1/*
   2 *  Generic process-grouping system.
   3 *
   4 *  Based originally on the cpuset system, extracted by Paul Menage
   5 *  Copyright (C) 2006 Google, Inc
   6 *
   7 *  Notifications support
   8 *  Copyright (C) 2009 Nokia Corporation
   9 *  Author: Kirill A. Shutemov
  10 *
  11 *  Copyright notices from the original cpuset code:
  12 *  --------------------------------------------------
  13 *  Copyright (C) 2003 BULL SA.
  14 *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
  15 *
  16 *  Portions derived from Patrick Mochel's sysfs code.
  17 *  sysfs is Copyright (c) 2001-3 Patrick Mochel
  18 *
  19 *  2003-10-10 Written by Simon Derr.
  20 *  2003-10-22 Updates by Stephen Hemminger.
  21 *  2004 May-July Rework by Paul Jackson.
  22 *  ---------------------------------------------------
  23 *
  24 *  This file is subject to the terms and conditions of the GNU General Public
  25 *  License.  See the file COPYING in the main directory of the Linux
  26 *  distribution for more details.
  27 */
  28
  29#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  30
  31#include <linux/cgroup.h>
  32#include <linux/cred.h>
  33#include <linux/ctype.h>
  34#include <linux/errno.h>
 
  35#include <linux/init_task.h>
  36#include <linux/kernel.h>
  37#include <linux/list.h>
  38#include <linux/magic.h>
  39#include <linux/mm.h>
  40#include <linux/mutex.h>
  41#include <linux/mount.h>
  42#include <linux/pagemap.h>
  43#include <linux/proc_fs.h>
  44#include <linux/rcupdate.h>
  45#include <linux/sched.h>
 
 
  46#include <linux/slab.h>
 
  47#include <linux/spinlock.h>
  48#include <linux/percpu-rwsem.h>
  49#include <linux/string.h>
  50#include <linux/sort.h>
  51#include <linux/kmod.h>
 
  52#include <linux/delayacct.h>
  53#include <linux/cgroupstats.h>
  54#include <linux/hashtable.h>
 
  55#include <linux/pid_namespace.h>
  56#include <linux/idr.h>
  57#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
 
 
 
  58#include <linux/kthread.h>
  59#include <linux/delay.h>
  60#include <linux/atomic.h>
  61#include <linux/cpuset.h>
  62#include <linux/proc_ns.h>
  63#include <linux/nsproxy.h>
  64#include <linux/proc_ns.h>
  65#include <net/sock.h>
  66
  67/*
  68 * pidlists linger the following amount before being destroyed.  The goal
  69 * is avoiding frequent destruction in the middle of consecutive read calls
  70 * Expiring in the middle is a performance problem not a correctness one.
  71 * 1 sec should be enough.
  72 */
  73#define CGROUP_PIDLIST_DESTROY_DELAY	HZ
  74
  75#define CGROUP_FILE_NAME_MAX		(MAX_CGROUP_TYPE_NAMELEN +	\
  76					 MAX_CFTYPE_NAME + 2)
  77
  78/*
  79 * cgroup_mutex is the master lock.  Any modification to cgroup or its
  80 * hierarchy must be performed while holding it.
  81 *
  82 * css_set_lock protects task->cgroups pointer, the list of css_set
  83 * objects, and the chain of tasks off each css_set.
 
 
 
  84 *
  85 * These locks are exported if CONFIG_PROVE_RCU so that accessors in
  86 * cgroup.h can use them for lockdep annotations.
 
 
 
  87 */
  88#ifdef CONFIG_PROVE_RCU
  89DEFINE_MUTEX(cgroup_mutex);
  90DEFINE_SPINLOCK(css_set_lock);
  91EXPORT_SYMBOL_GPL(cgroup_mutex);
  92EXPORT_SYMBOL_GPL(css_set_lock);
  93#else
  94static DEFINE_MUTEX(cgroup_mutex);
  95static DEFINE_SPINLOCK(css_set_lock);
  96#endif
  97
  98/*
  99 * Protects cgroup_idr and css_idr so that IDs can be released without
 100 * grabbing cgroup_mutex.
 
 
 101 */
 102static DEFINE_SPINLOCK(cgroup_idr_lock);
 
 
 
 103
 104/*
 105 * Protects cgroup_file->kn for !self csses.  It synchronizes notifications
 106 * against file removal/re-creation across css hiding.
 107 */
 108static DEFINE_SPINLOCK(cgroup_file_kn_lock);
 109
 110/*
 111 * Protects cgroup_subsys->release_agent_path.  Modifying it also requires
 112 * cgroup_mutex.  Reading requires either cgroup_mutex or this spinlock.
 
 113 */
 114static DEFINE_SPINLOCK(release_agent_path_lock);
 
 115
 116struct percpu_rw_semaphore cgroup_threadgroup_rwsem;
 
 
 
 
 117
 118#define cgroup_assert_mutex_or_rcu_locked()				\
 119	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&			\
 120			   !lockdep_is_held(&cgroup_mutex),		\
 121			   "cgroup_mutex or RCU read lock required");
 122
 123/*
 124 * cgroup destruction makes heavy use of work items and there can be a lot
 125 * of concurrent destructions.  Use a separate workqueue so that cgroup
 126 * destruction work items don't end up filling up max_active of system_wq
 127 * which may lead to deadlock.
 128 */
 129static struct workqueue_struct *cgroup_destroy_wq;
 130
 131/*
 132 * pidlist destructions need to be flushed on cgroup destruction.  Use a
 133 * separate workqueue as flush domain.
 134 */
 135static struct workqueue_struct *cgroup_pidlist_destroy_wq;
 136
 137/* generate an array of cgroup subsystem pointers */
 138#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys,
 139static struct cgroup_subsys *cgroup_subsys[] = {
 140#include <linux/cgroup_subsys.h>
 141};
 142#undef SUBSYS
 143
 144/* array of cgroup subsystem names */
 145#define SUBSYS(_x) [_x ## _cgrp_id] = #_x,
 146static const char *cgroup_subsys_name[] = {
 147#include <linux/cgroup_subsys.h>
 148};
 149#undef SUBSYS
 150
 151/* array of static_keys for cgroup_subsys_enabled() and cgroup_subsys_on_dfl() */
 152#define SUBSYS(_x)								\
 153	DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key);			\
 154	DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key);			\
 155	EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key);			\
 156	EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key);
 157#include <linux/cgroup_subsys.h>
 158#undef SUBSYS
 159
 160#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_enabled_key,
 161static struct static_key_true *cgroup_subsys_enabled_key[] = {
 162#include <linux/cgroup_subsys.h>
 163};
 164#undef SUBSYS
 165
 166#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_on_dfl_key,
 167static struct static_key_true *cgroup_subsys_on_dfl_key[] = {
 168#include <linux/cgroup_subsys.h>
 
 
 
 
 
 169};
 170#undef SUBSYS
 171
 172/*
 173 * The default hierarchy, reserved for the subsystems that are otherwise
 174 * unattached - it never has more than a single cgroup, and all tasks are
 175 * part of that cgroup.
 176 */
 177struct cgroup_root cgrp_dfl_root;
 178EXPORT_SYMBOL_GPL(cgrp_dfl_root);
 179
 180/*
 181 * The default hierarchy always exists but is hidden until mounted for the
 182 * first time.  This is for backward compatibility.
 183 */
 184static bool cgrp_dfl_visible;
 185
 186/* Controllers blocked by the commandline in v1 */
 187static u16 cgroup_no_v1_mask;
 188
 189/* some controllers are not supported in the default hierarchy */
 190static u16 cgrp_dfl_inhibit_ss_mask;
 191
 192/* some controllers are implicitly enabled on the default hierarchy */
 193static unsigned long cgrp_dfl_implicit_ss_mask;
 194
 195/* The list of hierarchy roots */
 196
 197static LIST_HEAD(cgroup_roots);
 198static int cgroup_root_count;
 199
 200/* hierarchy ID allocation and mapping, protected by cgroup_mutex */
 201static DEFINE_IDR(cgroup_hierarchy_idr);
 202
 203/*
 204 * Assign a monotonically increasing serial number to csses.  It guarantees
 205 * cgroups with bigger numbers are newer than those with smaller numbers.
 206 * Also, as csses are always appended to the parent's ->children list, it
 207 * guarantees that sibling csses are always sorted in the ascending serial
 208 * number order on the list.  Protected by cgroup_mutex.
 209 */
 210static u64 css_serial_nr_next = 1;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 211
 212/*
 213 * These bitmask flags indicate whether tasks in the fork and exit paths have
 214 * fork/exit handlers to call. This avoids us having to do extra work in the
 215 * fork/exit path to check which subsystems have fork/exit callbacks.
 216 */
 217static u16 have_fork_callback __read_mostly;
 218static u16 have_exit_callback __read_mostly;
 219static u16 have_free_callback __read_mostly;
 220
 221/* cgroup namespace for init task */
 222struct cgroup_namespace init_cgroup_ns = {
 223	.count		= { .counter = 2, },
 224	.user_ns	= &init_user_ns,
 225	.ns.ops		= &cgroupns_operations,
 226	.ns.inum	= PROC_CGROUP_INIT_INO,
 227	.root_cset	= &init_css_set,
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 228};
 229
 230/* Ditto for the can_fork callback. */
 231static u16 have_canfork_callback __read_mostly;
 232
 233static struct file_system_type cgroup2_fs_type;
 234static struct cftype cgroup_dfl_base_files[];
 235static struct cftype cgroup_legacy_base_files[];
 236
 237static int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask);
 238static void cgroup_lock_and_drain_offline(struct cgroup *cgrp);
 239static int cgroup_apply_control(struct cgroup *cgrp);
 240static void cgroup_finalize_control(struct cgroup *cgrp, int ret);
 241static void css_task_iter_advance(struct css_task_iter *it);
 242static int cgroup_destroy_locked(struct cgroup *cgrp);
 243static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
 244					      struct cgroup_subsys *ss);
 245static void css_release(struct percpu_ref *ref);
 246static void kill_css(struct cgroup_subsys_state *css);
 247static int cgroup_addrm_files(struct cgroup_subsys_state *css,
 248			      struct cgroup *cgrp, struct cftype cfts[],
 249			      bool is_add);
 250
 251/**
 252 * cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID
 253 * @ssid: subsys ID of interest
 254 *
 255 * cgroup_subsys_enabled() can only be used with literal subsys names which
 256 * is fine for individual subsystems but unsuitable for cgroup core.  This
 257 * is slower static_key_enabled() based test indexed by @ssid.
 258 */
 259static bool cgroup_ssid_enabled(int ssid)
 260{
 261	if (CGROUP_SUBSYS_COUNT == 0)
 262		return false;
 263
 264	return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
 265}
 
 266
 267static bool cgroup_ssid_no_v1(int ssid)
 268{
 269	return cgroup_no_v1_mask & (1 << ssid);
 270}
 271
 272/**
 273 * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
 274 * @cgrp: the cgroup of interest
 275 *
 276 * The default hierarchy is the v2 interface of cgroup and this function
 277 * can be used to test whether a cgroup is on the default hierarchy for
 278 * cases where a subsystem should behave differnetly depending on the
 279 * interface version.
 280 *
 281 * The set of behaviors which change on the default hierarchy are still
 282 * being determined and the mount option is prefixed with __DEVEL__.
 283 *
 284 * List of changed behaviors:
 285 *
 286 * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
 287 *   and "name" are disallowed.
 288 *
 289 * - When mounting an existing superblock, mount options should match.
 290 *
 291 * - Remount is disallowed.
 292 *
 293 * - rename(2) is disallowed.
 294 *
 295 * - "tasks" is removed.  Everything should be at process granularity.  Use
 296 *   "cgroup.procs" instead.
 297 *
 298 * - "cgroup.procs" is not sorted.  pids will be unique unless they got
 299 *   recycled inbetween reads.
 300 *
 301 * - "release_agent" and "notify_on_release" are removed.  Replacement
 302 *   notification mechanism will be implemented.
 303 *
 304 * - "cgroup.clone_children" is removed.
 305 *
 306 * - "cgroup.subtree_populated" is available.  Its value is 0 if the cgroup
 307 *   and its descendants contain no task; otherwise, 1.  The file also
 308 *   generates kernfs notification which can be monitored through poll and
 309 *   [di]notify when the value of the file changes.
 310 *
 311 * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
 312 *   take masks of ancestors with non-empty cpus/mems, instead of being
 313 *   moved to an ancestor.
 314 *
 315 * - cpuset: a task can be moved into an empty cpuset, and again it takes
 316 *   masks of ancestors.
 317 *
 318 * - memcg: use_hierarchy is on by default and the cgroup file for the flag
 319 *   is not created.
 320 *
 321 * - blkcg: blk-throttle becomes properly hierarchical.
 322 *
 323 * - debug: disallowed on the default hierarchy.
 324 */
 325static bool cgroup_on_dfl(const struct cgroup *cgrp)
 326{
 327	return cgrp->root == &cgrp_dfl_root;
 328}
 329
 330/* IDR wrappers which synchronize using cgroup_idr_lock */
 331static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
 332			    gfp_t gfp_mask)
 333{
 334	int ret;
 335
 336	idr_preload(gfp_mask);
 337	spin_lock_bh(&cgroup_idr_lock);
 338	ret = idr_alloc(idr, ptr, start, end, gfp_mask & ~__GFP_DIRECT_RECLAIM);
 339	spin_unlock_bh(&cgroup_idr_lock);
 340	idr_preload_end();
 341	return ret;
 342}
 343
 344static void *cgroup_idr_replace(struct idr *idr, void *ptr, int id)
 345{
 346	void *ret;
 347
 348	spin_lock_bh(&cgroup_idr_lock);
 349	ret = idr_replace(idr, ptr, id);
 350	spin_unlock_bh(&cgroup_idr_lock);
 351	return ret;
 352}
 
 353
 354static void cgroup_idr_remove(struct idr *idr, int id)
 355{
 356	spin_lock_bh(&cgroup_idr_lock);
 357	idr_remove(idr, id);
 358	spin_unlock_bh(&cgroup_idr_lock);
 359}
 360
 361static struct cgroup *cgroup_parent(struct cgroup *cgrp)
 362{
 363	struct cgroup_subsys_state *parent_css = cgrp->self.parent;
 364
 365	if (parent_css)
 366		return container_of(parent_css, struct cgroup, self);
 367	return NULL;
 368}
 369
 370/* subsystems visibly enabled on a cgroup */
 371static u16 cgroup_control(struct cgroup *cgrp)
 372{
 373	struct cgroup *parent = cgroup_parent(cgrp);
 374	u16 root_ss_mask = cgrp->root->subsys_mask;
 375
 376	if (parent)
 377		return parent->subtree_control;
 378
 379	if (cgroup_on_dfl(cgrp))
 380		root_ss_mask &= ~(cgrp_dfl_inhibit_ss_mask |
 381				  cgrp_dfl_implicit_ss_mask);
 382	return root_ss_mask;
 383}
 384
 385/* subsystems enabled on a cgroup */
 386static u16 cgroup_ss_mask(struct cgroup *cgrp)
 387{
 388	struct cgroup *parent = cgroup_parent(cgrp);
 389
 390	if (parent)
 391		return parent->subtree_ss_mask;
 392
 393	return cgrp->root->subsys_mask;
 394}
 395
 396/**
 397 * cgroup_css - obtain a cgroup's css for the specified subsystem
 398 * @cgrp: the cgroup of interest
 399 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
 400 *
 401 * Return @cgrp's css (cgroup_subsys_state) associated with @ss.  This
 402 * function must be called either under cgroup_mutex or rcu_read_lock() and
 403 * the caller is responsible for pinning the returned css if it wants to
 404 * keep accessing it outside the said locks.  This function may return
 405 * %NULL if @cgrp doesn't have @subsys_id enabled.
 406 */
 407static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
 408					      struct cgroup_subsys *ss)
 409{
 410	if (ss)
 411		return rcu_dereference_check(cgrp->subsys[ss->id],
 412					lockdep_is_held(&cgroup_mutex));
 413	else
 414		return &cgrp->self;
 415}
 416
 417/**
 418 * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
 419 * @cgrp: the cgroup of interest
 420 * @ss: the subsystem of interest (%NULL returns @cgrp->self)
 421 *
 422 * Similar to cgroup_css() but returns the effective css, which is defined
 423 * as the matching css of the nearest ancestor including self which has @ss
 424 * enabled.  If @ss is associated with the hierarchy @cgrp is on, this
 425 * function is guaranteed to return non-NULL css.
 426 */
 427static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
 428						struct cgroup_subsys *ss)
 429{
 430	lockdep_assert_held(&cgroup_mutex);
 431
 432	if (!ss)
 433		return &cgrp->self;
 434
 435	/*
 436	 * This function is used while updating css associations and thus
 437	 * can't test the csses directly.  Test ss_mask.
 438	 */
 439	while (!(cgroup_ss_mask(cgrp) & (1 << ss->id))) {
 440		cgrp = cgroup_parent(cgrp);
 441		if (!cgrp)
 442			return NULL;
 443	}
 444
 445	return cgroup_css(cgrp, ss);
 446}
 447
 448/**
 449 * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
 450 * @cgrp: the cgroup of interest
 451 * @ss: the subsystem of interest
 452 *
 453 * Find and get the effective css of @cgrp for @ss.  The effective css is
 454 * defined as the matching css of the nearest ancestor including self which
 455 * has @ss enabled.  If @ss is not mounted on the hierarchy @cgrp is on,
 456 * the root css is returned, so this function always returns a valid css.
 457 * The returned css must be put using css_put().
 458 */
 459struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
 460					     struct cgroup_subsys *ss)
 461{
 462	struct cgroup_subsys_state *css;
 463
 464	rcu_read_lock();
 465
 466	do {
 467		css = cgroup_css(cgrp, ss);
 468
 469		if (css && css_tryget_online(css))
 470			goto out_unlock;
 471		cgrp = cgroup_parent(cgrp);
 472	} while (cgrp);
 473
 474	css = init_css_set.subsys[ss->id];
 475	css_get(css);
 476out_unlock:
 477	rcu_read_unlock();
 478	return css;
 479}
 480
 481/* convenient tests for these bits */
 482static inline bool cgroup_is_dead(const struct cgroup *cgrp)
 483{
 484	return !(cgrp->self.flags & CSS_ONLINE);
 485}
 486
 487static void cgroup_get(struct cgroup *cgrp)
 488{
 489	WARN_ON_ONCE(cgroup_is_dead(cgrp));
 490	css_get(&cgrp->self);
 491}
 
 
 
 
 
 492
 493static bool cgroup_tryget(struct cgroup *cgrp)
 494{
 495	return css_tryget(&cgrp->self);
 496}
 497
 498struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
 499{
 500	struct cgroup *cgrp = of->kn->parent->priv;
 501	struct cftype *cft = of_cft(of);
 502
 503	/*
 504	 * This is open and unprotected implementation of cgroup_css().
 505	 * seq_css() is only called from a kernfs file operation which has
 506	 * an active reference on the file.  Because all the subsystem
 507	 * files are drained before a css is disassociated with a cgroup,
 508	 * the matching css from the cgroup's subsys table is guaranteed to
 509	 * be and stay valid until the enclosing operation is complete.
 510	 */
 511	if (cft->ss)
 512		return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
 513	else
 514		return &cgrp->self;
 515}
 516EXPORT_SYMBOL_GPL(of_css);
 517
 518static int notify_on_release(const struct cgroup *cgrp)
 519{
 520	return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
 521}
 522
 523/**
 524 * for_each_css - iterate all css's of a cgroup
 525 * @css: the iteration cursor
 526 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
 527 * @cgrp: the target cgroup to iterate css's of
 528 *
 529 * Should be called under cgroup_[tree_]mutex.
 530 */
 531#define for_each_css(css, ssid, cgrp)					\
 532	for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++)	\
 533		if (!((css) = rcu_dereference_check(			\
 534				(cgrp)->subsys[(ssid)],			\
 535				lockdep_is_held(&cgroup_mutex)))) { }	\
 536		else
 537
 538/**
 539 * for_each_e_css - iterate all effective css's of a cgroup
 540 * @css: the iteration cursor
 541 * @ssid: the index of the subsystem, CGROUP_SUBSYS_COUNT after reaching the end
 542 * @cgrp: the target cgroup to iterate css's of
 543 *
 544 * Should be called under cgroup_[tree_]mutex.
 545 */
 546#define for_each_e_css(css, ssid, cgrp)					\
 547	for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++)	\
 548		if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
 549			;						\
 550		else
 551
 552/**
 553 * for_each_subsys - iterate all enabled cgroup subsystems
 554 * @ss: the iteration cursor
 555 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
 556 */
 557#define for_each_subsys(ss, ssid)					\
 558	for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT &&		\
 559	     (((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
 560
 561/**
 562 * do_each_subsys_mask - filter for_each_subsys with a bitmask
 563 * @ss: the iteration cursor
 564 * @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
 565 * @ss_mask: the bitmask
 566 *
 567 * The block will only run for cases where the ssid-th bit (1 << ssid) of
 568 * @ss_mask is set.
 569 */
 570#define do_each_subsys_mask(ss, ssid, ss_mask) do {			\
 571	unsigned long __ss_mask = (ss_mask);				\
 572	if (!CGROUP_SUBSYS_COUNT) { /* to avoid spurious gcc warning */	\
 573		(ssid) = 0;						\
 574		break;							\
 575	}								\
 576	for_each_set_bit(ssid, &__ss_mask, CGROUP_SUBSYS_COUNT) {	\
 577		(ss) = cgroup_subsys[ssid];				\
 578		{
 579
 580#define while_each_subsys_mask()					\
 581		}							\
 582	}								\
 583} while (false)
 584
 585/* iterate across the hierarchies */
 586#define for_each_root(root)						\
 587	list_for_each_entry((root), &cgroup_roots, root_list)
 588
 589/* iterate over child cgrps, lock should be held throughout iteration */
 590#define cgroup_for_each_live_child(child, cgrp)				\
 591	list_for_each_entry((child), &(cgrp)->self.children, self.sibling) \
 592		if (({ lockdep_assert_held(&cgroup_mutex);		\
 593		       cgroup_is_dead(child); }))			\
 594			;						\
 595		else
 596
 597/* walk live descendants in preorder */
 598#define cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp)		\
 599	css_for_each_descendant_pre((d_css), cgroup_css((cgrp), NULL))	\
 600		if (({ lockdep_assert_held(&cgroup_mutex);		\
 601		       (dsct) = (d_css)->cgroup;			\
 602		       cgroup_is_dead(dsct); }))			\
 603			;						\
 604		else
 605
 606/* walk live descendants in postorder */
 607#define cgroup_for_each_live_descendant_post(dsct, d_css, cgrp)		\
 608	css_for_each_descendant_post((d_css), cgroup_css((cgrp), NULL))	\
 609		if (({ lockdep_assert_held(&cgroup_mutex);		\
 610		       (dsct) = (d_css)->cgroup;			\
 611		       cgroup_is_dead(dsct); }))			\
 612			;						\
 613		else
 614
 615static void cgroup_release_agent(struct work_struct *work);
 
 616static void check_for_release(struct cgroup *cgrp);
 617
 618/*
 619 * A cgroup can be associated with multiple css_sets as different tasks may
 620 * belong to different cgroups on different hierarchies.  In the other
 621 * direction, a css_set is naturally associated with multiple cgroups.
 622 * This M:N relationship is represented by the following link structure
 623 * which exists for each association and allows traversing the associations
 624 * from both sides.
 625 */
 626struct cgrp_cset_link {
 627	/* the cgroup and css_set this link associates */
 628	struct cgroup		*cgrp;
 629	struct css_set		*cset;
 630
 631	/* list of cgrp_cset_links anchored at cgrp->cset_links */
 632	struct list_head	cset_link;
 633
 634	/* list of cgrp_cset_links anchored at css_set->cgrp_links */
 635	struct list_head	cgrp_link;
 636};
 637
 638/*
 639 * The default css_set - used by init and its children prior to any
 640 * hierarchies being mounted. It contains a pointer to the root state
 641 * for each subsystem. Also used to anchor the list of css_sets. Not
 642 * reference-counted, to improve performance when child cgroups
 643 * haven't been created.
 644 */
 645struct css_set init_css_set = {
 646	.refcount		= ATOMIC_INIT(1),
 647	.cgrp_links		= LIST_HEAD_INIT(init_css_set.cgrp_links),
 648	.tasks			= LIST_HEAD_INIT(init_css_set.tasks),
 649	.mg_tasks		= LIST_HEAD_INIT(init_css_set.mg_tasks),
 650	.mg_preload_node	= LIST_HEAD_INIT(init_css_set.mg_preload_node),
 651	.mg_node		= LIST_HEAD_INIT(init_css_set.mg_node),
 652	.task_iters		= LIST_HEAD_INIT(init_css_set.task_iters),
 653};
 654
 655static int css_set_count	= 1;	/* 1 for init_css_set */
 
 656
 657/**
 658 * css_set_populated - does a css_set contain any tasks?
 659 * @cset: target css_set
 660 */
 661static bool css_set_populated(struct css_set *cset)
 662{
 663	lockdep_assert_held(&css_set_lock);
 664
 665	return !list_empty(&cset->tasks) || !list_empty(&cset->mg_tasks);
 666}
 667
 668/**
 669 * cgroup_update_populated - updated populated count of a cgroup
 670 * @cgrp: the target cgroup
 671 * @populated: inc or dec populated count
 672 *
 673 * One of the css_sets associated with @cgrp is either getting its first
 674 * task or losing the last.  Update @cgrp->populated_cnt accordingly.  The
 675 * count is propagated towards root so that a given cgroup's populated_cnt
 676 * is zero iff the cgroup and all its descendants don't contain any tasks.
 677 *
 678 * @cgrp's interface file "cgroup.populated" is zero if
 679 * @cgrp->populated_cnt is zero and 1 otherwise.  When @cgrp->populated_cnt
 680 * changes from or to zero, userland is notified that the content of the
 681 * interface file has changed.  This can be used to detect when @cgrp and
 682 * its descendants become populated or empty.
 683 */
 684static void cgroup_update_populated(struct cgroup *cgrp, bool populated)
 685{
 686	lockdep_assert_held(&css_set_lock);
 687
 688	do {
 689		bool trigger;
 690
 691		if (populated)
 692			trigger = !cgrp->populated_cnt++;
 693		else
 694			trigger = !--cgrp->populated_cnt;
 695
 696		if (!trigger)
 697			break;
 698
 699		check_for_release(cgrp);
 700		cgroup_file_notify(&cgrp->events_file);
 701
 702		cgrp = cgroup_parent(cgrp);
 703	} while (cgrp);
 704}
 705
 706/**
 707 * css_set_update_populated - update populated state of a css_set
 708 * @cset: target css_set
 709 * @populated: whether @cset is populated or depopulated
 710 *
 711 * @cset is either getting the first task or losing the last.  Update the
 712 * ->populated_cnt of all associated cgroups accordingly.
 713 */
 714static void css_set_update_populated(struct css_set *cset, bool populated)
 715{
 716	struct cgrp_cset_link *link;
 717
 718	lockdep_assert_held(&css_set_lock);
 719
 720	list_for_each_entry(link, &cset->cgrp_links, cgrp_link)
 721		cgroup_update_populated(link->cgrp, populated);
 722}
 723
 724/**
 725 * css_set_move_task - move a task from one css_set to another
 726 * @task: task being moved
 727 * @from_cset: css_set @task currently belongs to (may be NULL)
 728 * @to_cset: new css_set @task is being moved to (may be NULL)
 729 * @use_mg_tasks: move to @to_cset->mg_tasks instead of ->tasks
 730 *
 731 * Move @task from @from_cset to @to_cset.  If @task didn't belong to any
 732 * css_set, @from_cset can be NULL.  If @task is being disassociated
 733 * instead of moved, @to_cset can be NULL.
 734 *
 735 * This function automatically handles populated_cnt updates and
 736 * css_task_iter adjustments but the caller is responsible for managing
 737 * @from_cset and @to_cset's reference counts.
 738 */
 739static void css_set_move_task(struct task_struct *task,
 740			      struct css_set *from_cset, struct css_set *to_cset,
 741			      bool use_mg_tasks)
 742{
 743	lockdep_assert_held(&css_set_lock);
 744
 745	if (to_cset && !css_set_populated(to_cset))
 746		css_set_update_populated(to_cset, true);
 747
 748	if (from_cset) {
 749		struct css_task_iter *it, *pos;
 750
 751		WARN_ON_ONCE(list_empty(&task->cg_list));
 752
 753		/*
 754		 * @task is leaving, advance task iterators which are
 755		 * pointing to it so that they can resume at the next
 756		 * position.  Advancing an iterator might remove it from
 757		 * the list, use safe walk.  See css_task_iter_advance*()
 758		 * for details.
 759		 */
 760		list_for_each_entry_safe(it, pos, &from_cset->task_iters,
 761					 iters_node)
 762			if (it->task_pos == &task->cg_list)
 763				css_task_iter_advance(it);
 764
 765		list_del_init(&task->cg_list);
 766		if (!css_set_populated(from_cset))
 767			css_set_update_populated(from_cset, false);
 768	} else {
 769		WARN_ON_ONCE(!list_empty(&task->cg_list));
 770	}
 771
 772	if (to_cset) {
 773		/*
 774		 * We are synchronized through cgroup_threadgroup_rwsem
 775		 * against PF_EXITING setting such that we can't race
 776		 * against cgroup_exit() changing the css_set to
 777		 * init_css_set and dropping the old one.
 778		 */
 779		WARN_ON_ONCE(task->flags & PF_EXITING);
 780
 781		rcu_assign_pointer(task->cgroups, to_cset);
 782		list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks :
 783							     &to_cset->tasks);
 784	}
 785}
 786
 787/*
 788 * hash table for cgroup groups. This improves the performance to find
 789 * an existing css_set. This hash doesn't (currently) take into
 790 * account cgroups in empty hierarchies.
 791 */
 792#define CSS_SET_HASH_BITS	7
 793static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
 
 794
 795static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
 796{
 797	unsigned long key = 0UL;
 798	struct cgroup_subsys *ss;
 799	int i;
 
 
 800
 801	for_each_subsys(ss, i)
 802		key += (unsigned long)css[i];
 803	key = (key >> 16) ^ key;
 804
 805	return key;
 806}
 807
 808static void put_css_set_locked(struct css_set *cset)
 809{
 810	struct cgrp_cset_link *link, *tmp_link;
 811	struct cgroup_subsys *ss;
 812	int ssid;
 813
 814	lockdep_assert_held(&css_set_lock);
 815
 816	if (!atomic_dec_and_test(&cset->refcount))
 817		return;
 818
 819	/* This css_set is dead. unlink it and release cgroup and css refs */
 820	for_each_subsys(ss, ssid) {
 821		list_del(&cset->e_cset_node[ssid]);
 822		css_put(cset->subsys[ssid]);
 823	}
 824	hash_del(&cset->hlist);
 825	css_set_count--;
 826
 827	list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
 828		list_del(&link->cset_link);
 829		list_del(&link->cgrp_link);
 830		if (cgroup_parent(link->cgrp))
 831			cgroup_put(link->cgrp);
 832		kfree(link);
 833	}
 834
 835	kfree_rcu(cset, rcu_head);
 836}
 837
 838static void put_css_set(struct css_set *cset)
 
 
 
 
 
 
 839{
 
 
 840	/*
 841	 * Ensure that the refcount doesn't hit zero while any readers
 842	 * can see it. Similar to atomic_dec_and_lock(), but for an
 843	 * rwlock
 844	 */
 845	if (atomic_add_unless(&cset->refcount, -1, 1))
 
 
 
 
 846		return;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 847
 848	spin_lock_bh(&css_set_lock);
 849	put_css_set_locked(cset);
 850	spin_unlock_bh(&css_set_lock);
 
 
 851}
 852
 853/*
 854 * refcounted get/put for css_set objects
 855 */
 856static inline void get_css_set(struct css_set *cset)
 857{
 858	atomic_inc(&cset->refcount);
 859}
 860
 861/**
 
 
 
 
 
 
 
 
 
 
 862 * compare_css_sets - helper function for find_existing_css_set().
 863 * @cset: candidate css_set being tested
 864 * @old_cset: existing css_set for a task
 865 * @new_cgrp: cgroup that's being entered by the task
 866 * @template: desired set of css pointers in css_set (pre-calculated)
 867 *
 868 * Returns true if "cset" matches "old_cset" except for the hierarchy
 869 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
 870 */
 871static bool compare_css_sets(struct css_set *cset,
 872			     struct css_set *old_cset,
 873			     struct cgroup *new_cgrp,
 874			     struct cgroup_subsys_state *template[])
 875{
 876	struct list_head *l1, *l2;
 877
 878	/*
 879	 * On the default hierarchy, there can be csets which are
 880	 * associated with the same set of cgroups but different csses.
 881	 * Let's first ensure that csses match.
 882	 */
 883	if (memcmp(template, cset->subsys, sizeof(cset->subsys)))
 884		return false;
 
 885
 886	/*
 887	 * Compare cgroup pointers in order to distinguish between
 888	 * different cgroups in hierarchies.  As different cgroups may
 889	 * share the same effective css, this comparison is always
 890	 * necessary.
 
