp->self) && !cgroup_is_dead(cgrp))
-		schedule_work(&cgrp->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)
-{
-	struct cgroup *cgrp =
-		container_of(work, struct cgroup, release_agent_work);
-	char *pathbuf = NULL, *agentbuf = NULL;
-	char *argv[3], *envp[3];
-	int ret;
-
-	mutex_lock(&cgroup_mutex);
-
-	pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
-	agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
-	if (!pathbuf || !agentbuf)
-		goto out;
-
-	spin_lock_irq(&css_set_lock);
-	ret = cgroup_path_ns_locked(cgrp, pathbuf, PATH_MAX, &init_cgroup_ns);
-	spin_unlock_irq(&css_set_lock);
-	if (ret < 0 || ret >= PATH_MAX)
-		goto out;
-
-	argv[0] = agentbuf;
-	argv[1] = pathbuf;
-	argv[2] = NULL;
-
-	/* minimal command environment */
-	envp[0] = "HOME=/";
-	envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
-	envp[2] = NULL;
-
-	mutex_unlock(&cgroup_mutex);
-	call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
-	goto out_free;
-out:
-	mutex_unlock(&cgroup_mutex);
-out_free:
-	kfree(agentbuf);
-	kfree(pathbuf);
-}
-
-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) &&
-			    strcmp(token, ss->legacy_name))
-				continue;
-			cgroup_disable_mask |= 1 << i;
-		}
-	}
-	return 1;
-}
-__setup("cgroup_disable=", cgroup_disable);
-
-static int __init cgroup_no_v1(char *str)
-{
-	struct cgroup_subsys *ss;
-	char *token;
-	int i;
-
-	while ((token = strsep(&str, ",")) != NULL) {
-		if (!*token)
-			continue;
-
-		if (!strcmp(token, "all")) {
-			cgroup_no_v1_mask = U16_MAX;
-			break;
-		}
-
-		for_each_subsys(ss, i) {
-			if (strcmp(token, ss->name) &&
-			    strcmp(token, ss->legacy_name))
-				continue;
-
-			cgroup_no_v1_mask |= 1 << i;
-		}
-	}
-	return 1;
-}
-__setup("cgroup_no_v1=", cgroup_no_v1);
-
-/**
- * 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 file_system_type *s_type = dentry->d_sb->s_type;
-	struct cgroup_subsys_state *css = NULL;
-	struct cgroup *cgrp;
-
-	/* is @dentry a cgroup dir? */
-	if ((s_type != &cgroup_fs_type && s_type != &cgroup2_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 css_release_work_fn() 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);
-}
-
-/**
- * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path
- * @path: path on the default hierarchy
- *
- * Find the cgroup at @path on the default hierarchy, increment its
- * reference count and return it.  Returns pointer to the found cgroup on
- * success, ERR_PTR(-ENOENT) if @path doens't exist and ERR_PTR(-ENOTDIR)
- * if @path points to a non-directory.
- */
-struct cgroup *cgroup_get_from_path(const char *path)
-{
-	struct kernfs_node *kn;
-	struct cgroup *cgrp;
-
-	mutex_lock(&cgroup_mutex);
-
-	kn = kernfs_walk_and_get(cgrp_dfl_root.cgrp.kn, path);
-	if (kn) {
-		if (kernfs_type(kn) == KERNFS_DIR) {
-			cgrp = kn->priv;
-			cgroup_get(cgrp);
-		} else {
-			cgrp = ERR_PTR(-ENOTDIR);
-		}
-		kernfs_put(kn);
-	} else {
-		cgrp = ERR_PTR(-ENOENT);
-	}
-
-	mutex_unlock(&cgroup_mutex);
-	return cgrp;
-}
-EXPORT_SYMBOL_GPL(cgroup_get_from_path);
-
-/**
- * cgroup_get_from_fd - get a cgroup pointer from a fd
- * @fd: fd obtained by open(cgroup2_dir)
- *
- * Find the cgroup from a fd which should be obtained
- * by opening a cgroup directory.  Returns a pointer to the
- * cgroup on success. ERR_PTR is returned if the cgroup
- * cannot be found.
