cgroup-v1.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2#include "cgroup-internal.h"
   3
   4#include <linux/ctype.h>
   5#include <linux/kmod.h>
   6#include <linux/sort.h>
   7#include <linux/delay.h>
   8#include <linux/mm.h>
   9#include <linux/sched/signal.h>
  10#include <linux/sched/task.h>
  11#include <linux/magic.h>
  12#include <linux/slab.h>
  13#include <linux/string.h>
  14#include <linux/vmalloc.h>
  15#include <linux/delayacct.h>
  16#include <linux/pid_namespace.h>
  17#include <linux/cgroupstats.h>
  18#include <linux/fs_parser.h>
  19
  20#include <trace/events/cgroup.h>
  21
  22/*
  23 * pidlists linger the following amount before being destroyed.  The goal
  24 * is avoiding frequent destruction in the middle of consecutive read calls
  25 * Expiring in the middle is a performance problem not a correctness one.
  26 * 1 sec should be enough.
  27 */
  28#define CGROUP_PIDLIST_DESTROY_DELAY	HZ
  29
  30/* Controllers blocked by the commandline in v1 */
  31static u16 cgroup_no_v1_mask;
  32
  33/* disable named v1 mounts */
  34static bool cgroup_no_v1_named;
  35
  36/* Show unavailable controllers in /proc/cgroups */
  37static bool proc_show_all;
  38
  39/*
  40 * pidlist destructions need to be flushed on cgroup destruction.  Use a
  41 * separate workqueue as flush domain.
  42 */
  43static struct workqueue_struct *cgroup_pidlist_destroy_wq;
  44
  45/* protects cgroup_subsys->release_agent_path */
  46static DEFINE_SPINLOCK(release_agent_path_lock);
  47
  48bool cgroup1_ssid_disabled(int ssid)
  49{
  50	return cgroup_no_v1_mask & (1 << ssid);
  51}
  52
  53static bool cgroup1_subsys_absent(struct cgroup_subsys *ss)
  54{
  55	/* Check also dfl_cftypes for file-less controllers, i.e. perf_event */
  56	return ss->legacy_cftypes == NULL && ss->dfl_cftypes;
  57}
  58
  59/**
  60 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
  61 * @from: attach to all cgroups of a given task
  62 * @tsk: the task to be attached
  63 *
  64 * Return: %0 on success or a negative errno code on failure
  65 */
  66int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
  67{
  68	struct cgroup_root *root;
  69	int retval = 0;
  70
  71	cgroup_lock();
  72	cgroup_attach_lock(CGRP_ATTACH_LOCK_GLOBAL, NULL);
  73	for_each_root(root) {
  74		struct cgroup *from_cgrp;
  75
  76		spin_lock_irq(&css_set_lock);
  77		from_cgrp = task_cgroup_from_root(from, root);
  78		spin_unlock_irq(&css_set_lock);
  79
  80		retval = cgroup_attach_task(from_cgrp, tsk, false);
  81		if (retval)
  82			break;
  83	}
  84	cgroup_attach_unlock(CGRP_ATTACH_LOCK_GLOBAL, NULL);
  85	cgroup_unlock();
  86
  87	return retval;
  88}
  89EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
  90
  91/**
  92 * cgroup_transfer_tasks - move tasks from one cgroup to another
  93 * @to: cgroup to which the tasks will be moved
  94 * @from: cgroup in which the tasks currently reside
  95 *
  96 * Locking rules between cgroup_post_fork() and the migration path
  97 * guarantee that, if a task is forking while being migrated, the new child
  98 * is guaranteed to be either visible in the source cgroup after the
  99 * parent's migration is complete or put into the target cgroup.  No task
 100 * can slip out of migration through forking.
 101 *
 102 * Return: %0 on success or a negative errno code on failure
 103 */
 104int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
 105{
 106	DEFINE_CGROUP_MGCTX(mgctx);
 107	struct cgrp_cset_link *link;
 108	struct css_task_iter it;
 109	struct task_struct *task;
 110	int ret;
 111
 112	if (cgroup_on_dfl(to))
 113		return -EINVAL;
 114
 115	ret = cgroup_migrate_vet_dst(to);
 116	if (ret)
 117		return ret;
 118
 119	cgroup_lock();
 120
 121	cgroup_attach_lock(CGRP_ATTACH_LOCK_GLOBAL, NULL);
 122
 123	/* all tasks in @from are being moved, all csets are source */
 124	spin_lock_irq(&css_set_lock);
 125	list_for_each_entry(link, &from->cset_links, cset_link)
 126		cgroup_migrate_add_src(link->cset, to, &mgctx);
 127	spin_unlock_irq(&css_set_lock);
 128
 129	ret = cgroup_migrate_prepare_dst(&mgctx);
 130	if (ret)
 131		goto out_err;
 132
 133	/*
 134	 * Migrate tasks one-by-one until @from is empty.  This fails iff
 135	 * ->can_attach() fails.
 136	 */
 137	do {
 138		css_task_iter_start(&from->self, 0, &it);
 139
 140		do {
 141			task = css_task_iter_next(&it);
 142		} while (task && (task->flags & PF_EXITING));
 143
 144		if (task)
 145			get_task_struct(task);
 146		css_task_iter_end(&it);
 147
 148		if (task) {
 149			ret = cgroup_migrate(task, false, &mgctx);
 150			if (!ret)
 151				TRACE_CGROUP_PATH(transfer_tasks, to, task, false);
 152			put_task_struct(task);
 153		}
 154	} while (task && !ret);
 155out_err:
 156	cgroup_migrate_finish(&mgctx);
 157	cgroup_attach_unlock(CGRP_ATTACH_LOCK_GLOBAL, NULL);
 158	cgroup_unlock();
 159	return ret;
 160}
 161
 162/*
 163 * Stuff for reading the 'tasks'/'procs' files.
 164 *
 165 * Reading this file can return large amounts of data if a cgroup has
 166 * *lots* of attached tasks. So it may need several calls to read(),
 167 * but we cannot guarantee that the information we produce is correct
 168 * unless we produce it entirely atomically.