 
 891	 */
 892	l1 = &cset->cgrp_links;
 893	l2 = &old_cset->cgrp_links;
 
 894	while (1) {
 895		struct cgrp_cset_link *link1, *link2;
 896		struct cgroup *cgrp1, *cgrp2;
 897
 898		l1 = l1->next;
 899		l2 = l2->next;
 900		/* See if we reached the end - both lists are equal length. */
 901		if (l1 == &cset->cgrp_links) {
 902			BUG_ON(l2 != &old_cset->cgrp_links);
 903			break;
 904		} else {
 905			BUG_ON(l2 == &old_cset->cgrp_links);
 906		}
 907		/* Locate the cgroups associated with these links. */
 908		link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
 909		link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
 910		cgrp1 = link1->cgrp;
 911		cgrp2 = link2->cgrp;
 912		/* Hierarchies should be linked in the same order. */
 913		BUG_ON(cgrp1->root != cgrp2->root);
 914
 915		/*
 916		 * If this hierarchy is the hierarchy of the cgroup
 917		 * that's changing, then we need to check that this
 918		 * css_set points to the new cgroup; if it's any other
 919		 * hierarchy, then this css_set should point to the
 920		 * same cgroup as the old css_set.
 921		 */
 922		if (cgrp1->root == new_cgrp->root) {
 923			if (cgrp1 != new_cgrp)
 924				return false;
 925		} else {
 926			if (cgrp1 != cgrp2)
 927				return false;
 928		}
 929	}
 930	return true;
 931}
 932
 933/**
 934 * find_existing_css_set - init css array and find the matching css_set
 935 * @old_cset: the css_set that we're using before the cgroup transition
 936 * @cgrp: the cgroup that we're moving into
 937 * @template: out param for the new set of csses, should be clear on entry
 938 */
 939static struct css_set *find_existing_css_set(struct css_set *old_cset,
 940					struct cgroup *cgrp,
 941					struct cgroup_subsys_state *template[])
 
 
 
 
 
 
 
 
 942{
 943	struct cgroup_root *root = cgrp->root;
 944	struct cgroup_subsys *ss;
 945	struct css_set *cset;
 946	unsigned long key;
 947	int i;
 
 
 
 
 948
 949	/*
 950	 * Build the set of subsystem state objects that we want to see in the
 951	 * new css_set. while subsystems can change globally, the entries here
 952	 * won't change, so no need for locking.
 953	 */
 954	for_each_subsys(ss, i) {
 955		if (root->subsys_mask & (1UL << i)) {
 956			/*
 957			 * @ss is in this hierarchy, so we want the
 958			 * effective css from @cgrp.
 959			 */
 960			template[i] = cgroup_e_css(cgrp, ss);
 961		} else {
 962			/*
 963			 * @ss is not in this hierarchy, so we don't want
 964			 * to change the css.
 965			 */
 966			template[i] = old_cset->subsys[i];
 967		}
 968	}
 969
 970	key = css_set_hash(template);
 971	hash_for_each_possible(css_set_table, cset, hlist, key) {
 972		if (!compare_css_sets(cset, old_cset, cgrp, template))
 973			continue;
 974
 975		/* This css_set matches what we need */
 976		return cset;
 977	}
 978
 979	/* No existing cgroup group matched */
 980	return NULL;
 981}
 982
 983static void free_cgrp_cset_links(struct list_head *links_to_free)
 984{
 985	struct cgrp_cset_link *link, *tmp_link;
 
 986
 987	list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
 988		list_del(&link->cset_link);
 989		kfree(link);
 990	}
 991}
 992
 993/**
 994 * allocate_cgrp_cset_links - allocate cgrp_cset_links
 995 * @count: the number of links to allocate
 996 * @tmp_links: list_head the allocated links are put on
 997 *
 998 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
 999 * through ->cset_link.  Returns 0 on success or -errno.
1000 */
1001static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
1002{
1003	struct cgrp_cset_link *link;
1004	int i;
1005
1006	INIT_LIST_HEAD(tmp_links);
1007
1008	for (i = 0; i < count; i++) {
1009		link = kzalloc(sizeof(*link), GFP_KERNEL);
1010		if (!link) {
1011			free_cgrp_cset_links(tmp_links);
1012			return -ENOMEM;
1013		}
1014		list_add(&link->cset_link, tmp_links);
1015	}
1016	return 0;
1017}
1018
1019/**
1020 * link_css_set - a helper function to link a css_set to a cgroup
1021 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
1022 * @cset: the css_set to be linked
1023 * @cgrp: the destination cgroup
1024 */
1025static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
1026			 struct cgroup *cgrp)
1027{
1028	struct cgrp_cset_link *link;
1029
1030	BUG_ON(list_empty(tmp_links));
1031
1032	if (cgroup_on_dfl(cgrp))
1033		cset->dfl_cgrp = cgrp;
1034
1035	link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
1036	link->cset = cset;
1037	link->cgrp = cgrp;
1038
 
1039	/*
1040	 * Always add links to the tail of the lists so that the lists are
1041	 * in choronological order.
1042	 */
1043	list_move_tail(&link->cset_link, &cgrp->cset_links);
1044	list_add_tail(&link->cgrp_link, &cset->cgrp_links);
1045
1046	if (cgroup_parent(cgrp))
1047		cgroup_get(cgrp);
1048}
1049
1050/**
1051 * find_css_set - return a new css_set with one cgroup updated
1052 * @old_cset: the baseline css_set
1053 * @cgrp: the cgroup to be updated
1054 *
1055 * Return a new css_set that's equivalent to @old_cset, but with @cgrp
1056 * substituted into the appropriate hierarchy.
1057 */
1058static struct css_set *find_css_set(struct css_set *old_cset,
1059				    struct cgroup *cgrp)
1060{
1061	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT] = { };
1062	struct css_set *cset;
1063	struct list_head tmp_links;
1064	struct cgrp_cset_link *link;
1065	struct cgroup_subsys *ss;
1066	unsigned long key;
1067	int ssid;
1068
1069	lockdep_assert_held(&cgroup_mutex);
 
 
 
1070
1071	/* First see if we already have a cgroup group that matches
1072	 * the desired set */
1073	spin_lock_bh(&css_set_lock);
1074	cset = find_existing_css_set(old_cset, cgrp, template);
1075	if (cset)
1076		get_css_set(cset);
1077	spin_unlock_bh(&css_set_lock);
1078
1079	if (cset)
1080		return cset;
1081
1082	cset = kzalloc(sizeof(*cset), GFP_KERNEL);
1083	if (!cset)
1084		return NULL;
1085
1086	/* Allocate all the cgrp_cset_link objects that we'll need */
1087	if (allocate_cgrp_cset_links(cgroup_root_count, &tmp_links) < 0) {
1088		kfree(cset);
1089		return NULL;
1090	}
1091
1092	atomic_set(&cset->refcount, 1);
1093	INIT_LIST_HEAD(&cset->cgrp_links);
1094	INIT_LIST_HEAD(&cset->tasks);
1095	INIT_LIST_HEAD(&cset->mg_tasks);
1096	INIT_LIST_HEAD(&cset->mg_preload_node);
1097	INIT_LIST_HEAD(&cset->mg_node);
1098	INIT_LIST_HEAD(&cset->task_iters);
1099	INIT_HLIST_NODE(&cset->hlist);
1100
1101	/* Copy the set of subsystem state objects generated in
1102	 * find_existing_css_set() */
1103	memcpy(cset->subsys, template, sizeof(cset->subsys));
1104
1105	spin_lock_bh(&css_set_lock);
1106	/* Add reference counts and links from the new css_set. */
1107	list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
1108		struct cgroup *c = link->cgrp;
1109
1110		if (c->root == cgrp->root)
1111			c = cgrp;
1112		link_css_set(&tmp_links, cset, c);
1113	}
1114
1115	BUG_ON(!list_empty(&tmp_links));
1116
1117	css_set_count++;
1118
1119	/* Add @cset to the hash table */
1120	key = css_set_hash(cset->subsys);
1121	hash_add(css_set_table, &cset->hlist, key);
1122
1123	for_each_subsys(ss, ssid) {
1124		struct cgroup_subsys_state *css = cset->subsys[ssid];
1125
1126		list_add_tail(&cset->e_cset_node[ssid],
1127			      &css->cgroup->e_csets[ssid]);
1128		css_get(css);
1129	}
1130
1131	spin_unlock_bh(&css_set_lock);
1132
1133	return cset;
1134}
1135
1136static struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
1137{
1138	struct cgroup *root_cgrp = kf_root->kn->priv;
1139
1140	return root_cgrp->root;
1141}
1142
1143static int cgroup_init_root_id(struct cgroup_root *root)
1144{
1145	int id;
1146
1147	lockdep_assert_held(&cgroup_mutex);
1148
1149	id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
1150	if (id < 0)
1151		return id;
1152
1153	root->hierarchy_id = id;
1154	return 0;
1155}
1156
1157static void cgroup_exit_root_id(struct cgroup_root *root)
1158{
1159	lockdep_assert_held(&cgroup_mutex);
1160
1161	if (root->hierarchy_id) {
1162		idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
1163		root->hierarchy_id = 0;
1164	}
1165}
1166
1167static void cgroup_free_root(struct cgroup_root *root)
1168{
1169	if (root) {
1170		/* hierarchy ID should already have been released */
1171		WARN_ON_ONCE(root->hierarchy_id);
1172
1173		idr_destroy(&root->cgroup_idr);
1174		kfree(root);
1175	}
1176}
1177
1178static void cgroup_destroy_root(struct cgroup_root *root)
1179{
1180	struct cgroup *cgrp = &root->cgrp;
1181	struct cgrp_cset_link *link, *tmp_link;
1182
1183	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1184
1185	BUG_ON(atomic_read(&root->nr_cgrps));
1186	BUG_ON(!list_empty(&cgrp->self.children));
1187
1188	/* Rebind all subsystems back to the default hierarchy */
1189	WARN_ON(rebind_subsystems(&cgrp_dfl_root, root->subsys_mask));
1190
1191	/*
1192	 * Release all the links from cset_links to this hierarchy's
1193	 * root cgroup
1194	 */
1195	spin_lock_bh(&css_set_lock);
1196
1197	list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
1198		list_del(&link->cset_link);
1199		list_del(&link->cgrp_link);
1200		kfree(link);
1201	}
1202
1203	spin_unlock_bh(&css_set_lock);
1204
1205	if (!list_empty(&root->root_list)) {
1206		list_del(&root->root_list);
1207		cgroup_root_count--;
1208	}
1209
1210	cgroup_exit_root_id(root);
1211
1212	mutex_unlock(&cgroup_mutex);
1213
1214	kernfs_destroy_root(root->kf_root);
1215	cgroup_free_root(root);
1216}
1217
1218/*
1219 * look up cgroup associated with current task's cgroup namespace on the
1220 * specified hierarchy
1221 */
1222static struct cgroup *
1223current_cgns_cgroup_from_root(struct cgroup_root *root)
1224{
1225	struct cgroup *res = NULL;
1226	struct css_set *cset;
1227
1228	lockdep_assert_held(&css_set_lock);
1229
1230	rcu_read_lock();
1231
1232	cset = current->nsproxy->cgroup_ns->root_cset;
1233	if (cset == &init_css_set) {
1234		res = &root->cgrp;
1235	} else {
1236		struct cgrp_cset_link *link;
1237
1238		list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
1239			struct cgroup *c = link->cgrp;
1240
1241			if (c->root == root) {
1242				res = c;
1243				break;
1244			}
1245		}
1246	}
1247	rcu_read_unlock();
1248
1249	BUG_ON(!res);
1250	return res;
1251}
1252
1253/* look up cgroup associated with given css_set on the specified hierarchy */
1254static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
1255					    struct cgroup_root *root)
1256{
 
1257	struct cgroup *res = NULL;
1258
1259	lockdep_assert_held(&cgroup_mutex);
1260	lockdep_assert_held(&css_set_lock);
1261
1262	if (cset == &init_css_set) {
1263		res = &root->cgrp;
 
 
 
 
 
1264	} else {
1265		struct cgrp_cset_link *link;
1266
1267		list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
1268			struct cgroup *c = link->cgrp;
1269
1270			if (c->root == root) {
1271				res = c;
1272				break;
1273			}
1274		}
1275	}
1276
1277	BUG_ON(!res);
1278	return res;
1279}
1280
1281/*
1282 * Return the cgroup for "task" from the given hierarchy. Must be
1283 * called with cgroup_mutex and css_set_lock held.
1284 */
1285static struct cgroup *task_cgroup_from_root(struct task_struct *task,
1286					    struct cgroup_root *root)
1287{
1288	/*
1289	 * No need to lock the task - since we hold cgroup_mutex the
1290	 * task can't change groups, so the only thing that can happen
1291	 * is that it exits and its css is set back to init_css_set.
1292	 */
1293	return cset_cgroup_from_root(task_css_set(task), root);
1294}
1295
1296/*
1297 * A task must hold cgroup_mutex to modify cgroups.
1298 *
1299 * Any task can increment and decrement the count field without lock.
1300 * So in general, code holding cgroup_mutex can't rely on the count
1301 * field not changing.  However, if the count goes to zero, then only
1302 * cgroup_attach_task() can increment it again.  Because a count of zero
1303 * means that no tasks are currently attached, therefore there is no
1304 * way a task attached to that cgroup can fork (the other way to
1305 * increment the count).  So code holding cgroup_mutex can safely
1306 * assume that if the count is zero, it will stay zero. Similarly, if
1307 * a task holds cgroup_mutex on a cgroup with zero count, it
1308 * knows that the cgroup won't be removed, as cgroup_rmdir()
1309 * needs that mutex.
1310 *
 
 
 
 
 
 
 
 
1311 * A cgroup can only be deleted if both its 'count' of using tasks
1312 * is zero, and its list of 'children' cgroups is empty.  Since all
1313 * tasks in the system use _some_ cgroup, and since there is always at
1314 * least one task in the system (init, pid == 1), therefore, root cgroup
1315 * always has either children cgroups and/or using tasks.  So we don't
1316 * need a special hack to ensure that root cgroup cannot be deleted.
 
 
 
 
 
 
 
 
 
 
 
 
1317 *
1318 * P.S.  One more locking exception.  RCU is used to guard the
1319 * update of a tasks cgroup pointer by cgroup_attach_task()
1320 */
1321
1322static struct kernfs_syscall_ops cgroup_kf_syscall_ops;
1323static const struct file_operations proc_cgroupstats_operations;
1324
1325static char *cgroup_file_name(struct cgroup *cgrp, const struct cftype *cft,
1326			      char *buf)
1327{
1328	struct cgroup_subsys *ss = cft->ss;
1329
1330	if (cft->ss && !(cft->flags & CFTYPE_NO_PREFIX) &&
1331	    !(cgrp->root->flags & CGRP_ROOT_NOPREFIX))
1332		snprintf(buf, CGROUP_FILE_NAME_MAX, "%s.%s",
1333			 cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name,
1334			 cft->name);
1335	else
1336		strncpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
1337	return buf;
1338}
1339
1340/**
1341 * cgroup_file_mode - deduce file mode of a control file
1342 * @cft: the control file in question
1343 *
1344 * S_IRUGO for read, S_IWUSR for write.
1345 */
1346static umode_t cgroup_file_mode(const struct cftype *cft)
1347{
1348	umode_t mode = 0;
1349
1350	if (cft->read_u64 || cft->read_s64 || cft->seq_show)
1351		mode |= S_IRUGO;
1352
1353	if (cft->write_u64 || cft->write_s64 || cft->write) {
1354		if (cft->flags & CFTYPE_WORLD_WRITABLE)
1355			mode |= S_IWUGO;
1356		else
1357			mode |= S_IWUSR;
1358	}
1359
1360	return mode;
1361}
 
1362
1363/**
1364 * cgroup_calc_subtree_ss_mask - calculate subtree_ss_mask
1365 * @subtree_control: the new subtree_control mask to consider
1366 * @this_ss_mask: available subsystems
1367 *
1368 * On the default hierarchy, a subsystem may request other subsystems to be
1369 * enabled together through its ->depends_on mask.  In such cases, more
1370 * subsystems than specified in "cgroup.subtree_control" may be enabled.
1371 *
1372 * This function calculates which subsystems need to be enabled if
1373 * @subtree_control is to be applied while restricted to @this_ss_mask.
1374 */
1375static u16 cgroup_calc_subtree_ss_mask(u16 subtree_control, u16 this_ss_mask)
1376{
1377	u16 cur_ss_mask = subtree_control;
1378	struct cgroup_subsys *ss;
1379	int ssid;
1380
1381	lockdep_assert_held(&cgroup_mutex);
 
 
 
 
 
1382
1383	cur_ss_mask |= cgrp_dfl_implicit_ss_mask;
 
 
 
 
 
1384
1385	while (true) {
1386		u16 new_ss_mask = cur_ss_mask;
 
 
1387
1388		do_each_subsys_mask(ss, ssid, cur_ss_mask) {
1389			new_ss_mask |= ss->depends_on;
1390		} while_each_subsys_mask();
1391
1392		/*
1393		 * Mask out subsystems which aren't available.  This can
1394		 * happen only if some depended-upon subsystems were bound
1395		 * to non-default hierarchies.
1396		 */
1397		new_ss_mask &= this_ss_mask;
1398
1399		if (new_ss_mask == cur_ss_mask)
1400			break;
1401		cur_ss_mask = new_ss_mask;
 
 
 
 
1402	}
1403
1404	return cur_ss_mask;
1405}
1406
1407/**
1408 * cgroup_kn_unlock - unlocking helper for cgroup kernfs methods
1409 * @kn: the kernfs_node being serviced
1410 *
1411 * This helper undoes cgroup_kn_lock_live() and should be invoked before
1412 * the method finishes if locking succeeded.  Note that once this function
1413 * returns the cgroup returned by cgroup_kn_lock_live() may become
1414 * inaccessible any time.  If the caller intends to continue to access the
1415 * cgroup, it should pin it before invoking this function.
1416 */
1417static void cgroup_kn_unlock(struct kernfs_node *kn)
1418{
1419	struct cgroup *cgrp;
 
1420
1421	if (kernfs_type(kn) == KERNFS_DIR)
1422		cgrp = kn->priv;
1423	else
1424		cgrp = kn->parent->priv;
1425
1426	mutex_unlock(&cgroup_mutex);
 
 
 
 
 
 
1427
1428	kernfs_unbreak_active_protection(kn);
1429	cgroup_put(cgrp);
1430}
1431
1432/**
1433 * cgroup_kn_lock_live - locking helper for cgroup kernfs methods
1434 * @kn: the kernfs_node being serviced
1435 * @drain_offline: perform offline draining on the cgroup
1436 *
1437 * This helper is to be used by a cgroup kernfs method currently servicing
1438 * @kn.  It breaks the active protection, performs cgroup locking and
1439 * verifies that the associated cgroup is alive.  Returns the cgroup if
1440 * alive; otherwise, %NULL.  A successful return should be undone by a
1441 * matching cgroup_kn_unlock() invocation.  If @drain_offline is %true, the
1442 * cgroup is drained of offlining csses before return.
1443 *
1444 * Any cgroup kernfs method implementation which requires locking the
1445 * associated cgroup should use this helper.  It avoids nesting cgroup
1446 * locking under kernfs active protection and allows all kernfs operations
1447 * including self-removal.
1448 */
1449static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn,
1450					  bool drain_offline)
1451{
1452	struct cgroup *cgrp;
 
 
 
 
 
 
 
 
 
 
 
1453
1454	if (kernfs_type(kn) == KERNFS_DIR)
1455		cgrp = kn->priv;
1456	else
1457		cgrp = kn->parent->priv;
 
 
1458
1459	/*
1460	 * We're gonna grab cgroup_mutex which nests outside kernfs
1461	 * active_ref.  cgroup liveliness check alone provides enough
1462	 * protection against removal.  Ensure @cgrp stays accessible and
1463	 * break the active_ref protection.
1464	 */
1465	if (!cgroup_tryget(cgrp))
1466		return NULL;
1467	kernfs_break_active_protection(kn);
1468
1469	if (drain_offline)
1470		cgroup_lock_and_drain_offline(cgrp);
1471	else
1472		mutex_lock(&cgroup_mutex);
 
1473
1474	if (!cgroup_is_dead(cgrp))
1475		return cgrp;
 
 
 
1476
1477	cgroup_kn_unlock(kn);
1478	return NULL;
 
 
 
 
 
 
 
 
 
1479}
1480
1481static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
1482{
1483	char name[CGROUP_FILE_NAME_MAX];
 
1484
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1485	lockdep_assert_held(&cgroup_mutex);
1486
1487	if (cft->file_offset) {
1488		struct cgroup_subsys_state *css = cgroup_css(cgrp, cft->ss);
1489		struct cgroup_file *cfile = (void *)css + cft->file_offset;
1490
1491		spin_lock_irq(&cgroup_file_kn_lock);
1492		cfile->kn = NULL;
1493		spin_unlock_irq(&cgroup_file_kn_lock);
1494	}
1495
1496	kernfs_remove_by_name(cgrp->kn, cgroup_file_name(cgrp, cft, name));
 
 
 
 
 
 
 
 
1497}
1498
1499/**
1500 * css_clear_dir - remove subsys files in a cgroup directory
1501 * @css: taget css
1502 */
1503static void css_clear_dir(struct cgroup_subsys_state *css)
1504{
1505	struct cgroup *cgrp = css->cgroup;
1506	struct cftype *cfts;
1507
1508	if (!(css->flags & CSS_VISIBLE))
1509		return;
1510
1511	css->flags &= ~CSS_VISIBLE;
1512
1513	list_for_each_entry(cfts, &css->ss->cfts, node)
1514		cgroup_addrm_files(css, cgrp, cfts, false);
1515}
1516
1517/**
1518 * css_populate_dir - create subsys files in a cgroup directory
1519 * @css: target css
1520 *
1521 * On failure, no file is added.
1522 */
1523static int css_populate_dir(struct cgroup_subsys_state *css)
1524{
1525	struct cgroup *cgrp = css->cgroup;
1526	struct cftype *cfts, *failed_cfts;
1527	int ret;
1528
1529	if ((css->flags & CSS_VISIBLE) || !cgrp->kn)
1530		return 0;
1531
1532	if (!css->ss) {
1533		if (cgroup_on_dfl(cgrp))
1534			cfts = cgroup_dfl_base_files;
1535		else
1536			cfts = cgroup_legacy_base_files;
 
 
 
1537
1538		return cgroup_addrm_files(&cgrp->self, cgrp, cfts, true);
1539	}
 
 
 
 
 
 
 
1540
1541	list_for_each_entry(cfts, &css->ss->cfts, node) {
1542		ret = cgroup_addrm_files(css, cgrp, cfts, true);
1543		if (ret < 0) {
1544			failed_cfts = cfts;
1545			goto err;
1546		}
1547	}
1548
1549	css->flags |= CSS_VISIBLE;
 
 
 
1550
1551	return 0;
1552err:
1553	list_for_each_entry(cfts, &css->ss->cfts, node) {
1554		if (cfts == failed_cfts)
1555			break;
1556		cgroup_addrm_files(css, cgrp, cfts, false);
1557	}
1558	return ret;
1559}
1560
1561static int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
 
 
 
 
 
 
1562{
1563	struct cgroup *dcgrp = &dst_root->cgrp;
1564	struct cgroup_subsys *ss;
1565	int ssid, i, ret;
1566
1567	lockdep_assert_held(&cgroup_mutex);
 
1568
1569	do_each_subsys_mask(ss, ssid, ss_mask) {
 
 
 
 
 
 
 
1570		/*
1571		 * If @ss has non-root csses attached to it, can't move.
1572		 * If @ss is an implicit controller, it is exempt from this
1573		 * rule and can be stolen.
1574		 */
1575		if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)) &&
1576		    !ss->implicit_on_dfl)
 
1577			return -EBUSY;
 
 
1578
1579		/* can't move between two non-dummy roots either */
1580		if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
1581			return -EBUSY;
1582	} while_each_subsys_mask();
 
 
1583
1584	do_each_subsys_mask(ss, ssid, ss_mask) {
1585		struct cgroup_root *src_root = ss->root;
1586		struct cgroup *scgrp = &src_root->cgrp;
1587		struct cgroup_subsys_state *css = cgroup_css(scgrp, ss);
1588		struct css_set *cset;
1589
1590		WARN_ON(!css || cgroup_css(dcgrp, ss));
1591
1592		/* disable from the source */
1593		src_root->subsys_mask &= ~(1 << ssid);
1594		WARN_ON(cgroup_apply_control(scgrp));
1595		cgroup_finalize_control(scgrp, 0);
1596
1597		/* rebind */
1598		RCU_INIT_POINTER(scgrp->subsys[ssid], NULL);
1599		rcu_assign_pointer(dcgrp->subsys[ssid], css);
1600		ss->root = dst_root;
1601		css->cgroup = dcgrp;
1602
1603		spin_lock_bh(&css_set_lock);
1604		hash_for_each(css_set_table, i, cset, hlist)
1605			list_move_tail(&cset->e_cset_node[ss->id],
1606				       &dcgrp->e_csets[ss->id]);
1607		spin_unlock_bh(&css_set_lock);
1608
1609		/* default hierarchy doesn't enable controllers by default */
1610		dst_root->subsys_mask |= 1 << ssid;
1611		if (dst_root == &cgrp_dfl_root) {
1612			static_branch_enable(cgroup_subsys_on_dfl_key[ssid]);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1613		} else {
1614			dcgrp->subtree_control |= 1 << ssid;
1615			static_branch_disable(cgroup_subsys_on_dfl_key[ssid]);
1616		}
 