- */
-struct cgroup *cgroup_get_from_fd(int fd)
-{
-	struct cgroup_subsys_state *css;
-	struct cgroup *cgrp;
-	struct file *f;
-
-	f = fget_raw(fd);
-	if (!f)
-		return ERR_PTR(-EBADF);
-
-	css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
-	fput(f);
-	if (IS_ERR(css))
-		return ERR_CAST(css);
-
-	cgrp = css->cgroup;
-	if (!cgroup_on_dfl(cgrp)) {
-		cgroup_put(cgrp);
-		return ERR_PTR(-EBADF);
-	}
-
-	return cgrp;
-}
-EXPORT_SYMBOL_GPL(cgroup_get_from_fd);
-
-/*
- * sock->sk_cgrp_data handling.  For more info, see sock_cgroup_data
- * definition in cgroup-defs.h.
- */
-#ifdef CONFIG_SOCK_CGROUP_DATA
-
-#if defined(CONFIG_CGROUP_NET_PRIO) || defined(CONFIG_CGROUP_NET_CLASSID)
-
-DEFINE_SPINLOCK(cgroup_sk_update_lock);
-static bool cgroup_sk_alloc_disabled __read_mostly;
-
-void cgroup_sk_alloc_disable(void)
-{
-	if (cgroup_sk_alloc_disabled)
-		return;
-	pr_info("cgroup: disabling cgroup2 socket matching due to net_prio or net_cls activation\n");
-	cgroup_sk_alloc_disabled = true;
-}
-
-#else
-
-#define cgroup_sk_alloc_disabled	false
-
-#endif
-
-void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
-{
-	if (cgroup_sk_alloc_disabled)
-		return;
-
-	/* Socket clone path */
-	if (skcd->val) {
-		cgroup_get(sock_cgroup_ptr(skcd));
-		return;
-	}
-
-	rcu_read_lock();
-
-	while (true) {
-		struct css_set *cset;
-
-		cset = task_css_set(current);
-		if (likely(cgroup_tryget(cset->dfl_cgrp))) {
-			skcd->val = (unsigned long)cset->dfl_cgrp;
-			break;
-		}
-		cpu_relax();
-	}
-
-	rcu_read_unlock();
-}
-
-void cgroup_sk_free(struct sock_cgroup_data *skcd)
-{
-	cgroup_put(sock_cgroup_ptr(skcd));
-}
-
-#endif	/* CONFIG_SOCK_CGROUP_DATA */
-
-/* cgroup namespaces */
-
-static struct ucounts *inc_cgroup_namespaces(struct user_namespace *ns)
-{
-	return inc_ucount(ns, current_euid(), UCOUNT_CGROUP_NAMESPACES);
-}
-
-static void dec_cgroup_namespaces(struct ucounts *ucounts)
-{
-	dec_ucount(ucounts, UCOUNT_CGROUP_NAMESPACES);
-}
-
-static struct cgroup_namespace *alloc_cgroup_ns(void)
-{
-	struct cgroup_namespace *new_ns;
-	int ret;
-
-	new_ns = kzalloc(sizeof(struct cgroup_namespace), GFP_KERNEL);
-	if (!new_ns)
-		return ERR_PTR(-ENOMEM);
-	ret = ns_alloc_inum(&new_ns->ns);
-	if (ret) {
-		kfree(new_ns);
-		return ERR_PTR(ret);
-	}
-	atomic_set(&new_ns->count, 1);
-	new_ns->ns.ops = &cgroupns_operations;
-	return new_ns;
-}
-
-void free_cgroup_ns(struct cgroup_namespace *ns)
-{
-	put_css_set(ns->root_cset);
-	dec_cgroup_namespaces(ns->ucounts);
-	put_user_ns(ns->user_ns);
-	ns_free_inum(&ns->ns);
-	kfree(ns);
-}
-EXPORT_SYMBOL(free_cgroup_ns);
-
-struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
-					struct user_namespace *user_ns,
-					struct cgroup_namespace *old_ns)
-{
-	struct cgroup_namespace *new_ns;
-	struct ucounts *ucounts;
-	struct css_set *cset;
-
-	BUG_ON(!old_ns);
-
-	if (!(flags & CLONE_NEWCGROUP)) {
-		get_cgroup_ns(old_ns);
-		return old_ns;
-	}
-
-	/* Allow only sysadmin to create cgroup namespace. */
-	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
-		return ERR_PTR(-EPERM);
-
-	ucounts = inc_cgroup_namespaces(user_ns);
-	if (!ucounts)
-		return ERR_PTR(-ENOSPC);
-
-	/* It is not safe to take cgroup_mutex here */
-	spin_lock_irq(&css_set_lock);
-	cset = task_css_set(current);