 169 *
 170 */
 171
 172/* which pidlist file are we talking about? */
 173enum cgroup_filetype {
 174	CGROUP_FILE_PROCS,
 175	CGROUP_FILE_TASKS,
 176};
 177
 178/*
 179 * A pidlist is a list of pids that virtually represents the contents of one
 180 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
 181 * a pair (one each for procs, tasks) for each pid namespace that's relevant
 182 * to the cgroup.
 183 */
 184struct cgroup_pidlist {
 185	/*
 186	 * used to find which pidlist is wanted. doesn't change as long as
 187	 * this particular list stays in the list.
 188	*/
 189	struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
 190	/* array of xids */
 191	pid_t *list;
 192	/* how many elements the above list has */
 193	int length;
 194	/* each of these stored in a list by its cgroup */
 195	struct list_head links;
 196	/* pointer to the cgroup we belong to, for list removal purposes */
 197	struct cgroup *owner;
 198	/* for delayed destruction */
 199	struct delayed_work destroy_dwork;
 200};
 201
 202/*
 203 * Used to destroy all pidlists lingering waiting for destroy timer.  None
 204 * should be left afterwards.
 205 */
 206void cgroup1_pidlist_destroy_all(struct cgroup *cgrp)
 207{
 208	struct cgroup_pidlist *l, *tmp_l;
 209
 210	mutex_lock(&cgrp->pidlist_mutex);
 211	list_for_each_entry_safe(l, tmp_l, &cgrp->pidlists, links)
 212		mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, 0);
 213	mutex_unlock(&cgrp->pidlist_mutex);
 214
 215	flush_workqueue(cgroup_pidlist_destroy_wq);
 216	BUG_ON(!list_empty(&cgrp->pidlists));
 217}
 218
 219static void cgroup_pidlist_destroy_work_fn(struct work_struct *work)
 220{
 221	struct delayed_work *dwork = to_delayed_work(work);
 222	struct cgroup_pidlist *l = container_of(dwork, struct cgroup_pidlist,
 223						destroy_dwork);
 224	struct cgroup_pidlist *tofree = NULL;
 225
 226	mutex_lock(&l->owner->pidlist_mutex);
 227
 228	/*
 229	 * Destroy iff we didn't get queued again.  The state won't change
 230	 * as destroy_dwork can only be queued while locked.
 231	 */
 232	if (!delayed_work_pending(dwork)) {
 233		list_del(&l->links);
 234		kvfree(l->list);
 235		put_pid_ns(l->key.ns);
 236		tofree = l;
 237	}
 238
 239	mutex_unlock(&l->owner->pidlist_mutex);
 240	kfree(tofree);
 241}
 242
 243/*
 244 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
 245 * Returns the number of unique elements.
 246 */
 247static int pidlist_uniq(pid_t *list, int length)
 248{
 249	int src, dest = 1;
 250
 251	/*
 252	 * we presume the 0th element is unique, so i starts at 1. trivial
 253	 * edge cases first; no work needs to be done for either
 254	 */
 255	if (length == 0 || length == 1)
 256		return length;
 257	/* src and dest walk down the list; dest counts unique elements */
 258	for (src = 1; src < length; src++) {
 259		/* find next unique element */
 260		while (list[src] == list[src-1]) {
 261			src++;
 262			if (src == length)
 263				goto after;
 264		}
 265		/* dest always points to where the next unique element goes */
 266		list[dest] = list[src];
 267		dest++;
 268	}
 269after:
 270	return dest;
 271}
 272
 273/*
 274 * The two pid files - task and cgroup.procs - guaranteed that the result
 275 * is sorted, which forced this whole pidlist fiasco.  As pid order is
 276 * different per namespace, each namespace needs differently sorted list,
 277 * making it impossible to use, for example, single rbtree of member tasks
 278 * sorted by task pointer.  As pidlists can be fairly large, allocating one
 279 * per open file is dangerous, so cgroup had to implement shared pool of
 280 * pidlists keyed by cgroup and namespace.
 281 */
 282static int cmppid(const void *a, const void *b)
 283{
 284	return *(pid_t *)a - *(pid_t *)b;
 285}
 286
 287static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
 288						  enum cgroup_filetype type)
 289{
 290	struct cgroup_pidlist *l;
 291	/* don't need task_nsproxy() if we're looking at ourself */
 292	struct pid_namespace *ns = task_active_pid_ns(current);
 293
 294	lockdep_assert_held(&cgrp->pidlist_mutex);
 295
 296	list_for_each_entry(l, &cgrp->pidlists, links)
 297		if (l->key.type == type && l->key.ns == ns)
 298			return l;
 299	return NULL;
 300}
 301
 302/*
 303 * find the appropriate pidlist for our purpose (given procs vs tasks)
 304 * returns with the lock on that pidlist already held, and takes care
 305 * of the use count, or returns NULL with no locks held if we're out of
 306 * memory.
 307 */
 308static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
 309						enum cgroup_filetype type)
 310{
 311	struct cgroup_pidlist *l;
 312
 313	lockdep_assert_held(&cgrp->pidlist_mutex);
 314
 315	l = cgroup_pidlist_find(cgrp, type);
 316	if (l)
 317		return l;
 318
 319	/* entry not found; create a new one */
 320	l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
 321	if (!l)
 322		return l;
 323
 324	INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
 325	l->key.type = type;
 326	/* don't need task_nsproxy() if we're looking at ourself */
 327	l->key.ns = get_pid_ns(task_active_pid_ns(current));
 328	l->owner = cgrp;
 329	list_add(&l->links, &cgrp->pidlists);
 330	return l;
 331}
 332
 333/*
 334 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 335 */
 336static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
 337			      struct cgroup_pidlist **lp)
 338{
 339	pid_t *array;
 340	int length;
 341	int pid, n = 0; /* used for populating the array */
 342	struct css_task_iter it;
 343	struct task_struct *tsk;
 344	struct cgroup_pidlist *l;
 345
 346	lockdep_assert_held(&cgrp->pidlist_mutex);
 347
 348	/*
 349	 * If cgroup gets more users after we read count, we won't have
 350	 * enough space - tough.  This race is indistinguishable to the
 351	 * caller from the case that the additional cgroup users didn't
 352	 * show up until sometime later on.