 
 
1617
1618		ret = cgroup_apply_control(dcgrp);
1619		if (ret)
1620			pr_warn("partial failure to rebind %s controller (err=%d)\n",
1621				ss->name, ret);
1622
1623		if (ss->bind)
1624			ss->bind(css);
1625	} while_each_subsys_mask();
1626
1627	kernfs_activate(dcgrp->kn);
1628	return 0;
1629}
1630
1631static int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
1632			    struct kernfs_root *kf_root)
1633{
1634	int len = 0;
1635	char *buf = NULL;
1636	struct cgroup_root *kf_cgroot = cgroup_root_from_kf(kf_root);
1637	struct cgroup *ns_cgroup;
1638
1639	buf = kmalloc(PATH_MAX, GFP_KERNEL);
1640	if (!buf)
1641		return -ENOMEM;
1642
1643	spin_lock_bh(&css_set_lock);
1644	ns_cgroup = current_cgns_cgroup_from_root(kf_cgroot);
1645	len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX);
1646	spin_unlock_bh(&css_set_lock);
1647
1648	if (len >= PATH_MAX)
1649		len = -ERANGE;
1650	else if (len > 0) {
1651		seq_escape(sf, buf, " \t\n\\");
1652		len = 0;
1653	}
1654	kfree(buf);
1655	return len;
1656}
1657
1658static int cgroup_show_options(struct seq_file *seq,
1659			       struct kernfs_root *kf_root)
1660{
1661	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1662	struct cgroup_subsys *ss;
1663	int ssid;
1664
1665	if (root != &cgrp_dfl_root)
1666		for_each_subsys(ss, ssid)
1667			if (root->subsys_mask & (1 << ssid))
1668				seq_show_option(seq, ss->legacy_name, NULL);
1669	if (root->flags & CGRP_ROOT_NOPREFIX)
1670		seq_puts(seq, ",noprefix");
1671	if (root->flags & CGRP_ROOT_XATTR)
1672		seq_puts(seq, ",xattr");
1673
1674	spin_lock(&release_agent_path_lock);
1675	if (strlen(root->release_agent_path))
1676		seq_show_option(seq, "release_agent",
1677				root->release_agent_path);
1678	spin_unlock(&release_agent_path_lock);
1679
1680	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags))
1681		seq_puts(seq, ",clone_children");
1682	if (strlen(root->name))
1683		seq_show_option(seq, "name", root->name);
 
1684	return 0;
1685}
1686
1687struct cgroup_sb_opts {
1688	u16 subsys_mask;
1689	unsigned int flags;
1690	char *release_agent;
1691	bool cpuset_clone_children;
1692	char *name;
1693	/* User explicitly requested empty subsystem */
1694	bool none;
 
 
 
1695};
1696
 
 
 
 
 
 
1697static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1698{
1699	char *token, *o = data;
1700	bool all_ss = false, one_ss = false;
1701	u16 mask = U16_MAX;
1702	struct cgroup_subsys *ss;
1703	int nr_opts = 0;
1704	int i;
 
 
 
1705
1706#ifdef CONFIG_CPUSETS
1707	mask = ~((u16)1 << cpuset_cgrp_id);
1708#endif
1709
1710	memset(opts, 0, sizeof(*opts));
1711
1712	while ((token = strsep(&o, ",")) != NULL) {
1713		nr_opts++;
1714
1715		if (!*token)
1716			return -EINVAL;
1717		if (!strcmp(token, "none")) {
1718			/* Explicitly have no subsystems */
1719			opts->none = true;
1720			continue;
1721		}
1722		if (!strcmp(token, "all")) {
1723			/* Mutually exclusive option 'all' + subsystem name */
1724			if (one_ss)
1725				return -EINVAL;
1726			all_ss = true;
1727			continue;
1728		}
1729		if (!strcmp(token, "noprefix")) {
1730			opts->flags |= CGRP_ROOT_NOPREFIX;
1731			continue;
1732		}
1733		if (!strcmp(token, "clone_children")) {
1734			opts->cpuset_clone_children = true;
1735			continue;
1736		}
1737		if (!strcmp(token, "xattr")) {
1738			opts->flags |= CGRP_ROOT_XATTR;
1739			continue;
1740		}
1741		if (!strncmp(token, "release_agent=", 14)) {
1742			/* Specifying two release agents is forbidden */
1743			if (opts->release_agent)
1744				return -EINVAL;
1745			opts->release_agent =
1746				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1747			if (!opts->release_agent)
1748				return -ENOMEM;
1749			continue;
1750		}
1751		if (!strncmp(token, "name=", 5)) {
1752			const char *name = token + 5;
1753			/* Can't specify an empty name */
1754			if (!strlen(name))
1755				return -EINVAL;
1756			/* Must match [\w.-]+ */
1757			for (i = 0; i < strlen(name); i++) {
1758				char c = name[i];
1759				if (isalnum(c))
1760					continue;
1761				if ((c == '.') || (c == '-') || (c == '_'))
1762					continue;
1763				return -EINVAL;
1764			}
1765			/* Specifying two names is forbidden */
1766			if (opts->name)
1767				return -EINVAL;
1768			opts->name = kstrndup(name,
1769					      MAX_CGROUP_ROOT_NAMELEN - 1,
1770					      GFP_KERNEL);
1771			if (!opts->name)
1772				return -ENOMEM;
1773
1774			continue;
1775		}
1776
1777		for_each_subsys(ss, i) {
1778			if (strcmp(token, ss->legacy_name))
 
1779				continue;
1780			if (!cgroup_ssid_enabled(i))
1781				continue;
1782			if (cgroup_ssid_no_v1(i))
1783				continue;
1784
1785			/* Mutually exclusive option 'all' + subsystem name */
1786			if (all_ss)
1787				return -EINVAL;
1788			opts->subsys_mask |= (1 << i);
1789			one_ss = true;
1790
1791			break;
1792		}
1793		if (i == CGROUP_SUBSYS_COUNT)
1794			return -ENOENT;
1795	}
1796
1797	/*
1798	 * If the 'all' option was specified select all the subsystems,
1799	 * otherwise if 'none', 'name=' and a subsystem name options were
1800	 * not specified, let's default to 'all'
1801	 */
1802	if (all_ss || (!one_ss && !opts->none && !opts->name))
1803		for_each_subsys(ss, i)
1804			if (cgroup_ssid_enabled(i) && !cgroup_ssid_no_v1(i))
1805				opts->subsys_mask |= (1 << i);
 
 
 
 
 
 
1806
1807	/*
1808	 * We either have to specify by name or by subsystems. (So all
1809	 * empty hierarchies must have a name).
1810	 */
1811	if (!opts->subsys_mask && !opts->name)
1812		return -EINVAL;
1813
1814	/*
1815	 * Option noprefix was introduced just for backward compatibility
1816	 * with the old cpuset, so we allow noprefix only if mounting just
1817	 * the cpuset subsystem.
1818	 */
1819	if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
 
1820		return -EINVAL;
1821
 
1822	/* Can't specify "none" and some subsystems */
1823	if (opts->subsys_mask && opts->none)
1824		return -EINVAL;
1825
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1826	return 0;
1827}
1828
1829static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
1830{
1831	int ret = 0;
1832	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1833	struct cgroup_sb_opts opts;
1834	u16 added_mask, removed_mask;
1835
1836	if (root == &cgrp_dfl_root) {
1837		pr_err("remount is not allowed\n");
1838		return -EINVAL;
1839	}
 
1840
1841	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
 
 
 
 
 
 
 
 
 
1842
1843	/* See what subsystems are wanted */
1844	ret = parse_cgroupfs_options(data, &opts);
1845	if (ret)
1846		goto out_unlock;
1847
1848	if (opts.subsys_mask != root->subsys_mask || opts.release_agent)
1849		pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
1850			task_tgid_nr(current), current->comm);
1851
1852	added_mask = opts.subsys_mask & ~root->subsys_mask;
1853	removed_mask = root->subsys_mask & ~opts.subsys_mask;
1854
1855	/* Don't allow flags or name to change at remount */
1856	if ((opts.flags ^ root->flags) ||
1857	    (opts.name && strcmp(opts.name, root->name))) {
1858		pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n",
1859		       opts.flags, opts.name ?: "", root->flags, root->name);
1860		ret = -EINVAL;
 
1861		goto out_unlock;
1862	}
1863
1864	/* remounting is not allowed for populated hierarchies */
1865	if (!list_empty(&root->cgrp.self.children)) {
1866		ret = -EBUSY;
1867		goto out_unlock;
1868	}
1869
1870	ret = rebind_subsystems(root, added_mask);
1871	if (ret)
1872		goto out_unlock;
1873
1874	WARN_ON(rebind_subsystems(&cgrp_dfl_root, removed_mask));
1875
1876	if (opts.release_agent) {
1877		spin_lock(&release_agent_path_lock);
1878		strcpy(root->release_agent_path, opts.release_agent);
1879		spin_unlock(&release_agent_path_lock);
1880	}
1881 out_unlock:
1882	kfree(opts.release_agent);
1883	kfree(opts.name);
 
1884	mutex_unlock(&cgroup_mutex);
 
1885	return ret;
1886}
1887
1888/*
1889 * To reduce the fork() overhead for systems that are not actually using
1890 * their cgroups capability, we don't maintain the lists running through
1891 * each css_set to its tasks until we see the list actually used - in other
1892 * words after the first mount.
1893 */
1894static bool use_task_css_set_links __read_mostly;
1895
1896static void cgroup_enable_task_cg_lists(void)
1897{
1898	struct task_struct *p, *g;
1899
1900	spin_lock_bh(&css_set_lock);
 
 
 
 
 
 
 
1901
1902	if (use_task_css_set_links)
1903		goto out_unlock;
 
1904
1905	use_task_css_set_links = true;
 
 
 
 
 
 
 
 
1906
1907	/*
1908	 * We need tasklist_lock because RCU is not safe against
1909	 * while_each_thread(). Besides, a forking task that has passed
1910	 * cgroup_post_fork() without seeing use_task_css_set_links = 1
1911	 * is not guaranteed to have its child immediately visible in the
1912	 * tasklist if we walk through it with RCU.
1913	 */
1914	read_lock(&tasklist_lock);
1915	do_each_thread(g, p) {
1916		WARN_ON_ONCE(!list_empty(&p->cg_list) ||
1917			     task_css_set(p) != &init_css_set);
1918
1919		/*
1920		 * We should check if the process is exiting, otherwise
1921		 * it will race with cgroup_exit() in that the list
1922		 * entry won't be deleted though the process has exited.
1923		 * Do it while holding siglock so that we don't end up
1924		 * racing against cgroup_exit().
1925		 */
1926		spin_lock_irq(&p->sighand->siglock);
1927		if (!(p->flags & PF_EXITING)) {
1928			struct css_set *cset = task_css_set(p);
1929
1930			if (!css_set_populated(cset))
1931				css_set_update_populated(cset, true);
1932			list_add_tail(&p->cg_list, &cset->tasks);
1933			get_css_set(cset);
1934		}
1935		spin_unlock_irq(&p->sighand->siglock);
1936	} while_each_thread(g, p);
1937	read_unlock(&tasklist_lock);
1938out_unlock:
1939	spin_unlock_bh(&css_set_lock);
1940}
1941
1942static void init_cgroup_housekeeping(struct cgroup *cgrp)
1943{
1944	struct cgroup_subsys *ss;
1945	int ssid;
1946
1947	INIT_LIST_HEAD(&cgrp->self.sibling);
1948	INIT_LIST_HEAD(&cgrp->self.children);
1949	INIT_LIST_HEAD(&cgrp->cset_links);
1950	INIT_LIST_HEAD(&cgrp->pidlists);
1951	mutex_init(&cgrp->pidlist_mutex);
1952	cgrp->self.cgroup = cgrp;
1953	cgrp->self.flags |= CSS_ONLINE;
1954
1955	for_each_subsys(ss, ssid)
1956		INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
 
 
 
 
 
1957
1958	init_waitqueue_head(&cgrp->offline_waitq);
1959	INIT_WORK(&cgrp->release_agent_work, cgroup_release_agent);
1960}
1961
1962static void init_cgroup_root(struct cgroup_root *root,
1963			     struct cgroup_sb_opts *opts)
1964{
1965	struct cgroup *cgrp = &root->cgrp;
1966
1967	INIT_LIST_HEAD(&root->root_list);
1968	atomic_set(&root->nr_cgrps, 1);
1969	cgrp->root = root;
1970	init_cgroup_housekeeping(cgrp);
1971	idr_init(&root->cgroup_idr);
1972
 
 
 
 
 
 
 
 
 
 
 
1973	root->flags = opts->flags;
1974	if (opts->release_agent)
1975		strcpy(root->release_agent_path, opts->release_agent);
1976	if (opts->name)
1977		strcpy(root->name, opts->name);
1978	if (opts->cpuset_clone_children)
1979		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
 
1980}
1981
1982static int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
1983{
1984	LIST_HEAD(tmp_links);
1985	struct cgroup *root_cgrp = &root->cgrp;
1986	struct css_set *cset;
1987	int i, ret;
1988
1989	lockdep_assert_held(&cgroup_mutex);
 
 
 
 
 
1990
1991	ret = cgroup_idr_alloc(&root->cgroup_idr, root_cgrp, 1, 2, GFP_KERNEL);
1992	if (ret < 0)
1993		goto out;
1994	root_cgrp->id = ret;
1995	root_cgrp->ancestor_ids[0] = ret;
1996
1997	ret = percpu_ref_init(&root_cgrp->self.refcnt, css_release, 0,
1998			      GFP_KERNEL);
1999	if (ret)
2000		goto out;
2001
2002	/*
2003	 * We're accessing css_set_count without locking css_set_lock here,
2004	 * but that's OK - it can only be increased by someone holding
2005	 * cgroup_lock, and that's us.  Later rebinding may disable
2006	 * controllers on the default hierarchy and thus create new csets,
2007	 * which can't be more than the existing ones.  Allocate 2x.
2008	 */
2009	ret = allocate_cgrp_cset_links(2 * css_set_count, &tmp_links);
2010	if (ret)
2011		goto cancel_ref;
2012
2013	ret = cgroup_init_root_id(root);
2014	if (ret)
2015		goto cancel_ref;
2016
2017	root->kf_root = kernfs_create_root(&cgroup_kf_syscall_ops,
2018					   KERNFS_ROOT_CREATE_DEACTIVATED,
2019					   root_cgrp);
2020	if (IS_ERR(root->kf_root)) {
2021		ret = PTR_ERR(root->kf_root);
2022		goto exit_root_id;
2023	}
2024	root_cgrp->kn = root->kf_root->kn;
2025
2026	ret = css_populate_dir(&root_cgrp->self);
2027	if (ret)
2028		goto destroy_root;
 
2029
2030	ret = rebind_subsystems(root, ss_mask);
2031	if (ret)
2032		goto destroy_root;
2033
2034	/*
2035	 * There must be no failure case after here, since rebinding takes
2036	 * care of subsystems' refcounts, which are explicitly dropped in
2037	 * the failure exit path.
2038	 */
2039	list_add(&root->root_list, &cgroup_roots);
2040	cgroup_root_count++;
2041
2042	/*
2043	 * Link the root cgroup in this hierarchy into all the css_set
2044	 * objects.
2045	 */
2046	spin_lock_bh(&css_set_lock);
2047	hash_for_each(css_set_table, i, cset, hlist) {
2048		link_css_set(&tmp_links, cset, root_cgrp);
2049		if (css_set_populated(cset))
2050			cgroup_update_populated(root_cgrp, true);
2051	}
2052	spin_unlock_bh(&css_set_lock);
2053
2054	BUG_ON(!list_empty(&root_cgrp->self.children));
2055	BUG_ON(atomic_read(&root->nr_cgrps) != 1);
2056
2057	kernfs_activate(root_cgrp->kn);
2058	ret = 0;
2059	goto out;
2060
2061destroy_root:
2062	kernfs_destroy_root(root->kf_root);
2063	root->kf_root = NULL;
2064exit_root_id:
2065	cgroup_exit_root_id(root);
2066cancel_ref:
2067	percpu_ref_exit(&root_cgrp->self.refcnt);
2068out:
2069	free_cgrp_cset_links(&tmp_links);
2070	return ret;
2071}
2072
2073static struct dentry *cgroup_mount(struct file_system_type *fs_type,
2074			 int flags, const char *unused_dev_name,
2075			 void *data)
2076{
2077	bool is_v2 = fs_type == &cgroup2_fs_type;
2078	struct super_block *pinned_sb = NULL;
2079	struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
2080	struct cgroup_subsys *ss;
2081	struct cgroup_root *root;
2082	struct cgroup_sb_opts opts;
2083	struct dentry *dentry;
2084	int ret;
2085	int i;
2086	bool new_sb;
2087
2088	get_cgroup_ns(ns);
2089
2090	/* Check if the caller has permission to mount. */
2091	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) {
2092		put_cgroup_ns(ns);
2093		return ERR_PTR(-EPERM);
2094	}
2095
2096	/*
2097	 * The first time anyone tries to mount a cgroup, enable the list
2098	 * linking each css_set to its tasks and fix up all existing tasks.
2099	 */
2100	if (!use_task_css_set_links)
2101		cgroup_enable_task_cg_lists();
2102
2103	if (is_v2) {
2104		if (data) {
2105			pr_err("cgroup2: unknown option \"%s\"\n", (char *)data);
2106			put_cgroup_ns(ns);
2107			return ERR_PTR(-EINVAL);
2108		}
2109		cgrp_dfl_visible = true;
2110		root = &cgrp_dfl_root;
2111		cgroup_get(&root->cgrp);
2112		goto out_mount;
2113	}
2114
2115	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
2116
2117	/* First find the desired set of subsystems */
 
2118	ret = parse_cgroupfs_options(data, &opts);
 
2119	if (ret)
2120		goto out_unlock;
2121
2122	/*
2123	 * Destruction of cgroup root is asynchronous, so subsystems may
2124	 * still be dying after the previous unmount.  Let's drain the
2125	 * dying subsystems.  We just need to ensure that the ones
2126	 * unmounted previously finish dying and don't care about new ones
2127	 * starting.  Testing ref liveliness is good enough.
2128	 */
2129	for_each_subsys(ss, i) {
2130		if (!(opts.subsys_mask & (1 << i)) ||
2131		    ss->root == &cgrp_dfl_root)
2132			continue;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2133
2134		if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) {
2135			mutex_unlock(&cgroup_mutex);
2136			msleep(10);
2137			ret = restart_syscall();
2138			goto out_free;
2139		}
2140		cgroup_put(&ss->root->cgrp);
2141	}
2142
2143	for_each_root(root) {
2144		bool name_match = false;
 
 
2145
2146		if (root == &cgrp_dfl_root)
2147			continue;
 
2148
2149		/*
2150		 * If we asked for a name then it must match.  Also, if
2151		 * name matches but sybsys_mask doesn't, we should fail.
2152		 * Remember whether name matched.
2153		 */
2154		if (opts.name) {
2155			if (strcmp(opts.name, root->name))
2156				continue;
2157			name_match = true;
2158		}
2159
2160		/*
2161		 * If we asked for subsystems (or explicitly for no
2162		 * subsystems) then they must match.
 
 
 
2163		 */
2164		if ((opts.subsys_mask || opts.none) &&
2165		    (opts.subsys_mask != root->subsys_mask)) {
2166			if (!name_match)
2167				continue;
2168			ret = -EBUSY;
2169			goto out_unlock;
2170		}
2171
2172		if (root->flags ^ opts.flags)
2173			pr_warn("new mount options do not match the existing superblock, will be ignored\n");
2174
 
 
 
 
 
2175		/*
2176		 * We want to reuse @root whose lifetime is governed by its
2177		 * ->cgrp.  Let's check whether @root is alive and keep it
2178		 * that way.  As cgroup_kill_sb() can happen anytime, we
2179		 * want to block it by pinning the sb so that @root doesn't
2180		 * get killed before mount is complete.
2181		 *
2182		 * With the sb pinned, tryget_live can reliably indicate
2183		 * whether @root can be reused.  If it's being killed,
2184		 * drain it.  We can use wait_queue for the wait but this
2185		 * path is super cold.  Let's just sleep a bit and retry.
2186		 */
2187		pinned_sb = kernfs_pin_sb(root->kf_root, NULL);
2188		if (IS_ERR(pinned_sb) ||
2189		    !percpu_ref_tryget_live(&root->cgrp.self.refcnt)) {
2190			mutex_unlock(&cgroup_mutex);
2191			if (!IS_ERR_OR_NULL(pinned_sb))
2192				deactivate_super(pinned_sb);
2193			msleep(10);
2194			ret = restart_syscall();
2195			goto out_free;
2196		}
2197
2198		ret = 0;
2199		goto out_unlock;
2200	}
2201
2202	/*
2203	 * No such thing, create a new one.  name= matching without subsys
2204	 * specification is allowed for already existing hierarchies but we
2205	 * can't create new one without subsys specification.
2206	 */
2207	if (!opts.subsys_mask && !opts.none) {
2208		ret = -EINVAL;
2209		goto out_unlock;
2210	}
2211
2212	/*
2213	 * We know this subsystem has not yet been bound.  Users in a non-init
2214	 * user namespace may only mount hierarchies with no bound subsystems,
2215	 * i.e. 'none,name=user1'
2216	 */
2217	if (!opts.none && !capable(CAP_SYS_ADMIN)) {
2218		ret = -EPERM;
2219		goto out_unlock;
2220	}
2221
2222	root = kzalloc(sizeof(*root), GFP_KERNEL);
2223	if (!root) {
2224		ret = -ENOMEM;
2225		goto out_unlock;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2226	}
2227
2228	init_cgroup_root(root, &opts);
2229
2230	ret = cgroup_setup_root(root, opts.subsys_mask);
2231	if (ret)
2232		cgroup_free_root(root);
2233
2234out_unlock:
 
2235	mutex_unlock(&cgroup_mutex);
2236out_free:
 
 
 
 
 
2237	kfree(opts.release_agent);
2238	kfree(opts.name);
 
 
2239
2240	if (ret) {
2241		put_cgroup_ns(ns);
2242		return ERR_PTR(ret);
2243	}
2244out_mount:
2245	dentry = kernfs_mount(fs_type, flags, root->kf_root,
2246			      is_v2 ? CGROUP2_SUPER_MAGIC : CGROUP_SUPER_MAGIC,
2247			      &new_sb);
2248
2249	/*
2250	 * In non-init cgroup namespace, instead of root cgroup's
2251	 * dentry, we return the dentry corresponding to the
2252	 * cgroupns->root_cgrp.
2253	 */
2254	if (!IS_ERR(dentry) && ns != &init_cgroup_ns) {
2255		struct dentry *nsdentry;
2256		struct cgroup *cgrp;
2257
2258		mutex_lock(&cgroup_mutex);
2259		spin_lock_bh(&css_set_lock);
2260
2261		cgrp = cset_cgroup_from_root(ns->root_cset, root);
2262
2263		spin_unlock_bh(&css_set_lock);
2264		mutex_unlock(&cgroup_mutex);
 
2265
2266		nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb);
2267		dput(dentry);
2268		dentry = nsdentry;
2269	}
2270
2271	if (IS_ERR(dentry) || !new_sb)
2272		cgroup_put(&root->cgrp);
 
 
2273
2274	/*
2275	 * If @pinned_sb, we're reusing an existing root and holding an
2276	 * extra ref on its sb.  Mount is complete.  Put the extra ref.
2277	 */
2278	if (pinned_sb) {
2279		WARN_ON(new_sb);
2280		deactivate_super(pinned_sb);
2281	}
2282
2283	put_cgroup_ns(ns);
2284	return dentry;
2285}
 
 
 
 
2286
2287static void cgroup_kill_sb(struct super_block *sb)
2288{
2289	struct kernfs_root *kf_root = kernfs_root_from_sb(sb);
2290	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
2291
2292	/*
2293	 * If @root doesn't have any mounts or children, start killing it.
2294	 * This prevents new mounts by disabling percpu_ref_tryget_live().
2295	 * cgroup_mount() may wait for @root's release.
2296	 *
2297	 * And don't kill the default root.
2298	 */
2299	if (!list_empty(&root->cgrp.self.children) ||
2300	    root == &cgrp_dfl_root)
2301		cgroup_put(&root->cgrp);
2302	else
2303		percpu_ref_kill(&root->cgrp.self.refcnt);
2304
2305	kernfs_kill_sb(sb);
 
2306}
2307
2308static struct file_system_type cgroup_fs_type = {
2309	.name = "cgroup",
2310	.mount = cgroup_mount,
2311	.kill_sb = cgroup_kill_sb,
2312	.fs_flags = FS_USERNS_MOUNT,
2313};
2314
2315static struct file_system_type cgroup2_fs_type = {
2316	.name = "cgroup2",
2317	.mount = cgroup_mount,
2318	.kill_sb = cgroup_kill_sb,
2319	.fs_flags = FS_USERNS_MOUNT,
2320};
2321
2322static char *cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
2323				   struct cgroup_namespace *ns)
2324{
2325	struct cgroup *root = cset_cgroup_from_root(ns->root_cset, cgrp->root);
2326	int ret;
2327
2328	ret = kernfs_path_from_node(cgrp->kn, root->kn, buf, buflen);
2329	if (ret < 0 || ret >= buflen)
2330		return NULL;
2331	return buf;
2332}
2333
2334char *cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
2335		     struct cgroup_namespace *ns)
2336{
2337	char *ret;
2338
2339	mutex_lock(&cgroup_mutex);
2340	spin_lock_bh(&css_set_lock);
2341
2342	ret = cgroup_path_ns_locked(cgrp, buf, buflen, ns);
2343
2344	spin_unlock_bh(&css_set_lock);
2345	mutex_unlock(&cgroup_mutex);
2346
2347	return ret;
2348}
2349EXPORT_SYMBOL_GPL(cgroup_path_ns);
2350
2351/**
2352 * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
2353 * @task: target task
2354 * @buf: the buffer to write the path into
2355 * @buflen: the length of the buffer
2356 *
2357 * Determine @task's cgroup on the first (the one with the lowest non-zero
2358 * hierarchy_id) cgroup hierarchy and copy its path into @buf.  This
2359 * function grabs cgroup_mutex and shouldn't be used inside locks used by
2360 * cgroup controller callbacks.
2361 *
2362 * Return value is the same as kernfs_path().
2363 */
2364char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
2365{
2366	struct cgroup_root *root;
2367	struct cgroup *cgrp;
2368	int hierarchy_id = 1;
2369	char *path = NULL;
2370
2371	mutex_lock(&cgroup_mutex);
2372	spin_lock_bh(&css_set_lock);
2373
2374	root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
2375
2376	if (root) {
2377		cgrp = task_cgroup_from_root(task, root);
2378		path = cgroup_path_ns_locked(cgrp, buf, buflen, &init_cgroup_ns);
2379	} else {
2380		/* if no hierarchy exists, everyone is in "/" */
2381		if (strlcpy(buf, "/", buflen) < buflen)
2382			path = buf;
2383	}
2384
2385	spin_unlock_bh(&css_set_lock);
2386	mutex_unlock(&cgroup_mutex);
2387	return path;
2388}
2389EXPORT_SYMBOL_GPL(task_cgroup_path);
2390
2391/* used to track tasks and other necessary states during migration */
2392struct cgroup_taskset {
2393	/* the src and dst cset list running through cset->mg_node */
2394	struct list_head	src_csets;
2395	struct list_head	dst_csets;
2396
2397	/* the subsys currently being processed */
2398	int			ssid;
2399
2400	/*
2401	 * Fields for cgroup_taskset_*() iteration.
2402	 *
2403	 * Before migration is committed, the target migration tasks are on
2404	 * ->mg_tasks of the csets on ->src_csets.  After, on ->mg_tasks of
2405	 * the csets on ->dst_csets.  ->csets point to either ->src_csets
2406	 * or ->dst_csets depending on whether migration is committed.
2407	 *
2408	 * ->cur_csets and ->cur_task point to the current task position
2409	 * during iteration.
2410	 */
2411	struct list_head	*csets;
2412	struct css_set		*cur_cset;
2413	struct task_struct	*cur_task;
2414};
2415
2416#define CGROUP_TASKSET_INIT(tset)	(struct cgroup_taskset){	\
2417	.src_csets		= LIST_HEAD_INIT(tset.src_csets),	\
2418	.dst_csets		= LIST_HEAD_INIT(tset.dst_csets),	\
2419	.csets			= &tset.src_csets,			\
 
 
 
 
 
