cgroup.c 147.4 KB
Newer Older
1 2 3 4 5 6
/*
 *  Generic process-grouping system.
 *
 *  Based originally on the cpuset system, extracted by Paul Menage
 *  Copyright (C) 2006 Google, Inc
 *
7 8 9 10
 *  Notifications support
 *  Copyright (C) 2009 Nokia Corporation
 *  Author: Kirill A. Shutemov
 *
11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
 *  Copyright notices from the original cpuset code:
 *  --------------------------------------------------
 *  Copyright (C) 2003 BULL SA.
 *  Copyright (C) 2004-2006 Silicon Graphics, Inc.
 *
 *  Portions derived from Patrick Mochel's sysfs code.
 *  sysfs is Copyright (c) 2001-3 Patrick Mochel
 *
 *  2003-10-10 Written by Simon Derr.
 *  2003-10-22 Updates by Stephen Hemminger.
 *  2004 May-July Rework by Paul Jackson.
 *  ---------------------------------------------------
 *
 *  This file is subject to the terms and conditions of the GNU General Public
 *  License.  See the file COPYING in the main directory of the Linux
 *  distribution for more details.
 */

#include <linux/cgroup.h>
30
#include <linux/cred.h>
31
#include <linux/ctype.h>
32
#include <linux/errno.h>
33
#include <linux/init_task.h>
34 35 36 37 38 39
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
40
#include <linux/proc_fs.h>
41 42
#include <linux/rcupdate.h>
#include <linux/sched.h>
43
#include <linux/backing-dev.h>
44 45 46 47 48
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/magic.h>
#include <linux/spinlock.h>
#include <linux/string.h>
49
#include <linux/sort.h>
50
#include <linux/kmod.h>
51
#include <linux/module.h>
B
Balbir Singh 已提交
52 53
#include <linux/delayacct.h>
#include <linux/cgroupstats.h>
54
#include <linux/hashtable.h>
55
#include <linux/namei.h>
L
Li Zefan 已提交
56
#include <linux/pid_namespace.h>
57
#include <linux/idr.h>
58
#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
59 60
#include <linux/eventfd.h>
#include <linux/poll.h>
61
#include <linux/flex_array.h> /* used in cgroup_attach_task */
62
#include <linux/kthread.h>
B
Balbir Singh 已提交
63

A
Arun Sharma 已提交
64
#include <linux/atomic.h>
65

66 67 68
/* css deactivation bias, makes css->refcnt negative to deny new trygets */
#define CSS_DEACT_BIAS		INT_MIN

T
Tejun Heo 已提交
69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84
/*
 * cgroup_mutex is the master lock.  Any modification to cgroup or its
 * hierarchy must be performed while holding it.
 *
 * cgroup_root_mutex nests inside cgroup_mutex and should be held to modify
 * cgroupfs_root of any cgroup hierarchy - subsys list, flags,
 * release_agent_path and so on.  Modifying requires both cgroup_mutex and
 * cgroup_root_mutex.  Readers can acquire either of the two.  This is to
 * break the following locking order cycle.
 *
 *  A. cgroup_mutex -> cred_guard_mutex -> s_type->i_mutex_key -> namespace_sem
 *  B. namespace_sem -> cgroup_mutex
 *
 * B happens only through cgroup_show_options() and using cgroup_root_mutex
 * breaks it.
 */
T
Tejun Heo 已提交
85 86 87 88
#ifdef CONFIG_PROVE_RCU
DEFINE_MUTEX(cgroup_mutex);
EXPORT_SYMBOL_GPL(cgroup_mutex);	/* only for task_subsys_state_check() */
#else
89
static DEFINE_MUTEX(cgroup_mutex);
T
Tejun Heo 已提交
90 91
#endif

T
Tejun Heo 已提交
92
static DEFINE_MUTEX(cgroup_root_mutex);
93

B
Ben Blum 已提交
94 95
/*
 * Generate an array of cgroup subsystem pointers. At boot time, this is
96
 * populated with the built in subsystems, and modular subsystems are
B
Ben Blum 已提交
97 98 99
 * registered after that. The mutable section of this array is protected by
 * cgroup_mutex.
 */
100
#define SUBSYS(_x) [_x ## _subsys_id] = &_x ## _subsys,
101
#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
B
Ben Blum 已提交
102
static struct cgroup_subsys *subsys[CGROUP_SUBSYS_COUNT] = {
103 104 105 106 107 108 109 110 111 112
#include <linux/cgroup_subsys.h>
};

/*
 * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the
 * subsystems that are otherwise unattached - it never has more than a
 * single cgroup, and all tasks are part of that cgroup.
 */
static struct cgroupfs_root rootnode;

T
Tejun Heo 已提交
113 114 115 116 117 118 119
/*
 * cgroupfs file entry, pointed to from leaf dentry->d_fsdata.
 */
struct cfent {
	struct list_head		node;
	struct dentry			*dentry;
	struct cftype			*type;
L
Li Zefan 已提交
120 121 122

	/* file xattrs */
	struct simple_xattrs		xattrs;
T
Tejun Heo 已提交
123 124
};

K
KAMEZAWA Hiroyuki 已提交
125 126 127 128 129 130 131 132 133 134
/*
 * CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
 * cgroup_subsys->use_id != 0.
 */
#define CSS_ID_MAX	(65535)
struct css_id {
	/*
	 * The css to which this ID points. This pointer is set to valid value
	 * after cgroup is populated. If cgroup is removed, this will be NULL.
	 * This pointer is expected to be RCU-safe because destroy()
T
Tejun Heo 已提交
135 136
	 * is called after synchronize_rcu(). But for safe use, css_tryget()
	 * should be used for avoiding race.
K
KAMEZAWA Hiroyuki 已提交
137
	 */
A
Arnd Bergmann 已提交
138
	struct cgroup_subsys_state __rcu *css;
K
KAMEZAWA Hiroyuki 已提交
139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156
	/*
	 * ID of this css.
	 */
	unsigned short id;
	/*
	 * Depth in hierarchy which this ID belongs to.
	 */
	unsigned short depth;
	/*
	 * ID is freed by RCU. (and lookup routine is RCU safe.)
	 */
	struct rcu_head rcu_head;
	/*
	 * Hierarchy of CSS ID belongs to.
	 */
	unsigned short stack[0]; /* Array of Length (depth+1) */
};

157
/*
L
Lucas De Marchi 已提交
158
 * cgroup_event represents events which userspace want to receive.
159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185
 */
struct cgroup_event {
	/*
	 * Cgroup which the event belongs to.
	 */
	struct cgroup *cgrp;
	/*
	 * Control file which the event associated.
	 */
	struct cftype *cft;
	/*
	 * eventfd to signal userspace about the event.
	 */
	struct eventfd_ctx *eventfd;
	/*
	 * Each of these stored in a list by the cgroup.
	 */
	struct list_head list;
	/*
	 * All fields below needed to unregister event when
	 * userspace closes eventfd.
	 */
	poll_table pt;
	wait_queue_head_t *wqh;
	wait_queue_t wait;
	struct work_struct remove;
};
K
KAMEZAWA Hiroyuki 已提交
186

187 188 189
/* The list of hierarchy roots */

static LIST_HEAD(roots);
190
static int root_count;
191

T
Tejun Heo 已提交
192 193 194 195 196
/*
 * Hierarchy ID allocation and mapping.  It follows the same exclusion
 * rules as other root ops - both cgroup_mutex and cgroup_root_mutex for
 * writes, either for reads.
 */
197
static DEFINE_IDR(cgroup_hierarchy_idr);
198

199 200 201
/* dummytop is a shorthand for the dummy hierarchy's top cgroup */
#define dummytop (&rootnode.top_cgroup)

202 203
static struct cgroup_name root_cgroup_name = { .name = "/" };

204
/* This flag indicates whether tasks in the fork and exit paths should
L
Li Zefan 已提交
205 206 207
 * check for fork/exit handlers to call. This avoids us having to do
 * extra work in the fork/exit path if none of the subsystems need to
 * be called.
208
 */
209
static int need_forkexit_callback __read_mostly;
210

211
static int cgroup_destroy_locked(struct cgroup *cgrp);
212 213
static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
			      struct cftype cfts[], bool is_add);
214

215 216 217 218 219
static int css_unbias_refcnt(int refcnt)
{
	return refcnt >= 0 ? refcnt : refcnt - CSS_DEACT_BIAS;
}

220 221 222 223 224
/* the current nr of refs, always >= 0 whether @css is deactivated or not */
static int css_refcnt(struct cgroup_subsys_state *css)
{
	int v = atomic_read(&css->refcnt);

225
	return css_unbias_refcnt(v);
226 227
}

228
/* convenient tests for these bits */
229
static inline bool cgroup_is_removed(const struct cgroup *cgrp)
230
{
231
	return test_bit(CGRP_REMOVED, &cgrp->flags);
232 233
}

234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252
/**
 * cgroup_is_descendant - test ancestry
 * @cgrp: the cgroup to be tested
 * @ancestor: possible ancestor of @cgrp
 *
 * Test whether @cgrp is a descendant of @ancestor.  It also returns %true
 * if @cgrp == @ancestor.  This function is safe to call as long as @cgrp
 * and @ancestor are accessible.
 */
bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor)
{
	while (cgrp) {
		if (cgrp == ancestor)
			return true;
		cgrp = cgrp->parent;
	}
	return false;
}
EXPORT_SYMBOL_GPL(cgroup_is_descendant);
253

254
static int cgroup_is_releasable(const struct cgroup *cgrp)
255 256
{
	const int bits =
257 258 259
		(1 << CGRP_RELEASABLE) |
		(1 << CGRP_NOTIFY_ON_RELEASE);
	return (cgrp->flags & bits) == bits;
260 261
}

262
static int notify_on_release(const struct cgroup *cgrp)
263
{
264
	return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
265 266
}

267 268 269 270 271 272 273
/*
 * for_each_subsys() allows you to iterate on each subsystem attached to
 * an active hierarchy
 */
#define for_each_subsys(_root, _ss) \
list_for_each_entry(_ss, &_root->subsys_list, sibling)

274 275
/* for_each_active_root() allows you to iterate across the active hierarchies */
#define for_each_active_root(_root) \
276 277
list_for_each_entry(_root, &roots, root_list)

278 279 280 281 282
static inline struct cgroup *__d_cgrp(struct dentry *dentry)
{
	return dentry->d_fsdata;
}

T
Tejun Heo 已提交
283
static inline struct cfent *__d_cfe(struct dentry *dentry)
284 285 286 287
{
	return dentry->d_fsdata;
}

T
Tejun Heo 已提交
288 289 290 291 292
static inline struct cftype *__d_cft(struct dentry *dentry)
{
	return __d_cfe(dentry)->type;
}

293 294 295 296
/**
 * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
 * @cgrp: the cgroup to be checked for liveness
 *
T
Tejun Heo 已提交
297 298
 * On success, returns true; the mutex should be later unlocked.  On
 * failure returns false with no lock held.
299
 */
300
static bool cgroup_lock_live_group(struct cgroup *cgrp)
301 302 303 304 305 306 307 308 309
{
	mutex_lock(&cgroup_mutex);
	if (cgroup_is_removed(cgrp)) {
		mutex_unlock(&cgroup_mutex);
		return false;
	}
	return true;
}

310 311 312
/* the list of cgroups eligible for automatic release. Protected by
 * release_list_lock */
static LIST_HEAD(release_list);
313
static DEFINE_RAW_SPINLOCK(release_list_lock);
314 315
static void cgroup_release_agent(struct work_struct *work);
static DECLARE_WORK(release_agent_work, cgroup_release_agent);
316
static void check_for_release(struct cgroup *cgrp);
317

318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335
/*
 * A cgroup can be associated with multiple css_sets as different tasks may
 * belong to different cgroups on different hierarchies.  In the other
 * direction, a css_set is naturally associated with multiple cgroups.
 * This M:N relationship is represented by the following link structure
 * which exists for each association and allows traversing the associations
 * from both sides.
 */
struct cgrp_cset_link {
	/* the cgroup and css_set this link associates */
	struct cgroup		*cgrp;
	struct css_set		*cset;

	/* list of cgrp_cset_links anchored at cgrp->cset_links */
	struct list_head	cset_link;

	/* list of cgrp_cset_links anchored at css_set->cgrp_links */
	struct list_head	cgrp_link;
336 337 338 339 340 341 342 343 344 345
};

/* The default css_set - used by init and its children prior to any
 * hierarchies being mounted. It contains a pointer to the root state
 * for each subsystem. Also used to anchor the list of css_sets. Not
 * reference-counted, to improve performance when child cgroups
 * haven't been created.
 */

static struct css_set init_css_set;
346
static struct cgrp_cset_link init_cgrp_cset_link;
347

348 349
static int cgroup_init_idr(struct cgroup_subsys *ss,
			   struct cgroup_subsys_state *css);
K
KAMEZAWA Hiroyuki 已提交
350

351 352 353 354 355 356
/* css_set_lock protects the list of css_set objects, and the
 * chain of tasks off each css_set.  Nests outside task->alloc_lock
 * due to cgroup_iter_start() */
static DEFINE_RWLOCK(css_set_lock);
static int css_set_count;

357 358 359 360 361
/*
 * hash table for cgroup groups. This improves the performance to find
 * an existing css_set. This hash doesn't (currently) take into
 * account cgroups in empty hierarchies.
 */
362
#define CSS_SET_HASH_BITS	7
363
static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
364

365
static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
366 367
{
	int i;
368
	unsigned long key = 0UL;
369 370

	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
371 372
		key += (unsigned long)css[i];
	key = (key >> 16) ^ key;
373

374
	return key;
375 376
}

377 378 379 380
/* We don't maintain the lists running through each css_set to its
 * task until after the first call to cgroup_iter_start(). This
 * reduces the fork()/exit() overhead for people who have cgroups
 * compiled into their kernel but not actually in use */
381
static int use_task_css_set_links __read_mostly;
382

383
static void __put_css_set(struct css_set *cset, int taskexit)
384
{
385
	struct cgrp_cset_link *link, *tmp_link;
386

387 388 389 390 391
	/*
	 * Ensure that the refcount doesn't hit zero while any readers
	 * can see it. Similar to atomic_dec_and_lock(), but for an
	 * rwlock
	 */
392
	if (atomic_add_unless(&cset->refcount, -1, 1))
393 394
		return;
	write_lock(&css_set_lock);
395
	if (!atomic_dec_and_test(&cset->refcount)) {
396 397 398
		write_unlock(&css_set_lock);
		return;
	}
399

400
	/* This css_set is dead. unlink it and release cgroup refcounts */
401
	hash_del(&cset->hlist);
402 403
	css_set_count--;

404
	list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
405
		struct cgroup *cgrp = link->cgrp;
406

407 408
		list_del(&link->cset_link);
		list_del(&link->cgrp_link);
L
Li Zefan 已提交
409 410 411 412 413 414 415

		/*
		 * We may not be holding cgroup_mutex, and if cgrp->count is
		 * dropped to 0 the cgroup can be destroyed at any time, hence
		 * rcu_read_lock is used to keep it alive.
		 */
		rcu_read_lock();
416 417
		if (atomic_dec_and_test(&cgrp->count) &&
		    notify_on_release(cgrp)) {
418
			if (taskexit)
419 420
				set_bit(CGRP_RELEASABLE, &cgrp->flags);
			check_for_release(cgrp);
421
		}
L
Li Zefan 已提交
422
		rcu_read_unlock();
423 424

		kfree(link);
425
	}
426 427

	write_unlock(&css_set_lock);
428
	kfree_rcu(cset, rcu_head);
429 430
}

431 432 433
/*
 * refcounted get/put for css_set objects
 */
434
static inline void get_css_set(struct css_set *cset)
435
{
436
	atomic_inc(&cset->refcount);
437 438
}

439
static inline void put_css_set(struct css_set *cset)
440
{
441
	__put_css_set(cset, 0);
442 443
}

444
static inline void put_css_set_taskexit(struct css_set *cset)
445
{
446
	__put_css_set(cset, 1);
447 448
}

449 450
/*
 * compare_css_sets - helper function for find_existing_css_set().
451 452
 * @cset: candidate css_set being tested
 * @old_cset: existing css_set for a task
453 454 455 456 457 458
 * @new_cgrp: cgroup that's being entered by the task
 * @template: desired set of css pointers in css_set (pre-calculated)
 *
 * Returns true if "cg" matches "old_cg" except for the hierarchy
 * which "new_cgrp" belongs to, for which it should match "new_cgrp".
 */
459 460
static bool compare_css_sets(struct css_set *cset,
			     struct css_set *old_cset,
461 462 463 464 465
			     struct cgroup *new_cgrp,
			     struct cgroup_subsys_state *template[])
{
	struct list_head *l1, *l2;

466
	if (memcmp(template, cset->subsys, sizeof(cset->subsys))) {
467 468 469 470 471 472 473 474 475 476 477 478 479
		/* Not all subsystems matched */
		return false;
	}

	/*
	 * Compare cgroup pointers in order to distinguish between
	 * different cgroups in heirarchies with no subsystems. We
	 * could get by with just this check alone (and skip the
	 * memcmp above) but on most setups the memcmp check will
	 * avoid the need for this more expensive check on almost all
	 * candidates.
	 */

480 481
	l1 = &cset->cgrp_links;
	l2 = &old_cset->cgrp_links;
482
	while (1) {
483
		struct cgrp_cset_link *link1, *link2;
484
		struct cgroup *cgrp1, *cgrp2;
485 486 487 488

		l1 = l1->next;
		l2 = l2->next;
		/* See if we reached the end - both lists are equal length. */
489 490
		if (l1 == &cset->cgrp_links) {
			BUG_ON(l2 != &old_cset->cgrp_links);
491 492
			break;
		} else {
493
			BUG_ON(l2 == &old_cset->cgrp_links);
494 495
		}
		/* Locate the cgroups associated with these links. */
496 497 498 499
		link1 = list_entry(l1, struct cgrp_cset_link, cgrp_link);
		link2 = list_entry(l2, struct cgrp_cset_link, cgrp_link);
		cgrp1 = link1->cgrp;
		cgrp2 = link2->cgrp;
500
		/* Hierarchies should be linked in the same order. */
501
		BUG_ON(cgrp1->root != cgrp2->root);
502 503 504 505 506 507 508 509

		/*
		 * If this hierarchy is the hierarchy of the cgroup
		 * that's changing, then we need to check that this
		 * css_set points to the new cgroup; if it's any other
		 * hierarchy, then this css_set should point to the
		 * same cgroup as the old css_set.
		 */
510 511
		if (cgrp1->root == new_cgrp->root) {
			if (cgrp1 != new_cgrp)
512 513
				return false;
		} else {
514
			if (cgrp1 != cgrp2)
515 516 517 518 519 520
				return false;
		}
	}
	return true;
}

521 522 523
/*
 * find_existing_css_set() is a helper for
 * find_css_set(), and checks to see whether an existing
524
 * css_set is suitable.
525 526 527 528
 *
 * oldcg: the cgroup group that we're using before the cgroup
 * transition
 *
529
 * cgrp: the cgroup that we're moving into
530 531 532 533
 *
 * template: location in which to build the desired set of subsystem
 * state objects for the new cgroup group
 */
534 535 536
static struct css_set *find_existing_css_set(struct css_set *old_cset,
					struct cgroup *cgrp,
					struct cgroup_subsys_state *template[])
537 538
{
	int i;
539
	struct cgroupfs_root *root = cgrp->root;
540
	struct css_set *cset;
541
	unsigned long key;
542

B
Ben Blum 已提交
543 544 545 546 547
	/*
	 * Build the set of subsystem state objects that we want to see in the
	 * new css_set. while subsystems can change globally, the entries here
	 * won't change, so no need for locking.
	 */
548
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
549
		if (root->subsys_mask & (1UL << i)) {
550 551 552
			/* Subsystem is in this hierarchy. So we want
			 * the subsystem state from the new
			 * cgroup */
553
			template[i] = cgrp->subsys[i];
554 555 556
		} else {
			/* Subsystem is not in this hierarchy, so we
			 * don't want to change the subsystem state */
557
			template[i] = old_cset->subsys[i];
558 559 560
		}
	}

561
	key = css_set_hash(template);
562 563
	hash_for_each_possible(css_set_table, cset, hlist, key) {
		if (!compare_css_sets(cset, old_cset, cgrp, template))
564 565 566
			continue;

		/* This css_set matches what we need */
567
		return cset;
568
	}
569 570 571 572 573

	/* No existing cgroup group matched */
	return NULL;
}

574
static void free_cgrp_cset_links(struct list_head *links_to_free)
575
{
576
	struct cgrp_cset_link *link, *tmp_link;
577

578 579
	list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
		list_del(&link->cset_link);
580 581 582 583
		kfree(link);
	}
}

584 585 586 587 588 589 590
/**
 * allocate_cgrp_cset_links - allocate cgrp_cset_links
 * @count: the number of links to allocate
 * @tmp_links: list_head the allocated links are put on
 *
 * Allocate @count cgrp_cset_link structures and chain them on @tmp_links
 * through ->cset_link.  Returns 0 on success or -errno.
591
 */
592
static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
593
{
594
	struct cgrp_cset_link *link;
595
	int i;
596 597 598

	INIT_LIST_HEAD(tmp_links);

599 600 601
	for (i = 0; i < count; i++) {
		link = kmalloc(sizeof(*link), GFP_KERNEL);
		if (!link) {
602
			free_cgrp_cset_links(tmp_links);
603 604
			return -ENOMEM;
		}
605
		list_add(&link->cset_link, tmp_links);
606 607 608 609
	}
	return 0;
}

610 611
/**
 * link_css_set - a helper function to link a css_set to a cgroup
612
 * @tmp_links: cgrp_cset_link objects allocated by allocate_cgrp_cset_links()
613
 * @cset: the css_set to be linked
614 615
 * @cgrp: the destination cgroup
 */
616 617
static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
			 struct cgroup *cgrp)
618
{
619
	struct cgrp_cset_link *link;
620

621 622 623
	BUG_ON(list_empty(tmp_links));
	link = list_first_entry(tmp_links, struct cgrp_cset_link, cset_link);
	link->cset = cset;
624
	link->cgrp = cgrp;
625
	atomic_inc(&cgrp->count);
626
	list_move(&link->cset_link, &cgrp->cset_links);
627 628 629 630
	/*
	 * Always add links to the tail of the list so that the list
	 * is sorted by order of hierarchy creation
	 */
631
	list_add_tail(&link->cgrp_link, &cset->cgrp_links);
632 633
}

634 635 636 637 638 639 640
/*
 * find_css_set() takes an existing cgroup group and a
 * cgroup object, and returns a css_set object that's
 * equivalent to the old group, but with the given cgroup
 * substituted into the appropriate hierarchy. Must be called with
 * cgroup_mutex held
 */
641 642
static struct css_set *find_css_set(struct css_set *old_cset,
				    struct cgroup *cgrp)
643
{
644
	struct css_set *cset;
645
	struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
646 647
	struct list_head tmp_links;
	struct cgrp_cset_link *link;
648
	unsigned long key;
649

650 651
	/* First see if we already have a cgroup group that matches
	 * the desired set */
652
	read_lock(&css_set_lock);
653 654 655
	cset = find_existing_css_set(old_cset, cgrp, template);
	if (cset)
		get_css_set(cset);
656
	read_unlock(&css_set_lock);
657

658 659
	if (cset)
		return cset;
660

661 662
	cset = kmalloc(sizeof(*cset), GFP_KERNEL);
	if (!cset)
663 664
		return NULL;

665 666
	/* Allocate all the cgrp_cset_link objects that we'll need */
	if (allocate_cgrp_cset_links(root_count, &tmp_links) < 0) {
667
		kfree(cset);
668 669 670
		return NULL;
	}

671
	atomic_set(&cset->refcount, 1);
672
	INIT_LIST_HEAD(&cset->cgrp_links);
673 674
	INIT_LIST_HEAD(&cset->tasks);
	INIT_HLIST_NODE(&cset->hlist);
675 676 677

	/* Copy the set of subsystem state objects generated in
	 * find_existing_css_set() */
678
	memcpy(cset->subsys, template, sizeof(cset->subsys));
679 680 681

	write_lock(&css_set_lock);
	/* Add reference counts and links from the new css_set. */
682
	list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
683
		struct cgroup *c = link->cgrp;
684

685 686
		if (c->root == cgrp->root)
			c = cgrp;
687
		link_css_set(&tmp_links, cset, c);
688
	}
689

690
	BUG_ON(!list_empty(&tmp_links));
691 692

	css_set_count++;
693 694

	/* Add this cgroup group to the hash table */
695 696
	key = css_set_hash(cset->subsys);
	hash_add(css_set_table, &cset->hlist, key);
697

698 699
	write_unlock(&css_set_lock);

700
	return cset;
701 702
}

703 704 705 706 707 708 709
/*
 * Return the cgroup for "task" from the given hierarchy. Must be
 * called with cgroup_mutex held.
 */
static struct cgroup *task_cgroup_from_root(struct task_struct *task,
					    struct cgroupfs_root *root)
{
710
	struct css_set *cset;
711 712 713 714 715 716 717 718 719
	struct cgroup *res = NULL;

	BUG_ON(!mutex_is_locked(&cgroup_mutex));
	read_lock(&css_set_lock);
	/*
	 * No need to lock the task - since we hold cgroup_mutex the
	 * task can't change groups, so the only thing that can happen
	 * is that it exits and its css is set back to init_css_set.
	 */
720 721
	cset = task->cgroups;
	if (cset == &init_css_set) {
722 723
		res = &root->top_cgroup;
	} else {
724 725 726
		struct cgrp_cset_link *link;

		list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
727
			struct cgroup *c = link->cgrp;
728