 353	 */
 354	length = cgroup_task_count(cgrp);
 355	array = kvmalloc_array(length, sizeof(pid_t), GFP_KERNEL);
 356	if (!array)
 357		return -ENOMEM;
 358	/* now, populate the array */
 359	css_task_iter_start(&cgrp->self, 0, &it);
 360	while ((tsk = css_task_iter_next(&it))) {
 361		if (unlikely(n == length))
 362			break;
 363		/* get tgid or pid for procs or tasks file respectively */
 364		if (type == CGROUP_FILE_PROCS)
 365			pid = task_tgid_vnr(tsk);
 366		else
 367			pid = task_pid_vnr(tsk);
 368		if (pid > 0) /* make sure to only use valid results */
 369			array[n++] = pid;
 370	}
 371	css_task_iter_end(&it);
 372	length = n;
 373	/* now sort & strip out duplicates (tgids or recycled thread PIDs) */
 374	sort(array, length, sizeof(pid_t), cmppid, NULL);
 375	length = pidlist_uniq(array, length);
 376
 377	l = cgroup_pidlist_find_create(cgrp, type);
 378	if (!l) {
 379		kvfree(array);
 380		return -ENOMEM;
 381	}
 382
 383	/* store array, freeing old if necessary */
 384	kvfree(l->list);
 385	l->list = array;
 386	l->length = length;
 387	*lp = l;
 388	return 0;
 389}
 390
 391/*
 392 * seq_file methods for the tasks/procs files. The seq_file position is the
 393 * next pid to display; the seq_file iterator is a pointer to the pid
 394 * in the cgroup->l->list array.
 395 */
 396
 397static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
 398{
 399	/*
 400	 * Initially we receive a position value that corresponds to
 401	 * one more than the last pid shown (or 0 on the first call or
 402	 * after a seek to the start). Use a binary-search to find the
 403	 * next pid to display, if any
 404	 */
 405	struct kernfs_open_file *of = s->private;
 406	struct cgroup_file_ctx *ctx = of->priv;
 407	struct cgroup *cgrp = seq_css(s)->cgroup;
 408	struct cgroup_pidlist *l;
 409	enum cgroup_filetype type = seq_cft(s)->private;
 410	int index = 0, pid = *pos;
 411	int *iter, ret;
 412
 413	mutex_lock(&cgrp->pidlist_mutex);
 414
 415	/*
 416	 * !NULL @ctx->procs1.pidlist indicates that this isn't the first
 417	 * start() after open. If the matching pidlist is around, we can use
 418	 * that. Look for it. Note that @ctx->procs1.pidlist can't be used
 419	 * directly. It could already have been destroyed.
 420	 */
 421	if (ctx->procs1.pidlist)
 422		ctx->procs1.pidlist = cgroup_pidlist_find(cgrp, type);
 423
 424	/*
 425	 * Either this is the first start() after open or the matching
 426	 * pidlist has been destroyed inbetween.  Create a new one.
 427	 */
 428	if (!ctx->procs1.pidlist) {
 429		ret = pidlist_array_load(cgrp, type, &ctx->procs1.pidlist);
 430		if (ret)
 431			return ERR_PTR(ret);
 432	}
 433	l = ctx->procs1.pidlist;
 434
 435	if (pid) {
 436		int end = l->length;
 437
 438		while (index < end) {
 439			int mid = (index + end) / 2;
 440			if (l->list[mid] == pid) {
 441				index = mid;
 442				break;
 443			} else if (l->list[mid] < pid)
 444				index = mid + 1;
 445			else
 446				end = mid;
 447		}
 448	}
 449	/* If we're off the end of the array, we're done */
 450	if (index >= l->length)
 451		return NULL;
 452	/* Update the abstract position to be the actual pid that we found */
 453	iter = l->list + index;
 454	*pos = *iter;
 455	return iter;
 456}
 457
 458static void cgroup_pidlist_stop(struct seq_file *s, void *v)
 459{
 460	struct kernfs_open_file *of = s->private;
 461	struct cgroup_file_ctx *ctx = of->priv;
 462	struct cgroup_pidlist *l = ctx->procs1.pidlist;
 463
 464	if (l)
 465		mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
 466				 CGROUP_PIDLIST_DESTROY_DELAY);
 467	mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
 468}
 469
 470static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
 471{
 472	struct kernfs_open_file *of = s->private;
 473	struct cgroup_file_ctx *ctx = of->priv;
 474	struct cgroup_pidlist *l = ctx->procs1.pidlist;
 475	pid_t *p = v;
 476	pid_t *end = l->list + l->length;
 477	/*
 478	 * Advance to the next pid in the array. If this goes off the
 479	 * end, we're done
 480	 */
 481	p++;
 482	if (p >= end) {
 483		(*pos)++;
 484		return NULL;
 485	} else {
 486		*pos = *p;
 487		return p;
 488	}
 489}
 490
 491static int cgroup_pidlist_show(struct seq_file *s, void *v)
 492{
 493	seq_printf(s, "%d\n", *(int *)v);
 494
 495	return 0;
 496}
 497
 498static ssize_t __cgroup1_procs_write(struct kernfs_open_file *of,
 499				     char *buf, size_t nbytes, loff_t off,
 500				     bool threadgroup)
 501{
 502	struct cgroup *cgrp;
 503	struct task_struct *task;
 504	const struct cred *cred, *tcred;
 505	ssize_t ret;
 506	enum cgroup_attach_lock_mode lock_mode;
 507
 508	cgrp = cgroup_kn_lock_live(of->kn, false);
 509	if (!cgrp)
 510		return -ENODEV;
 511
 512	task = cgroup_procs_write_start(buf, threadgroup, &lock_mode);
 513	ret = PTR_ERR_OR_ZERO(task);
 514	if (ret)
 515		goto out_unlock;
 516
 517	/*
 518	 * Even if we're attaching all tasks in the thread group, we only need
 519	 * to check permissions on one of them. Check permissions using the
 520	 * credentials from file open to protect against inherited fd attacks.