 
2420}
 
2421
2422/**
2423 * cgroup_taskset_add - try to add a migration target task to a taskset
2424 * @task: target task
2425 * @tset: target taskset
2426 *
2427 * Add @task, which is a migration target, to @tset.  This function becomes
2428 * noop if @task doesn't need to be migrated.  @task's css_set should have
2429 * been added as a migration source and @task->cg_list will be moved from
2430 * the css_set's tasks list to mg_tasks one.
2431 */
2432static void cgroup_taskset_add(struct task_struct *task,
2433			       struct cgroup_taskset *tset)
2434{
2435	struct css_set *cset;
2436
2437	lockdep_assert_held(&css_set_lock);
2438
2439	/* @task either already exited or can't exit until the end */
2440	if (task->flags & PF_EXITING)
2441		return;
2442
2443	/* leave @task alone if post_fork() hasn't linked it yet */
2444	if (list_empty(&task->cg_list))
2445		return;
2446
2447	cset = task_css_set(task);
2448	if (!cset->mg_src_cgrp)
2449		return;
2450
2451	list_move_tail(&task->cg_list, &cset->mg_tasks);
2452	if (list_empty(&cset->mg_node))
2453		list_add_tail(&cset->mg_node, &tset->src_csets);
2454	if (list_empty(&cset->mg_dst_cset->mg_node))
2455		list_move_tail(&cset->mg_dst_cset->mg_node,
2456			       &tset->dst_csets);
2457}
2458
2459/**
2460 * cgroup_taskset_first - reset taskset and return the first task
2461 * @tset: taskset of interest
2462 * @dst_cssp: output variable for the destination css
2463 *
2464 * @tset iteration is initialized and the first task is returned.
2465 */
2466struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset,
2467					 struct cgroup_subsys_state **dst_cssp)
2468{
2469	tset->cur_cset = list_first_entry(tset->csets, struct css_set, mg_node);
2470	tset->cur_task = NULL;
2471
2472	return cgroup_taskset_next(tset, dst_cssp);
 
 
 
2473}
 
2474
2475/**
2476 * cgroup_taskset_next - iterate to the next task in taskset
2477 * @tset: taskset of interest
2478 * @dst_cssp: output variable for the destination css
2479 *
2480 * Return the next task in @tset.  Iteration must have been initialized
2481 * with cgroup_taskset_first().
2482 */
2483struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
2484					struct cgroup_subsys_state **dst_cssp)
2485{
2486	struct css_set *cset = tset->cur_cset;
2487	struct task_struct *task = tset->cur_task;
2488
2489	while (&cset->mg_node != tset->csets) {
2490		if (!task)
2491			task = list_first_entry(&cset->mg_tasks,
2492						struct task_struct, cg_list);
2493		else
2494			task = list_next_entry(task, cg_list);
2495
2496		if (&task->cg_list != &cset->mg_tasks) {
2497			tset->cur_cset = cset;
2498			tset->cur_task = task;
2499
2500			/*
2501			 * This function may be called both before and
2502			 * after cgroup_taskset_migrate().  The two cases
2503			 * can be distinguished by looking at whether @cset
2504			 * has its ->mg_dst_cset set.
2505			 */
2506			if (cset->mg_dst_cset)
2507				*dst_cssp = cset->mg_dst_cset->subsys[tset->ssid];
2508			else
2509				*dst_cssp = cset->subsys[tset->ssid];
2510
2511			return task;
2512		}
2513
2514		cset = list_next_entry(cset, mg_node);
2515		task = NULL;
2516	}
 
 
2517
2518	return NULL;
 
 
 
 
 
 
 
 
 
 
2519}
 
2520
2521/**
2522 * cgroup_taskset_migrate - migrate a taskset
2523 * @tset: taget taskset
2524 * @root: cgroup root the migration is taking place on
2525 *
2526 * Migrate tasks in @tset as setup by migration preparation functions.
2527 * This function fails iff one of the ->can_attach callbacks fails and
2528 * guarantees that either all or none of the tasks in @tset are migrated.
2529 * @tset is consumed regardless of success.
2530 */
2531static int cgroup_taskset_migrate(struct cgroup_taskset *tset,
2532				  struct cgroup_root *root)
2533{
2534	struct cgroup_subsys *ss;
2535	struct task_struct *task, *tmp_task;
2536	struct css_set *cset, *tmp_cset;
2537	int ssid, failed_ssid, ret;
2538
2539	/* methods shouldn't be called if no task is actually migrating */
2540	if (list_empty(&tset->src_csets))
2541		return 0;
2542
2543	/* check that we can legitimately attach to the cgroup */
2544	do_each_subsys_mask(ss, ssid, root->subsys_mask) {
2545		if (ss->can_attach) {
2546			tset->ssid = ssid;
2547			ret = ss->can_attach(tset);
2548			if (ret) {
2549				failed_ssid = ssid;
2550				goto out_cancel_attach;
2551			}
2552		}
2553	} while_each_subsys_mask();
2554
2555	/*
2556	 * Now that we're guaranteed success, proceed to move all tasks to
2557	 * the new cgroup.  There are no failure cases after here, so this
2558	 * is the commit point.
2559	 */
2560	spin_lock_bh(&css_set_lock);
2561	list_for_each_entry(cset, &tset->src_csets, mg_node) {
2562		list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list) {
2563			struct css_set *from_cset = task_css_set(task);
2564			struct css_set *to_cset = cset->mg_dst_cset;
2565
2566			get_css_set(to_cset);
2567			css_set_move_task(task, from_cset, to_cset, true);
2568			put_css_set_locked(from_cset);
2569		}
2570	}
2571	spin_unlock_bh(&css_set_lock);
 
 
 
2572
2573	/*
2574	 * Migration is committed, all target tasks are now on dst_csets.
2575	 * Nothing is sensitive to fork() after this point.  Notify
2576	 * controllers that migration is complete.
2577	 */
2578	tset->csets = &tset->dst_csets;
2579
2580	do_each_subsys_mask(ss, ssid, root->subsys_mask) {
2581		if (ss->attach) {
2582			tset->ssid = ssid;
2583			ss->attach(tset);
2584		}
2585	} while_each_subsys_mask();
2586
2587	ret = 0;
2588	goto out_release_tset;
2589
2590out_cancel_attach:
2591	do_each_subsys_mask(ss, ssid, root->subsys_mask) {
2592		if (ssid == failed_ssid)
2593			break;
2594		if (ss->cancel_attach) {
2595			tset->ssid = ssid;
2596			ss->cancel_attach(tset);
2597		}
2598	} while_each_subsys_mask();
2599out_release_tset:
2600	spin_lock_bh(&css_set_lock);
2601	list_splice_init(&tset->dst_csets, &tset->src_csets);
2602	list_for_each_entry_safe(cset, tmp_cset, &tset->src_csets, mg_node) {
2603		list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
2604		list_del_init(&cset->mg_node);
2605	}
2606	spin_unlock_bh(&css_set_lock);
2607	return ret;
2608}
2609
2610/**
2611 * cgroup_may_migrate_to - verify whether a cgroup can be migration destination
2612 * @dst_cgrp: destination cgroup to test
 
2613 *
2614 * On the default hierarchy, except for the root, subtree_control must be
2615 * zero for migration destination cgroups with tasks so that child cgroups
2616 * don't compete against tasks.
2617 */
2618static bool cgroup_may_migrate_to(struct cgroup *dst_cgrp)
2619{
2620	return !cgroup_on_dfl(dst_cgrp) || !cgroup_parent(dst_cgrp) ||
2621		!dst_cgrp->subtree_control;
2622}
 
 
 
 
 
 
 
 
 
 
 
 
2623
2624/**
2625 * cgroup_migrate_finish - cleanup after attach
2626 * @preloaded_csets: list of preloaded css_sets
2627 *
2628 * Undo cgroup_migrate_add_src() and cgroup_migrate_prepare_dst().  See
2629 * those functions for details.
2630 */
2631static void cgroup_migrate_finish(struct list_head *preloaded_csets)
2632{
2633	struct css_set *cset, *tmp_cset;
2634
2635	lockdep_assert_held(&cgroup_mutex);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2636
2637	spin_lock_bh(&css_set_lock);
2638	list_for_each_entry_safe(cset, tmp_cset, preloaded_csets, mg_preload_node) {
2639		cset->mg_src_cgrp = NULL;
2640		cset->mg_dst_cgrp = NULL;
2641		cset->mg_dst_cset = NULL;
2642		list_del_init(&cset->mg_preload_node);
2643		put_css_set_locked(cset);
2644	}
2645	spin_unlock_bh(&css_set_lock);
2646}
2647
2648/**
2649 * cgroup_migrate_add_src - add a migration source css_set
2650 * @src_cset: the source css_set to add
2651 * @dst_cgrp: the destination cgroup
2652 * @preloaded_csets: list of preloaded css_sets
2653 *
2654 * Tasks belonging to @src_cset are about to be migrated to @dst_cgrp.  Pin
2655 * @src_cset and add it to @preloaded_csets, which should later be cleaned
2656 * up by cgroup_migrate_finish().
2657 *
2658 * This function may be called without holding cgroup_threadgroup_rwsem
2659 * even if the target is a process.  Threads may be created and destroyed
2660 * but as long as cgroup_mutex is not dropped, no new css_set can be put
2661 * into play and the preloaded css_sets are guaranteed to cover all
2662 * migrations.
2663 */
2664static void cgroup_migrate_add_src(struct css_set *src_cset,
2665				   struct cgroup *dst_cgrp,
2666				   struct list_head *preloaded_csets)
2667{
2668	struct cgroup *src_cgrp;
2669
2670	lockdep_assert_held(&cgroup_mutex);
2671	lockdep_assert_held(&css_set_lock);
 
 
 
 
2672
2673	/*
2674	 * If ->dead, @src_set is associated with one or more dead cgroups
2675	 * and doesn't contain any migratable tasks.  Ignore it early so
2676	 * that the rest of migration path doesn't get confused by it.
2677	 */
2678	if (src_cset->dead)
2679		return;
2680
2681	src_cgrp = cset_cgroup_from_root(src_cset, dst_cgrp->root);
2682
2683	if (!list_empty(&src_cset->mg_preload_node))
2684		return;
2685
2686	WARN_ON(src_cset->mg_src_cgrp);
2687	WARN_ON(src_cset->mg_dst_cgrp);
2688	WARN_ON(!list_empty(&src_cset->mg_tasks));
2689	WARN_ON(!list_empty(&src_cset->mg_node));
2690
2691	src_cset->mg_src_cgrp = src_cgrp;
2692	src_cset->mg_dst_cgrp = dst_cgrp;
2693	get_css_set(src_cset);
2694	list_add(&src_cset->mg_preload_node, preloaded_csets);
2695}
2696
2697/**
2698 * cgroup_migrate_prepare_dst - prepare destination css_sets for migration
2699 * @preloaded_csets: list of preloaded source css_sets
2700 *
2701 * Tasks are about to be moved and all the source css_sets have been
2702 * preloaded to @preloaded_csets.  This function looks up and pins all
2703 * destination css_sets, links each to its source, and append them to
2704 * @preloaded_csets.
2705 *
2706 * This function must be called after cgroup_migrate_add_src() has been
2707 * called on each migration source css_set.  After migration is performed
2708 * using cgroup_migrate(), cgroup_migrate_finish() must be called on
2709 * @preloaded_csets.
2710 */
2711static int cgroup_migrate_prepare_dst(struct list_head *preloaded_csets)
2712{
2713	LIST_HEAD(csets);
2714	struct css_set *src_cset, *tmp_cset;
2715
2716	lockdep_assert_held(&cgroup_mutex);
2717
2718	/* look up the dst cset for each src cset and link it to src */
2719	list_for_each_entry_safe(src_cset, tmp_cset, preloaded_csets, mg_preload_node) {
2720		struct css_set *dst_cset;
2721
2722		dst_cset = find_css_set(src_cset, src_cset->mg_dst_cgrp);
2723		if (!dst_cset)
2724			goto err;
2725
2726		WARN_ON_ONCE(src_cset->mg_dst_cset || dst_cset->mg_dst_cset);
2727
2728		/*
2729		 * If src cset equals dst, it's noop.  Drop the src.
2730		 * cgroup_migrate() will skip the cset too.  Note that we
2731		 * can't handle src == dst as some nodes are used by both.
2732		 */
2733		if (src_cset == dst_cset) {
2734			src_cset->mg_src_cgrp = NULL;
2735			src_cset->mg_dst_cgrp = NULL;
2736			list_del_init(&src_cset->mg_preload_node);
2737			put_css_set(src_cset);
2738			put_css_set(dst_cset);
2739			continue;
2740		}
2741
2742		src_cset->mg_dst_cset = dst_cset;
 
 
2743
2744		if (list_empty(&dst_cset->mg_preload_node))
2745			list_add(&dst_cset->mg_preload_node, &csets);
2746		else
2747			put_css_set(dst_cset);
2748	}
 
2749
2750	list_splice_tail(&csets, preloaded_csets);
2751	return 0;
2752err:
2753	cgroup_migrate_finish(&csets);
2754	return -ENOMEM;
2755}
 
2756
2757/**
2758 * cgroup_migrate - migrate a process or task to a cgroup
2759 * @leader: the leader of the process or the task to migrate
2760 * @threadgroup: whether @leader points to the whole process or a single task
2761 * @root: cgroup root migration is taking place on
2762 *
2763 * Migrate a process or task denoted by @leader.  If migrating a process,
2764 * the caller must be holding cgroup_threadgroup_rwsem.  The caller is also
2765 * responsible for invoking cgroup_migrate_add_src() and
2766 * cgroup_migrate_prepare_dst() on the targets before invoking this
2767 * function and following up with cgroup_migrate_finish().
2768 *
2769 * As long as a controller's ->can_attach() doesn't fail, this function is
2770 * guaranteed to succeed.  This means that, excluding ->can_attach()
2771 * failure, when migrating multiple targets, the success or failure can be
2772 * decided for all targets by invoking group_migrate_prepare_dst() before
2773 * actually starting migrating.
2774 */
2775static int cgroup_migrate(struct task_struct *leader, bool threadgroup,
2776			  struct cgroup_root *root)
2777{
2778	struct cgroup_taskset tset = CGROUP_TASKSET_INIT(tset);
2779	struct task_struct *task;
 
 
 
 
 
 
 
 
 
 
 
 
 
2780
 
 
2781	/*
2782	 * Prevent freeing of tasks while we take a snapshot. Tasks that are
2783	 * already PF_EXITING could be freed from underneath us unless we
2784	 * take an rcu_read_lock.
2785	 */
2786	spin_lock_bh(&css_set_lock);
2787	rcu_read_lock();
2788	task = leader;
2789	do {
2790		cgroup_taskset_add(task, &tset);
2791		if (!threadgroup)
2792			break;
2793	} while_each_thread(leader, task);
2794	rcu_read_unlock();
2795	spin_unlock_bh(&css_set_lock);
2796
2797	return cgroup_taskset_migrate(&tset, root);
2798}
2799
2800/**
2801 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
2802 * @dst_cgrp: the cgroup to attach to
2803 * @leader: the task or the leader of the threadgroup to be attached
2804 * @threadgroup: attach the whole threadgroup?
2805 *
2806 * Call holding cgroup_mutex and cgroup_threadgroup_rwsem.
2807 */
2808static int cgroup_attach_task(struct cgroup *dst_cgrp,
2809			      struct task_struct *leader, bool threadgroup)
2810{
2811	LIST_HEAD(preloaded_csets);
2812	struct task_struct *task;
2813	int ret;
2814
2815	if (!cgroup_may_migrate_to(dst_cgrp))
2816		return -EBUSY;
2817
2818	/* look up all src csets */
2819	spin_lock_bh(&css_set_lock);
2820	rcu_read_lock();
2821	task = leader;
2822	do {
2823		cgroup_migrate_add_src(task_css_set(task), dst_cgrp,
2824				       &preloaded_csets);
2825		if (!threadgroup)
2826			break;
2827	} while_each_thread(leader, task);
 
 
 
 
 
2828	rcu_read_unlock();
2829	spin_unlock_bh(&css_set_lock);
2830
2831	/* prepare dst csets and commit */
2832	ret = cgroup_migrate_prepare_dst(&preloaded_csets);
2833	if (!ret)
2834		ret = cgroup_migrate(leader, threadgroup, dst_cgrp->root);
2835
2836	cgroup_migrate_finish(&preloaded_csets);
2837	return ret;
2838}
2839
2840static int cgroup_procs_write_permission(struct task_struct *task,
2841					 struct cgroup *dst_cgrp,
2842					 struct kernfs_open_file *of)
2843{
2844	const struct cred *cred = current_cred();
2845	const struct cred *tcred = get_task_cred(task);
2846	int ret = 0;
2847
2848	/*
2849	 * even if we're attaching all tasks in the thread group, we only
2850	 * need to check permissions on one of them.
2851	 */
2852	if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
2853	    !uid_eq(cred->euid, tcred->uid) &&
2854	    !uid_eq(cred->euid, tcred->suid))
2855		ret = -EACCES;
 
 
 
 
 
2856
2857	if (!ret && cgroup_on_dfl(dst_cgrp)) {
2858		struct super_block *sb = of->file->f_path.dentry->d_sb;
2859		struct cgroup *cgrp;
2860		struct inode *inode;
 
 
 
 
 
 
 
 
2861
2862		spin_lock_bh(&css_set_lock);
2863		cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
2864		spin_unlock_bh(&css_set_lock);
 
 
 
 
 
 
 
2865
2866		while (!cgroup_is_descendant(dst_cgrp, cgrp))
2867			cgrp = cgroup_parent(cgrp);
 
 
 
 
 
2868
2869		ret = -ENOMEM;
2870		inode = kernfs_get_inode(sb, cgrp->procs_file.kn);
2871		if (inode) {
2872			ret = inode_permission(inode, MAY_WRITE);
2873			iput(inode);
 
 
 
 
 
 
 
 
2874		}
2875	}
2876
2877	put_cred(tcred);
2878	return ret;
 
 
 
 
 
 
 
 
 
2879}
2880
2881/*
2882 * Find the task_struct of the task to attach by vpid and pass it along to the
2883 * function to attach either it or all tasks in its threadgroup. Will lock
2884 * cgroup_mutex and threadgroup.
2885 */
2886static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,
2887				    size_t nbytes, loff_t off, bool threadgroup)
2888{
2889	struct task_struct *tsk;
2890	struct cgroup_subsys *ss;
2891	struct cgroup *cgrp;
2892	pid_t pid;
2893	int ssid, ret;
2894
2895	if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
2896		return -EINVAL;
2897
2898	cgrp = cgroup_kn_lock_live(of->kn, false);
2899	if (!cgrp)
2900		return -ENODEV;
2901
2902	percpu_down_write(&cgroup_threadgroup_rwsem);
2903	rcu_read_lock();
2904	if (pid) {
2905		tsk = find_task_by_vpid(pid);
2906		if (!tsk) {
2907			ret = -ESRCH;
2908			goto out_unlock_rcu;
 
2909		}
2910	} else {
 
 
 
 
 
 
 
 
 
 
 
 
2911		tsk = current;
2912	}
2913
2914	if (threadgroup)
2915		tsk = tsk->group_leader;
2916
2917	/*
2918	 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2919	 * trapped in a cpuset, or RT worker may be born in a cgroup
2920	 * with no rt_runtime allocated.  Just say no.
2921	 */
2922	if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) {
2923		ret = -EINVAL;
2924		goto out_unlock_rcu;
 
2925	}
2926
2927	get_task_struct(tsk);
2928	rcu_read_unlock();
2929
2930	ret = cgroup_procs_write_permission(tsk, cgrp, of);
2931	if (!ret)
2932		ret = cgroup_attach_task(cgrp, tsk, threadgroup);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2933
2934	put_task_struct(tsk);
2935	goto out_unlock_threadgroup;
2936
2937out_unlock_rcu:
2938	rcu_read_unlock();
2939out_unlock_threadgroup:
2940	percpu_up_write(&cgroup_threadgroup_rwsem);
2941	for_each_subsys(ss, ssid)
2942		if (ss->post_attach)
2943			ss->post_attach();
2944	cgroup_kn_unlock(of->kn);
2945	return ret ?: nbytes;
2946}
2947
2948/**
2949 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
2950 * @from: attach to all cgroups of a given task
2951 * @tsk: the task to be attached
2952 */
2953int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
2954{
2955	struct cgroup_root *root;
2956	int retval = 0;
2957
2958	mutex_lock(&cgroup_mutex);
2959	for_each_root(root) {
2960		struct cgroup *from_cgrp;
2961
2962		if (root == &cgrp_dfl_root)
2963			continue;
2964
2965		spin_lock_bh(&css_set_lock);
2966		from_cgrp = task_cgroup_from_root(from, root);
2967		spin_unlock_bh(&css_set_lock);
2968
2969		retval = cgroup_attach_task(from_cgrp, tsk, false);
2970		if (retval)
2971			break;
2972	}
2973	mutex_unlock(&cgroup_mutex);
2974
2975	return retval;
2976}
2977EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
2978
2979static ssize_t cgroup_tasks_write(struct kernfs_open_file *of,
2980				  char *buf, size_t nbytes, loff_t off)
2981{
2982	return __cgroup_procs_write(of, buf, nbytes, off, false);
2983}
2984
2985static ssize_t cgroup_procs_write(struct kernfs_open_file *of,
2986				  char *buf, size_t nbytes, loff_t off)
 
 
 
 
 
 
2987{
2988	return __cgroup_procs_write(of, buf, nbytes, off, true);
 
 
 
 
 
2989}
 
2990
2991static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
2992					  char *buf, size_t nbytes, loff_t off)
2993{
2994	struct cgroup *cgrp;
2995
2996	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
2997
2998	cgrp = cgroup_kn_lock_live(of->kn, false);
2999	if (!cgrp)
3000		return -ENODEV;
3001	spin_lock(&release_agent_path_lock);
3002	strlcpy(cgrp->root->release_agent_path, strstrip(buf),
3003		sizeof(cgrp->root->release_agent_path));
3004	spin_unlock(&release_agent_path_lock);
3005	cgroup_kn_unlock(of->kn);
3006	return nbytes;
3007}
3008
3009static int cgroup_release_agent_show(struct seq_file *seq, void *v)
 
3010{
3011	struct cgroup *cgrp = seq_css(seq)->cgroup;
3012
3013	spin_lock(&release_agent_path_lock);
3014	seq_puts(seq, cgrp->root->release_agent_path);
3015	spin_unlock(&release_agent_path_lock);
3016	seq_putc(seq, '\n');
 
3017	return 0;
3018}
3019
3020static int cgroup_sane_behavior_show(struct seq_file *seq, void *v)
3021{
3022	seq_puts(seq, "0\n");
3023	return 0;
3024}
3025
3026static void cgroup_print_ss_mask(struct seq_file *seq, u16 ss_mask)
 
 
 
3027{
3028	struct cgroup_subsys *ss;
3029	bool printed = false;
3030	int ssid;
3031
3032	do_each_subsys_mask(ss, ssid, ss_mask) {
3033		if (printed)
3034			seq_putc(seq, ' ');
3035		seq_printf(seq, "%s", ss->name);
3036		printed = true;
3037	} while_each_subsys_mask();
3038	if (printed)
3039		seq_putc(seq, '\n');
3040}
3041
3042/* show controllers which are enabled from the parent */
3043static int cgroup_controllers_show(struct seq_file *seq, void *v)
3044{
3045	struct cgroup *cgrp = seq_css(seq)->cgroup;
3046
3047	cgroup_print_ss_mask(seq, cgroup_control(cgrp));
3048	return 0;
3049}
3050
3051/* show controllers which are enabled for a given cgroup's children */
3052static int cgroup_subtree_control_show(struct seq_file *seq, void *v)
3053{
3054	struct cgroup *cgrp = seq_css(seq)->cgroup;
3055
3056	cgroup_print_ss_mask(seq, cgrp->subtree_control);
3057	return 0;
3058}
3059
3060/**
3061 * cgroup_update_dfl_csses - update css assoc of a subtree in default hierarchy
3062 * @cgrp: root of the subtree to update csses for
3063 *
3064 * @cgrp's control masks have changed and its subtree's css associations
3065 * need to be updated accordingly.  This function looks up all css_sets
3066 * which are attached to the subtree, creates the matching updated css_sets
3067 * and migrates the tasks to the new ones.
3068 */
3069static int cgroup_update_dfl_csses(struct cgroup *cgrp)
3070{
3071	LIST_HEAD(preloaded_csets);
3072	struct cgroup_taskset tset = CGROUP_TASKSET_INIT(tset);
3073	struct cgroup_subsys_state *d_css;
3074	struct cgroup *dsct;
3075	struct css_set *src_cset;
3076	int ret;
3077
3078	lockdep_assert_held(&cgroup_mutex);
3079
3080	percpu_down_write(&cgroup_threadgroup_rwsem);
3081
3082	/* look up all csses currently attached to @cgrp's subtree */
3083	spin_lock_bh(&css_set_lock);
3084	cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3085		struct cgrp_cset_link *link;
 
 
3086
3087		list_for_each_entry(link, &dsct->cset_links, cset_link)
3088			cgroup_migrate_add_src(link->cset, dsct,
3089					       &preloaded_csets);
 
 
 
 
 
 
 
 
3090	}
3091	spin_unlock_bh(&css_set_lock);
3092
3093	/* NULL dst indicates self on default hierarchy */
3094	ret = cgroup_migrate_prepare_dst(&preloaded_csets);
3095	if (ret)
3096		goto out_finish;
3097
3098	spin_lock_bh(&css_set_lock);
3099	list_for_each_entry(src_cset, &preloaded_csets, mg_preload_node) {
3100		struct task_struct *task, *ntask;
3101
3102		/* src_csets precede dst_csets, break on the first dst_cset */
3103		if (!src_cset->mg_src_cgrp)
3104			break;
3105
3106		/* all tasks in src_csets need to be migrated */
3107		list_for_each_entry_safe(task, ntask, &src_cset->tasks, cg_list)
3108			cgroup_taskset_add(task, &tset);
3109	}
3110	spin_unlock_bh(&css_set_lock);
3111
3112	ret = cgroup_taskset_migrate(&tset, cgrp->root);
3113out_finish:
3114	cgroup_migrate_finish(&preloaded_csets);
3115	percpu_up_write(&cgroup_threadgroup_rwsem);
3116	return ret;
3117}
3118
3119/**
3120 * cgroup_lock_and_drain_offline - lock cgroup_mutex and drain offlined csses
3121 * @cgrp: root of the target subtree
3122 *
3123 * Because css offlining is asynchronous, userland may try to re-enable a
3124 * controller while the previous css is still around.  This function grabs
3125 * cgroup_mutex and drains the previous css instances of @cgrp's subtree.
3126 */
3127static void cgroup_lock_and_drain_offline(struct cgroup *cgrp)
3128	__acquires(&cgroup_mutex)
3129{
3130	struct cgroup *dsct;
3131	struct cgroup_subsys_state *d_css;
3132	struct cgroup_subsys *ss;
3133	int ssid;
3134
3135restart:
3136	mutex_lock(&cgroup_mutex);
3137
3138	cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3139		for_each_subsys(ss, ssid) {
3140			struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3141			DEFINE_WAIT(wait);
3142
3143			if (!css || !percpu_ref_is_dying(&css->refcnt))
3144				continue;
3145
3146			cgroup_get(dsct);
3147			prepare_to_wait(&dsct->offline_waitq, &wait,
3148					TASK_UNINTERRUPTIBLE);
3149
3150			mutex_unlock(&cgroup_mutex);
3151			schedule();
3152			finish_wait(&dsct->offline_waitq, &wait);
3153
3154			cgroup_put(dsct);
3155			goto restart;
3156		}
 
 
 
 
 
 
3157	}
3158}
3159
3160/**
3161 * cgroup_save_control - save control masks of a subtree
3162 * @cgrp: root of the target subtree
3163 *
3164 * Save ->subtree_control and ->subtree_ss_mask to the respective old_
3165 * prefixed fields for @cgrp's subtree including @cgrp itself.
3166 */
3167static void cgroup_save_control(struct cgroup *cgrp)
3168{
3169	struct cgroup *dsct;
3170	struct cgroup_subsys_state *d_css;
3171
3172	cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3173		dsct->old_subtree_control = dsct->subtree_control;
3174		dsct->old_subtree_ss_mask = dsct->subtree_ss_mask;
3175	}
3176}
3177
3178/**
3179 * cgroup_propagate_control - refresh control masks of a subtree
3180 * @cgrp: root of the target subtree
3181 *
3182 * For @cgrp and its subtree, ensure ->subtree_ss_mask matches
3183 * ->subtree_control and propagate controller availability through the
3184 * subtree so that descendants don't have unavailable controllers enabled.
3185 */
3186static void cgroup_propagate_control(struct cgroup *cgrp)
3187{
3188	struct cgroup *dsct;
3189	struct cgroup_subsys_state *d_css;
3190
3191	cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3192		dsct->subtree_control &= cgroup_control(dsct);
3193		dsct->subtree_ss_mask =
3194			cgroup_calc_subtree_ss_mask(dsct->subtree_control,
3195						    cgroup_ss_mask(dsct));
3196	}
3197}
3198
3199/**
3200 * cgroup_restore_control - restore control masks of a subtree
3201 * @cgrp: root of the target subtree
3202 *
3203 * Restore ->subtree_control and ->subtree_ss_mask from the respective old_
3204 * prefixed fields for @cgrp's subtree including @cgrp itself.
3205 */
3206static void cgroup_restore_control(struct cgroup *cgrp)
3207{
3208	struct cgroup *dsct;
3209	struct cgroup_subsys_state *d_css;
3210
3211	cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3212		dsct->subtree_control = dsct->old_subtree_control;
3213		dsct->subtree_ss_mask = dsct->old_subtree_ss_mask;
 