729 730 731 732 733 734 735 736 737 738 739
			if (c->root == root) {
				res = c;
				break;
			}
		}
	}
	read_unlock(&css_set_lock);
	BUG_ON(!res);
	return res;
}

740 741 742 743 744 745 746 747 748 749
/*
 * There is one global cgroup mutex. We also require taking
 * task_lock() when dereferencing a task's cgroup subsys pointers.
 * See "The task_lock() exception", at the end of this comment.
 *
 * A task must hold cgroup_mutex to modify cgroups.
 *
 * Any task can increment and decrement the count field without lock.
 * So in general, code holding cgroup_mutex can't rely on the count
 * field not changing.  However, if the count goes to zero, then only
750
 * cgroup_attach_task() can increment it again.  Because a count of zero
751 752 753 754 755 756 757 758 759 760 761 762 763
 * means that no tasks are currently attached, therefore there is no
 * way a task attached to that cgroup can fork (the other way to
 * increment the count).  So code holding cgroup_mutex can safely
 * assume that if the count is zero, it will stay zero. Similarly, if
 * a task holds cgroup_mutex on a cgroup with zero count, it
 * knows that the cgroup won't be removed, as cgroup_rmdir()
 * needs that mutex.
 *
 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
 * (usually) take cgroup_mutex.  These are the two most performance
 * critical pieces of code here.  The exception occurs on cgroup_exit(),
 * when a task in a notify_on_release cgroup exits.  Then cgroup_mutex
 * is taken, and if the cgroup count is zero, a usermode call made
L
Li Zefan 已提交
764 765
 * to the release agent with the name of the cgroup (path relative to
 * the root of cgroup file system) as the argument.
766 767 768 769 770 771 772 773 774 775 776
 *
 * A cgroup can only be deleted if both its 'count' of using tasks
 * is zero, and its list of 'children' cgroups is empty.  Since all
 * tasks in the system use _some_ cgroup, and since there is always at
 * least one task in the system (init, pid == 1), therefore, top_cgroup
 * always has either children cgroups and/or using tasks.  So we don't
 * need a special hack to ensure that top_cgroup cannot be deleted.
 *
 *	The task_lock() exception
 *
 * The need for this exception arises from the action of
777
 * cgroup_attach_task(), which overwrites one task's cgroup pointer with
L
Li Zefan 已提交
778
 * another.  It does so using cgroup_mutex, however there are
779 780 781
 * several performance critical places that need to reference
 * task->cgroup without the expense of grabbing a system global
 * mutex.  Therefore except as noted below, when dereferencing or, as
782
 * in cgroup_attach_task(), modifying a task's cgroup pointer we use
783 784 785 786
 * task_lock(), which acts on a spinlock (task->alloc_lock) already in
 * the task_struct routinely used for such matters.
 *
 * P.S.  One more locking exception.  RCU is used to guard the
787
 * update of a tasks cgroup pointer by cgroup_attach_task()
788 789 790 791 792 793 794 795 796
 */

/*
 * A couple of forward declarations required, due to cyclic reference loop:
 * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir ->
 * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations
 * -> cgroup_mkdir.
 */

797
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
A
Al Viro 已提交
798
static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);
799
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
800 801
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
			       unsigned long subsys_mask);
802
static const struct inode_operations cgroup_dir_inode_operations;
803
static const struct file_operations proc_cgroupstats_operations;
804 805

static struct backing_dev_info cgroup_backing_dev_info = {
806
	.name		= "cgroup",
807
	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
808
};
809

K
KAMEZAWA Hiroyuki 已提交
810 811 812
static int alloc_css_id(struct cgroup_subsys *ss,
			struct cgroup *parent, struct cgroup *child);

A
Al Viro 已提交
813
static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
814 815 816 817
{
	struct inode *inode = new_inode(sb);

	if (inode) {
818
		inode->i_ino = get_next_ino();
819
		inode->i_mode = mode;
820 821
		inode->i_uid = current_fsuid();
		inode->i_gid = current_fsgid();
822 823 824 825 826 827
		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
		inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info;
	}
	return inode;
}

828 829 830 831 832 833 834 835 836 837 838
static struct cgroup_name *cgroup_alloc_name(struct dentry *dentry)
{
	struct cgroup_name *name;

	name = kmalloc(sizeof(*name) + dentry->d_name.len + 1, GFP_KERNEL);
	if (!name)
		return NULL;
	strcpy(name->name, dentry->d_name.name);
	return name;
}

839 840 841 842 843 844 845 846 847 848 849 850 851 852 853
static void cgroup_free_fn(struct work_struct *work)
{
	struct cgroup *cgrp = container_of(work, struct cgroup, free_work);
	struct cgroup_subsys *ss;

	mutex_lock(&cgroup_mutex);
	/*
	 * Release the subsystem state objects.
	 */
	for_each_subsys(cgrp->root, ss)
		ss->css_free(cgrp);

	cgrp->root->number_of_cgroups--;
	mutex_unlock(&cgroup_mutex);

854 855 856 857 858 859 860
	/*
	 * We get a ref to the parent's dentry, and put the ref when
	 * this cgroup is being freed, so it's guaranteed that the
	 * parent won't be destroyed before its children.
	 */
	dput(cgrp->parent->dentry);

861 862
	ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id);

863 864
	/*
	 * Drop the active superblock reference that we took when we
865 866
	 * created the cgroup. This will free cgrp->root, if we are
	 * holding the last reference to @sb.
867 868 869 870 871 872 873 874 875 876 877
	 */
	deactivate_super(cgrp->root->sb);

	/*
	 * if we're getting rid of the cgroup, refcount should ensure
	 * that there are no pidlists left.
	 */
	BUG_ON(!list_empty(&cgrp->pidlists));

	simple_xattrs_free(&cgrp->xattrs);

878
	kfree(rcu_dereference_raw(cgrp->name));
879 880 881 882 883 884 885 886 887 888
	kfree(cgrp);
}

static void cgroup_free_rcu(struct rcu_head *head)
{
	struct cgroup *cgrp = container_of(head, struct cgroup, rcu_head);

	schedule_work(&cgrp->free_work);
}

889 890 891 892
static void cgroup_diput(struct dentry *dentry, struct inode *inode)
{
	/* is dentry a directory ? if so, kfree() associated cgroup */
	if (S_ISDIR(inode->i_mode)) {
893
		struct cgroup *cgrp = dentry->d_fsdata;
894

895
		BUG_ON(!(cgroup_is_removed(cgrp)));
896
		call_rcu(&cgrp->rcu_head, cgroup_free_rcu);
T
Tejun Heo 已提交
897 898 899 900 901 902 903
	} else {
		struct cfent *cfe = __d_cfe(dentry);
		struct cgroup *cgrp = dentry->d_parent->d_fsdata;

		WARN_ONCE(!list_empty(&cfe->node) &&
			  cgrp != &cgrp->root->top_cgroup,
			  "cfe still linked for %s\n", cfe->type->name);
L
Li Zefan 已提交
904
		simple_xattrs_free(&cfe->xattrs);
T
Tejun Heo 已提交
905
		kfree(cfe);
906 907 908 909
	}
	iput(inode);
}

910 911 912 913 914
static int cgroup_delete(const struct dentry *d)
{
	return 1;
}

915 916 917 918 919 920 921 922 923
static void remove_dir(struct dentry *d)
{
	struct dentry *parent = dget(d->d_parent);

	d_delete(d);
	simple_rmdir(parent->d_inode, d);
	dput(parent);
}

924
static void cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft)
T
Tejun Heo 已提交
925 926 927 928 929 930
{
	struct cfent *cfe;

	lockdep_assert_held(&cgrp->dentry->d_inode->i_mutex);
	lockdep_assert_held(&cgroup_mutex);

931 932 933 934
	/*
	 * If we're doing cleanup due to failure of cgroup_create(),
	 * the corresponding @cfe may not exist.
	 */
T
Tejun Heo 已提交
935 936 937 938 939 940 941 942
	list_for_each_entry(cfe, &cgrp->files, node) {
		struct dentry *d = cfe->dentry;

		if (cft && cfe->type != cft)
			continue;

		dget(d);
		d_delete(d);
943
		simple_unlink(cgrp->dentry->d_inode, d);
T
Tejun Heo 已提交
944 945 946
		list_del_init(&cfe->node);
		dput(d);

947
		break;
948
	}
T
Tejun Heo 已提交
949 950
}

951 952 953 954 955 956 957 958
/**
 * cgroup_clear_directory - selective removal of base and subsystem files
 * @dir: directory containing the files
 * @base_files: true if the base files should be removed
 * @subsys_mask: mask of the subsystem ids whose files should be removed
 */
static void cgroup_clear_directory(struct dentry *dir, bool base_files,
				   unsigned long subsys_mask)
T
Tejun Heo 已提交
959 960
{
	struct cgroup *cgrp = __d_cgrp(dir);
961
	struct cgroup_subsys *ss;
T
Tejun Heo 已提交
962

963 964 965 966 967
	for_each_subsys(cgrp->root, ss) {
		struct cftype_set *set;
		if (!test_bit(ss->subsys_id, &subsys_mask))
			continue;
		list_for_each_entry(set, &ss->cftsets, node)
968
			cgroup_addrm_files(cgrp, NULL, set->cfts, false);
969 970 971 972 973
	}
	if (base_files) {
		while (!list_empty(&cgrp->files))
			cgroup_rm_file(cgrp, NULL);
	}
974 975 976 977 978 979 980
}

/*
 * NOTE : the dentry must have been dget()'ed
 */
static void cgroup_d_remove_dir(struct dentry *dentry)
{
N
Nick Piggin 已提交
981
	struct dentry *parent;
982
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
N
Nick Piggin 已提交
983

984
	cgroup_clear_directory(dentry, true, root->subsys_mask);
985

N
Nick Piggin 已提交
986 987
	parent = dentry->d_parent;
	spin_lock(&parent->d_lock);
988
	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
989
	list_del_init(&dentry->d_u.d_child);
N
Nick Piggin 已提交
990 991
	spin_unlock(&dentry->d_lock);
	spin_unlock(&parent->d_lock);
992 993 994
	remove_dir(dentry);
}

B
Ben Blum 已提交
995
/*
B
Ben Blum 已提交
996 997 998
 * Call with cgroup_mutex held. Drops reference counts on modules, including
 * any duplicate ones that parse_cgroupfs_options took. If this function
 * returns an error, no reference counts are touched.
B
Ben Blum 已提交
999
 */
1000
static int rebind_subsystems(struct cgroupfs_root *root,
1001
			      unsigned long final_subsys_mask)
1002
{
1003
	unsigned long added_mask, removed_mask;
1004
	struct cgroup *cgrp = &root->top_cgroup;
1005 1006
	int i;

B
Ben Blum 已提交
1007
	BUG_ON(!mutex_is_locked(&cgroup_mutex));
T
Tejun Heo 已提交
1008
	BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
B
Ben Blum 已提交
1009

1010 1011
	removed_mask = root->actual_subsys_mask & ~final_subsys_mask;
	added_mask = final_subsys_mask & ~root->actual_subsys_mask;
1012 1013
	/* Check that any added subsystems are currently free */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
L
Li Zefan 已提交
1014
		unsigned long bit = 1UL << i;
1015
		struct cgroup_subsys *ss = subsys[i];
1016
		if (!(bit & added_mask))
1017
			continue;
B
Ben Blum 已提交
1018 1019 1020 1021 1022 1023
		/*
		 * Nobody should tell us to do a subsys that doesn't exist:
		 * parse_cgroupfs_options should catch that case and refcounts
		 * ensure that subsystems won't disappear once selected.
		 */
		BUG_ON(ss == NULL);
1024 1025 1026 1027 1028 1029 1030 1031 1032 1033
		if (ss->root != &rootnode) {
			/* Subsystem isn't free */
			return -EBUSY;
		}
	}

	/* Currently we don't handle adding/removing subsystems when
	 * any child cgroups exist. This is theoretically supportable
	 * but involves complex error handling, so it's being left until
	 * later */
1034
	if (root->number_of_cgroups > 1)
1035 1036 1037 1038 1039 1040
		return -EBUSY;

	/* Process each subsystem */
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
		unsigned long bit = 1UL << i;
1041
		if (bit & added_mask) {
1042
			/* We're binding this subsystem to this hierarchy */
B
Ben Blum 已提交
1043
			BUG_ON(ss == NULL);
1044
			BUG_ON(cgrp->subsys[i]);
1045 1046
			BUG_ON(!dummytop->subsys[i]);
			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1047 1048
			cgrp->subsys[i] = dummytop->subsys[i];
			cgrp->subsys[i]->cgroup = cgrp;
1049
			list_move(&ss->sibling, &root->subsys_list);
1050
			ss->root = root;
1051
			if (ss->bind)
1052
				ss->bind(cgrp);
B
Ben Blum 已提交
1053
			/* refcount was already taken, and we're keeping it */
1054
		} else if (bit & removed_mask) {
1055
			/* We're removing this subsystem */
B
Ben Blum 已提交
1056
			BUG_ON(ss == NULL);
1057 1058
			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1059
			if (ss->bind)
1060
				ss->bind(dummytop);
1061
			dummytop->subsys[i]->cgroup = dummytop;
1062
			cgrp->subsys[i] = NULL;
1063
			subsys[i]->root = &rootnode;
1064
			list_move(&ss->sibling, &rootnode.subsys_list);
B
Ben Blum 已提交
1065 1066
			/* subsystem is now free - drop reference on module */
			module_put(ss->module);
1067
		} else if (bit & final_subsys_mask) {
1068
			/* Subsystem state should already exist */
B
Ben Blum 已提交
1069
			BUG_ON(ss == NULL);
1070
			BUG_ON(!cgrp->subsys[i]);
B
Ben Blum 已提交
1071 1072 1073 1074 1075 1076 1077 1078
			/*
			 * a refcount was taken, but we already had one, so
			 * drop the extra reference.
			 */
			module_put(ss->module);
#ifdef CONFIG_MODULE_UNLOAD
			BUG_ON(ss->module && !module_refcount(ss->module));
#endif
1079 1080
		} else {
			/* Subsystem state shouldn't exist */
1081
			BUG_ON(cgrp->subsys[i]);
1082 1083
		}
	}
1084
	root->subsys_mask = root->actual_subsys_mask = final_subsys_mask;
1085 1086 1087 1088

	return 0;
}

1089
static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
1090
{
1091
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
1092 1093
	struct cgroup_subsys *ss;

T
Tejun Heo 已提交
1094
	mutex_lock(&cgroup_root_mutex);
1095 1096
	for_each_subsys(root, ss)
		seq_printf(seq, ",%s", ss->name);
1097 1098
	if (root->flags & CGRP_ROOT_SANE_BEHAVIOR)
		seq_puts(seq, ",sane_behavior");
1099
	if (root->flags & CGRP_ROOT_NOPREFIX)
1100
		seq_puts(seq, ",noprefix");
1101
	if (root->flags & CGRP_ROOT_XATTR)
A
Aristeu Rozanski 已提交
1102
		seq_puts(seq, ",xattr");
1103 1104
	if (strlen(root->release_agent_path))
		seq_printf(seq, ",release_agent=%s", root->release_agent_path);
1105
	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags))
1106
		seq_puts(seq, ",clone_children");
1107 1108
	if (strlen(root->name))
		seq_printf(seq, ",name=%s", root->name);
T
Tejun Heo 已提交
1109
	mutex_unlock(&cgroup_root_mutex);
1110 1111 1112 1113
	return 0;
}

struct cgroup_sb_opts {
1114
	unsigned long subsys_mask;
1115
	unsigned long flags;
1116
	char *release_agent;
1117
	bool cpuset_clone_children;
1118
	char *name;
1119 1120
	/* User explicitly requested empty subsystem */
	bool none;
1121 1122

	struct cgroupfs_root *new_root;
1123

1124 1125
};

B
Ben Blum 已提交
1126 1127
/*
 * Convert a hierarchy specifier into a bitmask of subsystems and flags. Call
B
Ben Blum 已提交
1128 1129 1130
 * with cgroup_mutex held to protect the subsys[] array. This function takes
 * refcounts on subsystems to be used, unless it returns error, in which case
 * no refcounts are taken.
B
Ben Blum 已提交
1131
 */
B
Ben Blum 已提交
1132
static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
1133
{
1134 1135
	char *token, *o = data;
	bool all_ss = false, one_ss = false;
1136
	unsigned long mask = (unsigned long)-1;
B
Ben Blum 已提交
1137 1138
	int i;
	bool module_pin_failed = false;
1139

B
Ben Blum 已提交
1140 1141
	BUG_ON(!mutex_is_locked(&cgroup_mutex));

1142 1143 1144
#ifdef CONFIG_CPUSETS
	mask = ~(1UL << cpuset_subsys_id);
#endif
1145

1146
	memset(opts, 0, sizeof(*opts));
1147 1148 1149 1150

	while ((token = strsep(&o, ",")) != NULL) {
		if (!*token)
			return -EINVAL;
1151
		if (!strcmp(token, "none")) {
1152 1153
			/* Explicitly have no subsystems */
			opts->none = true;
1154 1155 1156 1157 1158 1159 1160 1161 1162
			continue;
		}
		if (!strcmp(token, "all")) {
			/* Mutually exclusive option 'all' + subsystem name */
			if (one_ss)
				return -EINVAL;
			all_ss = true;
			continue;
		}
1163 1164 1165 1166
		if (!strcmp(token, "__DEVEL__sane_behavior")) {
			opts->flags |= CGRP_ROOT_SANE_BEHAVIOR;
			continue;
		}
1167
		if (!strcmp(token, "noprefix")) {
1168
			opts->flags |= CGRP_ROOT_NOPREFIX;
1169 1170 1171
			continue;
		}
		if (!strcmp(token, "clone_children")) {
1172
			opts->cpuset_clone_children = true;
1173 1174
			continue;
		}
A
Aristeu Rozanski 已提交
1175
		if (!strcmp(token, "xattr")) {
1176
			opts->flags |= CGRP_ROOT_XATTR;
A
Aristeu Rozanski 已提交
1177 1178
			continue;
		}
1179
		if (!strncmp(token, "release_agent=", 14)) {
1180 1181 1182
			/* Specifying two release agents is forbidden */
			if (opts->release_agent)
				return -EINVAL;
1183
			opts->release_agent =
1184
				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
1185 1186
			if (!opts->release_agent)
				return -ENOMEM;
1187 1188 1189
			continue;
		}
		if (!strncmp(token, "name=", 5)) {
1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206
			const char *name = token + 5;
			/* Can't specify an empty name */
			if (!strlen(name))
				return -EINVAL;
			/* Must match [\w.-]+ */
			for (i = 0; i < strlen(name); i++) {
				char c = name[i];
				if (isalnum(c))
					continue;
				if ((c == '.') || (c == '-') || (c == '_'))
					continue;
				return -EINVAL;
			}
			/* Specifying two names is forbidden */
			if (opts->name)
				return -EINVAL;
			opts->name = kstrndup(name,
1207
					      MAX_CGROUP_ROOT_NAMELEN - 1,
1208 1209 1210
					      GFP_KERNEL);
			if (!opts->name)
				return -ENOMEM;
1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226

			continue;
		}

		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss == NULL)
				continue;
			if (strcmp(token, ss->name))
				continue;
			if (ss->disabled)
				continue;

			/* Mutually exclusive option 'all' + subsystem name */
			if (all_ss)
				return -EINVAL;
1227
			set_bit(i, &opts->subsys_mask);
1228 1229 1230 1231 1232 1233 1234 1235 1236 1237
			one_ss = true;

			break;
		}
		if (i == CGROUP_SUBSYS_COUNT)
			return -ENOENT;
	}

	/*
	 * If the 'all' option was specified select all the subsystems,
1238 1239
	 * otherwise if 'none', 'name=' and a subsystem name options
	 * were not specified, let's default to 'all'
1240
	 */
1241
	if (all_ss || (!one_ss && !opts->none && !opts->name)) {
1242 1243 1244 1245 1246 1247
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
			struct cgroup_subsys *ss = subsys[i];
			if (ss == NULL)
				continue;
			if (ss->disabled)
				continue;
1248
			set_bit(i, &opts->subsys_mask);
1249 1250 1251
		}
	}

1252 1253
	/* Consistency checks */

1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267
	if (opts->flags & CGRP_ROOT_SANE_BEHAVIOR) {
		pr_warning("cgroup: sane_behavior: this is still under development and its behaviors will change, proceed at your own risk\n");

		if (opts->flags & CGRP_ROOT_NOPREFIX) {
			pr_err("cgroup: sane_behavior: noprefix is not allowed\n");
			return -EINVAL;
		}

		if (opts->cpuset_clone_children) {
			pr_err("cgroup: sane_behavior: clone_children is not allowed\n");
			return -EINVAL;
		}
	}

1268 1269 1270 1271 1272
	/*
	 * Option noprefix was introduced just for backward compatibility
	 * with the old cpuset, so we allow noprefix only if mounting just
	 * the cpuset subsystem.
	 */
1273
	if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
1274 1275
		return -EINVAL;

1276 1277

	/* Can't specify "none" and some subsystems */
1278
	if (opts->subsys_mask && opts->none)
1279 1280 1281 1282 1283 1284
		return -EINVAL;

	/*
	 * We either have to specify by name or by subsystems. (So all
	 * empty hierarchies must have a name).
	 */
1285
	if (!opts->subsys_mask && !opts->name)
1286 1287
		return -EINVAL;

B
Ben Blum 已提交
1288 1289 1290 1291 1292 1293
	/*
	 * Grab references on all the modules we'll need, so the subsystems
	 * don't dance around before rebind_subsystems attaches them. This may
	 * take duplicate reference counts on a subsystem that's already used,
	 * but rebind_subsystems handles this case.
	 */
1294
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
B
Ben Blum 已提交
1295 1296
		unsigned long bit = 1UL << i;

1297
		if (!(bit & opts->subsys_mask))
B
Ben Blum 已提交
1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309
			continue;
		if (!try_module_get(subsys[i]->module)) {
			module_pin_failed = true;
			break;
		}
	}
	if (module_pin_failed) {
		/*
		 * oops, one of the modules was going away. this means that we
		 * raced with a module_delete call, and to the user this is
		 * essentially a "subsystem doesn't exist" case.
		 */
1310
		for (i--; i >= 0; i--) {
B
Ben Blum 已提交
1311 1312 1313
			/* drop refcounts only on the ones we took */
			unsigned long bit = 1UL << i;

1314
			if (!(bit & opts->subsys_mask))
B
Ben Blum 已提交
1315 1316 1317 1318 1319 1320
				continue;
			module_put(subsys[i]->module);
		}
		return -ENOENT;
	}

1321 1322 1323
	return 0;
}

1324
static void drop_parsed_module_refcounts(unsigned long subsys_mask)
B
Ben Blum 已提交
1325 1326
{
	int i;
1327
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
B
Ben Blum 已提交
1328 1329
		unsigned long bit = 1UL << i;

1330
		if (!(bit & subsys_mask))
B
Ben Blum 已提交
1331 1332 1333 1334 1335
			continue;
		module_put(subsys[i]->module);
	}
}

1336 1337 1338 1339
static int cgroup_remount(struct super_block *sb, int *flags, char *data)
{
	int ret = 0;
	struct cgroupfs_root *root = sb->s_fs_info;
1340
	struct cgroup *cgrp = &root->top_cgroup;
1341
	struct cgroup_sb_opts opts;
1342
	unsigned long added_mask, removed_mask;
1343

1344 1345 1346 1347 1348
	if (root->flags & CGRP_ROOT_SANE_BEHAVIOR) {
		pr_err("cgroup: sane_behavior: remount is not allowed\n");
		return -EINVAL;
	}

1349
	mutex_lock(&cgrp->dentry->d_inode->i_mutex);
1350
	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1351
	mutex_lock(&cgroup_root_mutex);
1352 1353 1354 1355 1356 1357

	/* See what subsystems are wanted */
	ret = parse_cgroupfs_options(data, &opts);
	if (ret)
		goto out_unlock;

1358
	if (opts.subsys_mask != root->actual_subsys_mask || opts.release_agent)
1359 1360 1361
		pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
			   task_tgid_nr(current), current->comm);

1362 1363
	added_mask = opts.subsys_mask & ~root->subsys_mask;
	removed_mask = root->subsys_mask & ~opts.subsys_mask;
1364

B
Ben Blum 已提交
1365 1366 1367
	/* Don't allow flags or name to change at remount */
	if (opts.flags != root->flags ||
	    (opts.name && strcmp(opts.name, root->name))) {
1368
		ret = -EINVAL;
1369
		drop_parsed_module_refcounts(opts.subsys_mask);
1370 1371 1372
		goto out_unlock;
	}

1373 1374 1375 1376 1377 1378 1379
	/*
	 * Clear out the files of subsystems that should be removed, do
	 * this before rebind_subsystems, since rebind_subsystems may
	 * change this hierarchy's subsys_list.
	 */
	cgroup_clear_directory(cgrp->dentry, false, removed_mask);

1380
	ret = rebind_subsystems(root, opts.subsys_mask);
B
Ben Blum 已提交
1381
	if (ret) {
1382 1383
		/* rebind_subsystems failed, re-populate the removed files */
		cgroup_populate_dir(cgrp, false, removed_mask);
1384
		drop_parsed_module_refcounts(opts.subsys_mask);
1385
		goto out_unlock;
B
Ben Blum 已提交
1386
	}
1387

1388
	/* re-populate subsystem files */
1389
	cgroup_populate_dir(cgrp, false, added_mask);
1390

1391 1392
	if (opts.release_agent)
		strcpy(root->release_agent_path, opts.release_agent);
1393
 out_unlock:
1394
	kfree(opts.release_agent);
1395
	kfree(opts.name);
T
Tejun Heo 已提交
1396
	mutex_unlock(&cgroup_root_mutex);
1397
	mutex_unlock(&cgroup_mutex);
1398
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
1399 1400 1401
	return ret;
}