 521	 */
 522	cred = of->file->f_cred;
 523	tcred = get_task_cred(task);
 524	if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
 525	    !uid_eq(cred->euid, tcred->uid) &&
 526	    !uid_eq(cred->euid, tcred->suid))
 527		ret = -EACCES;
 528	put_cred(tcred);
 529	if (ret)
 530		goto out_finish;
 531
 532	ret = cgroup_attach_task(cgrp, task, threadgroup);
 533
 534out_finish:
 535	cgroup_procs_write_finish(task, lock_mode);
 536out_unlock:
 537	cgroup_kn_unlock(of->kn);
 538
 539	return ret ?: nbytes;
 540}
 541
 542static ssize_t cgroup1_procs_write(struct kernfs_open_file *of,
 543				   char *buf, size_t nbytes, loff_t off)
 544{
 545	return __cgroup1_procs_write(of, buf, nbytes, off, true);
 546}
 547
 548static ssize_t cgroup1_tasks_write(struct kernfs_open_file *of,
 549				   char *buf, size_t nbytes, loff_t off)
 550{
 551	return __cgroup1_procs_write(of, buf, nbytes, off, false);
 552}
 553
 554static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
 555					  char *buf, size_t nbytes, loff_t off)
 556{
 557	struct cgroup *cgrp;
 558	struct cgroup_file_ctx *ctx;
 559
 560	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
 561
 562	/*
 563	 * Release agent gets called with all capabilities,
 564	 * require capabilities to set release agent.
 565	 */
 566	ctx = of->priv;
 567	if ((ctx->ns->user_ns != &init_user_ns) ||
 568	    !file_ns_capable(of->file, &init_user_ns, CAP_SYS_ADMIN))
 569		return -EPERM;
 570
 571	cgrp = cgroup_kn_lock_live(of->kn, false);
 572	if (!cgrp)
 573		return -ENODEV;
 574	spin_lock(&release_agent_path_lock);
 575	strscpy(cgrp->root->release_agent_path, strstrip(buf),
 576		sizeof(cgrp->root->release_agent_path));
 577	spin_unlock(&release_agent_path_lock);
 578	cgroup_kn_unlock(of->kn);
 579	return nbytes;
 580}
 581
 582static int cgroup_release_agent_show(struct seq_file *seq, void *v)
 583{
 584	struct cgroup *cgrp = seq_css(seq)->cgroup;
 585
 586	spin_lock(&release_agent_path_lock);
 587	seq_puts(seq, cgrp->root->release_agent_path);
 588	spin_unlock(&release_agent_path_lock);
 589	seq_putc(seq, '\n');
 590	return 0;
 591}
 592
 593static int cgroup_sane_behavior_show(struct seq_file *seq, void *v)
 594{
 595	seq_puts(seq, "0\n");
 596	return 0;
 597}
 598
 599static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
 600					 struct cftype *cft)
 601{
 602	return notify_on_release(css->cgroup);
 603}
 604
 605static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
 606					  struct cftype *cft, u64 val)
 607{
 608	if (val)
 609		set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
 610	else
 611		clear_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
 612	return 0;
 613}
 614
 615static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
 616				      struct cftype *cft)
 617{
 618	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
 619}
 620
 621static int cgroup_clone_children_write(struct cgroup_subsys_state *css,
 622				       struct cftype *cft, u64 val)
 623{
 624	if (val)
 625		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
 626	else
 627		clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
 628	return 0;
 629}
 630
 631/* cgroup core interface files for the legacy hierarchies */
 632struct cftype cgroup1_base_files[] = {
 633	{
 634		.name = "cgroup.procs",
 635		.seq_start = cgroup_pidlist_start,
 636		.seq_next = cgroup_pidlist_next,
 637		.seq_stop = cgroup_pidlist_stop,
 638		.seq_show = cgroup_pidlist_show,
 639		.private = CGROUP_FILE_PROCS,
 640		.write = cgroup1_procs_write,
 641	},
 642	{
 643		.name = "cgroup.clone_children",
 644		.read_u64 = cgroup_clone_children_read,
 645		.write_u64 = cgroup_clone_children_write,
 646	},
 647	{
 648		.name = "cgroup.sane_behavior",
 649		.flags = CFTYPE_ONLY_ON_ROOT,
 650		.seq_show = cgroup_sane_behavior_show,
 651	},
 652	{
 653		.name = "tasks",
 654		.seq_start = cgroup_pidlist_start,
 655		.seq_next = cgroup_pidlist_next,
 656		.seq_stop = cgroup_pidlist_stop,
 657		.seq_show = cgroup_pidlist_show,
 658		.private = CGROUP_FILE_TASKS,
 659		.write = cgroup1_tasks_write,
 660	},
 661	{
 662		.name = "notify_on_release",
 663		.read_u64 = cgroup_read_notify_on_release,
 664		.write_u64 = cgroup_write_notify_on_release,
 665	},
 666	{
 667		.name = "release_agent",
 668		.flags = CFTYPE_ONLY_ON_ROOT,
 669		.seq_show = cgroup_release_agent_show,
 670		.write = cgroup_release_agent_write,
 671		.max_write_len = PATH_MAX - 1,
 672	},
 673	{ }	/* terminate */
 674};
 675
 676/* Display information about each subsystem and each hierarchy */
 677int proc_cgroupstats_show(struct seq_file *m, void *v)
 678{
 679	struct cgroup_subsys *ss;
 680	bool cgrp_v1_visible = false;
 681	int i;
 682
 683	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
 684	/*
 685	 * Grab the subsystems state racily. No need to add avenue to
 686	 * cgroup_mutex contention.
 687	 */
 688
 689	for_each_subsys(ss, i) {
 690		cgrp_v1_visible |= ss->root != &cgrp_dfl_root;
 691
 692		if (!proc_show_all && cgroup1_subsys_absent(ss))
 693			continue;
 694
 695		seq_printf(m, "%s\t%d\t%d\t%d\n",
 696			   ss->legacy_name, ss->root->hierarchy_id,
 697			   atomic_read(&ss->root->nr_cgrps),
 698			   cgroup_ssid_enabled(i));
 699	}
 700
 701	if (cgrp_dfl_visible && !cgrp_v1_visible)
 702		pr_info_once("/proc/cgroups lists only v1 controllers, use cgroup.controllers of root cgroup for v2 info\n");
 703
 704
 705	return 0;
 706}
 707
 708/**
 709 * cgroupstats_build - build and fill cgroupstats
 710 * @stats: cgroupstats to fill information into
 711 * @dentry: A dentry entry belonging to the cgroup for which stats have
 712 * been requested.