 
 
 
 
 
 
 
3214	}
 
3215}
3216
3217static bool css_visible(struct cgroup_subsys_state *css)
 
 
 
3218{
3219	struct cgroup_subsys *ss = css->ss;
3220	struct cgroup *cgrp = css->cgroup;
 
3221
3222	if (cgroup_control(cgrp) & (1 << ss->id))
3223		return true;
3224	if (!(cgroup_ss_mask(cgrp) & (1 << ss->id)))
3225		return false;
3226	return cgroup_on_dfl(cgrp) && ss->implicit_on_dfl;
3227}
3228
3229/**
3230 * cgroup_apply_control_enable - enable or show csses according to control
3231 * @cgrp: root of the target subtree
3232 *
3233 * Walk @cgrp's subtree and create new csses or make the existing ones
3234 * visible.  A css is created invisible if it's being implicitly enabled
3235 * through dependency.  An invisible css is made visible when the userland
3236 * explicitly enables it.
3237 *
3238 * Returns 0 on success, -errno on failure.  On failure, csses which have
3239 * been processed already aren't cleaned up.  The caller is responsible for
3240 * cleaning up with cgroup_apply_control_disble().
3241 */
3242static int cgroup_apply_control_enable(struct cgroup *cgrp)
3243{
3244	struct cgroup *dsct;
3245	struct cgroup_subsys_state *d_css;
3246	struct cgroup_subsys *ss;
3247	int ssid, ret;
3248
3249	cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
3250		for_each_subsys(ss, ssid) {
3251			struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3252
3253			WARN_ON_ONCE(css && percpu_ref_is_dying(&css->refcnt));
3254
3255			if (!(cgroup_ss_mask(dsct) & (1 << ss->id)))
3256				continue;
3257
3258			if (!css) {
3259				css = css_create(dsct, ss);
3260				if (IS_ERR(css))
3261					return PTR_ERR(css);
3262			}
3263
3264			if (css_visible(css)) {
3265				ret = css_populate_dir(css);
3266				if (ret)
3267					return ret;
3268			}
3269		}
3270	}
3271
3272	return 0;
3273}
3274
3275/**
3276 * cgroup_apply_control_disable - kill or hide csses according to control
3277 * @cgrp: root of the target subtree
3278 *
3279 * Walk @cgrp's subtree and kill and hide csses so that they match
3280 * cgroup_ss_mask() and cgroup_visible_mask().
3281 *
3282 * A css is hidden when the userland requests it to be disabled while other
3283 * subsystems are still depending on it.  The css must not actively control
3284 * resources and be in the vanilla state if it's made visible again later.
3285 * Controllers which may be depended upon should provide ->css_reset() for
3286 * this purpose.
3287 */
3288static void cgroup_apply_control_disable(struct cgroup *cgrp)
3289{
3290	struct cgroup *dsct;
3291	struct cgroup_subsys_state *d_css;
3292	struct cgroup_subsys *ss;
3293	int ssid;
3294
3295	cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
3296		for_each_subsys(ss, ssid) {
3297			struct cgroup_subsys_state *css = cgroup_css(dsct, ss);
3298
3299			WARN_ON_ONCE(css && percpu_ref_is_dying(&css->refcnt));
3300
3301			if (!css)
3302				continue;
3303
3304			if (css->parent &&
3305			    !(cgroup_ss_mask(dsct) & (1 << ss->id))) {
3306				kill_css(css);
3307			} else if (!css_visible(css)) {
3308				css_clear_dir(css);
3309				if (ss->css_reset)
3310					ss->css_reset(css);
3311			}
3312		}
3313	}
3314}
3315
3316/**
3317 * cgroup_apply_control - apply control mask updates to the subtree
3318 * @cgrp: root of the target subtree
3319 *
3320 * subsystems can be enabled and disabled in a subtree using the following
3321 * steps.
3322 *
3323 * 1. Call cgroup_save_control() to stash the current state.
3324 * 2. Update ->subtree_control masks in the subtree as desired.
3325 * 3. Call cgroup_apply_control() to apply the changes.
3326 * 4. Optionally perform other related operations.
3327 * 5. Call cgroup_finalize_control() to finish up.
3328 *
3329 * This function implements step 3 and propagates the mask changes
3330 * throughout @cgrp's subtree, updates csses accordingly and perform
3331 * process migrations.
3332 */
3333static int cgroup_apply_control(struct cgroup *cgrp)
3334{
3335	int ret;
3336
3337	cgroup_propagate_control(cgrp);
3338
3339	ret = cgroup_apply_control_enable(cgrp);
3340	if (ret)
3341		return ret;
3342
3343	/*
3344	 * At this point, cgroup_e_css() results reflect the new csses
3345	 * making the following cgroup_update_dfl_csses() properly update
3346	 * css associations of all tasks in the subtree.
3347	 */
3348	ret = cgroup_update_dfl_csses(cgrp);
3349	if (ret)
3350		return ret;
3351
3352	return 0;
 
 
 
3353}
3354
3355/**
3356 * cgroup_finalize_control - finalize control mask update
3357 * @cgrp: root of the target subtree
3358 * @ret: the result of the update
3359 *
3360 * Finalize control mask update.  See cgroup_apply_control() for more info.
3361 */
3362static void cgroup_finalize_control(struct cgroup *cgrp, int ret)
3363{
3364	if (ret) {
3365		cgroup_restore_control(cgrp);
3366		cgroup_propagate_control(cgrp);
 
 
 
 
 
3367	}
3368
3369	cgroup_apply_control_disable(cgrp);
3370}
3371
3372/* change the enabled child controllers for a cgroup in the default hierarchy */
3373static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
3374					    char *buf, size_t nbytes,
3375					    loff_t off)
3376{
3377	u16 enable = 0, disable = 0;
3378	struct cgroup *cgrp, *child;
3379	struct cgroup_subsys *ss;
3380	char *tok;
3381	int ssid, ret;
3382
3383	/*
3384	 * Parse input - space separated list of subsystem names prefixed
3385	 * with either + or -.
3386	 */
3387	buf = strstrip(buf);
3388	while ((tok = strsep(&buf, " "))) {
3389		if (tok[0] == '\0')
3390			continue;
3391		do_each_subsys_mask(ss, ssid, ~cgrp_dfl_inhibit_ss_mask) {
3392			if (!cgroup_ssid_enabled(ssid) ||
3393			    strcmp(tok + 1, ss->name))
3394				continue;
3395
3396			if (*tok == '+') {
3397				enable |= 1 << ssid;
3398				disable &= ~(1 << ssid);
3399			} else if (*tok == '-') {
3400				disable |= 1 << ssid;
3401				enable &= ~(1 << ssid);
3402			} else {
3403				return -EINVAL;
3404			}
3405			break;
3406		} while_each_subsys_mask();
3407		if (ssid == CGROUP_SUBSYS_COUNT)
3408			return -EINVAL;
3409	}
3410
3411	cgrp = cgroup_kn_lock_live(of->kn, true);
3412	if (!cgrp)
3413		return -ENODEV;
3414
3415	for_each_subsys(ss, ssid) {
3416		if (enable & (1 << ssid)) {
3417			if (cgrp->subtree_control & (1 << ssid)) {
3418				enable &= ~(1 << ssid);
3419				continue;
3420			}
3421
3422			if (!(cgroup_control(cgrp) & (1 << ssid))) {
3423				ret = -ENOENT;
3424				goto out_unlock;
3425			}
3426		} else if (disable & (1 << ssid)) {
3427			if (!(cgrp->subtree_control & (1 << ssid))) {
3428				disable &= ~(1 << ssid);
3429				continue;
3430			}
3431
3432			/* a child has it enabled? */
3433			cgroup_for_each_live_child(child, cgrp) {
3434				if (child->subtree_control & (1 << ssid)) {
3435					ret = -EBUSY;
3436					goto out_unlock;
3437				}
3438			}
3439		}
3440	}
3441
3442	if (!enable && !disable) {
3443		ret = 0;
3444		goto out_unlock;
3445	}
3446
3447	/*
3448	 * Except for the root, subtree_control must be zero for a cgroup
3449	 * with tasks so that child cgroups don't compete against tasks.
3450	 */
3451	if (enable && cgroup_parent(cgrp) && !list_empty(&cgrp->cset_links)) {
3452		ret = -EBUSY;
3453		goto out_unlock;
3454	}
3455
3456	/* save and update control masks and prepare csses */
3457	cgroup_save_control(cgrp);
 
 
 
 
3458
3459	cgrp->subtree_control |= enable;
3460	cgrp->subtree_control &= ~disable;
 
 
3461
3462	ret = cgroup_apply_control(cgrp);
 
 
 
3463
3464	cgroup_finalize_control(cgrp, ret);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3465
3466	kernfs_activate(cgrp->kn);
3467	ret = 0;
3468out_unlock:
3469	cgroup_kn_unlock(of->kn);
3470	return ret ?: nbytes;
3471}
3472
3473static int cgroup_events_show(struct seq_file *seq, void *v)
3474{
3475	seq_printf(seq, "populated %d\n",
3476		   cgroup_is_populated(seq_css(seq)->cgroup));
 
3477	return 0;
3478}
3479
3480static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
3481				 size_t nbytes, loff_t off)
 
 
 
3482{
3483	struct cgroup *cgrp = of->kn->parent->priv;
3484	struct cftype *cft = of->kn->priv;
3485	struct cgroup_subsys_state *css;
3486	int ret;
3487
3488	if (cft->write)
3489		return cft->write(of, buf, nbytes, off);
3490
3491	/*
3492	 * kernfs guarantees that a file isn't deleted with operations in
3493	 * flight, which means that the matching css is and stays alive and
3494	 * doesn't need to be pinned.  The RCU locking is not necessary
3495	 * either.  It's just for the convenience of using cgroup_css().
3496	 */
3497	rcu_read_lock();
3498	css = cgroup_css(cgrp, cft->ss);
3499	rcu_read_unlock();
3500
3501	if (cft->write_u64) {
3502		unsigned long long v;
3503		ret = kstrtoull(buf, 0, &v);
3504		if (!ret)
3505			ret = cft->write_u64(css, cft, v);
3506	} else if (cft->write_s64) {
3507		long long v;
3508		ret = kstrtoll(buf, 0, &v);
3509		if (!ret)
3510			ret = cft->write_s64(css, cft, v);
3511	} else {
3512		ret = -EINVAL;
3513	}
3514
3515	return ret ?: nbytes;
3516}
 
 
 
 
3517
3518static void *cgroup_seqfile_start(struct seq_file *seq, loff_t *ppos)
3519{
3520	return seq_cft(seq)->seq_start(seq, ppos);
 
 
 
3521}
3522
3523static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
 
 
 
3524{
3525	return seq_cft(seq)->seq_next(seq, v, ppos);
 
 
3526}
3527
3528static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
 
3529{
3530	seq_cft(seq)->seq_stop(seq, v);
3531}
3532
3533static int cgroup_seqfile_show(struct seq_file *m, void *arg)
3534{
3535	struct cftype *cft = seq_cft(m);
3536	struct cgroup_subsys_state *css = seq_css(m);
3537
3538	if (cft->seq_show)
3539		return cft->seq_show(m, arg);
 
3540
3541	if (cft->read_u64)
3542		seq_printf(m, "%llu\n", cft->read_u64(css, cft));
3543	else if (cft->read_s64)
3544		seq_printf(m, "%lld\n", cft->read_s64(css, cft));
3545	else
3546		return -EINVAL;
 
 
 
 
 
 
 
 
 
 
3547	return 0;
3548}
3549
3550static struct kernfs_ops cgroup_kf_single_ops = {
3551	.atomic_write_len	= PAGE_SIZE,
3552	.write			= cgroup_file_write,
3553	.seq_show		= cgroup_seqfile_show,
3554};
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3555
3556static struct kernfs_ops cgroup_kf_ops = {
3557	.atomic_write_len	= PAGE_SIZE,
3558	.write			= cgroup_file_write,
3559	.seq_start		= cgroup_seqfile_start,
3560	.seq_next		= cgroup_seqfile_next,
3561	.seq_stop		= cgroup_seqfile_stop,
3562	.seq_show		= cgroup_seqfile_show,
3563};
3564
3565/*
3566 * cgroup_rename - Only allow simple rename of directories in place.
 
 
 
 
 
 
3567 */
3568static int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
3569			 const char *new_name_str)
3570{
3571	struct cgroup *cgrp = kn->priv;
3572	int ret;
3573
3574	if (kernfs_type(kn) != KERNFS_DIR)
3575		return -ENOTDIR;
3576	if (kn->parent != new_parent)
3577		return -EIO;
3578
3579	/*
3580	 * This isn't a proper migration and its usefulness is very
3581	 * limited.  Disallow on the default hierarchy.
3582	 */
3583	if (cgroup_on_dfl(cgrp))
3584		return -EPERM;
3585
3586	/*
3587	 * We're gonna grab cgroup_mutex which nests outside kernfs
3588	 * active_ref.  kernfs_rename() doesn't require active_ref
3589	 * protection.  Break them before grabbing cgroup_mutex.
3590	 */
3591	kernfs_break_active_protection(new_parent);
3592	kernfs_break_active_protection(kn);
3593
3594	mutex_lock(&cgroup_mutex);
 
3595
3596	ret = kernfs_rename(kn, new_parent, new_name_str);
 
 
3597
3598	mutex_unlock(&cgroup_mutex);
 
 
3599
3600	kernfs_unbreak_active_protection(kn);
3601	kernfs_unbreak_active_protection(new_parent);
3602	return ret;
3603}
3604
3605/* set uid and gid of cgroup dirs and files to that of the creator */
3606static int cgroup_kn_set_ugid(struct kernfs_node *kn)
3607{
3608	struct iattr iattr = { .ia_valid = ATTR_UID | ATTR_GID,
3609			       .ia_uid = current_fsuid(),
3610			       .ia_gid = current_fsgid(), };
 
 
 
 
3611
3612	if (uid_eq(iattr.ia_uid, GLOBAL_ROOT_UID) &&
3613	    gid_eq(iattr.ia_gid, GLOBAL_ROOT_GID))
 
 
3614		return 0;
3615
3616	return kernfs_setattr(kn, &iattr);
3617}
 
 
 
3618
3619static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
3620			   struct cftype *cft)
3621{
3622	char name[CGROUP_FILE_NAME_MAX];
3623	struct kernfs_node *kn;
3624	struct lock_class_key *key = NULL;
3625	int ret;
3626
3627#ifdef CONFIG_DEBUG_LOCK_ALLOC
3628	key = &cft->lockdep_key;
3629#endif
3630	kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
3631				  cgroup_file_mode(cft), 0, cft->kf_ops, cft,
3632				  NULL, key);
3633	if (IS_ERR(kn))
3634		return PTR_ERR(kn);
3635
3636	ret = cgroup_kn_set_ugid(kn);
3637	if (ret) {
3638		kernfs_remove(kn);
3639		return ret;
3640	}
3641
3642	if (cft->file_offset) {
3643		struct cgroup_file *cfile = (void *)css + cft->file_offset;
3644
3645		spin_lock_irq(&cgroup_file_kn_lock);
3646		cfile->kn = kn;
3647		spin_unlock_irq(&cgroup_file_kn_lock);
 
 
3648	}
3649
3650	return 0;
 
 
3651}
3652
3653/**
3654 * cgroup_addrm_files - add or remove files to a cgroup directory
3655 * @css: the target css
3656 * @cgrp: the target cgroup (usually css->cgroup)
3657 * @cfts: array of cftypes to be added
3658 * @is_add: whether to add or remove
3659 *
3660 * Depending on @is_add, add or remove files defined by @cfts on @cgrp.
3661 * For removals, this function never fails.
3662 */
3663static int cgroup_addrm_files(struct cgroup_subsys_state *css,
3664			      struct cgroup *cgrp, struct cftype cfts[],
3665			      bool is_add)
3666{
3667	struct cftype *cft, *cft_end = NULL;
3668	int ret = 0;
3669
3670	lockdep_assert_held(&cgroup_mutex);
3671
3672restart:
3673	for (cft = cfts; cft != cft_end && cft->name[0] != '\0'; cft++) {
3674		/* does cft->flags tell us to skip this file on @cgrp? */
3675		if ((cft->flags & __CFTYPE_ONLY_ON_DFL) && !cgroup_on_dfl(cgrp))
3676			continue;
3677		if ((cft->flags & __CFTYPE_NOT_ON_DFL) && cgroup_on_dfl(cgrp))
3678			continue;
3679		if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgroup_parent(cgrp))
3680			continue;
3681		if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgroup_parent(cgrp))
3682			continue;
3683
3684		if (is_add) {
3685			ret = cgroup_add_file(css, cgrp, cft);
3686			if (ret) {
3687				pr_warn("%s: failed to add %s, err=%d\n",
3688					__func__, cft->name, ret);
3689				cft_end = cft;
3690				is_add = false;
3691				goto restart;
3692			}
3693		} else {
3694			cgroup_rm_file(cgrp, cft);
3695		}
3696	}
3697	return ret;
3698}
3699
3700static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
3701{
3702	LIST_HEAD(pending);
3703	struct cgroup_subsys *ss = cfts[0].ss;
3704	struct cgroup *root = &ss->root->cgrp;
3705	struct cgroup_subsys_state *css;
3706	int ret = 0;
3707
3708	lockdep_assert_held(&cgroup_mutex);
3709
3710	/* add/rm files for all cgroups created before */
3711	css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
3712		struct cgroup *cgrp = css->cgroup;
3713
3714		if (!(css->flags & CSS_VISIBLE))
3715			continue;
3716
3717		ret = cgroup_addrm_files(css, cgrp, cfts, is_add);
3718		if (ret)
3719			break;
3720	}
3721
3722	if (is_add && !ret)
3723		kernfs_activate(root->kn);
3724	return ret;
3725}
3726
3727static void cgroup_exit_cftypes(struct cftype *cfts)
3728{
3729	struct cftype *cft;
3730
3731	for (cft = cfts; cft->name[0] != '\0'; cft++) {
3732		/* free copy for custom atomic_write_len, see init_cftypes() */
3733		if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
3734			kfree(cft->kf_ops);
3735		cft->kf_ops = NULL;
3736		cft->ss = NULL;
3737
3738		/* revert flags set by cgroup core while adding @cfts */
3739		cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL);
3740	}
3741}
3742
3743static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
 
 
3744{
3745	struct cftype *cft;
3746
3747	for (cft = cfts; cft->name[0] != '\0'; cft++) {
3748		struct kernfs_ops *kf_ops;
3749
3750		WARN_ON(cft->ss || cft->kf_ops);
3751
3752		if (cft->seq_start)
3753			kf_ops = &cgroup_kf_ops;
3754		else
3755			kf_ops = &cgroup_kf_single_ops;
3756
3757		/*
3758		 * Ugh... if @cft wants a custom max_write_len, we need to
3759		 * make a copy of kf_ops to set its atomic_write_len.
3760		 */
3761		if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {
3762			kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);
3763			if (!kf_ops) {
3764				cgroup_exit_cftypes(cfts);
3765				return -ENOMEM;
3766			}
3767			kf_ops->atomic_write_len = cft->max_write_len;
3768		}
3769
3770		cft->kf_ops = kf_ops;
3771		cft->ss = ss;
3772	}
3773
3774	return 0;
3775}
3776
3777static int cgroup_rm_cftypes_locked(struct cftype *cfts)
3778{
3779	lockdep_assert_held(&cgroup_mutex);
3780
3781	if (!cfts || !cfts[0].ss)
3782		return -ENOENT;
 
 
 
 
3783
3784	list_del(&cfts->node);
3785	cgroup_apply_cftypes(cfts, false);
3786	cgroup_exit_cftypes(cfts);
3787	return 0;
3788}
 
3789
3790/**
3791 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
3792 * @cfts: zero-length name terminated array of cftypes
3793 *
3794 * Unregister @cfts.  Files described by @cfts are removed from all
3795 * existing cgroups and all future cgroups won't have them either.  This
3796 * function can be called anytime whether @cfts' subsys is attached or not.
3797 *
3798 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
3799 * registered.
3800 */
3801int cgroup_rm_cftypes(struct cftype *cfts)
3802{
3803	int ret;
3804
3805	mutex_lock(&cgroup_mutex);
3806	ret = cgroup_rm_cftypes_locked(cfts);
3807	mutex_unlock(&cgroup_mutex);
3808	return ret;
3809}
3810
3811/**
3812 * cgroup_add_cftypes - add an array of cftypes to a subsystem
3813 * @ss: target cgroup subsystem
3814 * @cfts: zero-length name terminated array of cftypes
3815 *
3816 * Register @cfts to @ss.  Files described by @cfts are created for all
3817 * existing cgroups to which @ss is attached and all future cgroups will
3818 * have them too.  This function can be called anytime whether @ss is
3819 * attached or not.
3820 *
3821 * Returns 0 on successful registration, -errno on failure.  Note that this
3822 * function currently returns 0 as long as @cfts registration is successful
3823 * even if some file creation attempts on existing cgroups fail.
3824 */
3825static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
3826{
3827	int ret;
3828
3829	if (!cgroup_ssid_enabled(ss->id))
3830		return 0;
3831
3832	if (!cfts || cfts[0].name[0] == '\0')
3833		return 0;
3834
3835	ret = cgroup_init_cftypes(ss, cfts);
3836	if (ret)
3837		return ret;
3838
3839	mutex_lock(&cgroup_mutex);
3840
3841	list_add_tail(&cfts->node, &ss->cfts);
3842	ret = cgroup_apply_cftypes(cfts, true);
3843	if (ret)
3844		cgroup_rm_cftypes_locked(cfts);
3845
3846	mutex_unlock(&cgroup_mutex);
3847	return ret;
3848}
 
3849
3850/**
3851 * cgroup_add_dfl_cftypes - add an array of cftypes for default hierarchy
3852 * @ss: target cgroup subsystem
3853 * @cfts: zero-length name terminated array of cftypes
3854 *
3855 * Similar to cgroup_add_cftypes() but the added files are only used for
3856 * the default hierarchy.
3857 */
3858int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
3859{
3860	struct cftype *cft;
3861
3862	for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
3863		cft->flags |= __CFTYPE_ONLY_ON_DFL;
3864	return cgroup_add_cftypes(ss, cfts);
3865}
3866
3867/**
3868 * cgroup_add_legacy_cftypes - add an array of cftypes for legacy hierarchies
3869 * @ss: target cgroup subsystem
3870 * @cfts: zero-length name terminated array of cftypes
3871 *
3872 * Similar to cgroup_add_cftypes() but the added files are only used for
3873 * the legacy hierarchies.
3874 */
3875int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
3876{
3877	struct cftype *cft;
3878
3879	for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
3880		cft->flags |= __CFTYPE_NOT_ON_DFL;
3881	return cgroup_add_cftypes(ss, cfts);
3882}
3883
3884/**
3885 * cgroup_file_notify - generate a file modified event for a cgroup_file
3886 * @cfile: target cgroup_file
3887 *
3888 * @cfile must have been obtained by setting cftype->file_offset.
3889 */
3890void cgroup_file_notify(struct cgroup_file *cfile)
3891{
3892	unsigned long flags;
3893
3894	spin_lock_irqsave(&cgroup_file_kn_lock, flags);
3895	if (cfile->kn)
3896		kernfs_notify(cfile->kn);
3897	spin_unlock_irqrestore(&cgroup_file_kn_lock, flags);
3898}
3899
3900/**
3901 * cgroup_task_count - count the number of tasks in a cgroup.
3902 * @cgrp: the cgroup in question
3903 *
3904 * Return the number of tasks in the cgroup.
3905 */
3906static int cgroup_task_count(const struct cgroup *cgrp)
3907{
3908	int count = 0;
3909	struct cgrp_cset_link *link;
3910
3911	spin_lock_bh(&css_set_lock);
3912	list_for_each_entry(link, &cgrp->cset_links, cset_link)
3913		count += atomic_read(&link->cset->refcount);
3914	spin_unlock_bh(&css_set_lock);
3915	return count;
3916}
3917
3918/**
3919 * css_next_child - find the next child of a given css
3920 * @pos: the current position (%NULL to initiate traversal)
3921 * @parent: css whose children to walk
3922 *
3923 * This function returns the next child of @parent and should be called
3924 * under either cgroup_mutex or RCU read lock.  The only requirement is
3925 * that @parent and @pos are accessible.  The next sibling is guaranteed to
3926 * be returned regardless of their states.
3927 *
3928 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3929 * css which finished ->css_online() is guaranteed to be visible in the
3930 * future iterations and will stay visible until the last reference is put.
3931 * A css which hasn't finished ->css_online() or already finished
3932 * ->css_offline() may show up during traversal.  It's each subsystem's
3933 * responsibility to synchronize against on/offlining.
3934 */
3935struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
3936					   struct cgroup_subsys_state *parent)
3937{
3938	struct cgroup_subsys_state *next;
3939
3940	cgroup_assert_mutex_or_rcu_locked();
3941
3942	/*
3943	 * @pos could already have been unlinked from the sibling list.
3944	 * Once a cgroup is removed, its ->sibling.next is no longer
3945	 * updated when its next sibling changes.  CSS_RELEASED is set when
3946	 * @pos is taken off list, at which time its next pointer is valid,
3947	 * and, as releases are serialized, the one pointed to by the next
3948	 * pointer is guaranteed to not have started release yet.  This
3949	 * implies that if we observe !CSS_RELEASED on @pos in this RCU
3950	 * critical section, the one pointed to by its next pointer is
3951	 * guaranteed to not have finished its RCU grace period even if we
3952	 * have dropped rcu_read_lock() inbetween iterations.
3953	 *
3954	 * If @pos has CSS_RELEASED set, its next pointer can't be
3955	 * dereferenced; however, as each css is given a monotonically
3956	 * increasing unique serial number and always appended to the
3957	 * sibling list, the next one can be found by walking the parent's
3958	 * children until the first css with higher serial number than
3959	 * @pos's.  While this path can be slower, it happens iff iteration
3960	 * races against release and the race window is very small.
3961	 */
3962	if (!pos) {
3963		next = list_entry_rcu(parent->children.next, struct cgroup_subsys_state, sibling);
3964	} else if (likely(!(pos->flags & CSS_RELEASED))) {
3965		next = list_entry_rcu(pos->sibling.next, struct cgroup_subsys_state, sibling);
3966	} else {
3967		list_for_each_entry_rcu(next, &parent->children, sibling)
3968			if (next->serial_nr > pos->serial_nr)
3969				break;
3970	}
3971
3972	/*
3973	 * @next, if not pointing to the head, can be dereferenced and is
3974	 * the next sibling.
3975	 */
3976	if (&next->sibling != &parent->children)
3977		return next;
3978	return NULL;
3979}
3980
3981/**
3982 * css_next_descendant_pre - find the next descendant for pre-order walk
3983 * @pos: the current position (%NULL to initiate traversal)
3984 * @root: css whose descendants to walk
3985 *
3986 * To be used by css_for_each_descendant_pre().  Find the next descendant
3987 * to visit for pre-order traversal of @root's descendants.  @root is
3988 * included in the iteration and the first node to be visited.
3989 *
3990 * While this function requires cgroup_mutex or RCU read locking, it
3991 * doesn't require the whole traversal to be contained in a single critical
3992 * section.  This function will return the correct next descendant as long
3993 * as both @pos and @root are accessible and @pos is a descendant of @root.
3994 *
3995 * If a subsystem synchronizes ->css_online() and the start of iteration, a
3996 * css which finished ->css_online() is guaranteed to be visible in the
3997 * future iterations and will stay visible until the last reference is put.
3998 * A css which hasn't finished ->css_online() or already finished
3999 * ->css_offline() may show up during traversal.  It's each subsystem's
4000 * responsibility to synchronize against on/offlining.
4001 */
4002struct cgroup_subsys_state *
4003css_next_descendant_pre(struct cgroup_subsys_state *pos,
4004			struct cgroup_subsys_state *root)
4005{
4006	struct cgroup_subsys_state *next;
4007
4008	cgroup_assert_mutex_or_rcu_locked();
4009
4010	/* if first iteration, visit @root */
4011	if (!pos)
4012		return root;
4013
4014	/* visit the first child if exists */
4015	next = css_next_child(NULL, pos);
4016	if (next)
4017		return next;
4018
4019	/* no child, visit my or the closest ancestor's next sibling */
4020	while (pos != root) {
4021		next = css_next_child(pos, pos->parent);
4022		if (next)
4023			return next;
4024		pos = pos->parent;
4025	}
4026
4027	return NULL;
4028}
4029
4030/**
4031 * css_rightmost_descendant - return the rightmost descendant of a css
4032 * @pos: css of interest
4033 *
4034 * Return the rightmost descendant of @pos.  If there's no descendant, @pos
4035 * is returned.  This can be used during pre-order traversal to skip
4036 * subtree of @pos.
4037 *
4038 * While this function requires cgroup_mutex or RCU read locking, it
4039 * doesn't require the whole traversal to be contained in a single critical
4040 * section.  This function will return the correct rightmost descendant as
4041 * long as @pos is accessible.
4042 */
4043struct cgroup_subsys_state *
4044css_rightmost_descendant(struct cgroup_subsys_state *pos)
4045{
4046	struct cgroup_subsys_state *last, *tmp;
4047
4048	cgroup_assert_mutex_or_rcu_locked();
4049
4050	do {
4051		last = pos;
4052		/* ->prev isn't RCU safe, walk ->next till the end */
4053		pos = NULL;
4054		css_for_each_child(tmp, last)
4055			pos = tmp;
4056	} while (pos);
4057
4058	return last;
4059}
4060
4061static struct cgroup_subsys_state *
4062css_leftmost_descendant(struct cgroup_subsys_state *pos)
4063{
4064	struct cgroup_subsys_state *last;
4065
4066	do {
4067		last = pos;
4068		pos = css_next_child(NULL, pos);
4069	} while (pos);
4070
4071	return last;
4072}
4073
4074/**
4075 * css_next_descendant_post - find the next descendant for post-order walk
4076 * @pos: the current position (%NULL to initiate traversal)
4077 * @root: css whose descendants to walk
4078 *
4079 * To be used by css_for_each_descendant_post().  Find the next descendant
4080 * to visit for post-order traversal of @root's descendants.  @root is
4081 * included in the iteration and the last node to be visited.
4082 *
4083 * While this function requires cgroup_mutex or RCU read locking, it
4084 * doesn't require the whole traversal to be contained in a single critical
4085 * section.  This function will return the correct next descendant as long
4086 * as both @pos and @cgroup are accessible and @pos is a descendant of
4087 * @cgroup.
4088 *
4089 * If a subsystem synchronizes ->css_online() and the start of iteration, a
4090 * css which finished ->css_online() is guaranteed to be visible in the
4091 * future iterations and will stay visible until the last reference is put.
4092 * A css which hasn't finished ->css_online() or already finished
4093 * ->css_offline() may show up during traversal.  It's each subsystem's
4094 * responsibility to synchronize against on/offlining.
4095 */
4096struct cgroup_subsys_state *
4097css_next_descendant_post(struct cgroup_subsys_state *pos,
4098			 struct cgroup_subsys_state *root)
4099{
4100	struct cgroup_subsys_state *next;
4101
4102	cgroup_assert_mutex_or_rcu_locked();
4103
4104	/* if first iteration, visit leftmost descendant which may be @root */
4105	if (!pos)
4106		return css_leftmost_descendant(root);
4107
4108	/* if we visited @root, we're done */
4109	if (pos == root)
4110		return NULL;
4111
4112	/* if there's an unvisited sibling, visit its leftmost descendant */
4113	next = css_next_child(pos, pos->parent);
4114	if (next)
4115		return css_leftmost_descendant(next);
4116
4117	/* no sibling left, visit parent */
4118	return pos->parent;
4119}
4120
4121/**
4122 * css_has_online_children - does a css have online children
4123 * @css: the target css
4124 *
4125 * Returns %true if @css has any online children; otherwise, %false.  This
4126 * function can be called from any context but the caller is responsible
4127 * for synchronizing against on/offlining as necessary.
4128 */
4129bool css_has_online_children(struct cgroup_subsys_state *css)
4130{
4131	struct cgroup_subsys_state *child;
4132	bool ret = false;
4133
4134	rcu_read_lock();
4135	css_for_each_child(child, css) {
4136		if (child->flags & CSS_ONLINE) {
4137			ret = true;
4138			break;
4139		}
4140	}
4141	rcu_read_unlock();
4142	return ret;
4143}
4144
4145/**
4146 * css_task_iter_advance_css_set - advance a task itererator to the next css_set
4147 * @it: the iterator to advance
4148 *
4149 * Advance @it to the next css_set to walk.
4150 */
4151static void css_task_iter_advance_css_set(struct css_task_iter *it)
 