1402
static const struct super_operations cgroup_ops = {
1403 1404 1405 1406 1407 1408
	.statfs = simple_statfs,
	.drop_inode = generic_delete_inode,
	.show_options = cgroup_show_options,
	.remount_fs = cgroup_remount,
};

1409 1410 1411 1412
static void init_cgroup_housekeeping(struct cgroup *cgrp)
{
	INIT_LIST_HEAD(&cgrp->sibling);
	INIT_LIST_HEAD(&cgrp->children);
T
Tejun Heo 已提交
1413
	INIT_LIST_HEAD(&cgrp->files);
1414
	INIT_LIST_HEAD(&cgrp->cset_links);
1415
	INIT_LIST_HEAD(&cgrp->allcg_node);
1416
	INIT_LIST_HEAD(&cgrp->release_list);
1417
	INIT_LIST_HEAD(&cgrp->pidlists);
1418
	INIT_WORK(&cgrp->free_work, cgroup_free_fn);
1419
	mutex_init(&cgrp->pidlist_mutex);
1420 1421
	INIT_LIST_HEAD(&cgrp->event_list);
	spin_lock_init(&cgrp->event_list_lock);
A
Aristeu Rozanski 已提交
1422
	simple_xattrs_init(&cgrp->xattrs);
1423
}
1424

1425 1426
static void init_cgroup_root(struct cgroupfs_root *root)
{
1427
	struct cgroup *cgrp = &root->top_cgroup;
1428

1429 1430
	INIT_LIST_HEAD(&root->subsys_list);
	INIT_LIST_HEAD(&root->root_list);
1431
	INIT_LIST_HEAD(&root->allcg_list);
1432
	root->number_of_cgroups = 1;
1433
	cgrp->root = root;
1434
	cgrp->name = &root_cgroup_name;
1435
	init_cgroup_housekeeping(cgrp);
1436
	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
1437 1438
}

1439
static int cgroup_init_root_id(struct cgroupfs_root *root)
1440
{
1441
	int id;
1442

T
Tejun Heo 已提交
1443 1444 1445
	lockdep_assert_held(&cgroup_mutex);
	lockdep_assert_held(&cgroup_root_mutex);

1446 1447 1448 1449 1450
	id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 2, 0, GFP_KERNEL);
	if (id < 0)
		return id;

	root->hierarchy_id = id;
1451 1452 1453 1454 1455
	return 0;
}

static void cgroup_exit_root_id(struct cgroupfs_root *root)
{
T
Tejun Heo 已提交
1456 1457 1458
	lockdep_assert_held(&cgroup_mutex);
	lockdep_assert_held(&cgroup_root_mutex);

1459
	if (root->hierarchy_id) {
1460
		idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
1461 1462
		root->hierarchy_id = 0;
	}
1463 1464
}

1465 1466
static int cgroup_test_super(struct super_block *sb, void *data)
{
1467
	struct cgroup_sb_opts *opts = data;
1468 1469
	struct cgroupfs_root *root = sb->s_fs_info;

1470 1471 1472
	/* If we asked for a name then it must match */
	if (opts->name && strcmp(opts->name, root->name))
		return 0;
1473

1474 1475 1476 1477
	/*
	 * If we asked for subsystems (or explicitly for no
	 * subsystems) then they must match
	 */
1478 1479
	if ((opts->subsys_mask || opts->none)
	    && (opts->subsys_mask != root->subsys_mask))
1480 1481 1482 1483 1484
		return 0;

	return 1;
}

1485 1486 1487 1488
static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
{
	struct cgroupfs_root *root;

1489
	if (!opts->subsys_mask && !opts->none)
1490 1491 1492 1493 1494 1495 1496
		return NULL;

	root = kzalloc(sizeof(*root), GFP_KERNEL);
	if (!root)
		return ERR_PTR(-ENOMEM);

	init_cgroup_root(root);
1497

1498
	root->subsys_mask = opts->subsys_mask;
1499
	root->flags = opts->flags;
T
Tejun Heo 已提交
1500
	ida_init(&root->cgroup_ida);
1501 1502 1503 1504
	if (opts->release_agent)
		strcpy(root->release_agent_path, opts->release_agent);
	if (opts->name)
		strcpy(root->name, opts->name);
1505 1506
	if (opts->cpuset_clone_children)
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->top_cgroup.flags);
1507 1508 1509
	return root;
}

1510
static void cgroup_free_root(struct cgroupfs_root *root)
1511
{
1512 1513 1514
	if (root) {
		/* hierarhcy ID shoulid already have been released */
		WARN_ON_ONCE(root->hierarchy_id);
1515

1516 1517 1518
		ida_destroy(&root->cgroup_ida);
		kfree(root);
	}
1519 1520
}

1521 1522 1523
static int cgroup_set_super(struct super_block *sb, void *data)
{
	int ret;
1524 1525 1526 1527 1528 1529
	struct cgroup_sb_opts *opts = data;

	/* If we don't have a new root, we can't set up a new sb */
	if (!opts->new_root)
		return -EINVAL;

1530
	BUG_ON(!opts->subsys_mask && !opts->none);
1531 1532 1533 1534 1535

	ret = set_anon_super(sb, NULL);
	if (ret)
		return ret;

1536 1537
	sb->s_fs_info = opts->new_root;
	opts->new_root->sb = sb;
1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548

	sb->s_blocksize = PAGE_CACHE_SIZE;
	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
	sb->s_magic = CGROUP_SUPER_MAGIC;
	sb->s_op = &cgroup_ops;

	return 0;
}

static int cgroup_get_rootdir(struct super_block *sb)
{
A
Al Viro 已提交
1549 1550
	static const struct dentry_operations cgroup_dops = {
		.d_iput = cgroup_diput,
1551
		.d_delete = cgroup_delete,
A
Al Viro 已提交
1552 1553
	};

1554 1555 1556 1557 1558 1559 1560 1561 1562 1563
	struct inode *inode =
		cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb);

	if (!inode)
		return -ENOMEM;

	inode->i_fop = &simple_dir_operations;
	inode->i_op = &cgroup_dir_inode_operations;
	/* directories start off with i_nlink == 2 (for "." entry) */
	inc_nlink(inode);
1564 1565
	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
1566
		return -ENOMEM;
A
Al Viro 已提交
1567 1568
	/* for everything else we want ->d_op set */
	sb->s_d_op = &cgroup_dops;
1569 1570 1571
	return 0;
}

A
Al Viro 已提交
1572
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
1573
			 int flags, const char *unused_dev_name,
A
Al Viro 已提交
1574
			 void *data)
1575 1576
{
	struct cgroup_sb_opts opts;
1577
	struct cgroupfs_root *root;
1578 1579
	int ret = 0;
	struct super_block *sb;
1580
	struct cgroupfs_root *new_root;
T
Tejun Heo 已提交
1581
	struct inode *inode;
1582 1583

	/* First find the desired set of subsystems */
B
Ben Blum 已提交
1584
	mutex_lock(&cgroup_mutex);
1585
	ret = parse_cgroupfs_options(data, &opts);
B
Ben Blum 已提交
1586
	mutex_unlock(&cgroup_mutex);
1587 1588
	if (ret)
		goto out_err;
1589

1590 1591 1592 1593 1594 1595 1596
	/*
	 * Allocate a new cgroup root. We may not need it if we're
	 * reusing an existing hierarchy.
	 */
	new_root = cgroup_root_from_opts(&opts);
	if (IS_ERR(new_root)) {
		ret = PTR_ERR(new_root);
B
Ben Blum 已提交
1597
		goto drop_modules;
1598
	}
1599
	opts.new_root = new_root;
1600

1601
	/* Locate an existing or new sb for this hierarchy */
D
David Howells 已提交
1602
	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);
1603
	if (IS_ERR(sb)) {
1604
		ret = PTR_ERR(sb);
1605
		cgroup_free_root(opts.new_root);
B
Ben Blum 已提交
1606
		goto drop_modules;
1607 1608
	}

1609 1610 1611 1612
	root = sb->s_fs_info;
	BUG_ON(!root);
	if (root == opts.new_root) {
		/* We used the new root structure, so this is a new hierarchy */
1613
		struct list_head tmp_links;
1614
		struct cgroup *root_cgrp = &root->top_cgroup;
1615
		struct cgroupfs_root *existing_root;
1616
		const struct cred *cred;
1617
		int i;
1618
		struct css_set *cset;
1619 1620 1621 1622 1623 1624

		BUG_ON(sb->s_root != NULL);

		ret = cgroup_get_rootdir(sb);
		if (ret)
			goto drop_new_super;
1625
		inode = sb->s_root->d_inode;
1626

1627
		mutex_lock(&inode->i_mutex);
1628
		mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1629
		mutex_lock(&cgroup_root_mutex);
1630

T
Tejun Heo 已提交
1631 1632 1633 1634 1635 1636
		/* Check for name clashes with existing mounts */
		ret = -EBUSY;
		if (strlen(root->name))
			for_each_active_root(existing_root)
				if (!strcmp(existing_root->name, root->name))
					goto unlock_drop;
1637

1638 1639 1640 1641 1642 1643 1644
		/*
		 * We're accessing css_set_count without locking
		 * css_set_lock here, but that's OK - it can only be
		 * increased by someone holding cgroup_lock, and
		 * that's us. The worst that can happen is that we
		 * have some link structures left over
		 */
1645
		ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
T
Tejun Heo 已提交
1646 1647
		if (ret)
			goto unlock_drop;
1648

1649 1650 1651 1652
		ret = cgroup_init_root_id(root);
		if (ret)
			goto unlock_drop;

1653
		ret = rebind_subsystems(root, root->subsys_mask);
1654
		if (ret == -EBUSY) {
1655
			free_cgrp_cset_links(&tmp_links);
T
Tejun Heo 已提交
1656
			goto unlock_drop;
1657
		}
B
Ben Blum 已提交
1658 1659 1660 1661 1662
		/*
		 * There must be no failure case after here, since rebinding
		 * takes care of subsystems' refcounts, which are explicitly
		 * dropped in the failure exit path.
		 */
1663 1664 1665 1666 1667

		/* EBUSY should be the only error here */
		BUG_ON(ret);

		list_add(&root->root_list, &roots);
1668
		root_count++;
1669

1670
		sb->s_root->d_fsdata = root_cgrp;
1671 1672
		root->top_cgroup.dentry = sb->s_root;

1673 1674 1675
		/* Link the top cgroup in this hierarchy into all
		 * the css_set objects */
		write_lock(&css_set_lock);
1676
		hash_for_each(css_set_table, i, cset, hlist)
1677
			link_css_set(&tmp_links, cset, root_cgrp);
1678 1679
		write_unlock(&css_set_lock);

1680
		free_cgrp_cset_links(&tmp_links);
1681

1682
		BUG_ON(!list_empty(&root_cgrp->children));
1683 1684
		BUG_ON(root->number_of_cgroups != 1);

1685
		cred = override_creds(&init_cred);
1686
		cgroup_populate_dir(root_cgrp, true, root->subsys_mask);
1687
		revert_creds(cred);
T
Tejun Heo 已提交
1688
		mutex_unlock(&cgroup_root_mutex);
1689
		mutex_unlock(&cgroup_mutex);
1690
		mutex_unlock(&inode->i_mutex);
1691 1692 1693 1694 1695
	} else {
		/*
		 * We re-used an existing hierarchy - the new root (if
		 * any) is not needed
		 */
1696
		cgroup_free_root(opts.new_root);
1697 1698 1699 1700 1701 1702 1703 1704

		if (((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) &&
		    root->flags != opts.flags) {
			pr_err("cgroup: sane_behavior: new mount options should match the existing superblock\n");
			ret = -EINVAL;
			goto drop_new_super;
		}

B
Ben Blum 已提交
1705
		/* no subsys rebinding, so refcounts don't change */
1706
		drop_parsed_module_refcounts(opts.subsys_mask);
1707 1708
	}

1709 1710
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1711
	return dget(sb->s_root);
1712

T
Tejun Heo 已提交
1713
 unlock_drop:
1714
	cgroup_exit_root_id(root);
T
Tejun Heo 已提交
1715 1716 1717
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&inode->i_mutex);
1718
 drop_new_super:
1719
	deactivate_locked_super(sb);
B
Ben Blum 已提交
1720
 drop_modules:
1721
	drop_parsed_module_refcounts(opts.subsys_mask);
1722 1723 1724
 out_err:
	kfree(opts.release_agent);
	kfree(opts.name);
A
Al Viro 已提交
1725
	return ERR_PTR(ret);
1726 1727 1728 1729
}

static void cgroup_kill_sb(struct super_block *sb) {
	struct cgroupfs_root *root = sb->s_fs_info;
1730
	struct cgroup *cgrp = &root->top_cgroup;
1731
	struct cgrp_cset_link *link, *tmp_link;
1732 1733 1734 1735 1736
	int ret;

	BUG_ON(!root);

	BUG_ON(root->number_of_cgroups != 1);
1737
	BUG_ON(!list_empty(&cgrp->children));
1738 1739

	mutex_lock(&cgroup_mutex);
T
Tejun Heo 已提交
1740
	mutex_lock(&cgroup_root_mutex);
1741 1742 1743 1744 1745 1746

	/* Rebind all subsystems back to the default hierarchy */
	ret = rebind_subsystems(root, 0);
	/* Shouldn't be able to fail ... */
	BUG_ON(ret);

1747
	/*
1748
	 * Release all the links from cset_links to this hierarchy's
1749 1750 1751
	 * root cgroup
	 */
	write_lock(&css_set_lock);
K
KOSAKI Motohiro 已提交
1752

1753 1754 1755
	list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
		list_del(&link->cset_link);
		list_del(&link->cgrp_link);
1756 1757 1758 1759
		kfree(link);
	}
	write_unlock(&css_set_lock);

1760 1761 1762 1763
	if (!list_empty(&root->root_list)) {
		list_del(&root->root_list);
		root_count--;
	}
1764

1765 1766
	cgroup_exit_root_id(root);

T
Tejun Heo 已提交
1767
	mutex_unlock(&cgroup_root_mutex);
1768 1769
	mutex_unlock(&cgroup_mutex);

A
Aristeu Rozanski 已提交
1770 1771
	simple_xattrs_free(&cgrp->xattrs);

1772
	kill_litter_super(sb);
1773
	cgroup_free_root(root);
1774 1775 1776 1777
}

static struct file_system_type cgroup_fs_type = {
	.name = "cgroup",
A
Al Viro 已提交
1778
	.mount = cgroup_mount,
1779 1780 1781
	.kill_sb = cgroup_kill_sb,
};

1782 1783
static struct kobject *cgroup_kobj;

L
Li Zefan 已提交
1784 1785 1786 1787 1788 1789
/**
 * cgroup_path - generate the path of a cgroup
 * @cgrp: the cgroup in question
 * @buf: the buffer to write the path into
 * @buflen: the length of the buffer
 *
1790 1791 1792 1793 1794 1795
 * Writes path of cgroup into buf.  Returns 0 on success, -errno on error.
 *
 * We can't generate cgroup path using dentry->d_name, as accessing
 * dentry->name must be protected by irq-unsafe dentry->d_lock or parent
 * inode's i_mutex, while on the other hand cgroup_path() can be called
 * with some irq-safe spinlocks held.
1796
 */
1797
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1798
{
1799
	int ret = -ENAMETOOLONG;
1800
	char *start;
1801

1802 1803 1804
	if (!cgrp->parent) {
		if (strlcpy(buf, "/", buflen) >= buflen)
			return -ENAMETOOLONG;
1805 1806 1807
		return 0;
	}

1808 1809
	start = buf + buflen - 1;
	*start = '\0';
1810

1811
	rcu_read_lock();
1812
	do {
1813 1814 1815 1816
		const char *name = cgroup_name(cgrp);
		int len;

		len = strlen(name);
1817
		if ((start -= len) < buf)
1818 1819
			goto out;
		memcpy(start, name, len);
1820

1821
		if (--start < buf)
1822
			goto out;
1823
		*start = '/';
1824 1825

		cgrp = cgrp->parent;
1826
	} while (cgrp->parent);
1827
	ret = 0;
1828
	memmove(buf, start, buf + buflen - start);
1829 1830 1831
out:
	rcu_read_unlock();
	return ret;
1832
}
B
Ben Blum 已提交
1833
EXPORT_SYMBOL_GPL(cgroup_path);
1834

1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866
/**
 * task_cgroup_path_from_hierarchy - cgroup path of a task on a hierarchy
 * @task: target task
 * @hierarchy_id: the hierarchy to look up @task's cgroup from
 * @buf: the buffer to write the path into
 * @buflen: the length of the buffer
 *
 * Determine @task's cgroup on the hierarchy specified by @hierarchy_id and
 * copy its path into @buf.  This function grabs cgroup_mutex and shouldn't
 * be used inside locks used by cgroup controller callbacks.
 */
int task_cgroup_path_from_hierarchy(struct task_struct *task, int hierarchy_id,
				    char *buf, size_t buflen)
{
	struct cgroupfs_root *root;
	struct cgroup *cgrp = NULL;
	int ret = -ENOENT;

	mutex_lock(&cgroup_mutex);

	root = idr_find(&cgroup_hierarchy_idr, hierarchy_id);
	if (root) {
		cgrp = task_cgroup_from_root(task, root);
		ret = cgroup_path(cgrp, buf, buflen);
	}

	mutex_unlock(&cgroup_mutex);

	return ret;
}
EXPORT_SYMBOL_GPL(task_cgroup_path_from_hierarchy);

1867 1868 1869
/*
 * Control Group taskset
 */
1870 1871 1872
struct task_and_cgroup {
	struct task_struct	*task;
	struct cgroup		*cgrp;
1873
	struct css_set		*cg;
1874 1875
};

1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946
struct cgroup_taskset {
	struct task_and_cgroup	single;
	struct flex_array	*tc_array;
	int			tc_array_len;
	int			idx;
	struct cgroup		*cur_cgrp;
};

/**
 * cgroup_taskset_first - reset taskset and return the first task
 * @tset: taskset of interest
 *
 * @tset iteration is initialized and the first task is returned.
 */
struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
{
	if (tset->tc_array) {
		tset->idx = 0;
		return cgroup_taskset_next(tset);
	} else {
		tset->cur_cgrp = tset->single.cgrp;
		return tset->single.task;
	}
}
EXPORT_SYMBOL_GPL(cgroup_taskset_first);

/**
 * cgroup_taskset_next - iterate to the next task in taskset
 * @tset: taskset of interest
 *
 * Return the next task in @tset.  Iteration must have been initialized
 * with cgroup_taskset_first().
 */
struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
{
	struct task_and_cgroup *tc;

	if (!tset->tc_array || tset->idx >= tset->tc_array_len)
		return NULL;

	tc = flex_array_get(tset->tc_array, tset->idx++);
	tset->cur_cgrp = tc->cgrp;
	return tc->task;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_next);

/**
 * cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
 * @tset: taskset of interest
 *
 * Return the cgroup for the current (last returned) task of @tset.  This
 * function must be preceded by either cgroup_taskset_first() or
 * cgroup_taskset_next().
 */
struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
{
	return tset->cur_cgrp;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);

/**
 * cgroup_taskset_size - return the number of tasks in taskset
 * @tset: taskset of interest
 */
int cgroup_taskset_size(struct cgroup_taskset *tset)
{
	return tset->tc_array ? tset->tc_array_len : 1;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_size);


B
Ben Blum 已提交
1947 1948 1949
/*
 * cgroup_task_migrate - move a task from one cgroup to another.
 *
1950
 * Must be called with cgroup_mutex and threadgroup locked.
B
Ben Blum 已提交
1951
 */
1952 1953 1954
static void cgroup_task_migrate(struct cgroup *old_cgrp,
				struct task_struct *tsk,
				struct css_set *new_cset)
B
Ben Blum 已提交
1955
{
1956
	struct css_set *old_cset;
B
Ben Blum 已提交
1957 1958

	/*
1959 1960 1961
	 * We are synchronized through threadgroup_lock() against PF_EXITING
	 * setting such that we can't race against cgroup_exit() changing the
	 * css_set to init_css_set and dropping the old one.
B
Ben Blum 已提交
1962
	 */
1963
	WARN_ON_ONCE(tsk->flags & PF_EXITING);
1964
	old_cset = tsk->cgroups;
B
Ben Blum 已提交
1965 1966

	task_lock(tsk);
1967
	rcu_assign_pointer(tsk->cgroups, new_cset);
B
Ben Blum 已提交
1968 1969 1970 1971 1972
	task_unlock(tsk);

	/* Update the css_set linked lists if we're using them */
	write_lock(&css_set_lock);
	if (!list_empty(&tsk->cg_list))
1973
		list_move(&tsk->cg_list, &new_cset->tasks);
B
Ben Blum 已提交
1974 1975 1976
	write_unlock(&css_set_lock);

	/*
1977 1978 1979
	 * We just gained a reference on old_cset by taking it from the
	 * task. As trading it for new_cset is protected by cgroup_mutex,
	 * we're safe to drop it here; it will be freed under RCU.
B
Ben Blum 已提交
1980
	 */
1981 1982
	set_bit(CGRP_RELEASABLE, &old_cgrp->flags);
	put_css_set(old_cset);
B
Ben Blum 已提交
1983 1984
}

L
Li Zefan 已提交
1985
/**
1986
 * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
B
Ben Blum 已提交
1987
 * @cgrp: the cgroup to attach to
1988 1989
 * @tsk: the task or the leader of the threadgroup to be attached
 * @threadgroup: attach the whole threadgroup?
B
Ben Blum 已提交
1990
 *
1991
 * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
1992
 * task_lock of @tsk or each thread in the threadgroup individually in turn.
B
Ben Blum 已提交
1993
 */
T
Tejun Heo 已提交
1994 1995
static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
			      bool threadgroup)
B
Ben Blum 已提交
1996 1997 1998 1999 2000
{
	int retval, i, group_size;
	struct cgroup_subsys *ss, *failed_ss = NULL;
	struct cgroupfs_root *root = cgrp->root;
	/* threadgroup list cursor and array */
2001
	struct task_struct *leader = tsk;
2002
	struct task_and_cgroup *tc;
2003
	struct flex_array *group;
2004
	struct cgroup_taskset tset = { };
B
Ben Blum 已提交
2005 2006 2007 2008 2009

	/*
	 * step 0: in order to do expensive, possibly blocking operations for
	 * every thread, we cannot iterate the thread group list, since it needs
	 * rcu or tasklist locked. instead, build an array of all threads in the
2010 2011
	 * group - group_rwsem prevents new threads from appearing, and if
	 * threads exit, this will just be an over-estimate.
B
Ben Blum 已提交
2012
	 */
2013 2014 2015 2016
	if (threadgroup)
		group_size = get_nr_threads(tsk);
	else
		group_size = 1;
2017
	/* flex_array supports very large thread-groups better than kmalloc. */
2018
	group = flex_array_alloc(sizeof(*tc), group_size, GFP_KERNEL);
B
Ben Blum 已提交
2019 2020
	if (!group)
		return -ENOMEM;
2021
	/* pre-allocate to guarantee space while iterating in rcu read-side. */
2022
	retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
2023 2024
	if (retval)
		goto out_free_group_list;
B
Ben Blum 已提交
2025 2026

	i = 0;
2027 2028 2029 2030 2031 2032
	/*
	 * Prevent freeing of tasks while we take a snapshot. Tasks that are
	 * already PF_EXITING could be freed from underneath us unless we
	 * take an rcu_read_lock.
	 */
	rcu_read_lock();
B
Ben Blum 已提交
2033
	do {
2034 2035
		struct task_and_cgroup ent;

2036 2037 2038 2039
		/* @tsk either already exited or can't exit until the end */
		if (tsk->flags & PF_EXITING)
			continue;

B
Ben Blum 已提交
2040 2041
		/* as per above, nr_threads may decrease, but not increase. */
		BUG_ON(i >= group_size);
2042 2043
		ent.task = tsk;
		ent.cgrp = task_cgroup_from_root(tsk, root);
2044 2045 2046
		/* nothing to do if this task is already in the cgroup */
		if (ent.cgrp == cgrp)
			continue;
2047 2048 2049 2050
		/*
		 * saying GFP_ATOMIC has no effect here because we did prealloc
		 * earlier, but it's good form to communicate our expectations.
		 */
2051
		retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
2052
		BUG_ON(retval != 0);
B
Ben Blum 已提交
2053
		i++;
2054 2055 2056

		if (!threadgroup)
			break;
B
Ben Blum 已提交
2057
	} while_each_thread(leader, tsk);
2058
	rcu_read_unlock();
B
Ben Blum 已提交
2059 2060
	/* remember the number of threads in the array for later. */
	group_size = i;
2061 2062
	tset.tc_array = group;
	tset.tc_array_len = group_size;
B
Ben Blum 已提交
2063

2064 2065
	/* methods shouldn't be called if no task is actually migrating */
	retval = 0;
2066
	if (!group_size)
2067
		goto out_free_group_list;
2068

B
Ben Blum 已提交
2069 2070 2071 2072 2073
	/*
	 * step 1: check that we can legitimately attach to the cgroup.
	 */
	for_each_subsys(root, ss) {
		if (ss->can_attach) {
2074
			retval = ss->can_attach(cgrp, &tset);
B
Ben Blum 已提交
2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086
			if (retval) {
				failed_ss = ss;
				goto out_cancel_attach;
			}
		}
	}

	/*
	 * step 2: make sure css_sets exist for all threads to be migrated.
	 * we use find_css_set, which allocates a new one if necessary.
	 */
	for (i = 0; i < group_size; i++) {
2087
		tc = flex_array_get(group, i);
2088 2089 2090 2091
		tc->cg = find_css_set(tc->task->cgroups, cgrp);
		if (!tc->cg) {
			retval = -ENOMEM;
			goto out_put_css_set_refs;
B
Ben Blum 已提交
2092 2093 2094 2095
		}
	}