 713 *
 714 * Build and fill cgroupstats so that taskstats can export it to user
 715 * space.
 716 *
 717 * Return: %0 on success or a negative errno code on failure
 718 */
 719int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
 720{
 721	struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
 722	struct cgroup *cgrp;
 723	struct css_task_iter it;
 724	struct task_struct *tsk;
 725
 726	/* it should be kernfs_node belonging to cgroupfs and is a directory */
 727	if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
 728	    kernfs_type(kn) != KERNFS_DIR)
 729		return -EINVAL;
 730
 731	/*
 732	 * We aren't being called from kernfs and there's no guarantee on
 733	 * @kn->priv's validity.  For this and css_tryget_online_from_dir(),
 734	 * @kn->priv is RCU safe.  Let's do the RCU dancing.
 735	 */
 736	rcu_read_lock();
 737	cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
 738	if (!cgrp || !cgroup_tryget(cgrp)) {
 739		rcu_read_unlock();
 740		return -ENOENT;
 741	}
 742	rcu_read_unlock();
 743
 744	css_task_iter_start(&cgrp->self, 0, &it);
 745	while ((tsk = css_task_iter_next(&it))) {
 746		switch (READ_ONCE(tsk->__state)) {
 747		case TASK_RUNNING:
 748			stats->nr_running++;
 749			break;
 750		case TASK_INTERRUPTIBLE:
 751			stats->nr_sleeping++;
 752			break;
 753		case TASK_UNINTERRUPTIBLE:
 754			stats->nr_uninterruptible++;
 755			break;
 756		case TASK_STOPPED:
 757			stats->nr_stopped++;
 758			break;
 759		default:
 760			if (tsk->in_iowait)
 761				stats->nr_io_wait++;
 762			break;
 763		}
 764	}
 765	css_task_iter_end(&it);
 766
 767	cgroup_put(cgrp);
 768	return 0;
 769}
 770
 771void cgroup1_check_for_release(struct cgroup *cgrp)
 772{
 773	if (notify_on_release(cgrp) && !cgroup_is_populated(cgrp) &&
 774	    !css_has_online_children(&cgrp->self) && !cgroup_is_dead(cgrp))
 775		schedule_work(&cgrp->release_agent_work);
 776}
 777
 778/*
 779 * Notify userspace when a cgroup is released, by running the
 780 * configured release agent with the name of the cgroup (path
 781 * relative to the root of cgroup file system) as the argument.
 782 *
 783 * Most likely, this user command will try to rmdir this cgroup.
 784 *
 785 * This races with the possibility that some other task will be
 786 * attached to this cgroup before it is removed, or that some other
 787 * user task will 'mkdir' a child cgroup of this cgroup.  That's ok.
 788 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
 789 * unused, and this cgroup will be reprieved from its death sentence,
 790 * to continue to serve a useful existence.  Next time it's released,
 791 * we will get notified again, if it still has 'notify_on_release' set.
 792 *
 793 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
 794 * means only wait until the task is successfully execve()'d.  The
 795 * separate release agent task is forked by call_usermodehelper(),
 796 * then control in this thread returns here, without waiting for the
 797 * release agent task.  We don't bother to wait because the caller of
 798 * this routine has no use for the exit status of the release agent
 799 * task, so no sense holding our caller up for that.
 800 */
 801void cgroup1_release_agent(struct work_struct *work)
 802{
 803	struct cgroup *cgrp =
 804		container_of(work, struct cgroup, release_agent_work);
 805	char *pathbuf, *agentbuf;
 806	char *argv[3], *envp[3];
 807	int ret;
 808
 809	/* snoop agent path and exit early if empty */
 810	if (!cgrp->root->release_agent_path[0])
 811		return;
 812
 813	/* prepare argument buffers */
 814	pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
 815	agentbuf = kmalloc(PATH_MAX, GFP_KERNEL);
 816	if (!pathbuf || !agentbuf)
 817		goto out_free;
 818
 819	spin_lock(&release_agent_path_lock);
 820	strscpy(agentbuf, cgrp->root->release_agent_path, PATH_MAX);
 821	spin_unlock(&release_agent_path_lock);
 822	if (!agentbuf[0])
 823		goto out_free;
 824
 825	ret = cgroup_path_ns(cgrp, pathbuf, PATH_MAX, &init_cgroup_ns);
 826	if (ret < 0)
 827		goto out_free;
 828
 829	argv[0] = agentbuf;
 830	argv[1] = pathbuf;
 831	argv[2] = NULL;
 832
 833	/* minimal command environment */
 834	envp[0] = "HOME=/";
 835	envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
 836	envp[2] = NULL;
 837
 838	call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
 839out_free:
 840	kfree(agentbuf);
 841	kfree(pathbuf);
 842}
 843
 844/*
 845 * cgroup_rename - Only allow simple rename of directories in place.
 846 */
 847static int cgroup1_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
 848			  const char *new_name_str)
 849{
 850	struct cgroup *cgrp = kn->priv;
 851	int ret;
 852
 853	/* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
 854	if (strchr(new_name_str, '\n'))
 855		return -EINVAL;
 856
 857	if (kernfs_type(kn) != KERNFS_DIR)
 858		return -ENOTDIR;
 859	if (rcu_access_pointer(kn->__parent) != new_parent)
 860		return -EIO;
 861
 862	/*
 863	 * We're gonna grab cgroup_mutex which nests outside kernfs
 864	 * active_ref.  kernfs_rename() doesn't require active_ref
 865	 * protection.  Break them before grabbing cgroup_mutex.