4152{
4153	struct list_head *l = it->cset_pos;
4154	struct cgrp_cset_link *link;
4155	struct css_set *cset;
4156
4157	lockdep_assert_held(&css_set_lock);
4158
4159	/* Advance to the next non-empty css_set */
4160	do {
4161		l = l->next;
4162		if (l == it->cset_head) {
4163			it->cset_pos = NULL;
4164			it->task_pos = NULL;
4165			return;
4166		}
 
 
 
 
 
 
4167
4168		if (it->ss) {
4169			cset = container_of(l, struct css_set,
4170					    e_cset_node[it->ss->id]);
4171		} else {
4172			link = list_entry(l, struct cgrp_cset_link, cset_link);
4173			cset = link->cset;
4174		}
4175	} while (!css_set_populated(cset));
4176
4177	it->cset_pos = l;
4178
4179	if (!list_empty(&cset->tasks))
4180		it->task_pos = cset->tasks.next;
4181	else
4182		it->task_pos = cset->mg_tasks.next;
4183
4184	it->tasks_head = &cset->tasks;
4185	it->mg_tasks_head = &cset->mg_tasks;
4186
4187	/*
4188	 * We don't keep css_sets locked across iteration steps and thus
4189	 * need to take steps to ensure that iteration can be resumed after
4190	 * the lock is re-acquired.  Iteration is performed at two levels -
4191	 * css_sets and tasks in them.
4192	 *
4193	 * Once created, a css_set never leaves its cgroup lists, so a
4194	 * pinned css_set is guaranteed to stay put and we can resume
4195	 * iteration afterwards.
4196	 *
4197	 * Tasks may leave @cset across iteration steps.  This is resolved
4198	 * by registering each iterator with the css_set currently being
4199	 * walked and making css_set_move_task() advance iterators whose
4200	 * next task is leaving.
4201	 */
4202	if (it->cur_cset) {
4203		list_del(&it->iters_node);
4204		put_css_set_locked(it->cur_cset);
4205	}
4206	get_css_set(cset);
4207	it->cur_cset = cset;
4208	list_add(&it->iters_node, &cset->task_iters);
 
 
 
 
 
 
 
4209}
4210
4211static void css_task_iter_advance(struct css_task_iter *it)
 
4212{
4213	struct list_head *l = it->task_pos;
4214
4215	lockdep_assert_held(&css_set_lock);
4216	WARN_ON_ONCE(!l);
4217
4218	/*
4219	 * Advance iterator to find next entry.  cset->tasks is consumed
4220	 * first and then ->mg_tasks.  After ->mg_tasks, we move onto the
4221	 * next cset.
4222	 */
4223	l = l->next;
4224
4225	if (l == it->tasks_head)
4226		l = it->mg_tasks_head->next;
4227
4228	if (l == it->mg_tasks_head)
4229		css_task_iter_advance_css_set(it);
4230	else
4231		it->task_pos = l;
4232}
4233
4234/**
4235 * css_task_iter_start - initiate task iteration
4236 * @css: the css to walk tasks of
4237 * @it: the task iterator to use
4238 *
4239 * Initiate iteration through the tasks of @css.  The caller can call
4240 * css_task_iter_next() to walk through the tasks until the function
4241 * returns NULL.  On completion of iteration, css_task_iter_end() must be
4242 * called.
4243 */
4244void css_task_iter_start(struct cgroup_subsys_state *css,
4245			 struct css_task_iter *it)
4246{
4247	/* no one should try to iterate before mounting cgroups */
4248	WARN_ON_ONCE(!use_task_css_set_links);
 
4249
4250	memset(it, 0, sizeof(*it));
4251
4252	spin_lock_bh(&css_set_lock);
4253
4254	it->ss = css->ss;
4255
4256	if (it->ss)
4257		it->cset_pos = &css->cgroup->e_csets[css->ss->id];
4258	else
4259		it->cset_pos = &css->cgroup->cset_links;
4260
4261	it->cset_head = it->cset_pos;
4262
4263	css_task_iter_advance_css_set(it);
4264
4265	spin_unlock_bh(&css_set_lock);
4266}
4267
4268/**
4269 * css_task_iter_next - return the next task for the iterator
4270 * @it: the task iterator being iterated
4271 *
4272 * The "next" function for task iteration.  @it should have been
4273 * initialized via css_task_iter_start().  Returns NULL when the iteration
4274 * reaches the end.
4275 */
4276struct task_struct *css_task_iter_next(struct css_task_iter *it)
4277{
4278	if (it->cur_task) {
4279		put_task_struct(it->cur_task);
4280		it->cur_task = NULL;
4281	}
4282
4283	spin_lock_bh(&css_set_lock);
4284
4285	if (it->task_pos) {
4286		it->cur_task = list_entry(it->task_pos, struct task_struct,
4287					  cg_list);
4288		get_task_struct(it->cur_task);
4289		css_task_iter_advance(it);
4290	}
4291
4292	spin_unlock_bh(&css_set_lock);
4293
4294	return it->cur_task;
4295}
4296
4297/**
4298 * css_task_iter_end - finish task iteration
4299 * @it: the task iterator to finish
4300 *
4301 * Finish task iteration started by css_task_iter_start().
4302 */
4303void css_task_iter_end(struct css_task_iter *it)
4304{
4305	if (it->cur_cset) {
4306		spin_lock_bh(&css_set_lock);
4307		list_del(&it->iters_node);
4308		put_css_set_locked(it->cur_cset);
4309		spin_unlock_bh(&css_set_lock);
 
 
 
 
 
 
 
 
 
 
4310	}
 
4311
4312	if (it->cur_task)
4313		put_task_struct(it->cur_task);
 
 
 
 
 
 
 
 
4314}
4315
4316/**
4317 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
4318 * @to: cgroup to which the tasks will be moved
4319 * @from: cgroup in which the tasks currently reside
4320 *
4321 * Locking rules between cgroup_post_fork() and the migration path
4322 * guarantee that, if a task is forking while being migrated, the new child
4323 * is guaranteed to be either visible in the source cgroup after the
4324 * parent's migration is complete or put into the target cgroup.  No task
4325 * can slip out of migration through forking.
4326 */
4327int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
4328{
4329	LIST_HEAD(preloaded_csets);
4330	struct cgrp_cset_link *link;
4331	struct css_task_iter it;
4332	struct task_struct *task;
4333	int ret;
4334
4335	if (!cgroup_may_migrate_to(to))
4336		return -EBUSY;
4337
4338	mutex_lock(&cgroup_mutex);
4339
4340	/* all tasks in @from are being moved, all csets are source */
4341	spin_lock_bh(&css_set_lock);
4342	list_for_each_entry(link, &from->cset_links, cset_link)
4343		cgroup_migrate_add_src(link->cset, to, &preloaded_csets);
4344	spin_unlock_bh(&css_set_lock);
4345
4346	ret = cgroup_migrate_prepare_dst(&preloaded_csets);
4347	if (ret)
4348		goto out_err;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4349
 
4350	/*
4351	 * Migrate tasks one-by-one until @from is empty.  This fails iff
4352	 * ->can_attach() fails.
4353	 */
4354	do {
4355		css_task_iter_start(&from->self, &it);
4356		task = css_task_iter_next(&it);
4357		if (task)
4358			get_task_struct(task);
4359		css_task_iter_end(&it);
4360
4361		if (task) {
4362			ret = cgroup_migrate(task, false, to->root);
4363			put_task_struct(task);
4364		}
4365	} while (task && !ret);
4366out_err:
4367	cgroup_migrate_finish(&preloaded_csets);
4368	mutex_unlock(&cgroup_mutex);
4369	return ret;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4370}
4371
4372/*
4373 * Stuff for reading the 'tasks'/'procs' files.
4374 *
4375 * Reading this file can return large amounts of data if a cgroup has
4376 * *lots* of attached tasks. So it may need several calls to read(),
4377 * but we cannot guarantee that the information we produce is correct
4378 * unless we produce it entirely atomically.
4379 *
4380 */
4381
4382/* which pidlist file are we talking about? */
4383enum cgroup_filetype {
4384	CGROUP_FILE_PROCS,
4385	CGROUP_FILE_TASKS,
4386};
4387
4388/*
4389 * A pidlist is a list of pids that virtually represents the contents of one
4390 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
4391 * a pair (one each for procs, tasks) for each pid namespace that's relevant
4392 * to the cgroup.
4393 */
4394struct cgroup_pidlist {
4395	/*
4396	 * used to find which pidlist is wanted. doesn't change as long as
4397	 * this particular list stays in the list.
4398	*/
4399	struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
4400	/* array of xids */
4401	pid_t *list;
4402	/* how many elements the above list has */
4403	int length;
 
 
4404	/* each of these stored in a list by its cgroup */
4405	struct list_head links;
4406	/* pointer to the cgroup we belong to, for list removal purposes */
4407	struct cgroup *owner;
4408	/* for delayed destruction */
4409	struct delayed_work destroy_dwork;
4410};
4411
4412/*
4413 * The following two functions "fix" the issue where there are more pids
4414 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
4415 * TODO: replace with a kernel-wide solution to this problem
4416 */
4417#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
4418static void *pidlist_allocate(int count)
4419{
4420	if (PIDLIST_TOO_LARGE(count))
4421		return vmalloc(count * sizeof(pid_t));
4422	else
4423		return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
4424}
4425
4426static void pidlist_free(void *p)
4427{
4428	kvfree(p);
4429}
4430
4431/*
4432 * Used to destroy all pidlists lingering waiting for destroy timer.  None
4433 * should be left afterwards.
4434 */
4435static void cgroup_pidlist_destroy_all(struct cgroup *cgrp)
4436{
4437	struct cgroup_pidlist *l, *tmp_l;
4438
4439	mutex_lock(&cgrp->pidlist_mutex);
4440	list_for_each_entry_safe(l, tmp_l, &cgrp->pidlists, links)
4441		mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, 0);
4442	mutex_unlock(&cgrp->pidlist_mutex);
4443
4444	flush_workqueue(cgroup_pidlist_destroy_wq);
4445	BUG_ON(!list_empty(&cgrp->pidlists));
4446}
4447
4448static void cgroup_pidlist_destroy_work_fn(struct work_struct *work)
4449{
4450	struct delayed_work *dwork = to_delayed_work(work);
4451	struct cgroup_pidlist *l = container_of(dwork, struct cgroup_pidlist,
4452						destroy_dwork);
4453	struct cgroup_pidlist *tofree = NULL;
4454
4455	mutex_lock(&l->owner->pidlist_mutex);
4456
4457	/*
4458	 * Destroy iff we didn't get queued again.  The state won't change
4459	 * as destroy_dwork can only be queued while locked.
4460	 */
4461	if (!delayed_work_pending(dwork)) {
4462		list_del(&l->links);
4463		pidlist_free(l->list);
4464		put_pid_ns(l->key.ns);
4465		tofree = l;
4466	}
4467
4468	mutex_unlock(&l->owner->pidlist_mutex);
4469	kfree(tofree);
4470}
4471
4472/*
4473 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
4474 * Returns the number of unique elements.
4475 */
4476static int pidlist_uniq(pid_t *list, int length)
 
 
 
 
4477{
4478	int src, dest = 1;
 
 
4479
4480	/*
4481	 * we presume the 0th element is unique, so i starts at 1. trivial
4482	 * edge cases first; no work needs to be done for either
4483	 */
4484	if (length == 0 || length == 1)
4485		return length;
4486	/* src and dest walk down the list; dest counts unique elements */
4487	for (src = 1; src < length; src++) {
4488		/* find next unique element */
4489		while (list[src] == list[src-1]) {
4490			src++;
4491			if (src == length)
4492				goto after;
4493		}
4494		/* dest always points to where the next unique element goes */
4495		list[dest] = list[src];
4496		dest++;
4497	}
4498after:
 
 
 
 
 
 
 
 
 
 
4499	return dest;
4500}
4501
4502/*
4503 * The two pid files - task and cgroup.procs - guaranteed that the result
4504 * is sorted, which forced this whole pidlist fiasco.  As pid order is
4505 * different per namespace, each namespace needs differently sorted list,
4506 * making it impossible to use, for example, single rbtree of member tasks
4507 * sorted by task pointer.  As pidlists can be fairly large, allocating one
4508 * per open file is dangerous, so cgroup had to implement shared pool of
4509 * pidlists keyed by cgroup and namespace.
4510 *
4511 * All this extra complexity was caused by the original implementation
4512 * committing to an entirely unnecessary property.  In the long term, we
4513 * want to do away with it.  Explicitly scramble sort order if on the
4514 * default hierarchy so that no such expectation exists in the new
4515 * interface.
4516 *
4517 * Scrambling is done by swapping every two consecutive bits, which is
4518 * non-identity one-to-one mapping which disturbs sort order sufficiently.
4519 */
4520static pid_t pid_fry(pid_t pid)
4521{
4522	unsigned a = pid & 0x55555555;
4523	unsigned b = pid & 0xAAAAAAAA;
4524
4525	return (a << 1) | (b >> 1);
4526}
4527
4528static pid_t cgroup_pid_fry(struct cgroup *cgrp, pid_t pid)
4529{
4530	if (cgroup_on_dfl(cgrp))
4531		return pid_fry(pid);
4532	else
4533		return pid;
4534}
4535
4536static int cmppid(const void *a, const void *b)
4537{
4538	return *(pid_t *)a - *(pid_t *)b;
4539}
4540
4541static int fried_cmppid(const void *a, const void *b)
4542{
4543	return pid_fry(*(pid_t *)a) - pid_fry(*(pid_t *)b);
4544}
4545
4546static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
4547						  enum cgroup_filetype type)
4548{
4549	struct cgroup_pidlist *l;
4550	/* don't need task_nsproxy() if we're looking at ourself */
4551	struct pid_namespace *ns = task_active_pid_ns(current);
4552
4553	lockdep_assert_held(&cgrp->pidlist_mutex);
4554
4555	list_for_each_entry(l, &cgrp->pidlists, links)
4556		if (l->key.type == type && l->key.ns == ns)
4557			return l;
4558	return NULL;
4559}
4560
4561/*
4562 * find the appropriate pidlist for our purpose (given procs vs tasks)
4563 * returns with the lock on that pidlist already held, and takes care
4564 * of the use count, or returns NULL with no locks held if we're out of
4565 * memory.
4566 */
4567static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
4568						enum cgroup_filetype type)
4569{
4570	struct cgroup_pidlist *l;
 
 
4571
4572	lockdep_assert_held(&cgrp->pidlist_mutex);
4573
4574	l = cgroup_pidlist_find(cgrp, type);
4575	if (l)
4576		return l;
4577
 
 
 
 
 
 
 
 
 
4578	/* entry not found; create a new one */
4579	l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
4580	if (!l)
 
4581		return l;
4582
4583	INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
 
4584	l->key.type = type;
4585	/* don't need task_nsproxy() if we're looking at ourself */
4586	l->key.ns = get_pid_ns(task_active_pid_ns(current));
 
4587	l->owner = cgrp;
4588	list_add(&l->links, &cgrp->pidlists);
 
4589	return l;
4590}
4591
4592/*
4593 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
4594 */
4595static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
4596			      struct cgroup_pidlist **lp)
4597{
4598	pid_t *array;
4599	int length;
4600	int pid, n = 0; /* used for populating the array */
4601	struct css_task_iter it;
4602	struct task_struct *tsk;
4603	struct cgroup_pidlist *l;
4604
4605	lockdep_assert_held(&cgrp->pidlist_mutex);
4606
4607	/*
4608	 * If cgroup gets more users after we read count, we won't have
4609	 * enough space - tough.  This race is indistinguishable to the
4610	 * caller from the case that the additional cgroup users didn't
4611	 * show up until sometime later on.
4612	 */
4613	length = cgroup_task_count(cgrp);
4614	array = pidlist_allocate(length);
4615	if (!array)
4616		return -ENOMEM;
4617	/* now, populate the array */
4618	css_task_iter_start(&cgrp->self, &it);
4619	while ((tsk = css_task_iter_next(&it))) {
4620		if (unlikely(n == length))
4621			break;
4622		/* get tgid or pid for procs or tasks file respectively */
4623		if (type == CGROUP_FILE_PROCS)
4624			pid = task_tgid_vnr(tsk);
4625		else
4626			pid = task_pid_vnr(tsk);
4627		if (pid > 0) /* make sure to only use valid results */
4628			array[n++] = pid;
4629	}
4630	css_task_iter_end(&it);
4631	length = n;
4632	/* now sort & (if procs) strip out duplicates */
4633	if (cgroup_on_dfl(cgrp))
4634		sort(array, length, sizeof(pid_t), fried_cmppid, NULL);
4635	else
4636		sort(array, length, sizeof(pid_t), cmppid, NULL);
4637	if (type == CGROUP_FILE_PROCS)
4638		length = pidlist_uniq(array, length);
4639
4640	l = cgroup_pidlist_find_create(cgrp, type);
4641	if (!l) {
4642		pidlist_free(array);
4643		return -ENOMEM;
4644	}
4645
4646	/* store array, freeing old if necessary */
4647	pidlist_free(l->list);
4648	l->list = array;
4649	l->length = length;
 
 
4650	*lp = l;
4651	return 0;
4652}
4653
4654/**
4655 * cgroupstats_build - build and fill cgroupstats
4656 * @stats: cgroupstats to fill information into
4657 * @dentry: A dentry entry belonging to the cgroup for which stats have
4658 * been requested.
4659 *
4660 * Build and fill cgroupstats so that taskstats can export it to user
4661 * space.
4662 */
4663int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
4664{
4665	struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
4666	struct cgroup *cgrp;
4667	struct css_task_iter it;
4668	struct task_struct *tsk;
4669
4670	/* it should be kernfs_node belonging to cgroupfs and is a directory */
4671	if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
4672	    kernfs_type(kn) != KERNFS_DIR)
4673		return -EINVAL;
4674
4675	mutex_lock(&cgroup_mutex);
4676
4677	/*
4678	 * We aren't being called from kernfs and there's no guarantee on
4679	 * @kn->priv's validity.  For this and css_tryget_online_from_dir(),
4680	 * @kn->priv is RCU safe.  Let's do the RCU dancing.
4681	 */
4682	rcu_read_lock();
4683	cgrp = rcu_dereference(kn->priv);
4684	if (!cgrp || cgroup_is_dead(cgrp)) {
4685		rcu_read_unlock();
4686		mutex_unlock(&cgroup_mutex);
4687		return -ENOENT;
4688	}
4689	rcu_read_unlock();
4690
4691	css_task_iter_start(&cgrp->self, &it);
4692	while ((tsk = css_task_iter_next(&it))) {
 
 
 
4693		switch (tsk->state) {
4694		case TASK_RUNNING:
4695			stats->nr_running++;
4696			break;
4697		case TASK_INTERRUPTIBLE:
4698			stats->nr_sleeping++;
4699			break;
4700		case TASK_UNINTERRUPTIBLE:
4701			stats->nr_uninterruptible++;
4702			break;
4703		case TASK_STOPPED:
4704			stats->nr_stopped++;
4705			break;
4706		default:
4707			if (delayacct_is_task_waiting_on_io(tsk))
4708				stats->nr_io_wait++;
4709			break;
4710		}
4711	}
4712	css_task_iter_end(&it);
4713
4714	mutex_unlock(&cgroup_mutex);
4715	return 0;
4716}
4717
4718
4719/*
4720 * seq_file methods for the tasks/procs files. The seq_file position is the
4721 * next pid to display; the seq_file iterator is a pointer to the pid
4722 * in the cgroup->l->list array.
4723 */
4724
4725static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
4726{
4727	/*
4728	 * Initially we receive a position value that corresponds to
4729	 * one more than the last pid shown (or 0 on the first call or
4730	 * after a seek to the start). Use a binary-search to find the
4731	 * next pid to display, if any
4732	 */
4733	struct kernfs_open_file *of = s->private;
4734	struct cgroup *cgrp = seq_css(s)->cgroup;
4735	struct cgroup_pidlist *l;
4736	enum cgroup_filetype type = seq_cft(s)->private;
4737	int index = 0, pid = *pos;
4738	int *iter, ret;
4739
4740	mutex_lock(&cgrp->pidlist_mutex);
4741
4742	/*
4743	 * !NULL @of->priv indicates that this isn't the first start()
4744	 * after open.  If the matching pidlist is around, we can use that.
4745	 * Look for it.  Note that @of->priv can't be used directly.  It
4746	 * could already have been destroyed.
4747	 */
4748	if (of->priv)
4749		of->priv = cgroup_pidlist_find(cgrp, type);
4750
4751	/*
4752	 * Either this is the first start() after open or the matching
4753	 * pidlist has been destroyed inbetween.  Create a new one.
4754	 */
4755	if (!of->priv) {
4756		ret = pidlist_array_load(cgrp, type,
4757					 (struct cgroup_pidlist **)&of->priv);
4758		if (ret)
4759			return ERR_PTR(ret);
4760	}
4761	l = of->priv;
4762
 
4763	if (pid) {
4764		int end = l->length;
4765
4766		while (index < end) {
4767			int mid = (index + end) / 2;
4768			if (cgroup_pid_fry(cgrp, l->list[mid]) == pid) {
4769				index = mid;
4770				break;
4771			} else if (cgroup_pid_fry(cgrp, l->list[mid]) <= pid)
4772				index = mid + 1;
4773			else
4774				end = mid;
4775		}
4776	}
4777	/* If we're off the end of the array, we're done */
4778	if (index >= l->length)
4779		return NULL;
4780	/* Update the abstract position to be the actual pid that we found */
4781	iter = l->list + index;
4782	*pos = cgroup_pid_fry(cgrp, *iter);
4783	return iter;
4784}
4785
4786static void cgroup_pidlist_stop(struct seq_file *s, void *v)
4787{
4788	struct kernfs_open_file *of = s->private;
4789	struct cgroup_pidlist *l = of->priv;
4790
4791	if (l)
4792		mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
4793				 CGROUP_PIDLIST_DESTROY_DELAY);
4794	mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
4795}
4796
4797static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
4798{
4799	struct kernfs_open_file *of = s->private;
4800	struct cgroup_pidlist *l = of->priv;
4801	pid_t *p = v;
4802	pid_t *end = l->list + l->length;
4803	/*
4804	 * Advance to the next pid in the array. If this goes off the
4805	 * end, we're done
4806	 */
4807	p++;
4808	if (p >= end) {
4809		return NULL;
4810	} else {
4811		*pos = cgroup_pid_fry(seq_css(s)->cgroup, *p);
4812		return p;
4813	}
4814}
4815
4816static int cgroup_pidlist_show(struct seq_file *s, void *v)
4817{
4818	seq_printf(s, "%d\n", *(int *)v);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4819
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4820	return 0;
4821}
 
 
 
 
 
 
 
 
4822
4823static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
4824					 struct cftype *cft)
4825{
4826	return notify_on_release(css->cgroup);
4827}
4828
4829static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
4830					  struct cftype *cft, u64 val)
 
4831{
 
4832	if (val)
4833		set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
4834	else
4835		clear_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
4836	return 0;
4837}
4838
4839static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
4840				      struct cftype *cft)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4841{
4842	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4843}
4844
4845static int cgroup_clone_children_write(struct cgroup_subsys_state *css,
4846				       struct cftype *cft, u64 val)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4847{
4848	if (val)
4849		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
4850	else
4851		clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
4852	return 0;
4853}
4854
4855/* cgroup core interface files for the default hierarchy */
4856static struct cftype cgroup_dfl_base_files[] = {
4857	{
4858		.name = "cgroup.procs",
4859		.file_offset = offsetof(struct cgroup, procs_file),
4860		.seq_start = cgroup_pidlist_start,
4861		.seq_next = cgroup_pidlist_next,
4862		.seq_stop = cgroup_pidlist_stop,
4863		.seq_show = cgroup_pidlist_show,
4864		.private = CGROUP_FILE_PROCS,
4865		.write = cgroup_procs_write,
4866	},
4867	{
4868		.name = "cgroup.controllers",
4869		.seq_show = cgroup_controllers_show,
 
 
 
4870	},
4871	{
4872		.name = "cgroup.subtree_control",
4873		.seq_show = cgroup_subtree_control_show,
4874		.write = cgroup_subtree_control_write,
 