	/*
2096 2097 2098
	 * step 3: now that we're guaranteed success wrt the css_sets,
	 * proceed to move all tasks to the new cgroup.  There are no
	 * failure cases after here, so this is the commit point.
B
Ben Blum 已提交
2099 2100
	 */
	for (i = 0; i < group_size; i++) {
2101
		tc = flex_array_get(group, i);
2102
		cgroup_task_migrate(tc->cgrp, tc->task, tc->cg);
B
Ben Blum 已提交
2103 2104 2105 2106
	}
	/* nothing is sensitive to fork() after this point. */

	/*
2107
	 * step 4: do subsystem attach callbacks.
B
Ben Blum 已提交
2108 2109 2110
	 */
	for_each_subsys(root, ss) {
		if (ss->attach)
2111
			ss->attach(cgrp, &tset);
B
Ben Blum 已提交
2112 2113 2114 2115 2116 2117
	}

	/*
	 * step 5: success! and cleanup
	 */
	retval = 0;
2118 2119 2120 2121 2122 2123 2124 2125
out_put_css_set_refs:
	if (retval) {
		for (i = 0; i < group_size; i++) {
			tc = flex_array_get(group, i);
			if (!tc->cg)
				break;
			put_css_set(tc->cg);
		}
B
Ben Blum 已提交
2126 2127 2128 2129
	}
out_cancel_attach:
	if (retval) {
		for_each_subsys(root, ss) {
2130
			if (ss == failed_ss)
B
Ben Blum 已提交
2131 2132
				break;
			if (ss->cancel_attach)
2133
				ss->cancel_attach(cgrp, &tset);
B
Ben Blum 已提交
2134 2135 2136
		}
	}
out_free_group_list:
2137
	flex_array_free(group);
B
Ben Blum 已提交
2138 2139 2140 2141 2142
	return retval;
}

/*
 * Find the task_struct of the task to attach by vpid and pass it along to the
2143 2144
 * function to attach either it or all tasks in its threadgroup. Will lock
 * cgroup_mutex and threadgroup; may take task_lock of task.
2145
 */
B
Ben Blum 已提交
2146
static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
2147 2148
{
	struct task_struct *tsk;
2149
	const struct cred *cred = current_cred(), *tcred;
2150 2151
	int ret;

B
Ben Blum 已提交
2152 2153 2154
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;

2155 2156
retry_find_task:
	rcu_read_lock();
2157
	if (pid) {
2158
		tsk = find_task_by_vpid(pid);
B
Ben Blum 已提交
2159 2160
		if (!tsk) {
			rcu_read_unlock();
2161 2162
			ret= -ESRCH;
			goto out_unlock_cgroup;
2163
		}
B
Ben Blum 已提交
2164 2165 2166 2167
		/*
		 * even if we're attaching all tasks in the thread group, we
		 * only need to check permissions on one of them.
		 */
2168
		tcred = __task_cred(tsk);
2169 2170 2171
		if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
		    !uid_eq(cred->euid, tcred->uid) &&
		    !uid_eq(cred->euid, tcred->suid)) {
2172
			rcu_read_unlock();
2173 2174
			ret = -EACCES;
			goto out_unlock_cgroup;
2175
		}
2176 2177
	} else
		tsk = current;
2178 2179

	if (threadgroup)
2180
		tsk = tsk->group_leader;
2181 2182

	/*
2183
	 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
2184 2185 2186
	 * trapped in a cpuset, or RT worker may be born in a cgroup
	 * with no rt_runtime allocated.  Just say no.
	 */
2187
	if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) {
2188 2189 2190 2191 2192
		ret = -EINVAL;
		rcu_read_unlock();
		goto out_unlock_cgroup;
	}

2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209
	get_task_struct(tsk);
	rcu_read_unlock();

	threadgroup_lock(tsk);
	if (threadgroup) {
		if (!thread_group_leader(tsk)) {
			/*
			 * a race with de_thread from another thread's exec()
			 * may strip us of our leadership, if this happens,
			 * there is no choice but to throw this task away and
			 * try again; this is
			 * "double-double-toil-and-trouble-check locking".
			 */
			threadgroup_unlock(tsk);
			put_task_struct(tsk);
			goto retry_find_task;
		}
2210 2211 2212 2213
	}

	ret = cgroup_attach_task(cgrp, tsk, threadgroup);

2214 2215
	threadgroup_unlock(tsk);

2216
	put_task_struct(tsk);
2217
out_unlock_cgroup:
T
Tejun Heo 已提交
2218
	mutex_unlock(&cgroup_mutex);
2219 2220 2221
	return ret;
}

2222 2223 2224 2225 2226 2227 2228 2229 2230 2231
/**
 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
 * @from: attach to all cgroups of a given task
 * @tsk: the task to be attached
 */
int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
{
	struct cgroupfs_root *root;
	int retval = 0;

T
Tejun Heo 已提交
2232
	mutex_lock(&cgroup_mutex);
2233 2234 2235 2236 2237 2238 2239
	for_each_active_root(root) {
		struct cgroup *from_cg = task_cgroup_from_root(from, root);

		retval = cgroup_attach_task(from_cg, tsk, false);
		if (retval)
			break;
	}
T
Tejun Heo 已提交
2240
	mutex_unlock(&cgroup_mutex);
2241 2242 2243 2244 2245

	return retval;
}
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);

2246
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
B
Ben Blum 已提交
2247 2248 2249 2250 2251
{
	return attach_task_by_pid(cgrp, pid, false);
}

static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
2252
{
2253
	return attach_task_by_pid(cgrp, tgid, true);
2254 2255
}

2256 2257 2258 2259
static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft,
				      const char *buffer)
{
	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
2260 2261
	if (strlen(buffer) >= PATH_MAX)
		return -EINVAL;
2262 2263
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
T
Tejun Heo 已提交
2264
	mutex_lock(&cgroup_root_mutex);
2265
	strcpy(cgrp->root->release_agent_path, buffer);
T
Tejun Heo 已提交
2266
	mutex_unlock(&cgroup_root_mutex);
T
Tejun Heo 已提交
2267
	mutex_unlock(&cgroup_mutex);
2268 2269 2270 2271 2272 2273 2274 2275 2276 2277
	return 0;
}

static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft,
				     struct seq_file *seq)
{
	if (!cgroup_lock_live_group(cgrp))
		return -ENODEV;
	seq_puts(seq, cgrp->root->release_agent_path);
	seq_putc(seq, '\n');
T
Tejun Heo 已提交
2278
	mutex_unlock(&cgroup_mutex);
2279 2280 2281
	return 0;
}

2282 2283 2284 2285
static int cgroup_sane_behavior_show(struct cgroup *cgrp, struct cftype *cft,
				     struct seq_file *seq)
{
	seq_printf(seq, "%d\n", cgroup_sane_behavior(cgrp));
2286 2287 2288
	return 0;
}

2289 2290 2291
/* A buffer size big enough for numbers or short strings */
#define CGROUP_LOCAL_BUFFER_SIZE 64

2292
static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
2293 2294 2295
				struct file *file,
				const char __user *userbuf,
				size_t nbytes, loff_t *unused_ppos)
2296
{
2297
	char buffer[CGROUP_LOCAL_BUFFER_SIZE];
2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308
	int retval = 0;
	char *end;

	if (!nbytes)
		return -EINVAL;
	if (nbytes >= sizeof(buffer))
		return -E2BIG;
	if (copy_from_user(buffer, userbuf, nbytes))
		return -EFAULT;

	buffer[nbytes] = 0;     /* nul-terminate */
2309
	if (cft->write_u64) {
K
KOSAKI Motohiro 已提交
2310
		u64 val = simple_strtoull(strstrip(buffer), &end, 0);
2311 2312 2313 2314
		if (*end)
			return -EINVAL;
		retval = cft->write_u64(cgrp, cft, val);
	} else {
K
KOSAKI Motohiro 已提交
2315
		s64 val = simple_strtoll(strstrip(buffer), &end, 0);
2316 2317 2318 2319
		if (*end)
			return -EINVAL;
		retval = cft->write_s64(cgrp, cft, val);
	}
2320 2321 2322 2323 2324
	if (!retval)
		retval = nbytes;
	return retval;
}

2325 2326 2327 2328 2329
static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
				   struct file *file,
				   const char __user *userbuf,
				   size_t nbytes, loff_t *unused_ppos)
{
2330
	char local_buffer[CGROUP_LOCAL_BUFFER_SIZE];
2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344
	int retval = 0;
	size_t max_bytes = cft->max_write_len;
	char *buffer = local_buffer;

	if (!max_bytes)
		max_bytes = sizeof(local_buffer) - 1;
	if (nbytes >= max_bytes)
		return -E2BIG;
	/* Allocate a dynamic buffer if we need one */
	if (nbytes >= sizeof(local_buffer)) {
		buffer = kmalloc(nbytes + 1, GFP_KERNEL);
		if (buffer == NULL)
			return -ENOMEM;
	}
L
Li Zefan 已提交
2345 2346 2347 2348
	if (nbytes && copy_from_user(buffer, userbuf, nbytes)) {
		retval = -EFAULT;
		goto out;
	}
2349 2350

	buffer[nbytes] = 0;     /* nul-terminate */
K
KOSAKI Motohiro 已提交
2351
	retval = cft->write_string(cgrp, cft, strstrip(buffer));
2352 2353
	if (!retval)
		retval = nbytes;
L
Li Zefan 已提交
2354
out:
2355 2356 2357 2358 2359
	if (buffer != local_buffer)
		kfree(buffer);
	return retval;
}

2360 2361 2362 2363
static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
						size_t nbytes, loff_t *ppos)
{
	struct cftype *cft = __d_cft(file->f_dentry);
2364
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2365

2366
	if (cgroup_is_removed(cgrp))
2367
		return -ENODEV;
2368
	if (cft->write)
2369
		return cft->write(cgrp, cft, file, buf, nbytes, ppos);
2370 2371
	if (cft->write_u64 || cft->write_s64)
		return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
2372 2373
	if (cft->write_string)
		return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
2374 2375 2376 2377
	if (cft->trigger) {
		int ret = cft->trigger(cgrp, (unsigned int)cft->private);
		return ret ? ret : nbytes;
	}
2378
	return -EINVAL;
2379 2380
}

2381 2382 2383 2384
static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
2385
{
2386
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2387
	u64 val = cft->read_u64(cgrp, cft);
2388 2389 2390 2391 2392
	int len = sprintf(tmp, "%llu\n", (unsigned long long) val);

	return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
}

2393 2394 2395 2396 2397
static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
			       struct file *file,
			       char __user *buf, size_t nbytes,
			       loff_t *ppos)
{
2398
	char tmp[CGROUP_LOCAL_BUFFER_SIZE];
2399 2400 2401 2402 2403 2404
	s64 val = cft->read_s64(cgrp, cft);
	int len = sprintf(tmp, "%lld\n", (long long) val);

	return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
}

2405 2406 2407 2408
static ssize_t cgroup_file_read(struct file *file, char __user *buf,
				   size_t nbytes, loff_t *ppos)
{
	struct cftype *cft = __d_cft(file->f_dentry);
2409
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
2410

2411
	if (cgroup_is_removed(cgrp))
2412 2413 2414
		return -ENODEV;

	if (cft->read)
2415
		return cft->read(cgrp, cft, file, buf, nbytes, ppos);
2416 2417
	if (cft->read_u64)
		return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
2418 2419
	if (cft->read_s64)
		return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
2420 2421 2422
	return -EINVAL;
}

2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442
/*
 * seqfile ops/methods for returning structured data. Currently just
 * supports string->u64 maps, but can be extended in future.
 */

struct cgroup_seqfile_state {
	struct cftype *cft;
	struct cgroup *cgroup;
};

static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
{
	struct seq_file *sf = cb->state;
	return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);
}

static int cgroup_seqfile_show(struct seq_file *m, void *arg)
{
	struct cgroup_seqfile_state *state = m->private;
	struct cftype *cft = state->cft;
2443 2444 2445 2446 2447 2448 2449 2450
	if (cft->read_map) {
		struct cgroup_map_cb cb = {
			.fill = cgroup_map_add,
			.state = m,
		};
		return cft->read_map(state->cgroup, cft, &cb);
	}
	return cft->read_seq_string(state->cgroup, cft, m);
2451 2452
}

2453
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
2454 2455 2456 2457 2458 2459
{
	struct seq_file *seq = file->private_data;
	kfree(seq->private);
	return single_release(inode, file);
}

2460
static const struct file_operations cgroup_seqfile_operations = {
2461
	.read = seq_read,
2462
	.write = cgroup_file_write,
2463 2464 2465 2466
	.llseek = seq_lseek,
	.release = cgroup_seqfile_release,
};

2467 2468 2469 2470 2471 2472 2473 2474 2475
static int cgroup_file_open(struct inode *inode, struct file *file)
{
	int err;
	struct cftype *cft;

	err = generic_file_open(inode, file);
	if (err)
		return err;
	cft = __d_cft(file->f_dentry);
2476

2477
	if (cft->read_map || cft->read_seq_string) {
2478 2479 2480 2481 2482 2483 2484 2485 2486 2487 2488
		struct cgroup_seqfile_state *state =
			kzalloc(sizeof(*state), GFP_USER);
		if (!state)
			return -ENOMEM;
		state->cft = cft;
		state->cgroup = __d_cgrp(file->f_dentry->d_parent);
		file->f_op = &cgroup_seqfile_operations;
		err = single_open(file, cgroup_seqfile_show, state);
		if (err < 0)
			kfree(state);
	} else if (cft->open)
2489 2490 2491 2492 2493 2494 2495 2496 2497 2498 2499 2500 2501 2502 2503 2504 2505 2506 2507 2508 2509
		err = cft->open(inode, file);
	else
		err = 0;

	return err;
}

static int cgroup_file_release(struct inode *inode, struct file *file)
{
	struct cftype *cft = __d_cft(file->f_dentry);
	if (cft->release)
		return cft->release(inode, file);
	return 0;
}

/*
 * cgroup_rename - Only allow simple rename of directories in place.
 */
static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
			    struct inode *new_dir, struct dentry *new_dentry)
{
2510 2511 2512 2513 2514 2515 2516 2517 2518 2519
	int ret;
	struct cgroup_name *name, *old_name;
	struct cgroup *cgrp;

	/*
	 * It's convinient to use parent dir's i_mutex to protected
	 * cgrp->name.
	 */
	lockdep_assert_held(&old_dir->i_mutex);

2520 2521 2522 2523 2524 2525
	if (!S_ISDIR(old_dentry->d_inode->i_mode))
		return -ENOTDIR;
	if (new_dentry->d_inode)
		return -EEXIST;
	if (old_dir != new_dir)
		return -EIO;
2526 2527 2528 2529 2530 2531 2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543

	cgrp = __d_cgrp(old_dentry);

	name = cgroup_alloc_name(new_dentry);
	if (!name)
		return -ENOMEM;

	ret = simple_rename(old_dir, old_dentry, new_dir, new_dentry);
	if (ret) {
		kfree(name);
		return ret;
	}

	old_name = cgrp->name;
	rcu_assign_pointer(cgrp->name, name);

	kfree_rcu(old_name, rcu_head);
	return 0;
2544 2545
}

A
Aristeu Rozanski 已提交
2546 2547 2548 2549 2550
static struct simple_xattrs *__d_xattrs(struct dentry *dentry)
{
	if (S_ISDIR(dentry->d_inode->i_mode))
		return &__d_cgrp(dentry)->xattrs;
	else
L
Li Zefan 已提交
2551
		return &__d_cfe(dentry)->xattrs;
A
Aristeu Rozanski 已提交
2552 2553 2554 2555 2556
}

static inline int xattr_enabled(struct dentry *dentry)
{
	struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
2557
	return root->flags & CGRP_ROOT_XATTR;
A
Aristeu Rozanski 已提交
2558 2559 2560 2561 2562 2563 2564 2565 2566 2567 2568 2569 2570 2571 2572 2573 2574 2575 2576 2577 2578 2579 2580 2581 2582 2583 2584 2585 2586 2587 2588 2589 2590 2591 2592 2593 2594 2595 2596 2597 2598 2599 2600 2601 2602 2603
}

static bool is_valid_xattr(const char *name)
{
	if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
	    !strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN))
		return true;
	return false;
}

static int cgroup_setxattr(struct dentry *dentry, const char *name,
			   const void *val, size_t size, int flags)
{
	if (!xattr_enabled(dentry))
		return -EOPNOTSUPP;
	if (!is_valid_xattr(name))
		return -EINVAL;
	return simple_xattr_set(__d_xattrs(dentry), name, val, size, flags);
}

static int cgroup_removexattr(struct dentry *dentry, const char *name)
{
	if (!xattr_enabled(dentry))
		return -EOPNOTSUPP;
	if (!is_valid_xattr(name))
		return -EINVAL;
	return simple_xattr_remove(__d_xattrs(dentry), name);
}

static ssize_t cgroup_getxattr(struct dentry *dentry, const char *name,
			       void *buf, size_t size)
{
	if (!xattr_enabled(dentry))
		return -EOPNOTSUPP;
	if (!is_valid_xattr(name))
		return -EINVAL;
	return simple_xattr_get(__d_xattrs(dentry), name, buf, size);
}

static ssize_t cgroup_listxattr(struct dentry *dentry, char *buf, size_t size)
{
	if (!xattr_enabled(dentry))
		return -EOPNOTSUPP;
	return simple_xattr_list(__d_xattrs(dentry), buf, size);
}

2604
static const struct file_operations cgroup_file_operations = {
2605 2606 2607 2608 2609 2610 2611
	.read = cgroup_file_read,
	.write = cgroup_file_write,
	.llseek = generic_file_llseek,
	.open = cgroup_file_open,
	.release = cgroup_file_release,
};

A
Aristeu Rozanski 已提交
2612 2613 2614 2615 2616 2617 2618
static const struct inode_operations cgroup_file_inode_operations = {
	.setxattr = cgroup_setxattr,
	.getxattr = cgroup_getxattr,
	.listxattr = cgroup_listxattr,
	.removexattr = cgroup_removexattr,
};

2619
static const struct inode_operations cgroup_dir_inode_operations = {
2620
	.lookup = cgroup_lookup,
2621 2622 2623
	.mkdir = cgroup_mkdir,
	.rmdir = cgroup_rmdir,
	.rename = cgroup_rename,
A
Aristeu Rozanski 已提交
2624 2625 2626 2627
	.setxattr = cgroup_setxattr,
	.getxattr = cgroup_getxattr,
	.listxattr = cgroup_listxattr,
	.removexattr = cgroup_removexattr,
2628 2629
};

A
Al Viro 已提交
2630
static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
2631 2632 2633 2634 2635 2636 2637
{
	if (dentry->d_name.len > NAME_MAX)
		return ERR_PTR(-ENAMETOOLONG);
	d_add(dentry, NULL);
	return NULL;
}

2638 2639 2640 2641 2642
/*
 * Check if a file is a control file
 */
static inline struct cftype *__file_cft(struct file *file)
{
A
Al Viro 已提交
2643
	if (file_inode(file)->i_fop != &cgroup_file_operations)
2644 2645 2646 2647
		return ERR_PTR(-EINVAL);
	return __d_cft(file->f_dentry);
}

A
Al Viro 已提交
2648
static int cgroup_create_file(struct dentry *dentry, umode_t mode,
2649 2650
				struct super_block *sb)
{
2651 2652 2653 2654 2655 2656 2657 2658 2659 2660 2661 2662 2663 2664 2665 2666 2667
	struct inode *inode;

	if (!dentry)
		return -ENOENT;
	if (dentry->d_inode)
		return -EEXIST;

	inode = cgroup_new_inode(mode, sb);
	if (!inode)
		return -ENOMEM;

	if (S_ISDIR(mode)) {
		inode->i_op = &cgroup_dir_inode_operations;
		inode->i_fop = &simple_dir_operations;

		/* start off with i_nlink == 2 (for "." entry) */
		inc_nlink(inode);
T
Tejun Heo 已提交
2668
		inc_nlink(dentry->d_parent->d_inode);
2669

2670 2671 2672 2673 2674 2675 2676 2677 2678
		/*
		 * Control reaches here with cgroup_mutex held.
		 * @inode->i_mutex should nest outside cgroup_mutex but we
		 * want to populate it immediately without releasing
		 * cgroup_mutex.  As @inode isn't visible to anyone else
		 * yet, trylock will always succeed without affecting
		 * lockdep checks.
		 */
		WARN_ON_ONCE(!mutex_trylock(&inode->i_mutex));
2679 2680 2681
	} else if (S_ISREG(mode)) {
		inode->i_size = 0;
		inode->i_fop = &cgroup_file_operations;
A
Aristeu Rozanski 已提交
2682
		inode->i_op = &cgroup_file_inode_operations;
2683 2684 2685 2686 2687 2688
	}
	d_instantiate(dentry, inode);
	dget(dentry);	/* Extra count - pin the dentry in core */
	return 0;
}

L
Li Zefan 已提交
2689 2690 2691 2692 2693 2694 2695 2696 2697
/**
 * cgroup_file_mode - deduce file mode of a control file
 * @cft: the control file in question
 *
 * returns cft->mode if ->mode is not 0
 * returns S_IRUGO|S_IWUSR if it has both a read and a write handler
 * returns S_IRUGO if it has only a read handler
 * returns S_IWUSR if it has only a write hander
 */
A
Al Viro 已提交
2698
static umode_t cgroup_file_mode(const struct cftype *cft)
L
Li Zefan 已提交
2699
{
A
Al Viro 已提交
2700
	umode_t mode = 0;
L
Li Zefan 已提交
2701 2702 2703 2704 2705 2706 2707 2708 2709 2710 2711 2712 2713 2714 2715

	if (cft->mode)
		return cft->mode;

	if (cft->read || cft->read_u64 || cft->read_s64 ||
	    cft->read_map || cft->read_seq_string)
		mode |= S_IRUGO;

	if (cft->write || cft->write_u64 || cft->write_s64 ||
	    cft->write_string || cft->trigger)
		mode |= S_IWUSR;

	return mode;
}

T
Tejun Heo 已提交
2716
static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
A
Aristeu Rozanski 已提交
2717
			   struct cftype *cft)
2718
{
2719
	struct dentry *dir = cgrp->dentry;
T
Tejun Heo 已提交
2720
	struct cgroup *parent = __d_cgrp(dir);
2721
	struct dentry *dentry;
T
Tejun Heo 已提交
2722
	struct cfent *cfe;
2723
	int error;
A
Al Viro 已提交
2724
	umode_t mode;
2725
	char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
2726

2727
	if (subsys && !(cgrp->root->flags & CGRP_ROOT_NOPREFIX)) {
2728 2729 2730 2731
		strcpy(name, subsys->name);
		strcat(name, ".");
	}
	strcat(name, cft->name);
T
Tejun Heo 已提交
2732

2733
	BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex));
T
Tejun Heo 已提交
2734 2735 2736 2737 2738

	cfe = kzalloc(sizeof(*cfe), GFP_KERNEL);
	if (!cfe)
		return -ENOMEM;

2739
	dentry = lookup_one_len(name, dir, strlen(name));
T
Tejun Heo 已提交
2740
	if (IS_ERR(dentry)) {
2741
		error = PTR_ERR(dentry);
T
Tejun Heo 已提交
2742 2743 2744
		goto out;
	}

2745 2746 2747 2748 2749
	cfe->type = (void *)cft;
	cfe->dentry = dentry;
	dentry->d_fsdata = cfe;
	simple_xattrs_init(&cfe->xattrs);

T
Tejun Heo 已提交
2750 2751 2752 2753 2754 2755 2756 2757 2758
	mode = cgroup_file_mode(cft);
	error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
	if (!error) {
		list_add_tail(&cfe->node, &parent->files);
		cfe = NULL;
	}
	dput(dentry);
out:
	kfree(cfe);
2759 2760 2761
	return error;
}

2762
static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
A
Aristeu Rozanski 已提交
2763
			      struct cftype cfts[], bool is_add)
2764
{
A
Aristeu Rozanski 已提交
2765
	struct cftype *cft;
T
Tejun Heo 已提交
2766 2767 2768
	int err, ret = 0;

	for (cft = cfts; cft->name[0] != '\0'; cft++) {
2769
		/* does cft->flags tell us to skip this file on @cgrp? */
2770 2771
		if ((cft->flags & CFTYPE_INSANE) && cgroup_sane_behavior(cgrp))
			continue;
2772 2773 2774 2775 2776
		if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
			continue;
		if ((cft->flags & CFTYPE_ONLY_ON_ROOT) && cgrp->parent)
			continue;

2777
		if (is_add) {
2778
			err = cgroup_add_file(cgrp, subsys, cft);
2779 2780 2781
			if (err)
				pr_warn("cgroup_addrm_files: failed to add %s, err=%d\n",
					cft->name, err);
T
Tejun Heo 已提交
2782
			ret = err;
2783 2784
		} else {
			cgroup_rm_file(cgrp, cft);
T
Tejun Heo 已提交
2785
		}
2786
	}
T
Tejun Heo 已提交
2787
	return ret;
2788 2789
}

2790 2791 2792 2793 2794 2795 2796 2797 2798 2799 2800 2801 2802 2803 2804 2805 2806
static DEFINE_MUTEX(cgroup_cft_mutex);

static void cgroup_cfts_prepare(void)
	__acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex)
{
	/*
	 * Thanks to the entanglement with vfs inode locking, we can't walk
	 * the existing cgroups under cgroup_mutex and create files.
	 * Instead, we increment reference on all cgroups and build list of
	 * them using @cgrp->cft_q_node.  Grab cgroup_cft_mutex to ensure
	 * exclusive access to the field.
	 */
	mutex_lock(&cgroup_cft_mutex);
	mutex_lock(&cgroup_mutex);
}

static void cgroup_cfts_commit(struct cgroup_subsys *ss,
A
Aristeu Rozanski 已提交
2807
			       struct cftype *cfts, bool is_add)
2808 2809 2810 2811 2812 2813 2814 2815 2816 2817 2818 2819 2820 2821 2822 2823 2824 2825 2826 2827 2828 2829 2830 2831 2832
	__releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
{
	LIST_HEAD(pending);
	struct cgroup *cgrp, *n;