 866	 */
 867	kernfs_break_active_protection(new_parent);
 868	kernfs_break_active_protection(kn);
 869
 870	cgroup_lock();
 871
 872	ret = kernfs_rename(kn, new_parent, new_name_str);
 873	if (!ret)
 874		TRACE_CGROUP_PATH(rename, cgrp);
 875
 876	cgroup_unlock();
 877
 878	kernfs_unbreak_active_protection(kn);
 879	kernfs_unbreak_active_protection(new_parent);
 880	return ret;
 881}
 882
 883static int cgroup1_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
 884{
 885	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
 886	struct cgroup_subsys *ss;
 887	int ssid;
 888
 889	for_each_subsys(ss, ssid)
 890		if (root->subsys_mask & (1 << ssid))
 891			seq_show_option(seq, ss->legacy_name, NULL);
 892	if (root->flags & CGRP_ROOT_NOPREFIX)
 893		seq_puts(seq, ",noprefix");
 894	if (root->flags & CGRP_ROOT_XATTR)
 895		seq_puts(seq, ",xattr");
 896	if (root->flags & CGRP_ROOT_CPUSET_V2_MODE)
 897		seq_puts(seq, ",cpuset_v2_mode");
 898	if (root->flags & CGRP_ROOT_FAVOR_DYNMODS)
 899		seq_puts(seq, ",favordynmods");
 900
 901	spin_lock(&release_agent_path_lock);
 902	if (strlen(root->release_agent_path))
 903		seq_show_option(seq, "release_agent",
 904				root->release_agent_path);
 905	spin_unlock(&release_agent_path_lock);
 906
 907	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags))
 908		seq_puts(seq, ",clone_children");
 909	if (strlen(root->name))
 910		seq_show_option(seq, "name", root->name);
 911	return 0;
 912}
 913
 914enum cgroup1_param {
 915	Opt_all,
 916	Opt_clone_children,
 917	Opt_cpuset_v2_mode,
 918	Opt_name,
 919	Opt_none,
 920	Opt_noprefix,
 921	Opt_release_agent,
 922	Opt_xattr,
 923	Opt_favordynmods,
 924	Opt_nofavordynmods,
 925};
 926
 927const struct fs_parameter_spec cgroup1_fs_parameters[] = {
 928	fsparam_flag  ("all",		Opt_all),
 929	fsparam_flag  ("clone_children", Opt_clone_children),
 930	fsparam_flag  ("cpuset_v2_mode", Opt_cpuset_v2_mode),
 931	fsparam_string("name",		Opt_name),
 932	fsparam_flag  ("none",		Opt_none),
 933	fsparam_flag  ("noprefix",	Opt_noprefix),
 934	fsparam_string("release_agent",	Opt_release_agent),
 935	fsparam_flag  ("xattr",		Opt_xattr),
 936	fsparam_flag  ("favordynmods",	Opt_favordynmods),
 937	fsparam_flag  ("nofavordynmods", Opt_nofavordynmods),
 938	{}
 939};
 940
 941int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param)
 942{
 943	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
 944	struct cgroup_subsys *ss;
 945	struct fs_parse_result result;
 946	int opt, i;
 947
 948	opt = fs_parse(fc, cgroup1_fs_parameters, param, &result);
 949	if (opt == -ENOPARAM) {
 950		int ret;
 951
 952		ret = vfs_parse_fs_param_source(fc, param);
 953		if (ret != -ENOPARAM)
 954			return ret;
 955		for_each_subsys(ss, i) {
 956			if (strcmp(param->key, ss->legacy_name) ||
 957			    cgroup1_subsys_absent(ss))
 958				continue;
 959			if (!cgroup_ssid_enabled(i) || cgroup1_ssid_disabled(i))
 960				return invalfc(fc, "Disabled controller '%s'",
 961					       param->key);
 962			ctx->subsys_mask |= (1 << i);
 963			return 0;
 964		}
 965		return invalfc(fc, "Unknown subsys name '%s'", param->key);
 966	}
 967	if (opt < 0)
 968		return opt;
 969
 970	switch (opt) {
 971	case Opt_none:
 972		/* Explicitly have no subsystems */
 973		ctx->none = true;
 974		break;
 975	case Opt_all:
 976		ctx->all_ss = true;
 977		break;
 978	case Opt_noprefix:
 979		ctx->flags |= CGRP_ROOT_NOPREFIX;
 980		break;
 981	case Opt_clone_children:
 982		ctx->cpuset_clone_children = true;
 983		break;
 984	case Opt_cpuset_v2_mode:
 985		ctx->flags |= CGRP_ROOT_CPUSET_V2_MODE;
 986		break;
 987	case Opt_xattr:
 988		ctx->flags |= CGRP_ROOT_XATTR;
 989		break;
 990	case Opt_favordynmods:
 991		ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
 992		break;
 993	case Opt_nofavordynmods:
 994		ctx->flags &= ~CGRP_ROOT_FAVOR_DYNMODS;
 995		break;
 996	case Opt_release_agent:
 997		/* Specifying two release agents is forbidden */
 998		if (ctx->release_agent)
 999			return invalfc(fc, "release_agent respecified");
1000		/*
1001		 * Release agent gets called with all capabilities,
1002		 * require capabilities to set release agent.