 
4875	},
4876	{
4877		.name = "cgroup.events",
4878		.flags = CFTYPE_NOT_ON_ROOT,
4879		.file_offset = offsetof(struct cgroup, events_file),
4880		.seq_show = cgroup_events_show,
4881	},
4882	{ }	/* terminate */
4883};
4884
4885/* cgroup core interface files for the legacy hierarchies */
4886static struct cftype cgroup_legacy_base_files[] = {
4887	{
4888		.name = "cgroup.procs",
4889		.seq_start = cgroup_pidlist_start,
4890		.seq_next = cgroup_pidlist_next,
4891		.seq_stop = cgroup_pidlist_stop,
4892		.seq_show = cgroup_pidlist_show,
4893		.private = CGROUP_FILE_PROCS,
4894		.write = cgroup_procs_write,
4895	},
4896	{
4897		.name = "cgroup.clone_children",
4898		.read_u64 = cgroup_clone_children_read,
4899		.write_u64 = cgroup_clone_children_write,
4900	},
4901	{
4902		.name = "cgroup.sane_behavior",
4903		.flags = CFTYPE_ONLY_ON_ROOT,
4904		.seq_show = cgroup_sane_behavior_show,
4905	},
4906	{
4907		.name = "tasks",
4908		.seq_start = cgroup_pidlist_start,
4909		.seq_next = cgroup_pidlist_next,
4910		.seq_stop = cgroup_pidlist_stop,
4911		.seq_show = cgroup_pidlist_show,
4912		.private = CGROUP_FILE_TASKS,
4913		.write = cgroup_tasks_write,
4914	},
4915	{
4916		.name = "notify_on_release",
4917		.read_u64 = cgroup_read_notify_on_release,
4918		.write_u64 = cgroup_write_notify_on_release,
4919	},
4920	{
4921		.name = "release_agent",
4922		.flags = CFTYPE_ONLY_ON_ROOT,
4923		.seq_show = cgroup_release_agent_show,
4924		.write = cgroup_release_agent_write,
4925		.max_write_len = PATH_MAX - 1,
4926	},
4927	{ }	/* terminate */
4928};
4929
4930/*
4931 * css destruction is four-stage process.
4932 *
4933 * 1. Destruction starts.  Killing of the percpu_ref is initiated.
4934 *    Implemented in kill_css().
4935 *
4936 * 2. When the percpu_ref is confirmed to be visible as killed on all CPUs
4937 *    and thus css_tryget_online() is guaranteed to fail, the css can be
4938 *    offlined by invoking offline_css().  After offlining, the base ref is
4939 *    put.  Implemented in css_killed_work_fn().
4940 *
4941 * 3. When the percpu_ref reaches zero, the only possible remaining
4942 *    accessors are inside RCU read sections.  css_release() schedules the
4943 *    RCU callback.
4944 *
4945 * 4. After the grace period, the css can be freed.  Implemented in
4946 *    css_free_work_fn().
4947 *
4948 * It is actually hairier because both step 2 and 4 require process context
4949 * and thus involve punting to css->destroy_work adding two additional
4950 * steps to the already complex sequence.
4951 */
4952static void css_free_work_fn(struct work_struct *work)
4953{
4954	struct cgroup_subsys_state *css =
4955		container_of(work, struct cgroup_subsys_state, destroy_work);
4956	struct cgroup_subsys *ss = css->ss;
4957	struct cgroup *cgrp = css->cgroup;
4958
4959	percpu_ref_exit(&css->refcnt);
4960
4961	if (ss) {
4962		/* css free path */
4963		struct cgroup_subsys_state *parent = css->parent;
4964		int id = css->id;
4965
4966		ss->css_free(css);
4967		cgroup_idr_remove(&ss->css_idr, id);
4968		cgroup_put(cgrp);
4969
4970		if (parent)
4971			css_put(parent);
4972	} else {
4973		/* cgroup free path */
4974		atomic_dec(&cgrp->root->nr_cgrps);
4975		cgroup_pidlist_destroy_all(cgrp);
4976		cancel_work_sync(&cgrp->release_agent_work);
4977
4978		if (cgroup_parent(cgrp)) {
4979			/*
4980			 * We get a ref to the parent, and put the ref when
4981			 * this cgroup is being freed, so it's guaranteed
4982			 * that the parent won't be destroyed before its
4983			 * children.
4984			 */
4985			cgroup_put(cgroup_parent(cgrp));
4986			kernfs_put(cgrp->kn);
4987			kfree(cgrp);
4988		} else {
4989			/*
4990			 * This is root cgroup's refcnt reaching zero,
4991			 * which indicates that the root should be
4992			 * released.
4993			 */
4994			cgroup_destroy_root(cgrp->root);
4995		}
4996	}
4997}
4998
4999static void css_free_rcu_fn(struct rcu_head *rcu_head)
5000{
5001	struct cgroup_subsys_state *css =
5002		container_of(rcu_head, struct cgroup_subsys_state, rcu_head);
5003
5004	INIT_WORK(&css->destroy_work, css_free_work_fn);
5005	queue_work(cgroup_destroy_wq, &css->destroy_work);
5006}
5007
5008static void css_release_work_fn(struct work_struct *work)
5009{
5010	struct cgroup_subsys_state *css =
5011		container_of(work, struct cgroup_subsys_state, destroy_work);
5012	struct cgroup_subsys *ss = css->ss;
5013	struct cgroup *cgrp = css->cgroup;
5014
5015	mutex_lock(&cgroup_mutex);
5016
5017	css->flags |= CSS_RELEASED;
5018	list_del_rcu(&css->sibling);
5019
5020	if (ss) {
5021		/* css release path */
5022		cgroup_idr_replace(&ss->css_idr, NULL, css->id);
5023		if (ss->css_released)
5024			ss->css_released(css);
5025	} else {
5026		/* cgroup release path */
5027		cgroup_idr_remove(&cgrp->root->cgroup_idr, cgrp->id);
5028		cgrp->id = -1;
5029
 
 
 
5030		/*
5031		 * There are two control paths which try to determine
5032		 * cgroup from dentry without going through kernfs -
5033		 * cgroupstats_build() and css_tryget_online_from_dir().
5034		 * Those are supported by RCU protecting clearing of
5035		 * cgrp->kn->priv backpointer.
5036		 */
5037		if (cgrp->kn)
5038			RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv,
5039					 NULL);
5040	}
5041
5042	mutex_unlock(&cgroup_mutex);
5043
5044	call_rcu(&css->rcu_head, css_free_rcu_fn);
5045}
5046
5047static void css_release(struct percpu_ref *ref)
5048{
5049	struct cgroup_subsys_state *css =
5050		container_of(ref, struct cgroup_subsys_state, refcnt);
5051
5052	INIT_WORK(&css->destroy_work, css_release_work_fn);
5053	queue_work(cgroup_destroy_wq, &css->destroy_work);
 
 
 
5054}
5055
5056static void init_and_link_css(struct cgroup_subsys_state *css,
5057			      struct cgroup_subsys *ss, struct cgroup *cgrp)
 
5058{
5059	lockdep_assert_held(&cgroup_mutex);
5060
5061	cgroup_get(cgrp);
5062
5063	memset(css, 0, sizeof(*css));
5064	css->cgroup = cgrp;
5065	css->ss = ss;
5066	INIT_LIST_HEAD(&css->sibling);
5067	INIT_LIST_HEAD(&css->children);
5068	css->serial_nr = css_serial_nr_next++;
5069	atomic_set(&css->online_cnt, 0);
5070
5071	if (cgroup_parent(cgrp)) {
5072		css->parent = cgroup_css(cgroup_parent(cgrp), ss);
5073		css_get(css->parent);
5074	}
5075
5076	BUG_ON(cgroup_css(cgrp, ss));
 
 
 
 
 
 
 
 
5077}
5078
5079/* invoke ->css_online() on a new CSS and mark it online if successful */
5080static int online_css(struct cgroup_subsys_state *css)
5081{
5082	struct cgroup_subsys *ss = css->ss;
5083	int ret = 0;
5084
5085	lockdep_assert_held(&cgroup_mutex);
5086
5087	if (ss->css_online)
5088		ret = ss->css_online(css);
5089	if (!ret) {
5090		css->flags |= CSS_ONLINE;
5091		rcu_assign_pointer(css->cgroup->subsys[ss->id], css);
5092
5093		atomic_inc(&css->online_cnt);
5094		if (css->parent)
5095			atomic_inc(&css->parent->online_cnt);
 
5096	}
5097	return ret;
5098}
5099
5100/* if the CSS is online, invoke ->css_offline() on it and mark it offline */
5101static void offline_css(struct cgroup_subsys_state *css)
5102{
5103	struct cgroup_subsys *ss = css->ss;
5104
5105	lockdep_assert_held(&cgroup_mutex);
5106
5107	if (!(css->flags & CSS_ONLINE))
5108		return;
5109
5110	if (ss->css_reset)
5111		ss->css_reset(css);
5112
5113	if (ss->css_offline)
5114		ss->css_offline(css);
5115
5116	css->flags &= ~CSS_ONLINE;
5117	RCU_INIT_POINTER(css->cgroup->subsys[ss->id], NULL);
5118
5119	wake_up_all(&css->cgroup->offline_waitq);
 
 
 
 
 
 
5120}
5121
5122/**
5123 * css_create - create a cgroup_subsys_state
5124 * @cgrp: the cgroup new css will be associated with
5125 * @ss: the subsys of new css
5126 *
5127 * Create a new css associated with @cgrp - @ss pair.  On success, the new
5128 * css is online and installed in @cgrp.  This function doesn't create the
5129 * interface files.  Returns 0 on success, -errno on failure.
5130 */
5131static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
5132					      struct cgroup_subsys *ss)
5133{
5134	struct cgroup *parent = cgroup_parent(cgrp);
5135	struct cgroup_subsys_state *parent_css = cgroup_css(parent, ss);
5136	struct cgroup_subsys_state *css;
5137	int err;
 
5138
5139	lockdep_assert_held(&cgroup_mutex);
 
 
5140
5141	css = ss->css_alloc(parent_css);
5142	if (IS_ERR(css))
5143		return css;
 
 
 
5144
5145	init_and_link_css(css, ss, cgrp);
5146
5147	err = percpu_ref_init(&css->refcnt, css_release, 0, GFP_KERNEL);
5148	if (err)
5149		goto err_free_css;
5150
5151	err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL);
5152	if (err < 0)
5153		goto err_free_percpu_ref;
5154	css->id = err;
5155
5156	/* @css is ready to be brought online now, make it visible */
5157	list_add_tail_rcu(&css->sibling, &parent_css->children);
5158	cgroup_idr_replace(&ss->css_idr, css, css->id);
5159
5160	err = online_css(css);
5161	if (err)
5162		goto err_list_del;
5163
5164	if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
5165	    cgroup_parent(parent)) {
5166		pr_warn("%s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
5167			current->comm, current->pid, ss->name);
5168		if (!strcmp(ss->name, "memory"))
5169			pr_warn("\"memory\" requires setting use_hierarchy to 1 on the root\n");
5170		ss->warned_broken_hierarchy = true;
 
 
 
 
 
 
 
 
 
5171	}
5172
5173	return css;
 
 
 
5174
5175err_list_del:
5176	list_del_rcu(&css->sibling);
5177	cgroup_idr_remove(&ss->css_idr, css->id);
5178err_free_percpu_ref:
5179	percpu_ref_exit(&css->refcnt);
5180err_free_css:
5181	call_rcu(&css->rcu_head, css_free_rcu_fn);
5182	return ERR_PTR(err);
5183}
5184
5185static struct cgroup *cgroup_create(struct cgroup *parent)
5186{
5187	struct cgroup_root *root = parent->root;
5188	struct cgroup *cgrp, *tcgrp;
5189	int level = parent->level + 1;
5190	int ret;
5191
5192	/* allocate the cgroup and its ID, 0 is reserved for the root */
5193	cgrp = kzalloc(sizeof(*cgrp) +
5194		       sizeof(cgrp->ancestor_ids[0]) * (level + 1), GFP_KERNEL);
5195	if (!cgrp)
5196		return ERR_PTR(-ENOMEM);
5197
5198	ret = percpu_ref_init(&cgrp->self.refcnt, css_release, 0, GFP_KERNEL);
5199	if (ret)
5200		goto out_free_cgrp;
5201
5202	/*
5203	 * Temporarily set the pointer to NULL, so idr_find() won't return
5204	 * a half-baked cgroup.
5205	 */
5206	cgrp->id = cgroup_idr_alloc(&root->cgroup_idr, NULL, 2, 0, GFP_KERNEL);
5207	if (cgrp->id < 0) {
5208		ret = -ENOMEM;
5209		goto out_cancel_ref;
5210	}
5211
5212	init_cgroup_housekeeping(cgrp);
 
5213
5214	cgrp->self.parent = &parent->self;
5215	cgrp->root = root;
5216	cgrp->level = level;
5217
5218	for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp))
5219		cgrp->ancestor_ids[tcgrp->level] = tcgrp->id;
5220
5221	if (notify_on_release(parent))
5222		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
 
 
 
 
 
 
 
 
 
5223
5224	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
5225		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
5226
5227	cgrp->self.serial_nr = css_serial_nr_next++;
 
5228
5229	/* allocation complete, commit to creation */
5230	list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);
5231	atomic_inc(&root->nr_cgrps);
5232	cgroup_get(parent);
5233
5234	/*
5235	 * @cgrp is now fully operational.  If something fails after this
5236	 * point, it'll be released via the normal destruction path.
5237	 */
5238	cgroup_idr_replace(&root->cgroup_idr, cgrp, cgrp->id);
5239
5240	/*
5241	 * On the default hierarchy, a child doesn't automatically inherit
5242	 * subtree_control from the parent.  Each is configured manually.
5243	 */
5244	if (!cgroup_on_dfl(cgrp))
5245		cgrp->subtree_control = cgroup_control(cgrp);
5246
5247	cgroup_propagate_control(cgrp);
 
 
 
 
 
 
 
 
 
 
 
5248
5249	/* @cgrp doesn't have dir yet so the following will only create csses */
5250	ret = cgroup_apply_control_enable(cgrp);
5251	if (ret)
5252		goto out_destroy;
 
 
 
 
5253
5254	return cgrp;
 
 
5255
5256out_cancel_ref:
5257	percpu_ref_exit(&cgrp->self.refcnt);
5258out_free_cgrp:
5259	kfree(cgrp);
5260	return ERR_PTR(ret);
5261out_destroy:
5262	cgroup_destroy_locked(cgrp);
5263	return ERR_PTR(ret);
 
 
 
 
 
5264}
5265
5266static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
5267			umode_t mode)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5268{
5269	struct cgroup *parent, *cgrp;
5270	struct kernfs_node *kn;
5271	int ret;
5272
5273	/* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
5274	if (strchr(name, '\n'))
5275		return -EINVAL;
5276
5277	parent = cgroup_kn_lock_live(parent_kn, false);
5278	if (!parent)
5279		return -ENODEV;
 
 
 
 
5280
5281	cgrp = cgroup_create(parent);
5282	if (IS_ERR(cgrp)) {
5283		ret = PTR_ERR(cgrp);
5284		goto out_unlock;
5285	}
5286
5287	/* create the directory */
5288	kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
5289	if (IS_ERR(kn)) {
5290		ret = PTR_ERR(kn);
5291		goto out_destroy;
5292	}
5293	cgrp->kn = kn;
5294
5295	/*
5296	 * This extra ref will be put in cgroup_free_fn() and guarantees
5297	 * that @cgrp->kn is always accessible.
 
5298	 */
5299	kernfs_get(kn);
5300
5301	ret = cgroup_kn_set_ugid(kn);
5302	if (ret)
5303		goto out_destroy;
5304
5305	ret = css_populate_dir(&cgrp->self);
5306	if (ret)
5307		goto out_destroy;
5308
5309	ret = cgroup_apply_control_enable(cgrp);
5310	if (ret)
5311		goto out_destroy;
5312
5313	/* let's create and online css's */
5314	kernfs_activate(kn);
5315
5316	ret = 0;
5317	goto out_unlock;
 
 
 
 
 
5318
5319out_destroy:
5320	cgroup_destroy_locked(cgrp);
5321out_unlock:
5322	cgroup_kn_unlock(parent_kn);
5323	return ret;
5324}
5325
5326/*
5327 * This is called when the refcnt of a css is confirmed to be killed.
5328 * css_tryget_online() is now guaranteed to fail.  Tell the subsystem to
5329 * initate destruction and put the css ref from kill_css().
5330 */
5331static void css_killed_work_fn(struct work_struct *work)
5332{
5333	struct cgroup_subsys_state *css =
5334		container_of(work, struct cgroup_subsys_state, destroy_work);
 
 
 
 
5335
 
 
5336	mutex_lock(&cgroup_mutex);
 
 
 
 
 
 
 
 
 
5337
5338	do {
5339		offline_css(css);
5340		css_put(css);
5341		/* @css can't go away while we're holding cgroup_mutex */
5342		css = css->parent;
5343	} while (css && atomic_dec_and_test(&css->online_cnt));
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5344
5345	mutex_unlock(&cgroup_mutex);
 
5346}
5347
5348/* css kill confirmation processing requires process context, bounce */
5349static void css_killed_ref_fn(struct percpu_ref *ref)
5350{
5351	struct cgroup_subsys_state *css =
5352		container_of(ref, struct cgroup_subsys_state, refcnt);
5353
5354	if (atomic_dec_and_test(&css->online_cnt)) {
5355		INIT_WORK(&css->destroy_work, css_killed_work_fn);
5356		queue_work(cgroup_destroy_wq, &css->destroy_work);
 
 
 
 
5357	}
5358}
5359
5360/**
5361 * kill_css - destroy a css
5362 * @css: css to destroy
5363 *
5364 * This function initiates destruction of @css by removing cgroup interface
5365 * files and putting its base reference.  ->css_offline() will be invoked
5366 * asynchronously once css_tryget_online() is guaranteed to fail and when
5367 * the reference count reaches zero, @css will be released.
5368 */
5369static void kill_css(struct cgroup_subsys_state *css)
5370{
5371	lockdep_assert_held(&cgroup_mutex);
5372
5373	/*
5374	 * This must happen before css is disassociated with its cgroup.
5375	 * See seq_css() for details.
5376	 */
5377	css_clear_dir(css);
5378
5379	/*
5380	 * Killing would put the base ref, but we need to keep it alive
5381	 * until after ->css_offline().
5382	 */
5383	css_get(css);
5384
5385	/*
5386	 * cgroup core guarantees that, by the time ->css_offline() is
5387	 * invoked, no new css reference will be given out via
5388	 * css_tryget_online().  We can't simply call percpu_ref_kill() and
5389	 * proceed to offlining css's because percpu_ref_kill() doesn't
5390	 * guarantee that the ref is seen as killed on all CPUs on return.
5391	 *
5392	 * Use percpu_ref_kill_and_confirm() to get notifications as each
5393	 * css is confirmed to be seen as killed on all CPUs.
5394	 */
5395	percpu_ref_kill_and_confirm(&css->refcnt, css_killed_ref_fn);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5396}
5397
5398/**
5399 * cgroup_destroy_locked - the first stage of cgroup destruction
5400 * @cgrp: cgroup to be destroyed
5401 *
5402 * css's make use of percpu refcnts whose killing latency shouldn't be
5403 * exposed to userland and are RCU protected.  Also, cgroup core needs to
5404 * guarantee that css_tryget_online() won't succeed by the time
5405 * ->css_offline() is invoked.  To satisfy all the requirements,
5406 * destruction is implemented in the following two steps.
5407 *
5408 * s1. Verify @cgrp can be destroyed and mark it dying.  Remove all
5409 *     userland visible parts and start killing the percpu refcnts of
5410 *     css's.  Set up so that the next stage will be kicked off once all
5411 *     the percpu refcnts are confirmed to be killed.
5412 *
5413 * s2. Invoke ->css_offline(), mark the cgroup dead and proceed with the
5414 *     rest of destruction.  Once all cgroup references are gone, the
5415 *     cgroup is RCU-freed.
5416 *
5417 * This function implements s1.  After this step, @cgrp is gone as far as
5418 * the userland is concerned and a new cgroup with the same name may be
5419 * created.  As cgroup doesn't care about the names internally, this
5420 * doesn't cause any problem.
5421 */
5422static int cgroup_destroy_locked(struct cgroup *cgrp)
5423	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
5424{
 
5425	struct cgroup_subsys_state *css;
5426	struct cgrp_cset_link *link;
5427	int ssid;
5428
5429	lockdep_assert_held(&cgroup_mutex);
 
 
 
5430
5431	/*
5432	 * Only migration can raise populated from zero and we're already
5433	 * holding cgroup_mutex.
 
 
5434	 */
5435	if (cgroup_is_populated(cgrp))
5436		return -EBUSY;
5437
5438	/*
5439	 * Make sure there's no live children.  We can't test emptiness of
5440	 * ->self.children as dead children linger on it while being
5441	 * drained; otherwise, "rmdir parent/child parent" may fail.
5442	 */
5443	if (css_has_online_children(&cgrp->self))
5444		return -EBUSY;
 
 
 
 
 
 
 
5445
5446	/*
5447	 * Mark @cgrp and the associated csets dead.  The former prevents
5448	 * further task migration and child creation by disabling
5449	 * cgroup_lock_live_group().  The latter makes the csets ignored by
5450	 * the migration path.
5451	 */
5452	cgrp->self.flags &= ~CSS_ONLINE;
 
 
 
 
 
 
 
 
 
 
 
 
 
5453
5454	spin_lock_bh(&css_set_lock);
5455	list_for_each_entry(link, &cgrp->cset_links, cset_link)
5456		link->cset->dead = true;
5457	spin_unlock_bh(&css_set_lock);
 
 
 
 
 
 
 
5458
5459	/* initiate massacre of all css's */
5460	for_each_css(css, ssid, cgrp)
5461		kill_css(css);
 
 
 
 
 
 
 
 
 
 
 
 
 
5462
5463	/*
5464	 * Remove @cgrp directory along with the base files.  @cgrp has an
5465	 * extra ref on its kn.
 
 
 
 
5466	 */
5467	kernfs_remove(cgrp->kn);
5468
5469	check_for_release(cgroup_parent(cgrp));
 
 
5470
5471	/* put the base reference */
5472	percpu_ref_kill(&cgrp->self.refcnt);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5473
 
 
5474	return 0;
5475};
5476
5477static int cgroup_rmdir(struct kernfs_node *kn)
5478{
5479	struct cgroup *cgrp;
5480	int ret = 0;
5481
5482	cgrp = cgroup_kn_lock_live(kn, false);
5483	if (!cgrp)
5484		return 0;
5485
5486	ret = cgroup_destroy_locked(cgrp);
5487
5488	cgroup_kn_unlock(kn);
5489	return ret;
5490}
 
5491
5492static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
5493	.remount_fs		= cgroup_remount,
5494	.show_options		= cgroup_show_options,
5495	.mkdir			= cgroup_mkdir,
5496	.rmdir			= cgroup_rmdir,
5497	.rename			= cgroup_rename,
5498	.show_path		= cgroup_show_path,
5499};
5500
5501static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
5502{
5503	struct cgroup_subsys_state *css;
 
5504
5505	pr_debug("Initializing cgroup subsys %s\n", ss->name);
5506
5507	mutex_lock(&cgroup_mutex);
 
 
 
 
 
5508
5509	idr_init(&ss->css_idr);
5510	INIT_LIST_HEAD(&ss->cfts);
 
 
5511
5512	/* Create the root cgroup state for this subsystem */
5513	ss->root = &cgrp_dfl_root;
5514	css = ss->css_alloc(cgroup_css(&cgrp_dfl_root.cgrp, ss));
5515	/* We don't handle early failures gracefully */
5516	BUG_ON(IS_ERR(css));
5517	init_and_link_css(css, ss, &cgrp_dfl_root.cgrp);
5518
5519	/*
5520	 * Root csses are never destroyed and we can't initialize
5521	 * percpu_ref during early init.  Disable refcnting.
5522	 */
5523	css->flags |= CSS_NO_REF;
 
 
5524
5525	if (early) {
5526		/* allocation can't be done safely during early init */
5527		css->id = 1;
5528	} else {
5529		css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL);
5530		BUG_ON(css->id < 0);
5531	}
 
5532
5533	/* Update the init_css_set to contain a subsys
5534	 * pointer to this state - since the subsystem is
5535	 * newly registered, all tasks and hence the
5536	 * init_css_set is in the subsystem's root cgroup. */
5537	init_css_set.subsys[ss->id] = css;
5538
5539	have_fork_callback |= (bool)ss->fork << ss->id;
5540	have_exit_callback |= (bool)ss->exit << ss->id;
5541	have_free_callback |= (bool)ss->free << ss->id;
5542	have_canfork_callback |= (bool)ss->can_fork << ss->id;
5543
5544	/* At system boot, before all subsystems have been
5545	 * registered, no tasks have been forked, so we don't
5546	 * need to invoke fork callbacks here. */
5547	BUG_ON(!list_empty(&init_task.tasks));
5548
5549	BUG_ON(online_css(css));
5550
5551	mutex_unlock(&cgroup_mutex);
5552}
 
5553
5554/**
5555 * cgroup_init_early - cgroup initialization at system boot
5556 *
5557 * Initialize cgroups at system boot, and initialize any
5558 * subsystems that request early init.
5559 */
5560int __init cgroup_init_early(void)
5561{
5562	static struct cgroup_sb_opts __initdata opts;
5563	struct cgroup_subsys *ss;
5564	int i;
5565
5566	init_cgroup_root(&cgrp_dfl_root, &opts);
5567	cgrp_dfl_root.cgrp.self.flags |= CSS_NO_REF;
5568
5569	RCU_INIT_POINTER(init_task.cgroups, &init_css_set);
5570
5571	for_each_subsys(ss, i) {
5572		WARN(!ss->css_alloc || !ss->css_free || ss->name || ss->id,
5573		     "invalid cgroup_subsys %d:%s css_alloc=%p css_free=%p id:name=%d:%s\n",
5574		     i, cgroup_subsys_name[i], ss->css_alloc, ss->css_free,
5575		     ss->id, ss->name);
5576		WARN(strlen(cgroup_subsys_name[i]) > MAX_CGROUP_TYPE_NAMELEN,
5577		     "cgroup_subsys_name %s too long\n", cgroup_subsys_name[i]);
5578
5579		ss->id = i;
5580		ss->name = cgroup_subsys_name[i];
5581		if (!ss->legacy_name)
5582			ss->legacy_name = cgroup_subsys_name[i];
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5583
5584		if (ss->early_init)
5585			cgroup_init_subsys(ss, true);
5586	}
5587	return 0;
5588}
5589
5590static u16 cgroup_disable_mask __initdata;
5591
5592/**
5593 * cgroup_init - cgroup initialization
5594 *
5595 * Register cgroup filesystem and /proc file, and initialize
5596 * any subsystems that didn't request early init.
5597 */
5598int __init cgroup_init(void)
5599{
5600	struct cgroup_subsys *ss;
5601	int ssid;
5602
5603	BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
5604	BUG_ON(percpu_init_rwsem(&cgroup_threadgroup_rwsem));
5605	BUG_ON(cgroup_init_cftypes(NULL, cgroup_dfl_base_files));
5606	BUG_ON(cgroup_init_cftypes(NULL, cgroup_legacy_base_files));
5607
5608	get_user_ns(init_cgroup_ns.user_ns);
5609
5610	mutex_lock(&cgroup_mutex);
5611
5612	/*
5613	 * Add init_css_set to the hash table so that dfl_root can link to
5614	 * it during init.
5615	 */
5616	hash_add(css_set_table, &init_css_set.hlist,
5617		 css_set_hash(init_css_set.subsys));
5618
5619	BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0));
5620
5621	mutex_unlock(&cgroup_mutex);
5622
5623	for_each_subsys(ss, ssid) {
5624		if (ss->early_init) {
5625			struct cgroup_subsys_state *css =
5626				init_css_set.subsys[ss->id];
5627
5628			css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2,
5629						   GFP_KERNEL);
5630			BUG_ON(css->id < 0);
5631		} else {
5632			cgroup_init_subsys(ss, false);
5633		}
5634
5635		list_add_tail(&init_css_set.e_cset_node[ssid],
5636			      &cgrp_dfl_root.cgrp.e_csets[ssid]);
5637
5638		/*
5639		 * Setting dfl_root subsys_mask needs to consider the
5640		 * disabled flag and cftype registration needs kmalloc,
5641		 * both of which aren't available during early_init.
5642		 */
5643		if (cgroup_disable_mask & (1 << ssid)) {
5644			static_branch_disable(cgroup_subsys_enabled_key[ssid]);
5645			printk(KERN_INFO "Disabling %s control group subsystem\n",
5646			       ss->name);
5647			continue;
5648		}
5649
5650		if (cgroup_ssid_no_v1(ssid))
5651			printk(KERN_INFO "Disabling %s control group subsystem in v1 mounts\n",
5652			       ss->name);
5653
5654		cgrp_dfl_root.subsys_mask |= 1 << ss->id;
5655
5656		if (ss->implicit_on_dfl)
5657			cgrp_dfl_implicit_ss_mask |= 1 << ss->id;
5658		else if (!ss->dfl_cftypes)
5659			cgrp_dfl_inhibit_ss_mask |= 1 << ss->id;
5660
5661		if (ss->dfl_cftypes == ss->legacy_cftypes) {
5662			WARN_ON(cgroup_add_cftypes(ss, ss->dfl_cftypes));
5663		} else {
5664			WARN_ON(cgroup_add_dfl_cftypes(ss, ss->dfl_cftypes));
5665			WARN_ON(cgroup_add_legacy_cftypes(ss, ss->legacy_cftypes));
5666		}
5667
5668		if (ss->bind)
5669			ss->bind(init_css_set.subsys[ssid]);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5670	}
5671
5672	/* init_css_set.subsys[] has been updated, re-hash */
5673	hash_del(&init_css_set.hlist);
5674	hash_add(css_set_table, &init_css_set.hlist,
5675		 css_set_hash(init_css_set.subsys));
5676
5677	WARN_ON(sysfs_create_mount_point(fs_kobj, "cgroup"));
5678	WARN_ON(register_filesystem(&cgroup_fs_type));
5679	WARN_ON(register_filesystem(&cgroup2_fs_type));
5680	WARN_ON(!proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations));
5681
5682	return 0;
5683}
5684
5685static int __init cgroup_wq_init(void)
5686{
5687	/*
5688	 * There isn't much point in executing destruction path in
5689	 * parallel.  Good chunk is serialized with cgroup_mutex anyway.
5690	 * Use 1 for @max_active.
5691	 *
5692	 * We would prefer to do this in cgroup_init() above, but that
5693	 * is called before init_workqueues(): so leave this until after.
5694	 */
5695	cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
5696	BUG_ON(!cgroup_destroy_wq);
5697
5698	/*
5699	 * Used to destroy pidlists and separate to serve as flush domain.
5700	 * Cap @max_active to 1 too.
5701	 */
5702	cgroup_pidlist_destroy_wq = alloc_workqueue("cgroup_pidlist_destroy",
5703						    0, 1);
5704	BUG_ON(!cgroup_pidlist_destroy_wq);
5705
5706	return 0;
5707}
5708core_initcall(cgroup_wq_init);
5709
5710/*
5711 * proc_cgroup_show()
5712 *  - Print task's cgroup paths into seq_file, one line for each hierarchy
5713 *  - Used for /proc/<pid>/cgroup.
 