	/* %NULL @cfts indicates abort and don't bother if @ss isn't attached */
	if (cfts && ss->root != &rootnode) {
		list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) {
			dget(cgrp->dentry);
			list_add_tail(&cgrp->cft_q_node, &pending);
		}
	}

	mutex_unlock(&cgroup_mutex);

	/*
	 * All new cgroups will see @cfts update on @ss->cftsets.  Add/rm
	 * files for all cgroups which were created before.
	 */
	list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {
		struct inode *inode = cgrp->dentry->d_inode;

		mutex_lock(&inode->i_mutex);
		mutex_lock(&cgroup_mutex);
		if (!cgroup_is_removed(cgrp))
2833
			cgroup_addrm_files(cgrp, ss, cfts, is_add);
2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857
		mutex_unlock(&cgroup_mutex);
		mutex_unlock(&inode->i_mutex);

		list_del_init(&cgrp->cft_q_node);
		dput(cgrp->dentry);
	}

	mutex_unlock(&cgroup_cft_mutex);
}

/**
 * cgroup_add_cftypes - add an array of cftypes to a subsystem
 * @ss: target cgroup subsystem
 * @cfts: zero-length name terminated array of cftypes
 *
 * Register @cfts to @ss.  Files described by @cfts are created for all
 * existing cgroups to which @ss is attached and all future cgroups will
 * have them too.  This function can be called anytime whether @ss is
 * attached or not.
 *
 * Returns 0 on successful registration, -errno on failure.  Note that this
 * function currently returns 0 as long as @cfts registration is successful
 * even if some file creation attempts on existing cgroups fail.
 */
A
Aristeu Rozanski 已提交
2858
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2859 2860 2861 2862 2863 2864 2865 2866 2867 2868
{
	struct cftype_set *set;

	set = kzalloc(sizeof(*set), GFP_KERNEL);
	if (!set)
		return -ENOMEM;

	cgroup_cfts_prepare();
	set->cfts = cfts;
	list_add_tail(&set->node, &ss->cftsets);
2869
	cgroup_cfts_commit(ss, cfts, true);
2870 2871 2872 2873 2874

	return 0;
}
EXPORT_SYMBOL_GPL(cgroup_add_cftypes);

2875 2876 2877 2878 2879 2880 2881 2882 2883 2884 2885 2886 2887
/**
 * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
 * @ss: target cgroup subsystem
 * @cfts: zero-length name terminated array of cftypes
 *
 * Unregister @cfts from @ss.  Files described by @cfts are removed from
 * all existing cgroups to which @ss is attached and all future cgroups
 * won't have them either.  This function can be called anytime whether @ss
 * is attached or not.
 *
 * Returns 0 on successful unregistration, -ENOENT if @cfts is not
 * registered with @ss.
 */
A
Aristeu Rozanski 已提交
2888
int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
2889 2890 2891 2892 2893 2894 2895 2896 2897 2898 2899 2900 2901 2902 2903 2904 2905
{
	struct cftype_set *set;

	cgroup_cfts_prepare();

	list_for_each_entry(set, &ss->cftsets, node) {
		if (set->cfts == cfts) {
			list_del_init(&set->node);
			cgroup_cfts_commit(ss, cfts, false);
			return 0;
		}
	}

	cgroup_cfts_commit(ss, NULL, false);
	return -ENOENT;
}

L
Li Zefan 已提交
2906 2907 2908 2909 2910 2911
/**
 * cgroup_task_count - count the number of tasks in a cgroup.
 * @cgrp: the cgroup in question
 *
 * Return the number of tasks in the cgroup.
 */
2912
int cgroup_task_count(const struct cgroup *cgrp)
2913 2914
{
	int count = 0;
2915
	struct cgrp_cset_link *link;
2916 2917

	read_lock(&css_set_lock);
2918 2919
	list_for_each_entry(link, &cgrp->cset_links, cset_link)
		count += atomic_read(&link->cset->refcount);
2920
	read_unlock(&css_set_lock);
2921 2922 2923
	return count;
}

2924 2925 2926 2927
/*
 * Advance a list_head iterator.  The iterator should be positioned at
 * the start of a css_set
 */
2928
static void cgroup_advance_iter(struct cgroup *cgrp, struct cgroup_iter *it)
2929
{
2930 2931
	struct list_head *l = it->cset_link;
	struct cgrp_cset_link *link;
2932
	struct css_set *cset;
2933 2934 2935 2936

	/* Advance to the next non-empty css_set */
	do {
		l = l->next;
2937 2938
		if (l == &cgrp->cset_links) {
			it->cset_link = NULL;
2939 2940
			return;
		}
2941 2942
		link = list_entry(l, struct cgrp_cset_link, cset_link);
		cset = link->cset;
2943
	} while (list_empty(&cset->tasks));
2944
	it->cset_link = l;
2945
	it->task = cset->tasks.next;
2946 2947
}

2948 2949 2950 2951 2952 2953
/*
 * To reduce the fork() overhead for systems that are not actually
 * using their cgroups capability, we don't maintain the lists running
 * through each css_set to its tasks until we see the list actually
 * used - in other words after the first call to cgroup_iter_start().
 */
2954
static void cgroup_enable_task_cg_lists(void)
2955 2956 2957 2958
{
	struct task_struct *p, *g;
	write_lock(&css_set_lock);
	use_task_css_set_links = 1;
2959 2960 2961 2962 2963 2964 2965 2966
	/*
	 * We need tasklist_lock because RCU is not safe against
	 * while_each_thread(). Besides, a forking task that has passed
	 * cgroup_post_fork() without seeing use_task_css_set_links = 1
	 * is not guaranteed to have its child immediately visible in the
	 * tasklist if we walk through it with RCU.
	 */
	read_lock(&tasklist_lock);
2967 2968
	do_each_thread(g, p) {
		task_lock(p);
2969 2970 2971 2972 2973 2974
		/*
		 * We should check if the process is exiting, otherwise
		 * it will race with cgroup_exit() in that the list
		 * entry won't be deleted though the process has exited.
		 */
		if (!(p->flags & PF_EXITING) && list_empty(&p->cg_list))
2975 2976 2977
			list_add(&p->cg_list, &p->cgroups->tasks);
		task_unlock(p);
	} while_each_thread(g, p);
2978
	read_unlock(&tasklist_lock);
2979 2980 2981
	write_unlock(&css_set_lock);
}

2982 2983 2984 2985 2986 2987 2988 2989 2990 2991 2992 2993 2994 2995 2996 2997 2998 2999 3000 3001 3002 3003 3004 3005 3006 3007 3008 3009 3010 3011 3012 3013 3014 3015 3016 3017 3018 3019 3020 3021 3022 3023 3024 3025 3026 3027 3028 3029 3030
/**
 * cgroup_next_sibling - find the next sibling of a given cgroup
 * @pos: the current cgroup
 *
 * This function returns the next sibling of @pos and should be called
 * under RCU read lock.  The only requirement is that @pos is accessible.
 * The next sibling is guaranteed to be returned regardless of @pos's
 * state.
 */
struct cgroup *cgroup_next_sibling(struct cgroup *pos)
{
	struct cgroup *next;

	WARN_ON_ONCE(!rcu_read_lock_held());

	/*
	 * @pos could already have been removed.  Once a cgroup is removed,
	 * its ->sibling.next is no longer updated when its next sibling
	 * changes.  As CGRP_REMOVED is set on removal which is fully
	 * serialized, if we see it unasserted, it's guaranteed that the
	 * next sibling hasn't finished its grace period even if it's
	 * already removed, and thus safe to dereference from this RCU
	 * critical section.  If ->sibling.next is inaccessible,
	 * cgroup_is_removed() is guaranteed to be visible as %true here.
	 */
	if (likely(!cgroup_is_removed(pos))) {
		next = list_entry_rcu(pos->sibling.next, struct cgroup, sibling);
		if (&next->sibling != &pos->parent->children)
			return next;
		return NULL;
	}

	/*
	 * Can't dereference the next pointer.  Each cgroup is given a
	 * monotonically increasing unique serial number and always
	 * appended to the sibling list, so the next one can be found by
	 * walking the parent's children until we see a cgroup with higher
	 * serial number than @pos's.
	 *
	 * While this path can be slow, it's taken only when either the
	 * current cgroup is removed or iteration and removal race.
	 */
	list_for_each_entry_rcu(next, &pos->parent->children, sibling)
		if (next->serial_nr > pos->serial_nr)
			return next;
	return NULL;
}
EXPORT_SYMBOL_GPL(cgroup_next_sibling);

3031 3032 3033 3034 3035 3036 3037
/**
 * cgroup_next_descendant_pre - find the next descendant for pre-order walk
 * @pos: the current position (%NULL to initiate traversal)
 * @cgroup: cgroup whose descendants to walk
 *
 * To be used by cgroup_for_each_descendant_pre().  Find the next
 * descendant to visit for pre-order traversal of @cgroup's descendants.
3038 3039 3040 3041 3042
 *
 * While this function requires RCU read locking, it doesn't require the
 * whole traversal to be contained in a single RCU critical section.  This
 * function will return the correct next descendant as long as both @pos
 * and @cgroup are accessible and @pos is a descendant of @cgroup.
3043 3044 3045 3046 3047 3048 3049 3050 3051
 */
struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
					  struct cgroup *cgroup)
{
	struct cgroup *next;

	WARN_ON_ONCE(!rcu_read_lock_held());

	/* if first iteration, pretend we just visited @cgroup */
3052
	if (!pos)
3053 3054 3055 3056 3057 3058 3059 3060
		pos = cgroup;

	/* visit the first child if exists */
	next = list_first_or_null_rcu(&pos->children, struct cgroup, sibling);
	if (next)
		return next;

	/* no child, visit my or the closest ancestor's next sibling */
3061
	while (pos != cgroup) {
3062 3063
		next = cgroup_next_sibling(pos);
		if (next)
3064 3065
			return next;
		pos = pos->parent;
3066
	}
3067 3068 3069 3070 3071

	return NULL;
}
EXPORT_SYMBOL_GPL(cgroup_next_descendant_pre);

3072 3073 3074 3075 3076 3077 3078
/**
 * cgroup_rightmost_descendant - return the rightmost descendant of a cgroup
 * @pos: cgroup of interest
 *
 * Return the rightmost descendant of @pos.  If there's no descendant,
 * @pos is returned.  This can be used during pre-order traversal to skip
 * subtree of @pos.
3079 3080 3081 3082 3083
 *
 * While this function requires RCU read locking, it doesn't require the
 * whole traversal to be contained in a single RCU critical section.  This
 * function will return the correct rightmost descendant as long as @pos is
 * accessible.
3084 3085 3086 3087 3088 3089 3090 3091 3092 3093 3094 3095 3096 3097 3098 3099 3100 3101 3102
 */
struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos)
{
	struct cgroup *last, *tmp;

	WARN_ON_ONCE(!rcu_read_lock_held());

	do {
		last = pos;
		/* ->prev isn't RCU safe, walk ->next till the end */
		pos = NULL;
		list_for_each_entry_rcu(tmp, &last->children, sibling)
			pos = tmp;
	} while (pos);

	return last;
}
EXPORT_SYMBOL_GPL(cgroup_rightmost_descendant);

3103 3104 3105 3106 3107 3108 3109 3110 3111 3112 3113 3114 3115 3116 3117 3118 3119 3120 3121 3122
static struct cgroup *cgroup_leftmost_descendant(struct cgroup *pos)
{
	struct cgroup *last;

	do {
		last = pos;
		pos = list_first_or_null_rcu(&pos->children, struct cgroup,
					     sibling);
	} while (pos);

	return last;
}

/**
 * cgroup_next_descendant_post - find the next descendant for post-order walk
 * @pos: the current position (%NULL to initiate traversal)
 * @cgroup: cgroup whose descendants to walk
 *
 * To be used by cgroup_for_each_descendant_post().  Find the next
 * descendant to visit for post-order traversal of @cgroup's descendants.
3123 3124 3125 3126 3127
 *
 * While this function requires RCU read locking, it doesn't require the
 * whole traversal to be contained in a single RCU critical section.  This
 * function will return the correct next descendant as long as both @pos
 * and @cgroup are accessible and @pos is a descendant of @cgroup.
3128 3129 3130 3131 3132 3133 3134 3135 3136 3137 3138 3139 3140 3141 3142
 */
struct cgroup *cgroup_next_descendant_post(struct cgroup *pos,
					   struct cgroup *cgroup)
{
	struct cgroup *next;

	WARN_ON_ONCE(!rcu_read_lock_held());

	/* if first iteration, visit the leftmost descendant */
	if (!pos) {
		next = cgroup_leftmost_descendant(cgroup);
		return next != cgroup ? next : NULL;
	}

	/* if there's an unvisited sibling, visit its leftmost descendant */
3143 3144
	next = cgroup_next_sibling(pos);
	if (next)
3145 3146 3147 3148 3149 3150 3151 3152
		return cgroup_leftmost_descendant(next);

	/* no sibling left, visit parent */
	next = pos->parent;
	return next != cgroup ? next : NULL;
}
EXPORT_SYMBOL_GPL(cgroup_next_descendant_post);

3153
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
3154
	__acquires(css_set_lock)
3155 3156 3157 3158 3159 3160
{
	/*
	 * The first time anyone tries to iterate across a cgroup,
	 * we need to enable the list linking each css_set to its
	 * tasks, and fix up all existing tasks.
	 */
3161 3162 3163
	if (!use_task_css_set_links)
		cgroup_enable_task_cg_lists();

3164
	read_lock(&css_set_lock);
3165
	it->cset_link = &cgrp->cset_links;
3166
	cgroup_advance_iter(cgrp, it);
3167 3168
}

3169
struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
3170 3171 3172 3173
					struct cgroup_iter *it)
{
	struct task_struct *res;
	struct list_head *l = it->task;
3174
	struct cgrp_cset_link *link;
3175 3176

	/* If the iterator cg is NULL, we have no tasks */
3177
	if (!it->cset_link)
3178 3179 3180 3181
		return NULL;
	res = list_entry(l, struct task_struct, cg_list);
	/* Advance iterator to find next entry */
	l = l->next;
3182 3183
	link = list_entry(it->cset_link, struct cgrp_cset_link, cset_link);
	if (l == &link->cset->tasks) {
3184 3185
		/* We reached the end of this task list - move on to
		 * the next cg_cgroup_link */
3186
		cgroup_advance_iter(cgrp, it);
3187 3188 3189 3190 3191 3192
	} else {
		it->task = l;
	}
	return res;
}

3193
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it)
3194
	__releases(css_set_lock)
3195 3196 3197 3198
{
	read_unlock(&css_set_lock);
}

3199 3200 3201 3202 3203 3204 3205 3206 3207 3208 3209 3210 3211 3212 3213 3214 3215 3216 3217 3218 3219 3220 3221 3222 3223 3224 3225 3226 3227 3228 3229 3230 3231 3232 3233 3234 3235 3236 3237 3238 3239 3240 3241 3242 3243 3244 3245 3246 3247 3248 3249 3250 3251 3252 3253 3254 3255 3256 3257 3258 3259 3260 3261 3262 3263 3264 3265 3266 3267 3268 3269 3270 3271 3272 3273 3274 3275 3276 3277 3278 3279 3280 3281 3282 3283 3284 3285 3286 3287 3288 3289 3290 3291 3292 3293 3294 3295 3296 3297 3298 3299 3300 3301 3302 3303 3304 3305 3306 3307 3308 3309 3310 3311 3312 3313 3314 3315 3316 3317 3318 3319 3320 3321 3322 3323 3324 3325 3326 3327 3328 3329 3330 3331 3332 3333 3334 3335
static inline int started_after_time(struct task_struct *t1,
				     struct timespec *time,
				     struct task_struct *t2)
{
	int start_diff = timespec_compare(&t1->start_time, time);
	if (start_diff > 0) {
		return 1;
	} else if (start_diff < 0) {
		return 0;
	} else {
		/*
		 * Arbitrarily, if two processes started at the same
		 * time, we'll say that the lower pointer value
		 * started first. Note that t2 may have exited by now
		 * so this may not be a valid pointer any longer, but
		 * that's fine - it still serves to distinguish
		 * between two tasks started (effectively) simultaneously.
		 */
		return t1 > t2;
	}
}

/*
 * This function is a callback from heap_insert() and is used to order
 * the heap.
 * In this case we order the heap in descending task start time.
 */
static inline int started_after(void *p1, void *p2)
{
	struct task_struct *t1 = p1;
	struct task_struct *t2 = p2;
	return started_after_time(t1, &t2->start_time, t2);
}

/**
 * cgroup_scan_tasks - iterate though all the tasks in a cgroup
 * @scan: struct cgroup_scanner containing arguments for the scan
 *
 * Arguments include pointers to callback functions test_task() and
 * process_task().
 * Iterate through all the tasks in a cgroup, calling test_task() for each,
 * and if it returns true, call process_task() for it also.
 * The test_task pointer may be NULL, meaning always true (select all tasks).
 * Effectively duplicates cgroup_iter_{start,next,end}()
 * but does not lock css_set_lock for the call to process_task().
 * The struct cgroup_scanner may be embedded in any structure of the caller's
 * creation.
 * It is guaranteed that process_task() will act on every task that
 * is a member of the cgroup for the duration of this call. This
 * function may or may not call process_task() for tasks that exit
 * or move to a different cgroup during the call, or are forked or
 * move into the cgroup during the call.
 *
 * Note that test_task() may be called with locks held, and may in some
 * situations be called multiple times for the same task, so it should
 * be cheap.
 * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
 * pre-allocated and will be used for heap operations (and its "gt" member will
 * be overwritten), else a temporary heap will be used (allocation of which
 * may cause this function to fail).
 */
int cgroup_scan_tasks(struct cgroup_scanner *scan)
{
	int retval, i;
	struct cgroup_iter it;
	struct task_struct *p, *dropped;
	/* Never dereference latest_task, since it's not refcounted */
	struct task_struct *latest_task = NULL;
	struct ptr_heap tmp_heap;
	struct ptr_heap *heap;
	struct timespec latest_time = { 0, 0 };

	if (scan->heap) {
		/* The caller supplied our heap and pre-allocated its memory */
		heap = scan->heap;
		heap->gt = &started_after;
	} else {
		/* We need to allocate our own heap memory */
		heap = &tmp_heap;
		retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
		if (retval)
			/* cannot allocate the heap */
			return retval;
	}

 again:
	/*
	 * Scan tasks in the cgroup, using the scanner's "test_task" callback
	 * to determine which are of interest, and using the scanner's
	 * "process_task" callback to process any of them that need an update.
	 * Since we don't want to hold any locks during the task updates,
	 * gather tasks to be processed in a heap structure.
	 * The heap is sorted by descending task start time.
	 * If the statically-sized heap fills up, we overflow tasks that
	 * started later, and in future iterations only consider tasks that
	 * started after the latest task in the previous pass. This
	 * guarantees forward progress and that we don't miss any tasks.
	 */
	heap->size = 0;
	cgroup_iter_start(scan->cg, &it);
	while ((p = cgroup_iter_next(scan->cg, &it))) {
		/*
		 * Only affect tasks that qualify per the caller's callback,
		 * if he provided one
		 */
		if (scan->test_task && !scan->test_task(p, scan))
			continue;
		/*
		 * Only process tasks that started after the last task
		 * we processed
		 */
		if (!started_after_time(p, &latest_time, latest_task))
			continue;
		dropped = heap_insert(heap, p);
		if (dropped == NULL) {
			/*
			 * The new task was inserted; the heap wasn't
			 * previously full
			 */
			get_task_struct(p);
		} else if (dropped != p) {
			/*
			 * The new task was inserted, and pushed out a
			 * different task
			 */
			get_task_struct(p);
			put_task_struct(dropped);
		}
		/*
		 * Else the new task was newer than anything already in
		 * the heap and wasn't inserted
		 */
	}
	cgroup_iter_end(scan->cg, &it);

	if (heap->size) {
		for (i = 0; i < heap->size; i++) {
3336
			struct task_struct *q = heap->ptrs[i];
3337
			if (i == 0) {
3338 3339
				latest_time = q->start_time;
				latest_task = q;
3340 3341
			}
			/* Process the task per the caller's callback */
3342 3343
			scan->process_task(q, scan);
			put_task_struct(q);
3344 3345 3346 3347 3348 3349 3350 3351 3352 3353 3354 3355 3356 3357 3358
		}
		/*
		 * If we had to process any tasks at all, scan again
		 * in case some of them were in the middle of forking
		 * children that didn't get processed.
		 * Not the most efficient way to do it, but it avoids
		 * having to take callback_mutex in the fork path
		 */
		goto again;
	}
	if (heap == &tmp_heap)
		heap_free(&tmp_heap);
	return 0;
}

3359 3360 3361 3362 3363
static void cgroup_transfer_one_task(struct task_struct *task,
				     struct cgroup_scanner *scan)
{
	struct cgroup *new_cgroup = scan->data;

T
Tejun Heo 已提交
3364
	mutex_lock(&cgroup_mutex);
3365
	cgroup_attach_task(new_cgroup, task, false);
T
Tejun Heo 已提交
3366
	mutex_unlock(&cgroup_mutex);
3367 3368 3369 3370 3371 3372 3373 3374 3375 3376 3377 3378 3379 3380 3381 3382 3383 3384 3385 3386
}

/**
 * cgroup_trasnsfer_tasks - move tasks from one cgroup to another
 * @to: cgroup to which the tasks will be moved
 * @from: cgroup in which the tasks currently reside
 */
int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
{
	struct cgroup_scanner scan;

	scan.cg = from;
	scan.test_task = NULL; /* select all tasks in cgroup */
	scan.process_task = cgroup_transfer_one_task;
	scan.heap = NULL;
	scan.data = to;

	return cgroup_scan_tasks(&scan);
}

3387
/*
3388
 * Stuff for reading the 'tasks'/'procs' files.
3389 3390 3391 3392 3393 3394 3395 3396
 *
 * Reading this file can return large amounts of data if a cgroup has
 * *lots* of attached tasks. So it may need several calls to read(),
 * but we cannot guarantee that the information we produce is correct
 * unless we produce it entirely atomically.
 *
 */

3397 3398 3399 3400 3401 3402 3403 3404 3405 3406 3407 3408 3409 3410 3411 3412 3413 3414 3415 3416 3417 3418 3419 3420 3421 3422 3423 3424 3425 3426 3427 3428
/* which pidlist file are we talking about? */
enum cgroup_filetype {
	CGROUP_FILE_PROCS,
	CGROUP_FILE_TASKS,
};

/*
 * A pidlist is a list of pids that virtually represents the contents of one
 * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
 * a pair (one each for procs, tasks) for each pid namespace that's relevant
 * to the cgroup.
 */
struct cgroup_pidlist {
	/*
	 * used to find which pidlist is wanted. doesn't change as long as
	 * this particular list stays in the list.
	*/
	struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
	/* array of xids */
	pid_t *list;
	/* how many elements the above list has */
	int length;
	/* how many files are using the current array */
	int use_count;
	/* each of these stored in a list by its cgroup */
	struct list_head links;
	/* pointer to the cgroup we belong to, for list removal purposes */
	struct cgroup *owner;
	/* protects the other fields */
	struct rw_semaphore mutex;
};

3429 3430 3431 3432 3433 3434 3435 3436 3437 3438 3439 3440 3441 3442 3443 3444 3445 3446 3447 3448 3449
/*
 * The following two functions "fix" the issue where there are more pids
 * than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
 * TODO: replace with a kernel-wide solution to this problem
 */
#define PIDLIST_TOO_LARGE(c) ((c) * sizeof(pid_t) > (PAGE_SIZE * 2))
static void *pidlist_allocate(int count)
{
	if (PIDLIST_TOO_LARGE(count))
		return vmalloc(count * sizeof(pid_t));
	else
		return kmalloc(count * sizeof(pid_t), GFP_KERNEL);
}
static void pidlist_free(void *p)
{
	if (is_vmalloc_addr(p))
		vfree(p);
	else
		kfree(p);
}

3450
/*
3451
 * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
3452
 * Returns the number of unique elements.
3453
 */
3454
static int pidlist_uniq(pid_t *list, int length)
3455
{
3456 3457 3458 3459 3460 3461 3462 3463 3464 3465 3466 3467 3468 3469 3470 3471 3472 3473 3474 3475 3476 3477 3478 3479 3480 3481 3482 3483 3484
	int src, dest = 1;

	/*
	 * we presume the 0th element is unique, so i starts at 1. trivial
	 * edge cases first; no work needs to be done for either
	 */
	if (length == 0 || length == 1)
		return length;
	/* src and dest walk down the list; dest counts unique elements */
	for (src = 1; src < length; src++) {
		/* find next unique element */
		while (list[src] == list[src-1]) {
			src++;
			if (src == length)
				goto after;
		}
		/* dest always points to where the next unique element goes */
		list[dest] = list[src];
		dest++;
	}
after:
	return dest;
}

static int cmppid(const void *a, const void *b)
{
	return *(pid_t *)a - *(pid_t *)b;
}

3485 3486 3487 3488 3489 3490 3491 3492 3493 3494 3495
/*
 * find the appropriate pidlist for our purpose (given procs vs tasks)
 * returns with the lock on that pidlist already held, and takes care
 * of the use count, or returns NULL with no locks held if we're out of
 * memory.
 */
static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
						  enum cgroup_filetype type)
{
	struct cgroup_pidlist *l;
	/* don't need task_nsproxy() if we're looking at ourself */
3496
	struct pid_namespace *ns = task_active_pid_ns(current);
3497