1003		 */
1004		if ((fc->user_ns != &init_user_ns) || !capable(CAP_SYS_ADMIN))
1005			return invalfc(fc, "Setting release_agent not allowed");
1006		ctx->release_agent = param->string;
1007		param->string = NULL;
1008		break;
1009	case Opt_name:
1010		/* blocked by boot param? */
1011		if (cgroup_no_v1_named)
1012			return -ENOENT;
1013		/* Can't specify an empty name */
1014		if (!param->size)
1015			return invalfc(fc, "Empty name");
1016		if (param->size > MAX_CGROUP_ROOT_NAMELEN - 1)
1017			return invalfc(fc, "Name too long");
1018		/* Must match [\w.-]+ */
1019		for (i = 0; i < param->size; i++) {
1020			char c = param->string[i];
1021			if (isalnum(c))
1022				continue;
1023			if ((c == '.') || (c == '-') || (c == '_'))
1024				continue;
1025			return invalfc(fc, "Invalid name");
1026		}
1027		/* Specifying two names is forbidden */
1028		if (ctx->name)
1029			return invalfc(fc, "name respecified");
1030		ctx->name = param->string;
1031		param->string = NULL;
1032		break;
1033	}
1034	return 0;
1035}
1036
1037static int check_cgroupfs_options(struct fs_context *fc)
1038{
1039	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1040	u16 mask = U16_MAX;
1041	u16 enabled = 0;
1042	struct cgroup_subsys *ss;
1043	int i;
1044
1045#ifdef CONFIG_CPUSETS
1046	mask = ~((u16)1 << cpuset_cgrp_id);
1047#endif
1048	for_each_subsys(ss, i)
1049		if (cgroup_ssid_enabled(i) && !cgroup1_ssid_disabled(i) &&
1050		    !cgroup1_subsys_absent(ss))
1051			enabled |= 1 << i;
1052
1053	ctx->subsys_mask &= enabled;
1054
1055	/*
1056	 * In absence of 'none', 'name=' and subsystem name options,
1057	 * let's default to 'all'.
1058	 */
1059	if (!ctx->subsys_mask && !ctx->none && !ctx->name)
1060		ctx->all_ss = true;
1061
1062	if (ctx->all_ss) {
1063		/* Mutually exclusive option 'all' + subsystem name */
1064		if (ctx->subsys_mask)
1065			return invalfc(fc, "subsys name conflicts with all");
1066		/* 'all' => select all the subsystems */
1067		ctx->subsys_mask = enabled;
1068	}
1069
1070	/*
1071	 * We either have to specify by name or by subsystems. (So all
1072	 * empty hierarchies must have a name).
1073	 */
1074	if (!ctx->subsys_mask && !ctx->name)
1075		return invalfc(fc, "Need name or subsystem set");
1076
1077	/*
1078	 * Option noprefix was introduced just for backward compatibility
1079	 * with the old cpuset, so we allow noprefix only if mounting just
1080	 * the cpuset subsystem.
1081	 */
1082	if ((ctx->flags & CGRP_ROOT_NOPREFIX) && (ctx->subsys_mask & mask))
1083		return invalfc(fc, "noprefix used incorrectly");
1084
1085	/* Can't specify "none" and some subsystems */
1086	if (ctx->subsys_mask && ctx->none)
1087		return invalfc(fc, "none used incorrectly");
1088
1089	return 0;
1090}
1091
1092int cgroup1_reconfigure(struct fs_context *fc)
1093{
1094	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1095	struct kernfs_root *kf_root = kernfs_root_from_sb(fc->root->d_sb);
1096	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1097	int ret = 0;
1098	u16 added_mask, removed_mask;
1099
1100	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1101
1102	/* See what subsystems are wanted */
1103	ret = check_cgroupfs_options(fc);
1104	if (ret)
1105		goto out_unlock;
1106
1107	if (ctx->subsys_mask != root->subsys_mask || ctx->release_agent)
1108		pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
1109			task_tgid_nr(current), current->comm);
1110
1111	added_mask = ctx->subsys_mask & ~root->subsys_mask;
1112	removed_mask = root->subsys_mask & ~ctx->subsys_mask;
1113
1114	/* Don't allow flags or name to change at remount */
1115	if ((ctx->flags ^ root->flags) ||
1116	    (ctx->name && strcmp(ctx->name, root->name))) {
1117		errorfc(fc, "option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"",
1118		       ctx->flags, ctx->name ?: "", root->flags, root->name);
1119		ret = -EINVAL;
1120		goto out_unlock;
1121	}
1122
1123	/* remounting is not allowed for populated hierarchies */
1124	if (!list_empty(&root->cgrp.self.children)) {
1125		ret = -EBUSY;
1126		goto out_unlock;
1127	}
1128
1129	ret = rebind_subsystems(root, added_mask);
1130	if (ret)
1131		goto out_unlock;
1132
1133	WARN_ON(rebind_subsystems(&cgrp_dfl_root, removed_mask));
1134
1135	if (ctx->release_agent) {
1136		spin_lock(&release_agent_path_lock);
1137		strscpy(root->release_agent_path, ctx->release_agent);
1138		spin_unlock(&release_agent_path_lock);
1139	}
1140
1141	trace_cgroup_remount(root);
1142
1143 out_unlock:
1144	cgroup_unlock();
1145	return ret;
1146}
1147
1148struct kernfs_syscall_ops cgroup1_kf_syscall_ops = {
1149	.rename			= cgroup1_rename,
1150	.show_options		= cgroup1_show_options,
1151	.mkdir			= cgroup_mkdir,
1152	.rmdir			= cgroup_rmdir,
1153	.show_path		= cgroup_show_path,
1154};
1155
1156/*
1157 * The guts of cgroup1 mount - find or create cgroup_root to use.
1158 * Called with cgroup_mutex held; returns 0 on success, -E... on
1159 * error and positive - in case when the candidate is busy dying.
1160 * On success it stashes a reference to cgroup_root into given
1161 * cgroup_fs_context; that reference is *NOT* counting towards the
1162 * cgroup_root refcount.
1163 */
1164static int cgroup1_root_to_use(struct fs_context *fc)
1165{
1166	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1167	struct cgroup_root *root;
1168	struct cgroup_subsys *ss;
1169	int i, ret;
1170
1171	/* First find the desired set of subsystems */
1172	ret = check_cgroupfs_options(fc);
1173	if (ret)
1174		return ret;
1175
1176	/*
1177	 * Destruction of cgroup root is asynchronous, so subsystems may
1178	 * still be dying after the previous unmount.  Let's drain the
1179	 * dying subsystems.  We just need to ensure that the ones
1180	 * unmounted previously finish dying and don't care about new ones
1181	 * starting.  Testing ref liveliness is good enough.
1182	 */
1183	for_each_subsys(ss, i) {
1184		if (!(ctx->subsys_mask & (1 << i)) ||
1185		    ss->root == &cgrp_dfl_root)
1186			continue;
1187
1188		if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt))
1189			return 1;	/* restart */
1190		cgroup_put(&ss->root->cgrp);
1191	}
1192
1193	for_each_root(root) {
1194		bool name_match = false;
1195
1196		if (root == &cgrp_dfl_root)
1197			continue;
1198
1199		/*
1200		 * If we asked for a name then it must match.  Also, if
1201		 * name matches but sybsys_mask doesn't, we should fail.