-	get_css_set(cset);
-	spin_unlock_irq(&css_set_lock);
-
-	new_ns = alloc_cgroup_ns();
-	if (IS_ERR(new_ns)) {
-		put_css_set(cset);
-		dec_cgroup_namespaces(ucounts);
-		return new_ns;
-	}
-
-	new_ns->user_ns = get_user_ns(user_ns);
-	new_ns->ucounts = ucounts;
-	new_ns->root_cset = cset;
-
-	return new_ns;
-}
-
-static inline struct cgroup_namespace *to_cg_ns(struct ns_common *ns)
-{
-	return container_of(ns, struct cgroup_namespace, ns);
-}
-
-static int cgroupns_install(struct nsproxy *nsproxy, struct ns_common *ns)
-{
-	struct cgroup_namespace *cgroup_ns = to_cg_ns(ns);
-
-	if (!ns_capable(current_user_ns(), CAP_SYS_ADMIN) ||
-	    !ns_capable(cgroup_ns->user_ns, CAP_SYS_ADMIN))
-		return -EPERM;
-
-	/* Don't need to do anything if we are attaching to our own cgroupns. */
-	if (cgroup_ns == nsproxy->cgroup_ns)
-		return 0;
-
-	get_cgroup_ns(cgroup_ns);
-	put_cgroup_ns(nsproxy->cgroup_ns);
-	nsproxy->cgroup_ns = cgroup_ns;
-
-	return 0;
-}
-
-static struct ns_common *cgroupns_get(struct task_struct *task)
-{
-	struct cgroup_namespace *ns = NULL;
-	struct nsproxy *nsproxy;
-
-	task_lock(task);
-	nsproxy = task->nsproxy;
-	if (nsproxy) {
-		ns = nsproxy->cgroup_ns;
-		get_cgroup_ns(ns);
-	}
-	task_unlock(task);
-
-	return ns ? &ns->ns : NULL;
-}
-
-static void cgroupns_put(struct ns_common *ns)
-{
-	put_cgroup_ns(to_cg_ns(ns));
-}
-
-static struct user_namespace *cgroupns_owner(struct ns_common *ns)
-{
-	return to_cg_ns(ns)->user_ns;
-}
-
-const struct proc_ns_operations cgroupns_operations = {
-	.name		= "cgroup",
-	.type		= CLONE_NEWCGROUP,
-	.get		= cgroupns_get,
-	.put		= cgroupns_put,
-	.install	= cgroupns_install,
-	.owner		= cgroupns_owner,
-};
-
-static __init int cgroup_namespaces_init(void)
-{
-	return 0;
-}
-subsys_initcall(cgroup_namespaces_init);
-
-#ifdef CONFIG_CGROUP_BPF
-void cgroup_bpf_update(struct cgroup *cgrp,
-		       struct bpf_prog *prog,
-		       enum bpf_attach_type type)
-{
-	struct cgroup *parent = cgroup_parent(cgrp);
-
-	mutex_lock(&cgroup_mutex);
-	__cgroup_bpf_update(cgrp, parent, prog, type);
-	mutex_unlock(&cgroup_mutex);
-}
-#endif /* CONFIG_CGROUP_BPF */
-
-#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;
-
-	spin_lock_irq(&css_set_lock);
-	rcu_read_lock();
-	cset = rcu_dereference(current->cgroups);
-	list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
-		struct cgroup *c = link->cgrp;
-
-		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();
-	spin_unlock_irq(&css_set_lock);
-	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;
-
-	spin_lock_irq(&css_set_lock);
-	list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
-		struct css_set *cset = link->cset;
-		struct task_struct *task;
-		int count = 0;
-
-		seq_printf(seq, "css_set %p\n", cset);
-
-		list_for_each_entry(task, &cset->tasks, cg_list) {
-			if (count++ > MAX_TASKS_SHOWN_PER_CSS)
-				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");
-	}
-	spin_unlock_irq(&css_set_lock);
-	return 0;
-}
-
-static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
-{
-	return (!cgroup_is_populated(css->cgroup) &&
-		!css_has_online_children(&css->cgroup->self));
-}
-
-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,
-	.legacy_cftypes = debug_files,
-};
-#endif /* CONFIG_CGROUP_DEBUG */