3498 3499 3500 3501 3502 3503 3504 3505 3506 3507 3508 3509 3510 3511 3512 3513 3514 3515 3516 3517 3518 3519 3520 3521
	/*
	 * We can't drop the pidlist_mutex before taking the l->mutex in case
	 * the last ref-holder is trying to remove l from the list at the same
	 * time. Holding the pidlist_mutex precludes somebody taking whichever
	 * list we find out from under us - compare release_pid_array().
	 */
	mutex_lock(&cgrp->pidlist_mutex);
	list_for_each_entry(l, &cgrp->pidlists, links) {
		if (l->key.type == type && l->key.ns == ns) {
			/* make sure l doesn't vanish out from under us */
			down_write(&l->mutex);
			mutex_unlock(&cgrp->pidlist_mutex);
			return l;
		}
	}
	/* entry not found; create a new one */
	l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
	if (!l) {
		mutex_unlock(&cgrp->pidlist_mutex);
		return l;
	}
	init_rwsem(&l->mutex);
	down_write(&l->mutex);
	l->key.type = type;
3522
	l->key.ns = get_pid_ns(ns);
3523 3524 3525 3526 3527 3528 3529 3530
	l->use_count = 0; /* don't increment here */
	l->list = NULL;
	l->owner = cgrp;
	list_add(&l->links, &cgrp->pidlists);
	mutex_unlock(&cgrp->pidlist_mutex);
	return l;
}

3531 3532 3533
/*
 * Load a cgroup's pidarray with either procs' tgids or tasks' pids
 */
3534 3535
static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
			      struct cgroup_pidlist **lp)
3536 3537 3538 3539
{
	pid_t *array;
	int length;
	int pid, n = 0; /* used for populating the array */
3540 3541
	struct cgroup_iter it;
	struct task_struct *tsk;
3542 3543 3544 3545 3546 3547 3548 3549 3550
	struct cgroup_pidlist *l;

	/*
	 * If cgroup gets more users after we read count, we won't have
	 * enough space - tough.  This race is indistinguishable to the
	 * caller from the case that the additional cgroup users didn't
	 * show up until sometime later on.
	 */
	length = cgroup_task_count(cgrp);
3551
	array = pidlist_allocate(length);
3552 3553 3554
	if (!array)
		return -ENOMEM;
	/* now, populate the array */
3555 3556
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
3557
		if (unlikely(n == length))
3558
			break;
3559
		/* get tgid or pid for procs or tasks file respectively */
3560 3561 3562 3563
		if (type == CGROUP_FILE_PROCS)
			pid = task_tgid_vnr(tsk);
		else
			pid = task_pid_vnr(tsk);
3564 3565
		if (pid > 0) /* make sure to only use valid results */
			array[n++] = pid;
3566
	}
3567
	cgroup_iter_end(cgrp, &it);
3568 3569 3570
	length = n;
	/* now sort & (if procs) strip out duplicates */
	sort(array, length, sizeof(pid_t), cmppid, NULL);
3571
	if (type == CGROUP_FILE_PROCS)
3572
		length = pidlist_uniq(array, length);
3573 3574
	l = cgroup_pidlist_find(cgrp, type);
	if (!l) {
3575
		pidlist_free(array);
3576
		return -ENOMEM;
3577
	}
3578
	/* store array, freeing old if necessary - lock already held */
3579
	pidlist_free(l->list);
3580 3581 3582 3583
	l->list = array;
	l->length = length;
	l->use_count++;
	up_write(&l->mutex);
3584
	*lp = l;
3585
	return 0;
3586 3587
}

B
Balbir Singh 已提交
3588
/**
L
Li Zefan 已提交
3589
 * cgroupstats_build - build and fill cgroupstats
B
Balbir Singh 已提交
3590 3591 3592
 * @stats: cgroupstats to fill information into
 * @dentry: A dentry entry belonging to the cgroup for which stats have
 * been requested.
L
Li Zefan 已提交
3593 3594 3595
 *
 * Build and fill cgroupstats so that taskstats can export it to user
 * space.
B
Balbir Singh 已提交
3596 3597 3598 3599
 */
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
{
	int ret = -EINVAL;
3600
	struct cgroup *cgrp;
B
Balbir Singh 已提交
3601 3602
	struct cgroup_iter it;
	struct task_struct *tsk;
3603

B
Balbir Singh 已提交
3604
	/*
3605 3606
	 * Validate dentry by checking the superblock operations,
	 * and make sure it's a directory.
B
Balbir Singh 已提交
3607
	 */
3608 3609
	if (dentry->d_sb->s_op != &cgroup_ops ||
	    !S_ISDIR(dentry->d_inode->i_mode))
B
Balbir Singh 已提交
3610 3611 3612
		 goto err;

	ret = 0;
3613
	cgrp = dentry->d_fsdata;
B
Balbir Singh 已提交
3614

3615 3616
	cgroup_iter_start(cgrp, &it);
	while ((tsk = cgroup_iter_next(cgrp, &it))) {
B
Balbir Singh 已提交
3617 3618 3619 3620 3621 3622 3623 3624 3625 3626 3627 3628 3629 3630 3631 3632 3633 3634 3635
		switch (tsk->state) {
		case TASK_RUNNING:
			stats->nr_running++;
			break;
		case TASK_INTERRUPTIBLE:
			stats->nr_sleeping++;
			break;
		case TASK_UNINTERRUPTIBLE:
			stats->nr_uninterruptible++;
			break;
		case TASK_STOPPED:
			stats->nr_stopped++;
			break;
		default:
			if (delayacct_is_task_waiting_on_io(tsk))
				stats->nr_io_wait++;
			break;
		}
	}
3636
	cgroup_iter_end(cgrp, &it);
B
Balbir Singh 已提交
3637 3638 3639 3640 3641

err:
	return ret;
}

3642

3643
/*
3644
 * seq_file methods for the tasks/procs files. The seq_file position is the
3645
 * next pid to display; the seq_file iterator is a pointer to the pid
3646
 * in the cgroup->l->list array.
3647
 */
3648

3649
static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
3650
{
3651 3652 3653 3654 3655 3656
	/*
	 * Initially we receive a position value that corresponds to
	 * one more than the last pid shown (or 0 on the first call or
	 * after a seek to the start). Use a binary-search to find the
	 * next pid to display, if any
	 */
3657
	struct cgroup_pidlist *l = s->private;
3658 3659 3660
	int index = 0, pid = *pos;
	int *iter;

3661
	down_read(&l->mutex);
3662
	if (pid) {
3663
		int end = l->length;
S
Stephen Rothwell 已提交
3664

3665 3666
		while (index < end) {
			int mid = (index + end) / 2;
3667
			if (l->list[mid] == pid) {
3668 3669
				index = mid;
				break;
3670
			} else if (l->list[mid] <= pid)
3671 3672 3673 3674 3675 3676
				index = mid + 1;
			else
				end = mid;
		}
	}
	/* If we're off the end of the array, we're done */
3677
	if (index >= l->length)
3678 3679
		return NULL;
	/* Update the abstract position to be the actual pid that we found */
3680
	iter = l->list + index;
3681 3682 3683 3684
	*pos = *iter;
	return iter;
}

3685
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
3686
{
3687 3688
	struct cgroup_pidlist *l = s->private;
	up_read(&l->mutex);
3689 3690
}

3691
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
3692
{
3693 3694 3695
	struct cgroup_pidlist *l = s->private;
	pid_t *p = v;
	pid_t *end = l->list + l->length;
3696 3697 3698 3699 3700 3701 3702 3703 3704 3705 3706 3707 3708
	/*
	 * Advance to the next pid in the array. If this goes off the
	 * end, we're done
	 */
	p++;
	if (p >= end) {
		return NULL;
	} else {
		*pos = *p;
		return p;
	}
}

3709
static int cgroup_pidlist_show(struct seq_file *s, void *v)
3710 3711 3712
{
	return seq_printf(s, "%d\n", *(int *)v);
}
3713

3714 3715 3716 3717 3718 3719 3720 3721 3722
/*
 * seq_operations functions for iterating on pidlists through seq_file -
 * independent of whether it's tasks or procs
 */
static const struct seq_operations cgroup_pidlist_seq_operations = {
	.start = cgroup_pidlist_start,
	.stop = cgroup_pidlist_stop,
	.next = cgroup_pidlist_next,
	.show = cgroup_pidlist_show,
3723 3724
};

3725
static void cgroup_release_pid_array(struct cgroup_pidlist *l)
3726
{
3727 3728 3729 3730 3731 3732 3733
	/*
	 * the case where we're the last user of this particular pidlist will
	 * have us remove it from the cgroup's list, which entails taking the
	 * mutex. since in pidlist_find the pidlist->lock depends on cgroup->
	 * pidlist_mutex, we have to take pidlist_mutex first.
	 */
	mutex_lock(&l->owner->pidlist_mutex);
3734 3735 3736
	down_write(&l->mutex);
	BUG_ON(!l->use_count);
	if (!--l->use_count) {
3737 3738 3739
		/* we're the last user if refcount is 0; remove and free */
		list_del(&l->links);
		mutex_unlock(&l->owner->pidlist_mutex);
3740
		pidlist_free(l->list);
3741 3742 3743 3744
		put_pid_ns(l->key.ns);
		up_write(&l->mutex);
		kfree(l);
		return;
3745
	}
3746
	mutex_unlock(&l->owner->pidlist_mutex);
3747
	up_write(&l->mutex);
3748 3749
}

3750
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
3751
{
3752
	struct cgroup_pidlist *l;
3753 3754
	if (!(file->f_mode & FMODE_READ))
		return 0;
3755 3756 3757 3758 3759 3760
	/*
	 * the seq_file will only be initialized if the file was opened for
	 * reading; hence we check if it's not null only in that case.
	 */
	l = ((struct seq_file *)file->private_data)->private;
	cgroup_release_pid_array(l);
3761 3762 3763
	return seq_release(inode, file);
}

3764
static const struct file_operations cgroup_pidlist_operations = {
3765 3766 3767
	.read = seq_read,
	.llseek = seq_lseek,
	.write = cgroup_file_write,
3768
	.release = cgroup_pidlist_release,
3769 3770
};

3771
/*
3772 3773 3774
 * The following functions handle opens on a file that displays a pidlist
 * (tasks or procs). Prepare an array of the process/thread IDs of whoever's
 * in the cgroup.
3775
 */
3776
/* helper function for the two below it */
3777
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
3778
{
3779
	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
3780
	struct cgroup_pidlist *l;
3781
	int retval;
3782

3783
	/* Nothing to do for write-only files */
3784 3785 3786
	if (!(file->f_mode & FMODE_READ))
		return 0;

3787
	/* have the array populated */
3788
	retval = pidlist_array_load(cgrp, type, &l);
3789 3790 3791 3792
	if (retval)
		return retval;
	/* configure file information */
	file->f_op = &cgroup_pidlist_operations;
3793

3794
	retval = seq_open(file, &cgroup_pidlist_seq_operations);
3795
	if (retval) {
3796
		cgroup_release_pid_array(l);
3797
		return retval;
3798
	}
3799
	((struct seq_file *)file->private_data)->private = l;
3800 3801
	return 0;
}
3802 3803
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
3804
	return cgroup_pidlist_open(file, CGROUP_FILE_TASKS);
3805 3806 3807
}
static int cgroup_procs_open(struct inode *unused, struct file *file)
{
3808
	return cgroup_pidlist_open(file, CGROUP_FILE_PROCS);
3809
}
3810

3811
static u64 cgroup_read_notify_on_release(struct cgroup *cgrp,
3812 3813
					    struct cftype *cft)
{
3814
	return notify_on_release(cgrp);
3815 3816
}

3817 3818 3819 3820 3821 3822 3823 3824 3825 3826 3827 3828
static int cgroup_write_notify_on_release(struct cgroup *cgrp,
					  struct cftype *cft,
					  u64 val)
{
	clear_bit(CGRP_RELEASABLE, &cgrp->flags);
	if (val)
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
	else
		clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
	return 0;
}

3829 3830 3831 3832 3833 3834 3835 3836 3837 3838 3839
/*
 * Unregister event and free resources.
 *
 * Gets called from workqueue.
 */
static void cgroup_event_remove(struct work_struct *work)
{
	struct cgroup_event *event = container_of(work, struct cgroup_event,
			remove);
	struct cgroup *cgrp = event->cgrp;

3840 3841
	remove_wait_queue(event->wqh, &event->wait);

3842 3843
	event->cft->unregister_event(cgrp, event->cft, event->eventfd);

3844 3845 3846
	/* Notify userspace the event is going away. */
	eventfd_signal(event->eventfd, 1);

3847 3848
	eventfd_ctx_put(event->eventfd);
	kfree(event);
3849
	dput(cgrp->dentry);
3850 3851 3852 3853 3854 3855 3856 3857 3858 3859 3860 3861 3862 3863 3864 3865 3866
}

/*
 * Gets called on POLLHUP on eventfd when user closes it.
 *
 * Called with wqh->lock held and interrupts disabled.
 */
static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
		int sync, void *key)
{
	struct cgroup_event *event = container_of(wait,
			struct cgroup_event, wait);
	struct cgroup *cgrp = event->cgrp;
	unsigned long flags = (unsigned long)key;

	if (flags & POLLHUP) {
		/*
3867 3868 3869 3870 3871 3872 3873
		 * If the event has been detached at cgroup removal, we
		 * can simply return knowing the other side will cleanup
		 * for us.
		 *
		 * We can't race against event freeing since the other
		 * side will require wqh->lock via remove_wait_queue(),
		 * which we hold.
3874
		 */
3875 3876 3877 3878 3879 3880 3881 3882 3883 3884
		spin_lock(&cgrp->event_list_lock);
		if (!list_empty(&event->list)) {
			list_del_init(&event->list);
			/*
			 * We are in atomic context, but cgroup_event_remove()
			 * may sleep, so we have to call it in workqueue.
			 */
			schedule_work(&event->remove);
		}
		spin_unlock(&cgrp->event_list_lock);
3885 3886 3887 3888 3889 3890 3891 3892 3893 3894 3895 3896 3897 3898 3899 3900 3901 3902 3903 3904 3905 3906 3907 3908 3909
	}

	return 0;
}

static void cgroup_event_ptable_queue_proc(struct file *file,
		wait_queue_head_t *wqh, poll_table *pt)
{
	struct cgroup_event *event = container_of(pt,
			struct cgroup_event, pt);

	event->wqh = wqh;
	add_wait_queue(wqh, &event->wait);
}

/*
 * Parse input and register new cgroup event handler.
 *
 * Input must be in format '<event_fd> <control_fd> <args>'.
 * Interpretation of args is defined by control file implementation.
 */
static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
				      const char *buffer)
{
	struct cgroup_event *event = NULL;
3910
	struct cgroup *cgrp_cfile;
3911 3912 3913 3914 3915 3916 3917 3918 3919 3920 3921 3922 3923 3924 3925 3926 3927 3928 3929 3930 3931 3932 3933 3934 3935 3936 3937 3938 3939 3940 3941 3942 3943 3944 3945 3946 3947 3948 3949 3950 3951 3952 3953 3954
	unsigned int efd, cfd;
	struct file *efile = NULL;
	struct file *cfile = NULL;
	char *endp;
	int ret;

	efd = simple_strtoul(buffer, &endp, 10);
	if (*endp != ' ')
		return -EINVAL;
	buffer = endp + 1;

	cfd = simple_strtoul(buffer, &endp, 10);
	if ((*endp != ' ') && (*endp != '\0'))
		return -EINVAL;
	buffer = endp + 1;

	event = kzalloc(sizeof(*event), GFP_KERNEL);
	if (!event)
		return -ENOMEM;
	event->cgrp = cgrp;
	INIT_LIST_HEAD(&event->list);
	init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
	init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
	INIT_WORK(&event->remove, cgroup_event_remove);

	efile = eventfd_fget(efd);
	if (IS_ERR(efile)) {
		ret = PTR_ERR(efile);
		goto fail;
	}

	event->eventfd = eventfd_ctx_fileget(efile);
	if (IS_ERR(event->eventfd)) {
		ret = PTR_ERR(event->eventfd);
		goto fail;
	}

	cfile = fget(cfd);
	if (!cfile) {
		ret = -EBADF;
		goto fail;
	}

	/* the process need read permission on control file */
A
Al Viro 已提交
3955
	/* AV: shouldn't we check that it's been opened for read instead? */
A
Al Viro 已提交
3956
	ret = inode_permission(file_inode(cfile), MAY_READ);
3957 3958 3959 3960 3961 3962 3963 3964 3965
	if (ret < 0)
		goto fail;

	event->cft = __file_cft(cfile);
	if (IS_ERR(event->cft)) {
		ret = PTR_ERR(event->cft);
		goto fail;
	}

3966 3967 3968 3969 3970 3971 3972 3973 3974 3975
	/*
	 * The file to be monitored must be in the same cgroup as
	 * cgroup.event_control is.
	 */
	cgrp_cfile = __d_cgrp(cfile->f_dentry->d_parent);
	if (cgrp_cfile != cgrp) {
		ret = -EINVAL;
		goto fail;
	}

3976 3977 3978 3979 3980 3981 3982 3983 3984 3985
	if (!event->cft->register_event || !event->cft->unregister_event) {
		ret = -EINVAL;
		goto fail;
	}

	ret = event->cft->register_event(cgrp, event->cft,
			event->eventfd, buffer);
	if (ret)
		goto fail;

3986
	efile->f_op->poll(efile, &event->pt);
3987

3988 3989 3990 3991 3992 3993 3994
	/*
	 * Events should be removed after rmdir of cgroup directory, but before
	 * destroying subsystem state objects. Let's take reference to cgroup
	 * directory dentry to do that.
	 */
	dget(cgrp->dentry);

3995 3996 3997 3998 3999 4000 4001 4002 4003 4004 4005 4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018
	spin_lock(&cgrp->event_list_lock);
	list_add(&event->list, &cgrp->event_list);
	spin_unlock(&cgrp->event_list_lock);

	fput(cfile);
	fput(efile);

	return 0;

fail:
	if (cfile)
		fput(cfile);

	if (event && event->eventfd && !IS_ERR(event->eventfd))
		eventfd_ctx_put(event->eventfd);

	if (!IS_ERR_OR_NULL(efile))
		fput(efile);

	kfree(event);

	return ret;
}

4019 4020 4021
static u64 cgroup_clone_children_read(struct cgroup *cgrp,
				    struct cftype *cft)
{
4022
	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4023 4024 4025 4026 4027 4028 4029
}

static int cgroup_clone_children_write(struct cgroup *cgrp,
				     struct cftype *cft,
				     u64 val)
{
	if (val)
4030
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4031
	else
4032
		clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4033 4034 4035
	return 0;
}

4036
static struct cftype cgroup_base_files[] = {
4037
	{
4038
		.name = "cgroup.procs",
4039
		.open = cgroup_procs_open,
B
Ben Blum 已提交
4040
		.write_u64 = cgroup_procs_write,
4041
		.release = cgroup_pidlist_release,
B
Ben Blum 已提交
4042
		.mode = S_IRUGO | S_IWUSR,
4043
	},
4044
	{
4045
		.name = "cgroup.event_control",
4046 4047 4048
		.write_string = cgroup_write_event_control,
		.mode = S_IWUGO,
	},
4049 4050
	{
		.name = "cgroup.clone_children",
4051
		.flags = CFTYPE_INSANE,
4052 4053 4054
		.read_u64 = cgroup_clone_children_read,
		.write_u64 = cgroup_clone_children_write,
	},
4055 4056 4057 4058 4059
	{
		.name = "cgroup.sane_behavior",
		.flags = CFTYPE_ONLY_ON_ROOT,
		.read_seq_string = cgroup_sane_behavior_show,
	},
4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079

	/*
	 * Historical crazy stuff.  These don't have "cgroup."  prefix and
	 * don't exist if sane_behavior.  If you're depending on these, be
	 * prepared to be burned.
	 */
	{
		.name = "tasks",
		.flags = CFTYPE_INSANE,		/* use "procs" instead */
		.open = cgroup_tasks_open,
		.write_u64 = cgroup_tasks_write,
		.release = cgroup_pidlist_release,
		.mode = S_IRUGO | S_IWUSR,
	},
	{
		.name = "notify_on_release",
		.flags = CFTYPE_INSANE,
		.read_u64 = cgroup_read_notify_on_release,
		.write_u64 = cgroup_write_notify_on_release,
	},
4080 4081
	{
		.name = "release_agent",
4082
		.flags = CFTYPE_INSANE | CFTYPE_ONLY_ON_ROOT,
4083 4084 4085 4086
		.read_seq_string = cgroup_release_agent_show,
		.write_string = cgroup_release_agent_write,
		.max_write_len = PATH_MAX,
	},
T
Tejun Heo 已提交
4087
	{ }	/* terminate */
4088 4089
};

4090 4091 4092 4093 4094 4095 4096 4097
/**
 * cgroup_populate_dir - selectively creation of files in a directory
 * @cgrp: target cgroup
 * @base_files: true if the base files should be added
 * @subsys_mask: mask of the subsystem ids whose files should be added
 */
static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
			       unsigned long subsys_mask)
4098 4099 4100 4101
{
	int err;
	struct cgroup_subsys *ss;

4102
	if (base_files) {
4103
		err = cgroup_addrm_files(cgrp, NULL, cgroup_base_files, true);
4104 4105 4106
		if (err < 0)
			return err;
	}
4107

4108
	/* process cftsets of each subsystem */
4109
	for_each_subsys(cgrp->root, ss) {
4110
		struct cftype_set *set;
4111 4112
		if (!test_bit(ss->subsys_id, &subsys_mask))
			continue;
4113

T
Tejun Heo 已提交
4114
		list_for_each_entry(set, &ss->cftsets, node)
4115
			cgroup_addrm_files(cgrp, ss, set->cfts, true);
4116
	}
4117

K
KAMEZAWA Hiroyuki 已提交
4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128
	/* This cgroup is ready now */
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
		/*
		 * Update id->css pointer and make this css visible from
		 * CSS ID functions. This pointer will be dereferened
		 * from RCU-read-side without locks.
		 */
		if (css->id)
			rcu_assign_pointer(css->id->css, css);
	}
4129 4130 4131 4132

	return 0;
}

4133 4134 4135 4136
static void css_dput_fn(struct work_struct *work)
{
	struct cgroup_subsys_state *css =
		container_of(work, struct cgroup_subsys_state, dput_work);
4137 4138
	struct dentry *dentry = css->cgroup->dentry;
	struct super_block *sb = dentry->d_sb;
4139

4140 4141 4142
	atomic_inc(&sb->s_active);
	dput(dentry);
	deactivate_super(sb);
4143 4144
}

4145 4146
static void init_cgroup_css(struct cgroup_subsys_state *css,
			       struct cgroup_subsys *ss,
4147
			       struct cgroup *cgrp)
4148
{
4149
	css->cgroup = cgrp;
P
Paul Menage 已提交
4150
	atomic_set(&css->refcnt, 1);
4151
	css->flags = 0;
K
KAMEZAWA Hiroyuki 已提交
4152
	css->id = NULL;
4153
	if (cgrp == dummytop)
4154
		css->flags |= CSS_ROOT;
4155 4156
	BUG_ON(cgrp->subsys[ss->subsys_id]);
	cgrp->subsys[ss->subsys_id] = css;
4157 4158

	/*
4159 4160 4161 4162
	 * css holds an extra ref to @cgrp->dentry which is put on the last
	 * css_put().  dput() requires process context, which css_put() may
	 * be called without.  @css->dput_work will be used to invoke
	 * dput() asynchronously from css_put().
4163 4164
	 */
	INIT_WORK(&css->dput_work, css_dput_fn);
4165 4166
}

T
Tejun Heo 已提交
4167 4168
/* invoke ->post_create() on a new CSS and mark it online if successful */
static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
4169
{
T
Tejun Heo 已提交
4170 4171
	int ret = 0;

4172 4173
	lockdep_assert_held(&cgroup_mutex);

4174 4175
	if (ss->css_online)
		ret = ss->css_online(cgrp);
T
Tejun Heo 已提交
4176 4177 4178
	if (!ret)
		cgrp->subsys[ss->subsys_id]->flags |= CSS_ONLINE;
	return ret;
4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190 4191
}

/* if the CSS is online, invoke ->pre_destory() on it and mark it offline */
static void offline_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
{
	struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];

	lockdep_assert_held(&cgroup_mutex);

	if (!(css->flags & CSS_ONLINE))
		return;

4192
	if (ss->css_offline)
4193
		ss->css_offline(cgrp);
4194 4195 4196 4197

	cgrp->subsys[ss->subsys_id]->flags &= ~CSS_ONLINE;
}

4198
/*
L
Li Zefan 已提交
4199 4200 4201 4202
 * cgroup_create - create a cgroup
 * @parent: cgroup that will be parent of the new cgroup
 * @dentry: dentry of the new cgroup
 * @mode: mode to set on new inode
4203
 *
L
Li Zefan 已提交
4204
 * Must be called with the mutex on the parent inode held
4205 4206
 */
static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
A
Al Viro 已提交
4207
			     umode_t mode)
4208
{
4209
	static atomic64_t serial_nr_cursor = ATOMIC64_INIT(0);
4210
	struct cgroup *cgrp;
4211
	struct cgroup_name *name;
4212 4213 4214 4215 4216
	struct cgroupfs_root *root = parent->root;
	int err = 0;
	struct cgroup_subsys *ss;
	struct super_block *sb = root->sb;