1202		 * Remember whether name matched.
1203		 */
1204		if (ctx->name) {
1205			if (strcmp(ctx->name, root->name))
1206				continue;
1207			name_match = true;
1208		}
1209
1210		/*
1211		 * If we asked for subsystems (or explicitly for no
1212		 * subsystems) then they must match.
1213		 */
1214		if ((ctx->subsys_mask || ctx->none) &&
1215		    (ctx->subsys_mask != root->subsys_mask)) {
1216			if (!name_match)
1217				continue;
1218			return -EBUSY;
1219		}
1220
1221		if (root->flags ^ ctx->flags)
1222			pr_warn("new mount options do not match the existing superblock, will be ignored\n");
1223
1224		ctx->root = root;
1225		return 0;
1226	}
1227
1228	/*
1229	 * No such thing, create a new one.  name= matching without subsys
1230	 * specification is allowed for already existing hierarchies but we
1231	 * can't create new one without subsys specification.
1232	 */
1233	if (!ctx->subsys_mask && !ctx->none)
1234		return invalfc(fc, "No subsys list or none specified");
1235
1236	/* Hierarchies may only be created in the initial cgroup namespace. */
1237	if (ctx->ns != &init_cgroup_ns)
1238		return -EPERM;
1239
1240	root = kzalloc(sizeof(*root), GFP_KERNEL);
1241	if (!root)
1242		return -ENOMEM;
1243
1244	ctx->root = root;
1245	init_cgroup_root(ctx);
1246
1247	ret = cgroup_setup_root(root, ctx->subsys_mask);
1248	if (!ret)
1249		cgroup_favor_dynmods(root, ctx->flags & CGRP_ROOT_FAVOR_DYNMODS);
1250	else
1251		cgroup_free_root(root);
1252
1253	return ret;
1254}
1255
1256int cgroup1_get_tree(struct fs_context *fc)
1257{
1258	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1259	int ret;
1260
1261	/* Check if the caller has permission to mount. */
1262	if (!ns_capable(ctx->ns->user_ns, CAP_SYS_ADMIN))
1263		return -EPERM;
1264
1265	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1266
1267	ret = cgroup1_root_to_use(fc);
1268	if (!ret && !percpu_ref_tryget_live(&ctx->root->cgrp.self.refcnt))
1269		ret = 1;	/* restart */
1270
1271	cgroup_unlock();
1272
1273	if (!ret)
1274		ret = cgroup_do_get_tree(fc);
1275
1276	if (!ret && percpu_ref_is_dying(&ctx->root->cgrp.self.refcnt)) {
1277		fc_drop_locked(fc);
1278		ret = 1;
1279	}
1280
1281	if (unlikely(ret > 0)) {
1282		msleep(10);
1283		return restart_syscall();
1284	}
1285	return ret;
1286}
1287
1288/**
1289 * task_get_cgroup1 - Acquires the associated cgroup of a task within a
1290 * specific cgroup1 hierarchy. The cgroup1 hierarchy is identified by its
1291 * hierarchy ID.
1292 * @tsk: The target task
1293 * @hierarchy_id: The ID of a cgroup1 hierarchy
1294 *
1295 * On success, the cgroup is returned. On failure, ERR_PTR is returned.
1296 * We limit it to cgroup1 only.
1297 */
1298struct cgroup *task_get_cgroup1(struct task_struct *tsk, int hierarchy_id)
1299{
1300	struct cgroup *cgrp = ERR_PTR(-ENOENT);
1301	struct cgroup_root *root;
1302	unsigned long flags;
1303
1304	rcu_read_lock();
1305	for_each_root(root) {
1306		/* cgroup1 only*/
1307		if (root == &cgrp_dfl_root)
1308			continue;
1309		if (root->hierarchy_id != hierarchy_id)
1310			continue;
1311		spin_lock_irqsave(&css_set_lock, flags);
1312		cgrp = task_cgroup_from_root(tsk, root);
1313		if (!cgrp || !cgroup_tryget(cgrp))
1314			cgrp = ERR_PTR(-ENOENT);
1315		spin_unlock_irqrestore(&css_set_lock, flags);
1316		break;
1317	}
1318	rcu_read_unlock();
1319	return cgrp;
1320}
1321
1322static int __init cgroup1_wq_init(void)
1323{
1324	/*
1325	 * Used to destroy pidlists and separate to serve as flush domain.
1326	 * Cap @max_active to 1 too.
1327	 */
1328	cgroup_pidlist_destroy_wq = alloc_workqueue("cgroup_pidlist_destroy",
1329						    WQ_PERCPU, 1);
1330	BUG_ON(!cgroup_pidlist_destroy_wq);
1331	return 0;
1332}
1333core_initcall(cgroup1_wq_init);
1334
1335static int __init cgroup_no_v1(char *str)
1336{
1337	struct cgroup_subsys *ss;
1338	char *token;
1339	int i;
1340
1341	while ((token = strsep(&str, ",")) != NULL) {
1342		if (!*token)
1343			continue;
1344
1345		if (!strcmp(token, "all")) {
1346			cgroup_no_v1_mask = U16_MAX;
1347			continue;
1348		}
1349
1350		if (!strcmp(token, "named")) {
1351			cgroup_no_v1_named = true;
1352			continue;
1353		}
1354
1355		for_each_subsys(ss, i) {
1356			if (strcmp(token, ss->name) &&
1357			    strcmp(token, ss->legacy_name))
1358				continue;
1359
1360			cgroup_no_v1_mask |= 1 << i;
1361			break;
1362		}
1363	}
1364	return 1;
1365}
1366__setup("cgroup_no_v1=", cgroup_no_v1);
1367
1368static int __init cgroup_v1_proc(char *str)
1369{
1370	return (kstrtobool(str, &proc_show_all) == 0);
1371}
1372__setup("cgroup_v1_proc=", cgroup_v1_proc);