 
 
 
 
 
5714 */
5715int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
5716		     struct pid *pid, struct task_struct *tsk)
 
5717{
5718	char *buf, *path;
 
 
5719	int retval;
5720	struct cgroup_root *root;
5721
5722	retval = -ENOMEM;
5723	buf = kmalloc(PATH_MAX, GFP_KERNEL);
5724	if (!buf)
5725		goto out;
5726
 
 
 
 
 
 
 
 
5727	mutex_lock(&cgroup_mutex);
5728	spin_lock_bh(&css_set_lock);
5729
5730	for_each_root(root) {
5731		struct cgroup_subsys *ss;
5732		struct cgroup *cgrp;
5733		int ssid, count = 0;
5734
5735		if (root == &cgrp_dfl_root && !cgrp_dfl_visible)
5736			continue;
5737
5738		seq_printf(m, "%d:", root->hierarchy_id);
5739		if (root != &cgrp_dfl_root)
5740			for_each_subsys(ss, ssid)
5741				if (root->subsys_mask & (1 << ssid))
5742					seq_printf(m, "%s%s", count++ ? "," : "",
5743						   ss->legacy_name);
5744		if (strlen(root->name))
5745			seq_printf(m, "%sname=%s", count ? "," : "",
5746				   root->name);
5747		seq_putc(m, ':');
5748
5749		cgrp = task_cgroup_from_root(tsk, root);
5750
5751		/*
5752		 * On traditional hierarchies, all zombie tasks show up as
5753		 * belonging to the root cgroup.  On the default hierarchy,
5754		 * while a zombie doesn't show up in "cgroup.procs" and
5755		 * thus can't be migrated, its /proc/PID/cgroup keeps
5756		 * reporting the cgroup it belonged to before exiting.  If
5757		 * the cgroup is removed before the zombie is reaped,
5758		 * " (deleted)" is appended to the cgroup path.
5759		 */
5760		if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) {
5761			path = cgroup_path_ns_locked(cgrp, buf, PATH_MAX,
5762						current->nsproxy->cgroup_ns);
5763			if (!path) {
5764				retval = -ENAMETOOLONG;
5765				goto out_unlock;
5766			}
5767		} else {
5768			path = "/";
5769		}
5770
5771		seq_puts(m, path);
5772
5773		if (cgroup_on_dfl(cgrp) && cgroup_is_dead(cgrp))
5774			seq_puts(m, " (deleted)\n");
5775		else
5776			seq_putc(m, '\n');
5777	}
5778
5779	retval = 0;
5780out_unlock:
5781	spin_unlock_bh(&css_set_lock);
5782	mutex_unlock(&cgroup_mutex);
 
 
5783	kfree(buf);
5784out:
5785	return retval;
5786}
5787
 
 
 
 
 
 
 
 
 
 
 
 
 
5788/* Display information about each subsystem and each hierarchy */
5789static int proc_cgroupstats_show(struct seq_file *m, void *v)
5790{
5791	struct cgroup_subsys *ss;
5792	int i;
5793
5794	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
5795	/*
5796	 * ideally we don't want subsystems moving around while we do this.
5797	 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
5798	 * subsys/hierarchy state.
5799	 */
5800	mutex_lock(&cgroup_mutex);
5801
5802	for_each_subsys(ss, i)
 
 
5803		seq_printf(m, "%s\t%d\t%d\t%d\n",
5804			   ss->legacy_name, ss->root->hierarchy_id,
5805			   atomic_read(&ss->root->nr_cgrps),
5806			   cgroup_ssid_enabled(i));
5807
5808	mutex_unlock(&cgroup_mutex);
5809	return 0;
5810}
5811
5812static int cgroupstats_open(struct inode *inode, struct file *file)
5813{
5814	return single_open(file, proc_cgroupstats_show, NULL);
5815}
5816
5817static const struct file_operations proc_cgroupstats_operations = {
5818	.open = cgroupstats_open,
5819	.read = seq_read,
5820	.llseek = seq_lseek,
5821	.release = single_release,
5822};
5823
5824/**
5825 * cgroup_fork - initialize cgroup related fields during copy_process()
5826 * @child: pointer to task_struct of forking parent process.
5827 *
5828 * A task is associated with the init_css_set until cgroup_post_fork()
5829 * attaches it to the parent's css_set.  Empty cg_list indicates that
5830 * @child isn't holding reference to its css_set.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5831 */
5832void cgroup_fork(struct task_struct *child)
5833{
5834	RCU_INIT_POINTER(child->cgroups, &init_css_set);
 
 
 
 
 
 
 
5835	INIT_LIST_HEAD(&child->cg_list);
5836}
5837
5838/**
5839 * cgroup_can_fork - called on a new task before the process is exposed
5840 * @child: the task in question.
5841 *
5842 * This calls the subsystem can_fork() callbacks. If the can_fork() callback
5843 * returns an error, the fork aborts with that error code. This allows for
5844 * a cgroup subsystem to conditionally allow or deny new forks.
5845 */
5846int cgroup_can_fork(struct task_struct *child)
5847{
5848	struct cgroup_subsys *ss;
5849	int i, j, ret;
5850
5851	do_each_subsys_mask(ss, i, have_canfork_callback) {
5852		ret = ss->can_fork(child);
5853		if (ret)
5854			goto out_revert;
5855	} while_each_subsys_mask();
5856
5857	return 0;
5858
5859out_revert:
5860	for_each_subsys(ss, j) {
5861		if (j >= i)
5862			break;
5863		if (ss->cancel_fork)
5864			ss->cancel_fork(child);
5865	}
5866
5867	return ret;
5868}
5869
5870/**
5871 * cgroup_cancel_fork - called if a fork failed after cgroup_can_fork()
5872 * @child: the task in question
5873 *
5874 * This calls the cancel_fork() callbacks if a fork failed *after*
5875 * cgroup_can_fork() succeded.
5876 */
5877void cgroup_cancel_fork(struct task_struct *child)
5878{
5879	struct cgroup_subsys *ss;
5880	int i;
5881
5882	for_each_subsys(ss, i)
5883		if (ss->cancel_fork)
5884			ss->cancel_fork(child);
5885}
5886
5887/**
5888 * cgroup_post_fork - called on a new task after adding it to the task list
5889 * @child: the task in question
5890 *
5891 * Adds the task to the list running through its css_set if necessary and
5892 * call the subsystem fork() callbacks.  Has to be after the task is
5893 * visible on the task list in case we race with the first call to
5894 * cgroup_task_iter_start() - to guarantee that the new task ends up on its
5895 * list.
5896 */
5897void cgroup_post_fork(struct task_struct *child)
5898{
5899	struct cgroup_subsys *ss;
5900	int i;
5901
5902	/*
5903	 * This may race against cgroup_enable_task_cg_lists().  As that
5904	 * function sets use_task_css_set_links before grabbing
5905	 * tasklist_lock and we just went through tasklist_lock to add
5906	 * @child, it's guaranteed that either we see the set
5907	 * use_task_css_set_links or cgroup_enable_task_cg_lists() sees
5908	 * @child during its iteration.
5909	 *
5910	 * If we won the race, @child is associated with %current's
5911	 * css_set.  Grabbing css_set_lock guarantees both that the
5912	 * association is stable, and, on completion of the parent's
5913	 * migration, @child is visible in the source of migration or
5914	 * already in the destination cgroup.  This guarantee is necessary
5915	 * when implementing operations which need to migrate all tasks of
5916	 * a cgroup to another.
5917	 *
5918	 * Note that if we lose to cgroup_enable_task_cg_lists(), @child
5919	 * will remain in init_css_set.  This is safe because all tasks are
5920	 * in the init_css_set before cg_links is enabled and there's no
5921	 * operation which transfers all tasks out of init_css_set.
5922	 */
5923	if (use_task_css_set_links) {
5924		struct css_set *cset;
5925
5926		spin_lock_bh(&css_set_lock);
5927		cset = task_css_set(current);
5928		if (list_empty(&child->cg_list)) {
5929			get_css_set(cset);
5930			css_set_move_task(child, NULL, cset, false);
 
 
 
 
 
 
 
 
 
5931		}
5932		spin_unlock_bh(&css_set_lock);
5933	}
5934
5935	/*
5936	 * Call ss->fork().  This must happen after @child is linked on
5937	 * css_set; otherwise, @child might change state between ->fork()
5938	 * and addition to css_set.
5939	 */
5940	do_each_subsys_mask(ss, i, have_fork_callback) {
5941		ss->fork(child);
5942	} while_each_subsys_mask();
5943}
5944
5945/**
5946 * cgroup_exit - detach cgroup from exiting task
5947 * @tsk: pointer to task_struct of exiting process
 
5948 *
5949 * Description: Detach cgroup from @tsk and release it.
5950 *
5951 * Note that cgroups marked notify_on_release force every task in
5952 * them to take the global cgroup_mutex mutex when exiting.
5953 * This could impact scaling on very large systems.  Be reluctant to
5954 * use notify_on_release cgroups where very high task exit scaling
5955 * is required on large systems.
5956 *
5957 * We set the exiting tasks cgroup to the root cgroup (top_cgroup).  We
5958 * call cgroup_exit() while the task is still competent to handle
5959 * notify_on_release(), then leave the task attached to the root cgroup in
5960 * each hierarchy for the remainder of its exit.  No need to bother with
5961 * init_css_set refcnting.  init_css_set never goes away and we can't race
5962 * with migration path - PF_EXITING is visible to migration path.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5963 */
5964void cgroup_exit(struct task_struct *tsk)
5965{
5966	struct cgroup_subsys *ss;
5967	struct css_set *cset;
5968	int i;
5969
5970	/*
5971	 * Unlink from @tsk from its css_set.  As migration path can't race
5972	 * with us, we can check css_set and cg_list without synchronization.
 
5973	 */
5974	cset = task_css_set(tsk);
5975
5976	if (!list_empty(&tsk->cg_list)) {
5977		spin_lock_bh(&css_set_lock);
5978		css_set_move_task(tsk, cset, NULL, false);
5979		spin_unlock_bh(&css_set_lock);
5980	} else {
5981		get_css_set(cset);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5982	}
 
5983
5984	/* see cgroup_post_fork() for details */
5985	do_each_subsys_mask(ss, i, have_exit_callback) {
5986		ss->exit(tsk);
5987	} while_each_subsys_mask();
5988}
5989
5990void cgroup_free(struct task_struct *task)
 
 
 
 
 
 
 
 
 
 
 
 
 
5991{
5992	struct css_set *cset = task_css_set(task);
5993	struct cgroup_subsys *ss;
5994	int ssid;
5995
5996	do_each_subsys_mask(ss, ssid, have_free_callback) {
5997		ss->free(task);
5998	} while_each_subsys_mask();
5999
6000	put_css_set(cset);
 
 
 
 
6001}
6002
6003static void check_for_release(struct cgroup *cgrp)
6004{
6005	if (notify_on_release(cgrp) && !cgroup_is_populated(cgrp) &&
6006	    !css_has_online_children(&cgrp->self) && !cgroup_is_dead(cgrp))
6007		schedule_work(&cgrp->release_agent_work);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6008}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6009
6010/*
6011 * Notify userspace when a cgroup is released, by running the
6012 * configured release agent with the name of the cgroup (path
6013 * relative to the root of cgroup file system) as the argument.
6014 *
6015 * Most likely, this user command will try to rmdir this cgroup.
6016 *
6017 * This races with the possibility that some other task will be
6018 * attached to this cgroup before it is removed, or that some other
6019 * user task will 'mkdir' a child cgroup of this cgroup.  That's ok.
6020 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
6021 * unused, and this cgroup will be reprieved from its death sentence,
6022 * to continue to serve a useful existence.  Next time it's released,
6023 * we will get notified again, if it still has 'notify_on_release' set.
6024 *
6025 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
6026 * means only wait until the task is successfully execve()'d.  The
6027 * separate release agent task is forked by call_usermodehelper(),
6028 * then control in this thread returns here, without waiting for the
6029 * release agent task.  We don't bother to wait because the caller of
6030 * this routine has no use for the exit status of the release agent
6031 * task, so no sense holding our caller up for that.
6032 */
6033static void cgroup_release_agent(struct work_struct *work)
6034{
6035	struct cgroup *cgrp =
6036		container_of(work, struct cgroup, release_agent_work);
6037	char *pathbuf = NULL, *agentbuf = NULL, *path;
6038	char *argv[3], *envp[3];
6039
6040	mutex_lock(&cgroup_mutex);
6041
6042	pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
6043	agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
6044	if (!pathbuf || !agentbuf)
6045		goto out;
6046
6047	spin_lock_bh(&css_set_lock);
6048	path = cgroup_path_ns_locked(cgrp, pathbuf, PATH_MAX, &init_cgroup_ns);
6049	spin_unlock_bh(&css_set_lock);
6050	if (!path)
6051		goto out;
6052
6053	argv[0] = agentbuf;
6054	argv[1] = path;
6055	argv[2] = NULL;
6056
6057	/* minimal command environment */
6058	envp[0] = "HOME=/";
6059	envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
6060	envp[2] = NULL;
6061
6062	mutex_unlock(&cgroup_mutex);
6063	call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
6064	goto out_free;
6065out:
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6066	mutex_unlock(&cgroup_mutex);
6067out_free:
6068	kfree(agentbuf);
6069	kfree(pathbuf);
6070}
6071
6072static int __init cgroup_disable(char *str)
6073{
6074	struct cgroup_subsys *ss;
6075	char *token;
6076	int i;
 
6077
6078	while ((token = strsep(&str, ",")) != NULL) {
6079		if (!*token)
6080			continue;
 
 
 
 
 
 
6081
6082		for_each_subsys(ss, i) {
6083			if (strcmp(token, ss->name) &&
6084			    strcmp(token, ss->legacy_name))
6085				continue;
6086			cgroup_disable_mask |= 1 << i;
 
6087		}
6088	}
6089	return 1;
6090}
6091__setup("cgroup_disable=", cgroup_disable);
6092
6093static int __init cgroup_no_v1(char *str)
6094{
6095	struct cgroup_subsys *ss;
6096	char *token;
6097	int i;
6098
6099	while ((token = strsep(&str, ",")) != NULL) {
6100		if (!*token)
6101			continue;
6102
6103		if (!strcmp(token, "all")) {
6104			cgroup_no_v1_mask = U16_MAX;
6105			break;
6106		}
 
 
6107
6108		for_each_subsys(ss, i) {
6109			if (strcmp(token, ss->name) &&
6110			    strcmp(token, ss->legacy_name))
6111				continue;
 
 
6112
6113			cgroup_no_v1_mask |= 1 << i;
6114		}
6115	}
6116	return 1;
6117}
6118__setup("cgroup_no_v1=", cgroup_no_v1);
6119
6120/**
6121 * css_tryget_online_from_dir - get corresponding css from a cgroup dentry
6122 * @dentry: directory dentry of interest
6123 * @ss: subsystem of interest
6124 *
6125 * If @dentry is a directory for a cgroup which has @ss enabled on it, try
6126 * to get the corresponding css and return it.  If such css doesn't exist
6127 * or can't be pinned, an ERR_PTR value is returned.
6128 */
6129struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
6130						       struct cgroup_subsys *ss)
6131{
6132	struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
6133	struct file_system_type *s_type = dentry->d_sb->s_type;
6134	struct cgroup_subsys_state *css = NULL;
6135	struct cgroup *cgrp;
6136
6137	/* is @dentry a cgroup dir? */
6138	if ((s_type != &cgroup_fs_type && s_type != &cgroup2_fs_type) ||
6139	    !kn || kernfs_type(kn) != KERNFS_DIR)
6140		return ERR_PTR(-EBADF);
6141
6142	rcu_read_lock();
6143
6144	/*
6145	 * This path doesn't originate from kernfs and @kn could already
6146	 * have been or be removed at any point.  @kn->priv is RCU
6147	 * protected for this access.  See css_release_work_fn() for details.
6148	 */
6149	cgrp = rcu_dereference(kn->priv);
6150	if (cgrp)
6151		css = cgroup_css(cgrp, ss);
6152
6153	if (!css || !css_tryget_online(css))
6154		css = ERR_PTR(-ENOENT);
6155
6156	rcu_read_unlock();
6157	return css;
 
6158}
 
6159
6160/**
6161 * css_from_id - lookup css by id
6162 * @id: the cgroup id
6163 * @ss: cgroup subsys to be looked into
6164 *
6165 * Returns the css if there's valid one with @id, otherwise returns NULL.
6166 * Should be called under rcu_read_lock().
 
 
 
 
6167 */
6168struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
6169{
6170	WARN_ON_ONCE(!rcu_read_lock_held());
6171	return id > 0 ? idr_find(&ss->css_idr, id) : NULL;
6172}
6173
6174/**
6175 * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path
6176 * @path: path on the default hierarchy
6177 *
6178 * Find the cgroup at @path on the default hierarchy, increment its
6179 * reference count and return it.  Returns pointer to the found cgroup on
6180 * success, ERR_PTR(-ENOENT) if @path doens't exist and ERR_PTR(-ENOTDIR)
6181 * if @path points to a non-directory.
6182 */
6183struct cgroup *cgroup_get_from_path(const char *path)
6184{
6185	struct kernfs_node *kn;
6186	struct cgroup *cgrp;
6187
6188	mutex_lock(&cgroup_mutex);
6189
6190	kn = kernfs_walk_and_get(cgrp_dfl_root.cgrp.kn, path);
6191	if (kn) {
6192		if (kernfs_type(kn) == KERNFS_DIR) {
6193			cgrp = kn->priv;
6194			cgroup_get(cgrp);
6195		} else {
6196			cgrp = ERR_PTR(-ENOTDIR);
6197		}
6198		kernfs_put(kn);
6199	} else {
6200		cgrp = ERR_PTR(-ENOENT);
6201	}
6202
6203	mutex_unlock(&cgroup_mutex);
6204	return cgrp;
6205}
6206EXPORT_SYMBOL_GPL(cgroup_get_from_path);
6207
6208/*
6209 * sock->sk_cgrp_data handling.  For more info, see sock_cgroup_data
6210 * definition in cgroup-defs.h.
6211 */
6212#ifdef CONFIG_SOCK_CGROUP_DATA
6213
6214#if defined(CONFIG_CGROUP_NET_PRIO) || defined(CONFIG_CGROUP_NET_CLASSID)
6215
6216DEFINE_SPINLOCK(cgroup_sk_update_lock);
6217static bool cgroup_sk_alloc_disabled __read_mostly;
6218
6219void cgroup_sk_alloc_disable(void)
6220{
6221	if (cgroup_sk_alloc_disabled)
 
 
6222		return;
6223	pr_info("cgroup: disabling cgroup2 socket matching due to net_prio or net_cls activation\n");
6224	cgroup_sk_alloc_disabled = true;
6225}
6226
6227#else
6228
6229#define cgroup_sk_alloc_disabled	false
 
 
 
 
 
 
 
6230
6231#endif
 
 
 
6232
6233void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
6234{
6235	if (cgroup_sk_alloc_disabled)
6236		return;
6237
6238	rcu_read_lock();
6239
6240	while (true) {
6241		struct css_set *cset;
6242
6243		cset = task_css_set(current);
6244		if (likely(cgroup_tryget(cset->dfl_cgrp))) {
6245			skcd->val = (unsigned long)cset->dfl_cgrp;
6246			break;
6247		}
6248		cpu_relax();
6249	}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6250
6251	rcu_read_unlock();
6252}
6253
6254void cgroup_sk_free(struct sock_cgroup_data *skcd)
6255{
6256	cgroup_put(sock_cgroup_ptr(skcd));
 
 
 
 
 
 
 
 
 
 
 
 
 
6257}
6258
6259#endif	/* CONFIG_SOCK_CGROUP_DATA */
6260
6261/* cgroup namespaces */
6262
6263static struct cgroup_namespace *alloc_cgroup_ns(void)
6264{
6265	struct cgroup_namespace *new_ns;
6266	int ret;
6267
6268	new_ns = kzalloc(sizeof(struct cgroup_namespace), GFP_KERNEL);
6269	if (!new_ns)
6270		return ERR_PTR(-ENOMEM);
6271	ret = ns_alloc_inum(&new_ns->ns);
6272	if (ret) {
6273		kfree(new_ns);
6274		return ERR_PTR(ret);
6275	}
6276	atomic_set(&new_ns->count, 1);
6277	new_ns->ns.ops = &cgroupns_operations;
6278	return new_ns;
6279}
 
 
 
 
 
 
 
6280
6281void free_cgroup_ns(struct cgroup_namespace *ns)
6282{
6283	put_css_set(ns->root_cset);
6284	put_user_ns(ns->user_ns);
6285	ns_free_inum(&ns->ns);
6286	kfree(ns);
6287}
6288EXPORT_SYMBOL(free_cgroup_ns);
6289
6290struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
6291					struct user_namespace *user_ns,
6292					struct cgroup_namespace *old_ns)
 
 
 
 
 
 
6293{
6294	struct cgroup_namespace *new_ns;
6295	struct css_set *cset;
6296
6297	BUG_ON(!old_ns);
6298
6299	if (!(flags & CLONE_NEWCGROUP)) {
6300		get_cgroup_ns(old_ns);
6301		return old_ns;
6302	}
6303
6304	/* Allow only sysadmin to create cgroup namespace. */
6305	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
6306		return ERR_PTR(-EPERM);
6307
6308	mutex_lock(&cgroup_mutex);
6309	spin_lock_bh(&css_set_lock);
6310
6311	cset = task_css_set(current);
6312	get_css_set(cset);
6313
6314	spin_unlock_bh(&css_set_lock);
6315	mutex_unlock(&cgroup_mutex);
6316
6317	new_ns = alloc_cgroup_ns();
6318	if (IS_ERR(new_ns)) {
6319		put_css_set(cset);
6320		return new_ns;
6321	}
6322
6323	new_ns->user_ns = get_user_ns(user_ns);
6324	new_ns->root_cset = cset;
6325
6326	return new_ns;
6327}
 
6328
6329static inline struct cgroup_namespace *to_cg_ns(struct ns_common *ns)
6330{
6331	return container_of(ns, struct cgroup_namespace, ns);
6332}
6333
6334static int cgroupns_install(struct nsproxy *nsproxy, struct ns_common *ns)
 
 
 
 
 
 
 
6335{
6336	struct cgroup_namespace *cgroup_ns = to_cg_ns(ns);
6337
6338	if (!ns_capable(current_user_ns(), CAP_SYS_ADMIN) ||
6339	    !ns_capable(cgroup_ns->user_ns, CAP_SYS_ADMIN))
6340		return -EPERM;
6341
6342	/* Don't need to do anything if we are attaching to our own cgroupns. */
6343	if (cgroup_ns == nsproxy->cgroup_ns)
6344		return 0;
6345
6346	get_cgroup_ns(cgroup_ns);
6347	put_cgroup_ns(nsproxy->cgroup_ns);
6348	nsproxy->cgroup_ns = cgroup_ns;
6349
6350	return 0;
6351}
6352
6353static struct ns_common *cgroupns_get(struct task_struct *task)
6354{
6355	struct cgroup_namespace *ns = NULL;
6356	struct nsproxy *nsproxy;
6357
6358	task_lock(task);
6359	nsproxy = task->nsproxy;
6360	if (nsproxy) {
6361		ns = nsproxy->cgroup_ns;
6362		get_cgroup_ns(ns);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6363	}
6364	task_unlock(task);
6365
6366	return ns ? &ns->ns : NULL;
6367}
6368
6369static void cgroupns_put(struct ns_common *ns)
 
 
 
6370{
6371	put_cgroup_ns(to_cg_ns(ns));
6372}
 
6373
6374const struct proc_ns_operations cgroupns_operations = {
6375	.name		= "cgroup",
6376	.type		= CLONE_NEWCGROUP,
6377	.get		= cgroupns_get,
6378	.put		= cgroupns_put,
6379	.install	= cgroupns_install,
6380};
6381
6382static __init int cgroup_namespaces_init(void)
6383{
6384	return 0;
 
 
 
 
6385}
6386subsys_initcall(cgroup_namespaces_init);
6387
6388#ifdef CONFIG_CGROUP_DEBUG
6389static struct cgroup_subsys_state *
6390debug_css_alloc(struct cgroup_subsys_state *parent_css)
6391{
6392	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);
6393
6394	if (!css)
6395		return ERR_PTR(-ENOMEM);
6396
6397	return css;
6398}
6399
6400static void debug_css_free(struct cgroup_subsys_state *css)
6401{
6402	kfree(css);
6403}
6404
6405static u64 debug_taskcount_read(struct cgroup_subsys_state *css,
6406				struct cftype *cft)
6407{
6408	return cgroup_task_count(css->cgroup);
6409}
6410
6411static u64 current_css_set_read(struct cgroup_subsys_state *css,
6412				struct cftype *cft)
 
 
 
 
6413{
6414	return (u64)(unsigned long)current->cgroups;
6415}
6416
6417static u64 current_css_set_refcount_read(struct cgroup_subsys_state *css,
6418					 struct cftype *cft)
6419{
6420	u64 count;
6421
6422	rcu_read_lock();
6423	count = atomic_read(&task_css_set(current)->refcount);
6424	rcu_read_unlock();
6425	return count;
6426}
6427
6428static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
 
 
6429{
6430	struct cgrp_cset_link *link;
6431	struct css_set *cset;
6432	char *name_buf;
6433
6434	name_buf = kmalloc(NAME_MAX + 1, GFP_KERNEL);
6435	if (!name_buf)
6436		return -ENOMEM;
6437
6438	spin_lock_bh(&css_set_lock);
6439	rcu_read_lock();
6440	cset = rcu_dereference(current->cgroups);
6441	list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
6442		struct cgroup *c = link->cgrp;
 
6443
6444		cgroup_name(c, name_buf, NAME_MAX + 1);
 
 
 
6445		seq_printf(seq, "Root %d group %s\n",
6446			   c->root->hierarchy_id, name_buf);
6447	}
6448	rcu_read_unlock();
6449	spin_unlock_bh(&css_set_lock);
6450	kfree(name_buf);
6451	return 0;
6452}
6453
6454#define MAX_TASKS_SHOWN_PER_CSS 25
6455static int cgroup_css_links_read(struct seq_file *seq, void *v)
6456{
6457	struct cgroup_subsys_state *css = seq_css(seq);
6458	struct cgrp_cset_link *link;
6459
6460	spin_lock_bh(&css_set_lock);
6461	list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
6462		struct css_set *cset = link->cset;
 
6463		struct task_struct *task;
6464		int count = 0;
6465
6466		seq_printf(seq, "css_set %p\n", cset);
6467
6468		list_for_each_entry(task, &cset->tasks, cg_list) {
6469			if (count++ > MAX_TASKS_SHOWN_PER_CSS)
6470				goto overflow;
6471			seq_printf(seq, "  task %d\n", task_pid_vnr(task));
6472		}
6473
6474		list_for_each_entry(task, &cset->mg_tasks, cg_list) {
6475			if (count++ > MAX_TASKS_SHOWN_PER_CSS)
6476				goto overflow;
6477			seq_printf(seq, "  task %d\n", task_pid_vnr(task));
6478		}
6479		continue;
6480	overflow:
6481		seq_puts(seq, "  ...\n");
6482	}
6483	spin_unlock_bh(&css_set_lock);
6484	return 0;
6485}
6486
6487static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
6488{
6489	return (!cgroup_is_populated(css->cgroup) &&
6490		!css_has_online_children(&css->cgroup->self));
6491}
6492
6493static struct cftype debug_files[] =  {
6494	{
 
 
 
 
6495		.name = "taskcount",
6496		.read_u64 = debug_taskcount_read,
6497	},
6498
6499	{
6500		.name = "current_css_set",
6501		.read_u64 = current_css_set_read,
6502	},
6503
6504	{
6505		.name = "current_css_set_refcount",
6506		.read_u64 = current_css_set_refcount_read,
6507	},
6508
6509	{
6510		.name = "current_css_set_cg_links",
6511		.seq_show = current_css_set_cg_links_read,
6512	},
6513
6514	{
6515		.name = "cgroup_css_links",
6516		.seq_show = cgroup_css_links_read,
6517	},
6518
6519	{
6520		.name = "releasable",
6521		.read_u64 = releasable_read,
6522	},
6523
6524	{ }	/* terminate */
6525};
6526
6527struct cgroup_subsys debug_cgrp_subsys = {
6528	.css_alloc = debug_css_alloc,
6529	.css_free = debug_css_free,
6530	.legacy_cftypes = debug_files,
 
 
6531};
6532#endif /* CONFIG_CGROUP_DEBUG */