T
Tejun Heo 已提交
4217
	/* allocate the cgroup and its ID, 0 is reserved for the root */
4218 4219
	cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
	if (!cgrp)
4220 4221
		return -ENOMEM;

4222 4223 4224 4225 4226
	name = cgroup_alloc_name(dentry);
	if (!name)
		goto err_free_cgrp;
	rcu_assign_pointer(cgrp->name, name);

T
Tejun Heo 已提交
4227 4228
	cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);
	if (cgrp->id < 0)
4229
		goto err_free_name;
T
Tejun Heo 已提交
4230

4231 4232 4233 4234 4235 4236 4237 4238 4239
	/*
	 * Only live parents can have children.  Note that the liveliness
	 * check isn't strictly necessary because cgroup_mkdir() and
	 * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
	 * anyway so that locking is contained inside cgroup proper and we
	 * don't get nasty surprises if we ever grow another caller.
	 */
	if (!cgroup_lock_live_group(parent)) {
		err = -ENODEV;
T
Tejun Heo 已提交
4240
		goto err_free_id;
4241 4242
	}

4243 4244 4245 4246 4247 4248 4249
	/* Grab a reference on the superblock so the hierarchy doesn't
	 * get deleted on unmount if there are child cgroups.  This
	 * can be done outside cgroup_mutex, since the sb can't
	 * disappear while someone has an open control file on the
	 * fs */
	atomic_inc(&sb->s_active);

4250
	init_cgroup_housekeeping(cgrp);
4251

4252 4253 4254
	dentry->d_fsdata = cgrp;
	cgrp->dentry = dentry;

4255 4256
	cgrp->parent = parent;
	cgrp->root = parent->root;
4257

4258 4259 4260
	if (notify_on_release(parent))
		set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);

4261 4262
	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &parent->flags))
		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags);
4263

4264
	for_each_subsys(root, ss) {
4265
		struct cgroup_subsys_state *css;
4266

4267
		css = ss->css_alloc(cgrp);
4268 4269
		if (IS_ERR(css)) {
			err = PTR_ERR(css);
4270
			goto err_free_all;
4271
		}
4272
		init_cgroup_css(css, ss, cgrp);
4273 4274 4275
		if (ss->use_id) {
			err = alloc_css_id(ss, parent, cgrp);
			if (err)
4276
				goto err_free_all;
4277
		}
4278 4279
	}

4280 4281 4282 4283 4284
	/*
	 * Create directory.  cgroup_create_file() returns with the new
	 * directory locked on success so that it can be populated without
	 * dropping cgroup_mutex.
	 */
T
Tejun Heo 已提交
4285
	err = cgroup_create_file(dentry, S_IFDIR | mode, sb);
4286
	if (err < 0)
4287
		goto err_free_all;
4288
	lockdep_assert_held(&dentry->d_inode->i_mutex);
4289

4290 4291 4292 4293 4294 4295 4296 4297
	/*
	 * Assign a monotonically increasing serial number.  With the list
	 * appending below, it guarantees that sibling cgroups are always
	 * sorted in the ascending serial number order on the parent's
	 * ->children.
	 */
	cgrp->serial_nr = atomic64_inc_return(&serial_nr_cursor);

4298 4299 4300 4301
	/* allocation complete, commit to creation */
	list_add_tail(&cgrp->allcg_node, &root->allcg_list);
	list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
	root->number_of_cgroups++;
T
Tejun Heo 已提交
4302

T
Tejun Heo 已提交
4303 4304
	/* each css holds a ref to the cgroup's dentry */
	for_each_subsys(root, ss)
4305
		dget(dentry);
4306

4307 4308 4309
	/* hold a ref to the parent's dentry */
	dget(parent->dentry);

T
Tejun Heo 已提交
4310 4311 4312 4313 4314
	/* creation succeeded, notify subsystems */
	for_each_subsys(root, ss) {
		err = online_css(ss, cgrp);
		if (err)
			goto err_destroy;
4315 4316 4317 4318 4319 4320 4321 4322 4323

		if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
		    parent->parent) {
			pr_warning("cgroup: %s (%d) created nested cgroup for controller \"%s\" which has incomplete hierarchy support. Nested cgroups may change behavior in the future.\n",
				   current->comm, current->pid, ss->name);
			if (!strcmp(ss->name, "memory"))
				pr_warning("cgroup: \"memory\" requires setting use_hierarchy to 1 on the root.\n");
			ss->warned_broken_hierarchy = true;
		}
4324 4325
	}

4326
	err = cgroup_populate_dir(cgrp, true, root->subsys_mask);
4327 4328
	if (err)
		goto err_destroy;
4329 4330

	mutex_unlock(&cgroup_mutex);
4331
	mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
4332 4333 4334

	return 0;

4335
err_free_all:
4336
	for_each_subsys(root, ss) {
4337
		if (cgrp->subsys[ss->subsys_id])
4338
			ss->css_free(cgrp);
4339 4340 4341 4342
	}
	mutex_unlock(&cgroup_mutex);
	/* Release the reference count that we took on the superblock */
	deactivate_super(sb);
T
Tejun Heo 已提交
4343 4344
err_free_id:
	ida_simple_remove(&root->cgroup_ida, cgrp->id);
4345 4346
err_free_name:
	kfree(rcu_dereference_raw(cgrp->name));
4347
err_free_cgrp:
4348
	kfree(cgrp);
4349
	return err;
4350 4351 4352 4353 4354 4355

err_destroy:
	cgroup_destroy_locked(cgrp);
	mutex_unlock(&cgroup_mutex);
	mutex_unlock(&dentry->d_inode->i_mutex);
	return err;
4356 4357
}

4358
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
4359 4360 4361 4362 4363 4364 4365
{
	struct cgroup *c_parent = dentry->d_parent->d_fsdata;

	/* the vfs holds inode->i_mutex already */
	return cgroup_create(c_parent, dentry, mode | S_IFDIR);
}

4366 4367
static int cgroup_destroy_locked(struct cgroup *cgrp)
	__releases(&cgroup_mutex) __acquires(&cgroup_mutex)
4368
{
4369 4370
	struct dentry *d = cgrp->dentry;
	struct cgroup *parent = cgrp->parent;
4371
	struct cgroup_event *event, *tmp;
4372
	struct cgroup_subsys *ss;
4373

4374 4375 4376 4377
	lockdep_assert_held(&d->d_inode->i_mutex);
	lockdep_assert_held(&cgroup_mutex);

	if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children))
4378
		return -EBUSY;
L
Li Zefan 已提交
4379

4380
	/*
4381 4382 4383 4384
	 * Block new css_tryget() by deactivating refcnt and mark @cgrp
	 * removed.  This makes future css_tryget() and child creation
	 * attempts fail thus maintaining the removal conditions verified
	 * above.
4385 4386 4387 4388
	 *
	 * Note that CGRP_REMVOED clearing is depended upon by
	 * cgroup_next_sibling() to resume iteration after dropping RCU
	 * read lock.  See cgroup_next_sibling() for details.
4389
	 */
4390 4391
	for_each_subsys(cgrp->root, ss) {
		struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
4392

4393 4394
		WARN_ON(atomic_read(&css->refcnt) < 0);
		atomic_add(CSS_DEACT_BIAS, &css->refcnt);
4395
	}
4396
	set_bit(CGRP_REMOVED, &cgrp->flags);
4397

4398
	/* tell subsystems to initate destruction */
4399
	for_each_subsys(cgrp->root, ss)
4400
		offline_css(ss, cgrp);
4401 4402 4403 4404 4405 4406 4407 4408

	/*
	 * Put all the base refs.  Each css holds an extra reference to the
	 * cgroup's dentry and cgroup removal proceeds regardless of css
	 * refs.  On the last put of each css, whenever that may be, the
	 * extra dentry ref is put so that dentry destruction happens only
	 * after all css's are released.
	 */
T
Tejun Heo 已提交
4409 4410
	for_each_subsys(cgrp->root, ss)
		css_put(cgrp->subsys[ss->subsys_id]);
4411

4412
	raw_spin_lock(&release_list_lock);
4413
	if (!list_empty(&cgrp->release_list))
4414
		list_del_init(&cgrp->release_list);
4415
	raw_spin_unlock(&release_list_lock);
4416 4417

	/* delete this cgroup from parent->children */
4418
	list_del_rcu(&cgrp->sibling);
4419 4420
	list_del_init(&cgrp->allcg_node);

4421
	dget(d);
4422 4423 4424
	cgroup_d_remove_dir(d);
	dput(d);

4425
	set_bit(CGRP_RELEASABLE, &parent->flags);
4426 4427
	check_for_release(parent);

4428 4429 4430
	/*
	 * Unregister events and notify userspace.
	 * Notify userspace about cgroup removing only after rmdir of cgroup
4431
	 * directory to avoid race between userspace and kernelspace.
4432 4433
	 */
	spin_lock(&cgrp->event_list_lock);
4434
	list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
4435
		list_del_init(&event->list);
4436 4437
		schedule_work(&event->remove);
	}
4438
	spin_unlock(&cgrp->event_list_lock);
4439

4440 4441 4442
	return 0;
}

4443 4444 4445 4446 4447 4448 4449 4450 4451 4452 4453
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
	int ret;

	mutex_lock(&cgroup_mutex);
	ret = cgroup_destroy_locked(dentry->d_fsdata);
	mutex_unlock(&cgroup_mutex);

	return ret;
}

4454 4455 4456 4457 4458 4459 4460 4461 4462 4463 4464 4465 4466 4467
static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
{
	INIT_LIST_HEAD(&ss->cftsets);

	/*
	 * base_cftset is embedded in subsys itself, no need to worry about
	 * deregistration.
	 */
	if (ss->base_cftypes) {
		ss->base_cftset.cfts = ss->base_cftypes;
		list_add_tail(&ss->base_cftset.node, &ss->cftsets);
	}
}

4468
static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
4469 4470
{
	struct cgroup_subsys_state *css;
D
Diego Calleja 已提交
4471 4472

	printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
4473

4474 4475
	mutex_lock(&cgroup_mutex);

4476 4477 4478
	/* init base cftset */
	cgroup_init_cftsets(ss);

4479
	/* Create the top cgroup state for this subsystem */
4480
	list_add(&ss->sibling, &rootnode.subsys_list);
4481
	ss->root = &rootnode;
4482
	css = ss->css_alloc(dummytop);
4483 4484 4485 4486
	/* We don't handle early failures gracefully */
	BUG_ON(IS_ERR(css));
	init_cgroup_css(css, ss, dummytop);

L
Li Zefan 已提交
4487
	/* Update the init_css_set to contain a subsys
4488
	 * pointer to this state - since the subsystem is
L
Li Zefan 已提交
4489 4490
	 * newly registered, all tasks and hence the
	 * init_css_set is in the subsystem's top cgroup. */
4491
	init_css_set.subsys[ss->subsys_id] = css;
4492 4493 4494

	need_forkexit_callback |= ss->fork || ss->exit;

L
Li Zefan 已提交
4495 4496 4497 4498 4499
	/* At system boot, before all subsystems have been
	 * registered, no tasks have been forked, so we don't
	 * need to invoke fork callbacks here. */
	BUG_ON(!list_empty(&init_task.tasks));

T
Tejun Heo 已提交
4500
	BUG_ON(online_css(ss, dummytop));
4501

4502 4503
	mutex_unlock(&cgroup_mutex);

4504 4505 4506 4507 4508 4509 4510 4511 4512 4513
	/* this function shouldn't be used with modular subsystems, since they
	 * need to register a subsys_id, among other things */
	BUG_ON(ss->module);
}

/**
 * cgroup_load_subsys: load and register a modular subsystem at runtime
 * @ss: the subsystem to load
 *
 * This function should be called in a modular subsystem's initcall. If the
T
Thomas Weber 已提交
4514
 * subsystem is built as a module, it will be assigned a new subsys_id and set
4515 4516 4517 4518 4519 4520
 * up for use. If the subsystem is built-in anyway, work is delegated to the
 * simpler cgroup_init_subsys.
 */
int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
{
	struct cgroup_subsys_state *css;
4521
	int i, ret;
4522
	struct hlist_node *tmp;
4523
	struct css_set *cset;
4524
	unsigned long key;
4525 4526 4527

	/* check name and function validity */
	if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
4528
	    ss->css_alloc == NULL || ss->css_free == NULL)
4529 4530 4531 4532 4533 4534 4535 4536 4537 4538 4539 4540 4541 4542 4543 4544
		return -EINVAL;

	/*
	 * we don't support callbacks in modular subsystems. this check is
	 * before the ss->module check for consistency; a subsystem that could
	 * be a module should still have no callbacks even if the user isn't
	 * compiling it as one.
	 */
	if (ss->fork || ss->exit)
		return -EINVAL;

	/*
	 * an optionally modular subsystem is built-in: we want to do nothing,
	 * since cgroup_init_subsys will have already taken care of it.
	 */
	if (ss->module == NULL) {
4545
		/* a sanity check */
4546 4547 4548 4549
		BUG_ON(subsys[ss->subsys_id] != ss);
		return 0;
	}

4550 4551 4552
	/* init base cftset */
	cgroup_init_cftsets(ss);

4553
	mutex_lock(&cgroup_mutex);
4554
	subsys[ss->subsys_id] = ss;
4555 4556

	/*
4557 4558 4559
	 * no ss->css_alloc seems to need anything important in the ss
	 * struct, so this can happen first (i.e. before the rootnode
	 * attachment).
4560
	 */
4561
	css = ss->css_alloc(dummytop);
4562 4563
	if (IS_ERR(css)) {
		/* failure case - need to deassign the subsys[] slot. */
4564
		subsys[ss->subsys_id] = NULL;
4565 4566 4567 4568 4569 4570 4571 4572 4573 4574 4575
		mutex_unlock(&cgroup_mutex);
		return PTR_ERR(css);
	}

	list_add(&ss->sibling, &rootnode.subsys_list);
	ss->root = &rootnode;

	/* our new subsystem will be attached to the dummy hierarchy. */
	init_cgroup_css(css, ss, dummytop);
	/* init_idr must be after init_cgroup_css because it sets css->id. */
	if (ss->use_id) {
4576 4577 4578
		ret = cgroup_init_idr(ss, css);
		if (ret)
			goto err_unload;
4579 4580 4581 4582 4583 4584 4585 4586 4587 4588 4589
	}

	/*
	 * Now we need to entangle the css into the existing css_sets. unlike
	 * in cgroup_init_subsys, there are now multiple css_sets, so each one
	 * will need a new pointer to it; done by iterating the css_set_table.
	 * furthermore, modifying the existing css_sets will corrupt the hash
	 * table state, so each changed css_set will need its hash recomputed.
	 * this is all done under the css_set_lock.
	 */
	write_lock(&css_set_lock);
4590
	hash_for_each_safe(css_set_table, i, tmp, cset, hlist) {
4591
		/* skip entries that we already rehashed */
4592
		if (cset->subsys[ss->subsys_id])
4593 4594
			continue;
		/* remove existing entry */
4595
		hash_del(&cset->hlist);
4596
		/* set new value */
4597
		cset->subsys[ss->subsys_id] = css;
4598
		/* recompute hash and restore entry */
4599 4600
		key = css_set_hash(cset->subsys);
		hash_add(css_set_table, &cset->hlist, key);
4601 4602 4603
	}
	write_unlock(&css_set_lock);

T
Tejun Heo 已提交
4604 4605 4606
	ret = online_css(ss, dummytop);
	if (ret)
		goto err_unload;
4607

4608 4609 4610
	/* success! */
	mutex_unlock(&cgroup_mutex);
	return 0;
4611 4612 4613 4614 4615 4616

err_unload:
	mutex_unlock(&cgroup_mutex);
	/* @ss can't be mounted here as try_module_get() would fail */
	cgroup_unload_subsys(ss);
	return ret;
4617
}
4618
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
4619

B
Ben Blum 已提交
4620 4621 4622 4623 4624 4625 4626 4627 4628 4629
/**
 * cgroup_unload_subsys: unload a modular subsystem
 * @ss: the subsystem to unload
 *
 * This function should be called in a modular subsystem's exitcall. When this
 * function is invoked, the refcount on the subsystem's module will be 0, so
 * the subsystem will not be attached to any hierarchy.
 */
void cgroup_unload_subsys(struct cgroup_subsys *ss)
{
4630
	struct cgrp_cset_link *link;
B
Ben Blum 已提交
4631 4632 4633 4634 4635 4636 4637 4638 4639 4640 4641

	BUG_ON(ss->module == NULL);

	/*
	 * we shouldn't be called if the subsystem is in use, and the use of
	 * try_module_get in parse_cgroupfs_options should ensure that it
	 * doesn't start being used while we're killing it off.
	 */
	BUG_ON(ss->root != &rootnode);

	mutex_lock(&cgroup_mutex);
4642

4643
	offline_css(ss, dummytop);
4644

T
Tejun Heo 已提交
4645
	if (ss->use_id)
4646 4647
		idr_destroy(&ss->idr);

B
Ben Blum 已提交
4648 4649 4650 4651
	/* deassign the subsys_id */
	subsys[ss->subsys_id] = NULL;

	/* remove subsystem from rootnode's list of subsystems */
4652
	list_del_init(&ss->sibling);
B
Ben Blum 已提交
4653 4654 4655 4656 4657 4658

	/*
	 * disentangle the css from all css_sets attached to the dummytop. as
	 * in loading, we need to pay our respects to the hashtable gods.
	 */
	write_lock(&css_set_lock);
4659 4660
	list_for_each_entry(link, &dummytop->cset_links, cset_link) {
		struct css_set *cset = link->cset;
4661
		unsigned long key;
B
Ben Blum 已提交
4662

4663 4664 4665 4666
		hash_del(&cset->hlist);
		cset->subsys[ss->subsys_id] = NULL;
		key = css_set_hash(cset->subsys);
		hash_add(css_set_table, &cset->hlist, key);
B
Ben Blum 已提交
4667 4668 4669 4670
	}
	write_unlock(&css_set_lock);

	/*
4671 4672 4673 4674
	 * remove subsystem's css from the dummytop and free it - need to
	 * free before marking as null because ss->css_free needs the
	 * cgrp->subsys pointer to find their state. note that this also
	 * takes care of freeing the css_id.
B
Ben Blum 已提交
4675
	 */
4676
	ss->css_free(dummytop);
B
Ben Blum 已提交
4677 4678 4679 4680 4681 4682
	dummytop->subsys[ss->subsys_id] = NULL;

	mutex_unlock(&cgroup_mutex);
}
EXPORT_SYMBOL_GPL(cgroup_unload_subsys);

4683
/**
L
Li Zefan 已提交
4684 4685 4686 4687
 * cgroup_init_early - cgroup initialization at system boot
 *
 * Initialize cgroups at system boot, and initialize any
 * subsystems that request early init.
4688 4689 4690 4691
 */
int __init cgroup_init_early(void)
{
	int i;
4692
	atomic_set(&init_css_set.refcount, 1);
4693
	INIT_LIST_HEAD(&init_css_set.cgrp_links);
4694
	INIT_LIST_HEAD(&init_css_set.tasks);
4695
	INIT_HLIST_NODE(&init_css_set.hlist);
4696
	css_set_count = 1;
4697
	init_cgroup_root(&rootnode);
4698 4699 4700
	root_count = 1;
	init_task.cgroups = &init_css_set;

4701 4702 4703 4704
	init_cgrp_cset_link.cset = &init_css_set;
	init_cgrp_cset_link.cgrp = dummytop;
	list_add(&init_cgrp_cset_link.cset_link, &rootnode.top_cgroup.cset_links);
	list_add(&init_cgrp_cset_link.cgrp_link, &init_css_set.cgrp_links);
4705

4706
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4707 4708
		struct cgroup_subsys *ss = subsys[i];

4709 4710 4711 4712
		/* at bootup time, we don't worry about modular subsystems */
		if (!ss || ss->module)
			continue;

4713 4714
		BUG_ON(!ss->name);
		BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
4715 4716
		BUG_ON(!ss->css_alloc);
		BUG_ON(!ss->css_free);
4717
		if (ss->subsys_id != i) {
D
Diego Calleja 已提交
4718
			printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
4719 4720 4721 4722 4723 4724 4725 4726 4727 4728 4729
			       ss->name, ss->subsys_id);
			BUG();
		}

		if (ss->early_init)
			cgroup_init_subsys(ss);
	}
	return 0;
}

/**
L
Li Zefan 已提交
4730 4731 4732 4733
 * cgroup_init - cgroup initialization
 *
 * Register cgroup filesystem and /proc file, and initialize
 * any subsystems that didn't request early init.
4734 4735 4736 4737 4738
 */
int __init cgroup_init(void)
{
	int err;
	int i;
4739
	unsigned long key;
4740 4741 4742 4743

	err = bdi_init(&cgroup_backing_dev_info);
	if (err)
		return err;
4744

4745
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
4746
		struct cgroup_subsys *ss = subsys[i];
4747 4748 4749 4750

		/* at bootup time, we don't worry about modular subsystems */
		if (!ss || ss->module)
			continue;
4751 4752
		if (!ss->early_init)
			cgroup_init_subsys(ss);
K
KAMEZAWA Hiroyuki 已提交
4753
		if (ss->use_id)
4754
			cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
4755 4756
	}

4757
	/* Add init_css_set to the hash table */
4758 4759
	key = css_set_hash(init_css_set.subsys);
	hash_add(css_set_table, &init_css_set.hlist, key);
4760 4761

	/* allocate id for the dummy hierarchy */
T
Tejun Heo 已提交
4762 4763 4764
	mutex_lock(&cgroup_mutex);
	mutex_lock(&cgroup_root_mutex);

4765
	BUG_ON(cgroup_init_root_id(&rootnode));
4766

T
Tejun Heo 已提交
4767 4768 4769
	mutex_unlock(&cgroup_root_mutex);
	mutex_unlock(&cgroup_mutex);

4770 4771 4772 4773 4774 4775
	cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
	if (!cgroup_kobj) {
		err = -ENOMEM;
		goto out;
	}

4776
	err = register_filesystem(&cgroup_fs_type);
4777 4778
	if (err < 0) {
		kobject_put(cgroup_kobj);
4779
		goto out;
4780
	}
4781

L
Li Zefan 已提交
4782
	proc_create("cgroups", 0, NULL, &proc_cgroupstats_operations);
4783

4784
out:
4785 4786 4787
	if (err)
		bdi_destroy(&cgroup_backing_dev_info);

4788 4789
	return err;
}
4790

4791 4792 4793 4794 4795 4796
/*
 * proc_cgroup_show()
 *  - Print task's cgroup paths into seq_file, one line for each hierarchy
 *  - Used for /proc/<pid>/cgroup.
 *  - No need to task_lock(tsk) on this tsk->cgroup reference, as it
 *    doesn't really matter if tsk->cgroup changes after we read it,
4797
 *    and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
4798 4799 4800 4801 4802 4803
 *    anyway.  No need to check that tsk->cgroup != NULL, thanks to
 *    the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
 *    cgroup to top_cgroup.
 */

/* TODO: Use a proper seq_file iterator */
4804
int proc_cgroup_show(struct seq_file *m, void *v)
4805 4806 4807 4808 4809 4810 4811 4812 4813 4814 4815 4816 4817 4818 4819 4820 4821 4822 4823 4824 4825 4826
{
	struct pid *pid;
	struct task_struct *tsk;
	char *buf;
	int retval;
	struct cgroupfs_root *root;

	retval = -ENOMEM;
	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!buf)
		goto out;

	retval = -ESRCH;
	pid = m->private;
	tsk = get_pid_task(pid, PIDTYPE_PID);
	if (!tsk)
		goto out_free;

	retval = 0;

	mutex_lock(&cgroup_mutex);

4827
	for_each_active_root(root) {
4828
		struct cgroup_subsys *ss;
4829
		struct cgroup *cgrp;
4830 4831
		int count = 0;

4832
		seq_printf(m, "%d:", root->hierarchy_id);
4833 4834
		for_each_subsys(root, ss)
			seq_printf(m, "%s%s", count++ ? "," : "", ss->name);
4835 4836 4837
		if (strlen(root->name))
			seq_printf(m, "%sname=%s", count ? "," : "",
				   root->name);
4838
		seq_putc(m, ':');
4839
		cgrp = task_cgroup_from_root(tsk, root);
4840
		retval = cgroup_path(cgrp, buf, PAGE_SIZE);
4841 4842 4843 4844 4845 4846 4847 4848 4849 4850 4851 4852 4853 4854 4855 4856 4857 4858 4859 4860
		if (retval < 0)
			goto out_unlock;
		seq_puts(m, buf);
		seq_putc(m, '\n');
	}

out_unlock:
	mutex_unlock(&cgroup_mutex);
	put_task_struct(tsk);
out_free:
	kfree(buf);
out:
	return retval;
}

/* Display information about each subsystem and each hierarchy */
static int proc_cgroupstats_show(struct seq_file *m, void *v)
{
	int i;

4861
	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
B
Ben Blum 已提交
4862 4863 4864 4865 4866
	/*
	 * ideally we don't want subsystems moving around while we do this.
	 * cgroup_mutex is also necessary to guarantee an atomic snapshot of
	 * subsys/hierarchy state.
	 */
4867 4868 4869
	mutex_lock(&cgroup_mutex);
	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
		struct cgroup_subsys *ss = subsys[i];
B
Ben Blum 已提交
4870 4871
		if (ss == NULL)
			continue;
4872 4873
		seq_printf(m, "%s\t%d\t%d\t%d\n",
			   ss->name, ss->root->hierarchy_id,
4874
			   ss->root->number_of_cgroups, !ss->disabled);
4875 4876 4877 4878 4879 4880 4881
	}
	mutex_unlock(&cgroup_mutex);
	return 0;
}

static int cgroupstats_open(struct inode *inode, struct file *file)
{
A
Al Viro 已提交
4882
	return single_open(file, proc_cgroupstats_show, NULL);
4883 4884
}

4885
static const struct file_operations proc_cgroupstats_operations = {
4886 4887 4888 4889 4890 4891
	.open = cgroupstats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

4892 4893
/**
 * cgroup_fork - attach newly forked task to its parents cgroup.
L
Li Zefan 已提交
4894
 * @child: pointer to task_struct of forking parent process.
4895 4896 4897 4898 4899
 *
 * Description: A task inherits its parent's cgroup at fork().
 *
 * A pointer to the shared css_set was automatically copied in
 * fork.c by dup_task_struct().  However, we ignore that copy, since
4900 4901 4902 4903
 * it was not made under the protection of RCU or cgroup_mutex, so
 * might no longer be a valid cgroup pointer.  cgroup_attach_task() might
 * have already changed current->cgroups, allowing the previously
 * referenced cgroup group to be removed and freed.
4904 4905 4906 4907 4908 4909
 *
 * At the point that cgroup_fork() is called, 'current' is the parent
 * task, and the passed argument 'child' points to the child task.
 */
void cgroup_fork(struct task_struct *child)
{
4910
	task_lock(current);
4911 4912
	child->cgroups = current->cgroups;
	get_css_set(child->cgroups);
4913
	task_unlock(current);
4914
	INIT_LIST_HEAD(&child->cg_list);
4915 4916
}

4917
/**
L
Li Zefan 已提交
4918 4919 4920
 * cgroup_post_fork - called on a new task after adding it to the task list
 * @child: the task in question
 *
4921 4922 4923 4924 4925
 * Adds the task to the list running through its css_set if necessary and
 * call the subsystem fork() callbacks.  Has to be after the task is
 * visible on the task list in case we race with the first call to
 * cgroup_iter_start() - to guarantee that the new task ends up on its
 * list.
L
Li Zefan 已提交
4926
 */
4927 4928
void cgroup_post_fork(struct task_struct *child)
{
4929 4930
	int i;

4931 4932 4933 4934 4935 4936 4937 4938 4939 4940 4941
	/*
	 * use_task_css_set_links is set to 1 before we walk the tasklist
	 * under the tasklist_lock and we read it here after we added the child
	 * to the tasklist under the tasklist_lock as well. If the child wasn't
	 * yet in the tasklist when we walked through it from
	 * cgroup_enable_task_cg_lists(), then use_task_css_set_links value
	 * should be visible now due to the paired locking and barriers implied
	 * by LOCK/UNLOCK: it is written before the tasklist_lock unlock
	 * in cgroup_enable_task_cg_lists() and read here after the tasklist_lock
	 * lock on fork.
	 */
4942 4943
	if (use_task_css_set_links) {
		write_lock(&css_set_lock);
4944 4945
		task_lock(child);
		if (list_empty(&child->cg_list))
4946
			list_add(&child->cg_list, &child->cgroups->tasks);
4947
		task_unlock(child);
4948 4949
		write_unlock(&css_set_lock);
	}
4950 4951 4952 4953 4954 4955 4956

	/*
	 * Call ss->fork().  This must happen after @child is linked on
	 * css_set; otherwise, @child might change state between ->fork()
	 * and addition to css_set.
	 */
	if (need_forkexit_callback) {
4957 4958 4959 4960 4961 4962 4963 4964 4965
		/*
		 * fork/exit callbacks are supported only for builtin
		 * subsystems, and the builtin section of the subsys
		 * array is immutable, so we don't need to lock the
		 * subsys array here. On the other hand, modular section
		 * of the array can be freed at module unload, so we
		 * can't touch that.
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
4966 4967 4968 4969 4970 4971
			struct cgroup_subsys *ss = subsys[i];

			if (ss->fork)
				ss->fork(child);
		}
	}
4972
}
4973

4974 4975 4976
/**
 * cgroup_exit - detach cgroup from exiting task
 * @tsk: pointer to task_struct of exiting process
L
Li Zefan 已提交
4977
 * @run_callback: run exit callbacks?
4978 4979 4980 4981 4982 4983 4984 4985 4986 4987 4988 4989 4990 4991 4992 4993 4994 4995 4996 4997 4998 4999 5000 5001 5002 5003 5004 5005
 *
 * Description: Detach cgroup from @tsk and release it.
 *
 * Note that cgroups marked notify_on_release force every task in
 * them to take the global cgroup_mutex mutex when exiting.
 * This could impact scaling on very large systems.  Be reluctant to
 * use notify_on_release cgroups where very high task exit scaling
 * is required on large systems.
 *
 * the_top_cgroup_hack:
 *
 *    Set the exiting tasks cgroup to the root cgroup (top_cgroup).
 *
 *    We call cgroup_exit() while the task is still competent to
 *    handle notify_on_release(), then leave the task attached to the
 *    root cgroup in each hierarchy for the remainder of its exit.
 *
 *    To do this properly, we would increment the reference count on
 *    top_cgroup, and near the very end of the kernel/exit.c do_exit()
 *    code we would add a second cgroup function call, to drop that
 *    reference.  This would just create an unnecessary hot spot on
 *    the top_cgroup reference count, to no avail.
 *
 *    Normally, holding a reference to a cgroup without bumping its
 *    count is unsafe.   The cgroup could go away, or someone could
 *    attach us to a different cgroup, decrementing the count on
 *    the first cgroup that we never incremented.  But in this case,
 *    top_cgroup isn't going away, and either task has PF_EXITING set,
5006 5007
 *    which wards off any cgroup_attach_task() attempts, or task is a failed
 *    fork, never visible to cgroup_attach_task.
5008 5009 5010
 */
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
{
5011
	struct css_set *cset;
5012
	int i;
5013 5014 5015 5016 5017 5018 5019 5020 5021

	/*
	 * Unlink from the css_set task list if necessary.
	 * Optimistically check cg_list before taking
	 * css_set_lock
	 */
	if (!list_empty(&tsk->cg_list)) {
		write_lock(&css_set_lock);
		if (!list_empty(&tsk->cg_list))
5022
			list_del_init(&tsk->cg_list);
5023 5024 5025
		write_unlock(&css_set_lock);
	}

5026 5027
	/* Reassign the task to the init_css_set. */
	task_lock(tsk);
5028
	cset = tsk->cgroups;
5029
	tsk->cgroups = &init_css_set;
5030 5031

	if (run_callbacks && need_forkexit_callback) {
5032 5033 5034 5035 5036
		/*
		 * fork/exit callbacks are supported only for builtin
		 * subsystems, see cgroup_post_fork() for details.
		 */
		for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
5037
			struct cgroup_subsys *ss = subsys[i];
5038

5039 5040
			if (ss->exit) {
				struct cgroup *old_cgrp =
5041
					rcu_dereference_raw(cset->subsys[i])->cgroup;
5042
				struct cgroup *cgrp = task_cgroup(tsk, i);
5043
				ss->exit(cgrp, old_cgrp, tsk);
5044 5045 5046
			}
		}
	}
5047
	task_unlock(tsk);
5048

5049
	put_css_set_taskexit(cset);
5050
}
5051

5052
static void check_for_release(struct cgroup *cgrp)
5053 5054 5055
{
	/* All of these checks rely on RCU to keep the cgroup
	 * structure alive */
5056 5057 5058 5059
	if (cgroup_is_releasable(cgrp) &&
	    !atomic_read(&cgrp->count) && list_empty(&cgrp->children)) {
		/*
		 * Control Group is currently removeable. If it's not
5060
		 * already queued for a userspace notification, queue
5061 5062
		 * it now
		 */
5063
		int need_schedule_work = 0;
5064

5065
		raw_spin_lock(&release_list_lock);
5066 5067 5068
		if (!cgroup_is_removed(cgrp) &&
		    list_empty(&cgrp->release_list)) {
			list_add(&cgrp->release_list, &release_list);
5069 5070
			need_schedule_work = 1;
		}
5071
		raw_spin_unlock(&release_list_lock);
5072 5073 5074 5075 5076
		if (need_schedule_work)
			schedule_work(&release_agent_work);
	}
}

5077
/* Caller must verify that the css is not for root cgroup */
5078 5079
bool __css_tryget(struct cgroup_subsys_state *css)
{
T
Tejun Heo 已提交
5080 5081
	while (true) {
		int t, v;
5082

T
Tejun Heo 已提交
5083 5084 5085
		v = css_refcnt(css);
		t = atomic_cmpxchg(&css->refcnt, v, v + 1);
		if (likely(t == v))
5086
			return true;
T
Tejun Heo 已提交
5087 5088
		else if (t < 0)
			return false;
5089
		cpu_relax();
T
Tejun Heo 已提交
5090
	}
5091 5092 5093 5094 5095
}
EXPORT_SYMBOL_GPL(__css_tryget);

/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css)
5096
{
5097
	int v;
5098

5099
	v = css_unbias_refcnt(atomic_dec_return(&css->refcnt));
5100
	if (v == 0)
5101
		schedule_work(&css->dput_work);
5102
}
B
Ben Blum 已提交
5103
EXPORT_SYMBOL_GPL(__css_put);
5104 5105 5106 5107 5108 5109 5110 5111 5112 5113 5114 5115 5116 5117 5118 5119 5120 5121 5122 5123 5124 5125 5126 5127 5128 5129 5130 5131

/*
 * Notify userspace when a cgroup is released, by running the
 * configured release agent with the name of the cgroup (path
 * relative to the root of cgroup file system) as the argument.
 *
 * Most likely, this user command will try to rmdir this cgroup.
 *
 * This races with the possibility that some other task will be
 * attached to this cgroup before it is removed, or that some other
 * user task will 'mkdir' a child cgroup of this cgroup.  That's ok.
 * The presumed 'rmdir' will fail quietly if this cgroup is no longer
 * unused, and this cgroup will be reprieved from its death sentence,
 * to continue to serve a useful existence.  Next time it's released,
 * we will get notified again, if it still has 'notify_on_release' set.
 *
 * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
 * means only wait until the task is successfully execve()'d.  The
 * separate release agent task is forked by call_usermodehelper(),
 * then control in this thread returns here, without waiting for the
 * release agent task.  We don't bother to wait because the caller of
 * this routine has no use for the exit status of the release agent
 * task, so no sense holding our caller up for that.
 */
static void cgroup_release_agent(struct work_struct *work)
{
	BUG_ON(work != &release_agent_work);
	mutex_lock(&cgroup_mutex);
5132
	raw_spin_lock(&release_list_lock);
5133 5134 5135
	while (!list_empty(&release_list)) {
		char *argv[3], *envp[3];
		int i;
5136
		char *pathbuf = NULL, *agentbuf = NULL;
5137
		struct cgroup *cgrp = list_entry(release_list.next,
5138 5139
						    struct cgroup,
						    release_list);
5140
		list_del_init(&cgrp->release_list);
5141
		raw_spin_unlock(&release_list_lock);
5142
		pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
5143 5144 5145 5146 5147 5148 5149
		if (!pathbuf)
			goto continue_free;
		if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
			goto continue_free;
		agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
		if (!agentbuf)
			goto continue_free;
5150 5151

		i = 0;
5152 5153
		argv[i++] = agentbuf;
		argv[i++] = pathbuf;
5154 5155 5156 5157 5158 5159 5160 5161 5162 5163 5164 5165 5166 5167
		argv[i] = NULL;

		i = 0;
		/* minimal command environment */
		envp[i++] = "HOME=/";
		envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
		envp[i] = NULL;

		/* Drop the lock while we invoke the usermode helper,
		 * since the exec could involve hitting disk and hence
		 * be a slow process */
		mutex_unlock(&cgroup_mutex);
		call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
		mutex_lock(&cgroup_mutex);
5168 5169 5170
 continue_free:
		kfree(pathbuf);
		kfree(agentbuf);
5171
		raw_spin_lock(&release_list_lock);
5172
	}
5173
	raw_spin_unlock(&release_list_lock);
5174 5175
	mutex_unlock(&cgroup_mutex);
}
5176 5177 5178 5179 5180 5181 5182 5183 5184

static int __init cgroup_disable(char *str)
{
	int i;
	char *token;

	while ((token = strsep(&str, ",")) != NULL) {
		if (!*token)
			continue;
5185
		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
5186 5187
			struct cgroup_subsys *ss = subsys[i];

5188 5189 5190 5191 5192 5193 5194 5195
			/*
			 * cgroup_disable, being at boot time, can't
			 * know about module subsystems, so we don't
			 * worry about them.
			 */
			if (!ss || ss->module)
				continue;

5196 5197 5198 5199 5200 5201 5202 5203 5204 5205 5206
			if (!strcmp(token, ss->name)) {
				ss->disabled = 1;
				printk(KERN_INFO "Disabling %s control group"
					" subsystem\n", ss->name);
				break;
			}
		}
	}
	return 1;
}
__setup("cgroup_disable=", cgroup_disable);
K
KAMEZAWA Hiroyuki 已提交
5207 5208 5209 5210 5211 5212 5213 5214 5215 5216

/*
 * Functons for CSS ID.
 */

/*
 *To get ID other than 0, this should be called when !cgroup_is_removed().
 */
unsigned short css_id(struct cgroup_subsys_state *css)
{
5217 5218 5219 5220 5221 5222 5223
	struct css_id *cssid;

	/*
	 * This css_id() can return correct value when somone has refcnt
	 * on this or this is under rcu_read_lock(). Once css->id is allocated,
	 * it's unchanged until freed.
	 */
5224
	cssid = rcu_dereference_check(css->id, css_refcnt(css));
K
KAMEZAWA Hiroyuki 已提交
5225 5226 5227 5228 5229

	if (cssid)
		return cssid->id;
	return 0;
}
B
Ben Blum 已提交
5230
EXPORT_SYMBOL_GPL(css_id);
K
KAMEZAWA Hiroyuki 已提交
5231

5232 5233 5234 5235 5236 5237
/**
 *  css_is_ancestor - test "root" css is an ancestor of "child"
 * @child: the css to be tested.
 * @root: the css supporsed to be an ancestor of the child.
 *
 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
5238
 * this function reads css->id, the caller must hold rcu_read_lock().
5239 5240 5241 5242 5243 5244
 * But, considering usual usage, the csses should be valid objects after test.
 * Assuming that the caller will do some action to the child if this returns
 * returns true, the caller must take "child";s reference count.
 * If "child" is valid object and this returns true, "root" is valid, too.
 */

K
KAMEZAWA Hiroyuki 已提交
5245
bool css_is_ancestor(struct cgroup_subsys_state *child,
5246
		    const struct cgroup_subsys_state *root)
K
KAMEZAWA Hiroyuki 已提交
5247
{
5248 5249
	struct css_id *child_id;
	struct css_id *root_id;
K
KAMEZAWA Hiroyuki 已提交
5250

5251
	child_id  = rcu_dereference(child->id);
5252 5253
	if (!child_id)
		return false;
5254
	root_id = rcu_dereference(root->id);
5255 5256 5257 5258 5259 5260 5261
	if (!root_id)
		return false;
	if (child_id->depth < root_id->depth)
		return false;
	if (child_id->stack[root_id->depth] != root_id->id)
		return false;
	return true;
K
KAMEZAWA Hiroyuki 已提交
5262 5263 5264 5265 5266 5267 5268 5269 5270 5271 5272 5273 5274
}

void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
{
	struct css_id *id = css->id;
	/* When this is called before css_id initialization, id can be NULL */
	if (!id)
		return;

	BUG_ON(!ss->use_id);

	rcu_assign_pointer(id->css, NULL);
	rcu_assign_pointer(css->id, NULL);
5275
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5276
	idr_remove(&ss->idr, id->id);
5277
	spin_unlock(&ss->id_lock);
5278
	kfree_rcu(id, rcu_head);
K
KAMEZAWA Hiroyuki 已提交
5279
}
B
Ben Blum 已提交
5280
EXPORT_SYMBOL_GPL(free_css_id);
K
KAMEZAWA Hiroyuki 已提交
5281 5282 5283 5284 5285 5286 5287 5288 5289

/*
 * This is called by init or create(). Then, calls to this function are
 * always serialized (By cgroup_mutex() at create()).
 */

static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
{
	struct css_id *newid;
T
Tejun Heo 已提交
5290
	int ret, size;
K
KAMEZAWA Hiroyuki 已提交
5291 5292 5293 5294 5295 5296 5297

	BUG_ON(!ss->use_id);

	size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
	newid = kzalloc(size, GFP_KERNEL);
	if (!newid)
		return ERR_PTR(-ENOMEM);
T
Tejun Heo 已提交
5298 5299

	idr_preload(GFP_KERNEL);
5300
	spin_lock(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5301
	/* Don't use 0. allocates an ID of 1-65535 */
T
Tejun Heo 已提交
5302
	ret = idr_alloc(&ss->idr, newid, 1, CSS_ID_MAX + 1, GFP_NOWAIT);
5303
	spin_unlock(&ss->id_lock);
T
Tejun Heo 已提交
5304
	idr_preload_end();
K
KAMEZAWA Hiroyuki 已提交
5305 5306

	/* Returns error when there are no free spaces for new ID.*/
T
Tejun Heo 已提交
5307
	if (ret < 0)
K
KAMEZAWA Hiroyuki 已提交
5308 5309
		goto err_out;

T
Tejun Heo 已提交
5310
	newid->id = ret;
K
KAMEZAWA Hiroyuki 已提交
5311 5312 5313 5314
	newid->depth = depth;
	return newid;
err_out:
	kfree(newid);
T
Tejun Heo 已提交
5315
	return ERR_PTR(ret);
K
KAMEZAWA Hiroyuki 已提交
5316 5317 5318

}

5319 5320
static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
					    struct cgroup_subsys_state *rootcss)
K
KAMEZAWA Hiroyuki 已提交
5321 5322 5323
{
	struct css_id *newid;

5324
	spin_lock_init(&ss->id_lock);
K
KAMEZAWA Hiroyuki 已提交
5325 5326 5327 5328 5329 5330 5331 5332 5333 5334 5335 5336 5337 5338 5339 5340 5341
	idr_init(&ss->idr);

	newid = get_new_cssid(ss, 0);
	if (IS_ERR(newid))
		return PTR_ERR(newid);

	newid->stack[0] = newid->id;
	newid->css = rootcss;
	rootcss->id = newid;
	return 0;
}

static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
			struct cgroup *child)
{
	int subsys_id, i, depth = 0;
	struct cgroup_subsys_state *parent_css, *child_css;
5342
	struct css_id *child_id, *parent_id;
K
KAMEZAWA Hiroyuki 已提交
5343 5344 5345 5346 5347

	subsys_id = ss->subsys_id;
	parent_css = parent->subsys[subsys_id];
	child_css = child->subsys[subsys_id];
	parent_id = parent_css->id;
5348
	depth = parent_id->depth + 1;
K
KAMEZAWA Hiroyuki 已提交
5349 5350 5351 5352 5353 5354 5355 5356 5357 5358 5359 5360 5361 5362 5363 5364 5365 5366 5367 5368 5369 5370 5371 5372 5373 5374 5375 5376 5377 5378 5379 5380 5381 5382 5383 5384 5385

	child_id = get_new_cssid(ss, depth);
	if (IS_ERR(child_id))
		return PTR_ERR(child_id);

	for (i = 0; i < depth; i++)
		child_id->stack[i] = parent_id->stack[i];
	child_id->stack[depth] = child_id->id;
	/*
	 * child_id->css pointer will be set after this cgroup is available
	 * see cgroup_populate_dir()
	 */
	rcu_assign_pointer(child_css->id, child_id);

	return 0;
}

/**
 * css_lookup - lookup css by id
 * @ss: cgroup subsys to be looked into.
 * @id: the id
 *
 * Returns pointer to cgroup_subsys_state if there is valid one with id.
 * NULL if not. Should be called under rcu_read_lock()
 */
struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
{
	struct css_id *cssid = NULL;

	BUG_ON(!ss->use_id);
	cssid = idr_find(&ss->idr, id);

	if (unlikely(!cssid))
		return NULL;

	return rcu_dereference(cssid->css);
}
B
Ben Blum 已提交
5386
EXPORT_SYMBOL_GPL(css_lookup);
K
KAMEZAWA Hiroyuki 已提交
5387

S
Stephane Eranian 已提交
5388 5389 5390 5391 5392 5393 5394 5395 5396
/*
 * get corresponding css from file open on cgroupfs directory
 */
struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
{
	struct cgroup *cgrp;
	struct inode *inode;
	struct cgroup_subsys_state *css;

A
Al Viro 已提交
5397
	inode = file_inode(f);
S
Stephane Eranian 已提交
5398 5399 5400 5401 5402 5403 5404 5405 5406 5407 5408 5409 5410
	/* check in cgroup filesystem dir */
	if (inode->i_op != &cgroup_dir_inode_operations)
		return ERR_PTR(-EBADF);

	if (id < 0 || id >= CGROUP_SUBSYS_COUNT)
		return ERR_PTR(-EINVAL);

	/* get cgroup */
	cgrp = __d_cgrp(f->f_dentry);
	css = cgrp->subsys[id];
	return css ? css : ERR_PTR(-ENOENT);
}

5411
#ifdef CONFIG_CGROUP_DEBUG
5412
static struct cgroup_subsys_state *debug_css_alloc(struct cgroup *cont)
5413 5414 5415 5416 5417 5418 5419 5420 5421
{
	struct cgroup_subsys_state *css = kzalloc(sizeof(*css), GFP_KERNEL);

	if (!css)
		return ERR_PTR(-ENOMEM);

	return css;
}

5422
static void debug_css_free(struct cgroup *cont)
5423 5424 5425 5426 5427 5428 5429 5430 5431 5432 5433 5434 5435 5436 5437 5438 5439 5440 5441 5442 5443 5444 5445 5446 5447 5448 5449 5450 5451 5452
{
	kfree(cont->subsys[debug_subsys_id]);
}

static u64 cgroup_refcount_read(struct cgroup *cont, struct cftype *cft)
{
	return atomic_read(&cont->count);
}

static u64 debug_taskcount_read(struct cgroup *cont, struct cftype *cft)
{
	return cgroup_task_count(cont);
}

static u64 current_css_set_read(struct cgroup *cont, struct cftype *cft)
{
	return (u64)(unsigned long)current->cgroups;
}

static u64 current_css_set_refcount_read(struct cgroup *cont,
					   struct cftype *cft)
{
	u64 count;

	rcu_read_lock();
	count = atomic_read(&current->cgroups->refcount);
	rcu_read_unlock();
	return count;
}

5453 5454 5455 5456
static int current_css_set_cg_links_read(struct cgroup *cont,
					 struct cftype *cft,
					 struct seq_file *seq)
{
5457
	struct cgrp_cset_link *link;
5458
	struct css_set *cset;
5459 5460 5461

	read_lock(&css_set_lock);
	rcu_read_lock();
5462
	cset = rcu_dereference(current->cgroups);
5463
	list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
5464 5465 5466 5467 5468 5469 5470
		struct cgroup *c = link->cgrp;
		const char *name;

		if (c->dentry)
			name = c->dentry->d_name.name;
		else
			name = "?";
5471 5472
		seq_printf(seq, "Root %d group %s\n",
			   c->root->hierarchy_id, name);
5473 5474 5475 5476 5477 5478 5479 5480 5481 5482 5483
	}
	rcu_read_unlock();
	read_unlock(&css_set_lock);
	return 0;
}

#define MAX_TASKS_SHOWN_PER_CSS 25
static int cgroup_css_links_read(struct cgroup *cont,
				 struct cftype *cft,
				 struct seq_file *seq)
{
5484
	struct cgrp_cset_link *link;
5485 5486

	read_lock(&css_set_lock);
5487 5488
	list_for_each_entry(link, &cont->cset_links, cset_link) {
		struct css_set *cset = link->cset;
5489 5490
		struct task_struct *task;
		int count = 0;
5491 5492
		seq_printf(seq, "css_set %p\n", cset);
		list_for_each_entry(task, &cset->tasks, cg_list) {
5493 5494 5495 5496 5497 5498 5499 5500 5501 5502 5503 5504 5505
			if (count++ > MAX_TASKS_SHOWN_PER_CSS) {
				seq_puts(seq, "  ...\n");
				break;
			} else {
				seq_printf(seq, "  task %d\n",
					   task_pid_vnr(task));
			}
		}
	}
	read_unlock(&css_set_lock);
	return 0;
}

5506 5507 5508 5509 5510 5511 5512 5513 5514 5515 5516 5517 5518 5519 5520 5521 5522 5523 5524 5525 5526 5527 5528 5529 5530
static u64 releasable_read(struct cgroup *cgrp, struct cftype *cft)
{
	return test_bit(CGRP_RELEASABLE, &cgrp->flags);
}

static struct cftype debug_files[] =  {
	{
		.name = "cgroup_refcount",
		.read_u64 = cgroup_refcount_read,
	},
	{
		.name = "taskcount",
		.read_u64 = debug_taskcount_read,
	},

	{
		.name = "current_css_set",
		.read_u64 = current_css_set_read,
	},

	{
		.name = "current_css_set_refcount",
		.read_u64 = current_css_set_refcount_read,
	},

5531 5532 5533 5534 5535 5536 5537 5538 5539 5540
	{
		.name = "current_css_set_cg_links",
		.read_seq_string = current_css_set_cg_links_read,
	},

	{
		.name = "cgroup_css_links",
		.read_seq_string = cgroup_css_links_read,
	},

5541 5542 5543 5544 5545
	{
		.name = "releasable",
		.read_u64 = releasable_read,
	},

5546 5547
	{ }	/* terminate */
};
5548 5549 5550

struct cgroup_subsys debug_subsys = {
	.name = "debug",
5551 5552
	.css_alloc = debug_css_alloc,
	.css_free = debug_css_free,
5553
	.subsys_id = debug_subsys_id,
5554
	.base_cftypes = debug_files,
5555 5556
};
#endif /* CONFIG_CGROUP_DEBUG */